Electron Irradiation Effects on Zinc Oxide Varistors

Multicomponent zinc oxide varistors were electron irradiated and the changes of electrical properties were measured. The electron beam energies were 800 keV, 1 MeV and 2 MeV. In the pre-breakdown region leakage current increased and the activation energy decreased. This degradation was symmetrical with respect to the applied field. In the breakdown region the nonlinear exponent decreased greatly and the breakdown voltage also decreased slightly. These results indicate that defects created by electron irradiation cause the increase of donor concentration, which lowers the activation energy of the thermionic emission. The degradation by 800 keV electron beam is the greatest and the difference between 1 MeV and 2 MeV is very small.