The effects of LSM coating on 444 stainless steel as SOFC interconnect

Abstract

The effect of oxide (La_0.9Sr_0.1MnO₃, LSM) coating on the commercial stainless steel (STS444) interconnect as SOFC interconnect was examined by measuring the polarization resistance (R _p) of LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8) cathodes of various electrolyte-supported cells (La_0.9Sr_0.1Ga_0.8Mg_0.2 [LSGM], Ce_0.9Gd_0.1O₂ [GDC10], or 8 mol% Y₂O₃-doped ZrO₂ [8YSZ]). The electrochemical impedance of LSCF cathodes was monitored during ∼140 h in air at 600 and 700°C to determine the cathodic R _p values. With or without interconnect contacts, the magnitude of cathodic R _p value of LSGM electrolyte was similar to that of GDC electrolyte and much smaller than that of YSZ electrolyte. However, no apparent difference in the rate of increase was observed among the cathodes on the different electrolytes. Although the R _p value of the LSCF cathode in contact with LSM-coated STS444 was much reduced from that with uncoated STS444, the coating was not perfect to prevent the Cr evaporation from the interconnect and thus to avoid the degradation of LSCF cathode. Thus new coating methods or materials are needed to protect the LSCF cathode from the Cr poisoning.