Structural studies of pseudobinary La(Cu 1− xNi x) 2 compounds and their hydrides

Abstract

The effect of Cu-for-Ni substitution on the structural and hydrogenation properties of the LaCu 2 compound with hexagonal AlB 2 type structure has been studied. An extended solid solution was found from LaCu 2 to La(Cu 0.35Ni 0.65) 2. The La(Cu 1− x Ni x ) 2 compounds easily absorb hydrogen at room temperature under 1 bar pressure, after preliminary activation treatment by heating in vacuum. Hydrogenation of LaCu 2 resulted in the formation of amorphous LaCu 2H 3.3 hydride. For all Ni-substituted compounds formation of crystalline hydrides with CeCu 2 or AlB 2 type structure of the metallic sublattice and hydrogen content up to 4.4 at.H/f.u was observed. As found, long-term exposure of the La(Cu 0.4Ni 0.6) 2H 4.2 and La(Cu 0.35Ni 0.65) 2H 4.0 hydrides to the air or their heating under vacuum up to 100 °C is accompanied by structural transition of the metallic sublattice to Fe 2P type structure, previously observed for Pr(Cu,Ni) 2-based hydrides.