Structural differences existing in bulk and nanoparticles of Y2Sn2O7: Investigated by experimental and theoretical methods (original) (raw)
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Improved luminescence from Y2Sn2O7:Tb3+ nanoparticles co-doped with Sb3+ ions
Optical Materials, 2011
Very small nanoparticles (size 3-5 nm) of Y 2 Sn 2 O 7 , Y 2 Sn 2 O 7 :Tb 3+ and Sb 3+ co-doped Y 2 Sn 2 O 7 :Tb 3+ were prepared at a relatively low temperature of 700°C. Y 2 Sn 2 O 7 host is characterised by an emission around 436 nm, which is arising from the oxygen vacancies present in the lattice. Tb 3+ emission improves significantly when Sb 3+ ions are co-doped with Y 2 Sn 2 O 7 :Tb 3+ nanoparticles. Incorporation of Sb 3+ ions at the Y 3+ site of Y 2 Sn 2 O 7 lattice and associated lattice distortion around Tb 3+ /Y 3+ ions brought about by the difference in the stable coordination number of Sb 3+ and Y 3+ ions are responsible for the improved Tb 3+ emission from the co-doped samples.
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.
EFFECT OF STRONTIUM DOPING ON NANOSTRUCTURE AND CHROMATICITY OF Y 2 O 3 :Eu COMPOUNDS
International Journal of Modern Physics B, 2011
In this work, various nano-sized samples of Y 2 O 3 , Y 2 O 3 :Eu and Y 2 O 3 :Eu, Sr were prepared by urea solution combustion method. Then the resultant nanopowders were investigated by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence emission spectra. Furthermore, the CIE color coordinate of samples were calculated from photoluminescence emission spectra. Results showed that by doping of strontium, the photoluminescence intensity and chromaticity of Y 2 O 3 :Eu phosphor was enhanced while crystallite size was decreased.
Optical Materials, 2014
Nano-sized yttria (Y 2 O 3 ) doped with Eu 3+ powders were successfully synthesized by co-precipitation method, where the quenching concentration for photoluminescence study of Eu 3+ ions is 12 mol% which is much higher than the micro-scaled powders. The effect of changing concentration of co-dopants (Li + , Na + and K + ) along with Eu 3+ (12 mol%) is studied on optical properties of Y 2 O 3 nanoparticles. The results showed that the incorporation of these metal ions can further improve the luminescence intensity. The highest emission intensity was observed with 6 mol% of Li + , 2 mol% of Na + , and 1 mol% of K + doping in Y 2 O 3 :Eu 3+ (12 mol%) nanoparticles given by the formula (Y 0.82mol% Eu 0.12mol% Li 0.06mol% ) 2 O 3 , (Y 0.86mol%-Eu 0.12mol% Na 0.02mol% ) 2 O 3 , and (Y 0.87mol% Eu 0.12mol% K 0.01mol% ) 2 O 3 respectively. The structural, morphological and optical properties were studied by X-ray diffraction, Rietveld refinement, transmission electron microscopy, Fourier transform infrared spectroscopy, and Photoluminescence spectroscopy. XRD studies followed by Rietveld refinement confirmed the body-centered cubic structure of doped nanophosphors. All the powders were well crystallized and the emission intensity was observed to increase further from quenching concentration of Eu 12 mol% with co-doped samples.
2009
The effect of incorporation of trace (Al +3 , B +3) in the Y 2 O 3 lattice on the luminescence efficiency of Y 2 O 3 :Eu +3 red phosphor has been investigated. It is observed that such incorporation causes an enhancement of 5 D 0 → 7 F 2 red luminescence efficiency as well as the associated excitation efficiency of Eu +3. It is concluded that there occurs a change in the polarity of the host rather than the site symmetry of Eu +3 due to incorporation of the hetero cations. Calculation of the Judd-Ofelt parameters gives similar results. In another study, to observe the effect of reduction of particle size on the luminescence efficiency of the Y 2 O 3 :Eu +3 , the change in luminescence efficiency of the phosphor with the reduction particle size and the stability of the different efficiencies with the elapse of time have been investigated. The samples with particle size below 100 nm showed a significant loss in luminescence efficiency and a change in their excitation profile with time. IR studies showed that although the freshly prepared samples were almost free from contaminated water, on ageing in air at room temperature, they absorb the latter. A phenomenon of hydration induced coupling of the excitonic state of Y 2 O 3 with one of its F u modes, has been detected in the case of the aged samples which susequently introduces newer non-radiative channels in the system causing a decrease in the luminescence efficiency of the phosphor. Because of larger surface to volume ratio, the effect is most pronounced in nanocrystalline samples.
Journal of Applied Physics, 2010
SnO 2 : Eu is a well-known luminescent material, emitting red and orange lines. The intensity ratio of red to orange emission, being sensitive to the deviation of Eu 3+ ions from symmetric location, finds wide application as sensor. The luminescence intensity of such lanthanide-doped sensors is generally optimized by high temperature annealing. However, for the present system ͑SnO 2 :Eu͒ it had been found that the red emission suddenly disappears while annealing beyond 900°C, which can however be recovered by dispersing the system in a secondary host matrix of Y 2 O 3. Understanding the mechanism of this recovery has important implication for designing of phosphor. In this work, we structurally explain this spectral evolution, by employing x-ray absorption fine structure technique. The initial disappearance of the red line is realized to be due to the formation of Eu 2 Sn 2 O 7 and the recovery, to the intercalation of the Eu 3+ ions from the SnO 2 surface into Y 2 O 3. Oxygen vacancy in Y 2 O 3 creates the asymmetric environment required for red line emission. The design implications of these findings are discussed.
Synthesis and optical properties of nanosized powders: lanthanide-doped Y2O3
Applied surface …, 1999
Y Nd O and Y Er O powder samples were prepared by combustion synthesis. X-ray diffraction showed that the 1.8 0.2 3 1.8 0.2 3 materials are nanostructured, with average coherence length 5-10 nm. The visible and infrared luminescence spectra of nanometric cubic Y Nd O and Y Er O show some important differences from those of the bulk materials. In the 1.8 0.2 3 1.8 0.2 3 case of Y Er O , faster relaxation of some excited states occurs, leading to changes in the relative intensities of several 1.8 0.2 3 optical transitions. As far as nanostructured Y Nd O is concerned, the 4 F ™ 4 I transition is characterized by a 1.8 0.2 3 3r2 9 r2
Journal of …, 2008
Luminescence, energy transfer, and upconversion mechanisms of nanophosphors (Y 2 O 3 : Eu 3+ , Tb 3+ , Y 2 O 3 : Tm 3+ , Y 2 O 3 : Er 3+ , Yb 3+ ) both in particle and colloidal forms were studied. The structure, phase, and morphology of the nanopowders and nanocolloidal media were determined by high-resolution TEM and X-ray diffraction. It was shown that the obtained nanoparticles have a round-spherical shape with average size in the range of 4 to 20 nm. Energy transfer was observed for Y 2 O 3 : Eu 3+ , Tb 3+ colloidal and powders, upconversion transitions were observed for both Y 2 O 3 : Er 3+ and Y 2 O 3 : Er 3+ , Yb 3+ nanophosphors. The dependence of photoluminescence (PL) spectra and decay times on doping concentration has been investigated. The infrared to visible conversion of emission in Y 2 O 3 : Er 3+ , Yb 3+ system was analyzed and discussed aiming to be applied in the photonic technology.
Japanese Journal of Applied Physics, 2006
Recently, lanthanide ion doped yttrium oxide (Y 2 O 3) compounds have been attracting attention in applications concerning opto-electronic materials such as laser devices and field-emission displays. Consequently, study on the excited state of lanthanide ion doped Y 2 O 3 is of major significance. In the present work, we report studies performed on the electronic excited states of undoped and Eu 3þ doped Y 2 O 3 as well as yttrium oxy-sulphide (Y 2 O 2 S) clusters using the time dependent density functional theory method to unveil the influence of europium ion in yttrium oxide compounds. The ground state electronic properties of undoped and europium ion doped clusters at different spin multiplicities were obtained using the density functional theory method. The calculated results were compared with the available experimental results. The calculated absorption spectrum of Eu doped Y 2 O 3 cluster shows quantitative agreement with experimental spectra. The absorption spectra of europium ion doped Y 2 O 3 and Y 2 O 2 S clusters have shown additional bands in the higher wavelength region due to the transitions between f-orbitals in the europium ion.
Luminescence and crystallinity of flame-made Y2O3:Eu3+ nanoparticles
Advanced Powder Technology, 2007
Cubic and/or monoclinic Y 2 O 3 :Eu 3+ nanoparticles (10-50 nm) were made continuously without post-processing by single-step, flame spray pyrolysis (FSP). These particles were characterized by X-ray diffraction, nitrogen adsorption and transmission electron microscopy. Photoluminescence (PL) emission and time-resolved PL intensity decay were measured from these powders. The influence of particle size on PL was examined by annealing (at 700-1300 • C for 10 h) as-prepared, initially monoclinic Y 2 O 3 :Eu 3+ nanoparticles resulting in larger 0.025-1 μm, cubic Y 2 O 3 :Eu 3+ . The influence of europium (Eu 3+ ) content (1-10 wt%) on sintering dynamics as well as optical properties of the resulting powders was investigated. Longer high-temperature particle residence time during FSP resulted in cubic nanoparticles with lower maximum PL intensity than measured by commercial micron-sized bulk Y 2 O 3 :Eu 3+ phosphor powder. After annealing as-prepared 5 wt% Eu-doped Y 2 O 3 particles at 900, 1100 and 1300 • C for 10 h, the PL intensity increased as particle size increased and finally (at 1300 • C) showed similar PL intensity as that of commercially available, bulk Y 2 O 3 :Eu 3+ (5 μm particle size). Eu doping stabilized the monoclinic Y 2 O 3 and shifted the monoclinic to cubic transition towards higher temperatures.