Negative permittivity behavior in the carbon/silicon nitride composites prepared by impregnation-carbonization approach

The carbon/silicon nitride (C/Si3N4) composites consisting of amorphous carbon dispersed in porous Si3N4 matrix were herein prepared by facile impregnation-carbonization process at low temperature. The microstructures and electrical properties of C/Si3N4 composites were investigated in detail. A percolation phenomenon and an insulator-conductor transition appeared in the composites with the increase of carbon content. The formation of continuous conducting carbon network led to the plasma-like negative permittivity behavior in the composites above the percolation threshold (between 8.1 and 10.9 vol%), and the frequency dispersions of negative permittivity can be fitted well by Drude model. Carbon materials can be regarded as a good candidate for realizing negative permittivity, and the preparation of C/Si3N4 composites by the facile impregnation-carbonization approach offers the important possibility of tuning the negative permittivity.