Rare earth sintered magnets, methods for manufacturing rare earth sintered magnets, rotors and rotating machines

Abstract

A rare earth sintered magnet (1) has a main phase (10) containing crystal grains satisfying the general formula (Nd, Pr, RH, R)-Fe-B and based on an Nd2Fe14B crystal structure, where RH denotes a heavy rare earth element containing at least one of Dy and Tb, and R denotes one or more rare earth elements selected from other than Nd, Pr, Dy, and Tb. The main phase has core sections (11c, 12c) and shell sections (11s, 12s) covering the core sections. The main phase has a first main phase (11) in which CNd > CPr and a second main phase (12) in which CNd < CPr, where CNd denotes the concentration of Nd in the core section and CPr denotes the concentration of Pr in the core section. The concentration of the heavy rare earth element RH in the core section (11c) of the first main phase is higher than the concentration of the heavy rare earth element RH in the core section (12c) of the second main phase. The first and second main phases are mixed.

Description

[Technical Field]

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

[0002] Tetragonal R2T 14 RTB-type permanent magnets, in which the B intermetallic compound is the main phase, are known. Here, R is a rare earth element, T is a transition metal element such as Fe (iron) or Fe partially substituted with Co (cobalt), and B is boron. RTB-type permanent magnets are used in various high-value-added components, including industrial motors. In particular, Nd-Fe-B sintered magnets, in which R is Nd (neodymium), are used in various components due to their excellent magnetic properties. Furthermore, since industrial motors are often used in high-temperature environments exceeding 100°C, attempts are being made 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 (terbium). However, Nd and heavy rare earth elements are expensive and their distribution is highly regionally uneven, posing procurement risks. Therefore, technologies to reduce the consumption of Nd and heavy rare earth elements are being researched.

[0004] Patent Document 1 contains R2T 14 An RTB-type sintered magnet is disclosed, comprising main phase particles made of B crystal, where R is one or more rare earth elements, with the heavy rare earth element RH being essential; T is one or more transition metal elements, with Fe or Fe and Co being essential; and B is boron. A portion of the main phase particles contains multiple low-heavy rare earth element crystal phases and multiple non-magnetic R-rich phases internally. Here, the low-heavy rare earth element crystal phase is R2T 14It consists of B crystals and is a phase with a relatively low concentration of heavy rare earth elements compared to the concentration of heavy rare earth elements in the entire main phase particles. The non-magnetic R-rich phase is a phase with an R content of 70 at.% or more and 100 at.% or less. Also, a part of the main phase particles has a core-shell structure having a core part and a shell part surrounding the core part, and the total heavy rare earth element concentration is lower than that of the core part. According to the technique described in Patent Document 1, an R-T-B sintered magnet with improved coercive force and low cost can be obtained.

[0005] In Patent Document 2, (R1 1-x R2 x ) a TM b B c M d represented by the composition formula, a first step of manufacturing a sintered body having a structure composed of a main phase and a grain boundary phase, a second step of subjecting the sintered body to hot plastic working to manufacture a rare earth magnet precursor, and a third step of diffusing and infiltrating a melt of an R3-M modified alloy into the grain boundary phase of the rare earth magnet precursor to manufacture a rare earth magnet are disclosed. Here, R1 is one or more rare earth elements including Y (yttrium), R2 is a rare earth element different from R1, TM is a transition metal containing one or more of Fe, Ni (nickel), Co, B is boron, and M is one or more of Ti (titanium), Ga (gallium), Zn (zinc), Si (silicon), Al (aluminum), Nb (niobium), Zr (zirconium), Ni, Co, Mn (manganese), V (vanadium), W (tungsten), Ta (tantalum), Ge (germanium), Cu (copper), Cr (chromium), Hf (hafnium), Mo (molybdenum), P (phosphorus), C (carbon), Mg (magnesium), Hg (mercury), Ag (silver), Au (gold). Also, x, a, b, c, d are 0.01 ≦ x ≦ 1, 12 ≦ a ≦ 20, b = 100 - a - c - d, 5 ≦ c ≦ 20, 0 ≦ d ≦ 3, and all are at.%. Also, R3 is a rare earth element containing R1 and R2. Hereinafter, the hot plastic working applied to the sintered body is called hot working. According to the technique described in Patent Document 2, it is possible to reduce the heavy rare earth elements and manufacture a rare earth magnet excellent not only in magnetization but also in coercive force performance even when the main phase ratio is high.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the R-T-B sintered magnet described in Patent Document 1, since the phase containing the heavy rare earth element exists in the main phase, the coercive force can be improved. However, in the microstructure of the R-T-B sintered magnet described in Patent Document 1, the residual magnetic flux density required for industrial motors and the like cannot be obtained, and the magnetic properties may deteriorate due to the heat load. Further, the rare earth magnet manufactured by the manufacturing method described in Patent Document 2 can reduce the heavy rare earth element and improve the coercive force. However, since the hot working is included in the manufacturing method, the particle size of the main phase becomes small. As a result, there is a problem that the magnetization performance deteriorates.

[0008] The present disclosure has been made in view of the above, and an object thereof is to obtain a rare earth sintered magnet capable of improving the coercive force without deteriorating the residual magnetic flux density and the magnetization performance as compared with the conventional ones.

Means for Solving the Problems

[0009] In order to solve the above-described problems and achieve the object, the rare earth sintered magnet according to the present disclosure uses RH as a heavy rare earth element containing at least one of Dy and Tb, and when R is one or more rare earth elements selected from outside Nd, Pr (praseodymium), Dy, and Tb, it satisfies the general formula (Nd, Pr, RH, R)-Fe-B, Nd2Fe 14It has a main phase containing crystal grains based on the B crystal structure. The main phase has a core part and a shell part covering the core part. The main phase has a first main phase where the concentration of Nd in the core part is CNd and the concentration of Pr in the core part is CPr, and CNd > CPr, and a second main phase where CNd < CPr. The concentration of the heavy rare earth element RH in the core part of the first main phase is higher than the concentration of the heavy rare earth element RH in the core part of the second main phase. The first main phase and the second main phase are mixed.

Advantages of the Invention

[0010] The rare earth sintered magnet according to the present disclosure has the effect that the coercive force can be improved without reducing the residual magnetic flux density and the magnetization performance as compared with the conventional ones.

Brief Description of the Drawings

[0011] [Figure 1] A diagram schematically showing an example of the structure of the sintered state of the rare earth sintered magnet according to Embodiment 1 [Figure 2] A diagram schematically showing an example of the structure of the sintered state of the rare earth sintered magnet according to Embodiment 2 [Figure 3] A diagram showing the atomic sites in the tetragonal Nd2Fe14B crystal structure [Figure 4] A flowchart showing an example of the procedure of the method for manufacturing a rare earth sintered magnet alloy according to Embodiment 3 [Figure 5] A flowchart showing an example of the procedure of the method for manufacturing a rare earth sintered magnet according to Embodiment 3 [Figure 6] A cross-sectional view schematically showing an example of the configuration of a rotor equipped with a rare earth sintered magnet according to Embodiment 4 [Figure 7] A cross-sectional view schematically showing an example of the configuration of a rotating machine according to Embodiment 5 [Figure 8] A diagram tracing the composition images obtained by analyzing the cross-sections of the rare earth sintered magnets according to Examples 1 to 8 by FE-EPMA [Figure 9] Nd elemental mapping obtained by analyzing the cross-sections of the rare earth sintered magnets according to Examples 1 to 8 by FE-EPMA [Figure 10]Elemental mapping of Pr obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. [Figure 11] Elemental mapping of Tb obtained by analyzing the cross-sections of rare-earth sintered magnets according to Examples 1 to 8 using FE-EPMA. [Figure 12] Elemental mapping of oxygen (O) obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. [Figure 13] Elemental mapping of Sm (samarium) obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. [Figure 14] Elemental mapping of La (lanthanum) obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. [Modes for carrying out the invention]

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

[0013] Embodiment 1. Figure 1 is a schematic diagram showing an example of the structure of the sintered state of a rare earth sintered magnet according to Embodiment 1. The rare earth sintered magnet 1 according to Embodiment 1 satisfies the general formula (Nd,Pr,RH,R)-Fe-B, and Nd2Fe 14 The rare earth sintered magnet 1 has a main phase 10 containing crystal grains based on a B crystal structure, and the main phase 10 has a core portion and a shell portion covering the core portion. Here, RH is a heavy rare earth element, for example Dy, Tb, Gd (gadolinium), Ho (holmium), and preferably RH is a heavy rare earth element containing at least one of Dy and Tb. R is one or more rare earth elements selected from Nd, Pr, and RH. The shell portion has a different composition from the core portion and is provided to cover the core portion. The rare earth sintered magnet 1 also has a sub-phase 20 existing between the main phase 10 and the main phase 10, but the sub-phase 20 will be described in Embodiment 2.

[0014] In the rare earth sintered magnet 1 according to Embodiment 1, when the Nd concentration in the core portions 11c and 12c is CNd and the Pr concentration in the core portions 11c and 12c is CPr, the main phase 10 has a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr, and the first main phase 11 and the second main phase 12 are mixed. Also, the concentration of the heavy rare earth element RH in the core portion 11c of the first main phase 11 is higher than the concentration of the heavy rare earth element RH in the core portion 12c of the second main phase 12. That is, when the concentration of the heavy rare earth element RH in the core portion 11c of the first main phase 11 is C1RH and the concentration of the heavy rare earth element RH in the core portion 12c of the second main phase 12 is C2RH, C1RH > C2RH. The first main phase 11 has a core portion 11c and a shell portion 11s that covers the core portion 11c and has a different composition from the core portion 11c. The second main phase 12 has a core portion 12c and a shell portion 12s that covers the core portion 12c and has a different composition from the core portion 12c.

[0015] Alternatively, in the rare earth sintered magnet 1 according to Embodiment 1, when the sum of the Nd concentration and the heavy rare earth element RH concentration in the core portions 11c and 12c is C(Nd,RH), the main phase 10 can be said to have a first main phase 11 where C(Nd,RH) > CPr and a second main phase 12 where C(Nd,RH) < CPr, and the first main phase 11 and the second main phase 12 are mixed.

[0016] In other words, the rare earth sintered magnet 1 has two types of main phases 10: a first main phase 11 and a second main phase 12. Focusing on the core portions 11c and 12c of the two types of main phases 10, in the first main phase 11, the sum of the concentration of Nd and the concentration of the heavy rare earth element RH is higher than the concentration of Pr, while conversely, in the second main phase 12, the concentration of Pr is higher than the sum of the concentration of Nd and the concentration of the heavy rare earth element RH. By mixing two types of main phases 10 having core-shell structures with different anisotropic magnetic fields, i.e., different magnetic anisotropy, and by selectively including the heavy rare earth element RH within the main phases 10, it is possible to reduce Nd and the heavy rare earth element RH while maintaining good magnetization and improving the residual magnetic flux density and coercivity. Furthermore, since the coercivity is greatly improved by adding the heavy rare earth element RH, it also contributes to suppressing the deterioration of magnetic properties due to temperature changes.

[0017] The concentration difference shown here, "C1RH>C2RH," means that mapping analysis using an electron probe microanalyzer (EPMA) clearly shows a difference in the detection intensity of heavy rare earth element RH between the core portion 11c of the first main phase 11 and the core portion 12c of the second main phase 12. Specifically, for the concentration of heavy rare earth element RH in the core portion 11c of the first main phase 11, the detection intensity by EPMA is higher than the average detection intensity of heavy rare earth element RH, while for the concentration of heavy rare earth element RH in the core portion 12c of the second main phase 12, the detection intensity by EPMA is near the lower limit of the detection intensity of heavy rare earth element RH. In one example, heavy rare earth element RH is present in the core portion 11c of the first main phase 11, but hardly present in the core portion 12c of the second main phase 12.

[0018] In addition, the concentration difference shown by "the first main phase 11 where C(Nd, RH) > CPr and the second main phase 12 where C(Nd, RH) < CPr" means that there is a clear difference between the detection intensity of Nd and heavy rare earth element RH and the detection intensity of Pr by mapping analysis using EPMA. Specifically, taking the case of the first main phase 11 as an example, for the concentrations of Nd and heavy rare earth element RH in the core part 11c, the detection intensity of EPMA is higher than the average of the detection intensities of Nd and heavy rare earth element RH, and for the concentration of Pr, the detection intensity of EPMA indicates near the lower limit of the detection intensity of Pr. It can be said that the second main phase 12 is opposite to the case of the first main phase 11.

[0019] Further, in the rare earth sintered magnet 1 according to Embodiment 1, when the Nd concentration in the core part 11c of the first main phase 11 is C1Nd, the Nd concentration in the core part 12c of the second main phase 12 is C2Nd, the Pr concentration in the core part 11c of the first main phase 11 is C1Pr, and the Pr concentration in the core part 12c of the second main phase 12 is C2Pr, the relational expressions of C1Nd > C2Nd and C1Pr < C2Pr are satisfied. That is, regarding the Nd concentration, the core part 11c of the first main phase 11 is higher than the core part 12c of the second main phase 12, and conversely, regarding the Pr concentration, the core part 12c of the second main phase 12 is higher than the core part 11c of the first main phase 11. The concentration difference here also means that there is a difference in the detection intensity of Nd and Pr by the mapping analysis using the above EPMA. Specifically, in the case of the Nd concentration, the EPMA detection intensity of Nd in the core part 11c of the first main phase 11 is higher than the average of the Nd detection intensity, and the EPMA detection intensity of Nd in the core part 12c of the second main phase 12 is lower than the average of the Nd detection intensity. In the case of the Pr concentration, the EPMA detection intensity of Pr in the core part 12c of the second main phase 12 is higher than the average of the Pr detection intensity, and the EPMA detection intensity of Pr in the core part 11c of the first main phase 11 is lower than the average of the Pr detection intensity. That is, a large amount of Pr exists in the core part 12c of the second main phase 12 where the Nd concentration is low, and conversely, a large amount of Nd exists in the core part 11c of the first main phase 11 where the Pr concentration is low. By controlling to such a tissue form, it becomes possible to obtain the rare earth sintered magnet 1 having excellent magnetic characteristics.

[0020] Further, in the rare earth sintered magnet 1 according to Embodiment 1, the first main phase 11 where C(Nd,RH) > CPr is made to exist more than the second main phase 12 where C(Nd,RH) < CPr. In other words, the number of the first main phases 11 having the composition formula of (Nd,RH)2Fe 14 B is larger than the number of the second main phases 12 having the composition formula of Pr2Fe 14 B. This means that increasing the number of the first main phases 11 having the composition formula of (Nd,RH)2Fe 14 B is more beneficial than increasing the number of the second main phases 12 having the composition formula of Pr2Fe 14This is because better magnetic properties and temperature characteristics can be obtained than by increasing the amount of the second main phase 12 having the composition formula of B. Furthermore, by controlling to such a microstructure, the refinement of the overall crystal grains is also suppressed, so that it is possible to obtain excellent magnetic properties compared with the prior art while ensuring the remanence.

[0021] Also, 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 concentration of Nd in the shell portions 11s and 12s is denoted as S Nd, the concentration of Pr in the shell portions 11s and 12s is denoted as S Pr, and the concentration of the heavy rare-earth element RH in the shell portions 11s and 12s is denoted as S RH, the first main phase 11 satisfies the relational expressions of C Nd > S Nd, C Pr < S Pr, and C RH > S RH, and the second main phase 12 satisfies the relational expressions of C Nd < S Nd, C Pr > S Pr, and C RH < S RH. Specifically, in the shell portion 11s of the first main phase 11, instead of the concentrations of Nd and the heavy rare-earth element RH being lower than those in the core portion 11c, the concentration of Pr is higher than that in the core portion 11c. Also, in the shell portion 12s of the second main phase 12, instead of the concentration of Pr being lower than that in the core portion 12c, the concentrations of Nd and the heavy rare-earth element RH are higher than those in the core portion 12c.

[0022] Or, in other words, 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 sum of the concentration of Nd and the concentration of the heavy rare-earth element RH in the shell portions 11s and 12s is denoted as S(Nd,RH), and the concentration of Pr in the shell portions 11s and 12s is denoted as S Pr, the first main phase 11 satisfies the relational expressions of C(Nd,RH) > S(Nd,RH) and C Pr < S Pr, and the second main phase 12 satisfies the relational expressions of C(Nd,RH) < S(Nd,RH) and C Pr > S Pr. Specifically, in the shell portion 11s of the first main phase 11, instead of the sum of the concentrations of Nd and the heavy rare-earth element RH being smaller than that in the core portion 11c, the concentration of Pr is higher than that in the core portion 11c. Also, in the shell portion 12s of the second main phase 12, instead of the concentration of Pr being smaller than that in the core portion 12c, the sum of the concentrations of Nd and the heavy rare-earth element RH is higher than that in the core portion 12c.

[0023] By forming a main phase 10 having a shell portion 11s with a high concentration of Pr, such as the first main phase 11, the coercivity can be improved. Furthermore, by forming a main phase 10 having a shell portion 12s with a high concentration of Nd and a high sum of heavy rare earth element RH, such as the second main phase 12, the decrease in residual magnetic flux density can be suppressed while maintaining coercivity. By selectively controlling the microstructure to achieve such a configuration, the rare earth sintered magnet 1 can exhibit superior magnetic properties compared to conventional magnets.

[0024] Furthermore, the average grain size of the crystal grains of the main phase 10 is preferably 100 μm or less, and more preferably 0.5 μm to 50 μm to improve magnetic properties. Moreover, by setting it to approximately 1 μm to 10 μm, the grain size will differ from that of the microstructure produced by hot working, maintaining good magnetization performance and making it possible to produce a rare earth sintered magnet 1 with superior magnetic properties compared to conventional magnets.

[0025] 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 the group Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn. Therefore, in the rare earth sintered magnet 1 according to Embodiment 1, if RH is a heavy rare earth element selected from the group Dy, Tb, Gd, and Ho, and R is Nd, Pr, and rare earth elements other than the heavy rare earth element RH, then the general formula is (Nd a Pr b R c RH d )Fe e B f M g It is expressed as follows. It is desirable that a, b, c, d, e, f, g satisfy the following relationship.

[0026] 5 ≤ a + b ≤ 20 0 <c+d<(a+b) 0 <d<10 70 ≤ e ≤ 90 0.5 ≤ f ≤ 10 0 ≤ g ≤ 5 a+b+c+d+e+f+g=100at.%

[0027] When the rare earth sintered magnet 1 according to Embodiment 1 uses R as one or more rare earth elements selected from other than Nd, Pr, and the heavy rare earth element RH, it satisfies the general formula (Nd, Pr, RH, R)-Fe-B, and in the main phase 10 containing crystal grains based on the Nd2Fe 14 B crystal structure, there exists a main phase 10 having core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c. The main phase 10 has a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr. The concentration of the heavy rare earth element RH in the first main phase 11 is higher than the concentration of the heavy rare earth element RH in the second main phase 12, and the first main phase 11 and the second main phase 12 are mixed. With such a configuration, it is possible to obtain the rare earth sintered magnet 1 with improved magnetic properties and magneto-adhesiveness as compared with the conventional ones while suppressing the use of Nd and the heavy rare earth element RH.

[0028] This document compares the RTB-type sintered magnet described in Patent Document 1 with the rare-earth sintered magnet 1 according to Embodiment 1. The RTB-type sintered magnet described in Patent Document 1 has one or more rare-earth elements, with heavy rare-earth element RH being essential, and has one type of main phase particle composed of a core portion and a shell portion. In other words, in Patent Document 1, heavy rare-earth element RH is contained in all main phase particles within the RTB-type sintered magnet. On the other hand, in the rare-earth sintered magnet 1 according to Embodiment 1, the main phase 10 has a first main phase 11 and a second main phase 12, and the concentration of heavy rare-earth element RH is lower in the second main phase 12 compared to the first main phase 11. In one example, the core portion 11c of the first main phase 11 contains heavy rare-earth element RH, but the core portion 12c of the second main phase 12 contains almost no heavy rare-earth element RH. In other words, heavy rare-earth element RH is selectively arranged within the main phase 10. Thus, compared to the RTB-type sintered magnet described in Patent Document 1, in which all of the single main phase must contain the heavy rare earth element RH, the rare earth sintered magnet 1 according to Embodiment 1, which has a main phase 10 comprising a first main phase 11 and a second main phase 12 having a lower concentration of the heavy rare earth element RH compared to the first main phase 11, can reduce the amount of heavy rare earth element RH used. In particular, when the second main phase 12 contains almost no heavy rare earth element RH, the heavy rare earth element RH is selectively arranged, and the amount of heavy rare earth element RH used can be reduced compared to the RTB-type sintered magnet described in Patent Document 1.

[0029] Compare the rare earth magnet manufactured by the technique described in Patent Document 2 with the rare earth sintered magnet 1 according to Embodiment 1. When attempting to obtain magnetic properties equivalent to those of the rare earth sintered magnet 1 according to Embodiment 1 in the rare earth magnet manufactured by the technique described in Patent Document 2, as shown in the examples described later, more heavy rare earth element RH must be added compared to the rare earth sintered magnet 1 according to Embodiment 1. That is, the rare earth sintered magnet 1 according to Embodiment 1 can suppress the usage amount of the heavy rare earth element RH compared to the technique described in Patent Document 2 when attempting to obtain the same magnetic properties. Alternatively, when the content of the heavy rare earth element RH in the rare earth magnet manufactured by the technique described in Patent Document 2 is made the same as the content of the heavy rare earth element RH in the rare earth sintered magnets 1 according to Embodiments 1 and 2, the magnetic properties of the rare earth magnet manufactured by the technique described in Patent Document 2 will be lower than those of the rare earth sintered magnets 1 according to Embodiments 1 and 2.

[0030] In the rare earth sintered magnet 1 according to Embodiment 1, the first main phase 11 and the second main phase 12 are made to satisfy the relational expressions of C1Nd > C2Nd and C1Pr < C2Pr. Alternatively, the number of the first main phase 11 is made larger than the number of the second main phase 12. Alternatively, the first main phase 11 is made to satisfy the relational expressions of CNd > SNd, CPr < SPr, and CRH > SRH, and the second main phase 12 is made to satisfy the relational expressions of CNd < SNd, CPr > SPr, and CRH < SRH. By this as well, it is possible to obtain the rare earth sintered magnet 1 in which the magnetic properties and the magnetization property are improved while suppressing the usage of Nd and the heavy rare earth element RH.

[0031] Furthermore, since the main phase 10 contains the heavy rare earth element RH, a rare earth sintered magnet 1 with a significantly improved coercive force compared to the prior art can be obtained. Also, as shown in the examples described later, a rare earth sintered magnet 1 with a better temperature coefficient of coercive force compared to the prior art can be obtained. For this reason, even when a thermal load is applied to the rare earth sintered magnet 1, the coercive force becomes larger compared to the prior art, and the decrease due to the temperature rise of the coercive force becomes gentler compared to the prior art. That is, since the coercive force is significantly improved compared to the conventional rare earth sintered magnet, the magnetic properties when a thermal load is applied to the rare earth sintered magnet 1 are also better compared to the prior art.

[0032] Embodiment 2 FIG. 2 is a diagram schematically showing an example of the structure of the sintered state of the rare earth sintered magnet according to Embodiment 2. The rare earth sintered magnet 1 according to Embodiment 2 has a main phase 10 and a secondary phase 20. The main phase 10 includes a first main phase 11 and a second main phase 12 as described in Embodiment 1, but in FIG. 2, the first main phase 11 and the second main phase 12 are collectively referred to as the main phase 10. The secondary phase 20 exists between the main phases 10.

[0033] In the rare earth sintered magnet 1 according to Embodiment 2, the case where La and Sm are selected as the rare earth element R is shown. When La and Sm are selected as the rare earth element R, while suppressing the use of Nd and the heavy rare earth element RH, the magnetic properties are improved, and the effect of having excellent magnetization properties as compared with the prior art becomes even greater. In this example, the main phase 10 has a composition formula of (Nd, Pr, RH, La, Sm)2Fe 14 B. The reason why the rare earth element R of the rare earth sintered magnet 1 having a tetragonal R2Fe 14 B crystal structure is a rare earth element containing La and Sm is that, from the calculation results of the magnetic interaction energy using the molecular orbital method, by setting the composition to which La and Sm are added, a practical rare earth sintered magnet 1 that can greatly suppress the deterioration of magnetic properties accompanying temperature rise can be obtained. Further, by intentionally segregating La and Sm also at the grain boundary which is an example of the secondary phase 20, Nd and Pr can be diffused into the main phase 10 relatively, and the crystal magnetic anisotropy of the main phase 10 can be enhanced. As a result, a core-shell structure in which a portion with high magnetic anisotropy and a portion with low magnetic anisotropy exist within the main phase 10 is formed, and the first main phase 11 with CNd > CPr and the second main phase 12 with CNd < CPr are mixed, and the concentration of the heavy rare earth element RH in the core portion 11c of the first main phase 11 is higher than the concentration of the heavy rare earth element RH in the core portion 12c of the second main phase 12, thus forming a state where it is easy to form the rare earth sintered magnet 1.

[0034] Furthermore, if the amounts of La and Sm added are too high, the amounts of Nd and Pr, which are elements with high magnetic anisotropy constants and saturation magnetic polarization, will decrease, leading to a decline in magnetic properties. For this reason, when the composition ratios of Nd, Pr, La, and Sm are A, B, C, and D, respectively, it is preferable that (A+B)>(C+D).

[0035] In the rare earth sintered magnet 1 according to Embodiment 2, when R = La, Sm, in addition to the first main phase 11 and second main phase 12 in Embodiment 1, there is a subphase 20. The subphase 20 has a crystalline first subphase 21 based on an oxide phase whose main component is represented as (Nd,Pr,RH,La,Sm)-O, and a crystalline second subphase 22 whose main component is represented as (Nd,Pr,RH,La)-O. O is oxygen. The concentration of Sm in the subphase 20 is characterized in that the first subphase 21 is higher than that of the second subphase 22. In other words, the first subphase 21 forms an Sm-enriched region 41 with a higher Sm concentration than the second subphase 22. This has the effect of suppressing the decrease in magnetic properties not only at room temperature but also with increasing temperature.

[0036] Here, "the concentration of Sm is higher in the first subphase 21 compared to the second subphase 22" means that, on average, the detection intensity of Sm is higher in the first subphase 21 than in the second subphase 22, as determined by mapping analysis using EPMA.

[0037] The crystalline subphase 20 is a collective term for the crystalline first subphase 21 and the crystalline second subphase 22, and exists between the main phase 10. The crystalline first subphase 21 is represented as (Nd,Pr,RH,La,Sm)-O, and the crystalline second subphase 22 is represented as (Nd,Pr,RH,La)-O. Here, (Nd,Pr,RH,La,Sm) means that some of Nd and Pr are substituted by the heavy rare earth elements RH, La, and Sm. Note that the main component elements are listed in parentheses here, so the first subphase 21 and the second subphase 22 may contain trace amounts of other components in addition to the elements shown in parentheses. For example, the second subphase 22 represented as (Nd,Pr,RH,La)-O contains a trace amount of Sm.

[0038] In the rare earth sintered magnet 1 according to Embodiment 2, there is a difference in the concentrations of La and Sm between the main phase 10 and the sub-phase 20, with La and Sm being more segregated in the sub-phase 20 than in the main phase 10. That is, the sum of the concentrations of La in the first sub-phase 21 and the second sub-phase 22 is greater than or equal to the concentration of La in the main phase 10, and the sum of the concentrations of Sm in the first sub-phase 21 and the second sub-phase 22 is greater than or equal to the concentration of Sm in the main phase 10. Specifically, the concentrations of La and Sm in the sub-phase 20 are greater than or equal to the concentrations of La and Sm in the main phase 10. Here, the concentration of La in the main phase 10 is the sum of the concentrations of La in the first main phase 11 and the second main phase 12. That is, the sum of the concentrations of La in the first sub-phase 21 and the second sub-phase 22 is higher than the sum of the concentrations of La in the first main phase 11 and the second main phase 12. Furthermore, the concentration of Sm in the main phase 10 is the sum of the concentration of Sm in the first main phase 11 and the concentration of Sm in the second main phase 12. In other words, the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is higher than the sum of the concentrations of Sm in the first main phase 11 and the second main phase 12.

[0039] Here, let X be the La concentration in the main phase 10, X1 be the La concentration in the first subphase 21, X2 be the La concentration in the second subphase 22, Y be the Sm concentration in the main phase 10, Y1 be the Sm concentration in the first subphase 21, and Y2 be the Sm concentration in the second subphase 22. Then the following relationship (1) is satisfied.

[0040] 1<(Y1+Y2) / Y<(X1+X2) / X ···(1)

[0041] Furthermore, from the viewpoint of improving magnetic properties, the following relationships (2) and (3) are satisfied for the concentrations of Nd and Pr contained in the main phase 10.

[0042] (CNd+SNd)>(X+Y) ····(2) (CPr+SPr)>(X+Y) ····(3)

[0043] In the above, the concentration of La in the main phase 10 was assumed to be the sum of the concentrations of La in the first main phase 11 and the second main phase 12, and the concentration of Sm in the main phase 10 was assumed to be the sum of the concentrations of Sm in the first main phase 11 and the second main phase 12. This indicates that both La and Sm are segregated more towards the subphase 20 than towards the main phase 10. However, when viewed locally, the sum of the concentrations of La and Sm in the first main phase 11 and the second main phase 12, and the sum of the concentrations of La and Sm in the first subphase 21 and the second subphase 22, may not satisfy the above relationship. Therefore, more specifically, the concentration of La in the main phase 10 represents the average of the concentrations of La in the first main phase 11 and the second main phase 12, and the concentration of Sm in the main phase 10 represents the average of the concentrations of Sm in the first main phase 11 and the second main phase 12. In this case, the concentration of La in subphase 20, i.e., the sum of the concentrations of La in the first subphase 21 and the second subphase 22, represents the average of the concentrations of La in the first subphase 21 and the second subphase 22, and the concentration of Sm in subphase 20, i.e., the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22, represents the average of the concentrations of Sm in the first subphase 21 and the second subphase 22.

[0044] La, due to its high concentration at grain boundaries during the manufacturing process, particularly the heat treatment process, relatively diffuses Nd and Pr into the main phase 10. As a result, in the rare-earth sintered magnet 1 of Embodiment 2, the Nd and Pr in the main phase 10 are not consumed at grain boundaries, and the crystalline magnetic anisotropy is improved. Similarly, Sm, being present in a high concentration in the subphase 20, particularly the first subphase 21, compared to the main phase 10, also relatively diffuses Nd into the main phase 10, improving the crystalline magnetic anisotropy.

[0045] As described above, since subphase 20 contains heavy rare earth elements RH, both the first subphase 21 and the second subphase 22 contain heavy rare earth elements RH, but the distribution of heavy rare earth elements RH differs between the first subphase 21 and the second subphase 22. In the second subphase 22, where the Sm concentration is lower than in the first subphase 21, the heavy rare earth elements RH are uniformly distributed within the second subphase 22. On the other hand, in the first subphase 21, which forms the Sm-enriched region 41, the heavy rare earth elements RH are not uniformly distributed within the first subphase 21, but rather selectively distributed between the outer periphery of the first subphase 21 and the Sm-enriched region 41, that is, in the inner periphery of the outer periphery of the first subphase 21. Specifically, heavy rare earth elements RH are present so as to selectively surround the outer periphery of the Sm-enriched region 41, where the Sm concentration of the first subphase 21 is high. From this, it can be said that the first subphase 21 has an Sm-enriched portion 41 and a heavy rare earth element-containing portion 42 in which heavy rare earth elements RH exist and selectively surround the outer edge of the Sm-enriched portion 41. The outer edge of the first subphase 21 is the boundary between the first subphase 21 and the main phase 10.

[0046] Thus, a first sub-phase 21 and a second sub-phase 22 containing heavy rare earth elements RH exist between the main phase 10 and the main phase 10. For this reason, it can be considered that heavy rare earth elements RH are incorporated into a portion of the surface of the main phase 10 that is in contact with the first sub-phase 21 and the second sub-phase 22 containing heavy rare earth elements RH. In other words, similar to Embodiment 1, Embodiment 2 also makes it possible to suppress the decrease in residual magnetic flux density while improving the coercivity of the rare earth sintered magnet 1.

[0047] Next, La and Sm are tetragonal R2Fe 14 This section explains which atomic sites in the B crystal structure are substituted. Figure 3 shows tetragonal Nd2Fe. 14 This figure shows the atomic sites in the B crystal structure. Note that the crystal structure shown in Figure 3 is, in one example, described in FIG. 1 of Reference 1 listed below. The substituted sites are determined by calculating the stabilization energy due to substitution using band calculations and the molecular field approximation of the Heisenberg model, and then determining the site based on that energy value. (Reference 1) JFHerbst et al. “Relationships between crystal structure and magnetic properties in Nd2Fe 14 PHYSICAL REVIEW B. 1984, Vol.29, No.7, p. 4176-4178.

[0048] First, let's explain how to calculate the stabilization energy in La. The stabilization energy in La is Nd8Fe 56 Using a B4 crystal cell, (Nd7La1)Fe 56 B4+Nd and Nd8(Fe 55 This can be determined by the energy difference between La1)B4+Fe. The smaller the energy value, the more stable the site is when an atom is substituted there. In other words, La is most likely to be substituted at the atomic site with the lowest energy. In this calculation, when La is substituted for the original atom, the result is tetragonal R2Fe 14 The lattice constant in the B crystal structure is assumed to remain unchanged regardless of the difference in atomic radius. Table 1 shows the stabilization energy of La at each substitution site when the ambient temperature is changed.

[0049] [Table 1]

[0050] According to Table 1, the stable substitution site for La is the Nd(f) site at temperatures above 1000K, and the Fe(c) site at temperatures of 293K and 500K. As will be described later, the rare earth sintered magnet 1 according to Embodiment 2 is formed by heating the raw materials for the rare earth sintered magnet 1 to a temperature above 1000K to melt them, and then rapidly cooling them. For this reason, the raw materials for the rare earth sintered magnet 1 are thought to maintain a temperature of above 1000K, i.e., above 727°C, preferably around 1300K, i.e., 1027°C. At this time, it is thought that La is substituted to either the Nd(f) site or the Nd(g) site. Here, it is thought that La is preferentially substituted to the energetically stable Nd(f) site, but substitution to the Nd(g) site, which has a smaller energy difference among the substitution sites for La, is also possible. For this reason, the Nd(g) site is also listed as a candidate substitution site for La.

[0051] Furthermore, when the rare earth sintered magnet 1 is manufactured by the manufacturing method described later, although the temperature during sintering is above 1000K, the Fe(c) sites listed in Table 1 are repeatedly maintained in an energetically stable temperature range through the first aging process, second aging process, third aging process, fourth aging process, and cooling process described later. In other words, the substitution of La at the Nd sites of the main phase 10 is maintained in an unstable energy state. That is, in the raw material stage of the rare earth sintered magnet 1, La was mainly substituted at the Nd sites of the main phase 10, but in the manufacturing method described later, by deliberately holding the rare earth sintered magnet 1 repeatedly in an unstable energy state temperature range relative to the Nd sites of the main phase 10, a certain amount of La is selectively released from the Nd sites of the main phase 10, resulting in La segregating into the subphase 20. As a result, the main phase 10 promotes the formation of a characteristic structure called a core-shell structure.

[0052] Next, we will explain how to calculate the stabilization energy in Sm. The stabilization energy of Sm is (Nd7Sm1)Fe 56 B4+Nd and Nd8(Fe 55 It can be determined by the energy difference between Sm1)B4+Fe. Through atomic substitution, tetragonal R2Fe14 The assumption that the lattice constant in the B crystal structure remains unchanged is the same as in the case of La. Table 2 shows the stabilization energy of Sm at each substitution site when the ambient temperature is changed.

[0053] [Table 2]

[0054] According to Table 2, unlike La, the stable substitution site for Sm is the Nd(g) site at all temperatures. In Sm, substitution is thought to preferentially occur at the energetically stable Nd(g) site, but substitution at the Nd(f) site, which has a smaller energy difference among the substitution sites of Sm, is also possible.

[0055] When the rare earth sintered magnet 1 is manufactured by the manufacturing method described later, the substitution of the Nd(g) site in the main phase 10 is the most energetically stable. However, as described above, by maintaining the magnet in a temperature range where the substitution of La to the Nd site in the main phase 10 becomes unstable, some Sm is also released from the Nd site in the main phase 10 along with La and segregates into the subphase 20. As a result, there is a concentration difference between the main phase 10 and the subphase 20 in terms of La and Sm concentrations. The sum of the concentrations of La in the first subphase 21 and the second subphase 22 is greater than or equal to the concentration of La in the main phase 10, and the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is greater than or equal to the concentration of Sm in the main phase 10. More specifically, the average concentration of La in the first subphase 21 and the second subphase 22 is greater than or equal to 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 subphase 21 and the second subphase 22 is greater than or equal to the average concentration of Sm in the first main phase 11 and the second main phase 12. In other words, La and Sm are segregated in subphase 20.

[0056] Comparing La and Sm, from an energetic standpoint, it is clear that La, which is held in an unstable energy state temperature range, is overwhelmingly more likely to segregate into the subphase 20. As a result, in the case of a rare-earth sintered magnet 1 prepared with similar concentrations of La and Sm, La segregates more into the subphase 20 than Sm. Repeated holding in this temperature range creates a concentration difference of Sm, which has a low segregation rate, in the subphase 20, leading to the formation of the first subphase 21 and the second subphase 22. This promotes the formation of the core-shell structure in the main phase 10.

[0057] In this explanation, we will primarily focus on Nd, as shown in Figure 3. However, since Nd and Pr occur as mixtures, as exemplified by didymium (Di), their energy levels are considered to be close. Therefore, the same can be said when Nd is replaced with Pr. By having both Nd and Pr present, it is possible to form a main phase 10 having two types of core-shell structures.

[0058] As described above, the rare earth sintered magnet 1 of Embodiment 2 satisfies the general formula (Nd,Pr,RH,R)-Fe-B when R is one or more rare earth elements selected from those other than Nd,Pr,RH, and Nd2Fe 14It has a main phase 10 containing crystal grains based on a B crystal structure. The main phase 10 has core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c. When R = La, Sm, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, it has a sub-phase 20. The sub-phase 20 has a crystalline first sub-phase 21 based on an oxide phase whose main component is represented by (Nd, Pr, RH, La, Sm)-O, and a crystalline second sub-phase 22 whose main component is represented by (Nd, Pr, RH, La)-O. Regarding the concentration of Sm, the first sub-phase 21 has a higher concentration than the second sub-phase 22, and the first sub-phase 21 has a Sm-concentrated portion 41 where Sm is selectively distributed. That is, two types of main phases 10 and two types of sub-phases 20 are present. Thereby, it becomes possible to provide a rare earth sintered magnet 1 having excellent magnetic properties such as temperature characteristics of magnetic properties as compared with the prior art. Also, by setting R as La, Sm, the main phase 10 is in a state where the first main phase 11 with C(Nd, RH)>CPr and the second main phase 12 with C(Nd, RH)<CPr are mixed. In other words, the rare earth sintered magnet 1 has a main phase 10 having two types of first main phases 11 and second main phases 12. Focusing on the core portions 11c, 12c of the two types of main phases 10, in the first main phase 11, the Nd concentration is higher than the Pr concentration, and conversely in the second main phase 12, the Pr concentration is higher than the Nd concentration, and the concentration of the heavy rare earth element RH in the first main phase 11 is higher than the concentration of the heavy rare earth element RH in the second main phase 12, so that a main phase 10 having two types of core-shell structures is likely to occur. As a result, while suppressing the use of Nd and the heavy rare earth element RH as compared with the prior art, the magnetic properties can be improved, and the effect of having excellent magnetization properties as compared with the prior art can be further enhanced.

[0059] Embodiment 3. In Embodiment 3, regarding the method for manufacturing the rare earth sintered magnet 1 described in Embodiments 1 and 2, it will be explained separately as a method for manufacturing a rare earth sintered magnet alloy as a raw material for the rare earth sintered magnet 1 and a method for manufacturing the rare earth sintered magnet 1 using the rare earth sintered magnet alloy.

[0060] Figure 4 is a flowchart showing an example of the procedure for manufacturing a rare earth sintered magnet alloy according to Embodiment 3. First, as shown in Figure 4, the method for manufacturing a rare earth sintered magnet alloy, which is the raw material for the rare earth sintered magnet 1, includes a melting step (step S1) in which the raw material for the rare earth sintered magnet alloy, which contains the elements constituting the rare earth sintered magnet 1, is heated to a temperature of 1000K or higher to melt it; a first cooling step (step S2) in which the molten raw material is cooled on a rotating body to obtain a solidified alloy; and a second cooling step (step S3) in which the solidified alloy is further cooled in a container. This makes it possible to manufacture a rare earth sintered magnet alloy. Each step will be described below.

[0061] In the melting step S1, the raw materials for the rare earth sintered magnet alloy are heated to a temperature of 1000K or higher in a crucible in an atmosphere containing an inert gas such as Ar (argon) or in a vacuum to melt them. This prepares a molten alloy of the molten rare earth sintered magnet alloy. Nd, Pr, RH, R, Fe, and B can be used as raw materials. When manufacturing the rare earth sintered magnet 1 of Embodiment 2, R becomes La and Sm. Examples of RH include Dy and Tb. Also, FeB may be used instead of B as a raw material. In this case, one or more elements selected from the group of Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn may be included as additive element M in the raw materials.

[0062] Next, in the first cooling step of step S2, the molten alloy prepared in the melting step is poured into a tundish and then onto a single roll, which is a rotating body. This rapidly cools the molten alloy on the single roll rotating in a predetermined direction, and a solidified alloy thinner than the ingot alloy is prepared on the single roll from the molten alloy. Here, a single roll is used as the rotating body, but it is not limited to this; rapid cooling may also be achieved by contacting a twin roll, a rotating disk, a rotating cylindrical mold, etc. From the viewpoint of efficiently obtaining a thin solidified alloy, the cooling rate in the first cooling step should be 10°C / second or more. 7 It is preferable to set it to ℃ / second or less, 10 3 ℃ / second or more 10 4It is more preferable to keep the temperature below °C / second. The thickness of the solidified alloy is in the range of 0.03 mm to 10 mm. Solidification of the molten alloy begins from the portion in contact with the single roll, and crystals grow in a columnar or needle-like shape in the thickness direction from the contact surface with the single roll.

[0063] Subsequently, in the second cooling step S3, the thin solidified alloy prepared in the first cooling step is placed in a tray container and cooled. The thin solidified alloy breaks down into flake-like rare earth sintered magnet alloy as it enters the tray container and cools. Depending on the cooling rate, ribbon-like rare earth sintered magnet alloy may also be obtained, and it is not limited to flake-like. From the viewpoint of obtaining a rare earth sintered magnet alloy with a microstructure that has good temperature characteristics for magnetic properties, the cooling rate in the second cooling step is 10 -2 ℃ / second or more 10 5 It is preferable to set it to ℃ / second or less, 10 -1 ℃ / second or more 10 2 It is more preferable to keep the temperature below °C / second.

[0064] The rare earth sintered magnet alloy obtained through these processes has a short-axis size of 3 μm to 10 μm and a long-axis size of 10 μm to 300 μm. In Embodiment 2, it has a fine crystalline structure containing a (Nd,Pr,RH,La,Sm)-Fe-B crystalline phase and a crystalline subphase 20 of an oxide represented by (Nd,Pr,RH,La,Sm)-O. Hereinafter, the crystalline subphase 20 of an oxide represented by (Nd,Pr,RH,La,Sm)-O will be referred to as the (Nd,Pr,RH,La,Sm)-O phase. The (Nd,Pr,RH,La,Sm)-O phase is a non-magnetic phase consisting of an oxide with a relatively high concentration of rare earth elements. The thickness of the (Nd,Pr,RH,La,Sm)-O phase corresponds to the width of the grain boundary and is 10 μm or less. Because the rare earth sintered magnet alloy produced by the above manufacturing method undergoes a rapid cooling process, its microstructure is refined compared to the rare earth sintered magnet alloy obtained by the mold casting method.

[0065] Next, a method for manufacturing a rare-earth sintered magnet 1 using a rare-earth sintered magnet alloy will be described. Figure 5 is a flowchart showing an example of the procedure for manufacturing a rare-earth sintered magnet according to Embodiment 3. As shown in Figure 5, the method for manufacturing a rare-earth sintered magnet 1 includes a grinding step (step S21) in which a rare-earth sintered magnet alloy having a (Nd,Pr,RH,La,Sm)-Fe-B crystal phase and a (Nd,Pr,RH,La,Sm)-O phase is ground; a molding step (step S22) in which a molded body is prepared by molding the powder of the ground rare-earth sintered magnet alloy; a sintering step (step S23) in which the molded body is sintered at a predetermined sintering temperature to obtain a sintered body; an aging step (step S24) in which the sintered body is aged to improve the magnetic properties of the rare-earth sintered magnet 1, such as its coercivity; and a cooling step (step S25) in which the aged sintered body is cooled. Each step will be described below.

[0066] In the grinding step S21, a rare earth sintered magnet alloy having a (Nd,Pr,RH,La,Sm)-Fe-B crystalline phase and a (Nd,Pr,RH,La,Sm)-O phase, manufactured according to the manufacturing method of rare earth sintered magnet alloy shown in Figure 4, is ground to obtain rare earth sintered magnet alloy powder with a particle size of 200 μm or less, preferably 0.5 μm to 100 μm, and further, considering magnetization performance, approximately 1 μm to 10 μm. The grinding of the rare earth sintered magnet alloy is carried out using, in one example, an agate mortar and pestle, a stamp mill, a jaw crusher, or a jet mill. In particular, when reducing the particle size of the powder, it is preferable to grind the rare earth sintered magnet alloy in an atmosphere containing an inert gas. Grinding the rare earth sintered magnet alloy in an atmosphere containing an inert gas can suppress the incorporation of oxygen into the powder. However, if the atmosphere during grinding does not affect the magnetic properties of the magnet, the grinding of the rare earth sintered magnet alloy may be carried out in air. Furthermore, when manufacturing the rare earth sintered magnet 1 of Embodiment 1, the La and Sm in the rare earth sintered magnet alloy used when manufacturing the rare earth sintered magnet 1 of Embodiment 2 can be replaced with rare earth elements R other than Nd, Pr and the heavy rare earth element RH. In other words, a rare earth sintered magnet alloy having a (Nd,Pr,RH,R)-Fe-B crystalline phase and a (Nd,Pr,RH,R)-O phase can be crushed.

[0067] In the molding process of step S22, the powder of the rare-earth sintered magnet alloy is compressed and molded in a mold under a magnetic field to prepare a molded body. Here, the applied magnetic field can be 2T in one example. Note that molding may be performed without applying a magnetic field.

[0068] In the sintering step S23, the compression-molded body is held at a sintering temperature of 950°C to 1300°C, preferably 1000°C to less than 1150°C, for a period of 0.1 hours to 10 hours, preferably 1.0 hour to 6.0 hours, to obtain a sintered body. Sintering is preferably carried out in an atmosphere containing an inert gas or in a vacuum to suppress oxidation. Sintering may also be carried out while applying a magnetic field.

[0069] In the case of Figure 5, the aging process in step S24 includes the first aging process in step S24-1, the second aging process in step S24-2, the third aging process in step S24-3, and the fourth aging process in step S24-4. The aging is preferably carried out in an atmosphere containing an inert gas or in a vacuum to suppress oxidation.

[0070] In the first aging step of step S24-1, the obtained sintered body is held at a first aging temperature which is below the sintering temperature, specifically in the range of 700°C to less than 950°C for 0.1 hours to 10 hours, preferably 0.5 hours to 5 hours.

[0071] In the second aging step of step S24-2, after the first aging step, the sintered body held in the first aging step is held at a second aging temperature which is lower than the first aging temperature, specifically in the range of 450°C or higher and less than 700°C for 0.1 hours or more and 10 hours or less, preferably 1.0 hour or more and 7 hours or less.

[0072] In the third aging step of step S24-3, after the second aging step, the sintered body held in the second aging step is raised again to the first aging temperature, specifically a temperature in the range of 700°C or more and less than 950°C, and held at the first aging temperature for a range of 0.1 hours or more and 10 hours or less, preferably 0.5 hours or more and 5 hours or less.

[0073] In the fourth aging step of step S24-4, after the third aging step, the sintered body held in the third aging step is again held at the second aging temperature, specifically at a temperature in the range of 450°C to less than 700°C, for 0.1 hours to 10 hours, preferably 1.0 hour to 7 hours.

[0074] Finally, in the cooling step of step S25, the sintered body held in the fourth aging step is held at a temperature lower than the second aging temperature, specifically, within a range of 200°C or higher and lower than 450°C for a range of 0.1 hour or longer and 5 hours or shorter. Thereafter, by cooling to room temperature, the rare earth sintered magnet 1 is completed. Cooling is preferably performed in an atmosphere containing an inert gas or in a vacuum in order to suppress oxidation.

[0075] As described above, by controlling the temperature and time in the sintering step, aging step, and cooling step, the sintered body is held several times in the temperature range of the unstable energy state. As a result, it is possible to mix the first main phase 11 composed of CNd > CPr and the second main phase 12 composed of CNd < CPr, and make the concentration of the heavy rare earth element RH in the first main phase 11 higher than the concentration of the heavy rare earth element RH in the second main phase 12. In other words, in the rare earth sintered magnet 1, there are two types of main phases 10, namely the first main phase 11 and the second main phase 12. Looking at the core portions 11c and 12c of the two types of main phases 10, the first main phase 11 has the sum of the Nd concentration and the heavy rare earth element RH concentration higher than the Pr concentration, and conversely, the second main phase 12 has the Pr concentration higher than the sum of the Nd concentration and the heavy rare earth element RH concentration. It is possible to manufacture the rare earth sintered magnet 1 having such characteristics.

[0076] Furthermore, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, a crystalline first secondary phase 21 based on an oxide phase whose main component is represented by (Nd, Pr, RH, La, Sm)-O, and a crystalline second secondary phase 22 whose main component is represented by (Nd, Pr, RH, La)-O are provided. Regarding the concentration of Sm, the first secondary phase 21 has a higher concentration than the second secondary phase 22, and it is possible to manufacture the rare earth sintered magnet 1 in which a Sm-enriched portion 41 is formed in the first secondary phase 21.

[0077] This makes it possible to provide a rare earth sintered magnet 1 having excellent magnetization performance and magnetic characteristics compared to the prior art while suppressing the use of Nd and the heavy rare earth element RH.

[0078] In Embodiment 3, a rare earth sintered magnet alloy powder is obtained by crushing a rare earth sintered magnet alloy having a (Nd,Pr,RH,La,Sm)-Fe-B crystalline phase and a (Nd,Pr,RH,La,Sm)-O phase. The powder is then molded, and the molded body is sintered to form a sintered body. After that, the sintered body is aged to produce a rare earth sintered magnet 1. This makes it possible to produce a rare earth sintered magnet 1 having the structure described in Embodiment 2. Furthermore, since the rare earth sintered magnet alloy is produced after the heavy rare earth elements are prepared to a desired concentration, and the rare earth sintered magnet 1 is produced using this rare earth sintered magnet alloy, the heavy rare earth element RH can easily enter the interior of the main phase 10.

[0079] In addition, in Embodiment 3, the temperature and time in the sintering process, the aging process, and the sintered body cooling process are controlled. In particular, in the first aging process, the obtained sintered body is maintained at a first aging temperature which is lower than the sintering temperature, specifically within the range of 700°C or higher and lower than 950°C, for 0.1 hour or longer and 10 hours or shorter, preferably within the range of 0.5 hour or longer and 5 hours or shorter. In the second aging process, the sintered body is maintained at a second aging temperature which is lower than the first aging temperature, specifically within the range of 450°C or higher and lower than 700°C, for 0.1 hour or longer and 10 hours or shorter, preferably within the range of 1.0 hour or longer and 7 hours or shorter. In the third aging process, the temperature is raised again to the first aging temperature, specifically within the range of 700°C or higher and lower than 950°C, and the sintered body is maintained at the first aging temperature for 0.1 hour or longer and 10 hours or shorter, preferably within the range of 0.5 hour or longer and 5 hours or shorter. In the fourth aging process, the sintered body is maintained again at the second aging temperature, specifically within the range of 450°C or higher and lower than 700°C, for 0.1 hour or longer and 10 hours or shorter, preferably within the range of 1.0 hour or longer and 7 hours or shorter. Thus, the temperature and time are controlled such that two sets of the first aging process and the second aging process are carried out. As a result, a state is created in which the sintered body is held several times in a temperature range of an unstable energy state. As a result, the first main phase 11 composed of CNd > CPr and the second main phase 12 composed of CNd < CPr are mixed, and it becomes possible to make the concentration of the heavy rare earth element RH in the first main phase 11 higher than the concentration of the heavy rare earth element RH in the second main phase 12. In other words, the rare earth sintered magnet 1 has two types of main phases 10, namely the first main phase 11 and the second main phase 12. Focusing on the core portions 11c and 12c of the two types of main phases 10, the first main phase 11 has the sum of the concentrations of Nd and the heavy rare earth element RH higher than the concentration of Pr, and conversely, the second main phase 12 has the concentration of Pr higher than the sum of the concentrations of Nd and the heavy rare earth element RH. The rare earth sintered magnet 1 can be selectively manufactured.

[0080] Furthermore, the above manufacturing process makes it possible to selectively produce a rare earth sintered magnet 1 having a characteristic microstructure in which a crystalline first subphase 21 is based on an oxide phase whose main component is (Nd,Pr,RH,La,Sm)-O, and a crystalline second subphase 22 whose main component is (Nd,Pr,RH,La)-O, and the concentration of Sm is higher in the first subphase 21 than in the second subphase 22, and an Sm-enriched region 41 is formed in the first subphase 21.

[0081] Compared to the RTB-type sintered magnet described in Patent Document 1, the RTB-type sintered magnet described in Patent Document 1 has one or more rare earth elements, with heavy rare earth element RH being essential, and has one type of main phase particle composed of a core portion and a shell portion. In other words, in Patent Document 1, all main phase particles contain the heavy rare earth element RH. On the other hand, the main phase 10 of the rare earth sintered magnet 1 according to Embodiment 1 is a mixture of a first main phase 11 in which the heavy rare earth element RH is contained in the core portion 11c, and a second main phase 12 in which the heavy rare earth element RH is hardly contained in the core portion 12c. In other words, the heavy rare earth element RH is selectively arranged in the first main phase 11 of the two types of main phases 10. Thus, compared to the RTB-type sintered magnet described in Patent Document 1, which requires that the heavy rare earth element RH be contained in all of the single type of main phase, the rare earth sintered magnet 1 according to Embodiment 1, which only requires that the heavy rare earth element RH be contained in the first main phase 11 of the two types of main phases 10, can reduce the amount of heavy rare earth element RH used. Furthermore, since the proportion of the volume of the subphase 20 to the total volume of the rare earth sintered magnet 1 is extremely small, even if the heavy rare earth element RH is diffused and present in the subphase 20, the amount of heavy rare earth element RH used can be reduced compared to the technology in Patent Document 1.

[0082] Furthermore, compared to the technology described in Patent Document 2, in order to obtain magnetic properties equivalent to those of the rare earth sintered magnet 1 according to Embodiment 1 using the method described in Patent Document 2, a large amount of heavy rare earth element RH must be added, as will be described later. In other words, when trying to obtain the same magnetic properties, the rare earth sintered magnet 1 according to Embodiment 1 can use less heavy rare earth element RH compared to the technology described in Patent Document 2. In addition, the method described in Patent Document 2 includes hot working, but the manufacturing method of the rare earth sintered magnet 1 according to Embodiment 3 does not include hot working. As a result, the reduction in particle size of the main phase 10 is suppressed, and the decrease in residual magnetic flux density and magnetization can be suppressed compared to the rare earth magnet manufactured using the technology described in Patent Document 2.

[0083] This makes it possible to obtain a rare-earth sintered magnet 1 that improves magnetic properties compared to conventional magnets while suppressing the use of heavy rare-earth elements RH compared to conventional magnets.

[0084] Embodiment 4. Embodiment 4 describes a rotor using the rare earth sintered magnet 1 from Embodiment 1 or Embodiment 2, manufactured by the manufacturing method of Embodiment 3. Figure 6 is a schematic cross-sectional view showing an example of the configuration of a rotor equipped with a rare earth sintered magnet according to Embodiment 4. Figure 6 shows a cross-section of the rotor 100 in a direction perpendicular to the rotation axis RA.

[0085] The rotor 100 is rotatable around the rotation axis RA. The rotor 100 comprises a rotor core 101 and rare earth sintered magnets 1 inserted into magnet insertion holes 102 provided in the rotor core 101 along the circumferential direction of the rotor 100. Figure 6 shows an example in which four magnet insertion holes 102 are provided in the rotor core 101 and four rare earth sintered magnets 1 are inserted into the magnet insertion holes 102, but the number of magnet insertion holes 102 and rare earth sintered magnets 1 may be changed according to the design of the rotor 100. The rotor core 101 is formed by stacking multiple disc-shaped electromagnetic steel sheets in the axial direction of the rotation axis RA.

[0086] The rare earth sintered magnets 1 are manufactured according to the manufacturing method described in Embodiment 3. The four rare earth sintered magnets 1 are each inserted into their corresponding magnet insertion holes 102. The four rare earth sintered magnets 1 are each magnetized such that the magnetic poles of the rare earth sintered magnets 1 on the radially outer side of the rotor 100 are different from those of adjacent rare earth sintered magnets 1.

[0087] Thus, the rotor 100 according to Embodiment 4 is equipped with a rare-earth sintered magnet 1 according to Embodiment 1 or Embodiment 2, which can achieve improved magnetic properties at room temperature and suppression of the decrease in magnetic properties with increasing temperature. In this way, the rare-earth sintered magnet 1 suppresses the decrease in magnetic properties with increasing temperature while suppressing the use of heavy rare-earth elements RH compared to conventional methods and maintaining high residual magnetic flux density and coercivity, so the decrease in magnetic properties is suppressed even in high-temperature environments exceeding 100°C. This makes it possible to replace expensive, geographically unevenly distributed, and procurement-risky Nd and heavy rare-earth elements RH with inexpensive rare-earth elements, while improving magnetic properties and magnetization, and stabilizing the operation of the rotor 100 even in high-temperature environments exceeding 100°C. Furthermore, since the rare-earth sintered magnet 1 according to Embodiment 1 or Embodiment 2 has superior magnetization performance compared to conventional methods, it is possible to magnetize the rotor 100 in an assembled state with the rare-earth sintered magnet 1 set, thus simplifying the manufacturing process. Furthermore, since a magnetization process with reduced voltage can be achieved, it also contributes to energy saving.

[0088] Embodiment 5. Embodiment 5 describes a rotating machine equipped with the rotor 100 from Embodiment 4. Figure 7 is a schematic cross-sectional view showing an example of the configuration of the rotating machine according to Embodiment 5. Figure 7 shows a cross-section perpendicular to the rotation axis RA of the rotor 100.

[0089] The rotating machine 120 comprises a rotor 100, as described in Embodiment 4, which is rotatable around a rotation axis RA, and an annular stator 130 provided coaxially with the rotor 100 and positioned opposite the rotor 100. The stator 130 is formed by stacking multiple electromagnetic steel sheets 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 adopted. The stator 130 has teeth 131 that protrude toward the rotor 100, provided along the inner surface of the stator 130. Windings 132 are attached to the teeth 131. In one example, the winding method of the windings 132 may be concentrated winding or distributed winding. In other words, the stator 130 has windings 132 attached to teeth 131 that protrude toward the rotor 100 on the inner surface on the side where the rotor 100 is located, and has an annular structure positioned opposite the rotor 100. The rotor 100 inside the rotating machine 120 has two or more magnetic poles; that is, there should be two or more rare-earth sintered magnets 1. Also, although Figure 7 shows an example of a magnet-embedded rotor 100, a surface-magnet type rotor 100 in which rare-earth sintered magnets 1 are fixed to the outer circumference with adhesive may also be used.

[0090] Thus, the rotating machine 120 in Embodiment 5 is equipped with a rare earth sintered magnet 1 according to Embodiment 1 or Embodiment 2, which can achieve improved magnetic properties at room temperature and suppression of the decrease in magnetic properties with increasing temperature. In this way, the rare earth sintered magnet 1 suppresses the decrease in magnetic properties with increasing temperature while suppressing the use of heavy rare earth elements compared to conventional methods and maintaining high residual magnetic flux density and coercivity. As a result, the decrease in magnetic properties is suppressed even in high-temperature environments exceeding 100°C. [Examples]

[0091] The details of the rare-earth sintered magnet 1 of this disclosure will be described below with reference to examples and comparative examples.

[0092] In Examples 1 to 8, rare earth sintered magnets 1 are manufactured using the method shown in Embodiment 3, employing samples of multiple rare earth sintered magnet alloys with different compositions, represented as (Nd,Pr,Tb,La,Sm)-Fe-B. In Examples 1 to 8, rare earth sintered magnets 1 are manufactured using rare earth sintered magnet alloys with varying Nd,Pr,Tb,La, and Sm content. In other words, in Examples 1 to 8, rare earth sintered magnets 1 are manufactured using rare earth sintered magnet alloys represented as (Nd,Pr,Tb,La,Sm)-Fe-B, employing the manufacturing method shown in Embodiment 3.

[0093] In Comparative Examples 1 to 14, rare earth sintered magnets 1 are experimentally manufactured using samples of multiple rare earth sintered magnet alloys R-Fe-B with different compositions, by a general method for manufacturing rare earth magnets as described in Patent Document 1 or Patent Document 2. In the samples of rare earth sintered magnets 1 from Comparative Examples 1 to 14, the R portion is changed.

[0094] In Comparative Examples 1 to 7, a rare earth sintered magnet 1 is manufactured using the manufacturing method described in Patent Document 1, either from a rare earth sintered magnet alloy where R is Nd, or from a rare earth sintered magnet alloy containing R = Nd and one or more elements selected from the group Tb, Pr, La, and Sm.

[0095] In Comparative Examples 8 to 14, rare earth sintered magnets 1 are manufactured using the manufacturing method shown in Patent Document 2, either from a rare earth sintered magnet alloy where R is Nd, or from a rare earth sintered magnet alloy containing R = Nd and one or more elements selected from the group Tb, Pr, La, and Sm. The manufacturing method shown in Patent Document 2 includes a step of hot working the sintered body.

[0096] Table 3 shows the general formulas, elemental content, microstructure analysis results, and magnetic properties and magnetization performance of rare earth sintered magnets for the examples and comparative examples. Table 3 shows the general formulas of the main phase 10 for each sample, which is the rare earth sintered magnet 1 of Examples 1 to 8 and Comparative Examples 1 to 14.

[0097] [Table 3]

[0098] Next, the method for analyzing the microstructure of the rare-earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 14 will be described. The microstructure morphology of the rare-earth sintered magnets 1 is determined by elemental analysis using a scanning electron microscope (SEM) and EPMA. Here, a field emission electron probe microanalyzer (FE-EPMA) (manufactured by JEOL Ltd., product name: JXA-8530F) is used as the SEM and EPMA. The conditions for elemental analysis are an acceleration voltage of 15.0 kV and an irradiation current of 2.271 e. -008 The result is A, with an irradiation time of 130ms, a pixel count of 512 pixels × 512 pixels, a magnification of 5000x, and a total of 1 integration cycle.

[0099] Next, the method for evaluating the magnetic properties of the rare-earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 14 will be described. The evaluation of magnetic properties is performed by measuring the coercivity of multiple samples using a pulse-excitation type BH tracer. The maximum applied magnetic field by the BH tracer is 6T or higher, which is the state in which the rare-earth sintered magnet 1 is fully magnetized. In addition to the pulse-excitation type BH tracer, if a DC recording magnetometer (also called a DC BH tracer), a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), a physical property measurement system (PPMS), etc. can be used, as long as a maximum applied magnetic field of 6T or higher can be generated. The measurement is performed in an atmosphere containing an inert gas such as nitrogen. The magnetic properties of each sample are measured by detecting the magnetization picked up by a search coil or magnetic sensor from the rare-earth sintered magnet 1 magnetized by the applied magnetic field. The magnetic properties are measured from the JH curve or BH curve, which is the measured magnetic hysteresis. Furthermore, the magnetic properties of each sample are measured at two different temperatures: a first measurement temperature T1 and a second measurement temperature T2. The temperature coefficient α [% / °C] 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, divided by the temperature difference (T2-T1). Similarly, the temperature coefficient β [% / °C] 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, 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 with respect to temperature rise is suppressed.

[0100] Furthermore, for the measurement of magnetization performance, the magnetization rate is obtained by calculating the ratio between the magnetic flux density measured from the magnetic hysteresis drawn by applying an arbitrary magnetic field and the magnetic flux density measured from the magnetic hysteresis drawn by applying a saturating magnetic field at a certain permeability coefficient. If a high magnetization rate can be obtained even at a lower magnetic field, it can be said that the magnetization performance is high.

[0101] First, the analysis results of each sample according to Examples 1 to 8 and Comparative Examples 1 to 14 will be described. FIG. 8 is a diagram tracing the composition image obtained by analyzing the cross-section of the rare earth sintered magnet according to Examples 1 to 8 by FE-EPMA. FIGS. 9 to 14 are element mappings obtained by analyzing the cross-section of the rare earth sintered magnet according to Examples 1 to 8 by FE-EPMA. FIG. 9 is the element mapping of Nd, FIG. 10 is the element mapping of Pr, FIG. 11 is the element mapping of Tb, FIG. 12 is the element mapping of O, FIG. 13 is the element mapping of Sm, and FIG. 14 is the element mapping of La. Note that FIGS. 9 to 14 are the element mappings of the region shown in FIG. 8. Also, since the rare earth sintered magnets 1 according to Examples 1 to 8 all show the same results, FIGS. 8 to 14 show the representative examples among Examples 1 to 8. Furthermore, the same reference numerals are assigned to the same components as in FIGS. 1 and 2.

[0102] As shown in FIGS. 9 to 11, in each sample of Examples 1 to 8, when RH is Tb and R is one or more rare earth elements selected from Nd, Pr, and other than RH, satisfying the general formula (Nd, Pr, Tb, R)-Fe-B, Nd2Fe 14 It can be confirmed that the main phase 10 containing crystal grains based on the B crystal structure has a core part 11c, 12c and a shell part 11s, 12s covering the core part 11c, 12c. It can also be confirmed that the first main phase 11 with CNd > CPr and the second main phase 12 with CNd < CPr are mixed in the main phase 10. It can also be confirmed that when the concentration of Tb in the first main phase 11 is C1Tb and the concentration of Tb in the second main phase is C2Tb, C1Tb > C2Tb.

[0103] Here, the concentration difference shown as "the first main phase 11 with CNd > CPr and the second main phase 12 with CNd < CPr" means that there is a clear difference between the detection intensity of Nd and the detection intensity of Pr in the mapping analysis using EPMA. Specifically, taking the case of the first main phase 11 as an example, the concentration of Nd in the core part 11c has a detection intensity of EPMA higher than the average, and the concentration of Pr shows a detection intensity of EPMA near the lower limit. It can be said that the second main phase 12 is opposite to the case of the first main phase 11.

[0104] More specifically, taking the Nd mapping diagram in Fig. 9 and the Pr mapping diagram in Fig. 10 as examples, the average value of the detection level of Nd by EPMA is 89, and the average value of the detection level of Pr is 46. In the case of the first main phase 11, CNd is higher than 89, and CPr is near the lower limit value, and there is a clear concentration difference. Also, since the second main phase 12 is opposite to the first main phase 11, CPr is higher than 46, and CNd is near the lower limit value, and there is a clear concentration difference.

[0105] Also, the concentration difference shown as "C1Tb > C2Tb" means that there is a clear difference between the detection intensity of Tb in the first main phase 11 and the detection intensity of Tb in the second main phase 12 in the mapping analysis using EPMA. Specifically, the concentration of Tb in the first main phase 11 has a detection intensity of EPMA higher than the average, and the concentration of Tb in the second main phase 12 shows a detection intensity of EPMA near the lower limit.

[0106] More specifically, taking the Tb mapping diagram in Fig. 11 as an example, the average value of the detection level of Tb by EPMA is 44. In the case of the first main phase 11, CTb is higher than 44, but in the case of the second main phase 12, CTb is near the lower limit, and there is a clear concentration difference.

[0107] As shown in FIGS. 12 to 14, when R = La, Sm, the rare earth sintered magnet 1 has, in addition to the first main phase 11 and the second main phase 12 in the first embodiment, a crystalline first secondary phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, Tb, La, Sm)-O, and a crystalline second secondary phase 22 whose main component is represented as (Nd, Pr, Tb, La)-O. It can also be confirmed that the concentration of Sm is higher in the first secondary phase 21 than in the second secondary phase 22.

[0108] In Table 3, when the sum of the concentration of Nd and the concentration of Tb which is a heavy rare earth element RH is denoted as C(Nd, Tb), for the samples in which the state of the first main phase 11 where C(Nd, RH)>CPr and the second main phase 12 where C(Nd, RH)<CPr could be confirmed, "〇" is entered in the columns of the first main phase 11 and the second main phase 12 respectively, and for the samples where it could not be confirmed, "×" is entered in the columns of the first main phase 11 and the second main phase 12 respectively. The concentration difference of the inequality means that there is a clear difference between the detection intensities of Nd and Tb and the detection intensity of Pr. Taking a specific example, in the case of the first main phase 11, the concentrations of Nd and Tb indicate that the detection intensity of EPMA is higher than the average, and the concentration of Pr indicates that the detection intensity of EPMA is near the lower limit value. It can be said that the situation in the case of the second main phase 12 is opposite to that in the case of the first main phase 11. When only C(Nd, RH)<CPr as in the second main phase 12 was confirmed, "〇" is entered only in the column of the second main phase 12, and "×" is entered in the column of the first main phase 11.

[0109] Furthermore, in Table 3, for samples having a crystalline first secondary phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, Tb, La, Sm)-O and a crystalline second secondary phase 22 whose main component is represented as (Nd, Pr, Tb, La)-O, and where it was confirmed that the concentration of Sm in the first secondary phase 21 is higher than that in the second secondary phase 22, an "〇" is entered in each of the columns for the first secondary phase 21 and the second secondary phase 22. For samples where this could not be confirmed, an "×" is entered in each of the columns for the first secondary phase 21 and the second secondary phase 22. Also, for those in which only one secondary phase 20 exists or there is no concentration difference in Sm between the secondary phases 20, assuming that only the first secondary phase 21 exists, an "〇" is entered only in the column for the first secondary phase 21, and an "×" is entered in the column for the second secondary phase 22. The concentration difference between the first secondary phase 21 and the second secondary phase 22 means that, by mapping analysis using EPMA, the detection intensity of Sm in the first secondary phase 21 is on average higher than that in the second secondary phase 22. Specifically, taking the Sm mapping diagram in Fig. 13 as an example, with the average value of the Sm detection level by EPMA being 15.0, the first secondary phase 21 is higher than 15.0, and the second secondary phase 22 is lower than 15.0, that is, it is in a state where detection is not possible in an aggregated state.

[0110] Also, it can be confirmed that there are more first primary phases 11 where C(Nd, RH)>CPr than the number of second primary phases 12 where C(Nd, RH)<CPr, from the intensity ratios of the elemental mappings obtained by FE-EPMA analysis. When focusing on the shell portions 11s, 12s of the core-shell structure, it can also be confirmed that the first primary phase 11 satisfies the relational expressions of CNd>SNd, CPr<SPr, CTb>STb, and the second primary phase 12 satisfies the relational expressions of CNd<SNd, CPr>SPr, CTb<STb.

[0111] Next, the measurement results of the magnetic properties of each sample in Examples 1 to 8 and Comparative Examples 1 to 14 will be described. The shape of each sample used for magnetic measurement is a block shape with length, width, and height all of 7 mm. The first measurement temperature T1 is 23°C, and the second measurement temperature T2 is 200°C. 23°C is room temperature. The second measurement temperature T2 of 200°C is a temperature that can occur in the operating environment of automotive motors and industrial motors.

[0112] First, the residual magnetic flux density and coercivity of each sample in Examples 1 to 8 and Comparative Examples 2 to 14 are determined in comparison with Comparative Example 1. If the residual magnetic flux density and coercivity values ​​of each sample at 23°C are within 1% of the values ​​in Comparative Example 1, which is considered to be within the measurement error, it is judged as "equivalent." If the values ​​are 1% or more higher, it is judged as "good." If the values ​​are 1% or less lower, it is judged as "poor."

[0113] Next, the temperature coefficient α of the remanent magnetic flux density is calculated using the remanent magnetic flux density at 23°C (first measurement temperature T1) and the remanent magnetic flux density at 200°C (second measurement temperature T2). Similarly, the temperature coefficient β of the coercivity is calculated using the coercivity at 23°C (first measurement temperature T1) and the coercivity at 200°C (second measurement temperature T2). The temperature coefficients of remanent magnetic flux density and coercivity for each sample from Examples 1 to 8 and Comparative Examples 2 to 14 are judged in comparison with Comparative Example 1. For each sample, if the values ​​are within ±1% of the absolute value of the temperature coefficient of remanent magnetic flux density |α| and the absolute value of the temperature coefficient of coercivity |β| compared with the sample from Comparative Example 1, it is judged as "equivalent," if the value is lower than -1%, it is judged as "good," and if the value is higher than +1%, it is judged as "poor." For samples judged as "good," the temperature coefficient is smaller, which suppresses the decrease in magnetic properties with increasing temperature. This makes it possible to provide a rare-earth sintered magnet 1 that has stable magnetic properties even in high-temperature environments.

[0114] Next, the magnetization performance is calculated from the ratio of the magnetic flux density at the intersection of the magnetic hysteresis and permeance coefficient Pc at an applied magnetic field of 20 kOe to the magnetic flux density at the intersection of the magnetic hysteresis and permeance coefficient Pc at an applied magnetic field of 80 kOe, which is the saturation magnetization state. The magnetization performance of each sample from Examples 1 to 8 and Comparative Examples 2 to 14 is judged in comparison to Comparative Example 1. In other words, for each sample, if the magnetization performance is greater than or equal to -1% compared to the magnetization performance of the sample from Comparative Example 1, which is considered to be a measurement error, it is judged as "equivalent or better," and if the value is lower than -1%, it is judged as "poor." For samples judged as "equivalent or better," a rare-earth sintered magnet 1 with high magnetization performance can be provided.

[0115] The results for determining the remanent magnetic flux density, coercivity, temperature coefficient of remanent magnetic flux density, temperature coefficient of coercivity, and magnetization performance are shown in Table 3.

[0116] Comparative Example 1 is a sample of a rare earth sintered magnet 1 prepared according to the manufacturing method described in Patent Document 1, using Nd, Tb, Fe, and FeB as raw materials so that it is (Nd, Tb)-Fe-B. When the microstructure of this sample is observed according to the method described above, since Pr, La, and Sm are not added, the core-shell structure in the main phase 10 cannot be confirmed, and the concentration of Sm in the sub-phase 20 cannot be confirmed to be higher in the first sub-phase 21 than in the second sub-phase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density B r It is 1.25T, and the coercivity H cJ The magnetic field strength is 1600 kA / m. The temperature coefficients of the remanent magnetic flux density and coercivity are |α| = 0.185% / °C and |β| = 0.455% / °C, respectively. The magnetic susceptibility is 98.6%. These values ​​from Comparative Example 1 are used as a reference.

[0117] Comparative Example 2 is a sample of rare earth sintered magnet 1, manufactured using Nd, Fe, and FeB as raw materials to form Nd-Fe-B, according to the manufacturing method described in Patent Document 1. When the microstructure of this sample is observed according to the method described above, since Pr, La, and Sm are not added, the core-shell structure in the main phase 10 cannot be confirmed, and the concentration of Sm in the sub-phase 20 cannot be confirmed to be higher in the first sub-phase 21 than in the second sub-phase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, since the heavy rare earth element RH, Tb, is not present in the main phase 10, the remanent magnetic flux density is "good" and the coercivity is "poor". In addition, the temperature coefficient of the remanent magnetic flux density is "equivalent", the temperature coefficient of the coercivity is "equivalent", and the magnetization performance is "equivalent or better".

[0118] Comparative Example 3 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method described in Patent Document 1, using Nd, Pr, Fe, and FeB as raw materials so that it is (Nd,Pr)-Fe-B. When the microstructure of this sample is observed according to the method described above, although the main phase 10, which is a mixture of Nd and Pr, can be confirmed due to the addition of Pr, it does not form a core-shell structure. Also, since La and Sm are not added, it cannot be confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. When the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density is "good" and the coercivity is "poor" because it does not contain Tb, which is a heavy rare earth element RH. Also, the temperature coefficient of coercivity is "poor" due to the addition of Pr. Since the manufacturing method does not include hot working, the magnetization performance is "equal or better". The temperature coefficient of the residual magnetic flux density is "equal". This result reflects the fact that while the addition of Pr increases the magnetic anisotropy of the main phase 10 and improves coercivity, it does not result in the optimal microstructure of the main phase 10 and the subphase 20.

[0119] Comparative Example 4 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method described in Patent Document 1, using Nd, Pr, Tb, Fe, and FeB as raw materials so that the structure is (Nd,Pr,Tb)-Fe-B. When the microstructure of this sample is observed according to the method described above, the main phase 10, which is a mixture of Nd and Pr, can be confirmed, but it does not form a core-shell structure. Also, since La and Sm are not added, it cannot be confirmed that the concentration of Sm in the subphase 20 is higher in the first subphase 21 than in the second subphase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density is "equivalent" because the addition of Tb, a heavy rare earth element RH, is the same as in Comparative Example 1. In addition, the addition of Pr, in addition to the addition of Tb, a heavy rare earth element RH, results in "good" coercivity and "poor" temperature coefficient of coercivity. Since the manufacturing method does not include hot working, the magnetization performance is "equivalent or better". Furthermore, the temperature coefficient of the residual magnetic flux density is "equivalent." This reflects the fact that, although the addition of Tb and Pr increases the magnetic anisotropy of the main phase 10 and improves coercivity, it does not result in the optimal microstructure of the main phase 10 and subphase 20.

[0120] Comparative Example 5 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method described in Patent Document 1, using Nd, La, Sm, Fe, and FeB as raw materials so that the structure is (Nd, La, Sm)-Fe-B. When the microstructure of this sample is observed according to the method described above, the core-shell structure of the main phase 10 cannot be confirmed because Pr is not added. Also, although the concentration of Sm is segregated into one sub-phase 20 due to the segregation of La, the second sub-phase 22 does not exist. Furthermore, it cannot be confirmed that the concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22. Also, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density is "good" and the coercivity is "poor" because Tb, a heavy rare earth element RH, is not present. The temperature coefficient of coercivity becomes "good" due to the addition of La and Sm. Since the manufacturing method does not include hot working, the magnetization performance is "equivalent or better". Furthermore, the temperature coefficient of the residual magnetic flux density is "equivalent." This reflects the fact that, although the presence of La and Sm in the main phase 10 or sub-phase 20 results in a good temperature coefficient of coercivity, the magnetic properties at room temperature do not improve, indicating that the microstructure in the main phase 10 and sub-phase 20 is not optimal.

[0121] Comparative Example 6 is a sample of a rare earth sintered magnet 1 prepared according to the manufacturing method described in Patent Document 1, using Nd, La, Sm, Fe, and FeB as raw materials so that the composition is (Nd, La, Sm)-Fe-B. The composition ratio of Nd, La, and Sm is different from that of Comparative Example 5. When the microstructure of this sample is observed according to the method described above, the core-shell structure of the main phase 10 cannot be confirmed because Pr is not added. Also, due to the addition of La and Sm, although the concentration of Sm is segregated into one sub-phase 20 due to the segregation of La, the second sub-phase 22 does not exist. Furthermore, it cannot be confirmed that the concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22. Also, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density is "good" and the coercivity is "poor" because the heavy rare earth element RH, Tb, is not present. Furthermore, by optimizing the amounts of La and Sm added, the temperature coefficient of the residual magnetic flux density becomes "good," and the temperature coefficient of coercivity becomes "good." Since the manufacturing method does not include hot working, the magnetization performance is "equal to or better." In Comparative Example 6, although the temperature coefficient of the magnetic properties shows good results due to the optimization of the amounts of La and Sm added, the magnetic properties at room temperature do not improve because the heavy rare earth element RH, Tb, is not added to the base material. This result reflects that the microstructure in the main phase 10 and sub-phase 20 is not optimal, and even if the composition ratio of Nd, La, and Sm is changed, almost the same results as in Comparative Example 5 can be obtained.

[0122] Comparative Example 7 is a sample of a rare earth sintered magnet 1 prepared according to the manufacturing method described in Patent Document 1, using Nd, Pr, La, Sm, Fe, and FeB as raw materials so that the structure is (Nd,Pr,La,Sm)-Fe-B. When the microstructure of this sample is observed according to the method described above, although a main phase 10 in which Nd and Pr are mixed can be confirmed due to the addition of Pr, it does not form a core-shell structure. Furthermore, although the concentration of Sm is segregated into one subphase 20 due to the segregation of La, a second subphase 22 does not exist. Moreover, it cannot be confirmed that the concentration of Sm in the first subphase 21 is higher than that of the second subphase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the residual magnetic flux density is "good" and the coercivity is "poor" because it does not contain Tb, which is a heavy rare earth element RH. Furthermore, while optimizing the amounts of La and Sm added should result in "good" temperature coefficients for residual magnetic flux density and coercivity, the addition of Pr has reduced the temperature coefficient of coercivity to "equivalent." Since the manufacturing method does not involve hot working, the magnetization performance is "equivalent or better."

[0123] Comparative Example 8 is a sample of rare earth sintered magnet 1, manufactured using Nd, Tb, Fe, and FeB as raw materials so that it is (Nd, Tb)-Fe-B, according to a manufacturing method including hot working described in Patent Document 2. When the microstructure of this sample is observed according to the method described above, since Pr, La, and Sm are not added, the core-shell structure in the main phase 10 cannot be confirmed, and the concentration of Sm in the sub-phase 20 cannot be confirmed as being higher in the first sub-phase 21 than in the second sub-phase 22. However, the refinement of the microstructure, which is a characteristic of magnets manufactured by hot working, can be confirmed. When the magnetic properties of this sample are evaluated according to the method described above, the coercivity is "good" and the temperature coefficient of coercivity is "equivalent" due to the refinement of the magnetic powder. Also, because the magnetic moments are not easily aligned, the residual magnetic flux density and magnetization performance are "poor". The temperature coefficient of residual magnetic flux density is "equivalent". This result reflects the fact that while the absolute value of coercivity and the temperature coefficient of coercivity improve with the refinement of magnetic powder through hot working, the magnetic moments are less likely to align, leading to a decrease in residual magnetic flux density and a deterioration in magnetization performance.

[0124] Comparative Example 9 is a sample of rare earth sintered magnet 1, manufactured using Nd, Fe, and FeB as raw materials to form Nd-Fe-B, according to a manufacturing method including hot working described in Patent Document 2. When the microstructure of this sample is observed according to the method described above, the core-shell structure in the main phase 10 cannot be confirmed because Pr, La, and Sm are not added, and the concentration of Sm in the sub-phase 20 cannot be confirmed to be higher in the first sub-phase 21 than in the second sub-phase 22. However, the refinement of the microstructure, which is characteristic of magnets manufactured by hot working, can be confirmed. When the magnetic properties of this sample are evaluated according to the method described above, the coercivity is "good" and the temperature coefficient of coercivity is "equivalent" due to the refinement of the magnetic powder. Also, the residual magnetic flux density and magnetization performance are "poor" because the magnetic moments are difficult to align. The temperature coefficient of residual magnetic flux density is "equivalent". This result reflects the fact that while coercivity improves with the miniaturization of magnetic powder through hot working, the difficulty in aligning the magnetic moments leads to a decrease in residual magnetic flux density and a deterioration in magnetization performance.

[0125] Comparative Example 10 is a sample of a rare earth sintered magnet 1, manufactured using Nd, Pr, Fe, and FeB as raw materials, such as (Nd,Pr)-Fe-B, according to a manufacturing method including hot working described in Patent Document 2. When the microstructure of this sample is observed according to the method described above, a core-shell structure is confirmed due to the addition of Pr and the hot working, but the core-shell structure is confirmed only in one type of main phase 10 where the Pr concentration in the core is high. Also, since La and Sm are not added, it cannot be confirmed that the concentration of Sm in the sub-phase 20 is higher in the first sub-phase 21 than in the second sub-phase 22. When the magnetic properties of this sample are evaluated according to the method described above, the coercivity is "good" due to the refinement of the magnetic powder, and the temperature coefficient of coercivity is "equivalent". Also, because the magnetic moments are difficult to align, the residual magnetic flux density and magnetization performance are "poor". The temperature coefficient of residual magnetic flux density is "equivalent". This is because the formation of a core-shell structure with a high Pr concentration in the core significantly improves the coercivity to the level of rare-earth sintered magnet 1 with added Tb, but other properties reflect the refinement of the microstructure due to hot working.

[0126] Comparative Example 11 is a sample of a rare earth sintered magnet 1, manufactured using Nd, Pr, Tb, Fe, and FeB as raw materials, such that it is (Nd,Pr,Tb)-Fe-B, according to a manufacturing method including hot working described in Patent Document 2. When the microstructure of this sample is observed according to the method described above, a core-shell structure is confirmed due to the addition of Pr and the hot working, but the core-shell structure is confirmed only in one type of main phase 10 where the Pr concentration in the core is high. Also, since La and Sm are not added, it cannot be confirmed that the concentration of Sm in the sub-phase 20 is higher in the first sub-phase 21 than in the second sub-phase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the coercivity is "good" due to the refinement of the magnetic powder, and the temperature coefficient of coercivity is "equivalent". Also, because the magnetic moments are difficult to align, the residual magnetic flux density and magnetization performance are "poor". The temperature coefficient of residual magnetic flux density is "equivalent". This material is produced by hot working, and its coercivity is significantly improved by the substitution of some of the highly anisotropic Tb with Nd. However, other properties reflect the refinement of the microstructure due to hot working.

[0127] Comparative Example 12 is a sample of a rare earth sintered magnet 1, manufactured using Nd, La, Sm, Fe, and FeB as raw materials, such as (Nd, La, Sm)-Fe-B, according to a manufacturing method including hot working described in Patent Document 2. When the microstructure of this sample is observed according to the method described above, the core-shell structure of the main phase 10 cannot be confirmed due to the absence of Pr addition. Furthermore, although the concentration of Sm is segregated into one sub-phase 20 due to the segregation of La, the second sub-phase 22 does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22. When the magnetic properties of this sample are evaluated according to the method described above, the coercivity and temperature coefficient of coercivity are "good" due to the refinement of the magnetic powder. Furthermore, the residual magnetic flux density and magnetization performance are "poor" because the magnetic moments are difficult to align. The temperature coefficient of the residual magnetic flux density is "good". This result reflects the fact that, although the temperature coefficient of the magnetic properties is good due to the presence of La and Sm in the main phase 10 or sub-phase 20, the residual magnetic flux density and magnetization performance at room temperature do not improve because the magnetic moments are not easily aligned, indicating that the microstructure of the main phase 10 and sub-phase 20 is not optimal.

[0128] Comparative Example 13 is a sample of a rare earth sintered magnet 1, manufactured using Nd, La, Sm, Fe, and FeB as raw materials, such that the composition is (Nd, La, Sm)-Fe-B, according to a manufacturing method including hot working described in Patent Document 2. The composition ratio of Nd, La, and Sm is different from that of Comparative Example 12. When the microstructure of this sample is observed according to the method described above, the core-shell structure of the main phase 10 cannot be confirmed due to the absence of Pr. Furthermore, although the concentration of Sm is segregated into one sub-phase 20 due to the segregation of La, the second sub-phase 22 does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22. When the magnetic properties of this sample are evaluated according to the method described above, the coercivity and temperature coefficient of coercivity are "good" due to the refinement of the magnetic powder. Furthermore, the residual magnetic flux density and magnetization performance are "poor" because the magnetic moments are difficult to align. The temperature coefficient of the remanent magnetic flux density is "good". This means that although the presence of La and Sm in the main phase 10 or sub-phase 20 results in a good temperature coefficient for the magnetic properties, the remanent magnetic flux density and magnetization performance at room temperature do not improve because the magnetic moments are not easily aligned. This reflects that the microstructure of the main phase 10 and sub-phase 20 is not optimal. Even when the composition ratio of Nd, La, and Sm is changed, results almost the same as in Comparative Example 12 are obtained.

[0129] Comparative Example 14 is a sample of a rare earth sintered magnet 1, manufactured using Nd, Pr, La, Sm, Fe, and FeB as raw materials, such that the composition is (Nd,Pr,La,Sm)-Fe-B, according to a manufacturing method including hot working described in Patent Document 2. When the microstructure of this sample is observed according to the method described above, a core-shell structure is confirmed due to the addition of Pr and the hot working, but the core-shell structure is confirmed only in one type of main phase 10 where the Pr concentration in the core is high. Furthermore, although the concentration of Sm is segregated into one sub-phase 20 due to the segregation of La, a second sub-phase 22 does not exist. Moreover, it cannot be confirmed that the concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22. Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the coercivity and temperature coefficient of coercivity are "good" due to the refinement of the magnetic powder. However, the residual magnetic flux density and magnetization performance are "poor" because the magnetic moments are difficult to align. The temperature coefficient of the residual magnetic flux density is "good". This is because the formation of a core-shell structure with a high Pr concentration in the core significantly improves the coercivity to the level of rare-earth sintered magnet 1 with added Tb, and the presence of La and Sm in the main phase 10 or sub-phase 20 results in a good temperature coefficient for the magnetic properties, especially the coercivity. However, because the magnetic moments are difficult to align, the residual magnetic flux density and magnetization performance at room temperature do not improve, which also reflects that the microstructure of the main phase 10 and sub-phase 20 is not optimal.

[0130] The samples in Examples 1 to 8 satisfy the general formula (Nd,Pr,Tb,R)-Fe-B, where Tb is the heavy rare earth element RH and R is one or more rare earth elements selected from those other than Nd,Pr, and Tb. 14It has a main phase 10 containing crystal grains based on the B crystal structure. The main phase 10 has core parts 11c, 12c and shell parts 11s, 12s that cover the core parts 11c, 12c. The main phase 10 is a rare earth sintered magnet 1 in which a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr are mixed, and the concentration of Tb, which is a heavy rare earth element RH, in the core part 11c of the first main phase 11 is higher than the concentration of Tb in the core part 12c of the second main phase 12. Also, the rare earth sintered magnets 1 of Examples 1 to 8 are the case where R = La, Sm. In addition to the first main phase 11 and the second main phase 12, it has a crystalline first sub-phase 21 based on an oxide phase whose main component is represented as (Nd, Pr, Tb, La, Sm)-O, and a crystalline second sub-phase 22 whose main component is represented as (Nd, Pr, Tb, La)-O. The concentration of Sm is higher in the first sub-phase 21 than in the second sub-phase 22, and it is characterized in that a Sm-enriched part 41 is formed in the first sub-phase 21. When the magnetic properties of the samples of Examples 1 to 8 are evaluated according to the method described above, the residual magnetic flux density is "good", the coercive force is "good", the temperature coefficient of the residual magnetic flux density is "good", the temperature coefficient of the coercive force is "good", and the magnetization performance is "equal to or better than". As a result, these rare earth sintered magnets 1 exhibit the effect of having excellent magnetic properties and magnetization compared to the conventional ones while suppressing the use of Nd and heavy rare earth element RH, which are expensive and have a high regional concentration and procurement risk.

[0131] Furthermore, as can be seen from Table 3, although the samples of Examples 1 to 8 contain less Tb, a heavy rare earth element RH, compared to the samples of Comparative Examples 1, 4, 8, and 11, the magnetic properties obtained are superior to those of the samples of Comparative Examples 1 to 14. In particular, in order to obtain magnetic properties equivalent to those of Examples 1 to 8 with the samples of Comparative Examples 8 and 11 manufactured by the manufacturing method of Patent Document 2, it is necessary to include even more Tb. For this reason, the rare earth sintered magnets 1 according to Embodiments 1 and 2 have the effect of reducing the amount of heavy rare earth element RH used compared to the technology of Patent Document 2. Alternatively, if the content of heavy rare earth element RH in the rare earth magnet manufactured by the manufacturing method of Patent Document 2 is the same as the content of heavy rare earth element RH in the rare earth sintered magnets 1 according to Embodiments 1 and 2, the magnetic properties of the rare earth magnet manufactured by the manufacturing method of Patent Document 2 will be lower than those of the rare earth sintered magnets 1 according to Embodiments 1 and 2. Furthermore, Table 3 shows that, compared to the samples of Comparative Examples 1 and 4 produced by the manufacturing method of Patent Document 1, the samples of Examples 1 to 8 can improve magnetic properties while reducing the content of the heavy rare earth element RH, Tb.

[0132] The configurations shown in the above embodiments are examples only, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention. [Explanation of Symbols]

[0133] 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, 41 Sm-enriched section, 42 Heavy rare earth element-containing section, 100 Rotor, 101 Rotor core, 102 Magnet insertion hole, 120 Rotating machine, 130 Stator, 131 Teeth, 132 Winding.

Claims

1. When RH is a heavy rare earth element containing at least one of Dy and Tb, and R is one or more rare earth elements selected from those other than Nd, Pr, Dy, and Tb, the general formula (Nd, Pr, RH, R)-Fe-B is satisfied, and Nd 2 Fe 14 It has a main phase containing crystal grains based on a B crystal structure, The main phase has a core portion and a shell portion that covers the core portion. The main phase comprises a first main phase where CNd > CPr and a second main phase where CNd < CPr, where the concentration of Nd in the core is CNd and the concentration of Pr in the core is CPr. The concentration of heavy rare earth elements RH in the core portion of the first main phase is higher than the concentration of heavy rare earth elements RH in the core portion of the second main phase. A rare earth sintered magnet characterized in that the first main phase and the second main phase are mixed together.

2. The rare earth sintered magnet according to claim 1, characterized in that the number of first main phases is greater than the number of second main phases.

3. When the concentration of Nd in the shell portion is SNd, the concentration of Pr in the shell portion is SPr, the concentration of heavy rare earth element RH in the core portion of the main phase is CRH, and the concentration of heavy rare earth element RH in the shell portion is SRH, The first main phase satisfies the following relationships: CNd > SNd, CPr < SPr, CRH > SRH. The rare earth sintered magnet according to claim 1, characterized in that the second main phase satisfies the relationships CNd < SNd, CPr > SPr, and CRH < SRH.

4. When R is La and Sm, the system further comprises a crystalline first subphase based on an oxide phase whose main component is represented as (Nd, Pr, RH, La, Sm)-O, and a crystalline second subphase whose main component is represented as (Nd, Pr, RH, La)-O. The rare earth sintered magnet according to claim 1, characterized in that the first subphase forms an Sm-enriched region with a higher Sm concentration compared to the second subphase.

5. A method for manufacturing a rare earth sintered magnet according to any one of claims 1 to 4, A melting step of melting the raw materials for a rare earth sintered magnet alloy containing the elements that constitute the rare earth sintered magnet, A first cooling step is performed in which the molten raw material from the melting step is cooled to obtain a solidified alloy, A second cooling step is performed to further cool the solidified alloy to obtain a rare earth sintered magnet alloy, A grinding step for grinding the rare earth sintered magnet alloy satisfying (Nd, Pr, RH, R)-Fe-B, A molding step is performed to prepare a molded body by molding the powder of the rare earth sintered magnet alloy that has been pulverized in the pulverization step, A sintering step to obtain a sintered body by sintering the molded body at a predetermined sintering temperature, A first aging step in which the sintered body is held at a first aging temperature which is below the sintering temperature, A second aging step is performed in which the sintered body held in the first aging step is held at a second aging temperature which is a temperature lower than the first aging temperature, A third aging step in which the sintered body held in the second aging step is again held at the first aging temperature, A fourth aging step in which the sintered body held in the third aging step is held at the second aging temperature, A cooling step for cooling the sintered body held in the fourth aging step, A method for manufacturing rare earth sintered magnets, characterized by containing [a specific ingredient / method].

6. Rotor core and A rare earth sintered magnet according to any one of claims 1 to 4 is provided in the rotor core, A rotor characterized by having the following features.

7. The rotor according to claim 6, An annular stator is positioned opposite the rotor, having a winding attached to teeth protruding toward the rotor on the inner surface of the side where the rotor is located, A rotating machine characterized by having the following features.

Images