Process for producing magnetic powder having high coercive force
AssigneeTDK Electronics Co., Ltd.
InventorsShinji Umeki, Toshihiro Hamabata, Kazuaki Onuki, Kazuo Takada
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Abstract
A magnetic iron oxide powder having high coercive force is produced by dispersing a magnetic iron oxide comprising a silicon component and a phosphorus component in an aqueous solution of a cobalt ion and adding a base to the dispersion to be an alkaline condition and heat-treating the dispersion whereby the cobalt ion is adsorbed and diffused in the surface layer of the magnetic iron oxide. A zinc component can be also incorporated in the crystal. The silicon component and the phosphorus component are preferably incorporated in the crystalline structure.
Claims5
A magnetic iron oxide powder which consists essentially of:
- an iron oxide selected from the group consisting of magnetite and .gamma.-ferric oxide;
- a silicon component in an amount of 0.05 to 10 wt %, as Si based on the iron oxide;
- a phosphorus component in an amount of 0.05 to 5 wt %, as P based on the iron oxide;
- and
- a cobalt component in an amount of at least 1.0 wt % as Co based on the iron oxide;
- wherein silicon and phosphorus are incorporated in the crystalline structure of the iron oxide and the cobalt component is diffused and adsorbed in the surface layer of the iron oxide.
A process for producing a magnetic iron oxide powder which comprises:
- dispersing a magnetic iron oxide consisting essentially of an iron oxide selected from the group consisting of magnetite and .gamma.-ferric oxide a silicon component, in an amount of 0.05 to 10 wt %, as Si based on the iron oxide, and a phosphorous component, in an amount of 0.05 to 5 wt %, as P based on the iron oxide, wherein silicon and phosphorus are incorporated in the crystalline structure of the iron oxide, in an aqueous solution of cobalt ion;
- adding a base to the dispersion so as to produce an alkaline condition;
- and, heating the dispersion so as to adsorb and diffuse the cobalt ion into the surface layer of the magnetic iron oxide.
Dependencies are inferred from the claim text.