Ceria doped with heterovalent cations, such as alkaline earth and rare earth ions, has been considered one of the most promising electrolyte materials for intermediate temperature solid oxide fuel cells. The present trend is to investigate the co-doping approach in ceria to improve further its electrical conductivity. In this study, Ce(NO3)(3).6H(2)O, Gd(NO3)(3).6H(2)O, Sm(NO3)(3).6H(2)O nitrate salts were used as the starting materials to form co-doped ceria electrolytes of Ce0.9-xGd0.1SmxO2-delta (x = 0, 0.05, 0.10) using the Pechini method. The samples were characterized by means of X-ray diffraction, scanning electron microscopy and electrochemical impedance spectroscopy methods. The results of the impedance spectroscopy revealed that Ce0.85Gd0.10Sm0.05O1.925 sample exhibited the highest ionic conductivity of 4:23 x 10(-2) Scm(-1) at 750 degrees C in air.