| NiZnCu ferrites are widely used in various fields, such as inductor, filter coil, radio-frequency communications, anti-electromagnetic interference etc. NiZnCu ferrites are suitable for application within 1-100 MHz because they have high magnetic permeability and electrical resistivity. In Near Field Communication(NFC) applications, the effective range is just several centimeters with high safety. However, due to electromagnetic interference, it needs to separate the chip from the source of interference in the communication process. The flexible NiZnCu sintered ferrite sheets will be able to achieve the purpose.In this thesis, In order to get NiZnCu ferrites magnetic powders with μ’=150±20%, μ’’≤3 at 13.56 MHz. By adjusting the composition, the process conditions and the additive, the properties of magnetic powders were continually optimized. NiZnCu ferrites magnetic powders((NiO) x(ZnO) y(CuO) z ? 50±σFe2O3, x=15-25 mol%, y=17-24 mol%, z=5-10 mol%, σ=±2-4) were prepared using traditional solid phase reaction method. The structure, morphology and magnetic properties were measured and studied by X-ray diffractometer, scanning electron microscope, vibrating sample magnetometer and high frequency impedance analyzer. The main results are as follows:1. The calcination temperature and the second milling time can influence on the particles size and magnetic properties of NiZnCu magnetic powders. According to the experiments results, we chose that the calcination temperature is from 800℃ to 920℃ and the second milling time is 4 hours.2. By adding proper amount of Bi2O3, the sintered temperature can be decreased and the sintered density can be enhanced. It was found that the permeability could meet requirements at 13.56 MHz when 0.15 wt% of Bi2O3 was added. In addition, the effect of adding proper amount of the glass powder is similar with that of Bi2O3. The permeability could meet requirements at 13.56 MHz when 0.20 wt% of Bi2O3 was added.3. The sintered temperature can be decreased by doping Cu2+ in the NiZn ferrites, at the same time the magnetic properties hardly changed. It was found that magnetic loss can be reduced by doping Co2+ in the Ni ZnCu ferrites, meanwhile the ferrite magnets have good temperature characteristic. |
