High-Pressure Syntheses of Lanthanide Polysulfides and Polyselenides LnX1.9 (Ln = Gd–Tm, X = S, Se)

Authors

  • Carola J. Müller,

    1. Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany
    2. Fachrichtung Chemie und Lebensmittelchemie, Technische Universität Dresden, Helmholtzstr. 10, 01062 Dresden, Germany
    3. Current address: Centre for Analysis and Synthesis, Polymer and Materials Chemistry, Lund University, Box 124, 22100 Lund, Sweden
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  • Ulrich Schwarz,

    1. Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany
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  • Thomas Doert

    Corresponding author
    1. Fachrichtung Chemie und Lebensmittelchemie, Technische Universität Dresden, Helmholtzstr. 10, 01062 Dresden, Germany
    • Fachrichtung Chemie und Lebensmittelchemie, Technische Universität Dresden, Helmholtzstr. 10, 01062 Dresden, Germany, Fax: +49-351-463-37287
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Abstract

The polysulfides LnS1.9 and polyselenides LnSe1.9 of the lanthanide metals from gadolinium to thulium were prepared by high-pressure high-temperature synthesis. The compounds adopt the tetragonal CeSe1.9 structure type in space group P42/n (No. 86) with lattice parameters of 8.531 Å ≤ a ≤ 8.654 Å and 15.563 Å ≤ c ≤ 15.763 Å for the sulfides and 8.869 Å ≤ a ≤ 9.076 Å and 16.367 Å ≤ c ≤ 16.611 Å for the selenides. The atomic pattern consists of puckered double slabs [LnX]+ and planar chalcogenide layers with ten possible chalcogen positions, of which eight are occupied by chalcogen atoms forming dinuclear X22– dianions, one by a single X2– ion and one remaining vacant. This resembles a √5×√5 × 2 superstructure of the ZrSSi aristotype. Structural relationships to the aristotype and the related lanthanide polychalcogenides LnX2–δ (Ln = La–Tm, X = S–Te, δ = 0 – 0.3) are discussed. The samples synthesized under high-pressure conditions (p > 1 GPa) decompose slowly under release of sulfur or selenium at ambient conditions. The crystal structure of a partially degraded thulium-polysulfide sample can be described as an incommensurate variant of the original TmS1.9 motif. Additionally, the isostructural ternary compound Gd(S1–xSex)1.9 was synthesized and characterized by powder X-ray diffraction.

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