International Journal of Engineering and Technology

Nanocrystalline form of pure ceria (CeO2) and metal (Mg or Sc) doped ceria was attempted for 10 mol %. Also, Mg and Sc co-doped ceria with Ce1-x(Mg0.5Sc0.5)xO2 (x=0-0.24) was prepared as an electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs) by co-precipitation method. The synthesized different compositions of pure and doped nanocrystalline powders were then subjected to powder X-ray diffraction (XRD) for phase and structural identification. All the nanocrystalline samples were found to be ceria based solid solutions of fluorite type structures. A.C. impedance spectroscopy measurements in the frequency range of 50Hz to 5MHz was carried out to study the grain, grain boundary and ionic conductivity of doped ceria samples in the temperature range of 400-600oC. The sample Ce0.84(Mg0.5Sc0.5)0.16O2 composition showed highest ionic conductivity i.e., 1.923 x 10-2 S/cm at 500oC. Its morphology and composition was investigated using scanning electron microscopic analysis (SEM) and energy dispersive X-ray spectrometry (EDS) and conductivity behavior was compared with those of pure ceria and singly doped ceria electrolytes namely Ce0.9Mg0.1O2 and Ce0.9Sc0.1O2. The impedance analysis reveals that the sample Ce0.9Mg0.1O2 was found to have higher ionic conductivity compared to Ce0.9Sc0.1O2 in the temperature range of 400–600°C. The co-doped ceria showed a much higher conductivity in air at 500oC in comparison to that of singly doped ceria. Therefore, these co-doped ceria are also the more ideal electrolyte materials for IT-SOFCs. Nyquist plot shows the major contributions were due to the grain boundary resistance contributions which accounts for the higher ionic conductivity in case of the dopants. These dopant effect on the ceria is discussed in detail.