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1.
The influence of fluoride on the luminescence of LiEuM2O8 (M=Mo, W) was studied. LiEuMo2O8 and LiEuW2O8 formed the whole range of solid solutions, which emitted intense red luminescence under the excitations by 395, 465 and 535 nm wavelengths. When doped with fluoride, the materials also formed solid solutions and the luminescent intensity was remarkably enhanced. The phosphor with optimized compositions in this system would be a promising red component for solid-state lighting devices based on GaN light-emitting diodes. 相似文献
2.
《Analytical letters》2012,45(12):933-946
Abstract A simple d.c. are emission spectrographic method is described for the determination of 12 trace impurities in phosphor grade CaWO4 in the range 5 to 250 ppm. A charge of 25 mgs containing sample mixed with graphite in the ratio 1:3 is excited in a 10 amp d.c. arc. Scandium is used as the internal standard. The precision of the method is ± 15%. Detailed discussion on the selection of the final parameters has been given with supporting data. 相似文献
3.
In this paper, Barium Strontium Tungstate (Ba1−xSrx)WO4 crystals with (x = 0; 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0) were prepared by standard wet milling ceramic preparation method. These crystals were structurally characterized by X-ray diffraction (XRD), Fourier transform Raman (FT-Raman) and Fourier transform infrared (FT-IR) spectroscopic techniques. The shape, growth and average crystal size distribution of these crystals were investigated by a scanning electron microscope (SEM). Their optical properties were investigated by ultraviolet visible (UV–vis) absorption and photoluminescence (PL) measurements. XRD patterns, Rietveld refinements data, FT-Raman and FT-IR spectroscopies indicate that all the crystals present a scheelite-type tetragonal structure without deleterious phases. FT-Raman spectra exhibited 6 Raman active modes in range from 100 to 1000 cm−1, while the FT-IR spectra presented 2 infrared active modes in range from 500 to 1000 cm−1. SEM micrographs showed well sintered BaWO4 grains, while the substitution of Sr induced modifications in the shape and reduction in the grain size. UV–vis absorption measurements evidenced an increase in the values of the optical band gap (from 4.36 to 4.53 eV) with the increase of Sr into BaWO4 lattice. Dielectric constant, temperature coefficient of resonant frequency (τf), quality factors were measured with Hakki–Coleman technique. The value of τf found −43.68 ppm/°C for BaWO4 which increased to −21.40 ppm/°C for the SrWO4. 相似文献
4.
Solid-solution red phosphors for white LEDs 总被引:1,自引:0,他引:1
Gwan-Hyoung Lee 《Journal of luminescence》2011,131(12):2582-2588
Solid solutions of Eu3+-doped metal tungstate and molybdate phosphors were synthesized by solid-state reactions. The crystal structure of the solid-solution phosphors was determined to be tetragonal with a space group of I41/c. The red-emitting solid-solution phosphors exhibited a broad absorption band in the range 220-340 nm and sharp excitation peaks in the near UV to green region. The emission intensities of the solid-solution phosphors were enhanced due to the stiff lattices, as a result of the ordered distribution of cations and anions according to differences in ionic size. The increase in the energy transfer is discussed in terms of metal-ligand distances, ionization potential of Mo and the relatively large overlap between the excitation and emission spectra. Such solid-solution phosphors with a bright red emission intensity, relatively short decay time and appropriate color chromaticity have potential for use as red-emitting materials for white LEDs. 相似文献
5.
Gwan-Hyoung Lee 《Journal of luminescence》2011,131(12):2606-2611
The correlation between the crystal structure and luminescent properties of Eu3+-doped metal tungstate phosphors for white LEDs was investigated. Red-emitting A4−3x(WO4)2:Eux3+ (A=Li, Na, K) and B(4−3x)/2(WO4)2:Eux3+ (B=Mg, Ca, Sr) phosphors were synthesized by solid-state reactions. The findings confirmed that these phosphors exhibited a strong absorption in the near UV to green range, due to the intra-configurational 4f-4f electron transition of Eu3+ ions. The high doping concentration of Eu3+ enhanced the absorption of near UV light and red emission without any detectable concentration quenching. Based on the results of a Rietveld refinement, it was attributed to the unique crystal structure. In the crystal structure of the Eu3+-doped metal tungstate phosphor, the critical energy transfer distance is larger than 5 Å so that exchange interactions between Eu3+ ions would occur with difficulty, even at a high doping concentration. The energy transfer between Eu3+ ions, which causes a decrease in red emission with increasing concentration of Eu3+, appears to be due to electric multi-polar interactions. In addition, the Eu-O distance in the host lattice affected the shape of emission spectrum by splitting of emission peak at the 5D0→7F2 transition of Eu3+. 相似文献
6.
V. Nagirnyi S. Chernov L. Grigorjeva L. Jönsson M. Kirm A. Kotlov 《辐射效应与固体损伤》2013,168(6-12):1123-1126
A systematic spectroscopic study of single ZnWO 4 :Fe crystals with different iron concentrations has been performed under excitation by ultraviolet light, by synchrotron radiation or under photostimulation by near-infrared light. The luminescence of Fe 3+ -related centres has been studied. It is shown that iron centres of different types efficiently promote the formation of crystal defects at low temperatures. Electrons and holes can be trapped near Fe 2+ or Fe 3+ ions, which is further revealed in phosphorescence, thermostimulated or photostimulated luminescence. At room temperature the main effect of iron impurity is to reduce the light yield of a ZnWO 4 scintillator. 相似文献
7.
应用ICP-AES法测定钨酸钇钾[kY(WO4)2]激光晶体中的Er和Nd。试样用磷酸分解,Tm被选作内标元素。Er和Nd的回收率分别为98.6%-105.3%和96.5%-105.8%,相对标准偏差分别为1.90%和1.60%。 相似文献
8.
Synthesis of Novel and Thermally Stable Water Insoluble Coumarin‐based Azo Dyes via a Mild and Green Procedure
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A series of novel azo coumarin dyes were synthesized by the diazotization of 7‐amino coumarins in the presence of catalytic amounts of tungstate sulfuric acid (TSA) followed by coupling with phenol derivatives. Tungstate sulfuric acid catalyzes this reaction at room temperature and short reaction time with high yields. 相似文献
9.
Silvia H. Santagneli Matthias T. Rinke Younes Messaddeq Hellmut Eckert 《Journal of Non》2011,357(10):2126-2131
Glasses were prepared in the pseudo-binary system (1 − x)AgPO3-xWO3 (0≤ × ≤ 0.6 mol%). The structural evolution of the vitreous network was studied as a function of composition by thermal analysis, Fourier Transform Infrared spectroscopy (FTIR), Raman scattering, high resolution 31P solid state NMR and XANES at the W-L1 absorption edge. For compositions with x ranging from 0 to 0.5 a pronounced increase in the glass transition temperature is observed, suggesting a significant increase in the glass network connectivity. At the same time Raman spectra indicate that tungsten atoms are linked to non-bridging oxygen atoms (W-O- or W=O bonded species) whereas the 31P MAS-NMR spectra indicate the successive formation of new P-O-W linkages. The formation of some anionic tungsten sites (if these are revealed by the presence of W-O terminal bonds) implies an increase in the average degree of polymerization of the phosphate network, which is consistent with the compositional evolution of the 31P MAS-NMR spectra at low x values. For higher x-values, the Raman spectra indicate the presence of W-O-W linkages. W-L1 XANES data indicate that at least 90% of tungsten atoms are octahedrally coordinated. 相似文献
10.
柱分离/预富集与原子光谱检测技术联用在痕量分析和形态分析中发挥着日益重要的作用,钨分离富集用的固定相在文献中已有一些报道,如活性炭'、阴离子交换树脂'、流基棉Dj以及高分子螫合吸附剂D-'等.基于生物碱类试剂在一定条件下可以与某些金属阴离于或者杂多酸根阴离子形成稳定的、组成确定的配合物的特性,本工作采用浸渍法将生物碱试剂奎宁负载在活性炭上,制得一种新的金属阴离子吸附材料--负载奎宁/活性炭.采厅ICP-AES检测手段对该吸附材料在静态吸附条件下对金属阴离子WOS吸附性能进行了详细考察;研究了影响待测物… 相似文献