Influence of intensive milling on the microstructure and electrical properties of ZnO–Bi2O3-based varistors

ZnO varistors were synthesized using Pr6O11 doped ZnO–Bi2O3 system as raw materials by ball milling. The effects of intensive milling on the microstructure and electrical properties of the varistors were investigated in detail. The results show the intensive milling decreases the particle size and distribution of the powders for ZnO varistors. The optimal samples obtained from the powders milled for 10 h have average crystalline grain size of about 4 μm and the gradient voltage of 565 V/mm, the leakage current of 0.45 μA, and the nonlinear coefficient of 75.