Synthesis and Characterisation of Y2O3: Eu/Ag powders (original) (raw)
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Optical Materials, 2015
This work reports on the synthesis and characterization of Y 2 O 3 :Eu 3+ powders obtained by the hydrothermal method. We studied the influence of different pH values (7-12) and Eu 3+ concentrations (2.5-25 mol%) on the structural, morphological and luminescent characteristics of Y 2 O 3 :Eu 3+ powders. The hydrothermal synthesis was performed at 200°C for 12 h by employing Y 2 O 3, HNO 3 , H 2 O and Eu (NO 3) 3 as precursors, in order to obtain two sets of samples. The first set of powders was obtained with different pH values and named Eu5PHx (x = 7, 8, 9, 10, 11, and 12), and the second set was obtained by using a constant pH = 7 with different Eu concentrations, named EuxPH7 (x = 2.5, 5, 8, 15, 20 and 25). The XRD spectra showed that the Y 2 O 3 :Eu 3+ powders exhibited a cubic phase, regardless of the pH values and Eu 3+ concentrations. The SEM observations indicated that pH influenced the morphology and size of phosphors; for instance, for pH = 7, hexagonal microplatelets were obtained, and microrods at pH values from 8 to 12. Doping Y 2 O 3 with various Eu 3+ concentrations (in mol%) also produced changes in morphology, in these cases, hexagonal microplatelets were obtained in the range of 2.5-5 mol%, and non uniform plates were observed at higher doping concentrations ranging from 8 to 25 mol%. According to our results, the microplatelets synthesized with a pH of 7 and an 8 mol% Eu 3+ concentration presented the highest luminescence under excitation at 254 nm. All of these results indicate that our phosphors could be useful for applications of controlled drug delivery, photocatalysis and biolabeling.
Luminescent properties of nano-sized Y 2O 3:Eu fabricated by co-precipitation method
Journal of Alloys and Compounds, 2010
Nano-sized yttria (Y 2 O 3 ) powders were successfully synthesized by co-precipitation method. The structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). All the powders were well crystallized and the grains were almost spherical with good dispersibility. The relationship between optical properties and the content of Eu 3+ and Li + ions was studied. The quenching concentration of Eu 3+ ions is 9 mol% which is much higher than the micro-scaled powders. The results also showed that the incorporation of Li + ions can greatly improve the luminescence intensity. The highest emission intensity was observed with 4 mol% Li + doped Y 2 O 3 :Eu powder ((Y 0.87 Eu 0.09 Li 0.04 ) 2 O 3 ) and the fluorescence intensity was increased by as much as 79%.
Photoluminescent properties of nanostructured Y2O3:Eu3+ powders obtained through aerosol synthesis
Optical Materials, 2010
Red emitting Y 2 O 3 :Eu 3+ (5 and 10 at.%) submicronic particles were synthesized through ultrasonic spray pyrolysis method from the pure nitrate solutions at 900°C. The employed synthesis conditions (gradual increase of temperature within triple zone reactor and extended residence time) assured formation of spherical, dense, non-agglomerated particles that are nanostructured (crystallite size $20 nm). The asprepared powders were additionally thermally treated at temperatures up to 1200°C. A bcc Ia-3 cubic phase presence and exceptional powder morphological features were maintained with heating and are followed with particle structural changes (crystallite growth up to 130 nm). Emission spectra were studied after excitation with 393 nm wavelength and together with the decay lifetimes for Eu 3+ ion 5 D 0 and 5 D 1 levels revealed the effect of powder nanocrystalline nature on its luminescent properties. The emission spectra showed typical Eu 3+ 5 D 0 ? 7 F i (i = 0, 1, 2, 3, 4) transitions with dominant red emission at 611 nm, while the lifetime measurements revealed the quenching effect with the rise of dopant concentration and its more consistent distribution into host lattice due to the thermal treatment.
2010
Red emitting Y 2 O 3 :Eu 3+ (5 and 10 at.%) submicronic particles were synthesized through ultrasonic spray pyrolysis method from the pure nitrate solutions at 900°C. The employed synthesis conditions (gradual increase of temperature within triple zone reactor and extended residence time) assured formation of spherical, dense, non-agglomerated particles that are nanostructured (crystallite size $20 nm). The asprepared powders were additionally thermally treated at temperatures up to 1200°C. A bcc Ia-3 cubic phase presence and exceptional powder morphological features were maintained with heating and are followed with particle structural changes (crystallite growth up to 130 nm). Emission spectra were studied after excitation with 393 nm wavelength and together with the decay lifetimes for Eu 3+ ion 5 D 0 and 5 D 1 levels revealed the effect of powder nanocrystalline nature on its luminescent properties. The emission spectra showed typical Eu 3+ 5 D 0 ? 7 F i (i = 0, 1, 2, 3, 4) transitions with dominant red emission at 611 nm, while the lifetime measurements revealed the quenching effect with the rise of dopant concentration and its more consistent distribution into host lattice due to the thermal treatment.
Luminescence properties of Eu3+ activated Y2MoO6 powders calcined at different temperatures
Processing and Application of Ceramics
In the last decade, an immense progress has been made in white LEDs, mainly due to the development of red-emitting phosphors. In this paper, we report on the synthesis of Eu 3+ activated Y 2 MoO 6 by a self-initiated and self-sustained method. The obtained powder was calcined at various temperatures in the 600-1400°C range and examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). The results revealed that all powders are single phase Y 2 MoO 6 :Eu 3+ , with particle size in the nanorange at lower treatment temperatures (600 and 800°C) and in the microrange at higher calcination temperatures (1000-1400°C). The obtained powders are promising materials for white light-emitting diodes as they can efficiently absorb energy in 324-425 nm region (near-UV to blue light region) and emit at 611 nm in the red region of the spectrum, while exhibiting high thermal and chemical stability.
Y2O3:Eu3+ (5mol%) with Ag nanoparticles prepared by citrate precursor
Journal of Solid State Chemistry, 2010
a b s t r a c t Y 2 O 3 :Eu 3 + (5 mol% Eu 3 + ) and Y 2 O 3 :Eu 3 + (5 mol% Eu 3 + ) containing 1 mol% of Ag nanoparticles were prepared by heat treatment of a viscous resin obtained via citrate precursor. TEM and EDS analyses showed that Y 2 O 3 :Eu 3 + (5 mol% Eu 3 + ) is formed by nanoparticles with an average size of 12 nm, which increases to 30 nm when Ag is present because the effect of metal induced crystallization occurs. Ag nanoparticles with a size of 9 nm dispersed in Y 2 O 3 :Eu 3 + (5 mol% Eu 3 + ) were obtained and the surface plasmon effect on Ag nanoparticles was observed. The emission around 612 nm assigned to the Eu 3 + ( 5 D 0 -7 F 2 ) transition enhanced when the Ag nanoparticles were present in the Y 2 O 3 :Eu 3 + luminescent material.
Luminescence and crystallinity of flame-made Y 2O 3:Eu 3+ nanoparticles
Advanced Powder Technol, 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.
Ceramics International, 2011
Herein we presented polymer complex solution method for production of well crystalline europium doped Y 2 O 3 nanopowders. Polyethylene glycol (PEG) of five different molecular weights is used both as a fuel and as a nucleation agent for the crystallization. Powders were cold-pressed and sintered to obtain ceramics. SEM images taken from ceramic pellets indicate formation of a dense structure, with a pronounced grain growth and low pore concentration. Luminescence emission spectra of powders and ceramics are similar, and in good agreement with theoretical data. Lifetimes of Eu 3+ 5 D 0 level in nanocrystalline powders are higher compared to one observed in bulk, confirming in this case theory of lifetime lengthening in nanophosphors due to the change of effective refraction index. As expected, lifetime values in ceramic samples decrease toward the value in bulk Y 2 O 3 . The optical filling factor is calculated from observed decay times, providing a measure of discrepancy between powder and bulk state regarding their luminescent properties. #
Synthesis and characterisation of europium activated yttrium oxide fine powders
Journal of Alloys and Compounds 434–435 (2007) 809–812, 2006
Abstract: In order to prepare fine powders of red emitting Y2O3:Eu phosphors, the reagent simultaneous addition (SimAdd) technique was developed and the influence of some preparative conditions on morpho-structural and optical properties of phosphors was studied. There was revealed that the precipitating reagent type and the pH of the precipitation medium influence on the photoluminescence (PL) properties as well as on the microstructure and morphology of phosphor particles. The SimAdd-technique enables us to prepare fine powders (<1 m) of Y2O3:Eu phosphors with relatively good PL performances to be used in modern optoelectronic devices.