Effect of the quantum confinement on the luminescent properties of sesquioxydes (original) (raw)
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Confinement effects in sesquioxydes
Journal of Luminescence, 2006
When the size of a particle is decreased to nano-scales, confinement effects induce strong changes. The luminescence of Eu 3+ -doped Gd 2 O 3 nanoparticles has been studied as a function of both the temperature and the size of the nanoparticles.
Optik, 2016
Intense blue emission is observed in Ce 3+-doped Y 2 O 3 nanophosphors, successfully prepared by simple sol gel method. The nano-powder is characterized by diffractometry (XRD) and room temperature steady photoluminescence. The XRD analysis shows that the crystallite size is 10 nm. The excitation and emission observed bands are assigned to 4f-5d transition and investigated. VASP code is used to performed the first principle calculations study of Y 2 O 3 :Ce 3+ nanomaterial system. The U eff parameter is tuned to give best agreement with experimental results. Hybrid functional (HSE06) is used calculated the band gap of Y 2 O 3 and 5d orbitals of Ce 3+ .
Optical spectroscopy and thermal quenching of the Ce3+ luminescence in yttrium oxysulfate, Y2O2[SO4]
Optical Materials, 2008
Photoluminescence and excitation spectrum of Ce 3+ activated yttrium oxysulfate, Y 2 O 2 [SO 4 ] has been investigated in the 10-300 K temperature region. The Stokes shift of the Ce 3+ emission is small (0.3 eV). The crystal field splitting and the centroid shift of the Ce 3+ 5d state have been derived from the low temperature excitation spectrum. At room temperature, the quantum efficiency of the Ce 3+ emission is low. The thermal quenching of Ce 3+ lifetime observed for T > 200 K is attributed to the photoionization of the Ce 3+ 5d electron. In Y 2 O 2 [SO 4 ], the Ce 3+ ions are coordinated with four ''free'' oxygen ions, which do not occur in the coordination polyhedra of the [SO 4 ] 2À groups. We present evidence from this work and from the data presented in the archival literature that the Ce 3+ luminescence efficiency is low at room or slightly above room temperature in materials, which offer ''free'' oxygen ions in the first coordination sphere of the Ce 3+ ion.
Journal of Physical Chemistry C, 2009
The UV-visible and vacuum ultraviolet emission and excitation spectra of Y 2 O 3 :Eu 3+ (1 and 0.1 atom %) nanomaterials, prepared by combustion syntheses with use of glycine or hydrazine, have been recorded in order to investigate spectral band shifts as a function of particle size. FT-IR spectra and site-selective emission spectra at low temperature show the presence of impurities for all of these samples, with the least impurities for the samples prepared using stoichiometric ratios of reactants, where (i) the relative intensity of the free exciton (FE) and the charge transfer (CT) bands changes significantly with Eu 3+ concentration, (ii) there is a small red-shift of the CT band position with decreasing particle size, and (iii) the shifts of the FE and band-to-band (CB) transitions are within a separation of 116 cm -1 (14 meV) at room temperature for samples of size 20-40 nm. The band positions change for samples synthesized when not using stoichiometric ratios of reactants.
Luminescence of Ce3+ in Y2SiO5 Nanocrystals: Role of Crystal Structure and Crystal Size
ChemInform, 2005
Luminescence D 6540 Luminescence of Ce 3+ in Y 2 SiO 5 Nanocrystals: Role of Crystal Structure and Crystal Size.-Ce doped Y2SiO5 nanoparticles are synthesized for the first time by a sol-emulsion-gel method. The emission at 430 nm and lifetime of the excited state of the samples are sensitive to the crystal structure, crystal size, and dopant concentration. The overall lifetime of 0.5 mol% Ce doped Y2SiO5 nanocrystals are 8.78 and 3.45 ns for 1000 and 1100°C heat-treated samples with the same crystal structure. However, a significant increase in the overall lifetime (35.21 ns) is observed for the 1300°C annealed sample having a different crystal structure.
2008
Photoluminescence and excitation spectrum of Ce 3+ activated yttrium oxysulfate, Y 2 O 2 [SO 4 ] has been investigated in the 10-300 K temperature region. The Stokes shift of the Ce 3+ emission is small (0.3 eV). The crystal field splitting and the centroid shift of the Ce 3+ 5d state have been derived from the low temperature excitation spectrum. At room temperature, the quantum efficiency of the Ce 3+ emission is low. The thermal quenching of Ce 3+ lifetime observed for T > 200 K is attributed to the photoionization of the Ce 3+ 5d electron. In Y 2 O 2 [SO 4 ], the Ce 3+ ions are coordinated with four ''free'' oxygen ions, which do not occur in the coordination polyhedra of the [SO 4 ] 2À groups. We present evidence from this work and from the data presented in the archival literature that the Ce 3+ luminescence efficiency is low at room or slightly above room temperature in materials, which offer ''free'' oxygen ions in the first coordination sphere of the Ce 3+ ion.
Diffusion and Defect Data Pt.B: Solid State Phenomena, 2007
Rare earth doped materials have many familiar applications (TV screens, solid lasers, scintillators…) thanks to their efficient and robust luminescence properties. In recent years, growing interest has been focused on the changes in their optical properties with the size of the host particles. In this work, nanomaterials were produced for the first time by using laser pyrolysis. Y, Gd, and Eu nitrates were dissolved in water and used as precursors. Cubic phases of Y 2 O 3 :Eu 3+ and Gd 2 O 3 :Eu 3+ were obtained with sizes ranging from 3 to 40 nm. The spectroscopic properties revealed a new and nanostructure-specific broad band in the excitation spectrum. The emission spectrum was found to be characteristic of nanostructured sesquioxides only when excited in this new band, which was finally assumed to be a new charge transfer band for the smallest nanoparticles in the sample.
Infrared Photoluminescence of Nd-Doped Sesquioxide and Fluoride Nanocrystals: A Comparative Study
Crystals
Lanthanide ions possess various emission channels in the near-infrared region that are well known in bulk crystals but are far less studied in samples with nanometric size. In this work, we present the infrared spectroscopic characterization of various Nd-doped fluoride and sesquioxide nanocrystals, namely Nd:Y2O3, Nd:Lu2O3, Nd:Sc2O3, Nd:YF3, and Nd:LuF3. Emissions from the three main emission bands in the near-infrared region have been observed and the emission cross-sections have been calculated. Moreover, another decay channel at around 2 μm has been observed and ascribed to the 4F3/2→4I15/2 transition. The lifetime of the 4F3/2 level has been measured under LED pumping. Emission cross-sections for the various compounds are calculated in the 1 μm, 900 nm, and 1.3 μm regions and are of the order of 10−20 cm2 in agreement with the literature results. Those in the 2 μm region are of the order of 10−21 cm2.
Size-dependent luminescence in Y2Si2O7 nanoparticles doped with Ce3+ ions
Applied Physics A, 2010
Powders and thin films of nanocrystalline yttrium disilicate (Y 2 Si 2 O 7 ) doped with Ce 3+ have been prepared by a sol-gel method. Structure and morphology of the synthesised samples have been determined and spectroscopic properties compared. The triclinic α-Y 2 Si 2 O 7 form (space group P 1-) for the powders annealed between 1000°C and 1200°C has been found. A total conversion into a thortveitite-type monoclinic β-Y 2 Si 2 O 7 polymorph after annealing of powder samples at 1400°C (space group C2/m) has been observed. In the case of films even at 1300°C the basically pure triclinic α-Y 2 Si 2 O 7 phase was observed with luminescent spectroscopy. The influence of grain size, controlled by thermal treatment, on the structure and luminescence properties of the fabricated materials are presented and discussed.
Cathodoluminescence of Nanocrystalline Y2O3:Eu3+ with Various Eu3+ Concentrations
ECS Journal of Solid State Science and Technology, 2014
Herein a study on the preparation and cathodoluminescence of monosized spherical nanoparticles of Y2O3:Eu3+ having a Eu3+ concentration that varies between 0.01 and 10% is described. The luminous efficiency and decay time have been determined at low a current density, whereas cathodoluminescence-microscopy has been carried out at high current density, the latter led to substantial saturation of certain spectral transitions. A novel theory is presented to evaluate the critical distance for energy transfer from Eu3+ ions in S6 to Eu3+ ions in C2 sites. It was found that Y2O3:Eu3+ with 1-2% Eu3+ has the highest luminous efficiency of 16lm/w at 15keV electron energy. Decay times of the emission from 5D0 (C2) and 5D1 (C2) and 5D0 (S6) levels were determined. The difference in decay time from the 5D0 (C2) and 5D1 (C2) levels largely explained the observed phenomena in the cathodoluminescence-micrographs recorded with our field emission scanning electron microscope.