JPH05275221A - Ferrite magnet and its manufacture - Google Patents

Abstract

PURPOSE:To get a ferrite magnet suitable for the miniaturization and perfor mance promotion of electronic equipment and its manufacture by finding out new manufacture from the viewpoint of the technical thought different from the manufacture of a ferrite core being adopted from before, and improving the density of residual magnetic fluxes and coercive force at the same time. CONSTITUTION:MO can exist in the grain boundary of a ferrite magnet after sinterning by making ferrite material powder, which has fundamental composition at required mol. ratio and is calcined and smashed, contain part of MO being the main ingredients of a ferrite magnet at sintering reaction, whereby the particles, the crystal structures of which are broken or the compositions of which have slipped down in the process of the fine smashing, etc., before molding, can be made in complete ferrite, and further the reaction for getting close is accelerated by increasing the quantity in liquid phase by a specified quantity of CaO and SiO2, thus an objective high-performance ferrite magnet can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance ferrite magnet and a novel manufacturing method, and more particularly to one of MO (M is at least one of Pb, Ba and Sr) which is the main component of the ferrite magnet. The present invention relates to a high-performance ferrite magnet having a high residual magnetic flux density (Br) and a high coercive force (iHc) by adding and containing a part during a sintering reaction, and a method for manufacturing the ferrite magnet that enables the provision thereof.

[0002]

2. Description of the Related Art Generally, ferrite magnets are widely used in electronic devices and the like because they have high magnetic properties and economical advantages obtained from inexpensive raw materials.
As the shift to higher performance is advanced, the residual magnetic flux density (B
There is a strong demand for high-performance magnets having high r) and coercive force (iHc). Conventionally, in ferrite magnets,
In order to improve the residual magnetic flux density, it is known to increase the crystal Is, the density of the sintered body and the crystal orientation. Further, regarding the coercive force, it has been necessary to increase the existence rate of single domain crystals.

In order to improve the performance of the ferrite magnet, various studies have been conducted on the composition, additives, manufacturing conditions, etc. of the ferrite magnet. However, since the ferrite magnet itself is a sintered body, the sintered body is inevitable. It was extremely difficult to enhance the residual magnetic flux density and the coercive force at the same time by increasing the density of the magnetic field.

Under these circumstances, the present applicant has previously proposed that a ferrite magnet having a basic composition having a specific molar ratio and a specific amount of CaO can be used as a ferrite magnet whose coercive force is improved without lowering the residual magnetic flux density. , SiO ₂ and C
A high-performance ferrite magnet containing a specific amount of CoO together with one or two of r ₂ O ₃ and Al ₂ O ₃ (Japanese Patent Laid-Open No. 63-
No. 186402) was proposed.

[0005]

The above proposal has made it possible to provide a ferrite magnet having an improved coercive force without lowering the residual magnetic flux density. However, due to the remarkable progress in miniaturization and high performance of electronic equipment. The magnetic properties do not always meet the requirements, and there has been a strong demand for further improvement in the magnetic properties.

The present invention has found a novel manufacturing method from the viewpoint of a technical idea different from the conventional manufacturing method of a ferrite magnet, and has improved the residual magnetic flux density and the coercive force at the same time, and the manufacturing method thereof. For the purpose of providing.

[0007]

SUMMARY OF THE INVENTION The present inventors have found that in the conventional method of manufacturing a ferrite magnet,
Even when various additives are contained, a certain composition ratio (Fe
₂ O ₃ / MO) and the above-mentioned C
aO, SiO ₂ etc. are added or contained, or Fe ₂ O
_{3 ■} A method of changing the composition of the ferrite calcination raw material powder by adding the additive in the step of reacting with MO is adopted, and the composition ratio of the ferrite magnet (Fe ₂ O ₃ It was noted that / MO) was determined when the calcination raw material powder was created.

Conventionally, with such a method, it was thought that the Is of the ferrite crystal could be determined by the composition determined when the calcination raw material powder was prepared. However, the crystal structure may be distorted by the subsequent steps such as fine pulverization. The composition is different,
When Is is finally made into a sintered body, the Is density is lowered, and even if the above-mentioned additives and the like are contained, if they have an effect of suppressing crystal growth, the sintered density is lowered. Alternatively, if it has an effect of improving the sintering density, it promotes the growth of crystals and causes a decrease in iHc, so that it is essentially impossible to prevent the Is and the sintering density of the ferrite crystals from decreasing. It is presumed that it is difficult to improve the residual magnetic flux density and the coercive force at the same time.

As a result of examining various manufacturing methods from the above viewpoints, the present inventors have found that the main component of ferrite magnets, M
By adding a part of O during the sintering reaction, the M
The presence of O in the ferrite magnet grain boundaries after sintering has the effect of forming particles with a completely broken ferrite, whose crystal structure is broken or the composition is deviated in the steps such as pulverization before forming. And a certain amount of C
The inventors have found that the desired high-performance ferrite magnet can be obtained by increasing the amount of liquid phase by aO and SiO ₂ to promote the densification reaction and completed the present invention.

That is, according to the present invention, the molar ratio of Fe ₂ O ₃ /
MO (where M is at least 1 of Pb, Ba and Sr)
(Seed) is a ferrite magnet having a basic composition of 4.5 to 6.15, and the main component of the MO is a basic molar ratio of Fe ₂ O ₃ / MO existing in the ferrite crystal forming the main phase. A ferrite magnet having a composition and a part of MO existing in a grain boundary.

The present invention also provides a molar ratio of Fe ₂ O ₃ / MO.
(However, M is at least one of Pb, Ba, and Sr) calcination and pulverization of a ferrite raw material powder having a basic composition of 5.8 to 6.2, CaO 0.2 wt% to 1.0 wt
%, SiO ₂ 0.3 wt% to 1.0 wt%, MO (however, M is at least one of Pb, Ba, and Sr) 0.05 wt% to 3.0 wt% is added, and then mixed, After fine pulverization, molding and sintering, the main component of MO is present in the ferrite crystal of the main phase and a part of MO is present in the grain boundaries, and the molar ratio Fe ₂ O ₃ / MO is 4.5 to 6. The method for producing a ferrite magnet is characterized by obtaining a ferrite magnet of 0.15.

Further, the present invention has the above-mentioned structure, and further contains one or two of Cr ₂ O ₃ and Al ₂ O ₃ as an additive.
A method for producing a ferrite magnet having a molar ratio of Fe ₂ O ₃ / MO of 4.5 to 6.15 containing 0.05 wt% to 5.0 wt% of a seed, and further, CoO0.05w.
Molar ratio Fe ₂ O ₃ / MO containing t% to 1.5 wt%
Is from 4.5 to 6.15.

Reasons for limitation In the present invention, the molar ratio Fe ₂ O ₃ / MO with Fe ₂ O ₃ MO (where M is at least one of Pb, Ba and Sr) which constitutes the ferrite calcination raw material powder in advance is The range in which the Is of the crystal was the highest, which was close to the stoichiometric composition, was selected to be 5.8 to 6.2. Further, in the sintering reaction, that is, when MO added to the raw material powder that has been calcined and pulverized at the above-mentioned molar ratio is less than 0.05 wt%, the effect of promoting densification is small, and when it exceeds 3.0 wt%. If added and contained, the amount of grain boundary phase increases and the magnet characteristics deteriorate, so 0.0
5 wt% to 3.0 wt%, preferably 0.05 wt
% To 2.0 wt%.

Both the MO added and contained when the above calcined raw material powder is constituted and the MO added and contained during the sintering reaction are directly M
Not only when added as O (oxide)
Known methods such as adding and containing as O ₃ (carbonate) or mixing and adding these can be adopted, and it is necessary to select so that the composition of MO at the time of adding and containing each is within the above range. ..

Furthermore, each of these M has a different action.
Once O becomes a sintered ferrite magnet, even if the composition is analyzed by a fluorescent X-ray analysis method or the like, it is impossible to distinguish between the MO in the ferrite crystal forming the main phase and the MO existing in the grain boundaries. The composition ratio (molar ratio Fe ₂ O ₃ / MO) in the total amount of these MOs is 4.5 to 6.15.

CaO and SiO ₂ are added because they have the effect of controlling the sintered density and the size of crystal grains.
If O is less than 0.2 wt% and SiO ₂ is less than 0.3 wt%, non-uniform grain growth occurs during sintering, resulting in a decrease in iHc. Also, CaO exceeds 1.0 wt% and SiO
_{When 2} exceeds 1.0, the non-magnetic phase in the magnet increases and B
This leads to a decrease in r. Therefore, the content range of each additive is CaO 0.2 wt% to 1.0 wt%, SiO ₂ 0.3
wt% to 1.0 wt%, preferably CaO 0.3
wt% to 0.8 wt%, SiO ₂ 0.3 wt% to 0.8
wt%.

Further, in the present invention, a predetermined amount of Cr ₂ O ₃ , Al ₂ O _3, CoO or the like can be added and contained depending on various properties required. The addition of Cr ₂ O ₃ and Al ₂ O ₃ is particularly effective in improving iHc, but in order to obtain such an effect, it is necessary to add at least 0.05 wt% each, and to increase the addition amount. Along with this, the sintered density decreases, and the solid solution reaction with the ferrite magnet causes a decrease in the crystal Is, resulting in a decrease in Br. Further, when the content exceeds 5.0 wt%, the decrease in Br is remarkably impractical. is there. Therefore, in the case of adding one or two of Cr ₂ O ₃ and Al ₂ O ₃ , the addition content range is 0.05 wt% to
5.0 wt%, preferably 0.05 wt% to 3.
It is 0 wt%.

CoO is the above CaO, SiO _2, Cr ₂ O ₃ ,
In the coexistence of Al ₂ O ₃ , it has a remarkable effect on the improvement of iHc, but if it is less than 0.05 wt%, the effect is small, and if it exceeds 1.5 wt%, the effect of characteristic improvement is saturated. Therefore, the addition content range of CoO is 0.05 wt% to 1.5
wt%, preferably 0.05 wt% to 1.0 wt
%.

In the present invention, various conditions such as the method for producing the raw material powder for calcination of ferrite, the mixing of the raw material powder for calcination of ferrite, the pulverization method, the molding and the sintering method are
Known conditions can be adopted as they are. For example,
Calcination conditions are 1250 ° C to 1350 ° C for 1 hour to 10
Time, the average particle size of the fine powder before molding is 0.3 μm to 1.0
[mu] m, the molding conditions are a molding pressure 200kg / cm ² ~500kg / cm ² in a magnetic field of 10KOe～18kOe, sintering conditions 1 hour to at 1180 ° C~1250 ° C in the atmosphere
It is desirable to appropriately select optimum conditions such as 10 hours according to the above composition. As a method for obtaining the calcined raw material powder of ferrite, for example, such a calcined raw material powder can be obtained by the manufacturing method of Japanese Patent Laid-Open No. 3-123004 proposed for obtaining a high-performance Sr ferrite magnet.

[0020]

The present invention has a basic composition of the required molar ratio, and by adding a part of MO, which is the main component of the ferrite magnet, to the ferrite raw material powder calcined and crushed during the sintering reaction, By allowing the MO to exist in the ferrite magnet grain boundaries after sintering, it is possible to form particles having a completely broken ferrite, a crystal structure being broken in a process such as fine pulverization before forming, or a composition shift, and a predetermined amount. CaO and Si
It is possible to obtain the desired high-performance ferrite magnet by increasing the amount of the liquid phase by O ₂ and promoting the densification reaction.

[0021]

[Example] Sample No. shown in Table 1 1-5, which shows an embodiment of the present invention, the ferrite material powder molar ratio of Fe ₂ O ₃ / SrO has a basic composition of 5.9 to 6.0, 1 hour provisionally at 1270 ° C After firing and crushing, CaO, SiO ₂ , Cr ₂ O ₃ , so that the magnet composition shown in Table 1 was obtained,
Al ₂ O _3, CoO, and SrO were mixed, mixed, and finely pulverized to obtain fine powder having an average particle size of 0.7 μm, and then 12 kOe.
In a magnetic field of 50 mm / cm ² at a molding pressure of 40 ×
A compact with a size of 10 mm was obtained, and the sintering conditions were 1
Sintered at 240 ° C for 1 hour. The density and magnetic characteristics of the obtained sintered body were measured and the results are shown in Table 1.
The values of the molar ratio Fe ₂ O ₃ / SrO in Table 1 are the values obtained by measuring the final product with a fluorescent X-ray analyzer.

Further, the sample No. * 6 to * 10
Shows a comparative example of the present invention, except that a ferrite raw material powder having a molar ratio of Fe ₂ O ₃ / SrO in Table 1 was used in advance and SrO was not additionally added and contained in the subsequent steps. All were manufactured under the same conditions as in the above example.

[0023]

[Table 1]

[0024]

As is apparent from Table 1, according to the present invention, a part of MO (M is at least one of Pb, Ba and Sr) which is the main component of the ferrite magnet is added during the sintering reaction. The ferrite magnet was compared with the ferrite magnet obtained by the conventional method shown in the comparative example (Sample No. 1 and * 6, 2 and * 7, 3 and * 8, 4 and * 9, 5 and * 10 were compared. ), High residual magnetic flux density (Br), high coercive force (iH
It is apparent that all of c) are equal to or more than the same, and it is possible to provide a high-performance ferrite magnet having excellent magnetic characteristics.

Claims (4)

[Claims] 1. A molar ratio of Fe ₂ O ₃ / MO (where M is Pb,
At least one of Ba and Sr) is 4.5 to 6.15.
A ferrite magnet having a basic composition of
Is present in the ferrite crystal forming the main phase to form a basic composition with a predetermined molar ratio of Fe ₂ O ₃ / MO,
A part of MO is present in the grain boundary, which is a ferrite magnet. 2. A molar ratio of Fe ₂ O ₃ / MO (where M is Pb,
At least one of Ba and Sr) has a basic composition of ferrite having a basic composition of 5.8 to 6.2, and is calcined and crushed, and then CaO 0.2 wt% to 1.0 wt% and SiO ₂ 0.
3 wt% to 1.0 wt% is added, and MO (however, M
Is at least one of Pb, Ba and Sr) 0.05
wt% to 3.0 wt% is added, and then mixed, finely pulverized, molded, and sintered, and the main component of MO is present in the ferrite crystal of the main phase and a part of MO is present in the grain boundary, and the mole Ratio Fe ₂
A method for producing a ferrite magnet, comprising obtaining a ferrite magnet having O ₃ / MO of 4.5 to 6.15. 3. A molar ratio of Fe ₂ O ₃ / MO (where M is Pb,
At least one of Ba and Sr) has a basic composition of ferrite having a basic composition of 5.8 to 6.2, and is calcined and crushed, and then CaO 0.2 wt% to 1.0 wt% and SiO ₂ 0.
3 wt% to 1.0 wt%, 0.05 wt% to 5.0 wt% of 1 type or 2 types of Cr ₂ O ₃ and Al ₂ O ₃ , and further MO (where M is at least Pb, Ba or Sr). 1
Seed) is added in an amount of 0.05 wt% to 3.0 wt% and then mixed, finely pulverized, molded, and sintered so that the main component of MO is in the ferrite crystal of the main phase and a part of MO is in the grain boundary. And a molar ratio of Fe ₂ O ₃ / MO of 4.5 to 6.15 to obtain a ferrite magnet. 4. A molar ratio of Fe ₂ O ₃ / MO (where M is Pb,
At least one of Ba and Sr) has a basic composition of ferrite having a basic composition of 5.8 to 6.2, and is calcined and crushed, and then CaO 0.2 wt% to 1.0 wt% and SiO ₂ 0.
3 wt% to 1.0 wt%, 0.05 wt% to 5.0 wt% of one or two of Cr ₂ O ₃ and Al ₂ O ₃ , CoO 0.
05 wt% to 1.5 wt% is added, and MO (however, M
Is at least one of Pb, Ba and Sr) 0.05
wt% to 3.0 wt% is added, and then mixed, finely pulverized, molded, and sintered, and the main component of MO is present in the ferrite crystal of the main phase and a part of MO is present in the grain boundary, and the mole Ratio Fe ₂
A method for producing a ferrite magnet, comprising obtaining a ferrite magnet having O ₃ / MO of 4.5 to 6.15.