Strong-fragile glass forming liquid concept applied to GeTe chalcogenide glasses

• Published in: Physica. B, Condensed matter Vol. 304; no. 1; pp. 228 - 236
• Main Authors: Chebli, K., Saiter, J.M., Grenet, J., Hamou, A., Saffarini, G.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2001; Elsevier
• Subjects: Chalcogenide glass; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Coordination number; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Elements, oxides, nitrides, borides, carbides, chalcogenides, etc; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Fragility; GeSe; GeTe; Glass transitions; Physics; Relaxation; Specific phase transitions; Chalcogenide glass; GeSe; Relaxation; Coordination number; GeTe; Fragility; Liquid state; Forming processes; Heat capacity; Germanium selenides; Glass transition temperature; Chalcogenide glasses; g-factor; Glass transition; Specific heat; Thermodynamics; DSC; Germanium tellurides; Activation energy
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/S0921-4526(01)00501-4

The values of the thermal heat-capacity changes at the glass transition temperature T g (Δ C p= C p l − C p g ) and the values of the apparent activation energy Δ h * of the sub T g relaxation process are determined for Ge x Te 1− x (0.15⩽ x⩽0.20) vitreous alloys by means of differential scanning calorimetry investigations. The values of Δ h * are then used to determine the values of the fragility index, m. The comparison of these new data to those already obtained on the Ge x Se 1− x vitreous system leads to conclude that both systems exhibit strong thermodynamic character. The stronger thermodynamic character is reached at the Phillips–Thorpe's floppy-to-rigid transition. On the other hand, we find that Ge x Te 1− x exhibits a kinetically fragile character which decreases as the amount of Ge increases in the alloy.