Evaluation of the activation energy of crystallization in Se79 1Te20Sb0 9 (original) (raw)
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Differential scanning calorimetry (DSC) technique was used to study the kinetics of amorphous to crystalline transformation in Se79.1Te20Sb0.9 chalcogenide glass. Non-isothermal measurements were performed at different heating rates (2–20 K/min). The activation energy of crystallization was determined by analyzing the data using the isoconversional methods of Friedman, Kissinger–Akahira–Sunose (KAS) and Vyazovkin. The present work shows that the activation energy of crystallization is not constant but varies with the degree of conversion and hence with temperature. The different values of the activation energy obtained from Friedman method as compared with KAS and Vyazovkin methods were attributed to possible errors involved in the Friedman method.
Indian Journal of Pure & Applied Physics, 2020
The ternary Se 79 Te 20 Pb 1 chalcogenide glass is prepared using melt quenching technique. Differential scanning calorimetry technique (DSC) is used to investigate the kinetics of crystallization of amorphous-crystallization (a-c) phase transformation under non-isothermal conditions at three different heating rates; 5, 10 and 15° C min -1 . The variation of crystallized activation energy ( E c ) with crystallized fraction ( ϰ ) and hence, with temperature ( T ) is investigated using five iso-conversional methods namely KAS, OFW, Friedman, Tang and Chen and Starink. It is found that E c is not constant but vary with ϰ as well as T . Thus, the iso-conversional analysis of investigated glass indicates that the assumption of constant E c is not appropriate
PHASE TRANSFORMATION AND CRYSTALLIZATION KINETICS OF Se90In8Sb2 CHALCOGENIDE GLASS
2008
The crystallization kinetics of Se 90 In 8 Sb 2 chalcogenide glass prepared by melt quenching technique, has been studied by Differential Scanning Calorimetry (DSC) under non-isothermal condition with six different heating rates i.e. 5,10,15,20,25,30 K/min. The DSC traces have been analyzed in terms of activation energy, stability and dimensionality of growth by four different models viz. Kissinger's, Augis-Bennett's, Matusita's and Gao-Wang's equations. The value of the Avarmi exponent comes out to be 2.85±0.25, which shows that crystallization process takes place via two-dimensional growth. Thermal stability has also been determined using various parameters. Besides these, the volume of fractioned crystallized and rate of crystallization as a function of temperature has also been studied. Further, an effort has been made to study the dependence of rate constant on temperature.
Physica B-condensed Matter, 2007
The kinetics of crystallization in a-Se 73.2 Te 21.1 Sb 5.7 were determined at different heating rates (2-99 K/min) using differential scanning calorimetric (DSC) technique. It is evident from this study that the effective activation energy associated with crystallization, E c in a-Se 73.2 Te 21.1 Sb 5.7 is not constant but heating rate dependent. Attempt is made to explain this variation in terms of recent theoretical models based on the concept of variable effective activation energy. Using isoconversional method, the temperature dependence of E c was determined. It is shown here that the apparent variation of E c with the heating rate is a result of this temperature dependence. It is also shown that the JMA-based models (Kissinger model etc.) which assume constant effective activation energy show clear deviation from linearity giving at least two values of effective activation energy. r
The activation energies of crystallization of Se 90 Te 10 glass were studied at different heating rates (4–50 K/min) under non-isothermal conditions using a differential scanning calorimetric (DSC) technique. The activation energy was determined by analyzing the data using the Matusita et al. method. A strong heating rate dependence of the activation energy was observed. The variation of the activation energy was analyzed by the application of the three isoconversional methods, of Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Vyazovkin. These methods confirm that the activation energy of crystallization is not constant but varies with the degree of crystallization and hence with temperature. This variation indicates that the transformation from amorphous to crystalline phase is a complex process involving different mechanisms of nucleation and growth. On the other hand, the validity of the Johnson–Mehl–Avrami (JMA) model to describe the crystallization process for the studied composition was discussed. Results obtained by directly fitting the experimental DSC to the calculated DSC curve indicate that the crystallization process of the Se 90 Te 10 glass cannot be satisfactorily described by the JMA model. In general, simulation results indicate that the Sestak–Berggren (SB) model is more suitable to describe the crystallization kinetics.
Kinetics study of non-isothermal crystallization in Se0.7Ge0.2Sb0.1 chalcogenide glass
Journal of Non-Crystalline Solids, 1991
Results of differential scanning calorimetry (DSC) at different heating rates on Se0.7Ge0.2Sb0.1 glass are reported and discussed. From the heating rate dependence of glass transition, crystallization onset and peak crystallization temperatures values for the glass transition activation energy, E t, and the crystallization activation energy, E~, were evaluated. The results are consistent with surface and one-dimensional crystallization for this glass. The calculated values of E t and E~ are 92_+6 and 134 + 6 kJ/mol, respectively.
Kinetics of crystallization in amorphous Se73 2Te21 1Sb5 7
The kinetics of crystallization in a-Se 73.2 Te 21.1 Sb 5.7 were determined at different heating rates (2-99 K/min) using differential scanning calorimetric (DSC) technique. It is evident from this study that the effective activation energy associated with crystallization, E c in a-Se 73.2 Te 21.1 Sb 5.7 is not constant but heating rate dependent. Attempt is made to explain this variation in terms of recent theoretical models based on the concept of variable effective activation energy. Using isoconversional method, the temperature dependence of E c was determined. It is shown here that the apparent variation of E c with the heating rate is a result of this temperature dependence. It is also shown that the JMA-based models (Kissinger model etc.) which assume constant effective activation energy show clear deviation from linearity giving at least two values of effective activation energy. r
Glass transition and crystallization kinetics of Sb 14.5 As 29.5 Se 53.5 Te 2.5 amorphous solid
physica status solidi (a), 2006
The results of differential scanning calorimetry (DSC) under non-isothermal conditions of the chalcogenide In x (Se 0.75 Te 0.25 ) 100−x (where 0 ≤ x ≤ 10 at.%) glasses are reported and discussed. The dependence of the characteristic temperatures "glass transition temperature (T g ), the crystallization onset temperature (T c ) and the crystallization peak temperature (T p ) on the heating rate (˛) utilized in the determination of the activation energy for the glass transition (E g ), the activation energy for crystallization (E c ) and the Avrami's exponent (n). The composition dependence of the T g , E g , and E c were discussed in terms of the chemical bond approach, the average heats of atomization (H s ) and the cohesive energy (CE). The diffractogram of the transformed material shows the presence of some crystallites of Se-Te and In-Se in the residual amorphous matrix.
2018
The effect of thermal history on cold crystallization and glass transition in glassy Se and Se90Te10 was studied using differential scanning calorimetry (DSC) technique. The amorphous Se and Se90Te10 materials were prepared using standard melt quench technique. The aged samples were stored in the dark for prolonged period of time (~ 5 years) at room temperature. All samples were thermally treated to remove thermal history using a rejuvenated procedure and then the same kinetic parameters were determined. A significant shift of the glass transition temperature along with the large endothermic signal was observed indicating of the important effect of thermal history on glass transition. No such effect was observed in the crystallization exothermic peaks. The activation energies for glass transition and crystallization thermal events in glassy Se and Se90Te10 were determined using Moynihan et al and Ozawa methods, respectively. It is found that the activation energy for glass transitio...
Non-isothermal crystallization kinetics of Sb10Ge10Se80 chalcogenide glass
Fizika A
A differential scanning calorimetry technique was used to study the crystallization kinetics of Sb10Ge10Se80 chalcogenide glass under non-isothermal conditions. The crystallization parameters such as the order parameter (n), the frequency factor (k0), the activation energy of crystallization (Ec), the activation energy of glass transition (Eg) and the activation energy of nucleation (En) were determined. The value of Ec was deduced by means of six methods and the average value was found to be equal to (76.10 ±11.10) kJmol-1. The most suitable method for crystallization kinetic studies was the Augis-Bennett approximated method at different heating rates, while the method of Coats-Redfern-Sestak was the most suitable one at constant heating rate. The results have been discussed on the basis of theoretical principles.