Effects of Ce-Zn co-substitution on structure, magnetic and microwave absorption properties of nickel ferrite nanoparticles

The novel Ce3+ and Zn2+ doped nickel ferrites Ni1-xCexFe2-xZnxO4 (x = 0, 0.05, 0.10, 0.15, 0.20) were prepared by sol-gel auto-combustion method. The structures and morphologies were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). All the XRD patterns showed the single phase of the spinel-type ferrite without other impurity when x <= 0.10, and the average crystallite size was about 34.2-53.1 nm. The lattice parameters became larger with the increasing substitution content. The other structure properties such as cation distribution, theoretical ionic radius of a tetrahedral site (r(A)) and an octahedral site (r(B)), theoretical lattice parameter (a(th)), O2- positional parameter (u), cation-cation and cation-anion distances and bond angles were also investigated. The result of FT-IR indicated that Ce3+ substituted Ni2+ in B sites and Zn2+ replaced Fe3+ in A sites. The M-s of substituted ferrites increased with the increase of substitution content when x <= 0.10. It was observed that substituted ferrites showed more excellent performance than pure nickel ferrite. The Ni0.9Ce0.1Fe1.9Zn0.1O4 had the best microwave absorption properties. The frequency (with respect to - 10 dB) started from 11.56 GHz, and the bandwidth reached about 6.44 GHz. The peak value of RL reached about -21.44 dB at a frequency of 15.52 GHz with a coating thickness of 2.5 mm. The analysis of microwave absorption mechanism indicated that the microwave absorption properties were mainly depended on the input impedance matching, the electromagnetic loss properties and the coating thickness. (C) 2016 Elsevier B.V. All rights reserved.