The present paper deals with the preparation, characterization, thermal expansion and the electrical conductivity of co-doped ceria Ce0.8-xSm0.2CaxO2-delta (0.0 <= x <= 0.1)electrolyte materials. These compositions were prepared through the sol-gel method. The phase identification and morphology was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The lattice parameter was determined by X-ray powder diffraction. The thermal expansion was measured using dilatometric technique in the temperature range 30-1000 degrees C. It was observed that the thermal expansion increased linearly with increasing temperature for all the samples. The electrical conductivity was studied using two-probe impedance spectroscopy and it was observed that the composition Ce0.78Sm0.2Ca0.02O2 (-) (delta) showed higher electrical conductivity and lower activation energy (0.79 +/- 0.02 eV) than samarium-doped ceria (SDC) at 700 degrees C. This composition is thus a possible candidate for use as electrolyte in intermediate temperature solid oxide fuel cells (IT-SOFC). (C) 2009 Elsevier B.V. All rights reserved.