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

Zr(Fe0.5Cr0.5)(2) Laves phase samples have been made to absorb different hydrogen amounts up to 3.3 H/f.u. XRD showed all ZrFeCrHy samples to have the C14 structure and, for 0< y<2.6, to be composed of a H-poor alpha-phase and a H-rich beta-phase having different c/a ratios. Both phases could be distinguished in the Mossbauer spectra. The beta-phase fraction was determined both from X-ray and Mossbauer analysis, with excellent agreement. beta-phase lattice constants and hyperfine parameters vs. y exhibited a small jump at y approximate to 1.75, suggesting a phase transition. Mossbauer spectra of ZrFeCrH3.3 in the 78-350 K range revealed that, for Fe at the 6 h site, quadrupole splitting and linewidth increased for decreasing temperature. These effects were attributed to H atomic jump diffusion, and an activation energy of approximate to 70 meV was estimated.