5.3.10 Measurement of Hysteresis Loop

Ferroelectric hysteresis loops can be experimentally measured using a Sawyer-Tower circuit, using a high frequency ac  field, and are observed on the screen of an oscilloscope.

The circuit is schematically drawn below.  A linear capacitor C₀  is connected in series with the crystal. In this configuration, the voltage across C₀ is proportional to the polarization of the crystal. This circuit not only measures the hysteresis loop, it also quantifies the spontaneous polarization P_s and coercive field E_c

A ferroelectric materials shows polarization of the order of 50-100 μC/cm².

Nowadays, one can get commercially available instruments such as Radiant Premier Precision Station from Radiant Technologies which can perform polarization measurements at varying field and frequencies. For device measurements, one needs to establish top and bottom contacts to the ferroelectric materials which is typically achieved using thin platinum electrodes in thin films and silver paste in bulk ceramics.