JP2006001752A - Method for production of ferrite magnetic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for production of a W-type ferrite improved in magnetic characteristic, particularly in coercive force. <P>SOLUTION: This method for producing the ferrite magnetic material having a hexagonal W-type ferrite as a main phase comprises a forming process for making a formed body containing a main ingredient and the first accessory ingredient comprising one, two or more selected from the ingredients of Ga, Al, W, Ce, Mo and Cr and a firing process for firing the resultant formed body. The formed body may comprise a calcined body containing both the main and the first accessory ingredients or may comprise a mixture of a calcined body composing the main ingredient with the first accessory ingredient. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a hard ferrite material, particularly a ferrite magnetic material that can be suitably used for a hexagonal W-type ferrite magnet.

A W-type ferrite magnet is known as a ferrite magnet that has the possibility of exhibiting magnetic properties that surpass the M-type ferrite magnets that have been the mainstream of sintered ferrite magnets. The W-type ferrite magnet has a saturation magnetization (4πIs) about 10% higher than that of the M-type ferrite magnet, and the anisotropic magnetic field is about the same.
For example, in Patent Document 1 (Japanese Patent Laid-Open No. 9-260124), W having a composition of SrO.2 (FeO) .nFe ₂ O ₃ fired in a non-oxidizing atmosphere while adding carbon as a reducing agent. Type ferrite is disclosed. The maximum energy product (BH) max) of this W-type ferrite has reached 5.3 MGOe. However, the coercive force is 2.5 kOe, which is lower than the level of 3 to 4 kOe of a general conventional M-type ferrite.

In Patent Document 2 (Japanese Patent Laid-Open No. 11-251127), the basic composition is MO.xFeO. (Yx / 2) Fe ₂ O ₃ (M is one of Ba, Sr, Pb, and La in atomic ratio). W type ferrite magnets represented by 1.7 ≦ x ≦ 2.1 and 8.8 ≦ y ≦ 9.3 are disclosed. The magnet having the composition of SrO.2FeO.8Fe ₂ O ₃ disclosed in Patent Document 2 has a maximum energy product (BH) max) of 5.5 MGOe. However, the coercive force is about 3 kOe, and further improvement is expected.

JP 9-260124 A Japanese Patent Laid-Open No. 11-251127

As described above, various studies have been made on W-type ferrite magnets, but higher magnetic properties are required. In particular, it is important for practical use of W-type ferrite that the coercive force be 3 kOe or more. Of course, in that case, it must be avoided that the residual magnetic flux density is lowered. That is, it is indispensable for practical use of W-type ferrite that both the coercive force and the residual magnetic flux density are at a high level.
The present invention has been made on the basis of such a technical problem, and an object thereof is to improve the magnetic properties of W-type ferrite, particularly the coercive force.

In order to achieve this object, the present inventor examined other subcomponents of the main component constituting the W-type ferrite, and found that Ga ₂ O ₃ , Al ₂ O ₃ , WO ₃ , CeO ₂ , MoO ₃ and Cr. _The inclusion of one or more of ₂ O ₃ is effective in improving the coercive force, and the effect of improving the coercive force can be made more remarkable by adopting the addition timing according to the type of subcomponent. It was confirmed.
That is, the present invention is a method for producing a ferrite magnetic material in which hexagonal W-type ferrite is the main phase, and is selected from a main component, a Ga component, an Al component, a W component, a Ce component, a Mo component, and a Cr component. A method for producing a ferrite magnetic material comprising: a molding step for producing a molded body containing a first subcomponent composed of seeds or two or more species; and a firing step for firing the molded body.

The ferrite magnetic material of the present invention can be produced by subjecting the raw material powder to basic steps of calcining, pulverizing, forming and firing. The first subcomponent can be added either before and / or after calcination.
When adding a 1st subcomponent before calcination, a molded object is comprised from the calcined body containing a main component and a 1st subcomponent.
When adding a 1st subcomponent after calcination, a molded object is comprised from the mixture of the calcined body which comprises a main component, and a 1st subcomponent. This mixture includes a first pulverization step of pulverizing the calcined body to a predetermined particle size, a step of heat-treating the pulverized product obtained in the first pulverization step in an atmosphere having an oxygen concentration of 10 vol% or less, and a heat treatment A second pulverization step of pulverizing the applied pulverized product to a predetermined particle size, and adding the first subcomponent in the first pulverization step and / or the second pulverization step.

In the present invention, the main component is AFe ²⁺ _a Fe ³⁺ _b O ₂₇ (1)
(However, 1.1 ≦ a ≦ 2.4, 12.3 ≦ b ≦ 16.1. A is at least one element selected from Sr, Ba and Pb) Is preferred.
In the present invention, the first subcomponent is preferably contained in the following range.
Ga component terms _of Ga ₂ O ₃ in Ga ₂ O _3: 0.05~15wt%
Al component is Al ₂ O _{3 in} terms of Al ₂ O ₃ : 0.01 to 1.5 wt%
W component is WO _{3 in} terms of WO ₃ : 0.01 to 0.6 wt%
Ce component is CeO _{2 in} terms of CeO ₂ : 0.01 to 0.6 wt%
Mo component is MoO _{3 in} terms of MoO ₃ : 0.001 to 0.16 wt%
Cr component is Cr ₂ O _{3 in} terms of Cr ₂ O ₃ : 0.01 to 3.5 wt%
In the present invention, it is preferable to add CaCO ₃ : 0.3 to ₃ wt%, SiO ₂ : 0.2 to 1.4 wt%, as the second subcomponent, one or two of Ca component and Si component.

  According to the present invention, the magnetic properties of the W-type ferrite, particularly the coercive force, can be improved.

Hereinafter, the present invention will be described in detail based on embodiments. The present invention is characterized in that a predetermined subcomponent is contained in the W-type ferrite material. By containing the subcomponent, a novel W-type ferrite having both a high residual magnetic flux density (Br) and a coercive force (HcJ) can be obtained.
The present invention can be widely used for W-type ferrites such as Fe ₂ W-type ferrite and ZnW-type ferrite.

<Composition>
When the ferrite magnetic material of the present invention is Fe ₂ W type ferrite, the main component is composed of the following composition formula (1).
AFe ²⁺ _a Fe ³⁺ _b O ₂₇ Formula (1)
However, in Formula (1), A is at least one element selected from Sr, Ba and Pb, 1.1 ≦ a ≦ 2.4, 12.3 ≦ b ≦ 16.1. In the above formula (1), a and b each represent a molar ratio.

In the above formula (1), a indicating the proportion of Fe ²⁺ is 1.1 ≦ a ≦ 2.4. When a is less than 1.1, an M phase and an Fe ₂ O ₃ (hematite) phase having a saturation magnetization (4πIs) lower than that of the W phase are generated, and the saturation magnetization (4πIs) is lowered. On the other hand, if a exceeds 2.4, a spinel phase is generated and the coercive force (HcJ) is lowered. Therefore, a is set to a range of 1.1 ≦ a ≦ 2.4. The preferable range of a is 1.6 ≦ a ≦ 2.1, and the more preferable range is 1.6 ≦ a ≦ 2.0.
Moreover, b which shows the ratio of Fe3 ⁺ shall be the range of 12.3 <= b <= 16.1. In the range of 1.1 ≦ a ≦ 2.4, if b is less than 12.3, a spinel phase is generated and the coercive force (HcJ) decreases. On the other hand, if b exceeds 16.1, the M phase and Fe ₂ O ₃ (hematite) phase are generated, and the saturation magnetization (4πIs) decreases. Therefore, b is set to a range of 12.3 ≦ b ≦ 16.1. The preferable range of b is 13.5 ≦ b ≦ 16.0.

In the Fe ₂ W type ferrite, it is more preferable that both Sr and Ba are selected as the A element and the main component is the composition of the following formula (2).
Sr _(1-x) Ba _x Fe ²⁺ _a Fe ³⁺ _b O ₂₇ Formula (2)
However, 0.03 ≦ x ≦ 0.80, 1.1 ≦ a ≦ 2.4, and 12.3 ≦ b ≦ 16.1. In the above formula (2), x, a, and b each represent a molar ratio.

Coexistence of two atoms, Sr and Ba, can improve the magnetic properties, particularly the coercive force (HcJ). The reason for the improvement of the coercive force is not clear, but it is understood that the coexistence of Sr and Ba makes the crystal grains constituting the sintered body finer, and that the refinement of the crystal grains contributes to the improvement of the coercive force. Is done.
In order to enjoy the effect of improving magnetic characteristics, in the above formula (2), it is preferable that x is in the range of 0.03 ≦ x ≦ 0.80. The reason why 1.1 ≦ a ≦ 2.4 and 12.3 ≦ b ≦ 16.1 in the above formula (2) is as described for the formula (1).

When the present invention is applied to a so-called ZnW type ferrite, it is preferable to employ a main component composed of the following composition formula (3).
AZn _c Fe _d O ₂₇ ··· formula (3)
However, in Formula (3), A is at least one element selected from Sr, Ba, and Pb, 1.1 ≦ c ≦ 2.1, and 13 ≦ d ≦ 17. In the above formula (3), c and d each represent a molar ratio.
A preferable range of c indicating the proportion of Zn is 1.3 ≦ c ≦ 1.9, and a more preferable range is 1.3 ≦ c ≦ 1.7. Moreover, the preferable range of d which shows the ratio of Fe is 14 <= d <= 16, and a more preferable range is 14.5 <= d <= 15.5.
In ZnW type ferrite, it is preferable to select at least one of Sr and Ba as the A element.

The ferrite magnetic material obtained by the present invention contains the first subcomponent in addition to the main components represented by the formulas (1), (2), and (3). The first subcomponent includes an Al component, a W component, and a Ce derived from one or more compositions of Ga ₂ O ₃ , Al ₂ O ₃ , WO ₃ , CeO ₂ , MoO _3, and Cr ₂ O _3. It is 1 type, or 2 or more types of a component, Mo component, Cr component, and Ga component.
In addition, for example, a Ca component and / or Si component derived from CaCO ₃ and SiO ₂ may be contained as the second subcomponent. By including these components, it is possible to adjust the coercive force (HcJ), the crystal grain size, etc., and obtain a ferrite sintered magnet having both high coercive force (HcJ) and residual magnetic flux density (Br). Can do.

Ga component terms _of Ga ₂ O ₃ in Ga ₂ O _3: it is preferred to include a range of 0.05~15wt%. When Ga ₂ O ₃ exceeds 15 wt%, it is difficult to enjoy the effect of improving the coercive force (HcJ) by adding the Ga component, and the residual magnetic flux density (Br) tends to decrease. Therefore, the Ga component in the present invention is Ga ₂ O ₃ : 0.05 to 15 wt% or less, preferably 0.02 to 10 wt%, more preferably 0.05 to 10 wt%.
Further, when the amount of Ga ₂ O ₃ is 0.02 to 3.0 wt%, more preferably 0.05 to 2.0 wt%, not only the coercive force (HcJ) but also the residual magnetic flux density (Br) Can also be expected. In particular, when it is desired to obtain a coercive force (HcJ) of 3500 Oe or higher while maintaining a residual magnetic flux density (Br) of 4500 G or higher, the amount of Ga ₂ O ₃ may be 0.02 to 3.0 wt%. It is valid.
On the other hand, when the amount of Ga ₂ O ₃ is 3.0 to 8.0 wt%, more preferably 4.0 to 7.0 wt%, a residual magnetic flux density (Br) in the vicinity of 4500 G or 4600 G or more is obtained. However, a coercive force (HcJ) of 3800 Oe or more, further 4000 Oe or more, preferably 4200 Oe or more can be obtained.

Al ₂ O In Al component in terms of Al ₂ O _{3 3} - preferably comprises 0.01~1.5wt%. If Al ₂ O ₃ is less than 0.01 wt%, the effect of addition is insufficient. On the other hand, when Al ₂ O ₃ exceeds 1.5 wt%, it is difficult to make the W phase the main phase, and the residual magnetic flux density (Br) tends to decrease. From the above, Al component in the present invention in terms of Al ₂ O ₃ in Al ₂ O _3: preferably contains 0.01~1.5wt%. A more preferable amount of Al ₂ O ₃ is 0.1 to 0.9 wt%, and a further preferable amount of Al ₂ O ₃ is 0.1 to 0.5 wt%.

W component terms _of WO ₃ with WO _3: preferably contains 0.01~0.6wt%. If WO ₃ is less than 0.01 wt%, the effect of addition is insufficient. On the other hand, when WO ₃ exceeds 0.6 wt%, it becomes difficult to make the W phase as the main phase, and the residual magnetic flux density (Br) tends to decrease. From the above, W component in the present invention terms _of WO ₃ with WO _3: preferably contains 0.01~0.6wt%. A more preferable amount of WO ₃ is 0.1 to 0.6 wt%, and a further preferable amount of WO ₃ is 0.1 to 0.4 wt%.

Ce component CeO ₂ in terms of CeO _2: preferably comprises 0.01~0.6wt%. When CeO ₂ is less than 0.01 wt%, the effect of addition is insufficient. Further, when CeO ₂ exceeds 0.6 wt%, it is difficult to make the W phase as the main phase, and the residual magnetic flux density (Br) tends to decrease. From the above, Ce component in the present invention is CeO ₂ in terms of CeO _2: preferably comprises 0.01~0.6wt%. A more preferable amount of CeO ₂ is 0.01 to 0.4 wt%, and a further preferable amount of CeO ₂ is 0.01 to 0.3 wt%.

Mo component calculated as MoO ₃ by MoO _3: preferably contains 0.001~0.16wt%. If MoO ₃ is less than 0.001 wt%, the effect of addition is insufficient. On the other hand, when MoO ₃ exceeds 0.16 wt%, it is difficult to make the W phase as the main phase, and the residual magnetic flux density (Br) tends to decrease. From the above, Mo component in the present invention is MoO calculated as MoO _{3 3:} preferably contains 0.001~0.16wt%. A more preferable amount of MoO ₃ is 0.005 to 0.10 wt%, and a further preferable amount of MoO ₃ is 0.01 to 0.08 wt%.

Cr ₂ O in Cr component terms of Cr ₂ O _{3 3} - preferably comprises 0.01~3.5wt%. If Cr ₂ O ₃ is less than 0.01 wt%, the effect of addition is insufficient. On the other hand, when Cr ₂ O ₃ exceeds 3.5 wt%, it is difficult to make the W phase the main phase, and the residual magnetic flux density (Br) tends to decrease. From the above, Cr component in the present invention terms of Cr ₂ O ₃ in Cr ₂ O _3: preferably contains 0.01~3.5wt%. A more preferable amount of Cr ₂ O ₃ is 0.1 to 2.5 wt%, and a further preferable amount of Cr ₂ O ₃ is 0.1 to 1.5 wt%.

The Ca component, an Si component in CaCO _3, SiO _{2 conversion, CaCO 3: 0.3~3wt%, SiO} 2: it is preferred to include a range of 0.2~1.4wt%.
When CaCO ₃ is less than 0.3 wt% or SiO ₂ is less than 0.2 wt%, the effect of adding CaCO ₃ or SiO ₂ is insufficient. On the other hand, if CaCO ₃ exceeds 3 wt%, Ca ferrite that causes a decrease in magnetic properties may be generated. Furthermore, when SiO ₂ exceeds 1.4 wt%, the residual magnetic flux density (Br) tends to decrease. From the above, Ca component in the present invention, the amount of Si component is CaCO _3, SiO _{2 conversion, CaCO 3: 0.3~3wt%, SiO} 2: a 0.2~1.4wt%. CaCO ₃ and SiO ₂ are preferably contained in the ranges of CaCO ₃ : 0.3 to 1.5 wt%, SiO ₂ : 0.2 to 1.0 wt%, respectively, and further CaCO ₃ : 0.3 to 1 .2 wt%, SiO ₂ : It is preferable to contain in the range of 0.3 to 0.8 wt%.

The Ca component can be added in the form of CaO in addition to CaCO ₃ . Si component, Ga component, Al component, W component, Ce component, Mo component, Cr component are also SiO ₂ , Ga ₂ O ₃ , Al ₂ O ₃ , WO ₃ , CeO ₂ , MoO ₃ , Cr ₂ O ₃ , respectively. It can also be added in the form of

The sintered ferrite magnet according to the present invention includes hexagonal W-type ferrite as a magnetic phase. The ferrite sintered magnet according to the present invention can have a coercive force (HcJ) of 3500 Oe or more, further 4000 Oe or more, 4000 G or more, and further a residual magnetic flux density (Br) of 4500 G or more.
In the sintered ferrite magnet according to the present invention, the first and second subcomponents may be present in the crystal grains in such a form that a part of elements such as Fe constituting the main component is replaced. It may exist in the grain boundary.

The composition of the ferrite magnetic material according to the present invention can be measured by fluorescent X-ray quantitative analysis or the like. Further, the present invention does not exclude the inclusion of components other than the main component and subcomponents. For example, a part of the Fe ²⁺ site or the Fe ³⁺ site in the Fe ₂ W type ferrite can be replaced with another element, or a part of the Zn site can be replaced with another element in the ZnW type ferrite. it can.

As described above, the ferrite magnetic material of the present invention constitutes one of a ferrite sintered magnet, a ferrite magnet powder, a bond magnet as a ferrite magnet powder dispersed in a resin, and a magnetic recording medium as a film-like magnetic phase. can do.
The sintered ferrite magnet and bonded magnet according to the present invention are processed into a predetermined shape and used for a wide range of applications as described below. For example, for automobiles such as fuel pump, power window, ABS (anti-lock brake system), fan, wiper, power steering, active suspension, starter, door lock, electric mirror, etc. It can be used as a motor. 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. , CD, LD, MD spindle, CD, LD, MD loading, CD, LD optical pickup, etc. Also, motors for home appliances such as air conditioner compressors, refrigerator compressors, electric tool drive, electric fan, microwave oven fan, microwave plate rotation, mixer drive, dryer fan, shaver drive, electric toothbrush, etc. Can also be used. Furthermore, it can also be used as a motor for FA devices such as a robot shaft, joint drive, robot main drive, machine tool table drive, and machine tool belt drive. Other applications include motorcycle generators, speaker / headphone magnets, magnetron tubes, MRI magnetic field generators, CD-ROM clampers, distributor sensors, ABS sensors, fuel / oil level sensors, magnet latches, isolators. Etc. are preferably used.

When the ferrite magnet powder of the present invention is a bonded magnet, the average particle size is preferably 0.1 to 5 μm. The more preferable average particle diameter of the powder for bonded magnets is 0.1 to 2 μm, and the more preferable average particle diameter is 0.1 to 1 μm.
When manufacturing a bonded magnet, ferrite magnet powder is kneaded with various binders such as resin, metal, rubber, etc., and molded in a magnetic field or in a non-magnetic field. As the binder, NBR (acrylonitrile butadiene) rubber, chlorinated polyethylene, and polyamide resin are preferable. After molding, it is cured to obtain a bonded magnet. In addition, before kneading ferrite magnet powder with a binder, it is preferable to perform the heat processing mentioned later.

  A magnetic recording medium having a magnetic layer can be produced using the ferrite magnetic material of the present invention. This magnetic layer includes a W-type ferrite phase represented by the above-described composition formulas (1) to (3). For example, vapor deposition or sputtering can be used to form the magnetic layer. When the magnetic layer is formed by sputtering, the sintered ferrite magnet according to the present invention can also be used as a target. Examples of the magnetic recording medium include a hard disk, a flexible disk, and a magnetic tape.

Next, the suitable manufacturing method of the ferrite magnetic material of this invention is demonstrated.
A suitable method for producing a sintered ferrite magnet of the present invention includes a blending step, a calcining step, a coarse pulverizing step, a fine pulverizing step, a forming step in a magnetic field, a compact heat treatment step, and a firing step. Here, the fine pulverization step is divided into a first fine pulverization and a second fine pulverization, and a powder heat treatment step is performed between the first fine pulverization and the second fine pulverization. The 1st subcomponent and the 2nd subcomponent should just be added before the shaping | molding process in a magnetic field, Specifically, it can add at a mixing | blending process and / or a fine grinding process.
In the following, the case of obtaining Fe ₂ W type ferrite will be mainly described, and the conditions for obtaining ZnW type ferrite will be referred to as appropriate.

<Mixing process>
Each raw material is weighed and then mixed and pulverized by a wet attritor, ball mill, etc. for about 1 to 16 hours. As the raw material powder, an oxide or a compound that becomes an oxide by sintering can be used. In the following, an example using SrCO ₃ powder, BaCO ₃ powder and Fe ₂ O ₃ (hematite) powder will be described. However, SrCO ₃ powder and BaCO ₃ powder may be added in a form other than carbonate. The same applies to Fe, and it can be added in a form other than Fe ₂ O ₃ . Furthermore, it is possible to use a compound containing Sr, Ba and Fe. In addition, in order to obtain ZnW type ferrite, ZnO powder is prepared in addition to SrCO ₃ powder, BaCO ₃ powder and Fe ₂ O ₃ (hematite) powder.

In this blending step, a first subcomponent and further a second subcomponent can be added. The addition amount is as described above. However, these subcomponents can be added after calcining SrCO ₃ powder, BaCO ₃ powder and Fe ₂ O ₃ powder without adding at this stage.
The blending ratio of each raw material can correspond to the composition desired to be finally obtained, but the present invention is not limited to this form. For example, any of SrCO ₃ powder, BaCO ₃ powder, and Fe ₂ O ₃ powder may be added after calcining to adjust the final composition.

<Calcination process>
The mixed powder material obtained in the blending step is calcined at 1100 to 1400 ° C. By performing this calcining in a non-oxidizing atmosphere such as nitrogen gas or argon gas, Fe ²⁺ is generated by reducing Fe ³⁺ in the Fe ₂ O ₃ (hematite) powder, and Fe ₂ W Type ferrite is produced. However, if a sufficient amount of Fe ²⁺ cannot be secured at this stage, an M phase or a hematite phase is present in addition to the W phase. In order to obtain W single-phase ferrite, it is effective to adjust the oxygen partial pressure. This is because when the oxygen partial pressure is lowered, Fe ³⁺ is reduced and Fe ²⁺ is easily generated.
On the other hand, when obtaining the ZnW type ferrite, the calcining may be performed in the atmosphere.
In addition, when the auxiliary component has already been added in the blending step, it is possible to obtain a ferrite magnet powder by pulverizing the calcined body to a predetermined particle size.

<Coarse grinding process>
Since the calcined body is generally granular, it is preferable to coarsely pulverize it. In the coarse pulverization step, treatment is performed using a vibration mill or the like until the average particle size becomes 0.5 to 10 μm. The powder obtained here is sometimes referred to as coarse powder.

<First fine grinding step>
In the first fine pulverization step, the coarse powder is wet or dry pulverized by an attritor, ball mill, jet mill or the like, and the average particle size is 0.08 to 0.8 μm, preferably 0.1 to 0.4 μm, more preferably. Grind to 0.1-0.2 μm. This first pulverization step is performed for the purpose of eliminating coarse powder and further reducing the structure after sintering in order to improve magnetic properties. The specific surface area (by the BET method) is 20 It is preferable to be in the range of ˜25 m ² / g.
Depending on the pulverization method, when the coarse powder is wet pulverized with a ball mill, it may be treated for 60 to 100 hours per 200 g of the coarse powder.
In order to improve the coercive force, it may be preferable to add the first subcomponent prior to the first fine grinding step. Prior to the first fine pulverization step, powders such as CaCO ₃ , SiO ₂ , SrCO ₃ , BaCO ₃ may be added in addition to the first subcomponent.

<Powder heat treatment process>
In the powder heat treatment step, a heat treatment is performed in which the fine powder obtained by the first fine pulverization is held at 600 to 1200 ° C., more preferably 700 to 1000 ° C., for 1 second to 100 hours.
By passing through the first fine pulverization, ultrafine powder that is powder of less than 0.1 μm is inevitably generated. If ultrafine powder is present, problems may occur in the subsequent molding process in a magnetic field. For example, when there is a large amount of ultrafine powder during wet molding, problems such as poor water drainage and molding cannot occur. Therefore, in the present embodiment, heat treatment is performed prior to the second fine pulverization. That is, in this heat treatment, the amount of the ultrafine powder is obtained by reacting the ultrafine powder of less than 0.1 μm generated by the first fine pulverization with the fine powder having a larger particle size (for example, 0.1 to 0.2 μm fine powder). The purpose is to reduce. By this heat treatment, ultrafine powder is reduced and the moldability can be improved.

The heat treatment atmosphere at this time is a non-oxidizing atmosphere in order to avoid that Fe ²⁺ generated by ^calcining becomes Fe ³⁺ due to oxidation. The non-oxidizing atmosphere in the present invention includes an inert gas atmosphere such as nitrogen gas and Ar gas. In addition, the non-oxidizing atmosphere of the present invention allows the inclusion of 10 vol% or less oxygen. If oxygen is contained at this level, the oxidation of Fe ²⁺ is negligible in the holding at the above temperature. The oxygen content in the heat treatment atmosphere is preferably 1 vol% or less, more preferably 0.1 vol% or less.
When obtaining a ZnW type ferrite, the heat treatment atmosphere at this time may be in the air.

<Second fine grinding step>
In the subsequent second pulverization step, the heat-treated finely pulverized powder is wet or dry pulverized by an attritor, ball mill, jet mill or the like, and is 0.8 μm or less, preferably 0.1 to 0.4 μm, more preferably 0.00. Grind to 1-0.2 μm. This second pulverization step is performed for the purpose of adjusting the particle size, removing necking, and improving the dispersibility of the additive. The specific surface area (by the BET method) is 10 to 20 m ² / g, and further 10 to 15 m. A range of ² / g is preferable. When the specific surface area is adjusted within this range, even if ultrafine particles are present, the amount thereof is small, and the moldability is not adversely affected. That is, through the first fine pulverization step, the powder heat treatment step, and the second fine pulverization step, it is possible to satisfy the requirement to refine the sintered structure without adversely affecting the formability.
Depending on the pulverization method, when wet pulverization is performed with a ball mill, the treatment may be performed for 10 to 40 hours per 200 g of finely pulverized powder. If the second pulverization step is performed under the same conditions as the first pulverization step, ultrafine powder will be generated again, and the desired particle size has already been obtained in the first pulverization step. Therefore, in the second fine pulverization step, the pulverization conditions are usually reduced as compared with the first fine pulverization step. Here, whether or not the pulverizing conditions are reduced is not limited to the pulverization time, but may be determined based on mechanical energy input during pulverization.
In order to improve the coercive force, the first subcomponent can be added prior to the second pulverization step. In addition to the first subcomponent, CaCO ₃ , SiO ₂ , or powder such as SrCO ₃ or BaCO ₃ may be added prior to the second pulverization step.

  A carbon powder that exhibits a reducing effect in the firing step can be added prior to the second pulverization step. The addition of carbon powder is effective in producing W-type ferrite in a state close to a single phase (or a single phase). Here, the amount of carbon powder added (hereinafter referred to as “carbon amount”) is preferably in the range of 0.05 to 0.7 wt% with respect to the raw material powder. By setting the amount of carbon within this range, it is possible to fully enjoy the effect of the carbon powder as a reducing agent in the firing step described later, and to obtain a higher saturation magnetization (σs) than when no carbon powder is added. Can do. A preferable carbon amount in the present invention is 0.1 to 0.65 wt%, and a more preferable carbon amount is 0.15 to 0.6 wt%. In addition, as carbon powder to add, well-known substances, such as carbon black, can be used.

In the present invention, in order to suppress the segregation of the added carbon powder in the molded body and to improve the degree of orientation during molding in a magnetic field, it is represented by the general formula C _n (OH) _n H _{n + 2} . It is preferable to add polyhydric alcohol and gluconic acid. Here, in the said general formula, carbon number n shall be 4 or more. When the carbon number n is 3 or less, the segregation suppressing effect of the carbon powder is insufficient. The preferable value of carbon number n is 4-100, More preferably, it is 4-30, More preferably, it is 4-20, More preferably, it is 4-12. As the polyhydric alcohol, sorbitol is preferable, but two or more polyhydric alcohols may be used in combination. In addition to the polyhydric alcohol used in the present invention, other known dispersants may be further used.

  The above general formula is a formula in the case where the skeleton is all a chain formula and does not contain an unsaturated bond. The number of hydroxyl groups and the number of hydrogen in the polyhydric alcohol may be slightly less than the number represented by the general formula. In the above general formula, not only a saturated bond but also an unsaturated bond may be included. The basic skeleton may be a chain or a ring, but is preferably a chain. Moreover, if the number of hydroxyl groups is 50% or more of the carbon number n, the effect of the present invention is realized, but it is preferable that the number of hydroxyl groups is large, and it is most preferable that the number of hydroxyl groups matches the number of carbon atoms. The amount of polyhydric alcohol added is 0.05 to 5.0 wt%, preferably 0.1 to 3.0 wt%, more preferably 0.3 to 2.0 wt% with respect to the added powder. That's fine. In addition, most of the added polyhydric alcohol is decomposed and removed in a molded body heat treatment step performed after the molding step in a magnetic field. The polyhydric alcohol remaining without being decomposed and removed in the compact heat treatment step is also decomposed and removed in the subsequent firing step.

<Molding process in magnetic field>
The molding step in a magnetic field can be performed by either dry molding or wet molding, but is preferably performed by wet molding in order to increase the degree of magnetic orientation. Therefore, after describing the preparation of the slurry for wet molding, the subsequent molding process in a magnetic field will be described.

When employing wet molding, the second pulverization step is performed wet, and the resulting slurry is concentrated to prepare a slurry for wet molding. Concentration may be performed by centrifugation, filter press, or the like. At this time, it is preferable that the ferrite magnet powder accounts for 30 to 80 wt% in the slurry for wet molding.
Next, molding in a magnetic field is performed using a slurry for wet molding. The molding pressure may be about 0.1 to 0.5 ton / cm ² and the applied magnetic field may be about 5 to 15 kOe. The dispersion medium is not limited to water and may be non-aqueous. When a non-aqueous dispersion medium is used, an organic solvent such as toluene or xylene can be used. When toluene or xylene is used as the non-aqueous dispersion medium, it is preferable to add a surfactant such as oleic acid.

<Molded body heat treatment process>
In this step, heat treatment is performed in which the compact is held at a low temperature of 100 to 450 ° C., more preferably 200 to 350 ° C. for 1 to 4 hours. By performing this heat treatment in the atmosphere, a part of Fe ²⁺ is oxidized to Fe ³⁺ . That is, in this step, by a certain extent the reaction proceeds from Fe ²⁺ to Fe ^3+, is to control the amount of Fe ²⁺ to a predetermined amount.
In addition, when obtaining a ZnW type | mold ferrite, this molded object heat treatment process is unnecessary.

<Baking process>
In the subsequent firing step, the compact is fired at a temperature of 1100 to 1270 ° C., more preferably 1160 to 1240 ° C. for 0.5 to 3 hours. The firing atmosphere is performed in a non-oxidizing atmosphere for the same reason as in the calcining step. In this step, the carbon powder added prior to the second pulverization step disappears.
When obtaining ZnW type ferrite, the firing atmosphere may be in the air.

Through the above steps, a W-type ferrite sintered magnet having high coercive force (HcJ) and residual magnetic flux density (Br) can be obtained. Among the W-type ferrite sintered magnets, according to the Fe ₂ W-type ferrite sintered body, the residual magnetic flux density (Br) of 4000 G or more, further 4500 G or more, and the coercive force (HcJ) of 3500 Oe or more, further 4000 Oe or more. Obtainable. Of the W-type ferrite sintered magnets, ZnW-type ferrite sintered magnets require 700 Oe or more while maintaining a residual magnetic flux density (Br) of 4500 G or more, further 4800 G or more without requiring any complicated atmosphere control. In addition, a coercive force (HcJ) of 720 Oe or more can be obtained.

  Further, in the present invention, the obtained W-type ferrite sintered magnet can be pulverized and used as a ferrite magnet powder. This ferrite magnet powder can be used for a bonded magnet.

The manufacturing method of the ferrite sintered magnet has been described above, but the same process can be adopted as appropriate when manufacturing the ferrite magnet powder. The ferrite magnet powder according to the present invention can be produced by two processes, that is, a case where it is produced from a calcined body and a case where it is produced from a sintered body.
When producing from a calcined body, the first subcomponent and the second subcomponent are added before the calcining step. The calcined body to which these are added is subjected to coarse pulverization, powder heat treatment, and fine pulverization to become a ferrite magnet powder. This ferrite magnet powder can be put to practical use as a ferrite magnet powder after the heat treatment described above. For example, a bonded magnet is produced using ferrite magnet powder that has been subjected to powder heat treatment. This ferrite magnet powder can be used not only for bonded magnets but also for producing sintered ferrite magnets. Therefore, it can be said that the ferrite magnet powder is manufactured during the manufacturing process of the ferrite sintered magnet. However, the grain size may differ between when used for a bonded magnet and when used for a sintered ferrite magnet.

When producing a ferrite magnet powder from a ferrite sintered magnet, the first subcomponent and the second subcomponent may be added at any stage prior to the firing step. Ferrite magnet powder can be produced by appropriately pulverizing the sintered ferrite magnet obtained by the above-described steps.
As described above, the ferrite magnet powder includes a calcined powder, a powder pulverized after calcining and firing, and a powder that is pulverized after calcining and then heat treated.

<First embodiment>
Fe ₂ O ₃ powder (primary particle size: 0.3 μm), SrCO ₃ powder (primary particle size: 2 μm) and BaCO ₃ powder (primary particle size: 0.05 μm) were prepared as raw material powders. This raw material powder was weighed in Sr _(1-x) Ba _x Fe ²⁺ _a Fe ³⁺ _b O ₂₇ so as to have a composition of a = 2, b = 16, x = 0.3, and then CaCo ₃ 0.33 wt% of powder (primary particle size: 1 μm) was added and mixed and pulverized with a wet attritor for 2 hours.
Next, calcination was performed. The calcination was performed using a tubular furnace under the condition of holding for 1 hour in an N ₂ gas atmosphere. The heating and holding temperature was 1300 ° C., and the rate of temperature rise to the heating and holding temperature and the rate of temperature drop from the heating and holding temperature was 5 ° C./min.
Subsequently, crushing was performed by a vibration mill. The crushing by the vibration mill was to treat the calcined body 220 g for 10 minutes.

The next pulverization was performed in two stages using a ball mill. In the first fine pulverization, 400 ml of water is added to 210 g of the coarsely pulverized powder and treated for 88 hours.
After the first fine pulverization, the finely pulverized powder was heat-treated in a N ₂ gas atmosphere at 800 ° C. for 1 hour. The rate of temperature increase to the heating and holding temperature and the rate of temperature decrease from the heating and holding temperature was 5 ° C./min.
Subsequently, second fine pulverization using a ball mill was performed for 25 hours to obtain a slurry for wet molding.

The Ga ₂ O ₃ powder (primary particle size: 2 μm) was not added, added during blending, added during the first fine pulverization, and added during the second fine pulverization. For each form, 0.6 wt% of SiO ₂ powder (primary particle diameter: 0.01 μm) and CaCO ₃ powder (primary particle diameter: primary particle diameter: with respect to the finely pulverized powder subjected to the heat treatment during the second pulverization. 1 μm) 0.35 wt%, SrCO ₃ powder (primary particle size: 2 μm) 0.7 wt%, BaCO ₃ powder (primary particle size: 0.05 μm) 1.4 wt%, carbon powder (primary particles) 0.4 wt% of each (diameter: 0.05 μm) was added, and 1.2 wt% of sorbitol (primary particle diameter: 10 μm) was added as a polyhydric alcohol.

The slurry obtained by performing the second pulverization was concentrated by a centrifugal separator, and molding was performed in a magnetic field using the concentrated slurry for wet molding. In addition, the applied magnetic field (longitudinal magnetic field) is 12 kOe (1000 kA / m), and the molded body has a cylindrical shape with a diameter of 30 mm and a height of 15 mm. There was no problem in any of the moldings. This molded body was heat treated in the atmosphere at 275 ° C. for 3 hours, and then fired in nitrogen at a heating rate of 5 ° C./min and a maximum temperature of 1190 ° C. for 1 hour to obtain a sintered body. The composition of the obtained sintered body was measured using a fluorescent X-ray quantitative analyzer SIMULTIX 3550 manufactured by Rigaku Corporation. As a result, it was found that in Sr _(1-x) Ba _x Fe ²⁺ _a Fe ³⁺ _b O ₂₇ , a = 1.76, b = 13.84, and x = 0.37.

  Further, the coercive force (HcJ) and the residual magnetic flux density (Br) were measured for the obtained sintered body. The measurement results of the coercive force (HcJ) are shown in Table 1, and the measurement results of the residual magnetic flux density (Br) are shown in Table 2. The coercive force (HcJ) and the residual magnetic flux density (Br) were evaluated using a BH tracer with a maximum applied magnetic field of 25 kOe after processing the upper and lower surfaces of the obtained sintered body.

As shown in Table 1, the coercive force (HcJ) can be improved by adding Ga ₂ O ₃ powder as a Ga component. However, Ga ₂ O ₃ are different in the effect of improving the powder coercivity by the timing of adding (HcJ), in formulation, i.e. than added before calcination, who added the Ga ₂ O ₃ powder after calcining Can provide a high coercive force (HcJ). In particular, it can be seen that the coercive force (HcJ) is highest when Ga ₂ O ₃ powder is added during the first fine pulverization after calcination. As shown in Table 2, the residual magnetic flux density (Br) is higher when Ga ₂ O ₃ powder is added after calcining than when it is added at the time of blending.

FIG. 1 shows the relationship between the added amount of Ga ₂ O ₃ powder and coercive force (HcJ), and FIG. 2 shows the relationship between the added amount of Ga ₂ O ₃ powder and residual magnetic flux density (Br). As shown in FIG. 1, the effect of improving the coercive force (HcJ) shows a peak when the added amount of Ga ₂ O ₃ powder is 4 to 6 wt%, and when it exceeds 12 wt%, Ga ₂ O ₃ powder is reduced. It approaches the value when it is not added. As shown in FIG. 2, the residual magnetic flux density (Br) tends to decrease by the addition of Ga ₂ O ₃ powder, but if the addition amount is 15 wt% or less, a residual magnetic flux density (Br) of 4000 G or more is obtained. It is understood that you can.

<Second embodiment>
Fe ₂ O ₃ powder (primary particle size: 0.3 μm) and SrCO ₃ powder (primary particle size: 2 μm) were weighed so as to have a composition of SrFe ²⁺ _2.1 Fe _15.8 O ₂₇ . After weighing, it was mixed and pulverized in a wet ball mill for 16 hours. Subsequently, the pulverized powder was dried and sized, and then calcined in N ₂ gas at 1350 ° C. for 1 hour to obtain a particulate calcined body. The calcined body was pulverized by a dry vibration mill for 10 minutes to obtain a powder having an average particle diameter of 1 μm.

Subsequently, CaCO ₃ powder (primary particle diameter: 1 μm), SiO ₂ powder (primary particle diameter: 0.01 μm), Al ₂ O ₃ powder (primary particle diameter: 0.5 μm) with respect to the calcined body. Was added in the amount shown in Table 3, and wet pulverized for 40 hours using a ball mill to obtain a slurry. The amount of calcined powder in the slurry is 33 wt%. Next, the slurry after pulverization was concentrated with a centrifugal separator to prepare a slurry for wet molding. Using this wet molding slurry, molding was performed in a magnetic field. In addition, the applied magnetic field (longitudinal magnetic field) is 12 kOe (1000 kA / m), and the molded body has a cylindrical shape with a diameter of 30 mm and a height of 15 mm.
The molded body was heat-treated at 250 ° C. for 3 hours in the atmosphere, and then fired in nitrogen at a heating rate of 5 ° C./min and a maximum temperature of 1200 ° C. for 1 hour to obtain a sintered body. After processing the upper and lower surfaces of the obtained sintered body, the magnetic properties were evaluated using a BH tracer with a maximum applied magnetic field of 25 kOe. The result is shown in FIG.

As shown in Table 3 and FIG. 3, when CaCO ₃ is 1.0 wt% and SiO ₂ is 0.5 wt%, the coercive force (HcJ) can be changed by adding Al ₂ O ₃ , By adding an appropriate amount of Al ₂ O ₃ , a coercive force (HcJ) exceeding 4 kOe can be realized. However, when the amount of Al ₂ O ₃ increases too much, the residual magnetic flux density (Br) decreases significantly. Therefore, in the present invention, the Al component is 0.01 to 1.5 wt% in terms of Al ₂ O ₃ . Incidentally, when the Al ₂ O ₃ content is in the range of 0.01 to 1.5 wt%, a coercive force (HcJ) of 3 kOe or more and a residual magnetic flux density (Br) of 4.4 kG or more can be obtained.

<Third embodiment>
After obtaining a fired body in the same manner as in the first example except that WO ₃ powder as the W component was used as the first subcomponent, the composition of the sintered body and the sintered body The coercive force (HcJ) and the residual magnetic flux density (Br) were measured. The results are shown in Tables 4 and 5.

As shown in Table 4, the coercive force (HcJ) can be improved by adding WO ₃ powder as a W component. However, as in the second example, the coercivity (HcJ) improvement effect varies depending on the timing of adding the WO ₃ powder. For WO ₃ powder, blended during, i.e. those who added before calcination, it is possible to obtain a high coercive force than the addition of WO ₃ powder after calcining (HcJ). Further, as shown in Table 5, it can be said that the residual magnetic flux density (Br) hardly varies depending on the addition timing of the WO ₃ powder.

Next, it was weighed so as to have a composition of Fe ₂ O ₃ powder (primary particle diameter: 0.3 μm) and SrCO ₃ powder (primary particle diameter: 2 μm) SrFe ²⁺ ₂ Fe ³⁺ ₁₆ O ₂₇ . After weighing, it was mixed and pulverized in a wet ball mill for 16 hours. Subsequently, the pulverized powder was dried and sized, and then calcined in N ₂ gas at 1350 ° C. for 1 hour to obtain a particulate calcined body. The calcined body was pulverized by a dry vibration mill for 10 minutes to obtain a powder having an average particle diameter of 1 μm.

Subsequently, CaCO ₃ powder (primary particle diameter: 1 μm), SiO ₂ powder (primary particle diameter: 0.01 μm), and WO ₃ powder (primary particle diameter: 0.5 μm) are displayed on the calcined body. The amount shown in 6 was added and wet pulverized for 40 hours using a ball mill to obtain a slurry. The amount of calcined powder in the slurry is 33 wt%. Next, the slurry after pulverization was concentrated with a centrifugal separator to prepare a slurry for wet molding. Using this wet molding slurry, molding was performed in a magnetic field. In addition, the applied magnetic field (longitudinal magnetic field) is 12 kOe (1000 kA / m), and the molded body has a cylindrical shape with a diameter of 30 mm and a height of 15 mm.
The molded body was heat-treated at 250 ° C. for 3 hours in the atmosphere, and then fired in nitrogen at a heating rate of 5 ° C./min and a maximum temperature of 1200 ° C. for 1 hour to obtain a sintered body. After processing the upper and lower surfaces of the obtained sintered body, the magnetic properties were evaluated using a BH tracer with a maximum applied magnetic field of 25 kOe. The results are shown in Table 6 and FIG.

As shown in Table 6 and FIG. 4, when CaCO ₃ is 0.7 wt% and SiO ₂ is 0.45 wt%, the coercive force (HcJ) can be improved by adding WO ₃ . In particular, the coercive force (HcJ) of less than 3.0 kOe was obtained only by adding CaCO ₃ and SiO ₂ , whereas the coercive force (HcJ) exceeding ₃ kOe can be realized by adding WO ₃ . However, as the amount of WO ₃ increases, the decrease in residual magnetic flux density (Br) becomes significant. Therefore, in the present invention, the W component is 0.01 to 0.6 wt% in terms of WO ₃ . In addition, when the amount of WO ₃ is in the range of 0.01 to 0.6 wt%, a coercive force (HcJ) of 3 kOe or more and a residual magnetic flux density (Br) of 4.4 kG or more can be obtained.

<Fourth embodiment>
Fe ₂ O ₃ powder (primary particle size: 0.3 μm) and SrCO ₃ powder (primary particle size: 2 μm) were prepared as raw material powders. This raw material powder was weighed so as to have a composition composition of SrFe ²⁺ ₂ Fe ³⁺ ₁₆ O ₂₇ . After weighing, it was mixed and pulverized in a wet ball mill for 16 hours. Subsequently, the pulverized powder was dried and sized, and then calcined in N ₂ gas at 1350 ° C. for 1 hour to obtain a particulate calcined body. The calcined body was crushed by a dry vibration mill for 10 minutes to obtain a coarse powder having an average particle diameter of 1 μm.

Subsequently, the coarse powder was finely pulverized. The fine pulverization was performed in two stages using a ball mill. The first fine pulverization is performed by adding 400 ml of water to 210 g of coarse powder and treating for 88 hours. After the first pulverization, heat treatment was performed under the condition that the fine powder was kept at 800 ° C. for 1 hour in an N ₂ gas atmosphere. The rate of temperature increase to the heating and holding temperature and the rate of temperature decrease from the heating and holding temperature was 5 ° C./min. Then, the 2nd fine grinding | pulverization which wet-grinds for 25 hours using a ball mill was performed, and the slurry for wet forming was obtained. Before the second pulverization, 0.9 wt% sorbitol, CaCO ₃ powder (primary particle diameter: 1 μm), SiO ₂ powder (primary particle diameter: 0.01 μm), CeO ₂ powder (primary particles) (Diameter: 0.8 μm) was added in the amount shown in Table 7, and wet pulverized for 40 hours using a ball mill to obtain a slurry. The amount of calcined powder in the slurry is 33 wt%. Next, the slurry after pulverization was concentrated with a centrifugal separator to prepare a slurry for wet molding. Using this wet molding slurry, molding was performed in a magnetic field. In addition, the applied magnetic field (longitudinal magnetic field) is 12 kOe (1000 kA / m), and the molded body has a cylindrical shape with a diameter of 30 mm and a height of 15 mm.
The molded body was heat-treated at 250 ° C. for 3 hours in the atmosphere, and then fired in nitrogen at a heating rate of 5 ° C./min and a maximum temperature of 1200 ° C. for 1 hour to obtain a sintered body. After processing the upper and lower surfaces of the obtained sintered body, the magnetic properties were evaluated using a BH tracer with a maximum applied magnetic field of 25 kOe. The results are shown in Table 7 and FIG.

Next, as shown in Table 7 and FIG. 5, when CaCO ₃ is 0.7 wt% and SiO ₂ is 0.6 wt%, the coercive force (HcJ) can be changed by adding CeO _2. it can. In particular, a coercive force (HcJ) of 3.3 kOe or more and a residual magnetic flux density (Br) of 4.6 kG or more can be obtained when the amount of CeO ₂ is 0.01 to 0.6 wt%.

<Fifth embodiment>
Fe ₂ O ₃ powder (primary particle size: 0.3 μm) and SrCO ₃ powder (primary particle size: 2 μm) were prepared as raw material powders. This raw material powder was weighed so as to have a composition composition of SrFe ²⁺ ₂ Fe ³⁺ ₁₆ O ₂₇ . After weighing, it was mixed and pulverized in a wet ball mill for 16 hours. Next, the pulverized powder was dried and sized, and then calcined in N ₂ gas at 1350 ° C. for 1 hour to obtain a powdery calcined body. The calcined body was pulverized for 10 minutes by a dry vibration mill to obtain a coarse powder having an average particle diameter of 1 μm.

Subsequently, the coarse powder was finely pulverized. The fine pulverization was performed in two stages using a ball mill. The first fine pulverization is performed by adding 400 ml of water to 210 g of coarse powder and treating for 88 hours. After the first pulverization, heat treatment was performed under the condition that the fine powder was kept at 800 ° C. for 1 hour in an N ₂ gas atmosphere. The rate of temperature increase to the heating and holding temperature and the rate of temperature decrease from the heating and holding temperature was 5 ° C./min. Then, the 2nd fine grinding | pulverization which wet-grinds for 25 hours using a ball mill was performed, and the slurry for wet forming was obtained. Before the second fine pulverization, 0.9 wt% of sorbitol, CaCO ₃ powder (primary particle size: 1 μm), SiO ₂ powder (primary particle size: 0.01 μm), MoO ₃ powder (primary particle size) : 0.8 μm) was added in the amount shown in Table 8, and wet pulverized for 40 hours using a ball mill to obtain a slurry. The amount of calcined powder in the slurry is 33 wt%. Next, the slurry after pulverization was concentrated with a centrifugal separator to prepare a slurry for wet molding. Using this wet molding slurry, molding was performed in a magnetic field. In addition, the applied magnetic field (longitudinal magnetic field) is 12 kOe (1000 kA / m), and the molded body has a cylindrical shape with a diameter of 30 mm and a height of 15 mm.
The molded body was heat-treated at 250 ° C. for 3 hours in the atmosphere, and then fired in nitrogen at a heating rate of 5 ° C./min and a maximum temperature of 1200 ° C. for 1 hour to obtain a sintered body. After processing the upper and lower surfaces of the obtained sintered body, the magnetic properties were evaluated in the following manner using a BH tracer having a maximum applied magnetic field of 25 kOe. The results are shown in Table 8 and FIG.

Next, as shown in Table 8 and FIG. 6, when CaCO ₃ is 0.7 wt% and SiO ₂ is 0.6 wt%, the coercive force (HcJ) can be changed by adding MoO _3. . In particular, a coercive force (HcJ) of 3.3 kOe or more and a residual magnetic flux density (Br) of 4.6 kG or more can be obtained when the amount of MoO ₃ is 0.001 to 0.16 wt%.

<Sixth embodiment>
After obtaining a fired body in the same manner as in the first example except that Cr ₂ O ₃ powder as the Cr component was used as the first subcomponent, the composition and sintering of the sintered body were also performed in the same manner as in the first example. Tables 9 and 10 show the results of measuring the coercive force (HcJ) and residual magnetic flux density (Br) of the body.

As shown in Table 9, the coercive force (HcJ) can be improved by adding Cr ₂ O ₃ powder as a Cr component. However, Cr ₂ O ₃ powder are different in the effect of improving the coercive force (HcJ) by the timing of the addition of, rather than added after calcination, in formulation, i.e. towards the addition of Cr ₂ O ₃ powder before calcination Can provide a high coercive force (HcJ). Further, as shown in Table 10, the residual magnetic flux density (Br) is higher when the Cr ₂ O ₃ powder is added at the time of blending than when it is added after calcining.

FIG. 7 shows the relationship between the added amount of Cr ₂ O ₃ powder and coercive force (HcJ), and FIG. 8 shows the relationship between the added amount of Cr ₂ O ₃ powder and residual magnetic flux density (Br). As shown in FIG. 7, a coercive force (HcJ) of 3.5 kOe or more can be obtained by adding 0.01 or more of Cr ₂ O ₃ powder. On the other hand, as shown in FIG. 8, the residual magnetic flux density (Br) tends to decrease due to the addition of Cr ₂ O ₃ powder, but if the added amount is 3.5 wt% or less, the residual magnetic flux density is 4000 G or more. (Br) can be obtained.

<Seventh embodiment>
Although the first to sixth embodiments described above relate to Fe ₂ W type ferrite, an experiment conducted for confirming the effect when a Ga component is added to ZnW type ferrite is shown as a seventh embodiment.
Fe ₂ O ₃ powder (primary particle size: 0.3 μm), SrCO ₃ powder (primary particle size: 2 μm) and ZnO powder (primary particle size: 0.8 μm) were prepared as raw material powders. The raw material powder was weighed so that the final composition was SrZn _1.5 Fe _15, and then mixed and pulverized with a wet attritor for 2 hours.
Next, calcination was performed in the air. The calcining temperature, the holding time, the temperature rising to the heating holding temperature and the rate of temperature falling from the heating holding temperature are the same as in the first embodiment.

Subsequently, crushing was performed with a vibration mill under the same conditions as in the first example.
The next pulverization was performed in two stages using a ball mill. Prior to the first pulverization, the first pulverization was performed under the same conditions as in the first example, except that 1.2 wt% of sorbitol (primary particle diameter: 10 μm) was added as a polyhydric alcohol.
After the first fine pulverization, heat treatment was performed under the condition that the finely pulverized powder was kept at 800 ° C. for 1 hour in the air. The rate of temperature rise to the heating and holding temperature and the rate of temperature drop from the heating and holding temperature are the same as in the first embodiment.
Then, the 2nd fine grinding | pulverization wet-ground using a ball mill was performed, and the slurry for wet forming was obtained. Before the second fine pulverization, 0.6 wt% of SiO ₂ powder (primary particle diameter: 0.01 μm) and CaCO ₃ powder (primary particle diameter: 1 μm) are applied to the finely pulverized powder subjected to the heat treatment. 0.35 wt% and sorbitol (primary particle diameter: 10 μm) were added at 1.2 wt%. In addition to these, Ga ₂ O ₃ powder (primary particle diameter: 2 μm) was added in an amount of 0 to 0.8 wt%.

  The slurry obtained by performing the second pulverization was concentrated by a centrifugal separator, and molding was performed in a magnetic field using the concentrated slurry for wet molding. In addition, the applied magnetic field (longitudinal magnetic field) is 12 kOe (1000 kA / m), and the molded body has a cylindrical shape with a diameter of 30 mm and a height of 15 mm. There was no problem in any of the moldings. The molded body was dried in the air, and then fired at a heating rate of 5 ° C./min and a maximum temperature of 1240 ° C. for 1 hour to obtain a sintered body.

  About the sintered compact obtained by the above, the coercive force (HcJ) and the residual magnetic flux density (Br) were measured in the same manner as in the first example. The results are shown in Table 11.

  As shown in Table 11, even when the Ga component was added to the ZnW type ferrite, the coercive force (HcJ) could be improved while suppressing the decrease in the residual magnetic flux density (Br).

In the first embodiment, it is a graph showing the relationship between the Ga ₂ O ₃ powder added amount and the coercive force (HcJ). In the first embodiment, it is a graph showing the relationship between the residual magnetic flux density and the addition amount of Ga ₂ O ₃ powder (Br). In the second embodiment, Al ₂ O ₃ powder added amount and the coercive force (HcJ), which is a graph showing the relationship between the residual magnetic flux density (Br). In a third embodiment, WO ₃ powder amount and the coercive force (HcJ), which is a graph showing the relationship between the residual magnetic flux density (Br). In the fourth embodiment, the amount of CeO ₂ powder and the coercive force (HcJ), which is a graph showing the relationship between the residual magnetic flux density (Br). In the fifth embodiment, MoO ₃ powder amount and the coercive force (HcJ), which is a graph showing the relationship between the residual magnetic flux density (Br). In the sixth embodiment, it is a graph showing the relationship between the Cr ₂ O ₃ powder added amount and the coercive force (HcJ). In the sixth embodiment, it is a graph showing the relationship between the Cr ₂ O ₃ powder amount and residual magnetic flux density (Br).

Claims (7)

A method for producing a ferrite magnetic material in which hexagonal W-type ferrite forms a main phase,
A molding process for producing a molded body including a main component and a first subcomponent consisting of one or more selected from a Ga component, an Al component, a W component, a Ce component, a Mo component, and a Cr component;
And a firing step of firing the molded body.   The method for producing a ferrite magnetic material according to claim 1, wherein the formed body is a calcined body including the main component and the first subcomponent.   2. The method for producing a ferrite magnetic material according to claim 1, wherein the molded body is composed of a mixture of a calcined body constituting the main component and the first subcomponent. A first grinding step of grinding the calcined body to a predetermined particle size;
A step of heat-treating the pulverized product obtained in the first pulverization step in an atmosphere having an oxygen concentration of 10 vol% or less;
A second pulverization step of pulverizing the pulverized product subjected to the heat treatment to a predetermined particle size;
The method according to claim 3, wherein the first subcomponent is added in the first pulverization step and / or the second pulverization step. The main component is AFe ²⁺ _a Fe ³⁺ _b O ₂₇ Formula (1)
(However, 1.1 ≦ a ≦ 2.4, 12.3 ≦ b ≦ 16.1. A is at least one element selected from Sr, Ba and Pb) The method for producing a ferrite magnetic material according to any one of claims 1 to 4. The Ga component terms _of Ga ₂ O ₃ in Ga ₂ O _3: 0.05~15wt%,
The Al component is Al ₂ O _{3 in} terms of Al ₂ O ₃ : 0.01 to 1.5 wt%,
The W component is WO _{3 in} terms of WO ₃ : 0.01 to 0.6 wt%,
The Ce component is CeO _{2 in} terms of CeO ₂ : 0.01 to 0.6 wt%,
The Mo component is MoO _{3 in} terms of MoO ₃ : 0.001 to 0.16 wt%,
The Cr component Cr ₂ O ₃ in terms of Cr ₂ O _3: method for producing a ferrite magnetic material according to any one of claims 1 to 5, characterized in that it is contained 0.01~3.5wt%. A second subcomponent, one or two of Ca component and Si component _{CaCO 3: 0.3~3wt%, SiO 2} : claim, characterized in that the addition 0.2~1.4wt% 1~ 6. A method for producing a ferrite magnetic material according to any one of 6 above.

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