Ultrahigh concentration surface oxygen vacancies in ferrite foams for broadened electromagnetic absorption bandwidth

Currently, the absorbing bandwidth of the Ferrites is enormously limited at X-band and Ku-band by the poor intrinsic dielectric properties. Thus, there are few reports about the pure Ferrites’ application at 8-18 GHz. In this paper, the Ferrites composite foams (NFC) with a high surficial oxygen vacancy concentration (48.1%) were prepared by the NH 4 NO 3 assisted solution-combustion strategy and solid phase sintering. Noteworthily, the concentration of surficial oxygen vacancy can be effectively regulated by the NH 4 NO 3 . This is facilitated to achieve balanced impedance matching. Therefore, the effective absorption bandwidth (EAB) of the NFC covered the whole X-band and Ku-band. Conduction loss and defect polarization relaxation realized by surficial oxygen vacancies were confirmed to be the key to such wide EAB for the NFC at 8-18 GHz. This work explores the important role of surficial oxygen vacancy engineering in regulating the dielectric parameters of the Ferrites, and provides a feasible strategy of surficial oxygen vacancy engineering for wide EAB electromagnetic performance at the high-frequency.