ABSTRACT
The terms “dielectric analysis” (DEA) and “broadband dielectric spectroscopy” (BDS) refer to the same materials science experimental technique that can measure several physical properties in polar materials, i.e., polarization, permittivity, conductivity, impedance, etc. DEA is an experimental technique analogous to dynamic mechanical analysis (DMA) with the significant difference in the imposed externally oscillating field, which is electrical rather than mechanical. As in the case of DMA, experimental data depend on the frequency of the applied field and the imposed temperature. The externally applied electric field forces dipoles (permanent or induced) and unbounded charges to be oriented parallel to its direction. The oscillation of the applied field causes a reorientation of dipolar groups and charge carriers, which is related to their inertia, the interactions with their molecular environment, and the “viscosity” of the medium. The outcome is the occurrence of relaxation phenomena, since the time scale of the exciting field might be shorter than the substance’s response time. Dielectric relaxations are observed in many materials, such as glasses, polymers, ceramics, liquid crystals, composite materials, and disordered materials. Generally speaking, relaxation is the reversion of a system perturbed by an external stimulus to equilibrium. Each relaxation process is characterized by a relaxation time (τ).
