| With the rapid growth of information demand, there is need to a higher request to the transmission no relay transmission distance, super-high-speed and super-big-capacity. The new optical fiber transmission amplifer can effectively broaden the optical fiber transmission band, comparative to the commercial use of the limited band of Er3+doped EDFA fiber amplifer. Since 2001, the report of infrared fluorescence from Bi doped silica glass, the NIR luminescence of bismuth has the potential use of telecommunication-wavelength region, which has been a hotpot research at home and abroad and focus point of many scholars. However, the Bi oped glasses are found to be very sensitive to the preparation and optical fiber drawing process, and the drawback of thermal stability of bismuth is of a problem for many scholars. The drawbacks severely are limited the searching of Bi activeed NIR emission of glasses and the actual application of Bi doped glass.As is known, the glass structure is composed of glass network, which is consistent of galss former and glass modified cations, and the glass matrix would affect the luminescent properties of bismuth ions. Furthermore, it is necessary to know the structure of glass matrix with the NIR emitting thermal stability of Bi actived glasses, which will be conduvtive to understand the Bi actived the NIR emission. To address this challenge, this project will be benefit of exploiting the design and ananlysis of glass structure, thus seeking to a better undstanding of the oringin of Bi actived NIR-emission, providing a theoretical basis for designing, preparing, and the principles of the thermal sability stabilization of Bi ions in glass. Therefor, the main work is based on adjusting and changing the matrix structure of glass, searching the influnce law of diffenent network modifier and network former on the thermal stability of Bi doped glass.The results show that alkali oxides and alkaline earth oxides as the network modified, the NIR-emission thermal stability of Bi actived centers decreasing with the increase radius of ionic ions heat-treatment temperature. The glasses of K2O and Na2O appeared some darkening parts and the fluorescence quenching phenomenon completely undergoing or near the glass transfer point. The results of TEM and XRD show that the darkening phenonmenon of Bi doped glass may be drived from the Bi metal after thermal treatment. The futher study show that the influence of the thermal stability of alkaline earth oxides depend on the radius of cation ions, which can obviously improve the NIR-emitting thermal stability of Bi actived glasses, and it do not appear darkening and obviously fluorescence quenching under the heat-treatment near the softening point. This can be understood by the diffusion or migration of Bi ions in the glass matrix, and the most important reason of reduction of glass defect which lead to the the lack of thermal sability. According to the comparitve results of alkali and alkaline earth, we propose that the main reason of the influence diffusion of Bi ions is the cationic fiel strength, but not the compactness of glass structure. The above phenomena can be understood by the relative higher cationic field strength of alkaline earth oxides may cause the more stable no-briding oxygens, which can restrin the thermally activated diffusion and improve the NIR-emitting centers of Bi ions. We investigated the cationic filed strength of modifiers and thermally treat NIR-emission behavior in air, vacuum and reductive atmosphere, which confirm that the modifier cations with network of higher field strength can improve the valence stability of Bi ions, which proved the important effect of field strength of modifier for the NIR-emitting thermal stability of Bi actived glasses.For further confirming the above conclusion, the comparative experiments of NIR-emission of Bi doped alkaline-earth and alkali mixed alkali effect (MAE) in aluminoborosilicate glasses. The results show that the MAE of alkaline earth oxides and Li2O complex coordination synergism in the alkaline earth oxides and lithium group. The glass network density has significant effect of mixed alkali, which significantly improve the density of the glass and the maximum is in the middle of the two groups. But NIR-emitting thermal stability of the glass is still the higher content of alkaline earth oxides, which is independent of the density of glass network. According to the previous system of mixed alkali silicate glass (Na-Ca) analysis of the structure and the thermal stability of near infrared luminescence, which confirmed the dominance of non-bridging oxygen (NBO) density and stability of the modified is the reason of the changing thermal stability. On the other hand, Effects of the different network formers (B2O3, P2O5 and GeO2) on thermal stability of Bi activated NIR-emitting lithium-aluminosilicate glasses were comparatively investigated. Results show that the different network formers have an obvious influence on the thermal stability of Bi doped lithium-aluminosilicate glasses. Experiments show that undergoing heat-treatment, the thermal stability of Bi activated NIR-emitting centers around 1150 nm in LAS glasses generally decrease with the increase treated temperature. Meanwhile, the dopants of P2O5 and GeO2 are beneficial to the improvement of the NIR emission luminescence of lithium-aluminosilicate glasses. However, the glass sample with B2O3 show worse thermal stability of Bi activated NIR luminescence, forming of trihedral [BO3] to loose the glass network.Accoding to the above reluts, we propose that the high cationic filed strength of rare earth ions (La3+, Gd3+ and Lu3+) may improve the Bi activated alkali-silicate glass effect of NIR-emitting thermal stability. Results show that the Lu3+ ions have high intensity of contraction in favor of enhancing the NIR-emitting thermal stability comparied to other ions. At the same time, we discussed the Bi actived the NIR-emitting thermal stability of the change of RE ions. In futher study, we found that with Lu3+up to 10 mol%, the NIR-emitting intensity of silicate glass can be improved much more than 5 mol% Lu3+... |
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