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Neeraj Mehta - One of the best experts on this subject based on the ideXlab platform.
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Correlation between threshold voltage and its Pre-Exponential Factor in resistive switching
Materials Chemistry and Physics, 2020Co-Authors: Ankita Srivastava, Shiv Kumar Pal, Neeraj MehtaAbstract:Abstract The phenomenon of resistive switching has drawn great attention in last one decade due to its promising applications in the memory technology. The analysis of resistive switching experiments on novel bulk Se–Te–Sn–Ag quaternary glass has been reported in this script. In the present work, we have observed that the Pre-Exponential Factor (Vth)0 of the threshold voltage Vth in thermally governed resistive switching characteristics follows an exponential dependence on the corresponding activation energy Eth as a signature of the compensation effect. Our results indicate that the resistive switching behaviour is influenced by these two parameters. Thus, the correlation between (Vth)0 and Eth may play a significant role in controlling resistive switching. The origin of this correlation is explained in terms of the transition probabilities for recombination/generation of the charge carriers as suggested in the barrier cluster model. The observations show that the threshold voltage of the glassy Se–Te–Sn–Ag system is reduced with the increase in the Ag concentration. An endeavor has been made for the explanation of the observed composition dependence on the basis of nature of bonding of Ag atoms and a decrease in the chemical disorder with composition.
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Dependence of activation energy and Pre-Exponential Factor on audio frequency in glassy Se80-xTe20Snx alloys
Journal of Alloys and Compounds, 2011Co-Authors: A. Sharma, Neeraj Mehta, A. KumarAbstract:Abstract In the present paper, we have studied the temperature and frequency dependence behaviours of ac conductivity in glassy system Se 80− x Te 20 Sn x ( x = 0, 2, 4, and 6). All the measurements have been done in the frequency range (1–500 KHz) and in the temperature range from room temperature to glass transition temperature T g . We have found that activation energy and Pre-Exponential Factor both vary with audio frequency according to Meyer–Neldel's relation (MNR). We have investigated MNR by two different approaches. In first approach, the temperature dependence of ac conductivity is studied at four different audio frequencies without changing the composition of the glassy system. In the second approach, the composition itself varies at a particular audio frequency. The results are explained in terms of compensation effect in relaxation time and the multi-excitation character of the processes suggested by Yelon and Movaghar responsible for MNR in chalcogenide glasses.
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Calorimetric studies of non-isothermal crystallization in amorphous CuxTi100−x alloys
Bulletin of Materials Science, 2011Co-Authors: Neeraj Mehta, Kedar Singh, N. S. SaxenaAbstract:The present paper reports the composition dependence of Pre-Exponential Factor and activation energy of non-isothermal crystallization in amorphous alloys of CuxTi100−x system using differential scanning calorimeter (DSC) technique. The applicability of Meyer-Neldel relation between the Pre-Exponential Factor and activation energy of non-isothermal crystallization for amorphous alloys of Cu-Ti system was verified.
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Effect of ionic irradiation on the Pre-Exponential Factor of thermally activated crystallization in Co66Si16B12Fe4Mo2 metallic glass
Journal of Physics and Chemistry of Solids, 2009Co-Authors: Neeraj Mehta, Kedar Singh, N. S. SaxenaAbstract:Abstract In the present paper, we report the Meyer–Neldel relation between the Pre-Exponential Factor and activation energy of non-isothermal crystallization of Co 66 Si 16 B 12 Fe 4 Mo 2 metallic glass. Differential scanning calorimeter (DSC) is employed to study the change in the above two kinetic parameters of the crystallization due to ionic irradiation at three different fluences with high-energy heavy ion; Ni 11+ of 150 MeV.
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Co-relation between Pre-Exponential Factor and activation energy of non-isothermal crystallization for virgin and irradiated Fe78B13Si9 metallic glass
Physica B: Condensed Matter, 2009Co-Authors: Neeraj Mehta, Kedar Singh, N. S. SaxenaAbstract:Abstract The present work shows the applicability of Meyer–Neldel relation between the Pre-Exponential Factor and activation energy of non-isothermal crystallization of Fe 78 B 13 Si 9 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 Ni 11+ having energy 150 MeV.
Jean-michel Savéant - One of the best experts on this subject based on the ideXlab platform.
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Reorganization energy and Pre-Exponential Factor from temperature-dependent experiments in electron transfer reactions. A typical example: the reduction of tert-nitrobutane
Physical chemistry chemical physics : PCCP, 2011Co-Authors: Cyrille Costentin, Cyril Louault, Marc Robert, Vincent Rogé, Jean-michel SavéantAbstract:The electrochemical one-electron reduction of tert-nitrobutane in N,N′-dimethylformamide is a typical reaction, which has been shown to follow the quadratic model of outersphere electron transfer. The variation of the standard rate constant with temperature allows a separate determination of the reorganization energy and of the Pre-Exponential Factor. The value found for the former is in agreement with independent estimates of the solvent and intramolecular reorganization energies. The value of the latter, significantly larger than the collision frequency, implies that the reaction starts to take place before close contact with the electrode surface.
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Reorganization energies and Pre-Exponential Factors in the one-electron electrochemical and homogeneous oxidation of phenols coupled with an intramolecular amine-driven proton transfer
Physical chemistry chemical physics : PCCP, 2010Co-Authors: Cyrille Costentin, Marc Robert, Jean-michel SavéantAbstract:Temperature variations of the kinetics of the electrochemical and homogeneous oxidation of the title compounds give rise to Arrhenius plots, the slopes of which give access to the heavy-atom (including solvent) reorganization energies. Information on the role of proton transfer in the dynamics of the concerted proton–electron transfer reaction (CPET) is potentially contained in the Pre-Exponential Factor. Previous analyses of the problem were based on equalling the Pre-Exponential Factor in the absence of barrier for proton transfer with the collision frequency. Taking into account that the reaction may take place at various distances from the electrode surface increases the value of this limiting Pre-Exponential Factor. Strategies are discussed for evaluating the impact of proton transfer in the CPET kinetics by comparing the experimental Pre-Exponential Factor with Pre-Exponential Factors characterizing simple outersphere electron transfers.
Samuel S. Okoya - One of the best experts on this subject based on the ideXlab platform.
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Reactive-diffusive equation with variable Pre-Exponential Factor
Mechanics Research Communications, 2004Co-Authors: Samuel S. OkoyaAbstract:Abstract We consider the steady-state solutions for the exothermic chemical reaction, taking the diffusion of the reactant in a slab into account and assuming an Arrhenius temperature dependence with variable Pre-Exponential Factor. We solve the resulting nonlinear boundary value problem using both numerical and analytical methods. This new analytical solution for the Frank-Kamenetskii parameter δ, as it is in terms of Bernoulli’s numbers, is in accordance with the numerical integration provided the activation energy parameter ϵ (≪1) is very small and for ϵ→0 it goes to the well-known Frank-Kamenetskii case. We determine numerically the transitional values of δ, ϵ and the dimensionless central temperature θm.
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The effect of variable Pre-Exponential Factor on the ignition time of a homogeneous system
International Communications in Heat and Mass Transfer, 2004Co-Authors: S. O. Ajadi, Samuel S. OkoyaAbstract:CT The influence of variable Pre-Exponential Factor on the ignition time of a system of homogeneous three step reaction mechanism is investigated. Based on simple numerical analysis, it is shown that for the ignition time over a broad range of realistic constant, the variation of Pre-Exponential Factor leads to significant departure from the Arrhenius case. Also the effect of different values for some fixed exponents are depicted graphically. In addition, we consider the ignition time for a two reactions steps in the limit of large activation energy and we obtain the solution in series form. This result is compared with the numerical solution and results are in good agreement with existing result.
S. O. Ajadi - One of the best experts on this subject based on the ideXlab platform.
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The structure of the thermal explosion limit with variable Pre-Exponential Factor
Russian Journal of Physical Chemistry B, 2010Co-Authors: S. O. Ajadi, Vl. Gol’dshteinAbstract:An approximate critical explosion parameter, which separates the slow and explosive reactions is determined with respect to the initial data, using the asymptotic technique to analyze a one step reaction mechanism with temperature dependent Pre-Exponential Factor. We obtained and analysed the effect of the variable Pre-Exponential Factor on the critical temperature, critical parameter for thermal explosion and the first order approximation of the slow curve. By introducing a new coordinate and using the Method of Invariant Manifold (MIM), we obtained corrections on the critical temperature. The results obtained are not only general; they also reveal some salient properties of the system hitherto unknown.
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The effect of variable Pre-Exponential Factor on the ignition time of a homogeneous system
International Communications in Heat and Mass Transfer, 2004Co-Authors: S. O. Ajadi, Samuel S. OkoyaAbstract:CT The influence of variable Pre-Exponential Factor on the ignition time of a system of homogeneous three step reaction mechanism is investigated. Based on simple numerical analysis, it is shown that for the ignition time over a broad range of realistic constant, the variation of Pre-Exponential Factor leads to significant departure from the Arrhenius case. Also the effect of different values for some fixed exponents are depicted graphically. In addition, we consider the ignition time for a two reactions steps in the limit of large activation energy and we obtain the solution in series form. This result is compared with the numerical solution and results are in good agreement with existing result.
A. Kumar - One of the best experts on this subject based on the ideXlab platform.
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Dependence of activation energy and Pre-Exponential Factor on audio frequency in glassy Se80-xTe20Snx alloys
Journal of Alloys and Compounds, 2011Co-Authors: A. Sharma, Neeraj Mehta, A. KumarAbstract:Abstract In the present paper, we have studied the temperature and frequency dependence behaviours of ac conductivity in glassy system Se 80− x Te 20 Sn x ( x = 0, 2, 4, and 6). All the measurements have been done in the frequency range (1–500 KHz) and in the temperature range from room temperature to glass transition temperature T g . We have found that activation energy and Pre-Exponential Factor both vary with audio frequency according to Meyer–Neldel's relation (MNR). We have investigated MNR by two different approaches. In first approach, the temperature dependence of ac conductivity is studied at four different audio frequencies without changing the composition of the glassy system. In the second approach, the composition itself varies at a particular audio frequency. The results are explained in terms of compensation effect in relaxation time and the multi-excitation character of the processes suggested by Yelon and Movaghar responsible for MNR in chalcogenide glasses.
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Pre-Exponential Factor for the crystallization of glassy Se80Te20 and Se75Te20M5 alloys: applicability of Meyer–Neldel rule
Phase Transitions, 2009Co-Authors: Shipra Saraswat, S. S. S. Kushwaha, A. KumarAbstract:The Meyer–Neldel rule or MN rule (also known as compensation effect) is an empirical law known since 1937. This rule is observed in wide range of phenomena in physics, chemistry, biology and electronics. Many activated phenomena, including solid state diffusion in crystals and polymers, dielectric relaxation, conduction and thermally stimulated processes in polymers, and electronic conduction in amorphous semiconductors obey the MN rule. In the present article, we report the MN rule in the non-isothermal crystallization in glassy Se80Te20 and Se75Te20M5 (M = Ag, Cd, In, Sb) alloys. We have observed MN rule between Pre-Exponential Factor K o and activation energy of crystallization E c in the present case for thermally activated non-isothermal crystallization.
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pre exponential Factor of arrhenius equation for the isothermal crystallization of some se ge se in and se te chalcogenide glasses
Journal of Materials Science, 2007Co-Authors: Neeraj Mehta, A. KumarAbstract:Compensation law or Meyer–Neldel rule is observed in many activated phenomena, including solid state diffusion in crystals and polymers, dielectric relaxation, conduction and thermally stimulated processes in polymers, and electronic conduction in amorphous semiconductors. In the present paper, we have reported the compensation effect for the isothermal crystallization of some Se–Ge, Se–In and Se–Te chalcogenide glasses. We have observed Meyer–Neldel rule between Pre-Exponential Factor K0 and activation energy of crystallization Ec in the present case.
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Pre-Exponential Factor for the crystallization of some chalcogenide glasses: applicability of Meyer-Neldel rule
The European Physical Journal Applied Physics, 2006Co-Authors: Neeraj Mehta, D. Kumar, A. KumarAbstract:In the present paper, we report the compensation effect for the crystallization of different binary and ternary systems of some chalcogenide glasses. We have observed Meyer-Neldel rule between the Pre-Exponential Factor K 0 of rate constant K ( T ) of crystallization and activation energy of crystallization E c in the present case.
