A COMPOSITE ELECTROLYTE FOR AN SOFC CONSISTING OF A CERIA SHEET AND A ZIRCONIA FILM DEPOSITED BY THE SOL-GEL METHOD

The authors investigated a composite electrolyte for solid oxide fuel cells prepared by coating a ceria sheet (Ce{sub 0.8}Gd{sub 0.2}O{sub 2{minus}d} or GDC) with a scandia alumina doped zirconia (0.850ZrO{sub 2}-0.110Sc{sub 2}O{sub 3}-0.04Al{sub 2}O{sub 3}) film by the sol-gel method. The sol-gel film annealed at 1,200 C was examined by X-ray diffraction analysis and found to be in a cubic phase at room temperature. The ionic conductivity of this film is comparable to that of bulk sintered at 1,620 C. Scanning electron microscope observations revealed that the film forms a good interface with the electrolyte of the ceria sheet, even though the annealing temperature is as low as 1,200 C. They fabricated a single cell consisting of a composite electrolyte, a La{sub 0.8}Sr{sub 0.2}MnO{sub 3} cathode and a Ni-YSZ anode. The composite electrolyte consisted of zirconia film about one micron thick deposited by the sol-gel method and a 0.2 mm thick ceria sheet. A cell operated with moist H{sub 2} and O{sub 2} gas exhibited an open circuit voltage of 1.00 V at 800 C. This value is much closer to the value of 1.13 V expected from the Nernst equation than the value of 0.76 V for a cellmore » with a ceria sheet but without the sol-gel film.« less