Diffusion in gadolinium doped ceria thin films: a combined Monte Carlo and molecular dynamics study

Abstract

The mobility of oxygen ions at surfaces and interfaces in solid oxide fuel materials is controversial. Experiments are complex and conflicting results for grain boundary and surface O²⁻ diffusion have been obtained. Thus, it is not clear what the necessary conditions are to optimise O²⁻ diffusion during the manufacturing process. To aid the interpretation of experimental results, combined Monte Carlo and molecular dynamics simulations were applied to model thin films of CeO₂ on binary oxide substrates. The objective of this work is to determine the effects of both tensile lattice strain and segregation on the calculated diffusion coefficients. The distribution of Gd³⁺ and O²⁻ ions has been interpreted as evidence for the formation of a space charge layer at both the interface and surface. The space charge layer impacts the calculated diffusion coefficients at the thin film surface. Moderate tensile strain in the CeO₂ thin film has little influence on the segregation of Gd³⁺ ions.