SiO_2-CaO-B_2O_3-Al_2O_3 Glass Ceramics as Sealant for Planar Intermediate Temperature Solid Oxide Fuel Cells

The sealant materials for planar intermediate temperature solid oxide fuel cells (ITSOFC) are required for the sealing of the different components to prevent from leakage. Besides the gas tightness, the sealants should show good wetting behavior, matching thermal expansion, chemical stability, dimension stability and insulation. It was investigated that a glass-ceramic based on the SiO2-CaO-B2O3-Al2O3 system as sealant material applied for ITSOFC operated at 850℃. After heat treatment at 850℃ for 2h, the glass ceramic maintained its shape, bonded with 8YSZ electrolyte and Ni-Cr bipolar producing a good gas-tight seal, and its thermal expansion coefficient of 8.9×10-6/℃ was close to 8YSZ. After 100h, no decrease in pressure caused by H2 or O2 leaking was observed, its micrograph showed a good connection with clear interface and the thickness of the diffusive layer of elements was less than 5-10μm. This study shows the glass ceramic sealant is suitable for ITSOFC.