Crystal structures of the compounds formed in DyCo2–DyGa2 pseudo-binary system at 773 K

DyCo2−xGax alloys with x from 0 to 2 were prepared by arc melting and investigated by X-ray powder diffraction. Six ternary compounds with different Ga contents x, DyCo2, DyCo1.33Ga0.67, DyCoGa, DyCo0.67–0.35Ga1.33–1.65, DyCo0.25–0.15Ga1.75–1.85, and DyGa2, were formed in the system. The crystal structures of these compounds were determined by Rietveld refinement method with TOPAS V3.0 software. The Rietveld refinements reveal that DyCo1.33Ga0.67 crystallized in the MgZn2-type structure (P63/mmc) with a = 5.414(1) and c = 8.452(1) Å, DyCoGa in the Co2Si-type structure (Pnma) with a = 7.052(1), b = 4.393(1) and c = 6.958(1) Å, DyCo0.5Ga1.5 in the GdPdSi-type structure (Imma) with a = 4.341(1), b = 7.007(1) and c = 7.551(1) Å, and DyCo0.2Ga1.8 in the AlB2-type structure (P6/mmm) with a = 4.339(1) and c = 3.634(1) Å. The relationships between these structures were discussed.