Determination of a phase diagram of TiH at high pressures and high temperatures for development of novel Ti-based hydrides

Endo, Naruki; Saito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori; Aoki, Katsutoshi

The phase diagram and the equation of state (EoS) of TiH at high pressures and high temperatures (HPHT) conditions are necessary (1) to detect the formation of TiH by disproportional reactions of Ti-based alloys at HPHT and (2) to investigate chemical reactions between TiH and other metal hydrides, which would yield new Ti-based alloy hydrides at HPHT. To our knowledge, few HPHT studies have examined TiH. Moreover, the phase diagram of TiH was not determined and the EoS of TiH was not reported. Hence, a more detailed study of TiH at HPHT is necessary. In the present study, we clearly determine the phase diagram of TiH at HPHT, and are the first to report the EoS of TiH with an fcc phase. Compression induced strain inhibits the phase transition from the low-temperature bct phase to the high-temperature fcc phase, making the phase diagram difficult to determine.