Fine-tuning of negative permittivity behavior in amorphous carbon/alumina metacomposites

In this work, amorphous carbon/alumina (C/Al 2 O 3 ) metacomposites with tunable negative permittivity were synthesized by a facile impregnation method. We analyzed the influence of carbon content and the carbonization temperature on the microstructure and electrical properties of the metacomposites. It was found that the conductive carbon networks were formed in the composites with the higher carbon contents and carbonization temperatures, which lead to the appearance of a metal-like conduction and negative permittivity behavior. Low-frequency plasmonic state provided by plenty of free electrons in the carbon networks resulted in the negative permittivity, and its numerical values could be effectively adjusted by controlling the carbon content and carbonization temperature, which could be well explained by Drude model. This work provides a feasible way to prepare metacomposites with tunable negative permittivity, which will expand their potential applications in shielding, absorbing and novel capacitor fields.