Strain Engineering in Ba₇Nb₄MoO₂₀ Hexagonal Perovskites for Enhanced Oxygen-Ion Conductivity

This study investigates how in-plane strain affects oxygen migration barriers in Ba 7 Nb 4 MoO 20, a high-performing hexagonal perovskite-derived oxygen-ion conductor, using Density Functional Theory calculations and the Nudged Elastic Band method. Our research examines the effects of in-plane strain across three orientations (uniaxial a, uniaxial b, and biaxial a + b ) within a range of −5% to +3% from the equilibrium geometry. We found that compressive strain decreases the energy barrier for oxygen-ion migration in all tested cases, with reductions of up to 0.14 eV compared with the energy barrier of 0.98 eV in the unstrained configuration. Continuous Symmetry Measure analysis is employed to elucidate the structural changes responsible for the decreased activation barriers. These findings have significant implications for optimizing epitaxially grown hexagonal perovskite structures through strategic substrate selection, which may potentially enhance energy conversion and storage technologies.