Investigation properties of BaO/RO-Al2O3-R2O3-B2O3-SiO2 glass-ceramic sealants for solid oxide fuel cell

Abstract

Glass-ceramics are commonly used as sealing materials for planar solid oxide fuel cells (SOFCs). The major requirements of stack and module builders for these materials are the stability of the coefficient of thermal expansion (CTE), the excellent bonding (sticking) behaviour and the absence of volatile ingredients, which can lead to changes of the material properties and the sealing ability. In this study, the thermal stability of glasses in the BaO-Al2O3-La2O3-B2O3-SiO2 system was investigated, to develop a suitable sealing glass for planar solid oxide fuel cell operating at 800-850 degrees C. The developed glasses were characterised through measurement of different properties, coefficient of thermal expansion (CTE), glass transition temperature (T-g), dilatometric softening temperature (Td), crystallisation behaviour during prolonged heat-treatment, density etc. At a target operating temperature of 750 degrees C, the long-term coefficient of thermal expansion (CTE) of one particular composition (G4) was found to be particularly stable, due to devitrification to a mixture of glasses and ceramic phases.