Electrical property changes of liquid carbon under high pressures

The homogeneous formation of liquid carbon without the partial melting of carbon specimen is very important to evaluate the physical properties of liquid carbon. The pyrolytic graphite was melted by the direct joule heating with current passed through the specimen along the direction parallel to c-plane. The resistivity of the liquid carbon at the melting point decreases from 630 to 470 μ Ωcm with increase of pressure of 1.4 to 4.0GPa and then increases 490 to 565 μ Ωcm with increase of 5.6 to 9.4GPa. The magnitude of resistivity of the liquid carbon at the melting point within this experiment indicates that the liquid carbon is a " poorly conductive metal ". On the other hand the resistivity of liquid carbon tends to change from metal like behaviour (the temperature coefficient of resistivity d ρ /dT> 0) to non-metal (or semiconductor) like one (d ρ /dT<0) at the pressure of around 4GPa-5.6GPa. These results are considered to fortify our previous conclusion about the existence of the structural transformation of carbon in the liquid state [1].