The pulse power capacitors can be used in military, medical, and aerospace fields due to their high power density and rapid charge-discharge capabilities. Despite these advantages, limited energy storage capacity and efficiency become challenges in achieving miniaturization and high-power performance. Among dielectric energy storage materials, antiferroelectric materials are regarded as promising for high-performance pulse power capacitors due to their distinctive double hysteresis loops, lower residual polarization, and higher energy storage efficiency. However, the breakdown strength decreases due to non-uniform electric field when the resistance of ceramic grain is equal to that of grain boundary, resulting in a decrease of energy storage density. Therefore, the enhancement of grain boundary impedance plays a key role in improving the dielectric breakdown strength of the system. In this paper, (Pb_(1-1.5x)Tm_x)(Zr_0.55Sn_0.44Ti_0.01)O₃ (x=0.00, 0.02, 0.04, 0.06) antiferroelectric ceramics were prepared via tape casting. The strategy of grain boundary impedance was constructed via enhancing the grain boundary quantity.

Powders of Pb₃O₄, Tm₃O₂, ZrO₂, SnO₂, and TiO₂ as raw materials were precisely weighed according to their chemical formulae after drying. The powders were mixed with alcohol and then ground in a ball mill for 24 h. Afterwards, the mixture was dried and pre-sintered at 850 ℃, and further ground in a ball mill for 24 h. The ground powders were mixed with toluene ethanol as a solvent, polyvinyl alcohol as an adhesive and butyl phthalate as a plasticizer. After 24 h milling, the mixture underwent degassing for 40 min, resulting in a slurry with an optimal fluidity. A flexible film with a thickness of 0.02 mm was produced via casting at a linear speed of 40 cm/min, and dried for 6 h. This film was then compressed into a block with the sizes of 10.0 mm×10.0 mm×0.5 mm. The samples were sintered in a muffle furnace via increasing the temperature from room temperature to 600 ℃ for 12 h to firstly remove the adhesive and then at 1 300 ℃. The sintered samples were cooled to room temperature.

The crystal structure of PTZST ceramics at room temperature was determined by X-ray diffraction. The ion vibration mode and the degree of disorder in the local structure were characterized by Raman spectroscopy. The surface morphology and grain size of the ceramic samples were analyzed by scanning electron microscopy. The particle sizes were determined by a software named Nano Measure. The dielectric temperature spectra were analyzed. The hysteresis curves were measured at various electric fields and temperatures as well as at a constant electric field intensity of 10 Hz, by a ferroelectric testing system. The test samples had a thickness of 0.1 mm and an electrode diameter of 2 mm. The impedance data were recorded by a high-temperature dielectric test system and subsequently analyzed by a software named ZView to evaluate the electrical performance of the samples.

All the PTZST ceramics exhibit a pronounced perovskite structure without elemental distortion, as evidenced by X-ray diffraction analysis. The orthogonal antiferroelectric phase of these ceramics is confirmed through superlattice diffraction and component selection analysis. The scanning electron microscopy images reveal that the grain size of the ceramics decreases with increasing Tm³⁺ content. This phenomenon is attributed to the formation of lead ion vacancies induced by the substitution of high valence Tm³⁺ for Pb²⁺, subsequently inhibiting oxygen vacancy formation and grain growth. Moreover, this modification increases the number of grain boundaries, enhancing the effectiveness of the grain boundary impedance strategy. However, excessive Tm³⁺ doping deteriorates the sample properties. The analysis of the P-E loops indicates a change in the energy storage density of PTZST ceramics. The PT4ZST ceramics demonstrate the maximum energy storage density (i.e., W_rec=9.37 J/cm³) and efficiency (i.e., η=77%). There is little variation in energy storage density at 30-120 ℃.

The impedance spectrum transformation from two semicircles to a single semicircle indicates the effective implementation of the grain boundary impedance strategy. This alteration enhances the dielectric breakdown strength of PTZST ceramics, thereby augmenting the energy storage density.

In exploring practical applications, charge-discharge tests were conducted. The discharge energy density of PT4ZST ceramics increases with increasing applied electric field, having the maximum value at a discharge energy density (i.e., W_dis=5.5 J/cm³) and a discharge rate (i.e., t_0.9=199.85 ns).

The original long-range ordered structure was disrupted via doping Tm³⁺ in the A-site to replace Pb²⁺, reducing a tolerance factor and stabilizing an antiferroelectric phase. Consequently, this led to an improved dielectric breakdown and an enhanced energy storage capability. The results indicated that the PT4ZST ceramics achieved a high dielectric breakdown (i.e., E_b=490 kV/cm) and a significant energy storage density (i.e., W_rec=9.37 J/cm³). These ceramics exhibited a high energy storage efficiency (i.e., 77%) and a substantial discharge energy density (i.e., W_dis=5.5 J/cm³), coupled with a rapid discharge rate (i.e., t_0.9=199.85 ns). Furthermore, the PT4ZST ceramic had a superior temperature stability at 30~120 ℃. The results indicated that the PT4ZST ceramic could be used as an effective material for high-temperature pulse power capacitors.