Achieving a high piezoelectric response and excellent stability is essential for practical applications of ferroelectric materials. Herein, large piezoelectricity of d33 = 167 pC/N and kt = 0.52 is found in a K0.7Na0.3NbO3 lead-free ferroelectric single crystal without poling, which is comparable to the artificially poled KNN crystals. The large piezoelectricity is maintained up to 196 °C, showing excellent thermal stability. It was demonstrated that the high piezoelectricity is associated with strong self-polarization in the crystals. The strong internal stress formed during crystal growth gives a preferred spontaneous polarization orientation, resulting in a net macro total polarization. In addition, the internal stress also pins domain wall motions and provides a \"restoring force\" for the domain switching. This work provides a strategy for designing and optimizing the piezoelectric performance of ferroelectric materials.

The ever-increasing demand for high-speed data transmission in telecommunications and data centers has driven the development of advanced on-chip integrated electro-optic modulators. Silicon modulators, constrained by the relatively weak carrier dispersion effect, face challenges in meeting the stringent requirements of next-generation photonic integrated circuits. Consequently, there has been a growing interest in Pockels effect-based electro-optic modulators, leveraging ferroelectric materials like LiNbO3, BaTiO3, PZT, and LaTiO3. Attributed to the large first-order electro-optic coefficient, researchers have delved into developing modulators with expansive bandwidth, low power consumption, compact size, and linear response. This paper reviews the working principles, fabrication techniques, integration schemes, and recent highlights in Pockels effect-based modulators.

Copolymers based on vinylidene fluoride are potential materials for ferroelectric memory elements. The trend in studies showing that a decrease in the degree of crystallinity can lead to an unexpected increase in the electric breakdown field is noted. An analysis of the literature data reveals that in fluorine-containing ferroelectric polymers, when using a bipolar triangular field, the hysteresis loop has an unclosed shape, with each subsequent loop being accompanied by a decrease in the dielectric response. In this work, the effect of the structure of self-polarized films of copolymers of vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene on breakdown processes was studied. The structure of the polymer films was monitored using infrared spectroscopy (IR) and X-ray diffraction. Kelvin probe force microscopy (KPFM) was applied to characterize the local electrical properties of the polymers. For the films of the first copolymer, which crystallize in the polar β-phase, asymmetry in the dielectric response was observed at fields greater than the coercive field. For the films of the copolymers of vinylidene fluoride with hexafluoropropylene, which crystallize predominantly in the nonpolar α-phase, polarization switching processes have also been observed, but at lower electric fields. The noted phenomena will help to identify the influence of the structure of ferroelectric polymers on their electrical properties.

Ferroelectric transistors are considered promising for next-generation 3D NAND technology due to their lower power consumption and faster operation compared to conventional charge-trap flash memories. However, ensuring their suitability for such applications requires a thorough investigation of array-scale reliability. This study specifically examines the suitability of hafnia-based ferroelectric transistors for advanced 3D NAND applications, with a specific focus on establishing a disturb-free voltage scheme to ensure the reliability of ferroelectric transistors within the array. Our key finding highlights the crucial role of optimal pass voltage in achieving disturb-free operation in both 2D and 3D ferroelectric NAND arrays. Additionally, the study indicates that read disturb remains negligible when an appropriate read voltage is applied. These insights provide a practical strategy for achieving reliable operation in 2D and 3D ferroelectric NAND, highlighting the potential of hafnia-based ferroelectric materials to meet the evolving requirements of high-density and reliable NAND flash memory applications.

Lead-free K0.5Bi0.5TiO3 (KBT) ceramics with high density (~5.36 g/cm3, 90% of X-ray density) and compositional purity (up to 90%) were synthesized using a solid-state reaction method. Strongly condensed KBT ceramics revealed homogenous local microstructures. TG/DSC (Thermogravimetry-differential scanning calorimetry) techniques characterized the thermal and structural stability of KBT. High mass stability (>0.4%) has proven no KBT thermal decomposition or other phase precipitation up to 1000 °C except for the co-existing K2Ti6O13 impurity. A strong influence of crystallites size and sintering conditions on improved dielectric and non-linear optical properties was reported. A significant increase (more than twice) in dielectric permittivity (εR), substantial for potential applications, was found in the KBT-24h specimen with extensive milling time. Moreover, it was observed that the second harmonic generation (λSHG = 532 nm) was activated at remarkably low fundamental beam intensity. Finally, spectroscopic experiments (Fourier transform Raman and far-infrared spectroscopy (FT-IR)) were supported by DFT (Density functional theory) calculations with a 2 × 2 × 2 supercell (P42mc symmetry and C4v point group). Moreover, the energy band gap was calculated (Eg = 2.46 eV), and a strong hybridization of the O-2p and Ti-3d orbitals at Eg explained the nature of band-gap transition (Γ → Γ).

The silicon (Si) anode is prone to forming a high electric field gradient and concentration gradient on the electrode surface under high-rate conditions, which may destroy the surface structure and decrease cycling stability. In this study, a ferroelectric (BaTiO3) interlayer and field polarization treatment are introduced to set up a built-in field, which optimizes the transport mechanisms of Li+ in solid and liquid phases and thus enhances the rate performance and cycling stability of Si anodes. Also, a fast discharging and slow charging phenomenon is observed in a half-cell with a high reversible capacity of 1500.8 mAh g-1 when controlling the polarization direction of the interlayer, which means a fast charging and slow discharging property in a full battery and thus is valuable for potential applications in commercial batteries. Simulation results demonstrated that the built-in field plays a key role in regulating the Li+ concentration distribution in the electrolyte and the Li+ diffusion behavior inside particles, leading to more uniform Li+ diffusion from local high-concentration sites to surrounding regions. The assembled lithium-ion battery with a BaTiO3 interlayer exhibited superior electrochemical performance and long-term cycling life (915.6 mAh g-1 after 300 cycles at a high current density of 4.2 A g-1). The significance of this research lies in exploring a new approach to improve the performance of lithium-ion batteries and providing new ideas and pathways for addressing the challenges faced by Si-based anodes.

Piezoelectric materials, capable of converting mechanical energy into electrical energy and vice versa, have emerged as promising candidates for designing intelligent drug delivery vehicles. Leveraging their inherent electrical properties, these materials respond to external stimuli, such as mechanical forces and electrical signals, to control drug release. By integrating piezoelectric materials into drug delivery systems, we can achieve exacting control over drug-release mechanisms. Piezoelectric materials hold enormous promise as smart delivery vehicles in cancer treatment, responding to mechanical and electrical cues, enabling site-specific drug release, reducing systemic toxicity and enhancing therapeutic effectiveness. Further advancements in the field are expected to lead to innovative piezoelectric-based systems that can revolutionize cancer treatment strategies, as explored in this review article.

van der Waals ferroic materials exhibit rich potential for implementing future generation functional devices. Among these, layered β\'-In2Se3 has fascinated researchers with its complex superlattice and domain structures. As opposed to ferroelectric α-In2Se3, the understanding of β\'-In2Se3 ferroic properties remains unclear because ferroelectric, antiferroelectric, and ferroelastic characteristics have been separately reported in this material. To develop useful applications, it is necessary to understand the microscopic structural properties and their correlation with macroscopic device characteristics. Herein, using scanning transmission electron microscopy (STEM), we observed that the arrangement of dipoles deviates from the ideal double antiparallel antiferroelectric character due to competition between antiferroelectric and ferroelectric structural ordering. By virtue of second-harmonic generation, four-dimensional STEM, and in-plane piezoresponse force microscopy, the long-range inversion-breaking symmetry, uncompensated local polarization, and net polarization domains are unambiguously verified, revealing β\'-In2Se3 as an in-plane ferrielectric layered material. Additionally, our device study reveals analogous resistive switching behaviors of different types owing to polarization switching, defect migration, and defect-induced charge trapping/detrapping processes.

Hafnia-based ferroelectrics have gained much attention because they can be used in highly scaled, advanced complementary metal-oxide semiconductor (CMOS) memory devices. However, thermal stability should be considered when integrating hafnia-based ferroelectric transistors in advanced CMOS devices, as they can be exposed to high-temperature processes. This work proposed that doping of Al in hafnia-based ferroelectric material can lead to high thermal stability. A ferroelectric capacitor based on Al-doped hafnia, which can be used for one-transistor-one-capacitor applications, exhibits stable operation even after annealing at 900 °C. Moreover, it demonstrates that the ferroelectric transistors based on Al-doped hafnia for one-transistor applications, such as ferroelectric NAND, retain their memory states for 10 years at 100 °C. This study presents a practical method to achieve thermally stable ferroelectric memories capable of enduring high-temperature processes and operation conditions.

The values of the surface potentials of two sides of films of polyvinylidene fluoride, and its copolymers with tetrafluoroethylene and hexafluoropropylene, were measured by the Kelvin probe method. The microstructures of the chains in the surfaces on these sides were evaluated by ATR IR spectroscopy. It was found that the observed surface potentials differed in the studied films. Simultaneously, it was observed from the IR spectroscopy data that the microstructures of the chains on both sides of the films also differed. It is concluded that the formation of the surface potential in (self-polarized) ferroelectric polymers is controlled by the microstructure of the surface layer. The reasons for the formation of a different microstructure on both sides of the films are suggested on the basis of the general regularities of structure formation in flexible-chain crystallizing polymers.