METHOD FOR PRODUCING SINTERED FERRIT MAGNET, AND SINTERED FERRITE MAGNET

摘要

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 Ca1-x-yRxAyFe2n-zCoz, 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 SiO2) based on the entire sintered ferrite magnet, and its production method.

主权项

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 Ca1-x-yRxAyFe2n-zCoz, 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≦0.2,0.03≦z≦0.65, and4≦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 1.8% or less by mass of SiO2 and 1-2% by mass (calculated as CaO) of CaCO3 being added to 100% by mass of said calcined body, before the pulverization step.