Analysis of complex dielectric spectra. I. One-dimensional derivative techniques and three-dimensional modelling

Several strategies for the analysis of isochronal and isothermal spectra as well as complete three-dimensional (3D) spectra are outlined and applied to data of (glass forming) liquids and polymers. Conduction-free loss spectra are calculated using a compact solution of the Kramers–Kronig transformation and an approximation based on ∂ε′/∂ ln ω. The usefulness of the dielectric modulus for data analysis is also evaluated. Apart from ∂ε′/∂ ln ω, other useful derivatives in the frequency and temperature domain are treated as well. Finally, we describe the evaluation of 3D-relaxation maps by means of 3D fitting.