A proposed electron transmission mechanism between Fe3+/Co2+ and Fe3+/Fe3+ in the spinel structure and its practical evidence in quaternary Fe0.5Ni0.5Co2S4

Abstract

This study is focused on the spinel structure of metal oxides and sulfides, from which the ternary (NiCo₂O₄/NiCo₂S₄) and quaternary (Fe_0.5Ni_0.5Co₂O₄/Fe_0.5Ni_0.5Co₂S₄) samples with hollow sphere structures were prepared. Among these samples, Fe_0.5Ni_0.5Co₂S₄ was highly effective in its ability to attenuate electromagnetic waves, wherein a broader absorption bandwidth of 6.2 GHz could be achieved with a thinner coating layer of 1.3 mm. The cation distribution rule for Fe, Co and Ni ions in the spinel structure is given according to hybrid orbital theory to support the excellent electromagnetic absorption properties. Relying on the distribution of Fe, Co and Ni cations, the probable electron transmission and coupling between Fe³⁺/Co²⁺ and Fe³⁺/Fe³⁺ adjacent cation ion pairs could occur at the octahedral site (B site), which reflects the enhanced dielectric loss.