Ternary stannides RETi6Sn4 (RE = Y, Gd–Tm, Lu) with rhombohedral LiFe6Ge4 type structure

The stannides RETi6Sn4 (RE = Y, Gd–Tm, Lu) were synthesized from the elements by arc-melting and subsequent annealing in an induction furnace. All samples were characterized by powder X-ray diffraction. The structures of TmTi6Sn4 and LuTi6Sn4 were refined from single crystal diffractometer data: LiFe6Ge4 type, R 3 ¯ m , a = 576.6 (1), c = 2271.4 (3) pm, wR = 0.0416, 538 F values, 18 parameters for Tm0.86Ti6Sn4.14 and a = 576.4 (1), c = 2260.6(2) pm, wR = 0.0676, 666 F values, 18 parameters for Lu0.92Ti6Sn4.08. Both 3a Wyckoff sites show a small degree of RE/Sn mixing. The RETi6Sn4 structure is composed of two basic structural motifs which show a layered arrangement. Motif A are layers of edges-sharing RESn8/2 hexagonal bipyramids (286–333 pm Lu–Sn in Lu0.92Ti6Sn4.08) and motif B Kagomé networks of the titanium atoms with 282–295 pm Ti–Ti in Lu0.92Ti6Sn4.08. ABB packages of these building units are stacked in the rhombohedral sequence. Temperature dependent magnetic susceptibility measurements show Curie–Weiss behavior in the high-temperature regime and no magnetic ordering down to 3 K. A 119Sn Mössbauer spectrum of the TmTi6Sn4 sample resolves the two crystallographically independent tin sites; weak (ΔEQ = 0.44(2) mm/s, δ = 1.82(1) mm/s) quadrupole splitting for the Sn2 and large (ΔEQ = 1.42(2) mm/s, δ = 1.92(1) mm/s) quadrupole splitting for the Sn1 site.