Preparation Of Phosphors For White LED And Their Luminescence Properties

White LED has gradually replaced the traditional lighting appliances with its advantages of environmental protection and energy saving.As an important part of LED lamp beads,phosphor has been widely concerned.In this paper,two kinds of red phosphors which can be excited by near ultraviolet chip were prepared.The inquiry content is as follows.?1?Ba₃Y₄O₉:Eu³⁺phosphors were prepared with high temperature solid phase method in a normal atmosphere,Its structure,morphology and luminescence properties were characterized by X-ray diffraction?XRD?,Scanning electron microscope?SEM?and fluorescence spectra.The influence of doping concentration of Eu³⁺and charge compensators Li⁺,Na⁺and K⁺on luminescence intensity of phosphors was studied.The results show that the phosphors can be stimulated by near-ultraviolet light at 393 nm and have strong and wide emission peaks at 609⁶23nm.When the doping concentration of Eu³⁺was 8%,Ba₃Y₄O₉:Eu³⁺phosphors had the strongest emission intensity.When the doping concentration is higher than 8%,the phenomenon of concentration quenching will occur.Within the doping concentration range of 4%¹0%,charge compensators Li⁺,Na⁺and K⁺all improved the luminescence intensity of phosphors to different degrees,among which Li⁺had the best luminescence enhancement effect due to its minimum radius,and the best doping molar concentration was 8%.The chromaticity coordinates of the phosphor are orange-red areas.Experimental data show that Ba₃Y₄O₉:Eu³⁺phosphors have the potential to be the emitting orange-red phosphors used in white light-emitting diodes.?2?Ba₂YAlO₅:Eu³⁺red phosphors were prepared with sol-gel method,Their luminescence properties and crystal structures were studied systematically.The influences of Eu³⁺doping concentration,calcination temperature and Bi³⁺doping on luminescence properties of phosphors were investigated.The results show that under the near-ultraviolet excitation at 260 nm,the phosphor has a strong and wide emission peak at 602⁶32 nm.The optimal doping concentration of Eu³⁺is 8%,and concentration quenching occurs when the doping concentration is higher than 8%.The best calcining temperature is 1250?,phosphor fluorescent powder samples of particles is uniform,good dispersibility at this time.The addition of Bi3+changed the excitation wavelength of the phosphor?260³27 nm?,and the emission peak was located at 320³65 nm,without changing the crystal structure of the phosphor.Bi³⁺absorbs ultraviolet light at 327 nm and transfers energy to Eu³⁺after being activated,so that the⁵D₀-⁷F₂ transition of Eu³⁺at 612 nm is significantly enhanced,that is,the emission peak of phosphor at 612 nm is increased.?3?The amorphous structure of SiO₂ microspheres was prepared by sol-gel method,with a large amount of hydroxyl groups?-OH?on the surface,which provided favorable conditions for the coating shell structure below.SiO₂@Ba₃Y₄O₉:Eu³⁺and SiO₂@Ba₂YAlO₅:Eu³⁺core-shell phosphors were prepared by coating the phosphors above on the surface of SiO₂ microspheres by sol gel method.The core-shell structure phosphor particles had good dispersion,and the wavelength of excitation light and the position of emission peak remained unchanged.The intensity of red emission light was enhanced.