The effects of heavy-ion irradiation on electrical properties and hydrogen isotope permeation behavior of ceramic coatings

Abstract

Tritium permeation through structural materials in fusion reactor blanket systems is a crucial problem in terms of fuel efficiency and radiological safety. A tritium permeation barrier has been developed using ceramic coatings for several decades to mitigate tritium leakage. Recent studies are focused on irradiation effects on microstructure and hydrogen isotope permeation behavior of the coatings. However, most of the analytical methods used in these studies were destructive and time-consuming, which is undesirable to apply to the actual reactor components. Here, we report the influence of irradiation damage on electrical properties and deuterium permeation behaviors of ion-irradiated zirconium oxide coatings fabricated by metal organic decomposition to develop a convenient approach for coating characterization. The undamaged and irradiated coatings decreased the deuterium permeation flux by a factor of more than 1000 in comparison with an uncoated substrate at 300 °C. The irradiated coatings had lower permeation flux than the undamaged coatings, suggesting that irradiation-induced grain growth reduced deuterium permeation. While the undamaged coating degraded in the measurement at around 450 °C, the irradiated coatings kept high permeation reduction performance after the measurement at 600 °C. The total electrical conductivities of the irradiated coatings were up to two orders of magnitude higher than those of the undamaged one below 400 °C and then increase linearly with inverse temperature. The dominant influence on the electrical conductivity was irradiation defects at low temperatures and the inherent conduction performance of the coating at high temperatures. Our results show that electrochemical impedance measurements are useful even for submicron-thick ceramic thin coatings and confirm the irradiation effects on electrical conductivity, especially in the low-temperature range.