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Fromille, Samuel S. IV. "Novel Concept for High Dielectric Constant Composite Electrolyte Dielectrics." Thesis, Monterey, California. Naval Postgraduate School, 2013. http://hdl.handle.net/10945/53408.
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Approved for public release<br>This research was part of an ongoing program studying the concept of multi-material dielectrics (MMD) with dielectric constants much higher than homogenous materials. MMD described in this study have dielectric constants six orders of magnitude greater than the best single materials. This is achieved by mixing conductive particles with an insulating surface layer into a composite matrix phase composed of high surface area ceramic powder and aqueous electrolyte. Specifically examined in this study was micron-scale nickel powder treated in hydrogen peroxide (H2O2) loaded into high surface area alumina powder and aqueous boric acid solution. This new class of dielectric, composite electrolyte dielectrics (CED), is employed in an electrostatic capacitor configuration and demonstrated dielectric constant of order 10 [raised to the 10th power] at approximately 1 Volt.
Additionally, it is demonstrated that treated nickel can be loaded in high volume fractions in the CED configuration. Prior studies of composite capacitors indicated a general limitation due to shorting. This results from the onset of percolation due to excess loading of conductive phases. Insulated particles described herein are successfully loaded up to 40% by volume, far above typical percolation thresholds. Simple models are presented to explain results.<br>Lieutenant, United States Navy
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Nicholls, Simon J. "High permittivity ceramics for dielectrically loaded applications." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/16354/.
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A temperature-stable, ultra-high permittivity dielectric ceramic, based on CTLNT, has been successfully fabricated at significantly reduced sintering temperatures with no deterioration of microwave properties, through the addition of a Bi_4B_2O_9 (BBO) sintering aid. This work has been an extension of previous findings where it was shown that 0.2CaTiO_3-0.8(Li_0.5Nd_0.5)TiO_3 (CTLNT) with 4wt% BBO as a liquid-phase sintering aid gives rise to exceptional microwave (MW) dielectric properties, (relative permittivity, ε_r = 127, quality factor, Qf_0 = 2700 GHz, and temperature coefficient of the resonant frequency, τ_f = +4 ppm/°C) at reduced sintering temperatures (1200°C). Prior to this, it has been exceptionally difficult to produce a large ε_r dielectric material, with both a low sintering temperature and near-zero temperature stability, without dramatic deterioration of the dielectric properties of the material. This contribution set out to investigate and understand the sintering mechanism between the CTLNT + xwt% BBO system, to aid in the development of designer sintering aids in the development of other microwave dielectric ceramic materials and devices. CTLNT + 1, 3, 4 and 5wt% BBO compositions were fabricated and a variety of analysis techniques were used, such as density, XRD, SEM, TEM, EDS and MW characterisation. Density increased with increasing BBO concentration and sintering temperature, and the MW results reflected the changes in density. The 1wt% BBO composition showed the greatest variation between the sintering temperatures, and 4wt% composition demonstrated optimum MW results of: ε_r=125, Qf_0=2518 GHz and τ_f=4 ppm/°C, at a sintering temperature of 1200°C. The variation of τ_f with changes in BBO concentration was non-linear, which suggested a chemical reaction was taking place. XRD results revealed no secondary phases, regardless of BBO concentration. SEM results showed increased crystal grain size as BBO concentration and sintering temperatures increased, as well as increased contrast variation on the polished surface and darker-contrast amorphous phase in the fracture surface. The contrast variation in the polished surfaces were also indicative of a chemical reaction. Using a combination of XRD, TEM and SEM it was demonstrated that highly polarisable Bi3+ ions entered the CTLNT perovskite lattice and locally increasing ε_r. The accompanying ex-solution of TiO2 precipitates, observed and analysed under SEM and TEM, as the BBO concentration increased implied the formation of Ti vacancies (V_Ti^'''') in the perovskite matrix to compensate for the extra positive charge of the Bi3+. The ex-solution of Ti indicates Bi3+ ions substitute onto the A-site of the perovskite crystal system for lower valence ionic elements, after the following generic defect equation: 4(A)_A^x+(Ti)_Ti^x⇒4(Bi)_A^∙+V_Ti^'''' The residual phase was found to be a boron-rich liquid-phase, which acted as the sintering aid, with a large negative τ_f which compensates for the positive τ_f of the CTLNT. The CTLST + xwt% BBO system (S = Sm) was then investigated to determine if a similar mechanism would occur. CTLST + 1, 2, 3 and 4wt% BBO compositions were fabricated and underwent the same analysis techniques. Density increased with increasing BBO concentration up to 1250°C, after which density fell for all samples; the 4wt% BBO composition exhibited the largest density, at 1250°C. The MW results reflected this trend, which saw a general increase in ε_r as BBO concentration and sintering temperature increased, which fell universally at 1300°C. 〖Qf〗_0 would generally increase with increased BBO concentration, across all sintering temperatures, while a dip was observed at 1250°C, and the 4wt% BBO composition demonstrated optimum properties of: ε_r = 105.7, Qf_0 = 3295 GHz and τ_f = -4 ppm/°C, sintered at 1200°C. Contrary to the CTLNT system, the variation of τ_f with BBO content and sintering temperature was linear. SEM reflected density changes, where crystal grain increased with increasing BBO concentration, up to 1250°C. At 1300°C, samples suffered from dissolution into the liquid-phase, increasing pore sizes, decreasing density and, thus, impacting on the MW properties of the samples. Similar to the CTLNT system, contrast variation was observed, in addition to darker B-rich liquid phase in the fracture surface. EDS from both SEM and TEM revealed that Bi was present within the CTLST matrix, however no TiO2 precipitates were observed. Large Zr contamination within CTLST is the likely cause of the difference in defect chemistry, as excess of Zr substitution onto the perovskite B-site compensates for Bi substitution onto the A-site, negating the need for TiO_2 precipitates to ex-solve. Multi-layer ceramic capacitors (MLCCs) of the CTLNT + 4wt% BBO composition were fabricated to determine whether the temperature stabilities of the material in conjunction with a large ε_r would allow the material to be a suitable candidate as a Class 1 C0G/NP0 MLCC device. Fabrication of the devices followed the conventional method, but required modification due to delamination. These modifications included: longer firing times to allow for binders and plasticisers to burn-out fully; calcined alumina powder base to fire and sinter samples upon, to avoid sticking issues; and solvent wetting of individual layers to adequately fuse layers together pre-firing and sintering. Successful MLCC devices had case sizes of EIA ‘2928’ and IEC ‘7472’. SEM and EDS revealed no mixing or exchange of materials between the dielectric and the platinum internal electrode, and generally good adhesion between both materials. Electrical tests revealed that, despite the temperature stability observed at 1-3 GHz in the MW study, that the MLCC devices would be classed as EIA “M8J” and IEC “P1000”, however maximum available test frequency of 1 MHZ is much lower than the average operating frequencies of class 1 devices, which lie between 100 MHz – 30 GHz.
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Waldron, Isaac James. "Ring Resonator Method for Dielectric Permittivity Measurements of Foams." Digital WPI, 2006. https://digitalcommons.wpi.edu/etd-theses/666.
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Dielectric permittivity measurements provide important input to engineering and scientific disciplines due to the effects of permittivity on the interactions between electromagnetic energy and materials. A novel ring resonator design is presented for the measurement of permittivity of low dielectric constant foams. A review of dielectric material properties and currently available measurement methods is included. Measurements of expanded polystyrene are reported and compared with results from the literature; good agreement between measurements and published results is shown.
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Duong, Danny. "The complex dielectric properties of aqueous ammonia from 2 GHz - 8.5 GHz in support of the NASA Juno mission." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42891.
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A new model for the complex dielectric constant, ε, of aqueous ammonia (NH4OH) has been developed based on laboratory measurements in the frequency range between 2-8.5 GHz for ammonia concentrations of 0-8.5 %NH3/volume and temperatures between 277-297 K. The new model has been validated for temperatures up to 313 K, but may be consistently extrapolated up to 475 K and ammonia concentrations up to 20 %NH3/volume. The model fits 60.26 % of all laboratory measurements within 2σ uncertainty. The new model is identical to the Meissner and Wentz (2004) model of the complex dielectric constant of pure water, but it contains a correction for dissolved ammonia. A description of the experimental setups, uncertainties associated with the laboratory measurements, the model fitting process, the new model, and its application to approximating jovian cloud opacity for NASA's Juno mission to Jupiter are provided.
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Xu, Yifan. "Studies on field effect transistors with conjugated polymer and high permittivity gate dielectrics using pulsed plasma polymerization." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1124219179.
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Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xx, 187 p.; also includes graphics (some col.). Includes bibliographical references (p. 174-187). Available online via OhioLINK's ETD Center
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Umaña, Juan Antonio. "Measurement of complex dielectric permittivity of pavement materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0004/MQ32519.pdf.
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Marais, Johannes Izak Frederik. "A permittivity measurement system for high frequency laboratories." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/580.
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Ravindran, Ramasamy. "Deposition and characterization of high permittivity thin-film dielectrics." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4530.
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Thesis (M.S.)--University of Missouri-Columbia, 2006.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Includes bibliographical references.
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Sloma, A. "Complex dielectric permittivity of water, inorganic and organic solutions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0019/MQ58086.pdf.
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Kahouli, Abdelkader. "Etude des propriétés physico-chimiques et (di-)électriques du parylène C en couche mince." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENT019.
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Ces travaux de thèse ont consisté à mener une étude approfondie des propriétés physico-chimiques duparylène C, qui est un polymère chloré, en lien avec ses propriétés électriques et diélectriques. Ces dernièresont cerné principalement le comportement de la constante diélectrique et des pertes diélectriques enfonction de la température (de l’azote jusqu’à 300 °C) sur une plage de fréquence étendue (10-4 Hz – 1 MHz).Les analyses par diffraction des rayons X ont montré que ce polymère présentait une structure cristalline a-monoclinique avec un taux de cristallinité de 45 % après élaboration. Ce taux est faiblement dépendant del’épaisseur pour des couches d’épaisseurs supérieures à 50 nm. Des recuits spécifiques appliqués sur leparylène C au dessus de la température de transition vitreuse ont permis de modifier le taux de cristallinité etdes valeurs de 30% à 75 % ont pu être obtenues. Une relation linéaire entre le taux de cristallinité et latempérature de recuit a été proposée. Les analyses diélectriques ont permis de mettre en évidence troismécanismes principaux de relaxation : La relaxation b, la relaxation g et la relaxation a. Par ailleurs, unmécanisme de polarisation interfaciale de type Maxwell-Wagner-Sillars (MWS) a été identifié à hautetempérature (au-delà de la transition vitreuse). La mobilité moléculaire des chaînes autour de la températurede transition vitreuse a été analysée en profondeur et les résultats (indice de fragilité, paramètresthermodynamiques…) ont été positionnés par rapport aux données de la littérature concernant d’autrespolymères<br>This work of thesis consisted in undertaking a thorough study of the physicochemical properties of theparylene C, which is a chlorinated polymer, in relationship with its electric and dielectric properties. These lastdetermined mainly the behavior of the permittivity and the dielectric losses according to the temperature (ofnitrogen up to 300 °C) on a wide frequency range (10-4Hz – 1 MHz). The analyses by x-rays diffraction showedthat this polymer had a a - monoclinical crystalline structure with a rate of crystallinity of 45 %. This rate isslightly depending on the thickness for layers thicknesses higher than 50 nm. Specific annealing applied to theparylene C made it possible to modify the rate of crystallinity and values from 30% to 75 % of crystallinitycould be obtained. A linear relation between the rate of crystallinity and the temperature of annealing wasproposed. The dielectric analyses made it possible to highlight three principal mechanisms of relaxation: b, g,a. In addition, a mechanism of interfacial polarization (Maxwell-Wagner-Sillars) was identified at hightemperature (beyond the glass transition). The molecular mobility of the chains around the glass transitionwas analyzed in-depth and the results (index of fragility, thermodynamic parameters...) were positionedcompared to the data of the literature concerning of other polymers
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Rai, Sheila. "Complex permittivity measurements by multi-mode microwave resonant cavity." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/11517.
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Stoyanov, Hristiyan. "Soft nanocomposites with enhanced electromechanical response for dielectric elastomer actuators." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5119/.
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Electromechanical transducers based on elastomer capacitors are presently considered for many soft actuation applications, due to their large reversible deformation in response to electric field induced electrostatic pressure. The high operating voltage of such devices is currently a large drawback, hindering their use in applications such as biomedical devices and biomimetic robots, however, they could be improved with a careful design of their material properties. The main targets for improving their properties are increasing the relative permittivity of the active material, while maintaining high electric breakdown strength and low stiffness, which would lead to enhanced electrostatic storage ability and hence, reduced operating voltage. Improvement of the functional properties is possible through the use of nanocomposites. These exploit the high surface-to-volume ratio of the nanoscale filler, resulting in large effects on macroscale properties.
This thesis explores several strategies for nanomaterials design. The resulting nanocomposites are fully characterized with respect to their electrical and mechanical properties, by use of dielectric spectroscopy, tensile mechanical analysis, and electric breakdown tests. First, nanocomposites consisting of high permittivity rutile TiO2 nanoparticles dispersed in thermoplastic block copolymer SEBS (poly-styrene-coethylene-co-butylene-co-styrene) are shown to exhibit permittivity increases of up to 3.7 times, leading to 5.6 times improvement in electrostatic energy density, but with a trade-off in mechanical properties (an 8-fold increase in stiffness). The variation in both electrical and mechanical properties still allows for electromechanical improvement, such that a 27 % reduction of the electric field is found compared to the pure elastomer. Second, it is shown that the use of nanofiller conductive particles (carbon black (CB)) can lead to a strong increase of relative permittivity through percolation, however, with detrimental side effects. These are due to localized enhancement of the electric field within the composite, which leads to sharp reductions in electric field strength. Hence, the increase in permittivity does not make up for the reduction in breakdown strength in relation to stored electrical energy, which may prohibit their practical use. Third, a completely new approach for increasing the relative permittivity and electrostatic energy density of a polymer based on 'molecular composites' is presented, relying on chemically grafting soft π-conjugated macromolecules to a flexible elastomer backbone. Polarization caused by charge displacement along the conjugated backbone is found to induce a large and controlled permittivity enhancement
(470 % over the elastomer matrix), while chemical bonding, encapsulates the PANI chains manifesting in hardly any reduction in electric breakdown strength, and hence resulting in a large increase in stored electrostatic energy. This is shown to lead to an improvement in the sensitivity of the measured electromechanical response (83 % reduction of the driving electric field) as well as in the maximum actuation strain (250 %). These results represent a large step forward in the understanding of the strategies which can be employed to obtain high permittivity polymer materials with practical use for electro-elastomer actuation.<br>Die Palette von elektro-mechanischen Aktuatoren, basierend auf dem Prinzip weicher dehnbarer Kondensatoren, scheint besonders für Anwendungen in der Medizin und für biomimetische Applikationen unbegrenzt. Diese Wandler zeichnen sich sowohl durch hohe Reversibilität bei großer mechanischer Deformation als auch durch ihre Flexibilität aus, wobei die mechanischen Deformationen durch elektrische Felder induziert werden. Die Notwendigkeit von hoher elektrischer Spannung zur Erzeugung dieser mechanischen Deformationen verzögert jedoch die technisch einfache und breite Markteinführung dieser Technologie. Diesem Problem kann durch eine gezielte Materialmodifikation begegnet werden. Eine Modifikation hat das Ziel, die relative Permittivität zu erhöhen, wobei die Flexibilität und die hohe elektrische Durchbruchsfeldstärke beibehalten werden sollten. Durch eine Materialmodifikation kann die Energiedichte des Materials bedeutend erhöht und somit die notwendige Betriebsspannung des Aktuators herabgesetzt werden. Eine Verbesserung der funktionalen Materialeigenschaften kann durch die Verwendung von Nanokompositen erzielt werden, welche die fundamentalen Eigenschaften der Nanopartikel, d.h. ein gutes Verhältnis von Oberfläche zu Volumen nutzen, um eine gezielte makroskopische Materialmodifikation zu bewirken.
Diese Arbeit behandelt die Anwendung innovativer Strategien für die Erzeugung von Nanomaterialien mit hoher Permittivität. Die so erzeugten Materialien und deren relevante Aktuatorkenngrößen werden durch elektrische und mechanische Experimente vollständig erfasst. Mittels der klassischen Mischansätze zur Erzeugung von Kompositmaterialen mit hoher Permittivität konnte durch nichtleitendes Titaniumdioxid TiO2 (Rutile) in einem Thermoplastischen-Block-Co-Polymer SEBS (poly-styrene-co-ethylene-cobutylene-co-styrene) die Permittivität bereits um 370 % erhöht und die elektrische Energiedichte um 570 % gesteigert werden. Diese Veränderungen führten jedoch zu einem signifikanten Anstieg der Steifigkeit des Materials. Aufgrund der positiven Rückkopplung von elektrischen und mechanischen Eigenschaften des Kompositmaterials ermöglicht bereits dieser einfache Ansatz eine Verbesserung der Aktuation, bei einer 27 %-igen Reduktion der Aktuatorbetriebsspannung. Eine direkte Verwendung von leitfähigen Nanopartikeln kann ebenso zu einem Anstieg der relativen Permittivität beitragen, wobei jedoch die Leitfähigkeit dieser Nanopartikel bedeutende Wechselwirkungen verursacht, welche somit die Energiedichte des Materials negativ beeinflusst und die praktische Verwendung dieses Kompositsystems ausschließt. Als ein völlig neuer Ansatz zur Steigerung der relativen Permittivität und Energiedichte und abweichend vom klassischen Mischverfahren, wird die Herstellung eines "Molekularen Komposits", basierend auf einem chemischen Propfverfahren, präsentiert. In diesem Ansatz wird ein π-konjugiertes leitfähiges Polymer (PANI) an die Hauptkette des Elastomers der Polymermatrix gebunden. Die daraus resultierende Ladungsverteilung entlang der Elastomerhauptkette bewirkt eine 470 %-ige Steigerung der Permittivität des "Molekularen Komposits" im Vergleich zur Permittivität des unbehandelten Elastomermaterials. Aufgrund der Verkapselung der chemischen Bindungen der PANI-Kette entstehen kaum negative Rückwirkungen auf die elektrischen und mechanischen Eigenschaften des so erzeugten Komposits. Diese Materialeigenschaften resultieren in einem signifikanten Anstieg der Energiedichte des Materials. Das mittels dieses Verfahrens erzeugte Komposit zeigt sowohl eine Steigerung der Sensitivität der elektromechanischen Antwort (Reduktion des elektrischen Felds um 83 %) als auch eine bedeutende Steigerung der maximalen Aktuation (250 %). Die Ergebnisse und Ideen dieser Arbeit stellen einen wesentlichen Sprung im Verständnis zur Permittivitätssteigerung in Polymermaterialien dar und werden deshalb in der Erforschung und Entwicklung von Elastomeraktuatoren Beachtung finden.
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Lee, Kyeonghwan. "A dielectric permittivity sensor for simultaneous measurement of multiple soil properties /." Search for this dissertation online, 2005. http://www.lib.umi.com/cr/ksu/main.
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SOUZA, JORGE ANGELO MITRIONE. "EFFECTS OF HIGH PERMITTIVITY DIELECTRIC SUBSTRATES APPLIED OVER MICROWAVE PRINTED CIRCUITS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24716@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>A presente tese descreve e analisa a utilização de substratos e superstratos dielétricos para a otimização do desempenho de antenas impressas configuradas através de microlinhas. São avaliadas as características de casamento de impedância, geração de ondas de superfície, ganho, diretividade, facilidade de montagem, facilidade de medição, diagrama de radiação e possibilidade de miniaturização. São avaliadas também as antenas configuradas através de guias dielétricos para aplicações na banda milimétrica e no domínio do Terahertz. Um procedimento inicial para seleção do substrato, do superstrato e do modelo de antena é sugerido. Várias antenas utilizando microlinhas são simuladas, realizadas e caracterizadas.<br>This work presents the research, design and optimization of the fundamental effects of dielectric substrate and superstrate over printed antennas performance. Impedance matching, surface waves generation, gain, directivity, assembling, pattern diagram and miniaturization are investigated. A new dielectric waveguide antenna is also investigated for millimetric and Terahertz applications. A initial criteria for choosing a more efficient substrate, superstrate for a specific antenna model is suggested. Several antennas models are simulated, realized and measured.
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Dib, Radwan. "Caractérisation de couches diélectriques et magnétiques de structures multicouches par cavité résonante microonde." Thesis, Saint-Etienne, 2014. http://www.theses.fr/2014STET4014/document.
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Cette thèse s’intéresse à la caractérisation de couches diélectriques et magnétiques de structures multicouches par cavité résonante microonde. Les matériaux multicouches ont des propriétés électromagnétiques spécifiques et sont utilisés dans beaucoup de secteurs industriels, par exemple, dans les radiocommunications. La caractérisation électromagnétique reste une priorité pour la compréhension des caractéristiques de propagation des ondes électromagnétiques dans ces milieux. Dans ce travail de thèse nous proposons une nouvelle approche expérimentale pour déterminer les propriétés diélectriques effectives d’une structure multicouches en fonction des propriétés et de l’épaisseur de chacune des couches. En particulier, nous appliquons les expressions de permittivités issues de la méthode des perturbations utilisée en cavité résonante au cas d’un échantillon rectangulaire bicouche. L’analyse théorique établie a montré qu’une expression de simple proportionnalité reliant les propriétés diélectriques moyennes d’un matériau bicouche avec les propriétés diélectriques relatives et les épaisseurs des couches constituantes peut être obtenue. Cette méthode a été appliquée avec succès sur différents matériaux bicouches. En particulier, elle a permis la caractérisation d’une couche de YIG d’épaisseur très mince (19.6 μm) déposée par pulvérisation cathodique sur un substrat d’alumine en connaissant l’épaisseur et les propriétés diélectriques du substrat. La comparaison avec les résultats expérimentaux a révélé un bon accord entre théorie et mesure. L’analyse de l’incertitude associée au calcul de la permittivité par la méthode a montré une bonne sensibilité. Enfin, nous donnons les courbes de variation de la perméabilité effective mesurée pour un empilement bicouche avec une couche mince de YIG<br>This thesis aimed at characterizing the dielectric and magnetic layers of multilayer structures by using the technique of microwave resonant cavity. Multilayer structures have specific electromagnetic properties and are becoming increasingly important in many industrial domains, such as in radio-communication systems. The electromagnetic characterization remains a priority for understanding the characteristics of electromagnetic wave propagation in such environments. The thesis proposed a new experimental approach to determine the effective dielectric properties in a bilayer structure as a function of the characteristics and thickness of each specific layer. In particular, we apply the expressions of permittivities derived from the perturbations method which are used in resonant cavities in case of a bilayer rectangular sample. The established theoretical analysis leads us to propose a new expression of simple proportionality describing a relationship between the mean dielectric properties of a bilayer material and the relative dielectric properties and thickness of the constituent layers. The presented method has been successfully applied to different bilayer materials. Particularly, it allowed the characterization of a very thin layer (YIG layer) of thickness 19.6 microns deposited by cathodic sputtering on an alumina substrate by knowing the thickness and dielectric properties of this substrate. The comparison with the experimental results revealed good agreement between theory and measurement. The analysis of the uncertainty associated to the calculation of the permittivity by the presented method showed good sensitivity. Finally, we provide the curves of variation of the effective permeability measured for a bilayer stack
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Noskov, А. V., О. V. Alekseeva, А. S. Kraev, and А. V. Agafonov. "Dielectric Parameters of Polystyrene / Fullerene Composite Films." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35431.
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The paper describes the frequency dependences of the electrophysical parameters (capacitance, dielectric
constant, dielectric loss tangent, and resistivity) of polystyrene films filled with small additions of fullerenes
(up to 1 wt % of C60). The composite materials obtained were concluded to be nonpolar. The dielectric
constant as a function of the film composition passes through a minimum at 0.035 wt of C60. The
polymer maintains good insulating properties when filled with fullerenes.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35431
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Meda, Venkatesh. "Integrated dual frequency permittivity analyzer using cavity perturbation concept." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38236.
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Optimal utilization of microwave energy requires more basic knowledge of the dielectric properties of the material under investigation. The dielectric properties of materials subjected to microwaves are known to depend on moisture content, temperature and density of the material as well as the frequency of the applied microwave field. This thesis is focussed on the development and evaluation of the new Permittivity Analyser to measure the dielectric properties of agri-food materials at 915 and 2450 MHz using cavity perturbation concept.<br>In this study, the dielectric properties measuring system was designed and developed using cavity perturbation concept to measure the essential and fundamental parameters of microwave-material interaction; dielectric constant and dielectric loss factor of selected agri-food substances and organic solvents. The TM010 mode of electromagnetic energy was selected and configured to operate at the peakresonant condition for both ISM (Industrial, Scientific and Medical) approved frequencies of .915 and 2450 MHz frequencies. The resonant perturbation cavities were designed, fabricated and tested using the network analyser and the permittivity analyser. High Q (ratio of energy supplied to absorbed) values were reported for both frequencies. Basic calibration of the measurement system was performed using standard media such as air, water and alcohol. Necessary mathematical steps and algorithms were written and integrated into a user-friendly software program (Visual basic 6.0) to carry out the entire measurement.<br>The dielectric properties (epsilon' & epsilon ″) of materials such as; edible oils---canola, soya and sunflower oils, neem oil/pulp, homogenized milk (1, 2 and 3.25% fat), organic solvents such as ethanol, hexane and their mixtures were determined at various temperatures and frequency (915, 2450 MHz) combinations, using cavity perturbation technique. Linear relationships between the dielectric properties and temperature found in the literature were confirmed to be valid for certain ranges in case of edible oils, organic solvents and milk samples tested with the cavity perturbation method. Repeatibility and variability aspects of the permittivity analyzer at both the frequencies are presented.
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Tkachov, Igor Ivanovich. "Millimeter wave complex dielectric permittivity and complex magnetic permeability measurements of absorbing materials /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2000.
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Thesis (Ph.D.)--Tufts University, 2000.<br>Adviser: Mohammed Nurul Afsar. Submitted to the Dept. of Electrical Engineering. Includes bibliographical references (leaves 183-192). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Boltaev, A. P., F. A. Pudonin, and I. A. Sherstnev. "Electrical and Dielectric Properties of Nanoisland Systems Below Percolation Threshold." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34818.
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Electric and dielectric properties of nanoisland metal films were studied in this work. Permittivity of
these films was determined from the analysis of the dependences of the susceptance of the films. It is found
that the effective permittivity of the researched structures has abnormally high positive value (107-108). The
temperature dependence of the permittivity of the films practically does not differ from the temperature
dependence of the conductivity of these films. Such behavior of these dependences is possible, if the reasons
for the change of permittivity and conductivity of the films with the temperature are of the same nature. With
the growth of the electric field effective permittivity of the films decreases and the conductivity increases. The
cause behind the high effective permittivity of the films is the island nature of these metal films, and it is
associated with the polarization of the dipoles, formed by couples negatively and positively charged metal
islands.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34818
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Alabaster, C. M. "The Microwave properties of tissue and other lossy dielectrics." Thesis, Cranfield University, 2004. http://hdl.handle.net/1826/251.
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This thesis describes work on the theoretical modelling and experimental measurement
of the complex permittivity of dielectrics. The main focus of research has been into the
characterisation of permittivity of planar and layered samples within the millimetre
wave band. The measurement method is based on the free-space measurement of the
transmission and reflection coefficients of samples. A novel analytical method of
determining the transmission and reflection coefficients as functions of frequency
arising from a generalised structure of planar dielectric layers is also described and
validated. The analytical method is based on signal flow techniques. The measurement
and analytical techniques have been applied in two main areas: firstly, the acquisition of
new data on human skin in the band 57 to 100GHz and secondly, the detection and
location of defects in composite materials for which a band of 90 to 100GHz was used.
Measurements have been made on the complex permittivity of a single sample of
excised human skin fixed in formaldehyde. The experimental results have been
corrected to account for the fixing process in formaldehyde and are projected to body
temperature. This data is, to the best of the author’s knowledge, the first of its kind to be
published. Predicted skin permittivity based on various relaxation models varies widely
and only partially fits the measured data. The experimental results have been used to
determine the parameters of a Cole-Cole function which gives the best fit to the
measured data. The measured skin data has also been used to calculate power deposition
in skin exposed to millimetre wave radiation. This work concludes that a skin surface
temperature rise of only 0.20C results from a thirty second exposure to signals of
100W/m2.
Experimental work with fibreglass composite samples has shown that defects such as
delaminations, voids, matrix cracks and improper cure result in resolvable differences in
the dielectric properties of the samples at 90 – 100GHz. The measurement technique is
particularly sensitive to the detection of cracks and its spatial resolution is 20mm or
better. Whilst confirming the general conclusions of previously published work, the
specific findings of this study are novel.
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Jenkins, Sharon. "Measurements of the complex permittivity of dielectric reference liquids and human tissues." Thesis, University of Bristol, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241174.
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Alabaster, Clive M. "The microwave properties of tissue and other lossy dielectrics." Thesis, Cranfield University, 2004. http://dspace.lib.cranfield.ac.uk/handle/1826/251.
Full textAbstract:
This thesis describes work on the theoretical modelling and experimental measurement of the complex permittivity of dielectrics. The main focus of research has been into the characterisation of permittivity of planar and layered samples within the millimetre wave band. The measurement method is based on the free-space measurement of the transmission and reflection coefficients of samples. A novel analytical method of determining the transmission and reflection coefficients as functions of frequency arising from a generalised structure of planar dielectric layers is also described and validated. The analytical method is based on signal flow techniques. The measurement and analytical techniques have been applied in two main areas: firstly, the acquisition of new data on human skin in the band 57 to 100GHz and secondly, the detection and location of defects in composite materials for which a band of 90 to 100GHz was used. Measurements have been made on the complex permittivity of a single sample of excised human skin fixed in formaldehyde. The experimental results have been corrected to account for the fixing process in formaldehyde and are projected to body temperature. This data is, to the best of the author’s knowledge, the first of its kind to be published. Predicted skin permittivity based on various relaxation models varies widely and only partially fits the measured data. The experimental results have been used to determine the parameters of a Cole-Cole function which gives the best fit to the measured data. The measured skin data has also been used to calculate power deposition in skin exposed to millimetre wave radiation. This work concludes that a skin surface temperature rise of only 0.20C results from a thirty second exposure to signals of 100W/m2. Experimental work with fibreglass composite samples has shown that defects such as delaminations, voids, matrix cracks and improper cure result in resolvable differences in the dielectric properties of the samples at 90 – 100GHz. The measurement technique is particularly sensitive to the detection of cracks and its spatial resolution is 20mm or better. Whilst confirming the general conclusions of previously published work, the specific findings of this study are novel.
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Vidal-Dho, Matthias. "Mécanismes de vieillissement liés à la pénétration d’humidité dans les matériaux diélectriques à faible permittivité des interconnexions." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT066.
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La réduction des dimensions des dispositifs micro-électroniques élémentaires, notamment des transistors et des cellules mémoires, a permis au cours des dernières décennies d’augmenter la densité d’éléments intégrés et donc d’obtenir plus de fonctions au sein d’une même puce. Cette réduction des dimensions a notamment nécessité l’introduction de matériaux diélectriques à faible permittivité, particulièrement sensibles à l’humidité.Cette thèse détaille les propriétés électriques de tels matériaux ainsi que les conséquences de leur contamination par l’humidité sur leurs caractéristiques. Le procédé de fabrication des interconnexions à base de cuivre et de matériau à faible permittivité est détaillé puis, le matériau à faible permittivité utilisé dans les interconnexions avancées, appelé SiOC :H, est caractérisé afin d’en déterminer les principales propriétés chimiques et structurelles, nécessaires à la compréhension des phénomènes physiques menant à la dégradation des performances électriques de ces matériaux. Ensuite, une importante étape de conception et de fabrication de structures de caractérisation permettant l’étude de l’impact de la pénétration d’humidité sur les performances électriques du matériau SiOC :H est détaillée. Enfin, les résultats de caractérisations électriques effectuées sur ces structures sont présentés, permettant une compréhension des processus physiques menant à la dégradation des performances du matériau SIOC :H utilisé dans l’industrie microélectronique<br>Over the past decades, scaling of microelectronic chips, in particular transistors and memory cells, has allowed to increase substantially both the density of integrated circuit and integrate the umber of functions offered. Such scaling required the introduction oflow permittivity dielectrics, which are particularly sensitive to moisture pollution. This thesis details the dielectrics main properties and the consequences of moisture ingress insuch low-permittivity dielectrics, also referred as SiOC :H dielectrics. The fabrication of low-κ/copper-based interconnects is detailed. Then, the SiOC :H dielectric material is characterised to determine its chemical and molecular structure in order to understand underlying physical phenomenon leading to the material electrical performances degradation. Then, the conception and fabrication of electrical test structures required to evaluate the impact of moisture on the electrical properties and performances of integrated SiOC :H dielectric material is presented. Finally, the results of electrical characterisations carried out on these structures provide a better understanding of physical phenomenon leading to electrical performance degradation of SiOC :H dielectric material used in the semiconductor industry
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Guihard, Vincent. "Homogénéisation de grandeurs électromagnétiques dans les milieux cimentaires pour le calcul de teneur en eau." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30165/document.
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La quantité et la distribution de l'eau interstitielle dans l'espace poral des milieux cimentaires sont des marqueurs fondamentaux de la durabilité des structures de Génie Civil en béton. La connaissance de ces grandeurs est également importante pour l'interprétation de certains essais non destructifs mis en œuvre pour évaluer les performances mécaniques des ouvrages ou détecter certains défauts. L'évaluation de la teneur en eau par méthode non-destructive requiert l'utilisation d'une grandeur intermédiaire telle que la permittivité diélectrique. La relation entre cette propriété électromagnétique et la teneur en eau dépend alors de la composition et donc de la formulation du béton. En électromagnétisme, les lois d'homogénéisation permettent de lier la permittivité effective d'un matériau hétérogène avec la permittivité intrinsèque et la fraction volumique de chaque hétérogénéité présente. Afin de pallier le temps important requis pour l'établissement d'une courbe de calibration expérimentale propre à chaque formulation, l'étude présentée propose la mise en place d'une démarche d'homogénéisation de la permittivité pour lier quantité d'eau présente dans un béton et permittivité macroscopique du matériau. Les travaux présentés rapportent la fabrication, la modélisation et l'utilisation de sondes coaxiales ouvertes pour la mesure de la permittivité complexe de matériaux solides et liquides. Le concept d'estimation de la teneur en eau par utilisation de lois d'homogénéisation est validé pour le cas d'un sable partiellement saturé en eau. Au vu des résultats prometteurs obtenus par modélisation analytique, des schémas d'homogénéisation sont combinés lors d'un processus de remontée d'échelle depuis celle des hydrates jusqu'à celle des granulats, en tenant compte de la morphologie de la microstructure. Les propriétés intrinsèques des principaux constituants d'un béton (granulats, hydrates, ciment anhydre) sont alors mesurées par sonde coaxiale et utilisées en données d'entrée du modèle construit. Une bonne cohérence est observée entre parties réelles de la permittivité simulées et mesurées, pour des échantillons de pâtes de ciment, mortiers et bétons. A la différence des lois expérimentales et empiriques, le modèle construit se caractérise par un temps de calcul quasi-instantané et peut être adapté d'une formulation de béton à une autre en fonction du type de ciment utilisé, de la nature et de la quantité de granulats ou encore de la porosité accessible à l'eau du matériau<br>Prediction of delayed behavior in concrete can be significantly improved by monitoring the amount and spatial distribution of water within a concrete structure over time. Water content of cement-based materials can also be required to interpret non-destructive tests such as ultrasonic and radar measurements. Electromagnetic properties of heterogeneous and porous materials, such as dielectric permittivity, are closely related to water content. Measurement of these properties is thus a common non-destructive technique used to assess the moisture content, but a calibration curve is required to link the measured permittivity to the saturation degree. This curve can be determined experimentally, or from empirical models. However, the first approach is tedious and time consuming, while the second one is not adapted to concrete. Hence, this contribution proposes an alternative route, relying on electromagnetic homogenization schemes, to connect the macroscopic permittivity of cement-based materials with the water content of the structure. Therefore, different open-ended coaxial probes were designed, modelled and tested in order to perform complex permittivity measurements of both solids and liquids. The homogenization approach is first validated on unsaturated sand. Then, the permittivity of concrete components (aggregates, hydrates, interstitial liquid, anhydrous cement) was assessed by means of coaxial probe measurements. Finally, a specific combination of analytical homogenization laws taking into account the microstructure's morphology of the material is built. Results show that there is a good correlation between the model and measurements acquired on different cement pastes, mortars and concretes, at different saturation degrees. The model is characterized by a quasi-instantaneous calculation time and can be adapted to different concretes depending on cement type, nature and quantity aggregates or porosity
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Amiet, Andrew. "Free space permittivity and permeability measurements at microwave frequencies." Monash University, Dept. of Electrical and Computer Systems Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9529.
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Liu, Yanhan. "mm Wave Near Field Spot Focus Technique in Free Space Dielectric Properties Evaluation Method." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298023.
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Radomes were invented to protect sensitive antenna systems from the disturbing environment. Estimation of their permittivity is a vital step for their design. This project studies the free- space method to measure the permittivity of radome materials. The free space method has the advantages of non-contacting and free-of-reshaping, which are suitable for sheet-shape samples. In this method, the sample is placed between two antennas, and the permitivity of the material is determined based on the S-parameters between the two antennas. To avoid the influence of energy diffraction at the edges of samples, a near field focus(NFF) antenna is used. NFF antennas have their focal point in the near field. Consequently, the energy diffraction at the edges is reduced if the sample is placed at the focal point of the NFF antenna. The measurement results are processed with the genetic algorithm. This method starts from a group of assumption values of permittivity. An optimal value is obtained after multiple iterations. Compared with the results from a cavity resonant method provided in the datasheet of the materials, the free space setup in this thesis measurement provides an average 2.80% error in permittivity, and an average 34.14% error in loss tangent. Therefore, the genetic algorithm is suitable for this free space setup. The error of this thesis measurement is affected by several factors, such as thickness value error and inaccurate operation.<br>Radom används för att skydda känsliga antennsystem från omgivningen. Det är viktigt att estimera permittiviteten av radom innan de designas. Med korrekt permittivitet kan radomets inverkan på systemet räknas ut. I det här projektet används en fri-rymdsmetod för att mäta permittivitet. Fri-rymdsmetoden har fördelarna av att vara kontaktfri och icke-invasiv, vilket gör den lämplig för permittivitetmätning av materialskivor. Med den här metoden placeras en materialskiva mellan två antenner. Permittiviteten kan beräknas från S-parametrarna mellan antennerna. För att undvika diffraktion från kanten av materialskivan används närfältsfokuserade (NFF) antenner i fri-rymdsmetoden. NFF antenner har en fokalpunkt i närfältet. Kantdiffraktionen minskas om materialskivan placeras i fokalpunkten av NFF antennen. Mätningarna efterbehandlas med en genetisk algoritm (GA). Denna metod gissar värden på permittiviteten. Ett optimalt värde räknas fram iterativt. Jämfört med specificerad permittivitet från tillverkaren skiljer sig fri-rymdsmätningarna i denna avhandling i medeltal 2.8% i realdelen för den relativa permittiviteten och 34.14% i förlusttangent. Felet i mätningen påverkas av flera faktorer, som fel i mätningen av materialskivans tjocklek och fel i mätuppställningen.
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Agrawal, Anshuman. "Multiscale characterisation of NMC 532 hierarchical electrodes in a lithium-ion battery using Broadband Dielectric Spectroscopy." Electronic Thesis or Diss., université Paris-Saclay, 2022. http://www.theses.fr/2022UPASF094.
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La spectroscopie diélectrique large bande (BDS) est utilisée pour étudier les mélanges de différentes compositions afin de caractériser leurs propriétés électriques, principalement la permittivité, et les conductivités effectives correspondantes, et cela sur une large gamme de fréquences (du Hz au GHz). Cela permet d'améliorer la compréhension sur les limitations liées au transport à travers les diverses interfaces dans les électrodes de batteries lithium-ion dont l'architecture est multi-hiérachique. Une plus grande importance est donnée au matériau actif NMC 532 à différents états (sec et humide avec soit un solvant, soit avec un électrolyte correspondant). Une étude distincte sur l'effet du noir de carbone sur les électrodes est également mise en évidence. Cela a permis de mieux comprendre et commenter les mesures globales des spectres BDS des électrodes NMC 532 fabriquées industriellement contenant du noir de carbone, à la fois sec et humide (solvant ou électrolyte)<br>Broadband dielectric spectroscopy (BDS) is used to study mixtures of varying composition, to characterize their electrical properties, namely permittivity, and its corresponding effective conductivity/resistivity over a broad range of frequencies (Hz to GHz regime). This permits a better understanding of transport limitations across the various interfaces of the multi-hierachical lithium-ion battery electrode. Emphasis is first placed on studying the active material NMC 532 at different states (dry and wet with either a solvent or with a corresponding electrolyte). A separate study on the effect of carbon black on electrodes is also evidenced. This allowed to better understand and comment on the global BDS spectra measurements of industrially made NMC 532 electrodes containing carbon black, both dry and wet (solvent or electrolyte)
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Kemppinen, E. (Esa). "Determination of the permittivity of some dielectrics in the microwave and millimetre wave region." Doctoral thesis, University of Oulu, 1999. http://urn.fi/urn:isbn:9514251954.
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Abstract
In the first part of this study, determination of the dielectric properties of the low loss microwave ceramic material, barium nonatitanate (Ba2Ti9O20), around 1 GHz is discussed. The structures under test were coaxial resonators, the cores of which were made of barium nonatitanate and the metallization was realised by thick film silver. The measured value of the real part of the relative dielectric constant was εr = 37 and that of the loss tangent was tan σ = 0.00014. The change of the resonance frequency of the coaxial resonators with temperature, in the range -20 … +80 C, was 4 ppm/ C. In addition, realisation of compact interdigital and comb-line bandpass filters was demonstrated for the 900 MHz mobile phone band. Besides Ba2Ti9O20, Ba(Sm,Nd)2Ti5O14 ceramic material with a dielectric constant of εr = 78 was also employed in order to improve the miniaturisation. The volume of the smallest filter was 2 cm3 and the weight was 9 g.
In the second part of this study, various measurement methods have been demonstrated to determine the real part of the relative permittivity of FR4 fibreglass circuit board. Test structures were straight asymmetric open-circuited strip lines. It was found that the real part of the relative permittivity decreased slightly with frequency. At 0.72 GHz and 4.5 GHz, εr values of 4.3 and 4.1, respectively, were measured. All the characterisation methods used gave consistent values for εr, and electromagnetic simulators were used to verify the results.
In the third part of this study, the structures under test were microstrip or strip line transmission lines, the S parameters of which were measured by using on-wafer measurement techniques. It was found that the insertion loss of the 10 mm long etched Cu microstrip was slightly less than that of the Ag microstrips which were manufactured by etching and gravure offset printing techniques, respectively. The performance of the Ag microstrips was, however, similar. In addition, a theoretical basis was established for the determination of εr of the dielectric substrate and the attenuation coefficient of the transmission lines under test. The calculations were based on signal flow diagrams. The method was applied to determine the dielectric and loss properties of a commercial, Kyocera, Japan, LTCC (Low Temperature Cofired Ceramic) material up to 50 GHz. The measured value of the real part of the relative permittivity was εr = 5.7, and the loss tangent was approximately tan σ = 0.003.
The essential idea behind the studies reported in this thesis was twofold. First, the studies aimed at characterising dielectric media which find usage in the realisation of UHF, microwave or millimetre wave circuits. Second, the studies aimed to obtain data of immediate value in practical design work. For this reason, the structures under test were transmission lines having extensive usage in practical high frequency circuit design.
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Kim, Ŭn-ji. "Interface and defect study of high permittivity dielectrics on Si and III-V semiconductors /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Kassem, Hussein. "Caractérisation et applications hyperfréquences de matériaux ferroélectriques en couches minces." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13784/document.
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Araujo, Steven. "Evaluation de la compacité des enrobés bitumineux et caractérisation large bande des propriétés diélectriques des roches." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR039/document.
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Le contrôle des chaussées neuves en génie civil est primordial pour assurer sa bonne miseen oeuvre et lui conférer une durée de vie optimale. Dans cet objectif, divers paramètresphysiques nécessitent d'être scrupuleusement calibrés et contrôlés afin d'éviter une dégradation précoce de la chaussée et des problèmes de sécurité pour les conducteurs qui l'empruntent. De plus, les coûts associés à la mise en place et à la maintenance des chaussées sont considérables. Parmi les propriétés qui requièrent une attention particulière, la compacité, qui est indicative de la quantité d'air en volume dans la chaussée, est celle qui nous intéresse dans cette étude. Actuellement, seulement deux méthodes en laboratoire (en Europe) sont considérées comme des méthodes normalisées pour déterminer la compacité. Néanmoins, ces techniques sont destructives et/ou nucléaires ce qui est un frein majeur à leur utilisation. Durant ces deux dernières décennies, de nouvelles techniques électromagnétiques (non nucléaires et non destructives) ont émergé et ont prouvé leur forte utilité dans le domaine de la géophysique et du génie civil et plus particulièrement pour la détermination de la compacité. Cependant, ces nouvelles techniques nécessitent de prendre un certain nombre de précautions pour déterminer la compacité. Tout d'abord, elles permettent de mesurer la permittivité diélectrique du matériau en question. Ainsi pour déterminer la compacité, il est nécessaire d'utiliser des lois de mélange électromagnétiques. L'utilisation de ces modèles requiert une connaissance précise des constituants qui composent la chaussée ainsi que de leurs propriétés (masse volumique et permittivité diélectrique). La première partie de ce travail démontre la pertinence d'utiliser un radar à sauts de fréquences pour déterminer la compacité. L'étude de plusieurs lois de mélange électromagnétiques a été réalisée et les modèles présentant les meilleurs résultats ont été sélectionnés. Cependant, ces techniques font face de nos jours à un problème majeur. En effet, l'utilisation de matériaux recyclés est de plus en plus fréquente pour la construction de nouvelles chaussées ce qui rend la détermination de la compacité encore plus difficile par des méthodes électromagnétiques. Par conséquent, plusieurs méthodologies ont été développées, et sont proposées pour déterminer la compacité d'une nouvelle autoroute qui comporte des matériaux recyclés. La seconde partie de ces travaux de recherche porte sur la caractérisation diélectrique de plusieurs roches qui sont les éléments principaux d'une chaussée. Cette caractérisation est validée de basses à hautes fréquences mais aussi en fonction de la température. Les résultats montrent que à haute fréquence, la permittivité est principalement dépendante de la densité et de la composition chimique de la roche. En revanche, lorsque la fréquence d'investigation diminue et que la température varie, d'autres phénomènes apparaissent et changent dramatiquement le comportement diélectrique de la roche. Il a également été montré que l'eau joue un rôle majeur dans le comportement diélectrique à basse fréquence de la roche. Ces phénomènes se répercutent à "haute fréquence" par de très faibles variations qui pourraient expliquer les déviations obtenues par les méthodes électromagnétiques capacitives qui fonctionnent dans la région du MHz et qui sont également utilisées pour le contrôle de la compacité des chaussées neuves<br>The control of new paved road is primordial to ensure its quality as well as its lifetime. Thus, several physical properties need to be well calibrated and controlled in order to avoid early degradations and safety issues for the drivers. Furthermore, the coast associated to the road building and the road maintenance is significant which makes the implementation of asphalt pavement according to the standard even more important. Among the properties that need attentions, the compactness which is indicative of the air void concentration in the asphalt pavement is the one we are interested in. Currently, only two methods in laboratory (in Europe) are considered as standards to assess the compactness. Nevertheless, these techniques are either nuclear or destructive which is a major hindrance. In the past two decades, new electromagnetic (EM) techniques have emerged and proved their great utility for geophysics or civil engineering applications and more importantly for the compactness assessment. However, these non-destructive and non-nuclear methods require many special precautions for the compactness assessment. First of all, they allow to measure the dielectric permittivity of the investigated material. Then to figure out the compactness, the use of EM mixing models is required. This leads to the accurate knowledge of every components constituting the asphalt pavement and their related properties (density and permittivity). The first main part of this work spotlights the relevance of using a step frequency radar for the compactness assessment. The study of several EM mixing models is performed to select the most appropriate ones. Nowadays, one of the challenges to address for these techniques is that the use of recycled materials is more and more commonly implemented for new roads building. Indeed, as the knowledge of the component properties is required, this makes the compactness assessment even more difficult. As a consequence, several methods have been developed and are proposed to assess the compactness of a new paved highway containing recycled asphalt pavement. The second main part of this research is the dielectric characterization of many rocks which are the main component of the asphalt pavement. This characterization is validated from low to high frequencies and also as a function of the temperature. The results show at high frequency that the permittivity is mainly dependent on the density and the chemical composition of the rock. However, as the frequency decreases and the temperature varies, this is not longer true and additional phenomena appear and drastically change the dielectric behavior of the rock. Also, it has been shown that the water plays a major role on the dielectric behavior at low frequency. This phenomena are reflected partially by small variations at "high frequency" that could explained the deviations obtained for capacitive techniques which work in the MHz region and which are used also for the compactness assessment
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Liu, Qin. "Amélioration des propriétés de conversion électromécanique dans les polymères électrostrictifs." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0022.
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La thèse est consacrée aux matériaux électro-actifs, qui sont développés et conçus pour faire de la conversion entre énergie électrique et énergie mécanique. Avec les nouvelles technologies émergentes de transduction électromécanique, les polymères électro-actifs (EAP) ont gagné une attention considérable. Ils présentent de grandes déformations quand ils sont soumis à un champ électrique. Cependant, ces matériaux présentent de faibles permittivités et exigent pour fonctionner l’application de forts champs électriques. Les recherches entreprises dans la thèse traitent de différentes méthodes ayant pour but d'augmenter la permittivité des polymères et par conséquent d’améliorer les propriétés électromécaniques sous des champs électriques modérés. Les différentes approches consistent à la mise au point de nouveaux matériaux, par la méthode de mélange de polymères ou en utilisant un nouveau type de polymère, et par l'incorporation de nano-charges spéciales dans la matrice polymère. Un mélange de polyuréthane (PU) et PEMG obtenu à partir d'un procédé en solution conduit à des valeurs plus basses de module de Young, mais aussi à de plus faibles permittivités diélectriques. Il est cependant mis en évidence une amélioration des propriétés électromécaniques, par exemple, à le gain à des champs électriques modérés est d’un facteur 2, avec seulement 9% en poids de PEMG. Deux types de Pebax sont testés comme matrice polymère. Des valeurs très élevées de permittivités sont obtenus plus particulièrement pour le Pebax1657 mais liés pour ce matériau à des valeurs élevées de conductivité. En dépit de ces permittivités élevées, seule une légère amélioration de la conversion électromécanique est observée par rapport au polyurethane. Nous nous sommes également intéressés aux nanocomposites de polyuréthane basés sur desnanoparticules d'argent recouvertes de polymère polyvinylpyrrolidone (PVP). Un fin revêtement de polymère sur les nanoparticules d'argent conduit à une meilleure dispersion des charges dans les films de polyuréthane, et des valeurs plus élevées de permittivité. Différentes quantités d'Ag-PVP sont testées jusqu'au seuil de percolation proche de 45% en poids de charges. À partir des mesures par interférométrie laser et du nouveau dispositif de caractérisation croisée, les propriétés électromécaniques optimales sont obtenues pour 20% en poids de Ag-PVP, avecun gain de 2 à 6 par rapport au polyuréthane pur. Afin d'expliquer la différence entre les résultats expérimentaux et attendus, et par conséquent pour parvenir à une meilleure compréhension du comportement électromécanique de ces différents matériaux, certaines hypothèses ont été discutées et testées. Nous avons montré notamment une baisse des permittivités diélectriques sous champs électriques pour les Pebax et les nanocomposites, des problèmes d'absorption d'eau pour les Pebax et une diminution de cristallinité dans le cas des nanocomposites PU-Ag<br>The thesis is devoted to electroactive materials, which are developed and designed to make conversion between the electricity and the mechanical form. With newer emerging electromechanical transduction technologies, electroactive polymers (EAP) have gained a considerable attention. The polymers are competitive in many applications such as actuators, sensors, robotic system and biological mimics since they are cheap, light, easy to process, and they present large electric field-induced strains. However, these materials suffer from the low permittivity and high voltage requirement to drive the actuations. The research undertaken for the thesis intends then to provide different methods in order to enhance the polymer permittivity and consequently the electromechanical activities at moderate electric fields. The different approaches consist on the development of new materials by polymer blend method or by using new kind of polymer, and on the incorporation of special nano-fillers in the polymer matrix. A blend of polyurethane (PU) and poly [ethylene-co-(methyl acrylate)-co-(glycidyl methacrylate) (PEMG) obtained from a simple solution method leads to lower values of Young modulus but also lower dielectric permittivities. The PU-PEMG blend presents however an improvement of the electromechanical capabilities, for example it is obtained a two fold increase of the strain at moderate fields with only 9%wt of PEMG.Two types of Polyetherblockamide (Pebax) are tested as polymer matrix. Very high values of permittivities are obtained particulary for Pebax1657 but accompanied for this material by high values of conductivity. Despite these high permittivities (more than 200000 for Pebax 1657 and 500 for Pebax 2533 at 0.1 Hz), only a moderate improvement of the electromechanical capability is observed compared to PU. We are also intererested on polyurethane nanocomposites based on silver nanoparticles coverered by PolyVinylPyrrolidone (PVP) polymer. A little polymer coating of the nanosilver leads to a better dispersion into the polyurethane films and higher values of permittivity. Different amounts of Ag-PVP are tested up to the percolation threshold close to 45%wt of fillers. Based on laser interferometer measurements and new cross characterization device, the optimal electromechanical properties are obtained for 20 %wt of Ag-PVP and a gain of 2 to 6 is obtained compared to pure polyurethane. In order to explain the difference between experimental and expected results and consequently to achieve a better understanding of the electromechanical behaviour of these different materials, some hypotheses were discussed and tested. We have shown particularly a drop of dielectric permittivities under electric fields for Pebax and nanocomposites, some problems of water absorption for Pebax and a decrease of crystallinity for the PU-Ag nanocomposites
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Hoq, Md Tanbhir. "Effect of Heat Treatment on Morphology and Dielectric Properties of Polyethylene." Thesis, KTH, Elektroteknisk teori och konstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-156467.
Full textAbstract:
Polyethylene is used extensively as an insulating material in high voltage power cables, it is therefore important to understand the behaviour of polyethylene under different conditions. This is a study regarding the relation of heat treatment and the effect of morphological changes on the dielectric properties of polyethylene samples. Polyethylene granulates were pressed to 1 mm thick circular plaque samples that were heat treated differently. The heat treatments were conducted in a vacuum oven. Heat treated samples were tested for morphological changes with Differential Scanning Calorimetry (DSC) and dielectric property changes were studied with an IDAX 300 Dielectric Spectroscopy Analyser and a TREK 30/30 high voltage amplifier, allowing measurements in the frequency range 0.1 mHz – 100 Hz for voltages up to 30 kV. The experimental results were analysed to understand the co-relation among these parameters. A literature review has been conducted on polyethylene morphology to understand their behaviour under different annealing conditions. A phenomenon that has been noticed during the experiments is that the samples swell with annealing; the thickness change effects the dielectric measurements as well. For this reason an extensive study has been conducted on the effect different temperature and time of heat treatment had on the samples. Heat treatment has effects on the properties of polyethylene samples, but the effect of heat treatment was not only on the morphology but also on the physical dimension of the samples. The samples change their thickness with heat treatment along with their morphology. The effect of morphological changes on the dielectric property of polyethylene samples has not been found to be eminent. This study was focused on relatively thicker samples (1 mm) compared to the existent scientific literature (0.1-0.2 mm). There are very limited research literatures available on the relation of morphology and electrical properties of polyethylene; this work is an attempt to contribute to the knowledge. Also the effect of samples swelling with annealing and its effect on electric measurements is not found in existing literatures. This work will also contribute understanding the effect of sample swelling on measurements.<br>Polyeten används i stor utsträckning som ett isolermaterial i högspänningskablar, och därför är det därför viktigt att förstå beteendet hos polyeten under olika förhållanden. Detta är en studie angående relationen mellan värmebehandling och effekten av morfologiska förändringar av de dielektriska egenskaperna hos polyeten. Polyeten granulat pressades till 1 mm tjocka cirkulära skivor som sedan värmebehandlades olika. Värmebehandlingarna utfördes i en vakuumugn. De värmebehandlade proverna testades för morfologiska förändringar med differentiell svepkalorimetri (DSC) och de dielektriskaegenskaperna studerades med en IDAX 300 Dielektrisk spektroskopi Analysator och en TREK 30/30 högspänningsförstärkare, vilken tillåter mätningar i frekvensområdet 0,1 mHz - 100 Hz för spänningar upp till 30 kV. De experimentella resultaten analyserades för att förstå relationen mellan dessa parametrar. En litteratur har utförts på polyeten morfologi för att förstå deras beteende under olika anlöpningsförhållanden. Ett fenomen som har uppmärksammats under experimenten är att proverna sväller med anlöpningenÄven tjockleken påverkar de dielektriska mätningar. Av denna anledning utfördes en omfattande studie av effekten av olika temperatur och tid för värmebehandling hade på proverna. Värmebehandling har effekter på egenskaperna för polyetenprover, men effekten av värmebehandlingen var inte bara på morfologin, utan också på den fysiska dimensionen av proverna. Effekten av morfologiska förändringar på den dielektriska egenskapen hos polyetenprover har inte befunnits vara framstående. Denna studie var inriktad på relativt tjockare prover (1 mm) jämfört med den existerande vetenskapliga litteraturen (0,1-0,2 mm). Det finns mycket lite litteratur kring relationen mellan morfologi och elektriska egenskaper hos polyeten; detta arbete är ett försök att bidra till kunskapen. Även effekten av provernas svällande efter anlöpning och dess effekt på dielektriska mätningar finns befintliga litteraturen.
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Gasi, Jasmin. "Design, Fabrication and Validation of High-permittivity Low-loss Microwave Material for Biomedical Sensor." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-364035.
Full textAbstract:
Abstract The purpose of this task is to synthesize a dielectric substrate material through a sintering process, which can be used for non-invasive physiological sensor development. Low loss, high dielectric constant ceramic material is used. Sintering process is employed to ensure stable structure and homogeneous dielectric properties of the substrate. Samples were prepared with TiO2 and in combination with CuO and Al2O3. All samples were measured and validated in 500 MHz to 20 GHz frequency range. Characterization measurements were performed with a Vector Network Analyzer, FieldFox N9918A, and connected to Keysight, open ended coaxial probe and performance probe. Reflection based measurement method was used due to its simplicity, speed and requirement of wideband data. The dielectric measurement results of developed samples show non-frequency dispersive behaviour, high dielectric constant and data was also selected at 2.45 GHz in aligned to the industrial, scientific and medical band. The resulting measurements show the highest dielectric constant of 16.6 at 2.45 GHz with a very low loss behaviour.<br>Målet är att syntetisera ett material, genom sintringsprocess, som kan användas som ett dielektriskt substrat för utveckling av sensorer. Det dielektriska materialet har keramisk materialstruktur och innehar högt dielektricitetskonstant med låga dielektriska materialförluster. Denna uppgift kräver att dielektriska materialet ska vara stabilt och inneha isotropiska egenskaper efter att genomgått sintringsprocess. Proverna förberedes med TiO2 och även i kombination med TiO2 tillsammans med CuO och Al2O3. Proverna mäts i frekvensområdet 500 MHz till 20 GHz. Mätningarna utförs med Vector Network Analyzer, FieldFox N9918A från Keysight. Resultat som visas och jämförs i arbetet är tagna vid 2.45 GHz eftersom det används och är standardiserat för medicinskt frekvensband. Högsta uppmätta dielektricitetskonstant har värdet av 16,6. Resultaten visar även låga förluster i dielektrikumet.
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Dong, Wen. "Defect Engineering in Controlling the Dielectric Behaviour of Rutile Titanium Dioxide." Phd thesis, Canberra, ACT : The Australian National University, 2017. http://hdl.handle.net/1885/128472.
Full textAbstract:
Defects have gained increasing attention for their capability in
tailoring the properties and/or exploring new functionalities in
oxide materials. For instance, the colossal permittivity (CP,
>103) was successfully achieved by introducing the acceptor/donor
co-doping in rutile TiO2. The resultant dielectric properties can
be either affected by the defect-induced polarisation or totally
dominated by the defects. The defect configurations and its
related dielectric properties vary with the different properties
of dopant ions, e.g. ionic size, electronegativity, valence
state, and so on. More interestingly, the different dopant ions
affect their nearby environment differently in structurally
strong correlated solid-state system, which may lead to special
defect complexes. The research on the dielectric properties of
defect-engineered rutile TiO2 is still at early stage and more
work need to be done in this field for comprehensive
understanding the defect chemistry and dielectric polarization
behaviours. This dissertation, therefore, aims to use defect
engineering to control the dielectric behaviour of rutile TiO2.
Stimulated by the excellent CP behaviour achieved in In+Nb
co-doped rutile TiO2, investigation was carried out on the CP
behaviour of Ga and Nb co-doped rutile TiO2 i.e.
Ga0.5xNb0.5xTi1-xO2 (x = 0.1%, 0.5%, 5%, 10%), where Ga3+ is from
the same group as In3+ but with a much smaller ionic radius.
Colossal permittivity up to 104 ~ 105 with an acceptably low
dielectric loss (tan δ = 0.05 ~ 0.1) over broad
frequency/temperature ranges is obtained at x = 0.5% after
systematic synthesis optimizations. Systematic structural, defect
and dielectric characterizations suggest that the CP in this
system is not dominated by the EPDD. Instead, multiple
polarisation mechanisms including defect dipoles, polaron-like
electron hopping/transport and a surface barrier layer capacitor
effect together make contributions to the CP behaviour observed
in this new material. This work provides a comprehensive guide
for the design of new CP materials by considering the choice of
the acceptor dopant.
CP materials have many important applications in electronics but
their development has generally been obscured due to the
difficulty in achieving a relatively low dielectric loss. A new
ionic co-doping material system, i.e. In+Ta co-doped TiO2 with
nominal compositions In0.5xTa0.5xTi1-xO2 (x = 0.5%, 5%, and 10%),
was also systematically investigated. This system manifests high
dielectric permittivity and low dielectric loss based on the
electron-pinned defect-dipole. The dielectric loss can be reduced
down to e.g. 0.002 at 1k Hz, giving high performance, less
temperature-independent dielectric property i.e. εr >104
meanwhile tan δ <0.02 in a broad temperature range of 50-400 K.
Density functional theory computation coupled with the defect
analysis uncover electron-pinned defect-dipoles (EPDDs), in the
formation of highly stable triangle-diamond and/or
triangle-linear dopant defect clusters with well-defined relative
positions for Ti reduction, are also presented in the host
material for the CP observed. Such a high-performance dielectric
property would thus help for practical applications and discovery
of promising new materials of this type.
Furthermore, synthesis of bivalent acceptor and pentavalent donor
co-doped rutile TiO2 was carried out to further understand the
EPDDs. A new EPDD in rutile TiO2 was made by co-doping Mg and Ta
with nominal composition Mgx/3Ta2x/3Ti1-xO2 (x = 0.5%, and 5%),
which was characterized to exhibit colossal permittivity (>7000)
as well as ultralow dielectric loss (e.g. 0.002 at 1 kHz) over a
broad frequency/temperature range after optimized process
conditions at x = 0.5%. Both experimental and theoretical
evidences indicate such a colossal permittivity and low
dielectric loss originate from the intragrain polarisation that
links to the electron pinned defect clusters with a specific
configuration, which differs from the defect cluster previously
reported in tri-/pent-valent ion co-doped rutile TiO2. This work
not only extends the research on colossal permittivity to
bi-/penta-valent ion co-doped rutile TiO2, but also for the first
time shows a likely defect cluster model existed in this system.
These results further benefit the development of colossal
permittivity materials and advance the defect chemistry in
solids.
With the success in synthesizing heavily Al+Ta co-substituted
rutile TiO2 structure with nominal composition
Al0.5xTa0.5xTi1-xO2 (x up to 50%), the dielectric properties of
this type materials were systematically investigated. Structural
characterizations and Raman spectra suggest that the materials
maintain rutile TiO2 phase even for x up to 50% and there is
signature of disorder. Defect analysis and dielectric
characterisations suggest the significantly low ratio of
Ti3+/Ta5+ as well as magnitude of permittivity (800~3000) in this
new system, both of which are much smaller than that of the
systems previously described or reported. Interestingly and
surprisingly, the permittivity increases as x increases up to 20%
and decreases after over 20% followed by exponential decrease of
relaxation frequency as well as significant increase of the
thermal activation temperature for defect dipole relaxation (e.g.
the thermal activation energy increases from 33.4 meV to 131.4
meV when x increases from 5% up to 50%). The system present a
typical dipole-glass character especially when x increases over
20%.
This dissertation also reports for the first time, by using
defect engineering, the linear polarisation behaviour of binary
oxide, e.g. rutile TiO2 can be changed to a nonlinear one at room
temperature. With slightly doping acceptor Mg into rutile TiO2, a
combination of electrical measurements and theoretical
calculations suggest that Mg-oxygen vacancy defect dipole can
facilitate certain neighboring Ti4+ with large move-off-center
ability, offering the doped rutile TiO2 an unexpected role as a
new family of room temperature nonlinear dielectrics. More
importantly, a poling induced internal electric field abnormally
varies with the direction of poling electric field can be
observable, which is quite different from that observed in
ferroelectrics and relaxor ferroelectrics. Despite its potential
novel applications in electronic and energy related areas, this
research provides a newly/fundamentally important picture about
the role of defects and its interaction with crystal
environment.
36
Naider, Jan. "Elektrické vlastnosti alternativních kapalin pro elektrotechniku." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221088.
Full text
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Smith, Joshua Dee. "Verifying Molecular Dynamics Using Dielectric Spectroscopy." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4221.
Full textAbstract:
The electrical properties of proteins in solution are important for their structure and function. Computational biophysics studies of proteins need accurate parameters to ensure that numerical simulations match physical reality. Past work in this eld has compared the electrical properties of proteins obtained from dielectric spectroscopy to numerical simulations of proteins in water with adjustment of pKa values to try to capture the inevitable changes in electrical conformation that will occur in a complex structure such as a folded protein. However, fundamental veri cation of the charge parameters of the amino acid building blocks in common molecular dynamics software packages with electrical experiments needs to be performed to have increased con dence in the results from numerical simulations. The aim of this thesis is to start from a fundamental building block, the single amino acid alanine, and to compare numerical simulations of this amino acid in water using parameters from commonly used charge structures in CHARMM, GROMOS, and OPLS, with electrical parameters obtained from dielectric spectroscopy experiments in the GHz range. To this end, multiple molecular dynamics simulations were performed to accurately determine how these different charge structures yield different dielectric increments. Additionally, a commercial RF dielectric measurement probe was modi ed to perform measurements on solutions containing alanine at different concentrations. Using regression, the dielectric increment of alanine is readily determined and compared with the numerical simulations. The results indicate that the CHARMM and OPLS parameters seem to adequately capture the charge con guration of alanine in solution, while the GROMOS parameters produce a dielectric increment but do not seem to adequately capture the charge con guration of alanine in solution. These studies lay the foundation for future studies of additional amino acids in solution as well as a stepping stone for larger simulations of the electrical properties of fully solvated proteins in solution.
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Seligman, Jeffrey M. "Spectral Characterization of Dielectric Materials Using Terahertz Measurement Systems." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/566237.
Full textAbstract:
The performance of modern high frequency components and electronic systems are often limited by the properties of the materials from which they are made. Over the past decade, there has been an increased emphasis on the development of new, high performance dielectrics for use in high frequency systems. The development of these materials requires novel broadband characterization, instrumentation, and extraction techniques, from which models can be formulated. For this project several types of dielectric sheets were characterized at terahertz (THz) frequencies using quasi-optical (free-space) techniques. These measurement systems included a Fourier Transform Spectrometer (FTS, scalar), a Time Domain Spectrometer (TDS, vector), a Scalar Network Analyzer (SNA), and a THz Vector Network Analyzer (VNA). Using these instruments the THz spectral characteristics of dielectric samples were obtained. Polarization based anisotropy was observed in many of the materials measured using vector systems. The TDS was the most informative and flexible instrument for dielectric characterization at THz frequencies. To our knowledge, this is the first such comprehensive study to be performed. Anisotropy effects within materials that do not come into play at microwave frequencies (e.g. ~10 GHz) were found, in many cases, to increase measured losses at THz frequencies by up to an order of magnitude. The frequency dependent properties obtained during the course of this study included loss tangent, permittivity (index of refraction), and dielectric constant. The results were largely consistent between all the different systems and correlated closely to manufacturer specifications over a wide frequency range (325 GHz-1.5 THz). Anisotropic behavior was observed for some of the materials. Non-destructive evaluation and testing (NDE/NDT) techniques were used throughout. A precision test fixture was developed to accomplish these measurements. Time delay, insertion loss, and S-parameters were measured directly, from which loss tangent, index of refraction, and permittivity was extracted. The test materials were low-loss dielectric slabs ranging in thickness from 1-60 mils. The substrate sheets were PTFE, fiberglass, and epoxy-ceramic composite substrates. The other group was polyethylene plastic sheets (LDPE/HDPE/UMHW) and 3D printer Photopolymers. The results were verified by using several online THz spectral databases and compared to manufacturer data sheets. Permittivity and loss of some of the test samples varied as a function of polarization angle. 0 - 90 degrees of rotation were tested (i.e., H-V, and 45 degrees polarization). Inter-molecular scattering in the composite materials raised the loss considerably. This effect was verified. Standard, well documented, material types were selected for the project for best comparison. These techniques can also be applied to analyze newer substances such as nanodielectrics.
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Berndt, Andreas. "Synthese und Charakterisierung lösungsprozessierbarer und vernetzbarer Methacrylat-Copolymere für den Einsatz als Dielektrika in der organischen Elektronik." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-211995.
Full textAbstract:
Der Einsatz von organischen Materialien, insbesondere von Polymeren, hat zahlreiche Vorteile gegenüber dem Einsatz klassischer Materialien in der Mikroelektronik. Zu diesen zählen Flexibilität, geringes Gewicht, Verarbeitbarkeit durch Verfahren aus Lösung bei Raumtemperatur ohne Notwendigkeit vakuumbasierter Prozesse zur Abscheidung und vieles mehr. Dies ermöglicht eine energie- und kosteneffiziente Herstellung elektronischer Bauteile wie organische Feldeffekttransistoren (OFETs) oder Leuchtdioden (OLEDs), welche durch Prozesse wie dem Rolle-zu-Rolle-Druckverfahren nicht länger auf kleine Flächen begrenzt sind.
Zur Herstellung polymerbasierter OFETs mit optimiertem Eigenschaftsprofil sind neben innovativen Halbleitern vor allem auch neue Dielektrika mit verbesserten elektrischen Eigenschaften erforderlich, zu deren Entwicklung die vorliegende Arbeit beitragen sollte. Das häufig verwendete Polymethylmethacrylat ist für den Einsatz als Gate-Dielektrikum für die organische und gedruckte Elektronik nur bedingt geeignet. Es zeigt einige Nachteile wie eine mangelnde Stabilität gegenüber bestimmten organischen Lösungsmitteln, was zu Quellung oder Anlösen des Dielektrikums während des Aufbringens weiterer Schichten führen kann. Durch Copolymerisation von Methylmethacrylat mit funktionalisierten Comonomeren sollten die Probleme gelöst und optimierte Methacrylat-Copolymere entwickelt werden.
Die Copolymere wurden über freie radikalische sowie RAFT-Polymerisation synthetisiert. Allen gemeinsam sind vernetzbare Comonomere, um die Lösungsmittelstabilität zu verbessern und somit die Durchbruchfeldstärke des Dielektrikums zu erhöhen. Als Vernetzer wurden 4-Benzoylphenylmethacrylat (BPMA) oder Propargylmethacrylat (PgMA) gewählt. BPMA ist UV-vernetzbar, Copolymere mit PgMA können in Gegenwart von mehrfunktionalen Aziden wie 1,3,5-Tris(azidomethyl)benzen (TAMB) durch Click-Reaktion thermisch vernetzt werden. Ein weiterer Aspekt ist die Erhöhung der relativen Permittivität des Dielektrikums zur Steigerung der Kapazität der dielektrischen Schicht, wodurch unter anderem die Betriebsspannung des Transistors reduziert werden kann. Dieses Ziel sollte durch Komposite mit BaTiO3-Nanopartikeln erreicht werden.
Zusätzlich zur Steigerung der Permittivität kann dies durch Verringerung der Filmdicke realisiert werden, was jedoch vermehrt zu Leckströmen führen könnte. Neben den dielektrischen Materialeigenschaften spielt vor allem auch die Grenzfläche zwischen Dielektrikum und Halbleiter eine wesentliche Rolle. Um die Interaktionen an dieser zu verbessern, wurden Comonomere mit selbstorganisierenden Seitenketten in die Polymerstruktur eingebracht. Die Kombination dieser Dielektrika mit chemisch angepassten Halbleitern mit vergleichbaren Seitenkettenfunktionalitäten soll dazu führen, dass die beiden Komponenten durch die Seitenketten verstärkt miteinander wechselwirken.
Monomersynthesen sowie anschließende Copolymerisationen waren in hohen Ausbeuten und ausreichenden Molmassen bezüglich der Copolymere erfolgreich. Die strahleninduzierte Vernetzung konnte durch systematische Untersuchungen optimiert und die thermische Vernetzung bei moderaten Temperaturen nachgewiesen werden. Die Vernetzbarkeit von Copolymeren mit selbstorganisierenden Seitenketten erwies sich als gehindert. Hierfür wurde ein Vorschlag zur Erhöhung der Flexibilität der Vernetzerseitenkette unterbreitet. Für die Copolymere P(MMA/BPMA) und P(MMA/PgMA) konnten die Durchbruchfeldstärken in Folge der Vernetzung von < 0.3 MV/cm für PMMA auf bis zu mehr als 5 MV/cm gesteigert werden. BaTiO3-Nanopartikel konnten durch geeignete Methoden erfolgreich synthetisiert werden.
Durch Variation der Reaktionsbedingungen war eine gezielte Steuerung der Primärpartikelgröße möglich. So wurden Partikel der Größe < 10 nm, 26 nm und 55 nm realisiert. Die Dispersion der Partikel in organischen Lösungsmitteln sowie in der Polymermatrix war stark abhängig von der Größe der Primärartikel, der Oberflächenmodifikation sowie der Neigung zur Agglomeration. Modifizierte Partikel mit einem Durchmesser < 10 nm konnten sehr gut in Lösungsmitteln wie auch in der Polymermatrix dispergiert werden (Abbildung 2). Eine Steigerung der relativen Permittivität der Nanokomposite blieb jedoch aufgrund der zu geringen Größe der Primärpartikel aus. Darüber hinaus wurden deutlich schlechtere Durchbruchfeldstärken beobachtet.
Copolymere mit der Fähigkeit zur Selbstorganisation sollten durch zwei Konzepte realisiert werden. Im ersten System führte die Polymerisation von x-[4-(4´-Cyanophenyl)phenoxy]alkylmethacrylaten mit Spacerlängen von x = 6 und x = 8 nur in Homopolymeren zu ausgeprägter Selbstorganisation. Copolymere mit 50 mol% waren weitgehend isotrop und wiesen zudem ungenügende dielektrische Eigenschaften auf. Das zweite System basiert auf semifluorierten Methacrylat-Copolymeren mit H10F10-Seitenketten (10 CH2- und 10 CF2-Gruppen). Diese zeigten schon ab einem Gehalt von circa 35 mol% gute Selbstorganisation und bildeten ein geordnetes alternierendes Schichtsystem aus Haupt- und Seitenketten im Bulk und in dünnen Filmen. Die dielektrischen Eigenschaften können mit denen bekannter fluorierter Polymerdielektrika wie CYTOP konkurrieren. Damit stehen die semifluorierten Copolymere zukunftsorientiert zur Kombination mit Halbleitern, welche die gleichen Seitenkettenfunktionalitäten tragen, bereit, um so durch starke Interaktionen zwischen Dielektrikum und Halbleiter die Grenzfläche zu optimieren.
Mit thermisch vernetztem P(MMA/PgMA) konnten OFETs mit den Halbleitern Pentacen bzw. C60 erfolgreich hergestellt und vermessen werden. Beide Transistoren liefern gute und mit Literaturwerten vergleichbare Kenngrößen. Die Ladungsträgermobilitäten und Ion/Ioff-Verhältnisse betragen 0.3 cm²/Vs und 6.0x10^5 im Pentacen-basierten Transistor beziehungsweise 1.3 cm²/Vs und 4.4x10^5 im OFET mit dem Halbleiter C60.
Damit konnte in dieser Arbeit die Steigerung der Durchbruchfeldstärke durch geeignete Vernetzung der Copolymere realisiert werden. Die thermische Vernetzung fand bei deutlich geringeren Temperaturen als zahlreiche in der Literatur beschriebene Reaktionen statt. Die Synthese und Modifizierung von BaTiO3-Nanopartikeln und auch die Bildung entsprechender PMMA-BaTiO3-Nanokomposite war erfolgreich, führte jedoch nicht wie erwartet zu einer Steigerung der relativen Permittivität der Dielektrika-Schichten.
Vernetzbare und selbstorganisierende semifluorierte Methacrylat-Copolymere konnten polymerisiert und charakterisiert werden und stehen als innovative dielektrische Materialien für Untersuchungen in OFETs zur Verfügung. Das Copolymer P(MMA/PgMA) wurde zielführend in organischen Feldeffekttransistoren eingesetzt und führte zu guten elektrischen Eigenschaften der Bauteile.
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Lodén, Jennie. "Radar Transparency and Paint Compatibility." Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-212982.
Full textAbstract:
This study focus on trying to understand what factors regarding bumper materials and coatings affect the radar transparency at 77 GHz. Dielectric spectroscopy was done at 25 unique samples, consisting of various plastic substrates, primers, basecoats and clearcoats with the Free-spaced method in the 60-90 GHz region. The plastic substrate consisted of Polypropylene-blend with different fillers such as talc, carbon black and metal flakes. The basecoats analyzed were 2 solid factory coatings (one black and one white), 5 factory coating containing different effect pigments such as metal flakes, Xiralic, and Mica, 1 factory PVD coating and 2 aftermarket basecoats. All samples were provided by a Volvo Cars’ supplier, however, some samples were repainted with the aftermarket coatings. The complex permittivites were calculated for each PP-blend and coating from the curve fitting of the measured S-parameters from the Free-spaced method. Material analysis such as thickness measurements of the plastic substrate and coatings, ATR-FTIR spectroscopy, TGA and DSC were done at all plastic substrates. The plastic substrates and the coating were also observed in optical microscope and in SEM. The calculated permittivities were compared with the results from the material analysis and correlations between increased metal content in the basecoat and higher real permittivity were found. Some relationship between the size of the metal flakes and the radar transparency could also be observed. Further, correlations between higher real permittivity with higher concentration of talc and carbon black were detected. MATLAB was used to provide an example for optimization of the plastic thickness for a given basecoat in order to have minimal reflection at 77 GHz.
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Atarah, Samuel. "Experimental investigation of carrier mobility degradation in metal oxide semiconductor field effect transistors of high permittivity gate dielectrics." Thesis, De Montfort University, 2006. http://hdl.handle.net/2086/13204.
Full textAbstract:
Scaling of electronic devices is driven, from the consumption side, by the need for compact electrical products, increase in device speed and from the production side, by lowering of production cost. However, aggressive scaling gives rise, among others, to high gate tunnelling currents in contemporary silicon dioxide (SiO2) based Metal-Oxide- Field Effect Transistors (MOSFETs). SiO2 is therefore expected to be replaced in future technologies with alternative dielectrics. Several dielectrics with high dielectric constants (high-κ) are being studied as candidates for integration into transistors. It is desirable that any dielectric that replaces SiO2 contains as much as possible the electrical properties for which the SiO2 dielectric has been so important in FET technology: high band-offset, low oxide/interface state density and consequently high mobility. However, mobility in transistors with high-κ gate dielectrics is generally lowered compared to their SiO2–based counterparts. Several factors are known to cause mobility degradation in SiO2-based MOSFETs. These include effect of charge scattering centres on the dielectric/Si interface as well as substrate ionized impurities. Also contributing to mobility reduction is phonon scattering, that is, vibration of lattice bonds. In this thesis, samples of high-κ based MOSFETs and MOS capacitors (MOS-C) were experimentally studied for causes of mobility reduction. The study was focused on devices of hafnium silicate gate dielectrics. The nature of interface traps in Hf silicate was completely characterized by determining the interface state density as well as the trap capture cross section. The interface state density levels in the devices was experimentally determined by use of two high resolution techniques: the ac conductance and the charge pumping techniques. Both methods gave similar values of mean interface state density, indicating the accuracy of the experimentally determined mean interface density in the Hf silicate dielectric. Additionally, the ac conductance method established the detailed interface trap distribution profile in Si energy band gap for the Hf silicate dielectric. This study represents the first in depth study of the nature of interface state density in Hf silicate gate dielectrics for CMOS applications x Coulomb limited mobility in Hf silicate based FETs was experimentally quantified by considering the mobility reduction relative to universal mobility values. Using a full quantum mechanical model the mobility limited by Coulomb scattering was calculated considering the physical parameters of the device under study. The calculated and experimentally determined Coulomb limited mobility components were compared using trap charge as the only parameter in the calculation. It was found that a higher trap charge density than determined experimentally was required to match the calculated and measured Coulomb limited mobility in Hf silicate based FETs. The disparity between the theory and the experiment implies that there are other Coulomb scatterers in addition to the interface trap charge. There has been little or no experimental study on the effect of phonons on mobility of Hf silicate based devices, especially, in the ultra thin regime since the first report of successful integration of Hf silicate as a gate dielectric of FETs (A.L.P. Rotondaro, 2002). In this thesis is presented, for the first time, experimental results of phonon-limited mobility in Hf silicate-based FETs by examining the mobility as a function of temperature over a wide range of temperatures below 300 K. Other high-κ based transistors were also studied in order to put the temperature dependence in Hf silicate in perspective. A new model for phonon limited mobility dependence on temperature has been proposed and applied on the experimentally measured data. Compared to the existing model, the new model was found to describe the temperature dependence very well over the entire temperature range studied and over a wide region in the mid-high effective electric field. As stated, scaling introduces difficulties in device characterization. Mobility reduction can not be described by the correct quantity if its evaluation introduces inaccuracies. As such several mobility extraction methods were applied on ultra thin high-κ based FETs to determine the carrier mobility. A comparison of the results (the determined mobility) from all methods showed the disadvantages of each method when applied on high-κ based devices in the ultra thin regime. It was found that the split-CV technique is most xi suitable for (research purposes) studying ultra thin devices – and is thus the preferred method applied throughout the thesis wherever mobility evaluation was required. In all Hf-based dielectrics as this study reveals, have low phonon limited mobility component. Its interface state density was determined to be fairly low compared to the reported values for other high-κ dielectrics and with process refinement, interface charge could be further reduced. Together with a high barrier height, it has already been shown to have a very low gate tunnelling current. All these characteristics make Hf silicate a good alternative to SiO2 in future scaled CMOS applications.
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Lazraq, Byström Joseph. "Characterization of Magneto-Dielectric Materials for Microwave Devices." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-419515.
Full textAbstract:
There is an increasing interest in using new composite materials in microwave devices, to reduce size and weight while maintaining similar performances. A new promising material group is named magneto-dielectric materials, which have the permittivity and permeability values both larger than one. Compared to the commercially used dielectric materials, magneto-dielectric materials can achieve a larger miniaturization factor with the equivalent properties as dielectric materials. There is a very limited availability of commercial magneto-dielectric materials. A recent addition was from Rogers Corporation with MAGTREX 555, [1], that is available as a printed circuit board laminate. The material is limited to 500 MHz operational frequency due to its increased magnetic and dielectric losses. In this thesis the purpose is to understand the loss mechanisms, characterize and understand the state-of-the-art magneto-dielectric materials at microwaves, and to produce a magneto-dielectric material in the lab to understand the material better. A new material was developed with magneto-dielectric properties. The material was based on a polymer base of polystyrene that serves as a dielectric material and doped with nickel nanoparticles that produce the magnetic properties. The contents of the nanoparticles in the mix is a design variable. Nickel-polystyrene samples with different nickel contents of 0%, 2.3% and 4.5%, were produced in the lab and measured in-house to understand the loss mechanism and RF performance.
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Mellor, Brett Lee. "Liquid Dielectric Spectroscopy and Protein Simulation." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3661.
Full textAbstract:
Protein electrical properties have been studied using dielectric relaxation measurements throughout the past century. These measurements have advanced both the theory and practice of liquid dielectric spectroscopy and have contributed to understanding of protein structure and function. In this dissertation, the relationship between permittivity measurements and underlying molecular mechanisms is explored. Also presented is a method to take molecular structures from the Protein Data Bank and subsequently estimate the charge distribution and dielectric relaxation properties of the proteins in solution. This process enables screening of target compounds for analysis by dielectric spectroscopy as well as better interpretation of protein relaxation data. For charge estimation, the shifted pKa values for amino acid residues are calculated using Poisson-Boltzmann solutions of the protein electrostatics over varying pH conditions. The estimated internal permittivity and estimated dipole moments through shifted pKa values are then calculated. Molecular dynamics simulations are additionally used to refine and approximate the solution-state conformation of the proteins. These calculations and simulations are verified with laboratory experiments over a large pH and frequency range (40 Hz to 110 MHz). The measurement apparatus is improved over previous designs by controlling temperature and limiting the electrode polarization effect through electrode surface preparation and adjustment of the cell's physical dimensions. The techniques developed in this dissertation can be used to analyze a wide variety of molecular phenomena experimentally and computationally, as demonstrated through various interactions amongst avidin, biotin, biotin-labeled and unlabeled bovine serum albumin, beta-lactoglobulin, and hen-lysozyme.
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Martínez, García Julio César. "Dynamics in orientationally disordered solids." Doctoral thesis, Universitat Politècnica de Catalunya, 2011. http://hdl.handle.net/10803/35856.
Full textAbstract:
The key features of dynamics of ultraslowing glass forming systems are their universality in diversity. Its
origin is recognized as one of the greatest challenges of condensed matter physics and materials
engineering in the XXI century. Similar phenomena are observed on approaching the glass transition in
low molecular weight supercooled liquids, polymers, colloidal fluids as well as in solids, for instance in
orientationally disordered crystals, spin glass-like magnetic, vortex glasses. Pre-vitreous dynamics is also
proposed as a general reference for the category of complex liquids/soft matter systems.
The upsurge of the primary relaxation time or related dynamical properties is the basic physical
phenomena of the still mysterious previtreous behavior. This means a much more pronounced slowing
down than the Arrhenius pattern observed far above the glass transition temperature. Portraying this
behavior constitutes one of key checkpoints for theoretical models developed to unwind the glass
transition puzzle. However, none of the aforementioned features can answer the understanding that
governs the increase of relaxation time in liquids upon cooling.
In this thesis we focus on the above questions studying the dynamics of some materials for which their
molecules can retain a translational order being orientationally disordered between them upon cooling,
which are referred to plastic phases or orientationally disordered (OD) crystalline phases. The work
presented in this thesis potentially extends the knowledge of dynamics of OD phases and orientationally
glasses (OG), a research topic which has gained interest during the last decades.
Through this study, especial attention has been devoted to the phenomenological equations accounting
to the temperature dependence of the mean relaxation time describing the orientational dynamics .The
study was carried out by the use of BDS as well as two complementary experimental techniques. We
show distortion-sensitive and derivative-based empirical analysis of the validity of leading equations for
portraying the previtreous evolution of primary relaxation time. A new method for studying the dynamics of
glass forming systems is introduced and the minimization procedure is validated and discussed.
We present the results divided in two topics, the dynamics of the pure compounds and mixed crystals and
the derivative analysis through different existing models.
In the first topic we focus on the dynamics of the pure compounds and mixed crystals formed between
cycloheptanol and cyclooctanol as well as the a-relaxation dynamics of 1-cyano-adamantane and its
mixtures with 1-chloro-adamantane. The second topic is divided in two groups of models, linearized and
non-linearized models. In the linearized models we show the application of the derivative based,
distortion-sensitive analysis to liquid crystals (LC) and OD phases. We also discuss the results concerning
to the cases of the olygomeric liquid epoxy resin (EPON828), neopentylalcohol and neopentylglycol
mixture, isooctylcyanobiphenyl and propylene carbonate. The possible empirical correlations between one
of the linearized models with the universal pattern for the high frequency wing of the loss curve for primary
relaxation time for LCs and OD phases is also shown.
In the final part we show that the form of the equation recently introduced by Mauro et al. does not allow a
similar straightforward linearization procedure. Unlike the previous models, the involved parameters are
not correlated with the slope and the intercept of a linear function. In order to solve this problem, we have
introduced the concept of the enthalpy space.
The evidences of the existence of crossovers as well as quantitative descriptions are discussed. We show
also a new procedure for detecting the crossover in a very easy way. A new kind of crossovers which
seems to be impossible to be detected by the classical Stickel transformation is presented.<br>La principal característica de la dinámica de sistemas vítreos viscosos, es su universalidad en la
diversidad. Su origen es uno de los mayores desafíos de la física de la materia condensada y de la
ingeniería de materiales en el siglo XXI. La fenomenología típica de las fases vítreas se observan cerca de
la transición vítrea en líquidos subenfriados de bajo peso molecular, polímeros, fluidos coloidales, así
como en los sólidos con fases orientacionalmente desordenadas. La imposibilidad de explicar las causas
del gran aumento del tiempo de relajación al enfriar un líquido, constituye uno de los problemas más
importantes no resueltos en materia condensada. Con el objetivo de dar respuesta a dicha interrogante, se
han propuesto modelos termodinámicos y dinámicos que han resultado inconsistentes.
En esta tesis nos centramos en dicha problemática, estudiando la dinámica orientacional de algunos
materiales que al ser enfriados pueden conservar un orden traslacional mientras que se conserva el
desorden orientacional de las moléculas que los forman. Dichas fases se conocen como fases plásticas u
orientacionalmente desordenadas (OD).
El trabajo presentado en esta tesis amplía el conocimiento de la dinámica de dichas fases, un tema de
investigación cuyo interés ha aumentado durante las últimas décadas.
Se ha dedicado una atención especial a las ecuaciones fenomenológicas que describen la dependencia del
tiempo de relajación con la temperatura. El estudio se ha llevado a cabo mediante el uso de espectroscopía
dieléctrica de banda ancha, así como mediante el uso de técnicas experimentales complementarias. Se ha
introducido un nuevo método para el estudio de la dinámica de los sistemas que dan lugar a fases vítreas.
El método ha sido validado y discutido.
Los resultados de esta tesis se presentan divididos en dos temas, por un lado, la dinámica de compuestos
puros y de los cristales mixtos y, por otro, el análisis mediante el método derivativo aplicado a los
diferentes modelos físicos existentes. En el primer tema nos centramos en la dinámica de los compuestos
puros y los cristales mixtos formados por cicloheptanol y ciclooctanol, así como la dinámica de la
relajación alfa en 1-ciano-adamantano y sus mezclas con 1-cloro-adamantano. El segundo tema se divide
en dos grupos de modelos, los modelos lineales y no lineales. En los modelos lineales se muestra la
aplicación del procedimiento de derivativo en los cristales líquidos (CL) y las fases OD. También se
discuten los resultados relativos a los casos de la resina líquida (EPON828), la mezcla neopentil-alcohol y
neopentil-glicol, el carbonato de propileno, así como el CL isooctilcianobifenil. Se discute también la
existencia de posibles correlaciones empíricas entre uno de los modelos lineales con el patrón universal
para la parte de alta frecuencia de la curva de pérdidas dieléctricas de la relajación primaria para las fases
CL y OD.
En la parte final se muestra que la forma de la ecuación introducida recientemente por Mauro et al. no
permite la linearización mediante el método derivativo. A diferencia de los modelos anteriores, los
diferentes parámetros no están correlacionados con la pendiente y el origen de coordenadas de una función
lineal. Para resolver este problema, hemos introducido el concepto del espacio entálpico.
Se analiza también la existencia de cambios de comportamiento dinámicos y se aportan descripciones
cuantitativas. Se muestra también un nuevo procedimiento para detectar los cambios dinámicos de una
manera fácil, que permite incluso detectar aquéllos que son obviados mediante el método clásico de
Stickel.
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Polák, Radek. "Měření komplexní permitivity materiálů v mikrovlnném pásmu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219856.
Full textAbstract:
This article describes some methods of measuring complex permitivity in milimeter – wave band, their characteristics, anvatages and disadvantages. Discused are here the reasons for their use in the construction of work place. On the basis these reasons is chosen the best method for practical measurement. That is cavity resonant method. Article contain description of designed measurement system. Whitch is verified by computer simulating of developed model in HFSS Ansoft. Text contain also result of simulations and execute computing of comlex permittivity and tangent loss. In Conclusion is desribed results of practical permittivity measure with realized measurement system.
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Moradi, Bahareh. "High dielectric permittivity materials in the development of resonators suitable for metamaterial and passive filter devices at microwave frequencies." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/384854.
Full textAbstract:
Los metamateriales (MTMs) representan una interesante área de investigación emergente que promete lograr un importante progreso tecnológico y científico en diversas áreas como las telecomunicaciones, la microelectrónica, radar, e imágenes médicas. La cantidad de artículos dedicados a la investigación en esta área (MTMs) se mantiene en pleno crecimiento en la actualidad. Las estructuras MTMs pueden sostener una fuerte resonancia electromagnética con longitudes de onda electricamente pequeñas y por lo tanto son potencialmente aplicables para la miniaturización de los componentes.
La miniaturización, optimización del rendimiento del dispositivo mediante la eliminación de frecuencias espurias, y la posibilidad de controlar el ancho de banda del filtro para amplios márgenes de frecuencias es un reto para los presentes y futuros dispositivos de comunicación.
Esta tesis se focaliza en el estudio de ambos temas (MTMs y miniaturización) centrándose en las nuevas estrategias para la miniaturización de componentes basados en MTMs.
Desde la aparición de estos, los resonadores dieléctricos (DR) son un nuevo tipo de MTMs distinguidos por sus pequeñas pérdidas, así como su fácil combinación con estructuras externas; son la elección adecuada para todo proceso de desarrollo. La principal ventaja de utilizar una alta constante dieléctrica como DR es miniaturizar el tamaño del filtro. El tamaño del filtro de DR es considerablemente menor que la dimensión de la guía de ondas de otros filtros que operan a la misma frecuencia. Dada una constante dieléctrica, tanto la frecuencia de resonancia como el factor de calidad Q se definen a partir de las dimensiones del resonador dieléctrico. Cuanto mayor es la constante dieléctrica, menor es el espacio en el que se concentran los campos, y por lo tanto las dimensiones necesarias para trabajar a una frecuencia de operación definida quedan reducidas.
Con el objetivo de miniaturizar las dimensiones del dispositivo, en este trabajo se propone un nuevo diseño para un filtro rechaza banda basado en la alta constante dieléctrica que proporciona una fina capa de pasta epoxy (TFDR) como material DRs excitado a través de una línea microstrip.
Además, se propone un filtro pasa banda diseñado en base a los resonadores dieléctricos incrustados (EDR), esto constituye un nuevo enfoque en el campo de los resonadores miniaturizados adaptado a los metamateriales, logrando evitar la degradación del factor Q inherente al coeficiente de acoplamiento basado en partículas eléctricamente pequeñas.
En esta tesis se propone también un nuevo filtro pasa de banda basado en resonadores de anillo dividido (SRRs), que es uno de los bloques de construcción MTMs más popular hoy en día. Los filtros de paso de banda basados en este concepto resultan prometedores para las aplicaciones donde la miniaturización y la compatibilidad con la tecnología de ondas planares milimétricas son los requisitos críticos del diseño. Además, para mayor miniaturización, tecnología DR de incrustado es reportada.
Otro enfoque para la reducción de tamaño se basa en modificar el resonador tradicional para generar modos adicionales, los cuales hacen que el resonador se comporte como un resonador multimodal. Por último, se propone un filtro compacto paso banda de banda ultra ancha (UWB) utilizando un resonador de anillo abierto conectado a tierra empleado como un resonador multimodal (MMR). Esta propuesta permite utilizar cinco resonancias para producir un ancho de banda fraccional del 128% dentro de la banda ultra ancha.
Para demostrar y validar la funcionalidad de los diseños, todos los dispositivos propuestos se han implementado y fabricado, con una excelente concordancia entre las simulaciones y las medidas experimentales. A través de estos métodos ha quedado demostrado que los modelos de sus circuitos equivalentes proporcionan una descripción precisa del comportamiento de las estructuras. En este trabajo se ha conseguido relacionar una relación directa entre las dimensiones físicas del dispositivo y su modelo equivalente eléctrico en forma de circuito.<br>Metamaterials (MTMs) represent an exciting emerging research area that promises to bring about important technological and scientific advancement in various areas such as telecommunication, radar, microelectronic, and medical imaging. The amount of research on this MTMs area has grown extremely quickly in this time. MTM structure are able to sustain strong sub-wavelength electromagnetic resonance and thus potentially applicable for component miniaturization.
Miniaturization, optimization of device performance through elimination of spurious frequencies, and possibility to control filter bandwidth over wide margins are challenges of present and future communication devices.
This thesis is focused on the study of both interesting subject (MTMs and miniaturization) which is new miniaturization strategies for MTMs component.
Since, the dielectric resonators (DR) are new type of MTMs distinguished by small dissipative losses as well as convenient conjugation with external structures; they are suitable choice for development process. The primary advantage in using a high dielectric constant as a DR is to miniaturize the filter size. The size of DR filter is considerably smaller than the dimension of waveguide filters operate at the same frequency. For a given dielectric constant, both resonant frequency and Q-factor are defined according to the dielectric resonator dimensions. That, the higher the dielectric constant, the smaller the space within which the fields are concentrated, the lower the dimension at a defined frequency.
To obtain the required compact sizes new stop-band filter is proposed in this work based on number of thick film high dielectric constant epoxy paste (TFDR) as DRs which excited with a microstrip line.
In addition, a band-pass filter is proposed based on embedded dielectric resonators (EDR) constitutes a new approach to the miniaturized resonators suitable for metamaterials design without the Q degradation inherent to the coupling coefficient based on sub-wavelength particles.
Also this thesis is proposed a new band-pass filter based on split ring resonators (SRRs), which is a one of the popular MTMs building blocks today. The band-pass filters based on this concept can be very promising for the applications where miniaturization and compatibility with planar millimeter wave technology are the important issues. Also, for further miniaturization, embedded DR technology is reported.
Another approach for size reduction is modifying the traditional resonator to generate additional modes, which make the resonator to behave as a multimode resonator. Finally a compact ultra-wide band-pass (UWB) band-pass filter using grounded open ring resonator as a multimode resonator (MMR) is proposed. The approach allows using five resonances to produce a 128% fractional bandwidth into the ultra-wide band. A general theoretic framework has been established using transmission matrix description of the filter constituent components.
To demonstrate and validate designs functionality, all the proposed devices are implemented and fabricated, which a good agreement between simulations and measurement are obtained. Through these methods it is demonstrated that their equivalent circuit models provide an accurate description of the considered structures. Indeed, a clear relationship between their equivalents circuit model and the layout physical dimensions were found.
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Lie, Fee Li. "Interface Formation Between High Dielectric Permittivity Films and III-V Compound Semiconductors using HF Chemistries and Atomic Layer Deposition." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/204301.
Full textAbstract:
In-based III-V compound semiconductors have higher electron mobilities than either Si or Ge and direct band gaps. These properties could enable the fabrication of low power, high-speed n-channel metal oxide semiconductor field effect transistors (MOSFETs) and optoelectronics combining MOS technology with photonics. Since thermal and native oxides formed on III-V surfaces exhibit large current leakage and high densities of trap states, a key to incorporating these materials into advanced devices is the development of processing steps that form stable interfaces with dielectric layers. In this thesis, a processing flow consisting of native oxide removal using HF chemistries and deposition of high dielectric permittivity films using atomic layer deposition was investigated. Understanding the reaction mechanisms of these processes could provide the means of controlling composition and structure, yielding a desired electronic behavior. Quantitative X-ray photoelectron spectroscopy analysis of surfaces was coupled with electrical measurements on MOS capacitors of the interface quality in order to understand the nature of high-k/III-V interface defects and their repair. Ex situ liquid phase HF etching removed InSb, InAs, and InGaAs(100) native oxides and produced an Sb- or As-enriched surface, which oxidized when exposed to air. A 5 to 22 °A thick As- and Sb-rich residual oxide was left on the surface after etching and < 5 min of air exposure. The results showed that group V enrichment originated from the reduction of group V oxides by protons in the solution and the preferential reaction of HF with the group III atom of the substrate. A sub-atmospheric in situ gas phase HF/H2O process removed native oxide from InSb, InAs, and InGaAs(100) surfaces, producing an In or Ga fluoride-rich sacrificial layer. A 50 to 90% oxide removal was achieved and a 10 to 25 °A-thick overlayer consisting of mainly In and Ga fluorides was produced. The composition and morphology of the sacrificial layer were controlled by the partial pressure of H2O as well as the ratio of HF to H2O used. Water played a critical role in the process by directly participating in the etching reaction and promoting the desorption of fluoride etching products. Accumulation of thick fluoride layer at high HF to water partial pressure ratios prevented adsorption and diffusion of etchant to the buried residual oxide. When oxide was removed, HF preferentially reacted with In or Ga atoms from the substrate, enriching the surface with group III fluorides and producing approximately one monolayer of elemental group V atoms at the interface. Interface reactions occurred during atomic layer deposition of Al2O3, in which trimethylaluminum (TMA) removed surface oxides and fluorides. Chemically sharp InSb/Al2O3 and InGaAs/Al2O3 interfaces were achieved for gas phase HF-etched InSb and liquid phase HF-etched InGaAs. A ligand transfer mechanism promotes nucleation of Al2O3 and removal of III-V atoms from the sacrificial oxide and fluoride layers as volatile trimethyl indium, gallium, arsenic, and antimony. These reactions have been explained by the relative bond strength of surface and precursor metal atoms with O and F. Interaction of a InSb(100) surface with TiCl4 as a model for metal halide ALD precursors showed that similar ligand transfer reactions occured. Adsorbed chlorine from the dissociative adsorption of TiCl4 on the InSb surface at elevated temperature, however, preferentially etched In atoms from the substrate and produced a roughened surface. The quality of InGaAs/Al2O3 interfaces prepared by solvent cleaning and liquid phase HF were assesed electrically using capacitance-voltage and conductance measurements. Surface recombination velocity (SRV) values were extracted from the measurements to represent the net effect of interface defects, which includes defect density and capture cross section. The InGaAs/Al2O3 interface prepared by solvent cleaning consisted of interfacial native oxides while that etched in liquid phase HF consisted of submonolayer arsenic oxide. The two chemically contrasting interfaces, however, gave similar SRV values of 34.4±3.7 and 28.9±13.4 cm/s for native oxide and liquid phase HF prepared samples, respectively. This suggests that the presence or absence of oxides was not the only determining factor. Post Al2O3 deposition annealing in forming gas and NH3 ambient significantly improved the electrical quality for both surfaces, as shown by SRV values between 1 to 4 cm/s which is comparable to that of an ideal H-terminated Si surface. XPS analysis showed that the contribution from elemental As and Ga2O3 at the interface of both surfaces increased after annealing in forming gas and NH3, likely due to thermal or hydrogen-induced reaction between interfacial As oxide and Ga atoms in the substrate. There was no correlation between the atomic coverages of interfacial elemental As and oxides to the SRV values. High activity defects at III-V/Al2O3 interfaces are associated with interfacial dangling bonds which were passivated thermally and chemically by annealing in forming gas and NH3.
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El, Khoury Diana. "Towards the use of electrostatic force microscopy to study interphases in nanodielectric materials." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS078/document.
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Les interphases sont souvent considérées comme responsables des propriétés physiques des nanodiélectriques inexplicables par les lois de mélange. La prédiction de la permittivité diélectrique des nanodiélectriques nécessite de reconsidérer la permittivité intrinsèque et le volume de l'interphase. Malgré le besoin d'une caractérisation locale de ces régions interfaciales nanométriques, aucune méthode expérimentale fiable n'a encore été développée. La Microscopie à Force Electrostatique (EFM) constitue une technique prometteuse pour atteindre ce but. L'objectif de cette thèse est de développer des protocoles expérimentaux et des méthodes d’interprétations du signal appropriés pour évaluer l’aptitude de l’EFM à l'étude des interphases dans les nanodiélectriques. Nous avons eu recours d’abord à des simulations numériques par éléments-finis pour approfondir notre compréhension de l'interaction entre une sonde EFM et plusieurs types d'échantillons nanostructurés, permettant par la suite de simuler la réponse spécifique face à un nanocomposite possédant une interphase. Nous avons proposé un modèle électrostatique de nanodiélectrique possédant trois phases, selon lequel, nous avons conçu et synthétisé des échantillons modèles aux propriétés connues afin de jouer le rôle de matériaux nanodiélectriques de référence pour les mesures EFM. Par conséquent, nous avons pu développer plusieurs protocoles expérimentaux et d’analyses du signal utilisant des modes DC et AC de détection du gradient de force pour caractériser les interphases dans des nanocomposites. Ces techniques constituent un ensemble polyvalent de méthodes d’étude des interphases avec un impact réduit des effets parasites communément convolués dans les signaux EFM. Enfin, une quantification de la permittivité de l'interphase de nos échantillons modèles a été possible par corrélation avec nos simulations numériques<br>Interphases are usually considered to be responsible for the physical properties of nanodielectrics unexplainable by general mixture laws. The prediction of the effective dielectric permittivity of these materials needs to reconsider the intrinsic permittivity and the volume of the interphase. Despite the urge for a local characterization of these nanometric interfacial regions, no reliable experimental method has been developed yet. The Electrostatic Force Microscope (EFM) constitutes a promising technique to fulfill this objective. The aim of this thesis is to develop appropriate experimental protocols and signal analysis to explore the ability of EFM to the study of interphases in nanodielectrics. We first resorted to finite-element numerical simulations in order to deeper our understanding of the interaction between an EFM probe and several types of nanostructured samples, allowing to simulate afterwards the specific response to a nanocomposite possessing an interphase. We proposed a three-phase electrostatic model of a nanodielectric, upon which, we designed and synthesized model samples of known properties to play the role of a reference nanodielectric material for EFM measurements. Consequently, we were able to develop several experimental protocols and signal analysis with both DC and AC force gradient EFM modes. These techniques offer versatile methods to characterize interphases with reduced impact of the parasitic effects commonly convoluted within EFM signals. Finally, a quantification of the interphase in our nanodielectric model samples was possible thanks to correlation with our numerical simulations
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Guiraud, Alexandre. "Intégration de matériaux à forte permittivité diélectrique dans les mémoires non volatile avancées." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4763/document.
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Ce travail de thèse porte sur l'intégration de matériaux de haute constante diélectrique (High-k) en tant que diélectrique interpoly dans les mémoires non volatiles de type Flash. L'objectif est de déterminer quel matériaux High-k seraient des candidats probables au remplacement de l'empilement ONO utilisé en tant que diélectrique interpoly. Une gamme de matériaux high-k ont été étudiés via des caractérisations électriques (I-V, C-V, statistique de claquage…) et physiques (TEM, EDX, XPS…) afin d'éliminer les matériaux ne répondant pas au cahier des charges d'un diélectrique interpoly. Les difficultés et les obstacles liés a l'intégration de matériaux High-k dans une chaine de procédés de fabrication de mémoires Flash ont été pris en compte, et des solutions ont été proposées<br>The work of this thesis is on integration of high dielectric constant materials (High-k) as dielectric interpoly in Flash non volatile memories. The objective is to determine which High-k materials are suitable as interpoly dielectric in place of the ONO stack currently used. A range of High-k materials have been studied by electrical characterizations (I-V, C-V, breakdown statistics…) and physical characterizations (TEM, EDX, XPS…) in order to select those with the best properties for an interpoly dielectric. The difficulties in integration of High-k materials in a Flash memory process flow have been taken in account and solutions have been proposed
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Singer, Farah. "Influence of the nonlocal effects on the near-field radiative heat transfer." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2338.
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Dans ce mémoire de thèse, nous étudions la validité de quelques modèles non locaux de la permittivité diélectrique (PD) dans le calcul du coefficient de transfert de chaleur par rayonnement (CTCR) entre deux matériaux diélectriques, semi- infinies, plans et parallèles, et séparés par un espace vide de largeur d.Dans les études théoriques antérieures, il a été montré que lorsque l'on considère un modèle local de la PD, le transfert de chaleur par rayonnement en champ proche (TCRCP) suit une loi 1/d² quand d devient de l'ordre ou inférieure à quelques centaines de nanomètres. Cette divergence non physique constitue la faille majeure du modèle local. Plusieurs efforts ont été fournis afin de développer un nouveau modèle de la PD qui tient compte des effets nonlocaux. Aucune correction non locale pour le TCRCP n’a été abordée dans le passé dans le cas des diélectriques. Cependant dans le cas des métaux, un travail complet a été effectué en utilisant le modèle non local de Lindhard-Mermin de la PD.Nos travaux portent sur l'étude de quatre modèles différents de la PD nonlocale. Nous exploitons ces modèles pour le calcul du CTCR entre deux plans de 6H-SiC. Nous montrons que le CTCR sature quand d tend vers zéro. La distance du début de saturation dépend grandement des paramètres clés de chaque modèle<br>In this thesis, we study the validity of few nonlocal models of the dielectric permittivity in the calculation of the radiative heat transfer coefficient (RHTC) between two semi-infinite parallel dielectric planes separated by a vacuum gap of width d.In past theoretical studies, it has been shown that upon considering a local model of the dielectric permittivity, near field radiative heat transfer (NFRHT) between two dielectric materials follows a 1/d2 law when d is of the order or less than few hundreds of nanometers. This nonphysical diverging increase has been the bottleneck of the local model. Overwhelming efforts have been deployed in order to come up with a new model in which the nonlocal effects of the dielectric permittivity are taken into account. To the best of our knowledge, no nonlocal correction to the NFRHT has been addressed in the past in the case of dielectrics. In the case of metals however, an important and complete work has been performed using the Lindhard-Mermin nonlocal dielectric permittivity model.Our work focuses on studying four different nonlocal models of the dielectric permittivity and on using them in the calculation of the RHTC between two solid semi-infinite parallel planes of 6H-SiC. We show that the RHTC saturates as the separation distance d tend to zero. The distance at which saturation starts to take place depends on key parameters involved in each model