Dielectric Constant and Loss Measurements on Barium Titanate Single Crystals While Traversing the Hysteresis Loop

A small amplitude high-frequency voltage has been superposed on a large amplitude low-frequency sweeping voltage to study the dielectric behavior of barium titanate single crystals while traversing the hysteresis loop. The output of a capacitance bridge (filtered to pass only the high-frequency component) is displayed on an oscilloscope as a function of either the applied sweeping voltage, the polarization, or the current to the sample. As a result, the bridge can be balanced for any portion of the sweeping voltage cycle desired. The dielectric constant and loss obtained in this manner have been studied as a function of measuring frequency, of sweeping frequency, of sweeping voltage and of rate of switching polarization (current). The measuring frequency and the switching current are shown to be the significant variables. The frequency dependence of the dielectric constant and loss can be described by a relaxation type of spectrum with a relaxation time of 5.5 microseconds.