La2O3–Al2O3–B2O3–SiO2 glasses for solid oxide fuel cell applications

La2O3–Al2O3–B2O3–SiO2 glasses free of alkaline earth metals were prepared in this study for SOFC applications to relieve the poison caused by BaCrO4 or SrCrO4 formation. The apparent densities, coefficients of thermal expansion (CTE), and softening points of the La2O3–Al2O3–SiO2–B2O3 glasses prepared in this study ranged respectively from 3.24 to 4.54 g/cm3, 4.1 to 8.1 ppm/°C, and 912 to 937 °C, depending on the glass composition. The CTE value dropped with the rise in SiO2 content and escalated with increase in La2O3 content. Crystallization of La9.51(SiO1.0404)6O2 and La4.67(SiO4)3O was observed in part of the glasses after soaking at 800 °C. Two CTE modifiers, MgO and SDC, effectively increased the CTE of La2O3–Al2O3–SiO2–B2O3 glasses. The composites of selected La2O3–Al2O3–B2O3–SiO2 glasses and SDC additive on the YSZ substrate were evaluated for use as sealing materials of solid oxide fuel cells (SOFCs). Results indicated that the leakage rates for the composites of A07 glass and 60–70 vol% SDC on the YSZ plate read less than 0.02 (sccm/cm)(kg/cm2) per min at 800 °C. This property seems highly promising for ensuring long-term stability of the sealing materials for SOFC applications.