The Experts below are selected from a list of 25902 Experts worldwide ranked by ideXlab platform

Dragan Damjanovic - One of the best experts on this subject based on the ideXlab platform.

  • the negative Piezoelectric Effect of the ferroelectric polymer poly vinylidene fluoride
    Nature Materials, 2016
    Co-Authors: Ilias Katsouras, Dragan Damjanovic, Kamal Asadi, Tim Brandt Van Driel, Kasper S Kjaer, Dong Zhao, Thomas Lenz, Paul W M Blom, Martin Nielsen, Dago M De Leeuw
    Abstract:

    Piezoelectricity describes interconversion between electrical charge and mechanical strain. As expected for lattice ions displaced in an electric field, the proportionality constant is positive for all Piezoelectric materials. The exceptions are poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene (P(VDF-TrFE)), which exhibit a negative longitudinal Piezoelectric coefficient. Reported explanations exclusively consider contraction with applied electric field of either the crystalline or the amorphous part of these semi-crystalline polymers. To distinguish between these conflicting interpretations, we have performed in situ dynamic X-ray diffraction measurements on P(VDF-TrFE) capacitors. We find that the Piezoelectric Effect is dominated by the change in lattice constant but, surprisingly, it cannot be accounted for by the polarization-biased electrostrictive contribution of the crystalline part alone. Our quantitative analysis shows that an additional contribution is operative, which we argue is due to an electromechanical coupling between the intermixed crystalline lamellae and amorphous regions. Our findings tie the counterintuitive negative Piezoelectric response of PVDF and its copolymers to the dynamics of their composite microstructure.

  • the negative Piezoelectric Effect of the ferroelectric polymer poly vinylidene fluoride
    Nature Materials, 2016
    Co-Authors: Ilias Katsouras, Kamal Asadi, Kasper S Kjaer, Dong Zhao, Thomas Lenz, Paul W M Blom, Mengyuan Li, Tim Brandt Van Driel, Yun Gu, Dragan Damjanovic
    Abstract:

    Poly(vinylidene fluoride) exhibits a negative longitudinal Piezoelectric coefficient. In situ X-ray diffraction measurements suggest that this Effect is dependent on electromechanical coupling between the intermixed crystalline lamellae and amorphous regions.

  • contributions to the Piezoelectric Effect in ferroelectric single crystals and ceramics
    Journal of the American Ceramic Society, 2005
    Co-Authors: Dragan Damjanovic
    Abstract:

    The Piezoelectric Effect in ferroelectric single crystals and ceramics is investigated considering intrinsic (lattice), and extrinsic (originating mainly from displacement of domain walls) contributions. The focus of the study of intrinsic properties is on Piezoelectric anisotropy, which was examined using the Landau-Ginsburg-Devonshire phenomenological theory. It is shown that the enhanced Piezoelectric response along nonpolar directions, observed in many perovskite systems, is a consequence of the flattening of the Gibbs free energy profile. This flattening is common for temperature-, composition-, and external field-induced enhancement of the Piezoelectric properties along nonpolar axes. A brief review of recent advances in understanding the origins of the Piezoelectric nonlinearity, hysteresis, and frequency dispersion is also given.

  • stress and frequency dependence of the direct Piezoelectric Effect in ferroelectric ceramics
    Journal of Applied Physics, 1997
    Co-Authors: Dragan Damjanovic
    Abstract:

    It is shown that at weak alternating stress the relationship between the Piezoelectrically induced charge and applied stress in ferroelectric ceramics has the same form as the Rayleigh law for magnetization versus magnetic field in ferromagnetic materials. Applicability of the Rayleigh law to the Piezoelectric Effect is demonstrated in detail for lead zirconate titanate (PZT) ceramics. Experimental results indicate that the dominant mechanism responsible for Piezoelectric hysteresis and the dependence of the Piezoelectric coefficient on the applied ac stress is the pinning of non-180° domain walls. The dependence of the Piezoelectric coefficient on the frequency of the driving stress is examined and is shown to be due to the frequency dispersion of both reversible and irreversible components of domain-wall displacement. Analysis of the stress dependence of the Piezoelectric phase angle reveals Piezoelectric hysteresis contributions that are not necessarily due to Rayleigh-type displacement of domain walls...

  • stress and frequency dependence of the direct Piezoelectric Effect in ferroelectric ceramics
    Journal of Applied Physics, 1997
    Co-Authors: Dragan Damjanovic
    Abstract:

    It is shown that at weak alternating stress the relationship between the Piezoelectrically induced charge and applied stress in ferroelectric ceramics has the same form as the Rayleigh law for magnetization versus magnetic field in ferromagnetic materials. Applicability of the Rayleigh law to the Piezoelectric Effect is demonstrated in detail for lead zirconate titanate (PZT) ceramics. Experimental results indicate that the dominant mechanism responsible for Piezoelectric hysteresis and the dependence of the Piezoelectric coefficient on the applied ac stress is the pinning of non-180 degrees domain walls. The dependence of the Piezoelectric coefficient on the frequency of the driving stress is examined and is shown to be due to the frequency dispersion of both reversible and irreversible components of domain-wall displacement. Analysis of the stress dependence of the Piezoelectric phase angle reveals Piezoelectric hysteresis contributions that are not necessarily due to Rayleigh-type displacement of domain walls. Piezoelectric properties of a modified lead titanate composition that exhibits non-Rayleigh type behavior are examined and compared with the properties of PZT ceramics. (C) 1997 American Institute of Physics.

Zhong Lin Wang - One of the best experts on this subject based on the ideXlab platform.

  • Piezo-phototronics Effect on nano/microwire solar cells. Energ Environ Sci 2012; 5: 6850–6
    2020
    Co-Authors: Yan Zhang, Ya Yang, Zhong Lin Wang
    Abstract:

    Wurtzite structures, such as ZnO, GaN, InN and CdS, are Piezoelectric semiconductor materials. A piezopotential is formed in the crystal by the Piezoelectric charges created by applying a stress. The inner-crystal piezopotential can Effectively tune/control the carrier separations and transport processes at the vicinity of a p-n junction or metal-semiconductor contact, which is called the piezo-phototronic Effect. The presence of Piezoelectric charges at the interface/ junction can significantly affect the performances of photovoltaic devices, especially flexible and printed organic/inorganic solar cells fabricated using Piezoelectric semiconductor nano/microwires. In this paper, the current-voltage characteristics of a solar cell have been studied theoretically and experimentally in the presence of the Piezoelectric Effect. The analytical results are obtained for a ZnO Piezoelectric p-n junction solar cell under simplified conditions, which provide a basic physical picture for understanding the mechanism of the Piezoelectric solar cell. Furthermore, the maximum output of the solar cell has been calculated numerically. Finally, the experimental results of organic solar cells support our theoretical model. Using the Piezoelectric Effect created by external stress, our study not only provides the first basic theoretical understanding about the piezo-phototronic Effect on the characteristics of a solar cell but also assists the design for higher performance solar cells

  • conjuncted pyro Piezoelectric Effect for self powered simultaneous temperature and pressure sensing
    Advanced Materials, 2019
    Co-Authors: Kai Song, Rudai Zhao, Zhong Lin Wang, Ya Yang
    Abstract:

    Ferroelectric materials use both the pyroelectric Effect and Piezoelectric Effect for energy conversion. A ferroelectric BaTiO3 -based pyro-Piezoelectric sensor system is demonstrated to detect temperature and pressure simultaneously. The voltage signal of the device is found to enhance with increasing temperature difference with a sensitivity of about 0.048 V °C-1 and with applied pressure with a sensitivity of about 0.044 V kPa-1 . Moreover, no interference appears in the output voltage signals when Piezoelectricity and pyroelectricity are conjuncted in the device. A novel 4 × 4 array sensor system is developed to sense real-time temperature and pressure variations induced by a finger. This system has potential applications in machine intelligence and man-machine interaction.

  • Piezoelectric Effect tuning on zno microwire whispering gallery mode lasing
    ACS Nano, 2018
    Co-Authors: Zheng Yang, Zhong Lin Wang, Yiyao Peng, Miaoling Que, Caofeng Pan
    Abstract:

    We report a dynamic tuning on coherent light emission wavelengths of single ZnO microwire by using the Piezoelectric Effect. Owing to the dominant role occupied by the Piezoelectric polarization Effect in the wurtzite-structure ZnO microwire, the Effective dielectric constant (or refraction index) of the gain media was modulated toward an increasing trend by applying a tensile strain, resulting in a shift of the strain-mediated whispering-gallery mode (WGM) lasing at room temperature. Also, the strain required to resolve the spectra in the two operating types of PL and lasing were systematically analyzed and compared. Because of the narrow line width in the lasing mode, the strain-dependent spectral resolution was improved by an order of magnitude, making it feasible for achieving high-precision, ultrasensitive, and noncontact stress sensing. Our results have an important impact on laser modulation, optical communication, and optical sensing technology.

  • converse Piezoelectric Effect induced transverse deflection of a free standing zno microbelt
    Nano Letters, 2009
    Co-Authors: Yifan Gao, Srikanth Singamaneni, Vladimir V Tsukruk, Zhong Lin Wang
    Abstract:

    We demonstrate the first electric field induced transverse deflection of a single-crystal, free-standing ZnO microbelt as a result of converse Piezoelectric Effect. For a microbelt growing along the c-axis, a shear stress in the a-c plane can be induced when an electric field E is applied along the a-axis of the wurtzite structure. As amplified by the large aspect ratio of the microbelt that grows along the c-axis, the strain localized near the root can be detected via the transverse deflection perpendicular to the ZnO microbelt. After an experimental approach was carefully designed and possible artifacts were ruled out, the experimentally observed degree of deflection of the microbelt agrees well with the theoretically expected result. The device demonstrated has potential applications as transverse actuators/sensors/switches and electric field induced mechanical deflectors.

Yaojin Wang - One of the best experts on this subject based on the ideXlab platform.

  • magnetoelectric Effect from mechanically mediated torsional magnetic force Effect in ndfeb magnets and shear Piezoelectric Effect in 0 7pb mg1 3nb2 3 o3 0 3pbtio3 single crystal
    Applied Physics Letters, 2008
    Co-Authors: Yaojin Wang, Helen Lai Wa Chan, Xiangyong Zhao, Haosu Luo
    Abstract:

    We experimentally and theoretically report the magnetoelectric Effect in a composite made by sandwiching one shear mode 0.7PbMg1∕3Nb2∕3O3–0.3PbTiO3 (PMN-PT) Piezoelectric single crystal plate between two longitudinally magnetized NdFeB permanent magnet bars along the length direction of the PMN-PT plate. The magnetoelectric Effect originates from the mechanically mediated product Effect of the torsional magnetic force Effect in the NdFeB bars and the shear Piezoelectric Effect in the PMN-PT plate. The composite exhibits a magnetoelectric voltage coefficient of ∼32.7mV∕cmOe with a flat frequency response in the measured range of 0.1–30kHz. The induced magnetoelectric voltage shows a good linear relationship to the applied ac magnetic field with amplitude varying from 10−7to10−3T. Other distinct features include no need to have a magnetostrictive phase, low Joule heating loss, and high scale-down capability. These suggest promising applications of the torsional-shear mode composite in power-free magnetic fi...

Ilias Katsouras - One of the best experts on this subject based on the ideXlab platform.

  • the negative Piezoelectric Effect of the ferroelectric polymer poly vinylidene fluoride
    Nature Materials, 2016
    Co-Authors: Ilias Katsouras, Dragan Damjanovic, Kamal Asadi, Tim Brandt Van Driel, Kasper S Kjaer, Dong Zhao, Thomas Lenz, Paul W M Blom, Martin Nielsen, Dago M De Leeuw
    Abstract:

    Piezoelectricity describes interconversion between electrical charge and mechanical strain. As expected for lattice ions displaced in an electric field, the proportionality constant is positive for all Piezoelectric materials. The exceptions are poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene (P(VDF-TrFE)), which exhibit a negative longitudinal Piezoelectric coefficient. Reported explanations exclusively consider contraction with applied electric field of either the crystalline or the amorphous part of these semi-crystalline polymers. To distinguish between these conflicting interpretations, we have performed in situ dynamic X-ray diffraction measurements on P(VDF-TrFE) capacitors. We find that the Piezoelectric Effect is dominated by the change in lattice constant but, surprisingly, it cannot be accounted for by the polarization-biased electrostrictive contribution of the crystalline part alone. Our quantitative analysis shows that an additional contribution is operative, which we argue is due to an electromechanical coupling between the intermixed crystalline lamellae and amorphous regions. Our findings tie the counterintuitive negative Piezoelectric response of PVDF and its copolymers to the dynamics of their composite microstructure.

  • the negative Piezoelectric Effect of the ferroelectric polymer poly vinylidene fluoride
    Nature Materials, 2016
    Co-Authors: Ilias Katsouras, Kamal Asadi, Kasper S Kjaer, Dong Zhao, Thomas Lenz, Paul W M Blom, Mengyuan Li, Tim Brandt Van Driel, Yun Gu, Dragan Damjanovic
    Abstract:

    Poly(vinylidene fluoride) exhibits a negative longitudinal Piezoelectric coefficient. In situ X-ray diffraction measurements suggest that this Effect is dependent on electromechanical coupling between the intermixed crystalline lamellae and amorphous regions.

S L Ho - One of the best experts on this subject based on the ideXlab platform.