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Title: Crystal structures of U(Ta,W){sub 5}O{sub 16} and U(Ta,W){sub 2}O{sub 8} revealed by high-resolution transmission electron microscopy

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 inmore » 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.« less

Authors:
;  [1]
  1. Stockholm Univ. (Sweden). Dept. of Inorganic Chemistry
Publication Date:
Sponsoring Org.:
Swedish National Science Research Council (Sweden)
OSTI Identifier:
349927
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 144; Journal Issue: 1; Other Information: PBD: Apr 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL STRUCTURE; URANIUM OXIDES; TANTALUM OXIDES; TUNGSTEN OXIDES; ELECTRON MICROSCOPY; X-RAY DIFFRACTION; LATTICE PARAMETERS; CRYSTAL DEFECTS; DATA

Citation Formats

Askeljung, C, and Sundberg, M. Crystal structures of U(Ta,W){sub 5}O{sub 16} and U(Ta,W){sub 2}O{sub 8} revealed by high-resolution transmission electron microscopy. United States: N. p., 1999. Web. doi:10.1006/jssc.1999.8135.
Askeljung, C, & Sundberg, M. Crystal structures of U(Ta,W){sub 5}O{sub 16} and U(Ta,W){sub 2}O{sub 8} revealed by high-resolution transmission electron microscopy. United States. doi:10.1006/jssc.1999.8135.
Askeljung, C, and Sundberg, M. Thu . "Crystal structures of U(Ta,W){sub 5}O{sub 16} and U(Ta,W){sub 2}O{sub 8} revealed by high-resolution transmission electron microscopy". United States. doi:10.1006/jssc.1999.8135.
@article{osti_349927,
title = {Crystal structures of U(Ta,W){sub 5}O{sub 16} and U(Ta,W){sub 2}O{sub 8} revealed by high-resolution transmission electron microscopy},
author = {Askeljung, C and Sundberg, M},
abstractNote = {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.},
doi = {10.1006/jssc.1999.8135},
journal = {Journal of Solid State Chemistry},
number = 1,
volume = 144,
place = {United States},
year = {1999},
month = {4}
}