Academic literature on the topic 'IBLC (internal barrier layer capacitance)'

CaCu3Ti4O12(CCTO) is well known to have colossal dielectric constant in the range of 105.It is widely accepted that this phenomenon may be attributed to internal layer barrier capacitance (IBLC) model. The dielectric properties of CCTO were reported to be strongly dependent on the processing conditions and grain size. In this work, CCTO samples with different grain sizes were produced by varying sintering temperature in order to investigate IBLC effect on dielectric properties of CCTO. The samples were sintered at four different temperatures, (T=1100°C, 1050°C, 1000°C and 950°C). Dielectric measurements were carried out for the samples in the frequency range of 102– 106Hz using impedance spectrometer. Electron micrographs showed that increasing temperature promoted the grain growth of CCTO while sintering. The internal crystalline defects are seen to play major role by increasing the grain conductivity in dipole formation and increased the dielectric constant of the samples.

CaCu3Ti4O12(CCTO) is a cubical perovskite phase and sintered ceramics exhibit very high dielectric constant at room temperature. The speculated origins of the high dielectric constant are the existence of insulative barrier layer at grain boundaries and domain boundaries which created an internal barrier layer capacitance (IBLC) at the microstructure of CCTO. The relation of grains and domains electrical resistance were studied in this work by using impedance spectroscopy (IS). A series of samples with different heat treatment temperature were tested to investigate their microstructure by using field emission scanning electron microscopy (FESEM). The grains and domains resistance was calculated from a wide frequency range of impedance complex plane measurement (100 Hz to 1 GHz). The FESEM and IS analyses showed the dependency of grains and domains resistance to average grains size of CCTO microstructure.

This paper reports on synthesis of polycrystalline complex perovskite CaCu3Ti4O[Formula: see text] (as CCTO) ceramic powders prepared by a sol–gel auto combustion method at different sintering temperatures and sintering times, respectively. The effect of sintering time on the structure, morphology, dielectric and electrical properties of CCTO ceramics is investigated. Tuning the electrical properties via different sintering times is demonstrated for ceramic samples. X-ray diffraction (XRD) studies confirm perovskite-like structure at room temperature. Abnormal grain growth is observed for ceramic samples. Giant dielectric permittivity was realized for CCTO ceramics. High dielectric permittivity was attributed to the internal barrier layer capacitance (IBLC) model associated with the Maxwell–Wagner (MW) polarization mechanism.

The CaCu3Ti4O12 samples with slight amount of doped bismuth were prepared and tested in this research. No second phase with bismuth was found in the doped samples. It was inferred that the bismuth ions has entered the lattice and take the place of the calcium ions. The grain size was diminished with the increase of the bismuth content. The bismuth atoms can inhibit the grains from growing large, and it could be used to modify the microstructure of CaCu3Ti4O12 ceramic. The reduction of the grain size resulted in the decrease of the relative dielectric constant, according to the “internal barrier layer capacitance (IBLC)” theory. The impedance measurements showed that the doped samples have less conductivity and lower potential barrier at the grain boundaries, and the substitution of the bismuth ions on the calcium cites might be the reason for it. As a result of the lowered potential barrier, the non-ohmic I-V property of the CaCu3Ti4O12 ceramic almost disappears in the doped ones.

Colossal permittivity (CP) in BaTiO3(BT)-based polycrystalline ceramics with normal grain sizes has been successfully obtained in yttrium (Y) doped BT ceramics (BYT) via a simple and effective method. Considering the necessary factors for CP formation mechanism, well designed doping condition and sintering procedure were carried out in the sample preparation. Characterizations show that BYT is with a pure tetragonal perovskite structure and the grain growth is depressed under the action of Y donor doping. The frequency independence of permittivity and Debye-like relaxation related to Maxwell-Wagner relaxation which occurred at the interfaces between semiconducting grains and insulating grain boundaries can be detected. These are induced by an internal barrier layer capacitance (IBLC)-type structure which formed under an overall and carefully designed synthesis procedure. But the temperature independence of permittivity does not arise because of the particular tetragonal structure and micron dimension grain sizes of BYT.

Purpose The work was aimed at preparation of green tapes based on a new material Bi2/3CuTa4O12, to achieve spontaneously formation of an internal barrier layer capacitor (IBLC), fabrication of multilayer elements using low temperature cofired ceramics (LTCC) technology and their characterization. Design/methodology/approach The study focused on tape casting, lamination and co-sintering procedures and dielectric properties of Bi2/3CuTa4O12 multilayer capacitors. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies of the ceramic elements were performed. Impedance spectroscopy was used for characterization of dielectric properties in the frequency range of 0.1 Hz to −2 MHz and in the temperature range from −55 to 400°C. DC conductivity was investigated in the temperature range 20 to 740°C. Findings SEM observations revealed a good compatibility of the applied commercial Pt paste with the ceramic layers. The EDS microanalysis showed a higher content of oxygen at grain boundaries. The dominant dielectric response, which was recorded in the low frequency range and at temperatures above 0°C, was attributed to grain boundaries. The dielectric response at low temperatures and/or high frequencies was related to grains. The fabricated multilayer capacitors based on Bi2/3CuTa4O12 exhibited a high specific capacitance. Originality/value A new material Bi2/3CuTa4O12 was applied for preparation of green ceramic tapes and utilized for fabrication of multilayer ceramic capacitors using the LTCC technology. This material belongs to the group of high permittivity nonferroelectric compounds with a complex perovskite structure of CaCu3Ti4O12, that causes the spontaneously formation of IBLCs.

Nanocrystalline powders of giant dielectric constant material, CaCu3Ti4O12 (CCTO), have been prepared successfully by the molten salt synthesis (MSS) using KCl at 750 °C/10 h, which is significantly lower than the calcination temperature (∼1000 °C) that is employed to obtain phase pure CCTO in the conventional solid-state reaction route. The water washed molten salt synthesized powder, characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) confirmed to be a phase pure CCTO associated with ∼150 nm sized crystallites of nearly spherical shape. The decrease in the formation temperature/duration of CCTO in MSS method was attributed to an increase in the diffusion rate or a decrease in the diffusion length of reacting ions in the molten salt medium. As a consequence of liquid phase sintering, pellets of as-synthesized KCl containing CCTO powder exhibited higher sinterability and grain size than that of KCl free CCTO samples prepared by both MSS method and conventional solid-state reaction route. The grain size and the dielectric constant of KCl containing CCTO ceramics increased with increasing sintering temperature (900 °C–1050 °C). Indeed the dielectric constants of these ceramics were higher than that of KCl free CCTO samples prepared by both MSS method and those obtained via the solid-state reaction route and sintered at the same temperature. Internal barrier layer capacitance (IBLC) model was invoked to correlate the observed dielectric constant with the grain size in these samples.

La problématique des condensateurs céramiques à très hautes performances est récurrente dansde nombreux secteurs de l’énergie électrique. Elle prend toute son acuité en microélectronique « nomade», où les circuits doivent être de plus en plus miniaturisés. Ces condensateurs, peuvent occuperjusqu’à 50 % de l’espace sur le circuit imprimé, réduire leurs dimensions devient donc un impératif.Dans ce contexte de nouveaux matériaux à permittivité colossale ont été découverts, commepar exemple CaCu3Ti4O12 (CCTO). Le mécanisme IBLC (Internal Barrier Layer Capacitance),décrivant des grains semi-conducteurs et des joints de grains isolants, permet aujourd’hui d’expliquerces fortes permittivités. Cependant l’origine de la semi-conductivité des grains ainsi quele caractère isolant des joints de grains donne encore matière à controverse. Ce travail a donc undouble objectif, d’une part concevoir un matériau possédant des propriétés diélectriques similairesà CCTO, et d’autre part comprendre les différents mécanismes responsables de ces permittivitésexceptionnelles. La première partie de ce manuscrit présente les caractéristiques d’usages descondensateurs, elle à également pour objectif de lister les mécanismes qui ont été proposés parla communauté scientifique pour tenter d’expliquer la forte permittivité de CCTO. La deuxièmepartie présente d’une part les techniques de caractérisations qui ont été utilisées pour analyserles composés présentés dans ce manuscrit, en insistant plus particulièrement sur la spectroscopied’impédance, largement utilisée dans cette étude. Elle présente d’autre part les techniques de synthèsesqui ont été expérimentées pour synthétiser un nouveau matériau à permittivité colossale :Ba4YMn3O11,5±δ. Les caractérisations structurale et micro-structurale de Ba4YMn3O11,5±δ serontévoquées dans la troisième partie de ce manuscrit. Enfin, les diverses optimisations qui ontété réalisées sur Ba4YMn3O11,5±δ, pour tenter d’améliorer ces propriétés diélectriques, serons évoquées.Nous détaillerons dans cette dernière partie les substitutions ayant été réalisées sur le sitedu baryum et du manganèse, ainsi que la création d’une phase possédant un cation différent del’actuel yttrium et présentant également des propriétés diélectriques très intéressantes
The problem of ceramic capacitors with very high performance is recurrent in many areas ofElectrical Energy. It takes all its acuteness in « nomadic » microelectronics (cell phone, tablet, mp3player...) where the circuits must be increasingly miniaturized. These capacitors can take up to50 % of the space on the PCB, reducing their size becomes an imperative. In this context newmaterials with colossal permittivity were discovered, such CaCu3Ti4O12 (CCTO). The mechanismIBLC (Internal Barrier Layer Capacitance), describing semiconductor grains and insulating grainboundaries can now explain these high permittivities. However, the origin of the semiconductivitygrains and the insulating character of grain boundaries give even controversial. The aim is thus twofold,on one hand to synthesize a material possessing similar dielectric properties to CCTO, and onthe other hand to understand the various mechanisms responsible for these exceptional permittivity.The first part of this thesis presents various characteristics of capacitors uses, it also aims to listthe mechanisms that have been proposed by the scientific community to try to explain the highpermittivity of CCTO. The second part presents firstly the characterization techniques whichwere used to analyze all the compounds described in this manuscript, with particular emphasison impedance spectroscopy. It presents on the other hand synthesis techniques that have beentried to synthesize a new material with colossal permittivity : Ba4YMn3O11,5±δ. Structural andmicro-structural characterizations of Ba4YMn3O11,5±δ will be discussed in the third part to themanuscript. Finally, the various optimizations that were performed on Ba4YMn3O11,5±δ, to try toimprove the dielectric properties, will be discussed. We detail in this last part substitutions havingbeen made on the site of barium and manganese and the creation of a phase having a differentcation in the present yttrium site and having dielectric properties very interesting also