Synthesis of photochromic oxygen-containing yttrium hydride

J. Montero; F. A. Martinsen; M. Lelis; S. Zh. Karazhanov; B. C. Hauback; E. S. Marstein

doi:10.1016/j.solmat.2017.02.001

paper

Synthesis of photochromic oxygen-containing yttrium hydride

arXiv:1610.08263 · doi:10.1016/j.solmat.2017.02.001

Abstract

Photochromic oxygen-containing yttrium hydride has been synthesized using a two step process. The process consists of an initial sputter deposition of oxygen-free yttrium hydride YH $_{x}$ , followed by a controlled reaction with air that causes incorporation of oxygen into the material. An in-situ study of the YH $_{x}$ as it reacted with oxygen was made possible by applying an aluminium capping layer with a low but non-zero oxygen permeability prior to air exposure. During the reaction, the visual appearance of the YH $_{x}$ went from dark and opaque to transparent and yellowish. This transition was accredited incorporation of oxygen into the material, as shown through analysis with energy dispersive x-ray spectroscopy (EDS) and x-ray photoemission spectroscopy (XPS). Grazing incidence x-ray diffraction (GIXRD) studies revealed an fcc structure both before and after oxygen exposure, with a lattice parameter that increased from 5.2 Å to 5.4 Å during the reaction. With the lattice parameter in the oxygen free YH $_{x}$ being equal to that reported earlier for YH $_{2}$ , our findings suggest that the non-reacted YH $_{x}$ in this study is in-fact YH $_{2}$ .