Wet process of preparing fine particles of ferrite of magnetoplumbite structure
US4551260A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 24, 1984 |
| Grant date | Nov 5, 1985 |
| Priority date | — |
| Expiry date | Jul 24, 2004 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC01P2006/42
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
In preparing fine and plate-shaped particles of a ferrite having the magnetoplumbite structure by hydrothermal treatment of a powder of .gamma.-Fe.sub.2 O.sub.3 or (FeO).sub.x.Fe.sub.2 O.sub.3, where O<x.ltoreq.1, and a compound of Ba, Sr or Pb in an aqueous alkali solution, Sn.sup.4+, or Sn.sup.4+ and M.sup.2+ such as Fe.sup.2+, Cu.sup.2+ or Zn.sup.2+, are introduced into the reaction system of the hydrothermal treatment such that Fe.sup.3+ in the obtained ferrite are partly substituted by Sn.sup.4+ or M.sup.2+ -Sn.sup.4'. The substitution has the effect of lowering the coercive force of the ferrite powder to a level suitable for use in magnetic recording media of the perpendicularly magnetizing recording type. By using an iron oxide powder having a mean particle size not larger than 500 .ANG. with addition of a surface-active agent, the particle size of the ferrite powder can be reduced to about 0.2 .mu.m.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.