Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session D10: Focus Session: Ferroelectrics III and Piezoelectrics |
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Sponsoring Units: DMP Chair: Alexei Grigoriev, University of Tulsa Room: 304 |
Monday, March 16, 2009 2:30PM - 2:42PM |
D10.00001: Light scattering answers precisely to the soft-mode in PbTiO$_{3}$ paraelectric phase Hwee Ping Soon, Hiroki Taniguchi, Yasuhiro Fujii, Mitsuru Itoh, Makoto Tachibana PbTiO$_{3}$ (PT) acts solely as the long-standing textbook example for the displacive-type phase transition; however, the precise observation of the soft-mode behavior of PT paraelectric phase still remains unavailable although it has been addressed by many research works [1-4]. In this study, we revisit the soft-mode behavior of PT single crystal by the confocal micro-Raman measurements. Opposing to the conventional belief that there occurs no first-order Raman scattering in the centrosymmetric PT paraelectric phase, the temperature dependence of the soft-mode has been precisely resolved for the first time due to the existence of macroscopic size Raman active regions ($\ge $ 780~nm). By evidently ruling out the possibility of defect-induced Raman scattering, the elasto-optical coupling serves as the most likely mechanism for the occurrence of these Raman active regions. [This work was supported by both KAKENHI (Grant No. 20248098) and Global COE program.] [1] G. Shirane, J. D. Axe, and J. Harada, Phys. Rev. B 2, 155 (1970). [2] M. Kempa et al., Phase Trans. 79, 351 (2006). [3] N. E. Tornberg and C. H. Perry, J. Chem. Phys. 53, 2946 (1970). [4] M. D. Fontana, H. Idrissi, and K. Wojcik, Europhys. Lett. 11, 419 (1990). [Preview Abstract] |
Monday, March 16, 2009 2:42PM - 2:54PM |
D10.00002: Pretransitional Diffuse Neutron Scattering in Ferroelectric KTa$_{1-x}$Nb$_{x}$O$_{3}$ Grace Yong, Ross Erwin, Oleksiy Svitelskiy, Jean Toulouse, Lynn Boatner, Bernard Hennion, Stephen Shapiro Pretransitional diffuse neutron scattering in ferroelectric KTa$_{1-x}$Nb$_{x}$O$_{3}$ occurs at (110), (111), and (130) with no diffuse scattering at (100), and (200). These observations will be discussed using the elastic structure factor and `uniform phase shift' description. [Preview Abstract] |
Monday, March 16, 2009 2:54PM - 3:06PM |
D10.00003: Nonlinear Driven Response of a Phase-Field Crystal in a Periodic Pinning Potential Cristian Achim, Jorge Ramos, Mikko Karttunen, Ken Elder, Enzo Granato, Tapio Ala-Nissila, See-Chen Ying We study numerically the phase diagram and the response under a driving force of the phase field crystal model for pinned lattice systems in one and two dimensions. The model describes the lattice system as a continuous density field in the presence of a periodic pinning potential, allowing for both elastic and plastic deformations of the lattice. We first present results for phase diagrams of the model in the absence of a driving force. The nonlinear response to a driving force on an initially pinned commensurate phase is then studied via overdamped dynamic equations of motion for different values of mismatch and pinning strengths. For large pinning strength the driven depinning transitions are continuous, and the sliding velocity varies with the force from the threshold with power- law exponents in agreement with analytical predictions. Transverse depinning transitions in the moving state are also found in two dimensions. Surprisingly, for sufficiently weak pinning potential we find a discontinuous depinning transition with hysteresis even in one dimension under overdamped dynamics. We also characterize structural changes of the system in some detail close to the depinning transition. [Preview Abstract] |
Monday, March 16, 2009 3:06PM - 3:18PM |
D10.00004: Mesoscopic nanostructures and long-time relaxation processes in ferroelectrics with coexisting ferroelectric and antiferroelectric phases V. Sobolev, V. Ishchuk, Z. Samoilenko Presentation contains results of experimental study of the kinetics of mesoscopic segregate structures formed in the vicinity of interphase domain boundaries separating the domains of the coexisting ferroelectric and antiferroelectric phases in two series of the lead zirconate titanate based solid solutions in which the isovalent complex (La$_{0.5 }$Li$_{0.5})^{2+}$ or the La$^{3+}$ ions are substituted for lead. These systems of solid solutions possess an extended interval of compositions for which the inhomogeneous state of coexisting ferroelectric and antiferroelectric domains is energetically favorable in comparison with homogeneous ferroelectric and antiferroelectric phases. The mechanisms that control the kinetics of formation of the segregates are investigated and compared for these two series of solid solutions [Preview Abstract] |
Monday, March 16, 2009 3:18PM - 3:30PM |
D10.00005: Accurate calculations of the full NMR chemical shielding tensor in perovskites: B3LYP embedded cluster results for $^{17}$O and $^{47, 49}$Ti Daniel L. Pechkis, Eric J. Walter, Henry Krakauer B3LYP calculations of $^{17}$O and $^{47, 49}$Ti NMR in BaTiO$_3$ and SrTiO$_3$ will be presented. These systems were modeled with finite size quantum clusters embedded in classical fields generated from arrays of point charges and pseudopotentials. For polar clusters, an external E-field was applied to eliminate spurious depolarization fields. The full $^{17}$O chemical shielding tensors, $\hat{\sigma}$(O), in BaTiO$_3$ and SrTiO$_3$ are in very good agreement with recent precise single crystal measurements.\footnote{ R. Blinc, et al., J. Phys: Cond. Matt. {\bf 20}, 085204 (2008).} The calculated Ti isotropic chemical shielding values are within the range of all reported measurements of BaTiO$_3$. Results will also be presented for the solid solution PZT series. [Preview Abstract] |
Monday, March 16, 2009 3:30PM - 3:42PM |
D10.00006: Local ordering and structural instabilities in (Na,Bi)TiO$_3$ perovskites Sahak Petrosyan, Marco Fornari, Boris Kozinsky, Nicola Marzari, Gerbrand Ceder Density functional theory is used to predict structural and electronic properties of lead-free piezoelectric titanate (Na,Bi)TiO$_3$. We studied the energetics of different phases in the phase diagram and investigated the tendency to local ordering on the A-site. In order to elucidate the mechanism for the phase transitions and the piezoelectric performance we also probed the dependence of ferrodistortive and antiferrodistortive instabilities upon pressure and chemical substitutions. Our results point to local tetragonal ordering and provide insight on possible strategies to improve the electromechanical properties. [Preview Abstract] |
Monday, March 16, 2009 3:42PM - 3:54PM |
D10.00007: Density-functional study of the Ba$_{x}$Bi$_{(1-x)}$(M$_{(1-x)/2})$Ti$_{(1+x)/2}$O$_3$ perovskite solid solution Dennis Jackson, David Roundy Using density-functional theory we predict properties of the solid solution perovskites Ba$_{x}$Bi$_{(1-x)}$(M$_{(1-x)/2})$Ti$_{(1+x)/2}$O$_3$ where M is Mg, Ni or Zn. These properties are strongly affected by the presence of both A-site and B-site disorder. We study all distinct orderings within a given $2\times2\times2$ supercell. [Preview Abstract] |
Monday, March 16, 2009 3:54PM - 4:06PM |
D10.00008: Predicting new structures in B-cation ordering perovskites Matthew Lords Material properties are intimately tied to crystal structure. Many materials, alloys in particular, share a common, underlying motif, such as an fcc, bcc, or hcp parent lattice but have different chemical orderings on the lattice. For example, the well-known structure in the Cu-Au system, L1{\_}0, has an underlying fcc lattice where each (001) plane contain only Cu or Au. The planes are stacked so that the Cu and Au layers alternate. Among the countably infinite possibilities for such chemical orderings, why does nature choose only the few it does? Are others possible or likely? We answer this question generally and give an example of the perovskite structure, important in ferroelectrics, catalysts, and superconductors. We show which structures are possible combinatorially and which might actually be observed in real materials. [Preview Abstract] |
Monday, March 16, 2009 4:06PM - 4:18PM |
D10.00009: First principles study of piezorotation in thin-film LaAlO$_3$ Alison Hatt, Nicola Spaldin We investigate the effect of biaxial strain on [001] thin-film LaAlO$_3$ using density functional calculations. We find that the essentially rigid rotations of the AlO$_6$ octahedra vary linearly with strain, a phenomenon which may be described as piezorotation by analogy with piezomagnetism or piezoelectricity [S. Denev, et al., Phys. Rev. Lett. 100, 257601 (2008).] Within a small range of experimentally achievable strain values, we find that epitaxial strain can stabilize several distinct modes of cooperative rotations not found in the bulk, and identify first order phase transitions between states with different piezorotative responses. Finally, we investigate how the electronic and elastic properties are affected by proximity to the strain-induced phase transitions. [Preview Abstract] |
Monday, March 16, 2009 4:18PM - 4:30PM |
D10.00010: Nano-electromechanical systems based on a piezoelectric single crystalline thin film on Silicon Jonghoo Park, Dustin J. Kreft, Robert H. Blick, Seung-Hyub Baek, Chang-Beom Eom, V. Vaithyanathan, Darrell G. Schlom, Vladimir Aksyuk Nano-electromechanical systems (NEMS) have shown great progress and promise as sensors and actuators. In spite of great progress, efficiency and integration techniques for actuating and tuning NEMS has remained a challenge. We have employed a single crystalline piezoelectric thin film on a silicon substrate to obtain a high piezoelectric coefficient and high electromechanical coupling for a NEMS device. The suspended NEMS device consists of Pt/Pb(Mg$_{x}$Nb$_{1-x})$-PbTiO$_{3}$/SrRuO$_{3}$/SiTiO$_{3}$ and is clamped at the ends via silicon substrate. Pt and SrRuO$_{3}$ are used as top and bottom electrodes, respectively, and SiTiO3 serves as a buffer layer to the silicon substrate. We have shown experimentally that the piezoelectric actuation based on PMN-PT devices consume less power and are more responsive than other NEMS devices of similar nature and size. [Preview Abstract] |
Monday, March 16, 2009 4:30PM - 4:42PM |
D10.00011: Structural Study of PMN-xPT by Neutron Diffraction D. Phelan, P.M. Gehring, Q. Huang, Z.-G. Ye, C. Stock, G. Xu, J. Wen Stark differences between x-ray and neutron measurements of the structures of ferroelectric-relaxors PMN-xPT ((1-x)Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$+xPbTiO$_3$) and PZN-xPT (Z=Zn) have been reported [1]. One explanation for these differences is that these crystals have strained surface layers on the order of several tens of $\mu$m thick, the crystal structure of which differs from that of the crystal bulk. This phenomenon has been coined the ``anomalous skin effect'' but has been recently challenged [2] and thus remains controversial. We reinvestigated the skin effect in PMN-xPT by considering the possibility that the oxygen stoichiometry might play a role. Two sets of powders (x=0.1, 0.2, 0.3, and 0.4) were grown, one with and one without oxygen annealing, and high resolution neutron powder diffraction measurements were carried out for both sets. For a given x, both sets of powders have the same structural phase, suggesting that the effects of oxygen annealing are minimal. For x=0.1 and x=0.2 both sets of powders are rhombohedral, which contrasts with the single crystal neutron diffraction measurements. This supports a skin effect in that the grain size of the powders is small enough that the Bragg peaks are dominated by the strained surface layer. References [1] G. Xu et al., Phase Transitions 79, 135 (2006) [2] E. H. Kisi and J.S. Forrester, J. Phys.:Condens. Matter 17, L381 (2005) [Preview Abstract] |
Monday, March 16, 2009 4:42PM - 4:54PM |
D10.00012: Complex local structures in lead based perovskite relaxors Guangyong Xu, Zhijun Xu, Jinsheng Wen, Peter Gehring, Chris Stock The lead-based, perovskite relaxors Pb(Zn$_{1/3}$Nb$_{2/3}$)O$_3$ (PZN), Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$ (PMN) and their solid solutions with PbTiO$_3$ (PT) continue to receive significant attention because they exhibit huge piezoelectric responses and are therefore technologically important. It is widely accepted that many of the special properties of relaxors are related to local (charge, chemical, and polar) order. In particular, short-range polar order, a.k.a. ``polar nano-regions'' (PNR), is believed to appear in relaxors at temperatures well above the Curie temperature T$_C$. The PNR contribute to the frequency dispersion of the dielectric properties and have recently been suggested to be associated with the high piezoelectric response. We have performed series of neutron diffuse scattering measurements on PMN-x\%PT and PZNx\%PT single crystals. Our results indicate that the local polar structure is complicated, having T1 and T2-type components with different polarizations. In particular, the T1 component with $\langle$001$\rangle$ polarization can be partially suppressed by an [001] field, the T2 component with $\langle$110$\rangle$ polarization can be affected by a [111] field. The T2 component also exhibits a strong coupling to the acoustic phonon while the T1 component is associated with the polar optic phonon. We will discuss the complex nature of the local structure in relaxors and their implications. [Preview Abstract] |
Monday, March 16, 2009 4:54PM - 5:06PM |
D10.00013: First-Principles Study of Diffuse Scattering in Pb(Sc$_{1/2}$Nb$_{1/2})$O$_{3}$ P. Ganesh, M. Ahart, R.E. Cohen, E. Cockayne, B. Burton Recent X-ray and neutron experiments show diffuse scattering with characteristic butterfly and rod shapes in relaxor ferroelectrics Pb(Sc$_{1/2}$Nb$_{1/2})$O$_{3 }$(PSN) and Pb(Zn$_{1/2}$Nb$_{1/2})$O$_{3 }$(PZN) [1]. We have simulated diffuse scattering in PSN using first-principles based simulations in the ferroelectric, relaxor and the paraelectric phases [2]. The model assumes quenched chemical order in the form of chemically ordered regions in a chemically disordered matrix. Below the Burns temperature, polar nanoregions (PNR) form, pinned spatially to the COR, but whose polarization evolve dynamically. In the relaxor phase we find ``butterfly'' shaped diffuse scattering around the [100] peaks and around the [110] peaks we find ``rod'' shaped diffuse scattering similar to experiments. As the system is driven towards the paraelectric phase, the diffuse patterns around all the Bragg peaks display radial streaks elongated towards the origin. We have determined that the rods and butterflies below the Burns temperature originate from the PNR, while the radial streaks above it arise from atomic displacements associated with chemical disorder. References: [1] G. Xu, Z. Zhong, H. Hiraka and G. Shirane, Phys. Rev. B, \textbf{70}, 174109 (2004) [2] S. Tinte, B. P. Burton, E. Cockayne and U. V. Waghmare, Phys. Rev. Lett., \textbf{97}, 137601 (2006) [Preview Abstract] |
Monday, March 16, 2009 5:06PM - 5:18PM |
D10.00014: High-pressure x-ray diffraction and Raman scattering studies of Pb(Mg$_{1/3}$Nb$_{2/3})$O$_{3}$-xPbTiO$_{3 }$ Mukhtar Ahart, Maddury Somayazulu, Ronald Cohen, Russell Hemley Motivated to determine and understand the compositional-pressure phase diagram for PMN-xPT solid solutions, we employed the angular dispersive x-ray diffraction methods (Advanced Photon Source, Argonne National Laboratory) and high pressure Raman scattering to investigate a series of PMN-xPT solid solutions (x=0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in a diamond anvil cell up to 20 GPa. The x-ray diffraction results show changes in Bragg peaks at about 6 or 7 GPa which indicate that PMN-xPT systems undergo a ferroelectric to a paraelectric phase transition. In addition, a new peak centered at 380 cm$^{-1}$ appears above 6 GPa for all the samples. The morphotropic phase boundary (x=0.33 to 0.37) with the monoclinic symmetry persists up to 7 GPa. Based on our results, we suggest a possible structure for high pressure phase, which is R3c. We suggest a phase diagram for PMN-PT system which is slightly different from the one predicted by B. Chaabane et al (Phys. Rev. B 70, 134114, 2004). [Preview Abstract] |
Monday, March 16, 2009 5:18PM - 5:30PM |
D10.00015: Molecular dynamics computational studies of relaxor ferroelectric behavior in Pb(Mg$_{1/4}$Ti$_{1/4}$Nb$_{1/2}$)O$_{3}$ (PMN-PT) Hiroyuki Takenaka, Ilya Grinberg, Andrew Rappe Relaxor ferroelectrics are of fundamental scientific interest and are also used in a variety of applications, such as piezoelectric transducers and capacitors. They exhibit permittivity peaks that are broad with respect to both temperature and frequency. We have developed a bond-valence model for Pb(Mg$_{1/4}$Ti$_{1/4}$Nb$_{1/2}$)O$_{3}$ (PMN-PT) and performed atomistic bond-valence molecular dynamics (BVMD) simulations of PMN-PT. We have studied relaxor behavior at a range of temperatures, in order to analyze polar nanoregion dynamics and relaxation lifetimes. We find that even for a fairly small simulation size of $6\times6\times6$ supercell (1080 atoms), the system exhibits frequency dispersion. We present the results of $6\times 6 \times 6$, $8\times 8\times 8$ and $10\times 10\times 10$ supercell BVMD simulations, analyze the pair distribution function of the PMN-PT and elucidate the local chemical origin of relaxor behavior. [Preview Abstract] |
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