Plasma-sprayed components for SOFC applications

The major challenge in the development of plasma sprayed components for SOFC was the fabrication of dense electrolytes by atmospheric plasma - spraying (APS) avoiding cracks typically generated during the spraying process. Compared to conventional plasma - sprayed ceramics both the number of micro - cracks and segmentation cracks have to be reduced considerably to achieve sufficiently low leakage rates.Based on a detailed understanding of the formation of plasma - sprayed coatings appropriate process conditions have been established to reach the target values. The major influencing factors are the particle properties in the plasma jet, the substrate temperature, the kind of movement of the gun during deposition, the particle size distribution of the used YSZ powder, and the powder feeding rate. In addition, also the used APS gun plays a major role. With the Triplex 11 gun it was possible to produce rather thin (<= 40 mu m) YSZ layers with sufficiently low leakage rates without any thermal post - treatment.As substrates tape - casted ferritic steel sheets have been used. The anode was also sprayed by APS using a separate injection of NiO and YSZ. Electrochemical performance was measured after wet - chemically applying a LSCF cathode. The values of the measured open circuit voltage (OCV) were comparable to the ones of sintered cells, indicating the high density of the produced electrolytes. The optimized cells showed at 0.7 V cell voltage a power density of 500 mW/cm(2) @ 1073 K. (c) 2006 Elsevier B.V. All rights reserved