Abstract
The new (Zn,Mg,Ni,Fe,Cd)Fe2O4 high entropy ferrite with average crystallite size 11.8 nm was synthesized in two stages by annealing of co-precipitated amorphous precursor. The dielectric spectroscopy confirms, that the electrical conductivity and polarization processes are associated with the mobility of electrons in the structure of ferrite. It was concluded, that the both, high frequency complex dielectric permittivity as well as complex magnetic permeability are strongly temperature and frequency dependent. The AC electrical conductivity is associated with quantum mechanical tunneling of electrons and related to the transfer of charge carriers between Fe2+ and Fe3+ ions. Moreover, the microwave absorption properties were determined. The best microwave absorption properties have been confirmed in the frequency range 1.9 to 2.1 GHz for a layer which is 0.8–1 cm thick. For this range, reflection loss (RL) is lower than −25 dB and shielding effectiveness (SE) lower than −50 dB.
Highlights
High entropy oxides (HEOs) are a new group of materials developed in 20151
The new method of synthesis of high entropy ferrite, which was proposed in present work, allowed us to synthesize nanostructure material with average crystallite size equal to 11.8 nm and random distribution of different ions, which was confirmed by analysis of scanning transmission electron microscopy (STEM)-Energy-dispersive X-ray (EDX) 2D maps
The analysis of X-ray photoelectron spectroscopy method (XPS) spectra can allow to state, that Zn2+ ions accumulate on the surface of high entropy ferrite (HEF)
Summary
High entropy oxides (HEOs) are a new group of materials developed in 20151. Recently, HEOs were tested in different applications, especially in electronics according to their dielectric properties. The introduced Me2+ ions can occupy tetrahedral and/or octahedral sites unlike the Fe2+ ions[7,8] This introduces the disorder into the structure, which in consequence leads to the altered magnetic and dielectric properties of ferrites[9,10,11,12]. It was confirmed, that the addition of cobalt and other ions such as Zn2+, Mn2+ and Ni2+ changes the magnetic properties of ferrites such as anisotropy, coercivity, Curie temperature, and saturation magnetization The modulation of these properties can allow synthesizing materials, which can be used in a wide range of medical applications such as drug delivery, biosensors, magnetic hyperthermia and magnetic resonance imaging[21]. According to our knowledge, such method was not reported earlier to synthesis of HEOx. Dielectric measurements of (Zn,Mg,Ni,Fe,Cd)Fe2O4 high entropy ferrite allowed us to determine its electrical conduction mechanism and microwave absorption properties. In present study EMI shielding properties were examined in RF frequency range from 100 MHz to 2.1 GHz and in broad temperature range (233–343 K) in order to determine possibility of using the (Zn,Mg,Ni,Fe,Cd)Fe2O4 high entropy ferrite as radio-frequency shielding agent
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