Ferrite sintered magnet and rotary electrical machine comprising the same

Patent metadata

Field	Value
Publication number	US-2021118598-A1
Application number	US-202017070469-A
Country	US
Kind code	A1
Filing date	Oct 14, 2020
Priority date	Oct 18, 2019
Publication date	Apr 22, 2021
Grant date	—

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

• H01F1/10

  non-metallic substances, e.g. ferrites {, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure} · CPC title

• C04B2235/85

  Intergranular or grain boundary phases · CPC title

• C04B2235/767

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

• C04B2235/3418

  Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint · CPC title

• C04B2235/3409

  Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax · CPC title