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Air plasma spraying of SOFC composite cathodes White, Bradley

Abstract

Air plasma spraying (APS) has been used to produce porous composite cathodes containing (La0.8Sr0.2)0.98Mn(LSM) and yttria stabilized zirconia (YSZ) for use in solid oxide fuel cells (SOFCs). Preliminary investigations focused on determining the range of plasma conditions under which each of the individual materials could be successfully deposited. A range of conditions was thereby determined that were suitable for the deposition of a composite cathode from pre-mixed LSM and YSZ powders. A proof of concept SOFC containing a plasma sprayed composite cathode was then produced and tested to confirm the desired electrochemical properties of the coating had been obtained. Many composite cathodes were then produced using different combinations of parameter values within the identified range. Successful coatings were then characterized for composition and microstructure using EDX and SEM. As a result of these tests, combinations of input parameter values were identified that are best suited to the production of coatings with microstructures appropriate for use in SOFC composite cathodes. A selection of coatings representative of the types of observed microstructures were then subjected to electrochemical testing to evaluate the performance of these cathodes. From these tests it was confirmed that the coatings that appeared to have the most suitable microstructures showed the best performance. Finally, a procedure was developed to allow for the deposition of cathode symmetric cells entirely by APS using porous metal interconnect substrates. This will allow for the electrochemical evaluation of cells produced as part of future optimization studies using a production process similar to that expected to be used in the eventual commercial production of SOFCs by APS. Keywords: Solid Oxide Fuel Cell, Air Plasma Spraying, Composite Cathode, LSM, YSZ

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