The Electrical Conductivity of Plasma-Sprayed Alumina and Spinel Irradiated at 400 and 500 deg C

The effects of radiation on electrical conductivity in ceramic insulators are briefly reviewed with particular emphasis on the radiation-induced electrical degradation (RIED) effect in which large increases in the intrinsic electrical conductivity have been observed following irradiation within a restricted, temperature range whilst subject to electric fields > 600V/cm. The aim of the present work was to extend the studies of the RIED effect to plasma-sprayed forms of alumina and spinel. The experimental arrangement using the Harwell Tandem accelerator is described along with the target which is capable of operating at temperatures up to 900 deg C in a vacuum of < 10(exp -6)mbar. Irradiations were performed on plasma-sprayed alumina and spinel at 400 and 500 deg C using 10MeV protons to damage doses of > 0.001 displacements per atom (dpa). An electric field of 1kV/cm was applied across the samples during irradiation. The irradiations were interrupted at intervals and the conductivity measured at the irradiation temperature. At the end of the irradiations the temperature dependence of the electrical conductivity was measured. The experimental results showed that for alumina the conductivity decreased for both irradiation temperatures. At the highest damage dose of 0.004 dpa the intrinsic conductivity for irradiation at 400 deg C had decreased by a factor of 3 and for the 500 deg C irradiation by a factor of 10. The conductivity of spinel irradiated at 400 deg C increased by factor of 3 whilst that irradiated at 500 deg C showed only a slight increase.