Kinetic Processes in Amorphous Materials Revealed by Thermal Analysis: Application to Glassy Selenium

Abstract

It is expected that viscous flow is affecting the kinetic processes in a supercooled liquid, such as the structural relaxation and the crystallization kinetics. These processes significantly influence the behavior of glass being prepared by quenching. In this paper, the activation energy of viscous flow is discussed with respect to the activation energy of crystal growth and the structural relaxation of glassy selenium. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and hot-stage infrared microscopy were used. It is shown that the activation energy of structural relaxation corresponds to that of the viscous flow at the lowest value of the glass transition temperature obtained within the commonly achievable time scale. The temperature-dependent activation energy of crystal growth, data obtained by isothermal and non-isothermal DSC and TMA experiments, as well as direct microscopic measurements, follows nearly the same dependence as the activation energy of viscous flow, taking into account viscosity and crystal growth rate decoupling due to the departure from Stokes–Einstein behavior.

Crystal Growth in Amorphous Selenium Thin Films─Reviewed and Revisited: Direct Comparison of Microscopic and Calorimetric Measurements

“…The legend in the graph also lists values of activation energies determined by a simple Arrhenius (linear) fit. (D) Temperature dependence of viscosity for bulk a-Se . The inset shows the temperature dependence of Ediger’s decoupling parameter ξ.…”

“…Note that such an evolution of the spherulitic structure is in agreement with the universally observed crystal growth behavior of "other" polymeric materials. 22 factored-in complexity, a general consensus has been reached in literature regarding the crystallization, 15,17 crystal growth rates, 20,21 and the activation energies 23 of these thermally activated processes.…”

Kinetic analysis of particle-size based complex kinetic processes

“…6A corresponding to the mixture of the 125 -180 + 300 -500 µm powder fractions. Note that powdered glassy selenium preferentially crystallizes from surface [33 -36] and even the bulk Se samples with very low amount of mechanically induced defects [31] exhibit non-negligible amount of surface crystallinity [53].…”

Structural relaxation and viscosity of Al2O3 doped magnesium phosphate glasses

“…The relation between the relaxation motions and the viscous flow process has been the subject of debate for a long timesee e.g. [32][33][34]. In general, the activation energies of these phenomena are often considered close or even similar.…”