Browsing by Author "Jin, Y. M."

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    Adaptive ferroelectric states in systems with low domain wall energy: Tetragonal microdomains
    Jin, Y. M.; Wang, Yu. U.; Khachaturyan, Armen G.; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2003-09-01)
    Ferroelectric and ferroelastic phases with very low domain wall energies have been shown to form miniaturized microdomain structures. A theory of an adaptive ferroelectric phase has been developed to predict the microdomain-averaged crystal lattice parameters of this structurally inhomogeneous state. The theory is an extension of conventional martensite theory, applied to ferroelectric systems with very low domain wall energies. The case of ferroelectric microdomains of tetragonal symmetry is considered. It is shown for such a case that a nanoscale coherent mixture of microdomains can be interpreted as an adaptive ferroelectric phase, whose microdomain-averaged crystal lattice is monoclinic. The crystal lattice parameters of this monoclinic phase are self-adjusting parameters, which minimize the transformation stress. Self-adjustment is achieved by application of the invariant plane strain to the parent cubic lattice, and the value of the self-adjusted parameters is a linear superposition of the lattice constants of the parent and product phases. Experimental investigations of Pb(Mg1/3Nb2/3)O-3-PbTiO3 and Pb(Zn1/3Nb2/3)O-3-PbTiO3 single crystals confirm many of the predictions of this theory. (C) 2003 American Institute of Physics.
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    Conformal miniaturization of domains with low domain-wall energy: Monoclinic ferroelectric states near the morphotropic phase boundaries
    Jin, Y. M.; Wang, Yu. U.; Khachaturyan, Armen G.; Li, Jiefang; Viehland, Dwight D. (American Physical Society, 2003-11-07)
    A theory is developed for intermediate monoclinic (FEm) phases near morphotropic phase boundaries in ferroelectrics of complex oxides. It is based on the conformal miniaturization of stress-accommodating tetragonal domains under the condition of low domain-wall energy density. The microdomain-averaged lattice parameters are determined and attributed to the parameters of an adaptive monoclinic phase. The theory is applied to the temperature, electric field, and compositional dependent FEm lattice parameters. The predictions of the theory are rigidly obeyed over the entire FEm stability range.