Effect of Fe/Ba mole ratios and surface-active agents on the formation and magnetic properties of co-precipitated barium hexaferrite

Nanocrystalline barium hexaferrite (BaFe12O19) powders have been synthesized through the co-precipitation route. The produced ferrite precursors were obtained from aqueous mixtures of barium and ferric chlorides by co-precipitation of barium and iron ions using 5M sodium hydroxide solution at pH 10 in room temperature. These precursors were calcined at temperatures of 800-1200 deg C for constant 2h in a static air atmosphere. The effect of Fe3+/Ba2+ mole ratio and addition of surface-active agents during co-precipitation step on the crystal structure, morphology and magnetic properties of produced ferrite powders were studied. The results obtained showed that the single phase BaFe12O19 powders was achieved by decreasing the Fe3+/Ba2+ molar ratio from the stoichiometric value 12 to 8 and increasing the calcination temperature > =1000 deg C. In addition, the Fe3+/Ba2+ mole ratio of 8 and presence of surface-active agents promoted the formation of homogeneous nanopowders (ca. 113nm) of BaFe12O19 at a low temperature of 800 deg C with good saturation magnetization (50.02emu/g) and wide coercivities (642.4-4580Oe).