Thermochimica Acta 566 (2013) 274–280 Contents lists available at SciVerse ScienceDirect Thermochimica Acta jo ur nal home p age: www.elsevier.com/locate/tca Crystallization study of Sn additive Se–Te chalcogenide alloys M.A. Abdel-Rahim, A. Gaber, A.A. Abu-Sehly, N.M. Abdelazim ∗ Physics Department, Faculty of Science, Assiut University, Assiut 71516, Egypt a r t i c l e i n f o Article history: Received 25 February 2013 Received in revised form 5 June 2013 Accepted 8 June 2013 Available online 18 June 2013 Keywords: Se–Te–Sn system Crystallization kinetics Chalcogenide glasses Thermal analysis a b s t r a c t Results of differential thermal analysis (DTA) under non-isothermal conditions of glasses Se 90 - x Te 10 Sn x (x = 0, 2.5, 5 and 7 at.%) are reported and discussed. The glass transition temperature (T g ), the onset crys- tallization temperature (T c ) and the peak temperature of crystallization (T p ) were found to be dependent on the compositions and the heating rate. Values of various kinetic parameters such as activation energy of glass transition (E g ), activation energy of crystallization (E c ), rate constant (K p ), Hurby number (H r ) and the order parameter (n) were determined. For the present systems, the results indicate that the rate of crystallization is related to thermal stability and glass forming ability (GFA). According to the Avrami exponent (n), the results show a one dimensional growth for the composition Se 90 Te 10 and a three dimen- sional growth for the three other compositions. The crystalline phases resulting from DTA and (SEM) have been identified using X-ray diffraction. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Chalcogenide glasses are of special interest due to their broad applications in modern electronics, optoelectronics, integrated optics, electro-photography, solar cells, electrical and optical mem- ory devices etc. [1–4]. Among the amorphous chalcogenide alloys, mostly selenium (Se) based materials are preferred due to its commercial use. Moreover, its device applications like switching memory and xerography etc., made it attractive. But, the pure Se has a short life time and low sensitivity [5] although is character- ized by high viscosity. The problem can be overcome by alloying selenium with some impurities such as Ge, Te etc., which in terms gives high sensitivity, greater hardness, high crystallization tem- perature and small aging effects as compared to pure Se glass [6]. Recently, it has been pointed out that Se–Te has some advan- tages over amorphous Se as far as their use in xerography is concerned [7] and the addition of Se to Te alloy improves the corro- sion resistance [8]. The Se–Te alloys are found to be useful from the technological point of view if these alloys are thermally stable with time and temperature during use. On the other hand, the addition of a third element Sn impurity to Se–Te system increase thermal stability of the material. It has been found that the glass transition temperature increases with doping Sn content, indicating a cross linking of the Se–Te chains with the addition of Sn [9]. ∗ Corresponding author. Tel.: +20 1223990118. E-mail address: nana841@hotmail.co.uk (N.M. Abdelazim). Structural studies of chalcogenide glasses are important in determining the transport mechanisms, thermally stability and practical applications. Different techniques have been used to study the structure of chalcogenide glasses, e.g. electron microscopy, X-ray diffraction and differential scanning calorimetry. The stud- ies of crystallization kinetics for these glasses using differential scanning calorimetry has been widely discussed in the liter- ature [10–12]. Different theoretical models were proposed to explain the results of the crystallization kinetics. The application of the model depends on the glass composition and preparation conditions [13]. The present work is concerned with the study of the crys- tallization kinetics and deduce the crystallization parameter for Se 90 - x Te 10 Sn x (where x = 0, 2.5, 5, 7.5 at. %) glasses using differen- tial thermal analysis (DTA) under non-isothermal conditions. The effect of composition on the crystallization mechanism is discussed using different kinetics models. 2. Experimental techniques The bulk materials of Se 90 - x Te 10 Sn x (x = 0, 2.5, 5, 7.5) were prepared by the usual melt quenching technique. The high pure materials (99.999%) were weighted according to their percent- ages and sealed in evacuated silica tubes then heated at 950 ◦ C for 20 h. During the melt, the tube was frequently rocked to inter- mix the constituents and to increase the homogenization of the melt. This treatment was followed by fast quenching in ice-water mixture. The glassy nature of the as-prepared and the crystalline phase structures for annealed samples was identified using a Philips 0040-6031/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.tca.2013.06.009