The effect of doping Bi2O3 on sintering temperature, microstructure, electrical nonlinearity and stability of high-voltage SnO2 varistors

One of the significant drawbacks of SnO 2 varistors compared to their old counterpart, ZnO varistors, in high-voltage applications is their higher sintering temperature. Although the researchers have been attempting to lower the sintering temperature by employing new techniques, the obtained varistors do not show an acceptable capability to absorb surge currents. In this research, by optimizing the Bi 2 O 3 amount added to the well-known SnO 2 varistor system, the sintering temperature of varistors reduced to 1250 °C. It is for the first time that the reduction in sintering temperature of SnO 2 varistors was accompanied not only with maintaining the nonlinearity of the obtained varistors, but also with an acceptable surge current performance. In the optimal amount of 0.05 mol% Bi 2 O 3 , a nearly full dense structure, a simple microstructure without any secondary phases, the nonlinearity coefficient of 45, the threshold of 5.1 kV/cm, and the surge current absorption to 900 A/cm 2 were acquired.