# US 9,520,216 B2 · R-T-B based sintered magnet

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- Number: US 9,520,216 B2
- Document ID: US9520216B2
- Status: Granted
- Kind: B2
- Application number: 14/254,220
- Filed: 2014-04-16
- Published: 2014-10-23
- Granted: 2016-12-13
- Earliest claimed: 2013-04-22
- Assignees: TDK Corporation
- Applicants: TDK Corporation
- Inventors: Yasushi Enokido; Kyung-Ku Choi; Ryuji Hashimoto; Daisuke Tanaka
- Web page: https://patentgrep.com/patent/US9520216B2

## CPC

- H01F 1/0536: {sintered}
- H01F 1/0577: {sintered}
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES

## Abstract

An R-T-B based magnet as raw material undergoes heating treatment for a long time and main phase grains turn core-shell like. The R-T-B based magnet includes main phase grains having core and shell portions that covers the core. When the mass concentration of R1 and Y in the core portion is set as αR1 and αY respectively and the mass concentration of R1 and Y in the shell portion is set as βR1 and βY respectively, the ratio (B/A) between the mass concentration ratio of R1 to Y in the shell portion (βR1/βY=B) and the mass concentration ratio of R1 to Y in the core portion (αR1/αY=A) is 1.1 or more. Thus, the decrease of coercivity caused by Y addition is prevented, and the increase effect of temperature characteristics caused by addition of Y will lead to improve the magnetic properties under high temperature.

## Claims

### Claim 1

A R-T-B based sintered magnet, comprising:
main phase grains having a core portion and a shell portion that covers the core, wherein:
R includes yttrium (Y) and R1,
R1 comprises neodymium (Nd) and does not comprise Y,
a content ratio of R1 to Y in the R-T-B based sintered magnet is in a range of from 50:50 to 90:10,
T is one or more transition metal elements including Fe or a combination of Fe and Co in the R-T-B based sintered magnet,
B in R-T-B is boron;
a ratio of E to A (E/A) is in a range of from 1.4 to 2.11, where:
E in E/A represents a mass concentration of R1 in the shell portion divided by a mass concentration of Y in the shell portion (εR1/εY); and
A represents a mass concentration of R1 in the core portion divided by a mass concentration of Y in the core portion (αR1/αY); and
the mass concentration of Y in the shell portion is less than the mass concentration of Y in the core portion.

### Claim 2 (depends on 1)

The R-T-B based sintered magnet according to claim 1, wherein R1 further comprises at least one rare earth element selected from the group consisting of Pr, Dy, Ho, and Tb.

### Claim 3 (depends on 1)

A rotating machine comprising the R-T-B based sintered magnet according to claim 1.