Dielectric anomaly in strontium borate–bismuth vanadate glass nanocomposite

Abstract

Transparent glass nanocomposites in the pseudo binary system (100− x) SrB 4O 7 (SBO)– x Bi 2VO 5.5 (BiV) (0≤ x≤70) were prepared by the splat quenching technique. The nano-crystallization of bismuth vanadate (BiV) in 50 SBO–50 BiV (in mol%) glass composite has been demonstrated. These were characterized for their structural, thermal and dielectric properties. As-quenched composites under study have been confirmed to be amorphous by X-ray powder diffraction (XRD) studies. The glass transition temperature ( T g) and crystallization temperatures ( T cr) were determined using differential thermal analyses (DTA). High resolution transmission electron microscopic (HRTEM) studies carried out on heat-treated samples reveal the presence of spherical nanosize crystallites of Bi 2VO 5.5 (BiV) dispersed in the glassy matrix of SrB 4O 7 (SBO). The dielectric constant (ϵ r) and the dielectric loss ( D) measurements were carried out on the as-quenched and heat-treated glass nanocomposite samples in the frequency range 100 Hz–10 MHz. The as-quenched and the heat-treated at two different temperatures (720 and 820 K) samples exhibited broad dielectric anomalies in the vicinity of the ferroelectric-to-paraelectric transition temperature 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.