In:
Acta Crystallographica Section C Structural Chemistry, International Union of Crystallography (IUCr), Vol. 75, No. 6 ( 2019-06-01), p. 740-749
Abstract:
Crystals with the La 18 W 10 O 57 -type structure (6H and 5H polytypes) were obtained by a self-flux method from high-temperature solutions. Some of the crystal samples were studied by single-crystal X-ray structure analysis. The diffraction patterns indicated that two phases co-exist in each sample. The hexagonal lattices have a common period of a ≈ 9.0 Å and are non-equal in length but have equally oriented superstructure periods 6 c (phase I) and 5 c (phase II), c ≈ 5.4 Å. The structures of phases I and II were solved in the symmetry groups P \overline{6}2 c and P 321, respectively, based on the X-ray data for crystals I and II, with predominant content of the first and second phase. The motif of isolated WO 6 prisms with W atoms on the cell edges is common to both phases. WO 6 octahedra, both isolated and joined by faces, are distributed along the c axis within the unit cells. Phase I contains extra layers of isolated WO 6 octahedra compared to phase II. Tungsten sites in joined octahedra are disordered and partially occupied. Disordering is more expressed in phase II, which in return contains rather more W and O per atom of La. The refined chemical compositions are La 18 W 10 O 57 for I and La 15 W 8.5 O 48 for II.
Type of Medium:
Online Resource
ISSN:
2053-2296
DOI:
10.1107/S2053229619006107
DOI:
10.1107/S2053229619006107/sk3724sup1.cif
DOI:
10.1107/S2053229619006107/sk3724Isup2.hkl
DOI:
10.1107/S2053229619006107/sk3724IIsup3.hkl
Language:
Unknown
Publisher:
International Union of Crystallography (IUCr)
Publication Date:
2019
detail.hit.zdb_id:
2025703-X
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