Ferrite sintered magnet

Patent metadata

Field	Value
Publication number	US-11615901-B2
Application number	US-202016777940-A
Country	US
Kind code	B2
Filing date	Jan 31, 2020
Priority date	Feb 5, 2019
Publication date	Mar 28, 2023
Grant date	Mar 28, 2023

Abstract

A ferrite sintered magnet comprises a plurality of main phase grains containing a ferrite having a hexagonal structure, wherein at least some of the main phase grains are core-shell structure grains each having a core and a shell covering the core; and wherein the minimum value of the content of La in the core is [La]c atom %; the minimum value of the content of Co in the core is [Co]c atom %; the maximum value of the content of La in the shell is [La]s atom %; the maximum value of the content of Co in the shell is [Co]s atom %; [La]c+[Co]c is 3.08 atom % or more and 4.44 atom % or less; and [La]s+[Co]s is 7.60 atom % or more and 9.89 atom % or less.

First claim

What is claimed is:

1. A ferrite sintered magnet comprising a plurality of main phase grains containing a ferrite having a hexagonal structure, wherein
at least some of the main phase grains are core-shell structure grains each having a core and a shell covering the core;
a minimum value of a content of La in the core is represented by [La]c atom %;
a minimum value of a content of Co in the core is represented by [Co]c atom %;
a maximum value of a content of La in the shell is represented by [La]s atom %;
a maximum value of a content of Co in the shell is represented by [Co]s atom %;
[La]c+[Co]c is 3.08 atom % or more and 4.44 atom % or less; and
[La]s+[Co]s is 7.60 atom % or more and 9.89 atom % or less.

2. The ferrite sintered magnet according to claim 1 , wherein ([La]s+[Co]s)/([La]c+[Co]c) is 1.75 or more and 2.69 or less.

3. The ferrite sintered magnet according to claim 1 , wherein
a maximum value of a content of Sr in the core is represented by [Sr]c atom %;
a minimum value of a content of Sr in the shell is represented by [Sr]s atom %; and
[Sr]c is higher than [Sr]s.

4. The ferrite sintered magnet according to claim 1 , wherein
a minimum value of a content of Ca in the core is represented by [Ca]c atom %;
a maximum value of a content of Ca in the shell is represented by [Ca]s atom %; and
[Ca]s is higher than [Ca]c.

5. The ferrite sintered magnet according to claim 1 , wherein
a maximum value of a content of Sr in the core is represented by [Sr]c atom %;
a minimum value of a content of Ca in the core is represented by [Ca]c atom %; and
[Sr]c is higher than [Ca]c.

6. The ferrite sintered magnet according to claim 1 , wherein
a minimum value of a content of Sr in the shell is represented by [Sr]s atom %;
a maximum value of a content of Ca in the shell is represented by [Ca]s atom %; and
[Ca]s is higher than [Sr]s.

7. The ferrite sintered magnet according to claim 1 , wherein
at least some of metal components contained in the ferrite sintered magnet is represented by formula (1):
Ca 1-w-x-y R w Sr x Ba y Fe z Co m   (1)

wherein R in the formula (1) is at least one element selected from the group consisting of rare earth elements and Bi, and R includes at least La;
w, x, y, z and m in the formula (1) satisfy formulae (2), (3), (4), (5), (6), (7), (8) and (9):
0.25 <w <0.5  (2)

0.01 <x <0.35  (3)

0 ≤y <0.013  (4)

y<x   (5)

8.5 <z <9.9  (6)

1.0 <w/m <2.1  (7)

0.017 <m/z <0.055  (8)

0<1- w - x - y <1  (9); and

the ferrite sintered magnet contains a Si component.

8. The ferrite sintered magnet according to claim 7 , wherein w, x and m in the formula (1) satisfy formulae (2a), (3a) and (10):
0.350 <w <0.420  (2a)

0.120 <x <0.180  (3a)

0.200 <m <0.280  (10); and

a content of B in the ferrite sintered magnet is 0.037 to 0.181% by mass in terms of H 3 BO 3 .

9. The ferrite sintered magnet according to claim 1 , wherein a content of Al in the ferrite sintered magnet is 0.05 to 0.3% by mass in terms of Al 2 O 3 .

10. The ferrite sintered magnet according to claim 1 , wherein
a proportion of the number of the core-shell structure grains to the total number of the main phase grains is 1% or more and 21.4% or less, and
the ferrite sintered magnet contains B and Al.

Assignees

• Tdk Corp

Inventors

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

Classifications

• C04B2235/3213

  Strontium oxides or oxide-forming salts thereof · CPC title

• C04B35/6261

  Milling · CPC title

• C04B35/2633 Primary

  containing barium, strontium or calcium · CPC title

• C04B2235/605

  Making or treating the green body or pre-form in a magnetic field · CPC title

• C04B35/2675

  Other ferrites containing rare earth metals, e.g. rare earth ferrite garnets · CPC title