Stability of Glass Ceramic Sealants in Atmospheres with Increased Water Contents

Abstract

Operating solid oxide cells (SOC) in the fuel cell moder as well as in electrolyser mode increases the demands on the stability of glass-based sealants due to higher cell voltages and water contents in the steam atmospheres. Glasses in the system BaO-CaO-Al2O3-SiO2 with B2O3 and La2O3-additions form glass ceramics with extraordinary high CTE-values, suitable as sealants compatible with Crofer 22 APU interconnect in electrolyte supported stacks. The intrinsic properties of a set of glasses are characterized. Sandwich type sealing samples are exposed to a dual atmosphere at 850 °C with an electric voltage of 1,3 V applied across the sealants and a water content of 50 % in the steam atmosphere. In this out-of-stack environment, the resistance of the sealants is recorded. Their resistance over aging time indicates degradation phenomena like interface reactions. By SEM analysis, reactions between sealants and steel interconnect can be correlated with insulating characteristics.