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The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials. Combining a perovskite ferroelectric with moderate piezoelectric properties and a nonpiezoelectric pervoskite relaxor can create a highly piezoelectric material. Here, the authors help explain this unusual result by quantifying how polar nanoregions in the material contribute to its piezoelectric response.

Phase transition describes a mutational behavior of matter states at a critical transition temperature or external field. Despite the phase-transition orders are well sorted by classic thermodynamic theory, ambiguous situations interposed between the first- and second-order transitions were exposed one after another. Here, we report discovery of phase-transition frustration near a tricritical composition point in ferroelectric Pb(Zr 1-x Ti x )O 3 . Our multi-scale transmission electron microscopy characterization reveals a number of geometrically frustrated microstructure features such as self-assembled hierarchical domain structure, degeneracy of mesoscale domain tetragonality and decoupled polarization-strain relationship. Associated with deviation from the classic mean-field theory, dielectric critical exponent anomalies and temperature dependent birefringence data unveil that the frustrated transition order stems from intricate competition of short-range polar orders and their decoupling to long-range lattice deformation. With supports from effective Hamiltonian Monte Carlo simulations, our findings point out a potentially universal mechanism to comprehend the abnormal critical phenomena occurring in phase-transition materials. Phase transition brings a plethora of exotic phenomena and intriguing effects such as spin and charge frustration. However, the phase transition order is not always explicit. Here, the authors discover phase transition frustration near a tricritical composition point in ferroelectric Pb(Zr,Ti)O 3 .

The integration of complex oxides with a wide spectrum of functionalities on Si, Ge and flexible substrates is highly demanded for functional devices in information technology. We demonstrate the remote epitaxy of BaTiO 3 (BTO) on Ge using a graphene intermediate layer, which forms a prototype of highly heterogeneous epitaxial systems. The Ge surface orientation dictates the outcome of remote epitaxy. Single crystalline epitaxial BTO 3-δ films were grown on graphene/Ge (011), whereas graphene/Ge (001) led to textured films. The graphene plays an important role in surface passivation. The remote epitaxial deposition of BTO 3-δ follows the Volmer-Weber growth mode, with the strain being partially relaxed at the very beginning of the growth. Such BTO 3-δ films can be easily exfoliated and transferred to arbitrary substrates like Si and flexible polyimide. The transferred BTO 3-δ films possess enhanced flexoelectric properties with a gauge factor of as high as 1127. These results not only expand the understanding of heteroepitaxy, but also open a pathway for the applications of devices based on complex oxides. The integration of epitaxial complex oxides on semiconductor and flexible substrates is required but challenging. Here, the authors report the highly heterogeneous epitaxy of transferrable BaTiO 3-δ membrane with enhanced flexoelectricity on Ge (011).

Lead hafnate (PbHfO3) has attracted a lot of renewed interest due to its potential as antiferroelectric (AFE) material for energy storage. However, its room temperature (RT) energy-storage performance has not been well established and no reports on the energy-storage feature of its high-temperature intermediate phase (IM) are available. In this work, high-quality PbHfO3 ceramics were prepared via the solid-state synthesis route. Based on high-temperature X-ray diffraction data, the IM of PbHfO3 was found to be orthorhombic, Imma space group, with antiparallel alignment of Pb2+ ions along the [001]cubic directions. The polarization–electric field (P–E) relation of PbHfO3 is displayed at RT as well as in the temperature range of the IM. A typical AFE loop revealed an optimal recoverable energy-storage density (Wrec) of 2.7 J/cm3, which is 286% higher than the reported data with an efficiency (η) of 65% at 235 kV/cm at RT. A relatively high Wrec value of 0.7 J/cm3 was found at 190 °C with an η of 89% at 65 kV/cm. These results demonstrate that PbHfO3 is a prototypical AFE from RT up to 200 °C, making it a suitable material for energy-storage applications in a wide temperature range.

In situ high-pressure/high-temperature Raman-scattering analyses on PbTiO 3 , 0.92PbTiO 3 - 0.08Bi(Zn 0.5 Ti 0.5 )O 3 and 0.83PbTiO 3 - 0.17Bi(Mg 0.5 Ti 0.5 )O 3 single crystals reveal an intensity transfer between the fine-structure components of the A 1 (TO) soft mode. The enhancement of the lowest-energy subpeak, which stems from intrinsic local non-tetragonal polar distortions, along with the suppression of the tetragonal A 1 (1TO) fundamental mode with increasing pressure and temperature indicates the key role of the local polarization fluctuations in transformation processes and emphasizes the significance of the order-disorder phenomena in both the pressure- and temperature-induced phase transitions of pure PbTiO 3 and its solid solutions with complex perovskites. Moreover, the temperature and pressure evolution of the fraction of the local non-tetragonal polar distortions is highly sensitive to the type of B-site substituent.

An intrinsic conflict between high deformability and rigidity hinders the development of electroactive polymer (EAP)-based soft robots. Here, we employ an external electric field to align Al 2 O 3 -coated carbon nanotubes (Al 2 O 3 @CNTs) in a poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) matrix. Compared with pure P(VDF-TrFE-CTFE), the thickness strain of nanocomposites with horizontally and vertically aligned Al 2 O 3 @CNTs increases by 473% and 814%, respectively. It results in a high bending angle up to 215° for their actuator beams. Importantly, the horizontally aligned Al 2 O 3 @CNTs enhance the local stiffness via ‘face-enhanced effect’, yielding a high output force per unit volume (1.25 mN/mm 3 at 30 V/μm). It is not only ~346% higher than pure P(VDF-TrFE-CTFE) but also higher than the reported ceramic actuators. Accordingly, the soft robots made by the designed nanocomposite actuators could climb slopes up to 52° and carry loads equivalent to eight times their body mass. Consequently, this modulating strategy develops a high-performance actuation for soft robots. Electroactive polymers can be used for soft robotics, though it is challenging to balance rigidity and deformability. Here the authors designed a polymer composite using an electric-field assisted tape-casting method to orient the Al 2 O 3 -coated carbon nanotubes to tailor the dielectric and mechanical properties.

A microfluidic chip with a controllable and integrated piezoelectric pump was proposed and demonstrated, where the pump was designed as a micro-actuator based on polyvinylidene fluoride (PVDF) organic piezoelectric film. In this case, the pump should integrate with the microfluidics device very well into one chip. The flow rate can be precisely controlled in the range of 0–300 µl/min for water by tuning the V pp and frequency of Alternating Current (AC) voltage applied on the diaphragm. To analyze the relationship between the flow rate and the deflection of diaphragm, the deformations of diaphragm at different voltages were researched. The displacement of diaphragm was defined as 17.2 µm at the voltages of 3.5 kV, 5 Hz when the pump chamber was full of water. We have used the integrated microfluidic chip with two pumps for droplet generation to demonstrate its great potential for application in droplet-based microfluidic chip.

An In2O3/ITO thin film thermocouple was prepared via screen printing. Glass additives were added to improve the sintering process and to increase the density of the In2O3/ITO films. The surface and cross-sectional images indicate that both the grain size and densification of the ITO and In2O3 films increased with the increase in annealing time. The thermoelectric voltage of the In2O3/ITO thermocouple was 53.5 mV at 1270 °C at the hot junction. The average Seebeck coefficient of the thermocouple was calculated as 44.5 μV/°C. The drift rate of the In2O3/ITO thermocouple was 5.44 °C/h at a measuring time of 10 h at 1270 °C.

PbZr1−xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1−xTixO3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter.

Relaxor ferroelectrics underpin high-performance actuators and sensors, yet the nature of polar heterogeneities driving their broadband dielectric response remains debated. Using a unified, multimodal structural refinement framework— simultaneously fitting complementary X-ray and neutron total scattering, X-ray absorption spectra, and diffuse scattering—we reconstruct 3D mesoscale polarization maps in the classic relaxor system PbMg 1/3 Nb 2/3 O 3 –PbTiO 3 . We uncover self-organized swirling polarization textures with half-skyrmion (meron) vortices, challenging models of independent polar nanoregions. These textures, characterized by smooth changes in the polarization direction, originate from overlapping volumes in which the projections of locally correlated polarization vectors onto each volume’s long axis share the same sign. Vortex cores correlate strongly with local charge and strain gradients imposed by compositional heterogeneities. In this work, our results suggest that chemical disorder, acting via depolarizing and strain fields, stabilizes topological vortex textures of the polarization field, offering a route for engineering new dielectric and ferroelectric functionalities. This work advances multimodal structural refinements to generate 3D polarization maps for relaxor ferroelectrics, revealing continuous textures with vortex meron features tied to chemical disorder and deepening understanding of relaxor phenomena.