High Voltage Gradient ZnO Nonlinear Resistor Doped with Rare-Earth Oxide

The U-I characteristics of ZnO nonlinear resistors (ZnO varistor) is very important on the protection performance of metal-oxide surge arresters, which protects power apparatus and electronic devices against surges. In this paper, the changes on U-I characteristics of ZnO nonlinear resistors are introduced when some rare-earth oxides are doped, as well as the mechanics which leads these changes. In the sintering process of ZnO varistors doped with rare-earth oxide, the growing speed of the ZnO grains is slowed up due to the stabilization of rare-earth oxide on ZnO grains. So the size of ZnO grains becomes very small, and the voltage gradient of varistor increases obviously and reaches a value higher than 400 V/mm