Abstract:

Glass-ceramics serve as one of sealing materials for solid oxide fuel cell （SOFC）， and their composition decisively influences the microstructure and coefficient of thermal expansion （CTE）. This work systematically investigated the effect of replacing BaO with MgO or CaO on the properties of BaO-Al₂O₃-SiO₂ glass-ceramics. The results show that partial substitution of BaO by MgO or CaO disrupts the silicate network structure of glass. Meanwhile， Mg²⁺ and Ca²⁺ ions with higher field strength enhance the cross-linking outside the silicate network， leading to an increase in the glass transition temperature T_g of the M-series and C-series glass-ceramics from 724 ℃ to 751 and 784 ℃， respectively. With increasing MgO/BaO mass ratio， the crystallization peak temperature T_p of the M-series glass-ceramics gradually decreases， the precipitation of BaAl₂Si₂O₈ is suppressed， while the formation of magnesium-containing crystalline phases is promoted. For the C-series， T_p decreases first and then rises with increasing CaO/BaO mass ratio， the precipitation of BaAl₂Si₂O₈ is also inhibited， and no other crystalline phases are formed. As the substitution amount of alkaline earth metal oxides increases， the CTE of the M-series glass-ceramics at 800 ℃ rises from 10.43×10^-6 ℃^-1 to 11.98×10^-6 ℃^-1， whereas the CTE of the C-series glass-ceramics exhibits a fluctuating downward trend. Except for the C20 sample， the CTE values of other samples fall within the compatible range （（9.73~11.98）×10^-6 ℃^-1） required for SOFC sealing materials.

Key words: sealing glass-ceramics, alkaline earth metal oxide, coefficient of thermal expansion, thermal property, network structure, crystallization behavior