Ordered and defect structures in the UO{sub 2}-WO{sub 3} system, revealed by HREM
- Stockholm Univ. (Sweden)
The four phases U(WO{sub 4}){sub 2}, UW{sub 3}O{sub 11}, UW{sub 4}O{sub 14}, and UW{sub 5}O{sub 17} in the UO{sub 2}-WO{sub 3} system have been identified by X-ray powder diffraction and high-resolution electron microscopy. U(WO{sub 4}){sub 2} is isotypic with the orthorhombic modification of Th(MoO{sub 4}){sub 2}, with eight-coordinated uranium and four-coordinated tungsten. The other three are related to orthorhombic UMo{sub 2}O{sub 8}. The structure of UW{sub 3}O{sub 11} is new and has been deduced from HREM images and verified by simulated image calculations. The unit cell dimensions are a = 13.802(2), b = 7.3998(4), and c = 4.0707(4) {Angstrom}. All three structures are built up of corner-sharing WO{sub 6} octahedra in ReO{sub 3}-type slabs of different width (n). The WO{sub 3} slabs are intergrown with slabs of edge-sharing polyhedra of pentagonal UO{sub 7} bipyramids (PB). These phases are denoted (n)-PB. Some isolated defects in terms of varying widths of the WO{sub 3} slabs have been observed. An ordered intergrowth structure, denoted (4,3,3,3,){sub 2}-PB, of (3)-PB and (4)-PB elements has also been found.
- OSTI ID:
- 223714
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 121; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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