Stability of La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 cathodes during sintering and solid oxide fuel cell operation

• Degradation of LSCF/CGO cathodes investigated by SEM, TEM and TOF-SIMS.
• TOF-SIMS analysis shows inter-diffusion regions between cathode and barrier layer.
• Significant Sr diffusion to the CGO–YSZ interface during firing at 1250 °C.
• Cr content in the LSCF cathode increased during cell testing.

Degradation phenomena of La0.58Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO) cathodes were investigated via post-mortem analyses of an experimental solid oxide fuel cell (SOFC) stack tested at 700 °C for 2000 h using advanced electron microscopy (SEM-EDS, HR-TEM-EDS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Similar studies were carried out on non-tested reference cells for comparison. The analysis focused on the LSCF/CGO cathode and the CGO barrier layer, as the cathode degradation can be a major contributor to the overall degradation in this type of SOFC. SEM-EDS and TOF-SIMS were used to investigate inter-diffusion across the barrier layer—electrolyte interface and the barrier layer—cathode interface. In addition, TOF-SIMS data were employed to investigate impurity distribution before and after testing. HR-TEM-EDS was used to investigate possible phase segregation in the LSCF and to look for reaction between the phases. The results show that phase separation and inter-diffusion across the cathode–barrier layer interface and the barrier layer–electrolyte interface happened mainly during sintering and cathode firing, and to a very little degree during the test period.

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