Effect of Al2O3 content on bonding characteristics of CaO-Al2O3-SiO2-TiO2-ZnO based glass-ceramic on ceramic substrate

This work studies the use of the CaO-Al2O3-SiO2-TiO2-ZnO (CASTZ)-based glass-ceramics, as a coating and bonding agent was observed according to the change in Al2O3 substitution amount. Heat-treatment at 1000 degrees C is the standard procedure for bonding glass-ceramics with Al2O3 ceramics. The properties of the glass-ceramics and coatings are examined using X-ray diffraction, scanning electron microscopy, hardness measurements, and Raman analyses, to confirm the actual bonding morphologies and thermal expansion coefficients. Titanite (CaTiSiO5) and willemite (Zn2SiO4) crystal phases are observed depending on the amount of Al2O3 substitution, and as the substitution amount increases, anorthite (CaAlSi2O8) crystal phases appear together. At this time, the microstructure densification and hardness change with variation in the heat-treatment temperature, indicating structural impact on glass, which is confirmed by Raman spectroscopy. A comparative analysis of the coefficients of thermal expansion between the substrate and glass-ceramic, along with actual bonding, reveals an increase in the bonding and wettability at higher Al2O3 substitution levels.