Oxygen diffusion in nanostructured perovskites

TL;DR

This paper presents an inhomogeneous diffusion model for oxygen transport in nanostructured perovskites, accounting for microstructural effects and enabling fitting of experimental electrochemical oxidation data.

Contribution

The authors develop an exact analytical solution for oxygen diffusion in nanostructured oxides using Laplace transforms, incorporating microstructural heterogeneity.

Findings

Model fits experimental data well

Diffusion parameters can be qualitatively evaluated

Microstructural effects significantly influence oxygen transport

Abstract

Nonstoichiometric perovskite-related oxides (such as ferrites and cobaltites, etc.) are characterized by fast oxygen transport at ambient temperatures, which relates to the microstructural texturing of these materials, consisting wholly of nanoscale microdomains. We have developed an inhomogeneous diffusion model to describe the kinetics of oxygen incorporation into nanostructured oxides. Nanodomain boundaries are assumed to be the high diffusivity paths for oxygen transport whereas diffusion into the domains proceeds much slower. Using Laplace transform methods, an exact solution is found for a ramped stepwise potential, allowing fitting of the experimental data to theoretical curves (in Laplace transforms). A further model generalization is considered by introducing additional parameters for the size distribution of domains and particles. The model has been applied for qualitative evaluation of oxygen diffusion parameters from the data on wet electrochemical oxidation of nano-structured perovskite SrCo_0.5Fe_0.2Ta_0.3O_{3-y} samples.