Hafnium zirconium oxides(HZO),which exhibit ferroelectric properties,are promising materials for nanoscale device fabrication due to their high complementary metal-oxide-semiconductor(CMOS) compatibility.In addition t...Hafnium zirconium oxides(HZO),which exhibit ferroelectric properties,are promising materials for nanoscale device fabrication due to their high complementary metal-oxide-semiconductor(CMOS) compatibility.In addition to piezoelectricity,ferroelectricity,and flexoelectricity,this study reports the observation of ferroelasticity using piezoelectric force microscopy(PFM) and scanning transmission electron microscopy(STEM).The dynamics of 90° ferroelastic domains in HZO thin films are investigated under the influence of an electric field.Switching of the retentive domains is observed through repeated wake-up measurements.This study presents a possibility of enhancing polarization in HZO thin films during wake-up processes.展开更多
The fascinating properties arising from the interaction between different ferroic states of two-dimensional(2D) materials have inspired tremendous research interest in the past few years.Under the first-principles cal...The fascinating properties arising from the interaction between different ferroic states of two-dimensional(2D) materials have inspired tremendous research interest in the past few years.Under the first-principles calculations,we predict the coexistence of antiferromagnetic and ferroelastic states in VOX(X=Cl,Br,I) monolayers.The results illustrate that the VOX monolayers exhibit indirect bandgap characteristics,i.e.,their gaps decrease with the halide elements changing from Cl to I.The ground states of all these VOX monolayers are antiferromagnetic(AFM) with the magnetic moments contributed by the V 3d electrons.Furthermore,the magnetic ground state changing from AFM to ferromagnetism(FM) can be realized by doping carriers.In addition,the moderate ferroelastic transition barrier and reversible switching signal ensure their high performances of nonvolatile memory devices.Our findings not only offer an ideal platform for investigating the multiferroic properties,but also provide candidate materials for potential applications in spintronics.展开更多
Raman scattering measurements of K_2 Sr(MoO_4)2 were performed in the temperature range of 25–750?C. The Raman spectrum of the low-temperature phase α-K_2 Sr(MoO_4)2 that was obtained by first-principle calcula...Raman scattering measurements of K_2 Sr(MoO_4)2 were performed in the temperature range of 25–750?C. The Raman spectrum of the low-temperature phase α-K_2 Sr(MoO_4)2 that was obtained by first-principle calculations indicated that the Raman bands in the wavenumber region of 250–500 cm-1 are related to Mo–O bending vibrations in MoO4 tetrahedra,while the Raman bands in the wavenumber region of 650–950 cm-1 are attributed to stretching vibrations of Mo–O bonds.The temperature-dependent Raman spectra reveal that K_2 Sr(MoO_4)2 exhibits two sets of modifications in the Raman spectra at ~ 150?C and ~ 475?C, attributed to structural phase transitions. The large change of the Raman spectra in the temperature range of 150?C to 475?C suggests structural instability of the medium-temperature phase β-K_2 Sr(MoO_4)2.展开更多
The 6–8 wt%yttria-stabilized zirconia with a tetragonal structure(t’-YSZ)is extensively employed in thermal barrier coatings.The exceptional fracture toughness of t’-YSZ can be attributed to its distinctive ferroel...The 6–8 wt%yttria-stabilized zirconia with a tetragonal structure(t’-YSZ)is extensively employed in thermal barrier coatings.The exceptional fracture toughness of t’-YSZ can be attributed to its distinctive ferroelastic toughening mechanism.Microstructure and interface tension play a critical role in ferroelastic variant switching at the micro-and nano-scale.This paper presents an original thermodynamically consistent phase field(PF)theory for analyzing ferroelastic variant switching at the micro-and nano-scale of t’-YSZ.The theory incorporates strain gradient elasticity using higher-order elastic energy and interface tension tensor via geometric nonlinearity to represent biaxial tension resulting from interface energy.Subsequently,a mixed-type formulation is employed to implement the higher-order theory through the finite element method.For an interface in equilibrium,the effects of strain gradient elasticity result in a more uniform distribution of stresses,whereas the presence of interface tension tensor significantly amplifies the stress magnitude at the interface.The introduction of an interface tension tensor increases the maximum value of stress at the interface by a factor of 4 to 10.The nucleation and evolution of variants at a pre-existing crack tip in a mono-phase t’-YSZ have also been studied.The strain gradient elasticity is capable of capturing the size effect of ferroelastic variant switching associated with microstructures in experiments.Specifically,when the grain size approaches that of the specimen,the critical load required for variant switching at the crack tip increases,resulting in greater dissipation of elastic energy during ferroelastic variant switching.Moreover,the interface tension accelerates the evolution of variants.The presented framework exhibits significant potential in modeling ferroelastic variant switching at the micro-and nano-scale.展开更多
Ferroelastic hybrid perovskite materials have been revealed the significance in the applications of switches,sensors,actuators,etc.However,it remains a challenge to design high-temperature ferroelastic to meet the req...Ferroelastic hybrid perovskite materials have been revealed the significance in the applications of switches,sensors,actuators,etc.However,it remains a challenge to design high-temperature ferroelastic to meet the requirements for the practical applications.Herein,we reported an one-dimensional organicinorganic hybrid perovskites(OIHP)(3-methylpyrazolium)CdCl_(3)(3-MBCC),which possesses a mmmF2/m ferroelastic phase transition at 263 K.Moreover,utilizing crystal engineering,we replace-CH_(3) with-NH_(2) and-H,which increases the intermolecular force between organic cations and inorganic frameworks.The phase transition temperature of(3-aminopyrazolium)CdCl_(3)(3-ABCC),and(pyrazolium)CdCl_(3)(BCC)increased by 73 K and 10 K,respectively.Particularly,BCC undergoes an unconventional inverse temperature symmetry breaking(ISTB)ferroelastic phase transition around 273 K.Differently,it transforms from a high symmetry low-temperature paraelastic phase(point group 2/m)to a low symmetry high-temperature ferroelastic phase(point group ī)originating from the rare mechanism of displacement of organic cations phase transition.It means that crystal BCC retains in ferroelastic phase above 273 K until melting point(446 K).Furthermore,characteristic ferroelastic domain patterns on crystal BCC are confirmed with polarized optical microscopy.Our study enriches the molecular mechanism of ferroelastics in the family of organic-inorganic hybrids and opens up a new avenue for exploring high-temperature ferroic materials.展开更多
The primary purpose of this work is to optimize the thermophysical properties of rare-earth tan-talate ceramics using the high-entropy effect.Here,the high-entropy rare-earth tantalate ceramic(Y_(0.1)Nd_(0.1)Sm_(0.1)G...The primary purpose of this work is to optimize the thermophysical properties of rare-earth tan-talate ceramics using the high-entropy effect.Here,the high-entropy rare-earth tantalate ceramic(Y_(0.1)Nd_(0.1)Sm_(0.1)Gd_(0.1)Dy_(0.1)Ho_(0.1)Er_(0.1)Tm_(0.1)Yb_(0.1)Lu_(0.1))TaO_(4)((10RE_(0.1))TaO_(4))is synthesized successfully.The lat-tice distortion and oxygen vacancy concentration are characterized firstly in the rare-earth tantalates.Notably,compared with single rare-earth tantalates,the thermal conductivity of(10RE_(0.1))TaO_(4) is reduced by 16%-45%at 100℃ and 22%-45%at 800℃,and it also presents lower phonon thermal conductivity in the entire temperature range from 100 to 1200℃.The phonon thermal conductivity(1.0-2.2 W m^(-1) K^(-1),100-1200℃)of(10RE_(0.1))TaO_(4) is lower than that of the currently reported high-entropy four-,five-and six-component rare-earth tantalates.This is the result of scattering by the ferroelastic domain,lattice distortion associated with size and mass disorder,and point defects,which target low-,mid-and high-frequency phonons.Furthermore,(10RE_(0.1))TaO_(4),as an improved candidate for thermal barrier coatings materials(TBCs),has a higher thermal expansion coefficient(10.5×10^(-6)K^(-1) at 1400℃),lower Young’s modulus(123 GPa)and better high-temperature phase stability than that of single rare-earth tantalates.展开更多
Multifunctional switchable materials are attracting tremendous interest because of their great application potential in signal processing,information encryption,and smart devices.Here,we reported an organic-inorganic ...Multifunctional switchable materials are attracting tremendous interest because of their great application potential in signal processing,information encryption,and smart devices.Here,we reported an organic-inorganic hybrid thermochromic ferroelastic crystal,[TMIm][CuCl_(4)](TMIm=1,1,3,3-tetramethylimidazolidinium),which undergoes two reversible phase transitions at 333 K and 419 K,respectively.Intriguingly,these three phases experience a remarkable ferroelastic-paraelastic-ferroelastic(2/m-mmm-2/m)transition,which remains relatively unexplored in ferroelastics.Moreover,the ferroelastic domains can be simultaneously switched under temperature and stress stimuli.Meanwhile,[TMIm][CuCl_(4)]exhibits thermochromic phenomenon,endowing it with extra spectral encryption possibilities during information processing.Combined with dielectric switching behavior,[TMIm][Cu Cl_(4)]are promising for practical applications in memory devices,next-generation sensors,and encryption technology.展开更多
Two-dimensional organic-inorganic hybrid ferroelastics with high-temperature reversible phase transitions are very rare and have become one of the research hotspots in the field of ferroelastic materials.Herein,we rep...Two-dimensional organic-inorganic hybrid ferroelastics with high-temperature reversible phase transitions are very rare and have become one of the research hotspots in the field of ferroelastic materials.Herein,we report three new layered organic-inorganic hybrid perovskites based on halogen-substituted phenethylaminium,(3-XC_(6)H_(5)CH_(2)CH_(2)NH_(3))_(2)[CdCl_(4)](X=F(1),CI(2)and Br(3)).They undergo structural phase transitions at 376/371 K,436/430 K,and 421/411 K,respectively,between the isomorphic hightemperature phases(space group I4/mmm,Z=2)and different room-temperature phases with the reduced structural symmetries,i.e.,P21/a(Z=2)in 1,Pi(Z=4)in 2,and P21/a(Z=4)in 3,respectively.These ferroelastic transitions arise from the order-disorder transition of organic cations together with the synchronous displacement of inorganic layers,accompanying with feroelastic spontaneous strains of 0.16,0.13 and 0.12 for 1-3,respectively.By enriching layered perovskite ferroelastics based on halogensubstituted cations,this work provides important clues for exploring new ferroic materials based on hybrid crystals.展开更多
Ferroelastic materials with switchable spontaneous strain possess widely potential applications in the field of energy and information conversion.Recently,organic-inorganic hybrid halide double perovskites (OIHHDPs) h...Ferroelastic materials with switchable spontaneous strain possess widely potential applications in the field of energy and information conversion.Recently,organic-inorganic hybrid halide double perovskites (OIHHDPs) have become a charming new platform for developing various functional materials,such as ferroelectrics,fluorescence and X–ray detection.Nevertheless,OIHHDP ferroelastic materials,especially high-temperature ones,are rare.Herein,we initially synthesized an OIHHDP ferroelastic,(2,2-difluoroethanamine)_(2)[(NH_(4))InCl_6](1),which possesses a ferroelastic phase transition at 407 K.Moreover,thanks to the flexible B-site for OIHHDPs,we replaced the NH_(4)^(+) ions within[(NH_(4))InCl_6]_n^(2n–)formworks with K^(+)ions,which endows with coordination bonds between 2,2-difluoroethanamine organic cations and[KInCl_6]_n^(2n–)formworks.Due to the existence of coordination bonds,the phase transition temperature of (2,2-difluoroethanamine)_(2)[KInCl_6](2) can reach 458 K.As far as we know,this value is the highest reported in OIHHDP ferroelastics.This work offers inspiration for the design of high-temperature OIHHDP phase transition materials including ferroelectrics and ferroelastics.展开更多
Lead-based organic-inorganic hybrids occupy a niche in the field of optoelectronics due to exceptional semiconducting properties and potential ferroelasticity.Nevertheless,the possible toxicity of lead restricts their...Lead-based organic-inorganic hybrids occupy a niche in the field of optoelectronics due to exceptional semiconducting properties and potential ferroelasticity.Nevertheless,the possible toxicity of lead restricts their widespread application to a certain extent.Herein,two new lead-free ferroelastic semiconductors are reported:[DMMClEA]_(3)Bi_(2)Br_(9)(compound 1)and[DMMClEA]_(3)Sb_(2)Br_(9)(compound 2)(DMMClEA=N-(chloromethyl)-N,N-dimethylethylammonium),in which the inorganic framework neatly arranges with[Bi_(2)Br_(9)]^(3−)/[Sb_(2)Br_(9)]^(3−)polyhedrons shared by face,forming an A_(3)B_(2)X_(9)-type structure.Both compounds 1 and 2 possess two-step phase transitions,including a3mF2/m-type ferroelastic phase transition,based on the Aizu rule.In addition,dual dielectric switches endow the application toward sensor devices.This finding enriches A_(3)B_(2)X_(9)-type zero-dimensional hybrid ferroelastics and provides an approach to designing high-performance,lead-free perovskite semiconductors with dielectric functionality.展开更多
The hysteresis phenomena of ferroelectric/ferroelastic material in polarization procedure are investigated. Some assumptions are presented based on the published experimental data. The electrical yielding criterion, m...The hysteresis phenomena of ferroelectric/ferroelastic material in polarization procedure are investigated. Some assumptions are presented based on the published experimental data. The electrical yielding criterion, mechanical yielding criterion and isotropic hardening model are established. The flow theory in incremental forms in polarization procedure is presented. The nonlinear constitutive law for electrical-mechanical coupling is proposed phenomenologically. Finally, the nonlinear constitutive law expressed in a form of matrices and vectors, which is immediately associated with finite element analysis, is formulated. In the example problem of a rectangular specimen subjected to a uniaxial electric field, the procedure from virgin state to fully polarized state is simulated. Afterward, a uniaxial compressive loading is applied to depolarizing the specimen. Results are in agreement with the experimental data.展开更多
The broad operating temperature range is sought for molecular ferroic materials who are expected to be applied to flexible and electronic materials.Hydrogen bonds,an effective force between molecules,are important to ...The broad operating temperature range is sought for molecular ferroic materials who are expected to be applied to flexible and electronic materials.Hydrogen bonds,an effective force between molecules,are important to regulate the molecule structure and their condition,helping a higher temperature range for ferroic materials.Here,we report a molecular perovskite ferroelastic(Me-Hdabco)Rb[BF_(4)]_(3)(Me-Hdabco=N-methyldabconium)which shows high temperature(T_(1)=322.5 K and T_(2)=381K)ferroelastic phase transitions.The ferroelastic phase transition temperature range of(Me-Hdabco)Rb[BF_(4)]_(3) is significantly increased by 71 K compared with[Meda-bco-F]Rb[BF_(4)]_(3)(Medabco-F=1-fluoro-4-methyl-1,4-diazoniabicyclo[2.2.2]octane).Structural analysis and thermal analysis demonstrate the ferroelastic phase transition is mainly attributed to dynamic cations order and disorder transformation.Therefore,new hydrogen bonds generated between cations and the Rb_(8)[BF_(4)]_(12) frame increase their intermolecular force,which is beneficial to improving the phase transition temperature.This finding has an important impact on the utilization of weak interactionforces to design and optimize functional materials.展开更多
Yttrium tantalate(YTaO_(4))is the next generation of higher service temperature thermal barrier coatings(TBCs)materials due to its smaller volume effect in phase change,lower thermal conductivity and unique ferroelast...Yttrium tantalate(YTaO_(4))is the next generation of higher service temperature thermal barrier coatings(TBCs)materials due to its smaller volume effect in phase change,lower thermal conductivity and unique ferroelastic domain structure.However,the low fracture toughness limits its application.We first characterized the diffraction patterns of variants,and two variants(M_(1)and M_(2))observed in transmission electron microscopy(TEM)results were determined from four possible variants by mechanical derivation.The role of Zr^(4+)doping in ferroelastic toughening was explained in detail.With the increase of Zr^(4+)doping concentration,the monoclinic angle β and the domain rotation angleαdecrease,respectively.The spontaneous strain component and the principal strain in the main space also have a similar decreasing trend.The decrease of the ferroelastic domain inversion energy barrier is beneficial to the improvement of fracture toughness.Combining the results of Vickers indentation,we found that Zr^(4+)could be enriched at the domain boundary to inhibit the generation of cracks.An appropriate amount of Zr^(4+)is conducive to the improvement of fracture toughness,and the excessive Zr^(4+)will reduce the fracture toughness due to the generation of by-product t-ZrO_(2).So,the optimal composition is Y_(0.44)Ta_(0.44)Zr_(0.12)O_(2) and the best fracture toughness(2.9–3.8MPa m^(1/2))is equivalent to the commercial 8YSZ.This result will promote the application of a new generation of TBCs.展开更多
Two-dimensional(2D)ferromagnetic and ferroelectric materials attract unprecedented attention due to the spontaneous-symmetry-breaking induced novel properties and multifarious potential applications.Here we systematic...Two-dimensional(2D)ferromagnetic and ferroelectric materials attract unprecedented attention due to the spontaneous-symmetry-breaking induced novel properties and multifarious potential applications.Here we systematically investigate a large family(148)of 2D MGeX3(M=metal elements,X=O/S/Se/Te)by means of the high-throughput first-principles calculations,and focus on their possible ferroic properties including ferromagnetism,ferroelectricity,and ferroelasticity.We discover eight stable 2D ferromagnets including five semiconductors and three half-metals,212D antiferromagnets,and 11 stable 2D ferroelectric semiconductors including two multiferroic materials.Particularly,MnGeSe3 and MnGeTe3 are predicted to be room-temperature 2D ferromagnetic half metals with Tc of 490 and 308 K,respectively.It is probably for the first time that ferroelectricity is uncovered in 2D MGeX3 family,which derives from the spontaneous symmetry breaking induced by unexpected displacements of Ge-Ge atomic pairs,and we also reveal that the electric polarizations are in proportion to the ratio of electronegativity of X and M atoms,and IVB group metal elements are highly favored for 2D ferroelectricity.Magnetic tunnel junction and water-splitting photocatalyst based on 2D ferroic MGeX3 are proposed as examples of wide potential applications.The atlas of ferroicity in 2D MGeX3 materials will spur great interest in experimental studies and would lead to diverse applications.展开更多
We prepared 300-nm GeTe thin films on(111)-oriented and piezoelectrically active 0.71 Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.29PbTiO_(3)(PMN-0.29 PT)single-crystal substrates by the pulsed laser deposition and investigated the e...We prepared 300-nm GeTe thin films on(111)-oriented and piezoelectrically active 0.71 Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.29PbTiO_(3)(PMN-0.29 PT)single-crystal substrates by the pulsed laser deposition and investigated the effects of in situ electric-field-controllable non-180ferroelastic domain switching of the PMN-0.29 PT on the electronic properties of the GeTe films.The in-plane strain of the PMN-0.29 PT could be modulated continuously and reversibly by electric fields in a nonvolatile manner and could be effectively transferred to the GeTe films.Based on this,we realized reversible and nonvolatile resistance switching and obtained multilevel stable nonvolatile resistance states with good stability and endurance at T=300 K by applying appropriate asymmetrical bipolar electric fields to the PMN-0.29 PT(111)substrates along the thickness direction.Such heterostructures may be used for multilevel data storage that allows each unit to store multiple bits of information and thus improve the memory density.Our investigation would be beneficial for the fabrication of nonvolatile memory devices using PMN-xPT-based heterostructures.展开更多
Organic–inorganic hybrid perovskites(OIHPs)have been a hot research topic due to their advanced structural and functional features that cover almost all the research fields of intelligent materials including ferroele...Organic–inorganic hybrid perovskites(OIHPs)have been a hot research topic due to their advanced structural and functional features that cover almost all the research fields of intelligent materials including ferroelectric,photovoltaic,fluorescent,and dielectric.However,the development of the construction of an OIHP ferroelastic semiconductor with optical-electrical response has been a huge challenge and infrequently reported.In this work,a rare and interesting hybrid perovskite ferroelastic semiconductor,[BFDA]PbBr_(3)(BFDA=benzyl-(2-fluoro-ethyl)-dimethyl-ammonium),was synthesized,which benefits from the structural advantage of a long tail BFDA to be balanced by the suitable inorganic framework.[BFDA]PbBr_(3) shows a high-temperature ferroelastic phase transition at 365 K and a direct band gap of 3.33 eV.In addition,it can emit charming orange-pink light under a 365 nm UV lamp.To combine this with the ferroelastic,optical,and dielectric properties,[BFDA]PbBr_(3) can be identified as a very rarely reported ferroelastic semiconductor.The above-mentioned synthesis strategy is also helpful for the enrichment and development of the hybrid perovskite family.展开更多
The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal the...The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal theories of high-T<sub>c</sub> superconductors, thereby applying the finding that the optimum hole concentration of σ<sub>o</sub> = 0.229 can be linked with the universal fractal constant δ<sub>1</sub> = 8.72109… of the renormalized quadratic Hénon map. The transition temperature obviously increases steeply with a domain structure of ever narrower size, characterized by Fibonacci numbers. However, also conventional BCS superconductors can be scaled with δ<sub>1</sub>, exemplified through the energy gap relation k<sub>B</sub>T<sub>c</sub> ≈ 5Δ<sub>0</sub>/δ<sub>1</sub>, suggesting a revision of the entire theory of superconductivity. A low mean cationic charge allows the development of a frustrated nano-sized fractal structure of possibly ferroelastic nature delivering nano-channels for very fast charge transport, in common for both high-T<sub>c</sub> superconductor and organic-inorganic halide perovskite solar materials. With this backing superconductivity above room temperature can be conceived for synthetic sandwich structures of less than 2+. For instance, composites of tenorite and cuprite respectively tenorite and CuI (CuBr, CuCl) onto AuCu alloys are proposed. This specification is suggested by previously described filamentary superconductivity of “bulk” CuO1﹣x samples. In addition, cesium substitution in the Tl-1223 compound is an option.展开更多
Thermal barrier coating(TBC)materials can improve energy conversion efficiency and reduce fossil fuel use.Herein,novel rare earth tantalates RETaO_(4),as promising candidates for TBCs,were reassembled into multi-compo...Thermal barrier coating(TBC)materials can improve energy conversion efficiency and reduce fossil fuel use.Herein,novel rare earth tantalates RETaO_(4),as promising candidates for TBCs,were reassembled into multi-component solid solutions with a monoclinic structure to further depress thermal conductivity via an entropy strategy.The formation mechanisms of oxygen vacancy defects,dislocations,and ferroelastic domains associated with the thermal conductivity are demonstrated by aberration-corrected scanning transmission electron microscopy.Compared to single-RE RETaO_(4)and 8YSZ,the intrinsic thermal conductivity of(5RE1/5)TaO4 was decreased by 35%–47%and 57%–69%at 1200℃,respectively,which is likely attributed to multi-scale phonon scattering from Umklapp phonon–phonon,point defects,domain structures,and dislocations.r¯3+RE/r5+Ta and low-temperature thermal conductivity are negatively correlated,as are the ratio of elastic modulus to thermal conductivity(E/κ)and high-temperature thermal conductivity.Meanwhile,the high defects’concentration and lattice distortion in high-entropy ceramics enhance the scattering of transverse-wave phonons and reduce the transverse-wave sound velocity,leading to a decrease in the thermal conductivity and Young’s modulus.In addition,5HEC-1 has ultra-low thermal conductivity,moderate thermal expansion coefficients,and high hardness among three five-component high-entropy samples.Thus,5HEC-1 with superior thermal barrier and mechanical properties can be used as promising thermal insulating materials.展开更多
Understanding phase transitions in multi-component crystals is of importance for regulating specified functional materials.Herein,we present two new organic-inorganic hybrid crystals,(Me_(3)NCH_(2)CH_(2)X)_(4)[Ni(NCS)...Understanding phase transitions in multi-component crystals is of importance for regulating specified functional materials.Herein,we present two new organic-inorganic hybrid crystals,(Me_(3)NCH_(2)CH_(2)X)_(4)[Ni(NCS)_6](X=Cl and Br),revealing distinct phase transitions.Specifically,the Clsubstituted cations weakly interact with discrete inorganic part hence reveal step-wise dynamic changes upon heating,which result in multi-step solid-solid phase transitions (P1-P2_1/n-A2/a-Cmce) including a ferroelastic one with a spontaneous strain of 0.0475.Whereas the Br-substituted cations with larger steric effect prevent the solid-solid phase transition but give a solid-liquid phase transition at above 419 K.The present instances well demonstrate the complicity for multi-component crystals arising from the delicate balance established by abundant weak intermolecular interactions,and inspire the design of novel phase-transition materials by judiciously assembling multi-component crystals.展开更多
基金Project supported by the the National Key Research and Development Program of China (Grant No. 2022YFA1402902)the National Natural Science Foundation of China (Grant Nos. 12074119, 12204171, 12134003, and 12374145)+1 种基金the Chenguang Program Foundation of Shanghai Education Development Foundation and Shanghai Municipal Education Commission, ECNU (East China Normal University) Multifunctional Platform for Innovation (006)the Fundamental Research Funds for the Central Universities。
文摘Hafnium zirconium oxides(HZO),which exhibit ferroelectric properties,are promising materials for nanoscale device fabrication due to their high complementary metal-oxide-semiconductor(CMOS) compatibility.In addition to piezoelectricity,ferroelectricity,and flexoelectricity,this study reports the observation of ferroelasticity using piezoelectric force microscopy(PFM) and scanning transmission electron microscopy(STEM).The dynamics of 90° ferroelastic domains in HZO thin films are investigated under the influence of an electric field.Switching of the retentive domains is observed through repeated wake-up measurements.This study presents a possibility of enhancing polarization in HZO thin films during wake-up processes.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12104344 and 61674003)the Shandong Provincial Natural Science Foundation,China(Grant No.ZR2021QA096)+1 种基金the Science and Technology Development Program of Weifang High-tech Industrial Development Zone,China(Grant No.2020KJHM03)the Doctoral Research Start-up Foundation of Weifang University,China(Grant No.2021BS05)。
文摘The fascinating properties arising from the interaction between different ferroic states of two-dimensional(2D) materials have inspired tremendous research interest in the past few years.Under the first-principles calculations,we predict the coexistence of antiferromagnetic and ferroelastic states in VOX(X=Cl,Br,I) monolayers.The results illustrate that the VOX monolayers exhibit indirect bandgap characteristics,i.e.,their gaps decrease with the halide elements changing from Cl to I.The ground states of all these VOX monolayers are antiferromagnetic(AFM) with the magnetic moments contributed by the V 3d electrons.Furthermore,the magnetic ground state changing from AFM to ferromagnetism(FM) can be realized by doping carriers.In addition,the moderate ferroelastic transition barrier and reversible switching signal ensure their high performances of nonvolatile memory devices.Our findings not only offer an ideal platform for investigating the multiferroic properties,but also provide candidate materials for potential applications in spintronics.
基金Project supported by the Natural Science Foundation of Anhui Province,China(Grant Nos.KJ2018A0588 and KJ2017A625)
文摘Raman scattering measurements of K_2 Sr(MoO_4)2 were performed in the temperature range of 25–750?C. The Raman spectrum of the low-temperature phase α-K_2 Sr(MoO_4)2 that was obtained by first-principle calculations indicated that the Raman bands in the wavenumber region of 250–500 cm-1 are related to Mo–O bending vibrations in MoO4 tetrahedra,while the Raman bands in the wavenumber region of 650–950 cm-1 are attributed to stretching vibrations of Mo–O bonds.The temperature-dependent Raman spectra reveal that K_2 Sr(MoO_4)2 exhibits two sets of modifications in the Raman spectra at ~ 150?C and ~ 475?C, attributed to structural phase transitions. The large change of the Raman spectra in the temperature range of 150?C to 475?C suggests structural instability of the medium-temperature phase β-K_2 Sr(MoO_4)2.
基金supported by the National Natural Science Foundation of China(Grant Nos.11890684,12032001&51590891)the Technology Innovation Leading Program of Shaanxi(Grant No.2022TD-28)Hunan Provincial Natural Science Innovation Research Group Fund(Grant No.2020JJ1005)。
文摘The 6–8 wt%yttria-stabilized zirconia with a tetragonal structure(t’-YSZ)is extensively employed in thermal barrier coatings.The exceptional fracture toughness of t’-YSZ can be attributed to its distinctive ferroelastic toughening mechanism.Microstructure and interface tension play a critical role in ferroelastic variant switching at the micro-and nano-scale.This paper presents an original thermodynamically consistent phase field(PF)theory for analyzing ferroelastic variant switching at the micro-and nano-scale of t’-YSZ.The theory incorporates strain gradient elasticity using higher-order elastic energy and interface tension tensor via geometric nonlinearity to represent biaxial tension resulting from interface energy.Subsequently,a mixed-type formulation is employed to implement the higher-order theory through the finite element method.For an interface in equilibrium,the effects of strain gradient elasticity result in a more uniform distribution of stresses,whereas the presence of interface tension tensor significantly amplifies the stress magnitude at the interface.The introduction of an interface tension tensor increases the maximum value of stress at the interface by a factor of 4 to 10.The nucleation and evolution of variants at a pre-existing crack tip in a mono-phase t’-YSZ have also been studied.The strain gradient elasticity is capable of capturing the size effect of ferroelastic variant switching associated with microstructures in experiments.Specifically,when the grain size approaches that of the specimen,the critical load required for variant switching at the crack tip increases,resulting in greater dissipation of elastic energy during ferroelastic variant switching.Moreover,the interface tension accelerates the evolution of variants.The presented framework exhibits significant potential in modeling ferroelastic variant switching at the micro-and nano-scale.
基金support from the National Natural Science Foundation of China(No.22175079)support from the National Natural Science Foundation of China(No.22205087)+2 种基金the Open Project Program of Jiangxi Provincial Key Laboratory of Functional Molecular Materials Chemistry,Jiangxi University of Science and Technology(No.20212BCD42018)National Natural Science Foundation of China(No.22275075)Natural Science Foundation of Jiangxi Province(Nos.20204BCJ22015 and 20202ACBL203001).
文摘Ferroelastic hybrid perovskite materials have been revealed the significance in the applications of switches,sensors,actuators,etc.However,it remains a challenge to design high-temperature ferroelastic to meet the requirements for the practical applications.Herein,we reported an one-dimensional organicinorganic hybrid perovskites(OIHP)(3-methylpyrazolium)CdCl_(3)(3-MBCC),which possesses a mmmF2/m ferroelastic phase transition at 263 K.Moreover,utilizing crystal engineering,we replace-CH_(3) with-NH_(2) and-H,which increases the intermolecular force between organic cations and inorganic frameworks.The phase transition temperature of(3-aminopyrazolium)CdCl_(3)(3-ABCC),and(pyrazolium)CdCl_(3)(BCC)increased by 73 K and 10 K,respectively.Particularly,BCC undergoes an unconventional inverse temperature symmetry breaking(ISTB)ferroelastic phase transition around 273 K.Differently,it transforms from a high symmetry low-temperature paraelastic phase(point group 2/m)to a low symmetry high-temperature ferroelastic phase(point group ī)originating from the rare mechanism of displacement of organic cations phase transition.It means that crystal BCC retains in ferroelastic phase above 273 K until melting point(446 K).Furthermore,characteristic ferroelastic domain patterns on crystal BCC are confirmed with polarized optical microscopy.Our study enriches the molecular mechanism of ferroelastics in the family of organic-inorganic hybrids and opens up a new avenue for exploring high-temperature ferroic materials.
基金financially supported by the Rare and Precious Metals Material Genetic Engineering Project of Yunnan Province(Nos.202102AB080019-1 and 202002AB080001-1)the Yun-nan Fundamental Research Projects(Nos.202101AW070011 and 202101BE070001-015).
文摘The primary purpose of this work is to optimize the thermophysical properties of rare-earth tan-talate ceramics using the high-entropy effect.Here,the high-entropy rare-earth tantalate ceramic(Y_(0.1)Nd_(0.1)Sm_(0.1)Gd_(0.1)Dy_(0.1)Ho_(0.1)Er_(0.1)Tm_(0.1)Yb_(0.1)Lu_(0.1))TaO_(4)((10RE_(0.1))TaO_(4))is synthesized successfully.The lat-tice distortion and oxygen vacancy concentration are characterized firstly in the rare-earth tantalates.Notably,compared with single rare-earth tantalates,the thermal conductivity of(10RE_(0.1))TaO_(4) is reduced by 16%-45%at 100℃ and 22%-45%at 800℃,and it also presents lower phonon thermal conductivity in the entire temperature range from 100 to 1200℃.The phonon thermal conductivity(1.0-2.2 W m^(-1) K^(-1),100-1200℃)of(10RE_(0.1))TaO_(4) is lower than that of the currently reported high-entropy four-,five-and six-component rare-earth tantalates.This is the result of scattering by the ferroelastic domain,lattice distortion associated with size and mass disorder,and point defects,which target low-,mid-and high-frequency phonons.Furthermore,(10RE_(0.1))TaO_(4),as an improved candidate for thermal barrier coatings materials(TBCs),has a higher thermal expansion coefficient(10.5×10^(-6)K^(-1) at 1400℃),lower Young’s modulus(123 GPa)and better high-temperature phase stability than that of single rare-earth tantalates.
基金supported by the National Natural Science Foundation of China(Nos.21975114,11904151 and 22105094)。
文摘Multifunctional switchable materials are attracting tremendous interest because of their great application potential in signal processing,information encryption,and smart devices.Here,we reported an organic-inorganic hybrid thermochromic ferroelastic crystal,[TMIm][CuCl_(4)](TMIm=1,1,3,3-tetramethylimidazolidinium),which undergoes two reversible phase transitions at 333 K and 419 K,respectively.Intriguingly,these three phases experience a remarkable ferroelastic-paraelastic-ferroelastic(2/m-mmm-2/m)transition,which remains relatively unexplored in ferroelastics.Moreover,the ferroelastic domains can be simultaneously switched under temperature and stress stimuli.Meanwhile,[TMIm][CuCl_(4)]exhibits thermochromic phenomenon,endowing it with extra spectral encryption possibilities during information processing.Combined with dielectric switching behavior,[TMIm][Cu Cl_(4)]are promising for practical applications in memory devices,next-generation sensors,and encryption technology.
基金supported by National Natural Science Foundation of China(NSFC,Nos.22071273 and 21821003)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01C161).
文摘Two-dimensional organic-inorganic hybrid ferroelastics with high-temperature reversible phase transitions are very rare and have become one of the research hotspots in the field of ferroelastic materials.Herein,we report three new layered organic-inorganic hybrid perovskites based on halogen-substituted phenethylaminium,(3-XC_(6)H_(5)CH_(2)CH_(2)NH_(3))_(2)[CdCl_(4)](X=F(1),CI(2)and Br(3)).They undergo structural phase transitions at 376/371 K,436/430 K,and 421/411 K,respectively,between the isomorphic hightemperature phases(space group I4/mmm,Z=2)and different room-temperature phases with the reduced structural symmetries,i.e.,P21/a(Z=2)in 1,Pi(Z=4)in 2,and P21/a(Z=4)in 3,respectively.These ferroelastic transitions arise from the order-disorder transition of organic cations together with the synchronous displacement of inorganic layers,accompanying with feroelastic spontaneous strains of 0.16,0.13 and 0.12 for 1-3,respectively.By enriching layered perovskite ferroelastics based on halogensubstituted cations,this work provides important clues for exploring new ferroic materials based on hybrid crystals.
基金supported financially by the National Key Research and Development Program of China (No. 2017YFA0204800)National Natural Science Foundation of China (Nos. 22175079 and 21875093)+1 种基金Natural Science Foundation of Jiangxi Province (Nos. 20204BCJ22015 and 20202ACBL203001)Jiangxi Provincial Department of Education Science and Technology Research Project (No. GJJ210812)。
文摘Ferroelastic materials with switchable spontaneous strain possess widely potential applications in the field of energy and information conversion.Recently,organic-inorganic hybrid halide double perovskites (OIHHDPs) have become a charming new platform for developing various functional materials,such as ferroelectrics,fluorescence and X–ray detection.Nevertheless,OIHHDP ferroelastic materials,especially high-temperature ones,are rare.Herein,we initially synthesized an OIHHDP ferroelastic,(2,2-difluoroethanamine)_(2)[(NH_(4))InCl_6](1),which possesses a ferroelastic phase transition at 407 K.Moreover,thanks to the flexible B-site for OIHHDPs,we replaced the NH_(4)^(+) ions within[(NH_(4))InCl_6]_n^(2n–)formworks with K^(+)ions,which endows with coordination bonds between 2,2-difluoroethanamine organic cations and[KInCl_6]_n^(2n–)formworks.Due to the existence of coordination bonds,the phase transition temperature of (2,2-difluoroethanamine)_(2)[KInCl_6](2) can reach 458 K.As far as we know,this value is the highest reported in OIHHDP ferroelastics.This work offers inspiration for the design of high-temperature OIHHDP phase transition materials including ferroelectrics and ferroelastics.
基金financially supported by the National Natural Science Foundation of China(grant no.21991141).
文摘Lead-based organic-inorganic hybrids occupy a niche in the field of optoelectronics due to exceptional semiconducting properties and potential ferroelasticity.Nevertheless,the possible toxicity of lead restricts their widespread application to a certain extent.Herein,two new lead-free ferroelastic semiconductors are reported:[DMMClEA]_(3)Bi_(2)Br_(9)(compound 1)and[DMMClEA]_(3)Sb_(2)Br_(9)(compound 2)(DMMClEA=N-(chloromethyl)-N,N-dimethylethylammonium),in which the inorganic framework neatly arranges with[Bi_(2)Br_(9)]^(3−)/[Sb_(2)Br_(9)]^(3−)polyhedrons shared by face,forming an A_(3)B_(2)X_(9)-type structure.Both compounds 1 and 2 possess two-step phase transitions,including a3mF2/m-type ferroelastic phase transition,based on the Aizu rule.In addition,dual dielectric switches endow the application toward sensor devices.This finding enriches A_(3)B_(2)X_(9)-type zero-dimensional hybrid ferroelastics and provides an approach to designing high-performance,lead-free perovskite semiconductors with dielectric functionality.
基金Supported by the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 2005247004)
文摘The hysteresis phenomena of ferroelectric/ferroelastic material in polarization procedure are investigated. Some assumptions are presented based on the published experimental data. The electrical yielding criterion, mechanical yielding criterion and isotropic hardening model are established. The flow theory in incremental forms in polarization procedure is presented. The nonlinear constitutive law for electrical-mechanical coupling is proposed phenomenologically. Finally, the nonlinear constitutive law expressed in a form of matrices and vectors, which is immediately associated with finite element analysis, is formulated. In the example problem of a rectangular specimen subjected to a uniaxial electric field, the procedure from virgin state to fully polarized state is simulated. Afterward, a uniaxial compressive loading is applied to depolarizing the specimen. Results are in agreement with the experimental data.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2017YFA0204800)and Southeast University。
文摘The broad operating temperature range is sought for molecular ferroic materials who are expected to be applied to flexible and electronic materials.Hydrogen bonds,an effective force between molecules,are important to regulate the molecule structure and their condition,helping a higher temperature range for ferroic materials.Here,we report a molecular perovskite ferroelastic(Me-Hdabco)Rb[BF_(4)]_(3)(Me-Hdabco=N-methyldabconium)which shows high temperature(T_(1)=322.5 K and T_(2)=381K)ferroelastic phase transitions.The ferroelastic phase transition temperature range of(Me-Hdabco)Rb[BF_(4)]_(3) is significantly increased by 71 K compared with[Meda-bco-F]Rb[BF_(4)]_(3)(Medabco-F=1-fluoro-4-methyl-1,4-diazoniabicyclo[2.2.2]octane).Structural analysis and thermal analysis demonstrate the ferroelastic phase transition is mainly attributed to dynamic cations order and disorder transformation.Therefore,new hydrogen bonds generated between cations and the Rb_(8)[BF_(4)]_(12) frame increase their intermolecular force,which is beneficial to improving the phase transition temperature.This finding has an important impact on the utilization of weak interactionforces to design and optimize functional materials.
基金the National Natural Science Foundation of China(Nos.11890684 and 52102142)the Foundation for Innovative Research Groups of Hunan Province(No.2020JJ1005)。
文摘Yttrium tantalate(YTaO_(4))is the next generation of higher service temperature thermal barrier coatings(TBCs)materials due to its smaller volume effect in phase change,lower thermal conductivity and unique ferroelastic domain structure.However,the low fracture toughness limits its application.We first characterized the diffraction patterns of variants,and two variants(M_(1)and M_(2))observed in transmission electron microscopy(TEM)results were determined from four possible variants by mechanical derivation.The role of Zr^(4+)doping in ferroelastic toughening was explained in detail.With the increase of Zr^(4+)doping concentration,the monoclinic angle β and the domain rotation angleαdecrease,respectively.The spontaneous strain component and the principal strain in the main space also have a similar decreasing trend.The decrease of the ferroelastic domain inversion energy barrier is beneficial to the improvement of fracture toughness.Combining the results of Vickers indentation,we found that Zr^(4+)could be enriched at the domain boundary to inhibit the generation of cracks.An appropriate amount of Zr^(4+)is conducive to the improvement of fracture toughness,and the excessive Zr^(4+)will reduce the fracture toughness due to the generation of by-product t-ZrO_(2).So,the optimal composition is Y_(0.44)Ta_(0.44)Zr_(0.12)O_(2) and the best fracture toughness(2.9–3.8MPa m^(1/2))is equivalent to the commercial 8YSZ.This result will promote the application of a new generation of TBCs.
基金This work is supported in part by the National Key R&D Program of China(No.2018YFA0305800)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB28000000)+2 种基金the National Natural Science Foundation of China(No.11834014)the Beijing Municipal Science and Technology Commission(No.Z118100004218001)the fundamental research funds for the central universities,and University of Chinese Academy of Sciences.
文摘Two-dimensional(2D)ferromagnetic and ferroelectric materials attract unprecedented attention due to the spontaneous-symmetry-breaking induced novel properties and multifarious potential applications.Here we systematically investigate a large family(148)of 2D MGeX3(M=metal elements,X=O/S/Se/Te)by means of the high-throughput first-principles calculations,and focus on their possible ferroic properties including ferromagnetism,ferroelectricity,and ferroelasticity.We discover eight stable 2D ferromagnets including five semiconductors and three half-metals,212D antiferromagnets,and 11 stable 2D ferroelectric semiconductors including two multiferroic materials.Particularly,MnGeSe3 and MnGeTe3 are predicted to be room-temperature 2D ferromagnetic half metals with Tc of 490 and 308 K,respectively.It is probably for the first time that ferroelectricity is uncovered in 2D MGeX3 family,which derives from the spontaneous symmetry breaking induced by unexpected displacements of Ge-Ge atomic pairs,and we also reveal that the electric polarizations are in proportion to the ratio of electronegativity of X and M atoms,and IVB group metal elements are highly favored for 2D ferroelectricity.Magnetic tunnel junction and water-splitting photocatalyst based on 2D ferroic MGeX3 are proposed as examples of wide potential applications.The atlas of ferroicity in 2D MGeX3 materials will spur great interest in experimental studies and would lead to diverse applications.
基金the National Natural Science Foundation of China(Grant Nos.51572278,51790491,11574126,51872278)the National Basic Research Programof China(Grant Nos.2016YFA0300103 and 2015CB921201)Support from Jiangxi Key Laboratory for Two-Dimensional Materials and Jiangxi Engineering Laboratory for Thin Films and Devices is also acknowledged.
文摘We prepared 300-nm GeTe thin films on(111)-oriented and piezoelectrically active 0.71 Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.29PbTiO_(3)(PMN-0.29 PT)single-crystal substrates by the pulsed laser deposition and investigated the effects of in situ electric-field-controllable non-180ferroelastic domain switching of the PMN-0.29 PT on the electronic properties of the GeTe films.The in-plane strain of the PMN-0.29 PT could be modulated continuously and reversibly by electric fields in a nonvolatile manner and could be effectively transferred to the GeTe films.Based on this,we realized reversible and nonvolatile resistance switching and obtained multilevel stable nonvolatile resistance states with good stability and endurance at T=300 K by applying appropriate asymmetrical bipolar electric fields to the PMN-0.29 PT(111)substrates along the thickness direction.Such heterostructures may be used for multilevel data storage that allows each unit to store multiple bits of information and thus improve the memory density.Our investigation would be beneficial for the fabrication of nonvolatile memory devices using PMN-xPT-based heterostructures.
基金financially supported by the National Natural Science Foundation of China(grant no.21991141)the Science Foundation of Zhejiang Province(no.LZ20B010001)Zhejiang Normal University.
文摘Organic–inorganic hybrid perovskites(OIHPs)have been a hot research topic due to their advanced structural and functional features that cover almost all the research fields of intelligent materials including ferroelectric,photovoltaic,fluorescent,and dielectric.However,the development of the construction of an OIHP ferroelastic semiconductor with optical-electrical response has been a huge challenge and infrequently reported.In this work,a rare and interesting hybrid perovskite ferroelastic semiconductor,[BFDA]PbBr_(3)(BFDA=benzyl-(2-fluoro-ethyl)-dimethyl-ammonium),was synthesized,which benefits from the structural advantage of a long tail BFDA to be balanced by the suitable inorganic framework.[BFDA]PbBr_(3) shows a high-temperature ferroelastic phase transition at 365 K and a direct band gap of 3.33 eV.In addition,it can emit charming orange-pink light under a 365 nm UV lamp.To combine this with the ferroelastic,optical,and dielectric properties,[BFDA]PbBr_(3) can be identified as a very rarely reported ferroelastic semiconductor.The above-mentioned synthesis strategy is also helpful for the enrichment and development of the hybrid perovskite family.
文摘The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal theories of high-T<sub>c</sub> superconductors, thereby applying the finding that the optimum hole concentration of σ<sub>o</sub> = 0.229 can be linked with the universal fractal constant δ<sub>1</sub> = 8.72109… of the renormalized quadratic Hénon map. The transition temperature obviously increases steeply with a domain structure of ever narrower size, characterized by Fibonacci numbers. However, also conventional BCS superconductors can be scaled with δ<sub>1</sub>, exemplified through the energy gap relation k<sub>B</sub>T<sub>c</sub> ≈ 5Δ<sub>0</sub>/δ<sub>1</sub>, suggesting a revision of the entire theory of superconductivity. A low mean cationic charge allows the development of a frustrated nano-sized fractal structure of possibly ferroelastic nature delivering nano-channels for very fast charge transport, in common for both high-T<sub>c</sub> superconductor and organic-inorganic halide perovskite solar materials. With this backing superconductivity above room temperature can be conceived for synthetic sandwich structures of less than 2+. For instance, composites of tenorite and cuprite respectively tenorite and CuI (CuBr, CuCl) onto AuCu alloys are proposed. This specification is suggested by previously described filamentary superconductivity of “bulk” CuO1﹣x samples. In addition, cesium substitution in the Tl-1223 compound is an option.
基金supported by the National Key R&D Program of China(No.2022YFB3708600)the Materials Genome Engineering of Rare and Precious Metal of Yunnan Province(No.202102AB080019-1)+1 种基金Yunnan Fundamental Research Projects(Nos.202101AW070011,202101BE070001-015)Kunming University of Science and Technology Analysis and Testing Fund(No.2022P20211130017).
文摘Thermal barrier coating(TBC)materials can improve energy conversion efficiency and reduce fossil fuel use.Herein,novel rare earth tantalates RETaO_(4),as promising candidates for TBCs,were reassembled into multi-component solid solutions with a monoclinic structure to further depress thermal conductivity via an entropy strategy.The formation mechanisms of oxygen vacancy defects,dislocations,and ferroelastic domains associated with the thermal conductivity are demonstrated by aberration-corrected scanning transmission electron microscopy.Compared to single-RE RETaO_(4)and 8YSZ,the intrinsic thermal conductivity of(5RE1/5)TaO4 was decreased by 35%–47%and 57%–69%at 1200℃,respectively,which is likely attributed to multi-scale phonon scattering from Umklapp phonon–phonon,point defects,domain structures,and dislocations.r¯3+RE/r5+Ta and low-temperature thermal conductivity are negatively correlated,as are the ratio of elastic modulus to thermal conductivity(E/κ)and high-temperature thermal conductivity.Meanwhile,the high defects’concentration and lattice distortion in high-entropy ceramics enhance the scattering of transverse-wave phonons and reduce the transverse-wave sound velocity,leading to a decrease in the thermal conductivity and Young’s modulus.In addition,5HEC-1 has ultra-low thermal conductivity,moderate thermal expansion coefficients,and high hardness among three five-component high-entropy samples.Thus,5HEC-1 with superior thermal barrier and mechanical properties can be used as promising thermal insulating materials.
基金supported by the National Natural Science Foundation of China(22193042,22125110,21833010,22075285,21875251,21921001,and U21A2069)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(ZDBS-LY-SLH024)the Youth Innovation Promotion of Chinese Academy of Sciences(2020307)。
基金supported by the National Natural Science Foundation of China(NSFC,Nos.22071273 and 21821003)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01C161)。
文摘Understanding phase transitions in multi-component crystals is of importance for regulating specified functional materials.Herein,we present two new organic-inorganic hybrid crystals,(Me_(3)NCH_(2)CH_(2)X)_(4)[Ni(NCS)_6](X=Cl and Br),revealing distinct phase transitions.Specifically,the Clsubstituted cations weakly interact with discrete inorganic part hence reveal step-wise dynamic changes upon heating,which result in multi-step solid-solid phase transitions (P1-P2_1/n-A2/a-Cmce) including a ferroelastic one with a spontaneous strain of 0.0475.Whereas the Br-substituted cations with larger steric effect prevent the solid-solid phase transition but give a solid-liquid phase transition at above 419 K.The present instances well demonstrate the complicity for multi-component crystals arising from the delicate balance established by abundant weak intermolecular interactions,and inspire the design of novel phase-transition materials by judiciously assembling multi-component crystals.