The formation mechanism of 3BaO center dot 2CoO center dot 12Fe(2)O(3) (CO(2)Z), 2BaO center dot 2CoO center dot 6Fe(2)O(3) (CO2Y) and BaO center dot 6Fe(2)O(3) (BaM) powders were prepared using chemical coprecipitation methods in this study using X-ray diffraction (XRD), thermo-gravimetry (TG), differential thermal analysis (DTA) and Fourier transform infrared spectroscopy (FTIR). It was found that the BaM phase was formed directly through the reaction of the preceding epsilon-Fe2O3 and amorphous BaCO3 for BaM precursor. For the Co-2 Y precursor, the intermediate phase, BaM, was obtained through the reaction of the earlier formed BaFe2O4 and alpha-Fe2O3. The Co2Y phase was obtained through a BaM and BaFe2O4 reaction. However, for the Co(2)Z precursors, the BaM phase was obtained directly from the BaCo3 and amorphous iron hydroxide reaction, with no alpha-Fe2O3 and BaFe2O4 formed as intermediates. Co(2)Z phase was obtained through the reaction of the two previous formed BaM and Co2Y phases. (c) 2007 Elsevier B.V. All rights reserved.