Synthesis of Stable Bismuth Silicate with Sillenite Structure in the Na2O–Bi2O3–SiO2 System

Abstract

A combined method for synthesizing a highly dispersed (0.8–2.5 μm) hydrophobic Na₂O–Bi₂O₃–SiO₂ powder (NBS powder) based on solutions of sodium methyl siliconate and bismuth nitrate is studied. The powder is synthesized at a reduced temperature (100°C). The microstructure and the phase composition of the resulting compounds in the Na₂O–Bi₂O₃–SiO₂ system at different processing temperatures are investigated. The structural phase transformations in the mineral phases of NBS powder are revealed in the temperature range of 100–500°C. The metastable bismuth silicate Bi₂SiO₅ at 400°C is transformed into stable sillenite with composition Bi₁₂SiO₂0 having a cubic crystal structure (a = 10.1050 Å). The synthesized NBS powder can be used as a filler to fabricate highly effective constructional radiation-shielding polymer composites with tailored properties.