The co-doped ceria-based materials with general composition formula Ce_0.8-xY_xSm_0.2O_2-δ (x = 0, 0.02, 0.04, 0.06) were prepared through the sol-gel method. The single phase of the prepared materials was confirmed by X-ray diffraction (XRD). The lattice parameters were determined by least square fitting of UNIT CELL programme. The linear variation of lattice parameter with concentration of Y into the samarium doped ceria (SDC) indicates the validity of Vegard’s law. The crystallite size of the samples obtained by using of Scherrer formula is in the range from 34 nm to 49 nm. The thermal expansion studies were carried out by using dilatometric technique in the temperature range from room temperature to 1000°C. It was observed that the thermal expansion increased linearly with increasing temperature for all the samples. The electrical conductivity was studied using impedance spectroscopy. It was observed that the composition Ce_0.74Y_0.06Sm_0.2O_2-δ showed higher electrical conductivity and lower activation energy (≈1.05 eV) than other compositions in the present investigation. This composition is thus a possible candidate for use the electrolyte in intermediate temperature solid oxide fuel cells (IT-SOFC).