Edge dislocation slows down oxide ion diffusion in doped CeO2 by segregation of charged defects

Abstract

Strained oxide thin films are of interest for accelerating oxide ion conduction in electrochemical devices. Although the effect of elastic strain has been uncovered theoretically, the effect of dislocations on the diffusion kinetics in such strained oxides is yet unclear. Here we investigate a 1/2<110>{100} edge dislocation by performing atomistic simulations in 4–12% doped CeO2 as a model fast ion conductor. At equilibrium, depending on the size of the dopant, trivalent cations and oxygen vacancies are found to simultaneously enrich or deplete either in the compressive or in the tensile strain fields around the dislocation. The associative interactions among the point defects in the enrichment zone and the lack of oxygen vacancies in the depletion zone slow down oxide ion transport. This finding is contrary to the fast diffusion of atoms along the dislocations in metals and should be considered when assessing the effects of strain on oxide ion conductivity. Electrochemical devices based on oxide materials, such as batteries or fuel cells, rely on the transport of ions through the crystal lattice. Here, the authors model ion diffusion through CeO2and observe that edge dislocations slow down ion diffusion, contrary to similar processes in metals.