Negative permittivity in titanium nitride‐alumina composite for functionalized structural ceramics

Abstract

The study on novel physical properties of structural ceramics or ceramic composites could make them more conducive to be function‐ and structure‐integrated materials. Herein, titanium nitride‐alumina (TiN–Al2O3) duplex ceramics were prepared and the dielectric spectra of the ceramics were studied from 10 MHz to 1 GHz. Negative permittivity appeared when TiN content exceeded 40 wt% due to the induced plasmonic state of massive delocalized electrons in connected TiN grain networks. Meanwhile, alternating current conduction behaviors of the duplex ceramics were discussed with percolation theory. Furthermore, the analysis of reactance by equivalent circuit models indicated that negative permittivity ceramics exhibited inductive character. This work realized negative dielectric behaviors in TiN–Al2O3 duplex ceramics and would promote the study of electromagnetic functionalization in wave shielding or attenuation for structural ceramics.

Graphene–Carbon Black/CaCu3Ti4O12 Ternary Metacomposites toward a Tunable and Weakly ε-Negative Property at the Radio-Frequency Region

“…The ε-negative (negative permittivity ε′) property has drawn tremendous attention in electromagnetic field because of its promising applications to novel sensors, high-permittivity capacitors, broadband photodetectors, patch antennas, information encoding devices, and so on. − Recently, the ε-negative property can be obtained in metamaterials with an artificially periodical arrangement of subwavelength units and metacomposites with percolative networks composed of randomly distributed conductive units. , Typically, ε-negative in metamaterials closely relates with the geometric configuration of structural units, resulting in some limitations such as narrow response bandwidth and complex preparation process. , In contrast, ε-negative in metacomposites depends on materials’ intrinsic properties , and can be tuned by optimizing the percolative networks, and so metacomposites provide a flexible alternative for metamaterials because of their large-scale production and low cost. , …”

Ceramic‐based dielectric metamaterials

“…It provides an effective approach for the cofiring and integration of this type of material in applications. Fan et al [ 112 ] prepared TiN–Al 2 O 3 composite ceramics for the electromagnetic functionalization of wave shielding or attenuation. They studied the dielectric spectra of the composite ceramics from 10 MHz to 1 GHz, which demonstrated a conversion from insulating to metallic behavior similar to that of dielectric–metal‐based systems, achieving negative permittivity.…”

Electrical Transport in Polyaniline–Barium Ferrite Nanocomposites with Negative Giant Magnetoresistance

“…As described in Figure 3B, tan δ of BaFe 12 O 19 /PANI nanocomposites increases, in contrast to that of pure PANI, which is on account of interfacial polarization occurred by the addition of BaFe 12 O 19 nanoparticles into the PANI matrix. 46 In Figure 3B(a), the peak in the tan δ curve of pure PANI is about 1.0 × 10 4 at a frequency of 700 Hz, whereas the peak in the tan δ curve of BaFe 12 O 19 /PANI nanocomposites with BaFe 12 O 19 nanoparticle loading of 20 wt % is 2.2 × 10 6 at a lower frequency of 500 Hz, Figure 3B(c). The peaks in the tan δ curve depicted in Figure 3B may be attributed to the relaxation phenomenon.…”