Formation mechanism of 3BaO centre dot 2CoO centre dot 12F_2O_3 powder synthesized using chemical coprecipitation

摘要

In this study, the formation mechanism of 3BaO centre dot 2CoO centre dot 12F_2O_3 (Co_2Z) 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 BaFe_(12)O_(19) (BaM) phase was obtained directly from the BaCO_3 and amorphous iron hydroxide reaction, with no alpha-Fe_2O_3 and BaFe_2O_4 formed as intermediates. The BaM and Ba_2Co_2Fe_(12)O_(22) (Co_2Y) phases coexisted in the calcined sample as the temperatures were <= 1000 deg C. The BaM constituents then diffused into the lattice of Co_2 Y to form Co_2Y* having a Co_2 Y phase crystal structure and Co_2Z chemical composition of at 1100 degC. The single Co_2Z phase was obtained through nucleation and growth from the Co_Y and Co_2Y* matrix at 1200 deg C.