Abstract
A series of barium-aluminum-borosilicate system glasses, designated as GC9, with the formula of 34BaO–4.5Al2O3–9.5B2O3–34SiO2–1ZrO2–xLa2O3–(17–x)CaO, where x = 0, 1, 3, 5, 7 in mol %, have been developed as the high-temperature sealants using for solid oxide fuel cells (SOFCs). The effects of lanthanum-to-calcium (La/Ca) ratios on the thermal and crystalline properties of the GC9 glass were investigated in the present study. The density, glass transition temperature (Tg), and softening temperature (Ts) of the GC9 glass increase with increasing the La/Ca ratio. The average coefficient of thermal expansion (CTE) in the temperature range from 25 to 650°C for the glass system varies from 8.25 × 10−6 to 9.49 × 10−6 K−1. The Tg, Ts and CTE for the optimized GC9 glass are 652, 745°C, and 9.48 × 10−6 K−1, respectively, at the La/Ca ratio of 0.833. After annealing at 750°C for 4 h in air, the crystallinity of the GC9 glass increases with increasing the La/Ca ratio and the crystalline phase is mainly Ba3La6(SiO4)6. In addition, the GC9 glass with a La/Ca ratio of 0.833 possesses well wetting and adhesion joining with metallic interconnect, and ceramic positive electrode-electrolyte-negative electrode (PEN) plate after sealed at 850°C for 4 h.
