Papers by Author: Xiang Yun Deng

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Authors: Jian Shao, Xiang Yun Deng, Xiao Long Zhang
Abstract: Lead-free (Ba0.97Ca0.03) (Zr0.18Ti0.82) O3 (BCZT) ceramic is prepared by sol-gel technique. The sample shows a pure perovskite structure through the XRD pattern. Well-developed grain morphology and a dense microstructure are acquired at an optimistic sintering temperature (~1330°C). The BCZT ceramic shows a surprisingly high piezoelectric coefficient of d33=675 pm/V. The switching current curves are acquired in the different external fields by TF-2000 Ferroelectric Analyzer. It is found that with increasing the temperature, there is a decrease in the coercive field (Ec), and with increasing the electric field, there is an increase in the switching current obviously. Sintering temperature has an effect on switching current. The effect of temperature and electrical field on switching current is analyzed from viewpoint of the energy.
Authors: Li Ming Wang, Xiang Yun Deng, Hai Tao Zhang, Jian Bao Li, Di Chen, Ri Ke Chen, Guo Qing Zhang, Kui Fan Su, Chun Peng Wang
Abstract: Barium titanate (BaTiO3) ceramics with grain size varied from 1000 to 8 nm were prepared by two step sintering method (TSS) and spark plasma sintering (SPS), respectively. Mixture structures of BaTiO3 ceramics were proved by in-situ temperature high resolution x-ray diffraction. Multiple ferroelectric domains present in nano-crystalline BaTiO3 ceramics were observed by transmission electron microscope. The evolution of phase transitions supported the existence of intrinsic mechanism. Dielectric loss of fine grain size BaTiO3 was higher than coarse grain size during Curie phase transition due to diffuse phase transition and grain boundary effects.
Authors: Xin Guan, Xiang Yun Deng, Jian Hao, Guang Hao Sun, Chuang Jun Huang
Abstract: Barium calcium titanate (Ba0.96Ca0.04)(Zr0.05Ti0.95)O3 ferroelectric ceramics were prepared by sol–gel technique. The ceramics were sintering at 1290°C-1370°C. X-ray diffraction was employed to investigate the microstructure, and the surface topography was investigated by SEM graphs. The dielectric constant vs temperature was measured by Temperature dielectric spectrometer, and TF Analyzer 2000 measured the ferroelectric properties. It can be found that all the ceramics show pure perovskite structure suggesting that solid solution were formed. SEM showed that the samples uniform in grain size at 1330 °C. Our study revealed that when the sintering temperature is 1330 °C the maximum dielectric constant was 29,600, the maximum piezoelectric coefficient d33 could reach 399pm/V and the remanent polarization (Pr) was 8.3 μc/cm2, respectively.
Authors: Yan Jie Zhang, Wei Guo Fu, Xiang Yun Deng, Ren Bo Yang, Zhong Wen Tan, Li Ren Han, Cheng Lu, Xiao Fen Guan
Abstract: Hysteresis loop and dielectric properties of lead-free BaTiO3-La2O3 piezoelectric ceramics and BaTiO3 ceramic compared with pure BaTiO3 has been systematically studied. The amount of La2O3 addition ranged from 0.3~0.5mol% by controlling the sintering temperature. Dielectric properties of BaTiO3-La2O3 were promoted after the addition of La2O3, the maximum value of dielectric constant reached 8,624, recently. The role of La2O3 on the solid-state sintering of BaTiO3 is discussed on the basis of the solid-solution defect model.
Authors: Hai Tao Zhang, Xiang Yun Deng, Xin Zheng Wu, Ri Ke Chen
Abstract: Highly-ordered titania nanotube arrays were fabricated in ethylene glycol polar organic electrolyte containing a certain amount of sodium fluoride. Series of patterned nanotube arrays with different outside diameter and aspect ratio were obtained via optimizing anodic voltage, the concentration of fluoride ion and reaction time. The as-prepared nanotube arrays were amorphous and transformed single anatase phase characterized by X-ray diffraction with annealing under the condition of 450oC for 3h. Cyclic voltammogram behaviors were discussed using electrochemical workstation. The pH value of electrolyte, the scanning rate, the crystal structure and morphology of the samples have a significant effect on the reductive/oxidative and H+ intercalation properties.
Authors: Ya Ni Jing, Cheng Ying Bai, Wen Kai Jiang, Xin Xing Liao, Xiang Yun Deng, Jian Bao Li
Abstract: The porous SiC-cordierite ceramics were prepared from SiC, calcined kaolin, talc, aluminum hydroxide, and graphite as pore-forming. The influence of pore-forming agent contents and sintering temperatures on the porosity and flexural strength of porous SiC-cordierite ceramics were investigated. The grain phases and the fracture surface micrograph were analyzed with XRD and SEM, respectively. The results show that the sample sintered at 1350°C for 3h with 15% graphite as the pore-forming agent exhibits the most excellent properties: flexural strength of 63.74MPa was achieved at a porosity of 31.80%.
Authors: Yi Shan Wang, Xiang Yun Deng, Yan Jie Zhang, Ren Bo Yang, Li Ren Han, Chuan Fang Wang, Xue Liang Yang, Xiao Long Zhang, Jia Liu, De Jun Li
Abstract: The different concentration La2O3-doped BaTiO3 ceramics were prepared by sol-gel method. The ferroelectric and dielectric properties of the ceramics are characterized by TF analyzer 2000. With the increased amount of La2O3-doped, the dielectric constant increase gradually, when the sintering temperature is 1250 °C, the dielectric constant has reached 4648 for La2O3 with 0.4%-doped. With the temperature increased the dielectric constant of La-BaTiO3 increase gradually, when the sintering temperature is 1290 °C, the dielectric constant has reached 7066 for La2O3 with 0.4%-doped.
Authors: Zhong Wen Tan, Wei Guo Fu, Xiang Yun Deng, Ren Bo Yang, Xiao Fen Guan, Cheng Lu, Yan Jie Zhang, Li Ren Han
Abstract: The(1-x)BaTi0.8Zr0.2O3-xBa0.7Ca0.3TiO3 ceramics have been prepared by sol-gel technique, where x is from 0.2 to 0.6. It reveals that the dense ceramics can be obtained when the sintered temperature is above 1250°C. It is lower than that of solid state reaction ceramics. In particular, when x=0.3, at which is near the MPB composition, the ferroelectric and piezoelectric properties are more excellent than the others. The maximum dielectric constant is above 9000, which can be observed in the butterfly shape curves of dielectric constant as a function of electric field. The maximum piezoelectric coefficient d33 can reach 400 pm/V, and it is obtained from the piezoelectric response loops.
Authors: Li Ren Han, Wei Guo Fu, Xiang Yun Deng, Xiao Fen Guan, Zhong Wen Tan, Cheng Lu, Ren Bo Yang, Yan Jie Zhang
Abstract: (Ba0.7Ca0.3)TiO3 (BCT) powders and ceramics have been prepared by sol-gel technique. Structural evolution of the BCT dry gels are investigated by thermal gravimetric analysis–differential scanning calorimetry. It is found that BCT crystallites can be formed before 800 . Well-sintered samples are synthesized at 1260 for 2h. The crystal structure of the BCT powders is studied by XRD and ferroelectric properties of the ceramics are characterized by TF analyzer 2000. The Curie temperature Tc of the BCT ceramics is at about 125 . The maximum dielectric constant (εr) reaches about 4851 at 125 and hysteresis loops are measured with the temperature range from 25 to 150 .
Authors: Ning Zhu, Li Jie Wang, Xiang Yun Deng
Abstract: BaTiO3 nanotube arrays are prepared by hydrothermal reaction using the TiO2 nantotubes prepared by anodic oxidation reaction. The element, structure, elementary composition and ferroelectric properties are researched by SEM, XRD and TF Analyzer. The result shows that the prepared BaTiO3 arranged orderly and have tetragonal structure after annealing. The diffracted intensity increased with the hydrothermal temperature rising up. With the increasing of Ba(OH)2 concentration, remnant polarization intensity and coercive field climbed up and then decreased. With the increasing of hydrothermal temperature, remnant polarization intensity and coercive field increased. When the Ba(OH)2 concentration is 0.3mol/L, the hydrothermal temperature is 260°C,the remnant polarization and coercive field of the samples reached the maximum and respectively reached 6.69mC/cm2 and 1.32 kV/cm.
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