Calorimetric studies of Se 80x Te 20 Bi x bulk samples N. Suri, K.S. Bindra, P. Kumar, R. Thangaraj * Semiconductors Laboratory, Department of Applied Physics, Guru Nanak Dev University, Amritsar 143005, India Available online 23 March 2007 Abstract The crystallization kinetics of the bulk Se 80x Te 20 Bi x chalcogenide glasses were studied by using differential scanning calorimetry with different heating rates (5,10,15 and 20 K/min) under non-isothermal conditions. The values of glass transition temperature, peak crys- tallization temperature and melting temperature are found to increase with increase in heating rate as well as with bismuth content. The activation energy for glass transition and that for crystallization have been determined using the Kissinger equation and Matusita equa- tion. The thermal stability and glass-forming tendency have also been studied. Ó 2007 Elsevier B.V. All rights reserved. PACS: 64.70.Pf; 68.60.Dv Keywords: Crystallization 1. Introduction Chalcogenide materials are becoming more and more popular due to their applications as infrared optical fibers, in reversible phase change optical recording etc. [1]. Among the various chalcogenide materials, Se–Te based alloys are preferred because of their higher photosensitivity, greater hardness, higher crystallization temperature (T c ) and smal- ler ageing effects as compared to pure selenium [2]. The addition of a third element like Sb, Sn, In, Pb has large effect on their structural, physical, optical, electronic and thermal properties [3]. An understanding of crystallization kinetics in these chalcogenide materials is very important to develop them for applications based on the amorphous to crystallization phase change and vice-versa. A differential scanning calorimetry analysis is generally used to study the crystallization kinetics. In calorimetric measurements, two basic methods viz., isothermal and non-isothermal are used [4]. In the present work the effect of Bi addition on crystallization kinetics of Se 80x Te 20 Bi x has been stud- ied using calorimetric measurements under non-isothermal conditions. From the heating rate dependence of glass tran- sition temperature (T g ) and peak crystallization tempera- ture (T p ) the apparent activation energy for glass transition and the activation energy for crystallization have been investigated. The thermal stability factor and the glass-forming tendency of Se 80x Te 20 Bi x for different bis- muth compositions have also been investigated. 2. Experimental Bulk samples of Se 80x Te 20 Bi x (x = 2, 4, 6, 8) were pre- pared by conventional melt quenching technique. The exact proportions of high purity (99.999%) elements in accor- dance with their atomic percentages were weighed using an electronic balance (make Sartorious, model no. GC1603S-OCE). Materials were sealed in a cleaned and evacuated quartz ampoule (length  5 cm and internal diameter 0.8 cm) in a vacuum of 10 5 mbar. The ampoule was kept inside a vertical furnace and the temperature was raised up to 1123 K slowly (3–4 K/min) and maintained for 48 h. The ampoule was inverted at regular intervals to ensure homogeneous mixing of the constituents. It was then quenched in ice-cold water. The material was sepa- rated from the quartz ampoule by dissolving it in 0022-3093/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2006.10.056 * Corresponding author. E-mail address: rthangaraj@rediffmail.com (R. Thangaraj). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 353 (2007) 1264–1267