The Structure And Luminescence Properties Of Rare Earth Ions Eu³⁺,Tb³⁺ Doped In SrF₂-YF₃-3SiO₂ Host Materials

Fluoride is a ideal matrix for stabling some important activated ions,therefore, the fluoride luminescent materials doped with rare earth ions become the research focus in recent years. Based on the potential applications of fluoride in optics, this paper adopts the sol-gel method to preparing rare earth luminescent materials which using SrF2-YF3-3SiO2 as composite matrix single doped and co-doped Eu3+, Tb3+, and studying the structure and luminescence properties of materials by IR, XRD, TEM, EDS, DTA-TG,excitation and emission spectral analysis.The prepared material of Eu3+:Sr2YF7 by structural test indicated that two kinds of crystal structure which are Sr2YF7 and SrF2 exist at the same time when the annealing temperature are at 600 and 800℃, and the relative content changed with the increase of the temperature, to 1000℃ the crystal structure tended to be perfect, only cubic phase structure of Sr2YF7 exists. Studying on luminescent properties of that material, optimal annealing temperature is800℃. Both 7F0â†'5L6 transition of 395 nm and 7F0â†'5D2 transition of 465 nm of Eu3+ are strong when the wavelength of the monitoring light is at 612 nm.The 5D0â†'7F1 magnetic dipole transition strength at 591 nm of Eu3+ is maximum when taking 395 nm as the excitation wavelength, regarded orange red light as principle. The 5D0â†'7F2 electric dipole transition strength at612 nm of Eu3+ is maximum when taking 465 nm as the excitation wavelength,regarded red light as principle. The optimal doping molar concentration of Eu3+ is 8.00 mol %.The prepared material of Eu3+:SrF2-YF3-3Si O2 by structural test indicated that before 504℃, material is mainly by the Sr(NO3)2 cubic phase structure, it favors the magnetic dipole transition of 5D0-7F1 of Eu3+ ions.Higher than 504℃ when the material is gradually transformed into SrF2 cubic crystal structure, the luminescence intensity due to 5D0-7F2 transition of Eu3+was decreased with increasing annealing temperature. At the annealing temperature of 900℃, SrF2 cubic phase structure and SrSiO3 monoclinic crystal phase structure co-existed in the material, and they enhance the emission of 612 nm. In the whole process, material mainly exists Si-O-Si bond.The luminescence properties show that the optimal formula of substrate SrF2-YF3 and SiO2 is 1:3, the optimum annealing temperature is 900℃, when the monitoring wavelength is 612 nm, the best excitation wavelength is 394 nm,the optimal doping molar concentration of Eu3+ is 8.00%.The prepared material of Tb3+:Sr2YF7-3SiO2 by structural test indicated that there is still nitrate are not decomposed before 526℃. After then Sr2YF7 tripartite crystal phase structure exists only. To 800℃ some Sr2SiO4 appeared and converted to Sr2 Si O4 completely after 932℃. In the whole process,material mainly existed Si-O-Si bond, too. The luminescence properties show that the optimum annealing temperature is 800℃. When the monitoringwavelength is 544 nm, the luminescence intensity due to 7F6â†'5L10 transition of Tb3+ is the strongest. When the excitation wavelength is at 378 nm, the luminescence intensity due to 5D4â†'7F5 transition of Tb3+ is the maximum which located in the green light zone, that is an excellent green luminescent material. The optimal formula of substrate Sr2YF7 and SiO2 is 1:3, the optimal doping molar concentration of Tb3+ is 9.00%.The prepared material of Eu3+/Tb3+:Sr2YF7-3SiO2 by structural measurements indicated that in the 200, 400, 600, 800, 1000℃ annealing process respectively go through Sr(NO3)2â†'Sr2YF7â†'SrSiO3 three kinds of crystal structure. In addition, the mixed crystal structure exists with Sr2YF7 and SrSiO3 at 800℃. The luminescence properties show that the optimum annealing temperature is 800℃. When the excitation wavelength is at 254 nm,materials appear red, green, and blue emission. The CIE color coordinate is located in the white light area. The optimal doping molar concentration of Eu3+ is 8.00%, the optimal doping molar concentration of Tb3+ is 9.00.And there is energy transfer of Tb3+â†'Eu3+ here. The result of this experiment has brought a new space for the development of the phosphor for white LED.