Factors controlling oxygen migration barriers in perovskites

TL;DR

This study uses ab initio calculations on over 40 perovskites to identify key factors influencing oxygen migration barriers, revealing correlations with metal-oxygen bond strength and B-site cation type, aiding the design of better oxygen conductors.

Contribution

It provides a comprehensive database of oxygen migration barriers and identifies new descriptors for designing improved oxygen ion conductors in perovskites.

Findings

Low barriers correlate with low metal-oxygen bond strength.

Perovskites with non-transition-metal B-site cations have the lowest migration barriers.

Weak correlation between migration barriers and structural ideality measures.

Abstract

Perovskites with fast oxygen ion conduction can enable technologies like solid oxide fuel cells. One component of fast oxygen ion conduction is low oxygen migration barrier. Here we apply ab initio methods on over 40 perovskites to produce a database of oxygen migration barriers ranging from 0.2 to 1.6 eV. Mining the database revealed that systems with low barriers also have low metal-oxygen bond strength, as measured by oxygen vacancy formation energy and oxygen p-band center energy. These correlations provide a powerful descriptor for the development of new oxygen ion conductors and may explain the poor stability of some of the best oxygen conducting perovskites under reducing conditions. Other commonly-cited measures of space, volume, or structure ideality showed only weak correlation with migration barrier. The lowest migration barriers (< 0.5 eV) belong to perovskites with non-transition-metal B-site cations, and may require vacancy-creation strategies that involve no dopants or low-association dopants for optimal performance.