Vacancy and interstitial oxide ion migration in heavily doped La2-xSrxCoO4 +/-delta

La2-xSrxCoO4 +/-delta, a K2NiF4-type structured oxide, is currently under investigation for its possible application as a cathode material in solid oxide fuel cells operating at intermediate temperature (IT-SOFCs). Here we report a combined energy minimization and molecular dynamics study of oxygen migration mechanisms in the La2-xSrxCoO4 +/-delta material for high Sr levels (x > 0.8). In the oxygen-deficient composition La0.8Sr1.2CoO3.9 the oxide-ion transport mainly occurs through the migration of oxygen vacancies within the perovskite layer of the structure, with possible vacancy paths between adjacent layers. In the oxygen-rich composition La1.2Sr0.8CoO4.1 interstitial oxygen transport is via an interstitialcy mechanism and within the ab plane.