Influence of the substituting Ni with Fe on the cycle stabilities of as-cast and as-quenched La0.7Mg0.3Co0.45Ni2.55 − xFex (x = 0-0.4) electrode alloys

The electrode alloys La0.7Mg0.3Co0.45Ni2.55 − xFex (x = 0, 0.1, 0.2, 0.3, 0.4) are fabricated by casting and rapid quenching techniques. The effects of the substitution of Fe for Ni on the cycle stabilities as well as the structures of the alloys have been investigated thoroughly. The results indicate that the substitution of Fe for Ni significantly enhances the cycle stability of the alloys. Furthermore, the positive impact of such substitution on the cycle stability has been observed to be more pronounced for the as-quenched alloy as compared to that for the as-cast one. Scanning electron microscopy (SEM) studies demonstrate that all the alloys exhibit a multiphase structure comprising of two major phases (La, Mg)Ni3 and LaNi5 along with a residual phase of LaNi2. The substitution of Fe for Ni has been observed to facilitate the formation of a like amorphous structure in the as-quenched alloy. With an increase in Fe contents, a significant grain refinement of the as-quenched alloy and an obvious enlargement in the lattice constants and the cell volumes of the alloys have been noticed.