TEM Characterization of Long Term Aged Interconnect Oxide Layers from Real Stack

Abstract

Interconnects from real SOFC stacks operated for 9000h and 20000h are characterized by means of SEM and TEM. This study focuses on the air side of the interconnect, which has been coated with manganese cobalt spinel oxide (MCO) doped with iron. Differences between the zones of air channel and interconnect rib are highlighted. Iron particles are found in the thermally grown oxide (TGO) exposed to the air channel. Manganese-rich crystals are observed close to the steel bulk for the rib contact zone, and in the bottom part of the TGO for the air channel zone. Cobalt is segregating at grain boundaries in the MCO after 20000h. More investigation is necessary to fully understand all mechanisms but the additional information gathered in the present study should help in better designing accelerated testing and modelling.