Study On Prepration And Upconversion Luminescence Properties Of Oxy-fluoro-tungstosilicate Glasses

Rare earth (RE) doped upconversion luminescence materials are attractive for realizing diode-pumped all-solid-state visible lasers, next-generation lighting or three dimensional display equipment, near-infrared photon detection devices, high-power fiber upconversion lasers and nanometer-sized biological labels, pumped by near-infrared laser diodes. Er3+-Yb3+ ions codoped glass is considered to be one of the most promising materials for upconversion luminescence which have attracted much interest under near infrared excitation. In order to obtain the high luminescence intensity, oxyfluoride glass has recently been used as ideal host materials due to their low cutoff phonon energies property and the luminescence intensity of rare-earth ions can be enhanced. Moreover, oxides possess higher chemical and mechanical stability.First, this thesis reviewed the development and application of rare earth ions doped oxy-fluoro-tungstosilicate glasses for upconversion luminescence. Second, the oxy-fluoro-tungstosilicate glasses and oxy-fluoro-tungstosilicate glass ceramics were prepared by melting-annealing/quenching/thermal treatment method. The structure and upconversion luminescence properties of oxy-fluoro-tungstosilicate glasses and oxy-fluoro-tungstosilicate glass ceramics were studied by absorption spectra, photoluminescence spectra, raman spectra, infrared spectra, differential thermal analysis, simultaneous thermal analysis and X-ray diffraction and so on. The details were listed as following:The intense upconversion luminecense of Er3+-Yb3+ ions co-doped oxy-fluoro-tungstosilicate glass samples were obtained prepared by melting-annealing method. The results indicated that the upconversion process was very sensitive to Er3+ concentration at a constant Yb2O3 concentration of 5 mol%:with the increase of Er3+ content from 0.5 to 1.5 mol%, the upconversion intensity increased gradually, while further increasing Er3+ ions content to 3.0 mol% resulted in a significant fluorescence quenching. The infrared spectra illustrated that the fluorescence quenching was most likely caused by Er3+ ions doped concentration but not by OH-1.The effects of glass network former and modifier on the structure and upconversion luminescence properties of oxy-fluoro-tungstosilicate were studied. The results showed that the intensity of raman spectra and upconversion luminescence increased as the content of network former GeO2 increased. Their intensity was the strongest when the GeO2 content was 50 mol%. This was due to the glass network became looser as GeO2 substituted for SiO2. So the dipole moments changed then the intensity of raman spectra increased. Meanwhile, the looser of the glass matrix network realized the better dispersibility of Er3+ and Yb3+ ions, so the intensity of upconversion luminescence increased. The low phonon energy of GeO2 was also beneficial to the upconversion emission. On the other hand, the raman spectra indicated that the ratio of octahedral [WO6] structural unit and tetrahedral [WO4] structural unit increased when adding CaWO4 to the samples. Moreover, the raman spectra exhibited the same change law and all increased after adding CaWO4 to the samples. Their intensity were the strongest when the ratio of CaWO4 and WO3 was 2.5 mol%:7.5 mol%.The oxy-fluoro-tungstosilicate glass ceramics were prepared by heat treatment heat treated at 720℃～760℃for 2 h～6 h. The effects of the heat treatment temperature and the heat treatment time on the structure and upconversion luminescence properties of the samples were investigated. The results showed that the WO3、Al12W and TiO2 microcrystal was formed after heat treatment at 740℃for 2 h～6 h. When heat treated at 760℃, the samples became opaque due to coexist of the WO3、Al12W、TiO2 phase and Ca4A16O12WO4 phase. On the other hand, the upconversion emission spectra indicated that the heat treated samples had better upconversion emission properties than that of without heat treatment. Its upconversion emission intensity was the strongest after the sample heat treated at 740℃for 4 h indicating that the better dispersibility of Er3+.