Dielectric anomaly in strontium borate-bismuth vanadate glass nanocomposite

Transparent glass nanocomposites in the pseudo binary system (100 - x) SrB4 O7 (SBO)-x Bi2VO5.5 (BiV) (0 less than or equal to n less than or equal to 70) were prepared by the splat quenching technique. The nano-crystallizatio n of bismuth vanadate (BiV) in 50 SBO-50 BiV (in mol%) glass composite has been demonstrated. These were characterized for their structural, thermal a nd dielectric properties. As-quenched composites under study have been conf irmed to be amorphous by X-ray powder diffraction (XRD) studies. The glass transition temperature (T-g) and crystallization temperatures (T-er) were d etermined using differential thermal analyses (DTA), High resolution transm ission electron microscopic (HRTEM) studies carried out on heat-treated sam ples reveal the presence of spherical nanosize crystallites of Bi2VO5.5 (Bi V) dispersed in the glassy matrix of SrB4O7 (SSO). The dielectric constant (epsilon (r)) and the dielectric loss (D) measurements were carried out on the as-quenched and heat-treated glass nanocomposite samples in the frequen cy range 100 Hz-10 MHz. The as-quenched and the heat-treated at two differe nt temperatures (720 and 820 K) samples exhibited broad dielectric anomalie s in the vicinity of the ferroelectric-to-paraelectric transition temperatu re of the parent BiV ceramics. The Curie-Weiss law was found to be valid at a temperature above the transition temperature, establishing the diffused nature of the transition. (C) 2001 Elsevier Science Ltd. All rights reserve d.