Gold-ion irradiation effects on electrical properties and deuterium permeation in ceramic coatings

Ceramic coatings are expected to suppress tritium permeation, corrosion of structural materials, and magnetohydrodynamic pressure drop of a liquid metal flow in fusion reactor blankets. Since the blanket environment involves high-energy neutron irradiation, it is essential to elucidate the effects of irradiation on the required coating performance. In this study, we conducted Au-ion irradiation with a low electronic-to-nuclear stopping power ratio to introduce damage into yttrium oxide and zirconium oxide coatings, followed by measurements of electrical conductivity and deuterium permeation. In the permeation test, the permeation flux was smaller than that of the unirradiated sample at the temperature range above 400 °C. The trend of temperature dependence of the permeation flux after permeation measurements at temperatures up to 550 °C was comparable with that of the Fe- or Ni-ion-irradiated samples in previous studies, due to the recovery of irradiation damage. On the other hand, the electrical conductivities of the Au-ion-irradiated coatings were higher than those of the previous Fe or Ni-ion-irradiated coatings. These results indicate that the nuclear stopping power introduces additional electronic energy levels in the forbidden band more than the electronic stopping power, increasing hopping conduction. These results suggest that electrical conductivity measurements can detect the irradiation effects more precisely than deuterium permeation measurements, and Au-ion irradiation is more suitable for simulating neutron irradiation. These results provide insights for the engineering design of irradiation-tolerant coatings in fusion environments, where both insulating performance and tritium retention must be maintained under neutron-equivalent damage conditions.