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Journal articles
New insight in the uranium valence state determination in U$_y$Nd$_{1−y}$O$_{2 \pm x}$
Abstract : The charge compensation mechanisms in U$_y$Nd$_{1−y}$O$_{2 \pm x}$ and its consequence on the overall O stoichi-ometry (or O/M ratio where M = Nd + U) have been studied through the uranium valence state mixture evolution as a function of Nd content up to y = 0.62 by means of high energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) at the U M$_4$-edge. Our results clearly demonstrate the formation of U$^{5+}$ at low Nd content (y < 0.15). Upon increasing the Nd content, oxygen vacancies and the formation of U$^{6+}$ appear as competing mechanisms for intermediate Nd concentrations, leading to the coexistence of U$^{4+}$/U$^{5+}$/U$^{6+}$ mixed valence and an overall hypostoichiometry (O/M < 2.00). Finally, the formation of U 6þ associated with strongly distorted U local environment is observed for high Nd concentrations (y = 0.62), leading to an overall hyperstoichiometry (O/M < 2.00).
Cited literature [35 references]
https://hal-cea.archives-ouvertes.fr/cea-02429995
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Submitted on : Tuesday, January 7, 2020 - 9:11:50 AM
Last modification on : Monday, January 10, 2022 - 10:16:07 AM
Contributor : Bibliothèque Cadarache Connect in order to contact the contributor
Submitted on : Tuesday, January 7, 2020 - 9:11:50 AM
Last modification on : Monday, January 10, 2022 - 10:16:07 AM
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