In this research, a straightforward polyol method has been successfully applied to synthesize Nd0.20GdxCe0.8-xO1.9-x/2 (x = 0, 0.05, 0.10, 0.15, 0.20), (NGDC) rare-earth-co-doped ceria electrolytes. Instead of the nitrate compounds generally used as starting materials, acetate compounds of cerium and dopants, triethylene glycol as solvent and reducing agent were used. A single fluorite phase was obtained after a low temperature (600 degrees C) calcination treatment. A series of NGDC electrolytes are fabricated at the sintering temperature of 1400 degrees C for 6 h. Most of them have relative densities more than 93%. According to the results of X-ray diffraction of neodymium and gadolinium doped electrolytes, all NGDC electrolytes can be produced in a single phase without any other impurity phase. Relative density of NGDC electrolytes increased first and then decreased with the increase of the Gd3+ additive ratio. The total ionic conductivity of the doped and co-doped ceria samples were studied in the temperature range 500 -800 degrees C by using the two-probe AC impedance spectroscopy. It was found that the incorporation of a small amount of cation Gd3+ into the solid solution Nd0.20GdxCe0.8-xO1.9-x/2 allowed an increase in the ionic conductivity of the Nd0.20Ce0.80O1.90 oxide electrolyte. (C) 2019 Elsevier B.V. All rights reserved.