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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]

This study reports on the synthesis of tellurium-based glasses that have a wide transmission far beyond the second atmospheric window. Several far-infrared(IR) transmitting glass systems including Ge-In-Te, Ge-Ga-Te, as well as some compositions containing alkali halides (KI, CsI) or metal halides (PbI2, CuI, AgI, CdI2 or ZnI2) are reported. Their glass-forming ability, thermal stability, and IR transmitting property are investigated. The results show that the broad absorption peak in the 15-20 μm disappear in the Fourier-transform infrared (spectrometer) spectra when gallium is replaced by indium. Te-based chalcogenide glasses containing metal-halides show superior glass-forming ability and better thermal stability than those containing alkali halides. Among these glasses, the ΔT of glass composition 65GeTe4-17In2Te6-18AgI can be as great as 115 °C. In ternary system, the glass composition Ge16Te69(AgI)15 (ΔT = 120 °C) is stable enough toward crystallization in combination with broad transmission region and good chemical durability to be drawn into optical fibers. [ABSTRACT FROM AUTHOR]

The crystallization behavior of the 70GeS-20InS-10CsI glass introduced with 2 mol% AgS system has been studied under non-isothermal condition. The beginning of transmission is shifted toward longer wavelength as a function of annealing temperature. Thermal properties were measured by the differential scanning calorimeter. From the heating rate dependence of crystallization temperature, the activation energy ( E) for crystallization and the crystallization rate constant ( K) were calculated. The K value of 2.44 × 10 for the InS phase is about 28 times larger than the second CP, this is why the controllable crystallization to transparent chalcogenide glass-ceramics with sole InS crystallites can be achieved. By heat treatment with various temperatures, the hardness of the glass enhanced from 204 to 230.8 kg mm, while retained the transmittance of the 8-11 μm. [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]

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: The thermal and electrical properties of Zn1.25Sb2Te3 film have been investigated for phase change memory (PCM) applications. Compared with the conventional Ge2Sb2Te5, Zn1.25Sb2Te3 film exhibits a higher crystallization temperature (∼200°C), greater activation energy (2.71eV), and better data retention of 10 years at 105°C. In addition, higher crystalline resistance and better resistance contrast are helpful to reduce RESET current and achieve a higher On/OFF ratio of PCM, respectively. Raman spectra of crystalline thin films suggests that the local bonding arrangement around Sb atoms changes; Sb2Te3 component is thus mainly responsible for the phase transition in Zn1.25Sb2Te3 alloys. [Copyright &y& Elsevier]

Abstract: A systematic series of (Ge20Se15Te65)1− x –(SnI2) x (x =0, 0.05, 0.1, 0.15) chalcogenide glasses have been prepared. The amorphous nature can be confirmed by XRD and SEM. With the SnI2 content increasing, the indirect optical band gaps are decreased from 0.662 to 0.622eV according to Tauc laws. The introduction of SnI2 makes the glasses much easier to prepare and more stable against crystallization, making them drawable as optical fibers. The highest ΔT (130°C) value for (Ge20Se15Te65)0.9–(SnI2)0.1 glass composition can be obtained. A slight red-shifting of the long-wavelength cutting-off edge from 18.4 to 19.4μm was shown and it seems that SnI2 in these glasses offers the improvement in the far-infrared properties. [Copyright &y& Elsevier]

Abstract: Dy3+ doped 40GeSe2–25Ga2Se3–35CsI (GGC) glass was synthesized, and optical spectrum, such as infrared transmission and Vis-Nir absorption was measured. Base on the Judd–Ofelt theory, the three Judd–Ofelt parameters Ω t (t =2, 4, 6) were calculated and the results were compared with other chalcogenide glasses. The small Ω 2 in GGC glass is ascribed to the weak covalency of Se–Dy bond. The theory of crystallization kinetics under non-isothermal condition was developed, and was applied to analyze this Dy3+ doped GGC glass. From the heating-rate dependence of crystallization temperature, the activation energy for crystallization E =148kJ/mol is obtained, and this value is much smaller than that of the undoped glass host, indicating the introduction of Dy3+ ions into the GGC glass will get the host crystallized easily. [Copyright &y& Elsevier]

Abstract: GeSe2–Ga2Se3–CsI chalcohalide glasses had been prepared by the melt-quenching technique. With the addition of CsI, the short wavelength cut-off edge of the glasses shifts to the short wavelength gradually, while the long wavelength cut-off edge located at ∼16μm is nearly unchanged. Thermal properties were measured by Differential Thermal Analysis (DTA). From the heating rate dependence of crystallization temperature, the activation energy for crystallization (E) and the order parameter (n) were calculated by the Kissinger equation. The results show that the activation energy of crystallization decreases dramatically with increasing of CsI content, and the most probable crystallization mechanism is volume controlled one-dimensional growth. [Copyright &y& Elsevier]

This study reports on the synthesis of tellurium-based chalcogenide films that have high thermal stability for phase change memory application. Several Te-based chalcogenide alloys of In-Bi-Te, Ag-Bi-Te, In-Sb-Te, Sn-Sb-Te, Zn-Ge-Te, and Ga-Ge-Te are reported. Their thermal, optical, and electrical properties are investigated. The results show that Bi-Te-based films have a higher crystallization temperature and greater activation energy compared with the other Sb-Te-based and Ge-Te-based films. Especially, In2.8Bi36.6Te60.6 film exhibits high crystallization temperature (252 °C) and great activation energy (5.16 eV), showing much improved amorphous thermal stability. A relatively wider optical band gap (0.674 eV) of thermal annealed In2.8Bi36.6Te60.6 film is obtained. In addition, it also has a higher amorphous/crystalline resistance ratio of about 105, implying that current consumption could be low in the phase-change memory operation. [ABSTRACT FROM AUTHOR]

The superior performance of Zn-doped Sb7Te3 films might be favorable for the application in phase change memory. It was found that Zn dopants were able to suppress phase separation and form single stable Sb2Te crystal grain, diminish the grain size, and enhance the amorphous thermal stability of Sb7Te3 film. Especially, Zn30.19(Sb7Te3)69.81 film has higher crystallization temperature (∼258 °C), larger crystallization activation energy (∼4.15 eV), better data retention (∼170.6 °C for 10 yr), wider band gap (∼0.73 eV), and higher crystalline resistance. The minimum times for crystallization of Zn30.19(Sb7Te3)69.81 were revealed to be as short as ∼10 ns at a given proper laser power of 70 mW. [ABSTRACT FROM AUTHOR]

Zn-doped Sb2Te films are proposed to present the feasibility for phase-change memory application. Zn atoms are found to significantly increase crystallization temperature of Znx(Sb2Te)1-x films and be almost linearly with the wide range of Zn-doping concentration from x = 0 to 29.67 at.%. Crystalline resistances are enhanced by Zn-doping, while keeping the large amorphous/crystalline resistance ratio almost constant at ∼105. Especially, the Zn26.07(Sb2Te)73.93 and Zn29.67(Sb2Te)70.33 films exhibit a larger resistance change, faster crystallization speed, and better thermal stability due to the formation of amorphous Zn-Sb and Zn-Te phases as well as uniform distribution of Sb2Te crystalline grains. [ABSTRACT FROM AUTHOR]

The structural stability of carbon (C) incorporated Sb 2 Te films was investigated during crystallization process. Variations in the transition temperature for the as-deposited films during crystallization show that these films exhibit their enhanced amorphous stability due to C incorporation, while more C content will lead to a difference in the degree of disorder in the crystalline state. XPS data reveals that C atoms do not bond with Sb and Te atoms and only present in the form of C C bonds. According to XRD and TEM results, C atoms presents amorphous and this can increase the degree of disorder in the crystalline films. The Sb 2 Te nanocrystals were surrounded by an amorphous C phase. A subsequent Raman analysis further provides the direct evidence of improvement in the degree of disorder in the crystalline state. The laser-induced crystallization process of C 37.4 (Sb 2 Te) 62.6 reveals that the degree of disorder in the crystalline state is relatively high and the reliability during the repetitive laser melt-quenching cycles is confirmed with fast crystallization as well as a low melting point of only 353 °C. Increasing degree of disorder in the Sb 2 Te films by C addition can improve the phase-change behavior and make this film suitable for data storage applications. [ABSTRACT FROM AUTHOR]

Abstract: Mg-doped Ge2Sb2Te5 (GST) films with different Mg doping concentrations have been prepared, and their crystallization behavior, structure and electrical properties have been systematically investigated for phase-change memory applications. The results show that the addition of Mg into GST films could result in an enhancement in crystallization temperature, activation energy and electrical resistance compared with the conventional GST films, indicating that a good amorphous thermal stability. On the other hand, the proper Mg concentration ranging from 13.6 to 31.1at.% can lead to a one-step crystallization process from amorphous to faced-centered cubic (fcc) phase and suppress the formation of the hexagonal close-packed (hcp) crystalline phase. X-ray photoelectron spectra (XPS) further confirm that the formation of covalent Mgcontribute to the enhanced thermal stability in Mg-doped GST films. [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]

We have reported the fabrication and characterization of Ge 23.5 Ga 11.5 Se 65 glasses and glass-ceramics with different Er 3+ concentrations. It was found that, the emission properties of the bulk glasses showed the fluorescence intensity and lifetime increased until they reached a maximum, and then decreased with increasing Er 3+ concentration. This is due to concentration quenching effect although the maximum dissolving concentration of Er 3+ can be up to ∼1 wt% of Er. A careful thermal process has led to the formation of ∼80 nm β-Ga 2 Se 3 crystalline particles in Ge 23.5 Ga 11.5 Se 65 glasses doped with 0.8 wt% of Er 3+ . By monitoring 4 I 13/2 → 4 I 15/2 Er 3+ transition, almost fourfold enhancement in the intensity and ∼0.57 ms prolongation in the lifetime of near-infrared fluorescence at 1.54 μm have been observed after crystallization. It was assigned to the decreasing phonon energy of the local environment of Er 3+ ions during the crystallization. [ABSTRACT FROM AUTHOR]

We systematically investigated the structural properties of as-deposited and annealed Ge x Sb y Se z ( x + y + z = 100, 9.5 ≤ x ≤ 59, 6.2 ≤ y ≤ 42.9, 34.8 ≤ z ≤ 51.5) chalcogenide films. For films with x < 34.5, some main Sb Sb homopolar bonds as well as Sb Se heteropolar bonds appeared in the as-deposited films, while increasing the Ge content replaced some Se atoms, forming Ge Se heteropolar bonds, which increased the optical band gap. For films with x ≥ 34.5, the structures of the as-deposited films were dominated by Ge Ge and Se Se homopolar bonds. The annealed Ge–Sb–Se films exhibited a phase transition from amorphous to crystalline for phase-change memory. We ascribed the crystal grains of the Ge x Sb y Se z films ( x = 9.5, 12.8) to be the Sb phase, while we confirmed those of the films ( x = 14.2, 21.3, 22.9, 25.2) to be a mixture of Sb and Sb 2 Se 3 phases. The films with high Ge content ( x = 40.2, 59) exhibited a stable amorphous phase for optical waveguide application. [ABSTRACT FROM AUTHOR]

The Mo-doped Sb 2 Te films were investigated for phase change memory applications. Compared with the pure Sb 2 Te, Mo 4.9 (Sb 2 Te) 95.1 film exhibits a higher crystallization temperature T c (211 °C), larger crystallization activation energy E a (4.36 eV), better data retention of 10 years at 138 °C due to the bond recombination among Mo, Sb and Te atoms. The formed Mo–Sb and Mo–Te phases with high thermal stability present in the form of amorphous content around the crystals, which suppress the crystal grain growth while keeping the precipitated hexagonal Sb 2 Te crystalline phase stable without phase separation, which ensures better stability for the application in practical device. [ABSTRACT FROM AUTHOR]

The thermal stability and crystallization characteristics of W-doped Sb 3 Te films have been studied systematically. It was found that W atoms presented in the form of amorphous content, which increased the crystallization temperature and crystalline resistance, sustained uniform single crystalline structure and refined their grain size of Sb 3 Te films. The optimized W 20.1 (Sb 3 Te) 79.9 film exhibits higher crystallization temperature (∼204 °C), larger crystalline activation energy (∼3.13 eV) and better data retention ability (∼123 °C for 10 yr) as well as a single stable Sb 2 Te phase for phase change memory application. [ABSTRACT FROM AUTHOR]

The Zn-doped Sb 2 Te 3 films have been investigated systematically during the phase transformation process. It was found that, the increase of crystallization temperature in the Zn-doped Sb 2 Te 3 films leads to its enhanced amorphous stability, and Zn incorporation can increase electrical resistance, widen optical band gap and refine crystalline grain size. The crystallization mechanism can be tuned into nucleation-dominated from growth-dominated type. Moreover, Sb 2 Te 3 film with high Zn-doping concentration such as Zn 38.8 (Sb 2 Te 3 ) 61.2 film was found to exhibit a higher crystallization temperature (233 °C), better data retention ability (keeping the amorphous state at 146.5 °C for ten years), and wider band gap (0.839 eV). A lower threshold of crystallization (~ 25 ns) can be realized in the Zn 38.8 (Sb 2 Te 3 ) 61.2 film irradiated at the laser power of 70 mW in comparison with that in the conventional Ge 2 Sb 2 Te 5 film. We confirm that the Zn doping is responsible for a fast switching and the Zn 38.8 (Sb 2 Te 3 ) 61.2 compound is stable against segregation with cycling. [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]

Highlights: [•] The amorphous Ge–Te–In films were prepared by magnetron co-sputtering method. [•] The Ge–Te–In film system has a high crystallization temperature. [•] Large redshift of the optical band gap is related to crystallization by annealing. [•] The structural rearrangements around Ge atoms occur during crystallization. [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]

Abstract: Transparent glass ceramics based on Bi2O3–B2O3–TiO2 ternary glass system were prepared by controlled one-step heat treatment method. X-ray diffraction measurement confirms the formation of Bi2O3 phase crystals in glass network. Z-scan measurements at a wavelength of 750nm were employed to investigate the third-order optical nonlinearities of these transparent glass ceramics. The results show that the nonlinear properties were significantly enhanced after crystallization process. [ABSTRACT FROM AUTHOR]