Strain engineering has emerged as a powerful strategy for tailoring the ferroelectric properties and interfacial charge transport behaviors in complex oxide heterostructures. However, the underlying coupling mechanisms between strain-induced polarization reversal and defect-mediated barrier modulation remain in-depth understanding. In this study, controllable strain gradients are introduced through the use of intermediate layers to simultaneously manipulate the polarization orientation of BaTiO₃ thin films and modulate interfacial barrier properties. We systematically investigate the interplay among strain states, polarization behavior, and oxygen vacancy dynamics. Opposing strain states induce distinct polarization orientations in BaTiO₃, as confirmed by phase reversal and local hysteresis loops. Vacuum annealing is employed to tune the overall oxygen vacancy concentration, while flexoelectric field induced by strain gradient governs the migration and spatial distribution of vacancies. Compressive and tensile strains respectively drive oxygen vacancy accumulation near the surface or at the bottom interface, thereby modulating the Schottky barrier height and associated rectifying behavior. These results reveal a synergistic mechanism whereby flexoelectric polarization and strain-driven redistribution of oxygen vacancy cooperatively regulate charge transport in ferroelectric heterostructures.

Antiferroelectric materials release and store a large amount of energy during field-induced phase transition, which is of great value in the field of energy storage. Lead-free silver niobate (AgNbO₃) antiferroelectric ceramics have attracted much attention as environmentally friendly energy storage materials. On the basis of a large number of existing studies, this paper introduces the latest development of lead-free antiferroelectric ceramics represented by AgNbO₃ in the field of dielectric energy storage from the perspective of structure characteristics and performance control. The existing methods of energy storage performance control are summarized from two perspectives of component control and process optimization, and the origin mechanism of energy storage enhancement is classified. The energy storage performance of silver niobate antiferroelectric ceramics is prospected. It is believed that this paper will provide new ideas for the future research on the improvement of energy storage performance of AgNbO₃-based antiferroelectric materials.

Strategies to improve the efficiency of piezoelectric catalysis have long focused on piezo-optical coupling and construction of heterojunctions. However, it is a challenge to reinforce the performance of piezoelectric catalysis in a single material. Herein the built-in nanopores in single-crystal ZnO rods are employed to form stress to intensify piezo-catalytic efficiency. The piezo-catalytic efficiency of the ZnO rods with built-in nanopores (holey ZnO NRs) for degrading dyes was about 1.7 times that of the ZnO rods without built-in nanopores (ZnO NRs). X-ray diffraction and Raman peaks of holey ZnO NRs appeared blue-shifted in comparison to ZnO NRs, uncovering the existence of tensile stress in holey ZnO NRs. The piezoelectric coefficient d₃₃ of holey ZnO NRs increased by 1.92 times, triggering the amplification of piezoelectric catalytic property. Additionally, the piezoelectric current, carrier lifetime, and diffusion length of holey ZnO NRs were larger than that of ZnO NRs, respectively. These factors all contribute to the enhanced piezoelectric catalytic efficiency of holey ZnO NRs. This work demonstrates that the method of induced stress with built-in nanopores is a promising strategy for improving the piezoelectric catalytic efficiency of single-crystal ZnO rods.

It is a challenge to obtain highly tunable multifunctional performances in one ferroelectric system by a simple approach to meet the miniaturization, integration, and functionalization requirements of advanced electronic components. Herein, rare earth erbium (Er) modulated 0.9K_0.5Na_0.5NbO₃-0.1Sr_(1-x)Er_xTi_(1-x/4)O₃, (0.9KNN-0.1ST: xEr) transparent-photoluminescent-ferroelectric energy storage multifunctional ceramics are prepared to solve this problem. The effect of lattice distortion and oxygen vacancies by Er doping on the optical and electrical properties is systematically investigated. The Er³⁺ ions can introduce a large distortion of the NbO₆ octahedron by replacing the A-site in KNN-based ceramics. Thanks to the higher c/a ratio and lower oxygen vacancy content are simultaneously obtained in 0.9KNN-0.1ST: 0.1Er ceramics. The effective energy storage density (W_rec) of 0.86 J/cm³, excellent near-infrared transmittance of 51.7% (1100 nm) and strong green upconversion photoluminescence are achieved in this multifunctional ceramic. This study provides a solid basis for rare earth ions doped ferroelectric ceramics with tunable multifunctional properties and has significant potential for applications in optoelectronic devices.

The resistive switching (RS) mechanism of hybrid organic-inorganic perovskites has not been clearly understood until now. A switchable diode-like RS behavior in MAPbBr₃ single crystals using Au (or Pt) symmetric electrodes is reported. Both the high resistance state (HRS) and low resistance state (LRS) are electrode-area dependent and light responsive. We propose an electric-field-driven inner p-n junction accompanied by a trap-controlled space-charge-limited conduction (SCLC) conduction mechanism to explain this switchable diode-like RS behavior in MAPbBr₃ single crystals.

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.