Fluorite oxides Ce 0.8 Y 0.18 M 0.02 O 2 − δ (denoted as MYDC for M = Ca, Sr, Fe and La), were prepared by the sol–gel method used as electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). X-ray diffraction data show that all the compositions were obtained with highly phase-pure cubic fluorite structure. The relatively density of all the samples sintered at 1400 °C is more than 95%. Surface morphology has been studied by scanning electron microscope showing a dense microstructure. AC impedance spectroscopy measurements have been carried out to study the ionic conductivity of the samples in the temperature range 400–800 °C. In all composition, Ce 0.8 Y 0.18 La 0.02 O 2 − δ shows the maximum conductivity of 0.057 S/cm at 800 °C and shows a good prospect of application in IT-SOFCs. [ABSTRACT FROM AUTHOR]