(V) INVITED: Strain Effects on Oxygen Point Defect Formation and Migration in Perovskite Oxides

Oxygen active materials are capable of rapidly transporting oxygen and exchanging it with the environment and have a wide range of applications, including solid oxide fuel cells, gas separation membranes, oxygen sensors, chemical looping devices, and memristors. Recent work has shown that epitaxial strain can play a significant role in altering the transport of oxygen through oxygen active materials, although there is still significant uncertainty about the scale and physics controlling strain coupling. In this talk we summarize our work using ab initio methods to explore the coupling of strain with oxygen vacancy formation and migration in perovksite materials.

For perovskites we focus on materials of the form LaBO₃, where B = [Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga]. We predict the formation volume and planar strain response of oxygen vacancy formation energy, demonstrating that non-linear coupling of strain and vacancy formation can yield responses qualitatively different than those expected from simple elasticity arguments. We also predict the migration volume and the planar strain response of oxygen migration energetics, here finding that values are quite consistent with a simple elastic strain model. We find that tensile (compressive) biaxial strain reduces (enhances) the oxygen vacancy migration barrier approximately linearly across the systems studied, and suggest a scale of the effect of about -70 ± 50 meV/% strain.