Cation diffusion in ionic conducting oxides was modelled. Example systems of Sr- and Mg-doped LaGaO3 (perovskite structure) and Y-doped ZrO2 (fluorite structure) were investigated. In both systems, the cation diffusion was governed by diffusion via lattice vacancies and not via interstitials. In the LaGaO3, the diffusion of all types of cations was correlated with the formation of a binary vacancy complex of two neighbouring vacancies, on the A and B sites of the perovskite lattice, which were migrating together. This led to very similar cation diffusion coefficients for all four cations. In the ZrO2, the calculated diffusion coefficients of the two cations differed significantly (Y was five times faster than Zr); in good agreement with experiment. The calculated activation enthalpies were close to the experimental ones, indicating that cation diffusion was mainly governed by the migration enthalpy, while the formation enthalpy of a cation vacancy was small.

Modelling of Cation Diffusion in Oxygen Ion Conductors using Molecular Dynamics. Kilo, M., Taylor, M.A., Argirusis, C., Borchardt, G., Jackson, R.A., Schulz, O., Martin, M., Weller, M.: Solid State Ionics, 2004, 175[1-4], 823-7