La 2O 3–Al 2O 3–B 2O 3–SiO 2 glasses for solid oxide fuel cell applications

Abstract

La 2O 3–Al 2O 3–B 2O 3–SiO 2 glasses free of alkaline earth metals were prepared in this study for SOFC applications to relieve the poison caused by BaCrO 4 or SrCrO 4 formation. The apparent densities, coefficients of thermal expansion (CTE), and softening points of the La 2O 3–Al 2O 3–SiO 2–B 2O 3 glasses prepared in this study ranged respectively from 3.24 to 4.54 g/cm 3, 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 SiO 2 content and escalated with increase in La 2O 3 content. Crystallization of La 9.51(SiO 1.0404) 6O 2 and La 4.67(SiO 4) 3O was observed in part of the glasses after soaking at 800 °C. Two CTE modifiers, MgO and SDC, effectively increased the CTE of La 2O 3–Al 2O 3–SiO 2–B 2O 3 glasses. The composites of selected La 2O 3–Al 2O 3–B 2O 3–SiO 2 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/cm 2) per min at 800 °C. This property seems highly promising for ensuring long-term stability of the sealing materials for SOFC applications.