JPH07249510A - Oxide permanent magnet and its manufacture - Google Patents

Abstract

PURPOSE:To provide a magnetoplumbite type oxide permanent magnet which has a uniform grain size distribution and excellent magnetic property and a manufacturing method by which the magnet can be manufactured without increasing the production cost. CONSTITUTION:A magnetoplumbite type oxide permanent magnet is manufactured by crushing and fine grinding a calcined body into particles having a volume mean diameter of <=4mum, with <=20vol.% particles having >=10-mum particle sizes, and molding the particles, and then, sintering the molded body. After sintering, the surfaces of the sintered body parallel to the axis of easy magnetization are subjected to specular finishing and thermal etching and the surfaces are observed under a scanning electron microscope. The volume mean diameter of the grains constituting the sintered body is <=1.0mum and the Rosin-Rammler distribution constant found from the volume distribution of the diameter of the equivalent circle of the grains is >=3.1. In addition, the squareness ratio of the grains is >=95.5%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoplumbite type oxide permanent magnet and a method for producing the same.

[0002]

2. Description of the Related Art Magnetoplumbite type oxide permanent magnets represented by sintered magnets of Sr ferrite and Ba ferrite are required to obtain crystal grains (grains) constituting a ferrite magnet sintered body in order to obtain high magnetic characteristics. It is important that the particle size of the particles is equal to or smaller than the critical diameter of a single magnetic domain, and that the particle size is fine and uniform. The single-domain critical diameter is about 1 μm for these ferrite magnets.

Conventionally, various methods have been tried in order to make the grain size of the crystal grains constituting the ferrite magnet sintered body equal to or less than the critical diameter of a single magnetic domain so as to be fine and uniform. For example, the average particle size of iron oxide as a raw material and the standard deviation of the particle size distribution are controlled (JP-A-1-147809), additives are added during calcination (JP-B-4-14484), or For example, the calcined powder crystal grains may be made fine and homogenized according to the firing temperature (Japanese Patent Publication No. 59-10564). By making the crystal particles of the calcined powder to be used fine and uniform, the grain size of the ferrite magnet is made to be equal to or smaller than the critical size of a single domain, and fine and uniform magnetic properties are obtained. Further, the above-mentioned JP-A-1-14
In Japanese Patent No. 7809, the average particle size of the raw iron oxide and the standard deviation of the particle size distribution are regulated, and then the average particle size of the fine powder used for magnetic field molding obtained by finely pulverizing the calcined powder and It also regulates the standard deviation of the particle size distribution. further,
Japanese Unexamined Patent Publication No. 4-320009 proposes classifying fine powder obtained by finely pulverizing calcined powder and adjusting average particle size, particle size distribution and the like in the production of Sr ferrite sintered magnet. There is. According to the proposed method, a ferrite sintered magnet having an improved Br (residual magnetic flux density) can be obtained.

It is important to make the crystal grains of the calcined body fine and homogeneous, but when crushing the obtained calcined body, the grain size of the sintered body obtained by sintering is defined as the single domain critical diameter. In order to achieve the following, even if the average particle size is reduced to about 0.8 μm or less by the conventional pulverization method, the particle size distribution of the obtained particles is wide, and the particle size of the grains of the sintered magnet obtained by using this powder is Hard to be uniform. Therefore, it has been difficult to obtain a magnet having further excellent magnetic characteristics. Also,
JP-A-1-147809 and JP-A-4-320
By adjusting the particle size distribution of the fine powder obtained by finely pulverizing the calcined powder using the method proposed in Japanese Patent Application No. 009, the sintered magnet having a more uniform grain size and high magnetic properties Is obtained. However, these proposed methods require a classification step, which leads to an increase in cost. When finely pulverizing the calcined powder, a wet pulverizing method is usually used, and a wet forming method is also usually used in the forming step. Since classification is usually carried out in a dry system, a fine powder drying step is required before classification, and it is necessary to add a new solvent in the molding step, increasing the manufacturing process and increasing the product cost in industrial production. Will be done. For this reason, there is a demand for a ferrite sintered magnet having a uniform grain size of the obtained grain and excellent magnetic characteristics without increasing the cost.

[0005]

The object of the present invention is to provide a magnetoplumbite type oxide which is easy to manufacture without increasing the number of manufacturing steps, has a uniform grain size distribution, and has excellent magnetic properties. A permanent magnet and a method for manufacturing the same are provided.

[0006]

The above objects are achieved by the present invention described in (1) to (6) below. (1) Magnetoplumbite-type oxide permanent magnet, where the surface parallel to the easy magnetization direction is mirror-finished and subjected to thermal etching, and the surface is observed by a scanning electron microscope. The volume average particle diameter is 1.
An oxide permanent magnet having a diameter of 0 μm or less, a uniform number of Rosin-Rammler plots obtained from the volume distribution of equivalent circle diameters of 3.1 or more, and a squareness ratio of 95.5% or more. (2) The oxide permanent magnet is replaced by the general formula MO · nFe ₂ O
_3. The oxide permanent magnet according to (1) above, wherein 5.80 ≦ n ≦ 6.40 when represented by ₃ (M is Sr and / or Ba). (3) 0.1 to 0.70 wt% SiO ₂ , CaO
0.05 to 1.0 wt% of CaO / Si
The oxide permanent magnet according to the above (1) or (2), wherein the molar ratio of O ₂ is 0.9 to 2.0. (4) The sample mixture is calcined, the calcined body is roughly crushed, then finely crushed, and the fine powder is used to perform molding in a magnetic field.
When the obtained molded body is sintered to manufacture an oxide permanent magnet, the calcined body is roughly pulverized so that the volume average particle size is 4 μm or less and the particle size of 10 μm or more is 20 vol% or less. A method for producing an oxide permanent magnet, wherein the oxide permanent magnet according to any one of (1) to (3) above is obtained. (5) The method for producing an oxide permanent magnet according to the above (4), wherein the calcination temperature is 1200 to 1330 ° C. (6) The method for producing an oxide permanent magnet according to the above (4) or (5), wherein the powder is not classified before and after the fine pulverization for adjusting the particle size distribution.

[0007]

FUNCTION AND EFFECT The magnetoplumbite-type oxide permanent magnet of the present invention has a grain volume average particle size of 1.0 μm.
m or less, that is, a single domain critical diameter or less. In addition, when a rosin-Rammler plot is performed using the equivalent circle diameter of the grains and the volume distribution obtained from the equivalent circle diameters, the obtained uniform number, that is, the slope is a high value of 3.1 or more. The distribution of diameters has the highest uniformity ever. Moreover, the squareness ratio is a high value of 95.5% or more. Therefore, Br (residual magnetic flux density) and HcJ (coercive force)
The oxide permanent magnet has excellent magnetic characteristics and a high magnetic potential calculated from

In the method for producing an oxide permanent magnet of the present invention, when the calcined body is crushed, the volume average particle size is set to 4 μm or less, and the particles of 10 μm or more are roughly crushed to 20 vol% or less. Then, this is finely pulverized, molded in a magnetic field, and sintered to obtain an oxide permanent magnet. The coarsely pulverized powder according to this production method is finer than the volume average particle diameter of the coarsely pulverized powder obtained in the coarse pulverization step which has been considered appropriate until now, and the proportion of particles having a particle size of 10 μm or more is low.

A classification step may be separately provided in order to adjust the volume average particle size and particle size distribution of the powder obtained by coarse pulverization to the above range, but preferably the composition and manufacturing conditions are within the preferred range of the present invention. According to the method of coarsely pulverizing the calcined body, the volume average particle size and the particle size distribution of which are within the range of the present invention, an oxide permanent magnet having high magnetic properties can be obtained without particularly providing a classification step. The production cost does not increase by providing the classification step.

[0010]

Specific Structure The specific structure of the present invention will be described in detail below.

The oxide permanent magnet of the present invention is a magnetoplumbite type oxide permanent magnet. A surface parallel to the easy magnetization direction (C axis) of this oxide permanent magnet is polished and mirror-finished by a conventional method, and then thermal etching is performed. Thermal etching is usually performed at 1070 ° C. for the purpose of slightly growing grains and making grain boundaries clearer.
Do it for 0 minutes. The obtained surface was scanned with an electron microscope (SE
Observe in (M), and determine the equivalent circle diameter of the grain from the area of the recognized grain. The volume average particle diameter obtained from the equivalent circle diameter is 1.0 μm or less, preferably 0.7 μm to 1.0
μm, more preferably 0.7 μm to 0.9 μm.
More specifically, the volume average particle size of the grain is obtained by approximating the grain boundary of the grain into a polygon and determining the equivalent circle diameter by image processing.
It is determined by setting the volume distribution to 50 vol% particle diameter obtained from the equivalent circle diameter. By setting the volume average particle diameter within the above range, the grain becomes smaller than the single domain critical diameter, and the coercive force (Hc
A magnet with a large J) can be obtained. When the volume average particle size exceeds the above range, the number of grains having a size exceeding the single domain critical diameter increases, and HcJ decreases.

Further, a histogram of the volume distribution of the grains is obtained from the distribution of the equivalent circle diameters of the grains, and the equal number of the Rosin-Rammler plots obtained by the method described later is calculated from this histogram. Or more, preferably 3.3 or more, more preferably 3.5 or more.
The Rosin-Rammler formula is used to display the particle size distribution, and the larger the uniform number of the formula, the narrower the particle size distribution of grains. When the number is equal to or more than the above, the grain size distribution is narrow and uniform, and the squareness ratio is 95.5%.
Above all, it is an excellent magnet having a magnetic property of 95.5% to 98%. When the uniform number is less than the above, the grain size distribution is wide and the magnetic properties such as the squareness ratio are deteriorated. According to the present invention, the upper limit of the uniform number is usually about 4.

The uniform number of Rosin-Rammler plots can be obtained as follows.

Assuming a mixed powder having a histogram of the volume distribution obtained from the equivalent circle diameters of grains, when this mixed powder is sieved, R is the volume on the sieve (%), D _p is the equivalent circle diameter, b and the n as a constant, a rosin-Rammler When indicating the (rosin-Rammler) equation, R = 100 · exp (-bD p n). If b = 1 / D _e ^{n in} this equation, R = 100 · exp {− (D _p / D _e ) ⁿ } is obtained (Rosin-Rammler-Bennet equation). Where D _e is
The particle size characteristic number (absolute size constant), and n is a uniform number (distribution constant).

By transforming the above formula of Rosin-Rammler-Bennet, ln {ln (100 / R)} = nlnD _p + C is obtained. Therefore, for lnD _p , ln {ln
If (100 / R)} is plotted, it becomes a straight line, and n can be obtained from the gradient of this straight line. In the present specification, the plot used to calculate n is in a range where the linearity correlation coefficient is 99.5% or more.

In this specification, the squareness ratio is the area occupied by the J (magnetization) -H (magnetic field) curve showing the magnetic characteristics, the vertical axis (J) and the horizontal axis (H) in the second quadrant. Then, the squareness ratio (%) = {S / (Br × HcJ)} × 100.

When the magnetoplumbite-type oxide permanent magnet of the present invention is represented by the general formula MO.nFe ₂ O ₃ (M is preferably Sr and / or Ba),
5.8 ≦ n ≦ 6.4 is preferable, and 5.8 is more preferable.
≦ n ≦ 6.2.

If the composition n is less than the above range, the crystal grains are likely to grow large during calcination and HcJ tends to decrease. On the other hand, if it is more than the above range, the ferritization reaction tends to be insufficient, and excess Fe ₂ O ₃ remains, so that Br tends to deteriorate.

Further, it is preferable that the oxide permanent magnet of the present invention contains SiO ₂ and CaO as a liquid phase component at the time of firing, which has the effect of promoting the sintering reaction or densifying the sintered body. . For each content,
SiO ₂ is 0.1 to 0.7 wt%, more preferably 0.
3 to 0.7 wt%, particularly 0.4 to 0.6 wt%, CaO 0.05 to 1.0 wt%, more preferably 0.4 to 1.0 wt%, 0.5 ~
It is preferable that the content of CaO / Si is 0.9 wt%.
The molar ratio of O ₂ is 0.9 to 2.0, more preferably 1.1.
˜1.8, and particularly preferably 1.2 to 1.7. With such a range, an oxide permanent magnet having a high Br and HcJ and a higher magnetic potential is likely to be obtained.

If the amount of SiO ₂ is less than the above range, the grains of the sintered body are likely to be coarsened and HcJ tends to be lowered. On the other hand, if the amount is too large, the density of the sintered body tends to decrease, and Br deteriorates. If the content of CaO is less than the above range, the density of the sintered body tends to decrease, and Br tends to deteriorate. On the other hand, if the amount is too large, the grains of the sintered body are likely to be coarsened and HcJ tends to be lowered. These CaO / S
If the molar ratio of iO ₂ is higher or lower than the above range, the magnetic potential tends to decrease.

The magnetic potential indicates the balance between HcJ and Br and serves as an index for judging the overall magnetic characteristics, and is defined as follows.

Magnetic potential = HcJ (measured value) + [B
r (measured value) -4000] × 3

The reason for this definition is as follows.

As for the relationship between Br and HcJ, within a normal range, HcJ may be increased by β when H is decreased by a certain ratio, or HcJ may be increased by α when Br is decreased by a certain ratio. It is easy to lower β. And this β /
The ratio of α is about 3.

In order to represent the essential potential of the material in a unified manner, when Br = 4000 G, the actual B
This is expressed by correcting the actual HcJ by multiplying the deviation of the data of r by a coefficient 3. That is, Br = 4000
The converted HcJ (Oe) in G is used as an index.

Furthermore, in the oxide permanent magnet of the present invention, Al ₂ O ₃ , Cr ₂ O _3, etc. having a function of appropriately controlling the growth of particles at the time of calcination or sintering, raw materials used, equipment used, etc. The total amount of MnO, ZnO, CuO and the like derived from the above may be 5 wt% or less.

Next, a method for manufacturing the oxide permanent magnet of the present invention will be described.

In the oxide permanent magnet of the present invention, a mixture containing iron oxide and a component which becomes SrO and / or BaO is calcined by sintering, the obtained calcined body is roughly pulverized, and then finely pulverized. Then, the fine powder obtained by finely pulverizing is used to perform molding in a magnetic field, and the obtained molded body is sintered to manufacture.

The raw materials to be used are not particularly limited, but usually, oxides or powders which become oxides by sintering are mixed and used. As the raw material powder containing elements such as Fe, Si, Sr, Ba, Ca, Al and Cr, oxides or carbonates are usually used, but hydroxides, nitrates, chlorides and the like can also be used. When powder is used as the raw material, the average particle size of the powder used is preferably about 0.5 to 3.0 μm.

As the mixture for calcination, in addition to the iron oxide and the components which become SrO and / or BaO by the above-mentioned sintering, Si is added for the purpose of further promoting the sintering during calcination and controlling the growth of particles. It is preferable to add compounds containing Ca and Ca, and if necessary, elements such as Al and Cr. The total amount of such additives added may be about 0.1 to 5.0 wt% in terms of stoichiometric oxide.

Raw materials containing such components are weighed and mixed, and either a wet method or a dry method may be used as a mixing method, and a ball mill, an attritor, a mixer or the like is used so that the raw materials are sufficiently mixed. It may be performed for 20 minutes to 2 hours.

The calcination temperature in the present invention is preferably 1
200 to 1330 ° C., more preferably 1210 to 132
It is 0 ° C., and particularly preferably 1220 to 1310 ° C. By calcining at such a temperature, the crystal grains at the time of calcining can be preferably controlled and can be sufficiently made into ferrite. If the calcination temperature is too low, the ferrite formation reaction does not proceed sufficiently, and the grain size of the crystal particles tends to be too small, and secondary particles tend to remain due to the subsequent fine pulverization, resulting in an orientation property. And the squareness ratio is likely to deteriorate. On the other hand, if the calcination temperature is too high, coarse crystal grains are likely to increase and HcJ deteriorates. The calcination may be performed by any method such as a batch method or a continuous method, but in mass production, for example, a continuous rotary kiln can be used. The calcination time may vary depending on the calcination temperature in a batch system, for example, but it is preferably 30 minutes to 5 hours, more preferably 1 to 3 hours. Further, in the case of the continuous type, since it depends on the calcination temperature and the flow rate per unit time, it is sufficient to experimentally obtain a flow rate that is equivalent to the above range in the batch type. The calcination time refers to the holding time at a predetermined calcination temperature.

Next, the obtained calcined body is pulverized. The pulverization may be a dry pulverization method or a wet pulverization method, but usually, coarse pulverization is performed by the dry pulverization method, and fine pulverization performed on the obtained coarse pulverized powder is performed by the wet pulverization method. It is preferable. Hereinafter, an example in which coarse pulverization is performed by a dry pulverization method and fine pulverization is performed by a wet pulverization method will be described, but these pulverization methods are not particularly limited.

The coarse pulverization may be carried out by a batch system or a continuous system, and a vibrating mill, roller mill, atomizer,
It may be performed using a super micron mill or the like. Usually, a dry crushing method is used. Further, when the calcined body forms a large lump, it may be carried out by the above method after crushing it with a jaw crusher or the like as necessary.

In the production method of the present invention, this coarse pulverization is performed by calcination so that the volume average particle size of the calcinated body is 4 μm or less, preferably 1 to 4 μm.
m, more preferably 1.5 to 3.5 μm and 10 μm
The particle size of m or more is 20 vol% or less, preferably 10 vol% or less. Since it is preferable that the number of particles having a particle size of 10 μm or more is as small as possible,
Particularly preferable is that particles having a size of 10 μm or more are not substantially contained. The effect of the present invention is exhibited by coarsely pulverizing the particles so that the volume average particle diameter and the particle diameter distribution are in such ranges. In order to obtain such a particle size distribution, a classification step may be separately provided, but it is not preferable because it causes a cost increase due to a decrease in yield, a complicated process and the like.

The particle size distribution of the coarsely pulverized powder of the calcined body can be obtained by a laser diffraction / scattering method. In the present specification, the volume average particle size of the coarsely pulverized powder of the calcined body means laser diffraction / scattering. The 50 vol% particle size obtained by the method is shown. In addition,
The phrase “substantially free of particles having a particle size of 10 μm or more” means that the content is below the detection limit of the above measuring method.

If the volume average particle size exceeds the above range or particles having a particle size of 10 μm or more remain in the calcined powder obtained by the coarse pulverization and exceed the above range, the fine particles will be described later. A large amount of secondary particles remain after pulverization. Therefore, the orientation is deteriorated and Br is deteriorated.

Next, the calcined powder obtained by coarse pulverization and having a volume average particle size and a particle size distribution in such a range is finely pulverized. The fine pulverization is carried out using an attritor, a ball mill or the like, but it is usually preferable to use the wet pulverization method because it is easier to pulverize to 1 μm or less as compared with the dry pulverization method. Any solvent may be used as the solvent of the slurry used in the wet pulverization method, and a solvent that is liquid at room temperature, such as water or various organic solvents, may be used. Water is used. The amount of the solvent added to the slurry is preferably 40 to 90 wt%, more preferably 50 to 80 wt%.

The fine pulverization is carried out by wet pulverization so that the specific surface area (SBET) by the BET method is preferably 6 to 13 m ² / g, more preferably 8 to 12 m ² / g, particularly preferably 9 to 11 m ² / g.
So that The particle size of such fine powder is represented by an average particle size of about 0.6 to 1.0 μm.
By this fine pulverization, the calcined body becomes a fine powder having a single domain critical diameter or less, a fine powder having a high HcJ, a small amount of secondary particles, and a good orientation. If SBET is too small, HcJ is likely to be deteriorated, and secondary particles are too much, and orientation, squareness, etc. are easily deteriorated. Further, if it is too large, the orientation is likely to deteriorate, and when performing wet-type molding in a magnetic field in the orientation step to be described later, the solvent easily escapes from the slurry and the formability may deteriorate. is there.

When the calcined body is crushed, CaCO ₃ and SiO ₂ are in a preferable content range after sintering for the purpose of promoting sintering during sintering and controlling grain growth. Is preferably added as described above. As described above, some of these components may be added before calcination. In this case, the addition amount before calcination is 70 wt% of the total content.
It should be less than or equal to%. The addition may be performed before the coarse pulverization or after the coarse pulverization, and may be added to the slurry to be finely pulverized. In addition to CaCO ₃ and SiO ₂ , if necessary, the above-mentioned components that may be added before calcination may be added in the same manner.

In order to adjust the particle size distribution of the fine powder of the calcined body thus obtained, the above-mentioned JP-A-1-14 was used.
In Japanese Patent No. 7809 and Japanese Patent Laid-Open No. 4-320009, a classification step is provided. However, in the manufacturing method of the present invention,
Since the powder having the volume average particle size and particle size distribution within the above range is coarsely pulverized, an oxide permanent magnet having excellent magnetic properties can be obtained without particularly providing a classification step.

The molding is preferably carried out under pressure in a magnetic field. The magnetic field is about 5 to 15 kOe, and the pressure is 0.1 to 0.6.
It may be about Ton / cm ² . Molding is preferably carried out by a wet molding method, using a slurry containing the fine powder of the calcined body according to a conventional method, for example, dehydrating the solvent in the slurry under pressure and removing it by suction.

Thereafter, the molded body was placed in the atmosphere at 1150 to
30 at 1250 ° C, especially 1200-1250 ° C
The oxide permanent magnet of the present invention can be obtained by firing for about 3 minutes to 3 hours.

The oxide permanent magnet thus obtained has Br, and the Sr ferrite sintered magnet has 3700-4.
400G, especially 3850-4400G, Ba ferrite sintered magnet, 3800-4300G, especially 4000-4
300G, HcJ is 300 for Sr ferrite sintered magnet
0-5200Oe, especially 3300-5000Oe, Ba ferrite sintered magnet, 2200-3500Oe, especially 22
00-3100 Oe, magnetic potential is 4000-4800 Oe in Sr ferrite sintered magnet, especially 4500-
With 4800 Oe, Ba ferrite sintered magnet, 2400-400
It becomes 3100 Oe, especially 2800-3100 Oe. Such an oxide permanent magnet is used for a motor for electric equipment, a motor for home appliances, and the like.

[0045]

EXAMPLES The present invention will be specifically described below with reference to examples of producing Sr ferrite sintered magnets. The same applies to Ba ferrite sintered magnets.

Example 1 Iron oxide Fe ₂ O ₃ (average particle size 1 μm), strontium carbonate SrCO ₃ and Al ₂ O ₃ were prepared as raw materials. Fe ₂ O ₃ / SrO molar ratio was 6.00, and further, Al ₂ O ₃ was blended so as to be 1.2 wt% by using a continuous rotary kiln.
Calcination was performed at 260 ° C. to obtain a calcined body. In addition, according to the result obtained experimentally, the calcination treatment by the rotary kiln corresponds to the treatment at 1230 ° C. for 2 hours when the batch furnace is used.

The obtained calcined body was vibrated by a vibration mill (batch type).
Was roughly crushed by a dry crushing method, and three kinds of samples were obtained by changing the crushing time. Table 1 shows the measurement results of the volume average particle size and the particle size distribution.

[0048]

[Table 1]

FIG. 1 is a graph showing the relationship between the particle size of these three types of samples and the cumulative frequency.

Using the obtained samples 1 to 3, S
Add 0.52 wt% of iO ₂ and 0.95 wt% of CaCO ₃ in terms of CaO, and further add water to 66 wt% of the slurry and wet using an attritor. Fine pulverization was performed by a pulverization method.

Each sample was finely pulverized so as to have SBET shown in Table 2, and was molded under a magnetic field of 10 kOe at a molding pressure of 0.56.
Wet molding with Ton / cm ² diameter 30mm, height 14mm
A molded body of was obtained. This molded body was sintered at 1226 ° C. for 1 hour in the atmosphere to obtain each sample of the sintered bodies of sample numbers 1-1 to 3-5 shown in Table 2. Sample numbers 1-1 to 1-
Reference numeral 5 denotes a sample obtained by finely pulverizing Sample 1 shown in Table 1, Sample Nos. 2-1 to 2-5 and Sample No. 3-1.
3-5 show samples obtained by finely pulverizing Samples 2 and 3 in the same manner. Br and HcJ of these sintered bodies
Was measured. Table 2 shows the SBET of each sample, the obtained results and the calculated magnetic potential.

Comparative Example 1 Iron oxide Fe ₂ O ₃ (average particle size 1 μm) and strontium carbonate SrCO ₃ were used as raw materials and compounded so as to be a ferrite magnet having a molar ratio of Fe ₂ O ₃ / SrO of 5.74. Calcination was performed at 1340 ° C. in the same manner as in Example 1 to obtain a calcined body having a composition outside the preferred range of the present invention (hereinafter, conventional material composition). According to the result obtained experimentally, this calcination treatment corresponds to the treatment at 1300 ° C. for 2 hours when using the batch furnace.

Using the obtained calcined body of the conventional material composition, coarse pulverization was performed for 17 minutes by the dry pulverization method under the same conditions as in the conventional art, that is, using a vibration mill, and the volume average particle diameter was 12 μm.
Sample 4 having a content ratio of particles of 10 μm or more of 55 vol% was obtained.

Using the obtained sample 4, SiO ₂ was added to 0.5
1wt%, CaCO ₃ converted to CaO 0.43wt%
, Al ₂ O ₃ were added so as to be 0.50 wt%, and pulverization, molding and sintering were carried out in the same manner as in Example 1 to obtain a molded body having a diameter of 30 mm and a height of 14 mm. This molded body was sintered in the atmosphere at 1226 ° C. for 1 hour, and sample numbers 4-1 to 4-5 were used.
Got Br and HcJ of the obtained sintered body were measured.
The SBET of each sample, the obtained results and the calculated magnetic potential are summarized in Table 2.

[0055]

[Table 2]

From Table 2, the conventional material composition of Comparative Example 1,
It can be seen that, in contrast to the material obtained by the conventional method, the material produced by the method of the present invention and having a composition within the preferable range of the present invention improves HcJ without degrading Br. Even when a material having a composition within the preferable range is used, under the condition that the volume average particle size and the particle size distribution are out of the range of the production method of the present invention, when the SBET is almost the same, the Br value is clearly different. It can be seen that the magnetic properties deteriorate and high magnetic properties cannot be obtained.

Comparative Example 2 Using the calcined body obtained in Comparative Example 1, coarse pulverization was performed in the same manner as in Example 1 and the pulverization time was the same as in Example 1 to obtain three types of samples. FIG. 2 shows a graph showing the relationship between the particle size of these three types of samples and the cumulative frequency.

From FIGS. 1 and 2, as compared with the calcined body having the conventional material composition, the calcined body within the preferred range of the present invention was
It can be seen that coarse pulverization makes it possible to easily obtain a finer and more uniform calcined powder.

Example 2 Iron oxide Fe ₂ O ₃ (average particle size 1 μm), strontium carbonate SrCO ₃ , SiO ₂ and CaCO ₃ were prepared as raw materials. In order to obtain a ferrite magnet having a molar ratio of Fe ₂ O ₃ / SrO of 6.20, SiO ₂ is further added to 0.1
5wt%, CaCO ₃ converted to CaO 0.07wt%
The resulting mixture was blended as follows and calcined at 1300 ° C. using a continuous rotary kiln to obtain a calcined body. In addition, according to the result obtained experimentally, the calcination treatment by the rotary kiln corresponds to the treatment at 1260 ° C. for 2 hours when the batch furnace is used.

The obtained calcined body was roughly pulverized by a dry pulverization method using a roller mill to give a volume average particle diameter of 6.0.
A sample 5 having a content of particles of 10 μm or more and 40 vol% was obtained. Sample 5 was further roughly crushed using a vibration mill to obtain Sample 6 having a volume average particle size of 3.5 μm and a content ratio of particles of 10 μm or more of 15 vol%.

For each of the obtained samples, S
The content of iO ₂ after sintering should be 0.52 wt%,
CaCO ₃ is converted to CaO and the content after sintering is 0.
66 wt% of each was added and finely pulverized in the same manner as in Example 1 to obtain a fine powder having a specific surface area of 9.5 m ² / g. In the same manner as in Example 1, each sintered body was obtained. . When the magnetic characteristics of this sintered body were measured, Sample 6 was
r was improved by 40 G, HcJ was equivalent, and an improvement in magnetic characteristics of 120 Oe in terms of magnetic potential was recognized.

Example 3 The calcined body obtained in Example 1 was roughly crushed using a vibration mill to obtain Sample 7 having a volume average particle size of 3.2 μm and a content ratio of particles having a particle size of 10 μm or more of 10 vol%. It was For this sample, S
Example 1 was carried out by adding 0.52 wt% of iO ₂ and 0.73 wt% of CaCO ₃ in terms of CaO.
Fine pulverization was carried out in the same manner as above to obtain fine powder having a specific surface area shown in Table 3.

These were molded in a magnetic field and sintered in the same manner as in Example 1 to obtain sintered body samples shown in Table 3. Br and HcJ of these sintered body samples were measured. SBE of each sample
T 3, the obtained results and the calculated magnetic potential are summarized in Table 3.

Comparative Example 3 The coarsely pulverized powder (Sample 4) used in Comparative Example 1 was classified to obtain Sample 8 having a volume average particle size of 2.2 μm and substantially not containing particles of 10 μm or more. For this sample, SiO ₂
Of 0.62 wt% and CaCO ₃ converted to CaO of 0.
47 wt% and Al ₂ O ₃ were added so as to be 0.60 wt%, and finely pulverized in the same manner as in Example 1 to obtain fine powder having a specific surface area shown in Table 3.

These were molded in a magnetic field and sintered in the same manner as in Example 1 to obtain the sintered body samples shown in Table 3. Br and HcJ of these sintered body samples were measured. SBE of each sample
T 3, the obtained results and the calculated magnetic potential are summarized in Table 3.

[0066]

[Table 3]

From Table 3, in the preferred composition range, the production method of the present invention has a conventional material composition, and is compared with coarsely pulverized ones classified under the same conditions as the conventional ones.
It can be seen that the magnetic potential is high.

Example 4 Sample No. 4-3, Sample No. 7-3 and Sample No. 8-3
For these three types of samples, the squareness ratio was determined, and the surface parallel to the C-axis was polished according to the ordinary method to be mirror-finished, and thermal etching was performed to observe the surface with an SEM. The equivalent circle diameter was calculated from the area calculated from the polygonal approximation of. Further, the volume distribution of grains was calculated from the distribution of the equivalent circle diameters of the grains, and the Rosin-Rammler plot was performed from the equivalent circle diameters and the volume distributions to determine the even numbers.

Table 4 shows the results of the volume average particle diameter, the uniform number and the squareness ratio, which were obtained from the equivalent circle diameters. The linearity correlation coefficient of each plot used to calculate n is 99.
It is in the range of 5% or more.

[0070]

[Table 4]

From Table 4, Sample No. 7-3 having the composition, the calcination temperature, the volume average particle size of the powder before fine pulverization and the particle size distribution within the scope of the present invention has a high even number, and the grain number of It shows that the particle size distribution is in a narrow range, and has an excellent squareness ratio of 95.5% or more.

Example 5 Sample 7 shown in Example 3 (volume average particle size after coarse pulverization: 3.
2 μm, the content ratio of particles of 10 μm or more was 10 vol%, and SiO ₂ and CaCO ₃ (CaO
(In terms of conversion) are added in an amount shown in Table 5 and finely pulverized in the same manner as in Example 1 so that SBET becomes 11.0 m ² / g. Then, a sintered body sample shown in Table 5 was obtained. Br and H of these sintered compact samples
cJ was measured. Table 5 shows the added CaO / SiO ₂ molar ratio, the magnetic property measurement results, and the calculated magnetic potential.
Are shown together.

[0073]

[Table 5]

From Table 5, it is apparent that when the SiO ₂ and CaO contents and the CaO / SiO ₂ molar ratio are within the preferred ranges of the present invention, the magnetic potential is 4500 Oe or more, and particularly excellent magnetic properties are exhibited. .

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the coarse pulverization time of a calcined body having a composition within the preferred range of the present invention, the particle size of the obtained powder, and the cumulative frequency.

FIG. 2 is a graph showing the relationship between the coarse pulverization time of a calcined body having a conventional material composition, the particle size of the obtained powder, and the cumulative frequency.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junji Nakano 1-13-1, Nihonbashi, Chuo-ku, Tokyo Inside TDC Corporation

Claims (6)

[Claims] 1. A magnetoplumbite-type oxide permanent magnet, wherein a surface parallel to the easy magnetization direction is mirror-finished and subjected to thermal etching, and the surface thereof is observed by a scanning electron microscope. Volume average diameter of circle equivalent is 1.0μ
An oxide permanent magnet having a diameter of m or less, a uniform number of Rosin-Rammler plots obtained from the volume distribution of the equivalent circle diameters of 3.1 or more, and a squareness ratio of 95.5% or more. 2. The oxide permanent magnet has a general formula MO · n.
The oxide permanent magnet according to claim 1, wherein when expressed by Fe ₂ O ₃ (M is Sr and / or Ba), 5.80 ≦ n ≦ 6.40. 3. Further, 0.1 to 0.70 wt% of SiO ₂ is added.
, CaO 0.05-1.0 wt% respectively, C
The oxide permanent magnet according to claim 1 or 2, wherein the aO / SiO ₂ molar ratio is 0.9 to 2.0. 4. A sample mixture is calcined, the calcined body is roughly crushed, then finely crushed, and the fine powder is molded in a magnetic field, and the obtained molded body is sintered and oxidized. When manufacturing the permanent magnet, the calcined body has a volume average particle size of 4 μm or less and
The method for producing an oxide permanent magnet according to any one of claims 1 to 3, wherein the oxide permanent magnet is coarsely pulverized so that particles having a size of µm or more are 20 vol% or less. 5. The method for producing an oxide permanent magnet according to claim 4, wherein the calcination temperature is 1200 to 1330 ° C. 6. The method for producing an oxide permanent magnet according to claim 4, wherein before and after the fine pulverization, the powder is not classified for adjusting the particle size distribution.