抄録
Our purposes are to produce a fine and uniform microstructure and to achieve high quality products from the MgZn ferrites including some impurities. The discontinuous grain growth contributed with the impurities is prevented by sintering under low oxygen partial pressure or Fe2O3-deficient MgZn ferrites. On those conditions, the second phase, (Mg,Zn,Fe)O, is formed and strongly affects core loss in MgZn ferrites. Substitution of CuO enables MgZn ferrites to be sintered at low temperatures, and it leads to the reduction of the core loss because of the formation of fine microstructure. The calcium sulfate is formed from impurities contained in the raw materials for MgZn ferrites during calcinations. When ferrite powders are not treated by water, the calcium sulfate remains within grains and the core loss increase. The relaxation phenomena of MgCuZn ferrites are interesting. From the analysis of frequency dispersion, the natural resonance frequency does not agree with the one calculated from Snoek's limit and the initial permeability measured in the MgCuZn ferrites.
