Jaroslav Bartak

Jaroslav Bartak
University of Pardubice · Department of Physical Chemistry

PhD

About

31
Publications
1,978
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227
Citations
Citations since 2017
12 Research Items
161 Citations
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201720182019202020212022202301020304050
201720182019202020212022202301020304050
201720182019202020212022202301020304050

Publications

Publications (31)
Article
Experimental viscosity data for (GeSe2)x(Sb2Se3)100-x melts (x = 50, 60 and 70), obtained by deploying the pressure-assisted melt filling technique (PAMFT), are presented. These data were combined with previously published literature data and fitted over a broad temperature range including glass, undercooled melt, and melt regions by the Mauro–Yue–...
Article
The crystallization behavior of the (GeSe2)x(Sb2Se3)1-x system for x = 0.6–0.9 was studied indirectly by using differential scanning calorimetry (DSC) under non-isothermal conditions. DSC experiments revealed a complex behavior consisting of several subprocesses. Using the direct observation method of infrared microscopy and X-ray diffractometry, w...
Article
The crystal growth kinetics of Sb2Se3 in (GeSe2)x(Sb2Se3)1-x with compositions (x = 0.4, 0.5) were studied using infrared microscopy. Direct observation revealed two types of crystal growth during the overall process of crystal nucleation and growth: lateral crystal growth at the surface and crystal growth in the volume of the bulk sample (“volume...
Article
The mobility of structural units in amorphous materials has a significant influence on crystal growth. In this study, we show that the motion of structural units from the amorphous matrix to the growing crystals in the volume of the Se95Te5 bulk samples can be adequately described by viscosity. Nevertheless, surface crystal growth results in a much...
Article
Surface diffusion is important for a broad range of chemical and physical processes that take place at the surfaces of amorphous solids, including surface crystallization. In this work, the temporal evolution of nanoholes is monitored with atomic force microscopy to quantify the surface dynamics of amorphous selenium. In molecular glasses, the surf...
Article
The pressure-assisted melt filling technique (PAMFT) is promising approach for integrating new materials such as glasses or semiconductor into fiber, while only a small amount of starting material (<0.1 mg) is actually required for the implementation of such hybrid optical fibers of length of several centimeters. PAMFT has also the capability to pr...
Article
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 (107.5–1012.5 Pa·s) can be described by a simple exponential Arrhenius type equation in the relatively narrow temperature region in which the measurements...
Article
The crystal nucleation behavior and kinetics in Ge1.8Sb36.8S61.4 thin films were studied using optical microscope coupled with computer-controlled heating stage. The single-stage in situ heat treatment method was chosen for the study of nucleation. In-situ experiments were performed in the temperature range of 236 – 295 °C. The time evolution of nu...
Article
Crystal growth in surface of selenium bulk samples and in selenium thin films of different thicknesses has been studied under isothermal conditions using different microscopy techniques (optical, infrared and scanning electron microscopy). The structure of formed crystals is described with respect to previous publications focused on crystal growth...
Article
Crystal growth rates in Ge18Sb28Se54 bulk glass and thin film were measured using optical and scanning electron microscopy under isothermal conditions. The studied temperature region was 255 – 346 °C and 254 – 286 °C for bulk glass and thin film, respectively. The compact crystalline layer growing from the surface into the amorphous core was formed...
Article
We demonstrate that pressure-induced amorphization in Ge-Sb-Te alloys across the ferroelectric-paraelectric transition can be represented as a mixture of coherently distorted rhombohedral Ge8Sb2Te11 and randomly distorted cubic Ge4Sb2Te7 and high-temperature Ge8Sb2Te11 phases. While coherent distortion in Ge8Sb2Te11 does not prevent the crystalline...
Article
The isothermal crystal growth kinetics in Se70Te30 thin films was investigated using the microscopy and in situ X-ray diffraction (XRD) measurements. Plate-like crystals grew linearly with time which is the sign of liquid-crystal interface kinetics. In the studied temperature range, from 68 °C to 88 °C, crystal growth rates exhibit simple exponenti...
Article
The isothermal crystal growth in a bulk supercooled liquid prepared by fast heating of amorphous Se was measured by infrared microscopy. The spherulitic crystals grew linearly in course of time that corresponds to crystal growth controlled by crystal-liquid interface kinetics. The crystal growth velocity data obtained for different thermal history...
Article
The crystal growth, viscosity, and melting were studied in Ge2Sb2Se5 bulk samples. The crystals formed a compact layer on the surface of the sample and then continued growing from the surface to the central part of the sample. The formed crystalline layer grew linearly with time which suggests that the crystal growth is controlled by liquid-crystal...
Article
Crystallization of amorphous Sb0.5Se99.5 glass in the form of bulk and powder with defined particle sizes (prepared in protective atmosphere of argon) was studied by DSC. Different forms of sample exhibit quite complex behavior involving crystallization on the surface and in the volume of the sample, and this is reflected in the shape of DSC curve....
Article
Full-text available
The dehydration of calcium oxalate trihydrate was studied using DSC method and open sample crucibles. The dehydration proceeds in two steps where first two molecules of water are released around 80 °C and consequently the last molecule of water is released at a temperature around 130 °C. The kinetic analysis of overlapping peaks was performed, and...
Article
The isothermal crystal growth in Se100?xTex bulk glasses (x = 10, 20, and 30) was studied directly using infrared microscopy. The crystals grew spherulitically and linearly in the course of time, which is typical for crystal growth controlled by liquid-crystal interface kinetics. An operative growth model was found using a combination of growth and...
Article
The crystal growth kinetics of germanium disulfide in undercooled melts has been studied by optical microscopy under isothermal conditions. The linear growth kinetics of GeS2 has been observed in the temperature range 672 ≤ T ≤ 711 K in thin film samples. The activation energy of crystal growth assuming Arrhenius behavior has been determined as E G...
Article
Full-text available
Sb2Se98 glass with the particle size of 20–50 μm was studied under non-isothermal conditions using differential scanning calorimeter. Upon heating, this glass shows a single glass transition and three overlapping crystallization peaks. The kinetic analysis of overlapping peaks was done: two peaks were described by autocatalytical model and the last...
Article
Full-text available
The crystallization behaviour of as-prepared and nucleated Ge17Sb23Se60 thin films was studied by means of differential scanning calorimetry, X-ray diffraction analysis and scanning electron microscopy. Detailed analysis of the non-isothermal crystal growth kinetics was performed; the apparent activation energy, kinetic model and value of the pre-e...
Article
Isothermal crystal growth kinetics in Se90Te10 and Se80Te20 thin films was studied by microscopy and in situ X-ray diffraction (XRD) measurements. The spherulite-like crystals grew linearly with time. In a narrow temperature range of between 65 and 85 °C, crystal growth rates exhibit simple exponential behavior with activation energies EG = 193 ± 4...
Article
Full-text available
Sb2Se98 glass with the particle size of 20–50 lm was studied under non-isothermal conditions using differential scanning calorimeter. Upon heating, this glass shows a single glass transition and three overlapping crystallization peaks. The kinetic analysis of overlapping peaks was done: two peaks were described by autocatalytical model and the last...
Article
The rates of isothermal nucleation and growth in chalcogenide glass thin films of (GeS2)0.9(Sb2S3)0.1 were studied using optical microscopy. Nucleation data was obtained from double stage heat treatment, followed by image analysis of polarized optical micrographs. The applicability of classical nucleation theory (CNT) to the nucleation data has bee...
Article
Sb2S3 crystal growth kinetics in (GeS2)x (Sb2S3)1–x thin films (x = 0.4 and 0.5) have been investigated through this study by optical microscopy in the temperature range of 575–623 K. Relative complex crystalline structures composed of submicrometer-thin Sb2S3 crystal fibers develop linearly with time. The data on temperature dependence of crystal...
Article
Full-text available
Non-isothermal measurements of dc conductivity were used to study crystallization in bulk glasses from the TexSe100−x system (x = 10, 20, and 30). In combination with infrared microscopy, it provides a very good qualitative picture of the complex crystallization processes, as the formation of conductive paths proceeds more or less separately for ea...
Article
The crystallization kinetics of antimony trisulphide in (GeS2)0.4(Sb2S3)0.6 glass has been studied by thermomechanical analyzer and microscopy. The linear crystal growth kinetics of Sb2S3 has been observed in the temperature range 293 °C ≤ T ≤ 327.5 °C. The activation energy determined of TMA method (E = 240 ± 5 kJ·mol-1) is relatively close to the...
Article
A novel method to study crystallization behavior in non-crystalline materials has been developed. The method is based on slowing down of sample deformation by viscous flow above the glass transition due to macroscopic crystal growth. This process might be detected by thermomechanical analysis (TMA). The influences of sample length, applied force an...
Article
Tato diplomová práce je zaměřena na studium krystalizace skel systému (GeS2)x(Sb2S3)1-x pomocí termomechanické analýzy (TMA). Krystalizace byla studována za neizotermních podmínek při různých rychlostech ohřevu. Z TMA křivek byly vyhodnoceny teploty měknutí Ts a teploty krystalizace Tc. Ze závislosti Tc na rychlosti ohřevu byla pro jednotlivá slože...

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