Physical ageing in Se–Te–Sb glasses

• Published in: The Journal of physics and chemistry of solids Vol. 74; no. 6; pp. 804 - 810
• Main Authors: Vanitha, M.K., Hanumantha Rao, M.V., Asokan, S., Ramesh, K.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2013
• Subjects: A. Chalcogenides; A. Glasses; C. Differential Scanning Calorimetry (DSC); D. Specific heat; D. Thermodynamic properties; C. Differential Scanning Calorimetry (DSC); A. Glasses; D. Specific heat; A. Chalcogenides; D. Thermodynamic properties
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2013.01.010

Bulk Se60−xTe40Sbx glasses in the composition range 0≤x≤14 were prepared by the melt quenching method. Differential Scanning Calorimetric (DSC) and thermal crystallization studies were performed to understand the thermodynamic property like glass transition and structural transformations. These glasses exhibit sharp endothermic peak at the glass transition (Tg). Disappearance of the endothermic peak at Tg in the rejuvenated samples clearly indicates the ageing effect in these glasses. Addition of Sb to Se–Te increases the connectivity of the structural network which is evidenced from the increase in Tg. A distinct change in the slope of the Tg at x=6, indicates a major change in the way the network is connected. The glass forming ability and the thermal stability also exhibit a maximum at x=6. Tg increases with the ageing time and the corresponding fictive temperature (Tf) calculated from the specific heat curves shows a decreasing trend. The molecular movements along the polymeric Se chains might cause the structural relaxation and the physical ageing. The physical ageing effect has been understood on the basis of the Bond Free Solid Angle (BFSA) model proposed by Kastner. Thermally crystallized samples show the formation of rhombohedral Sb2Te3, rhombohedral Sb2Se3 and hexagonal Te phases. ► Bulk Se60−xTe40Sbx glasses prepared by themelt quenching method. ► A sharp endothermic peak has been observed at Tg due to the ageing effect. ► Tg is found to increase and Tf is found to decrease with ageing. ► The variation of Tg with composition shows a slope at x=6. ► The enthalpy and entropy are found to decrease with ageing.