JP6569408B2 - Rare earth permanent magnet - Google Patents

Description

The present invention relates to a rare earth permanent magnet, and more particularly to a permanent magnet using high magnetic anisotropy containing Pr in a part and all of a rare earth element.

Rare earth magnets mainly composed of intermetallic compounds of rare earth elements and transition metal elements such as Fe and Co have high crystal magnetic anisotropy, so that they can be used as high-performance permanent magnets in consumer, industrial and transportation equipment. Widely used in In recent years, there has been an increasing demand for miniaturization of various electric devices, and in order to meet the demand, a high-performance permanent magnet having higher magnetic properties is required.

It is known that a rare earth permanent magnet (R is a rare earth element, T is Fe or Fe partially substituted by Co) having excellent magnetic properties, and the main phase is a tetragonal R ₂ T ₁₄ B compound. Since the invention in 1982 (Patent Document 1), it is a typical high-performance permanent magnet.

An R-T-B type permanent magnet in which the rare earth element R is made of Nd, Pr, Dy, Ho, and Tb has a large anisotropic magnetic field Ha and is preferable as a permanent magnet material. Among these, Nd—Fe—B permanent magnets in which the rare earth element R is Nd are widely used because they have a good balance of saturation magnetization Is, Curie temperature Tc, and anisotropic magnetic field Ha.

Patent Document 2 proposes a magnetic material having a high Fe concentration in the main phase and a high saturation magnetic flux density in a permanent magnet having an R—T compound having a TbCu _7- type crystal structure as a main phase.

Further, Patent Document 3 proposes a magnetic material having the highest Fe concentration in the main phase among the permanent magnets, the main phase being an RT compound having a ThMn ₁₂ type crystal structure. Non-Patent Document 1 discloses a high saturation magnetic flux density of 1.62 T in an Nd (Fe _0.93 Co _0.02 Mo _0.05 ) ₁₂ N _y thin film having a crystal structure of main phase particles of ThMn ₁₂ type, 693 kA / A high coercive force of m has been reported.

On the other hand, in order to use permanent magnets for a wider range of applications, such as drive motors for electric vehicles and hybrid vehicles, for which demand has been increasing recently, it is necessary to have sufficient magnetic properties even at high temperatures. In order to realize magnetic characteristics, it is necessary to have a high coercive force at room temperature. However, the present R—T—B system permanent magnets mainly made of Nd do not have a sufficient coercive force, and it is necessary to use rare and expensive heavy rare earths.

JP 59-46008 A JP-A-6-172936 JP-A-4-346202

Journal of Applied Physics, 75, 6009, 1994

The present invention has been made in view of these circumstances, and an object of the present invention is to provide a rare earth permanent magnet having a high coercive force as a rare earth permanent magnet.

In order to solve the above-described problems and achieve the object, the rare earth permanent magnet of the present invention has an abundance ratio when the number of trivalent Pr atoms in the main phase particles is P3 and the number of tetravalent Pr atoms is P4. P4 / (P3 + P4) is characterized by P4 / (P3 + P4) ≧ 0.1. Thereby, the effect | action of the improvement of the magnetic anisotropy derived from tetravalent Pr is acquired. As a result, a rare earth permanent magnet having a high coercive force can be obtained.

The rare earth permanent magnet of the present invention is an R-T-X compound in which the main phase particles have an Nd ₂ Fe ₁₄ B type crystal structure (space group P4 ₂ / mnm), and R is Y, La, in which Pr is essential. Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, a rare earth element, T is one or more transition metal elements essential to Fe, Fe, and Co , X is preferably B or an element obtained by substituting B and a part thereof with Be, C, or Si. As a result, the effect of improving the magnetic anisotropy derived from tetravalent Pr is obtained, and as a result, a rare earth permanent magnet having a high coercive force in which the main phase particles have an Nd ₂ Fe ₁₄ B type crystal structure can be obtained. .

The rare earth permanent magnet of the present invention is an RT compound in which the main phase particles have a TbCu ₇ type crystal structure (space group P6 / mmm), and R is Y, La, Ce, Nd, Sm, in which Pr is essential. Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu are preferably one or more rare earth elements, and T is preferably one or more transition metal elements essentially comprising Fe or Fe and Co. Thereby, the effect | action of the improvement of the magnetic anisotropy derived from tetravalent Pr is acquired. As a result, it is possible to obtain a rare earth permanent magnet whose main phase particles have a TbCu ₇ type crystal structure and a high coercive force.

An RT compound having the TbCu _7- type crystal structure (space group P6 / mmm), wherein the main phase particles further include an intrusion element Z (Z is an element composed of one or more of N, H, Be, and C). It is preferable to contain. The intrusion element Z provides an effect of improving magnetic anisotropy. As a result, the coercive force can be improved.

It is an RT compound having the TbCu _7- type crystal structure (space group P6 / mmm), and the main phase particles preferably have R partially substituted with Zr. The effect of improving magnetic anisotropy is obtained by Zr substitution. As a result, the coercive force can be improved.

The rare earth permanent magnet of the present invention is an RT compound in which the main phase particles have a ThMn ₁₂ type crystal structure (space group I4 / mmm), and R is Y, La, Ce, Nd, Sm, in which Pr is essential. Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and a rare earth element composed of one or more of Lu, T is one or more transition metal elements essential for Fe or Fe and Co, or a part thereof An element substituted with M (one or more of Ti, V, Cr, Mo, W, Zr, Hf, Nb, Ta, Al, Si, Cu, Zn, Ga, and Ge) is preferable. Thereby, the effect | action of the improvement of the magnetic anisotropy derived from tetravalent Pr is acquired. As a result, it is possible to obtain a rare earth permanent magnet whose main phase particles have a ThMn ₁₂ crystal structure and a high coercive force.

An RT compound having the ThMn ₁₂ type crystal structure (space group I4 / mmm), wherein the main phase particles are further intrusive elements Z (Z is an element composed of one or more of N, H, Be, and C). It is preferable to contain. The intrusion element Z provides an effect of improving magnetic anisotropy. As a result, the coercive force can be improved.

In the rare earth permanent magnet of the present invention, the ratio of the number of trivalent Pr atoms and the number of tetravalent Pr atoms in the main phase particles is preferably calculated by electron energy loss spectroscopy (EELS: Electron Energy-Loss Spectroscopy). .

According to the present invention, by adjusting the interatomic distance between the nearest element and Pr by the combination of elements, Pr becomes a tetravalent state, and has a high coercive force utilizing the high magnetic anisotropy of tetravalent Pr. A permanent magnet can be realized.

Hereinafter, preferred embodiments of the present invention will be described in detail. The embodiments do not limit the invention but are exemplifications, and all features and combinations described in the embodiments are not necessarily essential to the invention.

In the present embodiment, the state in which two electrons enter the 4f orbit of the Pr element is a trivalent Pr state because it has an electronic structure similar to that of the trivalent Pr in the ionic crystal, while the Pr element has the 4f orbital. A state in which one electron is contained is defined as a tetravalent Pr state because it has an electronic structure similar to that of tetravalent Pr in an ionic crystal.

In the rare earth permanent magnet, the inventors have stabilized the state in which one electron has entered the 4f orbit of Pr by adjusting the interatomic distance between Pr in the crystal and surrounding elements, and this is caused by the tetravalent Pr state. It has been found that a permanent magnet having high magnetic anisotropy can be obtained.

In the rare earth permanent magnet, the electrons in the Pr element behave as conduction electrons, but by adjusting the distance from the Pr peripheral element, one 4f electron enters and a flat shape that contracts the most in the direction of the symmetry axis in the 4f electron system. The present inventors consider that a state in which the 4f orbit is stabilized can be realized.

High magnetic anisotropy can be expected due to the presence of one electron in the Pr4f orbit, that is, the expression of a tetravalent Pr state, which is a flat electron cloud that is most contracted in the direction of the symmetry axis in the rare earth permanent magnet.

That is, a rare earth permanent magnet having high magnetic anisotropy can be realized by adjusting the interatomic distance between Pr and peripheral elements and stabilizing one electron in the Pr4f orbit.

Furthermore, the present inventors have found that a permanent magnet exhibiting a high coercive force can be obtained by realizing a tetravalent Pr in the range of P4 / (P3 + P4) ≧ 0.1. When P4 / (P3 + P4) is less than 0.1, no improvement in coercive force was observed even at room temperature. The inventors consider that this is because the amount of Pr in the tetravalent state is not sufficient, and the effect of high uniaxial magnetic anisotropy of the tetravalent Pr is not sufficiently obtained.

The main phase of the rare earth permanent magnet in this embodiment is Pr—Fe, Pr—Fe—N, Pr—Fe—B, Pr—Co, Pr—Co—N, or Pr—Co—B. Although what is contained is mentioned, it is not restrict | limited at all to these, A part of Pr may be substituted with another rare earth element, and a rare earth permanent magnet may be formed by using 2 or more types together. . Further, the crystal structure of the main phase of the rare earth permanent magnet in the present embodiment is Nd ₂ Fe ₁₄ B type crystal structure (space group P4 ₂ / mnm), TbCu ₇ type crystal structure (space group P6 / mmm), ThMn ₁₂ type. Crystal structure (space group I4 / mmm), CaCu ₅ type crystal structure (space group P6 / mmm), Zn ₁₇ Th ₂ type crystal structure (space group R-3m), Nd ₅ Fe ₁₇ type crystal structure (space group P6 ₃ However, the present invention is not limited to these, and a rare earth permanent magnet may be formed by using two or more kinds in combination.

An R-T-X compound in which the main phase particles have an Nd ₂ Fe ₁₄ B type crystal structure (space group P4 ₂ / mnm), which is one of the embodiments, will be specifically described. In the present embodiment, an R-T-X compound having an Nd ₂ Fe ₁₄ B-type crystal structure (space group P4 ₂ / mnm) is hereinafter referred to as an Nd ₂ Fe ₁₄ B-type R-T-X compound.

R of the Nd ₂ Fe ₁₄ B type R-T-X compound is 1 of Y, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, which requires Pr. It is a rare earth element composed of more than seeds. Pr can be expected to have high magnetic anisotropy due to the presence of one electron in the 4f orbit, that is, the expression of a tetravalent state. That is, high magnetic anisotropy can be expected by increasing the amount of Pr, and the coercivity of the permanent magnet can be increased. The ratio of Pr in the total rare earth elements is preferably at least 50 at% or more, more preferably 75 at% or more.

The amount of R in the Nd ₂ Fe ₁₄ B type RTX compound is preferably 6 at% or more and 35 at% or less. When the amount of R is less than 6 at%, the main phase is not sufficiently generated, and α-Fe having soft magnetism is precipitated, and the coercive force is remarkably lowered. On the other hand, when R exceeds 35 at%, the volume ratio of the main phase decreases, and the saturation magnetic flux density decreases.

T in the Nd ₂ Fe ₁₄ B-type R—T—X compound is one or more transition metal elements in which Fe or Fe and Co are essential. The amount of T consists of the remainder of R and X. The saturation magnetic flux density can be improved by adding an appropriate amount of Co. Further, the Curie temperature can be improved by increasing the amount of Co, and the decrease in coercive force with respect to the temperature rise can be suppressed to a small level. Further, the corrosion resistance of the rare earth permanent magnet can be improved by increasing the amount of Co. An excessive increase in the amount of Co causes a decrease in saturation magnetic flux density but tends to increase the coercive force, and it is possible to realize a rare earth permanent magnet having high magnetic anisotropy over the entire Co amount.

X in the Nd ₂ Fe ₁₄ B type RTX compound is an element obtained by substituting B or B and a part thereof with Be, C or Si. The amount of X is desirably 3 at% or more and 15 at% or less. When X is B, the interatomic distance between Pr and the nearest element takes an optimum value, and the expression of a tetravalent Pr state can be expected. Therefore, it is desirable that the ratio of B in X is larger.

Further, an RT compound in which the main phase particles have a TbCu ₇ type crystal structure (space group P6 / mmm), which is one of the present embodiments, will be specifically described. In the present embodiment, an RT compound having a TbCu ₇ type crystal structure (space group P6 / mmm) is hereinafter referred to as a TbCu ₇ type RT compound.

R in the TbCu ₇ type RT compound is a rare earth composed of one or more of Y, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, which require Pr. Elemental. Pr can be expected to have high magnetic anisotropy due to the presence of one electron in the 4f orbit, that is, the expression of a tetravalent state. That is, high magnetic anisotropy can be expected by increasing the amount of Pr, and the coercivity of the permanent magnet can be increased. The ratio of Pr in the total rare earth elements is preferably at least 50 at% or more, more preferably 75 at% or more.

The amount of R in the TbCu ₇ type RT compound is preferably 6.3 at% or more and 37.5 at% or less. When the amount of R is less than 6.3 at%, the main phase is not sufficiently generated, and α-Fe having soft magnetism is precipitated, and the coercive force is remarkably lowered. On the other hand, when R exceeds 37.5 at%, the volume ratio of the main phase decreases, and the saturation magnetic flux density decreases.

T in the TbCu ₇ type RT compound is one or more transition metal elements that essentially require Fe or Fe and Co. Further, the corrosion resistance of the rare earth permanent magnet can be improved by increasing the amount of Co.

The TbCu ₇ type RT compound may contain an interstitial element Z, where Z is an element composed of one or more of N, H, Be, and C. The amount of Z is preferably 0 at% or more and 10 at% or less. The coercive force can be improved by the penetration of Z into the crystal lattice. This is presumably because the magnetocrystalline anisotropy is improved by the intruding elements.

A part of R of the TbCu ₇ type RT compound may be substituted with Zr. Zr substitution is preferably greater than 0 at% and less than 50 at% relative to the total amount of R. By setting it as this range, a saturation magnetic flux density can be improved. This is presumably because the substitution of Zr promotes the localization of Fe 3d electrons.

In addition, an RT compound in which the main phase particles have a ThMn ₁₂ type crystal structure (space group I4 / mmm), which is one of the embodiments, will be specifically described. In the present embodiment, an RT compound having a ThMn ₁₂ type crystal structure (space group I4 / mmm) is hereinafter referred to as a ThMn ₁₂ type RT compound.

R of the ThMn ₁₂ type RT compound is a rare earth composed of one or more of Y, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, which require Pr. Elemental. Pr can be expected to have high magnetic anisotropy due to the presence of one electron in the 4f orbit, that is, the expression of a tetravalent state. That is, high magnetic anisotropy can be expected by increasing the amount of Pr, and the coercivity of the permanent magnet can be increased. The ratio of Pr in the total rare earth elements is preferably at least 50 at% or more, more preferably 75 at% or more.

The amount of R in the ThMn ₁₂ type RT compound is preferably 4.2 at% or more and 25.0 at% or less. When the amount of R is less than 4.2 at%, the main phase is not sufficiently generated, α-Fe or the like having soft magnetism is precipitated, and the coercive force is remarkably lowered. On the other hand, when R exceeds 25.0 at%, the volume ratio of the main phase decreases and the saturation magnetic flux density decreases. By setting it as this range, a saturation magnetic flux density can be improved.

T of the ThMn ₁₂ type RT compound is one or more transition metal elements essential for Fe or Fe and Co, or a part thereof is M (Ti, V, Cr, Mo, W, Zr, Hf, Nb , Ta, Al, Si, Cu, Zn, Ga, and Ge). The saturation magnetic flux density can be improved by adding an appropriate amount of Co. Further, the corrosion resistance of the rare earth permanent magnet can be improved by increasing the amount of Co. The M amount is preferably 0.4 at% or more and 25 at% or less with respect to the total T amount. When M is less than 0.4 at% with respect to the total amount of T, soft magnetic R ₂ Fe ₁₇ and α-Fe precipitate and the volume ratio of the main phase decreases, and when it exceeds 25 at%, the saturation magnetic flux density significantly decreases. .

The ThMn ₁₂ type RT compound may contain an intruding element Z, and Z is an element composed of one or more of N, H, Be, and C. The amount of Z is preferably 0 at% or more and 14 at% or less. The coercive force can be improved by the penetration of Z into the crystal lattice. This is presumably because the magnetocrystalline anisotropy is improved by the intruding elements.

All rare earth permanent magnets according to this embodiment allow the inclusion of other elements. For example, elements such as Bi, Sn, and Ag can be appropriately contained. Further, the rare earth element may contain impurities derived from the raw material.

Hereinafter, preferred examples of the production method of the present invention will be described.
An example of a method for manufacturing a sintered magnet will be described. First, a raw material alloy capable of obtaining a rare earth permanent magnet having a desired composition is prepared. The raw material alloy can be produced by a strip casting method or other known melting methods in a vacuum or an inert gas, preferably in an Ar atmosphere. In the strip casting method, a molten metal obtained by melting a raw metal in a non-oxidizing atmosphere such as an Ar gas atmosphere is ejected onto the surface of a rotating roll. The melt rapidly cooled by the roll is rapidly solidified in the form of a thin plate or flakes (scales). This rapidly solidified alloy has a homogeneous structure with a crystal grain size of 1 μm to 50 μm. The raw material alloy can be obtained not only by the strip casting method but also by a melting method such as high frequency induction melting. In order to prevent segregation after dissolution, for example, it can be solidified by pouring into a water-cooled copper plate. An alloy obtained by the reduction diffusion method can also be used as a raw material alloy.

As a raw material alloy, it is based on the application of a so-called single alloy method in which a permanent magnet is made from one type of alloy, but the main phase alloy (low R alloy) that is the main phase particles and R from the low R alloy. A so-called mixing method using an alloy (a high R alloy) that contains a large amount and contributes effectively to the formation of grain boundaries can also be applied.

The raw material alloy is subjected to a grinding process. In the case of the mixing method, the low R alloy and the high R alloy are pulverized separately or together. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, the raw material alloy is coarsely pulverized until the particle size becomes about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Prior to coarse pulverization, it is effective to perform pulverization by allowing hydrogen to be stored in the raw material alloy and then releasing it. The hydrogen releasing treatment is performed for the purpose of reducing hydrogen as an impurity as a sintered magnet. The heating and holding temperature for storing hydrogen is 200 ° C. or higher, preferably 350 ° C. or higher. The holding time varies depending on the relationship with the holding temperature, the thickness of the raw material alloy, etc., but is at least 30 minutes or longer, preferably 1 hour or longer. The hydrogen release treatment is performed in a vacuum or Ar gas flow. The hydrogen storage process and the hydrogen release process are not essential processes. This hydrogen pulverization can be regarded as coarse pulverization, and mechanical coarse pulverization can be omitted.

After the coarse pulverization process, the process proceeds to the fine pulverization process. A jet mill is mainly used for fine pulverization, and a coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 2.5 μm to 6 μm, preferably 3 μm to 5 μm. The jet mill releases a high-pressure inert gas from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, collides with the coarsely pulverized powder, and collides with the target or the container wall. It is a method of generating a collision and crushing.

Wet grinding may be used for fine grinding. A ball mill, a wet attritor, or the like is used for the wet pulverization, and the coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 1.5 μm to 5 μm, preferably 2 μm to 4.5 μm. In the wet pulverization, by selecting an appropriate dispersion medium, the pulverization proceeds without the magnet powder coming into contact with oxygen, so that a fine powder having a low oxygen concentration can be obtained.

Fatty acids or fatty acid derivatives and hydrocarbons for the purpose of improving lubrication and orientation during molding, such as zinc stearate, calcium stearate, aluminum stearate, stearamide, oleamide, stearic acid or oleic acid Further, ethylene bisisostearic acid amide, hydrocarbon paraffin, naphthalene and the like can be added in an amount of about 0.01 wt% to 0.3 wt% during pulverization.

The finely pulverized powder is subjected to molding in a magnetic field. The molding pressure in the magnetic field molding may be in the range of 0.3 ton / cm ^{2 to 3} ton / cm ² (30 MPa to 300 MPa). The molding pressure may be constant from the beginning to the end of molding, may be gradually increased or gradually decreased, or may vary irregularly. The lower the molding pressure is, the better the orientation is. However, if the molding pressure is too low, the strength of the molded body is insufficient and handling problems occur. Therefore, the molding pressure is selected from the above range in consideration of this point. The final relative density of the molded body obtained by molding in a magnetic field is usually 40% to 60%.

The applied magnetic field may be about 960 kA / m to 1600 kA / m. The applied magnetic field is not limited to a static magnetic field, and may be a pulsed magnetic field. A static magnetic field and a pulsed magnetic field can also be used in combination.

The formed body is subjected to a sintering process. Sintering is performed in a vacuum or an inert gas atmosphere. The sintering holding temperature and sintering holding time need to be adjusted according to various conditions such as crystal structure, composition, pulverization method, difference in average particle size and particle size distribution, etc., but about 700 ° C. to 1200 ° C. for 20 hours or more. The temperature is lowered after an appropriate holding time. In the above-described sintering step, pressurization with a pressure of 2.0 GPa or more in a direction perpendicular to the easy axis is effective in increasing the difference in shrinkage between the orientation direction and the perpendicular direction. In this way, by changing the distance between Pr contained in the composition and adjacent atoms, the tetravalent Pr state is structurally most stable, and the high magnetic anisotropy of Pr, which is a feature of the present invention, is obtained. The inventors consider that it is expressed.

After sintering, the obtained sintered body can be subjected to an aging treatment.

Next, an example of a method for manufacturing a bonded magnet will be described. First, the sintered body obtained by the method for producing a sintered magnet is pulverized. The method described in [0048], [0049], and [0050] can be applied to the pulverization step.

When the intruding element Z is N or H, nitriding treatment or hydrogenation treatment can be performed at this stage. The sintered body powder is heat-treated in a nitrogen gas or a hydrogen gas at 0.001 to 10 atmospheres at a temperature of 200 to 1000 ° C. for 0.1 to 100 hours. The atmosphere for the heat treatment may be a mixture of nitrogen gas and hydrogen gas, or a nitrogen compound gas such as ammonia.

Thereafter, the resin binder containing the resin and the main sintered body powder are kneaded by a pressure kneader such as a pressure kneader, for example, and a bond magnet compound (composition) containing the resin binder and the main sintered body powder is obtained. Prepare. Resins include thermosetting resins such as epoxy resins and phenol resins, styrene, olefin, urethane, polyester and polyamide elastomers, ionomers, ethylene propylene copolymer (EPM), ethylene-ethyl acrylate copolymer There are thermoplastic resins such as coalescence. Among them, the resin used for compression molding is preferably a thermosetting resin, and more preferably an epoxy resin or a phenol resin. The resin used for injection molding is preferably a thermoplastic resin. Moreover, you may add a coupling agent and another additive to the compound for bonded magnets as needed.

Moreover, it is preferable that the content ratio of the main sintered body powder and the resin in the bonded magnet includes, for example, 0.5 wt% or more and 20 wt% or less of the resin with respect to 100 wt% of the main sintered body powder. If the resin content is less than 0.5 wt% with respect to 100 wt% of the sintered body powder, shape retention tends to be impaired, and if the resin content exceeds 20 wt%, sufficiently excellent magnetic properties are obtained. It tends to be difficult to obtain.

After preparing the above-described bonded magnet compound, the bonded magnet compound can be obtained by injection molding the bonded magnet compound and including the sintered body powder and the resin. When producing a bonded magnet by injection molding, the bonded magnet compound is heated to the melting temperature of the binder (thermoplastic resin) as necessary to obtain a fluid state, and then the bonded magnet compound has a predetermined shape. Injection into the mold and molding. Then, it cools and the molded article (bond magnet) which has a predetermined shape is taken out from a metal mold | die. In this way, a bonded magnet is obtained. The manufacturing method of the bonded magnet is not limited to the above-described injection molding method. For example, a bonded magnet containing the sintered body powder and the resin may be obtained by compression molding a bonded magnet compound. Good. In the case of producing a bonded magnet by compression molding, after preparing the above-mentioned bonded magnet compound, the bonded magnet compound is filled into a mold having a predetermined shape, and pressure is applied to form the predetermined shape from the mold. Take out the molded product (bonded magnet). When forming and taking out a bonded magnet compound with a mold, a compression molding machine such as a mechanical press or a hydraulic press is used. Then, a bonded magnet is obtained by making it harden | cure by putting in furnaces, such as a heating furnace and a vacuum drying furnace, and applying heat.

The shape of the bonded magnet obtained by molding is not particularly limited, and depending on the shape of the mold to be used, for example, the plate shape, the columnar shape, the cross-sectional shape may be changed according to the shape of the bonded magnet, such as a ring shape. Can do. Further, the obtained bonded magnet may be plated or painted on the surface in order to prevent deterioration of the oxide layer, the resin layer, and the like.

When the bonded magnet compound is molded into a desired predetermined shape, a molded body obtained by molding by applying a magnetic field may be oriented in a certain direction. Thereby, since a bonded magnet orientates in a specific direction, an anisotropic bonded magnet with stronger magnetism is obtained.

As mentioned above, although the form regarding the manufacturing method for implementing this invention suitably was demonstrated, next, the method of analyzing the composition in a main phase particle | grain and Pr valence about the rare earth permanent magnet of this invention is demonstrated.

The composition in the main phase particles can be determined by energy dispersive X-ray spectroscopy (EDS: Energy Dispersive Spectroscopy). After confirming that the main generated phase is assigned to the target crystal structure by X-ray diffraction (XRD), the sintered magnet or bonded magnet is then focused on the focused magnet. It is processed into a thin piece with a thickness of 100 nm using a focused ion beam (FIB) apparatus, and the vicinity of the center of the main phase particles is analyzed using an EDS apparatus provided in a scanning transmission electron microscope (STEM). The composition of the main phase particles can be quantified by using the thin film correction function. If there is an element that is difficult to detect with an EDS apparatus, it can be supplemented by using an infrared absorption method or mass spectrometry.

The abundance ratio P4 / (P3 + P4) when the number of Pr atoms in the main phase particles is PT, the number of trivalent Pr atoms is P3, and the number of tetravalent Pr atoms is P4 is the electron energy loss spectroscopy provided in the STEM ( It can be determined by using an EELS (Electron Energy-Loss Spectroscopy) apparatus.

An EELS spectrum is obtained by adjusting to a position where main phase particles can be observed with STEM, and irradiating the observation position with an electron beam at an acceleration voltage of 300 kV. The standard samples PrO ₂ and PrPO ₄ are ionic crystals, and the valence of each Pr is tetravalent or trivalent. By using the EELS spectrum of these standard samples, the abundance ratio P4 / (P3 + P4) in the main phase particles can be calculated (see Applied Physics Letters, 68, 3817, 1996).

The ratio of the M4 and M5 peaks of the EELS spectra of the standard samples PrO ₂ and PrPO ₄ is M4 (4 +) / M5 (4+), M4 (3 +) / M5 (3+), and the M4 and M5 peaks of the main phase particle spectrum It is possible to calculate P4 / (P3 + P4) by defining the ratio as M4 / M5 and comparing using [Formula 1] and [Formula 2].

[Formula 1]
M4 / M5 = P4 / (P3 + P4) × M4 (4 +) / M5 (4 +) + P3 / (P3 + P4) × M4 (3 +) / M5 (3+)

[Formula 2]
P3 + P4 = PT

Examples of R-T-X compounds in which main phase particles have an Nd ₂ Fe ₁₄ B type crystal structure (space group P4 ₂ / mnm) will be described. Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1 to Example 18, Comparative Example 1 to Comparative Example 15]
A predetermined amount of Pr metal, R metal, Fe metal and X are weighed so that the composition of the main phase particles (Pr _1-a R _a ) ₂ Fe ₁₄ X has the composition shown in Table 1, and a thin plate is formed by strip casting. Pr-R-Fe-X alloy was prepared. This alloy was heat-treated while stirring in a hydrogen stream, and then coarse powder was added. Then, oleic acid amide was added as a lubricant, and fine powder (average particle size 3 μm) in a non-oxidizing atmosphere using a jet mill. I made it. The obtained fine powder is filled into a mold (opening size: 20 mm × 18 mm), and uniaxial pressure molding is performed at a pressure of 2.0 ton / cm ² while applying a magnetic field of 1600 kA / m in a direction perpendicular to the pressing direction. did. The obtained molded body was heated up to the optimum sintering temperature and held at a sintering temperature of 700 ° C. to 1200 ° C. under a pressure of 1.0 GPa to 10.0 GPa in a direction perpendicular to the easy axis for 15 hours to 30 hours. After cooling to room temperature, an aging treatment was performed at 800 ° C. for 1 hour and 600 ° C. for 1 hour to obtain a sintered magnet. Table 1 shows the manufacturing conditions of each example and comparative example, and the magnetic properties of the sintered magnet measured with a BH tracer.

The obtained sintered magnet is cut perpendicularly to the direction of magnetic field application during molding, which is an easy magnetization axis, and the main generated phase is attributed to the Nd ₂ Fe ₁₄ B type crystal structure (space group P4 ₂ / mnm) by XRD. It was confirmed. Next, after processing into a 100 nm-thick flake with an FIB apparatus, analysis was performed near the center of the main phase particles with an EDS apparatus provided in the STEM, and the composition of the main phase particles was quantified using a thin film correction function. . In addition, since the EDS apparatus has low sensitivity to light elements, it is difficult to quantify B. Therefore, based on the fact that the main generation phase, which has been confirmed in advance by XRD, is the Nd ₂ Fe ₁₄ B type crystal structure (space group P4 ₂ / mnm), the composition ratio of the main phase particles The composition was determined. Subsequently, it adjusted to the position which can observe a main phase particle | grain with STEM, and obtained the EELS spectrum. Table 1 shows the composition of each main phase particle and P4 / (P3 + P4) calculated from the EELS spectrum.

In addition, for each main phase particle composition, the predicted value of the coercive force HcJ when Pr is in the trivalent state and the rate of increase of the experimental value from the predicted value were calculated. For the calculation, a sintered magnet was produced under the following conditions. The composition of the main phase particles is Pr ₂ Fe ₁₄ B, Y ₂ Fe ₁₄ B, Gd ₂ Fe ₁₄ B, Ce ₂ Fe ₁₄ B, Nd ₂ Fe ₁₄ B, Dy ₂ Fe ₁₄ B, and the sintering pressure is set In addition, the other production conditions were the same as in Example 1. As a result of evaluating the valence of Pr for the produced Pr ₂ Fe ₁₄ B sintered magnet in the same manner as in [0065], P4 / (P3 + P4) was less than 0.1, that is, the trivalent state was mainly used.

Using the coercive force HcJ measurement results (Comparative Examples 1 to 6) of these sintered magnets with a BH tracer, predicted values of coercive force HcJ corresponding to the main phase particle compositions of Examples 12 to 18 and Comparative Examples 14 and 15 Was calculated. In the calculation, [Formula 3] was used assuming that the main phase particle composition and the coercive force HcJ correspond linearly. Here, the main phase particle composition is (Pr _1-a R _a ) ₂ Fe ₁₄ B, Pr ₂ Fe ₁₄ B has a coercive force HcJ of HcJ (Pr), and R ₂ Fe ₁₄ B has a coercive force HcJ of HcJ (R). It is defined as The ratio of the experimental value to the calculation result is shown in Table 1 as the rate of increase from HcJ (composition expected value) when Pr in the trivalent state is main.

[Formula 3]
HcJ (predicted composition value) = (1-a) × HcJ (Pr) + a × HcJ (R)

[Examples 1 to 3, Comparative Example 7]
To Pr ₂ Fe ₁₄ B, is varied only sintering temperature to 800 ° C. to 1200 ° C.. When the sintering temperature is 850 ° C. to 1200 ° C. (Examples 1 to 3), P4 / (P3 + P4) is high and the coercive force HcJ is also high, but when the sintering temperature is 800 ° C. (Comparative Example 7), P4 / (P3 + P4) was low, and the coercive force HcJ was also reduced. It was found that the shrinkage changes depending on the sintering temperature and the tetravalent Pr state is stabilized, so that a high coercive force appears in the main phase particles.

[Examples 1, 4, 5 and Comparative Example 8]
For Pr ₂ Fe ₁₄ B, only the sintering time was changed from 15 h to 30 h. When the sintering time is 20 hours or more (Examples 1, 4, and 5) (P4 / (P3 + P4)), the coercive force HcJ has a high value. As the sintering time becomes longer, P4 / (P3 + P4), the coercive force HcJ. Both increased. On the other hand, when the sintering time was 15 h (Comparative Example 8), both P4 / (P3 + P4) and coercive force HcJ were lower than when the sintering time was 20 h or longer. As a result, it was found that the difference in the shrinkage ratio was remarkable due to a sufficient sintering time, the stabilization of the tetravalent Pr state was promoted, and the main phase particles were increased in coercive force.

[Example 5, Comparative Example 9]
For Pr ₂ Fe ₁₄ B, the sintering time was changed to 750 ° C. and 1050 ° C. only for the sintering time at 30 h. When the sintering temperature was 750 ° C. (Comparative Example 9), both P4 / (P3 + P4) and coercive force HcJ were remarkably reduced as compared with the case of 1050 ° C. (Example 5). From this, it was found that the shrinkage ratio changed with sufficient sintering temperature and sintering time, the tetravalent Pr state was stabilized in the main phase particles, and the coercive force increased.

[Examples 1, 6-8, Comparative Example 10]
For Pr ₂ Fe ₁₄ B, only the sintering pressure was changed from 1.0 GPa to 10.0 GPa. When the sintering pressure is 2.0 GPa to 10.0 GPa (Examples 1 and 6 to 8), P4 / (P3 + P4) has a high coercive force HcJ, and as the sintering pressure increases, P4 / (P3 + P4). ) And the coercive force HcJ showed an increasing tendency. On the other hand, the case where the sintering pressure was 1.0 GPa (Comparative Example 10), the case where the sintering pressure was not applied, and the case where 3.0 GPa was applied isotropically were examined, but both P4 / (P3 + P4) were 0.00. It was less than 1, and a high coercive force was not obtained.

[Examples 1 and 9 to 11, Comparative Examples 11 to 13]
In the above examples and comparative examples, if the proportion of B in X is large, a coercive force HcJ equivalent to the case where the total amount of X is B was obtained, and P4 / (P3 + P4) also showed a large value. On the other hand, when the total amount of X is an element other than B (Be, C, Si), the coercive force HcJ is remarkably small, and P4 / (P3 + P4) is also a small value. From this, it was found that even if a part of B in X is an element other than B (Be, C, Si), a high coercive force due to tetravalent Pr can be obtained.

[Examples 1, 12 to 15, Comparative Examples 14 and 15]
In the above Examples and Comparative Examples, the smaller the R substitution amount a, that is, the larger the Pr amount, the higher P4 / (P3 + P4), which was larger than the value of the coercive force HcJ predicted from the rare earth element composition ratio. . However, in the case of a = 0.75 (Comparative Examples 14 and 15), the values of P4 / (P3 + P4) and coercive force HcJ were remarkably reduced. From this, it was found that the change in the Pr valence state contributes to the magnetic anisotropy in the main phase, and is responsible for the increase in coercive force of HcJ (composition expected value) or more.

[Examples 13, 15-18]
In the above Examples and Comparative Examples, a tetravalent Pr state was confirmed for any R element, which was a value larger than HcJ (composition expected value). Therefore, if Pr is contained, a permanent magnet having a high magnetic anisotropy can be obtained regardless of the element of R, and in particular, R = Y, Gd, and Ce have an increase rate from HcJ (composition expected value). I found it expensive.

Next, examples of the RT compound in which the main phase particles have a TbCu ₇ type crystal structure (space group P6 / mmm) will be described. Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 19 to 26, Comparative Examples 16 to 19]
A predetermined amount of Pr metal and Fe metal were weighed so that the composition of the main phase particles was PrFe _7, and a thin plate-like Pr—Fe alloy was produced by strip casting. This alloy was heat-treated while stirring in a hydrogen stream, and then coarse powder was added. Then, oleic acid amide was added as a lubricant, and fine powder (average particle size 3 μm) in a non-oxidizing atmosphere using a jet mill. I made it. The obtained fine powder is filled into a mold (opening size: 20 mm × 18 mm), and uniaxial pressure molding is performed at a pressure of 2.0 ton / cm ² while applying a magnetic field of 1600 kA / m in a direction perpendicular to the pressing direction. did. The obtained molded body was heated to the optimum sintering temperature and held at a sintering temperature of 700 ° C. to 950 ° C. for 15 hours to 30 hours under a pressure of 1.0 GPa to 10.0 GPa in a direction perpendicular to the easy axis. After cooling to room temperature, an aging treatment was performed at 600 ° C. for 1 hour to obtain a sintered magnet. Table 2 shows the production conditions of each example and comparative example.

The magnetic properties of the obtained sintered magnet were measured by applying a magnetic field of ± 5600 kA / m in the easy axis direction using a BH tracer. The magnetic flux density was confirmed to be within a range of ± 5% when +4800 kA / m was applied and when +5600 kA / mT was applied, and the value when +5600 kA / m was applied was defined as the saturation magnetic flux density. Table 2 shows the saturation magnetic flux density and the coercive force HcJ thus measured.

It was confirmed by XRD that the resulting sintered magnet was assigned to a TbCu ₇ type crystal structure (space group P6 / mmm) as a main product phase. Next, after processing the sintered magnet into a flake shape having a thickness of 100 nm with FIB, the vicinity of the center of the main phase particles was analyzed with EDS provided in the STEM to quantify the composition of the main phase particles. Subsequently, it adjusted to the position which can observe a main phase particle | grain with STEM, and obtained the EELS spectrum. Table 2 shows the composition of each main phase particle and P4 / (P3 + P4) calculated from the EELS spectrum.

[Examples 19 to 21, Comparative Example 16]
For PrFe ₇ , only the sintering temperature was changed from 700 ° C to 950 ° C. When the sintering temperature is 750 ° C. to 950 ° C. (Examples 19 to 21), P4 / (P3 + P4) is high and the coercive force HcJ is also high, but when the sintering temperature is 700 ° C. (Comparative Example 16), P4 / (P3 + P4) was low, and the coercive force HcJ was also reduced. It was found that the shrinkage changes depending on the sintering temperature and the tetravalent Pr state is stabilized, so that a high coercive force appears in the main phase particles.

[Examples 19, 22, 23, Comparative Example 17]
For PrFe ₇ , only the sintering time was changed from 15 h to 30 h. When the sintering time was 20 hours or more (Examples 19, 22, and 23), P4 / (P3 + P4) showed a high value for both coercive forces HcJ, but the behavior was saturated even if the sintering time was increased. Met. On the other hand, when the sintering time was 15 h (Comparative Example 17), both P4 / (P3 + P4) and coercive force HcJ were lower than when the sintering time was 20 h or longer. As a result, it was found that the difference in the shrinkage ratio was remarkable due to a sufficient sintering time, the stabilization of the tetravalent Pr state was promoted, and the main phase particles were increased in coercive force.

[Example 23, Comparative Example 18]
For PrFe ₇ , the sintering time was changed to 650 ° C. and 850 ° C. only for 30 hours with a sintering time. When the sintering temperature was 650 ° C. (Comparative Example 18), both P4 / (P3 + P4) and coercive force HcJ were significantly reduced as compared with the case of 850 ° C. (Example 23). From this, it was found that the shrinkage ratio changed with sufficient sintering temperature and sintering time, the tetravalent Pr state was stabilized in the main phase particles, and the coercive force increased.

[Examples 19, 24 to 26, Comparative Example 19]
For PrFe ₇ , only the sintering pressure was changed from 1.0 GPa to 10.0 GPa. When the sintering pressure is 2.0 GPa or more (Examples 19, 24 to 26), P4 / (P3 + P4) has a high coercive force HcJ, and as the sintering pressure increases, P4 / (P3 + P4) The magnetic force HcJ showed an increasing tendency. On the other hand, the case where the sintering pressure was 1.0 GPa (Comparative Example 19), the case where the sintering pressure was not applied, and the case where 3.0 GPa was applied isotropically were also examined, but P4 / (P3 + P4) was 0. It was less than 1, and a high coercive force was not obtained.

[Examples 27 to 37, Comparative Examples 20 to 28]
Pr metal, R metal, and Fe metal are weighed in predetermined amounts so that the composition of the main phase particles (Pr _{1 -b} R _b ) Fe ₇ has a composition excluding nitrogen element or hydrogen element in Table 3, and strip casting is used. A thin plate-like Pr—R—Fe alloy was prepared. A sintered body was obtained from this alloy in the same manner as in [0084]. However, the manufacturing conditions of the sintered compact corresponding to each Example and a comparative example are as showing in Table 3. Furthermore, after this sintered body was heat-treated with stirring in a hydrogen stream, it was made into a coarse powder, oleic acid amide was added as a lubricant, and a fine powder (averaged in a non-oxidizing atmosphere using a jet mill) The particle size was 3 μm). If necessary, this fine powder was heat-treated in nitrogen gas or hydrogen gas at 1 atm at a temperature of 400 ° C. for 10 hours. Thereafter, fine powder and paraffin were packed in a case, and a magnetic field was applied at 1600 kA / m in a state where the paraffin was melted to orient the fine powder to form a bonded magnet.

The obtained bonded magnet was evaluated for BH tracer, XRD, EDS, and EELS under the same conditions as the above-mentioned TbCu ₇ type RT compound sintered magnet. In the case where the main phase particle contains the intruding element Z, the composition of the main phase particle was calculated by performing the infrared absorption method and taking the result into consideration. The results are shown in Table 3.

In addition, for each main phase particle composition, the predicted value of the coercive force HcJ when Pr is in the trivalent state and the rate of increase of the experimental value from the predicted value were calculated. For calculation, a bonded magnet was produced under the following conditions. The composition of the main phase particles is PrFe ₇ N _0.6 , YFe ₇ N _0.6 , GdFe ₇ N _0.6 , CeFe ₇ N _0.6 , NdFe ₇ N _0.6 , DyFe ₇ N _0.6 The other production conditions were the same as in Example 28, with no sintering pressure applied. As a result of evaluating the valence of Pr for the produced PrFe ₇ N _0.6 bonded magnet in the same manner as in [0086], P4 / (P3 + P4) was less than 0.1, that is, the trivalent state was mainly used.

Using the coercive force HcJ measurement results (Comparative Examples 20 to 25) of these bonded magnets with a BH tracer, the predicted values of the coercive force HcJ corresponding to the main phase particle compositions of Examples 30 to 36 and Comparative Examples 26 and 27 were calculated. Calculated. In the calculation, [Formula 4] was used assuming that the main phase particle composition and the coercive force HcJ correspond linearly. Here, the main phase particle composition is (Pr _1-b R _b ) Fe ₇ N _0.6 , the coercive force HcJ of PrFe ₇ N _0.6 is HcJ (Pr), and the coercive force HcJ of RFe ₇ N _0.6 is It is defined as HcJ (R). The ratio of the experimental value to the calculation result is shown in Table 3 as the rate of increase from HcJ (predicted composition value) when Pr in the trivalent state is main.

[Formula 4]
HcJ (predicted composition value) = (1−b) × HcJ (Pr) + b × HcJ (R)

[Examples 19 and 27]
A sintered magnet and a bonded magnet were prepared for PrFe ₇ . In the case of the sintered magnet (Example 19) and the case of the bonded magnet (Example 27), P4 / (P3 + P4) was high and the coercive force HcJ was also high. From this, it was found that both the sintered magnet and the bonded magnet can obtain a high coercive force due to tetravalent Pr.

[Examples 27 to 29]
PrFe ₇ was prepared by nitriding before hydrogenation and by hydrogenation. In the case of the nitrided bond magnet (Example 28) and the hydrogenated bond magnet (Example 29), both P4 / (P3 + P4) were high and the coercive force HcJ was also high. From this, it was found that a high coercive force due to tetravalent Pr can be obtained even after introduction of the intruding element Z. Further, it was found that the coercive force was improved by introducing the intruding element Z as compared with the case without the intruding element (Example 27).

[Examples 28, 30 to 33, Comparative examples 26 and 27]
In the above Examples and Comparative Examples, the smaller the R substitution amount b, that is, the larger the Pr amount, the higher P4 / (P3 + P4), which was larger than the value of the coercive force HcJ predicted from the rare earth element composition ratio. . However, in the case of b = 0.75 (Comparative Examples 26 and 27), both the values of P4 / (P3 + P4) and coercive force HcJ were significantly reduced. From this, it was found that the change in the Pr valence state contributes to the magnetic anisotropy in the main phase, and is responsible for the increase in coercive force of HcJ (composition expected value) or more.

[Examples 31, 33 to 36]
In the above Examples and Comparative Examples, a tetravalent Pr state was confirmed for any R element, which was a value larger than HcJ (composition expected value). From this, a permanent magnet having high magnetic anisotropy resulting from tetravalent Pr can be obtained regardless of the element of R, and in particular, R = Ce has a high increase rate from HcJ (predicted composition value). I understood.

[Examples 35 and 37, Comparative Example 28]
A bonded magnet in which a part of the rare earth element was substituted with Zr for Example 35 was produced. The main phase particle composition was set to the composition described in Example 37, and the production conditions were the same as in Example 35. For comparison, a bonded magnet was also produced in the case where Pr was in a trivalent state without applying sintering pressure and the other production conditions were the same as in Example 37 (Comparative Example 28). Even when Zr substitution was performed (Example 37), it had a high P4 / (P3 + P4) ratio, and the coercive force HcJ was also higher than that in the case of the Pr trivalent state (Comparative Example 28). From this, it was found that a high coercive force due to tetravalent Pr can be obtained regardless of whether or not Zr is substituted. Further, it was found that both the coercive force HcJ and the saturation magnetic flux density were improved when Zr substitution was performed (Example 37) than when Zr substitution was not performed (Example 35).

Next, an example of the RT compound in which the main phase particles have a ThMn ₁₂ type crystal structure (space group I4 / mmm) will be described. Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 38 to 45, Comparative Examples 29 to 32]
A predetermined amount of Pr metal, Fe metal, and Ti metal were weighed so that the composition of the main phase particles was PrFe ₁₁ Ti, and a thin plate-like Pr—Fe—Ti alloy was prepared by strip casting. This alloy was heat-treated while stirring in a hydrogen stream, and then coarse powder was added. Then, oleic acid amide was added as a lubricant, and fine powder (average particle size 3 μm) in a non-oxidizing atmosphere using a jet mill. I made it. The obtained fine powder is filled into a mold (opening size: 20 mm × 18 mm), and uniaxial pressure molding is performed at a pressure of 2.0 ton / cm ² while applying a magnetic field of 1600 kA / m in a direction perpendicular to the pressing direction. did. The obtained molded body was heated to the optimum sintering temperature, and held at a sintering temperature of 750 ° C. to 1050 ° C. for 15 hours to 30 hours under a pressure of 1.0 GPa to 10.0 GPa in a direction perpendicular to the easy axis. After cooling to room temperature, an aging treatment was performed at 600 ° C. for 1 hour to obtain a sintered magnet. Table 4 shows the production conditions of each example and comparative example.

The magnetic properties of the obtained sintered magnet were measured by applying a magnetic field of ± 5600 kA / m in the easy axis direction using a BH tracer. The magnetic flux density was confirmed to be within a range of ± 5% when +4800 kA / m was applied and when +5600 kA / mT was applied, and the value when +5600 kA / m was applied was defined as the saturation magnetic flux density. Table 4 shows the saturation magnetic flux density and the coercive force HcJ thus measured.

It was confirmed by XRD that the resulting sintered magnet was attributed to a ThMn ₁₂ type crystal structure (space group I4 / mmm) by XRD. Next, after processing the sintered magnet into a flake shape having a thickness of 100 nm with FIB, the vicinity of the center of the main phase particles was analyzed with EDS provided in the STEM to quantify the composition of the main phase particles. Subsequently, it adjusted to the position which can observe a main phase particle | grain with STEM, and obtained the EELS spectrum. Table 4 shows the composition of each main phase particle and P4 / (P3 + P4) calculated from the EELS spectrum.

[Examples 38 to 40, Comparative Example 29]
Only the sintering temperature was changed from 800 ° C. to 1050 ° C. with respect to PrFe ₁₁ Ti. When the sintering temperature is 850 ° C. to 1050 ° C. (Examples 38 to 40), P4 / (P3 + P4) is high and the coercive force HcJ is also high, but when the sintering temperature is 800 ° C. (Comparative Example 29), P4 / (P3 + P4) was low, and the coercive force HcJ was also reduced. It was found that the shrinkage changes depending on the sintering temperature and the tetravalent Pr state is stabilized, so that a high coercive force appears in the main phase particles.

[Examples 38, 41, and 42, Comparative Example 30]
For the PrFe ₁₁ Ti, only the sintering time was changed from 15 h to 30 h. When the sintering time was 20 hours or more (Examples 38, 41, and 42), P4 / (P3 + P4) and coercive force HcJ both showed high values, but the behavior was saturated even when the sintering time was prolonged. Met. On the other hand, when the sintering time was 15 h (Comparative Example 30), both P4 / (P3 + P4) and coercive force HcJ were lower than when the sintering time was 20 h or longer. As a result, it was found that the difference in the shrinkage ratio was remarkable due to a sufficient sintering time, the stabilization of the tetravalent Pr state was promoted, and the main phase particles were increased in coercive force.

[Example 42, comparative example 31]
With respect to PrFe ₁₁ Ti, the sintering time was changed to 750 ° C. and 950 ° C. only for 30 hours. When the sintering temperature was 750 ° C. (Comparative Example 31), both P4 / (P3 + P4) and the coercive force HcJ were significantly reduced as compared with the case of 950 ° C. (Example 42). From this, it was found that the shrinkage ratio changed with sufficient sintering temperature and sintering time, the tetravalent Pr state was stabilized in the main phase particles, and the coercive force increased.

[Examples 38, 43 to 45, Comparative Example 32]
Only the sintering pressure was changed from 1.0 GPa to 10.0 GPa with respect to PrFe ₁₁ Ti. When the sintering pressure is 2.0 GPa or more (Examples 38 and 43 to 45), P4 / (P3 + P4) has a high coercive force HcJ, and as the sintering pressure increases, P4 / (P3 + P4) The magnetic force HcJ showed an increasing tendency. On the other hand, the case where the sintering pressure was 1.0 GPa (Comparative Example 32), the case where the sintering pressure was not applied, and the case where 3.0 GPa was applied isotropically were also examined, but P4 / (P3 + P4) was 0. It was less than 1, and a high coercive force was not obtained.

[Examples 46 to 55, Comparative Examples 33 to 40]
A predetermined amount of Pr metal, R metal, Fe metal, and Ti metal are weighed so that the composition of the main phase particles (Pr _1-c R _c ) Fe ₁₁ Ti has a composition excluding the nitrogen element or hydrogen element of Table 5. A thin plate-like Pr—R—Fe—Ti alloy was produced by strip casting. A sintered body was obtained from this alloy in the same manner as in [0102]. However, the manufacturing conditions of the sintered compact corresponding to each Example and a comparative example are as showing in Table 5. Furthermore, after this sintered body was heat-treated with stirring in a hydrogen stream, it was made into a coarse powder, oleic acid amide was added as a lubricant, and a fine powder (averaged in a non-oxidizing atmosphere using a jet mill) The particle size was 3 μm). If necessary, this fine powder was heat-treated in nitrogen gas or hydrogen gas at 1 atm at a temperature of 400 ° C. for 10 hours. Thereafter, fine powder and paraffin were packed in a case, and a magnetic field was applied at 1600 kA / m in a state where the paraffin was melted to orient the fine powder to form a bonded magnet.

The obtained bonded magnet was evaluated for BH tracer, XRD, EDS, and EELS under the same conditions as the ThMn ₁₂ type RT compound sintered magnet described above. In the case where the main phase particle contains the intruding element Z, the composition of the main phase particle was calculated by performing the infrared absorption method and taking the result into consideration. The results are shown in Table 5.

In addition, for each main phase particle composition, the predicted value of the coercive force HcJ when Pr is in the trivalent state and the rate of increase of the experimental value from the predicted value were calculated. For calculation, a bonded magnet was produced under the following conditions. The composition of the main phase particles is PrFe ₁₁ TiN _1.5 , YFe ₁₁ TiN _1.5 , GdFe ₁₁ TiN _1.5 , CeFe ₁₁ TiN _1.5 , NdFe ₁₁ TiN _1.5 , DyFe ₁₁ TiN _1.5. The other fabrication conditions were the same as in Example 47, with no sintering pressure applied. As a result of evaluating the valence of Pr for the produced PrFe ₁₁ TiN _1.5 bonded magnet in the same manner as in [0104], P4 / (P3 + P4) was less than 0.1, that is, the trivalent state was mainly.

Using the coercive force HcJ measurement results (comparative examples 33 to 38) of these bonded magnets with a BH tracer, the predicted values of coercive force HcJ corresponding to the main phase particle compositions of Examples 49 to 55 and Comparative Examples 39 and 40 were calculated. Calculated. In the calculation, [Formula 5] was used assuming that the main phase particle composition and the coercive force HcJ correspond linearly. Here, the main phase particle composition _{(Pr 1-c R c)} Fe 11 TiN 1.5, the coercivity HcJ _(Pr), the coercive force of the RFe 11 _{TiN 1.5} of PrFe 11 _{TiN 1.5} is HcJ ( R). The ratio of the experimental value to the calculation result is shown in Table 5 as the rate of increase from HcJ (predicted composition value) when Pr in the trivalent state is main.

[Formula 5]
HcJ (predicted composition value) = (1-c) × HcJ (Pr) + c × HcJ (R)

[Examples 38 and 46]
Sintered magnets and bonded magnets were prepared for PrFe ₁₁ Ti. In the case of the sintered magnet (Example 38), in the case of the bonded magnet (Example 46), P4 / (P3 + P4) was high and the coercive force HcJ was also high. From this, it was found that both the sintered magnet and the bonded magnet can obtain a high coercive force due to tetravalent Pr.

[Examples 46 to 48]
PrFe ₁₁ Ti was prepared by nitriding before hydrogenation and by hydrogenation. In the case of the nitrided bond magnet (Example 47) and in the case of the hydrogenated bond magnet (Example 48), both P4 / (P3 + P4) were high and the coercive force HcJ was also high. From this, it was found that a high coercive force due to tetravalent Pr can be obtained even after introducing the intruding elements N and H. Further, it was found that the coercive force was improved by introducing the intruding element as compared with the case without the intruding element (Example 46).

[Examples 47 and 49 to 52, Comparative Examples 39 and 40]
In the above Examples and Comparative Examples, the smaller the R substitution amount c, that is, the larger the Pr amount, the higher P4 / (P3 + P4), which was larger than the coercive force HcJ value expected from the rare earth element composition ratio. . However, in the case of c = 0.75 (Comparative Examples 39 and 40), the values of P4 / (P3 + P4) and coercive force HcJ were remarkably reduced. From this, it was found that the change in the Pr valence state contributes to the magnetic anisotropy in the main phase, and is responsible for the increase in coercive force of HcJ (composition expected value) or more.

[Examples 50, 52 to 55]
In the above Examples and Comparative Examples, a tetravalent Pr state was confirmed for any R element, which was a value larger than HcJ (composition expected value). From this, a permanent magnet having high magnetic anisotropy resulting from tetravalent Pr can be obtained regardless of the element of R, and in particular, R = Y, Gd, and Ce are increased from HcJ (expected composition value). It turns out that the rate is high.

Claims (7)

The existence ratio P4 / (P3 + P4) is P4 / (P3 + P4) ≧ 0.1 when the number of trivalent Pr atoms in the main phase particle is P3 and the number of tetravalent Pr atoms is P4. a rare earth permanent magnet, an R-T-X compound main phase particles have a _Nd 2 _{Fe 14} B crystal structure, R represents an essential component Pr Y, La, Ce, Nd , Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, a rare earth element, T is one or more transition metal elements essential to Fe or Fe and Co, X is B or B and its A rare earth permanent magnet which is an element partially substituted with Be, C or Si. The existence ratio P4 / (P3 + P4) is P4 / (P3 + P4) ≧ 0.1 when the number of trivalent Pr atoms in the main phase particle is P3 and the number of tetravalent Pr atoms is P4. a rare earth permanent magnet, an R-T compounds main phase particles have a the TbCu ₇ crystal structure, Y R is essentially containing Pr, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm, Yb and Lu, a rare earth element, wherein T is one or more transition metal elements essentially comprising Fe or Fe and Co. 3. The rare earth permanent magnet according to claim 2 , wherein the main phase particles further contain an intruding element Z (Z is an element composed of one or more of N, H, Be, and C). magnet. A rare earth permanent magnet according to claim 2 or claim 3, rare earth permanent magnets, characterized in that the main phase grains, by replacing part of the R in Zr. The existence ratio P4 / (P3 + P4) is P4 / (P3 + P4) ≧ 0.1 when the number of trivalent Pr atoms in the main phase particle is P3 and the number of tetravalent Pr atoms is P4. a rare earth permanent magnet, an R-T compounds main phase particles have a ThMn ₁₂ type crystal structure, Y R is essentially containing Pr, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm, Yb and Lu, a rare earth element, T is Fe or one or more transition metal elements essential to Fe and Co, or a part thereof is M (Ti, V, Cr , Mo, W, Zr, Hf, Nb, Ta, Al, Si, Cu, Zn, Ga, and Ge). 6. The rare earth permanent magnet according to claim 5 , wherein the main phase particles further contain an intruding element Z (Z is an element composed of one or more of N, H, Be, and C). magnet. The rare earth permanent magnet according to any one of claims 1 to 6, wherein the abundance ratio of trivalent Pr atoms and tetravalent Pr atoms in the main phase particles is calculated by electron energy loss spectroscopy. A rare earth permanent magnet.