Study And Preparation On Li₂O-Al₂O₃-SiO₂ Transparent Glass-ceramic

Li₂O-Al₂O₃-SiO₂ system transparent glass ceramic(LAS), one of the most important glass ceramic systems, has been extensively investigated and commercialized in electron, chemical , military and so on. In this text, LAS system glass ceramic was studied. The influence of the different heat treatment, composition on the miorostructure and the mechanical properties of glass ceramic was researched by DTA, XRD, SEM, mechanics and thermal coefficient tests. And it has a deep research on the composition, teat-treatment, micro-structure and capability. Then it will draw some conclusions that reason composition and heat-treatment and high-performance glass ceramic substrate.First, we research on the connection of MgO and ZnO-doping content with the glass ceramic's microstructure, mechanical performance and thermal expenditure. The results demonstrate that MgO and ZnO doping make the temperature of melt felled obviously. The crystals were enlarged in the same heat-treatment and other crystal precipitated. The measure of crystalline particle is near 100nm. With the content increasing of MgO and ZnO doping, the thermal expenditure coefficient increased and mechanics properties decreased and when doping 1.5wt%MgO and 0.5wt%ZnO, the sample's properties were best.Second, we research on the heat-treatment. We analyze the effect of the heat-treatments alterations on the mechanical performance, thermal expenditure and transparent rate. And the results demonstrate that the best heat-treatment is 600℃/2h-840℃/2h. The visible light transparent rate of glass ceramic reach 70% and infrared transparent rate reach 90%. The fracture toughness reach 115MPa, the coefficient of the thermal expenditure is 0.2×10^-7℃ (20 400 ℃).At last, we research on the change of nucleation agents(TiO₂ and ZrO₂) for avoiding pigmentation and their effect on the glass ceramic. The results demonstrate that TiO₂, one of the nucleation agents(TiO₂ and ZrO₂) decrease from 2.3wt% to 1.3wt%, the glass ceramic appear noncolor, but the properties decreased obviously. With decreasing of the TiO₂ /ZrO₂ rate, both the melt temperature and viscosity increased. The measure of crystalline particle enlarged quickly. When the ZrO₂-doping reach 4.0wt%, the glass ceramic become jealous sample. With the TiO₂ /ZrO₂ rate decrease, the strength decreased and the strength decreased and the coefficient of thermal expenditure increased.