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1.
Y2O3:Eu3+, Tb3+ phosphors with white emission are prepared with different doping concentration of Eu3+ and Tb3+ ions and synthesizing temperatures from 750 to 950 °C by the co-precipitation method. The resulted phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The results of XRD indicate that the crystallinity of the synthesized samples increases with enhancing the firing temperature. The photoluminescence spectra indicate the Eu3+ and Tb3+ co-doped Y2O3 phosphors show five main emission peaks: three at 590, 611 and 629 nm originate from Eu3+ and two at 481 and 541 nm originate from Tb3+, under excitation of 250-320 nm irradition. The white light luminescence color could be changed by varying the excitation wavelength. Different concentrations of Eu3+ and Tb3+ ions were induced into the Y2O3 lattice and the energy transfer from Tb3+→Eu3+ ions in these phosphors was found. The Commission International de l’Eclairage (CIE) chromaticity shows that the Y2O3:Eu3+, Tb3+ phosphors can obtain an intense white emission.  相似文献   

2.
Newly synthesized reference MgLaLiSi2O7 and red luminescent Eu3+:MgLaLiSi2O7 powder phosphors have been successfully developed by a solid-state reaction method to analyze their emission and structural properties from the measurement of their XRD, SEM, FTIR and PL spectra. Emission spectra of Eu3+ powder phosphors have shown strong red emissions at 613 nm (5D07F2). These phosphors have also shown bright red emissions under a UV source. Based on the red emission performance, the Eu3+ concentration has been optimized to be at 0.3 mol%.  相似文献   

3.
Eu3+ activated M6AlP5O20 (where M=Sr/Ba/Mg) phosphors prepared by combustion synthesis and the completion of the synthesis was confirm by XRD (X-ray diffraction) patterns. The surface morphology studied by scanning electron microscopy (SEM) and photoluminescence (PL) properties has been reported in this paper. The Eu3+ PL emission spectrum was observed in M6AlP5O20 phosphors (where M=Sr/Ba/Mg) at 592 (orange) and 618 nm (red) region, the spectrum due to 5D07F1 and 5D07F2 transitions at mercury free excitation, respectively. Its considerable emission intensity under 350 nm excitations makes it possible candidate materials as red component of tricolor luminescence materials and for near ultra violet light emitting diode (n-UVLED) phosphors.  相似文献   

4.
In this paper, a novel phosphor, Y6W2O15:Eu3+ was synthesized by thermal decomposition and phase transition of its decatungstate gel precursor. With stepwise increase of temperature to 750 °C, a crystalline phase of Y6W2O15:Eu3+forms that gives intense red emission when excited at 466 nm, the emission is attributed to the Eu3+ ions transitions from 5D0 excited states to 7FJ (J=0-4) ground states. The long excitation wavelength proves the Eu3+ transition follows the photoexcitation of the oxygen-metal (O→W lmct) charge transfer bands in yttrium tungstate. Some structural information regarding Y6W2O15 provided by luminescence is in accord with that characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The long-wavelength excitation properties of this material may find application in the production of red phosphors for white light-emitting diodes (LEDs).  相似文献   

5.
This study evaluated potential applications of green to yellow-emitting phosphors (Sr1−xSi2O2N2: Eu2+x) in blue pumped white light emitting diodes. Sr1-xSi2O2N2: Eu2+x was synthesized at different Eu2+ doping concentrations at 1450 °C for 5 h under a reducing nitrogen atmosphere containing 5% H2 using a conventional solid reaction method. The X-ray diffraction patterns of the prepared phosphor (Sr1-xSi2O2N2: Eu2+x) were indexed to the SrSi2O2N2 phase and an unknown intermediate phase. The photoluminescence properties of these phosphors (Sr1−xSi2O2N2: Eu2+x) showed that the samples were excited from the UV to visible region due to the strong crystal field splitting of the Eu2+ ion. The emission spectra under excitation of 450 nm showed a bright color at 545-561 nm. The emission intensity increased gradually with increasing Eu2+ doping concentration ratio from 0.05 to 0.15. However, the emission intensity decreased suddenly when the Eu2+ concentration ratio was >0.2. As the doping concentration of Eu2+ was increased, there was a red shift in the continuous emission peak. These results suggest that Sr1-xSi2O2N2: Eu2+x phosphor can be used in blue-pumped white light emitting diodes.  相似文献   

6.
Transparent Li-doped Gd2O3:Eu3+ thin-film phosphors were prepared by a modified sol-gel method. The effect of the Li+ ions on luminescent properties of the thin film was investigated. The results indicated that incorporation of Li+ ions into Gd2O3 lattice could result in a remarkable increase on photoluminescence or X-ray excited luminescence, and the strongest emission was observed from Gd1.84Li0.08Eu0.08O3−δ film, in which the intensity was increased by a factor of 1.9 or 2.3 in comparison with that of Gd1.92Eu0.08O3 film. And it could be achieved the highest intensity for sintering the Gd1.84Li0.08Eu0.08O3−δ film at 700 °C. Such a temperature is much lower than the typical solid-state reaction temperature for its powder phosphors. This kind of transparent thin-film phosphors may promise for application to micro X-ray imaging system.  相似文献   

7.
The co-doping of Li+ and Al3+ ions drastically enhances the luminescence of cubic Eu2O3. The integrated emission intensity of 5D07FJ bands (J=1-4) at 580-710 nm increases by a factor of about 6.7 in the co-doped Eu2O3 compared to the un-doped Eu2O3. In order to confirm that the co-doped ions were actually incorporated into the host lattice, the structural characteristics were studied using Raman spectroscopy, XPS, XRD, photoluminescence lifetime, and an SEM. These analyses consistently indicate a certain structural evolution in their results with an increase in the co-doping concentration. Variations in the crystal structure, the crystal morphology, and the intensity variation of the Raman modes at 465 and 483 cm−1 are presented as the evidences showing the incorporation of the co-doped ions into the host. The luminescence enhancement is discussed in terms of concentration quenching, reduction of defect sites, and the modification of the local symmetry of the Eu3+ ions, especially in the inversion symmetry sites.  相似文献   

8.
Y2O3:Eu3+ phosphor is a very attractive material for use as a red phosphor in many fields. SrAl2O4:Eu2+ belongs to long lasting phosphor (LLP) and it is a useful bluish-green luminescence material, which can also be a promising candidate as a simple and easy-to-use radiation detection element for visual display of two dimensional radiation distributions. In the present study, both these two kinds of phosphors were synthesized using high temperature solid state reactions. In our work, the influence of gamma-ray irradiation on the properties of these two kinds of phosphors was studied by comparing photoluminescence, brightness and the decay curve of unirradiated and gamma-ray-irradiated samples. Conclusions from the present work can be briefly summarized as follows. In irradiated samples, the brightness is decreased without sensible change in the wavelength distribution of the luminescence spectrum and in the decay kinetic upon gamma exposure. Moreover, the emission due to Eu3+→Eu2+ conversion in Y2O3:Eu3+ phosphors was not observed in our sample after irradiation to high exposure. Also the brightness of SrAl2O4:Eu2+ phosphor turned out to decrease after the exposition to ionizing radiation while the luminescence wavelength distribution remained unchanged. The reason for the effect of gamma-ray irradiation on the properties of phosphors is also discussed in the paper.  相似文献   

9.
Nanosized barium aluminate materials was doped by divalent cations (Ca2+, Sr2+) and Eu2+ having nominal compositions Ba1−xMxAl12O19:Eu (M=Ca and Sr) (x=0.1-0.5), were synthesized by the combustion method. These phosphors were characterized by XRD, scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS) and photoluminescence measurement. The photoluminescence characterization showed the presence of Eu ion in divalent form which gave emission bands peaking at 444 nm for the 320 nm excitation (solid-state lighting excitation), while for 254 nm it gave the same emission wavelength of low intensity (1.5 times) compared to 320 nm excitation. It was also observed that alkaline earth metal (Ca2+ and Sr2+) dopants increase the intensity of Eu2+ ion in BaAl12O19 lattice, thus this phosphor may be useful for solid-state lighting.  相似文献   

10.
A series of NaY1−yEuy(WO4)2−x(MoO4)x (x=0−2 and y=0.06−0.15) phosphors have been prepared by a combustion route. X-ray powder diffraction, photoluminescence excitation and emission spectra were used to characterize the resulting samples. The excitation spectra of these phosphors show the strongest absorption at about 396 nm, which matches well with the commercially available n-UV-emitting GaN-based LED chip. Their emission spectra show an intense red emission at 616 nm due to the 5D07F2 electric dipole transition of Eu3+. As the Mo content increases, the intensity of the 5D07F2 emission of Eu3+ activated at wavelength of 396 nm increases and reaches a maximum when the relative ratio of Mo/W is 2:3. The intense red-emission of the tungstomolybdate phosphors at near-UV excitation suggests that the material is a potential candidate for white light emitting diode (WLEDs).  相似文献   

11.
A red-emitting phosphor NaSrB5O9:Eu3+ was synthesized by employing a solid-state reaction (SSR) method. The structures of the phosphors were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Raman studies. The band at ~282 nm in the excitation spectra indicated the charge transfer band (CTB) of B-O in the host, whereas the CTB of Eu-O was observed at ~275 nm for the NaSrB5O9:Eu3+ (Eu3+=1 at.%) phosphor, which was supported by diffuse reflectance spectroscopy (DRS) measurements. The photoluminescence (PL) measurements exhibited a strong red emission band centered at about 616 nm (5D07F2) under an excitation wavelength of 394 nm (7F05L6). Upon host excitation at 282 nm, the pristine NaSrB5O9 exhibited a broad UV emission centered at ~362 nm. The energy transfer from host to Eu3+ ions was confirmed from luminescence spectra, excited with a 355 nm Nd:YAG laser. In addition, the asymmetric ratios indicate a higher local symmetry around the Eu3+ ion in the host. The calculated CIE (Commission International de l′Eclairage) coordinates displayed excellent color purity efficiencies (around 99.7%) compared to other luminescent materials.  相似文献   

12.
Europium (Eu3+) doped YBa3B9O18 were synthesized by conventional solid state solidification methods. (Y1−xEux)Ba3B9O18 formed solid solutions in the range of x=0–1.0. The luminescence property measurements upon excitation in ultraviolet–visible range show well-known Eu3+ excitation and emission. The charge transfer excitation band of Eu3+ dominates the excitation spectra. The emission spectrum of Eu3+ ions consists mainly of several groups of lines in the 550–720 nm region, due to the transitions from the 5D0 level to the levels 7FJ (J=0, 1, 2, 3, 4) of Eu3+ ions. The dependence of luminescence intensity on Eu3+ concentration shows no concentration quenching for fully concentrated EuBa3B9O18. Eu3+ doped YBa3B9O18 are promising phosphors for applications in displays and optical devices.  相似文献   

13.
In this article, Sr2CeO4:x mol% Eu3+ and Sr2CeO4:5 mol%Eu3+, 3 mol% Dy3+ phosphors were synthesized from assembling hybrid precursors by wet chemical method. As-prepared samples present uniform grain-like morphology and the particle size is about 0.2 μm. The luminescence spectra of Sr2CeO4:x mol% Eu3+ have been measured to examine the influence of the intensity of red emission lines for Eu3+ on the concentration of Eu3+, showing that the intensity of the red emission increases with an increase of the concentration from 1 to 5 mol%. Additionally, from the emission spectra of Sr2CeO4:5 mol%Eu3+, 3 mol% Dy3+ phosphors, the characteristic lines of Dy3+ have also been observed. This result indicates that there also exists an energy transfer process between Sr2CeO4 and Dy3+.  相似文献   

14.
Eu3+ activated Ca1−xEuxZrO3 (x = 0.01–0.05) phosphor with perovskite structure has been synthesized by sol–gel combustion method. The structure, morphology and optical properties of materials were characterized by X-ray diffraction, scanning electron microscopy and fluorescence spectrometry. The XRD results indicate that crystals of CaZrO3:Eu3+ belongs to orthorhombic perovskite structure. The phosphors can be effectively excited by UV light and the emission spectra results indicate that red luminescence of CaZrO3:Eu3+ due to electric dipole transition 5D0 → 7F2 at 616 nm is dominant. Thus, these prepared phosphors show remarkable luminescent properties which find applications in display devices.  相似文献   

15.
A novel green phosphor, Tb3+ doped Bi2ZnB2O7 was synthesized by conventional solid state reaction method. The phase of synthesized materials was determined using the XRD, DTA/TG and FTIR. The photoluminescence characteristics were investigated using spectrofluorometer at room temperature. Bi2ZnB2O7:Tb3+ phosphors excited by 270 nm and 485 nm wavelengths. The emission spectra were composed of three bands, in which the dominated emission of green luminescence Bi2ZnB2O7:Tb3+ attributed to the transition 5D4 → 7F5 is centered at 546 nm. The dependence of the emission intensity on the Tb3+ concentration for the Bi2−xTbxZnB2O7 (0.01 ≤ x ≤ 0.15) was studied and observed that the optimum concentration of Tb3+ in phosphor was 13 mol% for the highest emission intensity at 546 nm.  相似文献   

16.
A blue emitting phosphor of the triclinic BaCa2Si3O9:Eu2+ was prepared by the combustion-assisted synthesis method and an efficient blue emission ranging from the ultraviolet to visible was observed. The luminescence and crystallinity were investigated using luminescence spectrometry and X-ray diffractometry (XRD), respectively. The emission spectrum shows a single intensive band centered at 445 nm, which corresponds to the 4f65d1→4f7 transition of Eu2+. The excitation spectrum is a broad extending from 260 to 450 nm, which matches the emission of ultraviolet light-emitting diodes (UV-LEDs). The critical quenching concentration of Eu2+ in BaCa2Si3O9:Eu2+ phosphor is about 0.05 mol. The corresponding concentration quenching mechanism is verified to be a dipole-dipole interaction. The CIE of the optimized sample Ba0.95Ca2Si3O9:Eu0.052+ was (x, y)=(0.164, 0.111). The result indicates that BaCa2Si3O9:Eu2+ can be potentially useful as a UV radiation-converting phosphor for white light-emitting diodes (LEDs).  相似文献   

17.
Intense red phosphors, AgGd1−xEux(W1−yMoy)2O8 (x=0.0-1.0, y=0.0-1.0), have been synthesized through traditional solid-state reaction and characterized by X-ray diffraction (XRD) and photoluminescence (PL). XRD results reveal that AgGd1−xEuxW2O8 synthesized at 1000 °C has a tetragonal crystal structure, which is named as high temperature phase (HTP) AgGdW2O8. All phosphors compositions with Eu3+ show red and green emission on excitation either in the charge-transfer or Eu3+ levels. Analysis of the emission spectra with different Eu3+ concentrations reveal that the optimum dopant concentration for Eu3+ is x=0.6 in the HTP AgGd1−xEuxW2O8 (x=0.0-1.0). Studies on the AgGd0.4Eu0.6(W1−yMoy)2O8 (y=0.0-1.0) and AgGd1−xEux(W0.7Mo0.3)2O8 (x=0.0-1.0) show that the emission intensity is maximum for compositions with y=0.3 and x=0.5, respectively, and a decrease in emission intensity is observed for higher y or x values. The Mo6+ and Eu3+ co-doped AgGd(WO4)2 phosphors show higher emission intensity in comparison with the singly Eu3+-doped AgGd(WO4)2 in UV region. The intense emission of the tungstate/molybdate phosphors under 394 and 465 nm excitations, respectively, suggests that these materials are promising candidates as red-emitting phosphors for near-UV/blue GaN-based white LED for white light generation.  相似文献   

18.
Zinc silicate phosphors co-doped with Eu3+ ions and also with both Eu3+ and Tb3+ ions were prepared by high temperature solid state reaction in air or reducing atmosphere. The luminescence characteristics of the prepared phosphors were investigated. While in the samples prepared in air, Eu3+ emission was found to be dominant over Tb3+ emission, in the samples prepared in reducing atmosphere, intense Eu2+ emission at 448 nm was found to be predominant over narrow Tb3+ emission. Luminescence studies showed that Eu3+ ions occupy asymmetric sites in Zn2SiO4 lattice. The intense f-f absorption peak of Eu3+ at 395 nm observed in these phosphors suggests their potential as red emitting phosphors for near ultra-violet light emitting diodes.  相似文献   

19.
The Eu2+-doped Ba3Si6O12N2 green phosphor (EuxBa3−xSi6O12N2) was synthesized by a conventional solid state reaction method. It could be efficiently excited by UV-blue light (250-470 nm) and shows a single intense broadband emission (480-580 nm). The phosphor has a concentration quenching effect at x=0.20 and a systematic red-shift in emission wavelength with increasing Eu2+ concentration. High quantum efficiency and suitable excitation range make it match well with the emission of near-UV LEDs or blue LEDs. First-principles calculations indicate that Ba3Si6O12N2:Eu2+ phosphor exhibits a direct band gap, and low band energy dispersion, leading to a high luminescence intensity. The origin of the experimental absorption peaks is clearly identified based on the analysis of the density of states (DOS) and absorption spectra. The photoluminescence properties are related to the transition between 4f levels of Eu and 5d levels of both Eu and Ba atoms. The 5d energy level of Ba plays an important role in the photoluminescence of Ba3Si6O12N2:Eu2+ phosphor. The high quantum efficiency and long-wavelength excitation are mainly attributed to the existence of Ba atoms. Our results give a new explanation of photoluminescence properties and could direct future designation of novel phosphors for white light LED.  相似文献   

20.
The excitation and emission spectra of octahedrally coordinated europium ion (Eu2+) ions in Cs2M2+P2O7 (M2+=Ca, Sr) are reported and discussed. The remarkable features of the Eu2+ luminescence in these phosphate materials include (a) very large Stokes shift of emission (∼1 eV), (b) high luminescence quenching temperature, and (c) unusually low energy of the emitted photons for Eu2+ luminescence in phosphate-based materials. The broad emission bands of Eu2+ in Cs2CaP2O7 and Cs2SrP2O7 peak at 607 and 563 nm, respectively. The Stokes shift, crystal field splitting, centroid shift and the red shift of the Eu2+ 4f65d1 electronic configuration have been estimated from the relevant optical data. The radiative lifetime of the Eu2+ emission in Cs2M2+P2O7 is ∼1.2 μs. The nature of the Eu2+ emission in Cs2M2+P2O7 is discussed and arguments are presented to associate the luminescence with an extreme case of normal 4f65d1→4f7[8S7/2] emission.  相似文献   

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