Effect of bismuth on the electrical properties of a-Ge20Se80 glasses

The present paper reports the effect of Bi impurity (low similar to 4 at. % and high similar to 10 at. %) on the ac conductivitey (sigma(ac)) of a-Ge20Se80 glass. Frequency dependent ac conductance and capacitance of the samples over a frequency range of 100 Hz to 50 kHz has been taken in the temperature range of 268 K to 360 K. At frequency 2 kHz and temperature 298 K, the value of ac conductivity (sigma(ac)) decreases at low concentration of Bi (4 at. %). However, the value of sigma(ac) increases at higher concentration of Bi (10 at. %). The ac conductivity is proportional to omega(s) for undoped and doped samples. The value of frequency exponent (s) decreases as the temperature increases. The dielectric constant (k) slightly decreases at low Bi concentration and increases at higher Bi concentration. These results have been explained on the basis of some structural changes at low and higher concentration of Bi impurity.