Abstract: Abstract The structure and conductivity of rare earth co-doped ceria Ce0.8Gd0.2–xPrxO1.9 (x=0, 0.02, 0.10) solid solutions synthesized by sol-gel method were characterized by X-ray diffraction , Raman , X-ray photoelectron spectroscopy and Impedance spectra. XRD measurement showed that all powders calcined at 800 ℃ crystallized in single cubic fluorite structure . The average grain sizes were between 23nm and 30 nm. X-ray photoelectron spectroscopy analysis suggested that the mixed valence Pr3+ and Pr4+ ions coexisted in the solid solutions. The Raman spectra analysed that the solid solution Ce0.8Gd0.2–xPrxO1.9 were cubic fluorite structure with the oxygen vacancies.The oxygen vacancy concentration could be increased by doped Pr in Ce0.8Gd0.2–xPrxO1.9. Impedance spectra showed that conductivity of rare earth co-doped ceria Ce0.8Gd0.2–xPrxO1.9 (x=0.02, 0.10) was higher than that of single rare earth doped ceria Ce0.8Gd0.2O1.9(σ600oc =1.62×10–3 S.cm–-1). Ce0.8Gd0.10Pr0.10O1.9 possessed maximum conductivity. At 600℃, the conductivity was 6.15×10–3 S.cm–1 and Ea=0.64eV (<400℃), Ea=0.82eV（>400℃），which was assigned to higher oxygen vacancy concentratin and the hopping electron transition of small polaron in Ce0.8Gd0.2–xPrxO1.9 samples.

Key words: sol-gel method, Ce0.8Gd0.2-xPrxO1.9 solid solution, X-ray photoelectron spectroscopy, Raman spectrum, conductivity