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The stannides RERhSn (RE = Ho - Yb) and ScTSn (T = Pd, Pt) - structure refinements and Sn-119 Mössbauer spectroscopy

 
: Mishra, R.; Pottgen, R.; Hoffmann, R.D.; Trill, H.; Mosel, B.D.; Piotrowski, H.; Zumdick, M.F.

Zeitschrift für Naturforschung. B 56b (2001), No.7, pp.589-597
ISSN: 0044-3174
ISSN: 0932-0776
English
Journal Article
Fraunhofer IFAM ()

Abstract
The stannides RERhSn (RE = Ho - Yb) and ScTSn (T = Pd, Pt) were prepared by reaction of the elements in sealed tantalum tubes in a high-frequency furnace, by are-melting, or by a tin-flux technique in quartz tubes. The rhodium based stannides crystallize with the ZrNiAl type structure, space group P (6) over bar 2m. The four structures were refined from single crystal X-ray data: a = 754.5(3), c = 377.1(1) pm, wR2 = 0.0357, 233 F-2 values for HoRhSn, a = 753.3(1), c = 372.16(8) pm, wR2 = 0.0721, 233 F-2 values for ErRhSn, a = 753.7(3), c = 369.0(2) pm, wR2 = 0.0671, 233 F-2 values for TmRhSn, and a = 753.17(5), c = 366.53(4) pm, wR2 = 0.0566, 180 F-2 values for YbRhSn with 14 parameters for each refinement. ScPdSn and ScPtSn adopt the HfRhSn type, a superstructure of ZrNiAl, space group P (6) over bar 2c: a = 747.5(1), c = 710.2(1) pm, for ScPdSn, and a = 738.37(9), c = 729.47(9) pm, wR2 = 0.0452, 369 F-2 values, 18 variables for ScPtSn. Structural motifs in these stannides are transition metal centered trigonal prisms formed by the rare earth and tin atoms. While these prisms are regular in the rhodiurn based stannides, significant distortions occur in ScPdSn and ScPtSn. The formation of the superstructure can be ascribed to packing reasons. The shortest interatomic distances occur between the transition metal (T) and tin atoms. These atoms form three-dimensional [TSn] networks in which the rare earth atoms fill distorted hexagonal channels. The series RERhSn displays a somewhat unique behavior. The a lattice parameter is more or less independent of the rare earth element, while the c lattice parameter shows the expected lanthanoid contraction. Sn-119 Mossbauer spectroscopic data of the rhodiurn stannides show signals at isomer shifts varying from 1.77 to 1.82 mm/s subject to quadrupole splitting between 0.75 to 0.82 mm/s.

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