Preparation and Properties of BaBiBO4–SiO2 Glasses

Abstract

Glasses in the new system (100−x) BaBiBO4–xSiO2 where x=10–50 (mol%) were prepared by the melt‐quench technique. The density of the glasses increases with an increase in BaBiBO4 content because of its higher molecular mass. Tg, Td, and Ts decrease while coefficient of thermal expansion increases with the increase in BaBiBO4 content. Vis‐NIR spectra reveal that with increasing melting temperature transmission of the glasses decreases due to auto thermal reduction of Bi3+ to Bi0 as confirmed by transmission electron microscopy and selected area electron diffraction analyses. Fourier transform infrared reflection spectroscopic spectra of the glasses indicate the formation of BiO6, BO3, and BO4 structural units. Ferroelectric BaBiBO4 crystalline phase is obtained from these glasses by controlled heat treatment at 580°C. X‐ray diffraction analysis reveals its 45–66 nm crystallite size range. Whereas, the field‐emission scanning electron microscopy images show the formation of polycrystalline spherical grains of 89–194 nm along with single‐crystalline microrods of average diameter of 0.5–1.5 μm. Dielectric constant of the glasses increases with increase in BaBiBO4 content, which is attributed to the combined effects of high polarization and ionic refraction of both Bi3+ and Ba2+ ions. It is shown here that BaBiBO4–SiO2 is a promising glass system for the synthesis of glass–ceramics of novel BaBiBO4 nonlinear optical crystal.