Browsing by Author "Khachaturyan, Armen G."

Now showing 1 - 7 of 7
  • Thumbnail Image
    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.
  • Thumbnail Image
    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.
  • Thumbnail Image
    Giant energy density in 001 -textured Pb(Mg1/3Nb2/3)O-3-PbZrO3-PbTiO3 piezoelectric ceramics
    Yan, Yongke; Cho, Kyung-Hoon; Maurya, Deepam; Kumar, Amit; Kalinin, Sergei; Khachaturyan, Armen G.; Priya, Shashank (AIP Publishing, 2013-01-01)
    Pb(Zr,Ti)O-3 (PZT) based compositions have been challenging to texture or grow in a single crystal form due to the incongruent melting point of ZrO2. Here we demonstrate the method for achieving 90% textured PZT-based ceramics and further show that it can provide highest known energy density in piezoelectric materials through enhancement of piezoelectric charge and voltage coefficients (d and g). Our method provides more than similar to 5x increase in the ratio d(textured)/d(random). A giant magnitude of d.g coefficient with value of 59 000 x 10(-15) m(2) N-1 (comparable to that of the single crystal counterpart and 359% higher than that of the best commercial compositions) was obtained. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789854]
  • Thumbnail Image
    Giant magnetoelectric coupling in laminate thin film structure grown on magnetostrictive substrate
    Park, Chee-Sung; Khachaturyan, Armen G.; Priya, Shashank (AIP Publishing, 2012-05-01)
    Highly dense 1 mu m-thick piezoelectric film was deposited on magnetostrictive substrate [platinized nickel-zinc ferrite (NZF)]. A strong magnetic coupling between the piezoelectric film and magnetostrictive NZF substrate was measured exhibiting the maximum magnetoelectric (ME) coefficient on the order of 140 mV/cm Oe at the conditions of H-DC = 50 Oe and H-AC = 1Oe at f = 1 kHz. This giant ME coupling under low DC magnetic field condition is attributed to effective elastic coupling. A rotation-type dynamic strain distribution was observed on the PZT film surface which provides information about the nature of elastic coupling. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4712132]
  • Thumbnail Image
    Giant magnetoelectric effect in sintered multilayered composite structures
    Islam, Rashed Adnan; Ni, Yong; Khachaturyan, Armen G.; Priya, Shashank (American Institute of Physics, 2008-08-15)
    Trilayer composites consisting of 0.9Pb(Zr(0.52)Ti(0.48))O(3)-0-1Pb(Zn(1/3)Nb(2/3))O(3) (0.9 PZT-0.1 PZN) and Ni(0.6)Cu(0.2)Zn(0.2)Fe(2)O(4) (NCZF) in the configuration NCZF-(0.9 PZT-0.1 PZN)-NCZF were synthesized using pressure assisted sintering. Composites with optimized magnetostrictive to piezoelectric thickness ratio showed a high magnetoelectric (ME) coefficient of 525 mV/cm Oe. Further enhancement in the magnitude of ME coefficient was obtained (595 mV/cm Oe) when the angle of applied dc magnetic field was changed to 45 degrees. Changing the intermediate piezoelectric layer from single to trilayer stack geometry configuration leads to the realization of giant ME response of 782 mV/cm Oe in sintered composites. (C) 2008 American Institute of Physics.
  • Thumbnail Image
    Modeling of magnetoelectric effect in polycrystalline multiferroic laminates influenced by the orientations of applied electric/magnetic fields
    Ni, Yong; Priya, Shashank; Khachaturyan, Armen G. (American Institute of Physics, 2009-04-15)
    By using coarse graining model, the dependence of magnetoelectric (ME) coupling on the mutual orientations of magnetic and electric fields with respect to the orientation of layers in polycrystalline multiferroic laminates is investigated. It is shown that the ME coefficient, described by polarization change in response to the applied magnetic field, is proportional to the trace of effective piezomagnetic strain tensor projected onto laminate interfaces. The piezomagnetic strain significantly depends on the orientation of applied magnetic fields. The results obtained here demonstrate that the magnetoelectric effect in layered composites can be significantly improved by optimizing the configuration of applied electric/magnetic fields.
  • Thumbnail Image
    Nanodispersed DO(3)-phase nanostructures observed in magnetostrictive Fe-19% Ga Galfenol alloys
    Bhattacharyya, Somnath; Jinschek, J. R.; Khachaturyan, Armen G.; Cao, Hu; Li, Jiefang; Viehland, Dwight D. (American Physical Society, 2008-03-10)
    Few nanometer large (<2 nm) inclusions of DO(3)-phase structure have been identified in the A2 matrix of highly magnetostrictive Fe-19% Ga alloys by high-resolution transmission electron microscopy (HRTEM). In addition, we have found that these nanostructures include a high density of {100} line defects with a Burgers vector of a(bcc)/2 < 100 >. This dispersion of DO(3)-phase nanostructures formed within the main A2 matrix and the lifting of their coherency by defects are consistent with a recent theory for the structure and properties of magnetostrictive Fe-Ga and Fe-Al alloys.