Structural and dielectric characteristics of 0.50 Bi/sub 2/O/sub 3/-0.25 V/sub 2/O/sub 5/-0.25 SrB/sub 4/O/sub 7/ glass-ceramic

Novel 0.50 Bi/sub 2/O/sub 3/-0.25 V/sub 2/O/sub 5/-0.25 SrB/sub 4/O/sub 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/spl deg/C. The X-ray powder diffraction (XRD) pattern of the heat treated sample could be indexed to an orthorhombic ferroelectric Bi/sub 2/VO/sub 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/sub 2/VO/sub 5.5/ (BiV) dispersed in the glassy matrix of strontium tetraborate, SrB/sub 4/O/sub 7/ (SBO) is confirmed in the heat treated (at 400/spl deg/C for 12 h) samples, by high resolution transmission electron microscopy (HRTEM). The dielectric constant (/spl epsiv//sub /spl tau//), measured as a function of temperature, exhibits an anomaly around the transition temperature of the parent crystalline BiV. The /spl epsiv//sub /spl tau// of the glass-ceramic at 300K is comparable with that predicted by Maxwell's model and logarithmic mixture rule.