Crystallization of glassy selenium during its plastic deformation

Crystallization of glassy selenium (Se) during its plastic deformation has been investigated in the temperature interval between 60°C and 95°C. We found that plastic reshaping of small Se pellets into thin discs greatly enhances the notoriously sluggish transition from glassy to crystalline state. However, the content of the crystalline phase in the deformed samples is found to be strongly dependent upon the temperature of the process. While the 30-min long reshaping at 60°C and 95°C gives only partially crystallized samples (6% and 10%, respectively), an equally long process at 80°C gives 100% crystallized samples. Average crystallite size in the samples prepared at 60°C and 80°C is very similar (25 nm and 15 nm, respectively), but in the sample prepared at 95°C the grains are much larger: about 80 nm. The results are discussed taking into account the possibility that the mechanism of plastic deformation enhances both the nucleation frequency and the rate of crystal growth.