Effect of Glass Cooling Rate on the Crystallization Behavior and Structure of Lithium Aluminosilicate Glass-ceramics

The glass cooling rate during forming process has significant effect on the crystallization behavior and structural uniformity of Li2O-Al2O3-SiO2 (LAS) glass-ceramics. Finite element analysis indicated that the cooling rate of 10 mm thick glass was notably lower than that of 2 mm thick glass. The central temperature of LAS glass was still above 700℃ even after the sample was cooled for 15 s, which led to the formation of crystal stones in the parent glass. The microstructure of LAS glass and glass-ceramics with different thickness were analyzed using DTA, IR and SEM. Since the 8 mm thick glass cooled slowly, primary crystal nuclei were generated in the glass interior. After heat treat- ment, a β-spodumene phase was formed in the interior, while a β-quartz solid solution phase formed on the surface. On the contrary, primary crystal nuclei were not generated in the 3 mm thick glass due to its high cooling rate. A single and uniform β-quartz solid solution phase was found after heat treatment. Therefore, the high glass cooling rate and the temperature uniformity of glass are very important for the preparation of structurally uniform LAS glass-ceramics.