Effect of half substitution of R (R = Nd, Gd and Er) for Ca on crystal structure and hydrogen storage properties of CaMgNi^sub 4

The effect of half substitution of R (R = Nd, Gd and Er) for Ca in CaMgNi4 compound on crystal structure and hydrogen storage properties was investigated. It was found that R0.5Ca0.5MgNi4 compounds have the C15b-type MgCu4Sn structure. The half substitution leads to the improvement of gaseous hydrogen absorption−desorption thermodynamics. Furthermore, each R0.5Ca0.5MgNi4 alloy electrode shows better cycle stability and high-rate discharge performance than CaMgNi4, especially in the case of half substitution of Nd.