Excellent microwave absorbing properties of ZnO/ZnFe2O4/Fe core-shell microrods prepared by a rapid microwave-assisted hydrothermal-chemical vapor decomposition method

Abstract To enhance the poor microwave absorption capabilities (MACs) of pure ZnO since its impedance mismatching and lack of magnetic loss ability, ZnO/ZnFe2O4/Fe core-shell microrods (CSMRs) and microflowers (CSMFs) were respectively fabricated by microwave hydrothermal-chemical vapor deposition and hydrothermal-chemical vapor deposition. The morphology, composition and resulting properties of as-prepared samples were affected by different deposition temperatures (Td) and Fe(CO)5 volumes. Due to the synergy of Fe(CO)5 adsorption and decomposition, the Fe/Zn ratio was controlled by varying Td from 300 °C to 500 °C, which conveniently modulated the static magnetic properties and MACs of ZnO/ZnFe2O4/Fe CSMRs and CSMFs. Results showed that the optimal reflection loss (RL) value was −46.88 dB at 6.88 GHz with absorber thickness as thin as 2.2 mm. When the RL was below −20 dB, 15.15 GHz was covered. The rod shaped heterostructure could be formed due to the presence of magnetic particles with Fe core/ZnFe2O4 shell embedding, promoting the orientation and interfacial polarizations, multiple relaxation and proper impedance matching. Our findings suggest that ZnO/ZnFe2O4/Fe CSMRs are a type of promising absorber material with high-performance MACs, broad bandwidths and thin thicknesses.