Non-isothermal structural relaxation and the glass transition temperature

The glass transition was studied by a new stepwise differential scanning calorimetry (DSC) technique on the model glasses As2Se3 and As2S3. The glass transition was separated to the two components: a reversible (thermodynamic) one, reflecting temperature changing of the vibrational amplitude, and an irreversible (kinetic) one, bears on structural relaxation. The value of the glass transition temperature, T-g, determined from the thermodynamic part of the glass transition was found to be independent both on the heating/cooling rate and the thermal history of glass. The value of T-g depends only on the chemical composition of the glass and thus it could be regarded as a material constant. The heating/cooling rate dependence of T-g, known from DSC or DTA measurements, is due to kinetic part of the glass transition. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.