CAO Wenbin (1988-), male, Associate Professor. E-mail: caowenbin@sust.edu.cn
The effect of heating rate on the microstructure and electrical properties of ZnO-Bi2O3-Sb2O3-Co2O3-MnO2-Cr2O3-SiO2 varistors was investigated. ZnO grains grow rapidly with decreasing the heating rate from 3℃/min to 1.5℃/min, resulting in the deterioration of the uniformity of the sample structure. When the heating rate increases from 3℃/min to 10℃/min, the defect diffusion becomes weakly, hindering the formation of the double Schottky barrier. When the heating rate is 3℃/min, the maximum nonlinear coefficient of the sample is 43.4, the minimum leakage current is 1.0 μA/cm2, the voltage gradient is 448 V/mm, the standard deviation is the minimum, and the stability of the sample is the optimum. The loss tangent tanδ under the action of an electric field at 200 Hz-2 MHz is less than 0.03. The optimum overall electrical performance of ZnO varistor can be obtained at a heating rate of 3℃/min. Also, the existence of the negatively charged a Bi-rich phase (i.e., Bi3.73Sb0.27O6.0+x) at the grain boundary has an influence on the electrical properties of ZnO varistors.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |