AC CONDUCTIVITY OF SB2O3-P2O5 GLASSES

ac resistivity has been measured for glasses in the system (Sb2O3)x (P2O5)(1-x) with 0.03 < x < 0. 2 over a frequency range 2-100 kHz for temperatures varying from 100 to 350 K. The resistivity shows a frequency dependence given by rho(omega) is-proportional-to omega-s with s having values in the range 0.8-0.95. The conductivity in these glasses arises due to the presence of Sb3+ and Sb5+ ions. A correlated-barrier-hopping model of bipolarons predicts hopping-length values which are inconsistent with the overall concentration of antimony ions in the glasses concerned. The overlapping-large-polaron model, on the other hand, gives the correct variation of tunneling distance with glass composition.