INVESTIGATION ON THE LUMINESCENCE PROPERTIES OF DY3+ AND EU3+ IN M3LN2(BO3)4 (M=CA, SR, BA, LN= LA, GD, Y)

In this paper, the luminescence properties of Dy3+ and Eu3+ in M3Ln2 (BO3)4 (M = Ca,Sr,Ba; Ln = La, Gd, Y) were systematically studied. The hypersensitive transitions of Dy3+ and Eu3+ were investigated in relation to the host compositions; the relationship between the energy of Eu3+ charge-transfer band and M2+ ion was discussed, and the concentration quenching of Dy3+ luminescence was reported.

YF[MoO4] and YCl[MoO4]: Two halide derivatives of yttrium ortho-oxomolybdate: Syntheses, structures, and luminescence properties

The halide derivatives of yttrium ortho-oxomolybdate YX[MoO4] (X = F, Cl) both crystallize in the monoclinic system with four formula units per unit cell. YF[MoO4] exhibits a primitive cell setting (space group P2(1)/c, a = 519.62(2) pm, b = 1225.14(7) pm, c = 663.30(3) pm, beta = 112.851(4)degrees), whereas the lattice of YCl[MoO4] shows face-centering (space group C2/m; a = 1019.02(5) pm, b = 720.67(4) pm, c = 681.50(3) pm, beta = 107.130(4)degrees). The two compounds each contain crystallographically unique Y3+ cations, which are found to have a coordination environment of six oxide and two halide anions. In the case of YF[MoO4], the coordination environment is seen as square antiprisms, and for YCl[MoO4], trigon-dodecahedra. are found. The discrete tetrahedral [MoO4](2-) units of the fluoride derivative are exclusively bound by six terminal Y3+ cations, while those of the chloride compound show a 5-fold coordination around the tetrahedra with one edge-bridging and four terminal Y3+ cations. The halide anions in each compound exhibit a coordination number of two, building up isolated planar rhombus-shaped units according to [Y2F2](4+) in YF[MoO4] and [Y2Cl2](4+) in YCl[MoO4], respectively. Both compounds were synthesized at high temperatures using Y2O3, MoO3, and the corresponding yttrium trihalide in a molar ratio of 1:3:1. Single crystals of both are insensitive to moist air and are found to be coarse shaped and colorless with optical band gaps situated in the near UV around 3.78 eV for the fluoride and 3.82 eV for the chloride derivative. Furthermore, YF[MoO4] seems to be a suitable material for doping to obtain luminescent materials because the Eu3+-doped compound shows an intense red luminescence, which has been spectroscopically investigated.

Electron donor sites on Y2O3 catalyst as a function of the activation temperature

Cochin University of Science and Technology

Surface Electron Donor Properties of Dy2O3,Y2O3 and Their Mixed Oxides with Alumina Catalyst

The limit of electron transfer in electron affinity from the oxide surface to the electron acceptor (EA) are reported from the adsorption of EA on DY203, mixed oxides of DY203 with alumina and mixed oxides of Y203 with y-alumina. The extent of electron transfer is understood from magnetic measurements.

Nickel catalysts supported on ZrO2, Y2O3-stabilized ZrO2 and CaO-stabilized ZrO2 for the steam reforming of ethanol: Effect of the support and nickel load

Catalysts with various nickel loads were prepared on supports of ZrO2, ZrO2-Y2O3 and ZrO2-CaO, characterized by XRD and TPR and tested for activity in ethanol steam reforming. XRD of the supports identified the monoclinic crystalline phase in the ZrO2 and cubic phases in the ZrO2-Y2O3 and ZrO2-CaO supports. In the catalysts, the nickel impregnated on the supports was identified as the NiO phase. In the TPR analysis, peaks were observed showing the NiO phase having different interactions with the supports. In the catalytic tests, practically all the catalysts achieved 100% ethanol conversion, H-2 yield was near 70% and the gaseous concentrations of the other co-products varied in accordance with the equilibrium among them, affected principally by the supports. It was observed that when the ZrO2 was modified with Y2O3 and CaO, there were big changes in the CO and CO2 concentrations, which were attributed to the rise in the number of oxygen vacancies, permitting high-oxygen mobility and affecting the gaseous equilibrium. The liquid products analysis showed a low selectivity to liquid co-products during the reforming reactions. (c) 2007 Published by Elsevier B.V.

Characterization of metallic electrical contacts to SnO2 thin films lightly doped with Eu3+ ions, and photo-induced resistivity

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo do comportamento térmico e da luminescência de filmes de quitosana com os íons Eu3+ e Tb3+

Films of chitosan with trivalent lanthanides ions Eu3+ and Tb3+ were respectively prepared in the ratio of 3:1 m/m (chitosan: lanthanide) and 6:1 m/m (chitosan: lanthanide). There were no formations of films in a ratio of 1:1 m/m (chitosan: lanthanides). The films of chitosan with the Tb3+ ion have the same transparent appearance than the pure chitosan films. The film of chitosan with Eu3+ ion has a muddy appearance. These films present good resistance to tear. The appearance of the compounds prepared in ratio 1:1m/m is a white powder. The films and compounds of chitosan were characterized by Elementary Analysis (CHN), Thermal Analysis (TG/DTG) and Spectroscopy of Luminescence. The CHN analysis was made only for compounds prepared in ratio 1:1m/m, suggesting that these compounds possess the formula QUILn.6H2O, where QUI = Chitosan and Ln = Lanthanide. The results of the curves TG/DTG indicated that there are strong interactions between Eu3+ or Tb3+ and chitosan, causing a lesser lost of mass in the films. The luminescence analysis showed that the films of chitosan with the ions Eu3+ and Tb3+ present emissions in the region of the visible one, with bands of the chitosan and of the Eu3+ ion. The luminescence analysis of the compounds of chitosan with the Eu3+ and Tb3+ ions suggest that the chitosan does not transfer into energy to the ions lanthanides, however the chemical neighborhood around of the ion lanthanides breaks the selection rules and, conseqüently the 4f-4f transitions of the lanthanide ions are observed

Interface Formation and Electrical Transport in SnO2:Eu3+/GaAs Heterojunction Deposited by Sol-Gel Dip-Coating and Resistive Evaporation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The role of the Eu3+ ions in structure and photoluminescence properties of SrBi2Nb2O9 powders

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis and Study of the Photophysical Properties of a New Eu3+ Complex with 3-Hydroxypicolinamide

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis, characterization and photophysical properties of Eu3+ doped in BaMoO4

In this work Ba0.99Eu0.01MoO4 (BEMO) powders were prepared by the first time by the Complex Polymerization Method. The structural and optical properties of the BEMO powders were characterized by Fourier Transform Infra-Red (FTIR), X-ray Diffraction (XRD), Raman Spectra, High-Resolution Scanning Electron Microscopy (HR-SEM) and Photoluminescent Measurements. XRD show a crystalline scheelite-type phase after the heat treatment at temperatures greater than 400 degrees C. The ionic radius of Eu3+ (0.109 nm) is lower than the Ba2+ (0.149 nm) one. This difference is responsible for the decrease in the lattice parameters of the BEMO compared to the pure BaMoO4 matrix. This little difference in the lattice parameters show that Eu3+ is expected to occupy the Ba2+ site at different temperatures, stayed the tetragonal (S-4) symmetry characteristic of scheelite-type crystalline structures of BaMoO4. The emission spectra of the samples, when excited at 394 nm, presented the D-5(1)-> F-7(0, 1 and 2) and D-5(0)-> F-7(0, 1, 2, 3 and 4) Eu3+ transitions at 523, 533, 554, 578, 589, 614, 652 and 699 nm, respectively. The emission spectra of the powders heat-treated at 800 and 900 degrees C showed a marked increase in its intensities compared to the materials heat-treated from 400 to 700 C. The decay times for the sample were evaluated and all of them presented the average value of 0.61 ms. Eu3+ luminescence decay time follows one exponential curve indicating the presence of only one type of Eu3+ symmetry site.

Visible and near-infrared luminescent Eu3+ or Er3+ doped laponite-derived xerogels and thick films: Structural and spectroscopic properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Correlation between the spectroscopic and structural properties with the occupation of Eu3+ sites in powdered Eu3+-doped LiTaO3 prepared by the Pechini method

In this work we studied the structural and optical properties of lithium tantalate (LiTaO3) powders doped with Eu3+ ions. We have examined the different sites occupied by the rare earth ion through the correlation of the DRX data analyzed with the Rietveld method and some spectroscopic parameters derived from the Eu3+ luminescence. Adirect relation was established between the lattice parameters and the occupation fraction of Eu3+ in each LiTaO3 site. The occupation fraction was set as the relative population of Eu3+ ions for each site obtained by means of the intensity, baricenter, and the spontaneous emission coefficients of the D-5(0)-> F-7(0) transitions. We concluded that the unit cell parameter a presents the same behavior of the Eu3+ occupation fraction in Ta5+ sites as a function of the Eu3+ content in LiTaO3. The same was observed for the variation in Eu3+ occupation fraction in the Li+ site and the unit cell parameter c with the Eu3+ content. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3204967]

Preparação de LiNbO3 e LiNbO3:Eu3+ pelo método dos precursores poliméricos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)