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EP-3939718-B1 - METASTABLE SINGLE-CRYSTAL RARE EARTH MAGNET FINE POWDER AND METHOD FOR PRODUCING SAME

EP3939718B1EP 3939718 B1EP3939718 B1EP 3939718B1EP-3939718-B1

Inventors

  • HIRAYAMA, YUSUKE
  • HOSOKAWA, Akihide
  • TAKAGI, KENTA

Dates

Publication Date
20260506
Application Date
20200313

Claims (9)

  1. A single crystal powder, represented by the following general formula: [Chemical Formula 1] (R 1-z M z )T x having a metastable crystal structure of TbCu 7 -type, and having an average particle size of 30 to 300 nm, wherein R is at least one element selected from the group consisting of Nd and Sm, M is at least one element selected from the group consisting of Zr, Y, and Ce, T is at least one element selected from the group consisting of Fe and Co, x is 7.0 ≤ x ≤ 10.0, and z is 0.0 ≤ z ≤ 0.3, wherein the average particle size is measured in accordance with the method described in the description.
  2. The single crystal powder according to claim 1, wherein R is Nd.
  3. The single crystal powder according to claim 1, wherein R is Sm.
  4. A single crystal powder, represented by the following general formula: [Chemical Formula 2] (R 1-z M z )T x N y having a metastable crystal structure of TbCu 7 -type, and having an average particle size of 30 to 300 nm, wherein R is at least one element selected from the group consisting of Nd and Sm, M is at least one element selected from the group consisting of Zr, Y, and Ce, T is at least one element selected from the group consisting of Fe and Co, x is 7.0 ≤ x ≤ 10.0, y is 1.0 ≤ y ≤ 2.0, and z is 0.0 ≤ z ≤ 0.3, wherein the average particle size is measured in accordance with the method described in the description.
  5. The single crystal powder according to claim 4, wherein R is Nd.
  6. The single crystal powder according to claim 4, wherein R is Sm.
  7. The single crystal powder according to any one of claims 1 to 6, wherein the single crystal powder is used as a permanent magnet material.
  8. A method for producing the single crystal powder according to any one of claims 1 to 3, the method comprising: using a mixed powder or an alloy powder of R (R is at least one element selected from the group consisting of Nd and Sm), M (M is at least one element selected from the group consisting of Zr, Y, and Ce), and T (T is at least one element selected from the group consisting of Fe and Co) as a raw material powder; evaporating a raw material metal powder; and lowering the temperature to room temperature in an inert gas atmosphere ; wherein the average particle size is measured in accordance with the method described in the description.
  9. A method for producing the single crystal powder according to any one of claims 4 to 6, the method comprising: penetrating nitrogen atoms, in a range of 200°C to 600°C, into a single crystal powder represented by the following general formula: [Chemical Formula 1] (R 1-z M z )T x having a metastable crystal structure of TbCu 7 -type, and having an average particle size of 30 to 300 nm, wherein R is at least one element selected from the group consisting of Nd and Sm, M is at least one element selected from the group consisting of Zr, Y, and Ce, T is at least one element selected from the group consisting of Fe and Co, x is 7.0 ≤ x ≤ 10.0, and z is 0.0 ≤ z ≤ 0.3; wherein the single crystal powder is produced by lowering the temperature to room temperature in an inert gas atmosphere; and wherein the average particle size is measured in accordance with the method described in the description.

Description

Technical Field The present invention relates to a rare earth anisotropic magnet material and a rare earth magnet material suitable for use in a permanent magnet with high characteristics, which are suitable for use in a wide range of fields such as electronics, information communication, medical, machine tool fields, and industrial and automobile motors. Background Art The magnetic compound currently used for the magnet with the highest performance is an Nd2Fe14B compound. This magnet has the main phase of the Nd-Fe-B magnet invented in 1982, the crystal structure thereof has been determined in 1984, and is currently utilized as the strongest permanent magnet material. Whereas, there has been reported a compound having a potential exceeding Nd2Fe14B that is the main phase of the NdFeB magnet. (SmZr)(FeCo)10Nx having a TbCu7-type structure shows anisotropy comparable to that of Nd2Fe14B, and a value of saturation magnetization higher by about 10% than that of Nd2Fe14B (refer to Non-Patent Literature 1). Furthermore, the this compound is known to be a metastable phase, and the preparation method is limited. For example, for a compound of Sm or Nd and Fe having a TbCu7-type structure, powder synthesis has been successful only by a liquid quenching method, a mechanical alloying method, or an HDDR method. (Refer to Non-Patent Literatures 2 and 3 and Patent Literature 1). However, in these processes, only an isotropic sample having no crystal orientation(i.e. poly crystalline) can be obtained, and there is no example of a report in which an anisotropic magnet that maximizes the potential of the compound can be prepared. Both the report by Sakurada et al. (Non-Patent Literature 1) and the report by Takagi et al. (Patent Literature 1) relate to isotropic samples, and have not achieved synthesis of a single crystal powder as a raw material that can be a high-performance magnet material, or a powder with aligned crystal directions. For example, in the case of the Nd-Fe-B magnet, it has been reported that an isotropic powder as the raw material powder is subjected to a hot working treatment or an HDDR treatment to provide a powder or a molded magnet with aligned crystal directions (refer to Patent Literatures 2 and 3); however, crystals are not aligned when the same treatment is performed for Sm-Fe, Nd-Fe, Sm-Fe-N, or Nd-FeN based magnet materials. Currently, the only method capable of obtaining a sample having crystal orientation is a sputtering method. However, the sputtering method takes much time and cost to provide a powder, and is not realistic as a method for synthesizing a powder. (Refer to Non-Patent Literature 4). Therefore, there has been no report so far on an example of obtaining a single crystal powder having a TbCu7-type structure as a raw material of an anisotropic magnet having a high potential, and thus there has been a problem of no alternative of the neodymium magnet having Nd2Fe14B as a main phase. Citation List Patent Literatures Patent Literature 1: JP 2015-5550 APatent Literature 2: JP 11-329810 APatent Literature 3: JP 2012-199462 APatent Literature 4 : JP 2017-055072 describes a samarium-iron-nitrogen based sintered magnet.Patent Literature 5 : US 2008-0277028 describes a rare earth alloy ingot. Non-Patent Literatures Non-Patent Literature 1: S. Sakurada et al., Journal of Applied physics, 79 (1996) 4611.Non-Patent Literature 2: Kai-Ying Wang et al., Solid state Communications, 88 (1993) 521.Non-Patent Literature 3: H. Nakamura et al., Materials Chemistry and Physics, 32 (1992) 280.Non-Patent Literature 4: T. Kusumori et al., Applied Physics Express 9, 043001 (2016) Summary of Invention Technical Problem In view of the above problem, an object of the present invention is to achieve synthesis of a single crystal powder having a TbCu7-type structure as a metastable phase and an average particle size of 30 to 300 nm. Solution to Problem As a result of intensive investigation to solve the above problem, the present inventor has found that a single crystal powder having an average particle size of 30 to 300 nm and having a TbCu7-type structure as a metastable phase is obtained in the process of temporarily converting a raw material metal into a gas phase by increasing the temperature and then cooling to room temperature, and has completed the present invention. The present invention provides a single crystal powder that is represented by (R1-zMz)Tx and (R1-zMz)TxNy, having a crystal structure of TbCu7-type, and having an average particle size of 30 to 300 nm, wherein R is at least one element selected from the group consisting of Nd and Sm, M is at least one element selected from the group consisting of Zr, Y, and Ce, T is at least one element selected from the group consisting of Fe and Co, x is 7.0 ≤ x ≤ 10.0, y is 1.0 ≤ y ≤ 2.0, and z is 0.0 ≤ z ≤ 0.3. Furthermore, the present invention provides a production method, including synthesis of a single crystal powder of (R1-zMz)Tx obtained in the p