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  • Author or Editor: J. Shánelová x
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Abstract  

Structural relaxation for simple and more complex thermal histories is described by a phenomenological model based on a non-exponential relaxation function, the reduced-time concept and the nonlinear structural contribution to the relaxation time. The history, development of experimental techniques and data analysis is described. It is shown that the volume and enthalpy relaxation response can conveniently be compared on the basis of a fictive relaxation rate, R f. A simple equation relating R f and the parameters of the phenomenological model is given. The calculated data for moderate departures from equilibrium are in good agreement with our experiments and data previously reported in the literature.

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Abstract  

The structural relaxation of Ge38S62 glass has been studied by length dilatometry and calorimetry. The Tool-Narayanaswamy-Moynihan model was applied on obtained data of structural relaxation and parameters of this model were determined: Δh*= 4832 kJ mol-1, ln(A/s)= -811, β= 0.70.1 and x=0.60.1. Both dilatometric and calorimetric relaxation data were compared on the basis of the fictive relaxation rate. It was found that the relaxation rates are very similar and well correspond to the prediction of phenomenological model.

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Summary Relaxation behavior of GeySe100-y (y=8 and 10) glasses related to the viscosity behavior was studied by dilatometry. The method of two consecutive temperature jumps was applied to study the volume relaxation. The relaxation response can be described by Tool-Narayanaswamy-Moynihan model and the parameters of this model ?h*, ß, x, A were determined using curve fitting method and characteristic times method. Viscosities of studied materials in the range of 108-1013 Pas were measured by penetration method. The calculated values of activation energies of viscous flow E? are close to the values of effective activation energies of relaxation ?h* for studied chalcogenide materials.

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