阅读说明：本技术 铁氧体烧结磁铁及具备其的旋转电机 (Ferrite sintered magnet and rotating electrical machine provided with same ) 是由 村川喜堂 森田启之 池田真规 室屋尚吾 石仓友和 于 2020-10-10 设计创作，主要内容包括：本发明涉及一种铁氧体烧结磁铁以及具备其的旋转电机。铁氧体烧结磁铁(100)具备M型铁氧体晶粒(4)及被三个以上的M型铁氧体晶粒(4)包围的多晶粒晶界(6b)。铁氧体烧结磁铁(100)至少含有Fe、Ca、B、及Si,以B-2O-3换算含有0.005～0.9质量％的B。多晶粒晶界(6b)含有Si及Ca,在将多晶粒晶界(6b)中的Ca相对于Si的摩尔比表示为(Ca/Si)-G的情况下满足下式。0.1＜(Ca/Si)-G＜0.9。(The present invention relates to a ferrite sintered magnet and a rotating electrical machine including the same. A ferrite sintered magnet (100) is provided with M-type ferrite crystal grains (4) and a multi-grain boundary (6b) surrounded by three or more M-type ferrite crystal grains (4). The ferrite sintered magnet (100) contains at least Fe, Ca, B, and Si, and B 2 O 3 Contains 0.005 to 0.9 mass% of B in terms of B. The multicrystalline grain boundary (6b) contains Si and Ca, and the molar ratio of Ca to Si in the multicrystalline grain boundary (6b) is expressed as (Ca/Si) G Satisfies the following equation. 0.1 < (Ca/Si) G ＜0.9。)

1. A ferrite sintered magnet, wherein,

the ferrite sintered magnet comprises M-type ferrite crystal grains and a multi-grain boundary surrounded by 3 or more of the M-type ferrite crystal grains,

the ferrite sintered magnet contains at least Fe, Ca, B and Si,

the ferrite sintered magnet is represented by B₂O₃Contains 0.005 to 0.9 mass% of B in terms of B,

the grain boundaries of the polycrystalline grains contain Si and Ca,

the molar ratio of Ca to Si in the multi-grain boundaries was expressed as (Ca/Si)_GIn the case of (2), the following formula is satisfied,

0.1＜(Ca/Si)_G＜0.9。

2. the ferrite sintered magnet according to claim 1,

also satisfies 0.1 < (Ca/Si)_G＜0.5。

3. The ferrite sintered magnet according to claim 1 or 2,

the M-type ferrite crystal grains are Sr ferrite crystal grains, and the multi-crystal grain boundary contains Sr.

4. The ferrite sintered magnet according to claim 3,

wherein the ratio of the number of Ca atoms to the total number of Fe, Sr, Ca and Si atoms in the M-type ferrite crystal grains is Mc1,

and Gc1 represents the ratio of the number of Ca atoms to the total number of Fe, Sr, Ca and Si atoms in the grain boundaries of the polycrystalline grains,

20＜Gc1/Mc1＜90。

5. the ferrite sintered magnet according to claim 4,

also satisfies 20 < Gc1/Mc1 < 70.

6. The ferrite sintered magnet according to claim 4 or 5,

mr1 represents the ratio of the number of atoms of Sr to the total number of atoms of Fe, Sr, Ca and Si in the M-type ferrite crystal grains,

and the ratio of the number of atoms of Sr to the total number of atoms of Fe, Sr, Ca and Si in the grain boundaries of the polycrystalline grains is Gr1, the following formula is satisfied,

2.0＜Gr1/Mr1＜3.2。

7. the ferrite sintered magnet according to any one of claims 3 to 6,

the Sr ferrite grains contain Zn, and the multi-grain boundaries contain Zn.

8. The ferrite sintered magnet according to claim 7,

the ratio of the number of atoms of Zn to the total number of atoms of Fe, Sr, Ca, Si and Zn in the M-type ferrite crystal grains is Mz2,

and the ratio of the number of Zn atoms to the total number of Fe, Sr, Ca, Si and Zn atoms in the grain boundaries of the polycrystalline grains is Gz2, satisfying the following formula,

0.2＜Gz2/Mz2＜2.9。

9. the ferrite sintered magnet according to claim 7 or 8,

the molar ratio of Sr to Zn in the multi-grain boundary is (Sr/Zn)_GWhen the following formula is satisfied,

40＜(Sr/Zn)_G＜700。

10. the ferrite sintered magnet according to any one of claims 7 to 9,

in the grain boundary of the multiple grainsThe molar ratio of Ca to Zn of (2) is (Ca/Zn)_GWhen the following formula is satisfied,

50＜(Ca/Zn)_G＜2000。

11. the ferrite sintered magnet according to any one of claims 7 to 10,

the molar ratio of Sr to Zn in the M-type ferrite grains is expressed as (Sr/Zn)_MIn the case of (2), the following formula is satisfied,

22＜(Sr/Zn)_M＜70。

12. the ferrite sintered magnet according to any one of claims 7 to 11,

the molar ratio of Ca to Zn in the M-type ferrite grains is (Ca/Zn)_MWhen the following formula is satisfied,

2.1＜(Ca/Zn)_M＜7.0。

13. the ferrite sintered magnet according to any one of claims 7 to 12,

the molar ratio of Fe to Zn in the M-type ferrite grains is (Fe/Zn)_MWhen the following formula is satisfied,

460＜(Fe/Zn)_M＜1500。

14. the ferrite sintered magnet according to any one of claims 7 to 13,

in the ferrite sintered magnet, the content of Si is SiO₂0.05 to 1.3% by mass in terms of CaO, 0.15 to 2.0% by mass in terms of Ca, 0.01 to 1.47% by mass in terms of ZnO, 0.25 to 1.5% by mass in terms of MnO, and Cr₂O₃Converted to 0.03 to 0.2 mass%.

15. The ferrite sintered magnet according to any one of claims 1 to 14,

the ferrite sintered magnet contains substantially no La or Co.

16. A rotating electric machine, wherein,

a sintered ferrite magnet as claimed in any one of claims 1 to 15.

Technical Field

The present invention relates to a ferrite sintered magnet and a rotating electrical machine including the same.

Background

As magnetic materials used for ferrite sintered magnets, Ba ferrite, Sr ferrite, and Ca ferrite having a hexagonal crystal structure are known. In recent years, among these materials, magnetoplumbite-type (M-type) ferrites have been mainly used as magnet materials for rotating electric machines such as motors. M type ferrite with AFe₁₂O₁₉Is represented by the general formula (II).

In recent years, as the M-type ferrite, ferrite containing no rare earth element and Co, for example, ferrite containing Na, has been developed from the viewpoint of reducing the raw material cost.

Documents of the prior art

Patent document

Patent document 1: WO2013/125600 publication

Patent document 2: WO2013/125601 publication

Disclosure of Invention

Technical problem to be solved by the invention

However, strength characteristics such as flexural strength are very important in ferrite sintered magnets. However, the conventional ferrite sintered magnet is not necessarily sufficient in strength. The present invention has been made in view of the above circumstances, and an object thereof is to provide a ferrite sintered magnet which may not contain a rare earth element and Co and is excellent in magnetic properties and strength, and a rotating electrical machine using the same.

Means for solving the technical problem

The ferrite sintered magnet according to the present invention is a ferrite sintered magnet comprising M-type ferrite grains and a multi-grain boundary surrounded by 3 or more of the M-type ferrite grains,

the ferrite sintered magnet contains at least Fe, Ca, B and Si,

the ferrite sintered magnet is represented by B₂O₃Contains 0.005 to 0.9 mass% of B in terms of B,

the grain boundaries of the polycrystalline grains contain Si and Ca,

the molar ratio of Ca to Si in the multi-grain boundaries was expressed as (Ca/Si)_GIn the case of (2), the following formula is satisfied,

0.1＜(Ca/Si)_G＜0.9。

here, the magnet can satisfy 0.1 < (Ca/Si)_G＜0.5。

In addition, the M-type ferrite crystal grains are Sr ferrite crystal grains, and the polycrystalline grain boundary may contain Sr.

Here, assuming that the ratio of the number of Ca atoms to the total number of atoms of Fe, Sr, Ca and Si in the M-type ferrite crystal grains is Mc1,

and Gc1 represents the ratio of the number of Ca atoms to the total number of Fe, Sr, Ca and Si atoms in the grain boundaries of the polycrystalline grains,

20＜Gc1/Mc1＜90。

further, 20 < Gc1/Mc1 < 70 can be satisfied.

The ratio of the number of Sr atoms to the total number of Fe, Sr, Ca, and Si atoms in the M-type ferrite crystal grains is Mr1,

and the ratio of the number of atoms of Sr to the total number of atoms of Fe, Sr, Ca and Si in the grain boundaries of the polycrystalline grains is Gr1, the following formula can be satisfied,

2.0＜Gr1/Mr1＜3.2。

in the magnet, the Sr ferrite grains may further contain Zn, and the polycrystalline grain boundaries may contain Zn.

Here, the ratio of the number of atoms of Zn to the total number of atoms of Fe, Sr, Ca, Si and Zn in the M-type ferrite crystal grains is Mz2,

and the ratio of the number of atoms of Zn to the total number of atoms of Fe, Sr, Ca, Si and Zn in the grain boundaries of the polycrystalline grains is Gz2, the following formula can be satisfied,

0.2＜Gz2/Mz2＜2.9。

the magnet has a molar ratio of Sr to Zn in the grain boundaries of the polycrystalline grains set to (Sr/Zn)_GThen, the following formula can be satisfied,

40＜(Sr/Zn)_G＜700。

in the magnet, the molar ratio of Ca to Zn in the grain boundaries of the polycrystalline grains is (Ca/Zn)_GThen, the following formula can be satisfied,

50＜(Ca/Zn)_G＜2000。

the molar ratio of Sr to Zn in the M-type ferrite grains is expressed as (Sr/Zn)_MIn the case of (2), the following equation can be satisfied,

22＜(Sr/Zn)_M＜70。

the molar ratio of Ca to Zn in the M-type ferrite crystal grains is (Ca/Zn)_MThen, the following formula can be satisfied,

2.1＜(Ca/Zn)_M＜7.0。

further, the molar ratio of Fe to Zn in the M-type ferrite crystal grains is (Fe/Zn)_MThen, the following formula can be satisfied,

460＜(Fe/Zn)_M＜1500。

in the ferrite sintered magnet, the content of Si is SiO₂0.05 to 1.3% by mass in terms of CaO, 0.15 to 2.0% by mass in terms of Ca, 0.01 to 1.47% by mass in terms of ZnO, 0.25 to 1.5% by mass in terms of MnO, and Cr₂O₃Converted to 0.03 to 0.2 mass%.

The ferrite sintered magnet may contain substantially no La or Co.

A rotating electrical machine according to the present invention includes any one of the ferrite sintered magnets described above.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a ferrite sintered magnet which does not substantially contain a rare earth element and Co and is excellent in magnetic properties and strength can be obtained.

Drawings

FIG. 1 is a schematic view showing an example of a cross-sectional structure of a sintered ferrite magnet according to the present invention.

Fig. 2 is a schematic sectional view of a motor having a ferrite sintered magnet of the present invention.

Fig. 3A is a perspective view of the ferrite sintered magnet S subjected to the bending strength test, and fig. 3B is a schematic view of the bending strength test.

Description of symbols:

4 … M-type ferrite grains (main phase), 6 … grain boundaries, 6a … two grain boundaries, 6b … multiple grain boundaries, 100 … ferrite sintered magnet.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings as necessary.

(ferrite sintered magnet)

As shown in fig. 1, a ferrite sintered magnet 100 according to an embodiment of the present invention includes: m-type ferrite grains (main phase) 4 having a hexagonal structure, and grain boundaries 6 existing between the M-type ferrite grains 4.

The grain boundaries 6 are disposed between the M-type ferrite grains 4. The grain boundary 6 has a two-grain boundary 6a formed between two M-type ferrite grains 4 and a multi-grain boundary 6b surrounded by 3 or more M-type ferrite grains 4.

(M type ferrite grain)

The M-type ferrite crystal grain can have M-type ferrite represented by formula (1) as a main component.

AX₁₂O₁₉ (1)

Here, a contains at least one selected from Sr, Ba, and Ca.

The M-type ferrite may be Sr ferrite in which Sr occupies 34 at% or more of A, Ba ferrite in which Ba occupies 34 at% or more of A, and Ca ferrite in which Ca occupies 34 at% or more of A. In the Sr ferrite, Ba ferrite, and Ca ferrite, Sr, Ba, and Ca can be the largest components in the atomic ratio of a.

The remaining element of a in the Sr ferrite can be at least one selected from Ba and Ca. The remaining element of a in Ba ferrite can be at least one selected from Sr and Ca. The remaining element of a in the Ca ferrite can be at least one selected from Sr and Ba.

X must contain Fe. The atomic ratio of Fe may be 50% or more. The remainder of X may be 1 or more elements selected from Zn (zinc), Mn (manganese), Al (aluminum), and Cr (chromium).

The M-type Sr ferrite can be represented by, for example, the following general formula (3).

Sr_1-zR_z(Fe_12-xM_x)_yO₁₉ (3)

In the above formula (3), x is, for example, 0.01 to 0.5, y is, for example, 0.7 to 1.2, and z is, for example, 0 to 0.5, and may be, for example, 0.01 to 0.49. R can be Ca and/or Ba.

The M-type ferrite is preferably Sr ferrite.

The M-type Ba ferrite can be represented by, for example, the following general formula (4).

Ba_1-zR_z(Fe_12-xM_x)_yO₁₉ (4)

In the above formula (4), x is, for example, 0.01 to 0.5, y is, for example, 0.7 to 1.2, and z is, for example, 0 to 0.5, and may be, for example, 0.01 to 0.49. R can be Sr and/or Ca.

The M-type Ca ferrite can be represented by, for example, the following general formula (5).

Ca_1-zR_z(Fe_12-xM_x)_yO₁₉ (5)

In the above formula (5), x is, for example, 0.01 to 0.5, y is, for example, 0.7 to 1.2, and z is, for example, 0 to 0.5, and may be, for example, 0.01 to 0.49. R can be Sr and/or Ba.

M in the above formulas (3) to (5) may be 1 or more elements selected from Zn (zinc), Mn (manganese), Al (aluminum), and Cr (chromium).

In addition, the ratios of the a site and the X site and the ratio of oxygen (O) in the above formulas (3) to (5) actually show values slightly deviating from the above ranges, and therefore, may slightly deviate from the above values.

In the case where the M-type ferrite in the ferrite sintered magnet is represented by the above formulas (3) to (5), M preferably contains Mn and Cr, and more preferably contains Mn, Cr, and Zn.

The M-type ferrite grains 4 are preferably Sr ferrite grains, and in this case, the multi-grain boundary 6b usually contains Sr. In addition, it is preferable that the Sr ferrite grains further contain Zn, and in this case, the polycrystalline grain boundary 6b usually contains Zn.

The molar ratio of Sr to Zn in the M-type ferrite grains 4 is (Sr/Zn)_MThen, (Sr/Zn)_MPreferably, the following formula is satisfied.

22＜(Sr/Zn)_M＜70

Thereby, the composition, size, and shape of the M-type ferrite crystal grains 4 are optimized.

(Sr/Zn)_MFor example, when the ratio of the number of atoms of Sr to the total number of atoms of Fe, Sr, Ca, Si, and Zn in the M-type ferrite crystal grains 4 is Mr2, and the ratio of the number of atoms of Zn to the total number of atoms of Fe, Sr, Ca, Si, and Zn in the M-type ferrite crystal grains 4 is Mz2, the calculation is performed as Mr2/Mz 2.

The molar ratio of Ca to Zn in the M-type ferrite grains 4 was (Ca/Zn)_MIn the case of (Ca/Zn)_MPreferably, the following formula is satisfied.

2.1＜(Ca/Zn)_M＜7.0

Thereby, the composition, size, and shape of the M-type ferrite crystal grains 4 are optimized.

(Ca/Zn)_MFor example, when the ratio of the number of Ca atoms in the M-type ferrite crystal grains 4 to the total number of atoms of Fe, Sr, Ca, Si, and Zn is Mc2, and the ratio of the number of Zn atoms in the M-type ferrite crystal grains 4 to the total number of atoms of Fe, Sr, Ca, Si, and Zn is Mz2, the calculation is performed as Mc2/Mz 2.

The molar ratio of Fe to Zn in the M-type ferrite grains 4 is (Fe/Zn)_MIn the case of (Fe/Zn)_MPreferably, the following formula is satisfied.

460＜(Fe/Zn)_M＜1500

Thereby, the composition, size, and shape of the M-type ferrite crystal grains 4 are optimized.

(Fe/Zn)_MFor example, the ratio of the number of atoms of Fe to the total number of atoms of Fe, Sr, Ca, Si, and Zn in the M-type ferrite crystal grains 4 is Mf2, and the ratio of the number of atoms of Zn to the total number of atoms of Fe, Sr, Ca, Si, and Zn in the M-type ferrite crystal grains 4 is Mf2Mz2, Mf2/Mz 2.

The mass fraction of the M-type ferrite in the M-type ferrite crystal grains is preferably 90% or more, more preferably 95% or more, and further preferably 97% or more.

The mass ratio of the M-type ferrite crystal grains (main phase) in the sintered ferrite magnet to the entire crystal grains is preferably 90% or more, more preferably 95% or more, and still more preferably 97% or more. In this way, the magnetic properties can be further improved by lowering the mass ratio of the crystal phase (heterogeneous phase) different from the M-type ferrite phase. The mass ratio (%) of the M-type ferrite phase in all the crystal grains of the sintered ferrite magnet can be confirmed by obtaining the existence ratio (mol%) of the M-type ferrite phase by X-ray diffraction. The presence ratio of the M-type ferrite phase in the sample is calculated by mixing powder samples of M-type ferrite, orthoferrite, hematite, spinel, and W-type ferrite at a predetermined ratio to obtain a reference, and comparing the X-ray diffraction intensities of the sample and the reference.

(grain boundary)

The main component of the grain boundary 6 is an oxide. In the grain boundary 6, the constituent elements other than oxygen of the oxide must contain Si (silicon) and Ca (calcium), and may contain B (boron). The constituent element may contain at least one selected from Sr (strontium), Ba (barium), Fe (iron), Mn (manganese), Zn (zinc), Cr (chromium), and Al (aluminum), or a combination of any 2 or more. Examples of the oxide include: SiO 2₂、CaO、BaO、SrO、Al₂O₃、ZnO、Fe₂O₃、MnO、Cr₂O₃、B₂O₃And the like. In addition, silicate glass may be contained. The oxide can occupy 90% by mass or more, more preferably 95% by mass or more, and still more preferably 97% by mass or more of the grain boundary 6.

The polycrystalline grain boundary 6B may contain Si, Ca, B, and the above-described elements, as in the case of the grain boundary 6.

The molar ratio of Ca to Si in the multi-grain boundaries 6b was (Ca/Si)_GIn the case of (2), the ferrite sintered magnet satisfies the following equation.

0.1＜(Ca/Si)_G＜0.9

(Ca/Si)_GFor example, Gc1/Gs1 is calculated when the ratio of the number of atoms of Ca to the total number of atoms of Fe, Sr, Ca, and Si in the multi-grain boundary 6b is Gc1 and the ratio of the number of atoms of Si to the total number of atoms of Fe, Sr, Ca, and Si in the multi-grain boundary 6b is Gs 1.

In the polycrystalline grain boundary 6b, it is preferable that 0.1 < (Ca/Si) is further satisfied_G＜0.5。

As described above, it is considered that when the ratio of Si to Ca is high in the multi-grain boundary 6b, the composition, size, and shape of the M-type ferrite grains 4 are optimized, and magnetic interaction between the M-type ferrite grains 4 can be suppressed, so that HcJ is improved and mechanical strength is improved.

Further, Ca is considered to be easily dissolved in the M-type ferrite crystal grains 4, and to improve the magnetocrystalline anisotropy and the coercive force.

The molar ratio of Sr to Zn in the multi-grain boundary 6b is (Sr/Zn)_GIn the case of (Sr/Zn)_GPreferably, the following formula is satisfied.

40＜(Sr/Zn)_G＜700

Thereby, the composition, size, and shape of the M-type ferrite crystal grains 4 are optimized.

(Sr/Zn)_GFor example, when the ratio of the number of atoms of Sr to the total number of atoms of Fe, Sr, Ca, Si, and Zn in the multi-grain boundary 6b is Gr2, and the ratio of the number of atoms of Zn to the total number of atoms of Fe, Sr, Ca, Si, and Zn in the multi-grain boundary 6b is Gz2, Gr2/Gz2 is calculated.

The molar ratio of Ca to Zn in the multi-grain boundaries 6b was (Ca/Zn)_GIn the case of (Ca/Zn)_GPreferably, the following formula is satisfied.

50＜(Ca/Zn)_G＜2000

Thereby, the composition, size, and shape of the M-type ferrite crystal grains 4 are optimized.

(Ca/Zn)_GAn example of (2) is a case where the ratio of the number of Ca atoms to the total number of Fe, Sr, Ca, Si and Zn atoms in the multi-grain boundary 6b is Gc2, andgc2/Gz2, where the ratio of the number of Zn atoms to the total number of Fe, Sr, Ca, Si, and Zn atoms in the polycrystalline grain boundary 6b is Gz 2.

(element ratio between M type ferrite grain and grain boundary of multiple grains)

It is preferable that the following formula is satisfied when the ratio of the number of Ca atoms to the total number of atoms of Fe, Sr, Ca, and Si in the M-type ferrite crystal grain 4 is Mc1, and the ratio of the number of Ca atoms to the total number of atoms of Fe, Sr, Ca, and Si in the multi-grain boundary 6b is Gc 1.

20＜Gc1/Mc1＜90

Here, it is more preferable that 20 < Gc1/Mc1 < 70 be satisfied.

Thereby, the interaction between the M-type ferrite grains 4 and the multi-grain boundary 6b is also optimized, and high magnetic characteristics and mechanical strength are obtained.

It is preferable that the following formula is satisfied, assuming that the ratio of the number of Sr atoms to the total number of atoms of Fe, Sr, Ca, and Si in the M-type ferrite crystal grains 4 is Mr1, and the ratio of the number of Sr atoms to the total number of atoms of Fe, Sr, Ca, and Si in the multi-grain boundary 6b is Gr 1.

2.0＜Gr1/Mr1＜3.2

Thus, it is considered that the Sr ratio in the multi-grain boundary 6b is lower than that of the M-type ferrite grains 4, and therefore, the composition, size, and shape of the M-type ferrite grains 4 are optimized, and the magnetic interaction between the M-type ferrite grains 4 can be suppressed, and therefore, HcJ is improved and mechanical strength is improved.

When the ratio of the number of atoms of Zn to the total number of atoms of Fe, Sr, Ca, Zn, and Si in the M-type ferrite crystal grains 4 is Mz2, and the ratio of the number of atoms of Zn to the total number of atoms of Fe, Sr, Ca, Zn, and Si in the multi-grain boundary 6b is Gz2, the following formula is preferably satisfied.

0.2＜Gz2/Mz2＜2.9

Thereby, the interaction between the M-type ferrite grains 4 and the multi-grain boundary 6b is also optimized, and high magnetic characteristics and mechanical strength are obtained.

(integral composition)

The ferrite sintered magnet according to the embodiment of the present invention is an oxide containing at least Fe, Ca, B, and Si.

Fe content in ferrite sintered magnet₂O₃The conversion is preferably 80 to 95% by mass, and more preferably 87 to 90% by mass. By setting the above range, favorable magnetic characteristics can be obtained.

The ferrite sintered magnet preferably contains Sr, and when the M-type ferrite grains in the ferrite sintered magnet are Sr ferrite grains, the Sr content in the ferrite sintered magnet is preferably 9 to 11 mass%, more preferably 9 to 10 mass%, in terms of SrO.

When the M-type ferrite grains in the ferrite sintered magnet are Ba ferrite grains, the content of Ba in the ferrite sintered magnet is preferably 13 to 17 mass%, more preferably 13 to 15 mass%, in terms of BaO.

When the M-type ferrite grains in the ferrite sintered magnet are Ca ferrite grains, the content of Ca in the ferrite sintered magnet is preferably 2 to 5 mass%, more preferably 2 to 4 mass%, in terms of CaO.

In a ferrite sintered magnet, M-type ferrite grains as a main phase contain Ca (calcium) even if the M-type ferrite grains are Sr ferrite grains or even Ba ferrite grains. When the main phase is Sr ferrite grains or Ba ferrite grains, the content of Ca in the ferrite sintered magnet is preferably 0.15 to 2.0 mass%, more preferably 0.4 to 1.0 mass%, and further preferably 0.47 to 0.62 mass%, in terms of CaO. Since HcJ tends to decrease when Ca is too large and Br tends to decrease when Ca is small, an optimum grain boundary is formed and high magnetic properties are easily obtained by setting the content of Ca within the above range.

The ferrite sintered magnet contains B. The content of B in the ferrite sintered magnet is B₂O₃Converted to 0.005 to 0.9 mass%. From the viewpoint of further improving the coercive force and squareness ratio (Hk/HcJ) of the ferrite sintered magnet, the content of B is defined as B₂O₃The conversion is preferably 0.01 mass% or more. In addition, from the viewpoint of further improving the residual magnetic flux density (Br) of the ferrite sintered magnet, the content of B is set toB₂O₃The content is preferably 0.4% by mass or less, and more preferably 0.2% by mass or less in terms of conversion.

It is considered that the addition of B increases the proportion of Si in the multi-grain boundary 6B, and therefore, the composition, size, and shape of the M-type ferrite grains 4 are optimized, and magnetic interaction between the M-type ferrite grains 4 can be suppressed, and therefore, HcJ is improved and mechanical strength is improved.

The ferrite sintered magnet contains Si (silicon). The content of Si in the ferrite sintered magnet is SiO₂The content is preferably 0.05 to 1.3% by mass, more preferably 0.2 to 0.5% by mass, and still more preferably 0.25 to 0.36% by mass in terms of the weight. SiO 2₂When too much, Br tends to decrease, and SiO is considered₂If too small, HcJ tends to decrease, and therefore, SiO is used₂When the content is within the above range, an optimum grain boundary is formed and high magnetic properties are easily obtained.

In the ferrite sintered magnet, Ba can be contained when the M-type ferrite crystal grains as the main phase are Sr ferrite crystal grains. The content of Ba is preferably 0 to 0.2 mass% in terms of BaO.

In the ferrite sintered magnet, when the M-type ferrite grains as the main phase are Ca ferrite grains, at least one selected from Sr and Ba may be contained, and the content of Ba is preferably 0 to 1.5 mass% in terms of BaO. The Sr content is preferably 0 to 1.0 mass% in terms of SrO.

In the ferrite sintered magnet, Sr can be contained when the M-type ferrite crystal grains as the main phase are Ba ferrite crystal grains. The Sr content is preferably 0 to 0.8 mass% in terms of SrO.

The ferrite sintered magnet can contain Mn. The content of Mn in the ferrite sintered magnet is preferably 0.25 to 1.5 mass% in terms of MnO. It is presumed that, by substituting the sites of Fe with Mn satisfying the above range, the effect of improving the magnetic properties is easily obtained, and the effect of promoting the solid solution of Zn is also obtained.

The ferrite sintered magnet may contain Cr. The content of Cr in the ferrite sintered magnet is Cr₂O₃The conversion is preferably 0.03 to 0.2 mass%. Substitution of the site of Fe by Cr satisfying the above rangeThe effect of improving magnetic properties is easily obtained, and the effect of promoting the solid solution of Zn is also measured.

The ferrite sintered magnet can contain Zn. The Zn content in the ferrite sintered magnet is 0.01 to 1.47 mass% in terms of ZnO. From the viewpoint of further improving the residual magnetic flux density (Br) of the ferrite sintered magnet, the content of Zn is preferably 0.08 mass% or more, and more preferably 0.15 mass% or more in terms of ZnO. In addition, the content of Zn is preferably 1.0 mass% or less, more preferably 0.5 mass% or less in terms of ZnO, from the viewpoint of further improving the coercive force and squareness ratio (Hk/HcJ) of the ferrite sintered magnet.

Accordingly, it is considered that the saturation magnetization is increased when Zn is solid-dissolved in ferrite grains, and that the composition, size, and shape of the M-type ferrite grains 4 are optimized when Zn is present in a multi-grain boundary, and magnetic interaction between the M-type ferrite grains 4 can be suppressed, so HcJ is increased and mechanical strength is improved.

It is considered that the saturation magnetization Br is increased by selectively replacing the sites of Fe having a magnetic moment oriented in an antiparallel direction with Zn. On the other hand, the coercivity is reduced because the crystal magnetic anisotropy is reduced by Zn substitution, but it is presumed that the effect of suppressing the magnetic interaction between the crystal grains works to suppress the reduction in coercivity and maintain the coercivity because the grain boundaries containing B are uniformly formed.

The ferrite sintered magnet preferably contains substantially no rare earth element and no Co (cobalt). The rare earth elements are Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

The ferrite sintered magnet may contain Ni, but preferably contains substantially no Ni. The concentration of Ni can be 0.02 mass% or less.

The ferrite sintered magnet may contain Cu, but preferably contains substantially no Cu. The Cu concentration can be 0.02 mass% or less.

By not containing these metals, the cost can be reduced.

Here, the ferrite sintered magnet containing substantially no element a means that the concentration of the element a in the ferrite sintered magnet is less than 0.005 mass% in terms of oxide. The concentration of the element a is preferably less than 0.001 mass% in terms of oxide.

The ferrite sintered magnet does not need to contain Al, but may contain Al. The content of Al is as follows₂O₃The conversion can be 0 to 0.2 mass%.

The ferrite sintered magnet does not need to contain Na, and preferably does not substantially contain Na. The content of Na is as Na₂The content of O is preferably 0.005% by mass or less in terms of O. Further, it is preferably 0.001 mass% or less. The smaller the Na content, the more excellent the moldability.

In addition to these components, the ferrite sintered magnet may contain impurities contained in the raw materials or inevitable components originating from the manufacturing equipment. Examples of such a component include oxides of Mg (magnesium), Ti (titanium), Mo (molybdenum), V (vanadium), and the like. The total content of these components is preferably 0.06% by mass or less.

The content of each component of the ferrite sintered magnet can be measured by fluorescent X-ray analysis and inductively coupled plasma emission spectroscopy (ICP analysis).

(organization structure)

In a cross section of the ferrite sintered magnet parallel to the c-axis, the arithmetic mean of the maximum diameters of the M-type ferrite grains 4 and the multi-grain boundaries 6b is preferably 0.5 to 2.0 μ M and 0.2 to 1.0 μ M, respectively. The maximum diameter is the diameter of the M-type ferrite grains 4 and the multi-grain boundary 6b measured in the maximum direction. The c-axis of the ferrite sintered magnet is the easy axis of magnetization of the ferrite sintered magnet.

(characteristics)

The residual magnetic flux density (Br) of the sintered ferrite magnet is preferably 420mT or more, more preferably 440mT or more, and still more preferably 450mT or more. The coercive force of the sintered ferrite magnet is preferably 260kA/m or more, more preferably 270kA/m or more, and still more preferably 280 kA/m. The squareness ratio (Hk/HcJ) of the ferrite sintered magnet is preferably 85% or more, more preferably 88% or more, and still more preferably 90% or more. In particular, the ferrite sintered magnet preferably has a remanence (Br) of 440mT or more and a squareness ratio (Hk/HcJ) of 85% or more. By having such excellent magnetic properties, the magnetic material can be further applied to a motor or a generator.

In addition, the ferrite sintered magnet can have sufficient mechanical strength. The ferrite sintered magnet having high mechanical strength can be handled easily, and breakage or loss during transportation can be effectively prevented, so that the product yield is improved, contributing to cost reduction. In addition, since the ferrite sintered magnet having high mechanical strength is not easily broken even after being incorporated into a product such as a motor, the reliability of the product can be improved.

The shape of the ferrite sintered magnet is not particularly limited, and various shapes such as a circular arc segment (C-shaped) shape and a flat plate shape, for example, can be adopted so that the end face is curved in a circular arc shape.

The ferrite sintered magnet can be used as a magnetic field generating member for a rotating electric machine such as a motor and a generator, a magnet for a speaker and a headphone, a magnetron, a magnetic field generating device for MRI, a holder for CD-ROM, a sensor for dispenser, a sensor for ABS, a fuel/fuel level sensor, a magnetic lock, an isolator, or the like. Further, the magnetic particles can also be used as a target (particle) for forming a magnetic layer of a magnetic recording medium by a vapor deposition method, a sputtering method, or the like.

(rotating electric machine)

Next, fig. 2 shows a motor according to an embodiment of the present invention. The motor 200 includes a stator 31 and a rotor 32. The rotor 32 has a shaft 36 and a rotor core 37. In the motor 200 of the present embodiment, the stator 31 is provided with a C-shaped ferrite sintered magnet 100 as a permanent magnet, and the rotor core 37 of the rotor 32 is provided with an electromagnet (coil).

Since ferrite sintered magnet 100 has a high Br, it can be made thinner, and therefore, the gap between stator 31 and rotor 32 can be sufficiently reduced. Therefore, the motor 200 can maintain its performance and be miniaturized.

In addition, a ferrite sintered magnet may be provided in the rotor, and an electromagnet (coil) may be provided in the stator. The form of the motor is not particularly limited. Another example of the rotating electric machine is a generator having a rotor and a stator. In this case, the ferrite sintered magnet may be provided in the rotor or the stator.

(production method)

Next, an example of a method for producing a ferrite sintered magnet will be described. A method for producing a ferrite sintered magnet comprises a blending step, a firing step, a pulverizing step, a molding step in a magnetic field, and a firing step. The details of each step will be described below.

The blending step is a step of preparing a mixed powder for calcination. The mixed powder for calcination may be a powder containing all the metal elements constituting the M-type ferrite. In the blending step, it is preferable that plural kinds of powders such as Fe-containing powder and Sr-containing powder are mixed by an attritor, a ball mill or the like for about 1 to 20 hours, and then pulverized to obtain a mixed powder.

In the mixing step, a powder containing a metal element other than the metal elements constituting the ferrite and a powder containing a semimetal element may be mixed. Examples of the other powders are Si-containing powder, Ca-containing powder, Zn-containing powder, and B-containing powder.

Examples of the powder containing each element are a simple substance, an oxide, a hydroxide, a carbonate, a nitrate, a silicate, and an organometallic compound of each element. One powder may contain two or more metal elements, and one powder may contain substantially only one metal element. A powder may also contain metallic elements and semimetallic elements.

An example of the powder containing Fe is Fe₂O₃。

An example of the Sr-containing powder is SrCO₃And SrO.

An example of the Si-containing powder is SiO₂。

An example of a Ca-containing powder is CaCO₃And CaO.

An example of the powder containing Zn is ZnO.

An example of the powder containing Ba is BaO.

An example of a powder containing B is H₃BO₃。

B is dissolved in water and tends to evaporate by heat, and therefore, it is preferable to put a large amount of B appropriately.

Particular preference is given to compounds containing B other than B₂O₃May be H₃BO₃The whole amount is added in the blending step. And B₂O₃By comparison, H₃BO₃The solubility in water is high, so that the dispersion can be made uniform at the molecular level (boric acid 5.7g/100ml, boric oxide 3.6g/100ml at 25 ℃), and the dispersion is easier when stirring and mixing (boric acid 1.5 g/cm) because the boric acid has a lower specific gravity³Boron oxide 1.9g/cm³Above). Further, even when undissolved portions remain, boric acid is decomposed at a relatively low temperature, and therefore uniform dispersion can be expected. (decomposition temperature: boric acid 171 ℃ C., boron oxide 450 ℃ C.). Further, by adding the entire amount in the blending step, the effect of forming a uniform structure of boron and other components at the time of firing can be obtained to the maximum.

That is, the entire amount of H is added in the blending step₃BO₃For example, the number N of large polycrystalline grain boundaries 6b can be reduced, the number P of small polycrystalline grain boundaries 6b can be increased, a two-grain boundary 6a having a large average thickness d can be formed, and the number Q of ferrite grains of 1 μm or less can be increased. Therefore, it is considered that high magnetic properties and high strength can be obtained.

The average particle size of the raw material powder is not particularly limited, and is, for example, 0.1 to 2.0 μm.

In addition, a small amount of additive elements such as Cr, Mn, Al, Ba, and the like contained in the ferrite sintered magnet to be a final product may be contained in the powder in advance. When the small amount of these elements is small in the above powder, Cr-containing powder (Cr) can be added in the blending step as necessary₂O₃) Mn-containing powder (MnO) and Al-containing powder (Al)₂O₃) And Ba-containing powder (BaO), to obtain a mixed powder for calcination.

The composition of the metal and semimetal elements in the mixed powder is substantially identical to that of the final product of the ferrite sintered magnet, but has elements that disappear in the manufacturing process, and therefore, is not exactly identical.

The calcination step is a step of calcining the mixed powder obtained in the blending step. The calcination can be carried out in an air or a moderately oxidizing atmosphere. The calcination temperature is preferably 850 to 1450 ℃, more preferably 900 to 1350 ℃, and further preferably 1000 to 1300 ℃, and the calcination time at the calcination temperature is preferably 1 second to 10 hours, and more preferably 1 minute to 3 hours. The content of the M-type ferrite in the calcined product obtained by the calcination is preferably 70 mass% or more, and more preferably 90 mass% or more. The primary particle size of the calcined product is preferably 10 μm or less, more preferably 3.0 μm or less.

The pulverization step is a step of pulverizing the calcined product to obtain a powder of an M-type ferrite magnet. The pulverization step may be performed in one stage, or may be performed in two stages, i.e., a coarse pulverization step and a fine pulverization step. Since the calcined product is usually in the form of particles or lumps, it is preferable to first perform a coarse pulverization step. In the coarse grinding step, the powder is ground in a dry manner using a vibrating rod mill or the like to prepare a ground powder having an average particle diameter of 0.5 to 5.0 μm. The pulverized powder thus prepared is subjected to wet pulverization using a wet mill, a ball mill, a jet mill or the like to obtain a fine powder having an average particle diameter of 0.08 to 5.0 μm, preferably 0.1 to 2.5 μm, more preferably 0.2 to 2 μm.

The specific surface area of the fine powder by the BET method is preferably 5 to 14m²(ii)/g, more preferably 7 to 12m²(ii) in terms of/g. The grinding time is, for example, 30 minutes to 20 hours in the case of using a wet grinder, and 5 to 50 hours in the case of using a ball mill. These times are preferably adjusted as appropriate according to the pulverization method.

In the pulverizing step, a powder containing a metal element and/or a semimetal element (e.g., Si, Ca, Ba, Sr, Zn, and B) and/or a powder containing a small amount of an additive element such as Cr, Mn, Al, and Ba may be added to the M-type ferrite magnet powder.

In order to increase the degree of magnetic orientation of the ferrite sintered magnet, it is preferable to add a polyol in the fine grinding step in addition to the above components. The amount of the polyhydric alcohol added is 0.05 to 5.0% by mass, preferably 0.1 to 3.0% by mass, and more preferably 0.1 to 2.0% by mass, based on the amount of the object to be added. The added polyol is thermally decomposed and removed in a firing step after the molding step in a magnetic field.

The in-magnetic-field molding step is a step of molding the fine powder obtained in the pulverization step in a magnetic field to produce a molded body. The molding step in a magnetic field can be performed by either dry molding or wet molding. From the viewpoint of improving the degree of magnetic orientation, wet molding is preferable. In the case of wet molding, the fine grinding step may be performed in a wet manner, and the obtained slurry may be adjusted to a predetermined concentration to obtain a slurry for wet molding. The concentration of the slurry can be performed by centrifugal separation, a filter press, or the like.

The content of the fine powder in the slurry for wet molding is preferably 30 to 85 mass%. As a dispersion medium of the slurry, water or a nonaqueous solvent can be used. In the slurry for wet molding, a surfactant such as gluconic acid, gluconate, or sorbitol may be added in addition to water. The slurry for wet molding is used for molding in a magnetic field. The molding pressure is, for example, 0.1 to 0.5 ton/cm²The applied magnetic field is, for example, 5 to 15 kOe.

The firing step is a step of firing the molded body to obtain a sintered body. The firing step is usually performed in an oxidizing atmosphere such as the atmosphere. The firing temperature is preferably 1050 to 1300 ℃, and more preferably 1150 to 1250 ℃. The firing time at the firing temperature is preferably 0.5 to 3 hours. Through the above steps, a sintered body, that is, a ferrite sintered magnet can be obtained. The method for producing a sintered ferrite magnet according to the present invention is not limited to the above-described method.

Examples

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

(production of ferrite sintered magnet)

First, the following starting materials were prepared.

·Fe₂O₃Powder (primary particle size: 0.3 μm)

·SrCO₃Powder (primary particle size: 2 μm)

·SiO₂Powder (primary particle size: 0.01 μm)

·CaCO₃Powder of

ZnO powder

·H₃BO₃Powder of

[ example 1]

Mixing Fe₂O₃Powder 1000g, SrCO₃Powder 161g, CaCO₃Powder 12.1g, SiO₂4.33g of powder, 3.5g of ZnO powder, and H₃BO₃0.34g of the powder was mixed by grinding with a wet grinder, and dried and granulated. The powder thus obtained was fired at 1250 ℃ for 1 hour in the air to obtain a granular calcined product. The calcined material was coarsely pulverized by a dry vibration rod mill to prepare a powder having a specific surface area of 1m by the BET method²Powder per gram.

A predetermined amount of sorbitol was added to 200g of the coarsely pulverized powder, and wet pulverization was performed for 24 hours using a ball mill to obtain a slurry. The amount of sorbitol added was 0.25 mass% based on the mass of the coarsely pulverized powder. The specific surface area of the pulverized micropowder is 8 to 10m²/g。

Then, the solid content concentration of the slurry was adjusted, and the slurry was molded in an applied magnetic field of 12kOe using a wet magnetic field molding machine to obtain a molded article. 3 such molded articles were produced. These molded bodies were fired in the air at 1180, 1195, and 1210 ℃ to obtain cylindrical ferrite sintered magnets (example 1).

Examples 2 to 6 and comparative example 1

Except for changing H₃BO₃Except for the amount of the added powder, the same procedure as in example 1 was carried out to obtain magnets of examples 2 to 6 and comparative example 1.

[ examples 7 to 8]

Magnets of examples 7 and 8 were obtained in the same manner as in example 4, except that the amount of Mn added was changed by selecting the brand of the raw material having a different Mn content.

[ examples 9 to 10]

Magnets of examples 9 and 10 were obtained in the same manner as in example 4, except that the amount of Cr to be added was changed by selecting the brand of the raw material having a different Cr content.

[ examples 11 to 12]

Magnets of examples 11 and 12 were obtained in the same manner as in example 4, except that the amount of ZnO to be added was changed.

[ examples 13 to 14]

Except for changing SiO₂Except for the amount of (c), the same procedures as in example 4 were carried out to obtain magnets of examples 13 and 14.

[ examples 15 to 16]

Except for changing CaCO₃Except for the amount of (c), the same procedures as in example 4 were carried out to obtain magnets of examples 15 and 16.

(evaluation of ferrite sintered magnet)

< analysis of composition of ferrite sintered magnet as a whole >

The compositions of the ferrite sintered magnets of the respective examples and comparative examples were measured by inductively coupled plasma emission spectrometry (ICP analysis). The ferrite sintered magnet detects elements (Ba, Al, Mn, Cr, etc.) derived from impurities contained in the starting materials, in addition to Fe, Sr, Si, Ca, Zn, B, etc.

Table 1 shows the results of converting detected Fe, Sr, Ba, Al, Si, Ca, Mn, Zn, Cr, Na and B into Fe₂O₃、SrO、BaO、Al₂O₃、SiO₂、CaO、MnO、ZnO、Cr₂O₃、Na₂O, and B₂O₃The content of (A) to (B). These contents are values (mass%) based on the whole of the ferrite sintered magnet.

< compositional analysis of Sr ferrite grains and grain boundaries of polycrystalline grains >

After a cross section parallel to the easy magnetization axis (c-axis) was obtained, the atomic concentration ratios of Fe, Sr, Ca, Si, and Zn at Sr ferrite grains (main phase) and polycrystalline grain boundaries were measured by TEM-EDX at a magnification of about 40000 times.

In one example or comparative example, the number of Sr ferrite grains measured was 10, the number of grain boundaries of polycrystalline grains was 5, and arithmetic mean was obtained.

Table 2 shows the atomic concentration when the total number of atoms of Fe, Sr, Ca, and Si is 100%, and table 3 shows the atomic concentration when the total number of atoms of Fe, Sr, Ca, Si, and Zn is 100%.

Further, Mf1, Mr1, Mc1, and Ms1 respectively represent atomic ratios (at%) of Fe, Sr, Ca, and Si to the total number of atoms of Fe, Sr, Ca, and Si in ferrite crystal grains, and Gf1, Gr1, Gc1, and Gs1 respectively represent atomic ratios (at%) of Fe, Sr, Ca, and Si to the total number of atoms of Fe, Sr, Ca, and Si in grain boundaries of polycrystalline grains.

Further, Mf2, Mr2, Mc2, Ms2, and Mz2 respectively represent atomic ratios (at%) of Fe, Sr, Ca, Si, and Zn to the total number of atoms of Fe, Sr, Ca, Si, and Zn in ferrite crystal grains, and Gf2, Gr2, Gc2, Gs2, and Gz2 respectively represent atomic ratios (at%) of Fe, Sr, Ca, Si, and Zn to the total number of atoms of Fe, Sr, Ca, Si, and Zn in grain boundaries of polycrystalline grains.

< evaluation of magnetic Properties >

After the upper and lower surfaces of the prepared cylindrical ferrite sintered magnet were processed, the magnetic properties were measured by using a B-H tracer with a maximum applied magnetic field of 25 kOe. In the measurement, the remanence (Br) and the coercive force (HcJ) were determined, and the external magnetic field strength (Hk) at 90% of the remanence (Br) was measured, and the rectangular ratio (Hk/HcJ) (%) was determined based on the strength. In each of the examples and comparative examples, the magnetic properties of the ferrite sintered magnets manufactured at 1195 ℃ having the best balance between the remanence (Br) and the squareness ratio (Hk/HcJ) among the ferrite sintered magnets manufactured at 1180 ℃, 1195 ℃ and 1210 ℃ are shown in table 4.

< evaluation of mechanical Strength >

The flexural strength (σ) of the ferrite sintered magnet was measured by a three-point bending test under the following conditions. First, in addition to the above-described cylindrical ferrite sintered magnet, an arc-shaped ferrite sintered magnet S as shown in fig. 3A was prepared (assuming that the length L was 34mm, the width W was 25.5mm, the thickness T was 3.7mm, and the angle R between the connection lines drawn from the center of the circle to both ends of the arc was 130 degrees in the case of the circle including the arc). The firing temperature was set to 1195 ℃.

Next, as shown in fig. 3B, an arc-shaped ferrite sintered magnet S was placed on a horizontal table 70, a load F (speed 3mm/min) was applied from above to below in the direction of the arrow by a jig 72, the maximum load F [ N ] of failure when the ferrite sintered magnet S was broken was measured, and the flexural strength (σ) was obtained by the following equation. The flexural strength (. sigma.) was an average of 30 samples. The results are shown in table 5.

σ[N/mm²]＝3×L×F/(2×W×T²)

[ Table 1]

[ Table 2]

[ Table 3]

[ Table 4]

[ Table 5]

As shown in tables 1 to 5, the sintered ferrite magnets of the examples had residual magnetic flux densities (Br) of 420mT or more. Further, the coercive force (HcJ) is 260kA/m or more, and the squareness ratio (Hk/HcJ) is 85% or more. In addition, the intensity σ also shows 172N/mm²The above. That is, it was confirmed that the ferrite sintered magnet of the present invention passed 0.1 < (Ca/Si)_G< 0.9, thereby exerting excellent magnetic properties and strength.