Ferrite sintered magnet and rotary electrical machine comprising the same

Patent metadata

Field	Value
Publication number	US-11521769-B2
Application number	US-202016825356-A
Country	US
Kind code	B2
Filing date	Mar 20, 2020
Priority date	Mar 27, 2019
Publication date	Dec 6, 2022
Grant date	Dec 6, 2022

Abstract

A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 having a hexagonal crystal structure, two-crystal grain boundaries 6 a formed between two of the 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 . This ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains B in an amount of 0.005 to 0.9 mass % in terms of B 2 O 3 , the two-crystal grain boundaries 6 a and the multiple-crystal grain boundaries 6 b contain Si and Ca, and in a cross-section parallel to a c-axis of the ferrite sintered magnet, when the number of multiple-crystal grain boundaries having a maximum length of 0.088 or more and less than 0.49 μm per cross-sectional area of 76 μm 2 is P, P is 8 or more.

First claim

What is claimed is:

1. A ferrite sintered magnet comprising:
M-type ferrite crystal grains having a hexagonal structure;
two-crystal grain boundaries formed between two of the 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 two-crystal grain boundaries and the multiple-crystal grain boundaries contain Si and Ca, and
in a cross-section parallel to a c-axis of the ferrite sintered magnet, when the number of multiple-crystal grain boundaries having a maximum length of 0.88 or more and less than 0.49 μm per cross-sectional area of 76 μm 2 is P, P is 8 or more.

2. The ferrite sintered magnet according to claim 1 ,
wherein when an area ratio of the two-crystal grain boundaries and the multiple-crystal grain boundaries in the cross-section parallel to the c-axis of the ferrite sintered magnet is Z, 2.51%<Z<5% is satisfied.

3. The ferrite sintered magnet according to claim 1 ,
wherein in a case where an average thickness of the two-crystal grain boundaries in the cross-section parallel to the c-axis of the ferrite sintered magnet is d, 0.683 nm<d<2 nm is satisfied.

4. The ferrite sintered magnet according to claim 1 ,
wherein in the cross-section parallel to the c-axis of the ferrite sintered magnet, when the number of M-type ferrite crystal grains having a maximum diameter of 1 μm or less per cross-sectional area of 76 μm 2 is Q, Q is 27 to 119.

5. The ferrite sintered magnet according to claim 1 ,
wherein a content of Si in the ferrite sintered magnet is 0.05 to 1.3 mass % in terms of SiO 2 .

6. The ferrite sintered magnet according to claim 1 ,
wherein a content of Mn in the ferrite sintered magnet is 0.25 to 1.5 mass % in terms of MnO.

7. The ferrite sintered magnet according to claim 1 ,
wherein a content of Cr in the ferrite sintered magnet is 0.03 to 0.2 mass % in terms of Cr 2 O 3 .

8. The ferrite sintered magnet according to claim 1 ,
wherein a content of Zn in the ferrite sintered magnet is 0.01 to 1.47 mass % in terms of ZnO.

9. The ferrite sintered magnet according to claim 1 ,
wherein the M-type ferrite crystal grains are M-type Sr ferrite crystal grains or M-type Ba ferrite crystal grains, and
a content of Ca in the ferrite sintered magnet is 0.15 to 2.0 mass % in terms of CaO.

10. The ferrite sintered magnet according to claim 1 ,
wherein the M-type ferrite crystal grains are M-type Ca ferrite crystal grains, and
a content of Ca in the ferrite sintered magnet is 2 to 5 mass % in terms of CaO.

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

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

Assignees

• Tdk Corp

Inventors

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

Classifications

• C04B2235/96

  Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance · CPC title

• C04B35/62675

  characterised by the treatment temperature · CPC title

• C04B35/2633

  containing barium, strontium or calcium · CPC title

• C04B35/6263

  characterised by their solids loadings, i.e. the percentage of solids · CPC title

• C04B2235/442

  Carbonates · CPC title