Chemical synthesis of micro-nano structure PbBi2S4 under different pressures with the aid of EDTA-2Na

The homologous Pb m Bi 2n X m+3n (X = S, Se, Te) is expected as solar cells or thermoelectric materials. Herein, stable phases of ternary PbBi 2 S 4 microspheres were successfully synthesized by two solution-phase-methods assisting with EDTA-2Na in aqueous media, namely traditional chemical reaction under atmospheric pressure and hydrothermal method under high pressure. Field-emission scanning electron microscopy and X-ray diffraction were used to characterize and determine the morphology and structure of the product. EDTA-2Na plays critical roles in the crystallization process of uniform PbBi 2 S 4 microspheres. A mechanistic model is proposed to account for these experimental findings. Furthermore, the optical band gaps of PbBi 2 S 4 were investigated as well.