Synthesis And Properties Of Several Color-Tunable Phosphors

White light emitting diodes?WLEDs?,with its advantages such as safety,energy saving,environment friendly,high brightness and long lifetime,was deemed to be the promising next generation solid-state lighting sources.Phosphor convert WLEDs?pc-WLEDs?,as the mainstream approach to achieve WLEDs,has been widely applied in displays,backlights,decorative illumination as well as general lighting fields.The developing lighting market requires the luminescent properties?such as emission colors,CIR and CCT?of pc-WLEDs can be fine controlled and the luminescent properties of pc-WLEDs are seriously depended on the emission colors of the phosphors.Therefore,it is of great significance to develop color-tunable phosphors that can be applied to pc-WLEDs.In this work,several corlor-tunable phosphors have been synthesized and theirs luminescent properties have been investigated,the detail research contents are listed as follow:1.A series Sr₃Lu?PO₄?₃:Dy³⁺,Eu³⁺ phosphors were prepared via a traditional high temperature solid state reaction.Under the excitation of near-UV light,Sr₃Lu?PO₄?₃:Dy³⁺ phosphor shows cool-white emission,Sr₃Lu?PO₄?₃:Eu³⁺ phosphor present orange-red emission.For Sr₃Lu?PO₄?₃:Dy³⁺,Eu³⁺ phosphor,Eu³⁺ ions compensate the red emission component to the cool-white emission of Dy³⁺ and the emission colors can be tuned from cool-white to red by controlling the doping concentrations of Dy³⁺ and Eu³⁺ ions.The energy transfer mechanism from Dy³⁺ to Eu³⁺ in Sr₃Lu?PO₄?₃:Dy³⁺,Eu³⁺ phosphor can be ascribed to the dipole-dipole interaction.All the results show that the single phase Sr₃Lu?PO₄?₃:Dy³⁺,Eu³⁺ white-emitting phosphors have potential application in NUV pc-WLEDs filed.2.Eulytite-type Sr₃?Lu,Tb??PO₄?₃:Ce³⁺/Eu³⁺ phosphors were synthesized by a solid state reaction.Under the excitation of UV light at 233 nm,the emission color of Sr₃?Lu,Tb??PO₄?₃ phosphor can be tuned from blue to green by adjusting the ratios of Tb³⁺/Lu³⁺ in host lattice.Sr₃Lu?PO₄?₃:0.07Ce³⁺ phosphor gives a bluish violet emission under the excitation of UV light at 280 nm,while the Sr₃Lu?PO₄?₃:0.30Eu³⁺ presents a red-emission with the excitation of NUV light at 395 nm.The efficiently energy transfer from Tb³⁺ to Eu³⁺ occurs when excited Sr₃Tb?PO₄?₃:Eu³⁺ phosphors using NUV light at 377 nm,the emission colors of Sr₃Tb?PO₄?₃:Eu³⁺ phosphors can be tuned from green to red by adjusting the Eu³⁺ contents.For Sr₃Tb?PO₄?₃:xCe³⁺ and Sr₃Lu_0.93-yTb_y?PO₄?₃:0.07Ce³⁺ phosphors,there is a efficiently energy transfer from Ce³⁺ to Tb³⁺ ions in host lattice,under the excitation of UV light at 280 nm,Sr₃Tb?PO₄?₃:Ce³⁺ phosphor gives a intense green-emitting while the emission colors of Sr₃Lu_0.93-yTb_y?PO₄?₃:0.07Ce³⁺ can be tuned from blue to green with the increasing Tb³⁺ contents.3.A series of Sr_1-xEu_xAl₂O₄ phosphors were prepared by a Pechini-type sol-gel method.Under the excitation of UV light at 262 nm,Sr_1-xEu_xAl₂O₄ phosphors present a red emission.Sr_0.92Eu_0.08Al_2-yB_yO₄ and Sr_0.92Eu_0.08Al₂O₄/yH3BO3 phosphors were prepared by adding boric acid into Sr_0.92Eu_0.08Al₂O₄ host material via two different ways.The addition of boric acid can reduce the phase formation temperature of Sr_1-xEu_xAl₂O₄?from 1200 to 1000 ??and enhance the red emission of Eu³⁺ effectively.Eu³⁺ can be partially reduced to Eu²⁺ when sintering Sr_1-xEu_xAl₂O₄ and Sr_0.92Eu_0.08Al_2-yB_yO₄ phosphors in reducing atmosphere,the green broadband emission spectra of Eu²⁺ located at 510 nm,the emission colors can be tuned from green,through warm-white,to red by changing the doping content of europium ions or boric acid.When sintering Sr_0.92Eu_0.08Al₂O₄/yH3BO3?y = 0.2 0.5?beyond 1100 ? in air,the phosphors present SrAl₂O₄ and Sr4Al2O7 mixed-phase,Eu³⁺ ions can be partially initiatively reduced to Eu²⁺,Eu²⁺ ions present a blue-green broadband emission at around 491 nm and the emission intensity ratios of Eu²⁺/Eu³⁺ ratios can be tuned by controlling the sintering temperature,boric acid contents as well as the wavelength of excitation light,thus the emission colors can be tuned from green blue,through white light region,to red.