Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session T41: Focus Session: Piezoelectrics, Relaxors and Tunable Dielectrics |
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Sponsoring Units: DMP DCOMP Chair: Tomas Sluka, EPFL Room: Mile High Ballroom 3C |
Thursday, March 6, 2014 11:15AM - 11:27AM |
T41.00001: ABSTRACT WITHDRAWN |
Thursday, March 6, 2014 11:27AM - 11:39AM |
T41.00002: A morphotropic phase boundary system with BiInO3-PbTiO3 thin films grown by pulsed laser deposition Hye-Jin Jin, Seol Hee Oh, William Jo Morphotropic phase boundary (MPB) systems attract interests because of huge dielectric and superior piezoelectric properties. At the MPB of perovskite type structure, tetragonal and rhombohedral phases are coexisting by coupling between two equivalent energy states [1]. BiInO3-PbTiO3(BI-PT) is a MPB system which can possess large dielectric constant and high transition temperature. BI and PT thin-films were deposited sequentially on Pt(111)/Ti/SiO2/Si and MgO(100) substrates by pulsed laser deposition under various deposition conditions. A multilayer of BI-PT was grown by depositing BI and PT sequentially. Using x-ray diffraction, phase formation and texture of the BI-PT thin-films were investigated. Dielectric constants and loss tangents of the materials were measured over a wide range of temperature. Piezoelectric force microscopy was used to examine local ferroelectric properties and domain switching of the BI-PT thin-films. Based on the observations, relation between transition temperature and component ratio is discussed. [1] R. E. Eitel et al., Jpn. J. Appl. Phys., Part 1 40, 5999 (2001) [Preview Abstract] |
Thursday, March 6, 2014 11:39AM - 11:51AM |
T41.00003: A comparative study of the phase transitions near the critical concentration in the relaxor $K_{1-x}Li_{x}TaO_{3}$ Ling Cai, Jean Toulouse, Leland Harriger, Greg Downing, Lynn Boatner Many characteristics of mixed relaxor ferroelectric systems are determined by the relative fractions and spatial distribution of the mixed ions. In this report, we illustrate this point with dielectric results that are shown to be remarkably different in crystals of the prototypical relaxor system $K_{1-x}Li_{x}TaO_{3}$ (KLT) with only slightly different $Li$ concentrations. The two KLT crystals studied both contain $Li$ concentrations that are just above the critical value for which a structural phase transition can take place. We have used dielectric spectroscopy and neutron diffraction techniques to study the relaxational (dynamic) and structural (static) properties of these two crystals. We present frequency dependent dielectric constant results as a function of temperature across $T_{C}$ and $T_{B}$, below which the characteristic polar nanodomains(PND) are formed. We also present Neutron diffraction measurements at the [100] Bragg reflection and elastic diffuse scattering near [110]. This comparative study sheds light on the the universality of the recently popularized random field theory. We conclude by showing that the random field theory, which has been used for heterovalent-substituted relaxor systems, can also satisfactorily describe the isovalently ones. [Preview Abstract] |
Thursday, March 6, 2014 11:51AM - 12:27PM |
T41.00004: Computational Study of Local Structure and Dynamics in a Relaxor Ferroelectric Invited Speaker: Hiroyuki Takenaka Relaxor ferroelectrics exhibit a stronger piezoelectric effect, diffuse phase transitions with high permittivity, and unique dielectric response with strong frequency dispersion which are exploited for technological applications and give rise to scientific interest. The diffuse phase transitions have been explained by widely accepted model of polar nanoregions inside a non-polar matrix. Recent experimental and theoretical results, however, suggest requirements of alternate interpretations of the origin of the relaxor behavior. Macroscopic elucidations of structure and dynamics in relaxors are still one of challenging topics in solid-state physics. We analyzed local structure and dynamics with dynamic pair distribution function and diffuse scattering techniques for 0.75PbMg$_{1/3}$Nb$_{2/3}$O$_3$-0.25PbTiO$_3$, a prototypical relaxor, performing molecular dynamics simulations. Our analysis showed phase transition temperatures in good agreement with experimental values. From inspections of in-phase motion correlations for Pb pairs, we found analogy between the phase transition from the paraelectric phase to the relaxor phase in the relaxor and the behavior of the couplings from high temperature to room temperature in water. We, therefore, propose alternate model. [Preview Abstract] |
Thursday, March 6, 2014 12:27PM - 12:39PM |
T41.00005: BZT and PMN: overt and covert soft quasi spin glasses? David Sherrington PMN (${\rm{PbMg}}_{1/3}{\rm{Nb}}_{2/3}{\rm{O}}_3$) is probably the most famous relaxor ferroelectric. BZT (${\rm{BaZr}}_{1-x}{\rm{Ti}}_{x}{\rm{O}}_3$) is a more recently discovered relaxor, within an appropriate concentration range. Both exhibit sharp frequency-dependent susceptibility peaks as a function of temperature, with evidence of polar nanodomains above this region. It will be argued that both BZT and PMN are effectively analogs of soft spin glasses, the former fairly overtly, the latter more covertly, reminiscent of metallic alloys with minority elements that are itinerant magnets in the bulk but without good local moments in isolation in the host. A further analogy with a Anderson localization explains both the features mentioned above. [Preview Abstract] |
Thursday, March 6, 2014 12:39PM - 12:51PM |
T41.00006: Anomalous Skin Effect in the Lead-Free Relaxor NBT Peter Gehring, Wenwei Ge, Daniel Phelan, Qinhui Zhang, Jie Fang Li, Dwight Viehland, Hasuo Luo, Lynn Boatner Several x-ray and neutron powder diffraction studies have shown that the room-temperature space group of the lead-free relaxor NBT is monoclinic Cc and not rhombohedral R3c, as was previously believed. Motivated by these findings, we performed room-temperature neutron scattering measurements on a large (3.5 gram) single crystal of the lead-free relaxor NBT. Our data confirm the R3c symmetry for bulk NBT and place a strict bound on the strength of the 1/2(111) superlattice reflection associated with the Cc space group based on the published atomic coordinates. We show that a skin effect, analogous to that reported in the relaxors PZN and PMN-10\%PT, can reconcile our single-crystal data with these other studied. We believe this represents the first evidence of the relaxor skin effect in a lead-free relaxor. [Preview Abstract] |
Thursday, March 6, 2014 12:51PM - 1:03PM |
T41.00007: High-Throughput Screening of Perovskite Alloys for Piezoelectric Performance and Formability Rickard Armiento, Boris Kozinsky, Geoffroy Hautier, Marco Fornari, Gerbrand Ceder We use high-throughput computational density functional theory to screen a large chemical space of perovskite alloys for systems with the right properties to accommodate a morphotropic phase boundary (MPB) in their composition-temperature phase diagram, a crucial feature for high piezoelectric performance. We start from alloy end-points previously identified in a high-throughput computational search. An interpolation scheme is used to estimate the relative energies between different perovskite distortions for alloy compositions with a minimum of computational effort. Suggested alloys are further screened for thermodynamic stability. The screening identifies alloy systems already known to host a MPB, and suggests a few new ones that may be promising candidates for future experiments. Our method of investigation may be extended to other perovskite systems, e.g., (oxy-)nitrides, and provides a useful methodology for any application of high-throughput screening of isovalent alloy systems. Preprint available at http://arxiv.org/abs/1309.1727 [Preview Abstract] |
Thursday, March 6, 2014 1:03PM - 1:15PM |
T41.00008: Two-dimensional electric vortices in soft ferroelectric cylindrical nano-particles Byounghak Lee, Serge Nakhmanson, Olle Heinonen We present a theory of electric vortices in cylindrical nano-particles. Recently it was predicted that Goldstone-like states (collective, close to zero frequency excitations, requiring practically no consumption of energy) can be induced in a layered perovksite PbSr$_2$Ti$_2$O$_7$ material, manifesting themselves as ``easy'' rotations of the in-plane polarization vector [1]. Utilizing the results of the first-principles simulations, we fit a Landau-Ginzburg-type energy expression for this compound that couples the ferroelectric order parameter with elastic strains. We then use this expression to demonstrate that competition among bulk anisotropy, ferroelectric exchange, and surface Coulomb energies can lead to an emergence of a variety of polarization vortex arrangements in cylinder-shaped nano-particles. We also discuss the possibility of in-situ mechanical control of such vortex structures.\\[4pt] [1] S.M. Nakhmanson and I. Naumov, Phys. Rev. Lett. 104, 097601 (2010). [Preview Abstract] |
Thursday, March 6, 2014 1:15PM - 1:27PM |
T41.00009: Origins of enhanced electromechanical coupling in ferroelectric BaTiO$_{3}$ Abhijit Pramanick, Souleymane Diallo, Olivier Delaire, Stuart Calder, Andrew Christianson, Xun-Li Wang, Jaime Fernandez-Baca The origins of enhanced piezoelectric coupling along non-polar crystallographic directions in ferroelectric BaTiO$_3$ are investigated using in situ neutron spectroscopy. It is observed that an electric field applied away from the equilibrium polarization direction causes a stiffening of the transverse acoustic (TA) phonon branch and consequently increases interaction between the TA and the transverse optic (TO) soft mode for a range of wave vectors extending from the Brillouin zone center. This provides a direct lattice dynamics mechanism for enhanced electromechanical coupling, and could act as a guide for designing improved piezoelectric materials. [Preview Abstract] |
Thursday, March 6, 2014 1:27PM - 1:39PM |
T41.00010: Polarization switching dynamics in BZT-0.5BCT lead free ferroelectric thin films Anagh Bhaumik, Y. Kolekar, P. Shaikh, C. Ramana, K. Ghosh We report polarization switching dynamics in lead (Pb) free BaTi$_{0.8}$Zr$_{0.2}$O$_{3}$-0.5Ba$_{0.7}$Ca$_{0.3}$TiO$_{3}$, (BZT- 0.5 BCT) ferroelectric thin films. High quality thin films of Pb free BZT- 0.5 BCT were grown on Pt/Ti/SiO$_{2}$/Si and SRO/LAO single crystal substrates using pulsed laser deposition (PLD). Polarization versus electric field data shows a hysteresis loop with a large remnant (35 micro C/cm$^{2}$) and saturation polarization (40 micro C/cm$^{2}$) and a small coercive field (1.5 kV/cm) which is essential for practical device applications. The polarization switching dynamics are well correlated with the structural distortion and phonon vibration observed in XRD and Raman spectroscopy. These results may stimulate to develop new Pb free ferroelectric thin films for future non-volatile random access memory and many other high-tech applications. [Preview Abstract] |
Thursday, March 6, 2014 1:39PM - 1:51PM |
T41.00011: Electronic and optical properties of Ba$_{\mathrm{x}}$Sr$_{\mathrm{1-x}}$TiO$_{3}$ from first-principles: the effect of epitaxial strain and composition Jawad Alsaei, Paul Tangney, Arash Mostofi Ferroelectrics such as Ba$_{\mathrm{x}}$Sr$_{\mathrm{1-x}}$TiO$_{3}$ (BST) solid solutions are very good candidates for tunable dielectric devices. BST in thin film form is of particular interest for its application to the manufacture of smaller device components and the potential to tailor its electronic properties both via composition $x$ and epitaxial strain. In this work, we use first-principles calculations to study the effect of composition and epitaxial strain on the band gap and optical properties of BST. Our simulations enable us to disentangle the effects of cell volume, cell shape and atomic relaxation on the electronic structure. Our results demonstrate the potential to exploit structure-property and composition-property relationships in thin-film BST and help to improve our fundamental scientific understanding of this technologically important class of materials. [Preview Abstract] |
Thursday, March 6, 2014 1:51PM - 2:03PM |
T41.00012: Colossal permittivity induced by lattice mirror reflection symmetry breaking in Ba$_{7}$Ir$_{3}$O$_{13+x}$(0 $\le $x$\le $ 1.5) epitaxial thin films Ludi Miao, Yan Xin, Huiwen Zhu, Hong Xu, Sijun Luo, Diyar Talbayev, T.N. Stanislavchuk, A.A. Sirenko, Zhiqiang Mao Materials with colossal permittivity (CP) at room temperature hold tremendous promise in modern microelectronics as well as high-energy-density storage applications. Despite several proposed mechanisms that lead torecent discoveries of a series of new CP materials such as Nb, In co-doped TiO$_{2}$ and CaCu$_{3}$Ti$_{4}$O$_{12}$ ceramics, it is imperative to find other approaches which can further guide the search for new CP materials. In this talk, we will demonstrate a new mechanism for CP: the breaking of mirror reflection symmetry of lattice can cause CP. This mechanism was revealed in a new layered iridate Ba$_{7}$Ir$_{3}$O$_{13+x}$ (BIO) thin film we recently discovered. Structural characterization of BIO films show that its mirror reflection symmetry is broken along $b$-axis, but preserved along $a$- and $c$-axes. Dielectric property measurements of BIO films at room temperature show a CP (10$^{3}$-10$^{4})$ along the in-plane direction, but a much smaller permittivity (10- 20) along the $c$-axis, in the 10$^{2}$- 10$^{6}$ Hz frequency range. Such unusually large anisotropy in permittivity testifies to the significant role of the structural in-plane mirror reflection symmetry breaking in inducing CP. [Preview Abstract] |
Thursday, March 6, 2014 2:03PM - 2:15PM |
T41.00013: \textit{Ab-initio} calculations of the elastic, piezoelectric and dielectric tensors of Diisopropylammonium bromide molecular ferroelectric Crystal Ahmad Alsaad, Nabil Al-Aqtash, Renat Sabirianov The elastic, piezoelectric and dielectric properties of Diisopropylammonium bromide molecular ferroelectric crystal are investigated by first-principles methods. The Born effective charge tensor is reported to reveal the relation between Br-N bond hybridization and the ferroelectric structural distortion. As the crystal symmetry is reduced, the Born effective charges of Br and N atoms show a relatively large anisotropic trend demonstrated by the off diagonal nonzero components. The spontaneous polarization is found to be 22.7 $\mu$C/cm$^2$, which is very close to the reported experimental value. The dielectric tensor is found by applying an external electric field of 0.02 $eV$/{AA}. The values of the principle components of the electronic contribution to the dielectric tensor are found to be about 50{\%} of the corresponding values of orthorhombic KNbO$_{3}$ ferroelectric crystal recently reported. The components of the piezoelectric tensor are calculated. The $e_{15}=$ 0.22 C/m$^{2}$ component is smaller than $e_{35}=$ - 0.203 because they correspond to applying uniaxial strain in the direction perpendicular to the Br-N bond. Therefore, a large change in polarization is expected upon strain in Br-N bonds because ferroelectric behavior in $P2_1(\alpha)$ phase is determined primarily by the strongly hybridized bond between the Br and N atoms. We calculated the elastic tensor and explain its relation with the crystal symmetry. We found the ionic relaxation contributions to the total elastic tensor to be larger than the lattice contributions. [Preview Abstract] |
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