Calcined ferrite, and sintered ferrite magnet and its production method
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; 2 n represents a molar ratio expressed by 2 n =(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≤(2 n - z )<11.0.
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.