The diffusion of host and dopant cations in doped ceria: A combined experimental and computational approach

• Applicants: Professor Roger De Souza, Ph.D.; Professor Dr. Steffen Neitzel-Grieshammer
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576674359

Materials based on cerium dioxide (CeO2) are prominent oxide-ion conductors with application in various solid-state electrochemical devices, including solid oxide fuel cells. Introduction of trivalent oxides such as Gd2O3 into the fluorite lattice results in the formation of oxygen vacancies which enable high ionic conductivity at elevated temperatures. Numerous experimental and computational studies have been devoted to the oxide-ion conductivity and its dependence on temperature, substituent type and concentration. However, cation diffusivity in CeO2 has been far less well studied. This is in contrast to the fact that cation ordering influences the oxide-ion conductivity in both the bulk and the grain boundaries. Knowledge of the cation diffusivity is important to understand the evolution of cation order, formation of space charge layers at the grain boundary, and the aging of the material during operation leading to a deterioration of the ionic conductivity. In addition, cation diffusivity has effect on the sintering behaviour and demixing processes. Consequently, knowledge of these diffusion processes is paramount for the characterization of the material beyond oxide-ion conductivity in the bulk. This project aims, through a combined experimental and computational approach, to measure host and impurity cation diffusivities in CeO2 and to determine the associated migration mechanisms. The ultimate goal is a better understanding of the cation diffusion process, the evolution of the cation ordering, and the effect on the oxide-ion conductivity at the grain boundaries. The dependence of cation diffusivity on temperature, oxygen partial pressure, and dopant concentration will be systematically investigated. Experimentally, the cation diffusivity will be determined from diffusion profiles, measured by secondary ion mass spectrometry (SIMS). On the computational side, we will combine various state-of-the-art methods to investigate defect energies, migration mechanisms, diffusion coefficients, and ordering parameters. This includes density functional theory (DFT), Kinetic Monte Carlo (KMC) simulations, machine learning potentials (MLP) and accelerated molecular dynamics (MD) simulations.

• DFG Programme: Research Grants