Residual Voltage Properties of ZnO Varistors Doped with Y2O3 for High Voltage Gradient

Rare-earth oxides can remarkably enhance the voltage gradient of ZnO varistors as growth inhibitor of ZnO grains. However, the effect of rare-earth oxides on the residual voltage properties of ZnO varistors has not been completely investigated. In this paper, ZnO varistor samples with various contents of Y(2)O(3) dopant were prepared and tested under different currents of 8/20 mu s impulse surge. When the doped Y(2)O(3) content is no more than 0.75mol%, the residual voltage ratio of ZnO varistor sample decreases with the increment of Y(2)O(3) content. When the doped Y(2)O(3) content reaches 1mol% or above, the residual voltage ratio of ZnO varistor sample increases remarkably. Such observed experimental results were explained based on the current localization phenomena inner ZnO varistor's microstructure.