Abstract We present a kinetic lattice Monte Carlo model for investigating the oxygen vacancy diffusion in praseodymium-doped ceria. The current approach uses a database of activation energies for oxygen vacancy migration, calculated using first-principles, for various migration pathways in praseodymium-doped ceria. Also, since our first-principles calculations revealed significant vacancy-vacancy repulsion, we investigate the importance of that effect by conducting simulations with and without a repulsive interaction. The two models show distinct maximum for ionic conductivity as a function of dopant concentration. Initially, as dopant concentrations increase, vacancies increase, so conductivity increases. However, at higher concentrations, vacancies interfere and repel one another, and dopants trap vacancies, creating a traffic jam that decreases conductivity, which is consistent with the experimental findings. The activation energy for vacancy migration increased with increasing dopant concentration in agreement with the experimental data. This effect is primarily due to the increasing likelihood of finding two Pr ions near an oxygen vacancy, requiring higher energy to overcome these barriers. There is also a smaller effect of vacancies impeding the movement of other vacancies due to repulsive forces. The current methodology comprising a blend of first-principle calculations and kinetic lattice Monte Carlo techniques provides a very powerful fundamental tool for predicting the optimal dopant concentration in ceria related materials.
Citation: Journal of Solid State Chemistry
Pub Type: Journals
Doped ceria, vacancy migration, kinetic lattice Monte Carlo mdoeling