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Sample records for relaxor ferroelectric behavior

  1. Unusual Relaxor Ferroelectric Behavior in Stairlike Aurivillius Phases.

    PubMed

    Steciuk, Gwladys; Boullay, Philippe; Pautrat, Alain; Barrier, Nicolas; Caignaert, Vincent; Palatinus, Lukas

    2016-09-01

    New ferroelectric layered materials were found in the pseudobinary system Bi5Nb3O15-ABi2Nb2O9 (A= Ba, Sr and Pb). Preliminary observations made by transmission electron microscopy indicate that these compounds exhibit a complex incommensurately modulated structure. A (3 + 1)D structural model is obtained using ab initio phasing by charge flipping based on the analysis of precession electron diffraction tomography data. The (3 + 1)D structure is further validated by a refinement against neutron powder diffraction. These materials possess a layered structure with discontinuous [Bi2O2] slabs and perovskite blocks. While these structural units are characteristics of Aurivillius phases, the existence of periodic crystallographic shear planes offers strong similarities with collapsed or stairlike structures known in high-Tc superconductors and related compounds. Using dielectric spectroscopy, we study the phase transitions of these new layered materials. For A = Ba and Sr, a Vögel-Fulcher-like behavior characteristic of the so-called relaxor ferroelectrics is observed and compared to "canonical" relaxors. For A = Sr, the absence of a Burns temperature separated from the freezing temperature appears as a rather unusual behavior. PMID:27525499

  2. Deviation from Curie-Weiss behavior in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Viehland, Dwight; Jang, S. J.; Cross, L. Eric; Wuttig, Manfred

    1992-10-01

    The deviation from Cure-Weiss behavior has been investigated in lead magnesium niobate relaxor ferroelectrics. At high temperatures, the susceptibility was found to follow the Curie-Weiss relationship. A Curie constant and temperature of 1.2×105 and 398 K, respectively, were obtained. With decreasing temperature the deviation was found to increase. It is proposed that this deviation arises due to short-range correlations between polar regions, and that these correlations at high temperatures are the precursor to a freezing of the polarization fluctuations into a glassy state. A local (glassy) order parameter was calculated from the susceptibility by analogy to spin glasses [D. Sherrington and S. Kirkpatrick, Phys. Rev. Lett. 35, 1972 (1975)]. These results are compared to the rms polarization [G. Burns and F. Dacol, Solid State Commun. 48, 853 (1983)] and to the measured remanent polarization. The frequency and field dependence has also been investigated.

  3. Electrocaloric effect in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pirc, R.; Kutnjak, Z.; Blinc, R.; Zhang, Q. M.

    2011-10-01

    A theoretical model for the electrocaloric effect (ECE) in relaxor ferroelectrics is presented. By solving a self-consistent relation for the ECE temperature change ΔT and minimizing numerically the mean field free energy for relaxors, the field and temperature dependence of ΔT is calculated. The corresponding harmonic Landau coefficient a =a(T), which differs from the ferroelectric case by always being positive, is derived from the spherical random bond-random field model, and the fourth-order coefficient b is treated as a phenomenological parameter, which can be either positive or negative. For b <0, a line of field-induced first-order relaxor-to-ferroelectric phase transitions exists in relaxors, which terminates at a liquid-vapor type critical point ECP,TCP. The critical behavior close to ECP,TCP is analyzed. It is shown that near the first-order phase transition a temperature or field interval or gap formally appears, where ΔT cannot be found. However, domain formation in the coexistence range should restore the continuous behavior of the ECE observed in real systems. Finally, it is shown that the ECE responsivity R1=ΔT /E reaches a maximum near the critical point, in agreement with recent experiments.

  4. Multidimensional dynamic piezoresponse measurements. Unraveling local relaxation behavior in relaxor-ferroelectrics via big data

    DOE PAGESBeta

    Vasudevan, Rama K.; Zhang, Shujun; Okatan, Mahmut Baris; Jesse, Stephen; Kalinin, Sergei V.; Bassiri-Gharb, Nazanin

    2015-08-19

    Compositional and charge disorder in ferroelectric relaxors lies at the heart of the unusual properties of these systems, such as aging and non-ergodicity, polarization rotations, and a host of temperature and field-driven phase transitions. However, much information about the field-dynamics of the polarization in the prototypical ferroelectric relaxor (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) remains unprobed at the mesoscopic level. We use a piezoresponse force microscopy-based dynamic multimodal relaxation spectroscopy technique, enabling the study of ferroelectric switching and polarization relaxation at mesoscopic length scales, and carry out measurements on a PMN-0.28PT sample with minimal polishing. Results indicate that beyond a threshold DC bias themore » average relaxation increases as the system attempts to relax to the previous state. Phenomenological fitting reveals the presence of mesoscale heterogeneity in relaxation amplitudes and clearly suggests the presence of two distinct amplitudes. Independent component analysis reveals the presence of a disorder component of the relaxation, which is found to be strongly anti-correlated with the maximum piezoresponse at that location, suggesting smaller disorder effects where the polarization reversal is large and vice versa. The disorder in the relaxation amplitudes is postulated to arise from rhombohedral and field-induced tetragonal phase in the crystal, with each phase associated with its own relaxation amplitude. As a result, these studies highlight the crucial importance of the mixture of ferroelectric phases in the compositions in proximity of the morphotropic phase boundary in governing the local response and further highlight the ability of PFM voltage and time spectroscopies, in conjunction with big-data multivariate analyses, to locally map disorder and correlate it with parameters governing the dynamic behavior.« less

  5. Multidimensional dynamic piezoresponse measurements: Unraveling local relaxation behavior in relaxor-ferroelectrics via big data

    NASA Astrophysics Data System (ADS)

    Vasudevan, Rama K.; Zhang, Shujun; Baris Okatan, M.; Jesse, Stephen; Kalinin, Sergei V.; Bassiri-Gharb, Nazanin

    2015-08-01

    Compositional and charge disorder in ferroelectric relaxors lies at the heart of the unusual properties of these systems, such as aging and non-ergodicity, polarization rotations, and a host of temperature and field-driven phase transitions. However, much information about the field-dynamics of the polarization in the prototypical ferroelectric relaxor (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) remains unprobed at the mesoscopic level. Here, we use a piezoresponse force microscopy-based dynamic multimodal relaxation spectroscopy technique, enabling the study of ferroelectric switching and polarization relaxation at mesoscopic length scales, and carry out measurements on a PMN-0.28PT sample with minimal polishing. Results indicate that beyond a threshold DC bias the average relaxation increases as the system attempts to relax to the previous state. Phenomenological fitting reveals the presence of mesoscale heterogeneity in relaxation amplitudes and clearly suggests the presence of two distinct amplitudes. Independent component analysis reveals the presence of a disorder component of the relaxation, which is found to be strongly anti-correlated with the maximum piezoresponse at that location, suggesting smaller disorder effects where the polarization reversal is large and vice versa. The disorder in the relaxation amplitudes is postulated to arise from rhombohedral and field-induced tetragonal phase in the crystal, with each phase associated with its own relaxation amplitude. These studies highlight the crucial importance of the mixture of ferroelectric phases in the compositions in proximity of the morphotropic phase boundary in governing the local response and further highlight the ability of PFM voltage and time spectroscopies, in conjunction with big-data multivariate analyses, to locally map disorder and correlate it with parameters governing the dynamic behavior.

  6. Multidimensional dynamic piezoresponse measurements. Unraveling local relaxation behavior in relaxor-ferroelectrics via big data

    SciTech Connect

    Vasudevan, Rama K.; Zhang, Shujun; Okatan, Mahmut Baris; Jesse, Stephen; Kalinin, Sergei V.; Bassiri-Gharb, Nazanin

    2015-08-19

    Compositional and charge disorder in ferroelectric relaxors lies at the heart of the unusual properties of these systems, such as aging and non-ergodicity, polarization rotations, and a host of temperature and field-driven phase transitions. However, much information about the field-dynamics of the polarization in the prototypical ferroelectric relaxor (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) remains unprobed at the mesoscopic level. We use a piezoresponse force microscopy-based dynamic multimodal relaxation spectroscopy technique, enabling the study of ferroelectric switching and polarization relaxation at mesoscopic length scales, and carry out measurements on a PMN-0.28PT sample with minimal polishing. Results indicate that beyond a threshold DC bias the average relaxation increases as the system attempts to relax to the previous state. Phenomenological fitting reveals the presence of mesoscale heterogeneity in relaxation amplitudes and clearly suggests the presence of two distinct amplitudes. Independent component analysis reveals the presence of a disorder component of the relaxation, which is found to be strongly anti-correlated with the maximum piezoresponse at that location, suggesting smaller disorder effects where the polarization reversal is large and vice versa. The disorder in the relaxation amplitudes is postulated to arise from rhombohedral and field-induced tetragonal phase in the crystal, with each phase associated with its own relaxation amplitude. As a result, these studies highlight the crucial importance of the mixture of ferroelectric phases in the compositions in proximity of the morphotropic phase boundary in governing the local response and further highlight the ability of PFM voltage and time spectroscopies, in conjunction with big-data multivariate analyses, to locally map disorder and correlate it with parameters governing the dynamic behavior.

  7. Topological Point Defects in Relaxor Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Nahas, Y.; Prokhorenko, S.; Kornev, I.; Bellaiche, L.

    2016-03-01

    First-principles-based effective Hamiltonian simulations are used to reveal the hidden connection between topological defects (hedgehogs and antihedgehogs) and relaxor behavior. Such defects are discovered to predominantly lie at the border of polar nanoregions in both Ba (Zr0.5 Ti0.5 )O3 (BZT) and Pb (Sc0.5 Nb0.5 )O3 (PSN) systems, and the temperature dependency of their density allows us to distinguish between noncanonical (PSN) and canonical (BZT) relaxor behaviors (via the presence or absence of a crossing of a percolation threshold). This density also possesses an inflection point at precisely the temperature for which the dielectric response peaks. Moreover, hedgehogs and antihedgehogs are found to be mobile excitations, and the dynamical nature of their annihilation is demonstrated (using simple hydrodynamical arguments) to follows laws, such as those of Vogel-Fulcher and Arrhenius, that are characteristic of dipolar relaxation kinetics of relaxor ferroelectrics.

  8. Topological Point Defects in Relaxor Ferroelectrics.

    PubMed

    Nahas, Y; Prokhorenko, S; Kornev, I; Bellaiche, L

    2016-03-25

    First-principles-based effective Hamiltonian simulations are used to reveal the hidden connection between topological defects (hedgehogs and antihedgehogs) and relaxor behavior. Such defects are discovered to predominantly lie at the border of polar nanoregions in both Ba(Zr_{0.5}Ti_{0.5})O_{3} (BZT) and Pb(Sc_{0.5}Nb_{0.5})O_{3} (PSN) systems, and the temperature dependency of their density allows us to distinguish between noncanonical (PSN) and canonical (BZT) relaxor behaviors (via the presence or absence of a crossing of a percolation threshold). This density also possesses an inflection point at precisely the temperature for which the dielectric response peaks. Moreover, hedgehogs and antihedgehogs are found to be mobile excitations, and the dynamical nature of their annihilation is demonstrated (using simple hydrodynamical arguments) to follows laws, such as those of Vogel-Fulcher and Arrhenius, that are characteristic of dipolar relaxation kinetics of relaxor ferroelectrics. PMID:27058101

  9. Partially transformed relaxor ferroelectric single crystals with distributed phase transformation behavior

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.

    2015-11-01

    Relaxor ferroelectric single crystals such as PMN-PT and PIN-PMN-PT undergo field driven phase transformations when electrically or mechanically loaded in crystallographic directions that provide a positive driving force for the transformation. The observed behavior in certain compositions is a phase transformation distributed over a range of fields without a distinct forward or reverse coercive field. This work focuses on the material behavior that is observed when the crystals are loaded sufficiently to drive a partial transformation and then unloaded, as might occur when driving a transducer to achieve high power levels. Distributed transformations have been modeled using a normal distribution of transformation thresholds. A set of experiments was conducted to characterize the hysteresis loops that occur with the partial transformations. In this work the normal distribution model is extended to include the partial transformations that occur when the field is reversed before the transformation is complete. The resulting hysteresis loops produced by the model are in good agreement with the experimental results.

  10. Mechanical flexible and electric fatigue resistant behavior of relaxor ferroelectric terpolymer

    NASA Astrophysics Data System (ADS)

    Fang, Fei; Yang, Wei; Yang, Wen

    2009-08-01

    Uniaxial tension and polarization evolution under cyclic electric field are investigated for poly(vinylidene fluoride-trifluorethylene-chlorofluoroethylene) terpolymer films prepared by different annealing conditions. The stress-strain behavior of the terpolymer film exhibits that of polymeric elastomers, with its fracture strain reaching 680%. Structure analysis demonstrates that the polymer chains undergo reorientation, and conformational change from nonpolar to polar phase takes place during uniaxial tension. Under cyclic electric field, the terpolymer film exhibits a narrow polarization loop typical of a ferroelectric relaxor. Conformational change from nonpolar to polar phase also occurs upon the electric field, and it reverses to the nonpolar phase when the field is removed. As the cycle number accumulates, the terpolymer film demonstrates excellent resistance to electric fatigue. Compared to the film annealed at 115 °C, the terpolymer film annealed at 100 °C has a larger volume fraction of crystallite/amorphous interfaces and shows better mechanical flexibility as well as electric fatigue resistance. The mechanical flexible and electric fatigue resistant terpolymer films hold promises for many applications, ranging from embedded sensors and actuators to flexible memory devices.

  11. Multiscale dynamics in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Toulouse, Jean; Cai, L.; Pattnaik, R. K.; Boatner, L. A.

    2014-01-01

    The multiscale dynamics of complex oxides is illustrated by pairs of mechanical resonances that are excited in the relaxor ferroelectric K1-xLixTaO3 (KLT). These macroscopic resonances are shown to originate in the collective dynamics of piezoelectric polar nanodomains (PNDs) interacting with the surrounding lattice. Their characteristic Fano lineshapes and rapid evolution with temperature reveal the coherent interplay between the piezoelectric oscillations and orientational relaxations of the PNDs at higher temperature and the contribution of heterophase oscillations near the phase transition. A theoretical model is presented, that describes the evolution of the resonances over the entire temperature range. Similar resonances are observed in other relaxors and must therefore be a common characteristics of these systems.

  12. Relaxor behavior of (Ba,Bi)(Ti,Al)O3 ferroelectric ceramic

    NASA Astrophysics Data System (ADS)

    Cui, Lei; Hou, Yu-Dong; Wang, Sai; Wang, Chao; Zhu, Man-Kang

    2010-03-01

    Perovskite type (Ba0.9Bi0.1)(Ti0.9Al0.1)O3 (BBTA) ceramics have been prepared through solid state reaction route. The room temperature x-ray diffraction study suggests that BBTA ceramics have single phase tetragonal symmetry with space group P4mm. In contrast to the sharp dielectric transition of pure BaTiO3, a broad dielectric anomaly coupled with the shift in dielectric maxima toward a higher temperature with increasing frequency has been observed in BBTA. The quantitative characterization based on empirical parameters (ΔTm, γ, ΔTrelax, and ΔTdiffuse(1 kHz)) confirms its relaxor nature. The dielectric relaxation which follows the Vogel-Fulcher relationship with Eα=0.011 eV, Tf=356 K, and f0=1.38×1010 Hz, further supports spin-glass-like characteristics. In this system, the relaxor behavior can be attributed to the dynamic response of the polar clusters induced by the combined substitutions of Bi3+ and Al3+ on the Ba2+ and Ti4+ site. Moreover, the curie temperature of BBTA shows the decreasing trend compared to that of pure BaTiO3, which doesn't follow the normal Vegard's law, confirming that no BiAlO3 sublattice formed in BBTA. All these features indicate that BBTA is a promising candidate for lead-free relaxors.

  13. Effects of composition and temperature on the large field behavior of [011]{sub C} relaxor ferroelectric single crystals

    SciTech Connect

    Gallagher, John A.; Lynch, Christopher S.; Tian, Jian

    2014-08-04

    The large field behavior of [011]{sub C} cut relaxor ferroelectric lead indium niobate–lead magnesium niobate–lead titanate, xPb(In{sub 1/2}Nb{sub 1/2})O{sub 3}-(1-x-y)Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-yPbTiO{sub 3}, single crystals was experimentally characterized in the piezoelectric d{sub 322}-mode configuration under combined mechanical, electrical, and thermal loading. Increasing the concentration of lead indium niobate and decreasing the concentration of lead titanate in compositions near the morphotropic phase boundary resulted in a decrease of mechanical compliance, dielectric permittivity, and piezoelectric coefficients as well as a shift from a continuous to a discontinuous transformation.

  14. Phonon localization drives polar nanoregions in a relaxor ferroelectric

    SciTech Connect

    Manley, Michael E; Lynn, Jeffrey; Specht, Eliot D; Delaire, Olivier A; Bishop, Alan; Sahul, Raffi; Budai, John D

    2014-01-01

    Relaxor ferroelectrics1, which are utilized as actuators and sensors2-4, exemplify a class of poorly understood materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. There is no definitive explanation for the onset of relaxor behavior (Burns temperature5, Td) or the origin of polar nanoregions (PNRs). Here we show a vibrational mode that localizes on cooling to Td, remains localized as PNRs form, and then delocalizes as PNRs grow using neutron scattering on relaxor (Pb(Mg1/3Nb2/3)O3)0.69-(PbTiO3)0.31 (PMN-31%PT). Although initially appearing like intrinsic local modes (ILMs)6-10, these modes differ below Td as they form a resonance with the ferroelectric phonon. At the resonance, nanoregions of standing ferroelectric phonons develop with a coherence length matching the PNRs. The size, shape, distribution, and temporal fluctuations of PNRs, and our observations, are explained by ferroelectric phonons trapped by disordered resonance modes via Anderson localization11-13. Our results show the size and shape of PNRs are not dictated by complex structural details, as always assumed, but by a phonon resonance wavevector. This simplification could guide the design of next generation relaxors.

  15. Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films

    NASA Astrophysics Data System (ADS)

    Miao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, Meihong; Zhang, Huiyun; Li, Qiang

    2016-01-01

    We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism.

  16. Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films

    PubMed Central

    Miao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, Meihong; Zhang, Huiyun; Li, Qiang

    2016-01-01

    We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism. PMID:26817516

  17. Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films.

    PubMed

    Miao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, Meihong; Zhang, Huiyun; Li, Qiang

    2016-01-01

    We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism. PMID:26817516

  18. Phonon localization drives polar nanoregions in a relaxor ferroelectric.

    PubMed

    Manley, M E; Lynn, J W; Abernathy, D L; Specht, E D; Delaire, O; Bishop, A R; Sahul, R; Budai, J D

    2014-01-01

    Relaxor ferroelectrics exemplify a class of functional materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. Although known for about 30 years, there is no definitive explanation for polar nanoregions (PNRs). Here we show that ferroelectric phonon localization drives PNRs in relaxor ferroelectric PMN-30%PT using neutron scattering. At the frequency of a preexisting resonance mode, nanoregions of standing ferroelectric phonons develop with a coherence length equal to one wavelength and the PNR size. Anderson localization of ferroelectric phonons by resonance modes explains our observations and, with nonlinear slowing, the PNRs and relaxor properties. Phonon localization at additional resonances near the zone edges explains competing antiferroelectric distortions known to occur at the zone edges. Our results indicate the size and shape of PNRs that are not dictated by complex structural details, as commonly assumed, but by phonon resonance wave vectors. This discovery could guide the design of next generation relaxor ferroelectrics. PMID:24718289

  19. Molecular dynamics computational studies of relaxor ferroelectric behavior in Pb(Mg1/4Ti1/4Nb1/2)O3 (PMN-PT)

    NASA Astrophysics Data System (ADS)

    Takenaka, Hiroyuki; Grinberg, Ilya; Rappe, Andrew

    2009-03-01

    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(Mg1/4Ti1/4Nb1/2)O3 (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 6x6x6 supercell (1080 atoms), the system exhibits frequency dispersion. We present the results of 6x6 x6, 8x8x8 and 10x10x10 supercell BVMD simulations, analyze the pair distribution function of the PMN-PT and elucidate the local chemical origin of relaxor behavior.

  20. A brief review on relaxor ferroelectrics and selected issues in lead-free relaxors

    NASA Astrophysics Data System (ADS)

    Ahn, Chang Won; Hong, Chang-Hyo; Choi, Byung-Yul; Kim, Hwang-Pill; Han, Hyoung-Su; Hwang, Younghun; Jo, Wook; Wang, Ke; Li, Jing-Feng; Lee, Jae-Shin; Kim, Ill Won

    2016-06-01

    Relaxor ferroelectricity is one of the most widely investigated but the least understood material classes in the condensed matter physics. This is largely due to the lack of experimental tools that decisively confirm the existing theoretical models. In spite of the diversity in the models, they share the core idea that the observed features in relaxors are closely related to localized chemical heterogeneity. Given this, this review attempts to overview the existing models of importance chronologically, from the diffuse phase transition model to the random-field model and to show how the core idea has been reflected in them to better shape our insight into the nature of relaxor-related phenomena. Then, the discussion will be directed to how the models of a common consensus, developed with the so-called canonical relaxors such as Pb(Mg1/3Nb2/3)O3 (PMN) and (Pb, La)(Zr, Ti)O3 (PLZT), are compatible with phenomenological explanations for the recently identified relaxors such as (Bi1/2Na1/2)TiO3 (BNT)-based lead-free ferroelectrics. This review will be finalized with a discussion on the theoretical aspects of recently introduced 0-3 and 2-2 ferroelectric/relaxor composites as a practical tool for strain engineering.

  1. Glassy aging in the relaxor-like ferroelectric Na1/2Bi1/2TiO3

    NASA Astrophysics Data System (ADS)

    Colla, Eugene V.; Sullivan, Kevin; Weissman, M. B.

    2016-01-01

    The dielectric susceptibility of the lead-free relaxor-like perovskite ferroelectric Na1/2Bi1/2TiO3 is shown to exhibit the same complicated spinglass-like aging behavior found in several cubic relaxors deep in the glassy state, in contrast to some uniaxial relaxors. The effects include rejuvenation and memory, including the ability to support multiple memories in parallel. Weak dependence of aging memories on changes in the electric field indicates that the aging is associated with relatively non-polar degrees of freedom, not with ferroelectric domains.

  2. Pressure as a probe of the physics of relaxor ferroelectrics

    SciTech Connect

    SAMARA,GEORGE A.

    2000-01-25

    Pressure studies have provided new insights into the physics of compositionally-disordered ABO{sub 3} oxide relaxors. Specifically, results will be presented and discussed on a pressure-induced ferroelectric-to-relaxer crossover phenomenon, the continuous evolution of the energetic and dynamics of the relaxation process, and the interplay between pressure and electric field in determining the dielectric response.

  3. Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics

    NASA Astrophysics Data System (ADS)

    Chen, Xiao-Bing; Hui, Rong; Zhu, Jun; Lu, Wang-Ping; Mao, Xiang-Yu

    2004-11-01

    Several polycrystalline samples of bismuth layer-structured ferroelectrics (BLSF) family doped by lanthanum, Bi4-xLaxTi3O12, SrBi4-xLaxTi4O15, Sr2Bi4-xLaxTi5O18, and (Bi,La)4Ti3O12-Sr(Bi,La)4Ti4O15, were prepared by the traditional solid-state reaction method. Their ferroelectric and dielectric properties were investigated. The dielectric measurement data showed that the content of lanthanum determined the ferroelectric characteristics of the compounds. In each series samples, they behaved as normal ferroelectrics for small x, but all of them tended to become relaxors when x was increased. The critical value of the La content causing relaxor characteristics is different for the different BLSFs due to the difference of the number of strontium atoms in their crystal structures. The appearance of the relaxor behavior was attributed to a ferroelectric microdomain state induced by random fields.

  4. Mesoscopic harmonic mapping of electromechanical response in a relaxor ferroelectric

    NASA Astrophysics Data System (ADS)

    Vasudevan, Rama K.; Zhang, Shujun; Ding, Jilai; Okatan, M. Baris; Jesse, Stephen; Kalinin, Sergei V.; Bassiri-Gharb, Nazanin

    2015-06-01

    Relaxor-ferroelectrics are renowned for very large electrostrictive response, enabling applications in transducers, actuators, and energy harvesters. However, insight into the dissimilar contributions (polarization rotation, wall motion) to the electromechanical response from electrostrictive strain, and separation of such contributions from linear piezoelectric response are largely ignored at the mesoscale. Here, we employ a band-excitation piezoresponse force microscopy (BE-PFM) technique to explore the first and second harmonics of the piezoelectric response in prototypical relaxor-ferroelectric 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-0.28PT) single crystals. Third order polynomial fitting of the second harmonic reveals considerable correlation between the cubic coefficient map and the first harmonic piezoresponse amplitude. These results are interpreted under a modified Rayleigh framework, as evidence for domain wall contributions to enhanced electromechanical response. These studies highlight the contribution of domain wall motion in the electromechanical response of relaxor ferroelectrics, and further show the utility of harmonic BE-PFM measurements in spatially mapping the mesoscopic variability inherent in disordered systems.

  5. Properties of Epitaxial Films Made of Relaxor Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Prosandeev, S.; Wang, Dawei; Bellaiche, L.

    2013-12-01

    Finite-temperature properties of epitaxial films made of Ba(Zr,Ti)O3 relaxor ferroelectrics are determined as a function of misfit strain, via the use of a first-principles-based effective Hamiltonian. These films are macroscopically paraelectric at any temperature, for any strain ranging between ≃-3% and ≃+3%. However, original temperature-versus-misfit strain phase diagrams are obtained for the Burns temperature (Tb) and for the critical temperatures (Tm,z and Tm,IP) at which the out-of-plane and in-plane dielectric response peak, respectively, which allow the identification of three different regions. These latter differ from their evolution of Tb, Tm,z, and/or Tm,IP with strain, which are the fingerprints of a remarkable strain-induced microscopic change: each of these regions is associated with its own characteristic behavior of polar nanoregions at low temperature, such as strain-induced rotation or strain-driven elongation of their dipoles or even increase in the average size of the polar nanoregions when the strength of the strain grows.

  6. Phenomenological theory of uniaxial relaxor ferroelectrics.

    PubMed

    Shirokov, V B; Pavlenko, A V; Yuzyuk, Yu I

    2016-10-01

    A phenomenological thermodynamic theory of uniaxial relaxor strontium barium niobate [Formula: see text] is developed using the Landau-Devonshire approach with two order parameters. The fourth-order thermodynamic potential allowed to explain the shape of the polarization hysteresis loops experimentally observed at different temperatures. We show that the broad maximum of the dielectric permittivity is not related to the phase transition and arise due to the coupling between polarization and true order parameter which has antiferroelectric nature. We found that the phase transition temperature is much higher than the maximum of the dielectric permittivity and very likely corresponds to so-called Burn's temperature. True order parameter has no simple relation with polar modes. PMID:27485244

  7. Relaxor-ferroelectric superlattices: high energy density capacitors.

    PubMed

    Ortega, N; Kumar, A; Scott, J F; Chrisey, Douglas B; Tomazawa, M; Kumari, Shalini; Diestra, D G B; Katiyar, R S

    2012-11-01

    We report the breakdown electric field and energy density of laser ablated BaTiO(3)/Ba((1-x))Sr(x)TiO(3) (x = 0.7) (BT/BST) relaxor-ferroelectric superlattices (SLs) grown on (100) MgO single crystal substrates. The dielectric constant shows a frequency dispersion below the dielectric maximum temperature (T(m)) with a merger above T(m) behaving similarly to relaxors. It also follows the basic criteria of relaxor ferroelectrics such as low dielectric loss over wide temperature and frequency, and 50 K shift in T(m) with change in probe frequency; the loss peaks follow a similar trend to the dielectric constant except that they increase with increase in frequency (~40 kHz), and satisfy the nonlinear Vogel-Fulcher relation. Well-saturated ferroelectric hysteresis and 50-80% dielectric saturation are observed under high electric field (~1.65 MV cm(-1)). The superlattices demonstrate an 'in-built' field in as grown samples at low probe frequency (<1 kHz), whereas it becomes more symmetric and centered with increase in the probe frequency system (>1 kHz) which rules out the effect of any space charge and interfacial polarization. The P-E loops show around 12.24 J cm(-3) energy density within the experimental limit, but extrapolation of this data suggests that the potential energy density could reach 46 J cm(-3). The current density versus applied electric field indicates an exceptionally high breakdown field (5.8-6.0 MV cm(-1)) and low current density (~10-25 mA cm(-2)) near the breakdown voltage. The current-voltage characteristics reveal that the space charge limited conduction mechanism prevails at very high voltage. PMID:23053172

  8. Giant strain in lead-free relaxor/ferroelectric piezocomposite ceramics

    NASA Astrophysics Data System (ADS)

    Dinh, Thi Hinh; Kang, Jin-Kyu; Nguyen, Hoang Thien Khoi; Duong, Trang An; Lee, Jae-Shin; Tran, Vu Diem Ngoc; Pham, Ky Nam

    2016-06-01

    The crystal structural, ferroelectric, and electric-field-induced-strain (EFIS) properties of leadfree relaxor/ferroelectric piezocomposites were investigated. The relaxor-matrix phases were mixed with the ferroelectric-seed phases by using a conventional ceramic processing route. The addition of the ferroelectric seed phase dramatically enhanced the EFIS of the relaxor matrix phase at low electric fields. Giant strains of 745 pm/V at 4 kV/mm and 466 pm/V at 3 kV/mm were obtained when the seed contents were 30 wt% and 50 wt%, respectively, which are much higher than those of the relaxor matrix phase without ferroelectric seeds (575 pm/V at 4 kV/mm and 327 pm/V at 3 kV/mm).

  9. Dielectric properties of material with random off-center defects: Monte Carlo simulation of relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Su, C.-C.; Vugmeister, B.; Khachaturyan, A. G.

    2001-12-01

    A Ginzburg-Landau type theory of interaction of randomly distributed local dipoles in a paraelectric crystal is developed. The interaction is caused by the polarization of the host lattice generated by these dipoles. The obtained effective Hamiltonian of the dipole-dipole interaction is employed for the Monte Carlo simulation of ferroelectric properties of a system with off-center dopant ions producing local dipoles. The computer simulation shows that at low dopant ion concentration the paraelectric state transforms into a macroscopically paraelectric state consisting of randomly oriented polar clusters. These clusters amplify the effective dipole moment and dramatically increase the dielectric constant. The interaction between the clusters results in a spectrum of relaxation time and transition to the relaxor state. The real and imaginary parts of the susceptibility of this state are calculated. At intermediate dopant concentration, the material undergoes a diffuse phase transition into a ferroelectric state smeared within a temperature range. A further increase in the dopant concentration makes the transition sharper and closer to the conventional ferroelectric transition. The results obtained are compared with the behavior of the K1-xLixTaO3 relaxor ferroelectric.

  10. Development of “fragility” in relaxor ferroelectrics

    SciTech Connect

    Wang, Yi-zhen; Chen, Lan; Xiong, Xiao-min; Zhang, Jin-xiu; Wang, Hai-yan; Frank Zhang, X.; Fu, Jun

    2014-02-07

    Relaxor ferroelectrics (RFs), a special class of the disordered crystals or ceramics, exhibit a pronounced slowdown of their dynamics upon cooling as glass-forming liquids, called the “Super-Arrhenius (SA)” relaxation. Despite great progress in glass-forming liquids, the “fragility” property of the SA relaxation in RFs remains unclear so far. By measuring the temperature-dependent dielectric relaxation in the typical relaxor Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-x%PbTiO{sub 3} (PMN − x%PT) with 0 ≤ x ≤ 20.0, we in-depth study the “fragility” properties of the SA relaxation in PMN − x%PT. Such fascinating issues as the mechanism of the “fragility” at an atomic scale, the roles of the systematic configurational entropy change and interaction among relaxing units (RUs, including polar nanoregions and free dipoles) and the relation between “fragility” and ferroelectric order are investigated. Our results show that both the “fragility” of the temperature-dependent SA relaxation and ferroelectric order in the PMN − x%PT systems investigated arise thermodynamically from the configurational-entropy loss due to the attractive interaction among RUs, and develops as a power law, possibly diverging at the finite critical temperature T{sub c}. A reasonable physical scenario, based on our “configurational-entropy-loss” theory and Nowick's “stress-induced-ordering” theory, was proposed.

  11. Single-crystal relaxor ferroelectric piezoactuators with interdigitated electrodes.

    PubMed

    Levy, Miguel; Vanga, Raghav; Moon, Kee S; Park, Heung K; Hong, Yong K

    2004-12-01

    We report on the fabrication and performance of (1-x) Pb(Zn(1/3)Nb(2/3))O3-xPbTiO3 (PZN-PT) single-crystal relaxor piezoactuators with interdigitated electrodes patterned on a single surface. An electric field gradient across the sample thickness induces a differential contraction between opposite faces, and it is responsible for the actuation. The samples are poled by energizing the electrodes at 100 degrees C and cooling in a field. Calculations of the piezoelectric response based on a periodically modulated dipolar field yield good agreement with experiment. Discrepancies with the model are ascribed to multidomain formation in the ferroelectric sample as a result of field reversals in the applied electric field along the sample length. PMID:15690720

  12. Temperature dependence of flexoelectric response in ferroelectric and relaxor polymer thin films

    NASA Astrophysics Data System (ADS)

    Poddar, Shashi; Ducharme, Stephen

    2014-09-01

    We report the temperature dependence of the flexoelectric response in thin films of both ferroelectric and relaxor forms of vinylidene fluoride polymers. The ferroelectric samples were depoled to minimize piezoelectric response by heating them beyond their Curie temperature and then cooling in zero applied electric field. In both the relaxor ferroelectric polymer and the paraelectric state of the ferroelectric copolymer, the flexoelectric coefficient was proportional to the dielectric constant over a limited range of temperatures, in agreement with general theoretical principles. The enhancements in flexoelectric response were also observed near the Curie transition temperature for the ferroelectric polymer and near the dielectric relaxation temperature for the relaxors. The broad dielectric anomaly in these systems provides greater temperature stability for these enhancements.

  13. Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review

    PubMed Central

    Zhang, Shujun; Li, Fei; Jiang, Xiaoning; Kim, Jinwook; Luo, Jun; Geng, Xuecang

    2014-01-01

    Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials’ behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor

  14. Visualization of dielectric constant-electric field-temperature phase maps for imprinted relaxor ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Frederick, J. C.; Kim, T. H.; Maeng, W.; Brewer, A. A.; Podkaminer, J. P.; Saenrang, W.; Vaithyanathan, V.; Li, F.; Chen, L.-Q.; Schlom, D. G.; Trolier-McKinstry, S.; Rzchowski, M. S.; Eom, C. B.

    2016-03-01

    The dielectric phase transition behavior of imprinted lead magnesium niobate-lead titanate relaxor ferroelectric thin films was mapped as a function of temperature and dc bias. To compensate for the presence of internal fields, an external electric bias was applied while measuring dielectric responses. The constructed three-dimensional dielectric maps provide insight into the dielectric behaviors of relaxor ferroelectric films as well as the temperature stability of the imprint. The transition temperature and diffuseness of the dielectric response correlate with crystallographic disorder resulting from strain and defects in the films grown on strontium titanate and silicon substrates; the latter was shown to induce a greater degree of disorder in the film as well as a dielectric response lower in magnitude and more diffuse in nature over the same temperature region. Strong and stable imprint was exhibited in both films and can be utilized to enhance the operational stability of piezoelectric devices through domain self-poling.

  15. Strain induced electric field driven relaxor ferroelectricity in BaZrxTi1-xO3 system

    NASA Astrophysics Data System (ADS)

    Maiti, Tanmoy; Guo, Ruyan; Bhalla, Amar

    2009-03-01

    A revised complete phase diagram of Ba(ZrxTi1-x)O3 (0.0<=x<=1.0) has been developed based on evaluation of their crystallographic, dielectric, and ferroelectric properties. A new understanding of the relaxor behavior in this system, e.g. associated with the local elastic strains at the nanoscale, has been gained and presented in this paper. Two different kinds of relaxor behaviors are observed in the BZT system; one is dominated by polar Ti-rich regions and another by non-polar Zr-rich regions. BZT relaxor compositions are characterized by measurement of their dielectric (under bias), pyroelectric, and thermal expansion properties in a wide range of temperatures. The structure of the BZT compositions was evaluated by X-ray and neutron diffraction studies. Their local structure has been also probed by micro-Raman spectra. Although the global symmetry of BZT relaxors is cubic from neutron diffraction studies, non-cubic local symmetry is evident based on the micro-Raman spectra of BZT relaxors.

  16. Neutron scattering study of the relaxor ferroelectric K 1-xLi xTaO 3

    NASA Astrophysics Data System (ADS)

    Wakimoto, S.; Samara, G. A.; Grubbs, R. K.; Venturini, E. L.; Boatner, L. A.

    2009-02-01

    Neutron scattering experiments using triple axis spectrometers have been performed for the relaxor ferroelectric materials K 1-xLi xTaO 3 ( x=0.05, 0.10) in order to study the behavior of the zone-center (ZC) transverse-optic (TO) phonon mode (ferroelectric mode). A major contrast between the x=0.05 and 0.10 samples is the ferroelectric transition-observed only for the latter material at T C=115 K on warming and as detected by dielectric measurements and neutron diffraction. The ZC TO mode for x=0.05 shows monotonic softening with decreasing temperature down to 10 K, whereas the x=0.10 sample shows a phonon component below T C which hardens with decreasing temperature in addition to a phonon mode which behaves similarly to that of the x=0.05 sample. This suggests a phase separation of the x=0.10 sample into ferroelectric and relaxor states below T C, possibly originating from a percolative nature of the ferroelectric state.

  17. First-principles-based effective Hamiltonian simulations of bulks and films made of lead-free Ba(Zr,Ti)O3 relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Prosandeev, Sergey; Wang, Dawei; Akbarzadeh, A. R.; Bellaiche, L.

    2015-06-01

    A review of the recent development and application of a first-principles-derived effective Hamiltonian technique to the study of lead-free Ba(Zr,Ti)O3 (BZT) relaxor ferroelectrics is provided. In addition to the computation and analysis of macroscopic properties (such as different types of dielectric responses and electric polarization) and their connections to previous published works, particular emphasis is given to microscopic insights arising from this atomistic technique. These include (i) the numerically-found determination of the physical origin of the relaxor behavior in BZT; and (ii) the prediction of polar nanoregions and the evolution of their morphology as a response to temperature, electric fields and epitaxial misfit strain. Other striking phenomena that were predicted in BZT compounds, such as Fano resonance and field-driven percolation, are also documented and discussed. Finally, a brief perspective of possible remaining computational studies to be conducted in relaxor ferroelectrics, in order to further understand them, is attempted.

  18. Elastic softening and polarization memory in PZN-PT relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Farnsworth, S. M.; Kisi, E. H.; Carpenter, M. A.

    2011-11-01

    Substantial elastic softening in the cubic phase of PZN-PT relaxor ferroelectric crystals is observed as a large hysteresis between the RUS frequencies from poled and depoled crystals. This is due to static switchable polar nanoregions (PNR) at T*, well below the conventional Burns temperature but ˜50 K above the ferroelectric transition. Elastic softening due to polarization of the PNR shows polarization memory through two phase transitions and is greater than the softening associated with polarization of the ferroelectric phases. This emphasizes that PNR dominate the material properties at all temperatures below T*.

  19. Evaluation of field enforced antiferroelectric to ferroelectric phase transition dielectrics and relaxor ferroelectrics for pulse discharge capacitors

    SciTech Connect

    Hoover, B.D.; Tuttle, B.A.; Olson, W.R.; Goy, D.M.; Brooks, R.A.; King, C.F.

    1997-09-01

    Discharge capacitors were designed based on materials with antiferroelectric (AFE) to ferroelectric (FE) field enforced transitions that had 10 times the capacitance of relaxor ferroelectric or state of the art BaTiO{sub 3} materials in the voltage range of interest. Nonlinear RLC circuit analysis was used to show that the AFE to FE materials have potentially more than 2 times the peak discharge current density capability of the BaTiO{sub 3} or lead magnesium niobate (PMN) based relaxor materials. Both lead lanthanum zirconium tin titanate (PLZST) AFE to FE field enforced phase transition materials and PMN based relaxor materials were fabricated and characterized for Sandia`s pulse discharge capacitor applications. An outstanding feature of the PLZST materials is that there are high field regimes where the dielectric constant increases substantially, by a factor of 20 or more, with applied field. Specifically, these materials have a low field dielectric constant of 1,000, but an effective dielectric constant of 23,000 in the electric field range corresponding to the FE to AFE transition during discharge. Lead magnesium niobate (PMN) based relaxor materials were also investigated in this project because of their high dielectric constants. While the PMN based ceramics had a low field dielectric constant of 25,000, at a field corresponding to half the charging voltage, approximately 13 kV/cm, the dielectric constant decreases to approximately 7,500.

  20. Electronic characterization of polar nanoregions in relaxor-type ferroelectric NaNbO3 films

    NASA Astrophysics Data System (ADS)

    Cai, Biya; Schwarzkopf, J.; Hollmann, E.; Braun, D.; Schmidbauer, M.; Grellmann, T.; Wördenweber, R.

    2016-06-01

    Strained NaNbO3 films of different thicknesses are epitaxially grown on (110) NdGaO3 substrates. A detailed analysis of the permittivity of these films demonstrates that strain not only leads to a modification of the permittivity and the ferroelectric transition temperature, it also results in a pronounced relaxor-type behavior and allows a direct estimation of the size and mobility of the polar nanoregions (PNRs). The compressive strain reduces the transition temperature to 125 K and enhances the corresponding permittivity up to ɛ'≈1500 for the thinnest film. Since the strain relaxes with increasing film thickness, both effects, reduction of phase transition temperature and enhancement of ɛ', depend on the thickness of the film. The films show a characteristic frequency and electric field dependence of ɛ', which is discussed in terms of the Vogel-Fulcher equation and Rayleigh law, respectively. Using the electric field dependence of the resulting freezing temperature TVF, allows a direct estimation of the volume of the PNRs at the freezing temperature, i.e. from 70 to 270 n m3 . Assuming an idealized spherical shape of the PNRs, diameters of a few nanometers (5.2-8 nm) are determined that depend on the applied ac electric field. The irreversible part of the polarization seems to be dominated by the presence and mobility of the PNRs. It shows a characteristic peak at low temperature around TVF, vanishes at a temperature where the activation energy of the PRNs extrapolates to zero, and shows a frequency dispersion that is characteristic for relaxor-type behavior.

  1. BaZr0.5Ti0.5O3 : Lead-free relaxor ferroelectric or dipolar glass

    NASA Astrophysics Data System (ADS)

    Filipič, C.; Kutnjak, Z.; Pirc, R.; Canu, G.; Petzelt, J.

    2016-06-01

    Glassy freezing dynamics was investigated in BaZr0.5Ti0.5O3 (BZT50) ceramic samples by means of dielectric spectroscopy in the frequency range 0.001 Hz-1 MHz at temperatures 10 ferroelectric state cannot be induced, in contrast to the case of typical relaxors. This suggests that—at least for the above field amplitudes—BZT50 effectively behaves as a dipolar glass, which can be characterized by a negative value of the static third order nonlinear permittivity. The relaxation spectrum has been analyzed by means of the frequency-temperature plot, which shows that the longest relaxation time obeys the Vogel-Fulcher relation τ =τ0exp [E0/(T -T0) ] with the freezing temperature of 48.1 K, whereas the corresponding value for the shortest relaxation time is ˜0 K, implying an Arrhenius type behavior. By applying a standard expression for the static linear permittivity of dipolar glasses and/or relaxors the value of the Edwards-Anderson order parameter q (T ) has been evaluated. It is further shown that q (T ) can be described by the spherical random bond-random field model of relaxors.

  2. Debye’s temperature and heat capacity for Sr0.15Ba0.85Bi2Nb2O9 relaxor ferroelectric ceramic

    NASA Astrophysics Data System (ADS)

    Peláiz-Barranco, A.; González-Abreu, Y.; Saint-Grégoire, P.; Guerra, J. D. S.; Calderón-Piñar, F.

    2016-02-01

    A lead-free relaxor ferroelectric, Sr0.15Ba0.85Bi2Nb2O9, was synthesized via solid-state reaction and the temperature-dependence of the heat capacity was measured in a wide temperature range. The dielectric permittivity was also measured between 500Hz and 5MHz in the same temperature range. No anomaly has been detected in the heat capacity curve for the whole temperature range covered in the present experiments, while broad peaks have been observed in the dielectric permittivity with high frequency dispersion. A typical relaxor behavior has been observed from the dielectric analysis. The Debye’s temperature has showed a minimum value near the freezing temperature. The results are discussed considering the spin-glass model and the high frequency dispersion, which has been observed for the studied relaxor system.

  3. Nanoscopic Study of the Polarization-Strain Coupling in Relaxor Ferroelectric and the Search for New Relaxor Materials for Transducer and Optical Applications

    SciTech Connect

    J. Toulouse

    2007-05-31

    SUMMARY Relaxor ferroelectrics exhibit a very unusual polarization behavior from which derive unique electrostrictive, piezoelectric and other properties. This behavior and these properties are due to the presence of nanoscale structural and polar order, the polar nanoregions (PNR), which can easily reorient under very modest external electric field, in stark contrast with conventional ferroelectrics. Moreover, when these nanoregions are aligned, their local distortions add up coherently to a macroscopic strain, hence their remarkable electrostrictive and piezoelectric properties. Initially, we demonstrated this effect in KTa1-xNbxO3 (KTN) and were able to identify the local internal symmetry of the PNR in KTN and explain their behavior under an applied electric field. We then extended the study to the more complicated lead relaxors, PbMg1/3Nb2/3O3 (PMN), PbZn1/3Nb2/3O3 (PZN) and (1-x)(PbZn1/3Nb2/3)O3-(x)PbTiO3 (PZN-PT). In particular, following the evolution of the diffuse intensity in neutron scattering and X-ray measurements, we were able to determine the evolution of the polar order from the pure PZN system to the mixed system, PZN-PT. This evolution with addition of PT, provides a physical basis for the remarkably easy polarization rotation that gives PZN-PT its unique properties for composition near the so-called morphotropic boundary (MPB). Through quasi-elastic and inelastic neutron and Raman scattering, we also obtained information about the local (nano)dynamics of these PNR’s. We thus identified three ranges in the evolution of the polarization with temperature: a purely dynamic range, a quasi-dynamic range when the PNR’s appear but can still reorient as “giant dipoles”, a quasi-static range when the system undergoes a series of “underlying” or partial transitions (on a mesoscopic scale) and, finally a frozen range below the last one of these transitions”. This work has provided a useful framework to describe the structural and temperature

  4. Critical Slowing Down in the Relaxor Ferroelectric K1-xLixTaO3(KLT)

    NASA Astrophysics Data System (ADS)

    Cai, Ling; Toulouse, Jean

    2012-02-01

    In this report, we illustrate an essential characteristic of mixed crystals such as KLT: the strong dependence of their macroscopic properties on the spatial distribution of the mixed ions in the crystal. As a prototypical relaxor ferroelectric, KLT exhibits a large dielectric constant, low frequency dispersion and a broad relaxation peak. Lithium randomly substitutes for potassium and, because of its smaller size, moves off-center in one of six possible <100> directions thus forming a local dipole. Correlations between these dipoles lead to the appearance of Polar Nanodomains (PNDs), the size and polarization of which depend on local density fluctuations or type of distribution of the Li ions (random homogeneous or locally clustered). The dielectric constant of two KLT crystals with almost identical average Li concentrations displays two radically different behaviors, which can be traced to two very different distributions of the lithium ions in the two crystals. This is particularly striking of the critical behaviors in the two separate crystals. A first order structural transition is observed in one crystal but critical slowing down is observed in the other. The type of spatial distribution present in each crystal can be inferred from the dielectric results.

  5. Thickness Dependent Properties of Relaxor-PbTiO3 Ferroelectrics for Ultrasonic Transducers

    PubMed Central

    Lee, Hyeong Jae; Zhang, Shujun; Luo, Jun; Li, Fei; Shrout, Thomas R.

    2011-01-01

    The electrical properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) based polycrystalline ceramics and single crystals were investigated as a function of scale ranging from 500 microns to 30 microns. Fine-grained PMN-PT ceramics exhibited comparable dielectric and piezoelectric properties to their coarse-grained counterpart in the low frequency range (<10 MHz), but offered greater mechanical strength and improved property stability with decreasing thickness, corresponding to higher operating frequencies (>40 MHz). For PMN-PT single crystals, however, the dielectric and electromechanical properties degraded with decreasing thickness, while ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) exhibited minimal size dependent behavior. The origin of property degradation of PMN-PT crystals was further studied by investigating the dielectric permittivity at high temperatures, and domain observations using optical polarized light microscopy. The results demonstrated that the thickness dependent properties of relaxor-PT ferroelectrics are closely related to the domain size with respect to the associated macroscopic scale of the samples. PMID:21954374

  6. Energy-storage properties and high-temperature dielectric relaxation behaviors of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Zhang, T. F.; Tang, X. G.; Liu, Q. X.; Jiang, Y. P.; Huang, X. X.; Zhou, Q. F.

    2016-03-01

    (1  -  x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (x  =  0, 5, and 10 mol%) ceramics were prepared using a conventional mixed oxide solid state reaction method. The low-temperature relaxor behavior of (1  -  x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics were examined in the temperature range from 120 to 523 K. A broad dielectric maximum that shifted to higher temperatures with increasing frequency, signified the relaxor-type behavior of these ceramics. The value of the relaxation parameter γ  =  1.61-1.94 estimated from the linear fit of the modified Curie-Weiss law indicated the relaxor nature. High-temperature dielectric relaxation phenomena were found in the temperature region 600-850 K. Energy-storage properties were also analyzed, and the energy-storage density calculated from hysteresis loops reached about 0.47 J cm-3 at room temperature.

  7. Machining induced defects in Relaxor ferroelectric PMN-PT crystals

    NASA Astrophysics Data System (ADS)

    Deng, Cheng

    The superior piezoelectric and dielectric properties of the relaxor based piezoelectric single crystals (PMN-PT) render them as prime candidates for Navy sonar detectors as well as in broad band medical ultrasonic imaging devices. Production of phased array probes utilizing these types of high performance ceramics requires dicing these crystals to arrays with pitches of less than the desired wavelength, ranging from tens to hundreds of micrometers. However, the relaxor based single crystals are very brittle with fracture toughness of about a third to a half that of typical PZT ceramics (0.4-0.8 MPa m ). Excessive chipping and cracking, either during the cutting or poling process, have been reported as major hurdles in processing, leading to spurious resonance and degradation of the distance resolution. In addition, residual stress from the cutting process could be major reliability degradation if it is not well quantified and minimized. In this work, we experimentally analyzed the machining induced damage in a group of Lead Magnesium Niobate-Lead Titanate solid solution single crystal {(1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT)} under simulated process parameters for cutting speeds and down feeds. The machined surfaces are examined by non-contact optical profilometer for planarity and roughness, scanning electron microscopy for subsurface damage, and by micro-raman spectroscopic analysis and X-ray diffraction analysis to uncover machining induced phase transformations. The analysis reveals the preferred process parameters for minimal machining induced damages.

  8. Pressure as a probe of the physics of ABO{sub 3} relaxor ferroelectrics

    SciTech Connect

    SAMARA,GEORGE A.

    2000-02-14

    Results on a variety of mixed ABO{sub 3} oxides have revealed a pressure-induced ferroelectric-to-relaxor crossover and the continuous evolution of the energetics and dynamics of the relaxation process with increasing pressure. These common features have suggested a mechanism for the crossover phenomenon in terms of a large decrease in the correlation length for dipolar interactions with pressure--a unique property of soft mode or highly polarizable host lattices. The pressure effects as well as the interplay between pressure and dc biasing fields are illustrated for some recent results on PZN-9.5 PT,PMN and PLZT 6/65/35.

  9. Direct evidence of correlations between relaxor behavior and polar nano-regions in relaxor ferroelectrics: A case study of lead-free piezoelectrics Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-x%BaTiO{sub 3}

    SciTech Connect

    Ge, Wenwei Luo, Chengtao; Devreugd, Christopher P.; Li, Jiefang; Viehland, D.; Zhang, Qinhui; Luo, Haosu; Ren, Yang

    2013-12-09

    Diffuse scattering and relaxor behavior in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} (NBT) and NBT-5.6 at. %BaTiO{sub 3} (NBT-5.6%BT) were investigated. X-ray diffraction revealed two types of diffuse scattering in NBT: (i) broad and (ii) asymmetric L-shaped. After modification with 5.6%BT, the broad diffuse scattering patterns became narrow, and the asymmetric L-shaped ones were replaced by symmetric ones. The symmetric diffuse scattering in NBT-5.6%BT disappeared with increasing dc electric field (E) for E ≥ 9.5 kV/cm where the frequency dispersion in the dielectric constant disappeared. These results demonstrate that the relaxor characteristics are directly correlated with the diffuse scattering and the presence polar nano-regions.

  10. Investigation of a relationship between dielectric peak diffuseness and elastic modulus variations in a ferroelectric relaxor

    NASA Astrophysics Data System (ADS)

    Sarasúa, L. G.; Moreno, A.; Favre, S.; Eiras, J. A.

    2014-03-01

    The dependence with temperature of elastic modulus of relaxor ferroelectric ceramics is modeled with a Landau-Devonshire-type cluster theory. The effective elastic modulus obtained from experimental data of ultrasonic longitudinal velocity in PCT and PLZT ferroelectric ceramics are compared with the proposed model. This comparison shows that the model is able to reproduce the dependence with temperature of elastic modulus c very well. We obtained that as impurity concentration increases in both families, the diffuseness of the transition shows important variations, but the strengths of the couplings between the polarization and the strain remain almost unchanged. In contrast, other models assigned a change in the strengths of the couplings between the polarization and the strain to explain the diffuse transition in these compounds.

  11. A high-k ferroelectric relaxor terpolymer as a gate dielectric for orgnaic thin film transistors

    SciTech Connect

    Wu, Shan; Shao, Ming; Burlingame, Quinn; Chen, Xiangzhong; Lin, Minren; Xiao, Kai; Zhang, Qiming

    2013-01-01

    Poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) is a ferroelectric terpolymer relaxor with a static dielectric constant of 50, which was developed using defect modification to eliminate remnant polarization in the normal ferroelectric PVDF. In this work, this solution processable terpolymer was used as the gate insulator in bottom gated organic thin-film transistors with a pentacene semiconductor layer. Due to the high dielectric constant of P(VDF-TrFE- CFE), a large capacitive coupling between the gate and channel can be achieved which causes a high charge concentration at the interface of the semiconductor and dielectric layers. In this device, an on/ off ratio of 104 and a low minimum operation gate voltage (5-10 V) were attained

  12. Phonon anomalies induced by polar nano-regions in a relaxor ferroelectric

    NASA Astrophysics Data System (ADS)

    Xu, Guangyong; Wen, Jinsheng; Stock, Chris; Gehring, Peter

    2007-03-01

    Inelastic neutron scattering was used to measure both acoustic and optic phonons polarized along (110) (T2 mode) in the relaxor ferroelectric compound PZN-4.5PT. In the low temperature rhombohedral phase, a single domain state was achieved by cooling the single crystal sample under an external electric field of 2 kV/cm along the [111] direction. Phonon measurements were performed near the (2,2,0) and (2,-2,0) Bragg peaks. We have found that the TA2 phonon couples closely to the diffuse scattering, which arises from polar nano-regions in the system. With the redistribution of diffuse scattering under the external field (see Ref. 1), a clear hardening of TA2 mode was observed near the (2,2,0) Bragg peak, while the TA2 mode near (2,-2,0) Bragg peak softens significantly and becomes over-damped. Our results indicate local inhomogeneities such as the PNR can have direct and significant effects on the lattice dynamics and stability of the whole system. Ref. 1: ``Electric-field-induced redistribution of polar nano-regions in a relaxor ferroelectric'', Guangyong Xu, Z. Zhong, Y. Bing, Z.-G. Ye, and G. Shirane, Nature Materials 5, 134, (2006).

  13. High performance relaxor-based ferroelectric single crystals for ultrasonic transducer applications.

    PubMed

    Chen, Yan; Lam, Kwok-Ho; Zhou, Dan; Yue, Qingwen; Yu, Yanxiong; Wu, Jinchuan; Qiu, Weibao; Sun, Lei; Zhang, Chao; Luo, Haosu; Chan, Helen L W; Dai, Jiyan

    2014-01-01

    Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60%) near the morphotropic phase boundary (MPB). Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc) and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed. PMID:25076222

  14. High Performance Relaxor-Based Ferroelectric Single Crystals for Ultrasonic Transducer Applications

    PubMed Central

    Chen, Yan; Lam, Kwok-Ho; Zhou, Dan; Yue, Qingwen; Yu, Yanxiong; Wu, Jinchuan; Qiu, Weibao; Sun, Lei; Zhang, Chao; Luo, Haosu; Chan, Helen L. W.; Dai, Jiyan

    2014-01-01

    Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33∼2000 pC/N, kt∼60%) near the morphotropic phase boundary (MPB). Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc) and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed. PMID:25076222

  15. Optimization of electrooptic and pieozoelectric coupling effects in tetragonal relaxor-PT ferroelectric single crystals

    PubMed Central

    Sun, Enwei; Sang, Shijing; Yuan, Zhongyuan; Qi, Xudong; Zhang, Rui; Cao, Wenwu

    2015-01-01

    The electrooptic and piezoelectric coupling effects in tetragonal relaxor-based ferroelectric 0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3 (PMN-0.38PT) and 0.88Pb(Zn1/3Nb2/3)O3-0.12PbTiO3 (PZN-0.12PT) single-domain crystals have been analyzed by the coordinate transformation. The orientation dependence of the electrooptic and half-wave voltage was calculated based on the full sets of refractive indices, electrooptic and piezoelectric coefficients. The optimum orientation cuts for achieving the best electrooptic coefficient and half-wave voltage were found. The lowset half-wave voltage is only 76 V for the PMN-0.38PT single-domain crystal. Compared to commonly used electrooptic crystal LiNbO3, tetragonal relaxor-PT ferroelectric single-domain crystals are much superior for optical modulation applications because of their much higher linear electrooptic coefficients and substantially lower half-wave voltages when the piezoelectric strain influence is considered. PMID:25954059

  16. Simulating the Radio-Frequency Dielectric Response of Relaxor Ferroelectrics: Combination of Coarse-Grained Hamiltonians and Kinetic Monte Carlo Simulations

    NASA Astrophysics Data System (ADS)

    Geneste, Grégory; Bellaiche, L.; Kiat, Jean-Michel

    2016-06-01

    The radio-frequency dielectric response of the lead-free Ba (Zr0.5Ti0.5)O3 relaxor ferroelectric is simulated using a coarse-grained Hamiltonian. This concept, taken from real-space renormalization group theories, allows us to depict the collective behavior of correlated local modes gathered in blocks. Free-energy barriers for their thermally activated collective hopping are deduced from this ab initio-based approach, and used as input data for kinetic Monte Carlo simulations. The resulting numerical scheme allows us to simulate the dielectric response for external field frequencies ranging from kHz up to a few tens of MHz for the first time and to demonstrate, e.g., that local (electric or elastic) random fields lead to the dielectric relaxation in the radio-frequency range that has been observed in relaxors.

  17. Simulating the Radio-Frequency Dielectric Response of Relaxor Ferroelectrics: Combination of Coarse-Grained Hamiltonians and Kinetic Monte Carlo Simulations.

    PubMed

    Geneste, Grégory; Bellaiche, L; Kiat, Jean-Michel

    2016-06-17

    The radio-frequency dielectric response of the lead-free Ba(Zr_{0.5}Ti_{0.5})O_{3} relaxor ferroelectric is simulated using a coarse-grained Hamiltonian. This concept, taken from real-space renormalization group theories, allows us to depict the collective behavior of correlated local modes gathered in blocks. Free-energy barriers for their thermally activated collective hopping are deduced from this ab initio-based approach, and used as input data for kinetic Monte Carlo simulations. The resulting numerical scheme allows us to simulate the dielectric response for external field frequencies ranging from kHz up to a few tens of MHz for the first time and to demonstrate, e.g., that local (electric or elastic) random fields lead to the dielectric relaxation in the radio-frequency range that has been observed in relaxors. PMID:27367408

  18. Structure and properties of Pb(Lu{sub 1/2}Nb{sub 1/2})O{sub 3}–0.2PbTiO{sub 3} relaxor ferroelectric crystal

    SciTech Connect

    Liu, Ying; Yang, Xiaoming; Lai, Fachun; Huang, Zhigao; Li, Xiuzhi; Wang, Zujian; He, Chao; Lin, Ju; Long, Xifa

    2015-07-15

    Graphical abstract: The relaxor state of the crystal was demonstrated by the dielectric behavior. - Highlights: • PLN–0.2PT ferroelectric crystal was obtained by the TSSG technique. • The super-lattice reflections were identified by XRD and TEM results. • The PLN–0.2PT crystal is a typical relaxor ferroelectric. - Abstract: Ferroelectric crystal Pb(Lu{sub 1/2}Nb{sub 1/2})O{sub 3}–0.2PbTiO{sub 3} (PLN–0.2PT) was successfully obtained by a top-seed solution growth technique. At room temperature the symmetry was orthorhomic according to X-ray diffraction (XRD). The super-lattice reflections were identified by XRD and transmission electron microscope (TEM). The micro-domain structure was detected by TEM. The temperature dependence of the dielectric constant (ϵ′) shows a typical relaxor behavior. The temperature dependence of coercive electric field and remnant polarizations were investigated, which also shows the relaxor feature.

  19. EIT-like effect due to hetero-phase oscillations near the phase transition of relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Toulouse, Jean; Pattnaik, Radha K.; Boatner, Lynn A.

    2012-02-01

    We report the observation of a remarkable ``transparency window'' in the dielectric resonant absorption spectrum of the relaxor ferroelectric K1-xLixTaO3 (KLT) in the vicinity of its weakly first order transition. This phenomenon is shown to be conceptually similar to the electro-magnetically induced transparency (EIT) phenomenon observed in certain atomic vapors. In KLT however, it reveals the presence of hetero-phase (cubic-tetragonal) fluctuations and provides unique information on the nature and mechanism of the phase transition in relaxors.

  20. Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications.

    PubMed

    Sun, Enwei; Cao, Wenwu

    2014-08-01

    In the past decade, domain engineered relaxor-PT ferroelectric single crystals, including (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) and (1-x-y)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT), with compositions near the morphotropic phase boundary (MPB) have triggered a revolution in electromechanical devices owing to their giant piezoelectric properties and ultra-high electromechanical coupling factors. Compared to traditional PbZr1-x Ti x O3 (PZT) ceramics, the piezoelectric coefficient d 33 is increased by a factor of 5 and the electromechanical coupling factor k 33 is increased from < 70% to > 90%. Many emerging rich physical phenomena, such as charged domain walls, multi-phase coexistence, domain pattern symmetries, etc., have posed challenging fundamental questions for scientists. The superior electromechanical properties of these domain engineered single crystals have prompted the design of a new generation electromechanical devices, including sensors, transducers, actuators and other electromechanical devices, with greatly improved performance. It took less than 7 years from the discovery of larger size PMN-PT single crystals to the commercial production of the high-end ultrasonic imaging probe "PureWave". The speed of development is unprecedented, and the research collaboration between academia and industrial engineers on this topic is truly intriguing. It is also exciting to see that these relaxor-PT single crystals are being used to replace traditional PZT piezoceramics in many new fields outside of medical imaging. The new ternary PIN-PMN-PT single crystals, particularly the ones with Mn-doping, have laid a solid foundation for innovations in high power acoustic projectors and ultrasonic motors, hinting another revolution in underwater SONARs and miniature actuation devices. This article intends to provide a comprehensive review on the development of relaxor-PT single crystals, spanning material discovery

  1. Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications

    PubMed Central

    Sun, Enwei; Cao, Wenwu

    2014-01-01

    In the past decade, domain engineered relaxor-PT ferroelectric single crystals, including (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) and (1-x-y)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT), with compositions near the morphotropic phase boundary (MPB) have triggered a revolution in electromechanical devices owing to their giant piezoelectric properties and ultra-high electromechanical coupling factors. Compared to traditional PbZr1-xTixO3 (PZT) ceramics, the piezoelectric coefficient d33 is increased by a factor of 5 and the electromechanical coupling factor k33 is increased from < 70% to > 90%. Many emerging rich physical phenomena, such as charged domain walls, multi-phase coexistence, domain pattern symmetries, etc., have posed challenging fundamental questions for scientists. The superior electromechanical properties of these domain engineered single crystals have prompted the design of a new generation electromechanical devices, including sensors, transducers, actuators and other electromechanical devices, with greatly improved performance. It took less than 7 years from the discovery of larger size PMN-PT single crystals to the commercial production of the high-end ultrasonic imaging probe “PureWave”. The speed of development is unprecedented, and the research collaboration between academia and industrial engineers on this topic is truly intriguing. It is also exciting to see that these relaxor-PT single crystals are being used to replace traditional PZT piezoceramics in many new fields outside of medical imaging. The new ternary PIN-PMN-PT single crystals, particularly the ones with Mn-doping, have laid a solid foundation for innovations in high power acoustic projectors and ultrasonic motors, hinting another revolution in underwater SONARs and miniature actuation devices. This article intends to provide a comprehensive review on the development of relaxor-PT single crystals, spanning material discovery

  2. Giant electrostrictive effects of NaNbO3-BaTiO3 lead-free relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zuo, Ruzhong; Qi, He; Fu, Jian; Li, Jingfeng; Shi, Min; Xu, Yudong

    2016-06-01

    A giant electrostrictive effect was observed in (1 - x)NaNbO3-xBaTiO3 relaxor ferroelectric ceramics, which exhibit a high electrostrictive coefficient Q33 of ˜0.046 m4/C2 twice as large as those of Pb- and Bi-based perovskite relaxor ferroelectric ceramics. The theoretical analysis suggests that Q33 should be strongly correlated with chemical species of cations in a perovskite structure in which a strong ionic bond is of great benefit compared with a covalent bond. A hysteresis-free large electrostrictive strain of ˜0.148% up to at least 70 Hz was obtained in the x = 0.25 sample, demonstrating significant advantages over piezoelectric effects in high-precision ceramic actuators.

  3. Electric field induced critical points and polarization rotations in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Blinc, Robert; Ishibashi, Y.

    2007-09-01

    The giant electromechanical response in ferroelectric relaxors such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) is of great importance for a number of ultrasonic and medical applications as well as in telecommunications. On the basis of the dielectric, heat capacity, and piezoelectric investigations on PMN-PT crystals of various PT compositions and bias fields, we have recently shown the existence of a line of critical points for the paraelectric to ferroelectric transformations in the composition-temperature-electric field (x-T-E) phase diagram. Here, we show the piezobehavior in more detail and present a theoretical evaluation of the Widom line and the critical line. This line effectively terminates a surface of first order transitions. Above this line, supercritical evolution has been observed. On approaching the critical point, both the enthalpy cost to induce the intermediate monoclinic states and thus the barrier for polarization rotations decrease significantly. The maximum of the piezoelectric response is not at E=0 , but at the critical field values. It is shown that the critical fluctuations in the proximity of the critical points are directly responsible for the observed enhancement of the electromechanical response in the PMN-PT system. In view of the large electric field dependence of the dielectric constant near the critical point, these systems may also be important as electric field tunable elements.

  4. Anomalous negative electrocaloric effect in a relaxor/normal ferroelectric polymer blend with controlled nano- and meso-dipolar couplings

    NASA Astrophysics Data System (ADS)

    Qian, Xiaoshi; Yang, Tiannan; Zhang, Tian; Chen, Long-Qing; Zhang, Q. M.

    2016-04-01

    In general, a dielectric material will eject (or absorb) heat when an electric field is applied and absorb (or eject) heat when the field is removed, under isothermal condition, which is known as the normal (or negative) electrocaloric (EC) effect. For some applications, it is highly desired that an EC material will absorb heat (cooling the surrounding) without subsequent heating under an electric pulse. Here, we show that such an EC material can be realized in a properly designed hybrid normal ferroelectric/relaxor ferroelectric polymer blend in which the normal ferroelectric component induces dipole ordering in the relaxor polymer in the poled state, which can be switched to a de-poled state by an external field. More importantly, the de-poled state can be maintained by the relaxor component when the de-poling field is removed. Consequently, the hybrid blend exhibits a large cooling (an isothermal entropy change ΔS = 11.5 J kg-1 K-1) without the subsequent heating upon the application of an electric pulse.

  5. FAST TRACK COMMUNICATION: Quasi-ferroelectric state in Ba(Ti1-xZrx)O3 relaxor: dielectric spectroscopy evidence

    NASA Astrophysics Data System (ADS)

    Bokov, A. A.; Maglione, M.; Ye, Z.-G.

    2007-03-01

    The dielectric spectroscopy of perovskite Ba(Ti0.675Zr0.325)O3 (BTZ325) relaxor ceramics is performed in a wide frequency range of 10-2-106 Hz. In contrast to other known relaxors, where the dipole dynamics is subject to non-Arrhenius slowing-down and freezing upon cooling so that the cubic ergodic relaxor phase transforms into a cluster dipolar-glass phase or a ferroelectric phase, none of these transformations are observed in BTZ325. In the course of cooling from the ergodic relaxor phase the characteristic time and the spectral width of the main relaxation process first increase rapidly in a Vogel-Fulcher manner, but then become almost temperature independent below the temperature of permittivity maximum, indicating the onset of the state which we call quasi-ferroelectric. The properties and the origin of this state are discussed.

  6. Interface stability of electrode/Bi-containing relaxor ferroelectric oxide for high-temperature operational capacitor

    NASA Astrophysics Data System (ADS)

    Nagata, Takahiro; Kumaragurubaran, Somu; Tsunekawa, Yoshifumi; Yamashita, Yoshiyuki; Ueda, Shigenori; Takahashi, Kenichiro; Ri, Sung-Gi; Suzuki, Setsu; Oh, Seungjun; Chikyow, Toyohiro

    2016-06-01

    The interface stability between electrodes (Pt, TaC, TiC, and RuO2) and a Bi-containing relaxor ferroelectric oxide, BaTiO3–Bi(Mg2/3Nb1/3)O3 (BT–BMN), applied to a high-temperature operational capacitor was investigated by hard X-ray photoelectron spectroscopy. All the electrodes showed electron filling at the Fermi level after annealing at 400 °C. However, Pt and TaC indicated electrical property degradations due to the thick intermediate layer formation and defect formation of the BT–BMN layer relating to the Bi diffusion into the electrodes. In contrast, TiC inhibited the Bi diffusion and did not show any change in the band alignment after annealing. Furthermore, RuO2 eliminated the defect formation in BT–BMN and showed no change in the band alignment although the Bi diffusion was also observed. These results suggest that the TiC/RuO2/BT–BMN stack structure is a potential candidate for the high-temperature operational capacitor.

  7. Effects of composition and temperature on the large-field behavior of [001]C relaxor single crystals.

    PubMed

    Gallagher, John; Lynch, Christopher; Tian, Jian

    2014-12-01

    The compositional dependence of the large-field behavior of [001]C-cut relaxor ferroelectric xPb(In1/2Nb1/2) O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 (PIN-PMN-PT) single crystals that are on the rhombohedral side of the morphotropic phase boundary was characterized under electrical, mechanical, and thermal loading. The effects of varying the concentrations of PIN and PT are discussed. Composition was found to impact the material constants and the field-induced phase transformation threshold in the piezoelectric d333-mode configuration. PMID:25474790

  8. Origin of the crossover between a freezing and a structural transition at low concentration in the relaxor ferroelectric K1 -xLixTaO3

    NASA Astrophysics Data System (ADS)

    Cai, Ling; Toulouse, Jean; Harriger, Leland; Downing, R. Gregory; Boatner, L. A.

    2015-04-01

    The origin of the relaxor behavior in K1 -xLixTaO3(KLT ) and other disordered perovskites is now recognized to be due to the reorientation of the polar nanodomains formed by the correlated dipoles of off-center ions. The collective dynamics of these systems evolve through several temperature stages. On decreasing temperature below the so-called Burns temperature TB, individual dipoles become correlated within nanosized regions. On further cooling, the slow dynamics of these polar regions allows local lattice distortions to take place and the formation of polar nanodomains at T*relaxors undergo a phase transition while others do not. In KLT, there is a critical Li concentration xc=0.022 above which the system undergoes a structural transition at Tc, and below which it freezes in a dipole glass state at Tf. To better understand the nature of this critical concentration, the changes that occur upon crossing it and the nature of the dipole glass state, the collective dynamics of KLT have been studied by dielectric spectroscopy and neutron diffraction for two Li concentrations (x =0.026 and 0.018 ) , close to but straddling the critical concentration xc. Two very different transitional behaviors are observed. Just below this critical concentration, KLT displays critical slowing down and the onset of freezing as seen in hydrogen-bonded molecular ferroelectrics, while just above this concentration, KLT undergoes a first-order structural transition.

  9. Effects of lanthanum dopants on the Curie–Weiss and the local order behaviors for Pb{sub 1−x}La{sub x}(Fe{sub 2/3}W{sub 1/3}){sub 0.7}Ti{sub 0.3}O{sub 3} relaxor ferroelectrics

    SciTech Connect

    Hong, Cheng-Shong; Chu, Sheng-Yuan; Hsu, Chi-Cheng; Su, Hsiu-Hsien

    2013-02-15

    Graphical abstract: The local order as a function of temperature by using (a) the spin-glass model and (b) the modified-Landau theory for Pb{sub 1−x}La{sub x}(Fe{sub 2/3}W{sub 1/3}){sub 0.7}Ti{sub 0.3}O{sub 3} ceramics with different amounts of lanthanum dopants. Display Omitted Highlights: ► The effects of La are investigated for Pb{sub 1−x}La{sub x}(Fe{sub 2/3}W{sub 1/3}){sub 0.7}Ti{sub 0.3}O{sub 3} ceramics. ► La can change their dielectric properties and ordering state. ► The spin glassy behaviors and the freezing process are also affected by La. ► The response mechanisms of La are proposed for the local polarization behavior. -- Abstract: The effects of lanthanum dopants are investigated on the dielectric responses for Pb{sub 1−x}La{sub x}(Fe{sub 2/3}W{sub 1/3}){sub 0.7}Ti{sub 0.3}O{sub 3} ceramics. According to the experimental data and fitting results, it is concluded that the dielectric characteristics are changed from a long-range-ordered (LRO) ferroelectric state to a short-range-ordered (SRO) relaxor by increasing the amounts of lanthanum dopants. Furthermore, the spin glassy behaviors and the freezing process of local polarizations are not only affected by the ordering degree of B-site cations but also affected by the defect polar pairs. Their response mechanisms are proposed that the growth of the 1:1 ordered domain Pb{sub 1−x}La{sub x}(Fe{sub 1/2}W{sub 1/2})O{sub 3} is impeded since its charge imbalance is enhanced by increasing the amounts of lanthanum dopants, and the defect polar pairs of lead, tungsten and oxygen vacancy are induced by the pyrochlore phase, PbWO{sub 4} or Pb{sub 0.99}La{sub 0.01}WO{sub 4}, when the amount of lanthanum dopants exceed 5 mol.%.

  10. Soft and central mode behaviour in PbMg(1/3)Nb(2/3)O(3) relaxor ferroelectric.

    PubMed

    Kamba, S; Kempa, M; Bovtun, V; Petzelt, J; Brinkman, K; Setter, N

    2005-06-29

    The relaxor ferroelectric PbMg(1/3)Nb(2/3)O(3) (PMN) is investigated by means of dielectric and Fourier transform far infrared transmission spectroscopy in the frequency range from 10 kHz to 15 THz at temperatures between 20 and 900 K using mostly thin films on infrared transparent sapphire substrates. While the thin film relaxors display reduced dielectric permittivity at low frequencies, their high frequency lattice response is shown to be the same as for single-crystal/ceramic specimens. In contrast to the results of inelastic neutron scattering, the optic soft mode is found to be underdamped at all temperatures. On heating, the TO1 soft phonon follows the Cochran law with an extrapolated critical temperature of 670 K near to the Burns temperature. Above 450 K the soft mode frequency levels off near 50 cm(-1) and above the Burns temperature it slightly hardens. Central-mode-type dispersion assigned to the dynamics of polar nanoclusters appears below the Burns temperature at frequencies near to but below the soft mode and slows down and broadens dramatically on cooling, finally, below the freezing temperature of 200 K, giving rise to frequency independent losses from the microwave range down. A new explanation of the phonon 'waterfall' effect in inelastic neutron scattering spectra is proposed. PMID:21690711

  11. Electro-optical properties in relaxor ferroelectric materials and the device applications

    NASA Astrophysics Data System (ADS)

    Jeong, Daeyong

    The electro-optic (E-O) effects of the relaxor ferroelectric materials, Lead Magnesium Niobate-Lead Titanate Pb(Mg 1/3Nb2/3)O3- PbTiO3 (PMN-PT) single crystals and poly(vinylidene fluoride-trifluoroethylene) [P( VDF-TrFE)] based polymers, are investigated here. The tetragonal 0.62PMN-0.38PT single crystals poled along the <001> direction (the spontaneous polarization direction) have a stable single domain and show high transparency from the visible to Near-IR range. Using the Mach-Zender interferometry method, large linear E-O coefficients r 33 = 70 pm/V, r 31 = 25 pm/V, and r 15 = 558 pm/V were characterized. P(VDF-TrFE) based terpolymers shows a large Kerr effect where a refractive index change of -2.6% can be induced under an electric field of 80 V/mu m. When combined with the electrostrictive strain, the terpolymer film exhibits a total -5.6% optical pathlength change under a field of 80 V/mum. Calculations based on density functional theory suggest that such a large E-O effect was caused mainly by the reorientation of the C-F dipoles in the crystalline regions under external field. With the large strain and E-O effect, the tunable graing and Fabry-Perot interferometers (FPIs) were fabricated. By changing the structure of comb-shape electrode for the bottom electrode and the polymer thickness, it was calculated that we could control the electric field distribution leading the different level of strain for grating. This new tunable grating has the advantage of simple fabrication and easy integration. In our first experimental demonstration, 24% of the first order diffraction efficiency was observed with 100 V/mum. For the strain tunable FPI, which for the terpolymer films under mechanically clamped condition is 1.3% under 100 V/mum field, we show that a tunable range of 22.5 nm can be obtained at wavelengths near 1.5 mum. On the other hand, the FPI using a terpolymer film directly as the cavity of the etalon shows a smaller tunability (0.78% under 100 V/mum) due

  12. Subterahertz dielectric relaxation in lead-free Ba(Zr,Ti)O3 relaxor ferroelectrics

    PubMed Central

    Wang, D.; Bokov, A. A.; Ye, Z.-G.; Hlinka, J.; Bellaiche, L.

    2016-01-01

    Relaxors are complex materials with unusual properties that have been puzzling the scientific community since their discovery. The main characteristic of relaxors, that is, their dielectric relaxation, remains unclear and is still under debate. The difficulty to conduct measurements at frequencies ranging from ≃1 GHz to ≃1 THz and the challenge of developing models to capture their complex dynamical responses are among the reasons for such a situation. Here, we report first-principles-based molecular dynamic simulations of lead-free Ba(Zr0.5Ti0.5)O3, which allows us to obtain its subterahertz dynamics. This approach reproduces the striking characteristics of relaxors including the dielectric relaxation, the constant-loss behaviour, the diffuse maximum in the temperature dependence of susceptibility, the substantial widening of dielectric spectrum on cooling and the resulting Vogel–Fulcher law. The simulations further relate such features to the decomposed dielectric responses, each associated with its own polarization mechanism, therefore, enhancing the current understanding of relaxor behaviour. PMID:27040174

  13. Subterahertz dielectric relaxation in lead-free Ba(Zr,Ti)O3 relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Wang, D.; Bokov, A. A.; Ye, Z.-G.; Hlinka, J.; Bellaiche, L.

    2016-04-01

    Relaxors are complex materials with unusual properties that have been puzzling the scientific community since their discovery. The main characteristic of relaxors, that is, their dielectric relaxation, remains unclear and is still under debate. The difficulty to conduct measurements at frequencies ranging from ~=1 GHz to ~=1 THz and the challenge of developing models to capture their complex dynamical responses are among the reasons for such a situation. Here, we report first-principles-based molecular dynamic simulations of lead-free Ba(Zr0.5Ti0.5)O3, which allows us to obtain its subterahertz dynamics. This approach reproduces the striking characteristics of relaxors including the dielectric relaxation, the constant-loss behaviour, the diffuse maximum in the temperature dependence of susceptibility, the substantial widening of dielectric spectrum on cooling and the resulting Vogel-Fulcher law. The simulations further relate such features to the decomposed dielectric responses, each associated with its own polarization mechanism, therefore, enhancing the current understanding of relaxor behaviour.

  14. Bi(Ni1/2Zr1/2)O3-PbTiO3 relaxor-ferroelectric films for piezoelectric energy harvesting and electrostatic storage

    NASA Astrophysics Data System (ADS)

    Xie, Zhenkun; Yue, Zhenxing; Ruehl, Griffin; Peng, Bin; Zhang, Jie; Yu, Qi; Zhang, Xiaohua; Li, Longtu

    2014-06-01

    In this Letter, we demonstrated that both a high energy-storage density and a large piezoelectric response can be attained simultaneously in relaxor-ferroelectric 0.4Bi(Ni1/2Zr1/2)O3-0.6PbTiO3 films prepared by chemical solution deposition. The as-prepared films had a pure-phase perovskite structure with an excellent crystalline morphology, featuring a moderate relative permittivity ( ɛ r ˜ 800-1100), a low dissipation factor ( tan δ < 5%) and strong relaxor-like behavior ( γ = 1.81). An ultra-high energy-storage density of 39.8 J/cm3 at 2167 kV/cm was achieved at room temperature. Moreover, the 0.4Bi(Ni1/2Zr1/2)O3-0.6PbTiO3 films exhibited a considerably large effective piezoelectric coefficient of 83.1 pm/V under substrate clamping, which is comparable to the values obtained for lead zirconate titanate films. Good thermal stabilities in both the energy-storage performance and the piezoelectric properties were obtained over a wide range of temperatures, which makes 0.4Bi(Ni1/2Zr1/2)O3-0.6PbTiO3 films a promising candidate for high energy-storage embedded capacitors, piezoelectric micro-devices, and specifically for potential applications in next-generation integrated multifunctional piezoelectric energy harvesting and electrostatic storage systems.

  15. An Ising-like Model to Predict Dielectric Properties of the Relaxor Ferroelectric Solid Solution Barium titanate - Bismuth(Zinc1/2Titanium 1/2)Oxide

    NASA Astrophysics Data System (ADS)

    Jackson, Dennis L.

    We developed a model to investigate the dielectric properties of the BaTiO3 - Bi(Zn 1/2Ti1/2)O3 (BT-BZT) solid solution, which is a relaxor ferroelectric and exhibits long range disorder. The model uses ab initio methods to determine all polarization states for every atomic configuration of 2x2x2 supercells of BT-BZT. Each supercell is placed on a lattice with an Ising-like interaction between neighboring cell polarizations. This method allows us to consider long range disorder, which is not possible with ab initio methods alone, and is required to properly understand relaxor ferroelectric materials. We analyze the Monte Carlo data for a single lattice configuration using the multiple histogram method, and develop a modified histogram technique to combine data from multiple lattice configurations. Our calculated values of dielectric constant, specific heat, and polarization agree reasonably well with experiment.

  16. Stress-modulated relaxor-to-ferroelectric transition in lead-free (N a1 /2B i1 /2 ) Ti O3-BaTi O3 ferroelectrics

    NASA Astrophysics Data System (ADS)

    Schader, Florian H.; Wang, Zhiyang; Hinterstein, Manuel; Daniels, John E.; Webber, Kyle G.

    2016-04-01

    The effect of external mechanical fields on relaxor 0.94 (N a1 /2B i1 /2 ) Ti O3-0.06 BaTi O3 was investigated by means of temperature- and stress-dependent dielectric constant measurements between 223 and 673 K. Analogous to previous investigations that showed an electric-field-induced ferroelectric long-range order in relaxor ferroelectrics, we show that compressive stress can also result in the transition to the long-range ferroelectric order, marked by the formation of an anomaly in the permittivity-temperature curves and a nonlinear, remanent change in permittivity during mechanical loading. In situ stress-dependent high-energy x-ray diffraction experiments were performed at room temperature and reveal an apparent phase transition during mechanical loading, consistent with previous macroscopic electrical measurements. The transition lines between the relaxor states and the stress-induced ferroelectric state were determined at constant temperatures with stress-dependent dielectric constant measurements, providing a stress-temperature phase diagram.

  17. New Dielectric Resonances in Mesoscopic Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pattnaik, R.; Toulouse, J.

    1997-12-01

    A new type of dielectric resonance has been observed in several mixed ferroelectrics, KTa1-xNbxO3 (KTN), K1-xLixTaO3 (KLT), and PbMg1/3Nb2/3O3 (PMN), also known as relaxor ferroelectrics. This resonance and its metastability (persistence over long periods of time) in KTN in the paraelectric phase provides clear evidence, in relaxors, for the presence of permanent polar nanoregions and strong polarization-strain coupling. The frequencies calculated from the elastic constant reveal the unexpected clamped nature of the resonance. These results point to the essential role of polar regions in the relaxor behavior.

  18. Grain-size-dependent spontaneous relaxor-to-ferroelectric phase transition in (Bi1/2K1/2)TiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Hagiwara, Manabu; Fujihara, Shinobu

    2015-07-01

    Dense and phase-pure (Bi1/2K1/2)TiO3 (BKT) ceramics with various average grain sizes from 0.18 to 1.01 μm were prepared from a hydrothermally synthesized powder and their phase transition behaviors were studied by means of dielectric measurements. A drastic increase of the maximum dielectric permittivity (ɛm) with increasing the grain size was found in the temperature dependence of permittivity. The sample with the largest grain size clearly showed both a frequency dependence of dielectric maximum temperature (Tm) and a dielectric anomaly with a strong thermal hysteresis at a temperature below Tm, demonstrating that the BKT ceramic is intrinsically a material exhibiting a spontaneous relaxor to normal ferroelectric (R-nFE) phase transition. On the other hand, the suppression of the R-nFE transition was observed in the sample with the smallest grain size, which was explained as an effect of avoiding the internal stress development caused by the volume increase occurring with the phase transition.

  19. Anisotropic phonon coupling in the relaxor ferroelectric (Na1/2Bi1/2)TiO3 near its high-temperature phase transition

    NASA Astrophysics Data System (ADS)

    Cai, Ling; Toulouse, Jean; Luo, Haosu; Tian, Wei

    2014-08-01

    The lead free relaxor Na1/2Bi1/2TiO3 (NBT) undergoes a structural cubic-to-tetragonal transition near 800 K which is caused by the cooperative rotations of O6 octahedra. These rotations are also accompanied by the displacements of the cations and the formation of the polar nanodomains (PNDs) that are responsible for the characteristic dielectric dispersion of relaxor ferroelectrics. Because of their intrinsic properties, spontaneous polarization, and lack of inversion symmetry, these PNDs are also piezoelectric and can mediate an interaction between polarization and strain or couple the optic and acoustic phonons. Because PNDs introduce a local tetragonal symmetry, the phonon coupling they mediate is found to be anisotropic. In this paper we present inelastic neutron scattering results on coupled transverse acoustic (TA) and transverse optic (TO) phonons in the [110] and [001] directions and across the cubic-tetragonal phase transition at TC˜800 K. The phonon spectra are analyzed using a mode coupling model. In the [110] direction, as in other relaxors and some ferroelectric perovskites, a precipitous drop of the TO phonon into the TA branch or "waterfall" is observed at a certain qwf˜0.14 r.l.u. In the [001] direction, the highly overdamped line shape can be fitted with closely positioned bare mode energies which are largely overlapping along the dispersion curves. Two competing lattice coupling mechanism are proposed to explain these observations.

  20. Pyroelectric waste heat energy harvesting using relaxor ferroelectric 8/65/35 PLZT and the Olsen cycle

    NASA Astrophysics Data System (ADS)

    Lee, Felix Y.; Goljahi, Sam; McKinley, Ian M.; Lynch, Christopher S.; Pilon, Laurent

    2012-02-01

    Waste heat can be directly converted into electrical energy by performing the Olsen cycle on pyroelectric materials. The Olsen cycle consists of two isothermal and two isoelectric field processes in the electric displacement versus electric field diagram. This paper reports on the electrical energy generated by lanthanum-doped lead zirconate titanate (8/65/35 PLZT) subjected to the Olsen cycle. The material was alternately dipped into a cold and a hot silicone oil bath under specified electric fields. A maximum energy density of 888 J l-1/cycle was obtained with a 290 µm thick 8/65/35 PLZT sample for temperatures between 25 and 160 °C and electric fields cycled between 0.2 and 7.5 MV m-1. To the best of our knowledge, this is the largest pyroelectric energy density experimentally measured with multiple cycles. It corresponded to a power density of 15.8 W l-1. The electrical breakdown strength and therefore the energy and power densities of the material increased as the sample thickness was reduced from 720 to 290 µm. Furthermore, a physical model for estimating the energy harvested by ferroelectric relaxors was further validated against experimental data for a wide range of electric fields and temperatures.

  1. Phonon coupling to dynamic short-range polar order in a relaxor ferroelectric near the morphotropic phase boundary

    SciTech Connect

    John A. Schneeloch; Xu, Zhijun; Winn, B.; Stock, C.; Gehring, P. M.; Birgeneau, R. J.; Xu, Guangyong

    2015-12-28

    We report neutron inelastic scattering experiments on single-crystal PbMg1/3Nb2/3O3 doped with 32% PbTiO3, a relaxor ferroelectric that lies close to the morphotropic phase boundary. When cooled under an electric field E∥ [001] into tetragonal and monoclinic phases, the scattering cross section from transverse acoustic (TA) phonons polarized parallel to E weakens and shifts to higher energy relative to that under zero-field-cooled conditions. Likewise, the scattering cross section from transverse optic (TO) phonons polarized parallel to E weakens for energy transfers 4 ≤ ℏω ≤ 9 meV. However, TA and TO phonons polarized perpendicular to E show no change. This anisotropic field response is similar to that of the diffuse scattering cross section, which, as previously reported, is suppressed when polarized parallel to E but not when polarized perpendicular to E. Lastly, our findings suggest that the lattice dynamics and dynamic short-range polar correlations that give rise to the diffuse scattering are coupled.

  2. Phonon coupling to dynamic short-range polar order in a relaxor ferroelectric near the morphotropic phase boundary

    DOE PAGESBeta

    John A. Schneeloch; Xu, Zhijun; Winn, B.; Stock, C.; Gehring, P. M.; Birgeneau, R. J.; Xu, Guangyong

    2015-12-28

    We report neutron inelastic scattering experiments on single-crystal PbMg1/3Nb2/3O3 doped with 32% PbTiO3, a relaxor ferroelectric that lies close to the morphotropic phase boundary. When cooled under an electric field E∥ [001] into tetragonal and monoclinic phases, the scattering cross section from transverse acoustic (TA) phonons polarized parallel to E weakens and shifts to higher energy relative to that under zero-field-cooled conditions. Likewise, the scattering cross section from transverse optic (TO) phonons polarized parallel to E weakens for energy transfers 4 ≤ ℏω ≤ 9 meV. However, TA and TO phonons polarized perpendicular to E show no change. This anisotropicmore » field response is similar to that of the diffuse scattering cross section, which, as previously reported, is suppressed when polarized parallel to E but not when polarized perpendicular to E. Lastly, our findings suggest that the lattice dynamics and dynamic short-range polar correlations that give rise to the diffuse scattering are coupled.« less

  3. Phonon coupling to dynamic short-range polar order in a relaxor ferroelectric near the morphotropic phase boundary

    NASA Astrophysics Data System (ADS)

    Schneeloch, John A.; Xu, Zhijun; Winn, B.; Stock, C.; Gehring, P. M.; Birgeneau, R. J.; Xu, Guangyong

    2015-12-01

    We report neutron inelastic scattering experiments on single-crystal PbMg1 /3Nb2 /3O3 doped with 32% PbTiO3, a relaxor ferroelectric that lies close to the morphotropic phase boundary. When cooled under an electric field E ∥ [001] into tetragonal and monoclinic phases, the scattering cross section from transverse acoustic (TA) phonons polarized parallel to E weakens and shifts to higher energy relative to that under zero-field-cooled conditions. Likewise, the scattering cross section from transverse optic (TO) phonons polarized parallel to E weakens for energy transfers 4 ≤ℏ ω ≤9 meV. However, TA and TO phonons polarized perpendicular to E show no change. This anisotropic field response is similar to that of the diffuse scattering cross section, which, as previously reported, is suppressed when polarized parallel to E but not when polarized perpendicular to E . Our findings suggest that the lattice dynamics and dynamic short-range polar correlations that give rise to the diffuse scattering are coupled.

  4. Nanoscale phase quantification in lead-free (Bi1 /2Na1 /2) TiO3-BaTiO3 relaxor ferroelectrics by means of 23Na NMR

    NASA Astrophysics Data System (ADS)

    Groszewicz, Pedro B.; Breitzke, Hergen; Dittmer, Robert; Sapper, Eva; Jo, Wook; Buntkowsky, Gerd; Rödel, Jürgen

    2014-12-01

    We address the unsolved question on the structure of relaxor ferroelectrics at the atomic level by characterizing lead-free piezoceramic solid solutions (100 -x ) (Bi1 /2Na1 /2) TiO3-x BaTiO3 (BNT -x BT ) (for x =1 ,4 ,6 , and 15). Based on the relative intensity between spectral components in quadrupolar perturbed 23Na nuclear magnetic resonance, we present direct evidence of the coexistence of cubic and polar local symmetries in these relaxor ferroelectrics. In addition, we demonstrate how the cubic phase vanishes whenever a ferroelectric state is induced, either by field cooling or changing the dopant amount, supporting the relation between this cubic phase and the relaxor state.

  5. Octahedral tilt transitions in the relaxor ferroelectric Na1/2Bi1/2TiO3

    NASA Astrophysics Data System (ADS)

    Meyer, Kai-Christian; Gröting, Melanie; Albe, Karsten

    2015-07-01

    The kinetics of octahedral tilt transitions in the lead-free relaxor material sodium bismuth titanate Na1/2Bi1/2TiO3 (NBT) is investigated by electronic structure calculations within density functional theory. Energy barriers for transitions between tetragonal, rhombohedral and orthorhombic tilts in cation configurations with [001]- and [111]-order on the A-sites are determined by nudged elastic band calculations. By tilting entire layers of octahedra simultaneously we find that the activation energy is lower for structures with 001-order compared to such with 111-order. The energetic coupling between differently tilted layers is, however, negligibly small. By introducing a single octahedral defect we create local tilt disorder and find that the deformation energy of the neighboring octahedra is less in a rhombohedral than in a tetragonal structure. By successively increasing the size of clusters of orthorhombic defects in a rhombohedral matrix with 001-order, we determine a critical cluster size of about 40 Å . Thus groups of about ten octahedra can be considered as nuclei for polar nanoregions, which are the cause of the experimentally observed relaxor behavior of NBT.

  6. Temperature evolution of the local order parameter in relaxor ferroelectrics (1 - x)PMN-xPZT

    NASA Astrophysics Data System (ADS)

    Gridnev, S. A.; Glazunov, A. A.; Tsotsorin, A. N.

    2005-09-01

    The temperature dependence of the local order parameter and relaxation time distribution function have been determined in (1 - x)PMN-xPZT ceramic samples via dielectric permittivity. Above the Burns temperature, the permittivity was found to follow the Currie-Weiss law, and with temperature decreasing the deviation was observed to increase. A local order parameter was calculated from the dielectric data using a modified Landau-Devonshire approach. These results are compared to the distribution function of relaxation times. It was found that a glasslike freezing of reorientable polar clusters occurs in the temperature range of diffuse relaxor transition. The evolution of the studied system to more ordered state arises from the increased PZT content.

  7. X-ray absorption spectroscopy of Ru-doped relaxor ferroelectrics with a perovskite-type structure

    NASA Astrophysics Data System (ADS)

    Vitova, T.; Mangold, S.; Paulmann, C.; Gospodinov, M.; Marinova, V.; Mihailova, B.

    2014-04-01

    X-ray absorption near-edge structure and extended x-ray absorption fine structure spectroscopy at the Ru K edge of Ru-doped PbSc0.5Ta0.5O3 (PST-Ru), PbSc0.5Nb0.5O3 (PSN-Ru), and 0.9PbZn1/3Nb2/3O3-0.1PbTiO3 (PZN-0.1PT-Ru) as well as at the Ta L3 edge of PST-Ru and the Nb K edge of PSN-Ru was applied to study the short- and intermediate-range atomic arrangements in perovskite-type (ABO3) relaxor ferroelectrics. The compounds were also analyzed by complementary Raman scattering, visible/near-visible absorption spectroscopy, and synchrotron x-ray single-crystal diffraction. The results show that Ru is octahedrally coordinated in all three relaxor host matrices but the average oxidation state of Ru in PST-Ru and PSN-Ru is ˜4.4, whereas it is ˜3.8 in PZN-0.1PT-Ru. In PbSc0.5B''0.5O3 (B'' = Ta, Nb) Ru substitutes for the B'' cations in the form of isolated point defects, while in PZN-0.1PT-Ru Ru replaces adjacent A and B sites, forming a chainlike structural species of face-sharing elongated octahedra. Chemical 1:1 B-site order as well as dynamic BO6 tilting is observed around both the Ru dopant and the major B'' cation in PST-Ru and PSN-Ru regardless of the fact that according to x-ray diffraction at ambient conditions, the average structure is cubic with weak or no long-range chemical order. Pb cations are off-center displaced from the prototypic cubic A site for all three compounds and in Ru-doped PbSc0.5B''0.5O3 the BO6 tilt angle correlates with the degree of coherent B-Pb distances.

  8. Chemically induced renormalization phenomena in Pb-based relaxor ferroelectrics under high pressure

    NASA Astrophysics Data System (ADS)

    Mihailova, B.; Waeselmann, N.; Maier, B. J.; Angel, R. J.; Prüßmann, T.; Paulmann, C.; Gospodinov, M.; Bismayer, U.

    2013-03-01

    The pressure-induced phase transition sequence in PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nb0.5O3 (PSN) heavily doped with homo- and heterovalent cations on the A- or B-site of the perovskite-type structure (ABO3) was analysed by in situ synchrotron x-ray diffraction and Raman spectroscopy up to pressures of 25 GPa. We focused on the structural phenomena occurring above the first pressure-induced phase transition at pc1 from a relaxor state to a non-polar rhombohedral phase with antiphase tilting of the BO6 octahedra. The samples studied were PST doped with Nb5+ and Sn4+ on the B-site, PST doped with Ba2+ and La3+ on the A-site and PSN doped with Sr2+ and La3+ on the A-site. All of them exhibit a second pressure-induced phase transition at pc2, similar to pure PST and PSN. The second transition involves the development of either order of antiparallel Pb2+ displacements and complementary a+b-b- octahedral tilts, or a-b-b- (0 ≤ a < b) tilting alone. As in pure PST and PSN, the second phase transition is preceded by the occurrence of unequal octahedral tilts on the local scale. The substitution of Nb5+ for Ta5+ as well as the coupled substitution of Sn4+ for Sc3+ + Ta5+ on the octahedral B sites increases the second critical pressure. The doping by Nb5+ also reduces the length of coherence of antipolar Pb2+ order developed at pc2. The isovalent substitution of the larger Ba2+ for Pb2+ on the A-site suppresses the antipolar Pb2+ order due to the induced local elastic stresses and thus significantly increases pc2. The substitution of smaller cations for Pb2+ on the A-site generally favours the development of long-range order of antiparallel Pb2+ displacements because of the chemically enhanced a-a-a- octahedral tilts. However, this ordering is less when the dopant is aliovalent, due to the charge imbalance on the A-site. For all of the relaxors studied here, the dynamic compressibility estimated from the pressure derivative of the wavenumber of the soft mode associated with

  9. Enhanced dielectric constant and relaxor behavior realized by dual stage sintering of Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6}

    SciTech Connect

    Rathore, Satyapal S. Vitta, Satish

    2014-04-24

    The relaxor ferroelectric compound, Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} (SBN50) was synthesized by solid state reaction followed by sintering under two different conditions: single and dual stage sintering. The impact of sintering process on structural and dielectric properties has been studied in detail using X-ray diffraction, scanning electron microscopy and broadband dielectric spectroscopy. The crystal structure determined by performing Rietveld refinement of X-ray diffractogram was found to be identical in both cases. SBN50 crystallizes in the ferroelectric tetragonal tungsten bronze, P4bm structure. It was observed that uniform grain growth can be controlled by dual stage sintering and relatively narrow distribution of grains can be achieved with an average grain size of ∼15 μm. The dielectric studies show that SBN50 exhibits a relaxor ferroelectric behavior with the transformation taking place at ∼ 380 K due to formation of polar nano regions. Although both single and dual stage sintered SBN50 exhibits relaxor behaviour, the maximum dielectric constant of dual stage sintered SBN50 is found to be 1550 compare to 1440 for single stage sintering.

  10. Relaxor Behavior and Dielectric Properties of Bi(Zn2/3Nb1/3)O3-Modified BaTiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Xiuli; Chen, Jie; Huang, Guisheng; Ma, Dandan; Fang, Lang; Zhou, Huanfu

    2015-12-01

    (1 - x)BaTiO3- xBi(Zn2/3Nb1/3)O3 [(1 - x)BT- xBZN, 0 ≤ x ≤ 0.2] ceramics were prepared via a conventional solid-state reaction method. X-ray diffraction (XRD) patterns and Raman spectra analysis show that the ceramics are tetragonal phase when x ≤ 0.02, and transform to pseudocubic phase as x ≥ 0.06. The temperature and frequency dependences of relative permittivity indicate a gradual crossover from a classic ferroelectric to relaxor ferroelectric. The dielectric relaxor behavior follows a modified Curie-Weiss law. The degree of the phase transition diffuseness ( γ) and the deviation from the Curie-Weiss law (Δ T_{{d}} ) increase to the maximum at x = 0.08, and subsequently decrease with further increasing x values, which associated with the appearance of polar nanoregions on account of the formation of random fields included local electric fields and elastic fields. Nevertheless, the random fields may decrease by reason of the interaction between the local electric fields and elastic fields.

  11. Determination of 60° polarization nanodomains in a relaxor-based ferroelectric single crystal

    SciTech Connect

    Kim, Kyou-Hyun; Zuo, Jian-Min; Payne, David A.

    2015-10-19

    Here, we report a determination of monoclinic nanodomains in PMN-xPT with x = 31%PT by using scanning convergent beam electron diffraction (SCBED). We show the presence of 60 ± α degree nanodomains with Cm-like symmetry as well as significant variations (α) in local polarization directions across lengths of ∼10 nm. The principle of our technique is general and can be applied for the determination of polarization domains in other ferroelectric materials of different symmetry.

  12. Influence of lanthanum doping on the dielectric, ferroelectric and relaxor behaviour of barium bismuth titanate ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Varma, K. B. R.

    2009-04-01

    Barium lanthanum bismuth titanate (Ba1-(3/2)xLaxBi4Ti4O15, x = 0-0.4) ceramics were fabricated using the powders synthesized via the solid-state reaction route. X-ray powder diffraction analysis confirmed the above compositions to be monophasic and belonged to the m = 4 member of the Aurivillius family of oxides. The effect of the partial presence of La3+ on Ba2+ sites on the microstructure, dielectric and relaxor behaviour of BaBi4Ti4O15 (BBT) ceramics was investigated. For the compositions pertaining to x <= 0.1, the dielectric constant at both room temperature and in the vicinity of the temperature of the dielectric maximum (Tm) of the parent phase (BBT) increased significantly with an increase in x while Tm remained almost constant. Tm shifted towards lower temperatures accompanied by a decrease in the magnitude of the dielectric maximum (ɛm) with an increase in the lanthanum content (0.1 < x <= 0.4). The dielectric relaxation was modelled using the Vogel-Fulcher relation and a decrease in the activation energy for frequency dispersion with increasing x was observed. The frequency dispersion of Tm was found to decrease with an increase in lanthanum doping, and for compositions corresponding to x >= 0.3, Tm was frequency independent. Well-developed P(polarization)-E(electric field) hysteresis loops were observed at 150 °C for all the samples and the remanent polarization (2Pr) was improved from 6.3 µC cm-2 for pure BBT to 13.4 µC cm-2 for Ba0.7La0.2Bi4Ti4O15 ceramics. Dc conductivities and associated activation energies were evaluated using impedance spectroscopy.

  13. Resonance Raman scattering of perovskite-type relaxor ferroelectrics under nonambient conditions

    NASA Astrophysics Data System (ADS)

    de la Flor, G.; Wehber, M.; Rohrbeck, A.; Aroyo, M. I.; Bismayer, U.; Mihailova, B.

    2014-08-01

    Resonance Raman scattering (RRS) of two model perovskite-type (ABO3) relaxor compounds PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nb0.5O3 (PSN) excited with a laser wavelength of 325 nm (3.8 eV) is studied at different temperatures and ambient pressure as well as at high pressures and room temperature (for PST). The origin of the observed RRS is reinspected by applying group-theory analysis of phonons compatible with symmetry-allowed electron transitions in cubic and possible polar and nonpolar rhombohedral ferroic structures. It is shown that the simultaneous enhancement of first- and second-order RRS generated by antisymmetric BO6 bending and stretching modes under resonance conditions when the photon energy is slightly above the energy gap Eg˜3.2eV results exclusively from spatial regions with coherent polar structural distortions. Upon cooling RRS appears in the vicinity of the characteristic temperature T*, and its total intensity significantly increases upon further temperature decrease. The predominate type of BO6 polarity changes from related to difference in B-O bonds to related to distorted O-B-O bond angles. At room temperature and high pressures RRS drops in intensity above the critical pressure of development of long-range antiphase octahedral tilting. However it persists up to 8.3 GPa, which is the highest pressure reached in the experiment, indicating that the high-pressure phase is polar due to the slight BO6 distortions accompanying the tilt order.

  14. Effect of dead layer and strain on diffuse phase transition of PLZT relaxor thin films.

    SciTech Connect

    Tong, S.; Narayanan, M.; Ma, B.; Koritala, R. E.; Liu, S.; Balachandran, U.; Shi, D.

    2011-02-01

    Bulk relaxor ferroelectrics exhibit excellent permittivity compared to their thin film counterpart, although both show diffuse phase transition (DPT) behavior unlike normal ferroelectrics. To better understand the effect of dead layer and strain on the observed anomaly in the dielectric properties, we have developed relaxor PLZT (lead lanthanum zirconate titanate) thin films with different thicknesses and measured their dielectric properties as a function of temperature and frequency. The effect of dead layer on thin film permittivity has been found to be independent of temperature and frequency, and is governed by the Schottky barrier between the platinum electrode and PLZT. The total strain (thermal and intrinsic) in the film majorly determines the broadening, dielectric peak and temperature shift in the relaxor ferroelectric. The Curie-Weiss type law for relaxors has been further modified to incorporate these two effects to accurately predict the DPT behavior of thin film and bulk relaxor ferroelectrics. The dielectric behavior of thin film is predicted by using the bulk dielectric data from literature in the proposed equation, which agree well with the measured dielectric behavior.

  15. Structured diffuse scattering and polar nano-regions in the Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} relaxor ferroelectric system

    SciTech Connect

    Liu Yun; Withers, Ray L. Wei Xiaoyong; Fitz Gerald, John D.

    2007-03-15

    The observation via electron diffraction of relatively sharp G{+-}{l_brace}001{r_brace}* sheets of diffuse intensity arising from the large amplitude excitation of inherently polar, transverse optical modes of distortion in Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} (BTS), 0.1{<=}x{<=}0.5, samples, both at room temperature as well as liquid nitrogen temperature, shows that the polar nano-regions (PNRs) in these relaxor ferroelectric materials correspond to the same highly anisotropic <001> chain dipoles as are characteristic of the normal ferroelectric end member BaTiO{sub 3} itself. The correlation length along the chain of these 1-d PNRs can, in principle, be determined from the width of the observed {l_brace}001{r_brace}* diffuse sheets in reciprocal space and is estimated to be at least 5 nm even for the higher x samples. The distribution of the substitutional Sn ions thus appears to have only a minor effect upon the correlation length along the <001> chain dipole directions. It is suggested that the role of the dopant Sn ions is not to directly induce PNRs but rather to set up random local strain fields preventing the condensation of long wavelength homogeneous strain distortions of the unit cell thereby suppressing transverse correlations of the <001> chain dipoles and the development of long-range ordered ferroelectric state/s. - Graphical abstract: The characteristic G{+-}{l_brace}001{r_brace}* sheets of diffuse intensity characteristic of the relaxor ferroelectric Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} (BTS), 0.1{<=}x{<=}0.5, system along with the inherently polar, transverse optical modes of distortion responsible.

  16. Interplay between pressure and local symmetry in (Pb1 -3 /2 xLax)(Zr60Ti40)O3: Emergence of a relaxor state

    NASA Astrophysics Data System (ADS)

    Nahas, Y.; Prokhorenko, S.; Kornev, I.

    2014-11-01

    This study aims at inquiring into the role of hydrostatic pressure in driving the relaxor behavior within a local-symmetry-based approach to relaxor ferroelectrics. Results reveal the occurrence of a pressure-induced ferroelectric-to-relaxor crossover, clearly reflected in the experiment-matching temperature-pressure phase diagram of lanthanum-modified lead zirconate titanate. Relaxor behavior is found to occur under pressure and upon cooling due to the nucleation of local order within fractal regions, as an incipient state towards percolating ferroelectric order. Further analysis of the geometrical features of ordering process points to a manifest nontrivial disruption of the balance between competing interactions under the conjugated effects of pressure and local-symmetry constraints.

  17. Variation of Piezoelectric properties and mechanisms across the relaxor-like/Ferroelectric continuum in BiFeO3- (K0.5Bi0.5)TiO3-PbTiO3 ceramics.

    PubMed

    Bennett, James; Shrout, Thomas R; Zhang, Shujun; Owston, Heather E; Stevenson, Tim J; Esat, Faye; Bell, Andrew J; Comyn, T P

    2015-01-01

    1- x - y)BiFeO3-x(K0.5Bi0.5)TiO3-yPbTiO3 (BFKBT- PT) piezoelectric ceramics were investigated across the compositional space and contrasted against the xBiFeO3- (1-x)(K0.5Bi0.5)TiO3 (BF-KBT) system, whereby a range of relaxor-like/ferroelectric behavior was observed. Structural and piezoelectric properties were closely related to the PbTiO3 concentration; below a critical concentration, relaxor-like behavior was identified. The mechanisms governing the piezoelectric behavior were investigated with structural, electrical, and imaging techniques. X-ray diffraction established that longrange non-centrosymmetric crystallographic order was evident above a critical PbTiO3 concentration, y > 0.1125. Commensurate with the structural analysis, electric-field-induced strain responses showed electrostrictive behavior in the PbTiO3-reduced compositions, with increased piezoelectric switching in PbTiO3-rich compositions. Positive-up-negative-down (PUND) analysis was used to confirm electric-field-induced polarization measurements, elucidating that the addition of PbTiO3 increased the switchable polarization and ferroelectric ordering. Piezoresponse force microscopy (PFM) of the BF-KBT-PT system exhibited typical domain patterns above a critical PbTiO3 threshold, with no ferroelectric domains observed in the BF-KBT system in the pseudocubic region. Doping of BiFeO3-PbTiO3 has been unsuccessful in the search for hightemperature materials that offer satisfactory piezoelectric properties; however, this system demonstrates that the partial substitution of alternative end-members can be an effective method. The partial substitution of PbTiO3 into BF-KBT enables long-range non-centrosymmetric crystallographic order, resulting in increased polar order and TC, compared with the pseudocubic region. The search for novel high-temperature piezoelectric ceramics can therefore exploit the accommodating nature of the perovskite family, which allows significant variance in chemical and physical

  18. Piezoelectric response enhancement in the proximity of grain boundaries of relaxor-ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Brewer, Steven; Deng, Carmen; Callaway, Connor; Kalinin, Sergei V.; Vasudevan, Rama K.; Bassiri-Gharb, Nazanin

    2016-06-01

    The influence of surface morphology on the local piezoelectric response of highly (100)-textured 0.70PbMg2/3Nb1/3O3-0.30PbTiO3 thin films is studied using piezoresponse force microscopy in band-excitation mode. The local electromechanical response is mostly suppressed in direct proximity of the grain boundaries. However, within 100-200 nm of the grain boundary, the piezoresponse is substantially enhanced, before decaying again within a region at the center of the grain itself. Nested piezoresponse hysteresis curves confirm the influence of topography descriptors on parameters affecting the hysteresis loop shape. The enhancement of the electromechanical response is rationalized through reduced lateral clamping in the grains with deep trenched boundaries, as well as an expected lower energy for complex domain wall structures, due to curved ferroelectric surfaces. The lower piezoresponse at the center of the grain is assigned to the lateral clamping by the surrounding piezoelectric material.

  19. Dielectric relaxation and resonance in relaxor ferroelectric K1-xLixTaO3

    NASA Astrophysics Data System (ADS)

    Pattnaik, R. K.; Toulouse, J.

    1999-09-01

    Polar regions are shown to mediate a strong coupling between polarization and strain in the paraelectric phase of the mixed ferroelectric K1-xLixTaO3 (KLT) and KTa1-xNbxO3 resulting in a field-induced piezoelectric response. The coupling is shown to result in a resonance in the dielectric spectrum of the crystals. In KLT, polar nanoregions can reorient via 180° (π relaxation) or 90° (π/2 relaxation) rotations. While the π relaxation is of no consequence, the π/2 relaxation has a strong influence on the overall character of the resonance. In addition to providing a mechanism for loss and degradation of the quality factor, this relaxation alters the character of the resonance as the two cross. Experimental results from dielectric spectroscopy above and below this crossover are presented and discussed. A simple theoretical Debye model involving the electrostrictive polarization-strain coupling is presented and the calculated spectrum is shown to reproduce the experimental spectrum. The parameters derived from the model are discussed. Most significantly, the electrostrictive coefficient of KLT is found to be 100 times larger than that of BaTiO3, and is due to the presence of polar nanoregions.

  20. Processing and Reduced Sintering Temperature of Relaxor Ferroelectric Lead Zinc Niobate - Lead Nickel Niobate/lead Titanate Ceramics for Capacitor Applications

    NASA Astrophysics Data System (ADS)

    Vierheilig, Albert A.

    This dissertation investigates processing and property issues between relaxor ferroelectric Lead Zinc Niobate(PZN) and Lead Nickel Niobate(PNN), and the normal ferroelectric, Lead Titanate(PT). These materials were studied with regard to dielectric properties for potential usage in capacitor applications. Compositions in the xPZN-(1-x)PNN binary system were prepared over a range of x = 0 to x = 0.94. The use of the mixed oxide processing technique resulted in substantial pyrochlore phase formation while use of the B-site precursor technique significantly reduced the pyrochlore phase. Peak dielectric constant was a maximum at x = 0.70, with a value of 8,800 at a T_ c of 46 ^circC, following firing at 1125^circC/2 hours. The addition of PT to the PZN-PNN system was performed to optimize dielectric properties. A composition was identified which possessed a room temperature dielectric constant of 12,000 (0.46PZN-0.46PNN-0.08PT). To further optimize dielectric properties, several processing variables were studied, including excess PbO additions to starting batches, firing configuration, powder purity and post-fire thermal annealing. Thermal annealing was found to improve dielectric constant by 50% in the x = 0.65, x = 0.75 and 0.46PZN-0.46PNN -0.08PT systems. The x = 0.75 composition showed an increase in dielectric constant, despite the increased amount of pyrochlore phase present with increased annealing time. The other compositions showed negligible pyrochlore phase for all firing temperatures studied. The increase in K was due to increased grain development and decreased grain boundary phase. A reduction in processing temperature from 1075 to 950^circC using lithium -based fluxing sintering aids was demonstrated in the 0.46PZN -0.46PNN-0.08PT composition, with an improvement in density to 96% with only a 1% Li^+ concentration. Despite this large improvement, dielectric constant improved minimally. A systematic study comparing the effects of LiNO _3, Li_2CO_3 and Li

  1. Novel optically active lead-free relaxor ferroelectric (Ba0.6Bi0.2Li0.2)TiO3

    NASA Astrophysics Data System (ADS)

    Borkar, Hitesh; Rao, Vaibhav; Dutta, Soma; Barvat, Arun; Pal, Prabir; Tomar, M.; Gupta, Vinay; Scott, J. F.; Kumar, Ashok

    2016-07-01

    We discovered a near-room-temperature lead-free relaxor-ferroelectric (Ba0.6Bi0.2Li0.2)TiO3 (BBLT) having A-site compositionally disordered ABO3 perovskite structure. Microstructure-property relations revealed that the chemical inhomogeneities and development of local polar nano-regions (PNRs) are responsible for dielectric dispersion as a function of probe frequencies and temperatures. Rietveld analysis indicates mixed crystal structure with 80% tetragonal structure (space group P4mm) and 20% orthorhombic structure (space group Amm2), which is confirmed by the high resolution transmission electron diffraction (HRTEM). Dielectric constant and tangent loss dispersion with and without illumination of light obey nonlinear Vogel–Fulcher (VF) relations. The material shows slim polarization–hysteresis (P–E) loops and excellent displacement coefficients (d 33 ~ 233 pm V‑1) near room temperature, which gradually diminish near the maximum dielectric dispersion temperature (T m ). The underlying physics for light-sensitive dielectric dispersion was probed by x-ray photon spectroscopy (XPS), which strongly suggests that mixed valence of bismuth ions, especially Bi5+ ions, comprise most of the optically active centers. Ultraviolet photoemission measurements showed most of the Ti ions are in 4 +  states and sit at the centers of the TiO6 octahedra; along with asymmetric hybridization between O 2p and Bi 6s orbitals, this appears to be the main driving force for net polarization. This BBLT material may open a new path for environmental friendly lead-free relaxor-ferroelectric research.

  2. Novel optically active lead-free relaxor ferroelectric (Ba0.6Bi0.2Li0.2)TiO3.

    PubMed

    Borkar, Hitesh; Rao, Vaibhav; Dutta, Soma; Barvat, Arun; Pal, Prabir; Tomar, M; Gupta, Vinay; Scott, J F; Kumar, Ashok

    2016-07-01

    We discovered a near-room-temperature lead-free relaxor-ferroelectric (Ba0.6Bi0.2Li0.2)TiO3 (BBLT) having A-site compositionally disordered ABO3 perovskite structure. Microstructure-property relations revealed that the chemical inhomogeneities and development of local polar nano-regions (PNRs) are responsible for dielectric dispersion as a function of probe frequencies and temperatures. Rietveld analysis indicates mixed crystal structure with 80% tetragonal structure (space group P4mm) and 20% orthorhombic structure (space group Amm2), which is confirmed by the high resolution transmission electron diffraction (HRTEM). Dielectric constant and tangent loss dispersion with and without illumination of light obey nonlinear Vogel-Fulcher (VF) relations. The material shows slim polarization-hysteresis (P-E) loops and excellent displacement coefficients (d 33 ~ 233 pm V(-1)) near room temperature, which gradually diminish near the maximum dielectric dispersion temperature (T m ). The underlying physics for light-sensitive dielectric dispersion was probed by x-ray photon spectroscopy (XPS), which strongly suggests that mixed valence of bismuth ions, especially Bi(5+) ions, comprise most of the optically active centers. Ultraviolet photoemission measurements showed most of the Ti ions are in 4 +  states and sit at the centers of the TiO6 octahedra; along with asymmetric hybridization between O 2p and Bi 6s orbitals, this appears to be the main driving force for net polarization. This BBLT material may open a new path for environmental friendly lead-free relaxor-ferroelectric research. PMID:27165848

  3. Chemical order and local structure of the lead-free relaxor ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}

    SciTech Connect

    Groeting, Melanie; Hayn, Silke; Albe, Karsten

    2011-08-15

    The A-site mixed perovskite sodium bismuth titanate (Na{sub 1/2}Bi{sub 1/2})TiO{sub 3} (NBT) is investigated by means of first-principles calculations based on density functional theory. By studying different geometries with varying occupations of the A-site, the influence of chemical order on the thermodynamic stability and local structure is explored. We find that the hybridization of Bi 6sp with O 2p-states leads to stereochemically active Bi{sup 3+} lone pairs and increases the stability of structures with high Bi concentrations in {l_brace}001{r_brace}-planes. This goes along with displacive disorder on the oxygen sublattice, which up to now has been neglected in experimental studies. The calculated ordering energies are, however, small as compared to the thermal energy and therefore only short-range chemical order can be expected in experiments. Thus, it is conceivable that chemically ordered local areas can act as nucleation sites for polar nano-regions, which would explain the experimentally observed relaxor behavior of NBT. - Graphical abstract: First-principles calculations give relative stabilities of different chemically ordered structures. The results suggest a new model for the local structure of Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} with 001-ordered nano-regions embedded in a chemically disordered matrix. Chemical order/disorder additionally induces displacive disorder within the oxygen sublattice. Highlights: > Lead-free relaxor ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} is studied by ab initio-calculations. > Structural relaxations in the oxygen sublattice are decisive for relative stabilities. > Chemical environment of oxygen determines relaxation ability. > Bi 6s{sup 2} lone pair formation is the driving force for relaxation. > New structure model: Chemically 001-ordered nano-regions embedded in disordered matrix.

  4. The effect of in-situ high-temperature high-pressure on the structural changes of single-crystal relaxor ferroelectrics PbSc1/2Ta1/2O3 (PST) and PbSc1/2Nb1/2O3 (PSN)

    NASA Astrophysics Data System (ADS)

    Waeselmann, Naemi; Mihailova, Boriana; Gospodinov, Marin; Bismayer, Ullrich

    2013-06-01

    Relaxor ferroelectrics (relaxor) of the perovskite structure (ABO3) have remarkably high dielectric permittivity dependent on temperature and frequency as well as remarkable piezoelectric and electro-optic coefficients. These structurally heterogeneous materials undergo a sequence of structural changes on the mesoscopic scale associated with characteristic temperatures resulting from the development of polar order on temperature decrease. Pressure increase on the other hand favors antiferrodistortive order at room temperature. To explore the importance of the antiferrodistortive coupling on the development of polar order simultaneous high-temperature high-pressure Raman studies were undertaken on single crystals of PST and PSN from 400-600 K over pressures extending to 9 GPa. We find that the first pressure-induced transition pc1 decreases with temperature while the second transition pc2 is relatively temperature independent. The behavior of pc1 is interpreted as a weakening of the polar coupling, which in turn facilitates the evolution of the preexisting medium-range antiferodistortive order into a long-range order. The near constant value of pc2 suggests that it is independent of the state of polar coupling and is mainly related to the initial correlation length of antiferrodistortive order. Thus the coexistence of both polar order and antiferrodistortive order is required for the occurrence of the relaxor state. Now at: University of Washington.

  5. Development of nanoscale polarization fluctuations in relaxor-based (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 ferroelectrics studied by Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Tsukada, Shinya; Hidaka, Yuki; Kojima, Seiji; Bokov, Alexei A.; Ye, Zuo-Guang

    2013-01-01

    The precursor dynamics of ferroelectric phase transitions in relaxor-based ferroelectric (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 single crystals, with x=0.07, 0.10, and 0.12, were investigated using inelastic light scattering from a longitudinal acoustic phonon. An acoustic anomaly in a broad temperature range, which is characteristic of relaxor ferroelectrics, was observed. We describe the anomalies in the paraelectric phase by assuming local piezoelectric coupling inside polar nanoregions, which are surrounded by a nonpolar matrix. On the basis of local piezoelectric coupling, a relaxation time τ and a dynamic characteristic length L of the order-parameter (polarization) fluctuations were determined to be in the order of 10-13 s and 10-9 m, respectively. The τ and L values increase sharply upon cooling from high temperatures but more gradually below the intermediate temperature T* (=493-510K). This result implies that the local polarization fluctuations grow rapidly upon cooling down to above T* and the growth rate decreases below T*. The inflexion point of this growth process in the paraelectric phase is related to the characteristic properties of relaxor-based solid solutions.

  6. Visualization of polar nanoregions in lead-free relaxors via piezoresponse force microscopy in torsional dual AC resonance tracking mode

    NASA Astrophysics Data System (ADS)

    Liu, Na; Dittmer, Robert; Stark, Robert W.; Dietz, Christian

    2015-07-01

    Polar nanoregions (PNRs) play a key role in the functionality of relaxor ferroelectrics; however, visualizing them in lead-free relaxor ferroelectrics with high lateral resolution is still challenging. Thus, we studied herein the local ferroelectric domain distribution of the lead-free bismuth-based (1 - x)(Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3) - x(Bi1/2Mg1/2TiO3) piezoceramics which show a relaxor behavior using dual AC resonance tracking (DART) piezoresponse force microscopy (PFM). By using excitation frequencies at either side of the contact resonance peak of the torsional cantilever vibration, an enhanced contrast in the amplitude and phase images of the piezoresponse can be achieved. Additionally, this tracking technique reduces the topographical crosstalk while mapping the local electromechanical properties. The true drive amplitude, drive phase, contact resonant frequency and quality factor can be estimated from DART-PFM data obtained with vertically or torsionally vibrating cantilevers. This procedure yields a three-dimensional quantitative map of the local piezoelectric properties of the relaxor ferroelectric samples. With this approach, torsional DART allowed for the visualization of fine substructures within the monodomains, suggesting the existence of PNRs in relaxor ferroelectrics. The domain structures of the PNRs were visualized with high precision, and the local electromechanical characteristics of the lead-free relaxor ferroelectrics were quantitatively mapped.Polar nanoregions (PNRs) play a key role in the functionality of relaxor ferroelectrics; however, visualizing them in lead-free relaxor ferroelectrics with high lateral resolution is still challenging. Thus, we studied herein the local ferroelectric domain distribution of the lead-free bismuth-based (1 - x)(Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3) - x(Bi1/2Mg1/2TiO3) piezoceramics which show a relaxor behavior using dual AC resonance tracking (DART) piezoresponse force microscopy (PFM). By using excitation

  7. Stress dependence of thermally driven pyroelectric charge release during FER-FEO phase transformations in [011] cut relaxor ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Dong, Wen D.; Finkel, Peter; Amin, Ahmed; Lynch, Christopher S.

    2012-06-01

    The stress dependence of thermally driven polarization change is reported for a ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut and poled Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT). A jump in polarization and strain is associated with a phase transformation of the ferroelectric material. The phase transformation temperature can be tuned, over a broad temperature range, through the application of bias stress. This phenomenon has applications in the field of energy harvesting and thermal sensing.

  8. Polarization-Strain Coupling in Mesoscopic Mixed Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pattnaik, Radha; Toulouse, Jean

    1998-03-01

    A new type of dielectric resonance has been observed in several mixed ferroelectrics, KTa(_1-x)Nb(_x)O(_3) (KTN), K(_1-x)Li(_x)TaO(_3) (KLT) and PbMg(_1/3)Nb(_2/3)O(_3) (PMN), also known as Relaxor Ferroelectrics. This resonance and its metastability (persistance over long periods of time) in the paraelectric phase of KTN provides clear evidence for the presence, in relaxors, of permenent polar nanoregions and of a strong polarization-strain coupling. The frequencies calculated from the elastic constant or modulus reveal the unexpected nature of the resonance. A comparative study of the polarization-strain coupling and dielectric relaxation in KTN and KLT is presented. These results provide the necessary elements for a microscopic description of the Relaxor behavior in disordered ferroelectrics.

  9. Re-entrant relaxor behavior of Ba{sub 5}RTi{sub 3}Nb{sub 7}O{sub 30} (R = La, Nd, Sm) tungsten bronze ceramics

    SciTech Connect

    Li, Kun; Li Zhu, Xiao; Qiang Liu, Xiao; Ming Chen, Xiang

    2013-03-18

    Ba{sub 5}RTi{sub 3}Nb{sub 7}O{sub 30} (R = La, Nd, Sm) tungsten bronze ceramics were prepared, and the dielectric and ferroelectric properties were investigated over a broad temperature range. The relaxor nature was determined for all compositions in their permittivity curves, and a second anomaly of the dielectric loss (tan {delta}) was observed around 250 K in Ba{sub 5}NdTi{sub 3}Nb{sub 7}O{sub 30} and around 275 K in Ba{sub 5}SmTi{sub 3}Nb{sub 7}O{sub 30}. Both the maximum and remanent polarization tended to decrease and vanish at low temperatures in the ferroelectric phase for all compositions, which was referred to as the low temperature re-entrant relaxor behavior. The remanent polarization increased with decreasing temperature first and then reached the maximum value at the re-entrant temperature (T{sub r}). For Ba{sub 5}RTi{sub 3}Nb{sub 7}O{sub 30} (R = La, Nd, Sm), T{sub r} decreased with the radius of R{sup 3+} cations and the applied field amplitude.

  10. Octahedral tilt transitions in the relaxor ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}

    SciTech Connect

    Meyer, Kai-Christian Gröting, Melanie; Albe, Karsten

    2015-07-15

    The kinetics of octahedral tilt transitions in the lead-free relaxor material sodium bismuth titanate Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} (NBT) is investigated by electronic structure calculations within density functional theory. Energy barriers for transitions between tetragonal, rhombohedral and orthorhombic tilts in cation configurations with [001]- and [111]-order on the A-sites are determined by nudged elastic band calculations. By tilting entire layers of octahedra simultaneously we find that the activation energy is lower for structures with 001-order compared to such with 111-order. The energetic coupling between differently tilted layers is, however, negligibly small. By introducing a single octahedral defect we create local tilt disorder and find that the deformation energy of the neighboring octahedra is less in a rhombohedral than in a tetragonal structure. By successively increasing the size of clusters of orthorhombic defects in a rhombohedral matrix with 001-order, we determine a critical cluster size of about 40 Å . Thus groups of about ten octahedra can be considered as nuclei for polar nanoregions, which are the cause of the experimentally observed relaxor behavior of NBT. - Graphical abstract: Nine orthorhombic oxygen octahedral tilt defects in a rhombohedral tilt configuration. - Highlights: • Chemical order influences energy barriers of octahedral tilt transitions. • The octahedral deformation energy is lower in rhombohedral phases. • Tilt defect clusters are more likely in rhombohedral structures. • Tilt defect clusters can act as nuclei for polar nanoregions.

  11. Critical Property in Relaxor-PbTiO3 Single Crystals --- Shear Piezoelectric Response

    PubMed Central

    Xu, Zhuo; Wei, Xiaoyong; Shrout, Thomas R.

    2011-01-01

    The shear piezoelectric behavior in relaxor-PbTiO3 (PT) single crystals is investigated in regard to crystal phase. High levels of shear piezoelectric activity, d15 or d24 >2000 pC N−1, has been observed for single domain rhombohedral (R), orthorhombic (O) and tetragonal (T) relaxor-PT crystals. The high piezoelectric response is attributed to a flattening of the Gibbs free energy at compositions proximate to the morphotropic phase boundaries, where the polarization rotation is easy with applying perpendicular electric field. The shear piezoelectric behavior of pervoskite ferroelectric crystals was discussed with respect to ferroelectric-ferroelectric phase transitions and dc bias field using phenomenological approach. The relationship between single domain shear piezoelectric response and piezoelectric activities in domain engineered configurations were given in this paper. From an application viewpoint, the temperature and ac field drive stability for shear piezoelectric responses are investigated. A temperature independent shear piezoelectric response (d24, in the range of −50°C to O-T phase transition temperature) is thermodynamically expected and experimentally confirmed in orthorhombic relaxor-PT crystals; relatively high ac field drive stability (5 kV cm−1) is obtained in manganese modified relaxor-PT crystals. For all thickness shear vibration modes, the mechanical quality factor Qs are less than 50, corresponding to the facilitated polarization rotation. PMID:21960942

  12. Role of random electric fields in relaxors

    PubMed Central

    Phelan, Daniel; Stock, Christopher; Rodriguez-Rivera, Jose A.; Chi, Songxue; Leão, Juscelino; Long, Xifa; Xie, Yujuan; Bokov, Alexei A.; Ye, Zuo-Guang; Ganesh, Panchapakesan; Gehring, Peter M.

    2014-01-01

    PbZr1–xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1–xTixO3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter. PMID:24449912

  13. 2-2 composites based on [011]-poled relaxor-ferroelectric single crystals: from the piezoelectric anisotropy to the hydrostatic response

    NASA Astrophysics Data System (ADS)

    Bowen, C. R.; Topolov, V. Y.; Betts, D. N.; Kim, H. A.

    2013-05-01

    In this paper effect of the orientation of the main crystallographic axes on the piezoelectric anisotropy and hydrostatic parameters of 2-2 parallel-connected single crystal (SC) / auxetic polymer composites is analysed. SCs are chosen among the perovskite-type relaxor-ferroelectric solid solutions of (1 - x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 and xPb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-(1 - x - y)PbTiO3. The SC layers in a composite sample are poled along the perovskite unit-cell [011] direction and characterised by mm2 symmetry. The orientation of the main crystallographic axes in the SC layer is observed to strongly influence the effective piezoelectric coefficients d*3j, g*3j, squared figured of merit d*3j g*3j, electromechanical coupling factors k*3j (j = 1, 2 and 3), and hydrostatic analogs of these parameters of the 2-2 composite. A comparison of values of d*3j g*3j was first carried out at d*31 ≠ d*32 in a wide range of orientations and volume-fraction. Large values of the effective parameters and inequalities | d*33 / d*3f | > 5 and | k*33 / k*3f | > 5 (f = 1 and 2) are achieved at specific orientations of the main crystallographic axes due to the anisotropy of elastic and piezoelectric properties of the SC component. The use of an auxetic polyethylene with a negative Poisson's ratio leads to a significant increase in the hydrostatic parameters of the 2-2 composite. Particular advantages of the studied composites over the conventional ceramic / polymer composites are taken into account for transducer, hydroacoustic and energyharvesting applications.

  14. Blockage of domain growth by nanoscale heterogeneities in a relaxor ferroelectric Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6}

    SciTech Connect

    Pertsev, N. A.; Gainutdinov, R. V.; Bodnarchuk, Ya. V.; Volk, T. R.

    2015-01-21

    The growth of localized subsurface domains in a relaxor ferroelectric Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6} is studied using the technique of piezoresponse force microscopy (PFM). Ferroelectric domains are created by applying moderate voltages of 10–50 V to the conductive tip of a scanning force microscope brought into contact with a nonpolar face of a Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6} crystal. PFM images of written domains are acquired and analyzed quantitatively to determine the domain length along the polar axis and its width in the transverse direction. The dependences of domain sizes on the applied voltage, pulse duration, and the time passed after completion of the voltage pulse are reported and analyzed theoretically. It is shown that the observed kinetics of domain growth can be explained by the creep of domain boundaries occurring in the presence of random electric fields inherent in Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6}. The comparison of measured domain sizes with their equilibrium values calculated with the aid of the thermodynamic theory demonstrates that the growth of subsurface domains in Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6} is blocked by nanoscale heterogeneities characteristic of this relaxor ferroelectric. These results may have important implications for the development of nonlinear optical devices based on nanoheterogeneous ferroelectrics.

  15. Relaxor-like ferroelectric behaviour favoured by short-range B-site ordering in 10% Ba{sup 2+} substituted MgFe{sub 2}O{sub 4}

    SciTech Connect

    Chithra Lekha, P.; Ramesh, G.; Revathi, V.; Subramanian, V.

    2014-05-01

    Graphical abstract: - Highlights: • Mechanism driving polarization in MgFe{sub 2}O{sub 4} is the Maxwell–Wagner polarization. • But Raman studies confirm the existence of local P4{sub 1}22/P4{sub 3}22 symmetry in MgFe{sub 2}O{sub 4}. • Ba{sup 2+} substitution increases ferroelectric ordering, ΔT{sub m} span, and masks electronic contribution. - Abstract: Using the molten salt method, pristine and Ba{sup 2+} substituted MgFe{sub 2}O{sub 4} are prepared. The relaxor-like behaviour observed in the dielectric dispersion indicates the existence of B-site short-range ordering with the local P4{sub 1}22/P4{sub 3}22 symmetry which is confirmed by the Raman spectroscopy. The paper further analyses the origin of polarization using Maxwell–Wagner fit and Nyquist plot. This work suggests a possible way to increase the relaxor-like ferroelectric ordering, larger span of relaxation temperature (ΔT{sub m}) and the effective masking of electronic contribution by the substitution of Ba{sup 2+} ion.

  16. Controlling dielectric and relaxor-ferroelectric properties for energy storage by tuning Pb0.92La0.08Zr0.52Ti0.48O3 film thickness.

    PubMed

    Brown, Emery; Ma, Chunrui; Acharya, Jagaran; Ma, Beihai; Wu, Judy; Li, Jun

    2014-12-24

    The energy storage properties of Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films grown via pulsed laser deposition were evaluated at variable film thickness of 125, 250, 500, and 1000 nm. These films show high dielectric permittivity up to ∼1200. Cyclic I-V measurements were used to evaluate the dielectric properties of these thin films, which not only provide the total electric displacement, but also separate contributions from each of the relevant components including electric conductivity (D1), dielectric capacitance (D2), and relaxor-ferroelectric domain switching polarization (P). The results show that, as the film thickness increases, the material transits from a linear dielectric to nonlinear relaxor-ferroelectric. While the energy storage per volume increases with the film thickness, the energy storage efficiency drops from ∼80% to ∼30%. The PLZT films can be optimized for different energy storage applications by tuning the film thickness to optimize between the linear and nonlinear dielectric properties and energy storage efficiency. PMID:25405727

  17. Temperature dependent polarization reversal mechanism in 0.94(Bi1/2Na1/2)TiO3-0.06Ba(Zr0.02Ti0.98)O3 relaxor ceramics

    NASA Astrophysics Data System (ADS)

    Glaum, Julia; Simons, Hugh; Hudspeth, Jessica; Acosta, Matias; Daniels, John E.

    2015-12-01

    The temperature at which the electric field induced long-range ordered ferroelectric state undergoes transition into the short-range ordered relaxor state, TF-R, is commonly defined by the onset of strong dispersion of the dielectric permittivity. However, this combined macroscopic property and structural investigation of the polarization reversal process in the prototypical lead-free relaxor 0.94(Bi1/2Na1/2)TiO3-0.06Ba(Zr0.02Ti0.98)O3 reveals that an applied electric field can trigger depolarization and onset of relaxor-like behavior well below TF-R. The polarization reversal process can as such be described as a combination of (1) ferroelectric domain switching and (2) a reversible phase transition between two polar ferroelectric states mediated by a non-polar relaxor state. Furthermore, the threshold fields of the second, mediated polarization reversal mechanism depend strongly on temperature. These results are concomitant with a continuous ferroelectric to relaxor transition occurring over a broad temperature range, during which mixed behavior is observed. The nature of polarization reversal can be illustrated in electric-field-temperature (E-T) diagrams showing the electric field amplitudes associated with different polarization reversal processes. Such diagrams are useful tools for identifying the best operational temperature regimes for a given composition in actuator applications.

  18. Local Polarization Dynamics and Bias-Induced Phase Transitions in Ferroelectric Relaxors: Time-resolved Spectroscopy and Ergodic Gap Mapping

    NASA Astrophysics Data System (ADS)

    Kalinin, S. V.; Rodriguez, B.; Nikiforov, M. P.; Balke, N.; Jesse, S.; Ovchinnikov, O. S.; Bokov, A. A.; Ye, Z.-G.

    2009-03-01

    Mesoscopic domain structure and dynamics in PMN-PT solis solutions is studied using spatially resolved time- and voltage spectroscopic imaging modes. For compositions close to the MPB, we observe the formation of classical ferroelectric domains with rough self-affine boundaries. In the ergodic phase (PMN and PMN-10PT), the formation of non-classical labyrinthine domain patterns characterized by a single characteristic length scale is observed. The (a) persistence of these patterns well above Tc and (b) the fact that cannot be switched by tip bias suggest that they can be attributed to the frozen polarization component. Spatial variability of polarization relaxation dynamics in PMN-10PT is studied. Local relaxation attributed to the reorientation of polar nanoregions was found to follow stretched exponential dependence, with β 0.4, much larger than the macroscopic value determined from dielectric spectra (β 0.09). The spatial inhomogeneity of relaxation time distribution with the presence of 100-200 nm ``fast'' and ``slow'' regions is observed. The results are analyzed to map the Vogel-Fulcher temperatures on the nanoscale. The applicability of this technique to map ``ergodic gap'' distribution on the surface is discussed. Research supported by the Division of Materials Science and Engineering, Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC.

  19. Ferroelectric switching behavior in morphology controlled ferroelectric-semiconductor polymer blends for organic memory

    NASA Astrophysics Data System (ADS)

    Lim, Eunhee; Su, Gregory; Kramer, Edward; Chabinyc, Michael

    2015-03-01

    Memory is a fundamental component of all modern electronic systems. Organic ferroelectric memories are advantageous because they are thin and lightweight devices that can be made printable, foldable, and stretchable. Organic ferroelectric memories comprise a physical blend of an organic semiconducting polymer and an insulating ferroelectric polymer as the active layer in a thin film diode. Controlling the thin film morphology in these blends is important for electrical properties of the resulting device. We have found that when a semiconducting thiophene polymer with polar alkanoate side chains (P3EPT) is blended with well-studied ferroelectric polymer poly [(vinylidenefluoride-co-trifluoroethylene] P (VDF-TrFE), the resulting film has low surface roughness and more controllable domain sizes compared to the widely used poly (3-hexylthiophene). This difference allows more reliable study of the ferroelectric switching behavior in devices with domain size of about 100nm. The influence of the 3D composition measured by a combination of methods, including soft x-ray microscopy, on the electrical characteristics will be presented.

  20. Auxetic behavior under electrical loads in an induced ferroelectric phase

    NASA Astrophysics Data System (ADS)

    Tan, X.; Jo, W.; Granzow, T.; Frederick, J.; Aulbach, E.; Rödel, J.

    2009-01-01

    The longitudinal and transverse strains were measured as a function of applied electric fields in a bulk ceramic sample of Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 at room temperature. Instead of a transverse contraction, a transverse expansion was observed in the electric-field-induced ferroelectric phase after the antiferroelectric-to-ferroelectric phase transition. Therefore, an auxetic behavior was established in monolithic ferroelectric polycrystalline ceramics under electrical loads. The behavior is characterized by a negative strain ratio that is analogous to the Poisson's ratio. The transverse expansion leads to a large hydrostatic piezoelectric coefficient dh, which suggests new applications of antiferroelectric ceramics in piezoelectric devices.

  1. Anomalous thermal hysteresis of two first order phase transitions in relaxor ferroelectric 0.945 Pb(Zn1/3Nb2/3)O3-0.055PbTiO3 crystals studied by Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Islam, Md. Saidul; Tsukada, Shinya; Kojima, Seiji

    2016-03-01

    The thermal hysteresis has been studied by Brillouin scattering in the relaxor ferroelectric (1 - x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 with x = 0.055 (i.e., below the morphotropic phase boundary composition x ˜ 0.08). On heating from room temperature, the first order rhombohedral to tetragonal phase transition occurs at TR-T = 397 K, then the first order tetragonal to cubic transition occurs at TT-C = 425 K. However, on cooling from high temperature, only the diffusive phase transition was observed around TC-R = 401 K. Such anomalous thermal hysteresis is attributed to the metastable non-equilibrium states induced by supercooling due to quenching of nano-domains by the random electric fields of the B-site charge disorder.

  2. Cathodoluminescence investigation of relaxor-based ferroelectrics Pb(Mg 1/3Nb 2/3)O 3-0.3PbTiO 3 (PMN-0.3PT) single-crystal

    NASA Astrophysics Data System (ADS)

    Ge, Wanyin; Zhu, Wenliang; Pezzotti, Giuseppe

    2010-01-01

    Relaxor-based ferroelectric lead magnesium niobate-lead titanate Pb(Mg 1/3Nb 2/3)O 3-PbTiO 3 (PMN-PT) possesses ultrahigh electromechanical coefficients near the morphotropic phase boundary (MPB). In this paper, the electro-stimulated emission characteristics of a [0 0 1]-oriented PMN-0.3PTsingle-crystal were studied using high resolution cathodoluminescence (CL) spectroscopy at room temperature. Four luminescence bands were observed in the range of 200-900 nm and they were assigned to polaron, nanometre cluster emission, interband emission and structure-related emission. Besides, it was found that the residual stress field ahead of a crack tip of a Vickers indentation had a considerable influence on these luminescence bands. The relationship between the intensities of CL bands and the residual stress field has been investigated and discussed in this paper.

  3. Aging in the relaxor and ferroelectric state of Fe-doped (1-x)(Bi{sub 1/2}Na{sub 1/2})TiO₃-xBaTiO₃ piezoelectric ceramics

    SciTech Connect

    Sapper, Eva; Dittmer, Robert; Rödel, Jürgen; Damjanovic, Dragan; Erdem, Emre; Keeble, David J.; Jo, Wook; Granzow, Torsten

    2014-09-14

    Aging of piezoelectric properties was investigated in lead-free (1–x)(Bi{sub 1/2}Na{sub 1/2})TiO₃-xBaTiO₃ doped with 1at.% Fe. The relaxor character of the un-poled material prevents macroscopic aging effects, while in the field-induced ferroelectric phase aging phenomena are similar to those found in lead zirconate titanate or barium titanate. Most prominent aging effects are the development of an internal bias field and the decrease of switchable polarization. These effects are temperature activated, and can be explained in the framework of defect complex reorientation. This picture is further supported by electron paramagnetic resonance spectra indicating the existence of (Fe{sub Ti}´-V{sub O}{sup ••}){sup •} defect complexes in the Fe-doped material.

  4. Optical interband transitions in relaxor-based ferroelectric 0.93Pb(Zn1∕3Nb2∕3)O3–0.07PbTiO3 single crystal

    PubMed Central

    Sun, Enwei; Zhang, Rui; Wang, Zhu; Xu, Dapeng; Li, Liang; Cao, Wenwu

    2010-01-01

    The optical transmission spectrum of [111]c poled relaxor-based ferroelectric single crystal 0.93Pb(Zn1∕3Nb2∕3)O3–0.07PbTiO3 (PZN–0.07PT) was measured in the range of ultraviolet to near infrared. The optical absorption edge has been determined and the wavelength dependence of the absorption coefficient was calculated. The direct energy gap Egd=3.144 eV, indirect energy gap Egi=2.915 eV, and phonon energy Ep=0.097 eV (or 782 cm−1) were determined based on the theory of band to band transitions. It was also confirmed by Raman spectra that the indirect transition for the [111]c poled PZN–0.07PT single crystal is mainly due to the contribution of 780 cm−1 phonon corresponding to the Nb–O–Zn bond stretching mode. PMID:20634967

  5. Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics.

    PubMed

    Bintachitt, P; Jesse, S; Damjanovic, D; Han, Y; Reaney, I M; Trolier-McKinstry, S; Kalinin, S V

    2010-04-20

    Nanoscale and mesoscopic disorder and associated local hysteretic responses underpin the unique properties of spin and cluster glasses, phase-separated oxides, polycrystalline ferroelectrics, and ferromagnets alike. Despite the rich history of the field, the relationship between the statistical descriptors of hysteresis behavior such as Preisach density, and micro and nanostructure has remained elusive. By using polycrystalline ferroelectric capacitors as a model system, we now report quantitative nonlinearity measurements in 0.025-1 microm(3) volumes, approximately 10(6) times smaller than previously possible. We discover that the onset of nonlinear behavior with thickness proceeds through formation and increase of areal density of micron-scale regions with large nonlinear response embedded in a more weakly nonlinear matrix. This observation indicates that large-scale collective domain wall dynamics, as opposed to motion of noninteracting walls, underpins Rayleigh behavior in disordered ferroelectrics. The measurements provide evidence for the existence and extent of the domain avalanches in ferroelectric materials, forcing us to rethink 100-year old paradigms. PMID:20368462

  6. Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics

    PubMed Central

    Bintachitt, P.; Jesse, S.; Damjanovic, D.; Han, Y.; Reaney, I. M.; Trolier-McKinstry, S.; Kalinin, S. V.

    2010-01-01

    Nanoscale and mesoscopic disorder and associated local hysteretic responses underpin the unique properties of spin and cluster glasses, phase-separated oxides, polycrystalline ferroelectrics, and ferromagnets alike. Despite the rich history of the field, the relationship between the statistical descriptors of hysteresis behavior such as Preisach density, and micro and nanostructure has remained elusive. By using polycrystalline ferroelectric capacitors as a model system, we now report quantitative nonlinearity measurements in 0.025–1 μm3 volumes, approximately 106 times smaller than previously possible. We discover that the onset of nonlinear behavior with thickness proceeds through formation and increase of areal density of micron-scale regions with large nonlinear response embedded in a more weakly nonlinear matrix. This observation indicates that large-scale collective domain wall dynamics, as opposed to motion of noninteracting walls, underpins Rayleigh behavior in disordered ferroelectrics. The measurements provide evidence for the existence and extent of the domain avalanches in ferroelectric materials, forcing us to rethink 100-year old paradigms. PMID:20368462

  7. Structural and dielectric relaxor behavior of Ba1-xNdxBi4Ti4O15 ceramics

    NASA Astrophysics Data System (ADS)

    Fang, Pinyang; Xi, Zengzhe; Long, Wei; Li, Xiaojuan; Chen, Shanchuan

    2016-04-01

    Ba1-xNdxBi4Ti4O14 (BNBT) ceramics were prepared by the convention solid state reaction method. Effect of neodymium substitution on the structural and dielectric properties of the BBT ceramic was investigated. Phase structure was characterized by using X-ray diffraction analysis (XRD). A broaden dielectric peak in frequency dependent dielectric spectrum is observed during the phase transition of the BNBT ceramics. The modified Curie-Weiss and Lorentz-type relationship were used to describe the phase transition behavior. The relaxor behavior could be described well by the Lorentz-type relationship. Effect of neodymium substitution on the Curie temperatures and degree of the diffuseness in the BNBT ceramics was discussed.

  8. Effect of doping by Bi and Ca on ferroelectric properties and relaxor character in the (Ba1-xCax)1-3y/2BiyTiO3 solid solution

    NASA Astrophysics Data System (ADS)

    Zaghouene, H.; Bahri, F.; Boujelbene, M.; Khemakhem, H.; Simon, A.

    2012-10-01

    The temperature dependence of the real and imaginary parts of dielectric permittivity for (Ba1-xCax)1-3y/2BiyTiO3 solid solution prepared using the solid-state reaction technique, suggests that the relaxor character in this solid solution depends strongly on the Bi than on the Ca doping percent.X-ray diffraction analysis show that Bi doping can be fully incorporated into the perovskite lattice of (Ba1-xCax)TiO3. Doping with Bi causes remarkable shift of the maximum of dielectric permittivity (Tm) at low temperatures and the evolution of ɛ‧r exhibiting strong frequency dispersion. For some compositions, we have observed a typical behavior of a well-known relaxors. On the other hand, we pointed out that the relaxor character is linked principally to the nature of the substituting element and not to the heterogeneity in general. So the Ca element does not have the same effect as the Bi one.

  9. Influence of electric field on local phase transformations in relaxor ferroelectrics PbSc0.5Ta0.5O3 and Pb0.78Ba0.22Sc0.5Ta0.5O3

    NASA Astrophysics Data System (ADS)

    Maier, B. J.; Steilmann, T.; Gospodinov, M.; Bismayer, U.; Mihailova, B.

    2012-12-01

    In situ temperature-dependent Raman-scattering experiments under an external dc electric field E have been performed on PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PST-Ba) in order to give further insights into the atomistic mechanism of polar coupling in perovskite-type (ABO3) relaxor ferroelectrics near the intermediate characteristic temperature T⋆. The polarized Raman spectra collected under an electric field E applied along the cubic [100], [110], or [111] crystallographic direction were analyzed in terms of hard-mode spectroscopy. The T⋆(E) dependence was derived from the behavior of the phonon mode near 230 cm-1 localized in off-centered B-site cations. In the case of stoichiometric PST, the increase of T⋆ with E is much stronger when the field is applied along [111] than when E is along [100] or [110]. This indicates that the actual polar B-cation shifts are along the cubic body diagonals, implying a rhombohedral structure of the polar nanoregions. The T⋆(E)-dependence reveals that the local structural distortions associated with locally coupled polar displacements of B-site cations reach saturation near 0.5 kV/cm. When Pb2+ is partially replaced by Ba2+, the strong increase of T⋆ with E occurs if the electric field is applied along the [110] direction. This indicates that the substitution disorder on the A-site lowers the symmetry of the polar nanoregions to orthorhombic or monoclinic. The T⋆(E) dependence determined from the B-cation localized mode shows saturation near 2.0 kV/cm, indicating that the zero-field structural state of PST-Ba exhibits less coupled polar shifts of B-site cations as compared to that of PST. According to the E-dependence of the Raman scattering near 55 cm-1, for both compounds the overall response of the Pb system to the external electric field in the vicinity of T⋆(E) resembles antiferroelectric behavior, which along with the fact that the coupling between the B-site cations is ferroelectric, suggests that

  10. Electric field effect of relaxor ferroelectric (1 ‑ x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 crystals near morphotropic phase boundary composition probed by Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Aftabuzzaman, Md; Kojima, Seiji

    2016-07-01

    The relaxor ferroelectric (1 ‑ x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (x = 0.30, PMN–30PT) single crystal was studied under the zero field and the externally applied dc electric field by using micro-Brillouin scattering and dielectric spectroscopies over a wide temperature range of 303–773 K. The noticeable thermal hysteresis of longitudinal acoustic (LA) shift (νB) was observed between zero field heating and zero field cooling processes. Under the electric field of 0.5 kV/cm along the [001] axis, the LA mode splitting was observed in νB due to the coexistence of ferroelectric macrodomain and nanodomain states caused by the random field, and in dielectric measurements the monoclinic (M) and tetragonal phases were appeared between rhombohedral and cubic phases. The LA mode splitting and M phase disappeared under the field of 1.0 kV/cm. The electric field dependence of LA velocity was studied at 304 K. The critical end point of the PMN–30PT single crystal was investigated.

  11. Ferroelastic aspects of relaxor ferroelectric behaviour in Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 perovskite

    NASA Astrophysics Data System (ADS)

    Nataf, Guillaume F.; Li, Qian; Liu, Yun; Withers, Ray L.; Driver, Sarah L.; Carpenter, Michael A.

    2013-03-01

    Elastic and anelastic properties of poled and depoled single crystals of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 with compositions close to the morphotropic boundary have been investigated over the temperature range 5-700 K by resonant ultrasound spectroscopy (RUS) at frequencies of 0.1-1.2 MHz. Steep elastic softening occurs in a temperature interval of at least 250 K as the Vogel-Fulcher freezing interval and cubic → tetragonal transition point, Tc, are approached from above. This is understood in terms of coupling between acoustic modes and central peak mode(s) associated with dynamic polar nano regions (PNR's) below the Burns temperature. Acoustic losses occur in a temperature interval of ˜50 K above Tc, associated with slowing down of the PNR dynamics. The cubic ↔ tetragonal and tetragonal ↔ rhombohedral transitions are accompanied by steep minima in elastic properties, closely analogous to the pattern of softening and stiffening observed in sequences of improper ferroelastic transitions in other perovskites. Variations in the magnitudes of acoustic losses at T < Tc correlate with the density of ferroelastic twin walls, from lowest for [001]c-poled and [111]c-poled crystals in the stability fields of the tetragonal and rhombohedral phases, respectively, to highest for unpoled crystals. A simple model of Debye-like peaks in acoustic loss near 100 K has yielded activation energies and attempt frequencies in the same range as those observed from dielectric data in the Vogel-Fulcher freezing interval. These highlight the fact that, in addition to conventional ferroelectric/ferroelastic twin walls, relaxor ferroelectrics contain local structural heterogeneities coupled to strain, which are probably related to the presence of static PNR's preserved even in poled crystals. RUS also provides a convenient and effective means of determining the mechanical quality factor of relaxor ferroelectrics, as functions of both poling history and temperature.

  12. Cooperative behavior during ferroelectric transitions in KNO3 powder

    NASA Astrophysics Data System (ADS)

    Westphal, M. J.

    1993-09-01

    Experimental evidence of cooperative behavior during the ferroelectric phase transitions in granular and powder KNO3 at atmospheric pressure is presented. Three different experimental studies were performed in which phase transitions were detected and characterized by heat flow calorimetry: (1) the distribution of SiC powder in granular KNO3 was varied; (2) the volume fraction of SiC in powdered KNO3 was varied; and (3) pure KNO3 powder was thermally cycled. All three studies provided evidence of cooperative behavior between the KNO3 particles during the III-II phase transition. The cooperative behavior reduced the temperature range of phase III stability from ˜97-124 °C to that characteristic of bulk material (˜110-124 °C). Separate KNO3 particles behaved as individual ferroelectric domains, with each particle making the phase transition independently near the expected Curie temperature. Particles of KNO3 in intimate physical contact tended to behave cooperatively as a single large ferroelectric domain leading to sharper phase transitions more characteristic of single crystals. The degree of cooperative behavior was dependent upon the extent to which the individual particles were in physical contact. The absence of the III-II phase transition in KNO3 powder that has been reported in the literature can be understood from the results obtained using SiC powder to separate KNO3 particles during heat flow calorimetry measurements.

  13. Unconventional resistive switching behavior in ferroelectric tunnel junctions.

    PubMed

    Mao, H J; Song, C; Xiao, L R; Gao, S; Cui, B; Peng, J J; Li, F; Pan, F

    2015-04-21

    We investigate an unconventional resistive switching (RS) behavior in La0.67Sr0.33MnO3/BaTiO3/metal (LSMO/BTO) ferroelectric tunnel junctions (FTJs), which is dominated by the variation of the barrier potential profile modulated by the migration of oxygen vacancies in the p-LSMO/n-BTO junction. The LSMO/BTO/Co junction exhibits a remarkable self-rectifying effect ascribed to the high-density interface state at the BTO/Co interface, in contrast to the symmetric conductivity when the top metal electrode is inert Pt. The effects of ferroelectric polarization on the RS behavior are also emphasized. Our work builds a bridge between FTJs and resistive random access memory devices. PMID:25789877

  14. Composition dependence of the diffuse scattering in the relaxor ferroelectric compound (1-x)Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-xPbTiO{sub 3} (0{<=}x{<=}0.40)

    SciTech Connect

    Matsuura, M.; Hirota, K.; Gehring, P. M.; Ye, Z.-G.; Chen, W.; Shirane, G.

    2006-10-01

    We have used neutron diffraction to characterize the diffuse scattering in five single crystals of the relaxor ferroelectric (1-x)Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-xPbTiO{sub 3} (PMN-xPT) with x=0, 10, 20, 30, and 40%. The addition of ferroelectric PbTiO{sub 3} modifies the well-known 'butterfly' and 'ellipsoidal' diffuse scattering patterns observed in pure PMN (x=0), which are believed to be associated with the presence of randomly oriented polar nanoregions. In particular, the anisotropy of the diffuse scattering diminishes as the PT content increases. The spatial correlation length {xi} along the [110] direction derived from the width of the diffuse scattering at room temperature increases from 12.6 A for PMN to 350 A for PMN-20%PT. In addition, the diffuse scattering intensity at q=0 grows and reaches a maximum value around the morphotropic phase boundary (MPB), which suggests that it is proportional to the dielectric susceptibility. Beyond x=30%, a concentration very close to the MPB, no diffuse scattering is observed below T{sub C}, and well-defined critical behavior appears near T{sub C}. By contrast, the diffuse scattering for x{<=}20% persists down to low temperatures, where the system retains an average cubic structure (T{sub C}=0). Finally, the anisotropic soft transverse optic (TO) modes observed in PMN are found to be isotropic for PMN-30%PT, which strongly suggests a connection between the anisotropic diffuse scattering and the TO modes.

  15. Losses in Ferroelectric Materials

    PubMed Central

    Liu, Gang; Zhang, Shujun; Jiang, Wenhua; Cao, Wenwu

    2015-01-01

    Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate-lead titanate and lead zinc niobate-lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy

  16. Second Harmonic Generation and Polarization Microscope Observations of Quantum Relaxor Lithium Doped Potasium Tantalate

    NASA Astrophysics Data System (ADS)

    Yokota, Hiroko; Uesu, Yoshiaki

    2008-04-01

    Polar state in a quantum relaxor K(1-x)LixTaO3 (KLT) is investigated using second harmonic generation (SHG) and polarization microscopes. Temperature dependences of SHG image and interference color image related to birefringence are observed on three different processes (zero field heating after zero field cooling, field heating after zero field cooling, and field heating after field cooling processes). A remarkable history dependence in the T-E space which is one of the characteristic behaviors of relaxor is observed in SHG and polarization microscope observations. Ferroelectric phase transition occurs below the transition temperature Tp with tiny domain structures which is beyond the optical microscope diffraction limit. Under an electric field, these micro domain structures change to macroscopic structures. Based on these experiments, we propose a polar state model of KLT below Tp.

  17. Domain switching mechanisms in polycrystalline ferroelectrics with asymmetric hysteretic behavior

    NASA Astrophysics Data System (ADS)

    Anton, Eva-Maria; García, R. Edwin; Key, Thomas S.; Blendell, John E.; Bowman, Keith J.

    2009-01-01

    A numerical method is presented to predict the effect of microstructure on the local polarization switching of bulk ferroelectric ceramics. The model shows that a built-in electromechanical field develops in a ferroelectric material as a result of the spatial coupling of the grains and the direct physical coupling between the thermomechanical and electromechanical properties of a bulk ceramic material. The built-in fields that result from the thermomechanically induced grain-grain electromechanical interactions result in the appearance of four microstructural switching mechanisms: (1) simple switching, where the c-axes of ferroelectric domains will align with the direction of the applied macroscopic electric field by starting from the core of each grain; (2) grain boundary induced switching, where the domain's switching response will initiate at grain corners and boundaries as a result of the polarization and stress that is locally generated from the strong anisotropy of the dielectric permittivity and the local piezoelectric contributions to polarization from the surrounding material; (3) negative poling, where abutting ferroelectric domains of opposite polarity actively oppose domain switching by increasing their degree of tetragonality by interacting with the surrounding domains that have already switched to align with the applied electrostatic field. Finally, (4) domain reswitching mechanism is observed at very large applied electric fields, and is characterized by the appearance of polarization domain reversals events in the direction of their originally unswitched state. This mechanism is a consequence of the competition between the macroscopic applied electric field, and the induced electric field that results from the neighboring domains (or grains) interactions. The model shows that these built-in electromechanical fields and mesoscale mechanisms contribute to the asymmetry of the macroscopic hysteretic behavior in poled samples. Furthermore, below a

  18. Continuous cross-over from ferroelectric to relaxor state and piezoelectric properties of BaTiO3-BaZrO3-CaTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Benabdallah, F.; Veber, P.; Prakasam, M.; Viraphong, O.; Shimamura, K.; Maglione, M.

    2014-04-01

    Optimal properties like piezoelectricity can be found in polarizable materials for which the structure changes sharply under small composition variations in the vicinity of their morphotropic phase boundary or the triple point in their isobaric temperature-composition phase diagram. In the latter, lead-free (Ba0.850Ca0.150)(Ti0.900Zr0.100)O3 ceramics exhibit outstanding piezoelectric coefficients. For the first time, we report the growth of piezoelectric lead-free single crystals in the BaTiO3-BaZrO3-CaTiO3 pseudo-ternary system. The stoichiometry control in the CaO-BaO-TiO2-ZrO2 solid solution led to single crystals with various compositions ranging from (Ba0.857Ca0.143)(Ti0.928Zr0.072)O3 to (Ba0.953Ca0.047)(Ti0.427Zr0.573)O3. We evidenced a continuous cross-over from a ferroelectric state at high titanium content to a relaxor one on increasing the zirconium content. Such a property tuning is rather seldom observed in lead-free ferroelectrics and confirms what was already reported for ceramics. Single crystal with (Ba0.838Ca0.162)(Ti0.854Zr0.146)O3 composition, which has been grown and oriented along [001] crystallographic direction, displayed electromechanical coefficients d31 and k31 of 93 pC.N-1 and 0.18, respectively, near the room temperature (T = 305 K).

  19. Continuous cross-over from ferroelectric to relaxor state and piezoelectric properties of BaTiO{sub 3}-BaZrO{sub 3}-CaTiO{sub 3} single crystals

    SciTech Connect

    Benabdallah, F.; Veber, P. Prakasam, M.; Viraphong, O.; Maglione, M.; Shimamura, K.

    2014-04-14

    Optimal properties like piezoelectricity can be found in polarizable materials for which the structure changes sharply under small composition variations in the vicinity of their morphotropic phase boundary or the triple point in their isobaric temperature-composition phase diagram. In the latter, lead-free (Ba{sub 0.850}Ca{sub 0.150})(Ti{sub 0.900}Zr{sub 0.100})O{sub 3} ceramics exhibit outstanding piezoelectric coefficients. For the first time, we report the growth of piezoelectric lead-free single crystals in the BaTiO{sub 3}-BaZrO{sub 3}-CaTiO{sub 3} pseudo-ternary system. The stoichiometry control in the CaO-BaO-TiO{sub 2}-ZrO{sub 2} solid solution led to single crystals with various compositions ranging from (Ba{sub 0.857}Ca{sub 0.143})(Ti{sub 0.928}Zr{sub 0.072})O{sub 3} to (Ba{sub 0.953}Ca{sub 0.047})(Ti{sub 0.427}Zr{sub 0.573})O{sub 3}. We evidenced a continuous cross-over from a ferroelectric state at high titanium content to a relaxor one on increasing the zirconium content. Such a property tuning is rather seldom observed in lead-free ferroelectrics and confirms what was already reported for ceramics. Single crystal with (Ba{sub 0.838}Ca{sub 0.162})(Ti{sub 0.854}Zr{sub 0.146})O{sub 3} composition, which has been grown and oriented along [001] crystallographic direction, displayed electromechanical coefficients d{sub 31} and k{sub 31} of 93 pC.N{sup −1} and 0.18, respectively, near the room temperature (T = 305 K)

  20. Freezing of the local dynamics in the relaxor ferroelectric [Pb(Zn1/3Nb2/3)O3]0.955[PbTiO3]0.045

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Wen, Jinsheng; Mamontov, E.; Stock, C.; Gehring, P. M.; Xu, Guangyong

    2012-10-01

    We report measurements of the neutron diffuse scattering in a single crystal of the relaxor ferroelectric material 95.5%Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (PZN-4.5%PT). We show that the diffuse scattering at high temperatures has a quasielastic component with energy width ≳0.1 meV. On cooling the total diffuse scattering intensity increases, but the intensity and the energy width of the quasielastic component gradually diminish. At 50 K the diffuse scattering is completely static (i.e., the energy width lies within the limits of our instrumental resolution). This suggests that the dynamics of the short-range correlated atomic displacements associated with the diffuse scattering freeze at low temperature. We find that this depends on the wave vector q as the quasielastic diffuse scattering intensities associated with <001> (T1-type) and <110> (T2-type) atomic displacements vary differently with temperature and electric field.

  1. Raman spectroscopic studies of disordered ferroelectric oxides

    NASA Astrophysics Data System (ADS)

    Savvinov, Alexey A.

    Relaxational properties of compositionally disordered AB03 perovskite oxides were studied. These oxides are the prototypical soft ferroelectric (FE) mode systems, and their interesting dipolar relaxational properties are determined by their long, strongly temperature-dependent correlation lengths for the dipolar interactions. The simple cases involve dilute chemical substitutions in the incipient ferroelectrics KTaO3 and SrTiO3, which exhibit relatively weak, low-temperature Debye-type relaxations. More complicated dipolar interactions are seen in B-site disordered Nb-doped KTaO3, which exhibits glass-like relaxor and relaxor-to-ferroelectric crossover behaviors at low temperatures. Finally, there is a class of more complex perovskites represented by PMN, PZN-PT and the PLT that exhibit strong, high-temperature relaxor and/or ferroelectric properties. The renewed interest in the KTa1-xNbxO (KTN) mixed perovskite materials, especially in high quality thin films, is connected with their remarkable dielectric properties in the dilute compositions. Off-center Nb ions in the highly polarizable KTaO3 lattice provide a drastic increase in the dielectric peak, up to 20 times in comparison with the pure KTaO3 and KNbO3. The effects of the substrate and the symmetry-breaking defects on their vibration spectra were studied by micro-Raman spectroscopy. An anomalous residual intensity of the forbidden first-order scattering modes in the cubic paraelectric phase of the KTN films was connected with the formation of polar microregions even far above the bulk Tc. On the whole, the KTN film behavior shows the existence of specific defects enhancing the perovskite unit cell in the film so that the activity of off-center Nb ions increases in producing larger electric dipoles and extending the precursor phase above Tc. In diluted compositions with low Nb concentrations KTN materials exhibit formation of polar nano regions and relaxor like behavior. This behavior is analogous with

  2. Rescaled temperature dependence of dielectric behavior of ferroelectric polymer composites

    NASA Astrophysics Data System (ADS)

    Dang, Zhi-Min; Wang, Lan; Wang, Hai-Yan; Nan, Ce-Wen; Xie, Dan; Yin, Yi; Tjong, S. C.

    2005-04-01

    Rescaled temperature dependence of dielectric behavior of ferroelectric polyvinylidene fluoride (PVDF) filled with electroactive ceramic particles of rocksalt-type Li and Ti codoped NiO (LTNO) was studied at wide frequency ranges. Dielectric behavior of the flexible PVDF-LTNO composites with LTNO filler at the volumetric function of 0.3 exhibits a dielectric constant value, ɛ ≈50 at broad temperature range (290-360 K), and the value is frequency independent from 103 to 106Hz. The dielectric response of the composite is almost in accordance to that of pure PVDF matrix polymer. It was found that though the dielectric constant value of the composites is high due to an introduction of the rock salt-type LTNO ceramic particles with high dielectric constant, the glass transition of the polymer and dielectric relaxation related to the wide-angle oscillation of polar groups attached to the main polymer chain determine the dielectric behavior of the composite.

  3. Relaxor fluorinated polymers: novel applications and recent developments

    NASA Astrophysics Data System (ADS)

    Bauer, François; Dos Santos, Domingues; Zhang, Qiming

    2011-04-01

    It has been found that by introducing defects into the P(VDF-TrFE) copolymers, it is possible to convert the polymer from a normal ferroelectric to a relaxor ferroelectric. A new class of ferroelectric polymers, i.e., the terpolymers of P(VDF-TrFE-CFE) or of P(VDF-TrFE-CTFE), was developed from the normal ferroelectric PVDF-TrFE polymer by employing proper defect modifications which eliminate detrimental effects associated with a normal first order F-P transition while maintaining high material responses. Relevant studies show that this class of electroactive polymers offers unique properties in comparison with other ferroelectric polymers. The syntheses of these relaxor ferroelectric polymers have been done by a combination of the suspension polymerization process and an oxygen-activated initiator at a temperature of 40 °C. Films from cast solution can be made in different length and thicknesses. Stretching of these films increases the performance as well as the mechanical properties. These relaxor-ferroelectric terpolymers P(VDF-TrFE-CFE), P(VDF-TrFE-CTFE) are multifunctional i.e. electrostrictive material, dielectric for electric energy storage. The terpolymer exhibits high electrostrictive strain (>7%) with relatively high modulus (>0.4GPa). Examples of devices applications using unimorphe systems are presented. Micropump and Optical device concerning a liquid-filled varifocal lens on a chip are described.

  4. Growth and characterization of ferroelectric Pb(Sc1/2Nb1/2)O3 single crystals

    NASA Astrophysics Data System (ADS)

    Huo, Siqi; Bokov, Alexei A.; Paterson, Alisa; Ye, Zuo-Guang

    2015-10-01

    Single crystals of Pb(Sc1/2Nb1/2)O3 were grown by the high-temperature solution method using PbO + B2O3 as flux. The size of the as-grown crystals varies from 1 to 2 mm. X-ray diffraction indicates a pure perovskite phase without B-site ordering. Polarized light microscopy shows that the crystals are of rhombohedral symmetry at room temperature and become cubic at TC = 112 °C on heating. A ferroelectric-to-relaxor phase transition is verified at TC by dielectric spectroscopy. Frequency-dependent permittivity is observed in dielectric measurements, revealing relaxor behavior above TC. Poling the crystal at room temperature does not change TC, but suppresses the permittivity. Typical ferroelectric hysteresis loop is displayed at room temperature, indicating the ferroelectric nature of the rhombohedral phase.

  5. In situ high-temperature high-pressure Raman spectroscopy on single-crystal relaxor ferroelectrics PbSc1/2Ta1/2O3 and PbSc1/2Nb1/2O3

    NASA Astrophysics Data System (ADS)

    Waeselmann, N.; Mihailova, B.; Gospodinov, M.; Bismayer, U.

    2013-04-01

    The effect of temperature on the pressure-induced structural changes in perovskite-type (ABO3) relaxor ferroelectrics is studied by in situ high-temperature high-pressure Raman spectroscopy on single crystals of PbSc1/2Ta1/2O3 (PST) and PbSc1/2Nb1/2O3 (PSN), which allowed us to elucidate the interplay between the polar and antiferrodistortive order coexisting on the mesoscopic scale at ambient conditions. High-pressure experiments were carried out at elevated temperatures below and above the characteristic intermediate temperature T*. The results were compared with those obtained at room temperature, which for PST is just above the paraelectric-ferroelectric phase transition TC, whereas for PSN is below TC. It is shown that the first critical pressure pc1, at which a transition from a relaxor to a non-polar rhombohedral state with antiphase octahedral tilt ordering occurs, decreases at elevated temperatures due to the weakening of the polar coupling, which in turn facilitates the evolution of the preexisting medium-range antiferrodistortive order into a long-range order. The critical pressure pc2 of the second phase transition, involving a change in the type of the antiferrodistortive order, is not affected by temperature, i.e. it is independent of the state of polar coupling and is mainly related to the initial correlation length of antiferrodistortive order. The strong influence of temperature on pc1, which occurs only when the mesoscopic polar order is suppressed, emphasizes the importance of coexisting ferroelectric and antiferrodistortive coupling for the occurrence of the relaxor states.

  6. Reversible phase transition and relaxor behavior in Te2V2O9 single crystals grown by Czochralski technique

    NASA Astrophysics Data System (ADS)

    Shet, Tukaram; Varma, K. B. R.

    2016-09-01

    Te2V2O9 single crystals were grown along the polar c-axis via the Czochralski crystal growth technique. Dielectric studies carried out along the polar axis in a wide temperature range at different frequencies confirmed the relaxor nature of the Te2V2O9 single crystals. Temperature dependent polarized light optical microscopy along a-axis established a reversible phase transition around 614 K. Relaxor nature of Te2V2O9 was attributed to the compositional heterogeneity at micro/nano scale within the grown crystal as vanadium was observed to be present in different oxidation states by X-ray photoelectron spectroscopic studies.

  7. Temperature independent shear piezoelectric response in relaxor-PbTiO3 based crystals

    PubMed Central

    Li, Fei; Zhang, Shujun; Xu, Zhuo; Wei, Xiaoyong; Luo, Jun; Shrout, Thomas R.

    2010-01-01

    The temperature dependence of the shear piezoelectric responses in relaxor-PbTiO3 based perovskite crystals with rhombohedral, orthorhombic, and tetragonal phases were investigated. Based on thermodynamic analysis, high shear piezoelectric coefficients (d24) and good thermal stability were predicted in orthorhombic crystals, owing to the “vertical” orthorhombic-rhombohedral phase boundary. By resonance measurements, shear piezoelectric coefficient d24 was found to be on the order of ∼2100 pC∕N at room temperature, maintaining same value over the temperature range of −50–100 °C. In contrast, the shear piezoelectric coefficients d15, with values of 3300, 3600, and 2000 pC∕N at room temperature for rhombohedral, orthorhombic, and tetragonal crystals, respectively, exhibited strong temperature dependent behavior due to their respective ferroelectric-ferroelectric phase transitions. PMID:21245942

  8. Ferroelectric and photocatalytic behavior of bismuth ferrite nano wire

    NASA Astrophysics Data System (ADS)

    William, R. V.; Marikani, A.; Madhavan, D.

    2016-05-01

    Multiferroic bismuth ferrite nanowires are prepared through polyol method with an average diameter of 35 nm with a narrow size distribution. The band gap was determined to be 2.10 eV, indicating their potential application as visible-light-response photo catalyst. The magnificent photocatalytic behaviors of BiFeO3 nanowires are understood from the methyl violet degradation under visible light irradiation. Moreover, the nano-wire takes only a lesser time for the diffusion of electron-hole pair from the surface of the sample. Further the BiFeO3 nano-wire was characterized using XRD, SEM, and U-V. The ferroelectric studies of BiFeO3 nano-wire show a frequency dependent property and maximum coercivity of 2.7 V/cm were achieved with a remanent polarization at 0.5 µC/cm2 at the frequency 4 kHz. The coercivity of BiFeO3 nano wire changes with variation of frequency from 1 kHz to 4 kHz.

  9. Targeted basic studies of ferroelectric and ferroelastic materials for piezoelectric transducer applications

    NASA Astrophysics Data System (ADS)

    Cross, L. E.; Newnham, R. E.; Barsch, G. R.; Biggers, J. V.

    1983-03-01

    The work reported covers the fifth and final year of the program of targeted basic studies of ferroelectric and ferroelastic materials for piezoelectric transducer applications. Major achievements include: the development of a physical approach to understanding active composites, leading to the development of several new families of PZT, polymer piezoelectric composites for hydrophone application. These are new advances in the phenomenology and microscopic theory of electrostriction, and the evolution of a new family of high strain ferroelectric relaxor materials for practical application. New basic understanding of the polarization mechanisms in ferroelectric relaxors has been aided by the study of order disorder of the cation arrangement in lead scandium tantalate, and the results correlate well with studies of relaxor behavior, and of shape memory effects in PLZT ceramics. Low temperature studies on pure and doped PZTs have given the first clear indication of the intrinsic (averaged) single domain in response and correlate exceedingly well with earlier phenomenological theory. Crystal growth and ceramic processing studies have developed hand in hand with program needs providing new forms of conventional materials, new grain oriented structures and single crystals.

  10. Ferroelectric precursor behavior in PbSc0.5Ta0.5O3 detected by field-induced resonant piezoelectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Aktas, Oktay; Salje, Ekhard K. H.; Crossley, Sam; Lampronti, Giulio I.; Whatmore, Roger W.; Mathur, Neil D.; Carpenter, Michael A.

    2013-11-01

    A novel experimental technique, resonant piezoelectric spectroscopy (RPS), has been applied to investigate polar precursor effects in highly (65%) B-site ordered PbSc0.5Ta0.5O3 (PST), which undergoes a ferroelectric phase transition near 300 K. The cubic-rhombohedral transition is weakly first order, with a coexistence interval of ˜4 K, and is accompanied by a significant elastic anomaly over a wide temperature interval. Precursor polarity in the cubic phase was detected as elastic vibrations generated by local piezoelectric excitations in the frequency range 250-710 kHz. The RPS resonance frequencies follow exactly the frequencies of elastic resonances generated by conventional resonant ultrasound spectroscopy (RUS) but RPS signals disappear on heating beyond an onset temperature, Tonset, of 425 K. Differences between the RPS and RUS responses can be understood if the PST structure in the precursor regime between Tonset and the transition point, Ttrans=300 K, has locally polar symmetry even while it remains macroscopically cubic. It is proposed that this precursor behavior could involve the development of a tweed microstructure arising by coupling between strain and multiple order parameters, which can be understood from the perspective of Landau theory. As a function of temperature the transition is driven by the polar displacement P and the order parameter for cation ordering on the crystallographic B site Qod. Results in the literature show that, as a function of pressure, there is a separate instability driven by octahedral tilting for which the assigned order parameter is Q. The two mainly displacive order parameters, P and Q, are unfavorably coupled via a biquadratic term Q2P2, and complex tweedlike fluctuations in the precursor regime would be expected to combine aspects of all the order parameters. This would be different from the development of polar nanoregions, which are more usually evoked to explain relaxor ferroelectric behavior, such as occurs in

  11. High energy-storage performance of 0.9Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.1PbTiO{sub 3} relaxor ferroelectric thin films prepared by RF magnetron sputtering

    SciTech Connect

    Wang, Xiaolin; Zhang, Le; Hao, Xihong An, Shengli

    2015-05-15

    Highlights: • High-quality PMN-PT 90/10 RFE thin films were prepared by RF magnetron sputtering. • The maximum discharged density of 31.3 J/cm{sup 3} was obtained in the 750-nm-thick film. • PMN-PT RFE films might be a promising material for energy-storage application. - Abstract: 0.9Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.1PbTiO{sub 3} (PMN-PT 90/10) relaxor ferroelectric thin films with different thicknesses were deposited on the LaNiO{sub 3}/Si (100) by the radio-frequency (RF) magnetron sputtering technique. The effects of thickness and deposition temperature on the microstructure, dielectric properties and the energy-storage performance of the thin films were investigated in detail. X-ray diffraction spectra indicated that the thin films had crystallized into a pure perovskite phase with a (100)-preferred orientation after annealed at 700 °C. Moreover, all the PMN-PT 90/10 thin films showed the uniform and crack-free surface microstructure. As a result, a larger recoverable energy density of 31.3 J/cm{sup 3} was achieved in the 750-nm-thick film under 2640 kV/cm at room temperature. Thus, PMN-PT 90/10 relaxor thin films are the promising candidate for energy-storage capacitor application.

  12. Note: High-power piezoelectric transformer fabricated with ternary relaxor ferroelectric Pb(Mg(1/3)Nb(2/3))O3-Pb(In(1/2)Nb(1/2))O3-PbTiO3 single crystal.

    PubMed

    Wang, Qing; Ma, Chuanguo; Wang, Feifei; Liu, Bao; Chen, Jianwei; Luo, Haosu; Wang, Tao; Shi, Wangzhou

    2016-03-01

    A plate-shaped piezoelectric transformer was designed and fabricated using ternary relaxor ferroelectric single crystal Pb(Mg(1/3)Nb(2/3))O3-Pb(In(1/2)Nb(1/2))O3-PbTiO3. Both the input and output sections utilized the transverse-extensional vibration mode. The frequency and load dependences of the electrical properties for the proposed transformer were systematically studied. Results indicated that under a matching load resistance of 14.9 kΩ, a maximum output power of 2.56 W was obtained with the temperature rise less than 5 °C. The corresponding power density reached up to 50 W/cm(3). This ternary single-crystal transformer had potential applications in compact-size converters requiring high power density. PMID:27036838

  13. Note: High-power piezoelectric transformer fabricated with ternary relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Ma, Chuanguo; Wang, Feifei; Liu, Bao; Chen, Jianwei; Luo, Haosu; Wang, Tao; Shi, Wangzhou

    2016-03-01

    A plate-shaped piezoelectric transformer was designed and fabricated using ternary relaxor ferroelectric single crystal Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbTiO3. Both the input and output sections utilized the transverse-extensional vibration mode. The frequency and load dependences of the electrical properties for the proposed transformer were systematically studied. Results indicated that under a matching load resistance of 14.9 kΩ, a maximum output power of 2.56 W was obtained with the temperature rise less than 5 °C. The corresponding power density reached up to 50 W/cm3. This ternary single-crystal transformer had potential applications in compact-size converters requiring high power density.

  14. Room-temperature ferromagnetic and ferroelectric behavior in polycrystalline ZnO-based thin films

    NASA Astrophysics Data System (ADS)

    Lin, Yuan-Hua; Ying, Minghao; Li, Ming; Wang, Xiaohui; Nan, Ce-Wen

    2007-05-01

    Polycrystalline ZnO-based thin films with Li and/or Co doping have been prepared by a sol-gel spin-coating method on silicon substrates. Magnetization measurements reveal that Li-doped ZnO film shows paramagnetic behavior. However, the Co-doped ZnO thin films show obvious room-temperature ferromagnetic properties, and ferromagnetic properties can be enhanced by the Li codoping, which may be ascribed to indirect exchange via Li-related defects. All ZnO-based films exhibit ferroelectric behavior, and ferroelectric properties can be tuned by the dopants.

  15. Role of point defects in bipolar fatigue behavior of Bi(Mg1/2Ti1/2)O3 modified (Bi1/2K1/2)TiO3-(Bi1/2Na1/2)TiO3 relaxor ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, Nitish; Ansell, Troy Y.; Cann, David P.

    2014-04-01

    Lead-free Bi(Mg1/2Ti1/2)O3-(Bi1/2K1/2)TiO3-(Bi1/2Na1/2)TiO3 (BMT-BKT-BNT) ceramics have been shown to exhibit large electromechanical strains under high electric fields along with negligible fatigue under strong electric fields. To investigate the role of point defects on the fatigue characteristics, the composition 5BMT-40BKT-55BNT was doped to incorporate acceptor and donor defects on the A and B sites by adjusting the Bi/Na and Ti/Mg stoichiometries. All samples had pseudo-cubic symmetries based on x-ray diffraction, typical of relaxors. Dielectric measurements showed that the high and low temperature phase transitions were largely unaffected by doping. Acceptor doping resulted in the observation of a typical ferroelectric-like polarization with a remnant polarization and strain hysteresis loops with significant negative strain. Donor-doped compositions exhibited characteristics that were indicative of an ergodic relaxor phase. Fatigue measurements were carried out on all of the compositions. While the A-site acceptor-doped composition showed a small degradation in maximum strain after 106 cycles, the other compositions were essentially fatigue free. Impedance measurements were used to identify the important conduction mechanisms in these compositions. As expected, the presence of defects did not strongly influence the fatigue behavior in donor-doped compositions owing to the nature of their reversible field-induced phase transformation. Even for the acceptor-doped compositions, which had stable domains in the absence of an electric field at room temperature, there was negligible degradation in the maximum strain due to fatigue. This suggests that either the defects introduced through stoichiometric variations do not play a prominent role in fatigue in these systems or it is compensated by factors like decrease in coercive field, an increase in ergodicity, symmetry change, or other factors.

  16. Study of glassy behavior in 60(Na0.5Bi0.5)TiO3-40SrTiO3 lead-free relaxor

    NASA Astrophysics Data System (ADS)

    Praharaj, S.; Rout, D.; Kar, B. B.; Subramanian, V.

    2016-05-01

    In this report, the glassy behavior of 60(Na0.5Bi0.5)TiO3-40SrTiO3 (NBT-40ST) lead-free perovskite relaxor was studied. The single phase ceramic sample was prepared with cubic symmetry by solid state reaction method. The temperature and frequency dependent dielectric data were analyzed in view point of relaxor and glassy behavior by employing various empirical models such as modified Curie-Weiss law, V-F law, Power law and Cheng's exponential relation. The diffuseness coefficient (γ~1.97) and the frequency dispersion of Tm (temperature corresponding to maximum dielectric constant) manifested strong relaxor behavior of NBT-40ST. The frequency dependent Tm analysis revealed greater interactions between the polar nano islands. Further, the study of dielectric behavior at much higher and lower temperature than Tm provided an idea about the production rate and concentration of these polar islands and distribution of freezing temperatures respectively.

  17. Study of the structure, dielectric and ferroelectric behavior of BaBi4+δTi4O15 ceramics

    NASA Astrophysics Data System (ADS)

    Khokhar, Anita; Goyal, Parveen K.; Thakur, O. P.; Sreenivas, K.

    2016-05-01

    The structure and ferroelectric properties of excess bismuth doped barium bismuth titanate BaBi4+δTi4O15 (δ = 2 - 10 wt.%)) ceramics prepared by solid-state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of a single phase material with a change in the orthorhombic distortion with varying excess of bismuth content. There is no change in the phase transition temperature (Tm) while the relaxor behaviour has been modified significantly with excess of bismuth doping. Saturated hysteresis loops with high remnant polarization (Pr ~ 12.5 µC/cm2), low coercive fields (Ec ~ 26 kV/cm) are measured and a high piezoelectric coefficient (d33 ~ 29 pC/N) is achieved in poled BaBi4Ti4O15 ceramics prepared with up to 8 wt.% of excess bismuth oxide. The improvement in the ferroelectric properties with increase in the excess bismuth content in BaBi4Ti4O15 ceramics has been explained in terms of changing oxygen vacancy concentration and structural relaxation. Tunable ferroelectric materials can be obtained by manipulating the doping amount of excess bismuth.

  18. Targeted basic studies of ferroelectric and ferroelastic materials for piezoelectric transducer applications

    NASA Astrophysics Data System (ADS)

    Cross, L. E.; Newnham, R. E.; Barsch, G. R.; Biggers, J. V.

    1983-03-01

    The report delineates the new progress made in the fifth and final year and discusses the major accomplishments of the full five year program both in the basic science and in the spin off to practical transducer applications. Possible new areas of study which are suggested by the present studies are briefly reported. Major achievements include the development of a physical approach to understanding active composites, leading to the development of several new families of PZT:polymer piezoelectric composites for hydrophone application. New advances in the phenomenology and microscopic theory of electrostriction, and the evolution of a new family of high strain ferroelectric relaxor materials for practical application. New basic understanding of the polarization mechanisms in ferroelectric relaxors has been aided by the study of order-disorder of the cation arrangement in lead scandium tantalate, and the results correlate well with studies of relaxor behavior, and of shape memory effects in PLZT ceramics. Low temperature studies on pure and doped PZTs have given the first clear indication of the intrinsic (averaged) single domain response and correlate exceedingly well with earlier phenomenological theory. Crystal growth and ceramic processing studies have developed hand-in-hand with program needs providing new forms of conventional materials, new grain oriented structures and single crystals.

  19. Piezo-/dielectric properties of perovskite-structure high-temperature relaxor ferroelectrics: The Pb(Lu{sub 1/2}Nb{sub 1/2})O{sub 3}–Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} ternary ceramics

    SciTech Connect

    Li, Tao; Long, Xifa

    2014-03-01

    Graphical abstract: - Highlights: • Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}-based ternary ferroelectric ceramics were prepared by solid-state synthesis method. • Morphotropic phase boundary region has been determined by XRD, di-/piezoelectric properties. • The compositions near MPB region exhibit excellent piezoelectric properties. - Abstract: A new compositional system of relaxor ferroelectrics was investigated based on the high piezoelectricity Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} ferroelectric perovskite family. Compositions were fabricated near an estimated morphotropic phase boundary (MPB) of the Pb(Lu{sub 1/2}Nb{sub 1/2})O{sub 3}–Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} (PLZNT) ternary system by a two-step synthetic process. Their structures have been analyzed by means of X-ray diffraction technique. On the basis of X-ray powder diffraction, the morphotropic phase boundary (MPB) region for the ternary system was obtained. The Curie temperature T{sub C} of ternary system varied from 240 °C to 330 °C and the coercive fields E{sub c}s > 10 kV/cm. The values of piezoelectric coefficients d{sub 33} vary in the range of 260–450 pC/N with different PZN contents. It is worth noting that the optimum compositions were located at MPB region but near the tetragonal phase. The new PLZNT ceramics exhibit wider range of T{sub C}s and E{sub c}s, making it a promising material for high-powder ultrasound transducers using in a large temperature range.

  20. Anisotropic behavior of water in ferroelectric liquid crystals.

    PubMed

    Singh, G; Choudhary, A; Prakash, G Vijaya; Biradar, A M

    2010-05-01

    The outcome of water addition in ferroelectric liquid crystal (FLC) has been investigated in uniform and defect-free homogeneous and homeotropically aligned monodomain sample cells from electro-optical and dielectric spectroscopic measurements. The lagging in optical response between nonconducting (spatially variable switching) and conducting (conventional switching) portions of water added FLC sample cell has been observed by frequency-dependent electro-optical studies. The bias-dependent water related new relaxation peak near the conventional Goldstone mode relaxation process has been observed only in the homogeneous alignment and not in the homeotropic one. Further, the significant increment in dielectric anisotropy as well as faster diffusion of water along long molecular axis than short molecular axis has also been monitored. These studies strongly suggest that the distribution of water is anisotropic in FLC medium and could be the reason for new relaxation peak in the water added FLC sample. PMID:20866247

  1. Relationship between ferroelectric properties and local structure of Pb1-xBaxZr0.40Ti0.60O3 ceramic materials studied by X-ray absorption and Raman spectroscopies

    NASA Astrophysics Data System (ADS)

    Mesquita, Alexandre; Michalowicz, Alain; Moscovici, Jacques; Pizani, Paulo Sergio; Mastelaro, Valmor Roberto

    2016-08-01

    This paper reports on the structural characterization of Pb1-xBaxZr0.40Ti0.60O3 (PBZT) ferroelectric ceramic compositions prepared by the conventional solid state reaction method. X-ray absorption spectroscopy (XAS) and Raman spectroscopy were used in the probing of the local structure of PBZT samples that exhibit a normal or relaxor ferroelectric behavior. They showed a considerable local disorder around Zr and Pb atoms in the samples of tetragonal or cubic long-range order symmetry. The intensity of the E(TO3) mode in the Raman spectra of PBZT relaxor samples remains constant at temperatures lower than Tm, which has proven the stabilization of the correlation process between nanodomains.

  2. Structure-property-performance relationships of new high temperature relaxors for capacitor applications

    NASA Astrophysics Data System (ADS)

    Stringer, Craig J.

    This thesis extends the investigations on perovskite solid solutions based on PbTiO3-Bi(Me',Me")O3 (Me' = Sc3+, Zn2+, Mg2+, Ni2+, In3+ , Fe3+, etc. and Me" = Ti4+, Nb 5+, W6+) systems. The ferroelectric transition temperature (TC) behavior was considered in the tetragonal phase region of the PbTiO 3-Bi(Me',Me")O3 systems. Trends in the TC compositional dependence exhibited three main cases: case 1, a continued increase in transition temperature above the end-member PbTiO3 (495°C); case 2, an increase and then decrease of the transition temperature; and case 3, a continuous decrease in the transition temperature with Bi(Me',Me")O 3 additions. New relaxor materials were developed from the PbTiO3-Bi(Me',Me")O 3 solid solutions; specifically, the Bi(Mg3/4W1/4)O 3-PbTiO3 (BMW-PT) binary solid solution and BiScO3-Pb(Mg 1/3Nb2/3)O3-PbTiO3 (BS-PMN-PT) ternary solid solution were investigated. Permittivity, polarization and pyroelectric measurements were performed on BMW-PT and BS-PMN-PT compositions with respect to temperature with characteristic relaxor behavior observed. The complex solid solution BMW-PT exhibited a morphotropic phase boundary at ˜48 mol% PbTiO3 with a corresponding TC of 205°C. On further structural analysis with diffraction contrast transmission electron microscopy along with x-ray diffraction, evidence of B-site ordering was observed. The BS-PMN-PT proved to be a model system with high temperature relaxor properties of Tmax ˜ 250°C to 300°C and εmax ˜ 14,000 to 17,000 at 1 kHz. The deviation temperature, TD, or temperature of the onset of local spontaneous polarization, was determined by thermal strain measurement and high temperature dielectric measurement to be approximately 600°C; up to 250°C higher than any reported value for relaxor ferroelectrics. The frequency dependence of the temperature of the permittivity maximum was found to follow the Vogel-Fulcher relationship, with an activation energy (EA) of ˜0.1 eV, and a freezing

  3. FAST TRACK COMMUNICATION: Re-entrant-like relaxor behaviour in the new 0.99BaTiO3 0.01AgNbO3 solid solution

    NASA Astrophysics Data System (ADS)

    Lei, Chao; Ye, Zuo-Guang

    2008-06-01

    A new solid solution of 0.99BaTiO3-0.01AgNbO3 was prepared by a solid state reaction. Its structural, dielectric and ferroelectric properties were investigated. Besides the three phase transitions associated with pure BaTiO3, the dielectric permittivity shows an additional peak around 100 °C. This peak exhibits a dielectric relaxation satisfying the Vogel-Fulcher law, indicating typical relaxor behaviour. The relaxor state occurs after the paraelectric to ferroelectric phase transition upon cooling, i.e., inside the ferroelectric phase, indicating a re-entrant-like phenomenon. This unusual phase transition sequence has never been reported in canonical lead-based ferroelectrics. Moreover, the relaxor state arises from a tetragonal phase rather than from a cubic phase as observed in conventional complex perovskite relaxors.

  4. Role of point defects in bipolar fatigue behavior of Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3} modified (Bi{sub 1/2}K{sub 1/2})TiO{sub 3}-(Bi{sub 1/2}Na{sub 1/2})TiO{sub 3} relaxor ceramics

    SciTech Connect

    Kumar, Nitish Ansell, Troy Y.; Cann, David P.

    2014-04-21

    Lead-free Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-(Bi{sub 1/2}K{sub 1/2})TiO{sub 3}-(Bi{sub 1/2}Na{sub 1/2})TiO{sub 3} (BMT-BKT-BNT) ceramics have been shown to exhibit large electromechanical strains under high electric fields along with negligible fatigue under strong electric fields. To investigate the role of point defects on the fatigue characteristics, the composition 5BMT-40BKT-55BNT was doped to incorporate acceptor and donor defects on the A and B sites by adjusting the Bi/Na and Ti/Mg stoichiometries. All samples had pseudo-cubic symmetries based on x-ray diffraction, typical of relaxors. Dielectric measurements showed that the high and low temperature phase transitions were largely unaffected by doping. Acceptor doping resulted in the observation of a typical ferroelectric-like polarization with a remnant polarization and strain hysteresis loops with significant negative strain. Donor-doped compositions exhibited characteristics that were indicative of an ergodic relaxor phase. Fatigue measurements were carried out on all of the compositions. While the A-site acceptor-doped composition showed a small degradation in maximum strain after 10{sup 6} cycles, the other compositions were essentially fatigue free. Impedance measurements were used to identify the important conduction mechanisms in these compositions. As expected, the presence of defects did not strongly influence the fatigue behavior in donor-doped compositions owing to the nature of their reversible field-induced phase transformation. Even for the acceptor-doped compositions, which had stable domains in the absence of an electric field at room temperature, there was negligible degradation in the maximum strain due to fatigue. This suggests that either the defects introduced through stoichiometric variations do not play a prominent role in fatigue in these systems or it is compensated by factors like decrease in coercive field, an increase in ergodicity, symmetry change, or other factors.

  5. Memristive behaviors in Pt/BaTiO{sub 3}/Nb:SrTiO{sub 3} ferroelectric tunnel junctions

    SciTech Connect

    Wen, Zheng; Wu, Di Li, Aidong

    2014-08-04

    We demonstrate memristive behaviors in Pt/BaTiO{sub 3}/Nb:SrTiO{sub 3} metal/ferroelectric/semiconductor ferroelectric tunnel junctions, in which the semiconductor electrode can be switched between the accumulated and the depleted states by polarization reversal in the BaTiO{sub 3} barrier via the ferroelectric field effect. An extra barrier, against electron tunneling, forms in the depleted region of the Nb:SrTiO{sub 3} electrode surface, which together with the ferroelectric barrier itself modulate the tunneling resistance with the change of effective polarization. Continuous resistance modulation over four orders of magnitude is hence achieved by application of programmed voltage pulses with different polarity, amplitude, and repetition numbers, as a result of the development of the extra barrier.

  6. Magnetoelectric relaxor and reentrant behaviours in multiferroic Pb(Fe2/3W1/3)O3 crystal

    PubMed Central

    Chen, Ling; Bokov, Alexei A.; Zhu, Weimin; Wu, Hua; Zhuang, Jian; Zhang, Nan; Tailor, Hamel N.; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Significant quenched disorder in crystal structure can break ferroic (magnetic or electric) long-range order, resulting in the development of ferroic glassy states at low temperatures such as magnetic spin glasses, electric dipolar glasses, relaxor ferroelectrics, etc. These states have been widely studied due to novel physical phenomena they reveal. Much less known are the effects of quenched disorder in multiferroics, i.e. the materials where magnetic and electric correlations coexist. Here we report an unusual behaviour in complex perovskite Pb(Fe2/3W1/3)O3 (PFW) crystals: the coexistence of electric relaxor, magnetic relaxor and antiferromagnetic (AFM) states. The most striking finding is the transformation of the AFM phase into a new reentrant-type magnetic glassy phase below Tg ≅ 10 K. We show that the behaviour at this transformation contrasts the typical behaviour of canonical spin glasses and is similar to the behaviour of relaxor ferroelectrics. Magnetoelectric effect is also observed in the AFM phase in the temperature range of the transition into electric relaxor phase at Tf ≅ 200. The mechanism of magnetic relaxor behaviour is supposed to arise from the frustrated interactions among the spins located at the AFM domain walls. Our results should inspire further studies of multirelaxor behaviour in other multiferroic systems. PMID:26936414

  7. Magnetoelectric relaxor and reentrant behaviours in multiferroic Pb(Fe2/3W1/3)O3 crystal

    NASA Astrophysics Data System (ADS)

    Chen, Ling; Bokov, Alexei A.; Zhu, Weimin; Wu, Hua; Zhuang, Jian; Zhang, Nan; Tailor, Hamel N.; Ren, Wei; Ye, Zuo-Guang

    2016-03-01

    Significant quenched disorder in crystal structure can break ferroic (magnetic or electric) long-range order, resulting in the development of ferroic glassy states at low temperatures such as magnetic spin glasses, electric dipolar glasses, relaxor ferroelectrics, etc. These states have been widely studied due to novel physical phenomena they reveal. Much less known are the effects of quenched disorder in multiferroics, i.e. the materials where magnetic and electric correlations coexist. Here we report an unusual behaviour in complex perovskite Pb(Fe2/3W1/3)O3 (PFW) crystals: the coexistence of electric relaxor, magnetic relaxor and antiferromagnetic (AFM) states. The most striking finding is the transformation of the AFM phase into a new reentrant-type magnetic glassy phase below Tg ≅ 10 K. We show that the behaviour at this transformation contrasts the typical behaviour of canonical spin glasses and is similar to the behaviour of relaxor ferroelectrics. Magnetoelectric effect is also observed in the AFM phase in the temperature range of the transition into electric relaxor phase at Tf ≅ 200. The mechanism of magnetic relaxor behaviour is supposed to arise from the frustrated interactions among the spins located at the AFM domain walls. Our results should inspire further studies of multirelaxor behaviour in other multiferroic systems.

  8. Magnetoelectric relaxor and reentrant behaviours in multiferroic Pb(Fe2/3W1/3)O3 crystal.

    PubMed

    Chen, Ling; Bokov, Alexei A; Zhu, Weimin; Wu, Hua; Zhuang, Jian; Zhang, Nan; Tailor, Hamel N; Ren, Wei; Ye, Zuo-Guang

    2016-01-01

    Significant quenched disorder in crystal structure can break ferroic (magnetic or electric) long-range order, resulting in the development of ferroic glassy states at low temperatures such as magnetic spin glasses, electric dipolar glasses, relaxor ferroelectrics, etc. These states have been widely studied due to novel physical phenomena they reveal. Much less known are the effects of quenched disorder in multiferroics, i.e. the materials where magnetic and electric correlations coexist. Here we report an unusual behaviour in complex perovskite Pb(Fe2/3W1/3)O3 (PFW) crystals: the coexistence of electric relaxor, magnetic relaxor and antiferromagnetic (AFM) states. The most striking finding is the transformation of the AFM phase into a new reentrant-type magnetic glassy phase below Tg ≅ 10 K. We show that the behaviour at this transformation contrasts the typical behaviour of canonical spin glasses and is similar to the behaviour of relaxor ferroelectrics. Magnetoelectric effect is also observed in the AFM phase in the temperature range of the transition into electric relaxor phase at Tf ≅ 200. The mechanism of magnetic relaxor behaviour is supposed to arise from the frustrated interactions among the spins located at the AFM domain walls. Our results should inspire further studies of multirelaxor behaviour in other multiferroic systems. PMID:26936414

  9. Debye Relaxations, Fano Resonances and Heterophase Oscillations in the Relaxor K1-xLixTaO3

    NASA Astrophysics Data System (ADS)

    Toulouse, Jean; Cai, Ling; Pattnaik, Radha; Boatner, Lynn

    2013-03-01

    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 K1-xLixTaO3 (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. This work was partially supported by grant DE-FG02-06ER46318 from the US Department of Energy.

  10. Dielectric properties of PbNb{sub 2}O{sub 6} ferroelectric ceramics at cryogenic temperatures

    SciTech Connect

    Guerra, J. de los S; Venet, M.; Garcia, D.; Eiras, J. A.; Guerrero, F.

    2007-08-06

    Complex dielectric permittivity measurements in PbNb{sub 2}O{sub 6} ceramics were performed in a frequency and temperature range of 1 kHz-1 MHz and from 15 to 900 K, respectively. The results revealed two dielectric anomalies showing typical characteristics of relaxor ferroelectric materials at cryogenic temperatures. Comparison with other tetragonal tungsten bronze (TTB) structure-type materials suggests the existence of successive phase transitions, which until now were not reported. The observed low temperature dielectric behaviors seem to be due to intrinsic physical characteristics related to the TTB structure.

  11. Oxygen-vacancy-related dielectric relaxation in SrBi2Ta1.8V0.2O9 ferroelectrics

    NASA Astrophysics Data System (ADS)

    Wu, Yun; Forbess, Mike J.; Seraji, Seana; Limmer, Steven J.; Chou, Tammy P.; Cao, Guozhong

    2001-05-01

    The strontium bismuth tantalate vanadate, SrBi2Ta1.8V0.2O9, (SBTV) layered perovskite ferroelectrics were made by solid state powder sintering. It was found that the SBTV ferroelectrics had the same crystal structure as that of strontium bismuth tantalate, SrBi2Ta2O9 (SBT), but an increased paraferroelectric transition temperature at ˜360 °C as compared to 305 °C for SBT. In addition, SBTV ferroelectrics showed a frequency dispersion at low frequencies and broadened dielectric peaks at the paraferroelectric transition temperature that shifted to a higher temperature with a reduced frequency. However, after a postsintering annealing at 850 °C in air for 60 h, SBTV ferroelectrics showed reduced dielectric constants and tangent loss, particularly at high temperatures. In addition, no frequency dependence of paraferroelectric transition was found in the annealed SBTV ferroelectrics. Furthermore, there was a significant reduction in dc conductivity with annealing. The prior results implied that the dielectric relaxation in the as-sintered SBTV ferroelectrics was most likely due to the oxygen-vacancy-related dielectric relaxation instead of relaxor ferroelectric behavior.

  12. Stress effects in ferroelectric perovskite thin-films

    NASA Astrophysics Data System (ADS)

    Zednik, Ricardo Johann

    The exciting class of ferroelectric materials presents the engineer with an array of unique properties that offer promise in a variety of applications; these applications include infra-red detectors ("night-vision imaging", pyroelectricity), micro-electro-mechanical-systems (MEMS, piezoelectricity), and non-volatile memory (NVM, ferroelectricity). Realizing these modern devices often requires perovskite-based ferroelectric films thinner than 100 nm. Two such technologically important material systems are (Ba,Sr)TiO3 (BST), for tunable dielectric devices employed in wireless communications, and Pb(Zr,Ti)O3 (PZT), for ferroelectric non-volatile memory (FeRAM). In general, the material behavior is strongly influenced by the mechanical boundary conditions imposed by the substrate and surrounding layers and may vary considerably from the known bulk behavior. A better mechanistic understanding of these effects is essential for harnessing the full potential of ferroelectric thin-films and further optimizing existing devices. Both materials share a common crystal structure and similar properties, but face unique challenges due to the design parameters of these different applications. Tunable devices often require very low dielectric loss as well as large dielectric tunability. Present results show that the dielectric response of BST thin-films can either resemble a dipole-relaxor or follow the accepted empirical Universal Relaxation Law (Curie-von Schweidler), depending on temperature. These behaviors in a single ferroelectric thin-film system are often thought to be mutually exclusive. In state-of-the-art high density FeRAM, the ferroelectric polarization is at least as important as the dielectric response. It was found that these properties are significantly affected by moderate biaxial tensile and compressive stresses which reversibly alter the ferroelastic domain populations of PZT at room temperature. The 90-degree domain wall motion observed by high resolution

  13. Experimental studies on physical deterioration and electrical fatigue behavior in ferroelectric polymers

    NASA Astrophysics Data System (ADS)

    He, Xiangtong

    Ferroelectric materials are widely used in various electronic applications based upon their excellent electrical bi-stabilities and dielectric performance in response to the applied electric field. They have been utilized to make nonvolatile electronic memories by exploiting the hysteretic behavior and high energy density capacitors in regard to the high capability of electrical energy storage. One critical issue is that the ferroelectrics are required to endure a large number of electrical cycles. A large body of scientific efforts has been devoted to high fatigue failure resistance of ferroelectric-based electronic devices. Fatigue failure of ferroelectric materials still needs to be solved. It is the objective of this work to explore the intrinsic origin of fatigue failure mechanisms. In this study, it was found that electric-field-induced stress relaxation in α-phase poly(vinylidene fluoride) (PVDF) films can be well described by using the Kohlraush function groups, also known as the stretched exponential relaxation function. The electric strength of the dielectric is strongly dependent on its elastic properties due to the electromechanical coupling effect. Our fitting result of the stretched exponent is in accordance with a Weibull cumulative distribution function. This indicates that the elastic properties of insulating polymers are crucial to the capability of electrical energy storage. In ferroelectric materials, the electromechanical coupling may be indicative of the microscopic origin of polarization fatigue. Further experiments were focused on the polarization fatigue in semi-crystalline poly(vinylidene fluoride trifluoroethylene) [P(VDF-TrFE)] copolymers films, whose ferroelectric response is superior to PVDF homopolymer films. Fatigue resistance of normal virgin P(VDF-TrFE) films was compared to that of P(VDF-TrFE) films modulated by using magnetic field. It was shown that normal P(VDF-TrFE) films exhibit a higher fatigue resistance. The artificially

  14. Grain size dependent phase transition and superparaelectric behavior of ferroelectric BST

    NASA Astrophysics Data System (ADS)

    Mondal, R. A.; Murty, B. S.; Murthy, V. R. K.

    2015-03-01

    In this article, we investigate the grain size dependent phase transition and polarization behavior of ferroelectric Ba0.9Sr0.1TiO3 (BST). Starting with nanocrystalline powders (crystalline size≈22 nm), various grain sizes were obtained in nano-submicron domain (202-745 nm) by regulating the sintering temperatures (Tsin) in the range of 1050-1300 °C. All samples were found to possess diffuse phase transition characteristics with frequency independent broad dielectric maxima near transition temperature due to the lattice strain contribution. Dielectric stiffness showed tarnished step-like anomalous behavior in the paraelectric state for Tsin≥1200 °C due to the existence of polar (superparaelectric) nano-regions generated by local polarization by off-centered Ti4+ ions exhibiting an exceptionally rare delicate polarization hysteresis loop.

  15. Observation of adsorption behavior of biomolecules on ferroelectric crystal surfaces with polarization domain patterns

    NASA Astrophysics Data System (ADS)

    Nakayama, Tomoaki; Isobe, Akiko; Ogino, Toshio

    2016-08-01

    Lithium tantalate (LiTaO3) is one of the ferroelectric crystals that exhibit spontaneous polarization domain patterns on its surface. We observed the polarization-dependent adsorption of avidin molecules, which are positively charged in a buffer solution at pH 7.0, on LiTaO3 surfaces caused by electrostatic interaction at an electrostatic double layer using atomic force microscopy (AFM). Avidin adsorption in the buffer solution was confirmed by scratching the substrate surfaces using the AFM cantilever, and the adsorption patterns were found to depend on the avidin concentration. When KCl was added to the buffer solution to weaken the electrostatic double layer interaction between avidin molecules and LiTaO3 surfaces, adsorption domain patterns disappeared. From the comparison between the adsorption and chemically etched domain patterns, it was found that avidin molecule adsorption is enhanced on negatively polarized domains, indicating that surface polarization should be taken into account in observing biomolecule behaviors on ferroelectric crystals.

  16. Structural, optical and ferroelectric behavior of hydrothermally grown ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Chand, Prakash; Gaur, Anurag; Kumar, Ashavani

    2013-12-01

    In the present study, zinc oxide (ZnO) nanostructures have been synthesized at 100 °C for different aging periods, 1, 24, 48 and 96 h by hydrothermal method. Structural, optical and ferroelectric properties were investigated using X-ray diffractometer, field emission scanning electron microscope, Transmission electron microscope, photoluminescence, UV-visible, Raman spectroscopy and P-E loop tracer. The X-ray diffractometer pattern indicates the pure phase formation of ZnO without any impurity for the samples synthesized from 1 to 96 h aging periods, respectively. Field emission scanning electron microscope and transmission electron microscope analysis also shows that the average diameter and length of these nanorods increases with increasing the aging periods. Moreover Raman and Photoluminescence spectrum also confirm the wurtzite phase formation of ZnO. The optical band gaps calculated through UV-visible spectroscopy are found to decrease from 3.81 to 3.45 eV with increase in aging periods, 1-96 h, respectively. Further, improved ferroelectric behavior has been observed for 48 and 96 h aged samples.

  17. Polarization and resistive switching behavior of ferroelectric tunnel junctions with transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Li, Tao; Lipatov, Alexey; Sharma, Pankaj; Lee, Hyungwoo; Eom, Chang-Beom; Sinitskii, Alexander; Gruverman, Alexei; Alexei Gruverman Team; Alexander Sinitskii Team; Chang-Beom Eom Team

    Transition metal dichalcogenides (TMDs) are emerging 2-dimensional (2D) materials of the MX2 type, where M is a transition metal atom (Mo, W, Ti, Sn, Zr, etc.) and X is a chalcogen atom (S, Se, or Te.). Comparing to graphene, TMDs have a sizable band gap and can be metal, half-metal, semiconductor or superconductor. Their band structures can be tuned by external bias voltage, mechanical force, or light illumination. Their rich physical properties make TMDs potential candidates for a variety of applications in nanoelectronics and optoelectronics. Ferroelectric tunnel junctions (FTJs) are actively studied as a next-generation of non-volatile memory elements. An FTJ comprises a ferroelectric tunnel barrier sandwiched between two electrodes. In this work, we investigate the resistive switching behavior of MoS2/BaTiO3-based FTJs. The ON/OFF ratio can be modulated via electric or mechanical control of the switched polarization fraction opening a possibility of tunable electroresistance effect. Effect of optical illumination on the polarization reversal dynamics has been observed and analyzed based on the polarization-induced modulation of the MoS2 layered electronic properties.

  18. Ferroelectric behavior of Li-doped ZnO thin films on Si(100) by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Joseph, M.; Tabata, H.; Kawai, T.

    1999-04-01

    Thin films of Li-doped ZnO of different compositions (Zn1-xLix)O, x=0.1, 0.17, and 0.3 have been prepared on Si(100) substrates, with no buffer layer, by the pulsed laser deposition method. Ferroelectric behavior with a memory window of 1.2 V has been observed in capacitance-voltage measurements. The peak maximum in the capacitance-temperature curve suggests that the ferroelectric phase transition occurs around 340 K.

  19. Structure and Relaxor Behaviour of Ba2+ Substituted NBT Ceramics

    NASA Astrophysics Data System (ADS)

    Rao, K. Sambasiva; Tilak, B.; Rajulu, K. Ch. Varada; Swathi, A.; Workineh, Haileeyesus; Ganagadharudu, D.

    2011-11-01

    In the course of search for environmental-friendly lead-free relaxor ferroelectrics, (Bi,Na)TiO3-(NBT) based ceramics show very good physical properties among several lead-free compositions. The NBT composition exhibits a strong ferroelectricity and high Curie temperature, and considered to be a good candidate for lead-free ceramics as a substitute for lead-based materials (e.g., PZT). In the present communication barium substituted NBT, (Na0.5Bi0.5)0.912Ba0.088TiO3-0.088BNBT composition has been prepared by conventional solid-state reaction process. The tolerance factor has been estimated and found to be 0.819, indicating the stability of the perovskite structure. The XRD analysis of the material revealed a pure perovskite with tetragonal structure. The average grain size as observed from SEM, was found to be 1.04μm. Detailed studies exhibit a relaxor behaviour with diffuse phase transition. The diffuseness parameter has been established to be 1.97. The dielectric relaxation obeyed the Vogel-Fulcher (V-F) relation. From the V-F plot, the obtained values are Tf = 305°C, Ea = 0.0131eV and νo = 2.95×105Hz, which provide the evidence of relaxor behaviour. The electrical behaviour has been probed through complex impedance spectroscopy. The frequency-dependent conductivity spectra obey the power law in the frequency range of 45Hz-5MHz and temperature range of 35 °C-60 °C.

  20. Electric-field-controlled interface strain coupling and non-volatile resistance switching of La{sub 1-x}Ba{sub x}MnO₃ thin films epitaxially grown on relaxor-based ferroelectric single crystals

    SciTech Connect

    Zheng, Ming; Zhu, Qiu-Xiang; Li, Xue-Yan; Yang, Ming-Min; Li, Xiao-Min; Shi, Xun; Luo, Hao-Su; Zheng, Ren-Kui; Wang, Yu

    2014-09-21

    We have fabricated magnetoelectric heterostructures by growing ferromagnetic La{sub 1-x}Ba{sub x}MnO₃ (x=0.2, 0.4) thin films on (001)-, (110)-, and (111)-oriented 0.31Pb(In{sub 1/2}Nb{sub 1/2})O₃-0.35Pb(Mg{sub 1/3}Nb{sub 1/2})O₃-0.34PbTiO₃ (PINT) ferroelectric single-crystal substrates. Upon poling along the [001], [110], or [111] crystal direction, the electric-field-induced non-180° domain switching gives rise to a decrease in the resistance and an enhancement of the metal-to-insulator transition temperature TC of the films. By taking advantage of the 180° ferroelectric domain switching, we identify that such changes in the resistance and TC are caused by domain switching-induced strain but not domain switching-induced accumulation or depletion of charge carriers at the interface. Further, we found that the domain switching-induced strain effects can be efficiently controlled by a magnetic field, mediated by the electronic phase separation. Moreover, we determined the evolution of the strength of the electronic phase separation against temperature and magnetic field by recording the strain-tunability of the resistance [(ΔR/R){sub strain}] under magnetic fields. Additionally, opposing effects of domain switching-induced strain on ferromagnetism above and below 197 K for the La₀.₈Ba₀.₂MnO₃ film and 150 K for the La₀.₆Ba₀.₄MnO₃ film, respectively, were observed and explained by the magnetoelastic effect through adjusting the magnetic anisotropy. Finally, using the reversible ferroelastic domain switching of the PINT, we realized non-volatile resistance switching of the films at room temperature, implying potential applications of the magnetoelectric heterostructure in non-volatile memory devices.

  1. Electric-field-controlled interface strain coupling and non-volatile resistance switching of La1-xBaxMnO3 thin films epitaxially grown on relaxor-based ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Zheng, Ming; Zhu, Qiu-Xiang; Li, Xue-Yan; Yang, Ming-Min; Wang, Yu; Li, Xiao-Min; Shi, Xun; Luo, Hao-Su; Zheng, Ren-Kui

    2014-09-01

    We have fabricated magnetoelectric heterostructures by growing ferromagnetic La1-xBaxMnO3 (x = 0.2, 0.4) thin films on (001)-, (110)-, and (111)-oriented 0.31Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb1/2)O3-0.34PbTiO3 (PINT) ferroelectric single-crystal substrates. Upon poling along the [001], [110], or [111] crystal direction, the electric-field-induced non-180° domain switching gives rise to a decrease in the resistance and an enhancement of the metal-to-insulator transition temperature TC of the films. By taking advantage of the 180° ferroelectric domain switching, we identify that such changes in the resistance and TC are caused by domain switching-induced strain but not domain switching-induced accumulation or depletion of charge carriers at the interface. Further, we found that the domain switching-induced strain effects can be efficiently controlled by a magnetic field, mediated by the electronic phase separation. Moreover, we determined the evolution of the strength of the electronic phase separation against temperature and magnetic field by recording the strain-tunability of the resistance [(ΔR/R)strain] under magnetic fields. Additionally, opposing effects of domain switching-induced strain on ferromagnetism above and below 197 K for the La0.8Ba0.2MnO3 film and 150 K for the La0.6Ba0.4MnO3 film, respectively, were observed and explained by the magnetoelastic effect through adjusting the magnetic anisotropy. Finally, using the reversible ferroelastic domain switching of the PINT, we realized non-volatile resistance switching of the films at room temperature, implying potential applications of the magnetoelectric heterostructure in non-volatile memory devices.

  2. Relaxor Behavior and Dielectric Relaxation in Lead-Free Solid Solutions of (1 - x)(Bi0.5Na0.5TiO3)- x(SrNb2O6)

    NASA Astrophysics Data System (ADS)

    Bajpai, P. K.; Singh, K. N.; Tamrakar, Preeti

    2016-02-01

    Lead-free compositions (1 - x) (Bi0.5Na0.5TiO3)- x(SrNb2O6) (BNT-SN) are synthesized by a simple solid state reaction route. SN diffuse in distorted perovskite BNT for low concentrations of SN ( x ≤ 0.03) and are stabilized in rhombohedral perovskite phase with experimentally observed relative density of the ceramics >92%. A temperature-dependent dielectric response exhibits a broad dielectric peak that shows frequency-dependent shifts towards higher temperatures reflecting typical relaxor behavior. Modified Curie-Weiss law and Lorentz-type empirical relationships are used to fit the dielectric data that exhibit almost complete diffuse phase transition characteristics. In addition, significant dielectric dispersion is observed in a low-frequency regime in both components of the dielectric response and a small dielectric relaxation peak is observed. Cole-Cole plots indicate the poly-dispersive nature of the dielectric relaxation.

  3. Fluctuating defects in the incipient relaxor K1-xLixTaO3 (x = 0 . 02)

    NASA Astrophysics Data System (ADS)

    Gehring, Peter; Stock, Chris; Xu, Guangyong; Lamago, Daniel; Reznik, Dmitry; Russina, Margarita; Wen, Jinsheng; Boatner, Lynn

    2015-03-01

    We have measured the structural correlations associated with the apparent relaxor transition near 70 K in K0.98Li0.02TaO3 (KLT(0.02)) with neutrons. No elastic diffuse scattering or soft mode anomaly is observed, a situation that diverges from that in other relaxors like PMN. The structural correlations in KLT(0.02) are dynamic at all temperatures with timescales of ~ THz. The fluctuations are overdamped, non-propagating, spatially uncorrelated, and absent in the parent material KTaO3. The temperature dependence correlates with the dielectric response, implying that the fluctuations are associated with local, ferroelectric regions induced by the Li-doping. The ferroelectric transition induced by the introduction of sufficient Li cations is thus characterized by quasistatic fluctuations, which is a stark contrast to the soft-harmonic-mode-driven transition observed in perovskite ferroelectrics like PbTiO3. The glass-like structural correlations in KLT(0.02) are much faster than those in random-field, lead-based relaxors, which occur on the ~ GHz timescale, and they are better correlated spatially. Our results support the view that random fields give rise to the relaxor phenomena, and that the glassy dynamics observed here represent a nascent response.

  4. Pressure as a probe of the glassy state of ferroelectrics with random site disorder

    SciTech Connect

    Samara, G.A.; Hansen, L.V.

    1998-03-10

    Results on lanthanum-modified lead zirconate-titanates (PLZTs) have revealed a pressure-induced crossover from a normal ferroelectric to a relaxor state and the continuous evolution of the dynamics and energetics of the relaxation process. This crossover appears to be a general feature of soft mode ferroelectrics with random site dipolar impurities or polar nanodomains and results from a large decrease in the correlation radius among polar nanodomains -- a unique property of soft mode ferroelectrics.

  5. Frequency-dependent ferroelectric behavior of BaMn3Ti4O14.25 at room temperature

    NASA Astrophysics Data System (ADS)

    Hossain, Muhammad E.; Liu, Shuangyi; O'Brien, Stephen; Li, Jackie

    2015-07-01

    We report the activation field and selective frequency-dependent ferroelectric behavior of BaMn3Ti4O14.25 (BMT-134) at room temperature. BMT-134, a recently discovered multiferroic complex oxide, exhibits antiferromagnetic and ferroelectric behavior and belongs to the hollandite crystal class. The microstructure can be manipulated through processing conditions to prepare a nanocrystalline textured tablet. We measured polarization-electric field (P-E) hysteresis loops and strain-electric field butterfly loops as a function of frequency in order to investigate the AC dynamics of domain switching and strain behavior. Under an electric field loading condition, a clear hysteresis loop of the electric field-displacement curve is obtained at 50 Hz, indicating that room temperature ferroelectricity is attainable under the right processing conditions. When the frequency is increased to 500 Hz, the coercive field also increases, until the frequency reaches 5 kHz, at which point the electric field versus electric displacement becomes linear indicating the limit of domain switching at high frequency.

  6. Relaxor-PT Single crystals: Observations and Developments

    PubMed Central

    Zhang, Shujun; Shrout, Thomas R.

    2011-01-01

    Relaxor-PT based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZNT) and Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) attracted lot of attentions in last decade due to their ultra high electromechanical coupling factors and piezoelectric coefficients. However, owing to a strongly curved morphotropic phase boundary (MPB), the usage temperature of these perovskite single crystals is limited by TRT - the rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature TC. Furthermore, the low mechanical quality factors and coercive fields of these crystals, usually being on the order of ~70 and 2–3kV/cm, respectively, restrict their usage in high power applications. Thus, it is desirable to have high performance crystals with high temperature usage range and high power characteristics. In this survey, different binary and ternary crystal systems were explored, with respect to their temperature usage range, general trends of dielectric and piezoelectric properties of relaxor-PT crystal systems were discussed related to their TC/TRT. In addition, two approaches were proposed to improve mechanical Q values, including acceptor dopant strategy, analogous to “hard” polycrystalline ceramics, and anisotropic domain engineering configurations. PMID:20889397

  7. Fluctuating defects in the incipient relaxor K1 -xLixTaO3 (x =0.02 )

    NASA Astrophysics Data System (ADS)

    Stock, C.; Gehring, P. M.; Xu, G.; Lamago, D.; Reznik, D.; Russina, M.; Wen, J.; Boatner, L. A.

    2014-12-01

    We report neutron scattering measurements of the structural correlations associated with the apparent relaxor transition in K1 -xLixTaO3 for x =0.02 [KLT(0.02)]. This compound displays a broad and frequency-dependent peak in the dielectric permittivity, which is the accepted hallmark of all relaxors. However, no evidence of elastic diffuse scattering or any soft-mode anomaly is observed in KLT(0.02) [J. Wen et al., Phys. Rev. B 78, 144202 (2008), 10.1103/PhysRevB.78.144202], a situation that diverges from that in other relaxors such as PbMg1 /3Nb2 /3O3 . We resolve this dichotomy by showing that the structural correlations associated with the transition in KLT(0.02) are purely dynamic at all temperatures, having a time scale on the order of ˜ THz. These fluctuations are overdamped, nonpropagating, and spatially uncorrelated. Identical measurements made on pure KTaO3 show that they are absent (within experimental error) in the undoped parent material. They exhibit a temperature dependence that correlates well with the dielectric response, which suggests that they are associated with local ferroelectric regions induced by the Li+ doping. The ferroelectric transition that is induced by the introduction of Li+ cations is therefore characterized by quasistatic fluctuations, which represents a stark contrast to the soft-harmonic-mode-driven transition observed in conventional perovskite ferroelectrics such as PbTiO3. The dynamic, glasslike structural correlations in KLT(0.02) are much faster than those measured in random-field-based lead-based relaxors, which exhibit a frequency scale of order ˜ GHz and are comparatively better correlated spatially. Our results support the view that static random fields give rise to the relaxor phenomena, and that the glasslike dynamics observed here characterize a nascent response.

  8. Dynamics of nanoscale polarization fluctuations in a uniaxial relaxor.

    PubMed

    Ondrejkovic, P; Kempa, M; Kulda, J; Frick, B; Appel, M; Combet, J; Dec, J; Lukasiewicz, T; Hlinka, J

    2014-10-17

    We have studied neutron diffuse scattering in a Sr(0.61)Ba(0.39)Nb(2)O(6) single crystal by neutron backscattering at sub-μeV energy resolution. We can identify two response components with transverse polarization: an elastic (resolution limited) central peak, which monotonically increases with decreasing temperature, and a quasielastic central peak, having a maximum intensity around the ferroelectric phase transition close to 350 K. In contrast to previous neutron experiments on this and other relaxor materials, we were able to observe a temperature dependence of the characteristic frequency of these fluctuations, obeying the same Vogel-Fulcher law as the dynamic part of the dielectric permittivity of this material. In this way our findings provide a first direct link between the Vogel-Fulcher-type frequency dependence of dielectric permittivity and dynamic nanoscale lattice modulations with a transverse correlation length of about 5-10 unit cells. PMID:25361280

  9. Lattice dynamics and dielectric spectroscopy of BZT and NBT lead-free perovskite relaxors - comparison with lead-based relaxors

    NASA Astrophysics Data System (ADS)

    Petzelt, Jan; Nuzhnyy, Dmitry; Bovtun, Viktor; Kempa, Martin; Savinov, Maxim; Kamba, Stanislav; Hlinka, Jiri

    2015-03-01

    Appearance of the polar nanoregions (PNR) and their manifestation in the dielectric spectra is discussed for lead-free Ba(ZrxTi1-x)O3 (BZT-x) and (Na1/2Bi1/2)TiO3 (NBT) ceramics. Phonon softening is not as pronounced as in the lead-based relaxors, but the relaxation contribution is dominating in all cases, caused by the dynamics of the off-centred ions (Ti4+, Bi3+, Pb2+). In the lead-based relaxors, where there is no relation between the quenched chemical clusters at the B-sites and PNR, which concern the A-site Pb-ion correlations, the relaxation dynamics follows the Vogel-Fulcher behaviour with a clear freezing. However, in BZT and NBT, the PNR are smaller, since they are localised within the small quenched chemical clusters of BaTiO3 and BiTiO3, respectively. Their dynamics is Arrhenius-like, which indicates hopping of the off-centred Ti4+ and Bi3+ ions, respectively, without their complete freezing. BZT can be classified as a dipolar glass and NBT as a nanoscopic ferroelectric with peculiar Bi-ion dynamics.

  10. Dielectric, piezoelectric, and ferroelectric properties of grain-orientated Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} ceramics

    SciTech Connect

    Liu Jing; Shen Zhijian; Yan Haixue; Reece, Michael J.; Kan Yanmei; Wang Peiling

    2007-11-15

    By dynamic forging during Spark Plasma Sintering (SPS), grain-orientated ferroelectric Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} (BLT) ceramics were prepared. Their ferroelectric, piezoelectric, and dielectric properties are anisotropic. The textured ceramics parallel and perpendicular to the shear flow directions have similar thermal depoling behaviors. The d{sub 33} piezoelectric coefficient of BLT ceramics gradually reduces up to 350 deg. C; it then drops rapidly. The broadness of the dielectric constant and loss peaks and the existence of d{sub 33} above the permittivity peak, T{sub m}, show that the BLT ceramic has relaxor-like behavior.

  11. Temperature dependences of ferroelectricity and resistive switching behavior of epitaxial BiFeO3 thin films

    NASA Astrophysics Data System (ADS)

    Lu, Zeng-Xing; Song, Xiao; Zhao, Li-Na; Li, Zhong-Wen; Lin, Yuan-Bin; Zeng, Min; Zhang, Zhang; Lu, Xu-Bing; Wu, Su-Juan; Gao, Xing-Sen; Yan, Zhi-Bo; Liu, Jun-Ming

    2015-10-01

    We investigate the resistive switching and ferroelectric polarization properties of high-quality epitaxial BiFeO3 thin films in various temperature ranges. The room temperature current-voltage (I-V) curve exhibits a well-established polarization-modulated memristor behavior. At low temperatures (< 253 K), the I-V curve shows an open circuit voltage (OCV), which possibly originates from the dielectric relaxation effects, accompanied with a current hump due to the polarization reversal displacement current. While at relative higher temperatures (> 253 K), the I-V behaviors are governed by both space-charge-limited conduction (SCLC) and Ohmic behavior. The polarization reversal is able to trigger the conduction switching from Ohmic to SCLC behavior, leading to the observed ferroelectric resistive switching. At a temperature of > 298 K, there occurs a new resistive switching hysteresis at high bias voltages, which may be related to defect-mediated effects. Project supported by the National Natural Science Foundation of China (Grant Nos. 51272078 and 51332007), the State Key Program for Basic Research of China (Grant No 2015CB921202), the Guangdong Provincial Universities and Colleges Pearl River Scholar Funded Scheme, China (2014), the International Science & Technology Cooperation Platform Program of Guangzhou, China (Grant No. 2014J4500016), and the Program for Changjiang Scholars and Innovative Research Team in University of China (Grant No. IRT1243).

  12. Polar octahedral rotations, cation displacement and ferroelectricity in multiferroic SmCrO3

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Dey, K.; Chakraborty, M.; Majumdar, S.; Giri, S.

    2014-08-01

    Our thorough synchrotron diffraction studies provide a clue on the origin of ferroelectricity in SmCrO3. Careful observation demonstrates that polar order develops in the paramagnetic state. Rietveld refinement of the diffraction data confirms that emergence of polar order is correlated with the structural transformation from centrosymmetric Pbnm to non-centrosymmetric Pna21 space group of the distorted orthorhombic structure. Rotations of polar CrO6 octahedra and Sm displacement are proposed to be correlated with the emergence of polar order, which is extended over a wide temperature range and increases gradually with decreasing temperature. This is consistent with the relaxor behavior as evident from the frequency-dependent dielectric response satisfying the Vogel-Fulcher law. A non-collinear to collinear spin transformation is suggested well below the spin reorientation transition. Appearance of ferroelectricity without any correlation to the antiferromagnetic order in SmCrO3 suggests a new class of ferroelectricity. All-electron full-potential first-principles calculation demonstrates significant Sm-Cr hybridization near the Fermi level, which substantiates the experimental findings.

  13. Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3

    PubMed Central

    Groszewicz, Pedro B.; Gröting, Melanie; Breitzke, Hergen; Jo, Wook; Albe, Karsten; Buntkowsky, Gerd; Rödel, Jürgen

    2016-01-01

    Lead-based relaxor ferroelectrics are key functional materials indispensable for the production of multilayer ceramic capacitors and piezoelectric transducers. Currently there are strong efforts to develop novel environmentally benign lead-free relaxor materials. The structural origins of the relaxor state and the role of composition modifications in these lead-free materials are still not well understood. In the present contribution, the solid-solution (100-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-xBT), a prototypic lead-free relaxor is studied by the combination of solid-state nuclear magnetic resonance (NMR) spectroscopy, dielectric measurements and ab-initio density functional theory (DFT). For the first time it is shown that the peculiar composition dependence of the EFG distribution width (ΔQISwidth) correlates strongly to the dispersion in dielectric permittivity, a fingerprint of the relaxor state. Significant disorder is found in the local structure of BNT-xBT, as indicated by the analysis of the electric field gradient (EFG) in 23Na 3QMAS NMR spectra. Aided by DFT calculations, this disorder is attributed to a continuous unimodal distribution of octahedral tilting. These results contrast strongly to the previously proposed coexistence of two octahedral tilt systems in BNT-xBT. Based on these results, we propose that considerable octahedral tilt disorder may be a general feature of these oxides and essential for their relaxor properties. PMID:27545094

  14. Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3.

    PubMed

    Groszewicz, Pedro B; Gröting, Melanie; Breitzke, Hergen; Jo, Wook; Albe, Karsten; Buntkowsky, Gerd; Rödel, Jürgen

    2016-01-01

    Lead-based relaxor ferroelectrics are key functional materials indispensable for the production of multilayer ceramic capacitors and piezoelectric transducers. Currently there are strong efforts to develop novel environmentally benign lead-free relaxor materials. The structural origins of the relaxor state and the role of composition modifications in these lead-free materials are still not well understood. In the present contribution, the solid-solution (100-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-xBT), a prototypic lead-free relaxor is studied by the combination of solid-state nuclear magnetic resonance (NMR) spectroscopy, dielectric measurements and ab-initio density functional theory (DFT). For the first time it is shown that the peculiar composition dependence of the EFG distribution width (ΔQISwidth) correlates strongly to the dispersion in dielectric permittivity, a fingerprint of the relaxor state. Significant disorder is found in the local structure of BNT-xBT, as indicated by the analysis of the electric field gradient (EFG) in (23)Na 3QMAS NMR spectra. Aided by DFT calculations, this disorder is attributed to a continuous unimodal distribution of octahedral tilting. These results contrast strongly to the previously proposed coexistence of two octahedral tilt systems in BNT-xBT. Based on these results, we propose that considerable octahedral tilt disorder may be a general feature of these oxides and essential for their relaxor properties. PMID:27545094

  15. Investigaction of Switching Behavior in a Ferroelectric Liquid Crystal Aligned on Obliquely Deposited SiO Films

    NASA Astrophysics Data System (ADS)

    Yamada, Yuichiro; Yamamoto, Norio; Inoue, Tetsuya; Orihara, Hiroshi; Ishibashi, Yoshihiro

    1989-01-01

    The effect of oblique evaporation of SiO on the chevron structure and the switching behavior in a ferroelectric liquid crystal have been investigated by means of the X-ray diffraction and the stroboscopic micrographs. It is found experimentally that the chevron direction and the domain structure appearing during the switching are determined by the direction of incidence of evaporated SiO. On the basis of the experimental results, it is clarified that the bow and the stern of the boat-shaped domain correspond to {+}2π and {-}2π internal disclinations, respectively. The structure of the zig-zag defect is determined.

  16. Ferroelectric Pump

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    2000-01-01

    A ferroelectric pump has one or more variable volume pumping chambers internal to a housing. Each chamber has at least one wall comprising a dome shaped internally prestressed ferroelectric actuator having a curvature and a dome height that varies with an electric voltage applied between an inside and outside surface of the actuator. A pumped medium flows into and out of each pumping chamber in response to displacement of the ferroelectric actuator. The ferroelectric actuator is mounted within each wall and isolates each ferroelectric actuator from the pumped medium, supplies a path for voltage to be applied to each ferroelectric actuator, and provides for positive containment of each ferroelectric actuator while allowing displacement of the entirety of each ferroelectric actuator in response to the applied voltage.

  17. Hysteresis loop behaviors of ferroelectric thin films: A Monte Carlo simulation study

    NASA Astrophysics Data System (ADS)

    M. Bedoya-Hincapié, C.; H. Ortiz-Álvarez, H.; Restrepo-Parra, E.; J. Olaya-Flórez, J.; E. Alfonso, J.

    2015-11-01

    The ferroelectric response of bismuth titanate Bi4Ti3O12 (BIT) thin film is studied through a Monte Carlo simulation of hysteresis loops. The ferroelectric system is described by using a Diffour Hamiltonian with three terms: the electric field applied in the z direction, the nearest dipole-dipole interaction in the transversal (x-y) direction, and the nearest dipole-dipole interaction in the direction perpendicular to the thin film (the z axis). In the sample construction, we take into consideration the dipole orientations of the monoclinic and orthorhombic structures that can appear in BIT at low temperature in the ferroelectric state. The effects of temperature, stress, and the concentration of pinned dipole defects are assessed by using the hysteresis loops. The results indicate the changes in the hysteresis area with temperature and stress, and the asymmetric hysteresis loops exhibit evidence of the imprint failure mechanism with the emergence of pinned dipolar defects. The simulated shift in the hysteresis loops conforms to the experimental ferroelectric response. Project sponsored by the research departments of the Universidad Nacional de Colombia DIMA and DIB under Project 201010018227-“Crecimiento y caracterización eléctrica y estructural de películas delgadas de BixTiyOz producidas mediante Magnetrón Sputtering” and Project 12920-“Desarrollo teóricoexperimental de nanoestructuras basadas en Bismuto y materiales similares” and “Bisnano Project.”

  18. Ferroelectricity in spiral magnets.

    PubMed

    Mostovoy, Maxim

    2006-02-17

    It was recently observed that the ferroelectrics showing the strongest sensitivity to an applied magnetic field are spiral magnets. We present a phenomenological theory of inhomogeneous ferroelectric magnets, which describes their thermodynamics and magnetic field behavior, e.g., dielectric susceptibility anomalies at magnetic transitions and sudden flops of electric polarization in an applied magnetic field. We show that electric polarization can also be induced at domain walls and that magnetic vortices carry electric charge. PMID:16606047

  19. Piezoelectric activity in Perovskite ferroelectric crystals.

    PubMed

    Li, Fei; Wang, Linghang; Jin, Li; Lin, Dabin; Li, Jinglei; Li, Zhenrong; Xu, Zhuo; Zhang, Shujun

    2015-01-01

    Perovskite ferroelectrics (PFs) have been the dominant piezoelectric materials for various electromechanical applications, such as ultrasonic transducers, sensors, and actuators, to name a few. In this review article, the development of PF crystals is introduced, focusing on the crystal growth and piezoelectric activity. The critical factors responsible for the high piezoelectric activity of PFs (i.e., phase transition, monoclinic phase, domain size, relaxor component, dopants, and piezoelectric anisotropy) are surveyed and discussed. A general picture of the present understanding on the high piezoelectricity of PFs is described. At the end of this review, potential approaches to further improve the piezoelectricity of PFs are proposed. PMID:25585387

  20. Enhanced piezoelectric response in the artificial ferroelectric polymer multilayers

    SciTech Connect

    Zhao, X. L.; Wang, J. L. E-mail: lin-tie@mail.sitp.ac.cn; Tian, B. B.; Liu, B. L.; Wang, X. D.; Sun, S.; Zou, Y. H.; Lin, T. E-mail: lin-tie@mail.sitp.ac.cn; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-12-01

    An actuator with a high piezoelectric response, the ferroelectric polymer multilayer actuator, is described. The ferroelectric polymer multilayers consisting of alternative ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer and relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) (P(VDF-TrFE-CFE)) terpolymer with different periodicities and fixed total thickness are prepared by the Langmuir-Blodgett technique. Both X-ray diffraction and Raman spectroscopic measurements indicate that the structure of the multilayer with thin alternating layer is similar to that of the ferroelectric copolymer. Compared with that of the copolymer, it is found that the piezoelectric coefficient of the multilayer could be improved by 57%. We attributed the enhanced piezoelectric response of the multilayers to the internal electric fields that arises from the electrostatic couplings between different layers.

  1. Enhanced tunable characteristics of the Na0.5Bi0.5TiO3-NaTaO3 relaxor-type system.

    PubMed

    Spreitzer, Matjaz; König, Jakob; Jancar, Bostjan; Suvorov, Danilo

    2007-12-01

    We have investigated the voltage-tunable characteristics of the Na(0.5)Bi(0.5)TiO(3)-NaTaO(3) homogeneity region, for which samples were prepared using a conventional solid-state reaction. The highest value of the relative tunability (n(r)) was obtained for the sample with 5 mol% of NaTaO(3), i.e., 47% at 1 MHz and a 70 kV/cm dc bias field. This sample also showed the highest value of the dielectric losses (tan delta) and temperature coefficient of the dielectric constant (tau(epsilon)), i.e., 0.05 and 4478 ppm/K, respectively. As the concentration of NaTaO(3) increased up to 90 mol% n(r), tan delta, and tau(epsilon) gradually decreased toward 22%, 0.0002 and -899 ppm/K, respectively. The dielectric constant of the samples varied in a similar manner between 662 and 130. At microwave frequencies, the dielectric losses of the samples substantially increased due to their relaxor-type nature. The lowest value was obtained for the samples with 90 mol% of NaTaO(3), i.e., 0.002. The tunable characteristics of the samples are related to the ferroelectric and dielectric properties, and it appears that the dielectric tunability of the Na(0.5)Bi(0.5)TiO(3)-NaTaO(3) system originates from its relaxor-type behavior. PMID:18276566

  2. SISGR -- Domain Microstructures and Mechanisms for Large, Reversible and Anhysteretic Strain Behaviors in Phase Transforming Ferroelectric Materials

    SciTech Connect

    Wang, Yu U.

    2013-12-06

    This four-year project (including one-year no-cost extension) aimed to advance fundamental understanding of field-induced strain behaviors of phase transforming ferroelectrics. We performed meso-scale phase field modeling and computer simulation to study domain evolutions, mechanisms and engineering techniques, and developed computational techniques for nanodomain diffraction analysis; to further support above originally planned tasks, we also carried out preliminary first-principles density functional theory calculations of point defects and domain walls to complement meso-scale computations as well as performed in-situ high-energy synchrotron X-ray single crystal diffraction experiments to guide theoretical development (both without extra cost to the project thanks to XSEDE supercomputers and DOE user facility Advanced Photon Source).

  3. Relaxor-based solid solutions for piezoelectric and electrostrictive applications

    NASA Astrophysics Data System (ADS)

    Alberta, Edward F.

    This thesis explores the dielectric, piezoelectric, and electrostrictive properties of a number of relaxor ferroelectric-based solid solution systems. The components of these solid solution systems have a variety of characteristics ranging from normal- to relaxor- to anti-ferroelectric. Some of the relaxor end-members investigated were Pb(In1/2Nb1/2)O3 [PIN], Pb(In1/2Ta1/2)O3 [PIT], Pb(Sc 1/2Nb1/2)O3 [PSN], Pb(Ni1/3Nb 2/3)O3 [PNN], Pb(Mg1/3Nb2/3)O 3 [PMN], and Pb(Zn1/3Nb2/3)O3 [PZN]. Several of these systems have Curie temperatures [Tc] that are among the highest known for MPB compositions. Some examples are PIN-0.38PT with a Tc of 319°C, PIT-0.38PT with a Tc of 248°C, and PSN 0.42PT with a Tc of 254°C. While these are slightly lower that those of typically found in PZT, the temperature dependence of the piezoelectric properties was found to be minimal. The electromechanical coupling coefficients were largely unchanged upon heating to as high as 150°C. This is approximately equal to the Tc of PMN-PT and PZN-PT and significantly exceeds the generally accepted maximum operating temperature for these materials. Many of the materials studied were found to have very large electromechanical coupling factors and produce extraordinarily high field-induced strains. Both PSN-0.42PT and PNN-0.15PZ-0.34PT were found to produce strain levels of ˜0.30% under unipolar drive with limited hysteresis. Peak-to-peak strain levels of as much as 0.60% were possible under bipolar drive conditions. Both of these MPB compositions had very large piezoelectric properties, with the slightly larger values of d33 = 810pC/N, kp = 0.69, kt = 0.56, and k33 = 0.80 occurring in PNN-PZ-PT. Each of the MPB compositions studied has features that can be exploited for specific applications. The combination of high Tc and coercive field found in both PIN-PT and Bi(Ni1/2T1/2)O3 -PT should allow these materials to be used at high drive levels and/or at high temperatures. The high strain, low hysteresis

  4. Supramolecular ferroelectrics

    NASA Astrophysics Data System (ADS)

    Tayi, Alok S.; Kaeser, Adrien; Matsumoto, Michio; Aida, Takuzo; Stupp, Samuel I.

    2015-04-01

    Supramolecular chemistry uses non-covalent interactions to coax molecules into forming ordered assemblies. The construction of ordered materials with these reversible bonds has led to dramatic innovations in organic electronics, polymer science and biomaterials. Here, we review how supramolecular strategies can advance the burgeoning field of organic ferroelectricity. Ferroelectrics -- materials with a spontaneous and electrically reversible polarization -- are touted for use in non-volatile computer memories, sensors and optics. Historically, this physical phenomenon has been studied in inorganic materials, although some organic examples are known and strong interest exists to extend the search for ferroelectric molecular systems. Other undiscovered applications outside this regime could also emerge. We describe the key features necessary for molecular and supramolecular dipoles in organic ferroelectrics and their incorporation into ordered systems, such as porous frameworks and liquid crystals. The goal of this Review is to motivate the development of innovative supramolecular ferroelectrics that exceed the performance and usefulness of known systems.

  5. Origin of ferroelectric polarization in tetragonal tungsten-bronze-type oxides

    NASA Astrophysics Data System (ADS)

    Olsen, Gerhard Henning; Aschauer, Ulrich; Spaldin, Nicola A.; Selbach, Sverre Magnus; Grande, Tor

    2016-05-01

    The origin of ferroelectric polarization in tetragonal tungsten-bronze- (TTB-) type oxide strontium barium niobate (SBN) is investigated using first-principles density functional calculations. We study in particular the relationship between the polarization and the cation and vacancy ordering on alkali-earth metal lattice sites. Lattice dynamical calculations for paraelectric structures demonstrate that all cation configurations that can be accommodated in a 1 ×1 ×2 supercell result in a single unstable polar phonon, composed primarily of relative Nb-O displacements along the polar axis, as their dominant instability. The majority of the configurations also have a second octahedral tilt-mode instability which couples weakly to the polar mode. The existence of the tilt mode is strongly dependent on the local cation ordering, consistent with the fact that it is not found experimentally. Our results suggest that ferroelectricity in the SBN system is driven by a conventional second-order Jahn-Teller mechanism caused by the d0 Nb5 + cations, and demonstrate the strong influence of the size of Sr and Ba on the lattice distortions associated with polarization and octahedral tilting. Finally, we suggest a mechanism for the relaxor behavior in Sr-rich SBN based on Sr displacement inside pentagonal channels in the TTB structure.

  6. Unusual Strong Incommensurate Modulation in a Tungsten-Bronze-Type Relaxor PbBiNb5O15.

    PubMed

    Lin, Kun; Zhou, Zhengyang; Liu, Laijun; Ma, Hongqiang; Chen, Jun; Deng, Jinxia; Sun, Junliang; You, Li; Kasai, Hidetaka; Kato, Kenichi; Takata, Masaki; Xing, Xianran

    2015-10-28

    Pb- or Bi-based perovskite oxides have been widely studied and used because of their large ferroelectric polarization features induced by stereochemically active 6s(2) lone pair electrons. It is intriguing whether this effect could exist in other related systems. Herein, we designed and synthesized a mixed Pb and Bi A site polar compound, PbBiNb5O15, with the TTB framework. The as-synthesized material turns out to be a relaxor with weak macroscopic ferroelectricity but adopts strong local polarizations. What's more, unusual five orders of incommensurate satellite reflections with strong intensities were observed under the electron diffraction, suggesting that the modulation is highly developed with large amplitudes. The structural modulation was solved with a (3 + 1)D superspace group using high-resolution synchrotron radiation combined with anomalous dispersion X-ray diffraction technique to distinguish Pb from Bi. We show that the strong modulation mainly originates from lone-pair driven Pb(2+)-Bi(3+) ordering in the large pentagonal caves, which can suppress the local polarization in x-y plane in long ranges. Moreover, the as-synthesized ceramics display strong relaxor ferroelectric feature with transition temperature near room temperature and moderate dielectric properties, which could be functionalized to be electromechanical device materials. PMID:26474121

  7. Second-harmonic generation and x-ray diffraction studies of the pretransitional region and polar phase in relaxor K(1-x)LixTaO3

    NASA Astrophysics Data System (ADS)

    Yokota, Hiroko; Uesu, Yoshiaki; Malibert, Charlotte; Kiat, Jean-Michel

    2007-05-01

    Optical second-harmonic generation (SHG) observations and precise x-ray diffraction experiments have been performed on quantum paraelectrics KTaO3 (KTO) and relaxors K(1-x)LixTaO3 with x=3% (KLT-3) and 7% (KLT-7). It is found in KLT-3 and KLT-7 that a pretransitional region exists between two characteristic temperatures TB and Tp(behavior of dielectric constant. These facts strongly suggest that polar nanoregions (PNRs) nucleate around TB and grow toward Tp . Below Tp , a larger deformation and a field-induced SH intensity start to develop, while no significant SHG appears in the zero-field-cooling (ZFC) process because of macroscopic inversion symmetry of the polydomain structure. The field-cooling (FC) process breaks the macroscopic inversion symmetry and the temperature dependence of SH intensity in field heating after FC coincides well with that of the tetragonality determined by x-ray diffraction experiments. The Landau-Devonshire phenomenological approach suggests that the ferroelectric phase transition at Tp is of first order and that it approaches the second-order transition with a decrease in the Li concentration. A marked increase of neutron-diffraction intensities below Tp , together with the disappearance of SHG intensity in a ZFC run, indicates that PNRs are transformed to ferroelectric microdomains at Tp . The microdomains become macroscopic below Tp in the FC process. In the lower-temperature region, nonergodic behavior was observed: The ZFC state cannot approach the thermodynamically equilibrium state under the electric field within finite time.

  8. Dielectric and Ferroelectric Behavior of Bismuth-Doped Barium Titanate Ceramic Prepared by Microwave Sintering

    NASA Astrophysics Data System (ADS)

    Mahapatra, A.; Parida, S.; Sarangi, S.; Badapanda, T.

    2015-08-01

    Bismuth-doped barium titanate ceramics with the general formula Ba1- x Bi2 x/3TiO3 ( x = 0.0, 0.01, 0.025, 0.05) have been prepared by the solid state reaction technique. The phase formation and structural property of all compositions have been studied by x-ray diffraction (XRD) pattern and Rietveld refinement. XRD pattern reports the single phase tetragonal crystal system with space group of P4mm. All compositions have been sintered at 1100°C in a microwave furnace for 30 min. The variation of dielectric constant with respect to temperature and frequency was studied and it was found that the dielectric constant decreases whereas transition temperature increased with the increase in Bi content. The diffusivity parameter was calculated by the modified Curie-Weiss law and the diffusivity increased with the increase in Bi content. The ferroelectric property was studied by the P-E hysteresis loop and it was observed that the saturation polarization decreased, but the coercive field increased with Bi content. The optical band gap was calculated from UV-Visible spectroscopy and found to decrease with Bi content.

  9. Observation of nonequilibrium behavior near the Lifshitz point in ferroelectrics with incommensurate phase

    NASA Astrophysics Data System (ADS)

    Rushchanskii, K. Z.; Molnar, A.; Bilanych, R.; Yevych, R.; Kohutych, A.; Vysochanskii, Yu. M.; Samulionis, V.; Banys, J.

    2016-01-01

    We have investigated nonequilibrium properties of proper uniaxial Sn2P2(SexS1-x) 6 ferroelectrics with the type II incommensurate phase above Lifshitz point xLP˜0.28 . We performed measurements of dielectric susceptibility in cooling and heating regimes with the rate ranging 0.002-0.1 K/min, as well as high-resolution ultrasound investigation and hypersound Brillouin scattering experiments. For samples with x ≥0.28 clear anomalies are observed at incommensurate second-order transition (Ti) and at first-order lock-in transition (Tc) in the regime of very slow cooling rate, whereas the intermediate incommensurate phase is not observed when the rate is faster than 0.1 K/min. In general, increasing the cooling rate leads to smearing of the anomaly at Tc. We relate this effect to cooling rate dependence of domain-wall concentration and their size: domain width decreases when cooling rate increases. At certain conditions, the size of domain is comparable to the incommensurate phase modulation period, which is in the micrometer range in the vicinity of Lifshitz point and leads to pinning of the modulation period by domain walls.

  10. Compressed H-bonds in solids. Pressure-dependent ferroelectric behavior of KDP/DKDP

    NASA Astrophysics Data System (ADS)

    Dolin, S. P.; Levin, A. A.; Mikhailova, T. Yu.

    2010-05-01

    Hydrostatic pressure effect on ferroelectric structural phase transition (SPT) in KDP (KH 2PO 4) and DKDP (KD 2PO 4) as typical examples of H-bonded solids is considered in the frames of pseudospin Hamiltonian, its parameters Ω(H/D) and J ij(H/D) describe the quantum motion of proton/deuteron along the H/D-bond and pair interaction between these nuclei at different bonds, respectively. These parameters are determined by means of the cluster non-empirical calculations (SCF, MP2-MP4, B3LYP) for the characteristic structural fragments of the compounds of interest. The clusters geometry was taken from the neutron-diffraction data, obtained for pressure values P = 0 and P = 16.5 kbar. The molecular field approximation (MFA) together with more refined Bethe cluster approach (BCA) were applied to study the T c of SPT on the base of the calculated values of Ω(H/D) and J ij(H/D). In agreement with the experiments for both techniques T c decreases with the growth of P due to the proton/deuteron transfer barrier width and height reduction as well as owing to the diminution of the protons/deuterons effective interaction. The related BCA results for KDP and DKDP are discussed in more details.

  11. Behavior of inclusions with different value and orientation of topological dipoles in ferroelectric smectic films

    SciTech Connect

    Dolganov, P. V. Dolganov, V. K.; Cluzeau, P.

    2009-07-15

    Cholesteric droplets in ferroelectric free-standing films with tunable anchoring on the droplet boundary are investigated. A droplet and satellite topological defect(s) form a topological dipole. We obtained droplets with different angles {alpha} between two radial lines from the droplet center to -1/2 topological defects. Droplets with parallel dipoles form linear chains in which the interparticle distances decrease with increasing the defect angle {alpha}. For the first time, the dependence of the interparticle distance on the angle between topological defects was measured. We can adjust the magnitude and orientation of topological dipoles formed by the droplets. For the first time, the droplets with antiparallel topological dipoles were prepared in a smectic film. Interaction of the droplets with parallel and antiparallel dipoles differs drastically. Formation of antiparallel dipoles leads to a decomposition of the droplet pairs and chains of droplets. Our observations may be used to change the magnitude, anisotropy of the interparticle interaction, and structures of inclusions in liquid crystal media.

  12. Anisotropic Optical Behavior of Ferroelectric Bismuth Titanate: A Comparison of Experiment and Theory

    NASA Astrophysics Data System (ADS)

    Roy, Amritendu; Prasad, Rajendra; Auluck, Sushil; Garg, Ashish

    2010-03-01

    Optical properties of bismuth titanate (Bi4Ti3O12 or BiT) are of technological interest as its band gap lies in the visible region. Here we compare the results of theoretical and experimental studies conducted on pure bismuth titanate single crystals. Highly oriented BiT single crystals were synthesized using flux growth method. Spectroscopic ellipsometry measurements were made between 300 to 800 nm for different sample orientations. To obtain the absorption coefficient near the band edge, optical transmission measurements were also made. The refractive index data was fitted to a two-term Sellmeier formula. We also calculated the optical constants for both ferroelectric and paraelectric phases of bismuth titanate using density functional theory as implemented in the Vienna ab-initio simulation package (VASP) in conjunction with projector augmented wave method (PAW). Our calculations show the anisotropy of the optical properties for the electric field parallel and perpendicular to the c-axis of the crystal. Our calculations are in good agreement with the experimental data.

  13. Ferroelectric HfO2 for Emerging Ferroelectric Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Florent, Karine

    The spontaneous polarization in ferroelectrics (FE) makes them particularly attractive for non-volatile memory and logic applications. Non-volatile FRAM memories using perovskite structure materials, such as Lead Zirconate Titanate (PZT) and Strontium Bismuth Tantalate (SBT) have been studied for many years. However, because of their scaling limit and incompatibility with CMOS beyond 130 nm node, floating gate Flash memory technology has been preferred for manufacturing. The recent discovery of ferroelectricity in doped HfO2 in 2011 has opened the door for new ferroelectric based devices compatible with CMOS technology, such as Ferroelectric Field Effect Transistor (FeFET) and Ferroelectric Tunnel Junctions (FTJ). This work began with developing ferroelectric hysteresis characterization capabilities at RIT. Initially reactively sputtered aluminum doped HfO 2 films were investigated. It was observed that the composition control using co-sputtering was not achievable within the existing capabilities. During the course of this study, collaboration was established with the NaMLab group in Germany to investigate Si doped HfO2 deposited by Atomic Layer Deposition (ALD). Metal Ferroelectric Metal (MFM) devices were fabricated using TiN as the top and bottom electrode with Si:HfO2 thickness ranging from 6.4 nm to 22.9 nm. The devices were electrically tested for P-E, C-V and I-V characteristics. Structural characterizations included TEM, EELS, XRR, XRD and XPS/Auger spectroscopy. Higher remanant polarization (Pr) was observed for films of 9.3 nm and 13.1 nm thickness. Thicker film (22.9 nm) showed smaller Pr. Devices with 6.4 nm thick films exhibit tunneling behavior showing a memristor like I-V characteristics. The tunnel current and ferroelectricity showed decrease with cycling indicating a possible change in either the structure or the domain configurations. Theoretical simulations using the improved FE model were carried out to model the ferroelectric behavior of

  14. Nonlinear-optic and ferroelectric behavior of lithium borate{endash}strontium bismuth tantalate glass{endash}ceramic composite

    SciTech Connect

    Senthil Murugan, G.; Varma, K. B. R.; Takahashi, Yoshihiro; Komatsu, Takayuki

    2001-06-18

    Transparent glasses in the system (100{endash}x) Li{sub 2}B{sub 4}O{sub 7}{endash}xSrBi{sub 2}Ta{sub 2}O{sub 9} (0{le}x{le}20) were fabricated via a splat-quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses. X-ray powder diffraction and transmission electron microscopic studies confirmed the amorphous nature of the as-quenched and crystallinity (40 nm) in the heat-treated (glass{endash}ceramic) samples. The dielectric constant ({epsilon}{sub r}) of the glass{endash}ceramic composite (x=20, heat treated at 773 K/8 h) was in between that of the parent host glass (Li{sub 2}B{sub 4}O{sub 7}) and strontium bismuth tantalate ceramics in the frequency range 100 Hz{endash}40 MHz at 300 K. These exhibited intense second-harmonic generation and a ferroelectric hysteritic behavior (P vs E loops) at 300 K. The coercive field (E{sub c}) and the remnant polarization (P{sub r}) were 1053 V/cm and 0.483 {mu}C/cm2, respectively. {copyright} 2001 American Institute of Physics.

  15. Measuring and Altering Ferroelectric Domain Structures in Lead Perovskite Single-Crystals

    NASA Astrophysics Data System (ADS)

    Harker, John Chamberlain

    Relaxor ferroelectric single-crystal materials PMN-PT and PZN-PT are currently of interest to the scientific community due to their enhanced properties and possible role as next-generation piezoelectric transducers in applications such as sonar and medical ultrasound. One key phenomenon affecting both the properties and the mechanical integrity of these materials is the ferroelectric domain structure within the material. In this work we examine the morphology and behavior of domain structures in PMN-29%PT. In order to do this we first present details of the construction and testing of a working piezo-response force microscope (PFM), and then use the PFM to verify a new domain observation technique called "relief polishing". Relief polishing is shown to reveal surface domains in the same manner as acid etching, preserving domain details as small as 0.5mum. Using these two techniques, we then determine that cutting and polishing strongly affect the surface and subsurface ferroelectric domain structures in PMN-29%PT. Specifically, we show that saw cutting can create characteristic striated domain structures as deep as 130mum within a sample, while straight polishing creates a characteristic domain structure known as the "fingerprint" pattern to a depth proportional to the size of the polishing grit, on the order of 0--12mum for grits as large as 15mum. We hypothesize that most samples contain these "skin effect" domain structures. In consequence, it is suggested that researchers presenting experimental results on domain structures should report the physical treatment history of the samples along with the experimental data.

  16. Collective dipole behavior and unusual morphotropic phase boundary in ferroelectric Pb(Zr(0.5)Ti(0.5))O3 nanowires.

    PubMed

    Fu, Xiujun; Naumov, Ivan I; Fu, Huaxiang

    2013-02-13

    Dipole collective behavior and phase transition in ferroelectric (FE) Pb(Zr(0.5)Ti(0.5))O(3) nanowires, caused by modulated electric fields, are reported. Our result also leads to the finding of a rather outstanding electromechanical d(31) response in a 8.4 nm diameter PZT wire, which may potentially outperform bulk PMN-PT and PZN-PT. Moreover, we further demonstrate the existence of a new type of morphotropic phase boundary (MPB) that bridges two dissimilar structure phases of different order parameters. Microscopic insights for understanding the collective behavior and the structural phase within the new MPB are provided. PMID:23256599

  17. High-temperature memory in (Pb/La)(Zr/Ti)O3 as intrinsic of the relaxor state rather than due to defect relaxation

    NASA Astrophysics Data System (ADS)

    Cordero, F.; Craciun, F.; Franco, A.; Galassi, C.

    2006-07-01

    It has been recently shown that the memory of multiple aging stages, a phenomenon considered possible only below the glass transition of some glassy systems, appears also above that temperature range in the relaxor ferroelectric (Pb/La)(Zr/Ti)O3 (PLZT). Doubts exist whether memory at such high temperature is intrinsic of the glassy relaxor state or is rather due to migration of mobile defects. It is shown that the memory in the electric susceptibility and elastic compliance of PLZT 9/65/35 is not enhanced but depressed by mobile defects like O vacancies, H defects, and mobile charges resulting from their ionization. In addition, memory is drastically reduced at La contents slightly below the relaxor region of the phase diagram, unless aging is protracted for long times (months at room temperature). This is considered as evidence that in the nonrelaxor case memory is indeed due to slow migration of defects, while in the La rich case it is intrinsic of the relaxor state, even above the temperature of the susceptibility maximum.

  18. Ferroelectric memory

    NASA Astrophysics Data System (ADS)

    Vorotilov, K. A.; Sigov, A. S.

    2012-05-01

    The current status of developments in the field of ferroelectric memory devices has been considered. The rapidly growing market of non-volatile memory devices has been analyzed, and the current state of the art and prospects for the scaling of parameters of non-volatile memory devices of different types have been considered. The basic constructive and technological solutions in the field of the design of ferroelectric memory devices, as well as the "roadmaps" of the development of this technology, have been discussed.

  19. Pressure-induced changes in the dielectric response of polymer relaxors

    SciTech Connect

    Hilczer, B.; Szafranski, M.; Hilczer, A.

    2012-01-30

    The effect of hydrostatic pressure on the dielectric response of P(VDF/TrFE)(50/50) irradiated with fast electrons has been studied. A non-linear upward shift of the glass transition temperature T{sub g} and the Curie temperature T{sub C} of the polymer relaxors was observed under pressure with the initial slope dT{sub g}/dp being considerably smaller than dT{sub C}/dp. Moreover, pressure was found to reduce the contribution to the low-frequency dielectric absorption originating from segmental motions in the amorphous phase whereas the contribution related to ferroelectric-paraelectric transition and that of polar nanoclusters in the crystalline phase were found to be enhanced.

  20. In situ transmission electron microscopy study of the microstructural origins for the electric field-induced phenomena in ferroelectric perovskites

    NASA Astrophysics Data System (ADS)

    Guo, Hanzheng

    an unusual behavior is attributed to the electric field-induced irreversible P4bm nanodomains coalescence into thin lamellar domains prior to the phase transition. In the (K0.5 Na0.5)NbO3-based ceramics, as demonstrated by an archetypical polymorphic phase boundary (PPB) composition of 0.948(K 0.5Na0.5)NbO3-0.052LiSbO3, the origin of the excellent piezoelectric performance is due to a tilted monoclinic phase that emerges from the tetragonal and orthorhombic PPB at the poling fields beyond 14 kV/cm. This monoclinic phase, as manifested by the appearance of blotchy domains and 1/2{oeo} superlattice diffraction spots, was determined to possess a Pm symmetry with a 0b+c0 oxygen octahedra tilting and antiparallel cation displacements. For the PPB composition of x = 0.5 in the (1-x)Ba(Zr0.2Ti0.8 )O3-x(Ba0.7Ca0.3)TiO 3 solid solution system, the original multi-domain state was found to transform into a unique single-domain state with orthorhombic symmetry at very moderate poling fields of 3 6 kV/cm. This single-domain state is suggested to be primarily responsible for the observed large piezoelectricity due to its significant elastic softening. In the electrical reversal process, a highly unusual phenomenon of electric field-induced ferroelectric-to-relaxor phase transition was directly observed in a lead-free composition of [(Bi1/2Na1/2)0.95 Ba0.05]0.98La0.02TiO3. It is manifested by the disruption of large ferroelectric domains with long range polar order into polar nanodomains with short range orders when the polarity of electric field is reversed. This observation was further rationalized by a phenomenological model that takes the large difference in kinetics between the phase transition and the polarization reversal processes into account. During the electrical cycling process, the microstructural mechanisms for electric fatigue behaviors of two ceramics were investigated. In 0.7Pb(Mg 1/3Nb2/3)O3-0.3PbTiO3, the frozen domain configuration after 103 cycles is

  1. Investigation of the ferroelectric switching behavior of P(VDF-TrFE)-PMMA blended films for synaptic device applications

    NASA Astrophysics Data System (ADS)

    Kim, E. J.; Kim, K. A.; Yoon, S. M.

    2016-02-01

    Synaptic plasticity can be mimicked by electronic synaptic devices. By using ferroelectric thin films as gate insulator for thin-film transistors (TFT), channel conductance can be defined as the synaptic plasticity, and gradually modulated by the variations in amounts of aligned ferroelectric dipoles. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)]-poly(methyl methacrylate) (PMMA) blended films are chosen and their switching kinetics are investigated by using the Kolmogorov-Avrami-Ishibashi model. The switching time for ferroelectric polarization is sensitively influenced by the amplitude of applied electric field and volumetric ratio of ferroelectric beta-phases in the P(VDF-TrFE)-PMMA films. The switching time of the P(VDF-TrFE) increases with decreasing the pulse amplitude and/or the ratio of ferroelectric beta-phases by incorporation of PMMA. The activation electric field is also found to increase as the increase in blended amount of PMMA. Synapse TFTs are fabricated using the P(VDF-TrFE)-PMMA as gate insulator and In-Ga-Zn-O active channels. The drain currents of the synapse TFTs gradually increased when the voltage pulse signals with given duration are repeatedly applied. This suggests that the synaptic weights can be modulated by the number of external pulse signals, and that the proposed synapse TFT can be applied for mimicking the operations of bio-synapses.

  2. Domains in Ferroelectric Nanostructures

    NASA Astrophysics Data System (ADS)

    Gregg, Marty

    2010-03-01

    Ferroelectric materials have great potential in influencing the future of small scale electronics. At a basic level, this is because ferroelectric surfaces are charged, and so interact strongly with charge-carrying metals and semiconductors - the building blocks for all electronic systems. Since the electrical polarity of the ferroelectric can be reversed, surfaces can both attract and repel charges in nearby materials, and can thereby exert complete control over both charge distribution and movement. It should be no surprise, therefore, that microelectronics industries have already looked very seriously at harnessing ferroelectric materials in a variety of applications, from solid state memory chips (FeRAMs) to field effect transistors (FeFETs). In all such applications, switching the direction of the polarity of the ferroelectric is a key aspect of functional behavior. The mechanism for switching involves the field-induced nucleation and growth of domains. Domain coarsening, through domain wall propagation, eventually causes the entire ferroelectric to switch its polar direction. It is thus the existence and behavior of domains that determine the switching response, and ultimately the performance of the ferroelectric device. A major issue, associated with the integration of ferroelectrics into microelectronic devices, has been that the fundamental properties associated with ferroelectrics, when in bulk form, appear to change quite dramatically and unpredictably when at the nanoscale: new modes of behaviour, and different functional characteristics from those seen in bulk appear. For domains, in particular, the proximity of surfaces and boundaries have a dramatic effect: surface tension and depolarizing fields both serve to increase the equilibrium density of domains, such that minor changes in scale or morphology can have major ramifications for domain redistribution. Given the importance of domains in dictating the overall switching characteristics of a device

  3. Interaction of Terahertz Radiation with Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Nelson, Keith

    2007-03-01

    Ferroelectric crystals have long been used as acoustic transducers and receivers. An extensive toolset has been developed for MHz-frequency acoustic wave generation, control, guidance, and readout. In recent years, an analogous toolset has been developed for terahertz wave transduction and detection. Femtosecond optical pulses irradiate ferroelectric crystals to generate responses in the 0.1-5 THz frequency range that are admixtures of electromagnetic and polar lattice vibrational excitations called phonon-polaritons. Spatiotemporal femtosecond pulse shaping may be used to generate additional optical pulses that arrive at specified times and sample locations for control and manipulation of the THz waves. Femtosecond laser machining may be used for fabrication of waveguides, resonators, and other structures that are integrated into the ferroelectric host crystal. Finally, real-space imaging of the THz fields can be executed with variably delayed femtosecond probe pulses, permitting direct visualization of THz wave spatial and temporal evolution. This ``polaritonics'' toolset enables multiplexed generation of arbitrary THz waveforms and use of the waveforms within the ferroelectric host crystal or after projection into free space or an adjacent medium. The polaritonics platform will be reviewed and several new developments and applications will be presented. These include spectroscopy of relaxor ferroelectrics, whose temperature-dependent dielectric responses in the GHz-THz regime reveal complex polarization dynamics on well separated fast and slow time scales; direct measurement of phonon-polariton lattice vibrational displacements through femtosecond time-resolved x-ray diffraction; generation of high polariton field amplitudes and pulse energies; use of large-amplitude polariton waves to drive nonlinear lattice vibrational responses; and enhancement of optical-to-THz conversion efficiency through a pseudo-phase-matching approach that circumvents the very large

  4. A flexible tactile-feedback touch screen using transparent ferroelectric polymer film vibrators

    NASA Astrophysics Data System (ADS)

    Ju, Woo-Eon; Moon, Yong-Ju; Park, Cheon-Ho; Choi, Seung Tae

    2014-07-01

    To provide tactile feedback on flexible touch screens, transparent relaxor ferroelectric polymer film vibrators were designed and fabricated in this study. The film vibrator can be integrated underneath a transparent cover film or glass, and can also produce acoustic waves that cause a tactile sensation on human fingertips. Poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] polymer was used as the relaxor ferroelectric polymer because it produces a large strain under applied electric fields, shows a fast response, and has excellent optical transparency. The natural frequency of this tactile-feedback touch screen was designed to be around 200-240 Hz, at which the haptic perception of human fingertips is the most sensitive; therefore, the resonance of the touch screen at its natural frequency provides maximum haptic sensation. A multilayered relaxor ferroelectric polymer film vibrator was also demonstrated to provide the same vibration power at reduced voltage. The flexible P(VDF-TrFE-CTFE) film vibrators developed in this study are expected to provide tactile sensation not only in large-area flat panel displays, but also in flexible displays and touch screens.

  5. Giant magnetoelectric effect in thin magnetic films utilizing inter-ferroelectric transitions

    NASA Astrophysics Data System (ADS)

    Finkel, Peter; Staruch, Margo

    There has recently been much interest to multiferroic magnetoelectric composites based on relaxor ferroelectric single crystals as potential candidates for devices such as magnetic field sensors, energy harvesters, or transducers. Large magnetoelectric coupling coefficient is prerequisite for superior device performance in a broad range of frequencies and functioning conditions. In magnetoelectric heterostructures based on ternary relaxors Pb(In1/2Nb1/2) O3-Pb(Mg1/3Nb2/3) O3-PbTiO3 (PIN-PMN-PT) crystal better operational range and temperature stability as compared to binary relaxors can be achieved. Giant linear converse magnetoelectric coupling up to 2 x 10-6 s m-1 were observed in heterostructural composites with multilayered FeCo/Ag deposited on (011) PIN-PMN-PT crystals. Further enhancement of magnetoelectric coupling is demonstrated by utilizing inter-ferroelctric rhombohedral - orthorhombic phase transitions in PIN-PMN-PT Mechanical clamping was a precondition to utilize this inter-ferroelectric transition mode to bring the crystal to a point just below its transformation threshold when very small perturbations at the input will cause large swings at the output generating a sharp uniaxial increase in strain (~0.5 %) and polarization change, giving rise to nonlinear effects. Details of these results and their implications will be presented. Giant magnetoelectric effect in thin magnetic fillms utilizing inter-ferroelectric transitions.

  6. Structural, dielectric, ferroelectric, and electrocaloric properties of 2% Gd2O3 doping (Na0.5Bi0.5)0.94Ba0.06TiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Turki, O.; Slimani, A.; Seveyrat, L.; Sebald, G.; Perrin, V.; Sassi, Z.; Khemakhem, H.; Lebrun, L.

    2016-08-01

    Structural, dielectric, and ferroelectric properties, and electrocaloric effects of pure and Gd doped ( Na0.5 Bi 0.5 ) 0.94 Ba 0.06 TiO 3 ceramics prepared by the conventional solid-solid method have been carried out. The X-ray diffraction analysis confirms a pure perovskite structure with the coexistence of tetragonal and rhombohedra structures in both powders. The thermal and frequency dependences of the dielectric constants of both ceramics revealed relaxor behavior. The two compounds exhibited two phase transitions: ferroelectric/antiferroelectric (FE/AFE) transition followed by an antiferroelectric/paraelectric (AFE/PE) transition at higher temperatures. Remarkably, we noticed that the small amount of Gd doping (2%) highly enhanced the dielectric properties of the parent compound by about 71%. The phase diagram was as well influenced by the Gd doping, where the FE/AFE transition temperature rose from 90 in the parent compound to 115 °C in the doped one whereas the AFE/PE transition temperature was decreased from 320 to 270 °C, respectively. The direct electrocaloric measurements performed on both compounds showed that the ferroelectric/antiferroelectric phase transition was accompanied by a significant electrocaloric effect. The Gd3+ doping improved the electrocaloric properties of the parent compound, where a remarkable temperature variation of 1.4 K was obtained in the doped ceramic. The results of the direct electrocaloric measurements will be compared and discussed with those derived from the indirect method.

  7. A theoretical study of soft mode behavior and ferroelectric phase transition in 18O-isotope exchanged SrTiO3: evidence of phase coexistence at the quantum critical point

    NASA Astrophysics Data System (ADS)

    Mkam Tchouobiap, S. E.

    2014-02-01

    Motivated by recent experiments, the dynamics of the ferroelectric soft mode and the ferroelectric phase transition mechanism in 18O isotope exchanged systems SrTi(16O1-x18Ox)3 (abbreviated as STO18-x) are reinvestigated as a function of the 18O isotope exchange rate x, within a quasiharmonic model (QHM) for quantum ferroelectric modes in double-Morse local potential with mean-field approximation interactions between modes. The approach was realized within the framework of the variational principle method at finite temperature through the quantum mean-field approximation and by taking into account the effect of isotope replacement through the predominant mass effect, the cell volume effect, homogeneity of the composition throughout the material and the concentration-dependent ferroelectric mode distortion effect. The dynamics of the lowest-frequency soft phonon mode clearly presents an increased softening phenomenon with increasing x and a complete one at the corresponding phase transition temperature Tc, demonstrating the perfect soft-mode-type quantum ferroelectric phase transition for x ⩾ xc. Also, a ferroelectric-paraelectric phase coexistence state has been found near the quantum critical point xc and its origin is discussed. The ferroelectric phase transition mechanism is analyzed and its nature discussed, where a second-order phase transition close to the tricritical point is predicted. In addition, the effect of quantum fluctuations on the soft mode dynamics is discussed which reveals its reduction with increasing x and the crossover of the soft mode dynamics from the quantum to the classic one at the full 18O exchange limit x = 1, for which the origin seems to lie in the new homogeneity associated with the direct reduction of quantum fluctuations effects on the soft mode behavior. Within the QHM, consistent agreement with some of the previous experimental results and theoretical predictions of quantum ferroelectricity throughout the full range of x are

  8. Why is the electrocaloric effect so small in ferroelectrics?

    NASA Astrophysics Data System (ADS)

    Guzmán-Verri, G. G.; Littlewood, P. B.

    2016-06-01

    Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity of their phase transitions, which may occur near room temperature. The magnitude of the effect, however, is too small for useful cooling applications even when they are driven close to dielectric breakdown. Insight from microscopic theory is therefore needed to characterize materials and provide guiding principles to search for new ones with enhanced electrocaloric performance. Here, we derive from well-known microscopic models of ferroelectricity meaningful figures of merit for a wide class of ferroelectric materials. Such figures of merit provide insight into the relation between the strength of the effect and the characteristic interactions of ferroelectrics such as dipolar forces. We find that the long range nature of these interactions results in a small effect. A strategy is proposed to make it larger by shortening the correlation lengths of fluctuations of polarization. In addition, we bring into question other widely used but empirical figures of merit and facilitate understanding of the recently observed secondary broad peak in the electrocalorics of relaxor ferroelectrics.

  9. Photoinduced cooperative phenomena in ferroelectric layered perovskites Pb2Bi4Ti5O18 studied by high resolution Raman scattering

    NASA Astrophysics Data System (ADS)

    Takesada, Masaki; Ueki, Ayaka; Onodera, Akira

    2009-02-01

    The UV photo induced effect in bismuth layered perovskite Pb2Bi4Ti5O18 has been investigated by a low frequency Raman scattering. The temperature dependences of Raman spectra both under and without a UV irradiation were observed around the ferroelectric to relaxor phase transition temperature. The central peak in the Raman spectrum shows narrowing under a UV irradiation below Tc. The correlation length of the ferroelectric fluctuation should be enhanced as a UV photo induced effect in the ferroelectric state.

  10. Electrical Properties of Barium and Zirconium Modified NBT Ferroelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Rao, K. Sambasiva; Tilak, B.; Rajulu, K. Ch. Varada; Swathi, A.; Workineh, Haileeyesus

    2011-11-01

    Recently a new wave of interest has risen on relaxor ferroelectrics with complex perovskite structure due to their wide use in fabrication of multilayer ceramic capacitors, electrostrictive actuators, and electromechanical transducers. The polycrystalline 0.93(Bi0.5Na0.5)Ba0.07Z0.04T0.96O3 (0.07BNBZT) ceramic material, which is in the vicinity of the morphotropic phase boundary (MPB) has been prepared by using high temperature solid state reaction method. The tolerance factor has been estimated and found to be 0.815. XRD analysis revealed a rhombohedral perovskite type structure. SEM micrographs showed highly dense grains with rectangular shape. The average grain size is found to be 1.51μm. Dielectric studies in the material ha indicated relaxor behaviour with diffuse phase transition. High value of ɛm>1958 is found at 1kHz, Tm (phase transition temperature) 335 °C, The diffuseness parameter was established to be 1.60 revealing the relaxor behaviour. Further, to confirm the relaxor behaviour in the material, Vogel-Fulcher (V-F) relation has been used. Estimated V-F parameters are found to be Tf = 138 °C, Ea = 0.080 eV and νo = 2.32×108 Hz. Cole-Cole analysis has shown a non-Debye type relaxation in the system. Conductivity studies in the material obeyed the Jonscher's power law in frequency range of (45Hz-5MHz) and temperature range of (35 °C-600 °C). The electric conduction in the system may be due to hopping/mobility/ transportation of charge carriers.

  11. Coherent coupling in ferroelectric superlattices

    SciTech Connect

    Li, S.; Eastman, J.A.; Vetrone, J.; Newnham, R.E.; Cross, L.E.

    1996-07-01

    The phase transition and dielectric behavior of ferroelectric multilayers have been discussed. The coherent interaction between ultra-thin layers can be significantly strong, resulting in a broad diffuse phase transition. The thicknesses of layers and their spatial distributions hold the keys of enhancing dielectric properties in a broad temperature range.

  12. Size effects in a relaxor: further insights into PMN.

    PubMed

    Grigalaitis, R; Ivanov, M; Macutkevic, J; Banys, J; Carreaud, J; Kiat, J M; Laguta, V V; Zalar, B

    2014-07-01

    Dielectric measurements of PbMg1/3Nb2/3O3 (PMN) powder and dense ceramics with grain sizes between 15 nm and two microns were carried out in a broad frequency range (20 Hz-1 GHz). Clear grain size dependence of relaxor behavior was evidenced. A progressive transformation from Vogel-Fulcher behavior towards the Arrhenius process in the PMN with reduction of grain size in both ceramics and powder was observed. In the case of ceramics we were able to extract deeper information from the distributions of relaxation times and an analysis using the Vogel-Fulcher law, revealing two main contributions: a fast part of distribution of relaxation times with a maximum close to 10(-11) s, which is almost grain-size independent and has a non-polar origin; whereas, a process with long relaxation times (in the time range of 10(-8) to 10(-5) s) is associated with the dynamics of the polar nanoregions and is strongly suppressed with reduction of grain size. The results of dielectric investigations are confirmed by Nuclear Magnetic Resonance experiments. PMID:24925462

  13. Size effects in a relaxor: further insights into PMN

    NASA Astrophysics Data System (ADS)

    Grigalaitis, R.; Ivanov, M.; Macutkevic, J.; Banys, J.; Carreaud, J.; Kiat, J. M.; Laguta, V. V.; Zalar, B.

    2014-07-01

    Dielectric measurements of PbMg1/3Nb2/3O3 (PMN) powder and dense ceramics with grain sizes between 15 nm and two microns were carried out in a broad frequency range (20 Hz-1 GHz). Clear grain size dependence of relaxor behavior was evidenced. A progressive transformation from Vogel-Fulcher behavior towards the Arrhenius process in the PMN with reduction of grain size in both ceramics and powder was observed. In the case of ceramics we were able to extract deeper information from the distributions of relaxation times and an analysis using the Vogel-Fulcher law, revealing two main contributions: a fast part of distribution of relaxation times with a maximum close to 10-11 s, which is almost grain-size independent and has a non-polar origin; whereas, a process with long relaxation times (in the time range of 10-8 to 10-5 s) is associated with the dynamics of the polar nanoregions and is strongly suppressed with reduction of grain size. The results of dielectric investigations are confirmed by Nuclear Magnetic Resonance experiments.

  14. Heterophase fluctuations near Tc in the relaxor ferroelectrics (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (x =0.09) studied by x-ray diffuse scattering and coherent x-ray scattering

    NASA Astrophysics Data System (ADS)

    Ohwada, Kenji; Mizuki, Jun'ichiro; Matsushita, Mitsuyoshi; Namikawa, Kazumichi

    2014-09-01

    The paraelectric (PE) to ferroelectric (FE) first-order phase transition of (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (x =0.09) (Tcc=455 K on cooling) has been studied by the complementary use of x-ray diffuse scattering (XDS) and coherent x-ray scattering (CXS). XDS was mainly used to investigate the FE regions, while CXS was mainly used to investigate the PE regions above Tcc on cooling. The diffuse scattering intensity due to the appearance of FE regions shows a maximum at Tmax=460 K. The diffuse scattering is dynamic in nature and the softening trend changes to a hardening trend at Tmax. This means that the FE instability is maximum at Tmax and therefore the FE regions are well stabilized below Tmax. The spatial autocorrelation function obtained by CXS, corresponding to the texture of PE regions, starts to rapidly change at about Tmax and is most unstable at Tcc. We conclude that a heterophase fluctuation occurs between Tcc and Tmax near the phase transition. The heterophase fluctuation can be expected to correlate to the low-frequency dielectric dispersion and contribute to the phase transition as a precursor phenomenon of the first-order phase transition.

  15. A comparative study of the phase transitions near the critical concentration in the relaxor K1 - xLixTaO3

    NASA Astrophysics Data System (ADS)

    Cai, Ling; Toulouse, Jean; Harriger, Leland; Downing, Greg; Boatner, Lynn

    2014-03-01

    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 K1 - x Lix TaO3 (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 TC and TB, 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.

  16. Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe Microscopy.

    PubMed

    Balke, Nina; Maksymovych, Petro; Jesse, Stephen; Herklotz, Andreas; Tselev, Alexander; Eom, Chang-Beom; Kravchenko, Ivan I; Yu, Pu; Kalinin, Sergei V

    2015-06-23

    Ferroelectricity in functional materials remains one of the most fascinating areas of modern science in the past several decades. In the last several years, the rapid development of piezoresponse force microscopy (PFM) and spectroscopy revealed the presence of electromechanical hysteresis loops and bias-induced remnant polar states in a broad variety of materials including many inorganic oxides, polymers, and biosystems. In many cases, this behavior was interpreted as the ample evidence for ferroelectric nature of the system. Here, we systematically analyze PFM responses on ferroelectric and nonferroelectric materials and demonstrate that mechanisms unrelated to ferroelectricity can induce ferroelectric-like characteristics through charge injection and electrostatic forces on the tip. We will focus on similarities and differences in various PFM measurement characteristics to provide an experimental guideline to differentiate between ferroelectric material properties and charge injection. In the end, we apply the developed measurement protocols to an unknown ferroelectric material. PMID:26035634

  17. Observation of bi-relaxor characteristic in multiferroic 0.70Bi0.90Ca0.10FeO3-0.30PbTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Tirupathi, Patri; Chandra, Amreesh

    2013-09-01

    The coexistence of bi-relaxor property, i.e. ferroelectric relaxor as well as spin glass type behaviour, is observed in disordered multiferroic ceramic 0.70Bi0.90Ca0.10FeO3-0.30PbTiO3. The real parts of dielectric permittivity and magnetic susceptibility show pronounced frequency dispersion near the corresponding phase transition temperatures, namely, Tc ≈ 550 K and TN ≈ 110 K, respectively. The relaxor behaviour observed in temperature-dependent dielectric constant measurement is confirmed by fitting of the Vogel-Fulcher equation. Similarly, magnetic spin glass behaviour is proven by power law fitting. The origin of such bi-relaxor in the present system can be attributed to the disorder and frustration among the uncompensated spins of the Fe-ion. This has been confirmed by analysing the x-ray photoelectron (XPS) spectrum of the sample under investigation. Using FESEM micrographs, the coexistence of nano-sized and bulk grains is shown. The importance of such coexistence is discussed and also presented in the paper.

  18. Ferroelectricity in Strain-Free SrTiO3 Thin Films

    SciTech Connect

    Jang, J H; Kumar, Amit; Denev, Sava; Biegalski, Michael D; Maksymovych, Petro; Bark, C; Nelson, Craig T; Folkman, C H; Baek, Seung Hyub; Balke, Nina; Brooks, Charles M.; Tenne, Demetri A.; Schlom, Darrell; Chen, Long-Qing; Pan, X Q; Kalinin, Sergei V; Gopalan, Venkatraman; Eom, Professor Chang-Beom

    2010-01-01

    Biaxial strain is known to induce ferroelectricity in thin films of nominally nonferroelectric materials such as SrTiO3. However, even strain-free SrTiO3 films and the paraelectric phase of strained films exhibit bulk frequency-dependent polarization hysteresis loops on the nanoscale at room temperature, and stable switchable domains at 50 K. By a direct comparison of the strained and strain-free SrTiO3 films using dielectric, ferroelectric, Raman, nonlinear optical and nanoscale piezoelectric property measurements, we conclude that SrTiO3 films and bulk crystals are relaxor ferroelectrics, and the role of strain is to stabilize longer-range correlation of preexisting nanopolar regions, likely originating from minute amounts of unintentional Sr-deficiency in nominally stoichiometric samples. These findings highlight the sensitive role of stoichiometry when exploring strain and epitaxy-induced electronic phenomena in oxidefilms, heterostructures and interfaces.

  19. Relaxor in KF-doped BaTi{sub 2}O{sub 5} ceramics by spark plasma sintering

    SciTech Connect

    Xu Jun; Akishige, Yukikuni

    2008-02-04

    Dense BaTi{sub 2}O{sub 5} ceramics with KF doping up to 5 at. % were synthesized by spark plasma sintering (SPS). The SPS method enabled us to overcome the densifying difficulty in conventional sintering which is caused by the limit of the decomposing temperature of this metastable phase. We observed drastic KF-doping effect on the ferroelectric (FE) properties of BaTi{sub 2}O{sub 5}. Although there is only very small change in lattice parameters upon KF doping, the peak temperature in dielectric constant strongly decreases in an exponential way. The diffuseness of phase transition increases and FE relaxor state sets in for KF content as low as 1 at. %. Possible structural reasons for the effect and the implication for the nature of FE phase transition in BaTi{sub 2}O{sub 5} are discussed.

  20. Ferroelectric ultrathin perovskite films

    DOEpatents

    Rappe, Andrew M; Kolpak, Alexie Michelle

    2013-12-10

    Disclosed herein are perovskite ferroelectric thin-film. Also disclosed are methods of controlling the properties of ferroelectric thin films. These films can be used in a variety materials and devices, such as catalysts and storage media, respectively.

  1. 180 deg. domain structure and its evolution in Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} ferroelectric single crystals of tungsten bronzes structure

    SciTech Connect

    Lu, C.J.; Nie, C.J.; Duan, X.F.; Li, J.Q.; Zhang, H.J.; Wang, J.Y.

    2006-05-15

    Ferroelectric domain structure and its evolution in uniaxial relaxor Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} single crystals were investigated using transmission electron microscopy. It was found that there exists a high density of 180 deg. domain walls in the crystals. The domains appear predominantly spike shaped along the polar axis and have a typical diameter of 50-500 nm. Domain wall motion was occasionally induced by electron beam irradiation. Macrodomains-to-microdomains switching has been observed corresponding to the normal-to-relaxor ferroelectrics transition during an in situ heating experiments. At temperature just below ferroelectric phase transition temperature T{sub C}, zero-field-cooled needlelike nanodomains were also observed.

  2. Ferroelectric properties and fatigue behavior of heteroepitaxial PbZr1-xTixO3 thin film fabricated by hydrothermal epitaxy below Curie temperature

    NASA Astrophysics Data System (ADS)

    Ahn, W. S.; Jung, W. W.; Choi, S. K.

    2006-01-01

    A heteroepitaxial PbZr1-xTixO3 (PZT) thin film was fabricated by means of hydrothermal epitaxy at 210 °C below Curie temperature without undergoing the paraelectric to ferroelectric phase transition. From transmission electron microscope and piezoresponse force microscope observations, it was confirmed that the fabricated PZT thin films had only a -c monodomain without an a domain in the as-synthesized state. The polarization-electric-field hysteresis curve and the fatigue behavior of the heteroepitaxial PZT capacitor with a Pt top and n-type semiconductor bottom electrode was observed. The remanent polarization 2Pr of the PZT capacitor was about 63 μC/cm2. This value was much lower compared to that of the PbTiO3 capacitor, which was also fabricated by means of hydrothermal epitaxy at 160 °C below Curie temperature. It was suggested that a lower polarization of the PZT capacitor was due to the nonswitchable interfacial layer grown in the initial growth stage. However, this layer did not exert an influence on the fatigue behavior of the PZT capacitor: the PZT capacitor with an ordinary Pt top electrode and a Nb-doped SrTiO3 semiconductor bottom electrode revealed fatigue-free behavior in up to 1011 switching cycles.

  3. Weak ferromagnetism and magnetoelectric effect in multiferroic xBa0.95Sr0.05TiO3-(1-x)BiFe0.9Gd0.1O3 relaxors

    NASA Astrophysics Data System (ADS)

    Miah, M. J.; Khan, M. N. I.; Hossain, A. K. M. Akther

    2016-03-01

    Multiferroic xBa0.95Sr0.05TiO3-(1-x)BiFe0.9Gd0.1O3 [xBST-(1-x)BFGO], where x=0.00-0.40, have been synthesized by the conventional solid-state reaction method. The crystalline phase, microstructure, relaxor behavior, ac conductivity, impedance spectroscopy, dc magnetic properties, complex initial permeability and magnetoelectric coefficient of these solid solutions have been investigated. The crystal structure is found to change from rhombohedral in BFGO rich compositions to cubic when x≥0.30. Room temperature dielectric properties are investigated within the frequency range from 1 kHz to 1 MHz and found to increase with BST content. The frequency dependence of high temperature dielectric measurements indicated that the composites with x≥0.20, exhibit relaxor ferroelectric behavior. The ac conductivity obeys the Jonscher's universal power law and BST helps to enhance the electrical conductivity of the composites. Studies of impedance spectroscopy suggest that only grains have the contribution to the conductivity mechanism in this material. Magnetizations as a function of applied magnetic field measurements show weak ferromagnetism for 0.10≤x≤0.30 composites. The maximum value of remnant magnetization is found to be 0.565×103 A/m (=0.08 emu/g) for x=0.25 which is better than previously reported BaTiO3-BiFeO3 systems. The complex initial permeability is found to improve with the increase in BST concentration due to the reduction of oxygen vacancies. In addition, an enhanced magnetoelectric (ME) coupling is also observed and determined by the ME coefficient. The maximum value of ME coefficient is found to be 21.71×10-4 V/A (=1.67 mV/cm Oe) for the x=0.25 composition. The BST-BFGO solid solutions show high-performance multiferroic properties and can be selected for further investigation.

  4. Ferroelectricity in corundum derivatives

    NASA Astrophysics Data System (ADS)

    Ye, Meng; Vanderbilt, David

    The search for new ferroelectric (FE) materials holds promise for broadening our understanding of FE mechanisms and extending the range of application of FE materials. The known FE materials LiNbO3 can be regarded as derived from the A2O3 corundum structure with cation ordering. Here we consider more general binary (AB O3) and ternary (A2 BB' O6) corundum derivatives as an extended class of potential FE materials, motivated by the fact that some members of this class have recently been synthesized. There are four structure types for these corundum derivatives, and the number of cation combinations is enormous, but in many cases the energy barriers for polarization reversal may be too large to allow FE behavior. Here we present a first-principles study of the polar structure, coherent FE barrier, and domain-wall switching barrier for a representative set of polar corundum derivatives, allowing us to identify several potentially new FE materials. We also discuss the conditions under which ferroelectricity is compatible with magnetic ordering. Finally, we identify several empirical measures that can provide a rule of thumb for estimating the barrier energies. Our results should assist in the experimental search for new FE materials in the corundum derivative family. This work is supported by ONR Grant No. N-00014-12-1-1035.

  5. Structural and relaxor-like dielectric properties of unfilled tungsten bronzes Ba5-5xSm5xTi5xNb10-5xO30

    NASA Astrophysics Data System (ADS)

    Wei, T.; Dong, Z.; Zhao, C. Z.; Guo, Y. Y.; Zhou, Q. J.; Li, Z. P.

    2016-03-01

    New unfilled tetragonal tungsten bronze (TTB) oxides, Ba5-5xSm5xTi5xNb10-5xO30 (BSTN-x), where 0.10 ≤ x ≤ 0.35, have been synthesized in this work. Their crystal structure was determined and analyzed based on Rietveld structural refinement. It is found that single TTB phase can be formed in a particular x range (i.e., 0.15 ≤ x ≤ 0.3) due to the competition interaction between tolerance factor and electronegativity difference. Furthermore, dielectric and ferroelectric results indicate that phase transitions and ferroelectric states are sensitive to x. Referring to the local chemistry, we suggest that the raise of vacancies at the A2-site compared with that of A1-site will intensely depress the normal ferroelectric phase and is in favor of relaxor ferroelectric state. Macroscopically, previous A-site size difference standpoint on fill TTB compounds cannot give a reasonable explanation about the variation of dielectric maximum temperature (Tm) for present BSTN-x compounds. Alternatively, tetragonality (c/a) is adopted which can well describe the variation of Tm in whole x range. In addition, one by one correspondence between tetragonality and electrical features can be found, and the compositions involving high c/a are usually stabilized in normal ferroelectric phase. It is believed that c/a is a more appropriate parameter to illustrate the variation of ferroelectric properties for unfilled TTB system.

  6. High Piezoelectric Response in (Li0.5Sm0.5)2+-Modified 0.93Bi0.5Na0.5TiO3-0.07BaTiO3 Near the Nonergodic-Ergodic Relaxor Transition

    NASA Astrophysics Data System (ADS)

    Xu, Jiwen; Li, Qinglin; Zhou, Changrong; Zeng, Weidong; Xiao, Jianrong; Ma, Jiafeng; Yuan, Changlai; Chen, Guohua; Rao, Guanghui; Li, Xuqiong

    2016-06-01

    The (Bi0.5Na0.5)TiO3-BaTiO3 system is a promising Pb-free piezoelectric material to substitute for environmentally undesirable Pb-based ferroelectrics. However, understanding the origin of its high piezoelectric response is a fundamental issue that has remained unclear for decades. Here, complex ions (Li0.5Sm0.5)2+ were introduced to dictate the stability of the electrically-induced ferroelectric state in 0.93(Bi0.5Na0.5)1- x (Li0.5Sm0.5) x TiO3-0.07BaTiO3 relaxor ceramics. The applied electric field induces a phase transition from a non-ergodic state to a ferroelectric state as well as the realignment of ferroelectric domains. The non-ergodic relaxor state with x = 0-0.02 is accompanied by relatively high piezoelectric activity and the strongest piezoelectricity is observed near the crossover from the nonergodic to the ergodic state. The stable␣ferroelectric state cannot survive after the removal of the application electric field for the high doping level due to the enhancement of the random field, which is responsible for the rapid decrease of piezoelectric properties for x > 0.02 compositions.

  7. Spontaneous vortex nanodomain arrays at ferroelectric heterointerfaces.

    PubMed

    Nelson, Christopher T; Winchester, Benjamin; Zhang, Yi; Kim, Sung-Joo; Melville, Alexander; Adamo, Carolina; Folkman, Chad M; Baek, Seung-Hyub; Eom, Chang-Beom; Schlom, Darrell G; Chen, Long-Qing; Pan, Xiaoqing

    2011-02-01

    The polarization of the ferroelectric BiFeO(3) sub-jected to different electrical boundary conditions by heterointerfaces is imaged with atomic resolution using a spherical aberration-corrected transmission electron microscope. Unusual triangular-shaped nanodomains are seen, and their role in providing polarization closure is understood through phase-field simulations. Heterointerfaces are key to the performance of ferroelectric devices, and this first observation of spontaneous vortex nanodomain arrays at ferroelectric heterointerfaces reveals properties unlike the surrounding film including mixed Ising-Néel domain walls, which will affect switching behavior, and a drastic increase of in-plane polarization. The importance of magnetization closure has long been appreciated in multidomain ferromagnetic systems; imaging this analogous effect with atomic resolution at ferroelectric heterointerfaces provides the ability to see device-relevant interface issues. Extension of this technique to visualize domain dynamics is envisioned. PMID:21247184

  8. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage.

    PubMed

    Cai, Ronggang; Kassa, Hailu G; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H; Ruzié, Christian; van Breemen, Albert J J M; Gelinck, Gerwin H; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M

    2016-03-21

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices. PMID:26927694

  9. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage

    NASA Astrophysics Data System (ADS)

    Cai, Ronggang; Kassa, Hailu G.; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H.; Ruzié, Christian; van Breemen, Albert J. J. M.; Gelinck, Gerwin H.; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M.

    2016-03-01

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices.Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction

  10. A quaternary lead based perovskite structured materials with diffuse phase transition behavior

    SciTech Connect

    Puli, Venkata Sreenivas; Martinez, R.; Kumar, Ashok; Scott, J.F.; Cavendish Laboratory, Dept. Physics, University of Cambridge, Cambridge CB0 3HE ; Katiyar, Ram S.

    2011-12-15

    Graphical abstract: (a) Curie-Weiss plot for the inverse of the relative dielectric permittivity and (b) log (1/{epsilon} - 1/{epsilon}{sub m}) as function of log (T - T{sub m}) for ceramics at 1 kHz. Highlights: Black-Right-Pointing-Pointer Retaining phase pure structure with quaternary complex stoichiometric compositions. Black-Right-Pointing-Pointer P-E loops with good saturation polarization (P{sub s} {approx} 30.7 {mu}C/cm{sup 2}). Black-Right-Pointing-Pointer Diffused relaxor phase transition behavior with {gamma} estimated is {approx}1.65. -- Abstract: A lead based quaternary compound composed of 0.25(PbZr{sub 0.52}Ti{sub 0.48}O{sub 3}) + 0.25(PbFe{sub 0.5}Ta{sub 0.5}O{sub 3}) + 0.25 (PbF{sub 0.67}W{sub 0.33}O{sub 3}) + 0.25(PbFe{sub 0.5}Nb{sub 0.5}O{sub 3}) - (PZT-PFT-PFW-PFN) was synthesized by conventional solid-state reaction techniques. It showed moderate high dielectric constant, low dielectric loss, and two diffuse phase transitions, one below the room temperature {approx}261 K and other above {approx}410 K. X-ray diffraction (XRD) patterns revealed a tetragonal crystal structure at room temperature where as scanning electron micrograph (SEM) indicates inhomogeneous surface with an average grain size of 500 nm-3 {mu}m. Well saturated ferroelectric hysteresis loops with good saturation polarization (spontaneous polarization, P{sub s} {approx} 30.68 {mu}C/cm{sup 2}) were observed. Temperature-dependent ac conductivity displayed low conductivity with kink in spectra near the phase transition. In continuing search for developing new ferroelectric materials, in the present study we report stoichiometric compositions of complex perovskite ceramic materials: (PZT-PFT-PFW-PFN) with diffuse phase transition behavior. The crystal structure, dielectric properties, and ferroelectric properties were characterized by XRD, SEM, dielectric spectroscopy, and polarization. 1/{epsilon} versus (T) plots revealed diffuse relaxor phase transition (DPT) behavior. The

  11. Scaling Behavior of Amplitude-Dependent Ferroelectric Hysteresis Loops in an Epitaxial PbZr0.2Ti0.8O3 Thin Film

    SciTech Connect

    Yang, Sang Mo; Jang, S. Y.; Kim, T. H.; Kim, Hun-Ho; Lee, Ho Nyung; Yoon, J. -G.

    2011-01-01

    We investigated the scaling behavior of ferroelectric (FE) hysteresis loops as a function of the applied field amplitude (E{sub 0}) in a high-quality epitaxial PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT) thin film. We observed that the areas of the polarization-electric field hysteresis loops (A) followed the scaling law A {proportional_to} E{sub 0}{sup {alpha}}, with the exponent {alpha} = 0.45 {+-} 0.01. This result is in excellent agreement with the theoretical prediction of {alpha} by the two-dimensional Ising model. In addition, we found that the coercive field (E{sub C}) showed E{sub C} {proportional_to} E{sub 0}{sup {gamma}} with the exponent {gamma} = 0.28 {+-} 0.01. We attribute this relationship to the difference in the sweep rate of the field amplitude E{sub 0}. From the obtained {gamma} value, the growth dimension of FE domains is found to be about 1.68 in our epitaxial PZT thin film.

  12. A light-modified ferroelectric resistive switching behavior in Ag/BaMoO{sub 4}/FTO device at ambient temperature

    SciTech Connect

    Zhao, W.X.; Sun, B.; Liu, Y.H.; Wei, L.J.; Li, H.W.; Chen, P.

    2014-12-15

    BaMoO{sub 4} powder was prepared by a facile hydrothermal synthesis. And the BaMoO{sub 4}/FTO device was fabricated by a spin-coated method, in which the thickness of BaMoO{sub 4} layer is about 20 µm. The bipolar resistive switching effect has been observed in Ag/BaMoO{sub 4}/FTO device. Moreover, the resistive switching effect of the device is greatly improved by white light irradiation. The resistive switching behavior is explained by the polarization reversal that changes the charge distribution and modulates the Schottky barriers. - Graphical abstract: We fabricate a resistive switching device based on Ag/BaMoO{sub 4}/FTO, the device shows superior white-light controlled bipolar resistive switching memristive characteristics. - Highlights: • The BaMoO{sub 4} nanosquares powder was prepared by a hydrothermal synthesis. • The resistive switching of the Ag/BaMoO{sub 4}/FTO device was observed for the first time. • It is shown that the resistive switching is greatly improved under the white light irradiation. • The mechanism of resistive switching is attributed to the ferroelectric polarization reversal.

  13. Super Stable Ferroelectrics with High Curie Point

    NASA Astrophysics Data System (ADS)

    Gao, Zhipeng; Lu, Chengjia; Wang, Yuhang; Yang, Sinuo; Yu, Yuying; He, Hongliang

    2016-04-01

    Ferroelectric materials are of great importance in the sensing technology due to the piezoelectric properties. Thermal depoling behavior of ferroelectrics determines the upper temperature limit of their application. So far, there is no piezoelectric material working above 800 °C available. Here, we show Nd2Ti2O7 with a perovskite-like layered structure has good resistance to thermal depoling up to 1400 °C. Its stable behavior is because the material has only 180° ferroelectric domains, complex structure change at Curie point (Tc) and their sintering temperature is below their Tc, which avoided the internal stresses produced by the unit cell volume change at Tc. The phase transition at Tc shows a first order behavior which involving the tilting and rotation of the octahedron. The Curie – Weiss temperature is calculated, which might explain why the thermal depoling starts at about 1400 °C.

  14. Super Stable Ferroelectrics with High Curie Point

    PubMed Central

    Gao, Zhipeng; Lu, Chengjia; Wang, Yuhang; Yang, Sinuo; Yu, Yuying; He, Hongliang

    2016-01-01

    Ferroelectric materials are of great importance in the sensing technology due to the piezoelectric properties. Thermal depoling behavior of ferroelectrics determines the upper temperature limit of their application. So far, there is no piezoelectric material working above 800 °C available. Here, we show Nd2Ti2O7 with a perovskite-like layered structure has good resistance to thermal depoling up to 1400 °C. Its stable behavior is because the material has only 180° ferroelectric domains, complex structure change at Curie point (Tc) and their sintering temperature is below their Tc, which avoided the internal stresses produced by the unit cell volume change at Tc. The phase transition at Tc shows a first order behavior which involving the tilting and rotation of the octahedron. The Curie – Weiss temperature is calculated, which might explain why the thermal depoling starts at about 1400 °C. PMID:27053338

  15. Super Stable Ferroelectrics with High Curie Point.

    PubMed

    Gao, Zhipeng; Lu, Chengjia; Wang, Yuhang; Yang, Sinuo; Yu, Yuying; He, Hongliang

    2016-01-01

    Ferroelectric materials are of great importance in the sensing technology due to the piezoelectric properties. Thermal depoling behavior of ferroelectrics determines the upper temperature limit of their application. So far, there is no piezoelectric material working above 800 °C available. Here, we show Nd2Ti2O7 with a perovskite-like layered structure has good resistance to thermal depoling up to 1400 °C. Its stable behavior is because the material has only 180° ferroelectric domains, complex structure change at Curie point (Tc) and their sintering temperature is below their Tc, which avoided the internal stresses produced by the unit cell volume change at Tc. The phase transition at Tc shows a first order behavior which involving the tilting and rotation of the octahedron. The Curie - Weiss temperature is calculated, which might explain why the thermal depoling starts at about 1400 °C. PMID:27053338

  16. Negative Capacitance transients in a ferroelectric capacitor

    NASA Astrophysics Data System (ADS)

    Khan, Asif; Chatterjee, Korok; Wang, Brian; Drapcho, Steven; You, Long; Serrao, Claudy; Bakaul, Saidur; Ramesh, Ramamoorthy; Salahuddin, Sayeef

    2015-03-01

    The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here we demonstrate the negative differential capacitance in a thin, single crystalline ferroelectric film, by constructing a simple R-C network and monitoring the voltage dynamics across the ferroelectric capacitor6. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time-in exactly the opposite direction to which voltage for a regular capacitor should change. The results are analyzed on the basis of the Landau-Khalatnikov equation, which shows that as the ferroelectric polarization switches its direction, it passes through the unstable negative capacitance region resulting in the characteristic ``negative capacitance transients.'' Analysis of this ``inductance''-like behavior from a capacitor allows us to calculate the value of the negative capacitance directly and presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material.

  17. Negative Capacitance in a Ferroelectric Capacitor

    NASA Astrophysics Data System (ADS)

    Khan, Asif; Chatterjee, Korok; Wang, Brian; Drapcho, Steven; You, Long; Serrao, Claudy; Bakaul, Saidur; Ramesh, Ramamoorthy; Salahuddin, Sayeef; UC Berkeley Team

    The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here we demonstrate the negative differential capacitance in an epitaxial ferroelectric film, by constructing a simple R-C network and monitoring the voltage dynamics across the ferroelectric capacitor. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time-in exactly the opposite direction to which voltage for a regular capacitor should change. The results are analyzed on the basis of the Landau-Khalatnikov equation, which shows that as the ferroelectric polarization switches its direction, it passes through the unstable negative capacitance region. Analysis of this behavior from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material.

  18. Electronic transitions and dielectric functions of relaxor ferroelectric Pb(In{sub 1∕2}Nb{sub 1∕2})O{sub 3}-Pb(Mg{sub 1∕3}Nb{sub 2∕3})O{sub 3}-PbTiO{sub 3} single crystals: Temperature dependent spectroscopic study

    SciTech Connect

    Zhu, J. J.; Zhang, J. Z.; Chu, J. H.; Xu, G. S.; Zhang, X. L.; Hu, Z. G.

    2014-03-31

    Optical properties and phase transitions of Pb(In{sub 1∕2}Nb{sub 1∕2})O{sub 3}-Pb(Mg{sub 1∕3}Nb{sub 2∕3})O{sub 3}-PbTiO{sub 3} (PIN-PMN-PT) crystals near morphotropic phase boundary (MPB) have been investigated by temperature dependent transmittance and reflectance spectra. Three critical point energies E{sub g} = 3.17–3.18 eV, E{sub a} = 3.41–3.61 eV, and E{sub b} = 4.74–4.81 eV can be assigned to the transitions from oxygen 2p to titanium d, niobium d, and lead 6p states, respectively. They show narrowing trends with increasing temperature, which can be caused by thermal expansion of the lattice and electron-phonon interaction. Deviation from the linear behaviors can be observed from E{sub a} and E{sub b} versus PT concentration, indicating a complex multiphase structure near MPB region.

  19. Ba and Ti co-doped BiFeO3 thin films via a modified chemical route with synchronous improvement in ferroelectric and magnetic behaviors

    NASA Astrophysics Data System (ADS)

    Wang, Yao; Li, Jing; Chen, Jingyi; Deng, Yuan

    2013-03-01

    A modified chemical route via the layer-by-layer alternative deposition of BaTiO3 and BiFeO3 two compositions followed by the solution processing has been developed to prepare Ba and Ti co-doped multiferroic BiFeO3 thin films. The Ba and Ti co-doped BiFeO3 films crystallize in single perovskite phase and are composed of uniformly distributed grains of tens of nanometers as evidenced by X-ray diffraction and scanning electron microscopy images, respectively. But the films show local composition fluctuation with further high-resolution transmission electron microscope analysis, which leads to increased inner strain and thus a phase transition from R3c to P4mm occurs as Ba and Ti contents reach 50 mol. %. Accompanying the structural phase transition, a saturated P-E hysteresis loop with Pr ˜ 27 μC/cm2 and Ps ˜ 87 μC/cm2 and, moreover, a transition from antiferromagnetic to ferromagnetic state with Mr ˜ 1.46 emu/cm3 and Hc ˜ 1000 Oe have been observed. A strain induced structural change is proposed to explain for the observed synchronous enhancement in ferroelectric and magnetic properties, and elastic energy calculation is carried out to verify the viewpoint on magnetic behavior. The modified multiferroic behaviors of Ba, Ti co-doped BiFeO3 film imply an improved magnetoelectric coupling, which makes the material good candidate as memory devices and sensors.

  20. Simultaneous Stress and Field Control of Sustainable Switching of Ferroelectric Phases

    NASA Astrophysics Data System (ADS)

    Finkel, P.; Staruch, M.; Amin, A.; Ahart, M.; Lofland, S. E.

    2015-09-01

    In ferroelectrics, manifestation of a strong electromechanical coupling is attributed to both engineered domain morphology and phase transformations. However, realization of large sustainable and reversible strains and polarization rotation has been limited by fatigue, nonlinearity and hysteresis losses. Here, we demonstrate that large strain and polarization rotation can be generated for over 40 × 106 cycles with little fatigue by realization of a reversible ferroelectric-ferroelectric phase transition in [011] cut Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) relaxor ferroelectric single crystal. Direct tuning of this effect through combination of stress and applied electric field, confirmed both macroscopically and microscopically with x-ray and Raman scattering, reveals the local symmetry while sweeping through the transition with a low applied electric field (<0.2 MV/m) under mechanical stress. The observed change in local symmetry as determined by x-ray scattering confirms a proposed polarization rotation mechanism corresponding to a transition between rhombohedral and orthorhombic phases. These results shed more light onto the nature of this reversible transformation between two ferroelectric phases and advance towards the development of a wide range of ferroic and multiferroic devices.

  1. Simultaneous Stress and Field Control of Sustainable Switching of Ferroelectric Phases

    PubMed Central

    Finkel, P.; Staruch, M.; Amin, A.; Ahart, M.; Lofland, S.E.

    2015-01-01

    In ferroelectrics, manifestation of a strong electromechanical coupling is attributed to both engineered domain morphology and phase transformations. However, realization of large sustainable and reversible strains and polarization rotation has been limited by fatigue, nonlinearity and hysteresis losses. Here, we demonstrate that large strain and polarization rotation can be generated for over 40 × 106 cycles with little fatigue by realization of a reversible ferroelectric-ferroelectric phase transition in [011] cut Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) relaxor ferroelectric single crystal. Direct tuning of this effect through combination of stress and applied electric field, confirmed both macroscopically and microscopically with x-ray and Raman scattering, reveals the local symmetry while sweeping through the transition with a low applied electric field (<0.2 MV/m) under mechanical stress. The observed change in local symmetry as determined by x-ray scattering confirms a proposed polarization rotation mechanism corresponding to a transition between rhombohedral and orthorhombic phases. These results shed more light onto the nature of this reversible transformation between two ferroelectric phases and advance towards the development of a wide range of ferroic and multiferroic devices. PMID:26345729

  2. Simultaneous Stress and Field Control of Sustainable Switching of Ferroelectric Phases.

    PubMed

    Finkel, P; Staruch, M; Amin, A; Ahart, M; Lofland, S E

    2015-01-01

    In ferroelectrics, manifestation of a strong electromechanical coupling is attributed to both engineered domain morphology and phase transformations. However, realization of large sustainable and reversible strains and polarization rotation has been limited by fatigue, nonlinearity and hysteresis losses. Here, we demonstrate that large strain and polarization rotation can be generated for over 40 × 10(6) cycles with little fatigue by realization of a reversible ferroelectric-ferroelectric phase transition in [011] cut Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) relaxor ferroelectric single crystal. Direct tuning of this effect through combination of stress and applied electric field, confirmed both macroscopically and microscopically with x-ray and Raman scattering, reveals the local symmetry while sweeping through the transition with a low applied electric field (<0.2 MV/m) under mechanical stress. The observed change in local symmetry as determined by x-ray scattering confirms a proposed polarization rotation mechanism corresponding to a transition between rhombohedral and orthorhombic phases. These results shed more light onto the nature of this reversible transformation between two ferroelectric phases and advance towards the development of a wide range of ferroic and multiferroic devices. PMID:26345729

  3. Effect of local elastic strain on the structure of Pb-based relaxors: A comparative study of pure and Ba- and Bi-doped PbSc0.5Nb0.5O3

    NASA Astrophysics Data System (ADS)

    Maier, B.; Mihailova, B.; Paulmann, C.; Ihringer, J.; Gospodinov, M.; Stosch, R.; Güttler, B.; Bismayer, U.

    2009-06-01

    The temperature evolution of the nanoscale structure of PbSc0.5Nb0.5O3 (PSN) and (Pb,A″)Sc0.5Nb0.5O3 , (A″=Ba,Bi) is analyzed by applying synchrotron single-crystal and high-resolution powder x-ray diffraction as well as polarized Raman spectroscopy. The study compares the effect of incorporation of two-valent cations with isotropic electron structure (Ba2+) and three-valent cations with stereochemically active lone pairs (Bi3+) on the structure of Pb-based perovskite-type relaxor ferroelectrics. The results reveal that the violation of the host system of cations with lone-pair electrons (Pb2+) , i.e., the reduction in ferroic species with coherent off-centered Pb atoms, is the major factor for the suppression of long-range ferroelectric ordering at low temperatures. The local charge imbalance associated with A site chemical disorder has negligible impact on the development of ferroelectric order if the second type of A -positioned cations also forms lone-pair electrons. The substitution of Bi3+ for Pb2+ even enhances the cubic-to-ferroelectric transformation processes in PSN and results in a structural state consisting of abundant ferroelectric domains, which are large enough to be identified by polarized Raman spectroscopy as crystalline, but with an average size close to the intrinsic detection limit of synchrotron single-crystal x-ray diffraction.

  4. Nanoscale ordering and multiferroic behavior in Pb(Fe1/2Ta1/2)O3

    NASA Astrophysics Data System (ADS)

    Martinez, R.; Palai, R.; Huhtinen, H.; Liu, J.; Scott, J. F.; Katiyar, R. S.

    2010-10-01

    We report on structural, microstructural, dielectric, electrical, magnetic, and spectroscopic (Raman and terahertz) properties of lead iron tantalate Pb(Fe1/2Ta1/2)O3 ceramics. Raman spectroscopy revealed the presence of nanoscale ordering though it is forbidden in bulk by crystal symmetry. The dielectric properties of Pb(Fe1/2Ta1/2)O3 show a typical relaxor ferroelectric behavior with long-range disorder while the magnetoelectric properties show an interesting multiferroic behavior (coexistence of ferroelectric and magnetic order) in the same phase. The temperature variation in field cooled magnetization shows anomalies at about 55(±5) and 180(±5)K indicating the existence of two Néel temperatures in agreement with theoretical predictions. The zero-field-cooled magnetization as a function temperature and field reveals the existence of spin-glasslike behavior at low temperature like single crystal. The electrical conduction behavior satisfies the modified Schottky equation of Simmons at all fields. The ac conductivity as a function of frequency shows an excellent fit to the universal power law. Terahertz spectroscopy shows an opaque nature of Pb(Fe1/2Ta1/2)O3 in midinfrared and far-infrared wavelengths.

  5. Non-resonant electromechanical energy harvesting using inter-ferroelectric phase transitions

    SciTech Connect

    Pérez Moyet, Richard; Rossetti, George A.; Stace, Joseph; Amin, Ahmed; Finkel, Peter

    2015-10-26

    Non-resonant electromechanical energy harvesting is demonstrated under low frequency excitation (<50 Hz) using [110]{sub C}-poled lead indium niobate-lead magnesium niobate-lead titanate relaxor ferroelectric single crystals with compositions near the morphotropic phase boundary. The efficiency of power generation at the stress-induced phase transition between domain-engineered rhombohedral and orthorhombic ferroelectric states is as much as four times greater than is obtained in the linear piezoelectric regime under identical measurement conditions but during loading below the coercive stress of the phase change. The phase transition mode of electromechanical transduction holds potential for non-resonant energy harvesting from low-frequency vibrations and does not require mechanical frequency up-conversion.

  6. Non-resonant electromechanical energy harvesting using inter-ferroelectric phase transitions

    NASA Astrophysics Data System (ADS)

    Pérez Moyet, Richard; Stace, Joseph; Amin, Ahmed; Finkel, Peter; Rossetti, George A.

    2015-10-01

    Non-resonant electromechanical energy harvesting is demonstrated under low frequency excitation (<50 Hz) using [110]C-poled lead indium niobate-lead magnesium niobate-lead titanate relaxor ferroelectric single crystals with compositions near the morphotropic phase boundary. The efficiency of power generation at the stress-induced phase transition between domain-engineered rhombohedral and orthorhombic ferroelectric states is as much as four times greater than is obtained in the linear piezoelectric regime under identical measurement conditions but during loading below the coercive stress of the phase change. The phase transition mode of electromechanical transduction holds potential for non-resonant energy harvesting from low-frequency vibrations and does not require mechanical frequency up-conversion.

  7. Possible ferroelectricity in perovskite oxynitride SrTaO2N epitaxial thin films

    PubMed Central

    Oka, Daichi; Hirose, Yasushi; Kamisaka, Hideyuki; Fukumura, Tomoteru; Sasa, Kimikazu; Ishii, Satoshi; Matsuzaki, Hiroyuki; Sato, Yukio; Ikuhara, Yuichi; Hasegawa, Tetsuya

    2014-01-01

    Compressively strained SrTaO2N thin films were epitaxially grown on SrTiO3 substrates using nitrogen plasma-assisted pulsed laser deposition. Piezoresponse force microscopy measurements revealed small domains (101–102 nm) that exhibited classical ferroelectricity, a behaviour not previously observed in perovskite oxynitrides. The surrounding matrix region exhibited relaxor ferroelectric-like behaviour, with remanent polarisation invoked by domain poling. First-principles calculations suggested that the small domains and the surrounding matrix had trans-type and a cis-type anion arrangements, respectively. These experiments demonstrate the promise of tailoring the functionality of perovskite oxynitrides by modifying the anion arrangements by using epitaxial strain.

  8. From spin induced ferroelectricity to dipolar glasses: Spinel chromites and mixed delafossites

    SciTech Connect

    Maignan, A.

    2012-11-15

    Magnetoelectric multiferroics showing coupling between polarization and magnetic order are attracting much attention. For instance, they could be used in memory devices. Metal-transition oxides are provided several examples of inorganic magnetoelectric multiferroics. In the present short review, spinel and delafossite chromites are described. For the former, an electric polarization is evidenced in the ferrimagnetic state for ACr{sub 2}O{sub 4} polycrystalline samples (A=Ni, Fe, Co). The presence of a Jahn-Teller cation such as Ni{sup 2+} at the A site is shown to yield larger polarization values. In the delafossites, substitution by V{sup 3+} at the Cr or Fe site in CuCrO{sub 2} (CuFeO{sub 2}) suppresses the complex antiferromagnetic structure at the benefit of a spin glass state. The presence of cation disorder, probed by transmission electron microscopy, favors relaxor-like ferroelectricity. The results on the ferroelectricity of ferrimagnets and insulating spin glasses demonstrate that, in this research field, transition-metal oxides are worth to be studied. - Graphical abstract: Electric polarization as a function of temperature is measured up to T{sub C} in three chromite ferrimagnetic spinels. Largest values are reached for spinels with Jahn-Teller cations at the A site (Ni or Fe). Highlights: Black-Right-Pointing-Pointer Electric polarization is evidenced in the ferrimagnetic state of the chromite spinels. Black-Right-Pointing-Pointer Jahn-Teller cations at the A site of these spinels lead to larger polarization values. Black-Right-Pointing-Pointer Vanadium substituted at the Cr (or Fe) site of delafossites changes the antiferromagnetic state to spin glass. Black-Right-Pointing-Pointer Electric polarization is not the result of magnetic ordering but magnetic disordering in Cr or Fe delafossites. Black-Right-Pointing-Pointer Relaxor-type ferroelectricity or spin induced ferroelectricity can be observed in the delafossites.

  9. Energy harvesting based on Ericsson pyroelectric cycles in a relaxor ferroelectric ceramic

    NASA Astrophysics Data System (ADS)

    Sebald, Gael; Pruvost, Sebastien; Guyomar, Daniel

    2008-02-01

    This work deals with energy harvesting from temperature variations. It is shown here that direct pyroelectric energy harvesting (connecting an adapted resistance, for example) is not effective, whereas Ericsson-based cycles give energy 100 times higher. The principle and experimental validation of the Ericsson cycle are shown with the example of 0.90Pb(Mg1/3Nb2/3)O3-0.10PbTiO3 ceramic. Harvested energy reached 186 mJ cm-3 for 50 °C temperature variation and electric field cycle of 3.5 kV mm-1. A correlation between the electrocaloric effect and pyroelectric energy harvesting is then shown. Harvested electric energy with Ericsson cycles can be simply expressed as electrocaloric heat multiplied by Carnot efficiency. Several examples are then given from materials with the highest known electrocaloric effect. This leads to energies of hundreds of mJ cm-3 for a limited 10 °C temperature variation. Compared to Carnot's efficiency, this is much higher than the best thermoelectric materials based on the Seebeck effect.

  10. Upper limit of the electrocaloric peak in lead-free ferroelectric relaxor ceramics

    NASA Astrophysics Data System (ADS)

    Le Goupil, Florian; Alford, Neil McN.

    2016-06-01

    The electrocaloric effect (ECE) of two compositions (x = 0.06 and 0.07) of (1 - x)(Na0.5Bi0.5)TiO3-xKNbO3 in the vicinity of the morphotropic phase boundary is studied by direct measurements. ΔTmax = 1.5 K is measured at 125 °C under 70 kV/cm for NBT-6KN while ΔTmax = 0.8 K is measured at 75 °C under 55 kV/cm for NBT-7KN. We show that the "shoulder," TS, in the dielectric permittivity, marks the upper limit of the ECE peak under high applied electric fields. These results imply that the range of temperature with high ECE can be quickly identified for a given composition, which will significantly speed up the process of materials selection for ECE cooling.

  11. Large Displacement in Relaxor Ferroelectric Terpolymer Blend Derived Actuators Using Al Electrode for Braille Displays

    PubMed Central

    Lu, S. G.; Chen, X.; Levard, T.; Diglio, P. J.; Gorny, L. J.; Rahn, C. D.; Zhang, Q. M.

    2015-01-01

    Poly(vinylidene fluoride) (PVDF) based polymers are attractive for applications for artificial muscles, high energy density storage devices etc. Recently these polymers have been found great potential for being used as actuators for refreshable full-page Braille displays for visually impaired people in terms of light weight, miniaturized size, and larger displacement, compared with currently used lead zirconate titanate ceramic actuators. The applied voltages of published polymer actuators, however, cannot be reduced to meet the requirements of using city power. Here, we report the polymer actuator generating quite large displacement and blocking force at a voltage close to the city power. Our embodiments also show good self-healing performance and disuse of lead-containing material, which makes the Braille device safer, more reliable and more environment-friendly. PMID:26079628

  12. Dissimilarity of polar displacements in barium and lead based relaxors

    NASA Astrophysics Data System (ADS)

    Phelan, D.; Millican, J. N.; Gehring, P. M.

    2010-08-01

    Powder neutron diffraction experiments were performed on the relaxor compound, Ba(Zn1/3Nb2/3)0.95Ti0.05O3, which was recently shown to have stronger frequency dependence in its permittivity than many Pb-based relaxors (PBR), such as PbMg1/3Nb2/3O3 [L. Khemakhem et al., J. Alloys Compd. 452, 451 (2008)]. Several notable differences in structural properties were observed in the present measurements compared to PBR. In particular, much smaller atomic displacement parameters were found, especially on the A (Ba) site, which indicates that the local shifts of the Ba atoms are much smaller than the Pb shifts in PBR. Moreover, no signature of electrostrictive strain is apparent in the thermal expansion, and instead the thermal expansion is much larger at low temperatures than for PBR.

  13. Investigation of diffuse phase transition in ferroelectric Pb2- x K1+ x Li x Nb5O15 (0 ≤ x ≤ 1.5) ceramics

    NASA Astrophysics Data System (ADS)

    Choukri, E.; Neqali, A.; Abkhar, Z.; Alimoussa, A.; Hajji, L.; Mezzane, D.; Belboukhari, A.; Amjoud, M.; Gagou, Y.; El Marssi, M.; Luk'yanchuk, I.

    2016-06-01

    Substitution of Pb with Li and K in the Pb2KNb5O15 phases leads to a new composition with chemical composition Pb2- x K1+ x Li x Nb5O15 which crystallizes with tetragonal tungsten bronze-type structure. Ferroelectric ceramics with different compositions were synthesized using solid-state reaction and complex dielectric permittivity measurements in these compounds were performed in a frequency and temperature range of 20 Hz-1 MHz and from 25 to 550 °C, respectively. Special attention was paid to the diffuse phase transition (DPT) that occurs close to the Curie temperature. The empirical equation proposed by Santos-Eiras for a phenomenological description of the temperature dependence of the dielectric permittivity (\\varepsilon_{{r}}^' }}) peak is used to calculate some characteristic parameters of DPT. From the results, it must be assumed that these compounds show a diffuse phase transition with non-relaxor behavior. A basic phase diagram showing the evolution of T m function of composition x is deduced from this study.

  14. Neutron Diffuse Scattering in Pure and Ba-Doped Single Crystals of the Relaxor NBT

    NASA Astrophysics Data System (ADS)

    Ge, Wenwei; Devreugd, Christopher; Phelan, Daniel; Gehring, Peter; Zhang, Qinhui; Ahart, Muhtar; Li, Jiefang; Luo, Haosu; Viehland, Dwight

    2013-03-01

    We report neutron diffuse scattering measurements on the lead-free relaxors Na1/2Bi1/2TiO3 (NBT) and NBT doped with 5.6% BaTiO3, 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% BaTiO3 reduces the correlation length associated with the tetragonal order by a factor of 10 while simultaneously enhancing the piezoelectric properties. This research was supported by NSF Grant DMR-0806592.

  15. Poling and Depoling Effects on Dielectric Properties and Domain Structures in Relaxor 24Pb(In1/2Nb1/2)O3-46Pb(Mg1/3Nb2/3)O3-30PbTiO3 near a Morphotropic Phase Boundary Composition

    NASA Astrophysics Data System (ADS)

    Hidayah, Nur; Yasuda, Naohiko; Ohwa, Hidehiro; Tachi, Yoshihito; Yamashita, Yohachi; Iwata, Makoto

    2012-09-01

    The temperature dependence of the complex relative permittivity in a relaxor ferroelectric solid solution 24Pb(In1/2Nb1/2)O3-46Pb(Mg1/3Nb2/3)O3-30PbTiO3 (PIN-PMN-PT) crystal poled and depoled was measured from room temperature to 200 °C at various frequencies. The poled sample exhibits transitions from the ferroelectric (FE) phase to the relaxor (RE) phase on heating, and after that, the depoled one exhibits those from the RE phase to the glassy freezing phase on cooling. An RE-type dielectric dispersion with a weak frequency (f) dependence was observed. Such a dielectric dispersion in the RE state was found to be based on tweed domain structures observed by polarization light microscopy (PLM) and piezoelectric force microscopy (PFM) due to the competition between the antiferroelectric (AFE) and FE coupling in the RE state. The temperature dependence of complex permittivity with resonance- and relaxor-type dielectric dispersions in the poled and depoled samples was characterized by hierarchical domain structures.

  16. Ferroelectric switching of elastin

    PubMed Central

    Liu, Yuanming; Cai, Hong-Ling; Zelisko, Matthew; Wang, Yunjie; Sun, Jinglan; Yan, Fei; Ma, Feiyue; Wang, Peiqi; Chen, Qian Nataly; Zheng, Hairong; Meng, Xiangjian; Sharma, Pradeep; Zhang, Yanhang; Li, Jiangyu

    2014-01-01

    Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 μC/cm2, whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications. PMID:24958890

  17. The interface between ferroelectric and 2D material for a Ferroelectric Field-Effect Transistor

    NASA Astrophysics Data System (ADS)

    Park, Nahee; Kang, Haeyong; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    We have studied electrical property of ferroelectric field-effect transistor which consists of graphene on hexagonal Boron-Nitride (h-BN) gated by a ferroelectric, PMN-PT (i.e. (1-x)Pb(Mg1/3Nb2/3) O3-xPbTiO3) single-crystal substrate. The PMN-PT was expected to have an effect on polarization field into the graphene channel and to induce a giant amount of surface charge. The hexagonal Boron-Nitride (h-BN) flake was directly exfoliated on the PMN-PT substrate for preventing graphene from directly contacting on the PMN-PT substrate. It can make us to observe the effect of the interface between ferroelectric and 2D material on the device operation. Monolayer graphene as 2D channel material, which was confirmed by Raman spectroscopy, was transferred on top of the hexagonal Boron-Nitride (h-BN) by using the conventional dry-transfer method. Here, we can demonstrate that the structure of graphene/hexagonal-BN/ferroelectric field-effect transistor makes us to clearly understand the device operation as well as the interface between ferroelectric and 2D materials by inserting h-BN between them. The phenomena such as anti-hysteresis, current saturation behavior, and hump-like increase of channel current, will be discussed by in terms of ferroelectric switching, polarization-assisted charge trapping.

  18. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    PubMed

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics. PMID:26487348

  19. Microscopic theory of superconductor-ferroelectric heterostructures: Interface charge redistribution

    NASA Astrophysics Data System (ADS)

    Pavlenko, N.; Schwabl, F.

    2003-03-01

    We present a theory of periodic ferroelectric-superconductor (FE-S) heterostructures containing ferroelectric layers sandwiched between superconducting planes. We analyze the electronic charge-carrier redistribution at the FE-S interface in the presence of the spontaneous polarization in the ferroelectric layer. On the other hand, we study the influence of the superconductor on the structural dynamics in the ferroelectric layer. The effect of FE-S contacts on the ferroelectrics is found to be crucial leading to a structural transformation from the state with the homogeneous-type polarization to the phase with a set of asymmetric stable polarization domains. FE-S interface phenomena induce a decrease of the temperature of the transition to the symmetric phase with two symmetric (negative and positive) polarization domains. Nevertheless, even above the ferroelectric critical temperature, we find in the ferroelectric layer a stable contact-induced enhanced spontaneous polarization. The domain structure in the symmetric phase appears as the response to the charge-carrier redistribution at the contact with the superconducting subsystem. An increase of the FE-S interface coupling results in a complex nonmonotonic behavior of the superconducting transition temperature and finally, for the strong-coupling regime, in a complete suppression of the superconductivity. The results are expected to be especially important for the analysis of high-temperature cuprate superconductor films grown on perovskite-type ferroelectrics.

  20. Relaxor-based single-crystal materials for ultrasonic transducer applications

    NASA Astrophysics Data System (ADS)

    Park, Seung Eek E.; Lopath, Patrick D.; Shung, K. Kirk; Shrout, Thomas R.

    1997-04-01

    Relaxor ferroelectric single crystals of Pb(Zn1/3Nb2/3)O3 (PZN), Pb(Mg1/3Nb2/3)O3 (PMN) and their solid solutions with normal ferroelectric PbTiO3 (PT) were investigated for ultrasonic transducer applications. Crystals offer adjustable properties not only by compositional tailoring but also by domain state engineering associated with different crystallographic orientation, which is not achievable in polycrystalline materials. Longitudinal coupling coefficients (k33) as high as 94% and dielectric constants (K3T) in the range of 3500 - 6000 were achieved with low dielectric loss (less than 1%) using <001> oriented rhombohedral crystals of (1-x)PZN-xPT and (1-y)PMN-yPT, where x less than 0.09 and y less than 0.35. Dicing direction as well as poling direction were critical for high coupling under laterally clamped condition. Dicing parallel to the (001) yields 90% of laterally clamped coupling (kbar) out of 94% longitudinal coupling (k33) for PZN-8%PT. On the other hand, samples diced parallel to (110) exhibited no dominant mode present. Thickness coupling (kT) as high as 64% and low dielectric constant (K3T) less than 600 with low loss (less than 1%) could be achieved using tetragonal crystals of (1-x)PZN-xPT and (1-y)PMN-yPT, where x greater than 0.1 and y greater than 0.4. The performance gains associated with these ultra-high coupling coefficients and range of dielectric constants are evident in relation to broader bandwidth and electrical impedance matching. Specifically, rhombohedral crystals offer the possibility of extremely broad bandwidth devices for transducer arrays and tetragonal crystals for single element transducers. Transducer simulation was performed using the KLM model. The pulse/echo response simulated a 124% bandwidth subdiced array element with a center frequency of 10 MHz. An optimized array design of the same geometry constructed of PZT 5H displays an 87% bandwidth.

  1. Local retention behaviors of epitaxial and polycrystalline PbMg1/3Nb2/3O3-PbTiO3 thin films by scanning force microscopy

    NASA Astrophysics Data System (ADS)

    Lee, J. H.; Choi, M. R.; Oh, Y. J.; Jo, W.

    2007-08-01

    The authors report the results of retention in epitaxial and polycrystalline PbMg1/3Nb2/3O3-PbTiO3 (PMN-PT) thin films on SrRuO3 (SRO) and Pt. The SRO electrodes were deposited by pulsed laser deposition and the PMN-PT thin films were coated by a sol-gel method. Local poling behaviors of the PMN-PT domains were investigated as a function of time in both single-poled and reverse-poled regions by scanning force microscopy. An extended exponential decay is observed in the PMN-PT/SRO heterostructures while a fluctuated relaxation is shown in the PMN-PT/Pt films, suggesting that crystal orientation and grain growth is critical to understand retention of relaxor ferroelectrics.

  2. The Existence of Ferroelectric Ice on Icy Bodies in Space: a Neutron Diffraction Study

    NASA Astrophysics Data System (ADS)

    Fukazawa, Hiroshi

    The complex behavior of water and the unusual properties of ferroelectric ice XI continue to attract much interest. Whether ice in the space exists as ice XI, is an important question, because long range electrostatic forces caused by the ferroelectricity might be an important factor for planet formation. From neutron diffraction experiments, we found the temperature and pressure conditions for the transformation of the largest fraction of ice into ferroelectric ice. It suggests that myriad big icy-bodies, which exist as dwarf planets and Kuiper Belt Object, consist of thick ferroelectric-ice surface. Furthermore, we report spectral and vibrational properties of ferroelectric ice investigated by inelastic neutron scattering and infrared absorption measurements. Because the spectral properties of ferroelectric ice are clearly different from those of ordinary ice, the distinct ferroelectric ice in the universe is detectable using infrared telescopes and planetary exploration.

  3. Relaxor-PT single crystals for broad bandwidth, high power sonar projectors

    NASA Astrophysics Data System (ADS)

    Sherlock, Nevin P.

    2010-06-01

    The high piezoelectric response of the ferroelectric relaxor (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 (PMNT) in single crystal form has generated significant interest in producing broad bandwidth SONAR systems. Both the piezoelectric coefficient (d33 > 2000 pC/N) and coupling coefficient (k33 > 0.90) are superior to those of conventional piezoelectric ceramics. Within the context of a high power acoustic projector, its high losses and low temperature stability have limited its development. Second generation single crystals with compositions modified from the base PMNT have been recently developed to decrease the electromechanical losses and mitigate the thermal property dependence. In this work, the electromechanical properties were measured using single crystals which have been modified in various ways. The modified crystals exhibit electromechanically "hard" behavior with lower losses (tan delta = 0.1--0.2% and QM = 230--950) than unmodified PMNT (tan delta = 0.26% and QM = 190). The measured d33 values of modified single crystals (d33 = 760--1490 pm/V) are also lower than unmodified PMNT (d33 = 1540 pm/V), but the lower piezoelectric response is compensated by the greater stability of the modified single crystals. These modified single crystal properties were also compared to conventional high power piezoelectric ceramics ( d33 = 240 pm/V and QM = 1050) to show similar losses but significantly greater response in the modified PMNT single crystals. Although most piezoelectric materials are measured under small signal conditions (small signal defined by a completely linear relationship between the input and output signals), the high power nature of SONAR projectors demands that these modified single crystals also be evaluated under high power conditions. A test procedure was developed to measure the electromechanical properties of each material as a function of applied electric field over a frequency range which includes the resonance frequency. Modified single crystals

  4. Effects of Interface Layers and Domain Walls on the Ferroelectric-Resistive Switching Behavior of Au/BiFeO3/La0.6Sr0.4MnO3 Heterostructures.

    PubMed

    Feng, Lei; Yang, Shengwei; Lin, Yue; Zhang, Dalong; Huang, Weichuan; Zhao, Wenbo; Yin, Yuewei; Dong, Sining; Li, Xiaoguang

    2015-12-01

    The electric field effects on the electric and magnetic properties in multiferroic heterostructures are important for not only understanding the mechanisms of certain novel physical phenomena occurring at heterointerfaces but also offering a route for promising spintronic applications. Using the Au/BiFeO3/La0.6Sr0.4MnO3 (Au/BFO/LSMO) multiferroic heterostructure as a model system, we investigated the ferroelectric-resistive switching (RS) behaviors of the heterostructure. Via the manipulation of the BFO ferroelectric polarizations, the nonvolatile tristate of RS is observed, which is closely related to the Au/BFO and BFO/LSMO interface layers and the highly conducting BFO domain walls (DWs). More interestingly, according to the magnetic field dependence of the RS behavior, the negative magnetoresistance effect of the third resistance state, corresponding to the abnormal current peak in current-pulse voltage hysteresis near the electric coercive field, is also observed at room temperature, which mainly arises from the possible oxygen vacancy accumulation and Fe ion valence variation in the DWs. PMID:26554671

  5. Study of the structure and ferroelectric behavior of BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} ceramics

    SciTech Connect

    Khokhar, Anita Sreenivas, K.; Goyal, Parveen K.; Thakur, O. P.

    2015-06-24

    The structure and ferroelectric properties of Lanthanum substituted barium bismuth titanate BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} (0 ≤ x ≤ 0.5) ceramics prepared by solid-state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of a single phase material. The distribution of lanthanum into the perovskite layers and (Bi{sub 2}O{sub 2}){sup 2+} layers of BaBi{sub 4}Ti{sub 4}O{sub 15} ceramics have been revealed through Raman spectroscopy. At lower value of x, it is seen that La{sup 3+} ions prefer to substitute A-site Bi{sup 3+} ions in the perovskite layers while for higher x values, La{sup 3+} ions get incorporated into the (Bi{sub 2}O{sub 2}){sup 2+} layers. A critical La content of x ∼ 0.2 in BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} is seen to exhibit a large remnant polarization (P{sub r}) with low coercive field (E{sub c}). The improvement in the ferroelectric properties of La substituted BaBi{sub 4}Ti{sub 4}O{sub 15} ceramics has been explained in terms of changing oxygen vacancy concentration and structural relaxation. Tunable ferroelectric materials can be obtained by manipulating the doping amount of lanthanum ion.

  6. Nanoscale mapping of heterogeneity of the polarization reversal in lead-free relaxor–ferroelectric ceramic composites

    DOE PAGESBeta

    Gobeljic, D.; Shvartsman, V. V.; Belianinov, A.; Okatan, B.; Jesse, S.; Kalinin, S. V.; Groh, C.; Rödel, J.; Lupascu, D. C.

    2016-01-05

    Relaxor/ferroelectric ceramic/ceramic composites have shown to be promising in generating large electromechanical strain at moderate electric fields. However, the mechanisms of polarization and strain coupling between grains of different nature in the composites remain unclear. To rationalize the coupling mechanisms we performed advanced piezoresponse force microscopy (PFM) studies of 0.92BNT-0.06BT-0.02KNN/0.93BNT-0.07BT (ergodic/non-ergodic relaxor) composites. PFM is able to distinguish grains of different phases by characteristic domain patterns. Polarization switching has been probed locally, on a sub-grain scale. k-Means clustering analysis applied to arrays of local hysteresis loops reveals variations of polarization switching characteristics between the ergodic and non-ergodic relaxor grains. Here,more » we report a different set of switching parameters for grains in the composites as opposed to the pure phase samples. These results confirm ceramic/ceramic composites to be a viable approach to tailor the piezoelectric properties and optimize the macroscopic electromechanical characteristics.« less

  7. Ferroelectric random access memories.

    PubMed

    Ishiwara, Hiroshi

    2012-10-01

    Ferroelectric random access memory (FeRAM) is a nonvolatile memory, in which data are stored using hysteretic P-E (polarization vs. electric field) characteristics in a ferroelectric film. In this review, history and characteristics of FeRAMs are first introduced. It is described that there are two types of FeRAMs, capacitor-type and FET-type, and that only the capacitor-type FeRAM is now commercially available. In chapter 2, properties of ferroelectric films are discussed from a viewpoint of FeRAM application, in which particular attention is paid to those of Pb(Zr,Ti)O3, SrBi2Ta2O9, and BiFeO3. Then, cell structures and operation principle of the capacitor-type FeRAMs are discussed in chapter 3. It is described that the stacked technology of ferroelectric capacitors and development of new materials with large remanent polarization are important for fabricating high-density memories. Finally, in chapter 4, the optimized gate structure in ferroelectric-gate field-effect transistors is discussed and experimental results showing excellent data retention characteristics are presented. PMID:23421123

  8. Ferroelectric optical image comparator

    SciTech Connect

    Butler, M.A.; Land, C.E.; Martin, S.J.; Pfeifer, K.B.

    1989-08-30

    The property of ferroelectric ceramics such as lead lanthanum zirconate titanate (PLZT) to store information has been known for many years. This relates to the property of ferroelectric ceramic materials to become permanently polarized when an electric signal is applied to the material. A ferroelectric optical image comparator has a lead lanthanum zirconate titanate thin-film device which is constructed with a semi-transparent or transparent conductive first electrode on one side of the thin film, a conductive metal second electrode on the other side of the thin film, and the second electrode is in contact with a nonconducting substrate. A photoinduced current in the device represents the dot product between a stored image and an image projected onto the first electrode. One-dimensional autocorrelations are performed by measuring this current while displacing the projected image. 5 figs.

  9. Applications of modern ferroelectrics.

    PubMed

    Scott, J F

    2007-02-16

    Long viewed as a topic in classical physics, ferroelectricity can be described by a quantum mechanical ab initio theory. Thin-film nanoscale device structures integrated onto Si chips have made inroads into the semiconductor industry. Recent prototype applications include ultrafast switching, cheap room-temperature magnetic-field detectors, piezoelectric nanotubes for microfluidic systems, electrocaloric coolers for computers, phased-array radar, and three-dimensional trenched capacitors for dynamic random access memories. Terabit-per-square-inch ferroelectric arrays of lead zirconate titanate have been reported on Pt nanowire interconnects and nanorings with 5-nanometer diameters. Finally, electron emission from ferroelectrics yields cheap, high-power microwave devices and miniature x-ray and neutron sources. PMID:17303745

  10. Large magnetocapacitance in electronic ferroelectric manganite systems

    SciTech Connect

    Chowdhury, Ujjal; Goswami, Sudipta; Bhattacharya, Dipten; Midya, Arindam; Mandal, P.; Das, Pintu; Mukovskii, Ya. M.

    2013-11-21

    We have observed a sizable positive magnetocapacitance (∼5%–90%) in perovskite Pr{sub 0.55}Ca{sub 0.45}MnO{sub 3} and bilayer Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7} system under 5 T magnetic field across 20–100 K below the magnetic transition point T{sub N}. The magnetodielectric effect, on the other hand, exhibits a crossover: (a) from positive to negative for the perovskite system and (b) from negative to positive for the bilayer system over the same temperature range. The bilayer Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7} system exhibits a sizable anisotropy as well. We have also noticed the influence of magnetic field on the dielectric relaxation characteristics of these systems. These systems belong to a class of improper ferroelectrics and are expected to exhibit charge/orbital order driven ferroelectric polarization below the transition point T{sub CO}. Large magnetocapacitance in these systems shows a typical multiferroic behavior even though the ferroelectric polarization is small in comparison to that of other ferroelectrics.

  11. Giant Electroresistive Ferroelectric Diode on 2DEG

    PubMed Central

    Kim, Shin-Ik; Jin Gwon, Hyo; Kim, Dai-Hong; Keun Kim, Seong; Choi, Ji-Won; Yoon, Seok-Jin; Jung Chang, Hye; Kang, Chong-Yun; Kwon, Beomjin; Bark, Chung-Wung; Hong, Seong-Hyeon; Kim, Jin-Sang; Baek, Seung-Hyub

    2015-01-01

    Manipulation of electrons in a solid through transmitting, storing, and switching is the fundamental basis for the microelectronic devices. Recently, the electroresistance effect in the ferroelectric capacitors has provided a novel way to modulate the electron transport by polarization reversal. Here, we demonstrate a giant electroresistive ferroelectric diode integrating a ferroelectric capacitor into two-dimensional electron gas (2DEG) at oxide interface. As a model system, we fabricate an epitaxial Au/Pb(Zr0.2Ti0.8)O3/LaAlO3/SrTiO3 heterostructure, where 2DEG is formed at LaAlO3/SrTiO3 interface. This device functions as a two-terminal, non-volatile memory of 1 diode-1 resistor with a large I+/I− ratio (>108 at ±6 V) and Ion/Ioff ratio (>107). This is attributed to not only Schottky barrier modulation at metal/ferroelectric interface by polarization reversal but also the field-effect metal-insulator transition of 2DEG. Moreover, using this heterostructure, we can demonstrate a memristive behavior for an artificial synapse memory, where the resistance can be continuously tuned by partial polarization switching, and the electrons are only unidirectionally transmitted. Beyond non-volatile memory and logic devices, our results will provide new opportunities to emerging electronic devices such as multifunctional nanoelectronics and neuromorphic electronics. PMID:26014446

  12. Symmetry breaking in molecular ferroelectrics.

    PubMed

    Shi, Ping-Ping; Tang, Yuan-Yuan; Li, Peng-Fei; Liao, Wei-Qiang; Wang, Zhong-Xia; Ye, Qiong; Xiong, Ren-Gen

    2016-07-11

    Ferroelectrics are inseparable from symmetry breaking. Accompanying the paraelectric-to-ferroelectric phase transition, the paraelectric phase adopting one of the 32 crystallographic point groups is broken into subgroups belonging to one of the 10 ferroelectric point groups, i.e. C1, C2, C1h, C2v, C4, C4v, C3, C3v, C6 and C6v. The symmetry breaking is captured by the order parameter known as spontaneous polarization, whose switching under an external electric field results in a typical ferroelectric hysteresis loop. In addition, the responses of spontaneous polarization to other external excitations are related to a number of physical effects such as second-harmonic generation, piezoelectricity, pyroelectricity and dielectric properties. Based on these, this review summarizes recent developments in molecular ferroelectrics since 2011 and focuses on the relationship between symmetry breaking and ferroelectricity, offering ideas for exploring high-performance molecular ferroelectrics. PMID:27051889

  13. Nanostructured ferroelectrics: fabrication and structure-property relations.

    PubMed

    Han, Hee; Kim, Yunseok; Alexe, Marin; Hesse, Dietrich; Lee, Woo

    2011-10-25

    With the continued demand for ultrahigh density ferroelectric data storage applications, it is becoming increasingly important to scale the dimension of ferroelectrics down to the nanometer-scale region and to thoroughly understand the effects of miniaturization on the materials properties. Upon reduction of the physical dimension of the material, the change in physical properties associated with size reduction becomes extremely difficult to characterize and to understand because of a complicated interplay between structures, surface properties, strain effects from substrates, domain nucleation, and wall motions. In this Review, the recent progress in fabrication and structure-property relations of nanostructured ferroelectric oxides is summarized. Various fabrication approaches are reviewed, with special emphasis on a newly developed stencil-based method for fabricating ferroelectric nanocapacitors, and advantages and limitations of the processes are discussed. Stress-induced evolutions of domain structures upon reduction of the dimension of the material and their implications on the electrical properties are discussed in detail. Distinct domain nucleation, growth, and propagation behaviors in nanometer-scale ferroelectric capacitors are discussed and compared to those of micrometer-scale counterparts. The structural effect of ferroelectric nanocapacitors on the domain switching behavior and cross-talk between neighboring capacitors under external electric field is reviewed. PMID:21919083

  14. Continuously-tuned tunneling behaviors of ferroelectric tunnel junctions based on BaTiO{sub 3}/La{sub 0.67}Sr{sub 0.33}MnO{sub 3} heterostructure

    SciTech Connect

    Ou, Xin; Xu, Bo Yin, Qiaonan; Xia, Yidong; Yin, Jiang; Liu, Zhiguo; Gong, Changjie; Lan, Xuexin

    2014-05-15

    In this work, we fabricate BaTiO{sub 3}/La{sub 0.67}Sr{sub 0.33}MnO{sub 3} (BTO/LSMO) ferroelectric tunnel junction on (001) SrTiO{sub 3} substrate by pulsed laser deposition method. Combining piezoresponse force and conductive-tip atomic force microscopy, we demonstrate robust and reproducible polarization-controlled tunneling behaviors with the resulting tunneling electroresistance value reaching about 10{sup 2} in ultrathin BTO films (∼1.2 nm) at room temperature. Moreover, local poling areas with different conductivity are finally achieved by controlling the relative proportion of upward and downward domains, and different poling areas exhibit stable transport properties.

  15. Ferroelectric tunneling element and memory applications which utilize the tunneling element

    DOEpatents

    Kalinin, Sergei V [Knoxville, TN; Christen, Hans M [Knoxville, TN; Baddorf, Arthur P [Knoxville, TN; Meunier, Vincent [Knoxville, TN; Lee, Ho Nyung [Oak Ridge, TN

    2010-07-20

    A tunneling element includes a thin film layer of ferroelectric material and a pair of dissimilar electrically-conductive layers disposed on opposite sides of the ferroelectric layer. Because of the dissimilarity in composition or construction between the electrically-conductive layers, the electron transport behavior of the electrically-conductive layers is polarization dependent when the tunneling element is below the Curie temperature of the layer of ferroelectric material. The element can be used as a basis of compact 1R type non-volatile random access memory (RAM). The advantages include extremely simple architecture, ultimate scalability and fast access times generic for all ferroelectric memories.

  16. Room-temperature ferroelectricity of SrTiO{sub 3} films modulated by cation concentration

    SciTech Connect

    Yang, Fang; Zhang, Qinghua; Yang, Zhenzhong; Gu, Junxing; Liang, Yan; Li, Wentao; Wang, Weihua; Jin, Kuijuan; Gu, Lin; Guo, Jiandong

    2015-08-24

    The room-temperature ferroelectricity of SrTiO{sub 3} is promising for oxide electronic devices controlled by multiple fields. An effective way to control the ferroelectricity is highly demanded. Here, we show that the off-centered antisite-like defects in SrTiO{sub 3} films epitaxially grown on Si (001) play the determinative role in the emergence of room-temperature ferroelectricity. The density of these defects changes with the film cation concentration sensitively, resulting in a varied coercive field of the ferroelectric behavior. Consequently, the room-temperature ferroelectricity of SrTiO{sub 3} films can be effectively modulated by tuning the temperature of metal sources during the molecular beam epitaxy growth. Such an easy and reliable modulation of the ferroelectricity enables the flexible engineering of multifunctional oxide electronic devices.

  17. Phase evolution in sonochemically synthesized Fe(3+) doped BaTiO3 nanocrystallites: structural, magnetic and ferroelectric characterisation.

    PubMed

    Dutta, Dimple P; Roy, Mainak; Maiti, Nandita; Tyagi, Avesh K

    2016-04-14

    The properties of nanomaterials are highly dependent on their size, morphology, crystal phase, etc., which in turn depend on the method of synthesis. We report here the electrical and magnetic characterisation of sonochemically synthesized Fe(3+) doped nano BaTiO3 samples. The dopant ion concentration has been optimized and the coexistence of ferromagnetism and ferroelectricity has been observed in the sample. With increase in Fe(3+) doping from 0 to 20 mol%, a gradual phase change from tetragonal to hexagonal occurred in these sonochemically synthesized BaTiO3 nanomaterials. Below 15 mol% Fe concentration the material displays ferroelectric behaviour with the absence of any magnetic ordering, while at an Fe concentration of ∼15 mol% the material exhibits both room temperature ferromagnetism and ferroelectricity. Ferromagnetism as well as relaxor type behaviour has been observed in the BaTiO3:Fe(3+)(20%) sample. We have studied the ferromagnetic and ferroelectric ordering in these sonochemically synthesized Fe(3+) doped BaTiO3 nanomaterials and have tried to correlate the results with their crystal structure and morphology. The origin of ferromagnetism in these materials has been attributed to both intrinsic as well as extrinsic factors. PMID:27003320

  18. Molecular ferroelectrics: where electronics meet biology

    PubMed Central

    Li, Jiangyu; Liu, Yuanming; Zhang, Yanhang; Cai, Hong-Ling; Xiong, Ren-Gen

    2013-01-01

    In the last several years, we have witnessed significant advances in molecular ferroelectrics, with ferroelectric properties of molecular crystals approaching those of barium titanate. In addition, ferroelectricity has been observed in biological systems, filling an important missing link in bioelectric phenomena. In this perspective, we will present short historical notes on ferroelectrics, followed by overview on the fundamentals of ferroelectricity. Latest development in molecular ferroelectrics and biological ferroelectricity will then be highlighted, and their implications and potential applications will be discussed. We close by noting molecular ferroelectric as an exciting frontier between electronics and biology, and a number of challenges ahead are also noted. PMID:24018952

  19. Domain switching of fatigued ferroelectric thin films

    SciTech Connect

    Tak Lim, Yun; Yeog Son, Jong E-mail: hoponpop@ulsan.ac.kr; Shin, Young-Han E-mail: hoponpop@ulsan.ac.kr

    2014-05-12

    We investigate the domain wall speed of a ferroelectric PbZr{sub 0.48}Ti{sub 0.52}O{sub 3} (PZT) thin film using an atomic force microscope incorporated with a mercury-probe system to control the degree of electrical fatigue. The depolarization field in the PZT thin film decreases with increasing the degree of electrical fatigue. We find that the wide-range activation field previously reported in ferroelectric domains result from the change of the depolarization field caused by the electrical fatigue. Domain wall speed exhibits universal behavior to the effective electric field (defined by an applied electric field minus the depolarization field), regardless of the degree of the electrical fatigue.

  20. Magnetocaloric effect in ferroelectric Ising chain magnet

    NASA Astrophysics Data System (ADS)

    Qi, Yan; Liu, Jia; Yu, Nai-sen; Du, An

    2016-05-01

    We investigate the magnetocaloric effect (MCE) in multiferroic chain system by adopting the elastic Ising-chain model. Based on the transfer-matrix method, the magnetothermal quantities of characterizing MCE behaviors including the entropy, entropy change and adiabatic cooling rate are rigorously determined. Combined with analysis of ground-state, we mainly discuss results in an antiferromagnetic regime associated with ferroelectric transition. Our results show that the entropy change is greatly enhanced near the saturation field as frustration parameter varies in this regime, and accompanied with remarkable inverse MCE, indicating the enormous potential of multiferroic system in low-temperature refrigeration. Meanwhile we also observe a prominent temperature variation in the isoentropy curves close to zero-temperature ferroelectric transition, but this enhancing MCE signal is very sensitive to the thermal fluctuations, and can be strongly suppressed even under a small temperature.

  1. Study of physical properties of integrated ferroelectric/ferromagnetic heterostructures

    SciTech Connect

    Martinez, R.; Kumar, A.; Palai, R.; Katiyar, R. S.; Scott, J. F.

    2010-06-15

    Superlattices (SLs) with different periodicity of ferromagnetic La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) and ferroelectric Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} as constitutive layers were fabricated on conducting LaNiO{sub 3} coated (001) oriented MgO substrates using pulsed laser deposition. The crystallinity, ferroelectric, and magnetic properties of the SLs were studied over a wide range of temperatures and frequencies. The structure exhibited ferromagnetic behavior at 300 K and ferroelectric behavior over a range of temperatures between 100 and 300 K. A frequency-dependent change in dielectric constant and tangent loss were observed above the ferromagnetic-paramagnetic temperature. The frequency-dependent dielectric anomalies are attributed to the change in metallic and magnetic nature of LSMO and also the interfacial effect of two different phases that are connected alternatively in series. The effect of ferromagnetic LSMO layers on ferroelectric properties of the SLs indicated strong influence of the interfaces. The asymmetric behavior of ferroelectric loop and the capacitance-voltage relationship suggest development of a built field in the SLs due to high strain across the interfaces.

  2. Automated System Tests Ferroelectric Capacitors

    NASA Technical Reports Server (NTRS)

    Lakata, Mark; Thakoor, Sarita

    1994-01-01

    Polarization-switching parameters measured under computer control. Ferroelectric-capacitor-testing system applies voltage pulses and measures responses of ferroelectric capacitor to determine write; "time dependence of polarization," polarization-retention and fatigue characteristics of capacitor. Highly integrated setup quite flexible, versatile, and interactive, and allows convenient computer storage and analysis of data.

  3. Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites

    SciTech Connect

    Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Mitoseriu, Liliana; Airimioaei, Mirela; Tascu, Sorin; Schileo, Giorgio; Galassi, Carmen

    2013-02-21

    Particulate composites of ferrite and ferroelectric phases with xNiFe{sub 2}O{sub 4} (NF) and (1 - x)Pb{sub 0.988}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.976}Nb{sub 0.024}O{sub 3} (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 Degree-Sign C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.

  4. Effect of A-site La and Ba doping on threshold field and characteristic temperatures of PbSc0.5Ta0.5O3 relaxor studied by acoustic emission

    NASA Astrophysics Data System (ADS)

    Dul'kin, E.; Mihailova, B.; Gospodinov, M.; Roth, M.

    2012-09-01

    The structural transitions in Pb1-xLaxSc(1+x)/2Ta(1-x)/2O3, x = 0.08 (PLST) relaxor crystals were studied by means of acoustic emission (AE) under an external electric field (E) and compared with those observed in pure PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST) [E. Dul'kin et al., EPL 94, 57002 (2011)]. Similar to both the PST and PBST compounds, in zero field PLST exhibits AE corresponding to a para-to-antiferroelectric incommensurate phase transition at Tn = 276 K, lying in the vicinity of dielectric temperature maximum (Tm). This AE signal exhibits a nontrivial behavior when applying E resembling the electric-field-dependence of Tn previously observed for both the PST and PBST, namely, Tn initially decreases with the increase of E, attains a minimum at a threshold field Eth = 0.5 kV/cm, accompanied by a pronounced maximum of the AE count rate Ṅ = 12 s-1, and then starts increasing as E enhances. The similarities and difference between PST, PLST, and PBST with respect to Tn, Eth, and Ṅ are discussed from the viewpoint of three mechanisms: (i) chemically induced random local electric field due to the extra charge on the A-site ion, (ii) disturbance of the system of stereochemically active lone-pair electrons of Pb2+ by the isotropic outermost electron shell of substituting ion, and (iii) change in the tolerance factor and elastic field to the larger ionic radius of the substituting A-site ion due to the different radius of the substituting ion. The first two mechanisms influence the actual values of Tn and Eth, whereas the latter is shown to affect the normalized Ṅ, indicating the fractions undergoing a field-induced crossover from a modulated antiferroelectric to a ferroelectric state. Creation of secondary random electric field, caused by doping-induced A-site-O ionic chemical bonding, is discussed.

  5. Conduction at a ferroelectric interface

    DOE PAGESBeta

    Marshall, Matthew S. J.; Malashevich, Andrei; Disa, Ankit S.; Han, Myung -Geun; Chen, Hanghui; Zhu, Yimei; Ismail-Beigi, Sohrab; Walker, Frederick J.; Ahn, Charles H.

    2014-11-05

    Typical logic elements utilizing the field effect rely on the change in carrier concentration due to the field in the channel region of the device. Ferroelectric-field-effect devices provide a nonvolatile version of this effect due to the stable polarization order parameter in the ferroelectric. In this study, we describe an oxide/oxide ferroelectric heterostructure device based on (001)-oriented PbZr₀̣.₂Ti₀.₈O₃-LaNiO₃ where the dominant change in conductivity is a result of a significant mobility change in the interfacial channel region. The effect is confined to a few atomic layers at the interface and is reversible by switching the ferroelectric polarization. More interestingly, inmore » one polarization state, the field effect induces a 1.7 eV shift of the interfacial bands to create a new conducting channel in the interfacial PbO layer of the ferroelectric.« less

  6. Conduction at a ferroelectric interface

    SciTech Connect

    Marshall, Matthew S. J.; Malashevich, Andrei; Disa, Ankit S.; Han, Myung -Geun; Chen, Hanghui; Zhu, Yimei; Ismail-Beigi, Sohrab; Walker, Frederick J.; Ahn, Charles H.

    2014-11-05

    Typical logic elements utilizing the field effect rely on the change in carrier concentration due to the field in the channel region of the device. Ferroelectric-field-effect devices provide a nonvolatile version of this effect due to the stable polarization order parameter in the ferroelectric. In this study, we describe an oxide/oxide ferroelectric heterostructure device based on (001)-oriented PbZr₀̣.₂Ti₀.₈O₃-LaNiO₃ where the dominant change in conductivity is a result of a significant mobility change in the interfacial channel region. The effect is confined to a few atomic layers at the interface and is reversible by switching the ferroelectric polarization. More interestingly, in one polarization state, the field effect induces a 1.7 eV shift of the interfacial bands to create a new conducting channel in the interfacial PbO layer of the ferroelectric.

  7. Ferroelectric optical image comparator

    DOEpatents

    Butler, M.A.; Land, C.E.; Martin, S.J.; Pfeifer, K.B.

    1993-11-30

    A ferroelectric optical image comparator has a lead lanthanum zirconate titanate thin-film device which is constructed with a semi-transparent or transparent conductive first electrode on one side of the thin film, a conductive metal second electrode on the other side of the thin film, and the second electrode is in contact with a nonconducting substrate. A photoinduced current in the device represents the dot product between a stored image and an image projected onto the first electrode. One-dimensional autocorrelations are performed by measuring this current while displacing the projected image. 7 figures.

  8. Ferroelectric optical image comparator

    DOEpatents

    Butler, Michael A.; Land, Cecil E.; Martin, Stephen J.; Pfeifer, Kent B.

    1993-01-01

    A ferroelectric optical image comparator has a lead lanthanum zirconate titanate thin-film device which is constructed with a semi-transparent or transparent conductive first electrode on one side of the thin film, a conductive metal second electrode on the other side of the thin film, and the second electrode is in contact with a nonconducting substrate. A photoinduced current in the device represents the dot product between a stored image and an image projected onto the first electrode. One-dimensional autocorrelations are performed by measuring this current while displacing the projected image.

  9. Morphotropic domain structures and dielectric relaxation in piezo-/ferroelectric Pb(In1/2Nb1/2)O3-Pb(Zn1/3Nb2/3)O3-PbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Li, Tao; Chen, Chang; Ye, Mao; Qiu, Ximei; Lin, Peng; Xiong, Xinbo; Zeng, Xierong; Huang, Haitao; Ke, Shanming

    2016-05-01

    The domain structures, phase transitions and dielectric relaxation of relaxor-based piezo-/ferroelectric (1-x)Pb(In1/2Nb1/2)O3-0.33Pb(Zn1/3Nb2/3)O3-xPbTiO3 (x=0.30, 0.34, 0.37, and 0.42) single crystals, abbreviated as PIN-PZN-PT, grown by flux method, have been analyzed by polarized light microscope and dielectric spectroscopy. The dielectric relaxation was described by the Curie-Weiss law and Lorentz-type quadratic equation. The substitution of Ti4+ ions for the B-site complex (Zn1/3Nb2/3)4+ and (In1/2Nb1/2)4+ ions results in a long-range symmetry breaking, as revealed by the formation of birefringent domains. Single crystal of PIN-PZN-PT with morphotropic compositions exhibit complex domain structures, which are composed of both rhombohedral and tetragonal phases intimately mixed together. The domain structures, the sequence and temperature of phase transitions have been interpreted in relation to the morphotropic phase boundary behavior of the PIN-PZN-PT system. The analysis of morphotropic domain structures and phase transitions provides a better understanding of the microscopic mechanisms of the enhanced piezoelectric properties recently disclosed in the PIN-PZN-PT and other PZN-based piezocrystals.

  10. A physically-derived nonquasi-static model of ferroelectric amplifiers for computer-aided device simulation - Part I: The ferroelectric common-drain amplifier

    NASA Astrophysics Data System (ADS)

    Sayyah, Rana; Hunt, Mitchell; Ho, Fat D.

    2013-08-01

    A physically-derived nonquasi-static model describing the behavior of the ferroelectric common-drain amplifier is presented. The model is based on the method of partitioned channel and ferroelectric layers and is valid in accumulation, depletion, and the three inversion cases: weak, moderate, and strong. The equations of this model are based on the standard MOSFET equations that have been modified to reflect the ferroelectric properties. The model code is written in MATLAB and outputs voltage plots with respect to time. The accuracy and effectiveness of the model are verified by a few test cases, where the modeled results are compared to empirically-derived oscilloscope plots.

  11. Ferroelectric Based Technologies for Accelerators

    SciTech Connect

    Kanareykin, A.; Jing, C.; Nenasheva, E.; Kazakov, S.; Tagantsev, A.; Yakovlev, V.

    2009-01-22

    Ferroelectrics have unique intrinsic properties that make them extremely attractive for high-energy accelerator applications. Low loss ferroelectric materials can be used as key elements in RF tuning and phase shifting components to provide fast, electronic control. These devices are under development for different accelerator applications for the X, Ka and L-frequency bands. The exact design of these devices depends on the electrical parameters of the particular ferroelectric material to be used--its dielectric constant, loss tangent and tunability. BST based ferroelectric-oxide compounds have been found to be suitable materials for a fast electrically-controlled tuners. We present recent results on the development of BST based ferroelectric compositions synthesized for use in high power technology components. The BST(M) ferroelectrics have been tested using both transverse and parallel dc bias fields to control the permittivity. Fast switching of a newly developed material has been shown and the feasibility of using of ferroelectric-based accelerator components in vacuum and in air has been demonstrated.

  12. Dynamic Properties of Dielectric Susceptibility in Ferroelectric Thin Films

    NASA Astrophysics Data System (ADS)

    Cui, Lian; Cui, Haiying; Wu, Chunmei; Yang, Guihua; He, Zelong; Wang, Yuling; Che, Jixin

    2016-02-01

    In this paper, frequency, temperature, film thickness, surface effects, and various parameters dependence of dielectric susceptibility is investigated theoretically for ferroelectric thin films by the modified Landau theory under an AC applied field. The dielectric susceptibility versus AC applied field shows butterfly-shaped behavior, and depends strongly on the frequency and amplitude of the field and temperature. Our study shows that the existence of the surface transition layer can depress the dielectric susceptibility of a ferroelectric thin film. These results are well consistent with the phenomena reported in experiments.

  13. Characterization of a Common-Source Amplifier Using Ferroelectric Transistors

    NASA Technical Reports Server (NTRS)

    Hunt, Mitchell; Sayyah, Rana; MacLeond, Todd C.; Ho, Pat D.

    2010-01-01

    This paper presents empirical data that was collected through experiments using a FeFET in the established common-source amplifier circuit. The unique behavior of the FeFET lends itself to interesting and useful operation in this widely used common-source amplifier. The paper examines the effect of using a ferroelectric transistor for the amplifier. It also examines the effects of varying load resistance, biasing, and input voltages on the output signal and gives several examples of the output of the amplifier for a given input. The difference between a commonsource amplifier using a ferroelectric transistor and that using a MOSFET is addressed.

  14. Ferroelectricity in corundum derivatives

    NASA Astrophysics Data System (ADS)

    Ye, Meng; Vanderbilt, David

    2016-04-01

    The search for new ferroelectric (FE) materials holds promise for broadening our understanding of FE mechanisms and extending the range of application of FE materials. Here we investigate a class of A B O3 and A2B B'O6 materials that can be derived from the X2O3 corundum structure by mixing two or three ordered cations on the X site. Most such corundum derivatives have a polar structure, but it is unclear whether the polarization is reversible, which is a requirement for a FE material. In this paper, we propose a method to study the FE reversal path of materials in the corundum derivative family. We first categorize the corundum derivatives into four classes and show that only two of these allow for the possibility of FE reversal. We then calculate the energy profile and energy barrier of the FE reversal path using first-principles density functional methods with a structural constraint. Furthermore, we identify several empirical measures that can provide a rule of thumb for estimating the energy barriers. Finally, the conditions under which the magnetic ordering is compatible with ferroelectricity are determined. These results lead us to predict several potentially new FE materials.

  15. SOFT MODE ANOMALIES IN THE PEROVSKITE RELAXOR Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}

    SciTech Connect

    GEHRING,P.M.; VAKRUSHEV,S.B.; SHIRANE,G.

    2000-03-09

    Neutron inelastic scattering measurements of the polar TO phonon mode in the cubic relaxor Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}, at room temperature, reveal anomalous behavior similar to that recently observed in Pb(Zn{sub 1/3}Nb{sub 2/3}){sub 0.92}Ti{sub 0.08}O{sub 3} in which the optic branch appears to drop precipitously into the acoustic branch at a finite value of the momentum transfer q = 0.2 {angstrom}{sub {minus}1}, measured from the zone center. By contrast, a recent neutron study indicates that PMN exhibits a normal TO phonon dispersion at 800 K. The authors speculate this behavior is common to all relaxor materials, and is the result of the presence of nanometer-scale polarized domains in the crystal that form below a temperature T{sub d}, which effectively prevent the propagation of long wavelength (q = 0) phonons.

  16. Spectroscopic signature for ferroelectric ice

    NASA Astrophysics Data System (ADS)

    Wójcik, Marek J.; Gług, Maciej; Boczar, Marek; Boda, Łukasz

    2014-09-01

    Various forms of ice exist within our galaxy. Particularly intriguing type of ice - ‘ferroelectric ice' was discovered experimentally and is stable in temperatures below 72 K. This form of ice can generate enormous electric fields and can play an important role in planetary formation. In this letter we present Car-Parrinello simulation of infrared spectra of ferroelectric ice and compare them with spectra of hexagonal ice. Librational region of the spectra can be treated as spectroscopic signature of ice XI and can be of help to identify ferroelectric ice in the Universe.

  17. Ferroelectricity and tunneling electroresistance effect in asymmetric ferroelectric tunnel junctions

    NASA Astrophysics Data System (ADS)

    Tao, L. L.; Wang, J.

    2016-06-01

    We report the investigation on the ferroelectricity and tunneling electroresistance (TER) effect in PbTiO3 (PTO)-based ferroelectric tunnel junctions (FTJs) using first-principles calculations. For symmetric FTJs, we have calculated the average polarizations of PTO film and effective screening lengths of different metal electrodes for a number of FTJs, which is useful for experimental research. For asymmetric FTJs, significant asymmetric ferroelectric displacements in PTO film are observed, which is attributed to the intrinsic field generated by the two dissimilar electrodes. Moreover, by performing quantum transport calculations on those asymmetric FTJs, a sizable TER effect is observed. It is found that the asymmetry of ferroelectric displacements in PTO barrier, which is determined by the difference of work functions of the electrodes, controls the observed TER effect. Our results will help unravel the TER mechanism of asymmetric FTJs in most experiments and will be useful for the designing of FTJ-based devices.

  18. Piezoelectric properties of rhombohedral ferroelectric materials with phase transition

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaofang; Soh, A. K.

    2015-12-01

    The temporal evolution of domain structure and its piezoelectric behavior of ferroelectric material BaTiO3 during the transition process from rhombohedral to tetragonal phase under an applied electric field have been studied by employing Landau-Ginzburg theory and the phase-field method. The results obtained show that, during the transformation process, the intermediate phase was monoclinic MA phase, and several peak values of piezoelectric coefficient appeared at the stage where obvious change of domain pattern occurred. In addition, by comparing the cases of applied electric field with different frequencies, it was found that the maximum piezoelectric coefficient obtained decreased with increasing frequency value. These results are of great significance in tuning the properties of engineering domains in ferroelectrics, and could provide more fundamentals to the design of ferroelectric devices.

  19. Electron emission from ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zhang, Weiming

    Ferroelectric emission (FE) was discovered at CERN in 1988. However, a diverse array of results and explanations concerning FE have appeared. This dissertation focused on understanding the influence of material properties and external parameters on this complex process. The sample preparation, pulse generator and other experimental techniques are described. Plasma emission (PE), FE and mixed PE and FE were observed and described. The field enhancement at the electrode-dielectric-vacuum triple point was suggested to be the basis for PE. An apparent delay time, instability, visible light generation and strong electrode erosion are features of PE. Comparatively, FE does not require an extraction field, exhibits no apparent delay time and a relatively stable emission, and generates either no or a very weak light signal. A direct relationship between the switching current and emission current exists for the FE. Different FE characteristics of antiferroelectric PLZT 2/95/5, "normal" ferroelectric PLZT 8/65/35 and nonferroelectric PLZT 15/65/35 were described. The strong relationship between the emission and switching current was demonstrated. Repeatable emission is exhibited by 2/95/5, which can also be pulsed at high frequency due to its fast antiferroelectric <=> ferroelectric phase transition. The strong degradation of FE from 8/65/35 was attributed to decrease in the remanent polarization. While no emission signal was detected from 15/65/35, which can be interpreted as an additional evidence that electron emission from the above two PLZT was indeed FE process. Based on the field and domain switching distribution model, sample geometry effect on FE was predicted, and verified using the results from different groups. Electron emission energy distribution of PLZT 8/65/35 showed a very narrow energy distribution (FWHM ≈ 10 eV to 20 eV), and the emission energy was on the order of the applied pulse potential. The possible application of FE for emissive flat panel

  20. Tunnel electroresistance through organic ferroelectrics

    PubMed Central

    Tian, B. B.; Wang, J. L.; Fusil, S.; Liu, Y.; Zhao, X. L.; Sun, S.; Shen, H.; Lin, T.; Sun, J. L.; Duan, C. G.; Bibes, M.; Barthélémy, A.; Dkhil, B.; Garcia, V.; Meng, X. J.; Chu, J. H.

    2016-01-01

    Organic electronics is emerging for large-area applications such as photovoltaic cells, rollable displays or electronic paper. Its future development and integration will require a simple, low-power organic memory, that can be written, erased and readout electrically. Here we demonstrate a non-volatile memory in which the ferroelectric polarisation state of an organic tunnel barrier encodes the stored information and sets the readout tunnel current. We use high-sensitivity piezoresponse force microscopy to show that films as thin as one or two layers of ferroelectric poly(vinylidene fluoride) remain switchable with low voltages. Submicron junctions based on these films display tunnel electroresistance reaching 1,000% at room temperature that is driven by ferroelectric switching and explained by electrostatic effects in a direct tunnelling regime. Our findings provide a path to develop low-cost, large-scale arrays of organic ferroelectric tunnel junctions on silicon or flexible substrates. PMID:27143121

  1. Ferroelectric capacitor with reduced imprint

    DOEpatents

    Evans, Jr., Joseph T.; Warren, William L.; Tuttle, Bruce A.; Dimos, Duane B.; Pike, Gordon E.

    1997-01-01

    An improved ferroelectric capacitor exhibiting reduced imprint effects in comparison to prior art capacitors. A capacitor according to the present invention includes top and bottom electrodes and a ferroelectric layer sandwiched between the top and bottom electrodes, the ferroelectric layer comprising a perovskite structure of the chemical composition ABO.sub.3 wherein the B-site comprises first and second elements and a dopant element that has an oxidation state greater than +4. The concentration of the dopant is sufficient to reduce shifts in the coercive voltage of the capacitor with time. In the preferred embodiment of the present invention, the ferroelectric element comprises Pb in the A-site, and the first and second elements are Zr and Ti, respectively. The preferred dopant is chosen from the group consisting of Niobium, Tantalum, and Tungsten. In the preferred embodiment of the present invention, the dopant occupies between 1 and 8% of the B-sites.

  2. Tunnel electroresistance through organic ferroelectrics.

    PubMed

    Tian, B B; Wang, J L; Fusil, S; Liu, Y; Zhao, X L; Sun, S; Shen, H; Lin, T; Sun, J L; Duan, C G; Bibes, M; Barthélémy, A; Dkhil, B; Garcia, V; Meng, X J; Chu, J H

    2016-01-01

    Organic electronics is emerging for large-area applications such as photovoltaic cells, rollable displays or electronic paper. Its future development and integration will require a simple, low-power organic memory, that can be written, erased and readout electrically. Here we demonstrate a non-volatile memory in which the ferroelectric polarisation state of an organic tunnel barrier encodes the stored information and sets the readout tunnel current. We use high-sensitivity piezoresponse force microscopy to show that films as thin as one or two layers of ferroelectric poly(vinylidene fluoride) remain switchable with low voltages. Submicron junctions based on these films display tunnel electroresistance reaching 1,000% at room temperature that is driven by ferroelectric switching and explained by electrostatic effects in a direct tunnelling regime. Our findings provide a path to develop low-cost, large-scale arrays of organic ferroelectric tunnel junctions on silicon or flexible substrates. PMID:27143121

  3. Tunnel electroresistance through organic ferroelectrics

    NASA Astrophysics Data System (ADS)

    Tian, B. B.; Wang, J. L.; Fusil, S.; Liu, Y.; Zhao, X. L.; Sun, S.; Shen, H.; Lin, T.; Sun, J. L.; Duan, C. G.; Bibes, M.; Barthélémy, A.; Dkhil, B.; Garcia, V.; Meng, X. J.; Chu, J. H.

    2016-05-01

    Organic electronics is emerging for large-area applications such as photovoltaic cells, rollable displays or electronic paper. Its future development and integration will require a simple, low-power organic memory, that can be written, erased and readout electrically. Here we demonstrate a non-volatile memory in which the ferroelectric polarisation state of an organic tunnel barrier encodes the stored information and sets the readout tunnel current. We use high-sensitivity piezoresponse force microscopy to show that films as thin as one or two layers of ferroelectric poly(vinylidene fluoride) remain switchable with low voltages. Submicron junctions based on these films display tunnel electroresistance reaching 1,000% at room temperature that is driven by ferroelectric switching and explained by electrostatic effects in a direct tunnelling regime. Our findings provide a path to develop low-cost, large-scale arrays of organic ferroelectric tunnel junctions on silicon or flexible substrates.

  4. Ferroelectric domain structure of anisotropically strained NaNbO{sub 3} epitaxial thin films

    SciTech Connect

    Schwarzkopf, J. Braun, D.; Schmidbauer, M.; Duk, A.; Wördenweber, R.

    2014-05-28

    NaNbO{sub 3} thin films have been grown under anisotropic biaxial strain on several oxide substrates by liquid-delivery spin metalorganic chemical vapor deposition. Compressive lattice strain of different magnitude, induced by the deposition of NaNbO{sub 3} films with varying film thickness on NdGaO{sub 3} single crystalline substrates, leads to modifications of film orientation and phase symmetry, which are similar to the phase transitions in Pb-containing oxides near the morphotropic phase boundary. Piezoresponse force microscopy measurements exhibit large out-of-plane polarization components, but no distinctive domain structure, while C-V measurements indicate relaxor properties in these films. When tensile strain is provoked by the epitaxial growth on DyScO{sub 3}, TbScO{sub 3}, and GdScO{sub 3} single crystalline substrates, NaNbO{sub 3} films behave rather like a normal ferroelectric. The application of these rare-earth scandate substrates yields well-ordered ferroelectric stripe domains of the type a{sub 1}/a{sub 2} with coherent domain walls aligned along the [001] substrate direction as long as the films are fully strained. With increasing plastic lattice relaxation, initially, a 2D domain pattern with still exclusively in-plane electric polarization, and finally, domains with in-plane and out-of-plane polar components evolve.

  5. Molecular Dynamics Modeling of Dielectric Polarization and Ferroelectricity in Poly(vinylidene fluoride) and Related Polymers

    NASA Astrophysics Data System (ADS)

    Calame, Jeffrey

    Molecular dynamics studies of the dielectric polarization response of a constrained bond length and bond angle, united-atom-based model of lamellar crystals of poly(vinylidene fluoride) (PVDF) are reported. Classical ferroelectricity is observed in PVDF, and when variations in the basic PVDF-like interaction parameters are allowed, a transition between classical and relaxor ferroelectricity is found to depend systematically on the polymer repeat unit dipole moment and on the united atom radius of the non-CH2 functional group. The effects of step and ramp electric field reversal are studied. A complicated sequence of reorientation processes occurs over a wide range of time scales, including a weak, temperature-independent response of 1-2 ps duration associated with local torsional motion, followed by a slow-rising delay regime lasting 10s of ns or longer that involves trans-gauche (TG) transitions in the amorphous phase. After the delay, a large-amplitude primary reorientation occurs over a relatively short additional duration (0.1 to 2 ns), which is due to rotation of large sub-segments in the crystalline phase with few TG transitions. The overall sequence concludes with a slow terminal rise lasting several 100s of ns involving an improvement in crystalline order. Work supported by the U.S. Office of Naval Research.

  6. Ferroelectric infrared detector and method

    DOEpatents

    Lashley, Jason Charles; Opeil, Cyril P.; Smith, James Lawrence

    2010-03-30

    An apparatus and method are provided for sensing infrared radiation. The apparatus includes a sensor element that is positioned in a magnetic field during operation to ensure a .lamda. shaped relationship between specific heat and temperature adjacent the Curie temperature of the ferroelectric material comprising the sensor element. The apparatus is operated by inducing a magnetic field on the ferroelectric material to reduce surface charge on the element during its operation.

  7. Structures, electrical properties, and leakage current behaviors of un-doped and Mn-doped lead-free ferroelectric K{sub 0.5}Na{sub 0.5}NbO{sub 3} films

    SciTech Connect

    Wang, Lingyan E-mail: wren@mail.xjtu.edu.cn; Ren, Wei E-mail: wren@mail.xjtu.edu.cn; Shi, Peng; Wu, Xiaoqing

    2014-01-21

    Lead-free ferroelectric un-doped and doped K{sub 0.5}Na{sub 0.5}NbO{sub 3} (KNN) films with different amounts of manganese (Mn) were prepared by a chemical solution deposition method. The thicknesses of all films are about 1.6 μm. Their phase, microstructure, leakage current behavior, and electrical properties were investigated. With increasing the amounts of Mn, the crystallinity became worse. Fortunately, the electrical properties were improved due to the decreased leakage current density after Mn-doping. The study on leakage behaviors shows that the dominant conduction mechanism at low electric field in the un-doped KNN film is ohmic mode and that at high electric field is space-charge-limited and Pool-Frenkel emission. After Mn doping, the dominant conduction mechanism at high electric field of KNN films changed single space-charge-limited. However, the introduction of higher amount of Mn into the KNN film would lead to a changed conduction mechanism from space-charge-limited to ohmic mode. Consequently, there exists an optimal amount of Mn doping of 2.0 mol. %. The 2.0 mol. % Mn doped KNN film shows the lowest leakage current density and the best electrical properties. With the secondary ion mass spectroscopies and x-ray photoelectron spectroscopy analyses, the homogeneous distribution in the KNN films and entrance of Mn element in the lattice of KNN perovskite structure were also confirmed.

  8. Ferroelectric domain formation in discotic liquid crystals: Monte Carlo study on the influence of boundary conditions.

    PubMed

    Bose, Tushar Kanti; Saha, Jayashree

    2015-10-01

    The realization of a spontaneous macroscopic ferroelectric order in fluids of anisotropic mesogens is a topic of both fundamental and technological interest. Recently we demonstrated that a system of dipolar achiral disklike ellipsoids can exhibit long-searched ferroelectric liquid crystalline phases of dipolar origin. In the present work, extensive off-lattice Monte Carlo simulations are used to investigate the phase behavior of the system under the influences of the electrostatic boundary conditions that restrict any global polarization. We find that the system develops strongly ferroelectric slablike domains periodically arranged in an antiferroelectric fashion. Exploring the phase behavior at different dipole strengths, we find existence of the ferroelectric nematic and ferroelectric columnar order inside the domains. For higher dipole strengths, a biaxial phase is also obtained with a similar periodic array of ferroelectric slabs of antiparallel polarizations. We have studied the depolarizing effects by using both the Ewald summation and the spherical cutoff techniques. We present and compare the results of the two different approaches of considering the depolarizing effects in this anisotropic system. It is explicitly shown that the domain size increases with the system size as a result of considering a longer range of dipolar interactions. The system exhibits pronounced system size effects for stronger dipolar interactions. The results provide strong evidence to the novel understanding that the dipolar interactions are indeed sufficient to produce long-range ferroelectric order in anisotropic fluids. PMID:26565261

  9. Ultrathin Hf0.5Zr0.5O2 Ferroelectric Films on Si.

    PubMed

    Chernikova, Anna; Kozodaev, Maksim; Markeev, Andrei; Negrov, Dmitrii; Spiridonov, Maksim; Zarubin, Sergei; Bak, Ohheum; Buragohain, Pratyush; Lu, Haidong; Suvorova, Elena; Gruverman, Alexei; Zenkevich, Andrei

    2016-03-23

    Because of their immense scalability and manufacturability potential, the HfO2-based ferroelectric films attract significant attention as strong candidates for application in ferroelectric memories and related electronic devices. Here, we report the ferroelectric behavior of ultrathin Hf0.5Zr0.5O2 films, with the thickness of just 2.5 nm, which makes them suitable for use in ferroelectric tunnel junctions, thereby further expanding the area of their practical application. Transmission electron microscopy and electron diffraction analysis of the films grown on highly doped Si substrates confirms formation of the fully crystalline non-centrosymmetric orthorhombic phase responsible for ferroelectricity in Hf0.5Zr0.5O2. Piezoresponse force microscopy and pulsed switching testing performed on the deposited top TiN electrodes provide further evidence of the ferroelectric behavior of the Hf0.5Zr0.5O2 films. The electronic band lineup at the top TiN/Hf0.5Zr0.5O2 interface and band bending at the adjacent n(+)-Si bottom layer attributed to the polarization charges in Hf0.5Zr0.5O2 have been determined using in situ X-ray photoelectron spectroscopy analysis. The obtained results represent a significant step toward the experimental implementation of Si-based ferroelectric tunnel junctions. PMID:26931409

  10. Semiconductor/relaxor 0-3 type composites without thermal depolarization in Bi0.5Na0.5TiO3-based lead-free piezoceramics

    NASA Astrophysics Data System (ADS)

    Zhang, Ji; Pan, Zhao; Guo, Fei-Fei; Liu, Wen-Chao; Ning, Huanpo; Chen, Y. B.; Lu, Ming-Hui; Yang, Bin; Chen, Jun; Zhang, Shan-Tao; Xing, Xianran; Rödel, Jürgen; Cao, Wenwu; Chen, Yan-Feng

    2015-03-01

    Commercial lead-based piezoelectric materials raised worldwide environmental concerns in the past decade. Bi0.5Na0.5TiO3-based solid solution is among the most promising lead-free piezoelectric candidates; however, depolarization of these solid solutions is a longstanding obstacle for their practical applications. Here we use a strategy to defer the thermal depolarization, even render depolarization-free Bi0.5Na0.5TiO3-based 0-3-type composites. This is achieved by introducing semiconducting ZnO particles into the relaxor ferroelectric 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 matrix. The depolarization temperature increases with increasing ZnO concentration until depolarization disappears at 30 mol% ZnO. The semiconducting nature of ZnO provides charges to partially compensate the ferroelectric depolarization field. These results not only pave the way for applications of Bi0.5Na0.5TiO3-based piezoceramics, but also have great impact on the understanding of the mechanism of depolarization so as to provide a new design to optimize the performance of lead-free piezoelectrics.

  11. Tuning of dielectric, pyroelectric and ferroelectric properties of 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 ceramic by internal clamping

    NASA Astrophysics Data System (ADS)

    Patel, Satyanarayan; Chauhan, Aditya; Kundu, Swarup; Madhar, Niyaz Ahamad; Ilahi, Bouraoui; Vaish, Rahul; Varma, K. B. R.

    2015-08-01

    This study systematically investigates the phenomenon of internal clamping in ferroelectric materials through the formation of glass-ceramic composites. Lead-free 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 (BNT-BT-ST) bulk ferroelectric ceramic was selected for the course of investigation. 3BaO - 3TiO2 - B2O3 (BTBO) glass was then incorporated systematically to create sintered samples containing 0%, 2%, 4% and 6% glass (by weight). Upon glass induction features like remnant polarization, saturation polarization, hysteresis losses and coercive field could be varied as a function of glass content. Such effects were observed to benefit derived applications like enhanced energy storage density ˜174 kJ/m3 to ˜203 kJ/m3 and pyroelectric coefficient 5.7x10-4 Cm-2K-1 to 6.8x10-4 Cm-2K-1 by incorporation of 4% glass. Additionally, BNT-BT-ST depolarization temperature decreased from 457K to 431K by addition of 4% glass content. Glass incorporation could systematically increases diffuse phase transition and relaxor behavior temperature range from 70 K to 81K and 20K to 34 K, respectively when 6% and 4% glass content is added which indicates addition of glass provides better temperature stability. The most promising feature was observed to be that of dielectric response tuning. It can be also used to control (to an extent) the dielectric behavior of the host ceramic. Dielectric permittivity and losses decreased from 1278 to 705 and 0.109 to 0.107 for 6% glass, at room temperature. However this reduction in dielectric constant and loss increases pyroelectric figures of merit (FOMs) for high voltage responsivity (Fv) high detectivity (Fd) and energy harvesting (Fe) from 0.018 to 0.037 m2C-1, 5.89 to 8.85 μPa-1/2 and 28.71 to 61.55 Jm-3K-2, respectively for 4% added ceramic-glass at room temperature. Such findings can have huge implications in the field of tailoring ferroelectric response for application specific requirements.

  12. Modeling of elastic nonlinearities in ferroelectric materials including nonlinear losses: application to nonlinear resonance mode of relaxors single crystals.

    PubMed

    Sebald, Gaël; Lebrun, Laurent; Guyomar, Daniel

    2005-04-01

    (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) and (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) single crystals are considered to behave like soft Pb(Zr,Ti)O3 (PZT) ceramics because of their small mechanical quality factor Qm and poor stability under external disturbances (Qm > 500-1000 for hard PZT ceramic, and Qm < 100 for soft PZT and PMN-PT and PZN-PT single crystals). At weak signal excitation of the first resonance mode, the displacement at the end of a lateral bar is proportional to the Q31d31 figure of merit that is very close to that found for hard PZT. Indeed the very large piezoelectric coefficient compensates the low Qm. But increasing alternating current (AC) field results in the appearance of strong non-linearities through a shift of the resonance frequency and jumps phenomenon observed on increasing and decreasing frequency sweep. It is shown in this paper that these nonlinearities are due to the nonlinear elastic compliance that can be modeled by a third order development of the constitutive piezoelectric equations. Experiments on PMN-PT and PZN-PT single crystals are used for comparison with the model to show the viability of the approach. Both the frequency shift and jumps phenomenon are simulated with a very good agreement with experimental results. The importance is also shown of losses associated with the third order term responsible for the large decrease of the mechanical quality factor for high strain levels. Thus, the nonlinear losses are related to the hysteresis of domain wall motion when subjected to large displacements. PMID:16060508

  13. Ground state of the relaxor ferroelectric Pb(Zn1/3Nb2/3)O3

    NASA Astrophysics Data System (ADS)

    Xu, Guangyong; Zhong, Z.; Bing, Y.; Ye, Z.-G.; Stock, C.; Shirane, G.

    2003-03-01

    High energy x-ray diffraction measurements on Pb(Zn1/3Nb2/3)O3 (PZN) single crystals show that the system does not have a rhombohedral symmetry at room temperature as previously believed. The phase (X) in the bulk of the crystal gives Bragg peaks similar to that of a nearly cubic lattice with a slight tetragonal distortion. The Bragg profile remains sharp with no evidence of size broadening due to the polar microcrystals. However, in our preliminary studies of the skin, we have found the expected rhombohedral (R) phase as a surface state. On the other hand, studies on an electric-field poled PZN single crystal clearly indicate a rhombohedral phase at room temperature.

  14. Micro- and nanodomain imaging in uniaxial ferroelectrics: Joint application of optical, confocal Raman, and piezoelectric force microscopy

    SciTech Connect

    Shur, V. Ya. Zelenovskiy, P. S.

    2014-08-14

    The application of the most effective methods of the domain visualization in model uniaxial ferroelectrics of lithium niobate (LN) and lithium tantalate (LT) family, and relaxor strontium-barium niobate (SBN) have been reviewed in this paper. We have demonstrated the synergetic effect of joint usage of optical, confocal Raman, and piezoelectric force microscopies which provide extracting of the unique information about formation of the micro- and nanodomain structures. The methods have been applied for investigation of various types of domain structures with increasing complexity: (1) periodical domain structure in LN and LT, (2) nanodomain structures in LN, LT, and SBN, (3) nanodomain structures in LN with modified surface layer, (4) dendrite domain structure in LN. The self-assembled appearance of quasi-regular nanodomain structures in highly non-equilibrium switching conditions has been considered.

  15. Coupled ferromagnetism and ferroelectricity in superlattices of non-ferroelectric antiferromagnetic manganites

    NASA Astrophysics Data System (ADS)

    Burton, J. D.; Rogdakis, K.; Seo, J. W.; Viskadourakis, Z.; Wang, Y.; Ah Qune, L.; Choi, E.; Tsymbal, E.; Lee, J.; Panagopoulos, C.

    2013-03-01

    Complex oxide heterostructures present a promising avenue for the design of multifunctional properties which may find application in a variety of technological systems. In heterostructures composed of transition metal oxides the disruption introduced by an interface can affect the balance of the competing interactions among spins, charges and orbitals. This has led to the emergence of properties absent in the original building blocks of a heterostructure. We will report on the discovery of magnetically tunable ferroelectricity in artificial tri-layer superlattices consisting of non-ferroelectric and non-ferromagnetic components: NdMnO3/SrMnO3/LaMnO3. Ferroelectricity was observed below 40 K exhibiting strong tunability by superlattice periodicity. Furthermore, magnetoelectric coupling resulted in 150% magnetic modulation of the polarization. First-principles calculations indicate that broken space inversion symmetry and mixed valency give rise to the observed behavior. This discovery highlights the importance of tri-layered systems for the engineering of emergent properties in oxide heterostructures. 1 University of Nebraska - Lincoln, 2 Foundation for Research and Technology - Hellas, Heraklion, Greece, 3 Nanyang Technological University, Nanyang, Singapore, 4 Sungkyunkwan University, Suwon, Republic of Korea

  16. Lead-free and lead-based ABO3 perovskite relaxors with mixed-valence A-site and B-site disorder: Comparative neutron scattering structural study of (Na1/2Bi1/2)TiO3 and Pb(Mg1/3Nb2/3)O3

    NASA Astrophysics Data System (ADS)

    Ge, Wenwei; Devreugd, Christopher P.; Phelan, D.; Zhang, Qinhui; Ahart, Muhtar; Li, Jiefang; Luo, Haosu; Boatner, Lynn A.; Viehland, Dwight; Gehring, Peter M.

    2013-11-01

    We report the results of neutron elastic-scattering measurements made between -250 °C and 620 °C on the lead-free relaxor (Na1/2Bi1/2)TiO3 (NBT). Strong, anisotropic, elastic diffuse scattering intensity decorates the (100), (110), (111), (200), (210), and (220) Bragg peaks at room temperature. The wave-vector dependence of this diffuse scattering is compared to that in the lead-based relaxor Pb(Mg1/3Nb2/3)O3 (PMN) to determine if any features might be common to relaxors. Prominent ridges in the elastic diffuse scattering intensity contours that extend along ⟨110⟩ are seen that exhibit the same zone dependence as those observed in PMN and other lead-based relaxors. These ridges disappear gradually on heating above the cubic-to-tetragonal phase transition temperature TCT = 523 °C, which is also near the temperature at which the dielectric permittivity begins to deviate from Curie-Weiss behavior. We thus identify the ⟨110⟩-oriented ridges as a relaxor-specific property. The diffuse scattering contours also display narrower ridges oriented along ⟨100⟩ that are consistent with the x-ray results of Kreisel [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.68.014113 68, 014113 (2003)]; these vanish near 320 °C, indicating that they have a different physical origin. The ⟨100⟩-oriented ridges are not observed in PMN. We observe no equivalent relaxor-specific elastic diffuse scattering from the homovalent relaxor analogues K0.95Li0.05TiO3 (A-site disordered) and KTa0.95Nb0.05O3 (B-site disordered). This suggests that the ⟨110⟩-oriented diffuse scattering ridges are correlated with the presence of strong random electric fields and invites a reassessment of what defines the relaxor phase. We find that doping NBT with 5.6% BaTiO3, a composition close to the morphotropic phase boundary with enhanced piezoelectric properties, increases the room-temperature correlation length along [11¯0] from 40 to 60 Å while doubling the associated integrated diffuse

  17. Nonlinear pyroelectric energy harvesting from relaxor single crystals.

    PubMed

    Khodayari, Akram; Pruvost, Sebastien; Sebald, Gael; Guyomar, Daniel; Mohammadi, Saber

    2009-04-01

    Energy harvesting from temperature variations in a Pb(Zn(1/3)Nb(2/3))(0.955)Ti(0.045)O(3) single crystal was studied and evaluated using the Ericsson thermodynamic cycle. The efficiency of this cycle related to Carnot cycle is 100 times higher than direct pyroelectric energy harvesting, and it can be as high as 5.5% for a 10 degrees C temperature variation and 2 kV/mm electric field. The amount of harvested energy for a 60 degrees C temperature variation and 2 kV/mm electric field is 242.7 mJ x cm(-3). The influence of ferroelectric phase transitions on the energy harvesting performance is discussed and illustrated with experimental results. PMID:19406698

  18. Ferroelectricity in undoped hafnium oxide

    NASA Astrophysics Data System (ADS)

    Polakowski, Patrick; Müller, Johannes

    2015-06-01

    We report the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 4-20 nm. The undoped films were fabricated using atomic layer deposition (ALD) and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation. Structural as well as electrical evidence for the appearance of a ferroelectric phase in pure hafnium oxide was collected with respect to film thickness and thermal budget applied during titanium nitride electrode formation. Using grazing incidence X-Ray diffraction (GIXRD) analysis, we observed an enhanced suppression of the monoclinic phase fraction in favor of an orthorhombic, potentially, ferroelectric phase with decreasing thickness/grain size and for a titanium nitride electrode formation below crystallization temperature. The electrical presence of ferroelectricity was confirmed using polarization measurements. A remanent polarization Pr of up to 10 μC cm-2 as well as a read/write endurance of 1.6 × 105 cycles was measured for the pure oxide. The experimental results reported here strongly support the intrinsic nature of the ferroelectric phase in hafnium oxide and expand its applicability beyond the doped systems.

  19. Ferroelectricity in undoped hafnium oxide

    SciTech Connect

    Polakowski, Patrick; Müller, Johannes

    2015-06-08

    We report the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 4–20 nm. The undoped films were fabricated using atomic layer deposition (ALD) and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation. Structural as well as electrical evidence for the appearance of a ferroelectric phase in pure hafnium oxide was collected with respect to film thickness and thermal budget applied during titanium nitride electrode formation. Using grazing incidence X-Ray diffraction (GIXRD) analysis, we observed an enhanced suppression of the monoclinic phase fraction in favor of an orthorhombic, potentially, ferroelectric phase with decreasing thickness/grain size and for a titanium nitride electrode formation below crystallization temperature. The electrical presence of ferroelectricity was confirmed using polarization measurements. A remanent polarization P{sub r} of up to 10 μC cm{sup −2} as well as a read/write endurance of 1.6 × 10{sup 5} cycles was measured for the pure oxide. The experimental results reported here strongly support the intrinsic nature of the ferroelectric phase in hafnium oxide and expand its applicability beyond the doped systems.

  20. The Modification of Ferroelectric Surfaces for Catalysis

    NASA Astrophysics Data System (ADS)

    Herdiech, Matthew William

    , the reactivity of the Cr2O3/LiNbO 3 system toward O and the reactivity of the RuO2/Pb(Zr 0.2Ti0.8)O3 system toward N, O, and NO was investigated. It is shown that well-ordered Cr2O3 films can be fabricated on positively and negatively poled LiNbO3 as evidenced by LEED, RHEED, XRD, and XPS; however, the conditions necessary to produce the films can cause Cr diffusion into the LiNbO3, potentially obscuring the film/substrate interface. It is also shown that surface Cr in the Cr 2O3 film can be oxidized to Cr5+ by atomic oxygen. Despite the suggestion that opposite compensating charges occur at the Cr2O3 surface on positively and negatively poled LiNbO3, no significant difference between O atom adsorption on Cr2O3 on the two polar substrates or on non-polar alpha-Al 2O3 (0001) could be detected. It is shown by NO TPD measurements that all RuO2-terminated Pb(Zr0.2Ti0.8)O3 surfaces were found to be active toward NO adsorption, although since 02 desorption was never detected it was determined that none of the surfaces were active toward NO dissociation. There were two active sites for NO adsorption for RuO2-terminated Pb(Zr0.2Ti0.8)O3: O on top of Ru and bare Ru sites. Little polarization dependence was observed for NO adsorption directly to Ru, with NO desorption occurring at 425 K for 1.7 ML RuO2 on positively poled Pb(Zr0.2Ti0.8)O 3 and 430 K for 1.8 ML RuO2 on negatively poled Pb(Zr 0.2Ti0.8)O3. However, significant polarization dependence was observed for adsorption to O on top of Ru, with NO desorption occurring at 285 K for 1.7 ML RuO 2 on positively poled Pb(Zr0.2Ti0.8)O3 and 230 K for 1.8 ML RuO2 on negatively poled Pb(Zr0.2Ti 0.8)O3. The stronger NO adsorption for RuO2 on positively poled Pb(Zr0.2Ti0.8)O3 is consistent with theoretical predictions, and shows that ferroelectric materials can be used as substrates in film/substrate systems with polarization dependent behavior. The lack of NO dissociation observed in the experiments is inconsistent with theoretical

  1. Finite-size effects of hysteretic dynamics in multilayer graphene on a ferroelectric

    SciTech Connect

    Morozovska, Anna N.; Pusenkova, Anastasiia S.; Varenyk, Oleksandr V.; Kalinin, Sergei V.; Eliseev, Eugene A.; Strikha, Maxym V.

    2015-06-11

    The origin and influence of finite-size effects on the nonlinear dynamics of space charge stored by multilayer graphene on a ferroelectric and resistivity of graphene channel were analyzed. In this paper, we develop a self-consistent approach combining the solution of electrostatic problems with the nonlinear Landau-Khalatnikov equations for a ferroelectric. The size-dependent behaviors are governed by the relations between the thicknesses of multilayer graphene, ferroelectric film, and the dielectric layer. The appearance of charge and electroresistance hysteresis loops and their versatility stem from the interplay of polarization reversal dynamics and its incomplete screening in an alternating electric field. These features are mostly determined by the dielectric layer thickness. The derived analytical expressions for electric fields and space-charge-density distribution in a multilayer system enable knowledge-driven design of graphene-on-ferroelectric heterostructures with advanced performance. We further investigate the effects of spatially nonuniform ferroelectric domain structures on the graphene layers’ conductivity and predict its dramatic increase under the transition from multi- to single-domain state in a ferroelectric. Finally, this intriguing effect can open possibilities for the graphene-based sensors and explore the underlying physical mechanisms in the operation of graphene field-effect transistor with ferroelectric gating.

  2. Finite-size effects of hysteretic dynamics in multilayer graphene on a ferroelectric

    DOE PAGESBeta

    Morozovska, Anna N.; Pusenkova, Anastasiia S.; Varenyk, Oleksandr V.; Kalinin, Sergei V.; Eliseev, Eugene A.; Strikha, Maxym V.

    2015-06-11

    The origin and influence of finite-size effects on the nonlinear dynamics of space charge stored by multilayer graphene on a ferroelectric and resistivity of graphene channel were analyzed. In this paper, we develop a self-consistent approach combining the solution of electrostatic problems with the nonlinear Landau-Khalatnikov equations for a ferroelectric. The size-dependent behaviors are governed by the relations between the thicknesses of multilayer graphene, ferroelectric film, and the dielectric layer. The appearance of charge and electroresistance hysteresis loops and their versatility stem from the interplay of polarization reversal dynamics and its incomplete screening in an alternating electric field. These featuresmore » are mostly determined by the dielectric layer thickness. The derived analytical expressions for electric fields and space-charge-density distribution in a multilayer system enable knowledge-driven design of graphene-on-ferroelectric heterostructures with advanced performance. We further investigate the effects of spatially nonuniform ferroelectric domain structures on the graphene layers’ conductivity and predict its dramatic increase under the transition from multi- to single-domain state in a ferroelectric. Finally, this intriguing effect can open possibilities for the graphene-based sensors and explore the underlying physical mechanisms in the operation of graphene field-effect transistor with ferroelectric gating.« less

  3. Emission from ferroelectric cathodes

    SciTech Connect

    Sampayan, S.E.; Caporaso, G.J.; Holmes, C.L.; Lauer, E.J.; Prosnitz, D.; Trimble, D.O.; Westenskow, G.A.

    1993-05-17

    We have recently initiated an investigation of electron emission from ferroelectric cathodes. Our experimental apparatus consisted of an electron diode and a 250 kV, 12 ohm, 70 ns pulsed high voltage power source. A planar triode modulator driven by a synthesized waveform generator initiates the polarization inversion and allows inversion pulse tailoring. The pulsed high voltage power source is capable of delivering two high voltage pulses within 50 ns of each other and is capable of operating at a sustained repetition rate of 5 Hz. Our initial measurements indicate that emission current densities above the Child-Langmuir Space Charge Limit are possible. We explain this effect to be based on a non-zero initial energy of the emitted electrons. We also determined that this effect is strongly coupled to relative timing between the inversion pulse and application of the main anode-cathode pulse. We also have initiated brightness measurements of the emitted beam. As in our previous measurements at this Laboratory, we performed the measurement using a pepper pot technique. Beam-let profiles are recorded with a fast phosphor and gated cameras. We describe our apparatus and preliminary measurements.

  4. First-principles theory, coarse-grained models, and simulations of ferroelectrics.

    PubMed

    Waghmare, Umesh V

    2014-11-18

    large-scale simulations while capturing the relevant microscopic interactions quantitatively. In this Account, we first summarize the insights obtained into chemical mechanisms of ferroelectricity using first-principles DFT calculations. We then discuss the principles of construction of first-principles model Hamiltonians for ferroelectric phase transitions in perovskite oxides, which involve coarse-graining in time domain by integrating out high frequency phonons. Molecular dynamics simulations of the resulting model are shown to give quantitative predictions of material-specific ferroelectric transition behavior in bulk as well as nanoscale ferroelectric structures. A free energy landscape obtained through coarse-graining in real-space provides deeper understanding of ferroelectric transitions, domains, and states with inhomogeneous order and points out the key role of microscopic coupling between phonons and strain. We conclude with a discussion of the multiscale modeling strategy elucidated here and its application to other materials such as shape memory alloys. PMID:25361389

  5. Ferroelectric memory based on nanostructures

    NASA Astrophysics Data System (ADS)

    Liu, Xingqiang; Liu, Yueli; Chen, Wen; Li, Jinchai; Liao, Lei

    2012-06-01

    In the past decades, ferroelectric materials have attracted wide attention due to their applications in nonvolatile memory devices (NVMDs) rendered by the electrically switchable spontaneous polarizations. Furthermore, the combination of ferroelectric and nanomaterials opens a new route to fabricating a nanoscale memory device with ultrahigh memory integration, which greatly eases the ever increasing scaling and economic challenges encountered in the traditional semiconductor industry. In this review, we summarize the recent development of the nonvolatile ferroelectric field effect transistor (FeFET) memory devices based on nanostructures. The operating principles of FeFET are introduced first, followed by the discussion of the real FeFET memory nanodevices based on oxide nanowires, nanoparticles, semiconductor nanotetrapods, carbon nanotubes, and graphene. Finally, we present the opportunities and challenges in nanomemory devices and our views on the future prospects of NVMDs.

  6. Ferroelectric memory based on nanostructures

    PubMed Central

    2012-01-01

    In the past decades, ferroelectric materials have attracted wide attention due to their applications in nonvolatile memory devices (NVMDs) rendered by the electrically switchable spontaneous polarizations. Furthermore, the combination of ferroelectric and nanomaterials opens a new route to fabricating a nanoscale memory device with ultrahigh memory integration, which greatly eases the ever increasing scaling and economic challenges encountered in the traditional semiconductor industry. In this review, we summarize the recent development of the nonvolatile ferroelectric field effect transistor (FeFET) memory devices based on nanostructures. The operating principles of FeFET are introduced first, followed by the discussion of the real FeFET memory nanodevices based on oxide nanowires, nanoparticles, semiconductor nanotetrapods, carbon nanotubes, and graphene. Finally, we present the opportunities and challenges in nanomemory devices and our views on the future prospects of NVMDs. PMID:22655750

  7. Ergodicity and nonergodicity in La-doped Bi1/2(Na0.82K0.18)1/2TiO3 relaxors

    NASA Astrophysics Data System (ADS)

    Dinh, Thi Hinh; Han, Hyoung-Su; Lee, Jae-Shin; Ahn, Chang-Won; Kim, Ill-Won; Bafandeh, Mohammad Reza

    2015-04-01

    The phase transition of La-doped [Bi1/2(Na0.82K0.18)1/2]TiO3 (BNKT) ceramics was investigated by using high-temperature X-ray diffraction and temperature-dependent dielectric measurements. Undoped BNKT was found to be a nonergodic relaxor, which was evidenced by the presence of a depolarization temperature below which polar nanoregions were frozen. However, La-doped BNKT ceramics are believed to be composites consisting of ergodic and nonergodic relaxors. The results suggest that a nonergodic relaxor with tetragonal symmetry might be distributed in an ergodic relaxor matrix with pseudocubic symmetry.

  8. Ferroelectric Fluid Flow Control Valve

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    1999-01-01

    An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.

  9. Ferroelectric gated electrical transport in CdS nanotetrapods.

    PubMed

    Fu, Wangyang; Qin, Shengyong; Liu, Lei; Kim, Tae-Hwan; Hellstrom, Sondra; Wang, Wenlong; Liang, Wenjie; Bai, Xuedong; Li, An-Ping; Wang, Enge

    2011-05-11

    Complex nanostructures such as branched semiconductor nanotetrapods are promising building blocks for next-generation nanoelectronics. Here we report on the electrical transport properties of individual CdS tetrapods in a field effect transistor (FET) configuration with a ferroelectric Ba(0.7)Sr(0.3)TiO(3) film as high-k, switchable gate dielectric. A cryogenic four-probe scanning tunneling microscopy (STM) is used to probe the electrical transport through individual nanotetrapods at different temperatures. A p-type field effect is observed at room temperature, owing to the enhanced gate capacitance coupling. And the reversible remnant polarization of the ferroelectric gate dielectric leads to a well-defined nonvolatile memory effect. The field effect is shown to originate from the channel tuning in the arm/core/arm junctions of nanotetrapods. At low temperature (8.5 K), the nanotetrapod devices exhibit a ferroelectric-modulated single-electron transistor (SET) behavior. The results illustrate how the characteristics of a ferroelectric such as switchable polarization and high dielectric constant can be exploited to control the functionality of individual three-dimensional nanoarchitectures. PMID:21513340

  10. First-principles prediction of a native ferroelectric metal

    NASA Astrophysics Data System (ADS)

    Iniguez, Jorge; Filippetti, Alessio; Fiorentini, Vincenzo; Ricci, Francesco; Delugas, Pietro

    The possibility that metals may support ferroelectricity is an intriguing open issue. Over the years, various compounds have been referred to as ferroelectric metals, including non-centrosymmetric metals as well as ferroelectrics whose polar distortion survives moderate metallicity induced by doping or proximity. Yet, we think none of these systems embodies a truly ferroelectric metal with native switchable polarization and native metallicity coexisting in a single phase. Here we report a first-principles prediction of such a material. We show that the layered perovskite Bi5Ti5O17 has a non-zero density of states at the Fermi level and metal-like conductivity, as well as a spontaneous polarization in zero field. Further, we predict that the polarization of Bi5Ti5O17 is switchable both in principle (the material complies with the sufficient symmetry requirements) and in practice (in spite of being a metal, Bi5Ti5O17 can sustain a sizable potential drop along the polar direction, as needed to revert its polarization by application of an electric bias). Our results also reveal striking behaviors - such as the self screening mechanism at work in thin Bi5Ti5O17 layers - emerging from the intimate interplay between polar distortions and free carriers in such an exotic material. Supported by MIUR-PRIN, Fondazione Banco di Sardegna, FNR Luxembourg, MINECO-Spain, CINECA-ISCRA and CESGA.

  11. Generalized Ferroelectricity in the Mesomorphic Phase of Nylon Polymers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongbo; Zhu, Lei; Litt, Morton

    Novel ferroelectric polymers, featured by narrow electric displacement-electric (D-E) hysteresis loop, are attractive for electric energy storage applications due to their high dielectric constant and low loss property. Currently, only poly(vinylidene fluoride) (PVDF)-based copolymers (e-beamed) and terpolymers show novel ferroelectric behavior. It is desired to achieve novel ferroelectricity in other polymers such as nylons by carefully modifying the chemical and crystal structures. In this presentation, isomorphic crystals are successfully achieved by copolymerization of nylon 11 and nylon 12 with different compositions. In this way, both chemical and structural defects (i.e., dangling amide groups and kinked bonds) are introduced into the mesomorphic phase. As a consequence, hydrogen bonding interaction is successfully weakened and thus enhanced ferroelectricity with higher maximum polarization and better polarizability is obtained. In addition, for the purpose of further disturbing the mesomorphic phase and pinning effect, partially methylated nylon copolymers are synthesized. With the help of N-methylation of amide groups, the methylated nylon copolymers show relatively narrow hysteresis loops, suggesting the pinning effect from the N-methylated amide moieties.

  12. Stabilizing the ferroelectric phase in doped hafnium oxide

    SciTech Connect

    Hoffmann, M.; Schroeder, U.; Schenk, T.; Shimizu, T.; Funakubo, H.; Sakata, O.; Pohl, D.; Drescher, M.; Adelmann, C.; Materlik, R.; Kersch, A.; Mikolajick, T.

    2015-08-21

    The ferroelectric properties and crystal structure of doped HfO{sub 2} thin films were investigated for different thicknesses, electrode materials, and annealing conditions. Metal-ferroelectric-metal capacitors containing Gd:HfO{sub 2} showed no reduction of the polarization within the studied thickness range, in contrast to hafnia films with other dopants. A qualitative model describing the influence of basic process parameters on the crystal structure of HfO{sub 2} was proposed. The influence of different structural parameters on the field cycling behavior was examined. This revealed the wake-up effect in doped HfO{sub 2} to be dominated by interface induced effects, rather than a field induced phase transition. TaN electrodes were shown to considerably enhance the stabilization of the ferroelectric phase in HfO{sub 2} compared to TiN electrodes, yielding a P{sub r} of up to 35 μC/cm{sup 2}. This effect was attributed to the interface oxidation of the electrodes during annealing, resulting in a different density of oxygen vacancies in the Gd:HfO{sub 2} films. Ab initio simulations confirmed the influence of oxygen vacancies on the phase stability of ferroelectric HfO{sub 2}.

  13. Ferroelectric, Thermal, and Magnetic Characteristics of Praseodymium Malonate Hexahydrate Crystals

    NASA Astrophysics Data System (ADS)

    Ahmad, Nazir; Ahmad, M. M.; Kotru, P. N.

    2016-04-01

    Gel-grown single crystals of [Pr2(C3H2O4)3(H2O)6] exhibit remarkably flat habit faces, the most predominant being {110}. High-resolution x-ray diffraction analysis showed that the crystals are free from structural grain boundaries, which is the key requirement for single crystals for use in the microelectronics industry to serve as low-dielectric-constant ferroelectric material. The dielectric behavior recorded on {110} planes of single crystals shows that the crystal is ferroelectric with transition temperature T c = 135°C, which differs from the Curie-Weiss temperature T 0 by 2°C (T 0 < T c). Material in pellet form is shown to exhibit slightly different dielectric behavior. Polarization versus electric field confirms the ferroelectric behavior of the material. The dielectric behavior is also supported by the results of thermal studies, viz. thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The magnetic susceptibility and magnetic moment are calculated to be 30.045 × 10-6 emu and 3.092 BM, respectively.

  14. Glassy polarization behavior in ferroelectric compounds Pb(Mg{1}/{3}Nb{2}/{3}) O3 and Pb(Zn{1}/{3}Nb{2}/{3}) O3

    NASA Astrophysics Data System (ADS)

    Burns, Gerald; Dacol, F. H.

    1983-12-01

    We report measurements of the temperature dependence of the optic index of refraction, n(T), at several wave lengths in two ferroelectric compounds that have the simple perovskite ABO 3 structure. The compounds are Pb(Mg{1}/{3}Nb{2}/{3}) O3 and Pb(Zn{1}/{3}Nb{2}/{3}) O3 where the B-site ions are disordered. Deviations from the high temperature linear n(T) can be observed starting at a temperature T d (far above the ferroelectric phase transition temperature T c). We assume a model in which these deviations arise from very local randomly oriented polarization (i.e. glassy polarization), P d. Then, using the quadratic electrooptic effect and the known coefficients, we determine P d and compare it to the normally observed ferroelectric reversible spontaneous polarization P r. Also, from infrared reflectivity data, we show that these materials are microscopically homogeneous. We believe that our model of the phase transition contains the basic physics describing ferroelectrics with diffuse phase transitions.

  15. True ferroelectric switching in thin films of trialkylbenzene-1,3,5-tricarboxamide (BTA).

    PubMed

    Gorbunov, A V; Putzeys, T; Urbanavičiūtė, I; Janssen, R A J; Wübbenhorst, M; Sijbesma, R P; Kemerink, M

    2016-08-24

    We have investigated the ferroelectric polarization switching properties of trialkylbenzene-1,3,5-tricarboxamide (BTA), which is a model system for a large class of novel organic ferroelectric materials. In the solid state BTAs form a liquid crystalline columnar hexagonal phase that provides long range order that was previously shown to give rise to hysteretic dipolar switching. In this work the nature of the polar switching process is investigated by a combination of dielectric relaxation spectroscopy, depth-resolved pyroelectric response measurements, and classical frequency- and time-dependent electrical switching. We show that BTAs, when brought in a homeotropically aligned hexagonal liquid crystalline phase, are truly ferroelectric. Analysis of the transient switching behavior suggests that the ferroelectric switching is limited by a highly dispersive nucleation process, giving rise to a wide distribution of switching times. PMID:27510767

  16. Dielectric and Magnetic Properties in Relaxor Magnet LuFeCoO4

    NASA Astrophysics Data System (ADS)

    Soda, Minoru; Masuda, Takatsugu

    2016-03-01

    Dielectric and magnetic properties in the relaxor magnet LuFeCoO4 having a triangular lattice are studied by permittivity, magnetization, and neutron diffraction measurements. We found that LuFeCoO4 has the nuclear diffuse scattering induced by Polar Nanoregions (PNRs) where local polarizations in nanoregions are randomly oriented. Synchronized changes in PNRs and magnetic short-range order with decreasing temperature are observed, which reveal the existence of the strong coupling between dielectricity and magnetism. The coincidence of the correlation lengths of the nuclear atoms and spins in the crystallographic a-b plane at the onset temperature of two-dimensional magnetic order is confirmed, suggesting that the magnetic order develops inside the PNRs. With further decreasing temperature, the magnetic correlation extends beyond the domain wall of the crystal cluster in contrast with another relaxor magnet BiFeO3-1/3BaTiO3.

  17. Dielectric studies of iron nanoparticles-ferroelectric liquid crystal mixture

    NASA Astrophysics Data System (ADS)

    Khushboo, Sharma, Puneet; Jayoti, Divya; Malik, Praveen; Raina, K. K.

    2016-05-01

    Iron nanoparticles doped ferroelectric liquid crystal mixtures have been prepared and studied in thin planar cell. The effect of temperature and frequency on permittivity behavior in SmC* phase has been studied. Permittivity increases with increasing the temperature in SmC* phase and show a reduction near the SmC*-SmA transition temperature. A Goldstone mode is clearly observed at ~100 Hz.

  18. Vibrational, magnetic, and dielectric behavior of La-substituted BiFeO3-PbTiO3

    NASA Astrophysics Data System (ADS)

    Mishra, K. K.; Satya, A. T.; Bharathi, A.; Sivasubramanian, V.; Murthy, V. R. K.; Arora, A. K.

    2011-12-01

    Phonons and magnetic and ferroelectric ordering in La-substituted (Bi1-xLax)0.5Pb0.5Fe0.5Ti0.5O3 for samples with 0.0 ≤ x ≤ 0.5 are investigated using Raman, magnetization, and polarization measurements as a function of temperature. The system is tetragonal for pure Bi0.5Pb0.5Fe0.5Ti0.5O3 with a large c/a ratio. The anisotropy is reduced when Bi is partially replaced by La (0 ≤ x ≤ 0.5), and it turns cubic for x ≥ 0.4. All the properties are found to change significantly with changes in the c/a ratio. Evidence of spin-glass-like magnetic ordering at low temperature is found in the case of x = 0.2. A mechanism for the systematic change of magnetic ordering temperature as a function of doping is also discussed. The phonon frequencies and line widths exhibit discontinuous changes across the tetragonal-cubic transition. Large polarization and forbidden Raman scattering in the cubic phase are explained on the basis of symmetry breaking due to the formation of a polar nano region, which leads to relaxor behavior.

  19. Relaxor-PbTiO3 single crystals for various applications.

    PubMed

    Zhang, Shujun; Li, Fei; Luo, Jun; Sahul, Raffi; Shrout, Thomas R

    2013-08-01

    Piezoelectric materials lie at the heart of electromechanical devices. Applications include actuators, ultrasonic imaging, high intensity focused ultrasound, underwater ultrasound, nondestructive evaluation transducer, pressure sensors, and accelerometers, to name a few. In this work, the advantages and disadvantages of relaxor-PbTiO(3)-based single crystals are discussed, based on the requirements (figure of merit) of various applications, with emphasis on recent developments of the shear properties of single crystals as a function of temperature and applied fields. PMID:25004527

  20. Relaxor-PbTiO3 Single Crystals for Various Applications

    PubMed Central

    Zhang, Shujun; Li, Fei; Luo, Jun; Sahul, Raffi; Shrout, Thomas R.

    2014-01-01

    Piezoelectric materials lie at the heart of electromechanical devices. Applications include actuators, ultrasonic imaging, high intensity focused ultrasound, underwater ultrasound, nondestructive evaluation transducer, pressure sensors, and accelerometers, to name a few. In this work, the advantages and disadvantages of relaxor-PbTiO3-based single crystals are discussed, based on the requirements (figure of merit) of various applications, with emphasis on recent developments of the shear properties of single crystals as a function of temperature and applied fields. PMID:25004527

  1. Pretransitional diffuse neutron scattering in the mixed perovskite relaxor K1-xLixTaO3

    NASA Astrophysics Data System (ADS)

    Yong, Grace; Toulouse, Jean; Erwin, Ross; Shapiro, Stephen M.; Hennion, Bernard

    2000-12-01

    Several previous studies of K1-xLixTaO3 (KLT) have revealed the presence, above the structural transition, of polar nanoregions. Recently, these have been shown to play an essential role in the relaxor behavior of KLT. In order to characterize these regions, we have performed a neutron-scattering study of KLT crystals with different lithium concentrations, both above and below the critical concentration. This study reveals the existence of diffuse scattering that appears upon formation of these regions. The rodlike distribution of the diffuse scattering along cubic directions indicates that the regions form in the shape of discs in the various cubic planes. From the width of the diffuse scattering we extract values for a correlation length or size of the regions as a function of temperature. Finally, on the basis of the reciprocal lattice points around which the diffuse scattering is most intense, we conclude that the regions have tetragonal symmetry. The large increase in Bragg intensities at the first-order transition suggests that the polar regions freeze to form large structural domains and the transition is triggered by the percolation of strain fields through the crystals.

  2. Nanoporous piezo- and ferroelectric thin films.

    PubMed

    Ferreira, Paula; Hou, Ru Z; Wu, Aiying; Willinger, Marc-Georg; Vilarinho, Paula M; Mosa, Jadra; Laberty-Robert, Christel; Boissière, Cédric; Grosso, David; Sanchez, Clément

    2012-02-01

    Nanoporous barium titanate and lead titanate thin films (∼100 nm calculated from ellipsometric data) are prepared starting from sol-gel solutions modified with a commercially available block-copolymer and evaporation-induced self-assembly methodology. The tuning of the thermal treatment followed by in situ ellipsometry allows the decomposition of the organic components and of the structuring agent leading to the formation of porous tetragonal crystalline perovskite structures as observed by XRD, HRTEM, SEM, and ellipsoporosimetry. Both nanoporous barium titanate and lead titanate thin films present local piezoelectric and ferroelectric behavior measured by piezoresponse force microscopy (PFM), being promising platforms for the preparation of the generation of new multifunctional systems. PMID:22206407

  3. Influence of lattice polarizability on interacting Li-induced dipoles distributed in incipient ferroelectric KTaO3

    NASA Astrophysics Data System (ADS)

    Ichikawa, Yuki; Tanaka, Koichiro

    2008-04-01

    Susceptibility purely originated from the Li-induced quasistatic dipoles in relaxor K1-xLixTaO3 has been extracted from low-frequency permittivity using terahertz time-domain spectroscopy. The temperature dependence of the extracted susceptibility has an anomaly at the critical temperature Ta near 100 K with the critical slowing down of the low-frequency relaxation process. From a detailed analysis of the extracted susceptibility, we attributed the main part of the susceptibility for x≤0.036 to the high-frequency relaxation process and concluded that there are two relevant interactions that govern the ferroelectric coupling between Li-induced dipoles and that the interplay of the two interactions gives rise to a complex temperature dependence of the susceptibility originated from Li-induced dipoles. Below the critical concentration x<0.022 , short-range interaction between individual Li ions should be dominant. Above the critical concentration, x>0.022 , Coulomb interaction should be dominant. The crossover from the low-temperature glasslike phase to the low-temperature ferroelectric domain-state across xc in K1-xLixTaO3 is attributed to the interplay of the two kinds of interaction.

  4. Structure-Curie temperature relationships in BaTiO3-based ferroelectric perovskites: Anomalous behavior of (Ba ,Cd )TiO3 from DFT, statistical inference, and experiments

    NASA Astrophysics Data System (ADS)

    Balachandran, Prasanna V.; Xue, Dezhen; Lookman, Turab

    2016-04-01

    One of the key impediments to the development of BaTiO3-based materials as candidates to replace toxic-Pb-based solid solutions is their relatively low ferroelectric Curie temperature (TC). Among many potential routes that are available to modify TC, ionic substitutions at the Ba and Ti sites remain the most common approach. Here, we perform density functional theory (DFT) calculations on a series of A TiO3 and Ba B O3 perovskites, where A =Ba , Ca, Sr, Pb, Cd, Sn, and Mg and B =Ti , Zr, Hf, and Sn. Our objective is to study the relative role of A and B cations in impacting the TC of the tetragonal (P 4 m m ) and rhombohedral (R 3 m ) ferroelectric phases in BaTiO3-based solid solutions, respectively. Using symmetry-mode analysis, we obtain a quantitative description of the relative contributions of various divalent (A ) and tetravalent (B ) cations to the ferroelectric distortions. Our results show that Ca, Pb, Cd, Sn, and Mg have large mode amplitudes for ferroelectric distortion in the tetragonal phase relative to Ba, whereas Sr suppresses the distortions. On the other hand, Zr, Hf, and Sn tetravalent cations severely suppress the ferroelectric distortion in the rhombohedral phase relative to Ti. In addition to symmetry modes, our calculated unit-cell volume also agrees with the experimental trends. We subsequently utilize the symmetry modes and unit-cell volumes as features within a machine learning approach to learn TC via an inference model and uncover trends that provide insights into the design of new high-TCBaTiO3 -based ferroelectrics. The inference model predicts CdTiO3-BaTiO3 solid solutions to have a higher TC and, therefore, we experimentally synthesized these solid solutions and measured their TC. Although the calculated mode strength for CdTiO3 in the tetragonal phase is even larger than that for PbTiO3, the TC of CdTiO3-BaTiO3 solid solutions in the tetragonal phase does not show any appreciable enhancement. Thus, CdTiO3-BaTiO3 does not follow the

  5. Structure and Dynamics of Domains in Ferroelectric Nanostructures. In-situ TEM Studies

    SciTech Connect

    Pan, Xiaoqing

    2015-06-30

    The goal of this project was to explore the structure and dynamic behaviors of ferroelectric domains in ferroelectric thin films and nanostructures by advanced transmission electron microscopy (TEM) techniques in close collaboration with phase field modeling. The experimental techniques used include aberration-corrected sub-Å resolution TEM and in-situ TEM using a novel scanning tunneling microscopy (STM) - TEM holder that allows the direct observation of nucleation and dynamic evolution of ferroelectric domains under applied electric field. Specifically, this project was aimed to (1) to study the roles of static electrical boundary conditions and electrical charge in controlling the equilibrium domain structures of BiFeO3 thin films with controlled substrate constraints, (2) to explore the fundamental mechanisms of ferroelectric domain nucleation, growth, and switching under an applied electric field in both uniform thin films and nanostructures, and to understand the roles of crystal defects such as dislocations and interfaces in these processes, (3) to understand the physics of ferroelectric domain walls and the influence of defects on the electrical switching of ferroelectric domains.

  6. Coupling of electrical and mechanical switching in nanoscale ferroelectrics

    NASA Astrophysics Data System (ADS)

    Cao, Ye; Li, Qian; Chen, Long-Qing; Kalinin, Sergei V.

    2015-11-01

    While electric field induced ferroelectric switching has been extensively studied and broadly utilized, pure mechanical switching via flexoelectric effect has recently opened up an alternative method for domain writing due to their highly localized, electrically erasable and electric damage free characteristics. Thus far, few studies have been made on the coupling effect of electro-mechanical switching in ferroelectric materials, likely due to the experimental difficulty in the accurate definition of the tip-surface contact area and in the identification of mechanical contribution from electrical effect. Here, we employed self-consistent phase-field modeling to investigate the bi-polar switching behavior of (001) oriented Pb(Zr0.2Ti0.8)O3 thin film under concurrent electric and strain field created via a piezoresponse force microscope probe. By separating the effects from electric field, homogeneous strain and strain gradient, we revealed that the homogeneous strain suppresses the spontaneous polarization and accordingly increases the coercive field, and the strain gradient favors unipolar switching and inhibit it in the reverse direction, thus causing lateral offset of the hysteresis loop. The uncertainty of flexoelectric coefficients and the influence of flexocoupling coefficients on switching have also been discussed. Our study could necessitate further understanding of the electric, piezoelectric, and flexoelectric contribution to the switching behavior in nanoscale ferroelectric oxides.

  7. Electrostatic engineering of strained ferroelectric perovskites from first principles

    NASA Astrophysics Data System (ADS)

    Cazorla, Claudio; Stengel, Massimiliano

    2015-12-01

    Design of novel artificial materials based on ferroelectric perovskites relies on the basic principles of electrostatic coupling and in-plane lattice matching. These rules state that the out-of-plane component of the electric displacement field and the in-plane components of the strain are preserved across a layered superlattice, provided that certain growth conditions are respected. Intense research is currently directed at optimizing materials functionalities based on these guidelines, often with remarkable success. Such principles, however, are of limited practical use unless one disposes of reliable data on how a given material behaves under arbitrary electrical and mechanical boundary conditions. Here we demonstrate, by focusing on the prototypical ferroelectrics PbTiO3 and BiFeO3 as test cases, how such information can be calculated from first principles in a systematic and efficient way. In particular, we construct a series of two-dimensional maps that describe the behavior of either compound (e.g., concerning the ferroelectric polarization and antiferrodistortive instabilities) at any conceivable choice of the in-plane lattice parameter, a , and out-of-plane electric displacement, D . In addition to being of immediate practical applicability to superlattice design, our results bring new insight into the complex interplay of competing degrees of freedom in perovskite materials and reveal some notable instances where the behavior of these materials depart from what naively is expected.

  8. Impact of substrate on structure and electrical properties in lead-based ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Valanoor, Nagarajan Venkatasubramanian

    polydomain formation on quasi-static and dynamic polarization switching. To correlate the material microstructure to switching, an activation field, alpha, is introduced. It is shown theoretically that alpha ∝ (c/a-1)3.5 and a good experimental fit can be obtained. However it is observed that polydomain formation does not impact the electromechanical and dielectric response significantly. It is shown experimentally and theoretically that stress-induced polarization varies only by 10%. Therefore to study the impact of in plane stresses induced by substrate on piezoelectric and dielectric response we chose a "soft" relaxor ferroelectric (RFE) wherein the Curie temperature is close to room temperature. In this case even a small application of stress can change the properties significantly. The relaxor composition chosen was PbMg1/3Nb 2/3O3(90%)-PbTiO3(10%). By systematically changing the substrate and the thickness, stresses in the film the electromechanical constants is varied. High-resolution electron microscopy revealed a distinct change in the microstructure as a function of thickness, and a probable answer as to why thin films show inferior properties compared to bulk materials is proposed. The last part of this thesis focuses on the effect of micro stresses. Two examples are demonstrated where the mechanical forces of interaction between the film and substrate are manipulated on a very local scale. We show that by inducing stresses at local regions one can induce polydomains in film thinner than previously calculated critical thickness, while by removing constraint at local regions we can enhance the d33 co-efficient to values higher than those shown by bulk ceramics.

  9. Domain engineered ferroelectric energy harvesters on a substrate

    NASA Astrophysics Data System (ADS)

    Münch, I.; Krauß, M.; Landis, C. M.; Huber, J. E.

    2011-05-01

    Phase-field modeling is used to study the domain evolution of nano-scaled ferroelectric devices influenced by the mechanical strain of an underlying substrate. The investigations focus on the design of the energy harvesting systems to convert mechanical into electrical energy. Mechanical energy is provided by an alternating in-plane strain in the substrate through bending or unidirectional stretching. Additionally, lattice mismatch between the substrate and the ferroelectric material induces epitaxial strain and controls the polarization behavior within the system. Further, electrical boundary conditions are used to stabilize the domain topology. Finite element simulations are employed to explore the performance of the engineered domain topologies in delivering electrical charge from mechanical deformation.

  10. Scaling of electroresistance effect in fully integrated ferroelectric tunnel junctions

    NASA Astrophysics Data System (ADS)

    Abuwasib, Mohammad; Lu, Haidong; Li, Tao; Buragohain, Pratyush; Lee, Hyungwoo; Eom, Chang-Beom; Gruverman, Alexei; Singisetti, Uttam

    2016-04-01

    Systematic investigation of the scalability for tunneling electroresistance (TER) of integrated Co/BaTiO3/SrRuO3 ferroelectric tunnel junctions (FTJs) has been performed from micron to deep submicron dimensions. Pulsed measurements of the transient currents confirm the ferroelectric switching behavior of the FTJs, while the hysteresis loops measured by means of piezoresponse force microscopy verify the scalability of these structures. Fully integrated functional FTJ devices with the size of 300 × 300 nm2 exhibiting a tunneling electroresistance (TER) effect of the order of 2.7 × 104% have been fabricated and tested. Measured current density of 75 A/cm2 for the ON state and a long polarization retention time of ON state (>10 h) show a lot of promise for implementation of high-density BaTiO3-based FTJ memory devices in future.

  11. Nanocharacterization of the negative stiffness of ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Alipour Skandani, A.; Ctvrtlik, R.; Al-Haik, M.

    2014-08-01

    Phase changing materials such as ferroelectric materials could exhibit negative stiffness under certain thermomechanical environments. This negative stiffness is embodied by a deflection along the opposite direction of the applied load. So far negative stiffness materials were investigated with the specific morphology of embedded inclusions in stiff matrices then the resulting composite is studied to measure the behavior of each constituent indirectly. In this study, a modified nonisothermal nanoindentation method is developed to measure the negative stiffness of triglycine sulfate single crystal directly. This in-situ method is intended to first demonstrate the feasibility of detecting the negative stiffness via nanoindentation and nanocreep of a ferroelectric material at its Curie point and then to quantify the negative stiffness without the need for embedding the crystal within a stiffer matrix.

  12. Ionic field effect and memristive phenomena in single-point ferroelectric domain switching

    SciTech Connect

    Ievlev, Anton; Morozovska, A. N.; Eliseev, E. A.; Shur, Vladimir Ya.; Kalinin, Sergei V

    2014-01-01

    Electric field induced polarization switching underpins most functional applications of ferroelectric materials in information technology, materials science, and optoelectronics. In the last 20 years, much attention has been focused on the switching of individual domains using scanning probe microscopy, both as model of ferroelectric data storage and approach to explore fundamental physics of ferroelectric switching. The classical picture of tip induced switching includes formation of cylindrical domain oriented along the tip field, with the domain size is largely determined by the tip-induced field distribution and domain wall motion kinetics. The polarization screening is recognized as a necessary precondition to the stability of ferroelectric phase; however, screening processes are generally considered to be uniformly efficient and not leading to changes in switching behavior. Here, we demonstrate that single-point tip-induced polarization switching can give rise to a surprisingly broad range of domain morphologies, including radial and angular instabilities. These behaviors are traced to the surface screening charge dynamics, which in some cases can even give rise to anomalous switching against the electric field (ionic field effect). The implications of these behaviors for ferroelectric materials and devices are discussed.

  13. Ferroelectric Stirling-Cycle Refrigerator

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    1999-01-01

    A Stirling-cycle refrigerator has a three-pump configuration and pumping sequence, in which one pump serves as a compressor. one pump serves as an expander, and one pump serves as a displacer. The pumps are ferroelectrically actuated diaphragm pumps which are coordinated by synchronizing the ferroelectric-actuator voltages in such a way that the net effect of the displacer is to reduce the deleterious effect of dead space; that is, to circulate a greater fraction of the working fluid through the heat exchangers than would be possible by use of the compressor and expander alone. In addition. the displacer can be controlled separately to make the flow of working fluid in the heat exchangers turbulent (to increase the rate of transfer of heat at the cost of greater resistance to flow) or laminar (to decrease the resistance to flow at the cost of a lower heat-transfer rate).

  14. Grain size effect on phase transition behavior and electrical properties of (Bi1/2K1/2)TiO3 piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Hagiwara, Manabu; Fujihara, Shinobu

    2015-10-01

    Dense and phase-pure (Bi1/2K1/2)TiO3 (BKT) ceramics with various grain sizes from 0.18 to 1.01 µm were prepared by conventional sintering of a hydrothermally synthesized fine powder. The decrease in grain size resulted in the reductions in tetragonality, remanent polarization, and the piezoelectric d33 coefficient, whereas the room-temperature dielectric permittivity slightly increased with decreasing grain size. The measurement of the temperature dependence of permittivity revealed that BKT exhibited the spontaneous relaxor-to-normal ferroelectric (R-nFE) phase transition. It was also found that the maximum permittivity was decreased and the R-nFE transition was inhibited by the reduction in grain size. In this paper, on the basis of the observed grain-size-dependent phase transition behaviors, microstructural models are proposed for both coarse- and fine-grained BKT ceramics, and the mechanism underlying the grain size effect on the electrical properties is discussed.

  15. Ferroelectric-dielectric tunable composites

    NASA Astrophysics Data System (ADS)

    Sherman, Vladimir O.; Tagantsev, Alexander K.; Setter, Nava; Iddles, David; Price, Tim

    2006-04-01

    The dielectric response of ferroelectric-dielectric composites is theoretically addressed. Dielectric permittivity, tunability (relative change of the permittivity driven by dc electric field), and loss tangent are evaluated for various composite models. The analytical results for small dielectric concentration and relative tunability are obtained in terms of the traditional electrostatic consideration. The results for large tunability are obtained numerically. A method is proposed for the evaluation of the tunability and loss at large concentrations of the dielectric. The basic idea of the method is to reformulate the effective medium approach in terms of electrical energies stored and dissipated in the composite. The important practical conclusion of the paper is that, for random ferroelectric-dielectric composite, the addition of small amounts of a linear dielectric into the tunable ferroelectric results in an increase of the tunability of the mixture. The loss tangent of such composites is shown to be virtually unaffected by the addition of moderate amounts of the low-loss dielectric. The experimental data for (Ba,Sr)TiO3 based composites are analyzed in terms of the theory developed and shown to be in a reasonable agreement with the theoretical results.

  16. Ferroelectric studies of excessive Sm{sup 3+} containing perovskite PZT and pyrochlore biphase ceramics

    SciTech Connect

    Babu, T. Anil; Sastry, D. L.; Ramesh, K. V.; Reddy, V. Raghavendra

    2014-04-24

    Polycrystalline samples of Sm{sup 3+} modified Pb{sub 1−x} Sm{sub 2x/3} (Zr{sub 0.6}Ti{sub 0.4}) O{sub 3} (PSZT) ceramics (where x = 0.1, 0.2, 0.3, 0.4) have been prepared by a high energy ball milling technique, followed by calcination at 950°C and sintering at 1150°C. As x is increased more than 0.1 mole%, considerable secondary phase has been formed. This phase has been identified as pyrochlore Sm{sub 2}Ti{sub 2}O{sub 7} from its X-ray diffraction (XRD) peaks. The XRD studies also indicate that the perovskte phases of the present systems undergo a dopant induced phase transformation from rhombohedral to tetragonal strucure. All the samples exhibit diffuse but non-relaxor type ferroelectric phase transition. The results of dielectric and hysteresis studies of these materials are presented.

  17. Structural, Dielectric, Piezoelectric and Ferroelectric Characterization of NBT-BT Lead-Free Piezoelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Shanmuga Sundari, S.; Kumar, Binay; Dhanasekaran, R.

    2013-05-01

    Lead free piezoelectric 0.94(Na0.5Bi0.5)TiO3-0.06BaTiO3 (NBT-BT) ceramics were synthesized in MPB composition by conventional solid state reaction method. The crystalline nature of NBT-BT ceramic was studied by XRD and the size of the grains are determined by SEM. The X- ray diffraction results reveal that Ba2+ diffuse into the Na0.5 Bi0.5TiO3 lattices to form a solid solution with a pure perovskite structure. Because of the strong ferroelectricity and MPB, the ceramics exhibit high piezoelectric properties: d33 = 206 pC/N. Td (depolarization temperature) and Tm (temperature at with the dielectric constant epsilonr reaches a maximum) were observed through the phase transition in dielectric studies. In addition, the prepared ceramic exhibits relaxor characteristic, which probably results from the cation disordering in the 12fold coordination sites. Pr and Ec of the prepared ceramics were determined from the P-E hysteresis loop.

  18. Scaling effects of relaxor-PbTiO3 crystals and composites for high frequency ultrasound

    PubMed Central

    Lee, Hyeong Jae; Zhang, Shujun; Shrout, Thomas R.

    2010-01-01

    The dielectric and piezoelectric properties of Pb(Mg1∕3Nb2∕3)O3–PbTiO3 (PMN-PT) and Pb(In1∕2Nb1∕2)O3–Pb(Mg1∕3Nb2∕3)O3–PbTiO3 (PIN-PMN-PT) ferroelectric single crystals were investigated as a function of thickness∕scale in monolithic and piezoelectric∕polymer 1–3 composites. For the case of PMN-PT single crystals, the dielectric (ε33T∕ε0) and electromechanical properties (k33) were found to significantly decrease with decreasing thickness (500–40 μm), while minimal thickness dependency was observed for PIN-PMN-PT single crystals. Temperature dependent dielectric behavior of the crystals suggested that the observed thickness dependence in PMN-PT was strongly related to their relatively large domain size (>10–20 μm). As anticipated, 1–3 composite comprised of PIN-PMN-PT crystals exhibited superior properties to that of PMN-PT composite at high frequencies (>20 MHz). However, the observed couplings, being on the order of 80%, were disappointedly low when compared to their monolithic counterparts, the result of surface damage introduced during the dicing process, as evidenced by the broadened [002] peaks in the x-ray diffraction pattern. PMID:20644658

  19. Quantum Monte Carlo simulation of the ferroelectric or ferrielectric nanowire with core shell morphology

    NASA Astrophysics Data System (ADS)

    Feraoun, A.; Zaim, A.; Kerouad, M.

    2016-09-01

    By using the Quantum Monte Carlo simulation; the electric properties of a nanowire, consisting of a ferroelectric core of spin-1/2 surrounded by a ferroelectric shell of spin-1/2 with ferro- or anti-ferroelectric interfacial coupling have been studied within the framework of the Transverse Ising Model (TIM). We have examined the effects of the shell coupling Js, the interfacial coupling JInt, the transverse field Ω, and the temperature T on the hysteresis behavior and on the electric properties of the system. The remanent polarization and the coercive field as a function of the transverse field and the temperature are examined. A number of characteristic behavior have been found such as the appearance of triple hysteresis loops for appropriate values of the system parameters.

  20. Polyimide thin-film dielectrics on ferroelectrics

    NASA Technical Reports Server (NTRS)

    Galiardi, R. V.

    1977-01-01

    Conducting layers of multi-layered thin-film ferroelectric device, such as is used in liquid crystal/ferroelectric display, can be electrically isolated using thin-film layer of polyimide. Ease of application and high electrical-breakdown strength allow dependable and economical means of providing dielectric for other thin-film microelectronic devices.

  1. A concept of ferroelectric microparticle propulsion thruster

    SciTech Connect

    Yarmolich, D.; Vekselman, V.; Krasik, Ya. E.

    2008-02-25

    A space propulsion concept using charged ferroelectric microparticles as a propellant is suggested. The measured ferroelectric plasma source thrust, produced mainly by microparticles emission, reaches {approx}9x10{sup -4} N. The obtained trajectories of microparticles demonstrate that the majority of the microparticles are positively charged, which permits further improvement of the thruster.

  2. Ferroelectric translational antiphase boundaries in nonpolar materials

    PubMed Central

    Wei, Xian-Kui; Tagantsev, Alexander K.; Kvasov, Alexander; Roleder, Krystian; Jia, Chun-Lin; Setter, Nava

    2014-01-01

    Ferroelectric materials are heavily used in electro-mechanics and electronics. Inside the ferroelectric, domain walls separate regions in which the spontaneous polarization is differently oriented. Properties of ferroelectric domain walls can differ from those of the domains themselves, leading to new exploitable phenomena. Even more exciting is that a non-ferroelectric material may have domain boundaries that are ferroelectric. Many materials possess translational antiphase boundaries. Such boundaries could be interesting entities to carry information if they were ferroelectric. Here we show first that antiphase boundaries in antiferroelectrics may possess ferroelectricity. We then identify these boundaries in the classical antiferroelectric lead zirconate and evidence their polarity by electron microscopy using negative spherical-aberration imaging technique. Ab initio modelling confirms the polar bi-stable nature of the walls. Ferroelectric antiphase boundaries could make high-density non-volatile memory; in comparison with the magnetic domain wall memory, they do not require current for operation and are an order of magnitude thinner. PMID:24398704

  3. Exploring and alleviating detrimental interface dipole effects in ultra-thin all-oxide metal-ferroelectric-metal heterostructures

    NASA Astrophysics Data System (ADS)

    Liu, Xiaohui; Wang, Yong; Lukashev, Pavel; Burton, J. D.; Tsymbal, Evgeny

    2012-02-01

    Ultrathin-film metal-ferroelectric-metal heterostructures present an exciting prospect for switchable nanoelectronic memories and devices such as ferroelectric tunnel junctions. The main challenge is to realize ferroelectricity in ultrathin-films where detrimental interface effects become increasingly more pronounced as ferroelectric film thicknesses approach the nanoscale. We studied the ferroelectric polarization of BaTiO3 in epitaxial SrRuO3/BaTiO3/SrRuO3 junctions by first-principles density functional theory and phenomenological modeling. The calculations show that the presence of a RuO2/BaO termination sequence at the SrRuO3/BaTiO3 interface leads to a pinned interface dipole and is therefore detrimental to the stability of ferroelectricity, leading to the disappearance of switchable polarization under a certain thickness. Here, we propose to alleviate this behavior by depositing a thin layer of SrTiO3 at this interface to suppress the RuO2/BaO interface termination sequence, thereby eliminating the associated unfavorable pinned interface dipole. By doing this we find, and experiments confirm, that a switchable ferroelectric state can be stabilized in much thinner heterostructures.

  4. Enhanced electrocaloric effect in displacive-type organic ferroelectrics

    SciTech Connect

    Ding, L. J. Zhong, Y.; Fan, S. W.; Zhu, L. Y.

    2015-08-07

    We explore the intrinsic feature of electrocaloric effect (ECE) accompanied by ferroelectric (FE)-paraelectric (PE) transition for displacive-type organic ferroelectrics using Green's function theory. It is demonstrated that decreasing elastic constant K or increasing spin-lattice coupling λ can enhance the ECE, as well as polarization P and transition temperature T{sub C}. Indeed, one expects that the optimal operating temperature for solid-state refrigeration is around room temperature, at which the ECE achieves its maximum. As T{sub C} is tuned to ∼310 K, it presents larger ECE response and remanent polarization with lower coercive field for smaller K value, suggesting that well flexible displacive-type organic ferroelectrics are excellent candidates both for electric cooling and data storage in the design of nonvolatile FE random-access memories. Furthermore, in an electric field, it provides a bridge between a Widom line that denotes FE-PE crossover above T{sub C} and a metaelectric transition line below T{sub C} that demonstrates an FE switching behavior with an antiparallel field.

  5. High Temperature Ferroelectrics for Actuators: Recent Developments and Challenges

    NASA Technical Reports Server (NTRS)

    Sehirlioglu, Alp; Kowalski, Benjamin

    2014-01-01

    A variety of piezoelectric applications have been driving the research in development of new high temperature ferroelectrics; ranging from broader markets such as fuel and gas modulation and deep well oil drilling to very specific applications such as thermoacoustic engines and ultrasonic drilling on the surface of Venus. The focus has been mostly on increasing the Curie temperature. However, greater challenges for high temperature ferroelectrics limit the operating temperature to levels much below the Curie temperature. These include enhanced loss tangent and dc conductivity at high fields as well as depoling due to thermally activated domain rotation. The initial work by Eitel et al. [Jpn. J. Appl. Phys., 40 [10, Part 1] 59996002 (2001)] increased interest in investigation of Bismuth containing perovskites in solid solution with lead titanate. Issues that arise vary from solubility limits to increased tetragonality; the former one prohibits processing of morphotropic phase boundary, while the latter one impedes thorough poling of the polycrystalline ceramics. This talk will summarize recent advances in development of high temperature piezoelectrics and provide information about challenges encountered as well as the approaches taken to improve the high temperature behavior of ferroelectrics with a focus on applications that employ the converse piezoelectric effect.

  6. Relaxor-like dielectric response of spin liquid CuCrO{sub 2}

    SciTech Connect

    Mazumder, N. Roy, R.; Ghorai, U. K.; Saha, S.; Chattopadhyay, K. K.

    2014-04-24

    Broadband dielectric analysis (10{sup −2}-10{sup 7} Hz) of layered triangular lattice CuCrO{sub 2} is performed (123 K - 473 K) and analyzed in connection with recently observed spin frustration in this multiferroic [M. Poienar et al. Phys. Rev. B 81, 104411, (2010); M. Frontzek et al. Phys. Rev. B 84, 094448, (2011)]. Most unexpectedly, this well known delafossite has found to have nontrivial charge degrees of freedom, being characterized by a relaxor-like dielectric relaxation around 375 K with FWHM of ∼100K. The result strongly suggests the existence of intermolecular Coulomb interaction between charge disproportionation induced electric dipoles.

  7. Thin Layer Composite Unimorph Ferroelectric Driver and Sensor

    NASA Technical Reports Server (NTRS)

    Helbaum, Richard F. (Inventor); Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor); Jalink, Antony, Jr. (Inventor); Rohrbach, Wayne W. (Inventor); Simpson, Joycelyn O. (Inventor)

    1995-01-01

    A method for forming ferroelectric wafers is provided. A prestress layer is placed on the desired mold. A ferroelectric wafer is placed on top of the prestress layer. The layers are heated and then cooled, causing the ferroelectric wafer to become prestressed. The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer. Wafers produced using this method have greatly improved output motion.

  8. Thin layer composite unimorph ferroelectric driver and sensor

    NASA Technical Reports Server (NTRS)

    Hellbaum, Richard F. (Inventor); Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor); Jalink, Jr., Antony (Inventor); Rohrbach, Wayne W. (Inventor); Simpson, Joycelyn O. (Inventor)

    2004-01-01

    A method for forming ferroelectric wafers is provided. A prestress layer is placed on the desired mold. A ferroelectric wafer is placed on top of the prestress layer. The layers are heated and then cooled, causing the ferroelectric wafer to become prestressed. The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer. Wafers produced using this method have greatly improved output motion.

  9. Thin Layer Composite Unimorph Ferroelectric Driver and Sensor

    NASA Technical Reports Server (NTRS)

    Hellbaum, Richard F. (Inventor); Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor)

    1997-01-01

    A method for forming ferroelectric wafers is provided. A prestress layer is placed on the desired mold. A ferroelectric wafer is placed on top of the prestress layer. The layers are heated and then cooled causing the ferroelectric wafer to become prestressed. The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer. Wafers produced using this method have greatly improved output motion.

  10. High photovoltages in ferroelectric ceramics

    NASA Technical Reports Server (NTRS)

    Brody, P. S.

    1976-01-01

    The short-circuit currents and photo-emfs were measured for various ceramics including barium titanate, lead metaniobate, and lead titanate. It is suggested that the emfs and currents arise from the presence of photoconductor-insulator sandwiches in the presence of space-charge-produced internal fields. Results are in agreement with the proposed theory and indicate that the ferroelectric ceramics are not only producers of high-voltage photoelectricity but a photo-battery, the polarity and magnitude of which can be switched by application of an electrical signal.

  11. Calligraphic Poling of Ferroelectric Material

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Strekalov, Dmitry; Savchenkov, Anatoliy; Matsko, Adrey; Maleki, Lute; Iltchenko, Vladimir

    2007-01-01

    Calligraphic poling is a technique for generating an arbitrary, possibly complex pattern of localized reversal in the direction of permanent polarization in a wafer of LiNbO3 or other ferroelectric material. The technique is so named because it involves a writing process in which a sharp electrode tip is moved across a surface of the wafer to expose the wafer to a polarizing electric field in the desired pattern. The technique is implemented by use of an apparatus, denoted a calligraphic poling machine (CPM), that includes the electrode and other components as described in more detail below.

  12. Structural studies on ferroelectric and ferrodistortive materials

    NASA Astrophysics Data System (ADS)

    Zou, Mingqin

    The structure of the piezoelectric material 0.68PbMg1/3Nb 2/3O3-0.32PbTiO3 have been studied by single crystal, powder x-ray diffraction techniques over the temperature range from 25°C to 200°C. The existence of twinned structures or coexistence of rhombohedral and tetragonal phases has been shown by the peak distortion of Bragg reflections. Superlattice structure was observed for all experimental PMN-PT crystals. Refinement results showed that the 2 x 2 x 2 superlattice resulted from anti-parallel displacement of oxygen in the adjacent conventional perovskite unit cells. No cation displacement in the paraelectric phase and little in the ferroelectric phase were shown by the refinement results. This unique feature associated with the ferroelectric mechanism of the material was explained by comparison with PbMg1/3Nb2/3O3. The crystals were extensively characterized by using powder x-ray diffraction, Laue back-reflection and electron backscatter diffraction (EBSD) techniques. The detailed orientation information such as misorientation of grains, location of grain boundaries and the orientation distribution was obtained from the automatic orientation mapping with the EBSD technique. The uniform orientation was confirmed for crystals with a "cellular-like" structure. A crystal growth model, the two-dimensional layer mechanism, was proposed by orientation analysis. Based on the model, some important comments were made on orientation problems under general growth conditions. The ferrodistortive phase transitions of tertramethylphosphonium tetrabromozincate [P(CH3)4]2ZnBr4 and tertramethylphosphonium tetraiodonzincate [P(CH3)4]2ZnI4 were thoroughly studied by a single crystal x-ray diffraction technique. An order parameter analysis by application of Landau theory showed that the two compounds undergo first-order phase transitions near a tricritical Lifshitz point. Transitions for both compounds appear to be first order, but with the iodo salt the transition is nearly

  13. Polarization of ferroelectric films through electrolyte

    NASA Astrophysics Data System (ADS)

    Toss, Henrik; Sani, Negar; Fabiano, Simone; Simon, Daniel T.; Forchheimer, Robert; Berggren, Magnus

    2016-03-01

    A simplified model is developed to understand the field and potential distribution through devices based on a ferroelectric film in direct contact with an electrolyte. Devices based on the ferroelectric polymer polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) were produced—in metal-ferroelectric-metal, metal-ferroelectric-dielectric-metal, and metal-ferroelectric-electrolyte-metal architectures—and used to test the model, and simulations based on the model and these fabricated devices were performed. From these simulations we find indication of progressive polarization of the films. Furthermore, the model implies that there is a relation between the separation of charge within the devices and the observed open circuit voltage. This relation is confirmed experimentally. The ability to polarize ferroelectric polymer films through aqueous electrolytes, combined with the strong correlation between the properties of the electrolyte double layer and the device potential, opens the door to a variety of new applications for ferroelectric technologies, e.g. regulation of cell culture growth and release, steering molecular self-assembly, or other large area applications requiring aqueous environments.

  14. Negative capacitance in multidomain ferroelectric superlattices.

    PubMed

    Zubko, Pavlo; Wojdeł, Jacek C; Hadjimichael, Marios; Fernandez-Pena, Stéphanie; Sené, Anaïs; Luk'yanchuk, Igor; Triscone, Jean-Marc; Íñiguez, Jorge

    2016-06-23

    The stability of spontaneous electrical polarization in ferroelectrics is fundamental to many of their current applications, which range from the simple electric cigarette lighter to non-volatile random access memories. Research on nanoscale ferroelectrics reveals that their behaviour is profoundly different from that in bulk ferroelectrics, which could lead to new phenomena with potential for future devices. As ferroelectrics become thinner, maintaining a stable polarization becomes increasingly challenging. On the other hand, intentionally destabilizing this polarization can cause the effective electric permittivity of a ferroelectric to become negative, enabling it to behave as a negative capacitance when integrated in a heterostructure. Negative capacitance has been proposed as a way of overcoming fundamental limitations on the power consumption of field-effect transistors. However, experimental demonstrations of this phenomenon remain contentious. The prevalent interpretations based on homogeneous polarization models are difficult to reconcile with the expected strong tendency for domain formation, but the effect of domains on negative capacitance has received little attention. Here we report negative capacitance in a model system of multidomain ferroelectric-dielectric superlattices across a wide range of temperatures, in both the ferroelectric and paraelectric phases. Using a phenomenological model, we show that domain-wall motion not only gives rise to negative permittivity, but can also enhance, rather than limit, its temperature range. Our first-principles-based atomistic simulations provide detailed microscopic insight into the origin of this phenomenon, identifying the dominant contribution of near-interface layers and paving the way for its future exploitation. PMID:27296225

  15. New perspectives for ferroelectric LC-polymers

    SciTech Connect

    Brehmer, M.; Gebhard, E.; Wittig, T.

    1996-10-01

    LC-Elastomers prepared from ferroelectric LC-polymers are interesting materials for two reasons. From a materials point of view they are interesting because of their ferroelectric, piezoelectric and pyrroelectric properties. From a scientific point of view they are fascinating because they allow us to study the interplay of electric and mechanical forces in a rubbery material The coupling between the director reorientation and the network can be modified by crosslinking at the end of the mesogens or in the range of the polymer chains . In the last case the coupling is minimal. Besides the planar orientation in SSFLC-cells, free standing films offer the possibility of a homeotropic alignment of smectic liquid crystals ferroelectric LC elastomers of a different topology can be obtained by mixing a low molar mass or an oligomeric ferroelectric LC with a bifunctional crosslinkable: liquid crystal and performing photochemically a crosslinking reaction in one switching state of the smectic C* phase. As a result non crosslinkable ferroelectric LC will form micro-droplets surrounded by a densely crosslinked network, which is formed by the crosslinked non-ferroelectric liquid crystals. This gives a two phasic Volume or Network Stabilized Ferroelectric Liquid Crystal.

  16. Polarization of ferroelectric films through electrolyte.

    PubMed

    Toss, Henrik; Sani, Negar; Fabiano, Simone; Simon, Daniel T; Forchheimer, Robert; Berggren, Magnus

    2016-03-16

    A simplified model is developed to understand the field and potential distribution through devices based on a ferroelectric film in direct contact with an electrolyte. Devices based on the ferroelectric polymer polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) were produced--in metal-ferroelectric-metal, metal-ferroelectric-dielectric-metal, and metal-ferroelectric-electrolyte-metal architectures--and used to test the model, and simulations based on the model and these fabricated devices were performed. From these simulations we find indication of progressive polarization of the films. Furthermore, the model implies that there is a relation between the separation of charge within the devices and the observed open circuit voltage. This relation is confirmed experimentally. The ability to polarize ferroelectric polymer films through aqueous electrolytes, combined with the strong correlation between the properties of the electrolyte double layer and the device potential, opens the door to a variety of new applications for ferroelectric technologies, e.g. regulation of cell culture growth and release, steering molecular self-assembly, or other large area applications requiring aqueous environments. PMID:26885704

  17. Ferroelectric Metal in Tetragonal BiCoO3/BiFeO3 Bilayers and Its Electric Field Effect

    PubMed Central

    Yin, Li; Mi, Wenbo; Wang, Xiaocha

    2016-01-01

    By first-principles calculations we investigate the electronic structure of tetragonal BiCoO3/BiFeO3 bilayers with different terminations. The multiferroic insulator BiCoO3 and BiFeO3 transform into metal in all of three models. Particularly, energetically favored model CoO2-BiO exhibits ferroelectric metallic properties, and external electric field enhances the ferroelectric displacements significantly. The metallic character is mainly associated to eg electrons, while t2g electrons are responsible for ferroelectric properties. Moreover, the strong hybridization between eg and O p electrons around Fermi level provides conditions to the coexistence of ferroelectric and metallic properties. These special behaviors of electrons are influenced by the interfacial electronic reconstruction with formed Bi-O electrovalent bond, which breaks OA-Fe/Co-OB coupling partially. Besides, the external electric field reverses spin polarization of Fe/Co ions efficiently, even reaching 100%. PMID:26839049

  18. Ferroelectric Metal in Tetragonal BiCoO3/BiFeO3 Bilayers and Its Electric Field Effect.

    PubMed

    Yin, Li; Mi, Wenbo; Wang, Xiaocha

    2016-01-01

    By first-principles calculations we investigate the electronic structure of tetragonal BiCoO3/BiFeO3 bilayers with different terminations. The multiferroic insulator BiCoO3 and BiFeO3 transform into metal in all of three models. Particularly, energetically favored model CoO2-BiO exhibits ferroelectric metallic properties, and external electric field enhances the ferroelectric displacements significantly. The metallic character is mainly associated to eg electrons, while t2g electrons are responsible for ferroelectric properties. Moreover, the strong hybridization between eg and O p electrons around Fermi level provides conditions to the coexistence of ferroelectric and metallic properties. These special behaviors of electrons are influenced by the interfacial electronic reconstruction with formed Bi-O electrovalent bond, which breaks OA-Fe/Co-OB coupling partially. Besides, the external electric field reverses spin polarization of Fe/Co ions efficiently, even reaching 100%. PMID:26839049

  19. Ferroelectric Metal in Tetragonal BiCoO3/BiFeO3 Bilayers and Its Electric Field Effect

    NASA Astrophysics Data System (ADS)

    Yin, Li; Mi, Wenbo; Wang, Xiaocha

    2016-02-01

    By first-principles calculations we investigate the electronic structure of tetragonal BiCoO3/BiFeO3 bilayers with different terminations. The multiferroic insulator BiCoO3 and BiFeO3 transform into metal in all of three models. Particularly, energetically favored model CoO2-BiO exhibits ferroelectric metallic properties, and external electric field enhances the ferroelectric displacements significantly. The metallic character is mainly associated to eg electrons, while t2g electrons are responsible for ferroelectric properties. Moreover, the strong hybridization between eg and O p electrons around Fermi level provides conditions to the coexistence of ferroelectric and metallic properties. These special behaviors of electrons are influenced by the interfacial electronic reconstruction with formed Bi-O electrovalent bond, which breaks OA-Fe/Co-OB coupling partially. Besides, the external electric field reverses spin polarization of Fe/Co ions efficiently, even reaching 100%.

  20. Direct observation of the recovery of an antiferroelectric phase during polarization reversal of an induced ferroelectric phase

    NASA Astrophysics Data System (ADS)

    Guo, Hanzheng; Tan, Xiaoli

    2015-04-01

    Electric fields are generally known to favor the ferroelectric polar state over the antiferroelectric nonpolar state for their Coulomb interactions with dipoles in the crystal. In this paper, we directly image an electric-field-assisted ferroelectric-to-antiferroelectric phase transition during polarization reversal of the ferroelectric phase in polycrystalline P b0.99{N b0.02[(Zr0.57Sn0.43) 0.92T i0.08] 0.98}O3 . With the electric-field in situ transmission electron microscopy technique, such an unlikely phenomenon is verified to occur by both domain morphology change and electron-diffraction analysis. The slower kinetics of the phase transition, compared with ferroelectric polarization reversal, is suggested to contribute to this unusual behavior.

  1. Implementation of Ferroelectric Memories for Space Applications

    NASA Technical Reports Server (NTRS)

    Philpy, Stephen C.; Derbenwick, Gary F.; Kamp, David A.; Isaacson, Alan F.

    2000-01-01

    Ferroelectric random access semiconductor memories (FeRAMs) are an ideal nonvolatile solution for space applications. These memories have low power performance, high endurance and fast write times. By combining commercial ferroelectric memory technology with radiation hardened CMOS technology, nonvolatile semiconductor memories for space applications can be attained. Of the few radiation hardened semiconductor manufacturers, none have embraced the development of radiation hardened FeRAMs, due a limited commercial space market and funding limitations. Government funding may be necessary to assure the development of radiation hardened ferroelectric memories for space applications.

  2. Static Characteristics of the Ferroelectric Transistor Inverter

    NASA Technical Reports Server (NTRS)

    Mitchell, Cody; Laws, crystal; MacLeond, Todd C.; Ho, Fat D.

    2010-01-01

    The inverter is one of the most fundamental building blocks of digital logic, and it can be used as the foundation for understanding more complex logic gates and circuits. This paper presents the characteristics of an inverter circuit using a ferroelectric field-effect transistor. The voltage transfer characteristics are analyzed with respect to varying parameters such as supply voltage, input voltage, and load resistance. The effects of the ferroelectric layer between the gate and semiconductor are examined, and comparisons are made between the inverters using ferroelectric transistors and those using traditional MOSFETs.

  3. Ultrafast Photovoltaic Response in Ferroelectric Nanolayers

    SciTech Connect

    Daranciang, Dan

    2012-02-15

    We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO3 via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on femtosecond timescales, photoinduced changes in the unit-cell tetragonality are observed. These are driven by the motion of photogenerated free charges within the ferroelectric and can be simply explained by a model including both shift and screening currents, associated with the displacement of electrons first antiparallel to and then parallel to the ferroelectric polarization direction.

  4. Strong ultrasonic microwaves in ferroelectric ceramics.

    PubMed

    Arlt, G

    1998-01-01

    It is well known that ferroelectric materials have piezoelectric properties which allow the transformation of electrical signals into mechanical signals and vice versa. The transducer action normally is restricted to frequencies up to the mechanical resonance frequency of the sample. There are, however, two mechanisms which allow transducer action in ferroelectric ceramics at much higher frequencies: one is the normal piezoelectric effect in a ferroelectric ceramic in which the crystallites have periodic domain structures, the other is a domain wall effect in which ferroelastic domain walls in a periodic domain structure are powerful shear wave emitters. Both mechanisms give rise to extensive dielectric losses in ceramics at microwave frequencies. PMID:18244152

  5. Ferroelectric ceramics in a pyroelectric accelerator

    SciTech Connect

    Shchagin, A. V.; Miroshnik, V. S.; Volkov, V. I.; Oleinik, A. N.

    2015-12-07

    The applicability of polarized ferroelectric ceramics as a pyroelectric in a pyroelectric accelerator is shown by experiments. The spectra of X-ray radiation of energy up to tens of keV, generated by accelerated electrons, have been measured on heating and cooling of the ceramics in vacuum. It is suggested that curved layers of polarized ferroelectric ceramics be used as elements of ceramic pyroelectric accelerators. Besides, nanotubes and nanowires manufactured from ferroelectric ceramics are proposed for the use in nanometer-scale ceramic pyroelectric nanoaccelerators for future applications in nanotechnologies.

  6. Ferroelectricity emerging in strained (111)-textured ZrO2 thin films

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Deng, Jinyu; Wang, Jingxian; Liu, Ziyan; Yang, Ping; Xiao, Juanxiu; Yan, Xiaobing; Dong, Zhili; Wang, John; Chen, Jingsheng

    2016-01-01

    (Anti-)ferroelectricity in complementary metal-oxide-semiconductor (CMOS)-compatible binary oxides have attracted considerable research interest recently. Here, we show that by using substrate-induced strain, the orthorhombic phase and the desired ferroelectricity could be achieved in ZrO2 thin films. Our theoretical analyses suggest that the strain imposed on the ZrO2 (111) film by the TiN/MgO (001) substrate would energetically favor the tetragonal (t) and orthorhombic (o) phases over the monoclinic (m) phase of ZrO2, and the compressive strain along certain ⟨11-2⟩ directions may further stabilize the o-phase. Experimentally ZrO2 thin films are sputtered onto the MgO (001) substrates buffered by epitaxial TiN layers. ZrO2 thin films exhibit t- and o-phases, which are highly (111)-textured and strained, as evidenced by X-ray diffraction and transmission electron microscopy. Both polarization-electric field (P-E) loops and corresponding current responses to voltage stimulations measured with appropriate applied fields reveal the ferroelectric sub-loop behavior of the ZrO2 films at certain thicknesses, confirming that the ferroelectric o-phase has been developed in the strained (111)-textured ZrO2 films. However, further increasing the applied field leads to the disappearance of ferroelectric hysteresis, the possible reasons of which are discussed.

  7. Characterization of a Common-Gate Amplifier Using Ferroelectric Transistors

    NASA Technical Reports Server (NTRS)

    Hunt, Mitchell; Sayyah, Rana; MacLeod, Todd C.; Ho, Fat D.

    2011-01-01

    In this paper, the empirical data collected through experiments performed using a FeFET in the common-gate amplifier circuit is presented. The FeFET common-gate amplifier was characterized by varying all parameters in the circuit, such as load resistance, biasing of the transistor, and input voltages. Due to the polarization of the ferroelectric layer, the particular behavior of the FeFET common-gate amplifier presents interesting results. Furthermore, the differences between a FeFET common-gate amplifier and a MOSFET common-gate amplifier are examined.

  8. Dynamic Observation of Brain-Like Learning in a Ferroelectric Synapse Device

    NASA Astrophysics Data System (ADS)

    Nishitani, Yu; Kaneko, Yukihiro; Ueda, Michihito; Fujii, Eiji; Tsujimura, Ayumu

    2013-04-01

    A brain-like learning function was implemented in an electronic synapse device using a ferroelectric-gate field effect transistor (FeFET). The FeFET was a bottom-gate type FET with a ZnO channel and a ferroelectric Pb(Zr,Ti)O3 (PZT) gate insulator. The synaptic weight, which is represented by the channel conductance of the FeFET, is updated by applying a gate voltage through a change in the ferroelectric polarization in the PZT. A learning function based on the symmetric spike-timing dependent synaptic plasticity was implemented in the synapse device using the multilevel weight update by applying a pulse gate voltage. The dynamic weighting and learning behavior in the synapse device was observed as a change in the membrane potential in a spiking neuron circuit.

  9. Universal Ferroelectric Switching Dynamics of Vinylidene Fluoride-trifluoroethylene Copolymer Films

    PubMed Central

    Hu, Wei Jin; Juo, Deng-Ming; You, Lu; Wang, Junling; Chen, Yi-Chun; Chu, Ying-Hao; Wu, Tom

    2014-01-01

    In this work, switching dynamics of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films are investigated over unprecedentedly wide ranges of temperature and electric field. Remarkably, domain switching of copolymer films obeys well the classical domain nucleation and growth model although the origin of ferroelectricity in organic ferroelectric materials inherently differs from the inorganic counterparts. A lower coercivity limit of 50 MV/m and 180° domain wall energy of 60 mJ/m2 are determined for P(VDF-TrFE) films. Furthermore, we discover in copolymer films an anomalous temperature-dependent crossover behavior between two power-law scaling regimes of frequency-dependent coercivity, which is attributed to the transition between flow and creep motions of domain walls. Our observations shed new light on the switching dynamics of semi-crystalline ferroelectric polymers, and such understandings are critical for realizing their reliable applications. PMID:24759786

  10. Nanoscale Electromechanics of Ferroelectric and Biological Systems: A New Dimension in Scanning Probe Microscopy

    SciTech Connect

    Kalinin, Sergei V; Rodriguez, Brian J; Jesse, Stephen; Karapetian, Edgar; Mirman, B; Eliseev, E. A.; Morozovska, A. N.

    2007-01-01

    Functionality of biological and inorganic systems ranging from nonvolatile computer memories and microelectromechanical systems to electromotor proteins and cellular membranes is ultimately based on the intricate coupling between electrical and mechanical phenomena. In the past decade, piezoresponse force microscopy (PFM) has been established as a powerful tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric and piezoelectric materials. Here, we give an overview of the fundamental image formation mechanism in PFM and summarize recent theoretical and technological advances. In particular, we show that the signal formation in PFM is complementary to that in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) techniques, and we discuss the implications. We also consider the prospect of extending PFM beyond ferroelectric characterization for quantitative probing of electromechanical behavior in molecular and biological systems and high-resolution probing of static and dynamic polarization switching processes in low-dimensional ferroelectric materials and heterostructures.

  11. TaN interface properties and electric field cycling effects on ferroelectric Si-doped HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Lomenzo, Patrick D.; Takmeel, Qanit; Zhou, Chuanzhen; Fancher, Chris M.; Lambers, Eric; Rudawski, Nicholas G.; Jones, Jacob L.; Moghaddam, Saeed; Nishida, Toshikazu

    2015-04-01

    Ferroelectric HfO2-based thin films, which can exhibit ferroelectric properties down to sub-10 nm thicknesses, are a promising candidate for emerging high density memory technologies. As the ferroelectric thickness continues to shrink, the electrode-ferroelectric interface properties play an increasingly important role. We investigate the TaN interface properties on 10 nm thick Si-doped HfO2 thin films fabricated in a TaN metal-ferroelectric-metal stack which exhibit highly asymmetric ferroelectric characteristics. To understand the asymmetric behavior of the ferroelectric characteristics of the Si-doped HfO2 thin films, the chemical interface properties of sputtered TaN bottom and top electrodes are probed with x-ray photoelectron spectroscopy. Ta-O bonds at the bottom electrode interface and a significant presence of Hf-N bonds at both electrode interfaces are identified. It is shown that the chemical heterogeneity of the bottom and top electrode interfaces gives rise to an internal electric field, which causes the as-grown ferroelectric domains to preferentially polarize to screen positively charged oxygen vacancies aggregated at the oxidized bottom electrode interface. Electric field cycling is shown to reduce the internal electric field with a concomitant increase in remanent polarization and decrease in relative permittivity. Through an analysis of pulsed transient switching currents, back-switching is observed in Si-doped HfO2 thin films with pinched hysteresis loops and is shown to be influenced by the internal electric field.

  12. Antiferroelectric-to-Ferroelectric Switching in CH3NH3PbI3 Perovskite and Its Potential Role in Effective Charge Separation in Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Sewvandi, Galhenage A.; Hu, Dengwei; Chen, Changdong; Ma, Hao; Kusunose, Takafumi; Tanaka, Yasuhiro; Nakanishi, Shunsuke; Feng, Qi

    2016-08-01

    Perovskite solar cells (PSCs) often suffer from large performance variations which impede to define a clear charge-transfer mechanism. Ferroelectric polarization is measured numerically using CH3NH3PbI3 (M A PbI3 ) pellets to overcome the measurement issues such as pinholes and low uniformity of thickness, etc., with M A PbI3 thin films. M A PbI3 perovskite is an antiferroelectric semiconductor which is different from typical semiconducting materials and ferroelectric materials. The effect of polarization carrier separation on the charge-transfer mechanism in the PSCs is elucidated by using the results of ferroelectric and structural studies on the perovskite. The ferroelectric polarization contributes to an inherent carrier-separation effect and the I - V hysteresis. The ferroelectric and semiconducting synergistic charge-separation effect gives an alternative category of solar cells, ferroelectric semiconductor solar cells. Our findings identify the ferroelectric semiconducting behavior of the perovskite absorber as being significant to the improvement of the ferroelectric PSCs performances in future developments.

  13. Shear mode properties of single crystal ferroelectrics

    NASA Astrophysics Data System (ADS)

    McLaughlin, E. A.; Robinson, H. C.

    2003-10-01

    Single crystal ferroelectrics or piezocrystals were recently introduced into the electroactive materials community. The 33-mode electromechanical coupling factor of piezocrystals is typically greater than 0.90, which is significantly larger than typical values for piezoelectric ceramics (0.62-0.74). For sonar projector applications this large k33 has been responsible for more than doubling the bandwidth of active sonar arrays over what is currently achievable with ceramics. Last year a crystal grower produced a cut of lead magnesium niobate-lead titanate (PMN-PT) single crystal with piezoelectric shear coefficient values of 7000 pm/V and shear coupling factors of 0.97. (For PZT5H, d15 is 730 pm/V.) This piezocrystal d15 coefficient implies significantly improved sensitivity and signal-to-noise ratio for accelerometers and hydrophones, while the high coupling promises bandwidth increases greater than those realized in 33-mode projectors using piezocrystals. This research studies the shear-mode behavior of PMN-PT piezocrystals for use in sensors and projectors. By measuring the response of the materials to high and low level electrical bias and excitation fields, frequency, and temperature, the materials' effective material properties as a function of these operational variables were determined. [Work sponsored by ONR and NUWC ILIR.

  14. Interface control of bulk ferroelectric polarization

    PubMed Central

    Yu, P.; Luo, W.; Yi, D.; Zhang, J. X.; Rossell, M. D.; Yang, C.-H.; You, L.; Singh-Bhalla, G.; Yang, S. Y.; He, Q.; Ramasse, Q. M.; Erni, R.; Martin, L. W.; Chu, Y. H.; Pantelides, S. T.; Pennycook, S. J.; Ramesh, R.

    2012-01-01

    The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon. PMID:22647612

  15. Thermally tunable ferroelectric thin film photonic crystals.

    SciTech Connect

    Lin, P. T.; Wessels, B. W.; Imre, A.; Ocola, L. E.; Northwestern Univ.

    2008-01-01

    Thermally tunable PhCs are fabricated from ferroelectric thin films. Photonic band structure and temperature dependent diffraction are calculated by FDTD. 50% intensity modulation is demonstrated experimentally. This device has potential in active ultra-compact optical circuits.

  16. An epitaxial ferroelectric tunnel junction on silicon.

    PubMed

    Li, Zhipeng; Guo, Xiao; Lu, Hui-Bin; Zhang, Zaoli; Song, Dongsheng; Cheng, Shaobo; Bosman, Michel; Zhu, Jing; Dong, Zhili; Zhu, Weiguang

    2014-11-12

    Epitaxially grown functional perovskites on silicon (001) and the ferroelectricity of a 3.2 nm thick BaTiO3 barrier layer are demonstrated. The polarization-switching-induced change in tunneling resistance is measured to be two orders of magnitude. The obtained results suggest the possibility of integrating ferroelectric tunnel junctions as binary data storage media in non-volatile memory cells on a silicon platform. PMID:25200550

  17. Fast Switching Ferroelectric Materials for Accelerator Applications

    NASA Astrophysics Data System (ADS)

    Kanareykin, A.; Nenasheva, E.; Yakovlev, V.; Dedyk, A.; Karmanenko, S.; Kozyrev, A.; Osadchy, V.; Kosmin, D.; Schoessow, P.; Semenov, A.

    2006-11-01

    Fast switching (<10 nsec) measurement results on the recently developed BST(M) (barium strontium titanium oxide composition with magnesium-based additions) ferroelectric materials are presented. These materials can be used as the basis for new advanced technology components suitable for high-gradient accelerators. A ferroelectric ceramic has an electric field-dependent dielectric permittivity that can be altered by applying a bias voltage. Ferroelectric materials offer significant benefits for linear collider applications, in particular, for switching and control elements where a very short response time of <10 nsec is required. The measurement results presented here show that the new BST(M) ceramic exhibits a high tunability factor: a bias field of 40-50 kV/cm reduces the permittivity by a factor of 1.3-1.5. The recently developed technology of gold biasing contact deposition on large diameter (110 cm) thin wall ferroelectric rings allowed ˜few nsec switching times in witness sample experiments. The ferroelectric rings can be used at high pulsed power (tens of megawatts) for X-band components as well as at high average power in the range of a few kilowatts for the L-band phase-shifter, under development for optimization of the ILC rf coupling. Accelerator applications include fast active X-band and Ka-band high-power ferroelectric switches, high-power X-band and L-band phase shifters, and tunable dielectric-loaded accelerating structures.

  18. Negative capacitance in multidomain ferroelectric superlattices

    NASA Astrophysics Data System (ADS)

    Zubko, Pavlo; Wojdeł, Jacek C.; Hadjimichael, Marios; Fernandez-Pena, Stéphanie; Sené, Anaïs; Luk’Yanchuk, Igor; Triscone, Jean-Marc; Íñiguez, Jorge

    2016-06-01

    The stability of spontaneous electrical polarization in ferroelectrics is fundamental to many of their current applications, which range from the simple electric cigarette lighter to non-volatile random access memories. Research on nanoscale ferroelectrics reveals that their behaviour is profoundly different from that in bulk ferroelectrics, which could lead to new phenomena with potential for future devices. As ferroelectrics become thinner, maintaining a stable polarization becomes increasingly challenging. On the other hand, intentionally destabilizing this polarization can cause the effective electric permittivity of a ferroelectric to become negative, enabling it to behave as a negative capacitance when integrated in a heterostructure. Negative capacitance has been proposed as a way of overcoming fundamental limitations on the power consumption of field-effect transistors. However, experimental demonstrations of this phenomenon remain contentious. The prevalent interpretations based on homogeneous polarization models are difficult to reconcile with the expected strong tendency for domain formation, but the effect of domains on negative capacitance has received little attention. Here we report negative capacitance in a model system of multidomain ferroelectric–dielectric superlattices across a wide range of temperatures, in both the ferroelectric and paraelectric phases. Using a phenomenological model, we show that domain-wall motion not only gives rise to negative permittivity, but can also enhance, rather than limit, its temperature range. Our first-principles-based atomistic simulations provide detailed microscopic insight into the origin of this phenomenon, identifying the dominant contribution of near-interface layers and paving the way for its future exploitation.

  19. Characterization, Modeling, and Energy Harvesting of Phase Transformations in Ferroelectric Materials

    NASA Astrophysics Data System (ADS)

    Dong, Wenda

    Solid state phase transformations can be induced through mechanical, electrical, and thermal loading in ferroelectric materials that are compositionally close to morphotropic phase boundaries. Large changes in strain, polarization, compliance, permittivity, and coupling properties are typically observed across the phase transformation regions and are phenomena of interest for energy harvesting and transduction applications where increased coupling behavior is desired. This work characterized and modeled solid state phase transformations in ferroelectric materials and assessed the potential of phase transforming materials for energy harvesting applications. Two types of phase transformations were studied. The first type was ferroelectric rhombohedral to ferroelectric orthorhombic observed in lead indium niobate lead magnesium niobate lead titanate (PIN-PMN-PT) and driven by deviatoric stress, temperature, and electric field. The second type of phase transformation is ferroelectric to antiferroelectric observed in lead zirconate titanate (PZT) and driven by pressure, temperature, and electric field. Experimental characterizations of the phase transformations were conducted in both PIN-PMN-PT and PZT in order to understand the thermodynamic characteristics of the phase transformations and map out the phase stability of both materials. The ferroelectric materials were characterized under combinations of stress, electric field, and temperature. Material models of phase transforming materials were developed using a thermodynamic based variant switching technique and thermodynamic observations of the phase transformations. These models replicate the phase transformation behavior of PIN-PMN-PT and PZT under mechanical and electrical loading conditions. The switching model worked in conjunction with linear piezoelectric equations as ferroelectric/ferroelastic constitutive equations within a finite element framework that solved the mechanical and electrical field equations

  20. Ferroelectric memristor based on Pt/BiFeO3/Nb-doped SrTiO3 heterostructure

    NASA Astrophysics Data System (ADS)

    Hu, Zhongqiang; Li, Qian; Li, Meiya; Wang, Qiangwen; Zhu, Yongdan; Liu, Xiaolian; Zhao, Xingzhong; Liu, Yun; Dong, Shuxiang

    2013-03-01

    We report a continuously tunable resistive switching behavior in Pt/BiFeO3/Nb-doped SrTiO3 heterostructure for ferroelectric memristor application. The resistance of this memristor can be tuned up to 5 × 105% by applying voltage pulses at room temperature, which exhibits excellent retention and anti-fatigue characteristics. The observed memristive behavior is attributed to the modulation effect of the ferroelectric polarization reversal on the width of depletion region and the height of potential barrier of the p-n junction formed at the BiFeO3/Nb-doped SrTiO3 interface.

  1. Ferroelectric-ferromagnetic multilayers: A magnetoelectric heterostructure with high output charge signal

    NASA Astrophysics Data System (ADS)

    Prokhorenko, S.; Kohlstedt, H.; Pertsev, N. A.

    2014-09-01

    Multiferroic composites and heterostructures comprising ferroelectric and ferromagnetic materials exhibit room-temperature magnetoelectric (ME) effects greatly exceeding those of single-phase magnetoelectrics known to date. Since these effects are mediated by the interfacial coupling between ferroic constituents, the ME responses may be enhanced by increasing the density of interfaces and improving their quality. A promising material system providing these features is a ferroelectric-ferromagnetic multilayer with epitaxial interfaces. In this paper, we describe theoretically the strain-mediated direct ME effect exhibited by free-standing multilayers composed of single-crystalline ferroelectric nanolayers interleaved by conducting ferromagnetic slabs. Using a nonlinear thermodynamic approach allowing for specific mechanical boundary conditions of the problem, we first calculate the polarization states and dielectric properties of ferroelectric nanolayers in dependence on the lattice mismatch between ferroic constituents and their volume fractions. In these calculations, the ferromagnetic component is described by a model which combines linear elastic behavior with magnetic-field-dependent lattice parameters. Then the quasistatic ME polarization and voltage coefficients are evaluated using the theoretical strain sensitivity of ferroelectric polarization and measured effective piezomagnetic coefficients of ferromagnets. For Pb(Zr0.5Ti0.5)O3-FeGaB and BaTiO3-FeGaB multilayers, the ME coefficients are calculated numerically as a function of the FeGaB volume fraction and used to evaluate the output charge and voltage signals. It is shown that the multilayer geometry of a ferroelectric-ferromagnetic nanocomposite opens the way for a drastic enhancement of the output charge signal. This feature makes biferroic multilayers advantageous for the development of ultrasensitive magnetic-field sensors for technical and biomedical applications.

  2. Ferroelectric-ferromagnetic multilayers: A magnetoelectric heterostructure with high output charge signal

    SciTech Connect

    Prokhorenko, S.; Kohlstedt, H.; Pertsev, N. A.

    2014-09-21

    Multiferroic composites and heterostructures comprising ferroelectric and ferromagnetic materials exhibit room-temperature magnetoelectric (ME) effects greatly exceeding those of single-phase magnetoelectrics known to date. Since these effects are mediated by the interfacial coupling between ferroic constituents, the ME responses may be enhanced by increasing the density of interfaces and improving their quality. A promising material system providing these features is a ferroelectric-ferromagnetic multilayer with epitaxial interfaces. In this paper, we describe theoretically the strain-mediated direct ME effect exhibited by free-standing multilayers composed of single-crystalline ferroelectric nanolayers interleaved by conducting ferromagnetic slabs. Using a nonlinear thermodynamic approach allowing for specific mechanical boundary conditions of the problem, we first calculate the polarization states and dielectric properties of ferroelectric nanolayers in dependence on the lattice mismatch between ferroic constituents and their volume fractions. In these calculations, the ferromagnetic component is described by a model which combines linear elastic behavior with magnetic-field-dependent lattice parameters. Then the quasistatic ME polarization and voltage coefficients are evaluated using the theoretical strain sensitivity of ferroelectric polarization and measured effective piezomagnetic coefficients of ferromagnets. For Pb(Zr₀.₅Ti₀.₅)O₃-FeGaB and BaTiO₃-FeGaB multilayers, the ME coefficients are calculated numerically as a function of the FeGaB volume fraction and used to evaluate the output charge and voltage signals. It is shown that the multilayer geometry of a ferroelectric-ferromagnetic nanocomposite opens the way for a drastic enhancement of the output charge signal. This feature makes biferroic multilayers advantageous for the development of ultrasensitive magnetic-field sensors for technical and biomedical applications.

  3. Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations

    DOE PAGESBeta

    Ihlefeld, Jon F.; Harris, David T.; Keech, Ryan; Jones, Jacob L.; Maria, Jon-Paul; Trolier-McKinstry, Susan

    2016-07-05

    Ferroelectric materials are well-suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro-optic devices, and non-volatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a non-centrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change of properties withmore » decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, while in bulk ceramics, changes in properties from the values of large-grained specimens is most notable in samples with grain sizes below several microns. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics are reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. Ultimately, in many cases, multiple mechanisms combine to produce the observed scaling

  4. Ferroelectric and ferromagnetic properties in BaTiO{sub 3} thin films on Si (100)

    SciTech Connect

    Singamaneni, Srinivasa Rao Prater, John T.; Punugupati, Sandhyarani; Hunte, Frank; Narayan, Jagdish

    2014-09-07

    In this paper, we report on the epitaxial integration of room temperature lead-free ferroelectric BaTiO{sub 3} thin (∼1050 nm) films on Si (100) substrates by pulsed laser deposition technique through a domain matching epitaxy paradigm. We employed MgO and TiN as buffer layers to create BaTiO{sub 3}/SrRuO{sub 3}/MgO/TiN/Si (100) heterostructures. C-axis oriented and cube-on-cube epitaxial BaTiO{sub 3} is formed on Si (100) as evidenced by the in-plane and out-of-plane x-ray diffraction, and transmission electron microscopy. X-ray photoemission spectroscopic measurements show that Ti is in 4(+) state. Polarization hysteresis measurements together with Raman spectroscopy and temperature-dependent x-ray diffraction confirm the room temperature ferroelectric nature of BaTiO{sub 3}. Furthermore, laser irradiation of BaTiO{sub 3} thin film is found to induce ferromagnetic-like behavior but affects adversely the ferroelectric characteristics. Laser irradiation induced ferromagnetic properties seem to originate from the creation of oxygen vacancies, whereas the pristine BaTiO{sub 3} shows diamagnetic behavior, as expected. This work has opened up the route for the integration of room temperature lead-free ferroelectric functional oxides on a silicon platform.

  5. Influence of interfacial dislocations on hysteresis loops of ferroelectric films

    NASA Astrophysics Data System (ADS)

    Li, Y. L.; Hu, S. Y.; Choudhury, S.; Baskes, M. I.; Saxena, A.; Lookman, T.; Jia, Q. X.; Schlom, D. G.; Chen, L. Q.

    2008-11-01

    We investigated the influence of dislocations, located at the interface of a ferroelectric film and its underlying substrate, on the ferroelectric hysteresis loop including the remanent polarization and coercive field using phase-field simulations. We considered epitaxial ferroelectric BaTiO3 films and found that the hysteresis loop is strongly dependent on the type and density of interfacial dislocations. The dislocations that stabilize multiple ferroelectric variants and domains reduce the coercive field, and consequently, the corresponding remanent polarization also decreases.

  6. Investigation of the relaxor behavior of sol gel processed lanthanum lead titanium ceramics

    NASA Astrophysics Data System (ADS)

    Limame, K.; Sayouri, S.; Yahyaoui, M. M.; Housni, A.; Jaber, B.

    2016-08-01

    A series of La doped lead titanate samples, with composition Pb1-xLaxTi1-x/4O3 (PLTx), where x=0.00; 0.02; 0.04; 0.06; 0.07; 0.08; 0.10; 0.12; 0.14; 0.16; 0.18; 0.21 and 0.22 was prepared using the sol-gel process. Addition of La gives rise to the two well-known phenomena: diffuseness and relaxation around the ferro-to-paraelectric transition; the two parameters related to these phenomena, and which give a satisfactory interpretation of them, have been estimated using the Uchino's quadratic law. This diffuse phase transition (DPT) has been investigated with the help of the Landau-Devonshire cluster theory and the model of Cheng et al., to show that polar regions may be generated around the DPT and far from the temperature, Tm, of the maximum of the dielectric permittivity, which have as a direct consequence a non vanishing polarization even if T>Tm.

  7. Room temperature p-type conductivity and coexistence of ferroelectric order in ferromagnetic Li doped ZnO nanoparticles

    SciTech Connect

    Awan, Saif Ullah E-mail: ullahphy@gmail.com; Hasanain, S. K.; Anjum, D. H.; Awan, M. S.; Shah, Saqlain A.

    2014-10-28

    Memory and switching devices acquired new materials which exhibit ferroelectric and ferromagnetic order simultaneously. We reported multiferroic behavior in Zn{sub 1−y}Li{sub y}O(0.00≤y≤0.10) nanoparticles. The analysis of transmission electron micrographs confirmed the hexagonal morphology and wurtzite crystalline structure. We investigated p-type conductivity in doped samples and measured hole carriers in range 2.4 × 10{sup 17}/cc to 7.3 × 10{sup 17}/cc for different Li contents. We found that hole carriers are responsible for long range order ferromagnetic coupling in Li doped samples. Room temperature ferroelectric hysteresis loops were observed in 8% and 10% Li doped samples. We demonstrated ferroelectric coercivity (remnant polarization) 2.5 kV/cm (0.11 μC/cm{sup 2}) and 2.8 kV/cm (0.15 μC/cm{sup 2}) for y = 0.08 and y = 0.10 samples. We propose that the mechanism of Li induced ferroelectricity in ZnO is due to indirect dipole interaction via hole carriers. We investigated that if the sample has hole carriers ≥5.3 × 10{sup 17}/cc, they can mediate the ferroelectricity. Ferroelectric and ferromagnetic measurements showed that higher electric polarization and larger magnetic moment is attained when the hole concentration is larger and vice versa. Our results confirmed the hole dependent coexistence of ferromagnetic and ferroelectric behavior at room temperature, which provide potential applications for switchable and memory devices.

  8. Studies of dielectric characteristics of BaBi 2Nb 2O 9 ferroelectrics prepared by chemical precursor decomposition method

    NASA Astrophysics Data System (ADS)

    Debasis, Dhak; Tanmay, Ghorai K.; Panchanan, Pramanik

    2007-01-01

    BaBiNb 2O 9 (BBN) powders in the nanometer range were prepared by chemical precursor decomposition method (CPD). TG-DTA showed that precursor sample got freed from organic contaminants at 575 °C. XRD showed that a single phase with the layered perovskite structure of BBN was formed after calcining at 600 °C. No intermediate phase was found during heat treatment at and above 600 °C. The crystallite size ( D) and the effective strain ( η) were found to be 26 nm and 0.000867, respectively, while the particle size obtained from TEM was 28 ± 2 nm. SEM revealed that the average grain size after sintering at 900 °C for 4 h was ˜1.67 μm. A relative density of ˜93% was obtained using a two-step sintering process at moderate pressure. Dielectric and ferroelectric properties were investigated in the temperature range 50-500 °C and frequencies from 1 kHz to 5 MHz. Strong dispersion of the complex relative dielectric constant was observed including typical relaxor features such as shift of permittivity maximum with frequency and broadening of the peak maximum. The high dielectric constant of 545 measured at 100 kHz and other properties of BBN ceramics were compared to that of BBN prepared by other conventional methods and found to be superior.

  9. Ferroelectric Thin-Film Capacitors As Ultraviolet Detectors

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita

    1995-01-01

    Advantages include rapid response, solar blindness, and relative invulnerability to ionizing radiation. Ferroelectric capacitor made to function as photovoltaic detector of ultraviolet photons by making one of its electrodes semitransparent. Photovoltaic effect exploited more fully by making Schottky barrier at illuminated semitransparent-electrode/ferroelectric interface taller than Schottky barrier at other electrode/ferroelectric interface.

  10. Dielectric constant tunability at microwave frequencies and pyroelectric behavior of lead-free submicrometer-structured (Bi0.5Na0.5)1-xBaxTiO3 ferroelectric ceramics.

    PubMed

    Martínez, Félix L; Hinojosa, Juan; Doménech, Ginés; Fernández-Luque, Francisco J; Zapata, Juan; Ruiz, Ramon; Pardo, Lorena

    2013-08-01

    In this article, we show that the dielectric constant of lead-free ferroelectric ceramics based on the solid solution (1-x)(Bi(0.5)Na(0.5))TiO(3)-xBaTiO(3), with compositions at or near the morphotropic phase boundary (MPB), can be tuned by a local applied electric field. Two compositions have been studied, one at the MPB, with x = 0.06 (BNBT6), and another one nearer the BNT side of the phase diagram, with x = 0.04 (BNBT4). The tunability of the dielectric constant is measured at microwave frequencies between 100 MHz and 3 GHz by a nonresonant method and simultaneously applying a dc electric field. As expected, the tunability is higher for the composition at the MPB (BNBT6), reaching a maximum value of 60% for an electric field of 900 V/cm, compared with the composition below this boundary (BNBT4), which saturates at 40% for an electric field of 640 V/cm. The high tunability in both cases is attributed to the fine grain and high density of the samples, which have a submicrometer homogeneous grain structure with grain size of the order of a few hundred nanometers. Such properties make these ceramics attractive for microwave tunable devices. Finally, we have tested these ceramics for their application as infrared pyroelectric detectors and we have found that the pyroelectric figure of merit is comparable to traditional lead-containing pyroelectrics. PMID:25004530

  11. Strain-Induced Ferroelectric Topological Insulator.

    PubMed

    Liu, Shi; Kim, Youngkuk; Tan, Liang Z; Rappe, Andrew M

    2016-03-01

    Ferroelectricity and band topology are two extensively studied yet distinct properties of insulators. Nonetheless, their coexistence has never been observed in a single material. Using first-principles calculations, we demonstrate that a noncentrosymmetric perovskite structure of CsPbI3 allows for the simultaneous presence of ferroelectric and topological orders with appropriate strain engineering. Metallic topological surface states create an intrinsic short-circuit condition, helping stabilize bulk polarization. Exploring diverse structural phases of CsPbI3 under pressure, we identify that the key structural feature for achieving a ferroelectric topological insulator is to suppress PbI6 cage rotation in the perovskite structure, which could be obtained via strain engineering. Ferroelectric control over the density of topological surface states provides a new paradigm for device engineering, such as perfect-focusing Veselago lens and spin-selective electron collimator. Our results suggest that CsPbI3 is a simple model system for ferroelectric topological insulators, enabling future studies exploring the interplay between conventional symmetry-breaking and topological orders and their novel applications in electronics and spintronics. PMID:26814668

  12. Enhanced energy harvesting in commercial ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

    2014-04-01

    Ferroelectric materials are used in a number of applications ranging from simple sensors and actuators to ferroelectric random access memories (FRAMs), transducers, health monitoring system and microelectronics. The multiphysical coupling ability possessed by these materials has been established to be useful for energy harvesting applications. However, conventional energy harvesting techniques employing ferroelectric materials possess low energy density. This has prevented the successful commercialization of ferroelectric based energy harvesting systems. In this context, the present study aims at proposing a novel approach for enhanced energy harvesting using commercially available ferroelectric materials. This technique was simulated to be used for two commercially available piezoelectric materials namely PKI-552 and APCI-840, soft and hard lead-zirconate-titanate (PZT) pervoskite ceramics, respectively. It was observed that a maximum energy density of 348 kJm-3cycle-1 can be obtained for cycle parameters of (0-1 ton compressive stress and 1-25 kV.cm-1 electric field) using APCI-840. The reported energy density is several hundred times larger than the maximum energy density reported in the literature for vibration harvesting systems.

  13. Ferroelectric HfO2-based materials for next-generation ferroelectric memories

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Chen, Jingsheng; Wang, John

    2016-05-01

    Ferroelectric random access memory (FeRAM) based on conventional ferroelectric perovskites, such as Pb(Zr,Ti)O3 and SrBi2Ta2O9, has encountered bottlenecks on memory density and cost, because those conventional perovskites suffer from various issues mainly including poor complementary metal-oxide-semiconductor (CMOS)-compatibility and limited scalability. Next-generation cost-efficient, high-density FeRAM shall therefore rely on a material revolution. Since the discovery of ferroelectricity in Si:HfO2 thin films in 2011, HfO2-based materials have aroused widespread interest in the field of FeRAM, because they are CMOS-compatible and can exhibit robust ferroelectricity even when the film thickness is scaled down to below 10 nm. A review on this new class of ferroelectric materials is therefore of great interest. In this paper, the most appealing topics about ferroelectric HfO2-based materials including origins of ferroelectricity, advantageous material properties, and current and potential applications in FeRAM, are briefly reviewed.

  14. Development and characterization of a ferroelectric non-volatile memory for flexible electronics

    NASA Astrophysics Data System (ADS)

    Mao, Duo

    Flexible electronics have received significant attention recently because of the potential applications in displays, sensors, radio frequency identification (RFID) tags and other integrated circuits. Electrically addressable non-volatile memory is a key component for these applications. The major challenges are to fabricate the memory at a low temperature compatible with plastic substrates while maintaining good device reliability, by being compatible with process as needed to integrate with other electronic components for system-on-chip applications. In this work, ferroelectric capacitors fabricated at low temperature were developed. Based on that, a ferroelectric random access memory (FRAM) for flexible electronics was developed and characterized. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer was used as a ferroelectric material and a photolithographic process was developed to fabricate ferroelectric capacitors. Different characterization methods including atomic force microscopy, x-ray diffraction and Fourier-transform infrared reflection-absorption spectroscopy were used to study the material properties of the P(VDF-TrFE) film. The material properties were correlated with the electrical characteristics of the ferroelectric capacitors. To understand the polarization switching behavior of the P(VDF-TrFE) ferroelectric capacitors, a Nucleation-Limited-Switching (NLS) model was used to study the switching kinetics. The switching kinetics were characterized over the temperature range from -60 °C to 100 °C. Fatigue characteristics were studied at different electrical stress voltages and frequencies to evaluate the reliability of the ferroelectric capacitor. The degradation mechanism is attributed to the increase of the activation field and the suppression of the switchable polarization. To develop a FRAM circuit for flexible electronics, an n-channel thin film transistor (TFT) based on CdS as the semiconductor was integrated with a P

  15. Electroactive fluorinate-based polymers: Ferroelectric and dielectric properties

    SciTech Connect

    Yu Zhi; Chen Ang

    2004-12-15

    The dielectric, ferroelectric, and electroactive strain behavior of poly(vinylidene fluoride-trifluoroethylene) copolymers and poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymers is studied in a wide temperature and frequency range. The dielectric response from two dielectric polarization processes, modes A(A{sup '}) and B, and the dielectric-background contribution can be identified for these polymers by using the Cole-Cole plot method. Therefore physically reasonable parameters are obtained by fitting the relaxation time to the Vogel-Fulcher relation. On the other hand, the dielectric relaxation step and high strain decrease simultaneously with decreasing temperature; this indicates that the dielectric relaxation process and high strain behavior are strongly correlated. The electron-irradiation effect in copolymers and the monomer effect in terpolymers are discussed.

  16. Deaging and Asymmetric Energy Landscapes in Electrically Biased Ferroelectrics

    SciTech Connect

    Tutuncu, Goknur; Damjanovic, Dragan; Chen, Jun; Jones, Jacob L.

    2015-09-01

    In ferroic materials, the dielectric, piezoelectric, magnetic, and elastic coefficients are significantly affected by the motion of domain walls. This motion can be described as the propagation of a wall across various types and strengths of pinning centers that collectively constitute a force profile or energetic landscape. Biased domain structures and asymmetric energy landscapes can be created through application of high fields (such as during electrical poling), and the material behavior in such states is often highly asymmetric. In some cases, this behavior can be considered as the electric analogue to the Bauschinger effect. The present Letter uses time-resolved, high-energy x-ray Bragg scattering to probe this asymmetry and the associated deaging effect in the ferroelectric morphotropic phase boundary composition 0.36BiScO{sub 3}-0.64PbTiO{sub 3}.

  17. Deaging and Asymmetric Energy Landscapes in Electrically Biased Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Tutuncu, Goknur; Damjanovic, Dragan; Chen, Jun; Jones, Jacob L.

    2012-04-01

    In ferroic materials, the dielectric, piezoelectric, magnetic, and elastic coefficients are significantly affected by the motion of domain walls. This motion can be described as the propagation of a wall across various types and strengths of pinning centers that collectively constitute a force profile or energetic landscape. Biased domain structures and asymmetric energy landscapes can be created through application of high fields (such as during electrical poling), and the material behavior in such states is often highly asymmetric. In some cases, this behavior can be considered as the electric analogue to the Bauschinger effect. The present Letter uses time-resolved, high-energy x-ray Bragg scattering to probe this asymmetry and the associated deaging effect in the ferroelectric morphotropic phase boundary composition 0.36BiScO3-0.64PbTiO3.

  18. Deaging and asymmetric energy landscapes in electrically biased ferroelectrics.

    PubMed

    Tutuncu, Goknur; Damjanovic, Dragan; Chen, Jun; Jones, Jacob L

    2012-04-27

    In ferroic materials, the dielectric, piezoelectric, magnetic, and elastic coefficients are significantly affected by the motion of domain walls. This motion can be described as the propagation of a wall across various types and strengths of pinning centers that collectively constitute a force profile or energetic landscape. Biased domain structures and asymmetric energy landscapes can be created through application of high fields (such as during electrical poling), and the material behavior in such states is often highly asymmetric. In some cases, this behavior can be considered as the electric analogue to the Bauschinger effect. The present Letter uses time-resolved, high-energy x-ray Bragg scattering to probe this asymmetry and the associated deaging effect in the ferroelectric morphotropic phase boundary composition 0.36BiScO3 - 0.64PbTiO3. PMID:22680904

  19. Ferroelectric Field Effect Transistor Model Using Partitioned Ferroelectric Layer and Partial Polarization

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat D.

    2004-01-01

    A model of an n-channel ferroelectric field effect transistor has been developed based on both theoretical and empirical data. The model is based on an existing model that incorporates partitioning of the ferroelectric layer to calculate the polarization within the ferroelectric material. The model incorporates several new aspects that are useful to the user. It takes into account the effect of a non-saturating gate voltage only partially polarizing the ferroelectric material based on the existing remnant polarization. The model also incorporates the decay of the remnant polarization based on the time history of the FFET. A gate pulse of a specific voltage; will not put the ferroelectric material into a single amount of polarization for that voltage, but instead vary with previous state of the material and the time since the last change to the gate voltage. The model also utilizes data from FFETs made from different types of ferroelectric materials to allow the user just to input the material being used and not recreate the entire model. The model also allows the user to input the quality of the ferroelectric material being used. The ferroelectric material quality can go from a theoretical perfect material with little loss and no decay to a less than perfect material with remnant losses and decay. This model is designed to be used by people who need to predict the external characteristics of a FFET before the time and expense of design and fabrication. It also allows the parametric evaluation of quality of the ferroelectric film on the overall performance of the transistor.

  20. PREFACE: 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity and 9th International Conference on Functional Materials and Nanotechnologies (RCBJSF-2014-FM&NT)

    NASA Astrophysics Data System (ADS)

    Sternberg, Andris; Grinberga, Liga; Sarakovskis, Anatolijs; Rutkis, Martins

    2015-03-01

    The joint International Symposium RCBJSF-2014-FM&NT successfully has united two international events - 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity (RCBJSF-12) and 9th International Conference Functional Materials and Nanotechnologies (FM&NT-2014). The RCBJSF symposium is a continuation of series of meetings on ferroelectricity, the first of which took place in Novosibirsk (USSR) in 1976. FM&NT conferences started in 2006 and have been organized by Institute of Solid State Physics, University of Latvia in Riga. In 2012 the International program committee decided to transform this conference into a traveling Baltic State conference and the FM&NT-2013 was organized by the Institute of Physics, University of Tartu, Estonia. In 2014 the joint international symposium RCBJSF-2014-FM&NT was organized by the Institute of Solid State Physics, University of Latvia and was part of Riga - 2014, the European Capital of Culture event. The purpose of the joint Symposium was to bring together scientists, students and high-level experts in solid state physics, materials science, engineering and related disciplines. The number of the registered participants from 26 countries was over 350. During the Symposium 128 high quality scientific talks (5 plenary, 42 invited, 81 oral) and over 215 posters were presented. All presentations were divided into 4 parallel sessions according to 4 main topics of the Symposium: Ferroelectricity, including ferroelectrics and multiferroics, pyroelectrics, piezoelectrics and actuators, integrated ferroelectrics, relaxors, phase transitions and critical phenomena. Multifunctional Materials, including theory, multiscale and multiphenomenal material modeling and simulation, advanced inorganic, organic and hybrid materials. Nanotechnologies, including progressive methods, technologies and design for production, investigation of nano- particles, composites, structures, thin films and coatings. Energy, including perspective materials and

  1. A Ferroelectric Oxide Made Directly on Silicon

    SciTech Connect

    Warusawithana, M.; Cen, C; Sleasman, C; Woicik, J; Li, Y; Fitting Kourkoutis, L; Klug, J; Li, H; Ryan, P; et. al.

    2009-01-01

    Metal oxide semiconductor field-effect transistors, formed using silicon dioxide and silicon, have undergone four decades of staggering technological advancement. With fundamental limits to this technology close at hand, alternatives to silicon dioxide are being pursued to enable new functionality and device architectures. We achieved ferroelectric functionality in intimate contact with silicon by growing coherently strained strontium titanate (SrTiO{sub 3}) films via oxide molecular beam epitaxy in direct contact with silicon, with no interfacial silicon dioxide. We observed ferroelectricity in these ultrathin SrTiO{sub 3} layers by means of piezoresponse force microscopy. Stable ferroelectric nanodomains created in SrTiO{sub 3} were observed at temperatures as high as 400 kelvin.

  2. Short range magnetic exchange interaction favors ferroelectricity

    PubMed Central

    Wan, Xiangang; Ding, Hang-Chen; Savrasov, Sergey Y.; Duan, Chun-Gang

    2016-01-01

    Multiferroics, where two or more ferroic order parameters coexist, is one of the hottest fields in condensed matter physics and materials science. To search multiferroics, currently most researches are focused on frustrated magnets, which usually have complicated magnetic structure and low magnetic ordering temperature. Here, we argue that actually simple interatomic magnetic exchange interaction already contains a driving force for ferroelectricity, thus providing a new microscopic mechanism for the coexistence and strong coupling between ferroelectricity and magnetism. We demonstrate this mechanism by showing that even the simplest antiferromagnetic insulator like MnO, could display a magnetically induced ferroelectricity under a biaxial strain. In addition, we show that such mechanism also exists in the most important single phase multiferroics, i.e. BiFeO3, suggesting that this mechanism is ubiquitous in systems with superexchange interaction. PMID:26956480

  3. Short range magnetic exchange interaction favors ferroelectricity

    NASA Astrophysics Data System (ADS)

    Wan, Xiangang; Ding, Hang-Chen; Savrasov, Sergey Y.; Duan, Chun-Gang

    2016-03-01

    Multiferroics, where two or more ferroic order parameters coexist, is one of the hottest fields in condensed matter physics and materials science. To search multiferroics, currently most researches are focused on frustrated magnets, which usually have complicated magnetic structure and low magnetic ordering temperature. Here, we argue that actually simple interatomic magnetic exchange interaction already contains a driving force for ferroelectricity, thus providing a new microscopic mechanism for the coexistence and strong coupling between ferroelectricity and magnetism. We demonstrate this mechanism by showing that even the simplest antiferromagnetic insulator like MnO, could display a magnetically induced ferroelectricity under a biaxial strain. In addition, we show that such mechanism also exists in the most important single phase multiferroics, i.e. BiFeO3, suggesting that this mechanism is ubiquitous in systems with superexchange interaction.

  4. Short range magnetic exchange interaction favors ferroelectricity.

    PubMed

    Wan, Xiangang; Ding, Hang-Chen; Savrasov, Sergey Y; Duan, Chun-Gang

    2016-01-01

    Multiferroics, where two or more ferroic order parameters coexist, is one of the hottest fields in condensed matter physics and materials science. To search multiferroics, currently most researches are focused on frustrated magnets, which usually have complicated magnetic structure and low magnetic ordering temperature. Here, we argue that actually simple interatomic magnetic exchange interaction already contains a driving force for ferroelectricity, thus providing a new microscopic mechanism for the coexistence and strong coupling between ferroelectricity and magnetism. We demonstrate this mechanism by showing that even the simplest antiferromagnetic insulator like MnO, could display a magnetically induced ferroelectricity under a biaxial strain. In addition, we show that such mechanism also exists in the most important single phase multiferroics, i.e. BiFeO3, suggesting that this mechanism is ubiquitous in systems with superexchange interaction. PMID:26956480

  5. Unusual Urbach tail in TlGaSe2 ferroelectric-semiconductor with incommensurate phase

    NASA Astrophysics Data System (ADS)

    Seyidov, Ð.œirHasan Yu.; Suleymanov, Rauf A.; Şale, Yasin

    2012-11-01

    An analysis of temperature behavior of optical absorption edge is performed for TlGaSe2 ferroelectric-semiconductor with incommensurate phase. Unusual behavior of the Urbach tail manifested by the shift of the absorption edge toward the higher energies with increasing temperature was observed. It was shown that such behavior is due to the specific temperature interval where Urbach energy decreases with the temperature. This interval corresponds to the incommensurate phase-commensurate phase transition region. Unusual behavior of the Urbach energy can be explained interpreting the incommensurate phase as some type of disordered state, and TlGaSe2 crystal as a disordered semiconductor with controllable disorder.

  6. Piezoelectricity and ferroelectricity of cellular polypropylene electrets films characterized by piezoresponse force microscopy

    SciTech Connect

    Miao, Hongchen; Sun, Yao; Zhou, Xilong; Li, Yingwei; Li, Faxin

    2014-08-14

    Cellular electrets polymer is a new ferroelectret material exhibiting large piezoelectricity and has attracted considerable attentions in researches and industries. Property characterization is very important for this material and current investigations are mostly on macroscopic properties. In this work, we conduct nanoscale piezoelectric and ferroelectric characterizations of cellular polypropylene (PP) films using piezoresponse force microscopy (PFM). First, both the single-frequency PFM and dual-frequency resonance-tracking PFM testings were conducted on the cellular PP film. The localized piezoelectric constant d{sub 33} is estimated to be 7–11pC/N by correcting the resonance magnification with quality factor and it is about one order lower than the macroscopic value. Next, using the switching spectroscopy PFM (SS-PFM), we studied polarization switching behavior of the cellular PP films. Results show that it exhibits the typical ferroelectric-like phase hysteresis loops and butterfly-shaped amplitude loops, which is similar to that of a poly(vinylidene fluoride) (PVDF) ferroelectric polymer film. However, both the phase and amplitude loops of the PP film are intensively asymmetric, which is thought to be caused by the nonzero remnant polarization after poling. Then, the D-E hysteresis loops of both the cellular PP film and PVDF film were measured by using the same wave form as that used in the SS-PFM, and the results show significant differences. Finally, we suggest that the ferroelectric-like behavior of cellular electrets films should be distinguished from that of typical ferroelectrics, both macroscopically and microscopically.

  7. Lead-Free α-La₂WO₆ Ferroelectric Thin Films.

    PubMed

    Carlier, Thomas; Chambrier, Marie-Hélène; Ferri, Anthony; Estradé, Sonia; Blach, Jean-François; Martín, Gemma; Meziane, Belkacem; Peiró, Francesca; Roussel, Pascal; Ponchel, Freddy; Rèmiens, Denis; Cornet, Albert; Desfeux, Rachel

    2015-11-11

    (001)-Epitaxial La2WO6 (LWO) thin films are grown by pulsed laser deposition on (001)-oriented SrTiO3 (STO) substrates. The α-phase (high-temperature phase in bulk) is successfully stabilized with an orthorhombic structure (a = 16.585(1) Å, b = 5.717(2) Å, c = 8.865(5) Å). X-ray-diffraction pole-figure measurements suggest that crystallographic relationships between the film and substrate are [100]LWO ∥ [110]STO, [010]LWO ∥ [11̅0]STO and [001]LWO ∥ [001]STO. From optical properties, investigated by spectroscopic ellipsometry, we extract a refractive-index value around 2 (at 500 nm) along with the presence of two absorption bands situated, respectively at 3.07 and 6.32 eV. Ferroelectricity is evidenced as well on macroscale (standard polarization measurements) as on nanoscale, calling for experiments based on piezo-response force-microscopy, and confirmed with in situ scanning-and-tunneling measurements performed with a transmission electron microscope. This work highlights the ferroelectric behavior, at room temperature, in high-temperature LWO phase when stabilized in thin film and opens the way to new functional oxide thin films dedicated to advanced electronic devices. PMID:26477357

  8. Monoclinic Cc-phase stabilization in magnetically diluted lead free Na1/2Bi1/2TiO3—Evolution of spin glass like behavior with enhanced ferroelectric and dielectric properties

    NASA Astrophysics Data System (ADS)

    Thangavelu, Karthik; Asthana, Saket

    2015-09-01

    The effect of magnetic cation substitution on the phase stabilization, ferroelectric, dielectric and magnetic properties of a lead free Na0.5Bi0.5TiO3 (NBT) system prepared by O2 atmosphere solid state sintering were studied extensively. Cobalt (Co) was chosen as the magnetic cation to substitute at the Ti-site of NBT with optimized 2.5 mol%. Rietveld analysis of x-ray diffraction data favours the monoclinic Cc phase stabilization strongly rather than the parent R3c phase. FE-SEM micrograph supports the single phase characteristics without phase segregation at the grain boundaries. The stabilized Cc space group was explained based on the collective local distortion effects due to spin-orbit stabilization at Co3+ and Co2+ functional centres. The phonon mode changes as observed in the TiO6 octahedral modes also support the Cc phase stabilization. The major Co3+-ion presence was revealed from corresponding crystal field transitions observed through solid state diffuse reflectance spectroscopy. The enhanced spontaneous polarization (Ps) from ≅38 μC cm-2 to 45 μC cm-2 could be due to the easy rotation of polarization vector along the {(1\\bar{1}0)}{{pc}} in Cc phase. An increase in static dielectric response (ɛ) from ɛ ≅ 42 to 60 along with enhanced diffusivity from γ ≅ 1.53 to 1.75 was observed. Magneto-thermal irreversibility and their magnetic field dependent ZFC/FC curves suggest the possibility of a spin glass like behaviour below 50 K. The monoclinic Cc phase stabilization as confirmed from structural studies was well correlated with the observed ferroic properties in magnetically diluted NBT.

  9. Ferroelectric Cathodes in Transverse Magnetic Fields

    SciTech Connect

    Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

    2002-07-29

    Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode.

  10. Switching Characteristics of Ferroelectric Transistor Inverters

    NASA Technical Reports Server (NTRS)

    Laws, Crystal; Mitchell, Coey; MacLeod, Todd C.; Ho, Fat D.

    2010-01-01

    This paper presents the switching characteristics of an inverter circuit using a ferroelectric field effect transistor, FeFET. The propagation delay time characteristics, phl and plh are presented along with the output voltage rise and fall times, rise and fall. The propagation delay is the time-delay between the V50% transitions of the input and output voltages. The rise and fall times are the times required for the output voltages to transition between the voltage levels V10% and V90%. Comparisons are made between the MOSFET inverter and the ferroelectric transistor inverter.

  11. Probing nanoscale ferroelectricity by ultraviolet Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Tenne, Dmitri

    2007-03-01

    Conventional vibrational spectroscopies operating in visible and infrared range fail to measure the phonon spectra of nanoscale ferroelectric structures because of extremely weak signals and the overwhelming substrate contribution. In this talk, application of ultraviolet (UV) Raman spectroscopy for studies of lattice dynamics and ferroelectric phase transitions in nanoscale ferroelectrics will be presented. We demonstrate that UV Raman spectroscopy is an effective technique allowing the observation of phonons and determination of the ferroelectric phase transition temperature (Tc) in nanoscale ferroelectrics, specifically, BaTiO3/SrTiO3 superlattices having the ferroelectric BaTiO3 layers as thin as 1 unit cell, and single BaTiO3 layers as thin as 4 nm. BaTiO3/SrTiO3 superlattices and ultrathin BaTiO3 films studied were grown by molecular beam epitaxy on SrTiO3 as well as GdScO3 and DyScO3 substrates. Excellent epitaxial quality and atomically abrupt interfaces are evidenced by X-ray diffraction and high resolution transmission electron microscopy. UV Raman results show that one-unit-cell thick BaTiO3 layers in BaTiO3/SrTiO3 superlattices are ferroelectric with the Tc as high as 250 K, and induce the polarization in much thicker SrTiO3 layers adjacent to them. The Tc in superlattices was tuned by hundreds of degrees from ˜170 to 650 K by varying the thicknesses of BaTiO3 and SrTiO3 layers. Using scandate substrates enables growth of superlattices with systematically changed coherent strain, thus allowing studying the stress effect on the ferroelectric phase transitions. UV Raman data are supported by the thermodynamic calculations of polarization in superlattices as a function of temperature. The work was done in collaboration with A. Soukiassian, W. Tian, D.G. Schlom, Y.L. Li, L.-Q. Chen, X.X. Xi (Pennsylvania State University), A. Bruchhausen, A. Fainstein (Centro Atomico Bariloche & Instituto Balseiro, Argentina), R. S. Katiyar (University of Puerto Rico), A

  12. Ferroelectric plasma thruster for microspacecraft propulsion

    SciTech Connect

    Kemp, Mark A.; Kovaleski, Scott D.

    2006-12-01

    This paper presents a technology in microthruster design: the ferroelectric plasma thruster (FEPT). The FEPT utilizes an applied rf electric field to create plasma on the surface of a ferroelectric dielectric. Acceleration of ions from this plasma provides thrust. Advantages of the FEPT include emission of both electrons and ions leading to self-neutralization, creation of plasma, and acceleration of ions with a single power supply, and application of thrust in a short amount of time. We present the concept of the thruster, operational physics, as well as experimental results demonstrating plasma creation and ion acceleration. These results along with plasma spectroscopy allow us to calculate thruster parameters.

  13. 95 GHz gyrotron with ferroelectric cathode.

    PubMed

    Einat, M; Pilossof, M; Ben-Moshe, R; Hirshbein, H; Borodin, D

    2012-11-01

    Ferroelectric cathodes were reported as a feasible electron source for microwave tubes. However, due to the surface plasma emission characterizing this cathode, operation of millimeter wave tubes based on it remains questionable. Nevertheless, the interest in compact high power sources of millimeter waves and specifically 95 GHz is continually growing. In this experiment, a ferroelectric cathode is used as an electron source for a gyrotron with the output frequency extended up to 95 GHz. Power above a 5 kW peak and ~0.5 μs pulses are reported; a duty cycle of 10% is estimated to be achievable. PMID:23215293

  14. Ab initio approach to structural, electronic, and ferroelectric properties of antimony sulphoiodide

    NASA Astrophysics Data System (ADS)

    Amoroso, Danila; Picozzi, Silvia

    2016-06-01

    By means of first-principles calculations for the SbSI semiconductor, we show that bare density functional theory fails to reproduce the experimentally observed ferroelectric phase, whereas a more advanced approach, based on hybrid functionals, correctly works. When comparing the paraelectric and ferroelectric phases, our results show polar displacements along the c direction of the Sb and S sublattices with respect to the iodine framework, leading to a predicted spontaneous polarization of P ≃20 μ C/cm2 , in good agreement with experiments. In the ferroelectric phase, the semiconducting behavior of SbSI is confirmed by relatively large values for the indirect and direct gaps (≃2.15 eV and 2.3 eV , respectively). An analysis of the electronic structure, in terms of density of states, charge density distribution, and anomalies in the Born effective charges, reveals (i) the clear presence of a Sb(III) lone pair and (ii) a large covalency in the SbSI bonding, based on the hybridization between Sb and S ions, in turn more ionically bonded to iodine anions. Finally, the interplay between ferroelectricity and spin-orbit coupling reveals a coexistence of Dresselhaus and Rashba relativistic effects and a spin texture that can be reversed by switching the polarization, of potential appeal in electrically controlled spintronics.

  15. Controlling the metal insulator transition using the ferroelectric field effect in rare earth nickelates

    NASA Astrophysics Data System (ADS)

    Marshall, Matthew; Disa, Ankit; Kumah, Divine; Chen, Hanghui; Ismail-Beigi, Sohrab; Walker, Fred; Ahn, Charles

    2013-03-01

    A ferroelectric field effect transistor (FE-FET) modulates conductivity in a non-volatile manner by electrostatically accumulating and depleting charge carriers at the interface between a conducting channel and ferroelectric gate. The rare earth nickelate LaNiO3 is metallic in bulk, while other rare earth nickelates, such as NdNiO3, exhibit metal-insulator transitions and anti-ferromagnetic behavior in the bulk. Here, we show that by coupling the ferroelectric polarization of Pb0.8Zr0.2TiO3 (PZT) to the carriers in a nickelate, we can dynamically induce a metal- insulator transition in ultra-thin films of LaNiO3, and induce large changes in the MIT transition temperature in NdNiO3. Density functional theory is used to determine changes in the physical and electronic Ni-O-Ni bond angle of the nickelate at the interface between PZT and LaNiO3. The effect of the ferroelectric polarization is to decrease the Ni-O-Ni bond angle from 180 degrees and increase the carrier effective mass. Related to this change in electronic structure, we observe a change in resistivity of approximately 80% at room temperature for an ultra-thin 3 unit cell thick film of LaNiO3. Work supported by FENA and the NSF under MRSEC DMR 1119826.

  16. CuInP2S6 Room Temperature Layered Ferroelectric

    DOE PAGESBeta

    Belianinov, Alex; He, Qian; Dziaugys, Andrius; Maksymovych, Petro; Eliseev, Eugene; Borisevich, Albina Y.; Morozovska, Anna N.; Banys, Juras; Vysochanskii, Yulian; Kalinin, Sergei V.

    2015-05-01

    In this paper, we explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP2S6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleaved bulk surfaces,more » whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V—likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. Finally, the existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing “graphene family”.« less

  17. CuInP2S6 Room Temperature Layered Ferroelectric

    SciTech Connect

    Belianinov, Alex; He, Qian; Dziaugys, Andrius; Maksymovych, Petro; Eliseev, Eugene; Borisevich, Albina Y.; Morozovska, Anna N.; Banys, Juras; Vysochanskii, Yulian; Kalinin, Sergei V.

    2015-05-01

    In this paper, we explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP2S6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleaved bulk surfaces, whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V—likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. Finally, the existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing “graphene family”.

  18. Field-induced phase transition and relaxor character in submicrometer-structured lead-free (Bi0.5Na0.5)0.94Ba0.06TiO3 piezoceramics at the morphotropic phase boundary.

    PubMed

    Pardo, Lorena; Mercadelli, Elisa; García, Alvaro; Brebøl, Klaus; Galassi, Carmen

    2011-09-01

    Submicrometer-structured (Bi(0.5)Na(0.5))(0.94)Ba(0.06)TiO(3) ceramics ((G) < 720 nm) from nanopowders were studied. The real part of the optimum room temperature set of piezoelectric coefficients obtained from resonances of the BNBT6 dense ceramic disks and shear plates [d(31) = (-37 + 1.33i) pC·N(-1), d(15) = (158.3 - 8.31i) pC·N(-1), k(t) = 40.4%, k(p) = 26.8%, and k(15) = 40.2%] and d(33) (148 pC·N(-1)) can be compared with the reported properties for coarse-grained ceramics. Shear resonance of thickness-poled plates is observed at T = 140°C. Permittivity versus temperature curves of poled samples show relaxor character up to T(i) = 230°C on heating and T(i) = 210°C on cooling of the depoled samples. The phase transition from the room-temperature ferroelectric (FE) to a low-temperature non-polar at zero field (LTNPZF) phase can be observed as a sharp jump in ε(δ)(33)'(T) curves or, as the degree of poling decreases, as a soft change of slope of the curves at T(FE-LTNPZF) = T(d) = 100°C. This dielectric anomaly is not observed on cooling of depoled samples, because the FE phase is field-induced. The observed macroscopic piezoelectric activity above T(d) is a consequence of the coexistence of nanoregions of the FE phase in the interval between T(FE-LTNPZF) and T(i). PMID:21937323

  19. First-principles study of interface doping in ferroelectric junctions

    PubMed Central

    Wang, Pin-Zhi; Cai, Tian-Yi; Ju, Sheng; Wu, Yin-Zhong

    2016-01-01

    Effect of atomic monolayer insertion on the performance of ferroelectric tunneling junction is investigated in SrRuO3/BaTiO3/SrRuO3 heterostrucutures. Based on first-principles calculations, the atomic displacement, orbital occupancy, and ferroelectric polarization are studied. It is found that the ferroelectricity is enhanced when a (AlO2)− monolayer is inserted between the electrode SRO and the barrier BTO, where the relatively high mobility of doped holes effectively screen ferroelectric polarization. On the other hand, for the case of (LaO)+ inserted layer, the doped electrons resides at the both sides of middle ferroelectric barrier, making the ferroelectricity unfavorable. Our findings provide an alternative avenue to improve the performance of ferroelectric tunneling junctions. PMID:27063704

  20. Carrier Density Modulation in Ge Heterostructure by Ferroelectric Switching

    SciTech Connect

    Ponath, Patrick; Fredrickson, Kurt; Posadas, Agham B.; Ren, Yuan; Vasudevan, Rama K.; Okatan, Mahmut Baris; Jesse, Stephen; Aoki, Toshihiro; McCartney, Martha; Smith, David J.; Kalinin, Sergei V.; Lai, Keji; Demkov, Alexander A.

    2015-01-14

    The development of nonvolatile logic through direct coupling of spontaneous ferroelectric polarization with semiconductor charge carriers is nontrivial, with many issues, including epitaxial ferroelectric growth, demonstration of ferroelectric switching, and measurable semiconductor modulation. Here we report a true ferroelectric field effect carrier density modulation in an underlying Ge(001) substrate by switching of the ferroelectric polarization in the epitaxial c-axis-oriented BaTiO3 (BTO) grown by molecular beam epitaxy (MBE) on Ge. Using density functional theory, we demonstrate that switching of BTO polarization results in a large electric potential change in Ge. Aberration-corrected electron microscopy confirms the interface sharpness, and BTO tetragonality. Electron-energy-loss spectroscopy (EELS) indicates the absence of any low permittivity interlayer at the interface with Ge. Using piezoelectric force microscopy (PFM), we confirm the presence of fully switchable, stable ferroelectric polarization in BTO that appears to be single domain. Using microwave impedance microscopy (MIM), we clearly demonstrate a ferroelectric field effect.

  1. Static ferroelectric memory transistor having improved data retention

    DOEpatents

    Evans, Jr., Joseph T.; Warren, William L.; Tuttle, Bruce A.

    1996-01-01

    An improved ferroelectric FET structure in which the ferroelectric layer is doped to reduce retention loss. A ferroelectric FET according to the present invention includes a semiconductor layer having first and second contacts thereon, the first and second contacts being separated from one another. The ferroelectric FET also includes a bottom electrode and a ferroelectric layer which is sandwiched between the semiconductor layer and the bottom electrode. The ferroelectric layer is constructed from a perovskite structure of the chemical composition ABO.sub.3 wherein the B site comprises first and second elements and a dopant element that has an oxidation state greater than +4 in sufficient concentration to impede shifts in the resistance measured between the first and second contacts with time. The ferroelectric FET structure preferably comprises Pb in the A-site. The first and second elements are preferably Zr and Ti, respectively. The preferred B-site dopants are Niobium, Tantalum, and Tungsten at concentrations between 1% and 8%.

  2. Indications of the existence of ferroelectric units in excitable-membrane channels.

    PubMed

    Leuchtag, H R

    1987-08-01

    Previous work in excitability has focused primarily on the mathematical description of the phenomena, while mechanisms postulated to explain these were simple mechanical interpretations of the terms of this description. The problem considered here is that of the physical mechanism underlying excitation. The experimental facts to be explained must be not only the electrical behavior of the membrane, but also its electromechanical, electro-optic and thermoelectric behavior. Previous work on the physically grounded electrodiffusion theory foundered not because of the incorrectness of the electrodiffusion approach, but because the assumed description of the dielectric properties of the membrane was too simple. Extension of the dielectric equation of state to a nonlinear polynomial form converts the classical electrodiffusion system of equations into a nonlinear polynomial form converts the classical electrodiffusion system of equations into a ferroelectric electrodiffusion system. The consideration of ferroelectric behavior in excitable channels makes possible straight-forward physical explanation of the phenomena of membrane swelling during action potential, currents induced by temperature changes, transition temperatures, current-voltage hysteresis, nonlinear electrical behavior, voltage-dependent birefringence and rectangular pulses from single channels. The hypothesis is therefore proposed that excitable channels contain ferroelectric transmembrane units. These may be crystals or liquid crystals. PMID:2448549

  3. Ferroelectric Material Application: Modeling Ferroelectric Field Effect Transistor Characteristics from Micro to Nano

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd, C.; Ho, Fat Duen

    2006-01-01

    All present ferroelectric transistors have been made on the micrometer scale. Existing models of these devices do not take into account effects of nanoscale ferroelectric transistors. Understanding the characteristics of these nanoscale devices is important in developing a strategy for building and using future devices. This paper takes an existing microscale ferroelectric field effect transistor (FFET) model and adds effects that become important at a nanoscale level, including electron velocity saturation and direct tunneling. The new model analyzed FFETs ranging in length from 40,000 nanometers to 4 nanometers and ferroelectric thickness form 200 nanometers to 1 nanometer. The results show that FFETs can operate on the nanoscale but have some undesirable characteristics at very small dimensions.

  4. High-frequency programmable acoustic wave device realized through ferroelectric domain engineering

    SciTech Connect

    Ivry, Yachin E-mail: cd229@eng.cam.ac.uk; Wang, Nan; Durkan, Colm E-mail: cd229@eng.cam.ac.uk

    2014-03-31

    Surface acoustic wave devices are extensively used in contemporary wireless communication devices. We used atomic force microscopy to form periodic macroscopic ferroelectric domains in sol-gel deposited lead zirconate titanate, where each ferroelectric domain is composed of many crystallites, each of which contains many microscopic ferroelastic domains. We examined the electro-acoustic characteristics of the apparatus and found a resonator behavior similar to that of an equivalent surface or bulk acoustic wave device. We show that the operational frequency of the device can be tailored by altering the periodicity of the engineered domains and demonstrate high-frequency filter behavior (>8 GHz), allowing low-cost programmable high-frequency resonators.

  5. Self-electroforming and high-performance complementary memristor based on ferroelectric tunnel junctions

    NASA Astrophysics Data System (ADS)

    Yan, Z. B.; Yau, H. M.; Li, Z. W.; Gao, X. S.; Dai, J. Y.; Liu, J.-M.

    2016-08-01

    Complementary resistive switching (CRS) has potential applications in ultra-high density three-dimensional crossbar arrays for resistive random access memories and Logic-in-Memories. For real applications, the good stability and electroforming-free character have become essential pre-requisites. In this work, we investigate the resistance switching behaviors of a CRS device based on two anti-serial Au/BaTiO3/Nb:SrTiO3 ferroelectric tunnel junctions (FTJs). This FTJ-based CRS device shows a stable butterfly-like resistance-voltage hysteresis, as well as self-electroforming, multi-switching, and good performance complementary switching behaviors. The present work presents a convincing demonstration of the complementary multi-switching states modulated by remnant ferroelectric polarization, making the FTJ structure good potentials for high-performance CRS memristors.

  6. Giant structural modulation & abnormal ferromagnetism in ferroelectric & ultrathin ferromagnetic digital superlattices

    NASA Astrophysics Data System (ADS)

    Guo, Hangwen; Wang, Zhen; Saghayezhian, Mohammad; Chen, Lina; Jin, Rongying; Plummer, Ward; Zhang, Jiandi; Dong, Shuai

    The nature of magnetoelectric coupling in oxide heterostructure remains interesting but illusive, largely because the complex nature of interface intermixing and diffusion. In this work, we present our ability to fabricate superlattices consist of ferroelectric BTO & ferromagnetic LSMO, with minimum interfacial intermixing confined within half a unit cell. Such high quality superlattices with sharp interfaces allow us to explore magnetoelectric coupling effect into ultrathin region (reduced dimensionality) and observe ferroelectric induced abnormal magnetic behavior. A detailed STEM study reveals that the traditional electron/hole carrier doping scenario does not play a major role. Instead, distinct modulation of lattice displacement and octahedron tilting is responsible for the coupling effect and abnormal magnetic behavior. Our study highlights the importance of structural-property relationship in oxide heterostructures. Supported by U.S. DOE under Grant No. DOE DE-SC0002136.

  7. Structural stability and depolarization of manganese-doped (Bi₀.₅Na₀.₅){sub 1−x}Ba{sub x}TiO₃ relaxor ferroelectrics

    SciTech Connect

    Wang, Sheng-Fen; Tu, Chi-Shun; Chang, Ting-Lun; Chen, Pin-Yi; Chen, Cheng-Sao; Hugo Schmidt, V.; Anthoniappen, J.

    2014-10-21

    This work reveals that 0.5 mol. % manganese (Mn) doping in (Bi₀.₅Na₀.₅){sub 1−x}Ba{sub x}TiO₃ (x = 0 and 0.075) solid solutions can increase structural thermal stability, depolarization temperature (T{sub d}), piezoelectric coefficient (d₃₃), and electromechanical coupling factor (kₜ). High-resolution X-ray diffraction and transmission electron microscopy reveal coexistence of rhombohedral (R) R3c and tetragonal (T) P4bm phases in (Bi₀.₅Na₀.₅)₀.₉₂₅Ba₀.₀₇₅TiO₃ (BN7.5BT) and 0.5 mol. % Mn-doped BN7.5BT (BN7.5BT-0.5Mn). (Bi₀.₅Na₀.₅)TiO₃ (BNT) and BN7.5BT show an R − R + T phase transition, which does not occur in 0.5 mol. % Mn-doped BNT (BNT-0.5Mn) and BN7.5BT-0.5Mn. Dielectric permittivity (ε′) follows the Curie-Weiss equation, ε′ = C/(T − T{sub o}), above the Burns temperature (TB), below which polar nanoregions begin to develop. The direct piezoelectric coefficient (d₃₃) and electromechanical coupling factor (kₜ) of BN7.5BT-0.5Mn reach 190 pC/N and 47%.

  8. Dynamical mechanism of phase transitions in A-site ferroelectric relaxor (Na1/2Bi1/2)TiO3

    NASA Astrophysics Data System (ADS)

    Deng, Guochu; Danilkin, Sergey; Zhang, Haiwu; Imperia, Paolo; Li, Xiaobing; Zhao, Xiangyong; Luo, Haosu

    2014-10-01

    The dynamical phase transition mechanism of (Na1/2Bi1/2)TiO3 (NBT) was studied using inelastic neutron scattering. Softening was observed of multiple phonon modes in the phase transition sequence of NBT. As usual, the softening of the zone center transverse optical modes Δ5 and Σ3 was observed in the (200) and (220) zones, showing the Ti vibration instabilities in TiO6 octahedra for both cubic-tetragonal (C-T) and tetragonal-rhombohedral (T-R) phase transitions. In these two phase transitions, however, Ti4+ has different preferential displacement directions. Surprisingly, the longitudinal optic mode also softens significantly toward the zone center in the range of the transition temperature, indicating the Na+/Bi3+ vibration instability against TiO6 octahedra during the T-R phase transition. Strong inelastic diffuse scattering shows up near M(1.5, 0.5, 0) and R(1.5, 1.5, 0.5) in the tetragonal and rhombohedral phases, respectively, indicating the condensations of the M3 and R25 optic modes for the corresponding transitions. This reveals the different rotation instabilities of TiO6 in the corresponding transition temperature range. Bottleneck or waterfall features were observed in the dispersion curves at certain temperatures but did not show close correlations to the formation of polar nanoregions. Additional instabilities could be the origin of the complexity of phase transitions and crystallographic structures in NBT.

  9. Study of ferroelectric-thin-film thickness effects on metal-ferroelectric-SiO2-Si transistors

    NASA Astrophysics Data System (ADS)

    Lin, Yih-Yin; Singh, Jasprit

    2002-06-01

    This article examines the thickness effects of ferroelectric films on gate tunneling suppression and charge control in metal-ferroelectric-insulator-semiconductor field-effect transistors (MFISFETs). The formalism used is based on a blocking-layer model for the ferroelectric film and a self-consistent solution of the Poisson and Schrödinger equation. We show that with a polar ferroelectric the threshold voltage of the FET can be altered by controlling the ferroelectric film thickness. We also study the thickness dependence of the capacitance-voltage curve and the surface charge density and the effects of ferroelectric hysteresis. The tunneling probability and leakage current calculation in a MFISFET device are provided in this article. Ferroelectrics-based transistors show higher sheet charges and lower tunneling currents than oxide-based devices.

  10. Observation of spontaneous ferroelectric polarization reversal in multiferroic Mn1-xNixWO4 (x ≈ 0.16)

    NASA Astrophysics Data System (ADS)

    Song, Young-Sang; Chung, Jae-Ho; Woo Shin, Kwang; Hoon Kim, Kee; Hwan Oh, In

    2014-06-01

    In this Letter, we report the effect of replacing Mn2+ ions with Ni2+ on the ferroelectricity of multiferroic MnWO4 single crystals. When the amount of substitution was close to 16%, the sign of ferroelectric polarization spontaneously became negative with respect to initial dc poling field at a few degrees below TC. Neutron diffraction intensities revealed a sudden change in the underlying spiral spin ordering that occurred coincidentally with the observed sign reversal. This unusual behavior in zero magnetic fields suggests that strong competitions between the two different magnetic ions may provide an efficient route to manipulation of existing multiferroics.

  11. Ferroelectric control of a Mott insulator

    PubMed Central

    Yamada, Hiroyuki; Marinova, Maya; Altuntas, Philippe; Crassous, Arnaud; Bégon-Lours, Laura; Fusil, Stéphane; Jacquet, Eric; Garcia, Vincent; Bouzehouane, Karim; Gloter, Alexandre; Villegas, Javier E.; Barthélémy, Agnès; Bibes, Manuel

    2013-01-01

    The electric field control of functional properties is an important goal in oxide-based electronics. To endow devices with memory, ferroelectric gating is interesting, but usually weak compared to volatile electrolyte gating. Here, we report a very large ferroelectric field-effect in perovskite heterostructures combining the Mott insulator CaMnO3 and the ferroelectric BiFeO3 in its “supertetragonal” phase. Upon polarization reversal of the BiFeO3 gate, the CaMnO3 channel resistance shows a fourfold variation around room temperature, and a tenfold change at ~200 K. This is accompanied by a carrier density modulation exceeding one order of magnitude. We have analyzed the results for various CaMnO3 thicknesses and explain them by the electrostatic doping of the CaMnO3 layer and the presence of a fixed dipole at the CaMnO3/BiFeO3 interface. Our results suggest the relevance of ferroelectric gates to control orbital- or spin-ordered phases, ubiquitous in Mott systems, and pave the way toward efficient Mott-tronics devices. PMID:24089020

  12. Ferroelectric polarization reversal in single crystals

    NASA Technical Reports Server (NTRS)

    Stadler, Henry L.

    1992-01-01

    Research on the reversal of polarization in ferroelectric crystals is reviewed. Particular attention is given to observation methods for polarization reversal, BaTiO3 polarization reversal, crystal thickness dependence of polarization reversal, and domain wall movement during polarization reversal in TGS.

  13. Strain Tuning of Ferroelectric Thin Films *

    NASA Astrophysics Data System (ADS)

    Schlom, Darrell G.; Chen, Long-Qing; Eom, Chang-Beom; Rabe, Karin M.; Streiffer, Stephen K.; Triscone, Jean-Marc

    2007-08-01

    Predictions and measurements of the effect of biaxial strain on the properties of epitaxial ferroelectric thin films and superlattices are reviewed. Results for single-layer ferroelectric films of biaxially strained SrTiO3, BaTiO3, and PbTiO3 as well as PbTiO3/SrTiO3 and BaTiO3/SrTiO3 superlattices are described. Theoretical approaches, including first principles, thermodynamic analysis, and phase-field models, are applied to these biaxially strained materials, the assumptions and limitations of each technique are explained, and the predictions are compared. Measurements of the effect of biaxial strain on the paraelectric-to-ferroelectric transition temperature (TC) are shown, demonstrating the ability of percent-level strains to shift TC by hundreds of degrees in agreement with the predictions that predated such experiments. Along the way, important experimental techniques for characterizing the properties of strained ferroelectric thin films and superlattices, as well as appropriate substrates on which to grow them, are mentioned.

  14. Ferroelectric polarization reversal via successive ferroelastic transitions.

    PubMed

    Xu, Ruijuan; Liu, Shi; Grinberg, Ilya; Karthik, J; Damodaran, Anoop R; Rappe, Andrew M; Martin, Lane W

    2015-01-01

    Switchable polarization makes ferroelectrics a critical component in memories, actuators and electro-optic devices, and potential candidates for nanoelectronics. Although many studies of ferroelectric switching have been undertaken, much remains to be understood about switching in complex domain structures and in devices. In this work, a combination of thin-film epitaxy, macro- and nanoscale property and switching characterization, and molecular dynamics simulations are used to elucidate the nature of switching in PbZr(0.2)Ti(0.8)O3 thin films. Differences are demonstrated between (001)-/(101)- and (111)-oriented films, with the latter exhibiting complex, nanotwinned ferroelectric domain structures with high densities of 90° domain walls and considerably broadened switching characteristics. Molecular dynamics simulations predict both 180° (for (001)-/(101)-oriented films) and 90° multi-step switching (for (111)-oriented films) and these processes are subsequently observed in stroboscopic piezoresponse force microscopy. These results have implications for our understanding of ferroelectric switching and offer opportunities to change domain reversal speed. PMID:25344784

  15. Ferroelectric control of metal-insulator transition

    NASA Astrophysics Data System (ADS)

    He, Xu; Jin, Kui-juan; Ge, Chen; Ma, Zhong-shui; Yang, Guo-zhen

    2016-03-01

    We propose a method of controlling the metal-insulator transition of one perovskite material at its interface with another ferroelectric material based on first principle calculations. The operating principle is that the rotation of oxygen octahedra tuned by the ferroelectric polarization can modulate the superexchange interaction in this perovskite. We designed a tri-color superlattice of (BiFeO3)N/LaNiO3/LaTiO3, in which the BiFeO3 layers are ferroelectric, the LaNiO3 layer is the layer of which the electronic structure is to be tuned, and LaTiO3 layer is inserted to enhance the inversion asymmetry. By reversing the ferroelectric polarization in this structure, there is a metal-insulator transition of the LaNiO3 layer because of the changes of crystal field splitting of the Ni eg orbitals and the bandwidth of the Ni in-plane eg orbital. It is highly expected that a metal-transition can be realized by designing the structures at the interfaces for more materials.

  16. Local polarization dynamics in ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Kalinin, Sergei V.; Morozovska, Anna N.; Qing Chen, Long; Rodriguez, Brian J.

    2010-05-01

    Ferroelectrics and multiferroics have recently emerged as perspective materials for information technology and data storage applications. The combination of extremely narrow domain wall width and the capability to manipulate polarization by electric field opens the pathway toward ultrahigh (>10 TBit inch-2) storage densities and small (sub-10 nm) feature sizes. The coupling between polarization and chemical and transport properties enables applications in ferroelectric lithography and electroresistive devices. The progress in these applications, as well as fundamental studies of polarization dynamics and the role of defects and disorder on domain nucleation and wall motion, requires the capability to probe these effects on the nanometer scale. In this review, we summarize the recent progress in applications of piezoresponse force microscopy (PFM) for imaging, manipulation and spectroscopy of ferroelectric switching processes. We briefly introduce the principles and relevant instrumental aspects of PFM, with special emphasis on resolution and information limits. The local imaging studies of domain dynamics, including local switching and relaxation accessed through imaging experiments and spectroscopic studies of polarization switching, are discussed in detail. Finally, we review the recent progress on understanding and exploiting photochemical processes on ferroelectric surfaces, the role of surface adsorbates, and imaging and switching in liquids. Beyond classical applications, probing local bias-induced transition dynamics by PFM opens the pathway to studies of the influence of a single defect on electrochemical and solid state processes, thus providing model systems for batteries, fuel cells and supercapacitor applications.

  17. Ferroelectric Devices Emit Charged Particles and Radiation

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Sherrit, Stewart; Bao, Xiaoqi; Felsteiner, Joshua; Karsik, Yakov

    2005-01-01

    Devices called solid-state ferroelectric- based sources (SSFBSs) are under development as sources of electrons, ions, ultraviolet light, and x-rays for diverse applications in characterization and processing of materials. Whereas heretofore it has been necessary to use a different device to generate each of the aforementioned species of charged particles or radiation, a single SSFBS can be configured and operated to selectively generate any of the species as needed using a single source. Relative to comparable prior sources based, variously, on field emission, thermionic emission, and gaseous discharge plasmas, SSFBSs demand less power, and are compact and lightweight. An SSFBS exploits the unique physical characteristics of a ferroelectric material in the presence of a high-frequency pulsed electric field. The basic building block of an SSFBS is a ferroelectric cathode -- a ferroelectric wafer with a solid electrode covering its rear face and a grid electrode on its front face (see figure). The application of a voltage pulse -- typically having amplitude of several kilovolts and duration of several nanoseconds -- causes dense surface plasma to form near the grid wires on the front surface.

  18. Local Polarization Dynamics in Ferroelectric Materials

    SciTech Connect

    Kalinin, Sergei V; Morozovska, A. N.; Chen, L. Q.; Rodriguez, Brian J

    2010-01-01

    Ferroelectrics and multiferroics have recently emerged as perspective materials for information technology and data storage applications. The combination of extremely narrow domain wall width and the capability to manipulate polarization by electric field opens the pathway towards ultrahigh (>10 TBit/in2) storage densities and small (sub-10 nm) feature sizes. The coupling between polarization and chemical and transport properties enables applications in ferroelectric lithography and electroresistive devices. The progress in these applications, as well as fundamental studies of polarization dynamics and the role of defects and disorder on domain nucleation and wall motion, requires the capability to probe these effects on the nanometer scale. In this review, we summarize recent progress in applications of Piezoresponse Force Microscopy (PFM) for imaging, manipulation, and spectroscopy of ferroelectric switching processes. We briefly introduce the principles and relevant instrumental aspects of PFM, with special emphasis on resolution and information limits. The local imaging studies of domain dynamics, including local switching and relaxation accessed through imaging experiments, and spectroscopic studies of polarization switching, are discussed in detail. Finally, we briefly review the recent progress on photochemical processes on ferroelectric surfaces, the role of surface adsorbates, and imaging and switching in liquids. Beyond classical applications, probing local bias-induced transition dynamics by PFM opens the pathway to studies of the influence of a single defect on electrochemical and solid state processes, thus providing model systems for batteries, fuel cells, and supercapacitor applications.

  19. Photovoltaics with Ferroelectrics: Current Status and Beyond.

    PubMed

    Paillard, Charles; Bai, Xiaofei; Infante, Ingrid C; Guennou, Maël; Geneste, Grégory; Alexe, Marin; Kreisel, Jens; Dkhil, Brahim

    2016-07-01

    Ferroelectrics carry a switchable spontaneous electric polarization. This polarization is usually coupled to strain, making ferroelectrics good piezoelectrics. When coupled to magnetism, they become so-called multiferroic systems, a field that has been widely investigated since 2003. While ferroelectrics are birefringent and non-linear optically transparent materials, the coupling of polarization with optical properties has received, since 2009, renewed attention, triggered notably by low-bandgap ferroelectrics suitable for sunlight spectrum absorption and original photovoltaic effects. Consequently, power conversion efficiencies up to 8.1% were recently achieved and values of 19.5% were predicted, making photoferroelectrics promising photovoltaic alternatives. This article aims at providing an up-to-date review on this emerging and rapidly progressing field by highlighting several important issues and parameters, such as the role of domain walls, ways to tune the bandgap, consequences arising from the polarization switchability, and the role of defects and contact electrodes, as well as the downscaling effects. Beyond photovoltaicity, other polarization-related processes are also described, like light-induced deformation (photostriction) or light-assisted chemical reaction (photostriction). It is hoped that this overview will encourage further avenues to be explored and challenged and, as a byproduct, will inspire other research communities in material science, e.g., so-called hybrid halide perovskites. PMID:27135419

  20. A Model for Ferroelectric Phase Shifters

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.; Qureshi, A. Haq

    2000-01-01

    Novel microwave phase shifters consisting of coupled microstrip lines on thin ferroelectric films have been demonstrated recently. A theoretical model useful for predicting the propagation characteristics (insertion phase shift, dielectric loss, impedance, and bandwidth) is presented here. The model is based on a variational solution for line capacitance and coupled strip transmission line theory.

  1. Quantum criticality in a uniaxial organic ferroelectric

    NASA Astrophysics Data System (ADS)

    Rowley, S. E.; Hadjimichael, M.; Ali, M. N.; Durmaz, Y. C.; Lashley, J. C.; Cava, R. J.; Scott, J. F.

    2015-10-01

    Tris-sarcosine calcium chloride (TSCC) is a highly uniaxial ferroelectric with a Curie temperature of approximately 130 K. By suppressing ferroelectricity with bromine substitution on the chlorine sites, pure single crystals were tuned through a ferroelectric quantum phase transition. The resulting quantum critical regime was investigated in detail and was found to persist up to temperatures of at least 30-40 K. The nature of long-range dipole interactions in uniaxial materials, which lead to non-analytical terms in the free-energy expansion in the polarization, predict a dielectric susceptibility varying as 1/T 3close to the quantum critical point. Rather than this, we find that the dielectric susceptibility varies as 1/T 2 as expected and observed in better known multi-axial systems. We explain this result by identifying the ultra-weak nature of the dipole moments in the TSCC family of crystals. Interestingly, we observe a shallow minimum in the inverse dielectric function at low temperatures close to the quantum critical point in paraelectric samples that may be attributed to the coupling of quantum polarization and strain fields. Finally, we present results of the heat capacity and electro-caloric effect and explain how the time dependence of the polarization in ferroelectrics and paraelectrics should be considered when making quantitative estimates of temperature changes induced by applied electric fields.

  2. Intrinsic ferroelectric switching from first principles

    NASA Astrophysics Data System (ADS)

    Liu, Shi; Grinberg, Ilya; Rappe, Andrew M.

    2016-06-01

    The existence of domain walls, which separate regions of different polarization, can influence the dielectric, piezoelectric, pyroelectric and electronic properties of ferroelectric materials. In particular, domain-wall motion is crucial for polarization switching, which is characterized by the hysteresis loop that is a signature feature of ferroelectric materials. Experimentally, the observed dynamics of polarization switching and domain-wall motion are usually explained as the behaviour of an elastic interface pinned by a random potential that is generated by defects, which appear to be strongly sample-dependent and affected by various elastic, microstructural and other extrinsic effects. Theoretically, connecting the zero-kelvin, first-principles-based, microscopic quantities of a sample with finite-temperature, macroscopic properties such as the coercive field is critical for material design and device performance; and the lack of such a connection has prevented the use of techniques based on ab initio calculations for high-throughput computational materials discovery. Here we use molecular dynamics simulations of 90° domain walls (separating domains with orthogonal polarization directions) in the ferroelectric material PbTiO3 to provide microscopic insights that enable the construction of a simple, universal, nucleation-and-growth-based analytical model that quantifies the dynamics of many types of domain walls in various ferroelectrics. We then predict the temperature and frequency dependence of hysteresis loops and coercive fields at finite temperatures from first principles. We find that, even in the absence of defects, the intrinsic temperature and field dependence of the domain-wall velocity can be described with a nonlinear creep-like region and a depinning-like region. Our model enables quantitative estimation of coercive fields, which agree well with experimental results for ceramics and thin films. This agreement between model and experiment suggests

  3. Intrinsic ferroelectric switching from first principles.

    PubMed

    Liu, Shi; Grinberg, Ilya; Rappe, Andrew M

    2016-06-16

    The existence of domain walls, which separate regions of different polarization, can influence the dielectric, piezoelectric, pyroelectric and electronic properties of ferroelectric materials. In particular, domain-wall motion is crucial for polarization switching, which is characterized by the hysteresis loop that is a signature feature of ferroelectric materials. Experimentally, the observed dynamics of polarization switching and domain-wall motion are usually explained as the behaviour of an elastic interface pinned by a random potential that is generated by defects, which appear to be strongly sample-dependent and affected by various elastic, microstructural and other extrinsic effects. Theoretically, connecting the zero-kelvin, first-principles-based, microscopic quantities of a sample with finite-temperature, macroscopic properties such as the coercive field is critical for material design and device performance; and the lack of such a connection has prevented the use of techniques based on ab initio calculations for high-throughput computational materials discovery. Here we use molecular dynamics simulations of 90° domain walls (separating domains with orthogonal polarization directions) in the ferroelectric material PbTiO3 to provide microscopic insights that enable the construction of a simple, universal, nucleation-and-growth-based analytical model that quantifies the dynamics of many types of domain walls in various ferroelectrics. We then predict the temperature and frequency dependence of hysteresis loops and coercive fields at finite temperatures from first principles. We find that, even in the absence of defects, the intrinsic temperature and field dependence of the domain-wall velocity can be described with a nonlinear creep-like region and a depinning-like region. Our model enables quantitative estimation of coercive fields, which agree well with experimental results for ceramics and thin films. This agreement between model and experiment suggests

  4. Modified Johnson model for ferroelectric lead lanthanum zirconate titanate at very high fields and below Curie temperature.

    SciTech Connect

    Narayanan, M.; Tong, S.; Ma, B.; Liu, S.; Balachandran, U.

    2012-01-01

    A modified Johnson model is proposed to describe the nonlinear field dependence of the dielectric constant ({var_epsilon}-E loop) in ferroelectric materials below the Curie temperature. This model describes the characteristic ferroelectric 'butterfly' shape observed in typical {var_epsilon}-E loops. The predicted nonlinear behavior agreed well with the measured values in both the low- and high-field regions for lead lanthanum zirconate titanate films. The proposed model was also validated at different temperatures below the ferroelectric-to-paraelectric Curie point. The anharmonic coefficient in the model decreased from 6.142 x 10{sup -19} cm{sup 2}/V{sup 2} to 2.039 x 10{sup -19} cm{sup 2}/V{sup 2} when the temperature increased from 25 C to 250 C.

  5. Ferroelectric properties of lead-free polycrystalline CaBi2Nb2O9 thin films on glass substrates

    NASA Astrophysics Data System (ADS)

    Ahn, Yoonho; Jang, Joonkyung; Son, Jong Yeog

    2016-03-01

    CaBi2Nb2O9 (CBNO) thin film, a lead-free ferroelectric material, was prepared on a Pt/Ta/glass substrate via pulsed laser deposition. The Ta film was deposited on the glass substrate for a buffer layer. A (115) preferred orientation of the polycrystalline CBNO thin film was verified via X-ray diffraction measurements. The CBNO thin film on a glass substrate exhibited good ferroelectric properties with a remnant polarization of 4.8 μC/cm2 (2Pr ˜9.6 μC/cm2), although it had lower polarization than the epitaxially c-oriented CBNO thin film reported previously. A mosaic-like ferroelectric domain structure was observed via piezoresponse force microscopy. Significantly, the polycrystalline CBNO thin film showed much faster switching behavior within about 100 ns than that of the epitaxially c-oriented CBNO thin film.

  6. High-Resolution Field Effect Sensing of Ferroelectric Charges

    SciTech Connect

    Ko, Hyoungsoo; Ryu, Kyunghee; Park, Hongsik; Park, Chulmin; Jeon, Daeyoung; Kim, Yong Kwan; Jung, Juhwan; Min, Dong-Ki; Kim, Yunseok; Lee, Ho Nyung; Park, Yoondong; Shin, Hyunjung; Hong, Seungbum

    2011-01-01

    Nanoscale manipulation of surface charges and their imaging are essential for understanding local electronic behaviors of polar materials and advanced electronic devices. Electrostatic force microscopy and Kelvin probe force microscopy have been extensively used to probe and image local surface charges responsible for electrodynamics and transport phenomena. However, they rely on the weak electric force modulation of cantilever that limits both spatial and temporal resolutions. Here we present a field effect transistor embedded probe that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 {micro}s. On the basis of the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 0.08 {micro}C/cm{sup 2}, which is equivalent to 1/20 electron per nanometer square at room temperature.

  7. High resolution field effect sensing of ferroelectric charges.

    SciTech Connect

    Ko, H.; Ryu, K.; Park, H.; Park, C.; Jeon, D.; Kim, Y. K.; Jung, J.; Min, D.-K.; Kim, Y.; Lee, H. N.; Park, Y.; Shin, H.; Hong, S.

    2011-03-04

    Nanoscale manipulation of surface charges and their imaging are essential for understanding local electronic behaviors of polar materials and advanced electronic devices. Electrostatic force microscopy and Kelvin probe force microscopy have been extensively used to probe and image local surface charges responsible for electrodynamics and transport phenomena. However, they rely on the weak electric force modulation of cantilever that limits both spatial and temporal resolutions. Here we present a field effect transistor embedded probe that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 {micro}s. On the basis of the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 0.08 {micro}C/cm{sup 2}, which is equivalent to 1/20 electron per nanometer square at room temperature.

  8. Properties of ferroelectric/ferromagnetic thin film heterostructures

    SciTech Connect

    Chen, Daming; Harward, Ian; Linderman, Katie; Economou, Evangelos; Celinski, Zbigniew; Nie, Yan

    2014-05-07

    Ferroelectric/ferromagnetic thin film heterostructures, SrBi{sub 2}Ta{sub 2}O{sub 9}/BaFe{sub 12}O{sub 19} (SBT/BaM), were grown on platinum-coated Si substrates using metal-organic decomposition. X-ray diffraction patterns confirmed that the heterostructures contain only SBT and BaM phases. The microwave properties of these heterostructures were studied using a broadband ferromagnetic resonance (FMR) spectrometer from 35 to 60 GHz, which allowed us to determine gyromagnetic ratio and effective anisotropy field. The FMR linewidth is as low as140 Oe at 58 GHz. In addition, measurements of the effective permittivity of the heterostructures were carried out as a function of bias electric field. All heterostructures exhibit hysteretic behavior of the effective permittivity. These properties indicate that such heterostructures have potential for application in dual electric and magnetic field tunable resonators, filters, and phase shifters.

  9. Macroscopic response and directional disorder dynamics in chemically substituted ferroelectrics

    NASA Astrophysics Data System (ADS)

    Parravicini, Jacopo; DelRe, Eugenio; Agranat, Aharon J.; Parravicini, Gianbattista

    2016-03-01

    Using temperature-resolved dielectric spectroscopy in the range 25-320 K we investigate the macroscopic response, phase symmetry, and order/disorder states in bulk ferroelectric K1-yLiyTa1-xNbx (KLTN). Four long-range symmetry phases are identified with their relative transitions. Directional analysis of the order/disorder states using Fröhlich entropy indicates global symmetry breaking along the growth axis and an anisotropic dipolar effective thermodynamic behavior, which ranges from disordered to ordered at the same temperature for different directions in the sample. Results indicate that the macroscopic polarization, driven by nanosized polar regions, follows a microscopic perovskite eight-sites lattice model.

  10. Properties of ferroelectric/ferromagnetic thin film heterostructures

    NASA Astrophysics Data System (ADS)

    Chen, Daming; Harward, Ian; Linderman, Katie; Economou, Evangelos; Nie, Yan; Celinski, Zbigniew

    2014-05-01

    Ferroelectric/ferromagnetic thin film heterostructures, SrBi2Ta2O9/BaFe12O19 (SBT/BaM), were grown on platinum-coated Si substrates using metal-organic decomposition. X-ray diffraction patterns confirmed that the heterostructures contain only SBT and BaM phases. The microwave properties of these heterostructures were studied using a broadband ferromagnetic resonance (FMR) spectrometer from 35 to 60 GHz, which allowed us to determine gyromagnetic ratio and effective anisotropy field. The FMR linewidth is as low as140 Oe at 58 GHz. In addition, measurements of the effective permittivity of the heterostructures were carried out as a function of bias electric field. All heterostructures exhibit hysteretic behavior of the effective permittivity. These properties indicate that such heterostructures have potential for application in dual electric and magnetic field tunable resonators, filters, and phase shifters.

  11. High-resolution field effect sensing of ferroelectric charges.

    PubMed

    Ko, Hyoungsoo; Ryu, Kyunghee; Park, Hongsik; Park, Chulmin; Jeon, Daeyoung; Kim, Yong Kwan; Jung, Juhwan; Min, Dong-Ki; Kim, Yunseok; Lee, Ho Nyung; Park, Yoondong; Shin, Hyunjung; Hong, Seungbum

    2011-04-13

    Nanoscale manipulation of surface charges and their imaging are essential for understanding local electronic behaviors of polar materials and advanced electronic devices. Electrostatic force microscopy and Kelvin probe force microscopy have been extensively used to probe and image local surface charges responsible for electrodynamics and transport phenomena. However, they rely on the weak electric force modulation of cantilever that limits both spatial and temporal resolutions. Here we present a field effect transistor embedded probe that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 μs. On the basis of the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 0.08 μC/cm(2), which is equivalent to 1/20 electron per nanometer square at room temperature. PMID:21375284

  12. Ferroelectric devices using lead zirconate titanate (PZT) nanoparticles.

    PubMed

    Paik, Young Hun; Kojori, Hossein Shokri; Kim, Sung Jin

    2016-02-19

    We successfully demonstrate the synthesis of lead zirconate titanate nanoparticles (PZT NPs) and a ferroelectric device using the synthesized PZT NPs. The crystalline structure and the size of the nanocrystals are studied using x-ray diffraction and transmission electron microscopy, respectively. We observe <100 nm of PZT NPs and this result matches dynamic light scattering measurements. A solution-based low-temperature process is used to fabricate PZT NP-based devices on an indium tin oxide substrate. The fabricated ferroelectric devices are characterized using various optical and electrical measurements and we verify ferroelectric properties including ferroelectric hysteresis and the ferroelectric photovoltaic effect. Our approach enables low-temperature solution-based processes that could be used for various applications. To the best of our knowledge, this low-temperature solution processed ferroelectric device using PZT NPs is the first successful demonstration of its kind. PMID:26788984

  13. Ferroelectric devices using lead zirconate titanate (PZT) nanoparticles

    NASA Astrophysics Data System (ADS)

    Paik, Young Hun; Shokri Kojori, Hossein; Kim, Sung Jin

    2016-02-01

    We successfully demonstrate the synthesis of lead zirconate titanate nanoparticles (PZT NPs) and a ferroelectric device using the synthesized PZT NPs. The crystalline structure and the size of the nanocrystals are studied using x-ray diffraction and transmission electron microscopy, respectively. We observe <100 nm of PZT NPs and this result matches dynamic light scattering measurements. A solution-based low-temperature process is used to fabricate PZT NP-based devices on an indium tin oxide substrate. The fabricated ferroelectric devices are characterized using various optical and electrical measurements and we verify ferroelectric properties including ferroelectric hysteresis and the ferroelectric photovoltaic effect. Our approach enables low-temperature solution-based processes that could be used for various applications. To the best of our knowledge, this low-temperature solution processed ferroelectric device using PZT NPs is the first successful demonstration of its kind.

  14. Ferroelectric domain engineering by focused infrared femtosecond pulses

    SciTech Connect

    Chen, Xin; Shvedov, Vladlen; Sheng, Yan; Karpinski, Pawel; Koynov, Kaloian; Wang, Bingxia; Trull, Jose; Cojocaru, Crina; Krolikowski, Wieslaw

    2015-10-05

    We demonstrate infrared femtosecond laser-induced inversion of ferroelectric domains. This process can be realised solely by using tightly focused laser pulses without application of any electric field prior to, in conjunction with, or subsequent to the laser irradiation. As most ferroelectric crystals like LiNbO{sub 3}, LiTaO{sub 3}, and KTiOPO{sub 4} are transparent in the infrared, this optical poling method allows one to form ferroelectric domain patterns much deeper inside a ferroelectric crystal than by using ultraviolet light and hence can be used to fabricate practical devices. We also propose in situ diagnostics of the ferroelectric domain inversion process by monitoring the Čerenkov second harmonic signal, which is sensitive to the appearance of ferroelectric domain walls.

  15. Ferroelectric domain wall motion induced by polarized light.

    PubMed

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F

    2015-01-01

    Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO₃ single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO₃ at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

  16. Molecule-displacive ferroelectricity in organic supramolecular solids

    PubMed Central

    Ye, Heng-Yun; Zhang, Yi; Noro, Shin-ichiro; Kubo, Kazuya; Yoshitake, Masashi; Liu, Zun-Qi; Cai, Hong-Ling; Fu, Da-Wei; Yoshikawa, Hirofumi; Awaga, Kunio; Xiong, Ren-Gen; Nakamura, Takayoshi

    2013-01-01

    Ferroelectricity is essential to many forms of current technology, ranging from sensors and actuators to optical or memory devices. In this circumstance, organic ferroelectrics are of particular importance because of their potential application in tomorrow's organic devices, and several pure organic ferroelectrics have been recently developed. However, some problems, such as current leakage and/or low working frequencies, make their application prospects especially for ferroelectric memory (FeRAM) not clear. Here, we describe the molecule-displacive ferroelectricity of supramolecular adducts of tartaric acid and 1,4-diazabicyclo[2.2.2]octane N,N′-dioxide. The adducts show large spontaneous polarization, high rectangularity of the ferroelectric hysteresis loops even at high operation frequency (10 kHz), and high performance in polarization switching up to 1 × 106 times without showing fatigue. It opens great perspectives in terms of applications, especially in organic FeRAM. PMID:23873392

  17. Molecule-displacive ferroelectricity in organic supramolecular solids

    NASA Astrophysics Data System (ADS)

    Ye, Heng-Yun; Zhang, Yi; Noro, Shin-Ichiro; Kubo, Kazuya; Yoshitake, Masashi; Liu, Zun-Qi; Cai, Hong-Ling; Fu, Da-Wei; Yoshikawa, Hirofumi; Awaga, Kunio; Xiong, Ren-Gen; Nakamura, Takayoshi

    2013-07-01

    Ferroelectricity is essential to many forms of current technology, ranging from sensors and actuators to optical or memory devices. In this circumstance, organic ferroelectrics are of particular importance because of their potential application in tomorrow's organic devices, and several pure organic ferroelectrics have been recently developed. However, some problems, such as current leakage and/or low working frequencies, make their application prospects especially for ferroelectric memory (FeRAM) not clear. Here, we describe the molecule-displacive ferroelectricity of supramolecular adducts of tartaric acid and 1,4-diazabicyclo[2.2.2]octane N,N'-dioxide. The adducts show large spontaneous polarization, high rectangularity of the ferroelectric hysteresis loops even at high operation frequency (10 kHz), and high performance in polarization switching up to 1 × 106 times without showing fatigue. It opens great perspectives in terms of applications, especially in organic FeRAM.

  18. Ferroelectricity and Phase Transitions in Monolayer Group-IV Monochalcogenides.

    PubMed

    Fei, Ruixiang; Kang, Wei; Yang, Li

    2016-08-26

    Ferroelectricity usually fades away as materials are thinned down below a critical value. We reveal that the unique ionic-potential anharmonicity can induce spontaneous in-plane electrical polarization and ferroelectricity in monolayer group-IV monochalcogenides MX (M=Ge, Sn; X=S, Se). An effective Hamiltonian has been successfully extracted from the parametrized energy space, making it possible to study the ferroelectric phase transitions in a single-atom layer. The ferroelectricity in these materials is found to be robust and the corresponding Curie temperatures are higher than room temperature, making them promising for realizing ultrathin ferroelectric devices of broad interest. We further provide the phase diagram and predict other potentially two-dimensional ferroelectric materials. PMID:27610884

  19. Ferroelectric domain wall motion induced by polarized light

    PubMed Central

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F.

    2015-01-01

    Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

  20. Empirical model studies on relaxor behaviour in Bi2.5La1.5Ti3O12 ceramic

    NASA Astrophysics Data System (ADS)

    Selvamani, Rachna; Pandey, Adityanarayan; Gupta, S. M.

    2016-05-01

    Relaxor like dielectric characteristics have been observed for high La-concentration substituted bismuth titanate Bi2.5La1.5Ti3O12 ceramic. Frequency dependent temperature of dielectric maxima has been fitted with models of non-interacting and interacting polar region. This study clearly reveals slowing down of nano-polar dynamics into cluster like glass as proposed by cluster glass model. La-substitution at Bi-site of Bi2O2 layer is responsible for the random field generation.