Solvent-free synthesis of hexagonal barium ferrite (BaFe₁₂O₁₉) particles

M-type barium ferrite (BaFe₁₂O₁₉) particles, from a mixture of barium nitrate, ferric nitrate, cetyltrimethylammonium bromide (CTAB), and ammonium carbonate, have been successfully prepared through simple grinding and calcination in the absence of any solvent. The products are characterized by X-ray diffraction, scanning electron microscope, and vibrating sample magnetometer, whose results indicate that they have well crystalline phase of BaFe₁₂O₁₉, typically hexagonal platelet-like structure, large saturation magnetization, even submicrometer particle size under the optimum condition. Meanwhile, the effects of Fe/Ba ratio, CTAB, and ammonium carbonate are also investigated. It has been found that the proper Fe/Ba ratio could suppress the intermediate phase such as α-Fe₂O₃ and BaFe₂O₄, CTAB could promote the crystallinity of BaFe₁₂O₁₉ and produce hexagonal crystal structure, and ammonium carbonate was the key for forming BaFe₁₂O₁₉ phase. This facile method may be helpful for the preparation of other multicomponent functional materials.