Aiming to the superior of phosphor pattern: Influence of SiO2 nanoparticles on photoluminescence intensification of YAG:Ce (original) (raw)
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Photoluminescence in sol-gel-derived YAG : Ce phosphors
Journal of Crystal Growth, 2007
Cerium-doped yttrium aluminium garnet (Y 3 Al 5 O 12 , YAG) microcrystals were grown using sol-gel technique. The samples were characterized by application of X-ray diffraction (XRD), photoluminescence (PL) spectroscopy and frequency-domain fluorescence lifetime measurements. The PL output, which is important for wavelength conversion in white light emitting diodes (LEDs), was studied as a function of Ce content and annealing temperature. XRD analysis evidenced that sintering of polycrystalline Y 3 Al 5 O 12 :Ce powders at 1000 1C results in the formation of monophasic garnet materials up to 10 mol% of Ce doping; however, concentration quenching is observed in samples with the Ce content exceeding $4% probably due to optical losses in the tail states of the imperfect lattice. PL output increased and the concentration quenching disappeared when a higher sintering temperature of 1300 1C was used. However, in high Ce content (44%) samples, the increase in sintering temperature was found to result in the formation of CeO 2 phase accompanied by an uncontrolled bouncing of PL intensity in powders with similar Ce content. r
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...
Comparative investigation on synthesis and photoluminescence of YAG:Ce phosphor
Phosphor yttrium aluminum garnet Y 3 Al 5 O 12 (YAG), activated with trivalent cerium (Ce 3+) was synthesized by different methods: solid-state reaction (SS), co-precipitation (CP) with ammonium bicarbonate, sol–gel (SG) with citric acid and combustion (CB) with urea. The crys-tallization, morphologies, particle size and luminescent character of the phosphors obtained under different experimental conditions were studied. The influences of various factors on the luminescence intensity of the phosphor were investigated, such as sintering time, repeated calcinations, reaction temperature, and quantities of urea used in CB.
Cerium activated yttrium silicate (Y 2 SiO 5 :Ce) phosphors were prepared by two different wet-chemical synthesis routes namely: simultaneous addition of reagents (SimAd) and solution combustion (SC) using yttriumcerium nitrate and urea as starting materials. TEOS or SiO 2 fume were used as Si sources. A comparative study regarding the morpho-structural and luminescent properties of Y 2 SiO 5 :Ce phosphors is presented. The influence of the silicon source, same as the firing temperature on the samples characteristics were discussed. TG-SDTA, FT-IR, SEM, XRD and photoluminescence investigations were used to characterize the precursors and the corresponding phosphors.
Journal of Non-Crystalline Solids, 2006
Luminescent Y 3 Al 5 O 12 :Tb 3+ (YAG:Tb 3+ ) phosphor thin films and powders have been successfully prepared by the sol-gel route from alkoxide precursors. Advanced coatings were produced by spray and dip-coating from stabilized sols. X-ray diffraction (XRD), attenuated total reflectance/Fourier transform infrared spectroscopy (ATR/FTIR) and atomic force microscopy (AFM) were used to investigate the structure and morphology of layers. YAG phases of high purity were obtained for both powders and films. AFM study revealed coatings of homogeneous topography, whatever the deposition technique. However, dip-coated samples exhibited a much smoother topography, characterized by a root mean square (rms) roughness much lower than that of spray-coated ones. Laser induced emission spectra and decay times of Tb 3+ ions in a spray-coated film were recorded. Measurements exhibit the characteristic green emission of Tb 3+ . Effectiveness of the Tb 3+ doped coatings under UV excitation is also illustrated by pictures.
Photoluminescence enhancement of YAG:Ce nanophosphors with SiO2 additions
Journal of Materials Science: Materials in Electronics, 2015
Co-precipitated Y 3 Al 5 O 12 :Ce nanophosphors with enhanced photoluminescence (PL) intensity were synthesized by introducing SiO 2 in the precursor. The role of SiO 2 on morphologies, PL enhancement and valence state of Ce was investigated by varying the amounts of SiO 2 from 0 to 1.0 wt%. The SiO 2 addition inhibited the crystal growth owing to the appearance of second phase. However, the PL intensity of YAG:Ce was largely improved with SiO 2 addition. The reason for the PL enhancement was that the incorporation of Si 4? into the YAG host suppressed the further oxidation of Ce 3? to Ce 4? owing to charge compensation.
Synthesis and characterization of Ce:YAG nano-phosphors and ceramics
Optical Materials Express, 2016
Yttrium aluminum garnet (YAG), Y 3 Al 5 O 12 is one of the most important optical materials with many applications such as optical windows, laser host materials, detectors and phosphors. Nano YAG could offer many advantageous over bulk materials and large grain size phosphors. In this work Ce doped YAG (Ce:YAG) nanophosphors (NP) were synthesized using simple chemical methods and crystalized by annealing at 800, 900 and 1100°C. Luminescence was recorded in the range of 200 to 800 nm using X-ray induced luminescence technique to detect all emission centers in the sample and evaluate their relative intensities. The effect of annealing temperature and the use of different complexing and polymerization agents on the particle morphology and luminescence were investigated. Trapping phenomena were studied in Ce:YAG NP and bulk ceramics by thermally stimulated luminescence spectroscopy and a comparison was made between them and Ce:YAG single crystals. Measurements concluded that trapping is dominated by crystal defects in single crystals and by trapping sites at the grain boundaries in ceramics. Ce:YAG NPs-on the other hand-are free of traps, which seems to be characteristic of their small grain structure. This study illustrates the effect of chemical agents and annealing temperatures on the structural and optical properties of Ce:YAG nanophosphors and shed light on the nature and characteristics of traps in YAG, which greatly affect its performance in a wide range of applications. Furthermore it reveals that different trapping mechanisms take place among single crystals, bulk ceramics and NPs which could have impact on understanding the optical and scintillation properties of various luminescent materials.
Template synthesis and luminescent properties of nano-sized YAG:Tb phosphors
Journal of Luminescence, 2006
Terbium-activated Y 3 Al 5 O 12 (YAG:Tb) phosphor nanoparticles with homogeneous grain size and crystallinity have been prepared at 700 1C by a novel gel-network coprecipitation route using gelatin as a template. The products were characterized by using TG-DTA, XRD and TEM techniques. The diffraction profile of YAG:Tb nanoparticles could be indexed as a garnet structure and exhibited peak broadening phenomenon, as revealed by X-ray diffraction (XRD) data. The products appeared to be regular spherical or elliptical and sizes ranged from 40 to 55 nm. Furthermore, the photoluminescence spectra of the YAG:Tb nanoparticles were investigated to determine the energy level of electron transition related to luminescence processes. The effects of Tb concentration and the average grain size on the PL spectra were also studied. r
Rare earth activated yttrium aluminate phosphors with modulated luminescence
Luminescence : the journal of biological and chemical luminescence, 2015
Yttrium aluminate (Y3 A5 O12 ) was doped with different rare earth ions (i.e. Gd(3+) , Ce(3+) , Eu(3+) and/or Tb(3+) ) in order to obtain phosphors (YAG:RE) with general formula,Y3-x-a Gdx REa Al5 O12 (x = 0; 1.485; 2.97 and a = 0.03). The synthesis of the phosphor samples was done using the simultaneous addition of reagents technique. This study reveals new aspects regarding the influence of different activator ions on the morpho-structural and luminescent characteristics of garnet type phosphor. All YAG:RE phosphors are well crystallized powders containing a cubic-Y3 Al5 O12 phase as major component along with monoclinic-Y4 Al2 O9 and orthorhombic-YAlO3 phases as the impurity. The crystallites dimensions of YAG:RE phosphors vary between 38 nm and 88 nm, while the unit cell slowly increase as the ionic radius of the activator increases. Under UV excitation, YAG:Ce exhibits yellow emission due to electron transition in Ce(3+) from the 5d level to the ground state levels ((2) F5/2 , ...
Synthesis of cerium activated yttrium gadolinium aluminate phosphors (Y,Gd)3Al5O12:Ce using the wet-chemical synthesis route via the reagent simultaneous addition technique (WCS-SimAdd) is reported for the first time. Y-Gd-Ce-Al precursors with variable Y:Gd ratios have been precipitated from metal nitrates and urea solutions that were simultaneously added, in an aqueous medium with controlled pH and temperature. The precursor nanopowders were intimately mixed with NH4Cl (flux) and calcined for 2 hrs at 1200C, in nitrogen flow and converted into micro-powders of phosphor with nominal formula Y2.97-xGdx Ce0.03 Al5O12 (where x=0; 0.75; 1.50; 2.25; 2.97). Chemical composition and thermal behaviour of precursors as well as the PL properties, and morphological and structural characteristics of phosphor powders were investigated in relation with the Gd amount. WCS-SimAdd route enables a good control of the synthesis conditions to prepare (Y,Gd)3Al5O12: Ce 3+ phosphors with cubic/garnet crystalline structure, regular particle dimensions and shapes and intense yellow-to-orange emission appropriate for use in LED type optoelectronic devices.