Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session M21: Focus Session: Relaxors, Nanostructures and Morphotropic Phase Boundaries |
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Sponsoring Units: DMP Chair: Patrycja Paruch, Universite de Geneve Room: 323 |
Wednesday, March 20, 2013 8:00AM - 8:12AM |
M21.00001: Spontaneous ferroelectric-ferroelectric phase transitions and giant electro-mechanical energy conversion in [011] cut relaxor ferroelectric crystals Peter Finkel, Ahmed Amin, Wen Dong We report on giant electro-mechanical energy conversion is demonstrated under a ferroelectric/ferroelectric phase transformation in [011] cut and poled lead titanate-based relaxor perovskite morphotropic Pb(In$_{1/2}$Nb$_{1/2})$O$_{3}$-Pb(Mg$_{1/3}$Nb$_{2/3})$O$_{3}$-PbTiO$_{3}$ (PIN-PMN-PT). single crystals. It is found that under mechanical pre-stress, a relatively small oscillatory stress drives the material reversibly between rhombohedral and orthorhombic phases with a remarkably high polarization and strain jumps induced at zero bias electric field and room temperature. The measured electrical output per cycle is more than an order of magnitude larger than that reported for linear piezoelectric materials. Ideal thermodynamic cycles are presented for this electro-mechanical energy conversion followed by a presentation and discussion of the experimental data. The stress dependence of thermally driven polarization change is reported for a ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut and poled. A giant jump in polarization and strain is associated with the phase transformation of the ferroelectric material. The phase transition temperature can be tuned, over a broad temperature range, through the application of bias stress. This phenomenon results in a new approach to applications in the field of energy harvesting [Preview Abstract] |
Wednesday, March 20, 2013 8:12AM - 8:24AM |
M21.00002: ABSTRACT WITHDRAWN |
Wednesday, March 20, 2013 8:24AM - 8:36AM |
M21.00003: Successive pressure-induced structural transitions in relaxor Pb(In$_{1/2}$Nb$_{1/2})$O$_{3}$ Muhetaer Aihaiti, Seiji Kojima, Naohiko Yasuda, Russell Hemley We employed Raman scattering and x-ray diffraction to investigate the behavior of disordered Pb(In$_{1/2}$Nb$_{1/2})$O$_{3}$ (PIN) under pressure up to 50 GPa at 300 K. The sharp peak centered at 370 cm$^{-1}$ increases its intensity with pressure. Two Raman peaks around 550 cm$^{-1}$ merge at 16 GPa and their linewidths increase with pressure. The structural phase transition is associated with a splitting of the 50 cm$^{-1}$ peak above 16 GPa. In most Pb-based relaxors, in contrast to PIN, the 50 cm$^{-1}$ peak shows a slight hardening with pressure and no splitting is observed. The pressure evolution of the diffraction patterns for PIN shows obvious splittings above 16 GPa, particularly for the pseudo-cubic [110], [111] and [220] diffraction peaks, indicative of a symmetry-lowering transition. Our results demonstrate that PIN undergoes successive structural phase transitions. The transition at 6 GPa is similar to that observed in other Pb-based relaxors and related to the octahedra tilting; the transition at 16 GPa could be a rhombohedral to orthorhombic transition, and the transition at 38 GPa is assigned to an orthorhombic to a monoclinic transition. [Preview Abstract] |
Wednesday, March 20, 2013 8:36AM - 8:48AM |
M21.00004: Strain, composition tuning and size effect in Pb$_{\mathrm{x}}$Sr$_{\mathrm{1-x}}$TiO$_3$ piezoelectric thin films and nanostructures Sylvia Matzen, Oleksiy Nesterov, Jeroen Heuver, Gijsbert Rispens, Michael Biegalski, Hans M. Christen, Beatriz Noheda Optimizing the piezoelectric performance at the nanoscale is one of the main challenges for future piezoelectric applications, especially in the field of vibrational energy harvesting. In this work, we have investigated the combined influence of epitaxial strain, compositional variation and size reduction on the crystallographic structure, ferroelectric domain configuration and piezoelectric properties of Pb$_{\mathrm{x}}$Sr$_{\mathrm{1-x}}$TiO$_{3}$ thin films and nanostructures epitaxially grown by Pulsed Laser Deposition on SrRuO$_{3}$-buffered (110)-DyScO$_{3}$ substrates. Theoretical predictions on the PbTiO$_{3}$-SrTiO$_{3}$ solid solution show an interesting phase transition, expected to give rise to enhanced piezoelectric properties, as a function of composition when the films are grown under strain on (110)-DyScO$_{3}$. A series of high quality epitaxial thin films has been grown with various Pb/Sr ratios. We have experimentally confirmed the predicted phase transition. Highly periodic domains with purely in-plane polarization have been observed by both X-ray diffraction and piezoresponse force microscopy. The piezoelectric properties have then been studied as a function of composition and of the lateral dimensions of nano-objects defined by Electron Beam Lithography. [Preview Abstract] |
Wednesday, March 20, 2013 8:48AM - 9:00AM |
M21.00005: Direct observation of intrinsic localized modes as precursors to polar nanoregions in a relaxor ferroelectric Michael Manley, Olivier Delaire, Jeffrey Lynn, Alan Bishop, Raffi Sahul, John Budai Displacive ferroelectric phase transitions can be understood in terms of a soft zone center phonon tending towards zero frequency as the material is cooled towards the transition. Relaxor ferroelectrics are less well understood but there is a growing consensus that dispersed polar nanoregions (PNRs), pinned by chemical inhomogeneities, are responsible for the behavior. Furthermore, it has been argued that PNRs form via soft localized phonon modes, modeled as intrinsic localized modes (ILMs), tending towards zero frequency as the material is cooled into the relaxor region, but these modes have never been observed directly. In this talk, neutron scattering measurements will be presented that reveal the existence of a dispersionless (localized) mode appearing near the Burns temperature in PMN-PT. The local mode softens and diminishes in intensity on cooling towards the relaxor region, ultimately vanishing as the PNRs form. [Preview Abstract] |
Wednesday, March 20, 2013 9:00AM - 9:12AM |
M21.00006: Structure and dynamics analyses of Pb(Mg$_{1/3}$,Nb$_{2/3})$O$_{3}$-PbTiO$_{3}$ Hiroyuki Takenaka, Diomedes Saldana-Greco, Ilya Grinberg, Andrew M. Rappe Relaxor ferroelectric materials are of importance in applications due to their giant piezoelectricity, anomalous dielectric response, and diffuse phase transitions. However, mechanisms of the anomalous physical properties are still ambiguous, especially local structure and dynamics. According to our recent molecular dynamics simulations using a rock salt random site B-cation arrangement, the relax local structure is analogous to the hydrogen bonded network in water. In this work, we present structure and dynamics obtained from Bond-Valence model atomistic molecular dynamics simulations with the random site model and fully disordered 0.75PMN-0.25PT using diffuse scattering and dynamic pair distribution function techniques and compare our results with the available experimental data. [Preview Abstract] |
Wednesday, March 20, 2013 9:12AM - 9:24AM |
M21.00007: Debye Relaxations, Fano Resonances and Heterophase Oscillations in the Relaxor K$_{\mathrm{1-x}}$Li$_{\mathrm{x}}$TaO$_3$ Jean Toulouse, Ling Cai, Radha Pattnaik, Lynn Boatner Besides characteristic dielectric relaxations, relaxor ferroelectrics have also been shown to exhibit strong resonances. These resonances are related to the ubiquitous presence of polar nanodomains in relaxors in their ``paraelectric'' phase below a certain temperature T*. In the relaxor K$_{\mathrm{1-x}}$Li$_{\mathrm{x}}$TaO$_{3}$ (KLT), the dielectric spectrum reveals pairs of coupled resonances with a Fano-type line shape that evolves dramatically with temperature. At higher temperature, the line shape reflects the close interplay between relaxations and resonances. Near the phase transition, it reveals the existence of coherent heterophase fluctuations. KLT provides a good example of the multiscale dynamics (from nano to macro) that is intrinsic to relaxors. [Preview Abstract] |
Wednesday, March 20, 2013 9:24AM - 9:36AM |
M21.00008: Finite-Temperature Properties of Ba(ZrTi)O3 Relaxors from First Principles Sergey Prosandeev, Ali Akbarzadeh, Eric Walter, Abdullah Al-Barakaty, Laurent Bellaiche A first-principles-based technique is developed to investigate the properties of Ba(ZrTi)O3 relaxor ferroelectrics as a function of temperature. The use of this scheme provides answers to important, unresolved and/or controversial questions such as the following. What do the different critical temperatures usually found in relaxors correspond to? Do polar nanoregions really exist in relaxors? If yes, do they only form inside chemically ordered regions? Is it necessary that antiferroelectricity develop in order for the relaxor behavior to occur? Are random fields and random strains really the mechanisms responsible for relaxor behavior? If not, what are these mechanisms? These ab initio based calculations also lead to deep microscopic insight into relaxors. [Preview Abstract] |
Wednesday, March 20, 2013 9:36AM - 10:12AM |
M21.00009: Resonant Ultrasonic Spectroscopy of O-18 and O-16 Strontium Titanate Invited Speaker: James F. Scott We have carried out [J. F. Scott, M. A. Carpenter, E. K. H. Salje et al., Phys. Rev. Lett. 106, 105502 (2011); 108, xxxxxx (2012)] resonant ultrasonic studies of bulk strontium titanate. Below 50K both O-18 and O-16 isotope studies reveal asymmetric Fano-lineshapes due to interaction between acoustic phonon branches related to C44 near 400 kHz and a continuum background due to Sr disorder along [111] directions, originally determined by the NMR studies of Blinc et al. The inference is that the ferroelectric phase of O-18 SrTiO3 has a disordered triclinic ground-state structure; this is compatible with the neutron studies by Bartkowiak et al. at ANSTO and helps reconcile paradoxes in the Brillouin studies of Shigenari et al. and Takesada, Yagi et al. For O-16 isotopic SrTiO3 the data show that the Brillouin splitting below ca. 50K previously misinterpreted as second sound by Courtens et al. and Tagantsev et al. is simply the required splitting of modes that would be degenerate in the tetragonal phase. The new studies show that the ferroelastic domains in O-16 SrTiO3 are polar and compatible with the 2012 flexoelectric model of Morozovska et al. [Preview Abstract] |
Wednesday, March 20, 2013 10:12AM - 10:24AM |
M21.00010: Neutron Diffuse Scattering in Pure and Ba-Doped Single Crystals of the Relaxor NBT Wenwei Ge, Christopher DeVreugd, Daniel Phelan, Peter Gehring, Qinhui Zhang, Muhtar Ahart, Jiefang Li, Haosu Luo, Dwight Viehland We report neutron diffuse scattering measurements on the lead-free relaxors Na$_{1/2}$Bi$_{1/2}$TiO$_3$ (NBT) and NBT doped with 5.6\% BaTiO$_3$, a composition that is located close to the morphotropic phase boundary. The diffuse scattering in NBT appears on cooling near 700 K, which coincides with the temperature at which the dielectric constant deviates from Curie-Weiss behavior. Strong, anisotropic diffuse scattering intensity is observed near the (100), (110), (200), (220), and (210) Bragg peaks. The reciprocal space distribution of the diffuse scattering is consistent with the presence of competing rhombohedral and tetragonal short-range structural correlations. Doping NBT with 5.6\% BaTiO$_3$ reduces the correlation length associated with the tetragonal order by a factor of 10 while simultaneously enhancing the piezoelectric properties. [Preview Abstract] |
Wednesday, March 20, 2013 10:24AM - 10:36AM |
M21.00011: Effects of electric field on acoustic properties of 0.83Pb(Mg$_{1/3}$Nb$_{2/3})$-0.17PbTiO$_{3}$ single crystals studied by Brillouin light scattering Tae Hyun Kim, Jae-Hyeon Ko, Seiji Kojima Relaxor-based ferroelectric Pb[(Mg$_{1/3}$Nb$_{2/3})_{1-x}$Ti$_{x}$]O$_{3}$ (PMN-xPT) single crystals have attracted great attention because of their exceptionally strong piezoelectric properties. This peculiar characteristic was attributed to the rotation of polarization directions and structural complexity. In this study, the phase transition behaviors of PMN-17PT single crystals have been investigated under an electric field applied along [001] by micro-Brillouin scattering. PMN-17PT single crystals were grown by the modified Bridgeman method. The two (001) surfaces were Au-coated to apply the electric field, and the coating was thin enough to allow the incident beam to transmit without much loss. The electric field of different values was applied to the sample along the [001] direction, and the Brillouin scattering spectrum was measured under both field-heating (FH) and field-cooling (FC) conditions. The electric field of 1kV/cm induced a new longitudinal acoustic (LA) mode component along with a broad Brillouin peak evolving continuously from the paraelectric phase during both FC and FH processes. This was attributed to the remnant polar nanoregions that were not aligned under the electric field due to quenched random fields. However, the splitting of the LA mode did not appear when the electric field was over 2kV/cm indicating a clear structural phase transition. [Preview Abstract] |
Wednesday, March 20, 2013 10:36AM - 10:48AM |
M21.00012: Polarization Reversal in Ferroelectric Nanowires using Terahertz Pulses Ryan Herchig, Kevin McCash, Inna Ponomareva Ferroelectric nanowires are very attractive for potential applications in nanodevices, nanosensors or ferroelectric computer memory, since they posses reversible polarization at the nanoscale. Here we report the possibility to remotely control the polarization direction in ferroelectric nanowires by the application of a small biased field in combination with a terahertz Gaussian-shaped pulse. Our study is carried out on Pb(Zr$_{0.4}$Ti$_{0.6}$)O$_3$ nanowires using classical molecular dynamics with first-principle-based effective Hamiltonian[1]. The conditions for which the polarization reversal in the nanowire can be achieved by the coupled effect of a biased field with the application of a terahertz pulse are investigated. In particular, we will report computational data on the polarization reversal by application of THz pulses of different amplitude, frequency and width. Furthermore the dependence of the polarization reversal on the temperature is considered. [Preview Abstract] |
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