Supported electrolyte membrane sofcs for reduced temperature using Zr(Sc)O2, Ce(Gd)O2, and (La,Sr)(Ga,Mg)O3

Supported electrolyte membrane type SOFCs were prepared by co-fire process using Zr(SC)O-2, Ce(Gd)O-2, and (La,Sr)(Ga,Mg)O-3 as electrolyte. Electrolyte films were prepared upon supports, such as NiO-cermet, by wet green film processes, such as electrophoretic deposition, doctor blade, slurry dip coat, and then co-fired. It was concluded that co-firing of Ce(Gd)O-2 electrolyte cell would not be feasible because of its fragility on sintering. It was also concluded that (La,Sr)(Ga,Mg)O-3 electrolyte cell is not suitable for co-fire process due to a mutual reaction between support and electrolyte, because it requires high temperature (1500degreesC) sintering. NiO-cermet supported Zr(SC)O-2 cells were prepared successfully. The optimum power density was 1.8 (900degreesC), 1.2 (800degreesC), 0.4 (700degreesC), 0.1 (600degreesC) W/cm(2). Improvement of electrode will be able to make the Ni-Zr(SC)O-2/Zr(SC)O-2/Pt- Zr(SC)O-2 cell operation below 700degreesC feasible. However, improvement of cathode by using (La,Sr)CoO3 was unsuccessful due to the formation of an insulating layer with Zr(Sc)O-2. Insertion of Ce(Gd)O-2 protective layer (2 mum) between Zr(Sc)O-2 and (La,Sr)CoO3 cathode was examined but the results were worse than the case of Pt- Zr(SC)O-2 cathode. It may be due to the formation of a poor conducting layer between, Ce(Gd)O-2, (La,Sr)CoO3, and Zr(Sc)O-2.