Sintered ferrite magnet and motor provided therewith

Patent metadata

Field	Value
Publication number	US-9589713-B2
Application number	US-201514638635-A
Country	US
Kind code	B2
Filing date	Mar 4, 2015
Priority date	Mar 7, 2014
Publication date	Mar 7, 2017
Grant date	Mar 7, 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, the sintered ferrite magnet does not substantially include a rare-earth element (R), and the following Formula (1) is satisfied, where a total amount of Sr, Ba and Ca is M3 in terms of mol, a total amount of Fe, Co, Mn, Zn, Cr and Al is M4 in terms of mol, and an amount of Si is M5 in terms of mol.

0.5≦{ M 3−( M 4/12)}/ M 5≦4.8  (1).

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,
the sintered ferrite magnet does not substantially include a rare-earth element (R), and
the following Formula (1) is satisfied, where a total amount of Sr, Ba and Ca is M3 in terms of mol, a total amount of Fe, Co, Mn, Zn, Cr and Al is M4 in terms of mol, and an amount of Si is M5 in terms of mol,
0.5≦{ M 3−( M 4/12)}/ M 5≦4.8  (1).

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

3. 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.

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

5. 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.

6. 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.

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

Assignees

• Tdk Corp

Inventors

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

Classifications

• C04B2235/3208

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

• C04B2235/3217

  Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina · CPC title

• C04B2235/3262

  Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO · CPC title

• C01P2006/12

  Surface area · CPC title

• C04B2235/3201

  Alkali metal oxides or oxide-forming salts thereof · CPC title