| White light emitting diodes (WLEDs) give a change on the illumination to take the place of traditional incandescent or filament lamps in recent years, due to its superiority of high energy efficiency, long-lived time, and environmental friendliness. In this study, Ba1-x(PO3)2:xEu2+, Ba0.97Sr0.99Mg1-xp2O8:Eu2+0.04, Mn2+X, and Sr10(1-x)Cl2(PO4)6:Eu2+10x phosphors were prepared by high temperature solid state method. Their photoluminescence properties, concentration quenching effect, temperature dependence luminescence, energy transfer mechanism were analysed.(1) A new blue-green Ba(PO3)2:Eu2+ phosphor was synthesized by solid state reaction at 650 ℃. The crystal structure and microtopography were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM), respectively. All the diffraction peaks of the phosphor samples can be well fitteded to the standard date of PDF#43-0518, and doping a little concentration of Eu2+ has no clear effect on the crystal structure. Also, no impurities are detected in the prepared product, suggesting that Eu2+ has been successfully incorporated in Ba(PO3)2. In Ba(PO3)2:0.02Eu2+ host, there is only one kind of Ba2+ site and this site coordinates with ten oxygen atoms. The microstructure of Ba(PO3)2:Eu2+ phosphor consists of irregular fine grains with the diameters ranging from 200-300 nm. It seems that the surface appearance of the particles is rough and every particle is composed of lots of tiny circular particles. The average crystalline size of the particles was calculated by the Debye-Scherrer equation, and the calculated crystal size of the phosphor is about 23 nm. The phosphors spectra shows the phosphor can be efficiency excited by near ultraviolet (NUV) light, making it remarkable as a new blue-green phosphor for LED applications. The Eu2+-Eu2+distance was calculated to be 18 A in Ba (PO3)2:Eu2+ phosphor, indicating the concentration quenching effect of Ba (PO3)2:Eu2+ phosphor is the multipole-multipole interaction mechanism. The Ea value obtained was 0.334eV. The CIE chromaticity can be varied within a certain range by adjusting the content of Eu2+, making it attractive as blue-green phosphor for LED applications.(2)A new white-light-emitting Ba0.97Sr0.99 Mg1-xP2O8:Eu2+0.04, Mn2+x phosphor was prepared by solid-state method at 1150℃. The emission spectrum consists of three main emission bands peaking at 443,550 and 614 nm, respectively, by co-doping Eu2+ and Mn2+in the host. The emission peak at 614 nm is attributed to the electron transitions of the Mn2+ from 4T1 to 6Ai, resulting in the red emission. Excited at 356 nm, the emission bands extend from 400 to 650 nm. With an increasing of doped-Mn2+ ions content, the CIE chromaticity coordinates of the Bao.97Sro.99Mgi-x(P04)2:Eu2+0.04, Mn2+x (x= 0.00-0.19) phosphors shift much closer to white light chromaticity coordinates. The temperature dependence of luminescence indicates Bao.97Sro.99Mg1-xP2O8:Eu2+0.04, Mn2+x have excellent thermal stability and the Ea is 0.2490eV. In Ba0.97Sr0.99Mg1-xP2O8: Eu2+0.04, Mn2+x phosphors, energy transfer from the Eu2+ to Mn2+ ions is mainly via a exchange interaction mechanism.(3) A new blue SrioCl2(PO4)6:Eu2+ phosphor was synthesized by solid state reaction at 850 ℃. All the XRD diffraction peaks of the phosphor samples can be well fitteded to the standard date of SnoCl2(PO4)6 (PDF 16-0666), and doping a little concentration of Eu2+has no obvious effect on the crystal structure. Also, no impurities are detected in the prepared product, suggesting that Eu2+has been successfully incorporated in Ba(PO3)2. As similar ionic radius, it was inferred that Sr2+ was replaced by Eu2+. The microstructure of Srio(i-x)Cl2(P04)6:Eu2+iox phosphor consists of irregular fine grains with the diameters about 1-3 μm. It seems that the surface appearance of the particles is smooth. The phosphors spectra shows the phosphor can be excited efficiently by near ultraviolet (NUV) light, making it remarkable as a new blue phosphor for LED applications. The CIE chromaticity can be varied within a certain range by adjusting the content of Eu2+, making it attractive as blue phosphor for LED applications. Concentration quenching mainly occurs because of the distance between activators is close enough at high Eu2+ of Sr10(1-x)Cl2(PO4)6:Eu2+iox phosphor. According to the theory of Dexter, the dominant concentration quenching mechanisms of Eu2+ is dipole-dipole interactions. The CIE chromaticity can be varied within a certain range by adjusting the content of Eu2+. |
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