Electrical Conductivity of Pure and Yttria‐Doped Uranium Dioxide

Abstract

The conductivities of both pure urania and urania doped with <10 mol% yttrium were measured as a function of the oxygen partial pressure between 800° and 1400°C. Yttrium enhances the p ‐type electronic conductivity for near‐stoichiometric oxygen concentrations, allowing the hole mobility to be determined as μ=(5547/ T ) exp(‐0.032 aJ/ k T) cm 2 /Vs, confirming a small polaron transport model. Using this mobility, the hole concentration in pure urania was calculated as a function of the degree of nonstoichiometry and temperature and then compared to models for the formation of defect clusters. Increasing numbers of mobile holes created per excess oxygen ion with increasing temperature indicate that the holes must dissociate from the oxygen defect clusters at high temperature and suggest that the oxygen defects may dissociate as well.