Low-Temperature Operation of Thin Film Solid Oxide Fuel Cells Prepared by RF Magnetron Sputtering

Thin film solid oxygen fuel cells (SOFC) with yttria-stabilized zirconia (YSZ) electrolyte films 3 to 12 mu m thick, grown by RF magnetron sputtering on porous Ni-YSZ cermet substrates for use as fuel electrodes, were studied to determine their power generation properties at lower operating temperatures in the vicinity of 700 degrees C. Single SOFCs with a YSZ electrolyte film thickness of 3 mu m could be effectively operated at 800 degrees C and had a V-I performance measure of 700 mV-300 mA/cm(2). The open circuit voltage (OCV) of the cells was nearly the same as the theoretical value. However, the OCV drop became larger as the thickness of the YSZ film was decreased, because grain boundaries and pores occurred in the film due to the surface roughness of the substrate. The voltage drop of the cells was due mainly to resistance loss in the YSZ film, and the dominance of this factor increased as the operating temperature decreased. The film conductivity at an operating temperature of 800 degrees C was two orders of magnitude smaller than the theoretical conductivity of the bulk electrolyte. (C) 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(6): 50-57, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10047