Synergistic effect of Fe-doping and stacking faults on the dielectric permittivity and microwave absorption properties of SiC whiskers

Previously, we have found that the stacking faults density in SiC whisker (SiCw) significantly affects its dielectric permittivity mainly through the enhanced dipolar loss mechanism. Doping has been considered as another effective way to increase the dielectric permittivity of granular SiC. In order to further investigate the possible synergistic effect of Fe-doping and stacking faults on permittivity, permeability, and microwave absorption properties, Fe-doped SiCw with various stacking faults densities were prepared. Experimental results indicate that the Fe-doped SiCw with internal stacking faults shows a higher dielectric permittivity than that of undoped SiCw with only stacking faults. Both dielectric permittivity and microwave absorption properties of Fe-doped SiCw increased significantly with the increase in dopant concentration. First-principle calculation reveals that Fe-doping tunes SiC to be half-metallic, and thus, its electric conductivity as well as conduction loss is enhanced. So, both the dielectric permittivity and microwave absorption properties of Fe-doped SiCw were significantly improved due to the synergistic effect of the enhanced conduction loss caused by Fe-doping and the dipolar loss induced by stacking faults. And, the measured weak magnetic loss contributes to that as well.