Highly stable nonlinear properties of ZnO-Pr6O11-CoO-Cr2O3-Y2O3-based varistor ceramics

The electrical nonlinear properties of varistors, composed of ZnO-Pr6O11-CoO-Cr2O3-Y2O3, (ZPCCY)-based ceramics, were investigated with various sintering times and its stability for DC accelerated aging stress. The increase of sintering time led to the decrease of nonlinearity. The highest nonlincarity was obtained from the varistor sintered for 1h, with 51.2 in nonlinear exponent and 1.3 muA in leakage current. The varistor sintered for 2 h exhibited not only relatively high nonlinearity, which the nonlinear exponent is 38.6 and the leakage current is 3.9 muA, but also the highest stability, in which the variation rates of varistor voltage, nonlinear exponent, and leakage current are - 0.8%, - 1.8%, and + 74.4%, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.