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WO1992013341A1 - Procede de preparation de poudre de ferrite de baryum hexagonal et poudre preparee par ce procede - Google Patents

Procede de preparation de poudre de ferrite de baryum hexagonal et poudre preparee par ce procede Download PDF

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Publication number
WO1992013341A1
WO1992013341A1 PCT/DE1991/000049 DE9100049W WO9213341A1 WO 1992013341 A1 WO1992013341 A1 WO 1992013341A1 DE 9100049 W DE9100049 W DE 9100049W WO 9213341 A1 WO9213341 A1 WO 9213341A1
Authority
WO
WIPO (PCT)
Prior art keywords
powder
ferrite
silicon dioxide
hexagonal
sio
Prior art date
Application number
PCT/DE1991/000049
Other languages
German (de)
English (en)
Inventor
Peter GÖRNERT
Manfred Jurisch
Rolf-Gerd Pfeiffer
Horst Rein
Michael RÖSLER
Thomas Schubert
Walter SCHÜPPEL
Hans Siegel
Ekkehard Sinn
Michael Wendt
Original Assignee
Physikalisch-Technisches Institut
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Physikalisch-Technisches Institut filed Critical Physikalisch-Technisches Institut
Priority to PCT/DE1991/000049 priority Critical patent/WO1992013341A1/fr
Publication of WO1992013341A1 publication Critical patent/WO1992013341A1/fr

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G11B5/70626—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances
    • G11B5/70642—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides
    • G11B5/70678—Ferrites

Definitions

  • the invention relates to a method for producing hexagonal barium ferrite powder and powder produced thereafter. Such powders are used in the manufacture of high-density magnetic information recording media.
  • ferrites with the smallest possible particle size are sought, which according to the The invention cited is achieved by partially replacing the boron oxides in the base glass with silicon oxide, silicon oxide fractions to the boron trioxide as the glass-forming component of the base glass in a molar ratio (SiO 2 ) / (SiO 2 ) + (H 2 O 3 ) of 0.05 to 0 s , 8 (preferably 0.1 to 0.5) must be observed.
  • the known ferrite powders in certain polymers tend to agglomerate and sediment strongly, which complicate the dispersing process or make it impossible to produce a homogeneous dispersion. It is the object of the invention to produce a hexagonal barium ferrite powder for use in magnetic recording media which has a specific saturation magnetization above 50 Am 2 / kg and a coercive field strength of 24 kA / m to 160 kA / m and this in the range of the annealing temperature during the Sintering process from 760 ° C to S00 ° C has as little dependency on the tempering temperature as possible and shows optimal dispersion properties in polymers.
  • the invention is based on the object, using glass ceramic production processes, of obtaining a hexagonal barium ferrite powder of the M type intended for magnetic recording media which, with grain sizes in the range from 0.01 .mu.m to 0.3 .mu.m, has as little scatter as possible of the desired grain size, a slight dependence on the Has coercive field strength from the tempering temperature during the process of glass crystallization and has very good dispersibility in polymers and can be obtained from the base glass matrix by washing and cleaning without a complex grinding process.
  • the invention is based on the discovery that, depending on the amount weighed into the glass melt and certain ferrite phases that form in the base glass, after the ferrite portion has been separated from the glass, finely divided ferrite particles that are inseparably encased with a silicon dioxide layer and have a very narrow particle size distribution surrender.
  • the object is achieved in that the melt weights are determined in such a way that in the ternary ferrite BaFe 12-2N Co N Ti N O 29 with a molar concentration of 0.05 to 0.08 in the base glass, a ratio of basic to acidic oxide (BaO / B 2 O 3 ) is set between 1.00 and 1.22 and the ratio of silicon dioxide to boron oxide as (SiO 2 ) / (SiO 2 ) + (B 2 O 3 ) between 0.007 and 0.15 is set.
  • the procedure for the invention is as follows.
  • a single-phase melt solution is produced from the mixed raw materials weighed in accordance with the invention by heating to 1400 ° C.
  • the melt is amorphized by means of a two-roll system with a circulation speed of 1 to 2 m / s by cooling rates of 10 3 to 10 5 to chips or the strip material in fragments.
  • the crystalline hexaferrite phase in these chips is formed by heat treatment in the temperature range from 700 to B60 ° C, preferably from 760 to 800 ° C, for times of 2 to 10 hours (preferably 6 to 5 hours).
  • the heating rate is set between 0.01 and 2 K / s, the cooling rate at the upper limit of this requirement.
  • the comminuted temper material is then treated in 20% acetic acid in the vicinity of the boiling point for 6 to 8 hours with vigorous stirring in order to extract the excreted hexaferrite crystallites from the surrounding matrix. About three times the amount of acid calculated on the stoichiometric conversion is used.
  • the fine powder is then separated by filtering or centrifuging alternating with a washing process in deionized water until no soluble Me compound can be detected.
  • the powder obtained by these process steps is characterized in that the powder released from the base glass has a silicon dioxide content of 0.3 to 6.0% and this content surrounds the ferrite particles in a shell-like manner.
  • the mean crystallite diameters obtained are preferably 0.05 .mu.m to 0.12 .mu.m with a diameter / thickness ratio of 5 to 7 if the silicon dioxide fractions in the melt are in the range defined according to the invention.
  • the addition of SiO 2 has no influence on the use of substituents.
  • a significant leveling of the temperature dependence of the coercive field strength can be determined (cf. 2).
  • the content of barium sinket in the glass matrix specified in this patent acts via the crystallization kinetics on the hexaferrite formation in such a way that magnetic pigments with a second non-magnetic phase of silicon dioxide are formed between the hexaferrite crystallites after working up.
  • the hexagonal ferrite crystallites are encased in a very fine silicon dioxide layer.
  • This proposed addition brings about a relatively small reduction in the saturation magnetization, which corresponds to the mass fraction of unmagnetic silicon dioxide in the powder mixture.
  • the hexaferrite powder with SiO 2 additive has approximately the same coercive field strengths at temperatures between 760 and 800 ° C, whereas, on the other hand, hexaferrite powder without SiO 2 additive can differ in their coercive field strengths by a few tens A / m under analogous treatment conditions.
  • Shifts in the absolute position of the coercive field strengths can be optimized with Co / Ti substitution. It is also advantageous with the proposed method that temperature deviations, such as those that occur in large-scale furnace systems, result in uniform hexaferrite powders in their magnetic properties. It should be noted, however, that the upper temperature limit is not exceeded locally, because an increase in the grain size and the distribution rate is caused by crystallite enlargements.
  • the magnetic pigments with a certain SiO 2 content obtained by the proposed production process, tend to agglomeration and sedimentation in polymers, which greatly facilitates their further processing into magnetic recording media.
  • the rectangular field 1 formed in the attached FIG. 1 is formed by the four corner points of the molar composition according to the invention.
  • Field 2 defines the area in which phase-pure barium hexaferrite of the M type is obtained, which can still be used for storage purposes.
  • Field 3 defines an area for barium hexaferrite mixed with other Fe-containing phases ( ⁇ -Fe 2 O 3 ) for (MeO) / (B 2 O 3 ) ⁇ 0.96).
  • FIG. 2 shows the dependence of the coercive field strength Hc on the tempering temperature T at an annealing time of 8 hours for the barium hexaferrite BaFe 10 , 50 Co 0.75 Tio, 75 O 19 according to the invention.

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  • Compounds Of Iron (AREA)
  • Hard Magnetic Materials (AREA)

Abstract

L'invention concerne un procédé pour la préparation de poudre de ferrite de baryum hexagonal ainsi que la poudre préparée par ce procédé. Ces poudres ont une application pour la fabrication de supports d'enregistrement magnétique à haute densité. L'invention a pour objectif d'obtenir, par application de procédés de fabrication propres aux vitrocéramiques, une poudre de ferrite de baryum hexagonal du type M convenant pour des supports d'enregistrement magnétique. Cet objectif est réalisé par le fait que les quantités pesées pour fusion sont fixées de telle manière que dans le diagrammen de phase ternaire MeO-B2O3-MeFe12-2xRIIxRIVxO19 le ferrite hexagonal BaFe12-2xCoxTixO19 est dissous dans le verre de base avec une concentration molaire de 0,05 à 0,08, le rapport de l'oxyde basique à l'oxyde acide (BaO/B2O3) étant compris entre 1,00 et 1,22 et le rapport du dioxyde de silicium au trioxyde de bore (SiO2)/(SiO2) + (B2O3) étant compris entre 0,007 et 0,15.
PCT/DE1991/000049 1991-01-21 1991-01-21 Procede de preparation de poudre de ferrite de baryum hexagonal et poudre preparee par ce procede WO1992013341A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/DE1991/000049 WO1992013341A1 (fr) 1991-01-21 1991-01-21 Procede de preparation de poudre de ferrite de baryum hexagonal et poudre preparee par ce procede

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/DE1991/000049 WO1992013341A1 (fr) 1991-01-21 1991-01-21 Procede de preparation de poudre de ferrite de baryum hexagonal et poudre preparee par ce procede

Publications (1)

Publication Number Publication Date
WO1992013341A1 true WO1992013341A1 (fr) 1992-08-06

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PCT/DE1991/000049 WO1992013341A1 (fr) 1991-01-21 1991-01-21 Procede de preparation de poudre de ferrite de baryum hexagonal et poudre preparee par ce procede

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WO (1) WO1992013341A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3405603A1 (de) * 1983-02-16 1984-08-23 Fuji Photo Film Co., Ltd., Minami Ashigara, Kanagawa Verfahren zur herstellung von magnetischen ferritteilchen fuer die magnetische aufzeichnung
EP0136599A2 (fr) * 1983-09-30 1985-04-10 Kabushiki Kaisha Toshiba Poudre magnétique de ferrite de baryum et milieu d'enregistrement l'utilisant
JPS60229307A (ja) * 1984-04-27 1985-11-14 Hitachi Metals Ltd 磁気記録用磁性粉の製造方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3405603A1 (de) * 1983-02-16 1984-08-23 Fuji Photo Film Co., Ltd., Minami Ashigara, Kanagawa Verfahren zur herstellung von magnetischen ferritteilchen fuer die magnetische aufzeichnung
EP0136599A2 (fr) * 1983-09-30 1985-04-10 Kabushiki Kaisha Toshiba Poudre magnétique de ferrite de baryum et milieu d'enregistrement l'utilisant
JPS60229307A (ja) * 1984-04-27 1985-11-14 Hitachi Metals Ltd 磁気記録用磁性粉の製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 10, no. 82 (E-392)2. April 1986 & JP-A-60 229 307 (HITACHI KINZOKU KK ) 14. November 1985 siehe das ganze Dokument *

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