Examination of U valence states in the brannerite structure by near-infrared diffuse reflectance and X-ray photoelectron spectroscopies

• Published in: Journal of nuclear materials Vol. 317; no. 1; pp. 46 - 53
• Main Authors: Finnie, Kim S., Zhang, Zhaoming, Vance, Eric R., Carter, Melody L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.04.2003; Elsevier
• Subjects: Applied sciences; Energy; Exact sciences and technology; Fuels; Nuclear fuels; Preparation and processing of nuclear fuels; W0100; C0400; A0700; U0200; S0200; Uranium; Valence; Sintering; Nuclear fuel; Oxidation; High temperature; Reflectance; Grain boundary; X-ray photoelectron spectra; Thorium
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/S0022-3115(03)00004-7

The valence state of uranium doped into a f 0 thorium analog of brannerite (i.e., thorutite) has been examined using near-infrared (NIR) diffuse reflectance (DRS) and X-ray photoelectron (XPS) spectroscopies. NIR transitions of U 4+, which are not observed in spectra of brannerite, have been detected in the samples of U x Th 1− x Ti 2O 6, and we propose that strong specular reflectance is responsible for the lack of U 4+ features in UTi 2O 6. Characteristic U 5+ bands have been identified in samples in which sufficient Ca 2+ has been added to nominally effect complete oxidation to U 5+. XPS results support the assignments of U 4+ and U 5+ by DRS. The presence of residual U 4+ bands in the spectra of the Ca-doped samples is consistent with segregation of Ca 2+ to the grain boundaries during high temperature sintering.