It had been observed that ceria doped with suitable aliovalent cationic dopants improved its ionic conductivity. To investigate this phenomenon, total energy calculations were performed within the framework of density functional theory in order to study oxygen vacancy migration in ceria and Pr-doped ceria. Activation energies for oxygen vacancy formation and migration in undoped ceria and for various migration pathways in Pr-doped ceria were reported. The activation energy value for oxygen vacancy migration in undoped ceria was found to be in reasonable agreement with the available experimental and theoretical results. Conductivity values for reduced undoped ceria calculated using theoretical activation energy and attempt frequency were found in reasonably good agreement with the experimental data. For Pr-doped ceria, oxygen vacancy formation and migration were investigated at first, second, and third nearest neighbour positions to a Pr ion. The second nearest neighbour site was found to be the most favourable vacancy formation site. Vacancy migration between first, second, and third nearest neighbours was calculated (nine possible jumps), with activation energies ranging from 0.41 to 0.78eV for first-nearest-neighbour jumps. Overall, the presence of Pr significantly affected vacancy formation and migration, in a complex manner requiring the investigation of many different migration events. A relationship was proposed which illuminated the role played by additional dopants in lowering the activation energy for vacancy migration in Pr-doped ceria.

Oxygen Vacancy Migration in Ceria and Pr-Doped Ceria: a DFT+U Study. P.P.Dholabhai, J.B.Adams, P.Crozier, R.Sharma: Journal of Chemical Physics, 2010, 132[9], 094104