Novel Refractory Alkaline Earth Silicate Sealing Glasses for Planar Solid Oxide Fuel Cells

"Refractory" Sr–Ca–Y–B–Si sealing glasses were developed for solid oxide fuel cells (SOFCs). The objective was to develop sealing glasses with appropriate thermal properties and minimal interfacial reactions with SOFC stack components, particularly ceramic electrolytes and metallic interconnects. The new glasses are described as refractory because their sealing temperatures are higher than traditional sealing temperatures for intermediate-temperature SOFC stacks . Six glasses were formulated and made by a conventional glass-making process. The glasses exhibited rapid crystallization kinetics during intermediate temperature heat-treatments. Their thermal properties were characterized in both the initial glassy state and the final crystallized state. Candidate glasses were also aged for at elevated temperatures. Thermal expansion measurements showed minimal change after aging. One candidate glass (YSO-1) was used to seal anode-supported electrolyte membranes to metallic interconnects at temperatures ranging from in air. Microstructure analysis revealed the presence of near the glass-ceramic/metal interface. The effect of composition on thermal properties and a possible reaction mechanism for the chromate formation are discussed.

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