Dielectric relaxation and charge carrier mechanism in nanocrystalline Ce-Dy ionic conductors

Ion dynamics in pure and Dy containing nanoceria has been investigated in the light of different defect associates and their mutual interactions. The samples were prepared through citrate-nitrate auto-ignition method and their single-phase cubic fluorite structure was confirmed from X-ray diffraction and high resolution transmission electron microscopy analysis. The complex impedance spectra showed both grain and grain boundary contribution to total conductivity. The concentration dependent conductivity variation has been discussed with the help of oxygen vacancy concentration and their interactions with the defect associates. The frequency dependence of dielectric permittivity and electric modulus has been analyzed using Havriliak-Negami formalism. The relaxation mechanism is found to be dependent on the formation of different dimers and trimers. Modulus analysis has established the charge re-orientation relaxation of the defects associates. The time-temperature superposition principle has been established by scaling of different spectra.