JP7056696B2 - Rare earth magnets and their manufacturing methods - Google Patents

Description

The present disclosure relates to an R-Fe-B-based rare earth magnet (R is a rare earth element) and a method for producing the same. The present disclosure specifically relates to (Ce, La) -Fe-B-based rare earth magnets and methods for producing the same.

Among the R-Fe-B-based rare earth magnets, the Nd-Fe-B-based rare earth magnets are the most representative. Various attempts have been made to improve specific characteristics of Nd-Fe-B-based rare earth magnets.

In Nd-Fe-B-based rare earth magnets, it is common to impart anisotropy by strongly processing a sintered body of Nd-Fe-B-based rare earth magnet powder. Since the processing rate for strong processing is as high as 30 to 70%, the sintered body is required to have high hot workability. Patent Document 1 describes an attempt to improve the hot workability of a sintered body by substituting a part of Nd in an Nd-Fe-B-based rare earth sintered magnet with Ce, La, and / or Y or the like. Is disclosed.

Further, conventionally, a modifying material containing an Nd-Cu alloy, an Nd-Cu-Dy alloy, / or an Nd-Cu-Tb alloy or the like is impregnated into an Nd-Fe-B-based rare earth magnet to obtain a coercive force. Attempts have been made to improve it.

Japanese Unexamined Patent Publication No. 4-21744

The above-mentioned modifier is non-magnetic. In Nd-Fe-B-based rare earth magnets, the magnetic phases can be magnetically separated from each other by infiltrating the non-magnetic modifier between the magnetic phases. As a result, it is possible to suppress the propagation of magnetization reversal across a plurality of magnetic phases, so that the coercive force is improved.

However, in the Nd-Fe-B-based rare earth magnet, the content of the non-magnetic material increases as the content of the modifier increases. Therefore, when a modifier is interposed between the magnetic phases of Nd-Fe-B-based rare earth magnets, the magnetization is generally lowered.

From these facts, the present inventors have found that in rare earth magnets, when the coercive force is improved by the penetration of the modifier, it is required to suppress the decrease in magnetization.

The present disclosure has been made to solve the above problems. It is an object of the present disclosure to provide a rare earth magnet and a method for producing the same, which can suppress a decrease in magnetization even if the coercive force is improved by permeation of a modifier.

The present inventors have made extensive studies in order to achieve the above object, and completed the rare earth magnet of the present disclosure and the method for producing the same. The summary is as follows.
<1> With the Prime Minister
The grain boundary phase existing around the main phase and
An intermediate phase sandwiched between the main phase and the grain boundary phase,
Equipped with
The overall composition is the formula ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r · (R ² _1-z M ² ). _z ) _s (However, R ¹ and R ² are rare earth elements other than Ce and La, T is one or more selected from Fe, Ni, and Co, and M ¹ is Ti, Ga, Zn. , Si, Al, Nb, Zr, Mn, V, W, Ta, Ge, Cu, Cr, Hf, Mo, P, C, Mg, Hg, Ag, and one or more selected from Au, and unavoidable impurities. M ² is an alloying element and an unavoidable impurity that lowers the melting point of R ²¹ _-z M ² _z below the melting point of R ² by alloying with R ² .
p, q, r, and s, and x, y, and z,
12.0 ≤ p ≤ 20.0,
5.0 ≤ q ≤ 20.0,
0 ≦ r ≦ 3.0,
1.0 ≤ s ≤ 11.0
0.1 ≤ x ≤ 0.5,
0 ≦ y ≦ 0.1 and 0.1 ≦ z ≦ 0.5
Is. ),
The total concentration of Ce and La is higher in the main phase than in the intermediate phase, and
The concentration of ^R2 is higher in the intermediate phase than in the main phase.
Rare earth magnet.
<2> The rare earth magnet according to item <1>, wherein the concentration of La is higher in the grain boundary phase than in the intermediate phase.
<3> The rare earth magnet according to <1> or <2>, wherein R ² is one or more selected from Nd, Pr, Dy, and Tb.
<4> In any one of <1> to <3>, the total concentration of Ce and La is 1.5 to 10.0 times higher in the main phase than in the intermediate phase. The rare earth magnets listed.
<5> The item according to any one of <1> to <4>, wherein the concentration of ^R2 is 1.5 to 10.0 times higher in the intermediate phase than in the main phase. Rare earth magnet.
<6> The item according to any one of <1> to <5>, wherein the concentration of La is 1.5 to 10.0 times higher in the grain boundary phase than in the intermediate phase. Rare earth magnet.
<7> The rare earth magnet according to any one of <1> to <6>, wherein x is 0.2 ≦ x ≦ 0.3.
<8> The rare earth magnet according to any one of <1> to <7>, wherein z is 0.2 ≦ z ≦ 0.4.
<9> The rare earth magnet according to any one of <1> to <8>, wherein the thickness of the intermediate phase is 5 to 50 nm.
<10> The rare earth magnet according to any one of <1> to <9>, wherein T is Fe.
<11> The overall composition is the formula ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r (where R ¹ is , Ce and La are rare earth elements, T is one or more selected from Fe, Ni and Co, and M ¹ is Ti, Ga, Zn, Si, Al, Nb, Zr, Mn and V. , W, Ta, Ge, Cu, Cr, Hf, Mo, P, C, Mg, Hg, Ag, and one or more selected from Au, and unavoidable impurities and p, q, and r, and x and y are
12.0 ≤ p ≤ 20.0,
5.0 ≤ q ≤ 20.0,
0 ≦ r ≦ 3.0,
0.1 ≦ x ≦ 0.5 and 0 ≦ y ≦ 0.1. )
To prepare a rare earth magnet precursor having a magnetic phase represented by (Ce, La, R ¹ ) and a rich phase existing around the magnetic phase.
R ² _1-z M ² _z (However, R ² is a rare earth element other than Ce and La, and M ² is alloyed with R ² to set the melting point of R ² _1-z M ² _z to R. Preparing a modifier containing an alloy element and an unavoidable impurity that lowers the melting point of ² and an alloy represented by 0.1 ≦ z ≦ 0.5).
The rare earth magnet precursor and the modified material are brought into contact with each other to obtain a contact body, and the contact body is heat-treated to melt the modified material inside the magnetic phase of the rare earth magnet precursor. Infiltrating the liquid,
A method for manufacturing a rare earth magnet, including.
<12> The R ² is one or more selected from Nd, Pr, Dy, and Tb, and the M ² is one or more selected from Cu, Al, and Co, and an unavoidable impurity. 11> The method according to item 11.
<13> The method according to <11> or <12>, wherein z is 0.2 ≦ z ≦ 0.4.
<14> The method according to any one of <11> to <13>, wherein the permeation amount of the modifier is 1.0 to 11.0 atomic% with respect to the rare earth magnet precursor. ..
<15> The method according to any one of <11> to <14>, wherein the heat treatment temperature is 600 to 800 ° C.
<16> The method according to any one of <11> to <15>, wherein x is 0.2 ≦ x ≦ 0.3.
<17> The method according to any one of <11> to <16>, wherein T is Fe.

According to the present disclosure, it is possible to provide a rare earth magnet and a method for producing the same, which can suppress a decrease in magnetization even if the coercive force is improved by permeation of a modifier by coexisting Ce and La. can.

FIG. 1 is a diagram schematically showing the structure of the rare earth magnet of the present disclosure. FIG. 2 is a diagram schematically showing the structure of a rare earth magnet precursor. FIG. 3 shows a rare earth magnet having an overall composition represented by ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r . It is a graph which shows the relationship between x and magnetization in a precursor. FIG. 4 is a diagram showing a BH curve for the sample of Example 1. FIG. 5 is a diagram showing a BH curve for a sample of a comparative example. FIG. 6 is a diagram showing a scanning transmission electron microscope image of a sample of a comparative example. FIG. 7 is a diagram showing the results of component analysis of the portion surrounded by the white line in FIG. FIG. 8 is a diagram summarizing the results of FIG. 7. FIG. 9 is a diagram showing a scanning transmission electron microscope image of the sample of Example 1. FIG. 10 is a diagram summarizing the results of component analysis along the white arrow line in FIG. FIG. 11 is a diagram showing a BH curve for the sample of Example 2.

Hereinafter, embodiments of a rare earth magnet and a method for manufacturing the rare earth magnet according to the present disclosure will be described in detail. The embodiments shown below do not limit the rare earth magnets and the manufacturing methods thereof according to the present disclosure.

The R-Fe-B-based rare earth magnet is obtained by liquid quenching the molten R-Fe-B-based alloy. A magnetic phase represented by R ₂ Fe ₁₄ B (hereinafter, such a phase may be referred to as “R ₂ Fe ₁₄ B phase”) is formed by liquid quenching or the like. In the residual liquid after the R ₂ Fe ₁₄ B phase is formed, the R rich phase is formed by the excess R that did not contribute to the formation of the R ₂ Fe ₁₄ B phase. The R-rich phase is formed around the R ₂ Fe ₁₄ B phase.

When the reforming material is infiltrated into such an R-Fe-B-based rare earth magnet, when the alloy in the reforming material mainly contains the same rare earth elements as the _R2 Fe ₁₄ B phase, the rare earth elements in the reforming material. Elements are difficult to penetrate into the R ₂ Fe ₁₄ B phase. For example, when a modifier containing an Nd—Cu alloy is permeated into an Nd—Fe—B rare earth magnet, Nd in the modifier tends to stay in the Nd rich phase and permeates into the Nd ₂ Fe ₁₄ B phase. It's difficult to do.

On the other hand, when the alloy in the reforming material mainly contains a rare earth element different from the R ₂ Fe ₁₄ B phase, the rare earth element in the reforming material easily permeates into the R ₂ Fe ₁₄ B phase. For example, when a modifier containing a Dy—Cu alloy is infiltrated into an Nd—Fe—B-based rare earth magnet, Dy in the modifier tends to permeate into the Nd ₂ Fe ₁₄ B phase.

When R of the R ₂ Fe ₁₄ B phase is mainly Ce and La and the modifier mainly contains rare earth elements other than Ce and La, the rare earth element of the alloy in the modifier is R. The present inventors have found that it is particularly easy to permeate into the ₂ Fe ₁₄ B phase.

In such a case, the present inventors have found that the decrease in magnetization is suppressed and the coercive force is improved even though the non-magnetic modifier is infiltrated.

The configuration of the rare earth magnet according to the present disclosure based on these findings will be described below.

(Overall composition)
The overall composition of the rare earth magnets disclosed in the present disclosure is the formula ((Ce _(1-x) La _x ) _(1-y) ^R1 _y ) _p T _(100-p-q-r) B _q M ¹ _r · (R). It is represented by ²¹ _-z M ² _z ) _s .

In the above formula, R ¹ and R ² are rare earth elements other than Ce and La. T is one or more selected from Fe, Ni, and Co. M is selected from Ti, Ga, Zn, Si, Al, Nb, Zr, Mn, V, W, Ta, Ge, Cu, Cr, Hf, Mo, P, C, Mg, Hg, Ag, and Au. One or more, as well as unavoidable impurities. M ² is an alloying element and an unavoidable impurity that lowers the melting point of R ² .

p is the total content of Ce, La, and R ¹ , q is the content of B (boron), r is the content of M ¹ , and s is the content of R ² and M ² . It is the total content, and the values of p, q, r, and s are atomic%, respectively.

x indicates the content ratio of Ce and La. y indicates the ratio of the total content of Ce and La to the content of ^R1 . z indicates the content ratio of R ² and M ² . The values of x, y, and z are molar ratios, respectively.

The rare earth magnet of the present disclosure is obtained by infiltrating a modifying material into a rare earth magnet precursor, as will be described later. The rare earth magnet precursor has an overall composition represented by the formula ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r . Have. ^The modifier contains an alloy having a composition represented by _R2-1z ^M2 _z .

The amount of alloy permeated into the rare earth magnet precursor is s atomic%, that is, 1.0 to 11.0 atomic%. Therefore, the overall composition of the rare earth magnets disclosed in the present disclosure is represented by ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r . It is the sum of the composition to be obtained and the composition represented by (R ²¹ _-z M ² _z ) s. The total composition of these is the formula ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r · (R ² _1- ). _z M ² _z ) Represented by _s .

In the rare earth magnet precursor, there is a phase represented by an appropriate amount of ((Ce _(1-x) La _x ) _(1-y) ^R1 _y ) ₂ T _{(100-p-q-r) 14} B. In order to do so, 12.0 ≦ p ≦ 20.0 and 5.0 ≦ q ≦ 20.0 may be used. Further, M ¹ can be contained within a range that does not impair the characteristics of the rare earth magnets of the present disclosure. M ¹ may contain unavoidable impurities. The unavoidable impurities refer to impurities such as impurities contained in raw materials that cannot be avoided or that cause a significant increase in manufacturing cost in order to avoid them. When r is 3.0 or less, the characteristics of the rare earth magnets of the present disclosure are not impaired. The values of p, q, and r are the same as in the case of a normal R-Fe-B type rare earth magnet.

T is classified as an iron group element, and the properties of Fe, Ni, and Co are common in that they exhibit ferromagnetism at normal temperature and pressure. Therefore, these may be interchanged with each other. The inclusion of Co improves the magnetization and raises the Curie point. This effect is exhibited when the Co content is 0.1 atomic% or more. From this point of view, the Co content is preferably 0.1 atomic% or more, more preferably 1 atomic% or more, and even more preferably 3 atomic% or more. On the other hand, since Co is expensive and Fe is the cheapest, economically, Fe is preferably 80 atomic% or more, more preferably 90 atomic% or more, and all of T is Fe. There may be.

(Main phase, grain boundary phase, and intermediate phase)
Next, the structure of the rare earth magnet of the present disclosure having the overall composition represented by the above formula will be described. FIG. 1 is a diagram schematically showing the structure of the rare earth magnet of the present disclosure. The rare earth magnet 100 includes a main phase 10, a grain boundary phase 20, and an intermediate phase 30.

From the viewpoint of ensuring the coercive force, the average particle size of the main phase 10 is preferably smaller, preferably 1000 nm or less, and more preferably 500 nm or less. On the other hand, the average particle size of the main phase 10 may be practically 1 nm or more, 50 nm or more, or 100 nm or more.

Here, the "average particle size" is, for example, the average value of the length t in the longitudinal direction of the main phase 10 shown in FIG. For example, a scanning electron microscope image or a transmission electron microscope image of a rare earth magnet 100 defines a certain region, and the average value of the length t of each of the main phases 10 existing in this fixed region is calculated and calculated as ". "Average particle size". When the cross-sectional shape of the main phase 10 is elliptical, the length of its major axis is t. When the cross section of the main phase is quadrangular, the length of the longer diagonal line is t.

The rare earth magnet 100 may contain a phase (not shown) other than the main phase 10, the grain boundary phase 20, and the intermediate phase 30. Examples of the phase other than the main phase 10, the grain boundary phase 20, and the intermediate phase 30 include oxides, nitrides, intermetallic compounds, and the like.

The characteristics of the rare earth magnet 100 are mainly exhibited by the main phase 10, the grain boundary phase 20, and the intermediate phase 30. Most of the phases other than the main phase 10, the grain boundary phase 20, and the intermediate phase 30 are impurities. Therefore, the total content of the main phase 10, the grain boundary phase 20, and the intermediate phase 30 with respect to the rare earth magnet 100 is preferably 95% by volume or more, more preferably 97% by volume or more, and even more preferably 99% by volume or more. ..

The rare earth magnet precursor has a composition represented by the formula ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r . .. FIG. 2 is a diagram schematically showing the structure of a rare earth magnet precursor. The rare earth magnet precursor 200 may be referred to as a magnetic phase 50 (hereinafter, “magnetic phase 50”) represented by ((Ce _(1-x) La _x ) _(1-y) ^R1 _y ) ₂ T ₁₄ B. .). The magnetic phase 50 is crystalline and granular. Around the magnetic phase 50, there is a (Ce, La, R ¹ ) rich phase 60. (Ce, La, R ¹ ) The rich phase 60 is formed of an element that did not contribute to the formation of the magnetic phase 50, and has a high concentration of Ce, La, and R ¹ .

When the modified material is infiltrated into the rare earth magnet precursor 200, the modified material passes through the (Ce, La, R ¹ ) rich phase 60 and the interface between the (Ce, La, R ¹ ) rich phase 60 and the magnetic phase 50. To reach. Then, a part of R ² in the modifier permeates from the (Ce, La, R ¹ ) rich phase 60 into the magnetic phase 50, and from the magnetic phase 50 (Ce, La, R ¹ ) rich phase 60. Ce and La are discharged to. As a result, the main phase 10, the grain boundary phase 20, and the intermediate phase 30 are formed in the rare earth magnet 100.

The grain boundary phase 20 exists around the main phase 10. The intermediate phase 30 is sandwiched between the main phase 10 and the grain boundary phase 20. The total concentration of Ce and La is higher in the main phase 10 than in the intermediate phase 30. Further, the concentration of R ² is higher in the intermediate phase 30 than in the main phase 10.

Since Ce and La are light rare earth elements, the anisotropic magnetic field can be increased when Ce and La in the magnetic phase are replaced with rare earth elements ^R2 other than Ce and La. Since the concentration of ^R2 is higher in the intermediate phase 30 than in the main phase 10, the anisotropic magnetic field is higher in the intermediate phase 30 (magnetic phase) than in the main phase 10 (central part of the magnetic phase). It becomes higher in the peripheral part). As a result, the main phases 10 which are the magnetic phases are magnetically more strongly separated by the intermediate phase 30 in addition to the grain boundary phase 20. As a result, the coercive force is improved. The anisotropic magnetic field is a physical characteristic value representing the magnitude of the coercive force of the permanent magnet.

When R ² is one or more selected from Nd, Pr, Dy, and Tb, the coercive force is further improved. This is because Nd, Pr, Dy, and Tb can further increase the anisotropic magnetic field as compared with other rare earth elements.

If the intermediate phase 30 is excessively thin, the anisotropic magnetic field is low and the coercive force is lowered. From this viewpoint, the thickness of the intermediate phase 30 is preferably 2 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. Here, the sensitivity of the thickness of the intermediate phase 30 to the magnetization varies depending on ^R2 . When the saturation magnetization of ^R2 (physical property value indicating the magnitude of magnetization of the permanent magnet) is larger than La and / or Ce (Nd and / or Pr), if the intermediate phase 30 is excessively thin, the magnetization decreases. From this viewpoint, the thickness of the intermediate phase 30 is preferably 2 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. On the other hand, when the saturation magnetization of R ² is smaller than La and / or Ce (Dy and / or Tb), when the intermediate phase 30 is excessively thin, the magnetization decreases. From this viewpoint, the thickness of the intermediate phase 30 is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less.

If the concentration of ^R2 is 1.5 times or more higher in the intermediate phase 30 (peripheral portion of the magnetic phase) than in the main phase 10 (central portion of the magnetic phase), the magnetic division can be recognized more clearly. On the other hand, when the concentration of R ² is 10.0 times higher in the intermediate phase 30 (peripheral portion of the magnetic phase) than in the main phase 10 (central portion of the magnetic phase), the effect of magnetic fragmentation is not saturated. Therefore, the concentration of R ² is preferably 1.5 to 10.0 times higher in the intermediate phase 30 than in the main phase 10. It is more preferably 1.5 to 5.0 times higher, and more preferably 1.5 to 3.0 times higher.

Further, in order for more ^R2 to permeate into the intermediate phase 30 after the intermediate phase is formed, it is preferable that more Ce and La are discharged from the intermediate phase 30 to the grain boundary phase 20. Since it takes time for R ² to reach the main phase 10, when more Ce and La are discharged from the intermediate phase 30 to the grain boundary phase 20, the total concentration of Ce and La becomes the intermediate phase 30. It is even higher in the main phase 10 than in. If the total concentration of Ce and La is 1.5 times or more higher in the main phase 10 than in the intermediate phase 30, more ^R2 permeation can be recognized more clearly. On the other hand, when the total concentration of Ce and La is 10.0 times higher in the main phase 10 than in the intermediate phase 30, the permeation of R ² is not saturated. Therefore, it is preferable that the total concentration of Ce and La is 1.5 to 10.0 times higher in the intermediate phase 30 than in the main phase 10. It is more preferably 1.5 to 5.0 times higher, and more preferably 1.5 to 3.0 times higher.

When Ce and La coexist in the magnetic phase 50, Ce is at the interface between the rich phase 60 and the magnetic phase 50 (Ce, La, ^R1 ) as compared with the case where La does not exist and Ce exists. And La and R ² are easy to move to each other. Then, when Ce and La coexist in the magnetic phase 50, many Ce and La move from the magnetic phase 50 to the (Ce, La, R ¹ ) rich phase 60, and many R ² (Ce, La). , R ¹ ) Move from the rich phase 60 to the magnetic phase 50. As a result, the main phase 10 and the intermediate phase 30 are formed, the total concentration of Ce and La is higher in the main phase 10 than in the intermediate phase 30, and the concentration of ^R2 is higher than in the main phase 10. It becomes higher in the intermediate phase 30. In the following description, when Ce and La coexist in the magnetic phase 50, (Ce, La, R ¹ ) Ce and La and R ² move to each other at the interface between the rich phase 60 and the magnetic phase 50. What is done is sometimes referred to as "mutual movement between Ce and La and ^R2 at the interface".

The smaller the amount of the rare earth element R ¹ other than Ce and La in the magnetic phase 50, the more likely it is that Ce and La and R ² interact with each other at the interface.

In the above equation, y is the allowable amount of the rare earth element ^R1 other than Ce and La in the magnetic phase 50. It is preferable that y is as small as possible, and 0 is ideal. However, the lower limit of y may be 0.03 in order to avoid an excessive increase in the manufacturing cost of the raw material. On the other hand, when y is 0.1 or less, even if the mutual movement between Ce and La and R ² is hindered, the problem is practically small. From this point of view, y is preferably 0.05 or less.

Ce and La may coexist in a blending ratio represented by Ce _(1-x) La _x . When x is 0.1 or more, the effect of facilitating mutual movement between Ce and La and R ² at the interface is exhibited. This effect is maximized when x is between 0.1 and 0.3. When x is 0.5 or less, an effect equal to or higher than that at the time of manifestation of this effect can be obtained. From these things, x is preferably 0.2 or more. Further, x is preferably 0.4 or less, more preferably 0.3 or less.

FIG. 3 shows a rare earth magnet having an overall composition represented by ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r . It is a graph which shows the relationship between x and the magnetization in the precursor 200. As can be seen from FIG. 3, when x is in the above range, the magnetization is improved in the rare earth magnet precursor 200 before the modifier is infiltrated. This is convenient in suppressing the decrease in magnetization even if the coercive force is improved by the penetration of the modifier.

Without being bound by theory, when Ce and La coexist, the following can be further considered. The magnetization and coercive force of the main phase 10 and the intermediate phase 30 and the substitution of Ce, La and R ² will be described separately.

First, the magnetization and coercive force of the main phase 10 and the intermediate phase 30 will be described. In the magnetic phase represented by Ce ₂ Fe ₁₄ B, many Ce are tetravalent. In tetravalent Ce, 4f electrons are not localized. The 4f electrons contribute to the improvement of the magnetization, but in the tetravalent Ce, the 4f electrons are not localized, so that it is considered that the magnetization is small. Therefore, when La is added to the magnetic phase to form a magnetic phase represented by (Ce, Nd) ₂ Fe ₁₄ B, the valence of many Ce becomes trivalent. In trivalent Ce, 4f electrons are localized, so that the magnetization is improved. That is, when Ce and La coexist, the magnetization of the main phase 10 and the intermediate phase 30 is improved. Further, by the penetration of the modifier, Ce and La of the intermediate phase 30 are replaced with R ² , and the anisotropic magnetic field becomes larger than that of the main phase 10. Then, the coercive force is improved by magnetically dividing the main phases 10 adjacent to each other.

Next, the substitution of Ce and La with R ² will be described. The lattice stabilizing energy of La ₂ Fe ₁₄ B is smaller than the lattice stabilizing energy of Ce ₂ Fe ₁₄ B. Therefore, the lattice stabilizing energy of (Ce, La) ₂ Fe ₁₄ B is smaller than the lattice stabilizing energy of Ce ₂ Fe ₁₄ B. As a result, when Ce and La coexist, Ce and La and R ² are more likely to move to each other at the above-mentioned interface as compared with the case where La does not exist and Ce exists, and La In ₂ Fe ₁₄ B and / or Ce ₂ Fe ₁₄ B, R ² is likely to be replaced at the position of La and / or Ce. It is considered that the concentration of R ² is higher in the intermediate phase 30 than in the main phase 10 because Ce and La and R ² are more likely to move to each other. Further, by substituting Nd (R ² ) at the positions of La and / or Ce, it is possible to suppress the decrease in magnetization. Further, also in the relationship between the grain boundary phase 20 and the intermediate phase 30, the lattice stabilizing energy of La ₂ Fe ₁₄ B is smaller than the lattice stabilizing energy of Ce ₂ Fe ₁₄ B. Therefore, in the intermediate phase 30, La ₂ Fe ₁₄ B is unlikely to exist and is easily discharged to the grain boundary phase 20 as La. As a result, the concentration of La becomes higher in the grain boundary phase 20 than in the intermediate phase 30. As a result, the decrease in magnetization can be suppressed by substituting Nd (R ² ) at the position of La ₂ Fe ₁₄ B. Further, the concentration of Nd (R ² ) in the intermediate phase 30 becomes high and the anisotropic magnetic field becomes large, which also contributes to the improvement of the coercive force.

The concentration of La may be 1.5 times or more, 3.0 times or more, or 4.5 times or more higher in the grain boundary phase 20 than in the intermediate phase 30, 10.0 times or less, 8.5 times. It may be twice or less, or 7.0 times or less higher.

As a result, the rare earth magnets of the present disclosure can suppress the decrease in magnetization even if the coercive force is improved by the penetration of the modifier.

(Production method)
Next, a method for manufacturing the rare earth magnet of the present disclosure will be described.

(Preparation of rare earth magnet precursor)
Prepare a rare earth magnet precursor 200 having an overall composition of the formula ((Ce _(1-x) La _x ) _(1-y) R ¹ _y ) _p T _(100-p-q-r) B _q M ¹ _r . do. R ¹ , T, M ¹ , and p, q, r, x, and y are as described above.

The rare earth magnet precursor 200 may be a magnetic powder or a sintered body of the magnetic powder. It may be a plastic working body obtained by subjecting a sintered body to hot working.

As a method for producing magnetic powder, a well-known method can be adopted. For example, a method of obtaining an isotropic magnetic powder having a nanocrystal structure by a liquid quenching method can be mentioned. Alternatively, a method of obtaining isotropic or anisotropic magnetic powder by an HDDR (Hydrogen Disproportionation Desorption Recombination) method can be mentioned.

The method of obtaining magnetic powder by the liquid quenching method is outlined. An alloy having the same composition as the overall composition of the rare earth magnet precursor 200 is melted at high frequency to prepare a molten metal. For example, in an Ar gas atmosphere decompressed to 50 kPa or less, the molten metal is discharged into a single copper roll to prepare a quenching thin band. This quenching thin band is pulverized to, for example, 10 μm or less.

Next, a method for obtaining a sintered body will be outlined. The magnetic powder obtained by pulverization is magnetically oriented and subjected to liquid phase sintering to obtain an anisotropic sintered body. Alternatively, the magnetic powder having an isotropic nanocrystal structure obtained by the liquid quenching method is sintered to obtain an isotropic sintered body. Alternatively, a magnetic powder having an isotropic nanocrystal structure is sintered, and the sintered body is further strongly processed to obtain a plastically processed body having anisotropy. Alternatively, the isotropic or anisotropic magnetic powder obtained by the HDDR method is sintered to obtain an isotropic or anisotropic sintered body.

(Preparation of modifier)
A modifier containing an alloy having a composition represented by _R21 ^- _z ^M2z is prepared. ^R2 is a rare earth element other than Ce and La. M ² is an alloying element and an unavoidable impurity that lowers the melting point of R ²¹ _-z M ² _z below the melting point of R ² by alloying with R ² . The ratio of R ² and M ² is 0.1 ≦ z ≦ 0.5.

The magnetic phase 50 of the rare earth magnet precursor 200 mainly contains Ce and La, whereas R ² is a rare earth element other than Ce and La. Therefore, in the heat treatment described later, ^R2 in the melt of the reforming material easily permeates into the magnetic phase 50 of the rare earth magnet precursor 200. As a result, the main phase 10 and the intermediate phase 30 containing R ² are obtained.

When R ² is one or more selected from Nd, Pr, Dy, and Tb, the coercive force is further improved. This is because Nd, Pr, Dy, and Tb can further increase the anisotropic magnetic field as compared with other rare earth elements. From these facts, it is preferable that R ² is one or more selected from Nd, Pr, Dy, and Tb.

Since M ² is an alloying element and an unavoidable impurity that lowers the melting point of R ²¹ _-z M ² _z from the melting point of R ² by alloying with R ² , the temperature of the heat treatment described later is excessive. The alloy in the modifier can be melted without increasing the temperature. As a result, the modified material can be infiltrated into the rare earth magnet precursor 200 without coarsening the structure of the rare earth magnet precursor 200. M ² may contain unavoidable impurities. The unavoidable impurities refer to impurities such as impurities contained in raw materials that cannot be avoided or that cause a significant increase in manufacturing cost in order to avoid them.

M ² is preferably one or more selected from Cu, Al, and Co and an unavoidable impurity. This is because Cu, Al, and Co have a small adverse effect on the magnetic properties of rare earth magnets and the like.

The alloys of R ² and M ² include Nd-Cu alloy, Pr-Cu alloy, Tb-Cu alloy, Dy-Cu alloy, La-Cu alloy, Ce-Cu alloy, Nd-Pr-Cu alloy, Nd-. Examples thereof include Al alloys, Pr-Al alloys, Nd-Pr-Al alloys, Nd-Co alloys, Pr-Co alloys, Nd-Pr-Co alloys and the like.

The ratio of R ² and M ² will be described. When z is 0.1 or more, the melting point of the alloy in the reforming material is appropriately lowered, so that the temperature of the heat treatment described later becomes appropriate. As a result, the structure of the rare earth magnet precursor 200 can suppress the coarsening. From the viewpoint of optimizing the melting point of the alloy, z is preferably 0.2 or more, more preferably 0.25 or more. On the other hand, when z is 0.5 or less, the content of R ² in the alloy is high, so that R ² can easily penetrate into the main phase 10 and the intermediate phase 30. From this point of view, z is preferably 0.4 or less, more preferably 0.35 or less. When R ² is two or more kinds of elements, it is the total. The same applies to M ² .

The method for producing the modified material is not particularly limited. Examples of the method for producing the modified material include a casting method and a liquid quenching method. The liquid quenching method is preferable from the viewpoint that the variation in the alloy component is small and the impurities such as oxides are small depending on the part of the reforming material.

(Preparation of contact body)
The rare earth magnet precursor 200 and the modifier are brought into contact with each other to obtain a contact body. When both the rare earth magnet precursor 200 and the modifier are bulk bodies, at least one surface of the rare earth magnet precursor 200 and at least one surface of the modifier are brought into contact with each other. The bulk body includes a lump body, a plate material, a strip, a green compact, a sintered body and the like. For example, when both the rare earth magnet precursor 200 and the modifier are thin bands, one side of the rare earth magnet precursor 200 and one side of the thin band may be brought into contact with each other, or the rare earth magnet precursor 200 may be modified. It may be sandwiched between the materials and the modified material may be brought into contact with both sides of the rare earth magnet precursor 200.

When the rare earth magnet precursor 200 is a bulk body and the modifier is powder, the powder of the modifier may be brought into contact with at least one surface of the rare earth magnet precursor 200. Typically, the powder of the modifier may be placed on the upper surface of the rare earth magnet precursor 200.

When both the rare earth magnet precursor 200 and the modifier are powders, the respective powders may be mixed with each other.

(Heat treatment)
The above-mentioned contact body is heat-treated to allow the melt of the modifier to permeate the inside of the rare earth magnet precursor 200. As a result, the melt of the modifier reaches the magnetic phase 50 of the rare earth magnet precursor 200 through the (Ce, La, R ¹ ) rich phase 60 of the rare earth magnet precursor 200, and the main phase 10 of the rare earth magnet 100. And the intermediate phase 30 is formed.

The permeation amount of the modifier is preferably 1.0 to 11.0 atomic% with respect to the rare earth magnet precursor 200. If the modified material penetrates into the rare earth magnet precursor 200 as much as possible, the rare earth magnet 100 of the present disclosure can be obtained. When the permeation amount of the modifier is 1.0 atomic% or more, the effect of the rare earth magnet 100 of the present disclosure can be clearly recognized. From this viewpoint, the permeation amount of the modifier is preferably 2.6 atomic% or more, more preferably 4.0 atomic% or more, and even more preferably 5.0 atomic% or more. On the other hand, if the permeation amount of the modifier is 11.0 atomic% or less, the effect of permeation of the modifier is not saturated. From this viewpoint, the permeation amount of the modifier is preferably 8.0 atomic% or less, more preferably 7.5 atomic% or less.

The heat treatment temperature is not particularly limited as long as the reforming material is melted and the melt of the reforming material can be infiltrated into the magnetic phase 50 of the rare earth magnet precursor 200.

The higher the heat treatment temperature, the easier it is for the melt of the modifier, particularly ^R2 , to penetrate into the magnetic phase 50 of the rare earth magnet precursor 200. From this point of view, the heat treatment temperature is preferably 600 ° C. or higher, more preferably 625 ° C. or higher, and even more preferably 675 ° C. or higher. On the other hand, the lower the heat treatment temperature, the easier it is to suppress the coarsening of the structure of the rare earth magnet precursor 200, particularly the magnetic phase 50. From this point of view, the heat treatment temperature is preferably 800 ° C. or lower, more preferably 775 ° C. or lower, and even more preferably 725 ° C. or lower.

The heat treatment atmosphere is not particularly limited, but the inert gas atmosphere is preferable from the viewpoint of suppressing oxidation of the rare earth magnet precursor 200 and the modifier. The inert gas atmosphere includes a nitrogen gas atmosphere.

Hereinafter, the rare earth magnet of the present disclosure and a method for producing the same will be described in more detail by way of examples. The rare earth magnet and the method for manufacturing the rare earth magnet of the present disclosure are not limited to the conditions used in the following examples.

(Preparation of sample of Example 1)
First, the rare earth magnet precursor 200 is prepared. (Ce _0.75 La _0.25 ) _12.47 Fe _81.23 Cu _0.20 B _5.73 Ga A molten alloy having a composition represented by _0.37 is liquid-quenched by a single roll method to form a thin band. Got As the conditions for liquid quenching, the molten metal temperature (discharge temperature) was 1450 ° C., and the peripheral roll speed was 30 m / s. Liquid quenching was performed under an atmosphere of reduced pressure with argon gas. It was confirmed by transmission electron microscopy (TEM) observation that the thin band had nanocrystals.

The strip was coarsely pulverized to obtain a powder, and the powder was charged into a die, pressurized and heated to obtain a sintered body. As the pressurizing and heating conditions, the pressing force was 400 MPa, the heating temperature was 650 ° C., and the holding time of pressurization and heating was 60 seconds.

The sintered body was hot-embedded (hot-strength work) to obtain a rare earth magnet precursor 200 (plastically worked body). As the hot stationary machining conditions, the machining temperature was 750 ° C. and the strain rate was 0.1 to 10.0 / s. It was confirmed by a scanning electron microscope (SEM) that the plastic work piece had oriented nanocrystals.

An Nd ₇₀ Cu ₃₀ alloy was produced as a modifier. Nd powder and Cu powder manufactured by High Purity Chemical Co., Ltd. were weighed, melted in an arc, and rapidly cooled to obtain a thin band.

The rare earth magnet precursor 200 (plastic work piece) and the modifier (thin band) were brought into contact with each other and heat-treated in a heating furnace. The amount of the modifier was 5.3 atomic% (10% by mass) with respect to the rare earth magnet precursor 200. As the heating furnace, a lamp furnace manufactured by ULVAC Riko Co., Ltd. was used. As the heat treatment conditions, the heat treatment temperature was 700 ° C. and the heat treatment time was 360 minutes.

(Preparation of sample of Example 2)
Except that the composition of the alloy for making the rare earth magnet precursor 200 is (Ce _0.50 La _0.50 ) _12.47 Fe _81.23 Cu _0.20 B _5.73 Ga _0.37 . A sample of Example 2 was prepared in the same manner as in Example 1.

(Preparation of sample of comparative example)
Comparison is performed in the same manner as in Example 1 except that the composition of the alloy for producing the rare earth magnet precursor 200 is Ce _12.47 Fe _81.23 Cu _0.20 B _5.73 Ga _0.37 . An example sample was prepared.

(Preparation of sample for reference example)
Reference is made in the same manner as in Example 1 except that the composition of the alloy for producing the rare earth magnet precursor 200 is Nd _13.86 Fe _79.91 Cu _0.20 B _5.66 Ga _0.37 . An example sample was prepared.

(evaluation)
The coercive force and magnetization were measured for the samples of Examples 1 and 2, Comparative Example, and Reference Example. The measurement was performed at room temperature using a vibrating sample magnetometer (VSM) manufactured by Lake Shore.

For the samples of Example 1 and Comparative Example, the structure was observed using a scanning transmission electron microscope (STEM), and component analysis (EDX ray analysis) was performed.

The evaluation results are shown in Table 1 and FIGS. 4 to 11. FIG. 4 is a diagram showing a BH curve (magnetic hysteresis curve) for the sample of Example 1. FIG. 5 is a diagram showing a BH curve (magnetic hysteresis curve) for the sample of the comparative example. FIG. 6 is a diagram showing a scanning transmission electron microscope (STEM) image of a sample of a comparative example. FIG. 7 is a diagram showing the results of component analysis (EDX ray analysis) of the portion surrounded by the white line in FIG. In FIG. 7, the white straight line indicates the part analyzed by EDX ray. FIG. 8 is a diagram summarizing the results of FIG. 7. FIG. 9 is a diagram showing a scanning transmission electron microscope (STEM) image of the sample of Example 1. FIG. 10 is a diagram summarizing the results of EDX ray analysis along the white arrow line in FIG. FIG. 11 is a diagram showing a BH curve (magnetic hysteresis curve) for the sample of Example 2.

As can be seen from Table 1, in the samples of Examples 1 and 2, it was confirmed that the decrease in magnetization could be suppressed even if the coercive force was improved by the permeation of the modifier.

As can be seen from FIGS. 6 to 8 for the comparative example, even if the rare earth element in the rare earth magnet is only Ce, the total concentration of Ce and La is higher in the main phase 10 than in the intermediate phase 30. , Nd (R ² ) is higher in the intermediate phase 30 than in the main phase 10.

On the other hand, the lattice stabilizing energy of La ₂ Fe ₁₄ B is smaller than the lattice stabilizing energy of Ce ₂ Fe ₁₄ B. Therefore, in the sample of Example 1, the coexistence of Ce and La facilitates the mutual movement of Ce and La and R ² , and also in La ₂ Fe ₁₄ B and / or Ce ₂ Fe ₁₄ B. It is considered that Nd ( ^R2 ) was replaced at the positions of La and / or Ce. That is, it is considered that the concentration of Nd (R ² ) was higher in the intermediate phase 30 than in the main phase 10 because the presence of La facilitates the mutual movement of Ce and La and R ² . Further, the suppression of the decrease in magnetization confirmed in Table 1 is considered to be due to the substitution of Nd (R ² ) at the positions of La and / or Ce.

When Ce and La coexist inside the rare earth magnet 100, the concentrations of Ce, La, and Nd (R ² ) in the main phase 10, the grain boundary phase 20, and the intermediate phase 30 are as follows. This was confirmed from FIG. That is, the total concentration of Ce and La was higher in the main phase 10 than in the intermediate phase 30. Further, the concentration of R ² was higher in the intermediate phase 30 than in the main phase 10. Furthermore, the concentration of La was higher in the grain boundary phase 20 than in the intermediate phase 30. The concentration of La was 1.5 to 10.0 times higher in the grain boundary phase 20 than in the intermediate phase 30. This is because the lattice stabilizing energy of La ₂ Fe ₁₄ B is smaller than the lattice stabilizing energy of Ce ₂ Fe ₁₄ B, so that La ₂ Fe ₁₄ B is unlikely to exist in the main phase 10 and the intermediate phase 30, and as La. It is considered that it was discharged to the grain boundary phase 20.

From the above results, the effect of the present invention could be confirmed.

10 Main phase 20 Grain boundary phase 30 Intermediate phase 50 Magnetic phase 60 (Ce, La, R ¹ ) Rich phase 100 Rare earth magnet 200 Rare earth magnet precursor

Claims (9)

With the Prime Minister
The grain boundary phase existing around the main phase and
An intermediate phase sandwiched between the main phase and the grain boundary phase,
Equipped with
The overall composition is the formula (Ce _(1-x) La _x ) _p T _(100-p-q-r) B _q M ¹ _r · (R ²¹ _-z M ² _z ) _s (where R ² is It is a rare earth element other than Ce and La, T is one or more selected from Fe, Ni, and Co, and M ¹ is Ti, Ga, Zn, Si, Al, Nb, Zr, Mn, V, One or more selected from W, Ta, Ge, Cu, Cr, Hf, Mo, P, C, Mg, Hg, Ag, and Au, as well as an unavoidable impurity, where M ² alloys with R ² . As a result, it is an alloying element and an unavoidable impurity that ^lower the melting point of R21 ^- _z M2z _below the melting point of ^R2 , and
p, q, r, and s, and x and z,
12.0 ≤ p ≤ 20.0,
5.0 ≤ q ≤ 20.0,
0 ≦ r ≦ 3.0,
1.0 ≤ s ≤ 11.0
0.25 ≤ x ≤ 0.5 0 , and 0.1 ≤ z ≤ 0.5
Is. ),
The total concentration of Ce and La is higher in the main phase than in the intermediate phase.
The concentration of ^R2 is higher in the intermediate phase than in the main phase, and
The concentration of La is higher in the grain boundary phase than in the intermediate phase.
Rare earth magnet. The rare earth magnet according to claim 1, wherein R ² is one or more selected from Nd, Pr, Dy, and Tb. The rare earth magnet according to claim 1 or 2, wherein the total concentration of Ce and La is 1.5 to 10.0 times higher in the main phase than in the intermediate phase. The rare earth magnet according to any one of claims 1 to 3, wherein the concentration of ^R2 is 1.5 to 10.0 times higher in the intermediate phase than in the main phase. The rare earth magnet according to any one of claims 1 to 4, wherein the concentration of La is 1.5 to 10.0 times higher in the grain boundary phase than in the intermediate phase. The rare earth magnet according to any one of claims 1 to 5, wherein x is 0.2 ≦ x ≦ 0.3. The rare earth magnet according to any one of claims 1 to 6, wherein z is 0.2 ≦ z ≦ 0.4. The rare earth magnet according to any one of claims 1 to 7, wherein the thickness of the intermediate phase is 5 to 50 nm. The rare earth magnet according to any one of claims 1 to 8, wherein T is Fe.

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