Synthesis And Luminescent Properties Of Rare Earth Ions Doped Borate Phosphors

Due to the unique electronic structure of the inner layer 4f,rare earth ions can exhibit extremely rich energy level transitions,which can absorb or emit light from?near?ultraviolet to infrared range,thus making the rare earth phosphors rich and various luminescence properties.Rare earth phosphors have been widely used in many fields such as white LED illumination,display imaging,sensors and biomedicine in recent years.Rare earth phosphors have become the most valuable phosphors due to their strong anti-ultraviolet radiation and high luminous efficiency.Borate phosphors can be used as one kind of materials for an excellent luminescent substrate doped with rare earth elements,because of their wide light transmission area,high optical damage threshold and fluorescence efficiency,low synthesis temperature,simple preparation process and good thermal stability.In this thesis,the rare earth phosphors based on LiBaBO₃ and LiSrBO₃ borate were prepared by high temperature solid phase method.The crystal phase and structure of different doping ions and different doping phosphors were determined by XRD.The morphology and luminescence properties were tested and characterized by SEM and PL spectrometer,and the effects of co-doped ions on the luminescence properties of the phosphors were investigated.The main research contents are as follows:1.The LiBaBO₃:Tb³⁺phosphors were prepared by the traditional solid phase method.The phase of the samples was determined to be pure phase by XRD,and the morphology of the phosphor was analyzed by SEM.At the same time,the luminescence properties of LiBa_1-x-x BO₃:xTb³⁺phosphors with different Tb³⁺doping amount were studied.Under 369 nm excitation,the main emission light of the sample is green light with a wavelength of 544 nm,and the emission peak is corresponding to⁵D₄?⁷F₅ transition of Tb³⁺.When the doping amount of Tb³⁺is x=0.05,the luminescence intensity of the phosphor reaches the highest.The CIE chromaticity coordinates of the samples are all in the green region,which are very close to the standard green color coordinates.Based on the optimal doping concentration of Tb³⁺,Bi³⁺and Tb³⁺co-doped LiBa_1-x-yBO₃:xTb³⁺,yBi³⁺phosphors which can be effectively excited by?near?ultraviolet light were prepared.At 254 nm excitation light,the phosphor has the strongest emission peak??=544 nm?in the green light range.As the doping amount of Bi³⁺increases,there is a dipole-dipole interaction between Bi³⁺and Tb³⁺for energy transfer.The CIE chromaticity coordinates of the phosphors show that the luminescent color exhibits a gradual trend from green to white.2.A series of rare earth ions and Bi³⁺co-doped LiSrBO₃:Bi³⁺,RE³⁺?RE=Eu,Sm,Tb?phosphors were prepared by solid phase reaction.The phase structure was pure phase LiSrBO₃ by XRD.The surface morphology and elemental composition of the sample were analyzed by SEM and EDS.The doping concentration of Eu³⁺was fixed,and a series of LiSrBO₃:Eu³⁺,Bi³⁺phosphors with different Bi³⁺contents were prepared.The samples are excited efficiently by UV,and LiSrBO₃:Eu³⁺,Bi³⁺phosphor can produce a typical red light emission at a wavelength of 613 nm,corresponding to the ⁵D₀?⁷F₂ transition of Eu³⁺.Compared with the single-doped Eu³⁺phosphor,the luminescence intensity of the co-doped phosphor is obviously enhanced,and when the sensitized ion Bi³⁺doping amount is x=0.03,the luminescence reaches the strongest,and the CIE color coordinate is?0.595,0.385?,located in the red light area.LiSrBO₃:Sm³⁺,Bi³⁺phosphors excited by?near?ultraviolet light were prepared by co-doped with Bi³⁺and Sm³⁺.The excitation spectrum indicates that the strongest excitation peak is located at 404 nm.With the increasing amount of sensitized ion Bi³⁺,the luminescence intensity of the sample firstly increased and then weakened,which is due to the energy transfer between Bi³⁺and Sm³⁺ions,mainly due to the dipole-dipole interaction.The CIE color coordinates of LiSrBO₃:Sm³⁺,Bi³⁺phosphors are located in the orange-red region,which has potential application prospects.In addition,LiSrBO₃:Tb³⁺,Bi³⁺phosphor with pure phase and good crystal phase is obtained by calcination under air atmosphere.When the amount of Bi³⁺gradually increased,the color of the phosphor can change from light yellowish green to green,and the luminescence intensity of the sample reaches the strongest at the optimal doping amount x=0.03.