The ternary system Sc–Co–In at 870 K: the isothermal section and the crystal structures of the compounds

Abstract

The isothermal section of the Sc–Co–In system at T = 870 K has been constructed using X-ray powder diffraction and SEM/EDX data. At the studied temperature, nine ternary compounds are formed: Sc50Co12.5In3.5 (Ag7+x Mg24−x -type structure, space group Fm 3 ‾ $\overline{3}$ , a = 17.7411 Å), Sc14Co3.10In2.59 (Lu14Co3In3 type, P42/nmc, a = 8.8913, c = 21.387 Å), Sc6Co2.18In0.82 (Ho6Co2Ga type, Immm, a = 8.867, b = 8.780, c = 9.321 Å), Sc2CoIn (Pt2ZnCd type, P4/mmm, a = 3.2887, c = 7.1642 Å), Sc11Co4In9 (Nd11Pd4In9 type, Cmmm, a = 13.836, b = 20.758, c = 3.351 Å), Sc5Co2In4 (Lu5Ni2In4 type, Pbam, a = 17.3400, b = 7.5940, c = 3.3128 Å), Sc3Co1.64In4 (Lu3Co2−x In4 type, P 6 ‾ $\overline{6}$ , a = 7.6702, c = 3.3595 Å), Sc10Co9In20 (Ho10Ni9In20 type, P4/nmm, a = 12.8331, c = 9.0226 Å), Sc0.5In0.5Co2 (ternary non-centrosymmetric derivative of the Laves phase MgNi2, P63 mc, a = 4.8910, c = 16.0166 Å, with a homogeneity range from 12.3 to 16.7 at% of indium). The cubic phase ScCo4In (MgCu4Sn type, F 4 ‾ $\overline{4}$ 3m, a = 6.9230(8) Å) is evidently present in the cast samples and disappears after the annealing procedure. A Sc/In substitution was observed for the solid solution Sc1−x In x Co2 (x = 0–0.26) with the structure of the cubic Laves phase (MgCu2 type) and also for the hexagonal Sc0.5In0.5Co2-type phase.