Antiferroelectric ceramic and multilayer ceramic capacitors have the advantages of high energy storage density, fast discharge speed, high discharge current, etc., which can improve the energy storage density of pulse power device and effectively suppress ripple in power electronic system, etc. Unlike ferroelectrics, antiferroelectric materials adjacent to the lattice of dipoles reverse parallel, and therefore do not show a macroscopic spontaneous polarization phenomenon. In a certain external electric field, the dipoles redirect, the antiferroelectric phase converts to a ferroelectric phase, the polarization intensity increases abruptly after the withdrawal of the external electric field, and it returns to an antiferroelectric phase. This polarization/phase transition behavior can be characterized by the hysteresis loop. In the hysteresis loop, antiferroelectric material shows a double loop, and it is divided into two kinds, i.e., "Square" and "Slant" according to the different shapes of the antiferroelectric hysteresis loop. The polarization effect of the antiferroelectric capacitor gives it the better energy storage characteristics and discharge performance, thus having an advantage in practical applications. General capacitors are polarized under a certain period of time and voltage in the factory. However, changes of external conditions (i.e., temperature, voltage, time, etc.) can depolarize the antiferroelectric capacitor. Also, some antiferroelectric capacitors need to consider the effect of polarity. As a result, the practical application of antiferroelectric MLCCs is different from that of conventional Class I or Class II MLCCs. Therefore, in this paper, antiferroelectric ceramics with hysteresis loop shapes of "square" and "slant" were prepared by a conventional solid-phase reaction method to investigate the polarization effect of antiferroelectric ceramics and capacitors, and provide a guidance for the application of antiferroelectric MLCCs.

For the preparation of the antiferroelectric ceramic, the raw materials were weighed according to the chemical formula. The excess Pb₃O₄ was used to compensate for lead loss in sintering. The weighed raw materials were mixed in a mass ratio of 1.0∶1.0∶1.5 and ground in anhydrous alcohol by grinding in a ball mill with zirconium balls at 300 rpm for 20 h. After ball-milling, the slurry was pre-fired at 850 ℃ for 3 h. The film was formed, and heated at 1 280 ℃ for 2 h. The samples were prepared after polished with sandpaper to a certain thickness (less than or equal to 0.1 mm) and sputtered with gold electrodes. The micro-morphology of the samples was measured by a model JSM-6390A scanning electron microscope (SEM, JOEL Co., Japan). The crystalline phase composition was determined by a model D/Max-2400 X-ray diffractometer (XRD, Rigaku Co., Japan), using Cu K_α rays, with a scanning range of 20°-70°. The hysteresis loops and polarization current curves of the samples were examined by a model TF Analyzer 2000 ferroelectric test system (aix-ACCT Co., Germany). The basic principle of the test was based on the Sawyer-Tower circuit. The test frequency was 1 Hz, and the voltage waveform was a triangular wave. The pulse discharge test used a self-built platform.

From the SEM images of the samples, the grains are uniform and have a good densification. From the XRD patterns of the samples, the prepared samples have a quadrilateral phase structure. The prepared samples have a typical double hysteresis loop, and the shapes of hysteresis loops for sample S1 and S2 are "square" and "slant". The hysteresis loops of the samples after and before polarization indicate that for the unpolarized ceramic sample, the transition field is higher, the stored energy density and energy conversion efficiency are lower. This phenomenon is also related to the shape of the hysteresis loops, so the polarization has a certain impact on the practical application of antiferroelectric ceramics. The electric hysteresis loop nearby transition field shows that for capacitors with antiferroelectric ceramic dielectrics, the antiferroelectric capacitor is unpolarized (or is depolarized) if the operating voltage is set nearby the transition field, thus leading to a weakening of its performance. To analyze whether high temperature should have an effect on the degree of polarization of antiferroelectric ceramics, the capacitances of the antiferroelectric ceramics are tested after depolarization at different temperatures, and the pulse discharge currents of the antiferroelectric MLCCs after depolarization at different temperatures are tested. The results show that if the antiferroelectric capacitor is overheated and warmed up, and although the temperature is recovered after using, the temperature still has a certain effect on the performance of antiferroelectric capacitor, especially at a lower applied voltage. To study the effect of polarity on the antiferroelectric material, the hysteresis loops of antiferroelectric ceramics in positive and negative electric fields were tested, and the pulse discharge of antiferroelectric MLCCs in different polarity electric fields was tested. The results show that the antiferroelectric domains are preferentially oriented, and the antiferroelectric domains have a memory effect after a certain direction of the electric field polarization, preventing its entry into the opposite direction of the ferroelectric domains. And this effect is more serious on the antiferroelectric ceramics with a "square" hysteresis loop.

The antiferroelectric polarization and polarity characteristics had dominant effects on their applications. Those effects above were lower although antiferroelectric capacitors were generally made of materials with "slant" hysteresis loops. However, since antiferroelectric materials were in an electric field that was slightly higher than the E_AFE-FE phase transition field, their depolarization and polarity characteristics still affected their performance. In addition, a slight attenuation of the antiferroelectric MLCCs performance still adversely affected the reliability of the whole system since some applications required an extremely high reliability. In practice, antiferroelectric MLCCs were bound to depolarize after soldering, and their performance could be greatly degraded if the applied electric filed was lower than the transition field.