, Volume 33, Issue 6, pp 562-568

Glass transformation studies in Ge-Se-Bi system

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Abstract

The thermal behavior of bulk glasses in the Ge20Se80 − x Bi x (x = 2.5, 4.0, 6.0 at %) system is studied using modulated differential scanning calorimetry (MDSC). All samples have the same thermal history as a result of heating to a temperature above the glass transition point, equilibrating, and then cooling. The total heat flow, modulated heat flow, reversing heat flow, and nonreversing heat flow under heating and cooling schedules are measured. The glass transition temperature T g , the relaxation enthalpy ΔH, the specific capacity C p , and the specific heat capacity difference ΔC p = C pl C pg , which characterize the thermal events in the glass transition region, are also determined. These parameters reveal an increase with x, which can be attributed to the increase in the average coordination number with an increase in the bismuth content (at %) in the composite. The ratio of heat capacities C pl /C pg , the width of the glass transition temperature range ΔT g , and the activation enthalpy for glass transition ΔH Tg are also studied. The values of the ratio C pl /C pg vary in the range between 1.038 and 1.112. The activation energy of crystallization is evaluated using the Kissinger, modified JMA, and Matusita equations, which is found to be in the range of 100.92 kJ/mol.

The text was submitted by the authors in English.