Synergistic effects of Gd and Co on the phase evolution mechanism and electrochemical performances of Ce₂Ni₇-type La-Mg-Ni-based alloys

The influences of Gd and Co co-substitution for La and Ni on phase structures, and electrochemical properties of La_0.83-xGd_xMg_0.17Ni_3.35-2xCo_2xAl_0.15 (x = 0-0.83) alloys were investigated. All the alloys contained A₂B₇-type (Ce₂Ni₇- and Gd₂Co₇-type) phase, Pr₅Co₁₉-type phase, PuNi₃-type phase and CaCu₅-type phase. The partial replacement of Gd and Co for La and Ni increased the phase abundance of the Ce₂Ni₇-type superstructure and decreased cell volumes, which contributed to a better hydrogen absorption capacity, cyclic stability and HRD. Compared to those of single Gd- or Co-substitutions, the synergistic effects of Gd and Co on the overall electrochemical properties of alloys were significant. Such a superior overall electrochemical performance may result from appropriate cell volumes and anti-pulverization abilities.