KR20150073759A - Process for preparing sintered magnets - Google Patents

Process for preparing sintered magnets Download PDF

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KR20150073759A
KR20150073759A KR1020130161813A KR20130161813A KR20150073759A KR 20150073759 A KR20150073759 A KR 20150073759A KR 1020130161813 A KR1020130161813 A KR 1020130161813A KR 20130161813 A KR20130161813 A KR 20130161813A KR 20150073759 A KR20150073759 A KR 20150073759A
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sintered magnet
formula
calcined product
raw material
following general
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KR1020130161813A
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Korean (ko)
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문경석
강영민
강영재
안경한
이상목
이제현
조근우
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삼성전자주식회사
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/0302—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity characterised by unspecified or heterogeneous hardness or specially adapted for magnetic hardness transitions
    • H01F1/0311—Compounds
    • H01F1/0313—Oxidic compounds
    • H01F1/0315—Ferrites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/06—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder
    • H01F1/08—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
    • H01F1/086—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together sintered
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Hard Magnetic Materials (AREA)
  • Magnetic Ceramics (AREA)

Abstract

Obtaining a raw material mixture; The raw material mixture is calcined at a temperature of 900 degrees Celsius to 1350 degrees Celsius to produce a calcined product comprising particles comprising M-type hexaferrite represented by the following general formula 1 or W-type hexaferrite represented by the following general formula 2 Obtaining a product;
[Formula 1]
A 1- x R x Fe 12 - y M y O 19
Wherein A is at least one selected from Sr, Ba and Ca, R is at least one selected from rare earth elements, M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, , 0? X? 0.6, 0? Y? 1.2;
[Formula 2]
AMe x Fe 16 - x O 27
Wherein A is at least one selected from Sr, Ba, and Ca; Me is at least one selected from Co, Cu, Zn, Mn, Zr , Ni, Ti, Al, Ge, To 2;
Mixing the calcined product with at least one sintering auxiliary selected from CoO, Co 2 O 4 , Co 3 O 4 , Mn 2 O 3 , Mn 3 O 4 , and Bi 2 O 3 to obtain a mixture; Molding the mixture under pressure to obtain a molded body; And a step of heat-treating the formed body at a temperature of 1000 degrees Celsius to 1300 degrees Celsius to obtain a sintered magnet.

Description

PROCESS FOR PREPARING SINTERED MAGNETS [0002]

To a sintered magnet manufacturing method and a sintered magnet produced therefrom.

Permanent magnets are characterized in that the applied magnetism is maintained permanently. Permanent magnets are used as components of rotating equipment, affecting the price, stability, size and efficiency of the system. Permanent magnets are widely used in motors for home electric appliances, motors for automobile parts, and permanent magnets for generators.

The ferrite sintered magnet produced from the hexaferrite magnetic powder is a kind of permanent magnet and is used for various purposes such as a generator, various motors, speakers, and the like. The hexaferrite magnetic powder may be produced by substituting Sr or Ba with a different metal such as Sr hexaferrite, Ba hexaferrite, or Sr or Ba hexaferrite, and / or partially replacing Fe with a metal such as Zn, Mg, ≪ RTI ID = 0.0 > hexaferrite. ≪ / RTI >

In recent years, studies have been actively carried out to improve the performance of ferrite sintered magnets in order to miniaturize and lighten the parts for automobile electronic parts and electronic devices. Since hexaferrite magnets used in parts for home appliances, automobile parts, and the like have a significant effect on the energy efficiency of the parts, it is desirable to develop a technique capable of improving the performance of the ferrite sintered magnet.

In one embodiment, the present invention is directed to a method of making a hexaferrite-based sintered magnet having high density and improved magnetic properties.

In another embodiment, the present invention is directed to a hexaferrite sintered magnet produced by the above method.

One embodiment provides a method of manufacturing a sintered magnet comprising the steps of:

Obtaining a raw material mixture;

Calcining the raw material mixture at a temperature of 900 ° C to 1350 ° C to obtain a calcined product comprising M-type hexaferrite represented by the following general formula 1 or W-type hexaferrite represented by the following general formula 2 ;

[Formula 1]

A 1- x R x Fe 12 - y M y O 19

Wherein A is at least one selected from Sr, Ba and Ca, R is at least one selected from rare earth elements, M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, , 0? X? 0.6, 0? Y? 1.2

[Formula 2]

AMe x Fe 16 - x O 27

Wherein A is at least one selected from Sr, Ba, and Ca; Me is at least one selected from Co, Cu, Zn, Mn, Zr , Ni, Ti, Al, Ge, Or more.

Mixing the calcined product with at least one sintering auxiliary selected from CoO, Co 2 O 4 , Co 3 O 4 , Mn 2 O 3 , Mn 3 O 4 , and Bi 2 O 3 to obtain a mixture;

Molding the mixture under pressure to obtain a molded body; And

And heat-treating the shaped body at a temperature of 1000 ° C to 1300 ° C to obtain a sintered magnet.

The method may further include a step of pulverizing the calcined product before mixing with the sintering auxiliary.

Wherein the raw material mixture contains a metal compound powder containing Sr, Ba, or Ca and an Fe oxide, and optionally an oxide powder of a rare earth metal; And a compound powder containing a metal M (where M is Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge, or As).

The sintering aids may be mixed with the calcined product in an amount of up to 2% by weight, based on the total weight of the calcined product.

The heat treatment may be performed at a temperature lower than the eutectic point of the hexaferrite.

The sintered magnet may have a density of 95% or more when measured by the Archimedes method.

The sintered magnet may have an average particle size of 0.7 mu m or less.

The sintered magnet may have a different phase including a metal element of the sintering auxiliary agent locally.

Another embodiment comprises a heterophasic composition comprising a M type hexapellite represented by the following general formula 1 or a W type hexapellite represented by the following general formula 2 and having a locally Co, Mn, Bi, The sintered magnet further comprises:

[Formula 1]

A 1- x R x Fe 12 - y M y O 19

Wherein A is at least one selected from Sr, Ba and Ca, R is at least one selected from rare earth elements, M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, , 0? X? 0.6, 0? Y? 1.2,

[Formula 2]

AMe x Fe 16 - x O 27

Wherein A is at least one selected from Sr, Ba, and Ca; Me is at least one selected from Co, Cu, Zn, Mn, Zr , Ni, Ti, Al, Ge, Or more.

The sintered magnet may have a content of Co, Mn, or Bi existing in the heterogeneous phase of 2% or less based on the total weight of the magnet.

The sintered magnet may have a density of 95% or more when measured by the Archimedes method.

The sintered magnet may have an average particle size of 0.7 mu m or less.

The sintered magnet may have a standard deviation of the particle size of 0.36 탆 or less.

It is possible to provide a permanent magnet material having a high density and a small particle size and exhibiting improved magnetism.

Fig. 1 shows a scanning electron microscope image of a sintered magnet in Example 1. Fig.
Fig. 2 shows a scanning electron microscope image of the sintered magnet in Example 2. Fig.
3 is a scanning electron microscope image of a sintered magnet in Comparative Example 1. [
4 is a scanning electron microscope image of the sintered magnet in Comparative Example 2. Fig.
Figs. 5 and 6 show SEM-EDS analysis results of Experimental Example 1. Fig.
Fig. 7 shows the result of particle size distribution in Experimental Example 2. Fig.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Thus, in some implementations, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise.

Also, singular forms include plural forms unless the context clearly dictates otherwise.

In one embodiment, the method of making a sintered magnet comprises the steps of:

Obtaining a raw material mixture;

Calcining the raw material mixture at a temperature of 900 ° C to 1350 ° C to obtain a calcined product comprising M-type hexaferrite represented by the following general formula 1 or W-type hexaferrite represented by the following general formula 2 ;

[Formula 1]

A 1- x R x Fe 12 - y M y O 19

Wherein A is at least one selected from Sr, Ba and Ca, R is at least one selected from rare earth elements, M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, , 0? X? 0.6, 0? Y? 1.2;

[Formula 2]

AMe x Fe 16 - x O 27

Wherein A is at least one selected from Sr, Ba, and Ca; Me is at least one selected from Co, Cu, Zn, Mn, Zr , Ni, Ti, Al, Ge, (For example, 0.001 to 1.99, 0.05 or more, and 1.8 or less, etc.).

Mixing the calcined product with at least one sintering auxiliary selected from CoO, Co 2 O 4 , Co 3 O 4 , Mn 2 O 3 , Mn 3 O 4 , and Bi 2 O 3 to obtain a mixture;

Molding the mixture under pressure to obtain a molded body; And

And heat-treating the shaped body at a temperature of 1000 ° C to 1300 ° C to obtain a sintered magnet.

The method may further include a step of pulverizing the calcined product before mixing with the sintering auxiliary.

The raw material mixture may comprise any metal compound / oxide used for the production of hexaferrite. For example, the raw material mixture may be a metal compound powder containing Sr, Ba, or Ca; Fe oxide; Optionally, an oxide powder of a rare earth metal; And optionally a carbonate (MCO 3 ) or oxide powder of a metal M, where M is Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge, or As. The metal compound powder containing Sr, Ba or Ca may be SrCO 3 , BaCO 3 , CaCO 3 , SrO, SrO 2 , BaO, BaO 2 , CaO, CaO 2 , . Fe oxide, Fe 2 O 3, FeO, Fe 3 O 4, or may be a combination thereof, but is not limited thereto. A rare earth metal oxide powder, La (OH) 3, CeO 2, Nd 2 O 3, Ce 2 O 3, CeO 2 Or a combination thereof. (MCO 3 ) of a metal M, a hydroxide of a metal M, or a metal M, wherein M is a metal (M is a metal such as Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge or As) Oxide powder. In the raw material mixture, the proportions of the respective compounds can be adjusted to obtain the desired composition of hexaferrite. The particle size of the powder for the raw material mixture is not particularly limited and can be appropriately selected. In a non-limiting example, the particle size of the powder for the raw material mixture may be in the range of 4 탆 or less, such as 0.5 탆 to 10 탆, but is not limited thereto.

The mixing of the raw material powders can be carried out by any method, for example, wet or dry. It is possible to mix the raw material powder more uniformly by stirring with a medium such as steel balls. As the wet mixing, water, ethanol, etc. may be used as the solvent, but the present invention is not limited thereto. In order to increase the dispersibility of the raw material powder, known dispersants such as ammonium polycarboxylate and calcium gluconate can be used. The mixed raw slurry can be dehydrated and used as a mixed raw material powder.

The raw material mixture is calcined to obtain calcined products containing particles of M type hexaferrite represented by the following general formula (1) or W type hexaferrite represented by the following general formula (2) (hereinafter referred to as hexa ferrite particles) Obtain a sintered product:

[Formula 1]

A 1- x R x Fe 12 - y M y O 19

Where A, R, M, x and y are as defined above.

[Formula 2]

AMe x Fe 16 - x O 27

Where A, Me, and x are as defined above.

The firing can be carried out by heating in an oxygen-containing atmosphere or a non-oxidizing atmosphere by using a known apparatus such as an electric furnace, a gas furnace or the like. The oxygen-containing atmosphere may be air or the like, but is not limited thereto. The non-oxidizing atmosphere may be an atmosphere having an oxygen partial pressure of 10 -3 atm or less. The non-oxidizing atmosphere may be a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, a combination thereof, or a vacuum atmosphere, but is not limited thereto. The firing temperature may range from 900 degrees to 1400 degrees, for example, from 1000 degrees to 1350 degrees, or from 1000 degrees to 1150 degrees. The firing time may be appropriately selected, and may be, for example, 30 minutes or more, for example, 1 hour to 10 hours, or 3 hours to 5 hours, but is not limited thereto.

The obtained calcined product can be pulverized before mixing with the sintering auxiliary. The pulverization method is not particularly limited and can be carried out according to a known method. In a non-limiting example, the calcined product is pulverized and obtained as a powder by a vibrating mill, a ball mill, an attritor or the like. The average particle size of the powder is not particularly limited, and may be, for example, 5 占 퐉 or less. Dry grinding and / or wet grinding may be used. For the wet grinding, water and / or a non-aqueous solvent (acetone, ethanol, etc.) may be used.

The calcined product or the pulverized calcined product is mixed with at least one sintering auxiliary selected from CoO, Co 2 O 4 , Co 3 O 4 , Mn 2 O 3 , Mn 3 O 4 , and Bi 2 O 3 to prepare a mixture. The content of the sintering aid may be up to 2% by weight, for example from 0.5 to 2% by weight, based on the calcined product. When the sintering assistant is contained within such a range, it is possible to obtain a sintered magnet having a high density even when the heat treatment temperature is low (for example, below the eutectic point of a given hexaferrite) in a heat treatment process described later, The increase of the particle size in the structure can be effectively suppressed. A microstructure sintered magnet having a small particle size while having a high density (i.e., with a reduced porosity) can exhibit improved magnetic properties (e.g., high coercive force, etc.) as described later.

The obtained mixture is molded under pressure to provide a molded article. Molding can be performed under a magnetic field or in the absence of a magnetic field. A dispersant, a lubricant and the like may be added to the mixture before molding, and the types thereof are known.

The obtained compact is heat-treated at a temperature of 1000 degrees Celsius or more, for example, 1100 degrees Celsius to 1300 degrees Celsius to obtain a sintered magnet. The heat treatment may be carried out in a known apparatus such as an electric furnace, a gas furnace or the like. The heat treatment may be performed in an air atmosphere or a reducing atmosphere. The heat treatment temperature may be lower than the eutectic point of the hexaferrite contained in the sintered body. The heat treatment time is not particularly limited and can be appropriately selected. For example, the heat treatment may be performed for 30 minutes or more, for example, 1 hour or more, for example, 1 hour to 10 hours, but is not limited thereto. Since the compact contains the above-described sintering assistant in the above-described range, it is possible to obtain a sintered magnet having a high density by decreasing pores in the compact even when heat treatment is performed at a relatively low temperature. In addition, it is possible to obtain a sintered magnet having a dense structure by effectively inhibiting the growth of particles in the heat treatment. The sintered magnet having such a fine structure can exhibit a high coercive force.

The sintered magnet produced by the above-mentioned method further includes a hexaferrite represented by the following general formula (1) or (2), and further includes a heterogeneous phase containing Co, Mn, Bi, or a combination thereof locally :

[Formula 1]

A 1- x R x Fe 12 - y M y O 19

Where A, R, M, x and y are as defined above.

[Formula 2]

AMe x Fe 16 - x O 27

Where A, x, and Me are as defined above.

In the sintered magnet, the content of Co, Mn, or Bi existing in the heterogeneous phase may be 2% by weight or less based on the weight of the sintered magnet. This dissimilar phase is formed by adding a sintering auxiliary agent to the calcined product. When the sintering aid is included in the raw material mixture for the calcined product, the Co, Mn, or Bi metal is uniformly present in the magnet particles as a whole, and this partially heterogeneous heterogeneous phase is not produced.

The sintered magnet may have a density of 95% or more, for example, 96% or more, or 97% or more when measured by the Archimedes method. In addition to having such a high density, the sintered magnet may have an average particle size of 0.7 mu m or less, for example, 1 mu m or less. The sintered magnet may have a standard deviation of the particle size of 0.36 탆 or less.

The sintered magnet is formed by forming (magnetic field) at least one selected from CoO, Co 2 O 4 , Co 3 O 4 , Mn 2 O 3 , Mn 3 O 4 , and Bi 2 O 3 as a calcination product and a sintering aid And heat treatment. Particularly, even when the heat treatment temperature is controlled to be equal to or lower than the eutectic point of hexaferrite contained in the calcined product, the porosity can be effectively reduced, so that a sintered magnet having a small particle size and a uniform and high density can be obtained, Magnets can exhibit high coercivity.

In other words, the sintered magnet has a microstructure controlled by the use and heat treatment of the above-described sintering aids, and thus can exhibit high coercive force and high density. In the prior art, CaCO 3 and / or SiO 2 are used as a sintering auxiliary agent, but in this case, usually, a heat treatment at a temperature equal to or higher than the eutectic point is required. However, the sintered magnet has a low sintered magnet content by including a mixture of at least one selected from CoO, Co 2 O 4 , Co 3 O 4 , Mn 2 O 3 , Mn 3 O 4 and Bi 2 O 3 as a sintering aid The heat treatment at a temperature can have a dense structure with a remarkably reduced pore volume, and has particles of suppressed size. While not intending to be bound by any particular theory, it is believed that such sintering aids can form high-density magnets at low temperatures by forming a liquid phase during heat treatment and effectively inhibit the growth of particles.

Hereinafter, specific embodiments of the present invention will be described. It is to be understood, however, that the embodiments described below are only for illustrative purposes or to illustrate the present invention, and the present invention should not be limited thereby.

[ Example ]

How to measure magnetic properties

MH magnetic hysteresis curves were obtained at room temperature (300 K) using PPMS-VSM (Quantum Design) (maximum applied field: 5T). From the curve, the saturation magnetization value was obtained in the magnetic field at 5T, and the coercive force was measured at the point where the magnetization value became zero.

Example 1 :

SrCO 3 powder (99.9%, manufacturer: High purity chemical) and Fe 2 O 3 powder (99.9%, 1 μm, manufacturer: High purity chemical) were weighed and mixed so that the Fe / Sr ratio was 10 to 12, and the weighed powder Is ball milled for 24 hours to obtain a slurry.

The slurry is placed in a container and dried in a vacuum oven for 1 hour to obtain a dried raw material mixture. The dried raw material mixture is calcined in air at a temperature of 1090 degrees C for 4 hours to obtain a calcined product.

Before calcination, sieving is performed with a sieve of 100 mesh. The calcined product is finely pulverized by planetary milling to obtain Sr magnetoplumbite-type ferrite powder (i.e., pulverized calcined product).

1 wt% of Co 3 O 4 is added to the ferrite powder, followed by ball milling for 24 hours and drying to obtain a mixture. The mixture is compression-molded by CIP (cold isostatic pressure) under a pressure of 200 MPa to obtain a molded article. The obtained compact was heat-treated in an electric furnace at a temperature of 1144 캜 for 2 hours using an alumina crucible at ambient pressure to obtain a sintered magnet.

The density of the sintered magnet is measured by the Archimedes method.

In addition, a magnetic hysteresis curve is obtained by the above-described method, and the saturation magnetization and the residual magnetization value are measured therefrom.

The surface of the manufactured sintered magnet was mirror-polished, heat-treated at 1000 ° C for 20 minutes and thermally etched, and analyzed by a scanning electron microscope (model: NOVA450, manufactured by FEI company) to obtain a SEM image. The results are shown in Fig.

Example 2 :

A sintered magnet was produced in the same manner as in Example 1, except that the heat treatment temperature of the compact was 1202 degrees. An SEM image is obtained in the same manner as in Embodiment 1. [ The results are shown in Fig.

Comparative Example 1 :

A sintered magnet was produced in the same manner as in Example 1, except that Co 3 O 4 was not added. The density, the saturation magnetization value, and the residual magnetization value of the produced sintered magnet were measured in the same manner as in Example 1. The results are summarized in Table 1. An SEM image (FIG. 3) is obtained in the same manner as in Embodiment 1. FIG.

Comparative Example 2 :

A sintered magnet was produced in the same manner as in Example 1, except that Co 3 O 4 was not added and the heat treatment temperature was changed to 1202 ° C. An SEM image (FIG. 4) is obtained in the same manner as in Example 1. FIG.

Example 3 :

A sintered magnet was produced in the same manner as in Example 1, except that Mn 3 O 4 was used instead of Co 3 O 4 as a sintering aid. The density, the saturation magnetization value, and the residual magnetization value of the produced sintered magnet were measured in the same manner as in Example 1. The results are summarized in Table 1.

Example 4 :

A sintered magnet was produced in the same manner as in Example 1, except that 2 wt% of Co 3 O 4 was used. The density, the saturation magnetization value, and the residual magnetization value of the produced sintered magnet were measured in the same manner as in Example 1. The results are summarized in Table 1.

division Sintering auxiliary density(%) Average particle size (占 퐉) Standard Deviation
(탆) Saturation magnetization value
Ms (emu / g) Coercivity
Hc (Oe) Comparative Example 1 - 89.3 0.73 0.40 67.2 3687 Example 1 Co 3 O 4 1 wt% 95.2 0.69 0.35 72.5 3843 Example 3 Mn 3 O 4 97.6 - - 71.5 3415 Example 4 Co 3 O 4 2wt% 96.8 - - 70.5 3115

From the results of Table 1, it can be confirmed that the magnets according to the examples have high density and high magnetic properties. It is confirmed that the addition of Co 3 O 4 decreases the average particle size and the standard deviation value and increases the density. In Example 1, the saturation magnetization (M s ) value and the coercive force (H c ) value are the most excellent. Thus, according to the embodiment, it is confirmed that the value of M s and H c can be maintained and the density can be improved. When 1 wt% of Mn 3 O 4 was added, the sintered density was more than 97%, and the coercive force (H c ) was 3415 Oe. The saturation magnetization (M s ) . Although not intending to be bound by any particular theory, the addition of the above-described sintering assistant to enhance the sintering density below the eutectic point of SrM changes the grain growth behavior due to the liquid phase formation at the sintering stage, It is thought that it can change.

Experimental Example 1 :

SEM-EDAX analysis was performed on the sintered magnet produced in Example 1, and the results are shown in Fig. 5 and Fig. From the results of FIGS. 5 and 6, it can be seen that the magnets produced according to the examples have a heterophase with locally Sr-Fe-Co-O system. The existence of such a heterogeneous phase is generated when a sintering auxiliary agent is added to the calcined powder.

Experimental Example 2 :

A particle size distribution diagram for the magnet of Comparative Example 1 and the magnet of Example 1 was prepared and is shown in Fig. In the particle size distribution diagram, it is confirmed that the particle size distribution width is narrowed by adding Co 3 O 4 .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

Claims (13)

A method for producing a sintered magnet comprising the steps of:
Obtaining a raw material mixture;
Calcining the raw material mixture at a temperature of 900 ° C to 1350 ° C to obtain a calcined product comprising M-type hexaferrite represented by the following general formula 1 or W-type hexaferrite represented by the following general formula 2 ;
[Formula 1]
A 1- x R x Fe 12 - y M y O 19
Wherein A is at least one selected from Sr, Ba and Ca, R is at least one selected from rare earth elements, M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, , 0? X? 0.6, 0? Y? 1.2;
[Formula 2]
AMe x Fe 16 - x O 27
Wherein A is at least one selected from Sr, Ba, and Ca; Me is at least one selected from Co, Cu, Zn, Mn, Zr, Ni, Ti, Al, Ge, To 2;
Mixing the calcined product with at least one sintering auxiliary selected from CoO, Co 2 O 4 , Co 3 O 4 , Mn 2 O 3 , Mn 3 O 4 , and Bi 2 O 3 to obtain a mixture;
Molding the mixture under pressure to obtain a molded body; And
And heat-treating the formed body at a temperature of 1000 ° C to 1300 ° C to obtain a sintered magnet. The method according to claim 1,
Further comprising the step of grinding the calcined product before mixing with the sintering auxiliary. The method according to claim 1,
Wherein the raw material mixture contains a metal compound powder containing Sr, Ba, or Ca and an Fe oxide, and optionally an oxide powder of a rare earth metal; And a compound powder containing a metal M (wherein M is Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge, or As). The method according to claim 1,
Wherein the sintering assistant is mixed with the calcined product in an amount of not more than 2% by weight based on the total weight of the calcined product. The method according to claim 1,
Wherein the heat treatment is performed at a temperature equal to or lower than the eutectic point of the hexaferrite. 6. The method of claim 5,
Wherein the sintered magnet has a density of 95% or more when measured by the Archimedes method. The method according to claim 1,
Wherein the sintered magnet has an average particle size of 0.7 mu m or less. The method according to claim 1,
Wherein the sintered magnet has a different phase including a metal element of a sintering auxiliary agent locally. 1. A sintered magnet comprising a heterogeneous phase comprising a M type hexapellite represented by the following general formula (1) or a W type hexapellite represented by the following general formula (2) and locally containing Co, Mn, Bi, :
[Formula 1]
A 1- x R x Fe 12 - y M y O 19
Wherein A is at least one selected from Sr, Ba and Ca, R is at least one selected from rare earth elements, M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, , 0? X? 0.6, 0? Y? 1.2;
[Formula 2]
AMe x Fe 16 - x O 27
Wherein A is at least one selected from Sr, Ba, and Ca; Me is at least one selected from Co, Cu, Zn, Mn, Zr , Ni, Ti, Al, Ge, ≪ / RTI > 10. The method of claim 9,
Wherein the sintered magnet has a content of Co, Mn, or Bi existing in the heterogeneous phase of 2% or less based on the total weight of the magnet. 10. The method of claim 9,
The sintered magnet has a density of 95% or more when measured by the Archimedes method. 10. The method of claim 9,
Wherein the sintered magnet has an average particle size of 0.7 m or less. 10. The method of claim 9,
Wherein the sintered magnet has a standard deviation of particle size of 0.36 탆 or less.
KR1020130161813A 2013-12-23 2013-12-23 Process for preparing sintered magnets KR20150073759A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20170074583A (en) * 2015-12-22 2017-06-30 삼성전자주식회사 Magnetic sheet, method of making the same and loud speaker comprising the same
CN112374880A (en) * 2020-11-16 2021-02-19 南通三优佳磁业有限公司 Preparation method of ferrite material for radio frequency identification transponder antenna

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20170074583A (en) * 2015-12-22 2017-06-30 삼성전자주식회사 Magnetic sheet, method of making the same and loud speaker comprising the same
CN112374880A (en) * 2020-11-16 2021-02-19 南通三优佳磁业有限公司 Preparation method of ferrite material for radio frequency identification transponder antenna
CN112374880B (en) * 2020-11-16 2022-10-18 南通三优佳磁业有限公司 Preparation method of ferrite material for radio frequency identification transponder antenna

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