High-pressure U{sub 3}O{sub 8} with the fluorite-type structure
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)
- Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637 (United States)
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.
- OSTI ID:
- 22334208
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 213; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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