The present article serves as a concise review of strain glass and its broader concept – ferroic glass. Strain glass is a frozen disordered strain state composed of nano‐sized strain domains, which ...is formed due to the frustration created by point defects or dopants. Such frustration creates glassy nano‐sized martensite‐like domains that do not grow into a macroscopic martensite during cooling and instead show typical glass‐freezing dynamics. Strain glass bears much resemblance with the glass phenomena found in other two types of ferroic systems, relaxor ferroelectric, and spin glass. These three ferroics‐based glasses are thus called ferroic glasses. Characteristics of strain glass, including recent in situ high‐resolution TEM images, are shown. Unusual properties associated with strain glass, such as superelasticity with narrow hysteresis, high‐damping, and low modulus, as well as Invar and Elinvar effect in cold‐rolled β‐Ti alloys are demonstrated.
Strain glass is a frozen disordered strain state composed of nano‐sized strain domains, which is formed due to the frustration created by point defects or dopants. It bears much resemblance with the glass phenomena found in other two types of ferroic systems: relaxor ferroelectric and cluster spin glass. Unusual properties associated with strain glass, such as superelasticity with narrow hysteresis, high damping and low modulus, as well as Invar and Elinvar effect in cold‐rolled β‐Ti alloys are demonstrated.
We report a non-Pb piezoelectric ceramic system Ba(Ti(0.8)Zr(0.2))O(3)-(Ba(0.7)Ca(0.3))TiO(3) which shows a surprisingly high piezoelectric coefficient of d(33) approximately 620 pC/N at optimal ...composition. Its phase diagram shows a morphotropic phase boundary (MPB) starting from a tricritical triple point of a cubic paraelectric phase (C), ferroelectric rhombohedral (R), and tetragonal (T) phases. The high piezoelectricity of the MPB compositions stems from the composition proximity of the MPB to the tricritical triple point, which leads to a nearly vanishing polarization anisotropy and thus facilitates polarization rotation between 001T and 111R states. We predict that the single-crystal form of the MPB composition of the present system may reach a giant d(33) = 1500-2000 pC/N. Our work may provide a new recipe for designing highly piezoelectric materials (both Pb-free and Pb-containing) by searching MPBs starting from a TCP.
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•A new theory named “crossover relaxor ferroelectrics” were reported.•Crossover relaxor 0.9BBNT-0.1SSN ceramic processes high Wrec of 2.02 J/cm3 and η of 90.18% at ...206 kV/cm.•0.9BBNT-0.1SSN ceramic exhibits strong chemical and electrical uniformity.•The excellent thermal stability, frequency stability, and cycle life stability have been achieved in 0.9BBNT-0.1SSN ceramic.
With a view to the rapid development of pulsed power capacitors, the demands for higher energy density, energy efficiency, and stability have increased significantly. A large amount of research has been devoted to the energy storage field of dielectric ceramics, however, scientific and effective strategy to design novel materials with excellent energy storage performance is still lacking. In this work, a new guideline was proposed that higher energy density and efficiency are easier obtained in crossover relaxor ferroelectrics, which is between normal ferroelectrics and relaxor ferroelectrics. Based on this theory, a series of lead-free (1-x)(0.65BaTiO3-0.35Bi0.5Na0.5TiO3)-xSr(Sc0.5Nb0.5)O3 ((1-x)BBNT-xSSN, x = 0, 0.05, 0.10, 0.15, 0.20) ceramics are designed and investigated. Optimal energy storage properties are achieved in 0.9BBNT-0.1SSN ceramic, with a large Wrec of 2.02 J/cm3 and a high η of 90.18% under a moderate electric field of 206 kV/cm. More importantly, both the Wrec and η of 0.9BBNT-0.1SSN ceramic show outstanding stability (including frequency, thermal, and cycle life stability) at 150 kV/cm, which is superior to other lead-free ceramics. These results demonstrate 0.9BBNT-0.1SSN ceramic is a promising candidate for practical energy storage applications.
Ferroelectric crystals are characterized by their asymmetric or polar structures. In an electric field, ions undergo asymmetric displacement and result in a small change in crystal dimension, which ...is proportional to the applied field. Such electric-field-induced strain (or piezoelectricity) has found extensive applications in actuators and sensors. However, the effect is generally very small and thus limits its usefulness. Here I show that with a different mechanism, an aged BaTiO3 single crystal can generate a large recoverable nonlinear strain of 0.75% at a low field of 200 V mm−1. At the same field this value is about 40 times higher than piezoelectric Pb(Zr, Ti)O3 (PZT) ceramics and more than 10 times higher than the high-strain Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) single crystals. This large electro-strain stems from an unusual reversible domain switching (most importantly the switching of non-180° domains) in which the restoring force is provided by a general symmetry-conforming property of point defects. This mechanism provides a general method to achieve large electro-strain effect in a wide range of ferroelectric systems and the effect may lead to novel applications in ultra-large stroke and nonlinear actuators.
Although extensive studies have been done on lead-free dielectric ceramics to achieve excellent dielectric behaviors and good energy storage performance, the major problem of low energy density has ...not been solved so far. Here, we report on designing the crossover relaxor ferroelectrics (CRFE), a crossover region between the normal ferroelectrics and relaxor ferroelectrics, as a solution to overcome the low energy density. CRFE exhibits smaller free energy and lower defect density in the modified Landau theory, which helps to obtain ultrahigh energy density and efficiency. The (1–x)Ba0.65Sr0.35TiO3–xBi(Mg2/3Nb1/3)O3 ((1–x)BST–xBMN) (x = 0, 0.08, 0.1, 0.18, 0.2) ceramic was synthesized by a solid-state reaction method. The solid solutions exhibit dielectric frequency dispersion, which suggests typical relaxor characteristics with the increasing BMN content. The crossover ferroelectrics of 0.9BST–0.1BMN ceramic possesses a high energy storage efficiency (η) of 85.71%, a high energy storage density (W) of 3.90 J/cm3, and an ultrahigh recoverable energy storage density (W rec) of 3.34 J/cm3 under a dielectric breakdown strength of 400 kV/cm and is superior to other lead-free BaTiO3 (BT)-based energy storage ceramics. It also exhibits strong thermal stability in the temperature range from 25 to 150 °C under an electric field of 300 kV/cm, with the fluctuations below 3% and with the energy storage density and energy efficiency at about 2.8 J/cm3 and 82.93%, respectively. The enhanced recoverable energy density and breakdown strength of BT-based materials with significantly high energy efficiency make it a promising candidate to meet the wide requirements for high power applications.
•The doping of SSN increased the band gap width and decreased the grain size.•The ceramic possesses an energy density of 4.42 J/cm3 and an efficiency of 60%.•The transmittance of the ceramic is 76.7% ...and 84.5% at 780 and 1378 nm, respectively.•0.825KNN-0.175SSN ceramic exhibited a small strain effect of 0.022%.
Lead-free transparent ferroelectric ceramics with superior energy storage properties are highly desirable for pulsed power technologies and the increased optical transparency demand. However, the transparency and energy storage density of lead-free bulk ceramics cannot meet the requirements of their wide applications due to the coarse microstructure and relatively low breakdown strength. In this study, a design strategy is proposed to optimize the energy storage characteristics and transparency of ceramics by introducing nanodomains, increasing the band gap energy and reducing the grain size. The results showed that submicron grain (0.21 μm) and large band gap energy (Eg = 3.21 eV) were achieved through the introduction of the second component Sr(Sc0.5Nb0.5)O3 (SSN). An excellent transparency of up to 84.5% in the near-infrared region (1378 nm), a high energy density (W) of ~4.42 J·cm−3 and an extremely small strain of ~0.022% were simultaneously achieved in the 0.825(K0.5Na0.5)NbO3-0.175Sr(Sc0.5Nb0.5)O3 (0.825KNN-0.175SSN) ceramics. These results revealed the potential applications of (K0.5Na0.5)NbO3-based ceramics for energy storage and provide a feasible approach of domain engineering to develop new lead-free energy storagetransparency materials.
Electromechanical materials with large electrostrain and low hysteresis are strongly desired for high-precision actuator applications. Despite extensive studies for more than half a century, it is ...still a challenge to obtain large electrostrain and low hysteresis simultaneously due to the so-called strain-hysteresis trade-off. Here, we report a mechanism to overcome this trade-off: a ceramic composition locating at a morphotropic relaxor boundary (MRB), exhibits enhanced electrostrain and reduced hysteresis as compared with off-MRB compositions. The MRB, a composition-induced boundary separating two relaxors with different local polar symmetries, is attained by transforming an morphotropic phase boundary (MPB) in Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) through doping lanthanum. The performances of large electrostrain of 0.227% and negligible hysteresis of 3% of MRB composition are the best, as evidenced by occupying a virgin region in the strain-hysteresis chart of relaxor electromechanical ceramics. Moreover, this MRB ceramic maintains the large electrostrain and low hysteresis over a temperature range from 35 to -35 °C. The understanding of abnormal effects of MRB is established through combining microstructure observations and Landau theory analysis: the MRB composition with morphotropic nanodomain structure and higher degree of local structural heterogeneity shows a flatter energy profile with much lower energy barrier, thereby leading to a large electrostrain and negligible hysteresis. Our work demonstrates that the MRB is an effective mechanism to design relaxor materials with large electrostrain and low hysteresis simultaneously. We predict that more high-performance MRB electromechanical materials will be found in properly doped MPB systems.
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In ferroelectric and relaxor-ferroelectric materials, piezoelectric and dielectric properties are significantly enhanced at the morphotropic phase boundary (MPB), a boundary between different ...ferroelectric phases with different macroscopic symmetries. By contrast, in relaxor systems, such an MPB does not exist because relaxors of different compositions possess the same macroscopic symmetry. Here, we report the existence of a morphotropic relaxor boundary (MRB) in the single phase relaxor region of a K0.5Na0.5NbO3−xBaTiO3 system, which is a composition-induced boundary between two relaxors with different local polar symmetries (tetragonal versus rhombohedral) but with the same macroscopic cubic symmetry. At the MRB the electrostrain increases by ∼3 times and the permittivity increases by ∼1.5 times over a wide temperature range of more than 100 K, as compared with off-MRB compositions. Our Letter demonstrates that the MRB may become an effective mechanism to enhance the dielectric and electrostrictive properties of relaxors.
Here, we report a new phenomenon of uniform and continuous transformation of a single polarization domain into alternating nanodomains of two polarization vectors with the same magnitude but ...different directions at ferroelectric morphotropic phase Boundary (MPB). The transformation is fully reversible and could enhance the piezoelectric coefficient d33. Further free energy calculations illustrate that such a polarization "decomposition" process occurs within the region on the Landau free energy curve with respect to the polarization direction where the second derivative becomes negative, which is similar to spinodal instability in phase transformations such as spinodal ordering or isostructural phase separation (e.g., spinodal decomposition). This "polarization spinodal" uncovers a new mechanism of polarization switching that may account for the ultrahigh ahysterestic piezoelectric strain at the MPB. This work could shed light on the development of phase transition theory and the design of novel ferroelectric memory materials.
Due to issues with Pb toxicity, there is an urgent need for high performance Pb-free alternatives to Pb-based piezoelectric ceramics. Although pure BaTiO3 material exhibits fairly low piezoelectric ...coefficients, further designing of such a material system greatly enhances the piezoelectric response by means of domain engineering, defects engineering, as well as phase boundary engineering. Especially after the discovery of a Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 system with extraordinarily high piezoelectric properties (d33 > 600 pC/N), BaTiO3-based piezoelectric ceramics are considered as one of the promising Pb-free substitutes. In the present contribution, we summarize the idea of designing high property BaTiO3 piezoceramic through domain engineering, defect-doping, as well as morphotropic phase boundary (MPB). In spite of its drawback of low Curie temperature, BaTiO3-based piezoelectric materials can be considered as an excellent model system for exploring the physics of highly piezoelectric materials. The relevant material design strategy in BaTiO3-based materials can provide guidelines for the next generation of Pb-free materials with even better piezoelectric properties that can be anticipated in the near future.
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