Precise regulation of weakly negative permittivity in CaCu3Ti4O12 metacomposites by synergistic effects of carbon nanotubes and grapheme

Precise control of value and dispersion characteristics of negative permittivity is still an unsolved problem in the practical application of random metamaterials. In this work, the ternary percolation nanocomposites (CNTs-GR-CCTO) were prepared via a low-temperature sintering process by using graphene (GR), carbon nanotubes (CNTs), and copper calcium titanate (CCTO). As the total carbon contents increased, the three-dimensional carbon network was formed, and negative permittivity is realized, which exhibits the Lorentz-type and Drude-type dispersion behaviors. The synergistic effect between GR and CNTs was studied in detail. While the GR sheets separate the CNTs, the CNTs also act as wires to connect the GR sheets. Controlled conductive paths were created by changing the ratio of CNTs to GR, achieving precise regulation of the negative permittivity, which is further certified by the equivalent circuit analysis. We provide a novel strategy for the precise regulation of negative permittivity of carbon-matrix metamaterials, which will greatly facilitate applications of metamaterials with negative permittivity.