Search

In this paper, a series of novel Sr3-xGa2Ge4O14:xDy3+ (x = 0 - 0. 40) (mole fraction) and Sr2.68Ga2Ge4O14 :0. 16Dy3+, 0. 16M+ (M = Li, Na, K) phosphors were prepared by high-temperature solid-phase method. EDS analysis confirms the presence of Sr, Ga, Ge, O and Dy elements in the phosphors. The series Sr3-xGa2Ge4O14 :xDy3+ produce strong yellow light emission with 568 nm as the dominant wavelength under 350 nm optical excitation, corresponding to the 4F9/2→6H13/2 transition. The emission spectra of the phosphor show that the emission intensity varies with the increase of Dy3+ concentration and reaches its maximum at x = 0. 16. The co-doping of alkali metal M(M = Li, Na, K) as a charge compensation ion, among which Li+ has the most obvious effect on increasing the emission intensity of Dy3+, led to the increase of the emission intensity of the phosphor to twice that of the phosphor in the absence of the charge compensation ion. In addition, the fluorescence lifetime of the phosphor decrease continuously with the increase of Dy3+ doping concentration. Finally, the CIE chromaticity coordinates and thermal stability of the phosphor Sr2.68Ga2Ge4O14 :0.16Dy3+, 0.16Li+ are explored, and its CIE chromaticity coordinates are (0. 371 9, 0.404 6), which are located in the yellow region, and its luminescence intensity at 453 K is about 95. 5% of its room temperature luminescence intensity. Therefore, Dy3+, Li+ co-doped Sr3-xGa2Ge4O14 phosphor is a potential candidate material for display devices and white light LED devices. [ABSTRACT FROM AUTHOR]

ncs-Si–SiOx:Sm structures formed by high-temperature air annealing of the SiOx films doped with samarium during thermal co-evaporation in vacuum of silicon monoxide and metallic Sm was studied. By measuring the spectra of photoluminescence (PL), it has been shown that doping of SiOx films with Sm stimulates their decomposition into Si and SiO2, and also reduces the transition temperature of silicon nanoparticle from the amorphous state to the crystalline one. With an increase in the impurity content up to 2 wt.%, along with the ncs-Si luminescence, the PL spectrum exhibits emission bands of Sm3+ and Sm2+ ions, which do not appear at a lower Sm concentration. The presence of silicon nanocrystals in SiOx films doped with Sm and annealed at 970 °C in air has been confirmed using Raman scattering spectra. A possible mechanism for interaction of samarium ions with the SiOx matrix and ncs-Si has been discussed. [ABSTRACT FROM AUTHOR]

We have measured photoluminescence spectra of an aqueous uranyl chloride solution under excitation by various light sources: semiconductor light-emitting diodes and cw laser. The excitation wavelength lay within a resonance absorption band of uranyl chloride, which ensured photoluminescence detection at exposure times of 10-3 s using an extremely small volume of the substance (10-9 cm3). The photoluminescence spectra were measured using a small minispectrometer, which allowed us to analyze the spectra in the range 200-1000 nm. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks assembled from Ln(III), Li(I) and rigid dicarboxylate ligand, formulated as [LiLn(BDC)2(H2O)·2(H2O)] (MS1-6,7a) and [LiTb(BDC)2] (MS7b) (Ln = Tb, Dy, Ho, Er, Yb, Y0.96Eu0.04, Y0.93Tb0.07, and H2BDC = terephthalic acid), were obtained under hydrothermal conditions. The isostructural MS1-6 crystallize in monoclinic P21/c space group. While, in the case of Tb3+ a mixture of at least two phases was obtained, the former one (MS7a) and a new monoclinic C2/c phase (MS7b). All compounds have been studied by single-crystal and powder X-ray diffraction, thermal analyses (TGA), vibrational spectroscopy (FTIR), and scanning electron microscopy (SEM-EDX). The structures of MS1-6 and MS7a are built up of inorganic-organic hybrid chains. These chains constructed from unusual four-membered rings, are formed by edge- and vertex-shared {LnO8} and {LiO4} polyhedra through oxygen atoms O3 (vertex) and O6-O7 (edge). Each chain is cross-linked to six neighboring chains through six terephthalate bridges. While, the structure of MS7b is constructed from double inorganic chains, and each chain is, in turn, related symmetrically to the adjacent one through the c glide plane. These chains are formed by infinitely alternating {LiO4} and {TbO8} polyhedra through (O2-O3) edges to create Tb-O-Li connectivity along the c-axis. Both MS1-6,7a and MS7b structures possess a 3D framework with 1D trigonal channels running along the a and c axes, containing water molecules and anhydrous, respectively. Topological studies revealed that MS1-6 and MS7a have a new 2-nodal 3,10-c net, while MS7b generates a 3D net with unusual β-Sn topology. The photoluminescence properties Eu- and Tb-doped compounds (MS5-6) are also investigated, exhibiting strong red and green light emissions, respectively, which are attributed to the efficient energy transfer process from the BDC ligand to Eu3+ and Tb3+. [ABSTRACT FROM AUTHOR]

A series of natural zircon samples (with U concentrations of 140-2600 ppm and ranging from well crystalline to severely radiation damaged) were investigated by means of REE3+ photoluminescence spectroscopy. We found systematic changes in REE3+ emissions depending on the accumulated radiation damage expressed by the effective time-integrated a-dose of zircon samples. Structural reconstitution as caused by dry annealing resulted in intensity gains and decreases of half-widths of REE3+ emissions. The band half-widths of distinct luminescence Stark's levels of the 4F9/2 → 6H13/2 transition of Dy3+ (~17 250 cm-1; ~580 nm wavelength) and the 4F3/2 → 4I9/2 transition of Nd3+ (~11 300 cm-1; ~885 nm wavelength) were found to correlate sensitively with the degree of radiation damage accumulated. These REE3+ emissions are proposed as potential measure of the irradiation-induced structural disorder of zircon. The two emissions are considered particularly suitable because (1) they are commonly detected in PL spectra of natural zircon, and (2) they are hardly biased by other emissions or Stark's levels. Preliminary calibration curves that relate band-width increases to the a dose were established using a suite of well-characterized Sri Lankan zircon. Band broadening upon increasing corpuscular self-irradiation is assigned to increasing structural destruction, i.e., the increasing perturbation of REE3+ cationic lattice sites. Possible advantages of REE3+ luminescence spectroscopy, complementary to Raman spectroscopy, as method to quantify structural radiation damage are discussed. [ABSTRACT FROM AUTHOR]

Rare-earth-doped aluminosilicates of alkaline earth MgAl2Si2O8: Eu3+, Dy3+ and MgAl2Si2O8: Eu3+, Gd3+ were synthesized by the solid state reaction method at 1300 oC. The phosphors were characterized by X-ray powder diffraction (XRD), photoluminescence (PL), thermoluminescence (TL) and scanning electron microscopy (SEM). X-ray powder diffraction studies show that the phosphors were crystallized in the triclinic crystal system. The phosphors show characteristic broad band phosphorescence of Eu3+. This broad band phosphorescence has red emission bands in the range of 580-705 nm corresponding to 5D0 → 7Fj (j:0,2,3,4) transitions of Eu3+. [ABSTRACT FROM AUTHOR]

In the present work, the photoluminescence (PL) spectra of bismuth germanate (BGO) doped with trivalent rare earth element (REE) ions with different doping concentrations (0.03 wt% Eu, 0.4 wt% Tm, and 1.1 wt% Nd) are reported in the temperature range from 10 to 300 K using different detectors, namely, photomultiplier tube (PMT), InGaAs (IGA), and Si. The luminescence in the NIR region was also measured at room temperature. Two broad emission bands attributed to undoped BGO were found at circa 1350 and 1800 nm, respectively. The broad-band emissions are replaced by narrow-band line emissions defined by the trivalent rare earth dopants. The emission spectra from rare earth ion–doped BGO extend from 500 to 2000 nm. Rare earth ions act as the dominant recombination centers and define the emission spectra. This is interpreted as resulting from direct charge transfer from intrinsic defect traps to rare earth recombination centers. The temperature-dependent luminescence of BGO doped with 0.4 wt% Tm is also presented. [ABSTRACT FROM AUTHOR]

Thermally stimulated luminescence (TSL) investigations of SrBPO:Eu and SrBPO:Eu phosphors were carried out in the temperature range of 300-650 K. In order to characterize the phosphors, X-ray diffraction and photoluminescence (PL) techniques were used. The emission spectrum of air heated SrBPO:Eu phosphor exhibited emission bands at 590, 614, 651 and 702 nm under 248 nm excitation, assigned to transitions of Eu ion. In phosphor prepared in reducing (Ar + 8% H) atmosphere, a broad emission band due to Eu ranging from 350 to 400 nm was observed with 340 nm excitation. EPR studies have confirmed the presence of Eu ions in the samples prepared in reducing atmosphere. TSL glow curve of SrBPO:Eu had shown intense peaks around 397, 510, 547 K and a weak peak around 440 K whereas in case of SrBPO:Eu system, glow peaks at 414, 478 and weak peak at 516 nm were observed. The shift in TSL glow pattern can be attributed to stabilization of different oxidation states of the dopant ion in the host lattice. Apart from this, TSL trap parameters such as trap depth and frequency factor were determined. Spectral characteristics of TSL emission have shown that Eu/Eu ion acts as the luminescent centre in the respective phosphors. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) and PL excitation (PLE) spectra of Si6-zAlzOzN8-z ([beta]-sialon):Eu2+ phosphors with small z values (z = 0.025-0.24) were studied at room temperature and 6 K. The PL and PLE spectra exhibit fine structure with the PL lines being as sharp as 45-55 nm even at room temperature; this fine structure was enhanced by decreasing the z value. These results can be used for expanding the color gamut of liquid crystal displays, particularly in the blue-green region. From low-temperature measurements, the fine PLE structure was ascribed to discrete energy levels of 7FJ states. The 4f65d excited states of Eu2+ are considered to be localized near the 4f orbital. This is because the bonding of Eu2+ with surrounding atoms is ionic rather than covalent. Lattice phonon absorptions were also observed in the PLE spectrum, revealing that the optically active Eu2+ ions are located in the [beta]-sialon crystal. The PL spectrum of the sample with the smallest z value (0.025) consists of a sharp zero-phonon line and lattice phonon replicas, which results in a sharp and asymmetric spectral shape. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis of Ce and Dy activated alkali lanthanide tungstates, ALa(WO)(where A = Na and Li), prepared by solid state reaction method. The prepared phosphors were characterized by X-ray diffraction and photoluminescence techniques. The NaLa(WO):Dy and LiLa(WO):Dy phosphors show two emission peaks at around 574 and 486 nm (λ = 354 nm). NaLa(WO):Ce and LiLa(WO):Ce show two emission peaks at around 378 and 425 nm (λ = 350 nm). Excitation wavelengths of Ce and Dy activated alkali lanthanide tungstates are in near UV region i.e. Hg free excitation. These characterizations of phosphors are applicable for solid state lighting. Accordingly, Ce and Dy activated NaLa(WO) and LiLa(WO) may be the promising materials for solid state lighting applications. [ABSTRACT FROM AUTHOR]

Zr–Sm (3 at.% Sm) alloy was prepared through a powder metallurgical method. Sm3+-doped ZrO2 nanotube arrays have been achieved directly by anodizing the Zr–Sm alloy. The effects of electrolyte and annealing temperature on the morphologies and structures of the nanotube arrays were studied. The photoluminescence properties of Sm3+-doped ZrO2 nanotube arrays prepared in aqueous solution and formamide  +  glycerol solution were studied in detail as well. Results show that tetragonal ZrO2 promoted the photoluminescence efficiency of this system. Under excitation at 407 nm, the sample prepared in aqueous solution annealed at 600 °C displayed the strongest emission peak at 571 nm, corresponding to the 4G5/2  →  6H5/2 samarium transition. [ABSTRACT FROM AUTHOR]

We report on the magneto-optical (MO) properties of heavily Tb3+-doped GeO2-B2O3-Al2O3-Ga2O3 glasses towards fiber-integrated paramagnetic MO devices. For a Tb3+ ion concentration of up to 9.7 × 1021 cm−3, the reported glass exhibits an absolute negative Faraday rotation of ~120 rad/T/m at 632.8 nm. The optimum spectral ratio between Verdet constant and light transmittance over the spectral window of 400-1500 nm is found for a Tb3+ concentration of ~6.5 × 1021 cm−3. For this glass, the crystallization stability, expressed as the difference between glass transition temperature and onset temperature of melt crystallization exceeds 100 K, which is a prerequisite for fiber drawing. In addition, a high activation energy of crystallization is achieved at this composition. Optical absorption occurs in the NUV and blue spectral region, accompanied by Tb3+ photoluminescence. In the heavily doped materials, a UV/blue-to-green photo-conversion gain of ~43% is achieved. The lifetime of photoluminescence is ~2.2 ms at a stimulated emission cross-section σem of ~1.1 × 10−21 cm2 for ~ 5.0 × 1021 cm−3 Tb3+. This results in an optical gain parameter σem*τ of ~2.5 × 10−24 cm2s, what could be of interest for implementation of a Tb3+ fiber laser. [ABSTRACT FROM AUTHOR]