Effect of Al2O3 content on BaO–Al2O3–B2O3–SiO2 glass sealant for solid oxide fuel cell

The glass structure, wetting behavior and crystallization of BaO–Al2O3–B2O3–SiO2 system glass containing 2–10 mol% Al2O3 were investigated. The introduction of Al2O3 caused the conversion of [BO3] units and [BO4] units to each other and it played as glass network former when the content was up to 10 mol%, accompanied by [BO4] → [BO3]. The stability of the glass improved first and then decreased as Al2O3 increased from 2 to 10 mol%, the glass with 5 mol% Al2O3 being the most stable one. The wetting behavior of the glasses indicates that excess Al2O3 leads to high sealing temperature. The glass containing 5 mol% Al2O3 characterized by a lower sealing temperature is suitable for SOFC sealing. Al2O3 improves the crystallization temperature of the glass. The crystal phases in the reheated glasses are mainly composed of Ba2Si3O8, BaSiO3, BaB2O4 and BaAl2Si2O8. Al2O3 helps the crystallization of BaSiO3 and BaAl2Si2O8.