A DFT+UStudy of Strain-Dependent Ionic Migration in Sm-Doped Ceria

Abstract

Recent experiments on thin films and hetero-structures of ionically conducting oxides have indicated enhancement of oxygen ion conduction typically ascribed to strain-related effects. We performed density functional theory (DFT) calculations with Hubbard U correction to investigate the effects of biaxial lattice strain on the oxygen anion diffusivity in Sm-doped ceria (SDC). Here we found that the migration barriers are strongly affected by the applied strain. The changes in the migration barriers can almost be linearly correlated with cation–anion bond-lengths between the migrating oxygen and its nearest neighbor cations. In this work, we reported various possible dopant configurations for oxygen ion migrations at the vicinity of the oxygen vacancy. Our results indicate that the ionic migration barriers can be lowered by both compressive and tensile strains. The insight gained from this study may enable us to engineer and to improve oxygen ion migration in ceria-based solid electrolyte materials by compression or tension of the lattice parameters.