Time Domain Polarisation Measurements with the Sawyer-Tower Method

A system for time domain polarisation measurements in a wide time range which is based on the well-known Sawyer-Tower method is presented. The time dependent polarisation of dielectric samples is measured after the application of a voltage step. To this aim the voltages on three reference capacitors in series to the sample are measured with different data acquisition systems. During the measurement the capacitors are switched off one after another to avoid self-discharge. In this way the polarisation of the dielectric can be determined in a time range from 10-6s to 104s, i. e. over 10 decades, with one single run. From these data the polarisation current can be calculated as time derivative of the polarisation. Furthermore, the dielectric permittivity in the frequency domain can be calculated from the data in the time domain by Fourier transformation. Additionally the system allows the measurement of the switching behaviour of ferroelectric samples with a three-pulse method.