Synthesis of Novel Metal Hydrides by High Pressure Technique

Abstract

High-pressure synthesis under giga-pascal hydrogen is attractive method to discover new metal hydrides with high hydrogen storage capacity. Recently, we have succeeded to prepare a series of new hydrides Mg₇MH_x (M=Ti, V, Nb, Hf, Ta, etc) with a cubic super-lattice structure (Ca₇Ge-type) at 8 GPa and 600°C. One of them, Mg₇TiH_x had the theoretical hydrogen capacity of 6.9 mass%, and exhibited lower hydrogen desorption temperatures of ca 150°C than MgH₂. The detailed crystal structure analysis showed that the Mg-H interatomic distance in Mg₇TiH_x was longer than that in MgH₂, explaining the lowered desorption temperature.