Effect of synthesis conditions on the preparation of BiFeO3 nanopowders using two different methods

Bismuth orthoferrite (BiFeO3) nanoparticles have been synthesized via the co-precipitation and the oxalate precursor methods. Effects of Bi source, annealing temperature, Bi/Fe molar ratio, oxalic acid ratio and Mn2+ ion on the crystal structure, crystallite size, microstructure and magnetic properties of the produced powders were systematically studied. The results revealed that bismuth oxychloride and iron oxide were formed using chlorides sources. A single phase of BiFeO3 was formed from as-made samples with Bi/Fe molar ratio 1.1 using nitrate sources and annealed at 500 and 600 degrees C for 2 h via the two pathways. The pure BiFeO3 phase appeared as spherical and pseudocubic-like structure using the co-precipitation and the oxalic acid precursor routes, respectively. A high saturation magnetization (3.94 emu/g) was achieved for powder formed from the oxalate precursor route with Bi/Fe molar ratio 1.0 annealed at 600 degrees C for 2 h as the result of the formation of Bi25FeO39. Moreover, Mn2+ ion addition affected BiFeO3 properties due to the formation of Bi2Fe2Mn2O10. Hence, the saturation magnetization and the coercive force of BiFeO3 were improved substantially by substitution of Mn2+ ions (BiFe1-XMnXO3, X = 0.1-0.2).