High-Pressure Synthesis of Transition-Metal Oxyhydrides with Double-Perovskite Structures

Abstract

We report on the high-pressure synthesis, crystal structure, and magnetic properties of four novel transition-metal oxyhydrides─Ba2NaVO3H3, Ba2NaVO2.4H3.6, Ba2NaCrO2.2H3.8, and Ba2NaTiO3H3─crystallizing in the double-perovskite structure. Notably, they have a higher hydride content in their anion sites (50%–63%) than known oxyhydrides with perovskite structures do (≤33%). Vanadium and chromium oxyhydrides exhibited Curie–Weiss magnetic susceptibilities with no magnetic ordering down to 2 K, which may be due to geometrical frustration in their face-centered lattices and weak magnetic interactions. Density functional theory calculations revealed that the transition metal–hydride bonding nature of the prepared oxyhydrides is more covalent than that observed for known perovskite oxyhydrides, as evidenced by the shorter bond lengths of the former. Remarkably, our double-perovskite oxyhydrides with a high hydride content may possess a bonding character intermediate between those of known oxyhydrides and hydrides.