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1.
The effects of Tb doping on the photoluminescence (PL) of Y2O3:Tb nanophosphors have been investigated. Nanophosphors were prepared by the glycine-nitrate solution combustion technique using yttria and terbia powders as precursors. PL excitation spectra at room temperature consist of two overlapping bands centered at 277 and 304 nm, whereas emission spectra comprise several groups of lines corresponding to the 5D47FJ (J=1-6) 4f electronic transitions of the Tb+3 ions. A direct comparison of nanophosphor and bulk concentration-quenching curves was obtained by annealing the nanophosphor powder and converting it to bulk material without altering the Tb concentration. The peak in the nanophosphor concentration-quenching curve occurs at a concentration ∼3 times higher than that of the bulk.  相似文献   

2.
Nanocrystalline Y2Si2O7:Eu phosphor with an average size about 60 nm is easily prepared using silica aerogel as raw material under ultrasonic irradiation and annealing temperature at 300-600 °C and this nanocrystalline decomposes into Y2O3:Eu and silica by heat treatment at 700-900 °C. The excitation broad band centered at 283 and 254 nm results from Eu3+ substituting for Y3+ in Y2Si2O7 and Y2O3/SiO2, respectively. Compared with Y2O3:Eu/SiO2 crystalline, the PL excitation and emission peaks of Y2Si2O7:Eu nanocrystalline red-shift and lead to the enhance of its luminescence intensity due to the different chemical surroundings of Eu3+ in above nanocrystallines. The decrease of PL intensity may be ascribed to quenching effect resulting from more defects in Y2O3:Eu/SiO2 crystalline.  相似文献   

3.
采用溶液反应和固相反应合成了CaF2:Ce,Tb和AlF3:Ce,Tb磷光体,研究了它们的光谱特性,结果发现,在CaF:Ce,Tb和AlF3:Ce,Tb中Ce^3+对Tb^3+的能量传递不能有效进行,有时Tb^3+甚至对Ce^3+起猝灭作用。  相似文献   

4.
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   

5.
The luminescence properties of Ce3+ in La3F3[Si3O9] are reported. Excitation and emission bands corresponding to 4f1→5d1 transitions of Ce3+ were identified. The center of gravity of the 5d states lies at remarkable high energy (43.2×103 cm−1) for Ce3+ in a silicate compound. This high value is attributed to the combined oxygen/fluoride coordination of the Ce3+ ion. Emission from the lowest 4f5d level to the 2F5/2 and 2F7/2 levels was found at 32.4×103 and 30.4×103 cm−1. These results are compared with literature data on silicates and fluorides. From the values found for Ce3+, predictions are made for the positions of the 4f5d bands of Pr3+ and Er3+ in La3F3[Si3O9]. For both ions, it is concluded that in this host lattice emission is expected from high lying 4fn energy levels.  相似文献   

6.
Oxonitridosilicate phosphors with compositions of (Y1−xCex)2Si3O3N4 (x=0−0.2) have been synthesized by solid state reaction method. The structures and photoluminescence properties have been investigated. Ce3+ ions have substituted for Y3+ ions in the lattice. The emission and excitation spectra of these phosphors show the characteristic photoluminescence spectra of Ce3+ ions. Based on the analyses of the diffuse reflection spectra and the PL spectra, a systematic energy diagram of Ce3+ ion in the forbidden band of sample with x=0.02 is given. The best doping Ce content in these phosphors is ∼2 mol%. The quenching temperature is ∼405 K for the 2 mol% Ce content sample. The luminescence decay properties were investigated. The primary studies indicate that these phosphors are potential candidates for application in three-phosphor-converted white LEDs.  相似文献   

7.
Crystalline Y2O3:Eu is of paramount significance in rare earth materials and research on luminescence spectra. In this work, the nanocrystalline Y2O3:Eu was coated with silica by a facile solid state reaction method at room temperature. The transmission electron microscope (TEM) photographs showed that the prepared Y2O3:Eu particle is polycrystalline with the size of 20 nm, the size of silica-coated particle is about 25 nm. The XPS spectra indicated that the silica layer is likely to interact with Y2O3:Eu by a Si-O-Y chemical bond. The luminescence spectra showed that the intensity of ground samples is lower than that of unground ones, the intensity of silica-coated phosphors is higher than that of the ground samples, while almost the same as that of the unground ones. Therefore, the silica coating decreases the surface defects of nanoparticles of the nanocrystalline Y2O3:Eu, thus increasing their luminescent intensity.  相似文献   

8.
Europium-doped yttrium oxide phosphors were obtained by firing precursors prepared by urea precipitation in ethanol and ethylenediamine. The precipitation in non-aqueous solution was carried out in an autoclave at 150°C to allow the decomposition of urea. The photoluminescent intensities of the phosphors prepared in ethanol and ethylenediamine increased by about 30% compared to that of the phosphor prepared by the conventional urea homogeneous precipitation in aqueous solution. Amorphous carbonates and amorphous hydroxides/carbonates mixtures were identified as precursors from ethanol and ethylenediamine, respectively. The morphology and particle size were studied by SEM and dynamic laser scattering method.  相似文献   

9.
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   

10.
The phosphors in the system Y3−xAl5-yO12:xCe3+,yCr3+ were synthesized by solid-state reactions and their photoluminescence properties were investigated. These phosphors have absorption in the visible light region and give luminescence in the far-red region (∼688 nm), which are suitable for the application in the device of luminescent solar concentrator (LSC). In these phosphors, Ce3+ located at Y3+ site can effectively transfer its absorbed energy to Cr3+ at Al3+ site.  相似文献   

11.
A coating method with precipitating process was developed to reduce the particle size and to improve the particle dispersion of Y3Al5O12:Tb3+ phosphor prepared by sol-gel method. The particle morphology was observed by using SEM and TEM; and the particle size and its dispersion was measured by using laser scattering technique. Several coating materials were tested. Among them, Al2(SiO3)3 coating not only reduced the particle size from several micrometers to ∼1 μm and improved the particle dispersion, but also well kept luminescent intensities and improved the duration of the phosphor under the bombardment of cathode ray. The mechanism of the particle size reduction was proposed.  相似文献   

12.
Eu2O3-doped yttrium oxide (3 mol%) [Y2O3:Eu(3 mol%)] with wire-like and near-spherical morphologies were prepared by a solvothermal treatment using water, ethanol, ethylene glycol and glycerol as reaction media followed by calcination. The powders prepared in water and ethanol possessed wire structure, where the powder treated in water showed high aspect ratio and that in ethanol showed low aspect ratio. The powders prepared in ethylene glycol and glycerol possessed well-dispersed near-spherical powders, which showed almost the same level of photoluminescence emission intensity as that of submicron particles prepared without solvothermal treatment.  相似文献   

13.
Thin Er3+, Yb3+ co-doped Y2O3 films were grown on (1 0 0) YAG substrates by pulsed laser deposition. Ceramic targets having different active ion concentration were used for ablation. The influence of the rare-earth content and oxygen pressure applied during the deposition on the structural, morphological and optical properties of the films were investigated. The films deposited at the lower pressure, 1 Pa, and at 1/10 Er to Yb doping ratio are highly textured along the (1 1 1) direction of the Y2O3 cubic phase. In addition to the crystalline structure, these films possess smoother surface compared to those prepared at the higher pressure, 10 Pa. All other films are polycrystalline, consisting of cubic and monoclinic phases of Y2O3. The rougher surface of the films produced at the higher-pressure leads to higher scattering losses and different behavior of the reflectivity spectra. Optical anisotropy in the films of less than 0.004 was measured regardless of the monoclinic structure obtained. Waveguide losses of about 1 dB/cm at 633 nm were obtained for the films produced at the lower oxygen pressure.  相似文献   

14.
Y2O3:Eu纳米晶中能量传递相互作用的研究   总被引:4,自引:0,他引:4       下载免费PDF全文
通过浓度猝灭曲线确定了引起Y2O3纳米晶中Eu3+发光浓度猝灭的是交换相互作用.测量了两种颗粒尺寸下Eu3+5D07F2跃迁发光衰减曲线随掺杂浓度的变化,利用交换相互作用的理论衰减曲线对实验衰减曲线进行拟合.计算Eu3+离子的交换相互作用能量传递的效率,分析了Y2O3关键词: 能量传递 2O3Eu纳米晶')" href="#">Y2O3Eu纳米晶 发光衰减  相似文献   

15.
Physical and electrical properties of sputtered deposited Y2O3 films on NH4OH treated n-GaAs substrate are investigated. The as-deposited films and interfacial layer formation have been analyzed by using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). It is found that directly deposited Y2O3 on n-GaAs exhibits excellent electrical properties with low frequency dispersion (<5%), hysteresis voltage (0.24 V), and interface trap density (3 × 1012 eV−1 cm−2). The results show that the deposition of Y2O3 on n-GaAs can be an effective way to improve the interface quality by the suppression on native oxides formation, especially arsenic oxide which causes Fermi level pinning at high-k/GaAs interface. The Al/Y2O3/n-GaAs stack with an equivalent oxide thickness (EOT) of 2.1 nm shows a leakage current density of 3.6 × 10−6 A cm−2 at a VFB of 1 V. While the low-field leakage current conduction mechanism has been found to be dominated by the Schottky emission, Poole-Frenkel emission takes over at high electric fields. The energy band alignment of Y2O3 films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y2O3/n-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively.  相似文献   

16.
Low thermal quenching and high-efficiency Ca3Sc2Si3O12:Ce3+ (CSSO:Ce3+) phosphors with co-doping Tb3+ ion were prepared by a solid state method and the properties of these phosphors were investigated. The results showed that co-doping of Tb3+ not only enhances the photoluminescence remarkably and decreases the thermal quenching of the phosphor, but also heightens the performances of the LEDs fabricated with the phosphor. A high-efficiency and low color temperature white LED was fabricated with the prepared CSSO:1%Ce3+, 0.5%Tb3+ and a red phosphor, indicating that CSSO:1%Ce3+,0.5%Tb3+ phosphor is a suitable green phosphor for the fabrication of high-efficiency white LEDs.  相似文献   

17.
The 4f energy levels and crystal-field parameters for several clusters representing the local coordination surroundings of Eu3+ in the bulk and nanocrystalline cubic Y2O3: Eu3+ crystals are obtained by using a method based on the combination of the DV-Xα calculation and the effective Hamiltonian method initialized by M.F. Reid et al. (J. Phys.: Condens. Matter, 2011, 23: 045501). The results are in reasonable agreement with the measured energy levels and the crystal-field parameters obtained from the least-square fitting. The charge transfer energies are also obtained for all the clusters from the DV-Xα calculation. The results indicate that, compared with the bulk Y2O3: Eu3+ crystal, the charge transfer band in the excitation spectra is red-shifted in the nanocrystal.  相似文献   

18.
In this paper, Y2O3 powder phosphors without metal activators were successfully prepared by the sol-gel method. The obtained sample shows an intense bluish-white emission (ranging from 350 to 600 nm, centered at 416 nm) under a wide range of UV light excitation (235-400 nm). The chromaticity coordinates of the sample are x=0.159, y=0.097, and the quantum yield is as high as 64.6%, which is a high value among the phosphor family without metal activators. The luminescent mechanisms have been ascribed to the carbon impurities in the Y2O3 host.  相似文献   

19.
The degradation of the cathodoluminescence (CL) intensity of cerium-doped yttrium silicate (Y2SiO5:Ce) phosphor powders was investigated for possible application in low voltage field emission displays (FEDs). Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and CL spectroscopy were used to monitor changes in the surface chemical composition and luminous efficiency of commercially available Y2SiO5:Ce phosphor powders. The degradation of the CL intensity for the powders is consistent with a well-known electron-stimulated surface chemical reaction (ESSCR) model. It was shown with XPS and CL that the electron stimulated reaction led to the formation of a luminescent silicon dioxide (SiO2) layer on the surface of the Y2SiO5:Ce phosphor powder. XPS also indicated that the Ce concentration in the surface layer increased during the degradation process and the formation of CeO2 and CeH3 were also part of the degradation process. The CL intensity first decreased until about 300 C cm−2 and then increased due to an extra peak arising at a wavelength of 650 nm.  相似文献   

20.
In this work, the complete matrix of optical spectral levels in trigonal symmetry of 3d2 (3d8) ions are established on basis of strong field coupling mechanism by using two spin–orbit coupling parameters model. The contribution of the spin–orbit coupling of ligand to the optical spectra has been included in these formulas. As an application, the optical spectra of Cr4+ in Y2Ti2O7 and Y2Sn2O7 have been studied by the complete diagonalization (energy matrix) method. The covalent effect has been studied and the difficulty about Dq parameter in explanation of optical spectra of Cr-doped Y2Ti2O7 and Y2Sn2O7 is removed. The theoretical results are in good agreement with observed data.  相似文献   

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