Characterization of Oxygen Defect Clusters in UO2+x Using Neutron Scattering and PDF Analysis

In hyper-stoichiometric uranium oxide, both neutron diffraction work and, more recently, theoretical analyses report the existence of clusters such as the 2:2:2 cluster, comprising two anion vacancies and two types of anion interstitials. However, little is known about whether there exists a region...

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Bibliographic Details
Published in:Inorganic chemistry 2018-06, Vol.57 (12), p.7064-7076
Main Authors: Ma, Yue, Garcia, Philippe, Lechelle, Jacques, Miard, Audrey, Desgranges, Lionel, Baldinozzi, Gianguido, Simeone, David, Fischer, Henry E
Format: Article
Language:English
Subjects:
Condensed Matter
Materials Science
Physics
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Summary:In hyper-stoichiometric uranium oxide, both neutron diffraction work and, more recently, theoretical analyses report the existence of clusters such as the 2:2:2 cluster, comprising two anion vacancies and two types of anion interstitials. However, little is known about whether there exists a region of low deviation-from-stoichiometry in which defects remain isolated, or indeed whether at high deviation-from-stoichiometry defect clusters prevail that contain more excess oxygen atoms than the di-interstitial cluster. In this study, we report pair distribution function (PDF) analyses of UO2 and UO2+x (x ≈ 0.007 and x ≈ 0.16) samples obtained from high-temperature in situ neutron scattering experiments. PDF refinement for the lower deviation from stoichiometry sample suggests the system is too dilute to differentiate between isolated defects and di-interstitial clusters. For the UO2.16 sample, several defect structures are tested, and it is found that the data are best represented assuming the presence of center-occupied cuboctahedra.
ISSN:0020-1669
1520-510X
DOI:10.1021/acs.inorgchem.8b00750