Conditions Extrêmes et Matériaux : Haute Température et Irradiation
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2025

ACL
doi

L.Desgranges, A.Canizares, 'Evidence of a phase transition from UO2-x to UO2+x', J. Nucl. Mater. 617 (2025) doi:10.1016/j.jnucmat.2025.156161

Uranium dioxide has been extensively studied for >70 years with regards to its importance as main nuclear fuel used worldwide. From a thermodynamic point of view, UO2 was considered up to now as a single phase, in which point defects would explain its sharp change of oxygen potential when going from hypo to hyper-stoichiometry. Here, we demonstrate using Raman spectroscopy, that the change from hypo to hyper-stoichiometry should be considered as a phase transition. This leads us to a change of paradigm about UO2 that is now a border between UO2-x and UO2+x