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Effect of pre-existing nuclei on crystallization during laser welding of Zr-based metallic glass
摘要： In this study, experiments are carried out in laser welding of a Zr-based (Zr52.5Ti5Al10Ni14Cu17.9) bulk metallic glass (BMG), pre-existing nuclei nucleus density has significant influence on its crystallization behavior. Based on the classical nucleation/growth theory, it is concluded that a small amount of pre-existing nuclei in a BMG can shift the time-temperature-transformation (TTT) curve from a well-known ‘C-shape’ to a ‘ε-shape.’ This result provides fundamental understanding on why the shape of the TTT curve for a heating process is different from that for a cooling process for the same BMG. Two quality factors were defined as a measure of the effect of pre-existing nucleus density. By integrating the classical nucleation/growth theory with the heat transfer model, the evolution of crystalline phase during laser welding for a BMG with pre-existing nuclei was studied, and the modeling predictions compared favorably with the experimental results.
关键词： Crystallization,Nucleation and growth,Laser processing,Metallic glasses,Amorphous alloys
更新于2025-11-28 14:24:20
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Robust CsPbX <sub/>3</sub> (X = Cl, Br, and I) perovskite quantum dot embedded glasses: nanocrystallization, improved stability and visible full-spectral tunable emissions
摘要： Currently, all inorganic perovskite quantum dots (QDs) of cesium lead halides (CsPbX3, X = Cl, Br, and I) have been mainly fabricated using wet chemical methods. Unfortunately, applications of perovskite QDs have been limited due to their poor stability. In the present work, the in situ growth of whole-family CsPbX3 (X = Cl, Br, and I) perovskite QDs in Zn–P–B–Sb based oxide glass via a glass crystallization strategy is reported. The as-prepared CsPbX3 QDs@glass nanocomposites exhibit typical excitonic recombination emissions and superior chemical stability benefited from the protection of the robust inorganic glass matrix. Through modifying the molar ratio of halide sources in glass, multi-color tunable emissions in the entire visible spectral range of 400–750 nm are achieved. As a result, light-emitting diode devices can be constructed by coupling blue-emissive CsPbBrCl2, green-emissive CsPbBr3 and red-emissive CsPbBr0.5I2.5 QDs@glass powders with a commercial ultraviolet chip, yielding bright white light luminescence with excellent optoelectronic performance.
关键词： stability,light-emitting diodes,tunable emissions,glass crystallization,perovskite quantum dots
更新于2025-11-20 15:33:11
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Energy transfer behaviors and tunable luminescence in Tb3+/Eu3+ codoped oxyfluoride glass ceramics containing cubic/hexagonal NaYF4 nanocrystals
摘要： For glass ceramics, glass crystallization and doping activators into nanocrystalline phases are the key factors determining optical performance, including energy transfer (ET) process. Herein, we propose a strategy to verify ET behaviors based on glass crystallization, elaborately selecting phase-transformed NaYF4: Tb3+, Eu3+ nanocrystals embedded transparent glass ceramics as a typical example. The ET behaviors from Tb3+ to Eu3+ are clarified via photoluminescence spectra, time-resolved spectra and decay curves. Impressively, the corresponding ET process in cubic NaYF4 turns out to be more efficient than that in hexagonal, in spite of a disorder-to-order transformation from cubic to hexagonal. The reason for this abnormal ET efficiency is that dopants prefer to be partitioned into the cubic NaYF4 rather than the hexagonal one during glass crystallization. This work provides keen insights into the relationship between glass crystallization and ET behaviors, which can also feed back to helpfully guide the design and fabrication of glass ceramics with superior optical performance.
关键词： glass crystallization,cubic/hexagonal NaYF4,energy transfer
更新于2025-11-20 15:33:11
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All-Thin-Film Tandem Cells Based on Liquid Phase Crystallized Silicon and Perovskites
摘要： Combining the emerging perovskite solar cell technology with existing silicon approaches in a tandem cell design offers the possibility for new low-cost high-performance devices. In this study, the potential of liquid phase crystallized silicon (LPC-Si) solar cells as a bottom cell in an all-thin-film tandem device is investigated. By optimizing the current output of a four terminal tandem using optical simulations and state-of-the-art electrical properties of the top and bottom cells, we show that an efficiency of 23.3% can be reached, where 7.2% are attributed to the LPC-Si bottom cell. Including the potential of future developments of both sub cells, efficiencies of over 28% are estimated. Electrical and optical measurements of the bottom cell are performed by attaching a perovskite and a cutoff filter to the front side of the interdigitated back contacted LPC-Si cells. The measurements using a cutoff filter show a high impact of the filtered incident light spectrum on the open circuit voltage of the LPC-Si cell. A comparison of the simulated and measured absorptance shows that especially the optical properties of the transparent conductive oxides and recombination losses in the LPC-Si cause high current losses. Combining the measured data of the filtered LPC-Si cells and the semitransparent perovskite cells, yields a realistic estimation for the efficiency of a state-of-the-art four-terminal tandem device of 19.3%.
关键词： tandem devices,Liquid phase crystallization (LPC),perovskite solar cells,thin film photovoltaics
更新于2025-11-14 15:25:21
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Light management in crystalline silicon thin-film solar cells with imprint-textured glass superstrate
摘要： The implementation of light management textures in thin-film solar cells often simultaneously causes an undesired deterioration of electronic performance. Here, we introduce a simple yet effective technique for improved light management in liquid phase crystallized silicon thin-film solar cells on glass. By imprinting pyramidal textures on the sun-facing side of the glass superstrate, absorber and functional layers of the device remain unaffected while light in-coupling is significantly increased. An increase of short-circuit current density by 2.5 mA cm2 was observed by texturing the glass in this way, corresponding to an enhanced power conversion efficiency from 12.9% to 13.8%. Optical simulations allow to attribute the increase in equal shares to an anti-reflective effect at the air-glass interface as well as light scattering and multiple passes through the glass. The technology allows for independent optimization of optical performance without compromising on electronic material issues and is therefore useable for any other solar cell technology using a glass superstrate.
关键词： Light management,Nano-imprint lithography,Liquid phase crystallization,Thin-film solar cells,Silicon
更新于2025-10-22 19:40:53
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Inorganic Protection of Polymer Nanocapsules: A Strategy to Improve the Efficiency of Encapsulated Optically Active Molecules
摘要： We demonstrate that the efficiency under ambient conditions of optically active molecules encapsulated in polymer nanocapsules can be significantly improved by depositing an inorganic layer onto the polymeric shell. A triplet-triplet annihilation upconversion (TTA-UC) system consisting of a porphyrin derivative and perylene is used as a representative case. Different inorganic materials are deposited on the surface of functionalized polymer nanocapsules synthesized by free-radical polymerization in miniemulsion. First, a silicate clay with formula [Si8(Mg5.45Li0.4)O20(OH)4]Na0.7 is deposited on the surface of positively charged polystyrene nanocapsules via layer-by-layer deposition. Second, controlled in situ mineralization of hydroxyapatite and cerium(IV) oxide are carried out on the surface of negatively charged polystyrene nanocapsules. In both cases the inorganic materials on the nanocapsule surface act as a scavenger and avoid the entry of oxygen from the external environment. By avoiding the entry of oxygen, the photo-oxidation process of perylene molecules is avoided within the system, and an increase in the TTA-UC properties occurs.
关键词： upconversion,nanocapsule,crystallization,layer-by-layer,miniemulsion polymerization
更新于2025-09-23 15:23:52
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Preparation of Bi<sub>2</sub>Gd<sub>1</sub>Fe<sub>5</sub>O<sub>12</sub> magnetic garnet films showing Faraday rotation of 36.3 deg./μm on glass substrates by metal organic decomposition method
摘要： We fabricated the Bi2Gd1Fe5O12 thin films on glass substrates with the Gd3Fe5O12 buffer layer by the metal organic decomposition (MOD) method. We found an optimum thickness of the Gd3Fe5O12 buffer layer and annealing temperature for crystallization giving the maximum Faraday rotation. The optimum sample showed Faraday rotation of as high as 36.3 deg./μm at the wavelength λ = 500 nm, which is 23 times larger than the sample without the Gd3Fe5O12 buffer layer, and as high as 90.1% of the single crystalline Bi2Gd1Fe5O12 thin films on an (111) SGGG single crystal substrate. These results are promising for applications in optical waveguide isolators and magneto-optic spatial light modulators.
关键词： metal organic decomposition,crystallization process,Faraday rotation,photonic integrated circuits,magnetic garnet
更新于2025-09-23 15:23:52
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Suppression of crystallization in ZBLAN glass by rapid heating and cooling processing
摘要： ZBLAN glass is a heavy metal fluoride glass that tends to undergo heavy devitrification, resulting in a crystalline material. It has many applications, including its use as an optical waveguide for fibre optic technology. However, when the glass is processed with traditional casting techniques, crystallites form readily that act as scattering centres, which results in large attenuation losses. In this study, it has been experimentally demonstrated that processing ZBLAN rapidly with a heating rate of 25,000 K/min and cooling rate of 4,000 K/min yields test samples that are fully amorphous and retain a disordered molecular arrangement characteristic of its molten state. This novel method was developed using a specifically designed equipment named a Rapid Electro-thermal Processing Device, or “REPD”. The REPD applies ohmic heating and thermal conduction to a heat sink to rapidly process the ZBLAN material. The absence of crystallites in the rapidly processed ZBLAN test samples were verified using transmission electron microscopy (TEM) analysis. Applying a theoretical algorithm, the critical cooling rate for yielding fully amorphous ZBLAN glass was determined to be 1081 K/min for a sample volume of 9.4 x 10-8 m3.
关键词： rapid cooling,microscopy,crystallization,ohmic heating,cooling rate,Joule heating,rapid heating,diffraction experiment,ZBLAN
更新于2025-09-23 15:23:52
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Resonance Tunneling Phenomena in Two-Dimensional Multilayer van der Waals Crystalline Systems
摘要： Works, mostly experimental, concerning the most interesting features of application of the resonant tunneling spectroscopy to a new type of heterosystems, van der Waals heterostructures, have been briefly reviewed. These heterostructures appeared after the recent discovery of two-dimensional crystals, which are a new class of materials beginning with graphene. The role of the angular matching of crystal lattices of conducting graphene electrodes of van der Waals systems in carrier tunneling between them has been analyzed together with the closely related problems of satisfaction of conservation laws in tunneling transitions. Manifestations of multiparticle correlation interactions between carriers in van der Waals systems such as Wigner crystallization of electrons in a two-dimensional electron gas in a magnetic field and Bose condensation of excitons in parallel two-dimensional electron gases have been briefly discussed.
关键词： angular matching,momentum conservation,resonant tunneling spectroscopy,graphene,two-dimensional crystals,Wigner crystallization,van der Waals heterostructures,Bose condensation
更新于2025-09-23 15:23:52
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Synthesis of Eu2O3 doped BaO-TiO2-GeO2 based glass-ceramics: Crystallization kinetics, optical and electrical properties
摘要： Eu3+ doped transparent glass-ceramics (GCs) containing non-centrosymmetric ferroelastic Ba2TiGe2O8 (BTG) crystals as the major crystalline phase have been synthesized. BTG crystal phase was generated in the glass matrix with mole percent composition 30BaO-15TiO2-55GeO2 synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. A di?usion controlled surface crystallization event with zero and constant nucleation rates was determined through a comparative study of some linear and nonlinear solid state reaction models. Nonlinear crystallization kinetics studies facilitated determination of the experimental ceramization temperature and time for fabrication of transparent glass-ceramics containing BTG nanocrystals. XRD, FTIR, TEM and FESEM measurements con?rmed the dispersion of BTG nanocrystals of size 20–100 nm in the glass matrix. Local crystal environment around Eu3+ ions facilitated the enhancement of photoluminescence of glass-ceramics with respect to the precursor glass. High dielectric constant, low loss and dissipation factors were observed for the GCs.
关键词： Refractive index,Glass-ceramics,Photoluminescence,Dielectric properties,Crystallization kinetics,Hysteresis loop
更新于2025-09-23 15:23:52