氧化铝对IT-SOFC硼酸盐封接玻璃体系的影响研究

Influence of Al_2O_3 on IT-SOFC Borate Sealing Glass System

以传统的玻璃制备方法熔融法制备出适用于固体氧化物燃料电池封接用的BaO-A12O3-B2O3-SiO2体系微晶玻璃封接材料。玻璃封接材料属于多组分玻璃,分别经700℃、800℃和900℃热处理100h后的XRD图谱分析表明,700℃时其主晶相为钡长石BaAl2Si2O8,800℃时析出的晶体也比较多而且较杂,但以钡长石为析出的主晶相。随着烧结温度升高到900℃,原料间的反应更完全,析出单一的钡长石相及少量的BaSiO3相。A12O3的含量适中(5mol%)时,A13+主要作为网络修饰体存在于玻璃网络结构之间,此时使[BO3]转变为[BO4],从而提高玻璃的稳定性;当A12O3超过一定量时,A13+开始作为网络形成体存在于玻璃网络结构之间,又使得[BO4]转变为[BO3],降低了玻璃的稳定性。增加A12O3含量可以提高玻璃的稳定性,降低玻璃的析晶趋势。A12O3含量为5mol%时,玻璃的稳定性比含量为2mol%及10mol%时更好。玻璃A1、A2和A3的热膨胀系数TEC(×10-6K-1)分别为10.68,10.81,10.52,均在允许范围之内。

BaO-Al2O3-B2O3-SiO2 glass-ceramic sealing material suitable for solid fuel cells was prepared by traditional melting method.It belongs to multi-component glass.The XRD analysis of the samples heat-treated 100 h at 700 ℃,800 ℃ and 900 ℃ shows that the main crystal phase is barium feldspar（BaAl2Si2O8） at 700 ℃;the barium feldspar from the precipitation is the main phase at 800 ℃;the reaction among raw materials is more complete and single-phase barium feldspar and a small amount of BaSiO3 crystals are produced at 900 ℃.When the content of Al2O3 is moderate（5 mol%）,Al3＋ exists in the glass system as a network modifier,which transforms into to improve the stability of glass;but with superfluous Al2O3,Al3＋ acts as a network former,which transforms into to decrease the stability of glass.The stability of glass can be improved and the crystal growth in the glass can be reduced by increasing the Al2O3 content.The stability of glass with 5 mol% Al2O3 is better than with 2 and 10 mol%.The thermal expansion coefficients of samples A1,A2 and A3 are 10.68,10.81 and 10.52,within the limits.