Preparation Of Eu²⁺/Tb³⁺ Co-doped Chlorophosphate-based Fluorescent Material And Its Luminescence Properties

White light-emitting diode?W-LED?is a new generation of energy-saving and environmentally friendly solid light source,which has been widely used in lighting and display fields.The near-ultraviolet chip and the three-primary phosphor are mixed and packaged to obtain a white LED device with high color rendering index and low color temperature.However,the number of conventional phosphor types that can be applied at present is lack and can no longer satisfy white light.The demand for LEDs severely limits the application of near-ultraviolet-excited white LED devices.To this end,in this paper,using chlorophosphate as a matrix material,the energy transfer of Eu²⁺ions to Tb³⁺ions was used to prepare Sr_5-x-2yEu_xTb_yNa_y?PO₄?₃Cl and Ba_5-x-2yEu_xTb_yNa_y?PO₄?₃Cl series phosphors.The main research work and the following results are as follows:?1?A series of Sr_5-x-2yEu_xTb_yNa_y?PO₄?₃Cl phosphors were synthesized by high temperature solid phase method.The results of XRD and FE-SEM showed that the doping of rare earth ions did not change the crystal structure of Sr₅?PO₄?₃Cl matrix.The particle morphology of phosphor samples was irregular and there was agglomeration.Fluorescence spectroscopy studies show that Sr_5-x?PO₄?₃Cl:xEu²⁺emits strong blue light and the main excitation peak is at 341 nm.Sr_5-2y?PO₄?₃Cl:yTb³⁺,yNa⁺emits strong green light,and the main excitation peak is at 230 nm.They are optimal doping concentrations were x=0.05 and y=0.35,respectively.?2?In the Eu²⁺/Tb³⁺co-doped Sr_5-x-2yEu_xTb_yNa_y?PO₄?₃Cl phosphors,the sample exhibits a blue-emitting emission with a center wavelength around 446 nm and a vicinity of 543 nm at a wavelength of 341 nm.The green light emission is derived from the 4f⁶5d¹?4f⁷ transition of Eu²⁺ions and the ⁵D₄-⁷F₅ transition of Tb³⁺ions,respectively.Modulation of the blue-green double primary color can be achieved by changing the Tb³⁺ion concentration.The Eu²⁺/Tb³⁺energy transfer mechanism belongs to the dipole-dipole moment interaction in this system.The Sr_4.15?PO₄?₃Cl:0.05Eu²⁺,0.40Tb³⁺,0.40Na⁺phosphors exhibit good thermal stability with an activation energy of 0.19 eV.?3?A series of Eu²⁺,Tb³⁺,Eu²⁺/Tb³⁺ion doped Ba₅?PO₄?₃Cl matrix fluorescent materials were synthesized by high temperature solid phase method.The phase purity,particle morphology and luminescence properties of the fluorescent materials were characterized by XRD,FE-SEM and PL.The results show that Ba_5-x?PO₄?₃Cl:xEu²⁺exhibits excellent blue fluorescence emission under near-ultraviolet excitation.The strongest peak is at 438 nm,and the Eu²⁺ion concentration with the strongest luminescence intensity is x=0.05.Ba_5-2y?PO₄?₃Cl:yTb³⁺,yNa⁺exhibits excellent purity of green light emission under near-ultraviolet excitation.The strongest peak is at 543 nm,and the Tb³⁺ion concentration with the strongest luminescence intensity is y=0.35.?4?In the Eu²⁺/Tb³⁺co-doped Ba_5-x-2yEu_xTb_yNa_y?PO₄?₃Cl phosphors,the resonance energy transfer of Eu²⁺to Tb³⁺was observed.At 330 nm excitation,the co-doped sample exhibited a blue light emission characteristic of Eu²⁺ions and a green light emission characteristic of Tb³⁺ions.Studies have shown that by adjusting the Tb³⁺/Eu²⁺doping concentration ratio,the relative luminescence intensity of Eu²⁺ions and Tb³⁺ion emission peaks in the fluorescent material can be accurately regulated,thereby realizing the shift of the luminescent color from the blue region?x=0.154,y=0.043?to the green region?x=0.220,y=0.217?.The resonance type of Eu²⁺energy transfer is dipole moment-quadrupole moment interaction.The Ba_4.15?PO₄?₃Cl:0.05Eu²⁺,0.40Tb³⁺,0.40Na⁺phosphor of activation energy is0.32 eV.The package results show that the color coordinates of the white LED device are?0.403,0.401?,the color rendering index is 90.7,the correlated color temperature is 3645 K,and the packaged white LED device exhibits a warm warm white light.This phosphor has potential applications in UV-LEDs.