Preparation And Luminescent Properties Of Rare Earth Doped Phosphors With Apatite Structure

Fluorescent powder,as the core component of white light emitting diode（LED）device,greatly affects the luminescence performance of lighting and display equipment.Exploration of a new and efficient phosphors suitable for ultraviolet-near ultraviolet light excitation has become a research hotspot.Phosphors with apatite structure have abundant crystallographic lattice positions,which can provide different crystal field environments for rare earth ions,and provide conditions for studying the relationship between the structure and properties of materials.Therefore,in this work,the Ba_10-x-yA_xM_y（PO₄）_6-z（BO₃）_zX₂:Eu²⁺/Ce³⁺（A=Gd,M=Na,X=Cl、F）series of phosphate phosphors with natural mineral apatite structures were prepared by high temperature solid phase method,and the effects of cationic,anion and channel anion analogic substitutions on the structures and luminescence properties of apatite were studied.The main research contents are as follows:（1）Ba₁₀（PO₄）₆F₂:Eu²⁺/Ce³⁺phosphors with apatite structure were prepared by high temperature solid phase method.The effects of phase composition and doping concentration on the luminescence properties of phosphors were studied.The results show that Ba₁₀（PO₄）₆F₂:0.07Eu²⁺and Ba₁₀（PO₄）₆F₂:0.03Ce³⁺phosphors posses the optimal crystallinity and luminescence properties,and can emit blue light under Ultraviolet light irradiation.（2）Cations(Gd³⁺,Na⁺)were substituted.A series of Ba_10-x-yA_xB_y（PO₄）₆F₂:Eu²⁺/Ce³⁺（A=Gd,B=Na,x=y=0-3）phosphors are fabricated by the high temperature solid-state strategy.The effects of cationic substitution on the structures and luminescence properties of phosphors were studied.The results show that with the substitution of Gd³⁺and Na⁺ions for Ba²⁺ions,the phase structure of phosphors switches from Ba₁₀（PO₄）₆F₂ to Ba₄Gd₃Na₃（PO₄）₆F₂.The average bond length between Eu-O and Ce-O decreases,the crystal field of Eu²⁺/Ce³⁺increases,and the energy level splitting of Eu²⁺/Ce³⁺increases,resulting in the emission peak of Ba_10-x-yGd_xNa_y（PO₄）₆F₂:Eu²⁺/Ce³⁺（x=y=0-3）is red-shifted.Among them,the luminescence color of Ba_10-x-yGd_xNa_y（PO₄）₆F₂:Eu²⁺（x=y=0-3）can be changed from blue to green.（3）The anion[（BO₃）^3-]was substituted.A series of Ba₄Gd₃Na₃（PO₄）_6-x/y（BO₃）_x/y F₂:Eu²⁺/Ce³⁺（x=y=0-2）phosphors were prepared by high temperature solid phase means.The performance of anion polyhedron substitution on the structures and luminescence properties of Ba₄Gd₃Na₃（PO₄）₆F₂ phosphors were analyzed.The results show that（BO₃）^3-replaces（PO₄）^3-,the lattice is distorted,the cell volume decreases gradually,the average bond lengthes between Eu and O increases,the crystal field of Eu²⁺weakened and the energy level splitting of Eu²⁺decreases,which results in a blue shift of emission peak position of Ba₄Gd₃Na₃（PO₄）_6-x（BO₃）_xF₂:Eu²⁺（x=0-2）.Due to the partial reabsorption of the excitation and emission spectrum of Ce³⁺,the crystal field of Ce³⁺is enhanced,resulting in the red shift of the emission peak position of Ba₄Gd₃Na₃（PO₄）_6-y（BO₃）_yF₂:Ce³⁺（y=0-2）.（4）Channel anion（Cl^-）replacement.A series of Ba₁₀（PO₄）₆X₂:Eu²⁺/Ce³⁺（X=Cl/F）phosphors were prepared by high temperature solid phase method.By replacing the F^-with Cl^-,the phase of the matrix transfers from Ba₁₀（PO₄）₆F₂ to Ba₁₀（PO₄）₆Cl₂,the cell volume gradually increases,and the emission peak of the series of samples has a slight red shift.Compared with the aforementioned（2）and（3）,the influence of channel anion substitution on structure regulation is smaller than that of cations and anions.Subsequently,the fluorescence spectra,fluorescence lifetime and luminescence mechanism of Eu²⁺and Ce³⁺co-doped Ba₁₀（PO₄）₆F_1.5Cl_0.5 phosphors were investigated.