Density functional theory investigation of the electronic structure and defect chemistry of Sr_1-xK xFeO₃

Solid oxide fuel cells (SOFCs) efficiently generate electricity, but high operating temperatures (T op > 800 °C) limit their utility. Reducing T op requires mixed ion-electron conducting (MIEC) cathode materials. Density functional theory is used here to investigate the role of potassium substitutions in the MIEC material Sr1-xK xFeO3 (SKFO). We predict that such substitutions are endothermic. SrFeO3 and SKFO have nearly identical metallic electronic structures. Oxygen vacancy formation energies decrease by ~0.2 eV when x K increases from 0 to 0.0625. SKFO is a promising SOFC MIEC cathode material; however, further experimental investigations must assess its long-term stability at the desired operating temperatures.