The Study Of Electronic Magnetic Properties Of The Low-Temperature-Sintered Hexagonal Ferrites

The crystal-structure, fabricating process and electronic-magnetic properties of the low-temperature-sintered hexagonal ferrites applied in Multilayer Chip Inductor(MLCI) are introduced in this paper. Usually the sintering temperature of the single phase of hexagonal ferrites is very high. So the main task of the paper is to lower the sintering temperature of hexagonal ferrites without largely degenerating the electronic magnetic properties.The spinel ferrites cannot be used as the inner magnetic dielectric in the MLCIs working in Ultra High Frequency(UHF) range. Due to special crystal-stucture the hexagonal ferrites has higher Snoek products and resonance frequency than the spinel ferrites. These advantages make it adapt to used as the inner magnetic dielectric in high frequency MLCIs. In order to decrease the sintered temperature of hexagonal ferrites two steps must be introduced: the first one is to add Cu in the formula, the last one is to mix it with some Bi₂O₃.The Co_2-XCu_XY type hexagonal ferrites was chosen to research because of its relative high nature resonance frequency. It is an effective way to decrease the sintering temperature that replacing the Co ion with Cu ion and mingle with some Bi₂O₃ in the Co₂Y type hexagonal ferrites. Twenty-five samples were prepared by changing the content of the Cu ion and the Bi₂O₃. All these samples were manufactured by the traditional solid-state reaction method. The sample which has a lower sintering temperature and optimal contents of the Cu ion and the Bi₂O₃ can be selected by analyzing the measured electronic-magnetic properties of all the samples. It is testified that the sintering temperature of the sample was decreased to 930℃by the Cu ion content X=1.0 and 5.0 wt% Bi₂O₃. In general all the relative permeabilities of these samples don't exceed 4.0. The relative permeability can reach at 11.3 by replacing some Co ion and Cu ion with Zn ion in the materials. It is a practicable method to tailor the permeability of hexagonal ferrites.