Structure And Luminescent Properties Of Eu³⁺/Tb³⁺ Doped SiO₂-B₂O₃ Prepared By Acid-base Two-step Sol-gel Method

White lighting emitting diodes is considered as the source of light in21 st century because of its long life,high efficiency,energy-efficient,environment friendly and other advantages.One frequently-used method to obtain W-LED lamp is combining a near ultraviolet lamp wick with red/blue/green phosphors.It gradually attracts scientists' attention on how to obtain different phosphors which can be efficiently excited by the ultraviolet light.Doping rare earth ions into the matrix whose main composition is SiO₂-B₂O₃ not only can omit the steps of blending the phosphors and polymeric adhesive,spraying the mixture on the glass matrix,but also performs well in monitoring cost.This may become a future direction for W-LED which is worth more research.This paper adopts the sol-gel method,taking ethyl orthosilicate,trim ethyl borate as raw material to obtain SiO₂-B₂O₃ mixed matrix.The matrix doped with Eu³⁺,Tb³⁺,Zn²⁺ or other metal ions can respectively obtain green,red and white phosphors.Moreover,the luminescent properties and the structure are characterized by IR,XRD,excitation and emission spectrum.This paper also focus on controlling the hydrolysis velocity of raw material-ethyl orthosilicate and trim ethyl borate,and obtaining well mixed phosphors with excellent luminous efficiency.SiO₂-B₂O₃:Tb³⁺ phosphors excited at 352 nm shows a strong green emission with great monochromaticity and intensity when the doping concentration is 3% after annealing treatment at 600?.The strongest emission is located at 544 nm,assigned to the 5D4-7F5 transition.At 488 nm,583nm,there are two weaker emission peaks which correspond to the 5D4-7F6 and the 5D4-7F4 transition of Tb³⁺.SiO₂-B₂O₃:Eu³⁺ phosphors excited at 395 nm shows a good red emission when the doping amount of Eu³⁺ is 7% after annealing treatment at600?.It can be seen that there is a strongest emission peak at 612 nm,and a weak emission peak at 590 nm which correspond to the 5D0-7F2 and the5D0-7F1 transition of Eu³⁺.By the analysis of IR and XRD,it is found that the annealing process will change.the crystal structure of the matrix from crystalline state to amorphous and a high temperature will help B doped in the network structure of Si-O-Si so that can be conducive to light emitting when the samples are amorphous after annealing treatment at 600? which exist Si-O-B,Si-O-Si,B-O and other bonds.Except that,it may occur temperature quenching because of rare earth ions' cluster when the temperature is higher than 600 ?.The paper analyzed the discrepancy in structure between different phosphors and the effects on the luminescent properties in different hydrolysis conditions,explored the hydrolysis mechanism of the two esters and the reasons which can obtain a strong emission by sol-gel method.It is proved that the mixture if Si O₂ and B₂O₃ can be more homogeneous and more favorable for the formation of Si-O-B bond so that can obtain the phosphor with excellent performance.Eu³⁺/Tb³⁺ co-doped Si O₂-B₂O₃ phosphors are synthesized by sol-gel method at room temperature.The possibility of synthesizing white light with different Eu³⁺/Tb³⁺ ratios is discussed by combining the excitation and emission spectra.Finally,the phosphor emits white light when Eu³⁺ doping content is 3% while Tb³⁺ doping content is 5% after annealing treatment at600 ? and the excited wavelength is 325 nm.The effects of different annealing temperature and excited wavelength on compositing white light and the reasons for the synthesis of white light are discussed in the paper with the energy transfer from Tb³⁺ to Eu³⁺.The luminescent properties of the phosphors are studied by excitation and emission spectrum when the sensitizer Zn²⁺ added into the products.It was found that the addition of Zn²⁺ doesn't change the position of the excitation–emission peak but increased the emission intensity of the rare earth ions' characteristic peaks.Combining the results of IR and XRD,the phosphor is amorphous after annealing at 600 ?.The doping of Zn²⁺reduces the lowest energy level of the conduction band,which is conducive to the improvement if the sample's luminous intensity.