Synthesis And Luminescent Properties Of Rare Earth Doped Phosphate Phosphors

Phosphate luminescent materials have the advantages of stable physicochemical properties,low raw material prices,mild preparation conditions,etc.,and have broad application prospects in the field of lighting and display.As a next-generation green lighting source,high-efficiency and energy-saving white LEDs have attracted people’s attention.At present,commercial white LEDs generate white light through the combination of blue chips and Y3Al5O12:Ce³⁺phosphors.However,due to the lack of green light and red light,the white LEDs obtained in this way have a low color rendering index,which limits their wide application.In contrast,white LEDs obtained by combining ultraviolet or near-ultraviolet chips with three primary colors（red,green,and blue）phosphors can solve the above problems.Therefore,the development of new single-color or single-phase multi-color phosphors has very important theoretical significance and practical application value.In order to meet the needs of ultraviolet or near-ultraviolet excitation conversion white LED fluorescent materials,this paper uses phosphate with apatite and whitlockite-type structure as the matrix,and rare earth or transition metal ions as doping ions,using high temperature solid phase method.A series of red,green,and blue phosphors were prepared,and the samples were characterized by X-ray powder diffraction,scanning electron microscopy,fluorescence spectrometer,and other equipment.The phase composition,micromorphology,and fluorescence spectra of the samples were systematically studied.The energy transfer mechanism between doped ions was discussed in depth.The main research contents and results are as follows:（1）Ca₃Na Gd（PO₄）₃F:Ce³⁺,Tb³⁺/Mn²⁺series phosphors with apatite structure were prepared by high temperature solid phase method,the ions doping concentration and energy transfer mechanism between Ce³⁺→Tb³⁺and Ce³⁺→Mn²⁺ions were studied.Fluorescence spectroscopy and fluorescence lifetime test confirmed that the mechanism of energy transfer between Ce³⁺→Tb³⁺and Ce³⁺→Mn²⁺is the quadrupole-quadrupole and dipole-dipole interaction,respectively.And by adjusting the doping concentration of Tb³⁺and Mn²⁺ions in the co-doped sample,the color of the sample can be controlled.（2）A series of Ca₈Na Gd（PO₄）₆F₂:Ce³⁺,Tb³⁺phosphors with apatite structure were designed and prepared,and the occupancy of Ce³⁺and Tb³⁺in Ca₈Na Gd（PO₄）₆F₂ matrix lattice was studied by XRD and structural refinement situation.By adjusting the doping concentration of Tb³⁺ions in the co-doped sample,the luminescent color of the sample can be changed from blue light to green light.The energy transfer mechanism between Ce³⁺-Tb³⁺was further confirmed by analyzing the fluorescence lifetime attenuation curve of the sample and calculating the critical distance between doped ions.In addition,the bacterial cellulose is compounded with the fluorescent powder to make paper with fluorescent anti-counterfeiting function,and its morphology and luminescence characteristics are studied.（3）Sr₃Gd Li（PO₄）₃F:Tb³⁺,Eu³⁺and Sr₃Gd Li（PO₄）₃F:Ce³⁺,Tb³⁺phosphors with fluoroapatite structure were designed and prepared.The effects of rare earth ion doping concentration,fluorescence thermal stability and other factors on the luminescent properties of the samples were studied.Fluorescence spectrum test results show that there is energy transfer between Tb³⁺→Eu³⁺and Ce³⁺→Tb³⁺.By adjusting the doping concentration of Eu³⁺and Tb³⁺in the co-doped sample,the luminescent color of the sample can be controlled and the sample shows good fluorescence thermal stability.（4）Red phosphors Ca8Mg Bi（PO4）7:Eu³⁺and green phosphors Ca8Mg Bi（PO4）7:Ce³⁺,Tb³⁺with whitlockite-type structure were designed and prepared,and The phase composition,rare earth ion doping concentration and luminescence mechanism of the sample were studied.By adjusting the doping concentration of Tb³⁺ions in Ca₈Mg Bi（PO₄）₇:Ce³⁺,Tb³⁺,the emission color of the sample can be adjusted from blue light to green light,which can be attributed to the energy transfer of Ce³⁺→Tb³⁺ions.The maximum transmission efficiency can reach 80.98%.