Rare Earth Sintering Magnet, Method for Producing a Rare Earth Sintering Magnet, Rotor and Rotary Machine

Abstract

A rare-earth sintered magnet (1) comprises: a main phase (10) satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare-earth elements selected to exclude Nd and Pr, wherein the main phase (10) consists of crystal grains based on an Nd2Fe 14 The B-crystal structure contains a subphase (20) that is present between a multitude of main phases (10). The main phase (10) includes a core section (11c, 12c) and a shell section (11s, 12s) that covers the core section (11c, 12c). The main phase (10) includes a first main phase (11) that satisfies CNd>CPr and a second main phase (12) that satisfies CNd

Description

Area

[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 producing a rare-earth sintered magnet, a rotor and a rotating machine. General state of the art

[0002] RTB-based permanent magnets featuring a tetragonal intermetallic R2T 14Permanent magnets with a B-compound as the main phase are known. Here, R stands for a rare-earth element, T for a transition metal element, such as Fe (iron) or Fe partially replaced by cobalt (Co), and B for boron. RTB-based permanent magnets are used in various high-value components, including, for example, industrial motors. In particular, Nd-Fe-B-based sintered magnets, where R stands for neodymium (Nd), are used in various components due to their excellent magnetic properties. Since industrial motors are often used in high-temperature environments exceeding 100 °C, attempts have also been made to improve coercivity by adding heavy rare-earth elements, such as dysprosium (Dy), to Nd-TB-based sintered magnets.

[0003] In recent years, the production of Nd-Fe-B-based sintered magnets has expanded, increasing the consumption of Nd and heavy rare-earth elements such as Dy and terbium (Tb). However, Nd and heavy rare-earth elements are expensive and pose a procurement risk due to their highly uneven distribution. Therefore, one possible measure to reduce the consumption of Nd and heavy rare-earth elements is to use a magnet that forms a main phase containing a low proportion of heavy rare earth elements, to use rare-earth elements other than r, such as praseodymium (Pr), cerium (Ce), lanthanum (La), samarium (Sm), scandium (Sc), gadolinium (Gd), yttrium (Y), and lutetium (Lu), or to employ a special production process, such as applying thermoplastic forming to a sintered body.In this document, plastic hot forming applied to a sintered body will be referred to as hot forming. Adding a heavy rare-earth element to the main phase significantly improves the coercivity but considerably degrades the residual magnetic flux density. Furthermore, replacing Nd, either wholly or partially, with elements such as Pr, Ce, La, Sm, Sc, Gd, Y, and Lu significantly worsens the magnetic properties of the residual magnetic flux density and the coercivity. Moreover, applying hot forming to the sintered body significantly degrades the magnetization due to the refinement of the crystal grains. Based on the above, it has thus far been difficult to achieve both a reduction in heavy rare-earth elements and excellent magnetic properties and magnetization.Therefore, conventional attempts have been made to develop a technology that improves magnetic properties at room temperature and prevents the deterioration of magnetic properties associated with temperature increases when using these elements to produce Nd-Fe-B-based sintered magnets. In particular, a rare-earth magnet is currently needed that allows for both a further reduction of heavy rare-earth elements and excellent magnetic properties and magnetization.

[0004] Patent literature 1 discloses a sintered magnet based on RTB containing main phase grains consisting of an R2T 14B-crystals, where R represents one or more types of rare-earth elements containing a heavy rare-earth element RH as an essential element, T represents one or more types of transition metal elements containing Fe or Fe and Co as an essential element, and B represents boron. A portion of the main phase grains of the RTB-based sintered magnet contains a variety of crystal phases with a low proportion of heavy rare-earth elements, and the crystal phase with a low proportion of heavy rare-earth elements is a phase consisting of an R2T 14 The B-crystal consists of a relatively low concentration of the heavy rare-earth element compared to the concentration of the heavy rare-earth element in the entire main phase grains. According to the technique described in patent literature 1, it is possible to obtain an RTB-based sintered magnet with improved magnetic properties at low cost.

[0005] Patent literature 2 discloses a rare-earth magnet that includes a main phase comprising an R2Fe 14The B-crystal structure, where R represents a rare-earth element, features a grain boundary phase surrounding the main phase. The main phase comprises a core section, a first shell section surrounding the core section, and a second shell section surrounding the first shell section. In the rare-earth magnet described in patent literature 2, the abundance ratio of Nd and Pr in the first shell section is higher than the abundance ratio of Nd and Pr in the core section and the second shell section. In the rare-earth magnet described in patent literature 2, the abundance ratio of the heavy rare-earth element in the second shell section is higher than the abundance ratio of the heavy rare-earth element in the first shell section. Consequently, a rare-earth magnet with a further improved coercivity is obtained. List of quotations Patent literature Patent literature 1: Japanese publication no. 2018-174313 Patent literature 2: Japanese publication no. 2021-174818 Brief description of the invention Problem to be solved by the invention

[0006] However, in the RTB-based sintered magnet described in patent literature 1, a phase containing a heavy rare-earth element is present in the main phase. This improves the coercivity but cannot provide the residual magnetic flux density required for industrial motors or similar applications, potentially leading to a deterioration of the magnetic properties. Furthermore, because heavy rare-earth elements are diffused into the main phase particles, the amount of these elements required is large, and procurement risk and costs cannot be reduced. Additionally, since the rare-earth magnet described in patent literature 2 also has a type of main phase, it lacks a structure in which the anisotropic magnetic field is sufficiently enhanced, making it difficult to achieve high magnetic properties.Furthermore, the shell section of the main phase in the rare-earth magnet described in patent literature 2 has a two-layer structure in which the abundance ratio of the heavy rare-earth element is different, and the heavy rare-earth element must be introduced into both shell sections, and thus there is also a problem in that it is difficult to improve magnetic properties with less heavy rare-earth element.

[0007] The present disclosure was prepared in light of the foregoing and one of its objectives is to obtain a rare-earth sintered magnet which is able to improve magnetic properties compared to the relevant prior art, while reducing the use of heavy rare-earth elements compared to the relevant prior art. Ways to solve the problem

[0008] To solve the problems described above and to fulfill the task, a rare-earth sintered magnet according to the present disclosure comprises the following: a main phase satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare-earth elements selected to the exclusion of Nd and Pr, wherein the main phase consists of crystal grains based on an Nd2Fe 14It contains a B-crystal structure; and a subphase that exists between a variety of main phases. The main phase includes a core section and a shell section that covers the core section. The main phase includes a first main phase that satisfies CNd>CPr, and a second main phase that satisfies CNd <CPr erfüllt, wobei CNd die Konzentration von Nd im Kernabschnitt ist und CPr die Konzentration von Pr im Kernabschnitt ist. Die erste Hauptphase und die zweite Hauptphase werden gemischt bereitgestellt. Ein schweres Seltenerd-Element ist auf mindestens einem Teil einer Oberfläche der ersten Hauptphase und der zweiten Hauptphase vorhanden. Effects of the invention

[0009] The rare-earth sintered magnet according to the present disclosure can achieve the effect of improving magnetic properties compared to the relevant prior art, while reducing the use of heavy rare-earth elements compared to the prior art. Brief description of the drawings Fig. Figure 1 is a representation that schematically illustrates an exemplary sintered structure of a rare-earth sintered magnet according to a first embodiment. Fig. Figure 2 is a representation that schematically illustrates an exemplary sintered structure of a rare-earth sintered magnet according to the second embodiment. Fig. Figure 3 is a representation that schematically illustrates an exemplary sintered structure of a rare-earth sintered magnet according to the third embodiment. Fig. 4 is an element map of Sm obtained by analyzing a cross-section of a rare-earth sintered magnet according to the third embodiment using an FE-EPMA. Fig. 5 is an element map of Tb obtained by analyzing a cross-section of a rare earth sintered magnet according to the third embodiment using an FE-EPMA. Fig. 6 is a representation showing the atomic positions in a tetragonal Nd2Fe 14 B-crystal structure illustrated. Fig. Figure 7 is a flowchart illustrating an exemplary process of a method for producing a rare-earth sintered magnet according to the fourth embodiment. Fig. Figure 8 is a flowchart illustrating an exemplary process of a production step for the rare earth sintered magnet alloy according to the fourth embodiment. Fig. Figure 9 is a flowchart illustrating an exemplary process of a production step for the diffusion precursor according to the fourth embodiment. Fig. Figure 10 is a cross-sectional view that schematically illustrates an exemplary configuration of a rotor equipped with a rare-earth sintered magnet according to the fifth embodiment. Fig. Figure 11 is a cross-sectional view that schematically illustrates an exemplary configuration of a rotary machine according to the sixth embodiment. Fig. Figure 12 is a sketch of a composition image obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 using an FE-EPMA. Fig. 13 is an elemental map of Nd obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 using an FE-EPMA. Fig. 14 is an element map of Pr obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 using an FE-EPMA. Fig. 15 is an element map of Dy obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 using an FE-EPMA. Fig. 16 is an elemental map of O obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 using an FE-EPMA. Fig. 17 is an elemental map of Sm obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 using an FE-EPMA. Fig. 18 is an elemental map of La obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 using an FE-EPMA. Description of embodiments

[0010] Subsequently, a rare-earth sintered magnet, a method for producing a rare-earth sintered magnet, a rotor and a rotary machine according to embodiments of the present disclosure are described in detail with reference to the drawings. First embodiment.

[0011] Fig. Figure 1 is a schematic representation illustrating an exemplary sintered structure of a rare-earth sintered magnet according to the first embodiment. The rare-earth sintered magnet 1 according to the first embodiment comprises a main phase 10 satisfying a general formula (Nd, Pr, R)-Fe-B and crystal grains based on an Nd₂Fe 14The B-crystal structure is present, and the main phase 10 comprises a core section and a shell section covering the core section. Here, R represents one or more rare-earth elements selected excluding Nd and Pr. The shell section has a composition different from that of the core section and is provided to cover the core section. The rare-earth sintered magnet 1 further comprises a subphase 20, which exists between the main phase 10 and a plurality of main phases 10. The subphase 20 is a phase based on an oxide phase represented by (Nd, Pr, R)-O as the main component.

[0012] In the rare-earth sintered magnet 1 according to the first embodiment, the main phase 10 includes a first main phase 11 that satisfies CNd>CPr, and a second main phase 12 that satisfies CNd <CPr erfüllt, wobei CNd für die Konzentration von Nd im Kernabschnitt steht und CPr für die Konzentration von Pr im Kernabschnitt steht und die erste Hauptphase 11 und die zweite Hauptphase 12 gemischt bereitgestellt sind. Die erste Hauptphase 11 beinhaltet einen Kernabschnitt 11c und einen Hüllenabschnitt 11s, der eine Zusammensetzung aufweist, die sich von der des Kernabschnitts 11c unterscheidet, und den Kernabschnitt 11c bedeckt. Die zweite Hauptphase 12 beinhaltet einen Kernabschnitt 12c und einen Hüllenabschnitt 12s, der eine Zusammensetzung aufweist, die sich von der des Kernabschnitts 12c unterscheidet, und den Kernabschnitt 12c bedeckt. CNd> CPr is fulfilled in core section 11c of the first main phase 11 and CNd <CPr ist im Kernabschnitt 12c der zweiten Hauptphase 12 erfüllt.

[0013] This means that the rare-earth sintered magnet 1 has two types of main phases 10, namely the first main phase 11 and the second main phase 12. Focusing on the core sections 11c and 12c of the two types of main phases 10, the Nd concentration in the first main phase 11 is higher than the Pr concentration, and conversely, in the second main phase 12, the Pr concentration is higher than the Nd concentration. As described above, by mixing two types of main phases 10, which have core-shell structures that differ in their anisotropic magnetic field (i.e., magnetic anisotropy), it is possible to reduce the Nd and heavy rare-earth elements and also to improve the residual magnetic flux density and coercivity while maintaining good magnetization. Furthermore, it also helps to prevent the deterioration of magnetic properties associated with temperature changes.Here, the concentration difference, which is fulfilled by "the first main phase 11, the CNd>CPr, and the second main phase 12, the CNd <CPr erfüllt“ angegeben wird, dass es eine klare Differenz in der Erfassungsintensität von Nd und Pr durch eine Abbildungsanalyse unter Verwendung eines Elektronenstrahlmikrosondenanalysegeräts (electronic probe microanalyzer - EPMA) gibt. Unter Bezugnahme auf den Fall der ersten Hauptphase 11 als Beispiel ist konkret die EPMA-Erfassungsintensität der Konzentration von Nd in dem Kernabschnitt 11c höher als der Durchschnitt der Erfassungsintensität von Nd und die EPMA-Erfassungsintensität der Konzentration von Pr gibt ungefähr den unteren Grenzwert der Erfassungsintensität von Pr an. Der Fall in der zweiten Hauptphase 12 ist das Gegenteil des Falls in der ersten Hauptphase 11.

[0014] The rare-earth sintered magnet 1 according to the first embodiment satisfies relational expressions of C1Nd>C2Nd and C1Pr <C2Pr, wobei C1Nd für die Nd-Konzentration des Kernabschnitts 11c der ersten Hauptphase 11 steht, C2Nd für die Nd-Konzentration des Kernabschnitts 12c der zweiten Hauptphase 12 steht, C1Pr für die Pr-Konzentration des Kernabschnitts 11c der ersten Hauptphase 11 steht und C2Pr für die Pr-Konzentration des Kernabschnitts 12c der zweiten Hauptphase 12 steht. Das heißt, die Nd-Konzentration ist in dem Kernabschnitt 11c der ersten Hauptphase 11 höher als in dem Kernabschnitt 12c der zweiten Hauptphase 12 und umgekehrt ist die Pr-Konzentration in dem Kernabschnitt 12c der zweiten Hauptphase 12 höher als in dem Kernabschnitt 11c der ersten Hauptphase 11. Die Konzentrationsdifferenz bedeutet hier ebenfalls, dass es eine Differenz bei der Erfassungsintensität von Nd und Pr durch die Abbildungsanalyse unter Verwendung des EPMA gibt.Specifically, in the case of Nd concentration, this means that the EPMA's detection intensity for Nd in core section 11c of the first main phase 11 is higher than the average detection intensity for Nd, and the EPMA's detection intensity for Nd in core section 12c of the second main phase 12 is lower than the average detection intensity for Nd. In the case of Pr concentration, this means that the EPMA's detection intensity for Pr in core section 12c of the second main phase 12 is higher than the average detection intensity for Pr, and the EPMA detection intensity for Pr in core section 11c of the first main phase 11 is lower than the average detection intensity for Pr.This means that in the core section 12c of the second main phase 12, which has a low Nd concentration, a large amount of Pr is present, and conversely, in the core section 11c of the first main phase 11, which has a low Pr concentration, a large amount of Nd is present. Controlling this structure leads to the rare-earth sintered magnet 1, which exhibits excellent magnetic properties.

[0015] In the rare-earth sintered magnet 1 according to the first embodiment, the first main phases 11, each satisfying CNd>CPr, are more abundant than the second main phase 12, each satisfying CNd <CPr erfüllt. Mit anderen Worten bedeutet dies, dass die Anzahl der ersten Hauptphasen 11, die die Zusammensetzungsformel von Nd2Fe 14 B is greater than the number of second main phases 12, which form the composition formula of Pr2Fe 14B. This is due to the increase in the first main phase 11, which has the compositional formula of Nd2Fe. 14 B exhibits, leads to more outstanding magnetic and temperature properties than increasing the second main phase 12, which gives the composition formula of Pr2Fe 14 B. Furthermore, the control for achieving such a structural shape also prevents a refinement of the crystal grains as a whole, so that it is possible to achieve excellent magnetic properties compared to the state of the art, while ensuring magnetization.

[0016] In the rare-earth sintered magnet 1 according to the first embodiment, with a focus on the shell sections 11s and 12s of the core-shell structures, the first main phase 11 fulfills the relational expressions of CNd>SNd and CPr. <SPr und erfüllt die zweite Hauptphase 12 die relationalen Ausdrücke von CNd<SNd und CPr> SPr, where SNd represents the concentration of Nd in shell regions 11s and 12s and SPr represents the concentration of Pr in shell regions 11s and 12s. Specifically, shell region 11s of the first main phase 11 has a higher concentration of Pr than core region 11c, instead of a lower concentration of Nd, and shell region 12s of the second main phase 12 has a higher concentration of Nd than core region 12c, instead of a lower concentration of Pr.By forming the first main phase 11, which includes the shell section 11s exhibiting a high concentration of Pr in the main phase 10, the coercive force can be improved. Furthermore, by forming the second main phase 12, which includes the shell section 12s exhibiting a high concentration of Nd in the main phase 10, it is possible to prevent a deterioration of the residual magnetic flux density while maintaining the coercive force. By selectively controlling the formation of such a structure, the rare-earth sintered magnet 1 can exhibit excellent magnetic properties compared to the relevant prior art.

[0017] Furthermore, main phase 10 includes a layer 31 containing a heavy rare-earth element, which is present on at least part of its surface. This means that a heavy rare-earth element is present on at least part of the surface of main phase 10, that is, the first main phase 11 and the second main phase 12. More specifically, the heavy rare-earth element is present on at least part of the outer circumferential surfaces of shell sections 11s and 12s, and the heavy rare-earth element does not penetrate into core sections 11c and 12c. The heavy rare-earth element is one or more elements selected from the group consisting of Dy, Tb, Gd, and Ho (holmium).As described above, the coercive force increases because the heavy rare-earth element penetrates the R-sites of the first main phase 11 and the second main phase 12, but does not penetrate the core section 11c, which is the interior of the first main phase 11, or the core section 12c, which is the interior of the second main phase 12, thus preventing a significant reduction in the residual magnetic flux density. That is, it is possible to prevent a reduction in the residual magnetic flux density while improving the coercive force. To achieve such an effect, the ratio of the heavy rare-earth element in main phase 10 is desirablely greater than 0 atomic percent but less than or equal to 10 atomic percent.

[0018] When comparing the magnetic properties between the case where the heavy rare-earth element is contained within the main phase 10 of the rare-earth sintered magnet 1 and the case where the heavy rare-earth element is contained in the surface layer of the main phase 10, it is known that the same magnetic properties can be obtained by containing the heavy rare-earth element in the surface of the main phase 10 at a lower concentration than when the heavy rare-earth element is contained within the main phase 10. That is, in the rare-earth sintered magnet 1 according to the first embodiment, where the heavy rare-earth element is contained in the surface layer of the main phase 10, the amount of the heavy rare-earth element used can be reduced compared to the case where the heavy rare-earth element is contained within the main phase 10.

[0019] Furthermore, the average grain size of the crystal grains of the main phase 10 is preferably 100 µm or less, and more preferably 0.5 µm to 50 µm, to improve the magnetic properties. Moreover, setting the average grain size to approximately 1 µm to 10 µm results in a grain size that differs from the microstructure produced by hot forming, leading to the rare-earth sintered magnet 1, which maintains good magnetization and exhibits excellent magnetic properties compared to the relevant prior art.

[0020] The rare-earth sintered magnet 1 according to the first embodiment can contain an additional element M that further improves the magnetic properties. The additional element M represents one or more elements selected from the group consisting of Ga (gallium), Cu (copper), Al (aluminum), Co, Zr (zirconium), Ti (titanium), Nb (niobium), and Mn (manganese). Therefore, in the rare-earth sintered magnet 1 according to the first embodiment, the general formula is replaced by (Nd a Pr b R c RH d ) Fe e B f M gExpressed, where RH represents a heavy rare-earth element that is one or more elements selected from the group consisting of Dy, Tb, Gd, and Ho, and R represents a rare-earth element other than Nd, Pr, and the heavy rare-earth element RH. The additional element M represents one or more elements selected from the group consisting of Ga, Cu, Al, Co, Zr, Ti, Nb, and Mn. It is desirable that a, b, c, d, e, f, and g satisfy the following relational expressions. 5≤a+b≤20 0 <c+d<(a+b) 0 <d<10 70≤e≤90 0.5≤f≤10 0≤g≤5 a+b+c+d+e+f+g=100 Atom−%

[0021] The rare-earth sintered magnet 1 according to the first embodiment includes the main phase 10, which fulfills a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare-earth elements selected to the exclusion of Nd and Pr, the main phase 10 being crystal grains based on an Nd2Fe 14 The B-crystal structure contains the main phase 10, which includes the core sections 11c and 12c, and the shell sections 11s and 12s cover the core sections 11c and 12c, wherein the main phase 10 is the first main phase 11, which satisfies CNd>CPr, and the second main phase 12, which satisfies CNd <CPr erfüllt, beinhaltet und die erste Hauptphase 11 und die zweite Hauptphase 12 gemischt bereitgestellt werden. Mit einer solchen Konfiguration ist es möglich, den Seltenerd-Sintermagneten 1 zu erlangen, bei dem magnetische Eigenschaften und Magnetisierung im Vergleich zum einschlägigen Stand der Technik verbessert sind, während die Verwendung von Nd und schweren Seltenerd-Elementen reduziert ist.

[0022] The first main phase 11 and the second main phase 12 satisfy the relational expressions of C1Nd>C2Nd and C1Pr <C2Pr. Alternativ ist die Anzahl der ersten Hauptphasen 11 größer als die Anzahl der zweiten Hauptphasen 12. Alternativ erfüllt die erste Hauptphase 11 die relationalen Ausdrücke von CNd> SNd and CPr <SPr und erfüllt die zweite Hauptphase 12 die relationalen Ausdrücke von CNd<SNd und CPr> SPr. This also makes it possible to obtain the rare earth sintered magnet 1, in which magnetic properties and magnetization are improved, while the use of Nd and heavy rare earth elements is reduced.

[0023] Furthermore, the heavy rare-earth element is present on at least a portion of the surface of the first main phase 11 and the second main phase 12, and is not present within the interior of the first main phase 11 and the second main phase 12. As a result, it is possible to obtain the rare-earth sintered magnet 1 in which the coercive force is improved compared to the relevant prior art, while the use of heavy rare-earth elements is reduced, and a significant decrease in the residual magnetic flux density is prevented. That is to say, the magnetic properties of the rare-earth sintered magnet 1 can be improved compared to the conventional case.

[0024] In the first embodiment, the first main phase 11 and the second main phase 12 have a core-shell structure with a layer of shell sections 11s and 12s, and the heavy rare-earth element only needs to be present on at least a portion of the surfaces of the shell sections 11s and 12s. In contrast, in patent literature 2, which has a two-layer core-shell structure, heavy rare-earth elements must be diffused into the two-layer core-shell section. Thus, the rare-earth sintered magnet 1 according to the first embodiment also has the effect of reducing the amount of heavy rare-earth elements used compared to patent literature 2. Second embodiment.

[0025] Fig. Figure 2 is a schematic representation illustrating an exemplary sintered structure of a rare-earth sintered magnet according to the second embodiment. It should be noted that components identical to those in the first embodiment are identified with the same reference numerals, and their descriptions are omitted. The rare-earth sintered magnet 1 according to the second embodiment comprises the main phase 10 and the subphase 20.

[0026] The main phase 10 has the same structure as that of the first embodiment. That is, the main phase 10 comprises the first main phase 11 and the second main phase 12, which have a core-shell structure, and the compositions of the core sections 11c and 12c and the compositions of the shell sections 11s and 12s are similar to those described in the first embodiment. However, in the second embodiment, the layer 31 containing a heavy rare-earth element is not present on the surface of the main phase 10.

[0027] Subphase 20 is a phase based on an oxide phase represented by (Nd, Pr, R)-O as the main component. In the second embodiment, however, subphase 20 contains a heavy rare-earth element. The heavy rare-earth element is distributed throughout the entire subphase 20. In one example, the heavy rare-earth element is uniformly distributed within subphase 20.

[0028] As described above, in the second embodiment, the subphase 20, which contains a heavy rare-earth element, is located between the main phase 10 and the main phase 10. It can also be considered that the heavy rare-earth element is uniformly distributed within the subphase 20 and penetrates a portion of the surface of the main phase 10 in contact with the subphase 20. That is, it is considered that the heavy rare-earth element does not penetrate the core sections 11c and 12c of the main phase 10, but rather a portion of the shell sections 11s and 12s. Therefore, similar to the first embodiment, it is possible to prevent a reduction in the residual magnetic flux density while improving the coercivity of the rare-earth sintered magnet 1.

[0029] As in Fig. As illustrated in Figure 2, the main phase 10 of the rare-earth sintered magnet 1 is in contact with another main phase 10 without the subphase 20 being inserted between them, or it is in contact with another main phase 10 via the subphase 20. This means that at least part of the surface of the main phase 10 is in contact with the subphase 20. The subphase 20 contains a heavy rare-earth element. Therefore, at least part of the surface of the main phase 10 is covered by the subphase 20 containing the heavy rare-earth element. Considering the shape of the distribution of the heavy rare-earth element relative to the main phase 10, the heavy rare-earth element is present on at least part of the surface of the main phase 10.That is, for the same rare-earth sintered magnet 1, the first embodiment shows the distribution of the heavy rare-earth element by focusing on the interface between the main phase 10 and the subphase 20, and the second embodiment shows the distribution of the heavy rare-earth element by focusing on the subphase 20. Thus, it can be said that the first embodiment and the second embodiment are the same rare-earth sintered magnet 1 viewed from different perspectives.

[0030] Furthermore, in the second embodiment, similar to the first embodiment, it is possible to obtain the rare-earth sintered magnet 1 in which the coercive force is improved compared to the relevant prior art, while the use of heavy rare-earth elements is reduced and a significant decrease in the residual magnetic flux density is prevented. That is to say, the magnetic properties of the rare-earth sintered magnet 1 can be improved compared to the conventional case. Third embodiment.

[0031] Fig. Figure 3 is a schematic representation illustrating an exemplary sintered structure of a rare-earth sintered magnet according to the third embodiment. The rare-earth sintered magnet 1 according to the third embodiment comprises the main phase 10 and the subphase 20. The main phase 10 comprises the first main phase 11 and the second main phase 12, as described in the first embodiment, but in Fig. The first main phase 11 and the second main phase 12 are jointly designated by main phase 10. Subphase 20 is present between main phases 10.

[0032] In the rare-earth sintered magnet 1 according to the third embodiment, a case is described in which La and Sm are selected as the rare-earth element R. In this case, the effect of improving the magnetic properties and achieving excellent magnetization compared to the relevant prior art, while reducing the use of Nd and heavier rare-earth elements, is further enhanced. In this example, the main phase 10 has the composition formula (Nd,Pr,La,Sm)₂Fe 14 B. The reason why the rare-earth element R of the rare-earth sintered magnet 1, which is a tetragonal R2Fe 14The B-crystal structure, representing rare-earth elements including La and Sm, is demonstrated by the calculation of the magnetic interaction energy using a molecular orbital method. This shows that a composition containing La and Sm can produce the rare-earth sintered magnet 1, which is suitable for practical use in that it significantly prevents the deterioration of magnetic properties associated with temperature increases. Furthermore, the intentional segregation of La and Sm at the grain boundary, which is an example of subphase 20, makes it possible to cause Nd and Pr to diffuse relatively far across the main phase 10, leading to enhanced magnetocrystalline anisotropy of the main phase 10.As a result, a core-shell structure is formed in which a section exhibiting high magnetic anisotropy and a section exhibiting low magnetic anisotropy are present in the main phase 10, and a state is formed in which the rare-earth sintered magnet 1, in which the first main phase 11, which CNd>CPr, and the second main phase 12, which CNd <CPr erfüllt, gemischt bereitgestellt werden, leicht gebildet.

[0033] It should be noted that excessive addition of La and Sm causes a decrease in the amount of Nd and Pr, which are elements exhibiting a high magnetic anisotropy constant and high magnetic saturation polarization, leading to a deterioration of magnetic properties. Therefore, preferably (A+B)>(C+D) is satisfied, where A, B, C, and D represent the composition ratios of Nd, Pr, La, and Sm, respectively.

[0034] In the rare-earth sintered magnet 1 according to the third embodiment, the rare-earth sintered magnet 1, when R = La and / or Sm, includes subphase 20 in addition to the first main phase 11 and the second main phase 12 in the first embodiment. Subphase 20 comprises a crystalline first subphase 21 based on an oxide phase, which has a major component represented by (Nd, Pr, La, Sm)-O, and a crystalline second subphase 22, which has a major component represented by (Nd, Pr, La)-O. The concentration of Sm in subphase 20 is higher in the first subphase 21 than in the second subphase 22. That is, the first subphase 21 forms an Sm enrichment section 41, which has a higher Sm concentration than the second subphase 22.This achieves the effect of not only preventing a deterioration of the magnetic properties at room temperature, but also a deterioration of the magnetic properties associated with a temperature increase.

[0035] Here, “the concentration of Sm is higher in the first subphase 21 than in the second subphase 22” means that the detection intensity of Sm by an imaging analysis using an EPMA is on average higher in the first subphase 21 than in the second subphase 22.

[0036] The crystalline subphase 20 is a general term for the crystalline first subphase 21 and the crystalline second subphase 22 and is present between the main phases 10. The crystalline first subphase 21 is represented by (Nd, Pr, La, Sm)-O, and the crystalline second subphase 22 is represented by (Nd, Pr, La)-O. Here, (Nd, Pr, La, Sm) means that some of the Nd and Pr are replaced by La and Sm. It should be noted that the elements of the main components are described in parentheses; therefore, the first subphase 21 and the second subphase 22 may contain a small amount of another component in addition to the elements given in parentheses. In one example, the second subphase 22, represented by (Nd, Pr, La)-O, contains an extremely small amount of Sm.

[0037] In the rare-earth sintered magnet 1 according to the third embodiment, there is a concentration difference of La and Sm between the main phase 10 and the subphase 20, and La and Sm are more strongly segregated in the subphase 20 than in the main phase 10. That is, the sum of the concentrations of La in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of La in the main phase 10, and the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of Sm in the main phase 10. Specifically, the concentrations of La and Sm in the subphase 20 are equal to or greater than the concentrations of La and Sm in the main phase 10. Here, the concentration of La in the main phase 10 is the sum of the concentration of La in the first main phase 11 and the concentration of La in the second main phase 12.This means that the sum of the La concentrations in the first subphase 21 and the second subphase 22 is higher than the sum of the La concentrations in the first main phase 11 and the second main phase 12. Here, the Sm concentration of main phase 10 is the sum of the Sm concentration of the first main phase 11 and the Sm concentration of the second main phase 12. That is, 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.

[0038] If X represents the concentration of La contained in main phase 10, X1 represents the concentration of La contained in first subphase 21, X2 represents the concentration of La contained in second subphase 22, Y represents the concentration of Sm contained in main phase 10, Y1 represents the concentration of Sm contained in first subphase 21, and Y2 represents the concentration of Sm contained in second subphase 22, then the relationship of formula (1) below is satisfied. 1<(Y1+Y2) / Y<(X1+X2) / X

[0039] Furthermore, with regard to improving the magnetic properties, the relationships of the following formulas (2) and (3) are satisfied with respect to the concentrations of Nd and Pr contained in the main phase 10. (CNd+SNd)>(X+Y) (CPr+SPr)>(X+Y)

[0040] In the preceding description, the concentration of La in main phase 10 is the sum of the concentrations of La in the first main phase 11 and the second main phase 12, and the concentration of Sm in main phase 10 is the sum of the concentrations of Sm in the first main phase 11 and the second main phase 12. This indicates that both La and Sm are more strongly segregated in subphase 20 than in main phase 10. However, upon local consideration, each of the sums of the concentrations of La and Sm in the first main phase 11 and the second main phase 12, and each of the sums of the concentrations of La and Sm in the first subphase 21 and the second subphase 22, may not satisfy the preceding relationship.Therefore, more specifically, the concentration of La in main phase 10 represents the average of the concentrations of La in the first main phase 11 and the second main phase 12, and the concentration of Sm in main phase 10 represents the average of the concentrations of Sm in the first main phase 11 and the second main phase 12. In this case, the concentration of La in subphase 20, that is, the sum of the concentrations of La in the first subphase 21 and the second subphase 22, represents the average of the concentrations of La in the first subphase 21 and the second subphase 22, and the concentration of Sm in subphase 20, that is, the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22, represents the average of the concentrations of Sm in the first subphase 21 and the second subphase 22.

[0041] La is present in a high concentration at the grain boundary during the production process, particularly during heat treatment, causing Nd and Pr to diffuse relatively throughout the entire main phase 10. Consequently, in the rare-earth sintered magnet 1 according to the third embodiment, Nd and Pr are not consumed at the grain boundary in the main phase 10, resulting in improved magnetocrystalline anisotropy. Furthermore, Sm is present in a higher concentration in the subphase 20, particularly in the first subphase 21, than in the main phase 10, causing Nd to diffuse relatively throughout the entire main phase 10, as in the case of La, resulting in improved magnetocrystalline anisotropy.

[0042] As described in the second embodiment, the first subphase 21 and the second subphase 22 contain the heavy rare earth element, since subphase 20 contains the heavy rare earth element. However, in the third embodiment, the distribution of the heavy rare earth element differs between the first subphase 21 and the second subphase 22. In the second subphase 22, which has a lower Sm concentration than the first subphase 21, the heavy rare earth element is uniformly distributed throughout the second subphase 22. In contrast, in the first subphase 21, which forms the Sm enrichment section 41, the heavy rare earth element is not uniformly distributed throughout the first subphase 21, but is selectively distributed between the outer contour of the first subphase 21 and the Sm enrichment section 41, that is, in the inner circumferential section of the outer contour of the first subphase 21.Specifically, the heavy rare-earth element is present in such a way that it selectively surrounds the outer contour of the Sm enrichment section 41, which has a high Sm concentration in the first subphase 21. Therefore, it can be said that the first subphase 21 comprises the Sm enrichment section 41 and a section 32 containing a heavy rare-earth element, in which the heavy rare-earth element is present, selectively surrounding the outer contour of the Sm enrichment section 41. The outer contour of the first subphase 21 is a boundary section between the first subphase 21 and the main phase 10.

[0043] Similar to the second embodiment, the first subphase 21 and the second subphase 22, which contain a heavy rare-earth element, are located between the main phase 10 and the main phase 10. It can be considered that the heavy rare-earth element penetrates a portion of the surface of the main phase 10 in contact with the first subphase 21 and the second subphase 22 containing the heavy rare-earth element. That is, it is considered that the heavy rare-earth element does not penetrate the core sections 11c and 12c of the main phase 10, but rather a portion of the shell sections 11s and 12s. Therefore, similar to the first embodiment, it is possible to prevent a reduction in the residual magnetic flux density while improving the coercivity of the rare-earth sintered magnet 1.

[0044] The Fig. 4 and Fig. 5 are element maps obtained by analyzing a cross-section of a rare-earth sintered magnet according to the third embodiment using a field emission electron probe microanalyzer (FE-EPMA). Fig. 4 is an element card of Sm and Fig. Figure 5 is an elemental map of Tb. These drawings illustrate a state in which subphase 20 exists between main phase 10 and main phase 10. Subphase 20 includes the first subphase 21, which has the Sm enrichment section 41, and the second subphase 22, which has a lower Sm concentration than the first subphase 21. In the second subphase 22, Tb, which is a heavy rare-earth element, is uniformly distributed, as described above. In the first subphase 21, however, the distribution of Tb is uneven. Referring to the Fig. 4 and Fig. 5. Section 32, containing a heavy rare-earth element, is positioned such that it selectively surrounds the Sm enrichment section 41, which has a high Sm concentration in the first subphase 21. Furthermore, almost no heavy rare-earth element is present in the Sm enrichment section 41. In addition, the concentration of the heavy rare-earth element selectively distributed around the Sm enrichment section 41 is higher than the concentration of the heavy rare-earth element completely distributed within the second subphase 22.

[0045] Next, it will be described at which atomic sites of the tetragonal R2Fe 14 B-crystal structure La and Sm are substituted. Fig. 6 is a representation showing the atomic positions in a tetragonal Nd2Fe 14 The B-crystal structure is illustrated. It should be noted that the in Fig. 6 illustrated crystal structure in an example in Fig. The substitution sites are determined based on the numerical value of the stabilization energy associated with the substitution, which is calculated using band calculations and the molecular field approximation based on the Heisenberg model. (Reference Literature 1): JF Herbst et al., “Relationships between crystal structure and magnetic properties in Nd₂Fe 14 B", PHYSICAL REVIEW B. 1984, Vol. 29, No. 7, pp. 4176-4178.

[0046] First, a method for calculating the stabilization energy in La is described. The stabilization energy in La can be defined as the energy difference between (Nd7La1)Fe 56 B4+Nd and Nd8 (Fe 55 La1) B4+Fe using Nd8Fe 56B4 crystal cells are calculated. The lower the energy value, the more stable it is when the atom is substituted at that position. That is, La is likely to be substituted at an atomic site with the lowest energy among the available sites. This calculation assumes that substituting La for the original atom changes the lattice constant in the tetragonal R2Fe 14 The B-crystal structure does not change due to the difference in atomic radius. Table 1 shows the stabilization energy of La at each substitution site at different ambient temperatures. [Table 1] [Table.1] (Table 1) Substitutionsites for La Temperature 293K 500K 1000K 1300K 1400K 1500K Nd(f) -136.372 -84.943 48.524 -40.132 -38.132 -35.451 Nd(g) -132.613 -82.740 -47.442 -38.211 -36.358 -34.753 Fe(k1) -135.939 -80.596 -41.428 -32.390 -30.237 -17.095 Fe(k2) -127.480 -75.638 -38.948 -30.482 -28.466 -26.719 Fe(j1) -124.248 -73.076 -38.003 -29.754 -27.791 -26.089 Fe(j2) -117.148 -71.400 -35.923 -28.816 -26.917 -25.271 Fe(e) -130.814 -77.593 -39.926 -31.235 -29.164 -27.371 Fe(c) -148.317 -87.850 -45.055 -35.179 -32.828 -30.789 Unit:eV

[0047] Table 1 indicates that the stable substitution sites for La are Nd(f) sites at temperatures of 1000 K and above, and Fe(c) sites at temperatures of 293 K and 500 K. As described later, according to the third embodiment, the raw material of the rare-earth sintered magnet 1 is heated and melted at a temperature of 1000 K or above and then rapidly cooled. Therefore, it is considered that the raw material of the rare-earth sintered magnet 1 is maintained at a temperature of 1000 K or above, i.e., 727 °C or above, and more preferably at about 1300 K, i.e., 1027 °C. In this case, it is assumed that La is substituted at Nd(f) or Nd(g) sites. It is assumed that La is preferentially substituted at energetically stable Nd(f) sites, but it may also be substituted at Nd(g) sites which have a small energy difference between the substitution sites for La.For this reason, Nd(g) places are also mentioned as candidates for the substitution places for La.

[0048] When the rare-earth sintered magnet 1 is produced using the production process described later, the temperature at the time of sintering is 1000 K or higher, but the Fe(c) sites described in Table 1 are repeatedly kept in an energetically stable temperature zone by the primary aging step, the secondary aging step, the tertiary aging step, the quaternary aging step, and the cooling step. In other words, the La substitution at Nd sites of the main phase 10 is maintained in an unstable energy state.This means that La is mainly substituted at Nd sites of the main phase 10 in the raw material stage of the rare-earth sintered magnet 1; however, in the rare-earth sintered magnet 1 produced by the production process described later, a certain amount of La is selectively released from the Nd sites of the main phase 10 by repeatedly and intentionally holding them in an unstable energy state within a temperature range, and as a result, La is segregated in the subphase 20. Consequently, the main phase 10 promotes the formation of the characteristic structure, namely the core-shell structure.

[0049] Next, a method for calculating the stabilization energy in Sm is described. The stabilization energy of Sm can be expressed as the energy difference between (Nd₇Sm₁)Fe and (Nd₇Sm₁)Fe. 56 B4+Nd and Nd8 (Fe 55Sm1) B4+Fe can be calculated. Similar to the case of La, the atomic substitution changes the lattice constant in the tetragonal R2Fe. 14 B-crystal structure not shown. Table 2 shows the stabilization energy of Sm at each substitution site at different ambient temperatures. [Table 2] [Table.2] (Table 2) Substitutionsites for Sm Temperature 293K 500K 1000K 1300K 1400K 1500K Nd(f) -164.960 -101.695 -56.921 -46.589 -44.128 -41.976 Nd(g) -168.180 -103.583 -57.865 -47.315 -44.803 -42.626 Fe(k1) -136.797 -81.098 -41.679 -32.583 -17.350 -16.343 Fe(k2) -127.769 -75.808 -38.482 -29.603 -28.528 -25.696 Fe(j1) -122.726 -73.304 -37.783 -28.392 -26.525 -24.681 Fe(j2) -124.483 -73.883 -38.072 -28.483 -26.610 -24.985 Fe(e) 125.937 72.525 35.301 26.633 24.450 22.782 Fe(e) -155.804 -94.457 -48.359 -37.720 -35.187 -32.992 Unit:eV

[0050] Table 2 indicates that, unlike in the case of La, stable substitution sites for Sm are Nd(g) sites at any given temperature. Sm is assumed to be preferentially substituted at energetically stable Nd(g) sites, but it may also be substituted at Nd(f) sites, which exhibit a small energy difference between the substitution sites for Sm.

[0051] When the rare-earth sintered magnet 1 is produced using the production process described later, the substitution at Nd(g) sites in the main phase 10 is most energy-stable. As described above, holding the magnet in a temperature range where the substitution of La at Nd sites in the main phase 10 is unstable causes some Sm to be released from the Nd sites of the main phase 10 along with La and segregated in the subphase 20. Consequently, the concentrations of La and Sm differ between the main phase 10 and the subphase 20: the sum of the concentrations of La in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of La in the main phase 10, and the sum of the concentrations of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the concentration of Sm in the main phase 10.More specifically, the average concentration of La in the first subphase 21 and the second subphase 22 is equal to or greater than the average concentration of La in the first main phase 11 and the second main phase 12, and the average concentration of Sm in the first subphase 21 and the second subphase 22 is equal to or greater than the average concentration of Sm in the first main phase 11 and the second main phase 12. That is, La and Sm can be described as segregated in subphase 20.

[0052] When comparing La and Sm, it is overwhelmingly more likely that La, held in an unstable energy state within a temperature range, is segregated with respect to energy in subphase 20. Consequently, in the case of the rare-earth sintered magnet 1, which is fabricated with nearly equal concentrations of La and Sm, La exhibits a larger segregation ratio with subphase 20 when comparing the La and Sm present in the rare-earth sintered magnet 1. By being repeatedly held within this temperature range, subphase 20 generates a concentration difference of Sm, which has a small segregation ratio, and the first subphase 21 and the second subphase 22 are formed. This promotes the formation of the core-shell structure in the main phase 10.

[0053] Here, Nd is represented as in Fig. Figure 6 illustrates this, but Nd and Pr are produced as a mixture, as represented by didymium (Di), and it is therefore assumed that the energy levels of Nd and Pr are close to each other. Accordingly, the same applies in a case where Nd is replaced by Pr. Since the two forms of Nd and Pr are present, the main phase 10, which has two types of core-shell structures, can be formed.

[0054] As described above, the rare-earth sintered magnet 1 according to the third embodiment includes the main phase 10, which satisfies a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare-earth elements selected to the exclusion of Nd and Pr, and the main phase 10 crystal grains based on an Nd2Fe 14The B-crystal structure includes the main phase 10 comprising core sections 11c and 12c and shell sections 11s and 12s covering the core sections 11c and 12c, and, if R=La and / or Sm, the rare-earth sintered magnet 1 includes the subphase 20 in addition to the first main phase 11 and the second main phase 12 described in the first embodiment. Subphase 20 comprises the crystalline first subphase 21, which has a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and the crystalline second subphase 22, which has a main component represented by (Nd, Pr, La)-O, and the concentration of Sm is higher in the first subphase 21 than in the second subphase 22. That is, the two types of main phases 10 and the two types of subphases 20 are present.Consequently, it is possible to provide the rare-earth sintered magnet 1, which exhibits excellent magnetic properties compared to the relevant prior art, such as temperature properties of magnetic properties. Furthermore, by setting R to La and Sm, the main phase 10 is in a state in which the first main phase 11, which satisfies CNd>CPr, and the second main phase 12, which satisfies CNd <CPr erfüllt, gemischt bereitgestellt werden.In other words, the rare-earth sintered magnet 1 consists of the main phase 10, which exhibits the two types of the first main phase 11, and the second main phase 12. By focusing on the core sections 11c and 12c of the two types of main phases 10, the main phase 10, which exhibits the two types of core-shell structures, is readily generated, with the Nd concentration in the first main phase 11 being higher than the Pr concentration, and conversely, the Pr concentration in the second main phase 12 being higher than the Nd concentration. Consequently, the effect of improving the magnetic properties and achieving excellent magnetization compared to the relevant prior art, while reducing the use of Nd and heavy rare-earth elements, can be further enhanced.

[0055] Furthermore, in the third embodiment, similar to the first embodiment, it is possible to obtain the rare-earth sintered magnet 1 in which the coercive force is improved compared to the relevant prior art, while the use of heavy rare-earth elements is reduced and a significant decrease in the residual magnetic flux density is prevented. That is to say, the magnetic properties of the rare-earth sintered magnet 1 can be improved compared to the conventional case. Fourth embodiment.

[0056] In the fourth embodiment, a method for producing the rare-earth sintered magnet 1 described in the first and second embodiments or the third embodiment is described. Fig. Figure 7 is a flowchart illustrating an exemplary step of a method for producing a rare-earth sintered magnet according to the fourth embodiment. As shown in Fig. As illustrated in Figure 7, the process for producing the rare-earth sintered magnet 1 includes a production step for a rare-earth sintered magnet alloy (step S10) to produce a rare-earth sintered magnet alloy to serve as raw material for a diffusion precursor, which is a sintered body before a heavy rare-earth element is diffused into the rare-earth sintered magnet 1; a production step for a diffusion precursor (step S20) to form a diffusion precursor; a grain boundary diffusion step (step S30) to diffuse the heavy rare-earth element into the diffusion precursor; and a cooling step (step S40) to cool the diffusion precursor that has diffused with the heavy rare-earth element to obtain the rare-earth sintered magnet 1.

[0057] First, details of the production step for the rare earth sintered magnet alloy are described in step S10. Fig. Figure 8 is a flowchart illustrating an exemplary process of a production step for the rare-earth sintered magnet alloy according to the fourth embodiment. As shown in Fig. As illustrated in Figure 8, the production step for a rare-earth sintered magnet alloy to serve as raw material for the diffusion precursor includes, firstly, a melting step (step S11) to heat and melt the raw material of the rare-earth sintered magnet alloy, which contains an element that forms the diffusion precursor, at a temperature of 1000 K or higher; secondly, a primary cooling step (step S12) to cool the molten raw material on a rotating body to obtain a solidified alloy; and thirdly, a secondary cooling step (step S13) to further cool the solidified alloy in a container. Thus, a rare-earth sintered magnet alloy can be produced. Each step is described below.

[0058] In melting step S11, the raw material of the diffusion precursor is heated and melted at a temperature of 1000 K or higher in a crucible in an atmosphere containing an inert gas, such as argon (Ar), or in a vacuum. Consequently, the rare-earth sintered magnet alloy melts into a molten alloy. When producing the rare-earth sintered magnet 1 of the first and second embodiments, Nd, Pr, Fe, and B can be used as raw materials. When producing the rare-earth sintered magnet 1 of the third embodiment, Nd, Pr, La, Sm, Fe, and B can be used as raw materials. FeB can be used instead of B as a raw material. At this stage, one or more elements selected from the group consisting of Al, Co, Zr, Ti, Nb, and Mn can be included in the raw material as the additive element M.

[0059] Next, in the primary cooling step S12, the molten alloy produced in the melting step is fed to an intermediate container and then to a single roller, which is a rotating body. Consequently, the molten alloy is rapidly cooled on the single roller, which rotates in a predetermined direction, and a solidified alloy thinner than the ingot alloy is produced on the single roller. In this example, the single roller is used as the rotating body, but the present disclosure is not limited to this, and twin rollers, a rotating disk, a rotating cylindrical shape, or the like can be used for rapid contact cooling. From the point of view of efficiently obtaining the thin solidified alloy, the cooling rate in the primary cooling step is preferably in the range of 10 °C / s to 10 °C / s. 7°C / s and preferably in the range of 10 3 °C / s up to 10 4 °C / s. The thickness of the solidified alloy ranges from 0.03 mm to 10 mm. The molten alloy begins to solidify at the section in contact with the individual roller, and crystals grow columnar or needle-like in the thickness direction from the contact surface with the individual roller. The primary cooling step in step S12 corresponds to the primary alloy cooling step.

[0060] Subsequently, in the secondary cooling step S13, the thin solidified alloy produced in the primary cooling step is placed in a tray container and cooled. Upon entering the tray container, the thin solidified alloy is broken down into scale-like (or flake-like) pieces of the rare-earth sintered magnet alloy and cooled. Depending on the cooling rate, ribbon-like pieces of the rare-earth sintered magnet alloy can also be obtained instead of scale-like pieces. From the perspective of obtaining a rare-earth sintered magnet alloy with a structure exhibiting advantageous temperature characteristics of the magnetic properties, the cooling rate in the secondary cooling step is preferably in the range of 10 -2 °C / s up to 10 5 °C / s and preferably in the range of 10 -1 °C / s up to 10 2 °C / s. The secondary cooling step in step S13 corresponds to the secondary alloy cooling step.

[0061] The rare-earth sintered magnet alloy obtained by these steps has a size in the minor axis direction of 3 µm to 10 µm and a size in the major axis direction of 10 µm to 300 µm. In the case of producing the rare-earth sintered magnet 1 of the third embodiment, the rare-earth sintered magnet alloy has a fine crystal structure containing an (Nd, Pr, La, Sm)-Fe-B crystal phase and the crystalline subphase 20 of an oxide represented by (Nd, Pr, La, Sm)-O. Hereinafter, in this document, the crystalline oxide subphase 20 represented by (Nd, Pr, La, Sm)-O will be referred to as the (Nd, Pr, La, Sm)-O phase. The (Nd, Pr, La, Sm)-O phase is a non-magnetic phase consisting of an oxide with a relatively high concentration of rare-earth elements. The thickness of the (Nd, Pr, La, Sm)-O phase is 10 µm or less, corresponding to the width of the grain boundary.After the rapid cooling step, the rare earth sintered magnet alloy produced by the preceding production step has a refined structure compared to the rare earth sintered magnet alloy obtained by casting.

[0062] Next, the production step for a diffusion precursor S20 will be carried out in Fig. 7 described. Fig. Figure 9 is a flowchart illustrating an exemplary production step for the diffusion precursor according to the fourth embodiment. The following describes the production of the rare-earth sintered magnet 1 of the third embodiment as an example; however, the rare-earth sintered magnet 1 of the first and second embodiments can be produced by changing the raw material of the rare-earth sintered magnet alloy to be used. As shown in Fig. As illustrated in Figure 9, the production step for a diffusion precursor includes a pulverization step (step S21) to pulverize the rare-earth magnet alloy, which has the (Nd, Pr, La, Sm)-Fe-B crystalline phase and the (Nd, Pr, La, Sm)-O phase; a forming step (step S22) to produce a shaped body by forming the pulverized rare-earth sintered magnet alloy; a sintering step (step S23) to obtain a sintered body by sintering the shaped body at a predetermined sintering temperature; an aging step (step S24) to age the sintered body to improve the magnetic properties, such as the coercivity of the rare-earth sintered magnet 1; and a cooling step for the sintered body (step S25) to cool the sintered body that has undergone the aging process. Each step is described below.

[0063] In the pulverization step in step S21, the rare-earth sintered magnet alloy, which fulfills the (Nd, Pr, R)-Fe-B requirements according to the production step for a rare-earth sintered magnet alloy in Fig. 8, produced, to rare-earth sintered magnet alloy powder having a particle size of 200 µm or less, preferably 0.5 µm to 100 µm, and more preferably about 1 µm to 10 µm, taking into account the magnetizing ability. The pulverization of the rare-earth sintered magnet alloy is carried out in one example using an agate mortar, a stamping mill, a jaw crusher, or a jet mill. In particular, to reduce the particle size of the powder, it is preferred to pulverize the rare-earth sintered magnet alloy in an atmosphere containing an inert gas. By pulverizing the rare-earth sintered magnet alloy in an atmosphere containing an inert gas, it is possible to prevent oxygen from mixing into the powder. Provided that the pulverization atmosphere does not impair the magnetic properties of the magnet, the rare-earth sintered magnet alloy can be pulverized in air.

[0064] In forming step S22, the rare-earth sintered magnet alloy powder is pressed into a mold under a magnetic field to produce a shaped body. Here, the applied magnetic field can be 2 T in one example. It should be noted that the forming process can also be carried out without a magnetic field.

[0065] In sintering step S23, the molded body produced by compression molding is held at a sintering temperature in the range of 950 °C to 1300 °C, preferably 1000 °C or higher but lower than 1150 °C, for a period of 0.1 to 10 hours, preferably 1.0 to 6.0 hours, thereby producing a sintered body. Sintering is preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation. Sintering can be performed under the application of a magnetic field.

[0066] In the case of Fig. 9. Aging step S24 comprises a primary aging step S24-1, a secondary aging step S24-2, a tertiary aging step S24-3, and a quaternary aging step S24-4. The aging is preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation.

[0067] The condition of the primary aging step S24-1 is that the resulting sintered body is held at a primary aging temperature, which is lower than the sintering temperature, for a period ranging from 0.1 to 10 hours, preferably from 0.5 to 5 hours. Specifically, the primary aging temperature is in the range of 700 °C or higher, but less than 950 °C, and is lower than the sintering temperature.

[0068] The condition of the secondary aging step S24-2 is that, following the primary aging step, the sintered body held in the primary aging step is maintained at a secondary aging temperature for a period ranging from 0.1 hours to 10 hours, preferably from 1.0 hour to 7 hours. This secondary aging temperature is lower than the primary aging temperature. Specifically, the secondary aging temperature is in the range of 450 °C or higher, but less than 700 °C, and is lower than the primary aging temperature.

[0069] The condition of the tertiary aging step S24-3 is that, after the secondary aging step, the sintered body held in the secondary aging step is heated again to the primary aging temperature, specifically a temperature of 700 °C or higher, but lower than 950 °C, and is held at the primary aging temperature for a period in the range of 0.1 hours to 10 hours, preferably for a period in the range of 0.5 hours to 5 hours.

[0070] The condition of the quaternary aging step S24-4 is that, after the tertiary aging step, the sintered body held in the tertiary aging step is held again at the second aging temperature, specifically a temperature of 450 °C or higher but lower than 700 °C, for a period in the range of 0.1 hours to 10 hours, preferably for a period in the range of 1.0 hours to 7 hours.

[0071] Finally, in the cooling step for the sintered body S25, the sintered body held in the quaternary aging step is kept at a cooling temperature of 200 °C or more, but less than 450 °C, for a period of 0.1 to 5 hours. Afterwards, the sintered body is cooled to room temperature, producing a diffusion precursor of the rare-earth sintered magnet 1. Cooling is also preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation.

[0072] As described above, a diffusion precursor is formed, which is a sintered body that has the shape of the final rare-earth sintered magnet 1.

[0073] With renewed reference to Fig. 7. In grain boundary diffusion step S30, a heat treatment is performed under the condition that the diffusion precursor formed in step S25 and the heavy rare-earth element are present, and the heavy rare-earth element undergoes grain boundary diffusion into the diffusion precursor. For example, a heat treatment is performed to maintain the diffusion precursor at a temperature lower than the sintering temperature in sintering step S23. The grain boundary diffusion step can be performed simultaneously with the aging step S24. In the grain boundary diffusion step, the heavy rare-earth element is selectively diffused into at least a portion of the outer contour of the Sm enrichment section 41 of the first subphase 21 and diffuses uniformly into the second subphase 22. A known grain boundary diffusion method can be used for the treatment in the grain boundary diffusion step.Various techniques have been proposed for grain boundary diffusion, depending on the method of introducing heavy rare-earth elements; representative methods include coating diffusion, sputtering diffusion, and vapor diffusion. These representative grain boundary diffusion methods are described below. <beschichtungsdiffusionsverfahren>

[0074] In the coating diffusion process, the grain boundary diffusion step includes a diffusion element adhesion step for adhering a feed section of a heavy rare earth element, which is a material containing a heavy rare earth element and serves as a feed source of the heavy rare earth element to the diffusion precursor, and a diffusion heat treatment step for performing a heat treatment to diffuse the heavy rare earth element from the feed section to the diffusion precursor. In the diffusion element adhesion step, a slurry, obtained by mixing a powdered mixture of a heavy rare earth element with water, an organic solvent, or the like, is adhered to the surface of the diffusion precursor. The slurry adhering to the surface of the diffusion precursor becomes a feed section of a heavy rare earth element.The slurry can be applied by spraying, dip coating, spin coating, screen printing, electroplating, or similar processes. In the diffusion heat treatment step, the diffusion precursor, to which the feed section of a heavy rare-earth element is attached, is subjected to heat treatment at a diffusion temperature lower than the sintering temperature in sintering step S23 to diffuse the heavy rare-earth element into the diffusion precursor. Conditions for the heat treatment include a diffusion temperature lower than the sintering temperature and a duration within the range of 0.1 hours to 100 hours. For example, the diffusion temperature could be in the range of 300 °C to 1000 °C, which is lower than the sintering temperature.The heat treatment is preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation. <sputter-diffusionsverfahren>

[0075] In the sputter diffusion process, the grain boundary diffusion step, similar to the coating diffusion process, also includes a diffusion element adhesion step and a diffusion heat treatment step. In the diffusion element adhesion step, a thin film, having a simple metal or alloy composition of a heavy rare-earth element, is formed on the surface of the diffusion precursor in a dry environment. The thin film formed on the surface of the diffusion precursor becomes a feed section for the heavy rare-earth element. The thin film is formed, for example, by a sputtering process.In the diffusion heat treatment step, the diffusion precursor, in which the feed section of a heavy rare-earth element is formed, is subjected to heat treatment at a diffusion temperature lower than the sintering temperature in sintering step S23, in order to diffuse the heavy rare-earth element into the diffusion precursor. Conditions for the heat treatment are a diffusion temperature lower than the sintering temperature and a duration within the range of 0.1 hours to 100 hours.

[0076] The diffusion temperature, for example, is a temperature in the range of 300 °C to 1000 °C, which is lower than the sintering temperature. The heat treatment is preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation. <dampfdiffusionsverfahren>

[0077] In the vapor diffusion process, a diffusion precursor and a feed source of a heavy rare-earth element are placed in a vacuum furnace. The diffusion precursor is then subjected to heat treatment at a temperature lower than the sintering temperature in sintering step S23 within the vacuum furnace to diffuse the heavy rare-earth element into the diffusion precursor. During the heat treatment, the feed source of the heavy rare-earth element is converted into a gas phase by vacuum heating, and the heavy rare-earth element is fed to the diffusion precursor via the gas phase. Conditions for the heat treatment include a diffusion temperature lower than the sintering temperature and a duration within the range of 0.1 hours to 100 hours. For example, the diffusion temperature is in the range of 600 °C to 900 °C, which is lower than the sintering temperature.Furthermore, in contrast to the coating diffusion process and the sputtering diffusion process, it is not necessary in the vapor diffusion process to attach the feed section of a heavy rare earth element to the diffusion precursor, and the diffusion element attachment step can be omitted, thus shortening the time of the grain boundary diffusion step.

[0078] With renewed reference to Fig. 7. In the final cooling step S40, the diffusion precursor, into which the heavy rare-earth element was diffused in the grain boundary diffusion step, is held at a temperature of less than 200 °C for 0.1 to 5 hours. Afterwards, the diffusion precursor is cooled to room temperature, thereby forming the rare-earth sintered magnet 1 described in the first to third embodiments.In the first embodiment, the rare-earth sintered magnet 1 is formed in which the heavy rare-earth element is present on at least a portion of the surface of the main phase 10; in the second embodiment, the rare-earth sintered magnet 1 is formed in which the heavy rare-earth element has diffused into the subphase 20; and in the third embodiment, the rare-earth sintered magnet 1 is formed in which the heavy rare-earth element has diffused such that it selectively surrounds the outer contour of the Sm enrichment section 41 of the first subphase 21 and has diffused uniformly into the second subphase 22. Cooling is preferably carried out in an atmosphere containing an inert gas or in a vacuum to prevent oxidation.

[0079] As described above, the rare-earth sintered magnet 1, which has a desired shape, is obtained by grain boundary diffusion of the heavy rare-earth element into the diffusion precursor, which has the final shape of the rare-earth sintered magnet 1.

[0080] As described above, the sintered body is repeatedly kept in an unstable energy state within a temperature range by controlling the temperature and time in the sintering step, the aging step, and the cooling step. As a result, the first main phase 11, consisting of CNd>CPr, and the second main phase 12, consisting of CNd <CPr besteht, gemischt werden. Mit anderen Worten weist der Seltenerd-Sintermagnet 1 zwei Arten von Hauptphasen 10 auf, nämlich die erste Hauptphase 11 und die zweite Hauptphase 12, und mit Fokus auf die Kernabschnitte 11c und 12c der zwei Arten von Hauptphasen 10 ist es möglich, den Seltenerd-Sintermagneten 1 zu produzieren, der dadurch gekennzeichnet ist, dass in der ersten Hauptphase 11 die Nd-Konzentration höher als die Pr-Konzentration ist und umgekehrt in der zweiten Hauptphase 12 die Pr-Konzentration höher als die Nd-Konzentration ist.

[0081] Furthermore, it is possible to produce the rare-earth sintered magnet 1 which, in addition to the first main phase 11 and the second main phase 12 described in the first embodiment, has the crystalline first subphase 21, which has a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and the crystalline second subphase 22, which has a main component represented by (Nd, Pr, La)-O, wherein the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.

[0082] Therefore, it is possible to provide the rare earth sintered magnet 1, which has excellent magnetizing ability and excellent magnetic properties compared to the relevant prior art, while reducing the use of Nd and heavy rare earth elements.

[0083] In the fourth embodiment, the rare-earth magnet alloy, which has the (Nd, Pr, La, Sm)-Fe-B crystalline phase and the (Nd, Pr, La, Sm)-O phase, is pulverized into rare-earth sintered magnet alloy powder, which is then shaped. The shaped body is then sintered to form a sintered body, and the sintered body is aged to become the rare-earth sintered magnet 1. Thus, the rare-earth sintered magnet 1 can be produced according to the third embodiment.

[0084] In the primary aging step, the resulting sintered body is held at the primary aging temperature, which is lower than the sintering temperature, for 0.1 to 10 hours, preferably 0.5 to 5 hours. In the secondary aging step, the sintered body is held at the secondary aging temperature, which is lower than the primary aging temperature, for 0.1 to 10 hours, preferably 1.0 to 7 hours. In the tertiary aging step, the sintered body is reheated to the primary aging temperature and held at this temperature for 0.1 to 10 hours, preferably 0.5 to 5 hours. In the quaternary aging step, the sintered body is again held at the secondary aging temperature for 0.1 to 10 hours, preferably 1.0 to 7 hours.In this way, by controlling the temperature and time to perform two sets of the primary and secondary aging steps, a state is created in which the sintered body is repeatedly held in an unstable energy state within a temperature range. As a result, it is possible to obtain the rare-earth sintered magnet 1, in which the first main phase 11 consists of CNd>CPr, and the second main phase 12 consists of CNd <CPr besteht, gemischt bereitgestellt werden.In other words, the rare-earth sintered magnet 1 has two types of main phases 10, namely the first main phase 11 and the second main phase 12, and by focusing on the core sections 11c and 12c of the two types of main phases 10 it is possible to selectively produce the rare-earth sintered magnet 1 in which the Nd concentration is higher than the Pr concentration in the first main phase 11 and conversely, the Pr concentration is higher than the Nd concentration in the second main phase 12.

[0085] Furthermore, the above production process makes it possible to selectively produce the rare-earth sintered magnet 1, which has the crystalline first subphase 21, which has a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and the crystalline second subphase 22, which has a main component represented by (Nd, Pr, La)-O, wherein the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.

[0086] In the process for producing the rare-earth sintered magnet 1 according to the fourth embodiment, the rare-earth sintered magnet alloy based on R-Fe-B, which contains Nd and Pr as the rare-earth element R, is pulverized, a powdered body of the rare-earth sintered magnet alloy based on R-Fe-B is sintered, and an aging process is carried out to form a diffusion precursor having the first main phase 11 and the second main phase 12. In the method for producing the rare-earth sintered magnet 1 according to the fourth embodiment, the rare-earth sintered magnet 1, in which the heavy rare-earth element is present on a part of the surfaces of the first main phase 11 and the second main phase 12, or the rare-earth sintered magnet 1, in which the heavy rare-earth element is present in the subphase 20, can be produced by a heat treatment in which the heavy rare-earth element is subjected to grain boundary diffusion into the diffusion precursor.As a result, it is possible to obtain the rare-earth sintered magnet 1, which is able to improve magnetic properties compared to the relevant prior art, while reducing the use of heavy rare-earth elements compared to the relevant prior art and preventing a deterioration of magnetic properties.

[0087] Furthermore, in the process for producing the rare-earth sintered magnet 1 according to the fourth embodiment, the rare-earth sintered magnet alloy based on R-Fe-B, containing Nd, Pr, La and Sm as the rare-earth element R, is pulverized, a powdered body of the rare-earth sintered magnet alloy based on R-Fe-B is sintered, and an aging process is carried out to form a diffusion precursor which, in addition to the first main phase 11 and the second main phase 12, has the first subphase 21, which has the Sm enrichment section 41 in which Sm is enriched, and the second subphase 22, which has a lower Sm concentration than the first subphase 21.In the method for producing the rare-earth sintered magnet 1 according to the fourth embodiment, the rare-earth sintered magnet 1, in which the heavy rare-earth element selectively surrounds the outer contour of the Sm enrichment section 41 in the first subphase 21 and the heavy rare-earth element is uniformly distributed in the second subphase 22, can be produced by a heat treatment in which the heavy rare-earth element is subjected to grain boundary diffusion into the diffusion precursor. As a result, it is possible to obtain the rare-earth sintered magnet 1, which is capable of improving magnetic properties compared to the relevant prior art, while reducing the use of heavy rare-earth elements compared to the relevant prior art and preventing a deterioration of magnetic properties. Fifth embodiment.

[0088] In the fifth embodiment, a rotor is described which uses the rare-earth sintered magnet 1 according to the first embodiment, the second embodiment or the third embodiment, which is produced using the production method according to the fourth embodiment. Fig. Figure 10 is a cross-sectional view that schematically illustrates an exemplary configuration of a rotor equipped with a rare-earth sintered magnet according to the fifth embodiment. Fig. Figure 10 represents a cross-section in a direction perpendicular to a rotation axis RA of a rotor 100.

[0089] The rotor 100 is rotatable about the rotation axis RA. The rotor 100 includes a rotor core 101 and the rare-earth sintered magnet 1, which is inserted into a magnet insertion hole 102 provided in the rotor core 101 along the circumferential direction of the rotor 100. Fig. Figure 10 illustrates an example in which the four magnet insertion holes 102 are provided in the rotor core 101 and the four rare-earth sintered magnets 1 are inserted into the magnet insertion holes 102, but the number of magnet insertion holes 102 and the number of rare-earth sintered magnets 1 can be changed according to the configuration of the rotor 100. The rotor core 101 is formed by a plurality of disk-shaped electromagnetic steel sheets stacked in the axial direction of the axis of rotation RA.

[0090] The rare-earth sintered magnets 1 are produced using the production method described in the fourth embodiment. Each of the four rare-earth sintered magnets 1 is inserted into the corresponding magnet insertion hole 102. The four rare-earth sintered magnets 1 are magnetized such that the magnetic poles of the rare-earth sintered magnets 1 on the radially outer side of the rotor 100 differ between adjacent rare-earth sintered magnets 1.

[0091] As described above, the rotor 100 according to the fifth embodiment includes the rare-earth sintered magnet 1 according to the first, second, or third embodiment, which is capable of improving magnetic properties at room temperature and preventing a deterioration of magnetic properties associated with a temperature increase. Thus, due to the rare-earth sintered magnet 1, which is capable of preventing a deterioration of magnetic properties associated with a temperature increase, while reducing the use of heavy rare-earth elements compared to the relevant prior art and maintaining a high residual magnetic flux density and coercivity, a deterioration of magnetic properties is prevented even in a high-temperature environment exceeding 100 °C.As a result, it is possible to improve magnetic properties and magnetization while substituting cost-effective rare-earth elements for Nd and heavy rare-earth elements, which are expensive and pose a procurement risk due to high distribution irregularities, and to stabilize the operation of the rotor 100 even in high-temperature environments exceeding 100 °C. Furthermore, since the rare-earth sintered magnet 1, according to the first, second, or third embodiment, exhibits excellent magnetizing capability compared to the relevant prior art, magnetization in an assembled state, with the rare-earth sintered magnet 1 mounted on the rotor 100, is possible, thus facilitating handling in the production process. In addition, the magnetization process can be implemented at a reduced voltage, contributing to energy savings. Sixth embodiment.

[0092] The sixth embodiment describes a rotary machine equipped with the rotor 100 according to the fifth embodiment. Fig. Figure 11 is a cross-sectional view that schematically illustrates an exemplary configuration of a rotary machine according to the sixth embodiment. Fig. Figure 11 represents a cross-section in a direction perpendicular to the rotation axis RA of the rotor 100.

[0093] The rotary machine 120 includes the rotor 100 described in the fifth embodiment, which is rotatable about the axis of rotation RA, and an annular stator 130, which is provided coaxially with the rotor 100 and faces it. The stator 130 is formed by stacking a plurality of electromagnetic steel laminations in the axial direction of the axis of rotation RA. Instead of the described configuration, another configuration of the stator 130 can be assumed. Teeth 131 are provided along the inner surface of the stator 130, projecting towards the rotor 100. Windings 132 are provided on the teeth 131. The winding type of the windings 132 can be, in one example, a concentrated winding or a distributed winding.That is, the annular stator 130 has an annular structure facing the rotor 100 and includes, on an inner surface on one side where the rotor 100 is placed, the teeth 131 projecting towards the rotor 100, and the windings 132 provided on the teeth 131. The number of magnetic poles of the rotor 100 in the rotating machine 120 should be no less than two, that is, the number of rare-earth sintered magnets 1 should be no less than two. Although in . Fig. Figure 11 illustrates an example of the rotor 100 of the internal magnet type; the rotor 100 can belong to the surface magnet type, in which the rare earth sintered magnets 1 are attached to the outer circumference with an adhesive.

[0094] As described above, the rotary machine 120 according to the sixth embodiment incorporates the rare-earth sintered magnet 1 according to the first, second, or third embodiment, which is capable of improving magnetic properties at room temperature and preventing a deterioration of magnetic properties associated with a temperature increase. Thus, due to the rare-earth sintered magnet 1, which is capable of preventing a deterioration of magnetic properties associated with a temperature increase, while reducing the use of heavy rare-earth elements compared to the relevant prior art and maintaining a high residual magnetic flux density and coercivity, a deterioration of magnetic properties is prevented even in a high-temperature environment exceeding 100 °C.As a result, it is possible to improve magnetic properties and magnetization, while substituting cost-effective rare earth elements for Nd and heavy rare earth elements, which are expensive and have a procurement risk due to high distribution irregularities, and to drive the rotor 100 stably and to stabilize the operation of the rotating machine 120 even in a high temperature environment exceeding 100 °C. [Examples]

[0095] The rare earth sintered magnet 1 according to the present disclosure is described in detail below with reference to examples and comparative examples.

[0096] In Examples 1 to 8, the rare-earth sintered magnet 1 is produced using the method described in the fourth embodiment, employing samples of a variety of rare-earth sintered magnet alloys based on (Nd, Pr, La, Sm)-Fe-B, which differ in their composition. In Examples 1 to 8, a rare-earth sintered magnet alloy in which the contents of Nd, Pr, La, and Sm vary is used to form a diffusion precursor, and Dy, as the heavy rare-earth element, is subjected to grain boundary diffusion into the diffusion precursor such that Dy is 0.10 atomic%, thereby producing the rare-earth sintered magnet 1.That is, in Examples 1 to 8, the rare-earth sintered magnet 1, in which Dy, which is a heavy rare-earth element, has diffused to 0.10 atomic %, is produced using the rare-earth sintered magnet alloy represented by (Nd, Pr, La, Sm)-Fe-B, using the production process described in the fourth embodiment.

[0097] In Comparative Examples 1 to 12, the rare-earth sintered magnet 1, which incorporates a heavy rare-earth element, is experimentally produced using R-Fe-B-based samples of a variety of rare-earth sintered magnet alloys differing in composition, using a general rare-earth magnet production process as disclosed in Patent Literature 1 or Patent Literature 2. The samples of the rare-earth sintered magnets 1 according to Comparative Examples 1 to 12 differ in R.

[0098] In comparative examples 1 to 6, the rare-earth sintered magnet 1, in which Dy, being a heavy rare-earth element, has diffused to 0.15 atomic %, is produced using a rare-earth sintered magnet alloy in which R contains Nd and one or more elements of Dy, Pr, La, and Sm, using the production method disclosed in patent literature 1.

[0099] In comparative examples 7 to 12, the rare-earth sintered magnet 1, in which Dy, being a heavy rare-earth element, has diffused to 0.15 atomic %, is produced using a rare-earth sintered magnet alloy in which R contains Nd and one or more elements of Dy, Pr, La, and Sm, using the production method disclosed in patent literature 2.

[0100] Table 3 shows the general formulas of the rare-earth sintered magnets according to the examples and comparative examples, the content of elements forming R, the results of the analysis of structural forms, and the results of the determination of magnetic properties. Table 3 shows the general formula of the main phase 10 of each sample, which is the rare-earth sintered magnet 1 according to examples 1 to 8 and comparative examples 1 to 12. [Table 3]

[0101] Next, a method for analyzing the structure of rare-earth sintered magnet 1 according to Examples 1 to 8 and Comparative Examples 1 to 12 is described. The structural shape of rare-earth sintered magnet 1 is determined by elemental analysis using a scanning electron microscope (SEM) and an EPMA. Here, an FE-EPMA (produced by JEOL Ltd., product name: JXA-8530F) is used as both the SEM and the EPMA. The conditions for the elemental analysis are as follows: accelerating voltage: 15.0 kV, irradiation current: 2.271 e -008 A, Irradiation time: 130 ms, Number of pixels: 512 pixels × 512 pixels, Magnification: 5000x, Cumulative number (number of integrations): one.

[0102] Next, a method for evaluating the magnetic properties of the rare-earth sintered magnet 1 according to Examples 1 to 8 and Comparative Examples 1 to 12 is described. The evaluation of the magnetic properties is carried out by measuring the coercivity of a variety of samples using a pulse-excited BH tracer. The maximum applied magnetic field obtained by the BH tracer is equal to or greater than 6 T, at which the rare-earth sintered magnet 1 is fully magnetized.The pulse-excited BH tracer can be replaced by a self-registering DC magnetometer, also called a DC BH tracer, a vibrating sample magnetometer (VSM), a magnetic property measurement system (MPMS), a physical property measurement system (PPMS), or the like, as long as a maximum applied magnetic field of 6 T or more can be generated. The measurement is performed in an atmosphere containing an inert gas, such as nitrogen. The magnetic properties of each sample are measured by detecting magnetization picked up by a search coil or magnetic sensor on the rare-earth sintered magnet 1, which is magnetized by an applied magnetic field.Magnetic properties are measured using a JH curve or a BH curve, which represents the measured magnetic hysteresis. The magnetic properties of each sample are measured at a first measurement temperature T1 and a second measurement temperature T2, which differ from each other. The temperature coefficient α [% / °C] of the residual magnetic flux density is a value obtained by calculating the ratio of the difference between the residual magnetic flux density at the first measurement temperature T1 and the residual magnetic flux density at the second measurement temperature T2 to the residual magnetic flux density at the first measurement temperature T1, and dividing this ratio by the temperature difference (T2-T1).The temperature coefficient β [% / °C] of the coercive force is a value obtained by calculating the ratio of the difference between the coercive force at the first measurement temperature T1 and the coercive force at the second measurement temperature T2 to the coercive force at the first measurement temperature T1, and dividing this ratio 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 effectively a deterioration of the magnet's magnetic properties with respect to a temperature increase is prevented.

[0103] First, the results of the analysis of the samples according to examples 1 to 8 and comparison examples 1 to 12 are described. Fig. Figure 12 is a sketch of a composite image obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 with an FE-EPMA. Fig. 13 to 18 are element maps obtained by analyzing a cross-section of a rare-earth sintered magnet according to Examples 1 to 8 using the FE-EPMA. Fig. 13 is an elemental map of Nd, Fig. 14 is an element map of Pr, Fig. 15 is an element card from Dy, Fig. 16 is an element card of O, Fig. 17 is an elemental map of Sm and Fig. 18 is an elemental chart from La. It should be noted that the Fig. 13 to 18 are the element cards, which are in Fig. 12 illustrated regions. Since the rare-earth sintered magnets 1 according to examples 1 to 8 all produce similar results, the Fig. 12 to 18 representative examples are shown, from 1 to 8. Furthermore, components that are included in Fig. 1 and Fig. 3 correspond, marked with the same reference symbols.

[0104] As in the Fig. 13 and Fig. As illustrated in Figure 14, each of the samples in Examples 1 to 8 contains the main phase 10, which satisfies a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected to the exclusion of Nd and Pr, the main phase 10 being crystalline grains based on an Nd2Fe 14 The B-crystal structure is present, with main phase 10 containing core sections 11c and 12c and shell sections 11s and 12s covering core sections 11c and 12c. Furthermore, it is confirmed that main phase 10 contains the first main phase 11, which satisfies CNd>CPr, and the second main phase 12, which satisfies CNd. <CPr erfüllt, gemischt bereitgestellt werden.

[0105] Here, the concentration difference, which is fulfilled by "the first main phase 11, the CNd>CPr, and the second main phase 12, the CNd <CPr erfüllt" angegeben wird, dass es eine klare Differenz in den Erfassungsintensitäten von Nd und Pr durch eine Abbildungsanalyse unter Verwendung eines EPMA gibt. Unter Bezugnahme auf den Fall der ersten Hauptphase 11 als Beispiel ist konkret die EPMA-Erfassungsintensität der Konzentration von Nd in dem Kernabschnitt 11c höher als der Durchschnitt und die EPMA-Erfassungsintensität der Konzentration von Pr gibt ungefähr den unteren Grenzwert an. Die zweite Hauptphase 12 ist das Gegenteil der ersten Hauptphase 11.

[0106] Referring to the representation of Nd in Fig. 13 and the representation of Pr in Fig. As examples, the average detection level of Nd according to the EPMA is 92, and the average detection level of Pr is 135. In the case of the first main phase 11, CNd is higher than 92, CPr is approximately at the lower limit, and there is a clear concentration difference. Since the second main phase 12 is the opposite of the first main phase 11, CPr is also higher than 135, CNd is approximately at the lower limit, and there is a clear concentration difference.

[0107] As in the Fig. As illustrated in Figures 16 to 18, the rare-earth sintered magnet 1, when R = La and / or Sm, comprises the first subphase 21, which is crystalline and has a major component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and the second subphase 22, which is crystalline and has a major component represented by (Nd, Pr, La)-O, in addition to the first main phase 11 and the second main phase 12 in the first embodiment. As described above, it is confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22, as described above.

[0108] In Table 3, “o” is entered in the columns of the first main phase 11 and the second main phase 12 for the samples in which the states of the first main phase 11 satisfy CNd>CPr and of the second main phase 12 satisfy CNd <CPr erfüllt, bestätigt sind und „x" ist in die Spalten der ersten Hauptphase 11 und der zweiten Hauptphase 12 für die Proben eingetragen, in denen solche Zustände nicht bestätigt sind. Die Konzentrationsdifferenz von Ungleichheitszeichen bedeutet, dass es eine klare Differenz bei den Erfassungsintensitäten von Nd und Pr gibt. Konkret ist in einem Beispiel im Fall der ersten Hauptphase 11 die EPMA-Erfassungsintensität der Konzentration von Nd höher als der Durchschnitt und liegt die EPMA-Erfassungsintensität der Konzentration von Pr ungefähr beim unteren Grenzwert. Der Fall in der zweiten Hauptphase 12 ist das Gegenteil des Falls in der ersten Hauptphase 11.If only CNd <CPr, wie in der zweiten Hauptphase 12 bestätigt ist, ist „o" nur in die Spalte der zweiten Hauptphase 12 eingetragen und ist „x" in die Spalte der ersten Hauptphase 11 eingetragen.

[0109] For samples that are confirmed to have the crystalline first subphase 21 based on an oxide phase having a main component represented by (Nd, Pr, La, Sm)-O and the crystalline second subphase 22 having a main component represented by (Nd, Pr, La)-O, and for which it is confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22, “o” is entered in each of the columns of the first subphase 21 and the second subphase 22 in Table 3, and for samples where this is not confirmed, “x” is entered in each of the columns of the first subphase 21 and the second subphase 22.Furthermore, in a case where there is only one subphase 20 or no Sm concentration difference between the subphases 20, "o" is entered only in the column of the first subphase 21 and "x" is entered in the column of the second subphase 22, assuming that only the first subphase 21 is present. It should be noted that the concentration difference between the first subphase 21 and the second subphase 22 means that the Sm detection intensity in a figure analysis using the EPMA is, on average, higher in the first subphase 21 than in the second subphase 22. Referring to the figure representation of Sm in... Fig. 17 as an example, more specifically the average value of the capture levels of Sm with the EPMA is 15.9 and the first sub-phase 21 is higher than 15.9, whereas the second sub-phase 22 is lower than 15.9, which indicates that capture in an aggregation state cannot be carried out.

[0110] Furthermore, the intensity ratio of the element map obtained through FE-EPMA analysis confirms that the number of first main phases 11, which are CNd>CPr, is greater than the number of second main phases 12, which are CNd <CPr sind. Mit Fokus auf die Hüllenabschnitte 11s und 12s der Kern-Hülle-Struktur wird zudem bestätigt, dass die erste Hauptphase 11 die relationalen Ausdrücke von CNd> SNd and CPr <SPr erfüllt und die zweite Hauptphase 12 die relationalen Ausdrücke von CNd<SNd und CPr> SPr fulfilled.

[0111] Next, the results of the magnetic property measurements in each sample, as shown in Examples 1 to 8 and Comparative Examples 1 to 12, are described. Each sample undergoing magnetic measurement is a block with a length, width, and height of 7 mm. The first measurement temperature, T1, is 23 °C, and the second measurement temperature, T2, is 200 °C. 23 °C is room temperature. The 200 °C measurement temperature, T2, is a temperature typical of environments where automotive and industrial motors operate.

[0112] First, the residual magnetic flux density and coercive force in each sample are determined according to Examples 1 to 8 and Comparison Examples 2 to 12 in comparison to Comparison Example 1. If the values ​​of the residual magnetic flux density and coercive force of each sample at 23 °C are within an allowable measurement error of 1% compared to the values ​​of Comparison Example 1, the values ​​are classified as "equivalent". Values ​​1% or more above this are classified as "good", and values ​​1% or more below are classified as "poor".

[0113] Next, the temperature coefficient α of the residual magnetic flux density is calculated using the residual magnetic flux density at the first measurement temperature T1 of 23 °C and the residual magnetic flux density at the second measurement temperature T2 of 200 °C. The temperature coefficient β of the coercive force is calculated using the coercive force at the first measurement temperature T1 of 23 °C and the coercive force at the second measurement temperature T2 of 200 °C. The temperature coefficient of the residual magnetic flux density and the temperature coefficient of the coercive force in each sample according to Examples 1 to 8 and Comparison Examples 2 to 12 are determined in comparison to Comparison Example 1.If the values ​​of each sample are within an allowable measurement error of 11% compared to the absolute value |α| of the temperature coefficient of the residual magnetic flux density and the absolute value |β| of the temperature coefficient of the coercive force in the sample of comparison example 1, the values ​​are classified as "equivalent". Values ​​1% or more below this value are classified as "good", and values ​​1% or more above this value are classified as "poor". Since the samples classified as "good" have a smaller temperature coefficient, it is possible to provide the rare-earth sintered magnet 1, which also exhibits stable magnetic properties in a high-temperature environment, while preventing the deterioration of magnetic properties associated with a temperature increase.

[0114] The results of the determination of the residual magnetic flux density, the coercive force, the temperature coefficient of the residual magnetic flux density and the temperature coefficient of the coercive force are shown in Table 3.

[0115] Comparative Example 1 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, which was produced in the form of Nd-Fe-B using the production process described in patent literature 1, with Nd, Fe, and FeB as raw materials. Based on observation of the structural shape of this sample produced by the above-described method, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr, La, and Sm, nor is it confirmed that the concentration of Sm in subphase 20 is higher in the first subphase 21 than in the second subphase 22. Evaluation of the magnetic properties of this sample using the above-described method shows that the residual magnetic flux density is 1.3 T and the coercive force 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.These values ​​from comparison example 1 are used as a reference.

[0116] Comparative Example 2 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, which was produced in the form of (Nd,Dy)-Fe-B using the production process described in patent literature 1, with Nd, Dy, Fe, and FeB as raw materials. Based on observation of the structural shape of this sample using the above-described method, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr, La, and Sm, and it is not confirmed that the concentration of Sm in subphase 20 is higher in the first subphase 21 than in the second subphase 22. Evaluation of the magnetic properties of this sample using the above-described method shows that the residual magnetic flux density is poor, the coercive force is good, the temperature coefficient of the residual magnetic flux density is equivalent, and the temperature coefficient of the coercive force is equivalent.This result reflects the fact that the coercive force is improved by substituting Dy, which exhibits high magnetocrystalline anisotropy, for some of the Nd. Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy, as a heavy rare-earth element, into such a diffusion precursor does not further improve the magnetic properties.

[0117] Comparative Example 3 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, which was produced in the form of (Nd,Pr)-Fe-B using the production process described in patent literature 1, with Nd, Pr, Fe, and FeB as raw materials. Based on the observation of the structural form of this sample produced using the above-described process, the main phase 10, in which Nd and Pr are provided in a mixture, is confirmed due to the addition of Pr; however, no core-shell structure is formed. Furthermore, due to the absence of La and Sm, it is not confirmed that the concentration of Sm in subphase 20 is higher in the first subphase 21 than in the second subphase 22.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "equivalent," the coercive force is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," and the temperature coefficient of the coercive force is "poor." This result reflects the fact that while the addition of Pr increases the magnetic anisotropy of the main phase 10 and improves the coercive force, the structural shape in the main phase 10 and the subphase 20 is not optimal. Furthermore, since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy, a heavy rare-earth element, into such a diffusion precursor does not improve the magnetic properties.

[0118] Comparative Example 4 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, produced in the form of (Nd, La, Sm)-Fe-B using the production process described in patent literature 1, with Nd, La, Sm, Fe, and FeB as raw materials. Based on the structural shape of this sample produced using the above-described method, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr. Furthermore, due to the addition of La and Sm, the concentration of Sm in one subphase 20 is segregated along with the segregation of La, but the second subphase 22 is not present. Moreover, it is also not confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is equivalent, the coercive force is equivalent, the temperature coefficient of the residual magnetic flux density is good, and the temperature coefficient of the coercive force is good. This result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase 20 yields a good result with respect to the temperature coefficient of the magnetic properties, but the magnetic properties at room temperature are not improved, and the structural shape in the main phase 10 and the subphase 20 is not optimal. Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy as a heavy rare-earth element into such a diffusion precursor does not improve the magnetic properties.

[0119] Comparative Example 5 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, produced in the form of (Nd, La, Sm)-Fe-B using the production process described in patent literature 1, with Nd, La, Sm, Fe, and FeB as raw materials. The compositional ratio of Nd, La, and Sm differs from that of Comparative Example 4. Based on the observation of the structural form of this sample produced using the above-described process, a core-shell structure in the main phase 10 is not confirmed due to the absence of Pr. Furthermore, due to the addition of La and Sm, the concentration of Sm in one subphase 20 is segregated along with the segregation of La, but the second subphase 22 is not present. Moreover, it is also not confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is equivalent, the coercive force is equivalent, the temperature coefficient of the residual magnetic flux density is good, and the temperature coefficient of the coercive force is good. This result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase 20 yields a good result for the temperature coefficient of the magnetic properties, but the magnetic properties at room temperature are not improved, and the structural shape in the main phase 10 and the subphase 20 is not optimal: changing the composition ratio of Nd, La, Sm leads to almost the same result as in comparative example 4.Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy as a heavy rare-earth element into such a diffusion precursor does not further improve the magnetic properties.

[0120] Comparative Example 6 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, which was produced in the form of (Nd, Pr, La, Sm)-Fe-B using the production process described in patent literature 1, with Nd, Pr, La, Sm, Fe, and FeB as raw materials. Based on the observation of the structural form of this sample produced using the above-described process, the main phase 10, in which Nd and Pr are provided in a mixture, is confirmed due to the addition of Pr; however, no core-shell structure is formed. Furthermore, due to the addition of La and Sm, the concentration of Sm in a subphase 20 is segregated along with the segregation of La, but the second subphase 22 is not present. Moreover, it is also not confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "equivalent," the coercive force is "good," the temperature coefficient of the residual magnetic flux density is "good," and the temperature coefficient of the coercive force is "equivalent." This result reflects the fact that the addition of Pr increases the magnetic anisotropy of the main phase 10 to improve the coercive force, and the presence of La and Sm in the main phase 10 or the subphase 20 improves the temperature coefficient of the magnetic properties, especially the temperature coefficient of the coercive force; however, the structural shape in the main phase 10 and the subphase 20 is not optimal.Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy as a heavy rare-earth element into such a diffusion precursor does not further improve the magnetic properties.

[0121] Comparative Example 7 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, produced in the form of Nd-Fe-B using the production process, which includes the hot forming process described in patent literature 2, and using Nd, Fe, and FeB as raw materials. Based on the observation of the structural shape of this sample produced using the above-described process, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr, La, and Sm, nor is it confirmed that the concentration of Sm in subphase 20 is higher in the first subphase 21 than in the second subphase 22. However, the refinement of the structure, which is a property of a magnet produced using the hot forming process, is confirmed.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercive force is "good," and the temperature coefficient of the residual magnetic flux density and the coercive force are "equivalent." This result reflects the reduction in the residual magnetic flux density, despite the improvement in coercive force associated with the refinement of the structure through the hot forming process. Furthermore, since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy, a heavy rare-earth element, into such a diffusion precursor does not improve the magnetic properties.

[0122] Comparative Example 8 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, produced in the form of (Nd, Dy)-Fe-B using the production process, which includes the hot forming process described in patent literature 2, and using Nd, Dy, Fe, and FeB as raw materials. Based on observation of the structural shape of this sample produced using the above-described method, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr, La, and Sm, nor is it confirmed that the concentration of Sm in subphase 20 is higher in the first subphase 21 than in the second subphase 22. Evaluation of the magnetic properties of this sample using the above-described method shows that the residual magnetic flux density is poor, the coercive force is good, the temperature coefficient of the residual magnetic flux density is equivalent, and the temperature coefficient of the coercive force is equivalent.This indicates that the coercivity is significantly improved for some Nd by substituting Dy, which exhibits high magnetocrystalline anisotropy, in addition to hot-working production, but the other properties reflect the structural refinement. Since the magnetic properties depend on the structure of the diffusion precursor as the base material, diffusion of Dy, a heavy rare-earth element, into such a diffusion precursor does not further improve the magnetic properties.

[0123] Comparative Example 9 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, produced in the form of (Nd, Pr)-Fe-B using the production process, which includes the hot forming process described in patent literature 2, and using Nd, Pr, Fe, and FeB as raw materials. Based on the observation of the structural shape of this sample produced using the above-described method, the core-shell structure is confirmed by hot forming in addition to the addition of Pr; however, there is only one type of main phase 10, which exhibits a high Pr concentration in the core region. Furthermore, due to the absence of La and Sm, it is not confirmed that the concentration of Sm in subphase 20 is higher in the first subphase 21 than in the second subphase 22.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercivity is "good," the temperature coefficient of the residual magnetic flux density is "equivalent," and the temperature coefficient of the coercivity is "equivalent." This indicates that the coercivity is significantly improved to the level of rare-earth sintered magnet 1 containing Dy due to the formation of the core-shell structure, which has a high Pr concentration in the core section. However, the other properties reflect the structural refinement. Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy as a heavy rare-earth element into such a diffusion precursor does not further improve the magnetic properties.

[0124] Comparative Example 10 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, produced in the form of (Nd, La, Sm)-Fe-B using the production process, which includes the hot forming process described in patent literature 2, and using Nd, La, Sm, Fe, and FeB as raw materials. Based on the observation of the structural shape of this sample produced using the above-described method, no core-shell structure is confirmed in the main phase 10 due to the absence of Pr. Furthermore, due to the addition of La and Sm, the concentration of Sm in one subphase 20 is segregated along with the segregation of La, but the second subphase 22 is not present. Moreover, it is also not confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercive force is "good," the temperature coefficient of the residual magnetic flux density is "good," and the temperature coefficient of the coercive force is "good." This result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase 20 yields a good result for the temperature coefficient of the magnetic properties, but the residual magnetic flux density at room temperature is not improved, and the structural shape in the main phase 10 and the subphase 20 is not optimal. Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy as a heavy rare-earth element into such a diffusion precursor does not improve the magnetic properties.

[0125] Comparative Example 11 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, produced in the form of (Nd, La, Sm)-Fe-B using the production process, which includes the hot forming process described in patent literature 2, and using Nd, La, Sm, Fe, and FeB as raw materials. The composition ratio of Nd, La, and Sm differs from that of Comparative Example 10. Based on the observation of the structural shape of this sample produced using the above-described method, a core-shell structure in the main phase 10 is not confirmed due to the absence of Pr. Furthermore, due to the addition of La and Sm, the concentration of Sm in one subphase 20 is segregated along with the segregation of La, but the second subphase 22 is not present. Moreover, it is also not confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercive force is "good," the temperature coefficient of the residual magnetic flux density is "good," and the temperature coefficient of the coercive force is "good." This result reflects the fact that the presence of La and Sm in the main phase 10 or the subphase 20 yields a good result for the temperature coefficient of the magnetic properties, but the residual magnetic flux density at room temperature is not improved, and the structural shape in the main phase 10 and the subphase 20 is not optimal. Changing the composition ratio of Nd, La, Sm leads to almost the same result as in comparative example 10.Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy as a heavy rare-earth element into such a diffusion precursor does not further improve the magnetic properties.

[0126] Comparative Example 12 is a sample of the rare-earth sintered magnet 1, in which 0.15 atomic percent Dy has diffused, produced in the form of (Nd, Pr, La, Sm)-Fe-B using the production process, which includes the hot forming process described in patent literature 2, and using Nd, Pr, La, Sm, Fe, and FeB as raw materials. Based on the observation of the structural shape of this sample produced using the above-described method, the core-shell structure is confirmed by hot forming in addition to the addition of Pr; however, there is only one type of main phase 10, which exhibits a high Pr concentration in the core region. Furthermore, due to the addition of La and Sm, the concentration of Sm in one subphase 20 is segregated along with the segregation of La, but the second subphase 22 is not present. Moreover, it is also not confirmed that the concentration of Sm in the first subphase 21 is higher than in the second subphase 22.The evaluation of the magnetic properties of this sample using the method described above shows that the residual magnetic flux density is "poor," the coercive force is "good," the temperature coefficient of the residual magnetic flux density is "good," and the temperature coefficient of the coercive force is "good." This indicates that the coercive force is significantly improved to the level of the rare-earth sintered magnet 1 containing Dy due to the formation of the core-shell structure, which has a high Pr concentration in the core section. Furthermore, the presence of La and Sm in the main phase 10 or subphase 20 improves the temperature coefficient of the magnetic properties, particularly the temperature coefficient of the coercive force. However, the result also reflects the fact that the residual magnetic flux density is not improved at room temperature and that the structural shape in the main phase 10 and subphase 20 is not optimal.Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy as a heavy rare-earth element into such a diffusion precursor does not further improve the magnetic properties.

[0127] The samples of examples 1 to 8 are the rare-earth sintered magnet 1, which includes the main phase 10 satisfying a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare-earth elements selected to the exclusion of Nd and Pr, and the main phase 10 crystal grains based on an Nd2Fe 14 The B-crystal structure contains the main phase 10, which includes the core sections 11c and 12c, and the shell sections 11s and 12s cover the core sections 11c and 12c, wherein the main phase 10 is the first main phase 11, which satisfies CNd>CPr, and the second main phase 12, which satisfies CNd <CPr erfüllt, beinhaltet und die erste Hauptphase 11 und die zweite Hauptphase 12 gemischt bereitgestellt werden. Wenn R=La und / oder Sm, sind die erste Subphase 21, die kristallin ist und eine Hauptkomponente auf Basis einer Oxidphase aufweist, die durch (Nd, Pr, La, Sm)-O dargestellt wird, und die zweite Subphase 22, die kristallin ist und eine Hauptkomponente aufweist, die durch (Nd, Pr, La)-O dargestellt wird, zusätzlich zu der ersten Hauptphase 11 und der zweiten Hauptphase 12 beinhaltet, und die Konzentration von Sm ist in der ersten Subphase 21 höher als in der zweiten Subphase 22.The evaluation of the magnetic properties of the samples from Examples 1 to 8 using the method described above shows that the residual magnetic flux density is "good", the coercive force is "good", the temperature coefficient of the residual magnetic flux density is "good", and the temperature coefficient of the coercive force is "good". As a result, these rare-earth sintered magnets 1 achieve the effect of exhibiting excellent magnetic properties compared to the relevant prior art, while reducing the use of Nd and heavy rare-earth elements, which are expensive and pose a procurement risk due to high distribution irregularities. Since the magnetic properties depend on the structure of the diffusion precursor as the base material, the diffusion of Dy as a heavy rare-earth element into the diffusion precursor, which has good magnetic properties, further improves the magnetic properties.In examples 1 to 8, the rare-earth sintered magnet 1, which exhibits good magnetic properties, can be obtained with a diffusion quantity of 0.10 atomic percent, which is lower than 0.15 atomic percent, the diffusion quantity of Dy in comparative examples 1 to 12. That is, compared to comparative examples 1 to 12, it is possible to obtain the rare-earth sintered magnet 1, which is capable of significantly improving the coercive force without reducing the residual magnetic flux density, while simultaneously reducing the amount of heavy rare-earth elements used.

[0128] The configurations described in the aforementioned embodiments are examples. These embodiments can be combined with other well-known technologies and with each other, and some of the configurations can be omitted or modified in a manner that does not deviate from the core principles. List of reference symbols

[0129] 1 Rare-earth sintered magnet; 10 Main phase; 11 First main phase; 11c, 12c Core section; 11s, 12s Shell section; 12 Second main phase; 20 Subphase; 21 First subphase; 22 Second subphase; 31 Layer containing a heavy rare-earth element; 32 Section containing a heavy rare-earth element; 41 Sm enrichment section; 100 Rotor; 101 Rotor core; 102 Magnet insertion hole; 120 Rotating machine; 130 Stator; 131 Teeth; 132 Windings. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2018-174313

[0005] JP 2021-174818

[0005] Cited non-patent literature

[0000] JF Herbst et al., “Relationships between crystal structure and magnetic properties in Nd2Fe 14 B", PHYSICAL REVIEW B. 1984, Vol. 29, No. 7, pp. 4176-4178

[0045] < / dampfdiffusionsverfahren> < / beschichtungsdiffusionsverfahren>

Claims

[1] Rare earth sintered magnet comprising: a main phase that satisfies a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected to the exclusion of Nd and Pr, wherein the main phase consists of crystal grains based on an Nd2Fe 14 contains B-crystal structure; and a subphase that exists between a multitude of the main phases, wherein the main phase includes a core section and a shell section that covers the core section, the main phase consists of a first main phase that satisfies CNd>CPr, and a second main phase that satisfies CNd <CPr erfüllt, beinhaltet, wobei CNd die Konzentration von Nd im Kernabschnitt ist und CPr die Konzentration von Pr im Kernabschnitt ist, the first main phase and the second main phase are provided in a mixed manner and a heavy rare earth element is present on at least part of a surface of the first main phase and the second main phase. [2] Rare earth sintered magnet, comprising: a main phase that satisfies a general formula (Nd, Pr, R)-Fe-B, where R represents one or more rare earth elements selected to the exclusion of Nd and Pr, wherein the main phase consists of crystal grains based on an Nd2Fe 14 contains B-crystal structure; and a subphase that exists between a multitude of the main phases, wherein the main phase includes a core section and a shell section that covers the core section, the main phase consists of a first main phase that satisfies CNd>CPr, and a second main phase that satisfies CNd <CPr erfüllt, beinhaltet, wobei CNd die Konzentration von Nd im Kernabschnitt ist und CPr die Konzentration von Pr im Kernabschnitt ist, the first main phase and the second main phase are provided in a mixed manner and A heavy rare earth element is present in the subphase. [3] Rare earth sintered magnet according to claim 1 or 2, where the number of first main phases is greater than the number of second main phases. [4] Rare earth sintered magnet according to claim 1 or 2, wherein the first main phase has relational expressions of CNd>SNd and CPr <SPr erfüllt und die zweite Hauptphase relationale Ausdrücke von CNd<SNd und CPr> SPr is satisfied, where SNd is the concentration of Nd in the shell section and SPr is the concentration of Pr in the shell section. [5] Rare earth sintered magnet according to claim 1, wherein if R is La and / or Sm, the subphase includes a first subphase that is crystalline and has a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and a second subphase that is crystalline and has a main component represented by (Nd, Pr, La)-O. The concentration of Sm is higher in the first subphase than in the second subphase. [6] Rare earth sintered magnet according to claim 2, wherein if R is La and / or Sm, the subphase includes a first subphase that is crystalline and has a main component based on an oxide phase represented by (Nd, Pr, La, Sm)-O, and a second subphase that is crystalline and has a main component represented by (Nd, Pr, La)-O. The first subphase forms an Sm enrichment section, which has a higher concentration of Sm than the second subphase. [7] Rare earth sintered magnet according to claim 6, wherein the heavy rare earth element is present such that it surrounds an outer contour of the Sm enrichment section in the first subphase. [8] Method for producing the rare-earth sintered magnet according to any one of claims 1 to 7, wherein the method comprises: a production step for a rare earth sintered magnet alloy to produce a rare earth sintered magnet alloy to serve as raw material for a diffusion precursor before the heavy rare earth element is diffused into the rare earth sintered magnet; a production step for a diffusion precursor to produce the diffusion precursor; a diffusion step for the diffusion of the heavy rare-earth element into the diffusion precursor; and a cooling step to cool the diffusion precursor in which the heavy rare earth element has diffused, wherein The production step for the rare earth sintered magnet alloy includes the following: a melting step to melt a raw material of a rare earth sintered magnet alloy containing an element that forms the diffusion precursor; a primary alloy cooling step to cool the raw material that was melted in the melting step in order to obtain a solidified alloy; and a secondary alloy cooling step to further cool the solidified alloy in order to obtain a rare earth sintered magnet alloy, The production step for the diffusion precursor includes the following: a pulverization step to pulverize the rare earth sintered magnet alloy that satisfies (Nd, Pr, R)-Fe-B; a forming step for producing a shaped body by forming a powder of the rare earth sintered magnetic alloy, which was pulverized in the pulverization step; a sintering step to obtain a sintered body by sintering the shaped body at a sintering temperature, which is a predetermined temperature; a primary aging step to maintain the sintered body at a primary aging temperature, which is a temperature lower than the sintering temperature; a secondary aging step to maintain the sintered body, which was maintained in the primary aging step, at a secondary aging temperature which is a temperature lower than the primary aging temperature; a tertiary aging step to re-maintain the sintered body, which was maintained in the secondary aging step, at the primary aging temperature; a quaternary aging step to re-maintain the sintered body, which was maintained in the tertiary aging step, at the secondary aging temperature; and a cooling step for the sintered body to cool the sintered body, which was held in the quaternary aging step, in order to obtain the diffusion precursor, and In the diffusion step, the diffusion precursor is subjected to heat treatment at a temperature lower than the sintering temperature, provided that the diffusion precursor and the heavy rare earth element are present. [9] Rotor, comprising: a rotor core; and the rare earth sintered magnet according to one of claims 1 to 7, which is provided in the rotor core. [10] Rotary machine comprising: the rotor according to claim 9; and a ring-shaped stator facing the rotor, comprising on an inner surface on one side where the rotor is placed windings provided on teeth projecting towards the rotor.

Images