Thermal Currents and the Internal Polarization in Carnauba Wax Electrets

Thermal currents have been obtained from carnauba wax electrets using a linear heating rate for various polarization fields, temperatures, times, and thickness of samples. The polarization is shown to be uniform, and hence space charges, resulting from either charge injection from the electrodes or macroscopic ion displacement, are ruled out as possible causes of the heterocharge. The case for dipole orientation is examined and it is shown that far too many dipoles must be aligned to produce the observed effects. Microscopic displacement of ions with trapping is proposed as the heterocharge mechanism. This model is consistent with the observed temperature dependence of the thermal currents, and does not appear to contradict any of the experimental facts. The thermal-current spectra consist of three overlapping peaks with activation energies of 1.7, 2.3, and 2.7 eV and temperature maxima of 47°, 59°, and 69°C, respectively. In the proposed model, these activation energies are to be associated with the ionic trap depths.