High Voltage ZnO Varistor Ceramics Doped with Sb2O3, SiO2 and MgO

The doping effects of Sb2O3, SiO2 and MgO on the microstructure and varistor voltage gradient of ZnO varistor ceramic materials were investigated. Results show that Sb2O3-doping is effective to increase the voltage gradient. However, high content of Sb2O3 leads to deterioration of the nonlinear characteristic of ZnO varistor ceramics. SiO2 is also an effective dopant to increase the voltage gradient, and the nonlinear characteristic is improved by the SiO2-doping. The voltage gradient can be further increased by doping MgO. When the doping contents of Sb2O3, SiO2 and MgO are 2.8 mol%, 0.3 mol% and 0.2 mol%, respectively, an high voltage gradient ZnO varistor ceramic is obtained with the voltage gradient, nonlinear coefficient and leakage current of 470 V/mm, 89 and 0.12 mu A, respectively, and the withstanding peak current density of 8/20 mu s surge wave is about 2.7 kA/cm(2).