Highly durable nano-oxide dispersed ferritic stainless steel interconnects for intermediate temperature solid oxide fuel cells

Abstract

Herein, ferritic stainless steel alloys are developed with the dispersion of nano-oxides of reactive elements to improve their oxidation characteristics for solid oxide fuel cell (SOFC) interconnects. Nano-oxides of yttrium, cerium, and lanthanum chromite are homogeneously dispersed in a ferritic stainless steel base powder and specimen pellets are prepared by pressing the powder and sintering it in hydrogen at 1400 °C. The nano-oxide dispersed alloys are tested for oxidation characteristics and electrical properties at 800 °C for 1000 h in air. The results show that the ferritic stainless steel with 3 wt% nano-ceria exhibits significantly improved area-specific resistance (ASR) characteristics. The increase in the ASR for this alloy is found to be only 15 mΩ cm2/kh and is ascribed to the thin dense oxide layer (~0.4 μm), the presence of spinel (MnCrO4) at the outer side of the oxide layer, and the improved oxide layer adherence to the metal substrate. The addition of reactive element oxides altered the oxidation kinetics of the Fe-Cr alloys, thus making nano-oxide dispersed ferritic stainless steel highly durable and most suitable for SOFC interconnects. The oxidation kinetics of the nano-oxide dispersed steel was also discussed as related to cation diffusion.