Design and analysis of negative permittivity behaviors in barium titanate/nickel metacomposites

As an important supplement to the metamaterials , negative permittivity in 'natural' materials has attracted increasing attention, while some fundamental regulation mechanisms and common theoretical principles have not yet been systematically explored. In this paper, the permittivity transition is investigated along with insulator-conductor conversion in BaTiO 3 /Ni composite. When the Ni content in BaTiO 3 /Ni composites is lower than and higher than the percolation threshold, Lorentz-like and Drude-type negative permittivity behaviors is obtained, respectively. In addition, the fundamental principles of negative permittivity are discussed, especially the validity of the Kramers–Kronig relations and the relationship between the negative permittivity and the reactance characters. Further, a universal regulatory mechanism of the Drude-type negative permittivity profile is qualitatively analyzed. Negative permittivity and negative permeability are achieved simultaneously in BaTiO 3 /Ni composites with 35.56 vol% of Ni loading, which show potential application in electromagnetic wave absorption and shielding.