A new graphical representation for dielectric data

Abstract

A method of graphically representing complex dielectric data is described, which is particularly useful for situations where the Cole–Cole representation is unsuitable. The representation emphasizes the orientational dipolar contribution to the conductivity by plotting σχ″=ωεv(ε′−ε∞) vs σχ′=ωεvε″. We discuss the utility of the representation for conducting dielectrics and for studying multirelaxation processes, particularly modes with smaller amplitudes (absorption) at high frequencies. For a Debye relaxation with dc conductivity, this representation leads to a semicircle, whereas the Cole–Cole plot shows a divergence. Even in the absence of conductivity, this representation is useful particularly at high frequencies, where it enables the identification of multirelaxation processes not apparent in the Cole–Cole representation. A particularly striking example is the clear observation of two relaxation processes in dielectric data on 1-propanol. We also show that in this σχ representation, all the well-known functional forms such as Cole–Cole and Cole–Davidson, approach an asymptotic slope at high frequencies. Applications of the σχ representation to analysis of dielectric spectra taken up to 20 GHz are discussed for pure glycerol and LiCl/propanol solutions.