Bridge for Accurate Measurement of Ferroelectric Hysteresis

Abstract

A new instrument has been designed for the undistorted display of ferroelectric hysteresis loops even in the presence of relatively high conductivity. The electrical characteristics of a sample are determined directly from dial settings and meter readings. The basic circuit of the bridge may be described as two parallel Sawyer and Tower circuits, one containing the sample and the other containing resistors and capacitors for the compensation of conductivity and dielectric constant at saturation. The compensated hysteresis loop is displayed on an oscilloscope with the aid of a calibrated differential amplifier. The spontaneous polarization and the applied voltage, as well as the coercive field, are read on an electronic peak voltmeter. An important feature of the bridge is that measurements are independent of the frequency and wave form of the applied voltage.