Ferrite sintered magnet and rotary electrical machine comprising the same

Patent metadata

Field	Value
Publication number	US-11626222-B2
Application number	US-202017070469-A
Country	US
Kind code	B2
Filing date	Oct 14, 2020
Priority date	Oct 18, 2019
Publication date	Apr 11, 2023
Grant date	Apr 11, 2023

Abstract

A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 and multiple-crystal grain boundaries 6 b surrounded by three or more of the M-type ferrite crystal grains 4 . The ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains 0.005 to 0.9 mass % of B in terms of B 2 O 3 . The multiple-crystal grain boundaries 6 b contain Si and Ca, and in a case where the molar ratio of Ca to Si in the multiple-crystal grain boundaries 6 b is represented by (Ca/Si) G , the following formula is satisfied.

0.1<(Ca/Si) G <0.9

First claim

What is claimed is:

1. A ferrite sintered magnet comprising:
M-type ferrite crystal grains; and
multiple-crystal grain boundaries surrounded by three or more of the M-type ferrite crystal grains,
wherein the ferrite sintered magnet contains at least Fe, Ca, B, and Si,
the ferrite sintered magnet contains 0.005 to 0.9 mass % of B in terms of B 2 O 3 ,
the multiple-crystal grain boundaries contain Si and Ca, and
in a case where the molar ratio of Ca to Si in the multiple-crystal grain boundaries is represented by (Ca/Si) G , the following formula is satisfied.
0.1<(Ca/Si) G <0.9

2. The ferrite sintered magnet according to claim 1 ,
wherein 0.1<(Ca/Si) G <0.5 is further satisfied.

3. The ferrite sintered magnet according to claim 1 ,
wherein the M-type ferrite crystal grains are Sr ferrite crystal grains and the multiple-crystal grain boundaries contain Sr.

4. The ferrite sintered magnet according to claim 3 ,
wherein when a ratio of the number of Ca atoms to the total number of Fe, Sr, Ca, and Si atoms in the M-type ferrite crystal grains is Mc1, and
a ratio of the number of Ca atoms to the total number of Fe, Sr, Ca, and Si atoms in the multiple-crystal grain boundaries is Gc1, the following formula is satisfied.
20< Gc 1/ Mc 1<90

5. The ferrite sintered magnet according to claim 4 ,
wherein 20<Gc1/Mc1<70 is further satisfied.

6. The ferrite sintered magnet according to claim 4 ,
wherein when a ratio of the number of Sr atoms to the total number of Fe, Sr, Ca, and Si atoms in the M-type ferrite crystal grains is Mr1, and
a ratio of the number of Sr atoms to the total number of Fe, Sr, Ca, and Si atoms in the multiple-crystal grain boundaries is Gr1, the following formula is satisfied.
2.0< Gr 1/ Mr 1<3.2

7. The ferrite sintered magnet according to claim 3 ,
wherein the Sr ferrite crystal grains contain Zn and the multiple-crystal grain boundaries contain Zn.

8. The ferrite sintered magnet according to claim 7 ,
wherein when a ratio of the number of Zn atoms to the total number of Fe, Sr, Ca, Si, and Zn atoms in the M-type ferrite crystal grains is Mz2, and
a ratio of the number of Zn atoms to the total number of Fe, Sr, Ca, Si, and Zn atoms in the multiple-crystal grain boundaries is Gz2, the following formula is satisfied.
0.2< Gz 2/ Mz 2<2.9

9. The ferrite sintered magnet according to claim 7 ,
wherein when a molar ratio of Sr to Zn in the multiple-crystal grain boundaries is (Sr/Zn) G , the following formula is satisfied.
40<(Sr/Zn) G <700

10. The ferrite sintered magnet according to claim 7 ,
wherein when a molar ratio of Ca to Zn in the multiple-crystal grain boundaries is (Ca/Zn) G , the following formula is satisfied.
50<(Ca/Zn) G <2000

11. The ferrite sintered magnet according to claim 7 ,
wherein in a case where a molar ratio of Sr to Zn in the M-type ferrite crystal grains is represented by (Sr/Zn) M , the following formula is satisfied.
22<(Sr/Zn) M <70

12. The ferrite sintered magnet according to claim 7 ,
wherein when a molar ratio of Ca to Zn in the M-type ferrite crystal grains is (Ca/Zn) M , the following formula is satisfied.
2.1<(Ca/Zn) M <7.0

13. The ferrite sintered magnet according to claim 7 ,
wherein when a molar ratio of Fe to Zn in the M-type ferrite crystal grains is (Fe/Zn) M , the following formula is satisfied.
460<(Fe/Zn) M <1500

14. The ferrite sintered magnet according to claim 7 ,
wherein in the ferrite sintered magnet, a content of Si is 0.05 to 1.3 mass % in terms of SiO 2 , a content of Ca is 0.15 to 2.0 mass % in terms of CaO, a content of Zn is 0.01 to 1.47 mass % in terms of ZnO, a content of Mn is 0.25 to 1.5 mass % in terms of MnO, and a content of Cr is 0.03 to 0.2 mass % in terms of Cr 2 O 3 .

15. The ferrite sintered magnet according to claim 1 ,
wherein the ferrite sintered magnet does substantially not contain La or Co.

16. A rotary electrical machine comprising the ferrite sintered magnet according to claim 1 .

Assignees

• Tdk Corp

Inventors

• Murakawa Yoshitaka
• Morita Hiroyuki
• Ikeda Masanori
• Muroya Shogo
• Ishikura Tomokazu

Classifications

• C04B35/2683

  Other ferrites containing alkaline earth metals or lead · CPC title

• H01F1/11 Primary

  in the form of particles {(for magnetic record carriers G11B5/70626)} · CPC title

• C04B2235/3262

  Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO · CPC title

• C04B2235/767

  Hexagonal symmetry, e.g. beta-Si3N4, beta-Sialon, alpha-SiC or hexa-ferrites · CPC title

• H01F1/0315 Primary

  Ferrites · CPC title