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Amorphous to crystalline phase transition in glassy Se65Te20Ag15 alloy
(2009) R.S. Tiwari; D. Kumar; N. Mehta
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 (Eg) and crystallization (Ec). 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 (Ko) of the rate constant (K) have been also determined.
Effect of Sb and Sn additives on the activation energies of glass transition and crystallization in binary Se85Te15 alloy
(2009) N. Mehta; K. Singh; S. Kumar
Calorimetric measurements have been performed in glassy Se75Te15M10 (M=Sb, Sn) alloys to study the effect of Sb and Sn additives on the kinetics of glass transition and crystallisation in glassy Se85Te15 alloy. Activation energy of glass transition (Eg) and the activation energy of crystallisation (Ec) have been determined using different non-isothermal methods. An excellent agreement is observed in the values of Ec and Eg for all the non-isothermal methods used in the present study. The composition dependence of the activation energies of glass transition and crystallisation processes shows that the value of Eg is higher in case of Sn additive while the value of Ec is higher in case of Sb additive. The results are explained in terms of Pauling's concept of average heat of atomisation and mean atomic weights of ternary alloys, respectively.
Effect of lithium-ion irradiation on the crystallization kinetics of glassy Se98In2
(2009) H. Kumar; N. Mehta; K. Singh; N.S. Saxena
Differential scanning calorimetry (DSC) has been used to study the crystallization kinetics of glassy Se98In2 both before and after irradiation of the alloy with high-energy (50 MeV) lithium ions. After the ion-irradiation, significant changes in the kinetic parameters of crystallization of the glass were observed. The results are explained in terms of a model involving irradiation-induced defects.
Further MN rule for thermally activated high field conduction in bulk samples of glassy Se100-xSbx alloys
(2009) N. Mehta; V.S. Kushwaha; A. Kumar
In the present paper, we report the observation of the Meyer-Neldel rule (MNR) in thermally activated high field conduction in bulk samples of glassy Se100-xSbx alloys. We have investigated Meyer-Neldel rule by two different approaches. In first approach, the temperature dependence of d.c. conductivity is studied at different electric fields without changing the composition of the glassy system. In the second approach, the composition itself varies at a particular electric field. We found that the conductivity obeys the Meyer-Neldel rule as the pre-exponential factor depends on activation energy. We also found a strong correlation between pre-factor σ00 and Meyer-Neldel energy in both cases. The observation of the correlation between pre-factor σ00 and Meyer-Neldel energy can be described by multiple excitations stimulated by phonon energy as described by Yelon and Movaghar. © 2009 Elsevier Ltd. All rights reserved.
On the glass transition phenomenon in Se-Te and Se-Ge based ternary chalcogenide glasses
(2009) N. Mehta; K. Singh; A. Kumar
The present paper reviews the results of non-isothermal differential scanning calorimetry (DSC) measurements on some ternary glassy systems of Se-Te and Se-Ge chalcogenide alloys for evaluation of activation of glass transition. The activation energy of glass transition (Eg) is calculated using Kissinger's relation, which is basically derived for amorphous to crystalline phase transition. The results show that Eg values obtained from Kissinger's relation are in good agreement with the Eg values which are obtained using Moynihan's relation based on the concept of thermal relaxation. This proves the applicability of Kissinger's relation for determination of activation energy of glass transition. © 2009 Elsevier B.V. All rights reserved.

2009

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