Synthesis of Bi2SiO5 powder by molten salt method

Abstract Pure Bi 2 SiO 5 powders were synthesized by molten salt method in NaCl–Na 2 SO 4 flux using Bi 2 O 3 and SiO 2 as raw materials. The results showed that the pure metastable state compound Bi 2 SiO 5 was obtained in NaCl–Na 2 SO 4 flux at 625 °C for 1 h, which was lower than that (generally 750 °C) of conventional solid state reaction. X-ray diffraction revealed that in the case of NaCl–Na 2 SO 4 molten salt, with increasing synthesis temperature (600 °C to 625 °C), stable state Bi 12 SiO 20 transformed into metastable state Bi 2 SiO 5 and with synthesis temperature increasing from 625 °C to 700 °C, metastable state Bi 2 SiO 5 transformed into stable state Bi 4 Si 3 O 12 gradually. Therefore, calcination temperature played a crucial role in the formation of Bi 2 SiO 5 powder. The field-emission scanning electron microscopy images disclosed that the Bi 2 SiO 5 samples showed nest like morphology, which was soft aggregation of Bi 2 SiO 5 nanosheets. Moreover, it also indicated that the mechanism of the process of molten salt synthesis was “dissolution–precipitation mechanism”.