Migration energies of the constituent ions in LaAlO3

Abstract

The calculated migration energies of the constituent elements of LaAlO₃ are comparable to the corresponding calculated migration energies of LaGaO₃ available in the literature. The resulting calculated ranking of the migration energies, $\Delta E_m^{\text{Oxygen}}<\Delta E_m^{\text{A site cation}}<\Delta E_m^{\text{B site cation}}$, is valid for various nominally undoped oxide perovskites (ABO₃). From this ranking it must be concluded that for a specific temperature the ranking of the self-diffusivities of the constituent elements in nominally undoped oxide perovskites reads $D_{\text{Oxygen}}\gg D_{\text{A site cation}}\gg D_{\text{B site cation}}$. The low cation mobilities in undoped oxide perovskites hamper the experimental determination of the diffusivities of the cations considerably. That is predominantly true for the B site elements which probably migrate via an antisite mechanism in the A sublattice. This conjecture is rationalized by an appropriate mechanistic model which is principally valid for any ternary oxide system with very different defect concentrations and cation mobilities in the two cation sublattices.