Rare earth sintered magnet, method for producing the same, motor, and automobile
View Patent ↗Provided is a rare earth sintered magnet 10 comprising a group of main phase grains 2 each composed of an R-T-B-based rare earth magnet comprising a core 4 and a shell 6 covering the core 4 , wherein a thickness of the shell 6 is 500 nm or less, R includes a light rare earth element and a heavy rare earth element, and a Zr compound 8 is present in a grain boundary phase 7 of the group of main phase grains 2 and/or the shell 6 . Also provided are a motor comprising the rare earth sintered magnet 10 and an automobile comprising the motor.
1. A rare earth sintered magnet comprising a group of main phase grains each composed of an R-T-B-based rare earth magnet comprising a core and a shell covering the core,
wherein a thickness of the shell is 500 nm or less,
R includes a light rare earth element and a heavy rare earth element, and
a Zr compound is present in the shell.
2. The rare earth sintered magnet according to claim 1 , wherein a Ga compound is further present in the grain boundary phase of the group of main phase grains.
3. The rare earth sintered magnet according to claim 1 , wherein a content of an oxygen element is 2500 ppm or less and a content of a carbon element is 500 ppm or more and 1500 ppm or less in the rare earth sintered magnet.
4. The rare earth sintered magnet according to claim 1 , wherein a content of a B element is 0.85 mass % or more and 0.98 mass % or less in the rare earth sintered magnet.
5. The rare earth sintered magnet according to claim 1 , wherein a total content of the rare earth element R is 29.0 mass % or more and 33.0 mass % or less in the rare earth sintered magnet.
6. The rare earth sintered magnet according to claim 1 , wherein a content of a Zr element is 0.05 mass % or more and 0.5 mass % or less in the rare earth sintered magnet.
7. A motor comprising the rare earth sintered magnet according to claim 1 .
8. An automobile comprising the motor according to claim 7 .
9. The rare earth sintered magnet according to claim 1 , wherein the Zr compound is present in a grain boundary phase of the group of main phase grains.
10. The rare earth sintered magnet according to claim 1 , wherein
the thickness of the shell is 30 nm or higher and 500 nm or less.