Temperature dependence of resistivity of carbon black-polyethlene composites below and above the percolation threshold

Temperature dependence of resistivity ρ of carbon black (CB)-polyethylene composites with volume fraction ρ below and above percolation threshold ρ_c is studied based on the electrical conduction mechanism. The temperature dependence of ρ of the composites with ρ below ρ_c can be explained with a tunneling conduction model by incorporating the effect of thermal expansion of the composites into a tunneling gap. On the other hand, the temperature dependence of ρ of the composites with ρ above ρ _c shows a negative TCR in low temperatures and the absolute value of TCR is getting larger with more CB loading. By assuming that the electrical conduction through percolating paths is a thermally activated process and incorporating the effect of thermal expansion into ρ, the temperature dependence of ρ above ρ_c has been well explained and the apparent activation energy is estimated at 0.14 eV