Ferrite sintered magnet

Abstract

A sintered ferrite magnet has magnetoplumbite-type ferrite grains (4) and two-grain boundaries (6a) between the ferrite grains (4), wherein the two-grain boundaries contain Ca and La, and the Ca / La atomic ratio in the two-grain boundaries is 0.3 to 3.0.

Description

Technical Field

[0001] This disclosure relates to ferrite sintered magnets. Background Technology

[0002] As magnetic materials for ferrite sintered magnets, Ba ferrite, Sr ferrite, and Ca ferrite with hexagonal crystal structures are known (see, for example, Patent Documents 1-3). Magneto-plumbite type (M-type) and W-type crystal structures are known for these ferrites. Among them, magneto-plumbite type (M-type) ferrites are mainly used as magnet materials for electric motors, etc. M-type ferrites are typically composed of AFe... 12 O 19 The general formula for is .

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-206360 (Japanese Patent No. 4591684)

[0006] Patent Document 2: Japanese Patent Application Publication No. 2005-45167

[0007] Patent Document 3: WO2017 / 200091 (Japanese Patent No. 6769482) Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In M-type ferrite sintered magnets, the remanent magnetic flux density Br and coercivity HcJ tend to be a trade-off. Therefore, attempts have been made to increase both Br and HcJ by adding oxides of Si or Ca. However, in M-type ferrite sintered magnets, there is a tendency that increasing the coercivity leads to a significant decrease in the remanent magnetic flux density.

[0010] The present invention was made in view of the above-mentioned technical problems, and its purpose is to provide a new ferrite sintered magnet that can improve coercivity without reducing the residual magnetic flux density.

[0011] Means for solving technical problems

[0012] One type of ferrite sintered magnet has magnetoplumboid ferrite grains and two-grain boundaries between the ferrite grains. The two-grain boundaries contain Ca and La, and the Ca / La atomic ratio in the two-grain boundaries is 0.3 to 3.0.

[0013] The Ca / La atomic ratio in the two-grain boundary can be 0.4 or higher.

[0014] The two-grain boundary also contains Si, and the Si / La atomic ratio in the two-grain boundary can be 0.02 to 2.0.

[0015] Invention Effects

[0016] According to the present invention, a novel ferrite sintered magnet is provided, which can improve coercivity without reducing remanent magnetic flux density. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a cross-section of a ferrite sintered magnet.

[0018] Symbol Explanation

[0019] 4... Ferrite grains

[0020] 6...grain boundary phase

[0021] 6a……Two-grain grain boundary

[0022] 6b...Multi-grained grain boundaries Detailed Implementation

[0023] The embodiments of the present invention will now be described in detail.

[0024] (Ferrite sintered magnet)

[0025] like Figure 1 As shown, the ferrite sintered magnet 100 of the embodiment of the present invention has M-type ferrite grains 4 having a magnetoplumboid (M-type) crystal structure and grain boundary phases 6 existing between the M-type ferrite grains 4.

[0026] (M-type ferrite grains)

[0027] The magnetoplumboid crystal structure belongs to the hexagonal crystal system. There are no particular restrictions on the composition of M-type ferrite grains as long as they are oxides with a magnetoplumboid crystal structure.

[0028] The crystal structure of the magnetoplumite type can be represented by the following formula (III).

[0029] QX 12 O 19 (III)

[0030] Here, metallic element A 1 And some metal element R enters Q (A site).

[0031] Fe, metal element M, and the balance metal element R enter X (B site). In addition, the atomic ratios of Q (A site) and X (B site) relative to O in the above formula (III) are shown to be values ​​that actually deviate slightly from the above range. Therefore, they can also deviate slightly from the above values, for example, by about 10%.

[0032] M-type ferrite grains 4 may contain at least one metallic element selected from Ca, Sr, Ba, and Pb. 1 And Fe. M-type ferrite grains 4 may also contain at least one metallic element R selected from Bi and rare earth elements, and / or at least one metallic element M selected from Zn (zinc), Cu (copper), Mn (manganese), Al (aluminum), Co (cobalt), Ni (nickel), and Cr (chromium). Rare earth elements refer to Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0033] For example, the composition of M-type ferrite grains can also be represented by equation (1).

[0034] A 1 Fe 12 O 19 (1)

[0035] A portion of Fe can be replaced by the metallic element M. The atomic ratio of Fe can be over 50%.

[0036] Ferrite grains can be Sr-dominated A 1 Sr ferrite with more than 34 at% can be used for Ba accounting for A 1 Ba ferrite with a content of 34 at% or more can be used to make up the proportion of Ca in A 1 Ferrite with more than 34 at% Ca can also be Pb with a high A content. 1 Pb ferrites with a content of 34 at% or higher. Regarding Sr ferrite, Ba ferrite, Ca ferrite, and Pb ferrite, in A... 1 At the given atomic ratio, Sr, Ba, Ca, and Pb can be the largest components, respectively.

[0037] Ferrite grains may also contain Ca, metallic elements R, Fe, and metallic elements M. The metallic composition of M-type ferrites may also be, for example, the following general formula (5).

[0038] Ca a A 2 b R c Fe d M e (5)

[0039] In equation (5) above, A 2It is selected from at least one of Sr, Ba and Pb. a is, for example, 0.15 or more and 0.7 or less, b is, for example, 0 to 0.5, c is, for example, 0.3 or more and 0.85 or less, d may also be more than 9.35 and less than 11.90, and e may also be 0.1 to 0.5. a+b+c=1.

[0040] (5) In the formula, a can be greater than 0.20 or greater than 0.30. a can be less than 0.65 or less than 0.60.

[0041] From the perspective of reducing the proportion of heterogeneous phases and further improving Br, HcJ and rectangularity, b in equation (5) can be above 0.01, above 0.02, or above 0.03. From the same perspective, it can be below 0.40 or below 0.45.

[0042] From the perspective that Br can be further increased and there is a tendency for low-temperature demagnetization that can suppress coercivity, c in equation (5) can be above 0.35 or above 0.40. From the same perspective, it can be below 0.80 or below 0.75.

[0043] From the perspective of increasing magnetization and further reducing heterogeneity, d in equation (5) can be above 9.50 or above 9.70. From the perspective of further improving Br, HcJ and rectangularity, it can be below 11.80 or below 11.78.

[0044] From the perspective of improving magnetization and coercivity and further reducing heterogeneity, e in equation (5) can be 0.15 or more, 0.20 or more, or 0.25 or more. From the same perspective, m in equation (1) can be 0.48 or less, or 0.47 or less.

[0045] In formula (5), R preferably contains at least La, and the proportion of La in R can be 50 at% or more, 70 at% or more, 80 at% or more, 90 at% or more, or 95 at% or more.

[0046] In formula (5), M preferably contains at least Co, and the proportion of Co in M ​​can be 50 at% or more, 70 at% or more, 80 at% or more, 90 at% or more, or 95 at% or more.

[0047] The mass fraction of M-type ferrite in the M-type ferrite grains is preferably 90% or more, more preferably 95% or more, and even more preferably 97% or more.

[0048] In ferrite sintered magnets, the mass proportion of M-type ferrite grains (main phase) to all grains is preferably 90% or more, more preferably 95% or more, and even more preferably 97% or more. This reduces the mass proportion of crystalline phases (heterogeneous phases) different from the M-type ferrite phase, further improving magnetic properties. The mass proportion (%) of the M-type ferrite phase in all grains of the ferrite sintered magnet can be confirmed by determining the presence proportion (mol%) of the M-type ferrite phase using X-ray diffraction. The presence proportion of the M-type ferrite phase is calculated by mixing powder samples of M-type ferrite, orthoferrite, hematite, spinel, and W-type ferrite in a specified proportion and comparing their X-ray diffraction intensities.

[0049] The average grain size of M-type ferrite grains in ferrite sintered magnets can be, for example, less than 5 μm, less than 4.0 μm, or 0.5–3.0 μm. Having such an average grain size improves coercivity. The average grain size of the ferrite grains can be determined using cross-sectional images observed via TEM or SEM. Specifically, based on the cross-sectional area of ​​each grain in an SEM or TEM cross-section containing hundreds of ferrite grains determined through image analysis, the diameter of the circle with that cross-sectional area (equivalent circle diameter) is defined as the grain size of that grain on that cross-section, and the grain size distribution is measured. The average value of the ferrite grain size based on the measured grain size distribution is calculated. This average value is then set as the average grain size of the ferrite grains.

[0050] Grain boundary phase 6 is disposed between M-type ferrite grains 4. The main component of grain boundary phase 6 is oxide, containing at least La and Ca. The grain boundary phase may also contain half-metallic elements such as B (boron) and Si (silicon); and metallic elements selected from Sr (strontium), Ba (barium), and Pb (lead). 2 Fe (iron); metallic element R; at least one or any combination of two or more metallic elements M selected from Mn (manganese), Zn (zinc), Cr (chromium), Co (cobalt), Ni (nickel), Cu (copper) and Al (aluminum). The oxide may account for more than 90% by mass of the grain boundary phase 6, more preferably more than 95% by mass, and even more preferably more than 97% by mass.

[0051] The types of metal elements contained in the grain boundary phase 6 can be the same as those contained in the M-type ferrite grain 4, but they do not need to be the same.

[0052] like Figure 1 As shown, the grain boundary phase 6 can have two-grained grain boundaries 6a formed between two M-type ferrite grains 4, and multi-grained grain boundaries 6b surrounded by three or more M-type ferrite grains 4. The presence of multi-grained grain boundaries 6b is arbitrary.

[0053] The two-grained grain boundary 6a contains Ca and La, and the Ca / La atomic ratio in the two-grained grain boundary 6a is 0.3 to 3.0. Preferably, the Ca / La atomic ratio in the two-grained grain boundary 6a is 0.4 or higher.

[0054] It is believed that La contributes to the crystallization of the grain boundary phase, while Ca (CaO) contributes to its amorphization. If the amorphization of the grain boundary phase increases, its magnetization decreases; therefore, there is a tendency for the coercivity of the sintered magnet to increase while its remanent magnetization decreases. On the other hand, it is believed that if the crystallinity of the grain boundary phase increases, its magnetization increases, which can maintain the remanent magnetization of the sintered magnet but makes it difficult to increase the coercivity. In this embodiment, since the ratio of Ca to La in the grain boundary phase is appropriately set, it is believed that the remanent magnetization of the sintered magnet can be maintained while the coercivity is increased.

[0055] The proportion of Ca in all metal atoms in the two-grained grain boundary 6a can be 1.0–20.0 atomic percent. The proportion of La in all metal atoms in the two-grained grain boundary 6a can be 3.0–20.0 atomic percent.

[0056] The ratio of Ca and La atoms in all metal atoms in the two-grained grain boundary 6a can be greater, less, or the same as the ratio in all metal atoms in the ferrite grain 4. Besides La and Ca, the two-grained grain boundary 6a may also contain metallic elements R other than La and / or metallic elements A other than Ca. 2 Furthermore, the two-grain boundary 6a can also contain the metallic element M.

[0057] The two-grain boundary may also contain Si, and the Si / La atomic ratio in the two-grain boundary 6a is preferably 0.02 to 2.0. Thus, this embodiment is highly effective in grain boundary phases containing a certain amount of Si, but it can also be implemented even with a lower amount of Si.

[0058] When the average thickness of the two-grain boundary 6a of the ferrite sintered magnet is set as d, d can be less than 1 nm. The average thickness d can be, for example, measured at the central part of a two-grain boundary where both ends are set as multi-grain boundaries, for 10 different two-grain boundaries, and set as the average of these measured values.

[0059] On the cross-section of the ferrite sintered magnet, the area ratio of grain boundary phase 6 to the total area of ​​ferrite grain 4 and grain boundary phase 6 can be set to 0.01 to 5%.

[0060] There are no particular limitations on the overall composition of the ferrite sintered magnet. The overall metallic composition of the ferrite sintered magnet can satisfy equation (5).

[0061] Ferrite sintered magnets may contain Si (silicon). The Si content in the ferrite sintered magnet, calculated as SiO2, is preferably 0.01 to 1.3% by mass, more preferably 0.01 to 0.5% by mass, and even more preferably 0.01 to 0.36% by mass. Since there is a tendency for Br to decrease if there is too much SiO2 and for HcJ to decrease if there is too little SiO2, by setting the SiO2 content within the above range, it is easy to form an optimal grain boundary phase and obtain high magnetic properties.

[0062] Ferrite sintered magnets may contain boron (B). The B content in ferrite sintered magnets, calculated as B₂O₃, is 0.001 to 0.9% by mass. From the viewpoint of further improving the coercivity and rectangularity ratio (Hk / HcJ) of ferrite sintered magnets, the B content, calculated as B₂O₃, is preferably 0.01% by mass or more. Furthermore, from the viewpoint of further improving the remanent magnetic flux density (Br) of ferrite sintered magnets, the B content, calculated as B₂O₃, is preferably 0.4% by mass or less, more preferably 0.23% by mass or less.

[0063] In addition to these components, ferrite sintered magnets may also contain impurities from the raw materials or unavoidable components from the manufacturing equipment. Examples of such components include oxides of Mg (magnesium), Ti (titanium), Mo (molybdenum), and V (vanadium). The combined content of these is preferably 0.06% by mass or less.

[0064] The metal element content ratio in ferrite grains and grain boundary phases can be determined by STEM-EDX, while the metal element content ratio of the sintered magnet as a whole can be determined by X-ray fluorescence spectroscopy, inductively coupled plasma emission spectroscopy (ICP emission spectroscopy), etc.

[0065] There are no particular limitations on the shape of ferrite sintered magnets. For example, they can be made into various shapes such as arc segments (C-shaped) with the end face bent into an arc shape, flat plate shapes, etc.

[0066] Ferrite sintered magnets can be used as magnetic field generating components in rotating electrical machines such as motors and generators, magnets for loudspeakers and headphones, magnetrons, magnetic field generating devices for MRI, clampers for CD-ROMs, sensors for distributors, sensors for ABS, fuel / oil level sensors, magnetic locks, or isolators. Additionally, they can be used as targets (particles) in the formation of magnetic layers for magnetic recording media via methods such as vapor deposition or sputtering.

[0067] (Manufacturing method of ferrite sintered magnets)

[0068] Next, an example of a method for manufacturing ferrite sintered magnets will be described. The manufacturing method described below includes a compounding process, a calcination process, a pulverizing process, a powder mixing process, a molding process, and a firing process. Details of each process will be explained below.

[0069] (Coordinating processes)

[0070] 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 ferrite, namely, the metallic elements Al and Fe, and, if necessary, the metallic elements M and R. In the blending process, it is preferable to mix the mixture of powders containing each element using an atritor or ball mill for about 1 to 20 hours, and then pulverize it to obtain the raw material powder.

[0071] Examples of powders containing various 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.

[0072] Examples of powders containing Ca include CaCO3. Examples of powders containing Sr include SrCO3. Examples of powders containing Ba include BaCO3. Examples of powders containing La include La2O3 and La(OH)3. Examples of powders containing Fe include Fe2O3. Examples of powders containing Co include Co3O4.

[0073] The proportions of each metal element in the raw material powder can be appropriately set according to the composition of the ferrite grains mentioned above.

[0074] There is no particular limitation on the average particle size of the raw material powder, for example, it is 0.1 to 2.0 μm.

[0075] After the mixing process, preferably as needed, the raw material composition is dried and coarse particles are removed by sieving.

[0076] (Calcination process)

[0077] In the calcination process, the raw material powder obtained in the combination process is calcined to obtain a calcined body. Calcination is preferably carried out in an oxidizing atmosphere, such as air. The calcination temperature can be, for example, 1100–1400°C or 1100–1350°C. The calcination time can be, for example, 1 minute–10 hours or 1 minute–3 hours. The proportion of the ferrite phase (M phase) in the calcined body containing ferrite grains obtained by calcination can be, for example, 70% by mass or more or 75% by mass or more. This proportion of the ferrite phase can be calculated in the same way as the proportion of the ferrite phase in a ferrite sintered magnet.

[0078] (Grinding process)

[0079] In the pulverization process, calcined material, which has been reduced to granules or lumps by the calcination process, is pulverized to obtain ferrite powder. 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).

[0080] Coarse grinding can be carried out using, for example, a vibratory mill, until the average particle size of the calcined body becomes 0.1 to 5.0 μm.

[0081] In micronization, the coarse powder obtained from coarse grinding is further pulverized using a wet mill, ball mill, spray mill, etc. Micronization can be carried out with the resulting particles having an average particle size of, for example, approximately 0.08–2.0 μm. The specific surface area of ​​the fine powder (e.g., determined by the BET method) is set, for example, to be 7–12 m². 2 Approximately / g. The preferred 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 ​​the resulting powder can be measured using a commercially available BET specific surface area measuring device (Mountech, trade name: HM Model-1210).

[0082] In the micronization process, because the magnetic orientation of the sintered body obtained after firing is improved, it is also possible to add, for example, the general formula C. n (OH) n H n+2 The polyol referred to herein. 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 in combination. Moreover, in addition to polyols, other known dispersants may also be used.

[0083] 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 can be removed by pyrolysis in the firing process described later.

[0084] (Additional powder mixing process)

[0085] Next, the ferrite powder and the additional powder are mixed to obtain a mixed powder.

[0086] The additional powder can also be mixed with the pulverized ferrite powder obtained in the pulverization process, but it is preferable to add the additional powder to the powder in the pulverization process so that the ferrite powder and the additional powder are mixed at the same time as the calcined body is pulverized.

[0087] The added powder must contain at least Ca and La. The atomic ratio of La and Ca in the added powder can be appropriately adjusted according to the desired metal atomic ratio of the grain boundary phase. The added powder may also contain metal elements other than Ca and La (e.g., metal element A). 2 The composition of the grain boundary phase after sintering largely depends on the metal and half-metal components in the added powder. However, sometimes the metal in the added powder diffuses into the main phase or the metal in the main phase diffuses into the grain boundary phase. Therefore, it is not the same as the metal and half-metal composition of the added powder.

[0088] The amount of additional powder is preferably set to 0.1 to 7% of the mass relative to the mass of the ferrite powder.

[0089] When the calcined body is crushed in two stages, additional powder can be added before or after the coarse crushing process, or the additional powder can be divided into two parts and added before and after the coarse crushing process respectively.

[0090] (Molding process)

[0091] In the molding process, the mixed powder obtained in the additional powder mixing process (e.g., the pulverizing process) is 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.

[0092] In the case of wet molding, for example, after obtaining a slurry by performing the above-mentioned micronization process 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 concentration of the slurry can be achieved by centrifugation or pressure filtration. The ferrite grain 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 grains in the slurry. Surfactants such as gluconic acid, gluconate, and sorbitol can also be added to the slurry. Non-aqueous solvents can 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 the dried ferrite grains after micronization.

[0093] 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).

[0094] (Firing process)

[0095] In the firing (formal 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 a moderately oxidizing atmosphere, such as the atmosphere. The firing temperature can be, for example, 1050–1300°C or 1080–1290°C. In addition, the firing time (the time to hold the firing temperature) is, for example, 0.5–3 hours.

[0096] During the firing process, the temperature can be increased from room temperature to approximately 100°C at a rate of approximately 0.5°C / min before reaching the sintering temperature. This allows the molded body to be thoroughly dried before sintering. Additionally, surfactants added during the molding process can be effectively removed. These treatments can be performed at the beginning of the firing process or separately before the firing process.

[0097] Furthermore, from the viewpoint of increasing the Ca / La ratio at the grain boundaries, it is preferable to set the cooling rate from the sintering temperature to 1000°C to 1–10°C / min, more preferably to less than 2°C / min. By slowing down the cooling rate in this way, there is a tendency for Ca to segregate in the grain boundary phase.

[0098] Therefore, it is possible to manufacture the aforementioned ferrite sintered magnets.

[0099] Example

[0100] The present invention 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.

[0101] (Comparative Examples A1-A3 and Examples A1-A11)

[0102] As raw materials, powders of barium carbonate (BaCO3), calcium carbonate (CaCO3), strontium carbonate (SrCO3), lanthanum hydroxide (La(OH)3), iron oxide (Fe2O3), and cobalt oxide (Co3O4) were prepared.

[0103] These raw material powders are combined to achieve the metal atomic ratios shown in Table 1. They are then mixed and pulverized using a wet mill and a ball mill to obtain a slurry (combination process). After drying and removing coarse particles, the slurry is calcined at 1310°C in air to obtain calcined powder (calcination process).

[0104]

[0105] The obtained calcined powder was coarsely ground using a small rod vibrating mill to obtain coarse powder (coarse grinding process).

[0106] The raw material powder is mixed in such a way as shown in Table 1 to obtain the additional powder. The additional powder is added at a rate of 1.0% relative to the mass of the coarse powder, and then the mixed powder is finely pulverized using a wet ball mill to obtain a slurry containing ferrite grains (pulverization and additional powder mixing process).

[0107] The water content of the slurry obtained after micronization is adjusted to obtain a wet molding slurry. The wet molding slurry is then molded using a wet magnetic field molding machine under 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).

[0108] The resulting molded body was dried in the atmosphere at room temperature, and then fired in the atmosphere at 1280°C (firing (formal firing) process). The cooling rate from the firing temperature to 1000°C was set as shown in Table 1. This yielded a cylindrical ferrite sintered magnet.

[0109] (Comparative Example B1, Examples B1 and B2)

[0110] Except for the changes to various conditions as shown in Table 2, everything else is the same as in Example 1.

[0111]

[0112] (Comparative Example C1, Example C1, C2)

[0113] Except for changing the various conditions as shown in Table 3, everything else is the same as in Example 1.

[0114]

[0115] <Evaluation of Magnetic Properties>

[0116] After machining the upper and lower 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.

[0117] <Composition Analysis>

[0118] Ferrite sintered magnets were processed using the FIB (Focused Ion Beam) method with a focused ion beam apparatus to obtain a 100 nm thick sheet. Using STEM-EDS, elemental line analysis was performed on this sheet, perpendicularly traversing the grain boundary phase from one ferrite grain to another, and the concentration changes of metallic elements along the line were measured. With a measurement interval of 3 nm, the metallic element concentration at the two-grain boundary was obtained. This measurement was performed at five grain boundaries and averaged to obtain the metallic element concentration of the grain boundary phase, from which the atomic ratio was calculated.

[0119] The results of the sintered magnets of each embodiment and comparative example are shown in Tables 1 to 3.

[0120] In embodiments where the Ca / La atomic ratio at the grain boundaries is within a specific range, it can be confirmed that HcJ is increased while Br is hardly decreased, and the balance between Br and HcJ is excellent. Furthermore, in Comparative Example A2, magnetic properties could not be measured because cracks formed in the sintered magnet. In Comparative Example C1, Ca, La, and Si were not detected at the grain boundaries.

Claims

1. A ferrite sintered magnet, wherein, The ferrite sintered magnet has magnetoplumboid ferrite grains and two grain boundaries between the ferrite grains. The ferrite grains contain Ca, metallic elements R, Fe, and metallic element M. The metallic element R is selected from Bi and rare earth elements. The metallic element M is selected from Zn, Cu, Mn, Al, Co, Ni, and Cr. The metallic composition of the ferrite sintered magnet satisfies the following formula (5): Ca a A 2 b R c Fe d M e (5) In the above formula (5), A 2 The sample is selected from at least one of Sr, Ba, and Pb, where a is 0.15 or more and 0.7 or less, b is 0 or more and 0.45 or less, c is 0.3 or more and 0.85 or less, d is greater than 9.35 and less than 11.90, e is 0.1 or more and less than 0.5, and a + b + c = 1. The two-grained grain boundary contains Ca and La, and the Ca / La atomic ratio in the two-grained grain boundary is 0.3 to 3.

0.

2. The ferrite sintered magnet according to claim 1, wherein, The Ca / La atomic ratio in the two-grain boundary is greater than 0.

4.

3. The ferrite sintered magnet according to claim 2, wherein, The two-grain boundary also contains Si, and the Si / La atomic ratio in the two-grain boundary is 0.02 to 2.

0.

4. A ferrite sintered magnet, wherein, The ferrite sintered magnet has magnetoplumboid ferrite grains and two grain boundaries between the ferrite grains. The two-grained grain boundary contains Ca and La, and the Ca / La atomic ratio in the two-grained grain boundary is 0.3 to 3.

0. The two-grain boundary also contains Si, and the Si / La atomic ratio in the two-grain boundary is 0.02 to 2.0.

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