Tunable Bandwidth of Negative Permittivity from Graphene-Silicon Carbide Ceramics
Abstract
With tunable bandwidth of negative permittivity, graphene-silicon carbide (GR-SiC) ceramics were sintered by spark plasma sintering process. Compositions and structure were investigated by field emission scanning electron microscopy and Raman spectroscopy. With its content increasing, GR interconnected into “GR clusters” with larger lateral dimensions, which tended to be connected into conductive pathways instead of agglomeration under the action of ball milling. Permittivity, alternating current conductivity (σac), dielectric loss and imaginary reactance were analyzed in detail. When the GR content exceeded 6.30 wt%, a significant electrical percolation phenomenon occurred, and the conductive mechanism changed from electronic jump conduction to a metal-like conduction. Fano-like resonance, appertained to permittivity, exhilaratingly transformed into the Lorentz model. Owing to the mutual dielectric screening between SiC and GR, the bandwidth of negative permittivity became wider and can be tuned via the GR content.