An insight into the structure, conductivity and ion dynamics of Sr-Sm co-doped ceria oxygen ion conductors: Effect of defect interaction

In this work, we investigate the structure, conductivity and ion dynamics of mixed di and tri-valent doped Ce0.8Sm0.2-xSrxO2-delta (x = 0-0.2) oxygen ion conductors. The lattice parameter and root mean square strain are significantly affected by the ionic radius of dopants and their solubility into ceria lattice. Due to the solubility limit of Sr2+ ions, SrCeO3 phase increases with the doping concentration of Sr2+. The increase of Sr2+ ions into ceria lattice promotes the formation of large defect clusters by expense of formed oxygen vacancies. The coulombic interaction between oxygen vacancies with substituted dopant cations enhances with Sr2+ ions due to decrease of the value of dielectric constant of the compositions. The defect interaction significantly affects the conductivity values by means of increase of SrCeO3 phase and defect clusters. The conductivity values are found to be consistent with the migration and association energy. The scaled spectra of dielectric tangent loss and real part of complex conductivity confirm the temperature and defect interaction independent nature of hoping mechanism in the compositions.