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.