Thermally Stimulated Current (TSC) A spectroscopy technique to explore the structural organization of materials

摘要

Thermally Stimulated Current (TSC) is based on the ability of polar molecules to bernmoved by an electric static field. The principle is the following: at a temperature T_p, a field isrnapplied during a time t_p long enough to let the dipoles to orient themselves and thisrnconfiguration is frozen by quenching in order to reach a temperature T_0. At this temperature,rnthe sample is short-circuited during a time t_0 to remove the space charges and to equilibraternthe temperature. The progressive and sequential release of the entities oriented previously canrnbe observed during a linear rise in temperature. The depolarization current is recorded as arnfunction of the temperature giving the complex spectrum. This latter could be decomposed inrna series of elementary spectra by using the Fractional Polarization Technique allowing therndescribtion of each dielectric manifestation in terms of relaxation times and dynamicsrnparameters (△H,△S).It consists in applying the terms of relaxation times and dynamics temperature range to permit the selective orientation of dipolar entities characterized by a single relaxation time. The TSC peak thus recorded is "elementary", i.e. it obeys Debye's law. The movement of the range along the temperature axis permits the identification of thernelementary components of the complex relaxation spectrum, which is then resolved in arndiscrete distribution function. The temperature dependence of the elementary relaxation timesrnis obtained, without prior hypothesis, thereby permitting identification of the molecular sourcernof the process observed. Different examples are given in different domains, pharmaceutical, food, coatings orrnpharmaceutical…..to demonstrate that data obtained thanks to this technique have allowed arnbetter understanding, for example, of the behavior of a material under the influence ofrntemperature, oxidation, plasticization, crystallization or to explore the chemical organizationrnof complex structures.