An experimental method, based on measurements of the expansion of a single crystal as a function of PO2 was used to determine the concentration of U vacancies in hyper-stoichiometric uranium dioxide. The results were consistent with the concentration of electrical carriers measured in the same conditions, they were also in qualitative agreement with a theoretical modelling proposed in the literature. However, an improved interpretation would require to take into account the clusters of O interstitials and vacancies.

Characterisation of Uranium Vacancies in Hyper-Stoichiometric Uranium Dioxide. L.Desgranges, M.Gramond, C.Petot, G.Petot-Ervas, P.Ruello, B.Saadi: Journal of the European Ceramic Society, 2005, 25[12], 2683-6