- 标题
- 摘要
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- 实验方案
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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
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Controlled nanoa??crystallization of IR frequencya??doubling Cd <sub/>4</sub> GeS <sub/>6</sub> crystal in chalcogenide glass
摘要： Crystallization of IR frequency-doubling nanocrystals in chalcogenide glasses is a promising approach to achieve novel nonlinear optical materials. However, controllable glass crystallization remains challenging. In this study, IR-transparent chalcogenide glass-ceramics containing novel Cd4GeS6 IR frequency-doubling na- nocrystals (about 60-80?nm) are fabricated through controlled nano-crystallization. Nanocrystalline structure of the Cd4GeS6 nano-crystallized glass-ceramics is inves- tigated in detail through X-ray diffractometer, field emission scanning electron mi- croscope, and Raman scattering techniques. The structural similarity of [Cd4GeS6] polyhedron in the network structure of as-prepared glass is found to be responsible for the nucleation of Cd4GeS6 crystal. A unique microstructure of Cd4GeS6 nanocrys- tals embedded GeS2 phase-separated structure is discovered in samples thermally treated at high temperatures (370°C and 380°C). This study would not only shed more light on glass crystallization mechanism but also provide a feasible approach for the design and fabrication of new IR frequency-doubling materials through glass crystallization.
关键词： Cd4GeS6,microstructure,glass-ceramics,chalcogenide glasses,crystallization
更新于2025-09-19 17:13:59
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Laser induced thermochromism and reversible upconversion emission modulation of a novel WO3:Yb3+,Er3+ ceramic: dual-modal fingerprint acquisition application
摘要： The quick and accurate identity recognition can be obtained by the acquisition of fingerprints in the financial, telecommunication, transportation, education and medical fields. However, conventional fingerprint acquisition technologies have many problems such as the high background interference, low detection sensitivity and complicated operation. In this work, the reversible modulation of laser induced thermochromism and upconversion luminescence of a novel WO3:Yb3+,Er3+ ceramic was achieved even after several cycles, exhibiting excellent repeatability. For the first time, we realized the dual-modal fingerprint acquisition by means of the laser induced thermochromism and upconversion luminescence of WO3:Yb3+,Er3+ ceramic. Particularly, this method shows ultrahigh stability, preserving the fingerprint patterns as long as one year. The results demonstrated that our technology is nondestructive, repeatable, highly effective and stable, paving the way for the development of the acquisition and storage of fingerprints.
关键词： Photo-thermal-chromism,Upconversion luminescence,WO3:Yb3+,Er3+ ceramics,Fingerprint acquisition
更新于2025-09-19 17:13:59
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Perovskite quantum dots growth in situ in transparent medium for short wavelength shielding
摘要： High energy ultraviolet (UV) and blue light (short wavelength) radiation is proved to be harmful to human eyes, skin, and biological genomes. However, developing effective shielding materials providing protect from short wavelength is still a great challenge. Here, Eu3+-doped CsPbBr3 embedded in a transparent glass medium is proved to shield the short wavelength from 200 to 475 nm with high performance, which is prepared by a facile and efficient melting-quenching technique. The uniform distribution of the CsPbBr3 quantum dots (QDs) growth in situ from the transparent glass matrix ensures the high transmittance (> 90%) at the long wavelength (520-800 nm). In addition, the excellent short wavelength shielding ability of the Eu3+-doped CsPbBr3 glass ceramics (EGC) is demonstrated even suffered with accelerated weathering tests as long as 480 h. Moreover, the cell viability of A549 cells is well preserved thanks to the completely blocked blue light by the as-obtained EGC, which unambiguously demonstrates the promising application of EGC as short wavelength shielding materials.
关键词： perovskites,glass-ceramics,short wavelength shielding,quantum dots
更新于2025-09-19 17:13:59
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Optical Electronics (An Introduction) || 3. Bulk solid-state lasers
摘要： Solid-state lasers use solid-state laser medium as the working substance. Usually, solid work materials are incorporated in the matrix with a small amount of activated ions. Laser transition occurs between different energy levels during ion activation. Matrix materials are mainly crystal, glass, and ceramics, and activated ions can be categorized as trivalent rare earth metal ions, divalent rare earth metal ions, transition metal ions, and actinide metal ions.
关键词： crystal,activated ions,laser medium,heat capacity laser,ceramics,LD-pumped,glass,solid-state lasers
更新于2025-09-16 10:30:52
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Coupled phase‐field modeling of domain and fracture evolution in anisotropic ferroelectric ceramics
摘要： The contribution presents a material model for the simulation of domain and fracture evolution in ferroelectric ceramics. Ferroelectric domains and cracks are modeled by using a phase field. While for the modeling of the ferroelectric domains we consider the vectorial electric polarization as order parameter, the modeling of cracks is based on a scalar damage variable. In the present contribution, we discuss the evolution of domains and cracks in an anisotropic ferroelectric solid.
关键词： domain evolution,ferroelectric ceramics,fracture evolution,phase-field modeling,anisotropy
更新于2025-09-16 10:30:52
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Highly sensitive optical thermometers based on unconventional thermometric coupled levels of Tm <sup>3+</sup> following a Boltzmann-type distribution in oxyfluoride glass ceramics
摘要： Oxyfluoride glass ceramics (GCs) containing b-PbF2 nanocrystals (NCs) doped with Tm3+ and Yb3+ were synthesized by a conventional melt-quenching method and a subsequent glass crystallization route. In b-PbF2:Tm3+/Yb3+ GCs, Tm3+/Yb3+ is surrounded by fluoride with a low phonon energy, ensuring its intense emissions at 362 (1D2 - 3H6), 450 (1D2 - 3F4), 478 (1G4 - 3H6), 648 (1G4 - 3F4), 700 (3F2,3 - 3H6) and 800 (3H4 - 3H6) nm excited by 976 nm laser. Furthermore, temperature-dependent upconversion luminescence (UCL) behaviors of b-PbF2:Tm3+/Yb3+ GCs were systematically investigated to explore the thermometric performance with the assistance of the fluorescence intensity ratio (FIR) method by employing conventional TCELs of 3F2,3/3H4 following a Boltzmann distribution and two unconventional coupled levels of 3F2,3/1D2 and 3F2,3/1G4 governed by a Boltzmann-type distribution. Impressively, the relative sensitivity (Sr) of 3F2,3/1D2 states (I700nm/I362nm), 3F2,3/1G4 states (I700nm/I478nm), and 3F2,3/3H4 states (I700nm/I800nm) was obtained in this work as values of 1.30% K-1, 1.38% K-1, and 0.87% K-1, respectively. Compared with the conventional TCELs of 3F2,3/3H4, the two unconventional coupled levels of 3F2,3/1D2 and 3F2,3/1G4 present preferable properties as temperature probes enabling optical ratiometric thermometers. The research in this work provides an important advance in exploring other innovative FIR methods for optical thermometers to enable an intense and precise probing signal and detect temperature accurately.
关键词： fluorescence intensity ratio,Yb3+,oxyfluoride glass ceramics,Tm3+,Boltzmann-type distribution,optical thermometers
更新于2025-09-16 10:30:52
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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
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Experimental Study on Ca3(PO4)2-Al2O3 Bio-ceramic Composite Using DPSS Laser
摘要： The DPSS lasers are mostly used in industries for laser based micromachining. The present experimental study investigates the laser micro grooving operation on a sheet of Calcium phosphate-Alumina (Ca3(PO4)2-Al2O3) bio-ceramic composite for bio-medical applications. The Ca3(PO4)2-Al2O3 bio ceramic has been fabricated by adding 20% weight of alumina with calcium phosphate to enhance the mechanical properties of the bio-ceramics. Bio ceramics were initially used as alternatives to metals to increase their biocompatibility. Ca3(PO4)2-Al2O3 bio ceramics shows the properties like bioactive and bio resorbable compounds.. Pulse frequency, pulse width, diode current and gas pressure has been taken as input parameters. Upper width, lower width and micro-grooving depth deviation has been considered as the output parameters for this present experiments for machining at different parametric combinations. This paper reports theoretical and experimental results of micro-grooved bio- ceramics with thicknesses of 3 mm by using pulsed DPSS laser. Taguchi based experimental design has been adopted to carry out experiments. Then Gray Relational Analysis (GRA) based multi response optimization of input process parameters for the outputs characteristics are performed to get the optimal conditions. The optimum machining parameters were found as; pulse frequency= 3 KHz, pulse width = 5% of duty cycle, diode current = 24 Amp and gas pressure=1.0 Kgf/cm2.Validity of the model has been checked through experiments and the error in upper width, lower width and micro-grooving depth deviation in the validation experiments are found to be satisfactory with minimal errors. Also Scanning Electron Microscopy (SEM) images after conformation test examined from cross-sections of the micro-grooved bio-ceramic samples.
关键词： GRA,Micro grooving,Taguchi,Bio-ceramics
更新于2025-09-16 10:30:52
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Kinetics of Cr <sup>3+</sup> to Cr <sup>4+</sup> ion valence transformations and intra-lattice cation exchange of Cr <sup>4+</sup> in Cr,Ca:YAG ceramics used as laser gain and passive Q-switching media
摘要： This paper focuses on the kinetics of Cr4+ formation in Cr,Ca:YAG ceramics prepared by solid-state reaction sintering. The kinetics of Cr4+ formation was studied by annealing of Cr,Ca:YAG ceramics in ambient air under different temperatures at different times, resulting in the transformation of Cr3+ to Cr4+. The activation energy (Ea) of Cr3+ oxidation determined by the Jander model was 2.7 ± 0.2 eV, which is in good correlation with the activation energy of innergrain oxygen diffusion in the YAG lattice. It is concluded that Cr3+ to Cr4+ transformation in YAG ceramics is limited by oxygen diffusion through the grain body. It was established that in Cr,Ca:YAG ceramics, the intralattice cation exchange, in which the Cr4+ ions exchange positions with the Al3+ ions, switching from “A” to “D” sites, is faster than Cr3+ to Cr4+ oxidation. In the temperature range of 900–1300 ○C, the reaction enthalpy of Al3+/Cr4+ ion exchange between octahedral “A” and tetrahedral “D” lattice sites is close to zero, and this exchange ratio is thermodynamically driven by entropy.
关键词： intralattice cation exchange,Cr4+:YAG ceramics,solid-state reaction sintering,oxygen diffusion,Cr3+ oxidation
更新于2025-09-16 10:30:52