Study of Li₂O addition on crystallization behavior and thermal expansion properties of CaO-Al₂O₃–SiO₂ (CAS) glass-ceramic and its application for joining SiC ceramic

Various glass-ceramics were prepared based on the CaO-Al₂O₃-SiO₂ system with the addition of Li₂O in an attempt to develop a suitable sealant for SiC ceramic. The effects of Li₂O content on crystallization behavior and thermal expansion properties were systematically investigated. The results revealed that the addition of Li₂O significantly reduced the crystallization activation energy of glass. Besides, as the Li₂O content increased, the precipitation of spodumene and wollastonite was promoted while the precipitation of anorthite was suppressed. By controlling the Li₂O content and crystallization treatment, the coefficient of thermal expansion (CTE) of glass-ceramic could be adjusted in a certain range, from 8.5 × 10⁻⁶/°C to 2.8 × 10⁻⁶/°C. When the content of Li₂O was 3 wt.%, the CTE of the formed glass-ceramic was well-matched with that of SiC ceramic. Furthermore, it was confirmed that this glass-ceramic possessed an excellent wettability and weldability to SiC ceramic.