- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Improved negative thermal quenching effect via high sensitizer doping content in NaGdF4 based active-core/active-shell architecture
摘要： The strategies of introducing interior defects and reducing mean particle size have been applied to improve negative thermal quenching effect (TQE) in Yb3+ sensitized fluoride upconversion (UC) nanocrystals (NCs) recently. Herein, an active-core/active-shell structure with high total Yb3+ doping content is used to enhance the absorption intensity of Er3+ ions. Moreover, the Er3+ activators are doped into the shell to enable the energy migration process from activators to surface defects. In this scenario, with the rise of temperature, the suppression degree of this energy migration process is enlarged followed by an improved negative TQE. Specifically, with rising the temperature from 293 K to 413 K, the integral upconversion emission intensity of 40Yb: NaGdF4@60Yb/2Er: NaGdF4 NCs increases by ~ 8.24 times, while that of NaGdF4@20Yb/2Er: NaGdF4 NCs with a similar mean particle size only enhances ~ 3.44 times.
关键词： Yb3+ concentration,upconversion,temperature sensing,negative thermal quenching
更新于2025-11-14 17:03:37
-
Structure variation and luminescence enhancement of BaLaMg(Sb, Nb)O6:Eu3+ double perovskite red phosphors based on composition modulation
摘要： A series of BaLaMgSb1-xNbxO6:Eu3+ double perovskite red phosphors was successfully obtained. X-ray diffraction and Rietveld refinement analyses were conducted to determine the phase information and the detailed structure parameters. The coordinate variations of both La3+/Eu3+ and Sb5+/Nb5+ were discussed to elucidate the influence of B-site ion doping on the lattice variation. Luminescence properties, excitation and emission spectra, were presented to show the advantages of doping with Nb5+ ion. Ultraviolet-vis diffuse reflectance spectra were performed to reveal the reason for the decreased emission intensity under the charge transfer band excitation. Moreover, band gap energy was estimated to clarify the relationship between the increased intensity (λex = 395 and 465 nm) and Nb5+ concentration. Intensity ratios of I(615)/I(590) were performed to show the symmetry variation of the lattice. Thermal quenching property was also investigated and the quenching mechanism was discussed in detail based on the ionization process.
关键词： White LED,Structure variation,Thermal quenching mechanism,Double perovskite
更新于2025-09-23 15:23:52
-
Luminescence quenching properties of Sr2Ga2GeO7: Pr3+ with and without traps participation
摘要： Thermal quenching has been extensively regarded as one of the most signi?cant challenges that limits the application of phosphors in today's world. Further e?ort is urgently required to understand the mechanism of thermal stability for achieving the improved performance of these phosphors. Sr2Ga2GeO7: Pr3+ has been synthesized by the conventional high temperature solid state reaction. A dominant green emitting is presented for the partial energy transition quenching process of the 3P0→3H4 emission. The defect states structure is improved via the introducing of co-solvents, and the thermal stability of 1D2→3H4 and 3P0→3H4 levels can be further adjusted. The intervalence charge transfer (IVCT) and traps are introduced to explain the luminescence quenching properties of Sr2Ga2GeO7: Pr3+. The synergy of various models will provide a new idea for improving the luminescence stability of phosphors in the future.
关键词： Partial energy transition,Thermal quenching,IVCT,Mechanism
更新于2025-09-23 15:23:52
-
Insights into anti-thermal quenching of photoluminescence from SrCaGa4O8 based on defect state and application in temperature sensing
摘要： Herein, a self-activated phosphor SrCaGa4O8 with excellent thermal stability was synthesized by high temperature solid state reaction method. It exhibited the broad emission range from 300 to 600 nm under 220 nm excitation, which may be caused by the intrinsic defects of host. Specifically, with the temperature increasing, the photoluminescence (PL) color changed from bluish to yellow-green and the maximum of PL intensity at 550 nm was obtained when reaching 493 K. From thermoluminescence curves and high temperature spectra, it was found that the anti-thermal quenching phenomenon could be dependent on the self-compensation of the carriers. Accordingly, the results of temperature-dependent intensity ratio and sensitivity show that SrCaGa4O8 may have potential in the optical temperature sensing.
关键词： Energy transfer,Self-activated phosphor,Optical properties,Anti-thermal quenching,Sensors
更新于2025-09-23 15:22:29
-
Temperature-dependent luminescence of Ce-doped SrO-B2O3 glasses
摘要： In this study, the photoluminescence (PL) and X-ray-induced scintillation of trivalent cerium, Ce3+, in strontium borate glasses was examined. As no precipitated crystallites were observed, the slight coloration of the glasses was attributed to the formation of defects that are inactive in electron spin resonance spectroscopy. Both the Ce3+/(Ce3++Ce4+) ratio, which was estimated based on the Ce LIII-edge in X-ray absorption near edge structure analysis, and the internal quantum efficiency of Ce-doped glasses increased as the amount of Ce(OCOCH3)3×H2O, which acted as a reducing agent, was increased. Although the PL intensity was independent of the temperature in the range of 10–300 K, the X-ray induced scintillation exhibited thermal quenching behavior with an activation energy of 0.14 eV.
关键词： borate glass,scintillation,thermal quenching,Ce L-edge X-ray absorption near edge structure (XANES),photoluminescence,cerium
更新于2025-09-23 15:21:01
-
Temperature-Dependent Luminescence of Red-Emitting Ba2Y5B5O17: Eu3+ Phosphors with Efficiencies Close to Unity for Near-UV LEDs
摘要： Solid state white light sources based on a near-UV LED chip are gaining more and more attention. This is due to the increasing e?ciency of near-UV-emitting LED chips and wider phosphors selection if compared to devices based on blue LED chips. Here, a brief overview is given of the concepts of generating white light employing near-UV LED and some optical properties of the available phosphors are discussed. Finally, the synthesis and optical properties of very e?cient red-emitting Ba2Y5B5O17:Eu3+ phosphor powder and ceramics is reported and discussed in terms of possible application as a red component in near-UV LED-based white light sources.
关键词： Eu3+,ceramics,near-UV LED,quantum e?ciency,luminous e?cacy,red phosphor,borate,CIE 1931 colour coordinates,thermal quenching
更新于2025-09-19 17:13:59
-
Luminescence declining behaviors in YAG:Ce transparent ceramics for high power laser lighting
摘要： High lumen-density laser lighting has become an advanced lighting technology. However, as an important component, transparent light-conversion materials exhibit low efficiency and luminescence declining behaviors, especially under high power density lasers, seriously restricting their potential applications. Herein, high quality YAG:Ce transparent ceramics (TCs) with different Ce concentrations and sizes were designed and fabricated for comparison with YAG:Ce single crystals to reveal the nature behind the above phenomena under the assistance of different encapsulated models of LED/LD devices. The highest luminous efficiency for the TCs of over 248 lm W?1 was achieved in the LED device, while only 170 lm W?1 could be reached for the LD devices. The strong thermal quenching and concentration quenching worked synergistically to result in the luminescence declining behavior in the 0.5 at% YAG:Ce ceramics, which have 80% and 20% responsibility after smart experimental comparison, respectively. Besides, the potential factors for the low efficiency in TC-based LD lighting were also revealed. Therefore, this work not only shows the optical performance of TCs in LED and LD applications, but also presents how the deep influence factors and excitation models lead to differences in their performance. It significantly reinforces the understanding of fundamental problems for TC-based high power laser lighting. These results are crucial for advancing TC-supported technologies in illumination, projection and scintillation.
关键词： transparent ceramics,concentration quenching,laser lighting,YAG:Ce,luminescence declining,thermal quenching
更新于2025-09-16 10:30:52
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Structured Auxiliary Mesh (SAM) Algorithm for Opto-Thermal Simulation of Laser-Based Lighting Systems
摘要： Laser-based lighting systems are an emerging technology, the next step in solid state lighting that revolutionized the way artificial light is generated. The configuration of interest here is the laser-excited remote phosphor (LRP) scheme that consists of a laser diode as the excitation source of an appropriately chosen phosphor sheet. The phosphor is employed for the down-conversion of the incident laser light and broadening of the output spectrum. Although some commercial applications have already been developed, the optimization of LRP systems has yet to be achieved. A bottleneck in their performance is the thermal dependency of the phosphor’s emission characteristics, a phenomenon also known as thermal quenching. As a result, the need for an opto-thermal simulation strategy arises that will enable the study and optimization of LRP systems [1]. The opto-thermal simulation model discussed here is based on Monte Carlo simulations for the optical part, where the absorbed radiant flux is calculated. These optical thermal losses are subsequently used as a volume heat source to solve the transient heat equation by applying the finite element method (FEM) [2]. As thermal quenching is a time-dependent phenomenon in nature, this is an iterative procedure, where the absorbed flux must be calculated for most of the time steps. Typical Monte Carlo ray tracing algorithms use voxel-based meshes to store any calculated properties / attributes. The problem that arises here is that the computational cost for converting the voxel-based mesh to an FEM mesh would be prohibiting for time-dependent analysis. The solution is to directly store the absorbed flux to the FEM mesh. However, the issue that now emerges is locating the interpolating point, namely the point in space where the absorption occurs, within the unstructured FEM mesh. The processing time of a brute force search would be too long, so more sophisticated solutions must be found. SAM algorithms, which were first introduced in [3], are part of a class of algorithms known as geometric search algorithms [4, 5] that deal with point location in unstructured meshes. We propose here a modified SAM algorithm that uses the optical voxel-based mesh as the auxiliary structured mesh for geometric searching. The two meshes, optical and FEM, are superimposed. As point location in voxel-based meshes is trivial, by mapping which elements of the FEM mesh belong to each voxel, we can easily narrow down the number of searches required. To this end, two maps, implemented as binary search trees, are implemented. The first map, maps the voxel number to the nodes of the FEM mesh that lie within it, while the second map, maps the elements of the unstructured mesh that these nodes belong to. The set-up times of these maps heavily depend on the density of the FEM mesh and the order of the elements used. The use of higher-order elements results in considerable set-up times. As higher order elements are not necessary for thermal analysis, this is not a critical issue here. On the other hand, the denser the optical mesh, the fewer FEM elements are mapped to each voxel. However, the size of voxels should be appropriately chosen, since too small voxels may lead to degenerative cases where there are voxels without any nodes lying in them. A distinct advantage of this method is that once the maps are assembled, the search time of elements is O(1). Simulation plays an increasingly crucial role in the study and optimization of optical systems. Due to the increase in computational capabilities, modelling of more complex phenomena can be included and the need of multi-physics approaches rises. The optical properties of materials often shift to temperature above tolerance levels that may render a particular optical design ineffective. In other cases, structural loads may be the critical issue as they can lead to misalignment of optical elements. The proposed SAM algorithm that enables a more efficient coupling of optical and FEM analysis is a valuable tool to such approaches of optical problems.
关键词： Laser-based lighting systems,opto-thermal simulation,Monte Carlo simulations,SAM algorithm,finite element method,thermal quenching
更新于2025-09-16 10:30:52
-
Optical Properties of Red-Emitting Rb2Bi(PO4)(MoO4):Eu3+ Powders and Ceramics with High Quantum Efficiency for White LEDs
摘要： There are several key requirements that a very good LED phosphor should meet, i.e., strong absorption, high quantum e?ciency, high colour purity, and high luminescence quenching temperature. The reported Rb2Bi(PO4)(MoO4):Eu3+ phosphors have all these properties. The Rb2Bi(PO4)(MoO4):Eu3+ phosphors emit bright red light if excited with near-UV radiation. The calculated colour coordinates show good stability in the 77–500 K temperature range. Moreover, sample doped with 50% Eu3+ possesses quantum e?ciency close to unity. Besides the powder samples, ceramic disks of Rb2Eu(PO4)(MoO4) specimen were also prepared, and the red light sources from these disks in combination with near-UV emitting LED were fabricated. The obtained results indicated that ceramic disks e?ciently absorb the emission of 375 and 400 nm LED and could be applied as a red component in phosphor-converted white LEDs.
关键词： thermal quenching,luminescent ceramics,red phosphor,colour coordinates,quantum e?ciency,luminous e?cacy
更新于2025-09-16 10:30:52
-
Phototransferred thermoluminescence of annealed synthetic quartz: Analysis of illumination-time profiles, kinetics and competition effects
摘要： Phototransferred thermoluminescence (PTTL) induced from annealed synthetic quartz using 470 nm blue light is reported. The quartz was annealed at 900oC for 10, 30 and 60 minutes prior to use. A glow curve of conventional TL measured at 1oC s-1 following irradiation to 200 Gy for the sample annealed for 10 minutes shows six peaks at 90, 122, 176, 210, 240 and 340oC. The sample annealed for 30 minutes has peaks at 80, 110, 136, 196, 240 and 330oC. Similarly, the sample annealed for 60 minutes also has six peaks at 80, 120, 134, 188, 235 and 340oC. For ease of reference, these are labelled I-VI respectively. Peaks observed under PTTL are referred to as A1 onwards. Of the six peaks, only the first three are reproduced under phototransfer for the sample annealed for 60 minutes. When the duration of annealing was reduced to 10 minutes, PTTL is induced only at peaks A1 and A3. Interestingly, for the intermediate duration of annealing of 30 minutes, the only peak that appears under phototransfer is the first one, A1. For quartz annealed for 10 minutes, the PTTL appears as long as the preheating temperature does not exceed 560oC. On the other hand, in the quartz annealed for 30 and 60 minutes, PTTL only appears for preheating to and below 450oC. This shows that the occupancy of deep electron traps at temperatures beyond 450 or 560oC is low in the said samples. The activation energy for peaks A1 and A3 was found to be about 0.68 eV. The PTTL peaks were studied for thermal quenching and peaks A1 and A3 were determined to be subject to this effect. The activation energy for thermal quenching was determined as 0.62 ± 0.04 eV in analysis using peak A1. In all cases, the PTTL intensity goes through a peak as a function of illumination time. The experimental dependence of PTTL intensity on illumination time is modelled using sets of coupled linear differential equations based on systems of donors and acceptors whose number is determined by preheating temperature. Competition effects involved in the PTTL have been discussed.
关键词： competition effects,phototransferred thermoluminescence,synthetic quartz,Annealing,thermal quenching
更新于2025-09-12 10:27:22