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Fabrication and mid-infrared property of Er:CaF2 transparent ceramics
摘要： High doped Er:CaF2 transparent ceramics (up to 10.0 at.%) were fabricated by hot pressing nanopowders which were synthesized by co-precipitation method. The composition and micrographs of the powders were characterized. The mid-infrared emission spectra and lifetimes of the 4I13/2 energy level of Er:CaF2 transparent ceramics were investigated for the first time. The mechanisms of energy transfer processes based on the emission spectra of different wavelengths were discussed. The enhanced 2.7 μm emission intensity and the reductions of near-infrared fluorescence lifetimes were observed indicating that the high concentrations of Er3+ ions are beneficial to overcome the self-termination effect and realize 2.7 μm laser output. It can be seen from these results that high concentrations Er-doped CaF2 transparent ceramics can be considered as promising host materials for the applications of mid-infrared lasers.
关键词： Transparent ceramic,Mid-infrared,Luminescence lifetime,Nanoparticle
更新于2025-09-23 15:23:52
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Photoluminescence, scintillation and TSL properties of Eu-doped Al2O3 transparent ceramics synthesized by spark plasma sintering method
摘要： We synthesized Al2O3 transparent ceramics doped with different concentrations of Eu (0.001, 0.01, 0.1 and 1.0%) by the spark plasma sintering (SPS) method, and then we investigated their photoluminescence (PL), scintillation and thermally-stimulated luminescence (TSL) properties. In the PL, the samples showed a broad emission peak at 400 nm due to the 5d-4f transitions of Eu2+ and several sharp emission peaks across 550–750 nm due to the 4f-4f transitions of Eu3+ and the 3d-3d transitions of Cr3+ impurity ion. In addition to these peaks over 550–750 nm, in scintillation, the samples exhibited two broad peaks over 300–400 nm possibly due to not the 5d-4f transitions of Eu2+ but F and F+ centers. In TSL, the glow curve consisted of peaks at approximately 100, 160, 210 and 320 °C. The TSL intensity of the 0.001% Eu-doped sample was the highest, and the TSL response was confirmed to be linear to irradiated X-ray dose in the range from 0.1 to 1000 mGy.
关键词： Transparent ceramic,Scintillator,Eu,Dosimeter,Al2O3
更新于2025-09-23 15:23:52
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Fabrication of fine-grained undoped Y2O3 transparent ceramic using nitrate pyrogenation synthesized nanopowders
摘要： Y2O3 ceramic is a promising optical material for mid-infrared (IR) windows and domes. Improvements in the mechanical and thermal performance of this material have become urgent if it is to perform adequately under extreme conditions. Herein, Y2O3 nanopowders were produced through the nitrate pyrogenation method. The final Y2O3 transparent ceramics were fabricated with a hybrid sintering method combining low temperature presintering and a subsequent hot isostatic pressing (HIP) treatment. The synthesis of nanopowders and the fabrication of the final ceramic products were investigated in detail. The Y2O3 ceramic sample that was presintered at 1350 °C provided the optimum microstructure for HIP treatment and resulted in an average grain size of 0.5 μm. Owing to the reduced grain size, the flexure strength and Vickers hardness of the sample were improved to 180 MPa and 8.4 GPa, respectively. Furthermore, the achieved pure Y2O3 ceramic demonstrated an excellent thermal conductivity at high temperature.
关键词： Nanopowders,Y2O3,Nitrate pyrogenation,Fine-grained transparent ceramic
更新于2025-09-23 15:23:52
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YAG:Ce <sup>3+</sup> Transparent Ceramic Phosphors Brighten the Next-Generation Laser-Driven Lighting
摘要： Y3Al5O12:Ce3+ (YAG:Ce3+) transparent ceramic phosphors (TCPs) are regarded as the most promising luminescent converter for laser-driven (LD) lighting. High-quality YAG:Ce3+ TCPs are still urgent for high efficiency LD lighting devices. YAG:Ce3+ TCPs in a vacuum ambience by using nano-sized raw materials are prepared. Controlling defects by adding nano-sized MgO and SiO2 simultaneously enables a high transmittance nearly 80%. After annealing in air furthermore, the luminous efficiency is enhanced greatly from 106 to 223 lm W?1, which is the best result reported now for LD lighting. These results demonstrate that the optimizing YAG:Ce3+ TCPs in a fitting strategy will brighten once again in the next-generation LD lighting. Based on scanning electron microscopy (SEM) coupled with a cathodoluminescence system, defects and Ce3+ distributions in grains are identified directly for the first time.
关键词： cathodoluminescence,laser-driven lighting,transparent ceramic phosphors,Mg2+–Si4+,YAG:Ce3+
更新于2025-09-23 15:21:01
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Spectroscopy and diode-pumped continuous-wave laser operation of Tm:Y2O3 transparent ceramic at cryogenic temperatures
摘要： We present the spectroscopic and laser characteristics of a 3 at.% Tm:Y2O3 transparent ceramic at cryogenic temperatures. An absorption cross section of 4.7 × 10?21 cm2 with a bandwidth of 0.7 nm centered at 793.3 nm and an emission cross section of 29.0 × 10?21 cm2 centered at 1930.9 nm were estimated at 80 K. Continuous-wave laser operation was achieved using broadband and VBG stabilized laser diodes emitting around 793 nm as pump sources. With the VBG pump diode, a maximum output power of 6.4 W was achieved at 80 K corresponding to a slope efficiency of 52.0% with respect to absorbed power.
关键词： cryogenic temperatures,diode-pumped,Tm:Y2O3,spectroscopy,continuous-wave laser,transparent ceramic
更新于2025-09-19 17:13:59
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Recorded color rendering index in single Ce,(Pr,Mn):YAG transparent ceramics for high-power white LEDs/LDs
摘要： Transparent ceramic (TC) is an incredibly promising color converter for high-power white LEDs/LDs. However, the preparation process of multiple structured TC with high color rendering index (CRI) is complicated and of technical challenge, and the inability of a single structured TC to achieve a high CRI significantly limits its real application. In this study, high quality single structured Ce,(Pr,Mn):YAG TCs with the 'wide peak' and 'narrow peak' red light emission were designed and fabricated by the solid-state reaction and vacuum sintering method. Compared with the emission spectra of the Ce:YAG TC, synchronous doping Pr3+ and Mn2+ ions into Ce:YAG TCs resulted in an inhomogeneous broaden of the full width at half maximum (FWHM) from 91.7 nm to 102.2 nm. Impressively, the CRI of the single Ce,(Pr,Mn):YAG TC based high-power white LEDs was as high as 84.8, and the correlated-color temperature (CCT) of the white LEDs/LDs were 5450 K and 3550 K, respectively. Furthermore, when the addition amounts of Pr3+ and Mn2+ were 0.2 at.% and 0.8 at.%, respectively, the prepared Ce,(Pr,Mn):YAG TC displayed a high quantum efficiency (IQE=48.14%) and an excellent color stability (only 5% fluctuation). Therefore, this work not only shows how to overcome the spectrum deficiencies of single structured TCs that restrains the intrinsic CRI improvement, but also provides a reference for the pursuit of a high luminescent property. It significantly reinforces the understanding of CRI problems of TC based high-power lighting, which is crucial for the real application of white LEDs/LDs.
关键词： color rendering index,Ce,(Pr,Mn):YAG,synchronous doping,high-power white LEDs/LDs,Transparent ceramic
更新于2025-09-19 17:13:59
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A double-layer white light converter with high efficiency heat transfer structure for high-power NUV LEDs/LDs
摘要： As a next-generation lighting technology, high-power light-emitting diodes (LEDs) and lasing diodes (LDs) lighting have attracted great attention to high-brightness applications. However, producing an efficient illumination-grade color converter with a conspicuous color rendering index (CRI) and a suitable correlated color temperature (CCT) remains an outstanding challenge in the field of high-power LEDs/LDs lighting. In this work, a double-layer white light converter with high efficiency heat transfer structure was designed and prepared by precisely coating a blue/green emitting phosphor-in-silicone (PIS) film on red emitting transparent ceramic substrate. The well-designed double-layer converter exhibits excellent optical properties that the optical-optical conversion efficiency can achieve 156 lm/W with conspicuous CRI (92.6), CIE chromaticity coordinate (0.332, 0.335) and suitable CCT (5511K), respectively. Furthermore, the heat transfer efficiency of the double-layer converter was analyzed and simulated by using infrared thermal imaging and steady state thermal simulation, which reduce the temperature efficiently than single-layer converter under high-power NUV LEDs/LDs excitation. These comprehensive performance show that the double-layer converters are promising as NUV LEDs/LDs-driven phosphors in high-power solid-state lighting devices.
关键词： high-power LED/LD,transparent ceramic,white light converter,thermal performance,double-layer structure
更新于2025-09-12 10:27:22
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Effect of calcium oxide doping on the microstructure and optical properties of YAG transparent ceramics
摘要： Yttrium aluminium garnet (YAG, Y3Al5O12) transparent ceramics were fabricated by vacuum sintering the co-precipitated raw powders with calcium oxide (CaO) as the sintering aid. The influence of CaO content on the phase composition, particle size and the morphologies of resultant YAG powders, as well as the microstructural and optical properties of YAG ceramics, was investigated in detail. Our results show that with increasing of CaO additives, the particle size and agglomeration degree of the powders were slightly increased and the grain growth of the ceramics was inhibited. Specifically, the grain size initially decreased dramatically till reaching a minimum value of 1.85 μm with 0.3 at% CaO, then slightly increased. In addition, for YAG ceramics with a high CaO doping level, the existence of liquid phase was observed for the first time and its sintering mechanism was discussed. The excess of CaO causes the formation of grain boundary phases and residual pores, which are detrimental for maintaining higher optical quality of YAG ceramics. We obtained a fully dense and pore-free YAG ceramic with an in-line transmittance of 80.8% at 1100 nm by adopting 0.1 at% level of CaO during sintering of the green bodies at 1780°C for 20 h in vacuum.
关键词： Microstructure evolution,YAG transparent ceramic,Co-precipitation method,CaO additives
更新于2025-09-10 09:29:36
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Sol-gel synthesis and characterization of ZnAl2O4 powders for transparent ceramics
摘要： The sol-gel synthesis of ZnAl2O4 ceramic powders from alkoxide and acetate sources of metals, as well as the microstucture and the hardness of the hot-pressed ZnAl2O4 specimens were considered. ZnAl2O4 powders were prepared by the hydrolysis of an alcohol solution of aluminium isopropoxide using an aqueous solution of zinc acetate followed by heat treatment. The thermal evolution of the ZnAl2O4 precursor was investigated. The effect of calcination temperature on the morphology and the specific surface area of ZnAl2O4 powders were also studied. The sintering of the resultant powders to the high transparent ceramic using a hot pressing with 1 wt% ZnF2, as a sintering additive was successfully demonstrated. The in-line transmittance of ZnAl2O4 ceramics (1 mm thickness) achieved 80% in the visible region and 85 % at 5 μm; Vickers hardness was 11.6 GPa.
关键词： transparent ceramic,powders,sol-gel synthesis,ZnAl2O4
更新于2025-09-10 09:29:36
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Dy <sup>3+</sup> -doped Y <sub/>3</sub> Al <sub/>5</sub> O <sub/>12</sub> transparent ceramic for high efficiency ultraviolet excited single-phase white-emitting phosphor
摘要： A kind of Dy-doped yttrium aluminum garnet (YAG) transparent ceramic for ultraviolet excited single-phase white light emitting phosphor was investigated, which has high quantum efficiency (45%). The temperature field of Dy:YAG transparent ceramic was calculated by steady state thermal simulation. Moreover, by combining with 365 nm LED chip directly, the CIE coordinate (x=0.33, y=0.35) is close to the standard equal energy white light illumination. The Dy:YAG transparent ceramic, possessing of good optical and thermal properties, is promising for applications in high-power LEDs devices.
关键词： single-phase white-emitting phosphor,Dy-doped YAG,high-power LEDs,transparent ceramic
更新于2025-09-09 09:28:46