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1.
Dheeraj Jain 《Journal of luminescence》2009,129(5):439-3684
Zinc phosphate glasses doped with Gd2O3:Eu nanoparticles and Eu2O3 were prepared by conventional melt-quench method and characterized for their luminescence properties. Binary ZnO-P2O5 glass is characterized by an intrinsic defect centre emission around 324 nm. Strong energy transfer from these defect centres to Eu3+ ions has been observed when Eu2O3 is incorporated in ZnO-P2O5 glasses. Lack of energy transfer from these defect centres to Eu3+ in Gd2O3:Eu nanoparticles doped ZnO-P2O5 glass has been attributed to effective shielding of Eu3+ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between the luminescent centre and Eu3+ ions. Both doped and undoped glasses have the same glass transition temperature, suggesting that the phosphate network is not significantly affected by the Gd2O3:Eu nanoparticles or Eu2O3 incorporation. 相似文献
2.
Non-radiative energy transfers (ET) from Ce3+ to Pr3+ in Y3Al5O12:Ce3+, Pr3+ and from Sm3+ to Eu3+ in CaMoO4:Sm3+, Eu3+ are studied based on photoluminescence spectroscopy and fluorescence decay patterns. The result indicates an electric dipole-dipole interaction that governs ET in the LED phosphors. For Ce3+ concentration of 0.01 in YAG:Ce3+, Pr3+, the rate constant and critical distance are evaluated to be 4.5×10−36 cm6 s−1 and 0.81 nm, respectively. An increase in the red emission line of Pr3+ relative to the yellow emission band of Ce3+, on increasing Ce3+ concentration is observed. This behavior is attributed to the increase of spectral overlap integrals between Ce3+ emission and Pr3+ excitation due to the fact that the yellow band shifts to the red spectral side with increasing Ce3+ concentration. In CaMoO4:Sm3+, Eu3+, Sm3+-Eu3+ transfer occurs from 4G5/2 of Sm3+ to 5D0 of Eu3+. The rate constant of 8.5×10−40 cm6 s−1 and the critical transfer distance of 0.89 nm are evaluated. 相似文献
3.
Red-emitting Y2O3:Eu3+ and green-emitting Y2O3:Tb3+ and Y2O3:Eu3+, Tb3+ nanorods were synthesized by hydrothermal method. Their structure and micromorphology have been analyzed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The photoluminescence (PL) property of Y2O3:Eu3+,Tb3+ phosphor was investigated. In the same host (Y2O3), upon excitation with ultraviolet (UV) irradiation, it is shown that there are strong emissions at around 610 and 545 nm corresponding to the forced electric dipole 5D0-7F2 transition of Eu3+ and 5D4-7F5 transition of Tb3+, respectively. Different qualities of Eu3+and Tb3+ ions are induced into the Y2O3 lattice. From the excitation spectrum, we speculate that there exists energy transfer from Tb3+ to Eu3+ ions .The emission color of powders reveals regular change in the separation of light emission. These powders can meet with the request of optical display material for different colors or can be potentially used as labels for biological molecules. 相似文献
4.
The energy transfer between Sm3+ and Er3+ ions in yttrium orthophosphate is studied. This choice of ions is based on the possibility of quantum cutting processes and the host material is selected according to the position of the 5d bands of the Sm3+ ion. The Sm3+ and Er3+ doped and Sm3+, Er3+ co-doped YPO4 have been synthesized. Spectroscopic studies were done in the ultraviolet and vacuum ultraviolet ranges. The energy transfer between Sm3+ and Er3+ is very efficient but it does not lead to Er3+ visible emission. Whatever the excitation wavelength, the emission of co-doped samples mainly occurs in the infrared range. 相似文献
5.
V. Sudarsan 《Journal of luminescence》2010,130(8):1379-1383
Binary (ZnO)0.5(P2O5)0.5 glasses doped with Eu2O3 and nanoparticles of Gd2O3:Eu were prepared by conventional melt-quench method and their luminescence properties were compared. Undoped (ZnO)0.5(P2O5)0.5 glass is characterized by a luminescent defect centre (similar to L-centre present in Na2O-SiO2 glasses) with emission around 324 nm and having an excited state lifetime of 18 ns. Such defect centres can transfer the energy to Eu3+ ions leading to improved Eu3+ luminescence from such glasses. Based on the decay curves corresponding to the 5D0 level of Eu3+ ions in both Gd2O3:Eu nanoparticles incorporated as well as Eu2O3 incorporated glasses, a significant clustering of Eu3+ ions taking place with the latter sample is confirmed. From the lifetime studies of the excited state of L-centre emission from (ZnO)0.5(P2O5)0.5 glass doped with Gd2O3:Eu nanoparticles, it is established that there exists weak energy transfer from L-centres to Eu3+ ions. Poor energy transfer from the defect centres to Eu3+ ions in Gd2O3:Eu nanoparticles doped (ZnO)0.5(P2O5)0.5 glass has been attributed to effective shielding of Eu3+ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between luminescent centre and Eu3+ ions. 相似文献
6.
7.
Gd2O3:Sm3+ and Gd2O3:Sm3+,Bi3+ powders were prepared by a combustion method. Their structures were determined using X-ray diffraction. UV-visible absorption and photoluminescence spectra were investigated for Gd2O3:Sm3+ and Gd2O3:Sm3+,Bi3+ at different annealing temperatures and different doping concentrations. The emission spectra of all samples presented the characteristic emission narrow lines arising from the 4G5/2→6HJ transitions (J=5/2, 7/2, and 9/2) of Sm3+ ions upon excitation with UV irradiation. The emission intensity of Sm3+ ions was largely enhanced with introducing Bi3+ ions into Gd2O3:Sm3+ and the maximum occurred at a Bi3+ concentration of 0.5 mol%. The relevant mechanisms were discussed with the sensitization theory by Dexter and the aggregation behavior of Bi3+ ions. 相似文献
8.
Zuoling Fu 《Journal of luminescence》2007,124(2):213-216
Y2O3:Eu3+ nanocrystals were prepared by combustion synthesis. The particle size estimated by X-ray powder diffraction (XRD) was about 10 nm. A blue-shift of the charge-transfer (CT) band in excitation spectra was observed in Y2O3:Eu3+ nanocrystals compared with bulk Y2O3:Eu3+. The electronic structure of Y2O3 is calculated by density functional method and exchange and correlation have been treated by the generalized gradient approximation (GGA) within the scheme due to Perdew-Burke-Ernzerhof (PBE). The calculated results show that the energy centroid of 5d orbital in nanocrystal has increasing trend compared with that in the bulk material. The bond length and bond covalency are calculated by chemical bond theory. The bond lengths of Y2O3:Eu3+ nanocrystal are shorter than those of the bulk counterpart and the bond covalency of Y2O3:Eu3+ nanocrystal also has an increasing trend. By combining centroid shift and crystal-field splitting, the blue-shift of the CT band is interpreted. 相似文献
9.
A nonhydrolytic hot solution synthesis technique was used to grow monodisperse ternary oxide nanocrystals of ZnGa2O4:Eu3+. The shape of ZnGa2O4:Eu3+ nanocrystals was a function of the type of precursor, and their size was controlled by changing the concentration ratio of Zn precursor to surfactant. The crystal structure of synthesized ZnGa2O4 nanocrystals was a cubic spinel with no detectable secondary phases. Photoluminescence of red-emitting ZnGa2O4:Eu3+ nanocrystals resulted in a high (5D0-7F2)/(5D0-7F1) intensity ratio, suggesting that the Eu3+ ions occupy tetrahedral Zn2+ sites or distorted octahedral Ga3+ sites with no inversion symmetry in ZnGa2O4 nanocrystals. 相似文献
10.
B.M. Mothudi O.M. Ntwaeaborwa A. Kumar K. Sohn H.C. Swart 《Physica B: Condensed Matter》2012,407(10):1679-1682
Long persistent SrAl2O4:Eu2+ phosphors co-doped with Dy3+ were prepared by the solid state reaction method. The main diffraction peaks of the monoclinic structure of SrAl2O4 were observed in all the samples. The broad band emission spectra at 497 nm for SrAl2O4:Eu2+, Dy3+ were observed and the emission is attributed to the 4f65d1 to 4f7 transition of Eu2+ ions. The samples annealed at 1100–1200 °C showed similar broad TL glow curves centered at 120 °C. The similar TL glow curves suggest that the traps responsible for them are similar. The long afterglow displayed by the phosphors annealed at different temperatures, may be attributed to the Dy3+ ions acting as the hole trap levels, which play an important role in prolonging the duration of luminescence. 相似文献
11.
Simas Sakirzanovas Artūras Katelnikovas Helga Bettentrup 《Journal of luminescence》2011,131(7):1525-1529
Luminescence and reflection spectra as well as luminescence kinetics of the 1 mol% Sm3+-doped crystalline lanthanum magnesium meta borate (LaMgB5O10) and gadolinium magnesium meta borate (GdMgB5O10) were analyzed. Materials were synthesized by conventional solid state route and showed bright orange-red emission under UV excitation. Emission spectra contain sharp and well resolved Sm3+4G5/2→6HJ transitions indicating a strong crystal-field effect. In case of gadolinium compound energy transfer between Gd3+ and Sm3+ was detected. The luminescent kinetics of the Sm3+ in analyzed powders is characterized by single exponential decay and experimental values vary in the range 2.2-2.4 ms. 相似文献
12.
Nanocrystalline powders with various Eu3+ concentration (from 1 to 10 mol %) doped La2O3 were prepared via a combustion route. Their structure and morphology were characterized using X-ray diffraction (XRD) and High-resolution transmission electron microscopy. The emission spectra of the as-synthesized samples show that the strongest emission position is centered at 626 nm corresponding to 5D0→7F2 transition of Eu3+ ions and the intensity change of 626 nm emission is considered as a function of ultraviolet (240 nm) irradiation time. The excitation spectra at 626 nm monitoring indicate that the charge transfer state band is varies with different Eu3+ ion concentration. These results are attributed to the surface defects of the nanocrystals. 相似文献
13.
Yukari Kishimoto 《Journal of luminescence》2009,129(9):1055-1059
Blue light-emitting glasses were successfully prepared by doping Eu2+ ions in the system Al2O3-SiO2. The Al2O3-SiO2 glasses doped with Eu3+ ions were synthesized using a sol-gel method, followed by heating in hydrogen gas atmosphere to reduce into the Eu2+ ions. The obtained glasses exhibited emission spectra with peak at ∼450 nm due to 4f65d→4f7 (8S7/2) transition, the intensities of which strongly changed depending on their glass composition and heating conditions. The emission quantum efficiency of 48% was achieved by heating the glass with the ratio of Al3+ to Eu3+ at about 6 at 1000 °C in hydrogen gas atmosphere. It was found that the Al2O3-SiO2 glasses were appropriate not only for homogeneously doping the Eu3+ ions in glass structure but also reducing to Eu2+ ions, resulting in enhanced blue light-emission properties. 相似文献
14.
The nanocrystalline Gd2O3:Eu3+ powders with cubic phase were prepared by a combustion method in the presence of urea and glycol. The effects of the annealing temperature on the crystallization and luminescence properties were studied. The results of XRD show pure phase can be obtained, the average crystallite size could be calculated as 7, 8, 15, and 23 nm for the precursor and samples annealed at 600, 700 and 800 °C, respectively, which coincided with the results from TEM images. The emission intensity, host absorption and charge transfer band intensity increased with increasing the temperature. The slightly broad emission peak at 610 nm for smaller particles can be observed. The ratio of host absorption to O2−-Eu3+ charge transfer band of smaller nanoparticles is much stronger compared with that for larger nanoparticles, furthermore, the luminescence lifetimes of nanoparticles increased with increasing particles size. The effects of doping concentration of Eu3+ on luminescence lifetimes and intensities were also discussed. The samples exhibited a higher quenching concentration of Eu3+, and luminescence lifetimes of nanoparticles are related to annealing temperature of samples and the doping concentration of Eu3+ ions. 相似文献
15.
Sr3MgSi2O8:Eu2+ and Sr2MgSi2O7:Eu2+ phosphors find uses in applications such as plasma display panel (PDP), solid-state lighting, longafter glow. Preparation of these phosphors by a modified combustion synthesis is described in this paper. As-prepared samples did not show photoluminescence. After reducing the samples at 900 °C, characteristic Eu2+ emission was observed. Preparation of these phosphors by using similar methods helped clarifying various results obtained for Sr3MgSi2O8:Eu2+ by different investigators. 相似文献
16.
Paula F.S. Pereira 《Journal of luminescence》2010,130(3):488-467
An evolutionary optimization process involving combination chemistry was employed in an attempt to develop Y3Al5O12 (YAG). The combination chemistry process utilized here consisted the doping of the YAG host with appropriate amounts of red (R), green (G), and blue (B) dopants in a single layer, for use in tricolor white light. The doped YAG was acieved by means of the non-hydrolytic sol-gel route. Four samples were prepared, three of which were mono-doped samples containing 1.0% of a certain lanthanide (Eu3+, Tb3+, or Tm3+) ion, while the fourth contained the three ions. The samples were characterized by X-ray diffractometry and photoluminescence. The diffraction pattern of the mono-doped samples synthered at 800 °C for 16 h displayed peaks corresponding to the Y3Al5O12 (YAG) phase, while the sample doped with the three ions revealed the presence of a mixture of Y3Al5O12 (YAG) and Y4Al2O9 (YAM) phases. The emission spectra of the three mono-doped YAG samples displayed the typical bands of the blue, green, and red emission of the corresponding lanthanide ions. As for the sample doped with the three lanthanide ions; it simultaneously emitted R, G and B lights. The green emission (546 nm) was more intense and narrow in relation to the red and blue emissions, which may be due to differences in the size of the three incorporated ions. 相似文献
17.
Simas Sakirzanovas Artūras Katelnikovas Danuta Dutczak 《Journal of luminescence》2011,131(11):2255-2262
Complete and partial samarium reduction was achieved under strong reducing atmosphere by solid-state and combustion synthesis of Sr3.96Sm0.04Al14O25. Dependence of different fluxing agents on the formation of various strontium aluminates was examined. The samples were investigated by X-ray powder diffraction, temperature dependent luminescence decay and photoluminescence measurements. Excitation with UV radiation resulted in sharp and well resolved emission lines of samarium ions. Distinct temperature behavior for Sm2+ and Sm3+ were detected in the range of 100-500 K. Estimated emission thermal quenching values (TQ1/2) for divalent samarium were approximately 270 K while for trivalent state around 660 K. Measured luminescence decay values of Sm2+ are substantially lower than for Sm3+,≈1.7 and ≈2.7 ms, respectively. The spectral feature of Sm2+ emission spectrum indicates that dopant occupies low symmetry site in Sr4Al14O25 compound. 相似文献
18.
三基色荧光粉中, 红色荧光粉性能较差, 为获得性能优良的红色荧光粉, 本文采用高温固相法合成了Eu2+, Cr3+单掺杂及共掺杂的碱土金属多铝酸盐MAl12O19 (M =Ca, Sr, Ba) 发光体. 实验表明, 在以上三种基质中均存在Eu2+→Cr3+的能量传递, 利用能量传递可以有效将Eu2+的蓝光或绿光转换为红光. 三种碱土金属多铝酸盐基质的晶体结构相似,但Eu2+, Cr3+发光受晶体场影响,导致在不同的基质中Eu2+, Cr3+间能量传递效率不同.通过光谱分析及能量传递效率计算发现, 相同掺杂浓度下,CaAl12O19中Eu2+→Cr3+的能量传递效率最高,SrAl12O19次之, BaAl12O19最低.红光转换率在CaAl12O19中最高. 相似文献
19.
Phosphors of nanoparticles LaSrAl3O7:RE3+(REEu, Tb) have been prepared by a sol–gel method. The structure and luminescent properties of LaSrAl3O7:Eu3+ and LaSrAl3O7:Tb3+ phosphors were characterized by X-ray diffraction and atomic force microscopy (AFM), photoluminescence excitation and emission spectra were utilized. From X-ray diffraction (XRD) patterns, it is indicated that the phosphor LaSrAl3O7 forms without impurity phase at 900 °C. From atomic force microscopy (AFM) images, it is shown that the crystal size of the phosphores are about 60–80 nm. Upon excitation with UV irradiation, it is shown that there is a strong emission at around 617 nm corresponding to the forced electric dipole 5D0–7F2 transition of Eu3+, and at around 545 nm corresponding to the 5D4–7F5 transition of Tb3+. The dependence of photoluminescence intensity on Eu3+(or Tb3+) concentration and annealing temperature were also studied in detail. 相似文献
20.
Jinping Huang Hongshan Luo Pingle Zhou Xibin Yu Yikang Li 《Journal of luminescence》2007,126(2):881-885
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