Gs. Murugan et Kbr. Varma, Structural, dielectric and optical properties of lithium borate-bismuth tungstate glass-ceramics, MATER RES B, 34(14-15), 1999, pp. 2201-2213
Glasses in the system (1 - x)Li2B4O7-xBi(2)WO(6) (0.1 less than or equal to
x less than or equal to 0.35) were prepared by splat quenching technique.
Powder X-ray diffraction (XRD) and differential thermal analysis (DTA) were
employed to characterize the as-quenched glasses. High-resolution transmis
sion electron microscopy (HR TEM) revealed the presence of fine, nearly sph
erical crystallites of Bi2WO6 varying from 1.5 to 20 nm in size, depending
on x in the as-quenched glasses. The glasses (corresponding to x = 0.3) hea
t-treated at 723 K for 6 h gave rise to a clear crystalline phase of Bi2WO6
embedded in the Li2B4O7 glass matrix, as observed by X-ray studies. The di
electric constants of the as-quenched glasses as well as the glass-ceramics
decreased with increase in frequency (40Hz-100 kHz) at 300 K, and the valu
e obtained for the glass-ceramic (x = 0.2) is in agreement with the values
predicted using Maxwell's model and the logarithmic mixture rule. The diele
ctric constants for both the as-quenched glass and the glass-ceramic increa
sed with increase in temperature (300 - 873 K) and exhibited anomalies clos
e to the onset of the crystallization temperature of the host glass matrix.
The optical transmission properties:of these glass-ceramics were found to
be compositional dependant. (C) 2000 Elsevier Science Ltd.