Low thermal stress and excellent gas tightness in BaO-CaO-Al2O3-B2O3-SiO2 glass-ceramic for long-term ITSOFC application

The increased coefficient of thermal expansion (CTE) mismatch and mechanical performance degradation of glass-based sealant-induced thermal stress are critical issues for long-term application of solid oxide fuel cell (SOFC). In this work, the double effect of MgO particle on dispersion strengthening, inhibition low-CTE phase transformation, thermal stress, and leakage rate in BaO-CaO-Al2O3-B2O3-SiO2 (BCABS) glass-ceramic were investigated and analyzed. The low-CTE mono-BaAl2Si2O8 phase was suppressed by the MgO particle reacting with BCABS glass-ceramic. Consequently, the CTE for BCABS glass-ceramic without MgO decreases from 11.47 at 1 h to 10.18 x10(-6)/degrees C at 1000 h and reduction rate is higher than 10%, bring about the thermal stress of sealant itself and interface had tripled (200 MPa) and leakage rate was high than 0.06 sccm/cm after 250 h. However, the CTE of 20 wt% MgO-reinforced BCABS glass-ceramic sealant only declined about 4.0% for 1000 h, resulting in slow increase or even decrease in the thermal stress (low than 60 MPa) and maintaining stable leakage rate below 0.04 sccm/cm for 1000 h with three thermal cycles. This study was useful for identifying optimal CTE matching and elastic modulus of glass-based sealant for efficient and stable long-term operation of SOFC.