Investigation on the Performance of Li_2O-Al_2O_3-SiO_2 System Glass-ceramics Doped with Rare Earth

Abstract: In this thesis, the research object is Li_2O-Al_2O_3-SiO_2 system glass-ceramics. According Li_2O-Al_2O_3-SiO_2 system glass phase diagram, a set of compositions are designed, and without the change of compositions La_2O_3 and other 4 rare earth are doped in the compositions for extra ingredient, then the glass-ceramics is produced by fusion. The influence of doping with rare earth on the viscosity and the melting temperature is studied and the influence of doping with La_2O_3 on the crystallization、 the structure and the performance is studied;the heat treatment was optimized.In the experiment, the viscosity is studied by means of High Temperature Viscometer, the structure and the appearance are studied by means of DTA、 XRD、 SEM and IR and so on. The performances are studied by means of heat expansion testing、 intension testing and visible light transmission testing and so on.The results indicate that with La_2O_3 and other 4 rare earth addition, the viscosity decreases, especially doping with La_2O_3. With a small amount of La_2O_3 addition, the structure of the LAS system glass-ceramics doesn't show obvious transformation. La_2O_3 doesn't enter the network of glass, but to be the modifier of the network which changes the bond length of Si-0 and the bond angle of Si-O-Si slightly. Because of this, the viscosity、 the glass melting temperature(1610℃) decrease, also La_2O_3 can accelerate the crystallization, but there is no influence on the main crystal phase which is β-quartz, and with adding La_2O_3 the dimension of the crystal and heat expansion coefficient increase, intension performance becomes lower. By repetitive experiment, in order to achieve the integrated performance with 0.5mol% La_2O_3 addition is suitable, and the best heat treatment is 590℃/1h→790℃/2h…
Key words: glass-ceramics; rare earth; the viscosity; the glass melting temperature

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