Effect of Al2O3 on the electrical properties of ZnO-Pr6O11-based varistor ceramics

The effect of Al2O3 on the electrical properties of ZnO-Pr6O11-based ceramics is investigated in this work. The average grain size of ZnO increased as the Al2O3 content increased from 10.3 to 13.5 μm. It was found that a sample doped with Al2O3 of 0.005 mol% showed the highest nonlinear current–voltage characteristics with a nonlinear exponent of 43.8 and a leakage current of 0.66 μA. When the Al2O3 content was increased, the donor concentration was increased from 0.51×1018/cm3 to 1.59×1018/cm3, but the barrier height was decreased from 1.01 to 0.87 eV. The best electrical stability against aging stress was obtained by doping Al2O3 of 0.001 mol%.