Study Of Long Afterglow And Photoexcitation Luminescence Properties Of Rare-earth-doped Orthosilicates

In today's society,inorganic long afterglow luminescent materials have been an important part of people's lives,in various fields of application more and more frequently.But with the advent of the era of big data and the development of science and technology,people's requirements for long afterglow luminescent materials have not only existed in the traditional range of applications,but the requirements for its performance have also been further enhanced.Silicates have a rich structure,good thermal stability,excellent water resistance,and outstanding physical and chemical properties,and aluminates compared to the lower synthesis temperature and easy access to raw materials,especially in water and moisture resistance,silicates have superiority,so as a synthetic phosphor substrate,silicates are very suitable.The light-excited luminescence,when the material is stimulated by external light,high-energy rays,or ions,can achieve energy storage by capturing charge carriers and then converting the energy into light through light stimulation.In this thesis,the development history and research status of long afterglow materials,optical excitation materials,and optical information storage materials are systematically investigated and analyzed.On this basis,this thesis selects rare-earth doped orthosilicate long afterglow and photoexcitation luminescence properties as the research content,and the main results obtained are as follows.(1)A new type of orthosilicate phosphor Ba_1.4Ca_0.6SiO₄:Eu²⁺,Dy³⁺was synthesized using the conventional high-temperature solid-phase method,and its X-ray diffraction pattern,photoluminescence and afterglow spectra,decay curve pattern,afterglow spectrum,pyrophoric spectrum,and photoexcited luminescence spectrum,and pyrophoric were systematically investigated.Their X-ray diffraction patterns showed good phase formation of the materials.The effects of different ion concentrations of Eu²⁺and Dy³⁺on the photoluminescence and afterglow spectra were investigated,and the photoluminescence and afterglow spectra showed that the two emission peaks in the 400 nm to 700 nm band were located at 450 nm and 504 nm,respectively,under the light excitation at 354 nm,with the strongest emission peak at 504 nm.where the emission peak at 450 nm and 504 nm was due to the 4f?5d jump of Eu²⁺and the emission peak at 450 nm in afterglow spectrum is due to the 4f_92/?6h_152/jump of Dy³⁺.The optimal doping amounts of Eu²⁺and Dy³⁺were determined to be 0.01 mol and 0.02 mol,respectively.The depth of the trap was analyzed and calculated by the curve of pyroelectric light.It was found that this material has good light-excited luminescence performance.In this thesis,we suggest that in Ba_1.4Ca_0.6SiO₄:Eu²⁺,Dy³⁺phosphor,Eu²⁺replaces two different sites of barium and calcium to act as the luminescence center of this phosphor,while the addition of Dy³⁺increases the density of the trap,resulting in a significant increase in the duration and luminescence intensity of the afterglow.(2)A new orthosilicate phosphor BaCaSiO₄:Eu²⁺,Pr³⁺was synthesized by the conventional high-temperature solid-phase method,and the photoluminescence and afterglow spectra showed that the strongest emission peak in the 400 nm to 700 nm band was at 505 nm,and this emission peak was attributed to the 4f?5d jump of Eu²⁺.The introduction of Pr³⁺does not change the number of traps,but increases the density of traps,prompting more electrons to be excited from the 4f to the 5d energy level,and the electrons jump from the 5d to the 4f level to produce luminescence,which eventually manifests as enhanced luminescence.The photoluminescence and afterglow spectra show that the strongest emission peaks are at505 nm,indicating that the main body of luminescence is Eu²⁺ion.Changing the concentration of Eu²⁺,its luminescence intensity is enhanced first and will decrease after reaching the optimal concentration,on the basis of which Pr³⁺ions are doped to select the sample with the best luminescence performance,which leads to the optimal concentrations of Eu²⁺and Pr³⁺of0.015 mol and 0.005 mol,respectively.The analysis of the thermoluminescence curves showed that more than half of the electrons were still preserved in the trap after 24 h of withdrawal of UV light.BaCaSiO₄:Eu²⁺,Pr³⁺was prepared as a flexible film,and the information in the flexible film was written by UV light at 254 nm and read out by thermal or optical excitation.Experiments show that this material is promising for the storage of optical information.