Oxyhydride

Oxyhydride is a term used for a class of compounds in which oxide (O2−) and hydride (H−) ions coexist within a single crystal lattice. These mixed-anion materials are often described by generic formulas such as MO1−xHx or REOxHy, where the relative amounts of oxide and hydride can vary. The metal cation is typically from the alkaline-earth or rare-earth groups and may include transition metals in some systems.

In terms of structure, oxyhydrides are commonly found in fluorite- or perovskite-related frameworks, with oxide and hydride occupying available anion sites in a partially ordered or disordered fashion. The introduction of hydride into an oxide lattice can modify lattice parameters and electronic structure, enabling tuning of optical properties and band gaps. The mixed-anion nature also affects defect chemistry and can influence ion and electron transport pathways in the material.

Synthesis methods for oxyhydrides vary but generally involve hydrogenation or reductive processing of oxide precursors. Approaches include high-temperature solid-state reactions under hydrogen, hydrogenation of oxide films, and other gas- or solid-state routes designed to incorporate hydride species while preserving the lattice. Many oxyhydrides are sensitive to air or moisture and may require controlled atmospheres to maintain hydride content, with some systems existing only as metastable phases.

Properties and potential applications of oxyhydrides arise from their tunable band gaps, electronic structure, and possible hydride mobility. Research on these materials explores uses in optoelectronics, photocatalysis, and solid-state ion conductors, as well as hydrogen storage-related contexts. Ongoing work aims to establish comprehensive structure–property relationships, reliable synthesis routes, and scalable processing for practical technologies.

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