Dielectric properties and conductivity enhancement on heat treatment of bismuth silicate glasses containing TiO2

The frequency and temperature dependent conductivity measurements for heat treated titanium bismuth silicate glasses of composition 5TiO(2)center dot(95-x)Bi2O3 center dot xSiO(2) (x = 30, 40 and 50 mol%) have been carried out by using impedance spectroscopy in the frequency range from 20 Hz to 1 MHz and temperature range from 210 to 360 degrees C. An enhancement in conductivity of about 10(1)-10(2) order is obtained in heat treated sample as compared to parent glass. In heat treated glass samples conductivity increases as the concentration of bismuth oxide increases. The absence of maxima in the dielectric permittivity (epsilon') spectra indicates the non-ferroelectric behavior of the samples. The loss factor (tan delta) is associated with the losses by conduction and it decreases with decrease in bismuth oxide. The effect of temperature on scaling of dielectric modulus indicates that the conductivity relaxation mechanism is temperature independent. The relaxation observed for the M ''(omega) or Z ''(omega) functions is correlated to both localized and long range conduction. The overlapping of the M ''(omega) and Z ''(omega) peaks at a given temperature suggests the same activation energy and existence of a single carrier that are related to the same relaxation process. (C) 2009 Elsevier B.V. All rights reserved.