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

doi:10.3724/SP.J.1077.2012.00400

Abstract

Abstract:

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 treatment, a b-spodumene phase was formed in the interior, while a b-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 b-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.

Key words: lithium aluminosilicate glass-ceramics, finite element analysis, cooling rate, structure

CLC Number:

TQ171

DONG Wei, LU Jin-Shan, FENG Zhi-Jun, LI Yao-Hui. Effect of Glass Cooling Rate on the Crystallization Behavior and Structure of Lithium Aluminosilicate Glass-ceramics[J]. Journal of Inorganic Materials, 2012, 27(4): 400-404.

Figures/Tables 10

Table 1 Composition of LAS glass /wt%

Composition	SiO₂	Al₂O₃	Li₂O	TiO₂	ZrO₂
Content	60.0	23.0	4.0	1.5	2.5
Composition	Na₂O	P₂O₅	BaO	ZnO	Sb₂O₃
Content	2.0	1.5	1.5	1.5	1.5

Table 2 Performance parameter of LAS glass (1650℃)

Parameter	Value
Specific heat/ (kJ·kg^-1·℃^-1)	1102.73
Thermal conductivity/(W·m^-1·K^-1)	10.584
Density/(g·cm^-3)	2.337
Viscosity/(dPa·s)	30

Fig. 1 Temperature distribution in 2 mm thick glass with different cooling time

Fig. 2 Temperature distribution in 10 mm thick glass with different cooling time

Fig. 3 Relationship between the central temperature of glass with different thicknesses and the cooling time

Fig. 4 Infrared spectra of LAS glass with different thicknesses

Fig. 5 DTA curves of LAS glasses with different thicknesses

Fig. 6 Digital picture of LAS glass-ceramics with different thicknesses

Fig. 7 XRD patterns of LAS glass-ceramics with different thicknesses

Fig. 8 FE-SEM images of LAS glass-ceramics

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