Balbir Singh Patial

A non-isothermal crystallization study of Se85Te15 chalcogenide glass using differential scanning calorimetry

The calorimetric parameters of Se85Te15 glass have been investigated using differential scanning calorimetry under non-isothermal conditions at four different heating rates (5, 10, 15 and 20 °C min−1). The glass transition temperature and peak temperature of crystallization are found to increase with increasing heating rate. The apparent activation energy for glass transition and for the crystallization peak has been determined using different empirical approaches. The kinetic parameters are calculated using methods recently developed for non-isothermal conditions. The calculated value of the kinetic exponent indicates one-dimensional growth for Se85Te15 chalcogenide glass. The average values of activation energy for glass transition and crystallization are found to be equal to (267.82±3.9) and (152.13±16.9)  kJ mol−1, respectively. The ease of glass formation and fragility has also been studied.

Impact of Pb content on the physical parameters of Se-Te-Pb system

In the present study, we have investigated the impact of Pb content on the physical parameters in Se-Te-Pb system via average coordination number, constraints, the fraction of floppy modes, cross-linking density, lone pairs electrons, heat of atomization, mean bond energy, cohesive energy and electronegativity. The bulk samples have been prepared by using melt quenching technique. X-ray diffraction pattern of various samples indicates the amorphous nature of investigated glassy alloys. It is observed that average coordination number, average number of constraints and cross-linking density increase with Pb content. However, lone-pair electrons, floppy modes, average heat of atomization, cohesive energy and mean bond energy are found to decrease with Pb atomic percentage.

Effect of Pb doping on temperature dependent electrical parameters of a-Se80Te20 alloy

In the present study, the dc conductivity of Se80-xTe20Pbx (x = 0, 1 and 2) glassy alloys has been measured from room temperature (298K) to 318K and in the voltage range 0-180V. I-V characteristics indicate that an ohmic behavior is observed at low electric field. However, at high electric field, non-ohmic behavior is observed. The activation energy (ΔE) and pre-exponential factor (σo) has been derived from temperature dependence of the dc conductivity, which indicates that conduction may be due to thermally assisted tunneling of charge carriers in the localized states present in the band tails.In the present study, the dc conductivity of Se80-xTe20Pbx (x = 0, 1 and 2) glassy alloys has been measured from room temperature (298K) to 318K and in the voltage range 0-180V. I-V characteristics indicate that an ohmic behavior is observed at low electric field. However, at high electric field, non-ohmic behavior is observed. The activation energy (ΔE) and pre-exponential factor (σo) has been derived from temperature dependence of the dc conductivity, which indicates that conduction may be due to thermally assisted tunneling of charge carriers in the localized states present in the band tails.

Kinetics of amorphous-crystallization transformation of Se85−xTe15Snx (x = 2, 4 and 6) alloys under non-isothermal conditions using Matusita's approach

The present study reports the assessment of activation energy for crystallization and crystallization reaction order (Avrami exponent n) for the crystallization process of Se85−xTe15Snx (x = 2, 4 and 6) amorphous alloys by means of differential scanning calorimetry (DSC) technique under non-isothermal conditions at four different heating rates (5, 10, 15 and 20°Cmin−1) using Matusitas approach. It is remarkable to note that double crystallization behaviour has been observed for Sn additive Se-Te investigated samples. In the present paper, the kinetic analysis of amorphous-crystallization transformation for the first peak has been reported and discussed.

Effect of Sb content on the physical properties of Ge-Se-Te chalcogenide glasses

In the present study, the bulk as-(Se80Te20)94-xGe6Sbx (x = 0, 1, 2, 4, 6, 8) glasses were synthesized using melt quenching technique. The physical properties viz coordination number, lone pair of electrons, number of constraints, glass transition temperature, mean bond energy, cohesive energy, electro-negativity and average heat of atomization of the investigated composition are reported and discussed. It is inferred that on increasing Sb content; average coordination number, average number of constraints, mean bond energy, cohesive energy and glass transition temperature increases but lone pair of electrons, average heat of atomization and deviation of stoichiometry decreases.In the present study, the bulk as-(Se80Te20)94-xGe6Sbx (x = 0, 1, 2, 4, 6, 8) glasses were synthesized using melt quenching technique. The physical properties viz coordination number, lone pair of electrons, number of constraints, glass transition temperature, mean bond energy, cohesive energy, electro-negativity and average heat of atomization of the investigated composition are reported and discussed. It is inferred that on increasing Sb content; average coordination number, average number of constraints, mean bond energy, cohesive energy and glass transition temperature increases but lone pair of electrons, average heat of atomization and deviation of stoichiometry decreases.

Dielectric measurements of Ge10Se90 glass

In the present study, investigation of dielectric parameters viz. dielectric constant(e′), dielectric loss(e″) measurements have been made for the Ge10Se90 chalcogenide glass in the frequency range 10 to 500 kHz within the temperature range from 300 to 390 K. The variation of dielectric constant and dielectric loss with frequency at room temperature is reported and discussed in the investigated chalcogenide binary alloy.

Effect of heating rate on the glass transition temperature in Se79Te15In6-xPbx bulk alloys using power-law behaviour

In the present study, the effect of heating rate on the glass transition temperature (Tg) in quaternary Se79Te15In6-xPbx (x = 0.5, 1, 2 and 4) chalcogenide bulk alloys using differential scanning calorimetry (DSC) experiment under non-isothermal conditions has been reported and discussed. The heating rate dependence of Tg has been investigated theoretically using power-law behaviour. An excellent agreement of Tg has been observed between experimental values obtained from DSC scans and theoretical values using power-law behaviour.

Heating rate dependence of the glass transition temperature in Se85–xTe15Inx amorphous alloys

In the present paper, heating rate dependence of glass transition temperature (Tg) of Se85-xTe15Inx (x = 0, 2, 6, 10 and 15) chalcogenide alloys under non-isothermal conditions using differential scanning calorimetry (DSC) technique has been reported and discussed. The glass transition temperature is found to increase with the increase in heating rate. The heating rate dependence of Tg has been investigated theoretically using power law behaviour. An excellent agreement of Tg has been observed between experimental values obtained from DSC scans and theoretical values using power law behaviour.

Estimation of the Activation Energy for the Non‐isothermal Crystallization in Amorphous Se70Te15In15 Alloy Using Iso‐conversional Methods

Differential scanning calorimetry (DSC) has been used to study the kinetics of amorphous to crystalline transformation in Se70Te15In15 glass under non‐isothermal conditions at four different heating rates of 5, 10, 15 and 20 °C/min. The activation energy of crystallization has been determined by analyzing the data using the iso‐conversional methods of Kissinger‐Akahira‐Sunose (KAS), Ozawa‐Flynn‐Wall (OFW) and Friedman. The present work shows that the activation energy of crystallization is not constant but varies with degree of conversion and hence with temperature.

Iso‐conversional Analysis of Amorphous‐Crystalline Transformation of Se75Te15Sn10 Glassy Alloy

Differential scanning calorimetry (DSC) has been performed under non‐isothermal conditions at four different heating rates (5, 10, 15 and 20 °C min−1) to study the activation energy for crystallization of Se75Te15Sn10 glassy alloy. The activation energy of crystallization has been determined by analyzing the data using three iso‐conversional methods of Kissinger‐Akahira‐Sunose (KAS), Ozawa‐Flynn‐Wall (OFW) and Friedman for different degrees of conversion (χ). The variation of activation energy for crystallization with degree of conversion (χ) and hence with temperature has been reported and discussed. The temperature dependence of activation energy is explained in the light of the nucleation theory of Turnbull and Fisher.