Isotopic effect of proton conductivity in gadolinium sesquioxide

Due to the higher hydrogen solubility and diffusivity, gadolinium sesquioxide (Gd₂O₃) could be expected as a proton conductive material. In this study, monoclinic Gd₂O₃ was used to evaluate the possible proton conductivity in Ar (${\sigma }_{\text{Ar}}$), Ar+4% H₂ (${\sigma }_{H_2}$), Ar+4% D₂ (${\sigma }_{D_2}$), Ar+H₂O (${\sigma }_{H_{2}O}$), Ar+D₂O (${\sigma }_{D_{2}O}$), and O₂ (${\sigma }_{O_2}$) atmospheres in the temperature range from 500°C to 1000°C, to understand its possible application in the DT fuel system of a nuclear fusion reactor. At all temperatures, the conductivity ${\sigma }_{D_2}$ was lower than that of the ${\sigma }_{H_2}$. Similarly, the ${\sigma }_{D_{2}O}$ was always lower than that of the ${\sigma }_{H_{2}O}$. The isotope dependence was appreciable at higher temperatures, indicating that Gd₂O₃ is a proton-conductive oxide at elevated temperatures. However, much improvement is required for the use of Gd₂O₃ in the DT fuel recovery, analysis, and purification system of fusion reactors.