Anisotropic rare earth sintered magnet and method for producing same

Abstract

Provided is an anisotropic rare earth sintered magnet represented by the formula (R1.aZra)x(Fe1-bCOb) 100-x-y(M11-cM2c)y (wherein R is at least one element selected from rare earth elements and Sm is essential; M1 is at least one element selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, A1, and Si; M2 is at least one element selected from the group consisting of Ti, Nb, Mo, Hf, Ta, and W; x, y, a, b, and c each satisfy 7 ≤ x ≤ 15 at%, 4 ≤ y ≤ 20 at%, 0 ≤ a ≤ 0.2, 0 ≤ b ≤ 0.5, and 0 ≤ ≤ c 0.9). The anisotropic rare earth sintered magnet includes 80% by volume or more of a main phase composed of a compound of a ThMn12 type crystal, the main phase having an average crystal grain size of 1 μm or more, and an intergranular grain boundary phase being formed between adjacent main phase grains. Also provided is a method for producing the anisotropic rare earth sintered magnet, including pulverizing an alloy containing a compound phase of a ThMn12 type crystal; compacting the pulverized alloy under application of a magnetic field to form a compact: and then sintering the compact at a temperature of 800°C or higher and 1400°C or lower. According to the present invention, it is possible to provide an anisotropic rare earth sintered magnet having a compound of a ThMn12 type crystal as a main phase and exhibiting good magnetic properties, and a method for producing the same. Figure 1

Description

Anisotropic rare earth sintered magnet and its manufacturing method

[0001] The present invention is １２ The present invention relates to an anisotropic rare earth sintered magnet having a compound of a crystalline structure as the main phase, and a method for producing the same.

[0002] Rare earth magnets, especially Nd-Fe-B sintered magnets, are widely used in the electrification of automobiles and 　 Due to the trend towards higher performance and energy saving in industrial motors, demand is expected to increase further and production volume is expected to further increase. However, due to concerns about the risk of the supply and demand balance of rare earth raw materials collapsing in the future, research into reducing the amount of rare earth used in rare earth magnets has been attracting attention in recent years. １２ The compound of the type crystal structure is R ２ Fe １４ Since it has a lower rare earth content than B compounds and has good magnetic properties, it is being actively researched as a next-generation magnetic material.

[0003] For example, in Patent Document 1, ThMn １２ A permanent magnet made of an alloy containing a hard magnetic phase and a non-magnetic phase with a tetragonal crystal structure has been reported. It has been shown that adding at least one element selected from Cu, Si, Mg, Sn, Pb, and In to an intermetallic compound mainly consisting of a rare earth element and Fe precipitates a phase that has a lower melting point than the main phase and is non-magnetic.

[0004] In addition, Patent Document 2 discloses a method for manufacturing a ferromagnetic alloy having a main phase and a grain boundary phase, in which the main phase is ThMn １２ A rare earth permanent magnet has been reported in which the R-T compound has a cubic crystal structure (R is one or more rare earth elements, with La being an essential element; T is Fe, or Fe and Co, or an element in which a portion of Fe and Co is substituted with M (one or more selected from Ti, V, Cr, Mo, W, Zr, Hf, Nb, Ta, Al, Si, Cu, Zn, Ga, and Ge)), the grain boundary phase has a cubic crystal structure, and the La-rich phase σ with an La composition ratio of 20 at % or more accounts for 20% or more of the cross-sectional area. The inclusion of a nonmagnetic cubic La-rich phase in the grain boundary portion is said to provide magnetic separation between the main phases and reduce the interfacial strain between the grain boundary phase and the main phase.

[0005] In Patent Document 3, ThMn１２ a main phase having a crystal structure of the Sm type; ５ Fe １７ System phase, SmCo ５ System phase, Sm ２ O ３ System phase, and Sm ７ Cu ３ There have been reports of rare earth magnets having subphases containing either of the Sm and Sm-based phases, with the subphase volume fraction being 2.3 to 9.5%. ５ Fe １７ SmCo-based phase ５ The Sm phase is a magnetic phase that exhibits higher magnetic anisotropy than the main phase, and it isolates the crystal grains of the main phase and prevents the movement of domain walls within the main phase, thereby improving the magnetization and coercive force of the magnet. ２ O ３ System phase and Sm ７ Cu ３ The Sm phase is a non-magnetic phase, and by isolating the crystal grains of the main phase, it is believed to prevent the magnetization reversal of the main phase from propagating to the surroundings, thereby improving the magnetization and coercive force of the magnet. ７ Cu ３ It is stated that the system phase is a non-equilibrium phase.

[0006] Patent Document 4 discloses an alloy having a main phase and one or more subphases, and the composition of the entire alloy is R(Fe, Co). ｗ－ｚ Ti ｚ Cu α (R is at least one rare earth element, 8≦w≦13, 0.42≦z<0.70, 0.40≦α≦0.70) have been reported. In addition, the subphase is mainly a crystalline phase with a Cu composition of 50 mol % or more of the entire subphase, and the crystalline structure of the subphase is KHg. ２ It is also stated that it is a type.

[0007] In Patent Document 5, R ｘ Fe １００－ｘ－ｙ (V １－ａ Si ａ ) ｙ (R is one or more rare earth elements including Y, x = 5.5 to 18 atomic %, y = 8 to 20 atomic %, a = 0.05 to 0.7), and the main phase is ThMn １２A rare earth permanent magnet with a body-centered tetragonal structure has been reported. This alloy consists of a main phase and a rare earth-rich phase, and RFe ２ It is described as being free of phases.

[0008] Japanese Patent Application Laid-Open No. 2001-189206 International Publication No. 2017 / 164312 Japanese Patent Application Laid-Open No. 2017-112300 Japanese Patent Application Laid-Open No. 2019-044259 Japanese Patent Application Laid-Open No. 06-231920

[0009] As mentioned above, ThMn １２ In order to obtain good magnetic properties in magnets having a main phase of this type compound, it has been proposed to create a structure consisting of a main phase and a grain boundary phase, as in Nd—Fe—B magnets, and non-magnetic phases such as the La-rich phase (Patent Document 2) and the R-Cu phase (Patent Documents 1 and 4) have been considered as the grain boundary phase. However, in reality, these phases segregate at grain boundary triple junctions and the like, making it difficult to form a grain boundary phase between two particles, and there has been a problem in that it is difficult to create a structure in which the surfaces of the main phase grains are covered by the grain boundary phase.

[0010] In addition, in Patent Document 3, Sm ５ Fe １７ SmCo phase ５ The surface of the main phase grains is surrounded by the ferrite phase, and the magnetic domain walls are pinned by this phase, improving the coercive force. １２ The grain surface of the compound is Sm ５ Fe １７ SmCo phase ５ It is difficult to achieve an organizational form that is encompassed by system phases.

[0011] On the other hand, in Patent Document 5, ThMn １２ An alloy consisting of a main phase and an R-rich phase has been proposed. However, in reality, the composition range in which only two phases are formed in the R-Fe-V-Si quaternary system is extremely limited, making it difficult to reproducibly produce this structure.

[0012] The present invention has been made in view of the above-mentioned problems, and provides a method for manufacturing a ThMn alloy having good magnetic properties. １２ The present invention aims to provide an anisotropic rare earth sintered magnet having a compound of the type crystal as the main phase.

[0013] As a result of extensive research to achieve the above object, the present inventors have discovered that ThMn １２ The present inventors have discovered that anisotropic rare earth sintered magnets having a main phase of a compound of the type crystal exhibit high coercivity when a grain boundary phase is formed between adjacent main phase grains.

[0014] Therefore, the present invention provides the following anisotropic rare earth sintered magnet and a method for producing the same: (1) A rare earth sintered magnet having a composition represented by the formula (R １－ａ Zr ａ ) ｘ (Fe １－ｂ Co ｂ ) １００－ｘ－ｙ (M １ １－ｃ M ２ ｃ ) ｙ (R is one or more rare earth elements, Sm being essential, M １ represents one or more elements selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si; M ２ is one or more elements selected from the group consisting of Ti, Nb, Mo, Hf, Ta, and W, and x, y, a, b, and c are each 7≦x≦15 atomic %, 4≦y≦20 atomic %, 0≦a≦0.2, 0≦b≦0.5, and 0≦c≦0.9, respectively, and an anisotropic rare earth sintered magnet is provided, in which ThMn １２ (1) An anisotropic rare earth sintered magnet comprising 80% by volume or more of a main phase consisting of a compound of a crystalline structure, the main phase having an average crystal grain size of 1 μm or more, and an intergranular phase between adjacent main phase grains. (2) An anisotropic rare earth sintered magnet according to (1), characterized in that the intergranular phase between adjacent grains contains 20 atomic % or more of R. (3) An anisotropic rare earth sintered magnet according to (1) or (2), characterized in that the intergranular phase between adjacent grains has a thickness of 0.5 nm or more. (4) An anisotropic rare earth sintered magnet according to any one of (1) to (3), characterized in that an R-rich phase is contained in the grain boundary portion. (5) R(Fe, Co) ２ (6) The anisotropic rare earth sintered magnet according to any one of (1) to (4), characterized in that the R-rich phase and the R(Fe, Co) phase are contained in the grain boundary portion. ２(7) The anisotropic rare earth sintered magnet according to (4) or (5), characterized in that the magnet contains a total of 1 volume % or more of the R-rich phase and the R(Fe, Co) phase. ２ (8) An anisotropic rare earth sintered magnet according to any one of (1) to (7), characterized in that the Sm / R ratio inside the main phase grains is lower than the Sm / R ratio in the outer periphery of the main phase grains. (9) An anisotropic rare earth sintered magnet according to (7) or (8), characterized in that the interiors of the main phase grains do not contain Sm. (10) An anisotropic rare earth sintered magnet according to any one of (1) to (9), characterized in that the magnet exhibits a coercive force of 5 kOe or more at room temperature and has a temperature coefficient β of coercive force of -0.5% / K or more. (11) An anisotropic rare earth sintered magnet according to any one of (1) to (9), characterized in that the Sm / R ratio inside the main phase grains is lower than the Sm / R ratio in the outer periphery of the main phase grains. １２ (12) A method for producing an anisotropic rare earth sintered magnet according to any one of (1) to (10), characterized in that an alloy containing a compound phase of a ThMn type crystal is pulverized, compacted under a magnetic field to form a green body, and then sintered at a temperature of 800°C or higher and 1400°C or lower. １２ (13) A method for producing an anisotropic rare earth sintered magnet according to (11), characterized in that an alloy containing a compound phase of the ThMn type crystal and an alloy having a higher R composition ratio and Sm / R ratio than the alloy containing the compound phase are crushed and mixed, and then compacted under a magnetic field to form a green compact. １２ (14) A method for producing an anisotropic rare earth sintered magnet according to (13), characterized in that the Sm-containing material brought into contact with the sintered body, the Sm-containing material being selected from the group consisting of Sm metal, Sm-containing alloy, Sm-containing compound, and Sm-containing vapor, and that the Sm-containing material is in the form of a powder, a thin film, a ribbon, a foil, and a gas. (15) A method for producing an anisotropic rare earth sintered magnet according to any one of (11) to (14), characterized in that the sintered body is heat-treated at a temperature of 300 to 900°C.

[0015] According to the present invention, ThMn １２In an anisotropic rare earth sintered magnet having a compound of the type crystal as the main phase, it is possible to obtain an anisotropic rare earth sintered magnet that exhibits excellent magnetic properties.

[0016] 1 is an HAADF image of the structure of the sintered magnet of Example 1 observed with STEM, FIG. 2 is an HAADF image of another location of the structure of the sintered magnet of Example 1 observed with STEM, and FIG. 3 is an HAADF image of the structure of the sintered magnet of Comparative Example 1 observed with STEM.

[0017] The following describes embodiments of the present invention. The anisotropic rare earth sintered magnet of the present invention has a composition represented by the following formula (R １－ａ Zr ａ ) ｘ (Fe １－ｂ Co ｂ ) １００－ｘ－ｙ (M １ １－ｃ M ２ ｃ ) ｙ and ThMn １２ The main phase is a compound of the type crystal, and ThMn １２ The anisotropic sintered magnet of the present invention contains 80% by volume or more of a main phase consisting of a compound of the crystalline structure, has an average crystal grain size of 1 μm or more, and has intergranular phases formed between adjacent main phase grains. Note that x, y, a, b, and c are 7≦x≦15 atomic %, 4≦y≦20 atomic %, 0≦a≦0.2, 0≦b≦0.5, and 0≦c≦0.9, respectively. Because of this wide composition range, the anisotropic rare earth sintered magnet of the present invention can be easily and reproducibly produced. First, each component is described below.

[0018] R is one or more elements selected from rare earth elements, and Sm is essential. Specifically, R is essential and may be a combination of Sm and one or more elements selected from Sc, Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. R is the main phase of ThMn １２ The R content is 7 atomic % or more and 15 atomic % or less. It is more preferable if it is 8 atomic % or more and 12 atomic % or less. If it is less than 7 atomic %, an α-Fe phase precipitates and sintering becomes difficult, while if it exceeds 15 atomic %, the α-Fe phase precipitates and sintering becomes difficult. １２The volume ratio of the ThMn type compound phase decreases, and good magnetic properties cannot be obtained. １２ When R is Sm, the anisotropy field H Ａ Therefore, Sm is essential for the anisotropic rare earth sintered magnet of the present invention. When there is no difference in Sm concentration between the interior and outer shell of the main phase grains, the Sm contained in R is preferably 5% or more of R in atomic ratio, more preferably 10% or more, and particularly preferably 20% or more. By having the Sm ratio in this range, H Ａ The effect of increasing the magnetic field is sufficient to obtain a high coercive force.

[0019] On the other hand, Sm is produced in smaller quantities than Y, La, Ce, Pr, Nd, etc., and is therefore limited in terms of resources. Therefore, it is preferable to utilize Sm as effectively as possible. Therefore, a structure in which Sm is concentrated in the outer periphery of the main phase grains may be used to obtain high coercivity with a lower Sm content. In such a structure in which the Sm concentration differs between the interior and outer periphery of the main phase grains, the Sm contained in R is preferably 0.1 atomic % to 50 atomic % of R in atomic ratio. 0.2 atomic % to 40 atomic % is more preferable, and 0.5 atomic % to 30 atomic % is particularly preferable. It is more preferable that R is a combination of Sm and one or more elements selected from Y, La, Ce, Pr, and Nd.

[0020] Zr is ThMn １２ The Zr that substitutes for R in the ThMn type compound has the effect of improving phase stability. The amount of Zr that substitutes for R is set to 20% or less of the amount of R in terms of atomic ratio. If it exceeds 20%, the Zr content will be reduced to 100%. １２ H type compounds Ａ decreases, making it difficult to obtain a high coercive force.

[0021] ThMn １２ It is known that for the crystalline structure to exist stably, a third element M is required in addition to the constituent elements R and Fe. １ is one or more elements selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, Al and Si, and plays the role of this third element. １ is M, which will be described later and also acts as a third element. ２Compared to Fe, ThMn is an element that tends to form compounds with R more easily than Fe, or tends to bond less easily with either Fe or R. One of the features of the anisotropic rare earth sintered magnet of the present invention is that in the magnet structure, the main phase, ThMn １２ Along with the type compound, R-rich phase and R(Fe, Co) phase are present at the grain boundary. ２ The phase exists at the point where M is present as a third element. １ By selecting the appropriate elements, it becomes easier to obtain a structure in which these three phases coexist stably. １ and M ２ If we combine these and write them as M, we get M １ The atomic ratio of M is at least 10% or more, preferably 30% or more, and more preferably 50% or more. １ If the content of M is less than 10%, the R-rich phase among the above three phases is not stably formed. １ and M ２ The total of M is 4 atomic % or more and 20 atomic % or less. When M is less than 4 atomic %, ThMn １２ The main phase of the R-type compound is not sufficiently formed, and if the content exceeds 20 atomic %, the amount of heterophase formed increases, resulting in poor magnetic properties. The R-rich phase is a phase with a higher concentration of rare earth elements than the main phase. ２ The phase is MgCu ２ The compound phase has a structure called a Laves phase.

[0022] M ２ is one or more elements selected from Ti, Nb, Mo, Hf, Ta and W. ２ ThMn １２ However, if contained in excess, ２ Carbides such as C phase and MgZn ２ (Fe, Co) type compound ２ M ２ Phases precipitate in the main phase and at grain boundaries. In particular, (Fe, Co) ２ M ２ The phase is, for example, Fe ２ Like the Ti phase, the composition may become Fe-richer than the stoichiometric composition, resulting in ferromagnetism, which adversely affects the magnetic properties of the sintered magnet.１ Excluding M ２ If only M is selected, the R-rich phase is unlikely to be formed stably. ２ In the case of a composition containing M, its content is set to at least 90% or less of M in atomic ratio.

[0023] The anisotropic rare earth sintered magnet of the present invention is made of Sm, M １ Furthermore, part of the Fe may be substituted with Co. The substitution with Co is １２ Curie temperature T of the compound ｃ and increase the saturation magnetization M ｓ The substitution rate of Co is set to 50% or less in atomic ratio. If the substitution rate exceeds 50%, M ｓ On the contrary, the ratio of Fe and Co is decreased. １ and M ２ However, in addition to this, it may contain unavoidable impurities that are taken in from raw materials or mixed in during the manufacturing process, specifically H, B, C, N, O, F, P, S, Mg, Cl, Ca, etc. up to a total of 3% by weight.

[0024] Next, the phases constituting the anisotropic rare earth sintered magnet of the present invention will be described. The main phase in the anisotropic rare earth sintered magnet of the present invention is ThMn １２ R (Fe, Co, M) type crystal structure １２ It is preferable that elements such as C, N, and O, which are inevitably mixed in during the process of producing a sintered magnet, are not included in the main phase. However, if C, N, or O elements are detected in a composition analysis using an EPMA (electron probe microanalyzer) due to measurement variations, the preparation method of the observation sample, or the influence of the detection signals of other elements, it is possible that the H of the main phase Ａ From the viewpoint of obtaining a good result, the upper limit of each is preferably up to 1 atomic %. The average crystal grain size of the main phase is 1 μm or more, and preferably 1 μm or more and 30 μm or less. A range of 1.5 μm or more and 20 μm or less is more preferable, and a range of 2 μm or more and 10 μm or less is particularly preferable. By setting the average crystal grain size in such a range, the remanence B due to the decrease in the degree of orientation of the crystal grains is improved. ｒ Decrease in coercive force H ｃＪ The volume fraction of the main phase is good.ｒ and H ｃＪ From the viewpoint of obtaining the above, the volume fraction of the main phase is 80% or more of the entire magnet, preferably 80% to less than 99% by volume, and even more preferably 90% to 95% by volume. The average crystal grain size of the main phase was measured as follows. The cross section of the sintered magnet was polished to a mirror finish, and then immersed in an etching solution (such as a mixture of nitric acid, hydrochloric acid, and glycerin) to selectively remove the grain boundary phase. Ten or more randomly selected points on the cross section were observed with a laser microscope. The cross-sectional area of ​​each particle was calculated from the obtained observation image by image analysis, and the average diameter when these were regarded as a circle was taken as the average crystal grain size. The volume fraction of the main phase was measured as follows. The anisotropic rare earth sintered magnet was subjected to structural observation and compositional analysis of each phase using an EPMA, and the main phase, R-rich phase, and R(Fe, Co) ２ The volume fraction of each phase was calculated as being equal to the area ratio in the backscattered electron image.

[0025] To effectively utilize Sm, a structure may be used in which Sm is concentrated in the outer periphery of the main phase grains and grains with a lower Sm concentration exist inside the main phase grains. In this case, the thickness of the high Sm outer periphery is not particularly limited, but from the viewpoint of sufficiently obtaining the effect of suppressing nucleation of reverse magnetic domains in the outer periphery of the main phase grains and preventing the Sm content of the entire sintered body from becoming too high and thus preventing the Sm reduction effect from being insufficient, a thickness of 1 nm to 2 μm is preferable, and a thickness of 2 nm to 1 μm is particularly preferable. Such a structure is suitable for an R-rich phase or an R(Fe, Co) ２ This occurs when the Sm / R ratio (atomic ratio of Sm to R) in the phase is higher than the Sm / R ratio inside the main phase grains. A structure that does not contain Sm inside the main phase grains is more preferable. Also, some main phase grains may contain a uniform Sm concentration distribution.

[0026] R-rich phase and R(Fe, Co) ２ The R-rich phase is formed at the grain boundary of the magnet structure. The grain boundary includes grain boundary triple junctions as well as grain boundary phases between two grains. Here, the R-rich phase is defined as a phase containing 40 atomic % or more of R. The inventors have １ When the above composition containing the elements is used, the main phase, R (Fe, Co) ２It has been found that it is easy to obtain a magnet containing three phases, namely, the M phase, the R-rich phase, and the M phase. １ In the case of Sm-Fe-Ti ternary sintered magnets that do not contain elements, Sm(Fe,Ti) １２ Main phase and SmFe ２ , Fe ２ There is a composition region where the three phases of Ti (excluding oxides, etc.) are in equilibrium, but Sm(Fe,Ti) １２ Since the main phase and the Sm-rich phase are difficult to equilibrate at low temperatures below 400°C, the Sm-rich phase is not formed as a stable phase. １ In the case of the Sm-Fe-V ternary system, which uses V as one of the elements, no Fe-V binary compound is formed, but instead a Sm-rich phase with a high Sm concentration is formed, resulting in Sm(Fe,V). １２ , SmFe ２ A magnet can be obtained that contains three phases: a Sm-rich phase and an Sm-rich phase. １ , M ２ In the Sm-Fe-V-Ti quaternary system, which contains both Sm(Fe, V, Ti) １２ , Fe ２ (V,Ti), SmFe ２ Based on this knowledge, the anisotropic rare earth sintered magnet of the present invention has an R-rich phase and an R(Fe, Co) phase at the grain boundary. ２ To form the phase, a predetermined amount of M １ A composition containing the elements is selected.

[0027] R-rich phase and R(Fe, Co) ２ The R-rich phase has four main effects. The first effect is to promote sintering. At the sintering temperature, both the R-rich phase and the R(Fe, Co) ２ Since the R-rich phase and the R(Fe, Co) phase are also melted and become a liquid phase, liquid phase sintering proceeds and sintering is completed more quickly than in the case of solid phase sintering when these phases are not included. ２ When both phases coexist, the liquid phase formation temperature tends to be lower than when only one phase is present, and liquid phase sintering proceeds more rapidly.

[0028] The second effect is cleaning of the main phase grain surfaces. Because the anisotropic rare earth sintered magnet of the present invention has a nucleation-type coercivity mechanism, it is desirable that the main phase grain surfaces be smooth so that nucleation of reverse magnetic domains is less likely to occur. ２ The phase is formed during the sintering process or the subsequent aging process. １２ This cleaning effect suppresses the nucleation of reverse magnetic domains, which is a factor in reducing coercivity. ２ The phase may be other phases with R less than 40 atomic % such as RM ３ , R.M. ２ , R(Fe,Co)M and R(Fe,Co) ２ M ２ Compared with compound phases such as ThMn １２ It has a relatively high wettability to the main phase and is easy to coat the surfaces of the main phase particles, resulting in a large cleaning effect.

[0029] The third effect is the formation of a grain boundary phase between two grains. In magnets containing an R-rich phase in the structure, the adjacent ThMn phase can be formed by optimal sintering or aging treatment. １２ Between the main phase grains of the ThMn type compound, a grain boundary phase containing more R than the main phase grains is formed. This weakens the magnetic interaction between the main phase grains, and the sintered magnet exhibits a high coercive force. １２ The composition region where only the two phases, the ThMn type compound main phase and the R-rich phase, are in equilibrium is extremely limited, and considering the compositional variations, it is difficult to stably manufacture such magnets. １２ Type compound main phase, R-rich phase and R(Fe, Co) ２ By producing a magnet containing these three phases, it is possible to stably form a structure in which the surfaces of the main phase grains are covered by the interparticle grain boundary phase. Furthermore, in a magnet that does not contain an R-rich phase, it is difficult to form the interparticle grain boundary phase, or for the interparticle grain boundary phase to cover the surfaces of the main phase grains, making it difficult to obtain a magnet that exhibits sufficient coercivity.

[0030] The fourth effect is to increase the Sm concentration in the grain boundary. When the grain boundary diffusion method is applied as a manufacturing method to make the Sm concentration different between the inside and outer periphery of the main phase grains, the R-rich phase and the R(Fe, Co) phase existing in the grain boundary are intermingled. ２ The R-rich phase or R(Fe, Co) phase becomes a liquid phase during the diffusion treatment and plays a role in diffusing and penetrating Sm placed on the sintered body into the interior. ２ The Sm / R ratio in at least one of the phases is higher than the Sm / R ratio inside the main phase grains. １２ By using an alloy mainly composed of a type compound phase and an alloy with a higher R composition ratio and Sm / R ratio than that, it is possible to obtain an R-rich phase or R(Fe, Co) ２ The Sm / R ratio in at least one of the R-rich phase and the R(Fe, Co) phase is higher than the Sm / R ratio inside the main phase grain. ２ As Sm becomes concentrated in the grain boundary phase, the Sm concentration in the outer periphery of the main phase grains that contact these grain boundary phases also increases, Ａ This improves the coercive force of the sintered magnet.

[0031] As described above, the R-rich phase contains at least 40 atomic % of R. If the R content is less than 40 atomic %, the wettability with the main phase is insufficient, making it difficult to obtain the above-mentioned effects. It is more preferable to contain 50 atoms or more of R, and particularly preferable to contain 60 atoms or more. The R-rich phase may be an R metal phase such as the Sm phase described above, or an amorphous phase or R ３ (Fe, Co, M), R ２ (Fe, Co, M), R ５ (Fe, Co, M) ３ , R (Fe, Co, M) and other intermetallic compounds with a high R composition and a low melting point. Furthermore, the alloy may contain up to 60 atomic % in total of impurity elements such as Fe, Co, and M elements, and H, B, C, N, O, F, P, S, Mg, Cl, and Ca.

[0032] On the other hand, R(Fe, Co) ２ The phase is MgCu ２However, when the composition is analyzed using EPMA or the like, taking into consideration measurement variations, the content of R is set to 20 atomic % or more and less than 40 atomic %. In addition, a part of Fe and Co may be substituted with the M element. However, the amount of substitution of M is MgCu. ２ The range is set so that the type crystal structure is maintained.

[0033] R (Fe, Co) in the anisotropic rare earth sintered magnet of the present invention ２ The magnetic phase is a ferromagnetic or ferrimagnetic phase, and has a Curie temperature T ｃ is a phase in which the temperature is above room temperature (23°C). ２ is CeFe ２ Except for T ｃ is above room temperature, and CeFe ２ However, if 10% or more of R is replaced by other elements, T ｃ On the other hand, RCo ２ is GdCo ２ Except for T ｃ is below room temperature or in the paramagnetic phase, but in the anisotropic rare earth sintered magnet of the present invention, the substitution atomic ratio of Fe by Co is 0.5 or less, so in most cases R(Fe, Co) ２ Generally, soft magnetic phases contained in the structure often have a negative effect on magnetic properties, but in the anisotropic rare earth sintered magnet of the present invention, the R(Fe, Co) ２ The cleaning effect of the phase on the main phase grain surface and the effect of forming a grain boundary phase between two particles are greater, and it is thought that even a magnetic phase contributes to an increase in coercivity.

[0034] R-rich phase and R(Fe, Co) ２ The total amount of the formed phases is preferably 1% by volume or more, more preferably 1% by volume or more and less than 20% by volume. Furthermore, 1.5% by volume or more and less than 15% by volume is even more preferable, and 2% by volume or more and less than 10% by volume is even more preferable. By setting the amount in this range, the area in contact with the main phase grains is secured, and the H ｃＪ It is easy to achieve the effect of increasing the ｒ The decrease in magnetic properties is also suppressed, making it easier to obtain the desired magnetic properties.

[0035] As described above, in the anisotropic rare earth sintered magnet of the present invention, the R-rich phase and the R(Fe, Co) phase are present at the grain boundaries. ２ The phase exists, and ThMn １２ The grain boundary phase between two adjacent main phase grains of the type compound is formed. The surface of the main phase grain is covered by the grain boundary phase between two adjacent grains, which weakens the magnetic interaction between the main phase grains and results in a high coercive force.

[0036] The grain boundary phase between two grains may be amorphous with a disordered atomic arrangement, or may have a regular atomic arrangement. ２ The grain boundary phase may be the same phase as the main phase. When observing the grain boundary phase between two particles using a device such as a scanning transmission electron microscope (STEM), its composition preferably contains 20 atomic % or more of R. By setting the content within this range, the magnetic coupling between the main phase grains can be sufficiently reduced, making it easier to obtain high coercivity. Furthermore, the thickness of the grain boundary phase between two particles is preferably 0.5 nm or more. This makes it easier to ensure the magnetic decoupling effect between the main phase grains, resulting in a sufficient improvement in coercivity. Furthermore, the thickness is preferably 1 μm or less, more preferably 0.5 μm or less, and even more preferably 100 nm or less. Within this range, it is easier to prevent the impact of the decrease in magnetic properties due to the decrease in the volume ratio of the main phase grains from exceeding the effect of the increase in coercivity. The thickness of the grain boundary phase between two particles was measured from STEM images as follows. Using a STEM device (JEM-ARM200F manufactured by JEOL Ltd.), observations were made of at least three or more locations on one sample where adjacent main phase grains contacted each other. The thickness of the grain boundary phase between two particles was measured from a high-angle annular dark field (HAADF) image obtained by the observation, and the average value of these thicknesses was taken as the thickness of the grain boundary phase between two particles.

[0037] In addition, the anisotropic rare earth sintered magnet of the present invention may contain R oxides, R carbides, R nitrides, M carbides, etc., which are formed by unavoidably mixed C, N, and O. From the viewpoint of suppressing deterioration of the magnetic properties, the volume ratio of these is preferably 10% by volume or less, more preferably 5% by volume or less, and particularly preferably 3% by volume or less.

[0038] It is preferable that the amount of phases other than those mentioned above is as small as possible. For example, R ２ (Fe, Co, M) １７ Phase, R ３ (Fe, Co, M) ２９ When the phases are present in the magnet structure, the amount of each of them is preferably less than 1% by volume in order to prevent the influence on the magnetic properties and the resulting decrease in coercivity. ２ M phase or RM with R less than 40 atomic % ３ , R.M. ２ , R(Fe,Co)M, R(Fe,Co) ２ M ２ and the like are each preferably less than 1% by volume. The total amount of these phases is preferably 3% by volume or less. Furthermore, from the viewpoint of preventing a significant deterioration in magnetic properties, it is preferable that the anisotropic rare earth sintered magnet of the present invention does not contain the α-(Fe, Co) phase.

[0039] Next, the manufacturing method will be described. The anisotropic rare earth sintered magnet of the present invention is manufactured by powder metallurgy. First, to prepare the raw material alloy, metal raw materials, alloys, ferroalloys, etc. of R, Fe, Co, and M are used, and adjustments are made so that the final sintered body has a predetermined composition, taking into consideration raw material losses during the manufacturing process. These raw materials are melted in a high-frequency furnace or arc furnace to prepare the alloy. The molten metal can be cooled by casting, or thin flakes can be obtained by strip casting. In the case of strip casting, it is preferable to adjust the cooling rate to prepare the alloy so that the average crystal grain size of the main phase or the average grain boundary spacing is 1 μm or more. If it is less than 1 μm, the powder after fine pulverization becomes polycrystalline, and the main phase crystal grains are not sufficiently oriented during the magnetic field molding process, resulting in B. ｒ If α-Fe precipitates in the alloy, it is necessary to remove the α-Fe and reconstitute the ThMn １２ The alloy may be heat-treated to increase the amount of the type compound phase formed. The alloy may be a single-composition alloy, or multiple alloys with different compositions may be prepared and their powders may be mixed in a subsequent process.

[0040] The raw alloy is coarsely pulverized to a powder with an average particle size of 0.05 to 3 mm using mechanical pulverization such as a Braun mill or hydrogen pulverization. Alternatively, the HDDR (Hydrogen Disproportionation Desorption Recombination) method, which is commonly used to manufacture Nd—Fe—B magnets, may be applied. The coarse powder is then finely pulverized using a ball mill or a jet mill using high-pressure nitrogen to obtain a powder with an average particle size of 0.5 to 20 μm, more preferably 1 to 10 μm. Lubricants may be added as needed before or after the fine pulverization process. Next, the alloy powder is compacted using a magnetic field press while aligning its easy axis of magnetization in an applied magnetic field to obtain a green compact. Compaction is preferably performed in a vacuum, nitrogen gas atmosphere, or an inert gas atmosphere such as Ar to prevent oxidation of the alloy powder.

[0041] The step of sintering the powder compact is carried out in a sintering furnace in a vacuum or inert atmosphere at a temperature of 800°C to 1400°C. At temperatures below 800°C, sintering does not proceed sufficiently, making it impossible to obtain a high sintered density. At temperatures above 1400°C, the ThMn １２ The main phase of the α-type compound decomposes, resulting in the precipitation of α-Fe. The sintering temperature is preferably in the range of 900 to 1300°C. The sintering time is preferably 0.5 to 20 hours, more preferably 1 to 10 hours. Sintering may be performed by raising the temperature and then holding it at a constant temperature. Alternatively, a two-stage sintering pattern may be used, in which the temperature is raised to a first sintering temperature and then held at a lower second sintering temperature for a predetermined time to refine the crystal grains. Multiple sintering processes may be performed, or a spark plasma sintering method may be applied. The cooling rate after sintering is not particularly limited, but it can be at least 600°C or less, preferably 200°C or less, preferably at a cooling rate of 1°C / min to 100°C / min, more preferably 5°C / min to 50°C / min. To improve the coercivity, an aging heat treatment at 300 to 900°C for 0.5 to 50 hours may be performed. By optimizing the sintering and aging conditions according to the composition and powder particle size, H ｃＪ The sintered body is then cut and ground into a desired shape and magnetized to produce a sintered magnet.

[0042] On the other hand, the Sm / R ratio inside the main phase grains is R-rich phase and R(Fe, Co) ２Examples of methods for producing an anisotropic rare earth sintered magnet in which the main phase grains have a lower Sm / R ratio than the phase include the two-alloy method and the grain boundary diffusion method.

[0043] When using the two-alloy method, two types of raw material alloys with different compositions are prepared using metal raw materials, alloys, ferroalloys, etc. of R, Fe, Co, and M. Three or more types of alloys may be used. １２ It is preferable to combine alloy A, which is mainly composed of a type compound phase and has a relatively low Sm / R ratio, with alloy B, which has a relatively higher R composition ratio and Sm / R ratio, and adjust the average composition to a predetermined composition. These alloys are produced by casting or strip casting and then pulverized. The process of mixing the alloy powders may be performed in a coarse powder state before fine pulverization or after fine pulverization. The mixture is then molded and sintered to form a sintered body. Aging heat treatment may be performed to improve coercivity.

[0044] In the two-alloy sintered magnet, the composition of alloy A is mainly responsible for the formation of ThMn １２ The main phase is composed of a Fe-type compound, and the R-rich phase and the R(Fe, Co) phase are mainly composed of the alloy B components. ２ Therefore, the R-rich phase and R(Fe, Co) phase formed at the grain boundary are formed. ２ The Sm / R atomic ratio in the grain boundary phase is higher than that inside the main phase grains. Furthermore, some of the Sm in the grain boundary phase substitutes for R atoms in the surface layer of the main phase grains, forming a core-shell structure with different Sm concentrations between the grain surface layer and the interior, increasing the coercive force.

[0045] On the other hand, in the grain boundary diffusion method, a sintered body is first prepared by the single alloy method or the two-alloy method in the same manner as described above. At this time, R in the sintered body composition may or may not contain Sm.

[0046] Next, the obtained sintered body is subjected to grain boundary diffusion of Sm. After cutting and grinding the sintered body as necessary, a diffusion material selected from compounds containing Sm, such as metals, alloys, oxides, fluorides, oxyfluorides, hydrides, and carbides, is applied to the surface in the form of powder, thin film, ribbon, foil, or the like. For example, a powder of the above material may be mixed with water or an organic solvent to form a slurry, which may be coated on the sintered body and then dried. Alternatively, the above material may be applied as a thin film on the surface of the sintered body by means of vapor deposition, sputtering, CVD, or the like. The amount applied is 10 to 1000 μg / mm ２ is preferred, and in particular 20 to 500 μg / mm ２ In this range, H ｃＪ Furthermore, by utilizing the high vapor pressure of Sm, Sm metal or an Sm alloy may be heat-treated together with the sintered body in the same chamber, and the Sm vapor may be brought into contact with the sintered body.

[0047] This sintered body, with Sm placed on the surface, is heat-treated in a vacuum or in an inert gas atmosphere. The heat treatment temperature is preferably 600°C or higher and lower than the sintering temperature, and particularly preferably 700°C or higher and 1100°C or lower. The heat treatment time is preferably 0.5 to 50 hours, and particularly preferably 1 to 20 hours. The cooling rate after heat treatment is not particularly limited, but is preferably 1 to 20°C / min, and particularly preferably 2 to 10°C / min. To improve the coercive force, an aging heat treatment may be further performed at 300 to 900°C for 0.5 to 50 hours.

[0048] The Sm arranged on the sintered body is transformed into an R-rich phase or an R(Fe, Co) phase by heat treatment. ２ As the Sm concentration in the grain boundary phase increases, Sm is substituted for R atoms in the surface layer of the main phase grains that contact the grain boundary phase, and the Sm / R ratio in the surface layer of the main phase grains becomes higher than the Sm / R ratio inside the main phase grains, resulting in the formation of H ｃＪ increases.

[0049] The anisotropic rare earth sintered magnet of the present invention produced in this manner has a residual magnetic flux density B of 5 kG or more at room temperature. ｒ and a coercive force H of at least 5 kOe or more.ｃＪ Room temperature H ｃＪ It is more preferable that the temperature coefficient β of the coercive force is -0.5% / K or more. Here, β=ΔH ｃＪ / ΔT×100 / H ｃＪ (20°C) (ΔH ｃＪ = H ｃＪ (20°C) -H ｃＪ (140°C), ΔT=20-140(°C)). The anisotropic rare earth sintered magnet of the present invention has a smaller change in coercive force with temperature than an Nd-Fe-B sintered magnet, making it suitable for use at high temperatures.

[0050] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0051] Example 1: A cast alloy was prepared by adjusting the composition using Sm metal, electrolytic iron, ferrovanadium, Al metal, and Si and melting the alloy in an Ar gas atmosphere using a high-frequency induction furnace. To eliminate primary α-Fe, the alloy was heat-treated at 900°C for 50 hours. The structure of the resulting alloy was observed using a laser microscope (Olympus Corporation, LEXT OLS4000), and the observed images confirmed that the average crystal grain size of the main phase was 5 μm or more. The alloy was subjected to a hydrogen absorption treatment and a dehydrogenation treatment by heating at 400°C in a vacuum to produce a coarse powder, which was then pulverized in a jet mill in a nitrogen gas flow to produce a fine powder with an average grain size of 1.8 μm. The fine powder was then filled into a mold of a molding machine in an inert gas atmosphere and oriented in a magnetic field of 15 kOe (=1.19 MA / m) while being subjected to a 0.6 Ton / cm pressure in the direction perpendicular to the magnetic field. ２ This powder compact was sintered in an Ar gas atmosphere at 1140° C. for 3 hours, and then cooled to room temperature at a cooling rate of 13° C. / min to obtain a sintered body.

[0052] The composition of the sintered body analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) using a high-frequency inductively coupled plasma optical emission spectrometer (Hitachi High-Tech Science Corporation, SPS3520UV-DD) was Sm １０．２ Fe ｂａｌ． V １４．９ Al ０．５ Si ０．２Furthermore, X-ray diffraction revealed that ThMn １２ Using an EPMA (JEOL Ltd., JXA-8500F), the structure of the sintered body was observed and the composition of the formed phase was analyzed, and it was found that the R-rich phase and the R(Fe, Co) phase were present at the grain boundary triple junction. ２ It was confirmed that the main phase, the R-rich phase, and the R(Fe, Co) phase were formed. ２ The volume ratio of the phase was calculated as being equal to the area ratio in the backscattered electron image. As a result, the grain boundary of the sintered body structure contained an R-rich phase and an R(Fe, Co) ２ The sintered body sample was etched and observed to determine that the average grain size of the main phase was 9.9 μm. ｃＪ is 8.5 kOe, and H ｃＪ The temperature coefficient β was −0.46% / K.

[0053] A thin specimen for observation was cut out from this sintered body using an FIB-SEM device (Scios Dual Beam manufactured by FEI) and observed using an STEM device (JEM-ARM200F manufactured by JEOL Ltd.). The obtained HAADF (High-Angle Annular Dark Field) images are shown in Figures 1 and 2. From Figure 1, it can be seen that an interparticle grain boundary phase 13 exists in the grain boundary portion sandwiched between two main phase grains 11 and 12. The thickness of the interparticle grain boundary phase 13 in this case was approximately 0.7 nm, and the composition obtained by EDX analysis (energy dispersive X-ray fluorescence analysis) was Sm ６１．２ Fe ｂａｌ． V ７．１ Al １．３ Si １．１ In addition, in FIG. 2, which shows another portion of the same sintered body, the grain boundary phase 13 between two particles is about 1.4 nm thick and has a composition of Sm ３１．９ Fe ｂａｌ． V ９．５ Al ２．７ Si ０．６ The results are shown in Tables 1 to 3 and 5.

[0054] [Comparative Example 1] The composition was adjusted using Sm metal, electrolytic iron, and Ti metal, and a cast alloy was produced in a high-frequency induction furnace in the same manner as in Example 1, and then heat-treated at 900°C for 50 hours. The structure of the obtained alloy was observed using a laser microscope, and it was confirmed from the observed image that the average crystal grain size of the main phase was 5 μm or more. As in Example 1, the alloy was crushed and compacted in a magnetic field, sintered in an Ar gas atmosphere at 1175°C for 3 hours, and then cooled to room temperature at a cooling rate of 13°C / min, to obtain a sintered body of Comparative Example 1. The composition value of the sintered body analyzed by ICP method was Sm ９．７ Fe ｂａｌ． Ti ８．１ Furthermore, from the X-ray diffraction measurement, it was found that the main phase of Comparative Example 1 was ThMn １２ The formation phase was examined by EPMA and found to be R(Fe, Co) ２ Although a phase was present, no R-rich phase was formed, and a fine TiC phase was precipitated. When the magnetic properties were measured using a B-H tracer, Comparative Example 1 exhibited a low coercive force of only 0.1 kOe at room temperature. The HAADF image obtained in Comparative Example 1 is shown in Figure 3. At the boundary between the two main phase grains 11 and 12, no intergranular grain phase was formed between the two grains, as was seen in Example 1. The results are shown in Tables 1 to 3.

[0055] [Examples 2 to 8] As in Example 1, cast alloys were prepared by adjusting the composition and high-frequency melting. To eliminate primary α-Fe, the alloys were heat-treated at 850 to 1100°C for 10 to 50 hours. The structure of the resulting alloys was observed using a laser microscope, and the images confirmed that the average grain size of the main phase was 1 μm or greater. Coarse powder was obtained by hydrogen absorption and dehydrogenation treatment at 450°C in a vacuum, followed by pulverization in a jet mill in a nitrogen stream to produce fine powder with an average grain size of 2 to 4 μm. The fine powder was then filled into a mold of a molding machine in an inert gas atmosphere and compacted in a magnetic field. This compact was sintered in an Ar gas atmosphere, cooled to room temperature, and further subjected to aging heat treatment to obtain sintered compact samples. Table 1 shows the composition of each sample analyzed by ICP analysis, the crystal structure of the main phase confirmed by X-ray diffraction, and the average grain size of the main phase of the sintered body. Table 2 shows the sintering conditions, cooling rate after sintering, aging conditions, and B measured at room temperature for each example. ｒ , HｃＪ , and H ｃＪ The temperature coefficient β of the sintering temperature is shown in Table 1. In Example 8, a two-stage sintering method was applied, in which the temperature was raised to the first sintering temperature, then immediately lowered to the second sintering temperature and maintained for a predetermined time. Table 3 also shows the composition and phase ratio of each phase analyzed by EPMA. In all of the samples in Examples 2 to 8, the structure contained an R-rich phase and an R(Fe, Co) ２ A phase was formed, and the samples exhibited a coercive force of 5 kOe or more at room temperature and a temperature coefficient β of -0.5% / K or more. Furthermore, when STEM observation was performed on these sintered body samples in the same manner as in Example 1, it was confirmed that an interparticle grain boundary phase was present in the grain boundary portion sandwiched between two main phase grains in all Examples. Table 5 shows the measured composition and thickness of the interparticle grain boundary phase.

[0056] [Comparative Examples 2 to 6] Sintered body samples of Comparative Examples 2 to 5 were produced in the same manner as in Example 2, except that the compositions were adjusted to those shown in Table 1. The results are shown in Tables 1, 2, and 4. In Comparative Example 2, the total amount of R was less than 7 atomic %, and the sintering was not sufficient, and a large amount of α-Fe phase was formed in the sintered body. In Comparative Example 3, the total amount of R exceeded 15 atomic %, and the volume ratio of the main phase was less than 80%. In Comparative Example 4, the total amount of M elements exceeded 20 atomic %, and no R-rich phase was observed, and an RFeSi phase of a PbClF type crystal was formed. In Comparative Example 5, KHg ２ RCu type crystal ２ Although the M element was present at the grain boundary triple junction, the total M content exceeded 20 atomic %, and no R-rich phase was found. １２ No Th type crystals were observed. ２ Zn １７ The main phase of the type crystal was formed.

[0057] Comparative Example 7: The composition was adjusted using Sm metal, electrolytic iron, Ti metal, and V metal, and the molten raw material was cooled on a Cu roll rotating at a peripheral speed of 20 m / sec to produce a quenched ribbon raw material alloy. The ribbon thickness was 10 to 50 μm, and the structure of the obtained alloy was observed using a laser microscope. From the observed image, it was confirmed that the average crystal grain size was too small to measure, but was at least smaller than 1 μm. This alloy ribbon was pulverized in a ball mill, and then powders of 300 μm or less were selected using a sieve and hot pressed at 750°C in an Ar atmosphere. The average crystal grain size of the main phase grains was as small as about 0.2 to 0.3 μm, and the compositions of the main phase and grain boundary phase could not be identified by EPMA. In addition, the easy axis of magnetization of the main phase was not aligned, resulting in a low B ｒ The results are shown in Tables 1, 2, and 4.

[0058] Example 9: The composition was adjusted using Nd metal, Y metal, electrolytic iron, pure Si, and Hf metal. The alloy was melted in an Ar gas atmosphere using a high-frequency induction furnace and then strip-cast on a water-cooled Cu roll to produce a quenched ribbon alloy with a thickness of approximately 0.2 to 0.4 mm and a composition of 7.5 atomic % Nd, 1.0 atomic % Y, 13.0 atomic % Si, 1.0 atomic % Hf, and the balance Fe. The average crystal grain size in the minor axis direction of the alloy, as determined from images observed with a laser microscope, was 2.5 μm. This alloy was subjected to a hydrogen absorption treatment at room temperature, followed by a dehydrogenation treatment by heating in a vacuum at 400°C to produce a coarse powder (referred to as Powder 9A). Meanwhile, an alloy ingot with a composition of 40 atomic % Sm, 10 atomic % Ga, 5 atomic % Cu, and the balance Co was produced using a high-frequency induction furnace from Sm metal and electrolytic iron, and mechanically pulverized to produce a coarse powder (referred to as Powder 9B). Powder 9A and powder 9B were mixed in a weight ratio of 95:5, and then pulverized in a jet mill in a nitrogen stream to produce a fine powder having an average particle size of 1.8 μm.

[0059] This mixed powder was subjected to compaction in a magnetic field in the same manner as in Example 1, sintered in an Ar gas atmosphere at 1200°C for 3 hours, cooled to room temperature at a cooling rate of 12°C / min, and further subjected to heat treatment in an Ar gas atmosphere at 650°C for 1 hour to obtain a sintered body of Example 9. The composition of the sintered body sample was Sm １．８ Nd ７．２ Y １．０ Feｂａｌ． Co １．０ Si １２．８ Ga ０．６ Cu ０．４ Hf １．０ Furthermore, X-ray diffraction measurements revealed that the main phase of this sintered body was ThMn １２ The composition of the main phase measured by EPMA was Nd ６．４ Y １．１ Fe ｂａｌ. Co １．０ Si １２．７ Ga ０．５ Cu ０．１ Hf １．１ does not contain Sm, but the outer shell of the grain contains Sm ３．５ Nd ３．０ Y １．０ Fe ｂａｌ. Co １．０ Si １３．０ Ga ０．４ Cu ０．１ Hf ０．９ It was confirmed that the Sm / R ratio inside the grains was lower than that in the surface layer. Furthermore, the structure of the sintered body was observed by EPMA and the composition of each phase was analyzed, and it was found that an R-rich phase and an R(Fe, Co) phase were present at the grain boundaries. ２ It was confirmed that the phase was present at 1% by volume or more. ２ The phase was confirmed. ２ (Fe, Co, M) １７ Phase, R ３ (Fe, Co, M) ２９ No α-Fe phase or α-Fe phase was observed. Note that the total of the phase ratios is less than 100% because oxide phases and other phases are also present.

[0060] R-rich phase, R(Fe, Co) ２ phase and RCu ２ The composition analysis values ​​of the phases are Sm ２６．８ Nd ３１．７ Y ０．１ Fe ｂａｌ. Si ３６．２ Ga ５．２ , Sm １７．２ Nd １７．４ Y ０．２ Fe ｂａｌ. Co ０．４ Si ０．３ Hf ０．１ , Sm １５．９Nd １８．６ Fe ｂａｌ. Cu ６５．２ From this, it was found that the Sm / R ratio inside the grains was R-rich phase and R(Fe, Co) ２ It was confirmed that the Sm / R ratio of the main phase was lower than that of the R(Fe, Co) phase. The average crystal grain size of the main phase was 8.6 μm. The coercive force of this sintered body was 5.6 kOe at room temperature, and the temperature coefficient β of the coercive force was −0.45% / K. ２ The Curie temperature T of an alloy of the same composition prepared based on the phase analysis value ｃ The temperature was 318°C. For Example 9, STEM observation was carried out in the same manner as in Example 1, and it was confirmed that an intergranular phase existed between two grains in the grain boundary portion sandwiched between two main phase grains. The measured composition of the intergranular phase between two grains was Sm ２１．７ Nd ２４．５ Fe ｂａｌ. Co ０．５ Si １２．８ Ga ２．６ Cu ８．０ The thickness was 35 nm.

[0061] Example 10: The composition was adjusted using Ce metal, La metal, electrolytic iron, Co metal, pure Si, and Mo metal. The alloy was melted in an Ar gas atmosphere using a high-frequency induction furnace and then strip-cast on a water-cooled Cu roll to produce an alloy ribbon approximately 0.2 to 0.4 mm thick. The average grain boundary phase spacing of this alloy was calculated to be 4.1 μm. The alloy was subjected to the same hydrogen absorption and dehydrogenation treatments as in Example 9 to produce a coarse powder, which was then pulverized in a jet mill in a nitrogen stream to produce a fine powder with an average particle size of 2.9 μm. The fine powder was then pressure-molded while oriented in a magnetic field, sintered in a vacuum at 950°C for 1.5 hours, cooled to room temperature at a cooling rate of 11°C / min, and removed to obtain a sintered body. This sintered body, along with Sm metal, was placed in a vacuum heat treatment furnace and heat-treated at 780°C for 8 hours. After being removed from the furnace, it was further aged at 520°C for 2 hours to obtain Example 10.

[0062] The sintered body sample of Example 10 was subjected to ICP analysis, and the composition was Sm ２．４ Ce ７．７ La １．１ Fe ｂａｌ. Co０．６ Si １２．６ Mo ０．９ From the X-ray diffraction measurement of the powder obtained by crushing a part of the sample, the crystal structure of the main phase was found to be ThMn １２ In addition, the structure of the sintered body was observed by EPMA, and the composition of each phase was analyzed. ２ It was confirmed that the R phase was present at 1% by volume or more. ２ (Fe, Co, M) １７ Phase, R ３ (Fe, Co, M) ２９ No α-Fe phase or α-Fe phase was observed. Note that the total of the phase ratios is less than 100% because oxide phases and other phases are also present.

[0063] The composition analysis values ​​of the center and outer shell of the main phase grains by EPMA were Ce, ７．３ La ０．１ Fe ｂａｌ. Co ０．５ Si １３．５ Mo １．０ , Sm ３．２ Ce ４．２ La ０．３ Fe ｂａｌ. Co ０．５ Si １３．５ Mo １．０ It was confirmed that the Sm / R ratio inside the grains was lower than that in the surface layer. ２ The composition analysis values ​​of the phases are Sm ３１．１ Ce １９．６ La ２３．２ Fe ｂａｌ. Co ２．７ Si ０．６ Mo ０．２ , Sm １５．０ Ce １８．９ La ０．５ Fe ｂａｌ. Co ０．２ Si ０．７ Mo ０．２ While Sm was not detected inside the main phase grains, the R-rich phase and R(Fe, Co) present at the grain boundaries were ２ It was confirmed that the phase contained Sm and had a high Sm / R ratio. R(Fe, Co) ２Based on the phase analysis values, an alloy with the same composition was prepared by arc melting and homogenized at 800°C for 20 hours. After that, magnetization-temperature measurements were carried out using a VSM. The Curie temperature T ｃ The average crystal grain size of the main phase calculated from the results of etching and observing the sintered body of Example 9 was 12.3 μm. Furthermore, when the magnetic properties were measured with a B-H tracer, the room temperature coercive force H ｃＪ The value of H was 6.3 kOe. ｃＪ The temperature coefficient β was −0.48% / K.

[0064] For Example 10, STEM observation was carried out in the same manner as in Example 1, and it was confirmed that a grain boundary phase between two grains was present in the grain boundary portion sandwiched between two main phase grains. The measured composition of the grain boundary phase between two grains was Sm ２１．２ Ce １５．５ La ２５．９ Fe ｂａｌ. Co １．０ Si ０．６ and the thickness was 92 nm.

[0065] Comparative Example 8 A sintered body of Comparative Example 9 was produced in the same manner as the sintered body of Example 10, except that the sintered body was subjected to aging treatment at 520°C for 2 hours without carrying out the heat treatment step simultaneously with Sm metal.

[0066] The sintered body composition of Comparative Example 8 is Ce containing no Sm. ８．３ La １．３ Fe ｂａｌ. Co ０．６ Si １３．０ Mo ０．９ and the composition analysis value of the main phase grains is Ce ７．５ La ０．３ Fe ｂａｌ. Co ０．６ Si １３．１ Mo ０．９ The grain boundary region contained R (Fe, Co). ２ No phase exists and the composition is Ce ３３．１ La ２９．６ Fe ｂａｌ. Si ３７．３ and Ce ２３．３ La ５４．３ Fe ｂａｌ. Co ０．８ Si ０．６ Mo ０．１Two types of R-rich phases were observed. ｃＪ The results are shown in Tables 6 to 9.

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076] 11,12 Main phase grain 13 Grain boundary phase between two grains

Claims

1. The composition is of the formula (R １－ａ Zr ａ ) ｘ (Fe １－ｂ Co ｂ ) １００－ｘ－ｙ (M １ １－ｃ M ２ ｃ ) ｙ (R is one or more rare earth elements, Sm being essential, M １ represents one or more elements selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si; M ２ is one or more elements selected from the group consisting of Ti, Nb, Mo, Hf, Ta, and W, and x, y, a, b, and c are each represented by 7≦x≦15 atomic %, 4≦y≦20 atomic %, 0≦a≦0.2, 0≦b≦0.5, and 0≦c≦0.9, respectively; １２ SUMMARY OF THE DISCLOSURE An anisotropic rare earth sintered magnet comprising: a main phase consisting of a compound having a crystalline structure of at least 80% by volume; an average crystal grain size of the main phase being at least 1 μm; and an interparticle grain boundary phase being formed between adjacent main phase grains.

2. The anisotropic rare earth sintered magnet according to claim 1, wherein the grain boundary phase between two particles contains 20 atomic % or more of R.

3. The anisotropic rare earth sintered magnet according to claim 1 or 2, characterized in that the grain boundary phase between two particles has a thickness of 0.5 nm or more.

4. The anisotropic rare earth sintered magnet according to any one of claims 1 to 3, characterized in that an R-rich phase is contained in the grain boundaries.

5. R (Fe, Co) ２ 5. The anisotropic rare earth sintered magnet according to claim 1, characterized in that the phase is contained at grain boundaries.

6. The R-rich phase and the R(Fe, Co) ２ 6. The anisotropic rare earth sintered magnet according to claim 4, characterized in that the phases are contained in a total amount of 1 volume % or more.

7. The Sm / R ratio inside the main phase grain is the same as that in the R-rich phase and the R(Fe, Co) ２ 7. The anisotropic rare earth sintered magnet according to claim 4, wherein the Sm / R ratio of the first phase is lower than the Sm / R ratio of the second phase.

8. An anisotropic rare earth sintered magnet as claimed in any one of claims 1 to 7, characterized in that the Sm / R ratio inside the main phase grain is lower than the Sm / R ratio in the outer periphery of the main phase grain.

9. The anisotropic rare earth sintered magnet according to claim 7 or 8, characterized in that the main phase grains do not contain Sm inside.

10. The anisotropic rare earth sintered magnet according to any one of claims 1 to 9, characterized in that it exhibits a coercive force of 5 kOe or more at room temperature and has a temperature coefficient β of coercive force of -0.5% / K or more.

11. ThMn １２ The method for producing an anisotropic rare earth sintered magnet according to any one of claims 1 to 10, characterized in that an alloy containing a compound phase of the type crystal is pulverized, compacted under application of a magnetic field to form a green body, and then sintered at a temperature of 800°C or higher and 1400°C or lower.

12. ThMn １２ 12. The method for producing an anisotropic rare earth sintered magnet according to claim 11, characterized in that an alloy containing a compound phase of the type crystal and an alloy having a higher R composition ratio and Sm / R ratio than those of the type crystal are pulverized and mixed, and then compacted under application of a magnetic field to form a green body.

13. ThMn １２ 13. The method for producing an anisotropic rare earth sintered magnet according to claim 11, characterized in that a material containing Sm is brought into contact with a sintered body having a compound phase of the type crystal as a main phase, and the material is heat-treated at a temperature of 600°C or higher and lower than the sintering temperature, thereby diffusing Sm into the sintered body.

14. A method for producing an anisotropic rare earth sintered magnet as described in claim 13, characterized in that the material containing Sm that is brought into contact with the sintered body is one or more selected from the group consisting of Sm metal, an alloy containing Sm, a compound containing Sm, and vapor containing Sm, and is in the form of one or more selected from the group consisting of powder, thin film, ribbon, foil, and gas.

15. The method for producing an anisotropic rare earth sintered magnet according to any one of claims 11 to 14, characterized in that the sintered body is subjected to a heat treatment at a temperature of 300 to 900°C.