Dielectric data analysis: recovering hidden relaxations by fourth-order derivative spectroscopy

Complex materials exhibit a dielectric behavior that can shed light on their chemo-physical structure through a comprehension of the physical mechanisms originating that behavior. For the interpretation of a complex dielectric shape, where multiple relaxations are present (and usually described by semi-empirical functions), a correct interpretation of each simple relaxation is necessary. The separation of often closely overlapped relaxation curves requires the verification of the meaningfulness of such multiple relaxations and to determine their number and relative magnitudes, in other words to resort to a fitting procedure. However, often the physical interpretation of the fitting parameters is not straightforward, and their physical meaning is arguable. The application of even-order derivative spectroscopy is here demonstrated to be able to detect the presence and location of multiple dielectric relaxations, acting on the experimental data without any "a priori" hypothesis.