JP2005259751A - Ferrite magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferrite magnet high in both remanent magnetization and a coersive force. <P>SOLUTION: The ferrite magnet comprises a W-type ferrite having, as a main phase, a hexagonal structure expressed as (1-x)SrO/(x/2)La<SB>2</SB>O<SB>3</SB>/2FeO/(n-y/2)Fe<SB>2</SB>O<SB>3</SB>/yCoO, where x, y and n refer to mol ratios and satisfy relations of 0.01≤x≤0.2, 0.01≤y≤0.2 and 7≤n≤9, and Co<SP>2+</SP>substitutes for Fe<SP>3+</SP>of the W-type ferrite. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnet having W-type ferrite as a main phase and a method for manufacturing the same.

Ferrite is a general term for compounds formed by divalent cationic metal oxides and trivalent iron, and ferrite magnets are used in various applications such as motors and generators. As a material of the ferrite magnet, Sr ferrite (SrFe ₁₂ O ₁₉ ) or Ba ferrite (BaFe ₁₂ O ₁₉ ) having a magnetoplumbite type hexagonal structure is widely used. These ferrites are produced at a relatively low cost by powder metallurgy using iron oxide and carbonate such as strontium (Sr) or barium (Ba) as raw materials.

The basic composition of magnetoplumbite-type ferrite (referred to as M-type) is usually expressed by the chemical formula MO · 6Fe ₂ O ₃ . The element M is a metal that becomes a divalent cation, and is selected from Sr, Ba, Pb, and others. The M-type ferrite has been improved in performance by various methods so far. Of particular importance among the characteristics of the permanent magnet, the residual magnetization B _r and the intrinsic coercive force H _cJ. Remanence B _r is determined by the density and degree of orientation of the magnet, and the saturation magnetization J _s which is determined by its crystal structure,
B _r = J _s × degree of orientation × density ratio × main phase ratio.

J _s of M-type Sr ferrite is about 0.465T. The density of the sintered magnet is a maximum of about 98% relative to the true density. The degree of orientation is substantially limits the highest about 98% in the magnetic orientation degree B _r / J _s represented by the ratio of the magnetization value J _s when applying a magnetic field B _r and 800 kA / m. Therefore, Br of magnets is limited to about 0.446T, to obtain a more high B _r 0.45 T is virtually impossible.

Further, the coercive force H _cJ is closely related to the anisotropy field H _a, the coercivity H _cJ also increases with increasing anisotropy field H _a theoretically. The anisotropy field H _a is expressed by the following equation.
H _a = 2K ₁ / J _s

Here, K ₁ is an anisotropy constant and J _s is a saturation magnetization. In order to improve the coercive force H _cJ is necessary to increase the anisotropy field H _a.

For M-type ferrite, it increased anisotropy field H _a is the addition of _{Al 2 O 3, Cr 2 O} 3, can be improved H _cJ is generally known.

  In particular, in M-type Ba ferrite, it is known that coercivity and magnetization are improved by substituting part of Ba with La and part of Fe with Co and Zn (Non-Patent Document). 1).

  In M-type Sr ferrite, it has been reported that coercivity and saturation magnetization are improved by substituting part of Sr with La and part of Fe with Co and Zn (Patent Literature). 1). Furthermore, it has been reported that saturation magnetization is improved by substituting part of Sr with La and part of Fe with Co, Ni, Mn and Zn (Patent Document 2).

There are various types of hexagonal ferrites depending on the combination of crystal structures. Among them, there is a W-type ferrite having a magnetocrystalline anisotropy constant K _{1 that} is similar to that of M-type ferrite and a high saturation magnetization of 0.500 T. In the case of this W-type ferrite, it is known that when Al ₂ O ₃ or Cr ₂ O ₃ is added, the coercive force is improved by increasing the anisotropy constant (Patent Document 3).

In addition, a high-performance ferrite magnet containing R (rare earth element), Co and Zn in W-type ferrite has been proposed. Since this W-type ferrite is calcined and sintered in the atmosphere, Fe in the W-type ferrite exists as stable Fe ³⁺ and hardly changes to Fe ²⁺ . For this reason, it is known that by adding Co ²⁺ and Zn ²⁺ , which are stable divalent metals in the atmosphere, the crystal structure of W-type ferrite is stabilized and the magnetic properties are improved (patent) Reference 4).
International Publication No. 98/38654 Pamphlet JP-A-11-97227 JP 9-260124 A JP 2003-124014 A Journal of Magnetism and Magnetic Materials vol.31-34, (1983) 793-794, Bull. Acad. Sci. USSR (Transl.), Phys. Sec. Vol.25 (1961) 1405-1408

However, in the case of W-type ferrite, when Al ₂ O ₃ , Cr ₂ O ₃ or the like is added, the coercive force is increased, but there is a problem that the saturation magnetization is greatly decreased.

  In addition, in the case of W-type ferrite added with R, Co, and Zn, calcined and sintered in the atmosphere, Co and Zn are likely to enter a divalent position, so that a dramatic improvement in magnetic properties cannot be expected. There's a problem.

  The present invention has been made in view of the above circumstances, and an object of the present invention can be achieved with a conventional hexagonal ferrite magnet by synthesizing W-type ferrite having both high saturation magnetization and anisotropic magnetic field. It is an object of the present invention to provide a ferrite magnet having a high remanent magnetization and coercive force.

The ferrite magnet of the present invention is a W type having a hexagonal crystal structure represented by (1-x) SrO. (X / 2) La ₂ O ₃ .2FeO. (Ny / 2) Fe ₂ O ₃ .yCoO. A ferrite magnet having ferrite as a main phase, wherein x, y, and n indicate molar ratios, and 0.01 ≦ x ≦ 0.2, 0.01 ≦ y ≦ 0.2, and 7 ≦ n ≦ 9 The relationship is satisfied, and Fe ^{3+ of the} W-type ferrite is substituted with Co ²⁺ .

The method of manufacturing a ferrite magnet according to the present invention includes a step of preparing a raw material mixed powder obtained by adding La oxide powder and Co oxide powder to a raw material powder of SrCO ₃ and Fe ₂ O ₃ , and a raw material mixed powder the by calcination in an inert gas atmosphere, (1-x) SrO · (x / 2) La 2 O 3 · 2FeO · (n-y / 2) Fe 2 O 3 · yCoO ( where, x, y and n represent molar ratios, and are mainly W-type ferrites having a hexagonal crystal structure expressed by 0.01 ≦ x ≦ 0.2, 0.01 ≦ y ≦ 0.2, and 7 ≦ n ≦ 9). And a step of forming a calcined body in which Fe ^{3+ of the} W-type ferrite is substituted with Co ²⁺ .

  The manufacturing method of the ferrite magnet by this invention includes the process of adding 0.1 wt%-1.5 wt% of carbon before calcination in the said manufacturing method.

  The method of manufacturing a ferrite magnet according to the present invention includes the step of pulverizing the calcined body, the step of forming the pulverized powder in a magnetic field, the step of drying the formed body, and the formed body after drying as an inert gas. The method further includes a step of sintering in an atmosphere and / or in a vacuum.

  The method for producing a ferrite magnet according to the present invention includes a step of pulverizing the calcined body, a step of heat-treating the pulverized powder in an inert gas atmosphere, a step of mixing the pulverized powder after heat treatment and a binder, The method further includes the step of molding the mixed powder in a magnetic field or in the absence of a magnetic field.

  The process of preparing the raw material mixed powder is not only when preparing such a raw material mixed powder from the beginning, but also when purchasing and using a raw material mixed powder prepared by another person, or a powder prepared by another person. Including the case of mixing.

According to the present invention, magnetization and by anisotropic magnetic field to synthesize both high W-type ferrite, a ferrite magnet having a high residual magnetization B _r and coercivity H _cj which could not be achieved with conventional hexagonal ferrite magnet Can be provided.

The magnet powder of the present invention has a ferrite main phase represented by (1-x) SrO. (X / 2) La ₂ O ₃ .2FeO. (Ny / 2) Fe ₂ O ₃ .yCoO. ing. A part of Sr is substituted with La, and the substitution amount x is in the range of 0.01 ≦ x ≦ 0.2. A part of Fe is substituted by Co, the substitution amount y is in the range of 0.01 ≦ y ≦ 0.2, and n is in the range of 7 ≦ n ≦ 9.

The above composition formula is represented by the composition ratio of each metal element as follows.
Sr: 4.8 atomic% or more, 5.8 atomic% or less,
La: 0.1 atomic% or more, 1.2 atomic% or less,
Fe: 92.9 atomic% or more, 94.1 atomic% or less,
Co: 0.1 atomic% or more and 1.2 atomic% or less.

  The manufacturing method of the magnet powder of this invention is demonstrated.

First, SrCO ₃ powder and Fe ₂ O ₃ powder are mixed in a molar ratio ranging from 1: 7 to 1: 9. At this time, La ₂ O ₃ and CoO are added to the raw material powder.

At this time, when carbon is added to the raw material powder, it functions as a reducing agent at the time of calcination in the next step, and can reduce the raw material powder, in particular, change Fe ³⁺ in the ferrite to Fe ²⁺ . The amount of carbon added is preferably 0.1 wt% to 1.5 wt%. If the amount of carbon added is less than 0.1 wt%, there is no effect under carbon, and if it exceeds 1.5 wt%, the reduction proceeds and spinel ferrite is generated, which is not preferable.

  As described above, La and Co are preferably added as oxide powders of La and Co as described above. However, powders other than oxides (for example, carbonate, hydroxide, nitrate, chloride, etc.) You may add in a powder state and a solution state.

  Carbon may be activated carbon powder, organic compound powder or solution. The organic compound is, for example, carboxylic acid or a salt thereof, stearic acid or a salt thereof, gluconic acid or a salt thereof.

With respect to the raw material powder, B ₂ O _3, H ₃ other compounds containing BO ₃ and the like may be added about 1 wt% if desired.

The mixed raw material powder is then heated to a temperature of 1200 ° C. to 1400 ° C. in an inert gas atmosphere using an electric furnace or the like to form a ferrite compound by a solid phase reaction. This process is called “calcination” and the resulting compound is called “calcination”. In this calcined body, ferrite expressed by (1-x) SrO. (X / 2) La ₂ O ₃ .2Fe ²⁺ O. (ny-2) Fe ³⁺ ₂ O ₃ .yCoO Form.

By performing this calcination in an inert gas atmosphere, Fe ^{3+ in} the ferrite changes to Fe ²⁺ , and Co ²⁺ can be replaced with Fe ³⁺ . Thereby, it is possible to obtain a ferrite magnet whose main phase is W-type ferrite having both high saturation magnetization and anisotropic magnetic field.

  The calcination time is preferably 0.5 to 5 hours. The inert gas used is preferably nitrogen, argon or helium. More preferably, it is nitrogen. The effect of the present invention is greatest when the temperature exceeds 1250 ° C. and becomes 1350 ° C. or less.

  Here, the reason for limiting the composition ratio will be described.

In the present invention, it is necessary to perform charge compensation in order to replace Fe ^{3+ of} W-type ferrite with Co ²⁺ having a different valence. In the present invention, the difference in valence is compensated by replacing part of Sr with La. Therefore, the substitution amount preferably satisfies x = y, but the present invention is not limited to the case of x = y.

When x = 0.01 or less, the effect of the present invention is not exhibited. When x = 0.2 or more, magnetite (Fe ₃ O ₄ ) or hematite (α-Fe ₂ O ₃ ) is generated during sintering, and the magnetic properties of the sintered body are deteriorated. When x = 0.3 or more, as shown in Table 1, spinel ferrite (Fe ₃ O ₄ or CoFe ₂ O ₄ ) is generated in the calcined body and the magnetic properties are deteriorated.

Magnetic properties (saturation magnetization and anisotropic magnetic field) of this calcined body were measured by VSM. The saturation magnetization was obtained by plotting the magnetization curve up to 100 kOe by 1 / H ² plot, and the anisotropic magnetic field was obtained by second-order differentiation of the magnetization curve up to 100 kOe (SPD method). The measured sample was a W-type single phase in the X-ray diffraction of the calcined body.

  As shown in Table 2, with increasing x, the saturation magnetization showed a maximum value at x = 0.2 and decreased at 0.3. The anisotropic magnetic field increased with increasing x.

In the calcination process, a ferrite phase is formed by a solid-phase reaction as the temperature rises and is completed at about 1100 ° C. Below this temperature, unreacted hematite (α-Fe ₂ O ₃ ) and M-type ferrite remain. The magnet properties are low. When the calcining temperature exceeds 1200 ° C., the effect of the present invention appears, but when the calcining temperature is 1200 to 1250 ° C., the proportion of the W-type ferrite of the present invention is small, and the amount of W-type ferrite generated as the calcining temperature increases. Will increase. On the other hand, when the calcining temperature exceeds 1350 ° C., spinel ferrite is generated and the magnetic properties are deteriorated. In addition, since the crystal grains grow too much, there is a possibility that inconveniences such as a long time for pulverization in the pulverization step may occur.

  From the above, it is preferable to set the calcination temperature within a temperature range exceeding 1250 ° C. and not exceeding 1350 ° C.

The calcined body obtained by this calcining step is represented by the chemical formula of (1-x) SrO. (X / 2) La ₂ O ₃ .2FeO. (Ny−2) Fe ₂ O ₃ .yCoO. The W-type ferrite main phase has an average particle size in the range of 0.1 to 10 μm.

  The calcined body is preferably composed of a W-type ferrite single phase, but may contain a small amount of M-type ferrite, X-type ferrite, spinel-type ferrite, hematite, and other intermediate products.

  Hereinafter, a method for producing a sintered ferrite magnet from the calcined body will be described.

  First, a calcined body is manufactured by the method described above.

  Next, the calcined body is pulverized into fine particles by a fine pulverization process using a vibration mill, a ball mill and / or an attritor. The average particle size of the fine particles is preferably about 0.4 to 0.8 μm (air permeation method). The fine pulverization step is preferably performed by combining dry pulverization and wet pulverization. In the wet pulverization, an aqueous solvent such as water or various non-aqueous solvents can be used. During the wet pulverization, a slurry in which the solvent and the calcined powder are mixed is generated. It is preferable to add various known dispersants and surfactants to the slurry.

Further, it is preferable to add CaCO ₃ for the purpose of improving the sinterability at the time of fine pulverization, SiO ₂ for the purpose of controlling the crystal grain size, and carbon for preventing the oxidation of Fe ²⁺ during the sintering. The addition amounts of CaCO ₃ , SiO ₂ and carbon are preferably 0.3 to 1.5 wt% as CaO, 0.1 to 0.6 wt% as SiO _{2 and} 0.05 to 0.5 wt% as C.

  Carbon may be activated carbon powder, organic compound powder or solution. The organic compound is, for example, carboxylic acid or a salt thereof, stearic acid or a salt thereof, gluconic acid or a salt thereof. These may be added alone or in combination of two or more.

  In addition, chromium oxide, aluminum oxide, cobalt oxide, zinc oxide, manganese oxide, nickel oxide, copper oxide, titanium oxide, zirconium oxide, tin oxide are added for the purpose of improving magnetic properties (residual magnetization and coercive force). Also good. Of these, chromium oxide and aluminum oxide are effective in improving the coercive force. Addition amounts of chromium oxide 5 wt% or less, aluminum oxide 5 wt% or less, cobalt oxide 3 wt% or less, zinc oxide 3 wt% or less, manganese oxide 3 wt% or less, nickel oxide 3 wt% or less, copper oxide 3 wt% or less, titanium oxide 3 wt% Hereinafter, zirconium oxide is 3 wt% or less and tin oxide is 3 wt% or less.

When a steel ball is used as a fine grinding medium, iron generated from the wear of the steel ball is mixed during grinding. This iron contamination reduces the magnetic properties. Therefore, it is preferable to add SrCO ₃ for the purpose of reacting with iron mixed in the sintering process. BaCO ₃ or CaCO ₃ may be used.

Thereafter, the powder is formed. This molding may be wet or dry. In the wet process, press molding is performed in a magnetic field or in the absence of a magnetic field while removing the solvent in the slurry. The magnetic field strength is preferably 4 kOe to 15 kOe. Molding pressure may be a ^{100kg / cm 2 ~500kg / cm 2} .

  After press molding, a ferrite magnet product is finally completed through known manufacturing processes such as a drying process, a sintering process, a processing process, a cleaning process, and an inspection process.

  In the case of wet molding, the drying step is preferably performed at 100 ° C. or higher and 200 ° C. or lower in the atmosphere of the molded body (called green) in a dryer. The drying temperature is preferably 150 ° C. or higher and 190 ° C. or lower, and more preferably 160 ° C. or higher and 180 ° C. or lower. The holding time is 1 hour or more and 10 hours or less, more preferably 2 hours or more and 5 hours or less.

  In the case of dry molding, the wet-pulverized slurry is dried with a dryer, and after drying, the powder is crushed, and after adding and mixing a binder, the slurry is molded in a magnetic field or in a non-magnetic field. The slurry is dried in the dryer at 100 ° C. or higher and 200 ° C. or lower for 1 hour or longer and 10 hours or shorter. The drying temperature is preferably 150 ° C. or higher and 190 ° C. or lower, and more preferably 160 ° C. or higher and 180 ° C. or lower. The holding time is preferably 2 hours or more and 5 hours or less.

What is necessary is just to grind | pulverize dry powder with a general dry-type grinder. For example, camphor or PVA (polyvinyl alcohol) may be used as the binder. The amount of binder added may be about 0.3 wt% to 1.5 wt% for camphor and about 0.1 wt% to 0.5 wt% for PVA. In the case of dry molding, the magnetic field strength may be 4 kOe to 15 kOe. Molding pressure may be a ^{300kg / cm 2 ~1000kg / cm 2} .

The sintering step may be performed in nitrogen at a temperature range of 1100 ° C. to 1250 ° C. for 0.5 to 2 hours. Moreover, it is preferable to control the oxygen partial pressure during sintering to 1 × 10 ⁻¹ Pa to ¹ × 10 ⁻² Pa.

  The crystal particle diameter of the sintered body is preferably 0.1 μm or more and 5 μm or less. Preferably they are 0.5 micrometer or more and 2 micrometers or less.

  Next, a method for producing a bond-type ferrite magnet from the calcined body will be described.

  A bonded magnet is produced by mixing and solidifying a ferrite magnet powder obtained by pulverizing and heat-treating a calcined body with a flexible rubber or a hard light plastic. In this case, after the magnet powder is mixed with the binder and the additive, the molding process is performed. The molding process is performed by a method such as injection molding, extrusion molding, or roll molding. Moreover, when using as said bond magnet, the heat processing of a ferrite magnet powder should just be performed for 0.1 to 3 hours in the temperature range of 700-1100 degreeC in inert gas. As for the temperature range of heat processing, 900-1000 degreeC is more preferable. The particle diameter of the ferrite magnet powder is 0.1 μm to 5 μm, preferably 0.5 μm to 2 μm.

  Note that at least one element selected from Ba, Ca, and Pb may be used instead of Sr. Further, instead of La or together with La, a part of Sr may be substituted with at least one element selected from rare earth elements (which may include yttrium) and Bi.

  Examples of the present invention will be described below.

(Example 1)
Using SrCO ₃ , Fe ₂ O ₃ , La ₂ O ₃ , and CoO as starting materials, the composition formula (1-x) SrO. (X / 2) La ₂ O ₃ .2FeO. (Ny / 2) Fe ₂ In O ₃ · yCoO, the raw material powder is blended so that x = y, x = 0, 0.05, 0.1, 0.15, 0.18, 0.2, n = 7.5, and C Was added at 0.5 wt%.

  And after mixing for 4 hours in a water solvent using a ball mill, the water | moisture content was dried and the raw material mixed powder was produced. This raw material mixed powder was fired at a set temperature of 1300 ° C. in a nitrogen atmosphere to obtain a calcined body.

Next, this calcined body was dry-pulverized, CaCO ₃ = 0.55 wt%, SiO ₂ = 0.33 wt%, and C = 0 to 0.2 wt% were added to the obtained pulverized powder, and the resulting mixture was used with a ball mill. It grind | pulverized until it became the magnitude | size of the average particle diameter of 0.6 micrometer (air permeation method) in the water solvent.

  The pulverized powder thus obtained was wet-molded in a magnetic field of 0.8 MA / m (10 kOe) to obtain a molded body, and then the molded body was dried at 100 ° C. to 200 ° C. with a dryer.

  Next, sintering was performed in a nitrogen atmosphere at a preset temperature of 1180 ° C. for 30 minutes, thereby producing a sintered magnet.

FIG. 1 shows the magnetic properties of the obtained sintered magnet. Data of "●" indicates the residual magnetization B _r, data of "▲" indicates the coercive force H _cJ. x = residual magnetization B _r in a range of 0.05-0.18 is increasing as compared to Comparative Example (x = 0), slightly increased relative coercivity H _cJ in Comparative Example (x = 0) doing.

Also, compared with Comparative Example to Example showing the same degree of H _cJ, as x increases, B _r is increasing.

(Example 2)
Of the sintered magnet obtained in Example 1, 0.2% of C was added to the powder before pulverization, and the molded body was dried at 170 ° C. (sample No. 1), before pulverization. Table 3 shows the magnetic properties of the powder obtained by adding 0.15% of C to the powder and drying the compact at 200 ° C. (sample No. 2).

(Comparative Example 1)
Under the same conditions as in Example 1, except that x = y, x = 0, C addition amount before pulverization is 0.175 wt%, and the drying temperature of the compact is 150 ° C. A sintered magnet was produced (Sample No. 3). Table 3 shows the magnetic properties of the obtained sintered magnet.

(Comparative Example 2)
Under the same conditions as in Example 1, except that x = y, x = 0, the addition amount of C before pulverization is 0.225 wt%, and the drying temperature of the molded body is 190 ° C. A sintered magnet was produced (Sample No. 4). Table 3 shows the magnetic properties of the obtained sintered magnet.

(Comparative Example 3)
Except for calcining in the air, the sample No. A sintered magnet was produced under the same conditions as in No. 2 (Sample No. 5). Table 3 shows the magnetic properties of the obtained sintered magnet.

(Comparative Example 4)
Sample No. 2 in Example 2 except for calcining in air and sintering in air. A sintered magnet was produced under the same conditions as in No. 2 (Sample No. 6). Table 3 shows the magnetic properties of the obtained sintered magnet.

As is apparent from Table 3, when the example (x = 0.1) and the comparative example (x = 0) are compared for the sample of B _r = 0.465T, BH _max and H _cJ are It can be seen that the example (x = 0.1) is superior to x = 0).

Further, when a sintered magnet calcined in a nitrogen atmosphere (sample No. 2) and a sintered magnet calcined in air (samples No. 5 and 6) were compared, the sintered magnet was calcined in a nitrogen atmosphere according to the present invention. The sintered magnet has improved magnetic properties, particularly Br and BH _max . This is considered to be due to Fe ^{3+ in} the ferrite changing to Fe ²⁺ by calcination in a nitrogen atmosphere, and Co ²⁺ replacing Fe ³⁺ . On the other hand, when calcined in the atmosphere, Fe in ferrite exists as stable Fe ³⁺ and hardly changes to Fe ²⁺ , so Co ²⁺ is likely to easily enter a divalent position. For this reason, the improvement in magnetic characteristics is slight.

  2 shows the sample No. of Example 2. 2 shows the magnetic characteristics of Comparative Example 3 (Sample No. 5) and Comparative Example 4 (Sample No. 6). As is apparent from FIG. 2, it can be seen that the sintered magnet according to the present invention is excellent in magnetic properties, particularly Br.

(Example 2)
In this example, the sintered body was produced in the same manner as in Example 1 while changing the drying temperature of the green body (green). FIG. 2 is a graph showing the relationship between the green drying temperature and the magnetic properties of the sintered body when x = y = 0.1.

As can be seen from FIG. 2, when the drying temperature was 180 ° C., the residual magnetization B _r and the coercive force H _cJ both _showed maximum values (B _r = 0.472 T, H _cJ = 204 kA / m). Preferred magnetic properties are obtained at a drying temperature of 150 to 190 ° C.

(Example 3)
In this example, x = y = 0.1, the n value was changed in the range of 6.75 to 9, and a sintered body was produced in the same manner as in Example 1. FIG. 3 shows the relationship between the n value and the magnetic properties of the sintered body. As can be seen from FIG. 3, the residual magnetization B _r represents the maximum value among the 7.5 to 8.25, the coercivity H _cJ were higher values between 7.5 to 9.0. As can be seen from FIG. 3, the n value is preferably in the range of 7.5 to 8.3, more preferably 7.75 to 8.3.

  According to the present invention, a ferrite magnet having both high remanent magnetization and coercive force is provided.

It is a graph which shows the relationship between x and the magnetic characteristic of a sintered compact, when La substitution amount x and Co substitution amount y are equal (x = y). It is a graph which shows the relationship between a calcination atmosphere and the magnetic characteristic of a sintered compact in the case of x = y = 0.1. It is a graph which shows the relationship between the green drying temperature and the magnetic characteristic of a sintered compact in the case of x = y = 0.1. It is a graph which shows the relationship between n value and the magnetic characteristic of a sintered compact in the case of x = y = 0.1.

Claims (5)

(1-x) SrO · ( x / 2) La 2 O 3 · 2FeO · (n-y / 2) ferrite as a main phase and W-type ferrite having a hexagonal structure expressed by Fe ₂ O ₃ · yCoO A magnet,
x, y and n represent molar ratios;
0.01 ≦ x ≦ 0.2,
0.01 ≦ y ≦ 0.2, and 7 ≦ n ≦ 9
And a ferrite magnet in which Fe ^{3+ of the} W-type ferrite is replaced by Co ²⁺ . Preparing a raw material mixed powder obtained by adding La oxide powder and Co oxide powder to the raw material powder of SrCO ₃ and Fe ₂ O ₃ ;
By calcining the starting material mixed powder in an inert gas atmosphere, (1-x) SrO · (x / 2) La 2 O 3 · 2FeO · (n-y / 2) Fe 2 O 3 · yCoO ( although , X, y and n represent molar ratios and have a hexagonal structure represented by 0.01 ≦ x ≦ 0.2, 0.01 ≦ y ≦ 0.2, and 7 ≦ n ≦ 9) Forming a calcined body in which ferrite is the main phase and Fe ^{3+ of} W-type ferrite is substituted with Co ²⁺ ;
For producing a ferrite magnet including   The method for producing a ferrite magnet according to claim 2, wherein 0.1 wt% to 1.5 wt% of carbon is added before calcination.   The method further includes a step of pulverizing the calcined body, a step of molding the pulverized powder in a magnetic field, a step of drying the molded body, and a step of sintering the molded body after drying in an inert gas atmosphere and / or in a vacuum. The manufacturing method of the sintered type ferrite magnet of Claim 2 or Claim 3.   A step of pulverizing the calcined body, a step of heat-treating the pulverized powder in an inert gas atmosphere, a step of mixing the pulverized powder after heat treatment and a binder, and a step of forming the mixed powder in a magnetic field or in a non-magnetic field. The manufacturing method of the bond type ferrite magnet of Claim 2 or Claim 3 containing.

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