Preparation And Properties Of White Light Phosphor With Apatite Structure For LED

White LED(WLED)has the advantages of energy saving,high safety factor and long life,and has attracted wide attention as the most promising new generation solid-state lighting source.Among them,the phosphor conversion WLED(pc-WLED)exhibits a huge advantage due to its low cost and simple preparation process.In recent years,apatite structure fluorescent materials have become an emerging material for phosphor conversion WLED research because of their physicochemical properties,low synthesis temperature and simple preparation method.In this paper,three new types of rare earth doped phosphors with apatite structure were prepared by high temperature solid phase method.The optical properties and luminescence mechanism were systematically studied,which provided a new idea for the research of WLED.(1)Sr₄Ca(PO₄)₂(Si O₄):Dy³⁺phosphor exhibits white light emission at 348 nm excitation due to the characteristic blue emission band(480 nm)and yellow light emission(574 nm)of Dy³⁺ions.In addition,by incorporating Li⁺,Na⁺or K⁺ions as charge compensators,the charge balance of the matrix and the symmetry of the crystal field were adjusted to study the effect on the luminescence properties.The results show that Sr₄Ca(PO₄)₂(Si O₄):Dy³⁺,M⁺(M=Li,Na,K)phosphors can be used as potential near-ultraviolet excitation white light-emitting diodes(w-LEDs).(2)Ba₃La Na(PO₄)₃F:Tm³⁺,Dy³⁺phosphors have both Tm³⁺:¹D₂-³F₄and Dy³⁺:⁴F_9/2-⁶H_J(J=15/2,13/2,11/2)transitions at 358 nm excitation,thus showing white light emission.Due to the effective energy transfer(ET)from Tm³⁺to Dy³⁺ions,the luminescent color of the sample was found to change from blue to white.According to the illuminating emission intensity,the maximum energy transfer efficiency is calculated to be about 72.6%,and the Dy³⁺ions optimal doping concentration is 0.04.In addition,through the theoretical model of Dexter,the dipole-dipole interaction was confirmed to be the energy transfer mechanism from Tm³⁺to Dy³⁺ions.(3)Sr₆Gd₂Na₂(PO₄)₆F₂:Tb³⁺,Eu³⁺phosphors achieve the color-adjustable properties of phosphors by adjusting the concentration ratio of Tb³⁺-Eu³⁺ions at 371 nm excitation.By regulating the ratio of Tb³⁺/Eu³⁺,the modulation and optimization of the luminescence properties are achieved.In addition,the energy transfer process between Tb³⁺and Eu³⁺ions was studied,and the energy transfer mechanism of Sr₆Gd₂Na₂(PO₄)₆F₂:Tb³⁺,Eu³⁺was analyzed.The results show that Sr₆Gd₂Na₂(PO₄)₆F₂:Tb³⁺,Eu³⁺phosphors have potential applications in the field of pc-WLED.