Influence of precursor Bi/Fe ion concentration on hydrothermal synthesis of BiFeO3 crystallites

In this study we investigated the effect of precursor Bi³⁺/Fe³⁺ ion concentration on the hydrothermal synthesis of BiFeO₃ crystallites. It is demonstrated that the phase-purity and morphology of the products is highly dependent on the metal ion concentration. Phase-pure BiFeO₃ crystals can be prepared at the Bi³⁺/Fe³⁺ ion concentration ranging from 0.025 to 0.0625 M. The samples prepared at n(Bi³⁺/Fe³⁺)=0.025, 0.0375, 0.05, and 0.0625 M, are composed, respectively, of cuboid-like particles (100–200 nm), regular spherical agglomerates (30–40 μm) made up of irregular grains with size about several hundred nanometers, irregular flower-like clusters formed from irregular grains of several hundred nanometers in size, and octahedron-shaped particles (500–600 nm). These samples have a similar bandgap energy of 2.20 eV and exhibit a typical antiferromagnetic behavior at room temperature.