| Owing to the increasing level of attention on the space exploration,resource exploration,medical diagnosis,and safety inspection,there is rapidly growing need for scintillating materials able to perform reliable radiation monitoring.Though scintillating crystals possess attractive advantages such as outstanding light yield and excellent radiation resistance,they still have limitations for practical applications in some special occasion because of the high cost,complex processing and difficulty in preparing high-resolution scintillating arrays.Hence,novel scintillating materials which can overcome these drawbacks are attracting increasing level of attention.Benefiting from the unique features such as easy fabrication,adjustable composition,great potential for fabrication into flexible scintillating arrays,glasses have become one of the important scintillators in recent years.Based on the classic Bi4Ge3O12 and Lu2Si2O7(Ce)crystals,we have designed and successfully fabricated a series of novel scintillating glasses including Bi2O3-GeO2,Lu2O3-A2O3-SiO2 and Lu2O3-SiO2,which hold attractive properties such as high-density and fast decay.Significantly,the performance of scintillating glasses can be further improved via the strategies including rare-earth ion doping,energy transfer control and crystallization.Furthermore,flexible scintillating fibers have been successfully fabricated and they exhibit high sensitivity to X-ray,point to promising applications for irradiation detection and high-resolution medical imaging.The research progress provides a valuable reference for design and application of novel scintillating glasses.The specific research contents and the results are summarized as follows.(1)One of the critical issue of Bi2O3-GeO2 scintillating glass involves the undesired heterogeneity and colorization caused by Bi element.In this research,we have proposed a collaborative strategy to solve this issue by two-step calcination and melting followed by the controllable glass relaxation.In addition,we have presented the success in the fabrication of the colorless Bi2O3-GeO2 scintillating glass by controlling the valence state of Bi element in glass.The homogeneous Bi2O3-GeO2 scintillating glass having the same stoichiometric ratio with Bi4Ge3O12 has been prepared.Interestingly,by heat-treatment of the glass at the glass transition temperature,the brown Bi2O3-GeO2 glass becomes the colorless one and the optical transmittance at 483 nm has a giant improvement from 11.65%to 73.17%.The physical mechanism of the undesired colorization process of Bi2O3-GeO2 glass has been studied through X-ray photo-electron spectroscopy and transmission electron microscopy,and it should be originated from the low valence state Bi centers.The obtained colorless Bi2O3-GeO2 scintillating glass can host various types of rare-earth dopants,such as Eu3+,Tb3+,Pr3+and Nd3+ions.The radiation-induced luminescence can be tuned in a wide wavelength region from visible to infrared waveband,and moreover,the intensity has a giant improvement compared with the as-made glass.The crystallization nature of Bi2O3-GeO2 glass heat-treated at different crystallization temperature has also been revealed by scanning electron microscopy,X-ray diffraction and Raman scattering spectra.When the temperature is close to the first crystallization temperature,the crystal phase of glass is Bi2GeO5 with the surface crystallization habit.The X-ray induced luminescence of the resultant sample is stronger compared with that of the colorless Bi2O3-GeO2 glass.The lifetime of Bi2GeO5 is estimated to be-4.76 ns.Upon further heat-treatment at the second crystallization temperature,the precipitated crystal phase belongs to Bi4Ge3O12 with a uniform crystallization habit.The obtained sample exhibits stronger luminescence compared with that of the sample embedded with Bi2GeO5.(2)To fabricate Lu2O3-SiO2 glass system at relative low temperature,Al2O3 has been introduced and it is supposed to act as a network intermediate for reducing the manufacturing temperature.The effect of various experimental parameters,including the fabrication conditions and co-dopants such as Y2O3 and Gd2O3,have been explored.It has been found that the melting at reduced atmosphere at 800? leads to the slight blue shift of the cut-off edge of glass and?142%enhancement in the scintillating performance.The effects of Y2O3 and Gd2O3 on the scintillating performance of glasses are different.Specially,Y2O3 acts as a negative role in the scintillating performance of Ce-doped glass.Gd2O3 is beneficial for improving the scintillating performance of Ce-activated glass,mainly associated with the energy transfer between Gd3+and Ce3+.The crystallization behavior of Lu2O3-Al2O3-SiO2 scintillating glass has been studied through scanning electron microscopy,X-ray diffraction and Raman spectra.The nanostructured glass embedded with monoclinic Lu2Si2O7 crystalline phase has been successfully constructed for the first time.Importantly,the thickness of crystalline layer in the nanostructured glass can be precisely tuned and?172.89%enhancement in the scintillating luminescence can be achieved.Interesting,the effect of Y2O3 and Gd2O3 on the scintillating luminescence in glass-ceramics is totally different from that in glasses.When the content of Y2O3 reaches to 6 mol%in Ce-activated scintillating glass-ceramics,the scintillating luminescence shows a-245%enhancement compared with that in the as-made glass.(3)The homogeneous Ce-activated Lu2O3-SiO2 scintillating glass having stoichiometric ratio the same with Lu2Si2O7 has been successfully fabricated via containerless processing method.The structure feature of Lu2O3-SiO2 glass has been studied through molecular dynamic simulation.The crystallization behavior of the glass has also been detailed analyzed by crystallization kinetics analysis,scanning electron microscopy,X-ray diffraction and Raman scattering spectra.The Ce-activated nanostructured glass homogeneously embedded with monoclinic Lu2Si2O7 phase has been successfully constructed and the crystallinity and optical transmittance reaches to 90.9%and 68.89%,respectively.The origin of the high transmittance of glass-ceramic has been explained based on the Mie scattering theory.Compared with the as-made glass,the mechanical properties and luminescence properties of Ce-doped Lu2O3-SiO2 transparent glass-ceramic have been greatly improved.The Vickers hardness and X-ray induced luminescence intensity exhibit?2.28 and?15.15 times improvement,respectively.Furthermore,the thermal stability of Lu2O3-SiO2 transparent glass-ceramic has also been greatly improved.(4)By using the constructed glass samples,various types of scintillating fibers with the large core size have been successfully fabricated and the scintillating performance has been studied.For examples,Eu-activated colorless Bi2O3-GeO2 scintillating fiber is a promising candidate for monitoring X-ray and the sensitivity is estimated to be?19.48 times higher than that of the as-made glass fiber.The optical properties of Ce-doped Lu2O3-Al2O3-SiO2 and Lu2O3-Gd2O3-Al2O3-SiO2 glass fibers have been studied and treatment at the reduced atmosphere is favourable for improving the performance.Moreover,Ce-activated Lu2O3-SiO2 scintillating fiber has been prepared via melt-in-tube method.Compared with the as-made glass fiber,the Lu2O3-SiO2 scintillating glass-ceramic fiber has been found to be superior than that of the as-made glass fiber and the X-ray detection sensitivity exhibits?13.51 times enhancement.Moreover,it exhibits excellent stability and after 100 cycles test,the scintillating glass-ceramics fiber still maintains a stable and reliable detection performance. |
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