Hexagonal and pyrochlore-type cesium tungstate synthesized from cesium peroxo-polytungstate and their redox chemistry
- Univ. of Tokyo (Japan)
Thermal decomposition of cesium peroxo-polytungstate, an amorphous precursor, yielded not only pyrochlore-type but also hexagonal WO[sub 3]-type cesium tungstate, depending on the Cs/W ratio (x) in the precursors; the former is in the range 0.48 [le] x [le] 0.54 and the latter 0.30 [le] x 0.34. Mixtures of these two phases were formed in the intermediate region of x. On reduction at 700[degrees]C, the pyrochlore phase gave a compound with the same framework, with its cubic cell parameter being elongated from 10.25 to 10.32 [Angstrom], but reoxidation resulted in a mixture of pyrochlore and hexagonal phases. In contrast, reduction and oxidation of the hexagonal phase at 600[degrees]C was reversible. Power XRD profile refinements were performed with reduced and oxidized hexagonal cesium tungstates (x = 0.30) in the space group P6[sub 3]/mcm. The former compounds (a = 7.4049(1) and c = 7.6098(1)) are based on an almost idealized h-WO[sub 3] framework with Cs sitting on its large 2b interstices (R[sub f] = 0.0240). The oxidized compounds (7.4012(18) and 7.6728(17) [Angstrom], R[sub f] = 0.007) possessed a lacunar tungsten sublattice. 12 refs., 11 refs., 2 tabs.
- OSTI ID:
- 6206570
- Journal Information:
- Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 103:1; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALI METAL COMPOUNDS
CESIUM COMPOUNDS
CESIUM TUNGSTATES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
DECOMPOSITION
DIFFRACTION
DISPERSIONS
LATTICE PARAMETERS
MINERALS
MIXTURES
OXIDATION
PHASE STUDIES
PYROCHLORE
PYROLYSIS
REDUCTION
SCATTERING
STOICHIOMETRY
SYNTHESIS
THERMOCHEMICAL PROCESSES
TUNGSTATES
X-RAY DIFFRACTION