JPS63170221A - Barium ferrite magnetic powder and its production - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic powder which is suitable for a magnetic recording medium for high-density recording and has narrow particle size distribution, high saturation magnetization and required coercive force, by subjecting slurry wherein a specified starting raw material is dissolved in water and NaOH is added to produce ppt. to hydrothermal treatment and thereafter mixing flux with the produced ppt. and calcining the mixture and washing it. CONSTITUTION:A starting raw material consisting of the compd. of respective elements having the proportion of 3-11g atom Fe<3+> for 1g atom Ba, (x)g atom M1 (one or more kinds of metals selected from among Ni, Co, Cu, Mg, Mn and Zn) and (x)g atom M2 (one or more kinds of metals selected from among Ta, Sb, Nb, Zr and Ti) for (12-2x-y)g atom Fe<3+> and (y)g atom Fe<2+> is dissolved in water. Then slurry wherein alkali hydroxide is added to this aq. soln. so that the concn. in the soln. after mixing is regulated to >=3mol/l to produce ppt. is subjected to hydrothermal treatment at 130-270 deg.C. After washing produced fine crystalline ppt. is washed with water, 10-180wt.% flux such as NaCl is mixed therewith and the mixture is calcined at 700-950 deg.C and washed and the titled hexagonal lamellate magnetic powder shown in a formula (n=0.8-1.0, x=0.5-1.5, y=0.01-1.5) is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hexagonal plate-shaped magnetoblanbite type barium ferrite magnetic powder and an H3M method thereof.

More specifically, the present invention has a specific surface area of 20 to 70 nr/a, which is suitable for use in a magnetic recording medium for high-density recording.
The present invention relates to a magnetobrambite barium ferrite magnetic powder having a coercive force of 300 to 15,000 e and a saturation magnetization improved by 8% or more compared to that obtained by conventional hydrothermal synthesis, and a method for producing the same.

In recent years, with the demand for higher density magnetic recording, development of perpendicular magnetic recording systems using barium ferrite magnetic powder as a magnetic recording medium has been progressing.

The barium ferrite magnetic powder used in the perpendicular magnetic recording system has a coercive force of an appropriate value (300 to 15,000e).
), the saturation magnetization is as high as possible, the magnetic properties of each particle are uniform, the particles are small and uniform, and particle aggregation,
A material that does not require sintering and has good dispersibility is desired.

In particular, since barium ferrite magnetic powder has a lower saturation magnetization than other magnetic powders for recording media, fine particles with as high a saturation magnetization as possible are desired.

(Conventional technology) Conventionally, the method for producing barium ferrite magnetic powder is as follows:
For example, various methods are known, such as coprecipitation, glass crystallization, and hydrothermal synthesis.
G-15574, and regarding the hydrothermal synthesis method, for example, JP-A-59-175707, JP-A-60-129.
Publication No. 73, Japanese Patent Publication No. 60-15576, Japanese Patent Publication No. 60-15576
This method has been proposed in JP 0-137002 and the like. −
All of the barium ferrite magnetic powders produced by the conventional method have the following formula Ba O-n Fe2O3.
Some of the valent Fe atoms are Co, T'i, Ni, and Mn.

Metal elements alone such as Cu, Zn, In, Ge, Nb, etc.
Or a combination thereof is used for substitution such that the total valence of the substituted atoms is equal to that of the trivalent Fe atom to be substituted.

(Problems to be Solved by the Invention) Barium ferrite magnetic powder obtained by hydrothermal synthesis generally has little particle aggregation, relatively good dispersibility, and fine particles, but the saturation magnetization is about 55<em>U10 or higher. I couldn't get a low rating either. This is because when the surface area of barium ferrite magnetic powder is 20d/Q or more, especially when the surface area of ultrafine particle magnetic powder is 50d19 or more, the non-magnetic layer on the particle surface cannot be ignored, and various additives are added to adjust the coercive force. It is thought that this is due to the metallic elements.

(Object of the Invention) An object of the present invention is to provide a fine barium ferrite magnetic powder having high saturation magnetization and a method for producing the same, which solves the above-mentioned difficulties in hydrothermal synthesis.

(Means for Solving the Problems) The present invention is based on the general formula %] (where Ml is a part or two or more selected from the group consisting of Ni, Co, C1, M9.Mn, and zn). represents a metal, M2 represents one or more metals selected from the group consisting of Ta, Sb, Nb, Zr, and T, n20.8 to 1.0, x=0.5 to 1.5, y=0.
It is a numerical value of 01 to 1.5. This invention relates to a hexagonal plate-shaped magnetobrambite barium ferrite magnetic powder represented by ) and a method for producing the same.

In the present invention, as starting materials, 3 to 11 gram atoms of trivalent iron and 1 gram atom of trivalent iron per 1 gram atom of barium are used.
2-2 Using a compound of each element in a ratio of X gram atoms of Ml and M2 and y gram atoms of divalent iron to x-y gram atoms, the starting materials are dissolved in water, and the starting materials are dissolved in water. The alkali hydroxide concentration in the solution after mixing is 3
Alkali hydroxide is added to form a precipitate so that the amount is mol/J or more, and the slurry containing the precipitate is
After hydrothermal treatment at ℃, a fluxing agent is mixed with the generated precipitate,
The hexagonal plate-shaped magnetobrambite barium ferrite magnetic powder is obtained by firing the mixture at 700 to 950°C and washing and staining the resulting fired product.

In the present invention, starting materials such as barium, trivalent iron, Ml, M2, and divalent iron are first dissolved in water, and alkali hydroxide is added thereto to form a precipitate.

As the barium compound, barium TIi'i acid, barium chloride, barium hydroxide, etc. are used. The amount of Valiram used is that the barium concentration is 0.03 to 0.23 mol/J.
In order to obtain particles with a good hexagonal plate shape, it is desirable to keep the particle diameter within this range.

As the trivalent iron compound, ferric nitrate, ferric chloride, etc. are used. The amount of trivalent iron used is 3 to 11 gram atoms per gram atom of barium. If the amount of trivalent iron is too small, the amount of magnetobrambite barium ferrite produced will be small and the shape will not be hexagonal plate-like. Furthermore, if the amount of trivalent iron is too large, bematite may be produced as a by-product, and barium ferrite particles may become large, resulting in poor magnetic properties.

Compounds of Ml include Ni, Co, CD, Mg, M
One or more metal chlorides, nitrates, etc. selected from the group consisting of n and Zn are used.

As the compound M2, one or more metal chlorides, nitrates, etc. selected from the group consisting of Ta, Sb, Nb, Zr, and Ti are used.

The amounts of Ml and M2 used are preferably such that Ml and M2 are each X gram atoms (x = 0.5 to 1.5) per 12-2x-y gram atoms of trivalent iron. The magnetic properties, mainly the coercive force, can be controlled by the value of X.

As the divalent iron compound, ferrous chloride, ferrous nitrate, etc. are used. The amount of divalent iron used is trivalent iron 12-2x-
For y gram atom, y gram atom (y=o, 01~1
．． 5, preferably 0.1 to 1.0>. It is thought that due to the addition of divalent iron, the crystal lattice of magnetoblanbite barium ferrite becomes deficient in O atoms, as expressed by the following formula %, and that this improves the saturation magnetization. .

In this case, the Fc(II) ion is a 4-coordinated Fe(III)
It is presumed that the ions are selectively substituted.

As the alkali hydroxide, sodium hydroxide, potassium hydroxide, etc. are used. The amount of alkali hydroxide used must be such that the alkali hydroxide concentration in the solution after mixing the alkali hydroxide is 3 mol/1 or more, and 4 to 8 mol/1.
A range of j is preferred.

If the amount of alkali hydroxide is too small, the particles become large, the particle size distribution becomes wide, and hematite is generated. Further, it is not economical to increase the amount of alkali hydroxide excessively.

There is no particular restriction on the method of mixing the alkali hydroxide into the aqueous solution of the starting material, but for example, there are methods of directly adding the alkali hydroxide or adding an aqueous solution of the alkali hydroxide to the aqueous solution of the starting material. . Alternatively, there is a method of adding a barium compound to the aqueous solution of alkali hydroxide and mixing this with an aqueous solution containing trivalent iron.

Furthermore, a small amount of water-soluble compounds such as Si and Ca, such as silicic acid, sodium silicate, calcium nitrate, and calcium chloride, can be added in advance to the aqueous solution of the starting material or the aqueous solution of alkali hydroxide. These additives are preferred for controlling particle shape.

Next, by hydrothermally treating the slurry containing the precipitate,
Fine crystals of barium ferrite are formed and precipitated. The temperature of hydrothermal treatment is 130-270℃, preferably 150-270℃
The temperature is 200°C. If the temperature is too low, crystal formation will not be sufficient, and if the temperature is too high, the particle size of the final barium ferrite powder will become large, which is undesirable.
The hydrothermal treatment time is usually about 0.5 to 20 hours, and an autoclave is usually employed for the hydrothermal treatment.

Next, the fine crystal precipitate produced by the hydrothermal treatment is washed with water to remove free alkali, and then a flux is mixed with the obtained precipitate. As the fluxing agent, at least one selected from sodium chloride, potassium chloride, barium chloride, strontium chloride, and sodium fluoride is used. The appropriate amount of the flux to be used is 10 to 180% by weight, preferably 30 to 120% by weight, based on the precipitate (based on dried material). If the amount of flux is too small, sintering of the particles will occur, and if it is too much, there is no advantage of sintering and it is not economical. After adding a fluxing agent to the slurry and wet-mixing, the slurry may be dried, or after drying the precipitate, a fluxing agent may be added and dry-mixing.

Next, the resulting mixture is fired to completely crystallize the barium ferrite.

Firing temperature is 700-950℃, preferably 800-93℃
It is 0°C. 7! & If the degree is too low, crystallization will not proceed and the saturation magnetization will become low. Also, if the temperature is too high, the particles will become large or sintering will occur, which is undesirable.The firing time is preferably about 10 minutes to 30 hours. The firing atmosphere is not particularly limited, but air, nitrogen, etc. are preferably used.

By washing, filtering and drying the obtained baked product,
Barium ferrite magnetic powder is obtained.

Cleaning may be carried out by any method as long as impurities such as flux and excess barium in the fired product can be sufficiently removed.
As the cleaning liquid, water, inorganic acids such as nitric acid and hydrochloric acid, and organic acids such as acetic acid and propionic acid can be used.

(Example) Example 1 Ferric nitrate [Fc (No3
)3 ・9H20]1239. Og, cobalt nitrate [C
0(NO3)2 .6to12o] 64.7 g, 422 g of tetra-f titanium (T r CJ , i ) and ferrous chloride [Fe CM 2-41-120] 11.
Separately, dissolve 7 g of barium hydroxide [Ba(OH)2.8H20] 140.2 g in 1300 mj of deionized water.
, 1480 g of caustic soda (NaOH) was dissolved, and the solutions were remixed to form a precipitate.

The resulting slurry containing the precipitate was placed in an autoclave;
Hydrothermal treatment was carried out at 190°C for 6 hours.Then, the resulting precipitate was thoroughly washed with water, filtered and dried at 92°C. The mixture was added to the precipitate in an amount of 100% by weight and mixed. This mixture was calcined at 860° C. for 2 hours under an air atmosphere. The obtained fired product was thoroughly washed with water, filtered and dried to obtain barium ferrite magnetic powder.

As a result of X-ray powder diffraction spectrum and compositional analysis, the obtained barium ferrite magnetic powder was found to contain BaO-0,98[
Fe(l1l) 10.3COo, -ts'l'io,
75FC(II) 0.20o17.91, and was a magnetobrambite type.

The barium ferrite magnetic powder was also examined using a transmission electron microscope (TEM) to determine its particle shape (particle diameter, particle thickness, and distribution).
Table 1 shows the results of measuring (average value of 100 particles) and the results of measuring magnetic properties using a vibrating sample magnetometer.

Example 2 1185.1 g of ferric nitrate in 1300 mj of deionized water
, cobalt it'i acid 69.0g, titanium tetrachloride 45.
Separately, 140.2 g of barium hydroxide and 1480 g of caustic soda were dissolved in 1300 mN of deionized water, and the solutions were remixed to form a precipitate.

The resulting slurry containing the precipitate was placed in an autoclave;
After hydrothermal treatment at 170°C for 8 hours, the resulting precipitate was thoroughly washed with water, filtered and dried, and added with a flux of Na Cj and Da cj2.2H20 in an ILF amount ratio of 1=1. A mixture of 100 ffI amount % based on the precipitate
Add and mix. This mixture was heated to 890'C under an air atmosphere.
Baked for 2 hours. After thoroughly washing the obtained fired product with water, it was filtered and dried to obtain barium ferrite magnetic powder.

The results of X-ray powder diffraction spectrum and composition analysis of the obtained barium ferrite magnetic powder.

DaO-0,97rFc(III), 90Co,
, 8oTi o, 8oFe(IF) , 5oO1,75
1, and was of the magnetobrambite type.

Furthermore, regarding this barium ferrite magnetic powder, transmission electron W4mg (T EM ) -Ca particle shape (TO particle f
Table 1 shows the results of measuring the magnetic properties (average value of 100 particles) and the magnetic properties using a vibrating sample magnetometer.

Comparative Example 1 Add 1263 mj of rIFi ferric iron to 1300 mj deionized water.
1g, cobalt nitrate 64.7g and titanium tetrachloride 42
Separately, 140.2 g of barium hydroxide and 1480 g of caustic soda were dissolved in 1300 ml of deionized water, and the solutions were mixed again to form a precipitate.

The resulting slurry containing the precipitate was placed in an autoclave;
Hydrothermal treatment was carried out at 190° C. for 6 hours.The resulting precipitate was then thoroughly washed with water, filtered and dried, and a flux of NaCJ and BaCj2.2I]20 was added in a weight ratio of 1:1. 100% by weight of the mixture was added to the precipitate and mixed. This mixture was baked at 860° C. for 2 hours under an air atmosphere. After washing the obtained baked product thoroughly with water, filtration,
After drying, barium ferrite magnetic powder was obtained.

As a result of X-ray powder diffraction spectrum and composition analysis, the obtained barium ferrite magnetic powder was found to be Ba o-0,98[
Fe(m) 1o, 5coo, 7sTj 0.75
o18. O] and was of the magnetobrambite type.

The barium ferrite magnetic powder was also examined using a transmission electron microscope (TEM) to determine its particle shape (particle diameter, particle thickness, and distribution).
Table 1 shows the results of measuring (average value of 100 particles) and the results of measuring magnetic properties using a vibrating sample magnetometer.

Comparative Example 2 1263.1 g of ferric nitrate in 1300 mN of deionized water
, titanium tetrachloride 422g, zinc nitrate [Zn(NO3)
2.6H20], and separately, 140°2 g of barium hydroxide and 1480 g of caustic soda were dissolved in 1300 ml of deionized water, and the solutions were remixed to form a precipitate.

The resulting slurry containing the precipitate was placed in an autoclave;
Hydrothermal treatment was carried out at 190°C for 6 hours.Then, the obtained precipitate was thoroughly washed with water, filtered and dried, and a flux of NaCl and Bacj 2.2H20 was added in a weight ratio of 1 100% by weight of the mixture was added to the precipitate and mixed. This mixture was heated at 860°C for 2 hours in an air atmosphere.
Baked for an hour. After washing the obtained fired product thoroughly with water,
It was filtered and dried to obtain barium ferrite magnetic powder.

As a result of X-ray powder diffraction spectrum and composition analysis, the obtained barium ferrite magnetic powder was found to contain BaO.o, 98
[F e(I[[) 1o, sZno, -tsT j
o, y501a, o] and was of the magnetobrambite type.

The barium ferrite magnetic powder was also examined using a transmission electron microscope (TEM) to determine its particle shape (particle diameter, particle thickness, and distribution).
Table 1 shows the results of measuring (average value of 100 particles) and the results of measuring magnetic properties using a vibrating sample magnetometer.

(Effect of the invention) According to the present invention, the general formula % represents one or more metals selected from the group consisting of %, and M2 is selected from the group consisting of Ta, Sb, Nb, Zr and Ti. Indicates one or more metals, n=
0.8~1.0, x=0.5~1.5, y=0.01~
The value is 1.5. ) A hexagonal plate-shaped magnetoblanbite-type barium ferrite magnetic powder is obtained. This barium ferrite magnetic powder was manufactured by the conventional water suspension synthesis method as shown in the above general formula.
Some of the trivalent Fc atoms represented by Fe2O3 are replaced with Co, T
i, Ni, Mn, Cu, Zn.

3 in which a metal such as In, Gc, Nb, etc. alone or a combination thereof is used, and the total valence of the substituent atoms is substituted.
The composition is different from that of barium ferrite magnetic powder which has been converted to 'Ji' so that it is equal to that of valent Fe atoms.

Furthermore, the magnetoplumbite type barium ferrite magnetic powder obtained in the present invention is a powder with an average particle diameter of 1100 nm or less, a sharp particle size distribution, and a standard deviation of 3 Q nm or less, and has a saturated state when the specific surface area is 3 Onf10 by the BET method. Magnetization is 60C u/.

Above, when 50 rrr/(l, the saturation magnetization is 56 e
mu/IJ or higher, which is 8% higher than that obtained by conventional hydrothermal synthesis.
.

The plate ratio of the muferrite magnetic powder is in the range of 2 to 15.

Furthermore, the coercive force can be freely controlled by changing the amounts of Ml and M2 added.

Claims (2)

[Claims] (1) General formula BaO・n[Fe(III)_1_2_-_2_x_-_
yM1_xM2_xFe(II)_yO_1_8_-_y
＿／＿２] (However, M1 is Ni, Co, Cu, Mo,
M2 represents one or more metals selected from the group consisting of Mn and Zn, M2 represents one or more metals selected from the group consisting of Ta, Sb, Nb, Zr and Ti, and n= 0.8-1.0, x=0.5-1.5,
y=a numerical value of 0.01 to 1.5. ) Hexagonal plate-shaped magnetoplumbite-type barium ferrite magnetic powder. (2) As a starting material, for 1 gram atom of barium, 3 to 11 gram atoms of trivalent iron, 12-2x-
Using a compound of each element in a ratio of M1 and M2 to x gram atoms and y gram atoms of divalent iron to y gram atoms, the starting materials are dissolved in water, and the solution after mixing Alkali hydroxide is added to form a precipitate so that the alkali hydroxide concentration in the alkali hydroxide is 3 mol/l or more, and the slurry containing the precipitate is hydrothermally treated at 130 to 270°C. Mix the flux and reduce the mixture to 70
General formula BaO・n[Fe(III)_1_2_-_2_x_-_, which is characterized by firing at 0 to 950°C and washing the obtained fired product.
yM1_xM2_xFe(II)_yO_1_8_-_y
＿／＿２] (However, M1 is Ni, Co, Cu, Mg,
M2 represents one or more metals selected from the group consisting of Mn and Zn; M2 represents one or more metals selected from the group consisting of Ta, Sb, Nb, Zr, and Ti; n =0.8~1.0, x=0.5~1.5
, y=a numerical value of 0.01 to 1.5. ) A method for producing hexagonal plate-shaped magnetoplumbite-type barium ferrite magnetic powder.