MWCNTs/BaTiO₃ metacomposite with negative permittivity behavior and electric percolation phenomenon in radio frequency

Negative permittivity has taken off as a research topic in percolative composites recent years. Comparing with the common conductive constituent element in the preparation of metamaterials such as metal, one-dimensional conductive carbon nanotubes (CNTs) provide another choice of functional phase. In this paper, barium titanate (BaTiO₃) with multi-walled carbon nanotubes (MWCNTs) uniformly dispersed in the ceramic matrix were prepared by traditional ceramic sintering technology. Field emission scanning electron microscopy, X-ray diffraction and Raman spectroscopy were used to characterize microstructures and phase composition of the metacomposites. With the increasing of CNTs content, the percolation phenomenon of electrical conductivity (9.95 wt%) was found and the conductive mechanism changed because of the formation of conductive MWCNTs networks. Moreover, the negative permittivity behavior was observed when the MWCNTs content reached 7 wt% and the plasma-like negative permittivity behavior could be well explained by the low frequency plasmonic state generated from conductive nanotube networks using the Drude model.