TiN/Al2O3 binary ceramics for negative permittivity metacomposites at kHz frequencies

Abstract

Metacomposites with negative permittivity have attracted much attention due to their potential applications in electromagnetic shielding, novel capacitances and sensors. In this work, percolative TiN/Al2O3 ceramic composites with different TiN content were sintered and the dielectric properties were investigated from 5 kHz to 1 MHz. When the filling content of TiN increased from 20 wt% to 30 wt%, percolating phenomenon was observed and TiN grains became interconnected rather than being isolated in Al2O3 ceramic matrix. Meanwhile, electric conductivity of the ceramic composites was enhanced as TiN was incorporated and the conduction mechanism changed from hopping conduction to metal-like conduction. Compared to pure Al2O3 ceramics, the enhancement of permittivity in composites with 10 wt% and 20 wt% TiN was caused by the increased interfacial polarizations, while negative permittivity observed in composites with 30 wt% and 40 wt% TiN was attributed to the plasmonic state of electrons in percolating networks formed by TiN grains. Thus, it’s demonstrated that TiN/Al2O3 binary ceramics can be negative permittivity metacomposites. This work enriched the electromagnetic properties of TiN/Al2O3 ceramic composites.