Facile Synthesis of LiH-Stabilized Face-Centered-CubicYH 3 High-Pressure Phase by Ball Milling Process

A face-centered-cubic (FCC) YH3 phase is known to be stable only under high pressure (HP) of more than gigapascal order, and it reverts to the hexagonal YH3 ambient-pressure phase when the pressure is released. We previously found that the FCC YH3 can be stabilized even at ambient pressure by substituting Y for 10 mol % Li (LiH-stabilized YH3, LSY). The LSY was synthesized by heat treatment under gigapascal HP, but this process is unfavorable for mass production; that is, only a few tens of milligrams of a sample can be obtained in a single batch. In this study, we overcame this problem by applying a ball milling (BM) process for synthesizing the LSY phase, and the yield by the BM process reached on the order of grams. We confirmed that the structure of the BM sample was the same as that of the HP sample by X-ray diffractometry, Raman spectroscopy, and neutron total scattering pair distribution function analyses. The crystallinity of the BM sample, however, was lower than that of the HP sample. The differ...