Oxygen ion diffusion in cation ordered/disordered GdBaCo₂O₅₊δ

Abstract

We use molecular dynamics in conjunction with an established set of Born model potentials to examine the oxygen ion diffusion mechanism in the double perovskite GdBaCo2O5+δ. We predict that the mechanism of oxygen diffusion is highly anisotropic diffusion occurring only in the Gd–O and adjacent Co–O layers. For GdBaCo2O5.5 the activation energy of oxygen diffusion is 0.5 eV. We investigate the effect that cation disorder of the Gd–Ba sublattice has upon the diffusivity, the anisotropy and the diffusion mechanism in GdBaCo2O5+δ, which is a model system for double perovskites and other layered compounds. Cation disorder results in a reduction of the oxygen diffusivity and the appearance of diffusion along the c-axis of the material. Oxygen diffusion becomes effectively isotropic when the cation sublattice is disordered.