A Study of Hydrogen Site Occupation in the Yttrium-Hydrogen Solid Solution Phase Using Inelastic Neutron Scattering

Abstract

The solid solution phase of YHx systems has a hcp structure and can exist with H/M ratios up to 24% at temperatures below 500 K. In this phase the hydrogen can occupy either tetrahedral (T) or Octahedral (O) sites. Existing neutron diffraction and NMR measurements however offer conflicting evidence as to the amount of hydrogen occupying each type of site. Neutron energy loss experiments have been successfully applied to the problem of locating hydrogen in solution in Zr and Ti. We therefore made further measurements on samples of YH0 · 1 and YH0 · 2 at 297 K and 104 K using a Be filter spectrometer. In all cases two peaks were observed centred around 137 and 102 meV. By comparison with previous solid solution and hydride phase measurements we attribute the higher energy peak to the T site and the lower peak to the O site.