Development and characterizations of BaO–CaO–Al2O3–SiO2 glass–ceramic sealants for intermediate temperature solid oxide fuel cell application

Several compositions based on BaO–CaO–Al2O3–SiO2 (BCAS) glass system have been studied in this investigation to see their applicability as sealant for solid oxide fuel cell (SOFC). The glasses as well as the corresponding glass–ceramics have been systematically characterized by differential thermal analysis, dilatometry, X-ray diffractometry, electron microscopy and impedance analysis to examine their suitability as sealant. While the glass transition temperature (Tg) determined from DTA are within 600–665 °C, the coefficient of thermal expansion (CTE) can be tailored between 9.5 and 13.0 × 10−6 K−1. These glasses are found to be well adhered with metallic interconnects, such as commercial ferritic steel (Crofer22APU), at an optimum sealing temperature of 850 °C. The shrinkage behavior of the developed glasses in their pellet form has also been investigated. The resistivities of the glass–ceramics, as obtained from impedance analysis, are found to be within 104–106 Ω cm at 800 °C. Under sandwiched condition between two metals, some of the developed compositions are found to maintain this high resistivity even after 100 h of operation. One of the glass compositions has shown a low leak-rate of the order of ∼10−7 Pa m2 s−1.