Synthesis of Pure Bi12SiO20 Powder by Molten Salt Method

Pure Bi12SiO20 powder was successfully prepared by a molten salt method using Bi2O3 and SiO2 as raw materials and using KCl-K2CO3 as flux at 635°C with the heating rate of 5°Cmin-1. The phase composition and microstructure of these products were analyzed by X-ray diffraction and scanning electron microscopy, and the effects of the processing parameters, such as the ratio of Bi2O3/SiO2, calciniation temperature, isothermal time and relative amount of salt, on the composition and particle size were investigated. The results indicated that regardless of changing the ratio of Bi2O3/SiO2, calciniation temperature, isothermal time or relative amount of salt the reaction only yielded Bi12SiO20 without Bi2SiO5 and Bi4Si3O12. Henceforth, KCl-K2CO3 molten salts may be considered as an ideal reaction medium to synthesize pure phase of Bi12SiO20. The particle size of Bi12SiO20 phase can be determined by changing the temperature, isothermal time and relative amount of salt.