Papers by Author: Xiao Hui Wang

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Authors: Jun Jie Hao, Xiao Hui Wang, Jian Ling Zhao, Long Tu Li
Abstract: Textured bismuth titanate ceramics were successfully produced by spark plasma sintering, using plate-like Bi4Ti3O12 particles prepared by a molten salt method. The microstructure and electric properties of the samples were investigated. The results show that the textured Bi4Ti3O12 ceramics electric property is anisotropic in different direction, and spark plasma sintering is an effective sintering technology to get textured dense Bi4Ti3O12 ceramics at a low temperature.
Authors: Lei Chen, Xiao Hui Wang, Long Tu Li, Zhi Lun Gui
Abstract: Titanate ferroelectric materials play more and more important roles in electronic industry due to their particular performances, so the synthesis of ultra-fine ferroelectric powder with high purity is the key issue to improve the performance of electronic components. In this paper, Ba(Ti0.85Zr0.15)O3 nano-powder with perovskite structure and homogeneous granularity was prepared by oxalate precipitation method, the particle size of the powder calcined at 800oC is about 50 nm. The sintering ability of the powder is excellent so that the compact ceramics can be obtained at sintering temperature of 1200°C, which is much lower than that of the powder prepared by the conventional solid method. With the powder prepared by oxalate precipitation method, we developed an ultrafine-grained dielectric material showing Y5V characteristics with the room temperature dielectric constant over 14,000, which can be used in base metal electrodes multilayer chip capacitors.
Authors: Long Tu Li, Tian Wang, Xiao Hui Wang, Jing Chang Zhao, Xian Li
Abstract: Dielectric characteristics of strontium titanate based ceramics doped with samarium were investigated within temperature range from –60oC to 150oC. XRD was used to identify the phase compositions of the ceramics and the microstructures were characterized by SEM. Good temperature coefficient of capacitance (TCC) was observed: TCC = +18% ~ −11% with high dielectric constant of 18000 and relative low dielectric loss. After further modification, the present ceramics might be promising candidates for the multilayer ceramic capacitors applications at high temperature.
Authors: Xiang Yun Deng, Bao Rang Li, Xiao Hui Wang, Long Tu Li, Zhi Lun Gui
Abstract: SrBi2Nb2O9 (SBN) with different Bi2O3 contents were prepared by solid-state reaction method and then spark plasma sintering. The Influence of Bi2O3 on the properties of SBN was studied. The results showed that the increased Bi2O3 contents can enhance densification and improve the dielectric properties. This might have close relation to the low melting point of Bi2O3 and special sintering way of SPS, which usually results in some change in micro-structure.
Authors: Yi Chi Zhang, Xiao Hui Wang, Jin Yong Kim, Long Tu Li
Abstract: Dispersion plays an important role in aqueous chemical coating process for the preparation of BaTiO3 based next generation BME MLCC powder, since it affects coating coverage and layer morphology of the BaTiO3 particles as well as the microstructure and dielectric properties of the ceramics. In this paper, Poly (acrylic acid-co-maleic acid) (PAM) is used as dispersant, its content influences are carefully investigated. It is known that low content of dispersant leads to not only poor dispersion, low coverage and irregular coating layer of BaTiO3 particles, but also bad temperature coefficient of capacitances and inhomogeneous microstructure of the resultant BaTiO3 ceramics, while excessive dispersant deteriorates the microstructure and performance by reducing the density of ceramic. With proper dispersant content, the particles are dispersed and coated perfectly, finally the dense X7R-satisfied ceramic are obtained with average grain size 103nm and fine microstructure, meeting the requirement of next generation MLCCs.
Authors: Han Wang, Xiao Hui Wang, Shao Peng Zhang, Long Tu Li, Zhao Hui Huang
Abstract: In this paper, the effect of gel-calcination on piezoelectric property in (1-x) BiScO3-xPbTiO3 with the composition of x=0.635 is investigated. According to previous work, the heating rate of 200°C/h and holding for 210min having been taken as the basic processing condition. The BSPT powders were obtained from the same sol solution but calcined at different temperatures, and then the powders were used to prepare BSPT ceramics. The result shows that for the bulk ceramics with higher relative density ( higher than 95%), with the increasing calcining temperature of the gel (from 420°C to 500°C), the piezoelectric coefficient d33 of ceramic specimens first increases to maximum of 636pC/N at 450°C, then shows a fluctuation. In this work how the powder activity and the grain size affect (which was leaded by powder particle size) piezoelectric properties of BSPT ceramics are discussed.
Authors: Lei Chen, Xiao Hui Wang, Long Tu Li, Zhi Lun Gui
Abstract: In this paper, the influence of nickel (Ni) nano-powders addition on the microstructures and dielectric properties of Ba(Ti,Zr)O3 based Y5V non-reducing ceramics were investigated. The X-ray diffraction (XRD) analysis indicated that the primary phase was Ba(Ti,Zr)O3 and no Ni phase appeared until the amount of Ni exceeded 5mol%. Scanning electron microscope (SEM) observation showed that the Ni particles distributed homogenously throughout BTZ ceramic matrix. The incorporation of Ni altered the perovskite lattice parameters and thus led to the change of polarization degree under electric field and the improvement of the dielectric constant at Curie temperature.
Authors: Tian Wang, Xiao Hui Wang, Guo Feng Yao, Yi Chi Zhang, Xun Xun Liao, Gang Yang, Tae Ho Song, Long Tu Li
Abstract: Ultrafine-grained ceramics based on nano-scale barium titanate for BME-MLCC applications have been prepared. Relationships of milling time, microstructures and dielectric properties have been investigated. With processing selected carefully, the present ceramics show ultrafine grain size (180nm) and homogeneous microstructures, well with high dielectric constant (ε25=2550), low dielectric loss (<0.02), high resistivity, high breakdown field and X7R temperature specifications, which would be promising materials for the next generation BME-MLCC applications.
Authors: Ren Zheng Chen, Xiao Hui Wang, Jian Ling Zhao, Jun Jie Hao, Zhi Lun Gui, Long Tu Li, Li Zhang
Abstract: The effect of rare earth oxides (Y2O3 and Dy2O3) on the microstructure and electrical properties of the X7R-type ceramics for base metal internal electrode multilayer ceramic capacitor (BME-MLCC) was investigated. As the amount of Y increased, the dielectric constants and the dielectric losses increased, while the temperature coefficient of capacitors (TCC) curve rotated in counterclockwise direction. On the contrary, the dielectric constants decreased with Dy, and the TCC curve remained the same. The grain growth can be inhibited by the Dy2O3, concluded from XRD analysis. The different influences on dielectric properties between Y2O3 and Dy2O3 were discussed by defect chemistry. Y3+ acted as acceptor, performing B-site substitution, while Dy3+ showed the amphoteric behavior. By optimizing appropriate qualities of Y2O3 and Dy2O3, the most-compatible composition for BME X7R ceramics can be obtained.
Authors: Ren Zheng Chen, Xiao Hui Wang, Long Tu Li, Zhi Lun Gui
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