Surface coated red phosphors with silica nanoparticles and silica nanocomposites: performance modifications (original) (raw)
Related papers
The effects of SiO2@Y2O2S:Eu 3+ phosphor on the optic characteristics of white light-emitting diodes
Indonesian Journal of Electrical Engineering and Computer Science, 2022
The study investigated the effectiveness of coating silica nanoparticles (SiO2) and resin-silica nanocomposites poly methyl methacrylate (PMMA)silica over the surface of Y2O2S:Eu 3+ red phosphors. The purpose of this surface coating is to enhance the optical properties, including the photoluminescence (PL) and long-term stability, of Y2O2S:Eu 3+. Two methods used to coat the phosphor with 5-mm silica nanoparticles are dipcoating and sol-gel (Stöber) methods. SiO2 nanoparticles were formed via hydrolysis and condensation reactions, while radical polymerization was performed to fabricate the poly (1-vinyl-2-pyrrolidone). The Y2O2S:Eu 3+ surface coating of PMMA-silica composite was performed via two reactions. One is the reaction of SiO2 nanoparticles with methyl methacrylate (MMA) monomer, and the other is MMA-tetraethyl orthosilicate (TEOS) reaction. The results showed that by using the latter method, Y2O2S:Eu 3+ yielded better PL and long-term stability. Additionally, surface coating with the PMMA-SiO2 nanocomposite using the second technique resulted in 5% enhancement in PL and stabilized the cathode luminescence (CL) intensity of Y2O2S:Eu 3+ , compared to those properties of uncoated Y2O3S:Eu 3+ phosphor particles.
Bulletin of Electrical Engineering and Informatics , 2022
The red phosphor Y2O2S:Eu 3+ coated with silica (SiO2) nanocomposite was synthesized using the sol-gel method with dip-coating technique. The purpose of coating the poly (methyl methacrylate) (PMMA)-SiO2 composite on Y2O2S:Eu 3+ phosphor's surface is to protect the phosphor and improve its scattering ability. The three primary ingredients of coating composition include methyl methacrylate (MMA) monomer, tetraethyl orthosilicate (TEOS), and SiO2 nanoparticles. Via Mie scattering theory, the scattering of SiO2 is examined, which primarily determines the scattering of PMMA-SiO2-coated Y2O2S:Eu 3+. The larger particles of SiO2 in the coating composite leads to better scattering properties. When being applied in the dual-film remote phosphor configuration of a LED, SiO2@Y2O2S:Eu 3+ considerably enhances the CRI and the color quality scale (CQS). The highest CRI and CQS can be observed at approximately 85 and 74 with 23 %wt. and 26 %wt. the concentration of SiO2@Y2O2S:Eu 3+ , respectively. Neverthless, the illuminating beam of the package gradually declines as the concentration of SiO2@Y2O2S:Eu 3+ go up, which might be ascribed to excessive scattering occurrences in the double-layer remote package.
International Journal of Electrical and Computer Engineering (IJECE), 2021
Yttrium aluminum garnet (YAG: RE) rare-earth-doped phosphors have great photoluminescence (PL) characteristics and are commonly used in lightemitting rectifying tubes. The RE elements used in these phosphors, however, are precious and in shortage. The production of phosphorus containing a limited amount of RE content is therefore essential. One solution is to manufacture Nano composite phosphors that use an inexpensive and more easily available content as a matrix for RE oxide. In this research, we developed a YAG: Ce/SiO2 Nano composite using a sol-gel procedure; in order to impulse micelle formation and agglomeration, poly (ethylene glycol) and urea have been added, respectively. X-ray diffraction, scanning and transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy were used to characterize the Nano composites. In proposing an explanation for this enhancement, we defined the concentration of SiO2 that produced optimum PL enhancement and used geometric models as well as the characterization consequences. Our results demonstrated that a 10% SiO2 concentration produced a 120% PL intensity of pure YAG:Ce. TEM analysis revealed that SiO2 nanoparticles filled the voids between the YAG:Ce crystals' single grain borders, hence inhibiting light scattering, resulting in increased PL. This procedure would be beneficial for the synthesis of low-RE and high-PL phosphors on a wide scale.
Morphology controlled Y2O3:Eu3+ nanophosphors with enhanced photoluminescence properties
Journal of Luminescence, 2015
Eu 3 þ doped Y 2 O 3 is prepared by a co-precipitation method using ammonium hydrogen carbonate as precipitating agent. In the present work we studied the effect of different molar concentrations of Poly vinyl pyrrolidone (PVP) and 1-Thio-glycerol (TG) as capping agents to enhance the optical and morphological properties of Y 2 O 3 :Eu 3 þ nanophosphors. In addition, variation of pH was studied to control the particle size of the synthesized product. The polymer concentration (TG and PVP) was also optimized at different pH to get higher luminescence of Eu 3 þ doped Y 2 O 3 nanoparticles (NPs). It was observed that pH of solution during synthesis and also its concentration affect the morphological and optical properties of Y 2 O 3 :Eu 3 þ . The structural, morphological and optical properties were studied by an X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and photoluminescence spectroscopy. XRD studies followed by Rietveld refinement confirmed the bodycentered cubic structure of doped nanophosphors. It was observed that at optimized pH and polymer concentration the nanoparticles of Y 2 O 3 :Eu 3 þ have narrow size distribution and exhibited enhanced photoluminescent properties.
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.
Color-tunable properties of Eu3+- and Dy3+-codoped Y2O3 phosphor particles
Nanoscale Research Letters, 2012
Rare-earth phosphors are commonly used in display panels, security printing, and fluorescent lamps, and have potential applications in lasers and bioimaging. In the present study, Eu 3+-and Dy 3+-codoped uniform-shaped Y 2 O 3 submicron particles were prepared using the urea homogeneous precipitation method. The structure and morphology of the resulting particles were characterized by X-ray diffraction, field emission scanning electron microscope, and field emission transmission electron microscope, whereas their optical properties were monitored by photoluminescence spectroscopy. The room-temperature luminescence color emission of the synthesized particles can be tuned from red to yellow by switching the excitation wavelength from 254 to 350 nm. The luminescence intensities of red and yellow emissions could be altered by varying the dopant concentration. Strong quenching was observed at high Eu 3+ and Dy 3+ concentrations in the Y 2 O 3 host lattice.
2015
Y2O3:Eu nanophosphors are prepared from different synthesis viz. Combustion synthesis, Precipitation Method, Sol-Gel. The samples are annealed from 600-14000C temperature. Effect of Temperature on luminescence intensity of Europium Doped Y2O3 phosphor prepared from different synthesisroutes is studied in the presented paper. Prepared samples are found to have monoclinic structure when compared with JCPDS standard data. The luminescence intensity increases with the increase of particle size and is affected by synthesis route. Eu doped Y2O3 particle shows sharp emission at 611nm at UV excitation. The samples are excited with different UV wavelength and maximum emission intensity is found when excited with 234nm wavelength. Powder X-Ray Diffraction (XRD) results indicated that high temperature leads to increase in the particle size. TEM photographs show the agglomeration of the samples at higher temperature.
Journal of Materials Research, 2007
A monodisperse spherical Y2O3:Eu3+ phosphor was prepared by a homogeneous precipitation method. The mean size of the phosphor particles (MSPP) was successfully controlled by changing the volume ratio of normal alcohol (RA) (propanol) in the solvents mixed between deionized water and normal propanol. When the RA was increased from 0 to 0.7, the MSPP decreased while maintaining a high yield of >95%. Although the prepared phosphor samples were fired at the same temperature, the thermal energy was delivered more efficiently into the inner side of the phosphor particles with the decrease of the MSPP. Therefore, the crystallinity and also the photoluminescence (PL) intensity of the phosphor increased with the decrease in the MSPP. In addition, because the numbers of Eu3+ ions located near the particle surfaces increased with the decrease of particle size, the ratio of PL intensity caused by the 5D0–7F2 transition to that caused by 5D0–7F1 transition increased from 10.8 to 12.7 with the...
Synthesis of Y 2 O 3 :Eu 3+ micro- and nanophosphors by sol-gel process
Journal of Physics: Conference Series, 2009
In this paper, optical properties of Y2O3:Eu 3+ micro-and nanophosphors synthesized by sol-gel process are reported. Citric acid and tartaric acid were employed as chelating agents. Different factors effecting structures and properties of the phosphors, such as concentration of Eu3+, sintered temperature and the ratio of metal ions to tartaric acid, were examined. Crystal structure of the particles was investigated by X-ray diffraction (XRD) technique. The results showed that the phosphor powders completely crystallized at 600°C. Morphology and particle size of the phosphors were studied by scanning electron microscope (SEM) and transmission electron microscope (TEM). The particle size of the obtained phosphors varied from 1 to 6 μm (using citric acid as chelating agent) and from 20 to 30 nm (using tartaric acid as chelating agent).
Eu3+-Doped Y2O3-SiO2 Nanocomposite Obtained by a Sol-Gel Method
MRS …, 2001
A Y 2 O 3 -SiO 2 nanocomposite doped with Eu 3+ was obtained by a sol-gel method and characterized by X-ray diffraction, IR, 29 Si NMR and laser-excited luminescence spectroscopy. It was found that small (2-3 nm) yttria nanoparticles are homogeneously dispersed in, and interacting with, the amorphous silica matrix. Luminescence spectroscopy indicates that the Eu 3+ ion is preferentially located inside or at the surface of highly disordered Y 2 O 3 nanoparticles. These luminescent nanocomposites form a class of materials which could find applications in the field of phosphors. Lanthanide ions in insulating host matrix find uses in a wide variety of applications, such as phosphors for fluorescent lighting, display monitors, X-ray imaging, laser and amplifiers for fiber-optic communication. Preparing nanoscale host materials can change the physical properties, which affect the luminescence and dynamics of the optically active dopant. Nanocrystalline Y 2 O 3 has been investigated as a host, due to its interesting applications in the field of the phosphors for lighting and for cathode ray tubes 1,2 . In the present work, we decided to investigate the optical properties of Eu 3+ doped Y 2 O 3 nanoparticles dispersed in a transparent medium such as amorphous SiO 2 , which can stabilize and protect the nanoparticles from aggregation 3 . The Eu 3+ ion was chosen on the basis of its high emission quantum yield, its relatively simple energy level scheme, its applications as structural probe for the sites occupied by the Ln 3+ in a given material, 4 and the technological importance of Y 2 O 3 :Eu 3+ as a phosphor 2 .