Effect of La2O3 doping on microstructure and electrical properties of flash-sintered ZnO-Bi2O3 varistor

The crystal phase combination, relative density, microstructure, varistor properties and dielectric properties of La2O3-doped ZnO-Bi2O3-based varistor at a furnace temperature of 950 °C were investigated under the electric field of 300 V/cm within 35 s. Obtained samples were fully densified and uniform in microstructure. The effect of doping with different contents of La2O3 on flash-sintered ZnO-Bi2O3-based varistor was systematically studied. The results showed that when doping La2O3 was 0 mol%, 0.1 mol%, 0.2 mol% and 0.3 mol%, the densities of the samples were 91.5%, 90.5%, 96.1% and 95.1%, respectively. When the La2O3 doping amount was 0.2 mol%, the nonlinear coefficient was the highest of 32.9, the leakage current was the lowest of 1.1μA, and the dielectric loss was less than 0.1. Therefore, uniform microstructure and excellent electrical property can be obtained by preparing La2O3-doped ZnO varistor ceramic via flash sintering.