JPS6369717A - Plate ba ferrite particulate powder for magnetic recording and its production - Google Patents

Abstract

PURPOSE:To obtain the title particulate powder having a high magnetization value and appropriate coercive force and having a low content of water-soluble Ba, by heating and baking plate Ba ferrite particles deposited with Zr hydroxide to dissolve the Zr into the particles. CONSTITUTION:Plate Ba ferrite particles are suspended in an aq. soln. of Zr hydroxide to obtain the plate Ba ferrite particles deposited with Zr hydroxide on their surfaces. The particles are separated by filtration, dried, and then heated and baked at 600-1,000 deg.C to dissolve zirconium in the vicinity of the surfaces of the plate Ba ferrite particles. The amt. of the Zr hydroxide to be deposited is controlled to 0.01-10.0wt%, based on the plate Ba ferrite particulate powder and expressed in terms of Zr. At <0.01wt%, the desired plate Ba ferrite particles cannot be obtained. At >10.0wt%, the magnetization value is reduced, and the obtained powder is not preferable as the magnetic particulate powder for magnetic recording.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a magnetic recording plate-shaped Ba ferrite particle comprising plate-shaped Ba ferrite particles in which zirconium is solidly dissolved near the particle surface.
A ferrite fine particle powder and a method for producing the same.

[Conventional technology]

In recent years, for example, as described in JP-A-55-861.03, ferromagnetic non-acicular particles having a large magnetization value, an appropriate coercive force, and an appropriate average particle size have been developed. There is an increasing demand for magnetic materials for recording, especially magnetic materials for perpendicular magnetic recording.

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

Conventionally, one of the manufacturing methods of plate-shaped Ba ferrite is B
A method is known in which an alkaline suspension containing a ions and FeQID is hydrothermally treated using an autoclave as a reaction device (hereinafter, this is simply referred to as a hydrothermal synthesis method).

First, regarding magnetic properties, it is necessary that the magnetization value of plate-shaped Ba ferrite particles for magnetic recording be as large as possible.
No. 328 [...] Magnetobrambite ferrite used as a magnetic recording medium abrasive is required to have as large a saturation magnetization as possible. ” as stated.

In addition, a coercive force of about 300 to 15,000 e is generally required, and the a
In order to reduce the coercive force of the ferrite M particles and obtain an appropriate coercive force, some of the Pe(2) in the ferrite is replaced with Ti(I).
V and Go(10 or Co(III and Mn, Zn
, It has been proposed to substitute divalent metal ions M (IQ) such as Ni.

Next, regarding powder characteristics, the particle size of the plate-shaped Ba ferrite fine particle powder for magnetic recording is as fine as possible.
In particular, it is required that the thickness be 0.3 μm or less.

This fact can be seen, for example, in JP-A-56-125219, which states, However, in order to perform sufficient recording and reproduction in this wavelength range, the crystal grain size of the ferrite must be approximately 0.3μ.
m or less is desirable. However, if it is about 0.01 μm, it will not exhibit the desired ferromagnetism, so a suitable crystal grain size is required to be about 0.01 to 0.3 μm. ” is as stated.

In addition, the specific surface area needs to be as large as possible in order to reduce the noise of the magnetic recording medium, especially 3 (Jr
Particles of d/g or higher are required.

This phenomenon can be seen, for example, in the Technical Research Report MR8 of the Institute of Electronics and Communication Engineers.
1-11, p. 27, 23-9, rFig, 3J, etc. rFig. 3J is a diagram showing the relationship between the specific surface area of the 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 holds true for the plate-shaped Ba ferrite particles as well.

By the way, the plate-like Ba obtained by the above-mentioned hydrothermal synthesis method
The ferrite particles contain excess Ba as a water-soluble component that does not contribute to the production of plate-shaped Ba ferrite particles, and the Ba ferrite particles containing this water-soluble Ba are used as magnetic particles to form a magnetic tape. It is known that when manufactured, the running properties of the magnetic tape deteriorate due to corrosion of the magnetic head and the like. This phenomenon is explained, for example, in Japanese Patent Publication No. Sho 60-15576, "... Regarding Ba-ferrite produced by an autoclave method (hydrothermal synthesis method)... Extracting and removing...''
No. 7118 [...A magnetic recording medium is used in a state where it is always in contact with a magnetic head or a guide ball. ...The magnetic layer is worn out by contact, and the worn pieces become powder and scatter. This powder adheres and accumulates on the guide ball, magnetic head, etc., and as a result, when reproducing the recorded information on the magnetic recording medium, This can occur as signal readout or dropout phenomena...", "...The cause of head corrosion is not only Na25O and NaCl, but if it is caused by electrolytes, it is likely that the same corrosion will occur. was recognized.

Therefore, in the present invention, an aqueous solvent is appropriately used to wash away water-soluble impurities. It is clear from the statement ``.

[Problem that the invention seeks to solve]

There is currently a demand for plate-shaped Ba ferrite particles having a large magnetization value, appropriate coercive force, appropriate average particle size and large specific surface area, and a low content of water-soluble Ba. In the hydrothermal synthesis method as described above, various Ba ferrite particles are precipitated by selecting reaction conditions. These precipitated particles usually have a hexagonal plate shape, and have different magnetic properties, particle size distribution, and average diameter depending on the generation conditions.Due to the generation mechanism, they contain a large amount of water-soluble Ba, for example, 500 ppm or more. It may contain.

The present inventor has been involved in the research and development of plate-shaped Ba ferrite particles using a hydrothermal synthesis method for many years.
It has been found that plate-shaped Ba ferrite fine particles having a diameter of ~0.3 μm can be obtained.

However, when trying to control the coercive force to 15000e or less, the plate-shaped Ba ferrite particles having the average diameter of 0.05 to 0.3 μm have a magnetization value of 50 emu/
It is difficult to maintain it above g.

Furthermore, a method is known in which the magnetization value is improved by heating and firing plate-shaped Ba ferrite fine particles produced from an aqueous solution by a hydrothermal synthesis method at a temperature of 800°C or higher (Japanese Patent Publication No. 12973/1983) ) However, when using this method, a high temperature of 600°C or higher is required in order to obtain a plate-shaped Ba ferrite fine particle powder with a magnetization value of 50 emu/g or higher, and in this case, the particles and the particles mutually interact with each other. The sintering between the particles becomes significant, resulting in lumpy particles, and as a result, the specific surface area becomes small, especially less than 20 rr+/g, which is not preferable as a magnetic particle powder for low-noise magnetic recording.

In addition, in order to control the coercive force of the plate-shaped Ba ferrite fine particles obtained by heating and firing to 15,000e or less, it is necessary to add a large amount of the above-mentioned coercive force reducing agent, which reduces the magnetization value. This may cause the coercive force to increase to 300 emu/g while maintaining a large magnetization value, especially 50 emu/g or more.
It was difficult to control the temperature within the range of ~15,000e.

Therefore, it has a large magnetization value and an appropriate coercive force, and
Water-soluble B with suitable average particle size and large specific surface area
There is a strong desire to establish a method for obtaining plate-like Ba ferrite particles with a small a content.

[Means for solving problems]

The present inventor has conducted various studies in order to obtain plate-shaped Ba ferrite particles having a large magnetization value, appropriate coercive force, appropriate average particle size, large specific surface area, and low content of water-soluble Ba. As a result, we have arrived at the present invention.

That is, the present invention provides a magnetic recording plate-shaped Ba ferrite particle powder consisting of plate-shaped Ba ferrite particles in which zirconium is solidly dissolved near the particle surface, and plate-shaped Ba ferrite particles in an aqueous solution containing zirconium hydroxide. to obtain plate-shaped Ba ferrite a particles with zirconium hydroxide deposited on the particle surface, filter the particles, dry them,
Next, the method for producing plate-shaped Ba ferrite fine particles for magnetic recording comprises dissolving zirconium in the vicinity of the particle surface of the plate-shaped Ba ferrite at particles by heating and firing at a temperature range of 600 to 1000 ° C. .

[For production]

First, the most important point in the present invention is that plate-shaped Ba ferrite particles are suspended in an aqueous solution containing zirconium hydroxide, and the plate-shaped Ba ferrite fine particles with zirconium hydroxide deposited on the particle surface are suspended in an aqueous solution containing zirconium hydroxide. This is due to the fact that when the particles are separated by p, dried, and then heated and fired at a temperature range of 600 to 1000 ° C., zirconium can be solid-dissolved in the vicinity of the particle surface of the plate-shaped Ba ferrite fine particles. As a result, it is possible to obtain plate-shaped Ba ferrite Hk particles having a large specific surface area, especially 30%/g or more, and also having a high coercive force. Because it has the effect of reducing the coercive force, it is possible to reduce the amount of the coercive force reducer that causes the decrease in the magnetization value, so it can effectively reduce the coercive force by 300 to 15,000 e while maintaining a large magnetization value. The point is that it can be controlled within the range of .

Another important point in the present invention is that, as shown in the Examples below, the excess water-soluble Ba content in the plate-shaped Ba ferrite fine particles reacts with a part of the added zirconium to form water-insoluble Ba3Znz03. Because a small amount of fine particles such as the following are produced, a plate-shaped Ba ferrite fine particle powder with a low water-soluble Ha content can be obtained.

In the present invention, the reason why plate-shaped Ba ferrite fine particles having a large specific surface area can be obtained and the coercive force can be controlled while maintaining a large magnetization value is explained by the following comparative example. As shown, zirconium is added during the formation reaction of plate-shaped Ba ferrite fine particles in the hydrothermal treatment method (for example, in JP-A-58-1999).
No. 56302, JP-A No. 61-40823), and when the particle surface of plate-shaped Ba ferrite fine particles is coated with zirconium hydroxide and/or oxide, the effects of the present invention can be obtained. Since there is no plate-like Ba
It is believed that this is due to the solid solution of zirconium near the particle surface of the Ferrai Hit particles.

In addition, as shown in Comparative Example 2 below, the present inventor has discovered that when using a method of adding zirconium when hydrothermally treating an alkaline iron hydroxide (2) suspension containing Ba ions, zirconium and Ba A reaction occurs with Ba3
ZrzO: + fine particles are generated, while the Fe component is B
Vf1 has confirmed that it is produced as hematite without reacting with a component.

Next, various conditions for implementing the present invention will be described.

The plate-shaped 8a fluorite fine particles as the starting material in the present invention are plate-shaped Ba(1·nFezos (4≦n≦8
) fine particles and those to which the well-known coercive force reducing agent mentioned above is added.In addition to plate-shaped Ba ferrite fine particles produced from an aqueous solution by hydrothermal synthesis, Ba ferrite particles produced by heating and calcining these, and Ba ions from an aqueous solution. After mixing and melting plate-shaped Ba ferrite fine particles obtained by a so-called co-precipitation method in which Fe ions and Fe ions are precipitated and the precipitate is heated and calcined, a component raw material of Ba ferrite and a glass forming substance are mixed and melted.
Any plate-shaped Ba ferrite fine particles obtained by the so-called glass melting method in which the melt is rapidly cooled can be used.

In the present invention, zirconium hydroxide can be deposited by suspending plate-shaped Ba ferrite fine particles in an aqueous solution containing zirconium hydroxide.

The amount of zirconium hydroxide deposited in the present invention is 0.01 in terms of Zr relative to the plate-shaped Ba ferrite fine particle powder.
~10.0% by weight. If the amount is 0.01% by weight or less, it is impossible to obtain the plate-shaped Ba ferrite a particle powder which is the object of the present invention. If it is 10.0% by weight or more, the magnetization value becomes small, which is not preferable as magnetic particles for magnetic recording. Considering the magnetization value of the obtained plate-shaped Ba ferrite fine particle powder, it is 0.01 to 6.0% by weight.
is preferred.

The heating and firing temperature in the present invention is 600 to 1000°C. If the temperature is 600° C. or lower, zirconium is not sufficiently dissolved in the vicinity of the particle surface of the plate-shaped Ba ferrite particles. If it is above 1000'cJN, sintering between particles and particles becomes significant, making it impossible to obtain plate-shaped Ba ferrite fine particles with a large specific surface area.

During heating and firing in the present invention, a well-known fluxing agent may be present if necessary, and in this case, a plate-shaped Ba ferrite fine particle powder having more preferable magnetic properties and powder properties can be obtained. As the flux, for example, one or more of halides and sulfates of alkali metals and alkaline earth metals can be used.

The amount of zirconium in the heated and fired product in the present invention is Zr
It is 0.01 to 10.0% by weight in terms of weight. If it is less than 0.01% by weight, the object of the present invention cannot be fully achieved. If it is 10.0% by weight or more, the magnetization value becomes small, which is not preferable as magnetic particles for magnetic recording.

In addition, in the present invention, as mentioned above, a trace amount of Ba3Z
Although rzOJ particles are separated and produced, these do not have any adverse effect on the magnetic properties and powder properties of the obtained plate-shaped Ba ferrite fine particle powder, as shown in the examples below.

〔Example〕

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

In addition, the average diameter of particles in the following Examples and Comparative Examples is a value measured by electron micrograph, and the specific surface area is a value measured by BET method. Further, the magnetization value and coercive force were measured in a powder state in a magnetic field of 1.0 KOe.

Example 1 By a hydrothermal synthesis method, 9.52 mol% of Ba, based on Fe,
Platy Ba ferrite fine particles containing 8.57 mol% Co and 2.86 mol% Ti were obtained.

100 g of the obtained fine particles were mixed with 0.002 mol of Zr0.
Dispersed and mixed in a CIz aqueous solution, and in p114, zirconium hydroxide (0.2% by weight in terms of Zr) was added to the particle surface.
Applies to. ) was precipitated, separated by F and dried.

Next, 50 g of this dry particle powder and 50 g of Na1 were mixed and then heated and calcined at 800° C. for 1.5 hours.

The fine particles obtained by heating and firing had an average diameter of 0.08 μm, a specific surface area of 48 m/g, a magnetism of 9700e for antimagnetic magnet 1c, and a magnetization value of 55.8 emu/g.

In addition, the amount of zirconium was determined to be 0.2 as a result of fluorescent X-ray analysis.
As a result of chemical analysis, the water-soluble Ba content is 8% by weight.
It was 0 ppln.

As shown in the X-ray diffraction diagram shown in FIG.
were mixed. In Figure 1, peak A is Ba ferrite I.
, beak B is Ba3Zr203.

Incidentally, the plate-shaped Ba ferrite fine particles containing CO and Ti obtained in the same manner as above except that zirconium hydroxide was not deposited had an average diameter of 0.15 μm and a specific surface area of 18 nr. /g, and the coercive force was 121.00e and the magnetization value was 54.4 emu/g.

Example 2 One plate-shaped Ba ferrite containing 10.0 mol % of Ba based on Fe was obtained by a hydrothermal synthesis method.

0.004 mol of ZrO3 was added to 100 g of the obtained fine particles.
After dispersing and mixing in an O4 aqueous solution and precipitating zirconium hydroxide (corresponding to 0.4% by weight in terms of Zr) on the particle surface at pl+ 6.0, it was separated in an oven, dried, and then heated at 750°C. It was heated and baked for 1.5 hours.

The fine particles obtained by heating and firing have an average diameter of 0.2 μm, a specific surface area of 38%/g, and a coercive force He of 11%.
500e, and the magnetization value was 53.2 emu/g. Furthermore, the amount of zirconium in solid solution was determined to be 0.0 as a result of fluorescent X-ray analysis.
It was 495 ppm. As a result of X-ray diffraction, it was found that this fine particle powder contained a trace amount of BaJ in the plate-shaped Ba ferrite fine particle powder.
rz(h was mixed.

Incidentally, the plate-shaped Ba ferrite fine particles obtained in the same manner as above except that zirconium hydroxide was not deposited had an average diameter of 0.2 μm and a specific surface area of 17rrf/
g, and the magnetism has a coercive force of 19800e and a magnetization value of 5.
3. Oemu/g.Example 3 Platy Ba ferrite containing 9.52 mol% Ba and 9.1 mol% CO based on Fe obtained by the hydrothermal synthesis method in the same manner as in Example 1. 100g of a particles 0.16m
Disperse and mix in Zr0(NO3)z aqueous solution of 95
After depositing zirconium hydroxide on the particle surface by hydrolysis at ℃ for 1 hour, it was separated in an oven and dried.
Then, it was heated and baked at 800° C. for 1.0 hour.

The fine particles obtained by heating and firing had an average diameter of 0.05 μm, a specific surface area of 67 rrf/g, and a magnetism of 5950e and a magnetization value of 54.5 emu/g. Further, the amount of solid solution of zirconium was 1.4% by weight as a result of fluorescent X-ray analysis, and the water-soluble Ba content was 85 ppm as a result of chemical analysis. This fine particle powder is
As a result of line diffraction, a trace amount of Ba3Zr203 was found to be mixed in the plate-shaped Ba ferrite fine particle powder.

The plate-shaped Ba ferrite Hk particles obtained in the same manner as above except that zirconium hydroxide was not deposited had an average diameter of 0.08 μm and a specific surface area of 19 i/g.
As for magnetism, the coercive force is 15800e and the magnetization value is 54.
．． It was Oemu/g.

Example 4 10.0 mol% Ba based on Fe by hydrothermal synthesis.

Platy Ba containing 9 mol% Co and 2 mol% Ti
Ferrite fine particles were obtained.

100 g of the obtained fine particles were mixed with 0.04 mol of ZrOCl.
After dispersing and mixing in an aqueous solution of zirconium hydroxide (corresponding to 4% by weight in terms of Zr) on the particle surface at pH 4, the particles were separated in an oven and dried.

Next, this dry particle powder was heated and calcined at 800° C. for 1.5 hours.

The fine particles obtained by heating and firing have an average diameter of 0.08 μm, a specific surface area of 65 d/g, and magnetism due to the coercive force of He.
was 7300e, and the magnetization value was 50.3 emu/g.

In addition, the amount of zirconium solid solution was determined by fluorescent X-ray analysis to be 4.
．． 1% by weight, and the water-soluble Ba content was 58 ppm as a result of chemical analysis.

Incidentally, the plate-shaped Ba ferrite fine particles containing Co and Ti obtained in the same manner as above except that zirconium hydroxide was not deposited had an average diameter of 0.15 μm and a specific surface area of LM. /g, and the magnetism is such that the coercive force is 1
1300e, and the magnetization value was 53.5 emu/g.

Comparative Example I Platy B was prepared in the same manner as in Example 1, except that zirconium hydroxide was not deposited on the plate-shaped Ba ferrite fine particles containing Go and Ti, and the firing temperature was 920°C.
a. Ferrite fine particles were obtained.

The BET specific surface area of the obtained plate-shaped Ba ferrite particles is 18n? /g, and the plate-shaped Ba ferrite H before heating and firing
This was significantly lower than the BET specific surface area of the k particles, 85 m 2 /H, indicating that sintering had occurred between the particles and between the particles.

Regarding magnetism, the coercive force He was 13500e, the magnetization value was 56, and Oemu/g.

Comparative example 2 Fe(NOs) 30.7 mol, Co(NO3)z
0.05mol, Zr(NO+)zO,05mol and Ba(OH)z・811zO0,078mol
An alkaline suspension of 8.4 mol of Na0tl was heated in an autoclave to 250°C and maintained at this temperature for 3 hours with mechanical stirring to form a precipitate.

After cooling to room temperature, the precipitate was filtered off, thoroughly washed with water, and then dried.

As a result of the X-ray diffraction shown in FIG. 2, the obtained particles were mainly composed of Ra3Zrzo and α-PezOi, and no Ba ferrite peak was observed.

In FIG. 2, peak A is [1azZrzOt, peak B is α
-Fe203.

Comparative Example 3 100 g of plate-shaped Ba ferrite fine particles obtained in the same manner as in Example 2, except that zirconium hydroxide was not deposited, were dispersed and mixed in an aqueous solution containing 0.004 mol of Zr05O4. After depositing zirconium hydroxide on the particle surface, it was separated in a furnace and heated at 150
Dry at °C.

The obtained plate-shaped Ba ferrite +-m particles have an average diameter of 0.0
2 μm, and the magnetism has a coercive force Hc of 20200e,
The magnetization value is 52. It was Oemu/g.

Comparative Example 4 A plate-shaped Ba ferrite was obtained in the same manner as Comparative Example 3, except that it was fired at 500°C instead of drying at 150°C.

The obtained plate-shaped Ba ferrite fine particles have an average diameter of 0.2μ
m, the specific surface area is 18rrr/g, and the magnetism is
Coercive force He is 19500e, magnetization value is 53. Oemu
/g.

〔effect〕

As shown in the previous example, the plate-shaped Ba ferrite particles according to the present invention have an average diameter of 0.05 to 0.3 μm and a specific surface area of 30 rd, with zirconium solidly dissolved on the particle surface.
/g or more, has a large magnetization value in a magnetic field of 10 KOe, and has a coercive force Hc of 300 to 15
000e and the content of water-soluble Ba is as small as possible, so it is optimal as a magnetic material for magnetic recording, particularly as a material for perpendicular magnetic recording.

[Brief explanation of the drawing]

1 and 2 are X-ray diffraction diagrams, FIG. 1 shows the powder particles obtained in Example 1, and FIG. 2 shows the powder particles obtained in Comparative Example 2. In Figure 1, peak A is Ba ferrite and peak B is Ba ferrite.
It is Zr207. In Figure 2, peak A is BaJr207
, peak B is α-Fe203.

Claims (2)

[Claims] (1) A plate-shaped Ba ferrite fine particle powder for magnetic recording comprising plate-shaped Ba ferrite fine particles in which zirconium is solidly dissolved near the particle surface. (2) Platy Ba ferrite fine particles are suspended in an aqueous solution containing zirconium hydroxide to obtain plate-like Ba ferrite fine particles having zirconium hydroxide deposited on the particle surface, and the particles are filtered. Dry, then 600-100
By heating and firing in a temperature range of 0°C, the plate-like B
A method for producing a plate-shaped Ba ferrite fine particle powder for magnetic recording, characterized by dissolving zirconium in the vicinity of the particle surface of the ferrite fine particles.