Sm-Fe-N based magnetic material and its manufacturing method

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 producing the same. 17 Type and Th2Ni 17 The present invention relates to an Sm-Fe-N based magnetic material having a main phase with at least one of the following crystal structures, and a method for producing the same. [Background technology]

[0002] Sm-Co and Nd-Fe-B magnetic materials have been put to practical use as high-performance magnetic materials, but in recent years, other magnetic materials have been investigated. For example, Th2Zn 17 Type and Th2Ni 17 Sm-Fe-N based magnetic materials (hereinafter sometimes simply referred to as "Sm-Fe-N based magnetic materials") having a main phase with at least one of the following crystal structures have been investigated.

[0003] Sm-Fe-N magnetic materials are Th2Zn 17 Type and Th2Ni 17 The magnetic material has a main phase with at least one of the following crystal structures. This main phase is believed to be formed by nitrogen being interstitially incorporated into a Sm-Fe-based crystal phase. Sm is essential for this main phase, but since Sm reserves are scarce, it is expected that the price of Sm will rise as Sm-Fe-N-based magnetic materials become more widespread. For this reason, attempts have 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 substituted with inexpensive La and / or Ce. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-53187 Summary of the Invention [Problem 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 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 saturation magnetization compared to conventional materials, and a method for producing the same. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to achieve the above object and have completed the Sm-Fe-N based magnetic material and its manufacturing method according to the present disclosure. The Sm-Fe-N based magnetic material and its manufacturing method according to the present disclosure include the following aspects. <1> Th2Zn 17 Type and Th2Ni 17 The present invention has a main phase having at least one of the following crystal structures: The main phase is a mixture of 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 (However, 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 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 Satisfying 2.9≦h≦3.1 Sm-Fe-N magnetic material. <2> The Sm—Fe—N based magnetic material according to <1>, wherein the 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 <1> or <2>, wherein the volume fraction of the main phase is 80% or more and 100% or less. <4> A method for producing the Sm-Fe-N based magnetic material according to <1>, 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 (However, R 1 preparing a magnetic material precursor having a crystalline phase having a composition expressed by the formula (x, y, y) where x 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 the formula (x, y, y) 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; nitriding the magnetic material precursor; A method for producing an Sm-Fe-N based magnetic material, comprising: <5> The method for producing an Sm—Fe—N based magnetic material according to <4>, wherein the x and y satisfy 0.16≦x≦0.31 and 0.24≦y≦0.45. [Effects of the Invention]

[0009] According to the present disclosure, by optimizing the molar ratio of Sm, La, and Ce, it is possible to provide an Sm-Fe-N based magnetic material and a method for producing the same, in which the amount of Sm used is further reduced while improving saturation magnetization compared to conventional materials. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a formation energy map in which the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 are plotted against the results of numerical calculations of the relationship between the molar ratios of the three elements Sm, La, and Ce and the formation energy. [Figure 2] FIG. 2 is a saturation magnetization map in which the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 are plotted against the results of numerical calculations of the relationship between the molar ratios of the three elements Sm, La, and Ce and the saturation magnetization. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the Sm-Fe-N magnetic material of the present disclosure (hereinafter, sometimes simply referred to as the "magnetic material of the present disclosure") and its manufacturing method will be described in detail. The magnetic material of the present disclosure and its manufacturing method are not limited to the embodiments described below.

[0012] Without being bound by theory, the findings of the present inventors regarding the reason why the amount of Sm used has been further reduced while improving saturation magnetization compared to conventional methods will be described.

[0013] La has been used as an element to substitute for Sm in the main phase. Compared to Sm, the ionic radius of La is much larger, so if a large amount of La is substituted for Sm in the main phase, the main phase becomes Th2Zn 17 Type and Th2Ni 17 On the other hand, since the ionic radius of Ce is only slightly larger than that of Sm, a larger amount of Ce can be substituted for Sm in the main phase than for La. However, if the amount of substitution is too large, the main phase may become a ThZn 17 Type and Th2Ni 17 It becomes difficult to maintain at least one of the crystal structures of the two types. 17 Type and Th2Ni 17 Even if at least one of the crystal structures can be maintained, if the amount of substitution is large, the saturation magnetization will be significantly reduced.

[0014] So, Th2Zn 17 Type and Th2Ni 17 When nitrogen is introduced into a crystalline phase having at least one of the following crystal structures, we have closely investigated the effect of the molar ratio of the three elements Sm, La, and Ce on the stability and saturation magnetization of the crystalline phase.

[0015] Specifically, using first-principles calculations, (Sm, La, Ce)2Fe 17 Depending on the molar ratio of Sm, La, and Ce in the N3 phase, (Sm, La, Ce)2Fe 17 The change in the formation energy of the N3 phase is calculated. Then, for that formation energy, a formation energy map showing the relationship between the molar ratio of the three elements Sm, La, and Ce and the formation energy is created using a regular solution approximation. Furthermore, structural parameters based on the lattice constants are calculated using first-principles calculations, and a saturation magnetization map is created for those structural parameters using a regular solution approximation. As a result, the present inventors discovered that by optimizing the molar ratio of Sm, La, and Ce, an Sm-Fe-N based magnetic material can be obtained that uses even less Sm while improving saturation magnetization compared to conventional materials.

[0016] The constituent elements of the magnetic material and the manufacturing method thereof according to the present disclosure, which have been completed based on the findings and the like described above, will now be described.

[0017] 《Magnetic materials》 The magnetic material of the present disclosure is Th2Zn 17 Type and Th2Ni 17 The magnetic material of the present disclosure exhibits magnetism due to the main phase. The main phase will be described below.

[0018] <Crystal structure of the main phase> The main phase is Th2Zn 17 Type and Th2Ni 17The main phase has at least one of the following crystal structures. In addition to the above structures, the crystal structure of the main phase may include a TbCu7-type crystal structure. 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 subjecting the magnetic material of the present disclosure to, for example, X-ray diffraction analysis.

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

[0020] <Composition of the main phase> 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 the above composition formula, Sm is samarium, La is lanthanum, Ce is cerium, Fe is iron, Co is cobalt, and Ni is nickel. 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 unavoidable impurity elements. Zr is zirconium. In the above formula, for the sake of convenience, Sm (1-x-y) La x Ce y R 1 z rare earth site, Fe (1-p-q-s) Co p Ni q M s are sometimes called iron group sites.

[0021] As can be seen 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, one or more elements in the rare earth site and one or more elements in the iron group site constitute a phase having the above-mentioned crystal structure, and h moles of nitrogen (N) are interstitially incorporated into this phase. The amount of nitrogen (N) incorporated is typically 3 moles, i.e., h = 3, but there may be partial sites in the crystal where no nitrogen is incorporated. As long as the amount is h moles (where h is 2.9 to 3.1), the above-mentioned crystal structure can be maintained. Details of nitrogen (N) in the main phase will be described later.

[0022] The rare earth sites are Sm, La, Ce, and R 1 Sm, La, Ce, and R 1 Each of them exists in a molar ratio of (1-xyz):x:y:z. Since (1-xyz)+x+y+z=1, a part of Sm is present in La, Ce, and R. 1 It means that the group is substituted with one or more elements selected from the group consisting of:

[0023] The iron group site consists of Fe, Co, Ni, and M, and Fe, Co, Ni, and M are present in a molar ratio of (1-pqs):p:q:s. Since (1-pqs)+p+q+s=1, this means that part of Fe is substituted with one or more elements selected from the group consisting of Co, Ni, and M.

[0024] The elements constituting the above formula and their content ratios (molar ratios) will be explained below.

[0025] <Sm> Sm is a major element that constitutes the above-mentioned crystal structure together with Fe and N. A part of Sm is mixed with La, Ce, and R. 1 Hereinafter, La, Ce, and R are substituted with one or more elements selected from the group consisting of 1 This article explains:

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

[0027] <Ce> Ce belongs to the so-called light rare earth elements, and is abundant in reserves (resources) and inexpensive compared to Sm. Because the ionic radius of Ce is only slightly larger than that of Sm, it is possible to substitute a large amount of Ce for a portion of the Sm. However, if the substitution amount is too large, it becomes difficult to maintain the crystal structure of the main phase. Furthermore, even if the crystal structure of the main phase can be maintained, if the substitution amount is too large, the saturation magnetization will decrease significantly. The substitution amount will be discussed later.

[0028] <R 1 〉 R 1 is one or more rare earth elements other than Sm, La, and Ce, and Zr. 1 R represents one or more elements that may be contained within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. The allowable amount will be described later. 1 Typically, when refining raw materials containing Sm, La, and Ce, it is difficult to completely separate them from the raw materials, and a small amount of rare earth elements other than Sm, La, and Ce remains in the raw materials. 1 The Sm may contain Zr. Although Zr is not a rare earth element, a portion of the Sm may be substituted with Zr. Even if a portion of the Sm is substituted with Zr, as long as the amount of substitution is small, the magnetic properties of the magnetic material of the present disclosure will not be significantly impaired.

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

[0030] <Fe> Fe is a main element that constitutes the above-mentioned crystal structure together with Sm and N. A portion 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 explained below.

[0031] <Co> Since Co belongs to the so-called iron group of elements, a portion of Fe may be substituted with Co. As long as the amount of substitution is within a predetermined range, it does not affect the formation energy of the main phase to an extent that would cause practical problems. The allowable amount will be described later. Substituting a portion of Fe with Co is advantageous because it increases the Curie temperature of the main phase and can suppress a decrease in saturation magnetization at high temperatures (403 to 473 K).

[0032] 〈Ni〉 Since Ni belongs to the so-called iron group elements, a part of Fe may be substituted with Ni. As long as the substitution amount is within a predetermined range, it does not affect the formation energy of the main phase to a degree that causes practical problems. The allowable amount will be described later.

[0033] <M> M represents one or more elements other than Fe, Co, Ni, and rare earth elements, as well as unavoidable impurity elements. M represents one or more elements and unavoidable impurity elements whose inclusion is permitted to the extent that it does not impair the magnetic properties of the magnetic material of the present disclosure. An unavoidable impurity element refers to an impurity element whose inclusion cannot be avoided during the production, etc., of the magnetic material of the present disclosure, or whose avoidance would result in a significant increase in production costs. Examples of such unavoidable impurity elements include impurity elements in raw materials, and elements in the bond that diffuse and / or penetrate into the surface of the main phase when forming a bonded compact, such as Cu (copper), Zn (zinc), Ga (gallium), Al (aluminum), and B (boron). Other examples include elements contained in lubricants used during molding that diffuse and / or penetrate into the surface of the main phase. Bonded compacts will be described later.

[0034] Examples of M excluding unavoidable 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 form nuclei during main phase generation, contributing to the promotion of refinement of the main phase and / or the suppression of grain growth of the main phase.

[0035] Furthermore, Zr may be included as M. As mentioned above, Zr is not a rare earth element, but a portion of Sm may be substituted with Zr, or a portion of Fe may be substituted with Zr. In either case, as long as the amount of substitution is small, the magnetic properties of the magnetic material are not significantly impaired.

[0036] <N> N is introduced interstitially into the main phase having the above-mentioned crystal structure. By introducing N to an extent that does not destroy the phase having the above-mentioned crystal structure, the magnetic moment in the main phase increases. 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 above and these constituent elements are present in the following proportions, the amount of Sm used can be further reduced while improving the saturation magnetization compared to conventional materials. Below, we will explain the ranges that satisfy the abundance ratios (molar ratios) of the constituent elements, i.e., the values ​​of x, y, z, p, q, s, and h in the above formula that represent the composition of the main phase.

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

[0039] For the first-principles calculations, we use the package (AkaiKKR) that applies the coherent potential approximation (CPA) of the Korringa-Kohn-Rostoker (KKR) method and the Vienna ab initio simulation package (VASP). Specifically, (Sm (1-x-y) La x Ce y )2Fe 17 The formation energy is calculated for a total of 52 points when x and y of the N3 phase are increased by 5% each.

[0040] A formation energy map is created for the 52 calculation results described above using the regular solution approximation formula, which is as follows: ΔE(x, y)=E RFN(x、y) -(1-xy)E SFN -xE LFN -yE CFN where ΔE(x, y), E RFN(x、y) , E SFN , E LFN , and E CFN is as follows: ΔE(x, y): The change in formation energy when the molar ratio of La and Ce is x and y. E RFN(x、y) : Total energy of Akai KKR when the molar ratio of La and Ce is x, y E SFN :SmFe 17 Total energy of AkaiKKR of N3 corrected by the enthalpy of formation of VASP E LFN :La2Fe 17 Total energy of AkaiKKR of N3 corrected by the enthalpy of formation of VASP E CFN :Ce2Fe 17 Total energy of AkaiKKR of N3 corrected by the enthalpy of formation of VASP

[0041] Fig. 1 is a formation energy map showing the relationship between the molar ratio of the three elements Sm, La, and Ce and the formation energy, in which the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11 described below are plotted.

[0042] In the formation energy map, in the region with low formation energy, (Sm (1-x-y) La x Ce y )2Fe 17 The N3 phase is stabilized. Basically, the more the amount of La substituted, that is, the value of x, increases, the more the (Sm (1-x-y) La x Ce y )2Fe 17 The formation energy map shows that when substituting part of Sm with La or Ce, the formation energy is lower when both La and Ce are substituted than when only La is substituted, i.e., (Sm (1-x-y) La x Ce y )2Fe 17 The N3 phase has been shown to be stable.

[0043] Ce2Fe 17 The N3 phase is Sm2Fe 17 Although it is more stable than the N3 phase, Ce2Fe17 If a phase more stable than the N3 phase, such as the CeFe2 phase, has already formed, then Ce2Fe 17 Since the formation of the N3 phase is difficult, the thermodynamic convex hull must be taken into consideration. For this reason, the molar ratios of the three elements Sm, La, and Ce in Examples 1 to 6 and Comparative Examples 1 to 11, which will be described later, are plotted in Figure 1.

[0044] In addition, structural parameters based on the lattice constants are calculated by first-principles calculations. The structural parameters are (Sm (1-x-y) La x Ce y )2Fe 17 These include the interatomic distances of the atoms constituting the N3 phase. VASP is used as the first-principles calculation method. Vegard's law is applied to the solid solution phase. A saturation magnetization map is then created using Akai KKR for the obtained structural parameters. Figure 2 is a saturation magnetization map showing the relationship between the molar ratio of the three elements Sm, La, and Ce and the saturation magnetization. Figure 2 also plots the molar ratios of the three elements Sm, La, and Ce for Examples 1 to 6 and Comparative Examples 1 to 11, which will be described later.

[0045] The formation energy is (Sm (1-x-y) La x Ce y )2Fe 17 The total magnetization moment is proportional to the magnetization, which is related to the stability of the N3 phase. Therefore, the formation energy map and saturation magnetization map show that (Sm (1-x-y) La x Ce y )2Fe 17The relationship between the stability of the N3 phase and saturation magnetization can be examined. These maps show that when substituting part of Sm with La or Ce, substitution with both La and Ce improves both stability and saturation magnetization compared to substitution with La alone. Without being bound by theory, the reason for the improvement in saturation magnetization is thought to be as follows. Ce exists in trivalent and tetravalent forms, and the magnetic material of the present disclosure contains a large amount of tetravalent Ce. In contrast, La is only trivalent. In tetravalent forms, magnetization is easily lost because 4f electrons are not localized, but La is trivalent and has 4f electrons localized, so it is thought that La improves magnetization.

[0046] From what has been explained so far, particularly from the description 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] Furthermore, 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 mentioned above, R 1 is one or more elements that can be contained 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, R 1 It does not take into account the existence of such R 1 The molar ratio of R, i.e., 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. 1 In other words, z may be 0. However, when producing the magnetic material of the present disclosure, the raw material may contain R1 It may be difficult to completely eliminate the inclusion of z. From this viewpoint, z may be 0.01 or more.

[0050] In the above formula representing the composition of the main phase, the value of p indicates the proportion (molar ratio) of Fe partially substituted with Co, and the value of q indicates the proportion (molar ratio) of Fe partially substituted with Ni.

[0051] As described above, Co and Ni are elements whose inclusion is permitted to a degree that does not affect the formation energy of the main phase to a practically problematic extent. This permissible range is expressed as the sum (p + q) of the molar ratio p of Co and the molar ratio q of Ni. The value of 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, or 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more. A value of p + q of 0 means that the main phase substantially does not contain Co or Ni.

[0052] 〈s〉 In the above formula representing the composition of the main phase, s represents the proportion (molar ratio) of Fe substituted with M. As described above, M represents one or more elements and unavoidable impurity elements that are permitted to be contained within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. Therefore, 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 contain no M at all, i.e., s may be 0, but it may be difficult to completely eliminate the unavoidable impurity elements in M. From this perspective, s may be 0.01 or more.

[0053] <h> In the above formula that represents the composition of the main phase, h indicates the degree of nitriding. 17 Nitriding the phase basically results in Sm2Fe 17 N h phase (where h=3). Nitriding is typically performed using the SmFe 17This is done by exposing a magnetic material precursor (hereinafter simply referred to as "precursor") having a nitriding phase to a nitrogen gas atmosphere at high temperature. Therefore, the degree of nitriding differs between the surface and the interior of the precursor, and h can vary within the range of 2.9 to 3.1. In the precursor, part of Sm is replaced by La, Ce, and / or R. 1 The same applies when Fe is substituted with 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 Form.

[0054] <Volume ratio of main phase> The magnetic material of the present disclosure comprises a main phase represented by the above-described compositional formula. The magnetic properties of the magnetic material of the present disclosure are expressed by the main phase. Therefore, a high volume fraction of the main phase relative to the entire magnetic material of the present disclosure is preferable. Specifically, the volume fraction of the main phase may be 80% or more, 85% or more, or 90% or more relative 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 temperature range in which phases other than the main phase represented by the above-described compositional formula are stable is present. In addition, it may be difficult to completely eliminate the inclusion of unavoidable impurity elements that do not constitute the main phase. For these reasons, while a volume fraction of the main phase of 100% is ideal, as long as the volume fraction of the main phase described above is ensured, a volume fraction of the main phase of 99% or less, 97% or less, or 95% or less is not a practical problem.

[0055] Phases other than the main phase typically exist at grain boundaries between the main phases, particularly at triple points. Typical examples of phases other than the main phase include the SmFe3 phase and its nitride phase. In the SmFe3 phase and its nitride phase, part of the Sm is replaced by La, Ce, and R. 1 a phase in which part of Fe is substituted with one or more elements selected from the group consisting of Co, Ni, and M, and a nitride phase thereof; a phase in which part of Sm is substituted with one or more elements selected from the group consisting of La, Ce, and R 1 and a phase in which part of Fe is substituted with one or more elements selected from the group consisting of Co, Ni, and M, and nitride phases thereof.

[0056] The volume fraction of the main phase was determined by measuring the overall composition of the magnetic material precursor before nitriding using inductively coupled plasma atomic emission spectroscopy (ICP-AES). From the measured value, it was determined that the precursor before nitriding contained the following elements: Sm, La, Ce, R 1 )2(Fe, Co, Ni, M) 17 phase and (Sm, La, Ce, R 1 ) (Fe, Co, Ni, M) 3 phase separation is assumed, and the volume fraction of the main phase is calculated. Specifically, after obtaining the mass concentration (mass fraction) of each element from the ICP measurement results, SmFe 17 The mass ratio of the SmFe3 phase and the SmFe3 phase is first calculated, and then the volume fraction is calculated from the density of each phase. 1 )2(Fe, Co, Ni, M) 17 The phase is SmFe 17 phase, Sm2Fe 17 Part of the Sm in the phase is Sm, La, Ce, and R 1 a phase substituted with one or more elements selected from the group consisting of SmFe 17 A phase in which part of the Fe in the phase is substituted with one or more elements selected from the group consisting of Co, Ni, and M, and SmFe 17 Part of the Sm in the phase is Sm, La, Ce, and R 1and is substituted with one or more elements selected from the group consisting of SmFe 17 It represents a phase in which a part of the Fe in the phase is substituted 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, in which part of the Sm in the SmFe3 phase is Sm, La, Ce, and R 1 a phase in which part of the Fe in the SmFe3 phase is substituted with one or more elements selected from the group consisting of Co, Ni, and M; and a phase in which part of the Sm in the SmFe3 phase is substituted with Sm, La, Ce, and R. 1 and is substituted with one or more elements selected from the group consisting of SmFe 17 The term "Fe phase" refers to a phase in which part of the Fe is substituted with one or more elements selected from the group consisting of Co, Ni, and M.

[0057] The overall composition of the magnetic material of the present disclosure (the sum of the main phase and phases other than the main phase) is such that, from the viewpoint of suppressing the appearance of the α-(Fe, Co, Ni, M) phase and its nitride phase during the production of the magnetic material of the present disclosure, the Sm, La, Ce, and R of the main phase are 1 That is, the overall composition of the magnetic material of the present disclosure can be set to a total mole number of (Sm (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 (wherein w is 2.00 to 3.00). In this case, 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 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, when the above-mentioned (Sm, La, Ce, R 1From the viewpoint 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> As long as the main phase of the magnetic material of the present disclosure has the crystal structure and composition described above, 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 More than 7.40g / cm 3 Above, 7.42g / cm 3 Above, 7.44g / cm 3 More than 7.46g / cm 3 Above, 7.48g / cm 3 or more, or 7.50 g / cm 3 may be equal to or greater than 8.80 g / cm 3 Below, 8.60g / cm 3 Below, 8.40g / cm 3 Below, 8.20g / cm 3 Below 8.00g / cm 3 Below, 7.80g / cm 3 or less, or 7.60 g / cm 3 It may be the following:

[0059] The density of the main phase can be obtained by pulverizing the magnetic material of the present disclosure to obtain a powder and measuring the density of the powder by a pycnometer method. As described above, in the magnetic material of the present disclosure, it is preferable that the volume fraction of the main phase is 80% or more. In addition, SmFe 17 The densities of the N3 and SmFe3 phases are 7.65 g / cm 3 and 8.25 g / cm 3 This means that the density of the main phase can be approximated by the value obtained by the above-mentioned measurement method.

[0060] 《Manufacturing method》 Next, a method for producing the Sm—Fe—N based magnetic material of the present disclosure (hereinafter sometimes referred to as the “production 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. Each step will be described below.

[0062] <Magnetic material precursor preparation process> In the manufacturing method of the present disclosure, 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 A magnetic material precursor having a crystalline phase with a composition represented by the following formula is prepared.

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

[0064] The crystalline phase of the magnetic material precursor is Th2Zn 17 Type and Th2Ni 17 The magnetic material precursor has at least one of the following crystal structures. When the magnetic material precursor is nitrided, the crystalline 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 is Th2Zn 17 Type and Th2Ni 17 The nitriding has at least one of the following crystal structures: Th2Zn 17 Type and Th2Ni 17 This is done to such an extent that the crystal structure of at least one of the types is maintained.

[0065] 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, the volume fraction of the crystalline phase in the magnetic material precursor can be considered to be 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 in the magnetic material precursor may be 80% or more, 85% or more, or 90% or more relative to the entire magnetic material precursor. When producing the magnetic material precursor, there may be a process in which a temperature range exists in which phases other than the crystalline phase represented by the above-mentioned composition formula are stable. It may also be difficult to completely eliminate the inclusion of unavoidable impurity elements that do not constitute the crystalline phase. While a crystalline phase volume fraction of 100% is ideal, as long as the volume fraction of the crystalline phase described above is maintained, a main phase volume fraction of 99% or less, 97% or less, or 95% or less is not a practical problem. The method for calculating the main phase volume fraction is as described above.

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

[0067] The overall composition of the magnetic material precursor (the sum of the crystalline phase and the phases other than the crystalline phase) is determined by the following factors: Sm, La, Ce, and R in the crystalline phase from the viewpoint of suppressing the appearance of the α-(Fe, Co, Ni, M) phase during the production of the magnetic material precursor. 1 In other words, the overall composition of the magnetic material precursor can be set to be equal to or greater than the total number of moles of (Sm (1-x-y-z) La x Ce y R 1 z ) w (Fe (1-p-q-s) Co p Ni q Ms ) 17 (wherein w is 2.00 to 3.00). In this case, 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 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, when the (Sm, La, Ce, R 1 From the viewpoint 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.

[0068] The magnetic material precursor can be obtained using a well-known manufacturing method. Examples of methods for obtaining the magnetic material precursor include melting and solidifying raw materials containing the elements that constitute the magnetic material precursor. Examples of methods for preparing the raw materials include loading 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 pouring the molten metal into a mold such as a book mold, or solidifying the molten metal in the crucible. From the viewpoints of suppressing coarsening of the crystalline phase in the magnetic material precursor and homogenizing the crystalline phase, it is preferable to increase the cooling rate of the molten metal. From this viewpoint, it is preferable to pour the molten metal into a mold such as a book mold. Furthermore, from the viewpoints of suppressing coarsening of the crystalline phase in the magnetic material precursor and homogenizing the crystalline phase, for example, the following method may be adopted. That is, the raw materials may be melted by high frequency or arc melting in a container, solidified, and then the resulting ingot may be melted again by high frequency melting or the like, and the resulting melt may be quenched using a strip casting method, a liquid quenching method, or the like to obtain flakes, which may then be used as the magnetic material precursor.

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

[0070] In order to suppress oxidation of the magnetic material precursor, the homogenization heat treatment is preferably carried out in an inert gas atmosphere. The inert gas atmosphere does not include a nitrogen gas atmosphere. When the homogenization heat treatment is carried out in a nitrogen gas atmosphere, Th2Zn 17 Type and / or Th2Ni 17 This is because the phase having the crystalline structure of this type is easily decomposed.

[0071] <Nitriding process> The magnetic material precursor is nitrided, whereby the crystalline phase in the magnetic material precursor is nitrided to form the main phase of the magnetic material of the present disclosure.

[0072] As long as the desired main phase can be obtained, the nitriding method is not particularly limited. Typical examples include exposing the magnetic material precursor to a nitrogen gas-containing atmosphere or a nitrogen (N)-containing gas atmosphere while heating it. Examples of the nitrogen gas-containing atmosphere include 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. Examples of the nitrogen (N)-containing gas atmosphere include an ammonia gas atmosphere or a mixed gas atmosphere of ammonia gas and hydrogen gas. The atmospheres exemplified above 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 preferred.

[0073] The magnetic material precursor may be pulverized before nitriding to obtain a magnetic material precursor powder, which may then be nitrided. By pulverizing the magnetic material precursor and then nitriding it, the crystalline phase present inside the magnetic material precursor can be sufficiently nitrided. The magnetic material precursor is preferably pulverized in an inert gas atmosphere. The inert gas atmosphere may include a nitrogen gas atmosphere. This can prevent the magnetic material precursor from being oxidized during pulverization. The particle size of the magnetic material precursor powder is D 50 The thickness 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. 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] Transform The magnetic material and manufacturing method thereof of the present disclosure are not limited to the embodiments described above and may be modified as appropriate within the scope of the claims. For example, the magnetic material of the present disclosure may be a powder or a compact of the powder. The compact may be a bonded compact or a sintered compact. In the case of a compact, a bonded compact is preferred because it is easy to avoid temperatures that would cause nitrogen (N) in the main phase to decompose during the molding process. Examples of the bond include resin and low-melting-point metal bond. Examples of the low-melting-point metal bond include metal zinc, zinc alloys, and combinations thereof. When a low-melting-point metal bond is used, pressure sintering may be performed at a low temperature at which nitrogen (N) in the main phase does not decompose. [Example]

[0076] The magnetic material and its manufacturing method according to the present disclosure will be described in more detail below with reference to examples and comparative examples. Note that the magnetic material and its manufacturing method according to the present disclosure are not limited to the conditions used in the following examples.

[0077] <Sample Preparation> A sample of the Sm-Fe-N magnetic material was prepared in the following manner.

[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 high-frequency melted at 1673 K (1400°C) and solidified to obtain a magnetic material precursor. During blending, the total number of moles of Sm, La, and Ce blended was set to be greater 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%. In this specification, for example, "metallic Sm" means unalloyed Sm. Of course, metallic Sm may contain unavoidable impurities.

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

[0080] The magnetic material precursor after the 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 The particle size was less than 20 μm.

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

[0082] "evaluation" The volume fraction and density of the main phase were determined for each sample using the measurement methods described above. Furthermore, the magnetic properties of each sample were measured using a physical property processing system (PPMS®-VSM) with a maximum magnetic field of 9 T applied. Regarding the magnetic property measurement, each nitrided sample powder was solidified in an epoxy resin while being magnetically oriented, and the magnetic properties of each solidified sample were measured at 300 K in the directions of the easy and hard axes of magnetization. The saturation magnetization Ms was calculated from the measured values ​​for the easy axis of magnetization using the law of saturation asymptotic approach.

[0083] The results are shown in Tables 1-1 and 1-2. In Table 1-2, A to C in the "Stability of the main phase" column mean that A is "good," B is "generally good," and C is "poor (the crystal structure of the main phase is destroyed)." As mentioned 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 Figures 1 and 2.

[0084] [Table 1-1]

[0085] [Table 1-2]

[0086] 1 and 2, it can be seen that in the samples of Examples 1 to 6, even when the total substitution amount of La and Ce is 0.51 or more in molar ratio, the saturation magnetization is higher than that in the case where Sm is not substituted with La and Ce (Comparative Example 5). This shows that the amount of Sm used is further reduced while the saturation magnetization is improved compared to conventional samples.

[0087] These results confirm the effectiveness of the magnetic material and manufacturing method thereof disclosed herein.

Claims

1. Th ２ Zn １７ Type and Th ２ Ni １７ The present invention has a main phase having at least one of the following crystal structures: The main phase is a compound 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 (However, R １ represents one or more rare earth elements other than Sm, La, and Ce, and Zr, and M represents 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 is satisfied; Sm-Fe-N magnetic material.

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

45.

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

4. A method for producing the Sm—Fe—N based magnetic material according to claim 1, 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 (However, R １ x≦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 nitriding the magnetic material precursor; A method for producing an Sm—Fe—N based magnetic material, comprising:

5. 5. The method for producing an Sm-Fe-N based magnetic material according to claim 4, wherein the x and y satisfy 0.16≦x≦0.31 and 0.24≦y≦0.45.

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