Crystal structure studies of tetragonal sodium tungsten bronzes, Na/sub x/WO/sub 3/. I. Na/sub 0/ /sub 33/WO/sub 3/ and Na/sub 0/ /sub 48/WO/sub 3/
The crystal structures of two sodium tungsten bronzes, Na/sub 0/./sub 33/WO/sub 3/ and Na/sub 0/./sub 48/WO/sub 3/, have been determined by three-dimensional single-crystal x-ray analysis. They were found to crystallize in the tetragonal space groups P anti 42/sub 1/m (a = 12.097, c = 3.754 A, Z = 10) and P4/mbm (a = 12.150, c = 3.769 A, Z = 10), respectively. The structures were solved by standard Patterson and Fourier techniques and refined by full-matrix least-squares to final conventional discrepancy indices of 8.9 percent for Na/sub 0/./sub 33/WO/sub 3/ and 8.4 percent for Na/sub 0/./sub 48/WO/sub 3/. In general, the oxygen atoms were found to be either twofold or fourfold disordered, suggesting that the WO/sub 6/ octahedra do not have axes exactly aligned parallel to the crystallographic c-axis. The structure found can be viewed as a composite of two kinds of domain structures. These domain structures would require a doubling of the c-axis along with selection of new a- and b-axes along the (anti 1 10) and (110) directions. There exist pentagonal and tetragonal sites in both these sodium tungsten bronzes for sodium atoms occupancy. In Na/sub x/WO/sub 3/, x = 0.48, all the pentagonal sites are filled and 40 percent of the smaller tetragonal sites are also occupied. As x decreases to 0.33 though, only the pentagonal sites are occupied. A relation between the x value and the Na/sub x/WO/sub 3/ crystal structures is postulated, extrapolating from the results found in these structure determinations.
- Research Organization:
- Ames Lab., IA
- OSTI ID:
- 7347935
- Journal Information:
- J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 18:2; ISSN JSSCB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALI METAL COMPOUNDS
CHALCOGENIDES
CRYSTAL STRUCTURE
DOMAIN STRUCTURE
FOURIER ANALYSIS
LEAST SQUARE FIT
MAXIMUM-LIKELIHOOD FIT
NUMERICAL SOLUTION
OXIDES
OXYGEN COMPOUNDS
PATTERSON METHOD
SODIUM COMPOUNDS
SODIUM OXIDES
SPACE GROUPS
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN COMPOUNDS
TUNGSTEN OXIDES