Affiliation: | a Solid State Physics Department, Indian Association For the Cultivation of Science, Calcutta 700 032, India b Department of Applied Chemistry, Tokai University, Kitakaname, Kanagawa 259-12, Japan |
Abstract: | We report on the experimental results of frequency dependent a.c. conductivity and dielectric constant of SrTiO3 doped 90V2O5–10Bi2O3 semiconducting oxide glasses for wide ranges of frequency (500–104 Hz) and temperature (80–400 K). These glasses show very large dielectric constants (102–104) compared with that of the pure base glass (≈102) without SrTiO3 and exhibit Debye-type dielectric relaxation behavior. The increase in dielectric constant is considered to be due to the formation of microcrystals of SrTiO3 and TiO2 in the glass matrix. These glasses are n-type semiconductors as observed from the measurements of the thermoelectric power. Unlike many vanadate glasses, Long's overlapping large polaron tunnelling (OLPT) model is found to be most appropriate for fitting the experimental conductivity data, while for the undoped V2O5–Bi2O3 glasses, correlated barrier hopping conduction mechanism is valid. This is due to the change of glass network structure caused by doping base glass with SrTiO3. The power law behavior (σac=A(ωs) with s<1) is, however, followed by both the doped and undoped glassy systems. The model parameters calculated are reasonable and consistent with the change of concentrations (x). |