Preparation of finely divided barium ferrite of high coercivity

Claim 1

A process for the preparation of barium ferrite of the formula BaFe 12 Fe 19 which comprises: (a) mixing an aqueous solution of a barium compound selected from the group consisting of barium chloride, barium sulfate and barium carbonate with an aqueous solution or an iron(III) compound selected from the group consisting of iron(III) chloride and iron(III) sulfate; (b) reacting the mixture formed in step (a) with an aqueous sodium carbonate solution; (c) completely dehydrating the resulting mixture from step (b) which consists essentially of sparingly soluble barium compound and iron(III) carbonate in an aqueous sodium salt solution; (d) heating the dry salt mixture from step (c) at a temperature above 680° C. but below the melting point of the sodium salt present; and (e) leaching the resulting product with water to dissolve the sodium salt and to isolate the finely divided, platelet-like barium ferrite.