Study On Crystallization Mechanism Of Li₂O-Al₂O₃-SiO₂ Glass-Ceramic Containing Fluoride And Phosphide

Li₂O—A1₂O₃ — SiO₂ is one of the most valuable and widely used glass ceramic systems. In this paper, fluoride and phosphide were added into LAS glass for supplying application basis. The crystallization mechanism, nucleation and crystallization, structure and performance of glass were analyzed.The crystallization mechanism of LAS glass containing fluoride and phosphide had been analyzed by DTA(Differential Thermal Analysis) and XRD(X-ray Diffraction) analysis. The kinetic parameters such as crystallization active energy were calculated by Kissinger, modified Kissinger, JMA equation and modified JMA equation to analyze the influence of compound content on glass crystallization kinetics. The phase separation, nucleation and crystallization, physical and chemical performances, crystal phase, crystal size and intensity of LAS, the influence of fluoride and phosphide on the heat treatment structure and performance of LAS glass were analytically studied by TEM(Transmission Electron Microscope), DTA, XRD, SEM(Scanning Electron Microscope). Physical and chemical performances of LAS glass ceramics containing fluoride and phosphide were studied.The mechanism of crystallization changes with different temperature zones. The grain formation dominated during the initiative low temperature while the diffusion played the important role during the high temperature. The crystallization active energy of LAS glass was 280.70KJ/mol when the ratio of F and P was 1:1. The crystallization peak temperature deduced with the input of fluoride. The crystallization active energy of LAS glass containing no fluoride and phosphide was 314.23KJ/mol. The crystallization active energy of LAS glasscontaining phosphide and no fluoride was 427.70KJ/mol .The fluoride decrease the crystallization peak temperature of LAS glass—ceramic, The free energy of crystallization of LAS glass-ceramiccontaining fluoride and phosphide was decreased by 140kJ/mol.The result of crystallization action research to LAS glass shows that fluoride and phosphide promoted the phase seperation of LAS glass, especially with the low concentration. The nucleation temperature and time increased while crystallization temperature raised a little with phosphide .On the contrary, the fluoride had a great effort on both nucleation and crystallization temperature. The P-spodumene phase with particlesize of 50-1 OOnm was prepared with both the fluoride and phosphide. The optimum nucleation system of LAS glass with 1:1 ratio of F and P was 700°C/lh while the crystallization system was 800°C/2h.Based on the study of mechanics and calorifics performance of LAS glass containing fluoride and phosphide and the analyze of the relationship between the microstructure and performance, the data shows that the LAS glass containing F and P had better mechanical intension, lower thermal expension coefficient > higher consistency and chemistry stability compared with the LAS glass no fluoride and phosphide high crystalline fraction, nano-microstructure have important influence on the performance of LAS glass-ceramic 0...