Sm-Fe-N BASED MAGNETIC MATERIAL AND METHOD FOR MANUFACTURING THE SAME

Abstract

To provide an Sm-Fe-N based magnetic material in which the amount of Sm to be used is further reduced while improving saturation magnetization as compared to conventional materials, and a method for manufacturing the same.SOLUTION: The present disclosure provides an Sm-Fe-N based magnetic material having a main phase including at least one of a Th2Zn17 type and a Th2 Ni17 type crystal structure, the main phase being represented by a molar ratio formula (Sm(1-x-y-z)LaxCeyR1z)2(Fe(1-p-q-s)CopNiqMs)17 Nh (here, R1 is one or more rare earth elements other than Sm, La, and Ce, and Zr, and M is one or more elements other than Fe, Co, Ni, and rare earth elements, and unavoidable impurity elements) and 0.09≤x≤0.31, 0.24≤y≤0.60, 0.51≤x+y≤0.75, 0≤z≤0.10, 0≤p+q≤0.10, 0≤s≤0.10, and 2.9≤h≤3.1 being satisfied, and a method for manufacturing the same.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an Sm-Fe-N based magnetic material and a method for manufacturing the same. In particular, the present disclosure relates to an Sm-Fe-N based magnetic material having a main phase with at least one of the crystal structures of the Th2Zn 17 type and the Th2Ni 17 type, and a method for manufacturing the same.

Background Art

[0002] As high-performance magnetic materials, Sm-Co based magnetic materials and Nd-Fe-B based magnetic materials have been put into practical use. In recent years, however, magnetic materials other than these have been studied. For example, an Sm-Fe-N based magnetic material (hereinafter sometimes simply referred to as "Sm-Fe-N based magnetic material") having a main phase with at least one of the crystal structures of the Th2Zn 17 type and the Th2Ni 17 type has been studied.

[0003] The Sm-Fe-N based magnetic material has a main phase with at least one of the crystal structures of the Th2Zn 17 type and the Th2Ni 17 type. It is considered that nitrogen has been introduced into the Sm-Fe based crystal phase in an interstitial type in this main phase. Although Sm is essential for such a main phase, since the amount of Sm incorporated is small, it is expected that the price of Sm will soar as the Sm-Fe-N based magnetic material becomes widespread. For this reason, attempts have conventionally been made to reduce the amount of Sm used.

[0004] For example, Patent Document 1 discloses an Sm-Fe-N based magnetic material in which part of Sm is replaced with inexpensive La and / or Ce.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the Sm-Fe-N-based magnetic material disclosed in Patent Document 1, the substitution rate of La and / or Ce is at most 50%, and a further reduction in the amount of Sm used has been desired.

[0007] An object of the present disclosure is to provide an Sm-Fe-N-based magnetic material in which the amount of Sm used is further reduced while improving the saturation magnetization, as compared with the prior art, and a method for producing the same.

Means for Solving the Problems

[0008] The present inventors have conducted intensive studies to achieve the above object, and have completed the Sm-Fe-N-based magnetic material and the method for producing the same of the present disclosure. The Sm-Fe-N-based magnetic material and the method for producing the same of the present disclosure include the following aspects. 〈1〉 Having a main phase having at least one crystal structure of the Th2Zn 17 type and the Th2Ni 17 type, wherein the main phase has a molar ratio formula (Sm (1-x-y-z) La x Ce y R 1 z )2(Fe (1-p-q-s) Co p Ni q M s ) 17 N h (wherein R 1 is one or more rare earth elements other than Sm, La, and Ce and Zr, and M is one or more elements other than Fe, Co, Ni, and rare earth elements and inevitable impurity elements), and 0.09 ≦ x ≦ 0.31, 0.24 ≦ y ≦ 0.60, 0.51 ≦ x + y ≦ 0.75, 0 ≦ z ≦ 0.10, 0 ≦ p + q ≦ 0.10, 0 ≦ s ≦ 0.10, and 2.9 ≦ h ≦ 3.1 are satisfied. Sm-Fe-N based magnetic material. 〈2〉The Sm-Fe-N based magnetic material according to item 〈1〉, wherein x and y satisfy 0.16 ≦ x ≦ 0.31 and 0.24 ≦ y ≦ 0.45. 〈3〉The Sm-Fe-N based magnetic material according to item 〈1〉 or 〈2〉, wherein the volume ratio of the main phase is 80% or more and 100% or less. 〈4〉A method for manufacturing the Sm-Fe-N based magnetic material according to item 〈1〉, in the molar ratio formula (Sm (1-x-y-z) La x Ce y R 1 z )2(Fe (1-p-q-s) Co p Ni q M s ) 17 (wherein R 1 is one or more rare earth elements other than Sm, La, and Ce and Zr, and M is one or more elements other than Fe, Co, Ni, and rare earth elements and inevitable impurity elements), and has a composition satisfying 0.09 ≦ x ≦ 0.31, 0.24 ≦ y ≦ 0.60, 0.51 ≦ x + y ≦ 0.75, 0 ≦ z ≦ 0.10, 0 ≦ p + q ≦ 0.10, and 0 ≦ s ≦ 0.10. Preparing a magnetic material precursor having a crystal phase, and nitriding the magnetic material precursor, A method for manufacturing an Sm-Fe-N based magnetic material, including the above. 〈5〉The method for manufacturing the Sm-Fe-N based magnetic material according to item 〈4〉, wherein x and y satisfy 0.16 ≦ x ≦ 0.31 and 0.24 ≦ y ≦ 0.45.

Advantages of the Invention

[0009] According to the present disclosure, by optimizing the molar ratios of Sm, La, and Ce, it is possible to provide an Sm-Fe-N based magnetic material and a method for manufacturing the same, in which the saturation magnetization is improved and the amount of Sm used is further reduced compared to the prior art.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the Sm—Fe—N-based magnetic material (hereinafter sometimes simply referred to as “the magnetic material of the present disclosure”) and a method for manufacturing the same will be described in detail. The embodiments shown below do not limit the magnetic material of the present disclosure and the method for manufacturing the same.

[0012] Although not bound by theory, the findings obtained by the present inventors regarding the reason why the amount of Sm used is further reduced while improving the saturation magnetization as compared with the prior art will be described.

[0013] As an element for substituting Sm in the main phase, La has been conventionally used. Since the ionic radius of La is very large as compared with Sm, when a large amount of La substitutes Sm in the main phase, it becomes difficult for the main phase to maintain at least one of the crystal structures of the Th2Zn 17 type and Th2Ni 17 type. On the other hand, since the ionic radius of Ce is only slightly larger than that of Sm, Sm in the main phase can be substituted with a large amount of Ce as compared with La. However, when the substitution amount is very large, it becomes difficult for the main phase to maintain at least one of the crystal structures of the Th2Zn 17 type and Th2Ni 17 type. Further, even if the main phase can maintain at least one of the crystal structures of the Th2Zn 17 type and Th2Ni 17 type, if the substitution amount is large, the saturation magnetization will decrease significantly.

[0014] Therefore, when nitrogen penetrates into a crystal phase having at least one of the crystal structures of the Th2Zn 17 type and the Th2Ni 17 type, the influence of the molar ratios of the three elements Sm, La, and Ce on the stability and saturation magnetization of the crystal phase was investigated in detail.

[0015] Specifically, using first-principles calculations, the formation energy of (Sm, La, Ce)2Fe 17 N3 phase was calculated based on the molar ratios of Sm, La, and Ce in the (Sm, La, Ce)2Fe 17 N3 phase to determine how it changes. Then, regarding the formation energy, using the regular solution approximation, a formation energy map showing the relationship between the molar ratios of the three elements Sm, La, and Ce and the formation energy was created. Also, by first-principles calculations, the structural parameters based on the lattice constant were calculated, and regarding the structural parameters, using the regular solution approximation formula, a saturation magnetization map was created. As a result, the present inventors found that by optimizing the molar ratios of Sm, La, and Ce, an Sm-Fe-N-based magnetic material can be obtained in which the saturation magnetization is improved and the amount of Sm used is further reduced compared to the prior art.

[0016] Next, the constituent requirements of the magnetic material and its manufacturing method of the present disclosure, which are completed based on the findings and the like described so far, will be described.

[0017] 《Magnetic Material》 The magnetic material of the present disclosure includes a main phase having at least one of the crystal structures of the Th2Zn 17 type and the Th2Ni 17 type. The magnetic material of the present disclosure exhibits magnetism due to the main phase. Hereinafter, the main phase will be described.

[0018] 〈Crystal Structure of the Main Phase〉 The main phase is of the Th2Zn 17 type and the Th2Ni 17It has at least any one of the crystal structures of the type. As the crystal structure of the main phase, in addition to the structures described above, a crystal structure of the TbCu7 type etc. may be included. Here, Th is thorium, Zn is zinc, Ni is nickel, Tb is terbium, and Cu is copper. The crystal structure of the main phase can be identified by, for example, performing X-ray diffraction analysis etc. on the magnetic material of the present disclosure.

[0019] The phase having the crystal structure described above can be achieved by various combinations (compositions) of elements, but the main phase of the magnetic material of the present disclosure is achieved by the following combination (composition) of elements. Hereinafter, the composition of the main phase of the magnetic material of the present disclosure will be described.

[0020] 〈Composition of the main phase〉 The main phase has a composition represented by the molar ratio formula (Sm (1-x-y-z) La x Ce y R 1 z )2(Fe (1-p-q-s) Co p Ni q M s ). 17 N h In the above composition formula, Sm is samarium, La is lanthanum, Ce is cerium, Fe is iron, Co is cobalt, and Ni is nickel. R 1 is one or more rare earth elements other than Sm, La, and Ce and Zr, and M is one or more elements other than Fe, Co, Ni, and rare earth elements and inevitable impurity elements. Here, Zr is zirconium. Also, in the above formula, for convenience of explanation, Sm (1-x-y) La x Ce y R 1 z is sometimes referred to as the rare earth site, and Fe (1-p-q-s) Co p Ni q M s is sometimes referred to as the iron group site.

[0021] As can be understood from the above formula, the main phase contains 2 moles of one or more elements in the rare earth site, 17 moles of one or more elements in the iron group site, and h moles of nitrogen (N). That is, a phase having the above crystal structure is composed of one or more elements in the rare earth site and one or more elements in the iron group site, and h moles of nitrogen (N) is introduced in an interstitial type into that phase. The amount of nitrogen (N) introduced is typically 3 moles, that is, h = 3. However, there may be sites in the crystal where nitrogen is not partially introduced. As long as it is h moles (where h is 2.9 to 3.1), the above crystal structure can be maintained. Details of the nitrogen (N) in the main phase will be described later.

[0022] The rare earth site consists of Sm, La, Ce, and R 1 and Sm, La, Ce, and R 1 each exist in a ratio of (1 - x - y - z):x:y:z in terms of molar ratio. Since (1 - x - y - z)+x+y+z = 1, it means that a part of Sm is replaced by one or more elements selected from the group consisting of La, Ce, and R 1

[0023] The iron group site consists of Fe, Co, Ni, and M, and Fe, Co, Ni, and M each exist in a ratio of (1 - p - q - s):p:q:s in terms of molar ratio. Since (1 - p - q - s)+p+q+s = 1, it means that a part of Fe is replaced by one or more elements selected from the group consisting of Co, Ni, and M.

[0024] Hereinafter, each element constituting the above formula and its content ratio (molar ratio) will be described.

[0025] 〈Sm〉 Sm is a main element that constitutes the above crystal structure together with Fe and N. A part of Sm is replaced by one or more elements selected from the group consisting of La, Ce, and R 1 Hereinafter, La, Ce, and R 1 will be described.

[0026] 〈La〉​ La belongs to the so-called light rare earth elements. Compared with Sm, it has a larger reserve (resource amount) and is inexpensive. It is also considered to contribute to the improvement of saturation magnetization. However, since the ionic radius of La is much larger than that of Sm, when partially substituting Sm with La, it becomes difficult to maintain the crystal structure of the main phase if the substitution amount is not appropriate. The substitution amount will be described later.

[0027] 〈Ce〉 Ce belongs to the so-called light rare earth elements. Compared with Sm, it has a larger reserve (resource amount) and is inexpensive. Since the ionic radius of Ce is only slightly larger than that of Sm, a large amount of Ce can be used to partially substitute Sm. However, if the substitution amount is very large, it becomes difficult to maintain the crystal structure of the main phase. Also, even if the crystal structure of the main phase can be maintained, if the substitution amount is large, the saturation magnetization will decrease significantly. The substitution amount will be described later.

[0028] 〈R 1 〉 R 1 is one or more rare earth elements other than Sm, La, and Ce and Zr. R 1 is one or more elements whose inclusion is allowed within the range that does not impair the magnetic properties of the magnetic material of the present disclosure. The allowable amount will be described later. R 1 is typically one or more rare earth elements other than Sm, La, and Ce that are difficult to completely separate from each of them when purifying the raw materials containing Sm, La, and Ce respectively, and remain in small amounts in the raw materials, etc. In addition to such rare earth elements, R 1 may contain Zr. Zr is not a rare earth element, but in some cases, a part of Sm may be substituted with Zr. Even if a part of Sm is substituted with Zr, if the substitution amount is small, it will not significantly impair the magnetic properties of the magnetic material of the present disclosure.

[0029] In this specification, the rare earth elements consist of 17 elements: Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).

[0030] 〈Fe〉 Fe is a major element that, together with Sm and N, constitutes the above-described crystal structure. A part of Fe may be substituted with one or more elements selected from the group consisting of Co, Ni, and M. Co, Ni, and M will be described below.

[0031] 〈Co〉 Since Co belongs to the so-called iron group elements, a part of Fe may be substituted with Co. If the substitution amount is within a predetermined range, it does not have a practically problematic influence on the formation energy of the main phase. The allowable amount will be described later. Substituting a part of Fe with Co raises the Curie temperature of the main phase and can suppress the decrease in saturation magnetization at high temperatures (403 - 473 K), which is advantageous.

[0032] 〈Ni〉 Since Ni belongs to the so-called iron group elements, a part of Fe may be substituted with Ni. If the substitution amount is within a predetermined range, it does not have a practically problematic influence on the formation energy of the main phase. The allowable amount will be described later.

[0033] 〈M〉 M is one or more elements other than Fe, Co, Ni, and rare earth elements, as well as inevitable impurity elements. M is one or more elements and inevitable impurity elements that allow their inclusion within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. Inevitable impurity elements refer to impurity elements that cannot be avoided during the manufacture of the magnetic material of the present disclosure, or that would cause a significant increase in manufacturing costs to avoid. Such inevitable impurity elements include impurity elements in raw materials, or elements such as Cu (copper), Zn (zinc), Ga (gallium), Al (aluminum), and B (boron), which, for example, when forming a bonded compact, etc., elements in the bond diffuse and / or penetrate into the surface of the main phase, etc. In addition, elements contained in lubricants, etc., used during forming, which diffuse and / or penetrate into the surface of the main phase, etc., are included. Note that the bonded compact will be described later.

[0034] Examples of M excluding inevitable impurity elements include one or more elements selected from the group consisting of Ti (titanium), Cr (chromium), Mn (manganese), V (vanadium), Mo (molybdenum), W (tungsten), and C (carbon). These elements, for example, form a nucleating substance during the formation of the main phase, contributing to the promotion of the refinement of the main phase and / or the suppression of the grain growth of the main phase.

[0035] Also, M may contain Zr. As described above, although Zr is not a rare earth element, in some cases, a part of Sm may be substituted with Zr, while in other cases, a part of Fe may be substituted with Zr. In any case, if the substitution amount is small, the magnetic properties of the magnetic material will not be significantly impaired.

[0036] 〈N〉 N is introduced in an interstitial type into the main phase having the above-described crystal structure. By introducing N to such an extent that it does not destroy the phase having the above-described crystal structure, the magnetic moment increases within the main phase. The abundance ratio (molar ratio) h of N in the main phase will be described later.

[0037] When the main phase of the magnetic material of the present disclosure is composed of the elements described so far and these constituent elements are present in the following ratios, it is possible to further reduce the amount of Sm used while improving the saturation magnetization as compared with the prior art. Hereinafter, the range in which the values of x, y, z, p, q, s, and h in the above formula representing the composition of the main phase, that is, the molar ratios of the constituent elements are satisfied will be described.

[0038] 〈x, y, and z〉 The stability of the main phase can be evaluated by the formation energy of the main phase. For this evaluation, a formation energy map showing the relationship between the molar ratios of the three elements Sm, La, and Ce and the formation energy is created.

[0039] As a method of first-principles calculation, a package (AkaiKKR) applying the coherent potential approximation (CPA) of the Korringa-Kohn-Rostoker (KKR) method and the Vienna ab initio simulation package (VASP) are used. Specifically, (Sm (1-x-y) La x Ce y )2Fe 17 For a total of 52 points when x and y of the N3 phase are each increased by 5%, the respective formation energies are calculated.

[0040] For the above-described 52 calculation results, a formation energy map is created using the regular solution approximation formula. The regular solution approximation formula is as follows. ΔE(x, y)=E RFN(x、y) -(1 - x - y)E SFN -xE LFN -yE CFN However, ΔE(x, y), E RFN(x、y) , E SFN , E LFN , and E CFN are as follows. ΔE(x, y): Change in formation energy when the molar ratios of La and Ce are x and y E RFN(x、y) : Total energy of AkaiKKR when the molar ratios of La and Ce are x and y E SFN : Sm2Fe 17 Value obtained by correcting the total energy of AkaiKKR of N3 with the formation enthalpy of VASP E LFN : La2Fe 17 Value obtained by correcting the total energy of AkaiKKR of N3 with the formation enthalpy of VASP E CFN : Ce2Fe 17 Value obtained by correcting the total energy of AkaiKKR of N3 with the formation enthalpy of VASP

[0041] Figure 1 is a formation energy map showing the relationship between the molar ratios of the three elements Sm, La, and Ce and the formation energy. In Figure 1, the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 described later are also shown (plotted).

[0042] In the formation energy map, in the region where the formation energy is small, (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase is stable. Basically, the more the substitution amount by La, that is, the value of x increases, the more unstable the (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase becomes. In the formation energy map, when a part of Sm is substituted with La or Ce, substituting with both La and Ce results in a lower formation energy than substituting with only La, that is, (Sm (1-x-y) La x Ce y )2Fe 17 It is shown that the N3 phase is stable.

[0043] Ce2Fe 17 The N3 phase is more stable than the Sm2Fe 17 N3 phase, but Ce2Fe17 If a phase more stable than the N3 phase, for example, the CeFe2 phase, has already formed, then Ce2Fe 17 Since it is difficult to form the N3 phase, it is necessary to consider the thermodynamic convex hull. Therefore, in FIG. 1, the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 described later are also shown (plotted).

[0044] Also, by first-principles calculations, the structural parameters based on the lattice constant are calculated. The structural parameters are the interatomic distances, etc. of the atoms constituting the (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase. As the method of first-principles calculation, VASP is used. Vegard's law is applied to the solid solution phase. Then, for the obtained structural parameters, a saturation magnetization map is created by AkaiKKR. FIG. 2 is a saturation magnetization map showing the relationship between the molar ratios of the three elements Sm, La, and Ce and the saturation magnetization. In FIG. 2, the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 described later are also shown (plotted).

[0045] The formation energy is related to the stability of the (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase, and the total magnetization moment is proportional to the magnetization. Therefore, from the formation energy map and the saturation magnetization map, the (Sm (1-x-y) La x Ce y )2Fe 17The relationship between the stability of the N3 phase and the saturation magnetization can be examined. These maps show that when a part of Sm is replaced with La or Ce, replacing with both La and Ce rather than only with La improves the stability and also the saturation magnetization. Although not restricted by theory, the reason for the improvement in the saturation magnetization is considered as follows. Ce has trivalent and tetravalent states, and there is a large amount of tetravalent Ce in the magnetic material of the present disclosure. In contrast, La has only the trivalent state. In the tetravalent state, magnetization is likely to disappear because the 4f electrons are not localized, but since La is trivalent and the 4f electrons are localized, it is considered that La improves the magnetization.

[0046] From what has been described so far, particularly from the descriptions of FIGS. 1 and 2, x may be 0.09 or more, 0.10 or more, 0.12 or more, 0.14 or more, or 0.16 or more, and may be 0.31 or less, 0.30 or less, 0.27 or less, 0.25 or less, 0.23 or less, 0.20 or less, or 0.17 or less.

[0047] Also, y may be 0.24 or more, 0.26 or more, 0.30 or more, 0.32 or more, or 0.34 or more, and may be 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, or 0.40 or less.

[0048] And x + y may be 0.51 or more, 0.54 or more, 0.56 or more, or 0.60 or more, and may be 0.75 or less, 0.70 or less, or 0.69 or less.

[0049] As described above, R 1 is one or more elements that allow inclusion within a range that does not impair the magnetic properties, particularly the saturation magnetization, of the magnetic material of the present disclosure. Therefore, in the first-principles calculation, the presence of R 1 is not considered. The molar ratio of such R 1 , that is, the range of z, may be 0.10 or less, 0.08 or less, 0.06 or less, 0.04 or less, or 0.02 or less. The magnetic material of the present disclosure may not contain any R 1 , that is, z may be 0, but when manufacturing the magnetic material of the present disclosure, R is present in the raw materials.1 In some cases, it may be difficult to make it contain none at all. From this perspective, z may be 0.01 or more.

[0050] 〈p and q〉 In the above formula representing the composition of the main phase, the value of p indicates the ratio (molar ratio) at which part of Fe is replaced by Co, and the value of q indicates the ratio (molar ratio) at which part of Fe is replaced by Ni.

[0051] As described above, Co and Ni are elements whose inclusion is allowed within a range where they do not have a practically problematic influence on the formation energy of the main phase. Such an allowable range is represented by the value of the sum p + q of the molar ratio p of Co and the molar ratio q of Ni. The value of such p + q may be 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less, and may be 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more. That p + q has a value of 0 means that the main phase substantially does not contain Co and Ni.

[0052] 〈s〉 In the above formula representing the composition of the main phase, s indicates the ratio (molar ratio) at which part of Fe is replaced by M. As described above, M is one or more elements and inevitable impurity elements whose inclusion is allowed within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. From this, s may be 0.10 or less, 0.08 or less, 0.06 or less, 0.04 or less, or 0.02 or less. On the other hand, the magnetic material of the present disclosure may not contain M at all, that is, s may be 0, but in some cases, it may be difficult to make it not contain any inevitable impurity elements among M. From this perspective, s may be 0.01 or more.

[0053] 〈h〉 In the above formula representing the composition of the main phase, h indicates the degree of nitridation. When the Sm2Fe 17 phase is nitrided, basically, Sm2Fe 17 N h phase (however, h = 3) is formed. Nitridation typically involves Sm2Fe 17A magnetic material precursor having a phase (hereinafter sometimes simply referred to as "precursor") is carried out by exposing it to a nitrogen gas atmosphere at a high temperature or the like. Therefore, since the degree of nitridation is different between the surface and the inside of the precursor, h can vary in the range of 2.9 to 3.1. In the precursor, a part of Sm is replaced by La, Ce, and / or R 1 The same applies when a part of Fe is replaced by Co, Ni, and / or M. That is, (Sm (1-x-y-z) La x Ce y R 1 z )2(Fe (1-p-q-s) Co p Ni q M s ) 17 When the phase is nitrided, (Sm (1-x-y-z) La x Ce y R 1 z )2(Fe (1-p-q-s) Co p Ni q M s ) 17 N h is formed.

[0054] 〈Volume ratio of main phase〉 The magnetic material of the present disclosure includes a main phase represented by the above composition formula. The magnetic properties of the magnetic material of the present disclosure are exhibited by the main phase. Therefore, for the entire magnetic material of the present disclosure, it is preferable that the volume ratio of the main phase is higher. Specifically, the volume ratio of the main phase may be 80% or more, 85% or more, or 90% or more with respect to the entire magnetic material of the present disclosure. On the other hand, when manufacturing the magnetic material of the present disclosure, there may be a process in which a phase other than the main phase represented by the above composition formula becomes a stable temperature region. Also, there may be cases where it is difficult to make the content of inevitable impurity elements that do not constitute the main phase zero. From these facts, although it is ideal for the volume ratio of the main phase to be 100%, as long as the volume ratio of the main phase described above is ensured, even if the volume ratio of the main phase is 99% or less, 97% or less, or 95% or less, there is no practical problem.

[0055] The phases other than the main phase typically exist at the grain boundaries between the main phases, particularly at the triple points. Examples of the phases other than the main phase typically include the SmFe3 phase and its nitrides. In the SmFe3 phase and its nitrides, a part of Sm is substituted with one or more elements selected from the group consisting of La, Ce, and R 1 and phases in which a part of Sm is substituted with one or more elements selected from the group consisting of La, Ce, and R and their nitrides, phases in which a part of Fe is substituted with one or more elements selected from the group consisting of Co, Ni, and M and their nitrides, and phases in which a part of Sm is substituted with one or more elements selected from the group consisting of La, Ce, and R 1 and a part of Fe is substituted with one or more elements selected from the group consisting of Co, Ni, and M, and their nitrides are included.

[0056] The volume fraction of the main phase is measured by using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for the overall composition of the magnetic material precursor before nitridation, and from the measured value, assuming that the precursor before nitridation is phase-separated into the (Sm, La, Ce, R 1 )2(Fe, Co, Ni, M) 17 phase and the (Sm, La, Ce, R 1 )(Fe, Co, Ni, M)3 phase, the volume fraction of the main phase is calculated. Specifically, after obtaining the mass concentration (mass ratio) of each element from the measurement result by ICP, first, the mass ratio of the Sm2Fe 17 phase and the SmFe3 phase is calculated, and the volume fraction is calculated from the density of each phase. Note that the (Sm, La, Ce, R 1 )2(Fe, Co, Ni, M) 17 phase includes the Sm2Fe 17 phase, a phase in which a part of Sm in the Sm2Fe 17 phase is substituted with one or more elements selected from the group consisting of Sm, La, Ce, and R 1 , a phase in which a part of Fe in the Sm2Fe 17 phase is substituted with one or more elements selected from the group consisting of Co, Ni, and M, and a phase in which a part of Sm in the Sm2Fe 17 phase is substituted with one or more elements selected from the group consisting of Sm, La, Ce, and R 1is replaced with one or more elements selected from the group consisting of, and Sm2Fe 17 represents a phase in which a part of Fe in the phase is replaced with one or more elements selected from the group consisting of Co, Ni, and M. Also, (Sm, La, Ce, R 1 )(Fe, Co, Ni, M)3 phase is a SmFe3 phase, a phase in which a part of Sm in the SmFe3 phase is replaced with one or more elements selected from the group consisting of Sm, La, Ce, and R 1 a phase in which a part of Fe in the SmFe3 phase is replaced with one or more elements selected from the group consisting of Co, Ni, and M, and a part of Sm in the SmFe3 phase is replaced with one or more elements selected from the group consisting of Sm, La, Ce, and R 1 is replaced with one or more elements selected from the group consisting of, and Sm2Fe 17 represents a phase in which a part of Fe in the phase is replaced with one or more elements selected from the group consisting of Co, Ni, and M.

[0057] The overall composition (the total of the main phase and the phases other than the main phase) of the magnetic material of the present disclosure can be set to be equal to or more than the total number of moles of Sm, La, Ce, and R in the main phase from the viewpoint of suppressing the formation of the α-(Fe, Co, Ni, M) phase and its nitrided phase during the production of the magnetic material of the present disclosure. That is, the overall composition of the magnetic material of the present disclosure is (Sm 1 La (1-x-y-z) La x Ce y R 1 z ) w (Fe (1-p-q-s) Co p Ni q M s ) 17 N h (where w is 2.00 to 3.00). At this time, x, y, z, p, q, s, and h may be the same as x, y, z, p, q, s, and h in the formula representing the composition of the above-mentioned main phase. From the viewpoint of suppressing the formation of the α-(Fe, Co, Ni, M) phase, w is more preferably 2.02 or more, 2.04 or more, 2.06 or more, 2.08 or more, 2.10 or more, 2.20 or more, 2.30 or more, 2.40 or more, or 2.50 or more. On the other hand, the above-mentioned (Sm, La, Ce, R 1)(From the perspective of reducing the volume fraction of the (Fe, Co, Ni, M)3 phase, w is more preferably 2.90 or less, 2.80 or less, 2.70 or less, or 2.60 or less.

[0058] 〈Density of the main phase〉 If the main phase of the magnetic material of the present disclosure has the crystal structure and composition described so far, there is no particular limitation on the density of the main phase. The density of the main phase is, for example, 7.38 g / cm 3 or more, 7.40 g / cm 3 or more, 7.42 g / cm 3 or more, 7.44 g / cm 3 or more, 7.46 g / cm 3 or more, 7.48 g / cm 3 or more, or 7.50 g / cm 3 or more, and may be 8.80 g / cm 3 or less, 8.60 g / cm 3 or less, 8.40 g / cm 3 or less, 8.20 g / cm 3 or less, 8.00 g / cm 3 or less, 7.80 g / cm 3 or less, or 7.60 g / cm 3 or less.

[0059] The density of the main phase is obtained by pulverizing the magnetic material of the present disclosure to obtain a powder and measuring the density of the powder by the pycnometer method. As described above, in the magnetic material of the present disclosure, the volume fraction of the main phase is preferably 80% or more. Also, the densities of the Sm2Fe 17 N3 phase and the SmFe3 phase are 7.65 g / cm 3 and 8.25 g / cm 3 respectively, and are not very different. From this, the density of the main phase can be approximated by the value obtained by the above-described measurement method.

[0060] 《Manufacturing method》 Next, the manufacturing method of the Sm-Fe-N-based magnetic material of the present disclosure (hereinafter sometimes referred to as "the manufacturing method of the present disclosure") will be described.

[0061] The manufacturing method of the present disclosure includes a magnetic material precursor preparation step and a nitriding step. Hereinafter, each step will be described.

[0062] 〈Magnetic Material Precursor Preparation Step〉 In the manufacturing method of the present disclosure, a magnetic material precursor having a crystal phase represented by the formula of molar ratio (Sm (1-x-y-z) La x Ce y R 1 z )2(Fe (1-p-q-s) Co p Ni q M s ) 17 is prepared.

[0063] In the formula representing the composition of the crystal phase, Sm, La, Ce, R 1 , Fe, Co, Ni, and M, as well as x, y, z, p, q, and s, are as described in "Magnetic Materials".

[0064] The crystal phase of the magnetic material precursor has at least one of the crystal structures of the Th2Zn 17 type and the Th2Ni 17 type. When the magnetic material precursor is nitrided, the crystal phase in the magnetic material precursor is nitrided, and the main phase of the magnetic material of the present disclosure is formed. The main phase of the Sm-Fe-N-based magnetic material of the present disclosure has at least one of the crystal structures of the Th2Zn 17 type and the Th2Ni 17 type. From this, nitriding is performed to such an extent that at least one of the crystal structures of the Th2Zn 17 type and the Th2Ni 17 type is maintained.

[0065] As described above, since the crystal phase in the magnetic material precursor is nitrided to form the main phase of the magnetic material of the present disclosure, the volume ratio of the crystal phase in the magnetic material precursor may be considered equivalent to the volume ratio of the main phase in the magnetic material of the present disclosure. From this, the volume ratio of the crystal phase of the magnetic material precursor may be 80% or more, 85% or more, or 90% or more with respect to the entire magnetic material precursor. When manufacturing the magnetic material precursor, there may be cases such as a process where a phase other than the crystal phase represented by the above composition formula becomes a stable temperature region. Also, there may be cases where it is difficult to completely eliminate the inclusion of inevitable impurity elements that do not constitute the crystal phase. Although it is ideal for the volume ratio of the crystal phase to be 100%, as long as the above-described volume ratio of the crystal phase is ensured, there is no practical problem even if the volume ratio of the main phase is 99% or less, 97% or less, or 95% or less. The calculation method of the volume ratio of the main phase is as described above.

[0066] Phases other than the crystal phase typically exist at the grain boundaries between the crystals, particularly at the triple points. Examples of phases other than the crystal phase typically include SmFe3 phases. In the SmFe3 phase, a part of Sm is replaced with one or more elements selected from the group consisting of La, Ce, and R 1 and a phase in which a part of Fe is replaced with one or more elements selected from the group consisting of Co, Ni, and M, and a phase in which a part of Sm is replaced with one or more elements selected from the group consisting of La, Ce, and R 1 and a part of Fe is replaced with one or more elements selected from the group consisting of Co, Ni, and M.

[0067] From the perspective of suppressing the formation of the α-(Fe, Co, Ni, M) phase during the production of the magnetic material precursor, the overall composition of the magnetic material precursor (the total of the crystal phase and the phases other than the crystal phase) can be set to be equal to or more than the total number of moles of Sm, La, Ce, and R in the crystal phase. That is, the overall composition of the magnetic material precursor is (Sm 1 La (1-x-y-z) Ce x R y 1 z ) w (Fe (1-p-q-s) Co p Ni q M​s ) 17 (However, w may be in the range of 2.00 to 3.00). At this time, x, y, z, p, q, and s may be the same as x, y, z, p, q, and s in the formula representing the composition of the above-mentioned main phase. From the viewpoint of suppressing the formation of the α-(Fe, Co, Ni, M) phase, w is more preferably 2.02 or more, 2.04 or more, 2.06 or more, 2.08 or more, 2.10 or more, 2.20 or more, 2.30 or more, 2.40 or more, or 2.50 or more. On the other hand, from the viewpoint of reducing the volume fraction of the (Sm, La, Ce, R 1 )(Fe, Co, Ni, M)3 phase, w is more preferably 2.90 or less, 2.80 or less, 2.70 or less, or 2.60 or less.

[0068] The magnetic material precursor can be obtained by using well-known manufacturing methods. Examples of methods for obtaining the magnetic material precursor include melting and solidifying raw materials containing the elements constituting the magnetic material precursor. Examples of methods for preparing the raw materials include charging the raw materials into a container such as a crucible, arc melting or high-frequency melting the raw materials in the container to obtain a molten metal, and then injecting the molten metal into a mold such as a book mold, or solidifying the molten metal in the crucible. From the viewpoints of suppressing the coarsening of the crystal phase and homogenizing the crystal phase in the magnetic material precursor, it is preferable to increase the cooling rate of the molten metal. From this viewpoint, it is preferable to inject the molten metal into a mold such as a book mold. Further, from the viewpoints of suppressing the coarsening of the crystal phase and enhancing the homogenization of the crystal phase in the magnetic material precursor, for example, the following method may be adopted. That is, an ingot obtained by high-frequency melting or arc melting and solidifying the raw materials in a container is melted again by high-frequency melting or the like, and the melt is rapidly cooled using a strip casting method, a liquid quenching method, or the like to obtain a thin sheet, and this thin sheet may be used as the magnetic material precursor.

[0069] Before nitriding described below, in order to homogenize the crystal grains in the magnetic material precursor, the magnetic material precursor may be heat-treated (hereinafter, such heat treatment may be referred to as "homogenization heat treatment"). The temperature of the homogenization heat treatment may be, for example, 1273 K or higher, 1323 K or higher, or 1373 K or higher, and may be 1523 K or lower, 1473 K or lower, or 1423 K or lower. The homogenization heat treatment time may be, for example, 6 hours or longer, 12 hours or longer, 18 hours or longer, or 24 hours or longer, and may be 48 hours or shorter, 42 hours or shorter, 36 hours or shorter, or 30 hours or shorter.

[0070] In order to suppress the oxidation of the magnetic material precursor, the homogenization heat treatment is preferably performed in an inert gas atmosphere. The inert gas atmosphere does not include a nitrogen gas atmosphere. When the homogenization heat treatment is performed in a nitrogen gas atmosphere, the phase having the Th2Zn 17 type and / or Th2Ni 17 type crystal structure is likely to decompose.

[0071] 〈Nitriding step〉 The above-described magnetic material precursor is nitrided. As a result, the crystal phase in the magnetic material precursor is nitrided, and the main phase of the magnetic material of the present disclosure is formed.

[0072] If a desired main phase can be obtained, there is no particular limitation on the nitriding method. Typically, for example, while heating the magnetic material precursor, exposing it to an atmosphere containing nitrogen gas, or exposing it to a gas atmosphere containing nitrogen (N), etc. can be mentioned. The atmosphere containing nitrogen gas includes, for example, a nitrogen gas atmosphere, a mixed gas atmosphere of nitrogen gas and an inert gas, and a mixed gas atmosphere of nitrogen gas and hydrogen gas, etc. The gas atmosphere containing nitrogen (N) includes, for example, an ammonia gas atmosphere, or a mixed gas atmosphere of ammonia gas and hydrogen gas, etc. The atmospheres exemplified so far may be combined. From the viewpoint of nitriding efficiency, an ammonia gas atmosphere, a mixed gas atmosphere of ammonia gas and hydrogen gas, and a mixed gas atmosphere of nitrogen gas and hydrogen gas are preferable.

[0073] Before nitriding, the magnetic material precursor may be pulverized to obtain a magnetic material precursor powder, and then the magnetic material precursor powder may be nitrided. By pulverizing the magnetic material precursor and then nitriding it, the crystal phase existing inside the magnetic material precursor can be sufficiently nitrided. The pulverization of the magnetic material precursor is preferably performed in an inert gas atmosphere. The inert gas atmosphere may include a nitrogen gas atmosphere. Thereby, oxidation of the magnetic material precursor during pulverization can be suppressed. As for the particle size of the magnetic material precursor powder, D 50 may be 5 μm or more, 10 μm or more, or 15 μm or more, and may be 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less.

[0074] The nitriding temperature may be, for example, 673 K or more, 698 K or more, 723 K or more, or 748 K or more, and may be 823 K or less, 798 K or less, or 773 K or less. Also, the nitriding time may be, for example, 4 hours or more, 8 hours or more, 12 hours or more, or 16 hours or more, and may be 48 hours or less, 36 hours or less, 24 hours or less, 20 hours or less, or 18 hours or less.

[0075] 《Modification》 The magnetic material and its manufacturing method of the present disclosure are not limited to the embodiments described so far, and within the scope described in the claims, modifications may be appropriately made. For example, the magnetic material of the present disclosure may be a powder or a molded body of the powder. The molded body may be a bonded molded body or a sintered molded body. In the case of a molded body, from the viewpoint of easily avoiding a temperature at which nitrogen (N) in the main phase dissociates (decomposes) in the molding process, a bonded molded body is preferable. Examples of the bond include resin and low melting point metal bonds. Examples of the low melting point metal bond include metallic zinc or zinc alloy and combinations thereof. When using a low melting point metal bond, pressure sintering may be performed at a low temperature at which nitrogen (N) in the main phase does not dissociate (decompose).

Example

[0076] Hereinafter, the magnetic material and its manufacturing method of the present disclosure will be described more specifically by way of examples and comparative examples. Note that the magnetic material and its manufacturing method of the present disclosure are not limited to the conditions used in the following examples.

[0077] 《Preparation of Samples》 Samples of Sm-Fe-N based magnetic materials were prepared as follows.

[0078] Metallic Sm, metallic La, Ce-Fe alloy, metallic Fe, metallic Co, and metallic Ni were blended so that the main phase had the composition shown in Table 1, and this was melted by high frequency at 1673 K (1400 °C) and solidified to obtain a magnetic material precursor. At the time of blending, the total number of moles of Sm, La, and Ce blended was made larger than the total number of moles of Sm, La, and Ce in the main phase so that the volume fraction of the main phase was 95 to 100%. Note that in this specification, for example, "metallic Sm" means unalloyed Sm. Of course, metallic Sm may contain inevitable impurities.

[0079] The magnetic material precursor was subjected to homogeneous heat treatment at 1373 K for 24 hours in an argon gas atmosphere.

[0080] The magnetic material precursor after homogeneous heat treatment was placed in a glove box and pulverized using a cutter mill in a nitrogen gas atmosphere. The particle size of the pulverized magnetic material precursor powder was D 50 and was 20 μm or less.

[0081] In a nitrogen gas atmosphere, the magnetic material precursor powder was heated to 748 K and nitrided for 16 hours. The amount of nitridation was grasped by the mass change of the magnetic material precursor powder before and after nitridation.

[0082] 《Evaluation》 For each sample, the volume fraction and density of the main phase were determined by the measurement methods described above. Also, for each sample, using a physical property processing system PPMS (registered trademark)-VSM, a maximum magnetic field of 9 T was applied, and the magnetic properties were measured. Regarding the measurement of the magnetic properties, each sample powder after nitridation was solidified while being magnetically oriented in an epoxy resin, and the magnetic properties of each solidified sample were measured at 300 K in the direction of the easy magnetization axis and the direction of the hard magnetization axis. The saturation magnetization Ms was calculated from the measured values in the direction of the easy magnetization axis using the saturation asymptote rule.

[0083] The results are shown in Table 1-1 and Table 1-2. For A to C in "Stability of the main phase" in Table 1-2, A means "good", B means "generally good", and C means "poor (the crystal structure of the main phase is destroyed)". Also, as described above, the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 in Table 1-1 and Table 1-2 were plotted in FIGS. 1 and 2.

[0084]

Table 1-1

[0085]

Table 1-2

[0086] From Table 1-1, Table 1-2, and FIGS. 1 and 2, it can be understood that for the samples of Examples 1 to 6, even when the total substitution amount of La and Ce is 0.51 or more in terms of molar ratio, the saturation magnetization is higher than that in the case where Sm is not substituted with La and Ce (Comparative Example 5). From this, it can be understood that the amount of Sm used is further reduced while improving the saturation magnetization as compared with the conventional case.

[0087] From these results, the effects of the magnetic material and its manufacturing method of the present disclosure can be confirmed.

Claims

1. Th ２ Zn １７ type and Th ２ Ni １７ comprises a main phase having a crystal structure of at least any one of the type and The main phase is represented by the molar ratio formula (Sm （１－ｘ－ｙ－ｚ） La ｘ Ce ｙ R １ ｚ )) ２ (Fe （１－ｐ－ｑ－ｓ） Co ｐ Ni ｑ M ｓ ) １７ N ｈ (where R １ is one or more rare earth elements other than Sm, La, and Ce and Zr, and M is one or more elements other than Fe, Co, Ni, and rare earth elements and inevitable impurity elements), and 0.09 ≤ x ≤ 0.31, 0.24 ≤ y ≤ 0.60, 0.51 ≤ x + y ≤ 0.75, 0 ≤ z ≤ 0.10, 0 ≤ p + q ≤ 0.10, 0 ≤ s ≤ 0.10, and 2.9 ≤ h ≤ 3.1, An Sm-Fe-N based magnetic material.

2. The Sm-Fe-N based magnetic material according to Claim 1, wherein x and y satisfy 0.16 ≤ x ≤ 0.31 and 0.24 ≤ y ≤ 0.

45.

3. The Sm-Fe-N based magnetic material according to Claim 1 or 2, wherein the volume fraction of the main phase is 80% or more and 100% or less.

4. A method for manufacturing an Sm-Fe-N based magnetic material according to Claim 1, The molar ratio formula (Sm （１－ｘ－ｙ－ｚ） La ｘ Ce ｙ R １ ｚ )) ２ (Fe （１－ｐ－ｑ－ｓ） Co ｐ Ni ｑ M ｓ )) １７ (wherein R １ is one or more rare earth elements other than Sm, La, and Ce and Zr, and M is one or more elements other than Fe, Co, Ni, and rare earth elements and inevitable impurity elements), and having a composition satisfying 0.09 ≦ x ≦ 0.31, 0.24 ≦ y ≦ 0.60, 0.51 ≦ x + y ≦ 0.75, 0 ≦ z ≦ 0.10, 0 ≦ p + q ≦ 0.10, and 0 ≦ s ≦ 0.10 to prepare a magnetic material precursor comprising a crystal phase, and, comprising nitriding the magnetic material precursor. A method for manufacturing an Sm-Fe-N based magnetic material.

5. The method for manufacturing an Sm-Fe-N based magnetic material according to Claim 4, wherein x and y satisfy 0.16 ≤ x ≤ 0.31 and 0.24 ≤ y ≤ 0.45.

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