Crystallization kinetics of overlapping phases in Se70Te15Sb15 using isoconversional methods

Abstract

The crystallization kinetics of Se 70 Te 15 Sb 15 chalcogenide glass was studied by Differential Scanning Calorimetry (DSC) under non-isothermal conditions. This glass was found to have a double glass transition and double overlapped crystalline phases. The overlapped crystalline phases were successfully separated using the Gaussian fit model. The activation energy, E c , and Avrami index, n, were determined by analyzing the data using the Matausita et. al. method. A strong heating rate depending on the activation energy for the two crystalline peaks was observed. The results indicated that the transformation from amorphous to crystalline phases is a complex process involving different mechanisms of nucleation and growth. The variation of activation energy with crystalline fraction was determined by Kissenger-Akahira-Sunose (KAS) method. The obtained results of directly fitting the experimental DSC data to the calculated DSC curves indicated that the crystallization process of Se 70 Te 15 Sb 15 glass cannot be satisfactorily described by the Johnson-Mehl-Avrami (JMA) model. Simulation results indicated that the SestakBerggren (SB) model is more suitable to describe the crystallization process for the studied glass. The crystalline phases for the two events were identified by using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Modeling of thermal studies on melt quenched Ge18Bi4Se78 chalcogenide

“…5, 208.3 0.1.5 kJ/mol for fixed crystallization fraction 0.3, 0.4, 0.5, 0.6, and 0.7, respectively. This behavior of changing E c with α is consistent with other literature[60,71]. The average value of E c is 204.2 kJ mol −1 which is recorded in table 5.…”

“…According to equation (24), at fixed temperatures, plots of Ln[-Ln(1-α)] against Ln(β) show straight lines as seen in Figure 17 of slopes equal Avrami exponent n. The values of n found to be 3.080.3, 2.23  0.4, 1.43 0.2, 0.95 0.2 and , 0.36 0.19 for the temperatures 375, 390, 405, 420 and 435 °C respectively. The decrease of n may be owed to the decrease in the nucleation rate due to saturation [59,60]. The average value of n is 1.610.…”

Isothermal and Isoconversional Modeling of Solid-State Nitroso Polymerization

“…The vast majority of kinetic studies in chemistry is based on experiments done at constant temperature . Consequently, isothermal models have been developed for the description of kinetic data, finding their use in different fields, such as physical-organic chemistry, protein agglomeration, material chemistry, and more. , However, isoconversional methods, based on constant heating rates, were used for the analysis of complex kinetic processes in bulk materials, such as thermal degradation, agglomeration, crystallization, glass transition, melting, and others. , Typically, these processes are difficult to adequately describe by mechanistic models. To compare different isothermal and isoconversional methods in solid-state systems, a simple model reaction is needed.…”

General Approach to the Nucleation and Crystal Growth in Sb0.5Se99.5 Glass Explaining the Shape of DSC Curves

“…The analysis of overlapping DSC or DTA peaks, without deconvolution, can be done partially when only the value of activation energy is determined from nonisothermal measurements [23][24][25] but the information about crystal growth morphology and mechanism is missing. However, some papers include deconvolution procedure followed by full kinetic analysis [26][27][28] . Nevertheless, deconvolution of data obtained under isothermal conditions 5,29 can be performed using selected kinetic model, which can significantly influence the interpretation of mechanism of crystallization.…”

“…Several kinetic models and their parameters are related with the concept of the crystal growth mechanism. , In the case of overlapping peaks, the full kinetic analysis can be performed after the deconvolution process, which can be done by numerical fitting using a general equation describing various shapes of DSC peaks such as Fraser–Suzuki function (only for non-isothermal conditions) − or deconvolution based on selected function. − The analysis of overlapping DSC or DTA peaks, without deconvolution, can be done partially when only the value of activation energy is determined from non-isothermal measurements, − but the information about the crystal growth morphology and mechanism is missing. However, some papers include the deconvolution procedure followed by full kinetic analysis. − Nevertheless, deconvolution of data obtained under isothermal conditions , can be performed using the selected kinetic model, which can significantly influence the interpretation of mechanism of crystallization. As mentioned above, the JMA model and its parameter provide the information about the mechanism of crystallization.…”