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1.
A series of Er3+-doped Bi2O3-B2O3-SiO2-Na2O glasses with different hydroxyl groups were prepared and the interaction between the Er3+ ions and OH groups was investigated. Infrared spectra were measured in order to calculate the exact content of OH groups in samples. The observed increase of the fluorescence lifetime with the oxygen bubbling time has been related to the reduction in the OH content concentration evidenced by infrared (IR) absorption spectra, which confirmed that the OH groups were dominant quenching centers of excited Er3+ and a cause of concentration quenching of 1.5 μm band emission. Various nonradiative decay rates from 4I13/2 of Er3+ with the change of OH content were determined from the fluorescence lifetimes and radiative decay rates, which were calculated on the basis of Judd-Ofelt theory.  相似文献   

2.
The comparative investigation on the spectroscopic properties of Er3+ in low phonon energy Bi2O3-GeO2-Ga2O3-Na2O glasses codoped with Ce3+ ion and added with B2O3 component, respectively, is presented. With increasing Ce2O3 content from 0 to 0.8 mol% or B2O3 content from 0 to 15 mol%, the lifetime of Er3+:4I11/2 level decreases dramatically from 607 to 283 μs or to 197 μs, and the upconversion fluorescence is quenched in both glass samples. The nonradiative energy transfer from Er3+:4I11/2→Ce3+:2F5/2 or the enhanced multiphonon relaxation process together with the energy transfer between Er3+ and OH groups are, respectively, responsible for the results. Meanwhile, the lifetime of 4I13/2 level remains almost unchanged in Er3+/Ce3+-codoped glasses whereas it decreases rapidly in B2O3-added cases. As a result, Er3+/Ce3+ codoping improves the 1.5 μm fluorescence emission intensity, however, B2O3 addition has a negative effect on it. The research results indicate that the Er3+/Ce3+-codoped bismuth glasses will be preferable for obtaining efficient 980 nm pumped EDFA.  相似文献   

3.
Exchange charge model of crystal field [B.Z. Malkin, in: A.A. Kaplyanskii, B.M. Macfarlane (Eds.), Spectroscopy of Solids Containing Rare-earth Ions, North-Holland, Amsterdam, 1987, pp. 33-50.] was used to analyze the energy level schemes of Ni2+ ion at both possible positions (octahedral and tetrahedral) in Ca3Sc2Ge3O12. The crystal field parameters were calculated from the crystal structure data; the crystal field Hamiltonian was diagonalised in the complete basis consisting of 25 wave functions of all LS terms of the Ni2+ ion. Results of calculations are in a good agreement with experimental data. From the experimental spectra available in the literature, the Huang-Rhys parameter S=3.5 and effective phonon energy were evaluated for the octahedral Ni2+ ion.  相似文献   

4.
LiBa2B5O10:RE3+ (RE=Dy, Tb and Tm) was synthesized by the method of high-temperature solid-state reaction and the thermoluminescence (TL) properties of the samples under the irradiation of the γ-ray were studied. The result showed that Dy3+ ion was the most efficient activator. When the concentration of Dy3+ was 2 mol%, LiBa2B5O10:Dy3+ exhibited a maximum TL output. The kinetic parameter of LiBa2B5O10:0.02Dy was estimated by the peak shape method, for which the average activation energy was 0.757 eV and the frequency factor was 1.50×107 s−1. By the three-dimensional (3D) TL spectrum, the TL of the sample was contributed to the characteristic f-f transition of Dy3+. The dose-response of LiBa2B5O10:0.02Dy to γ-ray was linear in the range from 1 to 1000 mGy. In addition, the decay of the TL intensity of LiBa2B5O10:0.02Dy was also investigated.  相似文献   

5.
Li2O-Nb2O5-ZrO2-SiO2 glasses mixed with different concentrations of V2O5 were crystallized. The samples were characterized by XRD, SEM and DTA techniques. The SEM pictures indicated that the samples contain well defined and randomly distributed crystal grains. The X-ray diffraction studies have revealed the presence of several crystalline phases in these samples. Optical absorption, ESR and photoluminescence spectral studies on these samples have indicated that a considerable proportion of vanadium ions do exist in V4+ state in addition to V5+ state and the redox ratio seems to be increasing with increase in the concentration of crystallizing agent V2O5. The infrared spectral studies have pointed out the existence of conventional SiO4, ZrO4, NbO6, VO structural units in the glass ceramic network. The study of dielectric properties suggested a decrease in the insulating character of the glass ceramics with increase in the crystallizing agent. A.C. conductivity in the high temperature region seems to be connected mainly with the polarons involved in the process of transfer from V4+↔V5+ ions.  相似文献   

6.
The optical and acoustic properties of tellurite glasses in the system TeO2/ZrO2/WO3 have been investigated. The refractive index at different wavelengths and the optical spectra of the glasses have been measured. From the refractive index and absorption edge studies for prepared glasses, the optical parameter viz; optical band gap (Eopt), Urbach energy, (ΔE), dispersion energy, Ed, and the average oscillator energy, E0, have been calculated. Sound velocities were measured by pulse echo technique. From these velocities and densities values, various elastic moduli were calculated. The variations in the refractive index, optical energy gap and elastic moduli with WO3 content have been discussed in terms of the glass structure. Quantitatively, we used the bond compression model for analyzing the room temperature elastic moduli data. By calculating the number of bonds per unit volume, the average stretching force constant, and the average ring size we can extract valuable information about the structure of the present glasses.  相似文献   

7.
[ ]Cd1−x Mnx Ga2S4 is a semimagnetic semiconductor and it has revealed an exceptional property namely ‘optical activity‘. Therefore, a spectroscopic investigation of chiral absorption bands has been carried out with the view to examine the role of d*-d states of manganese atoms. It has been found that inner transitions of Mn++ dominate the spectral region with a special feature, indicating that these transitions show the presence of a substantial contribution from the magnetic dipole moment which rotates the electric vector of the incident polarized radiation. The origin is associated to the lack of a symmetry center caused by the ordered vacancies in this defect compound.  相似文献   

8.
The pure SrNb2O6 powders were prepared at 1400 °C by a conventional solid-state method and characterized by X-ray powder diffraction and UV-vis diffuse reflection spectrum. The powders of Nb2O5 and SrNb2O6 were ball-milled together and annealed to form the Nb2O5/SrNb2O6 composite. Photocatalytic activities of the composites were investigated on the degradation of methyl orange. The results show that the proportion of Nb2O5 to SrNb2O6 and the annealing temperature greatly influence the photocatalytic activities of the composites. The best photocatalytic activity occurs when the weight proportion of Nb2O5 to SrNb2O6 is 30% and the annealing temperature is 600 °C. The tremendously enhanced photocatalytic activity of the Nb2O5/SrNb2O6 composite compared to Nb2O5 or SrNb2O6 is ascribed to the heterojunction effect taking place at the interface between particles of Nb2O5 and SrNb2O6. The powders also show a higher photocatalytic activity than commercial anatase TiO2.  相似文献   

9.
Transparent Ni2+-doped MgO–Al2O3–SiO2 glass ceramics without and with Ga2O3 were synthetized. The precipitation of spinel nanocrystals, which was identified as solid solutions in the glass ceramics, could be favored by Ga2O3 addition and their sizes were about 7.6 nm in diameter. The luminescent intensity of the Ni2+-doped glass ceramics was largely enhanced by Ga2O3 addition which could mainly be caused by increasing of Ni2+ in the octahedral sites and the reduction of the mean frequency of phonon density of states in the spinel nanocrystals of solid solutions. The full width at half maximum (FWHM) of emissions for the glass ceramics with different Ga2O3 content was all more than 200 nm. The emission lifetime increased with the Ga2O3 content and the longest lifetime is about 250 μs. The Ni2+-doped transparent glass ceramics with Ga2O3 addition have potential application as broadband optical amplifier and laser materials.  相似文献   

10.
Dielectric properties, viz. dielectric constant ε′, loss tan δ and a.c conductivity σac (over a wide range of frequency and temperature) and dielectric breakdown strength of PbO-Sb2O3-As2O3 glasses doped with V2O5 (ranging from 0 to 0.5 mol%) are studied. Analysis of these results, based on optical absorption and ESR spectra, indicates that the insulating strength of the glasses is comparatively high when the concentration of V2O5 is about 0.3 mol% in the glass matrix.  相似文献   

11.
The MgO-Ga2O3-SiO2 glass-ceramic (GC) containing MgGa2O4 nanocrystals and glasses doped with Eu3+ ions were prepared by the sol-gel method. The down-conversion and up-conversion luminescence (UCL) properties were studied. The results indicated that the relative intensity of f-f transitions of Eu3+ decreased in contrast with that of charge transfer (CT) absorption with the increase in heating temperature. Using a Xe lamp and 800 nm femtosecond (fs) laser excitation, strong red luminescence of Eu3+ in MgO-Ga2O3-SiO2 glasses and GC was observed.  相似文献   

12.
This paper reports the emission analysis of green-emitting Tb3+-doped MgAl2O4 phosphors. Uniformity of the phase of the Tb3+-doped MgAl2O4 phosphor has been checked by X-ray diffraction (XRD) technique and show common bands existing in the results of Fourier transform infrared (FT-IR). This phosphor exhibits weak blue, orange emissions and a strong emission at λexci=350 nm. The blue and green-orange emissions are ascribed to 5D37FJ and 5D47FJ (where J=3-6) transitions of Tb3+ ions, respectively. These phosphors have shown a strong, more prominent green emission from 5D47F5 at 543 nm. The results have indicated that MgAl2O4:Tb3+ could be a potential candidate as agreen-emitting powder phosphor.  相似文献   

13.
Temperature behaviour of optical absorption edge in Cu6PS5I1−xBrx mixed crystals is studied in the interval 77-325 K. It is shown that the absorption edge has Urbach shape in the 215-325 K temperature interval. The influence of temperature and compositional disorder on the Urbach absorption edge parameters is presented. The mechanism of the Urbach bundle formation and the effect of I→Br anionic substitution on the exciton-phonon interaction parameters is elucidated.  相似文献   

14.
Erbium and ytterbium codoped double tungstates NaY(WO4)2 crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290-2000 nm have been recorded at room temperature. The Judd-Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er3+ ions in NaY(WO4)2 crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb3+ to Er3+ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels.  相似文献   

15.
The optical phonon spectrum of the semiconductor Cu2SnTe3, that crystallizes in the orthorhombic structure with space group Imm2 (), have been studied by measuring unpolarized Raman scattering between 10 and 300 K. The experimental frequencies of the phonon modes observed were compared to those calculated by using simplified lattice dynamical models reported in the literature. From combined analysis of these results together with the factor group analysis of the zone-center vibrational modes, valuable information about these modes was obtained and their possible symmetry was assigned. A1 modes at 71, 123, 167, 176 and 190 cm−1; A2 modes 115 and 131 cm−1; B1 modes at 76, 142 and 152 cm−1; B2 modes at 89, 100 and 206 cm−1; a overtone at 246 cm−1, and combinations at 218, 270 and 292 cm−1; have been observed in this compound.  相似文献   

16.
Preparation of Cu2ZnSnS4 thin films by hybrid sputtering   总被引:2,自引:0,他引:2  
In order to fabricate Cu2ZnSnS4 thin films, hybrid sputtering system with two sputter sources and two effusion cells is used. The Cu2ZnSnS4 films are fabricated by the sequential deposition of metal elements and annealing in S flux, varying the substrate temperature. The Cu2ZnSnS4 films with stoichiometric composition are obtained at the substrate temperature up to 400 °C, whereas the film composition becomes quite Zn-pool at the substrate temperature above 450 °C. The Cu2ZnSnS4 film shows p-type conductivity, and the optical absorption coefficient and the band gap of the Cu2ZnSnS4 film prepared in this experiment are suitable for fabricating a thin film solar cell.  相似文献   

17.
Variable angle spectroscopic ellipsometry has been applied to characterize the optical constants of bulk Cu(In0.7Ga0.3)5Se8 and Cu(In0.4Ga0.6)5Se8 crystals grown by the Bridgman method. The spectra were measured at room temperature over the energy range 0.8-4.4 eV. Adachi’s model was used to calculate the dielectric functions as well as the spectral dependence of complex refractive index, absorption coefficient, and normal-incidence reflectivity. The calculated data are in good agreement with the experimental ones over the entire range of photon energies. The parameters such as strength, threshold energy, and broadening, corresponding to the E0, E1A, and E1B interband transitions, have been determined using the simulated annealing algorithm.  相似文献   

18.
Room temperature photoluminescence quantum efficiency of the alloy of Ca1−xEuxGa2S4 was measured as a function of x, and was found to be nearly unity under excitation at peak wavelength of excitation spectrum (510 nm) in the x range of 0.01≤x≤0.2. At larger x values, it tends to decrease, but still as high as 30% for stoichiometric compound EuGa2S4. Taking these backgrounds into account, pump-probe experiments were done with Ca1−xEuxGa2S4 for searching optical gain at x=0.2. The optical gain of nearly 30 cm−1 was confirmed to exist, though the pumping induced transient absorption which seems to limit the higher gain was found.  相似文献   

19.
J. Feng  B. Xiao  J.C. Chen  C.T. Zhou  Y.P. Du  R. Zhou   《Solid State Communications》2009,149(37-38):1569-1573
AgCuO2 and Ag2Cu2O3 are new types of semiconductor materials. A theoretical study is presented for both the electronic and optical properties of these new photovoltaic materials in the framework of density functional theory (DFT). The calculated cohesive energy is −3.606 eV/atom and −3.723 eV/atom for Ag2Cu2O3 and AgCuO2, respectively. Electronic calculations indicate that AgCuO2 is a small band gap semiconductor and Ag2Cu2O3 is metallic in nature. The valency state of Cu is divalent in Ag2Cu2O3 and trivalent in AgCuO2. The largest absorption coefficient of CuO2 is 332 244, which is significantly greater than that of CuInSe2, CdTe, GaAs, etc.  相似文献   

20.
Nanostructured europium-doped yttrium oxide thin films with lithium as a co-dopant were prepared using pulsed laser ablation technique. X-ray diffraction studies of the films indicated amorphous nature of the as deposited films and a transformation to crystalline phase with increase of annealing temperature. In this transformation, lithium co-doped films showed early crystallization. Lithium substitution resulted not only in enhancement of photoluminescence at 612 nm, resulting from 5D0-7F2 transition within europium, but also found to reduce the required processing temperature for intense photoemission. The deviation observed in the value of lattice constant of films annealed at different temperatures is found to be sensitive to annealing temperature. In the light of this, the dependence of photoluminescence intensity on the magnitude of lattice imperfection is also discussed. The morphology and transmittance of the films are also found to be sensitive to annealing process and lithium doping.  相似文献   

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