SYNTHESIS OF BARIUM HEXAFERRITE BY THE OXIDATION OF A METALLIC BARIUM-IRON PRECURSOR

Tapes of the hard magnetic ferrite, BaFe12O19, mere synthesized by the oxidation of metallic barium and iron precursors. Milled mixtures of barium flakes and iron powder (Ba:Fe atomic ratio = 1:12) mere sealed within fugitive silver tubes and then compacted and formed into tapes by rolling at room temperature. Oxidation and postoxidation heat treat ments mere conducted over the temperature range 300 degrees-1250 degre es C (the silver mas removed after heat treatment at 900 degrees C). P hase-pure BaFe12O19 tapes mere produced after heat treatments at peak temperatures of greater than or equal to 1080 degrees C. Such tapes ex hibited room-temperature magnetization values of greater than or equal to 65.0 emu/g in an applied field of 16.5 kOe (1.32 x 10(6) A/m). A c oercivity of 3.44 kOe (2.75 x 10(5) A/m) was achieved in a fine-graine d (submicrometer) BaFe12O19 tape that had been annealed for 24 h at a peak temperature of 1080 degrees C.