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Crystal structure of monophosphate tungsten bronze K1.33P4W8O32 at 110 K

Title data

Dusek, Michal ; Lüdecke, Jens ; van Smaalen, Sander:
Crystal structure of monophosphate tungsten bronze K1.33P4W8O32 at 110 K.
In: Journal of Materials Chemistry B. Vol. 12 (2002) Issue 5 . - pp. 1408-1414.
ISSN 2050-7518
DOI: https://doi.org/10.1039/B109982P

Official URL: Volltext

Abstract in another language

K1.33P4W8O32 belongs to the homologous series of monophosphate tungsten bronzes with hexagonal tunnels Ax(PO2)4(WO3)2m with 0 < x < 2 and 4 < m < 14. K1.33P4W8O32 exhibits a phase transition at Tc = 165 K, that is characterized by an anomaly in the temperature dependence of the electrical resistivity and by the occurrence of extra reflections in the X-ray scattering. Here we report the 2a times b times c superstructure at T = 120 K{,} as it was measured by X-ray diffraction with synchrotron radiation. The superstructure is found to be monoclinic P21 with lattice parameters a = 13.373(7) A{,} b = 5.3282(1) A{,} c = 8.926(4) A{,} and small beta = 100.65degree. The structure was refined within the superspace approach with superspace group P21(small alpha{,} 0{,} gamma) with small alpha = 0.5 and gamma = 0. Final agreement was obtained at R = 0.032 (R = 0.025 for the main reflections and R = 0.153 for the superstructure reflections). The maximum shift out of the average position was 0.25 A for one of the oxygen atoms. An analysis of the displacements and variations of interatomic distances is used to show that the mechanism of the phase transition is to resolve the internal strain between the K atoms and the surrounding PO4 groups. The comparison with the CDW structure of (PO2)4(WO3)2m shows that the phase transition is not a charge-density wave{,} but rather that the anomaly in the resistivity is caused by the changes in the structure when going through the phase transition.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography > Chair Crystallography - Univ.-Prof. Dr. Sander van Smaalen
Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
Date Deposited: 21 Mar 2016 10:28
Last Modified: 21 Mar 2016 10:28
URI: https://eref.uni-bayreuth.de/id/eprint/31924