Atomic Modeling and Electronic Structure of Mixed Ionic–Electronic Conductor SrTi1–xFexO3–x/2+δ Considered as a Mixture of SrTiO3 and Sr2Fe2O5

Abstract

As mixed ionic–electronic conductors (MIECs), ABO3 perovskite oxides and derivative compounds are candidates for applications such as solid oxide fuel and electrolysis cells. Understanding the atomic configuration and electronic structure of MIECs is important because they form the basis of ionic and electronic conductivities; but it is challenging because the materials tend to be non-dilute systems with substantial partial occupancies of the perovskite sublattices. In this work, we present a computational model for Fe-substituted SrTiO3 (STF, SrTi1–xFexO3–x/2+δ), a representative perovskite-derivative MIEC, by considering it as a mixture of perovskite SrTiO3 (x = 0, δ = 0) and brownmillerite Sr2Fe2O5 (x = 1, δ = 0). Our model accounts for disorder in the form of Ti and Fe species on the perovskite B-site sublattice and of O atoms and vacancies VO on the oxygen sublattice. The defect chemistry and electronic structure of STF across the full composition range 0 ≤ x ≤ 1 and for small |δ| is addressed within...