Preparation And Luminescence Properties Of Phosphate Phosphors For White LEDs

In the field of general lighting,more than 75%of WLEDs?White Light-Emitting Diodes,WLEDs?are pc-WLEDs?phosphor-converted WLEDs?that use phosphors for spectral conversion.In recent years,near-ultraviolet LED chips and trichromatic phosphor or single matrix white phosphors have been combined to realize pc-WLED and other methods,which have the advantages of high color rendering index,adjustable color temperature and low energy loss.Research hotspots in the field of powder.Therefore,it is important to study novel trichromatic phosphors or single-substrate white phosphors.In this paper,the following phosphors were prepared by high temperature solid phase method using novel Na₃Gd?PO₄?₂ phosphate as matrix,and their luminescent properties were studied:?1?Synthesis of Na₃Gd?PO₄?₂:A(A=Sm³⁺,Tb³⁺,Ce³⁺)trichromatic phosphors.The emission spectra of Na₃Gd?PO₄?₂:Sm³⁺phosphors are composed of three emission peaks centered at 565,600 and 647 nm,respectively,which are attributed from the excited state ⁴G_5/2 to the ground level ⁶H_5/2?⁶H_7/2 and ⁶H_9/2 energy transition,emitting red light.The emission spectrum of Na₃Gd?PO₄?₂:Tb³⁺phosphor shows a strong emission peak at 545 nm,which is in the green region,corresponding to the ⁵D ₄?⁷F₅level transition of Tb³⁺.Na₃Gd?PO₄?₂:Ce³⁺phosphor,due to the transition of Ce³⁺4f⁶5d¹?⁴f⁷,its emission spectrum has a broad spectrum of 350-450 nm,showing strong blue light emission.The device package of the LED is obtained by blending the ratio of the phosphor of the three primary colors to obtain white light.?2?Synthesis of Na₃Gd?PO₄?₂:Dy³⁺/Eu³⁺single matrix white phosphor.In the excitation spectrum,the emission band of Eu³⁺has a large overlap with Dy³⁺.After the Eu3+ion acts as a sensitizer for Dy³⁺ions to transfer energy to Dy³⁺,the red light emitted by Eu³⁺ions can be well correlated with the cool white light emitted by Dy³⁺.By changing the doping concentration of Eu³⁺,white light of different color temperatures can be obtained.When the doping concentration of Eu³⁺is x=0.03,the color coordinates of the phosphor are?0.3472,0.3493?,and the standard white light close to the International Commission on Illumination is obtained.?3?Synthesis of Na₃Gd?PO₄?₂:Eu²⁺/Mn²⁺single matrix white phosphor.In the emission spectrum,there is an effective energy transfer between the sensitizer Eu²⁺ion and the activator Mn²⁺ion,which belongs to the electric multipole interaction,which makes the phosphor have higher fluorescence efficiency.By changing the doping ratio of Mn²⁺,the CIE of the phosphor shows that the emitted light can be converted from blue light to white light to red light.When the Mn²⁺doping concentration is 0.01,the color coordinates of the phosphor are?0.3334,0.3204?,and a single matrix white phosphor is obtained.