The aim of this study is to prepare Er and Sm co-doped CeO(2)electrolytes via the Pechini method and investigate the effects of simultaneous addition of Sm and Er on the structural and electrical features of CeO2. The structural, functional group analysis, microstructures, and electrical properties of the electrolyte samples are conducted by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and impedance spectroscopy (IS). All the calcined and sintered electrolytes were obtained with cubic fluorite crystal structure without secondary oxide phases. After sintering at 1400 degrees C, highly dense electrolytes were achieved (> 90%). The IS measurements indicated that the highest ionic conductivity was observed for the singly doped Ce0.80Sm0.20O1.90(sigma(750 degrees C)= 3.86 x 10(-2)S/cm) electrolyte. sigma(750 degrees C)was found to be 3.82 x 10(-2), 1.73 x 10(-2), 0.61 x 10(-2)S/cm for Ce0.80Er0.05Sm0.15O1.90, Ce(0.80)Er(0.10)Sm(0.10)O(1.90)and Ce0.90Er0.10O1.95, respectively.