Ferrite sintered magnet

Patent metadata

Field	Value
Publication number	US-11380466-B2
Application number	US-201916295156-A
Country	US
Kind code	B2
Filing date	Mar 7, 2019
Priority date	Mar 28, 2018
Publication date	Jul 5, 2022
Grant date	Jul 5, 2022

Abstract

The present invention provides a ferrite sintered magnet comprising (1) main phase grains containing a ferrite having a hexagonal structure, (2) two-grain boundaries formed between two of the main phase grains, and (3) multi-grain boundaries surrounded by three or more of the main phase grains. The above ferrite sintered magnet comprises Ca, R, Sr, Fe and Co, with R being at least one element selected from the group consisting of rare earth elements and Bi, and comprising at least La. The number Nm of the above main phase grains and the number Ng of the above multi-grain boundaries in the cross section including the direction of the easy magnetization axis of the above ferrite sintered magnet satisfy the formula (1A):50%≤Nm/(Nm+Ng)≤65%  (1A).

First claim

What is claimed is:

1. A ferrite sintered magnet comprising;
main phase grains containing a ferrite having a hexagonal structure;
two-grain boundaries formed between two of the main phase grains; and
multi-grain boundaries surrounded by three or more of the main phase grains,
wherein the ferrite sintered magnet comprises Ca, R, Sr, Fe and Co;
wherein R is at least one element selected from the group consisting of rare earth elements and Bi and comprises at least La; and
wherein the number Nm of the main phase grains and the number Ng of the multi-grain boundaries in a cross section including a direction of the easy magnetization axis of the ferrite sintered magnet satisfy the formula (1A):
50%≤ Nm /( Nm+Ng )≤65%  (1A).

2. The ferrite sintered magnet according to claim 1 , further comprising Al;
wherein a content of Al is 0.03 to 0.3 mass % in terms of Al 2 O 3 .

3. The ferrite sintered magnet according to claim 1 , further comprising B;
wherein a content of B is 0.037 to 0.181 mass % in terms of H 3 BO 3 .

4. The ferrite sintered magnet according to claim 2 , further comprising B;
wherein a content of B is 0.037 to 0.181 mass % in terms of H 3 BO 3 .

5. A ferrite sintered magnet comprising;
main phase grains comprising a ferrite having a hexagonal structure;
two-grain boundaries formed between two of the main phase grains; and
multi-grain boundaries surrounded by three or more of the main phase grains,
wherein the ferrite sintered magnet comprises Ca, R, Sr, Fe and Co;
wherein R is at least one element selected from the group consisting of rare earth elements and Bi and comprises at least La; and
wherein a total area Am of the main phase grains and a total area Ag of the multi-grain boundaries in a cross section including a direction of the easy magnetization axis of the ferrite sintered magnet satisfy the formula (1B):
85%≤ Am /( Am+Ag )≤98%  (1B).

6. The ferrite sintered magnet according to claim 5 , further comprising Al;
wherein a content of Al is 0.03 to 0.3 mass % in terms of Al 2 O 3 .

7. The ferrite sintered magnet according to claim 5 , further comprising B;
wherein a content of B is 0.037 to 0.181 mass % in terms of H 3 BO 3 .

8. The ferrite sintered magnet according to claim 6 , further comprising B;
wherein a content of B is 0.037 to 0.181 mass % in terms of H 3 BO 3 .

Assignees

• Tdk Corp

Inventors

• Morita Hiroyuki
• Ikeda Masanori
• Murakawa Yoshitaka
• Ono Hiroyuki
• Murase Taku

Classifications

• C04B2235/656

  characterised by specific heating conditions during heat treatment · CPC title

• C01P2004/04

  obtained by TEM, STEM, STM or AFM · CPC title

• C04B35/2641

  Compositions containing one or more ferrites of the group comprising rare earth metals and one or more ferrites of the group comprising alkali metals, alkaline earth metals or lead · CPC title

• C04B2235/6562

  Heating rate · CPC title

• C01G49/0036

  containing one alkaline earth metal, magnesium or lead · CPC title