Phase stability and neutron diffraction studies of Laves phases Zr(Cr1−xMx)2with M = (Cu0.5Ni0.5) and 0 < x < 0.2 and their hydrides

Laves phases of composition Zr(Cr1−xMx)2with M = (Cu0.5Ni0.5) and 0 ⩽ x ⩽ 0.2 have been synthesised with the hexagonal C14- and/or cubic C15-type structures. By X-ray and neutron diffraction we have determined the structures of the alloys, and in particular the sites for the 3d metal substitution. The position of the hydrogen atoms in the structures and the occupation of the different sites of the hydrides have been determined. Purity and quality of polycrystalline alloys have been checked by using scanning electron microscopy and energy dispersive X-ray analysis techniques. The effects of the M/Cr substitution have been studied for phase stability, maximum hydrogen content and hydrogen site stability and analyzed in view of applications as electrodes in HM batteries.