Crystallization kinetics in Se-Te glassy system-Effect of long-term material degradation

The influence of long-term laboratory-temperature degradation on the crystallization kinetics of the Se90Te10, Se80Te20 and Se70Te30 chalcogenide glasses was studied by differential scanning calorimetry. Periodical measurements during the 6 months aging period have shown that the fine Se-Te powders degraded largely, large degree of crystallinity occurred even though the materials were stored well below their glass transition temperature. The degradation increased with Te content. The defects-based residual crystallization kinetics exhibited by the fine Se-Te powders was not influenced significantly by the continuous degradation. Coarse Se-Te powders, on the other hand, exhibited only weak degradation with low amount of crystallinity occurring during the 6 months period but the crystallization kinetics of the degraded glasses changed markedly. The degraded coarse Se-Te powders have shown increased nuclei-based volume-located growth of crystallites, which indicates that nucleation proceeded significantly below the glass transition; the effect increased largely with Te content.