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.