Electrical insulating property of ceramic coating materials in radiation and high-temperature environment

The electrical insulating performance of Er2O3, Y2O3 and CaZrO3 disc specimens made by a sintering method has been examined under gamma-ray irradiation at high temperature. The conductivities without irradiation, which were on the order of 10−14–10−13 S/m at room temperature, increased during heating. In contrast, the conductivities under the irradiation of 4.5–8.8 Gy/s were on the order of 10−12–10−10 S/m and significant temperature dependence of the conductivities was not observed up to ∼250 °C for Er2O3, ∼400 °C for Y2O3 and ∼250 °C for CaZrO3, respectively. At higher temperatures, the conductivities without and under irradiation were of almost the same magnitude and increased with temperature. Similar behavior in insulating performance was observed also for an Er2O3 coating layer of 1.6 μm in thickness. The present results indicate that the degradation of insulating performance due to the radiation induced conductivity (RIC) weakly depends on temperature and would be negligible for maintaining of the required performance in the radiation and high-temperature environment of a fusion blanket.