Evaluation of Metallic Interconnects for use in Intermediate Temperature SOFC

Abstract

Foil samples of Haynes 230 and 430 stainless steel were coated with thin layers of Mn and La metal, oxidized in air and humidified hydrogen atmospheres at 800°C for various periods of time, and evaluated for use as metallic interconnects in planar SOFC. A Mn-coating on the interconnects promoted the formation of the spinel phase (Mn, Cr) 3 O 4 while suppressing the formation of Cr 2 O 3 during oxidation. The area specific resistance (ASR) of the oxide layer on the Mn-coated Haynes 230 samples (-0.24 Ωcm 2 at 800°C) was significantly less than that formed on the uncoated sample (-1.2 Ωcm 2 at 800°C). The oxide layer formed on the La-coated Haynes 230 consisted primarily of the perovskite phase La(Cr, Mn)O 3 . The ASR of the perovskite oxide layer formed on the La-coated Haynes 230 was an order of magnitude lower than the oxide layer, primarily Cr 2 O 3 , formed on uncoated Haynes 230. Planar SOFC stacks operated with coated interconnects delivered double the maximum power and exhibited half the total stack resistance as compared to stacks operated with uncoated Haynes 230 interconnects.