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Oxygen Lattice Distortions and U Oxidation State in UO2+x Fluorite Structures

Published online by Cambridge University Press:  01 February 2011

Lionel Desgranges  and
Gianguido Baldinozzi
Lionel Desgranges
Affiliation:
lionel.desgranges@cea.fr, CEA, DEN/DEC, Saint-Paul lez Durnace, France
Gianguido Baldinozzi
Affiliation:
gianguido.baldinozzi@ecp.fr, CNRS-Ecole Centrale Paris, SPMS, Matériaux fonctionnels pour l'énergie, Châtenay-Malabry, France
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Abstract

The structural changes induced by the changes of the uranium oxidation state in the ideal fluorite lattice of pure UO2 are discussed. Experimental results evidence strong distortions of the oxygen sub-lattice due to dynamic (at high temperature) or static (at low temperature) fluctuations of the local charges in the cationic sublattice. These changes in the oxidation state are often described using the Vegard’s law because a linear dependence of lattice parameter is observed over a wide range of compositions. Nevertheless, an ideal solid solution model cannot explain this behavior where the elastic effects are directly related to the ionic radii of the cations. Strong evidence is provided that enthalpy effects are relevant in these systems and that they are directly associated with the local structural changes observed during neutron scattering experiments.

Keywords

nuclear materialsdefectsoxide
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1124: Symposium Q – Scientific Basis for Nuclear Waste Management XXXII , 2008 , 1124-Q06-03-O07-03
Copyright
Copyright © Materials Research Society 2009

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