Defect-driven transport phenomena are fundamental to the operation of fast ion-conducting solid electrodes and electrolytes. During operation, intrinsic or extrinsic defects serve as the primary pathways for ionic migration. Among these defects, the critical role of oxygen vacancies extends to a broad class of fast-ion conductors, where their presence and mobility directly impact the efficiency of oxygen-ion transport. Materials that accommodate high concentrations of oxygen vacancies, such as fluorite and perovskite crystals, often exhibit enhanced ionic conductivity and redox behaviour, which are vital for applications including solid oxide fuel cells (SOFCs) and oxygen separation membranes. Within this context, perovskite crystals have garnered significant attention due to their tunable defect chemistry and fast oxygen-ion conduction, particularly the perovskite La0.5Sr0.5CoO3, known for its excellent mixed ionic-electronic conduction.
In this work, EQUALITY partners from Fraunhofer ENAS employ first-principles calculations to systematically investigate the impact of 3d transition-metal doping on the oxygen vacancy formation energies in the perovskite. Two magnetic states, namely the ferromagnetic and paramagnetic states, are considered in their models to capture the influence of magnetic effects on oxygen vacancy energetics. The author's results reveal that the oxygen vacancy formation energies are strongly dependent on both the dopant species and the magnetic state. Notably, the magnetic states alter the vacancy formation energy in a dopant-specific manner due to double exchange interactions, indicating that relying solely on the ferromagnetic ground state may result in misleading trends in doping behaviour. These findings emphasise the importance of accounting for magnetic effects when investigating oxygen vacancy properties in perovskite oxides.
Read the paper: https://doi.org/10.48550/arXiv.2507.07614
