Influence of sintering temperature on semi-conductivity and nonlinear electrical properties of TiO2-based varistor ceramics

Based on the single sinter process, five disk samples of (Sr, Bi, Si, Ta)-doped TiO2-based varistor ceramics, which were sintered separately at the temperature of 1200-1400 °C for 2.5 h, were fabricated. The influence of sintering temperature on semi-conductivity and nonlinear electrical properties of these samples were investigated by measuring the properties of complex impedance, grain resistance, grain boundary resistance, breakdown voltage and nonlinear coefficient. It was found that, between 1200 and 1400 °C, breakdown voltage, nonlinear coefficient, and grain boundary resistance decreases gradually with decreasing sintering temperature, meanwhile grain resistance increases. It is suggested that the sintering temperature should be about 1350 °C considering both grain semi-conductivity and nonlinear electrical properties of the TiO2-based varistor ceramics.