Structure and hydrogen storage properties of the hexagonal Laves phase Sc(Al1−xNix)2

The crystal structures of hydrogenated and unhydrogenated Sc(Al1−xNix)2 Laves phases have been studied by combining several diffraction techniques and it is shown that hydrogen is situated interstitially in the A2B2-sites, which have the maximum number of scandium neighbours. The hydrogen absorption/desorption behaviour has also been investigated. It is shown that a solid solution of hydrogen forms in the mother compound. The hydrogen storage capacity exceeds 1.7 H/f.u. at 374 K, and the activation energy of hydrogen desorption was determined to 4.6 kJ/mol H2. It is shown that these compounds share the same local coordination as Frank–Kasper-type approximants and quasicrystals, which opens up the possibility of finding many new hydride phases with these types of crystal structures.