Ferrite sintered magnet, and method for manufacturing a ferrite sintered magnet

Abstract

To provide a sintered ferrite magnet capable of increasing both residual magnetic flux density and coercive force, and a manufacturing method of the sintered ferrite magnet.SOLUTION: A ferrite magnet includes a hexagonal ferrite main phase and a second phase. The second phase is an oxide phase including an element A which is at least one selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth elements, a transition metal element T containing at least Fe, and an element G which is at least one selected from the group consisting of Si, Al, B, F, K, Na, Li, P, and S. When the total number of atoms of the element A, the transition metal element T, and the element G in the second phase is 100 at%, the element A accounts for 30 to 80 at%, the element G accounts for 15 to 40 at%, and the transition metal element T accounts for less than 4 at%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a ferrite sintered magnet and a method for manufacturing the same. [Background technology]

[0002] Various hexagonal ferrites, such as magnetoprumbite-type (M-type) ferrite, are known as magnetic materials used in ferrite sintered magnets (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 4591684 [Patent Document 2] Japanese Patent Publication No. 2005-45167 [Patent Document 3] Patent No. 6769482 [Overview of the project] [Problems that the invention aims to solve]

[0004] In conventional hexagonal ferrite sintered magnets, attempts have been made to increase both the remanent magnetic flux density (Br) and coercivity (HcJ) by adding silicon oxides and other materials. However, with ferrite-based materials containing La, for example, it was difficult to achieve sufficient improvement in properties.

[0005] This invention has been made in view of the above problems, and aims to provide a novel ferrite sintered magnet and a method for manufacturing the same that can increase both residual magnetic flux density and coercivity. [Means for solving the problem]

[0006] A sintered magnet according to one aspect of the present invention is a ferrite sintered magnet comprising a hexagonal ferrite main phase and a second phase, The aforementioned second phase is Element A is at least one selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth elements. A transition metal element T containing at least Fe, An oxide phase comprising element G, which is at least one element selected from the group consisting of Si, Al, B, F, K, Na, Li, P, and S, When the total number of atoms of element A, transition metal element T, and element G in the aforementioned second phase is set to 100 at%, Element A accounts for 30-80 at%, Element G accounts for 15-40 at%, Transition metal elements T account for less than 4 at%.

[0007] Here, the sintered magnet may contain 0.05 to 10% by mass of the second phase.

[0008] Furthermore, the second phase is La 4.67 This may include apatite compounds that use the [SiO4]3O phase as a prototype.

[0009] The aforementioned hexagonal ferrite can be a magnetoprumbite ferrite.

[0010] A method for manufacturing a sintered magnet according to one aspect of the present invention includes the steps of obtaining a calcined body by calcining a raw material powder, A step of crushing the calcined body to obtain hexagonal ferrite powder, The process involves adding additional powder to the ferrite powder to obtain a mixed powder, The process of molding the mixed powder to obtain a molded body, and The process includes firing the molded body, The additional powder comprises element A, which is at least one selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth metal elements, and element G, which is at least one selected from the group consisting of Si, Al, B, F, K, Na, Li, P, and S. When the total number of atoms of element A, transition metal element T, and element G in the aforementioned additional powder is set to 100 at%, Element A accounts for 30-80 at%, Element G occupies 15 to 40 at%, and transition metal element T occupies less than 4 at%.

[0011] In the above method, the addition amount of the additional powder can be more than 0.05% by mass and at most 8.0% by mass.

[0012] In the above method, the additional powder can contain 4.67 an apatite compound having a [SiO4]3O phase as a prototype.

[0013] In the above method, the hexagonal ferrite can be a magnetoplumbite-type ferrite. [Advantages of the Invention]

[0014] According to the present invention, there are provided a ferrite sintered magnet capable of increasing both the residual magnetic flux density and the coercive force, and a method for producing the same. [Brief Description of the Drawings]

[0015] [Figure 1] FIG. 1 is a schematic cross-sectional view of a ferrite sintered magnet. [Embodiments for Carrying Out the Invention]

[0016] Some embodiments of the present invention will be described in detail below.

[0017] (Sintered Magnet) FIG. 1 is a schematic cross-sectional view of a ferrite sintered magnet 100 according to an embodiment of the present invention. The ferrite sintered magnet 100 according to an embodiment of the present invention has a hexagonal ferrite main phase (crystal grains) 4 and a second phase ⑥ existing between the hexagonal ferrite main phases (crystal grains) 4. A grain boundary phase 7 can further exist between the hexagonal ferrite main phases 4.

[0018] (Hexagonal Ferrite Main Phase) Hexagonal ferrite is a type of ferrite that has a hexagonal crystal structure. Examples of such ferrites include magnetoprumbite (M-type) ferrite, W-type ferrite, X-type ferrite, Y-type ferrite, and Z-type ferrite. Among these, M-type ferrite is preferred.

[0019] Hexagonal ferrite is an oxide comprising at least one element A1 selected from the group consisting of Ca, Sr, and Ba, at least one element A2 selected from the group consisting of rare earth metals and Bi, and a transition metal element T containing at least Fe.

[0020] Examples of rare earth elements include yttrium (Y), scandium (Sc), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadollium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0021] Examples of transition metal elements T other than Fe include Co, Zn, Ti, V, Cr, Mn, Ni, and Cu.

[0022] Element A1 preferably contains at least Ca, and if it contains Ca, element A1 may also contain Sr and / or Ba.

[0023] Element A2 preferably contains at least La.

[0024] Element T preferably contains Co in addition to Fe.

[0025] In a hexagonal ferrite-dominant phase, when the total number of atoms of elements A1 and A2 is set to 1, the number of atoms of element T can be 8 to 13, and preferably 10 to 13.

[0026] When the total number of atoms of element T is set to 100 at%, the atomic percentage of Fe can be 90 to 100 at%, and preferably 96 to 100 at%. Furthermore, the atomic percentage of Co is preferably 0 to 5 at%.

[0027] In a hexagonal ferrite-dominant phase, when the total number of atoms of element A1 and element A2 is set to 1, the ratio of atoms of element A2 can be 0.1 to 1.0, and preferably 0.4 to 1.0.

[0028] In a hexagonal ferrite-dominant phase, it is preferable that the ratio of La atoms to the total number of atoms of elements A1 and A2 is 0.4 or more.

[0029] In a hexagonal ferrite-dominant phase, it is preferable that the ratio of Ca atoms to the total number of A1 atoms (where A1 is 1) is 0.1 or greater.

[0030] M-type ferrite can be represented by the following equation (III). MX 12 O 19 (III) The M site can contain elements A1 and a portion of element A2. The X site can contain elements T and a portion of element A2.

[0031] Note that the ratios of M (site A) and X (site B) and the ratio of oxygen (O) in equation (III) above will actually deviate somewhat from the above range, so they may be off by about 10% from the above values.

[0032] In this specification, "main phase" refers to the crystalline phase that has the largest mass proportion in a ferrite sintered magnet. The hexagonal ferrite main phase may constitute 70% or more, 80% or more, 90% or more, or 95% or more of the total mass of the sintered magnet. The mass ratio of the hexagonal ferrite main phase can be determined by X-ray diffraction measurement or the like.

[0033] The average grain size of the hexagonal ferrite phase (crystal grains) in a ferrite sintered magnet may 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 increase the coercivity. The average grain size of the ferrite phase (crystal grains) can be determined using cross-sectional observation images obtained by TEM or SEM. Specifically, the cross-sectional area of ​​each hexagonal ferrite main phase in a cross-section of an SEM or TEM containing several hundred ferrite phases (crystal grains) is determined by image analysis, and the diameter of the circle having that cross-sectional area (equivalent circle diameter) is defined as the grain size of the main phase particles in that cross-section, and the grain size distribution is measured. From the measured grain size distribution based on the number of particles, the average value of the grain size of the hexagonal ferrite main phase (crystal grains) is calculated based on the number of particles. The average value measured in this way is taken as the average grain size of the hexagonal ferrite main phase.

[0034] (Second phase) Phase 6 is an oxide phase comprising element A, which is selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth metal elements (including Y); transition metal element T, which contains at least Fe; and element G, which is selected from the group consisting of Si, Al, B, F, K, Na, Li, P, and S. When the total number of atoms of element A, transition metal element T, and element G is set to 100 at%, the second phase consists of 30-80 at% of element A, 15-40 at% of element G, and less than 4 at% of transition metal element T. When the total number of atoms of element A, transition metal element T, and element G is set to 100 at%, the total of element A and element G in the second phase can be 80 at% or more, 90 at% or more, and 95 at% or more.

[0035] In another example, the second phase 6 is an oxide phase containing element A, which is at least one selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth metal elements (including Y), a transition metal element T which contains at least Fe, and Si. In this case, when the total number of atoms of all metallic elements and all metalloid elements is set to 100 at%, the second phase may consist of 30-80 at% element A, 10-40 at% Si (which may be 15 at% or more), and less than 4 at% transition metal element T. When the total number of atoms of all metallic elements and all metalloid elements is set to 100 at%, the total amount of elements A and Si in the second phase may be 80 at% or more, 90 at% or more, or 95 at% or more.

[0036] Element A may contain both at least one selected from the group consisting of Ca, Sr, and Ba, and at least one selected from the group consisting of Bi and rare earth metal elements. Element A may contain both at least one selected from the group consisting of Ca, Sr, and Ba, and La. Element A may contain Ca and La.

[0037] When the total of all metallic elements and metalloid elements is set to 100 at%, or when the total of element A, transition metal element T, and element G is set to 100 at%, the total proportion of at least one element selected from the group consisting of Ca, Sr, and Ba in the second phase can be 0 to 80 at%, and in particular, the proportion of Ca can be 5 to 50 at%.

[0038] When the total of all metallic and metalloid elements is set to 100 at%, or when the total of element A, transition metal element T, and element G is set to 100 at%, the total proportion of at least one element selected from the group consisting of Bi and rare earth metals in the second phase can be 30 to 80 at%, and in particular, the proportion of La can be 10 to 65 at%.

[0039] When the total of element A, transition metal element T, and element G is 100 at%, the atomic proportion of element G in the second phase is 15 to 40 at%, but 18 to 40 at%, and 20 to 40 at%, is also preferred. In this case, when the total of element A, transition metal element T, and element G is 100 at%, the atomic proportion of Si in the second phase may be 5 at% or more, 10 at% or more, 15 at% or more, 18 at% or more, 20 at% or more, 25 at% or more, or 30 at% or more. When the total amount of all metallic and metalloid elements is 100 at%, the atomic proportion of Si in the second phase may be 10 to 40 at%, but it may also be 15 to 40 at%, 18 to 40 at%, and 20 to 40 at%.

[0040] When the total amount of all metallic elements and metalloid elements is set to 100 at%, or when the total number of atoms of element A, transition metal element T, and element G is set to 100 at%, the atomic proportion of Fe in the second phase can be 4 at% or less, or 3 at% or less.

[0041] When the total amount of all metallic and metalloid elements is set to 100 at%, or when the total number of atoms of element A, transition metal element T, and element G is set to 100 at%, the atomic proportion of Co in the second phase can be set to 4 at% or less, and Zn can be set to 4 at% or less.

[0042] The second phase can be 0.05 to 10 mass% of the total mass of the sintered magnet.

[0043] Phase two is La 4.67 This can include apatite compounds with the [SiO4]3O phase as a prototype. This structure is called an oxyapatite structure. For example, the above structure is Q 4.67 When written as [EO4]3O, Q is element A, and E can be element G (containing Si) or transition metal element T. This compound may have a P63 / m structure.

[0044] The second phase may contain compounds having a Pnma structure in addition to compounds having an oxyapatite structure. This structure is called an orthoferrite structure.

[0045] The second phase may be a mixture of compounds with an oxyapatite structure and compounds with an orthoferrite structure.

[0046] In the second phase, the mass ratio of the oxyapatite structure compound to the orthoferrite structure compound can be 3 or greater, 4 or greater, or 5 or greater. The upper limit can be 40 or less, 30 or less, 25 or less, or 20 or less. The mass ratio can be determined from the ratio of the maximum peaks of each structure in XRD measurements using CuKα radiation.

[0047] XRD and TEM electron diffraction of the second phase confirm that at least a portion of the second phase has an oxyapatite structure. The crystal structure and composition of the second phase can be confirmed by XRD and STEM-EDX, respectively.

[0048] There are no particular limitations on the shape of the ferrite sintered magnet; for example, it can take various shapes such as a curved arc segment (C-type) shape with an arc-shaped end face, or a flat plate shape.

[0049] The coercivity of a ferrite sintered magnet at 20°C can be, for example, 300 kA / m or more. The remanent magnetic flux density Br of a ferrite sintered magnet at 20°C can be 400 mT or more. The ferrite sintered magnet of this embodiment can be excellent in both coercivity (HcJ) and remanent magnetic flux density (Br).

[0050] The mass ratio of metallic and metalloid elements in the hexagonal ferrite main phase and secondary phase of a ferrite sintered magnet can be measured by STEM-EDX X-ray fluorescence analysis.

[0051] (Method of manufacturing ferrite sintered magnets) Next, an example of a method for manufacturing a ferrite sintered magnet according to the embodiment will be described. The manufacturing method described below includes a compounding step, a calcination step, a grinding step, an additional powder mixing step, a molding step, and a firing step. Details of each step will be described below.

[0052] (Blending process) The blending process is the process of preparing the raw material powder for calcination. The raw material powder for calcination contains the constituent elements of the hexagonal ferrite main phase, that is, elements A1, A2, and T. In the blending process, it is preferable to obtain the raw material powder by mixing a mixture of powders containing each element in an attritor or ball mill for about 1 to 20 hours and then grinding it.

[0053] Examples of powders containing each element include the element itself, its oxides, hydroxides, carbonates, nitrates, silicates, and organometallic compounds. A single powder may contain two or more metallic elements, or it may contain substantially only one metallic element.

[0054] An example of a powder containing Ca is CaCO3. An example of a powder containing Sr is SrCO3. An example of a powder containing Ba is BaCO3. Examples of powders containing La are La2O3 and La(OH)3. An example of a powder containing Fe is Fe2O3. An example of a powder containing Co is Co3O4.

[0055] The ratio of each metal element in the raw material powder can be appropriately set according to the composition of the hexagonal ferrite-dominant phase described above.

[0056] The average particle size of the raw material powder is not particularly limited, and is, for example, 0.1 to 5.0 μm.

[0057] After the blending process, it is preferable to dry the raw material composition and remove coarse particles by sieving, if necessary.

[0058] (Calibration process) In the calcination process, the raw material powder obtained in the blending process is calcined to obtain a calcined body. The calcination is preferably carried out, for example, in an oxidative atmosphere such as air. The calcination temperature may be, for example, 1100 to 1400 °C, or may be 1100 to 1350 °C. The calcination time may be, for example, 1 minute to 10 hours, or may be 1 minute to 3 hours. The ratio of the hexagonal ferrite phase in the calcined body obtained by calcination may be, for example, 70% by mass or more, or may be 75% by mass or more. This ratio of the hexagonal ferrite phase can be determined in the same manner as the ratio of the hexagonal ferrite phase in the ferrite sintered magnet.

[0059] (Grinding Process) In the grinding process, the calcined body that has become granular or块状 in the calcination process is ground to obtain a ferrite powder. The grinding process may be carried out, for example, in two steps: first, the calcined powder is ground (coarse grinding process) to become a coarse powder, and then this is further finely ground (fine grinding process).

[0060] Coarse grinding can be carried out, for example, using a vibration mill or the like until the average particle size of the calcined body becomes 0.1 to 10.0 μm.

[0061] In fine grinding, the coarse powder obtained by coarse grinding is further ground by a wet attritor, ball mill, jet mill, etc. In fine grinding, the grinding can be carried out so that the average particle size of the obtained particles becomes, for example, about 0.08 to 5.0 μm. The specific surface area of the fine powder (obtained, for example, by the BET method.) is, for example, 7 to 12 m 2 / g or so. The suitable grinding time varies depending on the grinding method. For example, in the case of a wet attritor, it is 30 minutes to 10 hours, and in the case of wet grinding by a ball mill, it is 10 to 50 hours. The specific surface area of the obtained powder can be measured using a commercially available BET specific surface area measuring device (manufactured by Mountech, product name: HM Model-1210).

[0062] In the fine grinding process, in order to increase the magnetic orientation degree of the sintered body obtained after firing, for example, the general formula C n (OH) n Hn+2 A polyhydric alcohol represented by the formula may be added. In the general formula, n may be, for example, 4 to 100 or 4 to 30. Examples of polyhydric alcohols include sorbitol. Two or more polyhydric alcohols may also be used in combination. Furthermore, in addition to polyhydric alcohols, other known dispersants may be used in combination.

[0063] When adding polyhydric alcohols, the amount added may be, for example, 0.05 to 5.0% by mass or 0.1 to 3.0% by mass relative to the material to be added (e.g., coarse powder). The polyhydric alcohols added in the fine grinding process are removed by thermal decomposition in the calcination process described later.

[0064] (Additional powder addition process) Next, the ferrite powder and the additional powder are mixed to obtain a mixed powder. The additional powder may be mixed with the ferrite powder obtained in the grinding process, but it is preferable to add the additional powder to the powder during the grinding process so that the ferrite powder and the additional powder are mixed simultaneously with the grinding of the calcined body and the additional powder.

[0065] The additional powder contains at least one element A selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth metal elements (including Y), and at least one element G selected from the group consisting of Si, Al, B, F, K, Na, Li, P, and S. When the total number of atoms of element A, transition metal element T, and element G in the additional powder is taken as 100 at%, element A accounts for 30-80 at%, element G accounts for 15-40 at%, and transition metal element T accounts for less than 4 at%. When the total number of atoms of element A, transition metal element T, and element G is taken as 100 at%, the total of element A and element G in the additional powder can be 80 at% or more, 90 at% or more, and 95 at% or more. In another example, the additional powder contains at least one element A selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth metal elements (including Y), and Si. When the total number of atoms of metal and metalloid elements in the additional powder is taken as 100 at%, element A accounts for 30-80 at%, Si accounts for 10-40 at%, (or 15 at% or more), and transition metal element T accounts for less than 4 at%. When the total number of atoms of all metal and metalloid elements is taken as 100 at%, the sum of elements A and Si in the additional powder can be 80 at% or more, 90 at% or more, and 95 at% or more.

[0066] Element A may contain both at least one selected from the group consisting of Ca, Sr, and Ba, and at least one selected from the group consisting of Bi and rare earth metal elements. Element A may contain both at least one selected from the group consisting of Ca, Sr, and Ba, and La. Element A may contain Ca and La.

[0067] When the total of all metallic elements and metalloid elements is set to 100 at%, or when the total of element A, transition metal element T, and element G is set to 100 at%, the total proportion of at least one element selected from the group consisting of Ca, Sr, and Ba in the above compound can be 0 to 80 at%, and in particular, the proportion of Ca can be 5 to 50 at%.

[0068] When the total of all metallic elements and metalloid elements is set to 100 at%, or when the total of element A, transition metal element T, and element G is set to 100 at%, the total proportion of at least one element selected from the group consisting of Bi and rare earth metals in the above compound can be 30 to 80 at%, and in particular, the proportion of La can be 10 to 65 at%.

[0069] When the total of element A, transition metal element T, and element G is set to 100 at%, the atomic proportion of element G in the above compound is 15 to 40 at%, preferably 18 to 40 at%, and also preferably 20 to 40 at%. In this case, when the total of element A, transition metal element T, and element G is set to 100 at%, the atomic proportion of Si in the above compound may be 5 at% or more, 10 at% or more, 15 at% or more, 18 at% or more, 20 at% or more, 25 at% or more, or 30 at% or more. When the total amount of all metallic elements and metalloid elements is set to 100 at%, the atomic proportion of Si in the above compound may be 10 to 40 at%, 15 to 40 at%, preferably 18 to 40 at%, and preferably 20 to 40 at%.

[0070] When the total of all metallic elements and metalloid elements is set to 100 at%, or when the total of element A, transition metal element T, and element G is set to 100 at%, the atomic concentration of Fe in the above compound is preferably 4 at% or less, and preferably 3 at% or less.

[0071] The above compound can have a Co content of 0-4 at% and a Zn content of 0-4 at% when the total amount of all metallic and metalloid elements is 100 at% or when the total amount of element A, transition metal element T, and element G is 100 at%.

[0072] The additional powder may be an oxide, or a salt such as a carbonate. The additional powder may be a mixture of various compounds, for example, a mixture of oxides, a mixture of salts, or a mixture of salts and oxides.

[0073] An example of an oxide is La 4.67 This is an oxyapatite compound with the [SiO4]3O phase as its prototype. An example of such an oxyapatite is La8Ca2[SiO2]6O2. The additional powder may also be a compound having an orthoferrite structure, or a mixture thereof. An example of a salt is CaCO3. The additional powder may contain 50% by mass or more of an oxyapatite structure compound, 70% by mass or more, or 90% by mass or more.

[0074] The amount of additional powder is preferably 0.05% by mass or more and less than 8.0% by mass, relative to 100 parts by mass of ferrite powder.

[0075] When the calcined body is crushed in two stages, the additional powder may be added either before or after the coarse crushing process, or the additional powder may be divided into two parts and added before and after the coarse crushing.

[0076] (molding process) In the molding process, the mixed powder obtained in the additional powder mixing process (e.g., the grinding process) is molded in a magnetic field to obtain a molded body. Molding can be performed by either dry molding or wet molding. From the viewpoint of increasing the degree of magnetic orientation, wet molding is preferred.

[0077] When molding by wet molding, for example, a slurry is obtained by performing the above-described fine grinding step in a wet manner, and then this slurry is concentrated to a predetermined concentration to obtain a slurry for wet molding. Molding can be performed using this slurry for wet molding. The slurry can be concentrated by centrifugation or by a filter press, etc. The ferrite particle content in the slurry for wet molding is, for example, 30 to 80% by mass. In the slurry, water can be used as a dispersion medium to disperse the ferrite particles. Surfactants such as gluconic acid, gluconate salts, and sorbitol may be added to the slurry. A non-aqueous solvent may be used as the dispersion medium. Organic solvents such as toluene and xylene can be used as non-aqueous solvents. In this case, surfactants such as oleic acid may be added. The slurry for wet molding may also be prepared by adding a dispersion medium to the dried ferrite particles after fine grinding.

[0078] In wet molding, the wet molding slurry is then subjected to molding in a magnetic field. In this case, the molding pressure is, for example, 9.8 to 196 MPa (0.1 to 2.0 ton / cm²). The applied magnetic field is, for example, 398 to 1194 kA / m (5 to 15 kOe).

[0079] (Firing process) In the firing (main firing) process, the molded body obtained in the molding process is fired to obtain a ferrite sintered magnet. The firing of the molded body can be carried out in an oxidizing atmosphere such as air. The firing temperature may be, for example, 1050 to 1300°C or 1080 to 1290°C. The firing time (the time to hold at the firing temperature) is, for example, 0.5 to 3 hours.

[0080] In the firing process, before reaching the sintering temperature, the molded body may be heated from room temperature to approximately 100°C at a heating rate of about 0.5°C / minute. This allows the molded body to be thoroughly dried before sintering progresses. It also allows for the thorough removal of surfactants added during the molding process. These treatments may be performed at the beginning of the firing process or separately before the firing process.

[0081] In this way, the above-mentioned ferrite sintered magnet can be manufactured.

[0082] For example, the molding and firing processes may be carried out according to the following procedure. Specifically, the molding process may be carried out by CIM (Ceramic Injection Molding) or PIM (Powder Injection Molding). In the CIM molding method, first, a dried mixed powder is heated and kneaded together with a binder resin to form pellets. These pellets are injection molded in a mold to which a magnetic field is applied to obtain a pre-molded body. A molded body is obtained by de-bindering this pre-molded body. Next, in the firing process, the de-bindered molded body is sintered, for example, in air at a temperature of preferably 1100 to 1300°C, more preferably 1160 to 1290°C, for about 0.2 to 3 hours to obtain a ferrite sintered magnet. [Examples]

[0083] The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0084] (Comparative Examples 1-4, 6-8, Examples 1-11, 14-21) As raw materials, we prepared powders of calcium carbonate (CaCO3), barium carbonate (BaCO3), strontium carbonate (SrCO3), lanthanum hydroxide (La(OH)3), iron oxide (Fe2O3), and cobalt oxide (Co3O4).

[0085] These raw material powders were blended so that the metal atom ratio matched the metal composition of the M-type ferrite main phase shown in Table 1. Mixing and grinding were performed using a wet attritor and a ball mill to obtain a slurry (blending step). After drying this slurry and removing the coarse particles, calcination was performed in air at 1280°C to obtain calcined powder (calcination step).

[0086] [Table 1]

[0087] The obtained calcined powder was coarsely ground using a small rod vibrating mill to obtain coarse powder. (Coarse grinding process)

[0088] The additional powders shown in Table 1 were prepared. The compositions of oxyapatite #1 to #14 are shown in Table 2. Each oxyapatite particle was obtained by weighing the raw material powders (calcium carbonate (CaCO3), barium carbonate (BaCO3), strontium carbonate (SrCO3), lanthanum hydroxide (La(OH)3), iron oxide (Fe2O3), cobalt oxide (Co3O4), zinc oxide (ZnO), silica (SiO2)) to achieve the metal composition shown in Table 2, mixing them in an agate mortar, firing the mixture in air, and then finely grinding it using a ball mill. The firing temperature was 1200°C.

[0089] Each additional powder was added to the coarse powder in the proportions shown in Table 1 relative to 100% of the mass of the coarse powder. The mixed powder was then finely ground using a wet ball mill to obtain a slurry containing ferrite particles (grinding and additional powder mixing process).

[0090] [Table 2]

[0091] A slurry for wet molding was obtained by adjusting the moisture content of the slurry obtained after fine grinding. This slurry for wet molding was molded using a wet magnetic field molding machine in an applied magnetic field of 796 kA / m (10 kOe) to obtain a cylindrical molded body with a diameter of 30 mm and a thickness of 15 mm (molding process).

[0092] The resulting molded body was dried in the air at room temperature, and then fired in the air at 1200°C (firing (main firing) process). In this way, a cylindrical ferrite sintered magnet was obtained.

[0093] (Examples 12, 13) The procedure was the same as in Example 1, except that the composition of the M-type ferrite main phase was changed as shown in Table 1.

[0094] <Evaluation of magnetic properties> After processing the top and bottom surfaces of the ferrite sintered magnet, Br and HcJ were measured at 20°C using a BH tracer with a maximum applied magnetic field of 29 kOe.

[0095] <Composition analysis> Thin sections approximately 100 nm thick were prepared from ferrite sintered magnets using focused beam ionization (FIB), and these sections were observed using a scanning transmission electron microscope (STEM). Using the EDX attached to the STEM, particles with a transition metal composition containing Fe or less as a percentage of the total metal and semimetallic atoms were identified as second-phase particles, and EDX point analysis was performed on these second-phase particles to obtain the composition of the second phase. Furthermore, XRD was used to confirm that the ferrite main phase is hexagonal, and the crystal structure and weight percentage of the second phase were also analyzed by XRD.

[0096] The results for each example and comparative example are shown in Tables 3 to 5.

[0097] [Table 3] [Table 4] [Table 5]

[0098] It was confirmed that in sintered magnets containing a second phase of a predetermined composition, both Br and Hcj were higher compared to Comparative Example 1, which did not contain this second phase. [Explanation of symbols]

[0099] 4...Hexagonal ferrite main phase, 6...Secondary phase.

Claims

1. A ferrite sintered magnet comprising a hexagonal ferrite main phase and a second phase, The aforementioned second phase is Element A is at least one selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth elements, A transition metal element T containing at least Fe, An oxide phase comprising element G, which is at least one element selected from the group consisting of Si, Al, B, F, K, Na, Li, P, and S, When the total number of atoms of element A, transition metal element T, and element G in the second phase is set to 100 at%, Element A accounts for 30-80 at%, Element G accounts for 15-40 at%, Transition metal elements T account for less than 4 at%, Ferrite sintered magnets in which La accounts for 10-65 at%.

2. The ferrite sintered magnet according to claim 1, wherein the atomic proportion of Fe in the second phase is 3 at% or less.

3. A ferrite sintered magnet according to claim 1 or 2, comprising 0.05 to 10% by mass of the second phase.

4. The second phase is La ４．６７ [SiO ４ ] ３ A ferrite sintered magnet according to any one of claims 1 to 3, comprising an apatite compound with an O phase as its prototype.

5. The ferrite sintered magnet according to any one of claims 1 to 4, wherein the hexagonal ferrite main phase is a magnetoprumbite type ferrite main phase.

6. A process of obtaining a calcined body by calcining the raw material powder. A step of crushing the calcined body to obtain hexagonal ferrite powder, The process involves adding additional powder to the ferrite powder to obtain a mixed powder, The process involves molding the mixed powder to obtain a molded body, and The process includes firing the molded body, The additional powder comprises at least one element A selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth metal elements, and at least one element G selected from the group consisting of Si, Al, B, F, K, Na, Li, P, and S. When the total number of atoms of element A, transition metal element T, and element G in the aforementioned additional powder is set to 100 at%, Element A accounts for 30-80 at%, Element G accounts for 15-40 at%, Transition metal elements T account for less than 4 at%, A method for manufacturing ferrite sintered magnets in which La accounts for 10 to 65 at%.

7. The method according to claim 6, wherein the amount of the additional powder added is 0.05% by mass or more and less than 8.0% by mass.

8. The aforementioned additional powder is La ４．６７ [SiO ４ ] ３ The method according to claim 6 or 7, comprising an apatite compound with an O phase as its prototype.

9. The method according to any one of claims 6 to 8, wherein the hexagonal ferrite powder is a magnetoprumbite type ferrite powder.

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