Influence of Different Doping Amounts of Ni₂O₃ on Alternating Current Aging Characteristics of ZnO Varistor

ZnO varistors doped with different molar fractions （0, 0.5 %, 1.0 %, 1.5 %） of Ni₂O₃ were fabricated. The influence of Ni₂O₃ doping amount on the alternating current aging characteristics of ZnO varistors was investigated by accelerated alternating current aging tests. The results show that as the Ni₂O₃ doping amount increased, grain growth was suppressed and the average grain size decreased; the current-voltage curves before alternating current aging shifted toward higher electric field strengths, and after aging the current-voltage curves shifted toward higher current densities. Raising the Ni₂O₃ doping amount enhanced the varistor voltage gradient, but yielded only limited improvement in the nonlinear coefficient and leakage current.. With the increase of Ni₂O₃ doping amount, the change rate of barrier height before and after aging first decreased then increased slightly, and finally decreased again, reaching the maximum value at the doping molar fraction of 1.50% Ni₂O₃.