Frequency dependent electrical conductivity and dielectric relaxation behavior in amorphous (90V 2O 5–10Bi 2O 3) oxide semiconductors doped with SrTiO 3

Abstract

We report on the experimental results of frequency dependent a.c. conductivity and dielectric constant of SrTiO 3 doped 90V 2O 5–10Bi 2O 3 semiconducting oxide glasses for wide ranges of frequency (500–10 4 Hz) and temperature (80–400 K). These glasses show very large dielectric constants (10 2–10 4) compared with that of the pure base glass (≈10 2) without SrTiO 3 and exhibit Debye-type dielectric relaxation behavior. The increase in dielectric constant is considered to be due to the formation of microcrystals of SrTiO 3 and TiO 2 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 V 2O 5–Bi 2O 3 glasses, correlated barrier hopping conduction mechanism is valid. This is due to the change of glass network structure caused by doping base glass with SrTiO 3. The power law behavior ( σ ac= A( ω s) 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).