O/M ratio determination and oxidation behaviour of Th0.80Am0.20O2−x

Prieur, Damien; Carvajal-Nunez, Ursula; Somers, J.

doi:10.1016/j.jnucmat.2012.12.011

Cited by 3 publications

(2 citation statements)

References 11 publications

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“…As a general trend, we can see in Figure that the lattice parameter decreases with time for each composition. This evolution of the unit cell is characteristic of an oxidation process, which is besides in perfect agreement with the very high specific area of the studied NPs. Considering the oxidation mechanism in UO 2 , , one can assume here that U IV has been oxidized into higher valence states in agreement with the O/M ratio greater than 2.00.…”

Section: Resultssupporting

confidence: 86%

Charge Distribution in U_1–xCe_xO_2+y Nanoparticles

et al. 2021

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In view of safe management of the nuclear wastes, a sound knowledge of the atomic-scale properties of U 1−x M x O 2+y nanoparticles is essential. In particular, their cation valences and oxygen stoichiometries are of great interest as these properties drive their diffusion and migration behaviors into the environment. Here, we present an in-depth study of U 1−x Ce x O 2+y , over the full compositional domain, by combining X-ray diffraction and high-energy resolution fluorescence detection X-ray absorption near-edge structure. We show, on one hand, the coexistence of U IV , U V , and U VI and, on the other hand, that the fluorite structure is maintained despite this charge distribution.

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Section: Resultssupporting

confidence: 86%

Charge Distribution in U_1–xCe_xO_2+y Nanoparticles

et al. 2021

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“…Although the open literature indicates that the O/M ratio may be derived using several methods including thermogravimetric analysis (TGA), − X-ray diffraction (XRD), − back-titration method, and thermodynamical modeling, the discrepancy of the results often encountered indicates that an accurate determination remains difficult. Indeed, TGA would be the natural method to measure the O/M ratio of an oxide, but in the case of a trivalent substituting cation, one can only assume both initial and final O/M values or rely on a significant change around the 2.0 ratio.…”

Section: Introductionmentioning

confidence: 99%

Aliovalent Cation Substitution in UO₂: Electronic and Local Structures of U_1–yLa_yO_2±x Solid Solutions

et al. 2018

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For nuclear fuel related applications, the oxygen stoichiometry of mixed oxides UMO is an essential property as it affects fuel properties and may endanger the safe operation of nuclear reactors. A careful review of the open literature indicates that this parameter is difficult to assess properly and that the nature of the defects, i.e., oxygen vacancies or U, in aliovalent cation-doped UO is still subject to controversy. To confirm the formation of U, we have investigated the room-temperature stable ULaO phase using several experimental methods (e.g., XRD, XANES, and NMR) confirmed by theoretical calculations. This paper presents the experimental proof of U and its effect we identified in both electronic and local structure. We observe that U is formed in quasi-equimolar proportion as La in ULaO (y = 0.06, 0.11, and 0.22) solid solutions. The fluorite structure is maintained despite the cationic substitution, but the local structure is affected as variations of the interatomic distances are found. Therefore, we provide here the definitive proof that the substitution of U with La is not accommodated by the creation of O vacancies as has often been assumed. The UO fluorite structure compensates the incorporation of an aliovalent cation by the formation of U in quasi-equimolar proportions.

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