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Huang Y.,Guilin University of Technology | Shi D.,Guilin University of Technology | Li G.,Guilin University of Technology | Wang Q.,Guilin University of Technology | And 3 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2013

Giant dielectric ceramics CaCu3Ti4O12 (CCTO) with non-ohmic electrical properties were prepared by a sol-gel processing method. Crystal structure and microstructure of the ceramics have been characterized using X-ray diffraction and Scanning electron microscopy. The effects of sintering duration and cooling rate on electrical properties of the ceramics were investigated by measuring the properties of permittivity, I-V and grain-boundary barriers. Prolonging holding time led to substantial improvement in permittivity, furthermore, the quenched sample showed larger dielectric permittivity than the furnace-cooling one. The non-ohmic behavior relating current density (J) to the applied electric field (E) at different temperatures was characterized. A low-voltage and giant dielectric permittivity CCTO varistor with breakdown voltages in the range of Eb = 0.2-3 kV cm -1, nonlinearity coefficient α = 2-6 and dielectric permittivity ε = 4,000-30,000 was obtained. A linear relationship between ln(J) and E1/2 indicated that a Schottky barrier should exist at the grain boundary. © 2012 Springer Science+Business Media New York. Source


Wang H.,China Three Gorges University | Sun Y.,China Three Gorges University | Fang L.,China Three Gorges University | Fang L.,Guilin University of Technology | And 4 more authors.
Thin Solid Films | Year: 2016

High transmittance Ga-doped ZnO thin films were deposited on glass substrates using sol-gel spin coating technique. Crystallinity levels, microstructures, optical and electrical properties of the thin films were systematically investigated by scanning electron microscope, X-ray diffractometer, UV–visible spectrophotometer, PL spectrometer and four-point probe method, respectively. All GZO thin films exhibited polycrystalline with a hexagonal wurtzite structure and slight (0 0 2) preferred orientation growth, which show excellent transmittance (> 95%) in the 380–780 nm wavelength range. The PL spectra of the GZO films revealed a strong ultraviolet emission peaks at around 393 nm and a weak blue emission peak at around 468 nm. When the Ga doping level was 4 at.%, the minimum resistivity of 1.12 × 10− 2 Ω·cm with the highest transmittance was reached. The optical band gaps (Eg) of the films were increased from 3.311 eV to 3.329 eV with the increase of Ga dopant concentration. © 2016 Elsevier B.V. Source


Zhou H.,Guilin University of Technology | Guo R.,Guilin University of Technology | Guo R.,Guangxi New Future Information Industry Co. | Chu D.,Guangxi New Future Information Industry Co. | And 3 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2013

The effects of Bi4Ti3O12 addition on the microstructure, electrical properties and aging characteristics of ZnO-based varistors were investigated. The addition of Bi4Ti3O 12 can reduce the formation of Zn2TiO4 spinel phase and promote the growth of ZnO grain. Bi4Ti3O 12 doped ZnO-based varistors sintered at 1,130 C possessed excellent performance of I L = 2.9 μA, E 1mA = 29.7 V/mm, α = 30.2, and good surge absorption capability with %â-E 1mA = -3.5 % for 500 A 8/20 μs impulse current. In addition, the varistors exhibited the most stable accelerated aging characteristics with %â-E 1mA = -0.3 % for DC accelerated aging stress of 125 C/7 h. These results revealed that Bi4Ti3O12 addition is highly beneficial to attain enhanced varistor properties of ZnO ceramics. © 2013 Springer Science+Business Media New York. Source


Guo R.,Guilin University of Technology | Fang L.,Guilin University of Technology | Zhou H.,Guilin University of Technology | Chen X.,Guilin University of Technology | And 3 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2013

The effects of SbVO4 addition on the microstructure, electrical properties and characteristics of grain and grain boundary of ZnO-V 2O5 based varistor ceramics were studied using SEM, E-J measurements and impedance spectroscopy. XRD analysis revealed that all the samples consist of main phase of ZnO and the second phase of BiVO4 and Zn7Sb2O12. The microstructural homogeneity of the ceramic was improved through adding SbVO4. With an increase of SbVO4, the average grain sizes decrease from 16.1 to 6.1 μm. The resistivity of grain boundary is approximately constant (∼103 Ω). The ZnO-V2O5-based varistor ceramics added with 0.3 mol % SbVO4 sintered at 940 C for 4 h exhibited good nonlinear properties of α = 51, J = 13.4 μA/mm2 and E 1mA = 416 V/mm. © 2013 Springer Science+Business Media New York. Source


Huang Y.,Guilin University of Technology | Liu L.,Guilin University of Technology | Liu L.,Guangxi New Future Information Industry Co. | Shi D.,Guilin University of Technology | And 7 more authors.
Ceramics International | Year: 2013

CaCu3Ti4O12 (CCTO) powder has been prepared by a molten salt method using the NaCl-KCl mixture. Crystal structure and microstructure of the powder and the resulting ceramics have been characterized by using X-ray diffraction (XRD) and scanning electron microcopy (SEM). Impedance analyzer and current-voltage meter were employed to analyze dielectric and nonlinear (I-V) properties of the CCTO ceramics with different sintering durations and subsequent cooling rates. The values of dielectric permittivity and nonlinear coefficient of the quenched sample were found to be higher than those of the slowly cooled sample. More specifically, the cooling methods (quenching and furnace-cooling) have allowed to adjust; (iu) the breakdown voltage within a rather low range of 0.3-4.4 kV cm-1; the nonlinear coefficient between 2 and 6 and the giant dielectric permittivity for the ceramics within a range from 5000 to 20000. A double Schottky barrier can be evidenced from the linear behavior between the ln J and E1/2 in grain boundary regions. The relationship between the electrical current density and the applied electrical field indicates that the potential barrier height ΦB is holding time dependent. © 2013 Elsevier Ltd and Techna Group S.r.l. Source

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