Preparation and characterization of Y2O3-Sm2O3 co-doped ceria electrolyte for IT-SOFCs

Y2O3-Sm2O3 co-doped ceria (YSDC) powder was synthesized by a gel-casting method using Ce(NO3)3.6H2O, Sm2O3 and Y2O3 as raw materials. Phase structure of the synthesized powders was characterized by X-Ray diffraction analysis. Sinterability of the powders was investigated by testing the relative density and observing the microstructure of the sintered YSDC samples. Electrical conductivity of the sintered YSDC samples was measured using impedance spectra method. Single solid oxide fuel cells based on the YSDC electrolyte were also assembled and tested. The results showed that YSDC powders with single-phase fluorite structure can be obtained by calcining the dried gelcasts at temperature above 800 deg. C. Average particle size of the YSDC powder is 50-100 nm. Relative density of more than 95% of the theoretical can be achieved by sintering the YSDC compacts at temperature above 1400 deg. C. The sintered YSDC sample has an ionic conductivity of 4.74 x 10-2 S cm-1 at 800 deg. C in air. Single fuel cells based on the YSDC electrolyte with 50 μm in thickness were tested using humidified hydrogen as fuel and air as oxidant, and maximum power densities of about 190 and 112 mW cm-2 were achieved at 700 and 600 deg. C, respectively.