Sintered ferrite magnet and motor provided therewith

Patent metadata

Field	Value
Publication number	US-9627112-B2
Application number	US-201514638819-A
Country	US
Kind code	B2
Filing date	Mar 4, 2015
Priority date	Mar 7, 2014
Publication date	Apr 18, 2017
Grant date	Apr 18, 2017

Abstract

A sintered ferrite magnet comprises a main phase of an M type Sr ferrite having a hexagonal crystal structure. An amount of Zn is 0.05 to 1.35 mass % in terms of ZnO and M 1 /M 2 is 0.43 or less when an amount of a rare-earth element (R) is M 1 in terms of mol and the amount of Zn is M 2 in terms of mol.

First claim

The invention claimed is:

1. A sintered ferrite magnet comprising a main phase of an M type Sr ferrite having a hexagonal crystal structure, wherein
an amount of Zn is 0.05 to 1.35 mass % in terms of ZnO and
M 1 /M 2 is 0.43 or less when an amount of a rare-earth element (R) is M 1 in terms of mol and the amount of Zn is M 2 in terms of mol.

2. The sintered ferrite magnet as set forth in claim 1 , wherein
an amount of Mn is less than 0.5 mass %, including 0 mass %, in terms of MnO.

3. The sintered ferrite magnet as set forth in claim 1 , wherein
a total amount of Sr, R, Ba and Ca is M 3 in terms of mol, a total amount of Fe, Co, Mn, Zn, Cr and Al is M 4 in terms of mol, an amount of Si is M 5 in terms of mol, and the following expression is satisfied
0.5≦{M3−(M4/12)}/M5≦1.2.

4. The sintered ferrite magnet as set forth in claim 2 , wherein
a total amount of Sr, R, Ba and Ca is M 3 in terms of mol, a total amount of Fe, Co, Mn, Zn, Cr and Al is M 4 in terms of mol, an amount of Si is M 5 in terms of mol, and the following expression is satisfied
0.5≦{M3−(M4/12)}/M5≦1.2.

5. The sintered ferrite magnet as set forth in claim 1 , wherein
an amount of Na is 0.01 to 0.09 mass % in terms of Na 2 O.

6. The sintered ferrite magnet as set forth in claim 1 , wherein
an average grain size of crystal grains of the Sr ferrite is 1.0 μm or less and
a ratio of the crystal grains having a grain size of 2.0 μm or more is 2% or less on the number basis.

7. The sintered ferrite magnet as set forth in claim 1 , wherein
a residual magnetic flux density (Br) is 440 mT or more and
a squareness ratio (Hk/HcJ) is 85% or more.

8. A motor, comprising:
the sintered ferrite magnet according to claim 1 .

Assignees

• Tdk Corp

Inventors

• Murakawa Yoshitaka
• Tanigawa Naoharu
• Minachi Yoshihiko
• Taguchi Hitoshi

Classifications

• C04B2235/3275

  Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite · CPC title

• C01P2004/61

  Micrometer sized, i.e. from 1-100 micrometer · CPC title

• C04B2235/3208

  Calcium oxide or oxide-forming salts thereof, e.g. lime · CPC title

• C04B35/26

  based on ferrites · CPC title

• C04B2235/605

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