Tunable negative permittivity in Ti3SiC2 MAX phase/Polymethyl methacrylate metacomposites at radio-frequency region

Metacomposites with negative permittivity have triggered tremendous fundamental and practical attention in recent years. In this paper, Ti3SiC2 MAX phase/Polymethyl methacrylate (PMMA) metacomposites with different Ti3SiC2 content were prepared. Weakly negative permittivity value (between -50 and 0) was observed near percolation (Ti3SiC2 content of 60 wt.%), attributing to moderate carrier concentration in Ti3SiC2 networks, and negative permittivity was tuned by tailoring conductive Ti3SiC2 networks. AC conductivity spectra and negative permittivity spectra of composites over percolation were explained by Drude model, indicating metal-like conduction behavior and low-frequency plasmonic oscillation in composites. The impedance response of composites was analyzed by equivalent circuit models, manifesting correspondence between inductor and negative permittivity. This work presented a new type of metacomposite constructed by Ti3SiC2 MAX phase and further revealed the generation mechanism of negative permittivity, which will greatly facilitate the practical applications of MAX phase in metacomposites.