Grain boundary capacitance effect in Iron-based magnetic composites for superior C-band microwave absorption

Urgently, the absorbing bandwidth of magnetic materials is enormously limited in C-band by the exorbitant magnetic response. There are few reports about C-band absorber. In this paper, iron-based magnetic composites with large-angle grain boundaries (120°) were prepared by gelatinized starch assisted separation nucleation and solid phase sintering. Noteworthily, grain boundary capacitance layer is formed at the grain boundaries, effectively enhancing its dielectric parameters. This is facilitated to achieve balanced impedance matching. Therefore, the effective absorption bandwidth (EAB) of FFC-B covered the whole C-band (4–8 GHz). Natural resonance and impedance matching realized by grain boundary capacitance effect were confirmed to be the key to such wide EAB for FFC-B in C-band. This work explores the important role of grain boundary capacitance effect in regulating the dielectric parameters of iron-based magnetic materials, and provides a feasible strategy of grain boundary engineering for the low-frequency and wide EAB electromagnetic performance.