Structural, dielectric and optical properties of transparent glasses and glass-ceramics of SrBi2B2O7

Optically clear glasses of SrBi2B2O7 (SBBO) were fabricated via the conventional melt-quenching technique. The amorphous nature of the as-quenched samples of this compound was confirmed by X-ray powder diffraction (XRD) studies. Its glassy nature was established by differential scanning calorimetry (DSC). However, the optical microscopy revealed the presence of isolated hexagonal shaped crystallites especially at the edges of the as-quenched glasses. The glass plates that were heat-treated around the onset of the glass transition temperature (670 K) for 12 h yielded transparent (similar to 60% transmission) glass-ceramics of SrBi2B2O7 (SBBO) with well defined microstructure. These were found to be textured associated with an orientation factor of about 0.77 (77%). The optical transmission studies carried out in the 100-1200 nm wavelength range confirmed both the as-quenched and heat-treated samples to be transparent from 400 to 1200 nm. The dielectric properties of the as-quenched as well as the heattreated (670 K/12 h) samples were studied as a function of frequency (100 Hz-10 MHz) at various temperatures (303-873 K). The dielectric dispersion at higher temperatures in the as-quenched glass was rationalized using Jonscher's dielectric dispersion relations. The prefactor A(T) and the exponent n(T) in the Jonscher's expression were found to be maximum and minimum respectively around the crystallization temperature (T) of the as-quenched SBBO glasses. (c) 2008 Elsevier B.V. All rights reserved.