Tesis sobre el tema "Glass doping"

The nonlinear optical properties of a semiconductor-doped glass (SDG) channel waveguide were measured on a picosecond time-scale; namely, fluence-dependent changes in the absorption and the refractive index as well as the relaxation time of the nonlinearity. Slower, thermally-induced changes in the refractive index were also observed. The saturation of the changes in the absorption and the refractive index with increasing optical fluence is explained using a plasma model with bandfilling as the dominant mechanism. The fast relaxation time of the excited electron-hole plasma (20 ps) is explained using a surface-state recombination model. A figure of merit for a nonlinear directional coupler fabricated in a material with a saturable nonlinear refractive index is presented. The measured nonlinear change in the refractive index of the SDG saturates below the value required to effect fluence-dependent switching in a nonlinear directional coupler. Experiments with a channel-waveguide directional coupler support this prediction. However, absorption switching due to differential saturation of the absorption in the two arms of the directional coupler was observed.

In this thesis study, fabrication and doping of silicon thin films prepared by electron beam evaporation equipped with effusion cells for solar cell applications have been investigated. Thin film amorphous Si (a-Si) layers have been fabricated by the electron beam evaporator and simultaneously doped with boron (B) and phosphorous (P) using effusion cells. Samples were prepared on glass substrates for the future solar cell operations. Following the deposition of a-Si thin film, crystallization of the films has been carried out. Solid Phase Crystallization (SPC) and Metal Induced Crystallization (MIC) have been employed to obtain thin film crystalline Si. Crystallization was performed in a conventional tube furnaces and Rapid Thermal annealing systems (RTA) as a function of process parameters such as annealing temperature and duration. Produced films have been characterized using chemical and structural characterization techniques such as Raman Spectroscopy, X-Ray Diffractometer and Secondary Ion Mass Spectrometer (SIMS). The electrical properties of the films have been studied using Hall Effect and I-V measurements as a function of doping. We have demonstrated successful crystallization of a-Si by SPC at temperatures above 600 &deg<br>C. The crystallization occurred at lower temperatures in the case of MIC. For doping, P was evaporated from the effusion cell at a temperature between 600 &deg<br>C and 800 &deg<br>C. For B, the evaporation temperature was 1700 &deg<br>C and 1900 &deg<br>C. The thickness and the band gap of the Si films were determined by ellipsometry method and the results were compared for different evaporation temperatures. The effect of doping was monitored by the I-V and Hall Effect measurements. We have seen that the doping was accomplished in most of the cases. For the samples annealed at relatively high temperatures, the measured doping type was inconsistent with the expected results. This was attributed to the contamination from the glass substrate. To understand the origin of this contamination, we analyzed the chemical structure of the film and glass by X-ray Fluorescence (XRF) and seen that the glass is the main source of contamination. In order to prevent this contamination we have suggested covering the glass substrate with Si3N4 (Silicon Nitride) which act as a good diffusion barrier for impurities.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-28Bitstream added on 2014-06-13T18:28:59Z : No. of bitstreams: 1 gordo_vo_me_ilha.pdf: 1058796 bytes, checksum: 2c8438704796726349dfe606c2595b4b (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Neste trabalho foi estudado o sistema vítreo (100-x)% (80% TeO2-20% WO3)-(x)% Yb2O3, onde x = 0; 0,1; 0,2; 0,3; 0,4 e 0,5%. As técnicas de difração de raios-X, espectroscopia no infravermelho, espectroscopia Raman e espectroscopia no UV-Vis foram usadas para caracterizar os efeitos da dopagem sobre as propriedades estruturais e ópticas dos vidros estudados. Usando os dados de espectroscopia na região espectral ultravioleta-visível foi possível observar que não houve mudança das freqüências de corte para cada composição e ainda calcular a energia de “gap” e a energia de cauda de Urbach. Usando os dados de fotoluminescência observam-se picos que indicam o desdobramento dos níveis de energia dos estados 2F7/2 e 2F5/2 dos íons de Yb3+. Para os comprimentos de onda de excitação de 514,5 a 488,0 nm, crescem as taxas de absorção do sistema vítreo TW, transferência de carga para o estado 2F5/2 do Yb3+ e da transição radiativa 2F5/2 2F7/2, aumentando, desta forma, a intensidade da fotoluminescência. Já para os comprimentos de onda de excitação 457,9 e 476,5 nm as taxas de absorção do sistema vítreo TW, a transferência de carga para o estado 2F5/2 do Yb3+ e a transição radiativa 2F5/2 2F7/2 são as mesmas e, consequentemente, a intensidade da fotoluminescência é constante.<br>This work presents the study on the glassy system (100-x)% (80% 20% TeO2-WO3) - (x)% Yb2O3 where x = 0, 0.1, 0.2, 0.3, 0.4 and 0 5%. The techniques of X-ray diffraction, infrared spectroscopy, Raman spectroscopy and UV-Vis were used to characterize the effects of Yb doping on the structural and optical properties of the glasses. Using data from spectroscopy ultraviolet-visible spectral region was observed that there was no change of cutting frequencies for each compound and were calculate the energy gap and Urbach tail energy. Using the data of photoluminescence peak is observed indicating the splitting of energy levels of states 2F7/2 and 2F5/2 of Yb3+ ions. The rate of electron transition probability is influenced by temperature. To the excitation wavelength of 514.5 to 488.0 nm, growing rates of absorption of the glass system TW, charge transfer to the state 2F5/2 of Yb3+ and the radiative transition 2F5/2 2F7/2, increasing thus the photoluminescence intensity. As for the excitation wavelength of 476.5 and 457.9 nm absorption rates of the TW glass system, the charge transfer state to the 2F5/2 of Yb3+ and the radiative transition 2F5/2 2F7/2 are the same and, hence the photoluminescence intensity is constant.

Chalcogenide glasses and glass-ceramics present a high interest for the production of thermal imaging lenses transparent in the 3-5 μm and 8-12 μm windows. However, chalcogenide glasses are conventionally synthesized in sealed silica ampoules which have two major drawbacks. First, the low thermal conductivity of silica limits the sample dimensions and second the silica tubes employed are single use and expensive, and represent up to 30% of the final cost of the material. The present work therefore addresses the development of innovative synthesis methods for chalcogenide glass and glass-ceramics that can present an alternative to the silica tube route. The method investigated involves melting the raw starting elements in reusable silica containers. This method is suitable for the synthesis of stable chalcogenide glasses compositions such as GeSe₄ but uncontrolled crystallization and homogenization problems are experienced for less stable compositions. The second approach involves preparation of amorphous chalcogenide powders by ball milling of raw elements. This mechanosynthesis step is followed by consolidation of the resulting powders to produce bulk glasses. Hot Uniaxial Pressing is suitable for compositions stable against crystallization. However, uncontrolled crystallization occurs for the unstable 80GeSe₂-20Ga₂Se₃ glass composition. In contrast consolidation through Spark Plasma Sintering (SPS) allows production of bulk glasses in a short duration at relatively low temperatures and is appropriate for the synthesis of unstable glasses. A sintering stage of only 2 min at 390°C is shown to be sufficient to obtain infrared transparent 80GeSe₂-20Ga₂Se₃ bulk glasses. This method enables the production of lenses with a 4-fold increase in diameter in comparison to those obtained by melt/quenching technique. Moreover, increasing the SPS treatment duration yielded infrared transparent glass-ceramics with enhanced mechanical properties. This innovative synthesis method combining mechanosynthesis and SPS has been patented in the framework if this study. The controlled etching of 80GeSe₂-20Ga₂Se₃ glass-ceramics in acid solution yields nanoporous materials with enhanced surface area. The porous layer created on the surface of the glass-ceramic is shown to play the role of anti-reflection coating and increase the optical transmission in the infrared range by up to 10%. These materials may have potential for the production of sensors with increased sensitivity in the infrared. The influence of indium and lead addition on the thermal and optical properties of the 80GeSe₂-20Ga₂Se₃ glass has also been assessed. Increased In or Pb contents tend to decrease the Tg of the glasses and shift the optical band gap toward higher wavelengths. A systematic ceramization study emphasizes the difficulty of controlling the crystallization for glasses in the systems GeSe₂-Ga₂Se₃-In₂Se₃ and GeSe₂-Ga₂Se₃-PbSe. No crystallization of the In₂Se₃ and PbSe crystalline phase was obtained. Finally, the possibility of producing rare-earth doped 80GeSe₂-20Ga₂Se₃ glass-ceramics transparent in the infrared region up to 16 μm is demonstrated. Enhanced photoluminescence intensity and reduced radiative lifetimes are observed with increased crystallinity in these materials.

Les verres de phosphates à faible Tg et forte stabilité thermique sont étudié dans le système (66-x)ZnO- xNa2O-33.4 P2O5. Les mesures DSC ont montré un écart Tx-Tg de 197 °C et une Tg de 339 °C pour x= 20. La RMN 31P 1D/2D révèle la diminution du désordre due à la substitution progressive de Zn par Na. Les formulations x=20 et x=33 ont été dopé par de l’Al2O3, B2O3 et SiO2 (1-4 % mol.) et ses effets sur les propriétés physiques comme la température de transition vitreuse, la stabilité thermique et la durabilité chimique ont été investiguées. La DRX et la RMN 31P ont été réalisés pour suivre le processus de cristallisation en isotherme à 130°C (au-delà de la Tg). La plus forte stabilité thermique a été identifiée pour les verres dopés au bore. Le Raman et la RMN 31P ont mis en évidence l’existence de connections P-O-X (X=27Al ou 11B). La RMN a entre autre montré la coordinence majoritaire VI, IV et IV respectivement pour l’aluminium, le bore et la silice. L’utilisation de D-INEPT, REDOR et DQ-SQ permet d’approfondir nos connaissances sur la structure particulièrement sur les connectivités P-O-X mais également la diversité des connections possibles<br>Pyrophosphate glass with low Tg and high stability is investigated within the (66-x) ZnO- xNa2O-33.4 P2O5 system. DSC measurement indicated Tx-Tg=197 °C with Tg = 339 °C at x= 20. 1D/2D 31P NMR revealed the decrease in extent of disorder with the progressive substitution of Zn by Na. The x=20 and x=33 formulations were doped with (1-4 mol.%) of Al2O3, B2O3 and SiO2 and its effect on the physical properties such as the glass transition temperature, thermal stability and chemical durability is investigated. XRD and 1D 31P solid state NMR were used to monitor the isothermal crystallization process occurring at 130 °C above Tg and the highest thermal stability is presented by the B-doped glasses. Raman and 31P NMR suggested the existence of P-O-X (X=27Al or 11B) bonds. The MAS NMR distinguished the dominant coordination states of doping elements AlVI , BIV and SiIV respectively. The use of D-INEPT, REDOR and DQ-SQ helped in producing deeper insights onto the glass structure about the P-O-X connectivity, the wide range of phosphate speciation

Orientador: Keizo Yukimitu<br>Banca: José Brás Barreto Oliveira<br>Banca: Noelio Oliveira Dantas<br>Resumo: Neste trabalho foi estudado o sistema vítreo (100-x)% (80% TeO2-20% WO3)-(x)% Yb2O3, onde x = 0; 0,1; 0,2; 0,3; 0,4 e 0,5%. As técnicas de difração de raios-X, espectroscopia no infravermelho, espectroscopia Raman e espectroscopia no UV-Vis foram usadas para caracterizar os efeitos da dopagem sobre as propriedades estruturais e ópticas dos vidros estudados. Usando os dados de espectroscopia na região espectral ultravioleta-visível foi possível observar que não houve mudança das freqüências de corte para cada composição e ainda calcular a energia de "gap" e a energia de cauda de Urbach. Usando os dados de fotoluminescência observam-se picos que indicam o desdobramento dos níveis de energia dos estados 2F7/2 e 2F5/2 dos íons de Yb3+. Para os comprimentos de onda de excitação de 514,5 a 488,0 nm, crescem as taxas de absorção do sistema vítreo TW, transferência de carga para o estado 2F5/2 do Yb3+ e da transição radiativa 2F5/2 2F7/2, aumentando, desta forma, a intensidade da fotoluminescência. Já para os comprimentos de onda de excitação 457,9 e 476,5 nm as taxas de absorção do sistema vítreo TW, a transferência de carga para o estado 2F5/2 do Yb3+ e a transição radiativa 2F5/2 2F7/2 são as mesmas e, consequentemente, a intensidade da fotoluminescência é constante.<br>Abstract: This work presents the study on the glassy system (100-x)% (80% 20% TeO2-WO3) - (x)% Yb2O3 where x = 0, 0.1, 0.2, 0.3, 0.4 and 0 5%. The techniques of X-ray diffraction, infrared spectroscopy, Raman spectroscopy and UV-Vis were used to characterize the effects of Yb doping on the structural and optical properties of the glasses. Using data from spectroscopy ultraviolet-visible spectral region was observed that there was no change of cutting frequencies for each compound and were calculate the energy gap and Urbach tail energy. Using the data of photoluminescence peak is observed indicating the splitting of energy levels of states 2F7/2 and 2F5/2 of Yb3+ ions. The rate of electron transition probability is influenced by temperature. To the excitation wavelength of 514.5 to 488.0 nm, growing rates of absorption of the glass system TW, charge transfer to the state 2F5/2 of Yb3+ and the radiative transition 2F5/2 2F7/2, increasing thus the photoluminescence intensity. As for the excitation wavelength of 476.5 and 457.9 nm absorption rates of the TW glass system, the charge transfer state to the 2F5/2 of Yb3+ and the radiative transition 2F5/2 2F7/2 are the same and, hence the photoluminescence intensity is constant.<br>Mestre

La modulation de la densité de charge est un aspect important de l'étude de les transitions de phase électroniques ainsi que des propriétés électroniques des matériaux et il est à la base de plusieurs applications dans la micro-électronique. L'ajustement de la densité des porteurs de charge (dopage) peut être fait par voie chimique, en ajoutant des atomes étrangers au réseau cristallin du matériau ou électrostatiquement, en créant un accumulation de charge comme dans un Transistor é Effet de Champ. Cette dernier m ethode est réversible et particuliérement appropriée pour les matériaux bidimensionnels (2D) ou pour des couches ultra-minces. Le Dopage par Charge d'Espace est une nouvelle technique inventée et développée au cours de ce travail de thèse pour le dopage electrostatique de matériaux déposés sur la surface du verre. Une charge d'espace est créée à la surface en provoquant le mouvement des ions sodium présents dans le verre sous l'effet de la chaleur et d'un champ électrique extérieur. Cette espace de charge induit une accumulation de charge dans le matériau déposé sur la surface du verre, ce qui peut être supérieure à 10^14/cm^2. Une caractérisation détaillée faite avec mesures de transport, effet Hall, mesures Raman et mesures de Microscopie a Force Atomique (AFM) montrent que le dopage est réversible, bipolaire et il ne provoque pas des modifications chimiques. Cette technique peut être appliquée a des grandes surfaces, comme il est montré pour le cas du graph ene CVD. Dans une deuxiéme partie le dopage par espace de charge est appliqué à des couches ultra-minces (&lt; 40 nm) de ZnO_(1-x). Le résultat est un abaissement de la résistance par carré de 5 ordres de grandeur. Les mesures de magnéto-transport faites à basse température montrent que les électrons dop es sont confinés en deux dimensions. Une transition remarquable de la localisation faible à l'anti-localisation est observée en fonction du dopage et de la température et des conclusions sont tirées à propos des phénoménes de diffusion qui gouverne le transport électronique dans des diff erentes conditions dans ce matériau<br>Carrier modulation is an important parameter in the study of the electronic phase transitions and the electronic properties of materials and at the basis for many applications in microelectronics. The tuning of charge carrier density (doping) can be achieved chemically, by adding foreign atoms to the crystal structure of the material or electrostatically, by inducing a charge accumulation like in a Field Eect Transistor device. The latter method is reversible and particularly indicated for use in two dimensional (2D) materials or ultra-thin films. Space Charge Doping is a new technique invented and developed during this thesis for the electrostatic doping of such materials deposited on a glass surface. A space charge is created at the surface by causing sodium ions contained in glass to drift under the Eect of heat and an external electric field. This space charge in turn induces a charge accumulation in the material deposited on the glass surface which can be higher than 10^14/cm^2. Detailed characterization using transport, Hall effect, Raman and AFM measurements shows that the doping is reversible, ambipolar and does not induce chemical changes. It can be applied to large areas as shown with CVD graphene. In a second phase the space charge doping method is applied to polycrystalline ultra-thin films (&lt; 40 nm) of ZnO_(1-x). A lowering of sheet resistance over 5 orders of magnitude is obtained. Low temperature magneto-transport measurements reveal that doped electrons are confined in two dimensions. A remarkable transition between weak localization and anti-localization isobserved as a function of doping and temperature and conclusions are drawn concerning the scattering phenomena governing electronic transport under different conditions in this material

L’accroissement de l’espérance de vie s’accompagne d’une détérioration de l’état de santé général des seniors et d’une recrudescence des maladies chroniques. Parmi les manifestations de la sénescence, l’atteinte de l’appareil locomoteur est particulièrement invalidante et accélère considérablement l’entrée en dépendance. C’est également le cas chez les plus jeunes lors d’atteintes traumatiques ou pathologiques. Ainsi, au niveau mondial 2,2 millions de greffes osseuses sont pratiquées chaque année, mais le taux de complications post-opératoires demeure élevé et est estimé à 15 % des interventions. Ces faits dessinent les contours d’un enjeu sociétal majeur ; les matériaux d’origine animale posent des problèmes d’histocompatibilité, de pathogénicité et donc de rejet. C’est pourquoi les efforts de recherche ciblent prioritairement le développement de biomatériaux synthétiques aptes à promouvoir la régénération osseuse. Actuellement les principaux substituts osseux sur le marché sont les « céramiques » bioactives (phosphates de calcium, verres bioactifs) qui présentent comme caractéristiques d’être biocompatibles, de se lier spontanément aux tissus osseux, de promouvoir l’adhésion des cellules osseuses et enfin d’être biorésorbables. Cependant, malgré cet ensemble de caractéristiques très satisfaisantes, la fragilité de ces matériaux en limite les applications. Pour pallier ce défaut, une solution ingénieuse est de s’inspirer de la structure particulière du tissu osseux. Celle-ci mêle intimement une phase inorganique, le minéral osseux constitué de cristaux d’apatite (phosphate de calcium résorbable), à une phase organique qui est majoritairement du collagène. De manière remarquable, une telle structure associe la rigidité de la partie inorganique à la ténacité des fibres de collagène. Pour obtenir des implants aux propriétés mécaniques proches du tissu osseux, la stratégie consiste donc à combiner céramiques bioactives et matière organique. À cette fin, l’équipe Biomatériaux du Laboratoire de Physique de Clermont (LPC) a récemment mis au point un procédé innovant qui permet la synthèse de matrices tridimensionnelles d’hybrides organique-inorganique à base de verre bioactif et de polymère biocompatible aux caractéristiques variées. Dans la continuité des travaux, il était alors question d’exploiter ce procédé afin de développer un substitut osseux hybride aux propriétés optimisées. Il s’agissait tout d’abord de sélectionner le polymère le plus adéquat pour la régénération osseuse, qui s’est avéré être le polycaprolactone, puis d’optimiser la synthèse (notamment la source de calcium), la structure macroporeuse et la proportion organique-inorganique. Le matériau hybride résultant a ensuite été dopé en éléments thérapeutiques à faible dose (&lt; 5 % de la masse totale) avec des ions strontium ou des nutriments tels que la fisétine et l’hydroxytyrosol qui possèdent un effet ostéogénique. Les mousses hybrides ainsi développées ont finalement été caractérisées in vitro afin de déterminer leurs propriétés physico-chimiques et biologiques, et in vivo afin d’évaluer leur performance. Après 3 mois d’implantation dans un défaut critique de la calvaria de souris, les résultats démontrent le potentiel de ce substitut osseux: comparé au matériau commercial de référence (os bovin traité) qui conduit à une reconstruction osseuse de 16% (± 5%), l’hybride permet une reconstruction allant de 32% (± 3%) lorsqu’il n’est pas dopé, jusqu’à 55% (± 7%) voire 58% (± 7%) lorsqu’il est dopé respectivement en fisétine ou en strontium. Ces travaux de thèse laissent entrevoir des perspectives prometteuses telles que l’association des dopants et l’impression 3D des mousses hybrides polycaprolactone-verre bioactif<br>The increase in life expectancy results in the decline of seniors’ health conditions and the resurgence of chronic diseases. Among the expressions of senescence, disorders of the musculoskeletal system are particularly disabling and considerably accelerate the state of dependency. This is also the case for young people who suffer from traumatic injuries or pathologic conditions. Thus, about 2.2 million bone grafts are performed worldwide every year. Yet, the level of postoperative complications remains high and is estimated at 15% of surgical operations. These facts outline a major societal concern: animal-based materials present a risk of histocompatibility issues and pathogenicity that may lead to implant failure. This is the reason why research efforts focus on the development of synthetic biomaterials capable of promoting bone regeneration. Currently, commercialised bone substitutes are mainly made of bioactive “ceramics” (calcium phosphates, bioactive glass) that are known to be biocompatible, to spontaneously bond to bone tissues, to promote bone cell adhesion and finally to be bioresorbable. However, despite these remarkable properties, the brittleness of these materials limits their applications. An ingenious solution to this brittleness can be learned from the particular structure of bone tissue. Bone tissue intimately blends an inorganic phase, the bone mineral, which is made of apatite crystals (resorbable calcium phosphates), with an organic phase that is mainly collagen. Such a structure associates the stiffness of the inorganic part with the toughness of collagen fibres. Therefore, in order to obtain implants with mechanical properties similar to that of bone, the strategy consists in combining bioactive ceramics with organic matter. To this end, the Biomatériaux team from the Laboratoire de Physique de Clermont (LPC) recently developed an innovative process that allows the synthesis of tridimensional organic-inorganic hybrids comprised of bioactive glass and biocompatible polymer. The objective of the thesis was to exploit this process in order to develop a hybrid bone substitute with optimal properties. First of all, polycaprolactone was selected as the polymer, especially because of its adequate degradation rate for long-term applications such as bone regeneration. Then, the synthesis process was improved (in particular, the calcium source was changed), the macroporous structure was optimised and the organic-inorganic ratio was chosen. Afterwards, elements that are known to induce an osteogenic effect were incorporated in the hybrid at low doses (&lt; 5% of total weight): an inorganic doping was performed using strontium ions and an organic doping was performed using nutrients such as fisetin or hydroxytyrosol. The resultant hybrid scaffolds were eventually characterised in vitro in order to determine their physicochemical and biological properties and in vivo in order to evaluate their performance. After 3 months of implantation in a mouse calvarial critical defect, results demonstrate the potential of this bone substitute: compared to the reference commercial material (treated bovine bone) that leads to a bone reconstruction of 16% (± 5%), the hybrid allows a reconstruction going from 32% (± 3%) when it is not doped, to 55% (± 7%) and even 58% (± 7%) when it is doped respectively with fisetin or strontium. This thesis paves the way to promising perspectives like the association of doping agents and the 3D printing of polycaprolactone-bioactive glass hybrid scaffolds

Made available in DSpace on 2014-10-09T12:51:51Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:06:32Z (GMT). No. of bitstreams: 0<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>Tese (Doutoramento)<br>IPEN/T<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP<br>FAPESP:00/11446-0

The influence of various dopants on the properties and local structure of glass samples was explored and a quantitative determination of the structural changes in the network as the dopant concentration was varied was achieved using 27Al, 29Si, 33S MAS NMR. Findings showed that silver- and copper-doping of phosphate based glass gave rise to unexpected connectivity between the phosphate units most likely due to some phase separation creating a different composition to that intended in the majority glass. This emphasises the importance of a careful and systematic approach to sample manufacture in achieving high sample stabilities, leading to a good degree of predictability in both structure and properties. Lanthanum and yttrium ions, despite their huge difference in ionic size, showed very little difference in their effect upon the phosphate coordination in the glass samples as they remain outside the phosphate network, cross-linking between the terminal oxygen atoms. The aluminium ions however, showed evidence of behaving in both a cross-linking manner and in a network forming, tetrahedral role and it appears energetically favourable for them to avoid any Al-O-Al linkage, hence resulting in the formation of AlO4 rather than exceeding the AlO5 or AlO6 quantities that would lead to this. The sulphur NMR looks to be a very promising method for future use in understanding sulphur speciation in glasses.

L'etude porte sur la variation de la conductivite electrique des systemes borotellurates et borophosphates suivants : lio::(2)-b::(2)o::(3)-te::(2)o::(4) et li::(2)o-b::(2)o::(3)-p::(2)o::(6)-lix (x=f, cl, br). L'effet de formateur mixte pour le premier systeme et l'effet de sel dopant dans le second systeme ont ete interpretes a l'aide de la theorie de l'electrolyte faible et d'un modele de solutions regulieres

Dans ce travail nous avons analyse de petits agregats metalliques en verre dans le but d'en determiner les proprietes structurales, leur lien avec la reponse optique et l'influence de l'ordre locale sur les proprietes de diffusion des metaux dans les verres alkalino-silicates. - verres silicates implantes cu : la structure des agregats de cu formes par implantation ionique dans la silice amorphe a ete etudiee au point de vue morphologique et locale. Les techniques de diffusion et diffraction de rayons x en incidence rasante ont ete utilisees et ont permis de determiner la taille des particules ainsi que leur phase cristalline. La technique de l'absorption des rayons x (xas) a ete utilisee pour determiner la structure locale des atomes de cu dans le verre ainsi que leur etat de valence. Les agregats metalliques ont ete observes et caracterises du point de vue structurale. Les agregats les plus petits montrent une reduction du parametre de maille ainsi que une augmentation du desordre statique. - l'etat de valence du cu dans les verres implantes. Les analyses des seuils d'absorption de rayons x ont montre que le cu peut etre loge dans le verre sous la forme de cu#+#1 ou cu#+#2 aussi que dans l'etat metallique. Nous avons trouve l'evidence que les ions metalliques a l'interieur du verre sont plus oxydes que ceux pres de la surface et proposons une explication pour ce phenomene. Verres soda-lime dopes par echange ionique : nous avons etudie des verres soda-lime dopes avec cu et ag par la methode de l'echange ionique prepares suivant differentes procedures. La structure atomique locale autour du metal a ete determine et ne depend pas des details de preparation de l'echantillon mais seulement du metal dopant. Agregation des metaux provoquee par bombardement ionique dans les verres la structure locale des atomes d'ag dans des verres traites par bombardement ionique a ete analysee et les phases structurales obtenues par differentes parametres de traitement ont ete determinees.

碩士<br>國立聯合大學<br>材料科學工程學系碩士班<br>106<br>As glass products become more and more popular, they also produce more glass waste, and how to recycle these materials has always been an important issue. From the perspective of a circular economy, if these glass wastes can be used as raw materials for the next process, the raw material cost of the process can be reduced and the amount of waste glass can be reduced. In this study, the recovered soda-lime glass is used, and it is desirable to use it as an alkali-resistant glass fiber by adding a zirconium-containing oxide during remelting to enhance the resistance in an alkaline environment. The Experimental results show that the density of glass, glass transition temperature and glass softening temperature all increase with the content of Zirconia in the glass increases. The intensity at about 990 cm-1 in the Raman spectrum increases with increasing zirconia content in the glass, this band can be assigned to the stretching vibration of Q3(Zr) units. The 29Si NMR spectrum and the 27Al NMR spectrum did not change much. In the alkali-resistant part, the weight loss of the glass after corrosion decreases as the content of zirconia in the glass increases, indicating that the alkali resistance is improved.

碩士<br>義守大學<br>材料科學與工程學系<br>103<br>This research is studied the effect of glass doping on the densification behavior and electrical properties of ZnO ceramics. The adding glass powder is ranged from 1 to 10 wt%. The glass doped ZnO ceramics is hot-pressed at sintering temperature of 1000°C to 1200°C under 150 kN pressure in a N2 atmosphere. The resultant data showed that addition of glass increased the densification rate and grain size of ZnO ceramics. The liquid phase of glass dopant assisted the densification of ZnO ceramics at lower sintering temperature. In addition, hot-pressing also promoted the densification of ZnO ceramics. As a result, the ZnO ceramics can reach to a 99.8% of theoretical density at 1000°C.

碩士<br>義守大學<br>材料科學與工程學系<br>103<br>A unique glass composition based on GeO2, MoO3 and V2O5 was designed to act as sintering aid to enhance the densification and to adjust the electrical properties of SnO2. This allows the low temperature processing of approximately 950 ◦C to be feasible with a desirable electrical property. The effect of metal oxide glass concentration on the densification behavior and electrical properties of SnO2 was investigated by Archimedes'' principle, x-ray diffractometer (XRD), scanning electron microscopy (SEM) techniques. The addition of glass was found not to affect the crystal structure of SnO2, but it increased the densification rate and the grain size of SnO2. The glass additive formed a thin continuous liquid phase and rearranged SnO2 particles into a dense microstructure at much low temperature. Applying the external press during hot pressing also assisted the densification rate of SnO2 and resulted in a relatively small grain size and denser microstructure. The electrical properties of were found to affect by the microstructure of glass doped SnO2 ceramics. At higher glass concentration doping, the possible formation amorphous phase around at grain boundary played a key role on the electrical properties of SnO2 ceramics. Further work on the identification of grain boundary phase is needed to perform as well as chemical composition of SnO2 grains.

博士<br>大同大學<br>材料工程學系(所)<br>98<br>In recent years, luminescent glass materials have attracted great attention, especially application for the solid state laser and amplifier devices. In various glass systems, phosphate glass has been widely studied because of it has high solubility of rare earth and low melting/forming temperatures. Moreover, some literatures reported that formation of microstructure in the glass matrix can change the environment of rare earth (such as in glass and crystalline phase). Photoluminescence intensity can be enhanced due to the light-scattering effect in the microstructural glass, which increases the population of rare earth ion on the high energy level. The purpose of this study is to explore the luminescence characteristic of the microstructural borosilicate and phosphate glasses doped with high content rare earth. The results are as follows: (a) Compositional Dependence of Phase Separation and Photoluminescence in Rare Earths-Doped Sodium Borosilicate Glasses In this study, the effects of the kind of rare earth (Er, Eu, and Nd), rare earth concentration (up to 3 mole%), and P2O5 addition (0 and 2 mole%) on the phase separation, optical absorption, and photoluminescence (PL) of the sodium borosilicate glasses were investigated. It was found that adding P2O5, increasing rare earth content and changing the kind of rare earth can enhance the phase separation of Na2O- B2O3-SiO2 glass. Adding P2O5 results in the simultaneous segregation of rare earth and P in sodium phosphate droplets. As a consequence, rare earth-bearing phosphate crystals developed within the droplets. Development of the droplet phase enhances both the light-scattering effect (enhancing the PL intensity) and the concentration quenching effect (reducing the PL intensity). (b) Compositional Dependence of Phase Separation and Photoluminescence in Er3+-Doped Alkali Borosilicate Glasses In this study, the effects of the kind of alkali (Li, Na, and K), Er2O3 concentration (up to 3 mol%), and P2O5 addition (0 and 2 mole%) on the phase separation, optical absorption, and photoluminescence (PL) of the alkali borosilicate glasses were investigated. The relationship between microstructure and optical properties of the glasses is discussed. It was found that the development of the droplet phase enhances both the light-scattering effect (enhancing the PL intensity) and the concentration quenching effect (reducing the PL intensity). As a result, the variation of the PL intensity of the Er3+ 4I13/2 - 4I15/2 transition with Er2O3 content is mainly caused by the conflict between the light-scattering effect and the concentration-quenching effect. The 1 mole% Er2O3-doped, P2O5-containing, sodium borosilicate glass has the optimum microstructure and thus the highest PL intensity. (c) Effects of Er3+ Doping on the Structure, Thermal Properties, and Crystallization Behavior of SnO-P2O5 Glass In this study, a new type of Er2O3–doped SnO–P2O5 glass with Er2O3 content of 0 – 8 mole% has been obtained. It was found that physical properties, thermal properties, and crystallization behavior of the glass exhibit discontinuities at Er2O3 content of 2 – 4 mole%. It was also noted that reheating the glass at 375°C, which is higher than the dilatometric softening temperature, results in the crystallization of a tin phosphate phase from glass surface when Er2O3 content is ≤ 0.5 mole%, resulting in serious cracking of the glass. Adding more Er2O3 (1 – 8 mole%) totally suppresses the surface crystallization, thus it is helpful to glass shaping processes. (d) Photoluminescence Characteristics of Er3+ Doped and Er3+/Yb3+ Co-Dpoed SnO-P2O5 Glass In this study, effects of Er2O3 (0 – 8 mole%) doping and Er2O3 and Yb2O3 co-doping (total 1 – 7 mole%) on the absorption cross-section, PL, and upconversion intensities of the SnO-P2O5 glass have been investigated. Precipitation of ErPO4 and (Yb, Er)PO4 crystalline phase in the SnO-P2O5 glass matrix when the total rare-earth oxide content is &amp;gt; 4 mole% plays an important role in determining the absorption cross-section, PL, and upconversion intensities. For Er3+-doped glass, the variation of PL characteristic with the Er2O3 content is obviously different from that for general rare-earth-doped glasses. This result is explained in terms of the light-scattering effect caused by the ErPO4 crystals and the constant Er-Er distance in ErPO4 crystals with the increasing Er2O3 content. After co-doping with Yb2O3, the PL intensity of the glass is enhanced by about 14.7 times at the optimum Yb2O3 content of 6 mole% (~1.81×1021 ions/cm3). Further increase in the Yb2O3 content results in the reduction of PL intensity which can be explained in terms of the APTE upconversion effect. (e) Effects of Er3+ Doping on the Structure, Thermal Properties, and Photoluminescence Characteristics of ZnO-P2O5 Glass In this study, Er2O3–doped ZnO–P2O5 glass with Er2O3 content of 0 – 4 mole% has been obtained. It was found that the fraction of Q0 (orthophosphate)-Q1 (pyrophosphate) structure increase in ZnO-P2O5 glass with the Er2O3 content increased. When Er2O3 content is 4 mole%, crystalline particles of ErPO4 have precipitated within the ZnO-P2O5 glass matrix. The physical and thermal properties of the glass linearly increased with increasing Er2O3 content. According to the result, absorption cross-section and PL intensity of the ZnO-P2O5 glass are higher than that of SnO-P2O5 glass, because of the ZnO-P2O5 glass has high ionic packing ratio which reduces the covalency of Er-O bond, and then increases the spontaneous emission probabilities. This result does not conform to the expectation, namely the stimulated emission cross-section of laser glass does not increase with the increasing refractive index.

碩士<br>國立臺灣科技大學<br>機械工程系<br>107<br>This study focuses on a novel microwave dielectric material - diopside (CaMgSi2O6) glass-ceramic. Diopside material has a unique character of low dielectric constant (k), low cost, high quality factor (Qxf value) and lower than 900℃ sintering temperature. Therefore, diopside is a potential candidate material for LTCC (Low Temperature Co-fired Ceramic) process. However, the negative temperature coefficient of resonance frequency (τf) is too large to be applied in microwave dielectric components. In this case, MgTiO3 was chosen to compensate the large negative temperature coefficient of resonance frequency (τf) of diopside glass-ceramics. The as-sintered specimens consist of Mg2SiO4 and CaTiO3, which result in high quality factor and an improved temperature coefficient of resonant frequency, because the Mg2SiO4 and CaTiO3 possess ultra-high Qxf and positive τf characteristics, respectively. In addition, the addition of (Zn(1-x)Mgx)2SiO4 improves crystallinity and quality factor. Followed by this result, the microstructure analysis and electrode inhibition after co-fired with silver and copper electrode were carried out by SEM-EDS in this work. In addition, It appears that this material system can be co-fired with a copper electrode under a reducing atmosphere. In the first part, in order to improve the sintering characteristic of diopside in reducing atmosphere, the addition of ZnO was carried out. The secondary phase Zn2SiO4 with a quality factor of 219,000 GHz is produced. Optimum processing temperature and microstructural development were investigated using heat treatment conditions of annealing from 820℃ to 960℃ for 2hrs. It has a significant quality factor improvement at 840℃, from 7153 to 8163 GHz. In addition, it was found in SEM-EDS that Zn2SiO4 and Mg2SiO4 were revealed in the diopside phase glass ceramics. The second part is to add 8wt% ceramic powder of MgTiO3 and/or 8wt% (Zn0.6Mg0.4)2SiO4 in diopside phase glass ceramics. Adding (Zn0.6Mg0.4)2SiO4 to the diopside phase glass ceramic can improve the quality factor of the dielectric material. We investigate the optimal annealing temperature and microstructures after the specimens were heat treated at a temperature from 820℃ to 960℃ for 2hrs. When 840℃/2hr was adopted, the material gains a significant quality factor increase due to nucleation and growth of the diopside phase glass phase ceramics. After heat treatment at 940℃/2hr, the best dielectrical properties of the material are K:7.133, Qxf: 8893 GHz, τf: -72 ppm /℃. In addition, 8 wt% of the ceramic powder MgTiO3 was added in the diopside phase glass ceramics, and processed at 820 to 900℃ and we observed the densities of the specimens were low. Materials need to be processed at temperatures higher than 900℃ to acquire better properties. From the X-ray mapping and structural analysis, it was observed that secondary phases CaTiO3 and ZnTiO3 was produced. Its best dielectric properties are K:7.813, Qxf: 7186, τf: -50ppm/℃. Electrode diffusion affects the operating frequency and efficiency of the component, and silver ions are oxidized in the sintering process to bond with the glass and diffuse to the diopside glass ceramic substrate, and therefore degrading material properties. We thus add ceramic powders MgTiO3 and (Zn0.6Mg0.4)2SiO4 to suppress elemental diffusion of electrode materials. MgTiO3 can be evenly distributed in the diopside glass ceramics and the particles are small, and effectively block the diffusion of silver ions to the substrate, the effect is better than adding (Zn0.6Mg0.4)2SiO4. In addition, the copper easily reacts with the co-firing substrate. The diopside phase glass ceramic was co-fired with copper under a reducing atmosphere of 960 ° C, and the secondary phase of Ca2CuO3 was observed by XRD analysis, but the secondary phase of Mg2SiO4 that can improve the quality factor. There was no significant diffusion of copper into the substrate under the mapping observation.

碩士<br>國立清華大學<br>材料科學工程學系<br>100<br>Owing to the unique properties, such as excellent mechanical performance, and nano-scale surface roughness, metallic glass can be applied in various novel fields. Meanwhile, the improvement of thermal stability and hardness is the common target in these applications. Minor alloying is an effective method to enhance the thermal and mechanical properties of metallic glasses. Different from elements used to be doped into metallic glass, the role nitrogen atoms play in metallic glass is quite distinct and critically important, owing to its strong electronegativity and small atomic radius. In this work, an alternative class of metallic glass is developed. By adding nitrogen into Zr-Cu-Al-Ag TFMG, the configuration energy of short range structure is greatly modified. From the viewpoint of thermal behavior, the evolution of Tg and elastic modulus with nitrogen could be well correlated, implying significant effect of nitrogen atoms on the potential energy landscape (PEL) of the TFMGs. Besides, more amounts of nitrogen addition lead to the increase of short range order structure in the amorphous matrix. That is, most metallic atoms are strongly attracted by nitrogen, forming the nitrogen-centered cluster, in which more energy is required to cause plastic deformation. On the other hand, a meta-stable state with lower energy is attained as indicated by the much higher Tx than normal Zr-based metallic glasses. However, the amorphicity region of nitrogen in Zr-Cu-Al-Ag metallic glass is not wide enough, restricting the enhancement amount of thermal and mechanical performances. By incorporating Ta firstly, the competing ZrN crystalline phase is destabilized, leading to the wider amorphicity region of nitrogen in Ta-Zr-Cu-Al-Ag TFMG. As a result, hardness over 10 GPa, Tg near 800 K, and supercool liquid region as wide as 112K is achieved in the nitrogen-doped Ta-Zr-Cu-Al-Ag TFMG.

碩士<br>明志科技大學<br>機械工程系機械與機電工程碩士班<br>105<br>In recent years, microwave dielectric materials and components such as filters, resonators, high-frequency antenna, medium antenna, medium guided wave circuit, etc. have been developed rapidly. In addition, high-frequency microwave substrate had been widely applied in different high-frequency communication systems. To effective cost reduction, low temperature co-firing ceramic (LTCC) technology is developed for fabrication of microwave dielectric materials and components. However, the silver diffusion happens easily during sintering for a co-firing with microwave dielectric ceramic and silver electrode. An reduced silver diffusion between microwave dielectric ceramic and Ag-electrode is an important issue for LTCC development. In this work, the low-k microwave materials using x wt% Al2O3 doped CaO-Al2O3-B2O3-SiO2 (x=0~30) (Al2O3 + glass) and x wt% SiO2 quartz (x = 0 ~ 6) doped CaO-Al2O3-B2O3-SiO2 glass were co-fired with silver electrode. The results show that the higher sintering temperature and the longer holding time increase silver diffusion and SiO2 doping can inhibit silver diffusion. the mechanical strength increases to 11.8 kpa and the dielectrical properties including k and Df values are 5.6 and 0.124, respectively. The 6 wt% SiO2 doped CaO-Al2O3-B2O3-SiO2 glass shows a silver diffusion distance ~ 7.8μm, which was shorter than that of 8wt% Al2O3 doped CaO-Al2O3-B2O3-SiO2 glass with a diffusion distance ~ 22.7μm. Meanwhile, the calculation of activation energies for the 8wt% Al2O3 + glass and 6wt% SiO2-8wt%Al2O3 co-doped glass are 296 kJ/mole and 373 kJ/mole, respectively. The CaO-Al2O3-B2O3-SiO2 glass with 6wt% SiO2-8wt%Al2O3 co-doping shows higher activation energy and restricts silver diffusion due to SiO2 addition.

Silver containing chalcogenide glasses have been extensively studied during the last few decades; the main interest in these materials being their electrical conductivity which changes by several orders of magnitude upon silver doping. Glassy chalcogenides doped with silver have applications in optical elements, gratings, micro-lenses, waveguides, bio & chemical sensors, solid electrolytes, batteries, etc. Chalcohalide glasses have become important in the recent times, from both scientific & technological points of view, due to the interesting properties exhibited by these glasses such as the transparency in the infrared region, the stability against devitrification, solubility of rare earth elements, etc. In this thesis work, the thermal properties and electrical switching behavior of certain silver and iodine doped chalcogenide glasses have been investigated The thesis contains five chapters: Chapter 1: This chapter is an introduction to the fundamental aspects of amorphous semiconductors with a particular reference to chalcogenide glasses. The advantages and applications of chalcogenide glasses are also described. Chapter 2: The methods of preparation and characterization of the glasses investigated are described in this chapter. Also, the details of the experiments undertaken, namely temperature modulated Alternating Differential Scanning Calorimetry (ADSC), electrical switching analysis, Photo-thermal Deflection Spectroscopy (PDS), etc, are outlined. Chapter 3: In this chapter, the thermal behavior and electrical switching of silver doped Ge-Se and As-Se chalcogenide glasses are described. Bulk, melt-quenched Se-rich Ge0.15Se0.85-xAgx glasses have been found to be microscopically phase separated and composed of Ag2Se clusters and GeSe2-Se network. When the silver concentration exceeds 10 atom %, the Ag2Se clusters embedded in the GeSe2-Se network percolate. The signature of this percolation threshold is clearly observed as the sudden appearance of two exothermic crystallization peaks in ADSC runs. Density, molar volume and micro hardness studies also strongly support the view of a percolation transition. The super-ionic conduction observed earlier in these glasses at higher silver proportions, is likely to be connected with the silver phase percolation. It has been found that Ge0.15Se0.85-xAgx glasses of lower silver concentration (x = 0.07 and 0.08) do not exhibit electrical switching at voltages up to 1100 V. A negative resistance behavior and threshold type electrical switching is seen in Ge0.15Se0.85-xAgx samples with x 0.09. Also, fluctuations are observed in the I-V characteristics of these samples, which have been attributed to the difference in thermal conductivities between the Ag2Se inclusions and the Ge-Se base glass. A sharp drop has been observed in the switching voltage with Ag concentration which is due to the more metallic nature of silver and the presence of Ag+ ions. Further, the saturation in the decrease of VT around x = 0.10, is related to silver phase percolation in these glasses. Bulk As20Se80-xAgx glasses (0 x 15) have been found to exhibit two endothermic glass transitions and two exothermic crystallization reactions on heating. Based on which it is suggested that As20Se80-xAgx glasses are also microscopically phase separated, containing Ag2Se phases embedded in an As-Se backbone. The occurrence of microscopic phase separation in As20Se80-xAgx glasses is also confirmed by SEM studies. With increasing silver concentration, the Ag2Se phase percolates in the As-Se matrix, with a well-defined percolation threshold at x = 8. This silver phase percolation is exemplified by sudden jumps in the composition dependence of the second crystallization peak and non-reversible heat-flow, Hnr obtained at the second glass transition reaction of As20Se80-xAgx glasses. The super-ionic conduction observed earlier in these glasses at higher silver proportions, is likely to be associated with the observed silver phase percolation. Like Ge0.15Se0.85-xAgx glasses, As20Se80-xAgx glasses also exhibit threshold type electrical switching with fluctuations in the I-V characteristics; these fluctuations have been attributed to the difference in thermal conductivities between the Ag2Se inclusions and the As-Se base glass. A sharp drop has been observed in the switching voltage with Ag concentration which is due to the more metallic nature of silver and the presence of Ag+ ions. Further, the saturation in the decrease of VT around x = 8, is found to be related to silver phase percolation in these glasses, which has been proposed on the basis of ADSC experiments. Chapter 4: The chapter 4 deals with thermal studies, electrical switching investigations and Photo-thermal Deflection Spectroscopic (PDS) measurements on certain Ge-Te-I and As-Te-I chalcohalide glasses. It has been found that the compositional variation of the glass transition temperature of Ge22Te78-xIx glasses, obtained by Alternating Differential Scanning Calorimetry (ADSC), exhibits a broad hump around 5 atom % of iodine. Further, a sharp minimum is seen in the composition dependence of non-reversing enthalpy (Hnr) of Ge22Te78-xIx glasses at x = 5, which is suggestive of a thermally reversing window at this composition. Electrical switching studies on Ge22Te78-xIx glasses indicate that these glasses exhibit memory type electrical switching. At lower iodine concentrations, a decrease is seen in switching voltages with an increase in iodine content (in comparison with the base Ge22Te78 glass), which is due to the decrease in network connectivity. The increase seen in switching voltages of Ge22Te78-xIx glasses at higher iodine contents, suggests that the influence of the metallicity is stronger at higher iodine proportions. It is also interesting to note that the composition dependence of the threshold voltages shows a slope change at x = 5, the inverse rigidity percolation threshold of the Ge22Te78-xIx system. . Further, it is found that the thermal diffusivities ( D) of Ge22Te78-xIx glasses decrease with the increase in iodine content, which has been understood on the basis of fragmentation of the Ge-Te network with the addition of iodine. Also, a cusp is seen in the composition dependence of thermal diffusivity at the composition x = 5 (average coordination number, r = 2.39), which has been identified to be the inverse rigidity percolation threshold of the system at which the network connectivity is lost. ADSC studies on As45Te55-xIx chalcohalide glasses (3 x 10) reveal that there is not much variation in the glass transition temperature of As45Te55-xIx glasses, even though there is a wide variation in r . Based on this observation we suggest that the variation in glass transition temperature of network glasses is dictated by the variation in average bond energy rather than the average coordination number. Further, the non-reversing enthalpy Hnr of As45Te55-xIx glasses is found to exhibit a sharp minimum at the composition x = 6. A broad hump is also seen in glass transition and crystallization temperatures in the composition range 5 x 7. These results indicate a narrow thermally reversing window in As45Te55-xIx glasses around the composition x = 6. As45Te55-xIx glasses have been found to exhibit a memory to threshold type change in switching behavior with iodine content (x 6), which has been understood on the basis of the sharp increase in thermal diffusivity above x = 6. It is also observed that the switching voltages do not change appreciably with composition/average coordination number. Though no pronounced signature of a stiffness transition is seen in the variation with composition of VT, fluctuations are seen in the switching voltages around x = 6, the composition corresponding to the sharp thermally revering window. PDS studies indicate that the thermal diffusivities () of As45Te55-xIx chalcohalide exhibit a sharp minimum at the composition x = 6. This result reasserts the presence of a sharp thermally reversing window in As45Te55-xIx glasses around the composition x = 6. Chapter 5: The significant results obtained in the present thesis work have been summarized in this chapter. Further, the scope for future work is also presented.