This work presents the ionic transport properties in some nanocrystalline double doped cerias, i.e., Ce0.8Gd0.1Pr0.1O2-delta and Ce0.8Gd0.15Pr0.05O2-delta with various average grain sizes, in the intermediate temperature region. The correlations between electrical and dielectric properties of these materials have been established and variation of conductivity with respect to temperature has been thoroughly discussed. All the materials are found to be ionic in nature and show high value of ionic conductivity at intermediate temperatures. The nanocrystalline Ce0.8Gd0.1Pr0.1O2-delta material (irrespective of grain size), shows lowest association energy, i.e., 0.03 eV, which is close to the theoretically predicted lowest value (0.02 eV) in double doped ceria. A repulsive force is expected between the free oxygen vacancies at the grain boundary regions at higher temperatures, which restricts the rise in grain boundary conductivity and results in decrease in total conductivity. (C) 2010 Elsevier Ltd. All rights reserved.