KR20050053081A - High performance ferrite sintered magnet and producing method of the same - Google Patents

Abstract

The present invention is to provide a ferrite sintered magnet excellent in magnetic properties and a method of manufacturing the same, the hexagonal ferrite sintered magnet according to the present invention has a composition of the formula (1).

[Formula 1]

A _1-x R _x Fe _2n-y M _y O _{3n ± θ}

(Wherein

A element is one or more selected from Sr, Ba, Ca, and Pb, R element is one or more selected from Ti, Zr, Sn, Ce, Y, La, Pr, Nd, and Sm, and M element Is at least one selected from Li, Na, K, and Rb,

x, y, n are molar ratios,

0.02 ≦ x ≦ 0.50, 0.02 ≦ y ≦ 0.50, 5.0 ≦ n ≦ 6.5)

In addition, the method of manufacturing a ferrite sintered magnet according to the present invention, after the calcination and coarsely pulverized by mixing the raw material to have a composition of the formula (1); Fine grinding to obtain an average particle diameter in the range of 0.4 to 0.8 mu m; Kneaded after drying or concentrating; Forming in a magnetic field in the state of a wet slurry; Sintering treatment is characterized.

Description

High performance ferrite sintered magnet and producing method of the same

The present invention relates to a ferrite sintered magnet of high characteristics and a method of manufacturing the same, which can be widely used in a home appliance or a car rotator, and more specifically, Sr or Ba of a ferrite magnet such as titanium (Ti), zirconium (Zr), Tin (Sn), cerium (Ce), yttrium (Y), lanthanum (La), praseodymium (Pr), neodymium (Nd), or samarium (Sm) elements and replace Fe with lithium (Li), sodium (Na) ), A ferrite sintered magnet having a high residual magnetic flux density and a method for producing the same by substituting the element with potassium, potassium (K), or rubidium (Rb).

In general, ferrite magnets are used in a variety of applications, including rotors, such as motors, generators. In particular, in recent years, in the field of automotive rotors, ferrite sintered magnets having higher magnetic properties are required for the purpose of miniaturization and weight reduction, and in the field of rotors for home appliances for high efficiency.

Conventional strontium (Sr) ferrite sintered magnet manufacturing method is as follows. First, iron oxide (Fe ₂ O ₃ ) and strontium carbonate (SrCO ₃ ) are mixed, and then a ferrite reaction is induced by calcination, and the calcined ferrite clinker is coarsely pulverized. Cr ₂ O ₃ and Al ₂ O ₃ are added for the purpose of controlling the sintering behavior of the coarsely pulverized powder, adding SrCO ₃ , CaCO ₃ , SiO ₂ , and controlling the coercive force (iHc). It adds and grind | pulverizes so that it may become 0.7-1.0 micrometer in average particle diameter. The finely ground slurry is wet molded while being oriented in a magnetic field to form a molded body. The molded body is subjected to a sintering process, which is densified in firing, and finally subjected to grinding to match the product dimensions.

In this general manufacturing method, the high characterization method of the ferrite sintered magnet can be largely classified into the following five kinds.

The first is to atomize. The coercive force (iHc) becomes maximum when the size of the crystal grains in the sintered body is about 0.9 µm, which is the critical terminal opening size of the M-Sr ferrite magnet. It is good to atomize a particle diameter to 0.7 micrometer or less. However, this method leads to adverse side effects of poor dehydration characteristics and wet production efficiency in the wet molding of the fine particles.

The second method is to make the grain size of the sintered body as uniform as possible. Ideally, it is best to have uniformity in the vicinity of the critical terminal sphere particle size of 0.9 mu m. This is because the coercive force is lowered even if the grain size is too large or small. The specific means of this method is to improve the particle size distribution of the finely ground powder, but considering the grinding mechanism in the ball mill or attritor, the extent of improvement is limited in the case of industrial production. There is. On the other hand, recently, a method for producing fine particles having a uniform particle size by the co-precipitation method and the sol-gel method has been published, but is not suitable for industrial mass production.

The third method is to improve the crystal orientation which influences magnetic anisotropy. Specific means of this method include a method of adding a surfactant to the finely ground slurry to improve the dispersibility of ferrite particles in the slurry, and a method of strengthening the magnetic field strength during orientation.

The fourth method is to improve the sintered compact. The theoretical density of Sr ferrite is 5.15 g / cm 3, and the density of Sr ferrite sintered magnets currently on the market ranges from 4.9 to 5.0 g / cm 3, which corresponds to 95 to 97% of the theoretical density. Although the residual magnetic flux density (Br) can be improved by densification, special densification means such as hot hydrostatic pressing (Hot Isostatic Press) is required to achieve this density. The introduction of this special process leads to an increase in the manufacturing cost, and loses the characteristics of the ferrite sintered magnet, which is a low-cost magnet.

The fifth method is to improve the saturation magnetization (σs) of the ferrite compound itself, the main composition constituting the ferrite magnet. This is because the improvement of saturation magnetization is a factor that can directly improve the residual magnetic flux density. The ferrite compound produced conventionally has a crystal structure of M-type (Magnetoplumbite). Recently, some studies have been conducted on W-ferrite having higher saturation magnetization than M-ferrite. However, due to the difficulty in controlling the atmosphere, the feasibility of mass production is quite slim.

In general, by applying the first to fourth methods in the Sr ferrite magnet mainly composed of a compound represented by SrO.nFe ₂ O ₃ , it is difficult to realize a certain level or more of magnetic properties.

The first reason is that the first to fourth methods have many side effects in terms of productivity, and include a content that is rarely feasible in consideration of the mass production process. The second reason is that the magnetic properties, especially the residual magnetic flux density, are already somewhat closer to theoretical values.

Accordingly, it is an object of the present invention to provide a ferrite sintered magnet having extremely excellent magnetic properties, in particular, a high residual magnetic flux density, and a method of manufacturing the same by the fifth method.

In order to achieve the above object, the present invention provides a part of the A element and Fe element among the elements of the composition represented by AO.nFe ₂ O ₃ (A element is at least one selected from Sr, Ba, Ca, and Pb) We devised a method of substituting for other kinds of elements.

For example, magneto plumbite, that is, the magnetism of M-Sr ferrite, is the source of the magnetic moment of Fe ions, and the magnetic moments are oriented in parallel and anti-parallel directions by the lattice site positions of Fe ions, and then disappear. It has a magnetic structure of ferrimagnetic material that has magnetism as much as the remaining magnetic moment.

Therefore, there may be two ways to improve the saturation magnetization by modifying the magnetic structure.

The first method is to replace Fe ions with magnetic moments facing in the antiparallel direction with other nonmagnetic elements with magnetic moments smaller than Fe ions. The second method is to replace Fe ions with magnetic moments pointing in parallel with other elements with magnetic moments larger than Fe ions.

With the above in mind, the present inventors have conducted experiments in which Fe ions are substituted with other elements, and as a result, the alkali metal elements Li, Na, K, and Rb, etc. improve the saturation magnetization and improve the magnetic properties. Found that.

However, simply adding the above element does not provide sufficient effect. The reason for this is that when Fe ions are replaced with other elements, an abnormality in the balance of ionic singers occurs. That is, in order to perform charge compensation, it is necessary to replace a part of the A ion lattice site with another element at the same time as Fe ion substitution, and for this purpose, in the present invention, Ti, Zr, Sn, Ce, Y, La, Pr, Nd , Sm and the like have been found to work particularly effectively.

The hexagonal ferrite sintered magnet according to the present invention has a composition of the following Chemical Formula 1.

A _1-x R _x Fe _2n-y M _y O _{3n ± θ}

(Wherein

A element is one or more selected from Sr, Ba, Ca, and Pb, R element is one or more selected from Ti, Zr, Sn, Ce, Y, La, Pr, Nd, and Sm, and M element Is at least one selected from Li, Na, K, and Rb,

x, y, n are molar ratios,

0.02 ≦ x ≦ 0.50, 0.02 ≦ y ≦ 0.50, 5.0 ≦ n ≦ 6.5)

In the hexagonal ferrite sintered magnet according to the present invention, when the R element is at least one selected from Ti, Zr, Sn, and Ce, which are (+) 4 valent metals, the substitution ratio x / y is 0.8 to 2.0. It is done.

In the hexagonal ferrite sintered magnet according to the present invention, when the R element is at least one selected from Y, La, Pr, Nd, and Sm which are (+) trivalent metals, the substitution ratio x / y is 1.6 to 4.0. It is characterized by.

Method for producing a ferrite sintered magnet according to the present invention, after the calcination and coarsely crushed by mixing the raw material to have a composition of the formula (1); Fine grinding to obtain an average particle diameter in the range of 0.4 to 0.8 mu m; Kneaded after drying or concentrating; Forming in a magnetic field in the state of a wet slurry; Sintering treatment is characterized.

In addition, the method for producing a ferrite sintered magnet according to the present invention is a ferrite raw material powder having n of 5.5 to 6.5 in SrO · nFe ₂ O ₃ of the initial stage of the pulverization process, and as a R element as Ti, Zr, Sn, Ce. At least one selected from the metal compounds of Y, La, Pr, Nd, and Sm, and at least one selected from the metal compounds of Li, Na, K, and Rb as the M element to have the composition of Formula 1. Adding at the same time and pulverizing to make the average particle diameter in the range of 0.4 to 0.8 mu m; Kneaded after drying or concentrating; Forming in a magnetic field in the state of a wet slurry; Sintering treatment is characterized by.

In the method for producing a ferrite sintered magnet according to the present invention, the metal compound of Ti, Zr, Sn, Ce, Y, La, Pr, Nd, and Sm selected as the R element is a metal oxide or a metal hydroxide. .

In the method for producing a ferrite sintered magnet according to the present invention, the metal compound of Li, Na, K, and Rb selected as the M element is a metal carbide, a metal oxide, or a metal hydroxide.

In the method for producing a ferrite sintered magnet according to the present invention, the dispersant is added at a solid content ratio of 0.1 to 1.0% in the fine grinding step or the kneading step.

In the present invention, the effect of the invention can be obtained even when one type alone or a combination of two or more of the elements among Li, Na, K, and Rb is obtained as the M element, but in the case of pursuing a particularly high residual magnetic flux density in magnetic properties. For this, monosubstitution of Li element is advantageous.

On the other hand, when a high coercive force is pursued while maintaining a relatively high residual magnetic flux density, it is preferable to substitute one of Na, K, and Rb alone.

In order to obtain good magnetic properties, in the range of A _1-x R _x Fe _2n-y M _y O _{3n ± θ} , the range of n value is preferably 5.0 to 6.5. If the n value is less than 5.0 or more than 6.5, a nonmagnetic phase (Hematite phase) other than the magneto plumbite phase, which is a magnetic phase, is generated, and the magnetic properties are significantly reduced.

Moreover, x and y values are good in the range of 0.02-0.5. Even with a small amount of substitution in which the molar ratio x is x = 0.02, the improvement of the magnetic properties is exhibited and maintained up to the range of 0.5. However, when x exceeds 0.5, the magnetic properties are inversely lowered.

The substitution ratio x / y value is preferably 1 for the purpose of charge compensation when the R element is (+) tetravalent Ti, Zr, Sn, or Ce, but relatively good results can be obtained even in the range of 0.8 to 2.0.

On the other hand, when the element R is Y, La, Pr, Nd, or Sm having a (+) trivalent value, the substitution ratio x / y value is preferably 2 for the purpose of charge compensation, but has a relatively good result even in the range of 1.6 to 4.0. You can get it.

The above basic composition is preferably formed in the calcination step during the standard manufacturing process of the ferrite magnet consisting of mixing-> calcination-> coarse pulverization-> fine pulverization-> molding-> sintering to be used as a raw powder.

In other words, the R and A elements are preferably added in the mixing step, since the high temperature heat treatment process of calcination and sintering is carried out twice, thereby inducing good solid diffusion and obtaining a uniform composition.

On the other hand, in order to obtain a high performance ferrite sintered body, it is preferable to add SrO (or SrCO ₃ ), CaO (or CaCO ₃ ), and SiO ₂ in the fine grinding step as a sintering aid for controlling the sintering phenomenon. SrO and CaO are additives for promoting grain growth, and their content is preferably 0.25 to 0.55%. When the content exceeds 0.55%, the grain growth proceeds excessively and the coercive force decreases. When the grain growth is less than 0.25%, the grain growth is excessively suppressed and the residual magnetic flux density decreases. On the other hand, SiO ₂ is an additive for suppressing crystal grain growth during sintering, and its content is suitably 0.30 to 0.50%. If it is less than 0.30%, the effect of inhibiting grain growth during sintering is not sufficient, and the coercive force is lowered. If it exceeds 0.50, the grain growth is excessively suppressed, and the improvement of the degree of orientation progressing with grain growth is not sufficient, so that the residual magnetic flux density Degrades.

In order to obtain a ferrite sintered body having the above characteristics with the composition, it is preferable to follow the following production method. That is, it is preferable that the average particle diameter of the composition be wet-pulverized to a range of 0.4 to 0.8 mu m, concentrated or dried, wet-molded after crushing and kneading, and subjected to a sintering process. When it is pulverized to less than 0.4㎛, abnormal grain growth occurs during sintering, it is difficult to obtain high characteristics, and dehydration becomes poor during wet molding. When it exceeds 0.8 micrometer, the abundance rate of coarse crystal grains in a sintered compact structure increases.

In order to obtain a high-performance ferrite sintered compact, it is important to prepare a ferrite powder in which the composition and physical properties are appropriately controlled, and to prevent the ferrite powder from agglomerating in the slurry. In order for the particles of the ferrite powder to be present independently in the slurry, the slurry containing the ferrite powder is pulverized and then dried or concentrated, followed by kneading by adding a dispersant in a high concentration slurry state. By addition of a dispersing agent, aggregation disintegrates, an orientation property improves and a magnetic property improves.

In addition, when the dispersing agent is added during kneading, the dispersing agent is adsorbed to the ferrite particles to improve the surface properties, whereby a good dispersion state is obtained, and the magnetic properties can be improved.

Surfactants, higher fatty acids, higher fatty acid esters and the like are known as dispersants, and by using a polycarboxylic acid dispersant which is a kind of anionic surfactant, the dispersibility of ferrite particles is improved and the aggregation of ferrite particles is effectively prevented. can do.

Although there are many kinds of polycarboxylic acid-based dispersants, polycarboxylic acid ammonium salts are particularly effective for improving the dispersibility of ferrite particles.

The addition amount of the dispersant is effective if it is 0.1% or more in the solid content ratio of the ferrite powder, and if it exceeds 1.0%, the residual magnetic flux density decreases.

Examples and comparative examples of the present invention will be described below in more detail the configuration and effects of the present invention. The following Examples and Comparative Examples illustrate the content of the present invention, but the content of the present invention is not limited thereto.

<Example 1>

In the present Example, as shown in Table 1 below, Ti, Zr, Sn, or Ce, which is a (+) 4 valent metal, is selected as an R element for substituting Sr, and Li, Na, K, Alternatively, a magnetic powder was prepared by selecting a metal element of Rb.

First, SrCO ₃ , Fe ₂ O ₃ , oxides of element R and carbides of element M are represented by the formula of Sr _1-x R _x Fe _2n-y M _y O _{3n ± θ} , where n = 5.90, x = y = 0.1 That is, it was mix | blended so that substitution ratio x / y = 1, it was mixed in wet form, and it dried and granulated, and calcined in air | atmosphere at 2250 degreeC for 2 hours.

In addition, as a comparative example, a conventional composition in which n = 5.90 and x = y = 0 in the above formula was produced in the same manner (Comparative Example 1).

The powdery calcined body (magnet powder) of Example 1 and Comparative Example 1 obtained after calcination was subjected to a magnetic field strength of 15 kOe by using a sample vibration magnetometer (VSM) to measure the saturation magnetization (σs) and the coercive force (iHc). In addition, by analyzing the generated phase (Phase) using an X-ray diffractometer, the results are shown in Table 1 below.

No. R element M element Saturation Magnetization (σs) Coercivity (iHc) Creation Comparative Example 1 - - 68.3 emu / g 3,170 Oe M phase ^* Example 1-1 Ti Na 72.6 3,400 M phase Example 1-2 Zr 72.9 2,990 M phase Example 1-3 Sn 73.4 2,720 M phase Example 1-4 Ce Li 72.7 3,270 M phase Example 1-5 Na 74.0 3,490 M phase Example 1-6 K 71.5 3,450 M phase Example 1-7 Rb 70.8 3,520 M phase

- ^* : M phase represents a phase with a crystal structure of magneto plumbite

As shown in Table 1 above, when Ti, Zr, Sn, or Ce is selected as the R element, and Li, Na, K, or Rb is selected as the substitution element, respectively, as compared with the conventional comparative material (Comparative Example 1) High saturation magnetization values and appropriate coercive force values were obtained.

Therefore, it can be seen that the magnet powder according to the present embodiment has a latent characteristic as a magnetic material that exhibits higher characteristics than conventional materials even in the bulk magnet after sintering.

<Example 2>

In the present embodiment, as shown in Table 2 below, Y, La, Pr, Nd, or Sm, which is a (+) trivalent metal, is selected as an R element for substituting Sr, and Li, Na, Magnetic powder was prepared by selecting a metal element of K, or Rb.

SrCO ₃ , Fe ₂ O ₃ , oxides of element R and carbides of element M include Sr _1-x R _x Fe _2n-y M _y O _{3n ??} In the chemical formula of n = 5.90, x = 0.2, y = 0.1, that is, a compounding amount ratio of x / y = 2, blended in a wet manner, dried and granulated, and calcined in air at 1250 ° C. for 2 hours. It was.

The powdery calcined body (magnet powder) of Example 2 obtained after calcination was subjected to a magnetic field strength of 15 kOe in a sample vibration type magnetometer (VSM) to measure saturation magnetization (σs) and coercive force (iHc). In addition, by analyzing the generated phase (Phase) using an X-ray diffractometer, the results are shown in Table 2 below.

No R element M element Saturation Magnetization (σs) Coercivity (iHc) Creation Example 2-1 Y Na 72.4 emu / g 3,230 Oe M phase ^* Example 2-2 Pr 70.9 3,150 M phase Example 2-3 Nd 71.3 3,080 M phase Example 2-4 Sm 69.1 3,290 M phase Example 2-5 La Li 72.1 3,050 M phase Example 2-6 Na 71.9 3,330 M phase Example 2-7 K 70.7 3,420 M phase Example 2-8 Rb 70.4 3,470 M phase

- ^* : M phase represents a phase with a crystal structure of magneto plumbite

As shown in Table 2 above, in the case of selecting Y, La, Pr, Nd, or Sm as the R element and Li, Na, K, or Rb as the M element, respectively, as a substitution element (Comparative Example 1 Higher saturation magnetization values and appropriate coercive force values were obtained.

Therefore, it can be seen that the magnet powder according to the present embodiment has a latent characteristic as a magnetic material that exhibits higher characteristics than conventional materials even in the bulk magnet after sintering.

<Example 3>

In the present embodiment, Ce is selected as the R element, and Na as the M element, respectively, and SrCO ₃ , Fe ₂ O ₃ , CeO ₂ , and Na ₂ CO ₃ are selected as Sr _1-x Ce _x Fe _2n-y Na _y O _{3n ± θ} In the chemical formula, the mixture was mixed so that n = 5.90 and x = y = 0 to 0.6, mixed in a wet manner, dried and granulated, and calcined in air at 1250 ° C. for 2 hours.

The powdery calcined body (magnetic powder) of Example 3 obtained after calcination was evaluated in the same manner as in Example 1, and the results are shown in FIG.

As shown in FIG. 1, it was clear that saturation magnetization was improved by simultaneously replacing Ce and Na. In addition, even in a small amount of substitution of x = 0.025, the effect of improving the saturation magnetization appeared, and the effect was maintained up to 0.5, but the effect was decreased rather than 0.5. Accordingly, the molar ratio x is preferably 0.02 to 0.5, and more preferably 0.07 to 0.3.

Even when the R element was Ti, Zr, Sn, Y, La, Pr, Nd, or Sm, the results in almost the same form as in FIG. 1 were obtained. Moreover, n value confirmed that the effect of the substantially equivalent level was obtained in the range of 5.0-6.5.

<Example 4>

In the present Example, the allowable range of substitution amount ratio (x / y) of the R element and the M element in the charge compensation relation was examined.

Ce is selected as the R element, and Na is selected as the M element, and SrCO ₃ , Fe ₂ O ₃ , CeO ₂ , Na ₂ CO _{3 is selected} from Sr _1-x Ce _x Fe _2n-y Na _y. In the formula of O _{3n ± θ} , fixed at n = 5.90 and x = 0.1, blended so as to be y = 0.025 to 0.15, mixed in a wet manner, dried and granulated, and calcined at 1250 ° C. for 2 hours in the air. It was.

The powdery calcined body (magnetic powder) of Example 4 obtained after calcination was evaluated in the same manner as in Example 1, and the results are shown in Table 3 below.

No x y x / y Saturation Magnetization (σs) Coercivity (iHc) Example 4-1 0.1 0.025 4.0 64.5 emu / g 3,670 Oe Example 4-2 0.05 2.0 70.4 3,360 Example 4-3 0.075 1.3 72.6 3,530 Example 4-4 0.1 1.0 74.0 3,490 Example 4-5 0.125 0.8 72.1 3,260 Example 4-6 0.20 0.5 67.3 2,940

As shown in Table 3 above, in the case where the R element is (+) tetravalent, if the substitution amount ratio x / y is in the range of 0.8 to 2.0 where the charge balance is fully satisfied, that is, x / y = 1, It can be seen that the improvement effect of magnetization is maintained and the effect of the present invention is maintained. On the other hand, in the case where the substitution amount ratio x / y value exceeds 2.0 and the case below 0.8, the magnetic properties are significantly lowered, and therefore, it is understood that the effective range of the x / y value is in the range of 0.8 to 2.0.

On the other hand, in the case where the R element is (+) trivalent, the effect of improving the saturation magnetization is maintained when the substitution amount ratio x / y is in the range of 1.6 to 4.0 where the charge balance is completely satisfied, that is, around x / y = 2. It was confirmed that the effects of the present invention are maintained.

Example 5

In this embodiment, Ce is selected as the R element, and Li, Na, K, or Rb is selected as the M element, and carbides of SrCO ₃ , Fe ₂ O ₃ , CeO _2, and M element are selected from Sr _1-x R _x Fe _In the chemical formula of _2n-y M _y O _{3n ± θ,} the mixture was blended so that n = 5.90 and x = y = 0.1, mixed in a wet manner, dried and granulated, and calcined at 1250 ° C. for 2 hours in the air.

The calcined powder was coarsely pulverized in a disc mill, and then wet pulverized in an attritor to obtain a slurry containing fine particles having an average particle diameter of 0.8 mu m.

As sintering aids, SrCO ₃ , CaCO ₃ , and SiO ₂ were added at the initial grinding stage by 0.5%, 0.8%, and 0.45%, respectively, in the weight ratio to the finely divided powder. This slurry was wet-molded in the magnetic field of 10 kOe, and the molded object was obtained. The molded body was fired in the air for 2 hours at a temperature range of 1170 to 1230 ° C, respectively, to obtain a sintered body.

In addition, a conventional comparative material having a composition of x = y = 0 was produced in the same manner (Comparative Example 2).

The sintered bodies obtained in Example 5 and Comparative Example 2 were measured by the hysteresis curve in the B-H Tracer (Tracer), the magnetic properties were evaluated, the results are shown in FIG.

As shown in FIG. 2, the sintered body substituted with Li has a particularly high level of residual magnetic flux density in the region of coercive force lower than that of the comparative material (Comparative Example 2), and thus it can be confirmed that the effect of improving the saturation magnetization is effective.

Therefore, Li-sintered sintered body is suitable for materials having high residual magnetic flux density, and Na, K, or Rb-sintered sintered body has relatively high residual magnetic flux density and coercive force at the same time, and thus is suitable as a high-performance ferrite material. . That is, it can be seen that the material according to the present embodiment is superior in magnetic properties as compared with the comparative material (Comparative Example 2).

<Example 6>

In the present embodiment, Ce is selected as the R element, and Na as the M element, respectively, and SrCO ₃ , Fe ₂ O ₃ , CeO ₂ , and Na ₂ CO ₃ are selected as Sr _1-x Ce _x Fe _2n-y Na _y O _{3n ± θ} In the chemical formula, the mixture was mixed so that n = 5.90 and x = y = 0.1, mixed in a wet manner, dried and granulated, and calcined in air at 1250 ° C. for 2 hours.

The calcined powder was coarsely pulverized in a disc mill, and then wet pulverized in an attritor to obtain a slurry containing fine particles having an average particle diameter of 0.8 mu m (Example 6-1). On the other hand, in a planetary mill, the slurry containing the microparticles | fine-particles whose average particle diameter is 0.4 micrometer was obtained (Example 6-2).

As sintering aids, SrCO ₃ , CaCO ₃ , and SiO ₂ were added at the initial grinding stage by 0.5%, 0.8%, and 0.45%, respectively, in the weight ratio to the finely divided powder.

The slurry containing 0.8 micrometer microparticles | fine-particles was wet-molded in the 10 kOe magnetic field as it was, and the molded object was obtained. On the other hand, the slurry containing the 0.4 micrometer microparticles | fine-particles was kneaded after drying. Kneading was performed using kneader, water was added so that the concentration of solids was 80%, and polycarboxylate was added 0.3% by weight of solids for the purpose of improving dispersibility. A molded article was produced by the method. Thereafter, the molded body was fired in the air for 2 hours at a temperature range of 1170 to 1230 ° C, respectively, to obtain a sintered body.

In addition, a conventional comparative material having a composition of x = y = 0 was produced in the same manner (Comparative Example 2).

The sintered bodies obtained in Example 6 and Comparative Example 2 were measured by the hysteresis curve in the B-H Tracer (Tracer), the magnetic properties were evaluated, the results are shown in FIG.

As shown in FIG. 3, it can be seen that the residual magnetic flux densities of the Ce and Na substituents are remarkably improved in both the relatively low coercive region in both the average particle diameters of 0.8 μm and 0.4 μm. Furthermore, it can be seen that the atomization up to the 0.4 μm region can improve the residual magnetic flux density of 150 G or more through the kneading treatment.

Examining the effect of the average particle diameter on the magnetic properties, the effect of improving the magnetic properties is not remarkable when the average particle diameter is larger than 0.8 mu m. On the contrary, when the average particle diameter is smaller than 0.4 mu m, the magnetic properties deteriorate due to abnormal grain growth. Most preferred is a range of 0.8 μm to 0.4 μm.

On the other hand, as a result of examining the influence of the amount of dispersant added during kneading on the magnetic properties, when the solid content ratio is less than 0.1%, the effect is not remarkable. The range of the dispersant addition amount is preferably 0.1% to 1.0%.

As shown in the above embodiment, according to the present invention, the saturation magnetization of the ferrite calcined powder is improved, whereby a sintered magnet of high characteristics can be obtained.

<Example 7>

In this example, SrCO ₃ and Fe ₂ O ₃ were blended to form a basic composition of SrO.nFe ₂ O ₃ (n = 5.9), wet mixed, and then calcined in air at 1250 ° C. for 2 hours.

The calcined powder was coarsely pulverized in a disk mill, and then finely pulverized in wet with Atlite to obtain a slurry containing fine particles having an average particle diameter of 0.8 mu m. At this time, 0.85% of CeO _{2 and} 0.25% of Li ₂ CO ₃ were added based on the weight of the crude powder at the beginning of the pulverization process. At this time, 0.85% of CeO _{2 and} 0.25% of Li ₂ CO ₃ were added in the formula Sr _1-x Ce _x Fe _2n-y Li _y O _{3n ± θ} , where x = y = 0.05 and n = 5.60. Corresponds to

As a comparative material, a slurry without adding CeO ₂ and Li ₂ CO ₃ was also produced (Comparative Example 2).

In Example 7 and Comparative Example 2, SrCO ₃ , CaCO ₃ , and SiO ₂ were added 0.5%, 0.8%, and 0.45%, respectively, in the weight ratio to the finely divided powder, at the beginning of the fine grinding process.

Each slurry was wet-molded in a 10 kOe magnetic field to obtain a molded body. The molded body was fired in the air for 2 hours at a temperature range of 1170 to 1230 ° C, respectively, to obtain a sintered body.

The sintered bodies of Example 7 and Comparative Example 2 measured the hysteresis curve in the B-H Tracer (Tracer), and evaluated the magnetic properties, the results are shown in FIG.

As shown in Figure 4, in the fine pulverization, a group without addition of CeO ₂ and Li ₂ CO _3, that is, x = y = the addition of CeO ₂ and Li ₂ CO ₃ than 0, the comparison material (Comparative Example 2), i.e. It can be seen that Example 7 with x = y = 0.05 has a high residual magnetic flux density of 100 G or more in the coercive force range of the same level.

In addition, according to the present embodiment, it was confirmed that in addition to adding the substitution element in the mixing step, the magnetic properties could be improved by the same effect even when added in the fine grinding step.

As described above, in the present invention, Sr or Ba of a ferrite magnet is replaced with Ti, Zr, Sn, Ce, Y, La, Pr, Nd, or Sm elements, and Fe is replaced with Li, Na, K, or Substitution with the Rb element provides a hexagonal ferrite sintered magnet having improved magnetic properties, particularly having a high residual magnetic flux density.

In the present invention, by substituting Fe with Li, Na, K, or Rb elements, the residual magnetic flux density is improved without lowering the coercive force, and as a result, the maximum energy is improved.

In addition, the method for producing a ferrite sintered magnet according to the present invention is a sintered magnet having excellent magnetic properties without changing the conventional manufacturing process of mixing, calcining, coarse pulverization, fine pulverization, molding sintering in the magnetic field Manufacturing is possible, and as a result, molding cycle time can be shortened and molding productivity can be improved.

Since the hexagonal ferrite sintered magnet according to the present invention has excellent magnetic properties such as high residual magnetic flux density, it is possible not only to reduce the size and weight of various DC power motors used in home appliances and automotive electronics, but also to achieve high efficiency. It also enables the manufacture of motors.

1 is a graph showing the results of measuring the magnetic properties of the ferrite magnet powder prepared in Example 3 of the present invention, showing the relationship between Ce and Na substitution amount and saturation magnetization.

2 is a graph showing the results of measuring the magnetic properties of the ferrite sintered magnet prepared in Example 5 of the present invention, the substitution effect of Li, Na, K, and Rb and comparison with the comparative material (Comparative Example 2) It is shown.

3 is a graph showing the results of measuring the magnetic properties of the ferrite sintered magnet produced in Example 6 of the present invention, showing the effect of the fine grinding and kneading treatment.

4 is a graph showing the results of measuring the magnetic properties of the ferrite sintered magnet prepared according to Example 7 of the present invention. ) Is shown.

Claims (8)

Hexagonal ferrite sintered magnet having a composition of the following formula (1). [Formula 1] A _1-x R _x Fe _2n-y M _y O _{3n ± θ} (Wherein A element is one or more selected from Sr, Ba, Ca, and Pb, R element is one or more selected from Ti, Zr, Sn, Ce, Y, La, Pr, Nd, and Sm, and M element Is at least one selected from Li, Na, K, and Rb, x, y, n are molar ratios, 0.02 ≦ x ≦ 0.50, 0.02 ≦ y ≦ 0.50, 5.0 ≦ n ≦ 6.5) The method of claim 1, Hexagonal ferrite sintered magnet, characterized in that the substitution ratio x / y is 0.8 ~ 2.0 when the R element is at least one selected from Ti, Zr, Sn, and Ce (+) tetravalent metal. The method of claim 1, Hexagonal ferrite sintered magnet, characterized in that the substitution ratio x / y is 1.6 to 4.0 when the R element is at least one selected from Y, La, Pr, Nd, and Sm which is a (+) trivalent metal. After calcination and coarsely pulverized by mixing the raw material to have a composition of the formula (1); Fine grinding to obtain an average particle diameter in the range of 0.4 to 0.8 mu m; Kneaded after drying or concentrating; Forming in a magnetic field in the state of a wet slurry; A method for producing a ferrite sintered magnet, characterized in that the sintering treatment. [Formula 1] A _1-x R _x Fe _2n-y M _y O _{3n ± θ} (Wherein A element is one or more selected from Sr, Ba, Ca, and Pb, R element is one or more selected from Ti, Zr, Sn, Ce, Y, La, Pr, Nd, and Sm, and M element Is at least one selected from Li, Na, K, and Rb, x, y, n are molar ratios, 0.02 ≦ x ≦ 0.50, 0.02 ≦ y ≦ 0.50, 5.0 ≦ n ≦ 6.5) Metal compound of Ti, Zr, Sn, Ce, Y, La, Pr, Nd, and Sm as an R element in a ferrite raw material powder having n of 5.5 to 6.5 in SrO · nFe ₂ O ₃ of the initial pulverization process and general composition At least one selected from among and at least one selected from the metal compounds of Li, Na, K, and Rb as M elements are simultaneously added to have a composition of Formula 1 so that the average particle diameter is in the range of 0.4 to 0.8 μm. Fine grinding; Kneaded after drying or concentrating; Forming in a magnetic field in the state of a wet slurry; A method for producing a ferrite sintered magnet, characterized in that the sintering treatment. [Formula 1] A _1-x R _x Fe _2n-y M _y O _{3n ± θ} (Wherein A element is one or more selected from Sr, Ba, Ca, and Pb, R element is one or more selected from Ti, Zr, Sn, Ce, Y, La, Pr, Nd, and Sm, and M element Is at least one selected from Li, Na, K, and Rb, x, y, n are molar ratios, 0.02 ≦ x ≦ 0.50, 0.02 ≦ y ≦ 0.50, 5.0 ≦ n ≦ 6.5) The method according to claim 4 or 5, A method for producing a ferrite sintered magnet, wherein the metal compound of Ti, Zr, Sn, Ce, Y, La, Pr, Nd, and Sm selected as the R element is a metal oxide or a metal hydroxide. The method according to claim 4 or 5, Method for producing a ferrite sintered magnet, characterized in that the metal compound of Li, Na, K, and Rb selected as the M element is a metal carbide, metal oxide, or metal hydroxide. The method according to claim 4 or 5, A method for producing a ferrite sintered magnet, characterized in that 0.1 to 1.0% of the dispersant is added at a solid content ratio in the fine grinding step or the kneading step.