Electromagnetic characteristics of a ceramic composite

Grain-size dependence of total complex permeability and complex permittivit y of ferrite composites made of Ni-Zn ferrite and SiO2 is investigated by u sing various ram SiO2 powders with different grain size (average grain size s: 29 mum, 30 nm, 12 nm, 7 nm). If the volume ratio of Ni-Zn ferrite is gre ater than that of SiO2, both complex permeability and complex permittivity of the ferrite composites obey the Lichtenecker's logarithm mixed law. Howe ver, if the volume ratio of Ni-Zn ferrite is less than that of SiO2 and the grain size of SiO2 is sufficiently smaller than that of Ni-Zn ferrite, the frequency dependence of complex permeability agrees with values calculated by assuming a model in which the grains of the magnetic materials are indi vidually located in the dielectric medium. These results show that the comp lex permeability of ferrite composites depends on the grain characteristics . The total complex permeability for the ferrite composites, whose grains a re contact to each other, also obeys the Lichtenecker's logarithm mixed law .