Synthesis and Characterization of ScMGa₅ (M = Fe, Co, Ni) and Yb₁₋ₓScₓCoGa₅ (0 ≤ x ≤ 1)

The crystal structures of ScMGa5 (M = Fe, Co, Ni) have been determined by single crystal X-ray diffraction for crystals grown from a gallium self-flux. The synthesis and characterization of Yb₁₋ₓScxCoGa₅ (0 ≤ x ≤ 1) is first reported here. ScMGa₅ (M = Fe, Co, Ni) adopts the HoCoGa5-structure type and crystallizes in the tetragonal space group P4/mmm (No. 123), Z = 1, a = 4.1367(7) Å and c = 6.6422(17) Å for ScFeGa₅, a = 4.1290(11) Å and c = 6.6034(16) Å for ScCoGa₅, and a = 4.1466(6) Å and c = 6.492(2) Å for ScNiGa₅. As the transition metal atomic size increases, from Ni to Fe, the volume of the unit cell increases from 111.63(5) ų to 113.66(4) ų. The compounds consist of alternating MGa₂ edgesharing rectangular prisms interweaved with face-sharing cuboctahedra of ScGa₃ that stack in the [001] direction. ScMGa₅ (M = Fe, Co, Ni) can be structurally compared to materials adopting the AuCu₃-structure type. Yb₁₋ₓScₓCoGa₅ (0 ≤ x ≤ 1) also adopts the HoCoGa₅-structure type and crystallizes in the tetragonal space group P4/mmm. The volume of the unit cell decreases linearly with increasing Sc concentration. Inhomogeneity was found to be maximized when the nominal molar ratios of Yb and Sc were equal.