Study of Activation Energy of Crystallization and Growth Morphology of Ge 25x Se 75 Sb x (x ¼ 12, 15, 18) Chalcogenide Glasses Naveen Tanwar and Vibhav K. Saraswat* In the present paper crystallization kinetics of Ge 25-x Se 75 Sb x (x ¼ 12, 15, 18) chalcogenide glasses has been investigated using thermal analysis (TA) technique. Ge 25-x Se 75 Sb x (x ¼ 12, 15, 18) chalcogenide glasses have been prepared by rapid quenching of melt technique. For structure characterization XRD technique has been used. Out of various TA techniques Differential Scanning Calorimetery (DSC) has been used for present study. DSC scans have been carried at different heating rates i.e. 5, 10, 15 and 20 K/min. For evaluation of activation energy of crystallization various theoretical models Kissinger, Ozawa, Augis-Bennet and Matusita-Sakka have been used. Activa- tion energy of crystallization increases with increase of Sb content in Ge 25- x Se 75 Sb x (x ¼ 12, 15, 18) glassy series. The value of Avrami index indicates bulk crystallization with one or two dimensional growth. 1. Introduction Chalcogenide glasses in recent years have been under investigation of researchers because of wide range of application in field of electronics and optics. [1–4] Amorphous Se because of its high glass forming ability acts as good host matrix for preparation of chalcogenide glasses. Doping of Ge further increases the glass forming region and also increase the strength and rigidity of structure. Antimony acts as good doping agent to modify the properties of Ge-Se chalcogenide glasses for specific technological application. Doping of Sb in Ge-Se glassy matrix reduces optical losses considerably making these materials suitable for fabrication of IR-optical fibers. [5–8] For production of high quality glass for Infrared optical application crystallization should be avoided. The study of crystallization kinetics gives information about activation energy of crystallization and growth morphology that helps to provide information about resistance to crystallization. Understanding of crystallization kinetics is essential to find the utility of a material for a specific application. For the study of crystallization kinetics Differential Scanning Calorimetery has been widely used. [9–12] Activation energy of crystalliza- tion has been evaluated using Kissinger, Ozawa, Augis-Bennet and Matusita  Sakka models. Matusita-Sakka model pro- vides information about Avrami Index and dimensionality of growth. 2. Material Preparation and Experiment Procedure Preparation of Ge 25-x Se 75 Sb x (x ¼ 12, 15, 18) glassy samples have been carried out using rapid quenching of melt technique. High purity (99.999 %) constituent materials Ge, Se and Sb has been taken in elemental powder form in proper atomic weight percentage and sealed in quartz ampoules under vacuum of 10 5 torr. The sealed ampoules have been kept inside a programmable furnace whose temperature was raised initially at rate of 3-4  C/min and was kept at this value for 2 hrs then maintained at 950  C for 17 hrs. Quenching has been done in ice- cooled water to get glassy state. Amorphous nature of so produced glassy samples has been confirmed by X-ray diffraction. Differential scanning calorimetery (DSC) Netschz 204 F1 Phoenix has been used for thermal studies under non- isothermal condition. DSC scans have been carried at four different heating rates 5, 10, 15, 20 K/min on accurately weighted samples sealed in aluminum pans. These scans were recorded from room temperature to 550  C. 3. Result and Discussion Figure 1(a–c) represents DSC thermograms of Ge 25x Se 75 Sb x (x ¼ 12, 15, 18) glasses. When glassy samples are subjected to DSC under constant heating rate they undergo phase transition, an endothermic peak is obtained corresponding to glass transition and exothermic peak corresponding to crystallization. 4. Kinetics of Crystallization The kinetic of crystallization has been studied under non- isothermal condition. Samples under test have been heated from room temperature to an elevated temperature at constant heating rate and the heat evolved is recorded as a function of N. Tanwar Department of Physics, Ahir College Rewari-123401, India V. K. Saraswat Department of Physics, Army Cadet College Wing, IMA Dehradun-248007, India E-mail: vibhav.spsl@gmail.com DOI: 10.1002/masy.201600185 Macromolecular Symposia Chalcogenide Glass www.ms-journal.de ARTICLE Macromol. Symp. 2017, 376, 1600185 © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1600185 (1 of 8)