Crystallization kinetics of amorphous selenium prepared by ball milling technique: Evidence of three crystallization regimes

Crystallization kinetics of amorphous selenium prepared by ball milling method has been studied using differential scanning calorimetry (DSC). Non-isothermal measurements were performed at different heating rates (3-20 K/min). The activation energy of crystallization was determined by analyzing the data using different kinetic models. A strong heating rate dependence of the activation energy was observed. The isoconversional methods confirm that the activation energy of crystallization is not constant but varies with the degree of crystallization and hence with temperature. This variation indicates that the transformation from amorphous to crystalline phase in a-Se is a complex process involving different mechanisms of nucleation and growth. The crystallization kinetics was further analyzed using Hoffman-Lauritzen theory and evidence of the presence of three regimes of crystallization is presented. Some features of crystallization process in the ball-milled a-Se can be understood in terms of the nanostructural glassy phase.