Method for producing sintered ferrite magnet, and sintered ferrite magnet

Patent metadata

Field	Value
Publication number	US-9773593-B2
Application number	US-201514807953-A
Country	US
Kind code	B2
Filing date	Jul 24, 2015
Priority date	Jun 30, 2009
Publication date	Sep 26, 2017
Grant date	Sep 26, 2017

Abstract

A sintered ferrite magnet comprising (a) a ferrite phase having a hexagonal M-type magnetoplumbite structure comprising Ca, an element R which is at least one of rare earth elements and indispensably includes La, an element A which is Ba and/or Sr, Fe, and Co as indispensable elements, the composition of metal elements of Ca, R, A, Fe and Co being represented by the general formula of Ca 1-x-y R x A y Fe 2n-z Co z , wherein the atomic ratios (1-x-y), x, y and z of these elements and the molar ratio n meet the relations of 0.3≦(1-x-y)≦0.65, 0.2≦x≦0.65, 0≦y≦0.2, 0.03≦z≦0.65, and 4≦n≦7, and (b) a grain boundary phase indispensably containing Si, the amount of Si being more than 1% by mass and 1.8% or less by mass (calculated as SiO 2 ) based on the entire sintered ferrite magnet, and its production method.

First claim

What is claimed is:

1. A method for producing a sintered ferrite magnet comprising (a) a ferrite phase having a hexagonal M-type magnetoplumbite structure, and (b) a grain boundary phase indispensably containing Si, said method comprising
a step of preparing calcined ferrite containing a ferrite phase having a hexagonal M-type magnetoplumbite structure, which comprises Ca, an element R which is at least one of rare earth elements and indispensably includes La, an element A which is Ba and/or Sr, Fe, and Co as indispensable elements, the composition of metal elements of Ca, R, A, Fe and Co being represented by the general formula of Ca 1-x-y R x A y Fe 2n-z Co z , wherein the atomic ratios of Ca (1-x-y), the element R (x), the element A (y) and Co (z), and the molar ratio of n meet the following relations:
0.3≦(1- x - y )≦0.65,

0.2≦ x≦ 0.65,

0≦ y≦ 0.2,

0.25≦ z≦ 0.65, and

4≦ n≦ 7;

a step of pulverizing said calcined body to powder;
a step of molding said powder to a green body; and
a step of sintering said green body to obtain a sintered body;
more than 1% by mass and 1.6% or less by mass of SiO 2 and 1.2-2% by mass (calculated as CaO) of CaCO 3 being added to 100% by mass of said calcined body, before the pulverization step,
a ratio of the amount (calculated as CaO) of CaCO 3 to the amount of SiO 2 being 0.9-1.1 when 0.25≦z≦0.3 and 1.1-1.4 when 0.3≦z≦0.65.

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

3. The method for producing a sintered ferrite magnet according to claim 1 , wherein (1-x-y), x, y and z and n meet the relations of
0.35≦(1- x - y )≦0.55,

0.4≦ x≦ 0.6,

0≦ y≦ 0.15,

0.25≦ z≦ 0.4, and

4.5≦ n≦ 6.

4. The method for producing a sintered ferrite magnet according to claim 1 , wherein said pulverization step comprises a first fine pulverization step, a step of heat-treating powder obtained by said first fine pulverization step, and a second fine pulverization step of pulverizing the heat-treated powder again.

5. A sintered ferrite magnet comprising
(a) a ferrite phase having a hexagonal M-type magnetoplumbite structure comprising Ca, an element R which is at least one of rare earth elements and indispensably includes La, an element A which is Ba and/or Sr, Fe, and Co as indispensable elements, the composition of metal elements of Ca, R, A, Fe and Co being represented by the general formula of Ca 1-x-y R x A y Fe 2n-z Co z , wherein the atomic ratios of Ca (1-x-y), the element R (x), the element A (y) and Co (z), and the molar ratio of n meet the following relations:
0.3≦(1- x - y )≦0.65,

0.2≦ x≦ 0.65,

0≦ y≦ 0.2,

0.25≦ z≦ 0.65, and

4≦ n≦ 7, and

(b) a grain boundary phase indispensably containing Si, and Ca in amounts determined by more than 1% by mass and 1.6% or less by mass of SiO 2 powder and 1.2-2% by mass (calculated as CaO) of CaCO 3 powder added to 100% by mass of said ferrite phase,
a ratio of the amount (calculated as CaO) of CaCO 3 to the amount of SiO 2 being 0.9-1.1 when 0.25≦z≦0.3, and 1.1-1.4 when 0.3≦z≦0.65.

6. The sintered ferrite magnet according to claim 5 , wherein the amount of SiO 2 powder added is 1.1-1.6% by mass based on 100% by mass of said ferrite phase.

7. The sintered ferrite magnet according to claim 5 , wherein (1-x-y), x, y and z and n meet the relations of
0.35≦(1- x - y )≦0.55,

0.4≦ x≦ 0.6,

0≦ y≦ 0.15,

0.25≦ z≦ 0.4, and

4.5≦ n≦ 6.

Assignees

• Hitachi Metals Ltd

Inventors

• Oda Etsushi
• Kobayashi Yoshinori

Classifications

• H01F1/348

  Hexaferrites with decreased hardness or anisotropy, i.e. with increased permeability in the microwave (GHz) range, e.g. having a hexagonal crystallographic structure · CPC title

• C04B2235/3277

  Co3O4 · CPC title

• C01G51/68

  containing rare earths, e.g. (La0.3Sr0.7)CoO3 · CPC title

• H01F7/02

  Permanent magnets {[PM]} · CPC title

• C04B2235/3409

  Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax · CPC title