Crystallization,Bioactivity And Photoluminescence Properties Of Europium-doped 45S5 Bioactive Glass

Since the discovery of 45S5 bioactive glasses by Hench, the bioactive glasses have been considered as a promising alternative as materials toregenerate, repair and replace the skeletal system. Bioactive glasses have a widely recognized ability to foster the growth of bone cells, and to bond strongly with hard and soft tissues. Compared with the conventional melt method, the bioglass prepared by sol-gel method has a higher surface area and porous structure, and shows a higher bioactivity; meanwhile, by changing the composition or process parameters, the structure and chemical properties of the bioactive glass are able to make adjustments in a wide range, which make it possible to meet different needs by controlling the glass composition and degradation rate of the composition.The d-f transition plays an important role in Eu²⁺ ions. The characteristics of Eu²⁺ luminescence is a broad band spectrum, high luminescent efficiency and variability of wavelength. 5d level of Eu²⁺ could be changed by modulating the crystal structure of the Eu surrounding. The luminescence spectra could be in the visible. The luminescence of Eu³⁺ ions is from transition f-f. The emission spectra are narrower than that of Eu²⁺. Eu³⁺ ion is a sensitive center for the crystal environment because the transition of electronic dipole and magnetic dipole. It could be used to probe the crystal environment of the rare earth ions to identify the crystal structure.In this work, the 45S5 bioactive glass was successfully prepared by the sol-gel method, and the effects of heat treatment temperature on the degree of crystallization, and its biological activity were characterized, respectively. At the same time, Eu²⁺, Eu³⁺ ions were introduced into the bioactive glass to research its photoluminescence properties and crystal structure, respectively.In the third chapter, the 45S5 bioactive glass was prepared by a sol-gel method. Its structure and biological activities were characterized using differential scanning calorimetry（DSC）, X-ray powder diffraction（XRD）, scanning electron microscope（SEM） and Energy Dispersive Spectrometer（EDS） measurements. The main phase was combeite, Na₂Ca₂Si₃O₉. The degree of crystallization of the 45S5 bioactive glass reached the minimum at 700℃ and the maximum at 1100℃. The biological activity was affected by the degree of crystallization of 45S5, reaching the best activity at 700℃. The hydroxyapatite（HA） layer was appeared on the surface of 45S5 after soaking in K2HPO4（0.25 M） solution at 37℃ for 5d.In the fourth chapter, Eu²⁺ ions in Na₂Ca₂Si₃O₉ phosphors derived from 45S5 glass-ceramics were first synthesized by sol-gel method. The crystal phase formations of the phosphors were detected by XRD measurements and the structure refinement. The photoluminescence spectra, the concentration quenching, the luminescence decay curves and the luminescence color chromaticity were measured, respectively. Two kinds of Eu²⁺ sites centered at 545 nm and 505 nm were discussed by analyzing the spectra, concentration-dependent luminescence intensity and lifetimes.In the fifth chapter, Na₂Ca₂Si₃O₉:Eu³⁺ pure phosphors derived from 45S5 glass-ceramics were synthesized by a sol-gel method. The XRD refinement was used to investigate the phase formation and microstructure. The photoluminescence excitation and emission spectra, the doping effect on the emission intensity, and decay curves of the phosphors were measured. They exhibited red light emission. The lifetimes of the phosphors were calculated for various concentrations of Eu³⁺ ions in Na₂Ca₂Si₃O₉. The CIE chromaticity coordinates calculated from the emission lies in the red-orange region. It suggested that the Na₂Ca₂Si₃O₉:Eu³⁺ could potentially be used for monitoring its mineralization process in situ.