Effect of Crystallization Temperature on Phase Composition and Thermal Expansion Coefficient of Li₂O-ZnO-Al₂O₃-SiO₂ Glass-ceramics

The effect of crystallization temperature on the phase composition and thermal expansion coefficient(TEC) of Li2O-ZnO-Al2O3-SiO2(LZAS) glass-ceramic was studied by means of DTA,XRD,SEM and thermal analyzer methods.The results show that the crystallization of βⅡ-Li2ZnSiO4 occurred after the glass was treated at 625 ℃,and cristobalite crystallite formed at 650 ℃;then β-quartz solid solutions replaced cristobalite crystallite gradually with the temperature increasing.The transformation from βⅡ-Li2ZnSiO4 to γ0-Li2ZnSiO4 took place at 750 ℃.The crystallization phases in the glass-ceramics obtained at the temperature higher than 800 ℃ were β-quartz solid solutions and γ0-Li2ZnSiO4,and the size of crystal particles increased gradually.The thermal expansion coefficient of the glass-ceramics which formed at different crystallization temperatures varied from 72×10-7 ℃-1 to 119×10-7 ℃-1 in the temperature range of 20-500 ℃,which increased first and reached to the maxinum at 650 ℃,then decreased and changed to be steady.