Formation mechanism of 3BaO·2CoO·12Fe₂O₃ powder synthesized using chemical coprecipitation

In this study, the formation mechanism of 3BaO·2CoO·12Fe₂O₃ (Co₂Z) ferrite obtained using the coprecipitation method was investigated using thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). It was found that the BaFe₁₂O₁₉ (BaM) phase was obtained directly from the BaCO₃ and amorphous iron hydroxide reaction, with no α-Fe₂O₃ and BaFe₂O₄ formed as intermediates. The BaM and Ba₂Co₂Fe₁₂O₂₂ (Co₂Y) phases coexisted in the calcined sample as the temperatures were ≦1000 °C. The BaM constituents then diffused into the lattice of Co₂Y to form Co₂Y^*, having a Co₂Y phase crystal structure and Co₂Z chemical composition of at 1100 °C. The single Co₂Z phase was obtained through nucleation and growth from the Co₂Y and Co₂Y^* matrix at 1200 °C.