Ferroelectrics/antiferroelectrics with high dielectric breakdown strength have the potential to store a great amount of electrical energy, attractive for many modern applications in electronic devices and systems. Here, it is demonstrated that a giant electric energy density (154 J cm⁻³, three times the highest value of lead‐based systems and five times the value of the best dielectric/ferroelectric polymer), together with the excellent fatigue‐free property, good thermal stability, and high efficiency, is realized in pulsed laser deposited (Bi_1/2Na_1/2)_0.9118La_0.02Ba_0.0582(Ti_0.97Zr_0.03)O₃ (BNLBTZ) epitaxial lead‐free relaxor thin films with the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases. This is endowed by high epitaxial quality, great relaxor dispersion, and the coexistence of the FE/AFE phases near the morphotropic phase boundary. The giant energy storage effect of the BNLBTZ lead‐free relaxor thin films may make a great impact on the modern energy storage technology.

A highly textured (111)-oriented Pb_0.8Ba_0.2ZrO₃ (PBZ) relaxor thin film with the coexistence of antiferroelectric (AFE) and ferroelectric (FE) phases was prepared on a Pt/TiO_x/SiO₂/Si(100) substrate by using a sol–gel method. A large recoverable energy storage density of 40.18 J/cm³ along with an efficiency of 64.1% was achieved at room temperature. Over a wide temperature range of 250 K (from room temperature to 523 K), the variation of the energy density is within 5%, indicating a high thermal stability. The high energy storage performance was endowed by a large dielectric breakdown strength, great relaxor dispersion, highly textured orientation, and the coexistence of FE and AFE phases. The PBZ thin film is believed to be an attractive material for applications in energy storage systems over a wide temperature range.

Flexoelectricity refers to the mechanical-electro coupling between strain gradient and electric polarization, and conversely, the electro-mechanical coupling between electric field gradient and mechanical stress. This unique effect shows a promising size effect which is usually large as the material dimension is shrunk down. Moreover, it could break the limitation of centrosymmetry, and has been found in numerous kinds of materials which cover insulators, liquid crystals, biological materials, and semiconductors. In this review, we will give a brief report about the recent discoveries in flexoelectricity, focusing on the flexoelectric materials and their applications. The theoretical developments in this field are also addressed. In the end, the perspective of flexoelectricity and some open questions which still remain unsolved are commented upon.

The dielectric properties of $\mathrm{Ca}{\mathrm{Cu}}_3{\mathrm{Ti}}_4{\mathrm{O}}_{12}$ (CCTO) ceramics have been investigated in a temperature range of $143–573\mathrm{K}$ and a frequency range of $1\mathrm{Hz}–10\mathrm{MHz}$ . A dielectric anomaly has been observed between 350 and $600\mathrm{K}$ . The broad dielectric peaks in ${\epsilon }^{\prime }\left(T\right)$ can be well fitted by a modified Curie-Weiss law and a Vogel-Fulcher relationship, which is indicative of a relaxor ferroelectric behavior. A slim $I\text{-}V$ loop as well as the $P\text{-}E$ hysteresis loop and broad maxima in ${\epsilon }^{″}\left(f\right)$ also suggest the existence of a relaxor ferroelectric behavior in CCTO ceramics.