Microwave absorbing properties of magnesium-substituted MnZn ferrites prepared by citrate-EDTA complexing method

Magnesium-substituted MnZn ferrites with composition of Mn_0.4Zn_0.6Mg_xFe_(2-x)O₄ (x=0.00, 0.05) were prepared by citrate-EDTA (ethylenediamine tetraacetic acid) complexing method. The crystal structure, surface morphology and electromagnetic properties of the calcined samples were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and network analyzer (Agilent 8722ET). All the XRD patterns showed the single phase of the spinel-type MnZn ferrite without other intermediate phase. The lattice parameter and average particle size increased with the substitution of magnesium. The microwave electromagnetic properties of the samples have been studied at the frequency range from 2 to 18 GHz. It was shown that the values of e{open}' and e{open}″ decreased slightly with the substitution of magnesium. The values of μ' and μ″ were improved significantly, and the peak of μ″ shifted to low frequency with Mg²⁺ ions substituting. Furthermore, the reasons have also been discussed by using electromagnetic theory. The reflection loss (RL) ascended after magnesium was substituted. Magnesium-substituted ferrite had excellent microwave absorption properties. The frequency (with respect to -10 dB) started from 11.3 GHz, and the bandwidth reached about 3.5 GHz. The peak value of RL was about -19 dB at a matching thickness of 3.1 mm.