| 摘要 |
PURPOSE:To prepare hexagonal ferrite magnetic powder having uniform particle size by forming coprecipitate from aq. soln. contg. Ba salt, etc. and Fe salt with alkali, treating the coprecipitate hydrothermally, and heat treating thereafter in aq. soln. of alkali. CONSTITUTION:Aq. soln. of alkali is added to an aq. soln. contg. Fe salt and at least one metal salt among Ba salt, Sr salt, and Pb salt. Obtd. coprecipitate is charged to an autoclave and treated hydrothermally at ca. 200-350 deg.C for 1-6hr to grow the hexagonal ferrite particles. Then, the ferrite particles, after it is dried, are dispersed in aq. alkali soln. of >=ca. 1mol/l alkali concn. and the fine particles are dissolved by heat-treating at >=ca. 150 deg.C while crystals of other particles are grown. By this process, hexagonal ferrite magnetic powder having narrow particle size distribution, namely contg. >=60% particles having particle size within a range of + or -50% based on the average particle size, as well as sharp distribution of coercive force causing deterioration of output in short wavelength region, is obtd.
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