title: Oxide ion transport in Sr2Fe1.5Mo0.5O(6-δ), a mixed ion-electron conductor: new insights from first principles modeling.
abstract: We use ab initio density functional theory + U calculations to characterize the oxide ion diffusion process in bulk Sr2Fe1.5Mo0.5O(6-δ) (SFMO) by analyzing the formation and migration of oxygen vacancies. We show that SFMO's remarkable ionic conductivity arises from its intrinsic content of oxygen vacancies and a predicted very low migration barrier of such vacancies. Theoretical analysis of the electronic structure reveals a crucial role played by strongly hybridized Fe 3d/O 2p states to achieve the attendant mixed ion-electron conductor character so important for intermediate temperature fuel cell operation. We predict a next-nearest-neighbor-type migration pathway for the O(2-) ion should dominate. The low energy barrier of this pathway is mainly related to electrostatic interactions with homogeneously distributed Mo in the SFMO sublattice. We identify the reasons why Fe-rich perovskites, with the key addition of a certain concentration of Mo, produce excellent electronic and ionic transport properties so crucial for efficient operation of intermediate temperature solid oxide fuel cells.
authors.affiliation: Department of Chemical Sciences, University of Naples Federico II, Naples 80126, Italy.
authors.forename: Ana B
authors.initials: AB
authors.lastname: Muñoz-García
authors.forename: Michele
authors.initials: M
authors.lastname: Pavone
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Ritzmann
authors.forename: Emily A
authors.initials: EA
authors.lastname: Carter