The dielectric modulus: Relaxation versus retardation

Experiments which access the quantity ε*(ω) are usually termed dielectric relaxation methods, although ε*(ω) and ε(t) actually refer to dielectric retardation. The true dielectric relaxation, the modulus M(t), corresponds to the decay of the electric field under the conditions of a constant dielectric displacement. We have measured the polarization in terms of a real dielectric relaxation technique by studying the decay of the electric field E(t) ∝ M(t) for times 10^-3 s ≤ t ≤ 10⁶ s under constant charge conditions. This conceptually straightforward method bears the advantage of the ability to measure extremely large retardation times. Using the equivalent thermally stimulated technique we also investigate the equilibrium and non-equilibrium dynamic response of amorphous condensed matter well below its caloric glass-transition.