EP0123445A1
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EP
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Barium ferrite particles for magnetic recording media
Assignee: Toda Kogyo Corp
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Filing: 1984-03-26
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Granted: —
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Expires: 2004-03-26
Abstract
Abstract Plate-like barium ferrite particles which have a BET specific surface area of 20 to 70 m 2 /g, an average particle diameter of 0.05 to 0.3 µm, a magnetization of higher than 30 emu/g in a field of 7.96 x 10° A m -1 (10 kOe) and a coercive force of 2.39 x 10 4 to 7,96 x 10 4 A m -1 (300 to 1,000 Oe) and which are represented by the formula BaCoxTiyFe12-x-yO19 wherein x and y are independently numbers from 0.1 to 0.5, are useful as the magnetic material for magnetic recording media.
Inventors
- 👤 Norimichi Nagai
- 👤 Nanao Horiishi
- 👤 Masao Kiyama
- 👤 Toshio Takada
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 03:17
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
101 words
1 . Plate-like barium ferrite particles which are represented by the formula BaCo x Ti y Fe 12-x-y O 19 wherein x and y independently are numbers from 0.1 to 0.5 and which have a BET specific surface area of from 20 to 70 m 2 /g, an average particle diameter of from 0.05 to 0.3 pm, a magnetization of larger than 30 emu/g in a magnetic field of 7.96 x 10 5 A m -1 (10 kO e) and a coercive force of from 2.39 x 10 4 to 7.96 x 10 4 A m- 1 (300 to 1,000 Oe).
Claim 2
Dependent Claim
101 words
1 . Plate-like barium ferrite particles which are represented by the formula BaCo x Ti y Fe 12-x-y O 19 wherein x and y independently are numbers from 0.1 to 0.5 and which have a BET specific surface area of from 20 to 70 m 2 /g, an average particle diameter of from 0.05 to 0.3 pm, a magnetization of larger than 30 emu/g in a magnetic field of 7.96 x 10 5 A m -1 (10 kO e) and a coercive force of from 2.39 x 10 4 to 7.96 x 10 4 A m- 1 (300 to 1,000 Oe).
Claim 3
Dependent Claim
20 words
Particles according to claim 1, having a BET specific surface area of from 45 to 6 5 m 2 /g.
Claim 4
Dependent Claim
20 words
3 . Particles according to claim 1 or 2, having an average particle diameter of from 0.05 to 0.25 pm.
Claim 5
Dependent Claim
35 words
Particles according to any one of the preceding claims, having a coercive force of from 3.18 x 10 4 to 6 . 36 x 1 0 4 A m -1 (400 to 800 Oe ).
Claim 6
Dependent Claim
17 words
Particles according to any one of the preceding claims, in which x is the same as y.
Claim 7
Dependent Claim
127 words
6 . A process for producing plate-like barium ferrite particles represented by the formula: wherein x and y independently are numbers from 0.1 to 0.5, which process comprises autoclaving at a temperature of from 250 to 320°C an aqueous alkaline suspension containing F e( III ), Co(II), Ti(IV) and Ba ions and a molar excess with respect to the total amount of Fe(III), Co(II), Ti( I V) and B a ions of an alkali metal hydroxide and in which suspension the atomic ratio of the total amount of Co(II) and Ti(IV) to the amount of Fe(III) is from 0.017 : 1 to 0.09 : 1 and the atomic ratio of Ba ions to the total sum of Fe (III), Co(II) and Ti(IV) is from 1:7 to 1:9.
Claim 8
Dependent Claim
127 words
6 . A process for producing plate-like barium ferrite particles represented by the formula: wherein x and y independently are numbers from 0.1 to 0.5, which process comprises autoclaving at a temperature of from 250 to 320°C an aqueous alkaline suspension containing F e( III ), Co(II), Ti(IV) and Ba ions and a molar excess with respect to the total amount of Fe(III), Co(II), Ti( I V) and B a ions of an alkali metal hydroxide and in which suspension the atomic ratio of the total amount of Co(II) and Ti(IV) to the amount of Fe(III) is from 0.017 : 1 to 0.09 : 1 and the atomic ratio of Ba ions to the total sum of Fe (III), Co(II) and Ti(IV) is from 1:7 to 1:9.
Claim 9
Dependent Claim
20 words
A process according to claim 6, wherein the source of Fe(III) is ferric chloride, ferric nitrate or powdery ferric oxyhydroxide.
Claim 10
Dependent Claim
20 words
A process according to claim 6 or 7, wherein the source of Ba ions is barium hydroxide or barium oxide.
Claim 11
Dependent Claim
22 words
A process according to any one of claims 6 to 8, wherein the source of Co(II) is cobalt nitrate or cobalt chloride.
Claim 12
Dependent Claim
22 words
A process according to any one of claims 6 to 9, wherein the source of Ti(IV) is titanium chloride or alkali titanate.
Claim 13
Dependent Claim
41 words
A process according to any one of claims 6 to 10, wherein the alkali metal hydroxide is present in an amount of up to a four-fold molar excess with respect to the total amount of Fe(III), Co(II), Ti(IV) and Ba ions.
Claim 14
Dependent Claim
31 words
A process according to any one of claims 6 to 11, wherein the molar amount of Co(II) in the aqueous alkaline suspension is the same as the molar amount of Ti(IV).
Claim 15
Dependent Claim
42 words
A magnetic recording medium in which the magnetic material comprises plate-like barium ferrite particles as claimed in any one of claims 1 to 5 or which have been prepared by a process as claimed in any one of claims 6 to 12.
References Cited (Backward Citations)
EP0072437A2
Cited
EP0072436A2
Cited
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