Hydrogen absorption effects in the Zr(Fe0.5Cr0.5)2 compound

Zr(Fe_0.5Cr_0.5)₂ Laves phase samples have been made to absorb different hydrogen amounts up to 3.3 H/f.u. XRD showed all ZrFeCrH _y samples to have the C14 structure and, for 0 < y < 2.6, to be composed of a H-poor α-phase and a H-rich β-phase having different c/a ratios. Both phases could be distinguished in the Mössbauer spectra. The β-phase fraction was determined both from X-ray and Mössbauer analysis, with excellent agreement. β-phase lattice constants and hyperfine parameters vs. y exhibited a small jump at y ≈ 1.75, suggesting a phase transition. Mössbauer spectra of ZrFeCrH_3.3 in the 78–350 K range revealed that, for Fe at the 6h site, quadrupole splitting and linewidth increased for decreasing temperature. These effects were attributed to H atomic jump diffusion, and an activation energy of ≈70 meV was estimated.