ChemInform Abstract: Fluoride Sulfides (LnFS) of the Lanthanides (Ln: La—Nd, Sm, Gd—Lu) with A- or PbFCl-Type Crystal Structure.
Abstract
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ChemInform Abstract
Phase-pure LnFS (Ln: La—Nd, Sm, Gd—Lu) compounds are prepared by reaction of 2:1:3 mixtures of Ln, LnF3, and sulfur at 850 °C (evacuated Pt-, Nb-, or Ta-tube, several days). Single crystals of LnFS (Ln: La—Nd, Sm, Gd—Er) are obtained in a NaCl flux. These compounds have a PbFCl-analogous A-type structure (tetragonal, space group P4/nmm, Z = 2). The Ln3+ cations are in monocapped square antiprismatic anionic coordination (4F- and 5S2-) and the anions exhibit tetrahedral (F-) and square-pyramidal (S2-) cationic coordination, respectively. In the case of TmFS, YbFS, and LuFS, the hexagonal B- or trigonal C-type modifications are formed, which can be transformed to the metastable tetragonal A-type polymorph at high pressure (20—60 kbar).
