Thermal properties and viscous flow behavior of As2Se3 glass

Abstract

Thermal deformation of the As2Se3 bulk samples polished to optical quality has been investigated in the undercooled liquid region using thermomechanical analyzer (TMA). During the non-isothermal measurements the change of sample height has been monitored under compression at different heating rates (1–5 °C/min). The coefficient of linear thermal expansion, glass transition temperature and two characteristic extrapolated temperatures T0, as beginning of sample deformation caused by viscous flow, and Tf, as temperature at which the deformation is stopped by crystal growth and the sample reaches the final height hf, were obtained from TMA measurements. It was found that the value of activation energy obtained from the shift of characteristic temperature Tf with heating rate using the Kissinger method is very close to activation energy of crystal growth obtained by direct monitoring using microscopic methods. The influences of applied force, sample dimensions and heating rate on the overall TMA crystallization curve are discussed. For the first time, theoretical simulations of crystal growth were used to correlate the course of the TMA curve with the direct microscopic observation of the crystallization process.