Discrete dipoles located near the crack tip play an important role in nonlinear electric fieldinduced fracture of piezoelectric ceramics.A physico-mathematical model of dipole is constructed of two gen-eralized concen...Discrete dipoles located near the crack tip play an important role in nonlinear electric fieldinduced fracture of piezoelectric ceramics.A physico-mathematical model of dipole is constructed of two gen-eralized concentrated piezoelectric forces with equal density and opposite sign.The interaction between crackand electric dipole in piezoelectricity is analyzed.The closed form solutions,including those for stress andelectric displacement,crack opening displacement and electric potential,are obtained.The function of pi-ezoelectric anisotropie direction,p_a(θ)=cosθ+p_asinθ,can be used to express the influence of a dipole’sdirection.In the case that a dipole locates near crack tip,the piezoelectric stress intensity factor is a powerfunction with-3/2 index of the distance between dipole and crack tip.展开更多
Piezoelectric nanowires are promising building blocks in various micro-electromechanical systems. Using firstprinciples calculations, we systematically investigate the influence of surface and volume changes on piezoe...Piezoelectric nanowires are promising building blocks in various micro-electromechanical systems. Using firstprinciples calculations, we systematically investigate the influence of surface and volume changes on piezoelectric coefficients in [001]-oriented ZnO nanowires and hollow nanowires. We find that the increased non-axial ion displacements under strain near the {100} surface cause a notable enhancement in piezoelectric coefficients for these nanowires. Furthermore, by introducing the obtained surface modifications, we break through the limitation of simulation size and obtain the piezoelectric coefficients at the experimental size. Our findings are of importance to expand simulations and guide experimental explorations.展开更多
A basic solution in series form for the three-phase composite cylindrical model in antiplanepiezoelectricity subjected to the action of a singularity in the intermediate matrix region is presented.The so-lution is obt...A basic solution in series form for the three-phase composite cylindrical model in antiplanepiezoelectricity subjected to the action of a singularity in the intermediate matrix region is presented.The so-lution is obtained through the complex potential approach in conjunction with the techniques of analytical con-tinuation,singularity analysis,Laurent series expansion in an annular region and Cauchy integral formulae,etc.Based on the complex potentials obtained,explicit expressions for the distribution of stress and electricdisplacement in the three regions are also derived.展开更多
An orthogonal ultrasonic irradiation system consisting of HIFU with frequency at 1.05 MHz combined with ultrasound with frequency at 28 kHz was applied in this paper.Effect of cavitation was detected by pH-value measu...An orthogonal ultrasonic irradiation system consisting of HIFU with frequency at 1.05 MHz combined with ultrasound with frequency at 28 kHz was applied in this paper.Effect of cavitation was detected by pH-value measurement and conductance measurement.The result shows that the effect of cavitation caused by ultrasound with frequency at 28 kHz is greatly enhanced by HIFU piezoelectricity transducer with frequency at 1.05 MHz.展开更多
First-principle calculations reveal that the configuration system of hexagonal boron nitride(h-BN) monolayer with triangular vacancy can induce obvious magnetism, contrary to that of the nonmagnetic pristine boron nit...First-principle calculations reveal that the configuration system of hexagonal boron nitride(h-BN) monolayer with triangular vacancy can induce obvious magnetism, contrary to that of the nonmagnetic pristine boron nitride monolayer.Interestingly, the h-BN with boron atom vacancy(VB-BN) displays metallic behavior with a total magnetic moment being 0.46μ_B per cell, while the h-BN with nitrogen atom vacancy(VN-BN) presents a half-metallic characteristic with a total magnetic moment being 1.0μ_B per cell. Remarkably, piezoelectric stress coefficient e_(11) of the VN-BN is about 1.5 times larger than that of pristine h-BN. Furthermore, piezoelectric strain coefficient d_(11)(12.42 pm/V) of the VN-BN is 20 times larger than that of pristine h-BN and also one order of magnitude larger than the value for the h-MoS_2 monolayer, which is mainly due to the spin-down electronic state in the V_N-BN system. Our study demonstrates that the nitrogen atom vacancies can be an efficient route to tailoring the magnetic and piezoelectric properties of h-BN monolayer, which have promising performances for potential applications in nano-electromechanical systems(NEMS) and nanoscale electronics devices.展开更多
The effect of piezoelectricity on phonon properties and thermal conductivity of gallium nitride(Ga N)nanofilms is theoretically investigated. The elasticity model is utilized to derive the phonon properties in spatial...The effect of piezoelectricity on phonon properties and thermal conductivity of gallium nitride(Ga N)nanofilms is theoretically investigated. The elasticity model is utilized to derive the phonon properties in spatially confined Ga N nanofilms. The piezoelectric constitutive relation in Ga N nanofilms is taken into account in calculating the phonon dispersion relation. The modified phonon group velocity and phonon density of state as well as the phonon thermal conductivity are also obtained due to the contribution of piezoelectricity. Theoretical results show that the piezoelectricity in Ga N nanofilms can change significantly the phonon properties such as the phonon group velocity and density of states,resulting in the variation of the phonon thermal conductivity of Ga N nanofilms remarkably. Moreover,the piezoelectricity of Ga N can modify the dependence of thermal conductivity on the geometrical size and temperature. These results can be useful in modeling the thermal performance in the active region of Ga N-based electronic devices.展开更多
It is difficult to establish a classical variational model for piezoelectricity. Following the semi inverse method of establishing generalized variational principles, an energy like trial functional with a certain unk...It is difficult to establish a classical variational model for piezoelectricity. Following the semi inverse method of establishing generalized variational principles, an energy like trial functional with a certain unknown function is constructed. The unknown function is easily identified step by step. A family of variational principles for the static behavior of the elastic and electric variables in the vicinity of a surface electrode attached to a piezoelectric ceramic is established directly from its field equations and boundary conditions.展开更多
The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 (KNN) crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. The...The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 (KNN) crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. The full potentiallinearized augumented plane wave plus local orbitals (APW-LO) method and the supercell method are used in the calculation for the KNN crystal with and without the La doping. The results show that the piezoelectricity originates from the strong hybridization between the Nb atom and the O atom, and the substitution of the K or Na atom by the La impurity atom introduces the anisotropic relaxation and enhances the piezoelectricity at first and then restrains the hybridization of the Nb-O atoms when the La doping content further increases.展开更多
Serial material model (Dilute model)and Limited Units (LU)method were employed to analyze the performance of binary piezo-composite system.The reckoned electric potential deployments illustrated difference while the p...Serial material model (Dilute model)and Limited Units (LU)method were employed to analyze the performance of binary piezo-composite system.The reckoned electric potential deployments illustrated difference while the particles were different.Their piezoelectricities were also calculated according to the model,and furthermore comparation suggested that small particles living in the tolerance improve the piezoelectricity of piezo-composite.Experiments coinciding with analyses were processed simultaneously. Ceramics were milled for different time in order to control the concentration of particle size.The results showed that the filled particles enhanced the piezoelectricity of binary piezo-composite system efficiently whereas too many chips deteriorated the performance of piezo-composites.展开更多
Using first-principles calculation, the contribution of A-site and B-site atoms to polarization and piezoelectricity d33 in the tetragonal Pb TiO_3/KNbO_3 and PbTiO_3/LaAlO_3 superlattices is investigated in this pape...Using first-principles calculation, the contribution of A-site and B-site atoms to polarization and piezoelectricity d33 in the tetragonal Pb TiO_3/KNbO_3 and PbTiO_3/LaAlO_3 superlattices is investigated in this paper. It is shown that PbTiO_3/KNbO_3 superlattice has larger polarization and d33 than PbTiO_3/LaAlO_3 superlattice, because there is stronger charge transfer between A(B)-site atoms and oxygen atom in PbTiO_3/KNbO_3 superlattice. InPbTiO_3/KNbO_3 superlattice,B-site atoms(Ti, Nb) make larger contribution to the total polarization and d33 than the A-site atoms(Pb, K) because of the strong covalent interactions between the transition metal(Ti, Nb) and the oxygen atoms, while piezoelectricity in PbTiO_3/LaAlO_3 superlattice mainly ascribes to piezoelectric contribution of Pb atom and Ti atom in PbTiO_3 component.Furthermore, by calculating the proportion of the piezoelectric contribution from Pb TiO_3 component in superlattices, we find there is different response of strain to piezoelectric contribution from Pb TiO_3 component in two superlattices but still with a value larger than 50%. InPbTiO_3/KNbO_3 superlattice, the c-axis strain reduces the proportion, especially under tensile condition. Meanwhile in PbTiO_3/LaAlO_3 superlattice, Pb TiO_3 plays a leading role to the total d33, especially under compressive condition, and the proportion decreases as the tensile strain increases.展开更多
The piezoelectric properties of K1-xNaxNbO3 are studied by using first-principles calculations within virtual crystal approximation. To understand the critical factors for the high piezoelectric response in K1-x Na x ...The piezoelectric properties of K1-xNaxNbO3 are studied by using first-principles calculations within virtual crystal approximation. To understand the critical factors for the high piezoelectric response in K1-x Na x Nb O3, the total energy,piezoelectric coefficient, elastic property, density of state, Born effective charge, and energy barrier on polarization rotation paths are systematically investigated. The morphotropic phase boundary in K1-x Na x Nb O3 is predicted to occur at x = 0.521, which is in good agreement with the available experimental data. At the morphotropic phase boundary, the longitudinal piezoelectric coefficient d33 of orthorhombic K0.5Na0.5NbO3 reaches a maximum value. The rotated maximum of d*33is found to be along the 50° direction away from the spontaneous polarization(close to the [001] direction). The moderate bulk and shear modulus are conducive to improving the piezoelectric response. By analyzing the energy barrier on polarization rotation paths, it is found that the polarization rotation of orthorhombic K0.5Na0.5NbO3 becomes easier compared with orthorhombic KNbO3, which proves that the high piezoelectric response is attributed to the flattening of the free energy at compositions close to the morphotropic phase boundary.展开更多
The uniqueness theorem and the theorem of reciprocity in the linearized porous piezoelectricity are established under the assumption of positive definiteness of elastic and electric fields.General theorems in the line...The uniqueness theorem and the theorem of reciprocity in the linearized porous piezoelectricity are established under the assumption of positive definiteness of elastic and electric fields.General theorems in the linear theory of porous piezoelectric materials are proved for the quasi-static electric field approximation.The uniqueness theorem is also proved without using the positive definiteness of the elastic field.An eigenvalue problem associated with free vibrations of a porous piezoelectric body is studied using the abstract formulation.Some properties of operators are also proved.The problem of frequency shift due to small disturbances,based on an abstract formulation,is studied using a variational and operator approach.A perturbation analysis of a special case is also given.展开更多
Designing stretchable and skin-conformal self-powered sensors for intelligent sensing and posture recognition is challenging.Here,based on a multi-force mixing and vulcanization process,as well as synergistically piez...Designing stretchable and skin-conformal self-powered sensors for intelligent sensing and posture recognition is challenging.Here,based on a multi-force mixing and vulcanization process,as well as synergistically piezoelectricity of BaTiO_(3)and polyacrylonitrile,an all-in-one,stretchable,and self-powered elastomer-based piezo-pressure sensor(ASPS)with high sensitivity is reported.The ASPS presents excellent sensitivity(0.93 V/104 Pa of voltage and 4.92 nA/104 Pa of current at a pressure of 10-200 kPa)and high durability(over 10,000 cycles).Moreover,the ASPS exhibits a wide measurement range,good linearity,rapid response time,and stable frequency response.All components were fabricated using silicone,affording satisfactory skinconformality for sensing postures.Through cooperation with a homemade circuit and artificial intelligence algorithm,an information processing strategy was proposed to realize intelligent sensing and recognition.The home-made circuit achieves the acquisition and wireless transmission of ASPS signals(transmission distance up to 50 m),and the algorithm realizes the classification and identification of ASPS signals(accuracy up to 99.5%).This study proposes not only a novel fabrication method for developing self-powered sensors,but also a new information processing strategy for intelligent sensing and recognition,which offers significant application potential in human-machine interaction,physiological analysis,and medical research.展开更多
Ferroelectric semiconductors have sparked growing attention in the field of optoelectronics,due to their unique ferroelectric photovoltaic effect.Recently,substantial efforts have been devoted to the development of fe...Ferroelectric semiconductors have sparked growing attention in the field of optoelectronics,due to their unique ferroelectric photovoltaic effect.Recently,substantial efforts have been devoted to the development of ferroelectric semiconductors,including inorganic oxides,organic-inorganic hybrids,and metal-free perovskites.Nevertheless,reports of ferroelectric semiconductors with a bandgap of less than 2 eV have been scarce.Here,in combination with the incorporation of triiodide(I_(3)−)and the introduction of chiral cations,we successfully constructed a pair of enantiomeric organic-inorganic hybrid ferroelectric semiconductors,(S-1,2-DAP·I)_(4)·I_(3)·BiI_(6)and(R-1,2-DAP·I)_(4)·I_(3)·BiI_(6)(R/S-1,2-DAP=(R/S)-(–)-1,2-diaminopropane),which possess high-temperature multiaxial ferroelectric phase transition with an Aizu notation of 422F2(s)at 405 K,a narrow bandgap of 1.56 eV comparable to that of CH3NH3PbI_(3)(∼1.5 eV),and an impressive piezoelectric response(piezoelectric coefficient,d22 of 35 pC/N)on par with PVDF(polyvinylidene fluoride,30 pC/N).With intriguing attributes,(S-1,2-DAP·I)_(4)·I_(3)·BiI_(6)and(R-1,2-DAP·I)_(4)·I_(3)·BiI_(6)exhibit great potential for application of self-power polarized-light detection and piezoelectric sensors.展开更多
Quantum materials have exhibited attractive electro-mechanical responses,but their piezoelectric coefficients are far from satisfactory due to the lack of feasible strategies to benefit from the quantum effects.We dis...Quantum materials have exhibited attractive electro-mechanical responses,but their piezoelectric coefficients are far from satisfactory due to the lack of feasible strategies to benefit from the quantum effects.We discovered the valley piezoelectric mechanism that is absent in the traditional piezoelectric theories yet promising to overcome this challenge.A theoretical model was developed to elucidate the valley piezoelectricity in 2D materials as originating from the strong spin-orbit coupling.Consistent analytical and density-functional-theory calculations validate the model and unveil the crucial dependence of valley piezoelectricity on valley/spin splitting and hybridization energy.Up to 50%of electro-mechanical responses in our tested twodimensional systems are attributed to the valley piezoelectric mechanisms.Rational strategies including doping,passivation,and external strain are proposed to optimize piezoelectricity,with a more than 127%increase in piezoelectricity demonstrated by density-functional-theory simulations.The general valley piezoelectric model not only opens an opportunity to achieve outstanding piezoelectricity via optimizing intrinsic variables but also makes the large family of valley materials promising for piezoelectric sensing and energy harvesting.展开更多
The flourishing development of emerging electromechanical applications has stimulated an urgent demand for ferroelectric ceramics with high piezoelectric properties and broad temperature usage range.However,it remains...The flourishing development of emerging electromechanical applications has stimulated an urgent demand for ferroelectric ceramics with high piezoelectric properties and broad temperature usage range.However,it remains a challenge to simultaneously obtain good piezoelectricity and reliable temperature stability in lead zirconate titanate(PZT)-based piezoelectric ceramics.To solve this issue,a synergetic strategy was proposed to introduce lead vacancies through niobium doping and construct morphotropic phase boundary(MPB).In this work,Pb_(0.905)Ba_(0.085)(V Pb″)_(0.01)[(Zr_(x)Ti_(1-x))_(0.98)Nb_(0.02)]O_(3)(PBZTN-x)material system was designed.Good comprehensive properties(d_(33)=864 pC/N,k_(p)=84%,T_(C)=201℃)and excellent temperature stability(less than 10%variation of electrical properties from 20℃ to 160℃)were obtained in PBZTN-0.540 ceramics.Good piezoelectricity can be attributed to high extrinsic contribution(domain wall motion)induced by Pb^(2+)vacancies and the existence of nano-domains emerged at MPB,while excellent temperature stability is mainly attributed to the minimized local stress in the lattice and the stable domain structure.展开更多
BiFeO_(3)-BaTiO_(3) based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature.Since the piezoelectric response of piez...BiFeO_(3)-BaTiO_(3) based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature.Since the piezoelectric response of piezoelectric ceramics just appears after poling engineering,in this work,the domain evolution and microscopic piezoresponse were observed in-situ using piezoresponse force microscopy(PFM)and switching spectroscopy piezoresponse force microscopy(SS-PFM),which can effectively study the local switching characteristics of ferroelectric materials especially at the nanoscale.The new domain nucleation preferentially forms at the boundary of the relative polarization region and expands laterally with the increase of bias voltage and temperature.The maximum piezoresponse(Rs),remnant piezoresponse(Rrem),maximum displacement(Dmax)and negative displacement(Dneg)at 45 V and 120C reach 122,69,127 pm and 75 pm,respectively.Due to the distinct effect of poling engineering in full domain switching,the corresponding d33 at 50 kV/cm and 120C reaches a maximum of 205 pC/N,which is nearly twice as high as that at room temperature.Studying the evolution of ferroelectric domains in the poling engineering of BiFeO_(3)-BaTiO_(3)ceramics provides an insight into the relationship between domain structure and piezoelectric response,which has implications for other piezoelectric ceramics as well.展开更多
The sodium(Na)and Ce co-doped calcium bismuth titanate(CBT;CaBi_(4)Ti_(4)O_(15))Aurivillius ceramics in a Ca_(1-x)(Na_(0.5)Ce_(0.5)),Bi_(4)Ti_(4)O_(15)(CNCBT;doping content(x)=0,0.03,0.05,0.08 and 0.12)system were syn...The sodium(Na)and Ce co-doped calcium bismuth titanate(CBT;CaBi_(4)Ti_(4)O_(15))Aurivillius ceramics in a Ca_(1-x)(Na_(0.5)Ce_(0.5)),Bi_(4)Ti_(4)O_(15)(CNCBT;doping content(x)=0,0.03,0.05,0.08 and 0.12)system were synthesized by the conventional solid-state sintering method.All compositions show a single-phase orthorhombic(space group:A2jam)structure at room temperature.The shift of the Curie point(T_(c))towards lower temperatures(T)on doping results from the increased tolerance factor(t).The substitution-enhanced ferroelectric performance with large maximum polarization(P_(m))and facilitated domain switching is evidenced by the developed electrical polarization-electric field(P-E)and electrical current-electric field(I-E)hysteresis loops.The piezoelectric coefficient(d_(33)=20.5±0.1 pC/N)of the x=0.12 sample is about four times larger than that of pure CBT.The improved piezoelectric properties can be attributed to the high remanent polarization(P_(r))and relatively high dielectric permittivity(ε′).In addition,multi-sized(micron and sub-micron)domain structures were observed in the CNCBT ceramics by the piezoresponse force microscope(PFM).The multiple-sized ferroelectric domain structure with smaller domains is beneficial to the easy domain switching,enhanced ferroelectric performance,and improved piezoelectric properties of the CNCBT ceramics.The designed Aurivillius-phase ferroelectric ceramics with the T_(c) around 765℃and high piezoelectric coefficient(d_(33))are suitable for high-temperature piezoelectric applications.展开更多
There has been a surge of research interest in the promising lead-free potassium-sodium niobate(KNN)-based ceramics,applications of which could be significantly promoted by improving thermal stability of piezoelectric...There has been a surge of research interest in the promising lead-free potassium-sodium niobate(KNN)-based ceramics,applications of which could be significantly promoted by improving thermal stability of piezoelectricity.Besides,endowing the KNN-based ceramics with photoluminescence property by rare-earth-ion doping can make them more completive lead-free counterparts in potential applications such as novel multifunctional sensing devices.Herein,a novel KNN-based ceramic material doped with Eu was elaborately designed to simultaneously obtain enhanced temperaturestable piezoelectricity and good luminescence property.By the introduction of diffused phase transition and the modulation of unit cell distortion,a large piezoelectric strain coefficient(d^(*)_(33))with a small variation(590±59 pm/V)over a wide temperature range(from room temperature to 110℃)was realized.The optimal composition also exhibited a considerable piezoelectric coefficient(d_(33))with small fluctuation(330±33 pC/N)from 20 to 80℃.In addition to the enhanced temperature-stable piezoelectricity,the luminescence of these ceramics was slightly enhanced with the elevation of BaZrO_(3)(BZ)doping contents,which could be attributed to the increased compositional disorder and the decreased unit cell distortion of the matrix material.Moreover,an optical characteristic was more prominent at ultra-low temperatures.This work unprecedentedly provides a novel paradigm for the design of multifunctional KNN-based ceramics with enhanced temperature-stable piezoelectricity and good luminescence property,revealing the great potential of the rare-earth-element-doped KNN material for future applications in the novel multifunctional devices.展开更多
High piezoelectric properties and low strain hysteresis(H)are both equally necessary for practical applications in precisely controlled piezoelectric devices and systems.Unlike most of previous reports,where enhanced ...High piezoelectric properties and low strain hysteresis(H)are both equally necessary for practical applications in precisely controlled piezoelectric devices and systems.Unlike most of previous reports,where enhanced piezoelectric performance is typically accompanied by large hysteresis in lead-/lead-free-based ceramics,in this work,we report a reconstructed relaxor ferroelectric composition in 0.68Pb(Mg_(1/3)Nb_(2/3))O3-0.32PbTiO_(3)(0.68PMN-0.32PT)ceramics through the introduction of(Bi_(0.5)Na_(0.5))ZrO(BNZ)to simultaneously achieve low strain hysteresis(~7.68%),superior piezoelectricity(~1040 pC·N^(-l)),and an electric field induced strain of 0.175%.Our work not only paves the way to simultaneously large piezoelectricity and negligible strain hysteresis in ceramic systems,but also lays the foundation for the further development of novel functional materials.展开更多
基金National Natural Science Foundation of China(No.10072033).
文摘Discrete dipoles located near the crack tip play an important role in nonlinear electric fieldinduced fracture of piezoelectric ceramics.A physico-mathematical model of dipole is constructed of two gen-eralized concentrated piezoelectric forces with equal density and opposite sign.The interaction between crackand electric dipole in piezoelectricity is analyzed.The closed form solutions,including those for stress andelectric displacement,crack opening displacement and electric potential,are obtained.The function of pi-ezoelectric anisotropie direction,p_a(θ)=cosθ+p_asinθ,can be used to express the influence of a dipole’sdirection.In the case that a dipole locates near crack tip,the piezoelectric stress intensity factor is a powerfunction with-3/2 index of the distance between dipole and crack tip.
文摘Piezoelectric nanowires are promising building blocks in various micro-electromechanical systems. Using firstprinciples calculations, we systematically investigate the influence of surface and volume changes on piezoelectric coefficients in [001]-oriented ZnO nanowires and hollow nanowires. We find that the increased non-axial ion displacements under strain near the {100} surface cause a notable enhancement in piezoelectric coefficients for these nanowires. Furthermore, by introducing the obtained surface modifications, we break through the limitation of simulation size and obtain the piezoelectric coefficients at the experimental size. Our findings are of importance to expand simulations and guide experimental explorations.
文摘A basic solution in series form for the three-phase composite cylindrical model in antiplanepiezoelectricity subjected to the action of a singularity in the intermediate matrix region is presented.The so-lution is obtained through the complex potential approach in conjunction with the techniques of analytical con-tinuation,singularity analysis,Laurent series expansion in an annular region and Cauchy integral formulae,etc.Based on the complex potentials obtained,explicit expressions for the distribution of stress and electricdisplacement in the three regions are also derived.
基金supported by National Natural Science Foundation of China(10574038)development project of high-tech industry of universities in Jiangsu(JHB05-08)Changzhou scientific and technological bureau(CE2005026).
文摘An orthogonal ultrasonic irradiation system consisting of HIFU with frequency at 1.05 MHz combined with ultrasound with frequency at 28 kHz was applied in this paper.Effect of cavitation was detected by pH-value measurement and conductance measurement.The result shows that the effect of cavitation caused by ultrasound with frequency at 28 kHz is greatly enhanced by HIFU piezoelectricity transducer with frequency at 1.05 MHz.
基金Project supported by the National Natural Science Foundation of China(Grant No.11474123)the Natural Science Foundation of Jilin Province,China(Grant No.20170101154JC)
文摘First-principle calculations reveal that the configuration system of hexagonal boron nitride(h-BN) monolayer with triangular vacancy can induce obvious magnetism, contrary to that of the nonmagnetic pristine boron nitride monolayer.Interestingly, the h-BN with boron atom vacancy(VB-BN) displays metallic behavior with a total magnetic moment being 0.46μ_B per cell, while the h-BN with nitrogen atom vacancy(VN-BN) presents a half-metallic characteristic with a total magnetic moment being 1.0μ_B per cell. Remarkably, piezoelectric stress coefficient e_(11) of the VN-BN is about 1.5 times larger than that of pristine h-BN. Furthermore, piezoelectric strain coefficient d_(11)(12.42 pm/V) of the VN-BN is 20 times larger than that of pristine h-BN and also one order of magnitude larger than the value for the h-MoS_2 monolayer, which is mainly due to the spin-down electronic state in the V_N-BN system. Our study demonstrates that the nitrogen atom vacancies can be an efficient route to tailoring the magnetic and piezoelectric properties of h-BN monolayer, which have promising performances for potential applications in nano-electromechanical systems(NEMS) and nanoscale electronics devices.
基金support received from the National Natural Science Foundation of China (11472243, 11302189, 11321202)the Doctoral Fund of Ministry of Education of China (20130101120175)
文摘The effect of piezoelectricity on phonon properties and thermal conductivity of gallium nitride(Ga N)nanofilms is theoretically investigated. The elasticity model is utilized to derive the phonon properties in spatially confined Ga N nanofilms. The piezoelectric constitutive relation in Ga N nanofilms is taken into account in calculating the phonon dispersion relation. The modified phonon group velocity and phonon density of state as well as the phonon thermal conductivity are also obtained due to the contribution of piezoelectricity. Theoretical results show that the piezoelectricity in Ga N nanofilms can change significantly the phonon properties such as the phonon group velocity and density of states,resulting in the variation of the phonon thermal conductivity of Ga N nanofilms remarkably. Moreover,the piezoelectricity of Ga N can modify the dependence of thermal conductivity on the geometrical size and temperature. These results can be useful in modeling the thermal performance in the active region of Ga N-based electronic devices.
文摘It is difficult to establish a classical variational model for piezoelectricity. Following the semi inverse method of establishing generalized variational principles, an energy like trial functional with a certain unknown function is constructed. The unknown function is easily identified step by step. A family of variational principles for the static behavior of the elastic and electric variables in the vicinity of a surface electrode attached to a piezoelectric ceramic is established directly from its field equations and boundary conditions.
基金supported by National Nature Science Foundation of China (No.11075110)
文摘The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 (KNN) crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. The full potentiallinearized augumented plane wave plus local orbitals (APW-LO) method and the supercell method are used in the calculation for the KNN crystal with and without the La doping. The results show that the piezoelectricity originates from the strong hybridization between the Nb atom and the O atom, and the substitution of the K or Na atom by the La impurity atom introduces the anisotropic relaxation and enhances the piezoelectricity at first and then restrains the hybridization of the Nb-O atoms when the La doping content further increases.
基金Funded by the State Key Basic Researching Subject (No.2002CB613303)
文摘Serial material model (Dilute model)and Limited Units (LU)method were employed to analyze the performance of binary piezo-composite system.The reckoned electric potential deployments illustrated difference while the particles were different.Their piezoelectricities were also calculated according to the model,and furthermore comparation suggested that small particles living in the tolerance improve the piezoelectricity of piezo-composite.Experiments coinciding with analyses were processed simultaneously. Ceramics were milled for different time in order to control the concentration of particle size.The results showed that the filled particles enhanced the piezoelectricity of binary piezo-composite system efficiently whereas too many chips deteriorated the performance of piezo-composites.
基金Project supported by the National Natural Science Foundation of China(Grant No.11372085)the Shenzhen Science and Technology Project(Grant No.JCYJ20150625142543461)
文摘Using first-principles calculation, the contribution of A-site and B-site atoms to polarization and piezoelectricity d33 in the tetragonal Pb TiO_3/KNbO_3 and PbTiO_3/LaAlO_3 superlattices is investigated in this paper. It is shown that PbTiO_3/KNbO_3 superlattice has larger polarization and d33 than PbTiO_3/LaAlO_3 superlattice, because there is stronger charge transfer between A(B)-site atoms and oxygen atom in PbTiO_3/KNbO_3 superlattice. InPbTiO_3/KNbO_3 superlattice,B-site atoms(Ti, Nb) make larger contribution to the total polarization and d33 than the A-site atoms(Pb, K) because of the strong covalent interactions between the transition metal(Ti, Nb) and the oxygen atoms, while piezoelectricity in PbTiO_3/LaAlO_3 superlattice mainly ascribes to piezoelectric contribution of Pb atom and Ti atom in PbTiO_3 component.Furthermore, by calculating the proportion of the piezoelectric contribution from Pb TiO_3 component in superlattices, we find there is different response of strain to piezoelectric contribution from Pb TiO_3 component in two superlattices but still with a value larger than 50%. InPbTiO_3/KNbO_3 superlattice, the c-axis strain reduces the proportion, especially under tensile condition. Meanwhile in PbTiO_3/LaAlO_3 superlattice, Pb TiO_3 plays a leading role to the total d33, especially under compressive condition, and the proportion decreases as the tensile strain increases.
基金supported by the National Basic Research Program of China(Grant No.2013CB632900)
文摘The piezoelectric properties of K1-xNaxNbO3 are studied by using first-principles calculations within virtual crystal approximation. To understand the critical factors for the high piezoelectric response in K1-x Na x Nb O3, the total energy,piezoelectric coefficient, elastic property, density of state, Born effective charge, and energy barrier on polarization rotation paths are systematically investigated. The morphotropic phase boundary in K1-x Na x Nb O3 is predicted to occur at x = 0.521, which is in good agreement with the available experimental data. At the morphotropic phase boundary, the longitudinal piezoelectric coefficient d33 of orthorhombic K0.5Na0.5NbO3 reaches a maximum value. The rotated maximum of d*33is found to be along the 50° direction away from the spontaneous polarization(close to the [001] direction). The moderate bulk and shear modulus are conducive to improving the piezoelectric response. By analyzing the energy barrier on polarization rotation paths, it is found that the polarization rotation of orthorhombic K0.5Na0.5NbO3 becomes easier compared with orthorhombic KNbO3, which proves that the high piezoelectric response is attributed to the flattening of the free energy at compositions close to the morphotropic phase boundary.
基金the University Grant Commission for providing the financial support for this work (No. 8(42)/2010 (MRP/NRCB))
文摘The uniqueness theorem and the theorem of reciprocity in the linearized porous piezoelectricity are established under the assumption of positive definiteness of elastic and electric fields.General theorems in the linear theory of porous piezoelectric materials are proved for the quasi-static electric field approximation.The uniqueness theorem is also proved without using the positive definiteness of the elastic field.An eigenvalue problem associated with free vibrations of a porous piezoelectric body is studied using the abstract formulation.Some properties of operators are also proved.The problem of frequency shift due to small disturbances,based on an abstract formulation,is studied using a variational and operator approach.A perturbation analysis of a special case is also given.
基金supported by the National Natural Science Foundation of China(Nos.62101513,51975542,52175554,and 62171414)China Postdoctoral Science Foundation(Nos.2022TQ0230 and 2022M712324)+2 种基金Shanxi“1331 Project”Key Subject Construction(No.1331KSC)the Fundamental Research Program of Shanxi Province(No.20210302124170)Young Academic Leaders of North University of China(No.11045501).
文摘Designing stretchable and skin-conformal self-powered sensors for intelligent sensing and posture recognition is challenging.Here,based on a multi-force mixing and vulcanization process,as well as synergistically piezoelectricity of BaTiO_(3)and polyacrylonitrile,an all-in-one,stretchable,and self-powered elastomer-based piezo-pressure sensor(ASPS)with high sensitivity is reported.The ASPS presents excellent sensitivity(0.93 V/104 Pa of voltage and 4.92 nA/104 Pa of current at a pressure of 10-200 kPa)and high durability(over 10,000 cycles).Moreover,the ASPS exhibits a wide measurement range,good linearity,rapid response time,and stable frequency response.All components were fabricated using silicone,affording satisfactory skinconformality for sensing postures.Through cooperation with a homemade circuit and artificial intelligence algorithm,an information processing strategy was proposed to realize intelligent sensing and recognition.The home-made circuit achieves the acquisition and wireless transmission of ASPS signals(transmission distance up to 50 m),and the algorithm realizes the classification and identification of ASPS signals(accuracy up to 99.5%).This study proposes not only a novel fabrication method for developing self-powered sensors,but also a new information processing strategy for intelligent sensing and recognition,which offers significant application potential in human-machine interaction,physiological analysis,and medical research.
基金This work was supported financially by the National Key Research and Development Program of China(No.2017YFA0204800)National Natural Science Foundation of China(Nos.22175079 and 21875093)+3 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)Jiangxi Provincial Natural Science Foundation of China(No.20212BAB214021)Science and Technology Project of Jiangxi Provincial Department of Education(No.GJJ200836).
文摘Ferroelectric semiconductors have sparked growing attention in the field of optoelectronics,due to their unique ferroelectric photovoltaic effect.Recently,substantial efforts have been devoted to the development of ferroelectric semiconductors,including inorganic oxides,organic-inorganic hybrids,and metal-free perovskites.Nevertheless,reports of ferroelectric semiconductors with a bandgap of less than 2 eV have been scarce.Here,in combination with the incorporation of triiodide(I_(3)−)and the introduction of chiral cations,we successfully constructed a pair of enantiomeric organic-inorganic hybrid ferroelectric semiconductors,(S-1,2-DAP·I)_(4)·I_(3)·BiI_(6)and(R-1,2-DAP·I)_(4)·I_(3)·BiI_(6)(R/S-1,2-DAP=(R/S)-(–)-1,2-diaminopropane),which possess high-temperature multiaxial ferroelectric phase transition with an Aizu notation of 422F2(s)at 405 K,a narrow bandgap of 1.56 eV comparable to that of CH3NH3PbI_(3)(∼1.5 eV),and an impressive piezoelectric response(piezoelectric coefficient,d22 of 35 pC/N)on par with PVDF(polyvinylidene fluoride,30 pC/N).With intriguing attributes,(S-1,2-DAP·I)_(4)·I_(3)·BiI_(6)and(R-1,2-DAP·I)_(4)·I_(3)·BiI_(6)exhibit great potential for application of self-power polarized-light detection and piezoelectric sensors.
基金supported by the National Natural Science Foundation of China(Grant Nos.52072417,and 11832019)NSFC Original Exploration Project(Grant No.12150001)+3 种基金Natural Science Foundation of Guangdong Province(Grant No.2018B030306036)Guangdong Science&Technology Project(Grant No.2019QN01C113)Project of Nuclear Power Technology Innovation Center of Science Technology and Industry for National Defense(Grant No.HDLCXZX-2021-HD-035)Guangdong International Science and Technology Cooperation Program(Grant No.2020A0505020005)。
文摘Quantum materials have exhibited attractive electro-mechanical responses,but their piezoelectric coefficients are far from satisfactory due to the lack of feasible strategies to benefit from the quantum effects.We discovered the valley piezoelectric mechanism that is absent in the traditional piezoelectric theories yet promising to overcome this challenge.A theoretical model was developed to elucidate the valley piezoelectricity in 2D materials as originating from the strong spin-orbit coupling.Consistent analytical and density-functional-theory calculations validate the model and unveil the crucial dependence of valley piezoelectricity on valley/spin splitting and hybridization energy.Up to 50%of electro-mechanical responses in our tested twodimensional systems are attributed to the valley piezoelectric mechanisms.Rational strategies including doping,passivation,and external strain are proposed to optimize piezoelectricity,with a more than 127%increase in piezoelectricity demonstrated by density-functional-theory simulations.The general valley piezoelectric model not only opens an opportunity to achieve outstanding piezoelectricity via optimizing intrinsic variables but also makes the large family of valley materials promising for piezoelectric sensing and energy harvesting.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52002252 and 52032007).
文摘The flourishing development of emerging electromechanical applications has stimulated an urgent demand for ferroelectric ceramics with high piezoelectric properties and broad temperature usage range.However,it remains a challenge to simultaneously obtain good piezoelectricity and reliable temperature stability in lead zirconate titanate(PZT)-based piezoelectric ceramics.To solve this issue,a synergetic strategy was proposed to introduce lead vacancies through niobium doping and construct morphotropic phase boundary(MPB).In this work,Pb_(0.905)Ba_(0.085)(V Pb″)_(0.01)[(Zr_(x)Ti_(1-x))_(0.98)Nb_(0.02)]O_(3)(PBZTN-x)material system was designed.Good comprehensive properties(d_(33)=864 pC/N,k_(p)=84%,T_(C)=201℃)and excellent temperature stability(less than 10%variation of electrical properties from 20℃ to 160℃)were obtained in PBZTN-0.540 ceramics.Good piezoelectricity can be attributed to high extrinsic contribution(domain wall motion)induced by Pb^(2+)vacancies and the existence of nano-domains emerged at MPB,while excellent temperature stability is mainly attributed to the minimized local stress in the lattice and the stable domain structure.
基金supported by the National Natural Science Foundation of China(52072028 and 52032007)the National Key Research and Development Program(2022YFB3807400).
文摘BiFeO_(3)-BaTiO_(3) based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature.Since the piezoelectric response of piezoelectric ceramics just appears after poling engineering,in this work,the domain evolution and microscopic piezoresponse were observed in-situ using piezoresponse force microscopy(PFM)and switching spectroscopy piezoresponse force microscopy(SS-PFM),which can effectively study the local switching characteristics of ferroelectric materials especially at the nanoscale.The new domain nucleation preferentially forms at the boundary of the relative polarization region and expands laterally with the increase of bias voltage and temperature.The maximum piezoresponse(Rs),remnant piezoresponse(Rrem),maximum displacement(Dmax)and negative displacement(Dneg)at 45 V and 120C reach 122,69,127 pm and 75 pm,respectively.Due to the distinct effect of poling engineering in full domain switching,the corresponding d33 at 50 kV/cm and 120C reaches a maximum of 205 pC/N,which is nearly twice as high as that at room temperature.Studying the evolution of ferroelectric domains in the poling engineering of BiFeO_(3)-BaTiO_(3)ceramics provides an insight into the relationship between domain structure and piezoelectric response,which has implications for other piezoelectric ceramics as well.
基金supported by the National Key R&D Program of China(Grant No.2022YFB3807404)the National Natural Science Foundation of China(Grant No.U19A2087)+1 种基金Zimeng Hu would like to acknowledge the China Scholarship Council(Grant No.201806370199)for supporting this workVladimir Koval acknowledges the support of the Grant Agency of the Slovak Academy of Sciences(Grant No.2/0034/23).
文摘The sodium(Na)and Ce co-doped calcium bismuth titanate(CBT;CaBi_(4)Ti_(4)O_(15))Aurivillius ceramics in a Ca_(1-x)(Na_(0.5)Ce_(0.5)),Bi_(4)Ti_(4)O_(15)(CNCBT;doping content(x)=0,0.03,0.05,0.08 and 0.12)system were synthesized by the conventional solid-state sintering method.All compositions show a single-phase orthorhombic(space group:A2jam)structure at room temperature.The shift of the Curie point(T_(c))towards lower temperatures(T)on doping results from the increased tolerance factor(t).The substitution-enhanced ferroelectric performance with large maximum polarization(P_(m))and facilitated domain switching is evidenced by the developed electrical polarization-electric field(P-E)and electrical current-electric field(I-E)hysteresis loops.The piezoelectric coefficient(d_(33)=20.5±0.1 pC/N)of the x=0.12 sample is about four times larger than that of pure CBT.The improved piezoelectric properties can be attributed to the high remanent polarization(P_(r))and relatively high dielectric permittivity(ε′).In addition,multi-sized(micron and sub-micron)domain structures were observed in the CNCBT ceramics by the piezoresponse force microscope(PFM).The multiple-sized ferroelectric domain structure with smaller domains is beneficial to the easy domain switching,enhanced ferroelectric performance,and improved piezoelectric properties of the CNCBT ceramics.The designed Aurivillius-phase ferroelectric ceramics with the T_(c) around 765℃and high piezoelectric coefficient(d_(33))are suitable for high-temperature piezoelectric applications.
基金supported by the National Natural Science Foundation of China (Nos.52002051 and 62074025)the Fundamental Research Funds for the Central Universities (No.ZYGX2020J009)the Applied Basic Research Program of Sichuan Province (No.2021JDGD0026).
文摘There has been a surge of research interest in the promising lead-free potassium-sodium niobate(KNN)-based ceramics,applications of which could be significantly promoted by improving thermal stability of piezoelectricity.Besides,endowing the KNN-based ceramics with photoluminescence property by rare-earth-ion doping can make them more completive lead-free counterparts in potential applications such as novel multifunctional sensing devices.Herein,a novel KNN-based ceramic material doped with Eu was elaborately designed to simultaneously obtain enhanced temperaturestable piezoelectricity and good luminescence property.By the introduction of diffused phase transition and the modulation of unit cell distortion,a large piezoelectric strain coefficient(d^(*)_(33))with a small variation(590±59 pm/V)over a wide temperature range(from room temperature to 110℃)was realized.The optimal composition also exhibited a considerable piezoelectric coefficient(d_(33))with small fluctuation(330±33 pC/N)from 20 to 80℃.In addition to the enhanced temperature-stable piezoelectricity,the luminescence of these ceramics was slightly enhanced with the elevation of BaZrO_(3)(BZ)doping contents,which could be attributed to the increased compositional disorder and the decreased unit cell distortion of the matrix material.Moreover,an optical characteristic was more prominent at ultra-low temperatures.This work unprecedentedly provides a novel paradigm for the design of multifunctional KNN-based ceramics with enhanced temperature-stable piezoelectricity and good luminescence property,revealing the great potential of the rare-earth-element-doped KNN material for future applications in the novel multifunctional devices.
基金supported by the National Natural Science Foundation of China(Nos.11874032,12204235,and 52202139)the Fundamental Research Funds for the Central Universities(Nos.30920041119 and 30922010402)+2 种基金the Natural Science Foundation of Jiangsu Province(No.BK20220923)the China Postdoctoral Science Foundation(No.2021M701716)Jiangsu Funding Program for Excellent Postdoctoral Talent(No.2022ZB248).
文摘High piezoelectric properties and low strain hysteresis(H)are both equally necessary for practical applications in precisely controlled piezoelectric devices and systems.Unlike most of previous reports,where enhanced piezoelectric performance is typically accompanied by large hysteresis in lead-/lead-free-based ceramics,in this work,we report a reconstructed relaxor ferroelectric composition in 0.68Pb(Mg_(1/3)Nb_(2/3))O3-0.32PbTiO_(3)(0.68PMN-0.32PT)ceramics through the introduction of(Bi_(0.5)Na_(0.5))ZrO(BNZ)to simultaneously achieve low strain hysteresis(~7.68%),superior piezoelectricity(~1040 pC·N^(-l)),and an electric field induced strain of 0.175%.Our work not only paves the way to simultaneously large piezoelectricity and negligible strain hysteresis in ceramic systems,but also lays the foundation for the further development of novel functional materials.
