Co-diffusion of hydrogen and oxygen for dense oxyhydride synthesis

Abstract: Oxyhydrides are gaining attention for their diverse functionality. However, evaluating electron, ion, and phonon transport properties and comprehending their mechanism remains challenging due to the difficulty in oxyhydride synthesis involving the trade-off between achieving density sintering and preventing hydrogen evolution. High-temperature treatments, often required to reduce intergranular resistance, typically cause hydrogen evolution before sufficient sintering. Instead of a post-annealing process aiming for strong chemical connections between oxyhydride particles, this research demonstrates a novel synthesis technique that converts pre-sintered bulk oxides into oxyhydrides while preserving the dense state. The process employs a high-pressure diffusion control method, facilitating the co-diffusion of hydride and oxide ions.