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

Abstract

The rare earth sintered magnet has: a main phase which satisfies the general formula (Nd, Pr, RH, R)-Fe-B-M when RH is an element including at least one of Dy and Tb, R is one or more rare earth elements other than Nd, Pr, Dy, and Tb, and M is one or more elements selected from Ga, Al, Cu, and Co, and which contains crystal grains based on an Nd2Fe14B crystal structure; and a secondary phase. The main phase has a core part and a shell part, and when the Nd concentration in the core part is CNd and the Pr concentration is CPr, the main phase has a first main phase in which CNd > CPr and a second main phase in which CNd < CPr. The core portion of the first main phase is higher than the core portion of the second main phase in terms of the concentration of the heavy rare earth element RH. The first main phase is mixed with the second main phase. The sub-phase has a first sub-phase and a second sub-phase, the main component of which is an oxide phase represented by (Nd, Pr, RH, La, Sm)-O containing element M as a trace component. The concentration of the element M in the second sub-phase is higher than that in the first sub-phase.

Description

Technical Field

[0001] This disclosure relates to permanent magnets, i.e., rare earth sintered magnets, which are made by sintering materials containing rare earth elements, methods for manufacturing rare earth sintered magnets, rotors, and rotating machines. Background Technology

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

[0003] In recent years, the production of Nd-Fe-B sintered magnets has been expanding, 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 geographically unevenly distributed, posing procurement risks. Therefore, research is underway to develop technologies to suppress the consumption of Nd and heavy rare earth elements.

[0004] Patent document 1 discloses an RTB-based sintered magnet, which contains R2T 14 RTB-based sintered magnets with B crystals as the main phase particles, where R is one or more rare earth elements with heavy rare earth elements RH as essential, T is Fe or one or more transition metal elements with Fe and Co as 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. Among them, the low-heavy rare earth element crystal phases are composed of R2T. 14 The phase is composed of B crystals, and the concentration of heavy rare earth elements is relatively low compared to the overall concentration of heavy rare earth elements in the main phase particles. The non-magnetic R-rich phase is a phase with an R content of 70 atomic% or more and 100 atomic% or less. In addition, a portion of the main phase particles has a core-shell structure, which has a core and a shell surrounding the core, with a total heavy rare earth element concentration lower than that of the core. According to the technology described in Patent Document 1, an RTB-based sintered magnet with improved coercivity and low cost is obtained.

[0005] Patent document 2 discloses a method for manufacturing rare earth magnets, which includes: manufacturing a rare earth magnet composed of (R1) 1-x R2 x ) a TM b B c M dThe process involves three steps: a first step of constructing a sintered body with a microstructure consisting of a main phase and grain boundary phases; a second step of thermoplastic processing of the sintered body to manufacture a rare-earth magnet precursor; and a third step of permeating the grain boundary phases of the rare-earth magnet precursor with the molten R3-M modified alloy to manufacture a rare-earth magnet. Specifically, R1 is one or more rare-earth elements including Y (yttrium), R2 is a rare-earth element different from R1, TM is one or more transition metals including Fe, Ni (nickel), and 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), and Au (gold). Furthermore, x, a, b, c, and d are 0.01≤x≤1, 12≤a≤20, b=100-acd, 5≤c≤20, and 0≤d≤3, all representing atomic percentages. Additionally, R3 is a rare earth element containing R1 and R2. The thermoplastic processing performed on the sintered body will be referred to as hot working. According to the technology described in Patent Document 2, it is possible to manufacture rare earth magnets that not only exhibit excellent magnetization but also superior coercivity while maintaining a high principal phase index, while reducing the amount of heavy rare earth elements.

[0006] Existing technical documents

[0007] Patent documents

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

[0009] Patent Document 2: Japanese Patent Application Publication No. 2015-153813 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the RTB-based sintered magnets described in Patent Document 1 contain phases of heavy rare earth elements within the main phase. Therefore, even if the coercivity is improved, the remanent magnetic flux density required for industrial motors and the like cannot be obtained, and the magnetic properties may decrease due to thermal load. Furthermore, while the rare earth magnets manufactured using the method described in Patent Document 2 can reduce the amount of heavy rare earth elements and improve coercivity, the manufacturing process includes hot working, resulting in a smaller particle size of the main phase. This leads to a deterioration in the remanent magnetic flux density and magnetization performance of the manufactured rare earth magnets.

[0012] This disclosure is made in view of the above and aims to obtain rare earth sintered magnets that can improve coercivity without reducing residual magnetic flux density and magnetization performance compared with the past.

[0013] Methods for solving problems

[0014] To address the aforementioned issues and achieve the objectives, the rare-earth sintered magnet disclosed herein comprises: a main phase that, when 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 (praseodymium), Dy, and Tb, and M is one or more elements selected from the group Ga, Al, Cu, and Co, satisfies the general formula (Nd, Pr, RH, R)-Fe-BM, containing Nd2Fe 14 The B crystal structure consists of basic grains and secondary phases formed between the main phases. The main phase has a core and a shell covering the core. When the concentration of Nd in the core is set as CNd and the concentration of Pr in the core is set as CPr, the main phase has a first main phase with CNd > CPr and a second main phase with CNd < CPr. The concentration of heavy rare earth element RH in the core of the first main phase is higher than that in the core of the second main phase. The first and second main phases are mixed. The secondary phases have a first and a second crystalline secondary phase, mainly composed of oxide phases (Nd, Pr, RH, La, Sm)-O containing element M as a trace component. The concentration of element M in the second secondary phase is higher than that in the first secondary phase.

[0015] The effects of the invention

[0016] The rare earth sintered magnet disclosed herein produces the following effect: it can improve coercivity without reducing the residual magnetic flux density and magnetization performance compared with the past. Attached Figure Description

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

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

[0019] Figure 3 To represent tetragonal Nd2Fe 14 A diagram of atomic sites in the B crystal structure.

[0020] Figure 4 This is a flowchart illustrating an example of the steps in a method for manufacturing a rare-earth sintered magnet alloy according to Embodiment 3.

[0021] Figure 5 This is a flowchart illustrating an example of the steps in a method for manufacturing a rare-earth sintered magnet according to Embodiment 3.

[0022] Figure 6A cross-sectional view is shown schematically to illustrate an example of the configuration of a rotor equipped with rare earth sintered magnets according to Embodiment 4.

[0023] Figure 7 A cross-sectional view schematically showing an example of the configuration of the rotating machine according to Embodiment 5.

[0024] Figure 8 This image is a compositional image obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using a Field Emission-Electron Probe Micro Analyzer (FE-EPMA).

[0025] Figure 9 The elemental surface scan of Nd obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0026] Figure 10 The elemental surface scan of Pr obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0027] Figure 11 The elemental surface scan of Tb obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0028] Figure 12 The elemental surface scan of Co obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0029] Figure 13 The elemental surface scan of O (oxygen) obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0030] Figure 14 The elemental surface scan of Sm (samarium) obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis.

[0031] Figure 15 The elemental surface scan of La (lanthanum) obtained by analyzing the cross-section of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA analysis. Detailed Implementation

[0032] The following description, based on the accompanying drawings, details the rare earth sintered magnets, the manufacturing method of the rare earth sintered magnets, the rotors, and the rotating machines involved in the embodiments of this disclosure.

[0033] Implementation method 1.

[0034] Figure 1This diagram schematically illustrates an example of the structure of a rare-earth sintered magnet according to Embodiment 1, showing its sintering state. The rare-earth sintered magnet 1 according to Embodiment 1 has a structure satisfying the general formula (Nd, Pr, RH, R)-Fe-BM, containing Nd2Fe... 14 B has a crystal structure consisting of a main phase 10 with basic grains and a secondary phase 20 existing between the main phase 10. The main phase 10 has a core and a shell covering the core. RH is a heavy rare earth element, in one example selected from Dy, Tb, Gd (gadolinium), and Ho (holmium). Preferably, RH is a heavy rare earth element containing at least one of Dy and Tb. R is a rare earth element selected from Nd, Pr, and RH. M is an element selected from the group consisting of Ga, Al, Cu, and Co. The shell has a different composition from the core and is arranged to cover the core.

[0035] Specifically, according to Embodiment 1, the rare earth sintered magnet 1, that is, the rare earth sintered magnet 1 comprising a main phase 10 and a secondary phase 20, if RH is selected from one or more heavy rare earth elements chosen from Dy, Tb, Gd, and Ho, R is a rare earth element other than Nd, Pr, and RH, and M is selected from one or more elements chosen from Ga, Al, Cu, and Co, then the general formula is derived from (Nd... a Pr b R c RH d Fe e B f M g Let a, b, c, d, e, f, and g preferably satisfy the following relation.

[0036] 5≤a+b≤20

[0037] 0 < c + d < (a + b)

[0038] 0 < d < 10

[0039] 70≤e≤90

[0040] 0.5≤f≤10

[0041] 0≤g≤5

[0042] a+b+c+d+e+f+g=100 atoms%

[0043] The main phase 10 has a tetragonal R2Fe structure in which a portion of the Nd sites are replaced by Pr, a heavy rare earth element RH, and one or more rare earth elements R selected from Nd, Pr, and heavy rare earth elements RH. 14 B crystal structure. That is, the main phase 10 has (Nd, Pr, RH, R)2Fe. 14The composition formula of B. Element M can enter the main phase 10. When element M is a transition element, i.e., Co or Cu, it is assumed that element M will enter Nd₂Fe. 14 Part of the Fe sites in the B crystal structure are replaced.

[0044] In the rare earth sintered magnet 1 according to Embodiment 1, when the Nd concentration of the core portions 11c and 12c is set to CNd and the Pr concentration of the core portions 11c and 12c is set to CPr, the main phase 10 has a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr, and the first main phase 11 and the second main phase 12 are mixed. Furthermore, the concentration of heavy rare earth element RH in the core portion 11c of the first main phase 11 is higher than the concentration of heavy rare earth element RH in the core portion 12c of the second main phase 12. That is, if the concentration of heavy rare earth element RH in the core portion 11c of the first main phase 11 is set to C1RH and the concentration of heavy rare earth element RH in the core portion 12c of the second main phase 12 is set to C2RH, then C1RH > C2RH. The first main phase 11 has a core portion 11c and a shell portion 11s that has a different composition from the core portion 11c and covers the core portion 11c. The second main phase 12 has a core portion 12c and a shell portion 12s that has a different composition from the core portion 12c and covers the core portion 12c.

[0045] Alternatively, in the rare earth sintered magnet 1 according to Embodiment 1, when the sum of the Nd concentration of the core 11c and 12c and the concentration of the heavy rare earth element RH is set as C(Nd,RH), it can also be said that the main phase 10 has a first main phase 11 with C(Nd,RH) > CPr and a second main phase 12 with C(Nd,RH) < CPr, and the first main phase 11 and the second main phase 12 are mixed.

[0046] That is, the rare-earth sintered magnet 1 contains two main phases 10: a first main phase 11 and a second main phase 12. Focusing on the cores 11c and 12c of these two main phases 10, it means that in the first main phase 11, the sum of the concentrations of Nd and the heavy rare-earth element RH is higher than the concentration of Pr. Conversely, in the second main phase 12, the concentration of Pr is higher than the sum of the concentrations of Nd and the heavy rare-earth element RH. By mixing the two main phases 10 with core-shell structures and anisotropic magnetic fields (i.e., magnetic anisotropy), and selectively containing the heavy rare-earth element RH within the main phases 10, it is possible to reduce Nd and the heavy rare-earth element RH, thereby increasing remanent flux density and coercivity while maintaining good magnetization. Furthermore, by adding the heavy rare-earth element RH and element M, the coercivity is significantly improved, thus also helping to suppress the reduction in magnetic properties associated with temperature changes.

[0047] The concentration difference indicated by "C1RH > C2RH" signifies a clear difference in the detection intensity of heavy rare earth element RH in the core 11c of the first main phase 11 and the core 12c of the second main phase 12, achieved through area scan analysis using an Electron Probe Micro Analyzer (EPMA). Specifically, for the concentration of heavy rare earth element RH in the core 11c of the first main phase 11, the EPMA detection intensity is higher than the average detection intensity of heavy rare earth element RH. For the concentration of heavy rare earth element RH in the core 12c of the second main phase 12, the EPMA detection intensity represents the lower limit of the detection intensity of heavy rare earth element RH, or the EPMA detection intensity is lower than the average detection intensity of heavy rare earth element RH. In one example, heavy rare earth element RH is present in the core 11c of the first main phase 11 but almost entirely absent in the core 12c of the second main phase 12.

[0048] Furthermore, the concentration difference shown in "first principal phase 11 with C(Nd, RH) > CPr and second principal phase 12 with C(Nd, RH) < CPr" indicates a clear difference between the detection intensity of Nd and heavy rare earth element RH and the detection intensity of Pr, achieved through area scan analysis using EPMA. Specifically, taking the case of first principal phase 11 as an example, for the concentrations of Nd and heavy rare earth element RH in the core 11c, the detection intensity of EPMA is higher than the average detection intensity of Nd and heavy rare earth element RH. For the concentration of Pr, the detection intensity of EPMA indicates the lower limit of the detection intensity of Pr, or the detection intensity of EPMA is lower than the average detection intensity of Pr. The second principal phase 12 can be said to be the opposite of the case of first principal phase 11.

[0049] Furthermore, according to Embodiment 1, when the concentration of Nd in the core 11c of the first main phase 11 is set to C1Nd, the concentration of Nd in the core 12c of the second main phase 12 is set to C2Nd, the concentration of Pr in the core 11c of the first main phase 11 is set to C1Pr, and the concentration of Pr in the core 12c of the second main phase 12 is set to C2Pr, the relationship C1Nd > C2Nd and C1Pr < C2Pr is satisfied. That is, for the Nd concentration, the core 11c of the first main phase 11 is higher than that of the core 12c of the second main phase 12, and conversely, for the Pr concentration, the core 12c of the second main phase 12 is higher than that of the core 11c of the first main phase 11. This concentration difference also means a difference in the detection intensity of Nd and Pr according to the surface scan analysis using EPMA described above. Specifically, at a certain Nd concentration, this means that the average detection intensity of EPMA of Nd in the core 11c of the first main phase 11 is higher than the average detection intensity of Nd, while the average detection intensity of EPMA of Nd in the core 12c of the second main phase 12 is lower than the average detection intensity of Nd. At a certain Pr concentration, this means that the average detection intensity of EPMA of Pr in the core 12c of the second main phase 12 is higher than the average detection intensity of Pr, while the average detection intensity of EPMA of Pr in the core 11c of the first main phase 11 is lower than the average detection intensity of Pr. That is, the core 12c of the second main phase 12, where the Nd concentration is low, contains a large amount of Pr, while the core 11c of the first main phase 11, where the Pr concentration is low, contains a large amount of Nd. By controlling this microstructure, a rare-earth sintered magnet 1 with excellent magnetic properties can be obtained.

[0050] Furthermore, in the rare earth sintered magnet 1 according to Embodiment 1, a first main phase 11 with C(Nd,RH) > CPr exists in large quantities compared to a second main phase 12 with C(Nd,RH) < CPr. In other words, this means that a (Nd,RH)₂Fe₂O₃ phase is present. 14 The first principal phase 11 of the composition of B has a ratio of Pr2Fe 14 The composition of B has a large number of second principal phases 12. This is because the addition of (Nd,RH)2Fe 14 The first principal phase 11 of the composition of B is increased with Pr2Fe 14 Compared to the second principal phase 12 of the B composition, superior magnetic and temperature properties are obtained. Furthermore, by controlling the microstructure to this extent, overall grain refinement is also suppressed, thus ensuring magnetization and achieving magnetic properties superior to those of the past.

[0051] Furthermore, in the rare earth sintered magnet 1 according to Embodiment 1, focusing on the shell portions 11s and 12s of the core-shell structure, when the Nd concentration in the shell portions 11s and 12s is set to SNd, the Pr concentration in the shell portions 11s and 12s is set to SPr, the heavy rare earth element RH concentration in the core portions 11c and 12c is set to CRH, and the heavy rare earth element RH concentration in the shell portions 11s and 12s is set to SRH, the first main phase 11 satisfies the relationship CNd > SNd, CPr < SPr, CRH > SRH, and the second main phase 12 satisfies the relationship CNd < SNd, CPr > SPr, CRH < SRH. Specifically, instead of the shell portion 11s having a lower Nd concentration and a lower heavy rare earth element RH concentration than the core portion 11c, the Pr concentration is higher in the shell portion 11s than in the core portion 11c. In addition, the concentration of Pr in the shell 12s, which replaces the second main phase 12, is lower than that in the core 12c, while the concentrations of Nd and heavy rare earth element RH are higher than those in the core 12c.

[0052] Alternatively, 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 Nd concentration and the heavy rare earth element RH concentration in the shell portions 11s and 12s is set as S(Nd,RH), and the Pr concentration in the shell portions 11s and 12s is set as SPr, the first main phase 11 satisfies the relationship C(Nd,RH) > S(Nd,RH) and CPr < SPr, and the second main phase 12 satisfies the relationship C(Nd,RH) < S(Nd,RH) and CPr > SPr. Specifically, instead of the sum of the Nd concentration and the heavy rare earth element RH concentration in the shell portion 11s of the first main phase 11 being smaller than that in the core portion 11c, the Pr concentration is higher than that in the core portion 11c. Similarly, instead of the sum of the Pr concentration in the shell portion 12s of the second main phase 12 being smaller than that in the core portion 12c, the Nd concentration and the heavy rare earth element RH concentration are higher than those in the core portion 12c.

[0053] By forming a main phase 10 with a high concentration of Pr in the shell portion 11s, as in the first main phase 11, coercivity can be improved. Furthermore, by forming a main phase 10 with a high sum of Nd and heavy rare earth element RH concentrations in the shell portion 12s, as in the second main phase 12, coercivity can be maintained while suppressing the decrease in remanent flux density. By selectively controlling the microstructure in this way, the rare earth sintered magnet 1 can exhibit superior magnetic properties compared to the past.

[0054] Furthermore, it is preferable that the average grain size of the main phase 10 is 100 μm or less, and more preferably 0.5 μm or more and 50 μm or less to improve magnetic properties. Furthermore, by setting it to about 1 μm or more and 10 μm or less, a grain size different from that of fine structures manufactured by heat processing is achieved, good magnetization performance is maintained, and rare earth sintered magnets 1 with superior magnetic properties compared to the past can be manufactured.

[0055] The secondary phase 20 comprises: a crystalline first secondary phase 21, whose main component is an oxide phase represented by (Nd, Pr, RH, R)-O containing element M as a trace element, and a crystalline second secondary phase 22, whose main component is an oxide phase represented by (Nd, Pr, RH, R)-O containing element M as a trace element. O represents oxygen. The crystalline secondary phase 20 is a collective term for the crystalline first secondary phase 21 and the crystalline second secondary phase 22. Here, (Nd, Pr, RH, R) means that a portion of Nd and Pr are replaced by the heavy rare earth element RH and the rare earth element R other than Nd and Pr. The R in the first secondary phase 21 and the R in the second secondary phase 22 can be the same rare earth element, a portion of different rare earth elements, or different rare earth elements. Furthermore, since the main component element is listed in parentheses, the first secondary phase 21 and the second secondary phase 22 may contain trace amounts of other components besides the elements shown in parentheses.

[0056] Subphase 20, namely the first subphase 21 and the second subphase 22, as described above, contains element M as a trace component. The concentration of element M in the first subphase 21 and the second subphase 22 is higher in the second subphase 22 than in the first subphase 21. That is, when the concentration of element M in the first subphase 21 is set as Cs1M and the concentration of element M in the second subphase 22 is set as Cs2M, the relationship Cs1M < Cs2M is satisfied.

[0057] The statement that "the concentration of element M is higher in the second subphase 22 than in the first subphase 21" means that, using EPMA area scan analysis, the average detection intensity of element M in the second subphase 22 is higher than that in the first subphase 21. More specifically, it means that the average intensity of element M detected by EPMA in the second subphase 22 is higher than the average intensity of element M detected by EPMA, while the average intensity of element M detected by EPMA in the first subphase 21 is lower than the average intensity of element M detected by EPMA.

[0058] Furthermore, in the secondary phase 20, element M exists at a high concentration in the second secondary phase 22, thus forming a non-magnetic phase that magnetically divides the main phases 10, contributing to the improvement of magnetic properties. That is, by adjusting the concentration of element M, the second secondary phase 22 is higher than that of the first secondary phase 21, thereby obtaining high magnetic properties, especially coercivity, and suppressing the decrease in magnetic properties associated with temperature increases.

[0059] According to Embodiment 1, the rare earth sintered magnet 1 has the following characteristics: when RH is a heavy rare earth element, R is selected from one or more rare earth elements other than Nd, Pr, and heavy rare earth element RH, and M is selected from one or more elements of Ga, Al, Cu, and Co, it satisfies the general formula (Nd, Pr, RH, R)-Fe-BM, and includes Nd2Fe. 14 B has a main phase 10 with a basic crystal structure and a secondary phase 20 existing between the main phases 10 and 10. The main phase 10 has cores 11c and 12c and shells 11s and 12s covering the cores 11c and 12c. In addition, the main phase 10 has a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr. The concentration of heavy rare earth element RH in the first main phase 11 is higher than that in the second main phase 12. The first main phase 11 and the second main phase 12 are mixed. The secondary phase 20 has a first secondary phase 21 and a second secondary phase 22 with crystalline oxide phases (Nd, Pr, RH, R)-O containing element M as trace elements as the main components. The concentration of element M contained in the first secondary phase 21 and the second secondary phase 22 is higher in the second secondary phase than in the first secondary phase 21. By employing this configuration, rare-earth sintered magnets 1 with improved magnetic properties and magnetization compared to previous methods can be obtained while suppressing the use of Nd and heavy rare-earth element RH. In particular, it is possible to suppress the significant decrease in remanent magnetic flux density and significantly improve coercivity, thereby obtaining rare-earth sintered magnets 1 with improved temperature coefficient of magnetic properties.

[0060] A comparison is made between the RTB-based sintered magnet described in Patent Document 1 and the rare-earth sintered magnet 1 according to Embodiment 1. The RTB-based sintered magnet described in Patent Document 1 contains one or more rare-earth elements, with RH being an essential heavy rare-earth element, and has a main phase particle consisting of a core and a shell. That is, in Patent Document 1, all the main phase particles in the RTB-based sintered magnet contain the heavy rare-earth element RH. 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 second main phase 12 has a lower concentration of the heavy rare-earth element RH than the first main phase 11. In one example, the core 11c of the first main phase 11 contains the heavy rare-earth element RH, but the core 12c of the second main phase 12 contains almost no heavy rare-earth element RH. That is, the heavy rare-earth element RH is selectively distributed within the main phase 10. Thus, compared to the RTB-based sintered magnet described in Patent Document 1, which requires all of the main phase to contain the heavy rare earth element RH, the rare earth sintered magnet 1 according to Embodiment 1, which includes a main phase 10 having a first main phase 11 and a second main phase 12 having a lower concentration of heavy rare earth element RH compared to the first main phase 11, can suppress 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, selectively configuring the heavy rare earth element RH can suppress the amount of heavy rare earth element RH used compared to the RTB-based sintered magnet described in Patent Document 1.

[0061] A rare-earth magnet manufactured using the technology described in Patent Document 2 is compared with the rare-earth sintered magnet 1 according to Embodiment 1. When it is necessary to obtain the same magnetic properties as the rare-earth sintered magnet 1 according to Embodiment 1 using the rare-earth magnet manufactured using the technology described in Patent Document 2, as shown in the embodiments 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, when obtaining the same magnetic properties, the rare-earth sintered magnet 1 according to Embodiment 1 can suppress the amount of heavy rare-earth element RH used compared to the technology described in Patent Document 2. Alternatively, when the content of heavy rare-earth element RH in the rare-earth magnet manufactured using the technology described in Patent Document 2 is the same as the content of heavy rare-earth element RH in the rare-earth sintered magnet 1 according to Embodiments 1 and 2, the magnetic properties of the rare-earth magnet manufactured using the technology described in Patent Document 2 are lower than the magnetic properties of the rare-earth sintered magnet 1 according to Embodiments 1 and 2.

[0062] In the rare-earth sintered magnet 1 according to Embodiment 1, the first principal phase 11 and the second principal phase 12 are made to satisfy the relationship C1Nd > C2Nd and C1Pr < C2Pr. Alternatively, the number of the first principal phase 11 is greater than the number of the second principal phase 12. Alternatively, the first principal phase 11 is made to satisfy the relationship CNd > SNd, CPr < SPr, and CRH > SRH, and the second principal phase 12 is made to satisfy the relationship CNd < SNd, CPr > SPr, and CRH < SRH. Thus, a rare-earth sintered magnet 1 with improved magnetic properties and magnetization can be obtained while suppressing the use of Nd and the heavy rare-earth element RH.

[0063] Furthermore, by including the heavy rare earth element RH in the main phase 10 and primarily including element M in the secondary phase 22, a rare earth sintered magnet 1 with significantly improved coercivity compared to the past is obtained. Additionally, as shown in the embodiments described later, a rare earth sintered magnet 1 with a better temperature coefficient of coercivity compared to the past is obtained. Therefore, even when subjected to a heat load, the coercivity of the rare earth sintered magnet 1 increases compared to the past, and the decrease in coercivity associated with temperature increases becomes more moderate compared to the past. In other words, the coercivity is significantly improved compared to the past rare earth sintered magnets, and therefore the magnetic properties of the rare earth sintered magnet 1 under heat load are also better than before.

[0064] Implementation method 2.

[0065] In Embodiment 2, the case where La and Sm are selected for the rare earth element R in the rare earth sintered magnet 1 according to Embodiment 1 is shown.

[0066] Figure 2 This figure schematically illustrates an example of the structure of the rare-earth sintered magnet in the sintering state according to Embodiment 2. It should be noted that the same reference numerals are used for the same constituent elements as in Embodiment 1, and their descriptions are omitted. The rare-earth sintered magnet 1 according to Embodiment 2 has a primary phase 10 and a secondary phase 20. The primary phase 10, as described in Embodiment 1, includes a first primary phase 11 and a second primary phase 12. The secondary phase 20, as described in Embodiment 1, includes a first secondary phase 21 and a second secondary phase 22.

[0067] When the rare earth element R is selected as La or Sm, the effect of improving magnetic properties and exhibiting superior magnetization compared to the past becomes even greater while suppressing the use of Nd and the heavy rare earth element RH. In this example, the main phase 10 has (Nd, Pr, RH, La, Sm)2Fe. 14 The composition of B. This gives R2Fe a tetragonal crystal. 14The reason for using rare earth elements R, which are La and Sm, in the rare earth sintered magnet 1 with a B-crystal structure is that, based on calculations of magnetic interaction energy using the molecular orbital method, by adding La and Sm to the composition, a practical rare earth sintered magnet 1 can be obtained that can significantly suppress the decrease in magnetic properties associated with temperature rise. Furthermore, by intentionally causing La and Sm to segregate at grain boundaries, which is an example of the secondary phase 20, Nd and Pr can be relatively diffused in the main phase 10, thereby improving the crystal magnetic anisotropy of the main phase 10. Thus, a core-shell structure with both high and low magnetic anisotropy regions is formed within the main phase 10, resulting in a rare earth sintered magnet 1 in which a first main phase 11 (CNd > CPr) and a second main phase 12 (CNd < CPr) are mixed, and the concentration of heavy rare earth element RH in the core 11c of the first main phase 11 is higher than the concentration of heavy rare earth element RH in the core 12c of the second main phase 12.

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

[0069] In the rare-earth sintered magnet 1 according to Embodiment 2, when R = La and Sm is set, the secondary phase 20 has: a crystalline first secondary phase 21 with an oxide phase of (Nd, Pr, RH, La, Sm)-O containing element M as a trace component as the main component; and a crystalline second secondary phase 22 with an oxide phase of (Nd, Pr, RH, La)-O containing element M as a trace component as the main component. Thus, the first secondary phase 21 has a higher Sm concentration in the secondary phase 20 compared to the second secondary phase 22. That is, in the secondary phase 20 of the rare-earth sintered magnet 1, the first secondary phase 21 forms an Sm-enriched portion with a higher Sm concentration than the second secondary phase 22. This achieves the effect of suppressing not only the magnetic properties at room temperature but also the reduction in magnetic properties associated with temperature increases.

[0070] Furthermore, within the first subphase 21, there are sometimes regions with high Sm concentrations, i.e., high-concentration regions 41, and regions with low Sm concentrations, i.e., low-concentration regions 42. In such cases, element M sometimes enters in the low-concentration regions 42, where the Sm concentration in the first subphase 21 is lower than the surrounding area. In this situation, the concentration of element M in the low-concentration regions 42 becomes higher than the concentration of element M in the high-concentration regions 41.

[0071] As described in Embodiment 1, the concentration of element M in the second subphase 22 is higher than that in the first subphase 21. Thus, Sm and element M segregate in different subphases 20. Sm exists at a high concentration in the first subphase 21, thereby causing Nd to diffuse relatively in the main phase 10, increasing the crystal magnetic anisotropy of the main phase 10. Furthermore, Sm also exists within the grains of the main phase 10, thus binding in the same magnetization direction as the strongly magnetic material, Fe, contributing to the increase in remanent magnetic flux density. Element M exists at a high concentration in the second subphase 22, thus forming a non-magnetic phase that magnetically separates the main phases 10, contributing to the improvement of magnetic properties. By having Sm and element M exist at high concentrations in different subphases 20, both remanent magnetic flux density and coercivity can be improved.

[0072] The statement that "the concentration of Sm in the first subphase 21 is higher than that in the second subphase 22" means that, using EPMA area scan analysis, the average detection intensity of Sm in the first subphase 21 is higher than that in the second subphase 22. More specifically, the average Sm intensity detected by EPMA in the first subphase 21 is higher than the average Sm intensity detected by EPMA, while the average Sm intensity detected by EPMA in the second subphase 22 is lower than the average Sm intensity detected by EPMA.

[0073] The crystalline secondary phase 20 is a collective term for the crystalline first secondary phase 21 and the crystalline second secondary phase 22, existing between the main phase 10. The crystalline first secondary phase 21 is represented by (Nd, Pr, RH, La, Sm)-O, containing element M as a trace component, and the crystalline second secondary phase 22 is represented by (Nd, Pr, RH, La)-O, containing element M as a trace component. Here, (Nd, Pr, RH, La, Sm) means that a portion of Nd and Pr is replaced by the heavy rare earth elements RH, La, and Sm. Furthermore, since the main component elements are listed in parentheses, the first secondary phase 21 and the second secondary phase 22 may also contain trace amounts of other components besides those shown in parentheses. In one example, the second secondary phase 22, represented by (Nd, Pr, RH, La)-O, containing element M as a trace component, contains trace amounts of Sm.

[0074] In the rare earth sintered magnet 1 according to Embodiment 2, there is a concentration difference between La and Sm in the main phase 10 and the secondary phase 20, and La and Sm are segregated in the secondary phase 20 compared to the main phase 10. That is, the sum of the La concentrations in the first secondary phase 21 and the second secondary phase 22 is greater than or equal to the La concentration in the main phase 10, and the sum of the Sm concentrations in the first secondary phase 21 and the second secondary phase 22 is greater than or equal to the Sm concentration in the main phase 10. Specifically, the La and Sm concentrations in the secondary phase 20 are greater than or equal to the La and Sm concentrations in the main phase 10. Here, the La concentration in the main phase 10 is the sum of the La concentration in the first main phase 11 and the La concentration in the second main phase 12. That is, the sum of the La concentrations in the first secondary phase 21 and the second secondary phase 22 is higher than the sum of the La concentrations in the first main phase 11 and the second main phase 12. In addition, the Sm concentration in the main phase 10 is the sum of the Sm concentrations in the first main phase 11 and the Sm concentration in the second main phase 12. That is, the sum of the concentrations of Sm in the first secondary phase 21 and the second secondary phase 22 is higher than the sum of the concentrations of Sm in the first primary phase 11 and the second primary phase 12.

[0075] Here, when the concentration of La contained in the main phase 10 is set as X, the concentration of La contained in the first subphase 21 is set as X1, the concentration of La contained in the second subphase 22 is set as X2, the concentration of Sm contained in the main phase 10 is set as Y, the concentration of Sm contained in the first subphase 21 is set as Y1, and the concentration of Sm contained in the second subphase 22 is set as Y2, the following relationship (1) is satisfied.

[0076] 1<(Y1+Y2) / Y<(X1+X2) / X (1)

[0077] Furthermore, from the perspective of improving magnetic properties, the concentrations of Nd and Pr contained in the main phase 10 satisfy the following relationships (2) and (3).

[0078] (CNd+SNd)>(X+Y) (2)

[0079] (CPr+SPr)>(X+Y) (3)

[0080] It should be noted that, as described above, the La concentration in the main phase 10 is the sum of the La concentrations in the first main phase 11 and the second main phase 12, and the Sm concentration in the main phase 10 is the sum of the Sm concentrations in the first main phase 11 and the second main phase 12. This indicates that both La and Sm segregate in the secondary phase 20 relative to the main phase 10. However, under localized observation, the sum of the individual concentrations of La and Sm in the first main phase 11 and the second main phase 12 may not always satisfy the aforementioned relationship with the sum of the individual concentrations of La and Sm in the first secondary phase 21 and the second secondary phase 22. Therefore, more specifically, the La concentration in the main phase 10 represents the average of the La concentrations in the first main phase 11 and the second main phase 12, and the Sm concentration in the main phase 10 represents the average of the Sm concentrations in the first main phase 11 and the second main phase 12. In this case, the concentration of La in the secondary phase 20, that is, the sum of the concentrations of La in the first secondary phase 21 and the second secondary phase 22, means the average concentration of La in the first secondary phase 21 and the second secondary phase 22, and the concentration of Sm in the secondary phase 20, that is, the sum of the concentrations of Sm in the first secondary phase 21 and the second secondary phase 22, means the average concentration of Sm in the first secondary phase 21 and the second secondary phase 22.

[0081] La exists at a high concentration at grain boundaries during manufacturing processes, particularly heat treatment, thereby relatively causing Nd and Pr to diffuse in the main phase 10. As a result, Nd and Pr in the main phase 10 of the rare-earth sintered magnet 1 in Embodiment 2 are not consumed at grain boundaries, and the crystal magnetic anisotropy is improved. Sm also exists at a high concentration in the secondary phase 20, especially the first secondary phase 21, compared to the main phase 10, thus, similarly with La, relatively causing Nd to diffuse in the main phase 10, improving the crystal magnetic anisotropy.

[0082] As described above, subphase 20 contains heavy rare earth element RH, therefore both the first subphase 21 and the second subphase 22 contain heavy rare earth element RH. However, in subphase 20, the concentration of heavy rare earth element RH in the first subphase 21 is higher than that in the second subphase 22. Furthermore, the first subphase 21 has a high-concentration portion 41 where the concentration of Sm is higher than the surrounding area, and a low-concentration portion 42 where the concentration of Sm is lower than that in the high-concentration portion 41. In subphase 20 with these characteristics, the distribution of heavy rare earth element RH differs between the first subphase 21 and the second subphase 22. In the second subphase 22, where the concentration of Sm is lower than that in the first subphase 21, heavy rare earth element RH is uniformly distributed. On the other hand, in the first subphase 21, heavy rare earth element RH is not uniformly distributed, but rather selectively distributed between the outer periphery of the first subphase 21 and the high-concentration portion 41, that is, within the inner periphery of the outer periphery of the first subphase 21. The inner periphery of the outer periphery of the first subphase 21 corresponds to the low-concentration portion 42. Specifically, a low-concentration portion 42 exists in such a way that the outer contour of the high-concentration portion 41 of the first subphase 21, where the Sm concentration is high, is selectively surrounded, and the heavy rare earth element RH is present in the low-concentration portion 42. Thus, it can be said that the first subphase 21 has a high-concentration portion 41 with concentrated Sm and a low-concentration portion 42 containing the heavy rare earth element RH, which is selectively surrounded by the outer contour of the high-concentration portion 41. The outer contour of the first subphase 21 is the boundary between the first subphase 21 and the main phase 10.

[0083] Thus, between the main phase 10 and the main phase 10, there exist a first secondary phase 21 and a second secondary phase 22 containing the heavy rare earth element RH. Therefore, it can be considered that the heavy rare earth element RH enters a portion of the surface of the main phase 10 that is in contact with the first secondary phase 21 and the second secondary phase 22 containing the heavy rare earth element RH. That is, similar to Embodiment 1, in Embodiment 2, it is possible to increase the coercivity of the rare earth sintered magnet 1 while suppressing the decrease in remanent magnetic flux density.

[0084] Secondly, for La and Sm in tetragonal R2Fe 14 Please explain which atomic sites in the B crystal structure are substituted. Figure 3 To represent tetragonal Nd2Fe 14 A diagram of the atomic sites in the B crystal structure. Furthermore, Figure 3 The crystal structure shown is described in, in one example, in the following reference document 1. Figure 1 The stabilization energy produced by the substitution is determined by band structure calculations and the molecular field approximation of the Heisenberg model. The value of this energy is then used to make a judgment.

[0085] (Reference Technical Document 1) JF Herbst et al. "Relationships between crystal structure and magnetic properties in Nd2Fe 14 B. PHYSICAL REVIEW B. 1984, Vol. 29, No. 7, pp. 4176-4178.

[0086] First, the calculation method for the stabilization energy of La is explained. The stabilization energy of La can be calculated using Nd8Fe. 56 B4 unit cell, utilizing (Nd7La1)Fe 56 B4+Nd and Nd8(Fe) 55 The energy difference between La1)B4+Fe and Fe1) is calculated. The lower the energy value, the more stable the atomic site is when it is substituted. That is, La is more easily substituted at the atomic site where the energy becomes the lowest. In this calculation, considering the substitution of La with the original atoms, the tetragonal R2Fe is assumed to be... 14 The lattice constant in the B crystal structure does not change with different atomic radii. Table 1 shows the stabilization energy of La at each substitution site when the ambient temperature is changed.

[0087] [Table 1]

[0088]

[0089] According to Table 1, stable substitution sites for La are Nd(f) sites at temperatures above 1000 K and Fe(c) sites at temperatures of 293 K and 500 K. As described below, the raw material for the rare earth sintered magnet 1 according to Embodiment 2 is heated to a temperature above 1000 K and melted, then rapidly cooled. Therefore, it is considered that the raw material for the rare earth sintered magnet 1 is maintained at a temperature above 1000 K, i.e., above 727 °C, preferably around 1300 K, i.e., 1027 °C. At this time, it is considered that La is substituted at either Nd(f) or Nd(g) sites. Here, it is considered that La is preferentially substituted at energy-stable Nd(f) sites, but substitution at Nd(g) sites with small energy differences is also possible among the La substitution sites. Therefore, Nd(g) sites are also considered as candidate substitution sites for La.

[0090] Furthermore, when manufacturing the rare earth sintered magnet 1 using the manufacturing method described later, although the sintering temperature is above 1000K, the Fe(c) sites listed in Table 1 are repeatedly maintained in an energy-stable temperature range through the first aging process, the second aging process, the third aging process, the fourth aging process, and the cooling process described later. In other words, the La substitution at the Nd sites of the main phase 10 is maintained in an unstable energy state. That is, in the raw material stage of the rare earth sintered magnet 1, La mainly substitutes for the Nd sites of the main phase 10, but in the rare earth sintered magnet 1 manufactured using the manufacturing method described later, by repeatedly maintaining the rare earth sintered magnet 1 in an unstable energy state temperature range for the Nd sites of the main phase 10, a certain degree of La is selectively released from the Nd sites of the main phase 10, resulting in La segregation in the secondary phase 20. As a result, the main phase 10 promotes the formation of a core-shell structure.

[0091] Secondly, the calculation method for the stabilization energy of Sm is explained. The stabilization energy of Sm can be calculated using (Nd7Sm1)Fe 56 B4+Nd and Nd8(Fe) 55 The energy difference of Sm1)B4+Fe is obtained. For tetragonal R2Fe obtained by atomic substitution... 14 The lattice constant remains unchanged in the B crystal structure, which is the same as in the La case. Table 2 shows the stabilization energy of Sm at each substitution site when the ambient temperature is changed.

[0092] [Table 2]

[0093]

[0094] According to Table 2, the stable substitution sites of Sm differ from those of La; at any temperature, they are all Nd(g) sites. For Sm, it is also assumed that substitution preferentially occurs at energy-stable Nd(g) sites. Among the substitution sites of Sm, substitution at Nd(f) sites with small energy differences is also possible.

[0095] When the rare-earth sintered magnet 1 is manufactured using the method described later, the substitution at the Nd(g) sites of the main phase 10 is most stable in terms of energy. However, as mentioned above, by maintaining the temperature range in which the substitution of La at the Nd sites of the main phase 10 becomes unstable, a portion of Sm is also released from the Nd sites of the main phase 10 along with La and segregates in the secondary phase 20. As a result, there is a concentration difference between the main phase 10 and the secondary phase 20, where the sum of the La concentrations in the first secondary phase 21 and the second secondary phase 22 is greater than the La concentration in the main phase 10, and the sum of the Sm concentrations in the first secondary phase 21 and the second secondary phase 22 is greater than the Sm concentration in the main phase 10. More specifically, the average La concentration in the first secondary phase 21 and the second secondary phase 22 is greater than the average La concentration in the first main phase 11 and the second main phase 12, and the average Sm concentration in the first secondary phase 21 and the second secondary phase 22 is greater than the average Sm concentration in the first main phase 11 and the second main phase 12. That is, it can be said that La and Sm segregate in the secondary phase 20.

[0096] Comparing La and Sm, from an energy perspective, it is known that La, maintained within a temperature range of unstable energy states, tends to overwhelmingly segregate in the secondary phase 20. Therefore, in the case of a rare-earth sintered magnet 1 prepared with La and Sm concentrations at equal levels, the segregation ratio of La in the secondary phase 20 increases among the La and Sm present in the rare-earth sintered magnet 1. By maintaining the rare-earth sintered magnet 1 in this temperature range multiple times, a concentration difference of Sm with a smaller segregation ratio is generated in the secondary phase 20, forming a first secondary phase 21 and a second secondary phase 22. This promotes the formation of a core-shell structure in the main phase 10.

[0097] Here, as Figure 3 As shown, representative Nd is explained as follows. As represented by Di (ジジム; didymium; neodymium), Nd and Pr are produced in a mixture, therefore their energy levels are considered to be close. Thus, it can be said that this holds true even when Nd is replaced by Pr. By incorporating Nd and Pr, both present in rare-earth sintered magnets 1, it is possible to form a main phase 10 with two core-shell structures.

[0098] As described above, the rare earth sintered magnet 1 of Embodiment 2 has the following characteristics: RH is one or more heavy rare earth elements selected from Dy, Tb, Gd, and Ho; R is one or more rare earth elements other than Nd, Pr, and RH; and M is one or more elements selected from Ga, Al, Cu, and Co, satisfying the general formula (Nd, Pr, RH, R)-Fe-BM, and containing Nd2Fe. 14B has a main phase 10 with a basic crystal structure and a secondary phase 20 existing between the main phase 10. The main phase 10 has cores 11c and 12c and shells 11s and 12s covering the cores 11c and 12c. When R = La and Sm, the secondary phase 20 has a first crystalline secondary phase 21 with a main component being an oxide phase of (Nd, Pr, RH, La, Sm)-O containing element M as a trace element, and a second crystalline secondary phase 22 with a main component being an oxide phase of (Nd, Pr, RH, La)-O containing element M as a trace element. For the concentration of Sm, the first secondary phase 21 is higher than the second secondary phase 22, and for the concentration of element M, the second secondary phase 22 is higher than the first secondary phase 21. That is, in the rare-earth sintered magnet 1, two main phases 10 and two secondary phases 20 exist, such that the concentrations of Sm and element M in the secondary phases 20 are different. The first secondary phase 21 has a Sm-concentrated region, i.e., a high-concentration region 41, where Sm is selectively distributed. Because Sm exists at a high concentration in the first secondary phase 21, Nd diffuses relatively in the main phase 10, thereby increasing the crystal magnetic anisotropy of the main phase 10. Furthermore, since Sm also exists within the grains of the main phase 10, it binds in the same magnetization direction as Fe, which is a strongly magnetic material, thus contributing to the increase in remanent magnetic flux density. Element M exists at a high concentration in the second secondary phase 22, thus forming a non-magnetic phase that magnetically separates the main phases 10, contributing to the improvement of magnetic properties. Sm and element M exist at high concentrations in the different secondary phases 20, thereby enabling a balanced improvement in remanent magnetic flux density and coercivity. In this way, the rare-earth sintered magnet 1 can provide magnetic properties such as temperature characteristics that are superior to those of previous magnets.

[0099] Furthermore, by setting R to La and Sm, the main phase 10 becomes a mixture of a first main phase 11 with C(Nd, RH) > CPr and a second main phase 12 with C(Nd, RH) < CPr. In other words, the rare earth sintered magnet 1 contains two main phases 10 with the first main phase 11 and the second main phase 12. If we focus on the cores 11c and 12c of the two main phases 10, it is easy to produce a main phase 10 with two core-shell structures, where the concentration of Nd in the first main phase 11 is higher than the concentration of Pr, and conversely, the concentration of Pr in the second main phase 12 is higher than the concentration of Nd, and the concentration of heavy rare earth element RH in the first main phase 11 is higher than the concentration of heavy rare earth element RH in the second main phase 12. As a result, the rare earth sintered magnet 1 of Embodiment 2 can further improve the following effects: compared with the past, it suppresses the use of Nd and heavy rare earth element RH, while improving magnetic properties and having superior magnetization than before.

[0100] Implementation method 3.

[0101] In Embodiment 3, the method for manufacturing the rare earth sintered magnet 1 described in Embodiments 1 and 2 is divided into a method for manufacturing a rare earth sintered magnet alloy that serves as the raw material for the rare earth sintered magnet 1 and a method for manufacturing a rare earth sintered magnet 1 using a rare earth sintered magnet alloy.

[0102] Figure 4 This is a flowchart illustrating an example of the steps in a method for manufacturing a rare-earth sintered magnet alloy according to Embodiment 3. For example... Figure 4 As shown, the method for manufacturing a rare earth sintered magnet alloy, which serves as the raw material for the rare earth sintered magnet 1, includes: a melting process (step S1) in which the raw material of the rare earth sintered magnet alloy, containing elements constituting the rare earth sintered magnet 1, is heated to a temperature of 1000K or higher to melt it; a first cooling process (step S2) in which the molten raw material is cooled on a rotating body to obtain a solidified alloy; and a second cooling process (step S3) in which the solidified alloy is further cooled in a container. Thus, a rare earth sintered magnet alloy can be manufactured. Each step will be described below.

[0103] In the melting process of step S1, the raw material of the rare earth sintered magnet alloy is heated to a temperature of 1000 K or higher in a crucible to melt it in an atmosphere containing an inert gas such as Ar (argon). This prepares a molten alloy of rare earth sintered magnet alloy. As raw materials, Nd, Pr, RH, R, Fe, B, and M can be used. In the case of manufacturing the rare earth sintered magnet 1 of Embodiment 2, R is La and Sm. As RH, one or more elements, including Dy and Tb, can be listed. As M, one or more elements selected from Ga, Al, Cu, and Co can be listed. Furthermore, FeB can be used instead of B as a raw material.

[0104] Secondly, in the first cooling step of step S2, the molten alloy prepared in the melting step is poured into a tundish, and then poured onto a single roller, which serves as a rotating body. This rapidly cools the molten alloy on the single roller rotating in a predetermined direction, producing a solidified alloy with a thickness thinner than the ingot alloy. While a single roller is used as the rotating body, it is not limited to this; it can also contact a double roller, a rotating disk, a rotating cylindrical mold, etc., to rapidly cool the molten alloy. From the viewpoint of efficiently obtaining a thin solidified alloy, the cooling rate in the first cooling step is preferably 10°C / second or more. 7 Below ℃ / second, more preferably 10 3 ℃ / second or higher and 10 4 Below ℃ / second. The thickness of the solidified alloy is in the range of 0.03 mm to 10 mm. The alloy melt begins to solidify from the part in contact with the single roller, and crystals grow in columnar or needle-like shapes in the thickness direction from the contact surface with the single roller.

[0105] Then, in the second cooling step of step S3, the thin solidified alloy prepared in the first cooling step is placed in a tray container for cooling. When the thin solidified alloy is placed in the tray container, it is pulverized into flake-like rare earth sintered magnet alloy, which is then cooled. Depending on the cooling rate, sometimes a ribbon-like rare earth sintered magnet alloy is also obtained, and it is not limited to a flake-like form. From the viewpoint of obtaining a rare earth sintered magnet alloy with a microstructure exhibiting good temperature characteristics and magnetic properties, the cooling rate in the second cooling step is preferably 10. -2 ℃ / second or higher and 10 5 Below ℃ / second, more preferably 10 -1 ℃ / second or higher and 10 2 Below ℃ / second.

[0106] The rare earth sintered magnet alloy obtained through these processes has a short axis dimension of 3 μm or more and 10 μm or less, and a long axis dimension of 10 μm or more and 300 μm or less. In Embodiment 2, the rare earth sintered magnet alloy has a fine crystalline structure containing a (Nd, Pr, RH, La, Sm)-Fe-B crystalline phase containing element M as a trace component and a crystalline secondary phase 20 of oxides containing element M as a trace component (Nd, Pr, RH, La, Sm)-O. The (Nd, Pr, RH, La, Sm)-Fe-B crystalline phase containing element M as a trace component is also referred to as the (Nd, Pr, RH, La, Sm)-Fe-B crystalline phase, and the crystalline secondary phase 20 of oxides containing element M as a trace component (Nd, Pr, RH, La, Sm)-O is also referred to as the (Nd, Pr, RH, La, Sm)-O phase. The (Nd, Pr, RH, La, Sm)-O phase is a non-magnetic phase formed by oxides 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 boundaries, and is less than 10 μm. Rare earth sintered magnet alloys manufactured using the above process exhibit a finer microstructure compared to rare earth sintered magnet alloys obtained by mold casting due to the rapid cooling process.

[0107] Secondly, the manufacturing method of rare earth sintered magnet 1 using rare earth sintered magnet alloy will be described. Figure 5 This is a flowchart illustrating an example of the steps in a method for manufacturing a rare-earth sintered magnet according to Embodiment 3. For example... Figure 5As shown, the manufacturing method of the rare earth sintered magnet 1 includes: a pulverizing step (step S21) of pulverizing a rare earth sintered magnet alloy having (Nd, Pr, RH, La, Sm)-Fe-B crystal phase and (Nd, Pr, RH, La, Sm)-O phase; a molding step (step S22) of preparing a molded body by molding the pulverized rare earth sintered magnet alloy powder; a sintering step (step S23) of sintering the molded body at a specified temperature, i.e., a sintering temperature, to obtain a sintered body; an aging step (step S24) of aging the sintered body to improve the magnetic properties such as coercivity of the rare earth sintered magnet 1; and a cooling step (step S25) of cooling the aged sintered body. Each step will be described below.

[0108] In the crushing process of step S21, the powder will be crushed according to... Figure 4 The method for manufacturing rare earth sintered magnet alloys produces rare earth sintered magnet alloy powder having (Nd, Pr, RH, La, Sm)-Fe-B and (Nd, Pr, RH, La, Sm)-O phases. The powder is pulverized to obtain rare earth sintered magnet alloy powder with a particle size of 200 μm or less, preferably 0.5 μm or more and 100 μm or less, and approximately 1 μm or more and 10 μm or less, taking magnetization performance into consideration. In one example, the pulverization of the rare earth sintered magnet alloy is carried out using an agate mortar, a stamping machine, a clamp crusher, or a jet mill. In particular, when reducing the particle size of the powder, it is preferable to pulverize the rare earth sintered magnet alloy in an atmosphere containing an inert gas. By pulverizing the rare earth sintered magnet alloy in an atmosphere containing an inert gas, the incorporation of oxygen into the powder can be suppressed. However, if the atmosphere during pulverization does not affect the magnetic properties of the magnet, the pulverization of the rare earth sintered magnet alloy can be carried out in the atmosphere. It should be noted that, in the case of manufacturing the rare earth sintered magnet 1 of Embodiment 1, the La and Sm of the rare earth sintered magnet alloy used in manufacturing the rare earth sintered magnet 1 of Embodiment 2 can be made to be rare earth elements R other than Nd, Pr, and the heavy rare earth element RH. That is, it is sufficient to simply crush the rare earth sintered magnet alloy having the (Nd,Pr,RH,R)-Fe-B crystal phase and the (Nd,Pr,RH,R)-O phase.

[0109] In step S22, the rare earth sintered magnetic alloy powder is compressed and molded in a mold under an applied magnetic field to prepare a molded body. In one example, the applied magnetic field can be set to 2T. Alternatively, molding can be performed without an applied magnetic field.

[0110] In the sintering process of step S23, a sintered body is obtained by holding the compressed molded body at a sintering temperature within the range of 950°C to 1300°C, preferably 1000°C to 1150°C, for a time within the range of 0.1 hours to 10 hours, preferably 1.0 hour to 6.0 hours. To suppress oxidation, sintering is preferably performed in an atmosphere containing inert gases or in a vacuum. Sintering can be carried out while a magnetic field is applied.

[0111] The aging process in step S24 is Figure 5 In this case, the process includes a first aging step (S24-1), a second aging step (S24-2), a third aging step (S24-3), and a fourth aging step (S24-4). To suppress oxidation, aging is preferably performed in an atmosphere containing inert gases or in a vacuum.

[0112] In the first aging process of step S24-1, the obtained sintered body is kept at a temperature below the sintering temperature, i.e. the first aging temperature, specifically between 700°C and 950°C, for a period of 0.1 hours to 10 hours, preferably between 0.5 hours and 5 hours.

[0113] In the second aging process of step S24-2, after the first aging process, the sintered body held in the first aging process is held at a temperature less than the first aging temperature, i.e., the second aging temperature, specifically at a temperature of 450°C or higher but less than 700°C, for a period of 0.1 hours or more but less than 10 hours, preferably 1.0 hours or more but less than 7 hours.

[0114] In the third aging process of step S24-3, after the second aging process, the sintered body held in the second aging process is heated again to the first aging temperature, specifically a temperature in the range of 700°C or higher and less than 950°C, and held at the first aging temperature for 0.1 hours or more and 10 hours or less, preferably 0.5 hours or more and 5 hours or less.

[0115] In the fourth aging process of step S24-4, after the third aging process, the sintered body that was maintained in the third aging process is again maintained at the second aging temperature, specifically at a range of 450°C or higher and less than 700°C, for a range of 0.1 hours or more and 10 hours or less, preferably 1.0 hours or more and 7 hours or less.

[0116] Finally, in the cooling process of step S25, the sintered body held in the fourth aging process is held at a temperature lower than the second aging temperature, specifically between 200°C and 450°C, for 0.1 hours and 5 hours. Then, by cooling to room temperature, the rare earth sintered magnet 1 is completed. To suppress oxidation, cooling is preferably carried out in an atmosphere containing inactive gases or in a vacuum.

[0117] As described above, by controlling the temperature and time in the sintering, aging, and cooling processes, the sintered body is repeatedly held within a temperature range of unstable energy states. As a result, a first main phase 11 composed of CNd > CPr and a second main phase 12 composed of CNd < CPr can be mixed, making the concentration of heavy rare earth element RH in the first main phase 11 higher than the concentration of heavy rare earth element RH in the second main phase 12. In other words, two main phases 10, the first main phase 11 and the second main phase 12, exist in the rare earth sintered magnet 1. If the core portions 11c and 12c of the two main phases 10 are considered, a rare earth sintered magnet 1 with the following characteristics can be manufactured: the sum of the concentrations of Nd and heavy rare earth element RH in the first main phase 11 is higher than the concentration of Pr, and conversely, the concentration of Pr in the second main phase 12 is higher than the sum of the concentrations of Nd and heavy rare earth element RH.

[0118] Furthermore, it is possible to manufacture a rare earth sintered magnet 1, which, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, also has a crystalline first secondary phase 21 with an oxide phase of (Nd, Pr, RH, La, Sm)-O containing element M as a trace component as the main component, and a crystalline second secondary phase 22 with an oxide phase of (Nd, Pr, RH, La)-O containing element M as a trace component as the main component. For the concentration of Sm, the first secondary phase 21 is higher than the second secondary phase 22, and for the concentration of element M, the second secondary phase 22 is higher than the first secondary phase 21. That is, in the aging and cooling processes, a crystalline first subphase 21 with the oxide phase represented by (Nd, Pr, RH, La, Sm)-O as the main component and a crystalline second subphase 22 with the oxide phase represented by (Nd, Pr, RH, La)-O as the main component are generated from the (Nd, Pr, RH, La)-O phase, depending on the concentration of element M. Furthermore, the second subphase 22 may contain trace amounts of Sm. Additionally, the concentration of Sm in the first subphase 21 is higher than that in the second subphase 22; therefore, in the subphase 20, it can be said that the first subphase 21 forms an Sm-enriched section. Furthermore, in the first subphase 21, there may sometimes be a high-concentration section 41 with a high Sm concentration and a low-concentration section 42 with a low Sm concentration; therefore, in this case, it can also be said that the high-concentration section 41 of the first subphase 21 forms an Sm-enriched section.

[0119] Thus, a rare earth sintered magnet 1 is provided that can suppress the use of Nd and heavy rare earth element RH, while having superior magnetization performance and magnetic properties compared to the past.

[0120] In Embodiment 3, rare earth sintered magnet alloy powder containing (Nd, Pr, RH, La, Sm)-Fe-B and (Nd, Pr, RH, La, Sm)-O phases is pulverized, and the shaped body is sintered to form a sintered body. The sintered body is then subjected to aging treatment to manufacture the rare earth sintered magnet 1. Thus, a rare earth sintered magnet 1 having the structure described in Embodiment 2 can be manufactured. Furthermore, by adjusting the concentration of the heavy rare earth element RH to a desired level and manufacturing the rare earth sintered magnet alloy, the heavy rare earth element RH can easily penetrate into the interior of the main phase 10.

[0121] Furthermore, in Embodiment 3, the temperature and time in the sintering, aging, and cooling processes are controlled. In one example, in the first aging process, the resulting sintered body is held at a temperature below the sintering temperature, specifically at the first aging temperature, within a range of 700°C or higher but less than 950°C, for a period of 0.1 hours or more but less than 10 hours, preferably 0.5 hours or more but less than 5 hours. In the second aging process, the sintered body is held at a temperature below the first aging temperature, specifically at the second aging temperature, specifically at a range of 450°C or higher but less than 700°C, for a period of 0.1 hours or more but less than 10 hours, preferably 1.0 hour or more but less than 7 hours. In the third aging process, the temperature is raised again to the first aging temperature, specifically within a range of 700°C or higher but less than 950°C, and the sintered body is held at the first aging temperature for a period of 0.1 hours or more but less than 10 hours, preferably 0.5 hours or more but less than 5 hours. In the fourth aging process, the sintered body is again held at the second aging temperature, specifically between 450°C and 700°C, for 0.1 hours to 10 hours, preferably 1.0 hour to 7 hours. In this way, the temperature and time are controlled so that the first and second aging processes are performed in two sets. This results in the sintered body being held in a state of unstable energy multiple times within a temperature range. As a result, the first main phase 11, composed of CNd > CPr, and the second main phase 12, composed of CNd < CPr, can be mixed, and the concentration of heavy rare earth element RH in the first main phase 11 is higher than that in the second main phase 12. In other words, regarding the rare earth sintered magnet 1, there are two main phases 10: a first main phase 11 and a second main phase 12. If we focus on the cores 11c and 12c of the two main phases 10, we can selectively manufacture a rare earth sintered magnet 1 in which the sum of the concentrations of Nd and heavy rare earth element RH in the first main phase 11 is higher than the concentration of Pr, and conversely, the concentration of Pr in the second main phase 12 is higher than the sum of the concentrations of Nd and heavy rare earth element RH.

[0122] Furthermore, by employing the aforementioned manufacturing process, rare earth sintered magnets 1 can be selectively manufactured, possessing the following characteristic microstructure: a crystalline first secondary phase 21 with a main component being an oxide phase of (Nd, Pr, RH, La, Sm)-O containing trace element M, and a crystalline second secondary phase 22 with a main component being an oxide phase of (Nd, Pr, RH, La)-O containing trace element M. In terms of Sm concentration, the first secondary phase 21 is higher than the second secondary phase 22, and in terms of element M concentration, the second secondary phase 22 is higher than the first secondary phase 21. Additionally, in the secondary phase 20, the Sm concentration of the first secondary phase 21 is higher than that of the second secondary phase 22. Therefore, it is possible to manufacture rare earth sintered magnets 1 with the following characteristic microstructure: a first secondary phase 21 with an Sm-enriched portion, i.e., Sm-enriched. Alternatively, if the first subphase 21 contains a high-concentration portion 41 with a high concentration of Sm and a low-concentration portion 42 with a low concentration of Sm, it is possible to manufacture a rare earth sintered magnet 1 with the following characteristic microstructure: having a high-concentration portion 41 as an Sm enrichment portion.

[0123] Compared to the RTB-based sintered magnet described in Patent Document 1, the RTB-based sintered magnet described in Patent Document 1 has a main phase particle consisting of a core and a shell, which is composed of one or more rare earth elements, with RH being an essential heavy rare earth element. That is, in Patent Document 1, the heavy rare earth element RH is included in all the main phase particles. 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 containing the heavy rare earth element RH in the core 11c and a second main phase 12 containing almost no heavy rare earth element RH in the core 12c. That is, the heavy rare earth element RH is selectively disposed in the first main phase 11 of the two main phases 10. Thus, compared to the RTB-based sintered magnet described in Patent Document 1, which requires the heavy rare earth element RH to be included in all of only one main phase, the rare earth sintered magnet 1 according to Embodiment 1, which only requires the heavy rare earth element RH to be included in the first main phase 11 of the two main phases 10, can suppress the amount of heavy rare earth element RH used. Furthermore, the proportion of the volume of the secondary phase 20 in the total volume of the rare earth sintered magnet 1 is extremely small. Therefore, even if the heavy rare earth element RH is diffusely present in the secondary phase 20, the amount of heavy rare earth element RH used can be suppressed compared with the technology of Patent Document 1.

[0124] Furthermore, compared to the technology described in Patent Document 2, to obtain the same magnetic properties as the rare earth sintered magnet 1 according to Embodiment 1 using the method described in Patent Document 2, as will be described later, a large amount of heavy rare earth element RH must be added. That is, to obtain the same magnetic properties, the amount of heavy rare earth element RH used in the rare earth sintered magnet 1 according to Embodiment 1 can be suppressed compared to the technology described in Patent Document 2. Additionally, the method described in Patent Document 2 includes heat processing, but the manufacturing method of the rare earth sintered magnet 1 according to Embodiment 3 does not include heat processing. Therefore, by suppressing the reduction in the particle size of the main phase 10, the decrease in remanent magnetic flux density and magnetization can be suppressed compared to the rare earth magnet manufactured using the technology described in Patent Document 2.

[0125] Therefore, it is possible to suppress the use of heavy rare earth element RH compared to the past, and at the same time obtain rare earth sintered magnets with improved magnetic properties compared to the past.

[0126] Implementation method 4.

[0127] In Embodiment 4, a rotor using the rare earth sintered magnet 1 from Embodiment 1 or Embodiment 2 manufactured by the manufacturing method of Embodiment 3 will be described. Figure 6 A cross-sectional view schematically illustrating an example of the configuration of a rotor equipped with a rare-earth sintered magnet according to Embodiment 4. Figure 6 The image shows a cross-section in a direction perpendicular to the rotation axis RA of the rotor 100.

[0128] The rotor 100 is capable of rotating about the rotation axis RA. The rotor 100 includes a rotor core 101 and rare-earth sintered magnets 1 inserted into magnet insertion holes 102 disposed along the circumference of the rotor 100 in the rotor core 101. Figure 6 The diagram shows an example where four magnet insertion holes 102 are provided in the rotor core 101, and four rare earth sintered magnets 1 are inserted into the magnet insertion holes 102. The number of magnet insertion holes 102 and rare earth sintered magnets 1 can be changed according to the design of the rotor 100. The rotor core 101 is formed by stacking multiple disc-shaped electromagnetic steel plates in the axial direction of the rotation shaft RA.

[0129] The rare earth sintered magnet 1 is manufactured according to the manufacturing method described in Embodiment 3. Four rare earth sintered magnets 1 are respectively inserted into the corresponding magnet insertion holes 102. The magnetic poles of the four rare earth sintered magnets 1 on the radially outer side of the rotor 100 are each magnetized in a different manner with respect to the adjacent rare earth sintered magnets 1.

[0130] The rotor 100 according to Embodiment 4 includes a rare-earth sintered magnet 1 according to Embodiment 1 or Embodiment 2, which can achieve improved magnetic properties at room temperature and suppress the decrease in magnetic properties associated with temperature rise. As described above, the rare-earth sintered magnet 1 according to Embodiment 1 or Embodiment 2, in order to suppress the use of heavy rare-earth element RH compared to the past, can maintain high remanent magnetic flux density and coercivity while suppressing the decrease in magnetic properties associated with temperature rise, and therefore also suppresses the decrease in magnetic properties in high-temperature environments such as above 100°C. As a result, Nd and heavy rare-earth element RH, which are expensive, geographically inhomogeneous, and have procurement risks, can be replaced with inexpensive rare-earth elements, while improving magnetic properties and magnetization, and stabilizing the operation of the rotor 100 in high-temperature environments such as above 100°C. Furthermore, the rare-earth sintered magnet 1 according to Embodiment 1 or Embodiment 2 has superior magnetization performance compared to the conventional version, thus magnetization is possible when the rare-earth sintered magnet 1 is placed in the rotor 100 assembly state, thereby simplifying the manufacturing process. Furthermore, a magnetization process with suppressed voltage can be achieved, which also contributes to energy saving.

[0131] Implementation method 5.

[0132] In Embodiment 5, a rotating machine equipped with the rotor 100 from Embodiment 4 will be described. Figure 7 A cross-sectional view schematically showing an example of the configuration of the rotating machine according to Embodiment 5. Figure 7 The image shows a cross-section in a direction perpendicular to the rotation axis RA of the rotor 100.

[0133] The rotating machine 120 includes: a rotor 100, as described in Embodiment 4, capable of rotating around a rotation axis RA; and an annular stator 130, coaxially arranged with and opposite to the rotor 100. The stator 130 is formed by stacking multiple electromagnetic steel plates in the axial direction of the rotation axis RA. The configuration of the stator 130 is not limited to this, and existing configurations can also be used. The stator 130 has teeth 131 protruding toward the rotor 100 along its inner surface. The teeth 131 have windings 132. In one example, the winding method of the windings 132 can be concentrated winding or distributed winding. That is, the stator 130 has windings 132 on the inner surface of the side where the rotor 100 is arranged, which are provided in the teeth 131 protruding toward the rotor 100, and has an annular structure opposite to the rotor 100. The rotor 100 located in the rotating machine 120 has two or more magnetic poles; that is, the rare-earth sintered magnet 1 only needs to have two or more. Furthermore, in Figure 7 The example shown is a magnet-embedded rotor 100, which can also be a surface magnet rotor 100 in which rare earth sintered magnets 1 are fixed to the outer periphery with an adhesive.

[0134] The rotating machine 120 in Embodiment 5 includes a rare-earth sintered magnet 1 according to Embodiment 1 or Embodiment 2, which can achieve improved magnetic properties at room temperature and suppress the decrease in magnetic properties associated with temperature rise. As described above, the rare-earth sintered magnet 1 according to Embodiment 1 or Embodiment 2 is a rare-earth sintered magnet 1 that, compared with the conventional one, suppresses the use of heavy rare-earth element RH, and can suppress the decrease in magnetic properties associated with temperature rise while maintaining high remanent magnetic flux density and coercivity. Therefore, the decrease in magnetic properties is also suppressed in high-temperature environments exceeding 100°C. As a result, Nd and heavy rare-earth element RH, which are expensive, geographically inhomogeneous, and have procurement risks, can be replaced with inexpensive rare-earth elements, while improving magnetic properties and magnetization. The rotor 100 can be stably driven even in high-temperature environments exceeding 100°C, thus stabilizing the operation of the rotating machine 120.

[0135] Example

[0136] The following examples and comparative examples will be used to describe in detail the rare earth sintered magnet 1 of this disclosure.

[0137] In Examples 1 to 8, rare earth sintered magnets 1 were manufactured using samples of (Nd, Pr, Tb, La, Sm)-Fe-B crystal phases and (Nd, Pr, Tb, La, Sm)-O phases containing element M as trace elements, with different compositions of various rare earth sintered magnet alloys. The method described in Example 3 was used to manufacture rare earth sintered magnets 1. In Examples 1 to 8, rare earth sintered magnets 1 were manufactured using rare earth sintered magnet alloys with varying contents of Nd, Pr, Tb, La, and Sm. Specifically, in Examples 1 to 8, rare earth sintered magnets 1 were manufactured using rare earth sintered magnet alloys containing (Nd, Pr, Tb, La, Sm)-Fe-B crystal phases and (Nd, Pr, Tb, La, Sm)-O phases containing element M as trace elements, using the manufacturing method described in Example 3. M is one or more elements selected from Ga, Al, Cu, and Co, with the case where M is Co listed as an example.

[0138] In Comparative Examples 1 to 18, rare earth sintered magnets 1 were experimentally manufactured using samples of multiple rare earth sintered magnet alloys R-Fe-BM with different compositions, employing the general rare earth magnet manufacturing method shown in Patent Document 1 or Patent Document 2. In the samples of rare earth sintered magnets 1 according to Comparative Examples 1 to 18, the portion of R was modified.

[0139] In Comparative Examples 1 to 9, rare earth sintered magnets 1 were manufactured using the manufacturing method shown in Patent Document 1, with R being Nd or with R containing Nd and one or more elements selected from Pr, Tb, La, and Sm, and M containing one or more elements selected from Ga, Al, Cu, and Co. Here, the case where M is Co is cited as an example. However, in Comparative Example 2, (Nd, Tb)-Fe-B without element M was produced, and in Comparative Example 3, Nd-Fe-BM without rare earth elements R other than Nd was produced.

[0140] In Comparative Examples 10 to 18, rare earth sintered magnets 1 were manufactured using the manufacturing method shown in Patent Document 2, with R being Nd or with R containing Nd and one or more elements selected from Pr, Tb, La, and Sm, and M containing one or more elements selected from Ga, Al, Cu, and Co. Here, the case where M is Co is cited as an example. However, in Comparative Example 11, Nd-Fe-BM containing no rare earth element R other than Nd was manufactured, and in Comparative Example 12, Nd-Fe-B containing no rare earth element R other than Nd and element M was manufactured. The manufacturing method shown in Patent Document 2 includes a step of heat-processing the sintered body.

[0141] Table 3 shows the general formula, the content of elements constituting R, the analysis results of microstructure, and the determination results of magnetic properties and magnetization performance of rare earth sintered magnets according to the examples and comparative examples. In Table 3, the general formula of the main phase 10 of the rare earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 18 is shown.

[0142] [Table 3]

[0143]

[0144] Next, the method for analyzing the microstructure of the rare earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 18 will be described. The microstructure of the rare earth sintered magnets 1 was determined by elemental analysis using a scanning electron microscope (SEM) and EPMA. FE-EPMA (manufactured by Nippon Electronics Corporation, product name: JXA-8530F) was used for both SEM and EPMA. The accelerating voltage was 15.0 kV and the irradiation current was 2.271 eΩ. -008 A, the illumination time is 130ms, the number of pixels is 512 pixels × 512 pixels, the magnification is 5000 times, and the cumulative number of times is 1.

[0145] Next, the evaluation method for the magnetic properties of the rare-earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 18 will be described. The evaluation of magnetic properties was performed by measuring the coercivity of multiple samples using a pulse-excited BH-Tracer. The maximum applied magnetic field generated by the BH-Tracer was 6T or more, which resulted in the rare-earth sintered magnet 1 being fully magnetized. Besides the pulse-excited BH-Tracer, any device capable of generating a maximum applied magnetic field of 6T or more, such as a DC self-recording magnetometer (also called a DC-type BH-Tracer), a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), or a physical property measurement system (PPMS), can be used. Measurements were performed in an atmosphere containing inert gases such as nitrogen. The magnetic properties of each sample were measured by detecting the magnetization picked up from the rare-earth sintered magnet 1 magnetized with the applied magnetic field using a search coil or a magnetic sensor. The magnetic properties were determined from the measured hysteresis, i.e., the JH curve or BH curve. Furthermore, the magnetic properties of each sample were measured at various temperatures, specifically a first measurement temperature T1 and a second measurement temperature T2. The temperature coefficient α [% / ℃] of the remanent magnetic flux density was calculated by dividing the ratio of the difference between the remanent magnetic flux density at the first measurement temperature T1 and the remanent magnetic flux density at the second measurement temperature T2 to the remanent magnetic flux density at the first measurement temperature T1 by the temperature difference (T2-T1). Similarly, the temperature coefficient β [% / ℃] of the coercivity was calculated by dividing the ratio of the difference between the coercivity at the first measurement temperature T1 and the coercivity at the second measurement temperature T2 to the coercivity at the first measurement temperature T1 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 effectively the decrease in the magnetic properties of the magnet associated with increasing temperature is suppressed.

[0146] Furthermore, the magnetization performance is determined by calculating the magnetic susceptibility by the ratio of the magnetic flux density measured using hysteresis applied under a given magnetic permeability and the magnetic flux density measured using hysteresis applied under a saturated magnetic field. High magnetization performance can be considered achieved as long as a high magnetic susceptibility is obtained even in lower magnetic fields.

[0147] First, the analytical results of each sample according to Examples 1 to 8 and Comparative Examples 1 to 18 will be explained. Figure 8 This is a diagram showing the compositional images obtained by analyzing cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. Figures 9 to 15 The elemental surface scans are obtained by analyzing the cross-sections of rare earth sintered magnets according to Examples 1 to 8 using FE-EPMA. Figure 9 For Nd element face scan, Figure 10 For the element face scan of Pr, Figure 11 For the element face scan of Tb, Figure 12 For the elemental surface scan of Co, Figure 13 For element face scan of O, Figure 14 For the element face scan of Sm, Figure 15 This is a surface scan of the elements of La. Furthermore, Figures 9 to 15 To Figure 8 The area shown is an elemental surface scan map. Furthermore, the rare-earth sintered magnets 1 according to Examples 1 to 8 all show the same results, therefore... Figures 8 to 15 Representative embodiments from Examples 1 to 8 are shown below. Furthermore, regarding... Figure 1 and Figure 2 The same constituent elements are labeled with the same reference numerals in the accompanying drawings.

[0148] like Figures 9 to 11 As shown, it can be confirmed that in each sample of Examples 1 to 8, the rare earth sintered magnet 1, which contains Nd2Fe, has RH as Tb, R as one or more rare earth elements selected from Nd, Pr, and RH, and satisfies the general formula (Nd, Pr, Tb, R)-Fe-BM. 14 The B-type crystal structure is based on a main phase 10 with cores 11c and 12c and shells 11s and 12s covering the cores 11c and 12c. Furthermore, it can be confirmed that in the main phase 10, a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr are mixed. Additionally, when the concentration of Tb in the first main phase 11 is set to C1Tb and the concentration of Tb in the second main phase 12 is set to C2Tb, it can also be confirmed that C1Tb > C2Tb.

[0149] The concentration difference shown in "first principal phase 11 (CNd > CPr) and second principal phase 12 (CNd < CPr)" indicates a clear difference between the detection intensities of Nd and Pr using area scan analysis with EPMA. Specifically, in the case of first principal phase 11, it means that the EPMA detection intensity is higher than average for Nd concentration in the core 11c, and lower than average for Pr concentration, indicating a situation near the lower limit. Second principal phase 12 can be considered the opposite of the first principal phase 11.

[0150] More specifically, with Figure 9 Nd surface scan and Figure 10Taking the surface scan of Pr as an example, the average detection level of Nd in EPMA is 89, and the average 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, indicating a clear concentration difference. In contrast, in the second main phase 12, CPr is higher than 46, and CNd is near the lower limit, indicating a clear concentration difference.

[0151] Furthermore, the concentration difference expressed as "C1Tb > C2Tb" signifies 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, achieved through area scan analysis using EPMA. Specifically, this means that the detection intensity of EPMA is higher than average for the concentration of Tb in the first main phase 11, and lower than average for the concentration of Tb in the second main phase 12, indicating a position near the lower limit.

[0152] More specifically, with Figure 11 Taking the Tb area scan as an example, the average Tb detection level of EPMA is 44. In the case of the first main phase 11, CTb is higher than 44, and in the case of the second main phase 12, CTb is near the lower limit, which clearly shows that a concentration difference has been generated.

[0153] like Figures 12 to 15 As shown, when R = La and Sm, the rare earth sintered magnet 1, in addition to the first main phase 11 and the second main phase 12 in Embodiment 1, has a crystalline first secondary phase 21 mainly composed of an oxide phase represented as (Nd, Pr, Tb, La, Sm)-O containing element M as a trace component, and a crystalline second secondary phase 22 mainly composed of an oxide phase represented as (Nd, Pr, Tb, La)-O containing element M as a trace component. Furthermore, it can be confirmed that, in terms of the concentration of Sm, the first secondary phase 21 is higher than the second secondary phase 22, and in terms of the concentration of Co, which is element M, the second secondary phase 22 is higher than the first secondary phase 21.

[0154] In Table 3, if the sum of the Nd concentration and the heavy rare earth element RH (Tb) concentration is represented as C(Nd,RH), for samples where the state of the first main phase 11 (C(Nd,RH) > CPr) and the second main phase 12 (C(Nd,RH) < CPr) can be confirmed, "〇" is entered in the columns for the first main phase 11 and the second main phase 12, respectively. For samples where the state cannot be confirmed, "×" is entered in the columns for the first main phase 11 and the second main phase 12, respectively. A concentration difference with an inequality sign indicates a clear difference between the detection intensity of Nd and Tb and the detection intensity of Pr. For example, in the case of the first main phase 11, the detection intensity of EPMA is higher than average for Nd and Tb concentrations, and lower than average for Pr concentration, which is represented as near the lower limit. In the case of the second main phase 12, the situation is the opposite of the first main phase 11. In cases where only C(Nd,RH) < CPr is confirmed as in the second principal phase 12, "〇" is entered in the column for the second principal phase 12, and "×" is entered in the column for the first principal phase 11.

[0155] Furthermore, in Table 3, for samples that can be identified as having a first secondary phase 21 with crystallinity as the main component of an oxide phase represented by (Nd, Pr, Tb, La, Sm)-O containing element M as a trace component, and a second secondary phase 22 with crystallinity as the main component of an oxide phase represented by (Nd, Pr, Tb, La)-O containing element M as a trace component, and where the concentration of element M in the second secondary phase 22 is higher than that in the first secondary phase 21, "〇" is entered in the "M Concentration First Secondary Phase < Second Secondary Phase" column of the "Secondary Phase" section under the "Mitology" item. For samples that cannot be identified, "×" is entered in the "M Concentration First Secondary Phase < Second Secondary Phase" column of the "Secondary Phase" section under the "Mitology" item. Additionally, for samples where only one secondary phase 20 exists or where there is no Sm concentration difference between secondary phases 20, "×" is entered in the "M Concentration First Secondary Phase < Secondary Phase" column of the "Secondary Phase" section under the "Mitology" item.

[0156] Furthermore, the concentration difference of Sm between the first subphase 21 and the second subphase 22 indicates that, using area scan analysis with EPMA, the average detection intensity of Sm in the first subphase 21 is higher than that in the second subphase 22. Specifically, with Figure 14 Taking the surface scan of Sm as an example, the average detection level of Sm by EPMA is 15.0, while the first subphase 21 is higher than 15.0 and the second subphase 22 is lower than 15.0, meaning that it was undetectable in a condensed state. Furthermore, the concentration difference of element M, i.e., Co, between the first subphase 21 and the second subphase 22 indicates that, using surface scan analysis with EPMA, the average detection intensity of Co is higher in the second subphase 22 compared to the first subphase 21. Specifically, taking... Figure 12Taking the surface scan of Co as an example, the average detection level of Co in EPMA is 31.8, while the second subphase 22 is higher than 31.8 and the first subphase 21 is lower than 31.8, that is, it is a state that could not be detected in the condensed state.

[0157] Furthermore, the intensity ratios of elemental surface scans obtained from FE-EPMA analysis confirm that, compared to the number of second principal phases 12 with C(Nd,RH) < CPr, a large number of first principal phases 11 with C(Nd,RH) > CPr exist. Focusing on the shell portions 11s and 12s of the core-shell structure, it is also confirmed that the first principal phase 11 satisfies the relationships CNd > SNd, CPr < SPr, and CTb > STb, while the second principal phase 12 satisfies the relationships CNd < SNd, CPr > SPr, and CTb < STb.

[0158] Next, the results of the magnetic property measurements of each sample according to Examples 1 to 8 and Comparative Examples 1 to 18 will be explained. Each sample for magnetic measurement was a block shape with dimensions of 7 mm in length, width, and height. The first measurement temperature T1 was 23°C, and the second measurement temperature T2 was 200°C. 23°C is room temperature. The second measurement temperature T2 of 200°C is a temperature that can be generated in the environment during the operation of automotive motors and industrial motors.

[0159] First, the remanent magnetic flux density and coercivity of each sample from Examples 1 to 8 and Comparative Examples 2 to 18 were determined in comparison with Comparative Example 1. The remanent magnetic flux density and coercivity values ​​of each sample at 23°C were determined to be "equivalent" if they were within 1% of the measurement error compared to the values ​​in Comparative Example 1, "good" if they were 1% or more higher, and "poor" if they were 1% or lower.

[0160] Secondly, the temperature coefficient α of the remanent magnetic flux density was calculated using the remanent magnetic flux density at 23°C of the first measurement temperature T1 and the remanent magnetic flux density at 200°C of the second measurement temperature T2. Similarly, the temperature coefficient β of the coercivity was calculated using the coercivity at 23°C of the first measurement temperature T1 and the coercivity at 200°C of the second measurement temperature T2. The temperature coefficients of the remanent magnetic flux density and the temperature coefficients of the coercivity in each sample of Examples 1 to 8 and Comparative Examples 2 to 18 were compared with those in Comparative Example 1. For each sample, compared with the absolute values ​​of the temperature coefficients of the remanent magnetic flux density (|α|) and the absolute values ​​of the temperature coefficients of the coercivity (|β|) in the sample of Comparative Example 1, values ​​within ±1% of the measurement error were judged as "equivalent," values ​​lower than -1% were judged as "good," and values ​​higher than +1% were judged as "poor." For samples judged as "good," since the temperature coefficients are smaller, the decrease in magnetic properties associated with temperature increases is suppressed, thus providing a rare-earth sintered magnet 1 with stable magnetic properties even at high temperatures.

[0161] Secondly, the magnetization performance was calculated by the ratio of the magnetic flux density (the intersection of the hysteresis and permeability Pc under an applied magnetic field of 20 kOe) to the magnetic flux density (the intersection of the hysteresis and permeability Pc under an applied magnetic field of 80 kOe). The magnetization performance of each sample from Examples 1 to 8 and Comparative Examples 2 to 18 was determined by comparing it with that of Comparative Example 1. Specifically, for each sample, if the magnetization performance compared to that of the sample from Comparative Example 1 showed a value greater than or equal to -1% of the measurement error, it was determined to be "equivalent or better"; if the value showed a value lower than -1%, it was determined to be "poor". For samples determined to be "equivalent or better", a rare-earth sintered magnet 1 with high magnetization performance can be provided.

[0162] The results of the determination of 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.

[0163] Comparative Example 1 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method described in Patent Document 1, using Nd, Tb, Fe, and FeB in a (Nd, Tb)-Fe-BM configuration, and further using Co as element M as a raw material. Observing the microstructure of this sample using the above method, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed, nor could it be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Furthermore, it could not be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. Additionally, evaluating the magnetic properties of this sample using the above method, the remanent magnetic flux density B... r The coercivity is 1.25T, and the coercivity H is 1.25T. cJThe remanent flux density is 1650 kA / m. The temperature coefficients of remanent flux density and coercivity are |α| = 0.185% / ℃ and |β| = 0.455% / ℃, respectively. Furthermore, the magnetic susceptibility is 98.6%. These values ​​from Comparative Example 1 can be used as a reference.

[0164] Comparative Example 2 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method described in Patent Document 1, using Nd, Tb, Fe, and FeB as raw materials in a (Nd, Tb)-Fe-B configuration. In Comparative Example 2, Co, as element M, was not added. Observing the microstructure of this sample using the method described above, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed, nor could it be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Furthermore, since Co was not added, it could not be confirmed that the concentration of Co in the second secondary phase 22 was higher than in the first secondary phase 21. In addition, evaluating the magnetic properties of this sample using the method described above, since Co, as element M, was not present, the remanent magnetic flux density was "poor," and the coercivity was "poor." Furthermore, the temperature coefficient of the remanent magnetic flux density was "equal," the temperature coefficient of the coercivity was "equal," and the magnetization performance was "equal or better."

[0165] 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, Fe, and FeB in an Nd-Fe-BM configuration and Co as element M. Observing the microstructure of this sample using the above method, since Pr, La, and Sm were not added, the core-shell structure in the main phase 10 could not be confirmed, nor could it be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Furthermore, it could not be confirmed that the concentration of Co in the second secondary phase 22 was higher than in the first secondary phase 21. In addition, evaluating the magnetic properties of this sample using the above method, Tb, as a heavy rare earth element RH, did not enter the main phase 10; therefore, the remanent magnetic flux density was higher than that of Comparative Example 1, resulting in a "good" grade. The coercivity was significantly lower than that of Comparative Example 1, resulting in a "poor" grade. Furthermore, the temperature coefficient of the remanent magnetic flux density was "equal," the temperature coefficient of the coercivity was "equal," and the magnetization performance was "equal or better."

[0166] 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, Fe, and FeB in a (Nd, Pr)-Fe-BM configuration and Co as element M. Observing the microstructure of this sample using the above method, although the addition of Pr confirmed the presence of a Nd and Pr mixed main phase 10, a core-shell structure was not formed. Furthermore, since La and Sm were not added, it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher than that of the second secondary phase 22. Similarly, it could not be confirmed that the concentration of Co in the second secondary phase 22 was higher than that in the first secondary phase 21. Evaluating the magnetic properties of this sample using the above method, the heavy rare earth element RH (Tb) was not added. Furthermore, the addition of Pr instead of Tb did not result in an increase in coercivity compared to Tb. Therefore, the remanent magnetic flux density was higher than that of Comparative Example 1, classifying it as "good," while the coercivity was lower than that of Comparative Example 1, classifying it as "poor." Furthermore, due to the addition of Pr, the temperature coefficient of coercivity, a characteristic of Pr, deteriorates, becoming "poor". Since no hot working is involved in the manufacturing process, the magnetization performance becomes "equivalent or better". Moreover, the temperature coefficient of remanent magnetic flux density becomes "equivalent". This reflects that although the addition of Pr increases the magnetic anisotropy and coercivity of the main phase 10, it is not the optimal microstructure of the main phase 10 and the secondary phase 20.

[0167] 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, Pr, Tb, Fe, and FeB in a (Nd, Pr, Tb)-Fe-BM configuration, and further using Co as element M as a raw material. Observing the microstructure of this sample using the above method, while the main phase 10, a mixture of Nd and Pr, was confirmed, a core-shell structure was not formed. Furthermore, since La and Sm were not added, it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Similarly, it could not be confirmed that the concentration of Co in the second secondary phase 22 was higher than in the first secondary phase 21. Furthermore, evaluating the magnetic properties of this sample using the above method, by adding Pr and Tb as a heavy rare earth element (RH), the remanent magnetic flux density and coercivity were improved, with the remanent magnetic flux density becoming "equal" and the coercivity becoming "good." However, the temperature coefficient of coercivity, a characteristic of Pr, deteriorated, becoming "poor." Since the manufacturing method does not involve hot working, the magnetization performance is "equivalent or better". Furthermore, the temperature coefficient of the remanent magnetic flux density is "equivalent". This reflects that although the magnetic anisotropy and coercivity of the main phase 10 are improved by the addition of Tb, Pr and Co, it is not the optimal microstructure of the main phase 10 and the secondary phase 20.

[0168] Comparative Example 6 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 in a (Nd, La, Sm)-Fe-BM configuration, and further using Co as element M as a raw material. Observing the microstructure of this sample using the above method, the core-shell structure of the main phase 10 could not be confirmed because Pr was not added. Furthermore, although the concentration of Sm segregated into a secondary phase 20 due to the segregation of La, a second secondary phase 22 was not present. Therefore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22, nor could it be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. Furthermore, evaluating the magnetic properties of this sample using the above method, since Tb, as a heavy rare earth element RH, was not present, the remanent magnetic flux density was "good," and the coercivity was significantly lower than that of Comparative Example 1, thus it was "poor." By adding La and Sm, with La and Sm present in either the principal phase 10 or the secondary phase 20, the temperature coefficients of the residual magnetic flux density and coercivity become "good". Since no hot working is involved in the manufacturing process, the magnetization performance becomes "equivalent or better". This reflects that although the temperature coefficient of coercivity shows good results due to the presence of La and Sm in either the principal phase 10 or the secondary phase 20, the magnetic properties at room temperature are not improved, indicating that the microstructure is not optimal in either the principal phase 10 or the secondary phase 20.

[0169] Comparative Example 7 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 in a (Nd, La, Sm)-Fe-BM configuration, and further using Co as element M as a raw material. The composition ratio of Nd, La, and Sm differs from that of Comparative Example 6. Observing the microstructure of this sample using the method described above, the core-shell structure of the main phase 10 could not be confirmed because Pr was not added. Furthermore, although the concentration of Sm segregated into a secondary phase 20 due to the segregation of La with the addition of La and Sm, a second secondary phase 22 was not present. Therefore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22, nor could it be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. In addition, evaluating the magnetic properties of this sample using the method described above, even after adjusting the amount of La and Sm added, there was no significant change compared to Comparative Example 6. That is, since Tb, as a heavy rare earth element RH, was not included, the remanent magnetic flux density was "good," and the coercivity was significantly reduced compared to Comparative Example 1, thus becoming "poor." Furthermore, the temperature coefficient of the remanent magnetic flux density was "good," and the temperature coefficient of the coercivity was "good." Since no hot working was performed in the manufacturing process, the magnetization performance was "equivalent or better." In Comparative Example 7, although the temperature coefficient of the magnetic properties showed good results due to the addition of La and Sm, the magnetic properties at room temperature were not improved because Tb, as a heavy rare earth element RH, was not added to the base material. This resulted in a microstructure that was not optimal among the main phase 10 and the secondary phase 20. Even changing the composition ratio of Nd, La, and Sm yielded results approximately the same as in Comparative Example 6.

[0170] Comparative Example 8 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method described in Patent Document 1, using Nd, Pr, La, Sm, Fe, and FeB in a (Nd, Pr, La, Sm)-Fe-BM configuration, and further using Co as element M as a raw material. Observing the microstructure of this sample using the above method, although the addition of Pr confirmed the presence of a main phase 10 composed of Nd and Pr, a core-shell structure was not formed. Furthermore, although the addition of La and Sm resulted in the segregation of Sm into a secondary phase 20 along with La segregation, a second secondary phase 22 was not present. Furthermore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22, nor could it be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. Furthermore, the magnetic properties of the sample were evaluated using the method described above. Since Tb, a heavy rare earth element (RH), was not present, the remanent magnetic flux density was rated as "good." Even with the addition of La, Sm, and Pr, the coercivity was not improved to the level seen with the addition of Tb; therefore, the coercivity was rated as "poor." Additionally, the temperature coefficients of the remanent magnetic flux density and coercivity should have been rated as "good," but the addition of Pr worsened the temperature coefficient of coercivity, a characteristic of Pr. Therefore, only the temperature coefficient of coercivity decreased to "equivalent." Since no heat treatment was performed during the manufacturing process, the magnetization performance was rated as "equivalent or better."

[0171] Comparative Example 9 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, La, Sm, Fe, and FeB in the form of (Nd, Pr, Tb, La, Sm)-Fe-BM, and further using Co as element M as a raw material. Observing the microstructure of this sample using the above method, although the addition of Pr confirmed the presence of a main phase 10 of Nd and Pr mixture, no core-shell structure was formed. Furthermore, although the concentration of Sm segregated into a secondary phase 20 due to La segregation, a second secondary phase 22 was not present. Furthermore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22, nor could it be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. Furthermore, the magnetic properties of the sample were evaluated according to the above method. Due to the addition of Tb, a heavy rare earth element (RH), the coercivity was significantly improved compared to Comparative Example 8, thus it was rated "Good". However, due to the failure to control the microstructure of the main phase 10 and the secondary phase 20, the remanent magnetic flux density was significantly reduced, resulting in a "Poor" rating. The temperature coefficients of the remanent magnetic flux density and coercivity were the same as those of Comparative Example 8, with the temperature coefficient of the remanent magnetic flux density rated "Good" and the temperature coefficient of the coercivity rated "Equal". Since no heat treatment was performed in the manufacturing process, the magnetization performance was rated "Equal or better".

[0172] Comparative Example 10 is a sample of a rare earth sintered magnet 1 manufactured according to the hot-processing manufacturing method described in Patent Document 2, using Nd, Tb, Fe, and FeB in a (Nd, Tb)-Fe-BM configuration, and further using Co as element M. Observing the microstructure of this sample using the above method, the core-shell structure of the main phase 10 could not be confirmed because Pr, La, and Sm were not added. Furthermore, it could not be confirmed that the first subphase 21 had a higher Sm concentration than the second subphase 22 in the subphase 20. Similarly, it could not be confirmed that the second subphase 22 had a higher Co concentration than the first subphase 21. However, the characteristic of magnets manufactured using hot processing, namely, the refinement of the microstructure, was confirmed. Evaluating the magnetic properties of this sample using the above method, the coercivity was rated as "good" due to the refinement of the magnetic powder caused by hot processing, and the temperature coefficient of coercivity was rated as "equal." However, because the magnetic moments were not easily aligned, the remanent magnetic flux density and magnetization performance decreased, resulting in a "poor" result. The temperature coefficient of the remanent magnetic flux density was rated as "equal." Although the magnetic powder is miniaturized due to thermal processing, and the absolute value of coercivity and the temperature coefficient of coercivity are increased, the magnetic moments are not easily aligned, thus resulting in a decrease in residual magnetic flux density and a deterioration in magnetization performance.

[0173] Comparative Example 11 is a sample of a rare earth sintered magnet 1 manufactured using Nd, Fe, and FeB in an Nd-Fe-BM configuration, and Co as element M as a raw material, according to the hot-processing manufacturing method described in Patent Document 2. Observing the microstructure of this sample using the above method, since Pr, La, and Sm were not added, the core-shell structure of the main phase 10 could not be confirmed, nor could it be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Furthermore, it could not be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. However, the characteristic of magnets manufactured using hot processing, namely, the refinement of the microstructure, was confirmed. Evaluating the magnetic properties of this sample using the above method, the coercivity was "good" due to the refinement of the magnetic powder, and the temperature coefficient of coercivity was "equal." Additionally, the magnetization performance was "poor" because the magnetic moments were not easily aligned. However, since Tb was not added, the significant decrease in remanent magnetic flux density was suppressed, reaching the same level as Comparative Example 1, and the remanent magnetic flux density was "equal." The temperature coefficient of the residual magnetic flux density becomes "equivalent". Although this is accompanied by the miniaturization of magnetic powder due to thermal processing and the improvement of coercivity, it also reflects the deterioration of magnetization performance because the magnetic moments are not easy to align.

[0174] Comparative Example 12 is a sample of a rare earth sintered magnet 1 manufactured using Nd, Fe, and FeB as raw materials in an Nd-Fe-B manner, according to the manufacturing method including hot processing described in Patent Document 2. In Comparative Example 12, Co, as element M, was not added. Observing the microstructure of the sample according to the above method, since Pr, La, and Sm were not added, the core-shell structure of the main phase 10 could not be confirmed, nor could it be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Furthermore, since Co was not added, it could not be confirmed that the concentration of Co in the second secondary phase 22 was higher than that in the first secondary phase 21. However, the characteristic of magnets manufactured by hot processing, namely, the fineness of the microstructure, was confirmed. Evaluating the magnetic properties of the sample according to the above method, the remanent magnetic flux density was "poor", the coercivity was "good", the temperature coefficient of the remanent magnetic flux density was "equal", the temperature coefficient of the coercivity was "equal", and the magnetization performance was "poor". Although the coercivity increases with the miniaturization of magnetic powder caused by thermal processing, and the temperature coefficients of residual magnetic flux density and coercivity become equal, the magnetic moments are not easily aligned, thus reflecting the decrease in residual magnetic flux density and the deterioration of magnetization performance.

[0175] Comparative Example 13 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method including hot processing described in Patent Document 2, using Nd, Pr, Fe, and FeB in a (Nd, Pr)-Fe-BM configuration, and further using Co as element M as a raw material. The microstructure of the sample was observed using the above method. In addition to the addition of Pr, hot processing was used to confirm a core-shell structure. The core-shell structure was confirmed only in the main phase 10, where the Pr concentration in the core is high. Furthermore, since La and Sm were not added, it could not be confirmed that the concentration of Sm in the secondary phase 20 was higher in the first secondary phase 21 than in the second secondary phase 22. Similarly, it could not be confirmed that the concentration of Co in the second secondary phase 22 was higher than in the first secondary phase 21. The magnetic properties of the sample were evaluated using the above method. Through the refinement of the magnetic powder, the coercivity was "good," and the temperature coefficient of coercivity was "equal." However, due to the difficulty in aligning the magnetic moments, the remanent magnetic flux density and magnetization performance were "poor." The temperature coefficient of the remanent magnetic flux density was "equal." Although the coercivity is greatly improved to the level of rare earth sintered magnet 1 with added Tb through the formation of a core-shell structure with a high concentration of Pr in the core, for other properties, it becomes a result of the micro-refinement of the microstructure caused by thermal processing.

[0176] Comparative Example 14 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method including hot processing described in Patent Document 2, using Nd, Pr, Tb, Fe, and FeB in the form of (Nd, Pr, Tb)-Fe-BM, and further using Co as element M as a raw material. The microstructure of the sample was observed using the above method. In addition to the addition of Pr, hot processing was used to confirm a core-shell structure, but only the main phase 10 with a high Pr concentration in the core was confirmed to have a core-shell structure. Furthermore, since La and Sm were not added, it could not be confirmed that the first subphase 21 had a higher Sm concentration than the second subphase 22 in the subphase 20. Similarly, it could not be confirmed that the second subphase 22 had a higher Co concentration than the first subphase 21. Furthermore, the magnetic properties of the sample were evaluated according to the above method. Through the refinement of the magnetic powder, the coercivity was "good," and the temperature coefficient of coercivity was "equal." However, due to the difficulty in aligning the magnetic moments, the remanent magnetic flux density and magnetization performance were "poor." The temperature coefficient of the residual magnetic flux density is "equivalent". This is because, in addition to the use of thermal processing, a portion of the Tb and Nd with high magnetic anisotropy in the crystal is replaced, which greatly improves the coercivity. However, for other properties, it becomes a result of the micro-refinement of the structure caused by thermal processing.

[0177] Comparative Example 15 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method including hot processing described in Patent Document 2, using Nd, La, Sm, Fe, and FeB in the form of (Nd, La, Sm)-Fe-BM, and further using Co as element M as a raw material. Observing the microstructure of this sample according to the above method, the core-shell structure of the main phase 10 could not be confirmed because Pr was not added. Furthermore, although the concentration of Sm segregated in a secondary phase 20 due to the segregation of La and Sm, a second secondary phase 22 was not present. Therefore, it could not be confirmed that the first secondary phase 21 had a higher concentration of Sm than the second secondary phase 22, nor could it be confirmed that the second secondary phase 22 had a higher concentration of Co than the first secondary phase 21. Furthermore, evaluating the magnetic properties of this sample according to the above method, the coercivity and temperature coefficient of coercivity were "good" due to the fineness of the magnetic powder. However, the remanent magnetic flux density and magnetization performance were "poor" because the magnetic moments were not easily aligned. The temperature coefficient of the remanent magnetic flux density was "good". Although the presence of La and Sm in the main phase 10 or the secondary phase 20 results in a good temperature coefficient of magnetic properties, the remanent magnetic flux density and magnetization at room temperature are not improved due to the difficulty in aligning the magnetic moments, which is a result that does not reflect the optimal morphology in the main phase 10 and the secondary phase 20.

[0178] Comparative Example 16 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method including hot processing described in Patent Document 2, using Nd, La, Sm, Fe, and FeB in the form of (Nd, La, Sm)-Fe-BM, and further using Co as element M as a raw material. The composition ratio of Nd, La, and Sm is different from that of Comparative Example 15. Observing the microstructure of this sample according to the above method, the core-shell structure of the main phase 10 could not be confirmed because Pr was not added. In addition, although the concentration of Sm segregated in a secondary phase 20 due to the segregation of La with the addition of La and Sm, a second secondary phase 22 was not present. Furthermore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22, nor could it be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. In addition, evaluating the magnetic properties of this sample according to the above method, the coercivity and temperature coefficient of coercivity were rated as "good" due to the miniaturization of the magnetic powder. Furthermore, due to the difficulty in aligning the magnetic moments, the remanent magnetic flux density and magnetization properties are deemed "poor." The temperature coefficient of the remanent magnetic flux density is deemed "good." Although this is because the presence of La and Sm in the main phase 10 or the secondary phase 20 results in a good temperature coefficient of magnetic properties, the difficulty in aligning the magnetic moments means that the remanent magnetic flux density and magnetization properties at room temperature are not improved, indicating that the microstructure is not optimal for either the main phase 10 or the secondary phase 20. Even changing the composition ratio of Nd, La, and Sm yields results approximately the same as in Comparative Example 15.

[0179] Comparative Example 17 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method including hot processing described in Patent Document 2, using Nd, Pr, La, Sm, Fe, and FeB in the form of (Nd, Pr, La, Sm)-Fe-BM, and further using Co as element M as a raw material. The microstructure of the sample was observed using the above method. In addition to the addition of Pr, hot processing was used to confirm a core-shell structure. The core-shell structure was confirmed only in a main phase 10 with a high concentration of Pr in the core. Furthermore, although the addition of La and Sm resulted in the segregation of Sm into a secondary phase 20 due to La segregation, a second secondary phase 22 was not present. Furthermore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22, nor could it be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. In addition, the magnetic properties of the sample were evaluated according to the above method. Through the refinement of the magnetic powder, the coercivity and the temperature coefficient of coercivity were rated as "good". Furthermore, due to the difficulty in aligning magnetic moments, the remanent magnetic flux density and magnetization performance are considered "poor." The temperature coefficient of the remanent magnetic flux density is considered "good." Although this is due to the formation of a core-shell structure with a high concentration of Pr in the core, which significantly increases the coercivity to the level of the rare-earth sintered magnet 1 with added Tb, and the presence of La and Sm in the main phase 10 or the secondary phase 20, resulting in a good temperature coefficient of magnetic properties, especially the temperature coefficient of coercivity, the remanent magnetic flux density and magnetization performance at room temperature are not improved due to the difficulty in aligning magnetic moments. This also reflects that the microstructure is not optimal in the main phase 10 and the secondary phase 20.

[0180] Comparative Example 18 is a sample of a rare earth sintered magnet 1 manufactured according to the manufacturing method including hot processing described in Patent Document 2, using Nd, Pr, Tb, La, Sm)-Fe-BM in the form of (Nd, Pr, Tb, La, Sm, Fe, and FeB), and further using Co as element M as a raw material. The microstructure of the sample was observed using the above method. In addition to the addition of Pr, hot processing was used to confirm a core-shell structure. It was confirmed that the core-shell structure consisted only of a main phase 10 with a high concentration of Pr in the core. Furthermore, although the addition of La and Sm resulted in the segregation of Sm into a secondary phase 20 due to La segregation, a second secondary phase 22 was not present. Furthermore, it could not be confirmed that the concentration of Sm was higher in the first secondary phase 21 than in the second secondary phase 22, nor could it be confirmed that the concentration of Co was higher in the second secondary phase 22 than in the first secondary phase 21. In addition, the magnetic properties of the sample were evaluated according to the above method. Through the refinement of the magnetic powder, the coercivity and the temperature coefficient of coercivity were rated as "good". Furthermore, due to the difficulty in aligning magnetic moments, the remanent magnetic flux density and magnetization performance are considered "poor." The temperature coefficient of the remanent magnetic flux density is considered "good." Although this is due to the formation of a core-shell structure with a high concentration of Pr in the core and the addition of Tb, which significantly improves coercivity, and the presence of La and Sm in the main phase 10 or the secondary phase 20, resulting in good temperature coefficients of magnetic properties, especially coercivity, the difficulty in aligning magnetic moments means that the remanent magnetic flux density and magnetization performance at room temperature are not improved. This also reflects that the microstructure is not optimal in the main phase 10 and the secondary phase 20.

[0181] The samples in Examples 1 to 8 are rare earth sintered magnets 1, which have the following characteristics: when the heavy rare earth element RH is set as Tb, R is set as one or more rare earth elements other than Nd, Pr, and Tb, and M is set as one or more elements selected from Ga, Al, Cu, and Co, the general formula (Nd, Pr, Tb, R)-Fe-BM is satisfied, and Nd2Fe is included. 14B has a basic crystal structure consisting of a main phase 10 with basic grains and a secondary phase 20 existing between the main phases 10 and 10. The main phase 10 has cores 11c and 12c and shells 11s and 12s covering the cores 11c and 12c. In addition, the main phase 10 has a first main phase 11 with CNd > CPr and a second main phase 12 with CNd < CPr. The concentration of Tb, which is a heavy rare earth element RH, in the first main phase 11 is higher than that in the second main phase 12. The first main phase 11 and the second main phase 12 are mixed. Furthermore, the rare earth sintered magnets 1 of Examples 1 to 8 are configured with R = La and Sm. They are characterized in that, in addition to the first main phase 11 and the second main phase 12, the secondary phase 20 has a crystalline first secondary phase 21 with an oxide phase represented as (Nd, Pr, Tb, La, Sm)-O containing element M as a trace component as the main component, and a crystalline second secondary phase 22 with an oxide phase represented as (Nd, Pr, Tb, La)-O containing element M as a trace component as the main component. The first secondary phase 21 has a higher Sm concentration than the second secondary phase 22, and the second secondary phase 22 has a higher M concentration than the first secondary phase 21. Additionally, a high-concentration section 41, which is an Sm enrichment section, is formed in the first secondary phase 21. The magnetic properties of the samples from Examples 1 to 8 were evaluated according to the above method. The remanent magnetic flux density was rated as "good", the coercivity as "good", the temperature coefficient of the remanent magnetic flux density as "good", the temperature coefficient of the coercivity as "good", and the magnetization performance as "equivalent or better". As a result, these rare earth sintered magnets 1 exhibit the following effects: suppressing the use of Nd and heavy rare earth element RH, which are expensive, geographically inhomogeneous, and involve procurement risks, while simultaneously demonstrating superior magnetic properties and magnetization compared to the past.

[0182] Furthermore, as shown in Table 3, in the samples of Examples 1 to 8, compared with the samples of Comparative Examples 1, 2, 5, 9, 10, 14, and 18, the content of Tb, which is a heavy rare earth element RH, is lower, and in terms of magnetic properties, the results are superior to those of the samples of Comparative Examples 1 to 18. In particular, if the samples of Comparative Examples 10, 14, and 18 manufactured using the manufacturing method of Patent Document 2 are to obtain the same magnetic properties as the samples of Examples 1 to 8, Tb must be further included. Therefore, the rare earth sintered magnet 1 according to Embodiments 1 and 2 has the effect of reducing the amount of heavy rare earth element RH used compared with the technology of Patent Document 2. Alternatively, when the content of heavy rare earth element RH in the rare earth magnet manufactured using the manufacturing method of Patent Document 2 is the same as the content of heavy rare earth element RH in the rare earth sintered magnet 1 according to Embodiments 1 and 2, the magnetic properties of the rare earth magnet manufactured using the manufacturing method of Patent Document 2 are lower than those of the rare earth sintered magnet 1 according to Embodiments 1 and 2. In addition, Table 3 shows that, compared with the samples of Comparative Examples 1, 2, 5, and 9 manufactured using the manufacturing method of Patent Document 1, the samples of Examples 1 to 8 can reduce the content of Tb, which is a heavy rare earth element RH, and improve the magnetic properties.

[0183] The above embodiments illustrate one example, and can also be combined with other known technologies, and embodiments can be combined with each other. Without departing from the spirit, some parts of the structure can be omitted or changed.

[0184] Explanation of reference numerals in the attached figures

[0185] 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 High concentration section, 42 Low concentration section, 100 Rotor, 101 Rotor core, 102 Magnet insertion hole, 120 Rotating machine, 130 Stator, 131 Tooth, 132 Wire winding.

Claims

1. A rare earth sintered magnet, characterized in that, It has: a main phase that satisfies the general formula (Nd, Pr, RH, R)-Fe-BM when RH is a heavy rare earth element containing at least one of Dy and Tb, R is a rare earth element selected from Nd, Pr, Dy, and Tb, and M is an element selected from Ga, Al, Cu, and Co; and contains Nd2Fe. 14 B has a crystal structure consisting of basic grains; and a secondary phase formed between the main phase and the main phase. The main phase has a core and a shell covering the core. When the concentration of Nd in the core is set to CNd and the concentration of Pr in the core is set to CPr, the main phase has a first main phase with CNd > CPr and a second main phase with CNd < CPr. The concentration of heavy rare earth element RH in the core of the first main phase is higher than that in the core of the second main phase, and the first main phase and the second main phase are mixed. The secondary phase has a first secondary phase and a second secondary phase, which are crystalline and mainly composed of oxide phases (Nd, Pr, RH, La, Sm)-O containing trace elements M. Regarding the concentration of element M, the second subphase is higher than the first subphase.

2. The rare earth sintered magnet according to claim 1, characterized in that, When analyzing the rare earth sintered magnet using an electron probe microanalyzer, the detection intensity of the electron probe microanalyzer is lower than the average detection intensity of element M for the concentration of element M in the first subphase, and higher than the average detection intensity of element M for the concentration of element M in the second subphase.

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

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

5. The rare earth sintered magnet according to claim 1, characterized in that, The secondary phase comprises: a first crystalline secondary phase, which is a crystalline oxide phase represented as (Nd, Pr, RH, La, Sm)-O with element M as a trace component when R is set to La and Sm, and a second crystalline secondary phase, which is a crystalline oxide phase represented as (Nd, Pr, RH, La)-O with element M as a trace component, wherein the first secondary phase has a higher concentration of Sm than the second secondary phase.

6. A method for manufacturing rare earth sintered magnets, comprising the method for manufacturing rare earth sintered magnets according to any one of claims 1 to 5, characterized in that, The process includes: a melting process of a raw material containing elements constituting the rare earth sintered magnet alloy, which is melted; a first cooling process of cooling the molten raw material in the melting process to obtain a solidified alloy; a second cooling process of further cooling the solidified alloy to obtain the rare earth sintered magnet alloy; a pulverizing process of pulverizing the rare earth sintered magnet alloy satisfying (Nd, Pr, RH, R)-Fe-BM; a molding process of forming the pulverized rare earth sintered magnet alloy powder in the pulverizing process into a molded body; and sintering the molded body at a specified temperature, i.e., a sintering temperature, to obtain the sintered magnet alloy. The process includes: a sintering process of the sintered body; a first aging process of holding the sintered body at a temperature below the sintering temperature, i.e., a first aging temperature; a second aging process of holding the sintered body held in the first aging process at a temperature below the first aging temperature, i.e., a second aging temperature; a third aging process of holding the sintered body held in the second aging process again at the first aging temperature; a fourth aging process of holding the sintered body held in the third aging process at the second aging temperature; and a cooling process of cooling the sintered body held in the fourth aging process.

7. A rotor, characterized in that, include: Rotor core; and the rare earth sintered magnets according to any one of claims 1 to 5 disposed on the rotor core.

8. A rotating machine, characterized in that, include: The rotor according to claim 7; The stator has a spiral with teeth protruding toward the rotor on the inner surface of one side where the rotor is disposed, and an annular stator disposed opposite to the rotor.

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