Study On Preparation And Characterization Of Doped High Performance Ni-Zn Ferrites Materials

Ni-Zn ferrites are the most versatile ferrites from the point of their large number of high frequency applications, due to their high value of magnetization, high permeability, low power loss at high frequencies, high Curie temperature, and high resistivity. Further enhancement in the performance of superpower soft ferrites in the condition of high frequency is presently the tendency of advanced soft ferrites products in China. Selecting the appropriate preparation and additives is the key to obtain high performance and high-quality ferrites. In this work, a"one-step synthesis"method was proposed to prepare Ni-Zn ferrite ceramic soft magnetic materials to adapt to the actual industrial production, avoid large-scale manufacture and replacement of equipments, reduce production costs and improve the electromagnetic properties of ferrites. And by this approach of single sintering and synthesis step, a series of doped Ni-Zn ferrite ceramic soft magnetic materials with overall composition Ni0.5Zn0.5MxFe2-xO4(M=Al, Pr, W; x=0~1) were prepared. The influence of Al2O3, Pr6O11 and WO3 doping into Ni-Zn ferrites on electromagnetic properties were investigated. The results showed that:(1) Ni-Zn ferrites successfully fabricated by both conventional"two-step synthesis"and new"one-step synthesis"methods had a typical pure spinel structure. The difference of both ferrites'coercivity (Hc), magnetization (Ms), Curie temperature (Tc), and resonance frequency (fr) were not significant. The dielectric constant (ε′) and dielectric loss (tanδ) for the ferrites prepared by"one-step synthesis"were lower than those for the ferrites prepared by"two-step synthesis".(2) All Ni-Zn ferrites doped with Al2O3 fabricated by"one-step synthesis"had a typical spinel structure. The addition of Al2O3 to Ni-Zn ferrite reduced Ms,μ′andμ″. And when keeping high value, Tc rose first, and then dropped down with increasing amounts of Al2O3 doped. As the applied frequency increased to higher than about 10 MHz, the permeability of non-doped ferrite became lower than that of ferrites doped with Al2O3. And the addition of Al2O3 made fr increase, driving the utility of magnetic permeability to much higher frequency.ε′and tanδdecreased after the doping of Al2O3.(3) All Ni-Zn ferrites doped with Pr6O11 prepared by"one-step synthesis"contained mainly ferrite spinel phase in combination of a small amount of a foreign phase, PrFeO3. Ms of the ferrites decreased with increasing doping amount of Pr6O11, while Hc showed a trend in increase. And their corresponding Tc kept constant, fluctuating between 308~320℃. Bothμ′andμ″of the ferrites decreased. fr increased, driving the utility of magnetic permeability to much higher frequency. The doping of Pr6O11 into Ni-Zn ferrites resulted in decrease in tanδin the frequency range from 1 MHz to 400 MHz.(4) All Ni-Zn ferrites doped with WO3 fabricated by"one-step synthesis"had a typical spinel structure. Ms of the ferrites rose first and then dropped down with more WO3 doped, while Hc,ε? and tanδshowed the opposite trend. With increasing the amount of WO3 doped, Tc increased, whileμ′andμ″of the ferrites decreased. The magnitude of fr didn't change much.ε? and tanδshowed their lowest value, when the substitution level x=0.02.