JP2000049005A - R-tm-b permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a guideline for developing an R-TM-B permanent magnet which exhibits high magnetic performance, particularly, a permanent magnet having a high coercive force. SOLUTION: In an R-TM-B permanent magnet, a magnetic phase composed mainly of an R2TM14B intermetallic compound (where, R and TM respectively represent a rare-earth element, including Y and a transition metal) in which a tetragonal crystal structure and a grain boundary phase containing an R-TM-O compound exist. In the grain boundary phase, the R-TM-O compound having a face-centered cubic crystal structure is precipitated near the boundary with the magnetic phase and the magnetic phase, and grain boundary phase are made to match with each other. The crystallomagnetic anisotropy of the magnetic phase is enhanced near the boundary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an R-TM-B permanent magnet (R: a rare earth element containing Y, TM: transition metal), and more particularly, to an R-TM-B permanent magnet raw material, TM-
The present invention relates to a B-based permanent magnet intermediate and an R-TM-B-based permanent magnet as a final product.

[0002]

2. Description of the Related Art R-TM-B permanent magnets have excellent magnetic properties and are used for various purposes. R-TM-B
There are various manufacturing methods for the system permanent magnet, and typical manufacturing methods include a sintering method and a super-quenching method. In the sintering method, for example, as disclosed in JP-A-59-46008, an ingot having a specific composition is pulverized into a single crystal fine powder having an average particle size of several μm, and the powder is oriented in a magnetic field. This is a method of obtaining a bulk magnet by molding into an arbitrary shape and then sintering.
The rapid quenching method is, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-9852, by rapidly quenching an alloy having a specific composition into an amorphous state by a method such as a roll quenching method, and then performing a heat treatment. This is a method of precipitating fine crystal grains.
The magnet alloy obtained by the rapid quenching method is usually in the form of a powder, and is generally used in the form of a bonded magnet by mixing and molding with a resin. Further, a method of pulverizing and sintering a quenched thin plate has also been used.

[0003]

In such a prior art, various conditions in the magnet manufacturing process are optimized by repeatedly performing sample preparation and evaluation, and the magnetic properties of the magnet are empirically improved. . However, with such an empirical method, it is difficult to achieve a dramatic improvement in magnetic properties. Further, when the composition of the permanent magnet is different, it is necessary to repeatedly perform sample preparation and evaluation.

The present invention provides an R-TM having high magnetic performance.
It is an object to provide a guide for designing a B-based permanent magnet.

[0005]

Means for Solving the Problems Conventionally, the magnetic properties of a magnet,
Above all, the structure of the interface between the main phase (ferromagnetic phase) that determines the coercive force and the grain boundary phase was unknown. For this reason, in the prior art, by optimizing various conditions in the magnet manufacturing process,
Experience has shown to improve the magnetic properties of magnets. Such an empirical method takes time and expense for sample preparation and evaluation, and has a limit in improving magnet properties.

The present inventors have investigated the fundamental problem of what the ideal interface structure should be, without relying on an empirical method. As a result, the present inventors have developed a nucleation-type coercive force generation mechanism. in various magnetic materials, ease of nucleation depends on the size of the crystal magnetic anisotropy in the outermost shell near the magnetic phase, the value of the anisotropy constant K ₁ of the outermost shell near at least showing It has been found that nucleation can be suppressed and the coercive force of the magnet can be increased by controlling it to be equal to or more than the inside, and as a result of further intensive research, the present invention has been completed.

According to a first aspect of the present invention, there is provided a magnetic phase mainly composed of an R ₂ TM ₁₄ B intermetallic compound (R: a rare earth element containing Y, TM: transition metal) having a tetragonal crystal structure; And a grain boundary phase containing a TM-O alloy, wherein a crystal structure of the grain boundary phase near an interface between the magnetic phase and the grain boundary phase is a face-centered cubic structure, and the magnetic phase and the grain The phases are consistent.

[0008] In the second viewpoint, an R-TM-O compound is precipitated near the interface of the grain boundary phase. In a third aspect, in the R ₂ TM ₁₄ B intermetallic compound,
The total of Nd and Pr in R is 50 at% or more, TM is Fe or Co, and the content of Fe in TM is 50 at% or more. In the R-TM-O compound, the ratio of R to the total of R and TM is 90 at%. %
That is, the ratio of O is 1 at% or more and 70 at% or less.
In a fourth aspect, the crystallographic orientation relationship near the interface between the magnetic phase and the grain boundary phase is:

[0009]

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And the angle of the misalignment in the azimuth relationship is within 5 °. In a fifth aspect, a magnetic phase having a tetragonal crystal structure and a grain boundary phase in which a compound containing oxygen and having a crystal structure having a face-centered cubic structure is present near an interface with the magnetic phase, The magnetic phase and the grain boundary phase are aligned across the interface.

According to the present invention, in a sixth aspect, R (R: Y
R ₂ TM ₁₄ B tetragonal crystal is precipitated from an alloy containing TM, a transition metal (TM), B and O, and R-TM- is formed around the R ₂ TM ₁₄ B tetragonal phase. By precipitating an O-face centered cubic phase, the R ₂ TM ₁₄ B tetragonal phase is matched with the R-TM-O face-centered cubic phase, and at least the R ₂ TM ₁₄ B tetragon near the aligned interface is matched. Increase the crystal magnetic anisotropy of the crystal phase. Preferably, R ₂ exhibiting ferromagnetism is used.
TM ₁₄ B intermetallic compound (R: rare earth element including Y, TM:
A transition metal) source and an R-TM-O compound source are used as raw materials.

Here, a main phase (ferromagnetic phase) mainly composed of an R ₂ TM ₁₄ B intermetallic compound (preferably a single crystal) and a grain boundary phase containing an R—TM—O compound are mainly used. The principle of the present invention will be described using the R-TM-B-based permanent magnet as an example. Incidentally, R-TM-B system in the permanent magnet B-rich phase _{(R 1+ α TM 4 B 4} ), it is known that such R-TM meta-stable phase is present, these phases The effect on the magnetic properties of the permanent magnet is secondary compared to the two phases of the main phase and the grain boundary phase.

The existence of the grain boundary phase is necessary for realizing a practical coercive force. Generally, when the R component necessary for forming the grain boundary phase becomes insufficient in the composition of the magnet, the coercive force decreases. This is R
Due to lack of components, the two phases of R ₂ TM ₁₄ B phase and R-TM phase cannot coexist in an equilibrium state, and instead a ferromagnetic phase such as R ₂ TM ₁₇ phase precipitates at the grain boundary of R ₂ TM ₁₄ B phase. However, it is considered that this becomes the starting point of the generation of the reverse magnetic domain, and the magnetization is easily inverted to lower the coercive force.

In order to give a practically sufficient coercive force to the R-TM-B permanent magnet produced by the sintering method, the main phase and the grain boundary phase, which are ferromagnetic phases, must be smooth without lattice defects. The necessity of contact at the interface is revealed by microscopic observation of the interface with a transmission electron microscope. The reason is described as follows: if a lattice defect or the like is present at the interface, this becomes the starting point of the generation of a reverse magnetic domain, and the magnetization is easily inverted to lower the coercive force.

In the above-mentioned prior art, in order to express the excellent magnetic properties possessed by the R-TM-B permanent magnet, the present inventors described the preferred form of the grain boundary phase constituting the permanent magnet as follows. It was found that there was a problem. That is, in the prior art, although knowledge about the composition region in which the R-TM grain boundary phase exists and the presence or absence of defects at the interface between the main phase and the grain boundary phase has been obtained, the crystal of the R-TM grain boundary phase has No known orientation relation between the structure and its main phase was known. Therefore, R-TM-B having a specific composition
It has not been possible to control the microstructure of the system-based permanent magnet to exhibit excellent magnetic properties. Instead, in the related art, the magnetic properties of the magnet are empirically improved by optimizing various conditions in the magnet manufacturing process.

That is, conventionally, since the magnetic properties of the magnet, especially the structure of the interface between the main phase and the grain boundary phase which determine the coercive force, were unknown, various processes which are considered to change the structure of the interface (for example, Heat treatment, etc.) is applied to the magnet to control the magnet properties while keeping the state of the interface as a black box. Such a method did not hinder the optimization of the manufacturing conditions for magnets of individual compositions, but without the guidelines for material development as to what the ideal interface structure should be, the magnet characteristics Is extremely difficult to further improve.

The present inventors conducted a microscopic analysis of the grain boundary phase of various R-TM-B permanent magnets using a transmission electron microscope (TEM), and found that all R-TM-B At the grain boundaries of the permanent magnet, there is always a grain boundary phase containing an R-TM-O compound (the ratio of R to the sum of R and TM is at least 90 at%), and the crystal of the grain boundary phase near the interface with the main phase is present. It has been found that excellent magnetic properties can be obtained when the structure has a face-centered cubic structure.

Further, the present inventors have proposed that the grain boundary phase and the main phase (R ₂ TM _{14) of} the R-TM-B permanent magnet in which the R-TM-O grain boundary phase having the above-mentioned face-centered cubic structure exists. The structure of the interface with the (B phase) was observed in detail using a high-resolution transmission electron microscope (HR-TEM) or scanning tunneling microscope. It has been found that the microstructure is controlled so as to have the highest magnetic properties when the microstructures are matched, and the present inventors completed the present invention as a result of further intensive studies.

Referring to FIGS. 1, 2 (A) and 2 (B),
The difference in the distribution of magnetocrystalline anisotropy near the interface between the case where the main phase (ferromagnetic phase) and the grain boundary phase match at the interface and the case where they do not match will be described. FIG. 1 or FIG.
In (A) and (B), the “outermost shell” on the horizontal axis indicates the position of the outermost atomic layer of the main phase, and the “second layer”, “third layer”
The “layer” indicates the positions of the second and third atomic layers counted from the outermost shell position toward the inside. The n-th layer indicates a position where the distance from the outermost shell is long and the influence from the interface can be ignored. In the graph of FIG. 1, the ordinate indicates the magnitude of the uniaxial anisotropy constant K ₁ (indicating the strength of crystal magnetic anisotropy) of the main phase,
As the value of K ₁ is larger, the direction of the spontaneous magnetization of the main phase is stabilized in the direction of the axis of easy magnetization (c-axis). In FIG. 1, the example (the present invention) shows the calculated value of K _{1 under} the condition that the main phase and the grain boundary phase match at the interface as shown in FIG. As shown in FIG. 2B, the calculated value of K ₁ is shown in the case where there is an interface mismatch due to a lack of a grain boundary phase or the like.

[0020] Referring to FIG. 1, in the comparative example, vary greatly in size of the anisotropy constant K ₁ by the distance from the interface, the value of K ₁ is significantly reduced compared to the inside of the outermost shell ing. On the other hand, in the embodiment, without much change in the magnitude of K ₁ by the distance from the interface, K ₁ in the outermost shell phase is rather increased. Therefore, according to the comparative example, the energy required for nucleation of the reverse magnetic domain in the outermost shell is locally reduced to facilitate nucleation and magnetization reversal, so that the coercive force of the magnet is reduced. On the other hand, according to the embodiment,
Since K _{1 in the} outermost shell is rather higher than in the interior, nucleation of reverse domains at the interface is suppressed, resulting in increased coercivity of the magnet.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described by taking a sintering method (powder metallurgy) as an example. In other known R-TM-B-based permanent magnet manufacturing methods, the specific method of developing a preferable interface structure is the same as that of the sintering method.

In the R-TM-B base alloy as the starting material, it is preferable that the total of Nd and Pr in R is at least 50 at%, because the coercive force and the residual magnetization of the obtained magnet are improved. Also, to improve coercive force, part of Nd is replaced with Dy
And substitution with Tb is also preferred. TM is especially Fe or Co
Is preferred. When the content of Fe in the TM is 50 at% or more, the coercive force and the residual magnetization are improved. In addition, it is also possible to add additional elements other than the above for various purposes.

The average composition of the permanent magnet according to the present invention is R
_A composition range in which at least two phases of the ₂ TM ₁₄ B phase and the R-TM-O phase (the ratio of R to the sum of R and TM is 90 at% or more) is preferable. For this, the composition range is R: 8-30at.
%, B: 2 to 40 at%, with the balance being mainly TM. Preferably, the composition range is R: 8 to 30 at%, B: 2 to 40 at%, Fe: 40
~ 90at%, Co: 50at% or less. Further, preferably, the composition range is R: 11 to 50 at%, B: 5 to 40 at%, and the balance is mainly T
M may be set. More preferably, the composition range is R: 12 to 1
6 at%, B: 6.5 to 9 at%, and the balance may be mainly TM.
More preferably, the composition range is R: 12 to 14 at%, B: 7 to 8 at%.
% And the remainder may be mainly TM. In addition, the raw materials used do not necessarily have to have a single required composition, and alloys having different compositions may be pulverized, then mixed and adjusted to the required composition before use.

In this specification, the description regarding the numerical range includes not only the upper and lower limits but also any intermediate value included in the numerical range.

Oxygen may be added to the raw materials, for example, to the Fe alloy or R alloy used as the raw materials, or may be added, for example, to a manufacturing process such as a pulverizing step. Note that industrially, the oxygen unavoidably contained in the raw material is converted to R-T
It can be used as an oxygen source for the MO compound, or oxygen can be incorporated during the manufacturing process (for example, incorporated into the raw material alloy or intermediate product alloy), and the incorporated oxygen can be used as R-TM-O It may be used as a source of oxygen for the compound.

In the main phase, part or most of B may be replaced by a so-called semi-metallic element such as C, Si, or P. For example, when B is replaced by C, B _1-x C _x ; preferably x can be at least 0.8.

The R-TM-B base alloy can be made into a powder by a known method such as a casting pulverization method, a quenched thin plate pulverization method, a super-quenching method, a direct reduction diffusion method, a hydrogen-containing disintegration method, or an atomizing method. You can choose. Average particle size of alloy powder
When the thickness is 1 μm or more, the powder hardly reacts with oxygen in the atmosphere and is hardly oxidized, and the magnetic properties after sintering are improved. Further, by setting the average particle size to 10 μm or less, the sintering density is increased, which is preferable. A more preferable range of the average particle size is 1 to 6 μm.

The obtained alloy powder is fed into a mold, and compression-molded while orienting in a magnetic field. At this time, as disclosed in, for example, JP-A-8-20801, spray granulation is performed by adding a binder to the alloy powder for the purpose of increasing the fluidity of the alloy powder and facilitating powder supply. Is also preferred.
Alternatively, as disclosed in JP-A-6-77028, it is also possible to add a binder to an alloy powder and form a complex-shaped product by a metal injection molding method. When these binders are used, it is preferable to remove the binder contained in the molded body by thermal decomposition before sintering.

The obtained compact is sintered in a vacuum or in an inert gas except nitrogen. The sintering conditions are appropriately selected according to the composition and particle size of the R-TM-B base alloy powder, but are preferably, for example, at 1000 to 1180 ° C. for 1 to 4 hours. The cooling rate after sintering is important for controlling the crystal structure of the grain boundary phase. That is, at the sintering temperature, the grain boundary phase is in a liquid phase, and if the cooling rate from the sintering temperature is too fast, the grain boundary phase contains many lattice defects or becomes amorphous, which is not preferable. .

In order for the grain boundary phase to have a face-centered cubic structure, the cooling rate from the sintering temperature is preferably in the range of 10 to 200 ° C./min. By allowing sufficient time for cooling in this way, the liquid grain boundary phase does not become supercooled, but can take a regular crystal structure during cooling. Since the grain boundary phase is not amorphous but has a face-centered cubic structure, the positional relationship between the atoms at the interface between the main phase and the grain boundary phase is regular, and the consistency between the two is maintained. The possibility of starting the occurrence is reduced, and a high coercive force is realized. A more preferable range of the cooling rate after sintering is 20 to 100 ° C./min.

In order for the grain boundary phase to have a face-centered cubic structure, it is preferable that the grain boundary phase contains oxygen as a component of the compound. For example, R-TM-
During the process of pulverizing, molding and sintering the B-based alloy, oxygen can be introduced into the magnet, and this oxygen is mainly dissolved in the grain boundary phase,
It becomes a component of the R-TM-O compound and stabilizes the face-centered cubic structure of the grain boundary phase. The R of the grain boundary phase thus formed is
The ratio of R to the sum of R and TM in the -TM-O compound is preferably at least 90 at%.

In addition, O in the R-TM-O compound of the grain boundary phase
When the ratio is 1 at% or more, the effect of stabilizing the face-centered cubic structure is large, an ideal interface can be formed to improve the coercive force, and the coercive force is improved. Is preferable because the effect of increasing the crystal magnetic anisotropy in the vicinity of the interface of the R ₂ TM ₁₄ B tetragonal phase is large and the coercive force is improved. Therefore, the ratio of O in the R-TM-O compound in the grain boundary phase is preferably at least 1 at% and at most 70 at%. That is, as described below, a non-stoichiometric R-TM-O compound having a wide range in the composition ratio of O (preferably, O is 1 at% or more and 70 at% or less) in the vicinity of the interface, as described below. ) Is preferably present. Further, preferably, the composition range may be O: 2 to 50 at%. More preferably, the composition range may be O: 4 to 15 at%, or O: 5 to 15 at%.

In order to obtain the effect of interface consistency, it is sufficient that the crystal structure of the grain boundary phase has a face-centered cubic structure in the range of at most several atomic layers near the interface between the main phase and the grain boundary phase. In addition, the main phase is generally formed earlier than the grain boundary phase, and the crystal grains constituting the main phase are single crystals. The crystal magnetic anisotropy in the crystal grains increases from the surface to the outer shell, and a high coercive force can be obtained.

It is preferable that a part or all of the crystal grains of each main phase is surrounded by a grain boundary phase, and the crystal grain size of the main phase is preferably in the range of 10 nm to 500 μm.
A more preferable range of the crystal grain size is, for example, in the case of the sintering method.
It varies from 10 to 30 μm, and 20 to 100 nm in the case of the ultra-quenching method, depending on the respective production method. If the main phase contains a grain boundary without a grain boundary phase, a twin grain boundary, a precipitate, or the like, the coercive force of the magnet decreases. Therefore, the main phase is preferably a single crystal.

In order to more ideally control the positional relationship between atoms at the interface between the main phase and the grain boundary phase, the crystallographic orientation relationship between the main phase and the grain boundary phase may be specified. Here, the symbol [hkl] indicates the direction of the normal line perpendicular to the crystal plane represented by the Miller index h, k, l. The subscript "main phase" of the symbol [hkl]
Alternatively, the “grain boundary phase” indicates that each direction is that of the main phase or the grain boundary phase. For example, the symbol [001] main phase indicates the direction of the c-axis of the R ₂ TM ₁₄ B phase that is the main phase. The symbol "//" written between a set of directions indicates that these directions are parallel to each other.

Next, the symbol (hkl) represents a crystal plane whose Miller index is represented by h, k, l, and the subscripts “main phase”, “grain boundary phase”, and the symbol “//” Has the same meaning as in the direction. Here, in the notation of the direction and the crystal plane for the same phase, the Miller index used is not a generalized index but indicates a specific crystal direction or crystal plane.

For example, the Miller index shown below is an index based on the fixed x, y, and z coordinates of the grain boundary phase. In other words, the (221) plane and the (212) plane are strictly distinguished. With such a notation method, the spatial orientation relationship between the main phase and the grain boundary phase is strictly defined.

[0038]

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The reason why the specific crystal orientation relationship at the interface improves the magnetic properties of the magnet is as follows. That is, in the vicinity of the interface of the main phase, the crystal field around the R atom that determines the crystal magnetic anisotropy of the main phase changes under the influence of the atomic arrangement of the adjacent grain boundary phase. When the crystal orientation of the R-TM-O grain boundary phase has the following relationship (A) to (C) with respect to the main phase, R atoms of the R-TM-O grain boundary phase and Since the R atoms and the R atoms are in a positional relationship that enhances the anisotropy of the crystal field, the magnetocrystalline anisotropy near the interface of the main phase increases. As a result, it is considered that the generation of a reverse magnetic domain near the grain boundary becomes difficult, and the magnetization reversal cannot be easily performed, so that the coercive force is improved.

[0040]

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In the above description, the atoms in the grain boundary phase that affect the crystal field of the R atoms in the main phase are limited to those near the interface adjacent to the main phase. Therefore, in the present invention, the orientation relationship between the crystal structure of the grain boundary phase (the main phase described above) and the grain boundary phase only needs to be established within a range of at most several atomic layers near the interface between the two phases.

As a method of realizing such a crystal orientation relationship, for example, there is a cooling rate control after sintering. For example,
From 800 ° C or higher where the R-TM-O grain boundary phase is in a liquid state,
By cooling the temperature range up to 300 ° C or less, where the diffusion of atoms becomes extremely slow, at a cooling rate of 10 to 200 ° C / min,
RT with a specific crystal orientation relationship compatible with the main phase
The MO grain boundary phase can be precipitated near the interface with the main phase. A more preferred cooling rate is 20 to 100 ° C / min.

At this time, since the ratio of the lattice constants of the main phase and the grain boundary phase differs depending on the component elements or the composition of the two phases, the crystal orientation may be slightly shifted. However, since the angle of this shift is at most 5 °, even if the angle is shifted, the effect on the crystal field of the R atoms in the main phase is small, and the desired effect can be exhibited.

In addition to controlling the cooling rate from a high temperature, the magnet once obtained by a sintering method, a super-quenching method, or the like is heated to a temperature of 300 to 800 ° C. below the melting point at which atoms in the grain boundary phase can easily diffuse. Heat treatment in the region is also effective in controlling the interface structure. Also in this case, the energy of the interface becomes the driving force, the crystal structure of the grain boundary phase is rearranged near the interface with the main phase, and a consistent interface is realized. Preferred cooling rate after heat treatment is 10 ~
200 ° C / min.

Although the embodiment has been described mainly with reference to the sintering method as an example, other methods for producing an R-TM-B-based permanent magnet also have a favorable interface structure. It is exactly the same.

In the case of a bulk magnet such as a sintered body, the permanent magnet material having excellent magnetic properties obtained by the above method is provided with a predetermined dimensional accuracy by grinding or the like and then subjected to a necessary surface treatment. And magnetized for use. At this time, it is also a preferable embodiment to perform a heat treatment after the processing in order to reduce the influence of the processing distortion. In the case of a bonded magnet, the obtained magnetic powder is mixed with a resin, molded, then, if necessary, subjected to a surface treatment and magnetized before use.

[Anisotropy Constant] In the permanent magnet according to the present invention, the value of the anisotropy constant K ₁ near the outermost shell of the ferromagnetic phase is preferably equal to or greater than that of the inside.
Equivalence in this case is at least 50% or more of the internal value. It is preferable that the magnetocrystalline anisotropy in the outermost shell of the ferromagnetic particles be enhanced as compared with the magnetocrystalline anisotropy of the outermost shell of the ferromagnetic particles in the absence of the grain boundary phase.

[Distribution of Crystalline Magnetic Anisotropy] At least one of a metal, alloy, or intermetallic compound which has a specific crystal structure which is not amorphous and which is ferromagnetic at room temperature.
In a permanent magnet composed of seed crystal grains, the crystal magnetic anisotropy at the outermost shell position of the crystal grains is equal to or improved within the crystal grains (center portion) where the influence of the crystal grains outside can be ignored. However, it is preferable that it does not greatly decrease compared to the inside. In order to obtain a practical coercive force, the crystal magnetic anisotropy at the outermost shell position of the crystal grain is preferably at least half of the internal crystal magnetic anisotropy where the influence of the crystal grain outside can be ignored.

[Enclosed Main Phase, Separated Structure] A main phase composed of a metal, alloy, or intermetallic compound having a specific non-amorphous crystal structure and being ferromagnetic at room temperature, and a metal, alloy, Alternatively, it is preferable to be composed of at least two phases of a grain boundary phase which are made of an intermetallic compound and exist around the main phase. The grain boundary phase can improve the coercive force by surrounding a part or all of the ferromagnetic phase (ferromagnetic particles) constituting the main phase. It is preferable that the ferromagnetic phase (ferromagnetic particles) is surrounded by a grain boundary phase by half or more. It is preferable that one ferromagnetic particle constituting the main phase and another ferromagnetic particle are separated from each other. Preferably, one ferromagnetic particle and another ferromagnetic particle are partially or wholly separated from each other by a substantially nonmagnetic grain boundary phase.

[Preferred Combination of Main Phase and Grain Boundary Phase] In the present invention, the metal, alloy or intermetallic compound preferable as the main phase preferably has excellent properties as the main phase of the permanent magnet. , A material having a high saturation magnetization and a sufficiently high Curie temperature at room temperature or higher.

In the present invention, the metal, alloy or intermetallic compound preferable as the grain boundary phase has a melting point or decomposition temperature higher than room temperature and lower than the melting point or decomposition rate of the main phase. What is easy to diffuse around the main phase by using is preferred. Further, it is preferable that the atoms constituting the grain boundary phase behave as cations with respect to the outermost shell atoms of the main phase to enhance the crystal magnetic anisotropy of the main phase. In particular, a crystal containing a cation source is precipitated at least in a grain boundary phase portion adjacent to the ferromagnetic particles, and in the crystal structure of the grain boundary phase adjacent to the ferromagnetic phase, a rare earth element located in the outermost shell of the ferromagnetic particles It is preferable to position the cation in the direction in which the 4f electron cloud of the ion extends. In addition to R in the R-TM-O compound, examples of metals satisfying the above conditions include Be, M
g, Ca, Sr, Ba, all transition metal elements (including Zn, Cd), and one or more of Al, Ga, In, Tl, Sn, and Pb.
Also, Be, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Mn,
Fe, Co, Ni, Cu, Zn, Ga, Sr, Zr, Nb, Mo, Cd, In, S
It is at least one of n, Ba, Hf, Ta, Ir, and Pb. In addition, alloys of these metals or intermetallic compounds can also be the grain boundary phase, but the examples given above do not limit the scope of the present invention.

The combination of the main phase and the grain boundary phase is preferably one in which both phases coexist in an equilibrium in a certain temperature range, such as the SmCo ₅ main phase and the Y grain boundary phase. Also, for example, Sm ₂ Fe ₁₇
Just as the intermetallic compound phase (Γ-FeZn) is formed by the reaction between the N ₃ main phase and the Zn phase, even if the main phase and the second phase react to form a preferable third phase at the grain boundary. Good. In the latter case, the third phase is the grain boundary phase in the present invention.

[Range of trace addition element] In the present invention,
It is a preferred embodiment to mainly add a trace amount of a metal element or a metalloid element in order to enhance the consistency between the main phase and the grain boundary phase or to enhance the magnetic properties. The above-mentioned trace added elements are concentrated and unevenly distributed in the grain boundary phase to enhance the wettability of the interface, or diffuse to an inconsistent position of the interface to adjust the lattice constant of the grain boundary phase to lower the interface energy, Has the effect of improving the coherence of the magnet, and as a result, the coercive force of the magnet improves.

[0054] The trace additive elements acting as described above include:
Elements that can form a solid solution in the grain boundary phase are preferred, for example, C,
N, Al, Si, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Z
There are n, Ga, Zr, Nb, Mo, and the above-mentioned metal elements other than these, but the examples given above do not limit the applicable scope of the present invention. The addition amount of the element to be added for the above purpose is 1.0% by weight or less with respect to the whole magnet to obtain a good residual magnetic flux density of the magnet, and the predetermined effect is obtained at 0.05% by weight or more. Is preferably 0.05 to 1.0 wt%.
A more preferred range is from 0.1 to 0.5 wt%. The addition method of the trace addition element can be appropriately selected according to the manufacturing method of the magnet, such as adding it to the mother alloy from the beginning or adding it later by a powder metallurgy technique. Further, the above-mentioned trace elements may invade the main phase (ferromagnetic phase) or replace the elements constituting the main phase.

[Crystal Structure of Magnetic Phase and Grain Boundary Phase] The crystal structure of the grain boundary phase is preferably similar to the crystal structure of the magnetic phase. Further, it is preferable that the crystal structure of the grain boundary phase and the crystal structure of the magnetic phase have a specific orientation relationship. by this,
The consistency between the specific atom on the grain boundary phase side and the specific atom on the main phase side is enhanced. For example, a main phase comprising a tetragonal R ₂ TM ₁₄ B intermetallic compound (a rare earth element containing R: Y, TM: Fe or Co);
In particular, in a permanent magnet composed of a grain boundary phase composed of an R-TM-O compound, the crystal structure of the grain boundary phase near the interface between the main phase and the grain boundary phase is preferably a face-centered cubic structure. . In particular, it is preferable that the R-TM-O compound is precipitated in the grain boundary phase near the interface. Further, with respect to the plane index and the orientation index, it is preferable that the crystallographic orientation relationship in the vicinity of the interface between the main phase and the grain boundary phase is any one of the combinations of the above (A) to (C).

Further, tetragonal R ₂ TM ₁₄ B intermetallic compound
In a permanent magnet composed of a main phase composed of (R: a rare earth element containing Y, TM: Fe or Co) and a grain boundary phase composed of an R ₃ TM alloy, the vicinity of the interface between the main phase and the grain boundary phase In the above, the crystal structure of the grain boundary phase is preferably an orthorhombic structure. Further, with respect to the direction vector and the plane index, the crystallographic orientation relationship near the interface between the main phase and the grain boundary phase is as follows.
It is preferably any one of the combinations of (D) to (G).

[0057]

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The grain boundary phase comprising the R-TM-O compound and R ₃
When a grain boundary phase composed of a TM alloy coexists, the crystallographic orientation relationship between the grain boundary phase and the main phase is any one of the combinations of the above (A) to (C) and the above (D) to (G). Each of them is preferably one of the combinations.

It is to be noted that R having the same crystal structure as the R-TM-O compound obtained by removing O from the R-TM-O compound.
-TM compound may coexist as a grain boundary phase, the crystallographic orientation relationship between the grain boundary phase and the main phase, (A) ~
It is preferably any one of the combinations of (C). Further, in the R-TM compound, the ratio of R to the total of R and TM is preferably at least 90 at%.

It is considered from a laboratory that it is possible to almost completely remove oxygen unavoidably contained in the raw material and further to make oxygen contamination almost completely zero during the manufacturing process. However, it is extremely difficult industrially. Therefore, industrially, R-TM-
It is preferable to match the O compound with the main phase.

The grain boundary phase may be any one as long as atoms in the vicinity of the interface with the main phase (at most several atomic layers) match the main phase.
It may be partially amorphous and mostly amorphous. Although the effect can be obtained when a part of the interface is matched, it is preferable that half or more of the interface is matched. The main phase and the grain boundary phase preferably have regularity without lattice defects near the interface and maintain continuity, but may have some lattice defects. Note that it is preferable that the main phase and the grain boundary phase match at least 50% at the interface.

In the permanent magnet according to the present invention, the ferromagnetic phase only needs to exhibit a practical coercive force under certain conditions, and may be formed of one or more of metals, alloys, intermetallic compounds, semimetals, and other compounds. It is possible to configure. In addition, the principle of the present invention is applied to permanent magnet raw materials, intermediates, permanent magnets as final products, and methods for producing them. For example, as raw materials for permanent magnets, casting and pulverization methods, quenched thin plate pulverization methods, ultra-quench methods, direct reduction methods, hydrogen-containing collapse methods,
There is a powder obtained by an atomizing method. Examples of the intermediate include a quenched thin plate that is pulverized and used as a raw material for the powder metallurgy method, and an amorphous body (part or all) that is partially or wholly crystallized by heat treatment. As permanent magnets as final products, magnets made by bulking these powders by sintering or bonding, cast magnets, rolled magnets, further sputtering method,
There is a thin film magnet by an ion plating method, a PVD method, a CVD method, or the like. Furthermore, as a method of manufacturing a permanent magnet as a permanent magnet raw material or a final product, a mechanical alloying method, a hot pressing method, a hot forming method,
There are a hot / cold rolling method, an HDR method, an extrusion method, a die upset method, and the like, and there is no particular limitation. R- based on the present invention
The TM-B permanent magnet is used for a motor, a medical MRI apparatus, a speaker, and the like.

[0063]

[Example 1] Nd13.0at%, B6.5at%, balance Fe,
The raw material consisting of unavoidable impurities is loaded into a quartz tube with an orifice diameter of φ0.3 mm, melted by high frequency in an Ar gas atmosphere, and melted on a copper roll rotating at a roll peripheral speed of 20 m / s. It was quenched by spraying to obtain a super-quenched ribbon. This was roughly pulverized until the whole amount passed through a mesh having an opening of 300 μm, and then heat-treated at 600 ° C. for 30 minutes in an Ar atmosphere and cooled to room temperature at a cooling rate of 100 ° C./min. The obtained R ₂ TM ₁₄ B-based magnet powder contained 2.3 at% of O (used as an O source in the R-TM-O compound) incorporated in the process. A small piece of the obtained magnet powder was sampled, and Ar
A sample for a transmission electron microscope was prepared by ion milling in the inside and observed. As a result, the average crystal grain size was 74 nm, and the grain boundary phase was a face-centered cubic Nd-Fe-O compound having a thickness of 5 nm. Table 1 shows the magnetic properties of the obtained magnet powder after magnetization.

[Comparative Example 1] A small piece of the coarsely crushed powder of the ultra-quenched ribbon obtained in Example 1 was directly sampled and observed with a transmission electron microscope. As a result, the average crystal grain size was 73 nm and the grain boundary phase was It was an amorphous Nd-Fe-O compound having a thickness of 4 nm.
Table 1 shows the magnetic properties of the obtained magnet powder after magnetization.

[0065]

[Table 1]

As is clear from the results in Table 1, the magnetic properties of R-TM-B permanent magnets having substantially the same crystal grain size and an amorphous grain boundary phase or a face-centered cubic structure were compared. Then, it can be seen that the face-centered cubic structure exhibits particularly excellent magnetic properties in terms of coercive force.

Example 2 Nd 14.0at%, Co3.0at%, B7.0
A raw material consisting of at%, balance Fe, and inevitable impurities
r High frequency melting was performed in a gas atmosphere to melt the alloy. Next, after roughly pulverizing the alloy, the alloy was pulverized to 420 μm or less by a jaw crusher and a disc mill, and further pulverized by a jet mill to obtain a powder having an average particle diameter of 3 μm. The obtained fine powder is fed into a die of 15 mm in length and 20 mm in width, and is oriented in a magnetic field of 11 kOe.
Molding was performed by applying a pressure of ton / cm ² . After taking out the molded body, the temperature is raised to 1100 ° C in a vacuum, and sintering is performed for 2 hours.
And then cooled to 300 ° C. at a rate of 100 ° C./min. Then, Ar was introduced and cooled to room temperature to obtain a sintered magnet. Although the size of the obtained sintered body was smaller than that of the molded body due to shrinkage, cracks, cracks, deformation and the like were not observed at all. Next, the magnet after sintering was kept in vacuum at 500 ° C. for 2 hours, and then cooled to room temperature at a rate of 20 ° C./min. The obtained sintered magnet is mainly composed of O (R-TM
-The O source in the -O compound) was contained at 4.5 at%. Table 2 shows the magnetic properties of the sintered magnet after magnetization.

A small piece of the obtained magnet was sampled, a sample for a transmission electron microscope was prepared by ion milling in Ar, and observed. As a result, the average crystal grain size was 12 μm.
m, the grain boundary phase was a 15 nm thick Nd-Fe-O compound having a face-centered cubic structure. Figure 3 is a high resolution transmission electron micrograph of the vicinity of the interface between the main phase and a grain boundary phase, the right half R ₂ T
M ₁₄ B main phase, the lattice image of the R-TM-O grain boundary phase is shown the left half. Both are in contact with each other at the interface. FIG.
Is a selected area electron diffraction image of the R ₂ TM ₁₄ B main phase on the right side in FIG. As a result of the analysis, as shown in FIG. 4, the diffraction point can be indexed by a tetragonal crystal having a lattice constant of a = 0.88 nm and c = 1.22 nm. From this index, it can be seen that the incident direction of the electron beam in this diffraction image is as follows.

[0069]

Embedded image

FIG. 5 is a selected area electron beam diffraction image of the R-TM-O grain boundary phase on the left side in FIG. The diffraction point is the result of the analysis,
As shown in FIG. 5, the lattice constant can be indexed by a face-centered cubic crystal with a = 0.54 nm. From the index, it can be seen that the incident direction of the electron beam in this diffraction image is [001]. The crystal orientation relationship between the main phase and the grain boundary phase at the interface shown in FIGS. 3 to 5 is expressed as follows.

[0071]

Embedded image

The deviation of the azimuth relationship is 5
°. Similarly, as a result of analyzing the crystal orientation of the grain boundary phase near the interface with the main phase with a selected area electron diffraction image, at most of the observed sites, any of the above (A), (B) or (C) It was found that there was a crystal orientation relationship of the following set.

Comparative Example 2 The magnet after sintering obtained in Example 2 was sampled without heat treatment and observed with a transmission electron microscope. As a result, the average crystal grain size was 12 μm, and the grain boundary phase was It was a 15 nm thick face-centered cubic Nd-Fe-O compound. However, as a result of analyzing the crystal orientation of the grain boundary phase near the interface with the main phase using a selected area electron beam diffraction image, no specific orientation relationship was found. Table 2 shows the magnetic properties of the obtained sintered magnet after magnetization.

[0074]

[Table 2]

As is evident from the results in Table 2, R of a face-centered cubic structure having almost the same crystal grain size and the same crystal structure of the grain boundary phase.
Comparing the magnetic properties of the -TM-B-based permanent magnets, it can be seen that particularly excellent magnetic properties are exhibited in terms of coercive force when the main phase and the neighboring grain boundary phase have a specific orientation relationship.

[0076]

According to the present invention, a guide is provided for designing an R-TM-B-based permanent magnet having high magnetic performance (particularly, high coercive force). Conventionally, the structure of the interface between the main phase and the grain boundary phase that determines the coercive force was unknown.
The elucidation of the ideal interface structure for improving the coercive force provides guidance for the development of a new R-TM-B-based permanent magnet, as well as the existing R-TM-B-based permanent magnet. The coercive force of the magnet can be further improved. As a result, it is easy to find a new magnet material, and it is also possible to commercialize an R-TM-B-based permanent magnet that has not been practically used because of its low coercive force.

The R-TM-B-based permanent magnet according to the present invention
The positional relationship between the atoms at the interface between the main phase and the grain boundary phase becomes regular, and the consistency between the two is maintained. As a result, the possibility that the interface becomes the starting point of generation of reverse magnetic domains is reduced, and a high coercive force can be obtained. . In addition, the R-TM-B permanent magnet according to the present invention makes it difficult to generate a reverse magnetic domain near the grain boundary, and cannot easily reverse the magnetization, so that the magnet having excellent magnetic properties with improved coercive force. Material.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a relationship between a distance from an interface and crystal magnetic anisotropy, in which a white circle indicates a uniaxial anisotropy constant K _{1 of} an example, and a black circle indicates a uniaxial anisotropy constant K of a comparative example. Indicates ₁ .

FIG. 2A is a model diagram showing a state where a main phase and a grain boundary phase match, and FIG. 2B is a model diagram showing a state where an interface between a main phase and a grain boundary phase does not match.

FIG. 3 is an electron micrograph of a permanent magnet in which a main phase and a grain boundary phase are matched.

FIG. 4 is a photograph of a crystal structure showing a selected area electron beam diffraction image of the main phase shown in FIG. 3;

5 is a photograph of a crystal structure showing a selected area electron beam diffraction image on the grain boundary phase side shown in FIG. 3;

Claims (6)

[Claims] 1. A magnetic phase mainly composed of an R ₂ TM ₁₄ B intermetallic compound having a tetragonal crystal structure (R: a rare earth element containing Y, TM: a transition metal), and a grain containing an R-TM-O compound. And a crystal structure of the grain boundary phase in the vicinity of the interface between the magnetic phase and the grain boundary phase is a face-centered cubic structure, and the magnetic phase and the grain boundary phase are matched. An R-TM-B permanent magnet characterized by the following. 2. The R-TM-O compound according to claim 1, wherein the R-TM-O compound having a face-centered cubic crystal structure is precipitated near the interface of the grain boundary phase. B type permanent magnet. 3. The R ₂ TM ₁₄ B intermetallic compound,
The total of Nd and Pr in R is 50 at% or more, TM is Fe or Co, and the content of Fe in TM is 50 at% or more. In the R-TM-O compound, the ratio of R to the total of R and TM is 90 at%. % Or more, and the ratio of O is 1 at% or more and 70 at% or less.
The R-TM-B-based permanent magnet as described. 4. The crystallographic orientation relationship in the vicinity of the interface between the magnetic phase and the grain boundary phase is as follows: The R-TM-B-based permanent magnet according to any one of claims 1 to 3, wherein the angle of deviation of the azimuthal relationship is within 5 °. 5. A magnetic phase having a tetragonal crystal structure, and a grain boundary phase in which a compound containing oxygen and having a face-centered cubic crystal structure is present in the vicinity of an interface with the magnetic phase, An R-TM-B-based permanent magnet, wherein a magnetic phase and the grain boundary phase are aligned with the interface interposed therebetween. 6. R (Rare earth element containing R: Y), TM (TM:
(Transition metal), an R ₂ TM ₁₄ B tetragonal crystal is precipitated from an alloy containing B and O, and an R-TM-O face-centered cubic phase is further precipitated around the R ₂ TM ₁₄ B tetragonal phase. Thereby aligning the R ₂ TM ₁₄ B tetragonal phase with the R-TM-O face-centered cubic phase, and increasing the crystal magnetic anisotropy of the R ₂ TM ₁₄ B tetragonal phase at least near the aligned interface. R-TM characterized by the following:
-A method for producing a B-based permanent magnet.