Structural investigations and luminescence properties of nanocrystalline europium-doped yttrium silicates prepared by a sol–gel technique (original) (raw)
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Open Chemistry, 2014
Yttrium silicate doped with cerium (Y2SiO5:Ce) was obtained from Y-Ce-Si based precursors prepared by the simultaneous addition of reagents (SimAdd) technique. The synthesis of the precursors was done in well controlled conditions using ammonium oxalate, ammonium carbonate or urea as precipitating agents. Results regarding the influence of precipitating agents on the morpho structural and photoluminescent characteristics of Y2SiO5:Ce are reported. The TG analysis in correlation with EGA, FT-IR and XRD investigations reveals the formation of oxalate, hydroxy-carbonate or hydroxy-nitrate based compounds, the same as the conversion of the precursors to well crystallized yttrium silicate. XRD patterns show that the precursors are amorphous except for the sample prepared with ammonium oxalate. Depending on the precipitation conditions, the phosphors phase composition varies from single phase (X2-Y2SiO5) to a mixture of phases (X2-Y2SiO5, X1-Y2SiO5, Y2O3). Under UV excitation, phosphors e...
Luminescence studies of europium doped yttrium oxide nano phosphor
Sensors and Actuators B: Chemical, 2012
Luminescence exhibiting europium doped yttrium oxide (Y 2 O 3 :Eu 3+) phosphor was prepared by solution combustion method, using disodium ethylene diamine tetra acetic acid (EDTA-Na 2) as fuel at ∼350 • C. Powder X-ray diffraction (PXRD) pattern of Y 2 O 3 :Eu 3+ revealed the cubic crystalline phase. The morphology of the samples was studied by scanning electron microscopy (SEM) and was foamy, fluffy and porous in nature. Fourier transformed infrared spectroscopy (FTIR) revealed prominent absorption with peaks at 3415, 1435, 875 and 565 cm −1. Optical absorption studies showed the energy gap of the synthesized samples to be 5.4-5.5 eV. The photoluminescence (PL) of Y 2 O 3 :Eu 3+ exhibiting emission peak at 611 nm under the excitation of 254 nm. Thermoluminescence of ␥-irradiated Y 2 O 3 :Eu 3+ showed two well resolved TL glows with peaks at 460 and 610 K and they were analyzed by glow curve shape method and the activation energies were found to be 0.421 eV and 1.016 eV respectively.
Nanocrystalline luminescent Eu3+-doped Y2SiO5 prepared by sol–gel technique
Optical Materials, 2005
The effect of the trivalent europium ion concentration upon the structure and luminescence properties of nanocrystalline luminescent Eu 3+ :Y 2 SiO 5 prepared by sol-gel method is investigated. In all the samples treated at 1100°C, monoclinic X 1 is the dominant phase for all europium concentrations, accompanied by cubic yttria and an hexagonal phase of yttrium oxide silicate phase (apatite, Y 4.67 (SiO 4 ) 3 O). The content of the less abundant phases increases with europium concentration at the expenses of the X 1 phase. The room temperature laser-excited luminescence spectra, excited at 488.0 nm, consist of 4f-4f emission transitions from 5 D 0 excited level of the Eu 3+ ions to the 7 F 0 , 7 F 1 , 7 F 2 , 7 F 3 and 7 F 4 levels. The intensity of the bands regularly increases with europium content and at the highest europium content the concentration quenching is not observed, differently from bulk samples. Ó 2005 Published by Elsevier B.V.
Cerium activated yttrium silicate phosphors show blue luminescence under UV excitation. Phosphor utilisation depends on powder characteristics and luminescence properties that are regulated during the synthesis stage. In this paper yttrium silicate based phosphors were prepared by solid state reaction using different molar ratio between SiO 2 and Y 2 O 3 . The effect of chemical composition and structure on luminescent properties of phosphors were investigated and discussed.
Spectra of europium-doped yttrium oxide and yttrium vanadate phosphors
Czechoslovak Journal of Physics, 1978
The spectral distributions of the visible absorption and fluorescence emission under electron beam excitation of Eu3+-doped (Y2O3) and (YVO4) powders have been detected and analyzed. (Y2O3: Eu3+) has a cubicC crystal structure with a unit cell dimension a=10·61 Å. Its observed transitions from7F 0 to many upper states have been recognized; the observed number of Stark components is in agreement with that based on theC 2 site symmetry of the Eu3+ ion in Y2O3. Eu3+-doped yttrium vanadate has a typical zircon tetragonal crystal structure with unit cell dimensions ofc=6·29 Å anda=7·11 Å. The observed transitions in (Eu3+: YVO4) have been identified and assigned in accordance with theD 2d site symmetry of the Eu3+ ion in this lattice.
Cathodoluminescence studies of yttrium silicate:cerium phosphors synthesised by a sol–gel process
Journal of Luminescence, 2002
Sol-gel chemistry has been used to produce a Y 2 SiO 5 :Ce phosphor with good chromaticity and brightness. Although, the chromaticity of Y 2 SiO 5 :Ce 1% was similar to that of a commercial Y 2 SiO 5 :Ce phosphor, it was B20-25% brighter. Yttrium silicate:cerium phosphors that contained a range of gadolinium concentrations were also prepared by the solgel route, and their luminescence properties under cathodoluminescent conditions were measured. Over the range of gadolinium concentrations, there was no significant change in the chromaticity of the phosphors, but the addition of gadolinium resulted in a B20% loss in brightness compared to Y 2 SiO 5 :Ce 1% synthesised by the sol-gel route. r
Solvothermal method to obtain europium-doped yttrium oxide
Journal of Solid State Chemistry, 2003
Pure yttrium oxide or mixed with europium oxide (3 at%) were treated in supercritical isopropanolic suspension at 5001C for 20 h and filling degree of 50%. Products were supercritically dried and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), infrared spectroscopy (IR) and luminescence spectroscopy (LS). Particle shape is irregular with an equivalent diameter of ca. 5 mm. Cubic crystalline phase is mainly obtained and hydroxide ion in low concentration is detected by IR vibrational spectrum. Europium in this concentration does not extensively change such observed characteristics from the pure yttrium oxide. Luminescence spectra show that the doped product is a mixture of the two oxides added by oxyhydroxide impurities. Nevertheless, this precursor sample, after being heated at 9001C during 1 h, has all characteristics, especially luminescent ones, of the P22 commercial phosphor. r
Photoluminescence Efficiencies of Nanocrystalline versus Bulk Y2O3:Eu Phosphor—Revisited
Highly efficient yttrium oxide doped with trivalent europium (Y 2 O 3 :Eu) phosphor was prepared through precursors synthesized by hydrothermal method. Crystalline precursors, namely europium-doped yttrium carbonate (Y 2 (CO 3 ) 3 . 2H 2 O:Eu) and europium-doped yttrium hydroxy carbonate (Y(OH)CO 3 :Eu), were prepared by varying the concentration of yttrium to europium ions and urea in the reaction mixture. The precursor materials on annealing at 7001C gave nanocrystalline Y 2 O 3 :Eu, which was further processed at high temperatures in the absence and presence of sintering aid to yield phosphor materials with varying crystallite size and morphology. The precursors and phosphor material were characterized using FTIR, TGA, powder XRD, SEM, TEM, and photoluminescence (PL) spectral studies. The emission efficiency was found to depend on the crystallite size, morphology, and particle size of the phosphor materials. It was observed that phosphor material with spherical morphology and particle size of 0.5-1.0 lm with crystallite size of 100 nm has the highest PL efficiency.
Research on Chemical Intermediates, 2014
The present paper reports the synthesis, photoluminescence (PL), and thermoluminescence (TL) studies of Eu 3?-doped yttrium oxide (Y 2 O 3) phosphor using inorganic materials like Y 2 O 3 , flux calcium fluoride, and europium oxide. The sample was prepared by the modified solid state reaction method, which is the most suitable for large-scale production. The prepared phosphor sample was characterized using powder X-ray diffraction, field emission gun scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy , PL, TL, and Commission Internationale de I'Eclairage techniques. The PL emission was observed in the range 417-632 nm ranges all visible regions for the Y 2 O 3 phosphor doped with Eu 3?. Excitation spectrum found at 254 nm. Sharp intense peaks found around 467, 534, 594, 612, and 632 nm with high intensity. From the XRD data, using the Scherer's formula, the calculated average crystallite size of Eu 3?doped Y 2 O 3 phosphor is around 45 nm. TL study was carried out for the phosphor with UV irradiation. The present phosphor can act as single host for white light emission in display devices.