Epsilon-negative behavior of BaTiO3/Ag metacomposites prepared by an in situ synthesis

Epsilon-negative behavior in metamaterials has attracted increasing attention recently. In this work, excessively percolating BaTiO3/Ag composites were synthesized by an in-situ preparation method to achieve negative permittivity. The epsilon-negative behavior is explained by low-frequency plasma oscillation of free electrons, which can be well fitted by the Drude model. Moreover, the negative permittivity of composites can be tuned by adjusting the content of randomly distributed Ag particles. The ac conductivity of excessively percolating BaTiO3/Ag composites shows a typical metal-like behavior. Furthermore, the investigation of reactance reveals that the inductive character derived from the conducive network is the main contributor to negative permittivity, as confirmed by the equivalent circuit analysis. This work provides a theoretical recipe for designing negative permittivity, supplements the family of metamaterials, and would further facilitate the practical applications of epsilon-negative materials in electromagnetic devices.