JP7087465B2 - A method for manufacturing a ferrite sintered magnet, a method for manufacturing ferrite particles, and a method for manufacturing a bonded magnet. - Google Patents

Description

The present invention relates to a method for producing a ferrite sintered magnet, a method for producing ferrite particles, and a method for producing a bonded magnet.

As the magnetic material used for the ferrite sintered magnet, Ba ferrite, Sr ferrite and Ca ferrite having a hexagonal crystal structure are known. As such a ferrite crystal structure, a magnetoplumbite type (M type), a W type, and the like are known. Among these, M-type ferrite is mainly adopted as a magnet material for motors and the like. The M-type ferrite is usually represented by the general formula of AFe ₁₂ O ₁₉ .

As an index of the magnetic characteristics of the ferrite sintered magnet, the residual magnetic flux density (Br), the coercive force (HcJ), and the square ratio (Hk / HcJ) are generally used. Conventionally, from the viewpoint of improving Br and HcJ, it has been attempted to add various elements different from the constituent elements of ferrite to ferrite. For example, in Patent Document 1, it is attempted to improve the magnetic properties by substituting a part of the element of A site with Ca and a rare earth element (R) and a part of Fe with Co.

International Publication No. 2008/146712

Motors, generators, etc., which are the main applications of ferrite sintered magnets, are being miniaturized in each technical field. For this reason, the internal structure is becoming complicated, and the installation space for magnets is becoming smaller. Therefore, it is conceivable to reduce the thickness in order to reduce the installation space. However, if the thickness is reduced, there is a concern that the ferrite sintered magnet will be demagnetized by the demagnetizing field.

An object of the present invention is to provide a method for producing a ferrite sintered magnet having excellent magnetic characteristics, a method for producing ferrite particles having excellent magnetic characteristics, and a method for producing a bonded magnet using the ferrite particles.

(Manufacturing method of ferrite sintered magnet)
The method for producing a ferrite sintered magnet according to one aspect of the present invention is a method for producing a ferrite sintered magnet containing a ferrite phase having a magnetoplumbite-type crystal structure, which comprises a raw material for the ferrite phase and a boron compound. It is provided with a calcining step of calcining a mixture to produce ferrite particles, a molding step of producing a compact from ferrite particles, and a calcining step of sintering the compact, for the production of ferrite sintered magnets. The whole amount of the ferrite phase raw material and the boron compound used are mixed before the calcining step, and the ferrite phase raw material is a compound of rare earth element R, a compound of alkaline earth metal element A, a compound of iron, and a compound of cobalt. Yes, R is at least one element selected from rare earth elements, and A is a combination of at least one alkaline earth metal element other than calcium and calcium, or only calcium, which is R relative to the total mass of the mixture. The ratio of the compound of A is 5.5% by mass or more and 19.9% by mass or less in terms of the mass of the oxide of R, and the ratio of the compound of A to the mass of the entire mixture is converted to the mass of the oxide of A. 1.7% by mass or more and 7.6% by mass or less, and the ratio of the iron compound to the total mass of the mixture is 45.3% by mass or more and 87.4% by mass or less in terms of the mass of the iron oxide. Yes, the ratio of the cobalt compound to the total mass of the mixture is 0.9% by mass or more and 18.9% by mass or less in terms of the mass of the cobalt oxide, and the ratio of the boron compound to the total mass of the mixture is ho. In terms of the mass of the acid, it is larger than 0.3% by mass and 2.5% by mass or less, and the metal component contained in the ferrite phase is expressed as R1 _-x A _x F my _Coy , where _x is. 0.2 ≤ x ≤ 0.8, y satisfies 0.1 ≤ y ≤ 0.65, m satisfies 3 ≤ m <14, and the boron content in the ferrite sintered magnet is B ₂ O. In terms of mass of ₃ , it is 0.1% by mass or more and 0.6% by mass or less.

The boron compound may contain boric acid.

(Manufacturing method of ferrite particles)
The method for producing ferrite particles according to one aspect of the present invention is a method for producing ferrite particles containing a ferrite phase having a magnetoplumbite-type crystal structure, in which a mixture containing a raw material for the ferrite phase and a boron compound is heated. A heating step for producing ferrite particles is provided, and the entire amount of the raw material for the ferrite phase and the boron compound used for producing the ferrite particles are mixed before the heating step, and the raw material for the ferrite phase is a compound of the rare earth element R and alkaline soil. Metallic elements A compounds, iron compounds, and cobalt compounds, R is at least one element selected from rare earth elements, and A is at least one alkaline earth metal element other than calcium and calcium. The ratio of the compound of R to the mass of the whole mixture is 5.5% by mass or more and 19.9% by mass or less in terms of the mass of the oxide of R, and the mass of the whole mixture. The ratio of the compound of A to the mass of the oxide of A is 1.7% by mass or more and 7.6% by mass or less, and the ratio of the compound of iron to the mass of the entire mixture is the mass of the oxide of iron. In terms of conversion, it is 45.3% by mass or more and 87.4% by mass or less, and the ratio of the cobalt compound to the total mass of the mixture is 0.9% by mass or more and 18.9% by mass in terms of the weight of the cobalt oxide. The ratio of the boron compound to the total mass of the mixture is less than 2.5% by mass, which is larger than 0.3% by mass in terms of the mass of boric acid, and the metal component contained in the ferrite phase is _R1 . -X A _x F my _-y Coy, _{x satisfies} 0.2 ≤ x ≤ 0.8, y satisfies 0.1 ≤ y ≤ 0.65, and m satisfies 3 ≤ m <14. The content of boron in the filled ferrite particles is 0.1% by mass or _more and 0.6% by mass or less in terms of mass of _B2O3 .

The boron compound may contain boric acid.

(Manufacturing method of bond magnet)
The method for manufacturing a bonded magnet according to one aspect of the present invention includes a step of manufacturing a molded body containing ferrite particles and a resin, and a step of curing the resin in the molded body, and the ferrite particles are produced as described above. Manufactured by the method.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a ferrite sintered magnet having excellent magnetic characteristics, a method for producing ferrite particles having excellent magnetic characteristics, and a method for producing a bonded magnet using the ferrite particles.

Hereinafter, preferred embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

(Manufacturing method of ferrite particles and manufacturing method of ferrite sintered magnet)
The method for manufacturing a ferrite sintered magnet according to the present embodiment is a method for manufacturing a ferrite sintered magnet containing a ferrite phase having a magnetoplumbite-type crystal structure. The method for producing ferrite particles according to the present embodiment is a method for producing ferrite particles containing a ferrite phase having a magnetoplumbite-type crystal structure.

The method for manufacturing a ferrite sintered magnet includes at least a mixing step, a calcining step, a molding step, and a firing step. In the mixing step, the raw material of the ferrite phase and the boron compound are mixed to prepare a mixture. In the calcination step, the mixture obtained in the mixing step is calcanely baked to produce ferrite particles (temporary baking powder). In the molding step, an intermediate material containing ferrite particles is molded to produce a molded body. In the firing step, the compact is sintered.

The method for producing ferrite particles includes at least a mixing step and a heating step. In the mixing step, the raw material of the ferrite phase and the boron compound are mixed to prepare a mixture. In the heating step, the mixture is heated to produce ferrite particles. The heating step in the method for manufacturing ferrite particles is equivalent to the calcining step in the method for manufacturing ferrite sintered magnets. That is, the method for manufacturing ferrite particles is substantially the same as the mixing step and the calcining step in the method for manufacturing ferrite sintered magnets. That is, the method for manufacturing ferrite particles is a part of the method for manufacturing ferrite sintered magnets.

The raw materials for the ferrite phase are a compound of rare earth element R, a compound of alkaline earth metal element A, a compound of iron (Fe), and a compound of cobalt (Co). The boron compound may be at least one selected from the group consisting of boric acid, boron oxide and calcium borate. The raw material mixture before calcination may contain water. In the mixing step, an aqueous solution of the boron compound may be mixed with the raw material of the ferrite phase.

In the mixing step, the raw material of the ferrite phase used for producing the ferrite sintered magnet and the ferrite particles and the total amount of the boron compound are mixed. That is, the raw materials of the ferrite phase used for producing the ferrite sintered magnet and the ferrite particles and the total amount of the boron compound are collectively mixed before the calcining step. On the other hand, neither the raw material of the ferrite phase nor the boron compound is added to the calcined powder (coarse ferrite particles) obtained in the calcining step. In the following, a mixture containing a raw material for a ferrite phase and a boron compound may be referred to as a “raw material mixture”.

The raw material mixture may contain a ferrite phase raw material and other additive components other than the boron compound. The intermediate material containing the calcined powder (ferrite particles) may also contain the raw material of the ferrite phase and other additive components other than the boron compound. The other additive component may be, for example, silicon dioxide (SiO ₂ ). In the mixing step, the whole amount of the ferrite phase raw material, the boron compound and the additive component may be mixed. The entire amount of the additive component used for producing the ferrite sintered magnet and the ferrite particles may be added to the calcined powder (ferrite particles). A part of the added component may be added to the raw material mixture before being calcined, or the rest of the added component may be added to the calcined powder (ferrite particles).

By mixing the whole amount of the raw material of the ferrite phase and the boron compound before the calcining step, ferrite particles and ferrite sintered magnets having excellent magnetic properties can be obtained. Excellent magnetic properties mean that the residual magnetic flux density (Br), coercive force (HcJ) and square ratio (Hk / HcJ) are well-balanced and high. Hk is a magnetic field corresponding to 90% of Br. The reason why ferrite particles and ferrite sintered magnets having excellent magnetic properties can be obtained is as follows.

By mixing the whole amount of the raw material of the ferrite phase and the boron compound before the calcining step, it is possible to obtain ferrite particles in which a uniform fine structure of the ferrite phase is formed at the time of calcining the raw material mixture. The fine structure formed in the ferrite particles is not easily lost in the pulverization step (fine pulverization) performed after the calcining step. Therefore, even in the firing step, it is possible to obtain a sintered body (ferrite sintered magnet) in which a densified ideal fine structure is formed.

Since boron is a lighter element than the metal elements (rare earth element R, alkaline earth metal elements A, Fe and Co) that compose the raw material of the ferrite phase, boron contained in the raw material mixture or ferrite particles is another element. Compared with, it tends to decrease by heating or dissolution in water. Therefore, the boron compound added to the calcined powder (ferrite particles) is easily separated from the ferrite particles in various steps after the calcining step. However, by mixing the raw material of the ferrite phase and the total amount of the boron compound before the calcining step, the total amount of the boron compound reacts with the raw material of the ferrite phase in the calcining step to quickly form a glass component. Boron in the glass component is difficult to decrease by heating and is difficult to elute into water, so that the decrease of boron in the ferrite particles due to various steps after the calcining step is suppressed. As a result, it is easy to maintain a uniform distribution of boron in the ferrite particles. Then, by firing the molded body in a state where boron is uniformly distributed throughout the molded body, the fine structure of the ferrite phase is uniformly formed in the entire sintered body (ferrite sintered magnet).

For the above reasons, it becomes possible to obtain ferrite particles and ferrite sintered magnets having excellent magnetic properties. Further, by mixing the whole amount of the raw material and the boron compound of the ferrite phase before the calcining step, the raw material and the boron compound are easily sintered from each other in the calcining step, so that the mechanical strength of the ferrite particles themselves is easily improved. Then, by sintering the ferrite particles having excellent mechanical strength with each other in the firing step, a ferrite sintered magnet having excellent mechanical strength can be obtained.

The ratio of the boron compound to the total mass of the raw material mixture is more than 0.3% by mass and 2.5% by mass or less in terms of the mass of boric acid. As a result, the content of boron in the ferrite particles or the ferrite sintered magnet can be easily adjusted to 0.1% by mass or _more and 0.6% by mass or less in terms of the mass of B2O3 _, and the ferrite particles and the ferrite sintered magnet can be easily adjusted. The magnetic characteristics of each are likely to improve. Since the magnetic properties of ferrite particles and ferrite sintered magnets tend to increase, the ratio of the boron compound to the total mass of the raw material mixture is 0.6% by mass or more and 1.5% by mass or less, or 0 in terms of the mass of boric acid. It may be 7.7% by mass or more and 1.2% by mass or less. For the same reason, the ratio of the boron compound to the total mass of the intermediate material containing the ferrite particles may be larger than 0.3% by mass and 2.5% by mass or less in terms of the mass of boric acid.

The boron compound preferably contains boric acid. The boron compound may consist only of boric acid. When the raw material mixture contains boric acid, the magnetic properties (particularly coercive force) of the ferrite particles and the ferrite sintered magnet are likely to be improved. The reason why the addition of boric acid to the raw material mixture improves the magnetic properties (particularly the coercive force) of the ferrite particles and the ferrite sintered magnet is as follows.

The solubility of boric acid in water is higher than the solubility of boron oxide in water. For example, the solubility of boric acid in water at 25 ° C. is about 5.7 g / 100 ml, and the solubility of boron oxide in water at 25 ° C. is about 3.6 g / 100 ml. Therefore, by mixing the raw material of the ferrite phase and boric acid with water, boric acid can be more uniformly dispersed at the molecular level in the raw material mixture than boron oxide. Further, since the specific gravity of boric acid (1.5 g / cm ³ ) is smaller than the specific gravity of boron oxide (1.9 g / cm ³ or more), boric acid is more easily dispersed by stirring and mixing than that of boron oxide. Furthermore, boric acid decomposes even at a relatively low temperature as compared with boron oxide. For example, boric acid decomposes at 171 ° C, while boron oxide decomposes at 450 ° C. Therefore, even if undissolved boric acid remains in the raw material mixture, boric acid is easily decomposed in the calcination step, and boron is easily dispersed uniformly in the ferrite particles.

Since there is a difference between boric acid and boron oxide as described above, variation in particle size of ferrite particles produced using boric acid is suppressed. Then, by sintering the ferrite particles having a substantially uniform particle size, a uniform fine structure is likely to be formed in the ferrite sintered magnet.

For the above reasons, the addition of boric acid to the raw material mixture tends to improve the magnetic properties (particularly the coercive force) of the ferrite particles and the ferrite sintered magnet.

When the raw material mixture contains silicon dioxide, the ratio of silicon dioxide to the total mass of the raw material mixture may be greater than 0% by mass and 5% by mass or less, or greater than 0% by mass and less than 0.2% by mass. Since the raw material mixture contains silicon dioxide, the raw material of the ferrite phase can be easily sintered in the calcining step, and ferrite particles having excellent magnetic properties can be easily obtained. That is, silicon dioxide functions as a sintering aid. Alternatively, since the intermediate material containing the ferrite particles contains silicon dioxide, the ferrite particles in the molded body can be easily sintered with each other in the firing step, and a ferrite sintered magnet having excellent magnetic properties can be easily obtained.

When the ratio of silicon dioxide in the raw material mixture before calcination is adjusted within the above range, silicon dioxide is not added to the ferrite particles (intermediate material before molding) obtained in the calcination step. It's okay. If the proportion of silicon dioxide in the mixture before calcination is outside the above range, the proportion of silicon dioxide in the intermediate material before molding may be adjusted within the above range. For example, if the proportion of silicon dioxide added to the mixture before the calcination step is too small, the proportion of silicon dioxide in the intermediate material can be increased by adding more silicon dioxide to the intermediate material before molding. It may be adjusted within the range.

The details of each process are as follows.

As described above, the method for manufacturing a ferrite sintered magnet may include a mixing step, a calcining step (heating step), a crushing step, a molding step, and a firing step. As described above, the mixing step and the calcining step in the method for manufacturing a ferrite sintered magnet correspond to the method for manufacturing ferrite particles.

In the mixing step, a plurality of raw materials for forming a ferrite phase and a boron compound are mixed to obtain a raw material mixture.

As described above, the raw materials for the ferrite phase are a compound of rare earth element R, a compound of alkaline earth metal element A, a compound of iron (Fe), and a compound of cobalt (Co). R is at least one element selected from rare earth elements. That is, R is scandium (Sc), yttrium (Y), lantern (La), cerium (Ce), placeodim (Pr), neodym (Nd), samarium (Sm), europium (Eu), gadrinium (Gd), terbium. It is at least one selected from the group consisting of (Tb), dysprosium (Dy), formium (Ho), elbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). A is a combination of at least one alkaline earth metal element other than calcium and calcium, or only calcium. The alkaline earth metal element other than calcium may be at least one of Sr and Ba. The raw material may be, for example, an oxide of each of R, A, Fe and Co, or a compound (carbonate, hydroxide, nitrate, etc.) that becomes these oxides by firing. Specific examples of raw materials include SrCO ₃ , La (OH) ₃ , Fe ₂ O ₃ , BaCO ₃ , CaCO ₃ and Co ₃ O ₄ . The raw material is preferably, for example, a powder. The average particle size of the raw material powder may be, for example, about 0.1 to 2.0 μm from the viewpoint of facilitating the blending of the raw materials.

The metal component contained in the ferrite phase (magnetoplumbite-type ferrite) formed from the above raw materials is represented by the following general formula (I). The atomic ratio x (molar ratio) in the general formula (I) satisfies the following formula (1). The atomic ratio y (molar ratio) in the general formula (I) satisfies the following formula (2). The atomic ratio m (molar ratio) in the general formula (I) satisfies the following formula (3).
R _{1-x A x} F my _Coy (I)
0.2 ≤ x ≤ 0.8 (1)
0.1 ≤ y ≤ 0.65 (2)
3 ≤ m <14 (3)

The ferrite phase (magnetoplumbite-type ferrite) is an oxide of R _{1-x A x} F my _Coy . For example, the magnetoplumbite type ferrite may be represented by the following formula (Ia). The x, y and m of the following formula (Ia) are the same as the x, y and m of the above formula (I). As long as the hexagonal structure of the magnetoplumbite-type ferrite is established, the atomic ratio z (molar ratio) of O in the following formula (Ia) is not limited. z may satisfy, for example, 11 <z <27. z may be 19. In a part of the ferrite particles or the ferrite sintered magnet, z may vary in the vicinity of 19.
R _{1-x A x} Fe my _{Coy Oz} (Ia)

The ratio of the rare earth element R to the total mass of the raw material mixture is 5.5% by mass or more and 19.9% by mass or less in terms of the mass of the oxide of R. When the ratio of the compound of R is 5.5% by mass or more and 19.9% by mass or less, the atomic ratio (1-x) of R in the above general formulas (I) and (Ia) is 0.2 ≦. It is easy to adjust to the range of 1-x ≦ 0.8.

The ratio of the compound of the alkaline earth metal element A to the total mass of the raw material mixture is 1.7% by mass or more and 7.6% by mass or less in terms of the mass of the oxide of A. Since the ratio of the compound of A is 1.7% by mass or more and 7.6% by mass or less, the atomic ratio x of A in the above general formulas (I) and (Ia) is 0.2 ≦ x ≦ 0. It is easy to adjust to the range of 8, and the atomic ratio (1-x) of R is easy to adjust to the range of 0.2 ≦ 1-x ≦ 0.8.

The ratio of the iron compound to the total mass of the raw material mixture is 45.3% by mass or more and 87.4% by mass or less in terms of the mass of iron oxide. Since the ratio of iron oxide is 45.3% by mass or more and 87.4% by mass or less, the atomic ratio (my) of Fe in the above general formulas (I) and (Ia) is 2.35. It is easy to adjust to the range of ≦ my <13.9.

The ratio of the cobalt compound to the total mass of the raw material mixture is 0.9% by mass or more and 18.9% by mass or less in terms of the mass of the cobalt oxide. Since the ratio of the cobalt oxide is 0.9% by mass or more and 18.9% by mass or less, the atomic ratio y of Co in the general formulas (I) and (Ia) is 0.1 ≦ y ≦ 0. It is easy to adjust to the range of 65, and the atomic ratio (my) of Fe is easy to adjust to the range of 2.35 ≦ my <13.9.

In the mixing step, each raw material and the boron compound are mixed so that the compounding ratio (mass ratio) of each raw material of the ferrite phase matches the composition represented by the general formula (I). Further, in the mixing step, the ratio of the boron compound to the total mass of the raw material mixture is adjusted to 2.5% by mass or less, which is larger than 0.3% by mass in terms of the mass of boric acid. Each of the mixed raw materials and the boron compound is mixed and pulverized for about 0.1 to 20 hours using a wet attritor, a ball mill or the like to obtain a raw material mixture. In the mixing step, a raw material (elemental substance or oxide, etc.) as an auxiliary component may be added to the raw material mixture, if necessary. By mixing and pulverizing each raw material, boron compound and water by a wet method, it is easy to obtain a raw material mixture in which the boron compound is uniformly dispersed.

In the calcining step (heating step), the raw material mixture obtained in the mixing step is calcined. By the calcination step, granular or lumpy calcination powder (coarse ferrite particles) is obtained. The calcining is preferably performed in an oxidizing atmosphere such as air. The temperature of the calcination may be 1100 to 1400 ° C, 1100 to 1300 ° C, or 1100 to 1250 ° C. The calcination time may be 1 second to 10 hours, or 1 second to 3 hours. The ratio of the ferrite phase (M phase) in the calcined powder (ferrite particles) obtained by calcining may be, for example, 70% by volume or more, or 75% by volume or more. The ratio of the ferrite phase is obtained by the same method as the ratio of the ferrite phase in the ferrite sintered magnet. If necessary, the following pulverization steps are carried out to complete the ferrite particles.

In the crushing step, the calcined powder (coarse ferrite particles) is crushed. The pulverization step may include, for example, a coarse pulverization step of coarsely pulverizing the calcination powder, and a fine pulverization step of further pulverizing the calcination powder following the coarse pulverization step. That is, the crushing step may be performed in two steps.

In the coarse pulverization step, for example, a vibration mill or the like may be used. The average particle size of the powder (coarse pulverized material) obtained by coarse pulverization of the calcination powder may be 0.5 to 5.0 μm. In the fine pulverization step, the coarse pulverized material is further pulverized by a wet attritor, a ball mill, a jet mill or the like. The average particle size of the pulverized material obtained by pulverization may be about 0.08 to 2.0 μm, 0.1 to 1.0 μm, or 0.2 to 0.8 μm. The specific surface area (BET specific surface area) of the finely pulverized material may be about 7 to 12 m ² / g. The suitable grinding time depends on the grinding method. For example, in the case of a wet attritor, the pulverization time may be 30 minutes to 10 hours. The time of wet pulverization by a ball mill may be about 10 to 50 hours.

When forming a ferrite sintered magnet from ferrite particles, the following steps are further carried out.

When forming a ferrite sintered magnet from ferrite particles, silicon dioxide may be added to the calcined powder prior to the pulverization step. Silicon dioxide may be added to the calcined powder at the time point between the coarse grinding step and the fine grinding step.

In the fine pulverization step, in order to increase the degree of magnetic orientation of the sintered body (ferrite sintered magnet) obtained in the firing step, for example, the polyhydric alcohol represented by the general formula C _n (OH) _n H _{n + 2} is transferred to the coarse pulverized material. May be added. N in the general formula for polyhydric alcohols may be 4 to 100, 4 to 30, 4 to 20 or 4 to 12. Examples of the polyhydric alcohol include sorbitol. Further, two or more kinds of polyhydric alcohols may be used in combination. Further, in addition to the polyhydric alcohol, other dispersants may be used in combination.

The amount of the polyhydric alcohol added is 0.05 to 5.0% by mass, 0.1 to 3.0% by mass, or 0.2 to 2.0% by mass with respect to the object to be added (for example, ferrite particles). May be%. The polyhydric alcohol added in the fine pulverization step is removed by thermal decomposition in the firing step described later.

By the above steps, an intermediate material containing ferrite particles can be obtained. In addition to the ferrite particles, the intermediate material may contain at least one selected from the group consisting of a sintering aid (silicon dioxide and the like), water, a polyhydric alcohol, and a dispersant. The intermediate material may be a slurry containing water.

In the molding step, an intermediate material containing ferrite particles is molded in a magnetic field to obtain a molded product. Molding can be performed by either drywall molding or wet molding. Wet molding is preferable from the viewpoint of increasing the degree of magnetic orientation.

In the case of wet molding, for example, by performing the above-mentioned fine pulverization step in a wet manner, a slurry of an intermediate material containing ferrite particles is obtained, and then this slurry is concentrated to obtain a slurry for wet molding. This wet molding slurry is molded. The slurry can be concentrated by centrifugation, filter press, or the like. The content of ferrite particles (finely pulverized material) in the wet forming slurry may be 30 to 80% by mass. In the slurry, water is preferable as the dispersion medium for dispersing the ferrite particles. In this case, a surfactant such as gluconic acid, gluconate, and sorbitol may be added to the slurry. Moreover, you may use a non-aqueous solvent as a dispersion medium. As the non-aqueous solvent, an organic solvent such as toluene or xylene can be used. In this case, it is preferable to add a surfactant such as oleic acid to the non-aqueous solvent. A wet molding slurry may be prepared by adding a dispersion medium or the like to the dried ferrite particles.

When the wet molding slurry is molded in a magnetic field, the molding pressure may be about 9.8 to 49 MPa (0.1 to 0.5 ton / cm ² ), and the applied magnetic field is 398 to 1194 kA / m (5). It may be about ~ 15 kOe).

In the firing step, the molded body obtained in the molding step is sintered to obtain a sintered body (ferrite sintered magnet). That is, a ferrite sintered magnet is formed by sintering the innumerable ferrite particles (fine pulverized materials) constituting the molded body to each other.

Firing can be performed in an oxidizing atmosphere such as the atmosphere. The firing temperature may be 1050 to 1270 ° C, or 1080 to 1240 ° C. The firing time (time for maintaining the firing temperature) may be about 0.5 to 3 hours.

When the molded product produced by wet molding is fired without being sufficiently dried, the dispersion medium or the like in the molded product may violently volatilize due to rapid heating, and cracks may occur in the molded product. From the viewpoint of suppressing cracks, before heating the molded body at the above firing temperature, the molded body is sufficiently dried by heating, for example, from room temperature to about 100 ° C. at a heating rate of about 0.5 ° C./min. It's okay. When the molded product contains a surfactant (dispersant) or the like, for example, the molded product is heated at a heating rate of about 2.5 ° C./min in a temperature range of about 100 to 500 ° C. to obtain a surfactant (a surfactant). Dispersant) and the like may be removed (defatting treatment). These heat treatments may be carried out at the beginning of the firing step, or may be carried out as a separate step prior to the firing step.

By the above steps, the ferrite sintered magnet is completed.

The above-mentioned molding step and firing step may be performed by the following procedure.

The molding step may be performed by a CIM (Ceramic Injection Molding) molding method or a PIM (Power Injection Molding, a type of powder injection molding). In the CIM molding method, first, a dried intermediate material (a type of powder injection molding) may be used. Ferrite particles) are heat-kneaded together with a binder resin to form pellets. The pellets are injection-molded in a mold to which a magnetic field is applied to obtain a preformed body. By debindering the preformed body. A molded product is obtained. A more detailed procedure will be described below.

The slurry of the intermediate material (slurry containing ferrite particles) obtained by wet grinding is dried. The drying temperature is preferably 80 to 150 ° C, more preferably 100 to 120 ° C. The drying time is preferably 1 to 40 hours, more preferably 5 to 25 hours. The average particle size of the primary particles of the intermediate material (ferrite particles) after drying is preferably 0.08 to 2 μm, more preferably 0.1 to 1 μm.

The dried intermediate material is kneaded with organic components such as binder resin, waxes, lubricants, plasticizers, and sublimable compounds, and molded into pellets with a pelletizer or the like. The proportion of the organic component in the molded product is preferably 35 to 60% by volume, more preferably 40 to 55% by volume. The kneading may be performed by, for example, a kneader. As the pelletizer, for example, a twin-screw single-screw extruder is used. Kneading and pellet molding may be carried out while heating depending on the melting temperature of the organic component used.

As the binder resin, a polymer compound such as a thermoplastic resin is used. Examples of the thermoplastic resin include polyethylene, polypropylene, ethylene vinyl acetate copolymer, atactic polypropylene, acrylic polymer, polystyrene, polyacetal and the like.

As the waxes, in addition to natural waxes such as carnauba wax, montan wax and beeswax, synthetic waxes such as paraffin wax, urethanized wax and polyethylene glycol are used.

Examples of the lubricant include fatty acid esters and the like. Examples of the plasticizer include phthalates.

The amount of the binder resin added is preferably 3 to 20% by mass with respect to 100% by mass of the ferrite particles. The amount of wax added is preferably 3 to 20% by mass with respect to 100% by mass of the ferrite particles. The amount of the lubricant added is preferably 0.1 to 5% by mass with respect to 100% by mass of the ferrite particles. The amount of the plasticizer added is preferably 0.1 to 5% by mass with respect to 100% by mass of the binder resin.

Next, the pellets are injected into the mold using a magnetic field injection molding device to form the pellets. Before the pellet is injected into the mold, the mold is closed and a magnetic field is applied to the mold with a cavity formed inside the mold. Inside the extruder, the pellets are heated and melted to 160-230 ° C. and ejected into the mold cavity by a screw. The temperature of the mold may be 20 to 80 ° C. The magnetic field applied to the mold may be 398 to 1592 kA / m (5 to 20 kOe). By such injection molding, a preformed body is obtained.

The obtained preformed body is heat-treated at a temperature of 100 to 600 ° C. in the air or nitrogen to perform a binder removal treatment to obtain a molded product. When a plurality of kinds of organic components are used, the binder removal treatment may be carried out in a plurality of times.

In the firing step, the molded body that has undergone the binder removal treatment is sintered in the air to obtain a ferrite sintered magnet. The firing temperature may be preferably 1100 to 1250 ° C, more preferably 1160 to 1230 ° C, and the firing time may be about 0.2 to 3 hours.

(Manufacturing method of bond magnet)
The method for manufacturing a bonded magnet in the present embodiment includes a step of manufacturing a molded body containing the ferrite particles and the resin manufactured by the above method, and a step of curing the resin in the molded body to obtain a bonded magnet. To prepare for. For example, a bonded magnet can be obtained by impregnating a molded product produced by the above molding step with a thermosetting resin and curing the thermosetting resin in the molded product by heating. The details of the manufacturing method of the bonded magnet are as follows.

The molded product is immersed in the resin-containing solution in the container. Seal the container containing the molded product and the resin-containing solution. The reduced pressure in the closed container defoams the molded body and allows the resin-containing solution to permeate into the voids in the molded body. The defoamed molded product is taken out from the resin-containing solution, and the excess resin-containing solution adhering to the surface of the molded product is removed. A centrifuge or the like may be used to remove the excess resin-containing solution.

Before immersing the molded body in the resin-containing solution, the molded body and the solvent (toluene, etc.) are placed in a closed container, and the molded body is immersed in the solvent while reducing the pressure inside the container to defoam the molded body. Is promoted. As a result, the resin easily penetrates into the molded body, and the voids in the molded body are easily reduced.

The method for manufacturing a bonded magnet is not limited to the above example. For example, a compound may be prepared by mixing ferrite particles and a resin, and the compound may be molded in a magnetic field to prepare a molded product containing the ferrite particles and the resin.

(Ferrite sintered magnet and ferrite particles)
The ferrite sintered magnet and the ferrite particles have a ferrite phase (main phase) having a magnetoplobite type crystal structure. The main phase refers to the crystal phase most contained in ferrite sintered magnets and ferrite particles. The ferrite sintered magnet and the ferrite particles may have a crystal phase (different phase) different from that of the main phase.

The metal component contained in the ferrite phase is represented by the following general formula (I) and satisfies the following formulas (1), (2) and (3). In the general formula (I), x, y and m are atomic ratios (molar ratios). As described above, R in the general formula (I) is at least one element selected from rare earth elements. A is a combination of Ca with at least one selected from Sr and Ba, or only Ca.
R _{1-x A x} F my _Coy (I)
0.2 ≤ x ≤ 0.8 (1)
0.1 ≤ y ≤ 0.65 (2)
3 ≤ m <14 (3)

X in the general formula (I) may be 0.7 or less, or may be 0.6 or less, from the viewpoint of further increasing the coercive force. From the same viewpoint, x may be 0.25 or more, or may be 0.3 or more. Y in the general formula (I) may be 0.6 or less or 0.5 or less from the viewpoint of further enhancing the magnetic characteristics. From the same viewpoint, y in the general formula (I) may be 0.15 or more, or may be 0.2 or more. M in the general formula (I) may be 4 or more or 5 or more from the viewpoint of further increasing the coercive force. From the same viewpoint, m in the general formula (I) may be 13 or less, or may be 12 or less.

From the viewpoint of enhancing the magnetic properties, it is preferable that A in the general formula (I) contains Ca and Sr as main components. A may consist only of Ca and Sr. From the viewpoint of increasing the magnetic properties, A may be Ca alone.

The metal component contained in the ferrite phase may be represented by the following general formula (II), and may satisfy the following formulas (4), (5), (6) and (7). In the general formula (II), x1, x2, y and m indicate the atomic ratio (molar ratio). X in the above general formula (I) is equal to x1 + x2 in the following general formula (II). R in the general formula (II) is at least one element selected from rare earth elements. E in the general formula (II) represents at least one element selected from the group consisting of Sr and Ba.
R _{1-x1-x2 Ca x1} E _x2 Fe my _Coy (II)
0.1 ≤ x 1 ≤ 0.65 (4)
0≤x2 <0.5 (5)
0.1 ≤ y ≤ 0.65 (6)
3 ≤ m <14 (7)

X1 in the general formula (II) may be 0.7 or less, or may be 0.6 or less, from the viewpoint of further increasing the coercive force. From the same viewpoint, x1 may be 0.20 or more, or may be 0.3 or more. X2 in the general formula (II) may be 0.4 or less or 0.3 or less from the viewpoint of further increasing the coercive force. X2 in the general formula (II) may be 0.

Y in the general formula (II) may be 0.6 or less or 0.5 or less from the viewpoint of further enhancing the magnetic characteristics. From the same viewpoint, y in the general formula (II) may be 0.15 or more, or may be 0.2 or more. The m in the general formula (II) may be 4 or more or 5 or more from the viewpoint of further increasing the coercive force. From the same viewpoint, m in the general formula (II) may be 13 or less, or may be 12 or less.

The content ratio of each element represented by the general formula (I) and the general formula (II) can be measured by fluorescent X-ray analysis. The content ratio of each element represented by the general formula (I) and the general formula (II) may be the same as the ratio of each element in the above-mentioned raw material mixture. The boron content can be measured by inductively coupled plasma emission spectroscopy (ICP emission spectroscopy).

The content of B in the ferrite sintered magnet and the ferrite particles is 0.1 to 0.6% by mass in terms of B ₂ O ₃ . From the viewpoint of further enhancing the magnetic properties, the content of B may be 0.5% by mass or less, or 0.4% by mass or less. From the same viewpoint, the content of B may be 0.1% by mass or more, 0.14% by mass or more, or more than 0.2% by mass.

E in the general formula (II) preferably contains Sr as a main component from the viewpoint of enhancing the magnetic properties. E may consist only of Sr.

R in the general formula (I) and the general (II) preferably contains one or more elements selected from the group consisting of La, Ce, Pr, Nd and Sm. It is more preferable that R contains La. R may consist only of La.

The ferrite sintered magnet and the ferrite particles may contain an element not represented by the above general formula (I) or (II) as a sub-component. Examples of the sub-ingredients include Si and Na. These subcomponents may be contained in the ferrite sintered magnet and the ferrite particles as, for example, the respective oxides or composite oxides.

The content of Si in the ferrite sintered magnet and the ferrite particles may be, for example, 0 to 3% by mass in terms of the mass of SiO ₂ .

The Na content in ferrite sintered magnets and ferrite particles is, for example, 0 to 0.2% by mass, 0.01 to 0.15% by mass, or 0.02 to 0.1% by mass in terms of mass of Na _2O . May be%.

Ferrite sintered magnets and ferrite particles may contain unavoidable impurities in addition to the above-mentioned components. Examples of this unavoidable impurity include Ti (titanium), Cr (chromium), Mn (manganese), Mo (molybdenum), V (vanadium), Al (aluminum) and the like. These components may be contained in the ferrite sintered magnet and the ferrite particles as the respective oxides or composite oxides. The contents of the above-mentioned sub-components, impurities and unavoidable components can be measured by fluorescent X-ray analysis or ICP emission spectroscopic analysis. The sub-component may be segregated at the grain boundaries of the ferrite crystal grains in the ferrite sintered magnet to form a heterogeneous phase.

The average particle size of ferrite particles (crystal grains containing a ferrite phase) 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. May be good. When the ferrite particles have the above average particle size, the coercive force can be further increased. The average particle size of the crystal grains in the ferrite sintered magnet may be measured by observing the cross section of the ferrite sintered magnet with a transmission electron microscope (TEM) or a scanning electron microscope (SEM). Image processing of an image of a cross section containing hundreds of crystal grains measures a particle size distribution based on the number of crystal grains contained in the cross section. From this particle size distribution, the average particle size based on the number of crystal grains is calculated. The average particle size of the powdery ferrite particles may be measured, for example, by a particle size distribution meter.

The shape of the ferrite sintered magnet is not limited. For example, the shape of the ferrite sintered magnet may be one selected from the group consisting of an arc segment type, a C-shape, a tile shape, a flat plate, a polygonal column, a cylinder, and an arch shape.

(Bond magnet)
The bonded magnet contains a cured resin and a plurality of the above-mentioned ferrite particles bonded to each other via the resin. The resin may be a thermosetting resin such as an epoxy resin, a phenol resin, a resin having a polyaromatic ring, or a resin having a triazine ring (triazine resin). The resin may include a polyamide-based elastomer such as styrene-based, olefin-based, urethane-based, polyester-based, and nylon, and a thermoplastic resin such as ionomer, ethylene propylene copolymer (EPM), and ethylene-ethyl acrylate copolymer. ..

The resin content in the bonded magnet may be, for example, 0.5 to 10% by mass from the viewpoint of achieving both excellent magnetic properties and excellent mechanical strength (stability of the shape of the magnet). It may be up to 5% by mass. From the same viewpoint, the content of ferrite particles in the bonded magnet may be, for example, 90 to 99.5% by mass or 95 to 99% by mass. The resin content in the bond magnet is adjusted by the concentration of the resin in the resin-containing solution used for production, the molding pressure in the molding process, and the like.

The shape of the bond magnet is not limited. For example, the shape of the bond magnet may be one selected from the group consisting of an arc segment shape, a C shape, a tile shape, a flat plate, a polygonal prism, a cylinder, and an arch shape.

(Use of ferrite sintered magnets and bonded magnets)
The ferrite sintered magnet and the bonded magnet according to this embodiment are excellent in magnetic properties. Therefore, even if the ferrite sintered magnet and the bond magnet are thinly processed for mounting on a small motor and generator, the efficiency of the motor or generator can be maintained at a sufficiently high level. ..

Ferrite sintered magnets and bond magnets are used, for example, for fuel pumps, power windows, ABS (anti-lock braking system), fans, wipers, power steering, active suspensions, starters, and door locks. , Can be used as a magnet for automobile motors such as for electric mirrors. Also, for FDD spindles, VTR capstans, VTR rotating heads, VTR reels, VTR loadings, VTR camera capstans, VTR camera rotating heads, VTR camera zooms, VTR camera focus, radio cassettes, etc. Ferrite sintered magnets and bonded magnets can be used as magnets for OA / AV equipment motors for CD / DVD / MD spindles, CD / DVD / MD loading, CD / DVD optical pickups, and the like. Further, ferrite sintered magnets and bond magnets can also be used as magnets for motors for home appliances such as air conditioner compressors, freezer compressors, electric tool drives, dryer fans, shaver drives, and electric toothbrushes. .. Furthermore, ferrite sintered magnets and bond magnets can also be used as magnets for FA equipment motors such as robot shafts, joint drives, robot main drives, machine equipment table drives, and machine equipment belt drives. ..

The contents of 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.

(Example 1)
[Manufacturing of ferrite sintered magnets]
<Mixing process>
Lanthanum hydroxide (La (OH) ₃ ), calcium carbonate (CaCO ₃ ), iron oxide (Fe ₂ O ₃ ) and cobalt oxide (Co ₃ O ₄ ) were used as raw materials for the ferrite phase. Boric acid (H ₃ BO ₃ ) was used as the boron compound. A slurry of a raw material mixture was prepared by mixing and pulverizing the above raw materials, boric acid, silicon dioxide (SiO ₂ ) and water for 10 minutes using a wet attritor. As described below, the proportion of each raw material in the raw material mixture was adjusted to match the composition of the metal component of the ferrite phase (component represented by the following general formula (Ib)) shown in Table 1 below. In the mixing step, the raw material of the ferrite phase used for manufacturing the ferrite sintered magnet and the total amount of boric acid were mixed.
La _{1-x Ca x} F my _Coy (Ib)

The ratio of the lanthanum compound (La (OH) ₃ ) in the raw material mixture was adjusted to the value (unit: mass%) shown in Table 1 below in terms of mass of La ₂ O ₃ .
The ratio of the calcium compound (CaCO ₃ ) in the raw material mixture was adjusted to the value (unit: mass%) shown in Table 1 below in terms of mass of CaO.
The ratio of the iron compound in the raw material mixture was the value (unit: mass%) shown in Table 1 below in terms of mass of Fe ₂ O ₃ .
The ratio of the cobalt compound in the raw material mixture was adjusted to the value (unit: mass%) shown in Table 1 below in terms of mass of Co ₃ O ₄ .
The ratio of the boron compound in the raw material mixture was adjusted to the value (unit: mass%) shown in Table 1 below in terms of mass of H ₃ BO ₃ .
The ratio of silicon dioxide (addition amount of SiO ₂ ) in the raw material mixture was adjusted to 0.19% by mass.

<Take-baking process (heating process)>
After drying the slurry of the raw material mixture, the raw material mixture was held at 1280 ° C. for 2 hours in the air to obtain calcined powder (coarse ferrite particles).

<Crushing process>
In the coarse pulverization step, the calcination powder was pulverized with a vibration mill for 9 minutes to adjust the BET specific surface area of the calcination powder to the range of 0.5 to 1.5 m ² / g. In the fine pulverization step following the coarse pulverization step, the calcined powder was further mixed and pulverized with a wet ball mill for 36 hours to obtain a slurry containing ferrite particles (slurry of an intermediate material). The BET specific surface area of the ferrite particles in the slurry was in the range of 7 to 10 m ² / g.

<Molding process>
The slurry of the intermediate material was dehydrated by a centrifuge to adjust the concentration of the solid content in the slurry within the range of 73 to 76% to obtain a slurry for wet molding. This slurry was molded in an applied magnetic field of 10 kOe to obtain a cylindrical molded body. A wet magnetic field molding machine was used for molding.

<Baking process>
The molded product was sufficiently dried in the air at room temperature. The dried molded body was held in the air at 1175 ° C. for 1 hour to obtain a sintered body (ferrite sintered magnet of Example 1).

[Analysis of composition]
The composition of the ferrite sintered magnet was analyzed by XRF method and ICP emission spectroscopy. The composition of the metal component contained in the ferrite sintered magnet of Example 1 is represented by the above general formula (1b), and the values of 1-x, x, my and y in the general formula (1b) are , It was confirmed that the values are shown in Table 1 below. It was confirmed that the content of boron in the ferrite sintered magnet is the value shown in Table 1 below in terms of the mass of boric acid (H ₃ BO ₃ ). It was confirmed that the content of boron in the ferrite sintered magnet is the value shown in Table 1 below in terms of the mass of elemental boron (B). It was confirmed that the content of boron in the ferrite sintered magnet is the value shown in Table 1 below in terms of mass of boron oxide ( _{B2O 3 )} .

[Measurement of magnetic characteristics]
After processing the upper surface and the lower surface of the cylindrical ferrite sintered magnet, the residual magnetic flux density Br (mT) and the coercive force HcJ (kA / m) of the ferrite sintered magnet were measured. A BH tracer having a maximum applied magnetic field of 25 kOe was used for the measurement. Br, HcJ and square ratio (Hk / HcJ) of Example 1 are shown in Table 1 below.

(Examples 2 to 9)
The ratio of boric acid (addition amount of H ₃ BO ₃ ) in each of the raw material mixtures of Examples 2 to 9 was adjusted to the value (unit: mass%) shown in Table 1 below. Ferrite sintered magnets of Examples 2 to 9 were produced in the same manner as in Example 1 except for the proportion of boric acid in the raw material mixture. The composition of each of the ferrite sintered magnets of Examples 2 to 9 was analyzed by the same method as in Example 1. The results of the analysis are shown in Table 1 below. The magnetic properties of the ferrite sintered magnets of Examples 2 to 9 were measured by the same method as in Example 1. The measurement results are shown in Table 1 below.

(Examples 10 to 13, Comparative Examples 1 to 4)
In Examples 10 to 13 and Comparative Examples 1 to 4, the ratio of each raw material (La compound, Ca compound, Fe compound, Cо compound) and boric acid in the raw material mixture is each value (unit:) shown in Table 1 below. Weight%) was adjusted. Ferrite sintered magnets of Examples 10 to 13 and Comparative Examples 1 to 4 were produced in the same manner as in Example 1 except for the composition of the raw material mixture. The compositions of the ferrite sintered magnets of Examples 10 to 13 and Comparative Examples 1 to 4 were analyzed by the same method as in Example 1. The results of the analysis are shown in Table 1 below. The magnetic properties of the ferrite sintered magnets of Examples 10 to 13 and Comparative Examples 1 to 4 were measured by the same method as in Example 1. The measurement results are shown in Table 1 below.

(Examples 14 to 16)
In Examples 14 to 16, boron oxide was used as the boron compound instead of boric acid. The ratio of boron oxide in each of the raw material mixtures of Examples 14 to 16 was adjusted to the value (unit: mass%) shown in Table 1 below in terms of mass of H ₃ BO ₃ . Except for these matters, ferrite sintered magnets of Examples 14 to 16 were produced in the same manner as in Example 1. The composition of each of the ferrite sintered magnets of Examples 14 to 16 was analyzed by the same method as in Example 1. The results of the analysis are shown in Table 1 below. The magnetic properties of the ferrite sintered magnets of Examples 14 to 16 were measured by the same method as in Example 1. The measurement results are shown in Table 1 below. It is preferable that Br is 310 mT or more, HcJ is 478 kA / m or more, and Hk / HcJ is 71% or more.

(Comparative Examples 21 and 22)
The mass of each raw material (lanthanum hydroxide, calcium carbonate, iron oxide and cobalt oxide) used in Comparative Examples 21 and 22 was the same as the mass of each raw material used in Example 5.

The total amount of boric acid used in Comparative Example 21 was 1.0% by mass with respect to the total mass of the raw material mixture of Comparative Example 21. However, in the mixing step of Comparative Example 21, 0.5% by mass of boric acid out of 1.0% by mass of boric acid was added to the raw material mixture. The remaining 0.5% by mass of boric acid was added to the calcined powder (ferrite particles) in the fine pulverization step after the calcining step.

The total amount of boric acid used in Comparative Example 22 was 1.0% by mass with respect to the total mass of the raw material mixture of Comparative Example 22. However, in the mixing step of Comparative Example 22, boric acid was not added to the raw material mixture. In the case of Comparative Example 22, the entire amount of boric acid was added to the calcined powder (ferrite particles) in the fine pulverization step after the calcining step.

Ferrite sintered magnets of Comparative Examples 21 and 22 were produced in the same manner as in Example 5 except for the timing of addition of boric acid. The compositions of the ferrite sintered magnets of Comparative Examples 21 and 22 were analyzed by the same method as in Example 1. The composition of the metal component of the ferrite phase of Comparative Examples 21 and 22 was the same as the composition of the metal component of the ferrite phase of Example 5. The boron content in the ferrite sintered magnets of Comparative Examples 21 and 22 was the value shown in Table 2 below in terms of mass of boric acid (H ₃ BO ₃ ). The magnetic properties of the ferrite sintered magnets of Comparative Examples 21 and 22 were measured by the same method as in Example 1. The measurement results are shown in Table 2 below.

(Comparative Examples 31 to 34)
The mass of each raw material (lanthanum hydroxide, calcium carbonate, iron oxide and cobalt oxide) used in Comparative Examples 31 to 34 was the same as the mass of each raw material used in Example 5. The mass of boric acid used in Comparative Examples 31 to 34 was also the same as the mass of boric acid used in Example 5.

In the mixing step of Comparative Example 31, 50 parts by mass of iron oxide out of the total amount of iron oxide (100 parts by mass) was added to the raw material mixture. The remaining 50 parts by mass of iron oxide was added to the calcined powder (ferrite particles) in the fine pulverization step after the calcining step.

In the mixing step of Comparative Example 32, cobalt oxide was not added to the raw material mixture. In the case of Comparative Example 32, the entire amount (100 parts by mass) of cobalt oxide was added to the calcined powder (ferrite particles) in the fine pulverization step after the calcining step.

In the mixing step of Comparative Example 33, lanthanum hydroxide was not added to the raw material mixture. In the case of Comparative Example 33, the entire amount (100 parts by mass) of lanthanum hydroxide was added to the calcined powder (ferrite particles) in the fine pulverization step after the calcining step.

In the mixing step of Comparative Example 34, calcium carbonate was not added to the raw material mixture. In the case of Comparative Example 34, in the fine pulverization step after the calcination step, the entire amount (100 parts by mass) of calcium carbonate was added to the calcination powder (ferrite particles).

Ferrite sintered magnets of Comparative Examples 31 to 34 were produced by the same method as in Example 5 except for the timing of addition of each raw material for the above ferrite phase. The composition of each of the ferrite sintered magnets of Comparative Examples 31 to 34 was analyzed by the same method as in Example 1. The composition of the metal component of the ferrite phase of each of Comparative Examples 31 to 34 was the same as the composition of the metal component of the ferrite phase of Example 5. The content of boron in each of the ferrite sintered magnets of Comparative Examples 31 to 34 was the same as that of Example 5 in terms of the mass of boric acid (H ₃ BO ₃ ). The content of boron in each of the ferrite sintered magnets of Comparative Examples 31 to 34 was the same as that of Example 5 in terms of the mass of elemental boron (B). The content of boron in each of the ferrite sintered magnets of Comparative Examples 31 to 34 was the same as that of Example 5 in terms of the mass of boron oxide ( _{B2O 3 )} . The magnetic properties of the ferrite sintered magnets of Comparative Examples 31 to 34 were measured by the same method as in Example 1. The measurement results are shown in Table 3 below.

According to the present invention, ferrite particles, ferrite sintered magnets and bonded magnets having excellent magnetic properties are provided. The ferrite sintered magnet or the above-mentioned bonded magnet according to the present invention is applied to, for example, a permanent magnet for a motor.

Claims (5)

A method for manufacturing a ferrite sintered magnet containing a ferrite phase having a magnetoplumbite-type crystal structure.
A calcining step of producing ferrite particles by calcining a mixture containing the raw material of the ferrite phase, a boron compound, and silicon dioxide .
A molding process for producing a molded product from the ferrite particles, and
The firing process for sintering the molded product and
Equipped with
The raw materials for the ferrite phase used in the production of the ferrite sintered magnet , the boron compound, and the total amount of the silicon dioxide are mixed before the calcining step.
The raw materials for the ferrite phase are a compound of rare earth element R, a compound of alkaline earth metal element A, a compound of iron, and a compound of cobalt.
R is at least one element selected from rare earth elements,
A is a combination of at least one alkaline earth metal element other than calcium and calcium, or only calcium.
The ratio of the compound of R to the total mass of the mixture is 5.5% by mass or more and 19.9% by mass or less in terms of the mass of the oxide of R.
The ratio of the compound of A to the total mass of the mixture is 1.7% by mass or more and 7.6% by mass or less in terms of the mass of the oxide of A.
The ratio of the iron compound to the total mass of the mixture is 45.3% by mass or more and 87.4% by mass or less in terms of the mass of iron oxide.
The ratio of the cobalt compound to the total mass of the mixture is 0.9% by mass or more and 18.9% by mass or less in terms of the mass of the cobalt oxide.
The ratio of the boron compound to the total mass of the mixture is more than 0.3% by mass and 2.5% by mass or less in terms of the mass of boric acid.
The ratio of the silicon dioxide to the total mass of the mixture is greater than 0% by mass and 0.19% by mass or less.
The metal component contained in the ferrite phase is represented by R _{1-x A x} F my _Coy .
x satisfies 0.2 ≦ x ≦ 0.8,
y satisfies 0.1 ≦ y ≦ 0.65,
m satisfies 3 ≦ m <14,
The content of boron in the ferrite sintered magnet is 0.1% by mass or _more and 0.6% by mass or less in terms of mass of _B2O3 .
Manufacturing method of ferrite sintered magnet. The boron compound contains boric acid.
The method for manufacturing a ferrite sintered magnet according to claim 1. A method for producing ferrite particles containing a ferrite phase having a magnetoplumbite-type crystal structure.
A heating step for producing ferrite particles by heating a mixture containing the raw material of the ferrite phase, a boron compound and silicon dioxide is provided.
The raw material of the ferrite phase used for producing the ferrite particles , the boron compound, and the total amount of the silicon dioxide are mixed before the heating step.
The raw materials for the ferrite phase are a compound of rare earth element R, a compound of alkaline earth metal element A, a compound of iron, and a compound of cobalt.
R is at least one element selected from rare earth elements,
A is a combination of at least one alkaline earth metal element other than calcium and calcium, or only calcium.
The ratio of the compound of R to the total mass of the mixture is 5.5% by mass or more and 19.9% by mass or less in terms of the mass of the oxide of R.
The ratio of the compound of A to the total mass of the mixture is 1.7% by mass or more and 7.6% by mass or less in terms of the mass of the oxide of A.
The ratio of the iron compound to the total mass of the mixture is 45.3% by mass or more and 87.4% by mass or less in terms of the mass of iron oxide.
The ratio of the cobalt compound to the total mass of the mixture is 0.9% by mass or more and 18.9% by mass or less in terms of the mass of the cobalt oxide.
The ratio of the boron compound to the total mass of the mixture is more than 0.3% by mass and 2.5% by mass or less in terms of the mass of boric acid.
The ratio of the silicon dioxide to the total mass of the mixture is greater than 0% by mass and 0.19% by mass or less.
The metal component contained in the ferrite phase is represented by R _{1-x A x} F my _Coy .
x satisfies 0.2 ≦ x ≦ 0.8,
y satisfies 0.1 ≦ y ≦ 0.65,
m satisfies 3 ≦ m <14,
The content of boron in the ferrite particles is 0.1% by mass or _more and 0.6% by mass or less in terms of mass of _B2O3 .
Method for manufacturing ferrite particles. The boron compound contains boric acid.
The method for producing ferrite particles according to claim 3. The process of manufacturing ferrite particles and
A step of producing a molded product containing the ferrite particles and a resin, and
The step of curing the resin in the molded body and
Equipped with
The ferrite particles are produced by the production method according to claim 3 or 4.
How to manufacture a bond magnet.