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 C. X-ray diffraction (XRD) analysis of the YCT powders calcined up to 1,400 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% H2 showed no significant differences in the temperature range of 25–800 C. The absolute values of the total electrical conductivity of the ceramics measured between 450 and 900 C in Ar/4% H2 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 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.