Samarium-iron-nitrogen-based magnet powder and samarium-iron-nitrogen-based magnet

Abstract

To provide samarium-iron-nitrogen based magnet powder improved in magnetization significantly.SOLUTION: Samarium-iron-nitrogen based magnet powder comprises lanthanoid series (Ln), iron (Fe), bismuth (Bi), tungsten (W), and nitrogen (N). In the samarium-iron-nitrogen based magnet powder, the lanthanoid series include samarium (Sm), the rate ((Bi / (Ln+Fe+Bi+W)) of bismuth to a sum total of atoms of lanthanoid series, iron, bismuth and tungsten is 1.00 at% or below; the rate ((W / (Ln+Fe+Bi+W)) of tungsten to the sum total of atoms of lanthanoid series, iron, bismuth and tungsten is 0.05 at% or above and 0.60 at% or below; the ratio (W / Bi) of tungsten to bismuth is 1.0 or above and 30.0 or below.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This invention relates to samarium-iron-nitrogen-based magnetic powder and samarium-iron-nitrogen-based magnets. [Background technology]

[0002] Samarium-iron-nitrogen magnets are expected to be high-performance magnets due to their high Curie temperature of 477°C, small temperature dependence of their magnetic properties, and high anisotropic magnetic field of 260 kOe, which is considered the theoretical value of their coercivity.

[0003] To manufacture high-performance magnets, it is necessary to sinter samarium-iron-nitrogen-based magnet powder.

[0004] However, samarium-iron-nitrogen-based magnetic powder has a problem in that its magnetic properties deteriorate when sintered at high temperatures. In particular, the coercivity of samarium-iron-nitrogen-based magnets decreases significantly after the sintering process.

[0005] To address these problems, Patent Document 1 describes adding bismuth to samarium-iron-nitrogen-based magnetic powder. Specifically, it describes that by using samarium-iron-bismuth-nitrogen-based magnetic powder, it is possible to increase the coercivity of the magnetic powder. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-57779 [Overview of the project] [Problems that the invention aims to solve]

[0007] Generally, coercivity and magnetization are in a trade-off relationship, and it is said to be difficult to increase both. For example, according to the inventors of this application, the samarium-iron-bismuth-nitrogen-based magnetic powder described in Patent Document 1 exhibits high coercivity, but it is difficult to say that its magnetization is sufficient.

[0008] Under these circumstances, there is a need for samarium-iron-nitrogen-based magnetic powder that possesses both high magnetization and high coercivity.

[0009] This invention has been made in view of the above background, and aims to provide a samarium-iron-nitrogen-based magnetic powder that combines high magnetization and high coercivity. Furthermore, this invention aims to provide a samarium-iron-nitrogen-based magnet that combines high magnetization and high coercivity. [Means for solving the problem]

[0010] In this invention, the samarium-iron-nitrogen-based magnetic powder is, It contains lanthanides (Ln), iron (Fe), bismuth (Bi), tungsten (W), and nitrogen (N), The lanthanide includes samarium (Sm), In atomic ratio, the ratio of bismuth to the sum of lanthanides + iron + bismuth + tungsten ((Bi / (Ln+Fe+Bi+W)) is 1.00 at% or less. In terms of atomic ratio, the ratio of tungsten to the sum of lanthanides + iron + bismuth + tungsten ((W / (Ln+Fe+Bi+W)) is between 0.05 at% and 0.60 at%. A samarium-iron-nitrogen-based magnetic powder is provided, in which the atomic ratio of tungsten to bismuth (W / Bi) is between 1.0 and 30.0. [Effects of the Invention]

[0011] In the present invention, it is possible to provide samarium-iron-nitrogen-based magnet powder having both high magnetization and high coercive force. Further, in the present invention, it is possible to provide a samarium-iron-nitrogen-based magnet having both high magnetization and high coercive force.

Brief Description of Drawings

[0012] [Figure 1] It is a flowchart schematically showing an example of a method for manufacturing samarium-iron-nitrogen-based magnet powder according to an embodiment of the present invention. [Figure 2] It is a flowchart schematically showing an example of a method for manufacturing a samarium-iron-bismuth-tungsten-nitrogen-based sintered magnet using the samarium-iron-nitrogen-based magnet powder according to an embodiment of the present invention. [Figure 3] It is a flowchart schematically showing an example of a method for manufacturing a samarium-iron-bismuth-tungsten-nitrogen-based non-sintered magnet using the samarium-iron-nitrogen-based magnet powder according to an embodiment of the present invention. [Figure 4] It is a graph showing the relationship between the coercive force and magnetization obtained in each example. [Figure 5] It is a diagram schematically showing a graph obtained when measuring the nitrogen release temperature. [Figure 6] It is a diagram schematically showing a graph obtained when measuring the decomposition temperature. [Figure 7] It is a graph showing the change rate ΔPa (%) of the lattice constant in the a-axis direction and the change rate ΔPc (%) of the lattice constant in the c-axis direction in each magnet powder.

Modes for Carrying Out the Invention

[0013] Hereinafter, an embodiment of the present invention will be described.

[0014] As described above, according to the inventors of the present application, the samarium-iron-bismuth-nitrogen-based magnet powder described in Patent Document 1 has a problem that although it shows high coercive force, its magnetization is not so high.

[0015] To address these problems, the inventors of the present invention have diligently conducted research and development on samarium-iron-nitrogen-based magnetic powders that possess both high magnetization and high coercivity. As a result, the inventors have discovered that by co-adding predetermined amounts of bismuth and tungsten to samarium-iron-nitrogen-based magnetic powders, thereby creating samarium-iron-bismuth-tungsten-nitrogen-based magnetic powders, the magnetization and coercivity of the magnetic powders can be significantly increased, leading to the present invention.

[0016] In other words, in one embodiment of the present invention, the samarium-iron-nitrogen-based magnetic powder is It contains lanthanides (Ln), iron (Fe), bismuth (Bi), tungsten (W), and nitrogen (N), The lanthanide includes samarium (Sm), In atomic ratio, the ratio of bismuth to the sum of lanthanides + iron + bismuth + tungsten ((Bi / (Ln+Fe+Bi+W)) is 1.00 at% or less. In terms of atomic ratio, the ratio of tungsten to the sum of lanthanides + iron + bismuth + tungsten ((W / (Ln+Fe+Bi+W)) is between 0.05 at% and 0.60 at%. A samarium-iron-nitrogen-based magnetic powder is provided, in which the atomic ratio of tungsten to bismuth (W / Bi) is between 1.0 and 30.0.

[0017] In this application, the samarium-iron-bismuth-tungsten-nitrogen-based magnetic powder according to one embodiment of the present invention is also referred to as "samarium-iron-nitrogen-based magnetic powder."

[0018] In the samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention, bismuth is added such that the ratio of bismuth to the sum of lanthanide (Ln) + iron + bismuth + tungsten ((Bi / (Ln+Fe+Bi+W))) is 1.00 at% or less. In addition, in the samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention, tungsten is added such that the ratio of tungsten to the sum of lanthanide + iron + bismuth + tungsten ((W / (Ln+Fe+Bi+W))) is between 0.05 at% and 0.60 at%. Furthermore, the ratio of tungsten to bismuth (W / Bi) is between 1.0 and 30.0.

[0019] By adding bismuth and tungsten in these proportions, a magnetic powder with high magnetization and high coercivity can be obtained in one embodiment of the present invention.

[0020] The reason why co-adding bismuth and tungsten yields magnetic powder with high magnetization and high coercivity is not yet fully understood. However, as will be described later, in the samarium-iron-nitrogen magnetic powder according to one embodiment of the present invention, it has been observed that both the lattice constant Pa in the a-axis direction and the lattice constant Pc in the c-axis direction are larger than those of basic samarium-iron-nitrogen magnetic powder. Therefore, it is possible that by co-adding bismuth and tungsten, at least a portion of the samarium and / or Fe is replaced by Bi and / or W, improving the stability of the crystal structure of the particles constituting the magnetic powder, and as a result, the coercivity can be increased without reducing the magnetization. In the samarium-iron-nitrogen magnetic powder according to one embodiment of the present invention, (Bi / (Ln+Fe+Bi+W)) is preferably 0.1 at% or less, and more preferably 0.05 at% or less.

[0021] Furthermore, in the samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention, W / (Ln+Fe+Bi+W) is preferably 0.41 at% or less.

[0022] Furthermore, in the samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention, the atomic ratio W / Bi is preferably 20.5 or less.

[0023] Furthermore, if (W / (Ln+Fe+Bi+W)) is less than 0.05 at% or greater than 0.60 at%, the improvement in magnetization trend will no longer be observed. Similarly, if the atomic ratio W / Bi is less than 1.0 or greater than 30.0, the improvement in magnetization trend will no longer be observed.

[0024] (Samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention) The following describes other characteristics of the samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention.

[0025] (composition) A samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention (hereinafter also simply referred to as "the magnetic powder of the present invention") contains a lanthanide. The lanthanide may contain only samarium, but may also contain at least one additional element selected from the group consisting of lanthanum (La), cerium (Ce), erbium (Er), thulium (Tm), and ytterbium (Yb).

[0026] Furthermore, in the magnetic powder of the present invention, the ratio of lanthanides to the sum of lanthanides + iron + bismuth + tungsten (Ln / (Ln+Fe+Bi+W)) is, for example, in the range of 10.0 at% to 15.0 at%.

[0027] On the other hand, in the magnetic powder of the present invention, the ratio of iron to the sum of lanthanides + iron + bismuth + tungsten (Fe / (Ln+Fe+Bi+W)) is, for example, in the range of 85.0 at% to 90.0 at%.

[0028] (form) The magnetic powder of the present invention contains a large number of particles. Each particle has a core portion, and a coating layer may be provided on at least a part of the core portion. The coating layer may cover the entire core portion. However, particles without a coating layer and particles consisting only of a core portion may also exist.

[0029] Typically, the core of a particle contains lanthanides, iron, bismuth, tungsten, and nitrogen.

[0030] Furthermore, the core of the particle is typically made of Th2Zn. 17 It has a crystalline structure.

[0031] For example, the core of the particle has a lanthanide-iron-nitrogen compound phase, such as Ln2Fe 17 It may also have an N3 phase. 17 At least a portion of the Ln in the N3 phase may be substituted with Bi and / or W. Similarly, Ln2Fe 17 At least a portion of the Fe in the N3 phase may be substituted with Bi and / or W.

[0032] On the other hand, the coating layer contains lanthanides and / or iron, but has a different crystalline structure from the core.

[0033] The coating layer may contain more lanthanides than the core. That is, the atomic ratio of lanthanides to iron in the coating layer (Ln / Fe) may be greater than the atomic ratio of lanthanides to iron in the core (Ln / Fe).

[0034] The average particle size of the particles is not particularly limited, but may be less than 1.5 μm, for example. In this case, the coercivity of the magnetic powder of the present invention can be further increased.

[0035] Furthermore, in the magnetic powder of the present invention, the number of particles with an aspect ratio of 2.0 or higher is preferably 10% or less, and more preferably 8% or less. When the number of particles with an aspect ratio of 2.0 or higher is 10% or less, the coercivity of the magnetic powder of the present invention can be further increased.

[0036] Furthermore, the magnetic powder of the present invention has the characteristic of having a high decomposition temperature. For example, the nitrogen release temperature of the magnetic powder of the present invention is 610°C or higher.

[0037] The coercivity of the magnetic powder of the present invention before heat treatment is, for example, 17 kOe or more. Furthermore, the magnetization of the magnetic powder of the present invention is, for example, 140 emu / g or more. Therefore, the magnetic powder of the present invention can be used as a magnetic powder possessing both high magnetization and high coercivity. In this application, magnetization refers to the value of magnetization when a magnetic field of 90 kOe is applied.

[0038] The magnetic powder of the present invention, having the characteristics described above, may be used in the manufacture of high-performance samarium-iron-nitrogen-based magnets.

[0039] (Samarium-iron-nitrogen magnets) A samarium-iron-nitrogen magnet according to one embodiment of the present invention (hereinafter also simply referred to as "the magnet of the present invention") contains the magnetic powder of the present invention.

[0040] The magnet of the present invention may be a samarium-iron-nitrogen sintered magnet or a samarium-iron-nitrogen bonded magnet.

[0041] The magnet of the present invention, specifically the rare earth magnet according to this embodiment, may have a metal phase other than Sm-Fe-N-based magnet powder. Such a metal phase may be, for example, an Fe phase.

[0042] The rare earth magnet according to this embodiment may further contain at least one element other than Sm, Fe, and N, such as C, Al, Si, P, Ti, Cr, Mn, Co, Cu, Zn, Y, Zr, and Sn. The content of elements other than Sm, Fe, and N is preferably 10% by mass or less, and more preferably 5% by mass or less.

[0043] (Method for producing samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention) Next, with reference to Figure 1, an example of a method for producing samarium-iron-nitrogen-based magnetic powder according to one embodiment of the present invention (hereinafter referred to as the "first method") will be described.

[0044] In the following description, the first method will be explained using the case where samarium alone is included as the lanthanide (Ln). However, it will be obvious to those skilled in the art that the same method can be applied when the lanthanide (Ln) includes samarium in addition to another lanthanide element (at least one of La, Ce, Er, Tm, and Yb).

[0045] Figure 1 shows a schematic example of the flow of the first method.

[0046] As shown in Figure 1, the first method is: The process of preparing the precursor powder (S110), The process (S120) involves reducing and diffusing the aforementioned precursor powder under an inert gas atmosphere to prepare a samarium-iron-bismuth-tungsten alloy powder, The process (S130) involves nitriding the samarium-iron-bismuth-tungsten alloy powder to prepare a samarium-iron-bismuth-tungsten-nitrogen alloy powder, The process of washing the samarium-iron-bismuth-tungsten-nitrogen alloy powder (S140), It has.

[0047] The following describes each step.

[0048] (Step S110) First, a precursor powder is prepared.

[0049] The precursor powder may be, for example, samarium-iron-bismuth-tungsten oxide powder or samarium-iron-bismuth-tungsten hydroxide powder. Hereinafter, samarium-iron-bismuth-tungsten oxide powder and samarium-iron-bismuth-tungsten hydroxide powder will be collectively referred to as samarium-iron-bismuth-tungsten (water) oxide powder.

[0050] Samarium-iron-bismuth-tungsten (water) oxide powder can be prepared by spray pyrolysis.

[0051] In this method, a solution containing samarium salt, iron salt, bismuth salt, and tungsten salt is first prepared. The composition of the samarium-iron-nitrogen-based magnetic powder can be controlled to a desired value by adjusting the amounts of samarium salt, iron salt, bismuth salt, and tungsten salt added.

[0052] Water can be used as the solvent in the solution, but organic solvents such as ethanol may also be used.

[0053] Furthermore, the counterions in samarium salts, iron salts, bismuth salts, and tungsten salts may be inorganic ions such as chloride ions, sulfate ions, or nitrate ions. Alternatively, the counterions may be organic ions such as alkoxides.

[0054] When adding bismuth salts and tungsten salts to a solution, it is preferable to adjust the pH to the acidic side in order to properly dissolve them. It is preferable to use nitric acid or the like for such pH adjustment. If the pH of the solution is neutral or alkaline, bismuth salts and tungsten salts tend to remain undissolved. As a result, the ratio of bismuth to tungsten in the resulting samarium-iron-nitrogen-based magnet powder tends to fall outside the desired range. By properly dissolving bismuth salts and tungsten salts in the solution, the bismuth and tungsten content of the resulting samarium-iron-nitrogen-based magnet powder can be controlled to the desired range.

[0055] Next, the prepared solution is supplied into a heated reaction tube, where it is thermally decomposed. When supplying the solution, an ultrasonic or two-fluid nozzle type atomizer may be used. In this case, fine droplets are formed from the solution, and these droplets are introduced into the reaction tube along with the carrier gas. The supplied solution or droplets are thermally decomposed within the reaction tube. The temperature inside the reaction tube is, for example, in the range of 400°C to 1000°C.

[0056] The particles generated by the thermal decomposition of the solution or droplets are then collected by a filter at the outlet of the reaction tube. This yields a samarium-iron-bismuth-tungsten (water) oxide powder.

[0057] The resulting precursor powder may then be handled in a non-oxidizing atmosphere, such as a glove box, until samarium-iron-nitrogen-based magnetic powder is produced. When using an inert gas atmosphere as the non-oxidizing atmosphere, the oxygen concentration is preferably 1 ppm or less.

[0058] The obtained precursor powder is preferably pre-reduced in a reducing atmosphere. This reduces the amount of calcium used in the subsequent reduction-diffusion step (step 1S20) and suppresses the generation of coarse samarium-iron-bismuth-tungsten alloy particles.

[0059] Pre-reduction of the precursor powder may be carried out, for example, by heating the precursor powder to 400°C or higher in a hydrogen atmosphere. The processing temperature is preferably in the range of 500°C to 800°C. When pre-reduction is carried out in this temperature range, samarium-iron-bismuth-tungsten alloy particles with uniform particle size can be obtained in a subsequent process.

[0060] (Process S120) Next, the precursor powder is subjected to reduction-diffusion treatment under an inert gas atmosphere to form a samarium-iron-bismuth-tungsten alloy powder (hereinafter simply referred to as "alloy powder I").

[0061] Methods for reducing and diffusing the precursor powder include, for example, mixing the precursor powder with calcium (Ca) or calcium hydride (CaH2) and then heating it to a temperature above the melting point of Ca (approximately 850°C).

[0062] During this process, samarium reduced by calcium diffuses through the calcium molten liquid and reacts with iron, bismuth, and tungsten to form alloy powder I.

[0063] There is a correlation between the temperature of the reduction-diffusion treatment and the particle size of the particles contained in alloy powder I; the higher the reduction-diffusion temperature, the larger the particle size of the particles contained in alloy powder I.

[0064] The average particle size of the particles contained in alloy powder I is preferably 3.0 μm or less. When the average particle size is 3.0 μm or less, the coercivity of the final magnetic powder becomes even higher.

[0065] Furthermore, in order to obtain alloy powder I containing particles of uniform size, it is preferable to subject the precursor powder to a reduction-diffusion treatment at 850°C to 1050°C for about 1 minute to 2 hours under an inert gas atmosphere.

[0066] Each particle of alloy powder I undergoes crystallization as reduction diffusion progresses, for example, Th2Zn 17 A core portion having a structure is formed. At this time, a coating layer is formed on at least a part of the surface of the core portion.

[0067] (Step S130) Next, the obtained alloy powder I is subjected to nitriding treatment to form a samarium-iron-bismuth-tungsten-nitrogen alloy powder (hereinafter simply referred to as "alloy powder II").

[0068] Methods for nitriding alloy powder I include heat treatment of alloy powder I at 300°C to 500°C in an atmosphere of ammonia, a mixture of ammonia and hydrogen, nitrogen, or a mixture of nitrogen and hydrogen.

[0069] When ammonia is used, alloy powder I can be nitrided in a short time. However, the nitrogen content in alloy powder II may become higher than the optimal value. In this case, it is preferable to anneal alloy powder II in hydrogen after the nitriding treatment. This allows excess nitrogen to be removed from the crystal lattice.

[0070] The particle composition contained in alloy powder II is Sm2Fe 17 It is preferable that it be N3.

[0071] For example, alloy powder I is heat-treated at 350°C to 450°C for 10 minutes to 2 hours in an ammonia-hydrogen mixed atmosphere, and then annealed at 350°C to 450°C for 30 minutes to 2 hours in a hydrogen atmosphere. This allows for the optimization of the nitrogen content in alloy powder II.

[0072] (Process S140) Next, the alloy powder II formed in step S130 is washed.

[0073] The alloy powder II formed in step S130 contains calcium compounds. A washing treatment is carried out to remove such calcium compounds.

[0074] The cleaning process is carried out using a cleaning solution such as water and / or alcohol. For example, by repeatedly adding water to alloy powder II and then performing stirring and decantation, most of the calcium compounds contained in alloy powder II can be removed.

[0075] The cleaning process may be performed before the nitriding treatment.

[0076] Through the above process, samarium-iron-bismuth-tungsten-nitrogen-based magnetic powder can be manufactured.

[0077] However, the following additional step (step S150) may be performed on the samarium-iron-bismuth-tungsten-nitrogen-based magnet powder obtained in step S140 (hereinafter simply referred to as "manufactured powder").

[0078] (Process S150) The manufactured powder obtained in step S140 is preferably subjected to vacuum drying.

[0079] The drying temperature is not particularly limited, but it is preferably in the range of room temperature to 100°C. By drying at a temperature of 100°C or lower, oxidation of the manufactured powder can be suppressed.

[0080] Furthermore, the manufactured powder may be subjected to a dehydrogenation treatment. Dehydrogenation treatment can remove hydrogen that has entered between the crystal lattices during the washing process.

[0081] The method of dehydrogenation treatment is not particularly limited. For example, dehydrogenation treatment may be performed by heating the manufactured powder under vacuum or in an inert gas atmosphere. For example, dehydrogenation treatment may be performed by heat-treating the manufactured powder at 150°C to 450°C for 1 hour under an argon atmosphere.

[0082] Furthermore, the manufactured powder may be subsequently crushed. This improves the residual magnetization and maximum energy product of the manufactured powder.

[0083] In this application, "crushing" is used as a separate term from "grinding."

[0084] In other words, "disintegration" means separating one or more particles from an aggregate when multiple particles have aggregated together. On the other hand, "pulverization" means dividing a single particle into multiple smaller pieces.

[0085] When crushing the manufactured powder, jet mills, dry and wet ball mills, vibratory mills, media stirring mills, etc., can be used.

[0086] It should be noted that the crushing process does not necessarily have to be carried out at this stage. For example, the crushing process may be carried out on the alloy powder I obtained in step S120.

[0087] (Manufacturing method for samarium-iron-bismuth-tungsten-nitrogen-based sintered magnets) Next, with reference to Figure 2, an example of a method for producing a samarium-iron-bismuth-tungsten-nitrogen-based sintered magnet using the magnetic powder of the present invention (hereinafter referred to as the "second method") will be described.

[0088] In the following description, the second method will be explained using the case where samarium alone is included as the lanthanide (Ln). However, it will be obvious to those skilled in the art that the same method can be applied when the lanthanide (Ln) includes samarium in addition to another lanthanide element (at least one of La, Ce, Er, Tm, and Yb).

[0089] Figure 2 schematically shows an example of the flow of the second method.

[0090] As shown in Figure 2, the second method is: The process of forming a molded body by molding samarium-iron-bismuth-tungsten-nitrogen-based magnet powder (step S210), The process of sintering the molded body (step S220), It has.

[0091] The following describes each step.

[0092] (Step S210) First, a samarium-iron-bismuth-tungsten-nitrogen-based magnetic powder having the characteristics described above is prepared. Then, this magnetic powder is molded to form a molded body.

[0093] The molding method is not particularly limited, and general molding methods for magnetic powder may be used. The pressure applied during molding is, for example, in the range of 10 MPa to 3000 MPa.

[0094] Furthermore, during molding, the magnetic powder may be molded while a magnetic field is applied to it. In this case, the magnetic powder contained in the molded body is oriented in a specific direction, resulting in an anisotropic magnet with high magnetic properties.

[0095] (Process S220) Next, the molded body is subjected to a sintering process.

[0096] The sintering method is not particularly limited, and general sintering methods such as the discharge plasma method and the hot press method may be used.

[0097] The sintering temperature may be in the range of, for example, 300°C to 650°C.

[0098] Furthermore, steps S210 and S220 may be carried out using the same apparatus.

[0099] Through the above process, a samarium-iron-bismuth-tungsten-nitrogen-based sintered magnet can be manufactured.

[0100] (Method for manufacturing samarium-iron-bismuth-tungsten-nitrogen-based non-sintered magnets) Next, with reference to Figure 3, an example of a method for manufacturing a samarium-iron-bismuth-tungsten-nitrogen-based non-sintered magnet (hereinafter referred to as the "third method") will be described.

[0101] In the following description, the third method will be explained using the case where samarium alone is included as the lanthanide (Ln). However, it will be obvious to those skilled in the art that the same method can be applied when the lanthanide (Ln) includes samarium in addition to another lanthanide element (at least one of La, Ce, Er, Tm, and Yb).

[0102] Figure 3 shows a schematic example of the flow of the third method.

[0103] As shown in Figure 3, the third method is The process of producing pellets from samarium-iron-bismuth-tungsten-nitrogen-based magnetic powder (process S310), The process of forming the aforementioned pellets (process S320), It has.

[0104] The following describes each step.

[0105] (Process S310) First, pellets are produced from samarium-iron-bismuth-tungsten-nitrogen-based magnetic powder.

[0106] Therefore, the magnetic powder and resin are mixed. The resin used may be a thermosetting resin or a thermoplastic resin. Thermoplastic resins are particularly preferred. Suitable thermoplastic resins include polyamide (PA) and polyphenylene sulfide (PPS), etc.

[0107] Next, this mixture is heated and kneaded, and the kneaded material is formed into pellets using a pelletizer or the like. The heating temperature may be, for example, in the range of 150°C to 330°C.

[0108] (Process S320) Next, the pellets produced in step S310 are molded.

[0109] Injection molding may be used for the molding process. In this case, a molded body can be obtained from pellets introduced into an injection molding apparatus, which is then injection-molded into a predetermined shape.

[0110] This allows you to obtain molded bonded magnets.

[0111] Furthermore, anisotropic bonded magnets may be obtained by molding pellets while applying a magnetic field to the mold.

[0112] Through the above process, a samarium-iron-bismuth-tungsten-nitrogen-based non-sintered magnet can be manufactured. [Examples]

[0113] Examples of the present invention will be described below. In the following description, Examples 1 to 9 are examples, and Examples 11 to 16 are comparative examples.

[0114] (Example 1) Magnetic powder was prepared using the following method.

[0115] (Preparation of precursor powder) 63.10 g of iron nitrate notahydrate, 12.63 g of samarium nitrate hexahydrate, 0.62 g of lanthanum nitrate hexahydrate, 0.77 g of bismuth nitrate pentahydrate, and 0.20 g of ammonium tungstate para pentahydrate were added to 1800 ml of water, and then 10.50 ml of nitric acid was added while stirring to dissolve each salt.

[0116] Next, the prepared solution was atomized into droplets using a spray pyrolysis apparatus, and the droplets were then pyrolyzed. This apparatus has an ultrasonic atomizer and a heated reaction tube at the inlet, and a filter is installed at the outlet of the reaction tube.

[0117] The solution introduced into the apparatus is transformed into fine droplets by an ultrasonic atomizer. These droplets are supplied into the reaction tube along with a carrier gas (atmosphere). The reaction tube is preheated, and the droplets are thermally decomposed within the tube. The thermal decomposition products are then collected by a filter. The temperature of the reaction tube was set to 900°C.

[0118] The pyrolysis products were collected using a filter at the outlet of the reaction tube.

[0119] Next, the obtained pyrolysis products were pre-reduced under a hydrogen atmosphere. The treatment temperature was 600°C and the treatment time was 6 hours. This yielded a precursor powder containing samarium and lanthanum as lanthanides.

[0120] (Reduction-diffusion treatment) Next, 5 g of precursor powder and 2.5 g of metallic calcium were placed in an iron crucible, and the precursor powder was reduced and diffused by heating at 975°C for 1 hour.

[0121] As a result, an alloy powder (hereinafter referred to as "alloy powder A") was prepared.

[0122] (nitriding treatment) Next, after cooling alloy powder A to room temperature, the alloy powder A was heated to 420°C in an ammonia + hydrogen mixed atmosphere with a volume ratio of 1:2, and held at this temperature for 1 hour to perform nitriding treatment.

[0123] This resulted in the production of alloy powder B.

[0124] Next, in order to optimize the nitrogen content in alloy powder B, further heat treatment was performed on alloy powder B. The heat treatment was carried out by annealing alloy powder B at 420°C for 1 hour under a hydrogen atmosphere, and then annealing alloy powder B again at 420°C for 0.5 hours under an argon atmosphere.

[0125] (Cleaning process) Next, alloy powder B, with an optimized nitrogen content, was washed five times with pure water to remove calcium compounds and other contaminants. This yielded alloy powder C.

[0126] (Vacuum drying process) Next, to remove any remaining water from alloy powder C, alloy powder C was immersed in a 2-propanol solution, and then alloy C was vacuum-dried at room temperature.

[0127] Furthermore, after vacuum drying, alloy powder C was dehydrogenated under vacuum at 200°C for 3 hours.

[0128] This resulted in the production of magnetic powder.

[0129] In the above method, each step from the pre-reduction treatment onward was carried out in a glove box under an argon atmosphere.

[0130] (Examples 2-6) Magnetic powder was prepared using the same method as in Example 1. However, in Examples 2 to 6, the composition of the precursor powder was changed from that in Example 1 to produce the magnetic powder. Other manufacturing conditions were the same as in Example 1.

[0131] (Example 7) Magnetic powder was prepared using the same method as in Example 1. However, in Example 7, no lanthanum compound was added when preparing the precursor powder. That is, a precursor powder containing only samarium as the lanthanide Ln was prepared. The reduction-diffusion treatment temperature was 1025°C. Other manufacturing conditions are the same as in Example 1.

[0132] (Examples 8-9) Magnetic powder was prepared using the same method as in Example 1. However, in Examples 8 and 9, the composition of the precursor powder was changed from that in Example 1 to prepare the magnetic powder. Other manufacturing conditions were the same as in Example 1.

[0133] (Examples 11-13) Magnetic powder was prepared using the same method as in Example 1. However, in Examples 11 to 13, lanthanum compounds, bismuth compounds, and tungsten compounds were not added when preparing the precursor powder. In other words, samarium-iron based precursor powder was prepared in Examples 11 to 13. Other manufacturing conditions were the same as in Example 1.

[0134] (Example 14) Magnetic powder was prepared using the same method as in Example 1. However, in Example 14, lanthanum and tungsten compounds were not added when preparing the precursor powder. In other words, in Example 14, a samarium-iron-bismuth precursor powder was prepared. The reduction-diffusion treatment temperature was 920°C. Other manufacturing conditions were the same as in Example 1.

[0135] (Examples 15-16) Magnetic powder was prepared using the same method as in Example 1. However, in Examples 15 and 16, the amount of each component added to the precursor powder was changed from that in Example 1 to prepare the magnetic powder. The reduction diffusion temperature was 930°C in Example 15 and 975°C in Example 16. Other manufacturing conditions were the same as in Example 1.

[0136] (evaluation) The following evaluations were performed using the magnetic powder obtained in each example.

[0137] (X-ray diffraction measurement) X-ray diffraction (XRD) spectra were measured using the magnetic powders in each example. The results showed that in all magnetic powders, the main phase was Th2Zn. 17 It was found to have a structure.

[0138] Furthermore, the nitrogen content of each magnet powder was measured using the inert gas fusion-thermal conductivity method. As a result, the nitrogen content of each magnet powder was found to be approximately 3.3% by mass.

[0139] (composition analysis) The composition of each magnetic powder was analyzed by high-frequency inductively coupled plasma atomic emission spectroscopy. As a result, it was confirmed that the magnetic powders in Examples 1 to 6 are samarium-lanthanum-iron-bismuth-tungsten-nitrogen-based magnetic powders, the magnetic powder in Example 7 is samarium-iron-bismuth-tungsten-nitrogen-based magnetic powder, and the magnetic powders in Examples 8 to 9 are samarium-lanthanum-iron-bismuth-tungsten-nitrogen-based magnetic powders.

[0140] Furthermore, it was confirmed that the magnetic powders in Examples 11 to 13 are samarium-iron-nitrogen-based magnetic powders, the magnetic powder in Example 14 is samarium-iron-bismuth-nitrogen-based magnetic powder, and the magnetic powders in Examples 15 to 16 are samarium-lanthanum-iron-bismuth-tungsten-nitrogen-based magnetic powders.

[0141] Table 1 below summarizes the composition and other characteristics of each magnetic powder.

[0142] [Table 1] In Table 1, "W / Bi" refers to the ratio (atomic ratio) of tungsten to bismuth in the magnetic powder.

[0143] (Measurement of average particle diameter and aspect ratio) The average particle size of each magnetic powder was measured using a scanning electron microscope (FE-SEM).

[0144] For the measurement, more than 200 particles were randomly selected, and the contour line was determined for each selected particle. The diameter of a circle with the same area as the region enclosed by this contour line was defined as the particle diameter of that particle. The arithmetic mean of the particle diameters obtained for each selected particle was taken as the average particle size of the particles contained in each magnetic powder.

[0145] Similarly, the aspect ratio was calculated for each selected particle. From these results, the proportion of particles with an aspect ratio of 2.0 or greater was determined. The aspect ratio was defined as the value obtained by dividing the length of the longer side by the length of the shorter side of a rectangle that circumscribes the particle's outline and has the smallest area.

[0146] (Observation of the coating layer) The following method was used to evaluate whether a coating layer was formed on the surface of the particle core in the magnetic powders according to Examples 1 to 9.

[0147] First, a sample was prepared by taking a portion of each magnet powder, mixing it with a thermosetting epoxy resin, and then thermosetting it. The sample was then etched using a focused ion beam (FIB) to expose its cross-section.

[0148] The cross-section of the sample was observed using a scanning transmission electron microscope (STEM) and energy-dispersive X-ray spectroscopy (EDS) to confirm the presence or absence of a coating layer.

[0149] Observations revealed that in the magnetic powders of Examples 1 to 9, a coating layer was present on the surface of the particle core.

[0150] The composition of the core and coating layer was analyzed by energy-dispersive X-ray spectroscopy (EDS). The results showed that the atomic ratio of lanthanides to iron (Ln / Fe) in the coating layer was greater than the atomic ratio of lanthanides to iron (Ln / Fe) in the core.

[0151] (Measurement of coercivity and magnetization) The coercivity and magnetization were measured using the magnetic powders related to each example.

[0152] First, the magnetic powder and thermoplastic resin were mixed, and then the mixture was oriented in a 20 kOe magnetic field to prepare a sample for measurement.

[0153] Next, the coercivity and magnetization of the sample were measured using a vibrating sample magnetometer (VSM). The measurement temperature was 27°C, and the maximum applied magnetic field was 90 kOe. The applied magnetic field was applied along the easy magnetization axis of the sample.

[0154] Here, magnetization refers to the value of magnetization obtained when a magnetic field of 90 kOe is applied.

[0155] Table 2 below summarizes the evaluation results obtained for each magnetic powder.

[0156] [Table 2] Figure 4 also shows the relationship between coercivity and magnetization obtained for each magnetic powder.

[0157] Figure 4 shows that the magnetic powders in Examples 1 to 9 exhibited higher coercivity and magnetization compared to the magnetic powders in Examples 11 to 16.

[0158] (Measurement of nitrogen release temperature and decomposition temperature) Using a thermogravimetric analyzer connected to a mass spectrometer, the nitrogen release temperature and decomposition temperature of each magnet powder were measured. The measurement conditions were a heating rate of 20 °C / min under an argon atmosphere.

[0159] Figure 5 schematically shows the graph obtained during the measurement of the nitrogen release temperature. In Figure 5, the horizontal axis is temperature, and the vertical axis is the ion current derived from N2 with a mass-to-charge ratio (m / z) of 28. + is the ion current.

[0160] The nitrogen release temperature is defined as follows: First, as shown in Figure 5, draw the first approximate straight line LP1 so as to correspond to the change in ion current in the temperature range of 500 °C to 550 °C. Next, find the temperature T 1max at which the change in ion current (the positive slope of the curve in Figure 5) is maximum, and draw the second approximate straight line LP2 in the region of T 1max ±10 °C centered on the temperature T 1max .

[0161] Find the nitrogen release temperature T N from the intersection point on the extension lines of the two approximate straight lines LP1 and LP2. If the first approximate straight line deviates significantly from the actual change in ion current, find the temperature region with relatively little variation within the temperature range of 400 °C to 60 **C (the temperature range is 50 °C. For example, 450 °C to 500 °C, etc.) and draw the first approximate straight line LP1 in this region.

[0162] As a result of the measurement, the nitrogen release temperatures of the magnet powders according to Examples 1 to 9 were all 610 °C or higher.

[0163] Figure 6 schematically shows the graph obtained during the measurement of the decomposition temperature. In Figure 6, the horizontal axis is temperature, and the vertical axis is the weight change.

[0164] The decomposition temperature is defined as follows: First, in Figure 6, a first approximate straight line LQ1 is drawn to correspond to the weight change in the temperature range of 500°C to 550°C. Next, the temperature T at which the negative change in the weight change curve (the negative slope of the curve in Figure 6) is maximized is determined. 2max Determine the temperature T 2max The center T 2max A second approximate line, LQ2, is drawn in the region of ±10℃.

[0165] From the intersection of the two approximate lines LQ1 and LQ2, the decomposition temperature T can be determined. d The following is determined. If the first approximate line deviates significantly from the actual change in decomposition temperature, a temperature region with relatively little fluctuation is found within the temperature range of 400°C to 600°C, and the first approximate line LQ1 is drawn in that region (with a temperature range of 50°C, for example, 450°C to 500°C).

[0166] The measurement results showed that the decomposition temperatures of the magnetic powders in Examples 1 to 9 were all 630°C or higher.

[0167] (Lattice constant) The lattice constants of each magnetic powder were measured using the following method.

[0168] A borosilicate glass capillary with an inner diameter of 0.3 mm was filled with magnetic powder.

[0169] Next, diffraction peaks were measured using synchrotron X-ray diffraction (transmission method) with a large Debye-Scherrer camera at beamline BL19B2 of SPring-8 (manufactured by the Japan Synchrotron Radiation Research Institute (JASRI)). The X-ray wavelength was set to 0.496103 Å, and a semiconductor detector was used. The exposure time for each exposure was 60 seconds, and the results of four exposures were integrated. The measurements were performed at room temperature.

[0170] The lattice constant of the magnetic powder was calculated from the obtained measurement results using Rietveld analysis.

[0171] Figure 7 shows the measurement results of the lattice constants obtained for each magnetic powder.

[0172] In Figure 7, the horizontal axis represents the rate of change ΔPa (%) of the lattice constant in the a-axis direction of the magnetic powder, and the vertical axis represents the rate of change ΔPc (%) of the lattice constant in the c-axis direction of the magnetic powder.

[0173] ΔPa and ΔPc can be calculated as follows:

[0174] First, the magnetic powder to be evaluated (for example, the magnetic powder related to Example 1) is determined. This magnetic powder will be referred to as the "target powder" below.

[0175] Next, a base powder corresponding to the target powder is prepared. The base powder is a samarium-iron-nitrogen magnetic powder, and therefore does not contain lanthanides (Ln), bismuth, or tungsten other than samarium. The samarium, iron, and nitrogen in the base powder have the same composition ratio as in the target powder.

[0176] Next, the lattice constant Pa (ref) in the a-axis direction and the lattice constant Pc (ref) in the c-axis direction of the base powder are measured. Additionally, the lattice constant Pa in the a-axis direction and the lattice constant Pc in the c-axis direction of the target powder are measured.

[0177] From the results obtained, ΔPa = {Pa / Pa(ref)} × 100, and ΔPc = {Pc / Pc(ref)} × 100 The lattice constant change rates ΔPa and ΔPc were evaluated.

[0178] Therefore, if the lattice constant change rate ΔPa exceeds 100%, it means that the a-axis direction of the target powder is expanding compared to the a-axis direction of the base powder. Conversely, if the lattice constant change rate ΔPa is less than 100%, it means that the a-axis direction of the target powder is contracting compared to the a-axis direction of the base powder.

[0179] The same can be said for the rate of change of the lattice constant ΔPc.

[0180] Figure 7 shows that in the magnetic powder according to Example 11, both the lattice constant change rates ΔPa and ΔPc are 100%. Therefore, it is assumed that the magnetic powder according to Example 11 has a crystal lattice structure similar to that of the base powder.

[0181] On the other hand, in the magnetic powders of Examples 1 to 4, it can be seen that both the lattice constant change rate ΔPa and ΔPc are greater than 100%. In other words, in the magnetic powders of Examples 1 to 4, it was found that the lattice expanded in both the a-axis direction and the c-axis direction compared to the respective base powders.

[0182] From these results, it is considered that in the magnetic powder according to one embodiment of the present invention, the crystal lattice expanded in both the a-axis and the c-axis, improving the stability of the particle crystal structure, and thus improving both magnetization and coercivity.

Claims

1. Samarium-iron-nitrogen-based magnetic powder, It contains lanthanides (Ln), iron (Fe), bismuth (Bi), tungsten (W), and nitrogen (N), The lanthanide includes samarium (Sm), In atomic ratio, the ratio of bismuth to the sum of lanthanides + iron + bismuth + tungsten ((Bi / (Ln+Fe+Bi+W)) is 1.00 at% or less. In atomic ratio, the ratio of tungsten to the sum of lanthanides + iron + bismuth + tungsten ((W / (Ln + Fe + Bi + W)) is between 0.05 at% and 0.60 at%. A samarium-iron-nitrogen-based magnetic powder in which the atomic ratio of tungsten to bismuth (W / Bi) is between 1.0 and 30.

0.

2. The samarium-iron-nitrogen-based magnetic powder according to claim 1, wherein the lanthanide further comprises at least one additional element selected from the group consisting of lanthanum, cerium, erbium, thulium, and ytterbium.

3. The samarium-iron-nitrogen-based magnetic powder has particles having a core portion and a coating layer that covers at least a part of the core portion. The core portion of the particle is Th ２ Zn １７ Having a crystalline structure, The samarium-iron-nitrogen-based magnetic powder according to claim 1 or 2, wherein the coating layer of the particles has a different crystal structure from the core portion.

4. The core portion of the particle is Ln ２ Fe １７ N ３ Having a characteristic, The samarium-iron-nitrogen-based magnetic powder according to claim 3, wherein in the phase, at least a portion of Ln and / or Fe is substituted with Bi and / or W.

5. The samarium-iron-nitrogen-based magnetic powder according to claim 3 or 4, wherein the coating layer of the particles comprises a lanthanide and iron.

6. The samarium-iron-nitrogen-based magnet powder according to claim 5, wherein the atomic ratio of lanthanide to iron (Ln / Fe) in the coating layer is greater than the atomic ratio of lanthanide to iron (Ln / Fe) in the core portion.

7. The aforementioned particles have an average particle diameter of less than 1.5 μm. The samarium-iron-nitrogen-based magnetic powder according to any one of claims 3 to 6, wherein the number of particles having an aspect ratio of 2.0 or more is 10% or less.

8. The samarium-iron-nitrogen-based magnetic powder according to any one of claims 1 to 7, wherein the nitrogen release temperature of the samarium-iron-nitrogen-based magnetic powder is 610°C or higher.

9. Samarium-iron-nitrogen magnets, A samarium-iron-nitrogen magnet containing the samarium-iron-nitrogen magnet powder described in any one of claims 1 to 8.

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