HomeMing He Cao

Papers by Author: Ming He Cao

Paper TitlePage

Feasibility Study of Nanomaterial Level Powder Preparation by Wet Ball Milling and the Performance Analysis of Ceramics

Authors: Gui Fang Zhang, Ming He Cao, Hua Hao, Han Xing Liu

Abstract: The purpose of this paper is to study the feasibility of nano-material (1~100nm) level powder preparation by wet ball milling. The powder was used to prepare the ceramic and the performance of the ceramic was analyzed. The experimental results show that the average particle size of the powder is close to nano-material level (around 120nm) and the ceramic possess high compactness, high dielectric constant and low dielectric loss.

Characterization and Energy Storage Density of BaTiO₃ - Ba(Mg_1/3Nb_2/3)O₃ Ceramics

Authors: Yi Qiu Li, Han Xing Liu, Zhong Hua Yao, Jing Xu, Yun Jiang Cui, Hua Hao, Ming He Cao, Zhi Yong Yu

Abstract: The energy storage density of (1-x) BaTiO3 – x Ba(Mg1/3Nb2/3)O3 (x = 0, 0.1, 0.2, 0.3) ceramics was investigated. The microstructure of samples was characterized by scanning electron microscopy (SEM). The energy storage density was calculated from the P-E hysteresis loops measured at room temperature. Experimental results show that the energy storage density of 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramics is highest among all compositions. At 15.8kV/mm electric field, the energy storage density of the sample can reach up to 1.07J/cm3, which is about 1.5 times higher than pure BaTiO3. The improvement of the energy density can be due to two factors: one is the improved breakdown strength caused by the optimized microstructure, the other is the decreased remnant polarization. This result indicates that bulk 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramic has advantages compared with pure BaTiO3 ceramic for energy storage applications, and with further improvements in microstructure and reduction of sintering temperature, could be a good candidate for energy storage capacitors.

2045

Effect of LiNbO₃ on Piezoelectric Properties of K_0.5Na_0.5NbO₃ Ceramics

Authors: Ming He Cao, Zhuo Li, Fan Li, Hua Hao, Han Xing Liu

Abstract: Lead-free (1-x)K0.5Na0.5NbO3–xLiNbO3 piezoelectric ceramics have been prepared by a conventional solid state process. The phase structure and the electrical properties of the ceramics were studied. A polymorphic phase transition (PPT) between the orthorhombic and tetragonal phases was identified in the composition range of 0.08

2037

Structure and Diffused Ferroelectric Properties in Ba(Ti_0.8Sn_0.2)O₃ Ceramics

Authors: Dong Yun Gui, Hua Hao, Yue Sun, Ming He Cao, Zhi Yong Yu, Li Hui Xue, Han Xing Liu

Abstract: Temperature-dependent Raman scattering, dielectric properties, and Impedance spectra have been carried out on Ba(Ti0.8Sn0.2)O3 ceramic sample. The number of modes observed for the compositions of cubic symmetry is more than that predicted by group theory, and the A1(TO1) and E(TO2) modes become Raman active below the critical temperature (around 300K) in the lower frequency region. This gives evidence that there are some deviations of the local structure from the average global symmetry. Moreover, The characteristic of A1(TO3) mode is confirmed be associated with the diffused dielectric properties. Impedance/modulus analyses indicate that a third resistance-capacitance (RC) response is present in the sample, in addition to the grain and grain-boundary RC elements above 573K. Thus, it probably inferred that the existence of inter- and/or intra-granular surface layers associate with the abnormal dielectric properties, which is different from the normal ferroelectrics. Variation of bulk ac conductivity as a function of temperature shows that Ba(Ti0.8Sn0.2)O3 follows the classical Arrhenius relation.The results show that the activation energy of grains and grain boundaries are 0.61 and ~1.08 eV, respectively.

1998