Browsing by Author "Li, YX"

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    Local microstructure evolution of local microstructure evolution of bismuth sodium titanate-based lead-free piezoelectric systems across the morphotropic phase boundary region
    (World Scientific Publishing Co, 2012-09-12) Liu, Y; Withers, RL; Wang, J; Norén, L; Studer, AJ; Li, YX
    Morphotropic phase boundary (MPB) containing piezoelectric systems generally exhibit enhanced piezoelectric performance at compositions within, or close to, the MPB region. The mechanism/s underlying such enhancement, however, are still contentious due to complex micro/nanostructure and apparently inherent local structural variability associated with octahedral tilt disorder/platelet precipitates in such piezoelectric materials. This paper reviews some recent structural analysis results from Bi0.5Na0.5TiO3 (BNT) and other binary, lead-free, piezoelectric materials systems derived from it via electron diffraction and in situ neutron diffraction. The results suggest that intrinsically existing local microstructure (LMS) in BNT essentially continues across the MPB region. The LMS, originating from inherent octahedral tilt disorder, is strongly temperature-, electric field-, pressure- and chemical composition-dependent, and may help to explain a series of phenomena observed in BNT-based binary materials systems, including the enhanced piezoelectric effect in the region of the MPB. © 2012 World Scientific Publishing Co.
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    Response of intergrown microstructure to an electric field and its consequences in the lead-free piezoelectric bismuth sodium titanate
    (Elsevier, 2012-03) Liu, Y; Norén, L; Studer, AJ; Withers, RL; Guo, YP; Li, YX; Yang, H; Wang, J
    We investigate the R3c average structure and micro-structure of the ceramic Bi 0.5Na 0.5TiO 3 (BNT) in situ under applied electric fields using diffraction techniques. Electron diffraction implies the presence of significant octahedral tilt twin disorder, corresponding to the existence of a fine scale intergrown microstructural (IGMS) 'phase' within the R3c rhombohedral average structure matrix. A careful neutron refinement suggests not only that the off-centre displacements of the cations relative to the oxygens in the R3c regions increases systematically on application of an electric field but also that the phase fraction of the IGMS regions increases systematically. The latter change in phase fraction on application of the electric field enhances the polar displacement of the cations relative to the oxygen anions and affects the overall strain response. These IGMS regions form local polar nano regions that are not correlated with one another, resulting in polarisation relaxation and strain behaviour observed in BNT-containing materials. © 2012 Elsevier Inc. All rights reserved.