Effect of geometrical uniformity of microstructure to electrical characteristics of ZnO varistors

The microstructure uniformity of ZnO varistors does not have a direct effect on the onset of the voltage upturn in the high current region. The obvious effect of improving the geometrical uniformity of ZnO varistors is to increase the global breakdown voltage and nonlinearity coefficient. Although the global breakdown voltage is directly related to the electrical characteristic uniformity of the microstructure, it is affected more easily by the breakdown path which is determined by the geometrical uniformity of microstructure. The smaller the average and standard deviation are, the more uniform the microstructure is and the better the global electrical characteristic