Effects of Scaling Up on the Phase Evolution of Microcrystalline Bismuth Ferrite during Hydrothermal Process

Abstract

Bismuth ferrite (BiFeO₃) was synthesized using hydrothermal method in two different size autoclaves (100- and 200-mL capacities). By fixing conditions including filling factor, quantity of precursors, KOH concentration, reaction temperature, and duration time, the properties of the resulting products were compared. In this work, different analytical techniques were applied to identify the phase evolution and morphology of the samples such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). The results demonstrated that the crystalline phases and the particle sizes were different when the dimension of the autoclave was greatly changed. Considering the reaction temperature and the autoclave size, we suggested that the heat transfer from the autoclave into the solution might be delayed and it may be the reason why the Bi₂₅FeO₄₀ phase was mainly obtained when the samples were prepared at 160°C for 6 h in the 200-mL autoclave.