Bismuth–iron-based precursor: preparation, phase composition, and two methods of thermal treatment

Bismuth ferrite (BiFeO(3)) is a promising Bi-based perovskite-type material, which is multiferroic due to the coexistence of anti-ferromagnetism and ferroelectricity. During the preparation of pure BiFeO(3) nanoparticles, however, the phase structures and species of bismuth–iron-based precursor (BFOH) were still unclear, and so related precursors were prepared. X-ray diffraction, Raman, Fourier transform infrared, and X-ray absorption near-edge structure techniques were used to probe the phase structure and species of the precursors. It was found that the precursor BFOH is composed of Bi(6)O(6)(NO(3))(4)(OH)(2)·2H(2)O, Bi(6)O(5)(NO(3))(5)(OH)(3)·3H(2)O, Fe(OH)(3), and α-Bi(2)O(3). Calcination treatment and hydrothermal synthesis were used to prepare the pure BiFeO(3) phase from the precursor BFOH. The calcination temperature was optimized as 400 °C for preparation of the pure BiFeO(3) phase. Meanwhile, hydrothermal conditions for the synthesis of the pure BiFeO(3) phase were also optimized as follows: the reaction solution was the mixture solution of Bi(NO(3))(3)·5H(2)O and Fe(NO(3))(3)·9H(2)O with cetyltrimethyl ammonium bromide (CTAB) as the surfactant and KOH as the mineralizer; the hydrothermal synthesis was performed at 180 °C for 48 h; the concentration of KOH should be at least 3 M; and the surfactant CTAB can be used to regulate the morphology of the as-prepared BiFeO(3) nanoparticles. From the point of view of the microstructure, BiFeO(3) nanoparticles prepared by calcination or hydrothermal methods have no notable differences. A formation mechanism from the precursor BFOH to the BiFeO(3) product is proposed. By providing an understanding of the precursors, this work is very helpful in the synthesis of bismuth–iron-based nanoparticles.