Abstract

The present thesis work focuses on the stability of intermediate temperature SOFC technologies and it is divided in two parts: (i)cathode stability in anode-supported cells and (ii)fabrication and operation of tubular metal supported SOFCs. In the first part, the stability of ferritic perovskite cathodes currently implemented at IK4-Ikerlan and SOFCpower (LSF-SDC and LSCF-GDC, respectively) was studied in a specific experimental DoE design. The influence of cathode processing and operation conditions together with intrinsic degradation mechanisms and extrinsic ones related to chromium poisoning and air humidification were analyzed in detail. Moreover, the effectiveness of two interconnect coating materials, MCO spinel and novel LNC perovskite against chromium poisoning of the cathode was studied. With this commitment, anode-supported half-cells manufactured by SOFCpower were used making profit of the verified high reproducibility of these cells. In parallel, work at IK4-Ikerlan in tubular MSC technology demonstrated critical instability related to the operation under high fuel utilization and deficient diffusion barrier layer (DBL) implementation. This allowed element interdiffusion during the manufacturing process between the metal support and the anode. In the second part of this thesis work, a second generation (G2) of tubular MSCs based on an innovative DBL has been developed in all aspects. This includes processing parameters optimization and stability studies. During this work, an intrinsic variable degradation mechanism related to the DBL and manufacturing process of MSC turned out to be critical in G2 cells stability during operation. At this point, understanding such a mechanism and determining its origin became the most fascinating challenge of my investigation. Overall, this thesis work focuses in the study of critical parameters in SOFCs stability. Factors affecting the stability of cell components over a wide range of operation conditions and degradation mechanisms related to the manufacturing process and operation are considered in detail.