Adjustable negative permittivity behavior of high entropy (Ti0.25Zr0.25Nb0.25Ta0.25)C ceramics with different sintering temperatures

The emergence of high-entropy ceramics has provided a new effective strategy for adjusting the electrical properties of ceramics. Herein, high-entropy (Ti_0.25Zr_0.25Nb_0.25Ta_0.25)C ceramics were successfully prepared by the hot-pressure sintering at different sintering temperatures, and the effect of sintering temperature on their composition, conductivity and dielectric properties was investigated. The conductivity of the ceramics showed a decreasing trend with increasing sintering temperature. The ceramics displayed negative permittivity, which arisen from the low-frequency plasma state of free electrons in ceramics. The values of negative permittivity became larger with increasing sintering temperature, which was well analyzed by the Drude model. As the sintering temperature raised, the enhanced lattice distortion could inhibit the movement of free electrons, thereby leading to the reduced conductivity and increased negative permittivity. This study for the first time reported tunable negative permittivity behavior in high entropy ceramics, which is helpful to expand the research scope of high entropy ceramics.