1982 Volume 90 Issue 1044 Pages 411-419
The glass formation region of the system was determined. Composition- and temperature-dependence of dc conductivity of the glasses were measured in the temperature range from 100°C to the temperature which was 10°-20°C below the glass transition temperature, Tg. Density, thermal expansivity, Tg and fraction of the reduced transition metal ion were measured. Conduction mechanism of the glass was discussed from the view point of the small polaron hopping theory by N. F. Mott. The adiabatic approximation, in which the tunnelling factor, α, was assumed to be nearly zero, was roughly applicable for these glasses within the errors of about one order of phonon frequencies, ν0, but the reasonable values of α and ν0 which agreed with other experimental results were not obtained. The activation energy was the predominant factor to determine the dependence of conductivity on the composition. The dc conductivity and the activation energy for conduction of the glasses containing less than about 10mol% of Fe2O3 depend on V2O5 content predominantly as in V2O5-P2O5 glasses. Fe2+ was not found by the measurement of Mossbauer spectra of these glasses. The contribution of Fe-ion pairs to conduction was concluded to be much less than V-ion pairs. The glasses containing more than about 20mol% of Fe2O3 had higher conductivity than V2O5-P2O5 glasses. Addition of Fe2O3, or substitution of V2O5 or P2O5 with more than 20mol% of Fe2O3 increased the conductivity and decreased the activation energy. Fe-ion seemed to contribute to the conduction together with V-ion. The observed conductivities of these glasses were much higher than the calculated values from the assumption for the adiabatic equation that the conduction path was composed of V-ion pairs or Fe-ion pairs independently. It was suggested that the hopping conduction between V- and Fe-ions could take place.
