Papers by Keyword: High Dielectric Constant

Abstract: xBaZn₂Ti₄O₁₁–(1-x)BaNd₂Ti₄O₁₂ (x = 0.18–0.30) ceramics were prepared by solid-state reaction method and their microwave dielectric properties were investigated with the purpose of finding a microwave ceramics with high dielectric constant (ε_r), high quality factor (Q×f ) and zero temperature coefficient of resonant frequency (τ_f).The two phase system BaZn₂Ti₄O₁₁–BaNd₂Ti₄O₁₂ affected the unit cell volume and the microstructure, the microwave dielectric properties (ε_r, Q×f, τ_f). As increasing x from 0.18 to 0.30, the main phase composition was BaNd₂Ti₄O₁₂. Therefore, the ε_r decreased from 64.9 to 60.3 and the Q×f values raised from 11,350GHz to 13,210GHz, and the τ_f values decreased from 7ppm/° to -5ppm/°.The 0.22BaZn₂Ti₄O₁₁–0.78BaNd₂Ti₄O₁₂ ceramics sintered at 1250°C for 4 h displayed the best dielectric constant ε_r,Q×f and τ_f, as 63.9, 12380 GHz and-0.1 ppm/° respectively.

Abstract: Silver nanowires–epoxy composites were prepared via cryomilling dispersion and hot-press forming process. The microstructure of the silver nanowires was studied by SEM. Dependence of dielectric properties of the composites on volume fraction of silver nanowires and frequency was investigated RF impedance material analyzer. The percolation threshold of the composites was 0.16, the value of the dielectric constant of the composite was as high as 100.

Abstract: Polymer-ceramic composites have been pursued as the most promising dielectric materials for embedded capacitors in the organic package. In this study, ceramic fillers such as Calcium Copper Titanate (CCTO) was used to produce epoxy thin film composites for the purpose to replace capacitor made of ceramic materials. Spin coating technique was used to produce epoxy thin film composites. The effect of fillers loading on tensile and dielectric properties of the epoxy thin film composites were determined. Results showed that epoxy thin film with 20 vol% filler loading showed good dielectric properties. However, an increase of the fillers content caused reduction in the tensile properties due to filler agglomeration and voids. Dielectric constants and dielectric losses of epoxy/inorganic composite films generally increase with addition of filler.

Abstract: The microstructure and dielectric properties of the graphene–epoxy composites prepared by cryomilling at liquid nitrogen temperature were studied by SEM and RF impedance material analyzer. The result indicated that both the dielectric constant and conductivity of the composites increased with the increase of the graphene content. The value of the dielectric constant of the composite with about 8 wt % of graphene was as high as 200. Moreover, the frequency dispersion behaviors of the conductivity within a certain frequency range accorded with the Jonscher's power law demonstrating that the conductive mechanism is hopping conduction. The negative reactance decreased with the increase of the testing frequency which indicated a capacitive character

Abstract: First main problem of the high dielectric polymer matrix composites, and discusses the research advances of ferroelectric ceramics, conductive particles (metal particles, graphite, carbon nanotube) modified high dielectric electric composite materials; highlights phthalocyanine, polyaniline modified organic high dielectric composites, discusses the main problems, and pointed out that to improve the dielectric constant, energy density, reduce the dielectric loss, and reduce the preparation cost is the future direction of development.

Abstract: To improve the electrical and physical properties of as-deposited BSTZ thin films, the oxygen plasma treatment process were used by a low temperature treatment. In this study, the BSTZ thin films were post-treated under 150°C and 25 mTorr in the inductively coupled plasma. After oxygen plasma process treatment, the capacitance of thin films increased from 150 to 300pF in C-V curves, and the passivation of oxygen vacancy and defect in leakage current density curves were found. The influence of oxygen plasma on the chemical bonding state and crystalline structure was investigated by using XPS and XRD measurement.

Abstract: In this study, we hoped to find the single-phase high dielectric FET gate-used ceramic materials, which will be used in the sputtering method and have the dielectric constants higher than those of SiO2 and Si3N4. TiO2, La2O3 and ZrO2 are mixed with SiO2 to format the (1-x) TiO2-x SiO2, (1-x) ZrO2-x SiO2 and (1-x) La2O3-x SiO2 compositions, where x is dependent on the different raw materials. The all compositions are calcined at 1100oC and sintered at 1400oC~ 1550oC for 2hrs, and the X-ray patterns are used to find the crystal phases of all sintered ceramics. Because of the existence of single-phase, the sintering and dielectric characteristics of 0.3 La2O3-0.7 SiO2 ceramic are further developed.

Abstract: Sr(Bi1-xSmx)8Ti7O27 ceramics were prepared by Sm2O3-substitution for Bi2O3 through solid-state reaction route. The dielectric properties of the sintered bodies such as er, Q and tf were investigated. The ceramics were characterized by SEM, XRD, DTA and TG, which behaved high dielectric constant of 128 ~154 at the frequency of 10 GHz.