Structural and dielectric characteristics of strontium tetraborate-bismuth vanadate glass-ceramics

Glasses of strontium tetraborate, containing up to 50 mole-percent bismuth vanadate [(1−x)SBO-xBiV (x = 0 to 0.50)], were prepared by splat quenching method. The glassy nature of these samples was confirmed by differential thermal analysis (DTA). The glass transition temperature (Tg) and the crystallization temperature (Tcr) of the glasses decrease with increase in bismuth vanadate, Bi2VO5.5 (BiV) content. High resolution transmission electron microscopic studies reveal the presence of spherical particles of amorphous BiV (less than 10 nm in size) dispersed in the glassy matrix of strontium tetraborate, SrB4O7 (SBO). The glasses of the compositions x = 0.25 to 0.50, on annealing at 500 °C (Tg) gave rise to crystalline BiV phase. Physical properties such as density, dielectric and optical transmission of these SBO:BiV glass-ceramics have been studied. The dielectric constant (ϵr) of these glass-ceramics increases with increasing BiV content. The measured ϵr values are found to be in good agreement with those predicted by the logarithmic mixture rule.