Evolution and characterization of fluorite-like nano-$SrBi_2Nb_2O_9$ phase in the $SrO-Bi_2O_3-Nb_2O_5-Li_2B_4O_7$ glass system

Abstract

Transparent glasses of various compositions in the system $(100−x)Li_2B_4O_7 - x(SrO-Bi_2O_3-Nb_2O_5)$ (where x=10, 20, 30, 40, 50 and 60, in molar ratio) were fabricated via splat quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses. X-ray powder diffraction (XRD) and transmission electron microscopic studies confirmed the amorphous nature of the as-quenched and crystallinity in the heat-treated samples. Fluorite phase formation prior to the perovskite $SrBi_2Nb_2O_9$ phase was analyzed by both the XRD and high-resolution transmission electron microscopy. Dielectric and the optical properties (transmission, optical band gap and Urbach energy) of these samples have been found to be compositional dependent. Refractive index was measured and compared with the values predicted by Wemple–Didomemenico and Gladstone–Dale relations. The glass nanocomposites comprising nanometer-sized crystallites of fluorite phase were found to be nonlinear optic active