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Title: High-pressure U{sub 3}O{sub 8} with the fluorite-type structure

A new high-pressure phase of U{sub 3}O{sub 8}, which has a fluorite-type structure, forms at pressures greater than ∼8.1 GPa that was confirmed by in situ x-ray diffraction (XRD) measurements. The fluorite-type U{sub 3}O{sub 8} is stable at pressures at least up to ∼40 GPa and temperatures to 1700 K, and quenchable to ambient conditions. Based on the XRD analysis, there is a huge volume collapse (>20%) for U{sub 3}O{sub 8} during the phase transition and the quenched high-pressure phase is 28% denser than the initial orthorhombic phase at ambient conditions. The high-pressure phase has a very low compressibility comparing with the starting orthorhombic phase. - Graphical abstract: α-U{sub 3}O{sub 8} is in a layered structure with orthorhombic symmetry, at high pressures, it transformed to a fluorite-type cubic structure. There are a lot of defects in the cubic structure, and it is a new kind of hyperstoichiometric uranium oxide, which is stable at ambient conditions. - Highlights: • A new fluorite-type high-pressure phase was found in hyperstoichometric UO{sub 2}+x (x∼0.8). • The new high-pressure structure is quenchable to ambient conditions. • Pressure driven phase transition in orthorhombic U{sub 3}O{sub 8} was first found.
Authors:
 [1] ; ; ;  [1] ;  [2] ;  [3] ;  [1] ;  [4]
  1. Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)
  2. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)
  3. Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637 (United States)
  4. (United States)
Publication Date:
OSTI Identifier:
22334208
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 213; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COMPRESSIBILITY; FLUORITE; ORTHORHOMBIC LATTICES; URANIUM OXIDES U3O8; X-RAY DIFFRACTION