scholarly journals Improvement in luminescent properties and thermo-optical conversion mechanism of Na2SiF6:Mn4+,K+@GQDs

RSC Advances ◽  
2021 ◽  
Vol 11 (37) ◽  
pp. 23023-23035
Author(s):  
Xue Zhong ◽  
Tianman Wang ◽  
Yuelan Li ◽  
Yan Yu ◽  
Long Chen ◽  
...  
Keyword(s):  
Thermal Energy ◽  
High Stability ◽  
Thermal Quenching ◽  
Luminescent Properties ◽  
Light Energy ◽  
Optical Conversion ◽  
Optimal Sample

The optimal sample exhibits high stability due to large negative thermal quenching. The mechanism of negative thermal quenching is suggested to be the conversion of thermal energy into light energy.

scholarly journals Formation and enhancement of negative thermal quenching in emission of KGdF4:Eu3+, Yb3+@GQDs

RSC Advances ◽  
2021 ◽  
Vol 11 (57) ◽  
pp. 36222-36229
Author(s):  
Zhigao Wu ◽  
Chang Chen ◽  
Yaxiong Wang ◽  
Chaolian Luo ◽  
Sen Liao ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Energy ◽  
Thermal Quenching ◽  
Light Energy ◽  
Optimal Sample

The optimal sample exhibits a high luminescence thermal stability, due to a large negative thermal quenching. The mechanism of the negative thermal quenching is suggested as the conversion of thermal energy into light energy.

Negative thermal quenching of K3AlF6:Mn4+@GQDs phosphors caused by enhancement of the conversion of heat energy into light energy

2021 ◽  
Author(s):  
Yuelan Li ◽  
Daishu Deng ◽  
Tianman Wang ◽  
Yan Yu ◽  
Xue Zhong ◽  
...  
Keyword(s):  
Thermal Quenching ◽  
Heat Energy ◽  
Light Energy

scholarly journals Synthesis and Luminescence Properties of a Novel Green-Yellow-Emitting Phosphor BiOCl:Pr3+ for Blue-Light-Based w-LEDs

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1296 ◽  
Author(s):  
Qi Wang ◽  
Meiling Xie ◽  
Minghao Fang ◽  
Xiaowen Wu ◽  
Yan’gai Liu ◽  
...  
Keyword(s):  
Blue Light ◽  
High Performance ◽  
Doping Concentration ◽  
Thermal Quenching ◽  
Luminescent Properties ◽  
Solid State Reaction Method ◽  
Exchange Effect ◽  
Light Emitting ◽  
Good Thermal Stability ◽  
Luminescence Efficiency

The development of white-light-emitting diodes (w-LEDs) makes it meaningful to develop novel high-performance phosphors excited by blue light. Herein, BiOCl:Pr3+ green-yellow phosphors were prepared via a high-temperature solid-state reaction method. The crystal structure, luminescent properties, lifetime, thermal quenching behavior, and quantum yield were studied in detail. The BiOCl:Pr3+ phosphors presented several emission peaks located in green and red regions, under excitation at 453 nm. The CIE coordinates could be tuned along with the changed doping concentration with fair luminescence efficiency. The results also indicated that the optimized doping concentration of Pr3+ ions was at x = 0.0075 because of the concentration quenching behavior resulting from an intense exchange effect. When the temperature reached 150 °C, the intensity of the emission peak at 495 nm could remain at 78% of that at room temperature. The activation energy of 0.20 eV also confirmed that the BiOCl:Pr3+ phosphor exhibited good thermal stability. All these results indicate that the prepared products have potential to be used as a high-performance green-yellow-light-emitting phosphor for blue-light-based w-LEDs.

Study on Luminescent Properties of YAG:Ce3+, Gd3+/La3+ Prepared by Co-Precipitation Method

2014 ◽  
Vol 1002 ◽  
pp. 29-34
Author(s):  
Rong Feng Guan ◽  
Ya Jun You ◽  
Juan Song ◽  
Gui Hua Hou
Keyword(s):  
Emission Intensity ◽  
Room Temperature ◽  
Thermal Quenching ◽  
Luminescent Properties ◽  
Ammonium Bicarbonate ◽  
Color Temperature ◽  
Precipitation Method ◽  
Structure Morphology ◽  
Relative Emission Intensity ◽  
Co Precipitation

The YAG:Ce3+, Gd3+/La3+ yellow phosphors were prepared by co-precipitation method with 0.1mol/L ammonium bicarbonate and aqueous ammonia as precipitants, and the crystal structure, morphology, luminescent properties were investigated. The results indicated that the emission peaks of the YAG:Ce3+, Gd3+/La3+ were redshifted from 535nm to 545.5nm /547nm, and the relative emission intensity declined from 330nm to 145/132 with doping content of Gd3+ /La3+ increased from 0 to 0.9mol at room temperature. Compared with Gd-doping phosphors, the redshift of La3+-doping phosphor was larger and the relative emission intensity declined more quickly. Compared with YAG:Ce3+, the thermal quenching characteristics of YAG:Ce,Gd and YAG:Ce,La were noticeably worse when the temperature increased, but the extents of peak wavelength redshifts were almost the same, about is 7-8nm in the experimental temperature range (50-200°C), have little relation with the doping concentration change. Doping concentrations of Gd or La couldn't be too high, and the suitable concentration was less than 0.6mol at the regulating color temperature and color index.

Preparation and Luminescent Properties of Sm3+-Doped High Thermal Stable Sodium Yttrium Orthosilicate Phosphor

2016 ◽  
Vol 16 (4) ◽  
pp. 3500-3505 ◽  
Author(s):  
Na Xue ◽  
Zhoufei Hei ◽  
Ze Zhao ◽  
Jing Wang ◽  
Ting Wang ◽  
...  
Keyword(s):  
Dopant Concentration ◽  
Red Light ◽  
Thermal Quenching ◽  
Luminescent Properties ◽  
Photoluminescence Properties ◽  
Quenching Temperature ◽  
Light Emitting ◽  
Red Phosphors ◽  
Bright Orange ◽  
White Light Emitting Diodes

Orange-red-emitting sodium yttrium orthosilicate NaYSiO4:xSm3+ (x = 0.005, 0.01, 0.02, 0.05, 0.10, 0.15, and 0.20) were synthesized. The phase structure and photoluminescence properties of these phosphors were investigated. The emission spectrum obtained by excitation into 406 nm contains exclusively the characteristic emissions of Sm3+ at 571 nm, 602 nm, 648 nm, and 710 nm, which correspond to the transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2, and 6H11/2 of Sm3+, respectively. The strongest one is located at 602 nm due to the 4G5/2 → 6H7/2 transition of Sm3+, generating bright orange–red light. The optimum dopant concentration of Sm3+ ions in NaYSiO4:xSm3+ is around 2 mol%, and the critical transfer distance of Sm3+ is calculated as 23 Å. The thermal quenching temperature is above 500 K. The fluorescence lifetime of Sm3+ in NaYSiO4:0.02Sm3+ is 1.83 ms. The NaYSiO4:Sm3+ phosphors may be potentially used as red phosphors for white light emitting diodes.

scholarly journals Blue-Light-Based White-LEDs based on a Novel Green-Yellow-Emitting Phosphor: Synthesis and Luminescence Properties

2019 ◽  
Author(s):  
Qi Wang ◽  
Meiling Xie ◽  
Minghao Fang ◽  
Xiaowen Wu
Keyword(s):  
Blue Light ◽  
High Performance ◽  
Doping Concentration ◽  
Thermal Quenching ◽  
Luminescent Properties ◽  
Exchange Effect ◽  
Light Emitting ◽  
White Leds ◽  
Good Thermal Stability ◽  
Luminescence Efficiency

The development of white-light-emitting diodes (w-LEDs) makes it meaningful to develop novel high-performance phosphors excited by blue light. Herein, BiOCl:Pr3+ green-yellow phosphors were prepared via a high-temperature solid-state reaction method. The crystal structure, luminescent properties, lifetime, thermal quenching behavior, and quantum yield were studied in detail. The BiOCl:Pr3+ phosphors presented several emission peaks located in green and red regions, under excitation at 453 nm. The CIE coordinates could be tuned along with the changed doping concentration with fair luminescence efficiency. The results also indicated that the optimized doping concentration of Pr3+ ions was at x = 0.0075 because of the concentration quenching behavior resulting from an intense exchange effect. When the temperature reached 150 °C, the intensity of the emission peak at 495 nm could remain at 78% of that at room temperature. The activation energy of 0.20 eV also confirmed that the BiOCl:Pr3+ phosphor exhibited good thermal stability. All these results indicate that the prepared products have potential to be used as a high-performance green-yellow-light-emitting phosphor for blue-light-based w-LEDs.

Conversion of thermal energy to light energy and energy transfer in KGdF4: Eu3+,Tb3+ phosphors

2021 ◽  
pp. 108549
Author(s):  
Junyu Ming ◽  
Yaxiong Wang ◽  
Shaokun Ling ◽  
Sen Liao ◽  
Yingheng Huang ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Thermal Energy ◽  
Light Energy

Characterization of a Nanofluid Volumetric Solar Absorber / Steam Generator

2011 ◽  
Author(s):  
Robert A. Taylor ◽  
Patrick Phelan ◽  
Ronald Adrian ◽  
Andrey Gunawan ◽  
Todd Otanicar
Keyword(s):  
Steam Generator ◽  
Thermal Energy ◽  
Bubble Dynamics ◽  
New Technologies ◽  
Pure Water ◽  
Solar Spectrum ◽  
Infrared Camera ◽  
Light Energy ◽  
Heat Transfer Analysis ◽  
Solar Thermal Energy

Solar thermal energy has shown remarkable growth in recent years — incorporating many new technologies into new applications [1]. Nanofluids — suspensions of nanoparticles in conventional fluids — have shown promise to make efficient volumetric-absorption solar collectors [2–4]. It has also been shown that concentrated light energy can efficiently cause localized phase change in a nanofluid [5]. These findings indicate that it may be advantageous to create a ‘direct, volumetric nanofluid steam generator’. That is, a solar collector design which could minimize the number of energy transfer steps, and thus minimize losses in converting sunlight (via thermal energy) to electricity. To study this, we use a testing apparatus where concentrated laser light at 532 nm — a wavelength very near the solar spectrum peak — is incident on a highly absorbing sample. The highly absorbing samples compared in this study are black dyes, black painted surfaces, and silver nanofluids — with de-ionized water as a base fluid. Each of these samples converts light energy to heat — to varying degrees — in a localized region. This region is monitored simultaneously with a digital camera and an infrared camera. The resulting observed temperature profile and bubble dynamics are compared for these fluids. For pure water with a black backing, some very high temperatures (>300 °C) are observed with a laser input of ∼75 W/cm2. Using a similar absorption potential, we observed higher temperatures in the nanofluids when compared to black dyes. A simplified boiling heat transfer analysis based on these results is also presented. We also noticed differences in bubble size and growth rates for the different samples. Overall, this study represents a proof-of-concept test for a novel volumetric, direct steam generator. These results of this test indicate that it may be possible to efficiently generate steam directly in a controlled, localized volume — i.e. without heating up passive system components.

Vapor Phase Synthesis and Characterization of Gallium Nitride Powders

2000 ◽  
Vol 639 ◽  
Author(s):  
Kazuhiko Hara ◽  
Yoshinori Matsuo ◽  
Yuuki Matsuno
Keyword(s):  
Atmospheric Pressure ◽  
Thermal Quenching ◽  
Luminescent Properties ◽  
Ammonia Gas ◽  
Phase Synthesis ◽  
Tube Reactor ◽  
Mean Size ◽  
The Mean ◽  
Vapor Phase Synthesis

ABSTRACTGaN crystalline powders have been synthesized by the reaction of a Ga vapor with an ammonia gas at the reaction temperature Tr = 900 - 1100°C in an atmospheric-pressure open-tube reactor. The size of GaN particles ranges from 0.2 to 2νm. It was found that the structural and luminescent properties depend strongly on Tr. The mean size of the GaN particles increased as Tr is raised. The GaN powders exhibited photoluminescence (PL) dominated by the band edge emissions. Thermal quenching is relatively significant for the powders synthesized at lower Tr. This is presumably due to enhanced non-radiative recombination at the surface because of their smaller particle size.

Rare-Earth Doped In1−xGaxP Prepared by Metalorganic Vapor Phase Epitaxy

1991 ◽  
Vol 240 ◽  
Author(s):  
A. J. Neuhalfen ◽  
B. W. Wessels
Keyword(s):  
Rare Earth ◽  
Vapor Phase ◽  
Alloy Composition ◽  
Energy Levels ◽  
Thermal Quenching ◽  
Luminescent Properties ◽  
Metalorganic Vapor Phase Epitaxy ◽  
Vapor Phase Epitaxy ◽  
General Applicability ◽  
Rare Earth Doped

ABSTRACTThe dependence of the luminescent properties of rare-earth impurities on the band structure of the host compound semiconductor has been investigated. Photoluminescence spectroscopy was used to characterize the optical properties of rare-earth doped Ini1−xGaxP layers prepared by metalorganic vapor phase epitaxy as a function of alloy composition. Thermal quenching of the Er3+, Yb3+, and Tm3+ related emission was observed over the temperature range of 15K to 360K with activation energies that depended on the alloy composition. From measurements of the thermally activated luminescence quenching, the energy levels of the isovalent erbium, ytterbium, and thulium in the alloys were determined. The variation of the position of the rare-earth related energy levels in the host semiconductor is explained in terms of a vacuum referred binding energy model that should have general applicability to other rare-earth doped semiconductor systems.

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