Radiation induced conductivity in alumina

Abstract

Studies have shown that the electrical resistivity of insulators such as alumina can be significantly degraded when irradiated with a bias voltage at elevated temperatures. This study is devoted to examining the effects of radiation induced conductivity and electrical degradation in polycrystalline alumina and sapphire. Experiments were carried out at temperatures up to 823 K and an applied electric field of 500 kV/m. Effects of proton, alpha and gamma radiations were examined. Experimental results show that radiation induced conductivity (RIC) in alumina consists of recoverable and permanent contributions when irradiated with charged particles. These two radiation induced effects are not completely separable and are both functions of irradiation dose. In polycrystalline alumina, a significant increase in the permanent conductivity was observed after an incubation dose of 10 −4 dpa. However only limited permanent electrical degradation was observed in single crystal samples at three times this damage level indicating the importance of grain boundaries in the radiation induced electrical degradation (RIED) process. Results from Rutherford backscattering spectroscopy (RBS) confirm that radiation enhanced diffusion of the gold contact is responsible for the degradation observed in the polycrystalline alumina specimens.