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1.
Infra-red luminescence (at wavelengths about 1600 and 2500 nm) from Er 3+ ions embedded in PbO–Bi 2O 3–Ga 2O 3–BaO glass hosts is reported for room and helium liquid temperatures. The substantial influence of energy transfer processes between the host and Er 3+ ions is shown experimentally through the dependences of photoluminescence on light polarization and excitation wavelength. Only the application of the polarized pumping YAG–Nd laser beam (λ=1060 nm) stimulates substantial luminescence with quantum efficiency up to 24%. The role of phonon-relaxation subsystem in the observed luminescence is discussed. 相似文献
2.
Y 2O 3:Eu 3+, Tb 3+ phosphors with white emission are prepared with different doping concentration of Eu 3+ and Tb 3+ 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 Eu 3+ and Tb 3+ co-doped Y 2O 3 phosphors show five main emission peaks: three at 590, 611 and 629 nm originate from Eu 3+ and two at 481 and 541 nm originate from Tb 3+, under excitation of 250-320 nm irradition. The white light luminescence color could be changed by varying the excitation wavelength. Different concentrations of Eu 3+ and Tb 3+ ions were induced into the Y 2O 3 lattice and the energy transfer from Tb 3+→Eu 3+ ions in these phosphors was found. The Commission International de l’Eclairage (CIE) chromaticity shows that the Y 2O 3:Eu 3+, Tb 3+ phosphors can obtain an intense white emission. 相似文献
3.
Binary (ZnO) 0.5(P 2O 5) 0.5 glasses doped with Eu 2O 3 and nanoparticles of Gd 2O 3:Eu were prepared by conventional melt-quench method and their luminescence properties were compared. Undoped (ZnO) 0.5(P 2O 5) 0.5 glass is characterized by a luminescent defect centre (similar to L-centre present in Na 2O-SiO 2 glasses) with emission around 324 nm and having an excited state lifetime of 18 ns. Such defect centres can transfer the energy to Eu 3+ ions leading to improved Eu 3+ luminescence from such glasses. Based on the decay curves corresponding to the 5D 0 level of Eu 3+ ions in both Gd 2O 3:Eu nanoparticles incorporated as well as Eu 2O 3 incorporated glasses, a significant clustering of Eu 3+ 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(P 2O 5) 0.5 glass doped with Gd 2O 3:Eu nanoparticles, it is established that there exists weak energy transfer from L-centres to Eu 3+ ions. Poor energy transfer from the defect centres to Eu 3+ ions in Gd 2O 3:Eu nanoparticles doped (ZnO) 0.5(P 2O 5) 0.5 glass has been attributed to effective shielding of Eu 3+ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between luminescent centre and Eu 3+ ions. 相似文献
4.
Zinc phosphate glasses doped with Gd 2O 3:Eu nanoparticles and Eu 2O 3 were prepared by conventional melt-quench method and characterized for their luminescence properties. Binary ZnO-P 2O 5 glass is characterized by an intrinsic defect centre emission around 324 nm. Strong energy transfer from these defect centres to Eu 3+ ions has been observed when Eu 2O 3 is incorporated in ZnO-P 2O 5 glasses. Lack of energy transfer from these defect centres to Eu 3+ in Gd 2O 3:Eu nanoparticles doped ZnO-P 2O 5 glass has been attributed to effective shielding of Eu 3+ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between the luminescent centre and Eu 3+ ions. Both doped and undoped glasses have the same glass transition temperature, suggesting that the phosphate network is not significantly affected by the Gd 2O 3:Eu nanoparticles or Eu 2O 3 incorporation. 相似文献
5.
The interaction of Eu 3+ with Sb 3+ ions during the room temperature synthesis of luminescent Sb 2O 3 nanorods is investigated using luminescence and vibrational spectroscopic techniques. Our results demonstrate that well crystalline, oriented Sb 2O 3 nanorods having length of around 3-4 μm, a width of around 100-200 nm and luminescence at around 390 nm can be synthesized at room temperature. Incorporation of Eu 3+ in these nanorods has been attempted and it is found that Eu 3+ ions do not have any interaction with nanorods and their orientation. Detailed Eu 3+ luminescence and XRD studies confirmed that a part of Sb 3+ ions reacts with Eu 3+ ions in the presence of hydroxyl ions (present in the medium) to form an amorphous antimony europium hydroxide compound. The amorphous compound on heating at high temperatures leads to its decomposition, giving hydrated Sb(V) oxides and Eu 2O 3 as major phases. 相似文献
6.
ABSTRACT According to the spectra of stationary X-ray excited luminescence (XEL) of BaF 2: Eu nanophosphors at 80 and 294 K, it was revealed that the thermal annealing of fine-grained nanoparticles ( d?=?35?nm) in the range of 400–1000°C, which is accompanied by an increase of their sizes in the range of 58–120?nm, does not result in effective changes of the charge state of Eu 3 + → Eu 2 + activator, in contrast to CaF 2: Eu nanoparticles. The maximum light output of X-ray excited luminescence of BaF 2: Eu nanophosphors in the 590?nm emission band of Eu 3+ ion was observed at an annealing temperature of 600°C with the average size of nanoparticles 67?nm. The subsequent growth of annealing temperatures, especially in the range of 800–1000°C, causes decrease in the light output of X-ray excited luminescence due to the increase of defect concentration in the lattice as a result of sharp increase of nanoparticle sizes and their agglomeration. In BaF 2: Eu nanoparticles of 58?nm size, according to the thermostimulated luminescence (TSL) spectrum, transformation of Eu 3+ → Eu 2+ under the influence of long-time X-ray irradiation was revealed for the peak of 151?K. Thus, X-ray excited luminescence spectra of BaF 2: Eu nanophosphors are formed predominantly due to the emission of Eu 3+ ions, while emission of Eu 2+ ions is observed in the TSL spectra. 相似文献
7.
The nanocrystalline Gd 2O 3:Eu 3+ 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 O 2−-Eu 3+ 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 Eu 3+ on luminescence lifetimes and intensities were also discussed. The samples exhibited a higher quenching concentration of Eu 3+, and luminescence lifetimes of nanoparticles are related to annealing temperature of samples and the doping concentration of Eu 3+ ions. 相似文献
8.
The luminescence properties of K 3Tb(PO 4) 2 activated by Eu 3+ were studied at excitation over the 120–300 nm wavelength range. It is demonstrated that Tb 3+ ions, exhibiting a strong absorption band in the vacuum‐ultraviolet (VUV), can provide efficient sensitisation of Eu 3+ emission in this wave length range, giving rise to intense red luminescence at 150 nm excitation. A proof is given for the concept of VUV sensitisation enabling the engineering of luminescence materials with enhanced conversion efficiency of VUV radiation into visible light. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
A red-emitting phosphor of Eu 3+-doped calcium–tellurium–zinc oxide, Ca 3Te 2(ZnO 4) 3, with a garnet-type structure was synthesized by high temperature solid-state reactions. This phosphor exhibited a strong red emission. The photoluminescence excitation spectrum showed that Ca 3Te 2(ZnO 4) 3:Eu 3+ can be effectively excited by UV–visible light. The property of long-wavelength excitation for this material has a benefit as a red phosphor in application of white light-emitting diodes. The colour coordinates were calculated. The excitation and emission spectra and luminescence decay curves were obtained using a pulsed, tunable, narrowband dye laser. Crystallographic sites and charge compensation mechanism of Eu 3+ ions were discussed. The emission line from Eu 3+ in intrinsic crystallographic site in the lattice was located at 579.56 nm. The emission line from Eu 3+ in another disturbed site, which is created by the defects created by the charge-compensation, was located at 580.88 nm. The disordered crystallographic sites of Eu 3+ are benefit for their strong red luminescence corresponding to the 5D 0→ 7F 2 transition. 相似文献
10.
According to stationary X-ray-excited luminescence spectra and thermally stimulated luminescence spectra of CaF 2:Eu nanophosphors, it was found that Eu 3+?→?Eu 2+ conversion can occur during thermal annealing of fine-grained ( d?=?25?nm) nanoparticles in the 200–800°C range, which is accompanied by an increase in their size within 40–189?nm. An important role of the exciton mechanism of Eu 2+ luminescence excitation was revealed according to the temperature dependence of X-ray-excited luminescence spectra of CaF 2:Eu nanoparticles of 114?nm size. The maximum of the X-ray-excited luminescence light output of CaF 2:Eu nanophosphors in the Eu 2+ ions’ emission band was traced out at 400–500°C annealing temperature and at the size of nanoparticles of 114–180?nm. The subsequent growth of the annealing temperatures, particularly in the 800–1000°C range, causes the reduction of X-ray-excited luminescence light output because of the increment of lattice defects’ concentration due to a sharp increase in the size of nanoparticles and their agglomeration. 相似文献
11.
Eu 3+-doped La 2O 3-3B 2O 3 crystal and glass were prepared by solid state reaction under different calcination temperature. The emission spectrum, phonon sideband (PSB), charge transfer band (C.T.B.) and lifetime of the Eu 3+ ion in the two materials, with the same composition but with different phase, were investigated. With excitation at 394 nm light, the glass presented intense 618 nm red luminescence; however, the crystal gave 696 nm red luminescence. This difference is ascribed to the discrepancy of the local structure around the Eu 3+ ion in the crystal and glass. To clarify the discrepancy, the coordination of Eu 3+ in the borate glass and crystal was investigated. The results show that Eu 3+ ions formed a complex Eu 3+-O 2−-B 3+ bond in glass; however, in the crystal, it formed a complex Eu 3+-O 2−-La 3+ bond. The lifetime of Eu 3+ ions in the crystal and the glass is 3.08 ms and 1.98 ms, respectively. This indicates that the discrepancy in the local structure around the Eu 3+ ions between the crystal and the glass leads to different fluorescence properties. 相似文献
12.
In this study, the red phosphors, Y 2W 1−xMo xO 6:Eu 3+ and Y 2WO 6:Eu 3+,Bi 3+, have been investigated for light-emitting diode (LED) applications. In Y 2WO 6:Eu 3+, the excitation band edge shifts to longer wavelength with the incorporation of Mo 6+ or Bi 3+ ions. The emission spectra exhibit 5D 0→ 7F 1 and 5D 0→ 7F 2 transition of Eu 3+ ion at 588, 593, and 610 nm, respectively. Moreover, the bluish-green luminescence of the WO 66− at about 460 nm is observed to decrease with the incorporation of Mo 6+, which results in pure red color. Thus, this study shows that the red phosphor, Y 2WO 6:Eu 3+, incorporated with Mo 6+ or Bi 3+ ions is advantageous for LEDs applications. 相似文献
13.
In this paper, a novel phosphor, Y 6W 2O 15:Eu 3+ 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 Y 6W 2O 15:Eu 3+forms that gives intense red emission when excited at 466 nm, the emission is attributed to the Eu 3+ ions transitions from 5D 0 excited states to 7F J ( J=0-4) ground states. The long excitation wavelength proves the Eu 3+ transition follows the photoexcitation of the oxygen-metal (O→W lmct) charge transfer bands in yttrium tungstate. Some structural information regarding Y 6W 2O 15 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
14.
Long persistent SrAl 2O 4:Eu 2+ phosphors co-doped with Dy 3+ were prepared by the solid state reaction method. The main diffraction peaks of the monoclinic structure of SrAl 2O 4 were observed in all the samples. The broad band emission spectra at 497 nm for SrAl 2O 4:Eu 2+, Dy 3+ were observed and the emission is attributed to the 4f 65d 1 to 4f 7 transition of Eu 2+ 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 Dy 3+ ions acting as the hole trap levels, which play an important role in prolonging the duration of luminescence. 相似文献
15.
The synthesis, morphological characterization, and optical properties of colloidal, Eu(III) doped Gd2O3 nanoparticles with different sizes and shapes are presented. Utilizing wet chemical techniques and various synthesis routes, we were able to obtain spherical, nanodisk, nanotripod, and nanotriangle-like morphology of Gd2O3:Eu3+ nanoparticles. Various concentrations of Eu3+ ions in the crystal matrix of the nanoparticles were tested in order to establish the levels at which the concentration quenching effect is negligible. Based on the luminescence spectra, luminescence lifetimes and optical parameters, which were calculated using the simplified Judd–Ofelt theory, correlations between the Gd2O3 nanoparticles morphology and Eu3+ ions luminescence were established, and allowed to predict the theoretical maximum quantum efficiency to reach from 61 to 98 %. We have also discussed the impact of the crystal structure of Gd2O3 nanoparticles, as well as coordinating environment of luminescent ions located at the surface, on the emission spectra. With the use of a tunable femtosecond laser system and the Z-scan measurement technique, the values of the effective two-photon absorption cross-section in the wavelength range from 550 to 1,200 nm were also calculated. The nonlinear optical measurements revealed maximum multi-photon absorption in the wavelength range from 600 to 750 nm. 相似文献
16.
We report on the preparation of Eu 2+-doped BaSi 2O 5 glass-ceramics by crystallizing an Eu 3+-doped barium-silicate glass at temperatures in the range from 750 to 1100 °C. Single phase BaSi 2O 5 glass ceramics can be obtained by thermal annealing at temperatures of about 950 °C. The luminescence intensity of Eu 2+ increases dramatically if monoclinic BaSi 2O 5 is formed. Monoclinic Eu 2+:BaSi 2O 5 shows efficient, broad band luminescence between 450 and 550 nm by excitation in the near UV. Annealing at temperatures >1000 °C leads to orthorhombic BaSi 2O 5 with much smaller Eu 2+ luminescence. Static and time-resolved luminescence measurements indicate that Eu 2+ ions are incorporated into the BaSi 2O 5 crystallites while Eu 3+ ions remain in the amorphous phase. 相似文献
17.
The emission intensity of the peak at 612 nm ( 5D 0→ 7F 2) of the Eu 3+ ions activated SnO 2 nanocrystals (doped and coated) is found to be sensitive to the nanoenvironment. We have compared the luminescence efficiencies of the nanocrystals of SnO 2 doped by Eu 2O 3 with those of SnO 2 coated by Eu 2O 3 and we found that the intensities are significantly higher in coated nanocrystals. Furthermore, it is clear from luminescence intensity measurements that Eu 3+ ions occupy low symmetry sites in the Eu 2O 3 coated SnO 2 nanocrystal. The analysis suggests that the radiative relaxation rate is higher in Eu 2O 3 coated SnO 2 nanocrystals than Eu 2O 3 doped SnO 2 nanocrystals due to the asymmetric environment of Eu 3+ ions in coated samples. 相似文献
18.
The luminescence properties of Ba 3Tb 0.9Eu 0.1(PO 4) 3 and Ba 3Gd 0.9Eu 0.1(PO 4) 3 phosphors were studied for excitation over the 120-300 nm wavelength range. It is found that Tb 3+, which exhibits a strong vacuum-ultraviolet (VUV) absorption band, provides sensitisation of Eu 3+ emission in this host. This effect can be used to develop phosphors with enhanced conversion efficiency of the VUV radiation into visible light. 相似文献
19.
Phosphors of nanoparticles LaSrAl 3O 7:RE 3+(REEu, Tb) have been prepared by a sol–gel method. The structure and luminescent properties of LaSrAl 3O 7:Eu 3+ and LaSrAl 3O 7:Tb 3+ 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 LaSrAl 3O 7 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 5D 0– 7F 2 transition of Eu 3+, and at around 545 nm corresponding to the 5D 4– 7F 5 transition of Tb 3+. The dependence of photoluminescence intensity on Eu 3+(or Tb 3+) concentration and annealing temperature were also studied in detail. 相似文献
20.
The shift of the emission band to longer wavelength (yellow-orange) of the Ba 2MgSi 2−xAl xO 7: 0.1Eu 2+ phosphor under the 350-450 nm excitation range has been achieved by adding the codoping element (Mn 2+) in the host. The single-host silicate phosphor for WLED, Ba 2MgSi 2−xAl xO 7: 0.1Eu 2+, 0.1Mn 2+ was prepared by high-temperature solid-state reaction. It was found experimentally that, its three-color emission peaks are situated at 623, 501 and 438 nm, respectively, under excitation of 350-450 nm irradiation. The emission peaks at 438 and 501 nm originate from the transition 5d to 4f of Eu 2+ ions that occupy the two Ba 2+ sites in the crystal of Ba 2MgSi 2−x Al xO 7, while the 623 nm emission is attributed to the energy transfer from Eu 2+ ions to Mn 2+ ions. The white light can be obtained by mixing the three emission colors of blue (438 nm), green (501 nm) and red (623 nm) in the single host. When the concentrations of the Al 3+, Eu 2+ and Mn 2+ ions were 0.4, 0.1 and 0.1 mol, respectively, the sample presented intense white emission. The addition of Al ion to the host leads to a substantial change of intensity ratio between blue and green emissions. White light could be obtained by combining this phosphor with 405 nm light-emitting diodes. The near-ultraviolet GaN-based Ba 2MgSi 1.7 Al 0.3O 7: 0.1Eu 2+, 0.1Mn 2+ LED achieves good color rendering of over 85. 相似文献
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