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The high permeability NiCuZn Ferrite Materials Research

Author: ZhangYunFeng
Tutor: YuZhong
School: University of Electronic Science and Technology
Course: Electronic Science and Technology
Keywords: NiCuZn ferrite microstructure initial permeability Q factor relative loss coefficient
CLC: TM277
Type: Master's thesis
Year: 2011
Downloads: 50
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Abstract


Owing to its widely operating frequency range, the NiCuZn ferrites with high initial permeability have been important materials in broadband network systems and anti-electromagnetic interference fields. Therefore, it has become the researching focus both domestic and international in recent years. NiCuZn ferrites were prepared by a solid-state reaction method in this dissertation. In order to achieve the target of high initial permeability, the influences of compositions, additives, calcining temperature and sintering processes on the microstructure, phase and magnetic properties of NiCuZn ferrites were investigated.The results indicated that: ZnO could accommodate magnetocrystalline anisotropy constant （K1） and magnetostriction coefficient （λs）, significantly improved material microstructure, then the initial permeability increased and the relative loss coefficient decreased. Meanwhile, the saturation magnetic induction and Curie temperature decreased monotonically. CuO could reduce the forming temperature of the spinel phase and induce liquid phase during sintering,which then enhance the densification and grain growth during sintering. With the increase of CuO content, the initial permeability increased, the relative loss coefficient increased initially and then decreased, and Curie temperature decreased monotonically. Adding appropriate MoO3 in NiCuZn ferrites could accelerate the grain growth, improve material microstructure and the initial permeability, and reduce the relative loss coefficient. With the increase of V2O5 additive from 0.00wt% to 0.30wt%, the grain size of NiCuZn ferrites increased obviously, the initial permeability increased initially and then decreased, the relative loss coefficient increased. Adding proper quantities of TiO2 could promote the grain growth of the NiCuZn ferrites, increase the initial permeability and relative loss coefficient. With the raise of calcining temperature from 800℃to 950℃, activity of ferrite powder declined, then the initial permeability, relative loss coefficient and grain size raised initially and then declined. With the raise of sintering temperature from 1030℃to 1180℃, the grain size increased, the initial permeability and relative loss coefficient raised initially and then declined. Appropriate temperature holding time, heating and cooling rate would be benefit to the densification and grain growth of the NiCuZn ferrite, so as to the improvement of magnetic properties and microstructure. Through adding some additives, calcining at 850℃, grounding for 1h or 4h during the first milling and the secend milling, for the sample with the composition of 49.6mol%Fe2O3, 34.0mol%ZnO, 5.5 mol%CuO and 10.9 mol%NiO, a NiCuZn ferrite with the followed properties has been synthesized at sintering temperature of 1050℃: initial permeabilityμi=2425, saturation magnetic induction Bs=305mT, Curie temperature Tc>110℃and relative loss coefficient tanδ/μi=9.0×10-6.

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CLC: > Industrial Technology > Electrotechnical > Electrical materials > Magnetic materials,ferrite > Ferrite,oxide magnetic materials
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