共查询到20条相似文献,搜索用时 46 毫秒
1.
A. Vedda M. Martini D. Di Martini V. V. Laguta M. Nikl E. Mihokova 《辐射效应与固体损伤》2013,168(6-12):1003-1007
Wavelength-resolved TSL measurements after x-ray irradiation at room temperature were performed on undoped, Ce- and (Ce, Zr)-doped Lu 3 Al 5 O 12 crystals. Several glow peaks were observed in the 20-450 v C temperature region, whose intensities and emission spectra are influenced by doping. Namely, the TSL spectra are governed by defect and trace impurity-related emissions in the undoped crystal, while only the Ce 3+ emission is detected in the doped crystals. Moreover, EPR measurements performed at 12 v K revealed typical spectra of Ce 3+ (4f 1 , S =1/2) occupying Lu 3+ substitutional positions. In situ light irradiation (250-330 v nm) of the crystals results in a step-like decrease of the Ce 3+ EPR intensity. Such a behaviour can reflect a creation of Ce 4+ ions under UV irradiation or an increase of the Ce 3+ population in the excited (5d) state. 相似文献
2.
Using electron spin resonance (ESR) and thermally stimulated luminescence (TSL) three different electron traps based on regular W sites perturbed by oxygen vacancies have been identified in PbWO 4 . Analysis of ESR spectra parameters ( g -factor values and principal axes orientations) has shown that revealed centers are (WO 3 ) m vacancy containing complex anions associated with a defect in Pb sublattice: (WO 3 ) m m A Pb complexes. One of the centers (W 1 ) is thermally stable up to 350-370 v K, while the other two (W 2 and W 3 ) only to 270-290 v K. Above these temperatures trapped electrons become free and recombine with localized holes, giving rise to TSL glow peaks at T\approx 323\,\hbox{K} and 365\,\hbox{K} . Using the initial rise method the 323\,\hbox{K} TSL peak-shape was fitted allowing the first order recombination kinetic that gives trap parameters E = 0.88\,\hbox{eV} and s\simeq 5\ast 10^{12}1/\hbox{s} . 相似文献
3.
R. Francini S. Pinelli A. Baraldi R. Capelletti E. Sani A. Toncelli 《辐射效应与固体损伤》2013,168(6-12):1009-1013
In the present work we report on the spectroscopic properties of the Ce 3+ ion in BaY 2 F 8 single crystals. The absorption and excitation spectra of the emission centered at 340 v nm have been measured in the temperature range 15-300 v K. The 340 v nm emission consists of two broad partially overlapping bands, peaking at 324 and 347 v nm (at 15 v K), respectively. The full width at half maximum is about 0.5 v eV at room temperature. The absorption spectrum of the lowest in energy component of the f M d transition of Ce 3+ reveals at low temperature a marked vibronic structure. High resolution (0.02 v cm m 1 ) Fourier transform infrared spectroscopy in the wave number range 500-5000 v cm m 1 and in the temperature range 9-300 v K has been exploited to monitor the f level splitting. The absorption transitions from the three Stark components of the 2 F 5/2 manifold to the four of the 2 F 7/2 one, have been monitored in the wave number range 2000-3400 v cm m 1 . The wave number separation at 9 v K between the lowest level of the ground 2 F 5/2 manifold and lowest one of the 2 F 7/2 manifold is found to be 2197.47 v cm m 1 in good agreement with the splitting detected between the two components of the d M f emission. 相似文献
4.
The energy level schemes of four rare-earth dopants (Ce 3+ , Nd 3+ , Dy 3+ , and Er 3+ ) in BaY 2 F 8 , as determined by optical absorption spectra, were fitted with a single-ion Hamiltonian and analysed within Newman's Superposition Model for the crystal field. A unified picture for the four dopants was obtained, by assuming a distortion of the F m ligand cage around the RE site; within the framework of the Superposition Model, this distortion is found to have a marked anisotropic behaviour for heavy rare earths, while it turns into an isotropic expansion of the nearest-neighbours polyhedron for light rare earths. It is also inferred that the substituting ion may occupy an off-center position with respect to the original Y 3+ site in the crystal. 相似文献
5.
High resolution (0.02 cm?1) Fourier transform spectroscopy was applied in the 9–300 K and 100–24,000cm?1 ranges, respectively, to detect in Er3? and Ce3? doped BaY2F8 single crystals (1) the narrow line spectra due to the intraconfigurational 4f→4f transitions of the rare earths (RE) and (2) the possible vibronic tails accompanying the zero-phonon lines. The 2F5/2→2F7/2 transition was monitored for the Ce3?-doping and the crystal field splitting of the initial and final manifold was determined. Weak vibronic spectra accompanying six among the nine investigated 4f→4f transitions of Er3? and the 2F5/2→2F7/2 transition of Ce3? were detected. The vibronic spectra amplitude was found to scale with the RE contents. On the basis of the IR- and Raman-active vibrational modes, either measured or quoted in the literature, most of the vibronic lines could be successfully assigned to the lattice modes. Violations of the selection rules were envisaged and discussed. 相似文献
6.
Electron paramagnetic resonance [EPR] and thermally stimulated luminescence [TSL] studies were conducted on self [α]-irradiated239Pu doped calcium chloro phosphate andγ-irradiated239Pu/238UO
2
2+
doped calcium chloro phosphate to elucidate the role of the electron/hole traps in thermally stimulated reactions and to
obtain trap parameters from both TSL and EPR data. TSL glow peaks around 135 K (# peak 1), 190 K (# peak 2), 435 K (# peak
5) and 490 K (# peak 7) were observed and their spectral characteristics have shown that Pu3+ and UO
6
6−
act as luminescent centres in calcium chloro phosphate with respective dopants. EPR studies have shown the formation of the
radical ions H0, PO
4
2−
, O−, O
2
−
and [ClO]2− under different conditions. Whereas the [ClO]2− radical being stable up to 700 K, was not found to have any role in TSL processes, the thermal destruction of other centres
was found to be primarily responsible for the TSL peaks observed. The trap depth values were determined both by using the
TSL data and also the temperature variation of EPR spectra of these centres. 相似文献
7.
S.M.V. Novais 《Journal of luminescence》2011,131(7):1283-1287
CdWO4 scintillator powders were produced via solid state reaction and investigated by thermally stimulated luminescence technique after UV irradiation. Under a heating rate of 0.1 K/s, the glow curve presented a superposition of peaks at low temperatures. Four peaks were identified below 80 K by partial heating method and their kinetic parameters were evaluated from the initial rise analysis. Measurements were also performed for heating rates of 0.05 and 0.2 K/s and allowed the kinetic study by peak position method. Surface effects due to the polycrystalline feature of the sample were investigated by comparing the results with those reported for CdWO4 single crystals. 相似文献
8.
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
9.
M. Kirm H. Lichtenberg V. N. Makhov E. Negodin T. V. Ouvarova E. Suljoti 《辐射效应与固体损伤》2013,168(6-12):911-914
Using energy- and time-resolved spectroscopy the luminescence properties of Er 3+ doped BaY 2 F 8 crystals were investigated at 10 v K under VUV synchrotron radiation excitation. Radiative intraconfigurational f - f and interconfigurational d - f transitions in Er 3+ ions were observed under f - d excitation. Whereas the onset of 4 S 3/2 population via f - d excitation starts at 59 900 v cm m 1 , efficient excitation of emissions arising from the 2 P 3/2 state begins only above 67 000 v cm m 1 in VUV region. Such behaviour can be explained by a cross-relaxation process of the type ( 2 F(2) 5/2 , 4 I 15/2 ) M ( 2 P 3/2 , 2 P 3/2 ) taking place within f -states of Er 3+ ions finally populating the emitting 2 P 3/2 state. 相似文献
10.
The structural and optical properties of solution-processed Eu3+:BaY2F8 were characterized and compared to those of the sample synthesized by a solid-state reaction method. Precipitated from solution Eu3+:BaY2F8 has the fluorite (CaF2) type of structure, which transforms completely into monoclinic form when powder is heated at 750 °C. This temperature is also sufficient for entire elimination of hydroxyl groups. The intensities of f-f emission transitions of Eu3+ in BaY2F8 were analyzed in the frame of Judd-Ofelt model and the values of 1.23×10−20 and 1.95×10−20 cm2 were determined for Ω2 and Ω4 intensity parameters. The experimental lifetimes of the 5D0 and 5D1 levels are equal to 8.4 and 2.3 ms, respectively. The quantum efficiency of Eu3+ in BaY2F8 was evaluated to be ∼35%. 相似文献
11.
Kaminskii A. A. Sarkisov S. E. Below F. Eichler H. -J. 《Optical and Quantum Electronics》1990,22(1):S95-S105
The luminescence and absorption properties of Ba(Y1−x Er x )2F8 (x=0.001, 0.01, 0.05, 0.1, 0.2 and 0.3) and the Er3+-ion decay kinetics of luminescent transitions from three initial laser states, the4S3/2,4F.9/2 and4I11/2 manifolds, were measured. The crystal-field splitting schemes for allJ-manifolds which are involved in (J →J′)-luminescence transitions and stimulated emission parameters of Er3+ -ions in BaY2F8 were determined. A comparison of laser powers and efficiencies of BaY2F8 and Y3Al5O12, Lu3Al5O12 and LiYF4 single crystals doped with Er3+-ions shows the similar performance of these materials.
相似文献12.
Suyin Zhang Yanlin Huang Liang Shi Xuebin Qiao Hyo Jin Seo 《Physica B: Condensed Matter》2009,404(21):4136-4141
A red-emitting phosphor of Eu3+-doped calcium–tellurium–zinc oxide, Ca3Te2(ZnO4)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 Ca3Te2(ZnO4)3:Eu3+ 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 Eu3+ ions were discussed. The emission line from Eu3+ in intrinsic crystallographic site in the lattice was located at 579.56 nm. The emission line from Eu3+ 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 Eu3+ are benefit for their strong red luminescence corresponding to the 5D0→7F2 transition. 相似文献
13.
The paper is dedicated to development of scintillators based on the single crystalline films of Ce3+ doped Lu2SiO5 (LSO:Ce) and Y2SiO5 (YSO:Ce) orthosilicates grown by Liquid Phase Epitaxy method onto YSO substrates from melt-solutions based on the PbO–B2O3 flux. We also compare the luminescent and scintillation properties of Ce doped LSO:Ce and YSO:Ce single crystalline films with those of their single crystal counterparts, grown by the Czochralski method. 相似文献
14.
Oleic acid (OA)-modified CaF2:Tb3+ nanoparticles with various Tb3+ concentrations and CaF2:Ce3+, Tb3+ nanoparticles were synthesized. The as-prepared nanoparticles were shown to be well dissolved in some common organic solvents, such as chloroform and toluene. The nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD) and transmission electron microscopy (TEM). The investigation of fluorescence properties of CaF2:Tb3+ nanoparticles showed that the Tb3+ ions could be sensitized efficiently by the surface coating of OA and CaF2:Tb3+ nanoparticles with 10 mol% Tb3+ concentrations possess the highest emission intensity. The comparison of emission for CaF2:Ce3+, Tb3+ and CaF2:Tb3+ (10 mol%) nanoparticles revealed that the emission intensity of the former is about 4.5 times as strong as that of the latter. 相似文献
15.
The aim of the present study was to investigate the absolute luminescence efficiency of gadolinium oxysulfide powder scintillators, doped with praseodymium, cerium and fluorine (Gd2O2S:Pr,Ce,F). Gd2O2S:Pr,Ce,F is a non-hygroscopic material, emitting green light with short decay time. For the purposes of this study, two scintillating screens with coating thicknesses 35.7 and 71.2 mg/cm2, were prepared in our laboratory from Gd2O2S:Pr,Ce,F powder (Phosphor Technology, Ltd) by sedimentation on silica substrates. The light emitted by the phosphors under investigation was evaluated by performing measurements of the absolute efficiency under X-ray exposure conditions with tube voltages ranging from 50 to 130 kV. Results were compared with previously published data for Gd2O2S:Eu screens. The spectral compatibility of Gd2O2S:Pr,Ce,F with various existing optical detectors, was investigated after emission spectra measurements. Particle size and morphology parameters of the Gd2O2S:Pr,Ce,F powder phosphor were verified via scanning electron microscope (SEM) micrographs. Absolute efficiency was found to maximize at 60 kVp for the 71.2 mg/cm2 and at 90 kVp for the 35.7 mg/cm2 Gd2O2S:Pr,Ce,F screens. Absolute efficiency of the 71.2 mg/cm2 Gd2O2S:Pr,Ce,F screen was higher in the whole X-ray tube voltage range showing potential interest for non-CT medical imaging (i.e. dental radiology) or industrial digital radiography. 相似文献
16.
By using metal nitrates as starting materials, SrAl2B2O7: Tb3+ and SrAl2B2O7: Ce3+, Tb3+ powder phosphors were prepared by sol-gel method. X-ray diffraction (XRD), photoluminescence excitation and emission, as well as kinetic decays were employed to characterize the resulting samples. The results show that energy transfers from Ce3+ to Tb3+ ions. The emission intensity of Tb3+ ions in SrAl2B2O7 could be greatly intensified when Ce3+ ions are doped into SrAl2B2O7: Tb3+. The decay times of SrAl2B2O7: Tb3+ were prolonged when Ce3+ ions were doped. The doping of Ce3+ ions not only improved the luminescent intensity, but also made the materials gets stable luminescent properties. 相似文献
17.
The influence of reducing annealing and repeated oxidizing annealing of the Li2B4O7:Mn single crystals on their thermostimulated luminescence (TSL) and X-ray luminescence (XL) has been studied. Because of the oxygen vacancies formation and the dopant ions reduction, the reducing annealing results in a drastic decrease of the luminescence intensity along with the simultaneous shift of a part of the maxima and redistribution of the peak intensities. The repeated annealing in the oxidizing environment leads only to the partial reduction of the luminescent properties of the Li2B4O7:Mn crystals. 相似文献
18.
We report an effective method to synthesize SrAl2O4:Eu2+,Dy3+ nanosheets. Sheet-like precursors were firstly synthesized by the solvothermal method, and acetate was used as the raw material. Then the final products were obtained by calcinating the precursor in a weak reductive atmosphere of H2. The crystal structure and particle morphology were investigated by X-ray diffraction (XRD) patterns, field-emission scanning electron microscopy and transmission electron microscopy (FE-SEM and TEM) , respectively. A possible growth mechanism was proposed to reveal the formation process. Luminescence properties of the SrAl2O4:Eu2+,Dy3+ long-lasting phosphor were analyzed by measuring the excitation spectra, the emission spectra, the afterglow decay curve and the thermoluminescence curve. Both the photoluminescence (PL) spectra and luminance decay revealed that the phosphors had efficient luminescent and long lasting properties compared with the phosphors prepared by using nitrates as the raw material. Furthermore, the photoluminescence intensity was even a little higher than commercial phosphors. 相似文献
19.
M. Pollnau W. Lüthy H. P. Weber K. Krämer H. U. Güdel R. A. McFarlane 《Applied physics. B, Lasers and optics》1996,62(4):339-344
The influence of Excited-State Absorption (ESA) on the green laser transition and the overlap of Ground-State Absorption (GSA) and ESA for 970 nm upconversion pumping in erbium is investigated in Er3+ : BaY2F8 and Cs3Er2Br9. Results are compared to Er3+ : LiYF4. In Er3+: BaY2F8, a good overlap between GSA and ESA is found at 969 nm in one polarization direction. The emission cross section at 550 nm is a factor of two smaller than in LiYF4. In Cs3Er2Br9, the smaller Stark splitting of the levels shifts the wavelengths of the green emission and ESA from4
I
1 3/2 off resonance. It enhances, however, ground-state reabsorption. The emission cross section at 550 nm is comparable to LiYF4. Upconversion leads to significant green fluorescence from2
H
9/2. A significant population of the4
I
11/2 level and ESA at 970 nm are not present under 800 nm pumping. 相似文献
20.
Lu2SiO5:Ce具有高密度、高光产额、快衰减等优点,是一种性能优异的新型X射线闪烁薄膜材料.本文采用溶胶-凝胶工艺和旋涂技术,以无机盐为原料、2-甲氧基乙醇为溶剂、聚乙二醇(PEG)为改性剂,在石英基片上成功制备出Lu2SiO5:Ce透明薄膜,较为详细地研究了PEG对该薄膜发光性能的影响.结果表明当采用浓度为12.... 相似文献