Morphology and optical absorption of Bi2Fe4O9 crystals via mineralizer-assisted hydrothermal synthesis

Abstract Submicron-sized Bi 2 Fe 4 O 9 crystals were successfully synthesized via the hydrothermal method, while micron-sized Bi 2 Fe 4 O 9 crystals with rod-like morphologies were obtained in the presence of the mineralizer KNO 3 . X-ray diffraction, scanning electron microscopy and transmission electron microscopy were employed to characterize the products. According to a series of time-dependent experiments, it was concluded that the likeliest formation mechanism for the microrods was the Ostwald ripening process. It was proposed that the blocking effect of NO 3 − contributed to the formation of the rod-like powders. Moreover, the optical absorption of the prepared Bi 2 Fe 4 O 9 crystals was measured using an UV–vis spectrophotometer, indicating that Bi 2 Fe 4 O 9 powders can be used as effective photocatalysts under visible light.