D. K. Dwivedi

Experimental studies of dielectric relaxation and thermally activated a.c. conduction in Se90Cd10−xSbx (2 ≤ x ≤ 8) chalcogenide glassy alloys using correlated barrier hopping model

Se90Cd10−xSbx (xxa0=xa02, 4, 6, 8) chalcogenide semiconducting alloys were prepared by melt quench technique. The prepared glassy alloys have been characterized by technique such as SEM and energy dispersive X-ray. Dielectric properties and a.c. conductivity of prepared glassy alloys have been measured in the frequency range 5xa0×xa0102–1xa0×xa0105xa0Hz and in temperature range 303–328xa0K. The analysis of experimental results indicate that dielectric constant (ε′), dielectric loss factor (ε″) and a.c. conductivity σac(ω) are temperature, frequency and concentration dependent. The frequency dependence of σac(ω) is found to be linear and obey the power law ωs where sxa0≤xa01. A strong dependence of σac(ω) and exponent s on temperature can be explained on the basis of correlated barrier hopping model. The maximum barrier height Wm has been calculated and results are found to be in good agreement with theory of hopping of charge carrier over potential barrier as per the theory proposed by Elliot for chalcogenide semiconductors.

Investigations of crystallization kinetics of Se82-xTe18Sbx (x =0, 4, 8, 12) glassy alloys by iso-conversional approach

Abstract At different heating rates, the crystallization temperature (T c ) are obtained from the non-isothermal differential scanning calorimetry (DSC) measurements of bulk Se82–x Te18Sb x (x = 0, 4, 8 and 12) chalcogenide glasses prepared by melt quench technique. It was observed that the crystallization temperatures increase with increasing heating rates and also by increasing Sb concentration in Se–Te system. The activation energy of crystallization (E c ), the Avrami exponent (n) and rate of crystallization (K p ) have been determined from the different models. Glassy nature of as prepared samples has been confirmed using DSC techniques.

Glass transition kinetics and thermal stability of Se82-xTe18Sbx (x = 0, 4, 8 and 12 at %) glassy alloys

Glass transition kinetics of Se82−xTe18Sbx (xu2009=u20090, 4, 8 and 12 at.%) glassy alloys has been studied using differential scanning calorimetry (DSC). DSC runs were taken at different heating rates (5, 10, 15 and 20u2009K/min) for each samples. Heating rate dependence of glass transition temperature (Tg) has been studied using Lasocka empirical relation. Activation energy of glass transition (Eg) has been determined using Kissinger and Moynihan’s relation. Effect of Sb concentration on glass transition temperature and activation energy has been studied. Thermal stability of Se82u2009−u2009xTe18Sbx glassy alloys has also been investigated using Dietzal relation, Saad and Poulin relation, Hurby parameter (Hr) and Lie and Liu parameter (γ). Compositional dependence of parameters investigated for thermal stability has also been studied.

Dielectric relaxation and AC conductivity studies of Se90Cd10−xInx glassy alloys

Abstract Chalcogenide glassy alloys of Se90Cd10−xInx (x = 2, 4, 6, 8) are synthesized by melt quench technique. The prepared glassy alloys have been characterized by techniques such as differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX). Dielectric properties of Se90Cd10−xInx (x = 2, 4, 6, 8) chalcogenide glassy system have been studied using impedance spectroscopic technique in the frequency range 42 Hz to 5 MHz at room temperature. It is found that the dielectric constants ɛ′, dielectric loss factor ɛ″ and loss angle Tan δ depend on frequency. ɛ′, ɛ″ and loss angle Tan δ are found to be decreasing with the In content in Se90Cd10−xInx glassy system. AC conductivity of the prepared sample has also been studied. It is found that AC conductivity increases with frequency where as it has decreasing trend with increasing In content in Se–Cd matrix. The semicircles observed in the Cole–Cole plots indicate a single relaxation process.

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

ABSTRACT Bulk amorphous samples of Sb-substituted Se78−xTe20Sn2Sbx (0 < x < 6) have been prepared using melt quench technique. The structure of Se78−xTe20Sn2Sbx (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 (Ec) has been determined using model-free approaches such as Kissinger, Ozawa, Tang and Starink methods. The Avrami index (n) and frequency factor (Ko) have been calculated by Matusita and Augis–Benett method.

Effect of antimony on glass transition and thermal stability of Se78−xTe18Sn2Sbx (x = 0, 2, 4 and 6 at.%) multicomponent glassy alloys

Multicomponent glassy alloys Se78−xTe18Sn2Sbx (xu2009=u20090, 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 Se78−xTe18Sn2Sbx (xu2009=u20090, 2, 4 and 6xa0at.%) glassy alloys has been examined using DSC. DSC runs have been recorded at different heating rates (5, 10, 15 and 20xa0Kxa0min−1) for each sample under investigation. Heating rate dependence of glass transition temperature (Tg) 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 Se78−xTe18Sn2Sbx (xu2009=u20090, 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.