Effect of impurity (Sb and Ag) incorporation on the a.c. conductivity and dielectric properties of a-Se70Te30 glassy alloy

The effect of additives (Sb and Ag) on a.c. conductivity and dielectric properties of Se70Te30 glassy alloy at temperature range 300-350 K and frequency range 1 kHz-5 MHz has been studied. Experimental results indicate that a.c. conductivity and dielectric parameters depend on temperature, frequency and the impurity incorporated in Se-Te glassy system. The a.c. conductivity in the aforesaid frequency range is found to obey the ωs law. A strong dependence of a.c. conductivity and exponent s in the entire temperature and frequency range contradicts quantum-mechanical tunneling (QMT) model and can be interpreted in terms of the correlated barrier hopping (CBH) model. The temperature and frequency dependence of the dielectric parameters are also studied and it is found that the results agrees by the theory of hopping of charge carriers over potential barrier as suggested by Elliott in chalcogenide glasses. The change in the dielectric parameters with the opposite influence of the replacement of Te by Sb on the one hand, and by Ag, on the other hand is being correlated by the nature of covalent character of the studied composition and with the change in density of defect states.