Calcined ferrite, and sintered ferrite magnet and its production method

Patent metadata

Field	Value
Publication number	US-2022246338-A1
Application number	US-202217724696-A
Country	US
Kind code	A1
Filing date	Apr 20, 2022
Priority date	Mar 24, 2020
Publication date	Aug 4, 2022
Grant date	—

Abstract

A sintered ferrite magnet having a composition of metal elements of Ca, R, A, Fe and Co, which is represented by the general formula of Ca 1−x−y R x A y Fe 2n−z Co z , wherein R is at least one of rare earth elements indispensably including La; A is Sr and/or Ba; x, y, z and n represent the atomic ratios of Ca, R, A, Fe and Co; 2n represents a molar ratio expressed by 2n=(Fe+Co)/(Ca+R+A); and x, y, z and n meet the conditions of 0.15≤x≤0.35, 0.05≤y≤0.40, (1−x−y)>y, 0<z≤0.18, and 7.5≤(2n−z)<11.0.

First claim

What is claimed is:

1 . A sintered ferrite magnet having a composition of metal elements of Ca, R, A, Fe and Co, which is represented by the general formula of Ca 1−x−y′ R x A y′ Fe 2n−z Co z , wherein R is at least one of rare earth elements indispensably including La; A is Sr; x, y′, z and n represent the atomic ratios of Ca, R, A, Fe and Co; 2n represents a molar ratio expressed by 2n=(Fe+Co)/(Ca+R+A); and x, y′, z and n meet the following conditions:
0.15≤ x≤ 0.35,

0.05≤ y′≤ 0.40,

(1- x−y ′)> y′,

0≤ z≤ 0.18, and

7.5≤(2 n−z )<11.0,

wherein said sintered ferrite magnet further contains more than 0% and 1.0% or less by mass of Si as SiO 2 .

2 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratio (1−x−y′) meets 0.40≤(1−x−y′)≤0.50.

3 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratio (1−x−y′) meets 0.425≤(1−x−y′)≤0.50.

4 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratio y′ meets 0.20≤y′ ≤0.40.

5 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratio y′ meets 0.20≤y′ ≤0.35.

6 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratio z meets 0≤z≤0.17.

7 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratio z meets 0≤z≤0.15.

8 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratio (2n−z) meets 7.5≤(2n−z)≤10.5.

9 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratio (2n−z) meets 7.5≤(2n−z)≤10.0.

10 . The sintered ferrite magnet according to claim 1 , wherein said atomic ratios z and (2n−z) meet 0.0084≤z/(2n−z)≤0.0167.

11 . A method for producing the sintered ferrite magnet recited in claim 1 , comprising the steps of
mixing raw material powders containing metal elements of Ca, R, A, Fe and Co to prepare a raw material powder mixture having a metal element composition represented by the general formula of Ca 1−x−y′ R x A y′ Fe 2n−z Co z , wherein R is at least one of rare earth elements indispensably including La; A is Sr; x, y′, z and n represent the atomic ratios of Ca, R, A, Fe and Co; 2n represents a molar ratio expressed by 2n=(Fe+Co)/(Ca+R+A); and x, y′, z and n meet the following conditions:
0.30≤(1− x−y ′)≤0.55,

0.25≤ x≤ 0.35,

0.15≤ y′≤ 0.40,

(1− x−y ′)> y′,

0≤ z≤ 0.18, and

9.0≤2 n−z< 11.0,

calcining the resultant raw material powder mixture, pulverizing the resultant calcined body, molding the resultant calcined body powder, and sintering the resultant green body,
wherein more than 0% and 1.0% or less by mass of SiO 2 is added to 100% by mass of said calcined body or calcined body powder, after said calcining step and before said molding step.

12 . The method for producing a sintered ferrite magnet according to claim 11 , wherein more than 0% and 1.5% or less by mass of CaCO 3 as CaO is further added to 100% by mass of said calcined body or calcined body powder, after said calcining step and before said molding step.

13 . The method for producing a sintered ferrite magnet according to claim 11 , wherein more than 0% and 0.7% or less by mass of CaCO 3 as CaO is further added to 100% by mass of said calcined body or calcined body powder, after said calcining step and before said molding step.

14 . The method for producing a sintered ferrite magnet according to claim 11 , wherein said atomic ratio (1−x−y′) meets 0.40≤(1−x−y′)≤0.50.

15 . The method for producing a sintered ferrite magnet according to claim 11 , wherein said atomic ratio (1−x−y′) meets 0.425≤(1−x−y′)≤0.50.

16 . The method for producing a sintered ferrite magnet according to claim 11 , wherein said atomic ratio z meets 0≤z≤0.15.

17 . The method for producing a sintered ferrite magnet according to claim 11 , wherein said atomic ratios z and (2n−z) meet 0.0084≤z/(2n−z)≤0.0167.

Assignees

• Hitachi Metals Ltd

Inventors

• TANIOKU Yasuaki
• Yoshimitsu Yushi
• Kobayashi Yoshinori

Classifications

• C04B2235/3227

  Lanthanum oxide or oxide-forming salts thereof · CPC title

• C04B2235/6562

  Heating rate · CPC title

• H01F1/11 Primary

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

• C04B2235/767

  Hexagonal symmetry, e.g. beta-Si3N4, beta-Sialon, alpha-SiC or hexa-ferrites · CPC title

• H01F41/0266

  Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11) · CPC title