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1.
U. Köbler 《Zeitschrift für Physik A Hadrons and Nuclei》1972,250(3):217-227
The concentration dependence of the energy transfer from the Eu3+ ions at lattice sites of point symmetryC 3 i to the Eu3+ ions at lattice sites of point symmetryC 2 in Y2O3 has been investigated by analyzing the nonexponential fluorescence decay curves of the donors measured after excitation by a short optical light pulse. The simple model of a fixed interaction rangeR 0 proved to be adequate to explain the experimental observations. An interaction range ofR 0=8.7 Å was found in agreement with previous steady state experiments. 相似文献
2.
J. Heber K. H. Hellwege U. Köbler H. Murmann 《Zeitschrift für Physik A Hadrons and Nuclei》1970,237(3):189-204
Besides the known energy levels of Eu3+ at lattice sites of symmetryC 2 in Y2O3, some transitions of this ion at lattice sites of symmetryC 3i in the same host crystal have been found and it was possible to construct the energy level scheme in part. Evidence for an energy transfer from Eu3+(C 3i ) to Eu3+(C 2) is given, the strength of which is measured as a function of the Eu2O3 concentration. The results lead to the assumption of a fixed distanceR 0 for the interaction responsible for the energy transfer. A temperature-independent value ofR 0=8.7 Å was found. The full explanation of the underlying quantum mechanical mechanism requires further experiments. 相似文献
3.
Dr. G. Schäfer 《Zeitschrift für Physik B Condensed Matter》1969,9(4):359-366
The paramagnetic resonance of trivalent Er and Ce in single crystals of Y2O3 on sites of crystal field symmetryC 3i andC 2 is investigated at 9.5 kMe/s. For Er3+ ions completing results to formerly published data are given. For Ce: Y2O3 the measured values of theg-tensors are:g ‖=0.394 andg ⊥=1.633 forC 3i -sites andg z =0,g x =2.938,g y =0.819 forC 2-sites. For ions on sites of symmetryC 2 the principal axesx andy ofg are tilted 29.7° against the [100] directions. 相似文献
4.
《Journal of luminescence》1987,37(3):159-165
The selective laser excitation of the flourescence of Eu3+ ions is used to investigate the defect sites in BaF2:Eu3+ for Eu3+ concentrations ranging from 0.03 to 2.43 mol%. We identified the fluorescence lines arising from the (Eu3+, F-i) dipole of C3v symmetry and established its energy level diagram. The compensating ion is an interstitial F-i ion located in the next-nearest-neighbour site, with respect to the Eu3+ ion. This (Eu3+, F-i) dipole dominates in BaF2. Fluorescence lines assignable to next-nearest-neighbour pairs of (Eu3+, F-i) dipoles have been found above 0.1 mol% dopant concentration. 相似文献
5.
《Journal of luminescence》1987,37(1):9-20
The Eu3+ ion occupies two different crystallographic sites in (Y1−xEux)2O3 and (Gd1−xEux)2O3, with site symmetry S6 and C2. Energy transfer over more than 7 Å occurs from Eu3+ (S6) ions to Eu3+ (C2) ions. This is shown to be a direct one-phonon assisted process, in combination with a one-site resonant two-phonon assisted process at higher temperatures. For x = 1 there is energy migration over the Eu3+ (C2) sublattice to quenching impurities. The presence of cooperative absorption points to superexchange interaction between the Eu3+ ions. 相似文献
6.
The photoluminescence (PL) property of Y2MoO6:Eu3+ doped with Li+ is investigated in this paper. The red luminescence of Eu3+ in Y2MoO6 lattice has greatly enhanced by codoping monovalent alkali metal ions Li+ into the lattice. The drastic increase in the luminescence intensity of Y2?xLixMoO6:Eu3+ originates from the reason that the Li+ ions may serve as a self-promoter for better crystallization to reduce the defect or as a lubricant for the complete incorporation of the Eu3+ ions into the Y2MoO6 host. 相似文献
7.
Low-temperature, dye-laser excitation spectroscopy of commercial Y2O3:Eu3+ phosphors reveals the presence of complex structure in the excitation lines of the 5D0 and 5D1 manifolds. The structure is associated with the presence of Eu3+ ion pairs. The kinetics of the emission decay are observed to be drastically different when excitation occurs either at the center or on the wings of the excitation lines, suggesting faster inter-level and/or inter-site energy transfer on exciting into the line wings. Low-temperature vibronic spectra are reported for the 7F0→5D0 transitions for both C2 and C3i sites. Evidence is presented for the detection of the highly forbidden 7F0→5D0 transition for the C3i site. 相似文献
8.
Atul D. Sontakke 《Physica B: Condensed Matter》2009,404(20):3525-3529
Photoluminescence properties of Bi3+ co-doped Eu3+ containing zinc borate glasses have been investigated and the results are reported here. Bright red emission due to a dominant electric dipole transition 5D0→7F2 of the Eu3+ ions has been observed from these glasses. The nature of Stark components from the measured fluorescence transitions of Eu3+ ions reveal that the rare earth ions could take the lattice sites of Cs or lower point symmetry in the zinc borate glass hosts. The significant enhancement of Eu3+ emission intensity by 346 nm excitation (1S0→3P1 of Bi3+ ions) elucidates the sensitization effect of co-dopant. The energy transfer mechanism between sensitizer (Bi3+) and activator (Eu3+) ions has been explained. 相似文献
9.
Eu3+ doped ZnO nanoparticles are known to have significance extent of surface Eu3+ ions due to a large difference in ionic radii. Effect of such Eu3+ ions on the luminescence properties of ZnO:Eu nanoparticles has been understood from the luminescence studies of ZnO:Eu nanoparticles covered with Y2O3 shell. Based on the asymmetric ratio of luminescence and extent of energy transfer, it is established that when ZnO:Eu nanoparticles are covered with Y2O3 shell, a part of Eu3+ ions present with ZnO:Eu core migrate to Y2O3 shell and occupy Y3+ lattice positions. 相似文献
10.
The red-emitting Y0.65−xGd0.25MxBO3:0.10Eu3+ (M=Li, Na, K 0.00≤x≤0.10) phosphors were synthesized by solid-state reaction and their photoluminescence characteristics were studied under vacuum ultraviolet (VUV) excitation. The emission intensity is significantly improved by adding alkali metal ions dopants because they introduce some bounded electron−hole pairs, which act as an intermediator for the excitation energy transfer from the host lattice to the activator Eu3+. The chromaticity was improved due to the distorted surrounding of Eu3+. The emission intensity of the Y0.65−xGd0.25 MxBO3:0.10Eu3+ increased up to maximum with alkali metal ions doped to a certain concentration and then decreased with the increase in of alkali metal dopants. 相似文献
11.
《Current Applied Physics》2014,14(1):72-81
Undoped and Eu3+-doped cubic yttria (Y2O3) nanophosphors of good crystallinity, with selective particle sizes ranging between 6 and 37 nm and showing narrow size distributions, have been synthesized by a complex-based precursor solution method. The systematic size tuning has been evidenced by transmission electron microscopy, X-ray diffraction, and Raman scattering measurements. Furthermore, size-modulated properties of Eu3+ ions have been correlated with the local structure of Eu3+ ion in different sized Y2O3:Eu3+ nanophosphors by means of steady-state and time-resolved site-selective laser spectroscopies. Time-resolved site-selective excitation measurements performed in the 7F0 → 5D0 peaks of the Eu3+ ions at C2 sites have allowed us to conclude that Eu3+ ions close to the nanocrystal surface experience a larger crystal field than those in the nanocrystal core. Under the site-selective excitation in the 7F0 → 5D0 peaks, energy transfer between the sites has also been observed. 相似文献
12.
Control of photoluminescence in Ca3–3x /7Y2x /7(PO4)2:Eu2+ phosphors by migration of the dopant
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A series of Ca3–3x /7Y2x /7(PO4)2:Eu2+ phosphors were synthesized by conventional solid‐state reaction. The photoluminescence spectra elucidate that the evolution of emission hue from violet–blue to blue–greenish could be realized by incorporating Y3+ ions. The aliovalent substitution of Y3+ for Ca2+ forms cationic vacancies (h denotes a vacancy) at Ca(4) site according to the formula 3Ca2+ = 2Y3+ + h, and then facilitates the migration of dopant Eu2+ from Ca(4) site to other sites in host lattice. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
13.
The spectral distributions of the visible absorption and fluorescence emission under electron beam excitation of Eu3+-doped (Y2O3) and (YVO4) powders have been detected and analyzed. (Y2O3: Eu3+) has a cubicC crystal structure with a unit cell dimension a=10·61 Å. Its observed transitions from7
F
0 to many upper states have been recognized; the observed number of Stark components is in agreement with that based on theC
2 site symmetry of the Eu3+ ion in Y2O3. Eu3+-doped yttrium vanadate has a typical zircon tetragonal crystal structure with unit cell dimensions ofc=6·29 Å anda=7·11 Å. The observed transitions in (Eu3+: YVO4) have been identified and assigned in accordance with theD
2d site symmetry of the Eu3+ ion in this lattice.The authors would like to express their deep gratitude to Professor G. F. J.Garlick, University of Hull, England, for offering experimental facilities in his Physics Department. 相似文献
14.
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
15.
《Infrared physics》1978,18(5-6):901-908
Far-infrared measurements (17–170 cm−1) are reported for SrF2:RE3+ (RE = Pr, Nd, Tb, Dy, Ho, Er, Tm).The vibrations of the F−i compensation ions reveal the local symmetry (Oh, C4v, C3v). The concentration of ions in each local site and the frequencies of the F−i vibrations in the C4v site show a regular evolution vs RE ionic radii.The study of electronic transitions within the ground manifold of the RE ions shows a similar evolution. For Dy3+ we detect lines already attributed to C3v (F−i) sites. New lines observed with Er3+ and Dy3+ can be attributed to C4v (F−i) sites, and the crystal field parameters that we have calculated are close to those of the C4v (F−i) site in CaF2.For Nd3+ the electronic line is close to a C4v level observed by EPR. 相似文献
16.
《Current Applied Physics》2015,15(6):748-752
Eu3+-doped Ba0.7Sr0.3TiO3 thin films were prepared by a chemical solution deposition method and characterized by X-ray diffraction, field emission scanning electron microscopy, photoluminescence and dielectric measurements. The thin films were well crystallized with a pure perovskite structure. A contraction of the unit cell was observed upon incorporation of Eu3+ ions below 2 mol%, while an expansion occurred as the Eu3+ concentration was further increased above 2 mol%, indicating that Eu3+ ions with different concentrations occupied different lattice sites. Photoluminescence spectra showed two prominent transitions of Eu3+ ions at 594 nm (5D0 → 7F1) and 618 nm (5D0 → 7F2) upon excitation at 395 nm (7F0 → 5L6). There existed two quenching concentrations at 2 mol% and 4 mol% due to different lattice sites of the Eu3+ ions. We also investigated the dielectric properties of the thin films. Our study suggests that Eu3+-doped Ba0.7Sr0.3TiO3 thin films have potential applications in multifunctional optoelectronic devices. 相似文献
17.
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
18.
The emission spectra and decay times of the Y2O3 CO-doped with Bi3+ and Eu3+ have been investigated using site-selective excitation and time-resolved spectroscopy in the temperature range 8–296 K. Evidence for an energy transfer from Eu3+(S6) to Eu3+(C2) is given. The critical transfer distance R0 = 8.6 Å was found from the decay curve. 相似文献
19.
20.
Y2O3:Eu3+ phosphor films have been developed by using the sol-gel process. Comprehensive characterization methods such as Photoluminescent (PL) spectroscopy, X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy were used to characterize the Y2O3:Eu3+ phosphor films. In this experiment, the XRD profiles show that the Y2O3:Eu3+ phosphor films crystallization temperature and optimum annealing temperature occur at about 650 and 750 °C, respectively. The optimum dopant concentration is 12 mol% Eu3+ and the critical transfer distance (Rc) among Eu3+ ions is calculated to be about 0.84 nm. Vacuum environment is more efficient than oxygen and nitrogen to eliminate the OH content and hence yields higher luminescent phosphor films. The PL emission intensity of Y2O3:Eu3+ phosphor films is also dependent on the annealing time. It was found that the H2O impurities were effectively eliminated after annealing time of 25 s at 750 °C in vacuum environment. From the experiment results, the schematic energy band diagram of Y2O3:Eu3+ phosphor films is constructed. 相似文献