Ferrite sintered magnet, ferrite particle, bonded magnet, and rotary electric machine

Abstract

The present invention relates to a ferrite sintered magnet, a ferrite particle, a bonded magnet, and a rotary electric machine. The magnet is a ferrite sintered magnet containing a ferrite phase having a crystal structure of a magnetoplumbite type, wherein at least Ca, a metal element A, a metal element R, Bi, Fe, and a metal element M are contained, the metal element A is at least one element selected from Sr, Ba, and Pb, the metal element R is at least one element selected from rare earth elements including Y and must contain La, the metal element M is at least one element selected from Co, Ni, Zn, Al, Cu, and Cr and must contain Co, and when atomic ratios of the metal elements are expressed by formula (1), in formula (1), c, a, r, b, f, and m satisfy the following formulae (2) to (8).

Description

Technical Field

[0001] This disclosure relates to a ferrite sintered magnet, ferrite particles, bonded magnet, and rotary motor. Background Technology

[0002] As magnetic materials used in ferrite sintered magnets, Ba ferrite, Sr ferrite, and Ca ferrite, which have hexagonal crystal structures, are known. Among these ferrites, the magnetoplumboid type (M-type) is known. M-type ferrites are typically composed of AFe... 12 O 19 The general formula for is .

[0003] As such an M-type ferrite, Patent Document 1 discloses a magnetic powder having a main phase of an M-type ferrite formed by replacing Fe with elements such as Zn (M) and replacing elements such as Sr or Ba with elements such as La (R).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 9-115715 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] However, magnetoplumbium-type (M-type) ferrites are used as magnet materials for motors and other applications, where small size and high torque are required. Therefore, higher magnetic properties are needed for sintered ferrite magnets.

[0009] Remanent flux density (Br) and rectangularity (Hk / HcJ) are used as indicators of the magnetic properties of ferrite sintered magnets. In the magnet powder disclosed in Patent Document 1, there is room for improvement in terms of Br and rectangularity.

[0010] One aspect of the present invention is to provide a Br and a ferrite sintered magnet with excellent rectangularity, etc.

[0011] Technical solutions for solving technical problems

[0012] One aspect of the present invention provides a ferrite sintered magnet, wherein the ferrite sintered magnet contains a ferrite phase having a magnetoplumb-type crystal structure, wherein it contains at least Ca, metal element A, metal element R, Bi, Fe, and metal element M, metal element A is at least one element selected from Sr, Ba, and Pb, metal element R is at least one element selected from rare earth elements including Y and must contain La, and metal element M is at least one element selected from Co, Ni, Zn, Al, Cu, and Cr and must contain Co, and when the atomic ratio of the metal elements is expressed by equation (1), in equation (1), c, a, r, b, f, and m satisfy the following equations (2) to (8).

[0013] Ca c A a R r Bi b Fe f M m (1)

[0014] 0.15≤c<0.5 (2)

[0015] 0.01≤a≤0.1 (3)

[0016] 0.45<r≤0.80 (4)

[0017] 0.01≤b<0.1 (5)

[0018] 9.35 < f < 11.90 (6)

[0019] 0.1≤m≤0.50 (7)

[0020] c + a + r + b = 1 (8)

[0021] In one embodiment, the ferrite sintered magnet described above may also satisfy the following equations (3-1), (5-1), (6-1) and (7-1).

[0022] 0.03≤a≤0.05 (3-1)

[0023] 0.01≤b≤0.05 (5-1)

[0024] 9.35<f≤11.25 (6-1)

[0025] 0.25≤m≤0.45 (7-1)

[0026] Another aspect of the present invention provides a rotary electric motor having the above-described ferrite sintered magnet.

[0027] Another aspect of the present invention provides a ferrite particle containing a ferrite phase having a magnetoplumb-type crystal structure, wherein it contains at least Ca, metal element A, metal element R, Bi, Fe, and metal element M, metal element A being at least one element selected from Sr, Ba, and Pb, metal element R being at least one element selected from rare earth elements including Y and must contain La, and metal element M being at least one element selected from Co, Ni, Zn, Al, Cu, and Cr and must contain Co, wherein when the atomic ratio of the metal elements is expressed by equation (1), in equation (1), c, a, r, b, f, and m satisfy the following equations (2) to (8).

[0028] Ca c A a R r Bi b Fe f M m (1)

[0029] 0.15≤c<0.5 (2)

[0030] 0.01≤a≤0.1 (3)

[0031] 0.45<r≤0.80 (4)

[0032] 0.01≤b<0.1 (5)

[0033] 9.35 < f < 11.90 (6)

[0034] 0.1≤m≤0.50 (7)

[0035] c + a + r + b = 1 (8)

[0036] Another aspect of the present invention provides a bonding magnet containing the aforementioned ferrite particles and resin.

[0037] Another aspect of the present invention provides a rotary motor having the aforementioned bonded magnet.

[0038] The effects of the invention

[0039] According to one aspect of the present invention, a Br and a ferrite sintered magnet with excellent rectangularity can be provided. Attached Figure Description

[0040] Figure 1 This is a cross-sectional schematic diagram of a ferrite sintered magnet or ferrite particles according to one embodiment.

[0041] Figure 2 This is a schematic cross-sectional view of a motor according to one embodiment.

[0042] Explanation of symbols:

[0043] 4… Ferrite phase (main phase), 6… Grain boundary phase, 31… Stator (stator cover), 32… Rotor, 36… Shaft, 37… Rotor core, 100… Ferrite sintered magnet or bonded magnet, 200… Motor. Detailed Implementation

[0044] The embodiments of the present invention will now be described. However, the present invention is not limited to the following embodiments.

[0045] (Ferrite sintered magnets and ferrite particles)

[0046] The ferrite sintered magnet and ferrite particles of this embodiment will be described.

[0047] The ferrite sintered magnet and ferrite particles of this embodiment contain a ferrite phase with a magnetoplumb-type crystal structure.

[0048] The ferrite sintered magnet and ferrite particles of this embodiment contain at least Ca, metal element A, metal element R, Bi, Fe, and metal element M.

[0049] Metal element A is at least one element selected from Sr, Ba and Pb.

[0050] To further improve the Br content and rectangularity, the atomic percentage of Ba in metallic element A can be 50 atomic% or higher, 70 atomic% or higher, 90 atomic% or higher, 95 atomic% or higher, 97 atomic% or higher, 99 atomic% or higher, or even 100 atomic%. There is no particular limitation on the percentage of atoms other than Ba ​​in metallic element A.

[0051] To further improve the Br content and rectangularity, the atomic ratio of Sr in metallic element A can be above 50 atomic%, above 70 atomic%, above 90 atomic%, above 95 atomic%, above 97 atomic%, above 99 atomic%, or even 100 atomic%. There is no particular limitation on the percentage of atoms other than Sr in metallic element A.

[0052] The metallic element R is selected from at least one rare earth element containing Y and must contain La.

[0053] The rare earth elements are yttrium (Y), scandium (Sc), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0054] In metallic element R, it can contain more than 50 atomic percent, more than 95 atomic percent, more than 99 atomic percent, or even 100 atomic percent of La.

[0055] The metallic element M is selected from at least one element chosen from Co, Ni, Zn, Al, Cu and Cr, and must contain Co.

[0056] In metallic element M, it can contain more than 50 atomic percent of Co, more than 95 atomic percent, more than 99 atomic percent, or even 100 atomic percent.

[0057] When metal element M contains Al, metal element M can contain more than 1 atomic percent of Al, more than 5 atomic percent of Al, less than 13 atomic percent of Al, or less than 10 atomic percent of Al.

[0058] When metal element M contains Ni, the metal element M can contain more than 1 atomic percent of Ni, more than 5 atomic percent of Ni, or less than 13 atomic percent of Ni.

[0059] When metal element M contains Zn, the metal element M can contain more than 1 atomic percent of Zn, more than 5 atomic percent of Zn, or less than 13 atomic percent of Zn.

[0060] When metal element M contains Cu, the metal element M can contain more than 1 atomic percent Cu, more than 5 atomic percent Cu, or less than 13 atomic percent Cu.

[0061] When metal element M contains Cr, the metal element M can contain more than 1 atomic% of Cr, more than 5 atomic% of Cr, or less than 15 atomic% of Cr.

[0062] Regarding the ferrite sintered magnet and ferrite particles of this embodiment, when the atomic ratio of the metal elements is expressed by equation (1), c, a, r, b, f and m in equation (1) satisfy the following equations (2) to (8).

[0063] Ca c A a R r Bi b Fe f M m (1)

[0064] 0.15≤c<0.5 (2)

[0065] 0.01≤a≤0.1 (3)

[0066] 0.45<r≤0.80 (4)

[0067] 0.01≤b<0.1 (5)

[0068] 9.35 < f < 11.90 (6)

[0069] 0.1≤m≤0.50 (7)

[0070] c + a + r + b = 1 (8)

[0071] In the case of the ferrite sintered magnet and ferrite particles in another embodiment, when the atomic ratio of the metal elements is expressed by equation (1), c, a, r, b, f and m in equation (1) satisfy the following equations (2) to (8).

[0072] Ca c A a R r Bi b Fe f M m (1)

[0073] 0.2≤c<0.5 (2)

[0074] 0.01≤a≤0.1 (3)

[0075] 0.45<r≤0.75 (4)

[0076] 0.01≤b<0.1 (5)

[0077] 9.35 < f < 11.90 (6)

[0078] 0.1≤m≤0.45 (7)

[0079] c + a + r + b = 1 (8)

[0080] (1) In the formula, c can be greater than 0.20, greater than 0.25, or greater than 0.30. c can be less than 0.45 or less than 0.40.

[0081] From the perspective of reducing the ratio of heterogeneous phases, and further improving Br, HcJ and rectangularity, a in equation (1) can be above 0.01 or above 0.03. From the same point of view, it can also be below 0.08 or below 0.05.

[0082] From the perspective of further increasing Br and tending to suppress low-temperature demagnetization of coercivity, r in equation (1) can be above 0.50 or above 0.55. From the perspective of having the tendency to suppress the decrease of coercivity and tending to be able to be fired even without high temperature, r can be below 0.80, below 0.75, below 0.70, or below 0.65.

[0083] From the perspective of lowering the calcination temperature and further improving the coercivity of the rectangle, b in equation (1) can be above 0.015 or above 0.020. From the perspective of further reducing the ratio of heterogeneous phases, it can be below 0.08, below 0.06, or below 0.05.

[0084] From the perspective of increasing magnetization and further reducing heterogeneity, f in equation (1) can be above 9.50 or above 9.70. From the perspective of further increasing Br, HcJ and rectangularity, it can be below 11.50 or below 11.25.

[0085] From the perspective of increasing magnetization and coercivity while further reducing out-of-phase, m in equation (1) can be 0.15 or more, 0.20 or more, or 0.25 or more. From the same perspective, m in equation (1) can also be 0.45 or less, or 0.40 or less.

[0086] From the perspective of further increasing HcJ and further reducing the ratio of heterogeneous phases, the ferrite sintered magnet and ferrite particles of this embodiment preferably also satisfy the following formulas (3-1), (5-1), (6-1) and (7-1).

[0087] 0.03≤a≤0.05 (3-1)

[0088] 0.01≤b≤0.05 (5-1)

[0089] 9.35<f≤11.25 (6-1)

[0090] 0.25≤m≤0.45 (7-1)

[0091] From the perspective of further improving HcJ, the ferrite sintered magnet and ferrite particles of this embodiment may also contain Si. From the perspective of further improving HcJ, the Si content in the ferrite sintered magnet and ferrite particles, calculated as SiO2, may be 0.01% by mass or more, 0.05% by mass or more, or 0.10% by mass or more. From the same viewpoint, the Si content in the ferrite sintered magnet and ferrite particles, calculated as SiO2, may be 0.70% by mass or less, 0.60% by mass or less, or 0.40% by mass or less.

[0092] From the perspective of further improving HcJ, the ferrite sintered magnet and ferrite particles of this embodiment may also contain Al. From the perspective of further improving HcJ, the Al content in the ferrite sintered magnet and ferrite particles, calculated as Al₂O₃, may be 0.01% by mass or more, 0.05% by mass or more, or 0.10% by mass or more. From the same viewpoint, the Al content in the ferrite sintered magnet and ferrite particles, calculated as Al₂O₃, may be 0.70% by mass or less, 0.60% by mass or less, or 0.40% by mass or less.

[0093] In addition to the components mentioned above, ferrite sintered magnets and ferrite particles may also contain impurities from the raw materials or unavoidable components from the manufacturing equipment. Examples of such components include Ti (titanium), Mn (manganese), Mo (molybdenum), and V (vanadium). These components may also be included in the ferrite sintered magnets and ferrite particles as their respective oxides or composite oxides. Secondary components may also segregate to the grain boundaries of the ferrite grains in the ferrite sintered magnet, forming heterogeneous phases.

[0094] The content ratio of metal elements in ferrite sintered magnets and ferrite particles can be determined by fluorescence X-ray analysis.

[0095] The content of half-metallic elements such as Si in ferrite sintered magnets and ferrite particles can be determined by inductively coupled plasma emission spectroscopy (ICP emission spectroscopy).

[0096] Figure 1 This is a cross-sectional schematic diagram of the ferrite sintered magnet (ferrite particles) 100 according to this embodiment. Figure 1 As shown, the ferrite sintered magnet (ferrite particles) 100 of this embodiment has: a ferrite phase (grain) 4 having a magnetoplumboid (M-type) crystal structure; and a grain boundary phase 6 existing between the ferrite phase (grain) 4.

[0097] M-type ferrites have a hexagonal crystal structure. An example of an M-type ferrite is the ferrite represented by the following formula (III).

[0098] AX 12 O 19 (III)

[0099] A must contain Ca and La, and may also contain Sr and / or Ba. M may also contain R. X contains Fe, and may also contain Co.

[0100] Furthermore, the ratio of A (site A) and X (site B) and the ratio of oxygen (O) in equation (III) above actually represent values ​​that deviate slightly from the above range. Therefore, they can also deviate slightly from the above values.

[0101] From the viewpoint of maximizing magnetic properties, the ferrite sintered magnet and ferrite particles of this embodiment preferably have the aforementioned ferrite phase 4 as the main phase. Furthermore, in this specification, "as the main phase" refers to the crystalline phase with the highest mass proportion in the ferrite sintered magnet and ferrite particles of this embodiment. The ferrite sintered magnet and ferrite particles of this embodiment may also have a crystalline phase different from the main phase (heterogeneous phase). Based on the ferrite phase (M phase), the proportion of heterogeneous phase can be 30% or less, 20% or less, 15% or less, 10% or less, or 5% or less.

[0102] Examples of heterogeneous phases include the Fe2O3 phase and the LaFeO3 phase. The ratio of the Fe2O3 phase was determined by measuring the XRD pattern of the ferrite sintered magnet or ferrite particles and dividing the peak intensity (2θ: 33.21°) of the (104) plane originating from the Fe2O3 phase by the peak intensity (2θ: 32.35°) of the (107) plane originating from the M-type phase. The ratio of the LaFeO3 phase was determined by measuring the XRD pattern of the ferrite sintered magnet or ferrite particles and dividing the peak intensity (2θ: 22.67°) of the (101) plane originating from the LaFeO3 phase by the peak intensity of the (107) plane originating from the M-type phase.

[0103] The average grain size of the ferrite phase (grains) in the ferrite sintered magnet of this embodiment can be, for example, 5 μm or less, 4.0 μm or less, or 0.5 to 3.0 μm. Having such an average grain size can further improve the coercivity (HcJ). The average grain size of the ferrite phase (grains) can be obtained using cross-sectional observation images obtained using TEM or SEM. Specifically, the cross-sectional area of ​​each main phase particle in the SEM or TEM cross-section containing hundreds of ferrite phases (grains) is obtained through image analysis. Then, the diameter of the circle having that cross-sectional area (circle equivalent diameter) is defined as the grain size of that main phase particle in that cross-section, and the grain size distribution is measured. Based on the measured grain size distribution based on the number of grains, the average value of the grain size based on the number of grains is calculated. This measured average value is set as the average grain size of the ferrite phase.

[0104] Grain boundary phase 6 has oxides as the main component. Specifically, examples of oxides include oxides having at least one selected from Si, Ca, Sr, Ba, Fe, Mn, Co, Cr, Zn, and Al, as well as composite oxides of two or more of them. Examples of such oxides include SiO2, CaO, BaO, SrO, Fe2O3, Co3O4, ZnO, Al2O3, MnO, and Cr2O3. Additionally, silicate glass may also be included. The mass percentage of oxides can be 90% by mass or more, or 95% by mass or more, or 97% by mass or more.

[0105] In the cross-section of the ferrite sintered magnet of this embodiment, the area ratio of the grain boundary phase 6 in the total area of ​​the ferrite phase 4 and the grain boundary phase 6 can be set to 0.1 to 5%.

[0106] The shape of the ferrite sintered magnet in this embodiment is not particularly limited. For example, it can be made into various shapes such as an arc segment shape (C-type) with the end face curved into an arc shape, a flat plate shape, etc.

[0107] Ferrite particles can be obtained, for example, through a pulverizing process described later. The average particle size of the ferrite particles is, for example, 0.1–7 μm. The average particle size of the ferrite particles, similar to the average particle size of the grains in ferrite sintered magnets, can also be determined using observation images of the ferrite particles obtained using TEM or SEM. Specifically, the area of ​​each main phase particle in an SEM or TEM image containing hundreds of ferrite particles is determined through image analysis. Then, the diameter of a circle having that area (equivalent diameter of the circle) is defined as the particle size of the ferrite particle, and the particle size distribution is measured. Based on the measured particle size distribution with a numerical basis, the average value of the particle size with a numerical basis is calculated. This measured average value is set as the average particle size of the ferrite particles.

[0108] In this embodiment, the Br content of the ferrite sintered magnet and ferrite particles at 23°C can be, for example, 4500G or more, 4600G or more, or 4700G or more.

[0109] In this embodiment, the HcJ of the ferrite sintered magnet and ferrite particles at 23°C can be, for example, 1800 Oe or more, 2000 Oe or more, or 2200 Oe or more.

[0110] The rectangularity of the ferrite sintered magnet and ferrite particles in this embodiment at 23°C can be 80% or more, 82% or more, or 85% or more.

[0111] The Br, HcJ, and rectangularity of the ferrite sintered magnet and ferrite particles in this embodiment can be measured using a DC self-recording fluxmeter.

[0112] (Effects)

[0113] The ferrite sintered magnet and ferrite particles of this embodiment are combined to contain Ca, metal element A, metal element R, Bi, Fe and metal element M, must contain La and must contain Co, and their contents are set to satisfy the range of equations (2) to (8), thereby achieving excellent Br and rectangularity.

[0114] In addition, the ferrite sintered magnet and ferrite particles of this embodiment are combined to contain Ca, metal element A, metal element R, Bi, Fe and metal element M, must contain La and must contain Co, and their contents are set to satisfy the range of equations (2) to (8), thereby having the tendency to be sintered at low temperature, with excellent HcJ, and reducing the ratio of heterogeneous phases.

[0115] (Bonded magnets)

[0116] Next, the adhesive magnet of this embodiment will be described.

[0117] The adhesive magnet of this embodiment contains ferrite particles and resin as described in the above embodiment. Examples of resins include: thermosetting resins such as epoxy resin, phenolic resin, resin with multiple aromatic rings, and resin with triazine rings (triazine resin); thermoplastic resins such as polyamide elastomers (styrene, olefins, polyurethanes, polyesters, nylon, etc.), ionomers, ethylene propylene copolymers (EPM), and ethylene-ethyl acrylate copolymers.

[0118] From the viewpoint of balancing excellent magnetic properties and excellent shape retention, the resin content in the bonded magnet of this embodiment can, for example, be 0.5 to 10% by mass, or 1 to 5% by mass. The resin content in the bonded magnet can be adjusted by changing the resin concentration in the resin-containing solution used during manufacturing or the molding pressure when forming the molded article. Similarly, from the same viewpoint, the ferrite particle content in the bonded magnet can, for example, be 90 to 99.5% by mass, or 95 to 99% by mass.

[0119] The shape of the bonded magnet is not particularly limited and can be the same as that of the ferrite sintered magnet.

[0120] The ferrite sintered magnets and bonded magnets of this embodiment can be used as magnetic field generating components for rotating electric machines such as motors and generators, magnets for loudspeakers and headphones, magnetrons, magnetic field generating devices for MRI, CD-ROM holders, sensors for power distributors, sensors for ABS, fuel / fuel level sensors, magnetic locks or isolators, etc. Furthermore, they can also be used as targets (granules) when forming magnetic layers of magnetic recording media by methods such as vapor deposition or sputtering.

[0121] (Rotary motor)

[0122] Next, in Figure 2 This refers to the motor 200 of this embodiment. 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 this embodiment, a C-shaped ferrite sintered magnet or bonded magnet 100, which is a permanent magnet, is provided on the stator 31, and an electromagnet (coil) is provided on the rotor core 37 of the rotor 32.

[0123] Alternatively, a motor can be constructed by mounting ferrite sintered magnets on the rotor and electromagnets (coils) on the stator. The type of motor is not particularly limited. Another example of a rotating electrical machine is a generator with both a rotor and a stator. Ferrite sintered magnets can be mounted on either the rotor or the stator.

[0124] (Manufacturing method of ferrite sintered magnets, etc.)

[0125] Next, an example of a manufacturing method for ferrite particles, ferrite sintered magnets, and bonded magnets will be described. The manufacturing method described below includes a mating process, a calcination process, a crushing process, a molding process, and a final firing process. Details of each process are described below.

[0126] The blending process is the step of preparing the mixed powder for calcination. The mixed powder for calcination can contain the constituent elements of ferrite, such as Ca, metal element A, metal element R, Bi, Fe, and metal element M. In the blending process, it is preferable to mix the powder containing each element using a mill or ball mill for about 1 to 20 hours, and then pulverize it to obtain the mixed powder.

[0127] Additive elements such as Si can be pre-included in the powders mentioned above, but other powders containing these additive elements can also be added during the compounding process to obtain a mixed powder for calcination. Examples of other powders include powders containing Si.

[0128] Examples of powders containing elements include the elemental form, oxides, hydroxides, carbonates, nitrates, silicates, and organometallic compounds. A powder may contain two or more metallic elements, or it may contain only one metallic element.

[0129] Examples of powders containing Ca include CaCO3 and CaO.

[0130] Examples of powders containing Sr include SrCO3 and SrO.

[0131] Examples of powders containing R are La2O3 and La(OH)3.

[0132] An example of a powder containing Bi is Bi2O3.

[0133] An example of a powder containing Fe is Fe2O3.

[0134] An example of a powder containing Co is Co3O4.

[0135] An example of a powder containing Zn is ZnO.

[0136] An example of a powder containing Al is Al2O3.

[0137] An example of a powder containing Si is SiO2.

[0138] The average particle size of the raw material powder is not particularly limited, for example, it is 0.1 to 2.0 μm.

[0139] After the optimal combination process, the raw material components are dried as needed, and coarse particles are removed by sieving.

[0140] In the calcination process, the raw material composition obtained in the blending process is calcined. Calcination is preferably carried out in an oxidizing atmosphere, such as air. The calcination temperature can be, for example, 1050–1350°C, 1200–1310°C, or 1220–1310°C. The calcination time can be, for example, 1 minute–10 hours, 1 minute–5 hours, or 1 minute–2 hours.

[0141] In the pulverization process, the calcined powder, which has become granular or lumpy through the calcination process, is pulverized. This yields ferrite particles. The pulverization process can also be divided into two stages, for example, pulverizing the calcined powder into coarse powder (coarse pulverization process) and then further pulverizing the coarse powder into fine powder (fine pulverization process).

[0142] Coarse grinding can be carried out using, for example, a vibratory mill, until the average particle size of the calcined powder is 0.1 to 5.0 μm.

[0143] In micronization, the coarse powder obtained from coarse grinding is further pulverized using a wet mill, ball mill, air jet mill, etc. Micronization aims to produce micronized powder (ferrite particles) with an average particle size of, for example, approximately 0.08–2.0 μm. The specific surface area of ​​the micronized powder (obtained, for example, by the BET method) is set to, for example, 7–12 m². 2 Approximately / g. The appropriate grinding time varies depending on the grinding method; for example, it is 30 minutes to 10 hours in the case of a wet mill, and 10 to 50 hours in wet grinding using a ball mill. The specific surface area of ​​ferrite particles can be measured using a commercially available BET specific surface area measuring device (manufactured by Mountech, trade name: HM Model-1210).

[0144] In the micronization process, to improve the magnetic orientation of the sintered body obtained after formal firing, substances such as general formula C can be added. n (OH) n H n+2 The polyol referred to herein. The number n in the general formula can be, for example, 4 to 100, or 4 to 30. Sorbitol is an example of a polyol. Furthermore, two or more polyols may be used together. In addition to polyols, other known dispersants may also be used.

[0145] When polyols are added, the amount added relative to the target material (e.g., coarse powder) can be, for example, 0.05 to 5.0% by mass, or 0.1 to 3.0% by mass. Furthermore, the polyols added in the micronization process are removed by thermal decomposition in the formal calcination process described later.

[0146] Furthermore, it is preferable not to mix all the raw material powders in the mixing process, but to add a portion of the raw material powders, such as a portion of CaCO3 powder, a portion or all of SiO2 powder, a portion or all of Al2O3 powder, and a portion or all of BaCO3 powder, in the coarse grinding and / or fine grinding processes. By adding powders containing such components after calcination, the sinterability in the formal firing process and the magnetic properties can be improved. In addition, these by-products sometimes flow out with the solvent in the slurry when wet molding is performed, thus allowing for a higher content than the target in 100% by mass of the ferrite sintered magnet.

[0147] For example, when a portion of powder containing Ca is added after calcination, the amount of Ca added, calculated as CaCO3, may be 0.01% by mass or more, or 1.60% by mass or less, relative to the overall ferrite magnet.

[0148] In the molding process, the ferrite particles obtained in the crushing process are molded in a magnetic field to obtain a molded body. Molding can be carried out by either dry molding or wet molding. From the viewpoint of improving magnetic orientation, wet molding is preferred.

[0149] In the case of wet molding, after obtaining a slurry by performing a micronization process as described above using a wet process, the slurry is concentrated to a specified concentration to obtain a wet molding slurry. This wet molding slurry can be used for molding. The slurry concentration can be performed by centrifugation or a filter press. The ferrite particle content in the wet molding slurry is, for example, 30-80% by mass. Water can be used as a dispersion medium for dispersing the ferrite particles in the slurry. Surfactants such as gluconic acid, gluconate, and sorbitol can also be added to the slurry. Non-aqueous solvents can also be used as dispersion media. Organic solvents such as toluene or xylene can be used as non-aqueous solvents. In this case, surfactants such as oleic acid can also be added. Furthermore, the wet molding slurry can also be prepared by adding a dispersion medium to micronized, dried ferrite particles.

[0150] In wet molding, the wet molding slurry is then molded in a magnetic field. In this case, the molding pressure is, for example, 9.8–196 MPa (0.1–2.0 ton / cm²). 2 The applied magnetic field is, for example, 398–1194 kA / m (5–15 kOe).

[0151] In the formal firing process, the molded body obtained in the forming process is fired to obtain a ferrite sintered magnet. The firing of the molded body can be carried out in a moderately oxidizing atmosphere. The firing temperature can be, for example, 1050–1350°C, 1200–1310°C, or 1200–1280°C. In addition, the firing time (the time to hold the firing temperature) can be, for example, 0.5–3 hours or 0.5–1 hour.

[0152] In the formal firing process, before reaching the sintering temperature, the temperature can be increased from, for example, room temperature to approximately 100°C at a rate of approximately 0.5°C / min. This allows the molded body to be thoroughly dried before sintering. Furthermore, it allows for the complete removal of surfactants added during the molding process. These treatments can be performed at the beginning of the formal firing process or separately before the formal firing process.

[0153] This allows for the manufacture of ferrite sintered magnets. In the case of manufacturing bonded magnets instead of ferrite sintered magnets, resin is permeated into the molded body obtained in the above molding process, and the resin is cured by heating, thereby obtaining a bonded magnet. Specifically, the molded body is immersed in a pre-prepared resin-containing solution, and degassing is performed in a sealed container under reduced pressure, allowing the resin-containing solution to permeate the pores of the molded body. Then, the molded body is removed from the resin-containing solution, and any remaining resin-containing solution adhering to the surface of the molded body is removed. A centrifuge or similar device can be used to remove the remaining resin-containing solution.

[0154] Before immersing in a resin-containing solution, the molded body is placed in a sealed container, kept under reduced pressure, and immersed in a solvent such as toluene. This promotes degassing and increases resin penetration, thereby reducing voids in the molded body.

[0155] The manufacturing methods for ferrite particles, ferrite sintered magnets, and bonded magnets are not limited to the examples described above. For instance, in the case of manufacturing bonded magnets, after the above-described pulverization process, the obtained ferrite particles and resin can be mixed and molded in a magnetic field to obtain a bonded magnet containing ferrite particles and resin.

[0156] Alternatively, the molding process and the formal firing process can also be performed using the following steps. Specifically, the molding process can be performed using CIM (Ceramic Injection Molding) or PIM (Powder Injection Molding). In CIM molding, firstly, dried ferrite particles are heated and mixed with a binder resin to form granules. These granules are then injection molded in a mold under a magnetic field to obtain a pre-molded body. The pre-molded body is then subjected to a binder removal treatment to obtain the final molded body. Next, in the formal firing process, the binder-removed molded body can be sintered, for example, in air at a temperature preferably 1100–1280°C, more preferably 1200–1280°C, for approximately 0.2–3 hours to obtain a ferrite sintered magnet.

[0157] Example

[0158] The present disclosure will be described in more detail with reference to the embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0159] [Manufacturing of Ferrite Sintered Magnets]

[0160] (Examples 1-21 and Comparative Examples 1-21)

[0161] As raw materials, powders of calcium carbonate (CaCO3), lanthanum hydroxide (La(OH)3), cobalt oxide (Co3O4), iron oxide (Fe2O3), barium carbonate (BaCO3), strontium carbonate (SrCO3), aluminum oxide (Al2O3), and bismuth oxide (Bi2O3) are prepared. These raw material powders are compounded in the atomic ratios shown in Tables 1 and 2. However, if aluminum oxide, calcium carbonate, and barium carbonate are added during the pulverization process as described later, these portions are pre-deducted. Then, these raw material powders are mixed and pulverized using a steel ball mill to obtain a slurry (combination process).

[0162] The slurry was dried to obtain a dried product. Next, coarse particles were removed from the dried product. Then, the dried product was calcined in atmosphere at the calcination temperatures shown in Tables 1 and 2 to obtain calcined powder (calcination process). Calcination was performed using an electric furnace (super-combustion). The obtained calcined powder was coarsely pulverized using a small rod vibratory mill to obtain coarse powder. Then, it was finely pulverized using a wet ball mill to obtain a slurry (pulverization process).

[0163] The moisture content of the slurry obtained after micronization was adjusted using a centrifuge to obtain a wet molding slurry. This wet molding slurry was then molded using a wet magnetic field molding machine under an applied magnetic field of 796 kA / m (10 kOe) to obtain a molded body (molding process). The molded body was cylindrical with a diameter of 30 mm and a thickness of 15 mm, and oriented in the thickness direction. The obtained molded body was dried in the atmosphere at room temperature. Next, the molded body was formally fired in the atmosphere at the temperatures shown in Tables 1 and 2 (formal firing process). An electric furnace (super-combustion) was used in the formal firing. This yielded a cylindrical ferrite sintered magnet.

[0164] (Examples 22-30)

[0165] Compared to the coarse powder, silicon oxide (SiO2) powder, calcium carbonate (CaCO3) powder, aluminum oxide (Al2O3) powder, barium carbonate (BaCO3) powder, and sorbitol were added in amounts shown in Table 3 relative to the mass of the ferrite sintered magnet. The mixture was then micronized using a wet ball mill to obtain a slurry. Otherwise, the process was carried out in the same manner as in Examples 1-21 and Comparative Examples 1-21 to obtain ferrite sintered magnets.

[0166] (Examples 31-52)

[0167] Except that the raw material powders were formulated in the manner shown in Table 4 with atomic ratios, the process was carried out in the same manner as in Example 1 to obtain ferrite sintered magnets.

[0168] [Table 1]

[0169]

[0170] [Table 2]

[0171]

[0172] [Table 3]

[0173]

[0174] [Table 4]

[0175]

[0176] [Evaluation of Ferrite Particles]

[0177] As ferrite particles, the XRD pattern of coarse powder was determined. A powder X-ray diffractometer manufactured by Rigaku Corporation was used in the determination. The determination conditions were set as follows: characteristic X-rays: Cu-Kα rays, sampling width: 2θ = 10-70°, scanning speed: 4.0° / min, X-ray tube voltage: 50 kV, X-ray tube current: 300 mA, diffusion slit: 1°, longitudinal width range of diffusion slit: 10 mm, and light-receiving slit: 0.3 mm. The ratio of Fe2O3 phase and LaFeO3 phase was calculated based on the obtained XRD pattern with the M-type phase set to 100%. The ratio of Fe2O3 phase was set as the peak intensity (2θ: 33.21°) of the (104) plane originating from the Fe2O3 phase divided by the peak intensity (2θ: 32.35°) of the (107) plane originating from the M-type phase. The ratio of the LaFeO3 phase was set as the peak intensity (2θ: 22.67°) of the (101) plane originating from the LaFeO3 phase divided by the peak intensity of the (107) plane originating from the M-type phase. The results are shown in Tables 5–7.

[0178] [Evaluation of Ferrite Sintered Magnets]

[0179] <Evaluation of Magnetic Properties>

[0180] After machining the upper and lower surfaces of the ferrite sintered magnet using a vertical grinding machine, Br, HcJ, Hk, and rectangularity (Hk / HcJ) were measured at 23℃ using a DC self-recording fluxmeter with a maximum applied magnetic field of 2389 kA / m. The results are shown in Tables 5-7.

[0181] <Composition Analysis>

[0182] The Si (silicon) content in ferrite sintered magnets was determined using the following steps: 0.1 g of a ferrite sintered magnet sample was mixed with 1 g of sodium peroxide and 1 g of sodium carbonate, and then heated to melt. The melt was dissolved in 40 ml of pure water and 10 ml of hydrochloric acid, and then pure water was added to prepare a 100 ml solution. Using this solution, the SiO2 content of silicon was determined by ICP-AES. An analytical apparatus (ICPS 8100CL) manufactured by Shimadzu Corporation was used for ICP-AES, and matrix matching was performed during the determination. The a, b, c, r, f, and m components in the ferrite sintered magnets were determined by X-ray fluorescence analysis. The results are shown in Tables 1, 2, and 4.

[0183] [Table 5]

[0184]

[0185] [Table 6]

[0186]

[0187] [Table 7]

[0188]

Claims

1. A ferrite sintered magnet, wherein, The ferrite sintered magnet contains a ferrite phase with a magnetoplumb-type crystal structure. The ferrite sintered magnet contains at least Ca, metal element A, metal element R, Bi, Fe, and metal element M. Metal element A is at least one element selected from Sr, Ba, and Pb. The metallic element R is selected from at least one rare earth element containing Y and must contain La. The metallic element M is at least one element selected from Co, Ni, Zn, Al, Cu, and Cr, and must contain Co. When the atomic ratio of metallic elements is expressed in equation (1), in equation (1), c, a, r, b, f, and m satisfy the following equations (2) to (8). Approx c A a R r Bi b Feb f M m (1) 0.15≤c＜0.5 (2) 0.01≤a≤0.1 (3) 0.45＜r≤0.80 (4) 0.01≤b＜0.1 (5) 9.35＜f＜11.90 (6) 0.1≤m≤0.50 (7) c+a+r+b=1 (8).

2. The ferrite sintered magnet according to claim 1, wherein, It also satisfies the following equations (3-1), (5-1), (6-1), and (7-1). 0.03≤a≤0.05 (3-1) 0.01≤b≤0.05 (5-1) 9.35＜f≤11.25 (6-1) 0.25≤m≤0.45 (7-1)。 3. A rotary electric motor, wherein, The ferrite sintered magnet as described in claim 1 or 2 is provided.

4. A ferrite particle, wherein, The ferrite particles contain a ferrite phase with a magnetoplumboid crystal structure. The ferrite particles contain at least Ca, metal element A, metal element R, Bi, Fe, and metal element M. Metal element A is at least one element selected from Sr, Ba, and Pb. The metallic element R is selected from at least one rare earth element containing Y and must contain La. The metallic element M is at least one element selected from Co, Ni, Zn, Al, Cu, and Cr, and must contain Co. When the atomic ratio of metallic elements is expressed in equation (1), in equation (1), c, a, r, b, f, and m satisfy the following equations (2) to (8). Approx c A a R r Bi b Feb f M m (1) 0.15≤c＜0.5 (2) 0.01≤a≤0.1 (3) 0.45＜r≤0.80 (4) 0.01≤b＜0.1 (5) 9.35＜f＜11.90 (6) 0.1≤m≤0.50 (7) c+a+r+b=1 (8).

5. A bonded magnet, wherein, It contains the ferrite particles and resin as described in claim 4.

6. A rotary electric motor, wherein, It has the adhesive magnet as described in claim 5.

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