Rare earth sintered magnet, manufacturing method of rare earth sintered magnet, rotor and rotating machine

Abstract

A rare earth sintered magnet (1) includes: main phases (10) that contain crystal grains, the basis of which is an Nd2Fe14B crystal structure, and that satisfy the general formula (Nd,Pr,R)-Fe-B, where R is defined as being one or more types of rare earth elements selected from elements other than Nd and Pr; and sub-phases (20) that are present between a plurality of main phases (10). Each of the main phases (10) has a core section (11c, 12c) and a shell section (11s, 12s) that covers the core section (11c, 12c). The main phases (10) include a first main phase (11) in which CNd > CPr and a second main phase (12) in which CNd < CPr, where the concentration of Nd in the core section (11c, 12c) is defined as being CNd and the concentration of Pr in the core section (11c, 12c) is defined as being CPr. The first main phase (11) and the second main phase (12) are mixed. A heavy rare earth element is present on at least part of the surface in the first main phase (11) and the second main phase (12).

Description

[Technical Field]

[0001] The present disclosure relates to a rare earth sintered magnet, which is a permanent magnet obtained by sintering a material containing a rare earth element, a method for manufacturing a rare earth sintered magnet, a rotor, and a rotating machine. [Background technology]

[0002] Tetragonal R2T 14 RTB-based permanent magnets are known, with a main phase consisting of a rare earth element (R), a transition metal element (T), such as Fe (iron) or Fe partially substituted with Co (cobalt), and B (boron). RTB-based permanent magnets are used in a variety of high-value-added components, including industrial motors. In particular, Nd-Fe-B sintered magnets, where R is Nd (neodymium), have been used in a variety of components due to their excellent magnetic properties. Furthermore, because industrial motors are often used in high-temperature environments exceeding 100°C, attempts have been made to improve coercivity by adding heavy rare earth elements such as Dy (dysprosium) to Nd-TB-based sintered magnets.

[0003] In recent years, the production volume of Nd-Fe-B sintered magnets has expanded, resulting in increased consumption of Nd and heavy rare earth elements such as Dy and Tb (terbium). However, Nd and heavy rare earth elements are expensive and unevenly distributed across regions, posing procurement risks. Possible strategies for reducing consumption of Nd and heavy rare earth elements include using magnets with a main phase containing a low heavy rare earth phase; using other rare earth elements such as Pr (praseodymium), Ce (cerium), La (lanthanum), Sm (samarium), Sc (scandium), Gd (gadolinium), Y (yttrium), and Lu (lutetium) for R; and using special manufacturing methods such as hot plastic working of sintered compacts. In the following, hot plastic working applied to sintered compacts is referred to as hot working. However, although incorporating a significant amount of heavy rare earth elements into the main phase contributes to improving coercivity, it also significantly reduces remanence. Furthermore, replacing all or part of the Nd with elements such as Pr, Ce, La, Sm, Sc, Gd, Y, and Lu significantly reduces the magnetic properties of remanence and coercivity. Furthermore, hot working the sintered compact significantly reduces the magnet's magnetizability due to the refinement of the crystal grains. For these reasons, it has been difficult to achieve both reduced heavy rare earth elements and excellent magnetic properties and magnetizability. Therefore, efforts have been made to develop technologies that can improve magnetic properties at room temperature and suppress the deterioration of magnetic properties as the temperature increases when these elements are used in the production of Nd-Fe-B sintered magnets. Currently, there is a particular demand for rare earth magnets that can further reduce the heavy rare earth element content while maintaining excellent magnetic properties and magnetizability.

[0004] Patent Document 1 describes R2T 14 An RTB sintered magnet containing main phase particles made of B crystals, wherein R is one or more rare earth elements essentially containing a heavy rare earth element RH, T is one or more transition metal elements essentially containing Fe or Fe and Co, and B is boron, and some of the main phase particles contain multiple lower heavy rare earth element crystalline phases therein, and the lower heavy rare earth element crystalline phases are R2T 14Patent Document 1 discloses an RTB sintered magnet characterized by being composed of B crystals, in which the concentration of heavy rare earth elements is relatively low compared to the concentration of heavy rare earth elements in the main phase particles as a whole. The technology described in Patent Document 1 makes it possible to obtain an RTB sintered magnet with improved magnetic properties and at low cost.

[0005] In Patent Document 2, R is a rare earth element, and R2Fe 14 Patent Document 2 discloses a rare earth magnet comprising a main phase having a B-type crystal structure and a grain boundary phase surrounding the main phase, the main phase having a core portion, a first shell portion surrounding the core portion, and a second shell portion surrounding the first shell portion. In the rare earth magnet described in Patent Document 2, the abundance ratio of Nd and Pr in the first shell portion is higher than the abundance ratios of Nd and Pr in the core portion and the second shell portion. Furthermore, in the rare earth magnet described in Patent Document 2, the abundance ratio of heavy rare earth elements in the second shell portion is higher than the abundance ratio of heavy rare earth elements in the first shell portion. This results in a rare earth magnet with even improved coercivity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-174313 [Patent Document 2] Patent Publication No. 2021-174818 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the R-T-B sintered magnet described in Patent Document 1, since the phase containing a heavy rare earth element exists in the main phase, even if the coercive force can be improved, the residual magnetic flux density required for industrial motors and the like cannot be obtained, and there is a possibility that the magnetic properties may deteriorate. Furthermore, in order to diffuse the heavy rare earth element into the main phase particles, the amount of the heavy rare earth element used increases, and there is a problem that the procurement risk and cost cannot be reduced. In addition, the rare earth magnet described in Patent Document 2 has only one type of main phase, so it does not have a microstructure with a sufficiently high anisotropy magnetic field, and there is a problem that it is difficult to obtain high magnetic properties. Also, in the rare earth magnet described in Patent Document 2, the shell portion of the main phase forms a two-layer structure with different proportions of the heavy rare earth element present, and since the heavy rare earth element must be added to both shell portions, there is also a problem that it is difficult to improve the magnetic properties with a smaller amount of the heavy rare earth element.

[0008] The present disclosure has been made in view of the above, and an object thereof is to obtain a rare earth sintered magnet capable of improving magnetic properties as compared with the prior art while suppressing the use of heavy rare earth elements as compared with the prior art.

Means for Solving the Problems

[0009] In order to solve the above-described problems and achieve the object, the rare earth sintered magnet according to the present disclosure satisfies the general formula (Nd, Pr, R)-Fe-B when R is one or more rare earth elements selected from other than Nd and Pr, and includes a main phase containing crystal grains based on the Nd2Fe 14 B crystal structure, and a secondary phase existing between a plurality of main phases. The main phase has a core portion and a shell portion covering the core portion. The main phase has a first main phase with CNd > CPr and a second main phase with CNd < CPr when the concentration of Nd in the core portion is CNd and the concentration of Pr in the core portion is CPr. The first main phase and the second main phase are mixed. A heavy rare earth element exists in at least a part of the surface of the first main phase and the second main phase.

Advantages of the Invention

[0010] The rare earth sintered magnet according to the present disclosure has the effect of being able to improve magnetic properties compared to conventional magnets while using less heavy rare earth elements than conventional magnets. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the structure of a rare earth sintered magnet in a sintered state according to the first embodiment. [Figure 2] FIG. 10 is a diagram schematically illustrating an example of the structure of a rare earth sintered magnet in a sintered state according to a second embodiment. [Figure 3] FIG. 10 is a diagram schematically illustrating an example of the structure of a rare earth sintered magnet in a sintered state according to a third embodiment. [Figure 4] Elemental mapping of Sm obtained by analyzing a cross section of the rare earth sintered magnet according to embodiment 3 with FE-EPMA [Figure 5] Elemental mapping of Tb obtained by analyzing a cross section of the rare earth sintered magnet according to embodiment 3 with FE-EPMA [Figure 6] Diagram showing atomic sites in the tetragonal Nd2Fe14B crystal structure [Figure 7] 10 is a flowchart showing an example of the steps of a method for producing a rare earth sintered magnet according to a fourth embodiment. [Figure 8] 10 is a flowchart showing an example of a procedure for manufacturing a rare earth sintered magnet alloy according to a fourth embodiment. [Figure 9] 10 is a flowchart showing an example of a procedure for a diffusion precursor manufacturing process according to a fourth embodiment. [Figure 10] FIG. 13 is a cross-sectional view schematically showing an example of the configuration of a rotor equipped with a rare earth sintered magnet according to a fifth embodiment. [Figure 11] FIG. 13 is a cross-sectional view schematically showing an example of the configuration of a rotating machine according to a sixth embodiment. [Figure 12] FIG. 1 is a trace of composition images obtained by analyzing cross sections of the rare earth sintered magnets according to Examples 1 to 8 with FE-EPMA. [Figure 13] Nd element mapping obtained by analyzing the cross section of the rare earth sintered magnets of Examples 1 to 8 with FE-EPMA [Figure 14]Elemental mapping of Pr obtained by analyzing the cross section of the rare earth sintered magnets of Examples 1 to 8 with FE-EPMA [Figure 15] Dy element mapping obtained by analyzing the cross section of the rare earth sintered magnets of Examples 1 to 8 with FE-EPMA [Figure 16] Elemental mapping of O obtained by analyzing the cross section of the rare earth sintered magnets according to Examples 1 to 8 with FE-EPMA [Figure 17] Sm element mapping obtained by analyzing the cross section of the rare earth sintered magnets of Examples 1 to 8 with FE-EPMA [Figure 18] Elemental mapping of La obtained by analyzing the cross section of the rare earth sintered magnets according to Examples 1 to 8 with FE-EPMA DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a rare earth sintered magnet, a method for manufacturing a rare earth sintered magnet, a rotor, and a rotating machine according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0013] Embodiment 1 FIG. 1 is a diagram schematically illustrating an example of the structure of a rare earth sintered magnet in a sintered state according to embodiment 1. The rare earth sintered magnet 1 according to embodiment 1 satisfies the general formula (Nd, Pr, R)-Fe-B, and has a structure of NdFe 14 The rare earth sintered magnet 1 has a main phase 10 containing crystal grains based on a B crystal structure, and the main phase 10 has a core portion and a shell portion covering the core portion. Here, R is one or more rare earth elements selected from among Nd and Pr. The shell portion has a different composition from the core portion and is provided to cover the core portion. The rare earth sintered magnet 1 also has subphases 20 that exist between main phases 10, i.e., between multiple main phases 10. The subphases 20 are basically oxide phases whose main component is (Nd,Pr,R)—O.

[0014] In the rare earth sintered magnet 1 according to Embodiment 1, when the concentration of Nd in the core portion is denoted as CNd and the concentration of Pr in the core portion is denoted as CPr, the main phase 10 has a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr, and the first main phase 11 and the second main phase 12 are mixed. The first main phase 11 has a core portion 11c and a shell portion 11s that covers the core portion 11c and has a different composition from the core portion 11c. The second main phase 12 has a core portion 12c and a shell portion 12s that covers the core portion 12c and has a different composition from the core portion 12c. In the core portion 11c of the first main phase 11, CNd > CPr, and in the core portion 12c of the second main phase 12, CNd < CPr.

[0015] That is, in the rare earth sintered magnet 1, there are two types of main phases 10, namely the first main phase 11 and the second main phase 12. Focusing on the core portions 11c and 12c of the two types of main phases 10, it means that in the first main phase 11, the Nd concentration is higher than the Pr concentration, and conversely, in the second main phase 12, the Pr concentration is higher than the Nd concentration. By mixing two types of main phases 10 having a core-shell structure with different anisotropic magnetic fields, that is, different magnetic anisotropies, it is possible to improve the residual magnetic flux density and coercive force while maintaining good magnetization while reducing Nd and heavy rare earth elements. Furthermore, it also contributes to suppressing the decrease in magnetic properties accompanying temperature changes. Here, the concentration difference indicated by "the first main phase 11 where CNd > CPr and the second main phase 12 where CNd < CPr" means that there is a clear difference in the detection intensities of Nd and Pr by mapping analysis using an electron probe micro analyzer (EPMA). Specifically, taking the case of the first main phase 11 as an example, regarding the concentration of Nd in the core portion 11c, the detection intensity of EPMA is higher than the average of the detection intensities of Nd, and regarding the concentration of Pr, the detection intensity of EPMA indicates near the lower limit of the detection intensity of Pr. It can be said that the second main phase 12 is opposite to the case of the first main phase 11.

[0016] Further, in the rare earth sintered magnet 1 according to Embodiment 1, when the Nd concentration in the core portion 11c of the first main phase 11 is C1Nd, the Nd concentration in the core portion 12c of the second main phase 12 is C2Nd, the Pr concentration in the core portion 11c of the first main phase 11 is C1Pr, and the Pr concentration in the core portion 12c of the second main phase 12 is C2Pr, the relational expressions C1Nd > C2Nd and C1Pr < C2Pr are satisfied. That is, regarding the Nd concentration, the core portion 11c of the first main phase 11 is higher than the core portion 12c of the second main phase 12, and conversely, regarding the Pr concentration, the core portion 12c of the second main phase 12 is higher than the core portion 11c of the first main phase 11. The concentration difference here also means that there is a difference in the detection intensity of Nd and Pr by the mapping analysis using the above EPMA. Specifically, in the case of the Nd concentration, the EPMA detection intensity of Nd in the core portion 11c of the first main phase 11 is higher than the average of the Nd detection intensity, and the EPMA detection intensity of Nd in the core portion 12c of the second main phase 12 is lower than the average of the Nd detection intensity. In the case of the Pr concentration, the EPMA detection intensity of Pr in the core portion 12c of the second main phase 12 is higher than the average of the Pr detection intensity, and the EPMA detection intensity of Pr in the core portion 11c of the first main phase 11 is lower than the average of the Pr detection intensity. That is, Pr is present in a large amount in the core portion 12c of the second main phase 12 where the Nd concentration is low, and conversely, Nd is present in a large amount in the core portion 11c of the first main phase 11 where the Pr concentration is low. By controlling to such a tissue form, it becomes possible to obtain the rare earth sintered magnet 1 having excellent magnetic characteristics.

[0017] Further, in the rare earth sintered magnet 1 according to Embodiment 1, more of the first main phase 11 where CNd > CPr is present than the second main phase 12 where CNd < CPr. In other words, the number of the first main phases 11 having the composition formula of Nd2Fe 14 B is larger than the number of the second main phases 12 having the composition formula of Pr2Fe 14 B. This means that increasing the number of the first main phases 11 having the composition formula of Nd2Fe 14 B is more beneficial than increasing the number of the second main phases 12 having the composition formula of Pr2Fe 14This is because more excellent magnetic properties and temperature characteristics can be obtained than increasing the second main phase 12 having the composition formula of B. Furthermore, by controlling to such a microstructure, the refinement of the overall crystal grains is also suppressed, so that it is possible to obtain excellent magnetic properties compared to the conventional ones while ensuring the coercivity.

[0018] Also, in the rare earth sintered magnet 1 according to Embodiment 1, focusing on the shell portions 11s, 12s of the core-shell structure, when the concentration of Nd in the shell portions 11s, 12s is denoted as S Nd and the concentration of Pr in the shell portions 11s, 12s is denoted as S Pr, the first main phase 11 satisfies the relational expression of C Nd > S Nd and C Pr < S Pr, and the second main phase 12 satisfies the relational expression of C Nd < S Nd and C Pr > S Pr. Specifically, in the shell portion 11s of the first main phase 11, instead of having a low concentration of Nd, the concentration of Pr is higher than that of the core portion 11c, and in the shell portion 12s of the second main phase 12, instead of having a low concentration of Pr, the concentration of Nd is higher than that of the core portion 12c. By forming the main phase 10 having the shell portion 11s with a high Pr concentration like the first main phase 11, the coercivity can be improved. Furthermore, by forming the main phase 10 having the shell portion 12s with a high Nd concentration like the second main phase 12, it is possible to suppress the decrease in the residual magnetic flux density while maintaining the coercivity. By selectively controlling to such a microstructure, the rare earth sintered magnet 1 can exhibit excellent magnetic properties compared to the conventional ones.

[0019] The main phase 10 also has a heavy rare-earth-element-containing layer 31 containing a heavy rare-earth element on at least a portion of its surface. That is, the heavy rare-earth element is present on at least a portion of the surface of the main phase 10, i.e., the first main phase 11 and the second main phase 12. More specifically, the heavy rare-earth element is present on at least a portion of the outer circumferential surface of the shell portions 11s and 12s, but the heavy rare-earth element is not present in the core portions 11c and 12c. The heavy rare-earth element is one or more elements selected from the group consisting of Dy, Tb, Gd, and Ho (holmium). Thus, the inclusion of the heavy rare-earth element in the R site of the first main phase 11 and the second main phase 12 increases the coercivity. However, the heavy rare-earth element does not penetrate into the core portion 11c inside the first main phase 11 or the core portion 12c inside the second main phase 12, thereby preventing a significant decrease in remanence. In other words, the coercivity can be improved while preventing a decrease in remanence. In order to obtain such an effect, it is desirable that the proportion of the heavy rare earth element in the main phase 10 is greater than 0 at. % and equal to or less than 10 at. %.

[0020] When comparing the magnetic properties of rare earth sintered magnet 1 containing a heavy rare earth element inside main phase 10 with those containing the heavy rare earth element in the surface layer, it is known that the same magnetic properties can be obtained by containing a lower concentration of heavy rare earth element on the surface of main phase 10 than when the heavy rare earth element is contained inside main phase 10. In other words, compared to when the heavy rare earth element is contained inside main phase 10, rare earth sintered magnet 1 according to embodiment 1 containing a heavy rare earth element in the surface layer of main phase 10 can use a smaller amount of heavy rare earth element.

[0021] Furthermore, the average grain size of the crystal grains in main phase 10 is preferably 100 μm or less, and more preferably 0.5 μm to 50 μm to improve magnetic properties. Furthermore, by setting the grain size to approximately 1 μm to 10 μm, the grain size will differ from the microstructure produced by hot working, maintaining good magnetization performance and enabling the production of a rare earth sintered magnet 1 with magnetic properties superior to conventional magnets.

[0022] The rare earth sintered magnet 1 according to Embodiment 1 may contain an additive element M for further improving magnetic properties. The additive element M is one or more elements selected from the group consisting of Ga (gallium), Cu (copper), Al (aluminum), Co, Zr (zirconium), Ti (titanium), Nb (niobium), and Mn (manganese). Therefore, when the heavy rare earth element RH in the rare earth sintered magnet 1 according to Embodiment 1 is one or more elements selected from the group consisting of Dy, Tb, Gd, and Ho, and R is a rare earth element other than Nd, Pr, and the heavy rare earth element RH, the general formula is (Nd a Pr b R c RH d )Fe e B f M g ). The additive element M is one or more elements selected from the group consisting of Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn. It is desirable that a, b, c, d, e, f, and g satisfy the following relational expressions.

[0023] 5 ≤ a + b ≤ 20 0 < c + d < (a + b) 0 < d < 10 70 ≤ e ≤ 90 0.5 ≤ f ≤ 10 0 ≤ g ≤ 5 a + b + c + d + e + f + g = 100 at. %

[0024] When the rare earth sintered magnet 1 according to Embodiment 1 uses one or more rare earth elements selected from other than Nd and Pr, it satisfies the general formula (Nd, Pr, R)-Fe-B, and in the main phase 10 containing crystal grains based on the Nd2Fe 14 B crystal structure, there exists a main phase 10 having core portions 11c, 12c and shell portions 11s, 12s that coat the core portions 11c, 12c. The main phase 10 has a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr, and the first main phase 11 and the second main phase 12 are mixed. With such a configuration, it is possible to obtain a rare earth sintered magnet 1 with improved magnetic properties and magnetization while suppressing the use of Nd and heavy rare earth elements as compared to the prior art.

[0025] In addition, the first main phase 11 and the second main phase 12 are made to satisfy the relational expressions C1Nd > C2Nd and C1Pr < C2Pr. Alternatively, the number of the first main phase 11 is made larger than the number of the second main phase 12. Alternatively, the first main phase 11 satisfies the relational expressions CNd > SNd and CPr < SPr, and the second main phase 12 satisfies the relational expressions CNd < SNd and CPr > SPr. Also by this, the rare earth sintered magnet 1 with improved magnetic properties and coercive force while suppressing the use of Nd and heavy rare earth elements can be obtained.

[0026] Furthermore, heavy rare earth elements are made to exist on at least a part of the surfaces of the first main phase 十一 and the second main phase 十二, and heavy rare earth elements are made not to exist inside the first main phase 十一 and the second main phase 十二. Also by this, the rare earth sintered magnet 1 with improved coercive force as compared with the conventional one and suppressing a remarkable decrease in the residual magnetic flux density while suppressing the use of heavy rare earth elements can be obtained. That is, it has the effect of being able to improve the magnetic properties of the rare earth sintered magnet 1 as compared with the conventional one.

[0027] In addition, in Embodiment 1, the first main phase 11 and the second main phase 1 are a core-shell structure having one-layer shell portions 11s and 12s, and it is sufficient that heavy rare earth elements exist on at least a part of the surfaces of the shell portions 11s and 12s. On the other hand, in Patent Document 2 having a two-layer core-shell structure, heavy rare earth elements have to be diffused into the two-layer core-shell portions. Thus, the rare earth sintered magnet 1 of Embodiment 1 also has the effect of being able to suppress the amount of use of heavy rare earth elements as compared with Patent Document 2.

[0028] Embodiment 2. FIG, 2 is a diagram schematically showing an example of the structure of the sintered state of the rare earth sintered magnet according to Embodiment 2. Note that the same components as those in Embodiment 1 are denoted by the same reference numerals and the description thereof is omitted. The rare earth sintered magnet 1 according to Embodiment 2 has a main phase 10 and a sub-phase 20.

[0029] The main phase 10 has the same structure as in embodiment 1. That is, the main phase 10 has a first main phase 11 and a second main phase 12 each having a core-shell structure, and the compositions of the core portions 11c and 12c and the shell portions 11s and 12s are the same as those described in embodiment 1. However, in embodiment 2, the heavy rare earth element-containing layer 31 does not exist on the surface of the main phase 10.

[0030] The subphase 20 is a phase based on an oxide phase represented by a main component of (Nd, Pr, R)—O. However, in the second embodiment, the subphase 20 contains a heavy rare earth element. The heavy rare earth element is distributed throughout the subphase 20. In one example, the heavy rare earth element is uniformly distributed within the subphase 20.

[0031] Thus, in the second embodiment, subphases 20 containing a heavy rare earth element are present between main phases 10. The heavy rare earth element is uniformly distributed within subphases 20, and it can be considered that the heavy rare earth element has penetrated into a portion of the surface of main phase 10 that contacts subphase 20. In other words, the heavy rare earth element does not penetrate into core portions 11c, 12c of main phase 10, but has penetrated into portions of shell portions 11s, 12s. Therefore, as in the first embodiment, the coercivity of rare earth sintered magnet 1 can be improved while suppressing a decrease in remanence.

[0032] As shown in FIG. 2 , in the rare earth sintered magnet 1, the main phase 10 contacts other main phases 10 without the subphase 20 therebetween, and also contacts other main phases 10 via the subphase 20. That is, at least a portion of the surface of the main phase 10 contacts the subphase 20. The subphase 20 also contains a heavy rare earth element. Therefore, at least a portion of the surface of the main phase 10 is covered by the subphase 20 containing the heavy rare earth element. When examining the distribution of the heavy rare earth element relative to the main phase 10, the heavy rare earth element is present on at least a portion of the surface of the main phase 10. In other words, for the same rare earth sintered magnet 1, Embodiment 1 shows the distribution of the heavy rare earth element at the interface between the main phase 10 and the subphase 20, while Embodiment 2 shows the distribution of the heavy rare earth element at the subphase 20. In this way, Embodiments 1 and 2 can be said to be the same rare earth sintered magnet 1 viewed from different angles.

[0033] As with embodiment 1, embodiment 2 also makes it possible to obtain a rare earth sintered magnet 1 that improves coercivity compared to conventional magnets and suppresses a significant decrease in remanence, while using less heavy rare earth elements. In other words, it has the effect of improving the magnetic properties of the rare earth sintered magnet 1 compared to conventional magnets.

[0034] Embodiment 3 3 is a diagram schematically illustrating an example of the structure of a rare earth sintered magnet according to embodiment 3 in a sintered state. The rare earth sintered magnet 1 according to embodiment 3 has a main phase 10 and a subphase 20. As described in embodiment 1, the main phase 10 includes a first main phase 11 and a second main phase 12, but in FIG. 2, the first main phase 11 and the second main phase 12 are collectively referred to as the main phase 10. The subphase 20 is present between the main phases 10.

[0035] In the rare earth sintered magnet 1 according to Embodiment 3, the case where La and Sm are selected as the rare earth element R is shown. When La and Sm are selected as the rare earth element R, while suppressing the use of Nd and heavy rare earth elements, the magnetic properties are improved, and the effect of having better magnetization than conventional ones becomes even greater. In this example, the main phase 10 has a composition formula of (Nd,Pr,La,Sm)2Fe 14 B. The rare earth sintered magnet 1 having a tetragonal R2Fe 14 B crystal structure has La and Sm as the rare earth element R because, from the calculation results of the magnetic interaction energy using the molecular orbital method, a practical rare earth sintered magnet 1 can be obtained by setting the composition to contain La and Sm, which can greatly suppress the deterioration of magnetic properties with temperature rise. Also, by intentionally segregating La and Sm to the grain boundary, which is an example of the secondary phase 20, Nd and Pr can be relatively diffused into the main phase 10, and the crystal magnetic anisotropy of the main phase 10 can be enhanced. As a result, a core-shell structure in which there are high and low magnetic anisotropy parts in the main phase 10 is formed, and a state is formed where it is easy to form a rare earth sintered magnet 1 in which the first main phase 11 with CNd > CPr and the second main phase 12 with CNd < CPr are mixed.

[0036] Note that if the addition amounts of La and Sm are too large, the amounts of Nd and Pr, which are elements with high magnetic anisotropy constants and saturation magnetic polarizations, decrease, leading to a deterioration of magnetic properties. Therefore, when the composition ratios of Nd, Pr, La, and Sm are A, B, C, and D, respectively, it is preferable that (A + B) > (C + D).

[0037] In the rare earth sintered magnet 1 according to the third embodiment, when R=La, Sm, the magnet has a subphase 20 in addition to the first and second main phases 11 and 12 of the first embodiment. The subphase 20 includes a crystalline first subphase 21 based on an oxide phase whose main component is expressed as (Nd, Pr, La, Sm)—O, and a crystalline second subphase 22 whose main component is expressed as (Nd, Pr, La)—O. The subphase 20 is characterized in that the first subphase 21 has a higher Sm concentration than the second subphase 22. That is, the first subphase 21 forms an Sm-enriched portion 41 whose Sm concentration is higher than that of the second subphase 22. This not only improves the magnetic properties at room temperature, but also suppresses degradation of the magnetic properties as the temperature increases.

[0038] Here, "the concentration of Sm is higher in the first subphase 21 than in the second subphase 22" means that, by mapping analysis using an EPMA, the detection intensity of Sm is higher on average in the first subphase 21 than in the second subphase 22.

[0039] The crystalline subphase 20 is a collective term for the crystalline first subphase 21 and the crystalline second subphase 22, which exist between the main phase 10. The crystalline first subphase 21 is represented by (Nd,Pr,La,Sm)-O, and the crystalline second subphase 22 is represented by (Nd,Pr,La)-O. Here, (Nd,Pr,La,Sm) means that some of the Nd and Pr are substituted with La and Sm. Note that, because the main component elements are listed in parentheses, the first subphase 21 and the second subphase 22 may contain trace amounts of other components in addition to the elements listed in parentheses. In one example, the second subphase 22 represented by (Nd,Pr,La)-O contains a trace amount of Sm.

[0040] In the rare earth sintered magnet 1 according to the third embodiment, there is a difference in the concentrations of La and Sm between the main phase 10 and the subphase 20, and La and Sm are more segregated in the subphase 20 than in the main phase 10. That is, the sum of the La concentrations in the first subphase 21 and the second subphase 22 is equal to or greater than the La concentration in the main phase 10, and the sum of the Sm concentrations in the first subphase 21 and the second subphase 22 is equal to or greater than the Sm concentration in the main phase 10. Specifically, the La and Sm concentrations in the subphase 20 are equal to or greater than the La and Sm concentrations in the main phase 10. The La concentration in the main phase 10 is the sum of the La concentration in the first main phase 11 and the La concentration in the second main phase 12. That is, the sum of the La concentrations in the first subphase 21 and the second subphase 22 is higher than the sum of the La concentrations in the first main phase 11 and the second main phase 12. The Sm concentration in the main phase 10 is the sum of the Sm concentration in the first main phase 11 and the Sm concentration in the second main phase 12. In other words, the sum of the Sm concentrations in the first subphase 21 and the second subphase 22 is higher than the sum of the Sm concentrations in the first main phase 11 and the second main phase 12.

[0041] Here, when the La concentration contained in the main phase 10 is X, the La concentration contained in the first subphase 21 is X1, the La concentration contained in the second subphase 22 is X2, the Sm concentration contained in the main phase 10 is Y, the Sm concentration contained in the first subphase 21 is Y1, and the Sm concentration contained in the second subphase 22 is Y2, the relationship of the following formula (1) is satisfied.

[0042] 1<(Y1+Y2) / Y<(X1+X2) / X ···(1)

[0043] Furthermore, from the viewpoint of improving magnetic properties, the concentrations of Nd and Pr contained in the main phase 10 satisfy the relationships of the following formulas (2) and (3).

[0044] (CNd+SNd)>(X+Y) (2) (CPr+SPr)>(X+Y) (3)

[0045] In the above, the La concentration in the main phase 10 is the sum of the La concentrations in the first main phase 11 and the second main phase 12, and the Sm concentration in the main phase 10 is the sum of the Sm concentrations in the first main phase 11 and the second main phase 12. This indicates that both La and Sm are segregated in the subphase 20 rather than in the main phase 10. However, when viewed locally, the sum of the La and Sm concentrations in the first main phase 11 and the second main phase 12 and the sum of the La and Sm concentrations in the first subphase 21 and the second subphase 22 may not satisfy the above-mentioned relationship. Therefore, more specifically, the La concentration in the main phase 10 indicates the average of the La concentrations in the first main phase 11 and the second main phase 12, and the Sm concentration in the main phase 10 indicates the average of the Sm concentrations in the first main phase 11 and the second main phase 12. In this case, the La concentration in the subphase 20, i.e., the sum of the La concentrations in the first subphase 21 and the second subphase 22, means the average La concentration in the first subphase 21 and the second subphase 22, and the Sm concentration in the subphase 20, i.e., the sum of the Sm concentrations in the first subphase 21 and the second subphase 22, means the average Sm concentration in the first subphase 21 and the second subphase 22.

[0046] La is present in high concentrations at grain boundaries during the manufacturing process, particularly during heat treatment, and thus relatively diffuses Nd and Pr into main phase 10. As a result, rare earth sintered magnet 1 in embodiment 3 improves magnetocrystalline anisotropy without consuming Nd and Pr in main phase 10 at grain boundaries. Sm is also present in higher concentrations in subphase 20, particularly first subphase 21, than in main phase 10, and thus, like La, relatively diffuses Nd into main phase 10, improving magnetocrystalline anisotropy.

[0047] As described in the second embodiment, the subphase 20 contains a heavy rare earth element, and therefore the first subphase 21 and the second subphase 22 also contain a heavy rare earth element. However, in the third embodiment, the distribution of the heavy rare earth element differs between the first subphase 21 and the second subphase 22. In the second subphase 22, which has a lower Sm concentration than the first subphase 21, the heavy rare earth element is uniformly distributed within the second subphase 22. On the other hand, in the first subphase 21 forming the Sm-enriched portion 41, the heavy rare earth element is not uniformly distributed within the first subphase 21, but is selectively distributed between the outer periphery of the first subphase 21 and the Sm-enriched portion 41, i.e., in the inner periphery of the outer periphery of the first subphase 21. Specifically, the heavy rare earth element is present so as to selectively surround the outer periphery of the Sm-enriched portion 41, where the Sm concentration of the first subphase 21 is high. Therefore, it can be said that the first subphase 21 has an Sm-enriched portion 41 and a heavy rare earth element-containing portion 32 in which a heavy rare earth element is present and which selectively surrounds the outer periphery of the Sm-enriched portion 41. The outer periphery of the first subphase 21 is the boundary between the first subphase 21 and the main phase 10.

[0048] As in the second embodiment, first and second subphases 21 and 22 containing a heavy rare earth element are present between the main phases 10. The heavy rare earth element can be considered to have penetrated into a portion of the surface of the main phase 10 that contacts the first and second subphases 21 and 22 containing the heavy rare earth element. In other words, the heavy rare earth element does not penetrate into the core portions 11c and 12c of the main phase 10, but does penetrate into portions of the shell portions 11s and 12s. Therefore, as in the first embodiment, the coercivity of the rare earth sintered magnet 1 can be improved while suppressing a decrease in remanence.

[0049] 4 and 5 show elemental mappings obtained by analyzing a cross section of the rare earth sintered magnet according to the third embodiment using a field emission electron probe microanalyzer (FE-EPMA). FIG. 4 shows the elemental mapping of Sm, and FIG. 5 shows the elemental mapping of Tb. These figures show the presence of subphases 20 between main phases 10. The subphases 20 also include a first subphase 21 having an Sm-enriched portion 41 and a second subphase 22 having a lower Sm concentration than the first subphase 21. As described above, the heavy rare earth element Tb is uniformly distributed in the second subphase 22. Meanwhile, the first subphase 21 has a biased distribution of Tb. Referring to FIGS. 4 and 5, the heavy rare earth element-containing portion 32 is present so as to selectively surround the Sm-enriched portion 41 in the first subphase 21, where the Sm concentration is high. Furthermore, there is almost no heavy rare earth element present in the Sm-enriched portion 41. Furthermore, the concentration of the heavy rare earth element selectively distributed around the Sm-enriched portion 41 is higher than the concentration of the heavy rare earth element distributed throughout the second subphase 22.

[0050] Next, La and Sm form tetragonal R2Fe 14 Figure 6 shows the atomic sites of the tetragonal NdFe B crystal structure. 14 This is a diagram showing atomic sites in the B crystal structure. Note that the crystal structure shown in FIG. 6 is, for example, shown in FIG. 1 of Reference 1 below. The substituted site is determined by the stabilization energy due to substitution calculated by band calculation and molecular field approximation of the Heisenberg model. (Reference 1) JFHerbst et al. “Relationships between crystal structure and magnetic properties in NdFe 14 PHYSICAL REVIEW B. 1984, Vol.29, No.7, p. 4176-4178.

[0051] First, we will explain how to calculate the stabilization energy in La. The stabilization energy in La is calculated by 56 Using a B4 crystal cell, (Nd7La1)Fe 56 B4+Nd and Nd8(Fe 55 The smaller the energy value, the more stable the site is when an atom is substituted. In other words, La is more likely to be substituted at the atomic site with the smallest energy. In this calculation, when La is substituted for the original atom, the tetragonal R2Fe 14 The lattice constant in the B crystal structure is said to be unchanged by the difference in atomic radius. Table 1 shows the stabilization energy of La at each substitution site when the environmental temperature is changed.

[0052] [Table 1]

[0053] According to Table 1, the stable substitution site for La is the Nd(f) site at temperatures above 1000 K, and the Fe(c) site at temperatures of 293 K and 500 K. As described below, the rare earth sintered magnet 1 according to the third embodiment is prepared by heating the raw materials for the rare earth sintered magnet 1 to a temperature above 1000 K, melting them, and then rapidly cooling them. Therefore, the raw materials for the rare earth sintered magnet 1 are believed to be maintained at a temperature above 1000 K, i.e., above 727°C, and preferably at approximately 1300 K, i.e., 1027°C. At this time, La is believed to be substituted at the Nd(f) site or the Nd(g) site. While La is believed to preferentially substitute for the energetically stable Nd(f) site, it is also possible for La to substitute for the Nd(g) site, which has a smaller energy difference among the La substitution sites. For this reason, the Nd(g) site is also considered a candidate for La's substitution site.

[0054] Furthermore, when rare earth sintered magnet 1 is produced using the manufacturing method described below, although the sintering temperature is above 1000 K, the Fe(c) sites listed in Table 1 are repeatedly maintained in an energetically stable temperature range through the first, second, third, fourth, and cooling aging steps. In other words, the substitution of La at the Nd sites of main phase 10 is maintained in an unstable energy state. In other words, when rare earth sintered magnet 1 is made from raw materials, La is primarily substituted at the Nd sites of main phase 10. However, in rare earth sintered magnet 1 produced using the manufacturing method described below, the Nd sites of main phase 10 are repeatedly maintained in a temperature range that is intentionally unstable in energy, resulting in the selective release of a certain amount of La from the Nd sites of main phase 10, resulting in the segregation of La into subphase 20. As a result, main phase 10 promotes the formation of a characteristic core-shell structure.

[0055] Next, we will explain how to calculate the stabilization energy of Sm. The stabilization energy of Sm is calculated using the formula (Nd7Sm1)Fe 56 B4+Nd and Nd8(Fe 55 Sm1)B4+Fe and the energy difference between them. By substituting atoms, the tetragonal R2Fe 14 The lattice constant in the B crystal structure remains unchanged, as in the case of La. Table 2 shows the stabilization energy of Sm at each substitution site when the ambient temperature is changed.

[0056] [Table 2]

[0057] According to Table 2, the stable substitution site for Sm is the Nd(g) site at all temperatures, unlike La. It is thought that Sm is preferentially substituted at the energetically stable Nd(g) site, but substitution at the Nd(f) site, which has a small energy difference among the Sm substitution sites, is also possible.

[0058] When rare earth sintered magnet 1 is produced by the production method described below, substitution at the Nd(g) site of main phase 10 is the most stable in terms of energy. However, as described above, by maintaining the temperature range in which substitution of La at the Nd site of main phase 10 becomes unstable, some Sm is released from the Nd site of main phase 10 along with La and segregates into subphase 20. As a result, there is a difference in the concentrations of La and Sm between main phase 10 and subphase 20. The sum of the La concentration in first subphase 21 and second subphase 22 is equal to or greater than the La concentration in main phase 10, and the sum of the Sm concentrations in first subphase 21 and second subphase 22 is equal to or greater than the Sm concentration in main phase 10. More specifically, the average La concentration in the first subphase 21 and the second subphase 22 is equal to or greater than the average La concentration in the first main phase 11 and the second main phase 12, and the average Sm concentration in the first subphase 21 and the second subphase 22 is equal to or greater than the average Sm concentration in the first main phase 11 and the second main phase 12. In other words, it can be said that La and Sm segregate in the subphase 20.

[0059] Comparing La and Sm, it can be seen that La, which is maintained in a temperature range where it is in an unstable energy state from an energetic perspective, is overwhelmingly more likely to segregate into subphase 20. As a result, in the case of a rare earth sintered magnet 1 prepared with La and Sm at approximately the same concentrations, La will segregate to a greater extent into subphase 20 than Sm present in rare earth sintered magnet 1. By repeatedly maintaining this temperature range, a concentration difference is created in subphase 20 for Sm, which has a lower segregation rate, and a first subphase 21 and a second subphase 22 are formed. This promotes the formation of a core-shell structure in main phase 10.

[0060] Here, we will explain Nd as a representative element, as shown in Figure 6. However, since Nd and Pr are produced as a mixture, as exemplified by Di (didymium), it is thought that the energy levels of Nd and Pr are close. Therefore, the same can be said when Nd is replaced with Pr. By having both Nd and Pr present, it is possible to form a main phase 10 with two types of core-shell structures.

[0061] As described above, when R is one or more rare earth elements selected from other than Nd and Pr, the rare earth sintered magnet 1 of Embodiment 3 satisfies the general formula (Nd, Pr, R)-Fe-B, and Nd2Fe 14 It has a main phase 10 containing crystal grains based on the Nd2FeB crystal structure. The main phase 10 has core portions 11c, 12c and shell portions 11s, 12s that cover the core portions 11c, 12c. When R = La, Sm, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, it has a secondary phase 20. The secondary phase 20 has a crystalline first secondary phase 21 based on an oxide phase whose main component is represented by (Nd, Pr, La, Sm)-O, and a crystalline second secondary phase 22 whose main component is represented by (Nd, Pr, La)-O. Regarding the concentration of Sm, the first secondary phase 21 is higher than the second secondary phase 22. That is, two types of main phases 10 and two types of secondary phases 20 are made to exist. Thereby, it becomes possible to provide the rare earth sintered magnet 1 having excellent magnetic properties such as temperature characteristics of magnetic properties as compared with the conventional ones. Further, by setting R to La and Sm, the main phase 10 is in a state where the first main phase 11 with CNd > CPr and the second main phase 12 with CNd < CPr are mixed. In other words, the rare earth sintered magnet 1 has a main phase 10 having two types of first main phases 11 and second main phases 12. Focusing on the core portions 11c, 12c of the two types of main phases 10, in the first main phase 11, the Nd concentration is higher than the Pr concentration, and conversely in the second main phase 12, the Pr concentration is higher than the Nd concentration, and a main phase 10 having two types of core-shell structures is likely to occur. As a result, while suppressing the use of Nd and heavy rare earth elements, the magnetic properties can be improved, and the effect of having excellent magnetization properties as compared with the conventional ones can be further enhanced.

[0062] Also, in Embodiment 3 as well, similar to Embodiment 1, it is possible to obtain the rare earth sintered magnet 1 that suppresses the use of heavy rare earth elements, improves the coercive force as compared with the conventional ones, and suppresses a significant decrease in the residual magnetic flux density. That is, it has the effect of improving the magnetic properties of the rare earth sintered magnet 1 as compared with the conventional ones.

[0063] Embodiment 4. In the fourth embodiment, a method for manufacturing the rare earth sintered magnet 1 described in the first, second, or third embodiment will be described. Fig. 7 is a flowchart showing an example of the steps of the method for manufacturing the rare earth sintered magnet according to the fourth embodiment. As shown in Fig. 7, the method for manufacturing the rare earth sintered magnet 1 includes a rare earth sintered magnet alloy manufacturing step (step S10) for manufacturing a rare earth sintered magnet alloy that serves as a raw material for a diffusion precursor, which is a sintered body before a heavy rare earth element is diffused into the rare earth sintered magnet 1, a diffusion precursor manufacturing step (step S20) for forming the diffusion precursor, a grain boundary diffusion step (step S30) for diffusing a heavy rare earth element into the diffusion precursor, and a cooling step (step S40) for cooling the diffusion precursor with the heavy rare earth element diffused therein to obtain the rare earth sintered magnet 1.

[0064] First, the rare earth sintered magnet alloy manufacturing process of step S10 will be described in detail. FIG. 8 is a flowchart showing an example of the procedure of the rare earth sintered magnet alloy manufacturing process according to the fourth embodiment. First, as shown in FIG. 8, the manufacturing process of the rare earth sintered magnet alloy that serves as the raw material for the diffusion precursor includes a melting step (step S11) in which raw materials for the rare earth sintered magnet alloy, including elements that constitute the diffusion precursor, are heated to a temperature of 1000 K or higher to melt them, a first cooling step (step S12) in which the molten raw materials are cooled on a rotating body to obtain a solidified alloy, and a second cooling step (step S13) in which the solidified alloy is further cooled in a container. In this way, the rare earth sintered magnet alloy can be manufactured. Each step will be described below.

[0065] In the melting step of step S11, the raw material of the diffusion precursor is heated to a temperature of 1000 K or higher in a crucible in an atmosphere containing an inert gas such as Ar (argon) or in a vacuum to melt it. This produces a molten alloy of a molten rare earth sintered magnet alloy. When producing the rare earth sintered magnet 1 of Embodiments 1 and 2, the raw materials can be Nd, Pr, Fe, and B. When producing the rare earth sintered magnet 1 of Embodiment 3, the raw materials can be Nd, Pr, La, Sm, Fe, and B. Furthermore, FeB can be used instead of B as a raw material. In this case, the raw materials can contain one or more elements selected from the group consisting of Al, Co, Zr, Ti, Nb, and Mn as an additional element M.

[0066] Next, in the first cooling step of step S12, the molten alloy prepared in the melting step is poured into a tundish and then onto a single roll, which is a rotating body. As a result, the molten alloy is rapidly cooled on the single roll rotating in a predetermined direction, and a solidified alloy thinner than the ingot alloy is prepared from the molten alloy on the single roll. Here, a single roll is used as the rotating body, but this is not limiting, and rapid cooling may also be achieved by contacting the molten alloy with a twin roll, a rotating disk, a rotating cylindrical mold, or the like. From the viewpoint of efficiently obtaining a thin solidified alloy, the cooling rate in the first cooling step is set to 10°C / sec or more and 10°C / sec or more. 7 ° C. / sec or less, and 3 °C / sec or more 10 4 It is more preferable to set the cooling rate at °C / sec or less. The thickness of the solidified alloy is in the range of 0.03 mm to 10 mm. The molten alloy begins to solidify from the part that comes into contact with the single roll, and columnar or needle-like crystals grow from the contact surface with the single roll in the thickness direction. The first cooling process in step S12 corresponds to the first alloy cooling process.

[0067] Thereafter, in the second cooling step of step S13, the thin solidified alloy prepared in the first cooling step is placed in a tray container and cooled. The thin solidified alloy is broken into flakes of rare earth sintered magnet alloy when it enters the tray container and is cooled. Depending on the cooling rate, a ribbon-shaped rare earth sintered magnet alloy may be obtained, and it is not limited to flakes. From the viewpoint of obtaining a rare earth sintered magnet alloy having a structure with good temperature characteristics of magnetic properties, the cooling rate in the second cooling step is set to 10 -2 °C / sec or more 10 5 ° C. / sec or less, and -1 °C / sec or more 10 2 ° C. / second or less. The second cooling step in step S13 corresponds to the second alloy cooling step.

[0068] The rare earth sintered magnet alloy obtained through these processes has a minor axis size of 3 μm to 10 μm and a major axis size of 10 μm to 300 μm. When the rare earth sintered magnet 1 of the third embodiment is manufactured, it has a fine crystalline structure containing a (Nd, Pr, La, Sm)-Fe-B crystalline phase and a crystalline subphase 20 of an oxide represented by (Nd, Pr, La, Sm)-O. Hereinafter, the crystalline subphase 20 of an oxide represented by (Nd, Pr, La, Sm)-O will be referred to as the (Nd, Pr, La, Sm)-O phase. The (Nd, Pr, La, Sm)-O phase is a nonmagnetic phase consisting of an oxide with a relatively high concentration of rare earth elements. The thickness of the (Nd, Pr, La, Sm)-O phase corresponds to the width of the grain boundary and is 10 μm or less. The rare earth sintered magnet alloy produced by the above manufacturing process has undergone a rapid cooling process, and therefore has a finer structure than the rare earth sintered magnet alloy obtained by mold casting.

[0069] Next, the diffusion precursor manufacturing process of step S20 in Fig. 7 will be described. Fig. 9 is a flowchart showing an example of the procedure of the diffusion precursor manufacturing process according to embodiment 4. The following describes the manufacturing of the rare earth sintered magnet 1 according to embodiment 3 as an example, but the rare earth sintered magnet 1 according to embodiments 1 and 2 can also be manufactured by changing the raw material of the rare earth sintered magnet alloy used. 9, the diffusion precursor production process includes a crushing step (step S21) of crushing a rare earth sintered magnet alloy having a (Nd,Pr,La,Sm)-Fe-B crystalline phase and a (Nd,Pr,La,Sm)-O phase, a compacting step (step S22) of compacting the crushed rare earth sintered magnet alloy powder to prepare a compact, a sintering step (step S23) of sintering the compact at a predetermined sintering temperature to obtain a sintered body, an aging step (step S24) of aging the sintered body to improve the magnetic properties such as the coercivity of the rare earth sintered magnet 1, and a sintered body cooling step (step S25) of cooling the aged sintered body. Each step is described below.

[0070] In the pulverization step of step S21, the rare earth sintered magnet alloy satisfying the (Nd,Pr,R)-Fe-B composition produced according to the rare earth sintered magnet alloy production process of FIG. 8 is pulverized to obtain rare earth sintered magnet alloy powder with a particle size of 200 μm or less, preferably 0.5 μm to 100 μm, and even 1 μm to 10 μm when considering magnetization performance. The rare earth sintered magnet alloy is pulverized, for example, using an agate mortar, stamp mill, jaw crusher, or jet mill. In particular, to reduce the particle size of the powder, it is preferable to pulverize the rare earth sintered magnet alloy in an atmosphere containing an inert gas. Pulverizing the rare earth sintered magnet alloy in an atmosphere containing an inert gas can prevent oxygen from being mixed into the powder. However, if the atmosphere during pulverization does not affect the magnetic properties of the magnet, the rare earth sintered magnet alloy may be pulverized in air.

[0071] In the compacting step S22, the rare earth sintered magnet alloy powder is compression-molded in a mold to which a magnetic field is applied to prepare a compact. In one example, the magnetic field applied here can be 2 T. Note that compacting can also be performed without applying a magnetic field, rather than in a magnetic field.

[0072] In the sintering step S23, the compression-molded compact is held at a sintering temperature in the range of 950°C to 1300°C, preferably 1000°C to less than 1150°C, for a time in the range of 0.1 to 10 hours, preferably 1.0 to 6.0 hours, to obtain a sintered body. Sintering is preferably carried out in an atmosphere containing an inert gas or in a vacuum to suppress oxidation. Sintering may also be carried out while applying a magnetic field.

[0073] 9, the aging step of step S24 includes a first aging step of step S24-1, a second aging step of step S24-2, a third aging step of step S24-3, and a fourth aging step of step S24-4. Aging is preferably carried out in an atmosphere containing an inert gas or in a vacuum to suppress oxidation.

[0074] The conditions for the first aging step in step S24-1 are to hold the sintered body at a first aging temperature, which is lower than the sintering temperature, for 0.1 to 10 hours, preferably 0.5 to 5 hours. The first aging temperature is specifically 700°C to 950°C, which is lower than the sintering temperature.

[0075] The second aging step in step S24-2 is carried out by holding the sintered body after the first aging step at a second aging temperature lower than the first aging temperature for 0.1 to 10 hours, preferably 1.0 to 7 hours. The second aging temperature is, specifically, 450°C to 700°C, lower than the first aging temperature.

[0076] The conditions for the third aging step in step S24-3 are as follows: after the second aging step, the sintered body held in the second aging step is again heated to the first aging temperature, specifically, a temperature in the range of 700°C or higher but lower than 950°C, and held at the first aging temperature for a time in the range of 0.1 to 10 hours, preferably 0.5 to 5 hours.

[0077] The conditions for the fourth aging step in step S24-4 are that, after the third aging step, the sintered body held in the third aging step is again held at the second aging temperature, specifically, at a temperature in the range of 450°C or higher and lower than 700°C, for a time in the range of 0.1 to 10 hours, preferably 1.0 to 7 hours.

[0078] Finally, in step S25, the sintered body cooling step, the sintered body held in the fourth aging step is held at a cooling temperature between 200°C and 450°C for a time period between 0.1 and 5 hours. The sintered body is then cooled to room temperature to produce a diffusion precursor of the rare earth sintered magnet 1. Cooling is preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation.

[0079] In this manner, a diffusion precursor is formed, which is a sintered body having the final shape of the rare earth sintered magnet 1.

[0080] Returning to FIG. 7 , in the grain boundary diffusion step of step S30, heat treatment is performed under conditions in which the diffusion precursor formed in step S25 and the heavy rare earth element are present, thereby diffusing the heavy rare earth element into the diffusion precursor through grain boundaries. In one example, heat treatment is performed by holding the diffusion precursor at a temperature lower than the sintering temperature in the sintering step of step S23. The grain boundary diffusion step may be performed simultaneously with the aging step of step S24. In the grain boundary diffusion step, the heavy rare earth element is selectively diffused into at least a portion of the outer periphery of the Sm-enriched portion 41 of the first subphase 21 and uniformly diffused into the second subphase 22. A known grain boundary diffusion method can be used for the grain boundary diffusion step. Various techniques have been proposed for the grain boundary diffusion method, depending on the supply form of the heavy rare earth element. Typical methods include coating diffusion, sputtering diffusion, and vapor diffusion. These typical grain boundary diffusion methods are described below.

[0081] <Coating and Diffusion Method> In the coating diffusion method, the grain boundary diffusion process includes a diffusion element attachment process in which a heavy rare earth element supplying part, which is a material containing a heavy rare earth element and serves as a heavy rare earth element supply source to the diffusion precursor, is attached to the diffusion precursor, and a diffusion heat treatment process in which heat treatment is performed to diffuse the heavy rare earth element from the heavy rare earth element supplying part into the diffusion precursor. In the diffusion element attachment process, a slurry prepared by mixing a powdered heavy rare earth element compound with water or an organic solvent is attached to the surface of the diffusion precursor. The slurry attached to the surface of the diffusion precursor becomes the heavy rare earth element supplying part. The slurry attachment can be performed by spraying, dip coating, spin coating, screen printing, electrodeposition, or the like. In the diffusion heat treatment process, the diffusion precursor with the heavy rare earth element supplying part attached is heat-treated at a diffusion temperature lower than the sintering temperature in the sintering process of step S23, thereby diffusing the heavy rare earth element into the diffusion precursor. The heat treatment conditions are a diffusion temperature lower than the sintering temperature and a time period ranging from 0.1 to 100 hours. The diffusion temperature is, for example, in the range of 300° C. to 1000° C., which is lower than the sintering temperature. The heat treatment is preferably carried out in an atmosphere containing an inert gas or in a vacuum to suppress oxidation.

[0082] <Sputter diffusion method> In the sputter diffusion method, as in the coating diffusion method, the grain boundary diffusion process includes a diffusion element deposition process and a diffusion heat treatment process. In the diffusion element deposition process, a thin film of a heavy rare earth element element metal or alloy composition is formed on the surface of the diffusion precursor in a dry environment. The thin film formed on the surface of the diffusion precursor becomes the heavy rare earth element supply portion. In one example, the thin film is formed by a sputtering method. In the diffusion heat treatment process, the diffusion precursor with the heavy rare earth element supply portion formed thereon is heat-treated at a diffusion temperature lower than the sintering temperature in the sintering process of step S23, thereby diffusing the heavy rare earth element into the diffusion precursor. The heat treatment conditions are a diffusion temperature lower than the sintering temperature and a time period ranging from 0.1 to 100 hours. In one example, the diffusion temperature is a temperature ranging from 300°C to 1000°C, lower than the sintering temperature. To suppress oxidation, the heat treatment is preferably performed in an atmosphere containing an inert gas or in a vacuum.

[0083] <Vapor diffusion method> In the vapor diffusion method, a diffusion precursor and a heavy rare earth element supply source are placed in a vacuum furnace, and then the diffusion precursor is heat-treated in the vacuum furnace at a temperature lower than the sintering temperature in step S23, thereby diffusing the heavy rare earth element into the diffusion precursor. In the heat treatment, the heavy rare earth element supply source is converted into a gas phase by vacuum heating, and the heavy rare earth element is supplied to the diffusion precursor through the gas phase. The heat treatment conditions are a diffusion temperature lower than the sintering temperature, and a time period ranging from 0.1 to 100 hours. The diffusion temperature is, for example, from 600 to 900°C, lower than the sintering temperature. Furthermore, unlike the coating diffusion method and sputter diffusion method, the vapor diffusion method does not require the attachment of a heavy rare earth element supply unit to the diffusion precursor, eliminating the need for the diffusion element attachment step, thereby shortening the time required for the grain boundary diffusion step.

[0084] Returning to Fig. 7, in the cooling step of the last step S40, the diffusion precursor in which the heavy rare earth element has diffused in the grain boundary diffusion step is held at a temperature below 200°C for a time within the range of 0.1 hour or more and 5 hours or less. Then, by cooling to room temperature, the rare earth sintered magnet 1 shown in Embodiments 1 to 3 is formed. In the case of Embodiment 1, a rare earth sintered magnet 1 in which a heavy rare earth element exists in at least a part of the surface of the main phase 10 is formed. In the case of Embodiment 2, a rare earth sintered magnet 1 in which the heavy rare earth element has diffused into the secondary phase 20 is formed. In the case of Embodiment 3, a rare earth sintered magnet 1 is formed in which the heavy rare earth element diffuses so as to selectively surround the outer periphery of the Sm-enriched portion 41 of the first secondary phase 21 and uniformly diffuses into the second secondary phase 22. Cooling is preferably performed in an atmosphere containing an inert gas or in a vacuum for suppressing oxidation.

[0085] As described above, by performing grain boundary diffusion of the heavy rare earth element on the diffusion precursor having the shape of the final rare earth sintered magnet 1, a rare earth sintered magnet 1 having a desired shape can be obtained.

[0086] As described above, by controlling the temperature and time in the sintering step, the aging step, and the sintered body cooling step, the sintered body will be held repeatedly in the temperature range of the unstable energy state. As a result, it becomes possible to mix the first main phase 11 composed of CNd > CPr and the second main phase 12 composed of CNd < CPr. In other words, in the rare earth sintered magnet 1, two types of main phases 10, the first main phase 11 and the second main phase 12, exist. Focusing on the core portions 11c and 12c of the two types of main phases 10, the first main phase 11 has a feature that the Nd concentration is higher than the Pr concentration, and conversely, the second main phase 12 has a feature that the Pr concentration is higher than the Nd concentration, and a rare earth sintered magnet 1 can be manufactured.

[0087] Furthermore, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, a crystalline first secondary phase 21 based on an oxide phase whose main component is represented by (Nd, Pr, La, Sm)-O and a crystalline second secondary phase 22 whose main component is represented by (Nd, Pr, La)-O are provided, and regarding the Sm concentration, a rare earth sintered magnet 1 in which the first secondary phase 21 is higher than the second secondary phase 22 can be manufactured.

[0088] This makes it possible to provide the rare-earth sintered magnet 1 having excellent magnetization performance and magnetic properties as compared with the conventional ones while suppressing the use of Nd and heavy rare-earth elements.

[0089] In Embodiment 4, rare-earth sintered magnet alloy powder obtained by pulverizing a rare-earth sintered magnet alloy having a (Nd, Pr, La, Sm)-Fe-B crystal phase and a (Nd, Pr, La, Sm)-O phase is molded, and after the molded compact is sintered to form a sintered body, the sintered body is aged to produce the rare-earth sintered magnet 1. By this, the rare-earth sintered magnet 1 according to Embodiment 3 can be manufactured.

[0090] Also, in the first aging step, the obtained sintered body is held at a first aging temperature which is a temperature lower than the sintering temperature for 0.1 hour or more and 10 hours or less, preferably 0.5 hour or more and 5 hours or less. In the second aging step, the sintered body is held at a second aging temperature which is a temperature lower than the first aging temperature for 0.1 hour or more and 10 hours or less, preferably 1.0 hour or more and 7 hours or less. In the third aging step, the temperature is raised again to the first aging temperature, and the sintered body is held at the first aging temperature for 0.1 hour or more and 10 hours or less, preferably. 0.5 hour or more and 5 hours or less. In the fourth aging step, the sintered body is held again at the second aging temperature for 0.1 hour or more and 10 hours or less, preferably 1.0 hour or more and 7 hours or less. Thus, by controlling the temperature and time so that two sets of the first aging step and the second aging step are carried out, a state is created in which the sintered body is held repeatedly in a temperature range of an unstable energy state. As a result, it is possible to obtain the rare-earth sintered magnet 1 in which the first main phase 11 composed of CNd > CPr and the second main phase 12 composed of CNd < CPr are mixed. In other words, the rare-earth sintered magnet 1 has two types of main phases 10, the first main phase 11 and the second main phase 12, and when focusing on the core portions 11c and 12c of the two types of main phases 10, the rare-earth sintered magnet 1 in which the Nd concentration of the first main phase 11 is higher than the Pr concentration and conversely the Pr concentration of the second main phase 12 is higher than the Nd concentration can be selectively manufactured.

[0091] Furthermore, the above manufacturing process makes it possible to selectively produce rare earth sintered magnets 1 having a characteristic structure in which the first subphase 21 is a crystalline subphase based on an oxide phase whose main component is (Nd, Pr, La, Sm)-O, and the second subphase 22 is a crystalline subphase whose main component is (Nd, Pr, La)-O, and the first subphase 21 has a higher Sm concentration than the second subphase 22.

[0092] In addition, in the method for producing the rare earth sintered magnet 1 according to the fourth embodiment, an R-Fe-B rare earth sintered magnet alloy containing rare earth elements R including Nd and Pr is pulverized, a powder compact of the R-Fe-B rare earth sintered magnet alloy is sintered, and the resulting compact is aged to form a diffusion precursor having the first main phase 11 and the second main phase 12. In the method for producing the rare earth sintered magnet 1 according to the fourth embodiment, a heat treatment is performed to cause the heavy rare earth element to diffuse through grain boundaries in the diffusion precursor, thereby producing a rare earth sintered magnet 1 in which the heavy rare earth element is present in part of the surfaces of the first main phase 11 and the second main phase 12, or a rare earth sintered magnet 1 in which the heavy rare earth element is present in the subphase 20. This makes it possible to obtain a rare earth sintered magnet 1 that uses less heavy rare earth element than conventional magnets, while suppressing degradation of magnetic properties and improving magnetic properties compared to conventional magnets.

[0093] Furthermore, in the method for producing the rare earth sintered magnet 1 according to the fourth embodiment, an R-Fe-B rare earth sintered magnet alloy containing rare earth elements R including Nd, Pr, La, and Sm is pulverized, a powder compact of the R-Fe-B rare earth sintered magnet alloy is sintered, and an aging treatment is performed to form a diffusion precursor having, in addition to the first main phase 11 and the second main phase 12, a first subphase 21 having an Sm-enriched portion 41 where Sm is concentrated, and a second subphase 22 having a lower Sm concentration than the first subphase 21. In the method for producing the rare earth sintered magnet 1 according to the fourth embodiment, a heat treatment is performed to cause the heavy rare earth element to diffuse through grain boundaries in the diffusion precursor, thereby producing a rare earth sintered magnet 1 in which the heavy rare earth element selectively surrounds the outer periphery of the Sm-enriched portion 41 in the first subphase 21 and the heavy rare earth element is uniformly distributed in the second subphase 22. This makes it possible to obtain a rare earth sintered magnet 1 that can improve magnetic properties compared to conventional magnets while suppressing the use of heavy rare earth elements compared to conventional magnets and preventing deterioration of magnetic properties.

[0094] Embodiment 5 In embodiment 5, a rotor using the rare earth sintered magnet 1 of embodiments 1, 2, and 3 manufactured by the manufacturing method of embodiment 4 will be described. Fig. 10 is a cross-sectional view schematically showing an example of the configuration of a rotor equipped with the rare earth sintered magnet according to embodiment 5. Fig. 10 shows a cross section perpendicular to the rotation axis RA of the rotor 100.

[0095] The rotor 100 is rotatable about the rotation axis RA. The rotor 100 includes a rotor core 101 and rare earth sintered magnets 1 that are inserted into magnet insertion holes 102 that are provided in the rotor core 101 along the circumferential direction of the rotor 100. While FIG. 10 shows an example in which four magnet insertion holes 102 are provided in the rotor core 101 and four rare earth sintered magnets 1 are inserted into the magnet insertion holes 102, the number of magnet insertion holes 102 and rare earth sintered magnets 1 may be changed depending on the design of the rotor 100. The rotor core 101 is formed by stacking a plurality of disk-shaped electromagnetic steel plates in the axial direction of the rotation axis RA.

[0096] The rare earth sintered magnets 1 are manufactured according to the manufacturing method described in embodiment 4. The four rare earth sintered magnets 1 are inserted into the corresponding magnet insertion holes 102. The four rare earth sintered magnets 1 are each magnetized so that the magnetic poles of the rare earth sintered magnets 1 on the radially outer side of the rotor 100 are different from adjacent rare earth sintered magnets 1.

[0097] Thus, the rotor 100 according to embodiment 5 includes the rare earth sintered magnet 1 according to embodiment 1, 2, or 3, which achieves improved magnetic properties at room temperature and suppresses degradation of magnetic properties with increasing temperature. Because the rare earth sintered magnet 1 uses less heavy rare earth elements than conventional magnets, maintaining high remanence and coercivity while suppressing degradation of magnetic properties with increasing temperature, degradation of magnetic properties is suppressed even in high-temperature environments exceeding 100°C. This allows for the substitution of inexpensive rare earth elements for expensive neodymium and heavy rare earth elements, which are unevenly distributed across regions and present procurement risks, while improving magnetic properties and magnetization, thereby stabilizing the operation of the rotor 100 even in high-temperature environments exceeding 100°C. Furthermore, because the rare earth sintered magnet 1 according to embodiment 1, 2, or 3 has superior magnetization performance compared to conventional magnets, it is possible to magnetize the rotor 100 in its assembled state by setting the rare earth sintered magnet 1 therein, thereby facilitating handling during the manufacturing process. Furthermore, the magnetization process can be performed with reduced voltage, which contributes to energy savings.

[0098] Embodiment 6 In the sixth embodiment, a rotating machine equipped with the rotor 100 according to the fifth embodiment will be described. Fig. 11 is a cross-sectional view schematically showing an example of the configuration of the rotating machine according to the sixth embodiment. Fig. 11 shows a cross section in a direction perpendicular to the rotation axis RA of the rotor 100.

[0099] The rotating machine 120 includes the rotor 100 described in the fifth embodiment, which is rotatable about the rotation axis RA, and an annular stator 130 that is coaxial with the rotor 100 and disposed opposite the rotor 100. The stator 130 is formed by laminating a plurality of electromagnetic steel sheets in the axial direction of the rotation axis RA. The configuration of the stator 130 is not limited to this, and an existing configuration can also be adopted. The stator 130 has teeth 131 that protrude toward the rotor 100 and are disposed along the inner surface of the stator 130. Windings 132 are attached to the teeth 131. The windings 132 may be wound in a concentrated winding or a distributed winding manner, for example. In other words, the stator 130 has windings 132 attached to the teeth 131 that protrude toward the rotor 100 on the inner surface on the side where the rotor 100 is disposed, and has an annular structure that is disposed opposite the rotor 100. The rotor 100 in the rotating machine 120 needs to have two or more magnetic poles, i.e., two or more rare earth sintered magnets 1. Also, while Fig. 11 shows an example of an embedded magnet rotor 100, it may also be a surface magnet rotor 100 in which the rare earth sintered magnets 1 are fixed to the outer periphery with an adhesive.

[0100] Thus, the rotating machine 120 in embodiment 6 includes the rare earth sintered magnet 1 according to embodiment 1, 2, or 3, which can improve magnetic properties at room temperature and suppress degradation of magnetic properties with increasing temperature. Because the rare earth sintered magnet 1 uses less heavy rare earth elements than conventional magnets and can suppress degradation of magnetic properties with increasing temperature while maintaining high remanence and coercivity, degradation of magnetic properties is suppressed even in high-temperature environments exceeding 100°C. As a result, the magnetic properties and magnetization are improved while replacing Nd and heavy rare earth elements, which are expensive, unevenly distributed across regions, and present a procurement risk, with inexpensive rare earth elements, enabling stable driving of the rotor 100 and stable operation of the rotating machine 120, even in high-temperature environments exceeding 100°C. [Example]

[0101] The rare earth sintered magnet 1 of the present disclosure will be described in detail below with reference to examples and comparative examples.

[0102] In Examples 1 to 8, rare earth sintered magnet 1 is manufactured by the method shown in Embodiment 4 using samples of rare earth sintered magnet alloys with different compositions represented by (Nd, Pr, La, Sm)-Fe-B. In Examples 1 to 8, rare earth sintered magnet alloys with different contents of Nd, Pr, La, and Sm are used to form a diffusion precursor, and Dy, a heavy rare earth element, is diffused into the diffusion precursor at grain boundaries so that the Dy content becomes 0.10 at.%, thereby manufacturing rare earth sintered magnet 1. In other words, in Examples 1 to 8, rare earth sintered magnet 1 with 0.10 at.% of Dy, a heavy rare earth element, diffused is manufactured from a rare earth sintered magnet alloy represented by (Nd, Pr, La, Sm)-Fe-B using the manufacturing method shown in Embodiment 4.

[0103] In Comparative Examples 1 to 12, samples of multiple rare earth sintered magnet alloys R-Fe-B with different compositions were used to experimentally produce rare earth sintered magnet 1 containing heavy rare earth elements using a general rare earth magnet manufacturing method such as that shown in Patent Document 1 or Patent Document 2. In the samples of rare earth sintered magnet 1 according to Comparative Examples 1 to 12, the R portion was changed.

[0104] In Comparative Examples 1 to 6, a rare earth sintered magnet 1 in which 0.15 at.% of the heavy rare earth element Dy is diffused is manufactured from a rare earth sintered magnet alloy in which R contains Nd and one or more elements from among Dy, Pr, La, and Sm, using the manufacturing method shown in Patent Document 1.

[0105] In Comparative Examples 7 to 12, a rare earth sintered magnet 1 in which 0.15 at.% of the heavy rare earth element Dy is diffused is produced from a rare earth sintered magnet alloy in which R contains Nd and one or more elements from among Dy, Pr, La, and Sm, using the manufacturing method shown in Patent Document 2.

[0106] Table 3 shows the general formula of the rare earth sintered magnets of Examples 1 to 8 and Comparative Examples 1 to 12, the contents of the elements constituting R, the results of morphology analysis, and the results of magnetic property evaluation. Table 3 also shows the general formula of the main phase 10 of each sample, which is the rare earth sintered magnet 1 of Examples 1 to 8 and Comparative Examples 1 to 12.

[0107] [Table 3]

[0108] Next, we will explain how to analyze the structure of the rare earth sintered magnet 1 of Examples 1 to 8 and Comparative Examples 1 to 12. The structure of the rare earth sintered magnet 1 is determined by elemental analysis using a scanning electron microscope (SEM) and an EPMA. Here, FE-EPMA (manufactured by JEOL Ltd., product name: JXA-8530F) is used as the SEM and EPMA. The elemental analysis conditions were an acceleration voltage of 15.0 kV, a probe current of 2.271 e -008 A, the irradiation time is 130 ms, the number of pixels is 512 pixels x 512 pixels, the magnification is 5000 times, and the number of accumulations is 1.

[0109] Next, we will explain how to evaluate the magnetic properties of the rare earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 12. The magnetic properties were evaluated by measuring the coercivity of multiple samples using a pulse-excitation BH tracer. The maximum magnetic field applied by the BH tracer was 6 T or higher, at which point the rare earth sintered magnet 1 was fully magnetized. In addition to pulse-excitation BH tracers, other devices capable of generating a maximum magnetic field of 6 T or higher, such as a DC magnetic fluxmeter (also known as a DC BH tracer), a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), or a physical property measurement system (PPMS), may also be used. Measurements are performed in an atmosphere containing an inert gas such as nitrogen. The magnetic properties of each sample were measured by detecting the magnetization of the rare earth sintered magnet 1 magnetized by an applied magnetic field using a search coil or magnetic sensor. The magnetic properties were measured from the measured magnetic hysteresis, i.e., the JH curve or BH curve. The magnetic properties of each sample were measured at a first measurement temperature T1 and a second measurement temperature T2, which were different from each other. The temperature coefficient α [% / °C] of remanence is the ratio of the difference between the remanence at the first measurement temperature T1 and the remanence at the second measurement temperature T2 to the remanence at the first measurement temperature T1, divided by the temperature difference (T2 - T1). The temperature coefficient β [% / °C] of coercivity is the ratio of the difference between the coercivity at the first measurement temperature T1 and the coercivity at the second measurement temperature T2 to the coercivity at the first measurement temperature T1, divided by the temperature difference (T2 - T1). Therefore, the smaller the absolute values ​​of the temperature coefficients of the magnetic properties |α| and |β|, the more suppressed the deterioration of the magnetic properties of the magnet with increasing temperature.

[0110] First, the analysis results of each sample according to Examples 1 to 8 and Comparative Examples 1 to 12 will be described. FIG. 12 is a diagram tracing the composition image obtained by analyzing the cross-section of the rare earth sintered magnet according to Examples 1 to 8 by FE-EPMA. FIGS. 13 to 18 are element mappings obtained by analyzing the cross-section of the rare earth sintered magnet according to Examples 1 to 8 by FE-EPMA. FIG. 13 is the element mapping of Nd, FIG. 14 is the element mapping of Pr, FIG. 15 is the element mapping of Dy, FIG. 16 is the element mapping of O, FIG. 17 is the element mapping of Sm, and FIG. 18 is the element mapping of La. Note that FIGS. 13 to 18 are the results of element mapping of the region shown in FIG. 12. Further, since the rare earth sintered magnets 1 according to Examples 1 to 8 all show the same results, FIGS. 12 to 18 show representative examples among Examples 1 to 8. Furthermore, the same components as those in FIGS. 1 and 3 are denoted by the same reference numerals.

[0111] As shown in FIGS. 13 and 14, in each sample of Examples 1 to 8, R is one or more rare earth elements selected from other than Nd and Pr, satisfying the general formula (Nd, Pr, R)-Fe-B, and in the main phase 10 containing crystal grains based on the Nd2Fe 14 B crystal structure, there exists a main phase 10 having core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c. It can also be confirmed that in the main phase 10, a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr are mixed.

[0112] [[ID=**10**]]Here, the concentration difference indicated by "the first main phase 11 where CNd > CPr and the second main phase 12 where CNd < CPr" means that there is a clear difference in the detection intensities of Nd and Pr by mapping analysis using EPMA. Specifically, taking the case of the first main phase 11 as an example, the concentration of Nd in the core portion 11c shows that the detection intensity of EPMA is higher than the average, and the concentration of Pr shows that the detection intensity of EPMA is near the lower limit. It can be said that the second main phase 12 is the reverse of the first main phase 11.

[0113] More specifically, taking the Nd mapping diagram in FIG. 13 and the Pr mapping diagram in FIG. 14 as examples, the average value of the detection level of Nd by EPMA is 92, and the average value of the detection level of Pr is 135. In the case of the first main phase 11, CNd is higher than 92, and CPr is near the lower limit value, indicating a clear concentration difference. Also, since the second main phase 12 is the reverse of the first main phase 11, CPr is higher than 135, and CNd is near the lower limit value, showing a clear concentration difference.

[0114] As shown in FIGS. 16 to 18, when R = La, Sm, the rare earth sintered magnet 1 has, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, a crystalline first secondary phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, La, Sm)-O, and a crystalline second secondary phase 22 whose main component is represented as (Nd, Pr, La)-O. Thus, it can be confirmed that the concentration of Sm is higher in the first secondary phase 21 than in the second secondary phase 22.

[0115] In Table 3, for the samples in which the states of the first main phase 11 where CNd > CPr and the second main phase 12 where CNd < CPr were confirmed, "〇" was entered in the columns of the first main phase 11 and the second main phase 12, respectively, and for the samples where it could not be confirmed, "×" was entered in the columns of the first main phase 11 and the second main phase 12, respectively. The concentration difference represented by the inequality means that there is a clear difference in the detection intensities of Nd and Pr. Specifically, in one example, in the case of the first main phase 11, the concentration of Nd has a detection intensity by EPMA higher than the average, and the concentration of Pr has a detection intensity by EPMA near the lower limit value. It can be said that the case of the second main phase 12 is the reverse of the case of the first main phase 11. When only CNd < CPr as in the second main phase 12 was confirmed, "〇" was entered only in the column of the second main phase 12, and "×" was entered in the column of the first main phase 11.

[0116] Furthermore, in Table 3, for samples having a crystalline first secondary phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, La, Sm)-O and a crystalline second secondary phase 22 whose main component is represented as (Nd, Pr, La)-O, and it was confirmed that the concentration of Sm in the first secondary phase 21 is higher than that in the second secondary phase 22, an "〇" is entered in each of the columns for the first secondary phase 21 and the second secondary phase 22, and for samples for which this could not be confirmed, an "×" is entered in each of the columns for the first secondary phase 21 and the second secondary phase 22. Also, for those in which only one secondary phase 20 exists or there is no concentration difference of Sm between the secondary phases 20, assuming that only the first secondary phase 21 exists, an "〇" is entered only in the column for the first secondary phase 21, and an "×" is entered in the column for the second secondary phase 22. The concentration difference between the first secondary phase 21 and the second secondary phase 22 means that, by mapping analysis using EPMA, the detection intensity of Sm in the first secondary phase 21 is on average higher than that in the second secondary phase 22. Specifically, taking the Sm mapping diagram of FIG. 17 as an example, with the average value of the Sm detection level of EPMA being 15.9, the first secondary phase 21 is higher than 15.9, and the second secondary phase 22 is lower than 15.9, that is, it is in a state where detection is not possible in an aggregated state.

[0117] Also, from the intensity ratios of the elemental mappings obtained by FE-EPMA analysis, it can also be confirmed that the number of the first primary phases 11 where CNd > CPr is larger than the number of the second primary phases 12 where CNd < CPr. When focusing on the shell portions 11s, 12s of the core-shell structure, it can also be confirmed that the first primary phase 11 satisfies the relational expressions CNd > SNd and CPr < SPr, and the second primary phase's 12 satisfies the relational expressions CNd < SNd and CPr > SPr.

[0118] Next, the measurement results of the magnetic properties in each of the samples according to Examples 1 to 8 and Comparative Examples 1 to 12 will be described. The shape of each sample for which magnetic measurement is performed is a block shape with a length, width, and height all of 7 mm. The first measurement temperature T1 is 23°C, and the second measurement temperature T2 is 200°C. 23°C is room temperature. 200°C for the second measurement temperature T2 is a temperature that can occur as the environment during the operation of automotive motors and industrial motors.

[0119] First, the remanence and coercivity of each sample in Examples 1 to 8 and Comparative Examples 2 to 12 are judged by comparing them with Comparative Example 1. If the remanence and coercivity values ​​at 23°C of each sample are within 1%, which is considered to be a measurement error, of the values ​​in Comparative Example 1, they are judged as "equivalent," if they are 1% or more higher, they are judged as "good," and if they are 1% or less lower, they are judged as "poor."

[0120] Next, the temperature coefficient α of the remanence is calculated using the remanence at the first measurement temperature T1 of 23°C and the remanence at the second measurement temperature T2 of 200°C. The temperature coefficient β of the coercivity is calculated using the coercivity at the first measurement temperature T1 of 23°C and the coercivity at the second measurement temperature T2 of 200°C. The temperature coefficients of the remanence and the coercivity of each sample in Examples 1 to 8 and Comparative Examples 2 to 12 are evaluated by comparing them with Comparative Example 1. For each sample, the absolute values ​​|α| of the temperature coefficient of the remanence and |β| of the temperature coefficient of the coercivity of the sample in Comparative Example 1 are compared. If the absolute values ​​are within ±1%, which is considered to be the measurement error, the sample is judged as "equivalent." If the absolute values ​​are lower than -1%, the sample is judged as "good." If the absolute values ​​are higher than +1%, the sample is judged as "poor." For samples judged to be "good," the temperature coefficient is smaller, which suppresses the deterioration of magnetic properties with increasing temperature, making it possible to provide a rare earth sintered magnet 1 with stable magnetic properties even in high-temperature environments.

[0121] The results of the evaluation of the residual magnetic flux density, coercive force, temperature coefficient of the residual magnetic flux density, and temperature coefficient of the coercive force are shown in Table 3.

[0122] Comparative Example 1 is a rare earth sintered magnet 1 sample prepared according to the manufacturing method described in Patent Document 1 using Nd, Fe, and FeB as raw materials, with 0.15 at.% Dy diffused therein to form an Nd—Fe—B magnet. Observation of the morphology of this sample using the method described above reveals that, since Pr, La, and Sm are not added, a core-shell structure in the main phase 10 is not confirmed, nor is it confirmed that the Sm concentration in the first subphase 21 in the subphase 20 is higher than that in the second subphase 22. Furthermore, evaluation of the magnetic properties of this sample using the method described above reveals a remanence of 1.3 T and a coercivity of 1250 kA / m. The temperature coefficients of the remanence and coercivity are |α| = 0.191% / °C and |β| = 0.460% / °C, respectively. These values ​​for Comparative Example 1 are used as references.

[0123] Comparative Example 2 is a sample of rare earth sintered magnet 1 prepared according to the manufacturing method described in Patent Document 1 using Nd, Dy, Fe, and FeB as raw materials, with 0.15 at.% Dy diffused therein to form a (Nd,Dy)-Fe-B structure. Observation of the morphology of this sample using the method described above reveals that, because Pr, La, and Sm are not added, a core-shell structure in the main phase 10 is not confirmed, nor is it confirmed that the Sm concentration in the first subphase 21 is higher than that in the second subphase 22. Furthermore, evaluation of the magnetic properties of this sample using the method described above reveals that the remanence is "poor," the coercivity is "good," the temperature coefficient of the remanence is "same," and the temperature coefficient of the coercivity is "same." This result reflects the improved coercivity due to the partial substitution of Nd with Dy, which has high magnetic crystal anisotropy. Furthermore, since the magnetic properties depend on the structure of the diffusion precursor, which is the base material, the magnetic properties do not improve even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor.

[0124] Comparative Example 3 is a sample of rare earth sintered magnet 1 prepared according to the manufacturing method described in Patent Document 1 using Nd, Pr, Fe, and FeB as raw materials, with 0.15 at.% Dy diffused therein to form a (Nd,Pr)-Fe-B structure. Observation of the morphology of this sample using the method described above confirmed the presence of a main phase 10 in which Nd and Pr were mixed, but no core-shell structure was formed. Furthermore, because La and Sm were not added, it was not possible to confirm that the Sm concentration in subphase 20 was higher in first subphase 21 than in second subphase 22. Evaluation of the magnetic properties of this sample using the method described above revealed the following results: the remanence was "same," the coercivity was "good," the temperature coefficient of remanence was "same," and the temperature coefficient of coercivity was "poor." This result reflects the fact that although the addition of Pr increases the magnetic anisotropy of the main phase 10 and improves the coercive force, it is not an optimal structure for the main phase 10 and the subphase 20. Furthermore, since the magnetic properties depend on the structure of the diffusion precursor, which is the base material, diffusing Dy, a heavy rare earth element, into such a diffusion precursor does not improve the magnetic properties.

[0125] Comparative Example 4 is a sample of rare earth sintered magnet 1 prepared according to the manufacturing method described in Patent Document 1 using Nd, La, Sm, Fe, and FeB as raw materials, with 0.15 at.% Dy diffused therein to form a (Nd, La, Sm)-Fe-B magnet. Observation of the morphology of this sample using the method described above reveals that, due to the absence of Pr, a core-shell structure of the main phase 10 is not observed. Furthermore, due to the addition of La and Sm, the Sm concentration is segregated to one subphase 20 in association with the segregation of La, but no second subphase 22 is present. Furthermore, it is not possible to confirm that the first subphase 21 has a higher Sm concentration than the second subphase 22. Furthermore, evaluation of the magnetic properties of this sample using the method described above reveals that the remanence is "similar," the coercivity is "similar," the temperature coefficient of remanence is "good," and the temperature coefficient of coercivity is "good." This result reflects that although the temperature coefficient of the magnetic properties is favorable due to the presence of La and Sm in the main phase 10 or the subphase 20, the magnetic properties at room temperature are not improved, and the magnetic properties are not optimal in the main phase 10 and the subphase 20. Furthermore, since the magnetic properties depend on the structure of the diffusion precursor, which is the base material, diffusing Dy, a heavy rare earth element, into such a diffusion precursor does not improve the magnetic properties.

[0126] Comparative Example 5 is a sample of rare earth sintered magnet 1 prepared according to the manufacturing method described in Patent Document 1 using Nd, La, Sm, Fe, and FeB as raw materials, with 0.15 at.% Dy diffused therein to form a (Nd, La, Sm)-Fe-B magnet. The composition ratio of Nd, La, and Sm differs from that of Comparative Example 4. Observation of the morphology of this sample using the method described above reveals that the absence of Pr results in no core-shell structure of the main phase 10. Furthermore, the addition of La and Sm results in the segregation of Sm into one subphase 20, but no second subphase 22. Furthermore, it is not possible to confirm that the first subphase 21 has a higher Sm concentration than the second subphase 22. Furthermore, evaluation of the magnetic properties of this sample using the method described above reveals that the remanence is "same," the coercivity is "same," the temperature coefficient of remanence is "good," and the temperature coefficient of coercivity is "good." This is because the presence of La and Sm in the main phase 10 or the subphase 20 results in a favorable temperature coefficient of the magnetic properties, but the magnetic properties at room temperature are not improved, reflecting the fact that the main phase 10 and the subphase 20 are not in an optimal structural form. Even if the composition ratio of Nd, La, and Sm is changed, results are obtained that are almost the same as those of Comparative Example 4. Furthermore, because the magnetic properties depend on the structural structure of the diffusion precursor, which is the base material, diffusing Dy, a heavy rare earth element, into such a diffusion precursor does not improve the magnetic properties.

[0127] Comparative Example 6 is a sample of rare earth sintered magnet 1 prepared according to the manufacturing method described in Patent Document 1 using Nd, Pr, La, Sm, Fe, and FeB as raw materials, with 0.15 at.% Dy diffused therein to form (Nd, Pr, La, Sm)-Fe-B. Observation of the morphology of this sample using the method described above reveals that the addition of Pr results in the formation of a main phase 10 in which Nd and Pr are mixed, but no core-shell structure is formed. Furthermore, the addition of La and Sm results in the segregation of Sm into a single subphase 20, but no second subphase 22 is present. Furthermore, it is not possible to confirm that the first subphase 21 has a higher Sm concentration than the second subphase 22. Furthermore, evaluation of the magnetic properties of this sample using the method described above reveals the following: the remanence is "same," the coercivity is "good," the temperature coefficient of the remanence is "good," and the temperature coefficient of the coercivity is "same." This result reflects the fact that, although the addition of Pr increases the magnetic anisotropy of the main phase 10 and improves the coercivity, and the presence of La and Sm in the main phase 10 or subphase 20 improves the temperature coefficient of the magnetic properties, particularly the temperature coefficient of coercivity, the magnetic properties are not optimal in the main phase 10 and subphase 20. Furthermore, because the magnetic properties depend on the structure of the diffusion precursor, which is the base material, diffusing Dy, a heavy rare earth element, into such a diffusion precursor does not improve the magnetic properties.

[0128] Comparative Example 7 is a sample of rare earth sintered magnet 1 produced using Nd, Fe, and FeB as raw materials, according to the manufacturing method including hot working described in Patent Document 2, in which 0.15 at.% Dy was diffused to form Nd—Fe—B. Observation of the microstructure of this sample using the method described above reveals that, because Pr, La, and Sm were not added, a core-shell structure in the main phase 10 was not observed, nor was it confirmed that the Sm concentration in the first subphase 21 in the subphase 20 was higher than that in the second subphase 22. However, the refined microstructure, characteristic of magnets produced by hot working, was confirmed. Evaluation of the magnetic properties of this sample using the method described above revealed that the remanence was “poor,” the coercivity was “good,” the temperature coefficient of remanence was “same,” and the temperature coefficient of coercivity was “same.” This result reflects the fact that the refined microstructure produced by hot working improves coercivity but reduces remanence. Furthermore, since the magnetic properties depend on the structure of the diffusion precursor, which is the base material, the magnetic properties do not improve even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor.

[0129] Comparative Example 8 is a sample of rare earth sintered magnet 1 prepared using Nd, Dy, Fe, and FeB as raw materials, according to the manufacturing method described in Patent Document 2, including hot working, to form (Nd,Dy)-Fe-B, with 0.15 at.% Dy diffused therein. Observation of the morphology of this sample using the method described above reveals that, because Pr, La, and Sm are not added, a core-shell structure in the main phase 10 is not observed, and the Sm concentration in the subphase 20 is not higher in the first subphase 21 than in the second subphase 22. Furthermore, evaluation of the magnetic properties of this sample using the method described above reveals that the remanence is "poor," the coercivity is "good," the temperature coefficient of remanence is "same," and the temperature coefficient of coercivity is "same." This reflects the fact that the magnet is prepared by hot working and that the coercivity is significantly improved by substituting Dy, which has high magnetic crystal anisotropy, for part of the Nd, but the other properties reflect the refined structure. Furthermore, since the magnetic properties depend on the structure of the diffusion precursor, which is the base material, the magnetic properties do not improve even if Dy, a heavy rare earth element, is diffused into such a diffusion precursor.

[0130] Comparative Example 9 is a sample of rare earth sintered magnet 1 prepared using Nd, Pr, Fe, and FeB as raw materials, according to the manufacturing method including hot working described in Patent Document 2, with 0.15 at.% Dy diffused therein, to form (Nd,Pr)-Fe-B. Observation of the morphology of this sample using the method described above confirmed the addition of Pr and the resulting core-shell structure due to the hot working. However, there is only one main phase 10 with a high Pr concentration in the core. Furthermore, because La and Sm were not added, it was not possible to confirm that the Sm concentration in the subphase 20 was higher in the first subphase 21 than in the second subphase 22. Evaluation of the magnetic properties of this sample using the method described above yielded results: the remanence was "poor," the coercivity was "good," the temperature coefficient of the remanence was "same," and the temperature coefficient of the coercivity was "same." This is because, although the formation of a core-shell structure with a high Pr concentration in the core significantly improves the coercivity to the level of rare earth sintered magnet 1 with added Dy, other properties reflect the refinement of the structure. Furthermore, because the magnetic properties depend on the structure of the diffusion precursor, which is the base material, diffusing Dy, a heavy rare earth element, into such a diffusion precursor does not improve the magnetic properties.

[0131] Comparative Example 10 is a sample of rare earth sintered magnet 1 produced using Nd, La, Sm, Fe, and FeB as raw materials, according to the manufacturing method including hot working described in Patent Document 2, with 0.15 at.% Dy diffused therein, to form (Nd, La, Sm)-Fe-B. Observation of the morphology of this sample using the method described above reveals that, due to the absence of Pr, a core-shell structure of the main phase 10 is not observed. Furthermore, due to the addition of La and Sm, the Sm concentration is segregated to one subphase 20 due to the segregation of La, but no second subphase 22 is present. Furthermore, it is not possible to confirm that the first subphase 21 has a higher Sm concentration than the second subphase 22. Furthermore, evaluation of the magnetic properties of this sample using the method described above reveals that the remanence is "poor," the coercivity is "good," the temperature coefficient of the remanence is "good," and the temperature coefficient of the coercivity is "good." This result reflects that although the temperature coefficient of the magnetic properties is favorable due to the presence of La and Sm in the main phase 10 or the subphase 20, the remanence at room temperature is not improved, and the magnetic properties are not optimal in the main phase 10 and the subphase 20. Furthermore, since the magnetic properties depend on the structure of the diffusion precursor, which is the base material, diffusing Dy, a heavy rare earth element, into such a diffusion precursor does not improve the magnetic properties.

[0132] Comparative Example 11 is a sample of rare earth sintered magnet 1 produced using Nd, La, Sm, Fe, and FeB as raw materials, according to the manufacturing method including hot working described in Patent Document 2, with 0.15 at.% Dy diffused therein, to form (Nd, La, Sm)-Fe-B. The composition ratio of Nd, La, and Sm differs from that of Comparative Example 10. When the morphology of this sample was observed using the method described above, the absence of Pr did not reveal a core-shell structure in the main phase 10. Furthermore, due to the addition of La and Sm, the Sm concentration segregates to one subphase 20 in association with the segregation of La, but the second subphase 22 does not exist. Furthermore, it was not possible to confirm that the Sm concentration in the first subphase 21 was higher than that in the second subphase 22. Furthermore, when the magnetic properties of this sample were evaluated according to the method described above, the remanence was "poor," the coercivity was "good," the temperature coefficient of the remanence was "good," and the temperature coefficient of the coercivity was "good." This result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase 20 resulted in a favorable temperature coefficient of the magnetic properties, but the remanence at room temperature did not improve, and this reflects the fact that the main phase 10 and the subphase 20 were not in an optimal structural form. Even when the composition ratio of Nd, La, and Sm was changed, results similar to those of Comparative Example 10 were obtained. Furthermore, because the magnetic properties depend on the structural structure of the diffusion precursor, which is the base material, diffusing the heavy rare earth element Dy into such a diffusion precursor did not improve the magnetic properties.

[0133] Comparative Example 12 is a sample of rare earth sintered magnet 1 prepared using Nd, Pr, La, Sm, Fe, and FeB as raw materials, according to the manufacturing method including hot working described in Patent Document 2, with 0.15 at.% Dy diffused therein, to form (Nd, Pr, La, Sm)-Fe-B. Observation of the morphology of this sample using the above-described method reveals that the addition of Pr and the hot working result in a core-shell structure, but there is only one main phase 10 with a high Pr concentration in the core. Furthermore, the addition of La and Sm results in the segregation of Sm into one subphase 20, but no second subphase 22. Furthermore, it is not possible to confirm that the first subphase 21 has a higher Sm concentration than the second subphase 22. Furthermore, when the magnetic properties of this sample were evaluated using the method described above, the remanence was "poor," the coercivity "good," the temperature coefficient of remanence "good," and the temperature coefficient of coercivity "good." This is because the formation of a core-shell structure with a high Pr concentration in the core significantly improved the coercivity to the level of rare earth sintered magnet 1 containing Dy. Furthermore, the presence of La and Sm in the main phase 10 or subphase 20 resulted in favorable temperature coefficients of the magnetic properties, particularly the coercivity. However, the remanence at room temperature did not improve, reflecting the suboptimal microstructure of the main phase 10 and subphase 20. Furthermore, because magnetic properties depend on the microstructure of the diffusion precursor, which is the base material, diffusing the heavy rare earth element Dy into such a diffusion precursor does not improve the magnetic properties.

[0134] In the samples of Examples 1 to 8, R is one or more rare earth elements selected from among those other than Nd and Pr, and the general formula (Nd, Pr, R)-Fe-B is satisfied, and NdFe 14The rare earth sintered magnet 1 has a main phase 10 containing crystal grains based on a B crystal structure. The main phase 10 has core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c. The main phase 10 is a mixture of a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr. Also, when R = La, Sm, in addition to the first main phase 11 and the second main phase 12, it has a crystalline first sub-phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, La, Sm)-O, and a crystalline second sub-phase 22 whose main component is represented as (Nd, Pr, La)-O, and the concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22. When the magnetic properties of the samples of Examples 1 to 8 are evaluated according to the method described above, the residual magnetic flux density is "good", the coercive force is "good", the temperature coefficient of the residual magnetic flux density is "good", and the temperature coefficient of the coercive force is "good". As a result, these rare earth sintered magnets 1 exhibit the effect of having excellent magnetic properties compared to the prior art while suppressing the use of Nd and heavy rare earth elements, which are expensive and have a high regional bias and procurement risk. Also, since the magnetic properties depend on the microstructure of the diffusion precursor, which is the base material, when Dy, which is a heavy rare earth element, is diffused into a diffusion precursor with good magnetic properties, the magnetic properties are further improved. Also, in Examples 1 to 8, a rare earth sintered magnet 1 with good magnetic properties can be obtained with a diffusion amount of 0.10 at.%, which is lower than the diffusion amount of Dy in Comparative Examples 1 to 12, which is 0.15 at.%. That is, compared to Comparative Examples 1 to 12, a rare earth sintered magnet 1 can be obtained that can greatly improve the coercive force without reducing the residual magnetic flux density while suppressing the amount of heavy rare earth elements used.

[0135] The configurations shown in the above embodiments are examples, and it is possible to combine with another known technique, combine the embodiments with each other, or omit or change a part of the configuration without departing from the gist.

Explanation of Reference Numerals

[0136] 1 rare earth sintered magnet, 10 main phase, 11 first main phase, 11c, 12c core portion, 11s, 12s shell portion, 12 second main phase, 20 subphase, 21 first subphase, 22 second subphase, 31 heavy rare earth element-containing layer, 32 heavy rare earth element-containing portion, 41 Sm-enriched portion, 100 rotor, 101 rotor core, 102 magnet insertion hole, 120 rotating machine, 130 stator, 131 teeth, 132 winding.

Claims

1. When R is one or more rare earth elements selected from among those other than Nd and Pr, the general formula (Nd, Pr, R)-Fe-B is satisfied, and Nd 2 Fe 14 a main phase including crystal grains based on a B crystal structure; a subphase present between a plurality of the main phases; Equipped with the main phase has a core portion and a shell portion that covers the core portion, the main phase has a first main phase satisfying CNd>CPr and a second main phase satisfying CNd<CPr, where CNd is a concentration of Nd in the core portion and CPr is a concentration of Pr in the core portion, the first main phase and the second main phase are mixed, A rare earth sintered magnet, characterized in that a heavy rare earth element is present on at least a portion of the surface of the first main phase and the second main phase.

2. When R is one or more rare earth elements selected from among those other than Nd and Pr, the general formula (Nd, Pr, R)-Fe-B is satisfied, and Nd 2 Fe 14 a main phase including crystal grains based on a B crystal structure; a subphase present between a plurality of the main phases; Equipped with the main phase has a core portion and a shell portion that covers the core portion, the main phase has a first main phase satisfying CNd>CPr and a second main phase satisfying CNd<CPr, where CNd is a concentration of Nd in the core portion and CPr is a concentration of Pr in the core portion, the first main phase and the second main phase are mixed, A rare earth sintered magnet characterized in that a heavy rare earth element is present in the subphase.

3. 3. The rare earth sintered magnet according to claim 1, wherein the number of the first main phases is greater than the number of the second main phases.

4. 3. The rare earth sintered magnet according to claim 1, wherein the first main phase satisfies the relationship CNd>SNd, CPr<SPr, and the second main phase satisfies the relationship CNd<SNd, CPr>SPr, where SNd is the neodymium concentration in the shell portion and SPr is the prism concentration in the shell portion.

5. The subphase has a crystalline first subphase based on an oxide phase whose main component is expressed as (Nd, Pr, La, Sm)-O, where R is La and Sm, and a crystalline second subphase whose main component is expressed as (Nd, Pr, La)-O, 2. The rare earth sintered magnet according to claim 1, wherein the first subphase has a higher Sm concentration than the second subphase.

6. The subphase has a crystalline first subphase based on an oxide phase whose main component is expressed as (Nd, Pr, La, Sm)-O, where R is La and Sm, and a crystalline second subphase whose main component is expressed as (Nd, Pr, La)-O, 3. The rare earth sintered magnet according to claim 2, wherein the first subphase forms an Sm-enriched portion having a higher Sm concentration than the second subphase.

7. 7. The rare earth sintered magnet according to claim 6, wherein the heavy rare earth element is present in the first subphase so as to surround the outer periphery of the Sm-enriched portion.

8. 3. The method for producing a rare earth sintered magnet according to claim 1 or 2, a rare earth sintered magnet alloy manufacturing process for manufacturing a rare earth sintered magnet alloy that serves as a raw material for a diffusion precursor before diffusing the heavy rare earth element into the rare earth sintered magnet; a diffusion precursor manufacturing step of manufacturing the diffusion precursor; a diffusion step of diffusing the heavy rare earth element into the diffusion precursor; a cooling step of cooling the diffusion precursor in which the heavy rare earth element has been diffused; Including, The rare earth sintered magnet alloy manufacturing process includes: a melting step of melting a raw material of the rare earth sintered magnet alloy containing the elements constituting the diffusion precursor; a primary alloy cooling step of cooling the raw material in a molten state in the melting step to obtain a solidified alloy; a second alloy cooling step of further cooling the solidified alloy to obtain a rare earth sintered magnet alloy; Including, The diffusion precursor manufacturing process includes: a pulverization step of pulverizing the rare earth sintered magnet alloy satisfying the (Nd, Pr, R)—Fe—B composition; a compacting step of preparing a compact by compacting the powder of the rare earth sintered magnet alloy pulverized in the pulverizing step; a sintering step of sintering the compact at a predetermined sintering temperature to obtain a sintered body; a first aging step of holding the sintered body at a first aging temperature that is lower than the sintering temperature; a second aging step of maintaining the sintered body maintained in the first aging step at a second aging temperature which is lower than the first aging temperature; a third aging step in which the sintered body held in the second aging step is held again at the first aging temperature; a fourth aging step of maintaining the sintered body maintained in the third aging step at the second aging temperature; a sintered body cooling step of cooling the sintered body held in the fourth aging step to obtain the diffusion precursor; Including, a sintered rare earth magnet having a thickness of 1000 nm and a thickness of 1000 nm; a sintered rare earth magnet having a thickness of 1000 nm and a thickness of 1000 nm;

9. A rotor core; The rare earth sintered magnet according to claim 1 or 2, which is provided in the rotor core; A rotor comprising:

10. The rotor according to claim 9 ; an annular stator disposed opposite the rotor, the stator having windings attached to teeth protruding toward the rotor on an inner surface on the side where the rotor is disposed; A rotating machine comprising:

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