Abstract
New mixed ion-electron conductors are desired to lower the operating temperature of solid oxide fuel cells. The O Frenkel energy and migration of O ions in PrBa(Co/Fe)(2)O-5.5 are studied for this purpose by density functional theory. The electronic structure and charge redistribution during defect formation are analyzed. We demonstrate that Co -> Fe substitution strongly affects the formation of defects and consequently the O migration. The low O Frenkel energy points to a high concentration of O vacancies. The migration of the O ions shows a distinct anisotropy.