Molten salt synthesis and luminescence properties of Bi₄Si₃O₁₂ powders

In this paper, Bismuth silicate (Bi₄Si₃O₁₂, BSO) powders were prepared by reaction in molten salts (NaCl and KCl) using Bi₂O₃ and SiO₂ powders as raw materials. The effects of salt contents and excessive contents of Bi₂O₃ and SiO₂ were characterized by X-ray diffraction and scanning electron microscopy. The properties of Bi₄Si₃O₁₂ powders were analyzed via fluorescence spectroscopy. Forming mechanism of platelets was discussed. The experimental results suggest that Bi₄Si₃O₁₂ powders are produced at 780 °C for 4 h with 40 wt% salts and 5 wt% excessive content of Bi₂O₃. The peaks of excitation spectrum and emission spectrum for BSO powders are separately located at 266 and 457.6 nm. Compared with crystal materials, the excitation spectrum and emission spectrum of Bi₄Si₃O₁₂ powders indicate blue shift. Interface reacting mechanism can be used to explain the coarsening process of bismuth silicate platelets produced in molten salt synthesis. In addition, dissolution–precipitation mechanism also plays an important role in the synthesis of bismuth silicate platelets.