Two complementary techniques: the thermal step technique and the thermally stimulated currents technique. Study of polycrystalline Al2O3

The information obtained using the Thermal Step Method (TSM) and the Thermally Stimulated Currents (TSC) technique are totally complementary. The TSM allows to determine and to localize the space charge density in insulating materials, while the TSC technique allows to obtain the average activation energies of the different processes of discharge or depolarization. In this paper, we discuss about the sensitivity of these two techniques to real charges and polarization. We show by coupling of these two methods that polycrystalline Al₂O₃ can accumulate space charges in the bulk (when the sample is poled under high DC voltage). These charges may be released when the TSC technique is applied to the sample. The charges distributions, given by the TSM, show polarization of the alumina when poled below 200°C, and a cathode electron injection above 200°C. The TSC gives the energy levels of the released charges corresponding to these phenomena