Showing papers on "Ferroelasticity published in 2018"

Crystal Adaptronics: Mechanically Reconfigurable Elastic and Superelastic Molecular Crystals.

Abstract: Mechanically reconfigurable molecular crystals-ordered materials that can adapt to variable operating and environmental conditions by deformation, whereby they attain motility or perform work-are quickly shaping a new research direction in materials science, crystal adaptronics. Properties such as elasticity, superelasticity, and ferroelasticity, which are normally related to inorganic materials, and phenomena such as shape-memory and self-healing effects, which are well-established for soft materials, are increasingly being reported for molecular crystals, yet their mechanism, quantification, and relation to the crystal structure of organic crystals are not immediately apparent. This Minireview provides a condensed topical overview of elastic, superelastic, and ferroelastic molecular crystals, new classes of materials that bridge the gap between soft matter and inorganic materials. The occurrence and detection of these unconventional properties, and the underlying structural features of the related molecular materials are discussed and highlighted with selected prominent recent examples.

Role of Reversible Phase Transformation for Strong Piezoelectric Performance at the Morphotropic Phase Boundary

Abstract: A functional material with coexisting energetically equivalent phases often exhibits extraordinary properties such as piezoelectricity, ferromagnetism, and ferroelasticity, which is simultaneously accompanied by field-driven reversible phase transformation. The study on the interplay between such phase transformation and the performance is of great importance. Here, we have experimentally revealed the important role of field-driven reversible phase transformation in achieving enhanced electromechanical properties using in situ high-energy synchrotron x-ray diffraction combined with 2D geometry scattering technology, which can establish a comprehensive picture of piezoelectric-related microstructural evolution. High-throughput experiments on various $\mathrm{Pb}/\mathrm{Bi}$-based perovskite piezoelectric systems suggest that reversible phase transformation can be triggered by an electric field at the morphotropic phase boundary and the piezoelectric performance is highly related to the tendency of electric-field-driven phase transformation. A strong tendency of phase transformation driven by an electric field generates peak piezoelectric response. Further, phase-field modeling reveals that the polarization alignment and the piezoelectric response can be much enhanced by the electric-field-driven phase transformation. The proposed mechanism will be helpful to design and optimize the new piezoelectrics, ferromagnetics, or other related functional materials.

A controllable robust multiferroic GaTeCl monolayer with colossal 2D ferroelectricity and desirable multifunctionality.

Abstract: We propose through first-principles investigation that the GaTeCl monolayer is an excellent two-dimensional (2D) multiferroic with giant mechanical anisotropy. The calculated phonon spectrum, molecular dynamic simulations, and elastic moduli confirm its dynamic and mechanical stability, and our cleavage energy analysis shows that exfoliating one GaTeCl monolayer from the existing GaTeCl bulk is feasible. The calculated in-plane ferroelectric polarization reaches 578 pC m-1. The energy barriers per formula unit of the ferroelastic 90° rotational and ferroelectric reversal transitions are 476 meV and 754 meV, respectively, being the greatest in the 2D multiferroics family so far. Importantly, on the other hand, a tensile stress of 4.7 N m-1 perpendicular to the polarization can drive the polarization to rotate by 90°. These can make the GaTeCl monolayer have not only robust ferroelasticity and ferroelectricity but also easy mechanical controllability. Furthermore, the GaTeCl monolayer has giant piezoelectricity and optical second harmonic generation, especially in the range of visible light, and a tensile stress of 0.3 N m-1 along the polarization can make the indirect gap transit to the direct gap. These interesting mechanical, electronic, and optical properties of the GaTeCl monolayer show its great potential in high-performance multi-functional applications.

Ferroelectricity and Ferroelasticity in Organic Inorganic Hybrid (Pyrrolidinium)3[Sb2Cl9]

Abstract: Perovskite-like materials exhibit desirable photophysical and electric properties that make them suitable for a remarkable breadth of applications in electronics and physics. In this contribution, we report on the multiphase ferroelectric and ferroelastic phenomena in a pyrrolidinium-based hybrid metal–organic material: (C4H8NH2)3[Sb2Cl9]. The title compound is the first pyrrolidinium derivative within the halobismuthates(III) and haloantimonates(III) families that is featured by the ferroelectric property. From a structural point of view, the crystal structure is built of [Sb2Cl9]3–∞ perovskite-like layers, interdigitated by layers of pyrrolidinium cations. The rich solid-state dynamics of pyrrolidinium cations endowed (C4H8NH2)3[Sb2Cl9] with a complex sequence of temperature-dependent phase transitions. Remarkably, polar properties have been found to occur in all six phases, including room-temperature Phase I. Insights from variable-temperature single-crystal X-ray diffraction, dielectric spectroscopy, ...

Transition-metal-doped group-IV monochalcogenides: a combination of two-dimensional triferroics and diluted magnetic semiconductors.

Abstract: We report the first-principles evidence of a series of two-dimensional triferroics (ferromagnetic + ferroelectric + ferroelastic), which can be obtained by doping transition-metal ions in group-IV monochalcogenide (SnS, SnSe, GeS, GeSe) monolayers, noting that a ferromagnetic Fe-doped SnS2 monolayer has recently been realized (Li B et al 2017 Nat. Commun. 8 1958). The ferroelectricity, ferroelasticity and ferromagnetism can be coupled and the magnetization direction may be switched upon ferroelectric/ferroelastic switching, rendering electrical writing + magnetic reading possible. They can be also two-dimensional half-metals or diluted magnetic semiconductors, where p/n channels or even multiferroic tunneling junctions can be designed by variation in doping and incorporated into a monolayer wafer.

Versatile Ferroelastic Deformability in an Organic Single Crystal by Twinning about a Molecular Zone Axis

Abstract: Ferroelasticity involves the generation of spontaneous strain in a solid by the application of mechanical stress. The phenomenon has been well-studied in metal alloys but relatively neglected in organic solid-state chemistry. Herein we present multiple discrete modes of mechanical twinning and a mechanistic analysis of ferroelasticity in 1,4-diethoxybenzene. Single crystals of the compound can be almost freely deformed, as multiple different twin domains are generated simultaneously. Within each domain, single-crystal character is preserved. Such extremely versatile, ferroelastic deformability is unprecedented in single crystals of any kind and defies the fragility and anisotropic mechanical behaviour of most organic crystals. The dissipated energy and critical stress associated with twinning deformation in 1,4-diethoxybenzene suggests that organic solids could be developed for absorbing weak mechanical shocks in such applications as mechanical damping and soft robotics.

Dynamic behavior of CH3NH3PbI3 perovskite twin domains

Abstract: The recent discovery of twin domains in MAPbI3 perovskites has initiated contentious discussion on the ferroic nature of hybrid perovskites. Ferroelectric polarization is thought to facilitate the dissociation of photoinduced electron-hole pairs, helping to explain the extraordinary photovoltaic performance exhibited by this class of materials. Alternate to ferroelectricity, which has yet to be unambiguously established despite considerable efforts to do so, ferroelasticity was also proposed in these materials. Meanwhile, given the coupling of ionic states and ferroelectricity and the interconnected nature of defect chemistry and ferroelasticity, the electrochemical reactivity can no longer be ignored. In this work, using band excitation piezoresponse force microscopy, we reveal the variation in elasticity between adjacent domains, indicating the ferroelasticity and the difference in the crystallographic states of the twin domain. Moreover, using band excitation contact Kelvin probe force microscopy, we dynamically map the evolution of the twinning structure under electric bias. These results help decipher the effect of the twin domains on ionic mobility and ion diffusion pathways. Combining these results, we reveal the interaction of twin domains and ionic activity in this material. Overall, this work provides insights into the twinning structure in MAPbI3 and its potential effects on the hybrid perovskite optoelectronics.

Linear and nonlinear optical probe of the ferroelectric-like phase transition in a polar metal, LiOsO 3

Abstract: LiOsO3 is one of the first materials identified in the recent literature as a “polar metal,” a class of materials that are simultaneously noncentrosymmetric and metallic In this work, the linear and nonlinear optical susceptibility of LiOsO3 is studied by means of ellipsometry and optical second harmonic generation (SHG) Strong optical birefringence is observed using spectroscopic ellipsometry The nonlinear optical susceptibility extracted from SHG polarimetry reveals that the tensor components are of the same magnitude as in the isostructural insulator LiNbO3, except the component along the polar axis d33 is suppressed by an order of magnitude Temperature-dependent SHG measurements in combination with Raman spectroscopy indicate a continuous order-disorder type polar phase transition at 140 K Linear and nonlinear optical microscopy measurements reveal 109°/71° ferroelastic domain walls, like in other trigonal ferroelectrics No 180° polar domain walls are observed to emerge across the phase transition

An organoferroelasticity driven by molecular conformational change

Abstract: A single crystal of adipic acid shows twinning ferroelasticity by the reversible molecular conformational change. The flexible nature of components in molecular solids raises the efficiency of energy dissipation using organoferroelasticity.

Twinning ferroelasticity facilitated by the partial flipping of phenyl rings in single crystals of 4,4'-dicarboxydiphenyl ether.

Abstract: Evidence of ferroelasticity in a non-planar organic molecular crystal is presented for 4,4′-dicarboxydiphenyl ether. Ferroelasticity has been demonstrated by the micro- and macroscopic mechanical characterization of single crystals, including recording of a full hysteretic stress–strain cycle. The underlying mechanism involves the partial flipping of phenyl rings.

Mechanosynthesis of Nanocrystalline Fully Stabilized bcc γ-phase of Bi2O3 without Any Additive: Manifestation of Ferroelasticity in Microstructure, Optical, and Transport Properties

Abstract: In the present work, polymorphic phase transformation of Bi2O3 nanoparticles by the mechanical alloying method has been investigated in detail X-ray diffraction study reveals that the room tempera

Ferroelastically and magnetically co-coupled resistive switching in Nd0.5Sr0.5MnO3/PMN-PT(011) multiferroic heterostructures

Abstract: The phase separation, i.e., the competition between coexisting multi-phases, can be adjusted by external stimuli, such as magnetic field, electric field, current, light, and strain. Here, a multiferroic heterostructure composed of a charge-ordered Nd0.5Sr0.5MnO3 thin film and a ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal is fabricated to investigate the lattice strain and magnetic field co-control of phase separation in resistive switching. The stable and nonvolatile resistance tuning is realized at room temperature using the electric-field-induced reversible ferroelastic strain effect, which can be enhanced by 84% under the magnetic field. Moreover, the magnetoresistance can be effectively tuned by the electrically driven ferroelastic strain. These findings reveal that the ferroelastic strain and the magnetic field strongly correlate with each other and are mediated by phase separation. Our work provides an approach to design strain-engineered multifunctional memory devices based on complex oxid...

Ferroelasticity and piezoelectricity of organic–inorganic hybrid materials with a one-dimensional anionic structure: so similar, yet so different

Abstract: The synthesis, structural aspects, thermal and dielectric analysis for new members of the ferroic family, polynuclear Bi(III) and Sb(III) halide complexes based on a pyrazolium cation with the formulas (C3N2H5)[BiCl4]·H2O and (C3N2H5)[SbCl4]·H2O, are presented. The former compound was found to undergo a ferroic phase transition of the ferroelastic type at 213/219 K (cooling/heating scans), whereas, the latter one exhibited a piezoelectric feature in the dielectric response function. The molecular motions of pyrazolium cations were analyzed based on the spin–lattice relaxation time of 1H NMR measurements.

Magnetic and electrical properties in Co-doped KNbO3 bulk samples

Abstract: Multiferroic materials exhibit in the same phase at least two of the ferroic properties: ferroelectricity, ferromagnetism, and ferroelasticity, which may be coupled to each other. In this work, we investigated bulk materials with a nominal composition KNb0.95Co0.05O3 (KN:Co) fabricated by the standard solid-state reaction technique. X-ray diffraction analysis of the polycrystalline sample shows the respective polycrystalline perovskite structure of the KNbO3 phase with only small variation due to the Co doping. No secondary or segregated phases are observed. The values of the extracted lattice parameters are very close to those reported in the literature for KNbO3 with orthorhombic symmetry (a = 5.696 A, b = 3.975 A, and c = 5.721 A) with space group Bmm2. Measurements of the electric polarization as a function of the electric field at different temperatures indicate the presence of ferroelectricity in our samples. Magnetic response of the pellets, detected by high sensitivity measurements of magnetizatio...

Intermittent dynamics in externally driven ferroelastics and strain glasses

Abstract: The interplay of elastic anisotropy and disorder dictates many of the properties of ferroic materials, specifically martensites. We use a phase-field model for ferroelastic athermal materials to study their response to an increasing external stress that couples to the strain order parameter. We show that these systems evolve through avalanches and study the avalanche-size distribution for ferroelastic systems (large anisotropy and/or small disorder) and for the strain glass (small anisotropy and/or large disorder) using various statistical analysis techniques, including the maximum likelihood method. The model predicts that in the former case the distribution is subcritical or power law (in agreement with experimental observations), whereas in the latter case it becomes supercritical. Our results are consistent with experiments on martensitic materials, and we predict specific avalanche behavior that can be tested and used as an alternative means to characterize strain glasses.

Stress-dependent crystal structure of lanthanum strontium cobalt ferrite by in situ synchrotron X-ray diffraction

Abstract: Lanthanum strontium cobalt ferrite La1-xSrxCo1-yFeyO3-δ (LSCF) is one of the most studied mixed ionic-electronic conductor materials due to electrical and transport properties, which are attractive for intermediate temperature solid oxide fuel cells (SOFCs), oxygen permeation membranes, and catalysis. The integration of such materials, however, depends on the thermal as well as mechanical behavior. LSCF exhibits nonlinear hysteresis during compressive stress-strain measurements, marked by a remanent strain and coercive stress, i.e., ferroelasticity. However, the origin of ferroelastic behavior has not been investigated under high compressive stress. This study, therefore, investigates the microscopic origin of stress-induced mechanical behavior in polycrystalline (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ using in situ synchrotron x-ray diffraction. The data presented here reveals that the strain response originates from the intrinsic lattice strain as well as the extrinsic domain switching strain without any apparent change in crystallographic symmetry. A comparison of the calculated microscopic strain contribution with that of a macroscopic measurement indicates a significant change in the relative contributions of intrinsic and extrinsic strain depending on the applied stress state, i.e., under maximum stress and after unloading. Direct evidence of the microscopic origin of stress-strain response outlined in this paper may assist in guiding materials design with the improved mechanical reliability of SOFCs.Lanthanum strontium cobalt ferrite La1-xSrxCo1-yFeyO3-δ (LSCF) is one of the most studied mixed ionic-electronic conductor materials due to electrical and transport properties, which are attractive for intermediate temperature solid oxide fuel cells (SOFCs), oxygen permeation membranes, and catalysis. The integration of such materials, however, depends on the thermal as well as mechanical behavior. LSCF exhibits nonlinear hysteresis during compressive stress-strain measurements, marked by a remanent strain and coercive stress, i.e., ferroelasticity. However, the origin of ferroelastic behavior has not been investigated under high compressive stress. This study, therefore, investigates the microscopic origin of stress-induced mechanical behavior in polycrystalline (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ using in situ synchrotron x-ray diffraction. The data presented here reveals that the strain response originates from the intrinsic lattice strain as well as the extrinsic domain switching strain without any appare...

Time and frequency dependent mechanical properties of LaCoO3-based perovskites: Internal friction and negative creep

Abstract: The internal friction and creep deformation behavior of La0.8Ca0.2CoO3 and pure LaCoO3 mixed ionic electronic conducting perovskite ceramics have been studied by Dynamic Mechanical Analysis and uniaxial compression under constant applied load, respectively. It was found that both the internal friction and creep strain were almost an order of magnitude higher for Ca2+ doped LaCoO3 as compared to pure undoped LaCoO3. The difference in Ca2+ doped LaCoO3 behavior was attributed to the much higher concentration of point defects (e.g., oxygen vacancies) in the structure and their interaction with other mobile defects, such as ferroelastic domain/twin walls, stacking faults, dislocations, etc. Such interactions of numerous point defects with domain walls produce energetic barriers and slow down the movement of ferroelastic domain walls under applied stress. At the same time, the defects' interactions increase the internal friction resulting in a much higher creep strain of La0.8Ca0.2CoO3 as compared to pure LaCoO3, as the creep strain is determined by the distance between the domain wall and its equilibrium position at the onset of the creep process. Therefore, the high friction will result in the larger distance the wall has to move to reach the equilibrium which in turn results in higher creep strain. The expansion of LaCoO3 under constant applied compressive stress, named here as negative creep, was also discovered to occur during room temperature creep experiments.The internal friction and creep deformation behavior of La0.8Ca0.2CoO3 and pure LaCoO3 mixed ionic electronic conducting perovskite ceramics have been studied by Dynamic Mechanical Analysis and uniaxial compression under constant applied load, respectively. It was found that both the internal friction and creep strain were almost an order of magnitude higher for Ca2+ doped LaCoO3 as compared to pure undoped LaCoO3. The difference in Ca2+ doped LaCoO3 behavior was attributed to the much higher concentration of point defects (e.g., oxygen vacancies) in the structure and their interaction with other mobile defects, such as ferroelastic domain/twin walls, stacking faults, dislocations, etc. Such interactions of numerous point defects with domain walls produce energetic barriers and slow down the movement of ferroelastic domain walls under applied stress. At the same time, the defects' interactions increase the internal friction resulting in a much higher creep strain of La0.8Ca0.2CoO3 as compared to pure LaCo...

Impact of mechanical stress on barium titanate-based positive temperature coefficient resistive material

Abstract: The sensitivity toward mechanical stress of barium titanate-based positive temperature coefficient resistor material was investigated by determining the resistance change with application of uniaxial stress from room temperature to 200 °C, which is well above the Curie temperature TC. Using the Landau–Ginsburg–Devonshire theory the resistance increases in the paraelectric state, the negligible impact of stress close to TC and the observed increase in TC with increasing stress could be rationalized. For the ferroelectric state, the stress-related resistance increase was attributed to ferroelasticity, a change in bulk permittivity and interfacial stress inducing a piezoelectric potential. The obtained results are also discussed with respect to recent endeavors to tune properties of potential barriers in piezoelectric semiconductors by mechanical stress.

Multiferroic properties of exotic double perovskite A2BB' O6

Abstract: Multiferroic material in which there co-exist at least two of the ferro-phases,namely ferroelectricity,(anti-) ferromagnetism,and ferroelasticity,has attracted considerable attention in recent years due to its intriguing physics and potential applications for advanced multifunctional devices.However,multiferroic materials are rare due to the contradictory requirements between electrical polarization and magnetism.So far,only several compounds have been reported to show above-room temperature multiferroics.Thus,it is essential to search for new materials.The two most significant strategies to obtain multiferroics are 1) to incorporate magnetic transition-metal ions into polar structures to obtain polar magnets,and 2) to introduce special magnetic structure to drive ferroelectricity (the so-called type-Ⅱ multiferroics).Exotic double perovskite-related oxide A2BB'O6 with small A-site cations is one of the most extensively studied multiferroic families in recent years. The small A-site cations give small perovskite tolerance factor (t),and mostly high-pressure synthesis is required to stabilize the exotic perovskite structure.The crystal structure of exotic A2BB' O6 oxides can crystallize into either the centrosymmetric alumina corundum (AL),ilmenite (IL),or distorted GdFeO3-type perovskite structure,or the polar LiNbO3(LN),Ni3TeO6(NTO),or ordered ilmenite (OIL) structure.The polar LN,NTO,and OIL structures can accommodate magnetic transition-metal ions at both the A and B/B'sites in octahedral coordination,giving enhanced magnetic interactions and thus robust magneto-electric effect and high spontaneous polarization as well (usually above 50 C/cm-2,more than twice that in the renown BaTiO3),examples include the LN-type Mn2FeNbO6,and Mn2FeTaO6,OIL-type Mn2FeMoO6,and NTO-type Mn2FeMoO6,Mn2FeWO6,and Mn2MnWO6.These polar magnets show potential multiferroic responses even above room temperature (e.g.,ferromagnetic ordering temperature up to 340 K in NTO-type Mn2FeMoO6) and magnetoelectric coupling effect as in Mn2MnWO6.Magnetoelectric coupling can also arise in centrosymmetric IL structure in the absence of helical spin structure,such as those that are observed in Mn2FeSbO6,which exhibits colinear ferrimagnetic spin arrangement but magnetostriction induced antiferroelectricity.The corundum derivatives (AL,LN,IL,OIL,and NTO) and perovskite phases are competitive,depending on the electron configuration and synthesis pressure,and usually higher pressure favors the formation of perovskite structure.Compared with polar magnets in the corundum family,the exotic double perovskite adopts distorted GdFeO3-type structure (P21/n) with eight-coordination of the A-sites.In some double perovskite materials,the electric polarization can be induced by the special magnetic order,such as the ⇈⇊ magnetic structure induced type-Ⅱ multiferroics exemplified by A2CoMnO6(A=Lu,Y,Yb,Lu).In this review paper,we first compare the structure features of conventional and exotic double perovskite A2BB'O6 derived from the simple ABO3 analog,then summarize the recent progress of multiferroics in exotic double perovskite family,such as the polar magnets with transition-metal (Mn and Ni) cations at the A sites,type-Ⅱ multiferroic Mn2FeSbO6,and A2CoMnO6(A=Lu,Y,Yb,Lu). Finally,the problems and prospection of multiferroics in exotic double perovskite A2BB'O6 are also discussed to give a reference for the future research.

Modeling ferroelectric domain wall interaction with point defects and losses: the damping function method

Abstract: The displacement of the ferroelectric domain wall l is modeled by the equation of a particle in a force field. The forces that act in the domain walls are due to the external electric field and the internal electric and elastic interactions, which are represented by the effective potential . The potential is chosen to describe a nonlinear dielectric response in a dc bias electric field. This model also correctly reproduces a real component of dielectric permittivity in a subswitching alternating electric field, but the predicted losses are lower than the experimental values. Subswitching dielectric losses are produced mostly by the interaction of domain walls with defects. Point defects can be modeled as a perturbation of the potential. Another way to model point defects is introducing a generalized damping function so that the average displacement of domain walls is determined by a single equation. The equivalence of both theoretical approaches is demonstrated. An analytical expression of the damping function is derived from the Rayleigh law. Simulations show that the method of the damping function correctly reproduces a nonlinear dielectric response and losses. The damping function method could be a useful theoretical framework to elucidate the friction force generated by the interaction of ferroelectric domain walls with defects, and it can be extended to study similar phenomena such as ferroelasticity and ferromagnetism.