Synthesis and characterization of Ytterbium and Samarium Co-doped ceria as an electrolyte for intermediate-temperature solid oxide fuel cell application

Co-doped samples of electrolytes (Ce1-x-ySmxYbyO2-delta (x = y = 0.05,0.1), have been prepared by Sol- gel method and characterized to explore their use as a solid electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). The crystal structure, microstructure, and ionic conductivity have been determined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectrometer (EDX), Raman Spectroscopy (Raman), and impedance spectroscopy respectively. The XRD result reveals that all the samples are single phase with cubic fluorite-type structure. The relative densities of samples sintered at1400 degrees C are about 96% of theoretical densities confirming their use as an electrolyte for IT- SOFC applications. The SEM micrograph confirmed formation of dean grains with distinct grain boundaries. The results of the Raman spectrum showed the formation of oxygen vacancies in YbSDC-samples which are responsible for the diffusion of oxygen ions in the lattice. Based on the impedance spectroscopy analysis, the conductivity of compositions Ce0.9Sm0.05Yb0.05O1.95, Ce0.85Sm0.05Yb0.1O1.925, Ce0.85SM0.1Yb0.05O1.925 and Ce0.8Sm0.1Yb0.1O1.9 found are 1.88 x 10(-3) S/cm, 4.4 x 10(-3) S/cm, 7.0 x 10(-3) S/cm and 6.59 x 10(-3) S/cm respectively at 500 degrees C in air atmosphere. Moreover, the composition Ce0.85Sm0.1Yb0.05O1.925 showed the highest ionic conductivities and least activation energies at all measuring temperatures than other samples in YbSDC-series. All the results have shown that Yb and Sm co-doped ceria are promising electrolytes for intermediate temperature solid oxide fuel cell applications.