An explanation of the peculiar behavior of TSDC peaks at Tg: a simple model of entropy relaxation

Abstract

Thermally Stimulated Depolarization Current (TSDC) signals measured in polymers at the glass transition T g often exhibit intricate shapes that much depend on the thermal history and on the non-stationary condition used during experiments. This peculiar behavior is frequently explained in terms of a physical singularity of the molecular motions. We show that this singularity, i.e. unexpected values for activation energy and pre-exponential factor, obtained around T g , result from the misuse of the Arrhenius law for treating the experimental data obtained in non-stationary experimental conditions. A simple model using time dependent configurational entropy for the material evolution and using a single Debye relaxation for the dielectric relaxation process is therefore proposed to explain the experimental behavior. The influence of the heating rate and of a non-Debye relaxation on the TSDC signal is also studied and clearly shows that the peculiar behavior of TSDC peaks can originate from the conjugated effects of entropy relaxation and non-Debye response.

Giant Discharge Current in Thermally Poled Silicate Glasses

“…This shows an incomplete depolarization of poled glasses in all earlier performed TSDC measurements except that reported in ref . Additionally, TSDC studies of polymers have shown the importance of the experiments at temperatures in the T g region. , …”

“…Additionally, TSDC studies of polymers have shown the importance of the experiments at temperatures in the T g region. 16,17 In this paper we report extremely high depolarization currents observed in poled silicate glasses above T g (550−800 °C). The measured currents were found to be 5−6 orders of magnitude higher than the ones reported in the aforementioned TSDC studies of similar glasses below T g (200−500 °C).…”