# US 12,603,200 B2 · Rare earth sintered magnet, method for producing rare earth sintered magnet, rotor, and rotary machine

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- Number: US 12,603,200 B2
- Document ID: US12603200B2
- Status: Granted
- Kind: B2
- Application number: 17/798,308
- Filed: 2020-04-08
- Published: 2023-03-16
- Granted: 2026-04-14
- Earliest claimed: 2020-04-08
- Assignees: Mitsubishi Electric Corporation
- Applicants: Mitsubishi Electric Corporation
- Inventors: Akito Iwasaki; Yukina Yoshioka; Yoshikazu Nakano; Yasutaka Nakamura
- Web page: https://patentgrep.com/patent/US12603200B2

## CPC

- H01F 1/0577: {sintered}
- B22F 3/16: in successive or repeated steps
- B22F 3/24: After-treatment of workpieces or articles {(B22F3/1146 takes precedence)}
- B22F 9/04: starting from solid material, e.g. by crushing, grinding or milling ({C22C1/1084 takes precedence}; crushing, grinding or milling, in general, see the relevant subclasses, e.g. B02C)
- C22C 38/005: {containing rare earths, i.e. Sc, Y, Lanthanides}
- H01F 41/0266: {Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11)}
- H02K 1/02: characterised by the magnetic material
- H02K 1/16: Stator cores with slots for windings
- H02K 1/27: Rotor cores with permanent magnets
- B22F 2003/248: {Thermal after-treatment}
- B22F 2301/355: Rare Earth - Fe intermetallic alloys
- C22C 2202/02: Magnetic
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

A rare earth sintered magnet according to the present disclosure includes: a main phase satisfying general formula (Nd, La, Sm)—Fe—B and including crystal grains based on R2Fe14B crystal structures; and a crystalline subphase based on an oxide phase represented by (Nd, La, Sm)—O. The subphase has a higher concentration of Sm than the main phase.

## Claims

### Claim 1

A rare earth sintered magnet comprising:
a main phase satisfying general formula (Nd, La, Sm)—Fe—B and including a crystal grain based on an R2Fe14B crystal structure; and
a crystalline subphase based on an oxide phase represented by (Nd, La, Sm)—O, wherein
a part of Nd in the crystalline subphase is replaced by La and Sm such that a concentration at % of Sm in the crystalline subphase is higher than a concentration at % of Sm in the main phase,
wherein 1<Y2/Y<X2/X1 is satisfied, where X1 represents the concentration at % of La contained in the main phase, X2 represents the concentration at % of La contained in the subphase, Y1 represents the concentration at % of Sm contained in the main phase, and Y2 represents the concentration at % of Sm contained in the subphase.

### Claim 2 (depends on 1)

The rare earth sintered magnet according to claim 1, wherein La is segregated in the subphase.

### Claim 3 (depends on 2)

The rare earth sintered magnet according to claim 2, wherein La segregated in the subphase coats at least a part of a surface of the main phase.

### Claim 4 (depends on 1)

The rare earth sintered magnet according to claim 1, wherein
the main phase includes a core portion and a shell portion provided on an outer periphery of the core portion, and
the shell portion has a higher concentration of Nd than the core portion.

### Claim 5 (depends on 1)

A rotor comprising:
a rotor core; and
the rare earth sintered magnet according to claim 1 provided in the rotor core.

### Claim 6 (depends on 5)

A rotary machine comprising:
the rotor according to claim 5; and
an annular stator facing the rotor and including, on an inner surface on a side where the rotor is placed, teeth protruding toward the rotor and windings provided on the teeth.

### Claim 7 (depends on 1)

A method for producing a rare earth sintered magnet, the rare earth sintered magnet according to claim 1, the method comprising:
pulverizing a rare earth magnet alloy satisfying (Nd, La, Sm)—Fe—B;
preparing a molded body by molding powder of the rare earth magnet alloy;
preparing a sintered body by holding the molded body at a sintering temperature in a range of 600° C. to 1300° C. for a period of time in a range of 0.1 hours to 10 hours; and
aging the sintered body.

### Claim 8 (depends on 7)

The method for producing a rare earth sintered magnet according to claim 7, wherein aging the sintered body comprises holding the sintered body at a temperature equal to or lower than the sintering temperature within a range of 0.1 hours to 20 hours.

### Claim 9 (depends on 7)

A rotor comprising:
a rotor core; and
the rare earth sintered magnet according to claim 7 provided in the rotor core.

### Claim 10 (depends on 9)

A rotary machine comprising:
the rotor according to claim 9; and
an annular stator facing the rotor and including, on an inner surface on a side where the rotor is placed, teeth protruding toward the rotor and windings provided on the teeth.