Synthesis of Solid Oxide Fuel Cell with Graded Structure from Aqueous Solution

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For the practical use of solid oxide fuel, the realization of lightweight and compact cell stack with large area and low electric resistance is necessary and the use of ceramic materials in thin film shape is important. Comparing with conventional methods for forming thin film, such as CVD, spattering and sol-gel method, synthesis of ceramic thin film from aqueous solution can form uniform thin film with large area and complicated shapes. This technique needs no heat treatment, which is injurious because of the possibility of deformation and crack of the thin film. It is low-cost process, because no expensive equipment is required. Using these characteristics of this technique, fuel cell with a graded structure can be made by gradually changing the composition of the solution. By making a fuel cell with graded structure, a coefficient of thermal expansion changes continuously and the fracture of the cell by thermal stress can be avoided. By adding boric acid, which can make stable comp … More lex with fluoride ion to metal-fluoro-complex solution, hydrolysis of the fluoro-complex proceeded. By using this reaction, zirconia and lanthanum-transition metal perovskite type oxide could be synthesized from aqueous solution. By synthesizing in a vacuum globe box, the influence of oxygen in air was eliminated and fine control of the material was conducted. By using LB films apparatus, the surface of substrates was finely controlled. The result of analyzing the mechanism made it clear that seed crystals play an important role in the synthesis from aqueous solution. By using this technique, LaMnO_3 particles could be deposited uniformly and in high density on an YSZ substrate at normal temperature and under normal pressure. It is supposed that partial dissolution of YSZ and deposition of LaMnO_3 proceeded simultaneously. This result suggests the possibility of manufacturing graded structure. A fuel cell with graded structure is promising solution for the fracture problem of the cell by thermal stress. The electrode is also expected remarkably high activity, because the surface of the LaMnO_3 particles has many irregularities. Less