KR20150048256A

KR20150048256A - Magnet powders, production methods thereof, and magnets including the same

Info

Publication number: KR20150048256A
Application number: KR1020130126510A
Authority: KR
Inventors: 강영민; 안경한; 사폴레토바 니나; 이상목; 강영재; 문경석; 이제현; 조근우
Original assignee: 삼성전자주식회사
Priority date: 2013-10-23
Filing date: 2013-10-23
Publication date: 2015-05-07

Abstract

Provided is a magnetic power including M type hexaferrite having FeO presented in the following general formula A_1-xR_xFe_12-yM_yO_19-d. Here, A is one or more types selected among Sr, Ba, and Ca; R is one or more types selected from a rare earth element and Bi; and M is one or more types selected from Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge, and As. 0 < x < 0.5, 0 <= y < 2, and d > 0.

Description

TECHNICAL FIELD [0001] The present invention relates to a magnetic powder, a method of manufacturing the same, and a magnet including the same. BACKGROUND ART [0002]

A magnetic powder having a high saturation magnetization, a method for producing the same, and a magnet including the same.

Hexafelite is produced by standard ceramic techniques in which the stoichiometric amount of oxide MO (M is Ba, Sr, Pb, etc.), Fe ₂ O ₃ , and MeO (Me is Zn, Mg, Mn, . &Lt; / RTI > The hexaferrite can be classified into M type, W type, Z type, Y type, X type, and U type depending on the chemical composition and they are obtained by different manufacturing methods, ) To exhibit other magnetic properties.

Of these, M type hexaferrite has been widely used in electric parts for vehicles and parts for electronic devices because it has excellent price performance and is less influenced by the environment. Research has been conducted to improve the magnetic properties of M-type hexaferrite in order to achieve miniaturization, light weight, and high efficiency of parts. For example, lanthanum and cobalt-substituted strontium type M-type hexaferrite have been proposed as means for increasing the coercive force without loss of saturation magnetization value. As another example, lanthanum and zinc substituted strontium type M hexaferrite have been proposed, but they have an improved saturation magnetization value, but exhibit a lower level of coercive force. Therefore, it is required to develop a magnetic material capable of realizing a more improved magnetic property.

In one embodiment, the invention is directed to an M-type hexaferrite magnetic powder capable of exhibiting a high saturation magnetization value while maintaining a coercive force at a satisfactory level.

In another embodiment, the present invention is directed to a method of making the M type hexaferrite magnetic powder.

In another embodiment, the invention is directed to a magnet comprising the M type hexaferrite magnetic powder.

An embodiment provides a magnetic powder comprising M type hexaferrite represented by the following general formula 1 and containing FeO as a major phase:

[Formula 1]

A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d

Wherein A is at least one element selected from Sr, Ba and Ca, R is at least one element selected from rare earth elements and Bi, and M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, And As, 0 < x < 0.5, 0? Y <2, and d> 0.

The M type hexaferrite may include La, Ce, Nd, Sm, or a combination thereof as a rare earth element.

The powder may have a saturation magnetization value reduced by 2% or more based on the saturation magnetization value before heat treatment when the heat treatment is performed in an oxygen-containing atmosphere at a temperature of 400 ° C to 700 ° C.

The magnetic powder may not include a W type phase.

The magnetic powder containing the M type hexaferrite may have a saturation magnetization value (Ms) of 74 emu / g or more.

The magnetic powder containing M type hexaferrite may have a coercive force (Hc) of 1.4 kOe or more.

The magnetic powder including the M type hexaferrite may have a maximum energy product (BH) of 5.7 or more.

Another embodiment provides a method of making an M-type hexaferrite magnetic powder comprising the steps of:

Obtaining a raw material mixture;

Calcining the raw material mixture in an oxygen-containing atmosphere at a temperature of 900 DEG C to 1350 DEG C, and pulverizing the obtained calcined product; And

Subjecting the pulverized calcined material to a heat treatment at a temperature of 1000 ° C to 1280 ° C in a non-oxidizing atmosphere to obtain an M-type hexaferrite magnetic powder having a ferrite phase represented by the following general formula 1 and containing FeO:

[Formula 1]

A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d

In the above method, the heat treatment can be performed at a temperature of 1200 degrees centigrade or less.

In another embodiment, there is provided a process for preparing an M-type hexaferrite magnetic powder comprising the steps of:

Obtaining a raw material mixture; And

The raw material mixture was calcined at a temperature of 1100 degrees Celsius to 1280 degrees Celsius in a non-oxidizing atmosphere, and the obtained calcined material was pulverized to obtain an M type hexaferrite magnetic powder having a ferrite phase represented by the following general formula 1 and containing FeO Steps to be taken:

[Formula 1]

A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d

A is at least one element selected from Sr, Ba and Ca, R is at least one element selected from rare earth elements and Bi, M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, 0 < x < 0.5, 0 < y < 2, and d > 0.

The raw material mixture may be a metal compound powder containing Sr, Ba, or Ca; Iron oxide powder; A rare earth metal or Bi oxide powder; (MCO ₃ ) or an oxide powder (wherein M is at least one selected from Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge, and As) .

The rare earth metal may be La, Ce, Nd, Sm, or a combination thereof.

The non-oxidizing atmosphere may be a nitrogen gas atmosphere, an argon gas atmosphere, a helium gas atmosphere, a combination thereof, or a vacuum.

In another embodiment, there is provided a magnet comprising a magnetic powder comprising an M type hexaferrite represented by the following general formula 1 and comprising FeO:

[Formula 1]

A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d

It is possible to provide a hexaferrite magnetic powder exhibiting an improved saturation magnetization value while having a satisfactory coercive force.

FIG. 1 shows the change in saturation magnetization according to the composition in the hexaferrite powder prepared according to Examples and Comparative Examples.
Fig. 2 shows the XRD spectrum of the hexaferrite powder prepared in Example 1. 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 magnetic powder comprises M type hexaferrite represented by the following general formula 1 and containing FeO as a major phase:

[Formula 1]

A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d

In the general formula 1, 0 <x <0.5, for example, 0 <x <0.3, 0≤y <2, such as 0≤y <0.3, and d may be 3 or less, for example, 2 or less and 1 or less. As used herein, the term "M-type hexaferrite as the main phase" means that the M-type hexaferrite is 70 vol% or more, for example, as shown in FIG. 2, Is of M-type hexaferrite.

The term "M type hexaferrite" refers to a basic composition of MeFe ₁₂ O ₁₉ (where Me is Sr, Ba and the like) and a basic composition of Me in which one part of Me is selected from rare earth elements such as La and bismuth Or a ferrite having a hexagonal crystal structure and having a composition substituted with at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, . M-type hexaferrite has a composition different from that of W-type hexaferrite having a basic composition of Me ₂ BaFe ₁₆ O ₂₇ , the arrangement of unit cells is different, and the magnetic characteristics are also different.

M-type hexaferrite is excellent in magnetic properties and excellent in price and performance, and its usefulness can be found in permanent magnets for motors and the like, and a lot of research has been conducted to improve its magnetic properties. For example, lanthanum-cobalt-substituted strontium-type M-type (La-Co substituted SrM) hexaferrite and lanthanum-zinc-substituted strontium-type M-type hexaferrite have been suggested as methods for improving magnetic properties. However, the lanthanum-cobalt-substituted strontium type M type hexaferrite can increase the coercive force, and it is difficult to achieve the improvement of the saturation magnetization value. In addition, the improvement of the saturation magnetization value of lanthanum-zinc substituted strontium type M hexaferrite is limited. The saturation magnetization value attainable at the present technology level is known to be about 71 emu / g. On the other hand, it is known that M type hexaferrite exists mainly in Fe ₂ O ₃ (that is, Fe ³ ⁺ ) and hardly exists in the form of Fe ² ⁺ (that is, FeO).

However, the M-type hexaferrite magnetic powder according to one embodiment contains FeO with the composition represented by the general formula (1). That is, when iron vacancies exist on the ferrite of the M type hexaferrite magnetic powder (that is, when d is larger than 0 in the general formula 1), Fe can be easily present as Fe ² ⁺ . Thus, M type hexaferrite magnetic powders including oxygen vacancies and FeO can exhibit remarkably improved saturation magnetization values and at the same time have a satisfactory level of coercive force.

But is also about to be bound by any particular theory, the following reasons, it is considered that these improvements can be achieved: Fe ⁺ ³ and Fe ⁺ ² is different from the value e-magnetic dipole moment. When Fe ² ⁺ is produced together with oxygen vacancies in the crystal structure of the M type hexaferrite magnetic powder, the generated bivalent iron ions are added to 4f 1 and 4f 2 having a down spin in the sublattice of the unit cell As a result, the degree of spin orientation of the ferrite phase is increased, and the total saturation magnetization value can be remarkably improved.

The d value in the general formula 1 can be defined by measuring the saturation magnetization increase due to oxygen vacancy and then calculating the magnetic moment variation of the Fe atom. The d value may be greater than zero and less than four. For example, if M-type hexaferrite powders of the same composition were increased by 5% without phase change, which was evidenced by a heat treatment at 1100 ° C in a reducing atmosphere, one iron of the 12 Fe ³ ⁺ Fe ² ⁺ . In order to satisfy the electrical neutrality, it can be concluded that the oxygen per unit molecule decreased from 19 to 17.5 (that is, the d value was 1.5). To explain the reason, M-type hexaferrite is formed by aligning up to 40 upward electron spins and 20 downward electron spins up and down by 12 Fe atoms per unit molecule, , i.e. 20, the bore and have a theoretical moments of the magnetron (μ _B), spin-down position (4f1, 4f2) in Fe is Fe ³ ⁺ increased moment of 5% in total of 21μ _B occurs when reduced to the Fe ² ⁺ in .

Typical M-type hexaferrite powders are very stable in structure and do not show a change in saturation magnetization value at temperatures much lower than the sintering temperature. However, the M-type hexaferrite magnetic powder having a ferrite phase in which FeO is present together with oxygen vacancies is formed in an oxygen-containing atmosphere at a temperature much lower than the sintering temperature (for example, at a temperature of 400 to 700 degrees Celsius) for 30 minutes , For example, more than 2%, for example, 3% or more, 4% or more, or 5% or more in the saturation magnetization value when heat treatment is performed for 1 hour or more, 2 hours or more or 3 hours or more. The smaller the particle size, the lower the heat treatment time. It can be confirmed from this physical property change that M type hexaferrite in which FeO exists together with oxygen vacancies exists in the magnetic powder.

The magnetic powder may not include a W type phase. When the W type phase is not included, remarkable improvement of the saturation magnetization value can be achieved without loss of coercive force.

In one embodiment, the M type hexaferrite may include La, Ce, Nd, Sm, or a combination thereof as the rare earth element.

In one embodiment, the M type hexaferrite is represented by the following general formula 1-1 and may have a ferrite phase containing FeO:

[Formula 1-1]

A _{1 -} _x La _x _- _a R ' _a Fe ₁₂ _- _y M _y O _{19 -} _d

M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge, and As, where A is Sr, Ba, or Ca, 0 <x <0.5, 0 <a <x, 0? Y <2, and d> 0.

The magnetic powder may have a saturation magnetization value (Ms) of 74 or more (e.g., 74.2 or more, 75 or more, 76 or more, and a maximum value of 79. Accordingly, the magnetic powder has a residual magnetic density Br May be equal to or higher than 4800 G, for example, equal to or higher than 5000 G. The magnetic powder may have such a high saturation magnetization value, while maintaining the coercive force (Hc) at a satisfactory level. , And 1.4 kOe or more, for example, 2.5 kOe to 3.8 kOe. Thus, the M-type hexaferrite magnetic powder may have a maximum energy product (BH) max of 5.7 or more.

The magnetic powder can be obtained by a production method described below.

In one embodiment, a method of making a magnetic powder comprises:

Obtaining a raw material mixture;

Calcining the raw material mixture in an oxygen-containing atmosphere at a temperature of 900 ° C to 1350 ° C, pulverizing the obtained calcined material, and

Subjecting the pulverized calcined material to a heat treatment at a temperature of 1000 to 1280 ° C in a non-oxidizing atmosphere to obtain a magnetic powder containing M-type hexaferrite represented by the following general formula 1 and containing FeO:

[Formula 1]

A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d

Where A, R, M, x, and y are as defined above and d > 0.

The raw material mixture may be a metal compound (e.g., carbonate) powder containing Sr, Ba, or Ca; Iron oxide powder; A powder of a compound (for example, an oxide) including a rare earth metal or bismuth; (MCO ₃ ) or an oxide powder (M is at least one selected from Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge, and As) ). As the kind of the raw material mixture, known compounds can be appropriately selected. For example, the metal carbonate powder containing Sr, Ba, or Ca may be SrCO ₃ , BaCO ₃ , CaCO ₃ , SrO, SrO ₂ , BaO, BaO ₂ , CaO, CaO ₂ , or a combination thereof. The iron oxide powder may be Fe ₂ O ₃ , FeO, Fe ₃ O ₄ , or a combination thereof. MCO ₃ or an oxide powder of a metal M wherein M is at least one selected from Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge and As is CaCO ₃ , CoO, Lt; / RTI > The rare earth metal oxide or Bi oxide may be La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ , Bi ₂ O ₃ , Ce ₂ O ₃ , CeO ₂ Or a combination thereof. The mixing ratio of these raw material mixtures can be suitably adjusted to obtain the desired composition of the M-type hexaferrite powder. 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 10 탆 or less, such as 0.5 탆 to 5 탆, but is not limited thereto.

The raw material mixture is, according to the selection, it may include a sintering aid (e. G., SiO _2, CaCO _3, etc.) in an amount of up to 1 wt% of the total raw material mixture, their types are known.

The raw material mixture is calcined under the above-mentioned conditions and the calcined material is pulverized to obtain a hexaferrite powder represented by the following general formula 2:

[Formula 2]

A _1- _x R _x Fe ₁₂ _- _y M _y O ₁₉

Wherein A is at least one element selected from Sr, Ba and Ca, R is at least one element selected from rare earth elements and Bi, and M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, And As, 0 < x < 0.5, 0 < y <2;

The pulverizing method is not particularly limited and can be appropriately selected. In a non-limiting example, the fired body is first crushed by a roller mill or a rod mill and then finely ground into a wet ball mill or a wet attritor. Dry milling can also be used. The particle diameter of the formed powder is not particularly limited and can be appropriately selected. For example, the particle diameter of the hexaferrite powder formed may be in a range of 5 mu m or less, for example, 0.3 mu m to 3 mu m, but is not limited thereto.

The obtained hexaferrite powder was heat-treated at a temperature of 1000 ° C. to 1280 ° C. in a non-oxidizing atmosphere to obtain a magnetic powder containing M-type hexaferrite represented by the general formula (1) (ie, having an oxygen vacancy) . In one embodiment, the heat treatment may be performed at a temperature below 1200 degrees Celsius, e.g., below 1150 degrees Celsius. The heat treatment may be performed for 30 minutes or more, for example, 40 minutes or more, 1 hour or more, 2 hours or more, 3 hours or more, 4 hours or more, or 10 hours or more. The non-oxidizing atmosphere may be a nitrogen gas atmosphere, an argon gas atmosphere, a helium gas atmosphere, or a vacuum. The obtained magnetic powder may not contain W phase hexaferrite. The non-oxidizing atmosphere may be a nitrogen gas atmosphere, an argon gas atmosphere, a helium gas atmosphere, or a vacuum.

In another embodiment, a method of making an M-type hexaferrite magnetic powder comprises:

Obtaining a raw material mixture;

The raw material mixture is calcined at a temperature of 1100 degrees Celsius to 1280 degrees Celsius in a non-oxidizing atmosphere, and the obtained calcined product is pulverized to obtain a magnetic powder containing M type hexaferrite represented by the following general formula 1 and containing FeO Step:

[Formula 1]

A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d

Where A, R, M, x, and y are as defined above and d > 0.

The contents of the raw material mixture, calcination, calcined water, pulverization, non-oxidizing atmosphere and the like are as described above.

In another embodiment, there is provided a magnet comprising an M type hexaferrite represented by the following general formula 1 and comprising FeO:

[Formula 1]

A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d

Where A, R, M, x, and y are as defined above and d > 0.

The content of the magnetic powder is as described above. The production of the magnet from the magnetic powder can be carried out according to any known method and is not particularly limited. In a non-limiting example, the magnetic powder may be wet / dry compressed under a magnetic field and annealed under a nitrogen atmosphere at a predetermined temperature (e.g., a temperature of 1100). In another non-limiting example, the magnetic powder may be made of a bond magnet using known adhesives (e.g., epoxy, rubber, resin, etc.).

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

Obtain the magnetic hysteresis curve of the hexaferrite powder prepared by the sample vibratory magnetometer (VSM) or the BH loop tracer method. The maximum applied magnetic field is 1.5 T or more, and a magnetic hysteresis curve or demagnetization curve is obtained by sweeping the magnetic field. The maximum saturation magnetization value and the coercive force are measured from the curve.

Comparative Example 1 :

SrCO ₃ powder (99.9%, average particle size: 5 microns, Manufacturer: high purity chemical (day)), Fe ₂ O ₃ powder (99.9%, average particle size: 5 microns, Manufacturer: high purity chemical (day)), La ₂ O ₃ powder (99.9%, average particle size: 5 microns, Manufacturer: high purity chemical (day)), CeO ₂ powder (99.9%, average particle size: 5 microns, Manufacturer: high purity chemical (day)), ZnO powder (99.9 %, Average particle diameter: 5 micrometers, manufacturer: high purity chemical (sun)) are weighed to obtain the composition of the following general formula, respectively, to obtain a powder mixture. The powder mixture is ball milled for 18 to 24 hours using a mixture of zirconia balls of different sizes using ethanol as a solvent to obtain a slurry:

_{La 0 .3- y Ce y Sr 0} .7 [Fe 11 .7 Zn 0 .3] B / 12 O 19 -d

(Where y is 0, 0.1, 0.2, 0.3, B = 11)

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 1100 degrees Celsius or 1200 degrees Celsius for 4 hours and the calcined product is pulverized by ball milling or pulverized manually for 5 minutes in a mortar, Powder is obtained. The saturation magnetization value and the coercive force were measured for the final ferrite powder according to the above-mentioned method and are summarized in Table 1.

Example 1 :

SrCO ₃ powder (purity: 99.9%, average particle diameter: 5㎛, Manufacturer: high purity chemical, Japan), Fe ₂ O ₃ powder (purity: 99.9%, average particle diameter: 5㎛, Manufacturer: chemical purity (Japan)), CeO ₂ powder (purity: 99.9%, average particle size: 5 탆, manufacturer: High Purity Chemical Co., Japan), La ₂ O ₃ powder (purity: 99.9%, average particle diameter: 5 탆, ZnO powder (purity: 99.9%, average particle size: 5 탆, manufacturer: High Purity Chemical (Japan)) were each weighed and mixed to obtain a composition of the following general formula to obtain a mixture. The mixture is slurried by ball milling for 18 to 24 hours in a vessel using ethanol as a solvent and a different size of zirconia ball mixture:

_{La 0 .3- y Ce y Sr 0} .7 [Fe 11 .7 Zn 0 .3] B / 12 O 19 -d (y is 0, 0.1, 0.2, 0.3, B = 11)

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 1200 degrees C for 4 hours, and the calcined product is pulverized by pulverizing to obtain a ferrite powder. The obtained ferrite powder is heat-treated at a temperature of 1100 DEG C for 12 hours in a nitrogen atmosphere to obtain a final ferrite powder. The saturation magnetization value and the coercive force were measured for the final ferrite powder according to the above-mentioned method and are summarized in Table 1.

Example 2 :

A ferrite powder was prepared in the same manner as in Example 1, except that the calcination conditions were as follows:

In the air, 1200 degrees, 4 hours

The saturation magnetization value and the coercive force were measured for the final ferrite powder according to the above-mentioned method and are summarized in Table 1.

Example 3 :

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 at a temperature of 1100 degrees Celsius for 4 hours in nitrogen, and the calcined product is pulverized in a mortar to obtain a final ferrite powder. The saturation magnetization value and the coercive force were measured for the final ferrite powder according to the above-mentioned method and are summarized in Table 1.

Example 4 :

A ferrite powder was prepared in the same manner as in Example 3, except that the calcination conditions were as follows:

Nitrogen atmosphere, 1200 degree seeds, 4 hours

Comparative Example 2 :

Nitrogen atmosphere, 1300 degree seeds, 4 hours

M: M-type hexaferrite

W: W-type hexaferrite

O: orthoferrite, (LaSr) FeO ₃

C: CeO ₂

F: Hematite, Fe ₂ O ₃

S: Spinel, Zn _x Fe ₁ _- _x Fe ₂ O ₄

The results of Table 1 are summarized in a graph. From the results shown in Table 1 and FIG. 1, it is confirmed that the magnetic powder containing oxygen vacancies and M ² -type hexaferrite containing Fe ² ⁺ can maintain a satisfactory level of coercive force with a remarkably improved saturation magnetization value .

Examples 5 to 7 :

A magnetic powder was prepared in the same manner as in Example 1 except that the composition and calcination / heat treatment conditions were as shown in Table 2 below, and the magnetic properties and the like were measured. The results are summarized in Table 2.

Furtherance Calcination atmosphere / temperature Saturation magnetization Coercivity Column (> 90 vol%) _{Sr 0 .9 Ce 0 .1 Fe 12} O 19 -d Air 1200 70 4.7 M-hexaferrite Comparative Example 3 _{Sr 0 .7 La 0 .3 Fe 11} .7 Zn 0 .3 O 19 -d Air 1200-> N ₂ 1200 77 1.7 M-hexaferrite Example 5 _{Sr 0 .9 Ce 0 .1 Fe 12} O 19 -d Air 1200-> N ₂ 1200 75 3.8 M-hexaferrite Example 6 Sr ₀ _.9 Ce ₀ _.1 Fe ₁₁ _.8 Zn ₀ _.2 O ₁₉ _-d Air 1200-> N ₂ 1200 78 2.5 M-hexaferrite Example 7

From the above Table 2, it is confirmed that the hexaferrite powders of Examples 5 to 7 can exhibit a satisfactory level of coercive force while having a very high saturation magnetization value.

Reference Example 1 :

A magnetic powder having the following composition was produced at a calcining temperature of nitrogen atmosphere / 1200 DEG C:

_{La 0 .3 Sr 0 .7 Fe 11} .7 Zn 0 .3 O 19

It is confirmed that when the prepared magnetic powders are heat treated in oxygen atmosphere (oxygen 99% or more) at 400 ° C for 2 hours, the saturation magnetization value decreases from 77 to 73 by 5% or more.

Reference Example 2 :

_{La 0 .2 Ce 0 .1 Sr 0} .7 Fe 11 .7 Zn 0 .3 O 19

It is confirmed that when the prepared magnetic powder is heat-treated at 500 ° C for 2 hours in an oxygen atmosphere (oxygen 99% or more), the saturation magnetization value decreases from 77 to 69 by 10% or more.

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

A magnetic powder comprising M type hexaferrite represented by the following general formula 1 and containing FeO as a major phase:
[Formula 1]
A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d
Wherein A is at least one element selected from Sr, Ba and Ca, R is at least one element selected from rare earth elements and Bi, and M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, And As, 0 < x < 0.5, 0? Y <2, and d> 0.

The method according to claim 1,
The M type hexapellite includes La, Ce, Nd, Sm, or a combination thereof as a rare earth element.

The method according to claim 1,
Wherein the powder has a saturation magnetization value reduced by 2% or more based on the saturation magnetization value before heat treatment when the heat treatment is performed in an oxygen-containing atmosphere at a temperature of 400 ° C to 700 ° C for 30 minutes or more.

The method according to claim 1,
A magnetic powder not containing W type phase.

The method according to claim 1,
A magnetic powder having a saturation magnetization value (Ms) of 74 or more.

The method according to claim 1,
A magnetic powder having a coercive force (Hc) of 1.4 kOe or more.

A method for producing a magnetic powder comprising the steps of:
Metal carbonate powder containing Sr, Ba, or Ca; Iron oxide; A rare earth metal or Bi oxide powder; And optionally obtaining a raw material mixture comprising a carbonate or oxide powder of metal M wherein M is at least one selected from Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, step;
Calcining the raw material mixture in an oxygen-containing atmosphere at a temperature of 900 DEG C to 1350 DEG C, and pulverizing the obtained calcined product; And
Subjecting the pulverized calcined material to a heat treatment at a temperature of 1000 ° C to 1280 ° C in a non-oxidizing atmosphere to obtain an M-type hexaferrite magnetic powder having a ferrite phase represented by the following general formula 1 and containing FeO:
[Formula 1]
A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d
Wherein A is at least one element selected from Sr, Ba and Ca, R is at least one element selected from rare earth elements and Bi, and M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, And As, 0 < x < 0.5, 0? Y <2, and d> 0.

A method for producing a magnetic powder comprising the steps of:
Metal carbonate powder containing Sr, Ba, or Ca; Iron oxide; A rare earth metal or Bi oxide powder; And optionally obtaining a raw material mixture comprising a carbonate or oxide powder of metal M wherein M is at least one selected from Co, Mn, Zn, Zr, Ni, Ti, Cu, Al, Ge, ; And
The raw material mixture was calcined at a temperature of 1100 degrees Celsius to 1280 degrees Celsius in a non-oxidizing atmosphere, and the obtained calcined material was pulverized to obtain an M type hexaferrite magnetic powder having a ferrite phase represented by the following general formula 1 and containing FeO Steps to be taken:
[Formula 1]
A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d
A is at least one element selected from Sr, Ba and Ca, R is at least one element selected from rare earth elements and Bi, M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, 0 < x < 0.5, 0 < y < 2, and d > 0.

9. The method according to claim 7 or 8,
Wherein the heat treatment or the calcination is performed at a temperature of 1200 degrees Celsius or less.

9. The method according to claim 7 or 8,
Wherein the non-oxidizing atmosphere is a nitrogen gas atmosphere, an argon gas atmosphere, a helium gas atmosphere, a combination thereof, or a vacuum.

Magnet comprising M type hexaferrite represented by the following general formula 1 and containing FeO:
[Formula 1]
A _{1 -} _x R _x Fe ₁₂ _- _y M _y O _{19 -} _d
Wherein A is at least one element selected from Sr, Ba and Ca, R is at least one element selected from rare earth elements and Bi, and M is at least one element selected from the group consisting of Co, Mn, Zn, Zr, Ni, Ti, Cu, And As, 0 < x < 0.5, 0? Y <2, and d> 0.

12. The method of claim 11,
The M type hexapellite includes La, Ce, Nd, Sm, or a combination thereof as a rare earth element.

12. The method of claim 11,
Wherein said M type hexaferrite exhibits a reduction of 2% or more in saturation magnetization value when heat-treated in an oxygen-containing atmosphere at a temperature of 400 to 700 degrees Celsius.

12. The method of claim 11,
Magnets not containing a W-type image.

12. The method of claim 11,
A magnet having a saturation magnetization value (Ms) of 74 or more.

12. The method of claim 11,
Magnet having a coercive force (Hc) of 1.4 KOe or more.