ac resistivity has been measured for glasses in the system (${\mathrm{Sb}}_2$${\mathrm{O}}_3$${)}_{\mathit{x}}$(${\mathrm{P}}_2$${\mathrm{O}}_5$${)}_{\left(1\mathrm{}\mathrm{-}\mathit{x}\right)}$ 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 ρ(ω)∝${\mathrm{\omega }}^{\mathrm{-}\mathit{s}}$ with s having values in the range 0.8–0.95. The conductivity in these glasses arises due to the presence of ${\mathrm{Sb}}^{3+}$ and ${\mathrm{Sb}}^{5+}$ 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.

• Received 1 October 1992

DOI:https://doi.org/10.1103/PhysRevB.47.16242