Preparation And Luminescence Properties Of Vanadate Phosphor For Light-emitting Diodes

With the development of LED and PDP, the requirement of the crystal size distribution, stability, luminesccnce efficiency and brightness of the powder has been increasing. Among the large number of luminescent materials, rare-earth vanadate host luminescent materials are well known for their good chemical and thermal stability. In this paper, phosphors Ca₃(VO₄)₂: Eu³⁺,Sm³⁺, Ca₃Y_0.8Gd_0.2(VO₄)₂.4(PO₄)0.6: Eu³⁺ and Ca₃(VO₄)_2-x(PO₄)x: Eu³⁺ were prepared by modified solid state reaction. And phosphor Na0.86CaEu0.14VO₄ and X3(VO₄)₂(X = Sr, Ba) were prepared by a combustion method. X-ray powder diffractometer (XRD), energy-dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and luminescence spectrometer (LS) were used to study the phase structure, the morphology, element analysis and the luminescent properties of the phosphor. The paper aims at finding new types of luminescent materials with high-performance and low-cost.Rare-earth ions co-activated red phosphors Ca₃(VO₄)₂: Eu³⁺,Sm³⁺ were synthesized by modified solid-state reactions. The luminescence measurements showed that the Eu-Sm system exhibits higher emission intensity than those of the Eu single-doped system and Sm separate-doped system under blue light. Samarium (III) ions are effective in broadening and strengthening absorptions around 467 nm. Furthermore, they exhibit enhanced luminescence emission. And the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a red light with a peak wavelength of 616 nm. The material has potential application as a phosphor for light-emitting diodes (LEDs).Eu³⁺-doped Ca₃Y_0.8Gd_0.2(VO₄)₂.4(PO₄)0.6 nanophosphors have been prepared by modified solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the formation of YVO₄. Photoluminescence (PL) results showed that the phosphor could be efficiently excited by UV-visible light from 350 to 550 nm, exhibiting bright orange-red emission(excited by 397) and red emission(excited by 467), which has potential application as a phosphor for UV and blue GaN-based light-emitting diodes (LEDs). TEM images show that the grain size of Ca₃Y0.45Eu0.35Gd0.2(VO₄)₂.4(PO₄)0.6 is about 39 nm, which is in full agreement with the theoretical calculation data from the XRD patterns.A novel orange-emitting phosphor, Na0.86CaEu0.14VO₄, was prepared by combustion method. X-ray powder diffraction (XRD) analysis confirmed the formation of NaCaVO₄. Photoluminescence (PL) results showed that the phosphor could be efficiently excited by UV-visible light from 350 to 550 nm, exhibiting bright orange emission. The effect of the doped-Eu³⁺ concentration in NaCaVO₄ on the PL was investigated in detail. The result showed that the relative PL intensity decreases with increasing Eu³⁺-concentration due to concentration quenching. TEM images show that the grain size of Na0.86CaEu0.14VO₄ is about 50 nm, which is in full agreement with the theoretical calculation from the XRD patterns.Eu³⁺-doped Ca₃(VO₄)_2-x(PO₄)x nanophosphors have been prepared by modified solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the formation of Ca₃(VO₄)₂. Photoluminescence (PL) results showed that the phosphor could be efficiently excited by UV-visible light from 350 to 550 nm, exhibiting bright orange-red emission. And the emission intensity increases with increasing P and the maximum is at x = 0.4 for Ca₃(VO₄)_2-x(PO₄)x: 6% Eu³⁺. The material has potential application as a phosphor for UV and blue GaN-based light-emitting diodes (LEDs).To find efficient and low-cost phosphors, the phosphors X3(VO₄)₂(X=Sr, Ba) have been successfully synthesized by combustion method at 850℃the first time. We have studied the influence of combustion temperature on fluorescence intensity of Phosphors. The samples were characterized by X-ray powder diffractometer (XRD), transmission electron microscopy (TEM) and luminescence spectrometer (LS). The results showed that under the excitation of 340 nm, the phosphor exhibits the broad band emission ranging from 400 to 600 nm.