The effects of mechanical activation in synthesizing ultrafine barium ferrite powders from co-precipitated precursors

Well dispersed and fine barium ferrite (BaFe12O19) powders have been successfully prepared by mechanically activating co-precipitated precursors, followed by calcination at 700 and 800 degrees C. When mechanically activated in a sodium chloride matrix for 20 hours, nanocrystallites of BaFe12O19, alpha-Fe2O3 and a spinel (gamma-Fe2O3) phase of < 10 nm in size were triggered in the co-precipitated precursor. Single phase barium ferrite platelets 50-100 nm in size were developed upon subsequent calcination at 800 degrees C for 1 hour. The resulting barium ferrite powder exhibits an intrinsic coercivity (H-i(c)) of 436.7 kA m(-1) and a saturation magnetization (M-s) of 67.8 A m(2) kg(-1). These magnetic properties compare favorably with those of the materials derived from conventional calcination of the co-precipitated precursor without prior mechanical activation, which led to very poor powder characteristics.