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Liu M.,Wuhan University of Technology | Hao H.,Wuhan University of Technology | Chen W.,Wuhan University of Technology | Zhou D.,Wuhan University of Technology | And 6 more authors.
Ceramics International | Year: 2015

The typical "core-shell" structure in BT ceramics can easily obtain double dielectric anomalies, which greatly improve the dielectric temperature stability for multilayer ceramic capacitors. In this paper, BaTiO3 particles were coated with 0.3BiAlO3-0.7BaTiO3 shell [xBT@(0.3BA-0.7BT)] by a sol-gel method. Core-shell structure was proved to exist in ceramic grains by transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). High-temperature X9R dielectrics were obtained when x=0.3 and 0.2, with a high dielectric constant (~1200) and low dielectric loss (<2.0%). Furthermore, the impedance data was fitted by an effective 4RC equivalent circuit, which could be assigned to the core, the shell, the grain boundary, and the ceramic/internal electrode interface regions. The activation energy of the core was found to decrease with x decreasing, while opposite tendency exists in the shell and the grain boundary. © 2015 Elsevier Ltd and Techna Group S.r.l. Source


Ye J.,FuJian Torch Electronic Technology Co.
Yadian Yu Shengguang/Piezoelectrics and Acoustooptics | Year: 2011

The chemical corrosion of BaNd2Ti4O12 multi-layer ceramic capacitors (MLCC) in the mixture of acid solution were investigated. The corrosion of ceramic was accelerated with increasing the concentration and/or high temperature of the acid solution as wellas the corrosion time. The solution temperature showed more effective than other two factors. The BaNd2Ti4O12 intercrystalline could not be etched as the HF was used instead of HNO3 in acid mixture. The optimized corrosion condition was as fellows: The 100 mL chemical solution composed of 3 mL HF (40%) and 12 mL HCl, and the ceramic sample was dipped in the 60°C solution for 30 s. Source


Wang M.-J.,Zhejiang University | Yang H.,Zhejiang University | Yang H.,Zhejiang California International NanoSystems Institute | Zhang Q.-L.,Zhejiang University | And 4 more authors.
Materials Research Bulletin | Year: 2014

The microstructures and dielectric properties of Y-Mg-Ga-Si co-doped barium titanate ceramics were investigated. Y3+dissolved in the lattice of BaTiO3replacing both Ba2+site and Ti4+site, and Mg2+replaced Ti4+site. The replacements of Y3+and Mg2+inhibit the grain growth, cause tetragonal-to-pseudocubic phase transition, reduce the dielectric loss, and flatten the temperature dependence of capacitance curve. The incorporation of Ga3+can improve sintering and increase permittivity. Y3+and Ga3+tended to remain close to the grain boundaries, and play an important role as a shell maker in the formation of the core-shell structure in the co-doped BaTiO3ceramics. Excellent dielectric properties: εr= ∼2487, tanδ = ∼0.7% (at 1 kHz), ΔC/C25< ∼6.56% (from -55 °C to 125 °C) and alternating current breakdown voltage E < ∼4.02 kV/mm can be achieved in the BaTiO3-0.02Y2O3-0.03MgO-0.01Ga2O3-0.005SiO2ceramics sintered at 1380 °C. This material has a potential application in alternating current multilayer ceramic capacitor. © 2014 Elsevier Ltd. All rights reserved. Source


Wang M.-J.,Zhejiang University | Yang H.,Zhejiang University | Yang H.,Zhejiang California International NanoSystems Institute | Zhang Q.-L.,Zhejiang University | And 4 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2014

The doping behaviors of yttrium, zinc and gallium and their effects on the dielectric properties and microstructures of BaTiO3 were investigated. Y3+ dissolved in the lattice of BaTiO3, replacing both Ba2+ site and Ti4+ site; while Zn 2+ and Ga3+ tended to occupy Ti4+ site. Compared with Y2O3 and Ga2O3, ZnO suppressed grain growth of BaTiO3 more effectively and promoted greater uniformity of grains, thus reducing the dielectric loss. The addition of Ga2O3 inhibited the appearance of second phase Y 2Ti2O7 and enhanced the sinterability, which was ascribed to the compensation mechanism and synergistic effect. Proper amount of Y2O3, Ga2O3 and ZnO significantly improved the dielectric temperature characteristics due to the formation of the core-shell structure in the codoped BaTiO3 ceramics. High performance dielectrics with εr of 2,690, tanδ of 1.0 % (at 1 kHz), and alternating current breakdown voltage E > 3.73 kV/mm, were achieved. © 2014 Springer Science+Business Media New York. Source


Wang M.-J.,Zhejiang University | Yang H.,Zhejiang University | Zhang Q.-L.,Zhejiang University | Yu D.,Zhejiang University | And 3 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2014

The effects of LiF addition on phase evolution, microstructure and dielectric properties of BaTiO3 based ceramics were investigated. The LiF addition lowered the sintering temperature of BaTiO3 based ceramics effectively from 1,380 to 1,100 °C. Orthorhombic-to-pseudocubic phase transition appeared as increasing sintering temperature or LiF content. Li+ dissolved in the lattice of BaTiO3, replaced Ti4+ site, produced oxygen vacancies and further inhibited the grain growth. F− entered into O2− site, might cause weakening of oxygen bond strength, together with the low-melting-point liquid phase sintering of LiF, facilitated the formation of uniform dense and fine-grained structure and maintained good dielectric properties. Samples with 2 wt% LiF sintered at 1,100 °C showed excellent dielectric properties: εr = 1,956, tanδ = 0.8 % (at 1 kHz), ΔC/C25 < 10.44 % (−55–125 °C) and alternating current breakdown voltage E > 4.50 kV/mm. © 2014, Springer Science+Business Media New York. Source

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