Investigation On Preparation And Luminescence Properties Of Rare Earth Ions Doped Scintillating Glass And Optical Fiber Plates

With the rapid development of high-energy physics,industrial detection and medical imaging and other fields,the demand for the scintillator materials in various fields of society keeps increasing,which turns it to be the hot focus of researchers.However,the applications of scintillation crystals are restricted due to their complicated preparation process,high cost,difficulty in large-scale and large-size production,and inhomogeneity of luminescent properties.In contrast,the scintillating glass attracts a great of attention due to its simple fabrication process,low cost,continuously adjustable in composition and performance,easy for large-scale production and excellent plastic deformation ability.So far,the study on their fundamental and application has become a hot spot in the field of high-performance scintillation material,and the great progress has been made.Even though,to select suitable glass matrix materials,improve and control the luminescent properties of various Rare Earth?RE?ions in different glass matrix is still an important open topic for the research on scintillating glass in the future.In this thesis,the gadolinium-barium-aluminosilicate oxyfluoride scintillating glass doped with Tb³⁺,Ce³⁺and Eu³⁺ions were selected to systematically investigate the effect of doping concentration on the microstructure and optical properties and reveal the luminescence mechanism of RE ions.The energy transfer mechanism between Gd³⁺ions and other RE ions in glass was also discussed.Subsequently,the effects of F^-and Gd³⁺ions content in the glass composition,sensitized ions of Ce³⁺,Dy³⁺on the luminescent properties of Tb³⁺ions in gadolinium-barium-aluminosilicate oxyfluoride glass was studied.Based on the Tb³⁺-activated scintillating glass with high X-ray detection efficiency,the fabrication technology of scintillating fiber plate was preliminarily explored.Main results of the investigation for this thesis are listed as follows:?1?Single Tb³⁺,Ce³⁺,Eu³⁺doped and Ce³⁺/Tb³⁺,Dy³⁺/Tb³⁺codoped Gd-Ba-aluminosilicate oxyfluoride scintillating glasses have been fabricated by using high-temperature melting method.The network of these glasses is mainly composed of[Si O₄]and[Al O₄]tetrahedrals,which is linked by vertex angle oxide ions.The Gd³⁺,Ba²⁺and other RE ions locate in the network gap.A part of F^-ions substitute for O²⁺ions to enter into the network.These glasses own such advantages as high density,good thermostability and high transmittance performance in the visible region.?2?The Tb³⁺doped scintillating glasses exhibited bright green light under the excitation of ultraviolet?UV?,which originates from the ⁵D₄?⁷F_J?J=6,5,4,3?transition.With the increase of Tb³⁺doping concentration,the luminescent intensity keeps enhancing,but the luminescence lifetime decreases.The cross relaxation between Tb³⁺ions is beneficial for the enhancement of ⁵D₄ emission intensity.The Ce³⁺doped scintillating glass emits strong purplish-blue light under UV excitation,which can be ascribed to 5d-4f electronic transition of Ce³⁺ion.With the increase of Ce³⁺doping concentration,the emission peak exhibits a red-shift,the emission intensity firstly increases and then decreases.The optimal Ce³⁺concentration can be determined to be 0.1mol%.The luminescence lifetime of Ce³⁺ion in glasses is in an order of nanosecords,which exhibits a decrease tendency with the increase of Ce³⁺doping concentration.The Eu³⁺doped scintillating glass emits strong red light under the UV excitation,which is mainly attributed to ⁵D₀?⁷F_J?J=0,1,2,3,4?transition of Eu³⁺ions.The luminescence lifetime of Eu³⁺is of milliseconds magnitude.The luminescence intensity and intensity ratio of ⁵D₀?⁷F₂ transiton to ⁵D₀?⁷F₁ transiton increases firstly and then decreases with the increase of Eu³⁺doping concentration,which reaches the maximum when the content of Eu₂O₃ was 6mol%.?3?The energy transfer process of Gd³⁺?Tb³⁺,Gd³⁺?Ce³⁺,and Gd³⁺?Eu³⁺could take place in Tb³⁺,Ce³⁺,Eu³⁺single doped scintillating glasses,and the energy-transfer efficiency increases as the doping concentration of RE ions increases.Electric dipole-dipole interaction is responsible for the energy transfer from Gd³⁺to Tb³⁺ions,while the energy transfer from Gd³⁺to Ce³⁺or Eu³⁺was caused by the electric quadrupole-quadrupole interaction.?4?The Tb³⁺,Ce³⁺or Eu³⁺doped scintillating glasses exhibite scintillating luminescence properties under X-ray excitation.Among them,the Tb³⁺doped scintillating glass shows the best performance,our glass with 6mol%content of Tb₂O₃ reaches 4.9 times stronger and 64%integral scintillation efficiency of BGO crystal.While the Ce³⁺doped scintillating glass exhibits the worst performance,and the integrated scintillation efficiency is only 6.5%of BGO crystal.The integrated scintillation efficiency of Eu³⁺doped scintillating glass is up to 32.4%of BGO crystal.Through the comparison,we can justify that the Tb³⁺doped scintillating glass are more suitable for X-ray detection,which can be used in the industrial nondestructive detection,medical imaging and so on.?5?With the increase of F^-ion concentration in Tb³⁺doped scintillating glass,the luminescence intensity of Tb³⁺ions in scintillating glass increases,but the density of glass decreases.In addition,a higher concentration of F^-ions will cause surface devitrification of glass in the casting process,which will affect the fiber drawing.Increasing the concentration of Gd³⁺ions can effectively increase the density of glass and enhance the luminescence intensity of Tb³⁺ions by energy transfer from Gd³⁺to Tb³⁺.However,once the concentration of Gd³⁺is too high,the luminescence intensity of Tb³⁺will decrease.The optimum Gd₂O₃content is found to be 6mol%.?6?The incorporation of Ce³⁺ions into Tb³⁺doped scintillating glasses can enhance the luminescence of Tb³⁺ions through the energy transfer of Ce³⁺?Tb³⁺.Under X-ray excitation,the optimal doping concentration of Ce³⁺ions is 0.4mol%,the integrated scintillation efficiency is increased to 82%and the emission intensity is 6.2 times of BGO crystal under X-ray excitation.However,the addition of Dy³⁺ions in Tb³⁺doped scintillating glasses exhibits a strong negative effect on the luminescence of Tb³⁺ions,resulting in a decrease in the emission intensity of Tb³⁺ions.Thus,it is not appropriate to select Dy³⁺ions as the sensitizer in the Gd-Ba-aluminosilicate oxyfluoride glass.?7?The Ce³⁺/Tb³⁺codoped scintillating glass with high X-ray detection efficiency was used as the core glass to prepare Tb³⁺-acitived scintillating fiber plate with different thicknesses.These fiber plates emit bright green light under X-ray excitation,and the luminescence intensity increases with increasing the thickness.