A composite electrolyte for an SOFC consisting of a ceria sheet and a zirconia film deposited by the sol-gel method

We investigated a composite electrolyte for solid oxide fuel cells prepared by coating a ceria sheet (Ce(0.8)Gd(0.2)O(2-d) or GDC) with a scandia alumina doped zirconia (0.850ZrO(2)-0.110Sc(2)O(3)-0.04Al(2)O(3)) film by the sol-gel method. The sol-gel film annealed at 1200 degrees 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 1620 degrees 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 1200 degrees C. We fabricated a single cell consisting of a composite electrolyte, a La(0.8)Sr(0.2)MnO(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(2) and O(2) gas exhibited an open circuit voltage of 1.00 V at 800 degrees 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 cell with a ceria sheet but without the sol-gel film.