Crystallization kinetics study of Pb4.3Se95.7 chalcogenide glass using DSC technique

Differential scanning calorimetry (DSC) technique was used to study the kinetics of amorphous to crystalline transformation in Pb_4.3Se_95.7 chalcogenide glass. Non-isothermal measurements were performed at different heating rates (5-60 K/min). The activation energy of crystallization was determined by analyzing the data using Matusita et al. method. A strong heating rate dependence of the activation energy was observed. The isoconversional methods of Kissinger-Akahira-Sunose (KAS) and Vyazovkin 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 in Pb_4.3Se_95.7 is a complex process involving different mechanisms of nucleation and growth.     

On the variation of activation energy for amorphous–crystallization phase transition in Se–Te–Sn chalcogenide glasses using iso-conversional analysis

In this paper, the variation of activation energy of amorphous–crystallization phase transition of as-Se_85–xTe₁₅Sn_x (x = 2, 4 and 6) chalcogenide glasses is investigated using iso-conversional analysis under non-isothermal conditions using differential scanning calorimetric (DSC) technique. The study is based on the variation of activation energy of crystallization with the degree of conversion and hence with temperature. The three iso-conversional methods of Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW) and Friedman are used to deduce the variation of activation energy with the extent of conversion and also with temperature. The KAS and OFW methods give the similar values while the Friedman method gives lower values of activation energy of crystallization for the investigated chalcogenide glasses.     

Model fitted and model free approaches for crystallization kinetics in Se85Te15-xBix glasses

In this research work, we have described the model-fitted and model free approaches for the study of crystallization kinetics in Se₈₅Te_15-xBi_x chalcogenide glasses. Se₈₅Te_15-xBi_x bulk alloys were synthesized by melt quenching technique. High Resolution X- Ray diffraction (HRXRD) was used to confirm the amorphous nature of prepared alloys. Non-isothermal Differential Scanning Calorimetry (DSC) measurements were done at heating rates of 5, 10, 15, 20 and 25 K/min for crystallization kinetics studies in Se₈₅Te_15-xBi_x glasses. The various characteristic temperatures, such as glass transition (T_g), on-set crystallization (T_c) temperature, peak crystallization temperature (T_p) and melting temperatures (T_m) have been obtained from various DSC thermograms. The activation energies of glass transition (ΔE_t) were calculated by using Kissinger and Moynihan approaches and found to be minimum for Se₈₅Te₁₂Bi₃ chalcogenide glass which indicates that this alloy has maximum probability to jump into a less configurational energy state and has larger stability. The model-free approaches; Kissinger–Akahira–Sunose (KAS), Flynn-Wall-Ozawa (FWO), Tang and Straink (TS) reveal that the activation energy of crystallization varies with crystallization degree and temperature both. This variation shows that amorphous to crystalline phase transformation in Se₈₅Te_15-xBi_x chalcogenide glasses is a complex process with various nucleation and growth mechanisms.     

Amorphous to crystalline phase transition in glassy Se65Te20Ag15 alloy

In the present work, the amorphous to crystalline phase transition of chalcogenide glass Se₆₅Te₂₀Ag₁₅ has been studied using differential scanning calorimetric (DSC) measurements. The heating rate dependence of crystallization peaks has been used for the determination of activation energies of glass transition (E _g) and crystallization (E _c). Different non-isothermal methods have been used for this purpose. Other useful kinetic parameters such as the order parameter (n), the numerical factor of crystallization mechanism (m) and the frequency factor (K _o) of the rate constant (K) have been also determined.     

Thermal features and physical properties of sulfur modified barium vanadate glasses

Differential scanning calorimetry (DSC) and XRD were used to investigate the role of sulfur in the network of V₂O₅–Fe₂O₃–BaO glasses. The crystallization kinetics of the glasses were investigated under non-isothermal conditions applying the formal theory of transformations for heterogeneous nucleation to the experimental data obtained by DSC. The activation energy for the glass transition (E _g) was derived from dependence of the glass-transition temperature (T _g) on the heating rate. Similarly the activation energy of the crystallization (E _c) and the frequency factor (K ₀) were determined. The results reveal the increase of the activation energy for glass transition was attributed to the increase in the rigidity and the cross-link density of these composites. The evaluated thermal stability decreases with increasing sulfur content. The phases of BaFe₂O₄, V₂O₅ and FeVO₄ micro-crystallites in the remaining amorphous matrix have been identified by X-ray diffraction.     

Crystallization kinetics and thermal stability in Se85-xTe15Sbx chalcogenide glasses

Crystallization process of Se_85-xTe₁₅Sb_x (x = 2.7, 7.5, 10 and 15 at %) chalcogenide glasses has been studied by using differential scanning calorimetry (DSC) with different heating rates. These glasses are found to have a double glasses transition and overlapped crystalline phases for Se₇₀Te₁₅Sb₁₅ glass while single glasses transition and single crystallization stage for other glasses. Glass transition temperature, T_g, onset crystallization temperature, T_c, and peak crystallization temperature, T_p, are found to be dependent on composition and heating rates. Values of various kinetic parameters such as activation energy of glass transition, E_g, activation energy of crystallization, E_c, Hurby number, H_r, thermal stability, S_p, rate constant, K_p, and Avrami exponent, n, are determined for the present systems. Results indicate that rate of crystallization is dependent on thermal stability and glass-forming ability. Crystallization mechanism occurs in two dimensions for studied compositions. Crystalline phases resulting from DSC and scanning electron microscopy have been identified by using X-ray diffraction.     

Crystallization kinetics of the TeO2–BaO glass system

Tellurite glasses of the system (100–x)TeO₂–xBaO, with x = 05, 10, 15 and 20 wt%, have been prepared and studied by differential scanning calorimetry (DSC). The crystallization kinetics of the glasses were investigated under non-isothermal conditions, applying the formal theory of transformations for heterogeneous nucleation to the experimental data obtained by DSC, using continuous-heating techniques. In addition, from the dependence of the glass-transition temperature (T _g) on heating rate, the activation energy for the glass transition was derived. Similarly, the activation energy of the crystallization process was determined and the crystallization mechanism characterized. The thermal stability of these glasses are considered in terms of the characteristic temperatures, T _g and T _in (the onset temperature of crystallization), via ΔT = T _in?T _g and a kinetic parameter K(T _g). The results confirm that thermal stability decreases with increasing BaO content. The phases into which the glass crystallizes have been identified by X-ray diffraction. Diffractograms of the transformed material indicate the presence of microcrystallites of α-TeO₂, γ-TeO₂ and BaTeO₃ in the remaining amorphous matrix.     

Kinetics of nonisothermal crystallization in Sn<Subscript>10</Subscript>Sb<Subscript>20−<Emphasis Type="Italic">x</Emphasis></Subscript>Bi<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Se<Subscript>70</Subscript> glassy semiconductors

The crystallization kinetics of Sn₁₀Sb_20−x Bi _x Se₇₀ (x=0,2,4,6,8) chalcogenide system has been studied. Crystallization studies using differential scanning calorimetry under nonisothermal conditions with different heating rates are reported. The glass transition temperature is found to increase with the increase in heating rate as well as with the addition of bismuth. The apparent activation energy for glass transition and that for crystallization have been determined using the Kissinger equation. Thermal stability and glass forming tendency have also been studied.     

Thermal characterization of Se78Ge22 and Se68Ge22M10 (M=Cd,In, Pb) chalcogenide glasses

The paper reports studies on the glass transition kinetics of Se₇₈Ge₂₂ and Se₆₈Ge₂₂M₁₀ (M?=?Cd, In, Pb) chalcogenide glasses. Differential scanning calorimetry (DSC) was performed at different heating rates under non-isothermal conditions. Different kinetic parameters, such as glass transition temperature (T _g) and the activation energy of the glass transition (E _t) have been calculated to investigate the effects of Cd, In and Pb additives on the glass transition kinetics of glassy Se₇₈Ge₂₂ alloy.     

Thermal and optical analysis of Te-substituted Sn–Sb–Se chalcogenide semiconductors

Bulk amorphous samples of Te-substituted Sn₁₀Sb₂₀Se_70−X Te _X (0≤X≤12) were prepared using a melt quenching technique. Calorimetric studies of the samples were performed using differential scanning calorimetry (DSC) and the glass transition temperature and crystallization temperature were evaluated from DSC scans. The glass transition temperature T _g exhibits a sharp decrease for small Te substitution of X=2, thereafter increases with increase in Te content up to X=10, and then decreases for further Te substitution. The apparent activation energy for glass transition and the activation energy for crystallization were calculated using Kissinger, modified Kissinger, and Matusita equations. The change in glass transition temperature T _g has been explained based on the bond formation energy of different heteropolar bonds. The optical band gap of thermally evaporated thin films of Sn₁₀Sb₂₀Se_70−X Te _X (0≤X≤12) was calculated from reflectance and transmittance data. The optical band gap variation with tellurium content exhibits a sharp decrease for an initial tellurium substitution of X=2 similar to that of the glass transition temperature and thereafter a peak is observed in optical band gap around X=4 composition.     

Glass transition,thermal stability and glass-forming ability of Se90In10− x Sb x (x = 0, 2, 4, 6, 8, 10) chalcogenide glasses

Differential scanning calorimetry (DSC) has been employed to investigate the glass transition activation energy E _g, thermal stability and glass-forming ability (GFA) of Se₉₀In_{10? x} Sb _x (x = 0, 2, 4, 6, 8, 10) chalcogenide glasses. DSC runs were performed at six different heating rates. Well-defined endothermic and exothermic peaks were obtained at glass transition and crystallization temperature. The dependence of glass transition temperature T _g on heating rate (α), as well as composition of Sb, has been studied. From the dependence of glass transition temperature on heating rate, the E _g has been calculated on the basis of the Kissinger [Anal. Chem. 29 (1957) p.1702] and Moynihan [J. Phys. Chem. 78 (1974) p.267] models. Thermal stability has been monitored through the calculation of temperature differences T _c–T _g, the stability parameter S, and the enthalpy released during crystallization H _c. The GFA has been investigated on the basis of the Hruby parameter H _r, which is strong indicator of GFA. Results for GFA are in good agreement with fragility index F _i calculations, indicating that Se₉₀In₆Sb₄ is an excellent glass-former.     

Creep strain recovery of Fe-Ni-B amorphous metallic ribbon

Creep strain recovery and structural relaxation of the amorphous metallic glass Fe₄₀Ni₄₁B₁₉ after longtime loading at different annealing temperatures below the glass transition temperature have been studied using anisothermal differential scanning calorimetry (DSC) and dilatometry (TMA). It has been demonstrated that structural relaxation effects depend on the stress-annealing temperature of the amorphous ribbon. The structural relaxation states of the amorphous ribbon annealed at different temperatures under and without applied stress have been compared. The activation energy spectra were calculated from the anisothermal dilatometric measurements using the modern method based on the Fourier transformation technique. The influence of the annealing temperature on the shape of creep strain recovery spectra has been analyzed.      

Studying the crystallization behavior of the Se85S10Sb5 chalcogenide semiconducting glass by DSC and X-ray diffraction

Crystallization kinetics of the Se₈₅S₁₀Sb₅ chalcogenide glassy alloy is studied by differential scanning calorimeter (DSC) non-isothermally. The glassy state of the as-prepared sample and the crystalline phases of the heat treated sample are characterized using X-ray diffraction. The glass transition activation energy E_g is found to be 65.2±0.8 kJ/mol and the crystallization activation energies for the first and the second crystallization peaks (E_c1 and E_c2) are found to be 70±0.8 and 85.2±0.8 kJ/mol, respectively. The determined kinetic parameters have made it possible to postulate the type of crystal growth exhibited in the crystallization process. The phases at which the alloy crystallizes after the thermal process have been identified by X-ray diffraction. The diffractogram of the transformed material indicates the presence of nanocrystallites of Sb₂Se₃, Se-S and Se, with a remaining additional amorphous matrix.     

Crystallization kinetics and Avrami index of Sb-doped Se–Te–Sn chalcogenide glasses

Bulk amorphous samples of Sb-substituted Se_78?xTe₂₀Sn₂Sb_x (0 < x < 6) have been prepared using melt quench technique. The structure of Se_78?xTe₂₀Sn₂Sb_x (x = 0, 2, 4, 6) glassy alloys has been investigated using X-ray diffraction technique. Calorimetric studies of the prepared samples have been performed under non-isothermal conditions using differential scanning calorimetry (DSC) and glass transition temperature as well as crystallization temperature has been evaluated using DSC scans. The activation energy of crystallization kinetics (E_c) has been determined using model-free approaches such as Kissinger, Ozawa, Tang and Starink methods. The Avrami index (n) and frequency factor (K_o) have been calculated by Matusita and Augis–Benett method.     

Thermal Behavior of Polypropylene-g-glycidyl Methacrylate Prepared by Melt Grafting

The thermal behaviors of glycidyl methacrylate (GMA)-grafted polypropylene (PP) (PP-g-GMA) with two different grafting degrees, namely, GPP1 and GPP2, were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA), and thermogravimetrical analysis (TGA). DSC results suggested that the GMA grafted PP exhibited higher crystallization temperature T_c, higher melting temperature T_m, and higher crystallinity compared with the neat PP. The isothermal crystallization kinetics was analyzed with the Avrami equation and the total crystallization activation energy was calculated. It was concluded that the crystallization processes of PP and the grafted PP were controlled by nucleation and the values of the crystallization activation energy of PP and the grafted PP were almost identical. POM results suggested that the GMA grafted PP exhibited smaller spherulites size compared with the neat PP. WAXD patterns indicated that the neat PP encouraged the formation of γ phase, compared with the grafted PP, during the crystallization process. DMA results showed that melt grafting did not induce a clear effect on the γ-transition and β-transition of the amorphous phase but resulted in a decrease in mobility of the PP chains in the crystals. TGA curves suggested that the melt grafting slightly improved the thermal stability of PP.     

Crystallization kinetics of Li2O-PbO-V2O5 glasses

Lead vanadate glasses of the system 5Li₂O−(45−x) PbO−(50+x) V₂O₅, with x=0, 5, 10, and 15 mol% have been prepared and studied by differential scanning calorimetry (DSC). The crystallization kinetics of the glasses were investigated under non-isothermal conditions applying the formal theory of transformations for heterogeneous nucleation to the experimental data obtained by DSC using continuous-heating techniques. In addition, from dependence of the glass-transition temperature (T_g) on the heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the crystallization process was determined and the crystallization mechanism was characterized. The results reveal the increase of the activation energy for glass transition which was attributed to the increase in the rigidity, the cross-link density and the packing density of these glasses. The phases into which the glass crystallizes have been identified by X-ray diffraction. Diffractograms of the transformed material indicate the presence of microcrystallites of Li_0.30V₂O₅, Li_0.67O₅V₂, LiV₆O₁₅, Li₄O₄Pb, and O₇Pb₂V₂ in a remaining amorphous matrix.     

Thermo-kinetic behaviour of Ge20Te75I5 glass for infrared optics

The iodine-doped GeTe₄ infrared chalcogenide glass was studied by means of differential scanning calorimetry DSC, X-ray diffraction XRD, Raman spectroscopy and infrared microscopy. Extensive non-isothermal thermo-kinetic characterisation of the glass transition, crystallisation and melting phenomena was performed in dependence on the particle size. The Tool–Narayanaswamy–Moynihan model was applied to describe the enthalpy relaxation processes: the compositional evolution of the relaxation parameters was then explained in terms of the structural changes and movements of the characteristic structural units. Mathematic deconvolution was applied to treat the complex crystallization kinetics – two crystal growth sub-processes were identified and described in terms of the autocatalytic ?esták-Berggren model. Based on the XRD and microscopic analyses the following crystallization mechanisms were revealed: initial precipitation of tellurium (surface-located) followed by a combined surface- and bulk-located formation of GeTe and GeI₄ phases. Based on the DSC results obtained for fine powders, the presence of mechanically induced defects was found to accelerate the Te precipitation, the consequences of which are discussed with regard to the performance of nowadays glass stability criteria.     

Study of crystallization kinetics of Se77.5Te15Sb7.5 glass using isoconversional models

The crystallization process of Se_77.5Te₁₅Sb_7.5 glass is studied by differential scanning calorimetry (DSC) technique under non-isothermal conditions at various heating rates. The crystallization parameters are deduced using different models. The validity of the Johnson–Mehl–Avrami (JMA) model to describe the crystallization process for the studied composition is investigated. Comparing experimental and calculated DSC curves indicate that the crystallization process of Se_77.5Te₁₅Sb_7.5 glass cannot satisfactorily be described by the JMA model. In general, simulation results indicate that the Sestak–Berggren model is more suitable to describe the crystallization kinetics. The crystalline phases are identified using the X-ray diffraction technique and scanning electron microscopy.     

Co-relation between pre-exponential factor and activation energy of non-isothermal crystallization for virgin and irradiated Fe78B13Si9 metallic glass

The present work shows the applicability of Meyer-Neldel relation between the pre-exponential factor and activation energy of non-isothermal crystallization of Fe₇₈B₁₃Si₉ metallic glass. Differential scanning calorimeter (DSC) technique is used to observe the variation in the above two kinetic parameters of the non-isothermal crystallization due to ionic irradiation at three different fluences with high-energy heavy ion Ni¹¹⁺ having energy 150 MeV.     

The effect of addition of gallium on the thermal stability and crystallization kinetic parameters of GaxSe100−x glass system

Differential scanning calorimetry (DSC) technique was used to study the kinetics of amorphous to crystalline transformation for Ga_xSe_100−x glass system (x=0, 2.5 and 5 at%). The kinetic parameters of Ga_xSe_100−x glass system under non-isothermal conditions are analyzed by the model-free and model-fitting models at different constant heating rates (5-50 K/min). A strong heating rate dependence of the effective activation energy of crystallization was observed. The analysis of the present data shows that the effective activation energy of crystallization is not constant but varies with the degree of crystallization and with temperature as well. The crystallization mechanisms examined using the local Avrami exponents indicate that one mechanism (volume nucleation with one-dimensional growth) is responsible for the crystallization process for heating rates 5-50 K/min for Se glass and two mechanisms (volume nucleation with two- and one-dimensional growth) are working simultaneously during the amorphous-crystalline transformation of the Ga_2.5Se_97.5 and Ga₅Se₉₅ glasses (5-50 K/min). The reaction model that may describe crystallization process of all the compositions of Ga_xSe_100−x glass system is Avrami-Erofeev model (g(α)=[−ln(1−α)]^1/n) with n=2 for Se glass. While for Ga_2.5Se_97.5 and Ga₅Se₉₅ glasses, the values of n are equal to 3 and 2 for the heating rates 5-20 and 35-50 K/min, respectively. A good agreement between the experimental and the reconstructed (α-T) curves has been achieved. The transformation from amorphous to crystalline phase in Ga_xSe_100−x glass system demonstrates complex multi-step involving several processes.