Abstract: A modified polyacrylamide gel method was used to fabricate BiFeO₃ nanoparticles. Thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffraction were used to investigate the thermal decomposition process of xerogel and the formation of BiFeO₃ phase. It is demonstrated that high phase purity BiFeO₃ nanoparticles can be prepared at a calcination temperature of 600 °C. Bisacrylamide, which acts as a crosslinking agent, plays an important role in tailoring the grain size of the resulting BiFeO₃ nanoparticles. With increasing bisacrylamide content, the grain size decreases gradually. As a result, a series of BiFeO₃ samples with average grain size of 52–110 nm have been prepared. Scanning electron microscopy reveals that the prepared BiFeO₃ nanoparticles are regularly spherical in shape with uniform particle size distribution. The photocatalytic activity of BiFeO₃ nanoparticles was investigated by the degradation of methyl orange (MO). The experimental results reveal that they exhibit a pronounced photocatalytic activity for the MO decomposition under ultraviolet and visible-light irradiation. With decrease in particle size, the reactive activity increases. The optimum conditions for the photocatalytic decolorization were determined to be initial MO concentration of ~10 mg/L and catalyst amount of ~2.5 g/L.

Key words: bismuth ferrite, nanoparticle, polyacrylamide gel method, grain-size tailoring, photocatalysis, methyl orange