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AC electrical properties of sol-gel-derived glasses in the Sb2O3-SiO2 system

Measurements of AC resistivity have been carried out on sol-gel-derived glasses in the system Sb2O3-(1-x)SiO2 with x=0.07 and 0.23 for frequencies from 2 kHz to 100 kHz in the temperature range 80-400 K. The AC resistivities show a sharp minimum at around 310 K. This is ascribed to a reduction in the ratio of (Sb5+) to (Sb3+) in these glasses as a function of temperature. Another minimum is observed at temperatures of 178 K and 209 K for glasses 1 and 2, respectively. The frequency exponent s for AC resistivity also shows a maximum as a function of temperature at around these temperatures. The correlated barrier hopping model has been used to explain the trend of s in the temperature range 170-290 K whereas the overlapping long polaron tunnelling mechanism appears to give the correct variation in the temperature range 100-170 K. Both the glasses show anomalously large values of dielectric constant in the range 1000-6000 at a frequency of 2 kHz at around 310 K. Analyses of all these data indicate that there are antimony-rich and antimony-deficient layers present in this glass system.