A Study On The Preparation And Properties Of Long Persistence Luminescent Material With Visible Light Response

Long persistence luminescent materials refer to the materials that continue to emit light after being excited by visible or ultraviolet light,which are widely used in lighting indication,security marking,information encryption,biological imaging and other fields.At present,the research on green long persistence luminescent materials SrAl₂O₄:Eu²⁺and Dy³⁺has been gradually systematized,while the blue and yellow long persistence luminescent materials have not been systematically studied,and there is a lack of commercially available blue and yellow long persistence luminescent materials with visible light response.In this thesis,two long persistence luminescent materials with visible light response are designed and developed to address the practical problems faced at this stage,and the material phase structure,photoluminescence,force luminescence,afterglow,trap distribution and afterglow mechanism are systematically studied.The main contents and conclusions are as follows:On the one hand,the yellow long persistence luminescent material Ca_2-xSr_xBO₃Cl:Eu²⁺,Dy³⁺was prepared by high-temperature solid phase method,and the material phase structure,photoluminescence performance,mechanical luminescence performance,afterglow performance,trap distribution,and afterglow mechanism of the sample were investigated.The structural refinement showed that the replacement of Ca²⁺by Sr²⁺solution led to the enhancement of electron binding ability of traps in the band gap and increased the difficulty of electron escape to improve the afterglow performance of the samples,which was increased from 12 h to46 h.The photoluminescence spectra and EPR tests demonstrated that the autoluminescence of oxygen vacancy traps existed in the sample in addition to the characteristic emission of Eu²⁺.The solid solution of Sr²⁺was beneficial to the formation of oxygen vacancy traps in the sample,and the autoluminescence of oxygen vacancy could be achieved by spectral modulation of the sample.The composite material prepared by mixing the samples with PDMS was tested for mechanical luminescence photoluminescence.It was showed that the mechanical luminescence performance was attributed to the fact that the solid solution of Sr²⁺destroyed the symmetry of the crystal,resulting in the release of the electrons bound by the deep traps in the samples,which led to the mechanical luminescence performance.According to the thermoluminescence curve analysis of the samples,the solid solution of Sr²⁺increased the number of traps in the samples,enhanced the depth and breadth of the traps and substantially improved the number of electrons captured in the shallow traps and the deep traps.The distribution of traps during the release of electrons is continuous,which also guaranteed the improvement of the luminescence performance of the samples.On the other hand,the blue long persistence luminescent material SrAl₂Si₂O₈:Eu²⁺,Dy³⁺.The photoluminescence spectra of the co-doped samples were consistent with those of the single-doped samples,indicating that Eu²⁺as the luminescent center and Dy³⁺as the trap center increased the afterglow performance of the samples.According to the photoluminescence spectra of the co-doped samples,it can be concluded that the samples displayed a wide-packet emission peak of 380-600 nm with the main peak located at 410 nm,and the excitation spectra of the samples overlapped with the UVA band in visible light,indicating that the samples can be excited by visible light.According to the phase structure analysis of the samples,the mechanical luminescence performance of the samples was attributed to the shortening of Sr-O bond length caused by the co-doping of Eu²⁺and Dy³⁺,which destroyed the asymmetry of Sr-O hexahedron and affected the symmetry of[Al O₄]tetrahedron and[Si O4]tetrahedron.The analysis of the long afterglow luminescence spectra of the samples showed that the doping of Dy³⁺caused the afterglow duration of the samples to increase from 2 h to 8 h,and the initial afterglow luminance increased to 185.24mcd/m².Finally,the trap distribution of the samples was briefly analyzed.The result demonstrated that continuous distribution of shallow traps and deep traps made the trapped electrons in the deep traps combine with the luminescent center to produce mechanical luminescence performance.