Oxygen Transport Resistant and Electrically Conductive Perovskite Coatings for Solid Oxide Fuel Cell Interconnects

Abstract

Samples of undoped (LM), Sr-doped (LSM), and Ti-doped (LTM) were fabricated by conventional solid-state ceramic processing methods. The objective of Ti doping was to suppress oxygen vacancy concentration/ion transport, while doping with Sr was to enhance oxygen vacancy concentration/ion transport in relation to undoped LM. Total conductivity, mainly electronic, was measured between 500 and in air. Coatings of LSM, LM, and LTM, thick, were deposited on Haynes 230 (H230) foils by sputtering. Uncoated and coated H230 samples were oxidized in air at for up to . Oxidation kinetics of uncoated and coated samples was studied by measuring oxide scale thickness as a function of time. In all coated samples, oxide scale formed under the coating. All coatings were found to suppress oxidation kinetics. Of the materials studied, LTM was the most protective while LSM was the least protective, in accord with defect chemistry, LTM with the lowest oxygen vacancy concentration and LSM with the highest. Area specific resistance (ASR) measurements showed that LTM-coated samples exhibited the lowest ASR, while the uncoated ones exhibited the highest ASR, again in accord with defect chemistry. A LTM coating should be sufficient to ensure a interconnect life at . A comparison of LTM coating to Mn–Cr–spinel of earlier work shows that LTM coating is times more effective than spinel coating in suppressing oxidation kinetics.