Under a relatively strong alternating electric field, the polarization intensity P of ferroelectric materials changes nonlinearly with the applied electric field. Within a certain temperature range, the polarization intensity P behaves as a double-valued function of the electric field strength E, resulting in a hysteresis phenomenon and forming the relationship curve between polarization intensity P and electric field strength E as shown in Figure 1, which is commonly referred to as the ferroelectric hysteresis loop.
This standard adopts the Sawyer-Tower circuit to measure the ferroelectric hysteresis loop. The alternating electric field is supplied by an ultra-low-frequency high-voltage source, and the hysteresis loop is recorded using an X-Y function recorder. Based on the measured hysteresis loop, the coercive electric field strength Ec, remanent polarization Pr, and spontaneous polarization Ps are calculated.