Synthesis, Structure and Properties of the High-pressure Modifications of the Ternary Compounds REPtSn (RE = La, Pr, Sm)

Abstract

The hexagonal high-pressure (HP) modifications of the ternary compounds REPtSn (RE = La, Pr, Sm) were prepared under multianvil high-pressure (9 - 14 GPa) high-temperature (1050 - 1400 °C) conditions from the orthorhombic normal-pressure (NP) modifications. The HP-REPtSn stannides were investigated by X-ray diffraction on powders and single crystals: ZrNiAl type, space group P6̅2m, a = 762.6(2), c = 418.55(7) pm, wR2 = 0.1147, 256 F2 values and 14 variables for HP-LaPtSn, a = 754.97(7), c = 412.64(3) pm, wR2 = 0.0782, 252 F2 values and 14 variables for HP-PrPtSn, and a = 750.1(2), c = 407.6(1) pm, wR2 = 0.1060, 229 F2 values and 14 variables for HP-SmPtSn. The high-pressure modifications have two crystallographically independent platinum positions in trigonal prismatic coordination, Pt1Sn6RE3 and Pt2Sn3RE6. The shortest interatomic distances occur between the platinum and tin atoms with in the three-dimensional [PtSn] networks. The rare earth atoms fill distorted hexagonal channels within these networks and they are bound through short RE-Pt contacts. Susceptibility measurements of HP-PrPtSn reveal paramagnetic behaviour with an experimental magnetic moment of 3.31(2) μB/Pr atom. Low-temperature susceptibility and specific heat data point to inhomogeneous magnetism in HP-PrPtSn.