Magnetic body and manufacturing method therefor

Abstract

A magnetic body, according to one embodiment, comprises grain boundaries between crystal grains, the magnetic body including a magnetic body comprising Fe and praseodymium (Pr), wherein a first ratio of the Fe composition to the Pr composition in the crystal grains is greater than a second ratio of the Fe composition to the Pr composition in the grain boundaries.

Description

Magnetic material and method for manufacturing the same

[0001] The present invention relates to a magnetic material and a method for manufacturing the same.

[0002] A Re-Fe-B magnet may be a permanent magnet having a composition of a rare earth element and a compound of iron and boron (B). The rare earth element (Re) may include neodymium (Nd), praseodymium (Pr), dysprosium (Dy), cerium (Ce), or terbium (Tb).

[0003] These permanent magnets have been developed and used for a long time, and are used in various fields such as electronics, automotive, medical devices, energy, transportation, mobile devices, and robotics. In particular, in line with the recent trend toward lightweight and miniaturized devices, they are being used in products such as machine tools, electronic information devices, home appliances, mobile phones, robot motors, wind turbines, robots, small motors for automobiles, and drive motors.

[0004] The magnetic properties of these rare-earth permanent magnets or magnetic materials can be expressed in terms of residual flux density (Br) and coercive force (HcJ). The residual flux density can be determined by the main phase fraction, density, and magnetic orientation of the rare-earth permanent magnet, and the coercive force is related to the microstructure of the rare-earth permanent magnet.

[0005] Accordingly, a technology has been developed to refine the particle size used in manufacturing rare earth permanent magnets to improve coercivity. However, as the particle size is refined, not only does the degree of oxidation increase, but the manufacturing cost also increases, making it impossible to refine the particle size indefinitely.

[0006] In addition, these rare earth permanent magnets have a problem in that eddy currents are easily generated inside the rare earth permanent magnets due to their high conductivity and low resistivity, which increases the temperature of the permanent magnets. The temperature increase of the rare earth permanent magnets can easily cause a decrease in magnetic flux density or irreversible demagnetization of the rare earth permanent magnets due to the increase in temperature, which causes a fatal performance decline.

[0007] Therefore, there is a demand for a new structure of Re-Fe-B magnetic material with improved coercivity, etc.

[0008] The embodiment provides a magnetic material having a grain boundary diffusion material disposed at a grain boundary, wherein the magnetic material includes Fe, Pr, and Nd, and the melting point is reduced by the grain boundary diffusion material and diffusion at low temperatures is increased, thereby preventing adjacent grains from reacting with each other at high temperatures, thereby providing a magnetic material with improved process efficiency and coercivity.

[0009] The embodiment can provide a magnetic material having improved coercivity by decreasing Fe and increasing Nd and Pr from grain to grain boundary.

[0010] In addition, the embodiment can provide a magnetic material in which the direction of magnetization is suppressed and the coercivity is improved as the Pr composition at the grain boundary becomes larger than the Fe composition or the Nd composition.

[0011] The problem to be solved in the embodiment is not limited to this, and it can be said that the purpose or effect that can be understood from the solution or implementation form of the problem described below is also included.

[0012] A magnetic body according to an embodiment includes a grain boundary between grains, wherein the magnetic body includes Fe and praseodymium (Pr), and a first ratio of the Fe composition to the Pr composition in the grains is greater than a second ratio of the Fe composition to the Pr composition in the grain boundaries.

[0013] The above magnetic material may include Nd.

[0014] The third ratio of Fe composition to Nd composition in the above crystal grains may be greater than the fourth ratio of Fe composition to Nd composition in the above crystal grain boundaries.

[0015] The fifth ratio of the Nd composition to the Pr composition in the above crystal grains may be greater than the sixth ratio of the Nd composition to the Pr composition in the above crystal grain boundaries.

[0016] The above first to sixth ratios can be satisfied within 500 μm by EDS (Energy Dispersive X-ray Spectroscopy) on the surface of the magnetic body.

[0017] The above Fe composition has a minimum peak at the grain and a maximum peak at the grain boundary, and the above Nd composition and Pr composition have a maximum peak at the grain boundary and a minimum peak at the grain, and each of the maximum peak and minimum peak can be measured within 500 μm from the surface by EDS (Energy Dispersive X-ray Spectroscopy).

[0018] The maximum peak of the Fe composition in the above crystal grains may be greater than the minimum peak of the Fe composition at the crystal grain boundary.

[0019] The minimum peak of the Pr composition in the above crystal grains may be smaller than the maximum peak of the Pr composition at the crystal grain boundary.

[0020] The minimum peak of the Nd composition in the above crystal grains may be smaller than the maximum peak of the Nd composition at the crystal grain boundary.

[0021] In the above crystal grain boundary, the average value of the Fe composition may be greater than the average value of the Nd composition.

[0022] At the above grain boundary, the minimum peak of the Fe composition may be larger than the maximum peak of the Nd composition.

[0023] At the above crystal grain boundary, the maximum peak of the Nd composition may be larger than the maximum peak of the Pr composition.

[0024] At the above crystal grain boundary, the maximum peak of the Pr composition may be larger than the minimum peak of the Fe composition or the maximum peak of the Nd composition.

[0025] In the above crystal grain boundary, the difference between the maximum peak and the minimum peak of the Pr composition may be greater than the difference between the maximum peak and the minimum peak of the Nd composition.

[0026] In the above crystal grain boundary, the difference between the maximum peak and the minimum peak of the Fe composition may be greater than the difference between the maximum peak and the minimum peak of the Nd composition.

[0027] The above magnetic material may include a first region in which the Nd composition is higher than the Pr composition at the crystal grain boundary.

[0028] The above magnetic material may include a second region in which the Nd composition is lower than the Pr composition at the crystal grain boundary.

[0029] The above magnetic material may include a third region in which the Pr composition is greater than the Fe composition at the grain boundary.

[0030] The above magnetic material may include a fourth region in which the Nd composition is greater than the Fe composition at the grain boundary.

[0031] The embodiment implements a magnetic material having a grain boundary diffusion material arranged at a grain boundary, wherein the magnetic material includes Fe, Pr, and Nd, and the melting point is reduced by the grain boundary diffusion material and diffusion at low temperatures is increased, thereby preventing adjacent grains from reacting with each other at high temperatures, thereby improving process efficiency and coercivity.

[0032] The embodiment can realize a magnetic material having improved coercivity by decreasing Fe and increasing Nd and Pr from grain to grain boundary.

[0033] In addition, the embodiment can realize a magnetic material in which the direction of magnetization is suppressed and the coercive force is improved as the Pr composition at the grain boundary becomes larger than the Fe composition or the Nd composition.

[0034] The various advantageous and beneficial effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0035] Fig. 1 is a perspective view of a magnetic body according to an embodiment.

[0036] Figure 2 is a drawing taken along line AA' in Figure 1.

[0037] Figure 3 is a drawing showing the boundary diffusion material removed from Figure 2.

[0038] Figure 4 is an enlarged view of part A in Figure 2.

[0039] Figure 5 is a graph showing the relative ratio of the composition of the magnetic material in the BB' region in Figure 4.

[0040] Figure 6 is an enlarged view of part K in Figure 5.

[0041] Fig. 7 is a graph showing the relative ratio of the composition of a magnetic body according to another example than Fig. 5.

[0042] Figure 8 is an enlarged view of portion L in Figure 7.

[0043] Fig. 9(a) is an HAADF image of one region of a magnetic material according to an embodiment, and Figs. 9(b) to 9(d) are EDS mapping images for Ga, Cu, and Pr, respectively.

[0044] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0045] However, the technical idea of ​​the present invention is not limited to some of the embodiments described, but can be implemented in various different forms, and within the scope of the technical idea of ​​the present invention, one or more of the components between the embodiments can be selectively combined or substituted for use.

[0046] In addition, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as having a meaning that can be generally understood by a person of ordinary skill in the technical field to which the present invention belongs, unless explicitly and specifically defined and described, and terms that are commonly used, such as terms defined in a dictionary, may be interpreted in consideration of the contextual meaning of the relevant technology.

[0047] Additionally, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0048] In this specification, the singular may also include the plural unless specifically stated otherwise in the phrase, and when it is described as “A and / or at least one (or more) of B, C”, it may include one or more of all combinations that can be combined with A, B, C.

[0049] Additionally, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used.

[0050] These terms are intended only to distinguish one component from another, and are not intended to limit the nature, order, or sequence of the component.

[0051] And, when a component is described as being 'connected', 'coupled' or 'connected' to another component, it may include not only cases where the component is directly connected, coupled or connected to the other component, but also cases where the component is 'connected', 'coupled' or 'connected' by another component between the component and the other component.

[0052] Additionally, when described as being formed or arranged "above or below" each component, "above" or "below" includes not only cases where the two components are in direct contact with each other, but also cases where one or more other components are formed or arranged between the two components. Furthermore, when expressed as "above" or "below", it can include the meaning of a downward direction as well as an upward direction based on one component.

[0053] Hereinafter, a magnetic body according to an embodiment will be described with reference to the drawings. The magnetic body may be called a 'permanent magnet', a 'magnet', a 'magnetic member', a 'sintered magnet', etc.

[0054] In addition, embodiments of the present invention can be applied to various fields of application. For example, the magnetic body or permanent magnet according to embodiments of the present invention can be used in various fields such as electronic information, automobile industry, medical devices, energy, and transportation. For example, the magnetic body or permanent magnet according to embodiments can be applied to products such as machine tools, electronic information devices, home electronic products, mobile phones, motors for robots, wind generators, small motors for automobiles, and drive motors. That is, the magnetic body or permanent magnet can be applied to various components that utilize magnetic force such as magnets in the joints or motors of humanoids, magnets in camera module (CM) actuators, motors, transformers, and inductors of vehicles.

[0055] Furthermore, when the permanent magnet or magnetic body according to the embodiment is applied to each of the above-described fields or products, the reliability of the product / application can be easily secured due to improved magnetic characteristics (such as coercivity) as described below. Furthermore, the magnet or magnetic body can easily satisfy the characteristics of each field or application (or component), while providing improved technical interoperability or compatibility with technologies required in each field (e.g., vehicles, robots, electronic devices, machine tools, energy devices, etc.).

[0056] Fig. 1 is a perspective view of a magnetic material according to an embodiment. Fig. 2 is a view taken along line AA' of Fig. 1. Fig. 3 is a view of Fig. 2 with the grain boundary diffusion material removed. Fig. 4 is an enlarged view of portion A of Fig. 2.

[0057] Referring to FIGS. 1 to 3, a magnetic body (1000) according to an embodiment may include a base portion (300) and a grain boundary diffusion metal (200) disposed in the base portion (300).

[0058] The base (300) may include a Re-Fe-B magnetic material. Re may include a rare earth element. Furthermore, Re may include a light rare earth element. For example, Re may include neodymium (Nd), praseodymium (Pr), dysprosium (Dy), cerium (Ce), or terbium (Tb).

[0059] The base portion (300) according to the embodiment can be formed by sintering magnetic powder. For example, rare earth oxide, iron, boron, and a reducing agent can be mixed and then heated. As a result, the rare earth oxide is reduced, and for example, Re2Fe 14 Magnetic powder on B can be formed. Then, the magnetic powder can be heated to a set temperature range to form a base portion (300).

[0060] And the base portion (300) can form a plurality of crystal grains (100) through this sintering process. Accordingly, a boundary can be formed between adjacent crystal grains in the base portion (300). That is, a grain boundary (GB) can be formed between adjacent crystal grains. Accordingly, the base portion (300) can include a plurality of crystal grains (100) and grain boundaries (GB) between the crystal grains.

[0061] In addition, in the magnetic body (1000) according to the embodiment, a grain boundary diffusion metal (200) may be arranged at a grain boundary (GB). For example, a grain boundary diffusion metal (or material) may be coated on the surface of the magnetic body (1000). Accordingly, the magnetic body (1000) may include a coating layer (CL) formed adjacent to the surface, and the coating layer (CL) may be made of the grain boundary diffusion metal (200). In addition, the coating layer by grain boundary diffusion may be located on outer surfaces facing each other or outer surfaces overlapping in one direction in the magnetic body (1000) or the base portion (300). For example, the magnetic body (1000) or the base portion (300) may be a hexahedron. In addition, the grain boundary diffusion metal (200) may be applied to the upper or lower surface of the magnetic body (1000) or the base portion (300). Accordingly, the coating layer (CL) may also be positioned on the upper or lower surface of the magnetic body (1000) or the base portion (300). Furthermore, the grain boundary diffusion metal (200) may also be applied to the side surface of the base portion (300). The grain boundary diffusion metal (or material) reduces the melting point and increases diffusion at low temperatures, thereby preventing adjacent crystal grains from reacting with each other at high temperatures, thereby implementing a magnetic body with improved process efficiency and coercivity.

[0062] For example, the grain boundary diffusion metal (200) can be processed from an ingot into powder. Then, the grain boundary diffusion metal (or material) of the powder can be applied to a base portion that has undergone the sintering process described above. Subsequently, a heat treatment can be performed at a set temperature. Accordingly, the grain boundary diffusion metal (or material) can be diffused into the interior of the base portion that has undergone the sintering process in the magnetic body. In detail, the grain boundary diffusion metal (or material) can be diffused into the grain boundaries. Accordingly, the grain boundary diffusion metal (200) can be arranged at the grain boundaries (GB). A detailed manufacturing method for this will be described later.

[0063] The intergranular diffusion metal (200) may include a material having a specific or designed composition and composition ratio. As an example, the intergranular diffusion metal (200) may include a light rare earth material. For example, the intergranular diffusion metal (200) may include praseodymium (Pr). For example, the intergranular diffusion metal (200) may include a metal compound including praseodymium (Pr). Specifically, the intergranular diffusion metal (200) may include Pr. In addition, the intergranular diffusion metal (200) may include at least one metal selected from the group consisting of copper (Cu), aluminum (Al), and gallium (Ga).

[0064] Additionally, the grain boundary diffusion metal (200) has a set composition ratio. The composition ratio of the grain boundary diffusion metal can be expressed in atomic percent.

[0065] Furthermore, referring to FIG. 4, the grain boundary diffused metal (200) may diffuse into the grain boundaries (GB) of the base portion (300) and may exist in large numbers at the grain boundaries (GB). In addition, some of the grain boundary diffused metal (200) may exist in some of the grains (100) of the base portion (300). For example, the grain boundary diffused metal (200) may not exist in one grain (100), but may exist in another grain (100). Therefore, within a predetermined distance from the surface of the magnetic material, the grain boundary diffused metal (200) may exist in large numbers at the grain boundaries (GB) relative to the grains (100).

[0066] In addition, in this specification, the content or composition of each composition of the magnetic body (including grain boundary diffusion metal) is expressed in atomic %, and the difference in the content or composition of each composition is explained in FIGS. 5 to 8. That is, the composition ratio of each composition of the magnetic body follows FIGS. 5 to 8 described below.

[0067] Figure 5 is a graph showing the relative ratio of the composition of the magnetic material in the BB' region in Figure 4, and Figure 6 is an enlarged view of the K portion in Figure 5.

[0068] In this specification, the ratio (elemental composition) or peak for the elements forming the magnetic body can be measured within 500 μm from the surface (see Fig. 2) by EDS (Energy Dispersive X-ray Spectroscopy). And each 'elemental composition (e.g., Pr composition, Fe composition, Nd composition, etc.)' can mean a qualitative amount or a quantitative amount. In addition, the surface can mean the facing side surfaces (e.g., the upper surface and the lower surface) of the magnetic body where the coating layer is located.

[0069] This energy dispersive spectroscopy (Energy Dispersive X-ray Spectroscopy, EDS) refers to equipment or technology that distinguishes each atom by utilizing the fact that each substance is composed of an atomic nucleus and electrons. For example, when an electron beam accelerated to more than several keV is irradiated on a magnetic material, electrons (e.g., K-shell electrons) (especially inner-shell electrons) that are orbiting in distinct orbits with principal quantum numbers such as K, L, and M can be knocked out by the electron beam. At this time, since it becomes an unstable excited state in terms of energy, energy can be released when an outer-shell electron (an electron that was in the next orbit (e.g., L-shell) or the next orbit (e.g., M-shell) of the knocked-out inner-shell electron) enters the orbit (inner-shell electron, e.g., K-shell) that it was previously knocked out of in order to become a stable energy state. EDS detects elements by scanning this emitted energy (e.g., X-rays).

[0070] And in the graphs shown in FIGS. 5 to 8, the X-axis represents the distance to adjacent grains and grain boundaries between adjacent grains. That is, an increase in the value of the X-axis may mean a region movement to one grain, grain boundary, and another grain. And the Y-axis may represent the composition ratio (Atom %). That is, the value of the Y-axis may mean the 'elemental composition' (e.g., Nd composition or Nd element ratio). And the graphs shown in FIGS. 5 to 8 may be profiles (grain-grain boundary-grain) by EDS.

[0071] Referring to FIGS. 5 and 6, FIGS. 5 and 6 illustrate ratios of elements constituting a magnetic body in a magnetic body according to an embodiment. Specifically, the magnetic body may include neodymium (Nd), iron (Fe), praseodymium (Pr), copper (Cu), and gallium (Ga). In addition, the elements constituting the magnetic body may be formed in different ratios in grains (100) and grain boundaries (GB). Specifically, the position-specific composition or ratio of each element of neodymium (Nd), iron (Fe), praseodymium (Pr), copper (Cu), and gallium (Ga) may be different in each grain and grain boundary.

[0072] Furthermore, the ratio between the compositions of each element in the magnetic material may be different. For example, the composition of Nd may be greater than the composition of Pr in some parts. Also, the composition of Nd may be less than the composition of Pr in other parts. In other words, the composition of each element may be non-uniform in the magnetic material. Also, the relationship between the compositions of each element within 500 μm from the surface of the magnetic material may be different from the relationship between the compositions of each element in the center of the magnetic material (the area exceeding 500 μm from the surface). For example, the relationship between the first ratio and the second ratio within 500 μm from the surface of the magnetic material, and the relationship between the first ratio and the second ratio in the center of the magnetic material may be different. In particular, the grain boundary diffused metal (or material) may be less or absent in the center of the magnetic material compared to the surface. In other words, the grain boundary diffused metal (or material) may exist in large quantities on the surface of the magnetic material, and its content may decrease as it penetrates into the interior.

[0073] In an embodiment, the composition (content) of at least one of Re (e.g., Nd), Fe, and B in a magnetic material may decrease from a grain (100) toward a grain boundary (GB). For example, at least one of Nd, Fe, and B may decrease from a grain toward a grain boundary (GB).

[0074] In addition, the element composition (content) of the grain boundary diffused metal (or material) may increase from the grain (100) toward the grain boundary (GB). For example, the composition of at least one of Pr, Cu, Al, and Ga may increase from the grain (100) toward the grain boundary (GB). Conversely, the composition of at least one of Pr, Cu, Al, and Ga may decrease from the grain boundary (GB) to the grain (100). That is, at least some of the elements Pr, Cu, Al, and Ga may partially diffuse from the grain boundary (GB) to the grain (100). The elements Pr, Cu, Al, and Ga may penetrate into the interior of the grain while diffusing from the grain boundary (GB).

[0075] More specifically, in the magnetic body according to the embodiment, the Fe composition may have a maximum peak (P12) at the grain (100) and a minimum peak (P11) at the grain boundary (GB). And the Pr composition in the magnetic body may have a minimum peak (P22) at the grain (100) and a maximum peak (P21) at the grain boundary (GB). In addition, the Nd composition in the magnetic body may have a minimum peak (P32) at the grain (100) and a maximum peak (P31) at the grain boundary (GB). In addition, the Ga composition may have a minimum peak (P42) at the grain (100) and a maximum peak (P41) at the grain boundary (GB). In addition, the Cu composition may have a minimum peak (P52) at the grain (100) and a maximum peak (P51) at the grain boundary (GB).

[0076] In this specification, a peak may refer to a measured value, as described above, for example, a qualitative quantity. Furthermore, in the profiles of FIGS. 5 to 7 within this specification, the Atom% on the y-axis or vertical axis represents intensity. Therefore, since a peak refers to the intensity of detected energy, the term "peak" may be used interchangeably with "intensity."

[0077] And since peak means 'intensity', a large peak means that the relative Atom% is large at that location. In other words, 'a large peak (or intensity)' means 'the relative element composition (content) is more or greater at that location.'

[0078] The Fe composition may decrease from the grain (100) toward the grain boundary (GB). Accordingly, the maximum peak (P12) of the Fe composition in the grain (100) may be larger than the minimum peak (P11) of the Fe composition at the grain boundary (GB). In addition, the maximum peak (P12) of the Fe composition in the grain (100) may be larger than the maximum peak of the Fe composition at the grain boundary (GB).

[0079] The Pr composition may increase from the grain (100) toward the grain boundary (GB). Accordingly, the minimum peak (P22) of the Pr composition in the grain (100) may be smaller than the maximum peak (P21) of the Pr composition at the grain boundary (GB). In addition, the maximum peak of the Pr composition in the grain (100) may be smaller than the maximum peak (P21) of the Pr composition at the grain boundary (GB).

[0080] The Nd composition may increase from the grain (100) toward the grain boundary (GB). Accordingly, the minimum peak (P32) of the Nd composition in the grain (100) may be smaller than the maximum peak (P31) of the Nd composition at the grain boundary (GB). In addition, the maximum peak of the Nd composition in the grain (100) may be smaller than the maximum peak (P21) of the Nd composition at the grain boundary (GB).

[0081] The Ga composition may increase from the grain (100) toward the grain boundary (GB). Accordingly, the minimum peak (P42) of the Ga composition in the grain (100) may be smaller than the maximum peak (P41) of the Ga composition at the grain boundary (GB). In addition, the maximum peak of the Ga composition in the grain (100) may be smaller than the maximum peak (P41) of the Ga composition at the grain boundary (GB).

[0082] The Cu composition may increase from the grain (100) toward the grain boundary (GB). Accordingly, the minimum peak (P52) of the Cu composition in the grain (100) may be smaller than the maximum peak (P51) of the Cu composition at the grain boundary (GB). In addition, the maximum peak of the Cu composition in the grain (100) may be smaller than the maximum peak (P51) of the Cu composition at the grain boundary (GB).

[0083] Additionally, the average value of the Fe composition at the grain boundary (GB) may be greater than the average value of the Nd composition. Additionally, the average value of the Fe composition at the grain boundary (GB) may be greater than the average value of the Pr composition.

[0084] By this configuration, the grain boundary diffusion material can diffuse at the grain boundaries and be arranged to surround the edges of the grains. Therefore, the melting point can be enhanced and the diffusion depth can be improved.

[0085] Furthermore, the minimum peak (P11) of the Fe composition at the grain boundary (GB) can be larger than the maximum peak (P31) of the Nd composition. By this configuration, the direction of magnetization can be easily suppressed.

[0086] Additionally, the maximum peak (P31) of the Nd composition at the grain boundary (GB) may be larger than the maximum peak (P21) of the Pr composition. By this configuration, the coercivity may be improved.

[0087] In addition, the difference between the maximum peak (P21) of Pr composition at the grain boundary (GB) and the minimum peak (P22) of Pr composition at the grain (100) may be greater than the difference between the maximum peak (P31) of Nd composition at the grain boundary (GB) and the minimum peak (P32) of Nd composition at the grain boundary (100). In addition, the difference between the maximum peak (P21) of Pr composition at the grain boundary (GB) and the minimum peak of Pr composition at the grain boundary (GB) may be greater than the difference between the maximum peak (P31) of Nd composition at the grain boundary (GB) and the minimum peak of Nd composition at the grain boundary (GB). In other words, the change in Pr composition at the grain boundary (GB) may be greater than the change in Nd composition. In addition, the maximum change in Pr composition at the grain and grain boundary may be greater than the change in Nd composition. Therefore, the Nd composition may be maintained within a certain range because the change in Pr composition at the grain and grain boundary is smaller than that of the Pr composition. Accordingly, the phenomenon of the direction of magnetization rotating can be suppressed.

[0088] Additionally, the difference between the maximum and minimum peaks of the Fe composition at grain boundaries (GB) may be greater than the difference between the maximum and minimum peaks of the Nd composition (P31). In other words, the variation in the Fe composition at grain boundaries (GB) may be greater than the variation in the Nd composition. As a result, the Nd composition can be maintained within a certain range with less variation compared to the Fe composition at grains and grain boundaries.

[0089] And according to an embodiment, the first ratio of the Fe composition to the Pr composition in the crystal grain (100) may be different from the second ratio of the Fe composition to the Pr composition in the grain boundary (GB). In this case, the ratio becomes 0 or infinity when Pr or Fe is absent, and in the present specification, the ratio means the case where both Pr and Fe are present in the grain boundary. Furthermore, the ratio in the grain boundary (GB) may mean the average value of the corresponding element in the grain boundary, or may mean the maximum or minimum peak.

[0090] And the first ratio means the Fe composition / Pr composition at the grain (100), and the second ratio means the Fe composition / Pr composition at the grain boundary (GB). Furthermore, the first ratio may be greater than the second ratio. That is, the Pr composition may not decrease in response to the decrease in the Fe composition at the grain boundary (GB). For example, the Fe composition at the edge of the grain boundary (GB) may be greater than the Fe composition at the center of the GB (at the bisection point of the width or the bisection point between the edges of adjacent grains). Conversely, the Pr composition at the edge of the grain boundary (GB) may be less than the Pr composition at the center of the grain boundary (GB). In this way, the Fe composition may decrease toward the center of the grain boundary (GB), but the Pr composition may increase. Furthermore, the Nd composition may also increase from the edge of the grain boundary (GB) toward the center of the grain boundary (GB).

[0091] By this configuration, a large amount of Pr, which is a grain boundary diffusion material, exists at the grain boundary (GB) compared to the grain (100), and penetration of the diffusion material into the grain (100) may become difficult. As a result, coercivity can be maintained or improved even when light rare earth elements are used instead of heavy rare earth elements. Furthermore, by using light rare earth elements instead of heavy rare earth elements, contamination due to refining, etc. can be suppressed, and manufacturing costs can be reduced.

[0092] Furthermore, the third ratio of the Fe composition to the Nd composition in the grain (100) may be different from the fourth ratio of the Fe composition to the Nd composition in the grain boundary (GB). The third ratio refers to the Fe composition / Nd composition in the grain (100), and the fourth ratio refers to the Fe composition / Nd composition in the grain boundary (GB). The Fe composition may decrease toward the grain boundary (GB), and the Nd composition may decrease toward the grain (100). As such, the third ratio may be greater than the fourth ratio. As such, the intergranular diffusion of the intergranular diffusion material may be improved by the Nd composition in the grain while maintaining the magnetic properties by the Fe composition in the grain.

[0093] Additionally, the fifth ratio of the Nd composition to the Pr composition in the grain (100) may be different from the sixth ratio of the Nd composition to the Pr composition in the grain boundary (GB). The fifth ratio refers to the Nd composition / Pr composition in the grain (100), and the sixth ratio refers to the Nd composition / Pr composition in the grain boundary (GB). Furthermore, the fifth ratio may be greater than the sixth ratio.

[0094] Additionally, the maximum peak (P21) of the Pr composition at the grain boundary (GB) may be smaller than the minimum peak of the Fe composition or the maximum peak (P31) of the Nd composition.

[0095] Additionally, the magnetic material may include a first region (AR1) in which the Nd composition is higher than the Pr composition at the grain boundary (GB). Additionally, the magnetic material may include a second region (AR2) in which the Pr composition is higher than the Nd composition at the grain boundary (GB). In the present example, the first region (AR1) or the second region (AR2) may exist at the grain boundary (GB).

[0096] The maximum peak (P31) of the Nd composition at the grain boundary (GB) may be larger than the maximum peak (P21) of the Pr composition at the grain boundary (GB). In addition, the minimum peak of the Nd composition at the grain boundary (GB) may be larger than the minimum peak of the Pr composition at the grain boundary (GB). Furthermore, the difference between the minimum peak of the Nd composition and the minimum peak of the Pr composition at the grain boundary (GB) may be larger than the difference between the maximum peak (P31) of the Nd composition and the maximum peak (P21) of the Pr composition at the grain boundary (GB). In addition, the difference (d3) between the maximum peak (P31) and the minimum peak of the Nd composition at the grain boundary (GB) may be smaller than the difference (d2) between the maximum peak (P21) and the minimum peak of the Pr composition at the grain boundary (GB). In other words, the rate of change of the Pr composition at the grain boundary (the rate of change between the maximum peak and the minimum peak) may be larger than the rate of change of the Nd composition. By this configuration, Pr exists in large numbers at the grain boundary surface, so internal penetration is suppressed, and thus the resulting decrease in coercivity can be suppressed.

[0097] Additionally, the difference (d1) between the minimum peak (P11) and the maximum peak of the Fe composition at the grain boundary (GB) may be greater than the difference (d3) between the maximum peak (P31) and the minimum peak of the Nd composition at the grain boundary (GB) or the difference (d2) between the maximum peak (P21) and the minimum peak of the Pr composition at the grain boundary (GB). Thus, the magnetic performance can be maintained.

[0098] Additionally, the second region (AR2) may be located between the first region (AR1). In the first region (AR1), the Nd composition is higher than the Pr composition, and the Nd composition and the Pr composition may increase toward the center of the first region or grain boundary (GB).

[0099] In addition, the Ga composition and Cu composition can decrease from the grain boundary (GB) toward the grain (100) as described above. The Ga composition and Cu composition can increase from the grain boundary (GB) toward the center. Therefore, since a large number of grain boundary diffusion materials exist at the grain boundary surface, the change in the magnetization direction due to heat can be easily suppressed. In addition, the Ga composition and Cu composition can be smaller than the Pr composition (or Nd composition, Fe composition).

[0100] Additionally, the Nd composition may be greater than the Pr composition in the crystal grain (100). For example, the minimum peak (P32) of the Nd composition may be greater than the minimum peak (P22) of the Pr composition. Furthermore, a region may exist at the grain boundary where the Nd composition is greater than the Pr composition. This allows for easier diffusion of the grain boundary diffusion material by Nd.

[0101] Fig. 7 is a graph showing the relative ratio of the composition of a magnetic body according to another example than Fig. 5, and Fig. 8 is an enlarged view of part L in Fig. 7.

[0102] Referring to FIGS. 7 and 8, the above-described contents may be equally applied, except for the contents described below. Furthermore, the relative ratio of the composition of the magnetic body according to another example may be obtained in a region different from FIGS. 5 and 6 within a region within 500 μm of the surface of the magnetic body. Furthermore, the profiles of FIGS. 7 and 8 may be graphs detected in a region different from the region where the profiles of FIGS. 5 and 6 were detected in the magnetic body.

[0103] FIGS. 7 and 8 illustrate the ratios of elements forming a magnetic body in a magnetic body according to an embodiment. Specifically, the magnetic body may include neodymium (Nd), iron (Fe), praseodymium (Pr), copper (Cu), and gallium (Ga). In addition, the elements forming the magnetic body may be formed in different ratios in grains (100) and grain boundaries (GB). Specifically, the position-specific composition or ratio of each element of neodymium (Nd), iron (Fe), praseodymium (Pr), copper (Cu), and gallium (Ga) may be different in each grain and grain boundary.

[0104] Additionally, as previously mentioned, the first ratio may be greater than the second ratio. The third ratio may be greater than the fourth ratio. Similarly, the fifth ratio may be greater than the sixth ratio.

[0105] The magnetic material may include a third region (AR3) in which the Pr composition is greater than the Fe composition at the grain boundary (GB). The third region (AR3) may partially overlap with the second region (AR2). Therefore, the Pr composition may increase toward the center of the third region (AR3). The maximum peak (P21) of the Pr composition at the grain boundary (GB) may be located in the third region (AR3). And the Fe composition at the grain boundary (GB) may decrease toward the center of the third region (AR3). In addition, the minimum peak (P11) of the Fe composition at the grain boundary (GB) may be located in the third region (AR3).

[0106] Additionally, the magnetic material may include a fourth region (AR4) in which the Nd composition is higher than the Fe composition at the grain boundary (GB). The fourth region (AR4) may overlap at least partially with the second region (AR2). Additionally, the fourth region (AR4) may overlap at least partially with the third region (AR3). The Nd composition at the grain boundary (GB) may increase toward the center of the third region (AR3) or the fourth region (AR4). And the maximum peak (P31) of the Nd composition at the grain boundary (GB) may be located in the third region (AR3) and the fourth region (AR4). Additionally, the maximum peak (P31) of the Nd composition at the grain boundary (GB) may be greater than the minimum peak (P11) of the Fe composition.

[0107] Furthermore, the Ga composition and the Cu composition may have maximum peaks at the grain boundaries (100). In particular, the maximum peaks of the Ga composition and the Cu composition, respectively, may be located in the second region (AR2) and the third region (AR3).

[0108] Furthermore, the minimum peak (P11) of the Fe composition at the grain boundary (GB) may be smaller than the maximum peak (P31) of the Nd composition. Furthermore, the minimum peak (P11) of the Fe composition at the grain boundary (GB) may be smaller than the maximum peak (P21) of the Pr composition. This allows for more effective diffusion of grain boundary diffusion materials.

[0109] The difference (d3) between the maximum peak (P31) and the minimum peak of the Nd composition at the grain boundary (GB) may be smaller than the difference (d2) between the maximum peak (P21) and the minimum peak of the Pr composition at the grain boundary (GB). And the difference (d1) between the minimum peak (P11) and the maximum peak of the Fe composition at the grain boundary (GB) may be larger than the difference (d3) between the maximum peak (P31) and the minimum peak of the Nd composition at the grain boundary (GB).

[0110] Accordingly, the rate of change in the Pr composition (the rate of change between the maximum peak and the minimum peak) at the grain boundary (GB) may be greater than the rate of change in the Nd composition. Furthermore, the rate of change in the Fe composition at the grain boundary (GB) may be greater than the rate of change in the Nd composition. With this configuration, Pr can exist in large quantities at the grain boundary, thereby suppressing the decrease in coercivity due to internal penetration.

[0111] In addition, the maximum peak (P31) of the Nd composition at the grain boundary (GB) may be smaller than the minimum peak (P11) of the Fe composition at the grain boundary (GB). In addition, the maximum peak (P21) of the Pr composition at the grain boundary (GB) may be larger than the minimum peak (P11) of the Fe composition or the maximum peak (P31) of the Nd composition at the grain boundary (GB). As a result, a large number of Nd atoms are arranged at the grain boundary, which helps grain boundary diffusion and suppresses the direction of magnetization from rotating. In other words, the coercivity can be maintained. Furthermore, because of the Nd, a large number of Pr atoms are also present at the grain boundary, which can further strengthen the maintenance of the coercivity.

[0112] Additionally, the average value of the Fe composition at the grain boundary (GB) may be greater than the average value of the Nd composition. Additionally, the average value of the Fe composition at the grain boundary (GB) may be greater than the average value of the Pr composition.

[0113] Fig. 9(a) is an HAADF image of one region of a magnetic material according to an embodiment, and Figs. 9(b) to 9(d) are EDS mapping images for Ga, Cu, and Pr, respectively.

[0114] Referring to FIGS. 9(a) to 9(d), a magnetic material may include grains (100) and grain boundaries (GB). Grain boundary diffusion materials may be located at the grain boundaries (GB). For example, praseodymium (Pr), copper (Cu), and gallium (Ga) may be located at the grain boundaries (GB). In particular, praseodymium (Pr) may surround a larger area of ​​the edge of the grains (100) at the grain boundaries (GB) than copper or gallium. As a result, the coercivity of the magnetic material may be significantly increased without significantly reducing magnetization.

[0115] Additionally, as illustrated, a large number of intergranular diffusion materials are arranged at the grain boundary or grain boundary, but some may be arranged in the grains. Furthermore, as illustrated, each element composition may be uniformly positioned in the grains and grain boundaries within the magnetic material.

[0116] In FIGS. 9(b) to 9(d), the degree of color darkening indicates a higher atomic % or atomic composition (content). For example, in FIG. 9(b), the color of the element (Ga) may be darker at the grain boundary (GB) compared to the grain (100). In FIG. 9(c), the color of the element (Cu) may be darker at the grain boundary (GB) compared to the grain (100). In FIG. 9(d), the color of the element (Pr) may be darker at the grain boundary (GB) compared to the grain (100).

[0117] Additionally, Pr may be uniformly positioned along the edges of the crystal grains (100) relative to Ga and Cu. In contrast, Ga and Cu may be unevenly positioned in some areas relative to Ga along the edges of the crystal grains (100).

[0118] A method for manufacturing a magnetic body or permanent magnet according to an embodiment may include a step of manufacturing a Re-Fe-B system pre-magnet including grains and grain boundaries, a step of applying a grain boundary diffusion material to a surface of the Re-Fe-B system pre-magnet, and a step of heat-treating the Re-Fe-B system pre-magnet and diffusing the grain boundary diffusion material into the grain boundaries.

[0119] First, a Re-Fe-B system pre-magnet including grains and grain boundaries can be manufactured. As described above with reference to FIG. 2, the Re-Fe-B system pre-magnet can include a plurality of grains of various shapes and sizes and grain boundaries positioned between adjacent grains. The pre-magnet can be a sintered magnet. The pre-magnet can correspond to the base portion described above. For example, the pre-magnet can be formed by power-processing an ingot of Re-Fe-B and then sintering the powder. For example, a Re-Fe-B system sintered magnet can be manufactured by casting a Re-Fe-B alloy ingot and then crushing Re-Fe-B magnetic powder. Specifically, the ingot can be melted, the molten alloy can be formed into a strip shape or the like, and then crushed by a milling device or the like to form the Re-Fe-B magnetic powder. In addition, it can also be manufactured by a HDDR process or the like. Then, the Re-Fe-B magnetic powder (or powders) can be molded into a desired shape to manufacture a Re-Fe-B system pre-magnet. During molding, a magnetic field may be applied if necessary. A sintering process may be performed during molding. The sintering process is not limited to a specific method. For example, the sintering process may include press sintering, hot isostatic pressing, plasma sintering, microwave sintering, etc. The sintering process can densely bind the magnetic powder, thereby densifying the pre-magnet. As a result, a Re-Fe-B system pre-magnet can be molded.

[0120] And, a grain boundary diffusion material can be applied to the surface of the Re-Fe-B system preliminary magnet. For this purpose, a powder of a grain boundary diffusion metal can be manufactured. The production of the grain boundary diffusion metal powder can be performed simultaneously with the production of the Re-Fe-B magnetic powder. The grain boundary diffusion metal powder can be manufactured by crushing an ingot, similar to the Re-Fe-B magnetic powder. Accordingly, the powder of a grain boundary diffusion metal can be applied to the surface of the Re-Fe-B system preliminary magnet.

[0121] A Re-Fe-B pre-magnet can be heat-treated, and a grain boundary diffusion material can be diffused into the grain boundaries. That is, a Re-Fe-B pre-magnet coated with a powder of a grain boundary diffusion metal can be heat-treated. Accordingly, a coating layer of a grain boundary diffusion material can be formed on the surface of the Re-Fe-B pre-magnet. As described above, the grain boundary diffusion material can include a rare earth element, thereby improving the grain boundary diffusion speed and dispersibility. In addition, the magnetic properties of a rare earth magnetic body or a permanent magnet can also be improved. Accordingly, a Re-Fe-B magnetic body according to an embodiment can be manufactured.

[0122] The features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to just one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified in other embodiments by those skilled in the art to which the embodiments pertain. Therefore, the contents related to such combinations and modifications should be construed as falling within the scope of the present invention.

[0123] In addition, although the above description focuses on embodiments, these are merely examples and do not limit the present invention. Those skilled in the art to which the present invention pertains will appreciate that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present embodiments. For example, each component specifically shown in the embodiments can be modified and implemented. In addition, differences related to such modifications and applications should be interpreted as being included within the scope of the present invention defined in the appended claims.

Claims

1. In a magnetic material including grain boundaries between grains, The above magnetic material contains Fe and praseodymium (Pr), A magnetic material in which the first ratio of the Fe composition to the Pr composition in the above crystal grains is greater than the second ratio of the Fe composition to the Pr composition in the above crystal grain boundaries.

2. In paragraph 1, The above magnetic material is a magnetic material containing Nd.

3. In paragraph 2, A magnetic material in which the third ratio of Fe composition to Nd composition in the above crystal grains is greater than the fourth ratio of Fe composition to Nd composition in the above crystal grain boundaries.

4. In paragraph 3, A magnetic material in which the fifth ratio of the Nd composition to the Pr composition in the above crystal grains is greater than the sixth ratio of the Nd composition to the Pr composition in the above crystal grain boundaries.

5. In paragraph 4, A magnetic body in which the first to sixth ratios are satisfied within 500 μm by EDS (Energy Dispersive X-ray Spectroscopy) on the surface of the magnetic body.

6. In paragraph 2, The above Fe composition has a minimum peak in the crystal grain and a maximum peak at the crystal grain boundary, The above Nd composition and Pr composition have a maximum peak at the grain boundary and a minimum peak at the grain, A magnetic material in which each maximum and minimum peak is measured within 500 μm from the surface by EDS (Energy Dispersive X-ray Spectroscopy).

7. In paragraph 6, A magnetic material in which the maximum peak of the Fe composition in the above crystal grains is greater than the minimum peak of the Fe composition in the above crystal grain boundaries.

8. In paragraph 6, A magnetic material in which the minimum peak of the Pr composition in the above crystal grains is smaller than the maximum peak of the Pr composition in the above crystal grain boundaries.

9. In paragraph 6, A magnetic material in which the minimum peak of the Nd composition in the above crystal grains is smaller than the maximum peak of the Nd composition in the above crystal grain boundaries.

10. In paragraph 6, A magnetic material in which the average value of the Fe composition at the above crystal grain boundary is greater than the average value of the Nd composition.

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