Preparation And Luminescence Performance Of Phosphate Series Phosphors

White light-emitting diodes（WLEDs）are regarded as the most valuable solid-state lighting source of the new generation because of their considerable electro-optical conversion efficiency,environmental friendliness,long operating life and low power consumption.Currently,phosphor-converted white LEDs（pc-WLEDs）have become a research hotspot in the field of luminescence,and UV/near-UV LED chips compounded with trichromatic luminescent materials are gradually becoming the most important means of white LEDs.However,rare-earth ions single doped phosphor excitation band single,through the mutual doping of rare-earth ions,expanded the excitation band,better match the excitation of the near-ultraviolet LEDs,the more excellent luminescence obtained,to achieve a color-controlled emission.Phosphate is of great interest to researchers because of its wide source,low cost,simple preparation and stable physicochemical properties.In this paper,a series of Eu³⁺,Dy³⁺,Sm³⁺and Tb³⁺doped metaphosphate and pyrophosphate phosphors were synthesized by high temperature solid phase method with phosphate matrix as the main body.The crystal structures and luminescence properties of the synthesized phosphors were investigated in detail by XRD,fluorescence spectroscopy,XPS and other characterization methods.Specific studies are summarized as follows:1.A series of Eu³⁺mono-doped Ca（PO₃）₂ phosphors and a new color-tunable Na Sr（PO₃）₃:Dy³⁺,Eu³⁺phosphor were prepared by high-temperature solid-phase method.In the Eu³⁺mono-doped Ca（PO₃）₂ phosphors,Rietveld refinement of X-ray diffraction showed that Eu³⁺ions occupied Ca²⁺sites in the Ca（PO₃）₂ lattice and had no effect on the crystal structure of the substrate.The self-reduction of Eu³⁺was studied and verified by fluorescence spectroscopy and X-ray photoelectron spectroscopy（XPS）.Under excitation at 238 nm,the sample exhibited an extensive blue Eu²⁺emission band in addition to the usual orange-red emission of Eu³⁺.The XPS results indicated that europium ions were present in the divalent and trivalent forms,and then the self-reduction mechanism of Eu³⁺was further discussed.On this basis,the effect of Eu concentration on the luminescence properties of Ca（PO₃）₂ phosphor was investigated in detail,and the luminescence color of the phosphor could be tuned from violet to red by controlling the Eu³⁺content.In the new color-tunable Na Sr（PO₃）₃:Dy³⁺,Eu³⁺phosphor,XRD results showed that the doping of Dy³⁺and Eu³⁺did not change the crystal structure of Na Sr（PO₃）₃.A series of characteristic emissions of Dy³⁺and Eu³⁺ were observed in the emission spectra under 350 nm excitation,corresponding to⁴F_9/2→⁶H_15/2（478 nm）and ⁴F_9/2→⁶H_13/2（573 nm）jumps of Dy³⁺,and ⁵D₀→⁷F₁（591nm）and ⁵D₀→⁷F₂（613 nm）jumps of Eu³⁺,respectively.The emission intensity of Dy³⁺gradually decreases with the increase of Eu³⁺concentration,which proves the existence of energy transfer from Dy³⁺to Eu³⁺in the Na Sr（PO₃）₃ phosphor.The CIE chromaticity coordinates are very sensitive to the addition of Eu³⁺,and the associated color temperature is improved with the introduction of Eu³⁺,and its luminescence color achieves tunable luminescence from yellow-green to orange-yellow.The results indicate that Dy³⁺/Eu³⁺-doped metaphosphate phosphors have a broad application prospect in the field of WLED solid-state lighting.2.A series of color-tunable Sr₂P₂O₇:Sm³⁺,Eu³⁺phosphors and a new Tb³⁺and Eu³⁺co-doped Na YP₂O₇ phosphor were prepared by high-temperature solid-phase method.In the Sr₂P₂O₇:Sm³⁺,Eu³⁺phosphor,XRD results showed that the introduction of Sm³⁺and Eu³⁺did not cause any change in the crystal structure of Sr₂P₂O₇.Under 402 nm excitation,the Sm³⁺-doped Sr₂P₂O₇ phosphor exhibited excellent orange-red luminescence,with the best luminescence performance when the Sm³⁺doping amount was 0.05.Further fixing the concentration of Sm³⁺in the co-doped Sr₂P₂O₇:0.05Sm³⁺,y Eu³⁺phosphor,the intensity of the characteristic emission peak of Sm³⁺gradually decreased with the increase of Eu³⁺concentration,while the intensity of the emission peak of Eu³⁺gradually increased.The results indicate that there is an energy transfer from Sm³⁺to Eu³⁺in the co-doped phosphor,and the phosphor has high quality red emission and achieves tunable luminescence from orange-red to deep red.In Tb³⁺and Eu³⁺co-doped Na YP₂O₇ phosphors.The results of the physical phase analysis showed that the Tb³⁺and Eu³⁺doping did not change the crystal structure of Na YP₂O₇.XPS showed that all the sample elements were present and no obvious impurity peaks were found,indicating the high purity of the synthesized samples.The Tb³⁺single-doped Na YP₂O₇ phosphor showed excellent green emission under 370 nm excitation.The introduction of Eu³⁺into the Tb³⁺-doped Na YP₂O₇ phosphor reveals a more significant enhancement of the excitation band intensity in the range of 330-380 nm than that of the Eu³⁺-single-doped sample,and the effective excitation range is also extended.The characteristic emission peaks in the blue ⁵D₄→⁷F₄（485 nm）and green ⁵D₄→⁷F₅（543nm）regions of Tb³⁺were observed in the emission spectra,and the characteristic emission peaks in the orange ⁵D₀→⁷F₁（592 nm）and red ⁵D₀→⁷F_2/3/4（619 nm,650 nm and 700 nm）regions corresponding to Eu³⁺were also observed.Further increase in the concentration of Eu³⁺leads to a decrease in the intensity of the Tb³⁺emission peak and an increase in the intensity of the Eu³⁺emission peak,and the results indicate a transfer of energy from Tb³⁺to Eu³⁺.By controlling the content of Tb³⁺and Eu³⁺,a high quality and wide range of tunable luminescence from green to yellow to red color can be achieved.Therefore,rare earth ion-doped pyrophosphate phosphors are expected to have potential applications in areas such as optical displays and WLEDs devices.