Glass-ceramic sealants for solid oxide fuel cells: Part I. Physical properties

A family of sealant materials has been developed for use in the solid oxide fuel cell (SOFC) and in other applications in the temperature range of 800–1000 °C. These materials are based on glasses and glass-ceramics in the SrO–La₂O₃–Al₂O₃–B₂O₃–SiO₂ system. The coefficients of thermal expansion (CTE) for these materials are in the range of 8–13 × 10⁻⁶/°C, a good match with those of the SOFC components. These sealant materials bond well with the ceramics of the SOFC and, more importantly, form bonds that can be thermally cycled without failure. At the fuel cell operating temperature, the sealants have viscosities in the range of 10⁴–10⁶ Pa-s, which allow them to tolerate a CTE mismatch of about 20% among the bonded substrates. The gas tightness of a sample seal was demonstrated in a simple zirconia-based oxygen concentration cell.