Gs. Murugan et Kbr. Varma, Characterization of lithium borate-bismuth tungstate glasses and glass-ceramics by impedance spectroscopy, SOL ST ION, 139(1-2), 2001, pp. 105-112
Transparent glasses in the system (1-x)Li2B4O7-xBi(2)WO(6) (0 less than or
equal to x less than or equal to 0.35) were prepared via melt quenching tec
hnique. Differential thermal analysis was employed to characterize the as-q
uenched glasses. Glass-ceramics with high optical transparency were obtaine
d by controlled heat-treatment of the glasses at 720 K for 6 h. The amorpho
us nature of the as-quenched glass and crystallinity of glass-ceramics were
confirmed by X-ray powder diffraction studies. High resolution transmissio
n electron microscopy (HRTEM) shows the presence of nearly spherical nanocr
ystallites of Bi2WO6 in Li2B4O7 glass matrix. Capacitance and dielectric lo
ss measurements were carried out as a function of temperature (300-870 K) i
n the frequency range 100 Hz-40 MHz. Impedance spectroscopy employed to rat
ionalize the electrical behavior of glasses and glass-ceramics suggest the
coexistence of electronic and ionic conduction in these materials. The ther
mal activation energies for the electronic conduction and ionic conduction
were also estimated based on the Arrhenius plots. (C) 3001 Published by Els
evier Science B.V.