Electrical properties and AC degradation characteristics of low voltage ZnO varistors doped with Nd2O3

The electrical properties and degradation characteristics of low voltage ZnO varistors were investigated as a function of Nd₂O₃ content. The varistor ceramics with 0.03 mol% Nd₂O₃ sintered at 1250 °C were far more densified than those with 0.06, 0.09 and 0.12 mol% Nd₂O₃. The addition of Nd₂O₃ to the low voltage ZnO varistors greatly improved the current–voltage characteristics; the nonlinear coefficient of varistors increase from 12.2 to 34.6 with increasing Nd₂O₃ content. The samples with 0.03 mol% Nd₂O₃ showed excellent stability due to high density and relatively good V–I characteristics, with the nonlinear coefficient of 22.5 and the leakage current of 9.6 μA. Their variation rate of varistor voltage and nonlinear coefficient and leakage current were −4.7%, −5.4%, 18.3%, respectively, under AC degradation stress (1.0 V_1 mA/125 °C/24 h).