Low-temperature sintering Graphene/CaCu3Ti4O12 nanocomposites with tunable negative permittivity

Since negative permittivity demonstrated in metamaterials, how to effectively tune negative permittivity still the challenge to satisfy practical applications. Meta-composites could provide alternative routes to tunable negative permittivity. In this paper, Graphene/CaCu3Ti4O12 (GR/CCTO) meta-composites with different GR content were fabricated by low-temperature pressureless sintering. Microstructures and compositions of GR/CCTO were investigated in detail. The electrical and dielectric properties of GR/CCTO nanocomposites were investigated at 10 kHz - 1 MHz and 20 MHz - 1 GHz region respectively. AC conductivity spectra showed different variation trends which were explained by Jonscher's power law or Drude model, indicating conductive mechanism transformation from hopping conduction to metal-like conduction. Lorentz-type and/or Drude-type negative permittivity behaviors were observed at radio-frequency region. Tunable negative permittivity were realized by changing GR content in GR/CCTO nanocomposites. Correspondence between inductive characteristic and negative permittivity was manifested by equivalent circuit analysis of impedance response of GR/CCTO composites. This work not only presents novel routes to tune negative permittivity, but also further clarifies negative permittivity generation mechanism, which will greatly facilitate applications in impedance matching, electromagnetic shielding and multi-layer high-k capacitors etc. (C) 2018 Elsevier B.V. All rights reserved.