JPWO2014058067A1 - Method for producing Sr ferrite powder and sintered Sr ferrite magnet, motor and generator - Google Patents

Abstract

A mixture containing an iron compound powder, a strontium compound powder, and a compound powder containing Li as a constituent element is fired at 850 to 1050 ° C. to contain Sr ferrite having a hexagonal crystal structure, and Li is converted to Li 2 O. Then, a calcining step for obtaining a calcined body containing 0.01 to 0.5% by mass, a crushing step for crushing the calcined body to obtain a pulverized powder containing Sr ferrite, and molding the pulverized powder in a magnetic field. The obtained compact is fired at 1000 to 1250 ° C. to obtain a Sr ferrite sintered magnet, and a method for producing a Sr ferrite sintered magnet is provided.

Description

  The present invention relates to a method for producing Sr ferrite powder and a sintered Sr ferrite magnet, and a motor and a generator including an Sr ferrite sintered magnet obtained by the production method.

As a magnetic material used for a ferrite sintered magnet, Ba ferrite, Sr ferrite, and Ca ferrite having a hexagonal crystal structure are known. In recent years, among them, magnetoplumbite type (M type) Sr ferrite is mainly used as a magnet material for motors and the like. The M-type ferrite is represented by a general formula of AFe ₁₂ O ₁₉ , for example. Sr ferrite has Sr at the A site of the crystal structure.

  In order to improve the magnetic properties of sintered Sr ferrite magnets, attempts were made to improve the magnetic properties by substituting some elements of the A site and B site with rare earth elements such as La and Co, respectively. It has been. For example, Patent Document 1 discloses a technique for improving the residual magnetic flux density (Br) and the coercive force (HcJ) by replacing a part of the A site and the B site with a specific amount of rare earth element and Co. .

  Typical applications of Sr ferrite sintered magnets include motors and generators. Sr ferrite magnets used in motors and generators are required to be reduced in size and weight, and in order to cope with this, it is required to further increase the magnetic characteristics.

JP-A-11-154604

  As shown in Patent Document 1, it is effective to improve the magnetic characteristics by controlling the composition of main crystal grains constituting the Sr ferrite sintered magnet. However, even if only the composition of the crystal grains is controlled, it is difficult to greatly improve the magnetic characteristics of the conventional Sr ferrite sintered magnet. As another means for improving the magnetic characteristics of the Sr ferrite sintered magnet, it is conceivable to refine the structure. As a means for refining the structure, it can be considered that the calcined body used as a raw material of the sintered Sr ferrite magnet is atomized. As a method for atomizing the calcined body, a method of mechanically crushing the calcined body and lengthening the crushing time can be mentioned. However, when the mechanically pulverized in this way, the particle size distribution becomes wide. In addition, there are concerns that the manufacturing cost increases due to increased power consumption, equipment wear, and the like, and the yield decreases.

  As for Sr ferrite sintered magnets, anisotropic Sr ferrite sintered magnets that are crystal-oriented in the c-axis direction are currently mainstream. When an anisotropic Sr ferrite sintered magnet is manufactured, it is necessary to advance the ferritization reaction sufficiently in the calcining step in order to increase the orientation of the ferrite particles by the magnetic field at the stage of forming the molded body. . For this reason, calcination and baking were generally performed at a high temperature of 1250 ° C. or higher. As a result, energy costs in the calcination step and the firing step increased, and ferrite particles were grown to several μm to several tens of μm. In order to improve the magnetic properties of the Sr ferrite sintered magnet, it is difficult to uniformly refine the ferrite particles thus grown to 1 μm or less. Moreover, there is a concern that the cost for pulverizing the calcined body also increases.

  As a method for obtaining a fine Sr ferrite powder, there are a coprecipitation method and a flux method in which a flux is added. When producing Sr ferrite powder by these methods, a step of cleaning the flux or preparing a solution, etc. This requires complicated operations, which complicates the process and increases the manufacturing cost. Under such circumstances, it is required to establish a production method capable of producing an Sr ferrite sintered magnet having high magnetic properties by a simple process at a low production cost.

  On the other hand, when the Sr ferrite sintered magnet is used for a motor or a generator, it is necessary to increase the magnetic flux density of the Sr ferrite sintered magnet in order to improve the torque of the motor or the efficiency of the generator. For this reason, a sintered Sr ferrite magnet having a high Br (saturation magnetic flux density) is required.

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of the Sr ferrite sintered magnet which can manufacture the Sr ferrite sintered magnet which has high Br by a simple process. To do. Moreover, it aims at providing the manufacturing method of Sr ferrite powder suitable for the manufacturing method of such a Sr ferrite sintered magnet. Furthermore, it aims at providing the motor and generator which have high efficiency by using the above-mentioned Sr ferrite sintered magnet.

  The present inventors have studied various methods for producing Sr ferrite powder used as a raw material in order to refine the structure of the sintered Sr ferrite magnet. As a result, it has been found that the temperature at which Sr ferrite is generated can be significantly reduced by adding a compound having Li as a constituent element. And it discovered that the Sr ferrite sintered magnet which has high Br can be manufactured by using Sr ferrite powder obtained by calcining at low temperature, and came to complete this invention.

That is, according to one aspect of the present invention, a mixture containing an iron compound powder, a strontium compound powder, and a compound powder containing Li as a constituent element is fired at 850 to 1050 ° C. to obtain a hexagonal crystal structure. Of a Sr ferrite powder including a calcined body or a pulverized powder thereof having a calcined step of obtaining a calcined body containing 0.01 to 0.5% by mass of Li in terms of Li ₂ O. A manufacturing method is provided.

According to the method for producing Sr ferrite powder described above, a fine Sr ferrite powder having high saturation magnetization (σ _s ) can be easily obtained. The present inventors presume this reason as follows. That is, in the method for producing Sr ferrite powder of the present invention, a mixture containing a powder of a compound having Li as a constituent element is used as a raw material for producing Sr ferrite powder. It is believed that this Li has the action of promoting the formation of Sr ferrite, and by this, Sr ferrite is generated at a calcining temperature of 800 to 1050 ° C. and a calcined body having a high saturation magnetization can be obtained. Yes. Since the above calcination temperature is lower than the conventional general calcination temperature, the grain growth of Sr ferrite can be sufficiently suppressed. If such a calcined body is pulverized as necessary, a sufficiently fine Sr ferrite powder having high saturation magnetization can be easily obtained. The Sr ferrite powder obtained in this way produces Sr ferrite sintered magnets that are required to have high Br because the particles are fine and have high uniformity and also have high saturation magnetization. It can be particularly suitably used as a raw material for the purpose.

  The method for producing Sr ferrite powder of the present invention preferably includes a pulverization step of pulverizing the calcined body to obtain a pulverized powder containing Sr ferrite. Thereby, the Sr ferrite powder excellent in sinterability can be produced by a simpler method.

The specific surface area by the BET method of the calcined body obtained in the calcining step is preferably 2 m ² / g or more and the saturation magnetization is 67 emu / g or more. Such a calcined body is finer and has a high saturation magnetization. For this reason, when the Sr ferrite powder containing this calcined body or its pulverized powder is sintered to produce a Sr ferrite sintered magnet, even if the sintering temperature is lowered, Sr ferrite sintered having a sufficiently high Br is obtained. A magnetized magnet can be manufactured.

  It is preferable that the mixture used in the calcining step further includes a powder of a compound having Na as a constituent element. Thus, it becomes possible to further promote the ferritization reaction by allowing Li and Na to coexist in the mixture. For this reason, the calcination temperature can be further lowered.

In another aspect of the present invention, a mixture containing a powder of an iron compound, a powder of a strontium compound, and a powder of a compound having Li as a constituent element is fired at 850 to 1050 ° C. to form Sr having a hexagonal crystal structure. A calcination step for obtaining a calcined body containing ferrite and containing 0.01 to 0.5% by mass of Li in terms of Li ₂ O, and pulverizing to obtain a pulverized powder containing Sr ferrite by crushing the calcined body Sr ferrite sintering comprising: a step, a molding step of forming a pulverized powder in a magnetic field to obtain a molded body, and a sintering step of firing the molded body at 1000 to 1250 ° C. to obtain a Sr ferrite sintered magnet A method for manufacturing a magnet is provided.

  According to the method for producing a sintered Sr ferrite magnet described above, a sintered Sr ferrite magnet having a high Br can be produced by a simple process. The present inventors infer that this reason is as follows. That is, in the method for producing a sintered Sr ferrite magnet of the present invention, the Sr ferrite sintered magnet is produced using a mixture containing a powder of a compound having Li as a constituent element. It is believed that this Li has an action of promoting the formation of Sr ferrite, whereby a calcined body having a high saturation magnetization can be obtained at a calcining temperature of 850 to 1050 ° C. Since the above calcination temperature is lower than the conventional general calcination temperature, the grain growth of Sr ferrite can be sufficiently suppressed. If such a calcined body is pulverized, a sufficiently fine Sr ferrite powder having a high saturation magnetization can be easily obtained.

  The Sr ferrite powder thus obtained has fine particles, high uniformity, and high saturation magnetization. For this reason, such a sintered Sr ferrite magnet has good sinterability, and an Sr ferrite sintered magnet can be obtained at a low sintering temperature. For this reason, it is considered that during sintering, abnormal grain growth is suppressed, the density is improved while maintaining a sufficiently fine structure, and an Sr ferrite sintered magnet having high Br can be obtained. In addition, Li added at the raw material stage is considered to exert an effect of promoting sintering, and this contributes to reduction of the sintering temperature and refinement of the structure of the sintered Sr ferrite magnet. Is also possible.

  Unlike the coprecipitation method and the flux method, the production method of the present invention is a production method using a mixture obtained by mixing raw material powders, so that Sr ferrite can be produced in a simple process without complicated operations. Sintered magnets can be manufactured. That is, it can be said that the manufacturing method of the Sr ferrite sintered magnet of the present invention is a manufacturing method suitable for mass production of the Sr ferrite sintered magnet.

  In the manufacturing method of this invention, it is preferable that a mixture contains the powder of the compound which has Na as a structural element. Thus, it becomes possible to further promote the ferritization reaction by allowing Li and Na to coexist in the mixture. As a result, the calcination temperature and the sintering temperature can be further lowered, and the structure of the sintered Sr ferrite magnet can be further refined.

  In still another aspect, the present invention provides a motor including a sintered Sr ferrite magnet obtained by the above-described manufacturing method. The motor of the present invention has high efficiency because it includes a sintered Sr ferrite magnet having a high Br.

  In still another aspect, the present invention provides a generator including a sintered Sr ferrite magnet obtained by the above-described manufacturing method. Since the generator of the present invention includes the sintered Sr ferrite magnet having a high Br, the generator has high efficiency.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the Sr ferrite sintered magnet which can manufacture the Sr ferrite sintered magnet which has high Br by a simple process can be provided. Moreover, the manufacturing method of Sr ferrite powder suitable for manufacturing such a Sr ferrite sintered magnet can be provided. Furthermore, a motor and a generator having high efficiency can be provided by using the Sr ferrite sintered magnet described above.

It is a perspective view which shows typically the Sr ferrite sintered magnet obtained by one Embodiment of the manufacturing method of this invention. It is an electron micrograph of Sr ferrite powder in Example 1-2. It is sectional drawing which shows typically suitable embodiment of the motor of this invention. FIG. 4 is a sectional view taken along line IV-IV of the motor shown in FIG. 3.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary.

  A preferred embodiment of the method for producing Sr ferrite powder of the present invention will be described. The manufacturing method of the Sr ferrite powder of the present embodiment includes an iron compound powder, a strontium compound powder, and a mixing step of preparing a mixture by mixing a compound powder having lithium (Li) as a constituent element, the mixture Are calcined at 850 to 1050 ° C. to obtain a calcined body containing Sr ferrite having a hexagonal crystal structure, and a pulverizing process for crushing the calcined body to obtain Sr ferrite powder. Hereinafter, details of each process will be described.

The mixing step is a step of preparing a mixture for calcination. In the mixing step, first, starting materials are weighed and blended at a predetermined ratio, and mixed with a wet attritor or a ball mill for about 1 to 20 hours and pulverized. Examples of the starting material include iron compound powder, strontium compound powder, and lithium compound powder having lithium as a constituent element. As the iron compound and the strontium compound, an oxide or a compound such as carbonate, hydroxide, or nitrate that becomes an oxide by firing can be used. Examples of such compounds include SrCO ₃ and Fe ₂ O ₃ . In addition to these components, La (OH) ₃ and Co ₃ O ₄ may be added. Examples of the lithium compound include oxides, carbonates, silicates, and organic compounds (dispersants) containing lithium.

The mixing amount of the lithium compound is such that the lithium content in the mixture obtained in the mixing step is 0.01 to 0.5% by mass, preferably 0.05 to 0.3% by mass in terms of Li ₂ O. Mix.

  In the mixing step, it is preferable to add a sodium compound having sodium as a constituent element in addition to the above-described lithium compound. By adding a sodium compound together with the lithium compound, the ferrite formation reaction is promoted, and a calcined body containing Sr ferrite can be obtained in a short time even if the calcining temperature in the calcining step is lowered. In addition, a calcined body having a higher Sr ferrite content can be obtained.

Mixing amount of sodium compound, the content of sodium in the mixture obtained in the mixing step, preferably 0.005 to 0.8% by mass in terms of Na ₂ O, more preferably a 0.01 to 0.6 wt% Mix to be. By setting the mixing amount of the sodium compound in such a range, Sr ferrite powder having a high saturation magnetization (σ _s ) can be produced in a shorter calcining time.

The total content of the lithium compound and the sodium compound in the mixture is preferably 0.01 to 1.0% by mass, more preferably 0.02 when the lithium compound and the sodium compound are converted into Li ₂ O and Na ₂ O, respectively. -0.5 mass. By setting it as such a range, Sr ferrite powder with high saturation magnetization ((sigma) _s ) can be manufactured in a shorter calcination time.

Other subcomponents may be added in addition to the lithium compound and the sodium compound. Examples of such subcomponents include SiO ₂ and CaCO ₃ . The average particle diameter of each starting material is not particularly limited and is, for example, 0.1 to 2.0 μm. The specific surface area of each starting material according to the BET method is preferably 2 m ² / g or more. Thereby, a finer Sr ferrite powder can be obtained. The mixture prepared in the mixing step may be in the form of a powder or may be dispersed in a slurry containing a solvent.

  The calcining step is a step of calcining the mixture obtained in the mixing step. Calcination can be performed in an oxidizing atmosphere such as air. The firing temperature (calcination temperature) in the calcination step is 850 to 1050 ° C. From the viewpoint of obtaining Sr ferrite powder having high saturation magnetization, the lower limit of the calcining temperature is preferably 900 ° C. On the other hand, from the viewpoint of obtaining sufficiently fine Sr ferrite powder, the upper limit of the calcining temperature is preferably 1000 ° C., more preferably 950 ° C.

  The calcination time at the calcination temperature is preferably 0.5 to 5 hours, more preferably 1 to 3 hours. The content of Sr ferrite in the calcined body obtained by calcining is preferably 70% by mass or more, and more preferably 90% by mass or more. In the manufacturing method of the present embodiment, since the mixture used in the calcining step contains a lithium compound, Sr ferrite having a hexagonal crystal structure can be sufficiently generated even at the calcining temperature described above.

  The saturation magnetization of the calcined body is preferably 67 emu / g or more, more preferably 70 emu / g or more, and further preferably 70.5 emu / g or more. By producing a calcined body having high saturation magnetization in this way, a sintered Sr ferrite magnet having higher magnetic properties can be obtained. The saturation magnetization in this specification can be measured using a commercially available vibrating sample magnetometer (VSM).

BET specific surface area of the calcined body, the finally obtained Sr ferrite sintered magnet tissue from the viewpoint of sufficiently fine, preferably 2m 2 ^{/ g} or more, more preferably 2.5 m ² / g or more. Further, the specific surface area of the calcined body by the BET method is preferably 15 m ² / g or less, more preferably 10 m ² / g or less, from the viewpoint of improving the moldability when producing a molded body. More preferably, it is 7 m ² / g or less. In addition, the specific surface area in this specification can be measured using the commercially available BET specific surface area measuring apparatus (The product made by Mounttech, brand name: HM Model-1210).

  In the pulverization step, the calcined body obtained by calcination of the mixture obtained in the mixing step is pulverized to prepare pulverized powder. The pulverization may be performed in one stage, or may be performed in two stages, a coarse pulverization process and a fine pulverization process. Since the calcined body is usually granular or massive, it is preferable to first perform a coarse pulverization step. In the coarse pulverization step, a coarse pulverized powder is prepared by performing dry pulverization using a vibrating rod mill or the like. The coarsely pulverized powder thus prepared is wet pulverized using a wet attritor, ball mill, jet mill or the like to obtain a finely pulverized powder. The grinding time is, for example, 30 minutes to 10 hours when using a wet attritor, and 5 to 50 hours when using a ball mill. These times are preferably adjusted appropriately depending on the pulverization method. In the manufacturing method of the present embodiment, calcination is performed at a temperature lower than that in the prior art, so the primary particles of Sr ferrite in the calcined body are finer than in the past. Therefore, the pulverization process (particularly the pulverization process) has a strong meaning of dispersing fine primary particles.

In the pulverization step, powders such as SiO ₂ , CaCO ₃ , SrCO _3, and BaCO ₃ that are subcomponents may be added. By adding such a subcomponent, sinterability can be improved and magnetic properties can be improved. In addition, since these subcomponents may flow out together with the solvent of the slurry when forming in a wet manner, it is preferable to add more than the target content in the sintered Sr ferrite magnet.

  In order to increase the degree of magnetic orientation of the sintered Sr ferrite magnet, it is preferable to add a polyhydric alcohol in the pulverization step in addition to the above-mentioned subcomponents. The addition amount of the polyhydric alcohol is 0.05 to 5.0% by mass, preferably 0.1 to 3.0% by mass, more preferably 0.3 to 2.0% by mass with respect to the addition target. . The added polyhydric alcohol is thermally decomposed and removed in the sintering process.

The specific surface area by the BET method of the pulverized powder obtained in the pulverization step is preferably 6 m ² / g or more, more preferably 8 m, from the viewpoint of sufficiently finening the structure of the finally obtained Sr ferrite sintered magnet. ² / g or more. In addition, the specific surface area of the pulverized powder by the BET method is preferably 12 m ² / g or less, more preferably 10 m ² / g or less, from the viewpoint of improving the moldability when producing a molded body. Since the pulverized powder having such a specific surface area is sufficiently fine and excellent in handleability and formability, the structure of the sintered Sr ferrite magnet is further refined while maintaining the simplicity of the process, and the Sr The magnetic properties of the sintered ferrite magnet can be further improved.

Sr ferrite powder can be obtained through the above steps. Since the Sr ferrite powder thus obtained is fired using a mixture containing lithium, it is sufficiently fine, has high particle uniformity, and has a high σ _s . The content of Sr ferrite having a hexagonal crystal structure in the Sr ferrite powder is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more.

The Sr ferrite powder may contain unreacted raw materials such as an iron compound and a strontium compound, a lithium compound, a sodium compound, and other components as components other than the Sr ferrite. Other components include oxides and composite oxides having at least one selected from K (potassium), Si (silicon), Ca (calcium), Sr (strontium) and Ba (barium). Examples of the oxide include K ₂ O, SiO ₂ , CaO, SrO, and BaO.

  The saturation magnetization of the Sr ferrite powder is preferably 67 emu / g or more, more preferably 70 emu / g or more, and further preferably 70.5 emu / g or more. By producing a calcined body having high saturation magnetization in this way, a sintered Sr ferrite magnet having higher magnetic properties can be obtained.

  Next, a preferred embodiment of the method for producing a sintered Sr ferrite magnet of the present invention will be described. The method for producing a sintered Sr ferrite magnet of this embodiment includes a mixing step of preparing a mixture by mixing an iron compound powder, a strontium compound powder, and a compound powder having lithium as a constituent element; A calcining step of obtaining a calcined body containing Sr ferrite having a hexagonal crystal structure by firing at 850 to 1050 ° C., a crushing step of crushing the calcined body to obtain Sr ferrite powder, and Sr ferrite powder in a magnetic field A molding step for obtaining a molded body by molding, and a sintering step for obtaining a Sr ferrite sintered magnet by firing the molded body at 1000 to 1250 ° C. The mixing step, calcination step, and pulverization step are the same as the above-described method for producing Sr ferrite powder. Here, the overlapping process will not be described, and the forming process and the sintering process will be described.

  In the molding step, first, molding in a magnetic field is performed in which the pulverized powder obtained in the pulverization step is molded in a magnetic field to produce a compact. The molding in the magnetic field may be performed by either dry molding or wet molding, and is preferably wet molding from the viewpoint of increasing the degree of magnetic orientation. In the case of performing wet molding, a slurry can be prepared by blending a pulverized powder and a dispersion medium and pulverizing to prepare a slurry, and a molded product can be produced using the slurry. Concentration of the slurry can be performed by centrifugation, filter press, or the like.

The solid content in the slurry is preferably 30 to 85% by mass. As the dispersion medium of the slurry, water or a non-aqueous solvent can be used. In addition to water, a surfactant such as gluconic acid, gluconate, or sorbitol may be added to the slurry. Using such a slurry, molding is performed in a magnetic field to produce a molded body. The molding pressure is, for example, 0.1 to 0.5 ton / cm ² , and the applied magnetic field is, for example, 5 to 15 kOe.

  Subsequently, in the firing step, the compact is fired to produce a sintered body. Firing is usually performed in an oxidizing atmosphere such as air. A calcination temperature is 1000-1250 degreeC, Preferably it is 1100-1200 degreeC. The firing time at the firing temperature is preferably 0.5 to 3 hours. Through the above steps, a sintered body, that is, a Sr ferrite sintered magnet can be obtained.

  In the method for producing a sintered Sr ferrite magnet of the present embodiment, since a fine calcined body having a large specific surface area is used, it is possible to obtain an Sr ferrite sintered magnet having a fine structure and high structure uniformity. . Since such Sr ferrite sintered magnet has high Br, it is suitably used as a magnet for a motor or a generator.

  FIG. 1 is a perspective view schematically showing a Sr ferrite sintered magnet obtained by the manufacturing method of the present embodiment. The anisotropic Sr ferrite sintered magnet 10 has a curved shape so that the end surface is arcuate, and generally has a shape called an arc segment shape, a C shape, a tile shape, or an arc shape. doing. The Sr ferrite sintered magnet 10 is suitably used as a magnet for a motor or a generator, for example.

Sr ferrite sintered magnet 10 contains crystal grains of M-type Sr ferrite having a hexagonal crystal structure as a main component. Sr ferrite is represented by the following formula (1), for example.
SrFe ₁₂ O ₁₉ (1)

In the Sr ferrite of the above formula (1), Sr at the A site and Fe at the B site may be partially substituted by impurities or intentionally added elements. Further, the ratio between the A site and the B site may be slightly shifted. In this case, the Sr ferrite can be expressed by, for example, the following general formula (2).
_{R x Sr 1-x (Fe} 12-y M y) z O 19 (2)
In the above formula (2), x and y are, for example, 0.1 to 0.5, and z is 0.7 to 1.2.

  M in the general formula (2) is, for example, one or more selected from the group consisting of Co (cobalt), Zn (zinc), Ni (nickel), Mn (manganese), Al (aluminum), and Cr (chromium). It is an element. R in the general formula (3) is, for example, one or more elements selected from the group consisting of La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), and Sm (samarium). .

The ratio of the Sr ferrite phase in the sintered Sr ferrite magnet 10 is preferably 95% or more, more preferably 97% or more, and further preferably 99% or more. Thus, by reducing the ratio of the crystal phase different from the Sr ferrite phase, the magnetic properties can be further enhanced. The ratio of Sr ferrite phase in Sr ferrite sintered magnet 10 (%) is the theoretical value of the saturation magnetization of the Sr ferrite sigma _t, when the actually measured values _{σ s, (σ s / σ} t) × 100 formula Can be obtained.

The Sr ferrite sintered magnet 10 contains a component different from Sr ferrite as a subcomponent. Examples of the subcomponent include alkali metal compounds having Li (lithium) and / or Na (sodium) as constituent elements. Examples of the alkali metal compound include oxides such as Li ₂ O and Na ₂ O and silicate glass. The content of Li in the Sr ferrite sintered magnet 10 is 0.01 to 0.5 wt% in terms of Li ₂ O, preferably from 0.01 to 0.3 wt%.

The content of Na in the Sr ferrite sintered magnet 10 is 0.01 to 0.2% by mass in terms of Na ₂ O. The total content of Li and Na in the Sr ferrite sintered magnet 10 is 0.02 to 0.5% by mass when Li and Na are converted into Li ₂ O and Na ₂ O, respectively. When the content of Li and / or Na in the Sr ferrite sintered magnet 10 becomes excessive, white powder tends to be generated on the surface. On the other hand, when the content of Li and / or Na in the Sr ferrite sintered magnet 10 becomes too small, the time required for sintering tends to become longer.

The Sr ferrite sintered magnet 10 may contain an arbitrary component in addition to the above-described alkali metal compound as a subcomponent. Examples of such components include oxides and composite oxides having at least one selected from K (potassium), Si (silicon), Ca (calcium), Sr (strontium), and Ba (barium). Examples of the oxide include K ₂ O, SiO ₂ , CaO, SrO, and BaO.

The Si content in the sintered Sr ferrite magnet 10 is, for example, 0.1 to 1.0% by mass in terms of SiO ₂ . The Sr content in the sintered Sr ferrite magnet 10 is, for example, 10 to 13% by mass in terms of SrO. The Sr ferrite sintered magnet 10 may contain Ba. The Ba content in the sintered Sr ferrite magnet 10 is, for example, 0.01 to 2.0 mass% in terms of BaO. The Ca content in the Sr ferrite sintered magnet 10 is, for example, 0.05 to 2% by mass in terms of CaO. In addition to these components, the Sr ferrite sintered magnet 10 may contain impurities contained in the raw materials and inevitable components derived from the manufacturing equipment. Examples of such components include Ti (titanium), Cr (chromium), Mn (manganese), Mo (molybdenum), V (vanadium), and Al (aluminum) oxides.

  The subcomponents are mainly contained in the grain boundaries of the Sr ferrite crystal grains in the Sr ferrite sintered magnet 10. The content of each component of the sintered Sr ferrite magnet 10 can be measured by fluorescent X-ray analysis and inductively coupled plasma emission spectroscopic analysis (ICP analysis).

  Sr ferrite sintered magnet 10 is, for example, for fuel pump, power window, ABS (anti-lock brake system), fan, wiper, power steering, active suspension, starter, door lock, It can be used as a magnet for an automobile motor such as an electric mirror. Also for FDD spindle, VTR capstan, VTR rotary head, VTR reel, VTR loading, VTR camera capstan, VTR camera rotary head, VTR camera zoom, VTR camera focus, radio cassette etc. It can be used as a magnet for motors for OA / AV devices such as CD / DVD / MD spindle, CD / DVD / MD loading, and CD / DVD optical pickup. Furthermore, it can also be used as a magnet for a motor for home appliances such as an air conditioner compressor, a freezer compressor, an electric tool drive, a dryer fan, a shaver drive, an electric toothbrush and the like. Furthermore, it can also be used as a magnet for a motor for FA equipment such as a robot shaft, joint drive, robot main drive, machine tool table drive, machine tool belt drive and the like.

  The Sr ferrite sintered magnet 10 is attached to the above-mentioned motor member and installed in the motor. Since the Sr ferrite sintered magnet 10 has high Br, various motors including the Sr ferrite sintered magnet 10 have high efficiency.

  FIG. 3 is a cross-sectional view schematically showing an embodiment of a motor 30 including the Sr ferrite sintered magnet 10. The motor 30 of the present embodiment is a DC motor with a brush, and includes a bottomed cylindrical housing 31 (stator) and a rotatable rotor 32 disposed concentrically on the inner peripheral side of the housing 31. The rotor 32 includes a rotor shaft 36 and a rotor core 37 fixed on the rotor shaft 36.

  A bracket 33 is fitted into the opening of the housing 31, and the rotor core is accommodated in a space formed by the housing 31 and the bracket 33. The rotor shaft 36 is rotatably supported by bearings 34 and 35 provided at the center portion of the housing 31 and the center portion of the bracket 33 so as to face each other. Two C-type Sr ferrite sintered magnets 10 are fixed to the inner peripheral surface of the cylindrical portion of the housing 31 so as to face each other.

  FIG. 4 is a cross-sectional view of the motor 30 in FIG. 3 taken along the line IV-IV. The Sr ferrite sintered magnet 10 that is a motor magnet is bonded to the inner peripheral surface of the housing 31 with an adhesive, with the outer peripheral surface serving as an adhesive surface. Since the Sr ferrite sintered magnet 10 has sufficiently suppressed the precipitation of foreign substances such as powder on the surface, the adhesion between the housing 31 and the Sr ferrite sintered magnet 10 is good. Therefore, the motor 30 has excellent reliability as well as excellent characteristics.

  Applications of the sintered Sr ferrite magnet 10 are not limited to motors and generators. For example, magnets for speakers and headphones, magnetron tubes, magnetic field generators for MRI, CD-ROM clampers, distributor sensors, ABS It can also be used as a member such as an engine sensor, a fuel / oil level sensor, a magnet latch, or an isolator. It can also be used as a target (pellet) when forming the magnetic layer of the magnetic recording medium by vapor deposition or sputtering.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments. For example, the shape of the Sr ferrite sintered magnet is not limited to the shape shown in FIG. 1 and can be appropriately changed to a shape suitable for each application described above. In the above-described embodiment, the calcined body is pulverized to obtain Sr ferrite powder. However, the Sr ferrite powder obtained by the production method of the present invention may be a calcined body that has not been pulverized.

  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.

[Preparation of Sr ferrite powder 1]
(Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-2)
The following starting materials were prepared: The specific surface area is a value measured by the BET method.
・ Fe ₂ O ₃ powder (specific surface area: 4.4 m ² / g) 220 g
・ SrCO ₃ powder (specific surface area: 5.0 m ^{2 /} g) 35.23 g

The above-mentioned Fe ₂ O ₃ powder and SrCO ₃ powder were mixed while being pulverized for 16 hours using a wet ball mill to obtain a slurry. To this slurry was added lithium carbonate powder. The addition amount at this time was 0.19 mass% in terms of Li ₂ O with respect to the total mass of the Fe ₂ O ₃ powder and the SrCO ₃ powder. Thereafter, the slurry was spray-dried to obtain a granular mixture having a particle size of about 10 μm. The mixture was fired in the air at a calcining temperature T ₁ (800 to 1100 ° C.) shown in Table 1 for 1 hour to obtain a granular calcined body containing Sr ferrite having a hexagonal crystal structure.

The magnetic properties (saturation magnetization and coercive force) of the obtained calcined body were measured using a commercially available vibrating sample magnetometer (VSM). The measurement method was as follows. Magnetization (σ) in a magnetic field (Hex) of 16 kOe to 19 kOe was measured by VSM (manufactured by Toei Industry Co., Ltd., trade name: VSM-3 type). Then, the value of σ (σ _s ) when Hex is infinite was calculated according to the saturation asymptotic rule. That is, σ was plotted against 1 / Hex ² and linear approximation was performed, and a value obtained by extrapolating 1 / Hex ² → 0 was obtained. The correlation coefficient at this time was 99% or more. Moreover, the specific surface area by BET method of the obtained calcined body was measured. These measurement results are summarized in Table 1.

The Li ₂ O equivalent content of Li in the obtained calcined body was measured using a commercially available ICP analyzer. As a result, the Li content in terms of Li ₂ O in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-2 was 0.19% by mass.

(Comparative Examples 1-3 to 1-9)
A granular mixture was obtained in the same manner as in Examples 1-1 to 1-5, except that potassium carbonate powder was used instead of lithium carbonate powder. The addition amount of the potassium carbonate powder was 0.46% by mass in terms of K ₂ O based on the total mass of the Fe ₂ O ₃ powder and the SrCO ₃ powder. The mixture was fired in the air at a calcining temperature T ₁ (800 to 1100 ° C.) shown in Table 2 for 1 hour to obtain a granular calcined body. The magnetic properties of the obtained calcined body were measured in the same manner as in Examples 1-1 to 1-5. The measurement results are summarized in Table 2.

(Comparative Examples 1-10 to 1-16)
A granular mixture was obtained in the same manner as in Examples 1-1 to 1-5, except that potassium silicate powder was used instead of lithium carbonate powder. The addition amount of the potassium silicate powder was 0.46% by mass in terms of K ₂ O with respect to the total mass of the Fe ₂ O ₃ powder and the SrCO ₃ powder. The mixture was fired in the air at a calcining temperature T ₁ (800 to 1100 ° C.) shown in Table 3 for 1 hour to obtain a granular calcined body. The magnetic properties of the obtained calcined body were measured in the same manner as in Examples 1-1 to 1-5. The measurement results are summarized in Table 3.

(Comparative Examples 1-17 to 1-23)
A granular mixture was obtained in the same manner as in Examples 1-1 to 1-5 except that the lithium carbonate powder was not added. The mixture was fired in the air at a calcining temperature T ₁ (800 to 1100 ° C.) shown in Table 4 for 1 hour to obtain a granular calcined body. The magnetic properties of the obtained calcined body were measured in the same manner as in Examples 1-1 to 1-5. The measurement results are summarized in Table 4.

  The calcined bodies of each Example and Comparative Example were pulverized with a ball mill for 22 hours to prepare pulverized powder (ferrite powder). The specific surface area of the pulverized powder of Comparative Example 1-20 was measured by the BET method. The measurement results are also shown in Table 4. In Tables 1 to 4, “-” indicates unmeasured.

  FIG. 2 is an electron micrograph of pulverized powder (Sr ferrite powder) obtained by wet pulverizing the calcined body of Example 1-2 with a ball mill. This pulverized powder did not contain coarse particles having a particle size of 1 μm or more.

[Production and Evaluation of Sr Ferrite Sintered Magnet 1]
(Example 2-1 to Example 2-3)
A granular calcined body containing Sr ferrite having a hexagonal crystal structure was obtained in the same manner as Example 1-2 (T ₁ : 900 ° C.). The content of Li in terms of Li ₂ O in the obtained calcined body was measured in the same manner as in Examples 1-1 to 1-5. As a result, the Li content in terms of Li ₂ O was 0.18% by mass.

Sorbitol, SiO ₂ powder and CaCO ₃ powder were added to 130 g of this calcined body. The amount of each additive was 1% by mass of sorbitol, 0.6% by mass of SiO ₂ powder, and 1.4% by mass of CaCO ₃ powder based on the calcined body. After these additives were added, the calcined body was wet-ground for 22 hours using a ball mill to obtain a slurry. The specific surface area of the Sr ferrite powder by the BET method of the pulverized powder after the wet pulverization was 12 m ² / g. After adjusting the concentration of the solid content (Sr ferrite powder) of the obtained slurry, it was molded in an applied magnetic field of 12 kOe using a wet magnetic field molding machine to obtain a cylindrical molded body. This molded body was fired in the atmosphere at a sintering temperature T ₂ (1160 to 1200 ° C.) for 1 hour to obtain Sr ferrite sintered magnets of Examples 2-1 to 2-3. Sintering temperature T ₂ of each example is as shown in Table 5.

After processing the upper and lower surfaces of the Sr ferrite sintered magnet of each example, the magnetic characteristics were measured using a BH tracer with a maximum applied magnetic field of 25 kOe. In the measurement, HcJ, Br, and 4PI _max were obtained, and the degree of orientation (Br / 4PI _max ) was calculated. Further, the density of the sintered Sr ferrite magnet and the content of Li in terms of Li ₂ O were measured by Archimedes method and fluorescent X-ray analysis, respectively. These results are shown in Table 5. The method for measuring the Li content in the sintered Sr ferrite magnet is the same as in Example 1-1, and the numerical values in Table 5 are the contents in terms of Li ₂ O.

(Comparative Example 2-1 to Comparative Example 2-3)
A granular calcined body containing Sr ferrite having a hexagonal crystal structure was obtained in the same manner as in Comparative Example 1-5 (T ₁ : 900 ° C.). The magnetic properties of the obtained calcined body were measured in the same manner as in Examples 2-1 to 2-3. As a result, σ _s : 67.2 emu / g, HcJ: 1985 Oe.

Sr ferrite sintered magnets were produced in the same manner as in Examples 2-1 to 2-3 except that the calcined body thus obtained was used. In addition, the specific surface area by BET method of the pulverized powder after wet pulverization was 12 m ² / g. Sintering temperature T ₂ of each of the comparative examples are as shown in Table 5. The magnetic properties of the obtained Sr ferrite sintered magnet were measured in the same manner as in Examples 2-1 to 2-3. Table 5 shows the measurement results.

(Comparative Example 2-4 to Comparative Example 2-6)
A granular calcined body containing Sr ferrite having a hexagonal crystal structure was obtained in the same manner as in Comparative Example 1-12 (T ₁ : 900 ° C.). The magnetic properties of the obtained calcined body were measured in the same manner as in Examples 2-1 to 2-3. As a result, σ: 55.9 emu / g and HcJ: 1985 Oe.

Sr ferrite sintered magnets were produced in the same manner as in Examples 2-1 to 2-3 except that the calcined body thus obtained was used. In addition, the specific surface area by BET method of the pulverized powder after wet pulverization was 12 m ² / g. Sintering temperature T ₂ of each of the comparative examples are as shown in Table 5. The magnetic properties of the obtained Sr ferrite sintered magnet were measured in the same manner as in Examples 2-1 to 2-3. These results are shown in Table 5.

(Comparative Example 2-7 to Comparative Example 2-9)
A granular mixture was obtained in the same manner as in Examples 1-1 to 1-5 except that sodium carbonate powder was used instead of lithium carbonate powder. The amount of sodium carbonate powder added was 0.46% by mass in terms of Na ₂ O with respect to the total mass of the Fe ₂ O ₃ powder and SrCO ₃ powder. The mixture was fired in the air at a calcining temperature T ₁ (900 ° C.) for 1 hour to obtain a granular calcined body. The magnetic properties of the obtained calcined body were measured in the same manner as in Examples 2-1 to 2-3. As a result, σ was 67.9 emu / g.

Sr ferrite sintered magnets were produced in the same manner as in Examples 2-1 to 2-3 except that the calcined body thus obtained was used. In addition, the specific surface area by BET method of the pulverized powder after wet pulverization was 12 m ² / g. Sintering temperature T ₂ of each of the comparative examples are as shown in Table 5. The magnetic properties of the obtained Sr ferrite sintered magnet were measured in the same manner as in Examples 2-1 to 2-3. These results are shown in Table 5.

(Comparative Example 2-10 to Comparative Example 2-12)
A granular calcined body containing Sr ferrite having a hexagonal crystal structure was obtained in the same manner as in Comparative Example 1-20 (T ₁ : 950 ° C.). Sr ferrite sintered magnets were produced in the same manner as in Examples 2-1 to 2-3 except that the calcined body thus obtained was used. In addition, the specific surface area by BET method of the pulverized powder after wet pulverization was 12 m ² / g. Sintering temperature T ₂ of each of the comparative examples are as shown in Table 5. The magnetic properties of the obtained Sr ferrite sintered magnet were measured in the same manner as in Examples 2-1 to 2-3. These results are shown in Table 5.

The Sr ferrite sintered magnets of Examples 2-1 to 2-3 were confirmed to have higher density, higher Br, and higher degree of orientation than those of the comparative examples without extremely decreasing HcJ. This is because the Sr ferrite powder having a fine and high σ _s obtained by adding Li in advance before calcination is used, so that the sintering is promoted to have such a high density and a high Br. It shows that an Sr ferrite sintered magnet was obtained.

[Preparation of Sr ferrite powder 2]
(Examples 3-1 to 3-3, Comparative example 3-1)
The following starting materials were prepared: The specific surface area is a value measured by the BET method.
・ Fe ₂ O ₃ powder (specific surface area: 4.4 m ² / g) 220 g
・ SrCO ₃ powder (specific surface area: 5.0 m ^{2 /} g) 35.23 g

The above-mentioned Fe ₂ O ₃ powder and SrCO ₃ powder were mixed while being pulverized for 16 hours using a wet ball mill to obtain a slurry. To this slurry, sodium silicate powder and lithium carbonate powder were added. The addition amount of the sodium silicate powder and the lithium carbonate powder at this time is 0.38% by mass in terms of Na ₂ O and Li ₂ O, respectively, with respect to the total mass of the Fe ₂ O ₃ powder and the SrCO ₃ powder. It was set to 0.09 mass%. Thereafter, the slurry was spray-dried to obtain a granular mixture having a particle size of about 10 μm. The mixture was fired in the air at a calcining temperature T ₁ (800 to 950 ° C.) shown in Table 6 for 1 hour to obtain a granular calcined body containing Sr ferrite having a hexagonal crystal structure.

  The magnetic properties (saturation magnetization and coercive force) of the obtained calcined body were measured in the same manner as in Example 1-1. The results are summarized in Table 6.

(Comparative Examples 3-2 to 3-5)
An Sr ferrite powder and an Sr ferrite sintered magnet were produced and evaluated in the same manner as Comparative Example 3-1 and Examples 3-1 to 3-3, except that the lithium carbonate powder was not added. The amount of sodium silicate powder added was 0.38% by mass in terms of Na ₂ O with respect to the total mass of Fe ₂ O ₃ powder and SrCO ₃ powder. Table 7 shows the evaluation results.

From the results shown in Table 6 and Table 7, a calcined body having a higher σ _s at a lower calcining temperature is obtained when both the lithium compound and the sodium compound are added than when only the sodium compound is added. It was confirmed that

[Production and Evaluation of Sr Ferrite Sintered Magnet 2]
(Example 4-1 to Example 4-6)
A granular calcined body containing Sr ferrite having a hexagonal crystal structure was obtained in the same manner as in Example 3-1 (T ₁ : 850 ° C.). Sorbitol, SiO ₂ powder and CaCO ₃ powder were added to 130 g of this calcined body. The amount of each additive was 1% by mass of sorbitol, 0.4% by mass of SiO ₂ powder, and 0.9% by mass of CaCO ₃ powder based on the calcined body. After adding these additives, the calcined body was wet-ground using a ball mill to obtain a slurry. Table 8 shows the wet pulverization time and the specific surface area of the Sr ferrite powder by the BET method after the wet pulverization.

After adjusting the concentration of the solid content (Sr ferrite powder) of the obtained slurry, it was molded in an applied magnetic field of 12 kOe using a wet magnetic field molding machine to obtain a cylindrical molded body. This molded body was fired in the atmosphere at a sintering temperature T ₂ (1140 to 1180 ° C.) for 1 hour to obtain Sr ferrite sintered magnets of Examples 4-1 to 4-6. Sintering temperature T ₂ of each example is as shown in Table 8. The magnetic properties and density of the Sr ferrite sintered magnet of each example were measured in the same manner as in Examples 2-1 to 2-3. These results are shown in Table 8.

(Comparative Examples 4-1 to 4-6)
An Sr ferrite powder and an Sr ferrite sintered magnet were produced and evaluated in the same manner as in Examples 4-1 to 4-6 except that the lithium carbonate powder was not added. The amount of sodium silicate powder added was 0.38% by mass in terms of Na ₂ O with respect to the total mass of Fe ₂ O ₃ powder and SrCO ₃ powder. The evaluation results are summarized in Table 8.

When the sintering temperature T ₂ are compared in the case of 1160 ° C., Sr ferrite sintered magnet of Example 4-1 to 4-6 with the addition of lithium carbonate powder, without HcJ it is extremely lowered, of each comparative example It had higher Br and higher degree of orientation than Sr ferrite sintered magnet. Since Examples 4-1 to 4-6 were higher in density than each comparative example, it was confirmed that the sinterability was improved by addition of lithium. In Examples 4-1 and 4-4, even with a lower sintering temperature T ₂ and 1140 ° C., sintering sufficiently proceeds, the Sr ferrite sintered magnet having high Br and high degree of orientation It was confirmed that it was obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the Sr ferrite sintered magnet which can manufacture the Sr ferrite sintered magnet which has high Br by a simple process can be provided. In addition, a sintered Sr ferrite magnet having high magnetic properties and high reliability can be provided. Furthermore, it is possible to provide a motor and a generator having high efficiency and high reliability.

DESCRIPTION OF SYMBOLS 10 ... Ferrite sintered magnet, 30 ... Motor, 31 ... Housing, 32 ... Rotor, 33 ... Bracket, 34, 35 ... Bearing, 36 ... Rotor shaft, 37 ... Rotor core.

Claims (8)

A mixture containing an iron compound powder, a strontium compound powder, and a compound powder containing Li as a constituent element is fired at 850 to 1050 ° C. to contain Sr ferrite having a hexagonal crystal structure, and Li is added to Li ₂ O. The manufacturing method of the Sr ferrite powder containing the calcined body or the ground powder which has a calcining process which obtains the calcined body which contains 0.01-0.5 mass% in conversion.   The manufacturing method of the Sr ferrite powder of Claim 1 which has the grinding | pulverization process which grind | pulverizes the said calcined body and obtains the pulverized powder containing Sr ferrite. The method for producing Sr ferrite powder according to claim 1 or 2, wherein the calcined body has a specific surface area by BET method of 2 m ² / g or more and a saturation magnetization of 67 emu / g or more.   The manufacturing method of the Sr ferrite powder as described in any one of Claims 1-3 in which the said mixture contains the powder of the compound which has Na as a structural element. A mixture containing an iron compound powder, a strontium compound powder, and a compound powder containing Li as a constituent element is fired at 850 to 1050 ° C. to contain Sr ferrite having a hexagonal crystal structure, and Li is added to Li ₂ O. A calcining step of obtaining a calcined body containing 0.01 to 0.5% by mass in terms of
Crushing the calcined body to obtain a pulverized powder containing Sr ferrite;
A molding step of molding the pulverized powder in a magnetic field to obtain a molded body;
And sintering the molded body at 1000 to 1250 ° C. to obtain a Sr ferrite sintered magnet.   The method for producing a sintered Sr ferrite magnet according to claim 5, wherein the mixture includes a powder of a compound having Na as a constituent element.   A motor provided with the sintered Sr ferrite magnet obtained by the manufacturing method according to claim 5 or 6. A generator provided with the sintered Sr ferrite magnet obtained by the manufacturing method according to claim 5 or 6.