Synthesis and characterization of rare-earth elements substituted Ni-Zn ferrites

ABSTRACT

The spinel Ni_0.7Zn_0.3RE_0.04Fe_1.96O₄ ferrites with RE?Ce and Y are fabricated by the polyacrylamide gel method. The effect of rare earth ions substitution for iron ions on the structure, morphology, electromagnetic and microwave-absorbing properties of Ni-Zn ferrites are investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric and differential thermal analysis (TG-DTA) and HP8510B network analyzer, respectively. The results indicate that Ni_0.7Zn_0.3RE_0.04Fe_1.96O₄ ferrites form a pure cubic spinel structure, and Ce³⁺ and Y³⁺ substitute into the crystal lattice. Both the real ?′ and imaginary ?″ parts values of complex permittivity for Ni_0.7Zn_0.3RE_0.04Fe_1.96O₄ ferrites are higher than those for Ni-Zn ferrites in X-band (8.2-12.4 GHz) frequency range. When RE ions substitute for iron ions, the real μ′ and imaginary μ″ parts values of complex permeability for Ni_0.7Zn_0.3RE_0.04Fe_1.96O₄ ferrites decrease and increase, respectively. The microwave-absorbing properties are better for RE-substituted Ni-Zn ferrites than Ni-Zn ferrites. For Ni_0.7Zn_0.3Ce_0.04Fe_1.96O₄ ferrites, the minimum loss is ?12.5 dB at 18 GHz for an absorber thickness of 2 mm.