共查询到20条相似文献,搜索用时 15 毫秒
1.
Li4(Sr0.96Eu0.04)(Ca1 − xMnx)(SiO4)2 phosphors were synthesized by solid-state reactions and photoluminescence (PL) properties were investigated. These phosphors have intense absorption in n-UV region, which is suitable for excitation of UV LEDs. The orange-reddish emission of Mn2+ can be adjusted by changing the Mn2+/Eu2+ ratio. Energy transfer from Eu2+ to Mn2+ is observed. Li4(Sr0.96Eu0.04)(Ca1 − xMnx)(SiO4)2 phosphors could be used in white LEDs. 相似文献
2.
V.P. Dotsenko S.M. Levshov G.B. Stryganyuk A.S. Voloshinovskii 《Journal of luminescence》2011,131(2):310-315
The luminescent properties of Eu2+ and Ce3+ ions in Li2SrSiO4 have been studied upon excitation in the 2-20 eV region. Based on the results of luminescent measurements, values of the crystal field splitting and the centroid shift of the Ce3+5d configuration in Li2SrSiO4 were found and compared with those of Ce3+ ions in some other inorganic compounds. The Eu2+ ions in Li2SrSiO4 exhibit a broad band emission with a maximum at 576 nm, which is due to the 4f65d→4f7 transition. It was shown that the long-wavelength position of the Eu2+ emission in Li2SrSiO4 is caused by the large crystal-field splitting of the Eu2+ 4f65d configuration and relatively high degree of covalency of the Eu-O bond. The stabilization of Eu2+ ions in Li2SrSiO4 during the synthesis process requires a strong reducing agent. Two phenomenological approaches to explain the low stability of Eu2+ in Li2SrSiO4 are also discussed. 相似文献
3.
Renguang Ye Shiqing Xu Degang Deng Youjie Hua Huanping Wang Chenxia Li Shilong Zhao Lihui Huang 《Journal of luminescence》2010,130(12):2385-2389
Transparent Eu2+/Mn2+ co-doped new glass ceramics (GC) containing β-Zn2SiO4 nanocrystals were prepared under a reduced atmosphere. The optical properties of these samples have been investigated. The emission spectra of Eu2+/Mn2+ co-doped glass ceramics show two broadband peakings at 458 and 560 nm under ultraviolet radiation, which can be attributed to 4f65d1→4f7 transition of Eu2+ and 4T1(4G)→6A1(6S) transition of Mn2+, respectively. Energy transfer (ET) from Eu2+ to Mn2+ is discovered by directly observing significant overlap of the excitation spectrum of Mn2+ and the emission spectrum of Eu2+. ET from Eu2+ to Mn2+ in glass ceramics is further confirmed by fluorescence studies performed on the samples with various activator (Mn2+) concentrations. The optimal composition generates white light with chromaticity coordinates (0.291, 0.344). The results indicate that Eu2+/Mn2+ co-doped glass ceramics is potential material for white light-emitting diodes (LEDs). 相似文献
4.
Eu2+ and Mn2+ co-doped Ca8Zn(SiO4)4Cl2 phosphors have been synthesized by a high temperature solid state reaction. Energy transfer from Eu2+ to Mn2+ is observed. The emission spectra of the phosphors show a green band at 505 nm of Eu2+ and a yellow band at 550 nm of Mn2+. The excitation spectra corresponding to 4f7-4f65d transition of Eu2+ cover the spectral range of 370-470 nm, well matching UV and/or blue LEDs. The shortening of fluorescent lifetimes of Eu2+ followed by simultaneous increase of fluorescent intensity of Mn2+ with increasing Mn2+ concentrations is studied based on energy transfer. Upon blue light excitation the present phosphor can emit intense green/yellow in comparison with other chlorosilicate phosphors such as Eu2+ and Mn2+ co-doped Ca8Mg(SiO4)4Cl2 and Ca3SiO4Cl2, demonstrating a potential application in phosphor converted white LEDs. 相似文献
5.
Eu2+ activated Ca5(PO4)3Cl blue-emitting phosphors were prepared by the conventional solid state method using CaCl2 as the chlorine source and H3BO3 as flux. The structure and luminescent properties of phosphors depend on the concentrations of Eu2+, the amount of CaCl2 and the usage of the H3BO3 flux were investigated systematically. Eu2+ and Mn2+ Co-doped Ca5(PO4)3Cl with blue and orange double-band emissions were also researched based on the optimal composition and synthesis conditions. The energy transfer between Eu2+ and Mn2+ was found in the phosphor Ca5(PO4)3Cl:Eu2+, Mn2+, and the Co-doped phosphor can be efficiently excited by near-UV light, indicating that the phoshor is a potentional candidate for n-UV LED used phosphor. 相似文献
6.
Enhai Song Weiren Zhao Wei Zhang Huachu Ming Yuchun Yi Mingkang Zhou 《Journal of luminescence》2010,130(12):2495-2499
Eu2+ and Mn2+ co-doped Ba2Ca(BO3)2 phosphors yield two emission bands consisting of green and red components under the excitation of 360 nm, which shows a great potential for white LEDs. Effective energy transfer occurs in Eu2+/Mn2+ co-doped Ba2Ca(BO3)2 host due to the large spectral overlap between the emission of Eu2+ and the excitation of Mn2+. The energy transfer from Eu2+ to Mn2+ is thoroughly investigated by their excitation, emission and photoluminescence decay behaviors, and is demonstrated to be via the dipole–quadrupole interaction. 相似文献
7.
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
8.
Electronic energy relaxation and decay dynamics of Eu3+ in Zn2SiO4:Eu3+ phosphors display evidence of intra-ion energy transfer from the 5D1 to the 5D0 manifold. The energy transfer timescale does not depend on Eu3+ concentration, or the addition of Mn2+ as a co-dopant and is estimated to be about 11 μs in Zn2SiO4. Evidence for intra-ion Eu3+ electronic energy transfer has also been observed in Eu-doped MgS as well as Eu3+ encapsulated in zeolite-Y. The energy transfer timescale in these other materials is shorter than in Zn2SiO4, most likely due to differences in Eu3+ surroundings or site symmetry. 相似文献
9.
Qilin Dai Hongwei Song Guohui Pan Xue Bai Hui Zhang Ruifei Qin Lanying Hu Haifeng Zhao Shaozhe Lu Xinguang Ren 《Journal of luminescence》2008,128(7):1205-1210
The ZnO@ZnWO4:Eu3+ core–shell composites were prepared by a two-step hydrothermal method and the photoluminescence properties of the composites were studied in contrast to the corresponding hexagonal ZnO and monoclinic ZnWO4: Eu3+ nanocrystals prepared by the one-step hydrothermal method. The results demonstrate that in the nanocomposites the Eu3+ ions in the ZnWO4 phase occupy two symmetry sites, one a well-crystalline inner site and one a disordered surface site; while in the ZnWO4: Eu3+ nanocrystals, the local environments surrounding Eu3+ ions are relatively disordered for both the inner and the surface sites. This indicates that in the composites, the crystallinity of the ZnWO4 becomes better, which have positive influence on the improvement of photoluminescence. The temperature stabilities for both the emissions of ZnO and Eu3+ ions are improved in contrast to the pure ZnO or ZnWO4:Eu3+ nanocrystals. 相似文献
10.
Chaofeng Zhu Guorong Chen S. Baccaro M. Falconieri 《Journal of Physics and Chemistry of Solids》2007,68(9):1721-1724
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
11.
Ce3+ and Dy3+ activated Li2CaGeO4 phosphors were prepared by a solid-state reaction method, and characterized by XRD (X-ray diffraction) and photoluminescence techniques. The characteristic emission bands of Dy3+ due to 4F9/2→6H15/2 (blue) and 4F9/2→6H13/2 (yellow) transitions were detected in the emission spectra of Li2CaGeO4:Dy3+. Ce3+ broad band emission was observed in Li2CaGeO4:Ce3+ phosphors at 372 and 400 nm due to 5d→4f transition when excited at 353 nm. Co-doping of Ce3+ enhanced the luminescence of Dy3+ significantly and concentration quenching occurs when Dy3+ is beyond 0.04 mol%. White-light with different hues can be realized by tuning Dy3+ concentration in the phosphors. 相似文献
12.
Lanying Hu Guohui Pan Bin Yan Ruifei Qin Qilin Dai Libo Fan Suwen Li Xue Bai 《Journal of luminescence》2007,127(2):371-376
In this work, the luminescence properties of samarium ions-doped titanium dioxide prepared by the sol-gel process were studied. A strong orange red emission (4G5/2−6H7/2 (orange) and 4G5/2-6H9/2 (red)) ascribed to the electron transitions in 4f5 configuration of Sm3+ ions was observed upon excitation into TiO2 host. The energy transfer from TiO2 to Sm3+ was verified and the relevant mechanism was discussed. In addition, the impacts of metal ion codopants upon the TiO2:Sm3+ luminescence properties were studied. The results indicated that the central excitation band shifted to blue in the bismuth-codoped materials (0.5-4% in molar ratio), while it shifted to red in the zirconium-codoped materials. Such materials may find applications in white light-emission diode (LED) and tunable solid lasers. 相似文献
13.
The spectral and kinetic parameters of LiCaAlF6:Pr and LiSrAlF6:Pr single crystals are studied at LHeT and room temperature (RT). Photon cascade emission (PCE), i.e., 1S0→1I6 and 3P0→3Hj, 3Fj transitions after Pr3+ excitation via 4f2→4f 5d absorption results in the conversion of the vacuum ultraviolet photon to two visible photons. The excitation and photoemission spectra as well as decay times have been measured and compared with those for CaF2:Pr and SrF2:Pr crystals. X-ray luminescence was measured to study the emission origin from both 1S0 and 3P0 states of Pr3+. An intense phosphorescence of LiSrAlF6:Pr was observed in the visible range after X-irradiation at RT, contrary to LiCaAlF6:Pr. 相似文献
14.
A photoluminescence (PL) study of the green-emitting SrGa2S4:Eu2+ phosphor is reported. Diffuse reflectance, excitation, and emission spectra were examined with the aim to enlarge the fundamental knowledge about the emission of the Eu2+ ion in this lattice. The thermal dependence of the radiative properties was investigated. In particular, the Stokes shift, the crystal field splitting and the activation energy of the thermal quenching were determined. By combining these results with the information presented in literature, we discussed the location of the Eu2+ levels relative to the valence and conduction bands of SrGa2S4. 相似文献
15.
Yanming Xue 《Journal of luminescence》2011,131(9):2016-2020
A series of yellow-green (Sr, Ca)3B2O6:Eu phosphors have been synthesized using precursors prepared via a facile sol-gel route. The solid-solution phases crystallized to materials with the formula of Sr3−x−yCaxEuyB2O6 with varied Ca2+ and Eu2+ contents. The emission peak centered at 540 nm under near-UV excitation exhibited a broad-band distribution in the range of 450-650 nm. The dependences of the luminescence intensity on the contents of Ca2+ substitution and Eu2+ dopant were also investigated. The composition in the host lattice sensitively affected the chromaticity index. Sr1.21Ca1.7Eu0.09B2O6 (SCB:0.09Eu) was shown to possess the highest intensity and broadest emission band. Calcining temperature was shown to greatly influence the luminescent properties of SCB:0.09Eu. It is concluded that SCB:0.09Eu can be used as an efficient yellow-green phosphor for white light-emitting diodes (white LEDs) applications. 相似文献
16.
N. Suriyamurthy 《Journal of luminescence》2008,128(11):1809-1814
The effects of nonstoichiometry and cationic substitution on photoluminescence and afterglow characteristics of strontium aluminate phosphor (Sr4Al14O25:Eu2+, Dy3+) were investigated. Photoluminescence intensity of both the strontium-deficit and -rich phosphors was enhanced, but no definite correlation was observed between the afterglow intensity and non-stoichiometry. The photoluminescence emission maxima were either blue or green shifted in case of non-stoichiometric phosphors, whereas the afterglow emission maxima were not affected by the non-stoichiometry. Substitution of strontium by calcium resulted in white afterglow emission at higher calcium concentration. The emission centers in case of photoluminescence and afterglow emission appear to be different. Addition of silver significantly enhanced the afterglow intensity due to increased trap density. 相似文献
17.
R.B. Jabbarov B.G. Tagiev N.N. Musayeva P. Benalloul 《Journal of Physics and Chemistry of Solids》2005,66(6):1049-1056
A photoluminescence study of the blue-green emitting BaGa2S4:Eu2+ phosphor is reported. Diffuse reflectance, excitation and emission spectra were examined with the aim to enlarge the fundamental knowledge about the emission of the Eu2+ rare earth ion in this lattice. The thermal dependence of the radiative properties and the influence of the Eu2+ concentration were investigated. The Stokes shift, the crystal field splitting and the activation energy of the thermal quenching were determined. By combining these results with data available in literature, we discussed the radiative properties of the BaAl2S4:Eu2+ blue phosphor in relation with those determined in this study for the isostructural BaGa2S4:Eu2+ phosphor. 相似文献
18.
Room temperature steady and time resolved emission spectra of LiIn1−xTmx(WO4)2 (where thulium concentration is 0, 0.5, 1, 5 and 10 at%) blue phosphors, under UV excitation energy have been investigated. The concentration quenching effect on the blue emission, due to the (WO4)−2 groups and 1G4→3H6 emission transition of Tm3+ were studied. Two energy transfer mechanisms are shown. The first takes place between excited (WO4)−2 groups and the 1G4 energy level of Tm3+, and is mainly analyzed by phonon-assisted energy transfer. The second mechanism is due to an energy transfer from the excited Tm3+ ions to the surrounding ground state Tm3+ ions. The non-exponential decay curves of the 1G4 level observed for higher concentrations are analyzed by the Inokuti–Hirayama model. We think that the quenching effect between Tm3+ ions is mainly linked to the dipole–dipole interactions. 相似文献
19.
Enhai Song Weiren Zhao Guoxiong Zhou Xihua Dou Huachu Ming Chunyu Yi 《Current Applied Physics》2011,11(6):1374-1378
A single phased white light emitting phosphors K2Ca1−x−yP2O7: xEu2+, yMn2+ were synthesized by solid state reaction method. The Effective energy transfer occurs in this phosphor due to the large spectral overlap between the emission of Eu2+ and the excitation of Mn2+. The emission hue of K2Ca1−x−yP2O7: xEu2+, yMn2+ from blue to white light can be obtained by tuning the Eu2+/Mn2+ content ratio. The energy transfer mechanism from Eu2+ to Mn2+ in this phosphor was carefully investigated and demonstrated to be via the dipole–quadrupole interaction. 相似文献
20.
Chongfeng Guo Ming LiYan Xu Ting LiZhaoyu Ren Jintao Bai 《Applied Surface Science》2011,257(21):8836-8839
A potential green emitting phosphor Ca8Mg(SiO4)4Cl2:Eu2+ was prepared by modified sol-gel method. The factors those affect the photoluminescence intensity including heating temperature, the usage of the chlorine source CaCl2 and the concentration of dopant Eu2+ were also investigated in detail. As comparison, the phosphor prepared by solid-state reaction was also prepared. The phosphors show intense absorption in the range of 375-450 nm, which makes it a potential candidate of green emitting phosphor used for near-UV or blue light excited white LEDs. 相似文献