FREQUENCY-DEPENDENT ELECTRICAL-CONDUCTIVITY AND DIELECTRIC-RELAXATIONBEHAVIOR IN AMORPHOUS (90V(2)O(5)-10BI(2)O(3)) OXIDE SEMICONDUCTORS DOPED WITH SRTIO3

We report on the experimental results of frequency dependent a.c. cond uctivity and dielectric constant of SrTiO3 doped 90V(2)O(5)-1OBi(2)O(3 ) semiconducting oxide glasses for wide ranges of frequency (500-10(4) Hz) and temperature (80-400 K). These glasses show very large dielect ric constants (10(2)-10(4)) compared with that of the pure base glass (approximate to 10(2)) without SrTiO, and exhibit Debye-type dielectri c relaxation behavior. The increase in dielectric constant is consider ed to be due to the formation of microcrystals of SrTiO3 and TiO2 in t he glass matrix. These glasses are n-type semiconductors as observed f rom 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 ho pping conduction mechanism is valid. This is due to the change of glas s network structure caused by doping base glass with SrTiO3. The power law behavior (sigma(ac) = A(w(s)) with s < 1) is, however, followed b y both the doped and undoped glassy systems. The model parameters calc ulated are reasonable and consistent with the change of concentrations (x). (C) 1997 Elsevier Science S.A.