Anisotropic O vacancy formation and diffusion in LaMnO3

Abstract

Anisotropy effects in solid oxide fuel cells are typically not considered because of high operating temperatures. Focusing on the prototypical perovskite LaMnO₃, we apply first-principles calculations to demonstrate that this approximation is no longer valid when the operating temperature is reduced and discuss the consequences for the material properties. In addition, we show that strain and Sr doping can be used to further increase the anisotropy. Tensile strain promotes both the O vacancy formation and diffusion in pristine and Sr doped LaMnO₃, while Sr doping enhances the O vacancy formation. Both in LaMnO₃ and La_0.75Sr_0.25MnO₃ the O diffusion is found to be favorable in the [011] and [01] directions.