PEG-controlled thickness of BiFeO 3 crystallites in microwave hydrothermal synthesis

Abstract Single-phase BiFeO3 powder consisting of ball-like aggregates resembling nanoflowers with petals, the thickness of which can be controlled by polyethylene glycol addition, was synthesized by microwave hydrothermal method. The powder was characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Scanning electron microscopy studies revealed that the mean thickness of petals is equal to 78 nm for the synthesis without PEG2000 and increases to 524 nm when the concentration of the PEG2000 reaches 10 wt.%. Variation in the petal thickness was found to enhance the magnetic properties of the nanopowder. The room temperature remnant magnetization of BiFeO3 with mean thickness of 524 nm was found to be comparable to the bulk value (0.006 Am2 kg−1), whereas for powder with thinnest petals it increases considerably to 0.15 Am2 kg−1. The changes in the magnetic properties were related both to the size effect and to uncompensated surface spins of Fe3+/Fe2+ ions.