CRYSTALLIZATION KINETICS OF THE Se80Te15Sb5 GLASS

Bulk Se80Te15Sb5 glass was prepared using the melt-quench technique. Differential thermal analysis (DTA) curves measured at different heat rates (5 K/min <=alpha <= 40 K/min) and X-ray diffractograms (XRD) are used to characterize the as-quenched glass. The normalized function z(x) has been used as a criterion check whether the JMA model can be orcan not be applied for the isochronal crystallization kinetics. The z(x) function attains its maximum limit when x(m) lies in the 0.36. <= x(m)<= 0.46 range. This range of x(m) confirms that the JMA model can not be applied for the isochronal crystallization kinetics of the investigated alloy. The Avrami exponent (n) and the activation energy for crystallization (E-c) of the Se80Te15Sb5 composition are equal 3 and 71.2 +/- 0.6 kJ/mol, respectively. The n. value indicates that only one crystallization (bulk) mechanism can be responsible for the amorphous-crystalline transformations inside the studied glass. Comparing the present isochronal kinetics with those previously reported for the binary Se80Te20 glass, implies that inserting 5 at. % of Sb on the expense of Te atoms decreases the E-c-value from 105 kJ/mol to 71.2 kJ/mol and increases the Avrami exponent from n =2 up to n =3. The latter n. value means that the mechanism of volume nucleation with two dimensional growth is responsible for the amorphous-crystalline transformations inside the investigated glass.