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Dielectric energy-storage capacitors are among the main enabling technologies in high-density power converters, in which lead-free relaxor ferroelectric ceramics have been paid particular attention to. However, low energy-storage performance at elevated temperature and high electric field, and the lack of application-oriented evaluation are among the primary blocks stumbling their progress. As a demonstration, 0.87BaTiO3-0.13Bi[Zn2/3(Nb0.85Ta0.15)1/3]O3 (BTBZNT) lead-free relaxor ferroelectric ceramics were modified by linear dielectric CaZrO3 (CZ) with various contents of 0, 0.1, 0.2, and 0.3 (CZ0, CZ1, CZ2, and CZ3). XRD and Raman results reveal major perovskite phases, and densely sintered ceramics were witnessed from the SEM images. Unchanged weakly coupled relaxor behavior was confirmed by the big critical coefficient of 1.6–1.8 from the modified Curie–Weiss law and the large activation energy of 0.29–0.32 eV from the Volgel–Fulcher fittings, and CZ was found to suppress high-temperature loss. From the normal polarization–electric field (P–E) loops, CZ0 is optimal for energy-storage owing to the highest discharged energy density and modest efficiency. Nevertheless, from the application-oriented DC-biased P–E loops, CZ1 is oppositely superior to CZ0 because of the higher permittivity and lower loss leading to higher discharged energy density and efficiency at DC-biased electric field. Moreover, CZ1 outperforms CZ0 in the higher capacitance density and lower temperature rise at higher temperature and electric field. Enhanced DC-biased energy-storage performance in BTBZNT ceramics modified by CZ was achieved, which should enlighten the advance of energy-storage ceramics targeting the application in high-density power converters. [ABSTRACT FROM AUTHOR]

With the development of the power industry and the increase in the capacity of power systems, vacuum switches have been developed rapidly. The distribution characteristics of the vacuum arc can reflect the working conditions of the vacuum switch. So, it is vital to understand the distribution characteristics in the vacuum arc burning process for understanding the interruption performance of vacuum switches. Based on the 3D magnetohydrodynamic model, we investigated the high-current vacuum arc burning process by modeling and numerical simulation. The research findings show a certain correspondence between the change in plasma parameters values and the change in arc current. The distribution of plasma parameters is uniform when the current is small. The distribution of plasma parameters in the first 1/4 cycle is more uniform than in the second 1/4 cycle. The evolution characteristics of the arc plasma parameters for interruption before the arc current maximum differ significantly from those for interruption after the arc current maximum and current maximum. The results of this study can provide a reference for the design and improvement of vacuum switches. [ABSTRACT FROM AUTHOR]

The boom in high-power-density electronics and advanced pulsed power systems has led to a requirement for high-energy-density dielectric capacitors, for which the key enabler is the availability of dielectric materials with high energy densities and high efficiencies. Although antiferroelectric ceramics are promising dielectric materials with high energy densities, they have low efficiencies. In this study, we address this problem through the core–shell structure design. A phase-field model is developed by considering the core as antiferroelectric and the shell as linear dielectric, and the polarization hysteresis loops are determined. The results show that the polarization–electric field loop of the core–shell sample is slanted, with a delayed saturation polarization, decreased maximum polarization, and declined hysteresis loss compared with the pure sample. This phenomenon becomes more distinct with increasing shell fraction and decreasing shell permittivity, and vanished hysteresis is achieved in samples with a high shell fraction and a low shell permittivity. Through deconvolution, it is determined that the underlying mechanism of energy storage is the difference in the antiferroelectric polarization contribution of various shell parameters. It is found that a giant energy density of 15.5 J/cm3 and an ultrahigh efficiency of 99.7% at the saturation polarization can be achieved concurrently for a certain core–shell sample; these values considerably exceed the corresponding values (5.0 J/cm3 and 52.8%) for the pure sample. The findings of this study can serve as guidance for engineering core–shell structures, thus paving the way for enhancing the energy-storage performance of antiferroelectric ceramics. [ABSTRACT FROM AUTHOR]