Density functional theory + U analysis of the electronic structure and defect chemistry of LSCF (La0.5Sr0.5Co0.25Fe0.75O3−δ). Issue 17 (15th April 2016)

• Record Type: Journal Article
• Authors: Ritzmann, Andrew M.; Dieterich, Johannes M.; Carter, Emily A.
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 17(2016)
• Page Start: 12260
• Page End: 12269
• Publication Date: 2016-04-15
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp01720g
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Density functional theory + U calculations of oxygen vacancy formation in La0.5 Sr0.5 Co0.25 Fe0.75 O3 reveal a preference for configurations. Abstract : Reducing operating temperatures is a key step in making solid oxide fuel cell (SOFC) technology viable. A promising strategy for accomplishing this goal is employing mixed ion–electron conducting (MIEC) cathodes. La1− x Sr x Co1− y Fe y O3− δ (LSCF) is the most widely employed MIEC cathode material; however, rational optimization of the composition of LSCF requires fundamental insight linking its electronic structure to its defect chemistry. To provide the necessary insight, density functional theory plus U (DFT+U) calculations are used to investigate the electronic structure of LSCF ( x Sr = 0.50, y Co = 0.25). The DFT+U calculations show that LSCF has a significantly different electronic structure than La1− x Sr x FeO3 because of the addition of cobalt, but that minimal electronic structure differences exist between La0.5 Sr0.5 Co0.25 Fe0.75 O3 and La0.5 Sr0.5 Co0.5 Fe0.5 O3 . The oxygen vacancy formation energy (Δ E f, vac ) is calculated for residing in different local environments within La0.5 Sr0.5 Co0.25 Fe0.75 O3 . These results show that configurations have the highest Δ E f, vac, while have the lowest Δ E f, vac and may act as traps for . We conclude that compositions with more Fe than Co are preferred because the additional sites would lead to higher overall Δ E f, vac (and lower concentrations), while the trapping strength of the sites is relatively weak (∼0.3 eV).