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Sodium calcium silicon high crystallization preparation and characterization of transparent glass ceramics system

Author: MeiYuZuo
Tutor: LuAnXian
School: Central South University
Course: Materials Science
Keywords: Yb3+ion Na2O-CaO-SiO2 transparent glass-ceramics microstructure Spectral properties
CLC: TQ171.1
Type: Master's thesis
Year: 2012
Downloads: 98
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Abstract


High crystalline and transparent Yb3+-doped Na2O-CaO-SiO2glass-ceramics were prepared. The optimum heat treatment schedule and crystallization process of the precursor glass were studied. The microstructure and luminescence behavior of the glass-ceramics were researched.In this paper, the Yb3+-doped Na2O-CaO-SiO2glass were prepared by conventional melt-quenching methods. The optimum heat treatment schedule were analysised by differential thermal analysis (DSC) and X-ray diffraction (XRD).The microstructure and luminescence behaviors of the glass-ceramics were studied by scanning electronic microscope (SEM), absorption spectrum and flourescent spectrum, respectively.The results indicate that the compositions of the crystals were Na4Ca4Si6O18 when Na2O-CaO-SiO2glass were heat treated under different conditions. The optimum heat treatment schedule is glass uncleated at595℃for5h and crystallinzed at730℃for1h. When the Na2O-CaO-SiO2glass is heat-treated at (595℃,5h)+(730℃,1h), the spherical crystals with gain size of about100μm are obtained, the crystallinity of the traparent glass reach up to82.93%. Glass-ceramic(B4) which was heated at595℃for nucleation, crystallized in diameter of0.5nm. Glass-ceramic(D1) crystallized in diameter of50μm with treatment of730℃for0.5h, after nucleation. Grains grew to100μm with the elongation of crystallzation time to1h. However, it remained the same with longer crystallzation time for1.5h,2h or3h. The arrangement of crystals was more compact. Degree of crystallization increased, along with macroscopic bubles in the glass matrix.The transmittance of samples AO, B4and D2are over90%,95%and80%, respectively.Because of the pores, the transmittance of sample D4reduce to70%. Both the absorption cross-section and the stimulated emission cross-section of the glass and glass-ceramics increase due to the elongation of crystallzation.With the degree of crystal crystallization increasing, luminescent intensity rises initially and then descends. Due to the pores, sample D4has the minimum luminescent intensity. Theoretical analysis shows that the fluorescece lifetime of precursor glass and glass-ceramics range from1.66to1.00ms. βmin and minimum absorbed pump intensity Imin first decreases and then increases with the heat treatment process. The pump saturation intensity Isat has a decreasing trend with the heat treatment process.The sample D2has the best comprehensive properties, which have a long flourescence lifetime (1.44ms) and the values of βmin, Isat and Imin are0.094,10.22kW/cm2and0.96kW/cm2, respectively.

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