R-T-B based sintered magnet

Patent metadata

Field	Value
Publication number	US-9514869-B2
Application number	US-201314378432-A
Country	US
Kind code	B2
Filing date	Feb 13, 2013
Priority date	Feb 13, 2012
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

The present invention provides an R-T-B based sintered magnet including R 2 T 14 B crystal grains wherein; a grain boundary is formed by two or more adjacent R 2 T 14 B crystal grains, an R—O—C concentrated part, in which concentrations of R, O and C are higher than those in the R 2 T 14 B crystal grains respectively, is in the grain boundary, and an area of the R—O—C concentrated part occupying in that of the grain boundary on a cut surface of the R-T-B based sintered magnet is within a range of 10% or more to 75% or less.

First claim

The invention claimed is:

1. An R-T-B based sintered magnet comprising R 2 T 14 B crystal grains and grain boundaries formed by two or more adjacent R 2 T 14 B crystal grains, wherein:
R represents at least one rare earth element;
T represents at least one transition metal element comprising Fe or Fe and Co;
the grain boundaries comprise R—O—C concentrated parts;
the R—O—C concentrated parts are entire areas of the grain boundaries have concentrations of R, O, and C that are higher than concentrations of R, O, and C in the R 2 T 14 B crystal grains;
an average area ratio of the total R—O—C concentrated parts to the entire grain boundaries is within a range of 14% or more to 71% or less, and
an average ratio (O/R) of O atom to R atom in the R—O—C concentrated parts is within a range of 0.41 or more to 0.70 or less.

2. The R-T-B based sintered magnet as set forth in claim 1 , wherein the R—O—C concentrated parts comprise a cubic crystal structure.

3. The R-T-B based sintered magnet as set forth in claim 2 , wherein the average area ratio of the total R—O—C concentrated parts to the entire grain boundaries is within a range of 35% or more to 71% or less.

4. The R-T-B based sintered magnet as set forth in claim 3 , wherein an oxygen amount included in the R-T-B based sintered magnet is 1940 ppm or less.

5. The R-T-B based sintered magnet as set forth in claim 4 , wherein “R” included in the R—O—C concentrated parts comprise a rare earth element that at least includes either or both of Nd and Pr (RL), and a rare earth element that at least includes either or both of Dy and Tb (RH).

6. The R-T-B based sintered magnet as set forth in claim 1 , wherein a coercivity of the R-T-B based sintered magnet is 1325 kA/m or more.

7. The R-T-B based sintered magnet as set forth in claim 1 , wherein a coercivity of the R-T-B based sintered magnet is 1325 kA/m to 2276 kA/m.

8. The R-T-B based sintered magnet as set forth in claim 1 , wherein a magnetic flux density of the R-T-B based sintered magnet is 1291 mT or more.

9. The R-T-B based sintered magnet as set forth in claim 1 , wherein a magnetic flux density of the R-T-B based sintered magnet is 1291 to 1418 mT.

10. An R-T-B based sintered magnet comprising R 2 T 14 B crystal grains and grain boundaries formed by two or more adjacent R 2 T 14 B crystal grains, wherein:
R represents at least one rare earth element;
T represents at least one transition metal element comprising Fe or Fe and Co;
the grain boundaries comprise R—O—C—N concentrated parts;
the R—O—C—N concentrated parts are entire areas of the grain boundaries that have concentrations of R, O, C, and N that are higher than concentrations of R, O, C, and N in the R 2 T 14 B crystal grains; and
an average area ratio of the total R—O—C—N concentrated parts to the entire grain boundaries is within a range of 13% or more to 72% or less.

11. The R-T-B based sintered magnet as set forth in claim 10 , wherein an average ratio (O/R) of O atom to R atom in the R—O—C—N concentrated parts is within a range of 0.41 or more to 0.70 or less.

12. The R-T-B based sintered magnet as set forth in claim 11 , wherein the R—O—C—N concentrated parts comprise a cubic crystal structure.

13. The R-T-B based sintered magnet as set forth in claim 12 , wherein the average area ratio of the total R—O—C—N concentrated parts to the entire grain boundaries is within a range of 36% or more to 72% or less.

14. The R-T-B based sintered magnet as set forth in claim 13 , wherein an oxygen amount included in the R-T-B based sintered magnet is 1950 ppm or less.

15. The R-T-B based sintered magnet as set forth in claim 14 , wherein “R” included in the R—O—C—N concentrated parts comprise a rare earth element that at least includes either or both of Nd and Pr (RL), and a rare earth element that at least includes either or both of Dy and Tb (RH).

16. The R-T-B based sintered magnet as set forth in claim 10 , wherein a coercivity of the R-T-B based sintered magnet is 1412 kA/m or more.

17. The R-T-B based sintered magnet as set forth in claim 10 , wherein a coercivity of the R-T-B based sintered magnet is 1412 to 2073 kA/m.

18. The R-T-B based sintered magnet as set forth in claim 10 , wherein a magnetic flux density of the R-T-B based sintered magnet is 1282 mT or more.

19. The R-T-B based sintered magnet as set forth in claim 10 , wherein a magnetic flux density of the R-T-B based sintered magnet is 1282 to 1391 mT.

Assignees

• Tdk Corp

Inventors

• Miwa Masashi
• Nakajima Haruna
• NISHIKAWA Ken-ichi
• Hidaka Tetsuya
• Hagiwara Jun
• Ishizaka Chikara

Classifications

• C22C38/16

  containing copper · CPC title

• C22C38/10

  containing cobalt · CPC title

• C22C38/002 Primary

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• B22F3/10

  Sintering only · CPC title

• C22C38/005

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title