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1.
The photoluminescent properties of a series of Tb3+-doped Na3GdP2O8 phosphors excitable by vacuum ultraviolet and ultraviolet light are reported. The host related absorption, f-f and f-d transitions of Gd3+ and Tb3+, and charge transfer of O2− → Gd3+ and O2− → Tb3+ are assigned. Under 147 nm light excitation, Na3GdP2O8:Tb3+ phosphors show efficient green emissions with a dominant peak at 545 nm. The optimal sample Na3Gd0.4Tb0.6P2O8 shows a shorter decay time and a comparable brightness when compared with the commercial Zn2SiO4:Mn2+ green phosphor. These results demonstrate that it is a potential candidate for plasma display panels application. 相似文献
2.
Taehyung Kim 《Materials Research Bulletin》2005,40(11):1945-1954
Nano-crystalline GdBO3:Eu3+ was prepared by a hydrothermal method and the effects of some processing variables such as pH, temperature were investigated. The as-synthesized powders were spherical shaped agglomerates of nanoparticles. The luminescent properties were compared with samples synthesized by conventional solid-state reaction method. Both the photoluminescence intensity and chromaticity were improved and a red-shift in the CT band was observed for the hydrothermally synthesized samples. Possible mechanisms of phase formation were investigated and explanations for the changes in optical properties are proposed. 相似文献
3.
A borate compound was adopted as a new host material of Eu3+ and Tb3+ activators to fabricate efficient luminescence materials. The phosphor compositions, Gd1−xEuxCa3(GaO)3(BO3)4 and Gd1−xTbxCa3(GaO)3(BO3)4, were synthesized by conventional solid-state reactions. The crystalline phases of the resulting powders were identified using an X-ray diffraction system. Their photoluminescence properties were investigated under long-wavelength UV excitation. The Eu3+-doped and Tb3+-doped GdCa3(GaO)3(BO3)4 phosphors efficiently emitted red and green light, respectively. The temperature dependency of emission intensity was measured in a range from room temperature to 150 °C. The emission intensities of the red and green phosphors at 150 °C are 87% and 91% of those at room temperature, respectively. In addition, the decay times of both the red and green phosphors are shorter than 3 ms. 相似文献
4.
Jing Li Jiyang Wang Huaijin Zhang Shouren Zhao Xiaoxia Wang 《Materials Research Bulletin》2004,39(9):1329-1334
Single crystal of erbium, ytterbium-codoped yttrium aluminum tetraborate Er,Yb:YAl3(BO3)4(Er,Yb:YAB) has been grown by the flux method. The absorption spectrum in the visible and NIR regions of Er,Yb:YAl3(BO3)4 crystal are measured at room temperature and fluorescence spectrum of Er,Yb:YAl3(BO3)4 crystal are also measured at room temperature, excited by 976 nm laser. Not only the strong NIR emission peaks located at 1548 nm was observed, but also the visible up-conversion luminescence has been found. The specific heat of the Er/Yb:YAB crystal at room temperature is 0.81 J/g °C. 相似文献
5.
Y2O3:Eu3+ red phosphors were prepared by surfactant assisted co-precipitation-molten salt synthesis method. The effects of surfactant content and annealing temperature on the structure and luminescence were investigated by X-ray diffraction and fluorescence spectrophotometer. The use of surfactant reduces the impurities on the surface of particles and promotes the reaction. The color purity of as-prepared Y2O3:Eu3+ red phosphors is improved with the presence of surfactant. In the excitation spectra, two strong bands at 394 and 466 nm are attributed to 7F0,1-5L6, 7F0,1-5D2 transitions of Eu3+ ions respectively. With the excitation of 394 or 466 nm, the as-fabricated samples reveal excellent red emission as high as that of samples monitored by 254 nm. Thus, the Y2O3:Eu3+ is a promising red phosphor for ultraviolet-visible light-emitting diodes. 相似文献
6.
Y2O2S co-doped with Bi3+,Eu3+ phosphors were prepared and their luminescence properties under vacuum ultraviolet (VUV) excitation were investigated. Much stronger red emission for Y2O2S:Eu3+,Bi3+ were observed under 147 nm excitation than that for Y2O2S:Eu3+. Investigation on photoluminescence and calculation of electronic structure of Y2O2S:Eu3+,Bi3+ revealed that the Bi3+ acts as a medium in energy transfer process and the great VUV luminescence enhancement of Y2O2S:Eu3+ by doping Bi3+ is due to effective energy transfer process: charge transfer (CT) transition of Y3+-O2− → Bi3+ → Eu3+. The Y2O2S:Eu3+,Bi3+ showed excellent optical properties when compared with the commercial (Y,Gd)BO3:Eu3+. Thus, the Y2O2S:Eu3+,Bi3+ would be a promising VUV-excited red phosphor. 相似文献
7.
The luminescent properties of Na3Y1−xSi3O9:xEu3+ (0.05 ≦ x ≦ 0.80) powder crystals were investigated in UV-VUV region. The Eu3+-O2− charge transfer band (CTB) was observed to be located at around 233 nm and the environmental parameter (he) was estimated to be about 0.730. The excitation spectrum monitoring the 613 nm red emission from Eu3+ ions reveals the host absorption band (HAB) to be around 145 nm. The calculated Commission Internationale de l’Eclairage (CIE) chromaticity coordinates indicate the emission by 233 nm rather than by 147 nm excitation has the better color purity and the possible mechanisms have been proposed. The Eu3+-emission showed high quenching concentration due to the isolated YO6 octahedra in the host and the small he for the Eu3+ ions and the optimum concentration was determined to be as high as x = 0.65 and 0.30 with 233 and 147 nm excitation, respectively. 相似文献
8.
Chuan HeYongfeng Guan Lianzeng YaoWeili Cai Xiaoguang LiZhen Yao 《Materials Research Bulletin》2003,38(6):973-979
We report nano-Y2O3:Eu3+ phosphors with particle size of about 50 nm and relatively high photoluminescence (PL) intensity which is close to the standard for application. The influences of the dope amount, the surfactant and the precipitation pH on the PL intensity, the particle size and the dispersion have been studied. It has been found that 4% is the best Eu3+ molar concentration to get the highest PL intensity for both nano- and micro-Y2O3:Eu3+. The addition of butanol as a surfactant inhibits the grain growth and the agglomeration of particles efficiently by reducing the oxygen bridge bonds. As the pH rises, the PL intensity and the particle size increase due to the formation of oxygen bridge bonds. 相似文献
9.
Shengliang Zhong Shijin Wang Qingyan Liu Yuling Wang Shangping Wang Jianjun Chen Rong Xu Longfei Luo 《Materials Research Bulletin》2009,44(12):2201-2205
Hexagonal microprisms of yttrium hydroxide (Y(OH)3) with tuned diameter and height have been successfully prepared for the first time via a facile hydrothermal process using sodium citrate as the shape modifying agent. Y(OH)3 microspheres with diameter of ca. 2.5 μm and microtubes with an average length about 13 μm, outer diameter about 3 μm and tube thickness about 800 nm were also obtained in current reaction systems. The possible formation mechanism for the Y(OH)3 microstructures was briefly proposed. Y2O3:Eu3+ (5%) microstructures with similar morphologies was obtained after thermal treatment of the as-prepared Y(OH)3:Eu3+ microstructures at 700 °C for 4 h. Results show that the relative emission intensity of the Y2O3:Eu3+ microprisms is about 8 times as those of the Y2O3:Eu3+ microtubes and microspheres under excitation of 259 nm ultraviolet light. The products were characterized by XRD, SEM, and EDS. 相似文献
10.
Yurong Shi 《Materials Research Bulletin》2011,46(7):1148-1150
Novel red phosphors Na2CaSiO4:xEu3+ were synthesized using high temperature solid-state reaction and their luminescence characteristics were investigated for the first time. The excitation spectra indicate that the Na2CaSiO4:xEu3+ phosphors can be effectively excited by ultraviolet (393 nm) light. The emission spectra of Na2CaSiO4:xEu3+ phosphors invariably exhibit four peaks assigned to the 5D0-7FJ (J = 1, 2, 3 and 4) transitions of Eu3+ under 393 nm excitation. The Commission Internationale de l’Eclairage (CIE) chromaticity coordinates and quantum efficiency (QE) are (0.66, 0.34) and 58.9%, respectively. The good color saturation and high quantum efficiency indicate that Na2CaSiO4:Eu3+ phosphors are potential candidate for light-emitting diodes. 相似文献
11.
The luminescent properties of Ca2Gd8(1−x)(SiO4)6O2:xDy3+ (1% ≤ x ≤ 5%) powder crystals with oxyapatite structure were investigated under vacuum ultraviolet excitation. In the excitation spectrum, the peaks at 166 nm and 191 nm of the vacuum ultraviolet region can be assigned to the O2− → Gd3+, and O2− → Dy3+ charge transfer band respectively, which is consistent with the theoretical calculated value using Jφrgensen's empirical formula. While the peaks at 183 nm and 289 nm are attributed to the f-d spin-allowed transitions and the f-d spin-forbidden transitions of Dy3+ in the host lattice with Dorenbos's expression. According to the emission spectra, all the samples exhibited excellent white emission under 172 nm excitation and the best calculated chromaticity coordinate was 0.335, 0.338, which indicates that the Ca2Gd8(SiO4)6O2:Dy3+ phosphor could be considered as a potential candidate for Hg-free lamps application. 相似文献
12.
Long afterglow phosphors (Ca1−xEux)2MgSi2O7 (0.002 ≤ x ≤ 0.02) were prepared by solid-state reactions under a weak reductive atmosphere. X-ray diffraction pattern, photoluminescence spectra, decay curve, afterglow spectra and thermoluminescence curves were investigated. The phosphors showed two emission peaks when they were excited by 343 nm, due to two types of Eu2+ centers existing in the Ca2MgSi2O7 lattice. However, only one emission peak can be found in their afterglow spectra. Energy transfer between Eu2+ ions in inequivalent sites was found. A possible mechanism was presented and discussed. The afterglow decay time of Ca1.998MgSi2O7:Eu0.002 was nearly 12.5 h which means it was a good long lasting phosphor. 相似文献
13.
New red Ca10K(PO4)7:Eu3+, K+ phosphors were synthesized by solid state reaction and their photoluminescence properties as well as those by co-doping Mo6+ under near ultraviolet excitation were investigated. From the excitation spectra monitored at 611 nm, it can be seen that the strongest excitation peak is situated at 393 nm, well matching with the emission wavelength of near-ultraviolet chips for white LEDs. Upon 393 nm excitation, the brightness of Ca9K(PO4)7:0.5Eu3+, 0.5 K+ with the optimal Eu3+-doping concentration is about 2.3 times stronger than that of the commercial red Y2O3:Eu3+ phosphor. The introducing of Mo6+, which results in a possible variety for the excited energy level of the host, can enhance the brightness of Eu3+ to be maximized by about 15%. The CIE chromaticity coordinates of Ca9K(PO4)7:0.5Eu3+, 0.5 K+ are calculated to (0.654, 0.345), which are close to the (0.67, 0.33) standard of the National Television System Committee. All the above results indicate Eu3+-activated Ca10K(PO4)7 is a potential candidate for white LEDs. 相似文献
14.
The phosphors in the system Sr2−x−yP2O7:xEu2+,yMn2+ were synthesized by solid-state reactions and their photoluminescence properties were investigated. These phosphors have strong absorption in the near UV region, which is suitable for excitation of ultraviolet light emitting diodes (UVLEDs). The orange-reddish emission of Mn2+ in these phosphors can be used as a red component in the tri-color system and may be enhanced by adjusting the Mn2+/Eu2+ ratio. The energy transfer from Eu2+ to Mn2+ is observed with a transfer efficiency of ∼0.45 and a critical distance of ∼10 Å. The results reveal that Sr2−x−yP2O7:xEu2+,yMn2+ phosphors could be used in white light UVLEDs. 相似文献
15.
M2Y8(SiO4)6O2: Tb3+ (M = Ca, Sr) phosphors have been synthesized with a new silicon source silane crosslinking reagent (N-2-aminoethylic-3-aminopropyldiethoxysilane [NH2(CH2)2NH(CH2)3SiCH3(OCH3)2], abbreviated as AEAPMMS) through the sol-gel process, both of which present the characteristic emission 5D4 → 7FJ (J = 6, 5, 4, 3) of Tb3+ ions. It is interesting to be found that the high energy level blue emission (5D3 → 7FJ (J = 6, 5, 4, 3) transition) still can be found in the emission spectrum of Ca2Y8(SiO4)6O2: Tb3+ while it disappears in the emission spectrum of Sr2Y8(SiO4)6O2: Tb3+ for the cross-relaxation-induced quenching. 相似文献
16.
Novel LiSrPO4:Dy3+ phosphors for white light-emitting diodes (w-LEDs) were synthesized by the conventional solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the phase formation of LiSrPO4:Dy3+ materials. Luminescence properties results showed that the phosphor could be efficiently excited by the UV–vis light region from 250 to 460 nm, and it exhibited blue (483 nm) and yellow (574 nm) emission corresponding to 4F9/2 → 6H15/2 transitions and 4F9/2 → 6H13/2 transitions, respectively. The luminescence intensity of LiSrPO4:xDy3+ phosphor firstly increased and then decreased with increasing Dy3+ concentration, and reached the maximum at x = 0.03. It was found that concentration quenching occurred as a result of dipole-dipole interaction according to the Dexter's theory. The decay time was also determined for various concentrations of Dy3+ in LiSrPO4. 相似文献
17.
The present investigation aims to demonstrate the potentiality of Tb3+ and Ce3+ co-doped Ca4Y6(SiO4)6O phosphors. By incorporation of Ce3+ into Ca4Y6(SiO4)6O: Tb3+, the excitation band was extended from short-ultraviolet to near-ultraviolet region. The energy transfer from Ce3+ to Tb3+ in Ca4Y6(SiO4)6O host was investigated and demonstrated to be a resonant type via a dipole–dipole mechanism with the critical distance of 10.2 Å. When excited by 352 nm, Ca4Y6(SiO4)6O: Ce3+, Tb3+ exhibited a brighter and broader violet-blue emission (421 nm) from the Ce3+ and an intense green emission (542 nm) from the Tb3+. Combining the two emissions whose intensities were adjusted by changing the doping levels of the co-activator, an optimized white light with chromaticity coordinates of (0.278, 0.353) is generated in Ca4Y6(SiO4)6O: 2% Ce3+, 8% Tb3+, and this phosphor could be potentially used in near-ultraviolet light-emitting diodes. 相似文献
18.
Xinghong Gong 《Materials Research Bulletin》2007,42(3):413-419
Pr3+-doped La2(WO4)3 single crystal with dimensions up to Ø 20 mm × 35 mm has been grown by the Czochralski method. The structure of the Pr3+:La2(WO4)3 crystal was determined by the X-ray powder diffraction and the Pr3+ concentration in this crystal was determined. The absorption and fluorescence spectra of Pr3+:La2(WO4)3 crystal were measured at room temperature, and the fluorescence lifetime of main emission multiplets were estimated from the recorded decay curves. The spectral properties related to laser performance of the crystal were evaluated. 相似文献
19.
(Gd1−x,Eux)2O2SO4 nano-phosphors were synthesized by a novel co-precipitation method from commercially available Gd2O3, Eu2O3, H2SO4 and NaOH starting materials. Composition of the precursor is greatly influenced by the molar ratio of NaOH to (Gd1−x,Eux)2(SO4)3 (the m value), and the optimal m value was found to be 4. Fourier transform infrared spectrum (FT-IR) and thermal analysis show that the precursor (m = 4) can be transformed into pure (Gd1−x,Eux)2O2SO4 nano-phosphor by calcining at 900 °C for 2 h in air. Transmission electron microscope (TEM) observation shows that the Gd2O2SO4 phosphor particles (m = 4) are quasi-spherical in shape and well dispersed, with a mean particle size of about 30-50 nm. Photoluminescence (PL) spectroscopy reveals that the strongest emission peak is located at 617 nm under 271 nm light excitation, which corresponds to the 5D0 → 7F2 transition of Eu3+ ions. The quenching concentration of Eu3+ ions is 10 mol% and the concentration quenching mechanism is exchange interaction among the Eu3+ ions. Decay study reveals that the 5D0 → 7F2 transition of Eu3+ ions has a single exponential decay behavior. 相似文献
20.
Xueyan WuHongpeng You Hongtao CuiXiaoqing Zeng Guangyan Hong Chang-Hong KimChong-Hong Pyun Byung-Yong YuCheol-Hee Park 《Materials Research Bulletin》2002,37(9):1531-1538
Vacuum ultraviolet excitation spectra of phosphors (La,Gd)PO4:RE3+ (RE=Eu or Tb) and X-ray photoelectron spectra of LaPO4 and GdPO4 are investigated. The vacuum ultraviolet excitation intensity of (La,Gd)PO4:RE3+ is enhanced with the increasing of Gd3+ content, which implies that Gd3+ plays an intermediate role in energy transfer from host absorption band to RE3+. When Gd3+ is doped into LaPO4:Eu3+, charge transfer band (CT band) begins to shift to higher energy region and the overlap degree of CT band and the host absorption band gets greater with more Gd3+ doped into LaPO4. These results suggest that the dopant (Gd3+) gives an important influence on energy transfer efficiency. The top of LaPO4 valance band is formed by the 2p level of O2−, whereas that of GdPO4 valance band is formed by the 2p level of O2− and the 4f level of Gd3+, showing the differences in band structures between LaPO4 and GdPO4. 相似文献