CRYSTALLIZATION KINETICS OF AMORPHOUS S20SE80

The effect of temperature on the crystallization kinetics of bulk amorphous S20Se80 has been studied using differential scanning calorimetry. Using the empricial Avrami expressions, a number of kinetic parameters has been determined. The order of the reaction n was found to be 2.3 for the range of temperature 340-365 K and 1.6 in the range of temperature between 370-400 K. This range of n indicates that the crystallization process is diffusion controlled growth with decreasing nucleation rate. The activation energy was found to be 3, 1.1 ev depending on the same range of temperatures. A time-temperature-transformation (TTT) curves has been plotted from isothermal results over the temperature range 340 K to 400 K showing the presence of minimum at 374 K. From the TTT curves the critical cooling rate required to avoid 25, 50, 75 and 100% crystallization was found to be 2.4, 1.79, 0.72 and 0.42-degrees-C/sec respectively.