Phase and morphology evolution of bismuth ferrites via hydrothermal reaction route

Phase-controlled synthesis of bismuth ferrites has been achieved via hydrothermal route by adjusting the KOH concentration. The as-prepared powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. The particle morphologies of the as-prepared powders evolve from nanoflakes, to self-assembled particles, and microparticles when the concentration of KOH was changed from 1.5 M, 2.5 M, to 3.5 M, and 5 M. Correspondingly, the main phase of the samples changed from orthorhombic Bi2Fe4O9, both Bi2Fe4O9 and BiFeO3, to pure rhombohedral BiFeO3. On the basis of these experiments, the phase formation and morphology evolution mechanism of the samples are discussed. Furthermore, the photocatalytic activity of the as-prepared samples was investigated by the photo-degradation of rhodamine-B solution.

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► Phase-controlled synthesis of Bi2Fe4O9 and BiFeO3 were realized by a facial hydrothermal route.
► KOH plays an important role in the phase formation and morphology evolution of the products.
► The layered structure feature and the differential affinity lead to the Bi2Fe4O9 nanoflakes.
► Pure BiFeO3 perovskite powders are of dense microparticles.