Oxygen ion conductivity of doped ceria: A Kinetic Monte Carlo study

The oxygen ion conductivity of rare-earth oxide doped ceria is investigated by means of Kinetic Monte Carlo (KMC) simulations. For the migration energies of oxygen ions our previously calculated values are used which were obtained by first-principles density functional theory calculations for ceria doped with a variety of rare-earth oxides. The aim of the KMC calculations is to obtain a better understanding of the mechanisms leading to the well known maximum in the oxygen ion conductivity as a function of dopant fraction. For this purpose three types of interactions in doped ceria are investigated: the dependence of the jump activation energy on the cation configuration, the trapping or repulsion of oxygen vacancies by dopant ions, and the repulsive interaction between oxygen vacancies. By switching them on and off in the KMC simulations, these three effects are investigated separately and in various combinations. In addition the dependence of the oxygen ion conductivity on temperature is analyzed. The results are discussed with respect to experimental data in the literature.