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1.
Synthesis and photoluminescence (PL) investigations of lithium metasilicate doped with Eu3+, Tb3+ and Ce3+ were carried out. PL spectra of Eu-doped sample showed peaks corresponding to the 5D07Fj (j=1, 2, 3 and 4) transitions under ultraviolet excitation. Strong red emission coming from the hypersensitive 5D07F2 transition of Eu3+ ion suggested the presence of the dopant ion in structurally disordered environment. Tb3+-doped silicate sample showed blue-green emission corresponding to the 5D47Fj (j=6, 5 and 4) transitions. Ce-doped sample under excitation from UV, showed a broad emission band in the region 350-370 nm with shoulders around 410 nm. The fluorescence lifetimes of Eu3+ and Tb3+ ions were found out to be 790 and 600 μs, respectively. For Ce3+, the lifetime was of the order of 45 ns. PL spectra of the europium- and terbium-doped samples were compared with commercial red (Y2O3:Eu3+) and green (LaPO4:Tb3+) phosphors, respectively. It was found that the emission from the doped silicate sample was 37% of the commercial phosphor in case of the Tb-doped sample and 8% of the commercial phosphor in case of the Eu-doped sample.  相似文献   

2.
Lithium titanate ceramics doped with three rare earth (RE) ions namely Eu3+, Dy3+ and Tb3+ were synthesized and their photoluminescence (PL) properties were investigated. PL spectra of Eu doped sample showed peaks corresponding to the 5D07Fj (j=0, 1, 2, 3 and 4) transitions under 230 nm excitation. Strong red emission coming from the hypersensitive 5D07F2 transition of Eu3+ ion suggested the presence of the dopant ion in a highly asymmetric environment. Dy doped samples showed the Dy3+ emission characteristic due to 4F9/26H15/2 and 4F9/26H13/2 transitions. Their relative intensity ratios also suggested the presence of asymmetric environment around the metal ion. In case of the Tb3+ doped sample blue-green emission corresponding to the 5D47Fj (j=6, 5 and 4) transitions was seen. The fluorescence lifetimes of Eu3+, Dy3+ and Tb3+ ions were found to be 645, 900 and 740 μs, respectively. PL intensity of the individual rare earth doped samples was compared with commercial red and green phosphors. It was found that the emission from Eu doped titanate sample was 46% of the commercial red phosphor and in case of the Tb samples it was 30% when excited at 230 nm. However, the synthesized Eu doped titanate sample showed better color purity as compared to the commercial phosphor. The titanate host was doped with all the three rare earths to get white light emission from the system. The individual rare earth ion content was optimized so as to get a near white light emission. The color coordinates of the triple doped systems were evaluated and plotted on the CIE xy diagram. Our results suggest that lithium titanate has enough potential to be a phosphor material.  相似文献   

3.
Phosphate (P2O5+K2O+BaO+Al2O3+Eu2O3) and fluorophosphate (P2O5+K2O+BaO+BaF2+Al2O3+Eu2O3) glasses with different Eu3+ ion concentrations have been prepared and characterized through optical absorption, photoluminescence and decay times. An intense red luminescence is observed from the 5D0 emitting level of Eu3+ ions in these glasses. The relative luminescence intensity ratio of 5D07F25D07F1 transitions has been evaluated to estimate the local site symmetry around the Eu3+ ions. The emission spectra of these glasses show a complete removal of degeneracy for the 5D07F1 and 5D07F2 transitions. Second and fourth rank crystal-field (CF) parameters have been calculated together with the CF strength parameter by assuming the C2v symmetry for the Eu3+ ions in both the phosphate and fluorophosphate glasses. Judd-Ofelt parameters have been evaluated from the luminescence intensity ratios of 5D07FJ (J=2, 4 and 6) to 5D07F1 transitions. These parameters have been used to derive radiative properties such as transition probabilities, branching ratios, radiative lifetimes and peak stimulated emission cross-sections for the 5D07FJ transitions. Decay curves of the 5D0 level of Eu3+ ions in these two Eu3+:glass systems have been measured by monitoring the 5D07F2 transition (611 nm) at room temperature. The experimental lifetime of the 5D0 level in the title glasses is found to be higher than Eu3+-doped niobium phosphate glasses. The analysis indicates that the lifetime of the 5D0 level is found to be less sensitive to the Eu3+ ion concentration and addition of BaF2 has no significant effect on the optical properties of Eu3+-doped phosphate glasses.  相似文献   

4.
The OA-modified CaF2: Eu nanocrystals that can be well dispersed in chloroform to form a clear solution were synthesized and characterized. The nanocrystals have a roughly spherical shape with particle diameter of about 10 nm. Possible mechanism was proposed to explain the growth process. Upon the excitation at 395 nm, the room-temperature emission spectrum of the nanocrystals in chloroform presents the characteristic transitions 5D07FJ of Eu3+ ions, with 5D07F2 (610 nm) transition as the most prominent group. The luminescence decay of Eu3+ ions in CaF2 nanocrystals was also investigated and two luminescence lifetimes of 737 μs (11.2%) and 2.08 ms (88.8%) were obtained.  相似文献   

5.
La2BaZnO5:Eu3+ (0.05 mol%) was prepared by a solid-state reaction at high temperature. X-ray powder diffraction analysis confirmed the formation of single phase La2BaZnO5. Luminescence properties of La2BaZnO5:Eu3+ are investigated by site-selective laser-excitation and emission spectroscopy at 18 K. Two different crystallographic sites for Eu3+ corresponding to the La3+ and Ba2+ sites are identified from the 7F05D0 excitation spectra obtained by monitoring the 5D07FJ (J=1, 2, …, 6) emissions. It is found that Eu3+ substituted for the Ba2+ ion experiences stronger crystal-field strength than Eu3+ substituted for the La3+ ion. Energy transfer between the two crystallographic Eu3+ centers is investigated by luminescence decay curves at 18 K.  相似文献   

6.
A series of phosphors Ca2BO3Cl:Eu3+ were synthesized by using a high-temperature solid-state reaction technique, and their UV–vis luminescence properties were investigated. The f–f transitions of Eu3+ in the host lattice were assigned and discussed. The excitation and emission spectra indicate that this phosphor can be effectively excited by ultraviolet (394 nm), and exhibit reddish orange emission corresponding to the 5D07FJ (J=0, 1, 2) transitions of Eu3+. The influence of the doping concentration and charge compensators on the relative emission intensity of Eu3+ was investigated, and the optimum doping concentration is 0.04. The critical distance Rc was estimated to be 17.1 Å in terms of the concentration quenching data. The present study suggests that Ca2BO3Cl:Eu3+ can be a potential candidate as an UV-convertible phosphor for white light-emitting diodes (LEDs).  相似文献   

7.
A sol-gel technique emphasizing the Pechini process has been employed for the preparation of nano-crystal Eu3+-doped YVO4 phosphor. The precursor powders were heated at 800 °C for 3 h to obtain good crystallinity with better luminescence. XRD results indicate that the second phase is not presented when the Eu3+ ion concentration is increased up to 50 mol%. The absorption and photoluminescent (PL) studies indicated that the energy is absorbed first by the host and then transferred to the emitting level of the Eu3+ ions. Excitation at 318 nm in terms of Eu3+ concentrations in YVO4 powders shows that the YVO4 phosphors display bright red luminescence at about 618 nm belonging to the 5D07F2 electric dipole transition, and a weak band in the orange region of the 5D07F1 transition at 594 nm. In addition, the time-resolved 5D07F2 transition presents a single-exponential decay behavior, revealing the decay mechanism of the 5D07F2 transition is a single decay component between Eu3+ ions only. The saturation of the emission intensity excited by the CTS when the Eu3+ concentration is 10 mol%. The concentration quenching is active when the Eu3+ concentration is larger than 10 mol%, and the critical distance is about 5.75 Å.  相似文献   

8.
The photoluminescence (PL) emission and excitation behavior of red-emitting Eu0.1GdxLa1.9−xTeO6 (0.02?x?0.1) powder phosphors is reported. Three dominant bands centered at 395, 466 and 534 nm characterized the excitation spectrum. Under the excitation of 395 nm UV light, the emission spectrum exhibits an intense peak centered at 616 nm corresponding to the 5D07F2 transition of Eu3+. Because the f→f transitions are located in the wavelength range of blue or near-UV range, optimized phosphor, Eu0.10Gd0.08La1.82TeO6, is a promising material for solid-state lighting based on GaN LEDs applications.  相似文献   

9.
In this paper, seven kinds of silane coupling reagents were employed as silicate sources to prepare CaSiO3:Eu3+ phosphors by the sol-gel method. The different silicate precursors were used to adjust the microstructure and size of the resulting phosphors. The crystallite size of phosphors is in the range of 30-35 nm and some of them show regular microstructure after high-temperature thermolysis. The photoluminescence properties show that all of them exhibit the characteristic fluorescence 5D07FJ (J=0, 1, 2, 3, 4) of the Eu3+ ion and the strongest one is the red emission at 610 nm. Furthermore, the emission quantum efficiency (η) of the 5D0 Eu3+ excited state has been calculated to be around 33% from the emission spectrum and the lifetime of the Eu3+ first excited level (τ, 5D0).  相似文献   

10.
Amorphous silica samples doped with 0.1 and 1 mol% of terbium (Tb) were synthesized by the sol–gel method. In addition to the green light associated with 5D47FJ transitions of Tb3+, the sample containing 0.1 mol% also emitted blue light as a result of 5D37FJ transitions during photoluminescence (PL) measurements. As a result of concentration quenching this blue emission was not observed for the samples doped with the higher concentration (1 mol%). However the blue 5D37FJ emission was observed in the 1 mol% doped samples during cathodoluminescence (CL) measurements. Since a rough calculation indicated that the excitation rate in the CL system where the blue emission is observed may be similar to a laser PL system under conditions where the blue emission is not observed, the difference is attributed to the nature of the excitation sources. It is suggested that during the CL excitation incident electrons can reduce non-luminescent Tb4+ ions in the silica, substituting for Si4+ ions, to the excited (Tb3+)? state and that these are responsible for the blue emission, which does not occur during PL excitation.  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.
This paper reports the emission analysis of green-emitting Tb3+-doped MgAl2O4 phosphors. Uniformity of the phase of the Tb3+-doped MgAl2O4 phosphor has been checked by X-ray diffraction (XRD) technique and show common bands existing in the results of Fourier transform infrared (FT-IR). This phosphor exhibits weak blue, orange emissions and a strong emission at λexci=350 nm. The blue and green-orange emissions are ascribed to 5D37FJ and 5D47FJ (where J=3-6) transitions of Tb3+ ions, respectively. These phosphors have shown a strong, more prominent green emission from 5D47F5 at 543 nm. The results have indicated that MgAl2O4:Tb3+ could be a potential candidate as agreen-emitting powder phosphor.  相似文献   

13.
Eu3+ ion-doped B2O3-, SiO2-, and P2O5-based glasses were prepared by the melt-quenching method, and their absorption, fluorescence, and excitation spectra were recorded and assigned. The glass composition dependence of the fluorescence was investigated to obtain the high brightness of the red fluorescence due to the 5D07F2 transition of the Eu3+ ion. The integrated intensity of the red fluorescence was the strongest at the Eu2O3 concentration of 3.5 mol% because the cross-relaxation (CR) processes, (5L65DJ)→(7FJ*7FJ#) and (5DJ5DJ)→(7FJ*7FJ#) (3≧J>J′≧0, 6≧J*>J#≧0) between the Eu3+ ions were promoted, but the CR processes, (5D07FJ)→∑m(7FJ*7FJ)m (6≧J′≧0, 6≧J*>J≧0), between the excited Eu3+ ion at the 5D0 level and m ions of Eu3+ in the 7FJ levels were depressed. The former CR processes, (5L65DJ)→(7FJ*7FJ#) and (5DJ5DJ)→(7FJ*7FJ#) were enhanced in the host glasses consisted of the cations with small ionic radius. In this study, a 70B2O3-30CaO-3.5Eu2O3 glass showed the strongest red fluorescence.  相似文献   

14.
This paper reports the photoluminescence and thermoluminescence properties of gamma ray induced rare earth doped yttrium gadolinium mixed oxide phosphor. The europium (Eu3+) was used as rare earth dopant. The phosphor was prepared by chemical co-precipitation method according to the formula (Y2−xyGdx) O3: Euy3+ (x=0.5; y=0.05). The photoluminescence emission spectrum of the prepared phosphor shows intense peaks in the red region at 615 nm for 5D07F2 transitions and the photoluminescence excitation spectra show a broad band located around 220–270 nm for the emission wavelength fixed at 615 nm. The thermoluminescence studies were carried out after irradiating the phosphor by gamma rays in the dose range from 100 Gy to 1 KGy. In the thermoluminescence glow curves, one single peak was observed at about 300 °C of which the intensity increases linearly in the studied dose range of gamma rays. The glow peak was deconvoluted by GlowFit program and the kinetic parameters associated with the deconvoluted peaks were calculated. The kinetic parameters were also calculated by various glow curve shape and heating rate methods.  相似文献   

15.
Xi Chen 《Journal of luminescence》2011,131(12):2697-2702
In this work, we report preparation, characterization and luminescent mechanism of a phosphor Sr1.5Ca0.5SiO4:Eu3+,Tb3+,Eu2+ (SCS:ETE) for white-light emitting diode (W-LED)-based near-UV chip. Co-doped rare earth cations Eu3+, Tb3+ and Eu2+ as aggregated luminescent centers within the orthosilicate host in a controlled manner resulted in the white-light phosphors with tunable emission properties. Under the excitation of near-UV light (394 nm), the emission spectra of these phosphors exhibited three emission bands: one broad band in the blue area, a second band with sharp lines peaked in green (about 548 nm) and the third band in the orange-red region (588-720 nm). These bands originated from Eu2+ 5d→4f, Tb3+5D47FJ and Eu3+5D07FJ transitions, respectively, with comparable intensities, which in return resulted in white light emission. With anincrease of Tb3+ content, both broad Eu2+ emission and sharp Eu3+ emission increase. The former may be understood by the reduction mechanism due to the charge transfer process from Eu3+ to Tb3+, whereas the latter is attributed to the energy transfer process from Eu2+ to Tb3+. Tunable white-light emission resulted from the system of SCS:ETE as a result of the competition between these two processes when the Tb3+ concentration varies. It was found that the nominal composition Sr1.5Ca0.5SiO4:1.0%Eu3+, 0.07%Tb3+ is the optimal composition for single-phased white-light phosphor. The CIE chromaticity calculation demonstrated its potential as white LED-based near-UV chip.  相似文献   

16.
In this work, Eu3+-doped lead borosilicate glasses (SiO2-B2O3-PbO2) synthesized by fusion method had their optical properties investigated as a function of temperature. Atomic Force Microscopy images obtained for a glass matrix annealed at 350 and 500 °C show a precipitated crystalline phase with sizes 11 and 21 nm, respectively. Besides, as the temperature increases from 350 to 300 K a strong Eu3+ photoluminescence (PL) enhancement takes place. This anomalous feature is attributed to the thermally activated carrier transfer process from nanocrystals and charged intrinsic defects states to Eu3+ energy levels. In addition, the PL peaks in this temperature range were assigned to the Eu3+ transitions 5D07F2, at 612 nm, 5D07F1, at 595 nm, and 5D07F0, at 585 nm. It was also observed that the 5D07F3 and 5D07F4 PL bands at 655 and 700 nm, respectively, show a continuous decrease in intensity as the temperature increases.  相似文献   

17.
Eu3+-doped La2O3 nanocrystalline powder was prepared by polymer complex solution method and further used for preparation of Eu3+-doped La(OH)3. Structural and optical characterization was carried out by powder X-ray diffraction and photoluminescent spectroscopy. XRD measurements confirmed the formation of hexagonal La2O3 and its recrystallization into La(OH)3 in a humid atmosphere. Excitation spectra show redshift of host lattice and charge transfer emission bands in La(OH)3 while bands that correspond to Eu3+f–f transitions are placed at same wavelengths in both samples. Photoluminescence spectra recorded over the temperature range from 10 K to 300 K show that intensities of emission lines in Eu3+-doped La2O3 do not depend on temperature as much as in La(OH)3 sample. Observed dominant 5D07F2 and markedly visible 5D07F0 emissions in doped La2O3 indicate that Eu3+ ion is located in a structural site without an inversion center. On the other hand, in Eu3+-doped La(OH)35D07F0 transition is barely visible while 5D07F2 is not prominent, and with temperature drop three 5D07FJ (J=1, 2, 4) transitions become almost of the same intensity. In both La2O3 and La(OH)3 structures Eu3+ ion replaces La3+ in non-centrosymmetric C3v and C3h crystallographic sites, respectively, and difference in symmetry of the crystal field around europium ion is explained by comparing shape and volume of these sites. Decay times of the 5D0- level recorded over the temperature range 10−300 K revealed that emission lifetime values in La2O3 (~0.7 ms) are almost two times higher than in La(OH)3 (~0.4 ms), and unlike in La2O3, lifetime in La(OH)3 is temperature dependent.  相似文献   

18.
The photoluminescent (PL) emission and excitation behaviour of green-emitting CaAl2S4:Eu2+ powder phosphor is reported in detail. CaAl2S4:Eu2+ emission provides good CIE colour coordinates (x=0.141; y=0.721) for the green component in display applications. Powder with a dopant concentration of 8.5 mol% shows the highest luminescence efficiency. Temperature dependence of the radiative properties, such as luminescence intensity and decay time, was investigated. In particular, the Stokes shift, the mean phonon energy, the redshift, the energy of the f→d and d→f transition and the crystal field splitting of the CaAl2S4:Eu2+ emission were determined. The thermal quenching of the emission was examined.  相似文献   

19.
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   

20.
Photoluminescence and lifetime decay properties of varied valence Eu were employed to investigate the luminescence mechanism of green-light emission positioned at ∼515 nm for full color emission LaAlO3 phosphor co-doped with Eu2+ and Eu3+. The enhanced 5D27F3 transition emission of Eu3+ was assigned for this green emission. Energy transfer between Eu2+ and 5D2 level of Eu3+ was proposed, which results in the enhancement of 5D27F3 transition emission. In addition, energy transfer relations between host-Eu and charge transfer state (CTS)-Eu were also discussed associated with the PLE spectra and band schemes.  相似文献   

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