Investigations On The Microstructure And Magnetic Properties Of Ni-Zn Ferrite Doped Rare-earth Oxides

As basic functional materials of electronic information and electronic industry, soft magnetic materials have been used extensively in fields including communication, power supply, computer, various electronic products and so on. With the improvement of information technology and the digitization of electronic products, the new demand of soft magnetic materials and component is put forward, such as miniaturization, slip, high frequency and low loss etc. In order to understand properly and use availably Ni-Zn ferrite materials, doping has become an effective investigating measure to improve ferrite properties.Ni-Zn ferrites were prepared by doping with Nd³⁺,Sm³⁺ and Y³⁺ rare-earth ions. Scanning electronic microscopy (SEM), X-ray diffraction (XRD) and Agilent 4294A impedance analyzer (1～100MHz) were used to investigate the microstructure, phase structure and magnetic properties. The effect of different doped contents and sintering temperatures on the microstructure, phase structure and magnetic properties of Ni-Zn ferrites were discussed. On this ground, the optimal sintering process has been determined, which has laid the foundation for the application and exploitation of Ni-Zn ferrites doped other rare-earth elements. In addition, the precipitation process of secondary phase and the effecting mechanism of magnetic properties were studied preliminarily, and some important conclusions were obtained:1. The microstructure and magnetic properties of Ni_0.4Zn_0.6Fe_2-xNd_xO₄(x = 0～0.07) doped Nd³⁺ were systematically investigated. The investigation shows that doping with Nd³⁺ ion leads to an increase of lattice constantÉ‘, and with the Nd³⁺ content increasing, the sintering density increases from 5.14g/cm³ to 5.29g/cm³. With increasing Nd³⁺ content, the initial permeability (μ′) and magnetic loss tangent(tgδ) decrease, while the cut-off frequency(fr) of sintered samples increases. Among all Ni_0.4Zn_0.6Fe_1.97Nd_0.03O₄ samples sintered at 1150℃,1200℃,1250℃and 1300℃respectively, the one sintered at 1250℃exhibits the highest permeability and higher sintered density, with the initial permeability reaching 365. 2. The microstructure and magnetic properties of Ni_0.4Zn_0.6Fe_2-xSm_xO₄(x = 0～0.07) doped Sm³⁺ were investigated and the results show that the small amount Sm³⁺ entering into the lattice of ferrite leads to an increase of lattice constantÉ‘and with the Nd³⁺ content increasing, the sintering density increases from 5.14g/cm³ to 5.25g/cm³. For x=0.01, a peak value of the initial permeability appears, and when x>0.01 the initial permeability decreases with the increase of x. Among all Ni_0.4Zn_0.6Fe_1.97Sm_0.03O₄ samples sintered at 1150℃, 1200℃, 1250℃and 1300℃, the sample sintered at 1250℃has the better comprehensive performances and the less loss.3. As to Ni_0.4Zn_0.6Fe_2-xY_xO₄(x = 0～0.07), 0 sample and Y1 sample are single cubic spinel structure, and the secondary phase appears in samples with different Y³⁺ contents when x = 0.03～0.07. With the Y³⁺ content increasing, the sintering density of samples increases from 5.14g/cm³ to 5.25g/cm³. The real permeability increases with the increase of x when x<0.01, and it reaches the peak of 495 when x=0.01, and then it reduces gradually when x increases from 0.03 to 0.07.4. The sintered density curves of Ni-Zn ferrite doped Nd³⁺,Sm³⁺ and Y³⁺ show the tendency of going up with three rare-earth ions content increasing. The sintered density of the samples with the same rare-earth ions increase in the sequence of Y³⁺,Sm³⁺ and Nd³⁺ .The changing trends and causes of initial permeability for Ni_0.4Zn_0.6Fe_2-xNd_xO₄, Ni_0.4Zn_0.6Fe_2-xSm_xO₄ and Ni_0.4Zn_0.6Fe_2-xY_xO₄ are different.