Structure and Properties of the Stannides CeAuSn, Ce₃Rh₄Sn₁₃, and Ce₃Ir₄Sn₁₃

Abstract

CeAuSn, Ce₃Rh₄Sn₁₃, and Ce₃lr₄Sn₁₃ were prepared by reaction of the elements in an arc-melting furnace and subsequent annealing at 970 K for two weeks. The three stannides were investigated by X-ray powder and single crystal techniques. CeAuSn crystallizes with the NdPtSb type, space group P6₃mc: a = 472.7(2), c = 771.6(3) pm, wR2 = 0.0230,208 F² values, 11 variable parameters, and BASF = 0.40(2). The gold and tin atoms form a pronounced two-dimensional [AuSn] polyanion which consists of slightly puckered Au₃Sn₃ hexagons. ,¹⁹Sn Mössbauer data at 78 K show one signal at an isomer shift of δ = 1.90(7) mm/s subjected to unresolved quadrupole splitting of ΔE_Q = 0.55(2) mm/s. Ce₃Rh₄Sn₁₃ and Ce₃lr₄Sn₁₃ adopt the cubic Yb₃Rh₄Sn₁₃ type structure, space group Pm3n: a = 970.51(3) pm, wR2 = 0.0721, 267 F² values (Ce₃Rh₄Sn₁₃) and a = 972.29(6) pm, wR2 = 0.0850, 267 F² values (Ce₃lr₄Sn₁₃) with 14 variable parameters for each refinement. Striking structural motifs in Ce₃Rh₄Sn₁₃ are condensed distorted trigonal [RhSn₆] prisms with Rh-Sn distances of 266 pm. The polyhe­dral network leaves two different cages which are occupied by cerium (6c position) and tin (2a position) atoms. The Sn2 atoms show occupancy parameters of only 92% (Ce₃Rh₄Sn₁₃) and 76% (Ce₃Ir₄Sn₁₃) and an extremely large displacement parameter indicating a rattling of these atoms within the icosahedral Sn₁₂ cages. Magnetic susceptibility measurements of Ce₃Rh₄Sn₁₃ show paramagnetic behavior down to 2 K with an experimental magnetic moment of 2.45(2) μ_B/Ce. No magnetic ordering is observed. Magnetization measurements show a moment of 0.78(2) μ_B/Ce at 2 K and 5.5 T. Resistivity data reveal only a very weak tem­perature dependence. The two crystallographically different tin sites are resolved in the ¹¹⁹Sn Mössbauer spectrum which shows a signal at δ = 2.12(1) mm/s subject to quadrupole splitting of 1.54(1) mm/s, superimposed by a singlet at δ = 2.47(1) mm/s. The Seebeck coefficient of Ce₃Rh₄Sn₁₃ is within a few μ V/K of zero over the temperature range of 10 - 300 K.