Synthesis and long-term test of borosilicate-based sealing glass for solid oxide fuel cells

A series of borosilicate-based glasses, ternary BaO–SiO2–B2O3 and quaternary BaO–SiO2–B2O3–Al2O3 systems, are prepared as sealing materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). The thermal expansion, crystalline phases, glass forming ability, and thermo-chemical stabilities of the glasses are characterized. Additionally, the effect of the B2O3/SiO2 ratio and Al2O3 and BaO contents on the coefficient of thermal expansion (CTE) are discussed and compared. Test results show that one glass (G6) can fully wet various substrates at the sealing temperature of 1000 °C and match thermal expansion. Possible interfacial reactions between the glass and those cell components aging up to 5000 h are investigated by element mapping, XRD, SEM, and EPMA. Leakage testing was also performed at temperatures up to 650 °C. The results show that the glass (G6) remains amorphous after 5000 h test and is stable under these conditions and compatible with the other fuel cell components.