A modulated differential scanning calorimetric study of As–Te–In glasses B.H. Sharmila a , J.T. Devaraju b , S. Asokan a, * a Department of Instrumentation, Indian Institute of Science, Bangalore 560012, India b Department of Electronic Science, Bangalore University, Bangalore 560056, India Abstract Bulk As–Te–In glasses have been prepared by conventional melt-quenching technique. Modulated differential scanning calorimetric studies have been undertaken to investigate the glass transition and crystallization behavior and also to understand the composition dependence of various thermal parameters. These studies indicate the occurrence of rigidity percolation and chemical thresholds at average coordinations hri¼ 2:65 and 2.70 respectively. Ó 2003 Elsevier B.V. All rights reserved. PACS: 81.70.P; 61.43.F; 64.70.P; 82.20.R 1. Introduction Differential scanning calorimetric (DSC) studies on chalcogenide glasses help us in not only un- derstanding the thermal behavior but also provide an insight to the structural effects occurring in these samples. The conventional DSC measures the total heat flow (HF) in a sample which sums up both the reversing and the non-reversing heat parts. However, the recent technique of modulated differential scanning calorimetry (MDSC) provides the possibility of deconvoluting the HF into a component that tracks the temperature modula- tion (reversing heat flow (RHF) rate), leaving the part which does not track the temperature modu- lation (non-reversing heat flow (NHF)). The re- versing component is ascribed to thermodynamic specific heat changes upon heating, whereas the NHF component is ascribed to kinetic processes and the enthalpic changes that accompany struc- tural reorganization in the glassy network [1]. The properties of chalcogenide network glasses have been found to be influenced by two network topological effects, namely the rigidity percolation and chemical ordering [2–4]. The rigidity percola- tion deals with the dimensionality and rigidity of a glassy network whereas the chemical ordering deals with arrangement of molecular species in a chalcogenide glass. The composition/average co- ordination number at which these two topological effects occur are known as the rigidity percolation threshold (RPT) and the chemical threshold (CT) respectively. At the RPT, the material undergoes a transformation from a floppy polymeric glass (which is under-coordinated) to rigid amorphous * Corresponding author. Tel.: +91-80 334 4411; fax: +91-80 334 1683. E-mail address: sasokan@isu.iisc.ernet.in (S. Asokan). 0022-3093/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0022-3093(03)00397-1 Journal of Non-Crystalline Solids 326&327 (2003) 154–158 www.elsevier.com/locate/jnoncrysol