| Silicate, borate, phosphate glass scintillators doped with trivalent rare earth (RE) ions such as Ce3+, Tb3+, Pr3+ions are promising alternatives to scintillating crystals for applications in nuclear physics, high energy physics, and industry detection, due to its advantages in low cost, easy shaping of elements, large size fabrication and drawing into fiber capability. Especially as an important nuclear radiation detection material, it can be applied in the field of thermal neutron, y-rays, X-rays and other high-energy rays (particles) detection, which have attracted more and more attention from nuclear physicists and materials scientists.In this paper, containing6Li glass scintillators doped with trivalent RE ions were chosen as research object, which is applied to the detection of thermal neutron and y-rays. The microstructure and optical properties of glass scintillators, including ultraviolet (UV)-visible light transmission and absorption, optical gap, refractive index, UV light excitation and emission, fluorescence emission efficiency under the excitation of X-rays and cathode-rays, have been investigated as a function of glass matrix composition and RE ions doping concentration. X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), X-ray absorption fine spectrum (XAFS), Fourier transform infrared spectroscopy (FT-IR), Inductively coupled plasma-mass spectrometry (ICP-MS), Optical microscopy (OM), Scan electron microscopy (SEM), Transmission electron microscopy (TEM) were used to investigate crystalline phase, composition and microstructure of glasses. The UV-visible transmission spectra, excitation and emission spectra, decay time spectra of glasses were recorded by using UV-visible spectrometer, Photoluminescence (PL), Photoluminescence excitation (PLE), Cathode-luminescence (CL), and X-rays excited luminescence (XEL) techniques.After a series of optimization of experiment parameters and fluorescence emission efficiencies of glass scintillators, the6Li isotope with a isotopic abundance of90.5%was introduced into the Ce3+ions-doped lithium silicate glass matrix. A standard glass scintillator with a size of ψ40mm×10mm has been fabricated by using melt quenching method. The pulse amplitude spectra and decay time spectra of the standard sample on the nuclear radiation of several typical spontaneous fission neutron source (241Am-Be,252Cf isotope point source), γ-rays source (137Cs,60Co isotope point source) were investigated by using single photon counting method.Main results of our experiments are listed as follows: (1) Single Ce3+ions-doped, Tb3+ions-doped, Pr3+ions-doped, and Ce3+/Tb3+ions-codoped silicate, borosilicate, borophosphosilicate glasses have been fabricated by using melt quenching method with a reducing atmosphere. The obtained glasses show some excellent optical properties, such as high uniformity, high transparence, well thermal stability and chemical stability. Ce+ions-doped lithium silicate glasses density are located in the wide range of2.467-3.142g/cm3. The UV-visible light transmittance rate in the range of380nm-800nm reach90%, direct optical band gap is adjustable in the range of3.2eV-5.3eV. For the Li2O-SiO2, Li2O-Al2O3-SiO2and Li20-MgO-Al203-Si02glass system, the glass density, refractive index, and the degree of amorphization glasses are evidently increased, but the optical band gap is significantly reduced with the increase of Ce3+ions doping concentration,(2) The5d energy level of Ce3+ion was splitted into five components because of the effect of an asymmetric crystal field of glass matrix. Accordingly, the excitation peaks, corresponding to the transition of4f→5d energy levels, are located at221nm,240nm,254nm,267nm,303nm. The higher the degree of disorder of glass matrix is, the higher the intensity of crystal field is, and the wider of5d energy level becomes, which result in a redshift of excitation spectra apparently.(3) Ce3+ions-doped glasses glow brightly UV-blue light under the excitation of UV light, cathode rays, and X-rays, and the emission peaks are located in the wide range of375nm-428.5nm. The emission spectra peak wavelength (color) are closely related to the optical basicity of the oxide components. The greater the optical basicity of the oxide components is, the closer to the infrared range of emission spectra peak wavelength is.(4) There existed four categories of fluorescence quenching centers in Ce3+ions-doped lithium silicate glass, as follows:(a) carbon inclusions, micron scale bubbles, holes and other microscopic defects associated with the glass melting process,(b) electric charge capture centers, such as non-bridging oxygen Si-O, anion vacancies within the glass matrix;(c) the self-absorption of high concentration of Ce4+ions, which are readily to form in a high doping concentration of cerium ions;(d) the non-radiative energy transfer between two closely Ce+ions within Ce-O-Ce nano-clusters.(5) The fluorescence emission efficiencies of the glass scintillators have been increased apparaently by adjusting the oxide composition and Ce3+ions doping concentration, as well as glass fabrication method. The XEL, CL integral luminescence efficiency of Ce3+ions-doped lithium silicate glass are about40%and500%of that of Bi4Ge3O12crystal, respectively.(6) Single Tb3+ions-doped, Ce3+/Tb3+ions-codoped glasses glow brightly green light under the excitation of UV light, cathode rays, and X-rays. There existed apparent energy transfer from5D3to5D4energy levels of Tb+within the two kinds of glass. With the increase of Tb3+ions dopoing concentration, the energy transfer efficiency increased, but the fluorescence lifetime of5D3,5D4excited states decreased. There existed apparent energy transfer from Ce3+ions to Tb3+ions in Ce3+/Tb3+co-doped glass. The optimal doping concentration of Ce2O3and Tb2O3in Ce3+/Tb3+-codoped30Li2O-10MgO-5Al2O3-55SiO2glasses is0.6mol%and0.8mol%, respectively.(7) The pulse amplitude spectra, decay time spectra of several typical spontaneous fission neutron source (241Am-Be,252Cf), y-rays source (60Co,137Cs) have been obtained using containing6Li silicate glass as front unit of scintillator detector. The light yield of containing6Li silicate glass under the radiation of thermal neutron, y-ray are almost identical with that of Saint gobain GS20Li-glass, and its response time is slightly shorter than the GS20product. It can ben concluded that several main performances such as light yield, scintillating response time of obtained containing6Li silicate glass have reached the standard of Saint gobain GS20product. The containing6Li silicate glasses show a higher application value in the field of thermal neutrons and y-rays detection.
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