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

Abstract

Abstract CeAuSn, Ce 3 Rh 4 Sn 13 , and Ce 3 lr 4 Sn 13 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 P6 3 mc: a = 472.7(2), c = 771.6(3) pm, wR2 = 0.0230,208 F 2 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 Au 3 Sn 3 hexagons. , 19 Sn 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. Ce 3 Rh 4 Sn 13 and Ce 3 lr 4 Sn 13 adopt the cubic Yb 3 Rh 4 Sn 13 type structure, space group Pm3n: a = 970.51(3) pm, wR2 = 0.0721, 267 F 2 values (Ce 3 Rh 4 Sn 13 ) and a = 972.29(6) pm, wR2 = 0.0850, 267 F 2 values (Ce 3 lr 4 Sn 13 ) with 14 variable parameters for each refinement. Striking structural motifs in Ce 3 Rh 4 Sn 13 are condensed distorted trigonal [RhSn 6 ] 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% (Ce 3 Rh 4 Sn 13 ) and 76% (Ce 3 Ir 4 Sn 13 ) and an extremely large displacement parameter indicating a rattling of these atoms within the icosahedral Sn 12 cages. Magnetic susceptibility measurements of Ce 3 Rh 4 Sn 13 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 119 Sn 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 Ce 3 Rh 4 Sn 13 is within a few μ V/K of zero over the temperature range of 10 - 300 K.