High Temperature Glass-ceramic Seals for SOFC Applications

A novel borosilicate glass, gc9, with the main compositions of BaO-Al2O3-B2O3-SiO2 and other minor additives, has been developed by INER as a high temperature seals for solid oxide fuel cell (SOFC) stacks. The glass transition temperature (Tg) and softening temperature (Ts) of gc9 glass are 652ºC and 745ºC, respectively. Its average coefficient of thermal expansion (CTE) is about 11.0 ppm/ºC (RT~800ºC), which is compatible with that of interconnect and MEA of a SOFC stack. Additionally, a proper balance of sealant properties, such as its viscosity and shrinkage behavior at different temperatures, is essential to have a successful sealing for a SOFC stack. The viscosity evolution and shrinkage amount of a gc9 glass powder pellet at elevated temperatures were measured using a high temperature parallel plate viscometer. Under an external loading of 0.080 MPa, the minimum viscosity, viscosity reflection point, and shrinkage percentage are 108 Pa•s, 806ºC, and 64%, respectively.