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Piezo-/ferroelectrics are essential materials for electromechanical sensors and actuators and energy harvesters in a wide range of technological applications. The demand for piezo-/ferroelectric materials with high Curie temperature (TC) arises from numerous emerging applications such as downhole oil and gas explorations, automobiles, petrochemistry, metallurgy, and nuclear energy and aerospace industries, in which the electromechanical devices have to operate at elevated temperatures. However, it is a long-standing challenge to simultaneously obtain high piezoelectricity and high TC. Recently, significant progress has been made on bismuth-based piezo-/ferroelectric single crystals (BPSCs) which show excellent piezoelectric performance and high TC, proving to be a promising family of novel materials for high-temperature electromechanical applications. In this highlight, we review the recent progress in BPSCs with focus on materials design, crystal growth, physical properties, crystal chemistry, and complex domain structures. In addition, the future perspectives of BPSCs are discussed.

Single-phase multiferroic BiFeO3-based perovskite solid solutions attract great research interest due to the coexistence of ferroelectric and magnetic orderings above room temperature. In this work...

Single crystals of organic–inorganic halide perovskites are well needed in order to fully explore their potential in optoelectronic applications and to gain a fundamental understanding of their intrinsic properties. Previously, inverse temperature crystallization (ITC) was used to grow halide perovskite crystals at high temperatures (≈100 °C). Here, we develop an effective synthetic technique by which the CH3NH3PbX3 (X = I, Br, and Cl) crystals are grown in polar solvents at room temperature (except for CH3NH3PbI3 grown at 45 °C) in a relatively short time. A constant supersaturation during the crystal growth is created to produce large single crystals, which is achieved during room temperature crystallization (RTC) through controlled solvent evaporation. We investigate the effects of the temperature and supersaturation level on the nucleation kinetics of CH3NH3PbCl3 as an example, and propose and compare the different growth pathways. The crystal structural analysis, steady-state absorption, photoluminescence, and charge-transport properties demonstrate excellent long-term stability (over 2 years) of the RTC-grown CH3NH3PbX3 (X = Br, Cl) crystals against environmental degradation and moisture. The crystal optical properties are studied by polarized light microscopy, revealing birefringent ferroelastic domain structures characteristic of the tetragonal (X = Br) or orthorhombic (X = Cl) symmetry and high optical quality. This work presents a general strategy for designing, controlling, and optimizing the growth of high-quality halide perovskite crystals, which is an important step forward toward realizing high-end and stable optoelectronic devices such as nonlinear absorbers, photocatalyst, and micro-electromechanical actuators.

Mutiferroic materials like bismuth ferrite BiFeO3 have attracted much interest in the last decade due to their promising potential for such applications as spintronics and magnetoelectric data storage devices. On the other hand, relaxor ferroelectrics have been intensively studied for their complex structures with quenched disorder and polar nanoregions which play an important role in their outstanding piezoelectric performance. Much less studied are the single-phase multiferroics that exhibit ferroelectric and/or magnetic relaxor behavior and the correlation between their structure and intricate magneto-electric interactions. In this work, we investigate the evolution of the structure and relaxor behavior in the solid solution between the complex perovskite multirelaxor Pb(Fe2/3W1/3)O3 [PFW] and canonical multiferroic BiFeO3 [BFO], (1-x)PFW-xBFO (with a solubility limit of x = 0.30). The temperature dependences of the dielectric permittivity and loss tangent measured in the frequency range from 100 Hz to 1 MHz indicate characteristic relaxor ferroelectric properties for compositions of x ≤ 0.15, with a frequency-dependent dielectric permittivity peak and its temperature, Tm, satisfying the Vogel-Fulcher law. Detailed studies of the evolution of the relaxor behavior with composition reveal that Tm decreases firstly with a small amount (x = 0.05) of BFO substitution and then increases with further increase of BFO concentration. The degree of relaxor character, as defined by ΔTm [Tm (1 MHz) - Tm (100 Hz)], increases monotonously with increasing BFO content, signifying an enhancement of relaxor behavior with BFO substitution, which is confirmed by the Lorenz-type quadratic variation of the static permittivity. A temperature - composition phase diagram is constructed in terms of the characteristic Burns temperature (TB) and freezing temperature (Tf), which delimits a paraelectric state (PE) above TB, a non-ergotic relaxor state (NR) below Tf, and an ergotic relaxor state (ER) in between. The observed enhancement of relaxor behavior is explained by an increase in the number and size distribution of polar nanoregions in the ER phase, resulting from increased compositional and charge disorders as a result of BFO substitution. The evolution of relaxor behavior and its microscopic mechanisms studied in this work are insightful for a better understanding the multirelaxor properties in multiferroics. Moreover, further substitution of BFO (x ≥ 0.2) flattens the permittivity curves and leads to a temperature-stable variation of high dielectric constant (≈ 103) in a wide temperature range, making the PFW-BFO solid solution attractive for such applications as high energy density capacitors.

A 3-inch Mn:PIN-36%PMN-32%PT (Generation III) relaxor ferroelectric crystal was grown using the Vertical Gradient Freeze method. Crystals of [1, 11] and [111] orientations were prepared and studied, evaluating their dielectric constants, piezoelectric coefficients, electromechanical coupling coefficients, loss tangents and pyroelectric coefficients. It is shown that in pyroelectric applications, [111]-poled crystals are particularly suitable for high performance sensors due to a relatively high pyroelectric coefficient, low loss tangent. In addition, the specific heat is lower as compared to LiTaO3. It is also shown that the alternating current (AC) poling has a more significant effect on the [001]-poled crystal than on the [011]- and [111]-poled crystals due to the lattice distortion induced by a strong electric field along the [001] direction.

Pb(Sc1/2Nb1/2)O3 (PSN) with a perovskite structure is a well-known ferroelectric material. The rapidly quenched PSN (PSN-D) shows a B-site disordered structure, and exhibits the noncanonical relaxo...

Bismuth scandate–lead titanate (BS–PT) solid solution is of great interest as a promising piezoelectric material for high-temperature electromechanical applications due to its excellent comprehensive electric performance and high Curie temperature. However, the full understanding of the ferro-/piezo-electric properties of BS–PT has been strongly hindered by the lack of detailed investigation of microscopic domain structures and successful growth of high-quality crystals. In this work, detailed structural and meso-/nano-scopic domain studies of the BS–PT crystals near the morphotropic phase boundary have been carried out by various characterization techniques. The multi-scale domain structures in the 〈001〉cub-cut 0.324BS–0.676PT single crystals were investigated by a unique combination of temperature-variable birefringence imaging microscopy and piezoresponse force microscopy, in conjunction with high-resolution X-ray diffraction in the temperature range of 30–500 °C. The crystal was found to exhibit tetragonal symmetry on average at room temperature and showed a transformation to cubic symmetry around 460 °C. Complex domain structures with small domain sizes (2–6 μm) and a high density of domain walls were imaged and analyzed from meso- to nano-scopic scale, and more interestingly, local crystal distortion was found in the vicinity of the dense domain walls. The domain evolution as a function of temperature and the correlation between the domain structure and the dielectric properties have been studied. These studies of domains, symmetries and phase transitions provide a better understanding of the structure of BS–PT crystals and other related ferro-/piezo-electric single crystals on multiple length scales, and help design novel high-TC, high performance ferro-/piezo-electric materials.

Ferroelectric single crystals of a ternary perovskite solid solution, BiScO3–Pb(Cd1/3Nb2/3)O3–PbTiO3 (BS–PCN–PT), have been successfully grown by the top-seeded solution growth method for the first time. The crystals with dimensions up to 2.5 × 2.5 × 1 cm3 were obtained. The structure of the BS–PCN–PT crystals has been studied by high-resolution X-ray diffraction, combined with polarized light microscopy, showing a tetragonal symmetry. The grown crystals exhibit a pseudo-cubic morphology with the (001) facets, suggesting a dominant {100}-growth process. Interestingly, a single ferroelastic domain state was found in most (001) platelets cut from the as-grown crystals. The domain structures and characteristics were carefully investigated by a combination of polarized light microscopy and piezoresponse force microscopy. The single-domain crystals possess a high average coercive field (Ec ∼ 30 kV cm−1) and a high remanent polarization (25 μC cm−2). An unpoled piezoelectric constant d33 of the single-domain crystal is up to 111 pC N−1 due to its self-polarization. The Curie temperature TC is found to be 423 °C by means of dielectric measurements, which is much higher than that of relaxor-based Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) piezocrystals. Moreover, the dielectric properties exhibit an excellent thermal stability up to 300 °C. A careful discussion about how the domain state may affect electromechanical properties has been carried out. The high TC, large coercive electric field, and high remanent polarization of the single-domain BS–PCN–PT crystals make this material a promising candidate for applications in a wider temperature range and at higher power compared to the PMN–PT crystals.

The coexistence of relaxor ferroelectric behaviour and ferromagnetic ordering in a single-phase material is of both fundamental interest and practical potential for applications. To study this rather unusual phenomenon, a series of multiferroic solid solutions of (1 − x)Pb(Fe0.5Nb0.5)O3–xBiFeO3 (PFN–BFO, with 0 ≤ x ≤ 0.6) were synthesized in the form of ceramics using the solid-state reaction technique and its relaxor and magnetic properties were systematically characterized in this work. Structural refinements based on X-ray diffraction data at room temperature reveal the phase evolution from a monoclinic phase with Cm symmetry to a pseudo-cubic phase with Pmm symmetry with increasing BFO content. The ferroelectric phase transition and relaxor behaviour were investigated via variable-temperature dielectric spectroscopy. A temperature–composition phase diagram was constructed in terms of TC, Tm, the Burns temperature (TB) and freezing temperature (Tf), which delimits a ferroelectric phase (FE) for x < 0.025 at T < TC, a non-ergotic relaxor state (NR) below Tf and an ergotic relaxor state (ER) at Tf < T < TB for 0.025 ≤ x ≤ 0.3, and a paraelectric state (PE) above TB for all the compositions. The differences in the microstructures and electrical properties between this work and those reported in the literature are carefully compared and discussed, which are closely related to the preparation conditions. In addition, the evolution of magnetic ordering with composition and temperature was investigated. A ferromagnetic order is induced by the substitution of a moderate amount of BFO (0.1 ≤ x ≤ 0.2), which exists up to room temperature. The complex magnetic phase diagram is established, which delimits an antiferromagnetic state (AFM1) for x = 0, two weakly ferromagnetic states, WFM1 and WFM2 for 0.1 ≤ x ≤ 0.2, another antiferromagnetic state (AFM2) for the compositions with x ≥ 0.25 at T ≤ TN, and a paramagnetic phase (PM) for all the compositions at T ≥ TN. The coexistence of relaxor behaviour and ferromagnetic ordering at room temperature makes the PFN–BFO solid solution a particularly interesting multiferroic material.

A novel relaxor solid solution of (1-x)Pb(Mg1/3Nb2/3)O3-xPb(Cd1/3Nb2/3)O3 [(1-x)PMN-xPCN] is synthesized by the solid-state reaction method. The crystal structure, electric properties and r...

Relaxor ferroelectrics are promising candidates for pulsed power dielectric capacitor applications because of their excellent energy-storage properties. Different from most relaxor ferroelectrics whose energy-storage density was improved by increasing the breakdown strength and reducing the remanent polarization, in this study, anti-ferroelectric (AFE) AgNbO3 (AN) was used to partially substitute the relaxor ferroelectric 0.76Bi0.5Na0.5TiO3–0.24SrTiO3 (BNT–ST) of morphotropic phase boundary (MPB) composition to reduce the remanent polarization while maintaining large maximum polarization. In this way, a large recoverable energy-storage density (2.03 J cm−3) was obtained in the BNT–ST–5AN ceramics under lower electric field of 120 kV cm−1, which is superior to other lead-free energy-storage materials under similar electric fields. Moreover, excellent temperature (25–175 °C) and frequency (1–100 Hz) stabilities are achieved. This performance demonstrates that the BNT–ST–5AN ceramics form a promising class of dielectric capacitive material for high-temperature pulsed power capacitors with large energy-storage density.

Domain structure plays a critical role in the functionality of ferroelectrics. In this work, the domain structure and local domain switching behaviors of a (001) C -oriented 0.38Bi(Zn 2/3 Nb 1/3 )O 3 -0.62PbTiO 3 single crystal with high Curie temperature (~ 430 °C) and high tetragonality ( c / a > 1.04, where c and a represent the lattice parameters of the tetragonal crystal), were studied by polarized light microscopy (PLM) and piezoresponse force microscopy (PFM). Local polar domains with typical sizes from several nanometers to micrometers were observed by PFM in the crystal. The local domain switching was realized by applying a voltage, indicating the ferroelectricity of the crystal. This work provides a better understanding of the micro-/nanodomain structure and related phenomena in ferroelectrics of complex perovskite structure.

How materials evolve at thermal equilibrium and under external excitations at small length and time scales is crucial to the understanding and control of material properties. X-ray photon correlation spectroscopy (XPCS) at X-ray free electron laser (XFEL) facilities can in principle capture dynamics of materials that are substantially faster than a millisecond. However, the analysis and interpretation of XPCS data is hindered by the strongly fluctuating X-ray intensity from XFELs. Here we examine the impact of pulse-to-pulse intensity fluctuations on sequential XPCS analysis. We show that the conventional XPCS analysis can still faithfully capture the characteristic time scales, but with substantial decrease in the signal-to-noise ratio of the g2 function and increase in the uncertainties of the extracted time constants. We also demonstrate protocols for improving the signal-to-noise ratio and reducing the uncertainties.

Effective Hamiltonian simulations are conducted to unveil the nature of the low-frequency polar modes in the prototype relaxor ferroelectric, $\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$. Above the so-called ${T}^{*}$ temperature, only a single soft-mode exists, with its frequency increasing under heating. On the other hand, for temperatures lower than the freezing temperature, this single soft-mode splits into two modes, with one mode slightly changing its low resonant frequency while the other exhibiting a resonant frequency sharply increasing under cooling, in agreement with previous measurements. More importantly, we present evidences that these two modes can be regarded as Goldstone-like and Higgs-like modes, inherent to the Mexican-hat-form of the atomic displacement potential we also reveal here, therefore extending the types of systems exhibiting Higgs-boson characteristics to relaxor ferroelectrics.

Pressure-induced phase transitions in single-crystal PbZr0.54Ti0.46O3 are investigated with high-pressure Raman scattering and x-ray single crystal and powder diffraction. The appearance of a Raman peak near 380cm(-1) indicates a structural transition at 3 GPa. A second transition, driven by an soft optical phonon, occurs at 9 GPa. A third transition occurs above 27 GPa, accompanied by a large changes in the Raman spectrum and splitting of the (pseudo-cubic) (111) and (220) diffraction lines. We identify the transitions as a monoclinic (Cm) to rhombohedral (R3m) transition at 3 GPa, followed by a rhombohedral (R3m) to rhombohedral (R-3c) transition at 9 GPa, and a further symmetry-lowering transition at 27 GPa.

Using various experimental methods including X-ray diffraction and electron microscopy, this work determines the range and nature of the chemical ordering in Pb(Cd1/3Nb2/3)O3 (PCN). The influence of the chemical ordering on the dielectric property is also discussed, based on the similarities and differences between PCN and other classical relaxors., Pure-phase Pb(Cd1/3Nb2/3)O3 (PCN) single crystals and ceramics with a complex perovskite structure are synthesized for the first time. The local chemical ordering in PCN has been investigated by X-ray diffraction (including diffuse scattering) and Cs-corrected transmission electron microscopy experiments. It is concluded that the PCN samples have large coherent chemical ordering regions that even extend to the long range, and the ordering model is consistent with β-type chemical ordered regions. The antiphase domain boundaries were also observed. Two dielectric anomaly peaks were found in these two types of samples, one of which indicates possible relaxor behaviour. The novel structure of the completely ordered regions and its relationship with the electrical properties make PCN a unique material for the fundamental understanding of chemically substituted perovskites.

A solid solution of (1-x) Pb(Mg1/3Nb2/3)O3-xBi(Zn2/3Nb1/3)O3 [(1-x)PMN-xBZN)] has been prepared in the form of ceramics with x = 0-0.20 by solid state reaction method. The crystal structure and dielectric properties are investigated. An enhanced relaxor behavior is found when incorporating BZN into canonical relaxor PMN due to the increased chemical disorder. The high temperature slope of dielectric constant as a function of temperature is consistent with the empirical quadratic law. The frequency dependence of the temperature of the dielectric maximum follows the Vogel-Fulcher (V-F) law.

In this work, a novel lead-reduced binary solid solution system (1-x)PbTiO3- xBi(Zn2/3Ta1/3)O3 was synthesized by the solid state reaction method. The crystal structure was analyzed by mean...

Ceramics of a perovskite solid solution, (1-x)PbTiO3-xDyFeO3, with x ≤ 0.4 are synthesized using the solid-state reaction method. The linear magnetization vs. magnetic field relation as well as the Curie-Weiss type temperature dependence of magnetic susceptibility observed in compositions with x ≤ 0.2 suggests the paramagnetic nature. When x ≥ 0.25, the weak ferromagnetic state can be induced. Moreover, the Dy3+ ions are enrolled into the superexchange coupling together with Fe3+ ions at low temperature, giving rise to magnetic phase transitions upon cooling in compositions with x = 0.4. Furthermore, the paraelectric subsystem is proposed to exist in weak ferromagnetic compositions.

Multiferroics that exhibit simultaneous electric and magnetic orders have attracted a great deal of interests both in fundamental science and practical applications. In general, high-performance single-phase multiferroics are extremely rare, owing to the incompatibility between ferroelectricity and magnetism. The most interesting property that makes multiferroics useful in device applications is the direct and significant magnetoelectric coupling at room temperature, resulting in a hysteretic magnetoelectric response. However, it still remains a great challenge to realize such a cross-coupling hysteresis loop between the ferroelectric and magnetic orders, i.e. an effective magnetic command of polarization, or an electric-field command of magnetization in a single-phase bulk material. Here we report the multiferroic behavior of chemically modified bismuth ferrite, Bi0.88Dy0.12Fe0.97Ti0.03O3+δ, which exhibits simultaneous (weak) ferromagnetism and ferroelectricity. More interestingly, this solid solution shows an evident magnetoelectric effect at a low magnetic field by demonstrating a hysteretic loop that characterizes the electric voltage signal as a function of bias magnetic field. Moreover, the room-temperature magnetoelectric effect with the saturated magnetoelectric coefficient up to ±0.23 mV/cm•Oe at ±250 Oe is obtained. The observed properties are attributed to the combination of linear magnetoelectric effect and domain wall motion. This result points to potential new applications of single-phase multiferroic materials in spintronic devices in which electric dipoles can be effectively tuned by a magnetic field.

La0.8Sr0.2CrO3/In2O3 ceramic-based thin film thermocouple (TFTC) was successfully fabricated by using radio frequency (RF) sputtering method. The phases structures and morphologies of La0.8Sr0.2CrO3 and In2O3 thin films were investigated by XRD and SEM, respectively. La0.8Sr0.2CrO3 thin film showed orthorhombic phase and shuttle structure through post-annealing. The crystalization properties of In2O3 thin film were enhanced with the post-annealing. At the same time, their electrical conductivities were improved with the post-annealing process. When the thermoelectric properties of La0.8Sr0.2CrO3 and In2O3 were investigated by coupling with Pt thin film electrodes, both of them showed good linear relationship with temperature difference. The TFTC fabricated by La0.8Sr0.2CrO3 and In2O3 thin films showed very good performance with good stable, reproducible thermoelectric voltage, and high sensitivity at higher temperature. The sensitivity of La0.8Sr0.2CrO3/In2O3 thin film thermocouple was 305.8 μV/oC. The dynamic thermal response of the TFTC demonstrated that it could monitor the real-time and in-situ temperature successfully.

Lead‐free bismuth sodium titanate and related compounds are of great interest as promising candidates for piezoelectric applications. However, the full understanding of this family of materials is still a challenge partly because of their structural complexity and different behaviors with or without the application of an external electric field. Here, piezoresponse force microscopy is used to gain insight into the mesoscopic‐scale domain structure of the morphotropic phase boundary (MPB) composition of (1‐x)Bi0.5Na0.5TiO3‐xBaTiO3 solid solution at x = 0.06 (abbreviated as BNT‐6BT). The evolution of the domains with the changes of the electric field and temperature has been thoroughly examined in conjunction with the crystal structure analysis and dielectric studies. It is found that ferroelectric domains with size of hundreds of nanometers are embedded in a relaxor state without visible domains on a mesoscopic scale, which are considered to contribute to the tetragonal and cubic phases in the material, respectively. Temperature‐independent domain configuration is observed in the unpoled sample from room temperature to 200°C. While, temperature‐dependent domain configuration is observed in the poled sample. The homogenously poled state breaks into the mixed domain configuration containing polydomain structure and invisible state around the so‐called depoling temperature. The structural changes on different length scales are also discussed. This work provides an in‐depth understanding of the structural and domain changes under an electric field and the temperature‐dependent domain evolution in both unpoled and poled states in the BNT‐BT solid solution of the MPB composition.

Besides outstanding multiferroic performance, BiFeO3 has recently demonstrated a potential for novel promising applications in domain wall nanoelectronics employing domain walls with different functional properties. Rarely observed in ferroelectrics, charged domain walls are of special interest for such applications as they possess enhanced electric conductivity. In this work, single crystals of the multiferroic (1–x)BiFeO3-xPbTiO3 solid solution were successfully grown using a flux method. Structural characterization by X-ray diffraction confirmed perovskite rhombohedral R3c and tetragonal P4mm phases in crystals with x ≈ 0.2 and x ≈ 0.6, respectively. The domain structure of crystals was established with the help of polarized light microscopy, scanning electron microscopy, and piezoresponse force microscopy. In tetragonal crystals, a complex hierarchical structure of 90° lamella domains is observed with the thickness of lamellae varying from dozens of nanometers to dozens of micrometers. In the rhombohe...

In order to understand the complex phase symmetry and phase transitions, and to illustrate the microscopic mechanisms of high piezoelectricity, single crystals of a new ternary complex perovskite system, Pb(Mg1/3Nb2/3)O3-Bi(Zn2/3Nb1/3)O3-PbTiO3, are grown by the high temperature solution growth method and their domain structure, dielectric and ferro-/piezoelectric properties, and phase transformation behavior are investigated by various techniques. Different phase symmetries including the rhombohedral, tetragonal and monoclinic are found in these crystals, indicating that the composition of the crystals is close to the morphotropic phase boundary (MPB) region. Most interestingly, unusual phase transformation sequences of rhombohedral → monoclinic → cubic, and monoclinic → cubic are directly observed by polarized light microscopy and confirmed by the dielectric and birefringence results. Moreover, an ultrahigh piezoelectric coefficient d33 ≈ 2000 pC/N is obtained in these crystals, making these crystals useful for applications as electromechanical transducers. The unusual phase transformation sequences and the high piezoelectric response are explained from the polarization rotation mechanism, which has been evidenced in this work. Based on these results, a temperature-composition phase diagram is established, which illustrates the complex phases present and their transformation behavior. These studies provide new insights into the intricate morphotropic phase symmetry and phase components in complex perovskite solid solutions, and a better understanding of the microscopic mechanisms of high piezoelectric response in relaxor-based piezocrystals, which in turn will be helpful for designing better piezoelectric single crystals.

Complex perovskite PbTiO3−Bi(Me′Me″)O3 solid solutions represent new materials systems that possess a higher Curie temperature (TC) than the relaxor-PbTiO3 solid solutions, and are useful for potential applications. To this end, novel ferroelectric single crystals of the (1–x)PbTiO3–xBi(Zn2/3Nb1/3)O3 (PT-BZN) solid solution were successfully grown by the high-temperature solution growth (HTSG) method. Powder X-ray diffraction shows that the symmetry of the grown crystals is tetragonal. The dielectric permittivity and optical domain structures were characterized by dielectric measurements and polarized light microscopy, respectively, as a function of temperature, revealing a first-order ferroelectric-paraelectric phase transition at a TC of 436 ± 2 °C. Based on the TC, the average composition of the crystal platelet was estimated to be 0.58PT-0.42BZN. Piezoresponse force microscopy measurements of the phase and amplitude as a function of voltage reveal the complex polar domain structure and demonstrate the ferroelectric switching behaviour of these materials. These results suggest that the PT-BZN single crystals indeed form a new family of high TC piezo-/ferroelectric materials which are potentially useful for the fabrication of electromechanical transducers for high-temperature applications.

Ferroelectric and piezoelectric materials with a high Curie temperature (TC) have attracted increasing interest due to their requirement in applications under extreme conditions. In this work, novel high-TC ferroelectric single crystals of (0.95 − x)BiScO3–0.05Pb(Cd1/3Nb2/3)O3–xPbTiO3 (BS–PCN–xPT) ternary solid solution with various compositions have been successfully grown. With increasing PT concentration, a composition-induced structural crossover from a rhombohedral phase, through a morphotropic phase boundary (MPB), to a tetragonal phase, is observed. A monoclinic phase (space group Pm) is found at the MPB region. The temperature dependences of the dielectric permittivity reveal high Curie-temperatures of 363–452 °C (at 1 MHz). The macroscopic and mesoscopic ferroelastic/ferroelectric domain structures systemically characterized by polarized light microscopy (PLM) and piezoresponse force microscopy (PFM) reveal the existence of monoclinic domains in the crystals with the MPB composition. In the monoclinic crystals, the remnant polarization (33.2 μC cm−2) is weaker than that in the rhombohedral phase. All compositions studied show a high coercive field (around EC = 40 kV cm−1). The presence of a high TC and a stable poled state signifies that the BS–PCN–xPT single crystals are promising candidates for applications such as electromechanical transducers that can be operated in a wide range of conditions.

Lead zirconate titanate (PZT) is one of the most widely studied piezoelectric materials, mainly because of its `mysterious' relationship between the so-called morphotropic phase boundary (MPB) and its strong piezoelectric coupling factor. Using results from a pair distribution function analysis, this paper examines how the complex local structure in PZT affects the long-range average structure across the MPB. A monoclinic M C type structure is discovered in PZT. A first-order transformation between the monoclinic M A and M C components in both the average and local structures explains the sudden change in piezoelectric effect around these compositions. The role of polarization rotation in the enhancement of the piezoelectric properties is discussed with respect to the composition of PZT. The structure–property relationship that is revealed by this study explains the unique properties of PZT, and may be applicable in the design of new MPB-type functional materials.

New target applications for microfluidic devices have been focused on home usability, wearability and cost-effectiveness. Towards these goals, in this work, a controllable, bendable, and all‑organic, nozzle‑diffuser microfluidic pump was designed, fabricated and tested. First, to resolve the crucial issue of high driving voltage, the ferroelectric polymer poly(vinylidene fluoride‑trifluoroethylene) (P(VDF‑TrFE)) was optimized by adding core‑shell structured Al2O3@CNT nanofillers. The membrane so developed with 1.1 wt% Al2O3@CNT showed an increase by nearly 7 times in the induced strain in comparison to the neat P(VDF‑TrFE) at low electric fields, because the modified membrane simultaneously achieved a lower coercive electric field and a higher polarization. Accordingly, the required operating voltage of the microfluidic pump integrated with optimized membrane significantly decreased from 1000 V to 160 V. Meanwhile, this pump exhibited a wider range of flow rates (13–135 µL/min) than the reported results, associated with the higher output pressure in our membranes. Importantly, the designed pump still possessed an excellent controllability of the fluidic processes, though it underwent a large bending up to 74°. Consequently, the extremely promising application of the as‑prepared microfluidic pump in wearable, biomedical devices was demonstrated.

Controlling spin dynamics through modulation of spin interactions in a fast, compact, and energy-efficient way is compelling for its abundant physical phenomena and great application potential in next-generation voltage controllable spintronic devices. In this work, we report electric field manipulation of spin dynamics—the two-magnon scattering (TMS) effect in Ni0.5Zn0.5Fe2O4 (NZFO)/Pb(Mg2/3Nb1/3)–PbTiO3 (PMN–PT) multiferroic heterostructures, which breaks the bottleneck of magnetostatic interaction-based magnetoelectric (ME) coupling in multiferroics. An alternative approach allowing spin-wave damping to be controlled by external electric field accompanied by a significant enhancement of the ME effect has been demonstrated. A two-way modulation of the TMS effect with a large magnetic anisotropy change up to 688 Oe has been obtained, referring to a 24 times ME effect enhancement at the TMS critical angle at room temperature. Furthermore, the anisotropic spin-freezing behaviors of NZFO were first determin...

Introducing patterned sensors onto polymer substrates has been regarded as a promising way to manufacture multifunctional and integrated flexible sensors, because of their huge potential applications in wearable devices. However, the scalable production of these electronic devices is still limited by the complex process required to achieve high quality. Here, we utilized poly(vinylidene fluoride) (PVDF) as the polymer substrate for its good toughness and environmental stability to fabricate flexible strain sensors with designed patterns. Thanks to the effective plasma pretreatment on PVDF with low activity, the piezoresistive ZnO nanolayer was directly deposited onto the surface of PVDF membrane via atomic layer deposition (ALD). Subsequently, the ZnO/PVDF based strain sensor exhibits a high performance to monitor the strain below 6%, and especially towards the very low strain ranging from 0.1% to 0.6%, which was difficult to be precisely detected by other methods. Interestingly, utilizing the low chemical activity of PVDF, the patterned deposition of ZnO could be facilely achieved via a relatively simple selective plasma pretreatment, which leaded to different wearable sensors be designed, and an array-style sensor be fabricated as in-situ sensors to detect the position under loading. Therefore, this work offers a new strategy to design and fabricate novel integrated wearable electronics.

The effects of ZnO modification on the microstructure and piezoelectric properties of Pb(Mg1/3Nb2/3)0.65Ti0.35O3 (PMNT) ceramics were investigated. The grain size tended to increase with increasing ZnO content. Secondary phases were observed in the ceramics with 4.0 and 11.0 mol%ZnO. The piezoelectric properties of the PMNT ceramics were enhanced by introduction of 0.4–4.0 mol%ZnO. The piezoelectric properties deteriorated when higher ZnO contents were used. Among all the investigated compositions, the highest piezoelectric performance was observed for the PMNT/0.4 mol%ZnO ceramic. This makes the PMNT/0.4 mol%ZnO ceramic promising for piezoelectric applications.

One of the central challenges in realizing multiferroics-based magnetoelectric memories is to switch perpendicular magnetic anisotropy (PMA) with a control voltage. In this study, we demonstrate electrical flipping of magnetization between the out-of-plane and the in-plane directions in (Co/Pt)3/(011) Pb(Mg1/3Nb2/3)O3–PbTiO3 multiferroic heterostructures through a voltage-controllable spin reorientation transition (SRT). The SRT onset temperature can be dramatically suppressed at least 200 K by applying an electric field, accompanied by a giant electric-field-induced effective magnetic anisotropy field (ΔHeff) up to 1100 Oe at 100 K. In comparison with conventional strain-mediated magnetoelastic coupling that provides a ΔHeff of only 110 Oe, that enormous effective field is mainly related to the interface effect of electric field modification of spin–orbit coupling from Co/Pt interfacial hybridization via strain. Moreover, electric field control of SRT is also achieved at room temperature, resulting in a ...

In ferroelectric materials, significant piezoelectric response only occurs after poling by an external electric field applied along a certain crystallographic direction, and the piezoelectric effect generally disappears upon heating to the Curie temperature (TC) where the poled state vanishes. This thermally induced depoling often restricts the temperature range for the applications of piezoelectric devices. It has been a challenge to develop materials that exhibit high piezoelectric performance that is not affected by electric poling, nor thermal depoling. Here we report an unusual piezoelectric effect found in Pb(Mg1/3Nb2/3)O3-PbSnO3-PbTiO3 ternary ferroelectric crystals which exhibit a relatively high piezoelectricity (with the piezoelectric coefficient d33 = 1350–1400 pC/N) without undergoing any poling process. Moreover, this high piezoelectric performance is retained after repeated thermal annealing at temperatures above TC, showing a piezoelectric memory effect. This uncommon piezoelectric effect is explained by a self-polarization mechanism based on the defect-dipoles formed in the crystals due to the presence of mixed valence states of Sn2+/4+. The defect-dipoles generate internal bias electric fields which, in turn, provide the stabilizing and restoring forces leading to preferred orientation states and the retention of spontaneous polarization. This mechanism offers a new perspective for designing novel piezoelectric materials with high performance and a wide temperature range of operation.

The aim of this work is to investigate the local structure of PbZr1−xTixO3 (PZT) single crystal with x = 0.44 under the application of electric field employing Synchrotron X-ray Absorption Near-Edge Structure (XANES) technique. In this experiment, PZT single crystal was subjected to 0.35 kV/mm and 0.70 kV/mm electric fields. The Ti K-edge XANES spectra reflect the significant change of the local structure of PZT unit cell before and after static electrical loading. From the XANES results, it was clearly seen that XANES spectral intensity gradually changed when the electrical load was applied. This can be caused by the shift of Ti atoms in the unit cell. The clear agreement between the measured and simulated XANES spectra was the supporting evidence of Ti off-center displacement in the PZT unit cell.

To develop high-performance piezo-/ferroelectric materials and to understand their underlying physical and chemical mechanisms, a novel ternary solid solution has been synthesized by a solid state reaction method in the form of ceramics with compositions across the morphotropic phase boundary (MPB). This ternary system is formed by incorporating Bi-based complex perovskite Bi(Zn2/3Nb1/3)O3 (BZN) into the relaxor-based binary solid solution of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT). The MPB structure, relaxor-to-ferroelectric phase transformation, local polar structure, ferroelectric properties and static and bipolar piezoelectric responses were investigated. X-ray diffraction analysis indicates that the (0.95 − x)PMN–0.05BZN–xPT solid solution transforms from a rhombohedral phase to a tetragonal phase when the composition is varied across the MPB which is located at x ∼ 0.30 to 0.33. Enhanced relaxor behaviour is found in this system and the relaxor state transforms into a ferroelectric phase spontaneously upon cooling, or under application of an electric field. The incorporation of BZN into PMN–PT results in the suppression of the MPB-related depoling (at TRT) and a significant enhancement of piezoelectric and ferroelectric properties compared with those of PMN–PT binary ceramics. The optimum properties are found in the MPB composition with a static piezoelectric coefficient d33 = 805 pC N−1, an electromechanical coupling factor kp = 0.57, a remanent polarization Pr = 30 μC cm−2 and a coercive field of EC = 7.9 kV cm−1. This enhancement of properties is attributed to the beneficial effects of BZN which enhances the structural distortion due to the lone-pair electrons on Bi3+ and the ferroelectrically active Zn2+ and Nb5+, and to the enhanced relaxor behaviour arising from the increase of the local disorder and the nanodomain effect. With its strengthened properties, the (0.95 − x)PMN–0.05BZN–xPT system becomes a promising electronic ceramic material for such devices as actuators, sensors, capacitors, and transducers for a wide range of applications.

In ferromagnets, the magnetic moment can generally be reversed by applying a sufficiently high external magnetic field of opposite polarity. Temperature, on the other hand, is usually known to affect only the magnitude of a magnetic moment, rather than its sign or polarity (most magnets exhibit a monotonic increase in magnetization upon cooling below their magnetic phase transition temperature). As a result, temperature-induced magnetization reversal (i.e. magnetic pole inversion) remains a very rare phenomenon which lacks proper understanding and explanation because of the extreme difficulties encountered in controlling the thermodynamics of magnetization of classical metal or metal oxide magnets. Herein, we report an unusual magnetic pole inversion behaviour in multiferroic (1 − x)BiFeO3–xDyFeO3 solid solution (alloy), which can be tuned by varying the concentration of the magnetic ion Dy3+ in the solid solution. It is found that the temperature-induced magnetic pole inversion occurs in a wide composition range (x = 0.14–0.90). Moreover, for the first time in any ferrites, multiple magnetic pole inversions are observed in the solid solution compounds of high Dy3+-concentrations. Our results may provide a better understanding of the temperature- and composition-induced magnetic pole inversion and related phenomena and point to new potential applications for magnetic and multiferroic materials.

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.

Ferroelectrics are usually inflexible oxides that undergo brittle deformation. We synthesized freestanding single-crystalline ferroelectric barium titanate (BaTiO3) membranes with a damage-free lifting-off process. Our BaTiO3 membranes can undergo a ~180° folding during an in situ bending test, demonstrating a super-elasticity and ultraflexibility. We found that the origin of the super-elasticity was from the dynamic evolution of ferroelectric nanodomains. High stresses modulate the energy landscape markedly and allow the dipoles to rotate continuously between the a and c nanodomains. A continuous transition zone is formed to accommodate the variant strain and avoid high mismatch stress that usually causes fracture. The phenomenon should be possible in other ferroelectrics systems through domain engineering. The ultraflexible epitaxial ferroelectric membranes could enable many applications such as flexible sensors, memories, and electronic skins.

Let's talk about your flaws\dots{} The authors present nondestructive examination of the crystallographic properties (including crystal size, facet shape, strain, and defects) of lone InP nanocrystals (NC) grown on Si nanostructures. This sort of three-dimensional structured imaging is of great significance in evaluating the quality of the active nanomaterials in fully processed nanoelectronic and nano-optoelectronic devices, even in an $o\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}o$ manner.

Doping is a widely used method to tune the physical properties of ferroelectric perovskites. Since doping can induce effective charges, it is important to understand how charges affect the chemical and physical properties of the doped perovskites. Here, we propose two charge compensation models, by adding the charge‐dipole interaction to the effective Hamiltonian, which has not been done previously, and numerically investigate how lanthanum doping affects the ferroelectric phase transition temperature and the hysteresis loop in BaTiO3. The consequences of the charge compensation models are compared and discussed, revealing that the electron compensation mechanism with some Ti4+ ions changing to Ti3+ is critical to understanding the donor‐doped perovskites.

Lead-based perovskite relaxor ferroelectrics are widely used as materials for numerous applications due to their extraordinary dielectric, piezoelectric, and electrostrictive properties. While the mechanisms of relaxor behavior are disputable, the importance of quenched (static) random electric fields created at nanoscale by the disordered heterovalent cations has been well recognized. Meanwhile, an increasing amount of scientific and technological efforts has been concentrated on lead-free perovskites, in particular, solid solutions of classical ferroelectric $\mathrm{BaTi}{\mathrm{O}}_{3}$ (BT), which better meet ecological requirements. Among BT-based solutions the homovalent systems are elaborately studied where strong random electric fields are absent, while the solubility limit of heterovalent solutions is typically too low to fully reveal the peculiarities of relaxor behavior. In this paper, we prepare a perovskite solid solution system $(1\ensuremath{-}x)\mathrm{B}{\mathrm{a}}^{2+}\mathrm{T}{\mathrm{i}}^{4+}{\mathrm{O}}_{3}\ensuremath{-}x\mathrm{D}{\mathrm{y}}^{3+}\mathrm{F}{\mathrm{e}}^{3+}{\mathrm{O}}_{3}$ ($0\ensuremath{\le}x\ensuremath{\le}0.3$) and study it as a model heterovalent lead-free system. We determine crystal structure, ferroelectric, and dielectric properties of ceramics in a wide range of temperatures and concentrations, construct a phase diagram, and find and analyze the concentration-induced crossover from normal ferroelectric to relaxor behavior. We demonstrate that quenched random electric fields of moderate strength promote the ferroelectric-to-relaxor crossover, but do not change qualitatively the peculiarities of relaxor behavior, while strong enough fields destroy the relaxor state, so that the material becomes an ordinary linear dielectric. The experimental results are compared with the predictions of known theories of relaxor ferroelectricity.