Effects of Doping and Oxygen Vacancy Concentrations on Oxygen Ion Migration in Sm_xCe_(1-x)O_(2-δ): a DFT + U Study

Influence of doping and oxygen vacancy concentrations on oxygen ion or oxygen vacancy(V)migration energies of SmxCe1-xO2-δ(x=0.0625,0.125,0.25 andδ=0.0625,0.125)systems using a GGA+U method are studied.Calculated results show that advantage migration types change from V→O2-to O2-→as x andδincrease.For V→O2-migrations of the Sm0.0625Ce0.9375O1.9375 and Sm0.125Ce0.875O1.9375 systems,electrostatic attractions between Sm"and V,defect associations between Ce3 and V,and steric hindrances of Sm3+affect the migration energies.For O2→V migrations of the Sm0.125Ce0.875O1.875 and Sm0.25Ce0.75O1.875 systems,migration energies of O2-are affected by electrostatic repulsions between Sm3+and O2-and defect associations between Ce3+and V.Increases of the oxygen vacancy and Sm3+doping concentrations benefit the oxygen ion and vacancy migrations,respectively.