Pressure induced disproportionation of rare-earth metal di-hydrides

Machida, Akihiko; Watanuki, Tetsu; Kawana, Daichi; Aoki, Katsutoshi

We have investigated the structural properties of rare-earth metal hydrides by using synchrotron radiation X-ray diffraction experiments under high pressure. Rare-earth metal di-hydrides generally exhibit the fcc metal lattice, which contains hydrogen atoms in only tetrahedral interstitial sites. It is expected that the hydrogen atoms transfer to another interstitial site by compression of metal lattice. We found the pressure-induced disproportionation of yttrium di-hydride previously. In order to demonstrate that this reaction occurs for other hydrides, we have performed synchrotron radiation X-ray diffraction experiments for lanthanum di-hydride under high pressure and have found the appearance of second phase.