Thumbnail
Access Restriction
Open

Author Askeljung, C. ♦ Sundberg, M.
Sponsorship Swedish National Science Research Council (Sweden)
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ CRYSTAL STRUCTURE ♦ URANIUM OXIDES ♦ TANTALUM OXIDES ♦ TUNGSTEN OXIDES ♦ ELECTRON MICROSCOPY ♦ X-RAY DIFFRACTION ♦ LATTICE PARAMETERS ♦ CRYSTAL DEFECTS ♦ DATA
Abstract Two new phases, U(Ta,W){sub 5}O{sub 16} and U(Ta,W){sub 2}O{sub 8}, were formed by solid state reaction of the binary oxides (U{sub 3}O{sub 8}, Ta{sub 2}O{sub 5}, and WO{sub 3}) and Ta metal powder. They were characterized by high-resolution transmission electron microscopy and X-ray powder diffraction techniques. The phases are orthorhombic with the following unit cell dimensions: U(Ta,W){sub 5}O{sub 16}, a = 10.052(1), b = 7.3207(5), and c = 7.9600(4) {angstrom}; and U(Ta,W){sub 2}O{sub 8}, a = 20.232(2), b = 7.4520(4), and c = 4.0652(2) {angstrom}. Both structures are built up of (Ta,W)O{sub 6}-octahedra arranged as ReO{sub 3}-type slabs two octahedra wide. In U(Ta,W){sub 5}O{sub 16} these slabs are connected by a thin lamella consisting of hexagonal UO{sub 8}-bipyramids and (Ta,W)O{sub 6}-octahedra alternating along both the b and c axes. EDS analysis indicated a composition of UTa{sub 1.5}W{sub 3.5}O{sub 16}. The structure is related to UMo{sub 5}O{sub 16}, but with every other layer displaced through {1/2}b. The second phase, U(Ta,W){sub 2}O{sub 8}, is isotypic with the orthorhombic modification of UMo{sub 2}O{sub 8}, in which the ReO{sub 3}-type slabs are intergrown with lamellas of edge-sharing pentagonal UO{sub 7}-bipyramids. The composition UTa{sub 0.5}W{sub 1.5}O{sub 8} was obtained by EDS analysis. Some defects in terms of three-octahedra-wide ReO{sub 3}-type slabs have been observed in U(Ta,W){sub 5}O{sub 16} crystals. EDS analyses of such crystals showed a high-tungsten and a low-tantalum content.
ISSN 00224596
Educational Use Research
Learning Resource Type Article
Publisher Date 1999-04-01
Publisher Place United States
Journal Journal of Solid State Chemistry
Volume Number 144
Issue Number 1


Open content in new tab

   Open content in new tab