Abstract
As described in Part I, the resistivity of ferrites is greatly increased by simultaneous addition of CaO and SiO2. In order to clarify the effect of impurities, various investigations have been carried out. The high resistivity thus obtained decreases with frequency. This suggests that the ferrites have an inhomogeneous dielectric structure consisting of poor-conducting layers separating relatively goodconducting grains. It was confirmed by autoradiograph and other techniques that the impurities were almost localized near the grain boundaries to form poor-conducting layers. The substance of grain boundary is considered as mixed oxide of the ferrite and the impurities, represented by (Ca1-xSixOγ)i-y(Ferrite)y. In fact, it was found that at certain composition of this series, the resistivity was extremely high and varied with firing conditions in the same mann eras the ferrite containing the impurities. It was concluded that the grain-boundary had profound effect on the resistivity of ferrite.
