Synthesis of Barium Hexaferrite by the Oxidation of a Metallic Barium–Iron Precursor

Tapes of the hard magnetic ferrite, BaFe 12 O 19 , were synthesized by the oxidation of metallic barium and iron precursors. Milled mixtures of barium flakes and iron powder (Ba:Fe atomic ratio = 1:12) were sealed within fugitive silver tubes and then compacted and formed into tapes by rolling at room temperature. Oxidation and postoxidation heat treatments were conducted over the temperature range 300°–1250°C (the silver was removed after heat treatment at 900°C). Phase‐pure BaFe 12 O 19 tapes were produced after heat treatments at peak temperatures of is greater than or equal to $1080°C. Such tapes exhibited room‐temperature magnetization values of is greater than or equal to $65.0 emu/g in an applied field of 16.5 kOe (1.32 × 10 6 A/m). A coercivity of 3.44 kOe (2.75 × 10 5 A/m) was achieved in a fine‐grained (submicrometer) BaFe 12 O 19 tape that had been annealed for 24 h at a peak temperature of 1080°C.