Browsing by Author "Rao, W. F."

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    Bridging domain mechanism for phase coexistence in morphotropic phase boundary ferroelectrics
    Rao, W. F.; Wang, Yu. U. (AIP Publishing, 2007-04-01)
    Computer modeling and simulation reveals a bridging domain mechanism that explains the phase coexistence commonly observed around the morphotropic phase boundaries of ferroelectric solid solutions. The simulation takes into account the important role of coupled ferroelectric and ferroelastic domain microstructures in phase coexistence phenomenon. It shows that minor domains of metastable phase spontaneously coexist with and bridge major domains of stable phase to reduce total system free energy, including bulk free energy, domain wall energy, and long-range electrostatic and elastostatic energies. The existence of bridging domains also explains the enhanced piezoelectric response in the vicinity of morphotropic phase boundaries. (C) 2007 American Institute of Physics.
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    Domain wall broadening mechanism for domain size effect of enhanced piezoelectricity in crystallographically engineered ferroelectric single crystals
    Rao, W. F.; Wang, Yu. U. (AIP Publishing, 2007-01-01)
    Computer modeling and simulation reveal a domain wall broadening mechanism that explains the domain size effect of enhanced piezoelectric properties in domain engineered ferroelectric single crystals. The simulation shows that, under electric field applied along the nonpolar axis of single crystal without domain wall motion, the domain wall broadens and serves as embryo of field-induced new phase, producing large reversible strain free from hysteresis. This mechanism plays a significant role in the vicinity of interferroelectric transition temperature and morphotropic phase boundary, where energy difference between stable and metastable phases is small. Engineered domain configuration fully exploits this domain wall broadening mechanism. (c) 2007 American Institute of Physics.
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    Grain size effect of phase coexistence around morphotropic phase boundary in ferroelectric polycrystalline ceramics
    Rao, W. F.; Wang, Yu. U. (AIP Publishing, 2008-03-01)
    Computer modeling and simulation reveals a grain size- and composition-dependent behavior of phase coexistence around the morphotropic phase boundaries in polycrystals of ferroelectric solid solutions. It shows that the width of phase coexistence composition range increases with decreasing grain sizes; phase-coexisting domain microstructures effectively reduce elastostatic, electrostatic, and domain wall energies; and grain boundaries impose internal mechanical and electric boundary conditions, which affect the phase-coexisting domain microstructures in the grains and give rise to the grain size effect of phase coexistence. (c) 2008 American Institute of Physics.
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    Microstructures of coherent phase decomposition near morphotropic phase boundary in lead zirconate titanate
    Rao, W. F.; Wang, Yu. U. (AIP Publishing, 2007-07-01)
    (c) 2007 American Institute of Physics. Microstructures of coherent phase decomposition near morphotropic phase boundary in lead zirconate titanate are investigated by using computer modeling and simulation. The model is based on the recently proposed incoherent equilibrium phase diagram [G. A. Rossetti, Jr. , Appl. Phys. Lett. 88, 072912 (2006)] and takes into account the coherency strain energy and electrostatic energy. It reveals characteristic multidomain microstructures, where nanoscale lamellar domains of tetragonal and rhombohedral phases coexist with well-defined crystallographic orientation relationships and produce coherent diffraction effects. The simulated microstructures provide important information for interpretation of diffraction data and identification of phases near morphotropic phase boundary. (c) 2007 American Institute of Physics.