Post-Test Characterization of an SOFC Short Stack After 17,000 hours of Steady Operation

A typical F-design SOFC short stack of Forschungszentrum Julich was metallographically analyzed after long-term steady-state operation for 17,000 h at 700 degrees C and 0.5 A/cm(2). After scheduled shut down, the stack was partly embedded in resin and subsequently various stack parts were cut from multiple places of interest. All important components (cell, metal parts, sealant, and contact layers) were characterized with respect to microstructural and chemical changes and interactions with the adjacent components. Surprisingly, the post-test characterization revealed less changes and interactions than expected. One clear feature that could be observed was the interaction between the (La,Sr)(Co,Fe)O-3 cathode and volatile chromium species. Another finding was spot-like corrosion in the metallic parts, but this did not cause severe damage. It can be concluded that by tailoring the component materials and the operational conditions, long-term operation of this type of SOFC stacks is possible.