共查询到20条相似文献,搜索用时 15 毫秒
1.
K.M. Nissamudeen 《Journal of Physics and Chemistry of Solids》2009,70(5):821-325
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
2.
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
3.
Botao Wu Shifeng Zhou Jinjun Ren Yanbo Qiao Danping Chen Congshan Zhu Jianrong Qiu 《Journal of Physics and Chemistry of Solids》2008,69(4):891-894
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
4.
G. Cabello L. Lillo B. Chornik R. del Río 《Journal of Physics and Chemistry of Solids》2010,71(9):1367-1372
Thin films of ZrO2 loaded with 10, 30 and 50 mol% Sm were prepared by a photochemical method using thin films of metal acetylacetonate complexes as precursors. The photolysis of these films induces the fragmentation of the acetylacetonate ligand and the partial reduction of metal ion together with volatile organic compounds. When the metallic complex is exposed to air, the product of the reaction is metal oxide. The photoreactivity of these films was monitored by FT-IR spectroscopy, followed by a post-annealing treatment process. The obtained films were characterized by X-ray photoelectron spectroscopy and atomic force microscopy.Photoluminescense studies of the films employed 400 nm radiation for excitation of the Sm ions present. The emission spectra showed signals arising from the 4G5/2→6HJ (J=3/2, 7/2, 9/2) transitions, where the 4G5/2→6H3/2 transition has the highest intensity. The concentration dependence of the PL intensity was also studied. A maximum PL intensity was observed with 10 mol% Sm content but then diminished with higher Sm concentrations. 相似文献
5.
Qiuhua Nie Tiefeng Xu Xiang Shen Xudong Zhang 《Journal of Physics and Chemistry of Solids》2007,68(4):477-481
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
6.
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
7.
This paper reports the growth and optical properties of Eu2+/Li+-co-doped SrB4O7 single crystals. High-quality Eu,Li:SrB4O7 crystals without macro-defects or cracks were grown using the top-seeded solution growth (TSSG) method. The absorption and luminescent properties were measured and different spectra were observed in the as-grown crystals. As the doping amount of lithium increases, the absorption peak at 300 nm becomes stronger and the emission peak shifts to a longer wavelength. This phenomenon could be attributed to the doping lithium ions, which might affect the electric field distribution in the lattice structure. 相似文献
8.
Shaoxuan Gu Zhijun Ma Changgui Lin Xiujian Zhao Yueqiu Gong 《Journal of Physics and Chemistry of Solids》2008,69(1):97-100
Utilizing Maker fringe (MF) method, second-harmonic generation (SHG) has been observed within the GeS2-Ga2S3-CdS pseudo-ternary glasses through thermal/electrical poling technique. The SHG phenomenon was considered to be the result of breakage of the glassy macroscopic isotropy originated from the reorientations of dipoles during the thermal/electrical poling process. Under the same poling condition conducted with 5 kV and 280 °C for 30 min, the maximum value of second-order nonlinear susceptibility χ(2) of the poled (100−x)GeS2·x(0.5Ga2S3·0.5CdS) glasses was obtained to be ≈4.36 pm/V when the value of x is equal to 30. Nonlinear dependence of χ(2) on compositions of these glasses can be well explained according to the theory related to the reorientation of dipoles. 相似文献
9.
Vesna Đorđević Željka AntićMarko G. Nikolić Miroslav D. Dramićanin 《Journal of Physics and Chemistry of Solids》2014
Eu3+-doped La2O3 nanocrystalline powder was prepared by polymer complex solution method and further used for preparation of Eu3+-doped La(OH)3. Structural and optical characterization was carried out by powder X-ray diffraction and photoluminescent spectroscopy. XRD measurements confirmed the formation of hexagonal La2O3 and its recrystallization into La(OH)3 in a humid atmosphere. Excitation spectra show redshift of host lattice and charge transfer emission bands in La(OH)3 while bands that correspond to Eu3+f–f transitions are placed at same wavelengths in both samples. Photoluminescence spectra recorded over the temperature range from 10 K to 300 K show that intensities of emission lines in Eu3+-doped La2O3 do not depend on temperature as much as in La(OH)3 sample. Observed dominant 5D0→7F2 and markedly visible 5D0→7F0 emissions in doped La2O3 indicate that Eu3+ ion is located in a structural site without an inversion center. On the other hand, in Eu3+-doped La(OH)35D0→7F0 transition is barely visible while 5D0→7F2 is not prominent, and with temperature drop three 5D0→7FJ (J=1, 2, 4) transitions become almost of the same intensity. In both La2O3 and La(OH)3 structures Eu3+ ion replaces La3+ in non-centrosymmetric C3v and C3h crystallographic sites, respectively, and difference in symmetry of the crystal field around europium ion is explained by comparing shape and volume of these sites. Decay times of the 5D0- level recorded over the temperature range 10−300 K revealed that emission lifetime values in La2O3 (~0.7 ms) are almost two times higher than in La(OH)3 (~0.4 ms), and unlike in La2O3, lifetime in La(OH)3 is temperature dependent. 相似文献
10.
I. Omkaram 《Journal of Physics and Chemistry of Solids》2008,69(8):2066-2069
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 5D3→7FJ and 5D4→7FJ (where J=3-6) transitions of Tb3+ ions, respectively. These phosphors have shown a strong, more prominent green emission from 5D4→7F5 at 543 nm. The results have indicated that MgAl2O4:Tb3+ could be a potential candidate as agreen-emitting powder phosphor. 相似文献
11.
M.E. Sánchez Vergara A. Ortiz Rebollo M. Rivera 《Journal of Physics and Chemistry of Solids》2008,69(1):1-7
Semiconductor-like thin films were grown using metallic phthalocyanines (MPc) (M=Fe, Pb, Co) and 1,8 dihydroxiantraquinone as initial compounds. The morphology of the deposited films was studied by using scanning electron microscopy and atomic force microscopy. The powder and thin-film samples of the synthesized materials, deposited by vacuum thermal evaporation, showed the same intra-molecular bonds as in IR spectroscopy studies, which suggests that the evaporation process does not alter these bonds. The optical band gap values of C60H28N8O8Fe, C60H28N8O8Pb and C60H28N8O8Co calculated from the absorption coefficient were found to be 1.60, 1.89 and 1.75 eV, respectively, arising from non-direct transitions. The effect of temperature on conductivity was also measured in these samples. It was found that the temperature-dependent electric current in all cases showed a semiconductor behavior with conductivities in the order of 10−6 Ω−1 cm−1 where the highest value corresponded to the cobalt material. The linear dependence observed in the films implies only one type of conduction mechanism in all cases, with mean activation energies of the order of 1.55, 1.77 and 1.50 eV for iron, lead and cobalt-based thin films, respectively. 相似文献
12.
Yong Su Xia Meng Yiqing Chen Qingtao Zhou Ling Li Yi Feng 《Journal of Physics and Chemistry of Solids》2009,70(7):1062-1065
In-doped Ga2O3 zigzag-shaped nanowires and undoped Ga2O3 nanowires have been synthesized on Si substrate by thermal evaporation of mixed powders of Ga, In2O3 and graphite at 1000 °C without using any catalyst via a vapor-solid growth mechanism. The morphologies and microstructures of the products were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and photoluminescence spectroscopy (PL). The nanowires range from 100 nm to several hundreds of nanometers in diameter and several tens of micrometers in length. A broad emission band from 400 to 700 nm is obtained in the PL spectrum of these nanowires at room temperature. There are two blue-emission peaks centering at 450 and 500 nm, which originate from the oxygen vacancies, gallium vacancies and gallium-oxygen vacancy pairs. 相似文献
13.
S. Rani Anshu A. Agarwal N. Kishore V.P. Seth 《Journal of Physics and Chemistry of Solids》2008,69(7):1855-1860
Studies of structural and electrical properties have been carried out on a number of glasses with wide ranging compositions in the glass systems Li2O·MO·Bi2O3·B2O3 (where M=Zn or Cd), in order to understand the effect of transition metal (TM) ions on the structure of these glasses. The density and molar volume measurements have also been made to understand the structural changes occurring in these glasses. The dc conductivity measured in the temperature range 423-623 K obeys Arrhenius law. It increases with increase in Li2O/MO ratio. The results of infrared spectra indicate that TM ions (Zn2+ or Cd2+) behave as network former in the present system. Boron exists in both tri- and tetra-hedral units in these glasses and no boroxol ring formation takes place in the glass structure. Values of theoretical optical basicity have also been reported. 相似文献
14.
V.V. Todkar C.D. Lokhande Oh-Shim Joo Moon-Young Yoon 《Journal of Physics and Chemistry of Solids》2008,69(7):1802-1807
Alkaline chemical synthesis of amorphous CdCr2S4 (CCS) thin films of different thicknesses using cadmium chloride, chromic acid, disodium salt of ethylenediaminetetra acetic acid and thiourea precursors is reported, and the structural and surface morphological properties of CCS using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) techniques are discussed. Films of aggregated grains with some void spaces are obtained. Change in band gap energy and electrical resistivity of CCS films are discussed as a function of film thickness. n-type conductivity is confirmed from the sign of thermally generated voltage across the cold and hot junctions. 相似文献
15.
Chiharu Hidaka Eri Yamagishi Takeo Takizawa 《Journal of Physics and Chemistry of Solids》2005,66(11):2058-2060
The single crystal of CaGa2S4:Eu is expected as a useful laser material with a high quantum efficiency of light emission. However, as far as our knowledge is concerned, the systematic study of the mixed compounds of Ca(1−x)EuxGa2S4 as a function of x has not been reported up to now. Here, we have first constructed the phase diagram of the CaGa2S4 and EuGa2S4 pseudo binary system, and show that it forms the solid solution. Then we have grown single crystals of these compounds. The maximum photoluminescence efficiency is achieved at x=0.25. From the three peak energies observed in the photoluminescence excitation (PLE) and absorption spectra, the 5d excited states are suggested to consist of three levels arising from the multiplets of Eu2+ ions. 相似文献
16.
Complex spectroscopic studies of (Ce,Gd)Sc3(BO3)4:Cr3+ (CSB:Cr3+) crystals (crystal growth, absorption and luminescence spectroscopy, crystal field calculations, analysis of the radiative and non-radiative decays) are presented. The main results of the paper include calculations of crystal field parameters and energy level scheme for Cr3+ at distorted octahedral Sc3+ sites, evaluation of the Huang-Rhys factor, effective phonon frequency, zero-phonon line energy, and parameters of radiative and non-radiative decays. Comparison with experimental results and other literature data is discussed. A very unusual value of the frequency factor (related to the non-radiative processes) is explained as being due to heterodesmic nature of chemical bonds in the CSB crystal. Cr3+-doped CSB crystals (with Cr3+ concentration 5.1×1019 cm−3 or 1%) are suggested as promising candidates for potential applications as active media for solid state lasers. 相似文献
17.
E. Cavalli 《Journal of Physics and Chemistry of Solids》2008,69(1):29-34
Single crystals of MWO4 (M=Mg, Zn, Cd) and MgMoO4 doped with Cr3+ have been grown by the flux growth method. Their optical spectra have been systematically measured and assigned on the basis of the classical Ligand Field Theory. The exchange charge model of the crystal field has then been applied to calculate the crystal field parameters (CFPs) and the energy levels of the Cr3+ ion in all studied crystals. These are in reasonable agreement with the experimental data. Systematic trends in the CFPs values, crystal field splittings and Racah parameters have been evidenced and their relation with sizes and symmetry properties of the host cavities occupied by Cr3+ has been pointed out. 相似文献
18.
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
19.
Z.A. Talib W.M. Daud E.Z.M. Tarmizi H.A.A. Sidek W.M.M. Yunus 《Journal of Physics and Chemistry of Solids》2008,69(8):1969-1973
Homogeneous CaO-P2O5 and Cu2O-CaO-P2O5 glasses were prepared using a melt-quenched method under controlled conditions. The binary glasses were found to be colourless and transparent while the ternary glasses changed from light green to dark green as the Cu2O content increased. From the absorption edge studies, the values of the optical band gap, Eopt and Urbach energy, ΔE were evaluated. The position of the absorption edge and hence the optical band gap were found to depend on the glass composition. Analysis of the optical band gap shows that for the binary glasses, the value increases as the content of CaO decreases, while for the ternary glasses, the value of the optical band gap increases as the content of the Cu2O decreases. The density of the glasses was also measured and was found to increase with the increase in CaO and Cu2O contents. 相似文献
20.
N.V. Joshi Jorge Luengo Silvana Alvarez J. Martin 《Journal of Physics and Chemistry of Solids》2005,66(11):2011-2014
[ ]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