The Si3N4 is one of the leader high-tech ceramic nowadays. As a result of numerous developments excellent mechanical properties of the material are increased by carbon additives. In our previous investigation the electrical effect of the additives was examined. In our work thermo radiation measurements were used by infrared camera technique on conductor Si3N4 ceramic composites in infrared wavelength range. The thermal properties of the developed ceramic composites were determined. This is not easy with the ordinary methods because of the fashioning and geometrical parameters of the material. During the experiments the emissivity of our composites was determined by infrared thermography measurements. Based on a theoretical thermal conductivity model an evaluation method that allows a derivation of thermal conductivities of special geometry conductive materials from results of infrared measurements was established.