Direct Observation Method of Electric Field in Dielectric Samples by using Piezoelectric Element Thicker than the Samples

This paper describes a novel method for direct observation of electric field profiles in dielectric films, based on an improved PEA technique. This method uses a very long pulse voltage and a piezoelectric element thicker than the dielectric films. The long pulse voltage generates pressure waves, which can be approximated by a step function. These waves are detected by the thick piezoelectric element, which acts as a pressure integrator. In contrast, the transducer acts as a differential circuit, resulting in an output signal shows the electric field profile. The effectiveness of this method is confirmed using PVDF with a thickness of 80 µm and PET films with thicknesses of 50 µm as the test samples. The results show that the electric field profiles can be clearly observed when the rise time of the long pulse voltage is less than a few ns. A spatial resolution of 10 mm can be achieved even without deconvolution treatment. Space charge distributions can also be derived by differentiating the measured electric fields.