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Lead‐free halide perovskite nanocrystals (HPNCs) are an emergent alternative of lead‐based halide perovskites owing to their environmentally benign nature. In this work, lead‐free Cs3Sb2Br9 HPNCs were precipitated firstly in chalcogenide glass through an elaborated composition design and appropriate crystallization process. The microstructural evolution and nanocrystallization behavior of the Cs3Sb2Br9 crystallized glass‐ceramics were analyzed by employing advanced characterization techniques. It is revealed that the crystallization process is temperature‐dependent and can be described as two stages. At the first crystallization stage, the nucleation and crystal growth of Cs3Sb2Br9 HPNCs occur due to the presence of structural similarity of [Sb2Br9]3− dioctahedral clusters in the precursor glass. And then the second crystalline phase of GeS2 is successively separated from the residual glassy matrix under high‐temperature treatment. This work should be of great guiding significance for developing novel glass‐ceramic materials embedded with lead‐free HPNCs. [ABSTRACT FROM AUTHOR]

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 nanocrystals (about 60‐80 nm) are fabricated through controlled nano‐crystallization. Nanocrystalline structure of the Cd4GeS6 nano‐crystallized glass‐ceramics is investigated in detail through X‐ray diffractometer, field emission scanning electron microscope, 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 nanocrystals 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. [ABSTRACT FROM AUTHOR]

Transparent chalcogenide glass‐ceramics containing CsPbCl3 perovskite nanocrystals were prepared through an elaborated composition design of 80GeS2·5Ga2S3·15CsPbCl3. Large size distribution of CsPbCl3 nanocrystals is observed ranging from 10 to 200 nm. XRD, Raman spectra, and SEM techniques were employed to study the further microstructural evolution after thermal treatment. The precipitation of PbGeS3 and GeS2, together with CsPbCl3, was identified according to the XRD patterns and Raman spectra. This work is of guiding significance for future design of cesium lead halide perovskite nanocrystals in chalcogenide glass‐ceramics. [ABSTRACT FROM AUTHOR]

The glass‐ceramics of AgI‐based electroconductive chalcogenide system was realized using an appropriate heat treatment at a fairly high temperature (Tg + 40°C) and different times ranging from 4 to 20 hours. The crystallization behavior and electroconductive properties of the heat‐treated samples were studied in detail. Transmission study was performed, and the results show that the cut‐off edge of the short wavelength is red‐shifted at prolonged annealing time but remains an excellent transmittance in the mid‐infrared (IR) region. XRD and scanning electron microscopy results indicated that the precipitated crystalline phases are mainly β‐/γ‐AgI. Moreover, a small amount of α‐AgI, which rarely existed at room temperature, is precipitated in the AgI‐rich chalcogenide glass‐ceramics. The ionic conductivity of all glass‐ceramics was enhanced by heat treatment in contrast to that of base glass. Raman analysis exhibited the structure variation in the glass sample after heat treatments. This study provided an observation of crystallization in chalcogenide glass containing large amounts of AgI and be of good guidance to fabricate novel AgI‐based chalcogenide glass‐ceramics that can be candidates in infrared optics and solid electrolyte applications. [ABSTRACT FROM AUTHOR]

Transparent glass-ceramics containing a mixture of ZnO and β-Zn 2 SiO 4 or solely ZnO are fabricated through a competitive crystallization behavior of ZnO and β-Zn 2 SiO 4 in a potassium zinc aluminosilicate glass. Both ZnO and β-Zn 2 SiO 4 are precipitated simultaneously at the initial stage of thermal treatment, whereas sole crystallization of ZnO occurs when thermal treatments are performed at a high temperature (> 640 °C for 20 h) or for a long period of time (> 10 h at 650 °C). A detailed Raman scattering study and microscopic observation suggest that this competitive crystallization is due to the decomposition of β-Zn 2 SiO 4 into ZnO and SiO 2 during thermal treatment. This work would be of interest to the fabrication of active ions doped luminescent glass-ceramics by selective crystallization of ZnO and β-Zn 2 SiO 4 . [ABSTRACT FROM AUTHOR]

Chalcogenide glasses are defined as a new category of non-crystalline solids on the basis of their characteristic covalent bonds and unique properties, such as broad infrared transmission window, low maximum phonon energy, high optical nonlinearity, semiconductivity, and photosensitivity. Inspired by the great successes that have been achieved in the development of oxide glass-ceramics, functionalized chalcogenide glass-ceramics have received intensive research attention. Moreover, the inherent properties of chalcogenide glasses have been explored and modified through controlled crystallization, to generate novel and unique features. This review aims to present a critical overview of the current state of the art in the controllable fabrication of functionalized chalcogenide glass-ceramics. The first section provides a brief introduction to chalcogenide glasses and glass-ceramics. The succeeding sections detail the fabrication strategies of chalcogenide glass-ceramics with various functions through different precipitated crystals and microstructures. This review provides a discussion of the mechanism that underlie the resultant properties of chalcogenide glass-ceramics. Furthermore, the crystallization mechanisms of chalcogenide glasses are discussed through the comparison of molecular-scale and nanoscale phase separation assisted crystallization mechanisms in oxide and oxyfluoride glasses. Finally, the remain section presents the key questions that remain unanswered, as well as provide perspectives on the future research trends. [ABSTRACT FROM AUTHOR]

Through a careful composition design, new oxyfluoride glass-ceramics (GCs) containing BaLiF3 nanocrystals with sizes of around 30 nm were prepared. Microstructural characterizations show interpenetrating phase separation in the sample with a composition of 15BaF2-15ZnF2-70SiO2, after thermal treatment at 580°C for 40 h which leads to the nanocrystallization of BaLiF3. The BaLiF3 nanocrystals embedded in the glassy matrix could provide Ba or Li sites for the incorporation of optically active rare earth and transition-metal ions, which provides a possibility to explore novel photonic properties by the codoping of rare earth and transition-metal ions in GC materials. [ABSTRACT FROM AUTHOR]

Glass-ceramics of PbS-doped 80 GeS2·20 Ga2 S3 were fabricated by heat treatments of base glasses at Tg+30°C for different durations. They exhibited improved mechanical properties such as hardness and resistance to crack propagation, and meanwhile retained their excellent infrared transmission. X-ray diffraction and Raman results indicated that Ga2 S3 and GeS2 crystals were precipitated inside glassy matrix. The crystallization kinetics of base glass was investigated using differential scanning calorimetry under nonisothermal conditions. Compared with the previous work concerning on 80 GeS2·20 Ga2 S3 glass, there exists some different features of crystallization behavior. Such variation is discussed and correlated with the network structure and crystallization kinetics in this glass system. [ABSTRACT FROM AUTHOR]

Glass-ceramics containing Ga2S3 nano-crystals were reproducibly fabricated from the 45GeS2·30Ga2S3·25Sb2S3 chalcogenide glass by heat treatment at 335°C (Tg +30°C) for different durations. The obtained glass-ceramics are still transparent in the IR region and show improved thermal stability. Crystallization mechanism was investigated using the non-isothermal method. The results show that the crystallization rate constant K at 335°C for the Ga2S3 phase is about 2 orders of magnitude larger than that of the second crystallization peak in the DSC curve. So it is easy to control the crystallization process with only Ga2S3 crystallites precipitated. With the above advantages, it has a great potential for drawing infrared transmitting glass-ceramic fibers with improved mechanical properties and enhanced luminescence for application in optical amplifiers. [ABSTRACT FROM AUTHOR]

65GeS⋅25InS⋅10CsCl chalcohalide glass-ceramics containing β-InS crystallites in the glassy matrix were prepared by traditional melt-quenching and subsequent heat-treatment at a fairly low temperature ( T+10 C) for different durations. The transmission spectra show that the cut-off edge of short wavelength is red-shifted with the prolongation of annealing time, but remains an excellent transmittance in the mid-IR region. Meanwhile, its crystallization behavior was investigated systematically. The results show that the precipitation of β-InS crystal phase is responsible for the first crystallization peak, and the second crystal phase is GeS, which precipitated in the interior after a heat treatment at a high temperature ( T+70 C). Furthermore, the crystallization mechanism was investigated using the non-isothermal method. The crystallization rate constant K value of 6.08×10 s at 346 C for the β-InS phase is about three times larger than that of the GeS phase, indicating a much easier crystallization mechanism of β-InS phase. Therefore, it is easy to control the precipitation of sole β-InS crystallite, and to avoid interference of the second crystal phase GeS. [ABSTRACT FROM AUTHOR]

Diagram of the phase transformation behavior of GeS2- Ga2 S3- CsI glasses is realized in this article and the structure-property dependence of the chalcogenide glasses is elucidated using differential scanning calorimetry and Raman spectroscopy. We observe the compositional threshold of crystallization behavior locates at x = 6-7 mol% in (100− x)(0.8 GeS2-0.2 Ga2 S3)- x CsI glasses, which is confirmed by the thermodynamic studies. Structural motifs are derived from the Raman result that [ Ge( Ga) S4], [ S2 GeI2], [ S3 GaI], and [ S3 Ga- GaS3] were identified to exist in this glass network. Combined with the information of structural threshold, local arrangement of these structural motifs is proposed to explain all the experimental observations, which provides a new way to understand the correlation between crystallization behavior and network structure in chalcogenide glasses. [ABSTRACT FROM AUTHOR]

Enhanced luminescence in rare-earth-doped chalcogenide glass-ceramics is of great interest for the potential integrated optoelectronic devices. However, fundamental mechanism on the enhancement of luminescence upon crystallization remains largely unknown. We report the fabrication and characterization of wide transmission chalcogenide glass and glass-ceramics based on the 25 GeS2·35 Ga2 S3·40 CsCl:0.3 Er glass composition, and discuss the mechanism of enhanced luminescence. By monitoring the 4 I9/2-4 I15/2 of Er3+ transition, up-conversion luminescence of 12 times higher was observed in glass-ceramics compared with that in base glass. Electron paramagnetic resonance (EPR) and Raman scattering spectroscopies were employed to obtain the information of selective environment of Er3+ ions and microstructural evolution with the crystallization progress. Both of them evidenced that the enhanced up-conversion luminescence was mainly related to the local environmental evolution from a mixed chlorine-sulfur coordination to a low phonon energy chlorine coordination in the residual glassy matrix of glass-ceramics. [ABSTRACT FROM AUTHOR]

Glass-ceramics of 80 GeS2·20 In2 S3 were fabricated by heat-treating the base glass at 402°C ( Tg + 30°C) for different durations. The glass-ceramics exhibited some improved mechanical properties such as hardness and resistance to crack propagation, and meanwhile remained an excellent infrared ( IR) transmission. The XRD and Raman results showed that only In2 S3 crystals were precipitated inside glassy matrix. The evolution of two crystallization peaks ( CPs) in differential scanning calorimeter ( DSC) curves were studied with samples heat-treated at 402°C for different durations. It was found that the precipitation of In2 S3 crystal phase is responsible for the low-temperature (first) CP, whereas the high-temperature (second) CP shifts to a higher temperature with the elongation of the heat-treatment duration. The crystallization of the higher temperature phase was inhibited with the precipitation of In2 S3. Furthermore, crystallization mechanism was investigated using the nonisothermal method. The computed results showed that strictly more energy (higher activation energy, Ec) is essential for the precipitation of the higher temperature phase, which is in accordance with the DSC study of crystallized samples. More noticeable, the crystallization rate constant ( K) value of 6.639 × 10−8 s−1 for the second CP is ~ 5 orders of magnitude smaller than that of the In2 S3 phase, and this significant difference makes the crystallization of higher temperature crystal phase very hard. Consequently, controllable crystallization of 80 GeS2·20 In2 S3 chalcogenide glass-ceramics with sole In2 S3 crystallites can be achieved easily. [ABSTRACT FROM AUTHOR]

Abstract: Novel chalcogenide glasses based on GeS2–In2S3–Sb2S3 system were prepared by conventional melt-quenching method and their physicochemical properties, e.g. glass transition temperature, density, and Vickers micro-hardness, were studied in detail. The results show that the thermal, mechanical, and optical properties depend largely on four-coordinated Ge or In entities and are sensitive to the variation of the connectivity in the GeS2–In2S3–Sb2S3 glass network. It is a promising chalcogenide glass system suitable for rare earth doping or crystallization of rare earth doped crystals, which aims at optical applications of IR optical amplifier or efficient solid state laser. [Copyright &y& Elsevier]

Transparent 90GeS⋅10GaS(G10) chalcogenide glass-ceramics containing β-GeS nanocrystals was successfully fabricated through controllable crystallization based on the knowledge of its nucleation-rate-like curve. Using the conventional Z-scan method, both large spectral dependence and crystallinity dependence of optical nonlinear parameters were learned under the excitation of different wavelengths that in proximity of the half-bandgap. In particular, a large value of figure of merit (FOM≈11.64) was obtained in the crystallized sample after the heat-treatment at 466°C for 40 h. Although it is not a straightforward process to select an appropriate medium for a specific application, this work opens a new way to construct suitable optical nonlinear properties (e.g., large FOM) though modifying the microstructure of chalcogenide glass-ceramics. [ABSTRACT FROM AUTHOR]

Abstract: The infrared transmitting surface crystallized chalcohalide glasses containing nontoxic and excellent nonlinear optical AgGaGeS4 crystallites were fabricated by heat-treatment of the as-prepared 30GeS2 ·35Ga2S3 ·35AgCl chalcohalide glass at 350°C (T g −10°C) for 24h. An intensive second harmonic generation (SHG) was observed clearly using the Maker fringe technique, and the origin of SHG was mainly ascribed to the AgGaGeS4 nonlinear optical crystallites contained in the surface crystallized layer. The thickness of the surface crystallized layer showing SHG activation is approximate 50μm. The χ (2) susceptibility of the prepared surface crystallized 30GeS2 ·35Ga2S3 ·35AgCl chalcohalide glass is calculated to be about 12.4pm/V at a fundamental wavelength of 1064nm, which indicates a promising nonlinear optical material in the infrared spectral region. [Copyright &y& Elsevier]

The confinement of CsPbX 3 (X = Cl, Br, and I) perovskite nanocrystals (NCs) in a stabilized inorganic glass matrix is a new strategy for improving their long-term stability and promoting their applications in the optoelectronic field. Here, in situ nanocrystallization strategy is developed to precipitate CsPbBr 3− x I x NCs with arbitrary I/Br ratio among an elaborately designed GeS 2 –Sb 2 S 3 -based chalcogenide glass matrix. Spherical CsPbBr 3− x I x NCs are homogeneously distributed in the glass matrix after thermal treatment. The photoluminescence (PL) spectra show that the emission peaks of CsPbBr 3− x I x NCs can be tuned from 570 nm to 722 nm with the replacement of Br by I. The fs transient absorption (TA) spectra reveal that there exists some structural defects in the NCs, leading to short PL decay life. This work would shed light on confining CsPbX 3 NCs into glassy matrices, facilitating their future applications in photoelectronic fields. [ABSTRACT FROM AUTHOR]

The glass-forming ability, crystallization behavior and physical properties of GeS 2 -Sb 2 S 3 -CsX (X = Cl, Br, I) glasses and glass-ceramics (GCs) are systematically studied by various characterization techniques. With the introduction of cesium halides, transparent chalcogenide GCs containing the single nanocrystals of CsX can be obtained in a controlled fashion. The crystallization behavior was investigated in the line of (100- x) (0.5GeS 2 -0.5Sb 2 S 3)- x CsX glasses. IR-transmitting chalcogenide GCs embedded with CsCl and CsBr nanocrystals of a large crystallinity have been fabricated successfully after thermal treatments, whereas surface crystallization of CsI is dominated in GeS 2 -Sb 2 S 3 –CsI glassy samples. Such distinct crystallization behaviors of CsX crystal phases are compared and discussed with microstructural results. We propose that the ionic diffusion ability of halogen in the GeS 2 -Sb 2 S 3 -CsX glassy network determines the nucleation and crystal growth of CsX. This finding is of guidance meaning for future design of chalcogenide GCs with novel optical functions and microstructures. [ABSTRACT FROM AUTHOR]

Black α-phase CsPbI 3 of cubic perovskite structure receives intense attentions recently for its unique combination of high photoluminescence quantum yield, suitable bandgap, and long lifetime. However, α-CsPbI 3 presents poor chemical and thermodynamic stability under atmosphere condition. Here, we report a strategy for confining the α-CsPbI 3 perovskite into chalcogenide glassy matrix through controllable glass nanocrystallization. In the chalcogenide glass with an elaborately designed composition of 80GeS 2 ·16Sb 2 S 3 ·4CsPbI 3 , spherical α-CsPbI 3 nanocrystals were formed and observed clearly, which present good red photoluminescence centered at 701 nm. With the increasing heat-treated temperature, the size of α-CsPbI 3 nanospheres increases, while the crystal quantity decreases. It is found that the nanocrystallization of α-CsPbI 3 nanospheres in chalcogenide glass is controlled by Ostwald-ripening process. [ABSTRACT FROM AUTHOR]

Controlling nanocrystalline structure in glasses renders the exploration of new composite multiphase (glass-ceramic) materials with novel functionalities that determined by the precipitated nanocrystals and residual glassy matrix. Previous microstructural investigation of glass-ceramics focused only on one aspect of nanocrystalline structures, e.g., nano-polycrystalline or single nanocrystalline. The recognition of the microscopic mechanism of nanostructure formation in glasses is absent. Here, we use advanced microscopic techniques to show the formation of different nanocrystalline structures composed of nano-polycrystals and single nanocrystals in 80GeS 2 ·20In 2 S 3 and 72.5GeS 2 ·14.5Sb 2 S 3 ·13RbCl glasses, respectively. Crystallization mechanism for controlling the nanocrystalline structure in glasses was revealed to depend on whether the glass network former participates in crystallization process. The results may shed light not only on glass crystallization mechanism, but also on the fundamental nature of the network structure of chalcogenide glasses. [ABSTRACT FROM AUTHOR]

Ge-rich glass-ceramics sandwiched by GeS crystalline layers were fabricated through 10 h thermal treatments at different temperatures. Surface crystallization is evidenced by XRD investigation of glass-ceramic samples polished by different times. SEM observation shows that the thickness of the crystalline layer is about 100 µm for the sample thermally treated at 395 °C for 10 h. The physical properties, including transmission spectra, density, Vickers hardness, and thermal expansion coefficient, were characterized and discussed with the evolution of GeS crystalline layers. This work not only establishes the correlation between microstructure and physical properties of chalcogenide glass-ceramics sandwiched by GeS, but also provides important evidence of structural similarity for understanding the network structure of Ge-S chalcogenide glasses. [ABSTRACT FROM AUTHOR]

Glassy and partially crystallized samples of (Ge 1−x Ga x )S 2 (0 mol% ≤ x ≤ 50 mol%) were prepared and investigated for the Ga effect on their physical and structural properties. For low Ga content (0 mol% ≤ x ≤ 30 mol%), homogeneous glassy samples were prepared and present good physical properties, such as high glass transition temperature (>400 °C) and Vickers hardness (>2.60 GPa). With the Ga substitution for Ge, the thermal stability of samples decreases, leading to the precipitation of α-Ga 2 S 3 crystallites when x > 40 mol%. Structural evolution of (Ge 1−x Ga x )S 2 samples was investigated by Raman spectra and X-ray diffraction techniques. The correlation between the physical properties and structural evolution was established. [ABSTRACT FROM AUTHOR]

As 2 Se 3 glass fibers measuring 250 μm in diameter were fabricated based on different draw processing parameters, including preform dropping temperatures (T 1 = T g + ΔT, ΔT = 20, 30, 40, 50 °C), fiber-drawing temperatures (T 2 = T g + ΔT, ΔT = 10, 20, 50 °C), and drawing speeds. Raman spectra indicated crystallization on fiber surface at high temperatures. After fiber drawing, oxygen was detected on fiber surface by energy dispersive X-ray spectra. High-quality fiber with minimum loss of 1.88 dB/m (at 9.05 µm) was achieved under optimal dropping temperature of 218.1 °C (T g + 30 °C), fiber-drawing temperature of 208.1 °C (T g + 20 °C), and drawing speed of 0.10 m/min. [ABSTRACT FROM AUTHOR]

Glass-ceramics embedded Te and α-GeTe particles were fabricated from (GeTe 4 ) 85 (AgI) 15 chalcohalide glass using an appropriate heat-treatment at fairly low temperatures ranging from 160 to 190 °C for different times. The crystallization behavior and physical properties of the obtained samples were studied in detail. The glass transition temperature of crystallized samples increases with the elongation of crystallization times. And the results of mechanical properties show that, compared with the base glass, the crystallized samples present improved thermal shock resistance and fracture toughness, and meanwhile still remain its good IR transmittance. This study could provide an initial observation of crystallization in telluride glasses, and be of good guidance to fabricate novel telluride glass-ceramics that operating in far-IR spectral region ranging from 2.5 μm to 25 μm. [ABSTRACT FROM AUTHOR]

• Transparent chalcogenide glass-ceramic sample embedded CsCl nanocrystals of ~50 nm was obtained. • Phase separation with different droplet and interpenetrating structures were observed in chalcogenide glasses. • Raman spectra of these samples are almost unchanged with the increasing CsCl content. • The network structure of chalcogenide glasses retains acts as a solvent for the dissolution of CsCl. The effect of CsCl addition on the nanocrystallization and phase separation behaviors of (100 − x)(0.5GeS 2 – 0.5Sb 2 S 3) – x CsCl (x = 0, 5, 10, 15, 20, 25, 35 and 40 mol%) samples was investigated systematically by various characterization techniques. Transparent chalcogenide glass-ceramic sample embedded CsCl nanocrystals of ~50 nm was obtained successfully through one-step melt-quenching method in a glass with elaborated composition of 37.5GeS 2 ·37.5Sb 2 S 3 ·25CsCl, which is around the critical solubility of CsCl in GeS 2 – Sb 2 S 3 based glasses. With the further addition of CsCl (x > 25 mol%), phase separation with different droplet and interpenetrating structures were observed for the first time in chalcogenide glasses. The recognition of these phenomena would be of guiding significance for the future design and fabrication of chalcogenide glass-ceramics with specific microstructures and optical functionalities. [ABSTRACT FROM AUTHOR]

Novel chalcogenide glasses and glass-ceramics of (100-x)(0.5GeS 2 –0.5Sb 2 S 3)–xPbCl 2 (x = 0, 3, 5, 8, 10, 15, 20, and 25) were prepared by single-step melt-quenching technique, and their transmission spectra and thermo-mechanical properties are characterized. The solubility and spontaneous crystallization behavior of PbCl 2 are investigated by employing various techniques of XRD, SEM, and Raman spectra. Two-stage crystal growth was found in these samples with the increase of PbCl 2 content (x). The crystallization behavior of oversaturation and recrystallization of PbCl 2 in glasses is totally different from the typical nucleation and crystal growth initiated by thermal treatment. Especially, transparent chalcogenide glass-ceramic embedded PbCl 2 nanoparticles (~20 nm) was successfully fabricated when x reaches 10 mol%. This study is of guidance significance for future design and elaboration of optically functionalized chalcogenide glass-ceramics. • Novel GeS 2 –Sb 2 S 3 –PbCl 2 chalcogenide glasses and glass-ceramics were prepared. • The solubility and spontaneous crystallization behavior of PbCl 2 are investigated. • The variation of transmission spectra and thermo-mechanical properties is investigated with the increasing x. • Transparent chalcogenide glass-ceramic embedded PbCl 2 nanoparticles (~20 nm) was successfully fabricated. [ABSTRACT FROM AUTHOR]