SOLID OXIDE FUEL-CELL WITH COMPOSITE ELECTROLYTE CONSISTING OF SAMARIA-DOPED CERIA AND YTTRIA-STABILIZED ZIRCONIA

A composite oxide containing samaria-doped ceria [SDC, (CeO2)(0.8)(SmO 1.5)(0.2)] and yttria-stabilized zirconia [YSZ, (ZrO2)(0.92)(Y2O3)(0.0 8)] was developed as an electrolyte for a solid oxide fuel cell (SOFC) . A SOFC with a YSZ electrolyte was characterized by a high open-circu it voltage (OCV) and a steep decrease in voltage, V, with increasing c urrent, I, whereas that with a SDC electrolyte exhibited a low OCV and a gradual decrease of its V-I curve. A biphasic electrolyte microstru cture with SDC and YSZ was proposed in which SDC grains are dispersed in a YSZ matrix. In this composite structure, the electronic conductio n caused by reduction of the SDC was effectively blocked by the YSZ ma trix. An SOFC with this composite electrolyte offered the advantages o f YSZ with its high OCV and SDC with its gradual decrease of the V-I c urve. The SDC content and the particle size significantly affected the power-generation characteristics of a cell with this composite electr olyte. The electrode polarization was significantly lowered by using t he SDC or the composite electrolyte.