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

Abstract

This rare earth sintered magnet (1) comprises: main phases (10) that satisfy general formula (Nd, Pr, R)-Fe-B-M and contain crystal grains based on the Nd2Fe14B crystal structure, where R is one or more rare earth elements selected from elements other than Nd and Pr, and M is one or more elements selected from the group consisting of Ga, Al, Cu, and Co; and a sub-phase (20) that is formed between the main phases. The main phases have a core portion and a shell portion that covers the core portion. The main phases have a first main phase (11) in which CNd>CPr and a second main phase (12) in which CNd<CPr, where CNd is the concentration of Nd in the core portion and CPr is the concentration of Pr in the core portion. The first and second main phases are mixed. The sub-phase has a crystalline first sub-phase (21) and a second sub-phase (22) mainly composed of an oxide phase that contains an element M as a trace component and is represented by (Nd, Pr, R)-O. The concentration of the element M is higher in the second sub-phase than in the first sub-phase.

Description

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

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

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

[0003] In recent years, the production volume of Nd—Fe—B sintered magnets has expanded, resulting in increased consumption of Nd and heavy rare earth elements such as Dy and Tb (terbium). However, Nd and heavy rare earth elements are expensive and unevenly distributed across regions, posing procurement risks. For this reason, research is being conducted into technologies to reduce the consumption of Nd and heavy rare earth elements.

[0004] In Patent Document 1, R2T 14 The present invention discloses an R-T-B based sintered magnet containing main phase particles made of B crystals, where R is one or more rare earth elements essentially containing a heavy rare earth element RH, T is one or more transition metal elements essentially containing Fe or Fe and Co, and B is boron, and some of the main phase particles contain multiple lower heavy rare earth element crystal phases and multiple nonmagnetic R-rich phases therein. Here, the lower heavy rare earth element crystal phase is R2T 14The nonmagnetic R-rich phase is a phase consisting of B crystals, in which the concentration of heavy rare earth elements is relatively low compared to the concentration of heavy rare earth elements in the main phase particles as a whole. The nonmagnetic R-rich phase is a phase in which the R content is 70 at. % or more and 100 at. % or less. Furthermore, some of the main phase particles have a single core-shell structure having a core portion and a shell portion surrounding the core portion and having a lower total heavy rare earth element concentration than the core portion. The technology described in Patent Document 1 makes it possible to obtain an R-T-B based sintered magnet with improved coercivity and at low cost.

[0005] In Patent Document 2, (R1 1-x R2 x ) a TM b B c M d The method for producing a rare earth magnet is disclosed, which comprises a first step of producing a sintered body having a structure represented by the composition formula below and consisting of a main phase and a grain boundary phase; a second step of producing a rare earth magnet precursor by hot plastic working the sintered body; and a third step of producing a rare earth magnet by diffusing and infiltrating a melt of an R3-M modified alloy into the grain boundary phase of the rare earth magnet precursor. Here, R1 is one or more rare earth elements including Y (yttrium), R2 is a rare earth element different from R1, TM is a transition metal including one or more of 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-a-c-d, 5≦c≦20, and 0≦d≦3, all in atomic percent. Furthermore, R3 is a rare earth element containing R1 and R2. Hereinafter, the hot plastic processing applied to the sintered body will be referred to as hot processing. The technology described in Patent Document 2 reduces the heavy rare earth element content and enables the production of rare earth magnets that exhibit excellent magnetization and coercive force performance, even when the main phase ratio is high.

[0006] JP 2018-174313 A JP 2015-153813 A

[0007] However, in the R-T-B based sintered magnet described in Patent Document 1, a phase containing a heavy rare earth element is present within the main phase, which allows for improved coercivity, but it does not achieve the remanence required for industrial motors, etc., and there is a possibility that the magnetic properties may deteriorate due to thermal load. Furthermore, rare earth magnets manufactured by the manufacturing method described in Patent Document 2 can reduce the heavy rare earth element content and improve coercivity, but because the manufacturing method includes hot working, the grain size of the main phase becomes smaller, which results in problems with the remanence and magnetization performance of the rare earth magnets manufactured.

[0008] The present disclosure has been made in light of the above, and aims to provide a rare earth sintered magnet that does not use heavy rare earth elements and that can improve coercivity without reducing remanence and magnetization performance compared to conventional magnets.

[0009] In order to solve the above-mentioned problems and achieve the object, the rare earth sintered magnet according to the present disclosure satisfies the general formula (Nd, Pr, R)-Fe-B-M, and has a structure of NdFe, where R is one or more rare earth elements selected from the group consisting of Nd and Pr (praseodymium), and M is one or more elements selected from the group consisting of Ga, Al, Cu, and Co. 14 The alloy has a main phase including crystal grains based on a B crystal structure, and a subphase formed between the main phase and the main phase. The main phase has a core portion and a shell portion covering the core portion. The main phase has a first main phase in which the Nd concentration in the core portion is CNd>CPr and a second main phase in which the Pr concentration in the core portion is CPr. The first and second main phases are mixed. The subphase has a crystalline first subphase and a second subphase, each of which is primarily composed of an oxide phase expressed as (Nd, Pr, R)-O containing element M as a trace component. The concentration of element M is higher in the second subphase than in the first subphase.

[0010] The rare earth sintered magnet according to the present disclosure has the advantage of being able to improve coercivity without using heavy rare earth elements and without reducing remanence and magnetization performance compared to conventional magnets.

[0011] FIG. 1 is a diagram showing an example of the structure of a rare earth sintered magnet in a sintered state according to embodiment 1. FIG. 2 is a diagram showing an example of the structure of a rare earth sintered magnet in a sintered state according to embodiment 2. Tetragonal NdFe 14 A diagram showing atomic sites in a B crystal structure. A flowchart showing an example of the procedure for manufacturing a rare earth sintered magnet alloy according to embodiment 3. A flowchart showing an example of the procedure for manufacturing a rare earth sintered magnet according to embodiment 3. A cross-sectional view showing a schematic example of the configuration of a rotor equipped with a rare earth sintered magnet according to embodiment 4. A cross-sectional view showing a schematic example of the configuration of a rotating machine according to embodiment 5. A cross-section of the rare earth sintered magnet according to examples 1 to 8 was analyzed using a field emission electron probe microanalyzer. Elemental mapping of Nd obtained by FE-EPMA analysis of the cross section of the rare earth sintered magnets of Examples 1 to 8; Elemental mapping of Pr obtained by FE-EPMA analysis of the cross section of the rare earth sintered magnets of Examples 1 to 8; Elemental mapping of Co obtained by FE-EPMA analysis of the cross section of the rare earth sintered magnets of Examples 1 to 8; Elemental mapping of O (oxygen) obtained by FE-EPMA analysis of the cross section of the rare earth sintered magnets of Examples 1 to 8; Elemental mapping of La (lanthanum) obtained by FE-EPMA analysis of the cross section of the rare earth sintered magnets of Examples 1 to 8; Elemental mapping of Sm (samarium) obtained by FE-EPMA analysis of the cross section of the rare earth sintered magnets of Examples 1 to 8

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

[0013] 1 is a diagram showing a schematic diagram of an example of the structure of a rare earth sintered magnet in a sintered state according to embodiment 1. The rare earth sintered magnet 1 according to embodiment 1 satisfies the general formula (Nd, Pr, R)-Fe-B-M, and is composed of NdFe. 14The alloy has a main phase 10 including crystal grains based on a B crystal structure, and a subphase 20 present between the main phases 10. The main phase 10 has a core portion and a shell portion covering the core portion. Here, R is one or more rare earth elements selected from the group consisting of Nd and Pr, and M is one or more elements selected from the group consisting of Ga, Al, Cu, and Co. The shell portion has a different composition from the core portion and is provided to cover the core portion.

[0014] Specifically, the rare earth sintered magnet 1 according to the first embodiment, that is, the rare earth sintered magnet 1 including the main phase 10 and the subphase 20, has a general formula of (Nd a Pr b R c ) Fe d B e M f It is desirable that a, b, c, d, e, and f satisfy the following relational expression.

[0015] 5≦a+b≦20 0<c<(a+b) 70≦d≦90 0.5≦e≦10 0≦f≦5 a+b+c+d+e+f=100at. %

[0016] The main phase 10 is a tetragonal RFe alloy in which some of the Nd sites are replaced with Pr and one or more rare earth elements R selected from the group consisting of Nd and Pr. 14 That is, the main phase 10 has a (Nd, Pr, R)Fe crystal structure. 14 The element M may be incorporated into the main phase 10. When the element M is Co or Cu, which are transition elements, the element M is NdFe 14 It is believed that it substitutes for part of the Fe site of the B crystal structure.

[0017] In rare earth sintered magnet 1 according to embodiment 1, when the concentration of Nd in the core portion is CNd and the concentration of Pr in the core portion is CPr, main phase 10 includes first main phase 11 in which CNd > CPr and second main phase 12 in which CNd < CPr, with first main phase 11 and second main phase 12 being mixed together. First main phase 11 includes core portion 11c and shell portion 11s, which has a different composition from core portion 11c and covers core portion 11c. Second main phase 12 includes core portion 12c and shell portion 12s, which has a different composition from core portion 12c and covers core portion 12c. In core portion 11c of first main phase 11, CNd > CPr, and in core portion 12c of second main phase 12, CNd < CPr.

[0018] In other words, rare earth sintered magnet 1 contains two types of main phases 10: first main phase 11 and second main phase 12. Focusing on the cores 11c and 12c of the two types of main phases 10, the Nd concentration is higher in first main phase 11 than in Pr, while the Pr concentration is higher in second main phase 12. By combining two types of main phases 10 with core-shell structures that have different anisotropy fields, i.e., different magnetic anisotropies, it is possible to reduce the amount of Nd and improve the remanence and coercivity while maintaining good magnetization without adding any heavy rare earth elements. Furthermore, the addition of element M significantly improves coercivity, thereby contributing to suppressing the deterioration of magnetic properties with temperature changes.

[0019] Here, the concentration difference shown between "the first main phase 11 where CNd > CPr and the second main phase 12 where CNd < CPr" means that a clear difference in the detected intensities of Nd and Pr is found by mapping analysis using an electron probe micro analyzer (EPMA). Specifically, taking the first main phase 11 as an example, the detected intensity of Nd in the core region 11c by EPMA is higher than the average detected intensity of Nd, and the detected intensity of Pr in the core region 11c by EPMA is near the lower limit of the detected intensity of Pr, or is lower than the average detected intensity of Pr. It can be said that the second main phase 12 is the opposite of the first main phase 11.

[0020] Furthermore, in rare earth sintered magnet 1 according to embodiment 1, when the Nd concentration in core region 11c of first main phase 11 is C1Nd, the Nd concentration in core region 12c of second main phase 12 is C2Nd, the Pr concentration in core region 11c of first main phase 11 is C1Pr, and the Pr concentration in core region 12c of second main phase 12 is C2Pr, the following relationship is satisfied: C1Nd > C2Nd, C1Pr < C2Pr. In other words, the Nd concentration is higher in core region 11c of first main phase 11 than in core region 12c of second main phase 12, and conversely, the Pr concentration is higher in core region 12c of second main phase 12 than in core region 11c of first main phase 11. This difference in concentration also means that there is a difference in the detection intensities of Nd and Pr in the mapping analysis using EPMA described above. Specifically, in the case of the Nd concentration, this means that the EPMA detection intensity of Nd in the core region 11c of the first main phase 11 is higher than the average Nd detection intensity, and the EPMA detection intensity of Nd in the core region 12c of the second main phase 12 is lower than the average Nd detection intensity. In the case of the Pr concentration, this means that the EPMA detection intensity of Pr in the core region 12c of the second main phase 12 is higher than the average Pr detection intensity, and the EPMA detection intensity of Pr in the core region 11c of the first main phase 11 is lower than the average Pr detection intensity. In other words, the core region 12c of the second main phase 12, which has a low Nd concentration, contains a large amount of Pr, and conversely, the core region 11c of the first main phase 11, which has a low Pr concentration, contains a large amount of Nd. By controlling the microstructure in this way, it is possible to obtain a rare earth sintered magnet 1 with excellent magnetic properties.

[0021] Furthermore, in the rare earth sintered magnet 1 according to the first embodiment, the first main phase 11, where CNd>CPr, is present in greater amounts than the second main phase 12, where CNd<CPr. In other words, NdFe 14 The number of the first main phases 11 having the composition formula of PrFe 14 This means that the number of the second main phases 12 having the composition formula of NdFe is greater than the number of the second main phases 12 having the composition formula of NdFe. 14 Increasing the first main phase 11 having the composition formula of PrFe 14This is because better magnetic properties and temperature characteristics can be obtained than by increasing the second main phase 12 having the composition formula of B. Furthermore, by controlling the structure in this way, the overall crystal grain size is also suppressed from becoming finer, so that it is possible to obtain better magnetic properties than before while maintaining magnetization.

[0022] Furthermore, in the rare earth sintered magnet 1 according to the first embodiment, 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 defined as SNd and the Pr concentration in the shell portions 11s and 12s is defined as SPr, the first main phase 11 satisfies the relational expressions CNd>SNd, CPr<SPr, and the second main phase 12 satisfies the relational expressions CNd<SNd, CPr>SPr. Specifically, the shell portion 11s of the first main phase 11 has a low Nd concentration but a higher Pr concentration than the core portion 11c, and the shell portion 12s of the second main phase 12 has a low Pr concentration but a higher Nd concentration than the core portion 12c. By forming a main phase 10 having shell portions 11s with a high Pr concentration, like the first main phase 11, the coercivity can be improved. Furthermore, by forming main phase 10 having shell portion 12s with a high concentration of Nd, like second main phase 12, it is possible to suppress a decrease in remanence while maintaining coercivity. By selectively controlling the structure to have this type of structure, rare earth sintered magnet 1 can exhibit magnetic properties that are superior to conventional magnets.

[0023] Furthermore, the average grain size of the crystal grains in main phase 10 is preferably 100 μm or less, and more preferably 0.5 μm to 50 μm to improve magnetic properties. Furthermore, by setting the grain size to approximately 1 μm to 10 μm, the grain size will differ from that of the microstructure produced by hot working, maintaining good magnetization performance and enabling the production of rare earth sintered magnet 1 with magnetic properties superior to conventional magnets.

[0024] The subphase 20 includes a crystalline first subphase 21 primarily composed of an oxide phase represented by the formula (Nd, Pr, R)-O, which includes the element M as a trace component, and a crystalline second subphase 22 primarily composed of an oxide phase represented by the formula (Nd, Pr, R)-O, which includes the element M as a trace component. O represents oxygen. The crystalline subphase 20 collectively refers to the crystalline first subphase 21 and the crystalline second subphase 22. Here, (Nd, Pr, R) means that a portion of Nd and Pr is replaced by a rare earth element R other than Nd and Pr. The R of the first subphase 21 and the R of the second subphase 22 may be the same rare earth element, may be partially different rare earth elements, or may be different rare earth elements. Note that, since the main component elements are listed in parentheses, the first subphase 21 and the second subphase 22 may contain trace amounts of other components in addition to the elements listed in parentheses.

[0025] As described above, the subphase 20, i.e., the first subphase 21 and the second subphase 22, contain the element M as a trace component. The concentration of the element M contained in the first subphase 21 and the second subphase 22 is higher in the second subphase 22 than in the first subphase 21. In other words, when the concentration of the element M in the first subphase 21 is Cs1M and the concentration of the element M in the second subphase 22 is Cs2M, the relationship Cs1M<Cs2M is satisfied.

[0026] Here, "the concentration of element M is higher in the second subphase 22 than in the first subphase 21" means that, by mapping analysis using EPMA, the detected intensity of element M is higher on average in the second subphase 22 than in the first subphase 21. More specifically, this means that the intensity of element M detected by EPMA in the second subphase 22 is higher than the average intensity of element M detected by EPMA, and the intensity of element M detected by EPMA in the first subphase 21 is lower than the average intensity of element M detected by EPMA.

[0027] Furthermore, in the subphase 20, the element M is present in high concentration in the second subphase 22, and therefore forms a non-magnetic phase that magnetically separates the main phases 10, thereby contributing to improving the magnetic properties. In other words, by making the concentration of element M higher in the second subphase 22 than in the first subphase 21, high magnetic properties, particularly coercivity, can be obtained without adding a heavy rare earth element, and deterioration of the magnetic properties with increasing temperature can be suppressed.

[0028] The rare earth sintered magnet 1 according to the first embodiment satisfies the general formula (Nd, Pr, R)-Fe-B-M, where R is one or more rare earth elements selected from the group consisting of Nd and Pr, and M is one or more elements selected from the group consisting of Ga, Al, Cu, and Co. 14 The alloy comprises a main phase 10 including crystal grains based on a B crystal structure, and a subphase 20 present between the main phase 10 and the main phase 10. The main phase 10 has core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c. The main phase 10 also has a first main phase 11 in which CNd > CPr and a second main phase 12 in which CNd < CPr, with the first main phase 11 and the second main phase 12 being mixed together. The subphase 20 has a crystalline first subphase 21 and a second subphase 22 that are primarily composed of an oxide phase expressed as (Nd, Pr, R)—O containing the element M as a trace component, and the concentrations of the element M contained in the first subphase 21 and the second subphase 22 are higher in the second subphase 22 than in the first subphase 21. With this configuration, it is possible to obtain a rare earth sintered magnet 1 that has high magnetic properties, specifically coercive force, without adding heavy rare earth elements, and that suppresses deterioration of the magnetic properties with increasing temperature.

[0029] Furthermore, in the rare earth sintered magnet 1 according to the first embodiment, the first main phase 11 and the second main phase 12 are configured to satisfy the relational expressions C1Nd>C2Nd and C1Pr<C2Pr. Alternatively, the number of first main phases 11 is greater than the number of second main phases 12. Alternatively, the first main phases 11 are configured to satisfy the relational expressions CNd>SNd and CPr<SPr, and the second main phases 12 are configured to satisfy the relational expressions CNd<SNd, CPr>SPr. This also makes it possible to obtain a rare earth sintered magnet 1 with improved magnetic properties and magnetization, without reducing the use of Nd and adding heavy rare earth elements.

[0030] Second Embodiment In a second embodiment, La and Sm are selected as the rare earth element R in the rare earth sintered magnet 1 according to the first embodiment.

[0031] 2 is a diagram schematically illustrating an example of the structure of a rare earth sintered magnet according to embodiment 2 in a sintered state. The same components as those in embodiment 1 are denoted by the same reference numerals, and their description will be omitted. The rare earth sintered magnet 1 according to embodiment 2 has a main phase 10 and a subphase 20. The main phase 10 includes a first main phase 11 and a second main phase 12, as described in embodiment 1. The subphase 20 includes a first subphase 21 and a second subphase 22, as described in embodiment 1.

[0032] When La and Sm are selected as the rare earth element R, the use of Nd is reduced and heavy rare earth elements are not used, thereby improving the magnetic properties and further increasing the effect of having superior magnetization compared to conventional magnets. In this example, the main phase 10 is (Nd, Pr, La, Sm)Fe 14 It has the formula RFeB. 14 The reason for using rare earth elements containing La and Sm as the rare earth element R in rare earth sintered magnet 1 having the B crystal structure is that calculations of magnetic interaction energy using molecular orbital methods indicate that adding La and Sm to a composition results in a practical rare earth sintered magnet 1 that can significantly suppress deterioration in magnetic properties with increasing temperature. Furthermore, intentionally segregating La and Sm to grain boundaries, which are an example of subphases 20, relatively diffuses Nd and Pr into main phase 10, thereby increasing the magnetocrystalline anisotropy of main phase 10. This forms a core-shell structure in which areas of high and low magnetic anisotropy exist within main phase 10, creating an environment that makes it easy to produce a rare earth sintered magnet 1 that includes a first main phase 11 where CNd > CPr and a second main phase 12 where CNd < CPr.

[0033] However, if the amounts of La and Sm added are too large, the amounts of Nd and Pr, which are elements with high magnetic anisotropy constants and saturation magnetic polarization, will decrease, resulting in a deterioration of magnetic properties. Therefore, when the composition ratios of Nd, Pr, La, and Sm are A, B, C, and D, respectively, it is preferable that (A+B)>(C+D).

[0034] In the rare earth sintered magnet 1 according to the second embodiment, where R = La and Sm, the subphase 20 includes a crystalline first subphase 21 primarily composed of an oxide phase expressed as (Nd, Pr, La, Sm)-O, containing the element M as a trace component, and a crystalline second subphase 22 primarily composed of an oxide phase expressed as (Nd, Pr, La)-O, containing the element M as a trace component. Thus, the first subphase 21 has a higher Sm concentration than the second subphase 22. In other words, in the subphase 20 of the rare earth sintered magnet 1, the first subphase 21 forms an Sm-enriched portion with a higher Sm concentration than the second subphase 22. This not only improves the magnetic properties at room temperature, but also suppresses degradation of the magnetic properties as the temperature increases.

[0035] Furthermore, there may be a high-concentration portion 41 where the concentration of Sm is high and a low-concentration portion 42 where the concentration of Sm is low within the first subphase 21. In such a case, the element M may enter the low-concentration portion 42 where the concentration of Sm in the first subphase 21 is lower than the surrounding area. In this case, the concentration of the element M in the low-concentration portion 42 is higher than the concentration of the element M in the high-concentration portion 41.

[0036] As described in the first embodiment, the concentration of element M is higher in the second subphase 22 than in the first subphase 21. Thus, Sm and element M segregate in different subphases 20. Because Sm is present in the first subphase 21 at a high concentration, it diffuses Nd relatively into the main phase 10, improving the magnetocrystalline anisotropy of the main phase 10. Furthermore, because Sm is also present within the crystal grains of the main phase 10, it couples with the ferromagnetic Fe in the same magnetization direction, thereby contributing to improving the remanence. Because element M is present in the second subphase 22 at a high concentration, it forms a nonmagnetic phase that magnetically separates the main phases 10, thereby contributing to improving the magnetic properties. The presence of Sm and element M in different subphases 20 at high concentrations makes it possible to simultaneously improve both the remanence and the coercivity.

[0037] Here, "the concentration of Sm is higher in the first subphase 21 than in the second subphase 22" means that, by mapping analysis using EPMA, the detected intensity of Sm is higher on average in the first subphase 21 than in the second subphase 22. More specifically, this means that the intensity of Sm detected by EPMA in the first subphase 21 is higher than the average intensity of Sm detected by EPMA, and the intensity of Sm detected by EPMA in the second subphase 22 is lower than the average intensity of Sm detected by EPMA.

[0038] The crystalline subphase 20 is a collective term for the crystalline first subphase 21 and the crystalline second subphase 22, which exist between the main phase 10. The crystalline first subphase 21 is represented by (Nd, Pr, La, Sm)-O containing the element M as a trace component, and the crystalline second subphase 22 is represented by (Nd, Pr, La)-O containing the element M as a trace component. Here, (Nd, Pr, La, Sm) means that Nd and Pr are partially substituted with La and Sm. Note that, since the main component elements are listed in parentheses, the first subphase 21 and the second subphase 22 may contain trace amounts of other components in addition to the elements listed in parentheses. In one example, the second subphase 22, represented by (Nd, Pr, La)-O containing the element M as a trace component, contains a trace amount of Sm.

[0039] In rare earth sintered magnet 1 according to the second embodiment, there is a difference in the concentrations of La and Sm between main phase 10 and subphase 20, and La and Sm are more segregated in subphase 20 than in main phase 10. That is, the sum of the La concentrations in first subphase 21 and second subphase 22 is equal to or greater than the La concentration in main phase 10, and the sum of the Sm concentrations in first subphase 21 and second subphase 22 is equal to or greater than the Sm concentration in main phase 10. Specifically, the La and Sm concentrations in subphase 20 are equal to or greater than the La and Sm concentrations in main phase 10. Here, the La concentration in main phase 10 is the sum of the La concentration in first main phase 11 and the La concentration in second main phase 12. That is, the sum of the La concentrations in first subphase 21 and second subphase 22 is higher than the sum of the La concentrations in first main phase 11 and second main phase 12. The Sm concentration in the main phase 10 is the sum of the Sm concentration in the first main phase 11 and the Sm concentration in the second main phase 12. In other words, the sum of the Sm concentrations in the first subphase 21 and the second subphase 22 is higher than the sum of the Sm concentrations in the first main phase 11 and the second main phase 12.

[0040] Here, when the concentration of La contained in the main phase 10 is X, the concentration of La contained in the first subphase 21 is X1, the concentration of La contained in the second subphase 22 is X2, the concentration of Sm contained in the main phase 10 is Y, the concentration of Sm contained in the first subphase 21 is Y1, and the concentration of Sm contained in the second subphase 22 is Y2, the relationship of the following formula (1) is satisfied.

[0041] 1<(Y1+Y2) / Y<(X1+X2) / X (1)

[0042] Furthermore, from the viewpoint of improving magnetic properties, the concentrations of Nd and Pr contained in the main phase 10 satisfy the relationships of the following formulas (2) and (3).

[0043] (CNd+SNd)>(X+Y)...(2) (CPr+SPr)>(X+Y)...(3)

[0044] In the above, the La concentration in the main phase 10 is the sum of the La concentrations in the first main phase 11 and the second main phase 12, and the Sm concentration in the main phase 10 is the sum of the Sm concentrations in the first main phase 11 and the second main phase 12. This indicates that both La and Sm are segregated in the subphase 20 rather than in the main phase 10. However, when viewed locally, the sum of the respective La and Sm concentrations in the first main phase 11 and the second main phase 12 and the sum of the respective La and Sm concentrations in the first subphase 21 and the second subphase 22 may not satisfy the above-mentioned relationship. Therefore, more specifically, the La concentration in the main phase 10 indicates the average of the La concentrations in the first main phase 11 and the second main phase 12, and the Sm concentration in the main phase 10 indicates the average of the Sm concentrations in the first main phase 11 and the second main phase 12. In this case, the La concentration in the subphase 20, i.e., the sum of the La concentrations in the first subphase 21 and the second subphase 22, means the average La concentration in the first subphase 21 and the second subphase 22, and the Sm concentration in the subphase 20, i.e., the sum of the Sm concentrations in the first subphase 21 and the second subphase 22, means the average Sm concentration in the first subphase 21 and the second subphase 22.

[0045] La is present in high concentrations at grain boundaries during the manufacturing process, particularly during heat treatment, and thus relatively diffuses Nd and Pr into main phase 10. As a result, rare earth sintered magnet 1 in embodiment 2 improves magnetocrystalline anisotropy without consuming Nd and Pr in main phase 10 at grain boundaries. Sm is also present in higher concentrations in subphase 20, particularly first subphase 21, than in main phase 10, and thus, like La, relatively diffuses Nd into main phase 10, improving magnetocrystalline anisotropy.

[0046] Next, La and Sm form tetragonal RFe 14 The following explains which atomic sites in the tetragonal NdFeB crystal structure are substituted. 143 is a diagram showing atomic sites in the B crystal structure. The crystal structure shown in FIG. 3 is, for example, shown in FIG. 1 of Reference Technical Document 1 below. The stabilization energy due to substitution is calculated by band calculation and molecular field approximation of the Heisenberg model, and the substituted site is determined by the value of that energy. (Reference Technical Document 1) JFHerbst et al. "Relationships between crystal structure and magnetic properties in Nd2Fe 14 PHYSICAL REVIEW B. 1984, Vol.29, No.7, p. 4176-4178.

[0047] First, we will explain how to calculate the stabilization energy in La. The stabilization energy in La is calculated by 56 Using a B4 crystal cell, (Nd7La1)Fe 56 B4 + Nd and Nd8 (Fe 55 The energy difference between La and B+Fe can be calculated. The smaller the energy value, the more stable the site is when an atom is substituted at that site. In other words, La is likely to be substituted at the atomic site with the smallest energy. In this calculation, when La is substituted for the original atom, the tetragonal RFe 14 The lattice constant in the B crystal structure is not changed by the difference in atomic radius. Table 1 shows the stabilization energy of La at each substitution site when the environmental temperature is changed.

[0048]

[0049] According to Table 1, the stable substitution site for La is the Nd(f) site at temperatures above 1000 K, and the Fe(c) site at temperatures of 293 K and 500 K. As described below, the rare earth sintered magnet 1 according to embodiment 2 is produced by heating the raw materials for the rare earth sintered magnet 1 to a temperature of 1000 K or above, melting them, and then rapidly cooling them. Therefore, the raw materials for the rare earth sintered magnet 1 are believed to be maintained at a temperature above 1000 K, i.e., 727°C or above, and preferably at approximately 1300 K, i.e., 1027°C. At this time, La is believed to be substituted at the Nd(f) site or the Nd(g) site. While La is believed to preferentially substitute for the energetically stable Nd(f) site, it is also possible for La to substitute for the Nd(g) site, which has a smaller energy difference among the La substitution sites. For this reason, the Nd(g) site is also considered a candidate for La substitution.

[0050] Furthermore, when rare earth sintered magnet 1 is produced using the manufacturing method described below, the temperature during sintering is above 1000 K. However, by undergoing the first, second, third, fourth, and cooling steps described below, the Fe(c) sites shown in Table 1 are repeatedly maintained in an energetically stable temperature range. In other words, the substitution of La at the Nd sites of main phase 10 is maintained in an unstable energy state. In other words, when rare earth sintered magnet 1 is produced as a raw material, La is primarily substituted at the Nd sites of main phase 10. However, in rare earth sintered magnet 1 produced using the manufacturing method described below, by repeatedly holding rare earth sintered magnet 1 in a temperature range that is intentionally unstable in energy relative to the Nd sites of main phase 10, a certain amount of La is selectively released from the Nd sites of main phase 10, resulting in La segregation in subphase 20. As a result, main phase 10 promotes the formation of a characteristic core-shell structure.

[0051] Next, we will explain how to calculate the stabilization energy of Sm. The stabilization energy of Sm is calculated by (Nd7Sm1)Fe 56 B4 + Nd and Nd8 (Fe 55 Sm1)B4 + Fe. By substituting atoms, tetragonal R2Fe14 The lattice constant in the B crystal structure does not change, as in the case of La. Table 2 shows the stabilization energy of Sm at each substitution site when the environmental temperature is changed.

[0052]

[0053] According to Table 2, the stable substitution site of Sm is the Nd(g) site at any temperature, unlike La. It is thought that Sm is preferentially substituted at the energetically stable Nd(g) site, but substitution at the Nd(f) site, which has a small energy difference among the substitution sites of Sm, is also possible.

[0054] When rare earth sintered magnet 1 is produced by the production method described below, substitution at the Nd(g) site of main phase 10 is most stable in terms of energy. However, as described above, by maintaining the temperature range in which substitution of La at the Nd site of main phase 10 becomes unstable, some Sm is released from the Nd site of main phase 10 along with La and segregates into subphase 20. As a result, there is a difference in the concentrations of La and Sm between main phase 10 and subphase 20. The sum of the La concentrations in first subphase 21 and second subphase 22 is equal to or greater than the La concentration in main phase 10, and the sum of the Sm concentrations in first subphase 21 and second subphase 22 is equal to or greater than the Sm concentration in main phase 10. More specifically, the average La concentration in the first subphase 21 and the second subphase 22 is equal to or greater than the average La concentration in the first main phase 11 and the second main phase 12, and the average Sm concentration in the first subphase 21 and the second subphase 22 is equal to or greater than the average Sm concentration in the first main phase 11 and the second main phase 12. In other words, it can be said that La and Sm segregate in the subphase 20.

[0055] Comparing La and Sm, it can be seen that, from an energetic perspective, La, which is maintained in a temperature range where the energy state is unstable, is overwhelmingly more likely to segregate into the subphase 20. As a result, in the case of a rare earth sintered magnet 1 prepared with La and Sm at approximately the same concentrations, La will segregate to a greater extent into the subphase 20 than Sm present in the rare earth sintered magnet 1. By repeatedly maintaining the rare earth sintered magnet 1 in this temperature range, a difference in the concentration of Sm, which has a low segregation rate, is created in the subphase 20, resulting in the formation of the first subphase 21 and the second subphase 22. This promotes the formation of a core-shell structure in the main phase 10.

[0056] Here, we will explain Nd as a representative element, as shown in Figure 3. However, because Nd and Pr are produced as mixtures, as exemplified by Di (didymium), it is believed that the energy levels of Nd and Pr are close. Therefore, the same can be said when Nd is replaced with Pr. By having both Nd and Pr present in rare earth sintered magnet 1, it is possible to form main phase 10 with two types of core-shell structures.

[0057] As described above, the rare earth sintered magnet 1 of the second embodiment satisfies the general formula (Nd, Pr, R)-Fe-B-M when R is one or more rare earth elements selected from the group consisting of Nd and Pr, and M is one or more elements selected from the group consisting of Ga, Al, Cu, and Co, and has a structure of NdFe. 14The composite material comprises a main phase 10 including crystal grains based on a B crystal structure, and a subphase 20 present between the main phase 10 and the main phase 10. The main phase 10 has core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c. When R=La, Sm, the subphase 20 comprises a crystalline first subphase 21 mainly composed of an oxide phase expressed as (Nd, Pr, La, Sm)-O containing the element M as a trace component, and a crystalline second subphase 22 mainly composed of an oxide phase expressed as (Nd, Pr, La)-O containing the element M as a trace component. The first subphase 21 has a higher Sm concentration than the second subphase 22, and the second subphase 22 has a higher element M concentration than the first subphase 21. In other words, the rare earth sintered magnet 1 has two main phases 10 and two subphases 20, with different concentrations of Sm and element M in the subphases 20. Because Sm is present in high concentrations in the first subphase 21, it relatively diffuses Nd into the main phase 10, improving the magnetocrystalline anisotropy of the main phase 10. Furthermore, because Sm is also present within the crystal grains of the main phase 10, it bonds with the ferromagnetic Fe in the same magnetization direction, contributing to improved remanence. Because element M is present in high concentrations in the second subphase 22, it forms a nonmagnetic phase that magnetically separates the main phases 10, contributing to improved magnetic properties. The presence of high concentrations of Sm and element M in different subphases 20 makes it possible to simultaneously improve remanence and coercivity. This makes it possible to provide a rare earth sintered magnet 1 with superior magnetic properties, such as temperature characteristics, compared to conventional magnets.

[0058] Furthermore, by setting R to La or Sm, main phase 10 is a mixture of first main phase 11, in which CNd > CPr, and second main phase 12, in which CNd < CPr. In other words, rare earth sintered magnet 1 has two main phases 10, the first main phase 11 and the second main phase 12. Focusing on cores 11c and 12c of the two main phases 10, it is easy to produce main phases 10 with two types of core-shell structures, in which the concentration of Nd is higher in first main phase 11 than in Pr, and conversely, the concentration of Pr is higher in second main phase 12 than in Nd. As a result, rare earth sintered magnet 1 of embodiment 2 can improve magnetic properties and further enhance the effect of having superior magnetizability compared to conventional magnets, without using heavy rare earth elements and while minimizing the use of Nd.

[0059] Embodiment 3 In embodiment 3, the method for producing the rare earth sintered magnet 1 described in embodiments 1 and 2 will be explained separately as a method for producing a rare earth sintered magnet alloy that is the raw material for the rare earth sintered magnet 1, and a method for producing the rare earth sintered magnet 1 using the rare earth sintered magnet alloy.

[0060] 4 is a flowchart showing an example of the steps of a method for producing a rare earth sintered magnet alloy according to embodiment 3. As shown in FIG. 4, the method for producing the rare earth sintered magnet alloy used as the raw material for the rare earth sintered magnet 1 includes a melting step (step S1) in which raw materials for the rare earth sintered magnet alloy, including the elements that make up the rare earth sintered magnet 1, are heated to a temperature of 1000 K or higher to melt them, a first cooling step (step S2) in which the molten raw materials are cooled on a rotating rotor to obtain a solidified alloy, and a second cooling step (step S3) in which the solidified alloy is further cooled in a container. This allows the rare earth sintered magnet alloy to be produced. Each step is described below.

[0061] In the melting step of step S1, the raw materials for the rare earth sintered magnet alloy are heated to a temperature of 1000 K or higher in a crucible in an atmosphere containing an inert gas such as Ar (argon) or in a vacuum to melt them. This produces a molten alloy of the rare earth sintered magnet alloy. The raw materials can be Nd, Pr, R, Fe, B, and M. When producing the rare earth sintered magnet 1 of embodiment 2, R is La and Sm. M can be one or more elements selected from the group consisting of Ga, Al, Cu, and Co. Furthermore, FeB may be used as a raw material instead of B.

[0062] Next, in the first cooling step of step S2, the molten alloy prepared in the melting step is poured into a tundish and then onto a single roll, which is a rotating body. As a result, the molten alloy is rapidly cooled on the single roll rotating in a predetermined direction, and a solidified alloy thinner than the ingot alloy is prepared from the molten alloy on the single roll. Here, a single roll is used as the rotating body, but this is not limiting, and the molten alloy may be rapidly cooled by contacting it with a twin roll, a rotating disk, a rotating cylindrical mold, or the like. From the viewpoint of efficiently obtaining a thin solidified alloy, the cooling rate in the first cooling step is set to 10°C / sec or more and 10°C / sec or more. 7 ° C. / sec or less, and 3 °C / sec or more 10 4 The melting rate is preferably set to 0.03°C / sec or less. The thickness of the solidified alloy is in the range of 0.03 mm to 10 mm. The molten alloy starts to solidify from the portion in contact with the single roll, and crystals grow in a columnar or needle shape in the thickness direction from the contact surface with the single roll.

[0063] Thereafter, in the second cooling step of step S3, the thin solidified alloy prepared in the first cooling step is placed in a tray container and cooled. The thin solidified alloy is broken into flakes of rare earth sintered magnet alloy when it enters the tray container and is cooled. Depending on the cooling rate, a ribbon-shaped rare earth sintered magnet alloy may be obtained, and the shape is not limited to flakes. From the viewpoint of obtaining a rare earth sintered magnet alloy having a structure with good temperature characteristics of magnetic properties, the cooling rate in the second cooling step is set to 10 -2 °C / sec or more 105 ° C. / sec or less, and -1 °C / sec or more 10 2 It is more preferable to set it to ° C. / sec or less.

[0064] The rare earth sintered magnet alloy obtained through these processes has a minor axis size of 3 μm to 10 μm and a major axis size of 10 μm to 300 μm. In the case of the second embodiment, the rare earth sintered magnet alloy has a fine crystalline structure containing a (Nd, Pr, La, Sm)-Fe-B crystalline phase containing element M as a trace component and a crystalline subphase 20 of an oxide represented by (Nd, Pr, La, Sm)-O containing element M as a trace component. Hereinafter, the (Nd, Pr, La, Sm)-Fe-B crystalline phase containing element M as a trace component will also be referred to as the (Nd, Pr, La, Sm)-Fe-B crystalline phase, and the crystalline subphase 20 of an oxide represented by (Nd, Pr, La, Sm)-O containing element M as a trace component will also be referred to as the (Nd, Pr, La, Sm)-O phase. The (Nd, Pr, La, Sm)-O phase is a non-magnetic phase composed of oxides with a relatively high concentration of rare earth elements. The thickness of the (Nd, Pr, La, Sm)-O phase corresponds to the width of the grain boundary and is 10 μm or less. The rare earth sintered magnet alloy produced by the above manufacturing method has undergone a rapid cooling process, and therefore has a finer structure than rare earth sintered magnet alloys obtained by mold casting.

[0065] Next, a method for manufacturing the rare earth sintered magnet 1 using a rare earth sintered magnet alloy will be described. FIG. 5 is a flowchart showing an example of the steps of the method for manufacturing the rare earth sintered magnet according to the third embodiment. As shown in FIG. 5, the method for manufacturing the rare earth sintered magnet 1 includes a crushing step (step S21) for crushing a rare earth sintered magnet alloy having a (Nd, Pr, La, Sm)-Fe-B crystalline phase and a (Nd, Pr, La, Sm)-O phase; a compacting step (step S22) for compacting the crushed rare earth sintered magnet alloy powder to prepare a compact; a sintering step (step S23) for sintering the compact at a predetermined sintering temperature to obtain a sintered body; an aging step (step S24) for aging the sintered body to improve the magnetic properties, such as the coercivity, of the rare earth sintered magnet 1; and a cooling step (step S25) for cooling the aged sintered body. Each step will be described below.

[0066] In the pulverization step S21, a rare earth sintered magnet alloy having a (Nd, Pr, La, Sm)-Fe-B crystalline phase and a (Nd, Pr, La, Sm)-O phase, produced according to the method for producing a rare earth sintered magnet alloy shown in FIG. 4, is pulverized to obtain a rare earth sintered magnet alloy powder having a particle size of 200 μm or less, preferably 0.5 μm to 100 μm, and further, when considering magnetization performance, approximately 1 μm to 10 μm. The rare earth sintered magnet alloy is pulverized, for example, using an agate mortar, stamp mill, jaw crusher, or jet mill. In particular, to reduce the particle size of the powder, it is preferable to pulverize the rare earth sintered magnet alloy in an atmosphere containing an inert gas. Pulverizing the rare earth sintered magnet alloy in an atmosphere containing an inert gas can suppress the incorporation of oxygen into the powder. However, if the atmosphere during pulverization does not affect the magnetic properties of the magnet, the rare earth sintered magnet alloy may be pulverized in air. When manufacturing the rare earth sintered magnet 1 of embodiment 1, the La and Sm in the rare earth sintered magnet alloy used to manufacture the rare earth sintered magnet 1 of embodiment 2 can be replaced with a rare earth element R other than Nd and Pr. In other words, it is sufficient to pulverize a rare earth sintered magnet alloy having a (Nd, Pr, R)—Fe—B crystalline phase and a (Nd, Pr, R)—O phase.

[0067] In the molding step of step S22, the rare earth sintered magnet alloy powder is compression molded in a mold to which a magnetic field is applied to prepare a molded body. Here, the magnetic field applied can be, for example, 2 T. Note that molding may be performed without applying a magnetic field, rather than in a magnetic field.

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

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

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

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

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

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

[0074] Finally, in the cooling step of step S25, the sintered body held in the fourth aging step is held at a temperature below the second aging temperature, specifically, at a temperature between 200°C and 450°C for 0.1 to 5 hours. The body is then cooled to room temperature, completing the rare earth sintered magnet 1. Cooling is preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation.

[0075] As described above, by controlling the temperature and time during the sintering, aging, and cooling processes, the sintered body can be repeatedly maintained in a temperature range where the energy is unstable. This allows for the coexistence of a first main phase 11 consisting of CNd > CPr and a second main phase 12 consisting of CNd < CPr. In other words, the rare earth sintered magnet 1 has two main phases 10, the first main phase 11 and the second main phase 12. Focusing on the cores 11c and 12c of the two main phases 10, the first main phase 11 has a higher Nd concentration than the Pr concentration, while the second main phase 12 has a higher Pr concentration than the Nd concentration. This allows for the production of a rare earth sintered magnet 1 with these characteristics.

[0076] Furthermore, in addition to the first main phase 11 and second main phase 12 of the first embodiment, a rare earth sintered magnet 1 can be produced that has a crystalline first subphase 21 that is primarily composed of an oxide phase expressed as (Nd, Pr, La, Sm)-O and that contains the element M as a trace component, and a crystalline second subphase 22 that is primarily composed of an oxide phase expressed as (Nd, Pr, La)-O and that contains the element M as a trace component, in which the first subphase 21 has a higher Sm concentration than the second subphase 22, and the second subphase 22 has a higher element M concentration than the first subphase 21. That is, in the aging process and cooling process, a crystalline first subphase 21 mainly composed of an oxide phase represented by (Nd, Pr, La, Sm)-O and a crystalline second subphase 22 mainly composed of an oxide phase represented by (Nd, Pr, La)-O are generated from the (Nd, Pr, La, Sm)-O phase, depending on the concentration of element M, for example. The second subphase 22 may contain a trace amount of Sm. Furthermore, since the Sm concentration of the first subphase 21 is higher than that of the second subphase 22, the first subphase 21 can be said to form an Sm-enriched portion in the subphase 20. Furthermore, the first subphase 21 may have a high-concentration portion 41 with a high Sm concentration and a low-concentration portion 42 with a low Sm concentration. In this case, the high-concentration portion 41 of the first subphase 21 can be said to form an Sm-enriched portion.

[0077] This makes it possible to provide a rare earth sintered magnet 1 that has superior magnetization performance and magnetic properties compared to conventional magnets, while not using heavy rare earth elements and limiting the use of Nd.

[0078] In the third embodiment, a rare earth sintered magnet alloy having a (Nd, Pr, La, Sm)-Fe-B crystalline phase and a (Nd, Pr, La, Sm)-O phase is pulverized to form a rare earth sintered magnet alloy powder, and the compact is sintered to form a sintered body, which is then aged to produce the rare earth sintered magnet 1. In this way, the rare earth sintered magnet 1 according to the second embodiment can be produced.

[0079] In addition, in the third embodiment, the temperatures and times in the sintering, aging, and cooling steps are controlled. In one example, in the first aging step, the obtained sintered body is held at a first aging temperature, which is a temperature lower than the sintering temperature, specifically within a range of 700°C to less than 950°C, for 0.1 to 10 hours, preferably 0.5 to 5 hours. In the second aging step, the sintered body is held at a second aging temperature, which is a temperature lower than the first aging temperature, specifically within a range of 450°C to less than 700°C, for 0.1 to 10 hours, preferably 1.0 to 7 hours. In the third aging step, the temperature is again raised to the first aging temperature, specifically within a range of 700°C to less than 950°C, and the sintered body is held at the first aging temperature for 0.1 to 10 hours, preferably 0.5 to 5 hours. In the fourth aging step, the sintered body is again held at the second aging temperature, specifically, at a temperature in the range of 450°C to less than 700°C for 0.1 to 10 hours, preferably 1.0 to 7 hours. In this way, the temperature and time are controlled so that two sets of the first and second aging steps are performed. This creates a state in which the sintered body is repeatedly held in a temperature range with an unstable energy state. As a result, a rare earth sintered magnet 1 is obtained that contains a mixture of a first main phase 11 consisting of CNd>CPr and a second main phase 12 consisting of CNd<CPr. In other words, the rare earth sintered magnet 1 has two types of main phases 10, a first main phase 11 and a second main phase 12, and when focusing on the core portions 11c, 12c of the two types of main phases 10, it is possible to selectively manufacture a rare earth sintered magnet 1 in which the first main phase 11 has a higher Nd concentration than the Pr concentration, and conversely, the second main phase 12 has a higher Pr concentration than the Nd concentration.

[0080] Furthermore, the above manufacturing process can selectively produce a rare earth sintered magnet 1 having a characteristic structure that includes a crystalline first subphase 21 primarily composed of an oxide phase expressed as (Nd, Pr, La, Sm)-O containing the element M as a trace component, and a crystalline second subphase 22 primarily composed of an oxide phase expressed as (Nd, Pr, La)-O containing the element M as a trace component, where the first subphase 21 has a higher Sm concentration than the second subphase 22, and the second subphase 22 has a higher M concentration than the first subphase 21. Furthermore, in the subphase 20, the first subphase 21 has a higher Sm concentration than the second subphase 22, so that a rare earth sintered magnet 1 can be produced that has a characteristic structure that includes an Sm-enriched portion, i.e., the first subphase 21 where Sm is enriched. Alternatively, if the first subphase 21 has a high-concentration portion 41 with a high Sm concentration and a low-concentration portion 42 with a low Sm concentration, it is possible to produce a rare earth sintered magnet 1 having a characteristic structural structure in which the high-concentration portion 41 is an Sm-enriched portion.

[0081] Embodiment 4 In embodiment 4, a rotor using the rare earth sintered magnet 1 of embodiment 1 or embodiment 2 manufactured by the manufacturing method of embodiment 3 will be described. Figure 6 is a cross-sectional view schematically showing an example of the configuration of a rotor equipped with a rare earth sintered magnet according to embodiment 4. Figure 6 shows a cross section perpendicular to the rotation axis RA of the rotor 100.

[0082] The rotor 100 is rotatable about a rotation axis RA. The rotor 100 includes a rotor core 101 and rare earth sintered magnets 1 that are inserted into magnet insertion holes 102 that are provided in the rotor core 101 along the circumferential direction of the rotor 100. While Fig. 6 shows an example in which four magnet insertion holes 102 are provided in the rotor core 101 and four rare earth sintered magnets 1 are inserted into the magnet insertion holes 102, the number of magnet insertion holes 102 and the number of rare earth sintered magnets 1 may be changed depending on the design of the rotor 100. The rotor core 101 is formed by stacking a plurality of disk-shaped electromagnetic steel plates in the axial direction of the rotation axis RA.

[0083] The rare earth sintered magnets 1 are manufactured according to the manufacturing method described in embodiment 3. The four rare earth sintered magnets 1 are inserted into the corresponding magnet insertion holes 102. The four rare earth sintered magnets 1 are each magnetized so that the magnetic poles of the rare earth sintered magnets 1 on the radially outer side of the rotor 100 are different from adjacent rare earth sintered magnets 1.

[0084] The rotor 100 according to embodiment 4 includes the rare earth sintered magnet 1 according to embodiment 1 or 2, which can achieve improved magnetic properties at room temperature and suppressed degradation of magnetic properties with increasing temperature. As described above, the rare earth sintered magnet 1 according to embodiment 1 or 2 is a rare earth sintered magnet 1 that can suppress degradation of magnetic properties with increasing temperature while maintaining high remanence and coercivity. Therefore, degradation of magnetic properties is suppressed even in high-temperature environments exceeding 100°C. As a result, while avoiding the use of heavy rare earth elements, which are expensive and unevenly distributed across regions and present procurement risks, and substituting inexpensive rare earth elements for Nd, it is possible to improve magnetic properties and magnetization, and stabilize the operation of the rotor 100 even in high-temperature environments exceeding 100°C. Furthermore, because the rare earth sintered magnet 1 according to embodiment 1 or 2 has superior magnetization performance compared to conventional magnetization magnets, it is possible to magnetize the rotor 100 in an assembled state with the rare earth sintered magnet 1 set therein, thereby facilitating handling in the manufacturing process. Furthermore, the magnetization process can be performed with reduced voltage, which contributes to energy savings.

[0085] Embodiment 5 In embodiment 5, a rotating machine equipped with rotor 100 according to embodiment 4 will be described. Fig. 7 is a cross-sectional view schematically showing an example of the configuration of a rotating machine according to embodiment 5. Fig. 7 shows a cross section in a direction perpendicular to rotation axis RA of rotor 100.

[0086] The rotating machine 120 includes a rotor 100 rotatable about the rotation axis RA described in the fourth embodiment, and an annular stator 130 disposed coaxially with the rotor 100 and facing the rotor 100. The stator 130 is formed by laminating a plurality of electromagnetic steel sheets in the axial direction of the rotation axis RA. The configuration of the stator 130 is not limited to this, and an existing configuration can also be adopted. The stator 130 has teeth 131 protruding toward the rotor 100 and disposed along the inner surface of the stator 130. Windings 132 are attached to the teeth 131. The windings 132 may be wound in a concentrated winding or a distributed winding manner, for example. In other words, the stator 130 has windings 132 attached to the teeth 131 protruding toward the rotor 100 on the inner surface on the side where the rotor 100 is disposed, and has an annular structure disposed facing the rotor 100. The rotor 100 in the rotating machine 120 needs to have two or more magnetic poles, i.e., two or more rare earth sintered magnets 1. Also, while Fig. 7 shows an example of an embedded magnet rotor 100, it may also be a surface magnet rotor 100 in which the rare earth sintered magnets 1 are fixed to the outer periphery with an adhesive.

[0087] The rotating machine 120 in embodiment 5 includes the rare earth sintered magnet 1 according to embodiment 1 or 2, which is capable of improving magnetic properties at room temperature and suppressing degradation of magnetic properties with increasing temperature. As described above, the rare earth sintered magnet 1 according to embodiment 1 or 2 is a rare earth sintered magnet 1 that can suppress degradation of magnetic properties with increasing temperature while maintaining high remanence and coercivity, and therefore suppresses degradation of magnetic properties even in high-temperature environments exceeding 100°C. As a result, while avoiding the use of heavy rare earth elements that are expensive, unevenly distributed across regions, and posing procurement risks, and substituting inexpensive rare earth elements for Nd, it is possible to improve magnetic properties and magnetization, stably drive the rotor 100, and stabilize the operation of the rotating machine 120, even in high-temperature environments exceeding 100°C.

[0088] The rare earth sintered magnet 1 of the present disclosure will be described in detail below with reference to examples and comparative examples.

[0089] In Examples 1 to 8, rare earth sintered magnet 1 was manufactured by the method shown in Embodiment 3 using samples of a (Nd, Pr, La, Sm)-Fe-B crystalline phase containing element M as a trace component and a (Nd, Pr, La, Sm)-O phase containing element M as a trace component from a plurality of rare earth sintered magnet alloys with different compositions. In Examples 1 to 8, rare earth sintered magnet 1 was manufactured using rare earth sintered magnet alloys with varying contents of Nd, Pr, La, and Sm. That is, in Examples 1 to 8, rare earth sintered magnet 1 was manufactured by the manufacturing method shown in Embodiment 3 using rare earth sintered magnet alloys containing a (Nd, Pr, La, Sm)-Fe-B crystalline phase containing element M as a trace component and a (Nd, Pr, La, Sm)-O phase containing element M as a trace component. M is one or more elements selected from the group consisting of Ga, Al, Cu, and Co. Here, the case where M is Co will be taken as an example.

[0090] In Comparative Examples 1 to 14, samples of a plurality of rare earth sintered magnet alloys with different compositions, represented by R-Fe-B-M, were used to experimentally produce rare earth sintered magnet 1 by a general rare earth magnet manufacturing method such as that shown in Patent Document 1 or Patent Document 2. In the samples of rare earth sintered magnet 1 according to Comparative Examples 1 to 14, the R portion was changed.

[0091] In Comparative Examples 1 to 7, rare earth sintered magnet 1 is manufactured using a rare earth sintered magnet alloy in which R includes Nd and either a heavy rare earth element Dy or one of Pr, La, and Sm, and M includes one or more elements selected from the group consisting of Ga, Al, Cu, and Co, using the manufacturing method described in Patent Document 1. Here, we take the example of a case in which M is Co. However, Comparative Example 1 uses Nd—Fe—B—M, which does not include any rare earth elements R other than Nd, and Comparative Example 2 uses Nd—Fe—B, which does not include any rare earth elements R other than Nd and does not include any element M.

[0092] In Comparative Examples 8 to 14, rare earth sintered magnet 1 is produced using a rare earth sintered magnet alloy in which R includes Nd and either a heavy rare earth element Dy or one of Pr, La, and Sm, and M includes one or more elements selected from the group consisting of Ga, Al, Cu, and Co, using the production method disclosed in Patent Document 2. Here, the case in which M is Co is taken as an example. However, Comparative Example 8 uses Nd—Fe—B—M, which does not include any rare earth elements R other than Nd, and Comparative Example 9 uses Nd—Fe—B, which does not include any rare earth elements R other than Nd and does not include element M. The production method disclosed in Patent Document 2 includes a step of hot working the sintered compact.

[0093] Table 3 shows the general formula of the rare earth sintered magnets of Examples 1 to 8 and Comparative Examples 1 to 14, the contents of the elements constituting R, the analysis results of the structural morphology, and the evaluation results of the magnetic properties and magnetization performance. Table 3 also shows the general formula of the main phase 10 of each sample, which is the rare earth sintered magnet 1 of Examples 1 to 8 and Comparative Examples 1 to 14.

[0094]

[0095] Next, a method for analyzing the structure of the rare earth sintered magnet 1 of Examples 1 to 8 and Comparative Examples 1 to 14 will be described. The structure of the rare earth sintered magnet 1 is determined by elemental analysis using a scanning electron microscope (SEM) and an electron probe microanalyzer (EPMA). Here, an FE-EPMA (manufactured by JEOL Ltd., product name: JXA-8530F) is used as the SEM and EPMA. The elemental analysis conditions were an acceleration voltage of 15.0 kV, a probe current of 2.271 e -008 A, the irradiation time is 130 ms, the number of pixels is 512 pixels x 512 pixels, the magnification is 5000 times, and the number of integrations is 1.

[0096] Next, we will explain how to evaluate the magnetic properties of the rare earth sintered magnets 1 of Examples 1 to 8 and Comparative Examples 1 to 14. The magnetic properties were evaluated by measuring the coercivity of multiple samples using a pulse-excitation BH tracer. The maximum magnetic field applied by the BH tracer was 6 T or more, at which point the rare earth sintered magnet 1 was fully magnetized. In addition to pulse-excitation BH tracers, other instruments capable of generating a maximum magnetic field of 6 T or more, such as a DC magnetic fluxmeter (also known as a DC BH tracer), a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), or a physical property measurement system (PPMS), may also be used. Measurements are performed in an atmosphere containing an inert gas such as nitrogen. The magnetic properties of each sample were measured by detecting the magnetization picked up by a search coil or magnetic sensor from the rare earth sintered magnet 1 magnetized by the applied magnetic field. The magnetic properties were measured from the measured magnetic hysteresis, which is the J-H curve or B-H curve. The magnetic properties of each sample were measured at a first measurement temperature T1 and a second measurement temperature T2, which were different from each other. The temperature coefficient α [% / °C] of remanence is the ratio of the difference between the remanence at the first measurement temperature T1 and the remanence at the second measurement temperature T2 to the remanence at the first measurement temperature T1, divided by the temperature difference (T2 - T1). The temperature coefficient β [% / °C] of coercivity is the ratio of the difference between the coercivity at the first measurement temperature T1 and the coercivity at the second measurement temperature T2 to the coercivity at the first measurement temperature T1, divided by the temperature difference (T2 - T1). Therefore, the smaller the absolute values ​​|α| and |β| of the temperature coefficients of the magnetic properties, the more suppressed is the degradation of the magnetic properties of the magnet with increasing temperature.

[0097] Furthermore, the magnetization performance can be measured by calculating the magnetization rate from the ratio of the magnetic flux density measured from the magnetic hysteresis curve when an arbitrary magnetic field is applied at a constant permeance coefficient to the magnetic flux density measured from the magnetic hysteresis curve when a saturating magnetic field is applied. If a high magnetization rate can be obtained even in a weaker magnetic field, it can be said that the magnetization performance is high.

[0098] First, we will explain the analysis results for each sample of Examples 1 to 8 and Comparative Examples 1 to 14. FIG. 8 is a trace of a composition image obtained by analyzing the cross section of the rare earth sintered magnet of Examples 1 to 8 with FE-EPMA. FIGS. 9 to 14 are elemental maps obtained by analyzing the cross section of the rare earth sintered magnet of Examples 1 to 8 with FE-EPMA. FIG. 9 is an elemental map of Nd, FIG. 10 is an elemental map of Pr, FIG. 11 is an elemental map of Co, FIG. 12 is an elemental map of O, FIG. 13 is an elemental map of La, and FIG. 14 is an elemental map of Sm. Note that FIGS. 9 to 14 are elemental maps of the region shown in FIG. 8. Furthermore, since the rare earth sintered magnets 1 of Examples 1 to 8 all showed similar results, FIGS. 8 to 14 show representative examples of Examples 1 to 8. Furthermore, the same components as those in FIGS. 1 and 2 are designated by the same reference numerals.

[0099] As shown in FIGS. 9 and 10, in each of the samples of Examples 1 to 8, R is one or more rare earth elements selected from among Nd and Pr, and the NdFe of rare earth sintered magnet 1 satisfies the general formula (Nd, Pr, R)-Fe-B-M. 14 The main phase 10 includes crystal grains based on the B crystal structure, and has core portions 11 c, 12 c and shell portions 11 s, 12 s that cover the core portions 11 c, 12 c. It can also be seen that the main phase 10 contains a mixture of a first main phase 11 in which CNd > CPr and a second main phase 12 in which CNd < CPr.

[0100] Here, the concentration difference shown between "the first main phase 11 where CNd > CPr and the second main phase 12 where CNd < CPr" means that a clear difference has been found between the detected intensity of Nd and the detected intensity of Pr by mapping analysis using EPMA. Specifically, taking the first main phase 11 as an example, the detected intensity of Nd in the core region 11c by EPMA is higher than the average, and the detected intensity of Pr in the core region 11c by EPMA is lower than the average, in this case showing values ​​near the lower limit. It can be said that the second main phase 12 is the opposite of the first main phase 11.

[0101] More specifically, taking the Nd mapping diagram of Fig. 9 and the Pr mapping diagram of Fig. 10 as examples, the average value of the Nd detection level by EPMA is 32.0, and the average value of the Pr detection level is 45. In the case of the first main phase 11, CNd is higher than 32.0, and CPr is near the lower limit, indicating a clear concentration difference. In addition, the second main phase 12 is the opposite of the first main phase 11, and therefore CPr is higher than 45, and CNd is near the lower limit, indicating a clear concentration difference.

[0102] 11 to 14 , when R = La, Sm, rare earth sintered magnet 1 has, in addition to first main phase 11 and second main phase 12 of embodiment 1, a crystalline first subphase 21 mainly composed of an oxide phase expressed as (Nd, Pr, La, Sm)-O containing element M as a trace component, and a crystalline second subphase 22 mainly composed of an oxide phase expressed as (Nd, Pr, La)-O containing element M as a trace component. It can also be confirmed that the concentration of Sm is higher in first subphase 21 than in second subphase 22, and the concentration of Co, which is element M, is higher in second subphase 22 than in first subphase 21.

[0103] In Table 3, for samples in which the first main phase 11, where CNd>CPr, and the second main phase 12, where CNd<CPr, were confirmed, "◯" was entered in the columns for the first main phase 11 and the second main phase 12, respectively. For samples in which this was not confirmed, "×" was entered in the columns for the first main phase 11 and the second main phase 12, respectively. The concentration difference indicated by an inequality sign means that there is a clear difference in the detected intensities of Nd and Pr. Specifically, in one example, in the case of the first main phase 11, the detected intensity of Nd by EPMA is higher than average, and the detected intensity of Pr by EPMA is near the lower limit. In the case of the second main phase 12, the situation is the opposite to that of the first main phase 11. In cases in which only CNd<CPr was confirmed, as in the case of the second main phase 12, "◯" was entered only in the column for the second main phase 12, and "×" was entered in the column for the first main phase 11.

[0104] Furthermore, in Table 3, for samples having a crystalline first subphase 21 mainly composed of an oxide phase expressed as (Nd, Pr, La, Sm)-O containing the element M as a trace component, and a crystalline second subphase 22 mainly composed of an oxide phase expressed as (Nd, Pr, La)-O containing the element M as a trace component, and for samples for which it was confirmed that the second subphase 22 had a higher concentration of element M than the first subphase 21, a "◯" is entered in the column for "M concentration first subphase < second subphase" under "Subphase" in the item "Structural morphology", and for samples for which it was not confirmed that this was the case, an "X" is entered in the column for "M concentration first subphase < second subphase" under "Subphase" in the item "Structural morphology". Furthermore, for those in which only one subphase 20 exists or there is no difference in Sm concentration between the subphases 20, an "X" is entered in the "M concentration first subphase < second subphase" column of the "Subphase" section of the "Organizational morphology" item.

[0105] The difference in Sm concentration between the first subphase 21 and the second subphase 22 means that, in a mapping analysis using EPMA, the detection intensity of Sm is higher on average in the first subphase 21 than in the second subphase 22. Specifically, taking the Sm mapping diagram of Figure 14 as an example, the average EPMA detection level of Sm is 5.4, whereas the first subphase 21 is higher than 5.4 and the second subphase 22 is lower than 5.4, i.e., the Sm is in an aggregated state and cannot be detected. Furthermore, the difference in Co concentration, which is the element M, between the first subphase 21 and the second subphase 22 means that, in a mapping analysis using EPMA, the detection intensity of Co is higher on average in the second subphase 22 than in the first subphase 21. Specifically, in the Co mapping diagram of FIG. 11 as an example, the average Co detection level of EPMA is 5.4, whereas the second subphase 22 is higher than 5.4 and the first subphase 21 is lower than 5.4, i.e., the two subphases are in an aggregated state and cannot be detected.

[0106] Furthermore, it can be confirmed from the intensity ratio of element mapping obtained by FE-EPMA analysis that the number of first main phases 11 in which CNd>CPr is greater than the number of second main phases 12 in which CNd<CPr is present. When focusing on the shell portions 11s and 12s of the core-shell structure, it can also be confirmed that the first main phases 11 satisfy the relational expressions CNd>SNd and CPr<SPr, and the second main phases 12 satisfy the relational expressions CNd<SNd, CPr>SPr.

[0107] Next, the measurement results of the magnetic properties of each sample in Examples 1 to 8 and Comparative Examples 1 to 14 will be described. Each sample used for magnetic measurement was a block with length, width, and height all measuring 7 mm. 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, 200°C, is a temperature that can occur in the operating environment of automotive motors and industrial motors.

[0108] First, the remanence and coercivity of each sample in Examples 1 to 8 and Comparative Examples 2 to 14 are judged by comparison with Comparative Example 1. If the remanence and coercivity values ​​at 23°C of each sample are within 1%, which is considered to be a measurement error, of the values ​​in Comparative Example 1, they are judged as "equivalent," if they are 1% or more higher, they are judged as "good," and if they are 1% or less lower, they are judged as "poor."

[0109] Next, the temperature coefficient α of the remanence is calculated using the remanence at the first measurement temperature T1 of 23°C and the remanence at the second measurement temperature T2 of 200°C. The temperature coefficient β of the coercivity is calculated using the coercivity at the first measurement temperature T1 of 23°C and the coercivity at the second measurement temperature T2 of 200°C. The temperature coefficients of the remanence and the coercivity for each sample in Examples 1 to 8 and Comparative Examples 2 to 14 are evaluated by comparing them with Comparative Example 1. For each sample, the absolute value |α| of the temperature coefficient of the remanence and the absolute value |β| of the temperature coefficient of the coercivity for the sample in Comparative Example 1 are compared. If the value is within ±1%, which is considered to be the measurement error, the sample is judged as "equivalent." If the value is lower than -1%, the sample is judged as "good." If the value is higher than +1%, the sample is judged as "poor." For samples judged to be "good," the temperature coefficient is smaller, which suppresses the deterioration of magnetic properties with increasing temperature, making it possible to provide a rare earth sintered magnet 1 with stable magnetic properties even in high-temperature environments.

[0110] Next, the magnetization performance is calculated as the ratio of the magnetic flux density at the intersection of the magnetic hysteresis and permeance coefficient Pc at an applied magnetic field of 20 kOe to the magnetic flux density at the intersection of the magnetic hysteresis and permeance coefficient Pc at an applied magnetic field of 80 kOe, which represents a saturated magnetization state. The magnetization performance of each sample in Examples 1 to 8 and Comparative Examples 2 to 14 is evaluated by comparing it with Comparative Example 1. That is, for each sample, if the magnetization performance shows a value of -1% or more, which is considered to be a measurement error, compared to the magnetization performance of the sample in Comparative Example 1, it is evaluated as "equal to or better," and if the value is lower than -1%, it is evaluated as "poor." Samples evaluated as "equal to or better" can provide rare earth sintered magnets 1 with high magnetization performance.

[0111] The evaluation results of the residual magnetic flux density, coercive force, temperature coefficient of residual magnetic flux density, temperature coefficient of coercive force, and magnetization performance are shown in Table 3.

[0112] Comparative Example 1 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Fe, and FeB, as well as Co as element M, as raw materials to form an Nd—Fe—B—M structure. When the structural morphology of this sample was observed according to the method described above, it was found that, since Pr, La, and Sm were not added, a core-shell structure in main phase 10 could not be confirmed, and it was also not confirmed that the concentration of Sm in subphase 20 was higher in first subphase 21 than in second subphase 22. Furthermore, when the magnetic properties of this sample were evaluated according to the method described above, it was found that the remanence B r is 1.32 T, and the coercive force H cJ is 1250 kA / m. The temperature coefficients of the residual magnetic flux density and the coercive force are |α| = 0.191% / °C and |β| = 0.460% / °C, respectively. The magnetization rate is 98.6%. These values ​​of Comparative Example 1 are used as references.

[0113] Comparative Example 2 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Fe, and FeB as raw materials to form an Nd—Fe—B magnet. In Comparative Example 2, Co, the element M, was not added. Observing the morphology of this sample using the method described above revealed that, because Pr, La, and Sm were not added, a core-shell structure in the main phase 10 could not be confirmed, and it could not be confirmed that the Sm concentration in the subphase 20 was higher in the first subphase 21 than in the second subphase 22. Because Co, the element M, was not added, it could not be confirmed that the Co concentration was higher in the second subphase 22 than in the first subphase 21. While the remanence and coercivity were "poor," the temperature coefficients of the remanence and coercivity were "same," and the magnetization performance was "same or better."

[0114] Comparative Example 3 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Dy, Fe, and FeB, as well as Co as element M, as raw materials to form a (Nd, Dy)-Fe-B-M structure. Observation of the morphology of this sample using the method described above reveals that, because Pr, La, and Sm were not added, a core-shell structure in main phase 10 was not confirmed, nor was it possible to confirm that the Sm concentration in subphase 20 was higher in first subphase 21 than in second subphase 22. Furthermore, it was not possible to confirm that the Co concentration was higher in second subphase 22 than in first subphase 21. Furthermore, evaluation of the magnetic properties of this sample using the method described above revealed that the remanence was "poor," the coercivity was "good," the temperature coefficient of remanence was "same," the temperature coefficient of coercivity was "same," and the magnetization performance was "same or better." This result reflects the fact that the coercive force is improved by substituting Dy, which has high crystalline magnetic anisotropy, for part of Nd and by adding Co, which is element M, to the subphase 20, but the residual magnetic flux density is poor due to the inability to control the structure of the main phase 10.

[0115] Comparative Example 4 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Pr, Fe, and FeB, as well as Co as element M, as raw materials to form a (Nd,Pr)-Fe-B-M structure. Observation of the morphology of this sample using the method described above confirmed the presence of main phase 10, in which Nd and Pr were mixed, due to the addition of Pr, but no core-shell structure was formed. Furthermore, because La and Sm were not added, it was not possible to confirm that the Sm concentration in subphase 20 was higher in first subphase 21 than in second subphase 22. Furthermore, it was not possible to confirm that the Co concentration in second subphase 22 was higher than in first subphase 21. Evaluation of the magnetic properties of this sample using the method described above revealed the following results: remanence was "same," coercivity was "good," the temperature coefficient of remanence was "same," the temperature coefficient of coercivity was "poor," and magnetization performance was "same or better." This result reflects the fact that although the addition of Pr and Co increases the magnetic anisotropy of the main phase 10 and improves the coercive force, the core-shell structure of the main phase 10 is not formed and the Co in the subphase 20 is not controlled, resulting in the same residual magnetic flux density and a poor temperature coefficient of coercive force.

[0116] Comparative Example 5 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, La, Sm, Fe, FeB, and Co as the element M as raw materials so as to form a (Nd, La, Sm)-Fe-B-M structure. Observing the morphology of this sample using the method described above reveals that, due to the absence of Pr, a core-shell structure of the main phase 10 cannot be confirmed. Furthermore, due to the addition of La and Sm, the concentration of Sm segregates to one subphase 20 in association with the segregation of La, but the second subphase 22 does not exist. Furthermore, it cannot be confirmed that the first subphase 21 has a higher Sm concentration than the second subphase 22, nor that the second subphase 22 has a higher Co concentration than the first subphase 21. Furthermore, when the magnetic properties of this sample are evaluated according to the method described above, the remanence is "same," the coercivity is "same," the temperature coefficient of the remanence is "good," the temperature coefficient of the coercivity is "good," and the magnetization performance is "same or better." This result reflects the fact that, although the temperature coefficient of the magnetic properties shows good results due to the presence of La and Sm in the main phase 10 or the subphase 20, the structure of the main phase 10 and the subphase 20 cannot be controlled due to the absence of Pr, resulting in the remanence and coercivity being equal.

[0117] Comparative Example 6 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, La, Sm, Fe, FeB, and Co as the element M as raw materials to form a (Nd, La, Sm)-Fe-B-M structure. The composition ratio of Nd, La, and Sm differs from that of Comparative Example 5. Observing the morphology of this sample using the above-described method reveals that the absence of Pr results in no core-shell structure of the main phase 10. Furthermore, the addition of La and Sm results in the segregation of Sm into a single subphase 20, but no second subphase 22. Furthermore, it is not possible to confirm that the first subphase 21 has a higher Sm concentration than the second subphase 22, nor is it possible to confirm that the second subphase 22 has a higher Co concentration than the first subphase 21. Furthermore, when the magnetic properties of this sample were evaluated according to the method described above, the remanence was "same," the coercivity was "same," the temperature coefficient of remanence was "good," the temperature coefficient of coercivity was "good," and the magnetization performance was "same or better." This indicates that even if the amounts of La and Sm added were adjusted, because Pr was not added, the structure of the main phase 10 and the subphase 20 could not be controlled, and the remanence and coercivity remained the same. In this way, even when the composition ratio of Nd, La, and Sm was changed, results almost similar to those of Comparative Example 5 were obtained.

[0118] Comparative Example 7 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method described in Patent Document 1 using Nd, Pr, La, Sm, Fe, FeB, and Co as the element M as raw materials to form a (Nd, Pr, La, Sm)-Fe-B-M structure. Observation of the morphology of this sample using the above-described method reveals that the addition of Pr results in the formation of a main phase 10 in which Nd and Pr are mixed, but no core-shell structure is formed. Furthermore, the addition of La and Sm results in the segregation of Sm into a single subphase 20, but no second subphase 22 is present. Furthermore, it is not possible to confirm that the first subphase 21 has a higher Sm concentration than the second subphase 22, nor is it possible to confirm that the second subphase 22 has a higher Co concentration than the first subphase 21. Furthermore, when the magnetic properties of this sample were evaluated according to the method described above, the remanence was "same," the coercivity was "good," the temperature coefficient of the remanence was "good," the temperature coefficient of the coercivity was "same," and the magnetization performance was "same or better." This result reflects the fact that, although the absolute value of the coercivity was improved by adding Pr to Comparative Example 6, the temperature coefficient of the coercivity was worse than that of Comparative Example 6 because the structure of the main phase 10 and the subphase 20 could not be controlled.

[0119] Comparative Example 8 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot working described in Patent Document 2, using Nd, Fe, and FeB, as well as Co as element M, as raw materials to form an Nd—Fe—B—M structure. Observation of the microstructure of this sample using the method described above reveals that, because Pr, La, and Sm were not added, a core-shell structure in main phase 10 was not confirmed, nor was it confirmed that the Sm concentration in subphase 20 was higher in first subphase 21 than in second subphase 22. Furthermore, it was not confirmed that the Co concentration in second subphase 22 was higher than in first subphase 21. However, the refined microstructure, which is a characteristic of magnets produced by hot working, was confirmed. Evaluation of the magnetic properties of this sample using the method described above revealed the following results: the remanence was "same," the coercivity was "good," the temperature coefficient of remanence was "same," the temperature coefficient of coercivity was "same," and the magnetization performance was "poor." This result reflects the fact that although the element M demagnetizes the crystal grain boundaries and improves the coercive force, the absence of Pr, La, and Sm prevents the structure of the main phase 10 and the subphase 20 from being controlled.

[0120] Comparative Example 9 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot working described in Patent Document 2, using Nd, Fe, and FeB as raw materials to obtain Nd—Fe—B. In Comparative Example 9, Co, the element M, was not added. When the microstructure of this sample was observed according to the method described above, it was found that Pr, La, and Sm were not added, so a core-shell structure in the main phase 10 was not confirmed, and it was also not confirmed that the Sm concentration in the subphase 20 was higher in the first subphase 21 than in the second subphase 22. Furthermore, since Co was not added, it was also not confirmed that the Co concentration was higher in the second subphase 22 than in the first subphase 21. However, the refinement of the microstructure, which is a characteristic of magnets produced by hot working, was confirmed. When the magnetic properties of this sample were evaluated according to the method described above, the remanence was "poor," the coercivity was "good," the temperature coefficient of remanence was "same," the temperature coefficient of coercivity was "same," and the magnetization performance was "poor." This is because, as the magnetic powder is refined by hot working, the coercivity improves and the temperature coefficients of remanence and coercivity become equal, but it is difficult to align the magnetic moments, resulting in a decrease in remanence and a deterioration in magnetization performance.

[0121] Comparative Example 10 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot working described in Patent Document 2 using Nd, Dy, Fe, FeB, and Co as element M as raw materials to form a (Nd, Dy)-Fe-B-M structure. Observation of the morphology of this sample according to the above-described method reveals that, because Pr, La, and Sm are not added, a core-shell structure in main phase 10 is not confirmed, and it is not confirmed that the Sm concentration in subphase 20 is higher in first subphase 21 than in second subphase 22. Furthermore, it is not confirmed that the Co concentration is higher in second subphase 22 than in first subphase 21. Furthermore, evaluation of the magnetic properties of this sample according to the above-described method reveals that the remanence is "poor," the coercivity is "good," the temperature coefficient of remanence is "same," the temperature coefficient of coercivity is "same," and the magnetization performance is "poor." This is because the magnetic powder is finely divided by hot working, and in addition, Dy, which has high crystalline magnetic anisotropy, is substituted for part of Nd, and the element M is added, which significantly improves the coercive force, and the temperature coefficients of the remanence and the coercive force are equivalent. However, since it is difficult to align the magnetic moments, the result reflects the decrease in the remanence and the deterioration of the magnetization performance.

[0122] Comparative Example 11 is a sample of rare earth sintered magnet 1 prepared according to the manufacturing method including hot working described in Patent Document 2, using Nd, Pr, Fe, FeB, and Co as the element M as raw materials to form a (Nd,Pr)-Fe-B-M structure. When the morphology of this sample was observed according to the method described above, a core-shell structure was confirmed due to the addition of Pr and the hot working. However, the core-shell structure was confirmed only in one type of main phase 10, where the core portion had a high Pr concentration. Furthermore, because La and Sm were not added, it was not possible to confirm that the first subphase 21 had a higher Sm concentration in the subphase 20 than the second subphase 22. Furthermore, it was not possible to confirm that the second subphase 22 had a higher Co concentration than the first subphase 21. When the magnetic properties of this sample were evaluated according to the method described above, the remanence was "poor," the coercivity "good," the temperature coefficient of remanence "same," the temperature coefficient of coercivity "same," and the magnetization performance "poor." This is because the hot working process refined the magnetic powder, and in addition to forming a core-shell structure with a high Pr concentration in the core, and the addition of Co significantly improved the coercivity to the level of rare earth sintered magnet 1 with added Dy, making the temperature coefficient of remanence and the temperature coefficient of coercivity equivalent, but because the magnetic moment was difficult to align, the result reflected a decrease in remanence and a deterioration in magnetization performance.

[0123] Comparative Example 12 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot working described in Patent Document 2 using Nd, La, Sm, Fe, FeB, and Co as the element M as raw materials to form a (Nd, La, Sm)-Fe-B-M structure. Observing the morphology of this sample using the method described above reveals that, due to the absence of Pr, a core-shell structure of the main phase 10 cannot be confirmed. Furthermore, due to the addition of La and Sm, the concentration of Sm segregates to one subphase 20 in association with the segregation of La, but the second subphase 22 does not exist. Furthermore, it cannot be confirmed that the first subphase 21 has a higher Sm concentration than the second subphase 22, nor that the second subphase 22 has a higher Co concentration than the first subphase 21. Furthermore, when the magnetic properties of this sample were evaluated according to the method described above, the remanence was "poor," the coercivity "good," the temperature coefficient of remanence "good," the temperature coefficient of coercivity "good," and the magnetization performance "poor." This is because, in addition to being produced by hot working, the addition of Co significantly improved the coercivity to the level of rare earth sintered magnet 1 to which Dy was added, and the presence of La and Sm in main phase 10 or subphase 20 refined the magnetic powder, resulting in good results for the temperature coefficient of remanence and the temperature coefficient of coercivity. However, the difficulty in aligning the magnetic moment reflected a decrease in remanence and a deterioration in magnetization performance.

[0124] Comparative Example 13 is a sample of rare earth sintered magnet 1 produced according to the manufacturing method including hot working described in Patent Document 2 using Nd, La, Sm, Fe, FeB, and Co as the element M as raw materials to form a (Nd, La, Sm)-Fe-B-M structure. The composition ratio of Nd, La, and Sm differs from that of Comparative Example 12. Observing the morphology of this sample using the method described above reveals that the absence of Pr results in no core-shell structure of the main phase 10. Furthermore, the addition of La and Sm results in the segregation of Sm into a single subphase 20, but no second subphase 22. Furthermore, it is not possible to confirm that the first subphase 21 has a higher Sm concentration than the second subphase 22, nor is it possible to confirm that the second subphase 22 has a higher Co concentration than the first subphase 21. Furthermore, when the magnetic properties of this sample were evaluated according to the method described above, the remanence was "poor," the coercivity "good," the temperature coefficient of remanence "good," the temperature coefficient of coercivity "good," and the magnetization performance "poor." This is because, in addition to being produced by hot working, the addition of Co significantly improved the coercivity to the level of rare earth sintered magnet 1 containing Dy. Furthermore, the presence of La and Sm in main phase 10 or subphase 20 refined the magnetic powder, resulting in good results for the temperature coefficient of remanence and the temperature coefficient of coercivity. However, the magnetic moment was difficult to align, resulting in a decrease in remanence and a deterioration in magnetization performance. Even when the composition ratio of Nd, La, and Sm was changed, results similar to those of Comparative Example 12 were obtained.

[0125] Comparative Example 14 is a sample of rare earth sintered magnet 1 prepared according to the manufacturing method including hot working described in Patent Document 2 using Nd, Pr, La, Sm, Fe, FeB, and Co as the element M, as raw materials to form a (Nd, Pr, La, Sm)-Fe-B-M structure. When the morphology of this sample was observed according to the above-described method, a core-shell structure was confirmed due to the addition of Pr and the hot working. However, the core-shell structure was confirmed only in one main phase 10, where the core portion had a high Pr concentration. Furthermore, due to the addition of La and Sm, the Sm concentration segregated to one subphase 20 due to the segregation of La, but the second subphase 22 was not present. Furthermore, it was not confirmed that the first subphase 21 had a higher Sm concentration than the second subphase 22, nor was it confirmed that the second subphase 22 had a higher Co concentration than the first subphase 21. Furthermore, when the magnetic properties of this sample were evaluated according to the method described above, the remanence was "poor," the coercivity "good," the temperature coefficient of remanence "good," the temperature coefficient of coercivity "good," and the magnetization performance "poor." This is because, in addition to being produced by hot working, the addition of Pr to form a core-shell structure with a high Pr concentration in the core, and the addition of Co, significantly improve the coercivity to the level of rare earth sintered magnet 1 containing Dy. The presence of La and Sm in main phase 10 or subphase 20 shows good results for the temperature coefficient of remanence and the temperature coefficient of coercivity. However, the difficulty in aligning the magnetic moments also reflects the result of a decrease in remanence and a deterioration in magnetization performance.

[0126] In the samples of Examples 1 to 8, when R is one or more rare earth elements selected from the group consisting of Nd and Pr, and M is one or more elements selected from the group consisting of Ga, Al, Cu, and Co, the general formula (Nd, Pr, R)-Fe-B-M is satisfied, and NdFe 14The rare earth sintered magnet 1 has a main phase 10 containing crystal grains based on a B crystal structure, and a subphase 20 existing between the main phases 10 and 10, the main phase 10 having core portions 11c, 12c and shell portions 11s, 12s covering the core portions 11c, 12c, and the main phase 10 is a mixture of a first main phase 11 in which CNd > CPr and a second main phase 12 in which CNd < CPr. When R=La, Sm, subphase 20 has a crystalline first subphase 21 mainly composed of an oxide phase expressed as (Nd, Pr, La, Sm)-O containing element M as a trace component, and a crystalline second subphase 22 mainly composed of an oxide phase expressed as (Nd, Pr, La)-O containing element M as a trace component, wherein the first subphase 21 has a higher Sm concentration than the second subphase 22, and the second subphase 22 has a higher M concentration than the first subphase 21. When the magnetic properties of the samples of Examples 1 to 8 were evaluated according to the above-described method, the remanence was evaluated as "good," the coercivity was evaluated as "good," the temperature coefficient of remanence was evaluated as "good," the temperature coefficient of coercivity was evaluated as "good," and the magnetization performance was evaluated as "equal to or better." As a result, these rare earth sintered magnets 1 do not use heavy rare earth elements, which are expensive, unevenly distributed across regions, and present a procurement risk, and they also use less Nd, while still achieving the effect of having superior magnetic properties and magnetizability compared to conventional magnets.

[0127] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0128] 1 Rare earth sintered magnet, 10 Main phase, 11 First main phase, 11c, 12c Core portion, 11s, 12s Shell portion, 12 Second main phase, 20 Subphase, 21 First subphase, 22 Second subphase, 41 High concentration portion, 42 Low concentration portion, 100 Rotor, 101 Rotor core, 102 Magnet insertion hole, 120 Rotating machine, 130 Stator, 131 Teeth, 132 Winding.

Claims

1. When R is one or more rare earth elements selected from the group consisting of Nd and Pr, and M is one or more elements selected from the group consisting of Ga, Al, Cu, and Co, the general formula (Nd, Pr, R)-Fe-B-M is satisfied, and Nd2Fe 14 1. A rare earth sintered magnet comprising: a main phase including crystal grains based on a B crystal structure; and a subphase formed between the main phase and the main phase; the main phase having a core portion and a shell portion covering the core portion; the main phase having a first main phase in which CNd>CPr and a second main phase in which CNd<CPr, where CNd is a Nd concentration in the core portion and CPr is a Pr concentration in the core portion; the first main phase and the second main phase are mixed; the subphase has a crystalline first subphase and a second subphase mainly composed of an oxide phase expressed as (Nd,Pr,R)-O containing an element M as a trace component; and the second subphase has a higher concentration of the element M than the first subphase.

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

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

4. The rare earth sintered magnet according to claim 1, characterized in that, when the concentration of Nd in the shell portion is SNd and the concentration of Pr in the shell portion is SPr, the first main phase satisfies the relational expressions CNd>SNd, CPr<SPr, and the second main phase satisfies the relational expressions CNd<SNd, CPr>SPr.

5. The rare earth sintered magnet according to claim 1, characterized in that the subphases include a crystalline first subphase mainly composed of an oxide phase expressed as (Nd, Pr, La, Sm)-O containing the element M as a trace component, where R is La or Sm, and a crystalline second subphase mainly composed of an oxide phase expressed as (Nd, Pr, La)-O containing the element M as a trace component, and the first subphase has a higher Sm concentration than the second subphase.

6. A method for producing a rare earth sintered magnet according to any one of claims 1 to 5, comprising: a melting step of melting raw materials of a rare earth sintered magnet alloy containing elements constituting the rare earth sintered magnet; a first cooling step of cooling the raw materials in a molten state in the melting step to obtain a solidified alloy; a second cooling step of further cooling the solidified alloy to obtain a rare earth sintered magnet alloy; a crushing step of crushing the rare earth sintered magnet alloy satisfying (Nd, Pr, R)-Fe-B-M; a molding step of preparing a compact by molding the powder of the rare earth sintered magnet alloy crushed in the crushing step; a sintering step of sintering the compact at a sintering temperature which is a set temperature to obtain a sintered body; a first aging step of holding the sintered body at a first aging temperature which is lower than the sintering temperature; and a second aging step of holding the sintered body held in the first aging step at a second aging temperature which is lower than the first aging temperature. a third aging step of again holding the sintered body held in the second aging step at the first aging temperature; a fourth aging step of holding the sintered body held in the third aging step at the second aging temperature; and a cooling step of cooling the sintered body held in the fourth aging step.

7. A rotor comprising: a rotor core; and a rare earth sintered magnet according to any one of claims 1 to 5 provided in the rotor core.

8. A rotating machine comprising: a rotor as claimed in claim 7; and an annular stator disposed opposite the rotor, the stator having windings attached to teeth protruding towards the rotor on the inner surface on the side on which the rotor is disposed.

Images