R-T-B based sintered magnet

Patent metadata

Field	Value
Publication number	US-9520216-B2
Application number	US-201414254220-A
Country	US
Kind code	B2
Filing date	Apr 16, 2014
Priority date	Apr 22, 2013
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

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.

First claim

What is claimed is:

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.

2. 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.

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

Assignees

• Tdk Corp

Inventors

• Enokido Yasushi
• Choi Kyung-Ku
• Hashimoto Ryuji
• Tanaka Daisuke

Classifications

• H01F1/0577 Primary

  sintered · CPC title

• H01F1/0536 Primary

  sintered · CPC title