Ternary vanadium oxide glasses in the system ${\mathrm{V}}_2{\mathrm{O}}_5{-\mathrm{C}\mathrm{o}\mathrm{O}-\mathrm{T}\mathrm{e}\mathrm{O}}_2$ are fabricated by press quenching of glass melts, and dc conductivities (σ) are investigated at temperatures from 330 to 475 K for different glass compositions. From the study of the phase diagram, the glass formation region is found to be in the range of ${\mathrm{V}}_2{\mathrm{O}}_5=0\mathrm{}–85\mathrm{mol}\%,$ $\mathrm{CoO}=0\mathrm{}–35\mathrm{mol}\%,$ and ${\mathrm{TeO}}_2=25\mathrm{}–100\mathrm{mol}\%.\mathrm{}$ These glasses contain microcrystalline clusters dispersed in the glass matrix. In the high-temperature regime above ${\Theta }_D/2\mathrm{}$ (${\Theta }_D$ is the Debye temperature), the small polaron hopping model is found to be applicable. In the low temperature (below ${\Theta }_D/2)$ regime, however, both Mott’s variable-range hopping and the Greaves’ intermediate range hopping models are found to be not applicable. The most probable transport for the entire range of temperature and compositions is concluded to be due to multiphonon tunneling of large polarons between the microclusters, supporting the model proposed by Shimakawa.

• Received 20 August 1998

DOI:https://doi.org/10.1103/PhysRevB.60.3230