Flash sintering behaviors of Y2O3-dopd high-voltage ZnO varistors

As the ultra-high-voltage (UHV) transmission technology develops, how to enhance the voltage of varistor became a valuable challenge. In this paper Y2O3-doped high-voltage ZnO–Bi2O3 varistors ceramics were obtained by flash sintering, and the effect of Y2O3 amount on the flash sintering process, microstructure, electrical performance was investigated. The results suggested that Y2O3-doping enhanced conductivity during flash sintering, while more than 0.3 mol% of Y2O3 will affect the Bi2O3 liquid phase, thereby reducing the electrical conductivity in the initial stage of flash sintering. The varistor with 0.2 at.% Y2O3 appeared a uniform grain boundary without pores, it also optimized varistor performance a lot. The nonlinear coefficient increased by 171.6%, the threshold voltage increased by 43.6%, and the leakage current increased by 4.5%. This study proved that it is feasible to control flash sintering process of ZnO varistor by controlling the forming and property of Bi2O3 liquid.