Electrical study and dielectric relaxation behavior in nanocrystalline Ce<inf>0.85</inf>Gd<inf>0.15</inf>O<inf>2-δ</inf> material at intermediate temperatures

The nanocrystalline material of 15 mol% Gd-doped ceria (Ce 0.85Gd0.15O2-δ ) was prepared by citrate auto ignition method. The electrical study and dielectric relaxation technique were applied to investigate the ionic transport process in this nanocrystalline material with an average grain size of 13 nm and the dynamic relaxation parameters are deduced in the temperature range of 300-600°C. The ionic transference number in the material is found to be 0.85 at 500°C at ambient conditions. The oxygen ionic conduction in the nanocrystalline Ce 0.85Gd0.15O2-δ material follows the hopping mechanism. The grain boundary relaxation is found to be associated with migration of charge carriers. The frequency spectra of modulus M exhibited a dielectric relaxation peak corresponding to defect associates (Gd-Vo ■ ■) ■. The material exhibits very low values of migration energy and association energy of the oxygen vacancies in the long-range motion, i.e., 0.84 and 0.07 eV, respectively. © 2009 Springer-Verlag.