Atomistic mechanisms that restrained the diffusion of oxygen vacancies in BaTiO3 doped with rare earth ions as donors were analyzed using molecular dynamics simulations. It was confirmed that the formation of cation vacancies and the reduction of lattice volume were sources of resistance to diffusion. The cation vacancies trapped the oxygen vacancies at the nearby O2- sites via an attractive force associated with Coulombic interaction. In contrast, the rare earth ions repelled the oxygen vacancies, which migrated via O2- sites, and accelerated the diffusion. This was one of the factors that determined the restraint behavior of the diffusion, which depended upon the type of rare earth ion in BaTiO3-based materials.

Molecular Dynamics Study of Oxygen Vacancy Diffusion in BaTiO3 Doped with Rare Earth Ions. Oyama, T., Wada, N., Sakabe, Y.: Key Engineering Materials, 2009, 388, 269-72