| It is the purpose of this project to investigate the possibility of using Plasma Enhanced Metalorganic Chemical Vapor Deposition (PE-MOCVD) as one of the fabrication step for thin-film Solid Oxide Fuel Cells (SOFC). This technique has the advantage to fabricate the state of the art electrolyte (Yttria Stabilized Zirconia or YSZ) at lower temperature than conventional methods such as Electrochemical Vapor Deposition or tape casting. In addition, this technique can fabricate the electrolyte as a thin film and with the desired properties. An important challenge in planar SOFC development is to reduce the operating temperature of ∼1000°C to 700–800°C. This task can be accomplished by reducing the electrolyte thickness (about 10 μ m) so that the IR drop becomes negligible with respect to the electrode polarization.; In this project the main parameters of the PE-MOCVD are identified and quantified. The precursor inlet concentrations are quantified by measuring vapor pressure and evaporation rates. The stability of precursors as function of temperature is investigated. The Y/Zr ratio is correlated to the crystalline phase of the film, and the morphology of the films is studied. The concentration profile is studied as a function of film depth. Thickness uniformity is investigated using transport theories and modeling. Film growth rates are studied as a function of substrate temperature and applied power. A thermal stress analysis is performed, and a new concept for the assembly of SOFC is suggested that significantly reduce thermal stresses in the three layers composite SOFC. Electrochemical characterization and performance is reported for the electrolyte and anode supported SOFCs. |
