Extended study of crystallization kinetics for Se-Te glasses

Crystallization kinetics of chosen compositions from Se-Te glassy system were studied under non-isothermal conditions depending on particle size using differential scanning calorimetry. The purpose of this article is to demonstrate the extent of information accessible by the modern kinetic analysis provided by the differential scanning calorimetry, and to suggest its importance and merit for the development of new, high-tech PCM materials. The crystallization kinetics was described in terms of the nucleation-growth Johnson-Mehl-Avrami model. Complexity of the crystallization process was in this case represented by very closely overlapping consecutive competing surface and bulk nucleation-growth mechanisms. Mutual interactions of both mechanisms as well as all other observed effects were explained in terms of thermal gradients, surface crystallization centers arising from the sample preparation treatments, and changing amount of volume nuclei originating from the combination of pre-nucleation period, and the very glass preparation phase. Accent was laid on the merits resulting from interpretations of characteristic kinetic functions. A new criterion for quick determination of the dominating crystallization mechanism-surface or bulk-was introduced.