Applicability of Meyer–Neldel rule for isothermal crystallization in glassy Se 70 Te 30-x Sb x alloys N. Mehta, A. Kumar ⁎ Department of Physics, Harcourt Butler Technological Institute, Kanpur-208 002, India Received 19 September 2005; accepted 1 October 2005 Available online 25 October 2005 Abstract 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 compensation law or Meyer–Neldel rule. In the present paper, we report the compensation effect in the isothermal crystallization in glassy Se 70 Te 30-x Sb x alloys. We have observed Meyer–Neldel rule between pre-exponential factor K o and activation energy of crystallization E c in the present case. © 2005 Elsevier B.V. All rights reserved. Keywords: Chalcogenide glasses; Meyer–Neldel rule; Pre-exponential factor; Isothermal crystallization; Rate constant 1. Introduction The Meyer–Neldel rule or MN rule (also known as compensation effect) is an empirical law known since 1937 [1]. This rule is observed in wide range of phenomena in physics, chemistry, biology and electronics [2–8]. It appears to be a fundamental property of many families of activated processes following an Arrhenius dependence on temperature: X ¼ X 0 expð-DE=kT Þ: ð1Þ Here X is the absolute rate of a thermally activated process, X 0 the pre-exponential factor, ΔE the activation enthalpy and k the Boltzmann constant. Commonly, by the evaluation of experimental data, the activation enthalpy is determined from the slope of (ΔE/k) of an Arrhenius plot of ln X vs. 1/T . It is frequently found that, when ΔE is varied with a family of processes (for example, related chemical reaction), then pre- exponential factor X 0 obeys the following empirical relation: X 0 ¼ X 00 expðDE=E MN Þ; ð2Þ where X 00 and E MN are positive constants. E MN is known as Meyer–Neldel energy for the process in question. This empirical relation is known as MN rule or compensation effect. The hallmarks of the MN rule, linear behavior of the Arrhenius plot and a characteristic temperature where the compensation is exact, are often recognized. This rule is generally observed in disordered materials. In the class of amorphous semiconductors, the MN rule has been reported in a- Si:H films in which ΔE is varied by doping, by surface absorption, light soaking or by preparing films under different conditions [9–11]. In case of chalcogenide glasses also, MN rule is observed by the variation of activation energy ΔE of d.c. conduction on changing the composition of the glassy alloys [12–16] in a specific glassy system or by the variation of intensity of light [17,18]. It has also been reported in literature [19] that, we could change ΔE by varying electric field across a particular sample and verify MN rule. Though evidence of MN rule has been reported for a number of activated phenomena such as solid state diffusion in crystals and polymers, dielectric relaxation and conduction in polymers, thermally stimulated processes in polymers and electronic conduction in amorphous semiconductors [2–8],a less effort has been done to observe MN rule in kinetic phenomena such as crystallization phenomenon. In this paper, we have reported the observation of MN rule for the isothermal crystallization in glassy Se 70 Te 30-x Sb x (0 ≤ x ≤ 10) Materials Letters 60 (2006) 725 – 729 www.elsevier.com/locate/matlet ⁎ Corresponding author. E-mail address: dr_ashok_kumar@yahoo.com (A. Kumar). 0167-577X/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2005.10.018