PHYSICAL AGING KINETICS IN VITREOUS SE-BASED ALLOYS

The effects of the annealing time on the structural relaxation of vitr eous As-Se alloys are studied by differential scanning calorimetry. Th e variations of the equilibrium relaxation time with annealing tempera ture (T-a < T-g) are explained from a model which takes into account t he enthalpic departure from equilibrium and the annealing temperature. The influence of the addition of arsenic (threefold coordinated) in a vitreous selenium matrix (twofold coordinated) is discussed in terms of average coordination number, m, and local structure. The comparison with the results obtained on the Ge-Se system shows the existence of critical values of m which are the same whatever the added element. Th en, the results are explained by the modifications of the mobilities o f different molecular species (called Se cells, Ge and As cells) when the medium changes from a linear to a quasi planar structure.