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 x 10(-6)/degrees C to 2.8 x 10(-6)/degrees 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.

Automated summary

The addition of Li2O reduced the crystallization activation energy of glass, promoted the precipitation of spodumene and wollastonite, and suppressed the precipitation of anorthite. By controlling the Li2O content and crystallization treatment, the coefficient of thermal expansion of glass-ceramic could be adjusted within a certain range. The glass-ceramic with 3 wt.% of Li2O showed a CTE that was well-matched with SiC ceramic, and exhibited excellent wettability and weldability.