Magnetic Properties of NiCuZn Ferrites with Addition of Tungsten Trioxide

초록

The NiCuZn ferrite materials have been widely used as materials for multilayer chip inductor. The effect of WO3 addition on microstructure and magnetic properties of NiCuZn ferrites, (NixCu0.2Zn0.8-xO)1.02 (Fe203)0.98, was investigated using microstructural characterization and electrical measurement. In application as a chip inductor, the reduction of magnetic loss at high frequency ranges is crucial to get a good performance for electronic components. In order to improve the electrical and magnetic properties of NiCuZn ferrites. WO3 was added up to 1.0wt.% and its bulk density, initial permeability μi and saturation magnetization were measured. When the content of WO3 was 0.4 wt.%, the high performance of NiCuZn ferrite was obtained as a maximum value in these compositions. The Q-factor in terms of loss characterization of NiCuZn ferrites increased with the larger amount of WO3. The μiQ measured at 1 MHz also showed the higher value in WO3-added NiCuZn ferrites than WO3-free composition. The permeability of ferrimagnetic materials, such as ferrites that exhibit Snoek's limit, can be affect by composition and processing. The real part of permeability decreases with the frequency and the imaginary part represents a broad peak, which is related to the relaxation phenomena. As the frequency of rf excitation increases, the materials reaches a point beyond which the spins cannot fully respond to the excitation. In characterization of frequency dependence of spinel ferrite materials, the dispersion due to relaxation can be observed at some frequency range and also related with the ferrite composition and its initial permeability. Therefore, this study is mainly described to determine the microsuuctures and variation of complex permeability with frequency for low-loss WO3-added NiCuZn ferrites.From the result of XPS analysis for WO3-added NiCuZn ferrites, it is found that the tungsten ions with different electronic valences as W4+/W6+ may be coexisted and provided