Ferroelastic Properties Research Articles

Two-dimensional ferroelastic semiconductors InXY (X = S, Se; Y = Cl, Br, I): Promising candidates for photocatalytic water splitting with tunable electronic anisotropy

We have identified a class of two-dimensional ferroelastic monolayers, denoted as InXY (where X = S, Se; Y = Cl, Br, I), through first-principles calculations. The dynamic, thermal, and mechanical stabilities of these InXY monolayers are validated by phonon dispersion spectra, AIMD calculations, and elastic constants, respectively. These monolayers exhibit semiconducting behavior with bandgaps ranging from 1.94 to 2.85 eV and possess excellent ferroelasticity with strong ferroelastic signals and moderate ferroelastic switching barriers. Notably, the band edge positions of InSBr and InSI monolayers are observed to stride the water redox potentials at pH = 0, indicating their potential as photocatalysts for water splitting in acidic environments. We also explored the effects of biaxial strain on the band edge alignments and photocatalytic performance of these monolayers. Moreover, the InXY monolayers exhibit excellent anisotropic optical absorption across the visible to ultraviolet regions, along with high anisotropic carrier transport. The coupling of ferroelastic and anisotropic properties in these monolayers offers promising opportunities for designing controllable electronic devices, thereby expanding their potential applications in multifunctional materials. Our findings reveal that the InXY monolayers are promising candidates for efficient photocatalytic water splitting and controllable optoelectronic applications.

Spatially controllable and mechanically switchable isomorphous organoferroeleastic crystal optical waveguides and networks

The precise, reversible, and diffusionless shape-switching ability of organic ferroelastic crystals, while maintaining their structural integrity, positions them as promising materials for next-generation hybrid photonic devices. Herein, we present versatile bi-directional ferroelasticity and optical waveguide properties of three isomorphous, halogen-based, Schiff base organic crystals. These crystals exhibit sharp bending at multiple interfaces driven by molecular movement around the CH = N bond and subsequent 180° rotational twinning, offering controlled light path manipulation. The ferroelastic nature of these crystals allowed the construction of robust hybrid photonic structures, including Z-shaped configurations, closed-loop networks, and staircase-like hybrid optical waveguides. This study highlights the potential of shape-switchable organoferroelastic crystals as waveguides for applications in programmable photonic devices.

Multiferroicity in a two-dimensional vanadium dioxide

Two-dimensional (2D) multiferroic materials have attracted great interest owing to the integration of ferroelastic and ferromagnetic properties. We identify a novel 2D multiferroic vanadium dioxide (VO₂) monolayer exhibiting a monoclinic phase with a C2/m space group using density functional theory (DFT) calculations. The energetic, dynamic, thermodynamic and mechanical analyses indicate that the monolayer exhibits excellent stability and can be prepared experimentally. The arrangement of the electronic energy bands is analogous to that of a type I heterostructure. The electron doping at a concentration of 0.2 electrons per V atom results in a significant increase in the Curie temperature (TC) from 11.2 to 184 K estimated by Monte Carlo simulations, and a transition from semiconductor to half-metallicity. In addition, the VO₂ monolayer exhibits 120° ferroelastic switching with a moderate switching energy barrier of 32 meV per atom, subsequently allowing 120° rotation of the easy magnetisation axis. Our work reveals the intrinsic multiferroicity of VO₂, which may provide a guidance on the design of next-generation mechanical/spintronic devices.

Halogen-Regulated Tc and X-ray Radiation Detection in 2D Hybrid Perovskite Ferroelastic Semiconductor.

Organic-inorganic hybrid perovskites (OIHPs) have received particular attention due to their characteristic structural tunability and flexibility. These features make OIHPs behave with excellent modifications on macroscopic properties, such as ferroicity or semiconductor performances, etc. Herein, we report two 2D hybrid stibium-based halide perovskite (C3H7N)3Sb2X9 (X = Br, 1; Cl, 2) ferroelastic semiconductor possessing dual switching properties of dielectric and second harmonic generation (SHG). Notably, these two hybrids exhibit halogen-regulated ferroelasticity and semiconductor properties. There is a significant difference in Curie temperature (Tc) and X-ray radiation detection sensitivity (S), i.e., the ΔTc and ΔS are 38 K and 87 μC Gyair-1 cm-2, respectively. Meanwhile, crystals 1 and 2 do not show dark current drift in cyclic measurements of different radiation doses with stable switching ratios of 30 and 10, separately. Meanwhile, these results were proven by scientific experimental results and density functional theory (DFT) calculations. Our work presents a facile and practical method to regulate macroproperties on the molecular level, providing a new vision to develop hybrid perovskite ferroic-photoelectric materials.

From binary PZT system to multi-component ferroactive materials

For the first time, ceramic solid solutions of the five-component system 1-x)(0.5(Na0.5K0.5)NbO3–0.5Pb(Zr0.5Ti0.5)O3)-x/2CdNb2O6 with concentrations of CdNb2O6x = 0.000; 0.025; 0.050; 0.075 were prepared. Experimental studies of crystalline and grain structure, dielectric, piezoelectric and ferroelastic properties have been carried out over a wide temperature range. X-ray diffraction data were used to construct a concentration diagram of the phase states and to establish correlations between the behaviour of the macroproperties of the solid solutions and the features of their crystal structure. A conclusion is made about the expediency of using the obtained results in the creation of similar materials and devices based on them.

Alkyl modification to optimize the ferroelastic properties of molecular crystals

Using alkyl modification, we obtained a ferroelastic material with three phase transitions, orange fluorescence and high-temperature ferroelasticity.

Organic-Inorganic Rare-Earth Double Perovskite Ferroelectric with Large Piezoelectric Response and Ferroelasticity for Flexible Composite Energy Harvesters.

Hybrid organic-inorganic perovskite (HOIP) ferroelectric materials have great potential for developing self-powered electronic transducers owing to their impressive piezoelectric performance, structural tunability and low processing temperatures. Nevertheless, their inherent brittle and low elastic moduli limit their application in electromechanical conversion. Integration of HOIP ferroelectrics and soft polymers is a promising solution. In this work, a hybrid organic-inorganic rare-earth double perovskite ferroelectric, [RM3HQ]2 RbPr(NO3 )6 (RM3 HQ = (R)-N-methyl-3-hydroxylquinuclidinium) is presented, which possesses multiaxial nature, ferroelasticity and satisfactory piezoelectric properties, including piezoelectric charge coefficient (d33 ) of 102.3 pCN-1 and piezoelectric voltage coefficient (g33 ) of 680×10-3 V m N-1 . The piezoelectric generators (PEG) based on composite films of [RM3HQ]2 RbPr(NO3 )6 @polyurethane (PU) can generate an open-circuit voltage (Voc ) of 30V and short-circuit current (Isc ) of 18µA, representing one of the state-of-the-art PEGs to date. This work has promoted the exploration of new HOIP ferroelectrics and their development of applications in electromechanical conversion devices.

Structural, nanomechanical, and piezoelectric properties of lead-free orthorhombic and tetragonal K0.35Na 0.65Nb0.97Sb0.03O3 piezo-ceramics

Materials based on ferroelectric ceramics exhibit piezoelectric, electro-optical, acousto-optical, and nonlinear optical coefficient properties. The synthesis of the lead-free ceramic was carried out by mechanical grinding. This article aims to accurately determine the tetragonal and orthorhombic phases of a lead-free ferroelectric ceramic K0.35Na0.65Nb0.97Sb0.03O3. As well as its structural analysis by Rietveld analysis, the chemical composition of the items contained VEELS and CEELS. The characteristic peak associated with perovskite structures is observed at 950 °C. Showing behavior different for each temperature, with an apparent orthorhombic structure at 950 °C and an apparent mixture of orthorhombic-tetragonal phases up to an apparent tetragonal dominant phase at 1200 °C.The mechanical and piezoelectric properties were evaluated using nanoindentation and SS-PFM, obtaining better ferroelastic and piezoelectric properties in the tetragonal phase than in the orthorhombic phase.

First principles study on the structural, electronic, and thermophysical properties of BiFeO3

Due to their special aspects and simple structure, perovskite structure materials are of enormous curiosity to scientists. Because of their ferroelectric, ferromagnetic, or ferroelastic properties, multiferroic materials could have interrelated electronic, magnetic, or structural order parameters. We represent the structural, electronic, and thermophysical properties in the ground state space group (221) of BiFeO3 according to Density Functional Theory (DFT). A BiFeO3 is investigated using Local Density Approximation (LDA) and Generalised Gradient Approximation (GGA) functional using ultrasoft pseudopotential. The present work calculated the structural, electronic, and thermophysical properties of BiFeO3 Perovskite. It demonstrates that the estimated structural properties of space group (221) BiFeO3 correspond well with existing research. The electronic attributes include band structure, total and projected density of states, electronic charge density, and Fermi surface topology. The thermophysical properties, like specific heat capacity, thermal expansion (α), Gruneisen parameter (γ), isothermal bulk modulus (B0), and Debye temperature (θD), were calculated in the temperature range of 0 K to 1073 K.

A notable reversible thermochromic (3,3-difluoropyrrolidinium)2[CuCl4] with ferroelectricity and ferroelasticity

The design and fabrication of sensitive and reversible thermochromics (TCs) remain challenging although they own enormous applications. Especially, there is a tough task to introduce multifold physical properties to them. Here, a temperature-response organic–inorganic metal halide hybrid (OIHM) (3,3-Difluoropyrrolidium)2CuCl4 ((DFP)2CuCl4) 1 is fabricated, utilizing a self-assembly method based on Cu2+ inorganic salt and fluoropyrrolidinium dexterously. It possesses two reversible phase transitions (PTs) comprising a ferroelectric to paraelectric PT at 194 K and a ferroelastic to paraelastic PT at 351 K. The ferroelastic and ferroelectric properties are mainly derived from the order–disorder transitions in the microstructure and the displacement of the charge center. Importantly, the high-temperature structural phase transition is accompanied by a reversible color change. Its crystals can be directly applied in reversible thermochromic materials, exhibit an obvious color change (green to yellow–brown at 351 K) with full reversibility, and are successfully used as inks for hand-painting. To the best of our knowledge, 1 is the first Cu(II)-based OIMH TC with both ferroelectricity and ferroelasticity. This work laid the foundation for further development of alternative TCs, ferroics and practical applications for TCs.

Piezoceramics based on lead zirconate titanate for creating highly sensitive ultrasonic equipment

Solid solutions of (1-x)Pb(Ti0.5Zr0.5)O3–xCdNb2O6 system with x = 0.0125 ÷ 0.0500, Δx = 0.0125 were obtained by two-stage solid phase synthesis followed by sintering using conventional ceramic technology and experimental studies of crystal structure, dielectric, piezoelectric, and ferroelastic properties. At 0.0250 ≤ x the studied samples belonged to the region with a tetragonal unit cell, at 0.0250 < x ≤ 0.0375 they consisted of tetragonal phases with close cell parameters, and at x > 0.0375 a heterogeneous region was formed with clusters of phases with non-tetragonal symmetry. A twofold increase in the piezoelectric parameters was achieved compared to the PZT-Pb(W,Cd)O3 composition.

First-principles study of ferroelectricity, antiferroelectricity, and ferroelasticity in two-dimensional γ -AlOOH

The exploration of two-dimensional (2D) ferroic materials and the investigation of ferroic couplings are highly desired in view of the design of next-generation functional devices. Herein, we report through first-principles calculations that the single-layer \ensuremath{\gamma}-AlOOH exhibits intrinsic ferroelectric (FE), antiferroelectric (AFE), and ferroelastic properties. The polarization and antipolarization originate from the orientational displacements of hydrogen atoms actuated by two soft phonon modes of the centrosymmetric phase. We studied a possible FE switching process and the FE-AFE transformation in the cases of monolayer and bulk, resulting in the prediction of a stable bulk AFE phase with similar energy to the FE ground state. Moreover, the \ensuremath{\gamma}-AlOOH monolayer shows a giant ferroelastic phase transition capable of efficiently tuning the ferroelectricity, which is able to accomplish a 90 \ifmmode^\circ\else\textdegree\fi{} switching of polarization and leads to an FE/AFE quadruple state. Our work adds a unique candidate to the family of 2D ferroics, broadening the platform for the design of ferroic-based devices.

Templating Influence of Regulated Inorganic Framework in Two-Dimensional Ferroelastic Perovskites: (C3 H5 CH2 NH3 )2 [MCl4 ] (M=Mn and Cd).

The remarkable material stability and structural diversity of two-dimensional (2D) organic-inorganic hybrid perovskites (OIHPs) constitute a vast available library of versatile materials. In particular, ferroelastic property, for which the spontaneous strain can be transformed by applying mechanical stress, is very promising for extensive nanotechnological applications. However, integrating ferroelastic property into 2D OIHPs is still in its infancy. Herein, we designed two new 2D OIHPs (C3 H5 CH2 NH3 )2 [MCl4 ] (M=Mn for 1 and Cd for 2), which undergo reversible ferroelastic phase transitions with an Aizu expression 4/mmmFmmm. The templating influence of the more distorted inorganic framework on the disordering of organic cations and the stronger hydrogen bonds has a key role in the striking improvement of Curie temperature from 246 K in 1 to 273 K in 2. Meanwhile, the minimized alteration of structural motif ensures the well maintaining of the ferroelastic performance in the forms of crystals and thin films, as demonstrated by the identifiable evolution of domain structures. This work will provide a fertile new ground for enlarging the limited number of 2D ferroelastic OIHPs with better practical utility.

A role of intermolecular interaction modulating thermal diffusivity in organosuperelastic and organoferroelastic cocrystals.

Although the finding of superelasticity and ferroelasticity in organic crystals has been serendipitous, an increasing number of organic crystals with such deformation properties have been witnessed. Understanding the structure-property relationship can aid in the rational selection of intermolecular interactions to design organic crystals with desired superelastic or ferroelastic properties. In this study, we investigated the mechanical deformation in two cocrystals, prepared with the parent compound, 1,4-diiodotetrafluorobenzene with two coformers, 1,2-bis(4-pyridyl)ethane and pyrene. The parent compound and coformers were chosen to introduce distinct weak interactions such as halogen bonds and C-H⋯F, and π⋯π interactions in the crystal structure. The two cocrystals exhibited different mechanical deformations, superelasticity, and ferroelasticity, respectively. The single-crystal X-ray diffraction and energy framework analysis of the crystal structure of the cocrystals revealed that both deformations were caused by mechanical twinning. Interestingly, a difference in the extent of deformation was observed, modulated by a combination of strong and weak intermolecular interactions in the superelastic cocrystal, and only weak interaction in the ferroelastic one. In this comparison, the superelastic cocrystal exhibited higher thermal diffusivity than the ferroelastic cocrystal, indicating the presence of symmetrical and relatively robust intermolecular interactions in the superelastic cocrystal.

Temperature symmetry breaking and properties of lead-free organic-inorganic hybrids: bismuth(III) iodide and antimony(III) iodide: (S(CH3)3)3[Bi2I9] and (S(CH3)3)3[Sb2I9

We have synthesized and characterized two novel lead-free organic-inorganic hybrid crystals: (S(CH3)3)3[Bi2I9] (TBI) and (S(CH3)3)3[Sb2I9] (TSI). Thermal DSC, TG, and DTA analyses indicate structural phase transitions (PTs) in both compounds; TBI undergoes two structural phase transitions at 314.2/314.8 K (cooling/heating) and at 181.5 K of first (I ↔ II) and second order (II ↔ III), respectively. The crystal structures of TBI are refined for phases I (325 K), II (200 K) and III (100 K). TBI exhibits ferroelastic properties since both PTs are accompanied by a change in the symmetry of crystals: P63/mmc → C2/c (I → II) and C2/c → P1̄ (II → III). The presence of a ferroelastic domain structure has been confirmed by optical observations. In turn, TSI also reveals two PTs: I ↔ II (at 303.9/304.1 K) and II ↔ III (212.9/221.4 K). To compare and obtain insight into the mechanism of the PTs of TBI, we have carried out temperature dependent single crystal X-ray diffraction studies. Additionally, to confirm the change in the dynamical states of molecules in PTs, dielectric measurements have been carried out between 100 K and 400 K in the frequency range of 200 Hz to 2 MHz. Moreover, the measurements of the 1H NMR spin-lattice relaxation time, T1, and a second moment, M2, of the 1H NMR line have been undertaken in the temperature range between 100 and 300 K.

Ferroelasticity in Organic–Inorganic Hybrid Perovskites

Molecular ferroelastics have received particular attention for potential applications in mechanical switches, shape memory, energy conversion, information processing, and solar cells, by taking advantages of their low-cost, light-weight, easy preparation, and mechanical flexibility. The unique structures of organic-inorganic hybrid perovskites have been considered to be a design platform for symmetry-breaking-associated order-disorder in lattice, thereby possessing great potential for ferroelastic phase transition. Herein, we review the research progress of organic-inorganic hybrid perovskite ferroelastics in recent years, focusing on the crystal structures, dimensions, phase transitions and ferroelastic properties. In view of the few reports on molecular-based hybrid ferroelastics, we look forward to the structural design strategies of molecular ferroelastic materials, as well as the opportunities and challenges faced by molecular-based hybrid ferroelastic materials in the future. This review will have positive guiding significance for the synthesis and future exploration of organic-inorganic hybrid molecular ferroelastics.

Phase Diagram of a Strained Ferroelectric Nanowire

Ferroelectric materials manifest unique dielectric, ferroelastic, and piezoelectric properties. A targeted design of ferroelectrics at the nanoscale is not only of fundamental appeal but holds the highest potential for applications. Compared to two-dimensional nanostructures such as thin films and superlattices, one-dimensional ferroelectric nanowires are investigated to a much lesser extent. Here, we reveal a variety of the topological polarization states, particularly the vortex and helical chiral phases, in loaded ferroelectric nanowires, which enable us to complete the strain–temperature phase diagram of the one-dimensional ferroelectrics. These phases are of prime importance for optoelectronics and quantum communication technologies.

The TiNI monolayer: a two-dimensional system with promising ferroelastic, topological, and thermoelectric properties.

We demonstrate using first-principles calculations that the TiNI monolayer simultaneously exhibits favorable ferroelastic, topological, and thermoelectric properties. Specifically, we discover a 90° lattice rotation with a moderate switching barrier of 56 meV per atom when a uniaxial tensile strain is applied to the system. Besides, the monolayer is found to be an intrinsic topological insulator with an inverted band structure, as characterized by the Z2 invariant of 1 and the presence of Dirac-like edge states at a critical width of 5.6 nm. Moreover, the thermoelectric ZT value of the system can reach as high as 1.4 at 600 K by fine tuning the carrier concentration. Collectively, these findings make the TiNI monolayer a promising multifunctional material to meet the various application requirements of nanoelectronic devices.

Intrinsic ferromagnetism with high Curie temperature and strong anisotropy in a ferroelastic VX monolayer (X=P, As)

Two-dimensional (2D) multiferroic materials, with combined large magnetic anisotropic energy (MAE) and high Curie temperature $({\mathbit{T}}_{C})$, have great potential in emerging electronic device applications, such as high-density multistate data storage and fast operation. However, various 2D spintronic materials fabricated in experiment, so far have small MAE and low ${\mathbit{T}}_{C}$. Using first-principles calculations, we proposed two $\mathrm{V}X$ $(X=\mathrm{P}, \mathrm{As})$ monolayers, which are identified to possess robust stability dynamically, thermally, and mechanically. $\mathrm{V}X$ monolayers are half-metals with coexisting ferroelastic and ferromagnetic properties. Moreover, their ground states exhibit significant in-plane MAEs of 101.48 and $262.68\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{eV}$ per V atom for VP and VAs monolayers, respectively. Additionality, the Curie temperatures of VP and VAs monolayers predicted from Heisenberg model are as high as 545 and 890 K, respectively, and the ferromagnetism could survive at room temperature. Our results are beneficial for further research on 2D multiferroics and provide the possibility for future nanodevices.

Ferroelastic deformation mechanism and mechanical properties of [001]-oriented YSZ film by indentation

The ferroelastic properties of zirconia-based ceramics are crucial for their use as structural and functional materials. In this study, [001]-oriented ferroelastic YSZ films are prepared on the (100) SrTiO3 (STO) substrates by pulsed laser deposition (PLD). The mechanical properties and ferroelastic deformation mechanism of the film have been studied in detail through experiments and modeling. The Hardness and Young’s modulus of the YSZ film are 19.3 ± 0.4 GPa and 293.8 ± 5.1 GPa, respectively, which are determined by nanoindentation tests with the continuous stiffness measurement (CSM) mode. Indentation experiments show that a 90° twin domain structure is produced on the surface of the film. By combining TEM and STEM analysis methods, it was experimentally confirmed for the first time that the YSZ film produces ferroelastic deformation under the compressive stress of the indenter, causing the ferroelastic domain switching mechanism. Then the phase field simulation reproduced the ferroelastic domain switching process in the film under the indenter load and obtained the ferroelastic domain switching mechanism of the YSZ film. This proves the fundamental reason for the excellent mechanical properties of the ferroelastic YSZ film.