Preparation And Properties Of Rare Earth Doped Phosphate Luminescent Materials

Compared with other known light sources,white LEDs have a series of advantages such as high lighting efficiency,long service life,low energy loss,convenient and easy installation,and environmental friendliness.They have become the most striking green light sources in the 21st century.Due to the high absorption of PO₄^3-in the ultraviolet region,more and more researchers use phosphate as a phosphor matrix.Phosphate-based phosphors have many advantages,such as simple synthesis methods,low calcination temperature,and no harm to the environment.Therefore,the following researches have been done in this paper:1.A series of white phosphors Na₃Ce?PO₄?₂:Dy³⁺were synthesized by high temperature solid-phase method,and their luminescence characteristics,attenuation life and color coordinates were analyzed and discussed.The results show that Na₃Ce_1-x?PO₄?₂:xDy³⁺can be effectively excited by near-ultraviolet light.From the fluorescence decay curve,When the mole fraction of Dy³⁺is x=0.01,the luminous intensity is the highest,the fluorescence lifetime is about 1.130 ms,and then it gradually decreases.The color coordinate position of the sample is in the white light area,which proves that the phosphor is a potential single-matrix white LED.2.Sr₂Mg₃P₄O₁₅ was used as the matrix.Sr_2-xMg₃P₄O₁₅:xEu²⁺,Sr₂Mg_2.96P₄O₁₅:0.04Tb³⁺,Sr_1.95Mg_3-yP₄O₁₅:0.05Eu²⁺,yTb³⁺and other ion co-doped phosphors were prepared by high temperature solid phase method.The fluorescence spectrum shows that at the wavelength of 350nm,the Sr_2-xMg₃P₄O₁₅:xEu²⁺series phosphors can be effectively excited,and the emission peak is located at 400-450 nm,and its color coordinates are displayed in blue.When the concentration of Eu²⁺is 13%,the luminous intensity is optimal.Then as the Eu²⁺concentration increases,the luminous intensity decreases.Doping with Tb³⁺will affect the chroma of Eu²⁺phosphors,so the color of the three primary color phosphors can be improved by changing the doping concentration of Tb³⁺.3.Cs₂CaP₂O₇:Eu³⁺and Cs₂CaP₂O₇:Tb³⁺phosphors were synthesized by high-temperature solid-phase method,and the luminescent properties of the materials were studied.The results show that:Cs₂Ca_0.98P₂O₇:0.02Eu³⁺is excited at 250 nm,and there are emission peaks at 587 nm,595 nm,611 nm,654 nm,and 703 nm,which finally emit orange-red light.These emission peaks should be attributed to the ⁵D₀?⁷F_J?J=0,1,2,3,4?transition of Eu³⁺.Under the excitation of 227 nm,Cs₂CaP₂O₇:Tb³⁺has 542 nm,550 nm,584 nm,and 623 nm emission peaks and finally emits green light.These emission peaks are due to the ⁵D₄?⁷F_J?J=6,5,4,3?energy level transition of Tb³⁺.The emission intensity of Cs₂Ca_1-xP₂O₇:xTb³⁺phosphor increases first and then decreases with the increase of Tb³⁺?1%-12%mol?doping concentration.