DYNAMICS OF GLASS-TRANSITION OF BULK A-SE AND SE CLUSTERS INCORPORATED INTO ZEOLITES

The dynamics of the glass transition of a-Se (both bulk and clusters i n zeolites) has been investigated with heat capacity data obtained by differential scanning calorimetry experiments. The heat capacity data were analyzed by the Moynihan formulation with a Kohlrausch-Williams-W atts relaxation function. We found that the confinement of a-Se into t he restricted pores in zeolites leads to an increase in the glass tran sition temperature, a decrease in the activation energy, and a decreas e in the nonexponentiality, beta. These results suggest that the therm okinetic dimension of the structural relaxation of Se becomes lower ow ing to the absence of inter-cluster (ring or chain) interaction due to the geometrical restriction in zeolites. These observations are compa red with the results observed when the network dimension of bulk a-Se is increased by the doping of three-coordinated As atoms up to 10 at.% . (C) 1998 Elsevier Science B.V. All rights reserved.