Journal of Materials Science, Vol.43, No.22, 7057-7065, 2008
Physical characterization of Y2O3-CeO2-TiO2 (YCT) mixed oxides and Ni/YCT cermets as anodes in solid oxide fuel cells
Mixed oxides in the binary Y2O3-CeO2 (YC) and ternary Y2O3-CeO2-TiO2 (YCT) systems as well as the corresponding Ni cermets were evaluated in terms of application as anodes in solid oxide fuel cells (SOFCs) between 650 and 900 degrees C. X-ray diffraction (XRD) analysis of the YCT powders calcined up to 1,400 degrees C showed the cubic fluorite structure of YC and also the formation of an additional phase with pyrochlore structure. The thermal expansion of the ceramics measured in air and Ar/4% H-2 showed no significant differences in the temperature range of 25-800 degrees C. The absolute values of the total electrical conductivity of the ceramics measured between 450 and 900 degrees C in Ar/4% H-2 increased by about 1-2 orders of magnitude compared to those measured in air. Ni/Y0.20Ce0.80O1.9 and Ni/Y0.20C0.75Ti0.05O1.9 cermets with 40 vol% Ni exhibited improved long-term stability regarding their electrical conductivity after annealing at 1,000 degrees C. The diffusion coefficient of Ce in the 8YSZ electrolyte was measured by compatibility tests. Electrochemical measurements on single SOFCs showed high polarization resistance at the anode/electrolyte interface.