Ni- and Cu-doping effects on formation and migration energies of oxygen vacancies in Ba0.5Sr0.5Fe1−x (Cu/Ni) xO3−δ perovskites: a DFT + U study

Abstract

The bulk oxygen vacancy formation, migration energy and surface migration energy of BSFCu and BSFNi are calculated in this article. Two important factors affecting the formation and migration energies: the vacancy concentration and Cu/Ni doping are studied. With Cu/Ni doping, the oxygen vacancy formation energy decreases [Evac (BSF \(>\) BSCF \(>\) BSFNi \(>\) BSFCu)]. The activation energies of BSFNi and BSFCu are lower than those of BSF and BSCF cathodes. Therefore, Cu/Ni-doped BSF shows the enhancement of electrochemical activity. We also calculated the surface migration energies of (011) Ba0.5Sr0.5Fe0.75Cu.0.25O3−δ for δ = 0.125, 0.25 and (001) Ba0.5Sr0.5Fe0.75(Cu/Ni)0.25O3−δ for δ = 0.125, which for (011) BSFCu are higher than the bulk value but for (001) BSFCu and BSFNi are lower than the bulk value due to geometry considerations.