Analysis of local sites of deuterium in Ti53Zr27Ni20 alloys

Abstract

TiZr-based alloys are known to absorb a large amount of hydrogen, and as such have been proposed as candidate materials for hydrogen storage applications. For the easy synthesis of samples, as-cast TiZrNi alloys were prepared and deuterated using a lab-built isotherm measurement system to locate the atomic positions of host metals with deuterium before evaluating their technical usefulness. Results of Rietveld refinements measured from simultaneous fit of X-ray and neutron diffraction patterns revealed that slowly cooled Ti53Zr27Ni20 alloys have a C14 Laves phase (P6(3)/mmc) with lattice constants of a = 5.27 and c = 8.31 angstrom with atomic compositions of 52.25, 28.27 and 19.48 at. % for Ti, Zr, and Ni, respectively. Deuterium atoms sit in tetrahedral sites formed by Ti2Zr2 and Zr2Ni2. The exact locations of the deuterium atoms are (0.412, 0.462, 0.594) and (0.430, 0.569, 0.250) of Wyckoff positions in a xyz coordinate system. The formation of a hydride phase was unavoidable even at low concentrations of deuterium, and was identified to TiD2.