Dielectric evolution of permittivity transition from positive to negative induced by percolation in ceramic composites

Abstract

Ceramic composites made up of well-selected components have enriched the varieties of the metamaterials with negative electromagnetic parameters. In this work, TiN/BaTiO3 ceramic composites were prepared with a simple dry-pressing and pressureless sintering process. Percolation was eventually determined to be the key inducements which caused the permittivity of the ceramic composites changing from positive to negative. Essentially, negative permittivity was closely related to the plasma oscillations of free electrons in percolation networks. Meanwhile, conduction mechanism of the composites varied owing to the changes in microstructure, where the percolation networks brought out pathways for electron migration and achieved high conductivity. In addition, ac impedance behavior with changes of the sign for reactance were also discussed, thus the transition from electrical capacitive to inductive for the percolative ceramic composites has been demonstrated. This work clarified the influence of percolation on the conductivity, impedance, and permittivity of ceramic composites altogether. The obtained negative permittivity composites have enormous potential in various electronic devices and electromagnetic apparatus.