Oxygen diffusion in relation to p-type doping in uranium dioxide

In this paper we show how electrical conductivity and intrinsic oxygen diffusion coefficient measurements can be used in conjunction to further our understanding of oxygen related point defects in UO2. Electrical conductivity measurements have enabled an estimate to be made of the positive charge carrier concentration in two sets of samples containing different levels of doping agents. The gas–solid isotopic exchange method was then used to load the samples with 18O tracer atoms the concentration profile of which were subsequently characterised using SIMS and chromatic confocal microscopy. At the oxygen potential and temperature studied (750 °C), application of point-defect theory to our experimental results points to oxygen migration proceeding via an interstitial mechanism and to the fact that impurities control the concentration of negatively charged point defects responsible for atomic migration.