Complex conductance of carnauba wax/polyaniline composites

Abstract

Complex conductance, σ* (f) = sigma;(f) + iσ (f), measurements of polyaniline/carnauba wax composites were carried out at room temperature in samples containing different amounts of PAni, While σ (f) ever grows as a function of the frequency f, σ(f) was observed to vary as fn(n ≈ 1) in the high frequency domain, and to be frequency-independent for lower frequencies. This is the quasi-universal behavior characteristic of conduction in a disordered medium. Superposed on this, another signal was observed to occur, and the whole impedance response was then analysed in an Argand Diagram, disclosing an electrode process in series with the bulk one. An equivalent conductance expression was used to explain such electrical behavior, in which the bulk properties of the composite were represented through the Random Free Energy Barrier model, while the composite-electrode interface by a simple parallel combination of a capacitor and a resistor. From the theoretical fittings it was concluded that the increase of PAni concentration acts in the sense of increasing not only the sample conductance, but also the bulk capacitance. The separation of the bulk and the interface contributions was then achieved.