Extreme multi-valence states in mixed actinide oxides

• DOI: 10.1038/s42004-019-0161-0
• Publication Date: 2019-05-29T10:02:24Z
• Authors: E. Epifano; M. Naji; D. Manara; A. C. Scheinost; C. Hennig; J. Lechelle; R. J. M. Konings; C. Guéneau; D. Prieur; T. Vitova; K. Dardenne; J. Rothe; P. M. Martin
• Keywords: X-ray absorption spectroscopy; Fluorite; Cationic polymerization; Stoichiometry

Abstract To assure the safety of oxide-fuel based nuclear reactors, knowledge atomic-scale properties U 1−y M y O 2±x materials is essential. These compounds show complex chemical properties, originating from fact that actinides and rare earths may occur with different oxidation states. In these mostly ionic materials, aliovalent cationic configurations can induce changes in oxygen stoichiometry, dramatic effects on fuel. First studies Am indicated exhibit particularly electronic local-structure configurations. Here we present an in-depth study compounds, over a wide compositional domain, by combining XRD, XAS Raman spectroscopy. We provide evidences co-existence four cations (U 4+ , 5+ 3+ ) which nevertheless maintain fluorite structure. Indeed, sublattice basically unaffected extreme multi-valence states, whereas defects are sublattice.