Preparation And Magnetic In The High-frequency Of MgCuZn Ferrite

Ferrites materials have high resistivity values and initial permeability, which make them useful for high-frequency magnetic loss material. The advantages of these ferrites are easier impedance match, wide loss band, simple preparation processes. Compared with traditional Ni Cu Zn ferrites, Ni Cu Zn ferrites with Ni replaced by Mg can reduce the cost of ferrites. Because of those benefits, Mg Cu Zn ferrites have an obvious application perspective. In this thesis, we have studied the high-frequency magnetic properties and sintering characteristics from 1MHz to 1GHz aiming to get a higher permeability and bigger magnetic loss. We have systematically discussed the effect of chemical compositions and sintering processes on the high-frequency properties of Mg Cu Zn ferrite. The main findings are given as follows.Firstly, we have studied the effect of different sintering temperatures on the Mg Cu Zn spinel ferrites with a standard composition of Mg0.45Cu0.1Zn0.45Fe2O4. We have analyzed the effect of the calcination temperature on the permeability, loss tangent and shrinkage rate, etc. The results show that when the calcination temperature is between 900 ℃ and 1000 ℃, higher permeability can be obtained with other magnetic properties unchanged.Secondly, we studied the effect of milling time on the properties of Mg Cu Zn ferrite(Mg0.6Cu0.10Zn0.3Fe2O4). The results show that with milling time increase, the particle size decreases, which result in compact samples. However, if the milling time is too long, it is found that permeability values decrease due to the introduction of impurities such as Fe. The ideal milling time should not exceed 12 hours.Thirdly, we have studied the effect of adding V2O5 into Mg Cu Zn ferrite(Mg0.5Cu0.2Zn0.3Fe2O4). The results show that adding V2O5 can enable us to get higher initial permeability and larger magnet loss due to the possible reason that V2O5 can promote sintering. The maximum of permeability can be achieved with 0.4 wt% V2O5 addition. Furthermore, with 0.6 wt % V2O5 addition, it is found that the sintering temperature is decreased to 950 ℃, which can be considered as a low-temperature sintering.Fourthly, we have also used Cu2+ ions to replace Mg2+ to study the substitution effect on the sintering characteristics and the permeability. It is found that with the increase of copper, the saturation magnetization is increased. When x is about 0.2, the maximum saturation magnetization can be 43 emu/g. Besides, we have found that higher sintering density, shrinkage rate and permeability value can be obtained. However, the magnet loss may increase as the cut-off frequency moves toward the lower frequency.Subsequently, we have studied the effect of Zn2+ contents in Mg Cu Zn ferrite(Mg0.9-x Cu0.1Znx Fe2O4). It is found that the increase of Zn O content can promote the uniform growth of grains, which results in an obvious enhancement of permeability values and magnetic losses. Therefore, tuning the content of Zn2+ ions in the composition is an effective approach to tune the high frequency magnetic properties for Mg Cu Zn ferrites.Finally, we have investigated the effect of Fe3+ contents in the compositions of Mg0.6Cu0.1Zn0.3Fe2+x O4+3/2x. Compared with the ferrites with a standard stoichiometric composition, higher saturation magnetization Ms and higher initial permeability can be achieved for composition with iron deficiency; it is also found that the microstructures are denser. However, on the case of compositions with rich iron, the initial permeability is found to decrease. While the cut-off frequency( fr) moves to a higher frequency. Iron-rich samples can be used for the absorption of electromagnetic wave noise.