Crystal growth kinetics in Se 87.5 Te 10 Sn 2.5 glass (original) (raw)
Related papers
A STUDY OF Se–Te–Sn GLASSES BASED ON ADVANCED KINETICS MODELLING AND MODULATED DSC
Chalcogenide Letters
The modulated differential scanning calorimetry study of amorphous Se 90-x Te 10 Sn x (x = 0, 2.5, 5, 7.5, and 10) is reported. The glass samples were fabricated using a conventional melt-quenching method. The processing of the non-isothermal data was performed using the advanced thermokinetics software package. To determine the variation of the activation energy for crystallisation as a function of reaction progress the main three isoconversional methods, namely the differential method of Friedman and the integral methods of Ozawa-Flynn-Wall and Vyazovkin, were used. Based on an ASTM E698 analysis of the data, the effect of Sn content was determined. The Avrami exponent of Se 90-x Te 10 Sn x was determined and found to be dependent on the Sn content, indicating different dimensions of growth. The prediction of the isothermal reaction progress was employed to calculate the reaction model, g(α). A very large increase in the specific heat values of Se 90-x Te 10 Sn x was observed at t...
The present article deals with the differential scanning calorimetric (DSC) study of Se-Te glasses containing Sn. DSC runs are taken at four different heating rates (10, 15, 20 and 25 K min -1 ). The crystallization data are examined in terms of modified Kissinger, Matusita equations, Mahadevan method and Augis and Bennett approximation for the non-isothermal crystallization. The activation energy for crystallization (E c ) is evaluated from the data obtained at different heating rates. Activation energy of glass transition is calculated by Kissinger's relation and Moynihan theory. The glass forming tendency is also calculated for each composition. The glass transition temperature and peak crystallization temperature increases with the increase in Sn % as well as with the heating rate.
Ternary Se 90 Te 10 À x Sn x (x ¼2, 4, 6, and 8) chalcogenide glassy alloys have been prepared by melt quenching technique. Various crystallization parameters, such as onset (T c) and peak (T p) crystallization temperatures, activation energy of crystallization (E c) and Avrami exponent (n) have been determined for these alloys. T c and T p have been determined directly from the non-isothermal differential scanning calorimeter (DSC) thermograms. The value of E c has been calculated from the variation of both T c and T p with the heating rate (β) according to Kissinger, Takhor, Augis–Bennett and Ozawa models while Augis– Bennett method has been used to deduce the value of n for the studied samples. The obtained values of the crystallization parameters have been correlated with the character and the energy of the chemical bonds through the calculation of the heteronuclear bond energies of the constituent atoms using Pauling principle. In addition to that, Tichy–Ticha model was used to estimate the mean bond energy of the average cross-linking per atom 〈E cl 〉, the average bond energy per atom of the remaining matrix 〈E rm 〉, and the overall mean bond energy 〈E〉 of the studied glasses. Results reveal that both of T c and T p decreases with increases Sn content. This is may be attributed to the decreasing in the overall mean bond energy 〈E〉. Besides, the plot of E c (and also T g) against 〈E〉 was found to be non linear, which contradicts the well known linear correlation between E c and T g with 〈E〉 as suggested by Tichy–Ticha model. This discrepancy may be due to the fact that the Tichy–Ticha linear correlation model was based on the assumption of covalent glassy network, while in the present glassy alloys, Se–Te binary doped with heavy elements such as Sn exhibit iono-covalent bonding. The calculated values of the ionicity are in support of this argument.
Journal of Thermal Analysis and Calorimetry
Se 80-x Te 20 Zn x (x = 2, 4, 6, 8, and 10) glasses have been prepared using conventional melt quenching technique. The kinetics of phase transformations (glass transition and crystallization) have been studied using differential scanning calorimetry (DSC) under non-isothermal condition at five different heating rates in these glasses. The activation energy of glass transition (E t ), activation energy of crystallization (E c ), Avrami exponent (n), dimensionality of growth (m), and frequency factor (K o ) have been investigated for the better understanding of growth mechanism using different theoretical models. The activation energy is found to be highly dependent on Zn concentration. The rate of crystallization is found to be lowest for Se 70 Te 20 Zn 10 glassy alloy. The thermal stability of these glasses has been investigated using various stability parameters. The values of these parameters were obtained using characteristic temperatures, such as glass transition temperature T g , onset crystallization temperature T c , and peak crystallization temperature T p . In addition to this, enthalpy-released during crystallization has also been determined. The values of stability parameters show that the thermal stability increases with the increase in Zn concentration in the investigated glassy samples.
Crystallization study of Sn additive Se–Te chalcogenide alloys
Results of differential thermal analysis (DTA) under non-isothermal conditions of glasses Se 90 − x Te 10 Sn x (x = 0, 2.5, 5 and 7 at.%) are reported and discussed. The glass transition temperature (T g), the onset crys-tallization temperature (T c) and the peak temperature of crystallization (T p) were found to be dependent on the compositions and the heating rate. Values of various kinetic parameters such as activation energy of glass transition (E g), activation energy of crystallization (E c), rate constant (K p), Hurby number (H r) and the order parameter (n) were determined. For the present systems, the results indicate that the rate of crystallization is related to thermal stability and glass forming ability (GFA). According to the Avrami exponent (n), the results show a one dimensional growth for the composition Se 90 Te 10 and a three dimensional growth for the three other compositions. The crystalline phases resulting from DTA and (SEM) have been identified using X-ray diffraction.
Journal of Thermal Analysis and Calorimetry, 2012
Bulk samples of Se 92 Te 8-x Sn x glassy alloys are obtained by melt quenching technique. Differential scanning calorimetry (DSC) technique (under non-isothermal conditions) has been applied to determine the thermal properties of Se-rich glassy alloys at different heating rates. Results of glass transition temperature, enthalpy released, fragility and specific heat of Se 92 Te 8-x Sn x (x = 0, 1, 2, 3, 4 and 5) chalcogenide glasses have been reported and discussed. The glass transition temperature (T g ), activation energy of glass transition and fragility are found to increase with increase in Sn content. The glass transition temperature (by Gibbs-Dimarzio equation) also has been calculated. Both values of T g (experimental as well as theoretical) are found to be in good agreement at a heating rate of 10 K min -1 . It has been observed that the value of specific heat (C p ) below glass transition and difference in the value of C p before and after glass transition (DC p ) is highly compositional dependent. The enthalpy release is related to the metastability of the glasses, and the least stable glasses are supposed to have maximum DH c .
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.
Crystallization kinetics of bulk amorphous Se 80−x Sb x Te 20
Journal of Materials Science, 1991
Crystallization kinetics of the Se80−x Sbx Te20 (0⩽x⩽9) alloys have been studied using differential scanning calorimetry. The activation energies for the glass transition and that for crystallization have been determined from the heating rate dependence of the glass transition temperature and the peak crystallization temperature. The results have been analysed using the modified Kissinger's and Matusita's equations for the non-isothermal crystallization of materials. The variation of glass transition temperature with composition suggests that a small amount of Sb (⩽ 4 at %) leads to an increase in the chain length of Se-Te, whereas further increase in Sb atomic per cent increases the number of Se-Te chains in the alloys.
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...