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Vanadium dioxide (VO2) exhibits remarkable properties during its metal–insulator transition, making it a compelling material for smart windows applications as a thermochromic material. In this study, Ti-doped VO2(M) (Ti–VO2(M)) powders were synthesized using the hydrothermal method by mixing VOC2O4·5H2O/Ti(SO4)2 at 50 and 60 °C, respectively. To comparatively analyze the crystalline microscopic morphology and phase transition properties of the synthesized Ti-doped VO2(M) powders, several characterization techniques were employed, including XRD, XPS, SEM/TEM, EDS, and DSC. The experimental results suggests that low mixing temperature is beneficial for the stable and homogeneous growth of VO2(M) grains when in the absence of Ti doping. On the other hand, high mixing temperatures are beneficial for the stable and homogeneous growth of VO2(M) grains when Ti(SO4)2 is introduced, resulting in enhanced phase transition stability of Ti–VO2(M). [ABSTRACT FROM AUTHOR]

Fluoride glass is considered as an excellent optical material owing to its ultralow phonon energy (578 cm−1). However, its high thermal expansion coefficient (15.87 × 10−6/K) and deformability severely limit applications under service environments with high temperature, high humidity, and high‐power irradiation. To overcome these limitations, we developed a ZBLAN‐based fluoride glass ceramics (CZBLAN GCs) contained the negative thermal expansion material‐CaZrF6 crystals by phase‐separation engineering. The ability to control the precipitation of the desired crystal phase was achieved by adequate compositional design for phase separation, yielding improved or new properties in the development of fluoride GCs. With the successful precipitation of very uniformly dispersed single CaZrF6 crystals in the glass phase (up to ∼40% crystallinity), a significantly lower thermal expansion coefficient (3.66 × 10−6/K) in the fluoride system was achieved. Moreover, enhanced fluorescence properties of Eu‐doped CZBLAN GCs were observed compared with those of Eu‐doped ZBLAN glass owing to the lower phonon energy in GCs. [ABSTRACT FROM AUTHOR]

This study aims to establish a simple and convenient method suitable for the market to grade the jade colors. Based on the HSL color model and with the assistance of the HSL analysis on green jade images acquired by camera flashlights, this study obtains the following six kinds of jade colors: melon green, emerald green, yellow green, bean green, light bean green, and light green, based on which the law governing the values and the value range can be determined, and the respective HSL value ranges ,together with their threshold values, for the seven green jades can be finally found, thus laying an important foundation for further researches on computer-based quick grading. It is also hoped that this method will be widely applied and promoted in the marketplace and realizes our ultimate goal of setting guidelines to commercial jade prices.

For transparent low melting inorganic glass, which is relevant for sealing and additional applications, Pb‐containing glasses have reached the lowest melting point and best comprehensive performance. Considering potential toxicity and regulatory limitations, there is urgent need to develop Pb‐free ultra‐low melting point glass. Herein, we systemically investigated the structure and luminescence evolution of the Pb‐free ultra‐low melting quaternary tin fluorophosphate glasses (NaF‐SnF2‐SnO‐P2O5), in which varied NaF content was tuned to affect the properties of glass. With NaF content increases, the Sn‐O and P‐O bonds have been gradually transformed to Sn‐F and P‐F bonds, and the phosphrous tetrahedron PO4 has been converted to PO3F. The weaken bonding results in the decrease of the ultra‐low melting point to 329°C when NaF increased to 15 a.t.%, 29oC lower than the ternary glass. The blue shifts of both absorption and photoluminescence spectra were observed due to the higher ionic character of glass structure with NaF increases. As reported previously in the ternary tin fluorophosphate glass, the quaternary glass system also shows a phosphorescence behavior (∼1 s) due to the existence of oxygen vacancies. Additionally, the changes in oxygen vacancy defects correlate with the NaF content, thus affecting the decay time as well. The ultra‐low melting point luminescent quaternary tin fluorophosphate glasses (NaF‐SnF2‐SnO‐P2O5) may be relevant for opto‐electronic applications such as the packaging in displays or light‐emitting diodes. [ABSTRACT FROM AUTHOR]

Fluoindinate glass (FIG) is considered an ideal material for fiber laser devices and mid‐infrared bulk optics components owing to its ultra‐low phonon energy and broad transparency window. However, the heat generated by devices fabricated with FIG during their operation limits its application. Therefore, there is an urgent need to study its high‐temperature properties. In this study, the thermal properties, microstructure, crystal phase behaviors, and optical and luminescent properties of high‐temperature FIG were comprehensively evaluated. We also attempted to reveal the changes in its structure at high temperatures using variable‐temperature Raman spectroscopy. We first found that the stretching vibration intensity of nonbridging F(Fnb) decreases, and the bending vibration of FIG increases with an increase in temperature, indicating that high temperatures could lead to the fracture of bridge bonds between some [InF6]3− octahedrons. Certainly, this will lead to glass structural instability, which will further increase the tendency of FIG to undergo devitrification in high‐temperature conditions. We believe that this work will provide a reference for the performance improvement and application of fluoride glass at high temperatures. [ABSTRACT FROM AUTHOR]

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We present the nonlinear optical properties of CsPb(Br/I)3 perovskite quantum dots (QDs) with high crystallinity. The perovskite QDs show better two-photon absorption response than the traditional metal chalcogenide QDs. And, the photoluminescence peak of the halogen vacancies in perovskite nanocrystals was experimentally observed for the first time. [ABSTRACT FROM AUTHOR]

Transparent glass-ceramics containing Er3+:CaF2 crystallites were prepared with the co-firing method. The formation process of the glass-ceramics was investigated by means of SEM, XRD, and DSC. The results reveal that the Er3+:CaF2 nanocrystals do not dissolve into the fluorophosphates ( FP) glassmelt until the co-firing temperature increase higher than about 920°C. Below this temperature, Er3+:CaF2 survives the co-firing process and the nanocrystals just grow to spherical crystals of micrometers in size. Co-firing temperature higher than this temperature leads to the dissolution of Er3+:CaF2 and the dissolved Er3+:CaF2 recrystallized during quenching process and takes the shape of dendrite. [ABSTRACT FROM AUTHOR]

For transparent low melting inorganic glass, which is relevant for sealing and additional applications, Pb‐containing glasses have reached the lowest melting point and best comprehensive performance. Considering potential toxicity and regulatory limitations, there is urgent need to develop Pb‐free ultra‐low melting point glass. Herein, we systemically investigated the structure and luminescence evolution of the Pb‐free ultra‐low melting quaternary tin fluorophosphate glasses (NaF‐SnF2‐SnO‐P2O5), in which varied NaF content was tuned to affect the properties of glass. With NaF content increases, the Sn‐O and P‐O bonds have been gradually transformed to Sn‐F and P‐F bonds, and the phosphrous tetrahedron PO4 has been converted to PO3F. The weaken bonding results in the decrease of the ultra‐low melting point to 329°C when NaF increased to 15 a.t.%, 29oC lower than the ternary glass. The blue shifts of both absorption and photoluminescence spectra were observed due to the higher ionic character of glass structure with NaF increases. As reported previously in the ternary tin fluorophosphate glass, the quaternary glass system also shows a phosphorescence behavior (∼1 s) due to the existence of oxygen vacancies. Additionally, the changes in oxygen vacancy defects correlate with the NaF content, thus affecting the decay time as well. The ultra‐low melting point luminescent quaternary tin fluorophosphate glasses (NaF‐SnF2‐SnO‐P2O5) may be relevant for opto‐electronic applications such as the packaging in displays or light‐emitting diodes. [ABSTRACT FROM AUTHOR]

Fluoride anions play a key role in human health and chemical engineering, such as in organic synthesis and biological processes. The development of high-sensitivity naked-eye detection sensors for fluoride anions in organic solutions is crucial and challenging. In this study, (3Z,3'Z)-3,3'-[4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno(1,2-b:5,6-b')dithiophene]-2,7-diylbis(methan-1-yl-1-ylidene) bis(6-bromo-indolin-2-one) (IDTI) was designed and used as a fluoride chemosensor for the first time. IDTI is a highly sensitive fluoride sensor with a detection limit of as low as 1 × 10 -7 M. In addition, upon the reaction of IDTI with fluoride anions in a tetrahydrofuran (THF) solution, color changes from red to yellow under ambient light and from purple to green under UV light were detectable by the naked eye. These studies indicate that IDTI is a promising fluoride chemosensor., (Copyright © 2020 Yuan, Shi, Wang, Du, Jiang, Jiang, Sui, Hao and Li.)

TiC-Ti-Al mixed powders and TC4 titanium alloy foils were overlapped layer-by-layer in the graphite die. The TC4-based laminated composite sheets reinforced by Ti aluminide and carbide were successfully fabricated via spark plasma sintering (SPS) at 1100 °C with a well-bonded interface. The composite layers were mainly composed of TiAl, Ti₃Al, Ti₂AlC, and Ti₃AlC₂ phases. The carbides particles distributed in the matrix played an important role in the deflection of cracks and the passivation of microcracks. TC4 titanium alloy layers had an obvious effect on the stress distribution during the loading process, and provided an energy dissipation mechanism, which could improve the mechanical properties of the laminated composite sheets obviously. When the theoretical amount of Ti₂AlC was 20 wt %, the flexural strength and fracture toughness of the laminated composite sheets reached the maximum value in the arrester direction, which were 1428.79 MPa and 64.08 MPa·m 1/2 , respectively., Competing Interests: The authors declare no conflict of interest.

A germanate-tellurite glass (GeO2-TeO₂-K₂O-Nb₂O₅-La₂O₃) with thulium doping has been investigated for application as a laser material around 2.0 μm regions. Under the 808 nm laser diode pumped, intense 1.8 μm emission is obtained. Based on the absorption spectra, radiative properties are predicted using Judd-Ofelt theory. The maximum value of emission cross-section of Tm(3+) around 1.8 μm can reach 1.46 × 10(-20) cm(2), which indicated that the germanate-tellurite glass may provide high gain as a good medium for efficient 1.8 μm laser system.

Er3+ doped CaF2-fluorophosphate (FP) glass microcomposites were produced by heat-treating the mixture of Er3+:CaF2 precipitate and FP glass powder above the melting temperature of the FP glass. The appearance of CaF2 crystallites in the resulting composites was confirmed by x ray diffraction. Despite the fact that the average diameter of the crystallites was around 10 μm as revealed by the micromorphology study, a transparent composite was obtained by matching the refractive index of FP glass to that of CaF2. Intense IR fluorescence at around 2.7 μm was observed in the composite, implying the composite would be a promising candidate for IR lasers and amplifiers.