Sintered ferrite magnet and its production method

Patent metadata

Field	Value
Publication number	US-9401235-B2
Application number	US-201113976841-A
Country	US
Kind code	B2
Filing date	Dec 26, 2011
Priority date	Dec 28, 2010
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A sintered ferrite magnet having a main phase composed of ferrite having a hexagonal, M-type magnetoplumbite structure, a grain boundary phase containing Si and Ca with a lower atomic ratio of La than in said main phase, and a third phase containing La at a higher atomic ratio than in said main phase, and a method for producing a sintered ferrite magnet having said third phase by calcining starting materials with more La than Ca, adding more than 1% and 1.8% or less by mass of SiO 2 and 1-2% by mass (calculated as CaO) of CaCO 3 to the calcined body, and pulverizing, molding and sintering it.

First claim

What is claimed is:

1. A method for producing a sintered ferrite magnet comprising Ca, La, an element A (Ba and/or Sr), Fe and Co, and having a main phase composed of ferrite having a hexagonal, M-type magnetoplumbite structure, a grain boundary phase containing Si and Ca with a lower atomic ratio of La than in said main phase, and a third phase containing La, Ca, Si and Fe in such proportions that La is 8-50 atomic %, Ca is 20-45 atomic %, Si is 20-45 atomic %, and Fe is 4-20 atomic %, based on the total amount (100 atomic %) of those elements, wherein the third phase contains La at a higher atomic ratio than in said main phase, said method comprising
a step of preparing a starting material powder having a metal element composition (by atomic ratio) represented by the general formula of Ca 1-x-y La x A y Fe 2n-z Co z , wherein 1−x−y, x, y and z, and n representing a molar ratio meet
0.3≦1− x−y< 0.65,

0.3< x≦ 0.65,
1− x−y<x,

0≦ y≦ 0.2,

0.25≦ z≦ 0.65, and

4.5≦ n≦ 7,

a step of calcining said starting material powder to obtain a calcined body;
a step of pulverizing said calcined body to powder;
a step of molding said powder to obtain a green body; and
a step of sintering said green body to obtain a sintered body;
more than 1% and 1.8% or less by mass of SiO 2 and 1-2% by mass (calculated as CaO) of CaCO 3 being added to 100% by mass of said calcined body before the pulverization step.

2. The method for producing a sintered ferrite magnet according to claim 1 , wherein the amount of said SiO 2 added is 1.1-1.6% by mass.

3. The method for producing a sintered ferrite magnet according to claim 1 , wherein the amount of said CaCO 3 added is 1.2-2% by mass (calculated as CaO).

Assignees

• Kobayashi Yoshinori
• Kawata Tsunehiro
• Hitachi Metals Ltd

Inventors

• Kobayashi Yoshinori
• Kawata Tsunehiro

Classifications

• C04B2235/80

  Phases present in the sintered or melt-cast ceramic products other than the main phase · CPC title

• C04B2235/3215

  Barium oxides or oxide-forming salts thereof · CPC title

• C04B35/2633

  containing barium, strontium or calcium · CPC title

• C04B2235/5436

  micrometer sized, i.e. from 1 to 100 micron · CPC title

• C04B2235/6585

  at an oxygen percentage above that of air · CPC title