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Jie Wang - One of the best experts on this subject based on the ideXlab platform.
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an isogeometric approach to Flexoelectric Effect in ferroelectric materials
International Journal of Solids and Structures, 2019Co-Authors: Chang Liu, Jie Wang, Marc Kamlah, Tongyi ZhangAbstract:Abstract Flexoelectricity is an electromechanical coupling Effect between the polarization and strain gradient in all dielectrics regardless of point group symmetry. Due to its significant influence on material behavior at the nanoscale, the Flexoelectric Effect has attracted more and more attention in recent years. In this paper, a real space phase field model for the Flexoelectric Effect in ferroelectric materials is developed by using isogeometric analysis (IGA). The IGA employs the same smooth and high-order basis functions to describe both the geometry of material and the solution of phase field, which is able to give an accurate and efficient description of the Flexoelectric Effect in ferroelectrics with arbitrary geometrical shapes and boundary conditions. To this end, phase field simulations on the Effect of Flexoelectricity are conducted for nanoscale ferroelectrics with different geometrical shapes and boundary conditions. The simulation results show that the Flexoelectric Effect has significant influence on the domain structures and domain switching of ferroelectric materials at the nanoscale. For ferroelectric nanobeam under bending load, due to the Flexoelectric Effect, the mechanical bending can break the symmetry of hysteresis loop between electric field and polarization. As for ferroelectric nanodots, the Flexoelectric Effect increases the magnitude of spontaneous polarizations and results in the tilting of polarization vortex. In addition, out-of-plane components appear in the polarization vortex of ferroelectric nanodots due to the Flexoelectric Effect, which increases the coercive field for the switching of polarization vortex and changes the switching process significantly. The present work not only presents an Effective nonlocal model for the domain evolution in ferroelectric materials with the consideration of the Flexoelectric Effect, but also asymmetric hysteresis loop between polarization and external electric field for ferroelectric beam, and new switching behavior of the polarization vortex in ferroelectric nanodots due to the Flexoelectric Effect.
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The enhanced piezoelectricity in compositionally graded ferroelectric thin films under electric field: A role of Flexoelectric Effect
Journal of Applied Physics, 2018Co-Authors: Ye Qiu, Jie Wang, Jia Lou, Zheng Zhang, Aiping Liu, Guozhong ChaiAbstract:Compositionally graded ferroelectric thin films are found to produce large strain gradients, which can be used to tune the physical properties of materials through the Flexoelectric Effect, i.e., the coupling of polarization and the strain gradient. The influences of the Flexoelectric Effect on the polarization distribution and the piezoelectric properties in compositionally graded Ba1−xSrxTiO3 ferroelectric thin films are investigated by using an extended thermodynamic theory. The calculation results show that the presence of the Flexoelectric Effect tends to enhance and stabilize polarization components. The polarization rotation induced by the Flexoelectric field has been predicted, which is accompanied by more uniform and orderly polarization components. A remarkable enhancement of piezoelectricity is obtained when the Flexoelectric field is considered, suggesting that compositionally graded Ba1−xSrxTiO3 ferroelectric thin films with a large strain gradient are promising candidates for piezoelectric devices.Compositionally graded ferroelectric thin films are found to produce large strain gradients, which can be used to tune the physical properties of materials through the Flexoelectric Effect, i.e., the coupling of polarization and the strain gradient. The influences of the Flexoelectric Effect on the polarization distribution and the piezoelectric properties in compositionally graded Ba1−xSrxTiO3 ferroelectric thin films are investigated by using an extended thermodynamic theory. The calculation results show that the presence of the Flexoelectric Effect tends to enhance and stabilize polarization components. The polarization rotation induced by the Flexoelectric field has been predicted, which is accompanied by more uniform and orderly polarization components. A remarkable enhancement of piezoelectricity is obtained when the Flexoelectric field is considered, suggesting that compositionally graded Ba1−xSrxTiO3 ferroelectric thin films with a large strain gradient are promising candidates for piezoelectric d...
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Giant electrocaloric Effect in ferroelectric ultrathin films at room temperature mediated by Flexoelectric Effect and work function
Journal of Applied Physics, 2017Co-Authors: Ye Qiu, Jie Wang, Jia Lou, Zheng Zhang, Aiping Liu, Takayuki Kitamura, Guozhong ChaiAbstract:In ferroelectric ultrathin films, built-in electric fields are often present due to the Flexoelectric Effect and the difference of work functions at asymmetric electrodes, which may change the properties of the materials. In this paper, the influence of build-in electric fields induced by Flexoelectric Effect and/or work function difference on the misfit strain-temperature phase diagrams, and the electrocaloric properties of epitaxial BaTiO3 ultrathin films are investigated by using an extended nonlinear thermodynamic theory. It is found that the Flexoelectric Effect, i.e., the coupling of polarization and strain gradient, changes the misfit strain-temperature phase diagrams notably, in which the phases with out-of-plane polarizations increase due to the presence of a built-in field. The electrocaloric properties are remarkably enhanced when the built-in fields induced by both the Flexoelectric Effect and work function difference are considered. In particular, a giant adiabatic temperature change of 7.89 ...
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Size-dependent electromechanical properties in piezoelectric superlattices due to Flexoelectric Effect
Theoretical and Applied Mechanics Letters, 2017Co-Authors: Chang Liu, Jie WangAbstract:Abstract Piezoelectric superlattice is a potential component for nanoelectromechanical systems. Due to the strong nonlocal Effect such as Flexoelectric Effect at interfaces, classical piezoelectric theory is unable to accurately describe the electromechanical response of piezoelectric superlattice at nanoscale scale. Based on the previous nonlocal thermodynamics theory with Flexoelectric Effect Liu et al. (2016), the size-dependent electromechanical properties of piezoelectric superlattices made of BaTiO 3 (BTO) and PbTiO 3 (PTO) layers are investigated systematically in the present work. Giant strain gradient is found near the interface between BTO and PTO layers, which leads to the significant enhancement of polarization in the superlattice due to the Flexoelectric Effect. For the piezoelectric BTO–PTO superlattices with different unit-cell sizes, the thickness of interface with nontrivial strain gradient is almost constant. The influence of strain gradient at the interface becomes significant when the size of superlattice decreases. As a result, a strong size dependence of electromechanical properties is predicted for the piezoelectric BTO–PTO superlattices. In particular, for the superlattices with a specific thickness ratio of BTO and PTO layers, the piezoelectric response can be several times larger than that of bulk structure. The present work demonstrates a practical way to design the piezoelectric superlattices with high piezoelectric coefficient by using the nonlocal Effect at nanoscale.
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giant piezoelectric response in piezoelectric dielectric superlattices due to Flexoelectric Effect
Applied Physics Letters, 2016Co-Authors: Chang Liu, Jie WangAbstract:Flexoelectricity describes the linear response of electrical polarization to a strain gradient, which can be used to enhance the piezoelectric Effect of piezoelectric material or realize the piezoelectric Effect in nonpiezoelectric materials. Here, we demonstrate from thermodynamics theory that a giant piezoelectric Effect exists in piezoelectric/dielectric superlattices due to Flexoelectric Effect. The apparent piezoelectric coefficient is calculated from the closed-form of analytical expression of the polarization distribution in the piezoelectric/dielectric superlattice subjected to a normal stress, in which the Flexoelectric Effect is included. It is found that there exists a strong nonlinear coupling between the Flexoelectric and piezoelectric Effects, which significantly enhances the apparent piezoelectric coefficient in the piezoelectric/dielectric superlattice. For a specific thickness ratio of the piezoelectric and dielectric layers, the enhanced apparent piezoelectric coefficient in the superlattice is ten times larger than that of its pure piezoelectric counterpart. The present work suggests an Effective way to obtain giant apparent piezoelectric Effect in piezoelectric/dielectric superlattices through Flexoelectric Effect.
Jagdish K Vij - One of the best experts on this subject based on the ideXlab platform.
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unexpected electric field induced antiferroelectric liquid crystal phase in the sm c α temperature range and the discrete Flexoelectric Effect
Physical Review E, 2019Co-Authors: Yoichi Takanishi, M A Osipov, Atsuo Iida, Neelam Yadav, Atsuo Fukuda, A Chandani D L Perera, Jagdish K VijAbstract:The unique nanometer-sized helical structure in SmC_{α}^{*} may sometimes evolve continuously to the micrometer-sized one in SmC^{*}; conceivably ferroelectric SmC_{α}^{*} is to be unwound by an applied electric field. By drawing electric-field-induced birefringence contours in the field-temperature phase diagram and by studying the superlattice structure of the field-induced subphase with resonant x-ray scattering, we established that an applied field unexpectedly stabilizes the well-known antiferroelectric four-layer biaxial subphase as well as the other prototypal ferrielectric three-layer one in the SmC_{α}^{*} temperature range; the Effective long-range interlayer interaction due to the discrete Flexoelectric Effect actually plays an important role in stabilizing not only the biaxial subphases but also the optically uniaxial SmC_{α}^{*} subphase, contrary to the notion that the competition between the direct interactions of the nearest-neighbor layers and those of the next-nearest-neighbor layers should be required for the nanometer-sized helical structure.
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Unexpected electric-field-induced antiferroelectric liquid crystal phase in the SmC_{α}^{*} temperature range and the discrete Flexoelectric Effect.
Physical review. E, 2019Co-Authors: Yoichi Takanishi, Atsuo Iida, Neelam Yadav, A D L Chandani Perera, Atsuo Fukuda, Mikhail A Osipov, Jagdish K VijAbstract:The unique nanometer-sized helical structure in SmC_{α}^{*} may sometimes evolve continuously to the micrometer-sized one in SmC^{*}; conceivably ferroelectric SmC_{α}^{*} is to be unwound by an applied electric field. By drawing electric-field-induced birefringence contours in the field-temperature phase diagram and by studying the superlattice structure of the field-induced subphase with resonant x-ray scattering, we established that an applied field unexpectedly stabilizes the well-known antiferroelectric four-layer biaxial subphase as well as the other prototypal ferrielectric three-layer one in the SmC_{α}^{*} temperature range; the Effective long-range interlayer interaction due to the discrete Flexoelectric Effect actually plays an important role in stabilizing not only the biaxial subphases but also the optically uniaxial SmC_{α}^{*} subphase, contrary to the notion that the competition between the direct interactions of the nearest-neighbor layers and those of the next-nearest-neighbor layers should be required for the nanometer-sized helical structure.
Daining Fang - One of the best experts on this subject based on the ideXlab platform.
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external uniform electric field removing Flexoelectric Effect in epitaxial ferroelectric thin films
arXiv: Materials Science, 2012Co-Authors: Hao Zhou, Jiawang Hong, Yihui Zhang, Yongmao Pei, Daining FangAbstract:Using the modified Landau-Ginsburg-Devonshire thermodynamic theory, it is found that the coupling between stress gradient and polarization, or Flexoelectricity, has significant Effect on ferroelectric properties of epitaxial thin films, such as polarization, free energy profile and hysteresis loop. However, this Effect can be completely eliminated by applying an optimized external, uniform electric field. The role of such uniform electric field is shown to be the same as that of an ideal gradient electric field which can suppress the Flexoelectricty Effect completely based on the present theory. Since the uniform electric field is more convenient to apply and control than gradient electric field, it can be potentially used to remove the Flexoelectric Effect induced by stress gradient in epitaxial thin films and enhance the ferroelectric properties.
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External uniform electric field removing the Flexoelectric Effect in epitaxial ferroelectric thin films
EPL (Europhysics Letters), 2012Co-Authors: Hao Zhou, Jiawang Hong, Yihui Zhang, Yongmao Pei, Daining FangAbstract:Using the modified Landau-Ginzburg-Devonshire thermodynamic theory, it is found that the coupling between stress gradient and polarization, or Flexoelectricity, has a significant Effect on ferroelectric properties of epitaxial thin films, such as polarization, free-energy profile and hysteresis loop. However, this Effect can be completely eliminated by applying an optimized external, uniform electric field. The role of such uniform electric field is shown to be the same as that of an ideal gradient electric field which can suppress the Flexoelectricty Effect completely based on the present theory. Since the uniform electric field is more convenient to apply and control than the gradient electric field, it can be potentially used to remove the Flexoelectric Effect induced by the stress gradient in epitaxial thin films and to enhance the ferroelectric properties.
Liying Jiang - One of the best experts on this subject based on the ideXlab platform.
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A Study of the Flexoelectric Effect on the Electroelastic Fields of a Cantilevered Piezoelectric Nanoplate
International Journal of Applied Mechanics, 2017Co-Authors: Xining Wang, Rui Zhang, Liying JiangAbstract:Flexoelectricity, a spontaneous polarization in linear response to strain gradients or non-uniform deformation, is believed to contribute to the size-dependent electromechanical coupling of piezoelectric materials at the nanoscale. In the current work, the Flexoelectric Effect upon the static bending behaviors of a cantilevered piezoelectric nanoplate (PNP) is studied. Based on the Kirchhoff plate model and the extended linear piezoelectric theory, the non-conventional governing equations and the boundary conditions of the PNP under both mechanical and electrical loads are derived with the incorporation of the Flexoelectric Effect. Finite difference method (FDM) is performed to get the numerical solution for the electroelastic fields of the plate. Simulation results show that the Flexoelectric Effect is more prominent for the thinner plates with smaller thickness. It is also found that the Flexoelectric Effect upon the electroelastic responses of the clamped PNP is also sensitive to some other factors, including the boundary conditions, the plate geometric ratio, and the applied mechanical and electrical loads. This work aims to provide an increased understanding of the size-dependent electromechanical coupling properties of a piezoelectric plate structure.
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Flexoelectric Effect on the electroelastic responses and vibrational behaviors of a piezoelectric nanoplate
Journal of Applied Physics, 2014Co-Authors: Zhengrong Zhang, Zhi Yan, Liying JiangAbstract:Flexoelectricity, referring to the coupling between electric polarization and strain gradients, is a universal Effect in all dielectrics and may become manifest at the nano-scale. The current work aims to investigate the Flexoelectric Effect on the electroelastic responses and the free vibrational behaviors of a piezoelectric nanoplate (PNP). Based on the conventional Kirchhoff plate theory and the extended linear piezoelectricity theory, the governing equation and the boundary conditions of a clamped PNP with the consideration of the static bulk Flexoelectricity are derived. Ritz approximate solutions of the electroelastic fields and the resonant frequencies demonstrate the size-dependency of the Flexoelectric Effect, which is more prominent for thinner plates with smaller thickness as expected. Simulation results also indicate that the influence of the Flexoelectricity upon the electroelastic fields of a bending PNP and the transverse vibration of the PNP is sensitive to the plate in-plane dimensions as well as the applied electric voltage. Moreover, it is suggested that the possible frequency tuning of a PNP resonator by adjusting applied electrical load warrants the consideration of the Flexoelectricity. This study is claimed to provide a theoretical predicition on the trend of the Flexoelectric Effect upon the static and dynamic behaviors of a bending PNP, thus sheding light on understanding the underlying physics of electromechanical coupling at the nano-scale to some extent.
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Effect of Flexoelectricity on the Electromechanical Coupling of Piezoelectric Nanoplates
Proceedings of the 2015 International Conference on Material Science and Applications, 2014Co-Authors: Zhengrong Zhang, Liying JiangAbstract:Flexoelectricity is referred as an instantaneous polarization of dielectrics in response to non-uniform strains or strain gradients. Due to the fact that strain gradients are inversely proportional to the feature size of structures, the Flexoelectricity is believed to be significant at the nano-scale. Based on the extended linear piezoelectricity theory, this work attempts to investigate the Flexoelectric Effect upon the electromechanical coupling of a piezoelectric nanoplate by developing a modified Kirchhoff plate model. Simulation results on the electroelastic fields indicate that the Flexoelectric Effect is size-dependent, which is more prominent for thinner plates with smaller thickness. It is also observed that the Effect of the Flexoelectricity upon the electromechanical coupling of the piezoelectric nanoplate is sensitive to the applied electric voltage. This study aims to establish a further understanding of the Flexoelectric Effect on the electromechanical coupling of piezoelectric nanomaterials, thus provide guidance for the design and applications of piezoelectric nanostructures.
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size dependent bending and vibration behaviour of piezoelectric nanobeams due to Flexoelectricity
Journal of Physics D, 2013Co-Authors: Zhi Yan, Liying JiangAbstract:Flexoelectricity, representing a spontaneous electric polarization induced by a non-uniform strain field (or strain gradient), is believed to become manifest and be responsible for the size-dependent properties of dielectric materials at the nanoscale. In this paper, the influence of the Flexoelectric Effect on the static bending and free vibration of a simply supported piezoelectric nanobeam is investigated based on the extended linear piezoelectricity theory and the Timoshenko beam model. The governing equations of the piezoelectric nanobeam with non-homogeneous boundary conditions are obtained from Hamilton's principle. Explicit expressions of the beam deflection and resonant frequency are derived to show the size-dependency of the Flexoelectric Effect. It is found that the Flexoelectricity has a significant Effect on the deflection of the bending beam and may reverse the deflection direction under certain loading conditions. Simulation results also indicate that the influence of the Flexoelectricity on the vibration behaviour of the piezoelectric nanobeam is more prominent for beams with smaller thickness. Thus, it is suggested that possible frequency tuning of piezoelectric nanobeams by adjusting the applied electrical load should incorporate the Flexoelectric Effect. The current study can be claimed as helpful for qualitatively characterizing the trend of the Flexoelectric Effect on the mechanical responses of piezoelectric nanobeams.
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Flexoelectric Effect on the electroelastic responses of bending piezoelectric nanobeams
Journal of Applied Physics, 2013Co-Authors: Zhi Yan, Liying JiangAbstract:Flexoelectricity, referring to a spontaneous electric polarization induced by strain gradient in dielectrics, presents a strong size dependency at the nanoscale. In the current work, the influence of the Flexoelectric Effect on the mechanical and electrical properties of bending piezoelectric nanobeams with different boundary conditions is investigated. Based on the extended linear piezoelectricity theory and the Euler beam model, analytical solutions of the electroelastic fields in the piezoelectric nanobeams subjected to both electrical and mechanical loads are obtained with the inclusion of the Flexoelectric Effect. Simulation results show that the Flexoelectric Effect on the elastic behavior of bending beams is sensitive to the beam boundary conditions and the applied electrical load. In addition, for a cantilever piezoelectric nanobeam, an axial relaxation strain is induced from the piezoelectric and Flexoelectric Effects, while these Effects induce a resultant axial force in both the clamped-clamped and simply supported piezoelectric nanobeams. Results also indicate that the Flexoelectric Effect plays a significant role in the contact stiffness and electric polarization of piezoelectric beams when their thickness is at the nanoscale. It is found that the Flexoelectric Effect on the electroelastic responses of piezoelectric nanobeams is more pronounced for the beams with smaller thickness. These results are useful for understanding the fundamental mechanical and physical properties of bending piezoelectric nanobeams.
Zhi Yan - One of the best experts on this subject based on the ideXlab platform.
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Investigation of pull-in behaviors of a nanoswitch tuned by piezoelectric and Flexoelectric Effects
International Journal of Mechanical Sciences, 2019Co-Authors: Y.p. Chen, Zhi YanAbstract:Abstract In this work, the static and dynamic pull-in behaviors of an electrostatically and piezoelectrically actuated nanoswitch are investigated. The nanoswitch is based on a cantilever nanobeam with a piezoelectric actuation layer attached. In the modeling, we consider the Flexoelectric Effect of the piezoelectric layer, the surface Effect of the unimorph as well as the Casimir Effect. The governing equation of the proposed model is derived using the Hamilton's principle and discretized by employing the Galerkin method. Firstly, the results of the proposed model are compared with the numerical and experimental data, providing the validity of this model. Then, simulations are performed to show the influence of Flexoelectricity on the static pull-in voltage and pull-in deflection of the nanoswitch with a lead zirconate titanate (PZT-5H) and a polyvinylidene fluoride (PVDF) actuation layer, respectively. Results indicate that the Flexoelectric Effect plays a significant role in determining the static pull-in behaviors of the nanoswitch and such an Effect is size-dependent at the nanoscale. Moreover, we show how the Flexoelectric Effect influences the unstable region of dynamic pull-in instability of the proposed nanoswitch. This work suggests that the Flexoelectric Effect of the piezoelectric layer can be used to tune the static and dynamic pull-in behaviors of a nanoswitch, which may guide the design and development of devices in the micro- and nano-electro-mechanical-systems (M/NEMS).
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Flexoelectric Effect on the electroelastic responses and vibrational behaviors of a piezoelectric nanoplate
Journal of Applied Physics, 2014Co-Authors: Zhengrong Zhang, Zhi Yan, Liying JiangAbstract:Flexoelectricity, referring to the coupling between electric polarization and strain gradients, is a universal Effect in all dielectrics and may become manifest at the nano-scale. The current work aims to investigate the Flexoelectric Effect on the electroelastic responses and the free vibrational behaviors of a piezoelectric nanoplate (PNP). Based on the conventional Kirchhoff plate theory and the extended linear piezoelectricity theory, the governing equation and the boundary conditions of a clamped PNP with the consideration of the static bulk Flexoelectricity are derived. Ritz approximate solutions of the electroelastic fields and the resonant frequencies demonstrate the size-dependency of the Flexoelectric Effect, which is more prominent for thinner plates with smaller thickness as expected. Simulation results also indicate that the influence of the Flexoelectricity upon the electroelastic fields of a bending PNP and the transverse vibration of the PNP is sensitive to the plate in-plane dimensions as well as the applied electric voltage. Moreover, it is suggested that the possible frequency tuning of a PNP resonator by adjusting applied electrical load warrants the consideration of the Flexoelectricity. This study is claimed to provide a theoretical predicition on the trend of the Flexoelectric Effect upon the static and dynamic behaviors of a bending PNP, thus sheding light on understanding the underlying physics of electromechanical coupling at the nano-scale to some extent.
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size dependent bending and vibration behaviour of piezoelectric nanobeams due to Flexoelectricity
Journal of Physics D, 2013Co-Authors: Zhi Yan, Liying JiangAbstract:Flexoelectricity, representing a spontaneous electric polarization induced by a non-uniform strain field (or strain gradient), is believed to become manifest and be responsible for the size-dependent properties of dielectric materials at the nanoscale. In this paper, the influence of the Flexoelectric Effect on the static bending and free vibration of a simply supported piezoelectric nanobeam is investigated based on the extended linear piezoelectricity theory and the Timoshenko beam model. The governing equations of the piezoelectric nanobeam with non-homogeneous boundary conditions are obtained from Hamilton's principle. Explicit expressions of the beam deflection and resonant frequency are derived to show the size-dependency of the Flexoelectric Effect. It is found that the Flexoelectricity has a significant Effect on the deflection of the bending beam and may reverse the deflection direction under certain loading conditions. Simulation results also indicate that the influence of the Flexoelectricity on the vibration behaviour of the piezoelectric nanobeam is more prominent for beams with smaller thickness. Thus, it is suggested that possible frequency tuning of piezoelectric nanobeams by adjusting the applied electrical load should incorporate the Flexoelectric Effect. The current study can be claimed as helpful for qualitatively characterizing the trend of the Flexoelectric Effect on the mechanical responses of piezoelectric nanobeams.
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Flexoelectric Effect on the electroelastic responses of bending piezoelectric nanobeams
Journal of Applied Physics, 2013Co-Authors: Zhi Yan, Liying JiangAbstract:Flexoelectricity, referring to a spontaneous electric polarization induced by strain gradient in dielectrics, presents a strong size dependency at the nanoscale. In the current work, the influence of the Flexoelectric Effect on the mechanical and electrical properties of bending piezoelectric nanobeams with different boundary conditions is investigated. Based on the extended linear piezoelectricity theory and the Euler beam model, analytical solutions of the electroelastic fields in the piezoelectric nanobeams subjected to both electrical and mechanical loads are obtained with the inclusion of the Flexoelectric Effect. Simulation results show that the Flexoelectric Effect on the elastic behavior of bending beams is sensitive to the beam boundary conditions and the applied electrical load. In addition, for a cantilever piezoelectric nanobeam, an axial relaxation strain is induced from the piezoelectric and Flexoelectric Effects, while these Effects induce a resultant axial force in both the clamped-clamped and simply supported piezoelectric nanobeams. Results also indicate that the Flexoelectric Effect plays a significant role in the contact stiffness and electric polarization of piezoelectric beams when their thickness is at the nanoscale. It is found that the Flexoelectric Effect on the electroelastic responses of piezoelectric nanobeams is more pronounced for the beams with smaller thickness. These results are useful for understanding the fundamental mechanical and physical properties of bending piezoelectric nanobeams.