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1.
采用高温固相法在空气中合成了Ba1.97-yZn1-xMgxSi2O7:0.03Eu,yCe3+系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba1.97-yZn1-xMgxSi2O7:0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu2+离子的4f65d1-4f7跃迁,590~725 nm红光区窄带谱源于Eu3+5D0-7FJ (J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu3+在Ba1.97-yZn1-xMgxSi2O7基质中被还原成了Eu2+;当x=0.1时,荧光粉Ba1.97Zn0.9Mg0.1Si2O7:0.03Eu的绿色发光最强,表明Eu3+被还原成Eu2+离子的程度最大。当共掺入Ce3+离子后,形成Ba1.97-yZn0.9Mg0.1Si2O7:0.03Eu,yCe3+荧光粉体系,其发光随着Ce3+离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba1.96Zn0.9Mg0.1Si2O7:0.01Ce3+,0.03Eu的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba2Zn0.9Mg0.1Si2O7基质中的能量传递与发光机理。  相似文献   

2.
以SrCO3,Si3N4,Eu2O3为原料,在N2气氛下,采用自还原高温固相法制备了SrSi2O2N2:Eu2+荧光粉。研究了该荧光粉的物相结构、发光性能和晶体形貌,同时对比在不同气氛下合成的荧光粉。结果表明,在N2气氛与N2/H2气氛下分别合成的SrSi2O2N2:Eu2+荧光粉物相结构和光谱特性基本一致。显示出合成了主晶相SrSi2O2N2,但还含有少量未知的中间项。Eu2+浓度的变化不影响激发状态,而发射光谱的波长在Eu2+浓度为1mol%-20mol%之间,从530 nm的绿光红移至550 nm的黄绿光区域。同时,激发光谱覆盖的范围宽,均能有效的被UV或蓝光激发,这意味着该类荧光粉在白光LED方面有可能得到广泛的应用。  相似文献   

3.
Orange Eu2+-doped phosphors are essential for light-emitting diodes for cornering lights to prevent fatal road accidents at night, but such phosphors require features of high thermal, chemical stability and facile synthesis. This study reports a series of yellow-orange-red emitting SrAl2Si3ON6:Eu2+ oxynitride phosphors, derived from the SrAlSi4N7 nitride iso-structure by replacing Si4+−N3− with Al3+−O2−. The introduction of a certain amount of oxygen enabled the facile synthesis under atmospheric pressure using the air-stable raw materials SrCO3, Eu2O3, AlN and Si3N4. SrAl2Si3ON6 has a smaller band gap and lower structure rigidity than SrAlSi4N7 (5.19 eV vs 5.50 eV, Debye temperature 719 K vs 760 K), but exhibits higher thermal stability with 100 % of room temperature intensity remaining at 150 °C compared to 85 % for SrAlSi4N7. Electron paramagnetic resonance, thermoluminescence and density functional theory revealed that the oxygen vacancy electron traps compensated the thermal loss. Additionally, no decrease in emission intensity was found after either being heated at 500 °C for 2 hours or being immersed in water for 20 days, implying both of the thermal and chemical stability of SrAl2Si3ON6:Eu2+ phosphors. The strategy of oxynitride-introduction from nitride promotes the development of low-cost thermally and chemically stable luminescent materials.  相似文献   

4.
采用优化的高温固相方法制备了稀土离子Eu3+和Tb3+掺杂的La7O6(BO3)(PO42系荧光材料,并对其物相行为、晶体结构、光致发光性能和热稳定性进行了详细研究。结果表明,La7O6(BO3)(PO42:Eu3+材料在紫外光激发下能够发射出红光,发射光谱中最强发射峰位于616 nm处,为5D07F2特征能级跃迁,Eu3+的最优掺杂浓度为0.08,对应的CIE坐标为(0.610 2,0.382 3);La7O6(BO3)(PO42:Tb3+材料在紫外光激发下能够发射出绿光,发射光谱中最强发射峰位于544 nm处,对应Tb3+5D47F5能级跃迁,Tb3+离子的最优掺杂浓度为0.15,对应的CIE坐标为(0.317 7,0.535 2)。此外,对2种材料的变温光谱分析发现Eu3+和Tb3+掺杂的La7O6(BO3)(PO42荧光材料均具有良好的热稳定性。  相似文献   

5.
SrAl2O4:Eu2+, Dy3+ powders were synthesized by sol–gel–combustion process using metal nitrates as the source of metal ions and citric acid as a chelating agent of metal ions. The amounts of citric acid in mole were two times those of the metal ions. By tracing the formation process of the sol–gel, it is found that decreasing the amount of NO3 in the solution is necessary for the formation of transparent sol and gel, and the dropping of ethanol into the precursor solution can decrease the amount of NO3 in the solution. By combusting citrate sol at 600 °C, followed by heating the resultant combustion ash at 1,100–1,300 °C in a weak reductive atmosphere containing active carbon, SrAl2O4:Eu2+, Dy3+ phosphors can prepared. X-ray diffraction, Thermogravimetry–differential thermal analysis, scanning electron microscopy and fluorescence spectrophotometer were used to investigate the formation process and luminescent properties of the as-synthesized SrAl2O4:Eu2+, Dy3+. The results reveal that the SrAl2O4 crystallizes completely when the combustion ash was sintered at 1,200–1,300 °C. The excitation and emission spectra indicate that excitation broadband mainly lies in a visible range and the phosphors emit strong light at 510 nm under the excitation of 348 nm. The afterglow of phosphors lasts for over 10 h when the excited source is cut off.  相似文献   

6.
In this work, Sr3Al2O6: Eu2+ (Eu3+), Dy3+ phosphors have been prepared by hydrothermal treatment and subsequently postannealing approach, using Sr(NO3)2, Al(NO3)3·9H2O, and CO(NH2)2 as starting materials. The as-obtained phosphors were characterized by means of XRPD, FESEM, and PL techniques. In addition, many reaction parameters were studied in detail, including the initial mole ratios, hydrothermal reaction temperature, calcination temperature and calcination atmosphere. Remarkably, two scientific merits exist herein: Sr3Al2O6: Eu2+ (Eu3+), Dy3+ phosphors can be selectively obtained in a reducing atmosphere (H2/Ar, 20%+80%) and in air, respectively; adding certain amount of sodium citrate can alter the shape and size of Sr3Al2O6: Eu2+ (Eu3+), Dy3+ phosphors in essence. Besides, the luminescent properties of Sr3Al2O6: Eu2+ (Eu3+), Dy3+ phosphors were studied by excitation spectra, emission spectra and decay curves.  相似文献   

7.
The photocatalytic activity of Bismuth‐codoped Sr4Al14O25: Eu2+, Dy3+ persistent phosphors is studied by monitoring the degradation of the blue methylene dye UV light irradiation. Powder phosphors are obtained by a combustion synthesis method and a postannealing process in reductive atmosphere. The XRD patterns show a single orthorhombic phase Sr4Al14O25: Eu2+, Dy3+, Bi3+ phosphors even at high Bismuth dopant concentrations of 12 mol%, suggesting that Bi ions are well incorporated into the host lattice. SEM micrographs show irregular micrograins with sizes in the range of 0.5–20 μm. The samples present an intense greenish‐blue fluorescence and persistent emissions at 495 nm, attributed to the 5d–4f allowed transitions of Eu2+. The fluorescence decreases as Bi concentration increases; that suggest bismuth‐induced traps formation that in turn quench the luminescence. The photocatalytic evaluation of the powders was studied under both 365 nm UV and solar irradiations. Sample with 12 mol% of Bi presented the best MB degradation activity; 310 min of solar irradiation allow 100% MB degradation, whereas only 62.49% MB degradation is achieved under UV irradiation. Our results suggest that codoping the persistent phosphors with Bi3+ can be an alternative to enhance their photocatalytic activity.  相似文献   

8.
Rare‐earth‐doped aluminosilicates of alkaline earth MgAl2Si2O8: Eu3+, Dy3+ and MgAl2Si2O8: Eu3+, Gd3+ were synthesized by the solid state reaction method at 1300 oC. The phosphors were characterized by X‐ray powder diffraction (XRD), photoluminescence (PL), thermoluminescence (TL) and scanning electron microscopy (SEM). X‐ray powder diffraction studies show that the phosphors were crystallized in the triclinic crystal system. The phosphors show characteristic broad band phosphorescence of Eu3+. This broad band phosphorescence has red emission bands in the range of 580–705 nm corresponding to 5D07Fj (j:0,2,3,4) transitions of Eu3+.  相似文献   

9.
The LiInW2O8:Eu3+, LiInW2O8:Dy3+ and LiInW2O8:Eu3+/Dy3+ phosphors were synthesized by solid-state reaction and their photoluminescence properties were studied. Under UV excitation, the LiInW2O8:Eu3+ phosphor exhibits an intense red emission whereas the LiInW2O8:Dy3+ and LiInW2O8:Dy3+/Eu3+ phosphors show a white emission. The WO6 octahedra play a major role in the luminescence of the host lattice, characterized by a blue emission under UV excitation. The emission of activator ion results from an efficient energy transfer from the LiInW2O8 host lattice to the Eu3+ and Dy3+ ions. The LiIn0.97Dy3+0.03W2O8 and LiIn0.965 Dy3+0.03Eu3+0.005W2O8 samples, optimized for white emission, are interesting candidates for solid-state lighting applications.  相似文献   

10.
采用高温固相法在空气中合成了Ba1.97-yZn1-xMgxSi2O7∶0.03Eu,y Ce3+系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba1.97-yZn1-xMgxSi2O7∶0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu2+离子的4f 65d1-4f 7跃迁,590~725 nm红光区窄带谱源于Eu3+的5D0-7FJ(J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu3+在Ba1.97-yZn1-xMgxSi2O7基质中被还原成了Eu2+;当x=0.1时,荧光粉Ba1.97Zn0.9Mg0.1Si2O7∶0.03Eu的绿色发光最强,表明Eu3+被还原成Eu2+离子的程度最大。当共掺入Ce3+离子后,形成Ba1.97-yZn0.9Mg0.1Si2O7∶0.03Eu,y Ce3+荧光粉体系,其发光随着Ce3+离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba1.96Zn0.9Mg0.1Si2O7∶0.03Eu,0.01Ce3+的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba2Zn0.9Mg0.1Si2O7基质中的能量传递与发光机理。  相似文献   

11.
采用优化的高温固相方法制备了稀土离子Eu~(3+)和Tb~(3+)掺杂的La_7O_6(BO_3)(PO_4)_2系荧光材料,并对其物相行为、晶体结构、光致发光性能和热稳定性进行了详细研究。结果表明,La_7O_6(BO_3)(PO_4)_2∶Eu~(3+)材料在紫外光激发下能够发射出红光,发射光谱中最强发射峰位于616 nm处,为5D0→7F2特征能级跃迁,Eu~(3+)的最优掺杂浓度为0.08,对应的CIE坐标为(0.610 2,0.382 3);La_7O_6(BO_3)(PO_4)_2∶Tb~(3+)材料在紫外光激发下能够发射出绿光,发射光谱中最强发射峰位于544 nm处,对应Tb~(3+)的5D4→7F5能级跃迁,Tb~(3+)离子的最优掺杂浓度为0.15,对应的CIE坐标为(0.317 7,0.535 2)。此外,对2种材料的变温光谱分析发现Eu~(3+)和Tb~(3+)掺杂的La_7O_6(BO_3)(PO_4)_2荧光材料均具有良好的热稳定性。  相似文献   

12.
In this paper, a heterogeneous precipitation method utilizing urea hydrolysis was adopted to coat a SiO2 layer on the surface of SrAl2O4:Eu2+, Dy3+ long persistence phosphors. To avoid phosphor hydrolysis in a water-containing coating medium, the hydrolysis and polymerization reactions of tetraethyl orthosilicate (TEOS) were concerned and carried out. The crystal phases, surface morphologies, hydrolysis stability and water resistance on afterglow properties of coated phosphors were investigated. Scanning electron microscopy, energy dispersive spectrum analysis, transmission electron microscope and Fourier transform infrared spectrum results confirmed that a continuous, uniform and compact SiO2 coating layer was successfully obtained on the phosphors surface. A theoretical coating amount of 5% or higher was found to be good for hydrolysis stability. Photoluminescence results revealed the coated phosphors showed much better water resistance on afterglow properties than the uncoated phosphor. We also discussed and proposed the hydrolysis restriction mechanism of SrAl2O4:Eu2+, Dy3+ in the water-containing coating medium.  相似文献   

13.
In general, the reduction of Eu3+ to Eu2+ in solids needs an annealing process in a reducing atmosphere. In this paper, it is of great interest and importance to find that the reduction of Eu3+ to Eu2+ can be realized in a series of alkaline-earth metal aluminum silicates MAl2Si2O8 (M=Ca, Sr, Ba) just in air condition. The Eu2+-doped MAl2Si2O8 (M=Ca, Sr, Ba) powder samples were prepared in air atmosphere by Pechini-type sol-gel process. It was found that the strong band emissions of 4f65d1-4f7 from Eu2+ were observed at 417, 404 and 373 nm in air-annealed CaAl2Si2O8, SrAl2Si2O8 and BaAl2Si2O8, respectively, under ultraviolet excitation although the Eu3+ precursors were employed. In addition, under low-voltage electron beam excitation, Eu2+-doped MAl2Si2O8 also shows strong blue or ultraviolet emission corresponding to 4f65d1-4f7 transition. The reduction mechanism from Eu3+ to Eu2+ in these compounds has been discussed in detail.  相似文献   

14.
The Ba2GdNbO6: Eu3+/Dy3+ and Li+-doped Ba2GdNbO6: Eu3+/Dy3+ phosphors were prepared by solid-state reaction process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and photoluminescence (PL) as well as lifetimes, was utilized to characterize the resulting phosphors. Under the excitation of ultraviolet light, the Ba2GdNbO6: Eu3+/Dy3+ and Li+-doped Ba2GdNbO6: Eu3+/Dy3+ show the characteristic emissions of Eu3+ (5D0-7F1,2,3 transitions dominated by 5D0-7F1 at 593 nm) and Dy3+ (4F9/2-6H15/2,13/2 transitions dominated by 4F9/2-6H15/2 at 494 nm), respectively. The incorporation of Li+ ions into the Ba2GdNbO6: Eu3+/Dy3+ phosphors has enhanced the PL intensities depending on the doping concentration of Li+, and the highest emission was obtained in Ba2Gd0.9NbO6: 0.10Eu3+, 0.01Li+ and Ba2Gd0.95NbO6: 0.05Dy3+, 0.07Li+, respectively. An energy level diagram was proposed to explain the luminescence process in the phosphors.  相似文献   

15.
This review includes research papers on different methods of preparation of Eu2+ and Dy3+-doped SrAl2O4 phosphors and papers reporting luminescence studies of the materials. The methods of preparation were compared and it was concluded that solid state reaction is the best method. Papers on characterization of these phosphors by X-ray diffraction and scanning electron microscopy are also discussed. The review ends with a few important conclusions.  相似文献   

16.
《Solid State Sciences》2012,14(5):607-610
Novel Eu2+ and Ce3+ activated BaMg8Al18Si18O72 phosphors was prepared by combustion method and their PL characteristics were investigated. The result shows that all samples can be excited efficiently by near UV excitation under 334 nm and 316 nm. The emission was observed for BaMg8Al18Si18O72:Eu2+ phosphor at 437 nm corresponding to d → f transition, under 334 nm broad-band excitation, whereas BaMg8Al18Si18O72:Ce3+ phosphor shows emission band at 376 nm under 316 nm excitation. Phase purity of the phosphor was checked with the help of XRD pattern. SEM analysis shows the external morphology of the combustion synthesized phosphor.  相似文献   

17.
Spherical SiO2 particles have been coated with rare earth oxide layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO2@RE2O3 (RE=rare earth elements) and SiO2@Gd2O3:Ln3+ (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO2@RE2O3 (RE=rare earth elements) and SiO2@Gd2O3:Ln3+ (Eu3+, Tb3+, Dy3+, Sm3+, Er3+, Ho3+) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles). Under the excitation of ultraviolet, the Ln3+ ion mainly shows its characteristic emissions in the core-shell particles from Gd2O3:Ln3+ (Eu3+, Tb3+, Sm3+, Dy3+, Er3+, Ho3+) shells.  相似文献   

18.
Eu3+ ions activated La2Ti2O7 (La2Ti2O7:xEu3+) phosphors have been successfully synthesized by a fractional precipitation method from commercially available La2O3, Eu2O3, HNO3, Ti(SO4)2·9H2O and NH3·H2O as the starting materials. Detailed characterizations of the synthetic products were obtained by fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential thermal analysis, thermogravimetry and derivative thermogravimetry (DTA-TG-DTG), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. The results show that the precursor is composed of amorphous particles with quasi-spherical in shape and about 50 nm in size. Moreover, the precursor could be converted into pure La2Ti2O7 phase by calcining at 1000 °C for 2 h in air. The as-synthesized La2Ti2O7 particles are approximate polyhedron in shape and about 100–200 nm in size. PL spectroscopy of La2Ti2O7:xEu3+ phosphors reveals that the strongest emission peak is located at 616 nm under 275 nm ultraviolet (UV) light excitation, which corresponds to the 5D07F2 transition of Eu3+ ions. The quenching concentration of Eu3+ ions is 10.0 mol%, and its corresponding fluorescence lifetime was 1.82 ms according to the linear fitting result. Decay study reveals that the 5D07F2 transition of Eu3+ ions has a single exponential decay behavior.  相似文献   

19.
The Eu3+-doped La2Zr2O7 phosphor with rod-like morphology was successfully synthesized by conventional solid state reaction and hydrothermal method. X-ray diffraction patterns, transmission electron microscopy, and photoluminescence spectra were employed to charac-terize its structure and morphology as well as luminescent properties. The results indicated that the red-emitting phosphor La2Zr2O7:Eu3+ had well crystallized and belonged to the cubic structure with space group of Fd3m. The as-obtained product mainly appeared as straight nanorods with an average diameter of 47 nm and length of 50-700 nm. The pos-sible growth mechanism was also discussed. It was found that under blue excitation with a wavelength of 466 nm, the La2Zr2O7:Eu3+ phosphor exhibited a characteristic red emission at 616 nm that was attributed to the hypersensitive 5DO7F2 electric dipole transition of Eu3+ ions. Meanwhile, it was more interesting to note that the emission of 5D17FJ (J=0, 1, 2) transitions and the splitting patterns of 5D07FJ (J=1, 2, 4) transitions of Eu3+ ions can be observed in the luminescent spectra of La2Zr2O7:Eu3+. It was demonstrated that Eu3+ preferred to occupy a low symmetry site.  相似文献   

20.
Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses were prepared using the melt-quenching process and analyzed by X-diffraction, Raman spectroscopy, excitation and emission spectra, and emission decay time profiles. The lack of X ray diffraction peaks revealed that all samples are amorphous. Vibrational modes associated with TeOTe and GeOGe related bonds and molecular oxygen were detected by Raman spectroscopy. The luminescence characteristics were studied upon excitations that correspond with the emission of InGaN (370–420 nm) based LEDs. The Eu3+ singly doped glass displayed reddish-orange global emission, with x = 0.601 and y = 0.349 CIE1931 chromaticity coordinates, upon 393 nm excitation. Neutral emission with x = 0.373 and y = 0.412 CIE1931 chromaticity coordinates and correlated color temperature (CCT) of 4400 K, was achieved in the Dy3+ singly doped glass excited at 388 nm. The Dy3+/Eu3+ co-doped glass exhibited warm, neutral and soft warm white emissions with CCT values of 3435, 4153 and 2740 K, under excitations at 382, 388 and 393 nm, respectively, depending mainly on the Dy3+ and Eu3+ relative excitation. The Dy3+ excitation bands observed in the Dy3+/Eu3+ glass by monitoring the 611 nm Eu3+ emission, suggest that Dy3+ → Eu3+ energy transfer takes place, despite the fact that the Dy3+ emission decays in the Dy3+ and Dy3+/Eu3+ doped glass, remain without changes. The shortening of Eu3+ decay in presence of Dy3+ was attributed to an Eu3+ → Dy3+ non-radiative energy transfer process, which according with the Inokuti-Hirayama model might be dominated through an electric quadrupole-quadrupole interaction, with efficiency and probability of 5.5% and 51.6 s−1, respectively.  相似文献   

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