Abstract
The ferrites which have a little excess of iron are relatively good-conducting, so far as the raw materials are extremely pure. When CaO, or SiO2 is added to the ferrites the resistivity is increased to some extent. When CaO and SiO2 are properly coexistent in ferrites the resistivity can be further increased, two maxima being found at the different ratio of the contents, one at the lower concentration of SiO2, the other at the higher. It was found that the effect of impurities was different not only by the kind of ferrite tested, but also by firing temperature and atmosphere. The combinations BaO and SiO2, SrO and SiO2, instead of CaO and SiO2, have been also studied. The experimental results will be discussed, in details, in Part II.
