Thermal and Structural Aspects of the Hydride-Conducting Oxyhydride La2LiHO3 Obtained via a Halide Flux Method

Øystein S Fjellvåg; Jeff Armstrong; Wojciech A Sławiński; Anja O Sjåstad

doi:10.1021/acs.inorgchem.7b01409

Thermal and Structural Aspects of the Hydride-Conducting Oxyhydride La₂LiHO₃ Obtained via a Halide Flux Method

Inorg Chem. 2017 Sep 18;56(18):11123-11128. doi: 10.1021/acs.inorgchem.7b01409. Epub 2017 Sep 1.

Authors

Øystein S Fjellvåg¹, Jeff Armstrong², Wojciech A Sławiński², Anja O Sjåstad¹

Affiliations

¹ Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo , P.O. Box 1033 Blindern, N-0315 Oslo, Norway.
² ISIS Facility, Rutherford Appleton Laboratory , Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K.

PMID: 28862439
DOI: 10.1021/acs.inorgchem.7b01409

Abstract

Oxyhydrides, in which oxide and hydride anions share the same anionic lattice, are relatively rare compounds. La₂LiHO₃ belongs to this family. We report the synthesis of La₂LiHO₃ by means of an alkali halide flux method, which allows the production of larger quantities of material relative to the usually adopted synthesis routes. Powder X-ray and neutron diffraction studies show that La₂LiHO₃ adopts an n = 1 Ruddlesden-Popper (RP)-type structure with an orthorhombic distortion (Immm) due to hydride and oxide anion ordering. No sign of polymorphism is observed. La₂LiHO₃ is seen to decompose in an oxygen atmosphere at ∼450 °C into La₂LiO_3.5. We show that the high mobility of hydride anions close to the decomposition temperature is likely the main factor in inducing the oxidation. The crystal structure of La₂LiO_3.5 is also determined and takes an n = 1 RP-type structure with an orthorhombic distortion (Fmmm). This newly reported large-scale synthesis approach, combined with the proven high thermal stability, is a key factor for potential practical applications of this oxyhydride in real devices.