Formation process of perovskite-type hydride LiNiH3: In situ synchrotron radiation X-ray diffraction study

The formation process of perovskite-type hydride LiNiH3 was investigated using in situ synchrotron X-ray diffraction measurements. A mixture of LiH and Ni was hydrogenated at 873 K and 3 GPa, and the structural changes associated with hydrogenation were observed. Time-resolved diffraction profiles showed a three-step reaction: hydrogenation of Ni to NiHx, formation of LiyNi1–yH solid solution, and conversion to perovskite-type hydride LiNiH3. The solid solution, which has never been reported, plays the role of the precursor in the perovskite formation and its presence is apparently critical for synthesizing perovskite-type hydrides.