Zirconium hydride-stabilized yttrium hydride (ZSY): Stabilization of a face-centered cubic YH3 phase by Zr substitution

Abstract Yttrium in YH3 was shown to be substituted by zirconium in a ball milling process, yielding FCC-YH3, a zirconium-hydride-stabilized YH3 (ZSY) structure. FCC-YH3, which is stable only under the pressure greater than 7.8 GPa, has previously been reported to be stabilized at ambient pressure by alkaline or alkaline earth metal substitution, but only in a limited compositional range. In contrast, we demonstrated solid solubility of Y and Zr in ZSY in a wide compositional range, with a Y/Zr molar ratio between 4 and 0.333, as confirmed by changes in the lattice constants of ZSY with various amounts of Zr. A color of ZSY changed from yellowish (transparent) to black by Zr substitution. The UV–vis spectroscopy revealed that Zr substitution narrowed the bandgap of YH3. At a molar fraction of 33 mol%, Zr-substituted ZSY was shown to maintain its FCC structure during dehydrogenation and rehydrogenation cyclirng, and its volume change ( Δ V ) was estimated to be 1%, with an accompanying H2 emission of 0.5 wt%. This volume change was significantly lower than that of conventional hydrogen storage alloys such as LaNi5 and Mg–La–Ni alloys, i.e., Δ V is about 10 ∼ 20% when they desorb same amount of hydrogen.