Synthesis of ceria-based nanopowders suitable for manufacturing solid oxide electrolytes

Co-precipitation method and hydrothermal synthesis were used to fabricate nanopowders of pure CeO2 and singly or co-doped ceria materials in the CeO2-Sm2O3-Y2O3 or CeO2-Gd2O3-Sm2O3 systems. All sintered powders and samples were found to be pure CeO2 and ceria-based solid solution of fluorite-type structure. The surface areas of CeO2-based nanopowders were measured by the one-point BET method. The morphologies of powders were observed by means of transmission electron microscopy. Particle sizes of ceria powders synthesised by the hydrothermal method ranged from 9 to 15 nm, the particle sizes of powders calcined at 800 degrees C ranged from 13 to 26 nm. The TEM observations indicated that all CeO2-based powders consisted of isometric in shape and agglomerated particles. Scanning electron microscope was used to observe the microstructure of the sintered samples. Electrical conductivity was studied by the a. c. impedance spectroscopy in the temperature range 200-700 degrees C. The oxygen transference number was determined from EMF measurements of oxide galvanic cells. It was found that co-doped ceria materials such as Ce0.8Sm0.1Y0.1O2 or Ce0.85Gd0.1Sm0.05O2 seem to be more suitable solid electrolytes than singly-doped ceria Ce1-xMxO2 (M-Sm, Gd, Y, x = 0.15 or 0.20) for electrochemical devices working in the temperature range 600 - 700 degrees C.