Preparation And Luminescence Properties Of Eu²⁺ Doped Phosphate Phosphor With Tunable Color

Recently,phosphor materials have attained great achievement and progress in various fields,including solid-state lighting,optical temperature sensors,flat panel displays,solar cells,and optical biomarkers.As next-generation lighting devices,phosphor-converted white light-emitting diodes?w-LEDs?have received much more attention since w-LEDs provide extraordinary superiorities,such as low electric consumption,high electro-optical conversion efficiency,high brightness,good stability,fast response,and environmental friendliness.Therefore,one of the works of this paper is to research emission-tunable phosphors which can be effectively stimulated by UV and near ultraviolet light.We selected phosphate as the matrix material.At present,the mainstream commercial W-LEDs in the market are fabricated by combining InGaN LED chips and yellow emitting Y₃Al₅O₁₂:Ce³⁺phosphors.Nevertheless,this kind of white light suffers from low color rendering index and high correlated color temperature due to the lack of red spectral component in the visible region.At present,W-LEDs fabricated using NUV chips coupled with a blend of yellow-and blue-emitting phosphors have revealed outstanding properties,such as tunable correlated color temperature,tunable Commission International de l'Eclairage?CIE?chromaticity coordinates,and an excellent color rendering index.Consequently,another work of this paper is to develop novel phosphors that can be effectively excited in the NUV range.The specific research includes the follow three aspects:?1?LiSrPO₄:Eu²⁺,Y³⁺phosphor was synthesized by a high temperature solid-state reaction method through CO reducing atmosphere.Under 340nm excitation,the Li SrPO₄:Eu²⁺samples shows the emission band in the400-650nm,With increasing Y³⁺content,the emission spectra are broadened and red-shifted gradually.Accordingly,the luminescence color has been tuned facilely,the emission color could be tuned from light blue to yellow-green.All the excitation spectra of the as-prepared samples show broad excitation bands from UV to blue,which can well match with the emission wavelength of the NUV LED chip.?2?Eu²⁺single doped phosphors Sr₉Lu?PO₄?₇:Eu²⁺and Eu²⁺/Mn²⁺co-doped phosphors Sr₉Lu?PO₄?₇:Eu²⁺,Mn²⁺were prepared through solid state reactions.Under the excitation of 365nm,Sr₉Lu?PO₄?₇:Eu²⁺phosphors shows bright yellowish-green emission,and the emission spectrum exhibits a wide emission band covering from 410 to 750nm.The optimal Eu²⁺concentration is 5mol%,and the emission intensity of the samples starts to decay beyond this Eu²⁺concentration due to concentration quenching.The dipole-dipole interaction is the major mechanism for concentration quenching in Sr₉Lu?PO₄?₇:Eu²⁺phosphors.?3?Sr₉Lu?PO₄?₇:Eu²⁺,Mn²⁺phosphor was synthesized by a high temperature solid-state reaction method through CO reducing atmosphere.Bright yellow light was emitted from the samples under the irradiation of365nm ultraviolet lamp.Under the excitation of 365nm,the emission spectrum of the sample almost covers the whole visible region.When the concentration of Eu²⁺ions is constant,the concentration of Mn²⁺ions is gradually increased.When the concentration of Mn²⁺ions is 10mol%,the luminescence intensity of Mn²⁺ions reaches the maximum,and then the luminescence intensity of Mn²⁺decreases gradually.In addition,the energy transfer from Eu²⁺to Mn²⁺ions has been demonstrated to be a resonant type via a dipole-quadrupole mechanism.