Crystal Growth Kinetics and Viscous Behavior in Ge2Sb2Se5 Undercooled Melt

Barták, Jaroslav; Košťál, Petr; Podzemná, Veronika; Shánělová, Jana; Málek, Jiřı́

doi:10.1021/acs.jpcb.6b05455

Cited by 10 publications

(20 citation statements)

References 44 publications

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“…This correlation between the structural relaxation time and the time of crystallization has been observed before (albeit with a slightly different slope) in several systems, for example in the case of stiripentol 20 and of indomethacine and celecoxib, 50 and also in binary mixtures of pharmaceutical compounds and 20 polymeric excipients. 51 The correlation between crystal growth rate and mobility (or equivalently, viscosity) above T g appears to be a general feature of glass formers (also nonpharmaceutical ones), 41 , 52 , 53 related to the fact that the crystallization rate is kinetically driven near the glass transition temperature.…”

Section: Resultsmentioning

confidence: 99%

Tuning the Kinetic Stability of the Amorphous Phase of the Chloramphenicol Antibiotic

et al. 2018

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We employ broadband dielectric spectroscopy to study the relaxation dynamics and crystallization kinetics of a broad-spectrum antibiotic, chloramphenicol, in its supercooled liquid form. Two dynamic processes are observed: the structural α relaxation, which becomes kinetically frozen at T g = 302 ± 1 K, and an intramolecular secondary relaxation. Under isothermal conditions, the supercooled drug displays interconversion between different isomers, followed by recrystallization. Recrystallization follows the Avrami law with Avrami exponent n = 1.3 ± 0.1, consistent with a one dimensional growth of crystalline platelets, as observed by electron microscopy. Exposure to humid atmosphere and subsequent heating to high temperature is found to degrade the compound. The partially degraded sample displays a much lower tendency to crystallize, likely because the presence of the degradation products results in spatial frustration. This sample exhibits enhanced conductivity and an additional relaxation, intermediate to the ones observed in the pure sample, which likely corresponds to the noncooperative dynamics of the main degradation product. We find that dispersing the antibiotic in polylactic acid results in an amorphous sample which does not crystallize at room temperature for relatively long times.

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Section: Resultsmentioning

confidence: 99%

Tuning the Kinetic Stability of the Amorphous Phase of the Chloramphenicol Antibiotic

et al. 2018

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“…Important parameters of the viscous flow were found from the experimental data and are listed in Table 3. The data are compared with previously published data on viscosity in Ge2Sb2Se5 glass and undercooled melt published by Barták et al [37]. According to the Table 3, the T12 temperature decreases with tellurium content in the Ge2Sb2Se5-xTex system.…”

Section: Temperature Dependence Of Viscositymentioning

confidence: 65%

“…The value 10 12 Pa•s is generally accepted convention. All the mentioned parameters (E, m and T12) were evaluated from the experimental viscosity data and are summarized in Table 3 together with previously found parameters for composition Ge2Sb2Se5, published by Barták et al [37].…”

Section: Viscositymentioning

confidence: 99%

Analysis of crystal growth and viscosity in Ge-Sb-Se-Te undercooled melts

Barták

Košťál

Málek

2019

Journal of Non-Crystalline Solids

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A comprehensive analysis on crystal growth and viscosity is presented for the Ge2Sb2Se5-xTex (x = 0.5 and 1) undercooled melts in this article. Temperature dependence of the measured viscosities (10 7.5 -10 12.5 Pa•s) can be described by a simple exponential Arrhenius type equation in the relatively narrow temperature region in which the measurements were performed. Fragility of the measured materials are all roughly equal to 43, which means that these materials belong to the so called "intermediate" liquids (lying in the middle between strong and fragile liquids) and cannot be described by simple Arrhenius type equation if the temperature region is expanded from glass transition to melting, which is important for description of crystal growth. Therefore, MYEGA equation is used to extrapolate the viscosity data into the temperature region of studied crystal growth. Nucleation and crystal growth started on a surface of studied samples. The isothermal growth rate of the formed surface crystalline layer was measured at various temperatures. Analysis of the growth data revealed a crystal growth driven by liquid-crystal interface kinetics. Therefore, the standard crystal growth models were used for description of crystal growth rates in the studied systems.

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“…The growth of crystalline GeSe 2 in Ge–Sb–Se glasses has often been demonstrated in controlled heat‐treated environments . Yet, in all these cases, the bulk Ge–Sb–Se glasses crystallized into at least two phases: Sb 2 Se 3 , with an activation energy of crystallization ( E c ) of 282.01 kJ/mol, and GeSe 2 , with an E c of 762.02 kJ/mol .…”

Section: Resultsmentioning

confidence: 99%

“…The growth of crystalline GeSe 2 in Ge-Sb-Se glasses has often been demonstrated in controlled heat-treated environments. 40,41 Yet, in all these cases, the bulk Ge-Sb-Se glasses crystallized into at least two phases: Sb 2 Se 3 , with an activation energy of crystallization (E c ) of 282.01 kJ/ mol, 41 and GeSe 2 , with an E c of 762.02 kJ/mol. 41 As a commonly crystallizing phase in Ge-Sb-Se glasses, with the lowest E c , the lack of Sb 2 Se 3 observed by XRD within in the surface crystallization at the stoichiometric Ge 25 Sb 10 Se 65 at.…”

Section: Crystallization In Ge-sb-se Glasses Relevant To Fiber Drawingmentioning

confidence: 99%

Compositional dependence of crystallization in Ge–Sb–Se glasses relevant to optical fiber making

et al. 2017

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For fiber-optic mid-infrared bio-and chemical-sensing, Ge-Sb-Se glass optical fibers are more attractive than Ge-As-Se because of: (i) lowered toxicity and (ii) lower phonon energy and hence transmission to longer wavelengths, with potential to reach the spectral "fingerprint region" for molecular sensing. There is little previous work on Ge-Sb-Se fibers. Here, fibers are fabricated from two glass compositions in the Ge x Sb 10 Se 90Àx atomic (at.) % series. Both glass compositions are of similar mean-coordination-number, lying in the overconstrained region, yet of different chemical composition: stoichiometric Ge 25 Sb 10 Se 65 at. % and non-stoichiometric Ge 20 Sb 10 Se 70 at. %. Thermal analysis on bulk glasses has previously shown that the former exhibited the maximum glass stability of the series. However, during fiber-drawing of Ge 25 Sb 10 Se 65 at. %, the preform tip is found to undergo surfacedevitrification to monoclinic GeSe 2 alone, the primary phase, no matter if the preform is an annealed, as-melted rod or annealed, extruded rod. The heating rate of the preform-tip to the fiber-drawing temperature is estimated to be up to~100°C/min tõ 490°C. Lower heating rates of 10°C/min using thermal analysis, in contrast, encourage crystallization of both Sb 2 Se 3 and GeSe 2 . The non-stoichiometric: Ge 20 Sb 10 Se 70 at. % composition drew successfully to low optical loss fiber, no matter whether the preform was an annealed, as-melted rod or annealed, extruded rod.

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Crystal Growth Kinetics and Viscous Behavior in Ge₂Sb₂Se₅ Undercooled Melt

Cited by 10 publications

References 44 publications

Tuning the Kinetic Stability of the Amorphous Phase of the Chloramphenicol Antibiotic

Tuning the Kinetic Stability of the Amorphous Phase of the Chloramphenicol Antibiotic

Analysis of crystal growth and viscosity in Ge-Sb-Se-Te undercooled melts

Compositional dependence of crystallization in Ge–Sb–Se glasses relevant to optical fiber making

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