Effects of lanthanum or cerium on the equilibrium of ZrNi 1.2Mn 0.6V 0.2Cr 0.1 and its related hydrogenation properties

Abstract

After annealing at 1000°C for one month, the equilibrium phases of ZrNi 1.2Mn 0.6V 0.2Cr 0.1 consist of the cubic C15 Laves phase with a precipitation of Zr 7Ni 10-type second phase. When lanthanum or cerium is added to prepare ZrNi 1.2Mn 0.6V 0.2Cr 0.1X 0.05 (X = La or Ce), the major phase is still the cubic C15 Laves phase, but the Zr 7Ni 10-type second phase disappears, and is replaced by the precipitation of LaNi or CeNi. Moreover, it is found that lanthanum or cerium does not dissolve in the Laves phase and the cell parameters of the Laves phase are the same before and after this addition. In solid-H 2 reaction, ZrNi 1.2Mn 0.6V 0.2Cr 0.1X 0.05 shows the same hydrogen absorbing capacities as ZrNi 1.2Mn 0.6V 0.2Cr 0.1, but exhibits much better activation behaviour; while in alkaline electrolyte, ZrNi 1.2Mn 0.6V 0.2Cr 0.1X 0.05 not only indicates better activation behaviour, but also shows higher discharge capacity. From the above results, it is believed that the addition of lanthanum or cerium improves the activation behaviour of Zr-based Laves phase alloy with cubic C15 structure, which is attributed to the precipitation of LaNi or CeNi in the matrix.