JP3088236B2 - Oxide permanent magnet and manufacturing method thereof - Google Patents

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 of manufacturing the same.

[0002]

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

Conventionally, various methods have been tried to make the grain size of crystal grains constituting a ferrite magnet sintered body smaller than the critical diameter of a single magnetic domain, and to make it 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 (Japanese Patent Application Laid-Open No. 1-147809), additives are added during calcination (Japanese Patent Publication No. 4-14484), And fineness and homogenization of the calcined powder crystal particles by the baking temperature or the like (Japanese Patent Publication No. 59-10564). In these methods, the crystal particles of the calcined powder to be used are made fine and homogenous to reduce the grain diameter of the grains of the ferrite magnet to a critical diameter of a single magnetic domain or less, and to obtain high magnetic properties as fine and uniform. Further, Japanese Patent Application Laid-Open No.
No. 7809, the average particle size of the raw material iron oxide and the standard deviation of the particle size distribution are regulated, and further, the average particle size and the average particle size of the fine powder used for molding in a magnetic field obtained by pulverizing the calcined powder are described. It also regulates the standard deviation of the particle size distribution. further,
Japanese Patent Application Laid-Open No. 4-320009 proposes that, in the production of a sintered Sr ferrite magnet, fine powder obtained by finely pulverizing calcined powder is classified to adjust the average particle size, particle size distribution, and the like. I have. According to the proposed method, a ferrite sintered magnet with particularly improved Br (residual magnetic flux density) can be obtained.

[0004] It is important to make the crystal grains of the calcined body fine and uniform. However, when the calcined body obtained is pulverized, the grain size of the grain of the sintered body obtained by sintering is determined by the critical diameter of a single magnetic domain. Even if the average particle size is reduced to, for example, 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 using this powder is reduced. Difficult to be uniform. For this reason, it has been difficult to obtain a magnet having more excellent magnetic properties. 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 Publication No. 009, a 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 the calcined powder is finely pulverized, a wet pulverization method is usually used, and a wet molding method is also used in the molding step. Classification is usually performed in a dry process, so a fine powder drying step is required before classification, and a new solvent needs to be added in the molding process.In industrial production, the number of manufacturing processes increases and product costs increase. Will be done. For this reason, there is a demand for a ferrite sintered magnet having a uniform grain size and excellent magnetic properties without increasing the cost.

[0005]

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

[0006]

This and other objects are achieved by the present invention which is defined below as (1) to (6). (1) A magnetoplumbite-type oxide permanent magnet that has a surface parallel to the direction of easy magnetization mirror-processed, is subjected to thermal etching, and its surface is observed with a scanning electron microscope. The volume average particle diameter of the diameter is 0.
An oxide permanent magnet having an average number of 7 to 1.0 μm, a rosin-Rammler plot obtained from the volume distribution of the circle equivalent diameter of 3.1 or more, and a squareness ratio of 95.5% or more. . (2) The oxide permanent magnet is represented by the general formula MO · nFe ₂ O
_3. The oxide permanent magnet according to the above (1), wherein 5.80 ≦ n ≦ 6.40 when M is Sr and / or Ba. (3) Further, 0.1 to 0.70 wt% of SiO ₂ and Ca
O each containing 0.05 to 1.0 wt%, and CaO /
The oxide permanent magnet according to the above (1) or (2), wherein the molar ratio of SiO ₂ is 0.9 to 2.0. (4) The sample mixture is calcined, the calcined body is coarsely pulverized, then finely pulverized, and molded in a magnetic field using the fine powder.
In producing the oxide permanent magnet by sintering the obtained molded body, the calcined body is roughly pulverized so that the volume average particle diameter is 4 μm or less and the particles having a volume average particle diameter of 10 μm or more become 20 vol% or less. A method for producing an oxide permanent magnet according to any one of (1) to (3). (5) The method for producing an oxide permanent magnet according to (4), wherein the calcination temperature is 1200 to 1330 ° C. (6) The method for producing an oxide permanent magnet according to (4) or (5), wherein the powder is not subjected to classification for adjusting the particle size distribution before and after the pulverization.

[0007]

Function and Effect The magnetoplumbite-type oxide permanent magnet of the present invention has a grain volume average particle diameter of 0.7 to 0.7.
1.0 μm, that is, less than the critical diameter of a single magnetic domain. Also,
When a rosin-Rammler plot is performed using the grain equivalent diameter of the grain and the volume distribution calculated from the circle equivalent diameter, the obtained uniform number, that is, the slope is a high value of 3.1 or more, and the grain size The distribution has unprecedented high uniformity. Also, the squareness ratio is a high value of 95.5% or more. Therefore, the oxide permanent magnet has excellent magnetic properties with a high magnetic potential calculated from Br (residual magnetic flux density) and HcJ (coercive force).

In the method for producing an oxide permanent magnet according to the present invention, when the calcined body is pulverized, the calcined body is coarsely pulverized so that the volume average particle diameter is 4 μm or less, and the particles of 10 μm or more are 20 vol% or less. Next, this is pulverized, molded in a magnetic field, and sintered to obtain an oxide permanent magnet. The coarsely pulverized powder obtained by 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 suitable so far, and has a low proportion of particles having a particle size of 10 μm or more.

A classification step may be separately provided to keep the volume average particle size and the particle size distribution of the powder obtained by the coarse pulverization within the above-mentioned ranges, but preferably the composition and the production conditions are within the preferable ranges of the present invention. According to the method of making the volume average particle size and the particle size distribution in the range of the present invention by coarse pulverization using a calcined body obtained as described above, it is possible to obtain an oxide permanent magnet having high magnetic properties without particularly providing a classification step. And the production cost does not increase by providing the classification step.

[0010]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

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 the oxide permanent magnet is polished and mirror-polished according to a conventional method, and thermal etching is performed. The thermal etching is usually performed at 1070 ° C. for 2 minutes so as to slightly grow the grains to make the grain boundaries more clear.
Perform for 0 minutes. The obtained surface was scanned with a scanning electron microscope (SE).
Observed in M), and the equivalent circle diameter of the grain is determined from the recognized grain area. The volume average particle diameter determined from the equivalent circle diameter is 0.7 μm to 1.0 μm, preferably 0.7 μm.
０．９0.9 μm. More specifically, the volume average particle diameter of the grain is determined by approximating the grain boundary of the grain with a polygon, obtaining an equivalent circle diameter by image processing, and setting the volume distribution to 50 vol% particle diameter obtained from the equivalent circle diameter. . By setting the volume average particle size in the above range, the grain becomes smaller than the critical diameter of a single magnetic domain, and a magnet having a large coercive force (HcJ) can be obtained. When the volume average particle diameter exceeds the above range, the number of grains whose grain size exceeds the critical diameter of a single magnetic domain increases, and the HcJ decreases.

Further, a histogram of the grain volume distribution is obtained from the distribution of the grain equivalent diameters of the grains, and the uniform number of the rosin-Rammler plot obtained by the method described later is calculated from the histogram. Above, preferably 3.3 or more, more preferably 3.5 or more.
The Rosin-Rammler equation is used to display the particle size distribution, and a larger number of equal numbers in this equation indicates that the grain size distribution is narrower. When the uniform number is equal to or more than the above, the grain size distribution of the grains is narrow and uniform, and the squareness ratio is 95.5%.
As described above, an excellent magnet having a magnetic characteristic of 95.5% to 98% is obtained. 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 equal number is usually about four.

The equivalent number of Rosin-Rammler plots can be determined as follows.

Assuming a mixed powder having a histogram of the volume distribution determined from the equivalent circle diameter of the grains, when this mixed powder is sieved, R is the volume above the sieve (%), _Dp 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). Putting a b = 1 / D _e ⁿ in the equation, R = 100 · exp - a _{{(D p / D e)} n} ( equation Rosin-Rammler-Bennet). Where _De is
The particle size characteristic number (absolute size constant), n is a uniform number (distribution constant).

By transforming the above Rosin-Rammler-Bennet equation, ln {ln (100 / R)} = n · lnD _p + C is obtained. Therefore, for lnD _p , ln ｛ln
When (100 / R)｝ is plotted, a straight line is obtained, and n is obtained from the gradient of the straight line. In the present specification, the plot used for calculating n is in a range where the linearity correlation coefficient is 99.5% or more.

In the present specification, the squareness ratio is defined as 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 preferred, and more preferably 5.8
≦ n ≦ 6.2.

If the composition is such that n is smaller than the above range, the crystal grains tend to grow large during calcination, and HcJ tends to decrease. On the other hand, if it is larger than the above range, the ferrite formation reaction tends to be insufficient, and excessive Fe ₂ O ₃ remains, so that Br tends to deteriorate.

Further, the oxide permanent magnet of the present invention preferably contains SiO ₂ and CaO as a liquid phase component at the time of firing, which has the effect of accelerating the sintering reaction or increasing the density of the sintered body. . As each content,
SiO ₂ is, 0.1~0.7wt%, more preferably 0.
3 to 0.7 wt%, particularly preferably 0.4 to 0.6 wt%, and CaO is 0.05 to 1.0 wt%, more preferably 0.4 to 1.0 wt%, 0.5 ~
0.9% by weight, and these CaO / Si
The molar ratio of O ₂ is 0.9 to 2.0, more preferably 1.1.
To 1.8, and particularly preferably 1.2 to 1.7. Within 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 content of SiO ₂ is less than the above range, the grains of the sintered body are likely to be coarse and HcJ is likely to be reduced. On the other hand, if the content 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 deteriorates. On the other hand, if the content is too large, the grains of the sintered body are likely to be coarse, and HcJ is likely to be reduced. These CaO / S
If the molar ratio of iO ₂ is too high or too low, the magnetic potential tends to decrease.

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

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

The definition is made for the following reason.

The relationship between Br and HcJ is such that, in a certain normal range, HcJ is increased by β when Br is decreased by α at a certain ratio, or conversely, by increasing α by increasing α by a slight change in manufacturing conditions. Is easily reduced by β. And this β /
The ratio of α is about 3.

In order to unify the intrinsic potential of the material, when Br = 4000 G, the actual B
The actual HcJ is corrected and expressed by multiplying the deviation of the r data by a coefficient 3. That is, Br = 4000
The converted HcJ (Oe) in G is used as an index.

Further, the oxide permanent magnet of the present invention includes Al ₂ O ₃ , Cr ₂ O _3, etc., which has an action of appropriately controlling the growth of particles during calcination or sintering, or the raw materials to be used or the equipment to be used. MnO, ZnO, CuO, and the like derived from the same may be contained in a range of about 5 wt% or less in total.

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

The oxide permanent magnet of the present invention is obtained by calcining a mixture containing iron oxide and a component to be SrO and / or BaO by sintering, coarsely pulverizing the obtained calcined body, and then finely pulverizing the calcined body. Then, molding is performed in a magnetic field using the fine powder obtained by pulverization, and the obtained molded body is manufactured by sintering.

The raw material used is not particularly limited, but is usually mixed with an oxide or a powder which becomes an oxide by sintering. As the raw material powder containing elements such as Fe, Si, Sr, Ba, Ca, Al and Cr, an oxide or a carbonate is usually used, but a hydroxide, a nitrate, a chloride or the like can also be used. When powder is used as a raw material, the average particle size of the powder used is preferably about 0.5 to 3.0 μm.

The calcined mixture includes, in addition to the iron oxide and the components that become SrO and / or BaO by the above-mentioned sintering, in addition to Si for the purpose of promoting sintering during calcination and controlling the growth of particles. And Ca, and further, if necessary, a compound containing an element such as Al or Cr is preferably added. The total amount of such additives may be about 0.1 to 5.0 wt% in terms of oxides having a stoichiometric composition.

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

The calcination temperature in the present invention is preferably 1
200 to 1330 ° C, more preferably 1210 to 132
The temperature is 0 ° C, and particularly preferred is 1220 to 1310 ° C. By calcining at such a temperature, the crystal grains at the time of calcining can be favorably controlled and can be sufficiently ferritized. If the calcination temperature is too low, the ferrite-forming reaction does not proceed sufficiently, and the grain size of the crystal particles tends to be too small. And the squareness ratio easily deteriorates. On the other hand, if the calcination temperature is too high, the number of coarse crystal grains tends to increase, and HcJ deteriorates. The calcination may be performed by any method such as a batch method and a continuous method, but for mass production, for example, a continuous rotary kiln can be used. The calcining time varies depending on the calcining temperature in a batch method, for example, but is preferably 30 minutes to 5 hours, more preferably 1 to 3 hours. In the case of the continuous method, the flow rate varies depending on the calcining temperature and the flow rate per unit time. Therefore, a flow rate that is equivalent to the above range in the batch method may be experimentally obtained. The term “calcination time” refers to the time during which a predetermined calcination temperature is maintained.

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 a dry pulverization method, and fine pulverization performed on the obtained coarsely pulverized powder is performed by a wet pulverization method. Is preferred. 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 a batch type or a continuous type, and may be performed by using a vibrating mill, a roller mill, an atomizer,
It may be performed using a supermicron mill or the like. Usually, a dry grinding method is used. When the calcined body forms a large lump, the calcined body may be pulverized using a jaw crusher or the like, if necessary, and then the above method may be used.

In the production method of the present invention, this coarse pulverization is carried out when the calcined body has a volume average particle size of 4 μm or less, preferably 1 to 4 μm.
m, more preferably 1.5 to 3.5 μm, and 10 μm
The treatment is performed so that the number of particles of m or more is 20 vol% or less, preferably 10 vol% or less. Since particles having a particle diameter of 10 μm or more are preferably as small as possible,
It is particularly preferable that particles containing particles of 10 μm or more are not substantially contained. The effect of the present invention is exerted by setting the volume average particle size and the particle size distribution in such ranges by coarse pulverization. In order to obtain such a particle size distribution, a separate classification step may be provided, but it is not preferable because a decrease in yield or complication of the step causes an increase in cost.

The particle size distribution of the coarsely ground powder of the calcined body can be obtained by a laser diffraction / scattering method. In this specification, the volume average particle diameter of the coarsely ground powder of the calcined body is defined as the laser diffraction / scattering It shows the 50 vol% particle size determined by the method. In addition,
The phrase "substantially not containing particles having a size of 10 µm or more" means that the content is not more than the detection limit of the above-mentioned measurement method.

If the calcined body powder obtained by the coarse pulverization has a volume average particle size exceeding the above range or particles having a particle size of 10 μm or more remaining outside the above range, the fine particles will be described later. Many secondary particles remain after pulverization. For this reason, the orientation deteriorates, and Br deteriorates.

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

The fine pulverization is carried out by wet pulverization, and 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.
And so on. The average particle size of such fine powder is about 0.6 to 1.0 μm.
By this fine pulverization, the calcined body becomes a fine powder having a diameter smaller than the critical diameter of a single magnetic domain, and a fine powder having a high HcJ, a small number of secondary particles and a good orientation can be obtained. If the SBET is too small, HcJ tends to deteriorate, and the secondary particles become too large, and the orientation, squareness, etc., tend to deteriorate. Also, if it is too large, the orientation tends to deteriorate, and in the orientation step described later, when performing molding in a magnetic field by a wet method, the solvent is easily removed from the slurry, which tends to deteriorate the moldability. is there.

In crushing the calcined body, CaCO ₃ and SiO ₂ have a preferable content range after sintering for the purpose of promoting sintering at the time of subsequent sintering and controlling the growth of grains. It is preferable to add them. These components may be partially added before calcination as described above. In this case, the amount added before calcination is 70 wt.
% Or less. The addition may be before or after the coarse pulverization, and may be performed as long as it is added to the slurry to be finely pulverized. Further, in addition to CaCO ₃ and SiO ₂ , the above-mentioned components which may be added before the calcination may be similarly added as necessary.

In order to adjust the particle size distribution of the fine powder of the calcined body obtained as described above, see JP-A-1-14 / 1990.
In Japanese Patent Application Laid-Open No. 7809 and Japanese Patent Application Laid-Open No. 4-320009, a classification step is provided. However, in the production method of the present invention,
Since the powder having the volume average particle size and the particle size distribution in the above ranges is obtained by coarse pulverization, an oxide permanent magnet having excellent magnetic properties can be obtained without providing a classification step.

The molding is preferably performed under pressure in a magnetic field. Magnetic field is about 5 to 15 kOe, pressure is 0.1 to 0.6
It may be about Ton / cm ² . The molding is preferably performed by a wet molding method, and a slurry containing the fine powder of the calcined body is used, and the solvent in the slurry may be subjected to pressure dehydration and suction removal according to a conventional method.

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

In the oxide permanent magnet thus obtained, Br was 3700 to 4% for the Sr ferrite sintered magnet.
400G, especially 3850-4400G, for a Ba ferrite sintered magnet, 3800-4300G, especially 4000-4
300G, HcJ is 300 for Sr ferrite sintered magnet
0-5200 Oe, especially 3300-5000 Oe, and 2300-3500 Oe, especially 22
00-3100 Oe, the magnetic potential is 4000-4800 Oe in the case of Sr ferrite sintered magnet, especially 4500
4800 Oe, Ba ferrite sintered magnet, 2400
It becomes 3100 Oe, especially 2800-3100 Oe. Such an oxide permanent magnet is used for a motor for electrical equipment, a motor for home appliances, and the like.

[0045]

EXAMPLES The present invention will be specifically described below with reference to examples of manufacturing a sintered Sr ferrite magnet. 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. A ferrite magnet having a molar ratio of Fe ₂ O ₃ / SrO of 6.00, Al ₂ O ₃ was further compounded to be 1.2 wt%, and 1 wt.
Calcination was performed at 260 ° C. to obtain a calcined body. According to the results obtained experimentally, the calcining treatment by the rotary kiln corresponds to the treatment at 1230 ° C. for 2 hours when using a batch furnace.

The obtained calcined body is subjected to a vibration mill (batch type).
Was subjected to coarse pulverization by a dry pulverization method, and three kinds of samples were obtained by changing the pulverization 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,
0.52 wt% of iO ₂ and 0.95 wt% of CaCO ₃ in terms of CaO are added, and water is added so as to be 66 wt% of the slurry. Fine pulverization was performed by a pulverization method.

Each sample was finely pulverized so that the SBET shown in Table 2 was obtained, and a molding pressure of 0.56 was applied in a magnetic field of 10 kOe.
Wet molding with Ton / cm ² , diameter 30mm, height 14mm
Was obtained. This molded body was sintered at 1,226 ° C. for 1 hour in the atmosphere to obtain samples of sintered bodies of Sample Nos. 1-1 to 3-5 shown in Table 2. In addition, sample numbers 1-1 to 1-
5 is a sample obtained by finely pulverizing the sample 1 shown in Table 1, and includes sample numbers 2-1 to 2-5 and sample number 3-1.
３−3-5 indicate samples obtained by similarly pulverizing samples 2 and 3. Br and HcJ of these sintered bodies
Was measured. Table 2 summarizes the SBET of each sample, the results obtained, 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 blended to form 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, a conventional material composition). In addition, according to the results obtained experimentally, this calcination treatment corresponds to a treatment at 1300 ° C. for 2 hours when a batch furnace is used.

Using the obtained calcined body of the conventional material composition, coarse pulverization was performed for 17 minutes by the dry pulverization method using a vibrating mill under the same conditions as in the past, and the volume average particle size 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, 0.5% of SiO ₂ was added.
1 wt%, CaCO ₃ is converted to CaO, 0.43 wt%
, Al ₂ O ₃ was added to a concentration of 0.50 wt%, and pulverization, molding and sintering were performed 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 at 1226 ° C. for 1 hour in the atmosphere, and sample numbers 4-1 to 4-5 were obtained.
I got Br and HcJ of the obtained sintered body were measured.
Table 2 summarizes the SBET of each sample, the results obtained, and the calculated magnetic potential.

[0055]

[Table 2]

As shown in Table 2, the composition of Comparative Example 1 has the conventional material composition.
It can be seen that a material produced by the method of the present invention with respect to the material obtained by the conventional method and having a composition within the preferred range of the present invention improves HcJ without deteriorating Br. Further, even when a material having a composition within the preferred range is used, when the volume average particle diameter and the particle size distribution are out of the range of the production method of the present invention, when the samples having substantially the same SBET are compared, Br is clearly higher. It can be seen that the magnetic properties are lowered and high magnetic properties cannot be obtained.

Comparative Example 2 The calcined body obtained in Comparative Example 1 was roughly pulverized in the same manner as in Example 1, and three types of samples were obtained with the same pulverization time as in Example 1. FIG. 2 is a graph showing the relationship between the particle size of these three samples and the cumulative frequency.

From FIG. 1 and FIG. 2, the calcined body within the preferred range of the present invention is compared with the calcined body having the conventional material composition.
It can be seen that fine and more uniform calcined powder can be easily obtained by coarse pulverization.

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. Further, SiO ₂ is added in an amount of 0.1 to obtain a ferrite magnet having a molar ratio of Fe ₂ O ₃ / SrO of 6.20.
5 wt%, CaCO ₃ is converted to CaO to 0.07 wt%
And calcined at 1300 ° C. using a continuous rotary kiln to obtain a calcined body. According to the results obtained experimentally, the calcining treatment by the rotary kiln corresponds to the treatment at 1260 ° C. for 2 hours when using a batch furnace.

The obtained calcined body is roughly pulverized by a dry pulverization method using a roller mill, and has a volume average particle size of 6.0.
A sample 5 having a particle size of 10 vol. The sample 5 was further coarsely pulverized using a vibration mill to obtain a 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%.

Each of the obtained samples was further subjected to S
In order that the content after sintering of iO ₂ becomes 0.52 wt%,
CaCO ₃ is converted into CaO, and the content after sintering is 0.1.
Each of the powders was added so as to be 66 wt% and 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. . When the magnetic properties of this sintered body were measured, Sample 6
r was improved by 40 G, HcJ was equivalent, and an improvement in magnetic properties of 120 Oe in terms of magnetic potential was observed.

Example 3 The calcined body obtained in Example 1 was roughly pulverized using a vibration mill to obtain a sample 7 having a volume average particle size of 3.2 μm and a content ratio of particles of 10 μm or more of 10 vol%. Was. For this sample, S
iO ₂ to 0.52wt%, implement CaCO _3, was added respectively so that the 0.73Wt% in terms of CaO Example 1
In the same manner as described above, fine powder having a specific surface area shown in Table 3 was obtained.

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

Comparative Example 3 The coarsely pulverized powder (sample 4) used in Comparative Example 1 was classified to obtain a sample 8 having a volume average particle size of 2.2 μm and substantially no particles of 10 μm or more. For this sample, SiO ₂
Is 0.62 wt%, and CaCO ₃ is converted to CaO by 0.1.
47 wt% and Al ₂ O ₃ were added to give 0.60 wt%, respectively, and 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 and sintered in a magnetic field in the same manner as in Example 1 to obtain sintered samples shown in Table 3. Br and HcJ of these sintered samples were measured. SBE of each sample
Table 3 summarizes T, the results obtained, and the calculated magnetic potential.

[0066]

[Table 3]

As shown in Table 3, when the composition is in a preferable range, the composition according to the production method of the present invention has a conventional material composition and is compared with a material obtained by classifying coarsely pulverized material under the same conditions as the conventional material.
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 and mirror-polished according to a conventional method, thermal etching was performed, and the surface was observed with a SEM. The circle equivalent diameter was determined from the area determined from the polygonal approximation. Further, the volume distribution of the grains was calculated from the distribution of the equivalent circle diameter of the grains, and a rosin-Rammler plot was performed from the equivalent circle diameter and the volume distribution to obtain an even number.

Table 4 shows the results of the volume average particle diameter, the uniform number, and the squareness ratio determined from the equivalent circle diameter. The linearity correlation coefficient of each plot used for the calculation of n was 99.
The range is 5% or more.

[0070]

[Table 4]

As shown in Table 4, Sample No. 7-3 in which the composition, the calcination temperature, the volume average particle size and the particle size distribution of the powder before pulverization were within the scope of the present invention had a high even number, and the grain number was high. This indicates 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 was 3.
2 μm, the content ratio of particles of 10 μm or more is 10 vol%), and SiO ₂ and CaCO ₃ (CaO ₃
(Expressed in terms of conversion)), and pulverized in the same manner as in Example 1 so that the SBET becomes 11.0 m ² / g. In this way, sintered body samples shown in Table 5 were obtained. Br and H of these sintered body samples
cJ was measured. Table 5 shows the molar ratio of the added CaO / SiO _2, the measurement results of the magnetic properties, and the calculated magnetic potentials.
Are shown together.

[0073]

[Table 5]

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

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the coarse pulverization time of a calcined body having a composition within a 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.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takahiko Kasahara, 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (72) Inventor Junji Nakano 1-13-1, Nihonbashi, Chuo-ku, Tokyo (56) References JP-A-4-38807 (JP, A)

Claims (6)

(57) [Claims] 1. A magnetoplumbite-type oxide permanent magnet, wherein a surface parallel to the direction of easy magnetization is mirror-polished, subjected to thermal etching, and the surface thereof is observed with a scanning electron microscope. Volume average particle diameter of equivalent circle diameter is 0.7 ~
An oxide permanent magnet having an average number of 1.0 μm, a rosin-Rammler plot obtained from the volume distribution of the circle equivalent diameter of 3.1 or more, and a squareness ratio of 95.5% or more. 2. The oxide permanent magnet is represented by a general formula MO · n
When expressed by Fe ₂ O ₃ (M is Sr and / or Ba), oxide permanent magnet according to claim 1 which is 5.80 ≦ n ≦ 6.40. 3. The composition according to claim 1, wherein said SiO ₂ is 0.1 to 0.70 wt%.
, CaO each containing 0.05 to 1.0 wt%,
aO-/ claim 1 or 2 oxide permanent magnet molar ratio of SiO ₂ is 0.9 to 2.0. 4. A sample mixture is calcined, the calcined body is roughly pulverized, then finely pulverized, and the fine powder is molded in a magnetic field, and the obtained molded body is sintered and oxidized. When producing a permanent magnet, the calcined body is prepared by mixing the calcined body with a volume average particle size of 4 μm or less, and
A 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 particle size of at least 20 µm are at most 20 vol%. 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 pulverization, the powder is not subjected to classification for adjusting the particle size distribution.