Influence of Al2O3 addition on the properties of Bi2O3–BaO–SiO2–RxOy (R = K, Zn, etc.) glass sealant

A series of Bi2O3–BaO–SiO2–RxOy (designated BiBaSi glass) glass sealants doped with different contents of α-Al2O3 have been investigated. Al2O3 was added as a modifier to affect the structure and the behavior of the glass. The thermal properties such as glass transition temperature (Tg), softening temperature (Tf) and coefficient of thermal expansion (CTE) were measured by a dilatometer. The sealing performance was investigated by sealing a SOFC single cell stack and measuring its open circuit voltage (OCV). Tg, Tf and suitable usage temperature of the sealants increased with increasing Al2O3 content in the glass, while CTE decreased. When the Al2O3 content was lower than 10 wt.%, excellent sealing performance was observed.

► Tg and Tf of the glass increase with the Al2O3 addition.
► The suitable usage temperature for SOFCs increase with the Al2O3 addition.
► The CTE of the glass decrease with the Al2O3 addition.
► New phases, Bi4(SiO4)3, Ba5Al2O8, Ba5Si8O21, form above 750 °C after aging 5–50 h.
► For BiBaSi glass, Al2O3 content should be lower than 10 wt.%.