Kinetics of processes in the volume and at the surface of amorphous materials

Abstract

The main aim of this dissertation thesis was to extend the knowledge of the crystal growth in chalcogenide glass-forming materials. Specifically, this thesis is focused on crystal growth kinetics. The crystal growth kinetics was studied in pure selenium (a-Se), Se95Te5 system and (GeSe2)x(Sb2Se3)1-x pseudobinary system. This study was performed using direct (i.e. microscopy techniques - Infrared microscopy and Scanning Electron Microscopy) and indirect methods (Differential Scanning Calorimetry, X-Ray Diffraction method, Thermomechanical Analysis). The suitable combination of all the above-mentioned methods gave a detailed knowledge about the crystallization process in the studied materials. Each and every experimental result was analyzed using the contemporary crystal growth theories. It is known that the crystal growth kinetics is driven by the transport of structural units through the melt-crystal interface. This transport is often described by diffusion process. Since diffusion data are often missing, they are substituted by the inverse value of viscosity according to the Stokes-Einstein relation (SE). For this reason, an exhaustive study of diffusion and viscous flow in chalcogenide glass-forming materials is also presented in this thesis. This thesis also focused in crystal growth mechanisms occurring in different types of samples. Many of the obtained experimental outcomes of such studies were published in several scientific papers.