阅读说明：本技术 铁氧体烧结磁铁及旋转电机 (Ferrite sintered magnet and rotating electrical machine ) 是由 室屋尚吾 村川喜堂 森田启之 池田真规 于 2021-03-22 设计创作，主要内容包括：本发明得到一种铁氧体烧结磁铁,其具有高的剩余磁通密度(Br)及高的矫顽力(HcJ),能够以更低成本进行制作。所述铁氧体烧结磁铁包含A、R、Fe及Co,并且具有能够表示成A-(1－x)R-x(Fe-(12－)-yCo-y)-zO-(19)(原子数比)的六方晶M型铁氧体。A为选自Sr、Ba及Pb中的1种以上。R为选自稀土元素中的1种以上。作为R,至少包含La。满足0.13≤x≤0.23、10.80≤(12－y)z≤12.10、0.13≤yz≤0.20。(The invention provides a ferrite sintered magnet which has high residual magnetic flux density (Br) and high coercive force (HcJ) and can be manufactured at lower cost. The ferrite sintered magnet comprises A, R, Fe and Co, and has a magnetic core represented by A 1－x R x (Fe 12－ y Co y ) z O 19 Hexagonal M-type ferrite (atomic ratio). A is more than 1 selected from Sr, Ba and Pb. R is more than 1 selected from rare earth elements. R is at least La. X is more than or equal to 0.13 and less than or equal to 0.23, z is more than or equal to 10.80 and less than or equal to 12.10 in (12-y), and yz is more than or equal to 0.13 and less than or equal to 0.20.)

1. A ferrite sintered magnet, wherein,

the ferrite sintered magnet comprises A, R, Fe and Co, and has a ratio A expressed by atomic number_1－xR_x(Fe_12－yCo_y)_zO₁₉The hexagonal M-type ferrite of (1), wherein,

a is more than 1 selected from Sr, Ba and Pb,

r is 1 or more selected from rare earth elements, and R is at least La,

x is more than or equal to 0.13 and less than or equal to 0.23

10.80≤(12－y)z≤12.10

0.13≤yz≤0.20。

2. The ferrite sintered magnet according to claim 1,

wherein the content of CaO is Mc by mass% when Ca contained in the sintered ferrite magnet is converted to oxides,

mc is more than or equal to 0.30 and less than or equal to 0.85.

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

converting Si contained in the ferrite sintered magnet into an oxide, SiO₂The content of (b) is set to Ms mass%,

ms is more than or equal to 0.35 and less than or equal to 0.60.

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

the content of BaO is Mb mass% when Ba contained in the ferrite sintered magnet is converted into oxide,

mb is more than or equal to 0 and less than or equal to 0.15.

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

converting Al contained in the ferrite sintered magnet into an oxide₂O₃The content of (c) is defined as Ma mass%,

ma is more than or equal to 0 and less than or equal to 0.90.

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

converting Cr contained in the ferrite sintered magnet into an oxide₂O₃The content of (b) is defined as Mr mass%,

mr is more than or equal to 0 and less than or equal to 0.10.

7. A rotating electric machine, wherein,

the rotating electrical machine has the ferrite sintered magnet according to any one of claims 1to 6.

Technical Field

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

Background

In order to obtain a ferrite sintered magnet having excellent magnetic characteristics (high remanence Br, high coercive force HcJ), there is known a hexagonal M-type ferrite using Sr ferrite containing at least Sr.

Patent document 1 discloses Sr ferrite containing at least La as a rare earth element and having a part of Fe substituted by Co, as the Sr ferrite. By using Sr ferrite containing La and Co as essential elements, a ferrite sintered magnet having high Br and high HcJ can be obtained.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 3337990

Disclosure of Invention

Technical problem to be solved by the invention

The invention aims to obtain a ferrite sintered magnet with high Br and high HcJ in a composition with a small amount of Co.

Technical solution for solving technical problem

In order to achieve the above object, the sintered ferrite magnet of the present invention comprises A, R, Fe and Co, and has a magnetic core represented by A_1－xR_x(Fe_12－yCo_y)_zO₁₉Hexagonal M-type ferrite (atomic ratio),

a is more than 1 selected from Sr, Ba and Pb,

r is 1 or more selected from rare earth elements, and R is at least La,

x is more than or equal to 0.13 and less than or equal to 0.23

10.80≤(12－y)z≤12.10

0.13≤yz≤0.20。

When the Ca contained in the sintered ferrite magnet is converted into an oxide, the content of CaO is Mc (mass%),

and can also satisfy 0.30-Mc 0.85.

Converting Si contained in the ferrite sintered magnet into an oxide, SiO₂Is set to Ms (mass%),

or can satisfy Ms of more than or equal to 0.35 and less than or equal to 0.60.

When Ba contained in the ferrite sintered magnet is converted into oxide, the content of BaO is Mb (mass%),

it is also possible to satisfy 0. ltoreq. Mb.ltoreq.0.15.

When Al contained in the ferrite sintered magnet is converted into oxideMixing Al₂O₃The content of (C) is Ma (mass%),

ma may be 0 or more and 0.90 or less.

Converting Cr contained in the ferrite sintered magnet into an oxide₂O₃The content of (D) is Mr (% by mass),

it is also possible to satisfy 0. ltoreq. Mr.ltoreq.0.10.

The rotating electric machine of the present invention includes the above ferrite sintered magnet.

Detailed Description

The present invention will be described below based on embodiments.

The ferrite sintered magnet of the present embodiment includes A, R, Fe and Co, and has a magnetic core represented by A_1－xR_x(Fe_12－yCo_y)_zO₁₉Hexagonal M-type ferrite (atomic ratio). In the present specification, the ferrite sintered magnet according to the present embodiment is sometimes referred to as a ferrite sintered magnet. A is more than 1 selected from strontium (Sr), barium (Ba) and lead (Pb). R is at least 1 selected from rare earth elements, and at least lanthanum (La), x, (12-y) z and yz satisfy the following formula.

0.13≤x≤0.23

10.80≤(12－y)z≤12.10

0.13≤yz≤0.20

The ferrite sintered magnet has a magnetic core represented by A_1－xR_x(Fe_12－yCo_y)_zO₁₉Hexagonal M-type (hexagonal magnetoplumbite-type) ferrite (atomic ratio).

Specifically, the ferrite sintered magnet includes a magnet represented by the formula A_1－xR_x(Fe_12－yCo_y)_zO₁₉Ferrite particles (atomic ratio). The ferrite particles are crystalline particles having a hexagonal magnetoplumbite-type crystal structure. The ferrite particles having a hexagonal magnetoplumbite type crystal structure can be confirmed by, for example, X-ray structural diffraction.

The ferrite sintered magnet has a low cobalt (Co) content (yz). Since the ferrite sintered magnet has a small amount of residual Co, the generation of a heterogeneous phase is suppressed, and a uniform microstructure is formed. Thus, the ferrite sintered magnet has high Br and high HcJ. Further, the ferrite sintered magnet has a small Co content (yz), and thus can be produced at low cost.

A is more than 1 selected from Sr, Ba and Pb. The Sr content in a may be 90 at% or more, or a may be Sr alone. The content of Ba in a may be 1 at% or less.

R is 1 or more selected from rare earth elements, and R is at least La. The content of La in R may be 90 at% or more, or R may be only La.

The ferrite sintered magnet may satisfy the following formula.

0.14≤x≤0.23

11.60≤(12－y)z≤12.10

0.13≤yz≤0.19

When x, (12-y) z and yz satisfy these expressions, Br and HcJ can be more easily increased.

When x is too small, Br decreases. In the case where x is too large, HcJ decreases. When x is 0.14. ltoreq. x.ltoreq.0.23, the production stability is easily improved. The production stability is a property that the change in magnetic properties (particularly HcJ) is small even if the firing temperature changes.

When (12-y) z is too small, HcJ decreases. In the case where (12-y) z is too large, Br and/or HcJ are decreased. Further, when z is 11.60. ltoreq. (12-y) 12.10, the production stability is easily improved.

When yz is too small, HcJ decreases. When yz is too large, Br is reduced, which leads to high cost. When yz satisfies 0.13. ltoreq. yz.ltoreq.0.19, the production stability is easily improved.

The ferrite sintered magnet may contain calcium (Ca). When the content of CaO in terms of oxides in the ferrite sintered magnet is Mc (mass%),

mc is more than or equal to 0.30 and less than or equal to 0.85, and Mc is more than or equal to 0.33 and less than or equal to 0.78.

The smaller the CaO content, the lower the Br content tends to be. The larger the CaO content, the more the HcJ content tends to decrease. When 0.33. ltoreq. Mc.ltoreq.0.78 is satisfied, the production stability is easily improved.

The ferrite sintered magnet may also contain silicon (Si). When Si contained in the ferrite sintered magnet is converted to an oxide, SiO is added₂Is set to Ms (mass%),

can satisfy Ms is more than or equal to 0.35 and less than or equal to 0.60, and can also satisfy Ms is more than or equal to 0.45 and less than or equal to 0.60.

SiO₂The smaller the content of (A), the more the HcJ tends to decrease. SiO 2₂The more the content of (b), the more the Br tends to decrease. Further, when Ms is 0.45. ltoreq. Ms.ltoreq.0.60, the production stability is easily improved.

The ferrite sintered magnet may contain Ba. When Ba contained in the ferrite sintered magnet is converted into oxide, the content of BaO is Mb (mass%),

mb is not less than 0 and not more than 0.15, Mb is not less than 0.03 and not more than 0.15, and Mb is not less than 0.08 and not more than 0.15.

If the content of BaO is too large, Br is liable to decrease. When 0.08. ltoreq. Mb.ltoreq.0.15 is satisfied, the production stability is easily improved.

Further, Ba is A_1－xR_x(Fe_12－yCo_y)_zO₁₉A of (A) may be contained in the ferrite sintered magnet as the other component A_{1－ x}R_x(Fe_12－yCo_y)_zO₁₉Other Ba compounds or Ba monomers may be contained in the ferrite sintered magnet.

The ferrite sintered magnet may contain aluminum (Al). When Al contained in the ferrite sintered magnet is converted into an oxide, Al is added₂O₃The content of (C) is Ma (mass%),

ma is more than or equal to 0 and less than or equal to 0.90, and Ma is more than or equal to 0.05 and less than or equal to 0.90.

In Al₂O₃When the content of (b) is too large, Br is likely to decrease.

The ferrite sintered magnet may contain chromium (Cr). In thatConverting Cr contained in the ferrite sintered magnet into oxide₂O₃The content of (D) is Mr (% by mass),

mr can be more than or equal to 0 and less than or equal to 0.10, and Mr can be more than or equal to 0.05 and less than or equal to 0.10.

If Cr is present₂O₃If the content of (b) is too large, Br tends to be reduced.

The ferrite sintered magnet may also contain manganese (Mn), magnesium (Mg), copper (Cu), nickel (Ni), and/or zinc (Zn) as impurities. The content of these impurities is not particularly limited, but the total content of these impurities may be 100 mass% and 0.5 mass% or less, respectively. These impurities may be contained in a total amount of 0.7% by mass or less.

The ferrite sintered magnet may further contain elements other than the above elements, specifically, elements other than a, R, Fe, Co, oxygen (O), Ca, Si, Al, Cr, Mn, Mg, Cu, Ni, and Zn as inevitable impurities. The total amount of the inevitable impurities may be 3% by mass or less, with the total amount of the ferrite sintered magnet being 100% by mass.

The method for calculating Mc will be described below. The same applies to the methods for calculating Ms, Mb, Ma, and Mr.

First, the content of Ca contained in the ferrite sintered magnet was measured by a general method in the art. Then, the content of Ca was converted to oxide (CaO). The above elements other than O contained in the ferrite sintered magnet are, specifically, a, R, Fe, Co, Ca, Si, Ba, Al, Cr, Mn, Mg, Cu, Ni, and Zn, and the contents are measured in the same manner and converted to oxides. Specifically, conversion to AO and R₂O₃、Fe₂O₃、Co₃O₄、CaO、SiO₂、BaO、Al₂O₃、Cr₂O₃MnO, MgO, CuO, NiO, ZnO. Further, the content of the inevitable impurities is measured in the same manner and appropriately converted to oxides.

Then, Mc can be calculated by dividing the CaO content by the total content of all the oxides.

The density of the ferrite sintered magnet is not particularly limited. For example, the density measured by the Archimedes method may be 4.9g/cm³Above 5.2g/cm³The following. The passing density is within the above range, particularly 5.0g/cm³Above, Br is likely to be good.

The method for producing the sintered ferrite magnet according to the present embodiment will be described below.

In the following embodiments, an example of a method for manufacturing a ferrite sintered magnet is shown. In the present embodiment, the ferrite sintered magnet can be manufactured through a blending step, a pre-firing step, a pulverizing step, a molding step, and a firing step. The respective steps will be explained below.

< working procedure of compounding >

In the blending step, a raw material of the ferrite sintered magnet is blended to obtain a raw material mixture. As the raw material of the ferrite sintered magnet, a compound (raw material compound) containing 1 or 2 or more of the elements constituting the raw material of the ferrite sintered magnet is exemplified. The raw material compound is preferably in a powder form, for example.

Examples of the raw material compound include oxides of the respective elements and compounds (carbonate, hydroxide, nitrate, etc.) which become oxides by firing. For example, SrCO can be exemplified₃、BaCO₃、PbCO₃，La₂O₃、Fe₂O₃、Co₃O₄、CaCO₃、SiO₂、MgO、Al₂O₃、Cr₂O₃MnO, MgO, NiO, CuO, ZnO, etc. The average particle diameter of the powder of the raw material compound may be about 0.1to 2.0. mu.m.

For example, the raw materials are weighed to obtain a desired composition of the ferrite magnetic material. Then, the mixture can be mixed and pulverized for about 0.1to 20 hours by using a wet mill, a ball mill, or the like. In this blending step, it is not necessary to mix all the raw materials, and a part of the raw materials may be added after the calcination described below.

< Pre-burning Process >

In the calcination step, the raw material mixture obtained in the blending step is calcined. The calcination can be performed in an oxidizing atmosphere such as air. The temperature of the pre-firing is preferably in the range of 1100 ℃ to 1300 ℃. The time for the calcination may be set to 1 second to 10 hours.

The calcined body obtained by the calcination may have a primary particle diameter of 10 μm or less.

< crushing Process >

In the pulverizing step, the calcined material that has been granulated or agglomerated in the calcining step is pulverized into a powder. This facilitates molding in a molding step described later. In the pulverizing step, as described above, a raw material that is not blended in the blending step (after the addition of the raw material) may be added. The pulverization step may be performed, for example, in a 2-stage step of pulverizing the calcined body into coarse powder (coarse pulverization) and then pulverizing the coarse powder more finely (fine pulverization).

The coarse pulverization is carried out, for example, using a vibration mill until the average particle diameter becomes 0.5 to 10.0. mu.m. In the fine pulverization, the coarsely pulverized material obtained in the coarse pulverization is further pulverized by a wet mill, a ball mill, a jet mill, or the like.

In the fine pulverization, the fine pulverization is carried out so that the average particle diameter of the obtained fine pulverized material is preferably about 0.08 μm to 1.00. mu.m. The specific surface area of the finely divided material (obtained by, for example, the BET method) can be set to 4m²/g～12m²And about/g. The grinding time varies depending on the grinding method, and for example, it can be about 30 minutes to 20 hours in the case of a wet grinder, and about 1 hour to 50 hours in the case of wet grinding by a ball mill.

In the fine pulverization step, in the case of a wet method, a nonaqueous solvent such as toluene or xylene can be used as a dispersion medium in addition to an aqueous solvent such as water. The use of the nonaqueous solvent tends to result in high orientation in wet molding described later. On the other hand, when an aqueous solvent such as water is used, it is advantageous from the viewpoint of productivity.

In the fine grinding step, for example, a known polyol and a dispersant may be added to improve the degree of orientation of the sintered body obtained after firing.

< Molding and firing Process >

In the molding and firing step, a molded body is obtained by molding a pulverized material (preferably a finely pulverized material) obtained after the pulverizing step, and then the molded body is fired to obtain a sintered body. The Molding can be performed by any of dry Molding, wet Molding, and Ceramic Injection Molding (CIM).

In the dry molding method, for example, a magnetic field is applied to dry magnetic powder while pressure molding is performed to form a molded body, and then the molded body is fired. In general, dry molding methods have an advantage that the time required for the molding step is short because dry magnetic powder is press-molded in a mold.

In the wet molding method, for example, a slurry containing magnetic powder is subjected to pressure molding in the presence of a magnetic field, while removing a liquid component to form a molded body, and then the molded body is fired. In the wet molding method, there is an advantage that the magnetic powder is easily oriented by a magnetic field during molding, and the magnetic properties of the sintered magnet are good.

The molding method using CIM is a method in which pellets (beads) formed by heating and kneading dry magnetic powder and a binder resin are injection-molded in a mold to which a magnetic field is applied to obtain a preliminary molded body, and the preliminary molded body is subjected to binder removal treatment and then fired.

The wet molding will be described in detail below.

(Wet Molding and baking)

When a ferrite sintered magnet is obtained by a wet molding method, the above-described fine pulverization step is performed in a wet manner to obtain a slurry. The slurry was concentrated to a predetermined concentration to obtain a slurry for wet molding. The molding can be performed using 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 grinding agent in the wet molding slurry can be about 30 to 80 mass% of the total amount of the wet molding slurry.

In the slurry, water can be used as a dispersion medium for dispersing the finely divided material. In this case, a surfactant such as gluconic acid, gluconate, sorbitol or the like may be added to the slurry. Further, as the dispersion medium, a nonaqueous solvent may also be used. As the nonaqueous solvent, an organic solvent such as toluene or xylene can be used. In this case, a surfactant such as oleic acid can be added.

The wet molding slurry may be prepared by adding a dispersion medium to the finely pulverized material in a dry state after the fine pulverization.

In the wet molding, the slurry for wet molding is then molded in a magnetic field. In this case, the molding pressure can be set to 9.8MPa to 98MPa (0.1 ton/cm)²～1.0ton/cm²) Left and right. The applied magnetic field can be about 400kA/m to 1600 kA/m. The pressing direction and the magnetic field application direction during molding may be the same direction or may be orthogonal to each other.

The firing of the molded article obtained by wet molding can be performed in an oxidizing atmosphere such as air. The firing temperature can be set to 1050 to 1270 ℃. The firing time (the time for maintaining the temperature at the firing temperature) can be set to about 0.5 to 3 hours. Then, the resultant was sintered to obtain a ferrite sintered magnet.

In addition, in the case of obtaining a molded article by wet molding, the molded article can be heated from room temperature to about 100 ℃ at a temperature rise rate of about 2.5 ℃/minute before reaching the firing temperature. By sufficiently drying the molded article, the occurrence of cracks can be suppressed.

Further, when a surfactant (dispersant) or the like is added, for example, in a temperature range of about 100 to 500 ℃, these can be sufficiently removed by heating at a temperature rise rate of about 2.0 ℃/min (degreasing treatment). These treatments may be performed at the initial stage of the firing step, or may be performed separately from the firing step.

Although the preferred method for producing the ferrite sintered magnet has been described above, the production method is not limited to the above, and the production conditions and the like can be changed as appropriate.

The shape of the ferrite sintered magnet of the present invention is not limited. For example, the ferrite sintered magnet may have various shapes such as an arc segment shape having anisotropy, a flat plate shape, a cylindrical shape, and a cylindrical shape. According to the ferrite sintered magnet of the present invention, high HcJ is maintained and high Br is obtained regardless of the shape of the magnet.

The use of the ferrite sintered magnet obtained by the present invention is not particularly limited, but the ferrite sintered magnet can be used for, for example, a rotating electrical machine. The rotating electric machine according to the present invention includes the above ferrite sintered magnet. Further, the kind of the rotating electric machine is not particularly limited. Examples thereof include a motor and a generator.

Examples

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

< working procedure of compounding >

SrCO was prepared as a starting material₃、La₂O₃、Fe₂O₃、Co₃O₄、CaCO₃、SiO₂、BaCO₃、Al₂O₃And Cr₂O₃The final composition of the ferrite sintered magnet was weighed out to the composition of each sample described in tables 1to 9.

Removing La from the above starting material₂O₃And Co₃O₄The other raw materials were mixed and pulverized by a wet mill to obtain a slurry-like raw material mixture.

< Pre-burning Process >

This raw material mixture was dried and then subjected to a calcination treatment at 1200 ℃ for 2 hours in the air to obtain a calcined body.

< crushing Process >

The obtained calcined body was coarsely pulverized by a rod mill to obtain a coarsely pulverized material. Then, La was added₂O₃And Co₃O₄Fine grinding for 28 hours by a wet ball mill,thus obtaining the slurry. The obtained slurry is prepared into a slurry for wet molding, the solid content concentration of which is adjusted to 70-75 mass%.

< Molding and firing Process >

Subsequently, a preliminary molded body was obtained using a wet magnetic field molding machine. The molding pressure was 50MPa, and the applied magnetic field was 800 kA/m. The pressing direction and the magnetic field application direction during molding are set to the same direction. The preliminary molded article obtained by wet molding was in the form of a disk having a diameter of 30mm and a height of 15 mm.

The green compact was fired in the air at the optimum firing temperature for 1 hour to obtain a ferrite sintered magnet as a sintered compact.

Hereinafter, a method of determining the optimum firing temperature in the present example will be described.

First, the composition of each experimental example was changed to 1190 to 1230 ℃ for each 10 ℃ firing temperature, and a sintered body was produced. That is, a total of 5 sintered bodies were prepared based on each experimental example. Then, the density of each sintered body was measured, and the sintering temperature of the sintered body having the highest density was set as the optimum sintering temperature. The density of the sintered body was measured by the archimedes method.

Quantitative fluorescent X-ray analysis was performed on each of the ferrite sintered magnets, and it was confirmed that each of the ferrite sintered magnets had the composition shown in tables 1to 9.

In addition, it was confirmed by X-ray diffraction measurement that each of the ferrite sintered magnets in tables 1to 9 had a hexagonal M-type structure.

< measurement of magnetic Properties (Br, HcJ) >

In each experimental example, after processing the upper and lower surfaces of each ferrite sintered magnet obtained by sintering at an optimum sintering temperature, the magnetic properties were measured in an atmosphere of 25 ℃ using a B-H tracer with a maximum applied magnetic field of 1989 kA/m. The results are shown in tables 1to 9.

< cost fence >

In the cost column of the present experimental example, regarding the content (yz) of Co as a high-cost raw material, the case where yz is not more than 0.20 is regarded as pass, and the case where yz > 0.20 is regarded as fail.

As is clear from tables 1to 9, in each of the examples in which x, (12-y) z and yz are within specific ranges, Br and HcJ were good, and the cost was excellent. Specifically, Br in all examples exceeded 420mT, and Br in examples 2-6, 8-18, 20-40, and 41 exceeded 435 mT. In addition, all examples had HcJ exceeding 330.0kA/m, and examples 2 to 6, 10 to 40 had HcJ exceeding 345 kA/m. On the other hand, when any of x, (12-y) z and yz is out of the specific range, Br, HcJ and/or cost are deteriorated.

CaO and SiO₂、BaO、Al₂O₃And/or Cr₂O₃When the amounts are included in the respective preferable ranges, the magnetic properties are more easily improved.