scholarly journals Cr3+ doped yttrium gallium garnet for phosphor-conversion light emitting diodes

2015 ◽  
Vol 55 (3) ◽  
Author(s):  
Akvilė Zabiliūtė-Karaliūnė ◽  
Henrikas Dapkus ◽  
Rokas Paulius Petrauskas ◽  
Skirmantė Butkutė ◽  
Artūras Žukauskas ◽  
...  
Keyword(s):  
Calcination Temperature ◽  
Diffuse Reflection ◽  
Internal Quantum Efficiency ◽  
Low Cost ◽  
Strong Dependence ◽  
Sol Gel ◽  
Broad Band ◽  
Luminescent Properties ◽  
Light Emitting ◽  
Calcination Temperatures

In this work Y3Ga5O12 doped with 8.7 mol% Cr3+ (YGG:Cr) far-red phosphor pellets calcined at 1000, 1200, 1300, and 1400 °C temperatures were synthesized by a simple and low cost sol–gel method. The YGG:Cr pellets were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the luminescent properties were studied by measuring diffuse reflection, photoluminescence (PL), PL excitation (PLE) and internal quantum efficiency (QE). The XRD and SEM results have shown that the material becomes more crystalline, uniform and less porous for higher calcination temperatures. XRD results have also shown that the material becomes strained due to the doping with Cr3+ ions for the calcination temperature of 1400 °C. The diffuse reflection and PLE spectra have shown three absorption and excitation bands in the UV, blue and red spectral regions. PL was characterized by a broad band in the far-red spectral region that peaked at about 711 nm. QE has shown a strong dependence on the calcination temperature. Furthermore, using the previously synthesized YGG:Cr phosphor powder and a commercial blue InGaN LED, a far-red–blue phosphor converted LED (pcLED) lamp was designed and characterized. Blue–far-red pcLEDs could be used in greenhouses in order to meet the photophysiological needs of plants.

The effect of silver concentration and calcination temperature on structural and optical properties of ZnO:Ag nanoparticles

2015 ◽  
Vol 29 (01) ◽  
pp. 1450254 ◽  
Author(s):  
M. Shayani Rad ◽  
A. Kompany ◽  
A. Khorsand Zak ◽  
M. E. Abrishami
Keyword(s):  
Calcination Temperature ◽  
Sol Gel ◽  
Visible Emission ◽  
X Ray Diffraction ◽  
Ag Nps ◽  
Zno Nps ◽  
Calcination Temperatures ◽  
Transmission Electron ◽  
Xrd Patterns ◽  
Average Size

Pure and silver added zinc oxide nanoparticles ( ZnO -NPs and ZnO : Ag -NPs) were synthesized through a modified sol–gel method. The prepared samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. In the XRD patterns, silver diffracted peaks were also observed for the samples synthesized at different calcination temperatures of 500°C, 700°C, 900°C except 1100°C, in addition to ZnO . TEM images indicated that the average size of ZnO : Ag -NPs increases with the amount of Ag concentration. The PL spectra of the samples revealed that the increase of Ag concentration results in the increase of the visible emission intensity, whereas by increasing the calcination temperature the intensity of visible emission of the samples decreases.

Synthesis and Characterization of CaMgSi2O6 Activated by Eu2+

2016 ◽  
Vol 881 ◽  
pp. 30-34
Author(s):  
Agatha Matos Misso ◽  
Hermi F. Brito ◽  
Lucas C.V. Rodrigues ◽  
Vinicius R. Morais ◽  
Chieko Yamagata
Keyword(s):  
High Efficiency ◽  
Low Cost ◽  
Sol Gel ◽  
Solid State Reactions ◽  
Phase Identification ◽  
Molten Salt Method ◽  
Persistent Luminescence ◽  
Light Emitting ◽  
Fluorescent Lamps ◽  
White Light Emitting Diodes

Rare earth silicate based MnMgSi2O5+n (M = Ca, Sr or Ba and n=1-2) phosphors, have attracted interest of researchers due to their high efficiency as a host, excellent thermal and chemical stability and high brightness adding to their low cost. These phosphors showed great potential in various applications such as fluorescent lamps, white light emitting diodes, and display components. High temperature solid-state reactions are usually employed to synthesize those compounds. This paper proposes an alternative method of obtaining nanophosphor host based on Eu-doped CaMgSi2O6 (CMS:Eu), persistent luminescence phosphor. Sol gel technique combined to a modified molten salt method was used. The resulted powder was calcined for 3h under an atmosphere of 5% H2 and 95% Ar2. Phase identification by XRD and the measurements of photoluminescence (PL) and photoluminescence excitation (PLE) were performed. Single phased CMS:Eu with persistent luminescence characteristics was prepared.

scholarly journals Highly Selective Syngas/H2 Production via Partial Oxidation of CH4 Using (Ni, Co and Ni–Co)/ZrO2–Al2O3 Catalysts: Influence of Calcination Temperature

Processes ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 141 ◽  
Author(s):  
Anis Hamza Fakeeha ◽  
Yasir Arafat ◽  
Ahmed Aidid Ibrahim ◽  
Hamid Shaikh ◽  
Hanan Atia ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Calcination Temperature ◽  
Partial Oxidation ◽  
Sol Gel ◽  
Analytical Techniques ◽  
Oxygen Storage Capacity ◽  
H2 Production ◽  
Oxygen Storage ◽  
Calcination Temperatures ◽  
Metal Support Interaction

In this study, Ni, Co and Ni–Co catalysts supported on binary oxide ZrO2–Al2O3 were synthesized by sol-gel method and characterized by means of various analytical techniques such as XRD, BET, TPR, TPD, TGA, SEM, and TEM. This catalytic system was then tested for syngas respective H2 production via partial oxidation of methane at 700 °C and 800 °C. The influence of calcination temperatures was studied and their impact on catalytic activity and stability was evaluated. It was observed that increasing the calcination temperature from 550 °C to 800 °C and addition of ZrO2 to Al2O3 enhances Ni metal-support interaction. This increases the catalytic activity and sintering resistance. Furthermore, ZrO2 provides higher oxygen storage capacity and stronger Lewis basicity which contributed to coke suppression, eventually leading to a more stable catalyst. It was also observed that, contrary to bimetallic catalysts, monometallic catalysts exhibit higher activity with higher calcination temperature. At the same time, Co and Ni–Co-based catalysts exhibit higher activity than Ni-based catalysts which was not expected. The Co-based catalyst calcined at 800 °C demonstrated excellent stability over 24 h on stream. In general, all catalysts demonstrated high CH4 conversion and exceptionally high selectivity to H2 (~98%) at 700 °C.

Synthesis of Zn0.2Ca0.8TiO3:0.1Pr3+ by Sol-Gel and its Luminescence Characterization

2013 ◽  
Vol 750-752 ◽  
pp. 877-880
Author(s):  
Yi Shen ◽  
Li Ying Han ◽  
Lu Yao Hou
Keyword(s):  
Treatment Process ◽  
Sintering Temperature ◽  
Sol Gel ◽  
Ultra Violet ◽  
Luminescent Properties ◽  
Luminescent Materials ◽  
Excitation Spectra ◽  
Surface Appearance ◽  
Calcination Temperatures ◽  
Characteristic Emission

The Zn0.2Ca0.8TiO3:0.1Pr3+ luminescent materials were prepared by sol-gel technology. The phase transformation of gel was studied by TG-DTA and XRD in heat treatment process. The luminescent properties of phosphor in different calcination temperatures were determined by fluorescence spectrophotometer, and then the best sintering temperature was confirmed. The luminescent properties of phosphor was obtained through the emission/ excitation spectra. The surface appearance measured with SEM. The results showed that the nanoZn0.2Ca0.8TiO3:0.1Pr3+ phosphor could be obtained by sol-gel, sintering at 900°C. It sent out red fluorescent under the Ultra Violet. This characteristic emission peak at 614nm is associated with the typical 1D23H4 transition of Pr3+ion.

scholarly journals Synthesis and Characterization of Polystyrene/CuO-Fe2O3 Nanocomposites from Natural Materials as Hydrophobic Photocatalytic Coatings

Crystals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 31
Author(s):  
Ratnawulan Ratnawulan ◽  
Ramli Ramli ◽  
Ahmad Fauzi ◽  
Sukma Hayati AE
Keyword(s):  
Contact Angle ◽  
Calcination Temperature ◽  
Sessile Drop ◽  
Sol Gel ◽  
Basic Material ◽  
Copper Ferrite ◽  
Natural Materials ◽  
Hydrophobic Coating ◽  
Calcination Temperatures

This study reports on the synthesis, characterization of polystyrene(PS)/CuO-Fe2O3 nanocomposites, and their application as hydrophobic coatings. CuO and Fe2O3 materials were synthesized from natural materials by the milling method. Meanwhile, the PS/CuO-Fe2O3 nanocomposites were synthesized by the sol-gel method. Furthermore, the hydrophobic coating on the glass substrate was made by the spin-coating. To obtain highest value of contact angle, the composition of both CuO and Fe2O3 in nanocomposite as well as calcination temperatures were varied. Sample characterization was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet visible (Uv-Vis) spectrophotometry analysis. The Sessile drop method was used to determine the contact angle of the layer. The results showed that PS/CuO-Fe2O3 nanocomposite was successfully obtained with a crystal size between 40–52 nm and grain size of 92 nm. In addition to the basic material of composites, hematite and tenorite, the presence of copper ferrite phase was also identified. The CuO-Fe2O3 composition and its large calcination temperature also plays an effective role in the magnitude of the contact angle. The highest value of contact angle obtained was 125.46° at 3:1 composition and calcination temperature of 200 °C. We found that the PS/CuO-Fe2O3 composite was hydrophobic, but the photocatalyst activity was very small at 0.24%.

Synthesis and Luminescent Properties of Mn2+-Doped Zinc Silicate Phosphors by Sol-Gel Method

2010 ◽  
Vol 434-435 ◽  
pp. 214-216 ◽  
Author(s):  
Ji Ming Zhang ◽  
Dong Lin Zhao ◽  
Zeng Min Shen
Keyword(s):  
Sol Gel ◽  
Green Light ◽  
Emission Spectra ◽  
Luminescent Properties ◽  
Nano Particles ◽  
Light Emitting ◽  
Gel Method ◽  
Sol Gel Method ◽  
Structural Details ◽  
Xrd Patterns

Abstract. Green light emitting Mn2+-doped Zn2SiO4 (Zn2SiO4:Mn2+) phosphor nano-particles were synthesized by sol-gel method combined with a furnace firing from the sol-gel solution made with ZnO, MnCO3 and tetraethoxysilan. The influences of annealing temperatures on the microstructures and photoluminescent properties of the Zn2SiO4:Mn2+ phosphors were investigated. The structural details of the phosphors were examined through XRD and SEM. The photoluminescent properties of the Zn2SiO4:Mn2+ phosphors were characterized by excitation and emission spectra. The results indicate that the XRD patterns of the Zn2SiO4:Mn2+ phosphors exhibit a willemite structure (-Zn2SiO4). Green photoluminescence whose emission peak is located at 525 nm were observed from the synthesized phosphor particles under UV excitation. The photoluminescent mechanisms of the Zn2SiO4:Mn2+ phosphors were discussed.

Phase Evolution and Crystallite Size of Ni0.25Zn0.75Fe2O4 at Different Calcination Temperatures

2014 ◽  
Vol 925 ◽  
pp. 290-294 ◽  
Author(s):  
Beh Hoe Guan ◽  
Hasan Soleimani ◽  
Noorhana Yahya ◽  
Noor Rasyada Ahmad Latiff
Keyword(s):  
Crystallite Size ◽  
Calcination Temperature ◽  
Temperature Increase ◽  
Spinel Structure ◽  
Sol Gel ◽  
Phase Evolution ◽  
Calcination Temperatures ◽  
Crystallite Sizes ◽  
Gel Technique ◽  
Scherrer Equation

The effects of calcination temperature varying from 700 to 1100°C on the phase evolution and crystallite size of Ni0.25Zn0.75Fe2O4 synthesized using Sol-Gel technique have been investigated. XRD results showed that the Fe2O3 phase was formed in Ni0.25Zn0.75Fe2O4 in the lower calcination temperature. The crystallization increased as the calcination temperature increased and the crystallite sizes of the Ni0.25Zn0.75Fe2O4 calculated from Scherrer equation were found to be ranged from 16 to 62 nm which increased when calcination temperature increase. Raman results further confirmed the presence of spinel structure in the samples.

scholarly journals Tuning the Pore Structures of Organosilica Membranes for Enhanced Desalination Performance via the Control of Calcination Temperatures

Membranes ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 392
Author(s):  
Rong Xu ◽  
Qian Liu ◽  
Xiuxiu Ren ◽  
Peng Lin ◽  
Jing Zhong
Keyword(s):  
Calcination Temperature ◽  
Sol Gel ◽  
Great Promise ◽  
Oh Groups ◽  
High Salinity Water ◽  
Calcination Temperatures ◽  
Pore Structures ◽  
Salinity Water ◽  
Gel Technique ◽  
Acid Catalyzed

Microporous organosilica membranes based on 1,2-bis(triethoxylsilyl)ethane (BTESE) were fabricated via an acid-catalyzed sol-gel technique. In the preparation process, the calcination temperature plays a significant role in structural and surface properties of the organosilica networks. With an increase in calcination temperature, the surface hydrophilicity decreased due to the enhanced condensation of Si-OH groups in the networks. N2 adsorption results suggest that the pore structures of BTESE membranes was clearly dependent on the calcination temperature. The pore sizes of the membranes were quantitatively determined by using the Normalized Knudsen-based permeance (NKP) model. In pervaporation tests, the membranes with higher calcination temperatures showed higher salt rejections and lower water permeances, which was attributed to the changes in pore size and surface chemistry of pore walls. The BTESE membranes calcined at 200 °C exhibited superior hydrothermal stability in temperature cycles up to 70 °C and high reproducibility in concentration cycles with NaCl concentrations of 0.2–13 wt%, showing great promise for desalination applications of high-salinity water.

scholarly journals Synthesis and Luminescent Properties of Carbon Nanodots Dispersed in Nanostructured Silicas

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3267
Author(s):  
Andrii Vasin ◽  
Dmytro Kysil ◽  
Andriy Rusavsky ◽  
Oksana Isaieva ◽  
Alexander Zaderko ◽  
...  
Keyword(s):  
Carbon Nanoparticles ◽  
Sol Gel ◽  
Luminescent Properties ◽  
Carbon Nanodots ◽  
Ultraviolet Emission ◽  
Organic Precursor ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
New Class ◽  
Nanostructured Silica

Luminescent carbon nanoparticles are a relatively new class of luminescent materials that have attracted the increasing interest of chemists, physicists, biologists and engineers. The present review has a particular focus on the synthesis and luminescent properties of carbon nanoparticles dispersed inside nanostructured silica of different natures: oxidized porous silicon, amorphous thin films, nanopowders, and nanoporous sol–gel-derived ceramics. The correlations of processing conditions with emission/excitation spectral properties, relaxation kinetics, and photoluminescence photodegradation behaviors are analyzed. Following the evolution of the photoluminescence (PL) through the “from-bottom-to-up” synthesis procedure, the transformation of molecular-like ultraviolet emission of organic precursor into visible emission of carbon nanoparticles is demonstrated. At the end of the review, a novel method for the synthesis of luminescent and transparent composites, in form of nanoporous silica filled with luminescent carbon nanodots, is presented. A prototype of white light emitting devices, constructed on the basis of such luminophores and violet light emitting diodes, is demonstrated.

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