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In this paper, AC measurements on lightly doped n-InP were carried out as a function of temperature down to about 16 K and at frequencies in the range from 120 Hz up to 10 5 Hz. The AC conductivity at low temperatures is of a single hopping nature following the universal law; σ(ω) ∼ ω s , where the exponent, s, is temperature-independent. At relatively high temperatures (but still below the room temperature) the AC conductivity is of a multiple hopping nature.

Temperature and concentration dependence of electrical resistance of butyl rubber filled with GPF carbon black was carried out. Current–voltage (I–V) characteristics at room-temperature were also investigated. The I–V characteristics show that the behavior is linear at small voltages up to approximately 0.15 V and currents up to 0.05 mA indicating that the conduction mechanism was probably due to electron tunneling from the end of conductive path to the other one under the action of the applied electric field. At higher voltages, a nonlinear behavior was noticed. The nonlinearity was attributed to the joule heating effects. Electrical resistance of the butyl/GPF composites was measured as a function of temperature during heating and cooling cycles from 300 K and upward to a specific temperature. When the specimens were heated up, the resistance was observed to increase continuously with the rise of temperature. However, when the samples were cooled down, the resistance was observed to decrease following a different path. The presence of conduction hysteresis behavior in the resistance–temperature curves during the heating and cooling cycles was then verified. The electrical conduction of the composite system is supposed to follow an activation conduction mechanism. Activation energy was calculated at different filler concentrations for both the heating and cooling processes.

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