Center for Energy Harvesting Materials and Systems (CEHMS)

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Browsing Center for Energy Harvesting Materials and Systems (CEHMS) by Author "An, Ke"

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    Enhanced piezoelectricity and nature of electric-field induced structural phase transformation in textured lead-free piezoelectric Na0.5Bi0.5TiO3-BaTiO3 ceramics
    Maurya, Deepam; Pramanick, Abhijit; An, Ke; Priya, Shashank (AIP Publishing, 2012-04-01)
    This letter provides a comparative description of the properties of textured and randomly oriented poly-crystalline lead-free piezoelectric 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO(3) (NBT-BT) ceramics. A high longitudinal piezoelectric constant of (d(33)) similar to 322 pC/N was obtained in (001)(PC) textured NBT-7BT ceramics, which is almost similar to 2x times the d(33) coefficient reported for randomly oriented ceramics of the same composition. In situ neutron diffraction experiments revealed that characteristically different structural responses are induced in textured and randomly oriented NBT-BT ceramics upon application of electric fields (E), which are likely related to the varying coherence lengths of polar nanoregions and internal stresses induced by domain switching. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4709404]
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    Origin of high piezoelectric response in A-site disordered morphotropic phase boundary composition of lead-free piezoelectric 0.93(Na0.5Bi0.5)TiO3-0.07BaTiO(3)
    Maurya, Deepam; Murayama, Mitsuhiro; Pramanick, A.; Reynolds, William T. Jr.; An, Ke; Priya, Shashank (American Institute of Physics, 2013-03-21)
    Perovskite piezoelectric compositions near the morphotropic phase boundary (MPB) are known to exhibit high piezoelectric response. In lead-based ABO(3) compound with B-site disorder, the origin of this enhancement has been associated with the presence of an intermediate monoclinic/orthorhombic state that bridges the adjacent ferroelectric rhombohedral and tetragonal phases. However, the origin of high piezoelectric response in lead-free ABO(3) compounds with A-site disorder has not been conclusively established. We describe a microscopic model derived from comparative analyses of high resolution transmission electron microscopy and neutron diffraction that explains the origin of high piezoelectric response in lead-free MPB compositions of 0.93(Na0.5Bi0.5)TiO3-0.07BaTiO3. Direct observation of nanotwins with monoclinic symmetry confirmed the presence of an intermediate bridging phase that facilitates a pathway for polarization reorientation. Monoclinic distortions of an average rhombohedral phase are attributed to localized displacements of atoms along the non-polar directions. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792729]