| 摘要 |
A process for preparing a microcrystalline hexagonal barium ferrite powder having the general formula BaO.n[(Fe1-mMm)2O3], in which M is at least one substituent element selected from the group comprising Co, Ti, Ni, Mn, Cu, Zn, In, Ge and Nb, m is from 0 to 0.2 and n is from 4.5 to 6, comprises the preparation of an aqueous alkaline dispersion which contains joint precipitates (coprecipitates) of the hydroxides of barium ions, iron(III) ions and optionally of the ions of the substituent elements M in a quantity ratio ("molar ratio") corresponding to the general formula of the barium ferrite, the dispersion having a pH of not less than approximately 12, heating the dispersion to temperatures of from approximately 150 DEG C to 300 DEG C in order to convert the coprecipitate into a precursor of the barium ferrite, calcining the precursor together with a water-soluble barium halide at temperatures of from approximately 700 DEG C to 1000 DEG C and washing the calcined product with water to remove the barium halide from the barium ferrite produced. The barium ferrite thus obtained is a microcrystalline powder composed of well-defined hexagonal platelets having an essentially uniform particle size in the range of from approximately 0.05 mu m to approximately 0.5 mu m, as a result of which the barium ferrite is particularly suitable for producing vertically recording magnetic recording media. <IMAGE>
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