Preparation,Structure And Luminescent Properties Of Eu³⁺/Tb³⁺/Ce³⁺ Doped A₂SiF₆/SiO₂ ?A=Na/K? Powders

Rare earth luminescent materials have important applications in lighting.Moreover,according to the needs of synthetic white LEDs,the development of rare earth trichromatic phosphors and single component white phosphors has become one of the hot research fields of current rare earth luminescent materials.The rare earth ion as a luminescent center have a special 4f5d electronic configuration,which can produce rich electronic transitions.Among them,Eu³⁺,Tb³⁺and Ce³⁺have special spectral characteristics and can emit red,green and blue primary colors.Fluorosilicate as a matrix has the characteristics of stable physicochemical properties and low phonon energy,and a large number of studies have shown that fluoride ion doping can improve the luminescence properties of silicate phosphors.Therefore,fluorosilicate phosphors are a new class of luminescent materials with potential applications.In this paper,A₂SiF₆/SiO₂?A=Na/K?were used as the main matrix,Eu³⁺,Tb³⁺and Ce³⁺were used as the luminescent centers.A series of rare earth ion single-doped trichromatic single-color phosphors and rare earth ion tri-doped white phosphors were synthesized by co-precipitation method.The structure and luminescence properties of the materials were characterized by XRD,IR?Raman?TG-DSC,TEM,HRTEM,EDS,fluorescence spectroscopy and calculated CIE color coordinates.The Eu³⁺,Tb³⁺and Ce³⁺mono-doped and ternary co-doped Na₂SiF₆:xRE³⁺phosphors were synthesized by co-precipitation method.The structure is hexagonal.The highest refractory temperature of the material is 400°C.And Eu³⁺,Tb³⁺and Ce³⁺are all in the host lattice which is completely doped with Na₂SiF₆ by substituting Na⁺.On luminescence,under specific ultraviolet light excitation,Na₂SiF₆:xEu³⁺,Na₂SiF₆:yTb³⁺and Na₂SiF₆:zCe³⁺materials exhibit Eu³⁺?⁵D₀?⁷F₂,red?,Tb³⁺?⁵D₄?⁷F₅,green?and Ce³⁺?5d?4f,blue?feature emission,respectively.In the Na₂SiF₆:xEu³⁺-yTb³⁺-zCe³⁺ternary co-doped system,Na₂SiF₆:0.03Eu³⁺-0.07Tb³⁺-0.07Ce³⁺material is represented.As the excitation wavelength of the ultraviolet light increases,the color of the material will change from white light to cool white light to warm white light to red orange light.Among them,the luminescence of the material excited by290 nm ultraviolet light is closest to the ideal white light.Therefore,this phosphor can be used as a one-component tonable white phosphor in a white LED.The Eu³⁺,Tb³⁺and Ce³⁺mono-doped and ternary co-doped K₂SiF₆:xRE³⁺ phosphors were synthesized by co-precipitation method.The structure is a cubic phase crystal system.The highest refractory temperature of the material is 500?.And Eu³⁺,Tb³⁺and Ce³⁺are all in the main lattice of K₂SiF₆completely doped by substitution of K⁺.On the luminescence,K₂SiF₆:xEu³⁺,K₂SiF₆:yTb³⁺and K₂SiF₆:zCe³⁺materials also exhibited Eu³⁺?⁵D₀?⁷F₂,red?,Tb³⁺?⁵D₄?⁷F₅,green?and Ce³⁺?5d?4f,blue?feature emission,respectively.Among them,the K₂SiF₆:yTb³⁺system also exhibits blue light emission of⁵D₃?⁷F₄?438nm?and ⁵D₃?⁷F₃?460nm?transition of Tb³⁺.The ternary co-doping material is represented by K₂SiF₆:0.04Eu³⁺-0.05Tb³⁺-0.05Ce³⁺material,and its emission spectrum exhibits full-color emission under the excitation of 265nm ultraviolet light,and its color coordinate falls on white light containing blue component,color cold.At 395 nm excitation,the luminescence of the material is reflected in the characteristic emission of the strongest Eu³⁺.Therefore,this phosphor can be used as a white phosphor with a color temperature and a cold color in a white LED.A series of Na₂SiF₆@xSiO₂:0.07Eu³⁺and Na₂SiF₆@ySiO₂:0.09Tb³⁺single-doped red and green monochromatic phosphors prepared by co-precipitation.Structurally,they are identical in structure to the Na₂SiF₆:0.07Eu³⁺and Na₂SiF₆:0.09Tb³⁺materials,respectively.The structure is hexagonal.The annealing temperature that can be withstood is increased to 500°C.At the same time,the optimum coating amount of SiO₂ is 1 times that of the raw material Na₂SiF₆.On the luminescence,the coating of SiO₂ has almost no effect on the color purity of the raw material.However,the luminescence properties of the materials also decrease,and the luminescence of Na₂SiF₆:0.07Eu³⁺material decrease more.Therefore,whether or not to coat SiO₂ is determined according to actual needs.A series of K₂SiF₆@xSiO₂:0.04Eu³⁺and K₂SiF₆@ySiO₂:0.05Tb³⁺single-doped red and green monochromatic phosphors were prepared by co-precipitation method.Structurally,they are identical in structure to the K₂SiF₂:0.04Eu³⁺and K₂SiF₆:0.05Tb³⁺materials,respectively.The structure is a cubic phase crystal system.The acceptable annealing temperature is also improved,both at 600°C.At the same time,the optimum coating amount of SiO₂ is 1 times and 2 times that of the raw material K₂SiF₆,respectively.On the luminescence,the coating of SiO₂ does not have much influence on the color purity of the material.However,the luminescence properties of the materials also decrease,and the luminescence of the K₂SiF₆:0.05Tb³⁺material decrease more.Therefore,whether or not to coat SiO₂ is also determined according to actual needs.