Excellent microwave absorption of FeCo/ZnO composites with defects in ZnO for regulating the impedance matching

FeCo/ZnO composites have been successfully prepared through liquid-phase reduction process for the formation of FeCo polyhedrons and sequentially thermal decomposition of colloidal mixture of FeCo and Zn(Ac)(2)center dot 2H(2)O under nitrogen atmospheres. ZnO nanoparticles are homogeneously deposited on the surface of FeCo polyhedrons and the level of oxygen-vacancy defects in ZnO can be elevated with the increase of ZnO content. By comparison with FeCo polyhedrons, FeCo/ZnO composites exhibit excellent microwave absorption. The optimal RL value can reach -34.8 dB at 14.8 GHz and effective bandwidth (RL < - 10 dB) is 5.1 GHz in the frequency range of 12.4-17.5 GHz with a matching thickness of 1.5 mm. The integrated bandwidth with RL < - 10 dB can reach 14.1 GHz covering 3.4-17.5 GHz. Theory analysis demonstrates the interfacial polarization, dipole polarization and high conductivity due to oxygen-vacancy defects in FeCo/ZnO composites contribute to enhancement of dielectric loss capacity, which is more favorable for impedance matching. (C) 2018 Elsevier B.V. All rights reserved.