Effects of Doping and Oxygen Vacancy Concentrations on Oxygen Ion Migration in SmxCe1-xO2-δ: a DFT + U Study

摘要

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 and δ =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-→V as x and δ increase.For V→O2-migrations of the Sm0.0625Ceo.9375Oi9375 and Smo.125Ce0.875Ol.9375 systems,electrostatic attractions between Sm3+ 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.