Oxygen Self-Diffusion and Conduction Mechanism of Thoria

The self-diffusion coefficient of oxygen in single crystal thoria was determined at 1,350°C in an 18O-enriched CO2 atmosphere of oxygen partial pressure 3×10−4 atm. The coefficient was close to the intrinsic self-diffusion coefficient determined in an oxygen atmosphere of 0.27 atm indicating the oxygen partial pressure independence. On the basis of the results, the mechanism was discussed for the conductivity data for thoria in the literature being due to the intrinsic diffusion and the extrinsic diffusion of oxygen ion and due to the intrinsic p-type electronic conduction predominant under high oxygen partial pressures.