Science.gov

Sample records for relaxor ferroelectric behavior

  1. Electromechanical behavior of relaxor ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Liu, Tieqi

    Relaxor ferroelectric PZN-xPT and PMN-xPT single crystals exhibit extraordinary electromechanical properties. They are under development for applications in sensors, actuators and transducers. The polarization switching and phase transition behavior of PZN-4.5%PT and PMN-32%PT single crystals under external loading has been investigated. Experimental investigation elucidates the polarization switching and phase transition behavior of relaxor ferroelectric crystals at different orientation cuts under combined temperature, electric field and stress loading. These crystals exhibit strong orientation dependence of electromechanical properties, and the applied fields all affect the poling and phase states of the crystals. Based on experimental investigation, crystal variant modeling was developed to compute the piezoelectric properties of multi-domain crystals at different orientation cuts from a set of properties for the single domain. Thermodynamics and work-energy analysis of field induced phase transitions in these single crystals sheds light on the phase transition mechanism of ferroelectric crystals. Fracture behavior of relaxor single crystals under non-uniform electric fields at a partial electrode edge has also been measured and analyzed.

  2. Monte Carlo simulation on dielectric and ferroelectric behaviors of relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Wang, X.; Liu, J.-M.; Chan, H. L. W.; Choy, C. L.

    2004-04-01

    The dielectric and ferroelectric behaviors of relaxor ferroelectrics over the ferroelectric transition range are simulated using Monte Carlo simulation. The simulation is based on the Ginzburg-Landau ferroelectric model lattice in which a random distribution of two types of defects (dopants) which will suppress and enhance the local polarization, respectively, is assumed. The simulation reveals an evolution of the ferroelectric transitions from a normal first-order mode toward a diffusive mode, with increasing defect concentration. The simulated lattice configuration shows the microdipole ordered clusters embedded in the matrix of paraelectric phase over a wide range of temperature, a characteristic of relaxor ferroelectrics. The relaxor-like behaviors are confirmed by the lattice free energy, dielectric susceptibility, and ferroelectric relaxation evaluated as a function of the defect concentration. Finally, we present a qualitative comparison of our simulated results with the simulation based on the coarse-grain model [C. C. Su, B. Vugmeister, and A. G. Khachaturyan, J. Appl. Phys. 90, 6345 (2001)].

  3. Relaxor ferroelectric behavior of poly(vinylidene fluoride-trifluorethylene) copolymer modified by low energy irradiation

    SciTech Connect

    Faria, Luiz O.; Welter, Cezar; Moreira, Roberto L.

    2006-05-08

    We report a relaxorlike modification in the ferroelectric poly(vinylidene fluoride-trifluorethylene) copolymer using ultraviolet (UV) irradiation. This behavior is clearly demonstrated by dielectric measurements. Besides the relaxor feature, the ferroelectric character of the material is retained, also exhibiting Curie transition at barely diminished temperatures. UV-Vis absorption measurements suggests that the UV radiation induces conjugated C=C bonds in the copolymer chains. The coexistence of both relaxor and ferroelectric behavior, the lack of chain cross-linking, and a weak reducing in the crystallinity suggest that the UV-induced defects are not sufficient to completely break up the polarization domains.

  4. 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.

  5. 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

  6. 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.

  7. Relaxor behavior of ferroelectric Ca0.22Sr0.12Ba0.66Nb2O6

    NASA Astrophysics Data System (ADS)

    Shekhar Pandey, Chandra; Schreuer, Jrgen; Burianek, Manfred; Mhlberg, Manfred

    2013-01-01

    The relaxor behavior of tetragonal tungsten bronze uniaxial relaxor ferroelectric calcium strontium barium niobate (Ca0.22Sr0.12Ba0.66Nb2O6 or CSBN-22) single crystal was studied by measuring elastic constants and thermal expansion with the aid of resonant ultrasound spectroscopy and dilatometry, respectively, in the temperature range 300 K-1503 K. Thermal expansion yields evidence of the Burns temperature TB and the intermediate characteristic temperature T*, which was also supported by the temperature evolutions of the elastic constants cij. CSBN-22 was found to be 2%-3% elastically stiffer than CBN-28. The presented results open the perspective to understand the relaxor behavior of CSBN.

  8. 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.

  9. Multiscale dynamics in relaxor ferroelectrics

    SciTech Connect

    Toulouse, J.; Cai, L; Pattnaik, R. K.; Boatner, Lynn 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 (PND) 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.

  10. Ferroelectric Relaxor Behavior and Impedance Spectroscopy of Pr and Sn-Doped LaBaMnO Ceramics

    NASA Astrophysics Data System (ADS)

    Rhouma, F. I. H.; Dhahri, A.; Lahmar, L.; Khirouni, K.; Dhahri, J.

    2015-03-01

    The ceramic sample is synthesized in the solid-state with a nominal chemical formula (LPBMS). X-ray diffraction patterns confirm the formation of a single-phase cubic crystal symmetry (. Furthermore, the complex impedance plots display a single semicircle highlighting the influence of grain resistance on the electrical behavior. A detailed study of impedance parameters shows the non-Debye temperature of relaxation phenomena in the system. Over four decades in frequency, sample Nyquist plots were fitted by adopting an equivalent circuit using constant phase elements. The temperature dependence of dielectric permittivity was investigated in the sample, and the dielectric relaxation behavior was observed in these ferroelectrics with diffused phase transition. Quasiferroeletric state theory has been introduced to explain the dielectric results of the LPBMS relaxors.

  11. 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.

  12. Effects of composition and temperature on the large field behavior of [011]C relaxor ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    The large field behavior of [011]C cut relaxor ferroelectric lead indium niobate-lead magnesium niobate-lead titanate, xPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3, single crystals was experimentally characterized in the piezoelectric d322-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.

  13. 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.

  14. 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

  15. 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

  16. 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.

  17. Field-induced percolation of polar nanoregions in relaxor ferroelectrics.

    PubMed

    Prosandeev, S; Wang, Dawei; Akbarzadeh, A R; Dkhil, B; Bellaiche, L

    2013-05-17

    A first-principles-based effective Hamiltonian is used to investigate low-temperature properties of Ba(Zr,Ti)O(3) relaxor ferroelectrics under an increasing dc electric field. This system progressively develops an electric polarization that is highly nonlinear with the dc field. This development leads to a maximum of the static dielectric response at a critical field, E(th), and involves four different field regimes. Each of these regimes is associated with its own behavior of polar nanoregions, such as shrinking, flipping, and elongation of dipoles or change in morphology. The clusters propagating inside the whole sample, with dipoles being parallel to the field direction, begin to form at precisely the E(th) critical field. Such a result, and further analysis we perform, therefore, reveal that field-induced percolation of polar nanoregions is the driving mechanism for the transition from the relaxor to ferroelectric state. PMID:25167451

  18. Aging and Barkhausen noise in the relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Chao, Lambert Key

    Relaxor ferroelectrics are disordered crystalline materials whose polar order is limited to mesoscopic-scaled nanodomains. There is no ferroelectric phase transition, but a faster than Arrhenius cooperative freezing into a glassy relaxor regime instead. It is not understood how the random fields and random interactions present in these dielectrics inhibit the formation of long-range ferroelectric order. This thesis presents two types of experiments aimed at shedding light on this issue: aging and Barkhausen noise. Aging shows low-temperature regimes with spin-glass-like behavior in relaxors with cubic perovskite crystalline structure that are not present in those with uniaxial tungsten-bronze crystalline structure. In particular, the cubic relaxor PMN/PT (90/10) [(PbMn1/3Nb2/3O3)1- x(PbTiO3)x, x = 0.1] shows aging that directly parallels that in re-entrant spin-glasses, with "hole-like" aging at low-temperature, where the uniaxial relaxor SBN:La (60/40) [Srx-yLayBa1- xNb2O6, x = 0.6, y = 0.01] shows cumulative, not "hole-like" aging. The Barkhausen experiments measure the noise from the abrupt reorientation of polar clusters driven by an ac field, giving a measure of a typical dynamic dipole step size in PMN/PT (90/10) of about 100 nanodomains in the paraelectric regime, which then abruptly freezes out on cooling into the relaxor regime. This suggests an abrupt growth of barriers associated with the dipoles. The presence of complicated spin-glass-like aging, requiring cooperativity between many aging units, combined with the relative insensitivity of aging effects to small field perturbations suggest that units much smaller than nanodomains are responsible for the aging. This points to a picture of the cubic relaxors where polar regions are coupled to canted moments orthogonal to the mean mid-scale polarization (Egami, 1999; Dkhil et al., 2001) which provide the glassy freezing, much like a re-entrant xy spin-glass. These canted moments are the unit cell analogs to tweed domain-patterning seen in PMN/PT compositions with large ferroelectric doping (Viehland et al., 1995; Xunhu et al., 1994). We note the relevance of a theory mapping the pre-martensitic tweed Hamiltonian onto a spin-glass Hamiltonian (Kartha et al., 1991; Sethna et al., 1992). We also present evidence of possible discrete polarization/depolarization steps in the pyroelectric current of SBN:La (60/40).

  19. Induction of relaxor state in ordinary ferroelectrics by isovalent ion substitution: A pretransitional martensitic texture case

    NASA Astrophysics Data System (ADS)

    Lente, M. H.; Moreira, E. N.; Garcia, D.; Eiras, J. A.; Neves, P. P.; Doriguetto, A. C.; Mastelaro, V. R.; Mascarenhas, Y. P.

    2006-02-01

    The understanding of the structural origin of relaxor ferroelectrics has been doubtlessly a long-standing puzzle in the field of ferroelectricity. Thus, motivated by the interest in improving the comprehension of this important issue, it a framework is proposed for explaining the origin of the relaxor state in ordinary ferroelectrics induced via the isovalent-ion substitution. Based on the martensitic transformation concepts, it is proposed that the continuous addition of isovalent ions in a so-called normal ferroelectric decreases considerably the elastic strain energy. This results in a gradual transformation of ferroelectric domain patterns from a micrometer polydomain structure (twins), through single domains, to nanometer-polar-tweed structures with glasslike behavior, that are, in turn, strongly driven by point defects and surface effects. The electrical interaction between these weakly coupled polar-tweed structures leads to a wide spectrum of relaxation times, thus resulting in a dielectric relaxation process, the signature of relaxor ferroelectrics.

  20. Development of "fragility" in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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(Mg1/3Nb2/3)O3-x%PbTiO3 (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 Tc. A reasonable physical scenario, based on our "configurational-entropy-loss" theory and Nowick's "stress-induced-ordering" theory, was proposed.

  1. Relaxor ferroelectric behavior and collective modes in the ?-d correlated anomalous metal ?-(BEDT-TSF)2FeCl4

    NASA Astrophysics Data System (ADS)

    Matsui, H.; Tsuchiya, H.; Suzuki, T.; Negishi, E.; Toyota, N.

    2003-10-01

    We have investigated the microwave response at 44.5 GHz with respect to temperature T and external magnetic field H in ?-(BEDT-TSF)2FeCl4 forming a quasi two-dimensional electronic system with ?-d correlations. At 8.3 K [=TMI, the metal-insulator (MI) transition temperature] ferroelectric transition, but of relaxor ferroelectric behaviors. It is expected that dielectric domains or stripes with less metallic conductions emerge inhomogeneously in the ? electronic systems. Above TFM, where microwave anomalies are not present, the interplane and intraplane microwave conductivities hold anisotropies ?c1/?b*1?103 and ?c1/?a*1?10. In the antiferromagnetic insulating state, ?c1 becomes much conductive in comparison with ?cdc. Together with low frequency data, ?c1 is found to exhibit a large frequency dispersion. The microwave response is not attributed to single particle excitations, but to some collective mode excitations associated with charge degrees of freedom. The H-T phase diagram of the MI transition determined by the present microwave measurements is independent of the orientations of H, and coincides well with the phase diagram obtained by the dc magnetoresistivity and magnetization. Spin waves for the hard axis are observed as an absorption peak in the width change for the microwave magnetic field applied parallel to both H and a*.

  2. Pressure as a Probe of the Physics of Relaxor Ferroelectrics

    SciTech Connect

    Samara, George A.

    1999-08-09

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

  3. Mechanism of Diffuse Phase Transition in Relaxor Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Tsurumi, Takaaki; Soejima, Kouji; Kamiya, Toshio; Daimon, Masaki

    1994-04-01

    Dielectric properties of lead magnesium niobate (PMN) and Ta-bearing strontium barium niobate (SBNT) were measured as a function of temperature, and the crystal structure of PMN was refined by the Rietveld analysis method. The results of structure refinement indicate that the volume of polar microregions (PMR) increases with decreasing temperature. The dielectric properties of PMN and SBNT are well explained by an advanced theory of dielectric dispersion. The anomalous behavior in dielectric permittivity (?) observed on the low temperature side of T m, the temperature of ? maximum, is explained by simple dielectric relaxation, while on the high-temperature side of T m is explained by the volume increase of PMR. It is concluded that these is no phase transition around T m, and the diffuse phase transition is an overlapping phenomenon of volume increase of PMR, freezing process of fluctuating dipoles in PMR and dielectric dispersion around the measuring frequrncy. A model of diffuse phase transition and relaxor ferroelectrics is proposed. The difference between normal ferroelectrics and relaxor ferroelectrics is discussed from the viewpoints of spreading of soft-mode phonons and disorder in the crystals.

  4. Normal ferroelectric to relaxor behavior in laser ablated Ca-doped barium titanate thin films

    NASA Astrophysics Data System (ADS)

    Victor, P.; Ranjith, R.; Krupanidhi, S. B.

    2003-12-01

    Ba1-xCaxTiO3 thin films (x=0.05 to 0.17) were deposited on Pt-coated Si substrates using a pulsed excimer laser ablation technique. X-ray diffraction and scanning electron microscope studies of the Ba1-xCaxTiO3 targets exhibit a polycrystalline nature and thin films also show the same but with a significant orientation along the (111) direction. Secondary ion mass spectrometer analysis reveals the presence of a sharper interface existing at the thin film substrate. The dielectric phase transition temperature of (Ba1-xCax)TiO3 targets were sharp and the transition temperature was found to decrease from 140 C to 110 C with an increase in the values of x (x>0.05 at. %). The laser ablated Ca-doped BaTiO3 thin films deposited at 100 mTorr exhibited a higher dielectric constant, lower dielectric loss, and an anomalous decrease in phase transition was observed. The anomalous phase transition decrease was ascribed to the occupancy of the Ca2+ in the Ti4+ site. There was a cross over from the sharp to diffused phase transition for a higher composition of Ca (>9 at. %) in BaTiO3 thin films. The diffuse transition behavior might be due to the larger number of the Ca2+ ions occupying the Ti4+ site, eventually introducing larger compositional and structural disorder and this occupancy leads to the generation of oxygen vacancies. The activation energy obtained from impedance spectroscopy was 1.05 eV, and was attributed to the oxygen vacancy motion.

  5. Anomalous elastic behavior of relaxor ferroelectric Ca0.28Ba0.72Nb2O6 single crystals

    NASA Astrophysics Data System (ADS)

    Pandey, Chandra Shekhar; Schreuer, Jrgen; Burianek, Manfred; Mhlberg, Manfred

    2011-11-01

    Full sets of elastic constants cij of tetragonal tungsten bronze relaxor ferroelectric Ca0.28Ba0.72Nb2O6 (CBN-28) single crystals are measured above Curie temperature up to 1503 K employing resonant ultrasound spectroscopy. Thermal expansion measurements on as-grown unpoled CBN-28 reveal the existence of a characteristic temperature T * (800 K) for CBN-28 between the Burns temperature Tb (1100 K) and the temperature of maximum dielectric permittivity Tm (600 K). The influence of polar nanoregions (PNRs) on the elastic properties of CBN-28 is studied in detail. The temperature evolution of cij shows pronounced anomalies. All independent elastic constants evolved differently, with temperature reflecting their coupling to different types of the reorientational motion of PNRs through their interaction with acoustic waves. The anisotropy of longitudinal elastic stiffness coefficients and the deviation from Cauchy relations for CBN-28 are also studied, showing the evolution of material anisotropy and the nature of bonding interactions with temperature, respectively.

  6. 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.

  7. 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.

  8. Multinuclear NMR studies of relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zhou, Donghua

    Multinuclear NMR of 93Nb, 45Sc, and 207Pb has been carried out to study the structure, disorder, and dynamics of a series of important solid solutions: perovskite relaxor ferroelectric materials (1-x) Pb(Mg1/3Nb 2/3)O3-x Pb(Sc1/2Nb1/2)O 3 (PMN-PSN). 93Nb NMR investigations of the local structure and cation order/disorder are presented as a function of PSN concentration, x. The superb fidelity and accuracy of 3QMAS allows us to make clear and consistent assignments of spectral intensities to the 28 possible nearest B-site neighbor (nBn) configurations, (NMg, NSc, NNb), where each number ranges from 0 to 6 and their sum is 6. For most of the 28 possible nBn configurations, isotropic chemical shifts and quadrupole product constants have been extracted from the data. The seven configurations with only larger cations, Mg 2+ and Sc3+ (and no Nb5+) are assigned to the seven observed narrow peaks, whose deconvoluted intensities facilitate quantitative evaluation of, and differentiation between, different models of B-site (chemical) disorder. The "completely random" model is ruled out and the "random site" model is shown to be in qualitative agreement with the NMR experiments. To obtain quantitative agreement with observed NMR intensities, the random site model is slightly modified by including unlike-pair interaction energies. To date, 45Sc studies have not been as fruitful as 93Nb NMR because the resolution is lower in the 45Sc spectra. The lower resolution of 45Sc spectra is due to a smaller span of isotropic chemical shift (40 ppm for 45Sc vs. 82 ppm for 93Nb) and to the lack of a fortuitous mechanism that simplifies the 93Nb spectra; for 93Nb the overlap of the isotropic chemical shifts of 6-Sc and 6-Nb configurations results in the alignment of all the 28 configurations along only seven quadrupole distribution axes. Finally we present variable temperature 207Pb static, MAS, and 2D-PASS NMR studies. Strong linear correlations between isotropic and anisotropic chemical shifts show that Pb-O bonds vary from more ionic to more covalent environments. Distributions of Pb-O bond lengthes are also quantitatively described. Such distributions are used to examine two competing models of Pb displacements; the shell model and the unique direction model. Only the latter model is able to reproduce the observed Pb-O distance distribution.

  9. Spherical random-bond-random-field model of relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pirc, R.; Blinc, R.

    1999-11-01

    A model of relaxor ferroelectrics based on the interacting polar clusters picture has been formulated. The electric dipole moment of a nanosized polar domain is allowed a large number of discrete orientations and its length is assumed to fluctuate in a broad interval. Introducing a set of quasicontinuous order parameter fields and imposing a global spherical constraint, the spherical random-bond-random-field (SRBRF) model is written down and its static properties are investigated. It is found that for weak random fields the scaled third-order nonlinear susceptibility a3=?3/?41 shows a nearly divergent behavior in the spherical glass phase, but there is no such anomaly in a random-field frustrated ferroelectric state. The probability distribution of local cluster polarization is calculated and its relation to the quadrupole perturbed NMR line shape of 93Nb in PMN is discussed. The fact that the observed line shape is Gaussian at all temperatures provides strong support to the SRBRF model.

  10. Mesoscopic cell structure of relaxor ferroelectrics at morphotropic phase boundary

    NASA Astrophysics Data System (ADS)

    Ahn, Sang-Jin; Kim, Jong-Jean

    2003-03-01

    Mesoscopic cell structure of relaxor ferroelectrics at morphotropic phase boundary Sang-Jin Ahn and Jong-Jean Kim Physics Department, KAIST, Taejon 305-701, Korea Relaxor-based ferroelectrics such as PZN-xPT and PMN-xPT have drawn a great attention due to an observation of a huge piezoelectric coefficient and an ultra high strain level. Although the first principle calculations on the basis of a single perovskite unit cell structure could explain much of the experimental observations, recent observations of a complex mesoscopic ordering and a heterogeneous domain structure suggest a composite cell of many perovskite units as a basic building block. Raman scattering spectra and observed stoichiometry of PZN-xPT and PMN-xPT allow for only a random pile-up structure of the composite block cells. Our composite block cell needs 27 perovskite unit cells to satisfy the morphotropic phase boundary conditions of structural and compositional variations. Using this mesoscopic block cell model we calculate for allowed mixing concentrations x at morphotropic phase boundaries of relaxor ferroelectrics, which agree with observed values.

  11. First-principles study of the relaxor ferroelectricity of Ba(Zr, Ti)O3

    NASA Astrophysics Data System (ADS)

    Yang, Li-Juan; Wu, Ling-Zhi; Dong, Shuai

    2015-12-01

    Ba(Zr, Ti)O3 is a lead-free relaxor ferroelectric. Using the first-principles method, the ferroelectric dipole moments for pure BaTiO3 and Ba(Zr, Ti)O3 supercells are studied. All possible ion configurations of BaZr0.5Ti0.5O3 and BaZr0.25Ti0.75O3 are constructed in a 2 2 2 supercell. For the half-substituted case, divergence of ferroelectric properties is found from these structures, which greatly depends on the arrangements of Ti and Zr ions. Thus our results provide a reasonable explanation to the relaxor behavior of Ba(Zr, Ti)O3. In addition, a model based on the thermal statistics gives the averaged polarization for Ba(Zr, Ti)O3, which depends on the temperature of synthesis. Our result is helpful to understand and tune the relaxor ferroelectricity of lead-free Ba(Zr, Ti)O3. Project supported by the National Natural Science Foundation of China (Grant Nos.51322206 and 11274060) and the Natural Science Foundation of Jiangsu Province, China (Grant No.15KJB140009).

  12. Molecular Dynamics Studies of Structure, Dynamics and Dielectric Response in a Relaxor Ferroelectric

    NASA Astrophysics Data System (ADS)

    Grinberg, Ilya

    2012-02-01

    Since the first synthesis of the classic PbMg1/3Nb2/3O3 (PMN) material in 1961, relaxor ferroelectrics have been the subject of ongoing experimental and theoretical investigation due to their fundamental scientific interest and their importance in technological applications. We use atomistic molecular dynamics simulations to study relaxor behavior in the 0.75PMN-0.25PT material. Even for a fairly small simulation size of 1000 atoms, the system exhibits frequency dispersion and deviation from the Curie-Weiss law typical of relaxor materials. Analysis of the time autocorrelation functions for individual atoms allows us to identify the Nb atoms with a high concentration of neighboring Ti atoms as the nucleation sites for the relaxor behavior. This is due to the higher coupling between the cation displacements induced by the presence of overbonded oxygen atoms. We also analyze local structure and dynamics in PMN-PT using instantaneous, time-averaged and frequency resolved pair distribution functions (PDF). We find that dynamic Pb and Ti off-centering is present even in the paraelectric phase, below Tb the rate of growth of local Pb off-centering increases, followed by the freezing in of the local displacement direction at an intermediate temperature Tc and a transition to a ferroelectric-like phase at Tf. Thus there is a sequence of four phases, PE, dynamic relaxor, mixed dynamic and frozen phase, and the non-ergodic frozen relaxor phase. We identify the average instantaneous local cation off-centering as the order parameter for the dynamic relaxor phase, and the time-averaged local cation off-centering as the order parameter for the two lower-temperatures relaxor phases. Examination of the dynamic PDF data reveals the shape and the range of correlation between the cation displacements. We also show that the relaxor phase is characterized by the appearance of strong nearest-neighbor correlation between the off-center displacements along the Cartesian directions.

  13. Properties of epitaxial films made of relaxor ferroelectrics.

    PubMed

    Prosandeev, S; Wang, Dawei; Bellaiche, L

    2013-12-13

    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. PMID:24483699

  14. Time-domain spectrum of dielectric relaxation in relaxor ferroelectrics: Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Liu, J.-M.; Dong, S.; Chan, H. L. W.; Choy, C. L.

    2006-10-01

    We perform Monte Carlo simulation on the dielectric relaxation behaviour of a model relaxor ferroelectric, based on the Ginzburg-Landau theory of ferroelectrics with dipole-defect induced random field. The coexistence of ferroelectric nanoclusters and paraelectric matrix is demonstrated. It is found that the time-domain spectrum for dielectric relaxation below the ferroelectric transition point exhibits a multi-peaked pattern rather than the diffusive single-peaked pattern, indicating the existence of multi-characteristic times for the dielectric relaxation. The extended multi-peaked time-domain spectrum is responsible for the diffusive ferroelectric transitions and frequency dispersion of the dielectric relaxation, usually observed for relaxor ferroelectrics.

  15. Relaxor-ferroelectric superlattices: high energy density capacitors

    NASA Astrophysics Data System (ADS)

    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 BaTiO3/Ba(1-x)SrxTiO3 (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 (Tm) with a merger above Tm 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 Tm 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.

  16. Electric field induced relaxor behavior in anisotropically strained SrTiO3 films

    NASA Astrophysics Data System (ADS)

    Dai, Y.; Schubert, J.; Hollmann, E.; Wördenweber, R.

    2016-03-01

    Electric fields can modify the dielectric response of ferroelectric and especially relaxor ferroelectric material. Since strained ferroelectric fields represent ideal candidates for relaxor ferroelectrics, we analyzed the impact of ac and dc electric fields and field orientation on the dielectric properties of anisotropically strained epitaxial SrTiO3 films in detail. The tensile strain in the SrTiO3 films causes an increase of the ferroelectric-dielectric phase transition temperature to 258 K and 288 K for small and large tensile strains, respectively. The resulting films represent relaxor-type ferroelectrics with properties that strongly depend on the applied electric field. While a dc bias field significantly suppresses the permittivity in the paraelectric regime ranging from 180 K to 320 K, an ac field leads to an even more pronounced enhancement of the permittivity in an even larger temperature regime (e.g. reduction of up to 50% versus enhancement of up to 380% for 0.5 V/μm dc bias or ac field, respectively). Furthermore the ac field dependence is nonlinear and cannot be explained by the classical Rayleigh law. Frequency dependent measurements show among others that the electric field dependences are strongly related to the relaxor-type behavior. The different dielectric responses are explained in terms of the mobility and dynamic of regimes of uniform polarization, the polar nanoregions, that are generally assumed to be responsible for the relaxor behavior.

  17. 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.

  18. Anisotropic dielectric function in polar nanoregions of relaxor ferroelectrics.

    PubMed

    Hlinka, J; Ostapchuk, T; Noujni, D; Kamba, S; Petzelt, J

    2006-01-20

    The Letter suggests treating the infrared reflectivity spectra of single crystal perovskite relaxors as fine-grained ferroelectric ceramics: locally frozen polarization makes the dielectric function strongly anisotropic in the phonon frequency range and the random orientation of the polarization at nanoscopic scale requires taking into account the inhomogeneous depolarization field. Employing a simple effective medium approximation (the Bruggeman symmetrical formula) turns out to be sufficient for reproducing all principal features of room temperature reflectivity of Pb(Mg(1/3)Nb(2/3))O3. One of the reflectivity bands is identified as a geometrical resonance entirely related to the nanoscale polarization inhomogeneity. The approach provides a general guide for systematic determination of the polar mode frequencies split by the inhomogeneous polarization at the nanometer scale. PMID:16486640

  19. 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-PT crystals are summarized to guide on-going and future research in the development of relaxor-PT crystals for the next generation electroacoustic transducers. PMID:25530641

  20. Investigation of nonlinear dielectric properties in Sr0.75Ba0.25Nb2O6 relaxor ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    de Los S. Guerra, J.; Mendes, R. G.; Eiras, J. A.; Santos, I. A.; Arajo, E. B.

    2008-01-01

    The ac and dc driving fields dependence of the dielectric permittivity for the strontium barium niobate relaxor ferroelectric thin films has been investigated. The nonlinear dielectric properties were obtained by using the measurements of the dielectric permittivity of the material as a function of the ac and dc "bias" electric field amplitude in wide frequency (100Hz-10MHz) and temperature (50-450K) intervals. The results hint the existence of a true mesoscopic dielectric relaxor response in the ferroelectric thin film, which is very similar to those observed in bulk relaxor ferroelectrics. An anomalous behavior of the NL dielectric response was observed when submitted to moderate dc electric fields levels, indicating a crossover from paraelectric to a glasslike behavior on cooling the sample toward the freezing transition. The obtained results were analyzed within the framework of the models proposed in the current literature.

  1. Solid State Multinuclear NMR Studies of Relaxor Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Hoatson, Gina; Zhou, Donghua; Fayon, Franck; Massiot, Dominique; Gan, Zhehong; Vold, Robert

    2002-03-01

    Multinuclear (207Pb, 45Sc, 93Nb) NMR has been used to investigate the local structure and cation disorder in solid solutions of (1-x) Pb(Mg1/3Nb2/3)O3: x Pb(Sc1/2Nb1/2)O3, as a function of concentration. The relaxor ferroelectrics have been well characterized by X-ray and dielectric response measurements(1). MAS, and 3QMAS spectra are presented for 93Nb at 14.0 and 19.6 Tesla. The 93Nb MAS lineshapes have been assigned to species with different arrangements of the nearest B-cation neighbors. It is necessary to include distributions of the electric field gradient parameters and dispersions in isotropic chemical shifts; these have been estimated from the data. The relative intensities of each spectral component are analyzed and the data strongly supports the modified Random Site model. To explain NMR intensities and to validate the model, Monte Carlo simulations will be presented. (1) P. K., Davies, L. Farber, M. Valant, and M. A. Akabas, AIP Conf. Proc. 535 (2000) 38-46.

  2. Relaxor ferroelectricity and magnetoelectric coupling in ZnO-Co nanocomposite thin films: beyond multiferroic composites.

    PubMed

    Li, D Y; Zeng, Y J; Batuk, D; Pereira, L M C; Ye, Z Z; Fleischmann, C; Menghini, M; Nikitenko, S; Hadermann, J; Temst, K; Vantomme, A; Van Bael, M J; Locquet, J-P; Van Haesendonck, C

    2014-04-01

    ZnO-Co nanocomposite thin films are synthesized by combination of pulsed laser deposition of ZnO and Co ion implantation. Both superparamagnetism and relaxor ferroelectricity as well as magnetoelectric coupling in the nanocomposites have been demonstrated. The unexpected relaxor ferroelectricity is believed to be the result of the local lattice distortion induced by the incorporation of the Co nanoparticles. Magnetoelectric coupling can be attributed to the interaction between the electric dipole moments and the magnetic moments, which are both induced by the incorporation of Co. The introduced ZnO-Co nanocomposite thin films are different from conventional strain-mediated multiferroic composites. PMID:24598535

  3. 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.

  4. Monte Carlo simulation on dielectric relaxation and dipole cluster state in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zhu, Chen; Liu, Jun-Ming

    2010-09-01

    The Ginzburg-Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of relaxor ferroelectrics. With the increase of random field, the dipole configuration evolves from the long-range ferroelectric order into the coexistence of short-range dipole-clusters and less polarized matrix. The dipole-cluster phase above the transition temperature and superparaelectric fluctuations far below this temperature are identified for the relaxor ferroelectrics. We investigate the frequency dispersion and the time-domain spectrum of the dielectric relaxation, demonstrating the Vogel-Fulcher relationship and the multi-peaked time-domain distribution of the dielectric relaxation.

  5. ^93Nb NMR Study of the Relaxor Ferroelectric Lead Magnesium Niobate (PMN)

    NASA Astrophysics Data System (ADS)

    Ailion, David; Ramesh, Kp

    2002-03-01

    Ferroelectric relaxors are interesting because of their unusual physical properties (e.g., giant electrostriction, diffuse phase transition, superparaelectric behavior). Results from a recent ^93Nb and ^207Pb NMR study^1 of the central transition (1/2 to -1/2) in PMN have been interpreted in terms of polar nanoclusters whose slow reorientational motions can be studied by quadrupole-perturbed NMR. It is thought that these motions likely play an important role in the above physical properties of relaxors. A theoretical study^2 suggests that rotating-frame relaxation time (T_1?) measurements performed on the NMR quadrupole satellites should be more sensitive to these motions than would similar measurements performed on the central transition. We report ^93Nb NMR lineshape and (T_1?) measurements of quadrupolar satellites in a single crystal of PMN, which reveal the low frequency fluctuations of the electric field gradient (EFG) tensor. The lineshape measurements were performed by measuring the spin-echo amplitude as a function of irradiation frequency, which was varied by about 600 kHz on either side of the central transition (1/2 to -1/2) and showed features that were attributed to the satellites. ^1 R. Blinc. et al. Phys. Rev. B 64, 024104 (2000). ^2 J. Seliger, J. Magn. Reson. A 116, 67 (1995).

  6. Temperature-dependent reversible and irreversible processes in Nb-doped PbZrO3 relaxor ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Ye, Mao; Huang, Haitao; Li, Tao; Ke, Shanming; Lin, Peng; Peng, Biaolin; Mai, Manfang; Sun, Qiu; Peng, Xiang; Zeng, Xierong

    2015-11-01

    The dielectric and ferroelectric nonlinearity of Nb-doped PbZrO3 relaxor ferroelectric thin films was investigated. The ac field dependence of the permittivity of relaxor ferroelectric thin films is demonstrated to be described by a Rayleigh type relation. Both reversible and irreversible components of dielectric permittivity decrease linearly with the logarithm of the frequency of the ac field. The irreversible Rayleigh coefficient α'(T) shows a peak around the "freezing temperature" Tf, which is probably according to the transition from polar nano-regions (PNRs) to dipole-glass state in relaxor ferroelectrics. The results demonstrate that the models describing the interaction of domain walls and randomly distributed pinning centers in ferroelectric materials can be extended to the displacement of nanoscale walls in relaxors.

  7. Spontaneous ferroelectric-ferroelectric phase transitions and giant electro-mechanical energy conversion in [011] cut relaxor ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Finkel, Peter; Amin, Ahmed; Dong, Wen

    2013-03-01

    We report on giant electro-mechanical energy conversion is demonstrated under a ferroelectric/ferroelectric phase transformation in [011] cut and poled lead titanate-based relaxor perovskite morphotropic Pb(In1/2Nb1/2) O3-Pb(Mg1/3Nb2/3) O3-PbTiO3 (PIN-PMN-PT). single crystals. It is found that under mechanical pre-stress, a relatively small oscillatory stress drives the material reversibly between rhombohedral and orthorhombic phases with a remarkably high polarization and strain jumps induced at zero bias electric field and room temperature. The measured electrical output per cycle is more than an order of magnitude larger than that reported for linear piezoelectric materials. Ideal thermodynamic cycles are presented for this electro-mechanical energy conversion followed by a presentation and discussion of the experimental data. The stress dependence of thermally driven polarization change is reported for a ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut and poled. A giant jump in polarization and strain is associated with the phase transformation of the ferroelectric material. The phase transition temperature can be tuned, over a broad temperature range, through the application of bias stress. This phenomenon results in a new approach to applications in the field of energy harvesting

  8. Lattice-based Monte Carlo simulations of the electrocaloric effect in ferroelectrics and relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Ma, Yang-Bin; Albe, Karsten; Xu, Bai-Xiang

    2015-05-01

    Canonical and microcanonical Monte Carlo simulations are carried out to study the electrocaloric effect (ECE) in ferroelectrics and relaxor ferroelectrics (RFEs) by direct computation of field-induced temperature variations at the ferroelectric-to-paraelectric phase transition and the nonergodic-to-ergodic state transformation. A lattice-based Hamiltonian is introduced, which includes a thermal energy, a Landau-type term, a dipole-dipole interaction energy, a gradient term representing the domain-wall energy, and an electrostatic energy contribution describing the coupling to external and random fields. The model is first parametrized and studied for the case of BaTiO3. Then, the ECE in RFEs is investigated, with particular focus on the influence of random fields and domain-wall energies. If the strength or the density of the random fields increases, the ECE peak shifts to a lower temperature but the temperature variation is reduced. On the contrary, if the domain-wall energy increases, the peak shifts to a higher temperature and the ECE becomes stronger. In RFEs, the ECE is maximum at the freezing temperature where the nonergodic-to-ergodic transition takes place. Our results imply that the presence of random fields reduces the entropy variation in an ECE cycle by pinning local polarization.

  9. 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*.

  10. Local Polarization Distribution and Edwards-Anderson Order Parameter of Relaxor Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Blinc, R.; Dolin Ek, J.; Gregorovi? , A.; Zalar, B.; Filipi? , C.; Kutnjak, Z.; Levstik, A.; Pirc, R.

    1999-07-01

    The temperature dependence of the Edwards-Anderson order parameter qEA and the local polarization distribution function W\\(p-->\\) have been determined in a PMN single crystal via 2D 93Nb NMR. A glasslike freezing of reorientable polar clusters occurs in the temperature range of the diffuse relaxor transition, whereas the NMR spectra corresponding to pinned nanodomains do not change with temperature. The obtained form of W\\(p-->\\) as well as the temperature dependence of qEA and the nonlinear dielectric susceptibility can be well described by a newly proposed spherical random bond-random field model of relaxor ferroelectrics.

  11. Ferroelectric-to-Relaxor Crossover and Oxygen Vacancy Hopping in Compositionally-Disordered Perovskites - KtA(1-x)Nb(x)O(3):Ca

    SciTech Connect

    Samara, G.A.; Boatner, L.A.

    1999-07-26

    It is shown that lattice disorder induced by Nb and Ca substitution has a strong influence on the dielectric and relaxational properties of KTaO{sub 3}. Both substituents are believed to occupy off-center positions at the Ta site, and the difference in valence between the Ca{sup 2+} and Ta{sup 5+} ions leads to the formation of oxygen vacancies (V{sub 0}). Specifically, for a KTa{sub 1{minus}x}Nb{sub x}O{sub 3}:Ca crystal with x = 0.023 and with a 0.055 at.% Ca doping they observe: (1) a ferroelectric transition at atmospheric pressure (1 bar); (2) a large enhancement of the transition temperature by Ca doping; (3) a pressure-induced crossover from ferroelectric-to-relaxor behavior; (4) the impending vanishing of the relaxor phase at high pressure; (5) the reorientation of the Ca-oxygen vacancy (Ca:V{sub 0}) pair defect; and (6) the variation of the energetics and dynamics of this reorientation with pressure. Most of these effects are associated with Nb- and Ca-induced dipolar entities and appear to be general features of soft mode ferroelectrics with random-site polar nanodomains. The ferroelectric-to-relaxor crossover can be understood in terms of a large decrease with pressure in the correlation length among polar nanodomains--a unique property of soft ferroelectric mode systems.

  12. 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.

  13. Dynamics of normal to diffuse and relaxor phase transition in lead metaniobate-based ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Venet, Michel; M'Peko, Jean-Claude; Zabotto, Fabio Luis; Guerrero, Fidel; Garcia, Ducinei; Eiras, Jos Antonio

    2009-04-01

    Tetragonal tungsten bronze-structured materials based on lead metaniobate (PbNb2O6) were studied in terms of thermal dynamics of dielectric properties, showing ferroelectric-to-paraelectric phase transition of diffuse and relaxor type in some specific cases. These features are normally ascribed to defects-induced structural disorder and compositional fluctuations associated with an arbitrary lattice site occupation between dopant and host ions. Nevertheless, for these lead metaniobate-based materials, the drastic change in the phase transition from normal to diffuse and relaxor is shown to take place when dopants are able to significantly shift the transition toward low temperatures, where these compounds are known to exhibit incommensurate superstructures that naturally present diffuse and relaxor dielectric characteristics.

  14. Order parameter and scaling behavior in BaZr{sub x}Ti{sub 1?x}O{sub 3} (0.3 < x < 0.6) relaxor ferroelectrics

    SciTech Connect

    Usman, Muhammad; Mumtaz, Arif Raoof, Sobia; Hasanain, S. K.

    2013-12-23

    We report the relaxor behavior of the zirconium doped barium titanate BaZr{sub x}Ti{sub 1?x}O{sub 3} solid solutions and discuss the temperature, frequency, and concentration dependence in terms of correlations among the polar nanoregions. The relaxor behavior is analyzed within the mean field theory by estimating the Edward-Anderson order parameter q{sub EA}. Additionally, we find that q{sub EA} calculated for the different concentrations obeys a scaling behavior q{sub EA}=1?(T/T{sub m}){sup n}, where T{sub m} are the respective dielectric maxima temperatures and n?=?2.0??0.1. The frequency dependence of the q{sub EA} also shows results consistent with the above mentioned picture.

  15. Giant Electro-Mechanical Energy Conversion in [011] cut Relaxor Ferroelectric Single Crystals

    NASA Astrophysics Data System (ADS)

    Finkel, Peter; Dong, Wen; Lynch, Chris; Amin, Ahmed

    2012-02-01

    Giant electro-mechanical energy conversion is demonstrated under a ferroelectric/ferroelectric phase transformation in [011] cut and poled lead titanate-based relaxor perovskite morphotropic single crystals. It is found that under mechanical pre-stress, a relatively small oscillatory stress drives the material reversibly between rhombohedral and orthorhombic phases with a remarkably high polarization and strain jumps induced at zero bias electric field and room temperature. The measured electrical output per cycle is more than an order of magnitude larger than that reported for linear piezoelectric materials. Ideal thermodynamic cycles are presented for this electro-mechanical energy conversion followed by a presentation and discussion of the experimental data.

  16. Uniaxial relaxor ferroelectrics: The ferroic random-field Ising model materialized at last

    NASA Astrophysics Data System (ADS)

    Kleemann, W.; Dec, J.; Lehnen, P.; Blinc, R.; Zalar, B.; Pankrath, R.

    2002-01-01

    Owing to their intrinsic charge disorder ferroelectric crystals of strontium-barium-niobate doped with Ce3+ materialize the three-dimensional ferroic random-field Ising model (RFIM) as evidenced by order paramenter and susceptibility criticalities with 93Nb NMR and dielectric spectroscopy, respectively. Upon cooling towards Tc, extreme critical slowing-down due to activated dynamic scaling gives rise to relaxor-like dispersion of the susceptibility and to a metastable ferroelectric nanodomain state with fractal size distribution as imaged by piezoelectric force microscopy.

  17. Nuclear magnetic resonance study of ion ordering and ion shifts in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Glinchuk, M. D.; Laguta, V. V.; Bykov, I. P.; Nokhrin, S.; Bovtun, V. P.; Leschenko, M. A.; Rosa, J.; Jastrabk, L.

    1997-04-01

    Nuclear magnetic resonance (NMR) spectra of 93Nb, 45Sc, and 207Pb, as well as dielectric permittivity temperature dependence in a wide frequency range, were investigated in the solid solution of ferroelectric relaxors (x)PbMg1/3Nb2/3O3(1-x)PbSc1/2Nb1/2O3 (0?x?1). The peculiar behavior of the observed quantities and parameters, e.g., disappearance of dielectric dispersion for x0.5, is revealed. The analysis of the dependence of 45Sc NMR spectra on x has shown that ordering of the regions containing Sc ions takes place for x>0.45. The investigation of the temperature dependence of 93Nb and 45Sc NMR linewidths in PbSc1/2Nb1/2O3 had shown that at T

  18. Thickness Dependent Properties of Relaxor-PbTiO(3) Ferroelectrics for Ultrasonic Transducers.

    PubMed

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

    2010-09-23

    The electrical properties of Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (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(In(1/2)Nb(1/2))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (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

  19. 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.

  20. Phase transition of chemically doped uniaxial relaxor ferroelectric

    NASA Astrophysics Data System (ADS)

    Chillal, S.; Koulialias, D.; Gvasaliya, S. N.; Cowley, R. A.; Ivleva, L. I.; Lushnikov, S. G.; Zheludev, A.

    2015-11-01

    We report a neutron scattering study of the ferroelectric phase transition in Sr0.585Ce0.025Ba0.39Nb2O6 (SBN-61:Ce). We find no evidence for a soft transverse optic phonon. We do, however, observe anisotropic diffuse scattering. This scattering has inelastic and elastic contributions. In the paraelectric phase the susceptibility associated with the elastic diffuse scattering from SBN-61:Ce increases on approaching the transition temperature. In the ferroelectric phase the lineshape of the elastic scattering is consistent with the form expected for the ferroelectric domain walls. In contrast to the macroscopic observations, the scattering properties of Ce-doped crystal do not exhibit important changes with respect to those of pure Sr0.61Ba0.39Nb2O6.

  1. Phase transition of chemically doped uniaxial relaxor ferroelectric.

    PubMed

    Chillal, S; Koulialias, D; Gvasaliya, S N; Cowley, R A; Ivleva, L I; Lushnikov, S G; Zheludev, A

    2015-11-01

    We report a neutron scattering study of the ferroelectric phase transition in Sr0.585Ce0.025Ba0.39Nb2O6 (SBN-61:Ce). We find no evidence for a soft transverse optic phonon. We do, however, observe anisotropic diffuse scattering. This scattering has inelastic and elastic contributions. In the paraelectric phase the susceptibility associated with the elastic diffuse scattering from SBN-61:Ce increases on approaching the transition temperature. In the ferroelectric phase the lineshape of the elastic scattering is consistent with the form expected for the ferroelectric domain walls. In contrast to the macroscopic observations, the scattering properties of Ce-doped crystal do not exhibit important changes with respect to those of pure Sr0.61Ba0.39Nb2O6. PMID:26445278

  2. Frustration of ferroelectricity in epitaxial film of relaxor ferroelectric PbSc1/2Nb1/2O3.

    PubMed

    Tyunina, M; Pintilie, I; Iuga, A; Stratulat, M S; Pintilie, L

    2014-08-13

    Relaxor-to-ferroelectric transformations induced by varying electric fields and temperatures are studied experimentally in acube-on-cubetype epitaxial PbSc(1/2)Nb(1/2)O3 film grown on La(1/2)Sr(1/2)CoO3/MgO(001). Dielectric response, quasi-static and dynamic polarization, and dynamic current-voltage characteristics evidence the absence of spontaneous relaxor-to-ferroelectric transition. The electricfield-induced transformation from a glass-like relaxor state to a new dynamic polar state is detected at low temperatures below 100 K only. The frustration of ferroelectricity is discussed in relation to orientational anisotropy of the dipolar system in the epitaxial (001) film. PMID:25030065

  3. 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.

  4. Direct evidence of correlations between relaxor behavior and polar nano-regions in relaxor ferroelectrics: A case study of lead-free piezoelectrics Na0.5Bi0.5TiO3-x%BaTiO3

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Diffuse scattering and relaxor behavior in Na0.5Bi0.5TiO3 (NBT) and NBT-5.6 at. %BaTiO3 (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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Sarasa, 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.

  7. 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

  8. 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

  9. 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

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

    PubMed

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

    2015-06-10

    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. PMID:25985266

  11. 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, crystal growth techniques, domain engineering concept, and full-matrix property characterization all the way to device innovations. It outlines a truly encouraging story in materials science in the modern era. All key references are provided and 30 complete sets of material parameters for different types of relaxor-PT single crystals are listed in the Appendix. It is the intension of this review article to serve as a resource for those who are interested in basic research and practical applications of these relaxor-PT single crystals. In addition, possible mechanisms of giant piezoelectric properties in these domain-engineered relaxor-PT systems will be discussed based on contributions from polarization rotation and charged domain walls. PMID:25061239

  12. 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, crystal growth techniques, domain engineering concept, and full-matrix property characterization all the way to device innovations. It outlines a truly encouraging story in materials science in the modern era. All key references are provided and 30 complete sets of material parameters for different types of relaxor-PT single crystals are listed in the Appendix. It is the intension of this review article to serve as a resource for those who are interested in basic research and practical applications of these relaxor-PT single crystals. In addition, possible mechanisms of giant piezoelectric properties in these domain-engineered relaxor-PT systems will be discussed based on contributions from polarization rotation and charged domain walls. PMID:25061239

  13. Relaxor ferroelectric-based electrocaloric polymer nanocomposites with a broad operating temperature range and high cooling energy.

    PubMed

    Li, Qi; Zhang, Guangzu; Zhang, Xiaoshan; Jiang, Shenglin; Zeng, Yike; Wang, Qing

    2015-04-01

    Electrocaloric nanocomposites simultaneously derive high electrocaloric strength from inorganic inclusions and high dielectric strength from the polymer matrix to display a pronounced electrocaloric effect (ECE). By designing the inorganic filler and polymer matrix, which are both relaxor ferroelectrics with the ambient-temperature phase transition and minimized hysteresis, a large ECE becomes accessible with high cooling efficiency over a broad temperature range at and near room temperature. PMID:25704400

  14. Effect of SHI irradiation on NBT-BT ceramics: Transformation of relaxor ferroelectric to ferroelectric nature

    NASA Astrophysics Data System (ADS)

    Shanmuga Sundari, S.; Kumar, Binay; Asokan, K.; Dhanasekaran, R.

    2013-01-01

    The lead free NBT-BT ceramics prepared by conventional solid state reaction method were irradiated with 120 MeV Au9+ ions with different fluences. The structural, dielectric and piezoelectric studies were carried out before and after irradiation. The agglomeration and increase of grain size are observed in SEM analysis after the irradiation. The diffuse phase transition disappeared after high fluence of irradiation and the material becomes ferroelectric in nature. The piezoelectric properties were decreased due to the reduced stability of the ferroelectric domains after the irradiation.

  15. Polarization-based perturbations to thermopower and electronic conductivity in highly conductive tungsten bronze structured (Sr,Ba)Nb2O6: Relaxors vs normal ferroelectrics

    NASA Astrophysics Data System (ADS)

    Bock, Jonathan A.; Trolier-McKinstry, Susan; Mahan, Gerald D.; Randall, Clive A.

    2014-09-01

    Electrical conductivity, thermopower, and lattice strain were investigated in the tetragonal tungsten bronze structured (Srx,Ba1-x)Nb2O6-? system for 0.7>x>0.4 with large values of ?. These materials show attractive thermoelectric characteristics, especially in single-crystal form. Here, the Sr/Ba ratio was changed in order to vary the material between a normal ferroelectric with long-range polarization to relaxor behavior with short-range order and dynamic polarization. The influence of this on the electrical conduction mechanisms was then investigated. The temperature dependence of both the thermopower and differential activation energy for conduction suggests that the electronic conduction is controlled by an impurity band with a mobility edge separating localized and delocalized states. Conduction is controlled via hopping at low temperatures, and as temperature rises electrons are activated above the mobility edge, resulting in a large increase in electrical conductivity. For relaxor ferroelectric-based compositions, when dynamic short-range order polarization is present in the system, trends in the differential activation energy and thermopower show deviations from this conduction mechanism. The results are consistent with the polarization acting as a source of disorder that affects the location of the mobility edge and, therefore, the activation energy for conduction.

  16. Compositional disorder, polar nanoregions and dipole dynamics in Pb(Mg1/3Nb2/3)O3-based relaxor ferroelectrics

    SciTech Connect

    Bokov, Alexei A.; Rodriguez, Brian; Zhao, X; Ko, JH; Jesse, Stephen; Long, X; Qu, W; Kim, TH; Budai, John D; Morozovska, A. N.; Kojima, S; Tan, X; Kalinin, Sergei V; Ye, Z.-G.

    2011-01-01

    The complex structure of relaxor ferroelectrics comprises polar nanoregions (PNRs) which appear upon cooling below the Burns temperature and quenched compositional (chemical) disorder. The relation between the polar nanostructure and compositionally ordered regions (CORs) often observed in relaxors has been the subject of extensive theoretical investigations; however, the experimental data, especially concerning Pb(B0 1=3B00 2=3)O3-type complex perovskite relaxors, are rather limited. In this paper, we analyse and discuss the results of our recent investigations of the morphology of CORs and the dynamics of PNRs in Pb(Mg1/3Nb2/3)O3-based solid solutions in which the degree of compositional disorder was varied by means of changing the composition and/or by means of high-temperature annealing. The samples were characterised using X-ray diffraction, transmission electron microscopy, piezoresponse force microscopy, Brillouin light scattering, dielectric spectroscopy, as well as by measuring pyroelectric effect and ferroelectric hysteresis loops. No influence of the size of CORs on the PNRs relaxation in the ergodic relaxor phase is found. Instead, the CORs size influences significantly the diffuseness of the transition from the field-induced ferroelectric phase to the ergodic relaxor state. The results are interpreted in the framework of a model suggesting the coexistence of static and dynamic PNRs in the ergodic relaxor phase.

  17. Absence of true critical exponents in relaxor ferroelectrics: the case for defect dynamics

    NASA Astrophysics Data System (ADS)

    Scott, J. F.

    2006-08-01

    It is argued that the large discrepancy ( 2 in strontium barium niobate SBN) between experimental values from different kinds of experiment for the critical exponent ? describing the temperature evolution of the order parameter in relaxors such as SBN arises from the fact that such ferroelectric systems, assumed to be [3D] random field Ising models by Kleemann et al (2002 Europhys. Lett. 57 14), are not in thermal equilibrium. These arguments are illustrated primarily in SBN61SrxBa1-xNb2O6:Ce with x = 0.61 and Ce = ca. 0.7%. An alternative model of Levanyuk and Sigov for defect-dominated dynamics is invoked. The inferred dimensionality of domain walls is also addressed, and the possibility of a d = 5/2 universality class controlled by domain dimensionality is considered as an alternative to defect dynamics; inter alia, four sets of d = 5/2 exponents (with ? = 1/2, 1/3, and 1/4) satisfy all known scaling and hyperscaling equalities. The present results support the scepticism about SBN critical exponents emphasized by Chao et al (2005 Phys. Rev. B 72 134105).

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    Relaxor/ferroelectric ceramic/ceramic composites have shown to be promising in generating large electromechanical strain at moderate electric fields. Nonetheless, 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. We report a different set of switching parameters for grains in the composites as opposed to the pure phase samples. Our results confirm ceramic/ceramic composites to be a viable approach to tailor the piezoelectric properties and optimize the macroscopic electromechanical characteristics.Relaxor/ferroelectric ceramic/ceramic composites have shown to be promising in generating large electromechanical strain at moderate electric fields. Nonetheless, 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. We report a different set of switching parameters for grains in the composites as opposed to the pure phase samples. Our results confirm ceramic/ceramic composites to be a viable approach to tailor the piezoelectric properties and optimize the macroscopic electromechanical characteristics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05032d

  19. Dielectric investigations in Sr0.75Ba0.25Nb2O6 relaxor ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Santos, I. A.; Mendes, R. G.; Eiras, J. A.; de Los S. Guerra, J.; Arajo, E. B.

    2009-06-01

    The dielectric properties of Sr0.75Ba0.25Nb2O6 relaxor ferroelectric thin films were carefully analyzed. In contrast to bulk samples which present three distinct dielectric relaxation phenomena Sr0.75Ba0.25Nb2O6 thin films present only two of them. The suppression of the third anomaly can be mainly attributed to the narrow grain size distribution of nanograins and weak tensile strains imposed to the film from the substrate. The whole set of results point to the interpretation of a dielectric response characteristic of mesoscopic structure, which is composed of clusters and nanodomains.

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

    PubMed

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

    2016-01-21

    Relaxor/ferroelectric ceramic/ceramic composites have shown to be promising in generating large electromechanical strain at moderate electric fields. Nonetheless, 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. We report a different set of switching parameters for grains in the composites as opposed to the pure phase samples. Our results confirm ceramic/ceramic composites to be a viable approach to tailor the piezoelectric properties and optimize the macroscopic electromechanical characteristics. PMID:26731664

  1. Local structure in perovskite relaxor ferroelectrics: high-resolution 93Nb 3QMAS NMR

    NASA Astrophysics Data System (ADS)

    Zhou, Donghua H.; Hoatson, Gina L.; Vold, Robert L.

    2004-04-01

    Solid solutions of (1- x)Pb(Mg 1/3Nb 2/3)O 3xPb(Sc 1/2Nb 1/2)O 3 (PMN/PSN) have been investigated using high-resolution 93Nb 3-quantum magic-angle spinning nuclear magnetic resonance experiments (3QMAS NMR). In previous MAS NMR investigations, the local B-cation ordering in these relaxor ferroelectric solid solutions was quantitatively determined. However, in conventional one-dimensional MAS spectra the effects of chemical shifts and quadrupole interaction are convoluted; this, in addition to the insufficient resolution, precludes reliable extraction of the values of isotropic chemical shift and quadrupole coupling product. In the current 3QMAS investigation, 93Nb spectra are presented for concentrations x=0, 0.1, 0.2, 0.6, 0.7, and 0.9 at high magnetic field (19.6 T) and fast sample spinning speed (35.7 kHz). Seven narrow peaks and two broad components are observed. The unique high-resolution of the two-dimensional 3QMAS spectra enables unambiguous and consistent assignments of spectral intensities to the specific 28 nearest B-site neighbor (nBn) configurations, ( NMg, NSc, NNb) where each number ranges from 0 to 6 and their sum is 6. It is now possible to isolate the isotropic chemical shift and quadrupole coupling product and separately determine their values for most of the 28 nBn configurations. The isotropic chemical shift depends linearly on the number of Mg 2+ cations in the configuration; ?isoCS=(13.70.1) NMg-9700.4 ppm, regardless of the ratio NSc/ NNb. For the seven Nb 5+-deficient configurations ( NMg, 6- NMg, 0) and the pure niobium configuration (0, 0, 6), the quadrupole coupling products (and hence the electric field gradients) are small ( PQ6-12 MHz) and for the remaining configurations containing small, ferroelectric active Nb 5+ ions, the quadrupole coupling products are significantly larger ( PQ40 MHz), indicating larger electric field gradients.

  2. Local structure in perovskite relaxor ferroelectrics: high-resolution 93Nb 3QMAS NMR.

    PubMed

    Zhou, Donghua H; Hoatson, Gina L; Vold, Robert L

    2004-04-01

    Solid solutions of (1'-x)Pb(Mg(1/3)Nb(2/3))O3xPb(Sc(1/2)Nb(1/2))O3 (PMN/PSN) have been investigated using high-resolution 93Nb 3-quantum magic-angle spinning nuclear magnetic resonance experiments (3QMAS NMR). In previous MAS NMR investigations, the local B-cation ordering in these relaxor ferroelectric solid solutions was quantitatively determined. However, in conventional one-dimensional MAS spectra the effects of chemical shifts and quadrupole interaction are convoluted; this, in addition to the insufficient resolution, precludes reliable extraction of the values of isotropic chemical shift and quadrupole coupling product. In the current 3QMAS investigation, 93Nb spectra are presented for concentrations x=0, 0.1, 0.2, 0.6, 0.7, and 0.9 at high magnetic field (19.6 T) and fast sample spinning speed (35.7 kHz). Seven narrow peaks and two broad components are observed. The unique high-resolution of the two-dimensional 3QMAS spectra enables unambiguous and consistent assignments of spectral intensities to the specific 28 nearest B-site neighbor (nBn) configurations, (NMg, NSc, NNb) where each number ranges from 0 to 6 and their sum is 6. It is now possible to isolate the isotropic chemical shift and quadrupole coupling product and separately determine their values for most of the 28 nBn configurations. The isotropic chemical shift depends linearly on the number of Mg2+ cations in the configuration; delta iso CS=(13.7 +/- 0.1)NMg-970 +/- 0.4 ppm, regardless of the ratio NSc/NNb. For the seven Nb5+-deficient configurations (NMg, 6-NMg, 0) and the pure niobium configuration (0, 0, 6), the quadrupole coupling products (and hence the electric field gradients) are small (PQ approximately 6-12 MHz) and for the remaining configurations containing small, ferroelectric active Nb5+ ions, the quadrupole coupling products are significantly larger (PQ approximately 40 MHz), indicating larger electric field gradients. PMID:15040979

  3. Relaxor behavior of CaxBa1-xNb2O6 (0.18?x?0.35) tuned by Ca/Ba ratio and investigated by resonant ultrasound spectroscopy

    NASA Astrophysics Data System (ADS)

    Pandey, Chandra Shekhar; Schreuer, Jrgen; Burianek, Manfred; Mhlberg, Manfred

    2013-03-01

    Dependence of relaxor behavior of incompletely filled tetragonal tungsten bronze uniaxial relaxor ferroelectric calcium barium niobate (CaxBa1-xNb2O6, CBN-x) on its composition was investigated by varying Ca/Ba ratio (0.18 ? x ? 0.35) and studying its thermal and elastic properties. Recently, we have reported the relaxor behavior CBN-28 with the evidence of the existence of the Burns temperature TB, and the intermediate characteristic temperature T* [Pandey , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.84.174102 84, 174102 (2011)]. In this work, we show that the dynamics of polar nanoregions (and hence the relaxor behavior) strongly varies with the Ca/Ba ratio. Evidence is found for a more pronounced relaxor behavior with increasing x. The Curie temperature and the Burns temperature are also very sensitive to the composition, whereas the characteristic temperature T* appears unaffected from the Ca/Ba ratio. The bonding interaction has been explained on the basis of bulk modulus, Poisson's ratio, and deviation from Cauchy relations. Presented results open the perspective to understand the variation of relaxor behavior of CBN-x (0.18?x?0.35) above Curie temperature.

  4. Relaxor behavior in Ba(Zn1/3Nb2/3)O3-PbTiO3 new solid solution.

    PubMed

    Long, Xifa; Ye, Zuo-Guang

    2007-12-01

    Relaxor behavior has been found in a new solid solution between complex perovskite Ba(Zn(1/3)Nb(2/3))O(3) (BZN) and ferroelectric PbTiO(3) (PT), prepared by solid state reactions. A strong dispersion of the maximum of dielectric permittivity (epsilon(')) appears around the temperature of T(m), which shifts toward higher temperatures with increasing frequency. The variation of T(m) with frequency follows the Vogel-Fulcher relationship. The variation of 1/epsilon(') with temperature above Tm deviates from the Curie-Weiss law, but satisfies a Lorentz-type function. The relaxor behavior becomes weaker upon increasing PT-content. PMID:18276562

  5. Phase transitions, relaxor behavior, and large strain response in LiNbO3-modified Bi0.5(Na0.80K0.20)0.5TiO3 lead-free piezoceramics

    NASA Astrophysics Data System (ADS)

    Hao, Jigong; Bai, Wangfeng; Li, Wei; Shen, Bo; Zhai, Jiwei

    2013-07-01

    The effect of LiNbO3 (LN) addition on the ferroelectric behavior and piezoelectric properties of Bi0.5(Na0.80K0.20)0.5TiO3 (BNKT20) lead-free piezoceramics were systematically investigated. Results showed that the LN substitution into BNKT20 induced a transition from coexistence of ferroelectric tetragonal and rhombohedral phases to relaxor pseudocubic phases, which is accompanied by the significant disruption of ferroelectric order and with the shift of the ferroelectric-relaxor transition temperature TF-R down to room temperature. Accordingly, a large accompanying normalized strain of 0.38% (corresponding to a large signal d33* of 475 pm/V) were obtained in BNKT20 with 2.5 mol. %LN addition near the phase boundary. Temperature-dependent measurements of both polarization and strain from room temperature to 120 C suggested that the origin of the large strain is due to a reversible field-induced ergodic relaxor-to-ferroelectric phase transformation. Moreover, an attractive property for application as high-temperature dielectrics was obtained in this system modified with 8 mol. %LN with a high permittivity of 1760 15% from room temperature up to 500 C, spanning a range of about 450 C.

  6. 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 ( ? r 800-1100), a low dissipation factor ( tan ? < 5%) and strong relaxor-like behavior ( ? = 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.

  7. Optical bandgap and phase transition in relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals: An inherent relationship

    NASA Astrophysics Data System (ADS)

    Zhang, X. L.; Hu, Z. G.; Xu, G. S.; Zhu, J. J.; Li, Y. W.; Zhu, Z. Q.; Chu, J. H.

    2013-07-01

    We report band to band transition behaviors of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) single crystals derived from temperature-dependent spectral transmittance. A typical bandgap formula with the temperature and composition (8 K≤Texp≤453 K, 0.1≤x≤0.4) has been presented. Moreover, the phase diagram of PMN-xPT crystals can be well proposed, which is based on the bandgap variations and can be explained by electronic structure evolution. It reveals an intrinsic relationship between fundamental bandgap and phase transition of PMN-xPT single crystals, which pioneers an effective methodology to explore the phase transition of ferroelectric oxides.

  8. (100) MgAl2O4 as a lattice-matched substrate for the epitaxial thin film deposition of the relaxor ferroelectric PMN-PT

    NASA Astrophysics Data System (ADS)

    Keogh, D.; Chen, Z.; Hughes, R. A.; Dabkowski, A.; Marinov, O.; Maunders, C.; Gunawan, L.; Deen, M. J.; Preston, J. S.; Botton, G. A.

    2010-01-01

    The (100) surface of MgAl2O4 is evaluated as a substrate for the thin film deposition of the relaxor ferroelectric PbMg1/3Nb2/3O3(65%)-PbTiO3(35%). With a lattice mismatch of less than 0.5%, this film-substrate combination presents a geometrical template for growth that is far superior to that formed with other commercially available oxide substrates. Films were deposited using the pulsed laser deposition technique and were characterized in terms of their crystallographic, microstructural, and dielectric properties. From a crystallographic perspective the films show excellent cube-on-cube epitaxy, are highly oriented, and show no evidence of the frequently observed parasitic pyrochlore phase. With the exception of a few faceted surface structures, the films microstructure is single-crystal-like, exhibiting a sharp film-substrate interface, a smooth top surface, and no discernable granularity. The dielectric response shows the frequency-dependent diffuse phase transition characteristic of a relaxor material, but with less frequency dispersion and a smaller maximum in the dielectric constant. Taken together, the results suggest that the (100) MgAl2O4 substrate could prove to be an effective substrate material, not only for the PbMg1/3Nb2/3O3(65%)-PbTiO3(35%) system, but also for a number of other important lattice-matched ferroelectric, relaxor, and ferroelectric superlattice systems.

  9. 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 ?m 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 (?m) 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.

  10. Relaxor ferroelectricity and electric-field-driven structural transformation in the giant lead-free piezoelectric (Ba ,Ca ) (Ti ,Zr ) O3

    NASA Astrophysics Data System (ADS)

    Brajesh, Kumar; Tanwar, Khagesh; Abebe, Mulualem; Ranjan, Rajeev

    2015-12-01

    There is great interest in lead-free (B a0.85C a0.15 ) (T i0.90Z r0.10 ) O3 (15/10BCTZ) because of its exceptionally large piezoelectric response [Liu and Ren, Phys. Rev. Lett. 103, 257602 (2009), 10.1103/PhysRevLett.103.257602]. In this paper, we have analyzed the nature of: (i) crystallographic phase coexistence at room temperature, (ii) temperature- and field-induced phase transformation to throw light on the atomistic mechanisms associated with the large piezoelectric response of this system. A detailed temperature-dependent dielectric and lattice thermal expansion study proved that the system exhibits a weak dielectric relaxation, characteristic of a relaxor ferroelectric material on the verge of exhibiting a normal ferroelectric-paraelectric transformation. Careful structural analysis revealed that a ferroelectric state at room temperature is composed of three phase coexistences, tetragonal (P 4 m m )+ orthorhombic(Amm 2 )+rhombohedral(R 3 m ) . We also demonstrate that the giant piezoresponse is associated with a significant fraction of the tetragonal phase transforming to rhombohedral. It is argued that the polar nanoregions associated with relaxor ferroelectricity amplify the piezoresponse by providing an additional degree of intrinsic structural inhomogeneity to the system.

  11. 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 TC800 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 qwf0.14 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.

  12. 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.

  13. 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

  14. 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 m 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 m. 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.

  15. 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 ?? ? ?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.

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

    PubMed

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

    2015-07-21

    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. PMID:26106953

  17. Relaxation and phase-transition characteristics of relaxor ferroelectric potassium lithium niobate

    NASA Astrophysics Data System (ADS)

    Jun, Byeong-Eog; Jeong, Jung Hyun; Choi, Byung Chun; Hwang, Yoon-Hwae

    2015-06-01

    The electric modulus relaxations were considered to be coupled phenomena between the polarization fluctuations < P 2 > due to local symmetry breaking and ionic hopping through nearest neighbor sites. The Nb-rich potassium lithium niobate (K5.595Li3.125Nb11.28O30) crystals exhibited a ferroelectric diffused phase transition around the dielectric maximum temperature T max = 350. The electric modulus relaxations were characterized by using the Cole-Davidson distribution of the electric modulus relaxation times at frequencies ranging from 100 Hz to 1 MHz. Although the lattice constants along the a-axes and the c-axes and the tetragonal unit cell volume showed linear expansions with increasing temperature T, the axial ratio c/a decreased with increasing T at temperatures below the Burn's temperature TB. The dielectric relaxation accompanied the high ionic conduction in the temperature range above T. The ac conductivity σ'( ω) was analyzed by using the formulae, where ω O is the crossover frequency. It was considered that a double-Arrhenius behavior of the dc conductivity σ dc at temperatures around the Burn's temperature T B was suspected of thermally activated motions in the random distribution of oxygen vacancies and lithium ions. The ac universality could result in a disordered configuration of the mobile ions, i.e., the dc conductivity at temperatures above T B . The slow relaxations of the nano-sized polar regions may contribute to the dc conductivity σ dc at temperatures below T B . The characteristic relaxation time τ CD showed a change in activation energy from 1.08 eV to 0.80 eV at temperatures around T B . The scaling factor increased in proportion to ( T B - T) at T T B , but was almost constant at T >T B , where ɛ'∞ is the high frequency dielectric constant and T is the temperature in Kelvin.

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

    NASA Astrophysics Data System (ADS)

    Meyer, Kai-Christian; Grting, 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 . 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.

  19. 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 ?m. 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.

  20. 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.

  1. Large enhancement of energy-storage properties of compositional graded (Pb1-xLax)(Zr0.65Ti0.35)O3 relaxor ferroelectric thick films

    NASA Astrophysics Data System (ADS)

    Zhang, Liwen; Hao, Xihong; Yang, Jichun; An, Shengli; Song, Bo

    2013-09-01

    In this letter, the compositionally graded multilayer (Pb1-xLax)(Zr0.65Ti0.35)O3 (PLZT) relaxor ferroelectric thick films were fabricated on LaNiO3/Si(100) substrates via a sol-gel method. The effects of composition-gradient sequence on the microstructure, dielectric properties, and energy-storage behaviors were investigated in detail. As compared to PLZT films with single composition, the compositionally graded PLZT films displayed significant enhancement in dielectric properties and energy-storage performance. The largest dielectric constant of 2170 at 100 kHz and the largest discharged energy-storage density of 12.4 J/cm3 at 800 kV/cm were achieved in the up-graded multilayer PLZT thick films.

  2. 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.

  3. Effect of electric field on uniaxial relaxor ferroelectric strontium barium niobate

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kazuya; Kojima, Seiji

    2015-10-01

    The effects of an electric field and the temperature dependence on the elastic properties of Sr0.61Ba0.39Nb2O6 were studied by micro-Brillouin scattering. In the ferroelectric phase, a dramatic increase in the longitudinal acoustic (LA) velocity, which is related to the elastic constant c33, was observed upon the application of a static electric field along the ferroelectric c-axis. A marked thermal hysteresis was observed below the Curie temperature, TC = 72 C, between field heating (FH) and zero field (ZFC) cooling. The effect of an electric field on the static polar nanoregions (PNRs) was examined by the temporal application of a static electric field at 140 C between TC and the intermediate temperature T* = 190 C. After turning off the applied field at 140 C, the LA velocity during ZFC was measured, and it is found that, below TC, the temperature dependence is similar to that during FH. This fact indicates that the alignment of local polarization in static PNRs between TC and T* is possible using an external electric field.

  4. 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.

  5. Theoretical and experimental investigation of Raman modes, ferroelectric and dielectric properties of relaxor Na0.5Bi0.5TiO3

    NASA Astrophysics Data System (ADS)

    Niranjan, Manish K.; Karthik, T.; Asthana, Saket; Pan, Jaysree; Waghmare, Umesh V.

    2013-05-01

    We use a combination of first-principles density functional theoretical analysis and experimental characterization to understand the lattice dynamics, dielectric and ferroelectric properties of lead-free relaxor ferroelectric Na0.5Bi0.5TiO3 (NBT) system. Vibrational spectrum determined through our calculations agrees well with the observed Raman spectrum, and allows assignment of symmetry labels to modes. The calculated Born effective charges reveal (a) two distinct types of Ti ions at the B-site with anomalous dynamical charges differing by up 1.6e, and (b) Na and Bi ions at the A-site exhibit disparate dynamical charges of about 1 and 5.5e, respectively. Thus, there exist hetero-polar activity at both A and B-sites in NBT, and disorder associated with these hetero-polar ions is responsible for its relaxor behaviour. Large dielectric response of NBT arises primarily from phonons, and specifically the modes involving Bi-O (109 cm-1) and Ti-O (246, 276 cm-1) vibrations, respectively.

  6. 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 characters in the exploration of new solid-solutions. PMID:25585388

  7. Anharmonic atomic vibrations in the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 under pressure

    NASA Astrophysics Data System (ADS)

    Yamanaka, Takamitsu; Ahart, Muhtar; Nakamoto, Yuki; Ye, Zuo-Guang; Gramsch, Stephen A.; Mao, Ho-kwang; Hemley, Russell J.

    2012-11-01

    Structural analyses of the relaxor ferroelectric material Pb(Mg1/3Nb2/3)O3 (PMN) with single-crystal x-ray diffraction under pressure in a diamond anvil cell indicate static atomic displacement and chemical disorder. A difference Fourier analysis within the framework of a harmonic oscillator model for the atomic vibrations reveals residual electron density on both the Pb and Nb(Mg) sites. Pb atoms in the A site of the ABO3 perovskite structure exhibit a greater displacement than the Nb(Mg) atoms in the B site, despite the fact that Pb is a much heavier atom. The displacement is interpreted in terms of an anharmonic statistical atomic motion. At pressures above 2.5 GPa the displacement disappears, consistent with previous observations. The difference Fourier maps reveal no residual electron densities greater than 1 e/3 at any atomic position, and these appear to be induced by the violation of local electrical neutrality arising from both Mg2+ and Nb5+ ions located at the octahedral site. Similar electron densities are observed at all experimental pressures and in refinements based on both harmonic and anharmonic models. The anharmonic parameters taken into account are the higher-order tensors of atomic elastic motion. At high pressure, where the relaxor transforms to a paraelectric phase, the residual electron densities disappear.

  8. 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.

  9. Detection of the critical end point in PbSc0.5Ta0.36Nb0.14O3 relaxor ferroelectrics crystals via acoustic emission

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    PbSc0.5Ta0.36Nb0.14O3 relaxor-ferroelectric crystals were studied by the means of dielectric and acoustic emission (AE) methods in the temperature range of 180-300 K. In zero dc electric field (E) no AE was detected at the smeared dielectric maximum Tm ≈ 260 K characteristic for canonical relaxor ferroelectrics. Under the E a phase transition appears at TC = 217 K for E ˜ 1 kV cm-1. The TC(E) dependence is linear with an anomaly point at E ˜ 1.3 kV cm-1, at which dTC/dE abruptly changes. At this E value the AE rate exhibits a maximum. The anomalous E point is assigned to be the critical end point for this solid solution.

  10. 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 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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01326g

  11. 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.

  12. Significant enhancement of energy-storage performance of (Pb0.91La0.09)(Zr0.65Ti0.35)O3 relaxor ferroelectric thin films by Mn doping

    NASA Astrophysics Data System (ADS)

    Liu, Yunying; Hao, Xihong; An, Shengli

    2013-11-01

    1.5-?m-thick (Pb0.91La0.09)(Zr0.65Ti0.35)O3 (PLZT) relaxor ferroelectric (RFE) films doped by Mn from 0 to 5 mol. % were deposited on LaNiO3/Si(100) substrates via a sol-gel method. The microstructure, dielectric properties, and energy-storage performance of PLZT thin films were investigated as a function of Mn content. X-ray diffraction patterns and scanning electron microscopy indicated that all the films possessed a similar microstructure with pure perovskite phase. However, the dielectric constant, average breakdown fields, and the difference between maximum polarization and remnant polarization of the films were improved by Mn doping. A giant recoverable energy-storage density of 30.8 J/cm3 was obtained in 1 mol. % Mn-doped films. Moreover, good temperature-dependent energy-storage stability was also observed in the films. These results indicated that Mn-doping was an efficient way to optimize the energy-storage behaviors of PLZT RFE films.

  13. 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.

  14. NMR study of ionic shifts and polar ordering in the relaxor ferroelectric Pb(Sc1/2Nb1/2)O3

    NASA Astrophysics Data System (ADS)

    Laguta, V. V.; Glinchuk, M. D.; Bykov, I. P.; Blinc, R.; Zalar, B.

    2004-02-01

    207Pb, 45Sc, and 93Nb nuclear-magnetic-resonance (NMR) spectra of partially ordered relaxor ferroelectric PbSc1/2Nb1/2O3 (PSN) have been studied at temperatures between 77 K and 420 K. The relatively narrow 45Sc and 207Pb NMR spectral components, arising from chemically ordered regions of the crystal, show marked anomalies at Tc? 360 K, where Tc is the temperature of the dielectric susceptibility maximum. The abrupt frequency shifts of these components below Tc are related to the first-order structural phase transition. In the coexisting broad spectral components, originating from compositionally disordered regions, such anomalies are barely detectable; they were not observed at all in the 93Nb NMR spectra. Our NMR data are compatible with an assumption of large, up to 0.04 nm, displacements of lead ions and smaller, 0.01 nm, displacements of scandium ions along the four polar rhombohedral axes, while Nb ions remain in the centers of oxygen octahedra. 207Pb NMR measurements in poled crystals reveal that long-range polar ordering is established solely in the chemically ordered parts of the crystal, whereas in the disordered regions a mixed ferro-glass order sets in. At low temperatures, both 207Pb and 93Nb resonances detect, in addition to the ferroelectric rhombohedral, a tetragonal distortion of the PSN lattice. This distortion appears at Tc and increases smoothly on decreasing temperature, possessing a second-order phase-transition character. The effective local symmetry of PSN at T<250 K thus lowers from the axial rhombohedral to the nonaxial orthorhombic with lead atom shifts deviating considerably from the [111] polar axes. Structural data, obtained via NMR, are compared with similar data obtained from neutron and x-ray-diffraction experiments.

  15. 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 ?50C 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

  16. Large enhancement of the recoverable energy storage density and piezoelectric response in relaxor-ferroelectric capacitors by utilizing the seeding layers engineering

    NASA Astrophysics Data System (ADS)

    Xie, Zhenkun; Yue, Zhenxing; Peng, Bin; Zhang, Jie; Zhao, Chuan; Zhang, Xiaohua; Ruehl, Griffin; Li, Longtu

    2015-05-01

    In this work, we demonstrate an approach to improve the recoverable energy-storage performance and piezoelectric response of 0.4Bi(Ni1/2Zr1/2)O3-0.6PbTiO3 (BNZ-PT) relaxor-ferroelectric film capacitors by utilizing the seeding layers engineering. Highly (100)-oriented BNZ-PT films were prepared through alternatively introducing PbO seeding layers, and the effects of PbO seeds on microstructure and electrical properties were investigated in details. Compared to the films without seeds, the PbO-seeded BNZ-PT films exhibit significant enhancement in dielectric and piezoelectric properties as well as energy-storage performance. The maximum energy-storage density of 56.1 2.4 J/cm3 and a piezoelectric coefficient as high as 125 10 pm/V have been achieved in the highly (100)-oriented BNZ-PT films at 2167 kV/cm, which are increased by 40.6% and 50.6% compared to the films without seeds, respectively. The observed tremendous enhancement of energy-storage performance and piezoelectric response can be attributed to the better crystallization quality and higher degree of (100)-preferred orientation in the films which would motivate higher domain-wall mobility.

  17. Role of random electric fields in relaxors

    PubMed Central

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

    2014-01-01

    PbZr1xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1xTixO3 (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

  18. Role of random electric fields in relaxors.

    PubMed

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

    2014-02-01

    PbZr(1-x)Ti(x)O3 (PZT) and Pb(Mg1/3Nb2/3)(1-x)Ti(x)O3 (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

  19. Frequency and temperature dependence of actuating performance of Bi1/2Na1/2TiO3-BaTiO3 based relaxor/ferroelectric composites

    NASA Astrophysics Data System (ADS)

    Groh, Claudia; Jo, Wook; Rdel, Jrgen

    2014-06-01

    Recently, composites of relaxors (matrix) and either ferroelectric or nonergodic relaxor (seed) were proposed as a solution to resolving one of the main drawbacks of incipient piezoceramics, namely the requirement for high driving electric fields. In this study, we investigate the temperature and frequency dependence of the actuating performance of Bi1/2Na1/2TiO3-BaTiO3-based composites. Apart from the reduction of driving field, the composite architecture offers an extra degree of freedom for tailoring the temperature stability for different operational conditions for actuators. High strain values appear to be sensitive especially to driving frequency. This is originated by the time-dependent process of the coalescence of polar nanoregions. In effect, proximity of driving field and poling field leads to high strain sensitivity. Hence, the driving electric field needs to be adjusted in order to meet the desired frequency specifications for given applications.

  20. Large Energy Storage Density and High Thermal Stability in a Highly Textured (111)-Oriented Pb0.8Ba0.2ZrO3 Relaxor Thin Film with the Coexistence of Antiferroelectric and Ferroelectric Phases.

    PubMed

    Peng, Biaolin; Zhang, Qi; Li, Xing; Sun, Tieyu; Fan, Huiqing; Ke, Shanming; Ye, Mao; Wang, Yu; Lu, Wei; Niu, Hanben; Zeng, Xierong; Huang, Haitao

    2015-06-24

    A highly textured (111)-oriented Pb0.8Ba0.2ZrO3 (PBZ) relaxor thin film with the coexistence of antiferroelectric (AFE) and ferroelectric (FE) phases was prepared on a Pt/TiOx/SiO2/Si(100) substrate by using a sol-gel method. A large recoverable energy storage density of 40.18 J/cm(3) along with an efficiency of 64.1% was achieved at room temperature. Over a wide temperature range of 250 K (from room temperature to 523 K), the variation of the energy density is within 5%, indicating a high thermal stability. The high energy storage performance was endowed by a large dielectric breakdown strength, great relaxor dispersion, highly textured orientation, and the coexistence of FE and AFE phases. The PBZ thin film is believed to be an attractive material for applications in energy storage systems over a wide temperature range. PMID:25996244

  1. Temperature-Pressure Phase Diagram of Relaxor Ferroelectric Pb(Mg1/3Nb2/3)O3

    NASA Astrophysics Data System (ADS)

    Deguchi, Kiyoshi; Hiroshima, Mika; Kasatani, Hirofumi; Ohwa, Hidehiro; Nakamoto, Yuki; Ahart, Muhtar; Yamanaka, Takamitsu

    2016-01-01

    The effects of hydrostatic pressure of up to 2.7 GPa on the dielectric constant and pyroelectric charge of Pb(Mg1/3Nb2/3)O3 single crystal were investigated. In addition to the broad and frequency-dependent dielectric anomaly of the relaxor state, a distinct secondary dielectric anomaly was found at pressures higher than approximately 0.7 GPa. This new dielectric anomaly was confirmed consistently by isothermal and isobaric measurements. The pressure dependences of the peak temperature of the dielectric constant, the freezing temperature, and the temperature at which the secondary dielectric anomaly disappeared (Ta) were investigated. The Ta line in the temperature-pressure phase diagram represents the phase boundary of the pressure-induced structural phase transition.

  2. Local structure of the lead-free relaxor ferroelectric ( Kx Na1-x )0.5 Bi0.5 Ti O3

    NASA Astrophysics Data System (ADS)

    Shuvaeva, V. A.; Zekria, D.; Glazer, A. M.; Jiang, Q.; Weber, S. M.; Bhattacharya, P.; Thomas, P. A.

    2005-05-01

    The local environment of Bi and Ti atoms in the lead-free relaxor ferroelectric solid-solution (KxNa1-x)0.5Bi0.5TiO3 has been studied as a function of K concentration and as a function of temperature for the x=0 end member by x-ray absorption fine structure (XAFS). It is found that the local environment of Bi is much more distorted than that determined from conventional diffraction experiments. The shortest Bi-O distances are determined to be 2.22 , and are 0.3 shorter than those calculated from the crystallographic data. Several possible models of the Bi coordination environment, which are consistent with the XAFS data and provide bond-valence sums for Bi that are closer to the theoretical values, are proposed. The Ti displacement from the center of the oxygen octahedron increases with K concentration while the shortest Bi-O distance shows no compositional dependence. In K0.5Bi0.5TiO3 the value of the Ti displacement is determined to be 0.18 . The changes of the macroscopic symmetry at the phase transition points in Na0.5Bi0.5TiO3 do not lead to changes of the radial atomic distribution around Ti, which is well off-center over the whole temperature range up to and including the paraelectric cubic phase. The results can be explained by assuming the presence of structural disorder.

  3. 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.

  4. 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.

  5. 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.

  6. Study of the Electrocaloric Effect in the Relaxor Ferroelectric Ceramic 0.75PMN-0.25PT

    NASA Astrophysics Data System (ADS)

    Kriaa, I.; Abdelmoula, N.; Maalej, A.; Khemakhem, H.

    2015-12-01

    Electrocaloric (EC) cooling based on the ability of materials to change temperature by applying an electric field under adiabatic conditions is a relatively new and challenging direction in ferroelectrics research. Analytical and simulation data for the electrocaloric effect (ECE) in 0.75Pb(Mg1/3Nb2/3)O3-0.25PbTiO3 (0.75PMN-0.25PT) bulk ceramic samples are reported. The adiabatic temperature change (? T) due to a change of the external electric field has been calculated indirectly from the entropy change. The temperature change increases with an increase in the applied electric field and reaches a maximum of 2.1 K in 25 kV/cm electric field shift near the Curie temperature of 398 K; that is, the cooling ? T per unit field (MV/m) is 0.896 10-6 m K/V. This value is significantly large for bulk ceramics and makes the compound promising for room-temperature electric cooling applications.

  7. 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.

  8. Aging in the relaxor and ferroelectric state of Fe-doped (1-x)(Bi{sub 1/2}Na{sub 1/2})TiO?-xBaTiO? piezoelectric ceramics

    SciTech Connect

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

    2014-09-14

    Aging of piezoelectric properties was investigated in lead-free (1x)(Bi{sub 1/2}Na{sub 1/2})TiO?-xBaTiO? 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.

  9. 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.

  10. 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.

  11. Electric-field-induced local structural phenomena in relaxor ferroelectric PbSc(0.5)Nb(0.5)O3 near the intermediate temperature T* studied by Raman spectroscopy.

    PubMed

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

    2014-04-30

    Raman spectroscopy at different temperatures and under an external electric field E was applied to PbSc0.5Nb0.5O3 single crystals in order to gain further insights into the mesoscopic-scale coupling processes in perovskite-type (ABO3) relaxor ferroelectrics. Parallel and cross-polarized Raman spectra were collected between 800-80?K with E applied along the cubic [1?0?0], [1?1?0] or [1?1?1] crystallographic directions. The analysis was focused on the field-induced changes in the temperature evolution of three low-energy phonon modes: the Pb-localized mode near 50?cm(-1), the Pb-BO3 translation mode near 150?cm(-1), and the B-cation-localized mode near 250?cm(-1). The results show that competitive ferroelectric (FE) and antiferroelectric (AFE) coupling exists within the system of off-centred Pb(2+) cations, within the system of off-centred B-site cations as well as between off-centred Pb(2+) and B-site cations. The strong AFE-type coupling between Pb(2+) cations along the cubic body diagonal significantly influences the coupling between the B-site cations via the Pb-BO3 mode and results in AFE-type behaviour of the 'microscopic' T* determined from the B-cation-localized mode near 250?cm(-1), which explains the previously reported non-trivial field dependence of the 'macroscopic' characteristic temperatures: the temperature of the dielectric-permittivity maximum Tm, T*, and the Burns temperature TB. The comparative analysis between PbSc0.5Nb0.5O3 and PbSc0.5Ta0.5O3 indicates that two major displacive order parameters couple to form a relaxor state in B-site complex perovskites: the FE order associated with polar shifts of B-site cations and the AFE order associated with polar shifts of A-site cations. The latter penetrates through both polar and non-polar regions, but it is highly frustrated due to the high density of translation-symmetry faults in the chemical NaCl-type B-site order. The frustrated AFE order of off-centred A-site cations might be the key factor for the existence of a relaxor state. PMID:24722533

  12. Switching behavior of ferroelectric thin films with deadlayers

    NASA Astrophysics Data System (ADS)

    Xia, Yifan; Wang, Jie

    2012-09-01

    Domain switching in ferroelectric thin films with deadlayers subjected to external electric fields is investigated by a phase field model. The simulation results show that the deadlayers of ferroelectric thin films induce a strong inhomogeneous depolarization field which makes polarizations deflect from the normal direction of thin films. The locations with larger depolarization fields are nucleation centers for new domains during the polarization switching and the switching process includes two sequential 90 polarization switchings, which decrease the coercive field significantly. It is found that the thickness of the deadlayer has a significant influence on the switching behavior of the ferroelectric thin films. Both the coercive field and remanent polarization are dependent on the thickness of the deadlayer.

  13. Relaxor ferroelectrics for electrostrictive transducer

    NASA Astrophysics Data System (ADS)

    Shrout, Thomas R.; Jang, Sei-Joo

    1992-01-01

    The objective of this program is to investigate the potential of electrostrictive actuator materials for use in NAVY-type sonar. The anticipated performance requirements for such materials is summarized in the following: Operating temperature range 0-30 C; High sensitivity; Large E-field induced strain; Minimal hysteresis and low loss; Frequency of operation; and Mechanically stiff (low compliance). Additional requirements include operational E-field strain under prestress, and duty cycles.

  14. Coupling between octahedral tilting and ferroelectric order in tetragonal tungsten bronze-structured dielectrics

    NASA Astrophysics Data System (ADS)

    Levin, Igor; Stennett, Martin C.; Miles, Gabrielle C.; Woodward, David. I.; West, Anthony R.; Reaney, Ian M.

    2006-09-01

    Strong coupling between local polar displacements and a commensurate octahedral tilting is proposed to explain the onset of classic ferroelectric behavior in tetragonal tungsten bronzelike dielectrics Ba2LaxNd1-xNb3Ti2O15. The ferroelectric phase transition is associated with a discontinuous non-lock-in transformation of an incommensurate tilted structure to a commensurate superstructure. In a manner reminiscent of perovskitelike oxides, the driving force for commensurate tilting increases as the average ionic radius of the rare-earth ion decreases; no classical ferroelectric transition is observed for compositions with x >0.75, which remain incommensurate and exhibit only relaxor behavior below room temperature.

  15. Crystal growth and dynamic ferroelectric hysteresis scaling behavior of molecular ferroelectric diisopropylammonium bromide

    NASA Astrophysics Data System (ADS)

    Jiang, Chunli; Lin, Hechun; Luo, Chunhua; Zhang, Yuanyuan; Yang, Jing; Peng, Hui; Duan, Chun-Gang

    2016-03-01

    The molecular ferroelectric, diisopropylammonium bromide (DIPAB) crystal with P21 phase is successfully prepared in an anhydrous environment at room temperature. The results illustrate that the water in the solvent / environment plays a key role in the phase of DIPAB single crystal during crystallization process. The scaling behavior of the dynamic hysteresis of DIPAB crystal is also investigated. The scaling relations of hysteresis area(A) against frequency (f) and applied electric field amplitude (E0) can be expressed with A ∝ f - 0 . 17E01 in the f-region I (30-6.6 Hz), A ∝ f 0 . 045E00.92 in the f-region II (200-50 Hz) and A ∝ f - 0 . 41E02 in the f-region III (500-250 Hz). This three-stage behavior between the loop area A and frequency is ascribed to the coexistence of order-disorder and displacive characters in the ferroelectric transition characters in such molecular ferroelectrics.

  16. Low temperature anomalous field effect in SrxBa1-xNb2O6 uniaxial relaxor ferroelectric seen via acoustic emission

    NASA Astrophysics Data System (ADS)

    Dul'kin, E.; Kojima, S.; Roth, M.

    2012-04-01

    Sr0.75Ba0.25Nb2O6 [100]-oriented uniaxial tungsten bronze relaxor crystals have been studied by means of dedicated acoustic emission during their thermal cycling in 150-300 K temperature range under dc electric field (E). A 1st order transition in a modulated incommensurate tetragonal phase has been successfully detected at Tmi = 198 K on heating and Tmi = 184 K on cooling, respectively. As field E enhances, a thermal hysteresis gradually narrows and vanishes in the critical point at Eth = 0.31 kV/cm, above which a phase transition becomes to 2nd order. The Tmi(E) dependence looks as a V-shape dip, not similar that previously has been looked as a smeared minimum between both the two polar and nonpolar tetragonal phases near Tm = 220 230 K in the same crystals (Dul'kin et al., J Appl. Phys. 110, 044106 (2011)). Due to such a V-shape dip is characteristic for Pb-based multiaxial perovskite relaxor, a rhombohedral phase is waited to be induced by a field E in the critical point temperature range. The emergence of this rhombohedral phase as a crucial evidence of an orthorhombic phase presumably existing within the modulated incommensurate tetragonal phase in tungsten bronze SrxBa1-xNb2O6 relaxor is discussed.

  17. Dielectric Spectroscopy and conductivity relaxation of PSN-PST relaxor thin films

    NASA Astrophysics Data System (ADS)

    Correa, Margarita; Baskaran, Natasan; Katiyar, Ram

    2007-03-01

    -abstract- Relaxor ferroelectric materials exhibit singular dielectric relaxation. They have large dielectric constant, high piezo and electrostrictive coefficients that make them useful for sensors, actuators and ferroelectric related devices. We have prepared PSN-PST relaxor thin films by pulsed laser deposition technique. Studies of dielectric properties, as a function of temperature (100-650K) and frequency (40 Hz --1 MHz) have shown that the materials have diffuse phase transition along with the frequency dispersion. The magnitude of dielectric constant and the temperature of maximum permitivitty (Tm) differ from those in the bulk form. However, its conductivity behavior follows similar trend in both bulk and thin film forms. The ac conductivity exhibits frequency independent plateau at lower frequencies followed by a dispersion region at higher frequencies. The observed dispersion of conductivity with frequency can be described by a power law ?( ?)=?dc+A?^n with n>1. The unusual high n value is due to glassy like nature of the relaxor system and it is explained in terms of polaron assisted ionic mechanism. Detailed results will be presented.

  18. 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

  19. 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.

  20. Electric field cycling behavior of ferroelectric hafnium oxide.

    PubMed

    Schenk, Tony; Schroeder, Uwe; Pešić, Milan; Popovici, Mihaela; Pershin, Yuriy V; Mikolajick, Thomas

    2014-11-26

    HfO2 based ferroelectrics are lead-free, simple binary oxides with nonperovskite structure and low permittivity. They just recently started attracting attention of theoretical groups in the fields of ferroelectric memories and electrostatic supercapacitors. A modified approach of harmonic analysis is introduced for temperature-dependent studies of the field cycling behavior and the underlying defect mechanisms. Activation energies for wake-up and fatigue are extracted. Notably, all values are about 100 meV, which is 1 order of magnitude lower than for conventional ferroelectrics like lead zirconate titanate (PZT). This difference is mainly atttributed to the one to two orders of magnitude higher electric fields used for cycling and to the different surface to volume ratios between the 10 nm thin films in this study and the bulk samples of former measurements or simulations. Moreover, a new, analog-like split-up effect of switching peaks by field cycling is discovered and is explained by a network model based on memcapacitive behavior as a result of defect redistribution. PMID:25365475

  1. 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)

  2. 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).

  3. 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 loss mechanisms are discussed in terms of compositions, crystal structures, temperature, domain configurations, domain sizes and grain boundaries. The intrinsic and extrinsic contributions to the total energy dissipation are quantified. In domain engineered ferroelectric single crystals and ceramics, polarization rotations, domain wall motions and mechanical wave scatterings at grain boundaries are believed to control the mechanical quality factors of piezoelectric resonators. We show that a thorough understanding on the kinetic processes is critical in analyzing energy loss behavior and other time-dependent properties in ferroelectric materials. At the end of the review, existing challenges in the study and control of losses in ferroelectric materials are analyzed, and future perspective in resolving these issues is discussed. PMID:25814784

  4. Optical evidences for an intermediate phase in relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolong; Zhang, Jinzhong; Xu, Guisheng; Jiang, Kai; Hu, Zhigao; Chu, Junhao

    2016-02-01

    The mechanism of low-temperature structural transformation and evolution of polar nano-structures in relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-xPbTiO3 (x = 0.33, 0.35, and 0.42) single crystals have been investigated with the aid of temperature dependent low-wavenumber Raman scattering (LWRS) and photoluminescence (PL) spectra. The E(TO1) phonon mode reveals the characteristic relaxational polarization fluctuations associated with the reorientation of either polar nano-regions or polar nano-domains. It was found that these mechanisms are not independent and they can be ascribed to the phonon localization. In addition, a short-range monoclinic phase (Mc) can be found below 250 K in the tetragonal phase region by LWRS, which is always associated with the morphotropic phase boundary (MPB) and excellent electromechanical properties. It is interesting that PL spectra confirm these results. The present work indicates that external field modulation and change of composition can result in the monoclinic phase and co-existence of multi-phase.

  5. 93Nb magic angle spinning NMR study of perovskite relaxor ferroelectrics (1- x)Pb(Mg1/3Nb2/3)O3- xPb(Sc1/2Nb1/2)O3

    NASA Astrophysics Data System (ADS)

    Hoatson, Gina L.; Zhou, Donghua H.; Fayon, Franck; Massiot, Dominique; Vold, Robert L.

    2002-12-01

    93Nb NMR has been used to investigate the local structure and cation order/disorder in solid solutions of (1-x)Pb(Mg1/3Nb2/3)O3- xPb(Sc1/2Nb1/2)O3, as a function of concentration x. These relaxor ferroelectric solid solutions have been well characterized by x-ray diffraction, transmission electron microscopy, and dielectric response measurements. NMR magic angle spinning (MAS) spectra are presented for 93Nb at 14.0 and 19.6 T. Seven narrow peaks and two broad components are observed. Narrow peaks are assigned to configurations of 93Nb nuclei with only Mg2+ and/or Sc3+ (no Nb5+) cations occupying the six nearest B neighbor sites (nBn); and are designated 0-6 according to the number of Mg2+ cations in the nBn configuration. The two broad components are assigned to configurations with more than one Nb5+ cation in the nearest B sites. In order to fit the MAS line shapes it is necessary to include distributions of the electric-field gradient parameters and dispersions in isotropic chemical shifts; these have been obtained from the data. The relative intensities of each spectral component are analyzed and the data strongly support a modified random site model of B-site order. Monte Carlo simulations of B cation ordering are presented to explain the observed NMR intensities and to validate the model.

  6. 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 (495C); 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 205C. 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 250C to 300C and ?max 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 600C; up to 250C 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 temperature (Tf) of 150C. Static and in-situ transmission electron microscopy investigations of the BS-PMN-PT compositions demonstrated a frustrated microstructure of nanometer scale regions and were used to establish structure-property relationships with different electric field and thermal histories. A comparative study of the key relaxor parameters, EA, T f, and TD was tabulated with previously investigated relaxor ferroelectrics. These parameters were found to scale relative to other lead-based perovskite relaxor ferroelectric compounds and solid solutions, with the BS-PMN-PT ternary system exhibiting the highest temperature behavior. Finally, to demonstrate one possible application area for these materials, multilayer ceramic capacitor devices were designed for operation at 300C and up to 10 kHz. The voltage saturation was found to be extremely encouraging at 300C with observed changes in capacitance (3%) on the application of 10 kV/cm. The insulation resistivity followed an Arrhenius behavior and at 300C was 1010 O-cm. Weibull statistics were used to estimate a characteristic breakdown field at 300C for the BS-PMN-PT multilayer capacitors of 40 kV/cm. Current-voltage measurements were performed to voltages up to breakdown and exhibited Ohmic behavior, indicating intrinsically controlled conduction. Highly accelerated life time tests were performed on BS-PMN-PT capacitors. It was observed that silver migration from termination electrodes caused premature failure at elevated temperature.

  7. Monte Carlo simulation of the dielectric susceptibility of Ginzburg-Landau mode relaxors

    NASA Astrophysics Data System (ADS)

    Liu, J.-M.; Wang, X.; Chan, H. L.; Choy, C. L.

    2004-03-01

    The electric dipole configuration and dielectric susceptibility of a Ginzburg-Landau model ferroelectric lattice with randomly distributed defects are simulated using the Monte Carlo method. The simulated characteristics of the lattice configuration and dielectric susceptibility indicate that the model lattice evolves from a normal ferroelectric state to a typical relaxor state with increasing defect concentration. Consequently, the energy and dielectric susceptibility characteristics associated with the ferroelectric phase transitions become smeared. The simulated results approve the applicability of the Ginzburg-Landau model in approaching relaxor ferroelectrics.

  8. Curie constant in relaxor ferroelectrics Pb(Zn1/3Nb2/3)O3-8%PbTiO3

    NASA Astrophysics Data System (ADS)

    Iwata, Makoto; Ido, Tomoya; Maeda, Masaki; Ishibashi, Yoshihiro

    2014-09-01

    The dielectric permittivity along the [001]c direction of the pseudocubic coordinate in Pb(Zn1/3Nb2/3)O3-8%PbTiO3 (PZN-8%PT) was investigated in a wide temperature range of 30-640 C. The determination of the Curie constant in PZN-8%PT was attempted, using the dielectric permittivity above the Burns temperature, to evaluate the bulk property in the ferroelectric phase as an average structure with reduced heterogeneity. It was confirmed that the reported temperature dependence of the spontaneous polarization can be quantitatively well reproduced on the basis of the Landau-type free energy.

  9. Microstructural effects on the dielectric and electromechanical properties of lead magnesium(1/3)niobium(2/3)oxygen(3) relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Koyuncu, Metin

    2000-10-01

    One of the major concerns with the electrostrictive PbMg1/3Nb 2/3O3 (PMN) based materials is the formation of a stable non-ferroelectric second phase in small amounts. One objective of this project is to clear the reason behind its formation and consistently achieve 100% pure perovskite phase using the columbite route. Second objective is to develop a model to understand the effect of non-ferroelectric second phases (pores and pyrochlore) in electrostrictive materials. Careful characterization of the raw materials showed that formation of pyrochlore was related directly to the quality of the MgO powder. 100% pure perovskite was formed consistently from stoichiometric compositions when this oxide was free of volatiles, i.e. hydrates and carbonates. Stoichiometric PMN produced in this way was seen to have the best combination of dielectric and mechanical properties, and deviation from MgO stoichiometry in any direction resulted in inferior material properties due to formation of pyrochlore or unreacted MgO. The effect of pores and second phases to dielectric and electromechanical properties of PMN were investigated by using a non-linear finite element model. Electric field dependence of mechanical properties was determined by the pulse-echo technique as a function of temperature and electric field in the range -50 to 70°C. The dependence of these properties at Tmax was implemented into the FEM. Electric field and mechanical stress dependence of polarization and strain was implemented into the model through the use of non-linear material properties. Electric field induced anisotropy and local change in material properties were taken into account on an element-to-element resolution, including local dielectric breakdown. The effects of pores and pyrochlore of similar geometry were found to be almost equal for identical geometries due to the high dielectric constant of PMN. The field concentrations were elevated between particles/pores if the distance in-between was less than approximately ten times the diameter of the particle. If dielectric breakdown occurred, the broken-down region grew into a tree shape and towards the electrodes as the applied field was increased. The developed model can be used in analysis or design of new electrostrictive materials/devices without the need for assumptions to simplify geometry, field distributions or material properties.

  10. A-site doping-induced renormalization of structural transformations in the PbSc{sub 0.5}Nb{sub 0.5}O{sub 3} relaxor ferroelectric under high pressure

    SciTech Connect

    Maier, B. J.; Welsch, A.-M.; Mihailova, B.; Paulmann, C.; Bismayer, U.; Angel, R. J.; Zhao, J.; Engel, J. M.; Schmitt, L. A.; Gospodinov, M.; Friedrich, A.

    2010-05-01

    The effect of A-site incorporated Ba{sup 2+} and Bi{sup 3+} on the pressure-driven structural transformations in Pb-based perovskite-type relaxor ferroelectrics has been studied with in situ x-ray diffraction and Raman scattering of PbSc{sub 0.5}Nb{sub 0.5}O{sub 3}, Pb{sub 0.93}Ba{sub 0.07}Sc{sub 0.5}Nb{sub 0.5}O{sub 3}, and Pb{sub 0.98}Bi{sub 0.02}Sc{sub 0.51}Nb{sub 0.49}O{sub 3} in the range from ambient pressure to 9.8 GPa. The substitution of Ba{sup 2+} for Pb{sup 2+} represents the case in which A-site divalent cations with stereochemically active lone-pair electrons are replaced by isovalent cations with a larger ionic radius and no active lone pairs, leading to formation of strong local elastic fields. In contrast, substitution of Bi{sup 3+} for Pb{sup 2+} involves the replacement of divalent A-site cations with active lone-pair electrons by aliovalent cations with nearly the same ionic radius and active lone pairs so it induces local electric fields but not strong elastic fields. The two types of dopants have rather distinct effects on the changes in the atomic structure under pressure. The embedding of Ba{sup 2+} and associated elastic fields hinders the development of pressure-induced ferroic ordering and thus smears out the phase transition. The addition of Bi{sup 3+} enlarges the fraction of spatial regions with a pressure-induced ferroic distortion, resulting in a more pronounced phase transition of the average structure, i.e., the preserved lone-pair order and the absence of strong local elastic fields enhances the development of the ferroic phase at high pressure. For all compounds studied, the high-pressure structure exhibits glide-plane pseudosymmetry associated with a specific octahedral tilt configuration.

  11. NMR study of local structure and chemical ordering in PbMg1/3Nb2/3O3 and PbSc1/2Nb1/2O3 relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Laguta, V. V.; Glinchuk, M. D.; Nokhrin, S. N.; Bykov, I. P.; Blinc, R.; Gregorovi?, A.; Zalar, B.

    2003-03-01

    The 93Nb and 45Sc nuclear-magnetic-resonance (NMR) spectra of disordered relaxor ferroelectrics PbSc1/2Nb1/2O3 (PSN) and PbMg1/3Nb2/3O3 (PMN) have been studied at T>Tm, where Tm?355 K and 265 K is the temperature of the dielectric susceptibility maximum for PSN and PMN, respectively. The analysis of the spectra was performed both on the basis of an analytical description of the NMR line shapes, allowing for homogeneous and inhomogeneous broadening related to a random distribution of the electric-field gradients, and a numerical Monte Carlo approach taking into account electric-field gradients originating from the random distribution of Mg, Sc, and Nb ions (which may be shifted or not) over B-type cation sites. 1/2?-1/2 NMR spectra of 93Nb and 45Sc in PSN contain a narrow (3 4 kHz) almost isotropic component and a broad strongly anisotropic component. These two components of the NMR spectra are related to the 1:1 Sc/Nb ordered and compositionally disordered regions of the crystal, respectively. It is shown that in the disordered regions, the Sc3+, Nb5+, and O2- ions are randomly shifted from their cubic lattice sites in one of the three possible directions: <100>, <110>, or <111>. In PMN, the NMR spectrum of 93Nb contains practically only the broad component. The portion of the unbroadened spectrum that may correspond to ideal 1:2 Mg/Nb ordered regions accounts only for 2 3 % of the total integral intensity. No evidence was obtained for the existence of 1:1 Mg/Nb regions in PMN. The NMR data demonstrate that in PMN the cubic symmetry at T>Tm is locally broken due to ion shifts similar to that in disordered PSN. The values of the ionic shifts have been estimated in the point-charge point-dipole approximation for the electric-field gradients both in PSN and PMN.

  12. 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.

  13. 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 PST with a lower degree of B-site order.

  14. 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.

  15. 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.

  16. Effect of Reoriented Nanodomains on Crystal Structure and Piezoelectric Properties of Polycrystalline Ferroelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Fan, Qiaolan; Zeng, Weidong; Zhou, Changrong; Cen, Zhenyong; Yuan, Changlai; Xiao, Jianrong; Ma, Jiafeng

    2015-10-01

    It has been widely accepted that electric fields induce a reversible structural phase transition and thus yield giant piezoelectric responses in ferroelectric ceramics. Based on detailed measurements of polycrystalline (Li0.5Nd0.5)2+-modified 0.95Bi0.5Na0.5TiO3-0.05BaTiO3 ceramics, we demonstrate in this study that coherent diffraction from nanodomains in ferroelectric ceramics masks the real crystal structure. The observed electric-field-induced phase transformation behavior is a consequence of relaxor-to-ferroelectric transformation caused by changes in the coherence length of the nanodomains. A driving mechanism of the structure-property relationship in which high piezoelectric properties originate from correlated ordering of nanodomains during poling is proposed.

  17. 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.

  18. 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.

  19. Generic influences of charged defects on the structure-property relationships of modified ferroelectric barium titanate and antiferroelectric sodium niobate

    NASA Astrophysics Data System (ADS)

    Zhang, Ruitao

    Structure-property relationships were investigated to reveal the generic influence of various substituents on ferroelectric (FE) BaTiO3 and antiferroelectric (AFE) NaNbO3. Simulations of defect distribution, using a preliminary cellular automaton (CA) model, were also carried out. Interrelationships between defect distributions and macroscopic properties are discussed. Compositional modification of ferroelectric BaTiO3 was systematically investigated for four types of aliovalent substitutions. A generic influence of charged defects in breaking down the ferroelectric domains was demonstrated. Relaxor behavior was induced in all four types of modified ferroelectric BaTiO 3. It was shown that the induced relaxor behavior was related to the concentration of charged defects, more so than the substituent type. La+3 (x) modified antiferroelectric NaNbO3 (NNL-x) was also systematically investigated for x ? 5. Emphasis was placed on the field-induced AFE-FE transition. La+3 modification was found to result in enhanced difficulties of the field-induced AFE-FE transition. With increasing La+3 concentration, it was found that higher fields were required to induce the ferroelectric state. In addition, La +3 substitution was found to have less impact on the dielectric properties of antiferroelectrics than ferroelectrics. A preliminary two-dimensional cellular automaton model of defect distribution was proposed based on space charge neutrality considerations. It used only pairwise nearest-neighbor interactions and neglected the elastic effects associated with lattice distortions. Simulations demonstrated a general distribution pattern for charged defects. With increasing substituent concentration, more and larger defect clusters formed, which might be related with the formation of polar nanodomains in the modified ferroelectric BaTiO3. The influence of charged defects on field-induced AFE-FE transition was discussed in terms of elastic strain effects.

  20. Dielectric properties of PbNb2O6 ferroelectric ceramics at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

    Complex dielectric permittivity measurements in PbNb2O6 ceramics were performed in a frequency and temperature range of 1kHz -1MHz and from 15to900K, 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.

  1. Nonlinear dielectric behavior in three-component ferroelectric superlattices

    NASA Astrophysics Data System (ADS)

    Sarkar, A.; Ranjith, R.; Krupanidhi, S. B.

    2007-07-01

    Three-component ferroelectric superlattices consisting of alternating layers of SrTiO3, BaTiO3, and CaTiO3 (SBC) with variable interlayer thickness were fabricated on Pt(111)/TiO2/SiO2/Si (100) substrates by pulsed laser deposition. The presence of satellite reflections in x-ray-diffraction analysis and a periodic concentration of Sr, Ba, and Ca throughout the film in depth profile of secondary ion mass spectrometry analysis confirm the fabrication of superlattice structures. The Pr (remnant polarization) and Ps (saturation polarization) of SBC superlattice with 16.4-nm individual layer thickness (SBC16.4) were found to be around 4.96 and 34 ?C/cm2, respectively. The dependence of polarization on individual layer thickness and lattice strain were studied in order to investigate the size dependence of the dielectric properties. The dielectric constant of these superlattices was found to be much higher than the individual component layers present in the superlattice configuration. The relatively higher tunability (55%) obtained around 300 K indicates that the superlattice is a potential electrically tunable material for microwave applications at room temperature. The enhanced dielectric properties were thus discussed in terms of the interfacial strain driven polar region due to high lattice mismatch and electrostatic coupling due to polarization mismatch between individual layers.

  2. Ferroelectric polymers

    SciTech Connect

    Lovinger, A.J.

    1983-06-10

    Piezoelectricity and pyroelectricity, traditionally encountered in certain single crystals and ceramics, have now also been documented in a number of polymers. Recently, one such polymer - poly(vinylidene fluoride) - and some of its copolymers have been shown to be ferroelectric as well. The extraordinary molecular and supermolecular structural requirements for ferroelectric behavior in polymers are discussed in detail, with particular emphasis on poly(vinylidene fluoride). Piezoelectric, pyroelectric, and ferroelectric properties are also briefly reviewed, as are some promising applications of such polymers. 8 figures, 1 table.

  3. 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

  4. 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.

  5. 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

  6. Glassy to inhomogeneous-ferroelectric crossover in (Pb, La)(Zr, Ti)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Bobnar, V.; Kutnjak, Z.; Levstik, A.

    2000-05-01

    The temperature dependence of the dielectric nonlinearity a3=?3/?14 has been determined in 9/65/35 (Pb, La)(Zr, Ti)O3 ceramics. In zero electric field a deep in the temperature behavior of the static a3 has been observed indicating a crossover from paraelectric-like to glass-like behavior on cooling towards the freezing transition. By varying a bias electric field another glass-to-ferroelectric crossover has been observed in the temperature dependence of the static a3. The observed crossovers as well as the temperature dependence of the linear static dielectric constant agree with the predictions of the spherical random-bond-random-field model of relaxor ferroelectrics.

  7. Confinement effect on coercive field in relaxor terpolymer nanowires

    NASA Astrophysics Data System (ADS)

    Liu, B. L.; Tian, B. B.; Sun, J. L.; Liu, Y.; Wang, J. L.; Sun, Sh.; Meng, X. J.; Chu, J. H.

    2015-11-01

    The confinement effect on the coercive field in relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)[P(VDF-TrFE-CFE)] terpolymer nanowires with different diameters ranging from 30 to 170 nm was studied using piezoelectric force microscope. It was found that the coercive field increases significantly as the diameter of terpolymer nanowires decreases. The results can be explained by the conversion of molecule conformation from T3G to Tm>4 in the terpolymer nanowires, which is supported by Fourier transform infrared spectroscope.

  8. Finite-temperature properties of the relaxor PbMg1 /3Nb2 /3O3 from atomistic simulations

    NASA Astrophysics Data System (ADS)

    Al-Barakaty, A.; Prosandeev, Sergey; Wang, Dawei; Dkhil, B.; Bellaiche, L.

    2015-06-01

    An atomistic numerical scheme is developed and used to study the prototype of relaxor ferroelectrics, that is PbMg1 /3Nb2 /3O3 (PMN), at finite temperatures. This scheme not only reproduces known complex macroscopic properties of PMN, but also provides a deep microscopic insight into this puzzling system. In particular, relaxor properties of PMN are found to originate from the competition between (1) random electric fields arising from the alloying of Mg and Nb ions belonging to different columns of the Periodic Table within the same sublattice; (2) the simultaneous condensation of several off-center k points as a result of a specific short-range, antiferroelectriclike interaction between lead-centered dipoles; and (3) ferroelectriclike interactions. Such origins contrast with those recently proposed for the homovalent Ba(Zr,Ti)O3 solid solution, despite the fact that these two materials have similar macroscopic propertieswhich therefore leads to a comprehensive understanding of relaxor ferroelectrics.

  9. 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.

  10. Relaxor-PT single crystals: observations and developments.

    PubMed

    Zhang, Shujun; Shrout, Thomas

    2010-10-01

    Relaxor-PT based ferroelectric single crystals Pb(Zn?/?)Nb(?/?)O?-PbTiO? (PZNT) and Pb(Mg?/?)Nb(?/?)O?-PbTiO? (PMNT) offer high performance with ultra-high electromechanical coupling factors k?? > 0.9 and piezoelectric coefficients d??s > 1500 pC/N. However, the usage temperature range of these perovskite single crystals is limited by T(RT)-the rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature T(C), a consequence of curved morphotropic phase boundaries (MPBs). Furthermore, these <001>-oriented crystals exhibit low mechanical quality Q and coercive fields, restricting their usage in high-power applications. In this survey, recent developments on binary and ternary perovskite relaxor-PT crystal systems are reviewed with respect to their temperature usage range. General trends of dielectric and piezoelectric properties of relaxor-PT crystal systems are discussed in relation to their respective T(C)/T(RT). In addition, two approaches have been implemented to improve mechanical Q, including acceptor dopants, analogous to hard polycrystalline ceramics, and anisotropic domain engineering, enabling low-loss crystals with high coupling for high-power applications. PMID:20889397

  11. 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.

  12. Influence of the A and B vacancies on the dielectric and structural properties of the PLZT 8/60/40 ferroelectric ceramic system

    NASA Astrophysics Data System (ADS)

    García-Zaldívar, O.; Peláiz-Barranco, A.; Guerra, J. D. S.; Mendoza, M. E.; Calderón-Piñar, F.; Hall, D. A.

    2011-04-01

    The lanthanum modified lead zirconate titanate (PLZT) ferroelectric ceramics, considering La/Zr/Ti ratio of 8/60/40 and vacancies in A or B sites of the perovskite structure, have been analyzed by using X-ray diffraction, dielectric response, polarized light microscopy and ferroelectric hysteresis. No remarkable differences are observed between samples with A or B vacancies from the X-ray diffraction patterns and ferroelectric hysteresis loops. However, the dielectric measurements have revealed a significant decrease in the maximum values for the real part of the dielectric permittivity and an enhancement of the relaxor behavior in the systems where A vacancies have been considered. On the other hand, the anomalies observed in the temperature dependence of the remanent polarization suggest a frozen out in the dynamic of Nanometric Polar Regions (PNRs) around the same region of temperatures for both samples.

  13. Orientation dependence of ferroelectric behavior of BiFeO{sub 3} thin films

    SciTech Connect

    Wu Jiagang; Wang, John

    2009-11-15

    Multiferroic BiFeO{sub 3} (BFO) thin films with (111), (100), (110) preferred, and random orientations were deposited by radio frequency magnetron sputtering on SrRuO{sub 3}-buffered SrTiO{sub 3}(111), SrTiO{sub 3}(100), SrTiO{sub 3}(110), and Pt(111)/Ti/SiO{sub 2}/Si(100) substrates, respectively. The orientation dependences of ferroelectric and fatigue behavior of the BFO thin films were investigated. As expected, the (111)-oriented BFO thin film exhibits the highest, giant ferroelectric polarization (2P{sub r}=196.9 muC/cm{sup 2}) at 1 kHz and room temperature using positive up negative down measurement, while the (100)-oriented BFO thin film possesses an almost fatigue-free behavior up to 5.25x10{sup 7} switching cycles when measured at 100 kHz and room temperature. The observed behavior confirms that the largest spontaneous polarization direction and the fatigue endurance are (111) and (100) for BFO thin films, respectively. Regardless of the film orientation, the charge carriers that are responsible for dielectric relaxation and conductivity are oxygen vacancies (V{sub O}) .

  14. 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 synchrotron x-ray diffraction indicates that a small effective restoring stress of about 1 MPa acts on the domain walls in these nano-crystalline PZT films. This insight allows reversible control of the ferroelectric and dielectric behavior of these important functional oxide materials, with important implications for associated integrated devices.

  15. 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 ?-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 introduced lattice reorientation in magnetic-field-modulated P(VDF-TrFE) films would be closely related to the fatigue resistance. Under an ac electric field, the correspondingly microstructures may also influence the electrically induced lattice defects. Polarization fatigue data in P(VDF-TrFE) films was also analyzed by a dynamic Coffin-Manson law, wherein the corresponding coefficients and the exponent of the function can be estimated via different Weibull distribution function. The smallest scale found to be significant in electrical fatigue is the irreversible atomic movements. Studies on electrical failure behavior were also performed in P(VDF-TrFE) copolymer films. Experiment results consistently show that the measured electric polarization near the breakdown limit with respect to the failure life cycles obeys the Coffin-Manson law that is the most widely used to describe the mechanical fatigue failure behavior. The corresponding Coffin-Manson exponents remain constant. Our experimental evidence indicates that accumulation of the disordered structure at the atomic level is closely related to the physical origin of the fatigue in dielectric materials. It is the intrinsic atomic movement that constitutes the major finding in this work.

  16. Phase field simulations of the poling process and nonlinear behavior of ferroelectric polycrystals with semiconducting grain boundaries

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Shu, Weilin; Fang, Hui; Kamlah, Marc

    2014-09-01

    The effect of grain boundary conductivity on the poling process and the nonlinear electromechanical behaviors of ferroelectric polycrystals are investigated through the use of a phase field model. The grain boundary is modeled as a semiconductor in the phase field model via Maxwells equations, which consider the drift of free charges under an electric field. The simulation results show that the poling electric field of the ferroelectric polycrystal with the semiconducting grain boundary is much larger than that of an insulating grain boundary, which is due to the screening of polarization-induced charges at the grain boundaries. The P-E hysteresis loop becomes narrow, and the ferroelectric property degrades in the presence of a semiconducting grain boundary; this indicates that the grain boundary conductivity has a significant influence on the nonlinear behavior of the ferroelectric polycrystals. On the other hand, the grain boundary conductivity, however, has less effect on the response of the ferroelectric polycrystals to a mechanical load. The present work provides an insight into the effect of the charge leakage, which is induced by the material defects, e.g., the grain boundary, on the electromechanical properties of piezoelectric ceramics.

  17. 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.

  18. Enhancing electromechanical properties of lead-free ferroelectrics with bilayer ceramic/ceramic composites.

    PubMed

    Ayrikyan, Azatuhi; Rojas, Virginia; Molina-Luna, Leopoldo; Acosta, Matias; Koruza, Jurij; Webber, Kyle G

    2015-06-01

    The macroscopic electromechanical behavior of lead-free bilayer composites was characterized at room temperature. One layer consisted of a nonergodic relaxor, (Bi1/2Na1/2)TiO3-7BaTiO3, with an electric-field-induced longrange ferroelectric order, whereas the other is understood to be an ergodic relaxor [(Bi1/2Na1/2)TiO3-25SrTiO3] that undergoes a reversible electric-field-induced macroscopic nonpolar-to-polar transition. Microstructural evidence of a bilayer with low diffusion between the two components is also demonstrated. By taking advantage of the different macroscopic strain- and polarization-electric-field responses of the two constituents, internal mechanical and electrical fields can be developed that enhance the unipolar strain over that expected by a rule of mixtures approximation, thereby improving the properties needed for application of such materials to actuator systems. It is possible through further tailoring of the volume fractions and macroscopic properties of the constituents to optimize the electromechanical properties of multilayer lead-free ferroelectrics. PMID:26067034

  19. Incommensurate modulations of relaxor ferroelectric Ca0.24Ba0.76Nb2O6 (CBN24) and Ca0.31Ba0.69Nb2O6 (CBN31).

    PubMed

    Graetsch, Heribert A; Pandey, Chandra Shehkar; Schreuer, Jrgen; Burianek, Manfred; Mhlberg, Manfred

    2014-08-01

    CBN crystals show a one- and a two-dimensionally modulated modification. The former is isotypic with orthorhombic Ba4Na2Nb10O30 and the latter with the tetragonal tungsten bronze type of crystal structure. The orthorhombic form irreversibly transforms to the tetragonal polymorph at the ferroelectric phase transition near 603?K. Orthorhombic and tetragonal CBN24 slightly differ in the distribution of the Ba and Ca atoms over the incompletely filled Me1 and Me2 sites. The tetragonal symmetry is further broken in orthorhombic CBN24 by different amplitudes of the positional modulations of O atoms which are symmetrically equivalent in the TTB structure. A similar orthorhombic phase of CBN31 could be obtained by quenching from 1473?K. PMID:25080253

  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 [(?R/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. The role of tetragonal side morphotropic phase boundary in modified relaxor-PbTiO3 crystals for high power transducer applications

    NASA Astrophysics Data System (ADS)

    Kong, Lingping; Liu, Gang; Zhang, Shujun; Liu, Haozhe

    2013-10-01

    Morphotropic phase boundary (MPB) in ferroelectric materials leads to improved properties due to the structural instability. The manganese modified Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals with MPB composition were investigated, the structure/property relationship was established. The tetragonal side MPB (coexistence of 91% tetragonal and 9% monoclinic phases) was confirmed by X-ray synchrotron data, while relaxor behavior was detected by Raman characterization and dielectric measurement. Crystals with such MPB composition possess high "figure of merit" (d33.Q33 106 pC/N), being one order higher when compared with their pure rhombohedral counterparts. Together with high Curie temperature (229 C) and temperature stability of properties, demonstrating a promising candidate for high power transducer applications.

  3. Evolution of multiple dielectric responses and relaxor-like behaviors in pure and nitrogen-ion-implanted (Ba, Sr)TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Gao, Y. H.; Yang, J.; Shen, H.; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-03-01

    Multiple dielectric responses are comparatively investigated in the pure and nitrogen-ion-implanted (Ba, Sr)TiO3 (BST) films. Larger diffusive degree of phase transition and more relaxor-like features than those of pure BST films are observed in implanted ones, where the long-range-dipolar-correlated-orders were further segregated into local polar orders after the implantation. Moreover, the implanted films possess a transition from local reorientations of groups of dipoles induced nearly constant-loss (NCL) type to oxygen vacancies (Vo) hopping type conduction at high temperature. Whereas, pure films behave as NCL type conduction along with a dielectric relaxation, which arises from the motions of defect complexes Vo2+-Ti3+.

  4. Evolution of multiple dielectric responses and relaxor-like behaviors in pure and nitrogen-ion-implanted (Ba, Sr)TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Gao, Yanhong; Bai, Wei; Zhang, Yuanyuan; Shen, Hong; Sun, Jinglan; Meng, Xiangjian; Duan, Chungang; Tang, Xiaodong; Chu, Junhao; meng xiangjian Team; chu junhao Team

    2015-03-01

    Multiple dielectric responses are comparatively investigated in the pure and nitrogen-ion-implanted (Ba, Sr)TiO3 (BST) films. Larger diffusive degree of phase transition and more relaxor-like features than those of pure BST films are observed in implanted ones, where the long-range-dipolar-correlated-orders were further segregated into local polar orders after the implantation. Moreover, the implanted films possess a transition from local reorientations of groups of dipoles induced nearly-constant-loss (NCL) type to oxygen vacancies (Vo) hopping type conduction at high temperature. Whereas, pure films behave as NCL type conduction along with a dielectric relaxation, which arises from the motions of defect complexes Vo2+ -Ti3+.

  5. 207Pb NMR study of the relaxor behavior in PbMg1/3Nb2/3O3

    NASA Astrophysics Data System (ADS)

    Blinc, R.; Gregorovi?, A.; Zalar, B.; Pirc, R.; Laguta, V. V.; Glinchuk, M. D.

    2001-01-01

    The local structure of the relaxor single crystal PMN has been studied via a measurement of the temperature dependences of the 207Pb spectra and relaxation times between 450 K and 15 K. The 207Pb NMR spectra are frequency distributions which reflect the existence of polar nanoclusters and which can be well described by the recently proposed spherical random-bond-random-field model. The temperature dependence of the Edwards-Anderson order parameter q has been determined together with the random bond coupling and the random field variance. The results agree with those obtained from the 93Nb NMR spectra and show that at any given instant of time the crystal consists of polar clusters with variable orientation and magnitude of the local polarization. The polar clusters are on the NMR time scale 10-4-10-5 s, dynamic entities which exist for a certain amount of time, disappear, and then reappear in a different form.

  6. Interfacial charge and strain effects on the ferroelectric behavior of epitaxial (001) PbTiO3 films on (110) DyScO3 substrates

    NASA Astrophysics Data System (ADS)

    Highland, M. J.; Fong, D. D.; Stephenson, G. B.; Fister, T. T.; Fuoss, P. H.; Streiffer, S. K.; Thompson, Carol; Richard, M.-I.; Eastman, J. A.

    2014-03-01

    In-situ synchrotron x-ray observations reveal that the ferroelectric behavior of epitaxial (001) PbTiO3 thin films grown on (110) DyScO3 substrates depends on both film thickness and interfacial electrical properties. A 92-nm-thick film was found to exhibit an a/c domain structure with a ferroelectric Curie temperature similar to that theoretically predicted based on the strain state. In contrast, 6-nm-thick films contained only c-oriented domains, and the ferroelectric behavior was found to depend strongly on the nature of the electrical boundary condition at the buried interface.

  7. Piezoresponse force microscopic study of ferroelectric (1 - x)Pb(Sc1/2Nb1/2)O3 - xPbTiO3 and Pb(Sc1/2Nb1/2)O3 single crystals

    NASA Astrophysics Data System (ADS)

    Guo, H. Y.; Bing, Y. H.; Ye, Z.-G.

    2012-09-01

    The microscopic piezoelectric response and ferroelectric domain switching in the (001)-oriented rhombohedral piezo-/ferroelectric (1 - x)Pb(Sc1/2Nb1/2)O3 - xPbTiO3 (PSN-PT) and relaxor Pb(Sc1/2Nb1/2)O3 (PSN) single crystals were studied by piezoresponse force microscopy. PSN-PT shows clear domain structures while the domain contrast of PSN is very weak. For PSN-PT, after being fully poled vertically, its lateral domain structure is still composed of a multi-domain state. Both PSN-PT and PSN crystals respond to positive and negative DC field drives through piezoelectricity. However, their poling behaviors are different. For PSN-PT, during successive applications of a positive external electric field, the areas with piezoresponse in phase with the electric field grow at the expense of domains of opposite piezoresponse, implying a domain switching process via sideway motion of domain walls. On the other hand, in the PSN single crystal, the piezoresponse contrast of the alternatively poled area shows a uniformly fading and enhancing pattern, depending on the direction of the polarization component of the domains relative to the external field. While the domain pattern of PSN-PT and its evolution under an external field behave like a normal ferroelectric material, the domain structure and domain evolution process of PSN appear to be abnormal for a ferroelectric, but consistent with the character of a relaxor.

  8. 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.

  9. Microwave dielectric dispersion process in perovskite ferroelectric systems

    NASA Astrophysics Data System (ADS)

    de Los S. Guerra, J.; Lente, M. H.; Eiras, J. A.

    2006-03-01

    The microwave dielectric dispersion process was investigated in relaxor and normal ferroelectric compositions of Pb1-xLaxTiO3 ceramics. The results revealed the following remarkable features: (i) the mechanism responsible for the microwave dielectric dispersion process in perovskite ferroelectric systems may be associated to the vibration of the boundaries of polar regions, independently of their size and dynamical properties; (ii) the characteristic frequency, fR, is governed by the ratio between the force constant and the effective mass of such boundaries; (iii) the temperature dependence of fR above the temperature of the maximum of the dielectric permittivity directly reflects the ferroelectric-type phase transition.

  10. Structural change in polar nanoregion in alkali niobate added Pb(Zn1/3Nb2/3)0.95Ti0.05O3 single crystal and its effect on ferroelectric properties

    NASA Astrophysics Data System (ADS)

    Park, Jong-Sung; Jung, Youngsoo; Lee, Jung-Kun

    2012-10-01

    Pb(Zn1/3Nb2/3)0.95Ti0.05O3 (PZNT) single crystals with 5 mol. % alkali niobate such as LiNbO3 (LN), NaNbO3 (NN), and KNbO3 (KN) were fabricated by using a flux method to investigate the effect of A-site cation radius on the structure and ferroelectric properties of PZNT under electric field (E-field). Their structure and properties showed different electric field dependence. Polarization versus electric field and strain versus electric field curves of PZNT-0.05LN showed E-field induced phase transition from a relaxor state to a normal ferroelectric state. However, only relaxor behavior was observed in PZNT-0.05NN and PZNT-0.05KN. The effect of A-site ion doping is attributed to the change in local lattice distortion and polar nano-region. When smaller cation such as Li ion substitutes Pb ion, the off-center displacement of Nb ion stabilizes rhombohedral lattice distortion. They, in turn, facilitate the development of macro-domains under electric field (E-field) in PZNT-0.05LN. In contrast, the substitution of Pb with larger cations such as Ni and K decreases the rhombohedral distortion of PZNT, which leads to the disappearance of unique E-field induced phase transition from rhombohedral to tetragonal phase in PZNT. Therefore, non-linear electrostrictive behavior of relaxor ferroelectrics is found in PZNT-0.05NN and PZNT-0.05KN.

  11. Temperature-dependent fatigue behaviors of ferroelectric ABO3-type and layered perovskite oxide thin films

    NASA Astrophysics Data System (ADS)

    Yuan, G. L.; Liu, J.-M.; Wang, Y. P.; Wu, D.; Zhang, S. T.; Shao, Q. Y.; Liu, Z. G.

    2004-04-01

    The temperature-dependent dielectric and ferroelectric fatigue behaviors of ABO3-type perovskite thin films Pb(Zr0.52Ti0.48)O3 (PZT) and Pb0.75La0.25TiO3 (PLT) and layered Aurivillius thin films SrBi2Ta2O9 (SBT) and Bi3.25La0.75Ti3O12 (BLT) with Pt electrodes are studied. The improved fatigue resistance of PZT and PLT at a low temperature can be explained by the defect-induced suppression of domain switch/nucleation near the film/electrode interface, which requires a long-range diffusion of defects and charges. It is argued that the fatigue effect of SBT and BLT is attributed to the competition between domain-wall pinning and depinning. The perovskitelike slabs and/or (Bi2O2)2+ layers act as barriers for long-range diffusion of defects and charges, resulting in localization of the defects and charges. Thus, the fatigued SBT and BLT can be easily rejuvenated by a high electric field over a wide temperature range.

  12. Crystal structure and ferroelectric properties of ABi2Ta2O9 (A=Ca, Sr, and Ba)

    NASA Astrophysics Data System (ADS)

    Shimakawa, Y.; Kubo, Y.; Nakagawa, Y.; Goto, S.; Kamiyama, T.; Asano, H.; Izumi, F.

    2000-03-01

    Crystal structures and ferroelectric properties of a series of Bi-layered compounds, CaBi2Ta2O9, SrBi2Ta2O9, and BaBi2Ta2O9, were investigated. The structures of CaBi2Ta2O9 and SrBi2Ta2O9 are orthorhombic, while that of BaBi2Ta2O9 is pseudotetragonal on the macroscopic scale but consists of microdomains with orthorhombic distortion. The ferroelectric Curie temperature of CaBi2Ta2O9 was over 600 C, and that of SrBi2Ta2O9 was over 300 C. BaBi2Ta2O9, in contrast, showed relaxor-type ferroelectric behavior; that is, in the plot of temperature dependence of dielectric constant, a broad peak appeared around 60 C. As the size of the A-site cation decreases from Ba2+ to Ca2+, the lattice mismatch between TaO2 and AO planes in the perovskite-type unit of ATa2O7 increases and the structural distortion becomes more pronounced. This distortion leads to the higher Curie temperature and the larger spontaneous ferroelectric polarization.

  13. 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.

  14. 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).

  15. Ferroelectric Behavior in Polyamides of m-Xylylenediamine and Dicarboxylic Acids

    NASA Astrophysics Data System (ADS)

    Murata, Yukinobu; Tsunashima, Kenji; Koizumi, Naokazu

    1995-12-01

    The ferroelectric properties were studied for polyamides consisting of m-xylylenediamine (MXD) and aliphatic dicarboxylic acids with the number of carbon atoms n=6 to 11, which were designated as nylon MXDn. Quenched samples of these polyamides exhibited the ferroelectric hysteresis loop with the remanent polarization P r of 25-67 mCm-2 which decreased with increasing n. Strip-biaxial and biaxial drawing of nylon MXD6 caused the preferential orientation of molecular chains parallel to the direction of drawing and to the film surface, respectively, and increased the value of P r. A reversible pyroelectric coefficient of 4 to 12 µC·m-2·K-1 was observed for nylons MXD6 and MXD7. The polarization was depolarized with increasing temperature and vanished at the glass transition temperature of the respective samples. The ferroelectricity of nylon MXDn is related to the amide groups aligned by the electric field in amorphous regions.

  16. Solid State Multinuclear NMR Studies of Relaxor Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zhou, Donghua; Hoatson, Gina; Fayon, Franck; Massiot, Dominique; Vold, Robert; Gan, Zhehong

    2001-11-01

    Multinuclear NMR has been used to investigate the local structure and cation disorder in solid solutions of (1-x) Pb(Mg1/3Nb2/3)O3: x Pb(Sc1/2Nb1/2)O3, as a function of concentration. Static, MAS, and 3QMAS spectra are presented for 93Nb and 45Sc at 7.0, 9.4, 14.0 and 19.6 Tesla. The 14 and 19.6 T 93Nb MAS lineshapes have been assigned to species with different numbers of Sc next nearest neighbours. It is necessary to include distributions of the electric field gradient parameters and dispersions in isotropic chemical shifts; these have been estimated from the data. The relative intensities of each spectral component are interpreted in terms of distributions of next nearest neighbor cations and the data strongly supports the Random Layer model. 7 T 207Pb 2D-PASS experiments show residual isotropic chemical shift dispersion reflecting the cation disorder. The anisotropic chemical shielding tensor elements are correlated with the isotropic chemical shifts: this is ascribed to more disordered PbO12 sites with increased covalency character of the PbO bond.

  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. 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.

  19. Evidence of ferroelectricity in SrFeO3-?

    NASA Astrophysics Data System (ADS)

    Manimuthu, P.; Venkateswaran, C.

    2012-01-01

    Perovskite SrFeO3-? belongs to the Ruddlesden-Popper class of system exhibiting interesting electronic and magnetic properties. Nanocrystalline SrFeO3-? synthesized successfully by the thermal decomposition method has the cubic phase as confirmed from x-ray diffraction. The non-stoichiometric nature is confirmed from the selected area electron diffraction pattern. Oxygen stoichiometry, which plays an important role in determining the physical properties, was found to be 2.91 from the iodometric titration. Mssbauer measurement reveals paramagnetic behaviour and suggests mixed valence state of Fe. Relaxor type ferroelectricity is evident from the dielectric plots, which is also reflected in the thermal study. Relaxor ferroelectric behaviour is reported for the first time in SrFeO2.91, arising due to mixed valency of Fe ion.

  20. Unusual High-Temperature Reversible Phase-Transition Behavior, Structures, and Dielectric-Ferroelectric Properties of Two New Crown Ether Clathrates.

    PubMed

    Tang, Yun-Zhi; Yu, Yin-Mei; Xiong, Jian-Bo; Tan, Yu-Hui; Wen, He-Rui

    2015-10-21

    Molecular ferroelectrics with high-temperature reversible phase-transition behaviors are very rare and have currently become one of the hotspots in the field of ferroelectric materials. Herein we display two new crown ether clathrates possessing unusual high-temperature ferroelectric phase-transition behaviors, cyclohexyl ammonium 18-crown-6 tetrafluoroborate (or perchlorate), [Hcha-(18-crown-6)](+) [BF4](-) (1) and [Hcha-(18-crown-6)](+)[ClO4](-) (2) (Hcha = protonated cyclohexyl ammonium). We have proven their reversible structural phase transitions by variable-temperature PXRD measurements and temperature evolutions of Raman bands. Both clathrates exhibit clear ferroelectric phase transitions at about 397 and 390 K, respectively, revealed by the thermal anomalies of differential scanning calorimetry (DSC) measurements, together with abrupt dielectric anomalies in the heating and cooling processes. The measurements on ferroelectric properties using the single crystals showed optimized spontaneous polarization (Ps) of ca. 3.27 ?C cm(-2) for 1 and 3.78 ?C cm(-2) for 2. PMID:26414811

  1. 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

  2. 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.

  3. Growth and characterization of piezo-/ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3-Bi(Zn1/2Ti1/2)O3 ternary single crystals

    NASA Astrophysics Data System (ADS)

    Belan, Reagan A.; Tailor, Hamel N.; Long, Xifa; Bokov, Alexei A.; Ye, Zuo-Guang

    2011-03-01

    In order to develop new piezo-/ferroelectric materials, single crystals of the Pb(Mg1/3Nb2/3)O3-PbTiO3-Bi(Zn1/2Ti1/2)O3 [PMN-PT-BZT] ternary complex perovskite system has been grown by a high temperature solution method using the mixture of PbO and H3BO3 as flux (in a molar ratio of 4:2) with an optimum flux:charge molar ratio of 6:1. It is found that the addition of BZT into the relaxor ferroelectric PMN-PT system reduces the number of spontaneous nucleations, resulting in large single crystals (5 mm×5 mm×14 mm) of good quality. The grown crystals exhibit a pseudo-cubic morphology and show evidence of two-dimensional growth mechanism. Examination by polarized light microscopy (PLM) reveals the formation of striation, which can be reduced by changing the growth conditions. The domain structure and phase transition of the PMN-PT-BZT crystals are investigated by PLM. The temperature and frequency dependences of the dielectric permittivity of the grown crystals show typical relaxor ferroelectric behavior, with the frequency dependence of the temperature of maximum permittivity (Tmax) following the Vogel-Fulcher law. The ferroelectric property is displayed in the crystals with a remnant polarization, Pr=21 μC/cm2 and a coercive field, EC=3.5 kV/cm. The piezoelectric coefficient, d33, is found to be 825 pC/N, a value much higher than that of the ternary ceramics.

  4. 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).

  5. 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

  6. 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.

  7. 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.

  8. Ferroelectric crossovers triggered by isovalent A-site substitution in Pb0.7La0.2TiO3

    NASA Astrophysics Data System (ADS)

    Soon, Hwee Ping; Wang, John

    2006-12-01

    A-site isovalent substitutions trigger ferroelectric transitions in Pb0.7(1-x)A0.7xLa0.2TiO3, where A =Ca, Sr, or Ba. The transitions are dependent on the type and amount of substitutions such as Ca2+, Sr2+, and Ba2+. A transition from normal ferroelectric (FE) to relaxor FE (RFE) is induced by Ca2+, Ba2+, and Sr2+ substitutions at x =0.30, 0.40, and 0.60, respectively. Interestingly, a further crossover to quantum paraelectriclike behavior occurred in Pb0.7(1-x)Ca0.7xLa0.2TiO3 with x =0.60, in addition to the transition from FE to RFE. The observed ferroelectric crossovers and temperature dependence of relative permittivity ?'(T) can be correlated to the structural parameters and breakdown in long-range polar order brought by the A-site isovalent substitution.

  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. 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.

  11. Large electrocaloric effect in ferroelectric polymers near room temperature.

    PubMed

    Neese, Bret; Chu, Baojin; Lu, Sheng-Guo; Wang, Yong; Furman, E; Zhang, Q M

    2008-08-01

    Applying an electrical field to a polar polymer may induce a large change in the dipolar ordering, and if the associated entropy changes are large, they can be explored in cooling applications. With the use of the Maxwell relation between the pyroelectric coefficient and the electrocaloric effect (ECE), it was determined that a large ECE can be realized in the ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer at temperatures above the ferroelectric-paraelectric transition (above 70 degrees C), where an isothermal entropy change of more than 55 joules per kilogram per kelvin degree and adiabatic temperature change of more than 12 degrees C were observed. We further showed that a similar level of ECE near room temperature can be achieved by working with the relaxor ferroelectric polymer of P(VDF-TrFE-chlorofluoroethylene). PMID:18687960

  12. La3Ni2SbO9: a relaxor ferromagnet.

    PubMed

    Battle, Peter D; Evers, Sophie I; Hunter, Emily C; Westwood, Mark

    2013-06-01

    A polycrystalline sample of La3Ni2SbO9 has been synthesized using a standard ceramic method and characterized by neutron diffraction and magnetometry. The compound adopts a monoclinic, perovskite-like structure with space group P2(1)/n and unit cell parameters a = 5.0675(1), b = 5.6380(1), c = 7.9379(2) Å, β = 89.999(6)° at room temperature. The two crystallographically distinct six-coordinate sites are occupied by Ni(2+) and a disordered distribution of Ni(2+)/Sb(5+), respectively; the Ni(2+) and Sb(5+) cations occupy the disordered site in a 1:2 ratio. Both ac and dc magnetometry indicate the presence of a spontaneous magnetization below 105 K. A magnetization of 1.5 μB per formula unit was measured at 2 K in a field of 40 kOe. However, no magnetic scattering was observed in neutron diffraction data collected at 5 K. It is proposed that, as a consequence of the cation disorder, La3Ni2SbO9 behaves as a relaxor ferromagnet, analogous to a relaxor ferroelectric, with magnetic domains too small to be detected by neutron diffraction forming below 105 K. PMID:23688332

  13. 93Nb NMR of the random-field-dominated relaxor transition in pure and doped SBN

    NASA Astrophysics Data System (ADS)

    Blinc, R.; Gregorovi?, A.; Zalar, B.; Pirc, R.; Seliger, J.; Kleemann, W.; Lushnikov, S. G.; Pankrath, R.

    2001-10-01

    The ferroelectric relaxor transitions in Sr0.61Ba0.39Nb2O6 (SBN61) and Sr0.61-yCeyBa0.39Nb2O6 (SBN61:Ce y=0.0066) have been studied by quadrupole perturbed 93Nb NMR. The spectra are inhomogeneous frequency distributions f(?) consisting of a central component due to the 1/2<-->-1/2 transition and a broad background due to the satellite transitions. From the temperature dependence of the width and position of the central component spectrum and from the T dependence of T2 we determined the T dependence of the Edwards-Anderson order parameter and of the normalized spontaneous polarization P. The random bond-random field Ising model parameters are J0=485 K, J=388 K, and ?/J2=0.14. The random-field contribution ?~=?/J2 is here by two orders of magnitude larger than in the perovskite relaxor PbMg1/3Nb2/3O3 (PMN).

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

    NASA Astrophysics Data System (ADS)

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

    2001-06-01

    Transparent glasses in the system (100-x) Li2B4O7-xSrBi2Ta2O9 (0?x?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-ceramic) samples. The dielectric constant (?r) of the glass-ceramic composite (x=20, heat treated at 773 K/8 h) was in between that of the parent host glass (Li2B4O7) and strontium bismuth tantalate ceramics in the frequency range 100 Hz-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 (Ec) and the remnant polarization (Pr) were 1053 V/cm and 0.483 ?C/cm2, respectively.

  15. 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.

  16. All-atom effective models for first-principles simulations of the temperature-dependent behavior of complex ferroelectric oxides

    NASA Astrophysics Data System (ADS)

    Iniguez, Jorge; Wojdel, Jacek C.; Hermet, Patrick; Ghosez, Philippe; Zanolli, Zeila

    2011-03-01

    Since its introduction in the 90's, the first-principles effective-Hamiltonian method has been successfully used to simulate temperature-driven phenomena in increasingly complex ferroelectrics, from classic compound BaTi O3 to multiferroic BiFe O3 . Currently, the emergence of nano-structured materials -- e.g., in the form of ultra-thin films or short-period superlattices -- poses new challenges to the simulations, and the development of predictive models seems to require a reconsideration of the traditional approach. Of particular interest are cases in which novel interfacial effects determine the behavior, as in the PbTi O3 - SrTi O3 superlattices of Bousquet et al. [Nature 452, 7188 (2008)]. In such situations a large number of structural distortions may become active, and it may be difficult to decide which ones need to be included in the model. In order to tackle these difficulties, we are extending the first-principles effective-Hamiltonian method so as to retain a full atomistic description of the material, thus removing the so-called local mode approximation. I will describe our new approach and show preliminary results for PbTi O3 . Work funded by the Spanish DGI and the FP7 program of the EU.

  17. 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.

  18. Polarization behavior of poly(vinylidene fluoride-trifluoroethylene) copolymer ferroelectric thin film capacitors for nonvolatile memory application in flexible electronics

    NASA Astrophysics Data System (ADS)

    Mao, D.; Mejia, I.; Stiegler, H.; Gnade, B. E.; Quevedo-Lopez, M. A.

    2010-11-01

    The time domain and electric field dependence of the polarization switching kinetics of poly(vinylidene fluoride-trifluoroethylene) copolymer based thin film metal-ferroelectric-metal capacitors have been characterized. At room temperature, the time required for complete switching polarization decreases from >1 s to <50 ?s as the voltage is increased from 6 to 12 V, while low nonswitching polarization is maintained. In the time domain, the ferroelectric switching polarization reversal behavior for devices biased above the coercive field follows the nucleation-limited-switching model. The exponential relationship between switching time and applied electric field indicates nucleation dominated switching kinetics. Switching behavior as a function of temperature was also characterized from -60 to 100 C in the voltage range of 6-12 V. Higher temperatures induce larger dc conductance leakage at low frequencies and increases nonswitching polarization for all the voltages studied. It is demonstrated that for certain frequencies, by controlling the switching voltage, our optimized ferroelectric thin film capacitor shows stable switching polarization in a temperature range compatible with flexible electronics applications.

  19. Anomalous Skin Effect in the Lead-Free Relaxor NBT

    NASA Astrophysics Data System (ADS)

    Gehring, Peter; Ge, Wenwei; Phelan, Daniel; Zhang, Qinhui; Li, Jie Fang; Viehland, Dwight; Luo, Hasuo; Boatner, Lynn

    2014-03-01

    Several x-ray and neutron powder diffraction studies have shown that the room-temperature space group of the lead-free relaxor NBT is monoclinic Cc and not rhombohedral R3c, as was previously believed. Motivated by these findings, we performed room-temperature neutron scattering measurements on a large (3.5 gram) single crystal of the lead-free relaxor NBT. Our data confirm the R3c symmetry for bulk NBT and place a strict bound on the strength of the 1/2(111) superlattice reflection associated with the Cc space group based on the published atomic coordinates. We show that a skin effect, analogous to that reported in the relaxors PZN and PMN-10%PT, can reconcile our single-crystal data with these other studied. We believe this represents the first evidence of the relaxor skin effect in a lead-free relaxor.

  20. Diffuse phase transition and relaxor behaviour of textured Sr0.63Ba0.37Nb2O6 ceramics

    NASA Astrophysics Data System (ADS)

    Venet, M.; Guerra, J. de Los S.; Santos, I. A.; Eiras, J. A.; Garcia, D.

    2007-01-01

    Textured Sr0.63Ba0.37Nb2O6 ferroelectric ceramics, with relaxor characteristics, were fabricated by the hot forging process. The analysis of the complex dielectric constant as a function of the temperature revealed the presence of three dielectric anomaly regions. In addition, the relaxor behaviour of this ceramic was also observed at microwave frequencies, evidencing the existence of active polar regions in a broad frequency range. Using the Vogel-Fulcher approximation, physical parameters such as the freezing temperature (Tf) were estimated. It was verified that the mechanisms of the dielectric response, in the microwave frequency range, are also affected by the presence of compositional fluctuations and local electric fields. A phenomenological equation was applied in order to investigate the nature of the polarization mechanisms at low frequencies. Also, a qualitative model was proposed to explain the anisotropic behaviour observed in the phase transition diffuseness between the different ceramic directions.

  1. 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

    Ferroelectrics are important materials due to their extensive technological applications, such as non-volatile memories, field-effect transistors, ferroelectric tunneling junctions, dielectric capacitors, piezoelectric transducers, sensors and actuators. As is well known, the outstanding dielectric, piezoelectric, and ferroelectric properties of these functional oxides originate from their ferroelectric domain arrangements and the corresponding evolution under external stimuli (e.g. electric field, stress, and temperature). Electric field has been known as the most efficient stimulus to manipulate the ferroelectric domains through polarization switching and alignment. Therefore, direct observation of the dynamic process of electric field-induced domain evolution and crystal structure transformation is of significant importance to understand the microstructural mechanisms for the functional properties of ferroelectrics. In this dissertation, electric field in situ transmission electron microscopy (TEM) technique was employed to monitor the real-time evolution of the domain morphology and crystal structure during various electrical processes: (1) the initial poling process, (2) the electric field reversal process, and (3) the electrical cycling process. Two types of perovskite-structured ceramics, normal ferroelectrics and relaxor ferroelectrics, were used for this investigation. In addition to providing the microscopic insight for some well-accepted phase transformation rules, discoveries of some new or even unexpected physical phenomena were also demonstrated. For the initial poling process, microstructural origins for the piezoelectricity development in the three most promising lead-free piezoceramic systems were investigated. For the non-ergodic relaxor ferroelectric compositions ( x = 6% - 9%) in the (1-x)(Bi1/2Na 1/2)TiO3-xBaTiO3 system, well-developed piezoelectricity was realized at poling fields far below the coercive field and phase transition field. Such 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 responsible for the pronounced functionality degradation. Both seed inhibition and domain wall pinning mechanisms were suggested to be the reasons for the observed fatigue behavior. In the polycrystalline ceramic of [(Bi1/2Na1/2)0.95Ba 0.05]0.98La0.02TiO3, a novel phenomenological mechanism of domain fragmentation was found in addition to the domain wall pinning mechanism. Domain fragmentation contributes to the switchable polarization reduction by breaking the long-range polar orders, as visualized by the decomposition of large domains into domain fragments upon bipolar electrical cycling.

  2. Ferroelectric behavior and reproducible Bi-stable resistance switching property in K-doped ZnO thin films as candidate for application in non-volatile memories

    NASA Astrophysics Data System (ADS)

    Lee, J. W.; Subramaniam, N. G.; Kang, T. W.; Shon, Yoon; Kim, E. K.

    2015-05-01

    Potassium-doped ZnO thin films electrodeposited on indium tin oxide (ITO) coated glass substrates exhibited ferroelectric behavior with a remnant polarization of 0.2 ?C/cm2. Especially, wave forms showing the applied input voltage Vi and output voltage Vo were obtained for Al/ZnO:K/ITO structure. It exhibits a superposition of Vi (input) and Vo (output) signal from Al/ZnO:K/ITO structure with a clear phase shift between the two wave forms which again confirms that the observed ferroelectric hysteresis curve is not related to leaky dielectric materials. The current-voltage characteristics of Al/ZnO:K/ITO structures measured for several cycles revealed bi-stable switching characteristics. The reproducible bi-stable switching characteristics for the mentioned structures had good retention in one particular resistance state. Around one order of switching was realized between low and high resistance states. The switching property thought to be polarization induced originating out from the ferroelectric properties of the potassium doped ZnO thin film. The switching between ZnO:K/ITO interface is assumed to be critical for stability in switching for several cycles. Possible application of this structure in non-volatile memories is explored.

  3. Effect of strain on ferroelectric and magnetic behavior in Pb(Zr0.52Ti0.48)O3-based magnetoelectric heterostructures.

    PubMed

    Huang, W; Zeng, H Z; Zhu, J; Hao, J H; Dai, J Y

    2011-12-01

    In this paper, the "sandwich" structured magnetoelectric composite films of Pb(Zr0.52Ti0.48)O3/ NiFe2O4/Pb(Zr0.52Ti0.48)O3 and Pb(Zr0.52Ti0.48)O3/CoFe2O4/Pb(Zr0.52Ti0.48)O3 are epitaxially grown on SrRuO3/SrTiO3 substrates by pulsed-laser deposition. The crystalline quality and microstructures of these heterostructures are investigated by X-ray diffraction technique. The effects of strain on the ferroelectric, magnetic and magnetoelectric coupling properties of these thin films are systematically studied. The results show that the strain effect induced by lattice mismatch between the ferroelectric/ferromagnetic layers plays an important role in the ferroelectric and magnetic properties of these composite films. Compared to the strained Pb(Zr0.52Ti0.48)O3/ CoFe2O4/Pb(Zr0.52Ti0.48)O3 heterostructure, improved ferroelectric properties with an out-of-plane polarization (2P(r)) of 34.2 microC/cm2 and electric coercivity field of 158 kV/cm are obtained in the strain-free Pb(Zr0.52Ti0.48)O3/NiFe2O4/Pb(Zr0.52Ti0.48)O3 heterostructure. The ME measurement results not only show that the strain induced by lattice mismatch has great influence on the ME behavior, but also provide an understanding of the multilayers with full control over the interface structure at the atomic-scale. PMID:22409090

  4. 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.

  5. 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.

  6. Giant electro-mechanical energy conversion in [011] cut ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    Giant electro-mechanical energy conversion is demonstrated under a ferroelectric/ferroelectric phase transformation in [011] cut and poled lead titanate-based relaxor perovskite morphotropic single crystals. It is found that under mechanical pre-stress, a relatively small oscillatory stress drives the material reversibly between rhombohedral and orthorhombic phases with a remarkably high polarization and strain jump induced at zero bias electric field and room temperature. The measured electrical output per cycle is more than an order of magnitude larger than that reported for linear piezoelectric materials. Ideal thermodynamic cycles are presented for this electro-mechanical energy conversion followed by a presentation and discussion of the experimental data.

  7. A high-temperature molecular ferroelectric Zn/Dy complex exhibiting single-ion-magnet behavior and lanthanide luminescence.

    PubMed

    Long, Jrme; Rouquette, Jrme; Thibaud, Jean-Marc; Ferreira, Rute A S; Carlos, Lus D; Donnadieu, Bruno; Vieru, Veaceslav; Chibotaru, Liviu F; Konczewicz, Leszek; Haines, Julien; Guari, Yannick; Larionova, Joulia

    2015-02-01

    Multifunctional molecular ferroelectrics are exciting materials synthesized using molecular chemistry concepts, which may combine a spontaneous electrical polarization, switched upon applying an electric field, with another physical property. A high-temperature ferroelectric material is presented that is based on a chiral Zn(2+) /Dy(3+) complex exhibiting Dy(3+) luminescence, optical activity, and magnetism. We investigate the correlations between the electric polarization and the crystal structure as well as between the low-temperature magnetic slow relaxation and the optical properties. PMID:25556721

  8. 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, the need to fully understand how size and morphology affect domain behaviour in small scale ferroelectrics is obvious. In this talk, observations from a programme of study examining domains in meso and nano-scale BaTiO3 shapes, that have been cut directly from bulk single crystal using focused ion beam milling, will be presented. In general, the equilibrium static domain configurations that occur appear to be the result of a simultaneous desire to minimize both the macroscopic strain and depolarizing fields developed on cooling through the Curie Temperature. While such governing factors might be obvious, the specific patterns that result as a function of morphology are often non-intuitive, and a series of images of domains in nanodots, rods and wires will be presented and rationalised. In addition, the nature in which morphological factors influence domain dynamics during switching will be discussed, with particular focus on axial switching in nanowires, and the manner in which local surface perturbations (such as notches and antinotches) affect domain wall propagation. In collaboration with Alina Schilling, Li-Wu Chang, Mark McMillen, Raymond McQuaid, and Leo McGilly, Queen's University Belfast; Gustau Catalan, Universitat Autonoma de Barcelona; and James Scott, University of Cambridge.

  9. Large strain response based on relaxor-antiferroelectric coherence in Bi0.5Na0.5TiO3-SrTiO3-(K0.5Na0.5)NbO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Liu, Laijun; Shi, Danping; Knapp, Michael; Ehrenberg, Helmut; Fang, Liang; Chen, Jun

    2014-11-01

    The effect of (K0.5Na0.5)NbO3 (KNN) addition on the ferroelectric and dielectric behavior of 90Bi0.5Na0.5TiO3-10SrTiO3 (BNT-ST) lead-free piezoceramics was investigated. Polarization and strain hysteresis loops indicate that a relaxor-antiferroelectric coherence will be produced with the addition of KNN as a replacement for ST up to 5% and the destabilization of the phase coherence is accompanied by an enhancement of the bipolar strain with the increase of temperature, which is 0.37% (corresponding to a large signal d33* of 530 pm/V at 90 C) at 5 mol. % KNN content. This strain was analyzed as derived from an electrostrictive effect at lower electric fields and a field-induced antiferroelectric-ferroelectric phase transition at higher electric fields. The large polar strain response would be of great interest for environmental friendly high-temperature actuators.

  10. Crystal Structure and Relaxor-Type Transition In Praseodymium Doped SBT

    NASA Astrophysics Data System (ADS)

    Mata, Jorge; Duran, Alejandro; Escamilla, Raul; Martinez, Eduardo; Heiras, Jesus; Siqueiros, Jesus

    2006-03-01

    The effects of Pr substitution and ferroelectric response for the Sr1-xPrxBi2Ta2O9 ceramic system were studied. Rietveld refined X-ray diffraction indicates that Pr ion progressively replaces Sr in the A21am space group structure. The solubility of Pr in the solid solution is around 15 %. The replacement induces change in the crystal structure and as consequence dielectric properties are affected. The displacement of TiO6 octahedra with respect to Bi2O2 along the polarization axis decreases as Pr is increased. A notable decrease in the transition temperature (Tm) is observed. With Pr substitution the Tm shifts gradually from 305 ^oC to 120 ^oC. Apparently, the rotation at the ab-plane (?) as well the octahedral distortion observed are strongly related to the coupling between Tm and x. However, the tilt angle (?) associated to the c-axis don't play an important role as it remains essentially constant. Relaxor type transition is observed as Pr increases due to polar microregions above the nominal ferroelectric transition. Local disorder induced by Pr ion is confirmed by the continuous increase in the diffuseness coefficient according to Isupov's model. Thanks to DGAPA-UNAM and CONACYT for funds through Proj. No. 40604-F, 47714-F, IN116703, IN100903 and to P. Casillas, J. Peralta, M. Sainz.

  11. 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 achieved.

  12. 180 domain structure and its evolution in Ca0.28Ba0.72Nb2O6 ferroelectric single crystals of tungsten bronzes structure

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

    Ferroelectric domain structure and its evolution in uniaxial relaxor Ca0.28Ba0.72Nb2O6 single crystals were investigated using transmission electron microscopy. It was found that there exists a high density of 180 domain walls in the crystals. The domains appear predominantly spike shaped along the polar axis and have a typical diameter of 50-500nm. 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 TC, zero-field-cooled needlelike nanodomains were also observed.

  13. Ferroelectric and electrical behavior of (Na{sub 0.5}Bi{sub 0.5})TiO{sub 3} thin films

    SciTech Connect

    Zhou, Z.H.; Xue, J.M.; Li, W.Z.; Wang, J.; Zhu, H.; Miao, J.M.

    2004-08-02

    Sodium bismuth titanate (Na{sub 0.5}Bi{sub 0.5})TiO{sub 3} (NBT) of perovskite structure is among the best known lead-free piezoelectric/ferroelectric that promises a number of applications in sensors and actuators. However, NBT in thin film form has not been properly investigated, although NBT in bulk ceramic form has been widely studied. In this letter, we report the growth of polycrystalline NBT thin films by radio-frequency magnetron sputtering and their ferroelectric behavior. The NBT thin films exhibit a well-defined hysteresis loop, with a remanent polarization of 11.9 {mu}C/cm{sup 2} and coercive field of 37.9 kV/cm when measured at room temperature. There is a steady decrease of dielectric constant in the range of 650-470 over the frequency range of 10-10{sup 5} Hz. A change in the controlling mechanism of electrical behavior from the grain interior to the grain boundary is observed for the NBT thin film with increasing temperature. Hopping of oxygen vacancies trapped at the grain boundaries is responsible for the high dielectric loss at low frequencies and high dc conductivity observed.

  14. Optical interband transitions in [111] poled relaxor-based ferroelectric 0.24Pb(In1/2Nb1/2)O3(0.76 ? x)Pb(Mg1/3Nb2/3)O3xPbTiO3 single crystal

    PubMed Central

    Wu, Fengmin; Yang, Bin; Sun, Enwei; Wang, Zhu; Yin, Yongqi; Pei, Yanbo; Yang, Wenlong

    2013-01-01

    Optical transmission spectra of single crystal 0.24Pb(In1/2Nb1/2)O3(0.76 ? x)Pb(Mg1/3Nb2/3)O3xPbTiO3 (x = 0.27, 0.33) were measured in the pseudo-cubic crystallographic directions [111] and [112?]. Ferroelectric domain structures were observed in order to explain the difference of transmittance for the two composition crystals. Wavelength dependence of the absorption coefficients was measured and the optical energy band gaps were calculated for both direct and indirect transitions, which are Egd = 3.093.18 eV and Egi = 2.892.96 eV, respectively, and the phonon energy is Ep = 0.070.08 eV. The transmission spectra were explained by the refractive indices and extinction coefficients measured by spectroscopic ellipsometry. PMID:25170190

  15. Solid-state single and triple-quantum 93Nb MAS NMR studies of ferroelectric Pb(Mg1/3Nb2/3)O3 and a related pyrochlore.

    PubMed

    Cruz, L P; Rocha, J; Pedrosa de Jesus, J D; Savariault, J M; Galy, J

    1999-12-01

    Pb(Mg1/3Nb2/3)O3 (PMN), a well-known relaxor ferroelectric material, and a related pyrochlore phase have been studied by single- and triple-quantum 93Nb MAS NMR spectroscopy. The assignment of the NMR resonances has been attempted. PMID:10672939

  16. Phase transitions in nanoscale ferroelectric structures.

    SciTech Connect

    Streiffer, S. K.; Fong, D. D.

    2009-01-01

    Over decades of effort, investigations of the intrinsic phase transition behavior of nanoscale ferroelectric structures have been greatly complicated by materials processing variations and by the common and uncontrolled occurrence of spacecharge, which interacts directly with the polarization and can obscure fundamental behavior. These challenges have largely been overcome, and great progress in understanding the details of this class of phase transitions has been made, largely based on advances in the growth of high-quality, epitaxial ferroelectric films and in the theory and simulation of ferroelectricity. Here we will discuss recent progress in understanding the ferroelectric phase transition in a particular class of model systems: nanoscale perovskite thin-film heterostructures. The outlook for ferroelectric technology based on these results is promising, and extensions to laterally confined nanostructures will be described.

  17. Ferroelectric domain wall relaxation in Ba0.25Sr0.75TiO3 films displaying Curie-Weiss behavior

    NASA Astrophysics Data System (ADS)

    Boikov, Yu. A.; Khamchane, K.; Claeson, T.

    2004-10-01

    Ferroelectric films may be used in integrated circuits for high frequency and memory applications. Losses and interfaces between films and electrodes are problematic. This work concerns the temperature and electric field response of the complex dielectric permittivity and the relaxation of domain walls in a ferroelectric layer that is of sufficient quality to show a Curie-Weiss behavior. Laser ablation was used to deposit 1200 nm thick Ba0.25Sr0.75TiO3 layers between metallic oxide, (100 nm) SrRuO3 and (120 nm) La0.67Ca0.33MnO3, films in epitaxial heterostructures. The electric field response (E ?80kV/cm) of the real ?' and imaginary ?? parts of the complex permittivity of the intermediate Ba0.25Sr0.75TiO3 layer in these parallel plane film capacitors was studied at temperatures above and below the phase transition point TCurie. The latter was determined from the temperature dependence of the inverse dielectric permittivity and its value, TCurie=145K, agrees well with that of bulk single crystal. ?' of the Ba0.25Sr0.75TiO3 layer could be suppressed about 80% by a field E =80kV/cm at temperatures close to TCurie?'(T,E) and ??(T,E) curves were used to gain insight into the relaxation dynamics of ferroelectric domain walls (DW) in the Ba0.25Sr0.75TiO3 layer. Their influence on ?' was noticed up to T =230K, well above TCurie. The most probable relaxation time ? of the DW in Ba0.25Sr0.75TiO3 follows a relation ? =?0exp[(?-??E )/kT], where ?0=1.210-10s?=75-105meV, and ? =4.710-24Jm1/2V-1/2.

  18. Time-dependent ferroelectric transition in Pb(1-x)(Zr0.4Ti0.6)(1-x/4)O3 - xLa system

    NASA Astrophysics Data System (ADS)

    Sun, Zhimin; Xue, Dezhen; Wu, Haijun; Ji, Yuanchao; Ding, Xiangdong; Wang, Dong; Yang, Yaodong; Ren, Xiaobing

    2013-06-01

    Ferroelectric transition involves tiny shift of ions within unit cell, thus being intrinsically a very fast process without apparent time-dependence. Contrary to this conventional wisdom, here we report a time-dependent ferroelectric transition, which occurs in hours. The system studied was Pb(1-x)(Zr0.4Ti0.6)(1-x/4)O3 - xLa system with relaxor-forming dopant La3+. The time-dependent ferroelectric transition occurs at the ferroelectric/relaxor crossover composition range of 0.09 < x ≤ 0.16. In these compositions, in situ Raman spectroscopy and transmission electron microscopy reveal very slow growth of ferroelectric phase. Dielectric measurement shows isothermal kinetics of the transition. The slow ferroelectric transition can be understood as being caused by the slowing-down of the otherwise fast growth of polar nano-domains due to the random local field caused by La3+, so that long time is needed to achieve long-range order macroscopic ferroelectric phase.

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

    SciTech Connect

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

    2011-11-22

    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(Bi{sub 0.5}Na{sub 0.5})Ba{sub 0.07}Z{sub 0.04}T{sub 0.96}O{sub 3}(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 1.51{mu}m. Dielectric studies in the material ha indicated relaxor behaviour with diffuse phase transition. High value of {epsilon}{sub m}>1958 is found at 1kHz, Tm (phase transition temperature) 335 deg. 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 T{sub f} = 138 deg. C, E{sub a} = 0.080 eV and {nu}{sub o} = 2.32x10{sup 8} 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 deg. C - 600 deg. C). The electric conduction in the system may be due to hopping/mobility/ transportation of charge carriers.

  20. A high energy density relaxor antiferroelectric pulsed capacitor dielectric

    NASA Astrophysics Data System (ADS)

    Jo, Hwan Ryul; Lynch, Christopher S.

    2016-01-01

    Pulsed capacitors require high energy density and low loss, properties that can be realized through selection of composition. Ceramic (Pb0.88La0.08)(Zr0.91Ti0.09)O3 was found to be an ideal candidate. La3+ doping and excess PbO were used to produce relaxor antiferroelectric behavior with slim and slanted hysteresis loops to reduce the dielectric hysteresis loss, to increase the dielectric strength, and to increase the discharge energy density. The discharge energy density of this composition was found to be 3.04 J/cm3 with applied electric field of 170 kV/cm, and the energy efficiency, defined as the ratio of the discharge energy density to the charging energy density, was 0.920. This high efficiency reduces the heat generated under cyclic loading and improves the reliability. The properties were observed to degrade some with temperature increase above 80 °C. Repeated electric field cycles up to 10 000 cycles were applied to the specimen with no observed performance degradation.

  1. Thermal diffusivity and 3D-XY critical behavior of ferroelectric semiconductors (PbxSn1-x)2P2Se6

    NASA Astrophysics Data System (ADS)

    Shvalya, V.; Oleaga, A.; Salazar, A.; Kohutych, A. A.; Vysochanskii, Yu. M.

    2016-01-01

    An ac photopyroelectric calorimeter has been used to study the thermal diffusivity of the ferroelectric semiconductors family (PbxSn1-x)2P2Se6 (x=0-1) from 30 K to room temperature. Phase transitions have been found for x=0, 0.05, 0.2, 0.47 but not for x=1 in the full temperature range. A continuous phase transition has been found for x=0, 0.05, 0.2 and 0.47 which corresponds to the paraelectric commensurate to incommensurate phase. It has been possible to study the critical behavior of this transition for x=0, 0.05 and the critical parameters obtained have been α=-0.019, A+/A-=1.00 and α=-0.026, A+/A-=1.03, respectively, having fitted at the same time both the low and high temperature branches of the transition as rigorous critical theory indicates; these results agree with the theoretical prediction from renormalization group theory that this kind of transition complies with the 3D-XY universality class (αtheor=-0.014, A+/A-=1.06), which has been experimentally confirmed only in a few materials. A first order incommensurate to ferroelectric phase transition has been characterized in x=0, 0.05 at lower temperature.

  2. 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.

  3. Ferroelectric and glassy states in La-modified lead zirconate titanate ceramics: A general picture

    NASA Astrophysics Data System (ADS)

    El Marssi, M.; Farhi, R.; Dellis, J.-L.; Glinchuk, M. D.; Seguin, L.; Viehland, D.

    1998-05-01

    Raman scattering, pyroelectric current, and dielectric susceptibility measurements have been carried out on a series of tetragonal and rhombohedral-structured Pb1-xLax(ZryTi1-y)1-x/4O3 (PLZT) ceramics, under zero-field heating after zero-field cooling (ZFH/ZFC) and zero-field heating after field-cooling (ZFH/FC) conditions. The results have been shown to be in good agreement with previous transmission electron microscopy observations. A dependence of the Raman spectra on light polarization (i.e., Raman selection rules or RSR), which are known to be a characteristic property of single crystals, has been observed in the PLZT compositions 9/65/35, 12/65/35, 6/40/60, and 12/40/60 illuminated with a 2 ?m wide laser spot (i.e., micro-Raman). The texture which has been observed by x-ray diffraction on 6/40/60 is discussed in conjunction with the Raman results. The combined data of Raman scattering experiments and electrical measurements, together with electromechanical and ferroelectric properties, are explained in terms of competing random fields. Furthermore, the disappearance of RSR in the ZFH/FC conditions for the ferroelectric relaxor PLZT 9/65/35 has given evidence for the existence of domains and grain boundaries in the field cooled conditions. Similar Raman spectra were found for the ferroelectric PLZT composition 5/65/35 in zero-field conditions. The occurrence of RSR in PLZT x/65/35 for x>8 (i.e., for only relaxor states with average cubic symmetry) are interpreted as resulting from second-order scattering effects. This supports a model of a cluster glass with short-range-ordered polar clusters rather than a multidomain state (i.e., a multitude of small ferroelectric domains) in these relaxor systems.

  4. Thickness-dependent ferroelectric behavior of predominantly (117)-oriented Bi3.15Nd0.85Ti3O12 thin-film capacitors

    NASA Astrophysics Data System (ADS)

    Yang, Feng; Zhang, Fuwei; Hu, Guangda; Zong, Zhihao; Tang, Minghua

    2015-04-01

    Ferroelectric hysteresis loops, remanent polarization, coercive field, and leakage current characteristics were investigated by increasing the film thickness (from 103 nm to 401 nm) of predominantly (117)-oriented Bi3.15Nd0.85Ti3O12 films. The thickness dependence of the coercive fields shows log coercive field vs. log thickness with a slope of approximately -0.65, which is characteristics of the Kay-Dunn scaling law. The films exhibited very low leakage current on the order of 10-7A/cm2 at an applied electric field of 100 kV/cm. Without a discernible thickness-dependence behavior, the leakage current characteristics, including both Schottky emission and space-charge-limited conduction, were well described by a modified Schottky contact model.

  5. 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.

  6. Ferroelastic Behavior in Relaxor 24Pb(In1/2Nb1/2)O3--46Pb(Mg1/3Nb2/3)O3--30PbTiO3 under Shear Stresses along [001] Direction

    NASA Astrophysics Data System (ADS)

    Yasuda, Naohiko; Hidayah, Nur; Ohwa, Hidehiro; Tachi, Yoshihito; Yamashita, Yohachi; Hlinka, Ing. Jiri; Iwata, Makoto; Terauchi, Hikaru; Ishibashi, Yoshihiro

    2013-05-01

    The ferroelastic behavior of relaxor 24Pb(In1/2Nb1/2)O3--46Pb(Mg1/3Nb2/3)O3--30PbTiO3 (PIN--PMN--PT) solid-solution single crystals was investigated under shear stresses using polarization light microscopy (PLM) and the scanning electron microscopy (SEM). Optical strain patterns along the \\{110\\}cub directions from the orthoscope images under crossed Nicol, induced by shear stresses applied along the [001]cub direction, making use of a Vickers microindenter with a square-base diagonal line oriented along the \\{100\\}cub directions of the crystal were observed on its (001)cub plate for the first time. These patterns at a diagonal position reveal a flowerlike pattern for ferroelastic transition from a square (S) lattice to a rectangular (R) lattice in a two-dimensional model system. A change in the interference color from yellow to blue through red toward the center in their flower leaves, according to the Michel--Levy birefringence chart, was observed. The patterns at the extinction position reveal starlike patterns coupled with lobes also due to orthorhombic and/or tetragonal twin domain structures. A blue shift (corresponding to addition in retardation) and a yellow shift (corresponding to subtraction in retardation) in color at each flower leaf in the [110]cub and [1\\bar{1}0]cub directions were respectively observed using a sensitive color plate. Such shifts in color correspond to oxygen octahedra being rotated in a staggered sense about the perovskite axis. The patterns appearing strongly along the \\{110\\}cub directions in spite of slip lines along the [100]cub, [010]cub, and [110]cub directions indicate the existence of a rotational preferred orientation in twin domain structures based on a pretransitional tweed domain structure due to platelets observed by SEM, leading to their superior piezoelectric properties due to large shear modes.

  7. 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.

  8. 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

    2016-02-01

    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.

  9. 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 compositional variation on the phase transition temperature, dielectric constant, and ferroelectric to paraelectric phase transitions are discussed.

  10. Study of nanostructural behavior and transport properties of BaTiO 3 doped vanadate glasses and glass-ceramics dispersed with ferroelectric nanocrystals

    NASA Astrophysics Data System (ADS)

    Al-Assiri, M. S.; El-Desoky, M. M.; Al-Hajry, A.; Al-Shahrani, A.; Al-Mogeeth, A. M.; Bahgat, A. A.

    2009-05-01

    Nanostructural behavior and electrical properties of BaTiO 3-(100- x)V 2O 5 glasses (where x=35, 40, 45 and 50 mol%) and their corresponding nanocrystalline glass-ceramics were studied. Scanning electron microscopy (SEM) of quenched glasses, confirm the amorphous nature of the glasses present. Also, the overall features of X-ray diffraction (XRD) confirm the amorphous nature of the present glasses. Transmission electron micrograph (TEM) and XRD of the corresponding heat treated sample indicate nanocrystals with a particle size of 20-35 nm. It was found that density ( d) increases gradually with the increase of the BaTiO 3 content in the nanocrystalline glass-ceramics. It is observed that the conductivity of the nanocrystalline glass-ceramics is higher than that of the corresponding glassy phase. The high conductivity of these nanocrystalline glass-ceramics is considered to be due to the presence of nanocrystals with a particle size of 20-35 nm. This is attributed to the formation of extensive and dense network of electronic conduction paths which are situated between V 2O 5 nanocrystals and on their surface. The electrical conductivity of this system can be fitted with Mott's model of nearest neighbor hopping at high temperature. From the best fits, reasonable values of various small polaron hopping (SPH) parameters are obtained. From dielectric permittivity of the as-cast glass samples, no ferroelectric behavior can be observed. Also, the dielectric permittivity ( ?) values of these glasses are found to be very high compared to familiar vanadium containing glasses. By annealing the glass system around 450 C for 1 h in air, nanocrystalline BaTiO 3 phase precipitates and the corresponding nanocrystalline glass-ceramics showed average broad peak around 352 K in the dielectric permittivity ( ?). It is interesting to note that pure nanocrystalline BaTiO 3 phase with average particle size less than 100 nm also shows ferroelectric phase transition around this temperature as predicted from the dielectric permittivity measurements. This observation of these glass-ceramics nanocrystals can be utilized to control BaTiO 3 particle size and hence transition temperature by proper adjustment of annealing time and BaTiO 3 content. Such a feature can be used for industrial applications where the shape of the application article is a necessary requirement.

  11. 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}?=?3.173.18?eV, E{sub a}?=?3.413.61?eV, and E{sub b}?=?4.744.81?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.

  12. Fatigue and ferroelectric behavior of La and Zn comodified BiFeO{sub 3} thin films

    SciTech Connect

    Wu Jiagang; Wang, John

    2010-07-15

    Bi{sub 0.90}La{sub 0.10}Fe{sub 0.95}Zn{sub 0.05}O{sub 3} (BLFZO) thin films were grown directly on Pt/TiO{sub 2}/SiO{sub 2}/Si(100) substrates without any buffer layer by off-axis radio frequency sputtering. The BLFZO thin film deposited at 580 deg. C possesses a single-phase purity, while those deposited at other temperatures exhibit a varying amount of second phases, indicating that the deposition temperature plays a critical role in the phase development of BLFZO thin films. Although La and Zn cosubstitutions lower the Curie temperature (T{sub c}) of BiFeO{sub 3} thin films, the resulting T{sub c} value ({approx}630 deg. C) is still much higher as compared to other lead-based or lead-free ferroelectric thin films. The BLFZO thin film exhibits a remanent polarization of 2P{sub r{approx}}131.7 {mu}C/cm{sup 2} and a coercive field of 2E{sub c{approx}}496 kV/cm, in association with the improvement in electrical resistance. On the basis of the studies for frequency (1 kHz{approx}1 MHz) and driving field (0.8E{sub c{approx}}2.0E{sub c}) dependences, the BLFZO thin film demonstrates the desired fatigue endurance and weak frequency and driving field dependence. La and Zn cosubstitutions are shown to contribute toward the high remanent polarization and fatigue endurance.

  13. 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

  14. Constitutive relations of ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Su, Yu

    The objective of this thesis is to obtain a better understanding on the fundamental constitutive behavior of ferroelectric ceramics based on the physics of phase transition, micromechanics of heterogeneous materials, and principles of irreversible thermodynamics. Within this framework, a self-consistent model is developed to investigate the electromechanical responses of ferroelectric polycrystals under temperature change and electromechanical loading. Cooling of a paraelectric crystal below its curie temperature Tc would result in spontaneous polarization, whereas electromechanical loading on a poled crystal could lead to domain switch. Domain growth and reorientation inside ferroelectric crystals are studied in light of these phase transition and domain switch. In this process, the change of the effective elastic, dielectric and piezoelectric constants during the evolution of microstructures are examined. In addition, hysteresis loops for the electric displacement and other related phenomena are computed under cyclic electric load. On top of all methods implemented in this work, the kinetic equation derived from the irreversible thermodynamics is the key to study the domain evolution in ferroelectric crystals. The kinetic relation not only governs the growth of new domain in a ferroelectric crystal, but it also determines the onset of phase transition. This characteristic is used to study the effect of hydrostatic pressure on the shift of Curie temperature of a ferroelectric crystal. Based on the derived expressions, it is observed that the deriving force can increase or decrease upon applied hydrostatic mechanical loading, depending on the change of electromechanical moduli, eigenstrain and electro-polarization. Several typical cases are computed and it is found that the change of the electromechanical moduli during phase transformation plays the key role in the shift of Curie temperature. Since ferroelectric ceramics are in a polycrystal form, a self-consistent model is used to examine the issues involved. In this model, each grain is represented by a spherical inclusion embedded in an infinitely extended piezoelectric matrix, and the inclusion further possesses an eigenstrain and eigen polarization. Secant relations between the polycrystal-matrix and the embedded inclusion are established by extending Hill's [1] incremental relations. An iterative computational program is developed for this self-consistent model.

  15. 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.

  16. Hierarchical Domain Structures in Relaxor 24Pb(In1/2Nb1/2)O3-46Pb(Mg1/3Nb2/3)O3-30PbTiO3 near a Morphotropic Phase Boundary Composition Grown by Bridgman Method

    NASA Astrophysics Data System (ADS)

    Yasuda, Naohiko; Fuwa, Tomohiro; Ohwa, Hidehiro; Tachi, Yoshihito; Yamashita, Yohachi; Fujita, Kazuhiko; Iwata, Makoto; Terauchi, Hikaru; Ishibashi, Yoshihiro

    2011-09-01

    The domain structures of the lead-based relaxor ferroelectric solid solution single crystal, 24Pb(In1/2Nb1/2)O3 (PIN)-46Pb(Mg1/3Nb2/3)O3 (PMN)-30PbTiO3 (PT), near a morphotropic phase boundary (MPB) composition grown by the Bridgeman method were studied by polarized light microscopy (PLM), piezoresponse force microscopy (PFM) and scanning electron microscopy (SEM). The change in domain structures with poling from rhombohedral spindlelike domains of 3-5 µm width to orthorhombic domains of ˜20 µm width with rectangular cells with a size of 3-5 µm, characterized with an antiferroelectic double hysteresis loop in the electric field-induced strain behavior, was found. Such domain structures were microscopically identified from SEM images as small circular tetragonal defects, planar monoclinic defects such as edge and screw dislocations with Burgers vector b along <110>cub and/or <100>cub directions and their agglomerate rectangular orthorhombic defects, also characterized by PFM. Hierarchical domain structures are discussed from the viewpoints of domain structures due to defects such as edge and screw dislocations originating in the chemical order region (COR) and the piezoelectric responses and dielectric properties.

  17. 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 intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00049e

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    Prez 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

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

    PubMed

    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

  7. 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.

  8. 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

  9. 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.

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

    SciTech Connect

    Maignan, A.; Canadian Centre for Electron Microscopy, McMaster University, Hamilton, ON L8S4M1

    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.

  11. Ferroelectric liquid crystal display

    NASA Technical Reports Server (NTRS)

    York, Paul K. (Inventor)

    1977-01-01

    A ferroelectric liquid crystal display device employs capacitance spoiling layers to minimize unneeded capacitances created by crossovers of X and Y address lines and to accurately define desired capacitances. The spoiler layers comprise low dielectric constant layers which space electrodes from the ferroelectric at crossover points where capacitance is not needed for device operation.

  12. Dielectric and Ferroelectric Properties of Lead Lanthanum Zirconate Titanate Thin Films for Capacitive Energy Storage

    NASA Astrophysics Data System (ADS)

    Tong, Sheng

    As the increasing requirement of alternative energy with less pollution influence and higher energy efficient, new energy source and related storage methods are hot topic nowadays. Capacitors that supply high instant power are one of the keys in this application for both economic and functional design aspects. To lower the cost and increases the volumetric efficiency and reliability, relaxor thin films are considered as one of the candidates of the next generation capacitors. The research mainly focuses on dielectric and ferroelectric properties of lead lanthanum zirconate titanate or Pb1-xLax(ZryTi1-y)O3 (PLZT, x/y/1-y) relaxor thin films deposited on silicon (Si) and nickel (Ni) substrates in a range of thickness with different bottom electrodes, e.g. Platinum (Pt) and LaNiO3 (LNO). The final fabricated PLZT film capacitors will show strong potential for the energy storage application. The method adopted is the acetic acid assisted sol-gel deposition for the PLZT thin films. The wet chemical process is cost-effective and easily to scale up for plant/industrial products. We investigated the different bottom electrode/substrate influence in structure, microstructure, phases/defects, and heat-treatment conditions to achieve the optimized PLZT thin films. Issues of basic physical size effects in the PLZT thin films were also investigated, including thickness effects in the dielectric and ferroelectric properties of the films in a wide range of temperatures, the phase transition of the thin-film relaxors, lanthanum content effect, electrode-dielectric junction, misfit strain effect, etc. Based on the results and analysis, optimum PLZT film capacitors can be determined of proper substrate/electrode/dielectric that achieves the desired dielectric properties required for different applications, especially a more cost-effective method to develop volumetrically efficient capacitors with high charge density, energy density, dielectric breakdown strength, energy storage efficiency, and low dielectric loss, leakage current density.

  13. Spontaneous long and short-range ferroelectric ordering in Pb0.55La0.30TiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Mastelaro, V. R.; Mascarenhas, Y. P.; Neves, P. P.; Mir, M.; Doriguetto, A. C.; Michalowicz, A.; Moscovici, J.; Lente, M. H.; Eiras, J. A.

    2010-06-01

    In this work, we investigated the temperature dependence of short and long-range ferroelectric ordering in Pb0.55La0.30TiO3 relaxor composition. High-resolution x-ray powder diffraction measurements revealed a clear spontaneous macroscopic cubic-to-tetragonal phase transition in the PLT relaxor sample at 60 K below the maximum of the dielectric constant peak (Tm). Indeed, the x-ray diffraction (XRD) data showed that at 300 K (above Tm but below the Burns temperature, TB) the long-range order structure corresponds to a macroscopic cubic symmetry, space group number 221 (Pm-3m), whereas the data collected at 20 K revealed a macroscopic tetragonal symmetry, space group number 99 (P4mm) with c /a=1.0078, that is comparable to that of a normal ferroelectric. These results show that for samples with tetragonal composition, the long-range ferroelectric order may be recovered spontaneously at cryogenics temperatures, in contrast to ferroelectric samples with rhombohedral symmetry. On the other hand, x-ray absorption spectroscopy investigations intriguingly revealed the existence of local tetragonal disorder around Ti atoms for temperatures far below Tm and above TB, for which the sample presents macroscopic tetragonal and cubic symmetries, respectively.

  14. Inherent optical behavior and structural variation in Na0.5Bi0.5TiO3-6%BaTiO3 revealed by temperature dependent Raman scattering and ultraviolet-visible transmittance

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    Optical properties of Na0.5Bi0.5TiO3-6%BaTiO3 (NBT-6%BT) single crystal have been studied by temperature dependent Raman and ultraviolet-visible spectra from 25 to 180 C. With increasing the temperature, the absorption edge approximately decreases from 3.13 to 3.04 eV. Moreover, abnormal changes of phonon mode and spectral transmission are observed at 83, 106, and 150 C, which can be unambiguously correlated with thermal evolutions of polar nano-regions and phase transition. It indicates that there is an inherent relationship between optical behavior and structural variation of NBT-6%BT, which provides a valid methodology to explore the phase transition of relaxor ferroelectric oxides.

  15. Ferroelectric switching of elastin.

    PubMed

    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

    2014-07-01

    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 ?C/cm(2), 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

  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. 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 VG 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

  18. Soft-mode behavior and incipient ferroelectricity in Na1/2Bi1/2Cu3Ti4O12

    NASA Astrophysics Data System (ADS)

    Ferrarelli, Matthew C.; Nuzhnyy, Dmitry; Sinclair, Derek C.; Kamba, Stanislav

    2010-06-01

    The correlation between crystal structure and intrinsic dielectric properties of the unusual cubic perovskite-related family of compounds ACu3Ti4O12 , where A=Ca , Cd, La2/3 , Bi2/3 , Na1/2La1/2 , Na1/2Bi1/2 , etc., (space group Im3 ) has been a controversial topic for several years, especially for the most studied member of the family CaCu3Ti4O12 (CCTO). Na1/2Bi1/2Cu3Ti4O12 (NBCTO) is isostructural with CCTO and retains centrosymmetric and cubic symmetry (space group Im3 ) down to 4 K. NBCTO ceramics exhibit high intrinsic relative permittivity of 145 at 300 K that rises on cooling and levels off below 50K with a value of 260 at 10 K without any signature of a structural transition. Such behavior is a typical feature of incipient ferroelectrics such as the perovskite CaTiO3 . Infrared and terahertz spectroscopy on NBCTO ceramics are presented and reveal a room-temperature soft polar optic mode at 34cm-1 that softens on cooling and is responsible for the temperature dependence of the relative permittivity. The temperature dependence of the soft-mode frequency obeys the Barrett formula with the onset of quantum fluctuations T1 occurring near 85 K and a hypothetical Curie temperature T0 of -155K . A fitted vibrational zero-point energy (kBT1)/2 is in good agreement with the measured soft-mode frequency. The crystal structure-intrinsic dielectric properties of NBCTO and possibly all cubic ACu3Ti4O12 phases are, therefore, consistent with that of other untilted/tilted TiO3 -based centrosymmetric perovskites such as CaTiO3 and SrTiO3 . The so-called giant permittivity values of >1000 reported for CCTO, NBCTO, and related phases from radio-frequency capacitance measurements near room temperature are an extrinsic effect associated with the semiconducting nature of these materials, as opposed to an intrinsic effect associated with their rather unusual perovskite-type crystal structure.

  19. 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

  20. Ferroelectric Light Control Device

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Kim, Jae-Woo (Inventor); Elliott, Jr., James R. (Inventor)

    2008-01-01

    A light control device is formed by ferroelectric material and N electrodes positioned adjacent thereto to define an N-sided regular polygonal region or circular region there between where N is a multiple of four.

  1. Wireless ferroelectric resonating sensor.

    PubMed

    Viikari, Ville; Seppa, Heikki; Mattila, Tomi; Alastalo, Ari

    2010-04-01

    This paper presents a passive wireless resonating sensor that is based on a ferroelectric varactor. The sensor replies with its data at an intermodulation frequency when a reader device illuminates it at 2 closely located frequencies. The paper derives a theoretical equation for the response of such a sensor, verifies the theory by simulations, and demonstrates a temperature sensor based on a ferroelectric varactor. PMID:20378440

  2. Dielectric Characteristics in BiFeO3-Modified SrTiO3 Incipient Ferroelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Juan; Qin, Ying; Liu, Xiao-Qiang; Chen, Xiang-Ming

    2015-02-01

    We investigate the dielectric and ferroelectric properties of Sr1-xBixTi1-xFexO3 solid solutions (x = 0, 0.05, 0.1, 0.15 and 0.2) together with their structures. Through the analysis of Rietveld refinement of powder x-ray diffraction, a cubic structure in space group Pm3m is determined for all the compositions. An obvious dielectric relaxation peak differing from SrTiO3 is observed in the present ceramics. The peak temperature Tm increases with increasing x, and it approaches room temperature at x = 0.2. The VogelFulcher law and CurieWeiss law fittings further confirm the relaxor ferroelectricity in the present ceramics.

  3. Possible ferrimagnetism and ferroelectricity of half-substituted rare-earth titanate: A first-principles study on Y0.5La0.5TiO3

    NASA Astrophysics Data System (ADS)

    An, Ming; Zhang, Hui-Min; Weng, Ya-Kui; Zhang, Yang; Dong, Shuai

    2016-04-01

    Titanates with the perovskite structure, including ferroelectrics (e.g., BaTiO3) and ferromagnetic ones (e.g., YTiO3), are important functional materials. Recent theoretical studies predicted multiferroic states in strained EuTiO3 and titanate superlattices, the former of which has already been experimental confirmed. Here, a first-principles calculation is performed to investigate the structural, magnetic, and electronic properties of Y half-substituted LaTiO3. Our results reveal that the magnetism of Y0.5La0.5TiO3 sensitively depends on its structural details because of the inherent phase competition. The lowest energy state is the ferromagnetic state, resulting in 0.25 μ B /Ti. Furthermore, some configurations of Y0.5La0.5TiO3 exhibit hybrid improper polarizations, which can be significantly affected by magnetism, resulting in the multiferroic properties. Because of the quenching disorder of substitution, the real Y0.5La0.5TiO3 material with random A-site ions may exhibit interesting relaxor behaviors.

  4. 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

  5. A ferroelectric memristor.

    PubMed

    Chanthbouala, André; Garcia, Vincent; Cherifi, Ryan O; Bouzehouane, Karim; Fusil, Stéphane; Moya, Xavier; Xavier, Stéphane; Yamada, Hiroyuki; Deranlot, Cyrile; Mathur, Neil D; Bibes, Manuel; Barthélémy, Agnès; Grollier, Julie

    2012-10-01

    Memristors are continuously tunable resistors that emulate biological synapses. Conceptualized in the 1970s, they traditionally operate by voltage-induced displacements of matter, although the details of the mechanism remain under debate. Purely electronic memristors based on well-established physical phenomena with albeit modest resistance changes have also emerged. Here we demonstrate that voltage-controlled domain configurations in ferroelectric tunnel barriers yield memristive behaviour with resistance variations exceeding two orders of magnitude and a 10 ns operation speed. Using models of ferroelectric-domain nucleation and growth, we explain the quasi-continuous resistance variations and derive a simple analytical expression for the memristive effect. Our results suggest new opportunities for ferroelectrics as the hardware basis of future neuromorphic computational architectures. PMID:22983431

  6. 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

  7. Giant Electroresistive Ferroelectric Diode on 2DEG.

    PubMed

    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(Zr(0.2)Ti(0.8))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 (>10(8) at 6 V) and I(on)/I(off) ratio (>10(7)). 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

  8. Polarization fatigue of organic ferroelectric capacitors

    PubMed Central

    Zhao, Dong; Katsouras, Ilias; Li, Mengyuan; Asadi, Kamal; Tsurumi, Junto; Glasser, Gunnar; Takeya, Jun; Blom, Paul W. M.; de Leeuw, Dago M.

    2014-01-01

    The polarization of the ferroelectric polymer P(VDF-TrFE) decreases upon prolonged cycling. Understanding of this fatigue behavior is of great technological importance for the implementation of P(VDF-TrFE) in random-access memories. However, the origin of fatigue is still ambiguous. Here we investigate fatigue in thin-film capacitors by systematically varying the frequency and amplitude of the driving waveform. We show that the fatigue is due to delamination of the top electrode. The origin is accumulation of gases, expelled from the capacitor, under the impermeable top electrode. The gases are formed by electron-induced phase decomposition of P(VDF-TrFE), similar as reported for inorganic ferroelectric materials. When the gas barrier is removed and the waveform is adapted, a fatigue-free ferroelectric capacitor based on P(VDF-TrFE) is realized. The capacitor can be cycled for more than 108 times, approaching the programming cycle endurance of its inorganic ferroelectric counterparts. PMID:24861542

  9. 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.

  10. Stress-dependent scaling behavior of subcoercive field dynamic ferroelectric hysteresis in Pb(Zn1/3Nb2/3)O3-modified Pb(Zr1/2Ti1/2)O3 ceramic

    NASA Astrophysics Data System (ADS)

    Yimnirun, R.; Wongdamnern, N.; Triamnak, N.; Unruan, M.; Ngamjarurojana, A.; Ananta, S.; Laosiritaworn, Y.

    2008-04-01

    Scaling behavior of subcoercive field dynamic ferroelectric hysteresis under influence of stress was investigated in Pb(Zn1/3Nb2/3)O3-modified Pb(Zr1/2Ti1/2)O3 (PZT) bulk ceramic. The scaling relation of hysteresis area ?A ? against frequency f, field amplitude E0, and stress ? for the minor loops takes a form of ?A-A? =0??f-0.42E03.65?0.24, which is very similar to that of soft and hard PZT ceramics. However, slightly faster responses to f and E0 indicate the ease of polarization orientation in this simpler domain structure ceramic as compared to commercial PZT ceramics.

  11. 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

  12. Time-Resolved, Electric-Field-Induced Domain Switching and Strain in Ferroelectric Ceramics and Crystals

    NASA Astrophysics Data System (ADS)

    Jones, Jacob L.; Nino, Juan C.; Pramanick, Abhijit; Daniels, John E.

    Ferroelectric materials are used in a variety of applications including diagnostic and therapeutic ultrasound, sonar, vibration and displacement sensors, and non-volatile random access memory. The electromechanical response in ferroelectric materials is comprised of both intrinsic (piezoelectric lattice strain) and extrinsic (e.g., domain wall motion) components that are expressed as characteristic changes in the diffraction pattern. By applying slow, step-wise changes in the electric field, prior quasi-dynamic diffraction measurements have demonstrated both lattice strains and non-180 ? domain switching at fields exceeding the macroscopically defined coercive field. However, the loading conditions which most replicate real device operation involve dynamic actuation with sub-coercive, cyclic electric fields. At these operating conditions, extrinsic irreversibilities lead to hysteresis, frequency dispersion and nonlinearity of macroscopic properties. Observation of strain and domain switching at these cyclic loading conditions is an area in which we have reported recent advances using stroboscopic techniques. This chapter highlights the electric-field-induced lattice strain and kinetics of domain switching in a number of materials including technologically-relevant lead zirconate titanate (PZT) ceramics and relaxor single crystals. An outlook on the continuing use of time-resolved diffraction techniques in the characterization of ferroelectric materials is also discussed.

  13. Converse magnetoelectric effect via strain-driven magnetization reorientations in ultrathin ferromagnetic films on ferroelectric substrates

    NASA Astrophysics Data System (ADS)

    Pertsev, N. A.

    2015-07-01

    A phenomenological theory is developed for the strain-driven magnetization reorientations occurring in ultrathin ferromagnetic films coupled to ferroelectric substrates experiencing electric-field-induced piezoelectric deformations. The theory takes into account the surface/interface magnetic anisotropy playing an important role in the energetics of such films and first describes the thickness-driven spin reorientation transitions emerging in the presence of substrate-induced lattice strains. Then the threshold and critical intensities of the electric field created in a ferroelectric substrate are calculated, at which different magnetic states acquire the same energy or become unstable in a strained ferromagnetic overlayer. To demonstrate stability ranges of various possible magnetization orientations, we introduce magnetoelectric orientational diagrams, where the electric-field intensity and film thickness are employed as two variables. Such diagrams are constructed for ultrathin Ni, Fe, and F e60C o40 films coupled to single crystals of classical and relaxor ferroelectrics. The inspection of these diagrams shows that the use of multiferroic hybrids comprising ultrathin ferromagnetic films significantly enlarges the range of ferroic materials suitable for experimental observations of the strain-mediated converse magnetoelectric effect.

  14. Classical ferroelectriclike behavior of highly ordered Pb (S c1 /2N b1 /2)O3 studied by dielectric and Brillouin scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Sivasubramanian, V.; Subramanian, V.; Kojima, S.

    2016-02-01

    The ferroelectric phase transition behavior in the highly ordered Pb (S c1 /2N b1 /2) O3 has been investigated by the dielectric and Brillouin spectroscopy. The dielectric permittivity ɛr exhibits a sharp maximum without any frequency dispersion at its Curie temperature Tc. In the temperature range far above Tc, it was noted that the dielectric permittivity exhibits a noticeable deviation from the Curie-Weiss law below the characteristic intermediate temperature T*=500 K , which is common to most of the Pb-based oxide perovskite relaxors. Upon cooling, the frequency of the longitudinal acoustic phonon mode exhibits a remarkable softening towards Tc. The relaxation time of the order parameter calculated using the Landau-Khalatnikov approach was determined to be more than one order of magnitude lower than that of the disordered Pb (S c1 /2N b1 /2)O3 and is very close to that observed in the paraelectric phase of the classical ferroelectric, BaTi O3 . The observed dielectric and relaxation features are qualitatively discussed in terms of the difference in the strength of the random electric fields.

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

    DOEpatents

    Kalinin, Sergei V. (Knoxville, TN) [Knoxville, TN; Christen, Hans M. (Knoxville, TN) [Knoxville, TN; Baddorf, Arthur P. (Knoxville, TN) [Knoxville, TN; Meunier, Vincent (Knoxville, TN) [Knoxville, TN; Lee, Ho Nyung (Oak Ridge, TN) [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. Depolarization field effect on dielectric and piezoelectric properties of particulate ferroelectric ceramic-polymer composites

    NASA Astrophysics Data System (ADS)

    Ma, Fengde D.; Wang, Yu U.

    2015-03-01

    The effects of depolarization field on the dielectric and piezoelectric properties of ferroelectric ceramic particle-filled polymer-matrix composites are investigated at the underlying domain level. Phase field modeling and simulation reveals that the macroscopic properties of the composites are dominated by depolarization field effect, which depends on the arrangement and alignment rather than the size or internal grain structure of the ferroelectric particulates. It is found that 0-3 particulate composites with random dispersion of ferroelectric particles behave essentially like linear dielectric rather than ferroelectric materials, and domain-level analysis reveals the physical mechanism for lack of domain switching or hysteresis as attributed to strong depolarization effect. Thus, without effective reduction or elimination of the depolarization field, the composites cannot benefit from the functional fillers regardless of their superior properties. In order to exhibit the desired ferroelectric behaviors, it necessitates continuous ferroelectric phase connectivity in the composites.

  17. Dynamic Local Distortions in Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Wang, Cheng-Zhang; Krakauer, Henry; Yu, Rici; Rabe, Karin M.; Waghmare, Umesh V.

    1998-03-01

    We have carried out molecular-dynamics simulations of KNbO_3, based on first-principles calculations, that reveal preformed dynamic chain-like structures.(H. Krakauer, R. Yu, C.-Z. Wang, K. Rabe, and U. Waghmare, preprint number cond-mat/9710088.) These are present even in the paraelectric phase and are related to the softening of phonon branches over large regions of the Brillouin zone. The phase sequence of ferroelectric transitions is correctly reproduced, showing that the first-principles effective Hamiltonian used in the simulations captures the essential behavior of the microscopic fluctuations driving the transitions. Real space dynamic chains provide a framework for understanding both the displacive and order-disorder characteristics of these phase transitions.

  18. Compositional instability and the resultant charge variations in mixed B-site cation relaxer ferroelectrics

    NASA Astrophysics Data System (ADS)

    Viehland, Dwight; Li, Jie-Fang

    1993-09-01

    A phenomenological model has been applied in an attempt to explain the inability of the ordered regions in the lead magnesium niobate family of relaxor ferroelectrics to coarsen. This approach is based on the concept that the free energy is lowered by an embryonic decomposition along a non-neutral direction. It is proposed that the excess free energy associated with the formation of the non-neutral phase is offset by the distortability of the perovskite structure toward the pyrochlore. The lack of coarsening is then explained as a balance of the electrostatic energy and gradient energy terms, following an earlier published report. This model is then applied to the La-modified (donor-doped) lead magnesium niobate, to explain the dependence of the size of the ordered regions on the degree of doping as observed by other workers.

  19. Electric field induced metastable ferroelectric phase and its behavior in (Pb, La)(Zr, Sn, Ti)O{sub 3} antiferroelectric single crystal near morphotropic phase boundary

    SciTech Connect

    Li, Yuanyuan; Li, Qiang Yan, Qingfeng; Gao, Jinghan; Zhuo, Fangping; Cao, Wenwu; Xi, Xiaoqing; Zhang, Yiling; Chu, Xiangcheng

    2014-02-03

    Antiferroelectric (AFE) (Pb, La)(Zr, Sn, Ti)O{sub 3} (PLZST) single crystal with composition near morphotropic phase boundary has been grown and studied. X-ray diffraction analysis and electrical properties reveal coexistence of antiferroelectric/ferroelectric (FE) phases, with the AFE phase dominated at room temperature. Temperature-dependent polarization and strain measurements indicate that the AFE phase can be induced into a metastable FE phase by electric field. The FE phase can be maintained in a wide temperature range above room temperature and recovers to AFE phase around a critical temperature of 90?C, accompanied with remarkable change in field-induced strain. The strain at 90?C (?0.50%) is ten times larger than that at room temperature (?0.04%), which makes the PLZST single crystal a promising candidate for thermal switch and actuator application.

  20. Phase Transition Behaviors in [011]-Oriented Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals Studied by Dielectric and Micro-Brillouin Spectroscopies

    NASA Astrophysics Data System (ADS)

    Kim, Tae Hyun; Ko, Jae-Hyeon; Kojima, Seiji

    2013-09-01

    Phase transition behaviors of unpoled and [011]-poled relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals were investigated over a wide temperature range by dielectric and Brillouin scattering spectroscopies. The [011]-poled crystal exhibited two discontinuous dielectric and acoustic anomalies at 119 and 126 C, which were attributed to two poling-induced structural phase transitions from rhombohedral to orthorhombic, and then to tetragonal symmetry. However, this poled crystal maintained the diffused phase transition behaviors of the unpoled one at higher temperatures above 126 C. The disappearance of the poling effect upon the diffuse phase transition near the TC suggests that the macroscopic ferroelectric domains formed by poling are decomposed into mesoscopic and nano size polar regions at 126 C. These polarization fluctuations and the coupling of these dynamic polar regions to the acoustic waves play the dominant role in the dielectric and acoustic anomalies, respectively. Therefore, a diffusive nature was commonly observed in both unpoled and poled single crystals near TC.

  1. 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

  2. Local Structure in PMSN Across the Ferroelectric Phase Transition

    NASA Astrophysics Data System (ADS)

    Vold, Robert

    2006-11-01

    Local structure and ^93Nb ion displacement play vital roles in the ferroelectric polarization and phase transitions of solid solutions with composition (1-x)PbMg1/3Nb2/3O3 -- x PbSc1/2Nb1/2O3 (PMSN). Here, we report variable temperature, high field (17.6Tesla) ^93Nb MAS and 3QMAS NMR studies of PMSN with compositions between x = 0.6 and 0 (pure PMN). In PMSN, six narrow components and one broad peak were observed. Spectral assignments agree with previous reports [D.H.Zhou, G.L.Hoatson, R.L.Vold, J. Magn. Reson. 167 (2004) 242-252 and references therein]. The broad peak is resolved only at temperatures below the dielectric susceptibility maximum (i.e., T ferroelectric relaxor phase transition, and allow conclusions to be drawn regarding the chemical composition of polar nanoclusters. In collaboration with Gina Hoatson and Murugesan Vijayakumar, College of William & Mary.

  3. 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.

  4. 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.

  5. Lead-free and lead-based ABO3 perovskite relaxors with mixed-valence A-site and B-site disorder: A comparative neutron scattering structural study of (Na1/2Bi1/2)TiO3 and Pb(Mg1/3Nb2/3)O3

    SciTech Connect

    Ge, Wenwei; Devreugd, Christopher; Phelan, Daniel; Zhang, Qinjui; Muhtar, Aheart; Li, Jiefang; Luo, Haosu; Boatner, Lynn A; Viehland, Dwight; Gehring, P. M.

    2013-01-01

    We report the results of neutron elastic scattering measurements between -250oC and 620oC on the lead-free relaxor Na1/2Bi1/2TiO3 (NBT). Strong, anisotropic, elastic diffuse scattering intensity decorates the (100), (110), (111), (200), (220), and (210) Bragg peaks at room temperature. The wavevector dependence of this diffuse scattering is compared to that in the lead-based relaxor PbMg1/3Nb2/3O3 (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 = 523oC, 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 et al. (2003); these vanish below 320oC 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 [1 1 0] from 40 to 60 while doubling the associated integrated diffuse scattering. Similar behavior was reported by Matsuura et al. (2006) for compositions of PMN doped with PbTiO3. Finally, we comment on the recent observation of monoclinicity in NBT at room temperature by placing a strict bound on the strength of the ( ) superlattice reflection associated with the Cc space group based on the atomic coordinates published in the x-ray study by Aksel et al. (2011) for NBT. We argue that a skin effect, analogous to that reported in the relaxors PZN and PMN-10%PT, can reconcile our single-crystal data with the powder data of Aksel et al. We believe this represents the first evidence of the relaxor skin effect in a lead-free relaxor.

  6. 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.

  7. Features of phase transitions in lanthanum-modified lead zirconate titanate ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Peliz-Barranco, A.; Mendoza, M. E.; Caldern-Piar, F.; Garca-Zaldvar, O.; Lpez-Noda, R.; de los Santos-Guerra, J.; Eiras, J. Antonio

    2007-12-01

    The dielectric behavior and the ferroelectric properties (hysteresis loops) of Pb 0.94La 0.06(Zr 0.80Ti 0.20) 0.985O 3 ferroelectric ceramics are analyzed considering the coexistence of the ferroelectric (FE) and the antiferroelectric (AFE) phases. The x-ray diffraction patterns and polarized light microscopy results reveal that FE and AFE ordering coexist. The dielectric analysis suggests two phase transitions. The first around 75 ?C, which is associatted to a ferroelectric (rhombohedral)-antiferroelectric (orthorhombic) phase transition; the second around 120 ?C, associated with an antiferroelectric (orthorhombic)-paraelectric (cubic) phase transition. The temperature dependence of hysteresis loops shows a double-loop-like behavior for temperatures above 75 ?C, showing a typical characteristic of an induced ferroelectric-antiferroelectric transformation.

  8. Scaling Effects on Ferro-Electrics: Application in Nanoelectronics and Characterization

    NASA Astrophysics Data System (ADS)

    Vilquin, B.; Gautier, B.; Brugère, A.; Moulet, J. S.

    2009-09-01

    Ferroelectric thin films have been attractive for multifunctional devices like nonvolatile memory (FeRAM) using hysteresis behavior, DRAM using high permittivity, micro-actuator using piezoelectricity, infrared sensor using pyroelectricity, optical switch shutter display, etc. Thin-film nanoscale device structures integrated onto Si chips have made inroads into the semiconductor industry. These applications need not only ferroelectric high quality materials but also ability to keep the ferroelectricity at low dimension after fabrication of nano-scale objects. For these reasons, advanced characterization techniques for probing the properties of ferroelectric materials at nano-scale dimensions are now required. Among them, techniques based on the Atomic Force Microscope (AFM) have proved their efficiency for mapping the ferroelectric behavior of thin films with a nanometric resolution.

  9. Electrophoresis of Ferroelectric Nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Xiya; Davidovic, Dragomir

    2006-03-01

    We have studied the electrophoresis of ferroelectric nanoparticles(Ba1-xSrxTiO3). We used de-ionized (DI) water as solvent and an optical microscope to observe the motion of suspended ferroelectric nanoparticles driven by AC electric fields. The immediate start and stop of motion were noticed when the driving electric field was turned on and off, which was similar to dielectricphoresis. Higher voltage generated higher speed as expected. In some instances, the dielectric constant ɛ of ferroelectric materials can increase greatly, which makes it possible that a low driving voltage (no larger than 10V) could induce a relatively high speed. At room temperature, we studied the frequency dependence of the motion speed. By comparing a serial of captured motion movies, we found that higher speeds were corresponding to lower frequencies of driving AC electric field. Further, we use well defined electrodes made by electron-beam lithography and high-vacuum deposition, which may regulate the electric field distribution. Consequently, we can characterize the electric force applied on those nanoparticles.

  10. Embedded ferroelectric nanostructure arrays.

    PubMed

    Clemens, S; Rhrig, S; Rdiger, A; Schneller, T; Waser, R

    2009-02-18

    Ferroelectrics hold promise for high-density non-volatile data storage device use. Their eventual performance will strongly depend on the available displacement current, which primarily scales with the area but might to some extent be enhanced by substrate-induced homogeneous strain while the interface at the same time controls the coercive field. As the lateral dimensions persistently decrease, the only way to keep track of the real figures of merit with realistic electrodes is to use a macroscopic configuration instead of scanning probe approaches with undefined interfaces. We report on a novel approach to integrating arbitrarily patterned, highly registered ferroelectric nanoislands fabricated by a template controlled chemical solution deposition approach into a matrix of a low-k dielectric spin-on glass. These structures with a narrow lateral size distribution below 100 nm are subsequently polished in a chemical-mechanical polishing step to expose their very tops, whose piezoelectrically active area depends on the polishing time. At this stage our findings indicate a full piezoelectric functionality of the locally exposed nanoislands. The structures are ready for macroscopic top electrodes to average the displacement current over hundreds of almost identical structures, to provide a nanoscale scaling behaviour of the individual ferroelectric capacitors. PMID:19417416

  11. 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??m. 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.

  12. Ferroelectric and dielectric properties of Ca0.28Ba0.72Nb2O6 single crystals of tungsten bronzes structure

    NASA Astrophysics Data System (ADS)

    Qi, Y. J.; Lu, C. J.; Zhu, J.; Chen, X. B.; Song, H. L.; Zhang, H. J.; Xu, X. G.

    2005-08-01

    Large Ca0.28Ba0.72Nb2O6 (CBN-28) single crystals exhibit saturated ferroelectric hysteresis loops under an electric field of 115kV/cm along the [001] direction. Their spontaneous polarization, remanent polarization and coercive field are 35.3?C/cm2, 32.2?C/cm2, and 38.1kV/cm, respectively. The dielectric constant and dielectric loss tan? of the crystals are 195 and 0.32 at 10 kHz, respectively. A diffused dielectric anomaly with relaxor characteristic was observed in the range of 325-500 C at low frequencies, while the CBN-28 crystals experienced a first-order normal-relaxor ferroelectric phase transition around 252 C on heating. A broad dielectric loss peak appears around 120 C and it is interpreted in terms of the migration of oxygen vacancies. The conductance activation energy was determined to be 1.33 eV in the high temperature regime (500-560 C).

  13. Conduction at a Ferroelectric Interface

    NASA Astrophysics Data System (ADS)

    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.

    2014-11-01

    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 work, we describe an oxide/oxide ferroelectric heterostructure device based on (001)-oriented PbZr0.2Ti0.8O3-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.

  14. Photovoltaic effect in Ferroelectric Materials

    NASA Astrophysics Data System (ADS)

    Katiyar, Rajesh K.; Panwar, Neeraj; Morell, G.; Katiyar, Ram S.

    2010-03-01

    Photovoltaic effect in ferroelectric materials is of much interest due to the anomalously large open circuit photovoltages when illuminated. It is concluded that this unprecedented high value of photovoltaic effect is due to the presence of non-centrosymmetry in the ferroelectric materials which gives rise to electron excitation, relaxation, and scattering processes. The photovoltaic efficiencies are, however, limited due to small current densities and the large band gap values of the ferroelectric materials. We have synthesized thin films of BiFeO3 (a low band gap material 2.67eV) and ferroelectric material SrBi2Ta2O9(SBT) on silicon substrates with ITO as the bottom electrode. The band gap of the SBT has been decreased by incorporating metallic particles Ag, Pt. in the ferroelectric matrix. The results will be presented.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. Polarization and interface charge coupling in ferroelectric/AlGaN/GaN heterostructure

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Kong, Yuechan; Zhou, Jianjun; Xue, Fangshi; Li, Liang; Jiang, Wenhai; Hao, Lanzhong; Luo, Wenbo; Zeng, Huizhong

    2012-03-01

    Asymmetrical shift behaviors of capacitance-voltage (C-V) curve with opposite direction are observed in two AlGaN/GaN metal-ferroelectric-semiconductor (MFS) heterostructures with Pb(Zr,Ti)O3 and LiNbO3 gate dielectrics. By incorporating the switchable polar nature of the ferroelectric into a self-consistent calculation, the coupling effect between the ferroelectric and the interface charges is disclosed. The opposite initial orientation of ferroelectric dipoles determined by the interface charges is essentially responsible for the different C-V characteristics. A critical fixed charge density of -1.27 1013cm-2 is obtained, which plays a key role in the dependence of the C-V characteristic on the ferroelectric polarization. The results pave the way for design of memory devices based on MFS structure with heteropolar interface.

  1. Imaging linear polarimetry using a single ferroelectric liquid crystal modulator.

    PubMed

    Gendre, Luc; Foulonneau, Alban; Bigué, Laurent

    2010-09-01

    In the field of polarimetry, ferroelectric liquid crystal cells are mostly used as bistable polarization rotators suitable to analyze crossed polarizations. This paper shows that, provided such a cell is used at its nominal wavelength and correctly driven, its behavior is close to that of a tunable half-wave plate, and it can be used with much benefit in lightweight imaging polarimetric setups. A partial Stokes polarimeter using a single digital video camera and a single ferroelectric liquid crystal modulator is designed and implemented for linear polarization analysis. Polarization azimuthal angle and degree of linear polarization are available at 150 frames per second with a good accuracy. PMID:20820209

  2. 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.

  3. 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.

  4. Combining Mott insulators and ferroelectrics

    NASA Astrophysics Data System (ADS)

    Barthelemy, Agn`Es

    2015-03-01

    We investigated the properties of high quality heterostructures consisting of a Mott insulator, (Ca,Ce)MnO3 (CCMO) and a ferroelectric, BiFeO3 in the supertetragonal phase (T-BFO) materials. In particular, we studied the electrical response induced by ferroelectric switching in both planar and vertical devices. In the planar geometry, we used thick T-BFO films to explore the possibility to electrically tune the properties of the CCMO compound in a ferroelectric field-effect device with a CCMO channel and a T-BFO gate. Upon polarization reversal of the T-BFO ferroelectric gate, the CMO channel exhibits a nonvolatile resistance switching by a factor of 4 around room temperature, and up to a factor of 10 at 200 K. We also studied Ferroelectric tunnel junctions (FTJs) composed of an ultrathin ferroelectric tunnel barrier of T-BFO sandwiched between a CCMO electrode and a Co/Pt counter-electrode. In these junctions, the tunneling current significantly depends on the orientation of the ferroelectric polarization, resulting in large electroresistance enabling a simple nondestructive readout of the ferroelectric state. FTJs based on ultrathin T-BFO films show fast, stable multistate switching with very high resistance ratios of up to four orders of magnitude. Combined piezoresponse force microscopy (PFM) and electrical measurements give a clear correlation between ferroelectric domain configurations and multiple resistance states They also provide insights into the switching dynamics in response to trains of nanosecond pulses. Additionnaly, we demonstrated the very good endurance and retention characteristics of these FTJs.

  5. 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 [110] from 40 to 60 while doubling the associated integrated diffuse scattering. Similar behavior was reported by Matsuura [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.74.144107 74, 144107 (2006)] for morphotropic compositions of PMN doped with PbTiO3. Finally, we comment on the recent observation of monoclinicity in NBT at room temperature by placing a strict bound on the strength of the () superlattice reflection associated with the Cc space group based on the atomic coordinates published in the x-ray study by Aksel [Appl. Phys. Lett.APPLAB0003-695110.1063/1.3573826 98, 152901 (2011)] for NBT. We show that a skin effect, analogous to that reported in the relaxors PZN-xPT and PMN-xPT, can reconcile our neutron single-crystal data with the x-ray powder data of Aksel [Appl. Phys. Lett.APPLAB0003-695110.1063/1.3573826 98, 152901 (2011)]. Our finding of a skin effect in a lead-free, A-site disordered, heterovalent relaxor supports the idea that it arises in the presence of strong random electric fields.

  6. Faceting oscillations in nano-ferroelectrics

    SciTech Connect

    Scott, J. F. E-mail: ashok553@nplindia.org; Kumar, Ashok E-mail: ashok553@nplindia.org

    2014-08-04

    We observe periodic faceting of 8-nm diameter ferroelectric disks on a 10?s time-scale when thin Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} film is exposed to constant high-resolution transmission electron microscopy beams. The oscillation is between circular disk geometry and sharply faceted hexagons. The behavior is analogous to that of spin structure and magnetic domain wall velocity oscillations in permalloy [Bisig et al., Nat. Commun. 4, 2328 (2013)], involving overshoot and de-pinning from defects [Amann et al., J. Rheol. 57, 149175 (2013)].

  7. Ferroelectric domain structure of anisotropically strained NaNbO{sub 3} epitaxial thin films

    SciTech Connect

    Schwarzkopf, J. Braun, D.; Schmidbauer, M.; Duk, A.; Wrdenweber, 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.

  8. Long-term retention in organic ferroelectric-graphene memories

    NASA Astrophysics Data System (ADS)

    Raghavan, Santosh; Stolichnov, Igor; Setter, Nava; Heron, Jean-Savin; Tosun, Mahmut; Kis, Andras

    2012-01-01

    Long-term stability of high- and low-resistance states in full-organic ferroelectrically gated graphene transistors is an essential prerequisite for memory applications. Here, we demonstrate high retention performance for both memory states with fully saturated time-dependence of the graphene channel resistance. This behavior is in contrast with ferroelectric-polymer-gated silicon field-effect-transistors, where the gap between the two memory states continuously decreases with time. Before reaching saturation, the current decays exponentially as predicted by the retention model based on the charge injection into the interface-adjacent layer. The drain current saturation attests to a high quality of the graphene/ferroelectric interface with low density of charge traps.

  9. 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.

  10. Annular electron beam generation using a ferroelectric cathode

    SciTech Connect

    Golkowski, C.; Flechtner, D.; Ivers, J.D.; Nation, J.A.; Schaechter, L.

    1998-06-01

    In this paper, the authors report on the emission of electrons from a ferroelectric cathode in a coaxial gun geometry. The electrons are emitted from the inner conductor of the coaxial system and are accelerated radially. An axial magnetic field causes the formation of an azimuthal annular electron flow. The electrostatic potential distribution then leads to the ejection of the annular beam from the anode-cathode region into the drift space. A beam energy of up to 50 keV and an electron current of up to 250 A is typical in this proof of principle experiment. The Hull cutoff condition is found to considerably underestimate the magnetic field required to insulate the radial electron current flow in the diode. The results obtained are consistent with earlier data showing that the behavior of the ferroelectric is closely coupled to the changing state of the ferroelectric.

  11. Ferroelectricity of Perovskites under Pressure

    NASA Astrophysics Data System (ADS)

    Kornev, Igor; Bellaiche, L.; Bouvier, P.; Janolin, P.-E.; Dkhil, B.; Kreisel, J.

    2006-03-01

    Ab-initio simulations and experimental techniques are combined to reveal that, unlike commonly accepted for more than 30 years, perovskites and related materials enhance their ferroelectricity as hydrostatic pressure increases above a critical value [1]. This unexpected high-pressure ferroelectricity is different in nature from conventional ferroelectricity because it is driven by an original electronic effect rather by long-range interactions. [1]. Igor A. Kornev, L. Bellaiche, P. Bouvier, P.-E. Janolin, B. Dkhil, and J. Kreisel, Phys. Rev. Lett. 95, 196804 (2005)

  12. Spectroscopic signature for ferroelectric ice

    NASA Astrophysics Data System (ADS)

    Wjcik, Marek J.; G?ug, Maciej; Boczar, Marek; Boda, ?ukasz

    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.

  13. Resonances in ferroelectric phononic superlattice

    NASA Astrophysics Data System (ADS)

    Ostrovskii, Igor; Cremaldi, Lucien

    2012-10-01

    The periodically poled ferroelectric wafer is a two-dimensional phononic superlattice. The important applications of such a solid include ultrasonic transducers at the micro/nano-scale for low intensity ultra-sonography, ferroelectric data storage, and development of very high frequency chips for next generation communication and information technologies, and others. In this work, we show theoretically and experimentally that a ferroelectric phononic superlattice has two distinctive resonances in acousto-electric transformation. They are associated with a split acoustic mode at the boundary between the first and second acoustic Brillouin zone.

  14. 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.

  15. 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

  16. 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.

  17. Ferroelectric capacitor with reduced imprint

    DOEpatents

    Evans, Jr., Joseph T. (13609 Verbena Pl., NE., Albuquerque, NM 87112); Warren, William L. (7716 Wm. Moyers Ave., NE., Albuquerque, NM 87122); Tuttle, Bruce A. (12808 Lillian Pl., NE., Albuquerque, NM 87122); Dimos, Duane B. (6105 Innsbrook Ct., NE., Albuquerque, NM 87111); Pike, Gordon E. (1609 Cedar Ridge, NE., Albuquerque, NM 87112)

    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.

  18. Ferroelectric infrared detector and method

    DOEpatents

    Lashley, Jason Charles (Sante Fe, NM); Opeil, Cyril P. (Chestnut Hill, MA); Smith, James Lawrence (Los Alamos, NM)

    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.

  19. 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

  20. 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

  1. Effect of local elastic strain on the structure of Pb-based relaxors: A comparative study of pure and Ba- and Bi-doped PbSc{sub 0.5}Nb{sub 0.5}O{sub 3}

    SciTech Connect

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

    2009-06-01

    The temperature evolution of the nanoscale structure of PbSc{sub 0.5}Nb{sub 0.5}O{sub 3} (PSN) and (Pb,A{sup ''})Sc{sub 0.5}Nb{sub 0.5}O{sub 3}, (A{sup ''}=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 (Ba{sup 2+}) and three-valent cations with stereochemically active lone pairs (Bi{sup 3+}) 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 (Pb{sup 2+}), 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 Bi{sup 3+} for Pb{sup 2+} 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.

  2. 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.

  3. 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

  4. Improved Ferroelectric Memories With Nondestructive Readout

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita; Thakoor, Anil P.

    1994-01-01

    Ferroelectric memories with enhanced photoresponse leading to improved nondestructive optoelectronic readout and lower power demand proposed. Memories improved versions of devices described in "Rapid, Nondestructive Readout From Ferroelectric Memory" (NPO-18551). In proposed application, array of nonvolatile ferroelectric memory cells fabricated by standard very-large-scale integrated-circuit techniques and flip-bonded onto similarly fabricated array of semiconductor lasers, {see "Optically Addressable, Ferroelectric Memory With NDRO" (NPO-18573)}.

  5. 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.

  6. 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.

  7. Finite-size effects of hysteretic dynamics in multilayer graphene on a ferroelectric

    NASA Astrophysics Data System (ADS)

    Morozovska, Anna N.; Pusenkova, Anastasiia S.; Varenyk, Oleksandr V.; Kalinin, Sergei V.; Eliseev, Eugene A.; Strikha, Maxym V.

    2015-06-01

    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. Here, 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. 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.

  8. Correlated nucleation and self-accommodating kinetic pathway of ferroelectric phase transformation

    NASA Astrophysics Data System (ADS)

    Zhou, Jie E.; Cheng, Tian-Le; Wang, Yu U.

    2012-01-01

    Mechanisms of nucleation and growth of domains during ferroelectric phase transformation are investigated by using theoretical and computational approaches. It is shown that ferroelectric phase transformation exhibits some peculiar behaviors due to strong long-range dipole-dipole-like interactions involved in the system. Incorporation of electrostatic and elastostatic energies into the classical Landau-Ginzburg-Devonshire theory effectively modifies the coefficients of the polynomial free energy function and introduces extra energy barrier for ferroelectric phase transformation. It is found that independent nucleation of ferroelectric phase in the context of classical nucleation theory is prohibited, because electrostatic interaction generates an insurmountable energy barrier to isolated nucleus. Phase field modeling and computer simulation reveals that, in order to circumvent such an energy barrier, ferroelectric nucleation exhibits strong spatial correlation and self-organization behaviors from the very beginning, and ferroelectric phase transformation proceeds via spatial and temporal evolution of self-accommodating domains that provide a low-energy kinetic pathway throughout the phase transformation process. Theoretical analysis of the critical wavelength of correlated nucleation agrees with the computer simulation. Heterogeneous nucleation as induced by externally applied local electric field and subsequent polarization evolution process is also simulated to further demonstrate such self-organized pattern formation behaviors.

  9. First-principles theory, coarse-grained models, and simulations of ferroelectrics.

    PubMed

    Waghmare, Umesh V

    2014-11-18

    CONSPECTUS: A ferroelectric crystal exhibits macroscopic electric dipole or polarization arising from spontaneous ordering of its atomic-scale dipoles that breaks inversion symmetry. Changes in applied pressure or electric field generate changes in electric polarization in a ferroelectric, defining its piezoelectric and dielectric properties, respectively, which make it useful as an electromechanical sensor and actuator in a number of applications. In addition, a characteristic of a ferroelectric is the presence of domains or states with different symmetry equivalent orientations of spontaneous polarization that are switchable with large enough applied electric field, a nonlinear property that makes it useful for applications in nonvolatile memory devices. Central to these properties of a ferroelectric are the phase transitions it undergoes as a function of temperature that involve lowering of the symmetry of its high temperature centrosymmetric paraelectric phase. Ferroelectricity arises from a delicate balance between short and long-range interatomic interactions, and hence the resulting properties are quite sensitive to chemistry, strains, and electric charges associated with its interface with substrate and electrodes. First-principles density functional theoretical (DFT) calculations have been very effective in capturing this and predicting material and environment specific properties of ferroelectrics, leading to fundamental insights into origins of ferroelectricity in oxides and chalcogenides uncovering a precise picture of electronic hybridization, topology, and mechanisms. However, use of DFT in molecular dynamics for detailed prediction of ferroelectric phase transitions and associated temperature dependent properties has been limited due to large length and time scales of the processes involved. To this end, it is quite appealing to start with input from DFT calculations and construct material-specific models that are realistic yet simple for use in 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

  10. RF gun with ferroelectric cathode

    NASA Astrophysics Data System (ADS)

    Khodak, Igor V.; Kushnir, Volodymyr A.

    2006-06-01

    RF guns generate bunched electron beams with pulse current Ip10 -1-10 3 A and current pulse duration ?p10 -6-10 -12 s. The parameters are defined by the type of a cathode used mainly. We propose to apply a ferroelectric cathode in RF gun for the generation of electron beams with Ip more than few amperes, ?p10 -8 s and current density of electron emission in a ferroelectric cathode jcfe may be 10 3 A/cm 2. We consider results of experimental study of S-band RF gun with ferroelectric plasma cathode. Obtained maximum Ip at RF gun output is 9 A with ?p?40-90 ns and electron energy We?500 keV.

  11. 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

  12. CuInP?S? Room Temperature Layered Ferroelectric.

    PubMed

    Belianinov, A; He, Q; Dziaugys, A; Maksymovych, P; Eliseev, E; Borisevich, A; Morozovska, A; Banys, J; Vysochanskii, Y; Kalinin, S V

    2015-06-10

    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. 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". PMID:25932503

  13. Ferroelectric, Thermal, and Magnetic Characteristics of Praseodymium Malonate Hexahydrate Crystals

    NASA Astrophysics Data System (ADS)

    Ahmad, Nazir; Ahmad, M. M.; Kotru, P. N.

    2016-01-01

    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. Coulomb microexplosions of ferroelectric ceramics.

    PubMed

    Yarmolich, D; Vekselman, V; Gurovich, V Tz; Krasik, Ya E

    2008-02-22

    Energetic neutral and extreme ultraviolet emission initiated by the dense plasma propagation along a ferroelectric surface has been found. It was shown that the emission of neutrals is characterized by a large divergence and velocities up to 7 x 10(7) cm/s. This phenomenon is explained by an extremely large electric field with amplitude > or =10(6) V/cm and rise time approximately 10(-10) s which appears at the plasma front due to the fast fall in the driving pulse. This electric field causes microexplosions of the ferroelectric surface due to inertia in the ion polarization response. PMID:18352565

  15. 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.

  16. Ferroelectric thin-films: The emancipation of ferroelectricity

    NASA Astrophysics Data System (ADS)

    Muralt, Paul

    2007-01-01

    Contrary to bulk materials, high-resolution microscopy of ultra-thin ferroelectric films finds only a weak coupling of polarization down to unit-cell dimensions. The established theoretical picture can be resurrected by the inclusion of epitaxial strain effects.

  17. Coupling of Magnetic and Ferroelectric Order Parameters in Improper Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Harris, A. Brooks

    2013-03-01

    This talk concerns systems for which the onset of incommensurate magnetic order induces ferroelectricity. I review how Landau theory provided a convenient phenomenological explanation of this phenomenon. In the simplest and most frequent scenario, as the temperature is lowered, one first induces collinear incommensurate magetic order. At a lower temperature transition, transverse magnetic components appear and these two different symmetry magnetic order parameters combine to induce ferroelectricity via a trilinear magnetoelectric coupling. I will present several examples of this mechanism, subsequently discussed by Mostovoy within a model of spiral magnetic order. Landau theory also explains a contrasting scenario in which ferroelectric and magnetic can order within a single phase transition as in RbFe(MoO4)2, whose magnetic spiral contradicts the Mostovoy construction, but which Kaplan has subsequently shown to be consistent with a more complete symmetry analysis of microscopic interactions. Other more exotic higher order magnetoelectric couplings, not easily accessible to an analysis of microscopic interactions, are also possible, especially in the presence of nonuniform magnetic order. I close with a few remarks on microscopic models for magnetically induced ferroelectricity.

  18. The Soft Mode Driven Dynamics in Ferroelectric Perovskites at the Nanoscale: An Atomistic Study

    NASA Astrophysics Data System (ADS)

    McCash, Kevin

    The discovery of ferroelectricity at the nanoscale has incited a lot of interest in perovskite ferroelectrics not only for their potential in device application but also for their potential to expand fundamental understanding of complex phenomena at very small size scales. Unfortunately, not much is known about the dynamics of ferroelectrics at this scale. Many of the widely held theories for ferroelectric materials are based on bulk dynamics which break down when applied to smaller scales. In an effort to increase understanding of nanoscale ferroelectric materials we use atomistic resolution computational simulations to investigate the dynamics of polar perovskites. Within the framework of a well validated effective Hamiltonian model we are able to accurately predict many of the properties of ferroelectric materials at the nanoscale including the response of the soft mode to mechanical boundary conditions and the polarization reversal dynamics of ferroelectric nanowires. Given that the focus of our study is the dynamics of ferroelectric perovskites we begin by developing an effective Hamiltonian based model that could simultaneously describe both static and dynamic properties of such materials. Our study reveals that for ferroelectric perovskites that undergo a sequence of phase transitions, such as BaTiO3. for example, the minimal parameter effective Hamiltonian model is unable to reproduce both static and dynamical properties simultaneously. Nevertheless we developed two sets of parameters that accurately describes the static properties and dynamic properties of BaTiO3 independently. By creating a tool that accurately models the dynamical properties of perovskite ferroelectrics we are able to investigate the frequencies of the soft modes in the perovskite crystal. The lowest energy transverse optical soft modes in perovskite ferroelectrics are known to be cause of the ferroelectric phase transition in these materials and affect a number of electrical properties. The performance of a ferroelectric device is therefore directly influenced by the dynamics of the soft mode. Interestingly, however, little study has been done on the effect of mechanical boundary conditions on the soft modes of perovskites. Understanding the effect of mechanical forces on the soft modes is critical to device applications as complicated growth structures often are the cause of pressures, stresses and strains. Using classical molecular dynamics we study the effect of hydrostatic pressure, uniaxial stress, biaxial stress and biaxial strain on the soft modes of the ferroelectric PbTiO 3. The results of this study indicate the existence of Curie-Weiss laws for not only hydrostatic pressure, which is well known, but also for uniaxial stress, biaxial stress and biaxial strain. The mode frequencies are also seen to respond very differently to these mechanical forces and lead to a more complete picture of the behavior of nanoscale ferroelectrics. One nanoscale geometry of perovskite ferroelectrics is the pseudo one-dimensional nanowire. These structures have very unique properties that are highly attractive for use as interconnects, nanoscale sensors or more directly in computer memory devices. Perovskite nanowires have only recently been synthesized and the techniques are not well developed. While progress has been made towards consistently fabricating uniform, high quality nanowires experimental investigation of their properties is prohibitively difficult. Of immediate interest is the polarization reversal dynamics of ferroelectric nanowires. The reading and writing of bits of information stored in a wire's polarization state is done by switching the polarization. Again using classical molecular dynamics we study the polarization reversal dynamics in ferroelectric nanowires made of Pb(Ti1-xZrx)O 3 disordered alloy. We find that there are two competing mechanisms for polarization reversal and that the interplay of these mechanisms is dependent on electric field strength. The dynamics in nanowires also sheds light on long standing theories about polarization reversal mechanisms in thin film and bulk geometries.

  19. Energy principle of ferroelectric ceramics and single domain mechanical model

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Li, Haijun; Wang, T. C.

    2007-10-01

    Many physical experiments have shown that the domain switching in a ferroelectric material is a complicated evolution process of the domain wall with the variation of stress and electric field. According to this mechanism, the volume fraction of the domain switching is introduced in the constitutive law of ferroelectric ceramic and used to study the nonlinear constitutive behavior of ferroelectric body in this paper. The principle of stationary total energy is put forward in which the basic unknown quantities are the displacement u i , electric displacement D i and volume fraction ρ I of the domain switching for the variant I. Mechanical field equation and a new domain switching criterion are obtained from the principle of stationary total energy. The domain switching criterion proposed in this paper is an expansion and development of the energy criterion. On the basis of the domain switching criterion, a set of linear algebraic equations for the volume fraction ρ I of domain switching is obtained, in which the coefficients of the linear algebraic equations only contain the unknown strain and electric fields. Then a single domain mechanical model is proposed in this paper. The poled ferroelectric specimen is considered as a transversely isotropic single domain. By using the partial experimental results, the hardening relation between the driving force of domain switching and the volume fraction of domain switching can be calibrated. Then the electromechanical response can be calculated on the basis of the calibrated hardening relation. The results involve the electric butterfly shaped curves of axial strain versus axial electric field, the hysteresis loops of electric displacement versus electric filed and the evolution process of the domain switching in the ferroelectric specimens under uniaxial coupled stress and electric field loading. The present theoretic prediction agrees reasonably with the experimental results given by Lynch.

  20. Controlling structure distortions in 3-layer ferroelectric Aurivillius oxides

    SciTech Connect

    Nichols, Eric J.; Shi, Jiawanjun; Huq, Ashfia; Vogel, Sven C.; Misture, Scott T.

    2013-01-15

    Combined Rietveld refinements of x-ray and neutron powder diffraction data were used to understand the subtle structure distortions in 3-layer Aurivillius oxides that yield off-centering displacements in ferroelectric and multiferroic compositions. Ferroelectric phases including Bi{sub 2}A{sub 2}Ti{sub 3}O{sub 12} (A=La, Pr, Nd, La/Pr, La/Nd, Pr/Nd), Bi{sub 2}A{sub 2}TiNb{sub 2}O{sub 12} (A=Ca/Sr, Sr, and Sr/Ba) and Bi{sub 2}A{sub 2}TiTa{sub 2}O{sub 12} (A=Ca/Sr, and Sr/Ba) were studied to separate the effects of cation size and charge on the structure distortions and properties. A new approach to describing the local coordination around the Ti, Nb, and/or Ta ions is presented, where the oxygen octahedra are characterized as containing kinks in three dimensions. The kink angles follow trends with the A-site ionic radius and the ferroelectric polarization. The driving force for extensive cation site mixing between the Bi and A-site cations has been clearly established, with site mixing required to maintain interlayer bonding. - Graphical abstract: Distortion of the oxygen octahedra from planar geometries can be controlled via choice of the perovskite A-site cation, and the kink angle correlates with cation off-centering and ferroelectric polarization. Highlights: Black-Right-Pointing-Pointer A-site cations define the tilt and distortion of the octahedral. Black-Right-Pointing-Pointer Distortions of oxygen octahedra, ignoring the central cation, link to ferroelectric polarization. Black-Right-Pointing-Pointer Bi ion occupancy in the perovskite causes distortion of the oxygen sublattice. Black-Right-Pointing-Pointer We predict multiferroic behavior from off-centering caused by the Bi ion lone pair.

  1. 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 m 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.

  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; Boissire, Cdric; Grosso, David; Sanchez, Clment

    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. Incommensurate modulation structure in ferroelectric Ca0.28Ba0.72Nb2O6 single crystals of tungsten bronze structure

    NASA Astrophysics Data System (ADS)

    Lu, C. J.; Qi, Y. J.; Li, J. Q.; Zhang, H. J.; Wang, J. Y.

    2006-11-01

    Incommensurate modulation structure in uniaxial relaxor ferroelectric Ca0.28Ba0.72Nb2O6 single crystals was investigated using transmission electron microscopy (TEM). The wave-modulation vector can be expressed as q =(1/2)c*+(1+?)(a*-b*)/4, where the incommensurability parameter ? was determined to be about 0.09 from [110] diffraction pattern. High-resolution TEM observations along [110] zone provided direct evidence of the incommensurate superstructure. Structural modulation was also evident by high-resolution TEM images through [001] zone, where a sinusoidal variation along [110] and [110] was identified. The incommensurate superlattice structure is caused by the uniform mixing of slabs of two orthorhombic cells.

  4. Coexistence of the soft mode and sub-THz central peak in ferroelectric BaTiO3/(Ba,Sr)TiO3 superlattices

    NASA Astrophysics Data System (ADS)

    Razumnaya, A. G.; Tikhonov, Yu. A.; Yuzyuk, Yu. I.; Zakharchenko, I. N.; Torgashev, V. I.; Ortega, N.; Kumar, A.; Katiyar, R. S.; El Marssi, M.; Lukyanchuk, I. A.

    2015-11-01

    Near- and sub-Terahertz dynamics of soft and Debye-type central modes was studied by the polarized Raman spectroscopy in ferroelectric BaTiO3/Ba0.3Sr0.7TiO3 (BT/BST) superlattice in the temperature range of 80-400 K where system undergoes the series of phase transitions: paraelectric-tetragonal-monoclinic in BT layers and paraelectric-orthorhombic-monoclinic in BST layers. It was shown that temperature evolution of these modes can be described within the model of coexisted damped harmonic oscillator and Debye relaxator. The occurrence of the pronounced central mode can explain the recently observed relaxor-like dielectric anomaly in such superlattice.

  5. 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.

  6. Ferroelectric Transitions at Ferroelectric Domain Walls Found from First Principles

    NASA Astrophysics Data System (ADS)

    Wojde?, Jacek C.; iguez, Jorge

    2014-06-01

    We present a first-principles study of model domain walls (DWs) in prototypic ferroelectric PbTiO3. At high temperature the DW structure is somewhat trivial, with atoms occupying high-symmetry positions. However, upon cooling the DW undergoes a symmetry-breaking transition characterized by a giant dielectric anomaly and the onset of a large and switchable polarization. Our results thus corroborate previous arguments for the occurrence of ferroic orders at structural DWs, providing a detailed atomistic picture of a temperature-driven DW-confined transformation. Beyond its relevance to the field of ferroelectrics, our results highlight the interest of these DWs in the broader areas of low-dimensional physics and phase transitions in strongly fluctuating systems.

  7. Nanoscale ferroelectric and piezoelectric phenomena in ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Valanoor, Nagarajan; Ganpule, Chandan; Liu, Bao Ting; Stanishevsky, Andrei; Melngailis, John; Roytburd, Alexander; Ramesh, Ramamoorthy; Maki, Kazunari

    2002-03-01

    This talk will focus on the nanoscale ferroelectric phenomena in Pb based ferroelectric thin films. We will present the domain dynamics of polarization relaxation, which has been modeled to the classical JMAK theory. The relaxation is observed via piezo response scanning force microscopy which allows very high spatial resolution (on the nm scale). This allows us to record sveral key events in the phenomenon of polarization relaxation, which will be presented. In this regard, we will also present the impact of domain pinning and faceting on the polarization relaxation. Secondly we will present data on obtaining intrinsic piezoresponse in nanoscale capacitors of PZT thin films. In the end we will discuss the movement of 90^odomains and their impact on piezoelectric properties in thin films.This work is supported by the University of Maryland NSF-MRSEC under contract No. DMR-00-80008.

  8. Ferroelectric transitions at ferroelectric domain walls found from first principles.

    PubMed

    Wojdeł, Jacek C; Íñiguez, Jorge

    2014-06-20

    We present a first-principles study of model domain walls (DWs) in prototypic ferroelectric PbTiO(3). At high temperature the DW structure is somewhat trivial, with atoms occupying high-symmetry positions. However, upon cooling the DW undergoes a symmetry-breaking transition characterized by a giant dielectric anomaly and the onset of a large and switchable polarization. Our results thus corroborate previous arguments for the occurrence of ferroic orders at structural DWs, providing a detailed atomistic picture of a temperature-driven DW-confined transformation. Beyond its relevance to the field of ferroelectrics, our results highlight the interest of these DWs in the broader areas of low-dimensional physics and phase transitions in strongly fluctuating systems. PMID:24996110

  9. Room temperature p-type conductivity and coexistence of ferroelectric order in ferromagnetic Li doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Awan, Saif Ullah; Hasanain, S. K.; Anjum, D. H.; Awan, M. S.; Shah, Saqlain A.

    2014-10-01

    Memory and switching devices acquired new materials which exhibit ferroelectric and ferromagnetic order simultaneously. We reported multiferroic behavior in Zn1-yLiyO(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 1017/cc to 7.3 1017/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 ?C/cm2) and 2.8 kV/cm (0.15 ?C/cm2) 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 1017/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.

  10. 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.

  11. Ferroelectric instability in nanotubes and spherical nanoshells

    NASA Astrophysics Data System (ADS)

    Qiu, R.; Bousquet, E.; Cano, A.

    2015-11-01

    The emergence of ferroelectricity in nanotubes and spherical nanoshells is studied theoretically. We determine semi-analytically the size and thickness dependence of the ferroelectric instability, as well as its dependence on the properties of the surrounding media and the corresponding interfaces. By properly tuning these factors, we demonstrate possible routes for enhancing the ferroelectric transition temperature and promoting the competition between irrotational and vortex-like states in the ultra-thin limit due to the specific topology of these nanoparticles.

  12. Class of Rashba ferroelectrics in hexagonal semiconductors

    NASA Astrophysics Data System (ADS)

    Narayan, Awadhesh

    2015-12-01

    We present a class of Rashba systems in hexagonal semiconducting compounds, where an electrical control over spin-orbital texture is provided by their bulk ferroelectricity. Our first-principles calculations reveal a number of such materials with large Rashba coefficients. We, furthermore, show that strain can drive a topological phase transition in such materials, resulting in a ferroelectric topological insulating state. Our findings can open avenues for interplay between Rashba effect, ferroelectricity, and topological phenomena.

  13. 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.

  14. 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.

  15. Electromigration of microspheres in ferroelectric smectic liquid crystals.

    PubMed

    Dierking, I; Cass, P; Syres, K; Cresswell, R; Morton, S

    2007-08-01

    When an electric field is applied to microspheres which are dispersed in a ferroelectric smectic liquid crystal, particle translation along the smectic layer plane, i.e., in a direction nearly perpendicular to that of the director, can be observed. Under certain electric field conditions the translation is shown to be linear in time. We have determined the stability regime of linear particle displacement in the parameter space of amplitude and frequency for various applied wave forms. This regime enlarges for increasing electric field amplitude and frequency, with a threshold behavior observed for small parameters. The upper stability boundary is related to the reciprocal ferroelectric switching time. The microspheres translational velocity is independent of the applied electric field amplitude, but increases linearly with applied frequency. The microsphere velocity also increases with increasing temperature, which is indicative of the respective decrease in liquid crystal viscosity. Possible mechanisms of electric-field-induced particle motion are discussed. PMID:17930054

  16. 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.

  17. 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.

  18. High-frequency programmable acoustic wave device realized through ferroelectric domain engineering

    NASA Astrophysics Data System (ADS)

    Ivry, Yachin; Wang, Nan; Durkan, Colm

    2014-03-01

    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.

  19. 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.

  20. 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.

  1. 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).

  2. Ferroelectric and Piezoelectric Properties of Ferroelectric Polymer Composite Systems.

    NASA Astrophysics Data System (ADS)

    Su, Ji.

    A co-melt-quenching processing technique was developed to produce new types of ferroelectric polymer composite systems: bilaminate films and powder blend films. The bilaminate films exhibited clear ferroelectric characteristics in the measurements of the electric displacement, D, versus the applied electric field, E. The poled films were also piezoelectrically active as seen in the measurements of the piezoelectric coefficients. The enhancement in both remanent polarization and piezoelectricity were observed when compared with the individual films which comprised the bilaminate films. The enhancements were indicated by the increased remanent polarization, P_ {r}, and piezoelectric strain and stress coefficients, d_{31} and e_{31}, as well as the hydrostatic coefficient, d_{h}, of the composite films. These properties were shown to depend on the relative thickness fraction of the constituents of the bilaminate films. FTIR-ATR and LIPP analysis of the nylon 11/PVF_2 bilaminate films showed that the effects of interface between the nylon 11 and PVF_2, which have differences in electric properties, play an important role in the observed enhancements. The experimental results indicated that both constituents in the bilaminate were well poled and that an accumulation of space charge might exist in the interface region between them. The accumulated space charge, associated with this heterogeneity, could then be considered as the main contributor to the enhanced piezoelectric response. Further investigations showed that the piezoelectric response of the bilaminate depended on the direction of the poling field applied on the bilaminate film and that the PVF _2/nylon 11/PVF_2 trilaminate film, having two interfaces symmetric to the central plane of the film, did not show the enhancement observed in the nylon 11/PVF_2 bilaminate. These results indicated that the characteristics of the interface are important to the ferroelectric and piezoelectric response of laminated ferroelectric films. The enhancement in ferroelectric and piezoelectric properties was also observed in powder blends of PVF_2/VF_2 -VF_3 copolymer films. These properties are also dependent on the relative fraction of the constituent polymers. Melt-pressed, quenched, uniaxially stretched blend films with equal weight percents showed the maximum response in the piezoelectric measurements, which suggest that the effects of the interface between the two oriented and poled constituents is due to the maximum amount of interface is reached when the constituents have equal amounts of powder in the blend films.

  3. Magnetic control of ferroelectric polarization.

    PubMed

    Kimura, T; Goto, T; Shintani, H; Ishizaka, K; Arima, T; Tokura, Y

    2003-11-01

    The magnetoelectric effect--the induction of magnetization by means of an electric field and induction of polarization by means of a magnetic field--was first presumed to exist by Pierre Curie, and subsequently attracted a great deal of interest in the 1960s and 1970s (refs 2-4). More recently, related studies on magnetic ferroelectrics have signalled a revival of interest in this phenomenon. From a technological point of view, the mutual control of electric and magnetic properties is an attractive possibility, but the number of candidate materials is limited and the effects are typically too small to be useful in applications. Here we report the discovery of ferroelectricity in a perovskite manganite, TbMnO3, where the effect of spin frustration causes sinusoidal antiferromagnetic ordering. The modulated magnetic structure is accompanied by a magnetoelastically induced lattice modulation, and with the emergence of a spontaneous polarization. In the magnetic ferroelectric TbMnO3, we found gigantic magnetoelectric and magnetocapacitance effects, which can be attributed to switching of the electric polarization induced by magnetic fields. Frustrated spin systems therefore provide a new area to search for magnetoelectric media. PMID:14603314

  4. Terahertz response of ferroelectric nanofibers.

    PubMed

    Tian, Zhen; Xin, Kun; Wang, Mingwei; Han, Jiaguang; Wang, Haizhen; Tian, Z Ryan; Zhang, Weili

    2011-11-01

    Far-infrared optical and dielectric properties of ferroelectric SrTiO3 and BaTiO3 nanofibers, prepared by hydrothermal syntheses, were studied using terahertz time-domain spectroscopy. The power absorption, refractive index, and complex dielectric function were characterized in the frequency range from 0.2 to 1.0 THz. The measured results are well reproduced by theoretical fittings based on the dielectric models and the effective medium model. The study reveals that the low-frequency dielectric properties of the ferroelectric SrTiO3 nanofibers are associated with the lowest transverse optical (TO) soft mode TO1 at 2.70 THz (90.0 cm(-1)), and that of the ferroelectric BaTiO3 nanofibers are related to the lowest pair of transverse optical (TO) and longitudinal optical (LO) modes near 5.35 THz, which are both consistent with their bulk single-crystal and thin-film counterparts. PMID:22413261

  5. Domain dynamics during ferroelectric switching

    NASA Astrophysics Data System (ADS)

    Pan, Xiaoqing; Gao, Peng; Nelson, Christopher; Jokisaari, Jacob; Baek, Seung-Hyub; Bark, Chung-Wung; Eom, Chang-Beom; Schlom, Darrell

    2012-02-01

    Ferroelectric materials are characterized by a spontaneous polarization that can be reoriented by an applied electric field. The ability to form and manipulate domains at the nanometer scale is key to device applications such as nonvolatile memories. The ferroelectric switching is mediated by defects and interfaces. Thus, it is critical to understand how the domain forms, grows, and interacts with defects. Here we show the nanoscale switching of a tetragonal PbZr0.2Ti0.8O3 thin film under an applied electric field using in situ transmission electron microscopy. We found that the intrinsic electric fields formed at ferroelectric/electrode interfaces determine the nucleation sites and growth rates of domains and the orientation and mobility of domain walls, while dislocations exert a weak pinning force on domain wall motion. We also show that localized 180 polarization switching initially form domain walls along unstable planes. After removal of the external field, they tend to relax to low energy orientations. In sufficiently small domains this process results in complete backswitching. Our results suggest that even thermodynamically favored domains are still subject to retention loss, which must be mitigated by overcoming a critical domain size.

  6. Kinetics of Ferroelectric Phase Transition: Nonlinear Pyroelectric Effect and Ferroelectric Solar Cell

    NASA Astrophysics Data System (ADS)

    Itskovsky, M.

    1999-08-01

    Kinetics of a ferroelectric phase transition in thin ferroelectric layer (film), coated with metallic films [metal-ferroelectric-metal (MFM) system] and overheated with various heating rates through phase transition temperature by solar or laser irradiation impulse, is investigated. Dynamical nonlinear pyroelectric effect (pyroelectric current and polarization) as well as anomalies of dielectric permittivity and specific heat are calculated as functions of changing in time temperature for various heating rates. Conversion efficiency during heating of the MFM system (served as ferroelectric solar cell), operating due to the nonlinear pyroelectric effect in the ferroelectric phase transition region, ranges from a few percent for ferroelectrics of the triglycine sulphate (TGS) type to above 10% for the NaNO2 type ferroelectrics, reaching the order of efficiency of photovoltaic solar cell.

  7. Ogranic-Assisted Solid-State Reaction Method for Fabrication of PNN-PT Ceramics with Superior Ferroelectric Properties

    NASA Astrophysics Data System (ADS)

    Ye, Yin

    Relaxor ferroelectric ceramic materials have attracted considerable attentions due to their high dielectric constants and superior piezoelectric properties. Since such properties are associated with single perovskite phase, the synthesis process is of utmost importance. The traditional solid-state reaction encounters difficulties in eliminating pyrochlore phases. To synthesize pyrochlore-free Pb-based relaxors, other methods have been proposed including the columbite route, the chemical method and the mechanochemical reaction approach. However, they involve complicated processing procedures, high fabrication cost and inevitable contamination. To tackle these problems, this study aims to develop a simple and economical method for synthesis of Pb-based relaxors that can attain single perovskite phase, excellent electrical properties and high electric fatigue resistance while accommodating the demand of mass production. The key idea is to introduce organic materials into the ball-milling process of the conventional solid-state reaction so that the oxygen in the organics could assist the formation of the perovskite phase. In this work, 0.64Pb(Ni1/3Nb2/3)O 3-0.36PbTiO3 powders and ceramics with single perovskite structure have been successfully fabricated using a polyethylene glycol(PEG)-assisted method. The details of studies on the improvements of material properties like phase structure, microstructure, electrical properties and electric fatigue resistance have been presented. The major contributions can be highlighted in three aspects: (1) the successful demonstration of organic-assisted solid-state reaction method by synthesizing pyrochlore-free Ni1/3Nb2/3)O3-0.36PbTiO 3 powders via a PEG-assisted method, which yields drastically improved properties of ceramics in density, dielectrics and piezoelectrics as compared to those derived without PEG; (2) the study of chemical functional groups by comparing the assisting effects of polyalcohol and polyether, which finds that the hydroxyl oxygen is more effective in assisting the formation of the perovskite phase than the ether oxygen; and (3) the characterization of the Ni1/3Nb2/3)O3-0.36PbTiO3 ceramics fabricated by the organic-assisted method, which show superior performance as compared to those fabricated without the organic, particularly for electrical properties and electric fatigue characteristics. In summary, the organic-assisted method has shown its great potential in fabricating single-phase perovskite i1/3Nb2/3)O 3-PbTiO3 ceramics with superior electrical performance, high electric fatigue resistance and mass productability, making it suitable for wide industrial applications such as capacitors, actuators and transducers, etc.

  8. Two-bit ferroelectric field-effect transistor memories assembled on individual nanotubes.

    PubMed

    Fu, W Y; Xu, Z; Liu, L; Bai, X D; Wang, E G

    2009-11-25

    Carbon nanotube (CNT) ferroelectric field-effect transistors (FeFETs) with well-defined memory switch behaviors are promising for nonvolatile, nondestructive read-out (NDRO) memory operation and ultralow power consumption. Here, we report two-bit CNT-FeFET memories by assembling two top gates on individual nanotubes coated with ferroelectric thin films. Each bit of the nanotube transistor memory exhibits a controllable memory switching behavior induced by the reversible remnant polarization of the ferroelectric films, and its NDRO operation is demonstrated. The low driving voltage of 2 V, high carrier mobility over 1000 cm2 V(-1) s(-1), and potential ultrahigh integration density over 200 Gbit inch(-2) of the two-bit FeFET memory are highlighted in this paper. PMID:19875879

  9. Noninvasive Optical Probe Of Ferroelectric Films

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita

    1993-01-01

    Thin films of ferroelectric materials probed by near-field, noninvasive mapping of photoresponse from film to obtain high-spatial-resolution information on distribution of polarization domains within film. Photoresponse technique yields data on microscopic structure of electric fields in ferroelectric material, without disturbing structure.

  10. 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

  11. 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.

  12. Enhanced electrocaloric effect in displacive-type organic ferroelectrics

    NASA Astrophysics Data System (ADS)

    Ding, L. J.; Zhong, Y.; Fan, S. W.; Zhu, L. Y.

    2015-08-01

    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 TC. Indeed, one expects that the optimal operating temperature for solid-state refrigeration is around room temperature, at which the ECE achieves its maximum. As TC 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 TC and a metaelectric transition line below TC that demonstrates an FE switching behavior with an antiparallel field.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Nonelectrical Poling in Ferroelectric Polycyanophenylenesulfides

    NASA Astrophysics Data System (ADS)

    Ide, Junya; Tasaka, Shigeru; Inagaki, Norihiro

    1999-04-01

    A new poling method utilizing the cooperativity of cyanophenyl groupswas proposed in ferroelectric polycyanophenylenesulfides (PCPS). The methodcalled surface energy poling takes advantage of the energy difference inthe top and bottom surfaces of a polar aggregate to form a remanentpolarization. The PCPS film sandwiched between a metal with higher surfaceenergy and polytetrafluoroethylene with lower surface energy was heated toTcp [1.2Tg (glass transition temperature)] and cooled slowly to roomtemperature. The remanent polarization that gives a pyroelectric constant of10 C/m2 K and an electrooptic coefficient (r33) of 80 pm/V in theresulting film was realized.

  18. 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.

  19. Microscopic mechanisms for improper ferroelectricity in multiferroic perovskites: a theoretical review

    SciTech Connect

    Picozzi, S.; Yamauchi, K.; Sergienko, Ivan A; Sen, Cengiz; Sanyal, B.; Dagotto, Elbio R

    2008-01-01

    Two microscopic mechanisms helping us to understand the multiferroic behavior of distorted rare-earth manganites are here briefly reviewed. The original work was carried out by means of Hamiltonian modeling and first-principles density functional simulations. Our first topic concerns the link between the Dzyaloshinskii Moriya interaction and ferroelectricity in incommensurate magnets. We argue that the Dzyaloshinskii Moriya interaction may play a key role since (i) it induces ferroelectric displacements of oxygen atoms and (ii) it favors the stabilization of a helical magnetic structure at low temperatures. Our second topic concerns the prediction, based on Landau theory, that the symmetry of the zigzag spin chains in the AFM-E (E-type antiferromagnetic) orthorhombic manganites (such as HoMnO3) allows a finite polarization along the c axis. The microscopic mechanism at the basis of ferroelectricity is interpreted through a gain in band energy of the eg electrons within the orbitally degenerate double-exchange model. Related Monte Carlo simulations have confirmed that the polarization can be much higher than what is observed in spiral magnetic phases. Density functional calculations performed on orthorhombic HoMnO3 quantitatively confirm a magnetically induced ferroelectric polarization up to 6 C cm 2, the largest reported so far for improper magnetic ferroelectrics. We find in HoMnO3, in addition to the conventional displacement mechanism, a sizable contribution arising from the purely electronic effect of orbital polarization. The relatively large ferroelectric polarization, present even with centrosymmetric atomic positions, is a clear sign of a magnetism-induced electronic mechanism at play, which is also confirmed by the large displacements of the Wannier function centers with respect to the corresponding ions in AFM-E HoMnO3. The final polarization is shown to be the result of competing effects, as shown by the opposite signs of the eg and t2g contributions to the ferroelectric polarization.

  20. 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 25C to 200C. 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 second order. The driving force for the transitions was found to be the uniaxial anion displacement with respect to the mirror plane in Pmcn phase, coupled with the rotation of the cation and anions. The abnormal thermal behaviors, such as thermal contraction of a-axis, non-linear behavior of thermal parameters versus temperature in both compounds and superheating of [P(CH3)4]2ZnBr4 , were explained by observing the Lifshitz point. The results from theoretical analysis of the free energy are consistent with all features of the phase transitions.

  1. Emergence of Negative Capacitance in Multidomain Ferroelectric-Paraelectric Nanocapacitors at Finite Bias.

    PubMed

    Kasamatsu, Shusuke; Watanabe, Satoshi; Hwang, Cheol Seong; Han, Seungwu

    2016-01-01

    The emergence of negative capacitance in an ultrathin ferroelectric/paraelectric bilayer capacitor under electrical bias is examined using first-principles simulation. An antiferroelectric-like behavior is predicted, and negative capacitance is shown to emerge when the monodomain state becomes stable after bias application. The polydomain-monodomain transition is also shown to be a source of capacitance enhancement. PMID:26568333

  2. 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%.

  3. Anomaly in the conductivity relaxation parameters at the phase transition of ferroelectric materials: A time domain study

    SciTech Connect

    Leyet, Y.; Guerrero, F.; Amorin, H.; Guerra, J. de Los S.; Eiras, J. A.

    2010-10-18

    The influence of the ferroelectric to paraelectric transition on the relaxation parameters of conductive processes in ferroelectric materials is studied in the time domain. Three well-known ferroelectric systems were chosen with transition temperatures in different regions, these are, high-temperature PbNb{sub 2}O{sub 6}-based ceramics; nanostructured Pb(Zr{sub 0.6}Ti{sub 0.4})O{sub 3} ceramics; and submicron BaTiO{sub 3}. The thermal evolution of relaxation parameters shows clear anomalies in their typical behavior when conductivity processes arise in the temperature range where the ferroelectric transition takes place. The method here described allows obtaining information about the correlation between charge transport and the motion of the off-center ions at the phase transition.

  4. 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

  5. Anomaly in the conductivity relaxation parameters at the phase transition of ferroelectric materials: A time domain study

    NASA Astrophysics Data System (ADS)

    Leyet, Y.; Guerrero, F.; Amorn, H.; Guerra, J. de Los S.; Eiras, J. A.

    2010-10-01

    The influence of the ferroelectric to paraelectric transition on the relaxation parameters of conductive processes in ferroelectric materials is studied in the time domain. Three well-known ferroelectric systems were chosen with transition temperatures in different regions, these are, high-temperature PbNb2O6-based ceramics; nanostructured Pb(Zr0.6Ti0.4)O3 ceramics; and submicron BaTiO3. The thermal evolution of relaxation parameters shows clear anomalies in their typical behavior when conductivity processes arise in the temperature range where the ferroelectric transition takes place. The method here described allows obtaining information about the correlation between charge transport and the motion of the off-center ions at the phase transition.

  6. 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

  7. Face shear piezoelectric properties of relaxor-PbTiO3 single crystals

    PubMed Central

    Zhang, Shujun; Li, Fei; Jiang, Wenhua; Luo, Jun; Meyer, Richard J.; Cao, Wenwu; Shrout, Thomas R.

    2011-01-01

    Poling relaxor-PbTiO3 single crystals along pseudocubic [011] results in a macroscopic symmetry of mm2, enabling a large face shear d36 in Zt45 cut crystals. In order to allow the determination of electrical properties by the resonance method, square samples are required. Using Pb(In0.5Nb0.5)O3Pb(Mg1?3Nb2?3)O3PbTiO3 crystals, piezoelectric d36 coefficients were determined to be in the range of 20002500 pC?N, with electromechanical coupling factor k36?0.800.83. Mechanical quality factor Q?180 and ultralow frequency constant of ?500 Hz m were obtained. Together with the wide temperature usage range (up to ?110 C) and high ac driving field stability (?5 kV?cm), such face shear crystals have a promising potential for ultralow-frequency-transducer applications. PMID:21629563

  8. Face shear piezoelectric properties of relaxor-PbTiO(3) single crystals.

    PubMed

    Zhang, Shujun; Li, Fei; Jiang, Wenhua; Luo, Jun; Meyer, Richard J; Cao, Wenwu; Shrout, Thomas R

    2011-05-01

    Poling relaxor-PbTiO(3) single crystals along pseudocubic [011] results in a macroscopic symmetry of mm2, enabling a large face shear d(36) in Zt45 cut crystals. In order to allow the determination of electrical properties by the resonance method, square samples are required. Using Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1?3)Nb(2?3))O(3)-PbTiO(3) crystals, piezoelectric d(36) coefficients were determined to be in the range of 2000-2500 pC?N, with electromechanical coupling factor k(36)?0.80-0.83. Mechanical quality factor Q?180 and ultralow frequency constant of ?500 Hz m were obtained. Together with the wide temperature usage range (up to ?110 C) and high ac driving field stability (?5 kV?cm), such face shear crystals have a promising potential for ultralow-frequency-transducer applications. PMID:21629563

  9. 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.

  10. 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

  11. Ferroelectric Plasma Cathodes for Plasma Propulsion

    NASA Astrophysics Data System (ADS)

    Dunaevsky, Alexander; Raitses, Yevgeny; Fisch, Nathaniel

    2002-11-01

    During last decade the phenomenon of strong ferroelectric emission was studied widely in many laboratories all around the world. It was shown that the application of a kilovolt-range driving pulse between solid rear and patterned front electrodes which cover a sample of a ferroelectric ceramics results in electron emission from the side of the front electrode. The current density of this electron emission varies from hundreds of mA to hundreds of A per cm^2. The duration of the current pulse is several hundreds of nanoseconds with the repetition rate up to several MHz. Recent investigations showed that the strong electron emission occurs from surface discharge plasma formed on the ceramic surface near the edges of the front electrode pattern. The surface plasma has a density of 10^11 - 10^13 cm-3, an electron temperature of 2-3 eV, and consists mostly from ions of ferroelectric ceramic material and the front electrode. Ferroelectric Plasma Cathodes (FPC) are used widely in electron guns, microwave sources, and high current switches. It was recently showed that a strong ferroelectric-gas discharge occurs at a background pressure about of 1 Torr. Dense plasma formed in the ferroelectric-gas discharge can be used either as a powerful cathodes-neutralizer or as a plasma source for an ion thruster. Ferroelectric segmented electrodes are also very promising for Hall thrusters in both emissive and nonemissive modes.

  12. Electric field induced short range to long range structural ordering and its influence on the Eu+3 photoluminescence in the lead-free ferroelectric Na1/2Bi1/2TiO3

    NASA Astrophysics Data System (ADS)

    Kalaskar, Abhijeet; Rao, Badari Narayana; Thomas, Tiju; Ranjan, Rajeev

    2015-06-01

    Eu+3 was incorporated into the lattice of a lead-free ferroelectric Na1/2Bi1/2TiO3 (NBT) as per the nominal formula Na0.5Bi0.5-xEuxTiO3. This system was investigated with regard to the Eu+3 photoluminescence (PL) and structural behaviour as a function of composition and electric field. Electric field was found to irreversibly change the features in the PL spectra and also in the x-ray diffraction patterns below the critical composition x = 0.025. Detailed analysis revealed that below the critical composition, electric field irreversibly suppresses the structural heterogeneity inherent of the host matrix NBT and brings about a long range ferroelectric state with rhombohedral (R3c) distortion. It is shown that the structural disorder on the nano-scale opens a new channel for radiative transition which manifests as a new emission line branching off from the main 5D0?7F0 line along with a concomitant change in the relative intensity of the other crystal field induced Stark lines with different J values. The study suggests that Eu+3 luminescence can be used to probe the relative degree of field induced structural ordering in relaxor ferroelectrics and also in high performance piezoelectric alloys where electric field couples very strongly with the lattice and structural degrees of freedom.

  13. Ferroelectric potassium niobate thin films

    SciTech Connect

    Tuttle, B.A.; Bunker, B.C.; Lamppa, D.L.; Tissot, R.G.; Yio, J.L.

    1989-01-01

    We report on the first ferroelectric measurements of chemically prepared KNbO/sub 3/ thin films. Polycrystalline KNbO/sub 3/ thin films were fabricated by dip coating substrates with methanolic solutions of potassium hydroxide and niobium ethoxide. Perovskite KNbO/sub 3/ was obtained for both bulk gels and films by using 800/degree/C firing treatments. For films, the intermediate temperature processing schedule was critical for the complete conversion of low temperature phases to perovskite KNbO/sub 3/. Raman spectroscopy and x-ray diffraction analysis confirmed that properly processed films possessed the orthorhombic distortion of the perovskite structure at room temperature. In response to a 1 kHz, sinusoidal field of 300 kV/cm amplitude, we measured the following ferroelectric properties: (1) a remanent polarization of 4.5 ..mu..C/cm/sup 2/, (2) a spontaneous polarization of 8.3 ..mu..C/cm/sup 2/, and (3) a coercive field of 55 kV/cm.

  14. 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.

  15. 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.

  16. Ferroelectric and electrical characterization of multiferroic BiFeO3 at the single nanoparticle level

    SciTech Connect

    Vasudevan, Rama K; Bogle, K A; Kumar, Amit; Jesse, Stephen; Magaraggia, R; Stamps, R; Ogale, S; Potdar, H S

    2011-01-01

    Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of 1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.

  17. 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

  18. 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.

  19. 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.

  20. Ultrafast photovoltaic response in ferroelectric nanolayers.

    SciTech Connect

    Daranciang, D.; Highland, M. J.; Wen, H.; Young, S. M.; Brandt, N. C.; Walko, D. A.; Dufresne, E. M.; Li, Y.; Fuoss, P. H.; Stephenson, G. B.

    2012-01-01

    We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO{sub 3} via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on femtosecond time scales, 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.

  1. 23 GHz ferroelectric electron gun based gyrotron

    NASA Astrophysics Data System (ADS)

    Ben-Moshe, R.; Einat, M.

    2011-04-01

    Ferroelectric cathodes have been explored as an alternative electron source for microwave tubes. Past experiments have demonstrated operation at frequencies of 2-10 GHz. Since the ferroelectric cathode is based on surface plasma, the relatively high energy spread limits the tube operation frequency. Hence, the possibility to obtain higher frequencies remained questionable. In this experimental work a gyrotron oscillator was designed with the operation frequency increased toward that of millimeter waves. A cylindrical tube with a cutoff frequency of ˜22 GHz was integrated to a ferroelectric electron gun. Pulses of ˜0.5 μs duration with a frequency of 23 GHz were obtained.

  2. 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.

  3. 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.

  4. Ferroelectric Memory Capacitors For Neural Networks

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita; Moopenn, Alexander W.; Stadler, Henry L.

    1991-01-01

    Thin-film ferroelectric capacitors proposed as nonvolatile analog memory devices. Intended primarily for use as synaptic connections in electronic neural networks. Connection strengths (synaptic weights) stored as nonlinear remanent polarizations of ferroelectric films. Ferroelectric memory and interrogation capacitors combined into memory devices in vertical or lateral configurations. Photoconductive layer modulated by light provides variable resistance to alter bias signal applied to memory capacitor. Features include nondestructive readout, simplicity, and resistance to ionizing radiation. Interrogated without destroying stored analog data. Also amenable to very-large-scale integration. Allows use of ac coupling, eliminating errors caused by dc offsets in amplifier circuits of neural networks.

  5. 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.

  6. 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

  7. Surface atomic and chemical structure of relaxor Sr0.63Ba0.37Nb2O6(001)

    NASA Astrophysics Data System (ADS)

    Wang, J. L.; Vilquin, B.; Gautier, B.; Dezanneau, G.; Barrett, N.

    2015-06-01

    The surface atomic and chemical structures of a Sr0.63Ba0.37Nb2O6(001) single crystal are studied using the low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy. Sharp, well-defined LEED patterns are observed, consisting of the superposition of two surface reconstructions, ( ?{ 5 } ?{ 5 } )R26.6 and ( 5 ?{ 2 } ?{ 2 } )R45, probably due to long-range ordering of the alkaline earth metal vacancies in A1 or A2 sites. The Sr/Ba stoichiometry is determined by high-resolution X-ray photoelectron spectroscopy. The Sr 3d core level has 2 components corresponding to the 12- and 15-fold coordinated A1 and A2 sites. The Ba 3d core level has only one component, consistent with the A2 site occupancy. The long-range order of the cation vacancies implies that it is rather the Sr/Ba occupancy of the A2 sites which is responsible for the local random fields at the origin of the relaxor behavior.

  8. 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.

  9. 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

  10. Negative capacitance in a ferroelectric capacitor.

    PubMed

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

    2015-02-01

    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 a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. 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. Analysis of this 'inductance'-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications. PMID:25502099

  11. Ferroelectric memory evaluation and development system

    NASA Astrophysics Data System (ADS)

    Bondurant, David W.

    Attention is given to the Ramtron FEDS-1, an IBM PC/AT compatible single-board 16-b microcomputer with 8-kbyte program/data memory implemented with nonvolatile ferroelectric dynamic RAM. This is the first demonstration of a new type of solid state nonvolatile read/write memory, the ferroelectric RAM (FRAM). It is suggested that this memory technology will have a significant impact on avionics system performance and reliability.

  12. Effect of crystal structure and cationic order on phonon modes across ferroelectric phase transformation in Pb(Fe0.5-xScxNb0.5)O3 bulk ceramics

    NASA Astrophysics Data System (ADS)

    Mallesham, B.; Viswanath, B.; Ranjith, R.

    2016-01-01

    Pb(Fe0.5-xScxNb0.5)O3 [(PFSN) (0 ≤ x ≤ 0.5)] multiferroic relaxors were synthesized and the temperature dependence of phonon modes across ferroelectric to paraelectric transition was studied. With varying Sc content from x = 0 to 0.25 the structure remains monoclinic and with further addition (x = 0.3 - 0.5) the structure transforms into rhombohedral symmetry. Structural refinement studies showed that the change in crystal structure from monoclinic to rhombohedral symmetry involves a volume increment of 34-36%. Associated changes in the tolerance factor (1.024 ≤ t ≤ 0.976) and bond angles were observed. Structure assisted B'-B″ cation ordering was confirmed through the superlattice reflections in selected area electron diffraction (SAED) pattern of Pb(Sc0.5Nb0.5)O3 (x = 0.5). Cation ordering is also evident from the evolution of Pb-O phonon mode in Raman spectra of compositions with rhombohedral symmetry (x ≥ 0.3). The high temperature Raman scattering studies show that the B-localized mode [F1u, ˜250 cm-1] and BO6 octahedral rotational mode [F1g, ˜200 cm-1], both originating from polar nano regions (PNRs) behave like coupled phonon modes in rhombohedral symmetry. However, in monoclinic symmetry they behave independently across the transition. Softening of B localized mode across the transition followed by the hardening for all compositions confirms the diffusive nature of the ferroelectric transformation. The presence of correlation between the B localized and BO6 rotational modes introduces a weak relaxor feature for systems with rhombohedral symmetry in PFSN ceramics, which was confirmed from the macroscopic dielectric studies.

  13. Ferroelectricity in free niobium clusters.

    PubMed

    Moro, Ramiro; Xu, Xiaoshan; Yin, Shuangye; de Heer, Walt A

    2003-05-23

    Electric deflections of gas-phase, cryogenically cooled, neutral niobium clusters [NbN; number of atoms (N) = 2 to 150, temperature (T) = 20to 300kelvin], measured in molecular beams, show that cold clusters may attain an anomalous component with very large electric dipole moments. In contrast, room-temperature measurements show normal metallic polarizabilities. Characteristic energies kBTG(N) [Boltzmann constant kB times a transition temperature TG(N)] are identified, below which the ferroelectric-like state develops. Generally, TG decreases [110 > TG(N) > 10K] as N increases, with pronounced even-odd alternations for N > 38. This new state of metallic matter may be related to bulk superconductivity. PMID:12764191

  14. Fast Switching Ferroelectric Materials for Accelerator Applications

    SciTech Connect

    Kanareykin, A.; Schoessow, P.; Nenasheva, E.; Yakovlev, V.; Dedyk, A.; Karmanenko, S.; Kozyrev, A.; Osadchy, V.; Kosmin, D.; Semenov, A.

    2006-11-27

    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 {approx}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.

  15. Ca doping dependence of resistive switching characteristics in ferroelectric capacitors comprising Ca-doped BiFeO3

    NASA Astrophysics Data System (ADS)

    Liu, Liang; Tsurumaki-Fukuchi, Atsushi; Yamada, Hiroyuki; Sawa, Akihito

    2015-11-01

    We have investigated the transport and ferroelectric properties of ferroelectric capacitors comprising Ca-doped BiFeO3 (BFO) to elucidate the correlation between resistive switching and ferroelectricity. A capacitor consisting of Ca-doped (3.6 at. %) BFO film exhibited polarization-voltage hysteresis, indicating ferroelectricity of the film. As the Ca-doping ratio was increased, the leakage current increased, and zero-crossing hysteretic current-voltage characteristics, i.e., bipolar resistive switching, were observed in capacitors consisting of Ca-doped BFO films with doping ratios of 6.4-13 at. %. A capacitor consisting of a highly Ca-doped BFO (23 at. %) film showed neither resistive switching nor ferroelectric behavior. Distinct changes in the retention and pulsed-voltage-induced resistive switching characteristics were observed around a Ca-doping ratio of 9.0 at. %. The Ca-doping dependence of the resistive switching appeared to correlate with the ferroelectric phase diagram of the Ca-doped BFO films [Yang et al., Nat. Mater. 8, 485 (2009)].

  16. Direct Observation of Ferroelectric Domains in Solution-Processed CH3NH3PbI3 Perovskite Thin Films.

    PubMed

    Kutes, Yasemin; Ye, Linghan; Zhou, Yuanyuan; Pang, Shuping; Huey, Bryan D; Padture, Nitin P

    2014-10-01

    A new generation of solid-state photovoltaics is being made possible by the use of organometal-trihalide perovskite materials. While some of these materials are expected to be ferroelectric, almost nothing is known about their ferroelectric properties experimentally. Using piezoforce microscopy (PFM), here we show unambiguously, for the first time, the presence of ferroelectric domains in high-quality ?-CH3NH3PbI3 perovskite thin films that have been synthesized using a new solution-processing method. The size of the ferroelectric domains is found to be about the size of the grains (?100 nm). We also present evidence for the reversible switching of the ferroelectric domains by poling with DC biases. This suggests the importance of further PFM investigations into the local ferroelectric behavior of hybrid perovskites, in particular in situ photoeffects. Such investigations could contribute toward the basic understanding of photovoltaic mechanisms in perovskite-based solar cells, which is essential for the further enhancement of the performance of these promising photovoltaics. PMID:26278441

  17. Effect of co-substitution of nitrogen and fluorine in BaTiO3 on ferroelectricity and other properties.

    PubMed

    Kumar, Nitesh; Pan, Jaysree; Aysha, N; Waghmare, Umesh V; Sundaresan, A; Rao, C N R

    2013-08-28

    BaTiO3, with both nitrogen and fluorine substituted for oxygen, has been prepared and the properties of the doped material with the composition BaTiO2:8N0:1F0:1 have been studied. The color of the sample changes to light green on doping, accompanying a broad visible absorption band with its edge at 2.5 eV. The first-order ferroelectric transition changes to a broad transition on doping along with a decrease in the dielectric constant. We have examined the local structure, electronic structure and polar lattice dynamical properties of N and F co-substituted BaTiO3 using first-principles density functional theory-based calculations and derived the mechanism of the diffuse ferroelectric transition observed here with a broad peak in the temperature-dependent dielectric response. The calculated Born charges clearly reveal a strong disparity in the interaction of N, O and F with Ti: N being the most ferro-active, with a highly anomalous charge, and F being the least active, with an almost nominal charge. This originates from an electronic structure in which the top-most valence band is constituted of the 2p states of N, while the electronic states of F lie deep in the energy band, resulting in a local structure with short covalent Ti–N and long ionic Ti–F bonds. Disorder in these hetero ferro-active anions leads to a relaxor-like diffuse phase transition and a reduction in polarization. Calculations confirm the reduction of 0.65 eV in the bandgap of BaTiO3, which changes from indirect to direct type. PMID:23912943

  18. Ferroelectric Phase Transitions from First Principles

    NASA Astrophysics Data System (ADS)

    Rabe, Karin M.

    1997-03-01

    For a deeper understanding of structural phase transitions in perovskite-structure oxides, first-principles calculations offer valuable access to microscopic information. With recent advances in algorithms and computational capabilities, structural energetics has been largely met, and high-accuracy density-functional studies for a wide range of perovskite compounds have been presented in the literature. The practical application of these methods to temperature-driven structural transitions involves the construction of an effective Hamiltonian with parameters determined from first-principles calculations. The lattice Wannier function method(K. M. Rabe and U. V. Waghmare, Phys. Rev. B52), 13236 (1995). offers a systematic approach for the construction of first-principles effective Hamiltonians applicable to complex structural transitions involving multiple unstable modes at arbitrary points in the Brillouin zone. The parameters appearing in the LWF effective Hamiltonians for ferroelectric PbTiO3 and antiferroelectric PbZrO3 are obtained from density-functional-theory linear response calculations of phonon frequencies, Z and ?_?, and total-energy calculations using the conjugate-gradients method with optimized pseudopotentials and a plane-wave basis set. The finite-temperature behavior of the model systems is studied using mean field theory and Monte Carlo simulation to yield values of the transition temperature, latent heat and various distribution functions for comparison with experiment. The role of strain coupling in producing the observed transition behavior is investigated. Recent work on the extension to mixed systems will be illustrated by results on Pb_1-xGe_xTe. The use of first-principles effective Hamiltonians to study the temperature dependence of dielectric and piezoelectric response, as well as phonon and domain wall dynamics, will be discussed.

  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. This paves the way for future modeling work of devices that incorporate phase transforming ferroelectrics. Studies on the energy harvesting capabilities of PIN-PMN-PT were conducted to gauge its potential as an energy harvesting material. Using the phase stability data collected in the characterization studies, an ideal energy harvesting cycle was designed and explored to ascertain the maximum energy harvesting density per cycle. The energy harvesting characteristics under non-ideal sinusoidal stress and constant electric load impedance were also investigated. Energy harvesting performance due to changes in loading frequency and electrical load impedance was reported.

  20. Ferroelectric distortions in doped ferroelectrics: BaTiO3:M (M=V-Fe)

    NASA Astrophysics Data System (ADS)

    Chandra, Hirak Kumar; Gupta, Kapil; Nandy, Ashis Kumar; Mahadevan, Priya

    2013-06-01

    A major challenge in the search for multiferroic materials among transition metal compounds has been that ferroelectricity is primarily found in d0 materials while magnetism is found in dn systems. Considering a well-known ferroelectric oxide, namely BaTiO3, the question we asked within a theoretical study was whether ferroelectric distortions disappeared for the slightest amount of doping. Surprisingly, in the case of V-doped BaTiO3, ferroelectricity was found to be stronger than in the undoped limit. Another surprise was that the presence of charged impurities rather than free carriers was found to be most detrimental to the presence of ferroelectric distortions. These ideas of the low doping limit were used to design alternative multiferroics.

  1. 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.

  2. Direct measurement of triaxial strain fields around ferroelectric domains using X-ray microdiffraction

    SciTech Connect

    Rogan, Robert C.; Tamura, Nobumichi; Swift, Geoffrey A.; Ustundag, Ersan

    2003-05-30

    Ferroelectric materials, such as BaTiO{sub 3}, have piezo electric properties that make them attractive for microelectronic and sensing applications. It is well known that the application of mechanical stress or electric field can alter the domain structure inferroelectrics. Indeed, the constitutive behavior of a ferroelectric is largely governed by the formation, movement and interact ion of its domains. Therefore, it is crucial that the micro mechanics of domains and their effect on internal stresses in ferroelectrics be understood. Here we show that the emerging technique of scanning X-ray micro diffraction can be used to measure directly, for the first time, the local triaxial strain fields around 90 degrees domains in single-crystal BaTiO{sub 3}. Specifically, residuals train maps in a region surrounding an isolated, approximately 40 {micro}m wide, 90 degrees domain were obtained with 3 {micro}m resolution, revealing significant residual strains. This information is critical for accurate micromechanical modeling of domain behavior in ferroelectrics.

  3. Silver-modified nanosized ferroelectrics as a novel photocatalyst.

    PubMed

    Su, Ran; Shen, Yajing; Li, Linglong; Zhang, Dawei; Yang, Guang; Gao, Chuanbo; Yang, Yaodong

    2015-01-14

    Monodispersed ferroelectric BaTiO3 nanoparticles are synthesized as a model system to investigate the effect of ferroelectricity on a photocatalytic process. The results demonstrate that ferroelectricity can directly affect the photocatalytic activity due to promotion of the separation of photo-excited carriers by spontaneous polarization in ferroelectric materials. Moreover, Ag nanoparticles are attached on these BaTiO3 to further improve the photocatalytic property. PMID:25186805

  4. Influence of interfacial dislocations on hysteresis loops of ferroelectric films

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Choudhury, S.; Baskes, Michael I.; Saxena, A.; Lookman, T.; Jia, Q.X.; Schlom, Darrell G.; Chen , L.Q.

    2008-11-15

    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.

  5. 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 technologies for renewable and hydrogen energy, fuel cells, photovoltaics, LEDs, OLEDs. Based on these reports, 48 papers are included in this volume of IOP Conference Series: Materials Science and Engineering. Additional information about RCBJSF-2014-FM&NT is available at the homepage http://www.fmnt.lu.lv. The Organizing Committee would like to thank all the speakers, contributors, session chairs, referees and other involved staff for their efforts in making the RCBJSF-2014-FM&NT successful. Sincerely, organizers of the event Andris Sternberg Liga Grinberga Anatolijs Sarakovskis Martins Rutkis

  6. 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.

  7. Temperature-dependent phonon Raman scattering and spectroscopic ellipsometry of pure and Ca-doped Sr x Ba1?x Nb2O6 ferroelectric ceramics across the phase transition region

    NASA Astrophysics Data System (ADS)

    Peng, Liang; Jiang, Kai; Zhang, Jinzhong; Hu, Zhigao; Wang, Genshui; Dong, Xianlin; Chu, Junhao

    2016-01-01

    Optical phonons and the phase transition of relaxor ferroelectric ceramics Sr x Ba1?x Nb2O6 (SBN) and Ca y (Sr0.5Ba0.5)1?y Nb2O6 (CSBN) with different composition (0.3?slant x?slant 0.5 , 0.1?slant y?slant 0.2 ) have been investigated by variable-temperature Raman scattering and spectroscopic ellipsometry. The anomalous temperature dependence of Tauc gap energy (E t ) is used to fit the phonon energy dependence of the permittivity, and the Raman intensity of some interesting optical phonons can be ascribed to the phase transition from a ferroelectric to a paraelectric structure. The Curie temperature of SBN decreases from 556 to 359 K with increasing Sr composition, which can be attributed to the substitution of smaller Sr2+?for Ba2+. On increasing the Ca composition, however, the phase transition temperature of CSBN remains nearly unchanged at about 350 K. This could be due to the fact that most doped Ca2+ ions move into the oxygen ion site and exhibit no obvious effect on the vibrational properties. Therefore, the general disorder which results from Sr2+ substituting Ba2+?, dominates the phase transition process for SBN-based ferroelectric oxides. Meanwhile, the dielectric functions from 200 to 600 K have been evaluated with the aid of the TaucLorentz model. The electronic transition is located at about 5?eV and decreases with increasing temperature for all the samples. Moreover, the phase transition temperature range derived from the spectroscopic ellipsometry agrees well with that from the Raman scattering. It reveals that the variation of the fundamental energy gap may be associated with the phase transition of SBN ceramics. Both Raman scattering and spectroscopic ellipsometry are proven to be a effective method of exploring the phase transition of ferroelectric oxides.

  8. Ab initio design of charge-mismatched ferroelectric superlattices

    NASA Astrophysics Data System (ADS)

    Cazorla, Claudio; Stengel, Massimiliano

    2014-07-01

    We present a systematic approach to modeling the electrical and structural properties of charge-mismatched superlattices from first principles. Our strategy is based on bulk calculations of the parent compounds, which we perform as a function of in-plane strain and out-of-plane electric displacement field. The resulting two-dimensional phase diagrams allow us to accurately predict, without performing further calculations, the behavior of a layered heterostructure where the aforementioned building blocks are electrostatically and elastically coupled, with an arbitrary choice of the interface charge (originated from the polar discontinuity) and volume ratio. By using the [PbTiO3]m/[BiFeO3]n system as test case, we demonstrate that interface polarity has a dramatic impact on the ferroelectric behavior of the superlattice, leading to the stabilization of otherwise inaccessible bulk phases.

  9. 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}.

  10. Lattice dynamics and ferroelectric instability of PZT from first principles

    NASA Astrophysics Data System (ADS)

    Bungaro, Claudia; Rabe, Karin M.

    2001-03-01

    The lattice dynamics of the prototypical cubic perovskite structure has long been considered central to the understanding of the ferroelectric and piezoelectric behavior of perovskite oxides. In solid solutions such as PZT, compositional disorder greatly complicates the theoretical study of the lattice dynamics. The virtual crystal approximation (VCA) is an easily implemented approach to the calculation of interatomic force constants (IFC) in solid solutions; however, as shown by comparison with full ab-initio calculations for ordered alloy configurations, it provides a poor description of the lattice dynamics of PZT. An alternative ab-initio based approach, proposed in [1], is to transfer the IFC's computed for the endpoint compounds to the solid solution. We will present results of the application of this approach to PZT and discuss the implications for effective Hamiltonian simulations of finite-temperature behavior. 1. Ph. Ghosez, E. Cockayne, U. V. Waghmare and K. M. Rabe, Phys. Rev. B60, 836 (1999).

  11. 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(VDF-TrFE) ferroelectric capacitor for a one-transistor-one-capacitor (1T1C) memory cell. The 1T1C devices were fabricated at low temperature and demonstrated a memory window (DeltaVBL) of 2.3 V and 3.5 V, depending on the device dimensions. Next, FRAM arrays (4-bit, 16-bit and 64-bit) based on the two-transistor-two-capacitor (2T2C) memory cell architecture were designed and fabricated using a photolithographic process with 9 masks. The fabricated FRAM arrays were packaged in 28-pin ceramic packages. The read/write schemes were developed and the FRAM arrays show successful program and erase with a memory window of approximately 1 V at the output of the sense amplifier.

  12. 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

  13. Ferroelectricity in the multiferroic hexagonal manganites

    NASA Astrophysics Data System (ADS)

    Lilienblum, Martin; Lottermoser, Thomas; Manz, Sebastian; Selbach, Sverre M.; Cano, Andres; Fiebig, Manfred

    2015-12-01

    Since their discovery in 1963 the hexagonal manganites have consolidated their role as exotic ferroelectrics with astonishing functionalities. Their introduction as room-temperature device ferroelectrics was followed by observations of giant flexoelectricity, multiferroicity with magnetoelectric domain and domain-wall coupling, protected vortex domain structures, topological domain-scaling behaviour and domain walls with tunable conductance and magnetism. Even after half a century, however, the emergence of the ferroelectric state has remained the subject of fierce debate. We resolve the interplay of electric polarization, topological trimerization and temperature by direct access to the polarization for temperatures up to 1,400 K. Nonlinear optical experiments and piezoresponse force microscopy, complemented by Monte Carlo simulations, reveal a single phase transition with ferroelectricity determined by topology rather than electrostatics. Fundamental properties of the hexagonal manganites, including an explanation for the two-phase-transition controversy as a finite-size scaling effect, are derived from this and highlight why improper ferroelectrics are an inherent source of novel functionalities.

  14. Structural phase diagram and pyroelectric properties of free-standing ferroelectric/non-ferroelectric multilayer heterostructures

    NASA Astrophysics Data System (ADS)

    Zhang, Jialan; Agar, Josh C.; Martin, Lane W.

    2015-12-01

    Ginzburg-Landau-Devonshire models are used to explore ferroelectric phases and pyroelectric coefficients of symmetric free-standing, thin-film trilayer heterostructures composed of a ferroelectric and two identical non-ferroelectric layers. Using BaTiO3 as a model ferroelectric, we explore the influence of temperature, in-plane misfit strain, and the non-ferroelectric layer (including effects of elastic compliance and volume fraction) on the phase evolution in the ferroelectric. The resulting phase diagram reveals six stable phases, two of which are not observed for thin films on semi-infinite cubic substrates. From there, we focus on heterostructures with non-ferroelectric layers of commonly available scandate materials which are widely used as substrates for epitaxial growth. Again, six phases with volatile phase boundaries are found in the phase diagram for the NdScO3/BaTiO3/NdScO3 trilayerheterostructures. The evolution of polarization and pyroelectric coefficients in the free-standing NdScO3 trilayer heterostructures is discussed with particular attention to the role that heterostructure design plays in influencing the phase evolution and temperature-dependence with a goal of creating enhanced pyroelectric response and advantages over traditional thin-film heterostructures.

  15. Tensile strain effect in ferroelectric perovskite oxide thin films on spinel magnesium aluminum oxide substrate

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaolan

    Ferroelectrics are used in FeRAM (Ferroelectric random-access memory). Currently (Pb,Zr)TiO3 is the most common ferroelectric material. To get lead-free and high performance ferroelectric material, we investigated perovskite ferroelectric oxides (Ba,Sr)TiO3 and BiFeO3 films with strain. Compressive strain has been investigated intensively, but the effects of tensile strain on the perovskite films have yet to be explored. We have deposited (Ba,Sr)TiO3, BiFeO3 and related films by pulsed laser deposition (PLD) and analyzed the films by X-ray diffractometry (XRD), atomic force microscopy (AFM), etc. To obtain inherently fully strained films, the selection of the appropriate substrates is crucial. MgAl2O4 matches best with good quality and size, yet the spinel structure has an intrinsic incompatibility to that of perovskite. We introduced a rock-salt structure material (Ni 1-xAlxO1+delta) as a buffer layer to mediate the structural mismatch for (Ba,Sr)TiO3 films. With buffer layer Ni1-xAlxO1+delta, we show that the BST films have high quality crystallization and are coherently epitaxial. AFM images show that the films have smoother surfaces when including the buffer layer, indicating an inherent compatibility between BST-NAO and NAO-MAO. In-plane Ferroelectricity measurement shows double hysteresis loops, indicating an antiferroelectric-like behavior: pinned ferroelectric domains with antiparallel alignments of polarization. The Curie temperatures of the coherent fully strained BST films are also measured. It is higher than 900C, at least 800C higher than that of bulk. The improved Curie temperature makes the use of BST as FeRAM feasible. We found that the special behaviors of ferroelectricity including hysteresis loop and Curie temperature are due to inherent fully tensile strain. This might be a clue of physics inside ferroelectric stain engineering. An out-of-plane ferroelectricity measurement would provide a full whole story of the tensile strain. However, a well suited electrode material that is both conducting, and full strained on the MgAl2O4 substrate is quite rare. We will supply some answers to this unique problem. XRD results show that Ni1-xAlxO1+delta (x=0.3, 0.4 & 0.5) film, although highly mixed with Al2O3, still takes rock-salt structure and is grown very well on the spinel MgAl 2O4 substrate, with perfect crystallization and a smooth surface. Ni0.7Al0.3O1+ delta and Ni 0.6Al0.4O1+ delta are good buffer layers for perovskite film on spinel MgAl2O4 substrate. Ni 0.5Al0.5O1+ delta could also be a good buffer layer. The structural transition from rock-salt to spinel was found at x=0.67. Tensile strain effects from thermal expansion difference of BiFeO3 films were found. Thermal expansion difference caused strain does not change the ferroelectric property greatly, due to film relaxation. BiFeO3 film with NAO buffer exhibit much larger strain.

  16. 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.

  17. Structural stability and depolarization of manganese-doped (Bi0.5Na0.5)1-xBaxTiO3 relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-Fen; Tu, Chi-Shun; Chang, Ting-Lun; Chen, Pin-Yi; Chen, Cheng-Sao; Hugo Schmidt, V.; Anthoniappen, J.

    2014-10-01

    This work reveals that 0.5 mol. % manganese (Mn) doping in (Bi0.5Na0.5)1-xBaxTiO3 (x = 0 and 0.075) solid solutions can increase structural thermal stability, depolarization temperature (Td), 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 (?') follows the Curie-Weiss equation, ?' = C/(T - To), 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%.

  18. 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 ?5 and ?3 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.

  19. Structural stability and depolarization of manganese-doped (Bi?.?Na?.?){sub 1?x}Ba{sub x}TiO? 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 (Bi?.?Na?.?){sub 1?x}Ba{sub x}TiO? (x?=?0 and 0.075) solid solutions can increase structural thermal stability, depolarization temperature (T{sub d}), piezoelectric coefficient (d??), and electromechanical coupling factor (k?). High-resolution X-ray diffraction and transmission electron microscopy reveal coexistence of rhombohedral (R) R3c and tetragonal (T) P4bm phases in (Bi?.?Na?.?)?.???Ba?.???TiO? (BN7.5BT) and 0.5?mol. % Mn-doped BN7.5BT (BN7.5BT-0.5Mn). (Bi?.?Na?.?)TiO? (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 (??) follows the Curie-Weiss equation, ???=?C/(T???T{sub o}), above the Burns temperature (TB), below which polar nanoregions begin to develop. The direct piezoelectric coefficient (d??) and electromechanical coupling factor (k?) of BN7.5BT-0.5Mn reach 190 pC/N and 47%.

  20. Monoclinic Cc-phase stabilization in magnetically diluted lead free Na1/2Bi1/2TiO3Evolution 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 ?C cm-2 to 45 ?C 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 (?) from ? ? 42 to 60 along with enhanced diffusivity from ? ? 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.

  1. Uncooled monolithic ferroelectric IRFPA technology

    NASA Astrophysics Data System (ADS)

    Belcher, James F.; Hanson, Charles M.; Beratan, Howard R.; Udayakumar, K. R.; Soch, Kevin L.

    1998-10-01

    Once relegated to expensive military platforms, occasionally to civilian platforms, and envisioned for individual soldiers, uncooled thermal imaging affords cost-effective solutions for police cars, commercial surveillance, driving aids, and a variety of other industrial and consumer applications. System prices are continuing to drop, and swelling production volume will soon drive prices substantially lower. The impetus for further development is to improve performance. Hybrid barium strontium titanate (BST) detectors currently in production are relatively inexpensive, but have limited potential for improved performance. The MTF at high frequencies is limited by thermal conduction through the optical coating. Microbolometer arrays in development at Raytheon have recently demonstrated performance superior to hybrid detectors. However, microbolometer technology lacks a mature, low-cost system technology and an abundance of upgradable, deployable system implementations. Thin-film ferroelectric (TFFE) detectors have all the performance potential of microbolometers. They are also compatible with numerous fielded and planned system implementations. Like the resistive microbolometer, the TFFE detector is monolithic; i.e., the detector material is deposited directly on the readout IC rather than being bump bonded to it. Imaging arrays of 240 X 320 pixels have been produced, demonstrating the feasibility of the technology.

  2. Piezoelectricity and ferroelectricity of cellular polypropylene electrets films characterized by piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Miao, Hongchen; Sun, Yao; Zhou, Xilong; Li, Yingwei; Li, Faxin

    2014-08-01

    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 d33 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.

  3. 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.

  4. Multiferroics: a magnetic twist for ferroelectricity

    NASA Astrophysics Data System (ADS)

    Cheong, Sang-Wook; Mostovoy, Maxim

    2007-01-01

    Magnetism and ferroelectricity are essential to many forms of current technology, and the quest for multiferroic materials, where these two phenomena are intimately coupled, is of great technological and fundamental importance. Ferroelectricity and magnetism tend to be mutually exclusive and interact weakly with each other when they coexist. The exciting new development is the discovery that even a weak magnetoelectric interaction can lead to spectacular cross-coupling effects when it induces electric polarization in a magnetically ordered state. Such magnetic ferroelectricity, showing an unprecedented sensitivity to ap plied magnetic fields, occurs in 'frustrated magnets' with competing interactions between spins and complex magnetic orders. We summarize key experimental findings and the current theoretical understanding of these phenomena, which have great potential for tuneable multifunctional devices.

  5. 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

  6. Vortex Domains in Ferroelectric Nano-Structures

    NASA Astrophysics Data System (ADS)

    Scott, James F.

    2011-03-01

    Recently the study of submicron-diameter ferroelectric disks and squares and rectangles fabricated from films of ca. 100-300 nm thick have revealed usual domain patterns, qualitatively different from the stripe domains commonly studied in macroscopic specimens in the past. These include doughnut-shaped domains, four-fold vertex closure domains, and fractal domains. The static configurations offer a variety of puzzles, and the structures differ from those in magnetic vortex domains, presumably due to the much larger anisotropy in ferroelectrics, which generally prohibits true vortex configurations with polarization forced out of plane. The dynamics also differ qualitatively from early studies: For decades ferroelectrics were thought to be highly Ising-like, but recent data and theoretical simulations favor Bloch walls and more Heisenberg-like kinetics. This talk will include data from Alina Schilling and Marty Gregg in Belfast, Marin Alexe in Halle, and modeling from Hlinka and Marton in Prague and Bellaiche and Prosandeev in Arkansas.

  7. 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

  8. Thermal depoling of high Curie point Aurivillius phase ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Yan, Haixue; Zhang, Hongtao; Reece, Michael J.; Dong, Xianlin

    2005-08-01

    The thermal depoling behavior of several different Aurivillius phase ferroelectric ceramics has been studied. This includes two-layer (CaBi2Nb2O9,Ca0.9Ba0.1Bi2Nb2O9,Bi3NbTiO9,Bi3Nb1.2Ti0.8O9), three-layer (Bi4Ti3O12), and four-layer [CaBi4Ti4O15,Ca0.94(Na,Ce)0.03Bi4Ti4O15] compounds. All of them have a high Curie point (Tc?675C). The orthorhombic structured materials show good resistance to thermal depoling up to temperatures close to their Curie points. However, Bi4Ti3O12, which has a monoclinic structure, shows a significant reduction in d33 well before its Curie point. The monoclinic distortion produces more non-180 ferroelectric domain structures, and it is the thermal instability of these that accounts for their thermal depoling behaviour. Excess Nb doping of Bi3NbTiO9 produces a significant reduction in its resistance to thermal depoling, suggesting that the doping produces a lowering of the crystallographic symmetry.

  9. 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

  10. Complex Internal Bias Fields in Ferroelectric Hafnium Oxide.

    PubMed

    Schenk, Tony; Hoffmann, Michael; Ocker, Johannes; Pei?, Milan; Mikolajick, Thomas; Schroeder, Uwe

    2015-09-16

    For the rather new hafnia- and zirconia-based ferroelectrics, a lot of questions are still unsettled. Among them is the electric field cycling behavior consisting of (1) wake-up, (2) fatigue, and (3) the recently discovered subcycling-induced split-up/merging effect of transient current peaks in a hysteresis measurement. In the present work, first-order reversal curves (FORCs) are applied to study the evolution of the switching and backswitching field distribution within the frame of the Preisach model for three different phenomena: (1) The pristine film contains two oppositely biased regions. These internal bias fields vanish during the wake-up cycling. (2) Fatigue as a decrease in the number of switchable domains is accompanied by a slight increase in the mean absolute value of the switching field. (3) The split-up effect is shown to also be related to local bias fields in a complex situation resulting from both the field cycling treatment and the measurement procedure. Moreover, the role of the wake-up phenomenon is discussed with respect to optimizing low-voltage operation conditions of ferroelectric memories toward reasonably high and stable remanent polarization and highest possible endurance. PMID:26308500

  11. Theoretical and experimental investigations of polarization switching in ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Picinin, A.; Lente, M. H.; Eiras, J. A.; Rino, J. P.

    2004-02-01

    The polarization switching process is certainly the most important feature of ferroelectric materials from fundamental as well as practical points of view. In this paper, a one-dimensional lattice model is presented in order to describe the polarization switching process in ferroelectric materials, incorporating the contribution of both dipolar defects and depolarizing fields to the domain reorientation. The influence of the interaction strength between switchable dipoles and dipolar defects, the medium viscosity, the depolarizing fields, and the frequency of the external electric field on the polarization switching were simulated. It was found that the degree of interaction between domains and dipolar defects has a strong influence on the coercive field, polarization, and backswitching behavior. Through an adequate analysis of the variables in the model it was also possible to describe the evolution of the polarization switching with the number of electric field cycles, which is commonly observed in the fatigue or depinning process. Comparison between simulated and experimental results revealed a remarkable concordance.

  12. Macroscopic description of nonlinear electromechanical coupling in ferroelectrics

    NASA Astrophysics Data System (ADS)

    Kamlah, Marc; Boehle, Ulrich; Munz, Dietrich; Tsakmakis, Ch.

    1997-06-01

    As in many cases piezoelectric devices are made of PZT, it is our objective to incorporate the nonlinearly coupled electro-mechanical behavior of ferroelectric PZT-ceramics into a finite element tool for reliability analyses. In this paper, we will present a phenomenological model for ferroelectrics which is conceived to be valid for complex electro-mechanical loading histories and simple enough to be implemented with acceptable effort in an FE-code. This has been achieved by introducing irreversible polarization and irreversible strain as internal variables besides stress, strain, electric field and polarization. The internal variables represent the loading history and are governed by ordinary differential equations. Each of these evolution equations is subjected to two loading conditions differing in nature. The first indicates the onset of irreversible change by domain switching, while the second characterizes the maximum amount of possible irreversible change corresponding to a totally switched domain structure. Polarization induced anisotropy is taken into account to the extent deemed necessary. For sake of simplicity, no rate effects are included. The model response to uniaxial electro-mechanical loading histories will be discussed and compared to known experimental results. By bilinear approximation the following characteristic macroscopic phenomena of PZT-ceramics can be represented: dielectric hysteresis, polarization induced piezoelectricity, butterfly hysteresis, ferroelastic hysteresis, mechanical depolarization, field dependent coercitive stress.

  13. Diisopropylammonium bromide is a high-temperature molecular ferroelectric crystal.

    PubMed

    Fu, Da-Wei; Cai, Hong-Ling; Liu, Yuanming; Ye, Qiong; Zhang, Wen; Zhang, Yi; Chen, Xue-Yuan; Giovannetti, Gianluca; Capone, Massimo; Li, Jiangyu; Xiong, Ren-Gen

    2013-01-25

    Molecular ferroelectrics are highly desirable for their easy and environmentally friendly processing, light weight, and mechanical flexibility. We found that diisopropylammonium bromide (DIPAB), a molecular crystal processed from aqueous solution, is a ferroelectric with a spontaneous polarization of 23 microcoulombs per square centimeter [close to that of barium titanate (BTO)], high Curie temperature of 426 kelvin (above that of BTO), large dielectric constant, and low dielectric loss. DIPAB exhibits good piezoelectric response and well-defined ferroelectric domains. These attributes make it a molecular alternative to perovskite ferroelectrics and ferroelectric polymers in sensing, actuation, data storage, electro-optics, and molecular or flexible electronics. PMID:23349285

  14. Ferroelectric Properties of Ultrathin Perovskite Heterostructures.

    NASA Astrophysics Data System (ADS)

    Junquera, Javier

    2004-03-01

    Due to their switchable spontaneous polarization, ferroelectric thin films can be used in non-volatile ferroelectric random access memories (FeRAMs). Recently, 30 Gbit/cm^2 data storage densities have been demonstrated for Pb(Zr_0.2Ti_0.8)O3 films on a metallic oxide electrode (T. Tybell et al.), Phys. Rev. Lett. 89, 097601 (2002). While industry's demands for ultrahigh density information storage imposes a reduction of the cell-sizes and thicknesses of the ferroelectric thin films, fundamental questions concerning thickness dependence of ferroelectricity and related properties becomes crucial. Using a first-principles density-functional-theory approach (J. M. Soler et al.), J. Phys.: Condens. Matter 14, 2745 (2002) we have simulated the behaviour at 0 K of a typical ferroelectric capacitor epitaxially grown on a SrTiO3 substrate and made of an ultrathin film of BaTiO3 in between two SrRuO3 electrodes in short circuit (J. Junquera and Ph. Ghosez, Nature 422), 506 (2003). Both the electrical and the mechanical boundary conditions were properly considered in the calculations. We predict the existence of a critical thickness for ferroelectricity of about six unit cells (26 Ang), and relate it to an incomplete screening of the depolarizing field by real metallic electrodes. Transposing these ideas into a first-principles-based model Hamiltonian, (U. V. Waghmare and K. M. Rabe, Phys. Rev. B 55), 6161 (1997) and using Monte Carlo simulations, we have analyzed the temperature dependence of the thickness evolution of the polarization and tetragonality of the samples, as well as the piezoelectric and dielectric tensors. Our theoretical results show good agreement with very recent experimental measurements.

  15. Ferroelectrics Nonlinearity to Realize Chaotic Circuits

    NASA Astrophysics Data System (ADS)

    Fortuna, L.; Frasca, M.; Graziani, S.

    2003-08-01

    In this paper the possibility of observing chaotic behaviour in an electronic circuit including a nonlinear ferroelectrics has been investigated. The ferroelectrics constitutes the medium interposed between the two plates of a capacitor, and is obtained by successive vapour deposition of Strontium, Tantalum and Bismuth on Platinum substrates in small areas. The device is characterized by a nonlinear hysteretic behaviour observed by estimating the output voltage by using a Sawyer-Tower configuration. Different circuits showing chaos and based on hysteretic behaviour of the nonlinearities have been reported in literature. In particular, in the circuit reported in [1] the nonlinearity consists of a piecewise linear resistor, only the two tracts with positive slope are effectively involved in the dynamics and an hysteretic behaviour switching between these two linear segments of the nonlinearity can be addressed as responsible of the emergence of iperchaos in the circuit. Starting from the chaos generator reported in [1], the following dimensionless equations have been developed: where f(x) is the nonlinearity due to the hysteresis of the ferroelectrics capacitor. The functional f(x) constitutes a simple model of the ferroelectrics device and is defined by two functions (the upper curve and the lower curve based on experimental data on the ferroelectrics). Chaotic solutions of system (1) were searched for, by performing numerical integration with respect to different values of the parameters. Finally, the circuit implementing equations (1) has been realized. Experimental results show that for a suitable range of parameter a chaotic attractor emerges. Fig. 1 shows the projection of the attractor onto the phase plane x1-x2. The paper addresses the possibility of exploiting the rich dynamics of ferroelectrics hysteresis to obtain new chaotic attractors with low cost circuits.

  16. Scanning pyroelectric microscopy for characterizing large-area printed ferroelectric sensors on the nanoscale

    NASA Astrophysics Data System (ADS)

    Stadlober, Barbara; Groten, Jonas; Zirkl, Martin; Haase, Anja; Sawatdee, A.; Scheipl, G.

    2012-10-01

    This work demonstrates a novel surface scanning method for the quantitative determination of the local pyroelectric coefficient in ferroelectric thin films. Such films find application in flexible and large-area printed ferroelectric sensors for gesture-controlled non-touch human-machine interface devices. The method is called Pyroelectric Scanning Probe Microscopy (PyroSPM)[1] and allows generating a map of the pyroelectric response with very high spatial resolution. In domains of previously aligned dipole moments small heat fluctuations are achieved by laser diode excitation from the bottom side thus inducing changes in the surface potential due to the pyroelectric effect. Simultaneously, the surface potential variations are detected by scanning surface potential microscopy thus forming the base for the pyroelectric coefficient map. The potential of the method is demonstrated on the basis of ferroelectric semi-crystalline copolymer thin films yielding local maxima of the pyroelectric coefficients around 40C/m2K. Another promising feature of PyroSPM is the ability to visualize "screened" polarization thus enabling in-depth profiling of polarization distributions and domain formation and to study the composition dependence and the time and frequency behavior of ferroelectric nano-domains.

  17. Investigation of the dielectric response in PbNb2O6 ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Leyet, Y.; Guerrero, F.; de Los S. Guerra, J.; Venet, M.; Eiras, J. A.

    2007-03-01

    High Curie temperature ferroelectrics are promising materials to construct transducers for high-temperature piezoelectric applications. Among them, the lead niobate system is one that displays such characteristic. In this work, the dielectric behavior of lead niobate ferroelectric ceramics was analyzed in the frequency range of 20 Hz-2 GHz. Ceramic samples with nominal formula PbNb2O6 (PN) were prepared by the solid-state reaction method. The phase transition was investigated with the Santos-Eiras' phenomenological model. The values of the parameter, which determine the phase transition character (?), are close to 1, indicating a conventional ferroelectric phase transition. The PN materials showed two different dispersion processes: (1) a typical high-frequency dispersion process, which may be associated with the polar region boundaries dynamics, as observed in ferroelectric materials in the microwave frequency region, and (2) that associated with the charge carrier conduction, observed in the lowest frequencies and high-temperature region. An additional dispersion process, in the intermediate frequency range (around 2 MHz), was identified, which may be related to the overlapping between both the normal dipolar process (characteristic of the dipolar materials) and the strong low-frequency conductive process.

  18. Electrical properties of NaSr2Nb5O15 ferroelectric ceramic

    NASA Astrophysics Data System (ADS)

    Behera, Banarji; Pradhan, Nihar; Nayak, P.

    2012-02-01

    Since the discovery of ferroelectricity, tungsten bronze (TB) ferroelectrics has been a rapid progress in search of new TB-type materials for applications such as capacitors, actuators, transducers, ferroelectric random access memory and display technologies. The materials with TB structure have potential advantages for devices because of their high dielectric constant and low tangent loss. In view of the above importance we have studied the electrical properties of NaSr2Nb5O15 (NSN) ferroelectric ceramic. The polycrystalline NaSr2Nb5O15 (NSN) was prepared by mixed oxide method at high temperature. Electrical properties of NSN have been studied using complex impedance spectroscopy (CIS) with wide range of frequency (10^2-10^6 Hz) and temperature. The complex impedance plot reveals the main contribution of bulk effect. The bulk resistance has been decreased with rise in temperature. The negative temperature coefficient of resistance (NTCR) manifests a semiconductor like behavior. The ac conductivity spectrum was found to obey Jonscher's universal power law.

  19. 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.

  20. Reversible chemical switching of a ferroelectric film.

    SciTech Connect

    Wang, R. V.; Fong, D. D.; Jiang, F.; Highland, M. J.; Fuoss, P. H.; Thompson, C.; Kolpak, A. M.; Eastman, J. A.; Streiffer, S. K.; Rappe, A. M.; Stephenson , G. B.; Northern Illinois Univ.; Univ. of Pennsylvania

    2009-01-01

    According to recent experiments and predictions, the orientation of the polarization at the surface of a ferroelectric material can affect its surface chemistry. Here we demonstrate the converse effect: the chemical environment can control the polarization orientation in a ferroelectric film. In situ synchrotron x-ray scattering measurements show that high or low oxygen partial pressure induces outward or inward polarization, respectively, in an ultrathin PbTiO{sub 3} film. Ab initio calculations provide insight into surface structure changes observed during chemical switching.

  1. 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.

  2. 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.

  3. Ultra-High-Density Ferroelectric Memories

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita

    1995-01-01

    Features include fast input and output via optical fibers. Memory devices of proposed type include thin ferroelectric films in which data stored in form of electric polarization. Assuming one datum stored in region as small as polarization domain, sizes of such domains impose upper limits on achievable storage densities. Limits approach 1 terabit/cm(Sup2) in all-optical versions of these ferroelectric memories and exceeds 1 gigabit/cm(Sup2) in optoelectronic versions. Memories expected to exhibit operational lives of about 10 years, input/output times of about 10 ns, and fatigue lives of about 10(Sup13) cycles.

  4. 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. Cantarero (University of Valencia, Spain), K.J. Choi, D.M. Kim, C.-B. Eom (University of Wisconsin), H.P. Sun, X.Q. Pan (University of Michigan), S.M. Nakhmanson; K.M. Rabe (Rutgers University), Q.X. Jia (Los Alamos National Laboratory)

  5. High-order face-shear modes of relaxor-PbTiO3 crystals for piezoelectric motor applications

    NASA Astrophysics Data System (ADS)

    Ci, Penghong; Liu, Guoxi; Chen, Zhijiang; Zhang, Shujun; Dong, Shuxiang

    2014-06-01

    The face-shear vibration modes of [011] poled Zt 45 cut relaxor-PT crystals and their applications for linear piezoelectric motors were investigated. Unlike piezoelectric ceramics, the rotated crystal was found to exhibit asymmetric face-shear deformations, and its two high-order face-shear modes degraded into two non-isomorphic modes. As an application example, a standing wave ultrasonic linear motor (10 10 2 mm3) operating in high-order face-shear vibration modes was developed. The motor exhibits a large driving force (1.5 N) under a low driving voltage (22 Vpp). These findings could provide guidance for design of crystal resonance devices.

  6. 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.

    2015-01-01

    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.

  7. 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%.

  8. 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.

  9. 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.

  10. Study of microstructural behavior and nonadiabatic small polaron hopping conduction in BaTiO3 doped lead-vanadate glass and glass-ceramics dispersed with ferroelectric nanocrystals

    NASA Astrophysics Data System (ADS)

    Sadhukhan, Manisha; Modak, D. K.; Chaudhuri, B. K.

    1999-04-01

    Multicomponent semiconducting oxide glasses like (80 V2O5-20 PbO)+xBaTiO3 (x=5-30 wt %) dispersed with nanocrystalline BaTiO3 have been prepared by a fast quenching technique. Results of microstructural study and transport properties (between 80 and 450 K) of these glasses and some glass ceramics have been reported in this article. It has been shown from x-ray diffraction, scanning electron microscopic, and other studies that homogeneous glasses are formed with wide concentrations of BaTiO3 (x?30 wt %). Transmission electron microscopic study, however, indicates the presence of nanocrystalline phases in the glass matrix. Mott's variable range (nonadiabatic) hopping conduction mechanism is found to be valid at the low temperature regime (below ?D/4, ?D being the Debye temperature) while in the high temperature regime (above ?D/2), the polaron hopping models of Schnakenberg as well as Emin and co-workers can quantitatively predict the conductivity data for all these special types of multicomponent glass-nanocrystal composites. The model parameters, obtained from best fit of the experimental data with these models, are consistent with the glass compositions. The dielectric constants of these glasses are found to be very high (comparable to that of bulk BaTiO3) and about two orders of magnitude higher than those of BaTiO3 free (80 V2O5-20 PbO) and other transition metal oxide glasses. This novel character is considered to be due to the embedded nanocrystalline BaTiO3 phases. The glass samples annealed at 300 C for 9 h in air also showed nano and microcrystalline BaTiO3 phase along with traces of PbV2O6, PbTiO3, TiO2, and Pb2V2O7 phases. Broad anomaly (with a maximum around 390 K) is observed from the thermal variation of dielectric constant data of these partially annealed glass-ceramic samples. This anomaly resembles to the anomaly observed around the Curie temperature (393 K) in bulk ferroelectric BaTiO3 crystal.

  11. Grain surface polarization: ferroelectric mantles?

    NASA Astrophysics Data System (ADS)

    Cassidy, A. M.; Balog, R.; Field, D.; Jones, N.; Plekan, O.

    2011-05-01

    Recent experiments have shown that films of molecules such as nitrous oxide, propane etc. spontaneously harbour very high electric fields exceeding 108 Vm-11 . This arises through dipole alignment with polarization at the film surface, giving rise to large voltages at the surface. Potentials are measured with a cold electron beam technique using the ASTRID synchrotron at Aarhus. The electric field within the film is constant. Since a spontaneous field is generated the films show ferroelectric properties. Figure 1 shows the amount of potential added per added monolayer (ML) of material, in this case on a gold surface. The absolute value of potential and the field generated is independent of the nature of the surface. If we assume the 'standard' onion skin model of mantle accretion on grains, then the outer layer of grains will be composed of almost pure CO. If a large fraction of CO is adsorbed into the mantle, as is the case in B682, the mantle of pure CO will be typically 10-100 MLs thick. We mark, in Figure 1, the position of CO with respect to dipole moment. It would therefore seem highly probable that CO would show dipole alignment, although we have not yet been able to measure this for the purely technical reason that our apparatus will not operate below 38K and CO requires 22K to condense. Thus the surface of such grains would show a positive potential, given that the O-atom sticks up (McCoustra, private communication). The polarization on the surface is expected to be >10-4 Cm-2, giving 75 apparent charges on a 0.1 micron radius grain, which will decay as electrons are captured. Coupled with an electric field within the CO ice mantle of > 10^7 Vm-1, this may have interesting implications in grain properties and their associated chemistry. This will be discussed in our contribution.

  12. Confinement of ferroelectric domain-wall motion at artificially formed conducting-nanofilaments in epitaxial BiFeO3 thin films.

    PubMed

    Kim, Woo-Hee; Son, Jong Yeog; Jang, Hyun Myung

    2014-05-14

    We report confinement of ferroelectric domain-wall motion at conducting-nanofilament wall in epitaxial BiFeO3 thin film on Nb-doped SrTiO3 substrate. The BiFeO3 film exhibited well-defined ferroelectric response and unipolar resistive switching behavior. We artificially formed conducting-nanofilaments in the BiFeO3 via conducting atomic force microscope techniques. The conducting-nanofilament wall, which does not possess any ferroelectric polarization, is then able to block domain propagation. Consequently, we demonstrate that the domain-wall motion is effectively confined within the conducting-nanofilament wall during polarization switching. This significant new insight potentially gives an opportunity for the artificial manipulation of nanoscale ferroelectric domain. PMID:24749974

  13. Semiconductor-ferroelectric nonvolatile memory using anomalous high photovoltages in ferroelectric ceramics

    NASA Technical Reports Server (NTRS)

    Brody, P. S.

    1981-01-01

    A small ferroelectric ceramic element is used with an insulating gate transistor and two diodes as an electrically addressed, nonvolatile memory device which is read out nondestructively. The device uses the anomalous photovoltaic effect in ferroelectric ceramics, an effect in which the polarity and magnitude of photovoltages depend on the direction and magnitude of remanent polarization. Experimental results give memory characteristics. The device could be programmed with pulses as short as 200 ns. There is long-time retention of stored data.

  14. Ferroelectric control of spin injection across the ferromagnet/ferroelectric interface

    NASA Astrophysics Data System (ADS)

    Liu, Xiaohui; Burton, J. D.; Tsymbal, Evgeny

    2014-03-01

    Magnetoelectric coupling has become one of the most attractive fields in modern materials research due their promise to electrically control spintronics-based devices. Previous investigations have shown that at the ferromagnet/ferroelectric interface, magnetization could be tuned by the reversal of ferroelectric polarization. We had previously predicted that ferroelectric polarization reversal can control the nature of the resistive contact at the SrRuO3/n-BaTiO3 heterojunction interface, going from the Ohmic to Schottky regimes with reversal of ferroelectric polarization. It is known, however, that SrRuO3 displays robust ferromagnetism below the Curie temperature of about 160K. In this work, using first-principles density functional calculations, we explore the effect of ferroelectric polarization of spin-polarized transmission across the SrRuO3/n-BaTiO3 interface. Our study reveals that the interface transmission is negatively spin-polarized, and that ferroelectric polarization reversal leads to a change in spin polarization from -65% for the Ohmic contact to -98% for the Schottky contact. This sizeable change in the spin polarization could provide an interesting non-volatile mechanism to electrically control spin injection into semiconductor-based spintronics devices.

  15. Large negative thermal expansion in non-perovskite lead-free ferroelectric Sn2P2S6.

    PubMed

    Rong, Yangchun; Li, Menglei; Chen, Jun; Zhou, Mei; Lin, Kun; Hu, Lei; Yuan, Wenxia; Duan, Wenhui; Deng, Jinxia; Xing, Xianran

    2016-02-17

    Functional materials showing both negative thermal expansion (NTE) and physical performance, such as ferroelectricity and magnetism, have been extensively explored in the past decade. However, among ferroelectrics a remarkable NTE was only found in perovskite-type PbTiO3-based compounds. In this work, a large NTE of -4.7 × 10(-5) K(-1) is obtained in the non-perovskite lead-free ferroelectric Sn2P2S6 from 243 K to TC (338 K). Structure refinements and first-principle calculations reveal the effects of the Sn(ii) 5s-S 3p interaction on spontaneous polarization and its correlation with NTE. Then the mechanism of spontaneous volume ferroelectrostriction (SVFS) is verified and it could well elucidate the nature of NTE in ferroelectric Sn2P2S6. This is the first case to demonstrate the unusual NTE behavior by SVFS in a non-perovskite lead-free ferroelectric material. PMID:26854264

  16. Piezoelectric and ferroelectric properties of lead-free LiNbO3-modified 0.97(Bi0.5Na0.5TiO3)-0.03BaZrO3 ceramics

    NASA Astrophysics Data System (ADS)

    Rahman, Jamil Ur; Hussain, Ali; Maqbool, Adnan; Malik, Rizwan Ahmed; Song, Tae Kwon; Kim, Myong Ho; Lee, Soonil; Kim, Won Jeong

    2015-02-01

    Lead-free piezoelectric ceramics (1- x) [(0.97Bi0.5Na0.5TiO3)]-0.03BaZrO3- xLiNbO3 (BNT-BZ3- xLN) with x = (0-0.07) were synthesized using the conventional solid-state reaction method, and their crystal structure, microstructure, and dielectric, ferroelectric and piezoelectric properties were investigated as a function of the LN content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNT-BZ ceramics in this study. The results indicate that the LN substitution into BNT-BZ3 induces a transition from a ferroelectric to a diffuse and/or relaxor state accompanying a field-induced strain of 0.20% for x = 0.05 at an applied field of 6 kV/mm. The corresponding dynamic piezoelectric coefficient for this composition was ( S max/ E max = 333 pm/V). A significant reduction of the coercive field ( E c) and enhancement of the piezoelectric constant ( d 33) from 98 pC/N for x = 0 to 117 pC/N x = 0.01 was observed.

  17. Are lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) ferroelectrics bioactive?

    PubMed

    Vilarinho, Paula Maria; Barroca, Nathalie; Zlotnik, Sebastian; Félix, Pedro; Fernandes, Maria Helena

    2014-06-01

    The use of functional materials, such as ferroelectrics, as platforms for tissue growth in situ or ex situ, is new and holds great promise. But the usage of materials in any bioapplication requires information on biocompatibility and desirably on bioactive behavior when bone tissue engineering is envisaged. Both requirements are currently unknown for many ferroelectrics. Herein the bioactivity of LiNbO3 and LiTaO3 is reported. The formation of apatite-like structures on the surface of LiNbO3 and LiTaO3 powders after immersion in simulated body fluid (SBF) for different soaking periods indicates their bioactive potential. The mechanism of apatite formation is suggested. In addition, the significant release of lithium ions from the ferroelectric powders in the very first minutes of soaking in SBF is examined and ways to overcome this likely hurdle addressed. PMID:24863240

  18. 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.

  19. Ferroelectric polarization relaxation in Au/Cu2O/ZnO/BiFeO3/Pt heterostructure

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Xiao, Juanxiu; Yao, Kui; Zeng, Kaiyang; Wang, John

    2015-03-01

    The stability of polarization in ferroelectric BiFeO3 thin film stacked with a p-n junction of Cu2O/ZnO was studied in the Au/Cu2O/ZnO/BiFeO3/Pt heterostructure. It was observed that the downward ferroelectric polarization of BiFeO3 gradually relaxes once the external electric field is removed, which is driven by the depolarization effect induced by the reduction of compensating charges due to the charge redistribution within Cu2O/ZnO. This work contributes to an improved understanding on the polarization behavior in multilayer thin film structures comprising ferroelectrics and p-n junctions for guiding relevant device design and performance analysis.

  20. Induction of ferroelectricity in the B2 phase of a liquid crystal composed of achiral bent-core molecules

    NASA Astrophysics Data System (ADS)

    Etxebarria, J.; Folcia, C. L.; Ortega, J.; Ros, M. B.

    2003-04-01

    We report the observation of a transition from the antiferroelectric B2 phase to a ferroelectric phase in a liquid crystal composed of achiral bent-core (banana-shaped) molecules. The transition is induced by an electric field of magnitude larger than the switching threshold and is not reversible, i.e., the original B2 phase does not reappear upon field removal. The transformation is accompanied by a dramatic texture change, resulting in an almost optically isotropic structure in the absence of field. The ferroelectric character assigned to the structure is based on the electro-optic behavior of the material and on previously reported dielectric measurements. A short-pitch smectic-C*-type structure is proposed for the ferroelectric phase.