Lowering the sintering temperature of a gadolinia-doped ceria functional layer using a layered Bi2O3 sintering aid for solid oxide fuel cells

Solid oxide fuel cells are promising renewable energy devices due to their high efficiency and fuel flexibility. As they operate at a higher temperature than other fuel cells, ceramic materials, such as perovskite-based La0.6Sr0.4CoO3 and La0.6Sr0.4Co0.2Fe0.8O3, can be used as electrodes to replace expensive noble metals. However, when the corresponding electrode and yttria-stabilized zirconia electrolyte are sintered together, SrZrO3 produced from a side reaction acts as an insulator and deteriorates the performance of the fuel cell. Thus, the dense functional layer of a ceria-based material should be introduced between the electrode and the electrolyte to suppress the formation of secondary phases. However, in the conventional cell manufacturing process, it is challenging to manufacture a dense functional layer under constrained sintering conditions. In this study, we develop a method for fabricating a dense gadolinia-doped ceria (GDC) functional layer, even under constrained sintering conditions, by using a sacrificial bismuth oxide, Bi2O3, sintering aid layer above the GDC layer. As thermal sintering progresses at 1000–1200 °C, the Bi2O3 sintering aid layer is sublimated, leaving only the pure GDC functional layer. The fabricated dense GDC functional layer characterized by various analysis methods shows improved solid oxide fuel cell performance.