A few compositions in the system, Ce1 - x - ySmxSryO1.90 have been prepared by citrate-nitrate auto-combustion method. X-ray diffraction data show that all the compositions are solid solution having cubic fluorite structure. Density of the samples sintered at 1350 degrees C has been found to be more than 95% of the theoretical value. Surface morphology has been studied by scanning electron microscope. AC impedance spectroscopy measurements have been carried out to study the grains, grain boundaries and total ionic conductivity of the samples in the temperature range 200-600 degrees C. The composition, Ce0.82Sm0.16Sr0.02O1.90 shows the maximum conductivity i.e. 2.67 x 10(-2) S-cm(-1) at 600 degrees C among all the compositions investigated. This is about two times higher than that of Ce0.80Sm0.20O1.90. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.