# Structural and dielectric characteristics of 0.50 $Bi_2O_3$ - 0.25 $V_2O_5$ - 0.25 $SrB_4O_7$ glass-ceramic.

Shankar, MV and Varma, KBR (1996) Structural and dielectric characteristics of 0.50 $Bi_2O_3$ - 0.25 $V_2O_5$ - 0.25 $SrB_4O_7$ glass-ceramic. In: Tenth IEEE International Symposium on Applications of Ferroelectrics, 1996. ISAF '96, 18-21 August, East Brunswick,USA, Vol.2, 817 -820.

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Novel 0.50 $Bi_2O_3$-0.25 $V_2O_5$ -0.25 $SrB_4O_7$ glasses have been prepared via a conventional splat-quenching technique. Differential thermal analysis (DTA) carried out on the as-quenched samples confirms their glassy nature and shows a prominent exothermic peak at 400°C. The X-ray powder diffraction (XRD) pattern of the heat treated sample could be indexed to an orthorhombic ferroelectric $Bi_2VO_{5.5}$ phase with the lattice parameters a=5.543, b=5.615 and c=15.321 A. The presence of nano-crystallites of bismuth vanadate, $Bi_2VO_{5.5}$ (BiV) dispersed in the glassy matrix of strontium tetraborate, $SrB_4O_7$ (SBO) is confirmed in the heat treated (at 400°C for 12 h) samples, by high resolution transmission electron microscopy (HRTEM). The dielectric constant $(\epsilon_r)$, measured as a function of temperature, exhibits an anomaly around the transition temperature of the parent crystalline BiV. The $\epsilon_r$ of the glass-ceramic at 300K is comparable with that predicted by Maxwell's model and logarithmic mixture rule.