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P. Rogl, V.V. Romaka, G. Rogl, A. Grytsiv, H. Michor, G. Giester:
"Phase Relations, Crystal Structures and Physical Properties in the Sc-rich Part of the Systems Sc-{Mn,Fe,Co,Ni}-Ga";
Vortrag: The International Conference on Solid Compounds of Transition Elements SCTE 2021, Wrocław, Poland; 12.04.2021 - 15.04.2021.

Although Sc/Ga are important alloying partners in high-strength Al-based alloys, Sc-systems with transition metals and gallium still reveal a lack of precise data on compounds and their stability/physical properties [1].
In this work, phase relations in the Sc-rich corner of the ternary systems Sc-{Mn,Fe,Co,Ni}-Ga have been established at 850°C based on X-ray powder and single crystal diffraction, metallography, SEM and EPMA techniques on about 30 Ar-arc melted and annealed alloys. The re-evaluation of the binary systems revealed the absence of compounds Sc₄T (T=Mn,Co,Ni), but confirmed cubic Sc₅₈Fe₁₂ ("Sc₂₉Fe₆" [1]) and the formation of Sc₂Ga. The Sc-rich corner in Sc-{Mn,Fe}-Ga is characterized by one ternary compound: Sc₅₄{Mn,Fe}₉Ga₈ (orthorhombic variant of the Hf₅₄Os₁₇-type); the systems with Co and Ni reveal a ternary kappa phase Sc₁₀(TxGa_1-x)₃ (x=0.32, Hf₉Mo₄B-type) as well as a novel compound: Sc₅₄Co₉Ga₈ with the Hf₅₄Os₁₇-type. Whereas Sc₁₀(Co_xGa_1-x)₃Co phases form a typical network of corner-connected empty octahedra Sc6, which encompass Sc-centered icosahedra Sc6Ga6 and Co-centered trigonal prisms Co[Sc₆], the Sc₅₄T(T,Ga)₁₇ phases exhibit (T,Ga)-centered defect icosahedron-clusters. Chemical bonding and charge transfer is elucidated from DFT calculations and eDOS and showed high electron localization inside the empty Sc₆ octahedra for all studied compounds and related kappa phases, which may attract small and highly electronegative elements. Specific heat and electrical conductivity measurements suggest metallic behavior. Sc₅₄Fe_9.4Ga_7.6 and Sc₅₄Co_7.3Ga_9.7 are almost TIPs; Sc₅₄Mn_8.5Ga_8.5 exhibits an approximate Curie-Weiss behaviour: χ₀ = 10^-3 emu/mol; Θ_p = 15.8 K, μ_eff =2.23 μ_B/Mn. At low temperatures it reveals a weakly interacting spin glass system with a spin-freezing anomaly at around 8 K.
Hardness and elastic moduli are in the range of typically polar intermetallics.
[1] B. Ya. Kotur, E. Gratz, "Handbook on the Physics and Chemistry of Rare Earths (ed. K.A. Gschneidner, L.R. Eyring), NH, vol. 27, 339-533 (1999).