Sintered ferrite magnet and its production method

Patent metadata

Field	Value
Publication number	US-9536646-B2
Application number	US-201314429502-A
Country	US
Kind code	B2
Filing date	Aug 30, 2013
Priority date	Sep 28, 2012
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

A sintered ferrite magnet comprising metal elements of Ca, La, Fe and Co, whose atomic ratios are represented by the general formula of Ca 1-x La x Fe 2n-y Co y , wherein x and y, and n representing a molar ratio meet 0.3≦x≦0.6, 0.25≦y≦0.5, and 3≦n≦6, and further comprising 0.2% to 0.35% by mass of SiO 2 .

First claim

What is claimed is:

1. A sintered ferrite magnet comprising metal elements of Ca, La, Fe and Co, whose atomic ratios are represented by the general formula:
Ca 1-x La x Fe 2n-y Co y ,

wherein x and y, and n representing a molar ratio meet
0.3≦x≦0.6,
0.25≦y≦0.5, and
3≦n≦6,

further comprising 0.2% to 0.35% by mass of SiO 2 , and containing no CaCO 3 as a sintering aid.

2. The sintered ferrite magnet according to claim 1 , wherein 0.2% to 0.3% by mass of SiO 2 is contained.

3. A method for producing a sintered ferrite magnet comprising the steps of mixing raw material powders to a composition comprising metal elements of Ca, La, Fe and Co, whose atomic ratios are represented by the general formula:
Ca 1-x La x Fe 2n-y Co y ,

wherein x and y, and n representing a molar ratio meet
0.3≦x≦0.6,
0.25≦y≦0.5, and
3≦n≦6,

thereby obtaining a raw material powder mixture;
calcining said raw material powder mixture to obtain a calcined body;
pulverizing said calcined body to obtain a calcined powder;
molding said calcined powder to obtain a green body; and
sintering said green body to obtain a sintered body;
a sintering aid being add after said calcining step and before said molding step;
said sintering aid indispensably comprising SiO 2 without CaCO 3 ; and
the amount of SiO 2 added being 0.2% to 0.35% by mass based on 100% by mass of said calcined body or said calcined powder.

4. A method for producing a sintered ferrite magnet comprising the steps of
mixing raw material powders to a composition comprising metal elements of Ca, La, Fe and Co, whose atomic ratios are represented by the general formula:
Ca 1-x La x Fe 2n-y Co y ,

wherein x and y, and n representing a molar ratio meet
0.3≦x≦0.6,
0≦y<0.5, and
3≦n≦6,

thereby obtaining a raw material powder mixture;
calcining said raw material powder mixture to obtain a calcined body;
pulverizing said calcined body to obtain a calcined powder;
molding said calcined powder to obtain a green body; and
sintering said green body to obtain a sintered body;
a raw material powder of Co being added after said calcining step and before said molding step, such that said y meets 0.25≦y≦0.5;
a sintering aid being add after said calcining step and before said molding step;
said sintering aid indispensably comprising SiO 2 without CaCO 3 ; and
the amount of SiO 2 added being 0.2% to 0.35% by mass based on 100% by mass of said calcined body or said calcined powder.

5. The method for producing a sintered ferrite magnet according to claim 3 , wherein 0.2% to 0.3% by mass of SiO 2 is added.

6. The method for producing a sintered ferrite magnet according to claim 4 , wherein 0.2% to 0.3% by mass of SiO 2 is added.

Assignees

• Hitachi Metals Ltd

Inventors

• Kobayashi Yoshinori
• Kawata Tsunehiro

Classifications

• C04B2111/10

  Compositions or ingredients thereof characterised by the absence or the very low content of a specific material · CPC title

• H01F1/11 Primary

  in the form of particles {(for magnetic record carriers G11B5/70626)} · CPC title

• C04B2111/00422

  Magnetic properties · CPC title

• C04B2235/72

  Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics · 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