JPS6246924A - Production of fine powder of magnetoplumbite type ferrite - Google Patents

Abstract

PURPOSE:To produce fine powder of magnetoplumbite type ferrite by mixing alpha-FeOOH particles doped with bi- and quatervalent metallic ions with a Ba, Sr or Ca compound in the presence of sodium silicate and baking the mixture. CONSTITUTION:alpha-FeOOH particles doped with equal amounts of bivalent metallic ions (MII) and quatervalent metallic ions (MIV) in 1:(0.017-0.09) atomic ratio of Fe:MII+MIV, alpha-Fe2O3 particles obtd. by dehydrating the doped alpha- FeOOH particles by heating, Fe3O4 particles obtd. by reducing the alpha-Fe2O3 particles, gamma-Fe2O3 particles obtd. by reducing and reoxidizing the alpha-Fe2O3 particles or alpha-Fe2O3 particles obtd. by further oxidizing the gamma-Fe2O3 particles under heating are used as starting material for iron oxide. The starting material is mixed with a compound of at least one among Ba, Sr and Ca in the presence of sodium silicate and the mixture is baked at 750-900 deg.C and pulverized. Thus, fine powder of magnetoplumbite type ferrite having proper coercive force is obtd. The particles of the powder have a large specific surface area and a narrow particle size distribution.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to magnetoplumbite-type ferrite particles.
This article relates to the manufacturing method of the magnetic material, and in detail, the coercive force (Ilc
The present invention relates to a method for producing magnetoplumbite-type ferrite particles that can obtain magnetoplumbite-type ferrite fine particles having a particle size of 1.) and a narrow particle size distribution.

[Prior art]

In recent years, ferromagnetic non-acicular particles with suitable coercive force (He) and large saturation magnetization and good dispersibility have been used as magnetic materials for recording.
In particular, it is becoming desired as a magnetic material for perpendicular magnetic recording.

Generally, barium ferrite particles are well known as ferromagnetic non-acicular particles.

Conventionally, barium ferrite particles have been used as a magnetic material for magnetic recording. Barium ferrite particles are obtained by mixing a barium metal compound and iron oxide to a predetermined molar ratio, firing and pulverizing them. It has been used as a permanent magnet material such as field magnet material, but recently, it has been used as a magnetic material for read-only magnetic cards after adjusting its particle size, focusing on its high coercive force.

[Problem that the invention seeks to solve]

However, the barium ferrite particle powder obtained by the above manufacturing method is heated at a temperature of at least 900°C or higher, usually 11°C.
Because it is fired at a high temperature of 00℃ or higher and the particle size is adjusted using a crusher, there is a limit to the size of the particles, which can be reduced to 1 to 2 nm at most.
(/g) BET ratio slope surface area powder has a wide particle size distribution, and the particles are distorted by mechanical impact, so the S/N ratio is poor as a recording material, and the coercive force 11c is 2000 ~ Since it is too high (more than 300,000), it is not suitable as a magnetic material for read/write magnetic recording.

Therefore, there is a need for a magnetic material for read/write magnetic recording that has fine particles, has an appropriate coercive force, and has a reduced noise level.

It is said that the reduction in noise level is influenced by the particle size and particle size distribution of the magnetic material powder used, and the value of the specific surface area of the magnetic particles is often used as a method to express the particle size of the magnetic particles. However, it is said that the noise level caused by the magnetic recording medium tends to decrease as the specific surface area of the magnetic particles increases.

This phenomenon can be seen, for example, in IEICE technical research report R81.
-11, page 27, 23-9, rFig 3 J, etc. rFt (34 is a diagram showing the relationship between the specific surface area of particles and the noise level in Co-coated acicular maghemite particle powder, and the noise level decreases linearly as the specific surface area of the particles increases.

This relationship also applies to magnetoplumbite type ferrite particles.

The present inventor has repeatedly studied methods for fine-graining magnetoplumbite-type ferrite particles and controlling coercive force as a magnetic material for high-density magnetic recording capable of recording and reproducing.

[Means for solving problems]

The inventor of the present invention has determined that when using magnetoplumbite-type ferrite particles as a magnetic material for read/write magnetic recording, an appropriate coercive force, for example, 5000e to 15000s, is used.
In order to obtain a coercive force in the range of
Furthermore, in order to reduce the noise level, we have been exploring magnetoplumbite-type ferrite particles with a larger specific surface area and narrower particle size distribution, and have been developing methods for controlling coercive force and fine particle size over many years. Numerous experiments have been carried out on the effects of various additives and methods of oxidation. As a result, a compound of at least one metal element selected from the group consisting of barium, strontium, and calcium and Fe as the iron oxide raw material were obtained.
For l atoms, M(13 and the sum of M planes (where M(I is 2
The valent metal ion, M(1) indicates a tetravalent metal ion, and the gates f11 and l'CM are equal ff1) is 0.017 to 0.0.
a -FeO(OH) particles doped to a ratio of 9, the α
-M
, M□-containing α-Fe203 particles, Fe2O3 particles, T-FezO= particles, and α-FezOa particles obtained by heating and oxidizing Fe, 0° particles or r-FezOx particles obtained by heat treatment of these particles. At the same time, water glass, water glass and Na2CO, or water glass, NagCOl, BaCl□, or SrCl2 water glass alone or the above-mentioned water glass are mixed and blended with any one iron raw material at a predetermined molar ratio. If one of the mixtures of The present invention was achieved by confirming that the obtained particles are magnetoplumbite-type ferrite particles having a large specific surface area, a narrow particle size distribution, and an appropriate coercive force. be.

That is, the present invention provides a method for producing magnetoplumbite-type ferrite particles comprising the steps of firing and pulverizing a mixture of iron oxide and a compound of at least one metal element selected from the group consisting of barium, strontium, and calcium. In , M(
1) and M(5) (where M(1) represents a divalent metal ion, M(5) represents a tetravalent metal ion, and A(1) and 1
(5) is α-Fed(0■) particles doped with N) of 0.017 to 0.09, and the α-Fed(OH)
ILM (α-Fetos particles containing rM, Fe3O4 particles, T-Fetos
Particles and F@3O4 particles or γ-Fe obtained by heat treating them! α-F obtained by heating and oxidizing ds particles
Using any one of e103 particles, water glass, water glass and NazCO=, or water glass and Na2CO3 and B
After mixing a compound of at least one metal element selected from the group consisting of barium, strontium, and calcium in the presence of either aC+2 or SrCl z, firing in a temperature range of 750 to 900 ° C. This is a method for producing a characteristic magnetoplumbite type ferrite fine particle powder.

[For production]

Next, the present invention will be explained in detail.

First, to explain the composition of the magnetoplumbite type ferrite particles of the present invention, the general formula A-M(I)
, 1M (1%5Je+z-zxO+w (however, 0.1≦
X≦0.5), A is Ba, Sr,
One or more types of Ca, with a composition ratio of Fe and M
fl[l, M(5) is contained in a ratio of about 1 atom to 12 total metal ions, and in the general formula
If the value is less than 0.1, II (1), ? ! @Hc system? i
The l effect is not significant, and if it is set to 0.5 or more, the saturation magnetization decreases significantly, which is not practical. If the composition ratio of A to Fe and all other metal ions deviates significantly from 1 = 12, a different phase will occur. I don't like it.

As the iron raw material in the present invention, M
Acicular α-Fed (011) particles doped with a sum of (1) and M(5) of 0.017 to 0.09, obtained by heat-treating the particles such as thermal dehydration, reduction, or reduction and reoxidation. M(II), l'1 (acicular α containing till
-Fel2O3, Fe5O4, 1-FezO, and α-Fe2O3 particles obtained by heating and oxidizing Fe30t or r-Fe2O3 obtained by heat treatment thereof, with a BET ratio normal surface area of 0 to 100 rrr/g are used. .

Doped M■ is C0% Zn, Mn, Ni,
Cu5h is a metal atom of Ti, Ge, or Zr.

In addition, the doping amount of M(1) and M plane is such that the sum of M(1) and M(5) is in the range of 0.017 to 0.09 with respect to Fel atoms. (IV) is equivalent. 0
．． 017 or less and 0.09 or more, the above-mentioned -catalytic type A-MG
0.1≦X≦ in DJQWxFe+x−zxo+q
A composition in the range of 0.5 is not obtained.

In addition, α-Fed (0) doped with Moon (1) and H (5)
11) The wet synthesis method of particles is illustrated below.

M(II) soluble in aqueous solutions of ferrous salts such as ferrous sulfate
Compounds such as Coα□ and M(5) compounds such as TiC
Adjust and mix Ia to a predetermined amount, then add alkali to C
Fe(OH) over 91110 including o and T(IV)
α-Fed (OH) particles containing co and T(IV) are obtained by passing an oxygen-containing gas such as air through the aqueous Z colloid solution at a heating temperature of 50° C. or higher.

In other generally well-known α-Fed (Oil) particle generation methods, when preparing the raw Fe aqueous solution, the water-soluble compounds M (I[) and M (5) are adjusted and mixed in predetermined amounts in the same manner as described above. H(
α-Fed (OH) particles doped with 1) and M(5) can be obtained.

BaCO5,5rCOi, CaC0, etc. can be used as raw materials for barium, strontium, and calcium, but Ba compounds, S compounds, and Ca compounds, which become BaO, SrO, and CaO when heated, can also be used.

Next, the additives in the present invention will be explained.

As the water glass in the present invention, water-soluble silicates such as sodium silicate and potassium silicate can be used.

Generally, it is economical to use No. 3 water glass.

In addition, the addition ff1 (amount to be present) is 0.05 to 0.05 to 0.0 g of Si0g relative to iron oxide (Fe203 conversion).
Effective between 1.45% by weight. If it is added in an amount of 1.45% by weight or more, the saturation magnetization of the product ferrite decreases, making it undesirable as a magnetic material.If it is added in an amount of 0.05% by weight or less, the desired effect of the present invention cannot be obtained.

In the present invention, the amount of NαCOx added is iron oxide (
It is effective in a range of 0.35 to 12.0% by weight based on Fe2O3 (calculated as Fe2O3). If the amount is less than 0.35% by weight, the effect of addition is small. If the amount is 12.0% by weight or more, it is possible to obtain the desired ferrite particles with fine particles and a narrow particle size distribution, but if it is added in excess, the specific surface area of the ferrite particles tends to become small, which is not desirable.

The amount of Baαg or SrCl2 added in the present invention is 1.5 to 7.0 with respect to iron oxide (Fears conversion).
Valid between % by weight. When the amount is 1.5% by weight or less, the effect of addition is small, while when it is 7.0% by weight or more, the specific surface area of the ferrite particles tends to become small.
Moreover, when considering the particle size and particle size distribution of the target ferrite particles, which are not economical, 1.5 to 7.0% by weight is preferable.

In addition, the appropriate time to add each additive in the present invention is immediately before the firing process. That is, in each of the raw material blending process, firing process, and pulverization process, it can be added at the time of raw material blending, which is the process immediately before the firing process.

In the present invention, the firing temperature range is between 750 and 900°C, but if it is below 750°C, it is insufficient to carry out the ferrite reaction, and if it is above 900°C, Grain growth of the ferrite particles themselves during the firing process and strong sintering between the particles make subsequent pulverization difficult, which is not preferable.

In addition, in the case of the above firing temperature, pulverization after firing can be carried out under relatively mild conditions using a normal pulverizer such as an atomizer or an attritor, or a special pulverizer or a powerful pulverizer. No grinding is necessary.

〔Example〕

Next, the present invention will be explained with reference to Examples and Comparative Examples.

In addition, the specific surface area of the particles in Examples and Comparative Examples was measured by the BET method, and X-rays were used for structural analysis of the products. Magnetic measurement uses a DC BH tracer (Yokoyo Denki Seisakusho Type 3257), and the measurement magnetic field is 10
Measured in KOe.

Example 1 CO and T(IV) are each 0.03 per Fe1 atom
1 Doped BET specific surface area is 43. Onf/
When mixing 1000 g of α-FeO(O) particle powder and 195 g of barium carbonate, No. 3 water glass 23
After adding and thoroughly mixing the mixture, the mixture was fired at 820°C for 2 hours, and then the fired product was pulverized with an atomizer.

As a result of X-ray analysis, the obtained particles were found to be magnetoplumbite type barium ferrite particles, and as a result of compositional analysis, Ba
con, 1sTio, 5sFe+ +, xo+*
Met.

Obtained magnetoplumbite barium ferrite i
Results of measuring the specific surface area of particle powder using the BET method 24
．． 5 rrr/g, and as a result of measuring the magnetic properties of this material, the saturation magnetization σS: 57. Oemu/g, coercive force 11c: 7300e.

Example 2 0.02 each of Co and T(IV) for Fel atoms
When mixing 1000 g of doped α-PeO(OH) particle powder with a BET specific surface area of 56.4r+f/g and 195 g of barium carbonate, No. 3 water glass 35.4 g was mixed with 195 g of barium carbonate.
g (equivalent to 1.12% by weight based on 5iO1 based on Feig4) and NαCOs 68 g (Fe3O4
After mixing thoroughly, the mixture was fired at 820°C for 3 hours, and then the fired product was pulverized with an atomizer. As a result of XvA analysis, the obtained particles were found to be magnetoplumbite type barium ferrite particles, and as a result of compositional analysis, Bacon,
T+ a, xsFe+ +, sso+9.

Results of measuring the specific surface area of the obtained magnetoplumbite type barium ferrite fine particle powder by BET method 33
．． 5n? /g, and as a result of measuring the magnetic properties of this material, the saturation magnetization σs: 63. Oemu/g.

Coercive force +1c: 8800e.

Example 3 Co and T(IV) are each 0.01 per Fel atom
Doped α with a BET specific surface area of 30.5 m'/g
- When mixing 1000 g of Fed (OH) particle powder and 145 g of strontium carbonate, No. 3 water glass 16
g (equivalent to 0.50% by weight in terms of SiO2 with respect to FezO4) and NαCOz 22.6g (Fe30a
(equivalent to 2.5% by weight) and 27 g of BaCIz
(equivalent to 3.0% by weight based on pezoa), and after thorough mixing, the mixture was fired at 800°C for 3 hours, and then the fired product was crushed with an atomizer and washed with water to remove water-soluble salts. was removed.

As a result of X-ray analysis, the obtained dry powder particles were found to be magnetoplumbite type strontium ferrite particles, and as a result of compositional analysis, 5rCoo, + tTLe, + zF
e+ 1. It was tio+9.

The specific surface area of the obtained magnetoplumbite type strontium ferrite fine particles measured by the BET method was 21.2rrr/g, and the magnetic properties of this material were measured, and the saturation magnetization σs: 65.5eIlu/
g, coercive force Hc: 11500e.

Example 4 In Example 1, α-Fed (
Off) BET specific surface area containing CO and T(IV) is 40.0 m/g by heating the particle powder at 300°C in air.
1000g of α-FezOz particle powder, 4gα-F
Barium ferrite particles were obtained under the same conditions as in Example 1 except that 900 g of e and O particles were used.

As a result of X-ray analysis, the obtained particles were found to be magnetoplumbite type barium ferrite particles, and as a result of compositional analysis, Ba
Coo, 5sTio, xsFe+ +, zO+
It was q.

Results of measuring the specific surface area of the obtained magnetoplumbite type barium ferrite fine particle powder by BET method 25
．． 0Id/g, and as a result of measuring the magnetic properties of this material, saturation magnetization σs: 58. Oemu/g, coercive force Hc: 7420e.

Example 5 In Example 2, α-Fed used in Example 2 in advance
(OH) particles were reduced at 350°C in a H2 stream to produce CO
and T(IV), the BET specific surface area is 42. ,
Barium was prepared under the same conditions as in Example 2, except that 870 g of black iron oxide powder was used, and the composition ratio of Fe(1)/Fe[E in M/g was 0.35. Ferrite particle powder was obtained.

As a result of X-ray analysis, the obtained particles were found to be magnetoplumbite type barium ferrite particles, and as a result of compositional analysis, Ba
Coo, xsTie, xsFe+ +, 54o1
．． Met.

Results of measuring the specific surface area of the obtained magnetoplumbite type barium ferrite fine particle powder by BET method 30
．． On? /g, and as a result of measuring the magnetic properties of this material, the saturation magnetization σs: 60. Oemu/g, coercive force He: 8400e.

Example 6 In Example 3, α-Fed (
011) After reducing the particle powder at 350°C in two air streams,
When oxidized in air at 300°C, the BET specific surface area containing Go and T(IV) is 25. On? /g r-Fe2O
3 particle powder, El 7-FezO, particle powder 900
Strontium ferrite particles were obtained under the same conditions as in Example 3 except that g was used.

As a result of X-ray analysis, the obtained particles were found to be magnetoplumbite type strontium ferrite particles, and as a result of compositional analysis, they were found to be 5rCoo, + zTio, + zFe+ +,
The tkO+ was 9.

The specific surface area of the obtained magnetoplumbite type strontium ferrite a particle powder measured by the 13ET method was 18.8 m/g, and the result of measuring the magnetic properties of this material was that the saturation magnetization σs: 67.6 effiu
/g% coercive force 11c: 10800e.

Comparative Example 1 α-Fed (OH) particle powder 1000 used in Example 1
g and 195 g of barium carbonate were thoroughly mixed, the mixture was fired at 1200°C for 3 hours, and the fired product was then pulverized in a vibrating ball mill for 60 minutes. As a result of X-ray analysis, the particles obtained were of the magnetoplumbite type. It was barium ferrite particle powder. As a result of measuring the magnetic properties of this material, the saturation magnetization σs is 265. Oemu/g, coercive force lie
: 13200e, but as a result of measuring the specific surface area by the BET method, it was 3.5 m/g, and the particles were coarse and the noise level Z was high and it was unsuitable as a magnetic material for magnetic recording.

Comparative Example 2 α-Fed (O old particles had a BET specific surface area of 43.0
Barium ferrite particles were obtained under the same conditions as in Example 1 except that 7 g of α-FeO(OH) particles were used. The BET specific surface area of the obtained particles was 26.0
Although the fine particles had a low noise level of 32,500 e and a high coercive force of 32,500 e, they were not suitable for read/write magnetic recording.

〔effect〕

According to the method for producing magnetoplumbite-type ferrite i-particle powder according to the present invention, as shown in the previous example, the particles have a large specific surface area, a narrow particle size distribution, and are controlled to a desired coercive force. Since fine particle powder of magnetoplumbite type ferrite can be obtained, it can be suitably used as a magnetic material for read/write magnetic recording with high recording density, which is currently required.

Claims (12)

[Claims] (1) In a method for producing magnetoplumbite-type ferrite particle powder, which comprises a step of firing and pulverizing a mixture of a compound of at least one metal element selected from the group consisting of barium, strontium, and calcium and iron oxide, oxidation M(II) and M per Fe1 atom as iron raw materials
The sum of (IV) (where M(II) is a divalent metal ion, M(IV)
represents a tetravalent metal ion, and M (II) and M (IV) are equivalent) are doped at a ratio of 0.017 to 0.09.
eO(OH) particles, α-Fe containing M(II) and M(IV) obtained by subjecting the α-FeO(OH) particles to heat dehydration, reduction, or reduction and reoxidation heat treatment using the α-FeO(OH) particles as a starting material.
_2O_3 particles, Fe_3O_4 particles, γ-Fe_2O
_3 particles and Fe_3O_ obtained by heat treating them
Using either one of α-Fe_2O_3 particles obtained by heating and oxidizing 4 particles or γ-Fe_2O_3 particles,
A magnetoplumbite characterized in that it is mixed with a compound of at least one metal element selected from the group consisting of barium, stronium and calcium in the presence of water glass, and then fired in a temperature range of 750 to 900°C. Method for producing type ferrite fine particles. (2) M(II) is cobalt, nickel, manganese, copper,
The method for producing a magnetoplumbite type ferrite fine particle powder according to claim 1, wherein zinc and M(IV) are titanium, germanium, and zirconium. (3) The amount of water glass present is 0.05 to 1.45% by weight in terms of SiO_2 based on the iron raw material (in terms of Fe_2O_3)
A method for producing a magnetoplumbite type ferrite fine particle powder according to claim 1 or 2. (4) A method for producing magnetoplumbite-type ferrite particles comprising the step of firing and pulverizing a mixture of a compound of at least one metal element selected from the group consisting of barium, strontium, and calcium and iron oxide. M(II) and M per Fe1 atom as iron raw materials
The sum of (IV) (where M(II) is a divalent metal ion, M(IV)
represents a tetravalent metal ion, and M (II) and M (IV) are equivalent) are doped at a ratio of 0.017 to 0.09.
eO(OH) particles, α-F containing M(II) and M(IV) obtained by subjecting the α-FeO(OH) particles to heat dehydration, reduction, or reduction and reoxidation heat treatment using the α-FeO(OH) particles as a starting material.
e_2O_3 particles, Fe_3O_4 particles, γ-Fe_2
O_3 particles and Fe_3O obtained by heating them
Barium,
After mixing with a compound of at least one metal element selected from the group consisting of stronium and calcium, 75
A method for producing a magnetoplumbite type ferrite fine particle powder, which comprises firing at a temperature range of 0 to 900°C. (5) M(II) is cobalt, nickel, manganese, copper,
5. The method for producing a magnetoplumbite type ferrite fine particle powder according to claim 4, wherein zinc and M(IV) are titanium, germanium, and zirconium. (6) The amount of water glass present is 0.05 to 1.45% by weight in terms of SiO_2 based on the iron raw material (in terms of Fe_2O_3)
A method for producing a magnetoplumbite type ferrite fine particle powder according to claim 4 or 5. (7) The abundance of Na_2CO_3 is
The method for producing a magnetoplumbite type ferrite fine particle powder according to any one of claims 4 to 6, wherein the amount is 0.35 to 12.0% by weight based on _3 conversion). (8) A method for producing magnetoplumbite-type ferrite particles comprising the step of firing and pulverizing a mixture of a compound of at least one metal element selected from the group consisting of barium, strontium, and calcium and iron oxide. M(II) and M per Fe1 atom as iron raw materials
The sum of (IV) (where M(II) is a divalent metal ion, M(IV)
represents a tetravalent metal ion, and M(II) and M(IV) are equivalent) doped at a ratio of 0.017 to 0.09.
FeO(OH) particles, α- containing M(II) and M(IV) obtained by subjecting the α-FeO(OH) particles to heat dehydration, reduction, or reduction and reoxidation heat treatment using the α-FeO(OH) particles as a starting material.
Fe_2O_3 particles, Fe_3O_4 particles, γ-Fe_
2O_3 particles and Fe_ obtained by heat treating them
Using either 3O_4 particles or α-Fe_2O_3 particles obtained by thermally oxidizing γ-Fe_2O_3 particles, a particle selected from the group consisting of barium, stronium, and calcium is used in the presence of water glass, Na_2CO_3, and BaCl_2 or SrCl_2. A method for producing a magnetoplumbite type ferrite fine particle powder, which comprises mixing the powder with a compound of at least one metal element, and then firing the powder at a temperature in the range of 750 to 900°C. (9) M(II) is cobalt, nickel, manganese, copper,
9. The method for producing a magnetoplumbite type ferrite fine particle powder according to claim 8, wherein zinc and M(IV) are titanium, germanium, and zirconium. (10) The magnetoplumbite type ferrite fine particles according to claim 8 or 9, wherein the amount of water glass present is 0.05 to 1.45% by weight in terms of SiO_2 based on the iron raw material (in terms of Fe_2O_3) Powder manufacturing method. (11) The abundance of Na_2CO_3 is
The method for producing a magnetoplumbite type ferrite fine particle powder according to any one of claims 8 to 10, wherein the amount is 0.35 to 12.0% by weight based on O_3 equivalent). (12) The magnetoplumbite type according to any one of claims 8 to 11, wherein the amount of BaCl_2 or SrCl_2 is 1.5 to 7.0% by weight based on the iron raw material (Fe_2O_3 equivalent). Manufacturing method of ferrite fine particle powder.