Abstract:The ambient electrical conductivity (AEC) of carbon cathode materials was investigated in respect to their open porosity, crystal structure and graphite content using hydrostatic method, four-probe technique and X-ray diffraction (XRD), respectively. The AEC is proportional to the specific conductivity (σ₀) and the exponential of (1-ε) (ε is porosity) by a quasi-uniform formula based on the percolation theory. The σ₀ can reflect the intrinsic conductivity of the carbon cathodes free of pores, and it depends on the mean crystallite size parallel to the layer (002). The exponent n is dependent on the materials nature of the cathode aggregates, while an averaged value, 4.65, can practically work well with 5 types of cathode materials. The calculation of σ₀ can be extended to the graphitic cathodes containing different aggregates using the simple rule of mixture.

Key words: carbon cathode; electrical conductivity; porosity; crystal structure; aluminium reduction cell