Interdiffusion studies of rare earth metals with liquid gallium

The gallium-rich side of some rare earth-gallium binary systems was studied using a diffusion couple technique. Diffusion couples were formed by annealing rare earth metals immersed in liquid gallium at various temperatures. The nature and composition of the compound layers formed at the rare earth metal-gallium interface were determined by metallographic and electron microprobe analysis. The results indicate that in the light rare earth metals (R ≡ La-Gd) the ε{lunate} phase extends from the stoichiometric composition RGa₂ to the gallium-rich compositions R_1-xGa_2+x. In these systems the RGa₆ layer is dominant in the diffusion region. No RGa₃ layer is present in these systems, in contrast with the two heavy rare earth-gallium couples (Tb-Ga and Dy-Ga) in which the ε{lunate} phase appears at the stoichiometric composition only and the RGa₃ layer is dominant.