Calcined ferrite, and sintered ferrite magnet and its production method

Patent metadata

Field	Value
Publication number	US-11404188-B2
Application number	US-202117171036-A
Country	US
Kind code	B2
Filing date	Feb 9, 2021
Priority date	Mar 24, 2020
Publication date	Aug 2, 2022
Grant date	Aug 2, 2022

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 Ca1-x-yRxAyFe2n-zCoz, 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 calcined ferrite 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 following conditions:
0.30≤(1-x-y)≤0.55,
0.25≤x≤0.35,
0.225≤y≤0.40,
(1-x-y)>y,
0<z≤0.18, and
9.0≤(2n-z)<11.0.

2. The calcined ferrite according to claim 1 , wherein said atomic ratio (1-x-y) meets 0.40≤(1-x-y)≤0.50.

3. The calcined ferrite according to claim 1 , wherein said atomic ratio y meets 0.225≤y≤0.35.

4. The calcined ferrite according to claim 1 , wherein said atomic ratio z meets 0<z≤0.17.

5. The calcined ferrite according to claim 1 , wherein said atomic ratio (2n-z) meets 9.0≤(2n-z)≤10.5.

6. The calcined ferrite according to claim 5 , wherein said atomic ratio (2n-z) meets 9.0≤(2n-z)≤10.0.

7. 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 following conditions:
0.15≤x≤0.35,
0.225≤y≤0.40,
(1-x-y)>y,
0<z≤0.18, and
7.5≤(2n-z)<11.0.

8. The sintered ferrite magnet according to claim 7 , wherein said atomic ratio (1-x-y) meets 0.40≤(1-x-y)≤0.50.

9. The sintered ferrite magnet according to claim 7 , wherein said atomic ratio y meets 0.225≤y≤0.35.

10. The sintered ferrite magnet according to claim 7 , wherein said atomic ratio z meets 0<z≤0.17.

11. The sintered ferrite magnet according to claim 7 , wherein said atomic ratio (2n-z) meets 7.5≤(2n-z)≤10.5.

12. The sintered ferrite magnet according to claim 11 , wherein said atomic ratio (2n-z) meets 7.5≤(2n-z)≤10.0.

13. The sintered ferrite magnet according to claim 7 , wherein said sintered ferrite magnet further contains more than 0% and 1.5% or less by mass of Si as SiO 2 .

14. A method for producing the sintered ferrite magnet recited in claim 7 , 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 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 following conditions:
0.30≤(1-x-y)≤0.55,
0.25≤x≤0.35,
0.225≤y≤0.40,
(1-x-y)>y,
0<z≤0.18, and
9.0≤2n-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.

15. The method for producing a sintered ferrite magnet according to claim 14 , wherein (a) more than 0% and 1.5% or less by mass of SiO 2 , or (b) more than 0% and 1.5% or less by mass of SiO 2 and more than 0% and 1.5% or less by mass of CaCO 3 as CaO, are added to 100% by mass of said calcined body or calcined body powder, after said calcining step and before said molding step.

16. The calcined ferrite according to claim 1 , wherein said atomic ratio (1-x-y) meets 0.40<(1-x-y)≤0.50.

17. The calcined ferrite according to claim 1 , wherein said atomic ratio (1-x-y) meets 0.425≤(1-x-y)≤0.50.

18. The calcined ferrite according to claim 1 , wherein said atomic ratio z meets 0<z≤0.15.

19. The calcined ferrite according to claim 1 , wherein said atomic ratios z and (2n-z) meet 0.0084≤z/(2n-z)≤0.0167.

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

21. The sintered ferrite magnet according to claim 7 , wherein said atomic ratios z and (2n-z) meet 0.0084≤z/(2n-z)≤0.0167.

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

23. The method for producing a sintered ferrite magnet according to claim 14 , wherein said atomic ratio (1-x-y) meets 0.425≤(1-x-y)≤0.50.

24. The method for producing a sintered ferrite magnet according to claim 14 , wherein said atomic ratio z meets 0<z≤0.15.

25. The method for producing a sintered ferrite magnet according to claim 14 , 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

• C04B2235/6586

  Processes characterised by the flow of gas · CPC title

• C04B2235/6567

  Treatment time · CPC title

• C04B35/26

  based on ferrites · CPC title

• H01F41/0266

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

• C04B2235/3275

  Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite · CPC title