Crystallization Mechanism Of Glass Research Articles

Highly crystalline Y3Al5O12:Ce3+ phosphor-in-silica glass ceramics for high-power solid-state lighting

The pursuit of high-brightness solid-state lighting (SSL) stimulates the development of all-inorganic color converters with high robustness. It is required that the fluorescent material is able to cope with the extreme condition generated from the irradiation of high-power-density excitation light. As such, in this work, we developed a new composite color converter, i.e., Y3Al5O12:Ce3+ phosphor-in-silica glass ceramic (YAG:Ce3+ PiSGC). Remarkably, the amorphous SiO2 matrix spontaneously transforms into tetragonal SiO2 crystallites during co-sintering with crystallization fraction reaching up to >90% (almost full ceramization). The activation energy for crystallization Ec and Avrami index n of amorphous silica oxide are 298.5 kJ/mol and 1.71, indicating the diffusion-controlled glass crystallization mechanism. The fabricated prototype high-power phosphor-converted white light-emitting diode (pc-wLED) and phosphor-converted white laser diode (pc-wLD) based on YAG:Ce3+ PiSGC show satisfactory photometric/colorimetric parameters. The developed color converters have combined merits of environmental protection property, cost-effective manufacturing, good luminescent performance, and easy scalability. This study highlights a new kind of opto-functional composite material and its application as an efficient color converter in high-power solid-state lightings.

Influence of Al2O3/SiO2 ratio in multicomponent LNAS glasses and glass-ceramics on the crystallization behavior, microstructure and mechanical performance

Transparent glass-ceramics containing eucryptite and nepheline crystalline phases were prepared from alkali (Li, Na) aluminosilicate glasses with various mole substitutions of Al2O3 for SiO2. The relationships between glass network structure and crystallization behavior of Li2O–Na2O–Al2O3–SiO2 (LNAS) glasses were investigated. It was found that the crystallization of the eucryptite and nepheline in LNAS glasses significantly depended on the concentration of Al2O3. LNAS glasses with the addition of Al2O3 from 16 to 18 mol% exhibited increasing Q4 (mAl) structural units confirmed by NMR and Raman spectroscopy, which promoted the formation of eucryptite and nepheline crystalline phases. With the Al2O3 content increasing to 19–20 mol%, the formation of highly disordered (Li, Na)3PO4 phase which can serve as nucleation sites was inhibited and the crystallization mechanism of glass became surface crystallization. Glass-ceramics containing 18 mol% Al2O3 showed high transparency ∼84% at 550 nm. Moreover, the microhardness, elastic modulus and fracture toughness are 8.56 GPa, 95.7 GPa and 0.78 MPa m1/2 respectively. The transparent glass-ceramics with good mechanical properties show high potential in the applications of protective cover of displays.

Determination of the crystallization mechanism of glasses in the system BaO/SrO/ZnO/SiO2 with differential scanning calorimetry

In order to identify suitable volume nucleation agents in glasses, heat treatments and subsequent traditional microscopic investigations are necessary. Those analyses are laborious and time-consuming. Therefore, often DSC methods are used to get information about the preferred crystallization mechanism or adequate nucleation and growth temperatures. In principle, these non-isothermal methods are much faster. In this study, different glasses from the system BaO–SrO–ZnO–SiO2 were prepared. The pairs show only slight compositional variations but a clearly different crystallization behavior. Each pair consists of one glass, which shows volume crystallization and another one, which crystallizes solely at the surface. The DSC results are correlated with the microstructures of the glass ceramics obtained from microscopic studies. It is shown that conventional DSC methods cannot give a distinct answer which crystallization mechanism really exists. One method was identified to securely determine the crystallization mechanism.

Controlled nano‐crystallization of IR frequency‐doubling Cd4GeS6 crystal in chalcogenide glass

AbstractCrystallization 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.

Unveiling crystallization mechanism for controlling nanocrystalline structure in glasses

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 80GeS2·20In2S3 and 72.5GeS2·14.5Sb2S3·13RbCl 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.

Stress-induced CsPbBr3 nanocrystallization on glass surface: Unexpected mechanoluminescence and applications

In this work, we discovered an unexpected mechanoluminescence (ML) phenomena occurring when transforming amorphous into crystalline, due to the stress-induced precipitation of CsPbBr3 perovskite nanocrystals on glass surface. It is revealed that, unlike the conventional thermal-induced phase transformation mechanism, the breakage of bonding of glass network provides the energy for nucleation and growth, and the shear stress avoids the long-range migration of structural units for crystallization. Such unique ML phenomenon enables the visualization of dynamical force that is inaccessible by common strategy, and so, opens up some novel applications, such as the pressuresensitive “glassy pencil” to learn people’s writing habits, and the Pb2+-detection with good sensitivity and selectivity. These findings not only demonstrate an effective route for the preparation of perovskite materials in a green, time-saving, low cost, and scalable way, enrich the knowledge of glass crystallization mechanism, but also exploit a useful avenue to quantitatively visualize the dynamical force.

Compositional effects on mechanical properties, viscosity, and crystallization of (Li2O, B2O3, MgO)-Al2O3-SiO2 glasses

Compositional effects on mechanical properties, viscosity, crystallization and crystallization kinetics of MgO-Al2O3-SiO2 based high-strength (HS) glass and glass fibers were examined in detail by varying (Li2O + B2O3)/MgO ratio (LB/M). A set of complementary techniques was applied to the crystallization studies, including differential scanning calorimetry (DSC), powder x-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive spectrometer (SEM/EDS). Phase identification and crystal morphology survey were made. Crystallization kinetics of the HS glass fibers under various thermal conditions was studied in detail to elucidate plausible crystallization mechanisms in relationships to LB/M. Our study showed that the combined, high concentration of Li2O and B2O3, at the expense of MgO, i.e., higher LB/M, suppressed crystal growth in glass. From the DSC studies, exothermic peaks came from formation of β-quartz (s.s.) below 900°Cand subsequent transformation into cordierite greater than 1000 °C according to XRD analysis of the heat-treated samples. For crystallization under the non-isothermal conditions, Kissinger and Matusita & Sakka methods were applied to elucidate glass crystallization mechanism(s). In addition, the HS glass fibers were shown to have 29% higher tensile strength and 15% higher modulus than E-Glass fibers commercially used for a wide range of composite applications.

Sol–Gel Synthesis and Crystal Nucleation of Photosensitive Au/Ag- Containing Glasses of Lithium Silicate System

A sol–gel method has been proposed for obtaining the sintering mixture used in the preparing of a photosensitive Au/Ag-containing glasses of the Li 2 O - SiO 2 system. It has been established that the use of sol–gel method for the production of the batch for synthesizing photosensitive Au/Ag-containing glasses gives more homogeneous distribution of Au/Ag metals in the bulk of the glass. Crystal-nucleation main characteristics have been defined in a large area of compounds of photo-structured compositions of a lithium–silicate system (23.4–46.0 Li 2 O mol % by analysis) both for spontaneous and catalyzed nucleations. The spontaneous (homogeneous) nucleation happened in the samples without any photosensitive metals and with photosensitive gold–silver additives (0.05 wt % above 100%) without irradiation; the catalyzed (heterogeneous) nucleation happened in the samples with photosensitive silver ore gold additives under x-ray CuK I± irradiation. The ranges of the compositions of the glasses in which the effect of catalyzing irradiation is reversed (suppressing nucleation in accordance with the autocatalytic mechanism) under certain conditions. The spontaneous and catalyzed nucleation of crystals in the glasses of Li 2 O – SiO 2 system caused by the addition of photosensitive impurities and X-ray irradiation was analyzed in glasses with a very wide range of compositions in Li 2 O – SiO 2 system. Composition ranges with positive (+) and negative (-) differences in the rates of catalyzed and spontaneous steady-state nucleation were established. This finding point is favorable for obtaining photostructured (photosensitive) materials. The concentration limit was determined to be 37.98 mol % Li 2 O. About this value, we observe a modification of the mechanism of nucleation of crystals. The behavior of crystal nucleation in photostructured glasses under X-ray irradiation changes to the reverse: autocatalytic nucleation is suppressed rather than induced by x-ray CuK I± irradiation. These peculiarities of crystallization mechanism in glasses under study give one the possibility to choose the correct composition range depending on the problems facing researchers.

Sol–Gel Synthesis and Crystal Nucleation of Photosensitive Au/Ag- Containing Glasses of Lithium Silicate System

A sol–gel method has been proposed for obtaining the sintering mixture used in the preparing of a photosensitive Au/Ag-containing glasses of the Li2O - SiO2 system. It has been established that the use of sol–gel method for the production of the batch for synthesizing photosensitive Au/Ag-containing glasses gives more homogeneous distribution of Au/Ag metals in the bulk of the glass. Crystal-nucleation main characteristics have been defined in a large area of compounds of photo-structured compositions of a lithium-silicate system (23.4–46.0 Li2O mol % by analysis) both for spontaneous and catalyzed nucleations. The spontaneous (homogeneous) nucleation happened in the samples without any photosensitive metals and with photosensitive gold–silver additives (0.05 wt % above 100%) without irradiation; the catalyzed (heterogeneous) nucleation happened in the samples with photosensitive silver ore gold additives under x-ray CuKa irradiation. The ranges of the compositions of the glasses in which the effect of catalyzing irradiation is reversed (suppressing nucleation in accordance with the autocatalytic mechanism) under certain conditions. The spontaneous and catalyzed nucleation of crystals in the glasses of Li2O–SiO2 system caused by the addition of photosensitive impurities and X-ray irradiation was analyzed in glasses with a very wide range of compositions in Li2O–SiO2 system. Composition ranges with positive (+) and negative (-) differences in the rates of catalyzed and spontaneous steady-state nucleation were established. This finding point is favorable for obtaining photostructured (photosensitive) materials. The concentration limit was determined to be 37.98 mol % Li2O. About this value, we observe a modification of the mechanism of nucleation of crystals. The behavior of crystal nucleation in photostructured glasses under X-ray irradiation changes to the reverse: autocatalytic nucleation is suppressed rather than induced by x-ray CuKa irradiation. These peculiarities of crystallization mechanism in glasses under study give one the possibility to choose the correct composition range depending on the problems facing researchers.

Devitrification behavior and preferred crystallization mechanism of glasses based on fluorrichterite (Na2CaMg5Si8O22F2) composition

This paper reports on the effect of different contents of fluorine on the thermal stability of glasses in the SiO2–MgO–CaO–Na2O–F system. Four glass compositions, with experimental fluorine contents varying from 2.12 to 4.39wt.%, were studied using differential scanning calorimetry (DSC). The devitrification behavior was assessed through the evaluation of both the glass stability (GS) and glass-forming ability (GFA) using different parameters calculated from the characteristic temperatures in non-isothermal DSC curves. The predominant crystallization mechanism was determined by the difference in the crystallization temperature (ΔTp) between fine and coarse glass samples. The results indicate that the studied melts exhibit a low tendency to devitrify during cooling, although this trend is increased with the fluorine content. The glass thermal stability is affected by the particle size, with it being easier to crystallize a glass powder sample than a coarse glass sample. The surface crystallization mechanism is predominant at the beginning of the devitrification process; however, the volume crystallization acquires importance with an increase in the fluorine content.

INVESTIGATION AND MODELING OF ZR-BASED BULK METALLIC GLASS CRYSTALLIZATION PROCESSES

The article describes the investigation and simulation of Zr-based bulk metallic glass crystallization kinetics using DSC and DIC techniques. The investigation of the kinetics of crystallization processes may eventually provide deeper understanding of the bulk metallic glass crystallization mechanism and promote the evidence-based selection of heat treatment to form desired structure and properties of bulk metallic glasses based composites.

Formation of Bi2ZnB2O7 Nanocrystals in ZnO–Bi2O3–B2O3 Glass Induced by Femtosecond Laser

We report on the formation of Bi2ZnB2O7 crystal structures with designated patterns in ZnO–Bi2O3–B2O3 glass by femtosecond laser direct writing. The crystallization mechanism in glass is investigated by crystallization kinetics analysis and simulation of the three‐dimensional temperature field distribution. The crystallized regions show larger third‐order optical nonlinearity than the unirradiated region in glass by Z‐scan technique. This finding is of great potential in application of nonlinear optical integrated devices and development of new nonlinear materials.

Crystallization Process and Some Properties of Li2O–SiO2Glass–Ceramics Doped with Al2O3and K2O

We report on the role of Al2O3and K2O on crystallization in glasses featuring a SiO2/Li2O ratio (3.13 to 4.88) far beyond that of lithium disilicate (LD, Li2Si2O5) stoichiometry. Glasses in both bulk and frit form were produced by the conventional melt‐quenching technique. Scanning electron microscopy analysis revealed surface nucleation as the dominant crystallization mechanism in glass–ceramics (GCs) derived from bulk glasses richer in Al2O3and K2O in the temperature range 800°–900°C and dendritic skeletal surface growth of lithium metasilicate crystalline phase (LS,Li2SiO3). The glasses with lower amounts of Al2O3and K2O showed an intermediate type of crystallization mechanism (simultaneous surface and volume nucleation) resulting in the preferential formation of Li2Si2O5. The formation of LD GCs by sintering and the crystallization of glass‐powder frits seems to occur via the precursor phase of LS, resulting in high‐strength materials.

Capacity of Granitoid-Based Glasses for Glass Ceramics Formation

The ability to form glass ceramics in glasses based on granitoids from the Republic of Belarus, which are a new type of petrological material for the silicate industry, is investigated. The concepts of the crystallization mechanism in glasses produced from mineral melts are formulated. It is established that the crystallization of the pyroxene phase proceeds according to the spherulite type on the stable chromium-picotite phase that is formed in glass cooling and persists up to the end of glass ceramics formation.

Non-isothermal crystallization kinetics of V2O5-MoO3-Bi2O3 glasses

Characteristic temperatures, such as T g (glass transition), T x (crystallization temperature) and T l (liquidus temperature) of glasses from the V2O5-MoO3-Bi2O3 system were determined by means of differential thermal analysis (DTA). The higher content of MoO3 improved the thermal stability of the glasses as well as the glass forming ability. The non-isothermal crystallization was investigated and following energies of the crystal growth were obtained: glass #1 (80V2O5·20Bi2O3) E G=280 kJ mol-1, glass #2 (40V2O5·30MoO3·30Bi2O3) E G=422 kJ mol-1 and glass #3 (80MoO3·10V2O5·10Bi2O3) E G=305 kJ mol-1. The crystallization mechanism of glass #1 (n=3) is bulk, of glass #3 (n=1) is surface. Bulk and surface crystallization was supposed in glass #2. The presence of high content of a vanadium oxide acts as a nucleation agent and facilitates bulk crystallization.

FORMATION AND CRYSTALLIZATION MECHANISM OF GLASSES IN NaBO2-B2O3 SYSTEM

The formation, thermal stability and crystallization mechanism of glasses in NaBO2-B2O3 system have been studied by means of thermal analysis, X-ray powder diffraction at high and room temperatures, and IR absorption spectra. The stable glasses are formed easily in this system. The crystallization processes are related to macroscopic state of samples. The crystallization temperature of bulk glasses is higher than that of amorphous powders. A part of components crystallizes as different phases. They melt directly at different temperatures. The crystal structure of crystallization products is close to glass structure.The ionic conductivity in NaBO2-B2O3 system was determined by ac impedance method. The conductivity of glasses are 2-3 orders higher than that of crystals with the same composition, while the activation energy of glasses lower than that of crystalline state for the same composition.