Systhesis And Luminescent Properties Of Ca₇Si₂P₂O₁₆:Re³⁺ Phosphors For LED

LED is under a broad application in many fields, but the research for red phosphors of LED with high efficiency and high stability is relatively slow, so researchers have been exploring many new materials to match the phosphors of different LED chip. In this paper, we focused on Ca₇Si₂P₂O₁₆:Re³⁺ red phosphors based on silicon phosphate system matched with near ultraviolet chip. The phase,morphology, luminescence properties, energy transfer and doping modification were investigated, and then the optical properties of LED which combining with Ca₇Si₂P₂O₁₆:Re³⁺ red phosphors and ultraviolet chip were characterized.Ca₇Si₂P₂O₁₆:Re³⁺ red phosphors were synthesized by sol-gel method, and characterized by the x-ray powder diffraction?XRD?, photoluminescence and scanning electron microscopy?SEM?. The results show that the single Ca7Si2P2O16 can successfully synthesise at 1500°C for 5h, the phosphors have two emission band which peaked at 593 nm and 617 nm, respectively, indicate that Eu3+ can occupy two different sites in the lattice. By monitored the two emission wavelengths, there have some band peaked at 266nm?361nm?380nm?393nm in samples excitation spectrum,and the strongest excitation peak is at 393 nm, which are consistent with the UVLED chip wavelength. The effect of rare earth ions in concentration on phosphors luminescent properties is also discussed. The emission intensity increases with Eu3+concentration increasing, and the best emission intensity can obtain at x=0.04. When Eu3+concentration exceeds 4%, the emission intensity decreases, and the experiment appearance of concentration quenching occurres.When different concentrations of Na+ ions as a charge compensation is doped,the luminescence intensity of Ca7Si2P2O16:4%Eu3+ phosphor is improved significantly.Moreover the effect of Li+, Na+, K+ concentration on the emission intensity of Eu3+ is also discussed, and the effect of alkaline-earth ions substitution on phase and luminescent properties is investigated. The results show that Ca2+replaced by Mg2+decrease the luminescent intensity of Ca₇Si₂P₂O₁₆:Re³⁺phosphors, but the luminescentintensity of Ca₇Si₂P₂O₁₆:Re³⁺ phosphors increased effectively with Ca2+ substituted by Sr2+and Ba2+, and the best luminescent intensity can obtain at x=3. The factor of SiO44-and PO43-replacing each other can also effectively improve the luminescent intensity of Ca7Si2xP2?2-x?O16:Eu3+ phosphors, and the highest luminescent intensity can obtain at x=1.2.The energy transfer exists in Ca7Si2P2O16 host with Eu3+-Ce3+co-doping. As for Ca₇Si₂P₂O₁₆:Re³⁺,Ce3+phosphors, when Eu3+concentration remains constant, the emission intensity of Eu3+ increase with the increasing of Ce3+ doping concentration.In the Ca₇Si₂P₂O₁₆:Re³⁺,Dy3+,when Dy3+ doping concentration is 3%mol, the emission intensity of the samples is relatively strong, and the color coordinate is close to white light.The luminescent properties of Sm3+ and Tb3+ doped Ca7Si2P2O16 phosphors were studied. The results show that Ca7Si2P2O16:Sm3+ phosphor can exhibit orange-red light under the excitation wavelength of 402 nm, and the strongest emission peaked at604 nm. Ca7Si2P2O16:Tb3+ phosphor can exhibit strong green light under 369 nm excitation, their emission spectrums are composed of two emission bands which peaked at 490 nm and 547 nm respectively.The as-prepared Ca₇Si₂P₂O₁₆:Re³⁺ phosphors were used for LED package test.The results show that the red emission of Ca₇Si₂P₂O₁₆:Re³⁺ phosphor increased by being modified, and the CIE color coordinates of the sample are closer to white light point. With the blue light becoming relatively weak, the color temperature and color purity decrease, but the color rendering index and luminescent efficiently increase,indicate that this phosphor is suitable for the warm white LED, and has significant research value in white LED fields.