Sulfur-doping effects on the oxygen vacancy formation of LaBO3 (B= Fe, Co, and Ni) perovskites

Abstract

Oxygen vacancy (VO) formation in perovskites plays an important role in improving their functional applications. Using density functional theory calculations, we investigated the effect of sulfur (S) doping on the VO formation of LaBO3 (B= Fe, Co, and Ni) perovskites, considering the HS, IS, and LS states of Co ions in LaCoO3 to examine the influence of spin states. Our results show that the weaker electronegativity of S2- relative to O2- leads to a decreased magnetic moment of B atoms directly adjacent to the substituted S and an increase in the electrical conductivity of the insulating systems. The formation energy Ef calculations suggest that S doping is beneficial for the VO formation. In particular, VO is more likely to form at oxygen positions adjacent to the S ion. Moreover, upon S doping, the spin state transition is not a necessary condition to lower the Ef. Instead, the main reason for reducing the Ef of VO is the decreased relaxation energy of the lattice following VO formation. Therefore, we revealed a common mechanism for S-doping promoted VO formation, which could be extended to other perovskites.