Solid electrolytes C%sSmo.2 xPrxO2-δ （x=0.02, 0.04, 0.06, 0.08） were prepared by citric-nitrate method. The microstructure and electrical properties of such materials were examined by X-ray diffraction （XRD）, atomic force microscopy （AFM）, Raman spec- troscopy （Raman）, X-ray photoelectron spectroscopy （XPS） and impedance spectroscopy analyses, Specifically, results from XRD analysis showed that samples calcined at 800 ℃ for 4 h possessed single-phase cubic fluorite structure, and the average grain size was found to be 36--45 nm. Further Raman spectral analysis indicated that oxygen vacancies should be present in the cubic fluorite struc- ture of Ce0.sSmo.laPr0.08Oe~, and Pr-doping seemed to increase their concentration significantly. AFM images showed that the grain size grew with the increase of Pr substitution. XPS analysis confirmed the existence of oxygen vacancies in the lattice of Ceo.sSmoA2Pro.osO2_~ in which Pr3＋ and Pr4＋ co-existed. AC impedance spectra indicated that the conductivity of Ceo.sSm0.2-xPrx02＋ increased with the increase of Pr-doping but the conduction activation energy decreased. Notably, it appeared that sample Ceo.sSmo.12Pro.o802-x （aaoooc=l.21xlO-z S/cm, Ea=0.77 eV） exhibited conductivity superior to Ceo.sSmo.2Ol.9 （aro0.c=2.22×10-3 S/cm, Ea= 1.02 eV） because it possessed higher conductivity and lower activation energy. At 600 ℃, the conductivity of Ce0.sSrno.12Pr0.0802m was 4.45 times higher than that of the un-doped material.
