Simultaneous Deposition of LSM and YSZ for SOFC Cathode Functional Layers by an APS Process

In order to reduce the manufacturing costs of SOFC layer systems the atmospheric plasma-spray (APS) process is an attractive technique. Especially the deposition of high performance cathodes, which are essential for a high power density of the SOFC, are of major importance. The cathode functional layer (CFL) has to provide a high amount of triple-phases boundaries to allow the cathodic oxidation reaction. A typical materials mixture used for such a CFL is the perovskite (La0.65,Sr0.3)MnO3 (LSM) and the fully Y₂O₃-stabilized zirconia (YSZ). A sufficiently porous layer has to be formed where both components are mixed on a sub-micrometer scale. In addition to the tough challenge concerning the creation of a suitable microstructure of a CFL deposited by an APS process two additional difficulties have to be solved: i.) a decomposition of the perovskite and ii.) a chemical reaction between the LSM and the YSZ during the atmospheric plasma-spray process must be avoided. Suitable spray processing strategies were developed to overcome these problems. Cathode functional layers were produced by an atmospheric plasma-spray process using a multi-cathode Triplex-APS torch. Coatings are characterized by SEM, EDX, XRD and the porosity was determined by digital image analysis. SOFC layer systems with the new developed CFL are tested in single fuel cell tests.