Sm-Fe-N-based magnetic material and method for producing same

Abstract

The invention discloses an Sm-Fe-N based magnetic material and a method for manufacturing the same. Provided are: an Sm-Fe-N-based magnetic material which has improved saturation magnetization compared to conventional magnetic materials and in which the amount of Sm used is further reduced; and a method for producing the Sm-Fe-N-based magnetic material. This Sm-Fe-N-based magnetic material is provided with a main phase having a crystal structure of at least one of the Th2Zn17 type and the Th2Ni17 type, the main phase being represented by the molar ratio formula (Sm (1-x-y-z) LaxCeyR1z) 2 (Fe (1-p-q-s) CopNiqMs) 17Nh, in the formula, R1 is one or more rare earth elements other than Sm, La and Ce and Zr, and R2 is one or more rare earth elements other than Sm, La and Ce; 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 are satisfied.

Description

Technical Field

[0001] The present disclosure relates to Sm-Fe-N based magnetic materials and a method for manufacturing the same. In particular, the present disclosure relates to Sm-Fe-N based magnetic materials having a main phase with at least one crystal structure of Th2Zn 17 type and 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, Sm-Fe-N based magnetic materials having a main phase with at least one crystal structure of Th2Zn 17 type and Th2Ni 17 type (hereinafter sometimes simply referred to as "Sm-Fe-N based magnetic materials") have been studied.

[0003] The Sm-Fe-N based magnetic material has a main phase with at least one crystal structure of Th2Zn 17 type and Th2Ni 17 type. It is considered that nitrogen is introduced into the crystal phase of the Sm-Fe system in an interstitial type in such a main phase. In such a main phase, Sm is essential, but since the reserves of Sm are small, it is expected that the price of Sm will increase as the Sm-Fe-N based magnetic material becomes more widespread. Therefore, attempts have been made to reduce the amount of Sm used.

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

[0005] Prior Art Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-53187 Summary of the Invention

[0007] In the Sm-Fe-N based magnetic material disclosed in Patent Document 1, the replacement rate of La and / or Ce is at most 50%, and it is desired to further reduce the amount of Sm used.

[0008] An object of the present disclosure is to provide a Sm-Fe-N based magnetic material and a method for manufacturing the same, which have a higher saturation magnetization than before and further reduce the amount of Sm used.

[0009] The present inventors have repeatedly conducted in-depth studies to achieve the above object, and have completed the Sm-Fe-N based magnetic material and the method for manufacturing the same of the present disclosure. The Sm-Fe-N based magnetic material and the method for manufacturing the same of the present disclosure include the following aspects.

[0010] <1>A Sm-Fe-N based magnetic material, comprising a main phase having at least one of the crystal structures of the Th2Zn 17 type and Th2Ni 17 type,

[0011] The main phase is represented by 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, M is one or more elements other than Fe, Co, Ni and rare earth elements and inevitable impurity elements, and satisfies

[0012] 0.09 ≤ x ≤ 0.31,

[0013] 0.24 ≤ y ≤ 0.60,

[0014] 0.51 ≤ x + y ≤ 0.75,

[0015] 0 ≤ z ≤ 0.10,

[0016] 0 ≤ p + q ≤ 0.10,

[0017] 0 ≤ s ≤ 0.10, and

[0018] 2.9 ≤ h ≤ 3.1.

[0019] <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.

[0020] <3>The Sm-Fe-N based magnetic material according to item <1> or <2>, wherein the volume fraction of the main phase is 80% or more and 100% or less.

[0021] <4>A method for manufacturing a Sm-Fe-N based magnetic material, which is a method for manufacturing the Sm-Fe-N based magnetic material according to item <1>, comprising the following steps:

[0022] Preparing a magnetic material precursor, the magnetic material precursor having a crystalline phase, the crystalline phase having a formula in terms of molar ratio (Sm (1-x-y-z) La x Ce y R1 z )2(Fe (1-p-q-s) Co p Ni q M s ) 17 The composition represented, where R 1 is one or more rare earth elements other than Sm, La, and Ce and Zr, 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, and 0 ≤ s ≤ 0.10 are satisfied; and

[0023] Nitride the magnetic material precursor.

[0024] <5>The method for manufacturing an 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.

[0025] According to the present disclosure, it is possible to provide an Sm-Fe-N-based magnetic material and a method for manufacturing the same in which the molar ratios of Sm, La, and Ce are optimized, thereby improving the saturation magnetization intensity compared to the prior art and further reducing the amount of Sm used. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a formation energy diagram showing the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11, plotted based on the result of numerically calculating the relationship between the molar ratios of the three elements Sm, La, and Ce and the formation energy.

[0027] Figure 2 is a saturation magnetization intensity diagram showing the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11, plotted based on the result of numerically calculating the relationship between the molar ratios of the three elements Sm, La, and Ce and the saturation magnetization intensity. DETAILED DESCRIPTION

[0028] 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 according to the present disclosure 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.

[0029] Although not bound by theory, the insights obtained by the present inventors regarding the reasons for improving the saturation magnetization intensity compared to the prior art and further reducing the amount of Sm used will be described.

[0030] As an element that replaces Sm in the substitution main phase, La has been used in the past. Compared with Sm, the ionic radius of La is very large. Therefore, if a large amount of La is used to replace Sm in the main phase, it becomes difficult to maintain at least any one of the crystal structures of the Th2Zn 17 type and Th2Ni 17 type. On the other hand, compared with Sm, the ionic radius of Ce is only slightly larger. Therefore, compared with La, a large amount of Ce can be used to replace Sm in the main phase. However, when the substitution amount is very large, it becomes difficult to maintain at least any one of the crystal structures of the Th2Zn 17 type and Th2Ni 17 type. In addition, even if the main phase can maintain at least any one of the crystal structures of the Th2Zn 17 type and Th2Ni 17 type, if the substitution amount is large, the saturation magnetization will also decrease significantly.

[0031] Therefore, a detailed investigation was carried out on the influence of the molar ratios of the three elements Sm, La, and Ce on the stability and saturation magnetization of the crystal phase when nitrogen penetrates into the crystal phase having at least any one of the crystal structures of the Th2Zn 17 type and Th2Ni 17 type.

[0032] Specifically, first-principles calculations were used to calculate how the formation energy of the (Sm, La, Ce)2Fe 17 N3 phase changes according to the molar ratios of Sm, La, and Ce in the (Sm, La, Ce)2Fe 17 N3 phase. Then, for this formation energy, a regular solution approximation was used to create a formation energy map showing the relationship between the molar ratios of the three elements Sm, La, and Ce and the formation energy. In addition, the structural parameters based on the lattice constant were calculated by first-principles calculations, and for this structural parameter, a regular solution approximation formula was used to create a saturation magnetization map. 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 with a saturation magnetization higher than that of the prior art and a further reduced usage amount of Sm can be obtained.

[0033] The components of the magnetic material and its manufacturing method of the present disclosure completed based on the insights described so far will be described below.

[0034] 〈Magnetic Material〉

[0035] The magnetic material of the present disclosure includes a crystal phase having at least any one of the crystal structures of the Th2Zn 17 type and Th2Ni 17The main phase of at least any one of the crystal structures in the type. The magnetic material of the present disclosure exhibits magnetism through the main phase. The main phase will be described below.

[0036] <Crystal Structure of the Main Phase>

[0037] The main phase has Th2Zn 17 type and Th2Ni 17 type of at least any one of the crystal structures. As the crystal structure of the main phase, in addition to the aforementioned structures, it may also include a crystal structure of the TbCu7 type, etc. Furthermore, 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, X-ray diffraction analysis of the magnetic material of the present disclosure.

[0038] The phase having the above crystal structure is achieved by a combination (composition) of various elements, but the main phase of the magnetic material of the present disclosure is achieved by the following combination (composition) of elements. The composition of the main phase of the magnetic material of the present disclosure will be described below.

[0039] <Composition of the Main Phase>

[0040] The main phase has a composition represented by the formula in 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 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. M is one or more elements other than Fe, Co, Ni, and rare earth elements, and inevitable impurity elements. Furthermore, Zr is zirconium. In addition, in the above formula, for the convenience of explanation, sometimes Sm (1-x-y) La x Ce y R 1 z is called the rare earth group site, and Fe (1-p-q-s) Co p Ni q M s is called the iron group site.

[0041] As can be understood from the above formula, the main phase contains more than one element in the rare earth group site of 2 moles, more than one element in the iron group site of 17 moles, and h moles of nitrogen (N). That is, more than one element in the rare earth group site and more than one element in the iron group site are used to form a phase having the above crystal structure, and h moles of nitrogen (N) are introduced into the phase in an interstitial type. The amount of nitrogen (N) introduced is typically 3 moles, that is, h = 3, but there may be some parts in the crystal where nitrogen is not introduced. If it is h moles (however, h is 2.9 to 3.1), the above crystal structure can be maintained. Details of nitrogen (N) in the main phase will be described later.

[0042] The rare earth group site is composed of Sm, La, Ce, and R 1 and Sm, La, Ce, and R 1 exist in the ratio of (1 - x - y - z):x:y:z in terms of molar ratio respectively. 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 La, Ce, and R 1 among them.

[0043] The iron group site is composed of Fe, Co, Ni, and M, and Fe, Co, Ni, and M exist in the ratio of (1 - p - q - s):p:q:s in terms of molar ratio respectively. 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 Co, Ni, and M.

[0044] Hereinafter, each element constituting the above formula and its content ratio (molar ratio) will be described.

[0045] <sm>

[0046] Sm is a main element that, together with Fe and N, constitutes the above crystal structure. A part of Sm is replaced by one or more elements selected from La, Ce, and R 1 among others. The following describes La, Ce, and R 1 in detail.

[0047] <la>

[0048] La belongs to the so-called light rare earth elements. Compared with Sm, it has a larger reserve (resource amount) and a lower price. In addition, it is considered to be helpful in increasing the saturation magnetization intensity. However, since the ionic radius of La is very large compared with that of Sm, when a part of Sm is replaced by La, if the replacement amount is not appropriate, it becomes difficult to maintain the crystal structure of the main phase. The replacement amount will be described later.

[0049] <ce>

[0050] Ce belongs to the so-called light rare earth elements. Compared with Sm, the burial amount (resource amount) is large and the price is low. Since the ionic radius of Ce is only a little larger than that of Sm, a part of Sm can be replaced by a large amount of Ce. However, if the replacement amount is very large, it becomes difficult to maintain the crystal structure of the main phase. In addition, even if the crystal structure of the main phase can be maintained, if the replacement amount is large, the saturation magnetization intensity also decreases significantly. The replacement amount will be described later.

[0051] <R 1 >

[0052] R 1 is one or more rare earth elements other than Sm, La, and Ce, and Zr. R 1 is one or more elements that can be contained 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. Typically, R 1 is one or more rare earth elements other than Sm, La, and Ce that are difficult to be completely separated from the respective raw materials containing Sm, La, and Ce during refining and remain in small amounts in the raw materials, etc. In addition to such rare earth elements, in R 1 Zr may also be included. Although Zr is not a rare earth element, sometimes a part of Sm is replaced by Zr. Even if a part of Sm is replaced by Zr, as long as the replacement amount is small, it will not significantly impair the magnetic properties of the magnetic material of the present disclosure.

[0053] In this specification, rare earth elements include 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).

[0054] <fe>

[0055] Fe is a main element that forms the above crystal structure together with Sm and N. A part of Fe can also be replaced by one or more elements selected from Co, Ni, and M. Co, Ni, and M will be described below.

[0056] <co>

[0057] Co belongs to the so-called iron group elements, so a part of Fe can be replaced by Co. If the replacement amount is within a specified range, it will not give an influence on the formation energy of the main phase to such an extent as to become a problem in practical use. The allowable amount will be described later. If a part of Fe is replaced by Co, the Curie temperature of the main phase rises, and it is suitable because the decrease in the saturation magnetization at high temperatures (403 to 473 K) can be suppressed.

[0058] <ni>

[0059] Ni belongs to the so-called iron group elements, so part of Fe can also be replaced by Ni. If the replacement amount is within a specified range, it will not give an influence on the formation energy of the main phase to an extent that becomes a problem in practical use. The allowable amount will be described later.

[0060] <m>

[0061] 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 are allowed to be contained within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. The so-called 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 if their inclusion were to be avoided. Examples of such inevitable impurity elements include impurity elements in the raw materials or elements in a binder (such as Cu (copper), Zn (zinc), Ga (gallium), Al (aluminum), and B (boron)) that diffuse and / or penetrate into the surface of the main phase, etc., when forming a bonded molded body, etc. In addition, elements that diffuse and / or penetrate into the surface of the main phase, etc., contained in a lubricant used during molding, etc., can be cited. Furthermore, the bonded molded body will be described later.

[0062] As M excluding inevitable impurity elements, for example, one or more elements selected from Ti (titanium), Cr (chromium), Mn (manganese), V (vanadium), Mo (molybdenum), W (tungsten), and C (carbon), etc., can be cited. These elements, for example, form nucleating substances during the formation of the main phase and contribute to promoting the refinement of the main phase and / or suppressing the grain growth of the main phase.

[0063] In addition, as M, Zr can be included. As described above, Zr is not a rare earth element, but there are cases where a part of Sm is replaced by Zr, and on the other hand, there are cases where a part of Fe is replaced by Zr. In either case, if the replacement amount is small, the magnetic properties of the magnetic material will not be significantly impaired.

[0064] <n>

[0065] N is introduced into the main phase having the above crystal structure in an interstitial type. By introducing N to such an extent that the phase having the above crystal structure is not destroyed, the magnetic moment increases in the main phase. The existing ratio (molar ratio) h of N in the main phase will be described later.

[0066] When the main phase of the magnetic material of the present disclosure adopts the element composition described so far and these constituent elements are present in the following proportions, the saturation magnetization can be increased compared with the past, and the amount of Sm used can be further reduced. Hereinafter, the ranges satisfied by the existing ratios (molar ratios) of the constituent elements, that is, the values of x, y, z, p, q, s, and h in the above formula representing the composition of the main phase will be described.

[0067] <x, y, and z>

[0068] The stability of the main phase can be evaluated using the formation energy of the main phase. To perform this evaluation, a formation energy diagram showing the relationship between the molar ratios of the three elements Sm, La, and Ce and the formation energy is created.

[0069] As a first-principles calculation method, the software packages (AkaiKKR) of the coherent potential approximation (Coherent Potential Approcimation (CPA)) and the Vienna ab initio simulation package (VASP) that apply the Korringa-Kohn-Rostoker (KKR) method are used. Specifically, for each of the total 52 points when x and y of the (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase are increased by 5% each time, the formation energy of each is calculated.

[0070] For the above 52 calculation results, a formation energy diagram is created using the regular solution approximation formula. The regular solution approximation formula is as follows.

[0071] ΔE(x, y) = E RFN(x，y) -(1 - x - y)E SFN -xE LFN -yE CFN

[0072] Among them, ΔE(x, y), E RFN(x，y) , E SFN , E LFN and E CFN are as follows.

[0073] ΔE(x, y): Change in formation energy when the molar ratios of La and Ce are x and y, respectively

[0074] E RFN(x，y) : Total energy of AkaiKKR when the molar ratios of La and Ce are x and y, respectively.

[0075] E SFN : Value obtained by correcting the total energy of AkaiKKR of Sm2Fe 17 N3 with the formation enthalpy of VASP

[0076] E LFN : Value obtained by correcting the total energy of AkaiKKR of La2Fe 17 N3 with the formation enthalpy of VASP

[0077] E CFN : Value obtained by correcting the total energy of AkaiKKR of Ce2Fe 17 N3 with the formation enthalpy of VASP

[0078] Figure 1 is a formation energy diagram showing the relationship between the molar ratios of the three elements Sm, La, and Ce and the formation energy. In Figure 1 are simultaneously recorded (plotted) the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 described later.

[0079] In the formation energy diagram, 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 greater the substitution amount achieved by La, i.e., the greater the x value, the more unstable the (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase becomes. It is shown in the formation energy diagram that when a part of Sm is replaced with La or Ce, the formation energy is lower when replaced with both La and Ce than when replaced only with La, i.e., (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase is stable.

[0080] Ce2Fe 17 N3 phase is more stable than Sm2Fe 17 N3 phase, but in the case where a phase more stable than Ce2Fe 17 N3 phase, such as CeFe2 phase, has already formed, it is difficult to form Ce2Fe 17 The N3 phase, so the thermodynamic convex hull needs to be considered. Therefore, 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 (plotted) below are recorded simultaneously.

[0081] In addition, by first-principles calculations, the structural parameters based on the lattice constants are calculated. The structural parameters are the interatomic distances between the atoms of the (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase, etc. As the method of first-principles calculations, VASP is used. For the solid solution phase, Vegard's law is applied. Then, for the obtained structural parameters, a saturation magnetization intensity map is produced by AkaiKKR. Figure 2 is a saturation magnetization intensity map showing the relationship between the molar ratios of the three elements Sm, La, and Ce and the saturation magnetization intensity. In Figure 2 the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 described (depicted) below are recorded simultaneously.

[0082] 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 magnetic moment is proportional to the magnetization intensity. Therefore, it is possible to study the relationship between the stability of the (Sm (1-x-y) La x Ce y )2Fe 17 N3 phase and the saturation magnetization intensity according to the formation energy map and the saturation magnetization intensity map. These figures show that when a part of Sm is replaced with La or Ce, compared with replacement with only La, replacement with both La and Ce improves the stability and increases the saturation magnetization intensity at the same time. Although not bound by theory, the reason for the increase in saturation magnetization intensity is considered as follows. Ce has trivalent and tetravalent states, and tetravalent Ce exists in a relatively large amount in the magnetic material of the present disclosure. In contrast, La is only trivalent. It is considered that in the tetravalent state, since there are no local 4f electrons, the magnetization easily disappears, but since La is trivalent and there are local 4f electrons, the magnetization intensity is increased by La.

[0083] According to the description so far, especially Figure 1 and Figure 2 the records, x can be 0.09 or more, 0.10 or more, 0.12 or more, 0.14 or more, or 0.16 or more, and can 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.

[0084] In addition, y can be 0.24 or more, 0.26 or more, 0.30 or more, 0.32 or more, or 0.34 or more, and can be 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, or 0.40 or less.

[0085] Moreover, x + y can be 0.51 or more, 0.54 or more, 0.56 or more, or 0.60 or more, and can be 0.75 or less, 0.70 or less, or 0.69 or less.

[0086] As described above, R 1 is one or more elements that can be contained within a range that does not impair the magnetic properties of the magnetic material of the present disclosure, particularly the saturation magnetization, and thus the presence of R is not considered in the first-principles calculation. 1 The molar ratio of such R, that is, the range of z, can 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 also contain no R at all, that is, z can also be 0, but it is sometimes difficult to make the raw materials completely free of R when manufacturing the magnetic material of the present disclosure. 1 From this point of view, z can also be 0.01 or more. 1 1 1 From this perspective, z can also be 0.01 or more.

[0087]

[0088] In the above formula representing the composition of the main phase, the value of p represents the ratio (molar ratio) in which a part of Fe is replaced by Co, and the value of q represents the ratio (molar ratio) in which a part of Fe is replaced by Ni.

[0089] As described above, Co and Ni are elements that can be contained within a range that does not give an influence to the extent that it becomes a problem in practical use on the formation energy of the main phase. Such an allowable range is represented by the total value p + q of the molar ratio p of Co and the molar ratio q of Ni. The value of such p + q can 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 can be 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more. The fact that the value of p + q is 0 means that the main phase substantially does not contain Co and Ni.

[0090] <s>

[0091] In the above formula representing the composition of the main phase, s represents the ratio (molar ratio) in which a part of Fe is replaced by M. As described above, M is one or more elements and inevitable impurity elements that are allowed to be contained within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. Therefore, s can 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 also be 0, but it is sometimes difficult to completely avoid the inevitable impurity elements in M. From this point of view, s can also be 0.01 or more.

[0092] <h>

[0093] In the above formula representing the composition of the main phase, h represents the degree of nitridation. If Sm2Fe 17 phase is nitrided, Sm2Fe 17 N h phase (where h = 3) is substantially formed. Typically, nitridation is carried out by exposing a magnetic material precursor having Sm2Fe 17 phase (hereinafter sometimes simply referred to as "precursor") to a nitrogen atmosphere at a high temperature and the like. Therefore, due to differences in nitridation of the surface and interior of the precursor and the like, h may 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 , and a part of Fe is replaced by Co, Ni, and / or M. That is, if (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 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.

[0094] <Volume fraction of the main phase>

[0095] 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 manifested by the main phase. Therefore, it is preferable that the volume fraction of the main phase is high with respect to the entire magnetic material of the present disclosure. Specifically, with respect to the entire magnetic material of the present disclosure, the volume fraction of the main phase may be 80% or more, 85% or more, or 90% or more. On the other hand, when manufacturing the magnetic material of the present disclosure, there may be a process in which the temperature is in the temperature range where phases other than the main phase represented by the above composition formula are stable, and the like. In addition, there may be a case where it is difficult to completely contain no inevitable impurity elements that do not constitute the main phase. Therefore, although it is ideal that the volume fraction of the main phase is 100%, if the above volume fraction of the main phase is ensured, even if the volume fraction of the main phase is 99% or less, 97% or less, or 95% or less, there is no problem in practical use.

[0096] Phases other than the main phase typically exist at the grain boundaries between the main phases, particularly at triple points. As phases other than the main phase, typically, the SmFe3 phase and its nitrides, etc. can be cited, including phases in which a part of Sm in the SmFe3 phase is replaced by one or more elements selected from La, Ce, and R 1 and their nitrides, phases in which a part of Fe is replaced by one or more elements selected from Co, Ni, and M and their nitrides, phases in which a part of Sm is replaced by one or more elements selected from La, Ce, and R 1 and a part of Fe is replaced by one or more elements selected from Co, Ni, and M and their nitrides.

[0097] The volume fraction of the main phase is determined by using high-frequency inductively coupled plasma atomic emission spectroscopy (ICP-AES) to measure the overall composition of the magnetic material precursor before nitridation. Assuming that the precursor before nitridation is phase-separated into (Sm, La, Ce, R 1 )2(Fe, Co, Ni, M) 17 phase and (Sm, La, Ce, R 1 )(Fe, Co, Ni, M)3 phase, the volume fraction of the main phase is calculated based on the measurement values. Specifically, after obtaining the mass concentration (mass fraction) of each element from the ICP-based measurement results, first, the mass ratio of the Sm2Fe 17 phase and the SmFe3 phase is calculated, and the volume fraction is calculated based on the density of each phase. Furthermore, the (Sm, La, Ce, R 1 )2(Fe, Co, Ni, M) 17 phase represents: the Sm2Fe 17 phase, phases in which a part of Sm in the Sm2Fe 17 phase is replaced by one or more elements selected from La, Ce, and R 1 , phases in which a part of Fe in the Sm2Fe 17 phase is replaced by one or more elements selected from Co, Ni, and M, and phases in which a part of Sm in the Sm2Fe 17 phase is replaced by one or more elements selected from La, Ce, and R 1 and a part of Fe in this phase is replaced by one or more elements selected from Co, Ni, and M. In addition, the (Sm, La, Ce, R 1 )(Fe, Co, Ni, M)3 phase represents: the SmFe3 phase, phases in which a part of Sm in the SmFe3 phase is replaced by one or more elements selected from La, Ce, and R 1 A phase in which one or more of the elements therein are replaced, a phase in which a part of Fe in the SmFe3 phase is replaced by one or more of the elements selected from Co, Ni, and M, and a part of Sm in the SmFe3 phase is replaced by one or more of the elements selected from La, Ce, and R 1 and a part of Fe in this phase is replaced by one or more of the elements selected from Co, Ni, and M.

[0098] From the viewpoint of suppressing the appearance of the α-(Fe, Co, Ni, M) phase and its nitrided phase when manufacturing the magnetic material of the present disclosure, 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 the total molar number of Sm, La, Ce, and R in the main phase or more. That is, the overall composition of the magnetic material of the present disclosure can be (Sm 1 La (1-x-y-z) Ce x R y ) 1 z (Fe w Co (1-p-q-s) Ni p M q ) s N 17 (where w is 2.00 to 3.00). At this time, x, y, z, p, q, s, and h can be the same as x, y, z, p, q, s, and h in the formula representing the composition of the main phase described above. From the viewpoint of suppressing the appearance 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 h )(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. 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.

[0099] <Density of the main phase>

[0100] If the main phase of the magnetic material of the present disclosure has the crystal structure and composition described so far, the density of the main phase is not particularly limited. The density of the main phase can be, 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 Above, it can be 8.80 g / cm 3 Below, 8.60 g / cm 3 Below, 8.40 g / cm 3 Below, 8.20 g / cm 3 Below, 8.00 g / cm 3 Below, 7.80 g / cm 3 Below, or 7.60 g / cm 3 Below.

[0101] The density of the main phase is obtained by pulverizing the magnetic material of the present disclosure to obtain 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. In addition, the density of the Sm2Fe 17 N3 phase and the SmFe3 phase are 7.65 g / cm 3 and 8.25 g / cm 3 , respectively, and the difference is not significant. Therefore, the density of the main phase can be approximated by the value obtained by using the above-described measurement method.

[0102] <Manufacturing Method>

[0103] 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.

[0104] The manufacturing method of the present disclosure includes a magnetic material precursor preparation step and a nitriding step. Each step will be described below.

[0105] <Magnetic Material Precursor Preparation Step>

[0106] In the manufacturing method of the present disclosure, a magnetic material precursor having a crystalline phase is prepared, and the crystalline phase has a composition represented by 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 The composition is represented.

[0107] In the formula representing the composition of the crystalline phase, regarding Sm, La, Ce, R 1 , Fe, Co, Ni, and M, and x, y, z, p, q, and s, as described in "<Magnetic Material>".

[0108] The crystalline phase of the magnetic material precursor has at least one crystal structure of the Th2Zn 17 type and Th2Ni 17 type. If the magnetic material precursor is nitrided, the crystalline phase in the magnetic material precursor is nitrided to form the main phase of the magnetic material of the present disclosure. The main phase of the Sm-Fe-N-based magnetic material of the present disclosure has at least one crystal structure of the Th2Zn 17 type and Th2Ni 17 type. Therefore, nitriding is carried out to maintain at least one crystal structure of the Th2Zn 17 type and Th2Ni 17 type.

[0109] As described above, the crystalline phase in the magnetic material precursor is nitrided to form the main phase of the magnetic material of the present disclosure. Therefore, it can be considered that the volume fraction of the crystalline phase in the magnetic material precursor is equivalent to the volume fraction of the main phase in the magnetic material of the present disclosure. Therefore, the volume fraction of the crystalline phase of the magnetic material precursor can 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 are cases where there is a process in which the temperature is in the temperature range where a phase other than the crystalline phase represented by the above compositional formula is stable, etc. In addition, there are cases where it is difficult to completely contain no inevitable impurity elements that do not constitute the crystalline phase. Although it is ideal that the volume fraction of the crystalline phase is 100%, if the above volume fraction of the crystalline phase is ensured, even if the volume fraction of the main phase is 99% or less, 97% or less, or 95% or less, there is no problem in practical use. The calculation method of the volume fraction of the main phase is as described above.

[0110] Phases other than the crystalline phase are typically present at the grain boundaries between the crystalline phases, especially at the triple points. As phases other than the crystalline phase, typically, SmFe3 phase and the like can be cited, including phases in which a part of Sm in the SmFe3 phase is replaced by one or more elements selected from La, Ce, and R 1 and phases in which a part of Fe is replaced by one or more elements selected from Co, Ni, and M, and phases in which a part of Sm is replaced by one or more elements selected from La, Ce, and R 1 and a part of Fe is replaced by one or more elements selected from Co, Ni, and M.

[0111] The overall composition of the magnetic material precursor (the sum of the crystalline phase and the phases other than the crystalline phase) can be equal to or more than the total number of moles of Sm, La, Ce, and R of the crystalline phase from the viewpoint of suppressing the appearance of the α-(Fe, Co, Ni, M) phase when manufacturing the magnetic material precursor. That is, the overall composition of the magnetic material precursor can be (Sm 1 La (1-x-y-z) Ce x Ce y R 1 z ) w (Fe (1-p-q-s) Co p Ni q M s ) 17 (wherein, w is 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 appearance 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.

[0112] The magnetic material precursor can be obtained by using well-known manufacturing methods. As a method for obtaining the magnetic material precursor, for example, the following can be cited: melting and solidifying raw materials containing elements constituting the magnetic material precursor. As a method for preparing the raw materials, for example, the following can be cited: loading the raw materials into a container such as a crucible, melting the raw materials by arc melting or high-frequency melting in the container to obtain a melt, and then injecting the melt into a mold such as a book mold (hinge mold: book mold), or solidifying the melt in the crucible, etc. From the viewpoints of suppressing the coarsening of the crystal phase and homogenizing the crystal phase in the magnetic material precursor, etc., it is preferable to increase the cooling rate of the melt. From this viewpoint, it is preferable to inject the melt into a mold such as a book mold. In addition, from the viewpoints of suppressing the coarsening of the crystal phase and improving the homogenization of the crystal phase in the magnetic material precursor, etc., for example, the following method can also be adopted. That is, it is also possible to: melt and solidify the raw materials by high-frequency melting or arc melting in a container to obtain an ingot, remelt the ingot by high-frequency melting, etc., and rapidly cool the melt using a strip casting method and a liquid quenching method, etc., to obtain a thin sheet, and use this thin sheet as the magnetic material precursor.

[0113] Before the nitridation 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 sometimes be referred to as "homogenization heat treatment"). The temperature of the homogenization heat treatment can be, for example, 1273 K or higher, 1323 K or higher, or 1373 K or higher, and can be 1523 K or lower, 1473 K or lower, or 1423 K or lower. The homogenization heat treatment time can be, for example, 6 hours or longer, 12 hours or longer, 18 hours or longer, or 24 hours or longer, and can be 48 hours or shorter, 42 hours or shorter, 36 hours or shorter, or 30 hours or shorter.

[0114] In order to suppress the oxidation of the magnetic material precursor, the homogenization heat treatment is preferably carried out in an inert gas atmosphere. This inert gas atmosphere does not include a nitrogen atmosphere. This is because if the homogenization heat treatment is carried out in a nitrogen atmosphere, the phase having a Th2Zn 17 type and / or Th2Ni 17 type crystal structure is likely to decompose.

[0115] <Nitridation process>

[0116] The above-mentioned magnetic material precursor is nitrided. As a result, the crystalline phase in the magnetic material precursor is nitrided to form the main phase of the magnetic material of the present disclosure.

[0117] As long as the desired main phase can be obtained, there is no particular limitation on the nitridation method. However, as a typical example, it can be cited: heating the magnetic material precursor while exposing it to an atmosphere containing nitrogen, or exposing it to a gas atmosphere containing nitrogen (N), etc. As an atmosphere containing nitrogen, for example, a nitrogen atmosphere, a mixed gas atmosphere of nitrogen and an inert gas, a mixed gas atmosphere of nitrogen and hydrogen, etc. can be cited. As a gas atmosphere containing nitrogen (N), for example, an ammonia atmosphere, or a mixed gas atmosphere of ammonia and hydrogen, etc. can be cited. The atmospheres exemplified so far can also be combined. From the viewpoint of nitridation efficiency, an ammonia atmosphere, a mixed gas atmosphere of ammonia and hydrogen, and a mixed gas atmosphere of nitrogen and hydrogen are preferred.

[0118] It is also possible to: pulverize the magnetic material precursor before nitridation to obtain a magnetic material precursor powder, and then nitride the magnetic material precursor powder. By nitriding after pulverizing the magnetic material precursor, the crystalline phase existing inside the magnetic material precursor can be sufficiently nitrided. The pulverization of the magnetic material precursor is preferably carried out in an inert gas atmosphere. This inert gas atmosphere may also include a nitrogen atmosphere. Thus, oxidation of the magnetic material precursor can be suppressed during pulverization. As the particle size of the magnetic material precursor powder, in terms of D 50 The gauge can be 5 μm or more, 10 μm or more, or 15 μm or more, and can be 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less.

[0119] The nitriding temperature can be, for example, 673 K or more, 698 K or more, 723 K or more, or 748 K or more, and can be 823 K or less, 798 K or less, or 773 K or less. Additionally, the nitriding time can be, for example, 4 hours or more, 8 hours or more, 12 hours or more, or 16 hours or more, and can be 48 hours or less, 36 hours or less, 24 hours or less, 20 hours or less, or 18 hours or less.

[0120] <Modification>

[0121] The magnetic material and its manufacturing method of the present disclosure are not limited to the embodiments described so far, and can also be appropriately modified within the scope described in the claims. For example, the magnetic material of the present disclosure can be powder or a molded body of the powder. The molded body can be a bonded molded body or a sintered molded body. In the case of a molded body, from the viewpoint of easily avoiding the temperature at which nitrogen (N) in the main phase dissociates (decomposes) during the molding process, a bonded molded body is preferred. Examples of the binder include resins and low-melting-point metal binders. Examples of the low-melting-point metal binder include metallic zinc or zinc alloys and their combinations. When using a low-melting-point metal binder, pressure sintering can also be performed at a low temperature at which nitrogen (N) in the main phase does not dissociate (decompose).

[0122] Examples

[0123] Hereinafter, the magnetic material and its manufacturing method of the present disclosure will be described more specifically through examples and comparative examples. Furthermore, the magnetic material and its manufacturing method of the present disclosure are not limited by the conditions used in the following examples.

[0124] <Preparation of Samples>

[0125] Samples of the Sm-Fe-N-based magnetic material were prepared according to the following procedure.

[0126] Metallic Sm, metallic La, Ce-Fe alloy, metallic Fe, metallic Co, and metallic Ni were mixed in such a way that the main phase had the composition shown in Table 1, and the mixture was melted by high-frequency heating at 1673 K (1400 °C) and then solidified to obtain a magnetic material precursor. When mixing, the total molar number of Sm, La, and Ce in the mixture was made to be more than the total molar number of Sm, La, and Ce in the main phase so that the volume fraction of the main phase was 95 - 100%. Furthermore, in this specification, for example, "metallic Sm" means Sm that is not alloyed. Of course, metallic Sm may contain inevitable impurities.

[0127] The magnetic material precursor is homogenized and heat-treated in an argon atmosphere at 1373 K for 24 hours.

[0128] The homogenized and heat-treated magnetic material precursor is placed in a glove box and pulverized using a cutter mill in a nitrogen atmosphere. The particle size of the pulverized magnetic material precursor powder is 20 μm or less in terms of D 50 as measured.

[0129] The magnetic material precursor powder is heated to 748 K in a nitrogen atmosphere and nitrided for 16 hours. The amount of nitridation is determined by the change in mass of the magnetic material precursor powder before and after nitridation.

[0130] <Evaluation>

[0131] For each specimen, the volume fraction and density of the main phase are determined by the above-described measurement method. In addition, for each specimen, the magnetic properties are measured using a Physical Property Measurement System PPMS (registered trademark)-VSM by applying a maximum magnetic field of 9 T. Regarding the measurement of magnetic properties, the powder of each nitrided specimen is magnetically oriented in epoxy resin and cured, and the magnetic properties of the cured specimens are measured at 300 K in the direction of the easy magnetization axis and the hard magnetization axis. Based on the measured values in the direction of the easy magnetization axis, the saturation magnetization Ms is calculated using the approach-to-saturation law.

[0132] The results are shown in Tables 1-1 and 1-2. Regarding A to C in "Stability of the Main Phase" in Table 1-2, A means "good", B means "substantially good", and C means "poor (the crystal structure of the main phase is destroyed)". In addition, 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 Tables 1-1 and 1-2 are plotted in Figure 1 and Figure 2 as well.

[0133] Table 1-1

[0134]

[0135] Table 1--2

[0136]

[0137] From Tables 1-1 and 1-2 and Figure 1 and Figure 2 It can be understood that: in the specimens 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 by La and Ce (Comparative Example 5). From this, it can be understood that: compared with the prior art, the saturation magnetization is increased and the usage amount of Sm is further reduced.

[0138] From these results, the effects of the magnetic material and the method for manufacturing the same according to the present disclosure can be confirmed.< / h> < / s> < / n> < / m> < / ni> < / co> < / fe> < / ce> < / la> < / sm>

Claims

1. A Sm-Fe-N magnetic material having Th2Zn 17 Type and Th2Ni 17 The main phase of at least one crystal structure of the type, 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 In other words, R 1 is one or more rare earth elements other than Sm, La and Ce and Zr, M is one or more elements other than Fe, Co, Ni and rare earth elements and inevitable impurity elements, and satisfies 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。 2. The Sm-Fe-N based magnetic material according to claim 1, The x and the 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, The volume fraction of the main phase is 80% or more and 100% or less.

4. A method for producing a Sm-Fe-N magnetic material, comprising the following steps: A magnetic material precursor is prepared, wherein the magnetic material precursor has a crystalline phase having a 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 Represents the composition, where R 1 is one or more rare earth elements other than Sm, La and Ce, and Zr, M is one or more elements other than Fe, Co, Ni and rare earth elements, and unavoidable impurity elements, and satisfies 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; and The magnetic material precursor is nitrided. 5 . The method for producing a 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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