Preparation of BiFeO₃ nanopowders using acetylacetone as stabilizer

The present investigation reports on the preparation of BiFeO₃ nanopowders by a sol-gel method using acetylacetone as a stabilizer. Single-phase BiFeO₃ nanopowders without any impurity or amorphous phases were obtained when the precursor was thermal treated at temperatures as low as 400 °C for 2 h. Acetylacetone (acac) plays an important role on lowering the formation temperature of pure phase BiFeO₃ nanopowders. It is found that Bi/acac molar ratio of 1/30 was favorable for a stable sol and for the lowest crystallization temperature of pure BiFeO₃ nanopowders. X-ray diffraction and Fourier transform infrared spectroscopy revealed that thermally induced crystallization process of BiFeO₃ nanopowders from Bi-Fe polymeric precursor. When the thermal treated temperature was below 200 °C, only amorphous phase existed. With the temperature increasing up to 300 °C, crystallized phase, carbonate, were detected. After annealed at 400 °C, Bi-Fe precursor totally changed to rhombohedral BiFeO₃ nanopowders. Scanning electron microscopy characterized morphologies of BiFeO₃ nanopowders calcined at 400 °C and 500 °C. The ferroelectric transition of BiFeO₃ nanopowders at 827 °C has been detected by differential thermal analysis.