Ion transport and dielectric relaxation studies in nanocrystalline Ce0.8Ho0.2O2-δ material

The ac electrical conductivity and dielectric relaxation properties of nanocrystalline 20 mol% Ho doped ceria (Ce0.8Ho0.2O2-delta) prepared by citrate auto ignition method, were studied in the temperature range 300-550 degrees C. The conductivity behaviour showed the absence of any precipitation of Ho inside the grains, even though it has the tendency of forming a C-type structure similar to Ho2O3 in association with oxygen vacancies. The frequency spectra of electric modulus M '' exhibits a single relaxation peak corresponding to relaxation reorientation of oxygen vacancy around the Ho+3 ions in the cubic nanostructured material. The migration of oxygen ions in the nanocrystalline Ce0.8Ho0.2O2-delta material takes place through hopping and the migration energy and association energy of oxygen vacancies in the long range order motion are found to be 1.02 and 0.24 eV, respectively. (C) 2009 Elsevier B.V. All rights reserved.