Rare-earth sintered magnet, method for producing rare-earth sintered magnet, rotor, and rotary machine

Abstract

Rare earth sintered magnets (1) possess the following characteristics: when R is set as one or more rare earth elements selected from Nd and Pr, they satisfy the general formula (Nd, Pr, R)-Fe-B, including Nd2Fe. 14 B has a crystal structure consisting of a main phase (10) with basic grains and a secondary phase (20) existing between multiple main phases (10). The main phase (10) has a core (11c, 12c) and a shell (11s, 12s) covering the core (11c, 12c). When the concentration of Nd in the core (11c, 12c) is set to CNd and the concentration of Pr in the core (11c, 12c) is set to CPr, the main phase (10) has a first main phase (11) with CNd > CPr and a second main phase (12) with CNd < CPr. The first main phase (11) and the second main phase (12) are mixed. Heavy rare earth elements are present on at least a portion of the surface of the first main phase (11) and the second main phase (12).

Description

Technical Field

[0001] This disclosure relates to rare earth sintered magnets as permanent magnets made by sintering materials containing rare earth elements, a method for manufacturing rare earth sintered magnets, rotors, and rotating machines. Background Technology

[0002] Given that the tetragonal crystal R2T 14 RTB-based permanent magnets are predominantly composed of intermetallic compounds. In this system, R represents rare earth elements, T represents Fe (iron) or transition metals such as Fe partially replaced by Co (cobalt), and B represents boron. RTB-based permanent magnets are primarily used in industrial motors and various high-value-added components. In particular, Nd-Fe-B sintered magnets with Nd (neodymium) as R are used in various components due to their excellent magnetic properties. Furthermore, industrial motors are often used in high-temperature environments exceeding 100°C; therefore, there have been attempts to improve coercivity by adding heavy rare earth elements such as Dy (dysprosium) to Nd-TB sintered magnets.

[0003] In recent years, the production of Nd-Fe-B sintered magnets has expanded, leading to increased consumption of Nd and heavy rare earth elements such as Dy and Tb. However, the high price and uneven regional distribution of Nd and heavy rare earth elements pose procurement risks. Therefore, as countermeasures to reduce Nd and heavy rare earth element consumption, considerations include: using magnets with a main phase containing low-heavy rare earth elements; using other rare earth elements such as Pr (praseodymium), Ce (cerium), La (lanthanum), Sm (samarium), Sc (scandium), Gd (gadolinium), Y (yttrium), and Lu (ruthenium); and employing special manufacturing methods that perform thermoplastic processing on the sintered body. Hereinafter, the thermoplastic processing performed on the sintered body will be referred to as hot working. However, while incorporating significant amounts of heavy rare earth elements into the main phase helps improve coercivity, it significantly reduces remanent flux density. Furthermore, when Nd is entirely or partially replaced by elements such as Pr, Ce, La, Sm, Sc, Gd, Y, and Lu, the magnetic properties of residual magnetic flux density and coercivity are significantly reduced. Moreover, when the sintered body undergoes hot processing, the magnetizability of the magnet is significantly reduced due to grain refinement. Because of these factors, it is difficult to simultaneously achieve both heavy rare earth element reduction and excellent magnetic properties and magnetizability. Therefore, in the past, when using these elements in the manufacture of Nd-Fe-B based sintered magnets, efforts have been made to develop techniques that can improve the magnetic properties at room temperature and suppress the decrease in magnetic properties associated with temperature increases. In particular, the current focus is on rare earth magnets that can achieve both further reduction of heavy rare earth elements and excellent magnetic properties and magnetizability.

[0004] Patent document 1 discloses an RTB-based sintered magnet that comprises R2T 14RTB-based sintered magnets with B crystal main phase particles are characterized in that R is one or more rare earth elements with heavy rare earth element RH as an essential element, T is Fe or one or more transition metal elements with Fe and Co as essential elements, B is boron, and a portion of the main phase particles contains multiple low heavy rare earth element crystal phases within them, the low heavy rare earth element crystal phases being formed by R2T 14 The phase is composed of B crystals, and the concentration of heavy rare earth elements is relatively low compared to the overall concentration of heavy rare earth elements in the main phase particles. Based on the technology described in Patent Document 1, an RTB-based sintered magnet with improved magnetic properties and low cost is obtained.

[0005] Patent document 2 discloses a rare earth magnet that uses R as a rare earth element and has the following properties: R2Fe 14 The B-type crystal structure consists of a main phase and a grain boundary phase surrounding the main phase. The main phase has a core, a first shell surrounding the core, and a second shell surrounding the first shell. In the rare-earth magnet described in Patent Document 2, the proportions of Nd and Pr in the first shell are higher than those in the core and the second shell. Furthermore, in the rare-earth magnet described in Patent Document 2, the proportion of heavy rare-earth elements in the second shell is higher than that in the first shell. This results in a rare-earth magnet with further improved coercivity.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-174313

[0009] Patent Document 2: Japanese Patent Application Publication No. 2021-174818 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, regarding the RTB-based sintered magnet described in Patent Document 1, since the phase containing heavy rare earth elements exists within the main phase, even if the coercivity can be improved, the residual magnetic flux density required for industrial motors and the like cannot be obtained, and the magnetic properties may be reduced. Furthermore, in order to diffuse the heavy rare earth elements within the main phase particles, the amount of heavy rare earth elements used increases, posing procurement risks and failing to reduce costs. Additionally, regarding the rare earth magnet described in Patent Document 2, since the main phase is singular, there is a problem that a microstructure sufficient to enhance the anisotropic magnetic field cannot be formed, making it difficult to obtain high magnetic properties. Furthermore, in the rare earth magnet described in Patent Document 2, the shell of the main phase forms a two-layer structure with different proportions of heavy rare earth elements, requiring the heavy rare earth elements to be placed in both shells, thus making it difficult to improve magnetic properties with less heavy rare earth elements.

[0012] This disclosure is made in view of the above, with the aim of obtaining a rare earth sintered magnet that, compared with the past, can suppress the use of heavy rare earth elements while improving the magnetic properties.

[0013] Methods for solving problems

[0014] To address the aforementioned issues and achieve the objectives, the rare earth sintered magnet disclosed herein comprises: a main phase that, when R is set to one or more rare earth elements selected from Nd and Pr, satisfies the general formula (Nd, Pr, R)-Fe-B, including Nd2Fe 14 B crystal structure consists of basic grains and secondary phases existing between multiple main phases. The main phases have a core and a shell covering the core. Regarding the main phases, when the Nd concentration in the core is set as CNd and the Pr concentration in the core is set as CPr, there is a first main phase with CNd > CPr and a second main phase with CNd < CPr. The first and second main phases are mixed. Heavy rare earth elements are present on at least a portion of the surface of both the first and second main phases.

[0015] The effects of the invention

[0016] The rare earth sintered magnet disclosed herein has the following effects: on the one hand, it suppresses the use of heavy rare earth elements compared with the past, and on the other hand, it can improve the magnetic properties compared with the past. Attached Figure Description

[0017] Figure 1 The diagram schematically illustrates an example of the structure of a rare earth sintered magnet in its sintered state according to Embodiment 1.

[0018] Figure 2 The diagram illustrates an example of the structure of a rare earth sintered magnet in its sintering state according to Embodiment 2.

[0019] Figure 3The diagram schematically illustrates an example of the structure of a rare-earth sintered magnet in its sintering state according to Embodiment 3.

[0020] Figure 4 The elemental mapping of Sm obtained by analyzing the cross-section of the rare earth sintered magnet according to Embodiment 3 using FE-EPMA.

[0021] Figure 5 The elemental mapping of Tb obtained by analyzing the cross-section of the rare earth sintered magnet according to Embodiment 3 using FE-EPMA.

[0022] Figure 6 To represent tetragonal Nd2Fe 14 A diagram of atomic sites in the B crystal structure.

[0023] Figure 7 This is a flowchart illustrating an example of the steps in a method for manufacturing a rare-earth sintered magnet according to Embodiment 4.

[0024] Figure 8 This is a flowchart illustrating an example of the steps in the rare earth sintered magnet alloy manufacturing process according to Embodiment 4.

[0025] Figure 9 This is a flowchart illustrating an example of the steps in the diffusion precursor manufacturing process according to Embodiment 4.

[0026] Figure 10 A cross-sectional view is shown schematically, illustrating an example of the configuration of a rotor equipped with rare earth sintered magnets according to Embodiment 5.

[0027] Figure 11 A cross-sectional view is shown schematically as an example of the configuration of the rotating machine according to Embodiment 6.

[0028] Figure 12 A compositional image obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA.

[0029] Figure 13 The elemental mapping of Nd obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0030] Figure 14 The elemental mapping of Pr obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0031] Figure 15 The elemental mapping of Dy obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0032] Figure 16The elemental mapping of O was obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA.

[0033] Figure 17 The elemental mapping of Sm obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0034] Figure 18 The elemental mapping of La was obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. Detailed Implementation

[0035] The following description, based on the accompanying drawings, details the rare earth sintered magnets, the manufacturing method of the rare earth sintered magnets, the rotors, and the rotating machine related to embodiments of the present disclosure.

[0036] Implementation method 1.

[0037] Figure 1 This diagram schematically illustrates an example of the structure of a rare-earth sintered magnet in its sintered state according to Embodiment 1. The rare-earth sintered magnet 1 according to Embodiment 1 has a structure satisfying the general formula (Nd, Pr, R)-Fe-B, containing Nd2Fe... 14 The B crystal structure is a main phase 10 with basic grains, which has a core and a shell covering the core. R is one or more rare earth elements selected from Nd and Pr. The shell has a different composition from the core and is arranged to cover the core. Additionally, the rare earth sintered magnet 1 also has a secondary phase 20 existing between the main phases 10, i.e., between multiple main phases 10. The secondary phase 20 is a basic phase consisting of an oxide phase represented by (Nd, Pr, R)-O as the main component.

[0038] In the rare earth sintered magnet 1 according to Embodiment 1, when the Nd concentration in the core is set to CNd and the Pr concentration in the core is set to CPr, the main phase 10 has a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr, and the first main phase 11 and the second main phase 12 are mixed. The first main phase 11 has a core 11c and a shell 11s that is different from the core 11c and covers the core 11c. The second main phase 12 has a core 12c and a shell 12s that is different from the core 12c and covers the core 12c. In the core 11c of the first main phase 11, CNd > CPr, and in the core 12c of the second main phase 12, CNd < CPr.

[0039] That is, in the rare earth sintered magnet 1, there are two main phases 10, namely a first main phase 11 and a second main phase 12. Focusing on the cores 11c and 12c of the two main phases 10, it means that the Nd concentration is higher than the Pr concentration in the first main phase 11, and conversely, the Pr concentration is higher than the Nd concentration in the second main phase 12. By mixing the two main phases 10 with core-shell structures and different magnetic anisotropy, Nd and heavy rare earth elements are reduced while maintaining good magnetization and improving remanent magnetic flux density and coercivity. Furthermore, it also helps to suppress the reduction of magnetic properties associated with temperature changes. Here, the concentration difference shown as "first main phase 11 with CNd > CPr and second main phase 12 with CNd < CPr" means that a clear difference is produced in the detection intensity of Nd and Pr by using mapping analysis with an Electron Probe Micro Analyzer (EPMA). Specifically, taking the case of the first main phase 11 as an example, the Nd concentration in the core 11c means that the detection intensity of EPMA is on average higher than the Nd detection intensity, and the Pr concentration means that the detection intensity of EPMA is near the lower limit of the Pr detection intensity. It can be said that the second main phase 12 is the opposite of the first main phase 11.

[0040] Furthermore, regarding the rare earth sintered magnet 1 according to Embodiment 1, when the Nd concentration of the core 11c of the first main phase 11 is set to C1Nd, the Nd concentration of the core 12c of the second main phase 12 is set to C2Nd, the Pr concentration of the core 11c of the first main phase 11 is set to C1Pr, and the Pr concentration of the core 12c of the second main phase 12 is set to C2Pr, the relationship C1Nd > C2Nd and C1Pr < C2Pr is satisfied. That is, for Nd concentration, the core 11c of the first main phase 11 is higher than the core 12c of the second main phase 12; conversely, for Pr concentration, the core 12c of the second main phase 12 is higher than the core 11c of the first main phase 11. This concentration difference also means a difference in the detection intensity of Nd and Pr obtained by the above-described mapping analysis using EPMA. Specifically, at the Nd concentration, this means that the average detection intensity of EPMA of Nd in the core 11c of the first main phase 11 is higher than the average detection intensity of Nd, while the average detection intensity of EPMA of Nd in the core 12c of the second main phase 12 is lower than the average detection intensity of Nd. At the Pr concentration, this means that the average detection intensity of EPMA of Pr in the core 12c of the second main phase 12 is higher than the average detection intensity of Pr, while the average detection intensity of EPMA of Pr in the core 11c of the first main phase 11 is lower than the average detection intensity of Pr. That is, a large amount of Pr exists in the core 12c of the second main phase 12 where the Nd concentration is low, and conversely, a large amount of Nd exists in the core 11c of the first main phase 11 where the Pr concentration is low. By controlling this microstructure, a rare-earth sintered magnet 1 with excellent magnetic properties can be obtained.

[0041] Furthermore, in the rare earth sintered magnet 1 according to Embodiment 1, a large amount of the first main phase 11, in which CNd > CPr, exists compared to the second main phase 12, in which CNd < CPr. In other words, this means that it has Nd2Fe 14 The proportion of the first principal phase 11 in the composition of B is greater than that of Pr2Fe. 14 The composition of B has a large number of second principal phases 12. This is because the addition of Nd2Fe... 14 The first principal phase 11 of the composition of B is increased with Pr2Fe 14 Compared to the second principal phase 12 of the B composition, superior magnetic and temperature properties are obtained. Furthermore, by controlling the microstructure to this extent, overall grain refinement is also suppressed, thus ensuring magnetization while simultaneously achieving better magnetic properties than before.

[0042] Furthermore, in the rare earth sintered magnet 1 according to Embodiment 1, focusing on the shell portions 11s and 12s of the core-shell structure, when the Nd concentration of the shell portions 11s and 12s is set to SNd and the Pr concentration of the shell portions 11s and 12s is set to SPr, the first main phase 11 satisfies the relationship CNd > SNd and CPr < SPr, and the second main phase 12 satisfies the relationship CNd < SNd and CPr > SPr. Specifically, for the shell portion 11s of the first main phase 11, although the Nd concentration is low, the Pr concentration is higher than that of the core portion 11c; for the shell portion 12s of the second main phase 12, although the Pr concentration is low, the Nd concentration is higher than that of the core portion 12c. By forming a main phase 10 with a shell portion 11s having a high Pr concentration, as in the first main phase 11, the coercivity can be improved. Furthermore, by forming a main phase 10 with a high Nd concentration in the shell 12s, such as the second main phase 12, it is possible to maintain coercivity while suppressing the decrease in remanent magnetic flux density. By selectively controlling the microstructure to achieve this, the rare-earth sintered magnet 1 can exhibit superior magnetic properties compared to the past.

[0043] Furthermore, the main phase 10 has a heavy rare earth element containing layer 31 on at least a portion of its surface. That is, heavy rare earth elements are present on at least a portion of the surfaces of the main phase 10, namely the first main phase 11 and the second main phase 12. More specifically, heavy rare earth elements are present on at least a portion of the outer peripheral surfaces of the shell portions 11s and 12s, while heavy rare earth elements do not enter the core portions 11c and 12c. The heavy rare earth elements are one or more elements selected from Dy, Tb, Gd, and Ho (holmium). In this way, the coercivity is increased by the entry of heavy rare earth elements into the R sites of the first main phase 11 and the second main phase 12, but since the heavy rare earth elements do not enter the interior of the first main phase 11, i.e., the core portion 11c, and the interior of the second main phase 12, i.e., the core portion 12c, a significant decrease in remanent magnetic flux density can be suppressed. That is, it is possible to increase the coercivity while suppressing the decrease in remanent magnetic flux density. To achieve this effect, the proportion of heavy rare earth elements in the preferred main phase 10 is greater than 0 atomic% and less than 10 atomic%.

[0044] Comparing the magnetic properties of a rare-earth sintered magnet 1 with those containing heavy rare-earth elements in the interior of the main phase 10 and those containing heavy rare-earth elements in the surface layer, it is known that to obtain the same magnetic properties, the surface of the main phase 10 can contain a lower concentration of heavy rare-earth elements than when the main phase 10 contains heavy rare-earth elements in the interior. That is, compared to the case where heavy rare-earth elements are contained in the interior of the main phase 10, the amount of heavy rare-earth elements used in the rare-earth sintered magnet 1 according to Embodiment 1, where heavy rare-earth elements are contained in the surface layer of the main phase 10, can be reduced.

[0045] Furthermore, the average grain size of the main phase 10 is preferably 100 μm or less, and more preferably 0.5 μm or more and 50 μm or less for improved magnetic properties. Furthermore, by setting it to about 1 μm or more and 10 μm or less, a grain size different from that of the fine structure manufactured by hot working can be formed, good magnetization performance can be maintained, and a rare earth sintered magnet 1 with superior magnetic properties than before can be produced.

[0046] The rare-earth sintered magnet 1 according to Embodiment 1 may contain an additive element M to further improve its magnetic properties. The additive element M is one or more elements selected from Ga (gallium), Cu (copper), Al (aluminum), Co, Zr (zirconium), Ti (titanium), Nb (niobium), and Mn (manganese). Therefore, regarding the rare-earth sintered magnet 1 according to Embodiment 1, when RH is set as a heavy rare-earth element selected from Dy, Tb, Gd, and Ho, and R is set as Nd, Pr, and a rare-earth element other than the heavy rare-earth element RH, the magnetic properties are improved by the general formula (Nd... a Pr b R c RH d )Fe e B f M g The addition of element M is selected from one or more elements chosen from Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn. Preferably, a, b, c, d, e, f, and g satisfy the following relationship.

[0047] 5≤a+b≤20

[0048] 0 < c + d < (a + b)

[0049] 0 < d < 10

[0050] 70≤e≤90

[0051] 0.5≤f≤10

[0052] 0≤g≤5

[0053] a+b+c+d+e+f+g = 100 atoms %

[0054] Regarding the rare earth sintered magnet 1 according to Embodiment 1, if R is set to one or more rare earth elements selected from Nd and Pr, then the rare earth element satisfying the general formula (Nd, Pr, R)-Fe-B, including Nd2Fe 14In the main phase 10, which has a B-type crystal structure as its basic grain, there exist main phase 10 with cores 11c and 12c and shells 11s and 12s covering the cores 11c and 12c. The main phase 10 has a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr, and the first main phase 11 and the second main phase 12 are mixed. With this configuration, a rare earth sintered magnet 1 can be obtained that improves magnetic properties and magnetization compared to the past while suppressing the use of Nd and heavy rare earth elements.

[0055] Furthermore, the first principal phase 11 and the second principal phase 12 are made to satisfy the relationship C1Nd > C2Nd and C1Pr < C2Pr. Alternatively, the number of the first principal phase 11 is greater than the number of the second principal phase 12. Alternatively, the first principal phase 11 is made to satisfy the relationship CNd > SNd and CPr < SPr, and the second principal phase 12 is made to satisfy the relationship CNd < SNd and CPr > SPr. Thus, it is also possible to obtain a rare earth sintered magnet 1 that improves magnetic properties and magnetization while suppressing the use of Nd and heavy rare earth elements.

[0056] Furthermore, heavy rare earth elements are present in at least a portion of the surfaces of the first main phase 11 and the second main phase 12, while heavy rare earth elements are absent from the interior of the first main phase 11 and the second main phase 12. Thus, a rare earth sintered magnet 1 can be obtained that simultaneously suppresses the use of heavy rare earth elements, improves coercivity compared to conventional magnets, and suppresses a significant decrease in remanent magnetic flux density. In other words, it has the effect of improving the magnetic properties of the rare earth sintered magnet 1 compared to conventional magnets.

[0057] Furthermore, in Embodiment 1, the first main phase 11 and the second main phase 12 are core-shell structures with one-layer shell portions 11s and 12s, requiring only that heavy rare earth elements are present on at least a portion of the surface of the shell portions 11s and 12s. On the other hand, in Patent Document 2, which has a two-layer core-shell structure, heavy rare earth elements must diffuse into both core and shell portions. Thus, the rare earth sintered magnet 1 of Embodiment 1 also has the effect of suppressing the amount of heavy rare earth elements used, compared to Patent Document 2.

[0058] Implementation method 2.

[0059] Figure 2 This figure schematically illustrates an example of the structure of the rare earth sintered magnet in its sintered state according to Embodiment 2. It should be noted that the same reference numerals are used for the same constituent elements as in Embodiment 1, and their descriptions are omitted. The rare earth sintered magnet 1 according to Embodiment 2 has a primary phase 10 and a secondary phase 20.

[0060] 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 with a core-shell structure, and the composition of the core portions 11c and 12c and the composition of 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 is not present on the surface of the main phase 10.

[0061] The secondary phase 20 is a phase based on an oxide phase represented by (Nd, Pr, R)-O as the main component. However, in Embodiment 2, the secondary phase 20 contains heavy rare earth elements. The heavy rare earth elements are distributed throughout the secondary phase 20. In one example, the heavy rare earth elements are uniformly distributed within the secondary phase 20.

[0062] Thus, in Embodiment 2, a secondary phase 20 containing heavy rare earth elements exists between the primary phases 10. It can also be assumed that the heavy rare earth elements are uniformly distributed within the secondary phase 20, and that they enter a portion of the surface of the primary phase 10 in contact with the secondary phase 20. That is, it is assumed that the heavy rare earth elements do not enter the core portions 11c and 12c of the primary phase 10, but do enter a portion of the shell portions 11s and 12s. Therefore, similar to Embodiment 1, it is possible to increase the coercivity of the rare earth sintered magnet 1 while suppressing the decrease in remanent magnetic flux density.

[0063] like Figure 2 As shown, in the rare earth sintered magnet 1, the main phase 10 is in contact with other main phases 10 without passing through the secondary phase 20, or is in contact with other main phases 10 via the secondary phase 20. That is, at least a portion of the surface of the main phase 10 is in contact with the secondary phase 20. Furthermore, the secondary phase 20 contains heavy rare earth elements. Therefore, at least a portion of the surface of the main phase 10 is covered by the secondary phase 20 containing heavy rare earth elements. When observing the distribution of heavy rare earth elements relative to the main phase 10, heavy rare earth elements are 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 focuses on the interface between the main phase 10 and the secondary phase 20 to represent the distribution of heavy rare earth elements, while Embodiment 2 focuses on the secondary phase 20 to represent the distribution of heavy rare earth elements. Thus, it can be said that Embodiment 1 and Embodiment 2 are observations of the same rare earth sintered magnet 1 from different perspectives.

[0064] According to Embodiment 2, similarly to Embodiment 1, a rare-earth sintered magnet 1 can be obtained that simultaneously reduces the use of heavy rare-earth elements, increases coercivity compared to the past, and suppresses a significant reduction in residual magnetic flux density. In other words, it has the effect of improving the magnetic properties of the rare-earth sintered magnet 1 compared to the past.

[0065] Implementation method 3.

[0066] Figure 3This diagram schematically illustrates an example of the structure of a rare-earth sintered magnet in its sintered state according to Embodiment 3. The rare-earth sintered magnet 1 according to Embodiment 3 has a primary phase 10 and a secondary phase 20. The primary phase 10, as described in Embodiment 1, includes a first primary phase 11 and a second primary phase 12. Figure 2 In this context, the first principal phase 11 and the second principal phase 12 are combined to represent principal phase 10. Sub-phase 20 exists between principal phases 10.

[0067] In the rare-earth sintered magnet 1 according to Embodiment 3, the case where the rare-earth element R is selected as La or Sm is shown. When the rare-earth element R is selected as La or Sm, the effect of improving magnetic properties and achieving superior magnetization compared to the past is even greater while suppressing the use of Nd and heavy rare-earth elements. In this example, the main phase 10 has (Nd, Pr, La, Sm)₂Fe. 14 The composition of B. This gives R2Fe a tetragonal crystal. 14 The reason why the rare earth element R of the B-crystal rare earth sintered magnet 1 contains La and Sm is that, based on the calculation results of the magnetic interaction energy using the molecular orbital method, a composition with added La and Sm is formed, thereby obtaining a practical rare earth sintered magnet 1 that can significantly suppress the decrease in magnetic properties associated with temperature rise. Furthermore, La and Sm are intentionally segregated at grain boundaries, which is an example of the secondary phase 20, thereby allowing Nd and Pr to diffuse relatively in the main phase 10, improving the magnetocrystalline anisotropy of the main phase 10. Thus, a core-shell structure with both high and low magnetic anisotropy regions is formed within the main phase 10, making it easier to generate a rare earth sintered magnet 1 with a mixture of a first main phase 11 (CNd > CPr) and a second main phase 12 (CNd < CPr).

[0068] It should be noted that if too much La and Sm are added, the amount of Nd and Pr, which are elements with high magnetic anisotropy constants and high saturation magnetic polarization, will decrease, leading to a reduction in magnetic properties. Therefore, when the composition ratios of Nd, Pr, La, and Sm are set to A, B, C, and D, respectively, it is preferable to set it to (A+B) > (C+D).

[0069] In the rare-earth sintered magnet 1 according to Embodiment 3, when R = La and Sm, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, a secondary phase 20 is provided. The secondary phase 20 has: a first secondary phase 21 with a crystalline structure based on an oxide phase with main components expressed as (Nd, Pr, La, Sm)-O, and a second secondary phase 22 with a crystalline structure based on (Nd, Pr, La)-O. It has the characteristic that, in terms of the concentration of Sm in the secondary phase 20, the first secondary phase 21 is higher than the second secondary phase 22. That is, the first secondary phase 21 forms an Sm-enriched portion 41 with a higher Sm concentration than the second secondary phase 22. This achieves the effect of suppressing the decrease in magnetic properties not only at room temperature but also with increasing temperature.

[0070] The statement that "in terms of Sm concentration, the first subphase 21 is higher than the second subphase 22" means that, using EPMA mapping analysis, the detection intensity of Sm in the first subphase 21 is on average higher than that in the second subphase 22.

[0071] The crystalline secondary phase 20 is a collective term for the crystalline first secondary phase 21 and the crystalline second secondary phase 22, existing between the main phase 10. The crystalline first secondary phase 21 is represented by (Nd, Pr, La, Sm)-O, and the crystalline second secondary phase 22 is represented by (Nd, Pr, La)-O. Here, (Nd, Pr, La, Sm) means that a portion of Nd and Pr are replaced by La and Sm. It should be noted that the elements of the main components are listed in parentheses here; therefore, the first secondary phase 21 and the second secondary phase 22 may contain trace amounts of other components besides those shown in parentheses. In one example, the second secondary phase 22, represented by (Nd, Pr, La)-O, contains trace amounts of Sm.

[0072] In the rare earth sintered magnet 1 according to Embodiment 3, a concentration difference of La and Sm exists in the main phase 10 and the secondary phase 20, and La and Sm segregate from the main phase 10 to the secondary phase 20. That is, the sum of the La concentrations in the first secondary phase 21 and the second secondary phase 22 is greater than or equal to the La concentration in the main phase 10, and the sum of the Sm concentrations in the first secondary phase 21 and the second secondary phase 22 is greater than or equal to the Sm concentration in the main phase 10. Specifically, the La and Sm concentrations in the secondary phase 20 are greater than or equal to the La and Sm concentrations in the main phase 10. Here, 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. That is, the sum of the La concentrations in the first secondary phase 21 and the second secondary phase 22 is higher than the sum of the La concentrations in the first main phase 11 and the second main phase 12. In addition, 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. That is, the sum of the concentrations of Sm in the first secondary phase 21 and the second secondary phase 22 is higher than the sum of the concentrations of Sm in the first primary phase 11 and the second primary phase 12.

[0073] Here, when the La concentration in the main phase 10 is set as X, the La concentration in the first subphase 21 is set as X1, the La concentration in the second subphase 22 is set as X2, the Sm concentration in the main phase 10 is set as Y, the Sm concentration in the first subphase 21 is set as Y1, and the Sm concentration in the second subphase 22 is set as Y2, the following relationship (1) is satisfied.

[0074] 1<(Y1+Y2) / Y<(X1+X2) / X · · · · (1)

[0075] Furthermore, from the perspective of improving magnetic properties, the concentrations of Nd and Pr contained in the main phase 10 satisfy the following relationships (2) and (3).

[0076] (CNd+SNd) >(X+Y) · · · · (2)

[0077] (CPr+SPr) >(X+Y) · · · · (3)

[0078] It should be noted that, as described 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 segregate from the main phase 10 to the secondary phase 20. However, under localized observation, the sum of the individual concentrations of La and Sm in the first main phase 11 and the second main phase 12 may not always satisfy the aforementioned relationship with the sum of the individual concentrations of La and Sm in the first secondary phase 21 and the second secondary phase 22. Therefore, more specifically, the La concentration in the main phase 10 represents 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 represents the average of the Sm concentrations in the first main phase 11 and the second main phase 12. In this case, the concentration of La in the secondary phase 20, i.e., the sum of the concentrations of La in the first secondary phase 21 and the second secondary phase 22, means the average concentration of La in the first secondary phase 21 and the second secondary phase 22, and the concentration of Sm in the secondary phase 20, i.e., the sum of the concentrations of Sm in the first secondary phase 21 and the second secondary phase 22, means the average concentration of Sm in the first secondary phase 21 and the second secondary phase 22.

[0079] In the case of La, Nd and Pr diffuse relatively into the main phase 10 by being present at high concentrations at the grain boundaries during the manufacturing process, particularly the heat treatment. As a result, Nd and Pr in the main phase 10 of the rare earth sintered magnet 1 in Embodiment 3 are not consumed at the grain boundaries, and the magnetocrystalline anisotropy is improved. In Sm, Nd also diffuses relatively into the main phase 10, particularly the first secondary phase 21, at a high concentration compared to the main phase 10, thus improving the magnetocrystalline anisotropy, similar to La.

[0080] As described in Embodiment 2, the subphase 20 contains heavy rare earth elements, therefore the first subphase 21 and the second subphase 22 contain heavy rare earth elements. In Embodiment 3, the distribution of heavy rare earth elements differs between the first subphase 21 and the second subphase 22. In the second subphase 22, where the Sm concentration is lower than that of the first subphase 21, the heavy rare earth elements are uniformly distributed within the second subphase 22. On the other hand, in the first subphase 21 where the Sm enrichment section 41 is formed, the heavy rare earth elements are not uniformly distributed within the first subphase 21, but are selectively distributed between the periphery of the first subphase 21 and the Sm enrichment section 41, that is, in the inner periphery of the periphery of the first subphase 21. Specifically, they exist in a manner that selectively surrounds the periphery of the Sm enrichment section 41 where the Sm concentration of the first subphase 21 is high. Thus, it can be said that the first subphase 21 has the Sm enrichment section 41 and a heavy rare earth element containing section 32 containing heavy rare earth elements that selectively surround the periphery of the Sm enrichment section 41. The outer periphery of the first subphase 21 is the boundary between the first subphase 21 and the main phase 10.

[0081] Similar to Embodiment 2, a first subphase 21 and a second subphase 22 containing heavy rare earth elements exist between the main phase 10 and the main phase 10. It can be assumed that the heavy rare earth elements enter a portion of the surface of the main phase 10 that is in contact with the first subphase 21 and the second subphase 22 containing heavy rare earth elements. That is, it is assumed that the heavy rare earth elements do not enter the core portions 11c and 12c of the main phase 10, but enter a portion of the shell portions 11s and 12s. Therefore, similar to Embodiment 1, it is possible to increase the coercivity of the rare earth sintered magnet 1 while suppressing the decrease in remanent magnetic flux density.

[0082] Figure 4 and Figure 5 The elemental mapping was obtained by analyzing the cross-section of the rare earth sintered magnet according to Embodiment 3 using a Field Emission-Electron Probe Micro Analyzer (FE-EPMA). Figure 4 For element mapping of Sm, Figure 5 This is an elemental mapping for Tb. These diagrams show the presence of a secondary phase 20 between the primary phase 10 and the secondary phase 10. Furthermore, within the secondary phase 20, there exists a first secondary phase 21 with an Sm concentration 41, and a second secondary phase 22 with a lower Sm concentration than the first secondary phase 21. In the second secondary phase 22, as described above, Tb, as a heavy rare earth element, is uniformly distributed. On the other hand, in the first secondary phase 21, a deviation occurs in the distribution of Tb. (Refer to...) Figure 4 and Figure 5The heavy rare earth element containing section 32 is selectively surrounded by the Sm enrichment section 41, which increases the Sm concentration in the first subphase 21. Furthermore, heavy rare earth elements are almost absent in the Sm enrichment section 41. Moreover, the concentration of heavy rare earth elements selectively distributed around the Sm enrichment section 41 is higher than the concentration of heavy rare earth elements uniformly distributed within the second subphase 22.

[0083] Secondly, regarding La and Sm in tetragonal R2Fe 14 Please explain which atomic sites in the B crystal structure were replaced. Figure 6 To represent tetragonal Nd2Fe 14 A diagram showing the atomic sites in the B crystal structure. This is explained below. Figure 6 The crystal structure shown is described in one example in reference 1 below. Figure 1 Regarding the substitution site, the stabilization energy generated by the substitution is calculated using band structure calculations and the molecular field approximation of the Heisenberg model, and the determination is made based on the value of this energy.

[0084] (Reference 1) JF Herbs et al. "Relationships between crys tal s structure and magnetic properties in Nd2Fe 14 B. PHYSICAL REVIEW B. 1984, Vol. 29, No. 7, pp. 4176-4178.

[0085] First, the calculation method for the stabilization energy of La is explained. Regarding the stabilization energy of La, Nd8Fe can be used... 56 B4 unit cell, through (Nd7La1)Fe 56 B4+Nd and Nd8(Fe) 55 The energy difference between La and B₄ + Fe is used to determine the stability. A lower energy value indicates greater stability when atoms are substituted at their sites. That is, for La, substitution is more likely to occur at the site with the lowest energy. In this calculation, it is assumed that when La replaces the original atom, the tetragonal R₂Fe... 14 The lattice constant in the B crystal structure does not change with different atomic radii. Table 1 shows the stabilization energy of La at each substitution site when the ambient temperature is changed.

[0086] [Table 1]

[0087] (Table 1)

[0088]

[0089] Unit: eV

[0090] According to Table 1, regarding stable substitution sites for La, Nd(f) sites are found at temperatures above 1000 K, while Fe(c) sites are found at temperatures of 293 K and 500 K. According to the rare-earth sintered magnet 1 of Embodiment 3, as described later, the raw material for the rare-earth sintered magnet 1 is heated to a temperature above 1000 K and melted, then rapidly cooled. Therefore, it is considered that the raw material for the rare-earth sintered magnet 1 is maintained at 1000 K or above, i.e., 727°C or above, preferably around 1300 K, i.e., 1027°C. At this time, it is considered that La is substituted at either the Nd(f) site or the Nd(g) site. Here, it is considered that the energy-stable Nd(f) site preferentially substitutes La, but substitution may also occur at the La substitution sites towards the Nd(g) site with a smaller energy difference. Therefore, the Nd(g) site is also mentioned as a candidate for La substitution sites.

[0091] Furthermore, in the case of manufacturing rare earth sintered magnet 1 using the manufacturing method described later, the sintering temperature is above 1000K, but by undergoing a first aging process, a second aging process, a third aging process, a fourth aging process, and a cooling process, the Fe(c) sites listed in Table 1 are repeatedly maintained in an energy-stable temperature range. In other words, the La substitution at the Nd sites of the main phase 10 is maintained in an unstable energy state. That is, in the raw material stage of rare earth sintered magnet 1, La mainly substitutes at the Nd sites of the main phase 10, but in the rare earth sintered magnet 1 manufactured by the manufacturing method described later, for the Nd sites of the main phase 10, by deliberately maintaining them multiple times within a temperature range of unstable energy states, a certain degree of La is selectively released from the Nd sites of the main phase 10, resulting in La segregation in the secondary phase 20. As a result, the main phase 10 promotes the formation of a core-shell structure.

[0092] Secondly, the calculation method for the stabilization energy of Sm is explained. The stabilization energy of Sm can be calculated using (Nd7Sm1)Fe 56 B4+Nd and Nd8(Fe) 55 The energy difference of Sm1)B4+Fe is used to determine the energy. For tetragonal R2Fe obtained by atomic substitution... 14 The lattice constant remains unchanged in the B crystal structure, similar to the case of La. Table 2 shows the stabilization energy of Sm at each substitution site when the ambient temperature is changed.

[0093] [Table 2]

[0094] (Table 2)

[0095]

[0096] Unit: eV

[0097] According to Table 2, the stable substitution sites in Sm differ from those in La; they are all Nd(g) sites at all temperatures. Even in Sm, it is considered that energy-stable Nd(g) sites preferentially substitute, but in Sm, substitution can also occur at Nd(f) sites with small energy differences.

[0098] When the rare-earth sintered magnet 1 is manufactured using the method described later, the substitution at the Nd(g) site in the main phase 10 is the most stable in terms of energy. However, as mentioned above, the temperature range in which the substitution at the Nd site in the main phase 10 in La becomes unstable is maintained, thereby releasing a portion of Sm along with La from the Nd site in the main phase 10 and segregating it in the secondary phase 20. As a result, there is a concentration difference between the main phase 10 and the secondary phase 20, where the sum of the La concentrations in the first secondary phase 21 and the second secondary phase 22 is greater than the La concentration in the main phase 10, and the sum of the Sm concentrations in the first secondary phase 21 and the second secondary phase 22 is greater than the Sm concentration in the main phase 10. More specifically, the average concentration of La in the first secondary phase 21 and the second secondary phase 22 is greater than the average concentration of La in the first main phase 11 and the second main phase 12, and the average concentration of Sm in the first secondary phase 21 and the second secondary phase 22 is greater than the average concentration of Sm in the first main phase 11 and the second main phase 12. That is, it can be said that La and Sm segregate in the secondary phase 20.

[0099] Comparing La and Sm, from an energy perspective, it is evident that La, when maintained in an unstable energy state at a temperature range, tends to overwhelmingly segregate in the secondary phase 20. Therefore, in the case of rare-earth sintered magnets 1 prepared with equal concentrations of La and Sm, the segregation ratio of La in the secondary phase 20 increases among the La and Sm present in the rare-earth sintered magnets 1. By maintaining this temperature range multiple times, a concentration gradient of Sm with a smaller segregation ratio is generated in the secondary phase 20, forming a first secondary phase 21 and a second secondary phase 22. This promotes the formation of a core-shell structure in the main phase 10.

[0100] This time, as Figure 6 The diagram illustrates a representative Nd, as represented by Di (ジジム). Nd and Pr are produced as a mixture, therefore their energy levels are considered to be close. Thus, it can be said that the same applies even if Nd is replaced with Pr. By allowing both Nd and Pr to exist, a main phase 10 with two core-shell structures can be formed.

[0101] As described above, regarding the rare earth sintered magnet 1 of Embodiment 3, when R is one or more rare earth elements selected from Nd and Pr, it has a structure that satisfies the general formula (Nd, Pr, R)-Fe-B and contains Nd2Fe. 14The B-crystal structure is based on a main phase 10 with cores 11c and 12c and shells 11s and 12s covering the cores 11c and 12c. When R = La and Sm, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, a secondary phase 20 is also present. The secondary phase 20 has a first secondary phase 21 with a crystallinity based on an oxide phase represented by (Nd, Pr, La, Sm)-O as the main component, and a second secondary phase 22 with a crystallinity based on (Nd, Pr, La)-O as the main component. The concentration of Sm is such that the first secondary phase 21 is higher than that of the second secondary phase 22. That is, two main phases 10 and two secondary phases 20 exist. As a result, a rare earth sintered magnet 1 with superior magnetic properties, such as temperature characteristics, compared to the past can be provided. Furthermore, by setting R to La and Sm, the main phase 10 becomes a mixture of a first main phase 11 (CNd > CPr) and a second main phase 12 (CNd < CPr). In other words, the rare-earth sintered magnet 1 contains a main phase 10 with two types of main phases 11 and 12. Focusing on the cores 11c and 12c of the two main phases 10, it is easy to generate a main phase 10 with two core-shell structures: a higher Nd concentration than Pr concentration in the first main phase 11, and conversely, a higher Pr concentration than Nd concentration in the second main phase 12. As a result, it is possible to further improve the magnetic properties while suppressing the use of Nd and heavy rare earth elements, achieving a magnetization that is superior to the past.

[0102] Furthermore, in Embodiment 3, similar to Embodiment 1, a rare-earth sintered magnet 1 can be obtained that simultaneously reduces the use of heavy rare-earth elements, increases coercivity compared to the conventional method, and suppresses a significant decrease in remanent magnetic flux density. In other words, it has the effect of improving the magnetic properties of the rare-earth sintered magnet 1 compared to the conventional method.

[0103] Implementation method 4.

[0104] In Embodiment 4, a method for manufacturing the rare earth sintered magnet 1 described in Embodiments 1, 2, or 3 will be explained. Figure 7 This is a flowchart illustrating an example of the steps in a method for manufacturing a rare-earth sintered magnet according to Embodiment 4. For example... Figure 7 As shown, the method for manufacturing rare earth sintered magnet 1 includes: a rare earth sintered magnet alloy manufacturing step (step S10) to manufacture a rare earth sintered magnet alloy as a raw material for a sintered body, i.e. a diffusion precursor, before the diffusion of heavy rare earth elements in the rare earth sintered magnet 1; a diffusion precursor manufacturing step (step S20) to form a diffusion precursor; a grain boundary diffusion step (step S30) to diffuse heavy rare earth elements in the diffusion precursor; and a cooling step (step S40) to cool the diffusion precursor that diffuses heavy rare earth elements to obtain the rare earth sintered magnet 1.

[0105] First, the details of the rare earth sintered magnet alloy manufacturing process in step S10 will be explained. Figure 8 This is a flowchart illustrating an example of the steps in the rare earth sintered magnet alloy manufacturing process according to Embodiment 4. First, as... Figure 8 As shown, the manufacturing process of rare earth sintered magnet alloys, which serve as diffusion precursors, includes: a melting process (step S11) in which the raw material of the rare earth sintered magnet alloy containing elements constituting the diffusion precursor is heated to a temperature of 1000 K or higher to melt it; a first cooling process (step S12) in which the molten raw material is cooled on a rotating body to obtain a solidified alloy; and a second cooling process (step S13) in which the solidified alloy is further cooled in a container. Thus, rare earth sintered magnet alloys can be manufactured. Each step will be described below.

[0106] In the melting process of step S11, the raw material of the diffusion precursor is heated to a temperature of 1000 K or higher and melted in a crucible in an atmosphere containing an inert gas such as Ar (argon) or in a vacuum. This prepares a melted alloy of rare earth sintered magnet alloy. When manufacturing the rare earth sintered magnet 1 of Embodiments 1 and 2, Nd, Pr, Fe, and B can be used as raw materials. When manufacturing the rare earth sintered magnet 1 of Embodiment 3, Nd, Pr, La, Sm, Fe, and B can be used as raw materials. Alternatively, FeB can be used instead of B as a raw material. In this case, as the added element M, the raw material can contain one or more elements selected from Al, Co, Zr, Ti, Nb, and Mn.

[0107] Secondly, in the first cooling step of step S12, the molten alloy prepared in the melting step is poured into a tundish, and then poured onto a single roller, which serves as a rotating body. This rapidly cools the molten alloy on the single roller rotating in a predetermined direction, producing a solidified alloy with a thickness thinner than the ingot alloy. While a single roller is used as the rotating body, it is not limited to this; it can also be in contact with a double roller, a rotating disk, or a rotating cylindrical mold for rapid cooling. From the viewpoint of efficiently obtaining a thin solidified alloy, the cooling rate in the first cooling step is preferably 10°C / second or higher. 7 Below ℃ / second, more preferably 10 3 ℃ / second or higher and 10 4 Below ℃ / second. The thickness of the solidified alloy is in the range of 0.03 mm to 10 mm. The alloy melt begins to solidify from the part in contact with the single roller, and crystals grow in the thickness direction from the contact surface with the single roller into columnar or needle-like shapes. The first cooling process in step S12 corresponds to the first alloy cooling process.

[0108] Then, in the second cooling step of step S13, the thin solidified alloy prepared in the first cooling step is placed into a tray container and cooled. When the thin solidified alloy is placed into the tray container, it is pulverized to become a flake-like rare earth sintered magnet alloy, which is then cooled. Depending on the cooling rate, sometimes a ribbon-like rare earth sintered magnet alloy is also obtained, and it is not limited to a flake-like shape. From the viewpoint of obtaining a rare earth sintered magnet alloy with a microstructure exhibiting good temperature characteristics and magnetic properties, the cooling rate in the second cooling step is preferably 10. -2 ℃ / second or higher and 10 5 Below ℃ / second, more preferably 10 -1 ℃ / second or higher and 10 2 Below ℃ / second. The second cooling process in step S13 corresponds to the second alloy cooling process.

[0109] Regarding the rare earth sintered magnet alloy obtained through these processes, the short-axis dimension is 3 μm or more and 10 μm or less, and the long-axis dimension is 10 μm or more and 300 μm or less. In the case of manufacturing the rare earth sintered magnet 1 of Embodiment 3, it has a fine crystalline structure containing a (Nd, Pr, La, Sm)-Fe-B crystalline phase and a crystalline secondary phase 20 of oxides represented by (Nd, Pr, La, Sm)-O. Hereinafter, the crystalline secondary phase 20 of oxides 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 non-magnetic phase composed of oxides 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. Regarding the rare earth sintered magnet alloys manufactured through the above manufacturing process, due to the rapid cooling process, the microstructure is refined compared to rare earth sintered magnet alloys obtained by mold casting.

[0110] Secondly, for Figure 7 The diffusion precursor manufacturing process of step S20 will be described. Figure 9 This is a flowchart illustrating an example of the steps in the diffusion precursor manufacturing process according to Embodiment 4. Hereinafter, the case of manufacturing the rare earth sintered magnet 1 of Embodiment 3 will be described as an example. By changing the raw materials of the rare earth sintered magnet alloy used, the rare earth sintered magnets 1 of Embodiments 1 and 2 can be manufactured. Figure 9As shown, the diffusion precursor manufacturing process includes: a pulverization step (step S21) of pulverizing a rare earth sintered magnet alloy having (Nd, Pr, La, Sm)-Fe-B and (Nd, Pr, La, Sm)-O phases; a molding step (step S22) of preparing a molded body by molding the pulverized rare earth sintered magnet alloy powder; a sintering step (step S23) of sintering the molded body at a determined sintering temperature; an aging step (step S24) of aging the sintered body to improve the magnetic properties such as coercivity of the rare earth sintered magnet 1; and a sintered body cooling step (step S25) of cooling the aging-treated sintered body. Each step will be described below.

[0111] In the crushing process of step S21, the powder will be crushed according to... Figure 8 The rare earth sintered magnet alloy manufacturing process produces (Nd, Pr, R)-Fe-B rare earth sintered magnet alloy powder with a particle size of 200 μm or less, preferably 0.5 μm or more and 100 μm or less, and further approximately 1 μm or more and 10 μm or less, taking magnetization performance into consideration. In one example, the rare earth sintered magnet alloy is pulverized using an agate mortar, a crusher, a jaw crusher, or a 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. By pulverizing the rare earth sintered magnet alloy in an atmosphere containing an inert gas, the incorporation of oxygen into the powder can be suppressed. However, if the atmosphere during pulverization does not affect the magnetic properties of the magnet, the rare earth sintered magnet alloy can also be pulverized in the atmosphere.

[0112] In step S22, the rare earth sintered magnetic alloy powder is compressed and molded in a mold with an applied magnetic field to prepare a molded body. In one example, the applied magnetic field can be set to 2T. It should be noted that molding can be performed without an applied magnetic field.

[0113] In the sintering process of step S23, a sintered body is obtained by holding the compressed molded body at a sintering temperature within the range of 950°C to 1300°C, preferably 1000°C to 1150°C, for a time within the range of 0.1 hours to 10 hours, preferably 1.0 hour to 6.0 hours. For sintering, in order to suppress oxidation, it is preferable to carry out the sintering in an atmosphere containing inactive gases or in a vacuum. Sintering can also be carried out while a magnetic field is applied.

[0114] Regarding the aging process in step S24, in Figure 9In this case, the process includes the first aging step S24-1, the second aging step S24-2, the third aging step S24-3, and the fourth aging step S24-4. Regarding aging, to suppress oxidation, it is preferable to carry out the process in an atmosphere containing inert gases or in a vacuum.

[0115] Regarding the conditions of the first aging process in step S24-1, the obtained sintered body is held at a temperature lower than the sintering temperature, i.e., the first aging temperature, for a period of 0.1 hours to 10 hours, preferably 0.5 hours to 5 hours. Specifically, the first aging temperature is a temperature in the range of 700°C to 950°C, which is a temperature lower than the sintering temperature.

[0116] Regarding the conditions for the second aging process in step S24-2, after the first aging process, the sintered body held in the first aging process is held at a temperature lower than the first aging temperature, i.e., the second aging temperature, for a period of 0.1 hours to 10 hours, preferably 1.0 hour to 7 hours. Specifically, the second aging temperature is a temperature in the range of 450°C to 700°C, which is lower than the first aging temperature.

[0117] Regarding the conditions of the third aging process in step S24-3, after the second aging process, the sintered body held in the second aging process is heated again to the first aging temperature, specifically a temperature in the range of 700°C or higher and less than 950°C, and held at the first aging temperature for a time in the range of 0.1 hours or more and 10 hours or less, preferably 0.5 hours or more and 5 hours or less.

[0118] Regarding the conditions of the fourth aging process in step S24-4, after the third aging process, the sintered body held in the third aging process is held again at the second aging temperature, specifically at a temperature in the range of 450°C or higher and less than 700°C, for a time of 0.1 hours or more and less than 10 hours, preferably 1.0 hours or more and less than 7 hours.

[0119] Finally, in the sintered body cooling process of step S25, the sintered body held in the fourth aging process is maintained at a temperature between 200°C and 450°C for a time between 0.1 hours and 5 hours. Then, by cooling to room temperature, a diffusion precursor for the rare earth sintered magnet 1 is manufactured. Regarding cooling, to suppress oxidation, it is preferable to perform the cooling in an atmosphere containing inactive gases or in a vacuum.

[0120] As described above, a diffusion precursor is formed as a sintered body having the shape of the final rare earth sintered magnet 1.

[0121] Back Figure 7 In the grain boundary diffusion process of step S30, the diffusion precursor formed in step S25 is heat-treated in the presence of heavy rare earth elements to allow the heavy rare earth elements to diffuse through grain boundaries in the diffusion precursor. In one example, the heat treatment to maintain the diffusion precursor is performed at a temperature lower than the sintering temperature in the sintering process of step S23. The grain boundary diffusion process can be performed simultaneously with the aging process of step S24. In the grain boundary diffusion process, the heavy rare earth elements are selectively diffused to at least a portion of the periphery of the Sm enrichment portion 41 of the first secondary phase 21, so that they are uniformly diffused into the second secondary phase 22. Known grain boundary diffusion methods can be used for the processing in the grain boundary diffusion process. Regarding grain boundary diffusion methods, various techniques have been proposed depending on the supply form of the heavy rare earth elements, with coating diffusion, sputtering diffusion, and vapor diffusion being representative methods. These representative grain boundary diffusion methods will be described below.

[0122] <Coating Diffusion Method>

[0123] In the coating diffusion method, the grain boundary diffusion process includes: a diffusion element attachment process in which a heavy rare earth element supply part, which is a material containing heavy rare earth elements and serves as a supply source of heavy rare earth elements to the diffusion precursor, is attached; and a diffusion heat treatment process in which the heavy rare earth elements are heat-treated to diffuse from the heavy rare earth element supply part to the diffusion precursor. In the diffusion element attachment process, a slurry made by mixing powdered heavy rare earth element compounds in 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 supply part. The slurry can be attached by spraying, dip coating, spin coating, screen printing, electrodeposition, etc. In the diffusion heat treatment process, the diffusion precursor with the attached heavy rare earth element supply part is heat-treated at a diffusion temperature below the sintering temperature in the sintering process of step S23, so that the heavy rare earth elements diffuse into the interior of the diffusion precursor. The heat treatment conditions are set to a time in the range of 0.1 hours to 100 hours below the diffusion temperature of the sintering temperature. Regarding the diffusion temperature, in one example, it is a temperature in the range of 300°C or higher and 1000°C or lower than the sintering temperature. Regarding the heat treatment, in order to suppress oxidation, it is preferable to carry out the treatment in an atmosphere containing inert gases or in a vacuum.

[0124] <Sputtering diffusion method>

[0125] In the sputtering diffusion method, similar to the coating diffusion method, the grain boundary diffusion process includes a diffusion element attachment process and a diffusion heat treatment process. In the diffusion element attachment process, a thin film composed of a single elemental metal or alloy of heavy rare earth elements 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 a heavy rare earth element supply portion. In one example, the thin film is formed using a sputtering method. In the diffusion heat treatment process, the diffusion precursor with the heavy rare earth element supply portion is heat-treated at a diffusion temperature lower than the sintering temperature in step S23, causing the heavy rare earth elements to diffuse into the interior of the diffusion precursor. The heat treatment conditions are set to a time range of 0.1 hours to 100 hours below the sintering temperature. In one example, the diffusion temperature is a temperature in the range of 300°C to 1000°C, which is lower than the sintering temperature. For the heat treatment, to suppress oxidation, it is preferable to perform the treatment in an atmosphere containing inactive gases or in a vacuum.

[0126] <Vapor Diffusion Method>

[0127] In the vapor diffusion method, after placing the diffusion precursor and the heavy rare earth element supply source in a vacuum furnace, the diffusion precursor is heat-treated in the vacuum furnace at a temperature lower than the sintering temperature in the sintering process of step S23, thereby performing heat treatment to diffuse the heavy rare earth elements into the interior of the diffusion precursor. During the heat treatment, the heavy rare earth element supply source is made into a gas phase by vacuum heating, and the heavy rare earth elements are supplied to the diffusion precursor via the gas phase. The heat treatment conditions are set to a time range of 0.1 hours to 100 hours at a diffusion temperature lower than the sintering temperature. Regarding the diffusion temperature, in one example, it is a temperature in the range of 600°C to 900°C, which is lower than the sintering temperature. Furthermore, in the vapor diffusion method, unlike the coating diffusion method and sputtering diffusion method, it is not necessary to attach the heavy rare earth element supply portion to the diffusion precursor, thus omitting the diffusion element attachment process and shortening the time of the grain boundary diffusion process.

[0128] Back Figure 7In the final cooling step S40, the diffusion precursor in which heavy rare earth elements are diffused during the grain boundary diffusion process is held at a temperature of less than 200°C for a period of 0.1 hours to 5 hours. Then, by cooling to room temperature, the rare earth sintered magnet 1 shown in Embodiments 1 to 3 is formed. In Embodiment 1, a rare earth sintered magnet 1 in which heavy rare earth elements are present on at least a portion of the surface of the main phase 10 is formed. In Embodiment 2, a rare earth sintered magnet 1 in which heavy rare earth elements diffuse in the secondary phase 20 is formed. In Embodiment 3, heavy rare earth elements diffuse in a manner that selectively surrounds the periphery of the Sm-enriched portion 41 of the first secondary phase 21, forming a rare earth sintered magnet 1 in which heavy rare earth elements diffuse uniformly in the second secondary phase 22. Regarding cooling, to suppress oxidation, it is preferable to perform the cooling in an atmosphere containing inactive gases or in a vacuum.

[0129] As described above, by diffusing heavy rare earth elements to the grain boundaries of the diffusion precursor having the final shape of the rare earth sintered magnet 1, the desired shape of the rare earth sintered magnet 1 is obtained.

[0130] As described above, by controlling the temperature and time in the sintering, aging, and cooling processes, the sintered body is held multiple times in a temperature region with an unstable energy state. As a result, a first principal phase 11 composed of CNd > CPr and a second principal phase 12 composed of CNd < CPr can be mixed. In other words, the rare earth sintered magnet 1 contains two principal phases 10, namely the first principal phase 11 and the second principal phase 12. If we focus on the cores 11c and 12c of the two principal phases 10, we can manufacture a rare earth sintered magnet 1 with the following characteristics: for the first principal phase 11, the Nd concentration is higher than the Pr concentration; conversely, for the second principal phase 12, the Pr concentration is higher than the Nd concentration.

[0131] Furthermore, it is possible to manufacture a rare earth sintered magnet 1 that, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, also has a first secondary phase 21 with a crystallinity based on an oxide phase whose main component is represented by (Nd, Pr, La, Sm)-O, and a second secondary phase 22 with a crystallinity based on (Nd, Pr, La)-O, wherein the concentration of Sm is higher in the first secondary phase 21 than in the second secondary phase 22.

[0132] Thus, a rare earth sintered magnet 1 can be provided that has superior magnetization performance and magnetic properties compared to the past while suppressing the use of Nd and heavy rare earth elements.

[0133] In Embodiment 4, a rare earth sintered magnet alloy powder having a (Nd, Pr, La, Sm)-Fe-B crystal phase and a (Nd, Pr, La, Sm)-O phase is pulverized, molded, and then sintered to form a sintered body. The sintered body is then subjected to an aging treatment to manufacture the rare earth sintered magnet 1. Thus, the rare earth sintered magnet 1 according to Embodiment 3 can be manufactured.

[0134] Furthermore, in the first aging process, the resulting sintered body is held at a temperature below the sintering temperature (i.e., the first aging temperature) for a period of 0.1 hours to 10 hours, preferably 0.5 hours to 5 hours. In the second aging process, the sintered body is held at a temperature below the first aging temperature (i.e., the second aging temperature) for a period of 0.1 hours to 10 hours, preferably 1.0 hour to 7 hours. In the third aging process, the temperature is raised again to the first aging temperature, and the sintered body is held at the first aging temperature for a period of 0.1 hours to 10 hours, preferably 0.5 hours to 5 hours. In the fourth aging process, the sintered body is again held at the second aging temperature for a period of 0.1 hours to 10 hours, preferably 1.0 hour to 7 hours. In this way, by controlling the temperature and time by performing two sets of first and second aging processes, a state is created in which the sintered body is held multiple times within a temperature range of unstable energy states. As a result, a rare earth sintered magnet 1 can be obtained, which is a mixture of a first main phase 11 composed of CNd > CPr and a second main phase 12 composed of CNd < CPr. In other words, regarding the rare earth sintered magnet 1, it is possible to selectively manufacture a rare earth sintered magnet 1 with two main phases 10, namely the first main phase 11 and the second main phase 12. If we focus on the cores 11c and 12c of the two main phases 10, for the first main phase 11, the Nd concentration is higher than the Pr concentration, and conversely, for the second main phase 12, the Pr concentration is higher than the Nd concentration.

[0135] Furthermore, through the above manufacturing process, it is possible to selectively manufacture rare earth sintered magnets 1 with the following microstructure characteristics: a first secondary phase 21 with a crystallinity based on an oxide phase represented by (Nd, Pr, La, Sm)-O as the main component, and a second secondary phase 22 with a crystallinity based on (Nd, Pr, La)-O as the main component, wherein the first secondary phase 21 has a higher concentration of Sm than the second secondary phase 22.

[0136] Furthermore, in the manufacturing method of the rare earth sintered magnet 1 according to Embodiment 4, a diffusion precursor having a first main phase 11 and a second main phase 12 is formed by pulverizing an R-Fe-B system rare earth sintered magnet alloy containing Nd and Pr as rare earth elements R, sintering a molded body of the R-Fe-B system rare earth sintered magnet alloy powder, and performing an aging treatment. In the manufacturing method of the rare earth sintered magnet 1 according to Embodiment 4, by heat treatment to diffuse heavy rare earth elements at grain boundaries in the diffusion precursor, it is possible to produce a rare earth sintered magnet 1 in which heavy rare earth elements are present on a portion of the surface of the first main phase 11 and the second main phase 12, or in which heavy rare earth elements are present in the secondary phase 20. Thus, a rare earth sintered magnet 1 that suppresses the use of heavy rare earth elements and suppresses the decrease in magnetic properties, while improving magnetic properties compared to the past, can be obtained.

[0137] Furthermore, in the manufacturing method of the rare earth sintered magnet 1 according to Embodiment 4, a diffusion precursor is formed by pulverizing an R-Fe-B system rare earth sintered magnet alloy containing Nd, Pr, La, and Sm as rare earth elements R, sintering a molded body of the R-Fe-B system rare earth sintered magnet alloy powder, and performing an aging treatment. This process forms a first secondary phase 21 having an Sm-enriched portion 41 with Sm enrichment in addition to the first primary phase 11 and the second primary phase 12, and a second secondary phase 22 having a lower Sm concentration than the first secondary phase 21. In the manufacturing method of the rare earth sintered magnet 1 according to Embodiment 4, by heat treatment to diffuse heavy rare earth elements at grain boundaries in the diffusion precursor, a rare earth sintered magnet 1 in which heavy rare earth elements selectively surround the periphery of the Sm-enriched portion 41 in the first secondary phase 21 and heavy rare earth elements are uniformly distributed in the second secondary phase 22 can be manufactured. Thus, a rare earth sintered magnet 1 can be obtained that, compared with the past, suppresses the use of heavy rare earth elements, suppresses the reduction of magnetic properties, and improves magnetic properties compared with the past.

[0138] Implementation method 5.

[0139] In Embodiment 5, the rotor of the rare earth sintered magnet 1 manufactured using the manufacturing method of Embodiment 4 in Embodiments 1, 2, and 3 will be described. Figure 10 A cross-sectional view illustrating an example of the configuration of a rotor equipped with a rare-earth sintered magnet according to Embodiment 5. Figure 10 The image shows a cross-section in a direction perpendicular to the rotation axis RA of the rotor 100.

[0140] The rotor 100 can rotate about the rotation axis RA. The rotor 100 includes: a rotor core 101, and rare-earth sintered magnets 1 inserted into magnet insertion holes 102 disposed along the circumference of the rotor 100 in the rotor core 101. Figure 10The diagram shows an example where 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. However, the number of magnet insertion holes 102 and rare earth sintered magnets 1 can be changed according to the design of the rotor 100. As for the rotor core 101, it is formed by stacking multiple disc-shaped electromagnetic steel plates in the axial direction of the rotation shaft RA.

[0141] The rare earth sintered magnet 1 is manufactured according to the manufacturing method described in Embodiment 4. Four rare earth sintered magnets 1 are respectively inserted into corresponding magnet insertion holes 102. As for the four rare earth sintered magnets 1, the magnetic poles of the rare earth sintered magnets 1 on the radially outer side of the rotor 100 are magnetized in different ways between adjacent rare earth sintered magnets 1.

[0142] Thus, the rotor 100 according to Embodiment 5 includes a rare-earth sintered magnet 1 according to Embodiments 1, 2, or 3, which can improve magnetic properties at room temperature and suppress the decrease in magnetic properties associated with temperature rise. Because the rare-earth sintered magnet 1 suppresses the use of heavy rare-earth elements, maintains high remanent magnetic flux density and coercivity compared to conventional methods, and suppresses the decrease in magnetic properties associated with temperature rise, the decrease in magnetic properties is also suppressed even in high-temperature environments exceeding 100°C. Therefore, while replacing expensive and geographically unevenly distributed Nd and heavy rare-earth elements with inexpensive rare-earth elements, which pose procurement risks, improves magnetic properties and magnetization, and stabilizes the operation of the rotor 100 even in high-temperature environments exceeding 100°C. Furthermore, the rare-earth sintered magnet 1 according to Embodiments 1, 2, or 3 has superior magnetization performance compared to conventional methods, making magnetization possible even when the rare-earth sintered magnet 1 is installed in the rotor 100 assembly state, thus simplifying the manufacturing process. Furthermore, it enables a magnetization process that suppresses voltage, thus contributing to energy conservation.

[0143] Implementation method 6.

[0144] In Embodiment 6, a rotating machine equipped with the rotor 100 of Embodiment 5 will be described. Figure 11 A cross-sectional view is shown schematically as an example of the configuration of the rotating machine according to Embodiment 6. Figure 11 The image shows a cross-section in a direction perpendicular to the rotation axis RA of the rotor 100.

[0145] The rotating machine 120 includes: a rotor 100, as described in Embodiment 5, which can rotate around a rotation axis RA; and an annular stator 130, which is coaxially arranged with and opposite to the rotor 100. The stator 130 is formed by stacking multiple electromagnetic steel plates in the axial direction of the rotation axis RA. The configuration of the stator 130 is not limited to this, and existing configurations can also be used. The stator 130 has teeth 131 protruding toward the rotor 100 along its inner surface. A winding 132 is provided on the teeth 131. Regarding the winding method of the winding 132, in one example, it can be concentrated winding or distributed winding. That is, the stator 130 has a ring-shaped structure with the winding 132 provided on the inner surface of the side where the rotor 100 is arranged, which is arranged opposite to the rotor 100. The rotor 100 located in the rotating machine 120 has two or more magnetic poles; that is, the rare-earth sintered magnet 1 only needs to have two or more. Furthermore, in Figure 11 The example shown is a magnet-embedded rotor 100, but it can also be a surface magnet rotor 100 in which rare earth sintered magnets 1 are fixed to the outer periphery with an adhesive.

[0146] Thus, the rotating machine 120 in Embodiment 6 includes a rare-earth sintered magnet 1 according to Embodiments 1, 2, or 3, which can improve magnetic properties at room temperature and suppress the decrease in magnetic properties associated with temperature rise. Because the rare-earth sintered magnet 1, compared to the past, suppresses the use of heavy rare-earth elements, maintains high remanent magnetic flux density and coercivity, and simultaneously suppresses the decrease in magnetic properties associated with temperature rise, the decrease in magnetic properties is also suppressed in high-temperature environments exceeding 100°C. As a result, while replacing expensive and geographically unevenly distributed Nd and heavy rare-earth elements with inexpensive rare-earth elements, and improving magnetic properties and magnetization, the rotor 100 can be stably driven even in high-temperature environments exceeding 100°C, and the operation of the rotating machine 120 can be stabilized.

[0147] Example

[0148] The following describes the details of the rare earth sintered magnet 1 disclosed herein through examples and comparative examples.

[0149] In Examples 1 to 8, rare earth sintered magnets 1 were manufactured using samples of (Nd, Pr, La, Sm)-Fe-B, representing multiple rare earth sintered magnet alloys with different compositions, by the method shown in Example 4. In Examples 1 to 8, rare earth sintered magnet alloys with varying contents of Nd, Pr, La, and Sm were used to form a diffusion precursor. Dy, as a heavy rare earth element, was diffused through grain boundaries in the diffusion precursor to a concentration of 0.10 atomic% at the Dy grain boundaries, thus manufacturing rare earth sintered magnets 1. That is, in Examples 1 to 8, rare earth sintered magnets 1 with 0.10 atomic% Dy, as a heavy rare earth element, diffused in the (Nd, Pr, La, Sm)-Fe-B rare earth sintered magnet alloy were manufactured using the manufacturing method shown in Example 4.

[0150] In Comparative Examples 1 to 12, rare earth sintered magnets 1 containing heavy rare earth elements were experimentally manufactured using samples of multiple rare earth sintered magnet alloys R-Fe-B with different compositions, according to the general rare earth magnet manufacturing method shown in Patent Document 1 or Patent Document 2. In the samples of rare earth sintered magnets 1 according to Comparative Examples 1 to 12, the portion of R was changed.

[0151] In Comparative Examples 1 to 6, a rare earth sintered magnet 1 was manufactured by using the manufacturing method shown in Patent Document 1, which uses a rare earth sintered magnet alloy containing Nd, Dy, Pr, La and Sm as elements, and Dy as a heavy rare earth element diffused in 0.15 atomic% of Dy.

[0152] In Comparative Examples 7 to 12, a rare earth sintered magnet 1 with 0.15 atomic% of Dy, a heavy rare earth element, diffused in a rare earth sintered magnet alloy containing Nd, Dy, Pr, La, and Sm was manufactured using the manufacturing method shown in Patent Document 2.

[0153] Table 3 shows the general formula, the content of elements constituting R, the analysis results of microstructure, and the determination results of magnetic properties of rare earth sintered magnets according to the examples and comparative examples. In Table 3, the general formula of the main phase 10 of each sample of rare earth sintered magnet 1 as Examples 1 to 8 and Comparative Examples 1 to 12 is shown.

[0154]

[0155] Next, the method for analyzing the microstructure of the rare earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 12 will be described. The microstructure of the rare earth sintered magnets 1 was determined by elemental analysis using a scanning electron microscope (SEM) and EPMA. FE-EPMA (manufactured by Nippon Electronics Corporation, product name: JXA-8530F) was used for both the SEM and EPMA. The accelerating voltage was 15.0 kV and the irradiation current was 2.271 eΩ. -008 A, the illumination time is 130ms, the number of pixels is 512 pixels × 512 pixels, the magnification is 5000 times, and the cumulative number of times is 1.

[0156] Next, the evaluation method for the magnetic properties of the rare earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 12 will be described. For the evaluation of magnetic properties, the coercivity of multiple samples was measured using a pulse-excited BH-Tracer. The maximum applied magnetic field generated by the BH-Tracer was 6T or more, which resulted in the rare earth sintered magnet 1 being fully magnetized. Besides the pulse-excited BH-Tracer, any device capable of generating a maximum applied magnetic field of 6T or more, such as a DC self-recording magnetometer (also called a DC-type BH-Tracer), a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), or a physical property measurement system (PPMS), can be used. The measurement was performed in an atmosphere containing inert gases such as nitrogen. The magnetic properties of each sample were measured by detecting the magnetization picked up by a search coil or a magnetic sensor on the rare earth sintered magnet 1 magnetized by the applied magnetic field. Magnetic properties are determined by measuring the hysteresis, i.e., the JH curve or BH curve. Furthermore, the magnetic properties of each sample are measured at various temperatures, specifically a first measurement temperature T1 and a second measurement temperature T2. The temperature coefficient α [% / ℃] of the remanent magnetic flux density is the ratio of the difference between the remanent magnetic flux density at the first measurement temperature T1 and the remanent magnetic flux density at the second measurement temperature T2 to the remanent magnetic flux density at the first measurement temperature T1, divided by the temperature difference (T2-T1). Similarly, the temperature coefficient β [% / ℃] of the 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 the decrease in the magnetic properties of the magnet relative to increasing temperature is suppressed.

[0157] First, the analytical results of each sample from Examples 1 to 8 and Comparative Examples 1 to 12 will be explained. Figure 12 This is a diagram showing the compositional images obtained by analyzing cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. Figures 13 to 18 The elemental mapping is obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. Figure 13 For the element mapping of Nd, Figure 14 For the element mapping of Pr, Figure 15 For the element mapping of Dy, Figure 16 A mapping of elements to O. Figure 17 For element mapping of Sm, Figure 18 This is an element mapping for La. Please explain. Figures 13 to 18 To Figure 12 The diagram shown is an elemental mapping of the region. Furthermore, the rare-earth sintered magnets 1 according to Examples 1 to 8 all show the same results, therefore... Figures 12 to 18 In this document, representative embodiments from Examples 1 to 8 are shown. Furthermore, in relation to... Figure 1 and Figure 3 The same constituent elements are labeled with the same reference numerals in the accompanying drawings.

[0158] like Figure 13 and Figure 14 As shown, in each sample of Examples 1 to 8, R is selected from one or more rare earth elements other than Nd and Pr, satisfies the general formula (Nd,Pr,R)-Fe-B, and contains Nd2Fe. 14 In the main phase 10, which has a B crystal structure as its basic grain, there exists a main phase 10 having cores 11c and 12c and shells 11s and 12s covering the cores 11c and 12c. In addition, in the main phase 10, it can be confirmed that a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr are mixed.

[0159] The concentration difference shown in "first principal phase 11, CNd > CPr, and second principal phase 12, CNd < CPr" indicates a clear difference in the detection intensity of Nd and Pr through mapping analysis with EPMA. Specifically, taking the first principal phase 11 as an example, the EPMA detection intensity is higher than average for Nd concentration in the core 11c, while the EPMA detection intensity is near the lower limit for Pr concentration. The second principal phase 12 can be considered the opposite of the first principal phase 11.

[0160] More specifically, with Figure 13 The mapping of Nd and Figure 14Taking the Pr mapping as an example, the average detection level of Nd by EPMA is 92, and the average 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, indicating a clear concentration difference. Furthermore, the second main phase 12 is the opposite of the first main phase 11, therefore CPr is higher than 135, and CNd is near the lower limit, again indicating a clear concentration difference.

[0161] like Figures 16 to 18 As shown, when R = La and Sm, the rare earth sintered magnet 1, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, also has a first secondary phase 21 with a crystalline structure based on an oxide phase with main components expressed as (Nd, Pr, La, Sm)-O, and a second secondary phase 22 with a crystalline structure based on (Nd, Pr, La)-O. Thus, it can be confirmed that, in terms of Sm concentration, the second secondary phase 22 has a higher concentration than the first secondary phase 21.

[0162] In Table 3, for samples where the states of the first main phase 11 (CNd > CPr) and the second main phase 12 (CNd < CPr) can be confirmed, enter “○” in the columns for the first main phase 11 and the second main phase 12, respectively. For samples that cannot be confirmed, enter “×” in the columns for the first main phase 11 and the second main phase 12, respectively. A concentration difference with an inequality sign indicates a clear difference in the detection intensity of Nd and Pr. Specifically, in one example, in the case of the first main phase 11, the detection intensity of EPMA is higher than average for Nd concentration, while the detection intensity of EPMA is near the lower limit for Pr concentration. In the case of the second main phase 12, the situation is the opposite of the first main phase 11. When only the state of CNd < CPr is confirmed in the second main phase 12, enter “○” in the column for the second main phase 12 and “×” in the column for the first main phase 11.

[0163] Furthermore, in Table 3, for samples that can be confirmed to have a first secondary phase 21 with crystallinity based on an oxide phase with main components (Nd, Pr, La, Sm)-O, a second secondary phase 22 with crystallinity based on (Nd, Pr, La)-O, and a higher Sm concentration in the first secondary phase 21 compared to the second secondary phase 22, "○" is entered in the columns for the first secondary phase 21 and the second secondary phase 22, respectively. For samples that cannot be confirmed, "×" is entered in the columns for the first secondary phase 21 and the second secondary phase 22, respectively. In addition, for cases where only one secondary phase 20 exists, or where there is no Sm concentration difference between secondary phases 20, it is assumed that only the first secondary phase 21 exists, so "○" is entered in the column for the first secondary phase 21, and "×" is entered in the column for the second secondary phase 22. To clarify, the concentration difference between the first subphase 21 and the second subphase 22 means that, on average, the detection intensity of Sm in the first subphase 21 is higher than that in the second subphase 22, achieved through mapping analysis with EPMA. Specifically, with Figure 17 Taking the Sm mapping diagram as an example, the average detection level of Sm in EPMA is 15.9. In contrast, the first subphase 21 is higher than 15.9, and the second subphase 22 is lower than 15.9, that is, it is a state that cannot be detected in the condensed state.

[0164] Furthermore, the intensity ratios of elemental mappings obtained from FE-EPMA analysis confirm that the number of first principal phases 11, where CNd > CPr, is significantly greater than the number of second principal phases 12, where CNd < CPr. Focusing on the shell portions 11s and 12s of the core-shell structure, it is also confirmed that the first principal phase 11 satisfies the relationship CNd > SNd and CPr < SPr, while the second principal phase 12 satisfies the relationship CNd < SNd and CPr > SPr.

[0165] Next, the results of the magnetic property measurements of the samples according to Examples 1 to 8 and Comparative Examples 1 to 12 will be explained. The samples for which magnetic measurements were performed were block-shaped, with dimensions of 7 mm in length, width, and height. The first measurement temperature T1 was 23°C, and the second measurement temperature T2 was 200°C. 23°C is room temperature. The second measurement temperature T2 of 200°C is a temperature that can be generated in the operating environment of automotive motors and industrial motors.

[0166] First, the residual magnetic flux density and coercivity of each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 were compared with Comparative Example 1. If the residual magnetic flux density and coercivity of each sample at 23°C showed a value within 1% of the measurement error compared with the value in Comparative Example 1, it was judged as "equivalent"; if it showed a higher value of 1% or more, it was judged as "good"; and if it showed a lower value of less than 1%, it was judged as "poor".

[0167] Secondly, the temperature coefficient α of the remanent magnetic flux density was calculated using the remanent magnetic flux density at 23°C of the first measurement temperature T1 and the remanent magnetic flux density at 200°C of the second measurement temperature T2. Similarly, the temperature coefficient β of the coercivity was calculated using the coercivity at 23°C of the first measurement temperature T1 and the coercivity at 200°C of the second measurement temperature T2. The temperature coefficients of the remanent magnetic flux density and the temperature coefficients of the coercivity in each sample according to Examples 1 to 8 and Comparative Examples 2 to 12 were compared with those in Comparative Example 1. For each sample, compared with the absolute values ​​of the temperature coefficients of the remanent magnetic flux density (|α|) and the temperature coefficients of the coercivity (|β|) in the sample according to Comparative Example 1, if a value within ±1% of the measurement error was shown, it was judged as "equivalent"; if a value lower than -1% was shown, it was judged as "good"; and if a value higher than +1% was shown, it was judged as "poor". For samples judged as "good", rare earth sintered magnets 1 can be provided to suppress the decrease in magnetic properties associated with temperature rise and have stable magnetic properties even at high temperature environments due to their smaller temperature coefficient.

[0168] The results of determining the remanent magnetic flux density, coercivity, temperature coefficient of remanent magnetic flux density, and temperature coefficient of coercivity are shown in Table 3.

[0169] Comparative Example 1 is a sample of a rare-earth sintered magnet 1 prepared by using Nd, Fe, and FeB as raw materials in an Nd-Fe-B configuration and according to the manufacturing method described in Patent Document 1, in which 0.15 atomic% Dy is diffused. The microstructure of this sample was observed using the method described above. Since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed. Regarding the Sm concentration in the secondary phase 20, it could not be confirmed that the first secondary phase 21 was higher than the second secondary phase 22. Furthermore, the magnetic properties of this sample were evaluated using the method described above. The remanent magnetic flux density was 1.3 T, and the coercivity was 1250 kA / m. The temperature coefficients of the remanent magnetic flux density and coercivity were |α| = 0.191% / ℃ and |β| = 0.460% / ℃, respectively. These values ​​of Comparative Example 1 can be used as a reference.

[0170] Comparative Example 2 is a sample of a rare-earth sintered magnet 1 prepared by using Nd, Dy, Fe, and FeB as raw materials in a (Nd, Dy)-Fe-B configuration and following the manufacturing method described in Patent Document 1, in which 0.15 atomic% Dy is diffused. Observing the microstructure of this sample using the method described above, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed. Regarding the concentration of Sm in the secondary phase 20, it could not be confirmed that the first secondary phase 21 was higher than the second secondary phase 22. Furthermore, evaluating the magnetic properties of this sample using the method described above, the remanent magnetic flux density was "poor," the coercivity was "good," the temperature coefficient of the remanent magnetic flux density was "equal," and the temperature coefficient of the coercivity was "equal." This reflects the following result: by replacing a portion of Nd with Dy, which has high magnetocrystalline anisotropy, the coercivity is improved. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor used as the parent material, even when Dy, a heavy rare-earth element, is diffused in such a diffusion precursor, the magnetic properties are not improved.

[0171] Comparative Example 3 is a sample of a rare-earth sintered magnet 1 prepared by using Nd, Pr, Fe, and FeB as raw materials in a (Nd, Pr)-Fe-B configuration and following the manufacturing method described in Patent Document 1, in which 0.15 atomic% Dy is diffused. The microstructure of this sample was observed using the method described above. Due to the addition of Pr, a main phase 10 of Nd and Pr mixture was confirmed, but a core-shell structure was not formed. Furthermore, since La and Sm were not added, the concentration of Sm in the secondary phase 20 could not be confirmed as higher in the first secondary phase 21 than in the second secondary phase 22. The magnetic properties of this sample were evaluated using the method described above. The remanent magnetic flux density was "equal," the coercivity was "good," the temperature coefficient of the remanent magnetic flux density was "equal," and the temperature coefficient of the coercivity was "poor." This reflects the following result: the addition of Pr improves the magnetic anisotropy and coercivity of the main phase 10, but it is not the optimal microstructure of the main phase 10 and the secondary phase 20. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor that serves as the parent material, even if Dy, a heavy rare earth element, is diffused in such a diffusion precursor, the magnetic properties are not improved.

[0172] Comparative Example 4 is a sample of a rare-earth sintered magnet 1 prepared by using Nd, La, Sm, Fe, and FeB as raw materials in a (Nd, La, Sm)-Fe-B configuration and manufactured according to the manufacturing method described in Patent Document 1, in which 0.15 atomic% Dy is diffused. The microstructure of this sample was observed using the method described above. Since Pr was not added, the core-shell structure of the main phase 10 could not be confirmed. Furthermore, due to the addition of La and Sm, the concentration of Sm segregated in one secondary phase 20 along with the segregation of La, but a second secondary phase 22 was not present. Furthermore, regarding the concentration of Sm, it could not be confirmed that the first secondary phase 21 was higher than the second secondary phase 22. In addition, the magnetic properties of this sample were evaluated using the method described above: the remanent magnetic flux density was "equal," the coercivity was "equal," the temperature coefficient of the remanent magnetic flux density was "good," and the temperature coefficient of the coercivity was "good." This results in the following: with La and Sm present in the main phase 10 or the secondary phase 20, the temperature coefficient of magnetic properties shows good results, but the magnetic properties at room temperature are not improved, and it is not the optimal microstructure in the main phase 10 and the secondary phase 20. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor as the parent material, even when Dy, as a heavy rare earth element, is diffused in such a diffusion precursor, the magnetic properties are not improved.

[0173] Comparative Example 5 is a sample of a rare-earth sintered magnet 1 prepared by using Nd, La, Sm, Fe, and FeB as raw materials in a (Nd, La, Sm)-Fe-B configuration and manufactured according to the manufacturing method described in Patent Document 1, in which 0.15 atomic% Dy is diffused. The composition ratio of Nd, La, and Sm differs from Comparative Example 4. Observing the microstructure of this sample using the method described above, the core-shell structure of the main phase 10 could not be confirmed since Pr was not added. Furthermore, with the addition of La and Sm, the concentration of Sm segregated in one secondary phase 20 due to La segregation, but the second secondary phase 22 was absent. Therefore, it could not be confirmed that the first secondary phase 21 had a higher concentration of Sm than the second secondary phase 22. Additionally, evaluating the magnetic properties of this sample using the method described above, the remanent magnetic flux density was "equal," the coercivity was "equal," the temperature coefficient of the remanent magnetic flux density was "good," and the temperature coefficient of the coercivity was "good." This results in the following: the presence of La and Sm in the main phase 10 or the secondary phase 20 produces good temperature coefficients for magnetic properties, but the magnetic properties at room temperature are not improved, indicating that these are not the optimal microstructures for the main phase 10 and the secondary phase 20. Even when the composition ratio of Nd, La, and Sm is changed, approximately the same results as in Comparative Example 4 are obtained. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor used as the parent material, even when Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties are not improved.

[0174] Comparative Example 6 is a sample of a rare-earth sintered magnet 1 prepared by using Nd, Pr, La, Sm, Fe, and FeB as raw materials in a (Nd, Pr, La, Sm)-Fe-B configuration, and manufactured according to the manufacturing method described in Patent Document 1, in which 0.15 atomic% Dy is diffused. The microstructure of the sample was observed using the method described above. Due to the addition of Pr, a main phase 10 of Nd and Pr mixture was confirmed, but no core-shell structure was formed. Furthermore, due to the addition of La and Sm, with respect to the concentration of Sm, segregation occurred in a secondary phase 20 due to La segregation, but a second secondary phase 22 was not present. Furthermore, it could not be confirmed that the concentration of the first secondary phase 21 was higher than that of the second secondary phase 22 in terms of Sm concentration. In addition, the magnetic properties of the sample were evaluated using the method described above: the remanent magnetic flux density was "equal," the coercivity was "good," the temperature coefficient of the remanent magnetic flux density was "good," and the temperature coefficient of the coercivity was "equal." This results in the following: the addition of Pr increases the magnetic anisotropy and coercivity of the main phase 10. Simultaneously, the presence of La and Sm in either the main phase 10 or the secondary phase 20 indicates an improvement in the temperature coefficient of magnetic properties, particularly the temperature coefficient of coercivity, but this is not the optimal microstructure for either the main phase 10 or the secondary phase 20. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor used as the parent material, even diffusion of Dy, a heavy rare earth element, into such a diffusion precursor does not improve the magnetic properties.

[0175] Comparative Example 7 is a sample of a rare-earth sintered magnet 1, manufactured using Nd, Fe, and FeB as raw materials in an Nd-Fe-B configuration, and produced according to the manufacturing method described in Patent Document 2, which includes a hot-working method, and diffuses 0.15 atomic% Dy. Observing the microstructure of this sample using the method described above, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed, and regarding the Sm concentration in the secondary phase 20, it could not be confirmed that the first secondary phase 21 was higher than the second secondary phase 22. However, the microstructure refinement characteristic of magnets manufactured using the hot-working method was confirmed. Evaluating the magnetic properties of this sample using the method described above, the remanent magnetic flux density was "poor," the coercivity was "good," the temperature coefficient of the remanent magnetic flux density was "equal," and the temperature coefficient of the coercivity was "equal." This results in the following: with the refinement of the microstructure produced by the hot-working method, the coercivity increased, but the remanent magnetic flux density decreased. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor that serves as the parent material, even if Dy, a heavy rare earth element, is diffused in such a diffusion precursor, the magnetic properties are not improved.

[0176] Comparative Example 8 is a sample of a rare-earth sintered magnet 1, manufactured using Nd, Dy, Fe, and FeB as raw materials in a (Nd, Dy)-Fe-B configuration, and produced according to the manufacturing method described in Patent Document 2, which includes a hot-working method, and diffuses 0.15 atomic% Dy. Observing the microstructure of this sample using the method described above, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed. Regarding the Sm concentration in the secondary phase 20, it could not be confirmed that the first secondary phase 21 was higher than the second secondary phase 22. Furthermore, evaluating the magnetic properties of this sample using the method described above, the remanent magnetic flux density was "poor," the coercivity was "good," the temperature coefficient of the remanent magnetic flux density was "equal," and the temperature coefficient of the coercivity was "equal." This results in the following: in addition to being manufactured through hot working, the coercivity was significantly improved by replacing a portion of Nd with Dy, which has high magnetocrystalline anisotropy; however, for other properties, the microstructure is finer. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor that serves as the parent material, even if Dy, a heavy rare earth element, is diffused in such a diffusion precursor, the magnetic properties are not improved.

[0177] Comparative Example 9 is a sample of a rare-earth sintered magnet 1, manufactured using Nd, Pr, Fe, and FeB as raw materials in a (Nd, Pr)-Fe-B configuration, and produced according to the manufacturing method described in Patent Document 2, which includes a hot-working method, resulting in the diffusion of 0.15 atomic% Dy. The microstructure of this sample was observed using the method described above. In addition to the addition of Pr, a core-shell structure was confirmed due to the hot-working process, but only the main phase 10, with a high Pr concentration in the core, was observed. Furthermore, since La and Sm were not added, it could not be confirmed that the first secondary phase 21 had a higher Sm concentration than the second secondary phase 22. The magnetic properties of this sample were evaluated using the method described above. The remanent flux density was rated as "poor," the coercivity as "good," the temperature coefficient of the remanent flux density as "equal," and the temperature coefficient of the coercivity as "equal." This resulted in the following: through the formation of a core-shell structure with a high Pr concentration in the core, the coercivity was significantly improved to the level of the rare-earth sintered magnet 1 with added Dy, but for other properties, the microstructure was refined. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor that serves as the parent material, even if Dy, a heavy rare earth element, is diffused in such a diffusion precursor, the magnetic properties are not improved.

[0178] Comparative Example 10 is a sample of a rare earth sintered magnet 1, manufactured using Nd, La, Sm, Fe, and FeB as raw materials in a (Nd, La, Sm)-Fe-B configuration, and produced according to the manufacturing method including a hot working method described in Patent Document 2, in which 0.15 atomic% Dy is diffused. The microstructure of this sample was observed using the method described above. Since Pr was not added, the core-shell structure of the main phase 10 could not be confirmed. Furthermore, due to the addition of La and Sm, the concentration of Sm segregated in one secondary phase 20 along with the segregation of La, but a second secondary phase 22 was not present. Therefore, it could not be confirmed that the concentration of the first secondary phase 21 was higher than that of the second secondary phase 22 in terms of Sm concentration. Additionally, the magnetic properties of this sample were evaluated using the method described above: the remanent magnetic flux density was "poor," the coercivity was "good," the temperature coefficient of the remanent magnetic flux density was "good," and the temperature coefficient of the coercivity was "good." This results in the following: the presence of La and Sm in the main phase 10 or the secondary phase 20 produces good temperature coefficients of magnetic properties, but the remanent magnetic flux density at room temperature does not increase, indicating that this is not the optimal microstructure for either the main phase 10 or the secondary phase 20. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor used as the parent material, even diffusion of Dy, a heavy rare earth element, into such a precursor does not improve the magnetic properties.

[0179] Comparative Example 11 is a sample of a rare earth sintered magnet 1, manufactured using Nd, La, Sm, Fe, and FeB as raw materials in a (Nd, La, Sm)-Fe-B configuration, and produced according to the manufacturing method including a hot working method described in Patent Document 2, in which 0.15 atomic% Dy is diffused. The composition ratio of Nd, La, and Sm is different compared to Comparative Example 10. Observing the microstructure of this sample using the method described above, the core-shell structure of the main phase 10 could not be confirmed since Pr was not added. Furthermore, due to the addition of La and Sm, the concentration of Sm segregated in a secondary phase 20 along with the segregation of La, but a second secondary phase 22 was not present. Therefore, it could not be confirmed that the first secondary phase 21 had a higher concentration of Sm than the second secondary phase 22. Additionally, evaluating the magnetic properties of this sample using the method described above, the remanent magnetic flux density was rated as "poor," the coercivity as "good," the temperature coefficient of the remanent magnetic flux density as "good," and the temperature coefficient of the coercivity as "good." This results in the following: the presence of La and Sm in the main phase 10 or the secondary phase 20 produces good temperature coefficients of magnetic properties, but the remanent magnetic flux density at room temperature does not increase, indicating that it is not the optimal microstructure for the main phase 10 and the secondary phase 20. Even changing the composition ratio of Nd, La, and Sm yields approximately the same results as in Comparative Example 10. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor used as the parent material, even when Dy, a heavy rare earth element, is diffused into such a diffusion precursor, the magnetic properties do not improve.

[0180] Comparative Example 12 is a sample of a rare earth sintered magnet 1, manufactured using Nd, Pr, La, Sm, Fe, and FeB as raw materials in a (Nd, Pr, La, Sm)-Fe-B configuration, and produced according to the manufacturing method described in Patent Document 2, which includes a hot-working method, and diffuses 0.15 atomic% Dy. Observing the microstructure of this sample using the method described above, in addition to the addition of Pr, a core-shell structure was confirmed due to the hot working, but only a main phase 10 with a high Pr concentration in the core was observed. Furthermore, due to the addition of La and Sm, the Sm concentration segregated in a secondary phase 20 along with La segregation, but a second secondary phase 22 was not present. Therefore, it could not be confirmed that the first secondary phase 21 had a higher Sm concentration than the second secondary phase 22. In addition, evaluating the magnetic properties of this sample using the method described above, the remanent magnetic flux density was "poor," the coercivity was "good," the temperature coefficient of the remanent magnetic flux density was "good," and the temperature coefficient of the coercivity was "good." This demonstrates the following results: through the formation of a core-shell structure with a high Pr concentration in the core, the coercivity is significantly increased to the level of rare-earth sintered magnet 1 with added Dy; and through the presence of La and Sm in the main phase 10 or the secondary phase 20, the temperature coefficient of magnetic properties, especially the temperature coefficient of coercivity, is good. However, this also reflects the following result: the remanent magnetic flux density at room temperature does not increase, and it is not the optimal microstructure among the main phase 10 and the secondary phase 20. Furthermore, regarding magnetic properties, since they depend on the microstructure of the diffusion precursor as the parent material, even when Dy, as a heavy rare-earth element, is diffused in such a diffusion precursor, the magnetic properties do not improve.

[0181] For the samples of Examples 1 to 8, the rare earth sintered magnet 1 is as follows: it has R being one or more rare earth elements selected from Nd and Pr, satisfying the general formula (Nd, Pr, R)-Fe-B, and containing Nd2Fe. 14B is a main phase 10 with a basic crystal structure. The main phase 10 has cores 11c and 12c and shells 11s and 12s covering the cores 11c and 12c. Regarding the main phase 10, a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr are mixed. In addition, it is characterized by the fact that, in the case where R = La and Sm, in addition to the first main phase 11 and the second main phase 12, there is a first secondary phase 21 with a crystallinity based on an oxide phase represented by (Nd, Pr, La, Sm)-O as the main component and a second secondary phase 22 with a crystallinity based on (Nd, Pr, La)-O as the main component. In terms of the concentration of Sm, the first secondary phase 21 is higher than the second secondary phase 22. The magnetic properties of the samples of Examples 1 to 8 were evaluated according to the above method, and the remanent magnetic flux density was rated as "good", the coercivity was rated as "good", the temperature coefficient of the remanent magnetic flux density was rated as "good", and the temperature coefficient of the coercivity was rated as "good". The results achieved the following effect: For these rare-earth sintered magnets 1, they exhibit superior magnetic properties compared to previous methods while suppressing the use of Nd and heavy rare-earth elements, which are expensive, geographically unevenly distributed, and subject to procurement risks. Furthermore, magnetic properties depend on the microstructure of the diffusion precursor used as the base material; therefore, if Dy, a heavy rare-earth element, is diffused into a diffusion precursor with good magnetic properties, the magnetic properties are further improved. In addition, in Examples 1 to 8, a diffusion amount of Dy of 0.10 atomic percent, lower than the 0.15 atomic percent in Comparative Examples 1 to 12, was used to obtain rare-earth sintered magnets 1 with excellent magnetic properties. That is, compared to Comparative Examples 1 to 12, rare-earth sintered magnets 1 that suppress the use of heavy rare-earth elements without reducing the remanent magnetic flux density and significantly improve coercivity can be obtained.

[0182] The above embodiments illustrate one example, and can also be combined with other known technologies, and embodiments can be combined with each other. Without departing from the spirit, some parts of the structure can be omitted or changed.

[0183] Explanation of reference numerals in the attached figures

[0184] 1. Rare earth sintered magnet, 10. Main phase, 11. First main phase, 11C, 12C core, 11S, 12S shell, 12. Second main phase, 20. Sub-phase, 21. First sub-phase, 22. Second sub-phase, 31. Heavy rare earth element containing layer, 32. Heavy rare earth element containing part, 41. Sm enrichment part, 100. Rotor, 101. Rotor core, 102. Magnet insertion hole, 120. Rotating machine, 130. Stator, 131. Tooth part, 132. Wire winding.

Claims

1. A rare earth sintered magnet, characterized in that, have: The main phase, which satisfies the general formula (Nd, Pr, R)-Fe-B when R is selected from one or more rare earth elements other than Nd and Pr, including Nd2Fe 14 B crystal structure consists of basic grains; and Sub-phases existing between multiple primary phases, The main phase has a core and a shell covering the core. When the concentration of Nd in the core is set to CNd and the concentration of Pr in the core is set to CPr, the main phase has a first main phase with CNd > CPr and a second main phase with CNd < CPr. The first main phase and the second main phase are mixed. Heavy rare earth elements are present on at least a portion of the surfaces of the first main phase and the second main phase.

2. A rare earth sintered magnet, characterized in that, have: The main phase, which satisfies the general formula (Nd, Pr, R)-Fe-B when R is selected from one or more rare earth elements other than Nd and Pr, including Nd2Fe 14 B crystal structure consists of basic grains; and Sub-phases existing between multiple primary phases, The main phase has a core and a shell covering the core. When the concentration of Nd in the core is set to CNd and the concentration of Pr in the core is set to CPr, the main phase has a first main phase with CNd > CPr and a second main phase with CNd < CPr. The first main phase and the second main phase are mixed. Heavy rare earth elements are present in the secondary phase.

3. The rare earth sintered magnet according to claim 1 or 2, characterized in that, The number of the first principal phase is greater than the number of the second principal phase.

4. The rare earth sintered magnet according to claim 1 or 2, characterized in that, When the concentration of Nd in the shell is set to SNd and the concentration of Pr in the shell is set to SPr, the first main phase satisfies the relationship CNd > SNd and CPr < SPr, and the second main phase satisfies the relationship CNd < SNd and CPr > SPr.

5. The rare earth sintered magnet according to claim 1, characterized in that, When R is set to La or Sm, the secondary phase has a first secondary phase with a crystalline structure based on an oxide phase whose main components are (Nd, Pr, La, Sm)-O, and a second secondary phase with a crystalline structure whose main components are (Nd, Pr, La)-O. In terms of Sm concentration, the first phase is higher than the second phase.

6. The rare earth sintered magnet according to claim 2, characterized in that, When R is set to La or Sm, the secondary phase has a first secondary phase with a crystalline structure based on an oxide phase whose main components are (Nd, Pr, La, Sm)-O, and a second secondary phase with a crystalline structure whose main components are (Nd, Pr, La)-O. The first subphase has an Sm concentration section with a higher Sm concentration compared to the second subphase.

7. The rare earth sintered magnet according to claim 6, characterized in that, The heavy rare earth elements are present in the first subphase in a manner that surrounds the periphery of the Sm enrichment.

8. A method for manufacturing a rare earth sintered magnet, as described in any one of claims 1 to 7, characterized in that, Include: The rare earth sintered magnet alloy manufacturing process for manufacturing rare earth sintered magnet alloys, wherein the rare earth sintered magnet alloy is the raw material of the diffusion precursor before the diffusion of the heavy rare earth elements in the rare earth sintered magnet. The diffusion precursor manufacturing process for manufacturing the aforementioned diffusion precursor; A diffusion process in which the heavy rare earth element diffuses in the diffusion precursor; and A cooling process that cools the diffusion precursor that allows the heavy rare earth element to diffuse. The manufacturing process of the rare earth sintered magnet alloy includes: A melting process in which raw materials containing elements constituting the diffusion precursor of a rare earth sintered magnet alloy are melted. The first alloy cooling process involves cooling the molten raw material in the melting process to obtain a solidified alloy; and The solidified alloy is further cooled to obtain a second alloy cooling process for rare earth sintered magnet alloys. The diffusion precursor manufacturing process includes: The crushing process of the rare earth sintered magnet alloy satisfying (Nd, Pr, R)-Fe-B. A molding process for preparing a molded body by molding the powder of the rare earth sintered magnet alloy pulverized in the crushing process. A sintering process in which the molded body is sintered at a sintering temperature defined as a sintering temperature to obtain a sintered body; The first aging process involves holding the sintered body at a first aging temperature below the sintering temperature. The second aging process involves holding the sintered body, which was held in the first aging process, at a second aging temperature lower than the first aging temperature. A third aging process is performed by holding the sintered body, which was maintained in the second aging process, at the same temperature as the first aging process. The sintered body held in the third aging process is then subjected to a fourth aging process at the second aging temperature; and The sintered body held in the fourth aging process is cooled to obtain the sintered body cooling process of the diffusion precursor. In the diffusion process, the diffusion precursor is heat-treated at a temperature below the sintering temperature in the presence of the diffusion precursor and the heavy rare earth element.

9. A rotor, characterized in that, have: Rotor core; and The rare earth sintered magnet of any one of claims 1 to 7 is disposed on the rotor core.

10. A rotating machine, characterized in that, have: The rotor as claimed in claim 9; and An annular stator is disposed opposite to the rotor, the annular stator having a winding on the inner surface of the side on which the rotor is disposed, which is provided with teeth protruding toward the rotor.

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