Calorimetric study of Te₁₅(Se_100−xBi_x)₈₅ glassy alloys using differential thermal analysis

Abstract

A calorimetric study of Te₁₅(Se_{100− x} Bi _x )₈₅ glassy alloys (x = 0, 1, 2, 3 and 4 at. %) is reported. Differential thermal analysis (DTA) was performed at heating rates of 10, 15, 20 and 25 K/min. The spectra were used to determine the glass transition temperature, T_g , the crystallisation temperature, T_c and the melting temperature, T_m . All these parameters shift to higher values with increasing heating rate, β. The glass transition temperature and the melting temperature increase, and the crystallisation temperature decreases, with increase in the Bi content, x. The activation energy of the glass transition, E_g , was evaluated using the Moynihan and Kissinger methods. The activation energy of crystallisation, E_c , was calculated using modified Kissinger and Matusita approaches. The thermal stability of these glasses has been studied and found to decrease with increase in Bi content. The results obtained are explained on the basis of a chemically ordered network model and an average coordination number.

Keywords:

• differential thermal analysis
• glass transition temperature
• activation energy
• chalcogenide glass

Acknowledgements

One of the authors (KK) is grateful to UGC, Delhi for providing a teacher fellowship under FIP. Two of the authors (SSB, NT) wish to thank UGC and DST for providing the necessary instrumentation facilities in the Departments of Physics and Chemistry at HP University Shimla via the SAP and FIST programmes.