Rare Earth ( RERE ) Gallides with Closely Related Compositions: RERE IrGa and RERE ₆6 Ir ₅5 Ga ₇7

摘要

> The ternary rare‐earth iridium gallides RE ₆ Ir ₅ Ga ₇ ( RE = Sc, Y, Nd, Sm, Gd – Tm, and Lu) were synthesized from the elements by arc‐melting or by induction melting in sealed niobium ampoules. The samples were structurally characterized by X‐ray powder diffraction. The structure of Sc ₆ Ir ₅ Ga ₇ was refined from single‐crystal X‐ray diffractometer data: Yb ₆ Ir ₅ Ga ₇ (Nb _6.4 Ir ₄ Al _7.6 ) type, P 6 ₃ / mcm, a = 912.84(7), c = 828.07(6) pm, wR ₂ = 0.0362, 504 F 2 values and 22 variables. The RE ₆ Ir ₅ Ga ₇ gallides crystallize with a fully ordered superstructure of the hexagonal Laves phase MgZn ₂ . The zinc substructure consists of ordered and condensed Ir ₃ Ga and IrGa ₃ tetrahedra. Further phase analytical studies in the RE ‐Ir‐Ga systems led to the new equiatomic gallides SmIrGa and LuIrGa with the orthorhombic, TiNiSi type structure, space group Pnma . The samarium compound shows a pronounced solid solution SmIr _{1– x} Ga _{1+ x} , which was confirmed by single crysta