Thermal stability and crystallization kinetics of ternary Se–Te–Sb semiconducting glassy alloys

This paper presents the results of kinematical studies of glass transition and crystallization in glassy Se_85?x Te₁₅Sb _x (x = 2, 4, 6 and 8) using differential scanning calorimetry (DSC). From the dependence on heating rates of, the glass transition temperatures (T _g), and temperature of crystallization (T _p) the activation energy for glass transition (E _g) and the activation energy for crystallization (E _c) are calculated and their composition dependence can be discussed in term of the average coordination number and cohesive energy. The thermal stability of Se_85?x Te₁₅Sb _x was evaluated in terms of criterion ΔT = T _c ? T _g and kinetic criteria K(T _g) and K(T _p). By analyzing the crystallization results, the crystallization mechanism is characterized. Two (two- and three-dimensional growth) mechanisms are working simultaneously during the amorphous–crystalline transformation of the Se₈₃Te₁₅Sb₃ alloy while only one (three-dimensional growth) mechanism is responsible for the crystallization process of the chalcogenides Se_85?x Te₁₅Sb _x (x = 4, 6 and 8) glass. The phases at which the alloy crystallizes after the thermal process have been identified by X-ray diffraction.     

Effect of antimony on glass transition and thermal stability of Se<Subscript>78−x</Subscript>Te<Subscript>18</Subscript>Sn<Subscript>2</Subscript>Sb<Subscript>x</Subscript> (<Emphasis Type="Italic">x</Emphasis> = 0, 2, 4 and 6 at.%) multicomponent glassy alloys

Multicomponent glassy alloys Se_78?xTe₁₈Sn₂Sb_x (x?=?0, 2, 4 and 6) have been synthesized using melt quench technique. The prepared samples have been characterized by X-ray diffraction technique and differential scanning calorimetry (DSC). Glass transition kinetics of Se_78?xTe₁₈Sn₂Sb_x (x?=?0, 2, 4 and 6 at.%) glassy alloys has been examined using DSC. DSC runs have been recorded at different heating rates (5, 10, 15 and 20 K min^?1) for each sample under investigation. Heating rate dependence of glass transition temperature (T_g) has been studied using Lasocka empirical relation. The activation energy of glass transition has been evaluated using Kissinger and Moynihan’s relation. The effect of antimony concentration on glass transition temperature and activation energy has been investigated in the prepared samples. Glass-forming ability and thermal stability of Se_78?xTe₁₈Sn₂Sb_x (x?=?0, 2, 4 and 6) glassy alloys have been monitored through the evaluation of thermal stability using Dietzal relation, Hurby parameter, and Saad and Poulin parameter. The above-mentioned parameters are found to be compositionally dependent, which indicates that among the studied glass samples the stability is maximum for Sb at 2% content.     

Kinetics of phase transition and thermal stability in Se80?x Te20Zn x (x?=?2, 4, 6, 8, and 10) glasses

Se_80?x Te₂₀Zn _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 Se₇₀Te₂₀Zn₁₀ 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.     

Comparative analysis of calorimetric studies in Se<Subscript>90</Subscript>M<Subscript>10</Subscript> (<Emphasis Type="Italic">M</Emphasis>=In,Te, Sb) chalcogenide glasses

Calorimetric measurements have been performed in glassy Se₉₀M₁₀ (M=In, Te, Sb) alloys to study the effect of In, Te and Sb additives on the kinetics of glass transition and crystallization in glassy Se₉₀M₁₀ system. Kinetic parameters of glass transition and crystallization such as the activation energy of glass transition (E _g), the activation energy of crystallization (M _c), the order parameter (n), the rate constant (K), etc. have been determined using different non-isothermal methods. The composition dependence of the activation energies of glass transition and crystallization processes is also discussed.     

Iso-conversional kinetic study of non-isothermal crystallization in glassy Se98Ag2 alloy

The crystallization kinetics of glassy Se₉₈Ag₂ alloy is studied at different heating rates (5, 10, 15, and 20?K?min^?1) using differential scanning calorimetric technique. Endothermic and exothermic peaks are obtained at glass transition (T _g) and crystallization temperature (T _c). Four iso-conversional methods (Kissinger?CAkahira?CSunose (KAS), Flynn?CWall?COzawa (FWO), Tang and Straink) were used to determine the various kinetic parameters (crystallization temperature T _?? , activation energy of crystallization E _??, order parameter n) in non-isothermal mode.     

Thermoanalysis of quasi-ternary As2(S,Se, Te)3 semiconductor glasses

In comparison with other chalcogenide glassy systems, less attention has been paid to the quasi-ternary (quaternary) system As₂(S, Se, Te)₃. In this paper, thermal methods were used to characterize ten different quaternary homogenous semiconductor glasses that were prepared by mixing the stoichiometric binary systems As₂S₃, As₂Se₃ and As₂Te₃. The ratios of the constituent binaries in the quasi-ternary glasses exerted a great influence on their thermal spectrum. The samples poor in As₂Te₃ showed neither the exothermic nor the endothermic peak due to crystallízation (T _c) and melting (T _m), respectively, but only the glass transition (T _g). Three transition temperatures,T _g, T_c andT _m, were detected for other compositions. On the other hand, a phase separation was observed in the samples rich in As₂Te₃. A cyclic scanning technique was used to investigate the thermally-induced phases during two consecutive heat ing-cooling cycles covering the temperature rangeT _g?T_m. The energy of decompositionE _d decreased on increase of the ratio As₂S₃/As₂Se₃ (at constant As₂Te₃), whereas it increased on increase of the ratio As₂Te₃/As₂Se₃ (at constant As₂Se₃ or As₂S₃).     

Calorimetric study of Sb-modified Ge–Se–Te glassy alloys

The glassy compositions of Ge ₁₆ Se ₅₂ Te _32?x Sb _x system, obtained using rapid melt quenching technique, have been characterized by calorimetric study at different heating rates in this study. A systematic investigation of the crystallization kinetics is carried out for these compositions. Composition corresponding to atomic % 8 of Sb has good thermal stability. The material exhibits the unique thermal properties, which makes it suitable to use for electrical or memory switching devices. Various thermal parameters, activation energies of glass transition and crystallization are calculated using relevant approaches.     

Effect of in impurity on crystallization kinetics of (Se.7Te.3)100−xInx system

The effect of In impurity on the crystallization kinetics and the changes taking place in the structure of (Se₇Te₃) have been studied by DTA measurements at different heating rates (α=5 deg·min^?1, 10 deg·min^?1, 15 deg·min^?1 and 20 deg·min^?1). From the heating rate dependence of the values ofT _g,T _c andT _p, the glass transition activation energy (E _t) and the crystallization activation energy (E _c) have been obtained for different compositions of (Se₇Te₃)_100?xIn_x (0≤×≤20). The variation of viscosity as a function of temperature has been evaluated using Vogel-Tamman-Fulcher equation. The crystallization data are analysed using Kissinger's and Matusita's approach for nonisothermic crystallization. It has been found that for samples containing In=0, 10, 15, 20 at%, three dimensional nucleation is predominant whereas for samples containing In=5 at%, two dimensional nucleation is the dominant mechanism. The compositional dependence ofT _g and crystallization kinetics are discussed in terms of the modification of the structure of the Se?Te system.     

Glass transition and crystallization study of chalcogenide Se<Subscript>70</Subscript>Te<Subscript>15</Subscript>In<Subscript>15</Subscript> glass

Differential scanning calorimetry data at different heating rates (5, 10, 15 and 20 °C min⁻¹) of Se₇₀Te₁₅In₁₅ chalcogenide glass is reported and discussed. The crystallization mechanism is explained in terms of recent analyses developed for use under non-isothermal conditions. The value of Avrami exponent (n) indicates that the glassy Se₇₀Te₁₅In₁₅ alloy has three-dimensional growth. The average values of the activation energy for glass transition, E _g, and crystallization process, E _c, are (154.16 ± 4.1) kJ mol⁻¹ and (98.81 ± 18.1) kJ mol⁻¹, respectively. The ease of glass formation has also been studied. The reduced glass transition temperature (T _rg), Hruby’ parameter (K _gl) and fragility index (F _i) indicate that the prepared glass is obtained from a strong glass forming liquid.     

Crystallization study of Sn additive Se–Te chalcogenide alloys

Calorimetric study of Se_85−x Te₁₅Sn _x (x = 0, 2, 4 and 6) glassy alloys have been performed using Differential Scanning Calorimetry (DSC) under non-isothermal conditions at four different heating rates (5, 10, 15 and 20 °C/min). The glass transition temperature and peak crystallization temperature are found to increase with increasing heating rate. It is remarkable to note that a second glass transition region is associated with second crystallization peak for Sn additive Se–Te investigated samples. Three approaches have been employed to study the glass transition region. The kinetic analysis for the first crystallization peak has been taken by three different methods. The glass transition activation energy, the activation energy of crystallization, and Avrami exponent (n) are found to be composition dependent. The crystallization ability is found to increase with increasing Sn content. From the experimental data, the temperature difference (T _p − T _g) is found to be maximum for Se₈₃Te₁₅Sn₂ alloy, which indicates that this alloy is thermally more stable in the composition range under investigation.     

Effect of Bi incorporation on the glass transition kinetics of Se<Subscript>85</Subscript>Te<Subscript>15</Subscript> glassy alloy

Bulk samples of Se_85-xTe₁₅Bi_x glassy alloys are obtained by melt quenching technique. Differential scanning calorimetry has been applied to determine the thermal properties of Se-rich Se_85-xTe₁₅Bix glassy alloys at different heating rates. The glass transition temperature (T _g) is found to shift to a higher temperature with increasing heating rate and with Bi addition. Activation energy and fragility of the system is also calculated. Specific heat is evaluated and a jump in heat capacity is observed at T _g. Theoretical parameters viz; density, molar volume, number of atoms per unit volume, lone pair electrons and cohesive energy of the system are also reported.     

Non-isothermal crystallisation kinetics study on Se90−xIn10Sbx (x = 0, 1, 2, 4, 5) chalcogenide glasses

The non-isothermal crystallisation kinetics of Se_90?xIn₁₀Sb_x (x = 0, 1, 2, 4, 5) chalcogenide glasses prepared by a conventional melt quenching technique was studied using the differential scanning calorimetry (DSC) measurement at different heating rates 5, 7, 10 and 12 °C min^?1. The values of the glass transition temperature T _g and the crystallisation temperature T _c are found to be composition and heating rate dependent. The activation energy of glass transition E _g, Avrami index n, dimensionality of growth m and activation energy of crystallisation E _c have been determined from different models.     

Glass-forming ability and thermal stability of Se<Subscript>100−x</Subscript>(Ge<Subscript>2</Subscript>Sb<Subscript>2</Subscript>Te<Subscript>5</Subscript>)<Subscript>x</Subscript> glassy alloys

Glassy Se_100?x(Ge₂Sb₂Te₅)_x (x?=?5, 10, 15 and 20) bulk alloys were prepared by melt-quenched technique and studied by using differential scanning calorimetry at different heating rates under non-isothermal condition. The detailed thermal analysis shows that the glass transition temperature (T_g) depends on heating rates and x content. In particular, it is found that the glass-forming ability, thermal stability (T_c???T_g) and crystallization activation energy (E_c) increase with increased x content in amorphous Se, whereas glass transition activation energy (E_g) and fragility index (F) decrease with increased x contents. Variation in these parameters can be explained on the basis of network-forming ability of Se and bonding arrangement among the constituent atoms of alloys.     

Crystallization kinetics of Ag-doped Se–Bi–Te chalcogenide glasses

Effect of Ag doping on the crystallization kinetics of amorphous Se_80.5Bi_1.5Te_18?yAg_y (for y = 0, 1.0, 1.5, and 2.0 at.%) glassy alloys has been studied by differential scanning calorimetry (DSC). The DSC curves recorded at four different heating rates are analyzed to determine the transition temperature, activation energy, thermal stability, glass forming ability, and dimensionality of growth during phase transformation. Present study shows that the thermal stability and the glass-forming ability increase with an increase in the Ag content which is in agreement with the earlier studies. Our results show that Se_80.5Bi_1.5Te₁₆Ag₂ composition is thermally more stable and has a little tendency to crystallize in comparison to other compositions under study. The increase in thermal stability with increasing Ag concentration is attributed to an increase in the cohesive energy.     

Thermal properties and kinetics of new-generation posterior bulk fill composite cured light-emitting diodes

In this study, the thermal behavior in terms of glass transition (T _g), degradation, and thermal stability of four commercial new-generation posterior bulk fill composites (Surefill SDR, Dentsply; Quixfill, Dentsply; Xtrabase, Voco; and Xtrafill, Voco) activated by light-emitting diodes (LEDs) was analyzed by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The activation energies (E _a) for the decomposition of the dental resins were calculated based on the Kissinger and Doyle kinetic models from the peaks of the endothermic curves obtained when the specimens were heated at four different temperatures (5, 10, 15, and 20 °C min^?1) during DSC. The results show that the Xtrabase composite displayed the highest T _g (120 °C at a 5 °C min^?1 heating rate) and E _a (157.64 kJ mol^?1) values associated with thermal degradation from the main chain of the polymer.     

Glass Stability and Glass Forming Ability of Ge25−xSe75Sbx (x = 12, 15, and 18) Chalcogenide Glasses Using Thermal Parameters

In the present communication glass stability (GS) and glass forming ability (GFA) of Ge_25−xSe₇₅Sb_x (x = 12, 15, and 18) chalcogenide glasses have been calculated in terms of certain thermal parameters, i.e., reduced glass transition temperature (T_rg), Hruby number (H), S-parameter (S), and ΔT. The glassy samples have been prepared by quenching of melt technique. For structure characterization, XRD technique has been used. For thermal analysis Differential Scanning Calorimetery (DSC) has been used. DSC scans have been recorded at different heating rates, i.e., 5, 10, 15, and 20 K min⁻¹. Stability of glassy samples has also been confirmed in terms of activation energy of glass transition calculated by Kissinger relation. All these parameters indicate that GS and GFA both decrease with increase of Sb content in Ge_25−xSe₇₅Sb_x (x = 12, 15, and 18) glassy series.     

Glass transition and crystallization kinetics analysis of Sb–Se–Ge chalcogenide glasses

Differential thermal analysis (DTA) has been employed to investigate the effect of Ge addition on the glass transition behavior and crystallization kinetics of Sb₁₀Se_90?xGe_x (x = 0, 19, 21, 23, 25, 27) alloys. The three characteristic temperatures viz. glass transition (T _g), crystallization (T _c), and melting (T _m) have been determined and found to vary with the heating rates and Ge content. Thermal stability and glass forming tendency have been evaluated in terms of ΔT (= T _c ? T _g) and reduced glass transition temperature. The activation energies for glass transition and crystallization have been used to analyze the nucleation and growth process. The activation energy analysis also determines the suitability of alloys to be used in switching applications. Results have been interpreted in terms of bond energies and structural transformations in the investigated alloys.     

Calorimetric study on Ge<Subscript>23</Subscript>Se<Subscript>67</Subscript>Sb<Subscript>10</Subscript>–0.5CsCl glass

The mechanical behavior of Ge₂₃Se₆₇Sb₁₀ glass can be improved by adding CsCl facilitating the nano-crystaline formation. Understanding the crystallization mechanism of chalcogenide glass can help in directing the subsequent annealing processing and tuning the microstructure and physical properties. In this work, 99.5Ge₂₃Se₆₇Sb₁₀–0.5CsCl glass was prepared and its transformation kinetics was investigated under non-isothermal conditions with heating rate up to 400 K min^?1. Using Vogel–Fulcher–Tammann equation, the ideal glass transition temperature was determined as T _0g = 434.1 K. Using the classical JMA theory, the average activation energy and average growth exponent were determined as 135.0 and 2.4 kJ mol^?1, while using the model considering impingements (MCI), the two parameters were determined as 120.9 and 3.2 kJ mol^?1, respectively. Compared to JMA theory, the MCI model can fit the transition curves better, and it shows that the growth mode of the present glass is between two-dimension and three-dimension. By comparing with the result of Ge₂₃Se₆₇Sb₁₀ glass, it is found that addition of CsCl can reduce the growth dimension and activation energy during crystallization.     

Differential scanning calorimetry study of Ge1−xSnxSe2.5 glasses

The glass-forming tendency and specific heat in ice cold water-quenched Ge_1?xSn_xSe_2.5 glassy alloys with 0H _f, the heat ΔH _c associated with the crystallization of an amorphous phase and the glass transition temperatureT _g were deduced from the DSC curves. The composition dependence of glass forming ability,T _g and crystallization behavior has been discussed.     

Determination de la capacite calorifique de quelques verres oxyazotes

Six oxygenated and oxynitrided glasses in the Ca-Si-Al-O-N system were prepared from pure lime, silica, alumina and aluminium nitride. Their enthalpies were measured by drop enthalpimetry with a Calvet calorimeter in a 100–1000° temperature range including glass transitionsT _g. Their heat capacityC _p in glassy and liquid states were deduced by derivation. TheC _p variations atT _g were calculated. The glass transition temperature were checked by differential calorimetric analysis.