Jinming Guo

Wurtzite‐type aluminum scandium nitride (AlScN) has emerged as a potential candidate for next‐generation ferroelectrics due to large polarization, high Curie temperature and compatibility with semiconductor technology. However, strategies that enable the low‐temperature growth of high‐quality films, and the exfoliation of freestanding membranes are still lacking, largely hindering integration in functional devices. Here, we demonstrate the growth of high‐quality AlScN films at the low temperature of 150°C on substrates with distinct crystal symmetries, achieved by using a two‐dimensional transition metal dichalcogenide (TMDC) monolayer as a buffer. The high crystallinity is stemmed from the quasi‐van der Waals epitaxy, which is universally demonstrated on a wide range of TMDC materials. The TMDC buffers further enable the fabrication of freestanding AlScN membranes, exhibiting excellent ferroelectric properties including high remanent polarization, low leakage current and rapid switching kinetics. Our findings provide a low‐thermal‐budget approach with high integration flexibility to develop wurtzite‐based ferroelectric, piezoelectric, and electro‐optic devices.

Dielectric capacitors offering ultrafast charge–discharge capability and superior reliability are essential for advanced electronic systems, but achieving both high energy density and efficiency within simple and eco‐friendly compositions remains a great challenge. Here, guided by machine learning, we achieve high‐efficiency and thermally stable capacitive energy storage in strontium titanate‐based ceramics. Through synergistic local structural engineering and optimized fabrication process, the materials exhibit enhanced polarization, reduced hysteresis loss, and improved breakdown strength. The designed materials deliver an ultrahigh energy density of 10.69 J cm ⁻³ with a near‐ideal efficiency of ∼97% and a record high figure of merit of 392 J cm ⁻³ at room temperature, and retains high performance at 150°C with a figure of merit of 152 J cm ⁻³ and an efficiency of ∼94%. This remarkable performance arises from the incorporation of Bi ³⁺ ions with high polarizability at the A‐sites of strontium titanate quantum paraelectrics, which breaks structural symmetry and induces lattice and octahedral distortions, leading to the formation of nanoscale polar clusters with highly dynamic fluctuations. These findings establish a compositionally simple, environmentally benign pathway for developing dielectrics with superior energy storage capability and thermal stability, offering new opportunities for high‐performance capacitive energy storage systems.

Sodium niobate (NaNbO₃), traditionally recognized as an antiferroelectric material, has garnered significant attention for its potential in energy storage, electromechanical devices, and electrocaloric applications. Central to unlocking its full potential is precise control over its ferroic orders, particularly the transition between antiferroelectric and ferroelectric phases. In this study, we propose a topochemical conversion strategy for fabricating pure ferroelectric NaNbO₃ membranes with a P2₁ma orthorhombic phase regardless of membrane thickness. Using Scanning transmission electron microscopy, we identify two distinct regions with large ( > 10°) or small ( < 1°) octahedral tilts in the ferroelectric NaNbO₃ membranes. Polarization analyses in these regions reveal that the ferroelectricity originates from the out-of-plane displacement of Nb⁵⁺ cations. Additionally, the pure ferroelectric NaNbO₃ membranes demonstrate thickness-dependent piezoelectric enhancement, achieving a d₃₃ value of 93.7 pm/V at 30 nm thickness, as well as pronounced resistance switching behaviors. This study introduces an innovative molten salt environment-controlled synthesis strategy, enabling efficient production of high-quality pure ferroelectric NaNbO₃ membranes, and advancing their integration into next-generation functional devices.

Spin-source materials for spintronic devices are required to convert charge currents into spin currents efficiently and maintain minimal electrical losses. However, conventional strategies to enhance charge-spin conversion often come at the cost of increasing ohmic dissipation. Here we demonstrate that introducing polar lattice distortions into a highly conductive metal can overcome this trade-off. We report the discovery of polar displacements in PtCoO₂ and show that these displacements enhance charge-spin conversion by two orders of magnitude compared with its non-polar phase. The coexistence of polarity and metallicity yields a room-temperature spin Hall conductivity of 1.6 × 10⁷ℏ/2e (Ω m)^-1. Electron ptychography reveals that the inversion-symmetry breaking originates from local polar nano-regions. Polar PtCoO₂ drives efficient spin-orbit torque switching with substantially reduced switching voltage and power compared with Pt-based control devices, and is compatible with silicon substrates, establishing a strategy for designing highly efficient spin-source materials.

Catalytic reactions involving multiple intermediates are fundamentally constrained by the limited functionality of single active sites. While multi‐site catalysts provide a promising route to decouple complex reaction steps, the rational design and realization of architectures that enable rapid and directional inter‐site intermediate spillover remains largely unexplored and highly challenging. Here, we report a strategy to program intermediate spillover and cascade catalysis in multielement dual‐heterostructured catalysts through gradient adsorption potentials. Using the acidic oxygen evolution reaction as a model, a dual‐heterostructured RuIr–Mo/WVOx catalyst is precisely engineered to integrate an oxyphilic WVOx matrix for rapid water dissociation, a Mo bridge for efficient ^* OHspillover, and a RuIr alloy for accelerated oxidation. Guided by first‐principles screening and differences in elemental reducibility, a continuous gradient adsorption sequence (WVOx → Mo → RuIr) is constructed from a multielement architecture, enabling directional ^* OH transport across cooperatively coupled active centers with balanced energetics for cascade catalysis. As a result, the optimized catalyst delivers an overpotential of 183 mV at 10 mA cm ^{− 2} and sustains stable operation for 450 h at 100 mA cm ^{− 2} , outperforming single‐interface and commercial benchmarks. This work establishes gradient adsorption engineering as a general design framework for programming cascade catalysis in multistep reactions.

The operational efficiency and reliability of lead‐free piezoceramics are critically limited by high dielectric loss and inadequate thermal stability. While enhancements in piezoelectricity have been achieved in (K,Na)NbO ₃ (KNN)‐based systems, a significant challenge remains: the effective co‐regulation of these two properties, as higher piezoelectricity often leads to increased dielectric loss and deteriorate thermal stability. This work presents a strategic solution which synergistically regulates carrier migration, and domain dynamics via defect engineering. In 0.3mol% CuO‐doped KNN‐based piezoceramics, we achieve an unprecedented ultra‐low dielectric loss of 0.3%, a superior piezoelectric coefficient ( d ₃₃ ) of 264 pC/N, high depolarization temperature ( T _d ) of 285°C, as well as excellent thermal‐aging and long‐term aging stability. Mechanistic studies reveal that the low loss originates from suppressed polarization switching and domain‐wall motion induced by oxygen vacancies, coupled with low ionic conductivity. While in situ heating transmission electron microscopy analysis shows that a stable hierarchical domain architecture underpins the superior piezoelectric thermal properties. This work establishes a new paradigm for designing lead‐free piezoceramics that simultaneously overcome the long‐standing challenges of dielectric loss and high depolarization temperature, paving the way for achieving highly efficient and reliable piezoelectric systems.

The pursuit of high performance dielectric capacitors necessitates a deep understanding of the atomic‐scale mechanism governing their polarization response. Entropy engineering is an effective strategy for tuning polarization properties. In particular, introducing specific elements into medium/high‐entropy systems can induce an antiferroelectric‐like polarization‐electric field ( P‐E ) hysteresis loop, which is highly desirable for high energy storage performance due to its high maximum polarization and low remnant polarization. However, their atomic‐scale origin remains unclear. Herein, atomic‐scale transmission electron microscopy (TEM) analyses reveal that this distinctive behavior originates from the synergistic effect of dislocation pinning and oxygen octahedral tilting mode transition. The pinning effect inhibits polarization switching, causing a non‐overlapping P‐E loop, while oxygen octahedral tilting directly contributes to the pinched loop. The a ⁰ a ⁰ c ^– oxygen octahedral tilting mode stabilizes a relaxor state with low remnant polarization. In situ TEM characterization under an electric field demonstrates an electric field‐induced transformation of the oxygen octahedral tilting mode from a ⁰ a ⁰ c ^– to a ⁰ a ⁰ a ⁰ , directly correlating structural evolution with antiferroelectric‐like behavior. These findings deliver atomic‐scale insights that defect pinning and oxygen octahedral tilting induce antiferroelectric‐like behavior, offering a novel strategy for designing energy storage ceramics.

Ceramic capacitors, although promising for advanced high-power energy storage, face challenges in energy density and efficiency at high temperatures, which restricts their practical applications. Guided by phase field simulations, we propose a structural design strategy to construct weakly coupled polar nanoclusters in superparaelectric state, and fabricate BaTiO₃-based multilayer ceramic capacitors via prototype device technology. The capacitors achieve an ultrahigh energy storage density of 19.0 J·cm^-3 and a high energy storage efficiency of 95.5% at room temperature. More importantly, both metrics are still on the order of > 10.0 J·cm^-3 and > 95.0%, respectively, over 25-160 ^oC, outperforming previously reported ceramic capacitors. The weaken coupling between adjacent nanoclusters caused by disordered polar configurations, suppresses nonlinear polarization response and temperature sensitivity, ultimately enabling superior energy storage performance, which is confirmed by atomic-scale microstructure analysis. This work advances next-generation electronics and provides insights for developing high-performance high-temperature ceramic capacitors.

Piezoelectric materials have been attracting wide research interest for decades due to their ability to interconvert mechanical and electrical energy. Various mechanisms from different perspectives have been proposed to explain high piezoelectricity; however, a unified framework across diverse perovskite piezoelectric systems remains elusive. Yao et al. introduced a concept termed fluctuating local polarization (FLP) as an effective index for high piezoelectricity in perovskite ferroelectrics. FLP describes the composition-dependent piezoelectric performance in individual solid solutions and also accounts for high piezoelectricity across distinct systems. The FLP metric integrates the magnitude of local electric dipoles and the disorder of their orientations. This concept does not supersede traditional viewpoints but rather rationalizes them under a common microscopic index: local polarization flexibility. FLP is not merely an explanatory fingerprint of high piezoelectricity; it can also serve as a practical reference for engineering the next generation of ferroelectric materials.