Sintered ferrite magnet and its production method
AssigneeHitachi Metals, Ltd.
InventorsSeiichi Hosokawa, Etsushi Oda, Hiroshi Iwasaki
Life of this patent
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Abstract
A sintered ferrite magnet comprising a first granular ferrite compound phase containing Ca, La, Fe and Co and having a Curie temperature Tc1 between 415° C. and 430° C., and a second granular ferrite compound phase containing Sr, La, Fe and Co and having a Curie temperature Tc2 between 437° C. and 455° C., the volume ratio of the first ferrite compound phase being 50-90%, and the volume ratio of the second ferrite compound phase being 10-50%, with their total volume ratio being 95% or more.
Claims16
A sintered ferrite magnet comprising a first granular ferrite compound phase containing Ca, La, Fe and Co and having a Curie temperature between 415° C. and 430° C., and a second granular ferrite compound phase containing Sr, La, Fe and Co and having a Curie temperature between 437° C. and 455° C., the volume ratio of said first granular ferrite compound phase being 50-90%, and the volume ratio of said second granular ferrite compound phase being 10-50%, with their total volume ratio being 95% or more.
A method for producing a sintered ferrite magnet comprising the steps of
- (1) mixing a first calcined ferrite in which the metal elements of Ca, La, (Ba+Sr), Fe and Co have a composition represented by the general formula:
- Ca1-x′-c′Lax′Ac′Fe2n′-y′Coy′, wherein A represents (Ba+Sr), and x′, c′ and y′ representing the atomic ratios of Ca, La, A, Fe and Co and n′ representing a molar ratio are numbers meeting the conditions of 0.4≦x′≦0.6, 0≦c′≦0.2, 0.2<y′≦0.5, and 4≦n′≦6, with a second calcined ferrite in which the metal elements of Sr, La, Fe and Co have a composition represented by the general formula:
- Sr1-x″Lax″Fe2n″-y″Coy″, wherein x″ and y″ representing the atomic ratios of Sr, La, Fe and Co and n″ representing a molar ratio are numbers meeting the conditions of 0.05≦x″≦0.3, 0.05≦y″≦0.3, and 5≦n″≦6, at a mass ratio of 90/10 to 50/50, to obtain a calcined ferrite mixture;
- (2) pulverizing said calcined ferrite mixture to obtain powder;
- (3) molding said powder to obtain a green body;
- and
- (4) sintering said green body to obtain a sintered body.
Dependencies are inferred from the claim text.