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

The glass structure, wetting behaviour and crystallisation of BaO-Al2O3-B2O3-SiO2 glass system containing 2-10 mol% Al2O3 were investigated. The introduction of Al2O3 caused the conversion of [BO3] units and [BO4] units into each other and it acted as glass network former when the content was up to 10 mol%, accompanied by the [BO4] to [BO3] transformation. The stability of the glass improved at first and then decreased as Al2O3 content increased from 2 to 10 mol%, the glass with 5 mol% Al2O3 being the most stable. The wetting behaviour of the glasses indicated that excess Al2O3 led to high sealing temperatures. The glass containing 5 mol% Al2O3 was characterised by a lower sealing temperature and is suitable for SOFC sealing. Al2O3 improved the crystallisation temperature of the glass. The crystal phases in the reheated glasses were mainly composed of Ba2Si3O8, BaSiO3, BaB2O4 and BaAl2Si2O8. Al2O3 helped the crystallisation of BaSiO3 and BaAl2Si2O8.