The Study On Intrinsic Properties And Temperature Stability Of NiZn Ferrite

Widely used in communications, computer, power and other types of electronicequipment, ferrites have become the very important functional material in electronicinformation industry. MnZn and NiZn ferrite are two commonly used soft ferrites.Compared to MnZn ferrite, NiZn ferrite with its high resistivity, high B_s, high magneticpermeability μ, low coercivity Hc, Curie temperature θf, low temperature coefficientμ,low loss tgδ, good high frequency characteristics, etc. over1MHz, have been widelyused.In this paper, with traditional ceramics process, ferrite samples were prepared usingNiO, ZnO, CuO and Fe₂O₃as raw materials. Systematic study of the preparation process,CuO doping, microstructure, Fe₂O₃content and NiO/ZnO mol ratio on the NiZn ferritemagnetic properties have been taken, and the temperature stability of the NiZn ferrite hasalso been investigated.The results show that pre-firing temperature, second grinding time, sinteringtemperature and sintering holding time impact on the magnetic properties of NiZn ferrite.And pre-firing temperature is the most important factor that impact on the initialpermeability of samples, followed by sintering temperature, while sintering holding timeis the minimal impact. Add CuO in NiZn ferrite can effectively promote the densificationduring sintering and grain growth, but excessive CuO content during sintering, the graindoes not cause continuous growth, porosity increases, leading to magnetic materialsconductivity decreases; Fe₂O₃content has great impact on the sample permeability,sintered density, coercive force Hc, saturation magnetic induction B_s, residualmagnetization B_r, and excessive Fe₂O₃content will lead to the deterioration ofelectromagnetic properties of the materials; Added by a certain amount of Zn²⁺canreduce the magnetic anisotropy constant K1and the saturation magnetostrictioncoefficient λ_s, increase saturation magnetization Ms, thus enhancing the initialpermeability of materials, while excessive Zn²⁺content will lead to most A position occupied by Zn²⁺, and other magnetic ions were pushed to B position, so super-exchangeinteraction between A and B position will disappear, otherwise antiparallel arrangementof magnetic ions in the B position will lead to the reduce of saturation magnetization Mseven close to0, causing a decline in permeability; High temperature stability samples ofGW440and GW840have been prepared by conventional ceramic method in this paper.Temperature coefficient, microstructure and Curie temperature were investigated. Theμof sample GW440, which permeability was440, was1.65×10^-6 between25℃⁷0℃and0.67×10^-6 between25℃¹57℃, and the curie temperature was170℃. Theμofsample GW840, which permeability was840, was1.38×10^-6 between25℃⁷0℃and0.15×10^-6 between25℃¹50℃, and the curie temperature was160℃. With a certainamout of Co doped, the sample temperature stability can be improved, however,excessive Co-doped will lead to the deterioration of the sample permeability andtemperature stability.