Samples of Ce0.8Sm0.2O2, and Ce0.8Sm0.2-xMxO2 (M=La, Y and 0 < x < 0.2) were sintered from fine powders obtained by co-precipitation/calcinations method. The preparation method and microstructure of samples are presented and discussed. All powders and sinters were found to be ceria-based solid solutions of the fluorite type structure. The results of hardness, fracture toughness and bending strength measurements are reported. The results of electrical properties of the samples investigated by a.c. impedance spectroscopy in temperature range 100-670 degrees C and for frequency range 10(-2)-10(7) Hz are also presented and discussed. The electrical properties of the ceria samples co-doped are found to be improved. The best oxygen-ion conductivity was found for Ce0.8Sm0.1Y0.1O2 compound. Testing results of this compound used as an electrolyte in oxygen-ion concentration cell are also reported. (c) 2008 Elsevier B.V. All rights reserved.