Electrical properties and stability of praseodymium oxide-based ZnO varistor ceramics doped with Er2O3

The electrical properties and its stability against DC accelerated aging stress of Pr6O11-based ZnO varistor ceramics were investigated with Er2O3 content and sintering time. The nonlinear exponent of varistors with increasing Er2O3 content varied with V-shape, reaching minimum at 1.0 mol% Er2O3. As sintering time is increased, the nonlinear exponent was decreased, whereas its stability for DC stress was improved. The varistor with 0.5 mol% Er2O3 sintered at 1340 °C for 2 h exhibited the best performance for the nonlinearity and stability. This varistor exhibited not only high nonlinearity, with the nonlinear exponent of 43.4 and the leakage current of 1.2 μA, but also high stability, with the variation rates of varistor voltage and nonlinear exponent is −1.5 and −2.5%, respectively, under DC stress, such as (0.80V1 mA/90 °C/12 h)+(0.85V1 mA/115 °C/ 12 h)+(0.90V1 mA/120 °C/12 h)+(0.95 V1 mA /125 °C/12 h) +(0.95V1 mA/150 °C/12 h).