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- 저자 : Guo-Zhong Zang (검색결과 4 건)
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Guo-Zhong Zang,Yan Wang,Xiu-Jie Yi,Juan Du,Zhi-Jun Xu 한국물리학회 2011 Current Applied Physics Vol.11 No.2
Lead-free (K_0.17Na_(0.83-x)Li_x)NbO_3 piezoceramics were synthesized by conventional solid state sintering and the effect of Li on the microstructure and electrical properties was investigated. The experimental results show that 4 mol% Li doping facilitates the grain growth and increases the density of the ceramics. The measurement of dielectric properties reveals that the orthorhombic-tetragonal (T_(O-T)) and tetragonalcubic (T_C) phase transition temperatures change linearly with increasing Li content and the sample with x = 0.06 exhibits the highest T_C of 429 ℃ and lowest T_(O-T) of 181 ℃. Because of the wide apart of T_(O-T) from room temperature, no polymorphic phase structures were obtained and the piezoelectric strain coeffi-cient d_33 and piezoelectric coupling constant k_p varied between low values of 57, 61 pC/N and 0.18, 0.24,respectively with less than 6 mol% Li doping.
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Varistor and dielectric properties of Cr2O3 doped SnO2eZn2SnO4 composite ceramics
Guo-Zhong Zang,Feng-Zi Zhou,Jing-Xiao Cao,Xiao-Fei Wang,Zhao-Wu Wang,Li-Ben Li,Guo-Rong Li 한국물리학회 2014 Current Applied Physics Vol.14 No.12
Cr2O3 doped SnO2eZn2SnO4 composite ceramics were prepared by traditional ceramic processing and the varistor, dielectric properties were investigated. With increasing Cr2O3 content, the breakdown electrical field EB increases from 11 to 92 V/mm and the relative dielectric constant εr measured at 1 kHz, 50 C decreases from 11,028 to 3412, respectively. The barrier height fB about 0.8e0.84 eV and the decreasing of SnO2 grain size suggest that the varistor behavior with high εr is originated from SnO2 eSnO2 or SnO2eZn2SnO4 grain boundary. In the dielectric spectra lower than 1 kHz, a dielectric peak is presented and depressed with increasing bias voltage. Similarly, at high temperature, the dielectric constant also presents a dielectric peak in the temperature spectra and the peak becomes faint with increasing frequency. The exhibition of the dielectric peak is thought to be attributed to the conduction of grain boundary since it is accompanied by the sharp increase of dielectric loss. In addition, a dielectric relaxation with the activation energy about 0.4e0.5 eV was observed in the temperature range of 20 e100 C. Based on the results, the formation mechanism of Schottky barriers at grain boundaries and the varistor behavior with high dielectric constant are well understood.
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Structural and dielectric properties in the (Ba1−xCax)(Ti0.95Zr0.05)O3 ceramics
Wei Li,Zhi-Jun Xu,Ruiqing Chu,Peng Fu,Guo-Zhong Zang 한국물리학회 2012 Current Applied Physics Vol.12 No.3
Lead-free (Ba1-xCax)(Ti0.95Zr0.05)O3 (x = 0.05e0.40) (BCZT) ceramics were prepared by solid-state reaction technique. XRD results show that the samples in the composition range of 0.05 ≤ x ≤ 0.25 exhibit pure perovskite structures and undergo a polymorphic phase transitions from orthorhombic to tetragonal phase around room temperature. The biphasic structures are detected at x ≥ 0.30 and the dielectric peaks become broad and dielectric constants decrease with increasing Ca content. Ca replacement at Ba site leads to diffuseness, whereas Ca occupancy at Ti site leads to decrease of the Tc.
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Peng Fu,Zhi-Jun Xu,Ruiqing Chu,Wei Li,Qian Xie,Guo-Zhong Zang 한국물리학회 2011 Current Applied Physics Vol.11 No.3
Eu_2O_3 (0―0.8 wt.%)-doped 0.82Bi_0.5Na_0.5TiO_3―0.18Bi_0.5K_0.5TiO_3 (BNKT18) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. The compositional dependence of phase structure and electrical properties of the BNKT18 ceramics was studied. X-ray diffraction (XRD) data shows that 0.2―0.8 wt.% Eu_2O_3 has diffused into the lattice of BNKT18 ceramics and forms a pure perovskite phase. SEM images indicate that the grain size of BNKT18 ceramics decreases with the increase of Eu_2O_3 content, and all the modified ceramics have a clear grain boundary and a uniformly distributed grain size. At room temperature, the ferroelectric and piezoelectric properties of the BNKT18ceramics have been improved with the addition of Eu_2O_3, and the BNKT18 ceramics doped with 0.4 wt.%Eu_2O_3 have the highest piezoelectric constant (d_33 = 145 pC/N), highest relative dielectric constant (ε_r = 1134) and lower dissipation factor (tan δ = 0.045) at a frequency of 10 kHz. The BNKT18 ceramics doped with 0.2 wt.% Eu_2O_3 have the highest planar coupling factor (k_p = 0.251). The temperature dependence of the relative dielectric constant shows T_m increases with the addition of Eu_2O_3.
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