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1

Theory of Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

Relaxor ferroelectric crystals are characterized by a broad region of critical fluctuations of polarization: the observed dielectric constants and elastic diffuse scattering extend over a wide region of temperatures and have unusual line shapes. Despite more than 50 years since the synthesis of the first relaxors, a satisfactory theory of relaxor ferroelectricity that accounts for this broad region of fluctuations remains elusive, partly because of the various energy scales: the deviation from Curie-Weiss law, the onset of the elastic diffuse scattering and the maximum in the dielectric susceptibility. We present a theory of the fluctuations of relaxors with a model of polarizable unit cells with dipolar forces, local anharmonic forces, and local random fields. The usual Lorentz field approximation to the local dipolar field fails to account for the critical fluctuations of polarization at any temperature since it violates the fluctuation-dissipation theorem of statistical mechanics. Thus, thermodynamic functions and temperature dependencies of the phonon frequencies are computed self-consistently using the Onsager field, which is the simplest necessary correction to the Lorentz field that guarantees the fluctuation-dissipation theorem. Compositional disorder is treated by a self-consistent method that relates the local polarization to the local random fields and to the susceptibility averaged over compositional disorder. Local anharmonic forces are treated within a quasi-harmonic approximation. We find that (i) arbitrarily small compositional disorder together with dipolar forces extend the region of critical fluctuations down to absolute zero temperature; (ii) the correlation functions of polarization are highly anisotropic and slowly varying with a power law component. We compare our results to the observed elastic diffuse scattering and dynamic dielectric constant.

Guzman Verri, Gian Giacomo

2

A Temperature-Dependent Hysteresis Model for Relaxor Ferroelectric Compounds  

E-print Network

subsequently incorporated the hysteretic low-temperature behavior through the development of domain wall modelsA Temperature-Dependent Hysteresis Model for Relaxor Ferroelectric Compounds Julie K. Raye- ature-dependent hysteresis and constitutive nonlinearities inherent to relaxor ferroelectric materials

3

Multi-scale Modeling of Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

We are studying complex perovskites Pb(Mn_1/3Nb_2/3)O3 (PMN) and PMN-PbTiO3 (PMN-PT) using frozen phonons, linear response, and molecular dynamics with a shell-model potential fitted to first-principles results. PMN is a relaxor with fascinating and controversial behavior, and is also the relaxor end member of the new high strain piezoelectric PMN-PT. For several ordered structures of PMN we have performed both total energy calculations with LAPW and linear response calculations using ABINIT (www.abinit.org) to obtain the phonon spectra for ordered 1:2 supercells along the (111) and (001) directions. We have computed the energies of the polar ferroelectric to non-polar antiferroelectric displacement pattern and find it to be shallow for both ordered structures. The PMN phonon spectra in various structures and their impact on the stability of the ferroelectric phase will be discussed. Whereas the first principles calculations yield some insight on the behavior of ordered PMN, the real PMN structure is a disordered solid solution. To simulate the properties of PMN we have fitted a shell potential model to the extensive first-principles data. We have calculated the temperature and applied field behavior of disordered PMN in the random site model using MD. Simulated diffuse x-ray scattering plots from theory will be compared to existing experimental results. We will also discuss our efforts to study PMN-PT using the transferability of the PT and PMN potentials.

Choudhury, Narayani; Asthagiri, Aravind; Wu, Zhigang; Cohen, Ronald; Sepliarsky, Marcelo

2004-03-01

4

Dielectric and optical behaviors in relaxor ferroelectric Pb(In1/2Nb1/2)1KxTixO3 crystal  

E-print Network

Dielectric and optical behaviors in relaxor ferroelectric Pb(In1/2Nb1/2)1KxTixO3 crystal C.-S. Tu a%) single crystal grown by the modified Bridgman method with Pb(Mg1/3Nb2/3)0.71Ti0.29O3 (PMNT29%) seed crystal. A diffused phase transition was observed in the temperature region of w430­460 K with strong

5

Phonon localization drives polar nanoregions in a relaxor ferroelectric  

SciTech Connect

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.

Manley, Michael E [ORNL] [ORNL; Lynn, Jeffrey [National Institute of Standards and Technology (NIST), Gaithersburg, MD] [National Institute of Standards and Technology (NIST), Gaithersburg, MD; Specht, Eliot D [ORNL] [ORNL; Delaire, Olivier A [ORNL] [ORNL; Bishop, Alan [Los Alamos National Laboratory (LANL)] [Los Alamos National Laboratory (LANL); Sahul, Raffi [TRS Technologies] [TRS Technologies; Budai, John D [ORNL] [ORNL

2014-01-01

6

Broadband dielectric response of Ba(Zr,Ti)O3 ceramics: From incipient via relaxor and diffuse up to classical ferroelectric behavior  

NASA Astrophysics Data System (ADS)

Dielectric responses of ceramics from the lead-free isovalent BaZrO3-BaTiO3 (BZT) system were investigated from Hz frequencies up to the infrared in a broad temperature range, 10-700 K. Pure BaZrO3 is a displacive weak-incipient ferroelectric with a simple cubic perovskite structure down to low temperatures, whose dielectric response is fully determined by polar phonons, the lowest-frequency one being of the Last type, unlike BaTiO3, where it is of the Slater type. BaZr0.4Ti0.6O3 is a relaxor ferroelectric whose dielectric anomaly is caused by a strong, overdamped excitation, which softens from the THz down to MHz range according to the Arrhenius law and merges into a constant-loss background at low temperatures. Such a reponse is similar to lead-containing and heterovalent relaxors, but unlike them, the lowest-frequency TO1 polar phonon does not soften appreciably. In the case of BaZr0.2Ti0.8O3 we have investigated the dynamic response connected with a diffuse ferroelectric phase transition. The main dielectric anomaly is again due to similar overdamped THz-microwave excitation, which, however, softens only to the GHz range near the transition temperature and below it merges with a near-constant-loss background. The picture of polar nanoregions in BZT differs from that in heterovalent relaxors, because they are pinned to the regions of the off-centered Ti4+ ions, which are frozen in our temperature range. Therefore we assign the soft relaxations to hopping of the off-centered Ti4+ ions. This is compared with the behavior of pure BaTiO3 ceramics, in which the hopping of the off-centered Ti4+ ions also substantially contributes to the phase transition dynamics. Unlike BaTiO3, the dynamic instability, which is responsible for the diffuse ferroelectric and relaxor behavior in BZT, is fully due to the hopping dynamics of the off-centered Ti4+ ions rather than due to soft phonons, and therefore the diffuse transition is of the order-disorder type.

Nuzhnyy, D.; Petzelt, J.; Savinov, M.; Ostapchuk, T.; Bovtun, V.; Kempa, M.; Hlinka, J.; Buscaglia, V.; Buscaglia, M. T.; Nanni, P.

2012-07-01

7

Phonon localization drives polar nanoregions in a relaxor ferroelectric  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

8

Development of "fragility" in relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

9

Temperature dependence of the dielectric constant of relaxor ferroelectrics  

Microsoft Academic Search

The temperature dependence of the dielectric constant under different frequencies is measured and analyzed for two different relaxor ferroelectrics, the solid solution ceramics of lead magnesium niobate and lead zinc niobate, respectively. Compared with the experimental results, the disadvantage of simulated results from different methods about the temperature dependence of the dielectric constant for relaxors is given. Based on this

Z.-Y. Cheng; R. S. Katiyar; X. Yao; A. S. Bhalla

1998-01-01

10

Paraelectric and ferroelectric states in a model for relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

We study the free-energy landscape of a minimal model for relaxor ferroelectrics. Using a variational method which includes leading correlations beyond the mean-field approximation as well as disorder averaging at the level of a simple replica theory, we find metastable paraelectric states with a stability region that extends to zero temperature. The free energy of such states exhibits an essential singularity for weak compositional disorder pointing to their necessary occurrence. Ferroelectric states appear as local minima in the free energy at high temperatures and become stable below a coexistence temperature Tc. We calculate the phase diagram in the electric-field-temperature plane and find a coexistence line of the polar and nonpolar phases which ends at a critical point. First-order phase transitions are induced for fields sufficiently large to cross the region of stability of the metastable paraelectric phase. These polar and nonpolar states have distinct structure factors from those of conventional ferroelectrics. We use this theoretical framework to compare and gain physical understanding of various experimental results in typical relaxors.

Guzmán-Verri, G. G.; Littlewood, P. B.; Varma, C. M.

2013-10-01

11

A TemperatureDependent Constitutive Model for Relaxor Ferroelectrics  

E-print Network

is incorporated through the quantification of energy required to bend and translate domain walls pinnedA Temperature­Dependent Constitutive Model for Relaxor Ferroelectrics Ralph C. Smith Center between the paraelectric and ferroelectric phases due to the chemical heterogeneity of the materials

12

Anisotropic Local Correlations and Dynamics in a Relaxor Ferroelectric  

NASA Astrophysics Data System (ADS)

Relaxor ferroelectrics have been a focus of intense attention due to their anomalous properties, and understanding the structure and dynamics of relaxors has been one of the long-standing challenges in solid-state physics. We investigate the local structure and dynamics in 75%PbMg1/3Nb2/3O3-25%PbTiO3 using molecular dynamics simulations and the dynamic pair distribution function technique. We show that relaxor transitions can be described by local order parameters. The relaxor phase is characterized by the presence of highly anisotropic correlations between the local cation displacements that resemble the hydrogen bond network in water. This contradicts the current model of polar nanoregion inside a nonpolar matrix. We therefore suggest a new model of a homogeneous random network of anisotropically coupled dipoles.

Takenaka, Hiroyuki; Grinberg, Ilya; Rappe, Andrew M.

2013-04-01

13

Polarization responses in lead magnesium niobate based relaxor ferroelectrics  

SciTech Connect

Changes in the electrostrictive coefficients Q{sub ij}, especially the volumetric coefficient, with temperature and bias field provides important information regarding the nature of the polarization in lead magnesium niobate based relaxor ferroelectrics. We show that the polarization response at temperatures near the dielectric constant maximum is mainly through the polar-vector reorientation of the nanopolar regions, as suggested by the polar glass model. As the temperature is lowered through the freezing transition, the polarization response is governed by the phase switching and intrinsic contributions rather than by the domain wall motions found in normal ferroelectrics. {copyright} {ital 1997 American Institute of Physics.}

Zhang, Q.M.; Zhao, J. [Materials Research Laboratory and Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Materials Research Laboratory and Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

1997-09-01

14

Orientation dependence of electromechanical properties of relaxor based ferroelectric single crystals  

E-print Network

extrinsic domain and domain wall contributions. For [011]c poled multi- domain crystals, the intrinsicOrientation dependence of electromechanical properties of relaxor based ferroelectric single of electromechan- ical properties of relaxor based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3­(6­7)%PbTiO3

Cao, Wenwu

15

Multi-scale Modeling of Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

The origin of the high piezoelectric response observed in complex solid solution perovskites like PbMg1/3Nb2/3O3-PbTiO3 (PMN-PT) is still not well understood. We have taken a multi-scale approach to examine PMN and PMN-PT by developing a shell potential model by fitting to extensive first-principles data that can then be used in molecular dynamics (MD) simulations. For PMN we have performed both total energy calculations with LAPW and linear response calculations using ABINIT to obtain the phonon spectra of ordered 1:2 supercells along the [111] and [001] directions. For both ordered structures, we find small energy differences between the polar ferroelectric and non-polar antiferroelectric structures and large LO-TO splittings. For the [111] structure, we find the ground state to be triclinic. The results above and similar results for PbTiO3 have been used to fit a shell model potential for PMN and PT. We will report the temperature and applied field behavior of disordered PMN and the phase diagram of PMN-PT obtained from MD simulations and compare to existing experimental data. Preliminary results for PMN indicate that we obtain qualitatively similar Raman spectra and bulk modulus to experiment. Work supported by the Office of Naval Research (contract number N000149710052) and the Carnegie Institution of Washington.

Asthagiri, Aravind; Choudhury, Narayani; Zhigang, Wu

2005-03-01

16

Compressible spherical dipolar glass model of relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

The interactions between the dielectric polarization and the fluctuations of the strain (stress) tensor in relaxor ferroelectrics are shown to give rise to the anisotropy of the anharmonic P4-term in the Landau-type free energy; however, the harmonic P2-term is still properly described by the rigid spherical random bond-random field model. These are the essential features of the compressible spherical dipolar glass model, which is used to calculate the singularities of the specific heat near field-induced critical points. The results agree with recent high-resolution calorimetric experiments in PMN [110].

Pirc, R.; Kutnjak, Z.; Novak, N.

2012-12-01

17

Orientation dependence of electromechanical properties of relaxor based ferroelectric single crystals  

E-print Network

wall contributions. For [011]c poled multi- domain crystals, the intrinsic orientation effect enhancesOrientation dependence of electromechanical properties of relaxor based ferroelectric single of relaxor based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3­(6­7)%PbTiO3 and Pb(Mg1/3Nb2/3)O3­ 33%PbTiO3

Cao, Wenwu

18

Local ordering in lead-based relaxor ferroelectrics.  

PubMed

Lead-based ferroelectric materials are both well-studied and widely used and have a wide range of applications from ultrasonics to energy harvesting and beyond. However, the use of Pb-containing materials is environmentally undesirable, due to the toxicity of lead. This is particularly highlighted by the disposal of Pb-based devices when their lifespan is through. Because of this large drawback, chemists have been searching for Pb-free ferroic materials that can replace PZN (PbZn1/3Nb2/3O3), PMN (PbMg1/3Nb2/3O3), PZT (PbZr1-xTixO3), and all their derivatives. Underlying much of materials chemistry is the idea that function arises from structure, so if we can determine the structure of a material, we can understand how its useful properties arise. This understanding can then lead to the tuning of these properties and the development of new materials. However, the question arises: What is meant by structure? Conventionally, structure is determined by X-ray or neutron diffraction, in which the Bragg peak intensities are measured and a unit cell is determined. In many materials, local ordering, order that persists only for few unit cells or nanometers, is important in determining the physical properties. This is very much the case in the relaxor ferroelectrics, an important class of functional oxides. Indeed, disorder, randomness, and short-range order (SRO) are all invoked to help explain many of the key properties. The local order in Pb-based ferroelectrics has been extensively studied, with the most definitive probe being single-crystal diffuse scattering. In this Account, I outline the current debate on the nature of the local order and explore how this information can inform the search for lead-free materials. Local order, as distinct from the overall average order revealed by conventional techniques, relates more closely to the crystal chemistry of the individual ions and so appears to give a better insight into how the crystal chemistry leads to the ferroelectric properties. PMID:23735073

Goossens, Darren J

2013-11-19

19

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

PubMed

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

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

20

Dielectric Aging Effects in Doped Lead Magnesium Niobate: Lead Titanate Relaxor Ferroelectric Ceramics  

Microsoft Academic Search

contribute to aging in normal macro-domain ferroelectrics No obvious dielectric aging effects have been observed in pure .9Pb(Mgl13Nb2,3)03:. 1PbTi03 relaxor ferroelectric ceramics in this study. The addition of small amounts of MnO however, induces aging effects. Aging effects preferentially reduce the dispersive component of the weak field permittivities above the aging temperature. Isothermal aging rates are observed to increase with

W. Pan; G. O. Dayton; L. E. Cross

1986-01-01

21

Polarization Rotation and Monoclinic Phase in Relaxor Ferroelectric PMN-PT Crystal  

E-print Network

Polarization Rotation and Monoclinic Phase in Relaxor Ferroelectric PMN-PT Crystal V. Hugo Schmidt. A monoclinic phase is evidenced between rhombohedral and cubic phases in a -cut single crystal PMN-33%PT#-type). However, the present -cut crystal seems to disfavor the tetragonal phase and persists

22

Development of phonon-polarization THz spectroscopy, and the investigation of relaxor ferroelectrics  

E-print Network

This thesis develops phonon-polariton based THz spectroscopy and uses this technique to make the first THz frequency dielectric measurements of a relaxor ferroelectric crystal, in particular KTao0.982Nb0.018O3 (KTN 1.8). ...

Paxton, Benjamin John

2006-01-01

23

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

NASA Astrophysics Data System (ADS)

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

Finkel, Peter; Amin, Ahmed; Dong, Wen

2013-03-01

24

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

SciTech Connect

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.

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

1997-09-01

25

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

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.

Usman, Muhammad; Mumtaz, Arif, E-mail: arif@qau.edu.pk; Raoof, Sobia; Hasanain, S. K. [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)] [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

2013-12-23

26

Electric-field-temperature phase diagram of the relaxor ferroelectric lanthanum-modified lead zirconate titanate  

NASA Astrophysics Data System (ADS)

Transition lines between various phases in the electric-field-temperature phase diagram of 9/65/35 lanthanum-modified lead zirconate titanate ceramics were determined by measurements of the temperature and electric-field-dependent dielectric constant. Above a critical field (EC) the dc bias electric field induces a transition from the relaxor (R) to the long-range ferroelectric (FE) phase. In the temperature direction of the approach to the FE phase the R-FE transition line was determined from the field-cooled-field-heated dielectric susceptibilities, while depolarization temperatures were obtained from the field-cooled-zero-field-heated dielectric susceptibilities. A considerably large shift was found for the above two R-FE transition lines demonstrating the strong impact of the electric field on the stability of the FE phase with increasing temperature. It was found that below EC ergodicity is broken due to the divergence of the longest relaxation time at the freezing temperature T0=259 K. Hence the system exhibits a transition line between the ergodic (ER) and nonergodic (NR) relaxor state. In the dc bias field direction of the approach to the FE phase, the temperature dependence of EC, i.e., the transition lines between ER or NR and FE phases were studied by measurements of the complex dielectric constant as a function of a dc bias field at several fixed temperatures. The experimental results are compared with the results of a spherical random bond-random field model of relaxor ferroelectrics.

Bobnar, Vid; Kutnjak, Zdravko; Pirc, Raša.; Levstik, Adrijan

1999-09-01

27

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

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.

Ge, Wenwei, E-mail: wenweige@gmail.com; Luo, Chengtao; Devreugd, Christopher P.; Li, Jiefang; Viehland, D. [Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Zhang, Qinhui; Luo, Haosu [Key Laboratory of Inorganic Functional Material and Device, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China)] [Key Laboratory of Inorganic Functional Material and Device, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); Ren, Yang [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2013-12-09

28

25 pyrochlore relaxor ferroelectric Cd2Nb2O7 and its Fe2  

E-print Network

2­5 pyrochlore relaxor ferroelectric Cd2Nb2O7 and its Fe2¿ �Fe3¿ modifications N. N. Kolpakova,a) P and glassy properties of the system. It is revealed that Cd2Nb2O7 pyrochlore is intolerant of the addition-phase pyrochlore, while the compositions Cd1.5Fe0.5 2 Nb2O7 and Cd1.5Fe0.5 3 Nb2O7 give CdNb2O6 columbite doped

Paris-Sud XI, Université de

29

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

SciTech Connect

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

Wu, Shan [Pennsylvania State University; Shao, Ming [ORNL; Burlingame, Quinn [Pennsylvania State University; Chen, Xiangzhong [Penn state university; Lin, Minren [Pennsylvania State University; Xiao, Kai [ORNL; Zhang, Qiming [Pennsylvania State University

2013-01-01

30

Acute and obtuse rhombohedrons in the local structures of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3  

NASA Astrophysics Data System (ADS)

The local structures around Nb and Pb in the prototypical relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 (PMN) were investigated by x-ray fluorescence holography. The separate atomic images of nearest Pb around Nb revealed acute and obtuse rhombohedral structures of the crystal unit cells. The Pb-Pb correlated images showed a local structure of body-center-like 2a0×2a0×2a0 superlattice, proving a rigid three-dimensional network structural model combining the two kinds of rhombohedrons. The Pb atoms in the networks are positionally stable, while the other Pb atoms are fluctuating. This superstructure and the fluctuating Pb and Nb atoms are believed to play an important role in the relaxor behavior of PMN at the atomic level.

Hu, Wen; Hayashi, Kouichi; Ohwada, Kenji; Chen, Jun; Happo, Naohisa; Hosokawa, Shinya; Takahasi, Masamitu; Bokov, Alexei A.; Ye, Zuo-Guang

2014-04-01

31

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

PubMed Central

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

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

32

Scale effects of low-dimensional relaxor ferroelectric single crystals and their application in novel pyroelectric infrared detectors.  

PubMed

Scaling effects of low-dimensional relaxor ferroelectric single crystals have induced large delocalization of domain switching, leading to a dramatic increase in pyro-electric performances by 2-5.5 times, and promoting the detectivity of fabricated pyroelectric detectors to an international leading level of 2.21 × 10(9) cmHz(1/2) /W at 10 Hz, 4 times higher than that of commercial LiTaO3 -based detectors. PMID:24497438

Li, Long; Zhao, Xiangyong; Li, Xiaobing; Ren, Bo; Xu, Qing; Liang, Zhu; Di, Wenning; Yang, Linrong; Luo, Haosu; Shao, Xiumei; Fang, Jiaxiong; Neumann, Norbert; Jiao, Jie

2014-04-23

33

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)

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.

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

2014-09-01

34

Dielectric, relaxor and ferroelectric characterization of La doped xPb(Mg{1/3}Nb{2/3})O3-(1-x)Pb(Zr{0.55}Ti0.45)O3 ceramics  

NASA Astrophysics Data System (ADS)

The relaxor ferroelectric ceramics of La doped xPb(Mg{1/3}Nb{2/3})O3-(1-x)Pb(Zr{0.55}Ti{0.45})O{3} are synthesized by columbite precursor method. Powder X-ray diffraction patterns of these compositions indicate pseudocubic phase formation. Grain growth is inhibited with La doping and is increased with PMN concentration in PMN-PZT ceramics. \\varepsilonRT and tan? are increased to 1.5 mole% La doped PMN-PZT compositions while \\varepsilonT_C and TC are decreased with La modification in PMN-PZT system. Pure and La modified 0.8PMN-0.2PZT compositions have shown the most promising relaxor behavior useful for multilayer capacitor (MLC) applications. The ferroelectric properties (Ec, Pr and Ps) are increased to 1.5 mole% La doped PMN-PZT composition. 77.84.Dy Niobates, titanates, tantalates, PZT ceramics, etc.

Ramam, K.; Luis, S. H.

2006-07-01

35

Dilatometric approach for the determination of the solid state reaction-onset of the lead based relaxor ferroelectric system  

SciTech Connect

Dilatometer based thermal expansion studies have been carried out on the starting oxide mixtures of some of the important relaxor ferroelectric compositions including lead iron niobate, lead magnesium niobate-lead titanate and lead zinc niobate-barium titanate. An anomalous thermal expansion behavior is observed between 550 and 650 deg. C corresponding to the onset of the solid state reaction. Further heating of the reaction mixture resulted in a decrease in the dimension of the sample. From the complementary evidence of DTA, X-ray diffraction (XRD) and scanning electron microscopy (SEM), it is shown that the initiation of solid state reaction results in the restructuring of the reacting grains to form the agglomerates of fine particles of reaction intermediates. This phenomenon is shown to be absent in the barium zinc niobate system where the pyrochlore intermediates do not exist. This novel dilatometric approach has been projected as a possible technique to identify optimum calcination temperatures to produce sinter-active powders in the above oxide system, thereby help in reducing the sintering temperatures.

Bhat, V.V.; Radhika Rao, M.V.; Umarji, A.M

2003-05-26

36

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

SciTech Connect

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.

Bokov, Alexei A. [Simon Fraser University, Canada; Rodriguez, Brian [University College, Dublin; Zhao, X [Iowa State University; Ko, JH [Hallym University, Korea; Jesse, Stephen [ORNL; Long, X [Simon Fraser University, Canada; Qu, W [Iowa State University; Kim, TH [Hallym University, Korea; Budai, John D [ORNL; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine; Kojima, S [University of Tsukuba, Japan; Tan, X [Iowa State University; Kalinin, Sergei V [ORNL; Ye, Z.-G. [Simon Fraser University, Canada

2011-01-01

37

Local Structure in Relaxor Ferroelectrics by 207 Donghua H. Zhou,1  

E-print Network

-adjusted spinning sidebands (2D-PASS) NMR experiments have been performed on (1 - x)PMN-xPSN relaxor ferro, Pb displacement, 2D-PASS NMR, T1 relaxation I. INTRODUCTION Lead based perovskite relaxor resolution static and MAS spectra. Only in 2D-PASS spectra, isotropic and anisotropic chemical shifts can

Vold, Robert

38

Raman scattering study of relaxor ferroelectric Pb(Sc1/2Nb1/2)O3 crystals  

NASA Astrophysics Data System (ADS)

The effects of B-site ordering and vacancies were studied in the relaxor ferroelectric Pb(Sc1/2Nb1/2)O3 (PSN) family by using Raman scattering spectroscopy. Differences with Raman spectra and the depolarization ratios were clearly observed among B-site disordered PSN (PSN-D), B-site ordered with lead/oxygen vacancies PSN (PSN- OV), and 0.7Pb(Sc1/2Nb1/2)O3-0.3PbTiO3 (PSN-30PT) single crystals. The temperature dependence of the depolarization ratio of PSN-30PT was also studied to clarify the ferroelectric phase transitions and the polarization fluctuations in the polar nanoregions.

Suzuki, Kohei; Kojima, Seiji; Ahart, Muhtar; Bing, Yonghong; Ye, Zuo-Guang

2013-04-01

39

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

SciTech Connect

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

Hong, Cheng-Shong, E-mail: cshong@nknu.edu.tw [Department of Electronic Engineering, National Kaohsiung Normal University, Kaohsiung 824, Taiwan, ROC (China)] [Department of Electronic Engineering, National Kaohsiung Normal University, Kaohsiung 824, Taiwan, ROC (China); Chu, Sheng-Yuan, E-mail: chusy@mail.ncku.edu.tw [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China) [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Tsai, Cheng-Che [Department of Electronics Engineering and Computer Science, Tung Fang Design University, Kaohsiung 829, Taiwan, ROC (China)] [Department of Electronics Engineering and Computer Science, Tung Fang Design University, Kaohsiung 829, Taiwan, ROC (China); Hsu, Chi-Cheng; Su, Hsiu-Hsien [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China)] [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China)

2013-02-15

40

Observation of relaxor ferroelectricity and multiferroic behaviour in nanoparticles of the ferromagnetic semiconductor La2NiMnO6  

NASA Astrophysics Data System (ADS)

We report a diffuse phase transition (extending over a finite temperature range of ˜50 K) in sol-gel derived nanoparticles (˜25 nm) of the ferromagnetic double perovskite La2NiMnO6. The macroscopic polarization (P-E hysteresis loop), validity of the Vogel-Fulcher relation and high dielectric permittivity (˜9 × 102) confirm relaxor ferroelectric phenomena in these magnetic nanoparticles. Compared to the corresponding bulk sample, appreciably large enhancement of the magnetocapacitive effect (MC ˜ 30%) is observed even under low magnetic field (0.5 T) around the broad relaxor dielectric peak temperature (˜220 K), which is close to the ferromagnetic transition temperature (?f ˜ 196 K). All of these features establish the multiferroic character of the La2NiMnO6 nanoparticles. The inhomogeneities arising from chemical and valence mixing in the present La2NiMnO6 nanoparticles and the inter-site, Ni/Mn-site disorder along with surface disorder of the individual nanoparticles resulting in local polar regions are attributed to the observed dielectric behaviour of the nanoparticles. The wave vector dependent spin-pair correlation is considered to be the plausible cause of the colossal magnetocapacitive response near the transition temperature. High permittivity and large magnetocapacitive properties make these ferromagnetic La2NiMnO6 nanoparticles technologically important.

Masud, Md G.; Ghosh, Arijit; Sannigrahi, J.; Chaudhuri, B. K.

2012-07-01

41

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

42

Residual stress and interface effect on dielectric mechanisms in poled ultrathin relaxor ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

We have investigated the dielectric performances and mechanism of super-thin Mn-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals, exhibiting significantly different dielectric behaviors compared with thick wafer. Dramatic decrease by 5 times and large frequency dispersion of permittivity, changed diffuse degree of phase transition, dielectric loss anomaly with frequency and dielectric performances with direct-current electric field for thin wafers are observed, proving the existence of large surface residual stress and interface effects. Additionally, a theoretical model of low-permittivity and low-ferroelectric surface damage layers is concurrently proposed. These observations have important implications for actual performances of thin wafers applied in practical devices.

Li, Long; Zhao, Xiangyong; Li, Xiaobing; Xu, Qing; Yang, Linrong; Wang, Sheng; Luo, Haosu

2014-05-01

43

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

44

Electric-field-temperature phase diagram of the ferroelectric relaxor system (1 - x)Bi1/2Na1/2TiO3 - xBaTiO3 doped with manganese  

NASA Astrophysics Data System (ADS)

The electric-field-temperature phase diagram for the lead-free relaxor material (1 - x)(Bi1/2Na1/2)TiO3 - xBaTiO3 (x = 0.03, 0.06, and 0.09) doped with 0.5 mol% Mn (BNT-100xBT:Mn) was established. Transition lines between ergodic or nonergodic relaxor states and the field-induced ferroelectric state were determined at constant temperatures with electric-field-dependent measurements of the polarization as well as of the piezoelectric coefficient and permittivity. Near the depolarization temperature Td, the switching between two ferroelectric poling directions occurs in two steps via an intermediate relaxor state. This effect is closely related to the pinching of the ferroelectric hysteresis loop.

Sapper, Eva; Novak, Nikola; Jo, Wook; Granzow, Torsten; Rödel, Jürgen

2014-05-01

45

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

46

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

47

Relaxor-like dielectric behavior in La 2NiMnO 6 double perovskite ceramics  

Microsoft Academic Search

The dielectric and conductive characteristics of La2NiMnO6 double perovskite ceramics were investigated together with the crystal structure. La2NiMnO6 ceramics crystallized in the monoclinic P21\\/n structure in which the Ni2+ and Mn4+ ions ordered periodically. Relaxor-like dielectric behavior combined with a giant dielectric constant step was observed in the present ceramics, and these unique dielectric characteristics should be attributed to the

Y. Q. Lin; X. M. Chen; X. Q. Liu

2009-01-01

48

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

49

Magnetism in Triangular Lattice System LuFeCoO4 having Relaxor Property  

NASA Astrophysics Data System (ADS)

Electric and magnetic measurements were carried out on a single crystalline sample of triangular lattice system LuFeCoO4. LuFeCoO4 has a relaxor-like behavior in the dielectric constant, which corresponds with the existence of the polar nanoregion (PNR). A magnetic correlation length along c-plane was estimated to be nano-size by our neutron diffraction measurements, and an anomalous magnetization was found below 200 K. Similar electric and magnetic behaviors were also observed in relaxor ferroelectrics 2/3BiFeO3-1/3BaTiO3, suggesting that the relaxor ferroelectrics having magnetic ions show commonly a nanomagnetism induced by PNRs.

Soda, Minoru; Aoyama, Takuya; Wakabayashi, Yusuke; Hirota, Kazuma

2011-09-01

50

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

NASA Astrophysics Data System (ADS)

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/Å3 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.

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

2012-11-01

51

Relaxor-like dynamics of ferroelectric K(Ta1-xNbx)O3 crystals probed by inelastic light scattering  

NASA Astrophysics Data System (ADS)

The relaxor-like dynamics of the cubic-tetragonal ferroelectric phase transition was studied by Brillouin and Raman scattering in K(Ta1-xNbx)O3 (KTN) crystals with x = 0.40 (KTN40). The local symmetry breaking by the polar nanoregions (PNRs) was observed in a paraelectric phase by Raman scattering on the A1(z) mode of the PNRs with R3m symmetry. Upon cooling from a high temperature, the remarkable increase in the LA phonon damping starts at 45 K above the cubic-tetragonal phase transition temperature of TC-T = 308 K, which is defined as the intermediate temperature, T* ˜ 353 K, indicating the start of the rapid growth of the PNRs. The coupling between the LA mode and fluctuation of the PNRs caused a remarkable elastic anomaly in the vicinity of TC-T. The analysis of the temperature dependent central peak shows a critical slowing down towards TC-T, which is the evidence for the order-disorder nature of a ferroelectric phase transition. The evolution of the dynamic PNRs is discussed by the estimation of their length scale, and it is found that it starts to increase near T* and gradually grows towards TC-T.

Rahaman, M. M.; Imai, T.; Miyazu, J.; Kobayashi, J.; Tsukada, S.; Helal, M. A.; Kojima, S.

2014-08-01

52

Relaxor ferro- and paraelectricity in anisotropically strained SrTiO3 films  

NASA Astrophysics Data System (ADS)

The ferroelectric properties of anisotropically strained SrTiO3 films are analyzed by detailed measurements of the complex dielectric constant as function of temperature, frequency, bias voltage, and electric field direction. At low temperatures, strain induces a relaxor-ferroelectric phase that persists up to room temperature. The transition temperature and characteristic parameters (e.g., Curie temperature, static freezing temperature, degree of diffuseness of the phase transition, activation energy) of the relaxor phase depend strongly on the orientation of the electric field and, therefore, on the amount of structural strain in the given electric field direction. Also above the ferroelectric transition temperature, a relaxation of the permittivity is visible, i.e., the strain causes a relaxor-paraelectric behavior. Only at high enough temperatures, the relaxation time constant tends to zero and the "classical" dielectric state is obtained. Frequency and time dependent relaxation experiments demonstrate an extremely large distribution of the relaxation rates in both relaxor states (ferroelectric and paraelectric), which is indicative for the large distribution in the mobility of polar SrTiO3 regions with randomly distributed directions of dipole moments in the film. The large distribution might be taken as an indication for a large distribution in size and orientation of nanosize domains in the anisotropically strained SrTiO3 film.

Wördenweber, R.; Schubert, J.; Ehlig, T.; Hollmann, E.

2013-04-01

53

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

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.

Li, Kun; Li Zhu, Xiao; Qiang Liu, Xiao; Ming Chen, Xiang [Department of Materials Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027 (China)] [Department of Materials Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027 (China)

2013-03-18

54

Role of random electric fields in relaxors  

PubMed Central

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

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

2014-01-01

55

Role of random electric fields in relaxors.  

PubMed

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

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

2014-02-01

56

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

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

57

Crystallographic dependence of loss in domain engineered relaxor-PT single crystals  

PubMed Central

Domain engineered ?001? oriented relaxor-PbTiO3 ferroelectric crystals exhibit high electromechanical properties and low mechanical Q values, analogous to “soft” piezoelectric ceramics. However, their characteristic low dielectric loss (?0.5%) and strain-electric field hysteresis are reflective of “hard” piezoelectric materials. In this work, the electromechanical behavior of relaxor-PT crystals was investigated as a function of crystallographic orientations. It was found that the electrical and mechanical losses in crystals depends on the specific engineered domain configuration, with high Q observed for the ?110? orientation. The high Q, together with high electromechanical coupling (?0.9) for ?110? oriented relaxor-PT crystals, make them promising candidates for resonant based high power transducer applications. PMID:19654880

Zhang, Shujun; Sherlock, Nevin P.; Meyer, Richard J.; Shrout, Thomas R.

2009-01-01

58

Phase transitions due to polar region structure in disordered ferroelectrics  

Microsoft Academic Search

We show clear experimental evidence for two phase transitions in titanium doped lead magnesium niobate compositional disordered ferroelectrics. One is the diffuse phase transition near the temperature of the dielectric permittivity maximum, which is often called the characteristic of relaxor ferroelectrics (relaxors). Another is a first-order transformation from relaxor ferroelectric to normal ferroelectric, corresponding to a zero-field spontaneous polar micro-macrodomain

Huiqing Fan; Lingbing Kong; Liangying Zhang; Xi Yao

1999-01-01

59

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

60

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

61

Aging in the relaxor and ferroelectric state of Fe-doped (1-x)(Bi1/2Na1/2)TiO3-xBaTiO3 piezoelectric ceramics  

NASA Astrophysics Data System (ADS)

Aging of piezoelectric properties was investigated in lead-free (1 - x)(Bi1/2Na1/2)TiO3-xBaTiO3 doped with 1at. % Fe. The relaxor character of the un-poled material prevents macroscopic aging effects, while in the field-induced ferroelectric phase aging phenomena are similar to those found in lead zirconate titanate or barium titanate. Most prominent aging effects are the development of an internal bias field and the decrease of switchable polarization. These effects are temperature activated, and can be explained in the framework of defect complex reorientation. This picture is further supported by electron paramagnetic resonance spectra indicating the existence of (FeTi'-VO••)• defect complexes in the Fe-doped material.

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

2014-09-01

62

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

63

Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics  

PubMed Central

Nanoscale and mesoscopic disorder and associated local hysteretic responses underpin the unique properties of spin and cluster glasses, phase-separated oxides, polycrystalline ferroelectrics, and ferromagnets alike. Despite the rich history of the field, the relationship between the statistical descriptors of hysteresis behavior such as Preisach density, and micro and nanostructure has remained elusive. By using polycrystalline ferroelectric capacitors as a model system, we now report quantitative nonlinearity measurements in 0.025–1 ?m3 volumes, approximately 106 times smaller than previously possible. We discover that the onset of nonlinear behavior with thickness proceeds through formation and increase of areal density of micron-scale regions with large nonlinear response embedded in a more weakly nonlinear matrix. This observation indicates that large-scale collective domain wall dynamics, as opposed to motion of noninteracting walls, underpins Rayleigh behavior in disordered ferroelectrics. The measurements provide evidence for the existence and extent of the domain avalanches in ferroelectric materials, forcing us to rethink 100-year old paradigms. PMID:20368462

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

2010-01-01

64

Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics.  

PubMed

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

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

2010-04-20

65

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

66

Correlation radius of polarization fluctuations in the disordered ferroelectrics  

Microsoft Academic Search

We calculate correlation radius of polarization fluctuations in the disordered ferroelectrics. The consideration is performed in the model suitable for relaxor ferroelectrics. We consider reference Burns phase in a mean field approximation subjected to random electric field E. The ``entire relaxor'' is then obtained by averaging of characteristics of the reference phase with distribution function of the random field. For

M. D. Glinchuk; E. A. Eliseev; V. A. Stephanovich; E. V. Kirichenko; L. Jastrabik

2002-01-01

67

Correlation radius of polarization fluctuations in the disordered ferroelectrics  

Microsoft Academic Search

We calculate correlation radius of polarization fluctuations in the disordered ferroelectrics. The consideration is performed in the model suitable for relaxor ferroelectrics. We consider reference Burns phase in a mean field approximation subjected to random electric field E. The “entire relaxor” is then obtained by averaging of characteristics of the reference phase with distribution function of the random field. For

M. D. Glinchuk; E. A. Eliseev; V. A. Stephanovich; E. V. Kirichenko; L. Jastrabik

2002-01-01

68

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

NASA Astrophysics Data System (ADS)

This thesis extends the investigations on perovskite solid solutions based on PbTiO3-Bi(Me',Me")O3 (Me' = Sc3+, Zn2+, Mg2+, Ni2+, In3+ , Fe3+, etc. and Me" = Ti4+, Nb 5+, W6+) systems. The ferroelectric transition temperature (TC) behavior was considered in the tetragonal phase region of the PbTiO 3-Bi(Me',Me")O3 systems. Trends in the TC compositional dependence exhibited three main cases: case 1, a continued increase in transition temperature above the end-member PbTiO3 (495°C); case 2, an increase and then decrease of the transition temperature; and case 3, a continuous decrease in the transition temperature with Bi(Me',Me")O 3 additions. New relaxor materials were developed from the PbTiO3-Bi(Me',Me")O 3 solid solutions; specifically, the Bi(Mg3/4W1/4)O 3-PbTiO3 (BMW-PT) binary solid solution and BiScO3-Pb(Mg 1/3Nb2/3)O3-PbTiO3 (BS-PMN-PT) ternary solid solution were investigated. Permittivity, polarization and pyroelectric measurements were performed on BMW-PT and BS-PMN-PT compositions with respect to temperature with characteristic relaxor behavior observed. The complex solid solution BMW-PT exhibited a morphotropic phase boundary at ˜48 mol% PbTiO3 with a corresponding TC of 205°C. On further structural analysis with diffraction contrast transmission electron microscopy along with x-ray diffraction, evidence of B-site ordering was observed. The BS-PMN-PT proved to be a model system with high temperature relaxor properties of Tmax ˜ 250°C to 300°C and ?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 600°C; up to 250°C higher than any reported value for relaxor ferroelectrics. The frequency dependence of the temperature of the permittivity maximum was found to follow the Vogel-Fulcher relationship, with an activation energy (EA) of ˜0.1 eV, and a freezing temperature (Tf) of ˜150°C. 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 300°C and up to 10 kHz. The voltage saturation was found to be extremely encouraging at 300°C with observed changes in capacitance (˜3%) on the application of 10 kV/cm. The insulation resistivity followed an Arrhenius behavior and at 300°C was ˜1010 O-cm. Weibull statistics were used to estimate a characteristic breakdown field at 300°C 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.

Stringer, Craig J.

69

Nanoscale behavior of ferroelectric domains in perovskite thin films  

NASA Astrophysics Data System (ADS)

Controlling the polarization of ferroelectrics plays an increasingly important role in many technological devices including ferroelectric memory, tunable communication filters, and vibrational energy scavengers. To advance the development of ferroelectric devices, we must improve our understanding of the complex internal domain structure of ferroelectric materials. Because these domains are only 50-500 nm wide, they have historically been difficult to probe. This dissertation demonstrates how nanoscale ferroelectric domain configurations can be tailored in epitaxial perovskite thin films by controlling the electromechanical boundary conditions of the film. Epitaxial films of BiFeO3 and Pb(Zr,Ti)O3 were used as model systems because the latter is a mainstay in piezoelectric sensing and actuating applications and the former is a promising Pb-free magnetoelectric-ferroelectric with large polarization, strong piezoelectricity, and multiple ferroelastic domain wall variants. The as-grown domain structures of epitaxial BiFeO3 films deposited on (001)-oriented SrTiO3 substrates were investigated using piezoelectric force microscopy. The equilibrium ground state consists of alternating domain stripes consisting of only two ferroelastic variants, separated by 71° domain walls. Selective activation of 71° and 109° ferroelastic switching---which is important for magnetoelectric applications---was achieved by controlling the strength of the applied electric field. A similar behavior was found in BiFeO3 films deposited on (110)-oriented SrTiO 3. The novel characterization technique of planar electrode piezoelectric force microscopy is introduced as a non-destructive method for viewing nanoscale domains at intermediate stages of the poling process. This apparatus was used to selectively enable 109° or 71° reversible rotation of the 71° domain stripes in BiFeO3 films. Domain stripe rotation was then used to achieve magnetoelectric switching of a permanent magnet, and also to modulate the photo-electric effect in BiFeO3 domain walls. A novel concept for harnessing electricity from ferroelastic domain wall motion is applied to vibrational energy scavenging. Methods for imaging domains while deforming the Pb(Zr,Ti)O3 or BiFeO3 film with a micromachined cantilever and magnetic actuation or by three-point bending are presented. Reverse polarized domains in BiFeO3 were found to grow under compressive strain by 180° domain wall motion that maintains the equilibrium 71° domain stripes.

Shafer, Padraic Corey

70

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

NASA Astrophysics Data System (ADS)

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).

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

2014-04-01

71

Pressure-induced phase transitions and structure of chemically ordered nanoregions in the lead-free relaxor ferroelectric Na1/2Bi1/2TiO3  

NASA Astrophysics Data System (ADS)

We investigate the phase stability of Na1/2Bi1/2TiO3, a prototype lead-free relaxor material, under pressure. By means of total energy calculations within density functional theory, we study the pressure stability of several structures with polar and antipolar distortions, in-phase and out-of-phase tilts, and different chemically ordered configurations. Under positive (compressive) pressure an orthorhombic Pbnm-like phase is stabilized above 3 GPa. At negative (tensile) pressure a non-tilted polar P4mm-like phase is stable. At zero pressure two phases are coexisting. The local chemical configuration determines whether the high-pressure Pbnm-like or another tilted and polar R3c-like structure is favored. Thus, two different variants of pressure phase diagrams depending on the cation arrangement are obtained, which raises the question of the existence of a mixed phase ground state in the disordered system. We discuss the stability of the mixed phase state in terms of lattice and tilt misfits and possible shapes and ferroic properties of the coexisting regions with different average structures. Our results clearly support the view that there are chemically ordered nanoregions with their own local ferroic properties embedded in a chemically disordered ferroelectric matrix representing the ground state.

Gröting, Melanie; Kornev, Igor; Dkhil, Brahim; Albe, Karsten

2012-10-01

72

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

73

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

NASA Astrophysics Data System (ADS)

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.

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

2003-03-01

74

Fano resonance and dipolar relaxation in lead-free relaxors.  

PubMed

Fano resonance is a phenomenon in which a discrete state interferes with a continuum of states and has been observed in many areas of science. Here, we report on the prediction of a Fano resonance in ferroelectric relaxors, whose properties are poorly understood: an ab initio molecular dynamic scheme reveals such resonance between the bare optical phonon mode of the Zr sublattice (the discrete state) and the bare optical phonon mode of the Ti sublattice (the continuum of states) in disordered lead-free Ba(Zr,Ti)O3. The microscopic origins of the discrete state and continuum of states are discussed in the context of relaxor properties. Furthermore, our simulations suggest that the T* characteristic temperature of relaxor is related to a hardening of the vibrational frequencies associated with fluctuation of the Ti sublattice. Finally, a terahertz relaxation mode reflecting reorientations of Ti dipoles and showing a thermally activated behaviour is predicted, in agreement with previous experiments. PMID:25369904

Wang, D; Hlinka, J; Bokov, A A; Ye, Z-G; Ondrejkovic, P; Petzelt, J; Bellaiche, L

2014-01-01

75

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)

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.

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

2014-04-01

76

Incipient ferroelectrics: Anomalous T1 behaviors and their rotor interpretation  

NASA Astrophysics Data System (ADS)

The quantum temperature (denoted by T1) behaviors of three typical incipient ferroelectrics, SrTiO 3, KTaO 3 and CaTiO 3, are studied. This quantity is argued to serve fundamentally in identifying the nature of the local mode responsible for the dielectric responses. Our main findings are as follows. For all compounds, T1 saturates at low temperatures. For CaTiO 3, T1 monotonically increases with temperature and no clear saturation is discernible at high temperatures. For KTaO 3, similar behaviors are observed but with a little twist: a dip shows up around 35 K, above which T1 increases but below it T1 decreases with temperature. Although it is hardly seeable in this compound, this dip might mark a transition, whose nature is unclear for the moment. In parallel with KTiO 3, SrTiO 3 also has a dip, which is much stronger and broader. It happens around 105 K, at which the famous anti-ferrodistortive (AFD) transition occurs. Were it not for this dip, T1 would drop to zero in SrTiO 3 at low temperatures and the ferroelectric (FE) transition would take place. The dip halts the drop and makes T1 rise up to a value that is enough to stabilize the FE instability. In this respect, the dip is essential in preventing the FE transition in SrTiO 3. Since the dip and the AFD transition occur at roughly the same temperature, we attempt to ascribe the former to the latter. This ascription is compatible with previous work [A. Yamanaka, M. Kataoka, Y. Inaba, K. Inoue, B. Hehlen, E. Courtens, Europhys. Lett., 50:(2000) 688]. To interpret the T1 behaviors, we utilize an anisotropic rotor model, according to which the local variable is supposed to move on a non-uniform sphere. By tuning the anisotropy parameter, ?, qualitative agreement can be achieved. Especially, a single ??100 can fit the T1 of CaTiO 3 over the entire temperature range under consideration, whereas the fitting for KTaO 3 requires two different ?, namely, ??260 above the dip temperature and ??40 below it. Analogously, two ? are also required for SrTiO 3. Below the dip temperature, a very good fitting can be obtained with ??40. We did not try to fit the high temperature data of SrTiO 3, because the data in this range are scarce and inaccurate. Nevertheless, we believe that a different and bigger ? should be at work, considering the case with KTaO 3. Assuming the AFD transition as the cause of the dip in SrTiO 3, we may claim that, the true role of the AFD transition in stabilizing the FE instability is to reduce the ? and then enhance quantum fluctuations.

Deng, Hai-Yao; Hu, Kaige; Lam, Chi Hang; Huang, Haitao

2012-01-01

77

Effects of Oxide Seeding Layers on Electrical Properties of Chemical Solution Deposition-Derived Pb(Mg1/3Nb2/3)O3-PbTiO3 Relaxor Thin Films  

NASA Astrophysics Data System (ADS)

Relaxor ferroelectrics Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have attracted considerable attention because of their excellent electrical properties, such as high dielectricity and piezoelectricity, for application to super capacitors, piezoelectric actuators, and so on. It is well known that the electrical properties of ferroelectric thin films depend on several parameters, such as crystal orientation, composition, and residual stress. In this study, the effects of the lead titanate and lanthanum nickel oxide seeding layers on the film orientation, electrical properties, and low-temperature crystallization behavior were investigated for Chemical Solution Deposition (CSD)-derived PMN-PT thin films. As a result, PMN-PT thin films with (001)C- and (111)C-preferred orientations were successfully obtained by designing the seeding layers. Both thin films exhibited very good ferroelectricity because of their good crystallinity and preferred orientation.

Arai, Takashi; Goto, Yasuyuki; Yanagida, Hiroshi; Sakamoto, Naonori; Ohno, Tomoya; Matsuda, Takeshi; Wakiya, Naoki; Suzuki, Hisao

2013-09-01

78

Electronic Structure and Ferroelectric Behavior of Lanthanum Substituted Bismuth Titanate  

Microsoft Academic Search

The effect of substituting La for Bi atoms in Bi4Ti3O12 is investigated from first-principles calculations using the full-potential linearized augmented plane wave (LAPW) method. A comparative study of the electronic structure and lattice-dynamics properties of Bi4Ti3O12 and La2Bi2Ti3O12 shows the role of covalent bonding in the ferroelectric instabilities. The displacement patterns displayed by unstable zone-center phonon modes and a detailed

R. Machado; M. G. Stachiotti

2006-01-01

79

Anisotropic behavior of water in ferroelectric liquid crystals.  

PubMed

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

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

2010-05-01

80

Multiwall carbon nanotubes doped ferroelectric liquid crystal composites: A study of modified electrical behavior  

NASA Astrophysics Data System (ADS)

We systematically investigated the role of carbon nanotubes and their nature of interaction with the high polarization ferroelectric liquid crystal molecules that causes a change in the dynamic behavior of the liquid crystals. The carbon nanotubes were functionalized with carboxyl group (-COOH) before dispersion in order to enhance their stability in the liquid crystal medium. For the systematic investigation of a non linear behavior of dispersed composite systems, results for various physical properties were determined by thermal, morphological and dielectric studies in the planer aligned 5 ?m thickness cells. An effort has also gone into detail to investigate these properties with varying concentration (0.02 wt%, 0.05 wt% and 0.1 wt%) of multiwall carbon nanotubes. The various carbon nanotubes doped ferroelectric liquid crystal thin film composites have shown enhanced dielectric strength and dielectric permittivity values as compared to the undoped sample.

Neeraj; Raina, K. K.

2014-02-01

81

1. Innovative Relaxor-Based PiezoCrystals: Phase Diagrams, Crystal Growth, Domain Structures and Electric Properties. 2. Piezo- and Ferroelectric Materials Based on Morphotropic Phase Boundary Synthesis, Characterization and Structure - Property Relations.  

National Technical Information Service (NTIS)

This final technical report is on the research work carried out in the area of design, synthesis and characterization of novel piezo- and ferroelectric materials, especially in the form of single crystals, with a view to developing new materials resources...

Z. G. Ye

2006-01-01

82

High-resolution studies of domain switching behavior in nanostructured ferroelectric polymers.  

PubMed

We have demonstrated an effective electrical control of polarization in the individual crystalline nanomesas of the ferroelectric polymer, poly(vinylidene fluoride)-trifluoroethylene (PVDF-TrFE) and its relation to the polymer structure. The mechanism of polarization reversal has been investigated via sub-10 nm real space imaging of domain pattern evolution under an applied electric field. The domain switching behavior revealed in PVDF-TrFE nanomesas is drastically different from that observed in inorganic solid-state crystalline ferroelectrics. The nanoscale features of the switching process include remote domain nucleation and spatially nonuniform wall velocity. Local switching spectroscopy and domain dynamics studies relate the observed switching features to a random-bond type disorder associated with defects in conformation and molecular packing. PMID:21462936

Sharma, Pankaj; Reece, Timothy J; Ducharme, Stephen; Gruverman, Alexei

2011-05-11

83

Defect-phase equilibrium and ferroelectric phase transition behavior in non-stoichiometric barium titanate under various equilibrium conditions  

Microsoft Academic Search

BaTiO3 has been systematically investigated with regard to the solubility region around stoichiometric BaTiO3 with a combination of techniques. This investigation uses mainly the nature of ferroelectric phase transition to define the relationships between phase equilibria, defect chemistry, and phase transition behavior in non-stoichiometric BaTiO 3 under various equilibrium conditions. The phase transition temperature (TC) between the paraelectric and ferroelectric

Soon Il Lee

2006-01-01

84

Phase diagram of polar states in doped ferroelectric systems  

NASA Astrophysics Data System (ADS)

We report a complete phase diagram that describes the relationships among all polar states in doped ferroelectrics, including the paraelectric (polar liquid), ferroelectric (polar crystal), relaxor (polar glass), and precursory states (partially frozen nanopolar domains). We employ a model that considers a randomly distributed local polarization field associated with point defects, which breaks the symmetry of the Landau free energy with respect to polarization. In the meantime, the model also takes into account the effect of point defects on the overall stability of the ferroelectric phase. Based on this model, the phase field simulations reproduce all the polar states and important characteristics associated with ferroelectric-glass (relaxor) transition observed in experiments, including rugged free energy, wide relaxation time, nanosized ferroelectric domain structure, “diffuse” transition, temperature dependence of third-order dielectric susceptibility, nonergodicity, frequency dependence of dielectric loss, and domain switching.

Wang, Dong; Ke, Xiaoqin; Wang, Yunzhi; Gao, Jinghui; Wang, Yu; Zhang, Lixue; Yang, Sen; Ren, Xiaobing

2012-08-01

85

Structure and Relaxor Behaviour of Ba2+ Substituted NBT Ceramics  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

86

Domain Configuration and Ferroelectric Related Properties of the (110)cub Cuts of Relaxor-Based Pb(Mg1\\/3Nb2\\/3)O3-PbTiO3 Single Crystals  

Microsoft Academic Search

Domain configuration and ferroelectric related properties of Pb(Mg1\\/3Nb2\\/3)O3-PbTiO3 were investigated as a function of applied electric field for the (110)cub cuts. It was found that a single domain orthorhombic state could be achieved by applying an electric field along the direction cub, but the state after removing the electric field strongly depends on the composition and electric field. A qualitative

Yiping Guo; Haosu Luo; Tianhou He; Haiqing Xu; Zhiwen Yin

2002-01-01

87

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

NASA Astrophysics Data System (ADS)

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 Maxwell’s 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.

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

2014-09-01

88

Ferroelectric domain wall relaxation in Ba{sub 0.25}Sr{sub 0.75}TiOâ films displaying Curie-Weiss behavior  

Microsoft Academic Search

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

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

2004-01-01

89

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

Microsoft Academic Search

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

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

2004-01-01

90

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)

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.

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

91

Effect of disorder potential on domain switching behavior in polymer ferroelectric films.  

PubMed

Nanoscale switching dynamics in spin-coated ferroelectric copolymer films of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE 75/25) has been investigated via high-resolution real-space imaging of electrically induced domain structure evolution using resonance-enhanced piezoresponse force microscopy. It has been shown that in strongly imprinted films application of switching pulses of opposite polarity results in qualitatively different domain switching dynamics. A distinct feature of domain dynamics is roughening of the domains walls during switching to the preferred polarization state as opposed to smooth domain boundaries during switching to the opposite direction. The observed switching behavior is explained by a combined effect of the spatially uniform built-in electric field and local disorder potential. Application of the external potential changes the balance between the two and creates conditions under which domain growth is dominated either by the average built-in electric field or local random-bond disorder potential. PMID:23221321

Sharma, Pankaj; Nakajima, Takashi; Okamura, Soichiro; Gruverman, Alexei

2013-01-11

92

Impact of compressive in-plane strain on the ferroelectric properties of epitaxial NaNbO3 films on (110) NdGaO3  

NASA Astrophysics Data System (ADS)

Epitaxial a-axis oriented NaNbO3 films are grown on (110) oriented NdGaO3 substrates. The lattice mismatch between substrate and film leads to compressive strain of ˜0.7% in the a-c plane. As a consequence, the in-plane permittivity and tunability are strongly enhanced compared to bulk NaNbO3, and a pronounced maximum in the temperature dependence of the permittivity occurs. Below the maximum at Tmax ? 250 K, ferroelectric behavior is observed that seems to vanish above Tmax. The pristine phase of the film at T < Tmax is antiferroelectric and is easily suppressed by small applied electric fields. The ferroelectric phase shows a relaxor type behavior.

Wördenweber, R.; Schwarzkopf, J.; Hollmann, E.; Duk, A.; Cai, B.; Schmidbauer, M.

2013-09-01

93

First Principles Phase Diagram Calculations for the System NaNbO3-KNbO3: can spinodal decomposition generate relaxor  

E-print Network

positions were fully relaxed. Pseudopotential valence electron configurations were: Na pv 2p6 3s1 ; K pv 3p6 generate relaxor ferroelectricity? B.P. Burton Materials Science and Engineering Laboratory, Ceramics-wave pseudopotentials23 with the generalized gradient approximation for exchange and correlation energies. Electronic

Burton, Benjamin P.

94

Dynamics of nanoscale polarization fluctuations in a uniaxial relaxor.  

PubMed

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

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

2014-10-17

95

Dynamics of Nanoscale Polarization Fluctuations in a Uniaxial Relaxor  

NASA Astrophysics Data System (ADS)

We have studied neutron diffuse scattering in a Sr0.61Ba0.39Nb2O6 single crystal by neutron backscattering at sub-?eV energy resolution. We can identify two response components with transverse polarization: an elastic (resolution limited) central peak, which monotonically increases with decreasing temperature, and a quasielastic central peak, having a maximum intensity around the ferroelectric phase transition close to 350 K. In contrast to previous neutron experiments on this and other relaxor materials, we were able to observe a temperature dependence of the characteristic frequency of these fluctuations, obeying the same Vogel-Fulcher law as the dynamic part of the dielectric permittivity of this material. In this way our findings provide a first direct link between the Vogel-Fulcher-type frequency dependence of dielectric permittivity and dynamic nanoscale lattice modulations with a transverse correlation length of about 5-10 unit cells.

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

2014-10-01

96

Domain wall roughness and creep behavior in nanoscale crystalline ferroelectric oxide and polymer films  

NASA Astrophysics Data System (ADS)

We have studied the static and dynamic properties of domain wall (DW) in nanoscale crystalline ferroelectric oxide Pb(Zr,Ti)O3 (PZT) and poly(vinylidene-fluoride-trifluorethylene) (PVDF-TrFE) films of 20 to 40 nm thick using piezo-response force microscopy. DW roughness exponent ? is extracted from the correlation function of DW displacement. At room temperature, ? of PVDF-TrFE is 0.4 to 0.48, much higher than those obtained on the PZT films (0.2-0.3). Combined with the dynamic studies of the DW creep behavior, this yields an effective dimensionality of 1.5 for PVDF-TrFE films, in sharp contrast to deff˜ 2.5 observed in PZT films. We have also thermally quenched the DWs after heating them at high temperatures. Thermal quench causes significant change in the DW configuration in PZT films with ? increasing to ˜ 0.5 after the films are heated close to the Curie temperature TC. On the other hand, the DWs in PVDF-TrFE films exhibit very weak temperature dependence. We attribute this distinctly different behavior to the strong anisotropy between in-plane and out-of-plane interaction in PVDF-TrFE, which is absent in PZT.

Xiao, Zhiyong; Poddar, Shashi; Ducharme, Stephen; Hong, Xia

2013-03-01

97

Ferroelectric phase transition and soft-mode behavior in BaxSr1-xTiO3: a refined treatment of a quasi-harmonic model  

NASA Astrophysics Data System (ADS)

The composition and temperature dependences of the soft-mode and ferroelectric phase transition in BaxSr1-xTiO3 (BST) are presented and analyzed within the framework of a refined treatment of a quasi-harmonic model (QHM) for quantum particles. The QHM involves generalized simple microscopic quantum particles with anharmonic on-site double-Morse-type potential and harmonic interactions. The theory uses the variational principle scheme at finite temperature in the mean-field approximation while taking into account the predominant mass effect, the cell volume effect as well as ferroelectric distortion. The soft-mode frequency and the Ba concentration (x) dependence of the ferroelectric phase transition temperature are analyzed and show good agreement with experimental results throughout the full x range (0 ? x ? 1). It is found that BST is paraelectric below the critical impurity concentration xc = 0.01 with a softening of the soft mode. It becomes ferroelectric above this critical concentration (x ? xc), and as the impurity concentration increases the predominant displacive soft-mode behavior stiffens in the ferroelectric phase with much less softening in crystals indicating a possible phase change at high x. Around x?c = 0.5, Tc deviates gradually from linear behavior with a rather slight round stagnation which might characterize an equilibrium ‘region’ where several ferroelectric phases coexist. The proposed x dependence of the soft-mode behavior indicates that the ferroelectric phase transition is of first order in BST with x > x?c, and of second order for low Ba concentrations (xc ? x < x?c), throughout the tricritical point at x = x?c. Finally, the quantum dynamics of the ferroelectric phase transition and the mode softening are also addressed and discussed, suggesting a net increase of quantum effects with a decrease of x for x ? 0.1, and a dominant Curie-Weiss law for x > 0.1.

Mkam Tchouobiap, S. E.; Dikande, A. M.; Mashiyama, H.

2014-09-01

98

Polar octahedral rotations, cation displacement and ferroelectricity in multiferroic SmCrO3  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

99

Unconventional ferroelectric behavior in nanosegregating liquid crystals with de Vries-like behavior.  

PubMed

Two nanosegregating siloxane-terminated mesogens with chiral (S,S)-2,3-epoxyoctyloxy side chains (E6, E11) have been synthesized. These compounds form chiral SmA? and SmC? phases and show an untypical behavior of the spontaneous polarization which increases with decreasing temperature in a convex manner while the tilt angle saturates. We compare these results with results obtained for two similar mesogens with chiral (R,R)-2,3-difluorooctyloxy side chains (F6, F11), which both show a typical concave curvature with decreasing temperature. A theoretical explanation is given for the unexpected temperature dependency of the spontaneous polarization. The materials also exhibited first-order SmC?-SmA? phase transitions and hence, very high values of the tilt angle. All substances show increased de Vries character in the range of 50%, which is substantially higher than 20% for the nonsiloxane analogs. Furthermore, for the latter materials, second-order phase transitions are common, while the siloxane materials exhibit first-order SmA?-SmC? phase transitions. These results clearly suggest that the achievement of nanosegregation is a powerful tool to induce de Vries behavior and to promote first-order SmA?-SmC? phase transitions. PMID:21230087

Nonnenmacher, Dorothee; Osipov, Mikhail A; Roberts, Jeffrey C; Lemieux, Robert P; Giesselmann, Frank

2010-09-01

100

Evidence of ferroelectricity in SrFeO3-?  

NASA Astrophysics Data System (ADS)

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. Mössbauer 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.

Manimuthu, P.; Venkateswaran, C.

2012-01-01

101

Ferroelectricity in spiral magnets.  

PubMed

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

Mostovoy, Maxim

2006-02-17

102

The polarizability model for ferroelectricity in perovskite oxides.  

PubMed

This article reviews the polarizability model and its applications to ferroelectric perovskite oxides. The motivation for the introduction of the model is discussed and nonlinear oxygen ion polarizability effects and their lattice dynamical implementation outlined. While a large part of this work is dedicated to results obtained within the self-consistent-phonon approximation, nonlinear solutions of the model are also handled, which are of interest to the physics of relaxor ferroelectrics, domain wall motions, and incommensurate phase transitions. The main emphasis is to compare the results of the model with experimental data and to predict novel phenomena. PMID:22718683

Bussmann-Holder, Annette

2012-07-11

103

Critical behavior near the Lifshitz point in Sn2P2(S1 - xSex)6 ferroelectric semiconductors from thermal diffusivity measurements  

NASA Astrophysics Data System (ADS)

The thermal diffusivity of the ferroelectric family Sn2P2(SexS1 - x)6 (0 <= x <= 1) has been measured by a high-resolution ac photopyroelectric technique, using single crystals, with the aim of studying the evolution of the ferroelectric transition with Se doping. Its change from second order character to first order while passing the Lifshitz point (x?0.28) has been evaluated, as well as the splitting of the transition at high Se concentrations. The critical behavior of the ferroelectric transition in terms of the different universality classes and their underlying physical dominant effects (tricriticality, long-range dipole interactions, Lifshitz point) has been discussed using thermal diffusivity measurements in the very close vicinity of the critical temperature. This study reveals that for Se concentrations around the Lifshitz point, long-range dipole interactions do not play a significant role and that the critical parameters are close to those predicted for the Lifshitz universality class.

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

2011-01-01

104

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

SciTech Connect

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).

Wang, Yu

2013-12-06

105

Piezoresponse force microscopy studies of switching behavior of ferroelectric capacitors on a 100-ns time scale.  

PubMed

Piezoresponse force microscopy is a powerful technique for nm-scale studies but is usually limited by response time. In this Letter, we report the first direct studies of ferroelectric capacitor switching on a submicrosecond time scale. Simultaneous domain imaging and sub-mus transient current measurements establish a direct relationship between polarization P(t) and domain kinetics. Switching times scale with capacitor size over an order of magnitude. Small capacitors, where polarization reversal is dominated by domain wall motion, switch faster at high fields but more slowly at low fields while larger capacitors do the reverse. PMID:18352748

Gruverman, A; Wu, D; Scott, J F

2008-03-01

106

Ferroelectric properties of vinylidene fluoride copolymers  

Microsoft Academic Search

Ferroelectric properties of copolymers of vinylidene fluoride with trifluoroethylene and tetrafluoroethylene are described with special interest in their polarization reversal and phase transition behavior. The ferroelectric phase consists of all-trans molecules packed in a parallel fashion while molecules adopt irregular TT, TG, T[Gbar] conformations in the paraelectric phase. In the ferroelectric phase, polarization reversal occurs at very high fields (>

Takeo Furukawa

1989-01-01

107

Evolution of nanodomains in the uniaxial relaxor Sr0.61Ba0.39Nb2O6:Ce.  

PubMed

The evolution of the nanodomain pattern of the uniaxial relaxor ferroelectric strontium barium niobate doped with cerium was studied by piezoresponse force microscopy (PFM). The fractal-like nanodomains observed at room temperature decay on heating. At temperatures up to about 15 K above the Curie temperature, Tc = 320 K, areas of correlated polarization are still visible. On cooling from the paraelectric state to below Tc, a slow isothermal growth of nanodomain was found. The mean domain size increases according to a logarithmic law as predicted for the three-dimensional random field Ising model. PMID:17186907

Shvartsman, Vladimir V; Kleemann, Wolfgang

2006-12-01

108

Ferroelectric barium titanate nanocubes as capacitive building blocks for energy storage applications.  

PubMed

Highly uniform polymer-ceramic nanocomposite films with high energy density values were fabricated by exploiting the unique ability of monodomain, nonaggregated BaTiO3 colloidal nanocrystals to function as capacitive building blocks when dispersed into a weakly interacting dielectric matrix. Monodisperse, surface-functionalized ferroelectric 15 nm BaTiO3 nanoparticles have been selectively incorporated with a high packing density into poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) leading to the formation of biphasic BaTiO3-P(VDF-HFP) nanocomposite films. A systematic investigation of the electrical properties of the nanocomposites by electrostatic force microscopy and conventional dielectric measurements reveals that polymer-ceramic film capacitor structures exhibit a ferroelectric relaxor-type behavior with an increased intrinsic energy density. The composite containing 7% BaTiO3 nanocrystals displays a high permittivity (? = 21) and a relatively high energy density (E = 4.66 J/cm(3)) at 150 MV/m, which is 166% higher than that of the neat polymer and exceeds the values reported in the literature for polymer-ceramic nanocomposites containing a similar amount of nanoparticle fillers. The easy processing and electrical properties of the polymer-ceramic nanocomposites make them suitable for implementation in pulse power capacitors, high power systems and other energy storage applications. PMID:25255863

Parizi, Saman Salemizadeh; Mellinger, Axel; Caruntu, Gabriel

2014-10-22

109

Crystal structure and dielectric properties of ferroelectric ceramics in the BaO-Sm 2O 3-TiO 2Nb 2O 5 system  

Microsoft Academic Search

Some tungsten–bronze ferroelectrics were synthesized and characterized in the BaO-Sm2O3-TiO2-Nb2O5 system. Ba4Sm2Ti4Nb6O30 and Ba5SmTi3Nb7O30 had the tetragonal filled tungsten–bronze structure; while Ba3Sm3Ti5Nb5O30 consisted of the orthorhombic tungsten–bronze major phase and the BaTi4O9 secondary phase. The present dielectric ceramics exhibited relaxor behavior with the maximum temperatures around 185, 285 and 130°C for Ba3Sm3Ti5Nb5O30, Ba4Sm2Ti4Nb6O30 and Ba5SmTi3Nb7O30, respectively. Moreover, Ba3Sm3Ti5Nb5O30 exhibited a

X. H. Zheng; X. M. Chen

2003-01-01

110

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

SciTech Connect

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

Dolganov, P. V., E-mail: pauldol@issp.ac.ru; Dolganov, V. K. [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation); Cluzeau, P. [Universite Bordeaux I, Centre de Recherche Paul Pascal, CNRS (France)

2009-07-15

111

Ferroelectric polymers  

Microsoft Academic Search

In the early 1970s it became clear that the polymer polyvinylidene fluoride is ferroelectric. There have been extensive studies of its properties and of the properties of copolymers of vinylidene fluoride with tri- or tetra-fluoroethylene. This work has led to a fairly complete understanding of the ferroelectric and related properties of these materials. The emphasis in this review is on

R. G. Kepler; R. A. Anderson

1992-01-01

112

Ferroelectric Materials  

NASA Astrophysics Data System (ADS)

Ferroelectric materials offer a wide range of useful properties. These include ferroelectric hysteresis (used in nonvolatile memories), high permittivities (used in capacitors), high piezoelectric effects (used in sensors, actuators and resonant wave devices such as radio-frequency filters), high pyroelectric coefficients (used in infra-red detectors), strong electro-optic effects (used in optical switches) and anomalous temperature coefficients of resistivity (used in electric-motor overload-protection circuits). In addition, ferroelectrics can be made in a wide variety of forms, including ceramics, single crystals, polymers and thin films - increasing their exploitability. This chapter gives an account of the basic theories behind the ferroelectric effect and the main ferroelectric material classes, discussing how their properties are related to their composition and the different ways they are made. Finally, it reviews the major applications for this class of materials, relating the ways in which their key functional properties affect those of the devices in which they are exploited.

Whatmore, Roger

113

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

NASA Astrophysics Data System (ADS)

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

Harker, John Chamberlain

114

Magnetic properties and dielectric behavior in ferrite/ferroelectric particulate composites  

NASA Astrophysics Data System (ADS)

Particulate composites of ferrite and ferroelectric phases having the general formula ( x)BaTiO 3+(1- x)Ni 0.92Co 0.03Cu 0.05Fe 2O 4 (where x is mole fraction of components that varies as 0.85, 0.70 and 0.55) were prepared by conventional double-sintering ceramic method. The presence of constituent phases was confirmed by X-ray diffraction (XRD) technique. The average grain size was determined by using scanning electron micrographs. The variation of dielectric constant and tan ? with frequency in the range 20 Hz-1 MHz was studied. The variation of loss tangent (tan ?) and dielectric constant with temperature at fixed frequencies of 1 kHz, 10 kHz, 100 kHz and 1 MHz was also studied. The saturation magnetization ( Ms) and magnetic moment ( ?B in Bohr magnetons) are reported for all composites. The static magnetoelectric (ME) voltage coefficient was measured as a function of intensity of applied DC magnetic field. The changes were observed in dielectric properties as well as in ME output with variation in molar fraction of constituent phases. A maximum ME conversion factor of 538.59 ?V/cm G was observed for the composites with 70% BaTiO 3+30% Ni 0.92Co 0.03Cu 0.05Fe 2O 4. The present ME composites may be useful in preparing devices such as magnetic sensors and cables, etc.

Devan, R. S.; Chougule, B. K.

2007-04-01

115

Ferroelectric/ferroelastic behavior and piezoelectric response of lead zirconate titanate thin films under nanoindentation  

SciTech Connect

The electromechanical response of pure lead zirconate titanate (PZT) and Mn-doped PZT thin ferroelectric films under nanoindentation forces of up to 500 mN was investigated. The stress-induced current transients were measured as a function of the externally applied load on films of different thicknesses using a spherical WC-Co cermet indenter of 500 {mu}m nominal radius. It was found that the quasi-static current generated through the direct piezoelectric effect is superimposed with a contribution from irreversible domain processes during the loading/unloading cycle. The film thickness dependency of the electrical transients and an asymmetry of the current-force curves are attributed to the in-plane clamping stress in the films produced by a dissimilar substrate. Analysis of corresponding charge-force hysteresis loops revealed a significant role for the residual stress state on the polarization switching in thin films. By the application of an indentation force, a portion of Barkhausen jumps was empirically estimated to increase as a consequence of reduction of the clamping effect on domains. The Rayleigh hysteretic charge-force curves showed recovery of the charge released during the load-unload stress cycle. For the thicker 700 nm films, the total charge released during loading was fully recovered with weak hysteresis. In contrast, strong in-plane clamping stresses in the 70 nm thick films are suggested to be reponsible for incomplete recovery upon unloading. A considerable domain-wall contribution to the electromechanical response was demonstrated by an enhanced polarization state, which was shown by an increase of the effective piezoelectric coefficient d{sub eff} of about 35% of its initial value for the thin films at a maximum force of 500 mN.

Koval, V.; Reece, M.J.; Bushby, A.J. [Department of Materials, Queen Mary University of London, Mile End Road, London, E1 4NS (United Kingdom)

2005-04-01

116

Geometric frustration in compositionally modulated ferroelectrics.  

PubMed

Geometric frustration is a broad phenomenon that results from an intrinsic incompatibility between some fundamental interactions and the underlying lattice geometry. Geometric frustration gives rise to new fundamental phenomena and is known to yield intriguing effects such as the formation of exotic states like spin ice, spin liquids and spin glasses. It has also led to interesting findings of fractional charge quantization and magnetic monopoles. Mechanisms related to geometric frustration have been proposed to understand the origins of relaxor and multiferroic behaviour, colossal magnetocapacitive coupling, and unusual and novel mechanisms of high-transition-temperature superconductivity. Although geometric frustration has been particularly well studied in magnetic systems in the past 20 years or so, its manifestation in the important class formed by ferroelectric materials (which are compounds with electric rather than magnetic dipoles) is basically unknown. Here we show, using a technique based on first principles, that compositionally graded ferroelectrics possess the characteristic 'fingerprints' associated with geometric frustration. These systems have a highly degenerate energy surface and display critical phenomena. They further reveal exotic orderings with novel stripe phases involving complex spatial organization. These stripes display spiral states, topological defects and curvature. Compositionally graded ferroelectrics can thus be considered the 'missing link' that brings ferroelectrics into the broad category of materials able to exhibit geometric frustration. Our ab initio calculations allow deep microscopic insight into this novel geometrically frustrated system. PMID:21307851

Choudhury, Narayani; Walizer, Laura; Lisenkov, Sergey; Bellaiche, L

2011-02-24

117

Reassessment of the Burns temperature and its relationship to the diffuse scattering, lattice dynamics, and thermal expansion in relaxor Pb(Mg1\\/3Nb2\\/3)O3  

Microsoft Academic Search

We have used neutron scattering techniques that probe time scales from 10-12 to 10-9s to characterize the diffuse scattering and low-energy lattice dynamics in single crystals of the relaxor PbMg1\\/3Nb2\\/3O3 (PMN) from 10 to 900 K. Our study extends far below Tc=213K , where long-range ferroelectric correlations have been reported under field-cooled conditions, and well above the nominal Burns temperature

P. M. Gehring; H. Hiraka; C. Stock; S.-H. Lee; W. Chen; Z.-G. Ye; S. B. Vakhrushev; Z. Chowdhuri

2009-01-01

118

Ferroelectric Materials  

Microsoft Academic Search

Ferroelectric materials offer a wide range of useful properties. These include ferroelectric hysteresis (used in nonvolatile memories), high permittivities (used in capacitors), high piezoelectric effects (used in sensors, actuators and resonant wave devices such as radio-frequency filters), high pyroelectric coefficients (used in infra-red detectors), strong electro-optic effects (used in optical switches) and anomalous temperature coefficients of resistivity (used in electric-motor

Roger Whatmore

2007-01-01

119

Ferroelectric memories  

Microsoft Academic Search

In the past year it has become possible to fabricate ferroelectric thin-film memories onto standard silicon integrated circuits that combine very high speed (30-nanosecond read\\/erase\\/rewrite operation), 5-volt standard silicon logic levels, very high density (2 by 2 micrometer cell size), complete nonvolatility (no standby power required), and extreme radiation hardness. These ferroelectric random-access memories are expected to replace magnetic core

J. F. Scott; C. A. Paz de Araujo

1989-01-01

120

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

PubMed

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

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

2011-12-01

121

Ferroelectric phase transitions in small particles and local regions.  

PubMed

Phase transitions in spherical particles of a cubic ferroelectric are considered within Landau-Ginzburg-Devonshire theory. Concentrating on effects of the depolarizing field, we study competition between states with homogeneous polarization and vortex structures. For large radii of the sphere (R>Rc), the phase transition is into a vortex state while for Rrelaxors. PMID:24033071

Levanyuk, A P; Blinc, R

2013-08-30

122

Long-ranged ferroelectric interactions in perovskite superlattices  

Microsoft Academic Search

Atomistic simulations show that there are long-ranged ferroelectric interactions between the ferroelectric layers in ferroelectric\\/paraelectric superlattices mediated by continuous chains of polarization running through the intervening paraelectric layers. The resulting behavior of the superlattice is strongly dependent on the modulation length. At short modulation lengths the superlattice acts as a single-component system; at long modulation lengths the individual ferroelectric layers

M. Sepliarsky; S. R. Phillpot; D. Wolf; M. G. Stachiotti; R. L. Migoni

2001-01-01

123

Long-ranged ferroelectric interactions in perovskite superlattices  

SciTech Connect

Atomistic simulations show that there are long-ranged ferroelectric interactions between the ferroelectric layers in ferroelectric/paraelectric superlattices mediated by continuous chains of polarization running through the intervening paraelectric layers. The resulting behavior of the superlattice is strongly dependent on the modulation length. At short modulation lengths the superlattice acts as a single-component system; at long modulation lengths the individual ferroelectric layers act almost independently.

Sepliarsky, M.; Phillpot, S. R.; Wolf, D.; Stachiotti, M. G.; Migoni, R. L.

2001-08-01

124

Optical interband transitions in [111] poled relaxor-based ferroelectric 0.24Pb(In1/2Nb1/2)O3-(0.76 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystal  

PubMed Central

Optical transmission spectra of single crystal 0.24Pb(In1/2Nb1/2)O3–(0.76 ? x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (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 = 3.09–3.18 eV and Egi = 2.89–2.96 eV, respectively, and the phonon energy is Ep = 0.07–0.08 eV. The transmission spectra were explained by the refractive indices and extinction coefficients measured by spectroscopic ellipsometry. PMID:25170190

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

2013-01-01

125

Electrical Properties of Barium and Zirconium Modified NBT Ferroelectric Ceramics  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

126

On the feasibility of synthesizing complex perovskite ferroelectric ceramics via a B-site oxide mixing route  

Microsoft Academic Search

Several relaxor-based complex perovskite ferroelectric ceramics were synthesized by conventional solid-state reaction method\\u000a via different routes, i.e., the B-site oxide mixing route, the straight calcination method and the columbite\\/wolframite precursor\\u000a method. Structure analysis and physical properties measurements prove that the B-site oxide mixing route is efficient and\\u000a feasible in the synthesizing of complex perovskite ferroelectrics since such a technique is

Bijun Fang; Renbing Sun; Yuejin Shan; Keitaro Tezuka; Hideo Imoto

2007-01-01

127

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)

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.

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

2014-09-01

128

Study of field-induced phase transitions in 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 relaxor single crystal by polarized micro-Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Polarized Raman spectroscopy has been performed to investigate the effects of the electric field on 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 (PMN-32PT) relaxor single crystal. Based on the group theory analysis, the Raman modes of PMN-32PT single crystal at zero-field are assigned to the monoclinic structure. The electric-field-evolution of Raman spectra reveal that a structural transition to tetragonal phase is initiated at a threshold electric field E1 and completed at higher field E2. In the intermediate field range from E1 to E2, the structure of the crystal is determined to be a coexistence of monoclinic and tetragonal phases. These results of the Raman spectra allow us to better understand the field-induced ultrahigh macroscopic strain in the relaxor ferroelectrics.

Chen, Chao; Deng, Hao; Li, Xiaobing; Zhang, Haiwu; Huang, Ting; Lin, Di; Wang, Sheng; Zhao, Xiangyong; Hu, Zhigao; Luo, Haosu

2014-09-01

129

Electric field and humidity effects on adsorbed water behavior on BaTiO3 ferroelectric domains studied by scanning probe microscopy  

NASA Astrophysics Data System (ADS)

Distribution of the adsorbed water on BaTiO3 ferroelectric single crystal (001) surface was investigated by means of scanning probe microscopy. Under high relative humidity, above 95%, the presence of water droplets was observed on domain surfaces. The droplets were up to 20 nm high and their morphology changed when electrical field was applied between the single crystal substrates and droplets via scanning probe microscopy. With an electric field applied parallel to the (001) top surface, the droplets on c domains spread out, followed by complete recovery upon switching the electric field off. However, few droplets on a domains tend to shrink with the electrical field application. It is shown that the screening surface charges and induced charges on droplets surface play a dominant role in droplets behavior.

He, D. Y.; Qiao, L. J.; Khodayari, Mehdi; Volinsky, Alex A.

2014-08-01

130

Ferroelectric phase transitions and dynamical behavior in KNbO{sub 3}/KTaO{sub 3} superlattices by molecular-dynamics simulation.  

SciTech Connect

The phase transitions and dynamical behavior of superlattices consisting of equal-thickness layers of a perovskite ferroelectric (KNbO{sub 3}) and a perovskite paraelectric (KTaO{sub 3}) are explored using molecular-dynamics simulation. We find that the response in the plane and in the modulation direction are essentially decoupled. The Curie temperature for the transition from a polarized to unpolarized state in the modulation direction decreases approximately linearly with modulation length, {Lambda}, for {Lambda}>12; for smaller modulation lengths, it is essentially constant. The Curie temperature in the plane appears to be only weakly modulation-length dependent. We relate our results to experimental findings on the same system.

Sepliarsky, M.; Phillpot, S. R.; Stachiotti, M. G.; Migoni, R. L.; Materials Science Division; Inst. de Fisica Rosario

2002-03-01

131

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)

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.

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

2013-05-01

132

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

SciTech Connect

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

Lu, C.J.; Nie, C.J.; Duan, X.F.; Li, J.Q.; Zhang, H.J.; Wang, J.Y. [Department of Materials Science and Engineering, Hubei University, Wuhan, Hubei 430062, (China) and Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Institute of Crystal Materials, Sandong University, Jinan 250100 (China)

2006-05-15

133

Dynamics of Ferroelectric Domain Walls  

Microsoft Academic Search

Dielectric data obtained in the ferroelectric phase of KH2PO4 and Rb2ZnCl4 single crystals as well as in PZT-ceramics are provided demonstrating qualitatively similar behavior in quite different ferroelectric\\u000a systems. The peculiar low frequency dispersion, nonlinearity, dielectric loss and ageing phenomena, respectively, reflect\\u000a the creep-like dynamics of highly susceptible domain walls. The significance of the domain wall-defect interaction becomes\\u000a evident from

Volkmar Mueller

2001-01-01

134

Ferroelectricity at the nanoscale  

NASA Astrophysics Data System (ADS)

The properties of ferroelectrics at the nanoscale are reviewed. The term nanoscale is here related to the ferroelectric film thickness (which is by an order of magnitude the size of the critical domain nucleus). The three aspects considered are ferroelectric switching, the scaling of the coercive field, and the bulk photovoltaic effect. While ferroelectricity at the nanoscale has a twenty-year history of study, it is only in the last few years that perovskite ferroelectric films have become a focus of interest.

Fridkin, V. M.; Ducharme, S.

2014-06-01

135

Ferroelectric domain wall relaxation in Ba{sub 0.25}Sr{sub 0.75}TiO{sub 3} films displaying Curie-Weiss behavior  

SciTech Connect

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 Ba{sub 0.25}Sr{sub 0.75}TiO{sub 3} layers between metallic oxide (100 nm) SrRuO{sub 3} and (120 nm) La{sub 0.67}Ca{sub 0.33}MnO{sub 3}, films in epitaxial heterostructures. The electric field response (E{<=}80 kV/cm) of the real {epsilon}{sup '} and imaginary {epsilon}{sup ''} parts of the complex permittivity of the intermediate Ba{sub 0.25}Sr{sub 0.75}TiO{sub 3} layer in these parallel plane film capacitors was studied at temperatures above and below the phase transition point T{sub Curie}. The latter was determined from the temperature dependence of the inverse dielectric permittivity and its value, T{sub Curie}=145 K, agrees well with that of bulk single crystal. {epsilon}{sup '} of the Ba{sub 0.25}Sr{sub 0.75}TiO{sub 3} layer could be suppressed about 80% by a field E=80 kV/cm at temperatures close to T{sub Curie}{epsilon}{sup '}(T,E) and {epsilon}{sup ''}(T,E) curves were used to gain insight into the relaxation dynamics of ferroelectric domain walls (DW) in the Ba{sub 0.25}Sr{sub 0.75}TiO{sub 3} layer. Their influence on {epsilon}{sup '} was noticed up to T=230 K, well above T{sub Curie}. The most probable relaxation time {tau} of the DW in Ba{sub 0.25}Sr{sub 0.75}TiO{sub 3} follows a relation {tau}={tau}{sub 0} exp[({phi}-{beta}{radical}(E))/kT], where {tau}{sub 0}=1.2x10{sup -10} s {phi}=75-105 meV, and {beta}=4.7x10{sup -24} J m{sup 1/2} V{sup -1/2}.

Boikov, Yu.A.; Khamchane, K.; Claeson, T. [Microtechnology and Nanoscience, Quantum Device Physics Laboratory, Chalmers University of Technology, SE-412 96 Goeteborg, Sweden and Ioffe Physico-Technical Institute Russian Academy of Science, 194 021 St. Petersburg (Russian Federation); Microtechnology and Nanoscience, Quantum Device Physics Laboratory, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden)

2004-10-15

136

Theoretical approach to study the effect of free volumes on the physical behavior of polymer stabilized ferroelectric liquid crystal molecules  

NASA Astrophysics Data System (ADS)

It was clearly indicative that the polymer chains make a tremendous interaction with the tilt angle in case of a polymer stabilized ferroelectric liquid crystal (PSFLC). After suitable consideration of such interaction, we expanded the Landau free energy for a PSFLC system. We theoretically demonstrated the effect of free volumes, which expected to create bulk self-energy, on the physical functionalities of a PSFLC system. Then we obtained spontaneous polarization, tilt angle, rotational viscosity and dielectric constant strongly correlated with the assumed interactions. We also observed a shift of transition temperature highly influenced by this interaction between polymer network and liquid crystal molecules. A microscopical picture of this polymer-liquid crystal interaction is provided in view of the free volume charge density present in the composite system.

Lahiri, T.; Majumder, T. Pal

2011-06-01

137

Anomalous Ferroelectric Hysteresis Loops.  

National Technical Information Service (NTIS)

Materials that exhibit anomalous ferroelectric hysteresis loops appear throughout the literature. These loops have irregular shapes that diverge from the normal hysteresis loop which is characteristic of most ferroelectrics. The observation of a unique hy...

F. J. Murdoch

1971-01-01

138

Ferroelectric ultrathin perovskite films  

DOEpatents

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.

Rappe, Andrew M; Kolpak, Alexie Michelle

2013-12-10

139

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)

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.

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

2011-09-01

140

Spontaneous vortex nanodomain arrays at ferroelectric heterointerfaces.  

PubMed

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

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

2011-02-01

141

Computational modeling of domain wall interactions with dislocations in ferroelectric crystals  

E-print Network

Computational modeling of domain wall interactions with dislocations in ferroelectric crystals framework to investigate the interactions between domain walls and arrays of dislocations in ferroelectric of ferroelectric behavior since they interact with domain walls at submicron scales. For example, Yang et al. (1999

142

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

NASA Astrophysics Data System (ADS)

The high piezoelectric response of the ferroelectric relaxor (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 (PMNT) in single crystal form has generated significant interest in producing broad bandwidth SONAR systems. Both the piezoelectric coefficient (d33 > 2000 pC/N) and coupling coefficient (k33 > 0.90) are superior to those of conventional piezoelectric ceramics. Within the context of a high power acoustic projector, its high losses and low temperature stability have limited its development. Second generation single crystals with compositions modified from the base PMNT have been recently developed to decrease the electromechanical losses and mitigate the thermal property dependence. In this work, the electromechanical properties were measured using single crystals which have been modified in various ways. The modified crystals exhibit electromechanically "hard" behavior with lower losses (tan delta = 0.1--0.2% and QM = 230--950) than unmodified PMNT (tan delta = 0.26% and QM = 190). The measured d33 values of modified single crystals (d33 = 760--1490 pm/V) are also lower than unmodified PMNT (d33 = 1540 pm/V), but the lower piezoelectric response is compensated by the greater stability of the modified single crystals. These modified single crystal properties were also compared to conventional high power piezoelectric ceramics ( d33 = 240 pm/V and QM = 1050) to show similar losses but significantly greater response in the modified PMNT single crystals. Although most piezoelectric materials are measured under small signal conditions (small signal defined by a completely linear relationship between the input and output signals), the high power nature of SONAR projectors demands that these modified single crystals also be evaluated under high power conditions. A test procedure was developed to measure the electromechanical properties of each material as a function of applied electric field over a frequency range which includes the resonance frequency. Modified single crystals showed twice the dynamic strain of unmodified PMNT as a function of electric field, and in many cases also showed greater maximum strain at failure (0.3% compared to 0.15% for unmodified PMNT). When QM was measured as a function of drive level, it was shown to sharply decrease under high dynamic strain. Modified single crystals with greater small signal QM values than unmodified PMNT maintain higher QM values under high drive, with Q M = 50--150 immediately prior to sample failure (Q M = 20 for base PMNT immediately prior to failure). The temperature dependence of modified PMNT single crystal electromechanical properties was also determined, and it was shown that modified crystals possess greater property stability than unmodified PMNT. While the base composition shows a limiting rhombohedral-tetragonal transition at 95 °C, modified single crystals using ternary PIN and PZT components show increased transition temperatures of 125 °C and 144 °C, respectively. The greater phase stability of the PIN ternary crystal was also examined through the coercive field, which was shown to be much greater than that of unmodified PMNT over the temperature range of interest (Ec = 5 kV/cm and 2 kV/cm, respectively, at room temperature). From the combined set of property measurements, the heat generation of each material was predicted for an arbitrary projector device. As a consequence of the lower losses, modified single crystals showed as little as 25% of the heat generation value for unmodified PMNT single crystals. Using this prediction as a performance metric, the crystals with the lowest heat generation were selected for device testing. Transducers with base PMNT and modified single crystals were designed using a finite element modeling approach. This model predicted approximately two octaves of bandwidth for the transducer geometry under investigation. A 5 dB decrease in acoustic output was observed when moving from base PMNT to highly modified crystals, but that result does not account for nonlinear material behavior. Transducers fabricated using mod

Sherlock, Nevin P.

143

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

SciTech Connect

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.

Maignan, A., E-mail: antoine.maignan@ensicaen.fr [Laboratoire CRISMAT, UMR 6508 CNRS/ENSICAEN, 6 bd du Marechal Juin, F-14050 CAEN Cedex 4 (France); Martin, C.; Singh, K.; Simon, Ch.; Lebedev, O.I. [Laboratoire CRISMAT, UMR 6508 CNRS/ENSICAEN, 6 bd du Marechal Juin, F-14050 CAEN Cedex 4 (France)] [Laboratoire CRISMAT, UMR 6508 CNRS/ENSICAEN, 6 bd du Marechal Juin, F-14050 CAEN Cedex 4 (France); Turner, S. [EMAT, University of Antwerp, B-2020 Antwerp (Belgium) [EMAT, University of Antwerp, B-2020 Antwerp (Belgium); Canadian Centre for Electron Microscopy, McMaster University, Hamilton, ON L8S4M1 (Canada)

2012-11-15

144

A light-modified ferroelectric resistive switching behavior in Ag/BaMoO4/FTO device at ambient temperature  

NASA Astrophysics Data System (ADS)

BaMoO4 powder was prepared by a facile hydrothermal synthesis. And the BaMoO4/FTO device was fabricated by a spin-coated method, in which the thickness of BaMoO4 layer is about 20 ?m. The bipolar resistive switching effect has been observed in Ag/BaMoO4/FTO device. Moreover, the resistive switching effect of the device is greatly improved by white light irradiation. The resistive switching behavior is explained by the polarization reversal that changes the charge distribution and modulates the Schottky barriers.

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

2014-12-01

145

Ferroelectric liquid crystal display  

NASA Technical Reports Server (NTRS)

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.

York, Paul K. (Inventor)

1977-01-01

146

Statistical mechanical origin of hysteresis in ferroelectrics  

NASA Astrophysics Data System (ADS)

Hysteresis in ferroelectric materials is a strong non-linear phenomenon, the origin of which has drawn considerable attention. Based on the hopping probability function of the lattice-center ion crossing the ferroelectric double-well potential, a statistical mechanical theory is proposed to model ferroelectric hysteresis behavior. The hopping probability function is obtained from the statistical distribution function of ions in energy space, which is derived from the mathematical permutation and combination of the occupy-states of lattice-center ion. The calculated hysteresis agrees well with experimental measurements. In particular, the model provides interesting explanations to the polarization current and the coercive field, which differ from traditional microscopic models and thermodynamic theories.

Yang, Feng; Hu, Guangda; Xu, Baixiang; Wu, Weibing; Yang, Changhong; Wu, Haitao

2012-08-01

147

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

NASA Astrophysics Data System (ADS)

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

Fukazawa, Hiroshi

148

Impact of the concentration in polymer on the dynamic behavior of Polymer Stabilized Ferroelectric Liquid Crystal using Snap-shot Mueller Matrix Polarimetry.  

PubMed

Experimental results are presented related to the dynamic behaviour of Polymer Stabilized Ferro-electric Liquid Crystal (PSFLC) samples under external applied electric field, using Snap-shot Mueller Matrix Polarimetry (SMMP) and Mueller Matrix (MM) formalism. Different polarimetric coefficients are simultaneously extracted from each channeled spectrum measured with this full-optical SMMP technique. The impact of the concentration of polymer present into the liquid crystal cell on this dynamic behaviour is studied, permitting a direct and quick characterisation of the material. The results obtained for PSFLC are compared with those already measured for pure Surface Stabilized Ferro-electric Liquid Crystal (SSFLC) samples, which correspond to a 0% concentration in polymer. PMID:23715883

Babilotte, Philippe; Silva, Vinicius N H; Dubreuil, Matthieu; Rivet, Sylvain; Dupont, Laurent; Le Jeune, Bernard

2013-05-01

149

Ferroelectric properties in Mn-modified BiFeO3-BaTiO3 ceramics  

NASA Astrophysics Data System (ADS)

Multiferroic 0.4 mol%-MnO2-doped 0.78BiFeO3-0.22BaTiO3 ceramics were prepared by a traditional ceramic process. The effects of doping and annealing on the dielectric and ferroelectric properties were intensively investigated. Dielectric dispersion like relaxor ferroelectrics was observed in the oxygen annealed sample, but disappeared in the vacuum annealed sample. Modification of the BiFeO3-BaTiO3 with MnO2 and annealing in vacuum improved DC resistivity obviously. The spontaneous polarization, remnant polarization, and coercive field are 65.2 ?C/cm2, 59.5 ?C/cm2 and 21.9 kV/cm, respectively under an applied field of 35 kV/cm.

Dai, Zhonghua; Akishige, Yukikuni

2014-12-01

150

Ferroelectric Light Control Device  

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

151

Investigation of ferroelectric liquid crystal orientation in the silica microcapillaries  

NASA Astrophysics Data System (ADS)

In the paper we present our recent results concerning the orientation of ferroelectric liquid crystal molecules inside silica micro capillaries. We have infiltrated the silica micro capillaries with experimental ferroelectric liquid crystal material W-260K synthesized in the Military University of Technology. The infiltrated micro capillaries were observed under the polarization microscope while both a polarizer and an analyzer were crossed. The studies on the orientation of ferroelectric liquid crystal molecules may contribute to further studies on behavior of this group of liquid crystal materials inside photonic crystal fiber. The obtained results may lead to design of a new type of fast optical fiber sensors.

Budaszewski, D.; Doma?ski, A. W.; Woli?ski, T. R.

2013-05-01

152

First-principles study on the differences of possible ferroelectric behavior and magnetic exchange interaction between Bi2NiMnO6 and La2NiMnO6  

NASA Astrophysics Data System (ADS)

The differences of possible ferroelectric behavior and magnetic exchange interaction between Bi2NiMnO6 and La2NiMnO6 have been investigated by first-principles calculation. Paying attention to the electronic structures, bonding interaction, and Born effective charges of the two compounds, the calculations reveal that ferroelectric distortion occurs only in Bi2NiMnO6 rather than La2NiMnO6. The calculation also indicates that the Ni-Mn ferromagnetic exchange interaction is weakened in Bi2NiMnO6 compared with that in La2NiMnO6. Thus the present work explains why Bi2NiMnO6 has a lower Curie temperature compared with La2NiMnO6. The mechanism why Bi2NiMnO6 has weaker Ni-Mn ferromagnetic exchange interaction than La2NiMnO6 is explored by considering the Kugel-Khomskii model. Finally, the electric polarizations of Bi2NiMnO6 with ferromagnetic and ferrimagnetic order are estimated to be 18.05 and 19.01 ?C/cm2, respectively, indicating the anomaly of electric polarization near the Curie temperature of Bi2NiMnO6.

Jian Zhao, Hong; Ming Chen, Xiang

2012-12-01

153

Ferroelectric domain wall injection.  

PubMed

Ferroelectric domain wall injection has been demonstrated by engineering of the local electric field, using focused ion beam milled defects in thin single crystal lamellae of KTiOPO4 (KTP). The electric field distribution (top) displays localized field hot-spots, which correlate with nucleation events (bottom). Designed local field variations can also dictate subsequent domain wall mobility, demonstrating a new paradigm in ferroelectric domain wall control. PMID:24136810

Whyte, Jonathan R; McQuaid, Raymond G P; Sharma, Pankaj; Canalias, Carlota; Scott, James F; Gruverman, Alexei; Gregg, J Marty

2014-01-15

154

Cryogenic temperature relaxor-like dielectric responses and magnetodielectric coupling in Aurivillius Bi5Ti3FeO15 multiferroic thin films  

NASA Astrophysics Data System (ADS)

Dielectric responses and magnetodielectric (MD) behavior of Aurivillius Bi5Ti3FeO15 multiferroics were systemically studied at cryogenic temperatures. Dielectric anomaly at ˜145 K was found by the temperature dependent dielectric spectroscopy, and relaxor-like relaxation dynamics was further confirmed unambiguously. Besides the two abnormal MD transitions at about 98 K and 220 K, remarkable MD couplings were observed near relaxation peak over the whole frequency range of 102-106 Hz. Finally, the possible mechanisms of the relaxation and MD properties were discussed in association with the occurrence of local Fe-O nano-clusters because of the antisite disorder defects in Aurivillius multiferroic phases.

Bai, Wei; Yin, Wenhao; Yang, Jing; Tang, Kai; Zhang, Yuanyuan; Lin, Tie; Meng, Xiangjian; Duan, Chun-Gang; Tang, Xiaodong; Chu, Junhao

2014-08-01

155

Ferroelectric thin films  

SciTech Connect

The area of ferroelectric thin films has expanded rapidly recently with the advent of high quality multi-oxide deposition technology. Advances in thin film quality has resulted in the realization of new technologies not achievable through classical bulk ceramic processing techniques. An example of this progress is the co-processing of ferroelectric thin films with standard semiconductor silicon and GaAs integrated circuits for radiation hard, non-volatile memory products. While the development of this class of products is still embryonic, the forecasted market potential is rapidly out distancing the combined developmental effort. Historically the greatest use of bulk ferroelectric material has been in sensor technology, utilizing the pyroelectric and piezoelectric properties of the material. By comparison, a relatively small development effort has been reported for ferroelectric thin film senor technology, a field sure to provide exciting advances in the future. The papers in this proceedings volume were presented at the first symposium dedicated to the field of ferroelectric thin films held by the Materials Research Society at the Spring 1990 Meeting in San Francisco, CA, April 16-20, 1990. The symposium was designed to provide a comprehensive tutorial covering the newest advances of ferroelectric thin films, including material systems, new deposition techniques and physical, electrical and electro-optic characterization.

Myers, E.R. (National Semiconductor Corp., Santa Clara, CA (United States)); Kingon, A.I. (North Carolina State Univ., Raleigh, NC (United States))

1990-01-01

156

Bending characteristics of ferroelectric poly(vinylidene fluoride trifluoroethylene) capacitors fabricated on flexible polyethylene naphthalate substrate  

Microsoft Academic Search

Ferroelectric capacitors using poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] were fabricated on the plastic polyethylene naphthalate (PEN) substrate for the various applications of flexible-type nonvolatile memories. It was successfully confirmed that the Au\\/P(VDF-TrFE)\\/Au capacitors showed sound ferroelectric characteristics even when they were fabricated using a lithography-compatible patterning process at low temperature below 150°C in the PEN. The behaviors of ferroelectric polarization and saturation

Sung-Min Yoon; Soon-Won Jung; Shinhyuk Yang; Sang-Hee Ko Park; Byoung-Gon Yu; Hiroshi Ishiwara

2011-01-01

157

Coexistence of ergodicity and nonergodicity in LaFeO3-modified Bi1/2(Na0.78K0.22)1/2TiO3 relaxors  

NASA Astrophysics Data System (ADS)

The effect of LaFeO3 addition to Bi1/2(Na0.78K0.22)1/2TiO3 ceramics on the phase stability and macroscopic functional properties was investigated. Similarly to other chemical modifiers known in the literature, LaFeO3 addition suppresses an electric-field-induced long-range ferroelectric order, giving rise to a giant unipolar strain of ˜0.3% at 2 mol% LaFeO3 addition. Time-dependent changes in polarization and strain hysteresis loops both during successive electrical cycling and after removal of the electric field suggest that a specimen with 2 mol% LaFeO3 consists of both ergodic and nonergodic phases, which is unique among the known relaxor materials.

Han, Hyoung-Su; Jo, Wook; Rödel, Jürgen; Hong, In-Ki; Tai, Weon-Pil; Lee, Jae-Shin

2012-09-01

158

Coexistence of ergodicity and nonergodicity in LaFeO3-modified Bi(1/2)(Na(0.78)K(0.22))(1/2)TiO3 relaxors.  

PubMed

The effect of LaFeO(3) addition to Bi(1/2)(Na(0.78)K(0.22))(1/2)TiO(3) ceramics on the phase stability and macroscopic functional properties was investigated. Similarly to other chemical modifiers known in the literature, LaFeO(3) addition suppresses an electric-field-induced long-range ferroelectric order, giving rise to a giant unipolar strain of ~0.3% at 2 mol% LaFeO(3) addition. Time-dependent changes in polarization and strain hysteresis loops both during successive electrical cycling and after removal of the electric field suggest that a specimen with 2 mol% LaFeO(3) consists of both ergodic and nonergodic phases, which is unique among the known relaxor materials. PMID:22907150

Han, Hyoung-Su; Jo, Wook; Rödel, Jürgen; Hong, In-Ki; Tai, Weon-Pil; Lee, Jae-Shin

2012-09-12

159

Critical behavior of director fluctuations in suspensions of ferroelectric nanoparticles in liquid crystals at the nematic to smectic-A phase transition.  

PubMed

By dynamic light scattering we studied the temperature dependence of scattered intensities and relaxation rates for pure twist and pure bend modes in a colloidal system of BaTiO(3) single domain nanoparticles and liquid crystal octylcyanobiphenyl (8CB) close to the nematic to smectic-A phase transition. From the experiments we obtained the critical exponents for the smectic correlation lengths, which in suspensions differ from the values for pure 8CB. The phase transition temperatures from isotropic to nematic phase (T(NI)) and from nematic to smectic-A phase (T(NA)) are both affected by the presence of the particles in two ways. The electric field around the ferroelectric particles increases the transition temperatures, whereas the disorder and probably also the excess of the surfactant cause a decrease of the transition temperatures compared to pure 8CB. The net effect is lower T(NI) and almost unchanged T(NA) in suspensions. After prolonged exposure to the external field the ferroelectric particles irreversibly aggregate, which results in the decrease of the internal electric field and, consequently, in the decrease of both transition temperatures. PMID:22463229

Mertelj, Alenka; Cmok, Luka; ?opi?, Martin; Cook, Gary; Evans, Dean R

2012-02-01

160

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

161

Polarization fatigue of organic ferroelectric capacitors  

PubMed Central

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

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

162

Polarization fatigue of organic ferroelectric capacitors  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

163

Large magnetocapacitance in electronic ferroelectric manganite systems  

SciTech Connect

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

Chowdhury, Ujjal; Goswami, Sudipta; Bhattacharya, Dipten, E-mail: dipten@cgcri.res.in [Nanostructured Materials Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata 700032 (India); Midya, Arindam; Mandal, P. [Experimental Condensed Matter Physics, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Das, Pintu [Institute of Physics, J.W. Goethe University, D-60438 Frankfurt (Germany); Mukovskii, Ya. M. [National Research Technological University, “MISiS,” Moscow 119049 (Russian Federation)

2013-11-21

164

Polarization fatigue of organic ferroelectric capacitors.  

PubMed

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 10(8) times, approaching the programming cycle endurance of its inorganic ferroelectric counterparts. PMID:24861542

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

165

Large magnetocapacitance in electronic ferroelectric manganite systems  

NASA Astrophysics Data System (ADS)

We have observed a sizable positive magnetocapacitance (˜5%-90%) in perovskite Pr0.55Ca0.45MnO3 and bilayer Pr(Sr0.1Ca0.9)2Mn2O7 system under 5 T magnetic field across 20-100 K below the magnetic transition point TN. The magnetodielectric effect, on the other hand, exhibits a crossover: (a) from positive to negative for the perovskite system and (b) from negative to positive for the bilayer system over the same temperature range. The bilayer Pr(Sr0.1Ca0.9)2Mn2O7 system exhibits a sizable anisotropy as well. We have also noticed the influence of magnetic field on the dielectric relaxation characteristics of these systems. These systems belong to a class of improper ferroelectrics and are expected to exhibit charge/orbital order driven ferroelectric polarization below the transition point TCO. Large magnetocapacitance in these systems shows a typical multiferroic behavior even though the ferroelectric polarization is small in comparison to that of other ferroelectrics.

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

2013-11-01

166

Compositional inversion symmetry breaking in ferroelectric perovskites  

PubMed

Cubic perovskite compounds of the form (A(1/3)A(')(1/3)A(")(1/3))BO3 and A(B(1/3)B(')(1/3)B(")(1/3))O3, in which the differentiated cations form an alternating series of monolayers, are studied using first-principles methods. Such compounds are representative of a possible new class of materials in which ferroelectricity is perturbed by compositional breaking of inversion symmetry. For isovalent substitution the ferroelectric double-well potential becomes asymmetric, so that minority domains may no longer survive. The symmetry breaking is enormously stronger for heterovalent substitution; here the double-well behavior is destroyed. Tuning between these behaviors may allow for the optimization of desired materials properties. PMID:10991013

Sai; Meyer; Vanderbilt

2000-06-12

167

Nanostructured ferroelectrics: fabrication and structure-property relations.  

PubMed

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

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

2011-10-25

168

Ferroelectric tunneling element and memory applications which utilize the tunneling element  

DOEpatents

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.

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

169

Coupling of ferroelectricity and ferromagnetism through Coulomb blockade in composite multiferroics  

NASA Astrophysics Data System (ADS)

Composite multiferroics are materials exhibiting the interplay of ferroelectricity, magnetism, and strong electron correlations. Typical example—magnetic nano grains embedded in a ferroelectric matrix. Coupling of ferroelectric and ferromagnetic degrees of freedom in these materials is due to the influence of ferroelectric matrix on the exchange coupling constant via screening of the intragrain and intergrain Coulomb interaction. Cooling typical magnetic materials the ordered state appears at lower temperatures than the disordered state. We show that in composite multiferroics the ordered magnetic phase may appear at higher temperatures than the magnetically disordered phase. In nonmagnetic materials such a behavior is known as inverse phase transition.

Udalov, O. G.; Chtchelkatchev, N. M.; Beloborodov, I. S.

2014-05-01

170

SOFT MODE ANOMALIES IN THE PEROVSKITE RELAXOR Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}  

SciTech Connect

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.

GEHRING,P.M.; VAKRUSHEV,S.B.; SHIRANE,G.

2000-03-09

171

Ferroelectric studies of excessive Sm3+ containing perovskite PZT and pyrochlore biphase ceramics  

NASA Astrophysics Data System (ADS)

Polycrystalline samples of Sm3+ modified Pb1-x Sm2x/3 (Zr0.6Ti0.4) O3 (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 Sm2Ti2O7 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.

Babu, T. Anil; Ramesh, K. V.; Reddy, V. Raghavendra; Sastry, D. L.

2014-04-01

172

Structure of ferroelectric surfaces  

Microsoft Academic Search

The structural characteristics of the surface layer of some of the well-known common ferroelectrics are examined in the light of recent experimental data obtained by a variety of analytical techniques, including Auger electron spectroscopy, UV and X-ray photoelectron spectroscopy, slow and fast electron diffraction analyses, and scanning electron microscopy. The discussion covers the electron and atomic structure, chemical composition, microstructure

Iu. Ia. Tomashpol'Skii

1987-01-01

173

Domain switching of fatigued ferroelectric thin films  

NASA Astrophysics Data System (ADS)

We investigate the domain wall speed of a ferroelectric PbZr0.48Ti0.52O3 (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.

Tak Lim, Yun; Yeog Son, Jong; Shin, Young-Han

2014-05-01

174

Complex structural-ferroelectric domain walls in thin films of hexagonal orthoferrites RFeO3 (R = Lu, Er)  

NASA Astrophysics Data System (ADS)

Hexagonal orthoferrites have recently attracted much attention as possible high-temperature ferromagnetic ferroelectrics. The ferroelectric domain structure of hexagonal RMnO3, their antiferromagnetic structural analogies, has recently shown an atypical and complicated behavior. Hexagonal RFeO3 are expected to exhibit similar domain structure that should coexist with weak ferromagnetic order and may represent a material with a unusual magnetoelectric interaction. In this report, we discuss microscopic ferroelectric domain structure of hexagonal orthoferrites in a thin-film state and demonstrate a distinct and unusual improper ferroelectric behavior of these oxide materials.

Roddatis, Vladimir V.; Akbashev, Andrew R.; Lopatin, Sergei; Kaul, Andrey R.

2013-09-01

175

Domain dynamics during ferroelectric switching.  

PubMed

The utility of ferroelectric materials stems from the ability to nucleate and move polarized domains using an electric field. To understand the mechanisms of polarization switching, structural characterization at the nanoscale is required. We used aberration-corrected transmission electron microscopy to follow the kinetics and dynamics of ferroelectric switching at millisecond temporal and subangstrom spatial resolution in an epitaxial bilayer of an antiferromagnetic ferroelectric (BiFeO(3)) on a ferromagnetic electrode (La(0.7)Sr(0.3)MnO(3)). We observed localized nucleation events at the electrode interface, domain wall pinning on point defects, and the formation of ferroelectric domains localized to the ferroelectric and ferromagnetic interface. These results show how defects and interfaces impede full ferroelectric switching of a thin film. PMID:22096196

Nelson, Christopher T; Gao, Peng; Jokisaari, Jacob R; Heikes, Colin; Adamo, Carolina; Melville, Alexander; Baek, Seung-Hyub; Folkman, Chad M; Winchester, Benjamin; Gu, Yijia; Liu, Yuanming; Zhang, Kui; Wang, Enge; Li, Jiangyu; Chen, Long-Qing; Eom, Chang-Beom; Schlom, Darrell G; Pan, Xiaoqing

2011-11-18

176

Molecular ferroelectrics: where electronics meet biology  

PubMed Central

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

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

2013-01-01

177

From spin induced ferroelectricity to spin and dipolar glass in a triangular lattice: The CuCr1-xVxO2 (0?x?0.5) delafossite  

NASA Astrophysics Data System (ADS)

The change from antiferromagnetism induced ferroelectricity to spin glass ferroelectric relaxor has been studied along the CuCr1-xVxO2 (0?x?0.5) solid solution of polycrystalline samples. As x increases from CuCrO2 (x=0) to CuCr0.82V0.18O2, it is found that the Néel temperature decreases from ?24 K down to ?13 K. This progressive weakening of the antiferromagnetism of CuCrO2 induces a rapid decrease of the spin induced ferroelectricity with polarization values going from ?44 ?C/m2 down to ?1.5 ?C/m2 for x=0.04 and x=0.08, respectively. Beyond x=0.18 (0.20?x?0.50), ac-magnetic susceptibility and magnetization measurements evidence a spin glass state while dielectric permittivity and polarization measurements point towards a relaxor behaviour. This shows that competing magnetic interactions in delafossites are an efficient way to transform a spin induced magnetoelectric into a multiglass (spin and dipolar) state.

Kumar, S.; Singh, K.; Miclau, M.; Simon, Ch.; Martin, C.; Maignan, A.

2013-07-01

178

Structure of ferroelectric surfaces  

NASA Astrophysics Data System (ADS)

The structural characteristics of the surface layer of some of the well-known common ferroelectrics are examined in the light of recent experimental data obtained by a variety of analytical techniques, including Auger electron spectroscopy, UV and X-ray photoelectron spectroscopy, slow and fast electron diffraction analyses, and scanning electron microscopy. The discussion covers the electron and atomic structure, chemical composition, microstructure and domains, and surface phase transitions of such ferroelectrics as BaTiO3, SrTiO3, PbTiO3, Bi4Ti3O12, Bi2Ti2O7, KNbO3, LiNbO3, and Pb5Ge3O11.

Tomashpol'Skii, Iu. Ia.

1987-12-01

179

Ferroelectric quantum criticality  

NASA Astrophysics Data System (ADS)

Paramagnets on the border of ferromagnetism at low temperatures are more subtle and complex than anticipated by the conventional theory of quantum critical phenomena. Could quantum criticality theory be more relevant in the corresponding case of quantum paraelectrics on the border of ferroelectricity? To address this question we have investigated the temperature dependence of the dielectric function of the displacive quantum paraelectrics SrTiO3, oxygen-18 substituted SrTiO3 and KTaO3. In all of these materials on the border of ferroelectricity we observe non-classical T2 temperature dependencies of the inverse dielectric function below 50 K, followed by anomalous upturns below a few kelvin extending into the millikelvin range. This non-classical behaviour can be understood quantitatively without adjustable parameters in terms of quantum criticality theory when extended to include the effects of long-range dipolar interactions and the coupling of the electric polarization field with acoustic phonons. The quantum critical regime in displacive ferroelectrics is thus strikingly different from that in the better-known ferromagnetic counterparts and offers unexpected prospects in the field of quantum phase transitions.

Rowley, S. E.; Spalek, L. J.; Smith, R. P.; Dean, M. P. M.; Itoh, M.; Scott, J. F.; Lonzarich, G. G.; Saxena, S. S.

2014-05-01

180

All-Union Conference on the Physics of Ferroelectric Materials, 11th, Chernovtsy, Ukrainian SSR, Feb. 1987, Proceedings  

Microsoft Academic Search

The papers contained in this volume provide an overview of fundamental and applied research in the physics of ferroelectrics conducted in the USSR. Topics discussed include the critical behavior of ferroelectrics with point and extended defects, thermodynamics of dipole glasses, static and dynamic properties of ferroelectrics of the system Sn(Pb)2P2S(Se)6, and induced photovoltaic effect in centrosymmetric ruby crystals. Papers are

L. A. Shuvalov

1987-01-01

181

Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites  

SciTech Connect

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

Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Mitoseriu, Liliana [Faculty of Physics, 'Al. I. Cuza' University of Iasi 700506, Iasi (Romania); Airimioaei, Mirela [Faculty of Chemistry, 'Al. I. Cuza' University of Iasi 700506, Iasi, Romania and Dept. Chemistry and Process Engineering, University of Genoa, P-le Kennedy no. 1, I-16129, Genoa (Italy); Tascu, Sorin [RAMTECH Faculty of Physics, 'Al. I. Cuza' University of Iasi 700506 (Romania); Schileo, Giorgio [Christian Doppler Laboratory for Advanced Ferroic Oxides, Sheffield Hallam University, Howard Street, Sheffield S1 1WB (United Kingdom); Galassi, Carmen [CNR-ISTEC, Via Granarolo no. 64, I-48018 Faenza (Italy)

2013-02-21

182

Quantification of Hysteresis and Nonlinear Effects on the Frequency Response of Ferroelectric and  

E-print Network

Quantification of Hysteresis and Nonlinear Effects on the Frequency Response of Ferroelectric. However, these materials also exhibit hysteresis and constitutive nonlinearities at all drive levels of hysteresis and nonlinearities on the frequency behavior of devices that employ these compounds. Whereas

183

Local Probing of Mesoscopic Physics of Ferroelectric Domain Walls  

Microsoft Academic Search

Domain wall dynamics in ferroic materials underpins functionality of data storage and information technology devices. Using localized electric field of a scanning probe microscopy tip, we experimentally demonstrate a surprisingly rich range of polarization reversal behaviors in the vicinity of the initially flat 180\\\\deg ferroelectric domain wall. The nucleation bias is found to increase by an order of magnitude from

Vasudeva Rao Aravind; A. N. Morozovska; I. Grinberg; S. Bhattacharyya; Y. Li; S. Jesse; S. Choudhury; P. Wu; K. Seal; E. A. Eliseev; S. V. Svechnikov; D. Lee; S. R. Phillpot; L. Q. Chen; A. M. Rappe; V. Gopalan; S. V. Kalinin

2010-01-01

184

Ferroelectric domain structure of anisotropically strained NaNbO3 epitaxial thin films  

NASA Astrophysics Data System (ADS)

NaNbO3 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 NaNbO3 films with varying film thickness on NdGaO3 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 DyScO3, TbScO3, and GdScO3 single crystalline substrates, NaNbO3 films behave rather like a normal ferroelectric. The application of these rare-earth scandate substrates yields well-ordered ferroelectric stripe domains of the type a1/a2 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.

Schwarzkopf, J.; Braun, D.; Schmidbauer, M.; Duk, A.; Wördenweber, R.

2014-05-01

185

Examining graphene field effect sensors for ferroelectric thin film studies.  

PubMed

We examine a prototype graphene field effect sensor for the study of the dielectric constant, pyroelectric coefficient, and ferroelectric polarization of 100-300 nm epitaxial (Ba,Sr)TiO3 thin films. Ferroelectric switching induces hysteresis in the resistivity and carrier density of n-layer graphene (n = 1-5) below 100 K, which competes with an antihysteresis behavior activated by the combined effects of electric field and temperature. We also discuss how the polarization asymmetry and interface charge dynamics affect the electronic properties of graphene. PMID:23924380

Rajapitamahuni, A; Hoffman, J; Ahn, C H; Hong, X

2013-09-11

186

Imaging linear polarimetry using a single ferroelectric liquid crystal modulator.  

PubMed

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

Gendre, Luc; Foulonneau, Alban; Bigué, Laurent

2010-09-01

187

Atomic-level simulation of ferroelectricity in perovskite solid solutions  

SciTech Connect

Building on the insights gained from electronic-structure calculations and from experience obtained with an earlier atomic-level method, we developed an atomic-level simulation approach based on the traditional Buckingham potential with shell model which correctly reproduces the ferroelectric phase behavior and dielectric and piezoelectric properties of KNbO{sub 3}. This approach now enables the simulation of solid solutions and defected systems; we illustrate this capability by elucidating the ferroelectric properties of a KTa{sub 0.5}Nb{sub 0.5}O{sub 3} random solid solution. (c) 2000 American Institute of Physics.

Sepliarsky, M. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Instituto de Fisica Rosario, CONICET-UNR, Rosario, (Argentina); Phillpot, S. R. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Wolf, D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Stachiotti, M. G. [Instituto de Fisica Rosario, CONICET-UNR, Rosario, (Argentina)] [Instituto de Fisica Rosario, CONICET-UNR, Rosario, (Argentina); Migoni, R. L. [Instituto de Fisica Rosario, CONICET-UNR, Rosario, (Argentina)] [Instituto de Fisica Rosario, CONICET-UNR, Rosario, (Argentina)

2000-06-26

188

Modeling of elastic nonlinearities in ferroelectric materials including nonlinear losses: application to nonlinear resonance mode of relaxors single crystals.  

PubMed

(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) and (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) single crystals are considered to behave like soft Pb(Zr,Ti)O3 (PZT) ceramics because of their small mechanical quality factor Qm and poor stability under external disturbances (Qm > 500-1000 for hard PZT ceramic, and Qm < 100 for soft PZT and PMN-PT and PZN-PT single crystals). At weak signal excitation of the first resonance mode, the displacement at the end of a lateral bar is proportional to the Q31d31 figure of merit that is very close to that found for hard PZT. Indeed the very large piezoelectric coefficient compensates the low Qm. But increasing alternating current (AC) field results in the appearance of strong non-linearities through a shift of the resonance frequency and jumps phenomenon observed on increasing and decreasing frequency sweep. It is shown in this paper that these nonlinearities are due to the nonlinear elastic compliance that can be modeled by a third order development of the constitutive piezoelectric equations. Experiments on PMN-PT and PZN-PT single crystals are used for comparison with the model to show the viability of the approach. Both the frequency shift and jumps phenomenon are simulated with a very good agreement with experimental results. The importance is also shown of losses associated with the third order term responsible for the large decrease of the mechanical quality factor for high strain levels. Thus, the nonlinear losses are related to the hysteresis of domain wall motion when subjected to large displacements. PMID:16060508

Sebald, Gaël; Lebrun, Laurent; Guyomar, Daniel

2005-04-01

189

Preparation and characterisation of Pb(Fe 1\\/2Ta 1\\/2)O 3 relaxor ferroelectric  

Microsoft Academic Search

The reaction sequences between the oxides at various calcining temperatures were examined through the identification of the reaction products. Formation of pyrochlore phase with tetragonal symmetry is a required preparatory step for subsequent generation of perovskite phase. Most of the pyrochlore phase turns into the perovskite phase in the temperature range of 700–800°C and this conversion persists up to 950°C.

W. Z Zhu; A Kholkin; P. Q Mantas; J. L Baptista

2000-01-01

190

Ferroelectric optical image comparator  

DOEpatents

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.

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

1993-11-30

191

Ferroelectric optical image comparator  

DOEpatents

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.

Butler, Michael A. (Albuquerque, NM); Land, Cecil E. (Albuquerque, NM); Martin, Stephen J. (Albuquerque, NM); Pfeifer, Kent B. (Los Lunas, NM)

1993-01-01

192

Micro- and nanodomain imaging in uniaxial ferroelectrics: Joint application of optical, confocal Raman, and piezoelectric force microscopy  

NASA Astrophysics Data System (ADS)

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.

Ya. Shur, V.; Zelenovskiy, P. S.

2014-08-01

193

Proper, improper and hybrid improper ferroelectricity in oxide perovkites and related compounds  

NASA Astrophysics Data System (ADS)

Ferroelectricity in oxide perovskites and related compounds has been a topic of intensive research for more than 60 years. Recently, the coupling of the ferroelectric mode with other structural distortions has attracted an increasing interest since it offers promising and still widely unexplored possibilities to couple ferroelectricity with other functional properties and even to produce unusual phenomena. In this context, the trilinear coupling between ferroelectric and oxygen rotational modes in naturally occuring and artificial layered perovskites appeared as a practical way to produce unusual dielectric properties or achieve enhanced magneto-electric coupling. Here, I will first briefly reintroduce the concepts of proper, improper and hybrid improper ferroelectricity, highlighting how to rationalize better the concept of improper ferroelectricity. I will contrast the intrinsic behavior of these three classes of compounds in ferroelectric capacitors. Taking then the prototypical example of BiFeO3/LaFeO3 superlattices, I will illustrate how hybrid improper ferroelectricity and trilinear mode coupling is a promising route to potentially achieve electric switching of the magnetization. Finally, considering the case of PbTiO3/SrTiO3 superlattices, I will discuss how to access from first-principles the phase-transition sequence and finite temperature properties of complex systems combining various structural instabilities, which still remains a challenging issue.

Ghosez, Philippe

2013-03-01

194

Journal of the Mechanics and Physics of Solids 56 (2008) 21172135 A study of electromechanical switching in ferroelectric  

E-print Network

is achieved using multirank laminates. It offers an advantage of specifying different types of domain wall switching in ferroelectric single crystals J.H. Yena , Y.C. Shua,Ã?, J. Shiehb , J.H. Yehb a Institute and experimental studies developed to investigate the switching behavior of ferroelectric single crystals

Shu, Yi-Chung

195

Pressure-induced polar phases in relaxor multiferroic PbFe0.5Nb0.5O3  

NASA Astrophysics Data System (ADS)

The structural, magnetic, and vibrational properties of PbFe0.5Nb0.5O3 relaxor multiferroic have been studied by means of x-ray, neutron powder diffraction, and Raman spectroscopy at pressures up to 30 GPa. Two successive structural phase transitions from the initial R3m polar phase to Cm and Pm monoclinic polar phases were observed at P = 5.5 and 8.5 GPa. Both transitions are associated with anomalies in pressure behavior of several stretching and bending modes of oxygen octahedra as well as Fe/Nb localized vibrational modes. The G-type antiferromagnetic order remains stable upon compression up to 6.4 GPa, assuming possible multiferroic properties of pressure-induced phases. The Néel temperature increases with a pressure coefficient (1/TN)dTN/dP=0.012 GPa-1. The observed pressure-induced phenomena in PbFe0.5Nb0.5O3 are in drastic contrast with conventional multiferroics, exhibiting a general tendency towards a suppression of polar phases and/or magnetoelectric coupling under pressure.

Kozlenko, D. P.; Kichanov, S. E.; Lukin, E. V.; Dang, N. T.; Dubrovinsky, L. S.; Liermann, H.-P.; Morgenroth, W.; Kamynin, A. A.; Gridnev, S. A.; Savenko, B. N.

2014-05-01

196

Ferroelectric Thin Films for Electronic Applications  

NASA Astrophysics Data System (ADS)

This study yokes together the feasibility of a family of PbO-based perovskite-structured ferroelectric thin films as functional elements in nonvolatile random access memories (NVRAMs), in high capacity dynamic RAMs, and in a new class of flexure wave piezoelectric ultrasonic micromotors. The dielectric and ferroelectric properties of lead zirconate titanate (PZT) thin films were dependent on thickness; at saturation, the films were characterized by a relative permittivity of 1300, remanent polarization of 36 muC/cm^2 and breakdown strength of over 1 MV/cm. The temperature dependence of permittivity revealed an anomalous behavior with the film annealing temperature. Based on the ferroelectric properties in the bulk, thin films in the lead zirconate -lead zinc niobate (PZ-PZN) solid solution system at 8-12% PZN, examined as alternate compositions for ferroelectric memories, feature switched charges of 4-14 mu C/cm^2, with coercive and saturation voltages less than the semiconductor operating voltage of 5 V. Rapid thermally annealed lead magnesium niobate titanate films were privy to weak signal dielectric permittivity of 2900, remanent polarization of 11 muC/cm^2, and a storage density of 210 fC/mum^2 at 5 V; the films merit consideration for potential applications in ultra large scale integrated circuits as also ferroelectric nonvolatile RAMs. The high breakdown strength and relative permittivity of the PZT films entail maximum stored energy density 10^3 times larger than a silicon electrostatic motor. The longitudinal piezoelectric strain coefficient d_{33 } was measured to be 220 pC/N at a dc bias of 75 kV/cm. The transverse piezoelectric strain coefficient d_{31} bore a nonlinear relationship with the electric field; at 200 kV/cm, d _{31} was -88 pC/N. The development of the piezoelectric ultrasonic micromotors from the PZT thin films, and the architecture of the stator structures are described. Nonoptimized prototype micromotors show rotational velocities of 100-300 rpm at drives of 3-5 V.

Udayakumar, K. R.

197

Spectroscopic signature for ferroelectric ice  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

198

Resonances in ferroelectric phononic superlattice  

NASA Astrophysics Data System (ADS)

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.

Ostrovskii, Igor; Cremaldi, Lucien

2012-10-01

199

Switching of ferroelectrics without domains.  

PubMed

A discussion of switching in polyvinyl difluoride copolymers is given (see L. Zhang, EPL 2010, 91, 47001) in terms of the general history of ferroelectric switching with and without domain wall participation. PMID:21170923

Scott, James F

2010-12-01

200

Polarization dependence of molecular adsorption on ferroelectrics.  

PubMed

The structural details of ferroelectric surfaces influence the effect of ferroelectric polarization on surface chemistry, and it is important to understand and control defect functionality as well as identify adsorption sites in ferroelectric materials. Ferroelectric domain polarization has been found to have a significant effect on surface properties and interactions. Here, both the structure and the presence of local electric fields are examined simultaneously. The surface structure and ferroelectric domain orientation are controlled while molecular adsorption effects are quantified. We use scanning tunneling microscopy (STM) to determine the surface and electronic effects of polarization-gas interactions on a model ferroelectric surface, BaTiO3 (001). PMID:23719697

Kraya, Laura Y; Kraya, Ramsey

2013-04-01

201

Polarization coupling in ferroelectric multilayers  

NASA Astrophysics Data System (ADS)

A thermodynamic model was developed to understand the role of charge compensation at the interlayer interfaces in compositionally graded monodomain ferroelectric multilayers. The polarization mismatch between the ferroelectric layers generates depoling fields with the polarization in each layer varying from its bulk uncoupled value as to adapt to the electrical boundary conditions. By treating the strength of the electrostatic field as a phenomenological parameter, it is shown that if there are localized charges to compensate for the polarization mismatch and relax the depolarization fields, ferroelectric layers behave independently of each other and exhibit a dielectric response that can be described as the sum of their corresponding intrinsic uncoupled dielectric properties. For perfectly insulating heterostructures with no localized charges, the depolarization field is minimized by lowering the polarization difference between layers, yielding a ferroelectric multilayer that behaves as if it were a single ferroelectric material. There exists an optimum value of coupling strength at which average polarization of the multilayer is maximized. Furthermore, ferroelectric multilayers may display a colossal dielectric response dependant upon the interlayer electrostatic interactions.

Okatan, M. B.; Mantese, J. V.; Alpay, S. P.

2009-05-01

202

Coupled ferromagnetism and ferroelectricity in superlattices of non-ferroelectric antiferromagnetic manganites  

NASA Astrophysics Data System (ADS)

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.[1] 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] K. Rogdakis et al, Nat Commun 3, 1064 (2012)

Burton, J. D.; Rogdakis, K.; Seo, J. W.; Viskadourakis, Z.; Wang, Y.; Qune, L. Ah; Choi, E.; Tsymbal, E.; Lee, J.; Panagopoulos, C.

2013-03-01

203

Multifractal analysis of electron beam stimulated process of polarization reversal in ferroelectrics  

NASA Astrophysics Data System (ADS)

This work deals with the application of multifractal methods to the analysis of polarization switching processes in ferroelectrics. The ferroelectric polarization reversal current was considered as a dynamic response of finite system with fractal behavior. The problem of fractal characteristics estimation was solved using fractal theory methods designed for nonstationary time series. The results of multifractal analysis were examined for polarization switching current of triglycine sulphate crystal obtained from electron beam induced polarization current mode.

Maslovskaya, A. G.; Barabash, T. K.

204

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

PubMed

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

Waghmare, Umesh V

2014-11-18

205

Domain switching in polycrystalline ferroelectric ceramics  

E-print Network

of ferroelectricity using density functional theory6­8 , crystallographic and domain-wall structure using atomisticARTICLES Domain switching in polycrystalline ferroelectric ceramics J. Y. LI1, R. C. ROGAN2,3, E electrical or mechanical loads. Domain switching is important in technological exploitation of ferroelectric

Li, Jiangyu

206

Ferroelectricity of carbon based materials  

NASA Astrophysics Data System (ADS)

We discuss the possibility of ferroelectric carbon-based materials: organic crystals, conducting polymers and graphene ribbons. Ferroelectricity related to the charge ordering was discovered in quasi-1D organic conductors (TMTTF)2X, and in layered compounds like ?-(EDT-TTFCONMe2)2Br. A microscopic picture is based on two coexisting symmetry lowering effects: the dimerization of bonds (which is build-in) and the dimerization of sites (which is a spontaneous symmetry breaking). Today we can look for a possibility of a ferroelectric polymer. The difference with respect to (TMTTF)2X is the reverse of the build-in (sites) and spontaneous (bonds) effects of dimerizations. Such an (AB)x polymer has already appeared, studied for nonlinear optical properties, but not tested for the the ferroelectricity. The theory predicted an existence of solitons with non-integer variable charges, both with and without spin i.e. walls separating domains with opposite electric polarisation. Their physics will serve to relate transient ferroelectric processes and the visible range optics. For the case of zigzag edges of graphene ribbons the build-in dimerization is originated by different chemical surrounding of carbon atoms and the spontaneous one can be the result of Peierls transition along the edges.

Kirova, Natasha; Brazovskii, Serguei

2010-03-01

207

Relaxor-like dielectric response of spin liquid CuCrO2  

NASA Astrophysics Data System (ADS)

Broadband dielectric analysis (10-2-107 Hz) of layered triangular lattice CuCrO2 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.

Mazumder, N.; Ghorai, U. K.; Roy, R.; Saha, S.; Chattopadhyay, K. K.

2014-04-01

208

Atomic-level simulation of ferroelectricity in perovskite solid solutions  

Microsoft Academic Search

Building on the insights gained from electronic-structure calculations and from experience obtained with an earlier atomic-level method, we developed an atomic-level simulation approach based on the traditional Buckingham potential with shell model which correctly reproduces the ferroelectric phase behavior and dielectric and piezoelectric properties of KNbO3. This approach now enables the simulation of solid solutions and defected systems; we illustrate

M. Sepliarsky; S. R. Phillpot; D. Wolf; M. G. Stachiotti; R. L. Migoni

2000-01-01

209

Coulomb Microexplosions of Ferroelectric Ceramics  

SciTech Connect

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 7x10{sup 7} cm/s. This phenomenon is explained by an extremely large electric field with amplitude {>=}10{sup 6} V/cm and rise time {approx}10{sup -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.

Yarmolich, D.; Vekselman, V.; Gurovich, V. Tz.; Krasik, Ya. E. [Physics Department, Technion, 32000 Haifa (Israel)

2008-02-22

210

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

NASA Astrophysics Data System (ADS)

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 polar

McCash, Kevin

211

Ferroelectric and optical properties in the 180° ferroelectric domain wall of tetragonal BaTiO3  

Microsoft Academic Search

The microscopic mechanism of spontaneous polarization and refractive indices in 180° ferroelectric domain walls of tetragonal barium titanate (BaTiO3) is discussed by using a microscopic model. This model is based on the orbital approximation in correlation with the dipole-dipole interaction due to the local field acting on all constituent ions within the domain wall. It is found that the behavior

H. Chaib; S. Grafstroem; T. Otto; Lukas M. Eng

2003-01-01

212

Face shear piezoelectric properties of relaxor-PbTiO3 single crystals Shujun Zhang,1,a  

E-print Network

Face shear piezoelectric properties of relaxor-PbTiO3 single crystals Shujun Zhang,1,a Fei Li,1TiO3 crystals, piezoelectric d36 coefficients were determined to be in the range of 2000­2500 p­4 It has been reported that large lon- gitudinal piezoelectric coefficients, d33 1500 p

Cao, Wenwu

213

Quantum breathers in lithium tantalate ferroelectrics  

NASA Astrophysics Data System (ADS)

Lithium tantalate is technologically one of the most important ferroelectric materials with a low poling field that has several applications in the field of photonics and memory switching devices. In a Hamiltonian system, such as dipolar system, the polarization behavior of such ferroelectrics can be well-modeled by Klein-Gordon (K-G) equation. Due to strong localization coupled with discreteness in a nonlinear K-G lattice, there is a formation of breathers and multi-breathers that manifest in the localization peaks across the domains in polarization-space-time plot. Due to the presence of nonlinearity and also impurities (as antisite tantalum defects) in the structure, dissipative effects are observed and hence dissipative breathers are studied here. To probe the quantum states related to discrete breathers, the same K-G lattice is quantized to give rise to quantum breathers (QBs) that are explained by a periodic boundary condition. The gap between the localized and delocalized phonon-band is a function of impurity content that is again related to the effect of pinning of domains due to antisite tantalum defects in the system, i.e., a point of easier switching within the limited amount of data on poling field, which is related to Landau coefficient (read, nonlinearity). Secondly, in a non-periodic boundary condition, the temporal evolution of quanta shows interesting behavior in terms of `critical' time of redistribution of quanta that is proportional to QB's lifetime in femtosecond having a possibility for THz applications. Hence, the importance of both the methods for characterizing quantum breathers is shown in these perspectives.

Biswas, Arindam; Adhikar, Sutapa; Choudhary, Kamal; Basu, Reshmi; Bandyopadhyay, A. K.; Bhattacharjee, A. K.; Mandal, D.

2013-08-01

214

On the physics of ferroelectrics.  

PubMed

The main physical properties of ferroelectric crystals are described, and the macroscopic and microscopic viewpoints are discussed along with some applications, such as in capacitors and nonlinear optics. The emphasis is on physical understanding, while the mathematical level is kept to a minimum or supplemented by graphical representations to make the article more accessible. PMID:15079997

Webb, J F

2003-01-01

215

First-principles calculations of size-dependent giant electroresistance effect in nanoscale asymmetric ferroelectric tunnel junctions  

NASA Astrophysics Data System (ADS)

Based on the first principle calculations, we predicted the electronic structures and ferroelectric instability of the asymmetric ferroelectric tunneling junction with the ferroelectric barrier thickness changing, and found two undiscovered and important behaviors, i.e., absence of the critical thickness for the positive polarization state and the larger critical thickness for the negative polarization state. Using nonequilibrium Green function's approach, the corresponding two-probe systems and their electronic transport properties at different ferroelectric barrier thickness have been constructed. It is found that reorienting the polarization direction in the ferroelectric barrier can dramatically change the internal electric field and macroscopic potential barrier, resulting in several orders of magnitude change in tunneling electroresistance ratio. Results also found that the tunneling electroresistance can be distinctly controlled by adjusting thickness of the ferroelectric barrier, which behavior is defined as the size-dependent giant electroresistance effect. Our results enable architectures of large density and high sensitivity in the next generation of ferroelectric random access memories with nondestructive resistive readout.

Luo, Xin; Zheng, Yue; Wang, Biao

2012-04-01

216

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

217

Nanocharacterization of the negative stiffness of ferroelectric materials  

NASA Astrophysics Data System (ADS)

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.

Alipour Skandani, A.; Ctvrtlik, R.; Al-Haik, M.

2014-08-01

218

Electromigration of microspheres in ferroelectric smectic liquid crystals.  

PubMed

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

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

2007-08-01

219

Page 277, AIP Conference Proceedings, Fundamental Physics of Ferroelectrics 2002. On Domain Wall Broadening in Ferroelectric  

E-print Network

Page 277, AIP Conference Proceedings, Fundamental Physics of Ferroelectrics 2002. On Domain Wall The local structure of a ferroelectric domain wall establishes a key link between atomic structure rotate across a domain wall from one orientation to another,[1] the strong coupling between ferroelectric

Gopalan, Venkatraman

220

Ferroelectric transitions at ferroelectric domain walls found from first principles.  

PubMed

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

Wojde?, Jacek C; Íñiguez, Jorge

2014-06-20

221

Ferroelectric Transitions at Ferroelectric Domain Walls Found from First Principles  

NASA Astrophysics Data System (ADS)

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.

Wojde?, Jacek C.; Íñiguez, Jorge

2014-06-01

222

Piezoresponse force microscopy studies on the domain structures and local switching behavior of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals  

NASA Astrophysics Data System (ADS)

The static domain structures and local switching behavior of relaxor ferroelectric 0.29Pb(In1/2Nb1/2)O3-0.44Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystals at three crystal orientations are studied using piezoresponse force microscopy (PFM). PFM domain imaging shows that both the [001] and [111] oriented crystals exhibit a labyrinth-like surface domain pattern while at the [110] crystal orientation the domains are preferentially aligned along <110> directions. Vertical and lateral PFM images are used in combination to discuss the polarization vector alignment underlying the observed domain behaviour. Piezoresponse hysteresis loops acquired from these crystals indicate that the [111] crystal orientation has distinct local switching characteristics from the other two orientations in terms of, e.g., coercive voltage. Moreover, we investigate the tip-induced domain growth kinetics on an externally poled [001] crystal, the results of which exemplify an important role of extrinsic factors, e.g., the charge injection effect, in the domain patterning process.

Li, Qian; Liu, Yun; Withers, Ray L.; Wan, Yuhui; Li, Zhenrong; Xu, Zhuo

2012-09-01

223

Magnetically induced ferroelectric order in frustrated magnets  

NASA Astrophysics Data System (ADS)

Magnetoelectric coupling between magnetic and ferroelectric properties has been the object of intense study over the last four decades. Our understanding of magnetoelectric materials has been greatly enhanced by a rigorous exploration of the symmetry requirements for promoting magnetic and ferroelectric orders. Multiferroic materials, having simultaneous magnetic and ferroelectric order, have recently been proposed for incorporation into a range of spintronic devices. However, many of the multiferroics identified to date have different transition temperatures for ferroelectric and magnetic orders, leading to reduced magnetoelectric coupling strengths. I will discuss some recent experiments on several new multiferroics, including TbMnO3, DyMnO3, and Ni3V2O8. These compounds are notable because the ferroelectric transition is coincident with magnetic ordering which leads to very large magnetoelectric couplings and large magnetocapacitive effects. Furthermore, using external magnetic fields to tune the magnetic structure has a pronounced effect on ferroelectricity in these systems. This allows us to destroy or promote ferroelectric order magnetically. While similar effects have been observed previously, these multiferroics remain poorly understood. I will present a model developed to explain the multiferroic order in Ni3V2O8, in which the magnetic order spontaneously breaks inversion symmetry, allowing for the development of ferroelectricity. This magnetically-induced ferroelectric order is expected to appear in a wide range of antiferromagnets, and offers a new approach for designing and understanding multiferroic materials.

Lawes, Gavin

2005-03-01

224

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

NASA Astrophysics Data System (ADS)

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.

Itskovsky, M.

1999-08-01

225

Ferroelectric liquid crystal optical interconnect switching systems  

Microsoft Academic Search

This grant explored the possible use of ferroelectric liquid crystals (FLC's) in the reamization of photonic switching fabrics. Problems addressed included device fabrication, switch architectures, and switch performance. Experimental versions of most architectures were constructed. The aim of the contract was to develop techniques for using ferroelectric liquid crystals (FLC's) for novel photonic switching architectures. Initial work was devoted to

Joseph W. Goodman

1993-01-01

226

Observation of Ferroelectric Domain Structure in TGS  

Microsoft Academic Search

Triglycine sulfate (TGS) is one of the most intensively investigated ferroelectrics. Though the domain structure is an important subject in the research of ferroelectricity, the domain in TGS is invisible by usual optical method. Many substitutive methods have been developed for the observation of static and dynamic domain structure in TGS. This review summarizes these methods mainly from a practical

N. Nakatani

2011-01-01

227

Ferroelectric translational antiphase boundaries in nonpolar materials.  

PubMed

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

Wei, Xian-Kui; Tagantsev, Alexander K; Kvasov, Alexander; Roleder, Krystian; Jia, Chun-Lin; Setter, Nava

2014-01-01

228

A phenomenological cohesive model of ferroelectric fatigue  

E-print Network

A phenomenological cohesive model of ferroelectric fatigue I. Arias b S. Serebrinsky a, M. Ortiz Abstract We develop a phenomenological model of electro-mechanical ferroelectric fatigue based to fatigue are localized in one or more planar-like regions, modelled by the cohesive surfaces. We validate

Huerta, Antonio

229

Polyimide thin-film dielectrics on ferroelectrics  

NASA Technical Reports Server (NTRS)

Conducting layers of multi-layered thin-film ferroelectric device, such as is used in liquid crystal/ferroelectric display, can be electrically isolated using thin-film layer of polyimide. Ease of application and high electrical-breakdown strength allow dependable and economical means of providing dielectric for other thin-film microelectronic devices.

Galiardi, R. V.

1977-01-01

230

A concept of ferroelectric microparticle propulsion thruster  

SciTech Connect

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.

Yarmolich, D.; Vekselman, V.; Krasik, Ya. E. [Physics Department, Technion, 32000 Haifa (Israel)

2008-02-25

231

Multiferroics: a magnetic twist for ferroelectricity  

Microsoft Academic Search

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

Sang-Wook Cheong; Maxim Mostovoy

2007-01-01

232

Constrained polarization study of ferroelectric KNO3  

NASA Astrophysics Data System (ADS)

Potassium nitrate has an interesting phase diagram that includes a reentrant ferroelectric phase (phase III, R3m), and it has been proposed as a promising material to be used in random-access memory devices. Recently, we have developed a method to compute the ground-state of an insulator under a fixed value of its polarization that can be used to gain insight into the properties of polar materials. In this talk we show the results of applying this method to study the structural behavior of potassium nitrate under polarization reversal, describing an unusual mechanism in which the reversal is accompanied by a rotation of the NO3 unit by 60^o. We also use our calculations as a basis for constructing first-principles based models that can be used to gain a deeper understanding of the switching behavior of this material. J. F. Scott, M. S. Zhang, R. B. Godfrey, C. Araujo, and L. McMillan, Phys. Rev. B 35, 4044 (1987). See: cond-mat/0511711 (www.arXiv.org).

Diéguez, Oswaldo; Vanderbilt, David

2006-03-01

233

Ferroelectric domain wall pinning at a bicrystal grain boundary in bismuth ferrite  

Microsoft Academic Search

The ferroelectric polarization switching behavior at the 24° (100) tilt grain boundary (GB) in an epitaxial multiferroic BiFeO3 bicrystal film is studied using piezoresponse force microscopy (PFM). The PFM amplitudes across positively and negatively poled GB regions suggest the presence of a frozen polarization component at the interface. The switching experiments demonstrate that the GB attracts the domain wall and

Brian J. Rodriguez; Y. H. Chu; R. Ramesh; Sergei V. Kalinin

2008-01-01

234

Fast electro-optical mode in photo-aligned reflective deformed helix ferroelectric liquid crystal cells.  

PubMed

The electro-optical behavior of deformed helix ferroelectric liquid crystal in reflective mode is described in this paper. The electrically controlled reflectance has been measured at subkilohertz driving voltage frequency for different polarizations of the incident light and compared quite successfully with the simulation results. PMID:22739902

Guo, Qi; Brodzeli, Zourab; Pozhidaev, Eugene P; Fan, Fan; Chigrinov, Vladimir G; Kwok, Hoi Sing; Silvestri, Leonardo; Ladouceur, Francois

2012-06-15

235

Observation of piezoelectric resonance in time domain transient current of ferroelectric ceramics and crystals  

Microsoft Academic Search

An abnormal resonance behavior was observed from the transient current in the time domain for both ferroelectric ceramics and single crystals excited with a stepwise electric field. The phenomenon can be accounted for as piezoelectric resonance. Corresponding resonant peaks in the frequency spectrum of impedance verified the piezoelectric origin of the abnormal resonance. Using a RLC series equivalent circuit of

Li Jin; Xi Yao; Xiaoyong Wei; Zengzhe Xi

2005-01-01

236

Effects of the spontaneous polarization on the structural and dynamic properties of ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

The creation, nearly 30 years ago, of chiral tilted smectic liquid crystals produced spontaneous polar order in a fluid for the first time. Unlike solid-state ferrolectrics in which the polarization is restricted by the symmetry of a crystal lattice, ferroelectric smectics can freely orient in two dimensions. Consequently, the liquid crystal polarization is extremely sensitive to interactions with external boundaries, electric field, and its own intrisic polarity. Optical and x-ray techniques have been used to study these interactions in the following three cases. Total Internal Reflection is used to probe the molecular organization at the interface between a solid substrate and a tilted chiral smectic liquid crystal at temperatures in the vicinity of the bulk antiferroelectric-ferroelectric phase transition. Optical reflectivity data are interpreted using an exact analytical solution of a real model for ferroelectric order at the surface. We discuss the conditions for polar order at the surface, and then demonstrate that in the mixture T3, ferroelectric surface order is expelled below the bulk ferroelectric-antiferroelectric transition. The continuously reorientable (XY-like) ferroelectric polarization density of a chiral smectic liquid crystal is shown experimentally to produce nearly complete screening of the applied electric field in an appropriate cell geometry. This screening, combined with the expulsion of polarization charge for large polarization materials, leads to semiconducting electrical behavior of the otherwise insulating liquid crystal and electrostatic control of the orientation of a uniform optic axis/polarization field. Finally, we determine the structure of an achiral ferroelectric liquid crystal in which the polarization spontaneously produces a periodically splayed structure. The structure of the smectic layers is determined by x-ray diffraction and the molecular order within the layers is deduced from polarized optical microscopy observations. On the basis of the x-ray measurements, we are able to differentiate between two optically-similar phases.

Coleman, David Anthony

2002-08-01

237

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

SciTech Connect

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.

Picozzi, S. [CNR-INFM, L-Aquila, Italy; Yamauchi, K. [CNR-INFM, L-Aquila, Italy; Sergienko, Ivan A [ORNL; Sen, Cengiz [Florida State University; Sanyal, B. [Uppsala University, Uppsala, Sweden; Dagotto, Elbio R [ORNL

2008-01-01

238

Resonance excitation of spin waves in ferroelectric\\/ferromagnets by oscillations of ferroelectric domain walls in an alternating electric field  

Microsoft Academic Search

The problem of the excitation of spin waves by oscillations of ferroelectric domain walls (in an alternating electric field) in ferroelectric\\/ferromagnets is considered. First the situation is studied where the equilibrium state of the magnetic subsystem is homogeneous. It is shown that due to the influence of the magnetic subsystem on the dynamics of ferroelectric domain walls in the ferroelectric

I. V. Manzhos

1994-01-01

239

Atomic-scale mapping of dipole frustration at 90° charged domain walls in ferroelectric PbTiO3 films  

NASA Astrophysics Data System (ADS)

The atomic-scale structural and electric parameters of the 90° domain-walls in tetragonal ferroelectrics are of technological importance for exploring the ferroelectric switching behaviors and various domain-wall-related novel functions. We have grown epitaxial PbTiO3/SrTiO3 multilayer films in which the electric dipoles at 90° domain-walls of ferroelectric PbTiO3 are characterized by means of aberration-corrected scanning transmission electron microscopy. Besides the well-accepted head-to-tail 90° uncharged domain-walls, we have identified not only head-to-head positively charged but also tail-to-tail negatively charged domain-walls. The widths, polarization distributions, and strains across these charged domain-walls are mapped quantitatively at atomic scale, where remarkable difference between these domain-walls is presented. This study is expected to provide fundamental information for understanding numerous novel domain-wall phenomena in ferroelectrics.

Tang, Y. L.; Zhu, Y. L.; Wang, Y. J.; Wang, W. Y.; Xu, Y. B.; Ren, W. J.; Zhang, Z. D.; Ma, X. L.

2014-02-01

240

Interface-Induced Polarization and Inhibition of Ferroelectricity in Epitaxial SrTiO3=Si  

SciTech Connect

We use SrTiO{sub 3}/Si as a model system to elucidate the effect of the interface on ferroelectric behavior in epitaxial oxide films on silicon. Using both first-principles computations and synchrotron x-ray diffraction measurements, we show that structurally imposed boundary conditions at the interface stabilize a fixed (pinned) polarization in the film but inhibit ferroelectric switching. We demonstrate that the interface chemistry responsible for these phenomena is general to epitaxial silicon-oxide interfaces, impacting on the design of silicon-based functional oxide devices.

Su, D.; Kolpak, A.M.; Walker, F.J.; Reiner, J.W.; Segal, Y.; Sawicki, M.S.; Broadbridge, C.C.; Zhang, Z.; Zhu, Y.; Ahn, C.H.; Ismail-Beigi, S.

2010-11-17

241

Thin Layer Composite Unimorph Ferroelectric Driver and Sensor  

NASA Technical Reports Server (NTRS)

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.

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

242

Thin Layer Composite Unimorph Ferroelectric Driver and Sensor  

NASA Technical Reports Server (NTRS)

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.

Hellbaum, Richard F. (Inventor); Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor)

1997-01-01

243

Thin layer composite unimorph ferroelectric driver and sensor  

NASA Technical Reports Server (NTRS)

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.

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

244

Is there ferroelectricity in DNA?  

NASA Astrophysics Data System (ADS)

This paper reports on a study of the dielectric properties of DNA (sodium salt from calf thymus, SIGMA) under heating and cooling of a sample within the temperature interval 20-60°C, which was conducted in air, in a humid environment, and in vacuum. It is shown that the data obtained can be accounted for by the sample conductivity increasing as a result of DNA releasing water into a separate phase with increasing temperature and the formation of a double electric layer at the DNA interface with metallic electrodes, without invoking the idea of ferroelectricity present in DNA.

Yarmarkin, V. K.; Shul'Man, S. G.; Lemanov, V. V.

2009-09-01

245

A ferroelectric-semiconductor-coupled solar cell with tunable photovoltage  

NASA Astrophysics Data System (ADS)

To confirm the feasibility of nanodipole photovoltaic devices, we designed a practicable method of phase segregation to extract CdS piezoelectric nanoparticles from CdSTe mixed film. The constituent components of such device are mixture of ferroelectric CdS nanodipoles and CdTe semiconductor absorber. We observed an analogous electric hysteresis of photovoltage in such devices. Piezoresponse grain boundaries are observed, which contribute significantly to the hysteresis behavior of photovoltage. Abnormal photovoltage polarity of CdS nanodipole devices is also observed. But such phenomena cannot be explained by classical junctional device theory. We believe these provide convincing evidence for the mechanism of nanodipoles.

Huang, Fang; Liu, Xiangxin

2013-03-01

246

Characterization of a Common-Gate Amplifier Using Ferroelectric Transistors  

NASA Technical Reports Server (NTRS)

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.

Hunt, Mitchell; Sayyah, Rana; MacLeod, Todd C.; Ho, Fat D.

2011-01-01

247

Attenuation characteristics of the guided THz wave in parallel-plate ferroelectric-graphene waveguides  

NASA Astrophysics Data System (ADS)

Guided THz wave characteristics in a parallel-plate waveguide (PPWG) consisting of ferroelectric film (LiNbO3 and LiTaO3) and multilayer graphene (MLG) is studied in this paper, with their low and tunable attenuation valley predicted. The electrical conductivity of MLG is calculated by a set of closed-form equations with the coupling effect between the bottom graphene layer (BGL) and its substrate taken into account carefully, while the dispersive behavior of ferroelectric film itself is described by the Lorentz model over an ultra-wide THz band. It is shown that the guided TM-mode propagation can be adjusted effectively by changing temperature, frequency, optical pumping intensity, MLG layer number, film thickness and its transverse optical-phonon frequency. Moreover, one low attenuation valley of TM-mode in such ferroelectric-graphene waveguide is captured, which can be exploited for developing some THz planar tunable waveguides with ultra-low loss.

Gu, Xiao-Qiang; Yin, Wen-Yan; Zheng, Ting

2014-11-01

248

Universal Ferroelectric Switching Dynamics of Vinylidene Fluoride-trifluoroethylene Copolymer Films  

NASA Astrophysics Data System (ADS)

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.

Hu, Wei Jin; Juo, Deng-Ming; You, Lu; Wang, Junling; Chen, Yi-Chun; Chu, Ying-Hao; Wu, Tom

2014-04-01

249

Universal ferroelectric switching dynamics of vinylidene fluoride-trifluoroethylene copolymer films.  

PubMed

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/m(2) 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

Hu, Wei Jin; Juo, Deng-Ming; You, Lu; Wang, Junling; Chen, Yi-Chun; Chu, Ying-Hao; Wu, Tom

2014-01-01

250

Polarization-control of the potential barrier at the electrode interfaces in epitaxial ferroelectric thin films.  

PubMed

Electrode interface is a key element in controlling the macroscopic electrical properties of the ferroelectric capacitors based on thin films. In the case of epitaxial ferroelectrics, the electrode interface is essential in controlling the leakage current and the polarization switching, two important elements in the read/write processes of nonvolatile memories. However, the relation between the polarization bound charges and the electronic properties of the electrode interfaces is not yet well understood. Here we show that polarization charges are controlling the height of the potential barriers at the electrode interfaces in the case of Pb(Zr,Ti)O3 and BaTiO3 epitaxial films. The results suggest that the height is set to a value allowing rapid compensation of the depolarization field during the polarization switching, being almost independent of the metals used for electrodes. This general behavior open a new perspective in engineering interface properties and designing new devices based on epitaxial ferroelectrics. PMID:24446901

Pintilie, Ioana; Teodorescu, Cristian Mihail; Ghica, Corneliu; Chirila, Cristina; Boni, Andra Georgia; Hrib, Luminita; Pasuk, Iuliana; Negrea, Raluca; Apostol, Nicoleta; Pintilie, Lucian

2014-02-26

251

Enhancing electrical energy storage density in anti-ferroelectric ceramics using ferroelastic domain switching  

NASA Astrophysics Data System (ADS)

Capacitors form an indispensable part of many modern electrical and electronic devices. An ideal capacitor is expected to possess high power and energy density along with enhanced energy recovery characteristics. Anti-ferroelectric materials form a suitable candidate for ceramic-based capacitor applications, owing to their low loss and high energy density. However, these materials show ample room for improvement through physical means. In this regard, the present work deals with mechanical tuning of the energy storage density and recoverable efficiency in known anti-ferroelectric materials. For this study, various configurations of (Pb1?xLax)(Zr0.90Ti0.10)1?x/4O3 (PLZTx) ceramics have been investigated. Both mechanical confinement and temperature applications have been shown to improve the performance characteristics of all selected compositions. This behavior has been explained on the basis of competing ferroelectric and ferroelastic domain rotations. The application of suitable stress/temperature reduces hysteresis losses and delays anti-ferroelectric ? ferroelectric phase transformation, which increases the electrical energy storage capacity of these materials. Mechanical confinement was observed to provide an increase in energy storage density and efficiency by approximately 38% and 25%, respectively, for the PLZT4 composition. The highest recoverable energy density of 698 m J cm?3 was achieved under compressive stress of a 100 MPa and 60 kV cm?1 applied electric field.

Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

2014-12-01

252

New perspectives for ferroelectric LC-polymers  

SciTech Connect

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.

Brehmer, M.; Gebhard, E.; Wittig, T. [Univ. Mainz (Germany)

1996-10-01

253

Structural Consequences of Ferroelectric Nanolithography  

SciTech Connect

Domains of remnant polarization can be written into ferroelectrics with nanoscale precision using scanning probe nanolithography techniques such as piezoresponse force microscopy (PFM). Understanding the structural effects accompanying this process has been challenging due to the lack of appropriate structural characterization tools. Synchrotron X-ray nanodiffraction provides images of the domain structure written by PFM into an epitaxial Pb(Zr,Ti)O{sub 3} thin film and simultaneously reveals structural effects arising from the writing process. A coherent scattering simulation including the superposition of the beams simultaneously diffracted by multiple mosaic blocks provides an excellent fit to the observed diffraction patterns. Domains in which the polarization is reversed from the as-grown state have a strain of up to 0.1% representing the piezoelectric response to unscreened surface charges. An additional X-ray microdiffraction study of the photon-energy dependence of the difference in diffracted intensity between opposite polarization states shows that this contrast has a crystallographic origin. The sign and magnitude of the intensity contrast between domains of opposite polarization are consistent with the polarization expected from PFM images and with the writing of domains through the entire thickness of the ferroelectric layer. The strain induced by writing provides a significant additional contribution to the increased free energy of the written domain state with respect to a uniformly polarized state.

J Young Jo; P Chen; R Sichel; S Bake; R Smith; N Balke; S Kalinin; M Holt; J Maser; et al.

2011-12-31

254

Photorefractive effect in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

In this paper, we review recent progress of research on the photorefractive effect of ferroelectric liquid crystals. The photorefractive effect is a phenomenon that forms a dynamic hologram in a material. The interference of two laser beams in a photorefractive material establishes a refractive index grating. This phenomenon is applicable to a wide range of devices related to diffraction optics including 3D displays, optical amplification, optical tomography, novelty filters, and phase conjugate wave generators. Ferroelectric liquid crystals are considered as a candidate for practical photorefractive materials. A refractive index grating formation time of 8-10 ms and a large gain coefficient are easily obtained in photorefractive ferroelectric liquid crystals.

Sasaki, Takeo; Naka, Yumiko

2014-03-01

255

Implementation of Ferroelectric Memories for Space Applications  

NASA Technical Reports Server (NTRS)

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.

Philpy, Stephen C.; Derbenwick, Gary F.; Kamp, David A.; Isaacson, Alan F.

2000-01-01

256

Ultrafast Photovoltaic Response in Ferroelectric Nanolayers  

SciTech Connect

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.

Daranciang, Dan

2012-02-15

257

Ferroelectricity and magnetoelectric coupling in magnetic ferroelectrics and artificial multiferroic heterostructures.  

E-print Network

??Multiferroic materials are those materials in which more than one ferroic order coexist. The most technologically appealing multiferroic materials are those showing ferromagnetism and ferroelectricity.… (more)

Fina Martínez, Ignasi

2012-01-01

258

High pressure applications of ferroelectric polymers  

NASA Astrophysics Data System (ADS)

Ferroelectric polymers are the most recent class piezoelectric and pyroelectric materials developed. The most common piezoelectric polymers are PVDF, based on the monomer CH2-CF2 and copolymers PVDF with C2F3H. Techniques to process PVDF and P(VDF-TrFE) copolymers such that their physical properties exhibit reproducibility approaching that of piezoelectric single crystals are presented. Instrinsic piezoelectric properties of such materials are presented in this paper. Under high hydrostatic pressure, piezoelectric polymers exhibit well defined piezoelectric response. Piezoelectric response of shock compresed PVDF film prepared with attention to mechanical and electrical processing exhibits precise, well defined reproducible behavior to 35 GPa. P(VDF-TrFE) copolymers exhibit unqiue piezoelectric properties over a wide range of temperature depending on the compositions. Under high shock pressure loading, unique piezoelectric response is also observed. In particular, thickness can range from one micron up to more than one mm. Small and large area sensors can be prepared. Charge mode and current mode sensors are presented. These copolymers have the potential for new shock wave sensors with unique characteristics.

Bauer, F.

1994-07-01

259

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

260

Interface effect on ferroelectricity at the nanoscale.  

PubMed

Interfaces play a critical role in nanoscale ferroelectricity. We perform a first-principles study of ultrathin KNbO(3) ferroelectric films placed between two metal electrodes, either SrRuO(3) or Pt. We show that bonding at the ferroelectric-metal interfaces imposes severe constraints on the displacement of atoms, destroying the bulk tetragonal soft mode. If the interface bonding is sufficiently strong, the ground-state represents a ferroelectric domain with an interface domain wall, driven by the intrinsic oppositely oriented dipole moments at the two interfaces. The critical thickness for the net polarization of the KNbO(3) film is predicted to be about 1 nm for Pt and 1.8 nm for SrRuO(3) electrodes. PMID:16522047

Duan, Chun-Gang; Sabirianov, Renat F; Mei, Wai-Ning; Jaswal, Sitaram S; Tsymbal, Evgeny Y

2006-03-01

261

Tunable metallic conductance in ferroelectric nanodomains.  

PubMed

Metallic conductance in charged ferroelectric domain walls was predicted more than 40 years ago as the first example of an electronically active homointerface in a nonconductive material. Despite decades of research on oxide interfaces and ferroic systems, the metal-insulator transition induced solely by polarization charges without any additional chemical modification has consistently eluded the experimental realm. Here we show that a localized insulator-metal transition can be repeatedly induced within an insulating ferroelectric lead-zirconate titanate, merely by switching its polarization at the nanoscale. This surprising effect is traced to tilted boundaries of ferroelectric nanodomains, that act as localized homointerfaces within the perovskite lattice, with inherently tunable carrier density. Metallic conductance is unique to nanodomains, while the conductivity of extended domain walls and domain surfaces is thermally activated. Foreseeing future applications, we demonstrate that a continuum of nonvolatile metallic states across decades of conductance can be encoded in the size of ferroelectric nanodomains using electric field. PMID:22181709

Maksymovych, Peter; Morozovska, Anna N; Yu, Pu; Eliseev, Eugene A; Chu, Ying-Hao; Ramesh, Ramamoorthy; Baddorf, Arthur P; Kalinin, Sergei V

2012-01-11

262

Interface control of bulk ferroelectric polarization  

SciTech Connect

The control of material interfaces at the atomic level has led to no- vel 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 em- ploy 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 un- derlayers extends the generality of this phenomenon.

Yu, P [University of California, Berkeley; Luo, Weidong [ORNL; Yi, D. [University of California, Berkeley; Zhang, J.-X. [University of California, Berkeley; Rossell, M.D. [Lawrence Berkeley National Laboratory (LBNL); Yang, C.-H. [Korea Advanced Institute of Science and Technology; You, L. [University of California, Berkeley; Singh-Bhalla, G. B. [University of California, Berkeley & LBNL; Yang, S.Y [University of California, Berkeley; He, Q [University of California, Berkeley; Ramasse, Q. M. [Lawrence Berkeley National Laboratory (LBNL); Erni, R. [Lawrence Berkeley National Laboratory (LBNL); Martin, L. W. [University of Illinois, Urbana-Champaign; Chu, Y. H. [University of California, Berkeley; Pantelides, Sokrates T [ORNL; Pennycook, Stephen J [ORNL; Ramesh, R. [University of California, Berkeley

2012-01-01

263

Ultrafast Photovoltaic Response in Ferroelectric Nanolayers  

E-print Network

We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO[subscript 3] via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering ...

Daranciang, Dan

264

Ferroelectric memory evaluation and development system  

NASA Astrophysics Data System (ADS)

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.

Bondurant, David W.

265

An epitaxial ferroelectric tunnel junction on silicon.  

PubMed

Epitaxially grown functional perovskites on silicon (001) and the ferroelectricity of a 3.2 nm thick BaTiO3 barrier layer are demonstrated. The polarization-switching-induced change in tunneling resistance is measured to be two orders of magnitude. The obtained results suggest the possibility of integrating ferroelectric tunnel junctions as binary data storage media in non-volatile memory cells on a silicon platform. PMID:25200550

Li, Zhipeng; Guo, Xiao; Lu, Hui-Bin; Zhang, Zaoli; Song, Dongsheng; Cheng, Shaobo; Bosman, Michel; Zhu, Jing; Dong, Zhili; Zhu, Weiguang

2014-11-01

266

Ferroelectric and ferromagnetic properties in BaTiO3 thin films on Si (100)  

NASA Astrophysics Data System (ADS)

In this paper, we report on the epitaxial integration of room temperature lead-free ferroelectric BaTiO3 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 BaTiO3/SrRuO3/MgO/TiN/Si (100) heterostructures. C-axis oriented and cube-on-cube epitaxial BaTiO3 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 BaTiO3. Furthermore, laser irradiation of BaTiO3 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 BaTiO3 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.

Singamaneni, Srinivasa Rao; Punugupati, Sandhyarani; Prater, John T.; Hunte, Frank; Narayan, Jagdish

2014-09-01

267

Magnetic control of ferroelectric interfaces.  

PubMed

We report the strong magnetic field dependence of ferroelectric PbZr(0.52)Ti(0.48)O(3) (PZT) films on half-metallic oxide La(0.67)Sr(0.33)MnO(3) (LSMO) electrodes. As the field H is increased, the hysteresis loop first broadens (becomes lossy) and then disappears at approximately H = 0.34 T and ambient temperatures. The data are compared with the theories of Pir? et al (2009 Phys. Rev. B 79 214114), Parish and Littlewood (2008 Phys. Rev. Lett. 101 166602) and Catalan (2006 Appl. Phys. Lett. 88 102902). The results are interpreted as due not to magnetocapacitance but to the sharp negative magnetoresistance in LSMO at low magnetic fields (Hwang et al 1996 Phys. Rev. Lett. 77 2041), which causes a dramatic increase in leakage current through the PZT. PMID:21540509

Dussan, S; Kumar, A; Katiyar, R S; Priya, S; Scott, J F

2011-05-25

268

Magnetic control of ferroelectric interfaces  

NASA Astrophysics Data System (ADS)

We report the strong magnetic field dependence of ferroelectric PbZr0.52Ti0.48O3 (PZT) films on half-metallic oxide La0.67Sr0.33MnO3 (LSMO) electrodes. As the field H is increased, the hysteresis loop first broadens (becomes lossy) and then disappears at approximately H = 0.34 T and ambient temperatures. The data are compared with the theories of Pir? et al (2009 Phys. Rev. B 79 214114), Parish and Littlewood (2008 Phys. Rev. Lett. 101 166602) and Catalan (2006 Appl. Phys. Lett. 88 102902). The results are interpreted as due not to magnetocapacitance but to the sharp negative magnetoresistance in LSMO at low magnetic fields (Hwang et al 1996 Phys. Rev. Lett. 77 2041), which causes a dramatic increase in leakage current through the PZT.

Dussan, S.; Kumar, A.; Katiyar, R. S.; Priya, S.; Scott, J. F.

2011-05-01

269

Ferroelectric-ferromagnetic multilayers: A magnetoelectric heterostructure with high output charge signal  

NASA Astrophysics Data System (ADS)

Multiferroic composites and heterostructures comprising ferroelectric and ferromagnetic materials exhibit room-temperature magnetoelectric (ME) effects greatly exceeding those of single-phase magnetoelectrics known to date. Since these effects are mediated by the interfacial coupling between ferroic constituents, the ME responses may be enhanced by increasing the density of interfaces and improving their quality. A promising material system providing these features is a ferroelectric-ferromagnetic multilayer with epitaxial interfaces. In this paper, we describe theoretically the strain-mediated direct ME effect exhibited by free-standing multilayers composed of single-crystalline ferroelectric nanolayers interleaved by conducting ferromagnetic slabs. Using a nonlinear thermodynamic approach allowing for specific mechanical boundary conditions of the problem, we first calculate the polarization states and dielectric properties of ferroelectric nanolayers in dependence on the lattice mismatch between ferroic constituents and their volume fractions. In these calculations, the ferromagnetic component is described by a model which combines linear elastic behavior with magnetic-field-dependent lattice parameters. Then the quasistatic ME polarization and voltage coefficients are evaluated using the theoretical strain sensitivity of ferroelectric polarization and measured effective piezomagnetic coefficients of ferromagnets. For Pb(Zr0.5Ti0.5)O3-FeGaB and BaTiO3-FeGaB multilayers, the ME coefficients are calculated numerically as a function of the FeGaB volume fraction and used to evaluate the output charge and voltage signals. It is shown that the multilayer geometry of a ferroelectric-ferromagnetic nanocomposite opens the way for a drastic enhancement of the output charge signal. This feature makes biferroic multilayers advantageous for the development of ultrasensitive magnetic-field sensors for technical and biomedical applications.

Prokhorenko, S.; Kohlstedt, H.; Pertsev, N. A.

2014-09-01

270

Extrinsic contributions to the response in ferroelectric ceramics  

SciTech Connect

The interest of this thesis is to investigate the electromechanical properties of ferroelectric ceramics in terms of the motion of domain walls, movement of boundaries between interphases, and interactions between grains and domains. A tentative phenomenological model has been proposed to evaluate the piezoelectric, elastic and dielectric parameters attributed to non-180[degrees] domain wall motions in ferroelectric ceramics. Observations of dielectricity and piezoelectricity at low and high temperatures, at small and large external fields, and at medium and high frequencies are discussed. From observed linear and nonlinear behavior of PZT ceramic systems, it can be concluded that the nonlinear effects are essentially extrinsic in nature, and domain wall motions play a major role in terms of the electromechanical coupling coefficients. Through X-ray diffraction analysis, the 90[degrees] domain reorientations under both electric fields and stress fields induced by the abrasion were examined in PZT ceramics, which showed that the coercive field is dependent upon 90[degrees]-domain reorientation processes. A simple and direct method has been proposed for quantitatively distinguishing the mechanisms of domain reorientation processes in polycrystalline materials. The polarization switching processes in the PZT ceramic with compositions near the morphotropic phase boundary is predominantly dependent upon two successive 90[degrees] domain wall reversal processes. Characterization of the domain structure has been made by scanning electron microscopy and etching techniques. The domain structure and grain morphology in PZT ceramics have been observed at the same time through SEM without using a coating technique. A modified lumped parameter method has been proposed suitable for microwave measurements of ferroelectric materials in the frequency range 10 MHz to 1G Hz. The dispersion of the complex dielectric coefficients of PZT ceramics was measured between 100 KHz-1 GHz.

Li, S.

1992-01-01

271

X-ray diffuse scattering study on ionic-pair displacement correlations in relaxor lead magnesium niobate  

Microsoft Academic Search

Ionic-pair equal-time displacement correlations in relaxor lead magnesium niobate, Pb(Mg1\\/3Nb2\\/3)O3, have been investigated at 300, 270, and 240 K in terms of an x-ray diffuse scattering technique. Functions of the distinct correlations have been determined quantitatively. The results show the significantly strong rhombohedral-polar correlations regarding Pb-O, Mg\\/Nb-O, and O-O' pairs. Their spatial distribution at 300 K forms an ellipse or

Naohisa Takesue; Yasuhiko Fujii; Hoydoo You

2001-01-01

272

Deaging and Asymmetric Energy Landscapes in Electrically Biased Ferroelectrics  

SciTech Connect

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}.

Tutuncu, Goknur; Damjanovic, Dragan; Chen, Jun; Jones, Jacob L. (EPFL); (UST - China); (Florida)

2012-09-05

273

Deaging and asymmetric energy landscapes in electrically biased ferroelectrics.  

PubMed

In ferroic materials, the dielectric, piezoelectric, magnetic, and elastic coefficients are significantly affected by the motion of domain walls. This motion can be described as the propagation of a wall across various types and strengths of pinning centers that collectively constitute a force profile or energetic landscape. Biased domain structures and asymmetric energy landscapes can be created through application of high fields (such as during electrical poling), and the material behavior in such states is often highly asymmetric. In some cases, this behavior can be considered as the electric analogue to the Bauschinger effect. The present Letter uses time-resolved, high-energy x-ray Bragg scattering to probe this asymmetry and the associated deaging effect in the ferroelectric morphotropic phase boundary composition 0.36BiScO3 - 0.64PbTiO3. PMID:22680904

Tutuncu, Goknur; Damjanovic, Dragan; Chen, Jun; Jones, Jacob L

2012-04-27

274

Ab initio design of charge-mismatched ferroelectric superlattices  

NASA Astrophysics Data System (ADS)

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.

Cazorla, Claudio; Stengel, Massimiliano

2014-07-01

275

Random local strain e#ects in homovalentsubstituted relaxor ferroelectrics: a firstprinciples study of BaTi 0.74 Zr 0.26 O 3  

E-print Network

, or almost cancelled. The type of a Ti displacement is entirely determined by the Ti/Zr distribution is a very active research area of constant interest over the past decades and with great relevance to both are characterized by a broad and frequency­ dependent maximum of the dielectric permittivity as a function

Recanati, Catherine

276

Dynamical mechanism of phase transitions in A-site ferroelectric relaxor (Na1/2Bi1/2)TiO3  

NASA Astrophysics Data System (ADS)

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.

Deng, Guochu; Danilkin, Sergey; Zhang, Haiwu; Imperia, Paolo; Li, Xiaobing; Zhao, Xiangyong; Luo, Haosu

2014-10-01

277

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

NASA Astrophysics Data System (ADS)

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%.

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

2014-10-01

278

Ferroelectricity in liquid crystals probed by second harmonic generation  

Microsoft Academic Search

Summary form only given. Ferroelectric liquid crystals (FLC) attract significant attention as promising materials for different applications and rare examples of two-dimensional (2D) ferroelectrics. It has been shown previously that a nonlinear optical probe of second harmonic generation (SHG) can be applied to study the structure and switching behaviour of FLC. In this study, ferroelectric properties and switching behaviour of

Yu. G. Fokin; T. V. Murzina; O. A. Aktsipetrov; S. Soria; G. Marowsky

2002-01-01

279

Neutron scattering studies of improper ferroelectric and incommensurate phase transitions  

Microsoft Academic Search

Results of neutron scattering studies are reviewed for ferroelectrics where the order parameter represents a soft phonon with wave vector unequal zero and forms an invariant with polarization (improper ferroelectric phase transition). An intermediate incommensurate phase may occur between the para- and ferroelectric phases due to the Lifshitz invariant. The group theoretical arguments for the existence of these invariants are

H. Grimm

1980-01-01

280

A Domain Wall Theory for Ferroelectric Hysteresis Ralph C. Smith  

E-print Network

A Domain Wall Theory for Ferroelectric Hysteresis Ralph C. Smith Center for Research in Scienti c and control design, we consider a theory for ferroelectric hysteresis which is based on domain wall dynamics been recognized that domain and domain wall mechanisms within ferroelectric materi- als result

281

A Domain Wall Theory for Ferroelectric Hysteresis Ralph C. Smith  

E-print Network

A Domain Wall Theory for Ferroelectric Hysteresis Ralph C. Smith Center for Research in Scientific and control design, we consider a theory for ferroelectric hysteresis which is based on domain wall dynamics been recognized that domain and domain wall mechanisms within ferroelectric materi­ als result

282

Enhanced energy harvesting in commercial ferroelectric materials  

NASA Astrophysics Data System (ADS)

Ferroelectric materials are used in a number of applications ranging from simple sensors and actuators to ferroelectric random access memories (FRAMs), transducers, health monitoring system and microelectronics. The multiphysical coupling ability possessed by these materials has been established to be useful for energy harvesting applications. However, conventional energy harvesting techniques employing ferroelectric materials possess low energy density. This has prevented the successful commercialization of ferroelectric based energy harvesting systems. In this context, the present study aims at proposing a novel approach for enhanced energy harvesting using commercially available ferroelectric materials. This technique was simulated to be used for two commercially available piezoelectric materials namely PKI-552 and APCI-840, soft and hard lead-zirconate-titanate (PZT) pervoskite ceramics, respectively. It was observed that a maximum energy density of 348 kJm-3cycle-1 can be obtained for cycle parameters of (0-1 ton compressive stress and 1-25 kV.cm-1 electric field) using APCI-840. The reported energy density is several hundred times larger than the maximum energy density reported in the literature for vibration harvesting systems.

Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

2014-04-01

283

Ferroelectricity in wurtzite structure simple chalcogenide  

NASA Astrophysics Data System (ADS)

The possibility of the new class ferroelectric materials of wurtzite structure simple chalcogenide was discussed using modern first-principles calculation technique. Ferroelectricity in the wurtzite structure (P63mc) can be understood by structure distortion from centrosymmetric P63/mmc by relative displacement of cation against anion along c-axis. Calculated potential surface of these compounds shows typical double well between two polar variants. The potential barriers for the ferroelectric polarization switching were estimated to be 0.25 eV/f.u. for ZnO. It is slightly higher energy to the common perovskite ferroelectric compound PbTiO3. Epitaxial tensile strain on the ab-plane (0001) is effective to lower the potential barrier. The potential barrier decreased from 0.25 to 0.15 eV/f.u. by 5% ab-plane expansion in wurtzite structure ZnO. Epitaxial ZnO thin film with donor type defect reduction should be a possible candidate to confirm this ferroelectricity in wurtzite structure simple chalcogenide.

Moriwake, Hiroki; Konishi, Ayako; Ogawa, Takafumi; Fujimura, Koji; Fisher, Craig A. J.; Kuwabara, Akihide; Shimizu, Takao; Yasui, Shintaro; Itoh, Mitsuru

2014-06-01

284

Ferroelectric field effect modulation of magnetism in composite multiferroics  

NASA Astrophysics Data System (ADS)

This work harnesses the strong charge-driven magnetoelectric coupling in Pb(Zr0.2Ti0.8)O3/La0.8Sr0.2MnO3 (PZT/LSMO) heterostructures to explore the sensitivity to charge of the electron transport and magnetic behavior of complex oxides. Epitaxial LSMO films that exhibit a highly ordered crystalline structure, as determined by in situ reflection high energy electron diffraction (RHEED) measurements and ex situ x-ray diffraction and transmission electron microscopy are grown by oxide molecular beam epitaxy. Off-axis RF magnetron sputtering is used to grow the PZT gate dielectric, which is characterized by square polarization-electric field hysteresis loops, with a large polarization and low leakage current. We use a combination of low-field magneto-transport and magneto-optic Kerr effect (MOKE) magnetometry to study the ferroelectric field effect induced changes in the magnetic coercive field in PZT/LSMO bilayers. A reversible shift in the coercive field is observed for the two polarization states of the ferroelectric, with a larger coercive field in polarization state that accumulates hole carriers at the PZT/LSMO interface. The reversible electrical control of magnetism in engineered heterostructures is opens new directions in the field of spintronics.

Hoffman, Jason; Vaz, Carlos; Segal, Yaron; Marshall, Matthew; Walker, Fred; Ahn, Charles

2011-03-01

285

Retention of resistance states in ferroelectric tunnel memristors  

NASA Astrophysics Data System (ADS)

Resistive properties of Co/BaTiO3/La2/3Sr1/3MnO3 ferroelectric tunnel junctions on (110) NdGaO3 substrates are investigated. A notable characteristic of these junctions is the memristive behavior—a dependence of resistance on amplitude and duration of a writing pulse, which is attributed to field-induced charge accumulation at the Co/BaTiO3 interface. It is found that retention of the resistance states depends on the thickness of the ferroelectric barrier: the junctions with the thinnest 4-unit-cell-thick BaTiO3 barrier exhibit significant relaxation of the low resistance state while the junctions with thicker barriers exhibit stable resistance. It is proposed that, in a thinner barrier, a larger depolarizing field triggers a faster dissipation of the accumulated charges, resulting in a recovery of interfacial tunnel barrier height and gradual transition from a low to a high resistance state.

Kim, D. J.; Lu, H.; Ryu, S.; Lee, S.; Bark, C. W.; Eom, C. B.; Gruverman, A.

2013-09-01

286

The Hunt for a Snark: Spatially Resolved Imaging of Nucleation Centers in Ferroelectrics  

NASA Astrophysics Data System (ADS)

Ferroelectric polarization switching in non-volatile memory and high density data storage devices is governed by a number of nucleation centers that are necessary to account for experimentally observed low values of coercive fields. Despite 50 years of extensive research addressing the role of conductivity, surface dead layers, charge injection, and other factors, the microstructural origins of the Landauer paradox (switching fields correspond to implausibly large nucleation activation energies) are still a mystery. Here, Switching Spectroscopy Piezoresponse Force Microscopy (SS-PFM) is developed as a quantitative tool for real-space mapping of imprint, coercive bias, remanent and saturation responses, work of switching, and nucleation biases in ferroelectrics. Several examples of switching behavior in low dimensional ferroelectrics are presented, including (a) pinning at grain boundaries in polycrystalline PZT, (b) non-uniform work of switching in ferroelectric nanodots and (c) switching in the vicinity of topographic defects. The ``abnormal'' hysteresis loops were observed in the vicinity of topographic defects in multiferroic thin films and PZT ceramics and attributed to the interaction of nascent domain with the strain field of the defect. The mapping of the spatial and energy distribution of Landauer switching centers is demonstrated.

Kalinin, Sergei; Jesse, Stephen; Rodriguez, Brian; Baddorf, Arthur

2007-03-01

287

Coexistence of toroidal and polar domains in ferroelectric systems: A strategy for switching ferroelectric vortex  

NASA Astrophysics Data System (ADS)

Phase field simulations have been conducted to investigate the vortex domain structure in ferroelectric nanodots epitaxially grown on ferroelectric nanofilm. It is found that the nanodot region has great impact on the domain evolution of the whole system. At suitable conditions (e.g., geometry, size, temperature, external strain, and electric field), the nanodot adopts a vortex domain pattern while the nanofilm maintains a polar domain. Interestingly, the vortex domain pattern of the nanodot can be switched by controlling the direction of the adjacent polar domain. Our study indicates an alternative strategy for controlling the chirality of vortex domain structure in nano-ferroelectrics.

Chen, W. J.; Zheng, Yue; Wang, Biao; Liu, J. Y.

2014-06-01

288

Ferroelectricity of polycrystalline GdMnO3 and multifold magnetoelectric responses  

NASA Astrophysics Data System (ADS)

The multiferroic behaviors of polycrystalline GdMnO3 are investigated by focusing on the ferroelectric response to the spin ordering sequence and external magnetic field. The polarization current shows sensitive response to both the Mn cycloidal spin order and Gd antiferromagnetic (AFM) order. The complicated magnetoelectric behaviors suggest that the Mn cycloidal spin order can be modulated by the Gd AFM order at low temperature via the Gd-Mn spin interaction. Due to the possible disorder and defects in polycrystalline nature, polycrystalline GdMnO3 may accommodate the cycloidal spin order in addition to the A-type AFM order at Mn sites, as illustrated by simulation based on the two-orbit double exchange model and measured hysteresis loops of polarization against magnetic field, indicating the switching of the ferroelectric domains coupled with the magnetic domains in response to magnetic field.

Lin, L.; Li, L.; Yan, Z. B.; Tao, Y. M.; Dong, S.; Liu, J.-M.

2013-09-01

289

Method of laser processing ferroelectric materials  

NASA Astrophysics Data System (ADS)

Processing methods transform ferroelectric precursor films into a desired crystalline structure without adversely heating nearby materials and circuitry such as those found associated with lead zirconate titanate films. The thin film sample is placed within an appropriate chamber, where a suitable ambient is in contact with the thin film sample. The ambient may be air, oxygen or any other ambient which is known in the art to be appropriate for annealing ferroelectric materials. In this regard annealing in air can do without the processing chamber. The process for annealing relies upon continuous wave (CW) laser annealing, pulse UV annealing with or without a laser and various combinations of thermal pretreatment and processing to allow solid state diffusion in accordance with parameters appropriate for a particular application. Methods of laser patterning thin film ferroelectrics without adversely damaging adjacent or underlying layers, e.g. electrodes, are also disclosed.

Russell, Stephen D.; Sexton, Douglas A.

1994-05-01

290

A Ferroelectric Oxide Made Directly on Silicon  

SciTech Connect

Metal oxide semiconductor field-effect transistors, formed using silicon dioxide and silicon, have undergone four decades of staggering technological advancement. With fundamental limits to this technology close at hand, alternatives to silicon dioxide are being pursued to enable new functionality and device architectures. We achieved ferroelectric functionality in intimate contact with silicon by growing coherently strained strontium titanate (SrTiO{sub 3}) films via oxide molecular beam epitaxy in direct contact with silicon, with no interfacial silicon dioxide. We observed ferroelectricity in these ultrathin SrTiO{sub 3} layers by means of piezoresponse force microscopy. Stable ferroelectric nanodomains created in SrTiO{sub 3} were observed at temperatures as high as 400 kelvin.

Warusawithana, M.; Cen, C; Sleasman, C; Woicik, J; Li, Y; Fitting Kourkoutis, L; Klug, J; Li, H; Ryan, P; et. al.

2009-01-01

291

Ferroelectric actuators in the electromechanical interface  

NASA Astrophysics Data System (ADS)

The requirements of a control actuator are examined, and the unique capabilities of the type of an actuator driven by ferroelectric materials that exhibit piezoelectric characteristics when electrically poled to meet these requirements are demonstrated. It is shown that, when substantial energy is required from an actuator, actuators configured as stacks of ferroelectric disks are most suitable. They develop high force, respond extremely fast, can be proportionately charged, have almost infinite resolution, require no holding current to maintain displacement, and are neither influenced by nor produce magnetic fields. In addition, ferroelectric actuators are not prone to corrosion and have no mechanically wearing components. A very fast and precise steering mirror system is described that employs a split stack assembly.

O'Neill, C. G.; O'Neill, C. H.

1990-11-01

292

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

PubMed

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

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

2014-05-14

293

Domain wall creep in epitaxial ferroelectric Pb(Zr(0.2)Ti(0.08)O(3) thin films.  

PubMed

Ferroelectric switching and nanoscale domain dynamics were investigated using atomic force microscopy on monocrystalline Pb(Zr(0.2)Ti(0.8))O(3) thin films. Measurements of domain size versus writing time reveal a two-step domain growth mechanism, in which initial nucleation is followed by radial domain wall motion perpendicular to the polarization direction. The electric field dependence of the domain wall velocity demonstrates that domain wall motion in ferroelectric thin films is a creep process, with the critical exponent mu close to 1. The dimensionality of the films suggests that disorder is at the origin of the observed creep behavior. PMID:12190438

Tybell, T; Paruch, P; Giamarchi, T; Triscone, J-M

2002-08-26

294

Observation of spontaneous ferroelectric polarization reversal in multiferroic Mn1-xNixWO4 (x ? 0.16)  

NASA Astrophysics Data System (ADS)

In this Letter, we report the effect of replacing Mn2+ ions with Ni2+ on the ferroelectricity of multiferroic MnWO4 single crystals. When the amount of substitution was close to 16%, the sign of ferroelectric polarization spontaneously became negative with respect to initial dc poling field at a few degrees below TC. Neutron diffraction intensities revealed a sudden change in the underlying spiral spin ordering that occurred coincidentally with the observed sign reversal. This unusual behavior in zero magnetic fields suggests that strong competitions between the two different magnetic ions may provide an efficient route to manipulation of existing multiferroics.

Song, Young-Sang; Chung, Jae-Ho; Woo Shin, Kwang; Hoon Kim, Kee; Hwan Oh, In

2014-06-01

295

Barkhausen jumps in the motion of a single ferroelectric domain wall  

Microsoft Academic Search

It is shown that the motion of a domain wall in the improper ferroelectric-ferroelastic gadolinium molybdate Gd2(MoO4)3 demonstrates a self-organized critical behavior under polarization reversal. Barkhausen pulses are measured experimentally\\u000a during the jumpwise motion of a single plane domain wall in monocrystalline plates with artificial pinning centers of the\\u000a “field inhomogeneity” type.

V. Ya. Shur; V. L. Kozhevnikov; D. V. Pelegov; E. V. Nikolaeva; E. I. Shishkin

2001-01-01

296

Time-resolved switching analysis of a ferroelectric liquid crystal by snapshot Mueller matrix polarimetry.  

PubMed

An experimental snapshot Mueller matrix polarimeter based on wavelength polarization coding is used to get a time-resolved description of electric-field-induced fast transition within a ferroelectric liquid-crystal cell. The parameters extracted from experimental Mueller matrices are linked to the molecule director distribution to further determine the average trajectory and the collective behavior of these molecules while they switch over to another state. PMID:20364203

Dubreuil, Matthieu; Rivet, Sylvain; Le Jeune, Bernard; Dupont, Laurent

2010-04-01

297

Ultra-High-Density Ferroelectric Memories  

NASA Technical Reports Server (NTRS)

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.

Thakoor, Sarita

1995-01-01

298

Ferroelectric Cathodes in Transverse Magnetic Fields  

SciTech Connect

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.

Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

2002-07-29

299

Classification of laminate domain patterns in ferroelectrics  

NASA Astrophysics Data System (ADS)

Ferroelectric crystals are known to adopt low-energy, compatible domain configurations. Observations show that these configurations are commonly multirank laminate patterns. In this work, a method to classify and enumerate the laminate domain patterns that can form is presented. The criteria of exact compatibility for laminates structures in a ferroelectric single crystal are used to find all the rank-2 arrangements of domains in the polar tetragonal crystal system. Surprisingly, only eight distinct rank-2 laminate patterns that satisfy compatibility conditions at all domain walls are found. These patterns are classified and correlated with observations of domains in single crystals, showing good agreement.

Tsou, N. T.; Potnis, P. R.; Huber, J. E.

2011-05-01

300

Ferroelectric plasma thruster for microspacecraft propulsion  

SciTech Connect

This paper presents a technology in microthruster design: the ferroelectric plasma thruster (FEPT). The FEPT utilizes an applied rf electric field to create plasma on the surface of a ferroelectric dielectric. Acceleration of ions from this plasma provides thrust. Advantages of the FEPT include emission of both electrons and ions leading to self-neutralization, creation of plasma, and acceleration of ions with a single power supply, and application of thrust in a short amount of time. We present the concept of the thruster, operational physics, as well as experimental results demonstrating plasma creation and ion acceleration. These results along with plasma spectroscopy allow us to calculate thruster parameters.

Kemp, Mark A.; Kovaleski, Scott D. [Department of Electrical and Computer Engineering, University of Missouri-Columbia, Columbia, Missouri 65211 (United States)

2006-12-01

301

95 GHz gyrotron with ferroelectric cathode.  

PubMed

Ferroelectric cathodes were reported as a feasible electron source for microwave tubes. However, due to the surface plasma emission characterizing this cathode, operation of millimeter wave tubes based on it remains questionable. Nevertheless, the interest in compact high power sources of millimeter waves and specifically 95 GHz is continually growing. In this experiment, a ferroelectric cathode is used as an electron source for a gyrotron with the output frequency extended up to 95 GHz. Power above a 5 kW peak and ~0.5 ?s pulses are reported; a duty cycle of 10% is estimated to be achievable. PMID:23215293

Einat, M; Pilossof, M; Ben-Moshe, R; Hirshbein, H; Borodin, D

2012-11-01

302

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

PubMed

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

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

2014-06-01

303

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

NASA Technical Reports Server (NTRS)

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.

Brody, P. S.

1981-01-01

304

Effect of stoichiometry on the dielectric properties and soft mode behavior of strained epitaxial SrTiO3 thin films on DyScO3 substrates  

SciTech Connect

The effect of stoichiometry on the dielectric properties and soft mode behavior of strained epitaxial Sr1-xTiO3 films grown on DyScO3 substrates is reported. Direct comparisons between nominally stoichiometric and non-stoichiometric films have been performed through measurements of lattice parameters, temperature-dependent permittivities, second harmonic generation, and terahertz dielectric spectra. The nominally stoichiometric film shows dispersion-free low-frequency permittivity with a 23 sharp maximum and pronounced soft mode behavior. Our results suggest that strained perfectlystoichiometric SrTiO3 films should not show relaxor behavior and that relaxor behavior emergesfrom defect dipoles that arise from non-stoichiometry in the highly polarizable strained SrTiO3 matrix

Lee, Che-Hui [Pennsylvania State University, University Park, PA; Skoromets, Volodymyr [Institute of Physics, Czech Republic; Biegalski, Michael D [ORNL; Lei, Shiming [Pennsylvania State University, University Park, PA; Haislmaier, Ryan [Pennsylvania State University, University Park, PA; Uecker, Reinhard [Leibniz Institute for Crystal Growth (IKZ); Bernhagen, Margitta [Leibniz Institute for Crystal Growth (IKZ); Xi, Xiaoxing [Temple University; Gopalan, Venkatraman [Pennsylvania State University, University Park, PA; Marti, Xavier [Institute of Physics, Czech Republic; Kamba, Stanislav [Institute of Physics, Czech Republic; Kuzel, Petr [Institute of Physics, Czech Republic; Schlom, Darrell [Cornell University

2013-01-01

305

Properties of ferroelectric/ferromagnetic thin film heterostructures  

NASA Astrophysics Data System (ADS)

Ferroelectric/ferromagnetic thin film heterostructures, SrBi2Ta2O9/BaFe12O19 (SBT/BaM), were grown on platinum-coated Si substrates using metal-organic decomposition. X-ray diffraction patterns confirmed that the heterostructures contain only SBT and BaM phases. The microwave properties of these heterostructures were studied using a broadband ferromagnetic resonance (FMR) spectrometer from 35 to 60 GHz, which allowed us to determine gyromagnetic ratio and effective anisotropy field. The FMR linewidth is as low as140 Oe at 58 GHz. In addition, measurements of the effective permittivity of the heterostructures were carried out as a function of bias electric field. All heterostructures exhibit hysteretic behavior of the effective permittivity. These properties indicate that such heterostructures have potential for application in dual electric and magnetic field tunable resonators, filters, and phase shifters.

Chen, Daming; Harward, Ian; Linderman, Katie; Economou, Evangelos; Nie, Yan; Celinski, Zbigniew

2014-05-01

306

Sub-critical field domain reversal in epitaxial ferroelectric films  

NASA Astrophysics Data System (ADS)

Domain nucleation in epitaxial (001)-oriented Pb(Zr0.2TiO0.8)O3 ultrathin ferroelectric films under a sub-critical field regime is investigated by means of piezoresponse force microscopy (PFM). Analytical fits to the domain radius and velocity as a function of time indicate that 180° domain nucleation and growth under a biased PFM tip exhibit a thermally activated, creep behavior. It is also found that an electric field of less than half of the local coercive (or critical) field E c l o c detected by PFM can create stable domains under prolonged bias application. Under these sub-critical bias conditions, it is the temporal evolution of the local electric-field profile due to the slow drift of screening charges or defects (e.g., ionic vacancies) that dictates domain nucleation and growth.

Chen, Jason; Gruverman, Alexei; Morozovska, Anna N.; Valanoor, Nagarajan

2014-09-01

307

High-Resolution Field Effect Sensing of Ferroelectric Charges  

SciTech Connect

Nanoscale manipulation of surface charges and their imaging are essential for understanding local electronic behaviors of polar materials and advanced electronic devices. Electrostatic force microscopy and Kelvin probe force microscopy have been extensively used to probe and image local surface charges responsible for electrodynamics and transport phenomena. However, they rely on the weak electric force modulation of cantilever that limits both spatial and temporal resolutions. Here we present a field effect transistor embedded probe that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 {micro}s. On the basis of the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 0.08 {micro}C/cm{sup 2}, which is equivalent to 1/20 electron per nanometer square at room temperature.

Ko, Hyoungsoo [Samsung Advanced Institute of Science and Technology, Korea; Ryu, Kyunghee [Kookmin University; Park, Hongsik [Samsung Advanced Institute of Science and Technology, Korea; Park, Chulmin [Samsung Advanced Institute of Science and Technology, Korea; Jeon, Daeyoung [Samsung Advanced Institute of Science and Technology, Korea; Kim, Yong Kwan [Samsung Advanced Institute of Science and Technology, Korea; Jung, Juhwan [Samsung Advanced Institute of Science and Technology, Korea; Min, Dong-Ki [Samsung Advanced Institute of Science and Technology, Korea; Kim, Yunseok [Max-Planck-Institut fur Mikrostrukturphysik, Germany; Lee, Ho Nyung [ORNL; Park, Yoondong [Samsung Advanced Institute of Science and Technology, Korea; Shin, Hyunjung [Kookmin University; Hong, Seungbum [Samsung Advanced Institute of Science and Technology, Korea

2011-01-01

308

High resolution field effect sensing of ferroelectric charges.  

SciTech Connect

Nanoscale manipulation of surface charges and their imaging are essential for understanding local electronic behaviors of polar materials and advanced electronic devices. Electrostatic force microscopy and Kelvin probe force microscopy have been extensively used to probe and image local surface charges responsible for electrodynamics and transport phenomena. However, they rely on the weak electric force modulation of cantilever that limits both spatial and temporal resolutions. Here we present a field effect transistor embedded probe that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 {micro}s. On the basis of the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 0.08 {micro}C/cm{sup 2}, which is equivalent to 1/20 electron per nanometer square at room temperature.

Ko, H.; Ryu, K.; Park, H.; Park, C.; Jeon, D.; Kim, Y. K.; Jung, J.; Min, D.-K.; Kim, Y.; Lee, H. N.; Park, Y.; Shin, H.; Hong, S. (Materials Science Division); (Samsung Advanced Inst. of Science and Technology); (Samsung Electronics); (Kookmin Univ.); (Brown Univ.); (Korea Univ.); (Max Planck Inst. Microstructure Physics); (ORNL)

2011-03-04

309

Magnetoelectric properties of magnetic/ferroelectric multilayer thin films  

NASA Astrophysics Data System (ADS)

Magnetic/ferroelectric multilayer thin films using PbZr0.52Ti0.48O3 (PZT) and two different magnetic materials, i.e., Terfenol-D and CuFe2O4 (CuFO) layers, were fabricated, and their magnetoelectric (ME) coupling behavior was investigated. The PZT layer was first coated onto Pt/Ti/SiO2/Si substrate by sol-gel spin coating method. Pt layer, which served as an electrode and a diffusion barrier, was grown on the PZT layer by using the ion-beam sputtering method. The ME voltage coefficients were calculated from the ME voltage data measured utilizing a magnetoelectric test system. The Terfenol-D/Pt/PZT films were found to show a higher in-plane ME voltage coefficient than that the CuFO/Pt/PZT films due primarily to the higher magnetostriction coefficient of Terfenol-D.

Hwang, Sung-Ok; Eum, You Jeong; Koo, Chang Young; Lee, Hee Young; Park, Jung Min; Ryu, Jungho

2014-07-01

310

Soft memory in a ferroelectric nanoparticle-doped liquid crystal  

NASA Astrophysics Data System (ADS)

A small quantity of BaTiO3 ferroelectric nanoparticles (FNP) was doped in a liquid crystal (LC), and the LC + FNP hybrid was found to exhibit a nonvolatile electromechanical memory effect in the isotropic phase. The permanent dipole moment of the FNPs causes the LC molecule to form short-range pseudonematic domains surrounding the FNPs. The FNP-induced short-range orders become more prominent in the isotropic phase when the global nematic order is absent. These short-range domains, being anisotropic in nature, interact with an external electric field, exhibiting a Fréedericksz-type transition. When the field is turned off, these domains stay oriented, showing a hysteresis effect due to the absence of any long-range order and restoring forces in the isotropic phase. The hysteresis graph for this memory effect shows a significant pretransitional behavior on approaching the nematic phase from the isotropic phase.

Basu, Rajratan

2014-02-01

311

FERROELECTRIC LIQUID CRYSTAL GLASSES FOR AMBLYOPIA RESEARCH  

Microsoft Academic Search

Ferroelectric Liquid Crystal (FLC) filters offer the speed of electronic light shutters and the vibration free operation. These characteristics make them ideal for applications requiring short exposure times and minimal blur, offering switching times of 0.0002 of a second. FLC filters can be used as the optical shutters for machine vision purposes, also in vision research. On the basis of

SERGEJS FOMINS; MARIS OZOLINSH; GUNTA KRUMINA; VARIS KARITANS

2008-01-01

312

A Model for Ferroelectric Phase Shifters  

NASA Technical Reports Server (NTRS)

Novel microwave phase shifters consisting of coupled microstrip lines on thin ferroelectric films have been demonstrated recently. A theoretical model useful for predicting the propagation characteristics (insertion phase shift, dielectric loss, impedance, and bandwidth) is presented here. The model is based on a variational solution for line capacitance and coupled strip transmission line theory.

Romanofsky, Robert R.; Qureshi, A. Haq

2000-01-01

313

Sideways dynamics of ferroelectric domain walls  

Microsoft Academic Search

Characteristic features of the sideways motion of domain walls in ferroelectrics are considered. The proposed model for calculating the mobility of domain walls for this type of motion is based on the approaches developed by D. G. Sannikov and M. A. Collins et al. We examine the dynamics of domain walls in the vicinity of second-order phase transitions. The calculated

L. Bakaleinikov; A. Gordon

2007-01-01

314

Transverse polarization in triglycine sulphate ferroelectric  

NASA Astrophysics Data System (ADS)

The results of measurements of the electric current's density along the non-polar c-axis direction in the triglycine sulphate ferroelectric have been shown. The pyroelectric properties have been observed in the same direction. Evidence of the occurrence of crystal's temperature-dependent transverse polarization has been given. A strong correlation between the transverse and longitudinal polarizations has been found out.

Fugiel, B.

2002-05-01

315

Graphene Ferroelectric Heterostructures Santosh Raghavan1  

E-print Network

Graphene Ferroelectric Heterostructures Santosh Raghavan1 , Dr. Jean-Savin Heron2 , Dr. Igor] Laboratory of Nanoscale Electronics and Structures, IEL, EPFL S D1 2 Doped Silicon SiO2 Graphene 3 4 1 2S D L Introduction Working Principle Graphene PVDF (-TrFE) PFM Measurements Retention Measurements Conclusion

Dalang, Robert C.

316

Ferroelectric polarization reversal in single crystals  

NASA Technical Reports Server (NTRS)

Research on the reversal of polarization in ferroelectric crystals is reviewed. Particular attention is given to observation methods for polarization reversal, BaTiO3 polarization reversal, crystal thickness dependence of polarization reversal, and domain wall movement during polarization reversal in TGS.

Stadler, Henry L.

1992-01-01

317

Scattering properties of ferroelectric domain walls  

Microsoft Academic Search

Ferroelectric domain walls have recently been considered as candidates for the occurrence of non-linear (soliton) excitations and roughening transitions. By means of X-ray or neutron scattering experiments, the domain walls may be observed directly and their width may be measured. The occurrence of a roughening transition would be observable by these techniques, and the roughening mechanism is suggested as an

D. A. Bruce

1981-01-01

318

Phenomenological theories of ferroelectric phase transitions  

E-print Network

-Phenomenological theories can be directly linked to ing domain walls in ferroelectric systems and antiferroelec­Devonshire type models, which can be con- antiphase structures and domain walls. Here two examplesstructed based example twins and domain walls. Phenomenological In phenomenological theories, the key quantity

Cao, Wenwu

319

A hybrid ferroelectric-flash memory cells  

NASA Astrophysics Data System (ADS)

A ferroelectric-flash (F-flash) memory cells having a metal-ferroelectric-nitride-oxynitride-silicon structure are demonstrated, and the ferroelectric materials were perovskite-dominated Pb(Zr,Ti)O3 (PZT) crystallized by Pt gate electrode. The PZT thin-film as a blocking layer improves electrical and memorial performance where programming and erasing mechanism are different from the metal-ferroelectric-insulator-semiconductor device or the conventional silicon-oxide-nitride-oxide-silicon device. F-flash cells exhibit not only the excellent electrical transistor performance, having 442.7 cm2 V-1 s-1 of field-effect mobility, 190 mV dec-1 of substhreshold slope, and 8 × 105 on/off drain current ratio, but also a high reliable memory characteristics, having a large memory window (6.5 V), low-operating voltage (0 to -5 V), faster P/E switching speed (50/500 ?s), long retention time (>10 years), and excellent fatigue P/E cycle (>105) due to the boosting effect, amplification effect, and energy band distortion of nitride from the large polarization. All these characteristics correspond to the best performances among conventional flash cells reported so far.

Park, Jae Hyo; Byun, Chang Woo; Seok, Ki Hwan; Kim, Hyung Yoon; Chae, Hee Jae; Lee, Sol Kyu; Son, Se Wan; Ahn, Donghwan; Joo, Seung Ki

2014-09-01

320

Thin film ferroelectric materials for microbolometer arrays  

NASA Astrophysics Data System (ADS)

This paper reviews the use of thin film ferroelectric materials for application in microbolometer infrared detector arrays. A key issue is the need for high temperature processing to achieve the required ferroelectric crystal phase. Results of thermal trials on silicon readout circuits are presented which indicate failure due to disruption of the AlCuSi metallisation. Higher temperatures can be used if oxygen is excluded. A low temperature lead zirconate titanate (PZT) sol-gel deposition is reported which has been used to fabricate fully integrated detector arrays directly on readout silicon wafers. Higher performance is obtained from dielectric bolometer materials, and materials merit figures nearly 4 times that of PZT are reported for sputtered lead scandium tantalate (PST) films. These require post-deposition annealing to temperatures above that allowable for silicon readout survival. Results on excimer laser annealing are presented which demonstrate crystallisation of a ferroelectric film without heating the underlying substrate. A new composite thermal detector array design is introduced, based on an indirect fabrication method. This uses a high density interconnect wafer as a high temperature substrate for ferroelectric film growth. After fabrication of the detector pixels, individual arrays are flip-chip bonded to readout silicon die.

Todd, Michael A.; Manning, Paul A.; Donohue, Paul P.; Brown, Alan G.; Watton, Rex

2000-12-01

321

Theory of prospective tetrahedral perovskite ferroelectrics  

E-print Network

Using first-principles methods, we predict the energy landscape and ferroelectric states of double perovskites of the form AA$'$BB$'$O$_6$ in which the atoms on both the A and B sites are arranged in rock-salt order. While we are not aware of compounds that occur naturally in this structure, we argue that they might be realizable by directed synthesis. The high-symmetry structure formed by this arrangement belongs to the tetrahedral $F\\bar{4}3m$ space group. If a ferroelectric instability occurs, the energy landscape will tend to have minima with the polarization along tetrahedral directions, leading to a rhombohedral phase, or along Cartesian directions, leading to an orthorhombic phase. We find that the latter scenario applies to CaBaTiZrO$_6$ and KCaZrNbO$_6$, which are weakly ferroelectric, and the former one applies to PbSnTiZrO$_6$, which is strongly ferroelectric. The results are modeled with a fourth- or fifth-order Landau-Devonshire expansion, providing good agreement with the first-principles calcul...

Roy, Anindya

2010-01-01

322

Local Polarization Dynamics in Ferroelectric Materials  

SciTech Connect

Ferroelectrics and multiferroics have recently emerged as perspective materials for information technology and data storage applications. The combination of extremely narrow domain wall width and the capability to manipulate polarization by electric field opens the pathway towards ultrahigh (>10 TBit/in2) storage densities and small (sub-10 nm) feature sizes. The coupling between polarization and chemical and transport properties enables applications in ferroelectric lithography and electroresistive devices. The progress in these applications, as well as fundamental studies of polarization dynamics and the role of defects and disorder on domain nucleation and wall motion, requires the capability to probe these effects on the nanometer scale. In this review, we summarize recent progress in applications of Piezoresponse Force Microscopy (PFM) for imaging, manipulation, and spectroscopy of ferroelectric switching processes. We briefly introduce the principles and relevant instrumental aspects of PFM, with special emphasis on resolution and information limits. The local imaging studies of domain dynamics, including local switching and relaxation accessed through imaging experiments, and spectroscopic studies of polarization switching, are discussed in detail. Finally, we briefly review the recent progress on photochemical processes on ferroelectric surfaces, the role of surface adsorbates, and imaging and switching in liquids. Beyond classical applications, probing local bias-induced transition dynamics by PFM opens the pathway to studies of the influence of a single defect on electrochemical and solid state processes, thus providing model systems for batteries, fuel cells, and supercapacitor applications.

Kalinin, Sergei V [ORNL; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine; Chen, L. Q. [Pennsylvania State University; Rodriguez, Brian J [ORNL

2010-01-01

323

Piezoelectric Materials with Ferroelectric-Antiferroelectric Low Pressure Transition Used for Mechanoelectric Energy Conversion.  

National Technical Information Service (NTIS)

Ferroelectric materials synthesis, electrical and thermodynamical characterization, and applications are studied. Ferroelectric ceramics with a perovskite structure ABO/sub 3/ are used in conversion by ferroelectric-antiferroelectric phase change. Composi...

G. Grange

1984-01-01

324

Pressure-induced crossover from long-to-short-range order in Pb,,Zn13Nb23...O30.905,,PbTiO3...0.095 single crystal  

E-print Network

...0.095 single crystal G. A. Samaraa) and E. L. Venturini Sandia National Laboratories, Albuquerque, New Mexico normal ferroelectric­to­relaxor behavior has been observed in single crystal Pb Zn1/3Nb2/3 O3 0.905 Pb with single crystals. Numerous attempts, extending over several decades, to grow PZT crystals of suitable size

325

Reassessment of the Burns temperature and its relationship to the diffuse scattering, lattice dynamics, and thermal expansion in relaxor Pb(Mg1/3Nb2/3)O3  

NASA Astrophysics Data System (ADS)

We have used neutron scattering techniques that probe time scales from 10-12 to 10-9s to characterize the diffuse scattering and low-energy lattice dynamics in single crystals of the relaxor PbMg1/3Nb2/3O3 (PMN) from 10 to 900 K. Our study extends far below Tc=213K , where long-range ferroelectric correlations have been reported under field-cooled conditions, and well above the nominal Burns temperature Td?620K , where optical measurements suggest the development of short-range polar correlations known as “polar nanoregions” (PNR). We observed two distinct types of diffuse scattering. The first is weak, relatively temperature independent, persists to at least 900 K, and forms bow-tie-shaped patterns in reciprocal space centered on (h00) Bragg peaks. We associate this primarily with chemical short-range order. The second is strong, temperature dependent, and forms butterfly-shaped patterns centered on (h00) Bragg peaks. This diffuse scattering has been attributed to the PNR because it responds to an electric field and vanishes near Td?620K when measured with thermal neutrons. Surprisingly, it vanishes at 420 K when measured with cold neutrons, which provide approximately four times superior energy resolution. That this onset temperature depends so strongly on the instrumental energy resolution indicates that the diffuse scattering has a quasielastic character and demands a reassessment of the Burns temperature Td . Neutron backscattering measurements made with 300 times better energy resolution confirm the onset temperature of 420±20K . The energy width of the diffuse scattering is resolution limited, indicating that the PNR are static on time scales of at least 2 ns between 420 and 10 K. Transverse acoustic (TA) phonon lifetimes, which are known to decrease dramatically for wave vectors q?0.2Å-1 and Tc

Gehring, P. M.; Hiraka, H.; Stock, C.; Lee, S.-H.; Chen, W.; Ye, Z.-G.; Vakhrushev, S. B.; Chowdhuri, Z.

2009-06-01

326

Ferroelectricity and antiferroelectricity in CuCrO2-type multiferroic semiconductors  

NASA Astrophysics Data System (ADS)

Multiferroic semiconductors of the CuCrO2 type are considered. These materials, in the presence of free charge carriers, allow for the existence of opposite domains (in the ferroelectric FE d phase), along with ordinary 180° domains (in the FE phase). The magnetization phase transition in a chiral multiferroic, allowing for piezoelectric effects in an antiferromagnet with a layered triangular structure which result in an incommensurate (helicoidal) spin structure, is phenomenologically described. The behavior of the ferroelectric polarization in the considered phases is characterized. The antiferroelectric is considered a system of parallel layers alternating in chirality sign with oppositely directed polarization vectors. The possibility of antiferroelectric phase transition due to the specific features of the dipole-dipole interaction is discussed.

Pikin, S. A.

2014-07-01

327

The effects of domain wall thickness on the nanoscale piezoresponse of ferroelectric domains  

NASA Astrophysics Data System (ADS)

The effects of domain wall thickness on the nanoscale piezoresponse of ferroelectric domains, including typical 180°, uncharged 90°, and charged 90° domains, are investigated via treating the domain wall as a piezoelectric medium, which possesses distinct piezoelectric coefficients from the adjacent domains. It is found that increasing the domain thickness can result in enhanced lateral piezoresponse force microscopy response of uncharged 90° domains and vertical piezoresponse force microscopy (VPFM) response of charged 90° domains, while it would reduce VPFM response of uncharged 90° domains. Good agreements with experiments are observed. The different enhancement behaviors maybe result from the distinction of average polarization orientation of those domain walls. These insights point to a new pathway to enhance nanoscale piezoresponse in ferroelectric materials.

Chen, L. Q.; Pan, K.; Liu, Y. Y.

2014-08-01

328

Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy  

NASA Astrophysics Data System (ADS)

Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180° polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results.

Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin

2014-07-01

329

Electron Energy-Loss Spectroscopy and the Electronic Structure of ABO3 Ferroelectrics: First Principle Calculations  

E-print Network

The electronic structures of ABO3 ferroelectrics are calculated within the density functional theory, and their evolution is analyzed as the crystal-field symmetry changes from cubic to rhombohedral via tetragonal phases. Electronic structure fingerprints that characterize each phase from their electronic spectra are identified. We carried out electron-energy loss spectroscopy experiments by using synchrotron radiation and compared these results to the theoretical spectra calculated within DFT-LDA. The dominant role of the BO6 octahedra in the formation of the energy spectra of ABO3 compounds was demonstrated. Anomalous behavior of plasmons in ferroelectrics was exhibited by the function representing the characteristic energy loss in the region of phase transition.

Simsek, Sevket; Ozbay, Ekmel

2012-01-01

330

Dynamic conductivity of ferroelectric domain walls in BiFeO?.  

PubMed

Topological walls separating domains of continuous polarization, magnetization, and strain in ferroic materials hold promise of novel electronic properties, that are intrinsically localized on the nanoscale and that can be patterned on demand without change of material volume or elemental composition. We have revealed that ferroelectric domain walls in multiferroic BiFeO(3) are inherently dynamic electronic conductors, closely mimicking memristive behavior and contrary to the usual assumption of rigid conductivity. Applied electric field can cause a localized transition between insulating and conducting domain walls, tune domain wall conductance by over an order of magnitude, and create a quasicontinuous spectrum of metastable conductance states. Our measurements identified that subtle and microscopically reversible distortion of the polarization structure at the domain wall is at the origin of the dynamic conductivity. The latter is therefore likely to be a universal property of topological defects in ferroelectric semiconductors. PMID:21486089

Maksymovych, Peter; Seidel, Jan; Chu, Ying Hao; Wu, Pingping; Baddorf, Arthur P; Chen, Long-Qing; Kalinin, Sergei V; Ramesh, Ramamoorthy

2011-05-11

331

Ferroelectric lithography: bottom-up assembly and electrical performance of a single metallic nanowire.  

PubMed

We report on both the assembly of noble-metal nanowires by means of the nanotechnological and large-scale integrable approach of ferroelectric lithography and their performance testing upon electrical transport. Our results on LiNbO(3) single crystal templates show that the deposition of different elemental metals from ionic solutions by photochemical reduction is confined to the ferroelectric 180 degrees domain walls. Current-voltage-characteristics recorded from such nanowires of typically 30-300 microm in length revealed an Ohmic behavior that even improved with time. Additionally, we also examined the local topographic and potentiostatic properties of such wires using dynamic scanning force microscopy in combination with Kelvin probe force microscopy. PMID:19159245

Haussmann, Alexander; Milde, Peter; Erler, Christiane; Eng, Lukas M

2009-02-01

332

Influence of nonstoichiometry on ferroelectric phase transition in BaTiO3  

NASA Astrophysics Data System (ADS)

The ferroelectric phase transition behavior in equilibrated nonstoichiometric BaTiO3 powder samples was characterized by a differential scanning calorimeter. The transition temperature (TC) and enthalpy of transition (?HTC) between the paraelectric and ferroelectric phases were varied systematically with defect concentrations through the Ba /Ti ratio, temperature, and oxygen partial pressure [p(O2)]. It was observed that the different defects such as titanium, barium, and oxygen vacancies all contribute to the changes of TC and ?HTC. The TC decreased with increasing concentration of TiO2 partial Schottky defects and BaO partial Schottky defects. The annealing temperature increased the TC due to a complex mechanism with the increase of full Schottky defect reactions. In terms of p(O2), TC is constant in the ionic compensation region, and increases with the nonstoichiometry in the electronically compensated p(O2) region.

Lee, Soonil; Liu, Zi-Kui; Kim, Myong-Ho; Randall, Clive A.

2007-03-01

333

Kinetics of 90° domain wall motions and high frequency mesoscopic dielectric response in strained ferroelectrics: a phase-field simulation.  

PubMed

The dielectric and ferroelectric behaviors of a ferroelectric are substantially determined by its domain structure and domain wall dynamics at mesoscopic level. A relationship between the domain walls and high frequency mesoscopic dielectric response is highly appreciated for high frequency applications of ferroelectrics. In this work we investigate the low electric field driven motion of 90°-domain walls and the frequency-domain spectrum of dielectric permittivity in normally strained ferroelectric lattice using the phase-field simulations. It is revealed that, the high-frequency dielectric permittivity is spatially inhomogeneous and reaches the highest value on the 90°-domain walls. A tensile strain favors the parallel domains but suppresses the kinetics of the 90° domain wall motion driven by electric field, while the compressive strain results in the opposite behaviors. The physics underlying the wall motions and thus the dielectric response is associated with the long-range elastic energy. The major contribution to the dielectric response is from the polarization fluctuations on the 90°-domain walls, which are more mobile than those inside the domains. The relevance of the simulated results wth recent experiments is discussed. PMID:24845806

Chu, P; Chen, D P; Wang, Y L; Xie, Y L; Yan, Z B; Wan, J G; Liu, J-M; Li, J Y

2014-01-01

334

Kinetics of 90° domain wall motions and high frequency mesoscopic dielectric response in strained ferroelectrics: A phase-field simulation  

NASA Astrophysics Data System (ADS)

The dielectric and ferroelectric behaviors of a ferroelectric are substantially determined by its domain structure and domain wall dynamics at mesoscopic level. A relationship between the domain walls and high frequency mesoscopic dielectric response is highly appreciated for high frequency applications of ferroelectrics. In this work we investigate the low electric field driven motion of 90°-domain walls and the frequency-domain spectrum of dielectric permittivity in normally strained ferroelectric lattice using the phase-field simulations. It is revealed that, the high-frequency dielectric permittivity is spatially inhomogeneous and reaches the highest value on the 90°-domain walls. A tensile strain favors the parallel domains but suppresses the kinetics of the 90° domain wall motion driven by electric field, while the compressive strain results in the opposite behaviors. The physics underlying the wall motions and thus the dielectric response is associated with the long-range elastic energy. The major contribution to the dielectric response is from the polarization fluctuations on the 90°-domain walls, which are more mobile than those inside the domains. The relevance of the simulated results wth recent experiments is discussed.

Chu, P.; Chen, D. P.; Wang, Y. L.; Xie, Y. L.; Yan, Z. B.; Wan, J. G.; Liu, J.-M.; Li, J. Y.

2014-05-01

335

Kinetics of 90? domain wall motions and high frequency mesoscopic dielectric response in strained ferroelectrics: A phase-field simulation  

PubMed Central

The dielectric and ferroelectric behaviors of a ferroelectric are substantially determined by its domain structure and domain wall dynamics at mesoscopic level. A relationship between the domain walls and high frequency mesoscopic dielectric response is highly appreciated for high frequency applications of ferroelectrics. In this work we investigate the low electric field driven motion of 90°-domain walls and the frequency-domain spectrum of dielectric permittivity in normally strained ferroelectric lattice using the phase-field simulations. It is revealed that, the high-frequency dielectric permittivity is spatially inhomogeneous and reaches the highest value on the 90°-domain walls. A tensile strain favors the parallel domains but suppresses the kinetics of the 90° domain wall motion driven by electric field, while the compressive strain results in the opposite behaviors. The physics underlying the wall motions and thus the dielectric response is associated with the long-range elastic energy. The major contribution to the dielectric response is from the polarization fluctuations on the 90°-domain walls, which are more mobile than those inside the domains. The relevance of the simulated results wth recent experiments is discussed. PMID:24845806

Chu, P.; Chen, D. P.; Wang, Y. L.; Xie, Y. L.; Yan, Z. B.; Wan, J. G.; Liu, J.-M.; Li, J. Y.

2014-01-01

336

Dual Nature of Improper Ferroelectricity in a Magnetoelectric Multiferroic  

Microsoft Academic Search

Using first-principles calculations, we study the microscopic origin of ferroelectricity (FE) induced by magnetic order in the orthorhombic HoMnO3. We obtain the largest ferroelectric polarization observed in the whole class of improper magnetic ferroelectrics to date. We find that the two proposed mechanisms for FE in multiferroics, lattice and electronic based, are simultaneously active in this compound: a large portion

Silvia Picozzi; Kunihiko Yamauchi; Biplab Sanyal; Ivan A Sergienko; Elbio R Dagotto

2007-01-01

337

Dual Nature of Improper Ferroelectricity in a Magnetoelectric Multiferroic  

SciTech Connect

Using first-principles calculations, we study the microscopic origin of ferroelectricity (FE) induced by magnetic order in the orthorhombic HoMnO3. We obtain the largest ferroelectric polarization observed in the whole class of improper magnetic ferroelectrics to date. We find that the two proposed mechanisms for FE in multiferroics, lattice and electronic based, are simultaneously active in this compound: a large portion of the ferroelectric polarization arises due to quantum-mechanical effects of electron orbital polarization, in addition to the conventional polar atomic displacements. An interesting mechanism for switching the magnetoelectric domains by an electric field via a 180 coherent rotation of Mn spins is also proposed.

Picozzi, S. [CNR-INFM, L-Aquila, Italy; Yamauchi, K. [CNR-INFM, L-Aquila, Italy; Sanyal, B. [Uppsala University, Uppsala, Sweden; Sergienko, Ivan A [ORNL; Dagotto, Elbio R [ORNL

2007-01-01

338

Electrical characterization of the metal ferroelectric oxide semiconductor and metal ferroelectric nitride semiconductor gate stacks for ferroelectric field effect transistors  

NASA Astrophysics Data System (ADS)

This paper presents our work on electrical characterization of metal-ferroelectric-oxide-semiconductor (MFeOS) and metal-ferroelectric-nitride-semiconductor (MFeNS) structures for nonvolatile memory applications. Thin films of lead zirconate titanate (PZT: 35:65) have been used as ferroelectric material on 2.5-5 nm thick thermally grown SiO2 and Si3N4 as buffer layer for MFeOS and MFeNS structures, respectively. Capacitance-Voltage (C-V) and Current-Voltage (I-V) characteristics were used for electrical characterization. Our comparative results reveal that the MFeNS structure with 2.5 nm thick buffer layer has higher memory window of about 3.6 V as compared to 3 V for similar MFeOS structure. Also superior electrical properties such as lower leakage current and higher dielectric strength were observed in MFeNS structures. Higher nitridation time was observed to deteriorate the polarization characteristics resulting in reduced memory window. The highest memory window of 6.5 V was observed for SiO2 buffer layer thickness of 5 nm. We also observed that the annealing temperature influences the leakage current characteristic and memory window of these structures.

Verma, Ram Mohan; Rao, Ashwath; Singh, B. R.

2014-03-01

339

A reassessment of the Burns temperature and its relationship to the diffuse scattering, lattice dynamics, and thermal expansion in the relaxor PMN  

Microsoft Academic Search

We have used neutron scattering techniques to characterize the diffuse\\u000ascattering and lattice dynamics in single crystals of the relaxor PMN from 10K\\u000ato 900K. We observed two distinct types of diffuse scattering. The first is\\u000aweak, relatively temperature independent, persists to at least 900 K, and forms\\u000abow-tie-shaped patterns in reciprocal space centered on (h00) Bragg peaks. We\\u000aassociate

P. M. Gehring; H. Hiraka; C. Stock; S.-H. Lee; W. Chen; Z.-G. Ye; S. B. Vakhrushev; Z. Chowdhuri

2009-01-01

340

Relaxor properties of single crystals of Na1/2Bi1/2TiO3-KTaO3 solid solutions  

NASA Astrophysics Data System (ADS)

Single crystals of Na1/2Bi1/2TiO3-KTaO3 (NBT-KT) solid solutions have been grown for the first time. The elemental composition of as-grown single crystals determined by X-ray diffraction corresponds to 0.81 NBT-0.19 KT. Measurements of the temperature dependences of dielectric characteristics showed that the obtained NBT-KT crystals possess clearly pronounced relaxor properties.

Pronin, I. P.; Syrnikov, P. P.; Zaitseva, N. V.; Kaptelov, E. Yu.; Senkevich, S. V.; Castro, R. A.; Lemanov, V. V.

2014-04-01

341

Formation of ferroelectrically defined Ag nanoarray patterns  

NASA Astrophysics Data System (ADS)

In order to produce the most effective Ag nanoarrays for plasmon enhanced fluorescence and Raman scattering made using ferroelectric substrates, the optimum conditions for the creation of arrays must be identified. We study here Ag nanopattern arrays formed using ferroelectric lithography based on periodically proton exchanged (PPE) template methods. We examine different conditions in regard to deposition of Ag nanoparticles and analyze the plasmon enhanced signal from the resulting nanoarray. We apply FLIM (fluorescence lifetime imaging) to assess different Ag nanoarray preparation conditions on fluorescence emission from selected fluorphores. In addition, we apply Raman and luminescence spectroscopy with AFM (atomic force microscopy) to study the plasmon enhancement of luminescence and Raman from the Ag nanoarrays.

Damm, Signe; Carville, N. Craig; Manzo, Michele; Gallo, Katia; Lopez, S.; Keyes, Tia E.; Forster, Robert J.; Rodriguez, Brian J.; Rice, James H.

2014-05-01

342

Ferroelectric liquid crystal optical interconnect switching systems  

NASA Astrophysics Data System (ADS)

This grant explored the possible use of ferroelectric liquid crystals (FLC's) in the reamization of photonic switching fabrics. Problems addressed included device fabrication, switch architectures, and switch performance. Experimental versions of most architectures were constructed. The aim of the contract was to develop techniques for using ferroelectric liquid crystals (FLC's) for novel photonic switching architectures. Initial work was devoted to mastering the technology of making FLC polarization rotation shutters, which formed the basis for the switching architecture work to follow. Much of this work was performed using the facilities of Stanford's Center for Integrated Systems. We were able to build such shutters with respectable properties, including reasonable uniformity, insertion losses of the order X dB, and extinction ratios of the order of Y db. Switching speeds observed were on the order of ZZZ. Having mastered the basic shutter technology, we moved on to employing such shutters in novel architectures.

Goodman, Joseph W.

1993-02-01

343

Thin film ferroelectric electro-optic memory  

NASA Technical Reports Server (NTRS)

An electrically programmable, optically readable data or memory cell is configured from a thin film of ferroelectric material, such as PZT, sandwiched between a transparent top electrode and a bottom electrode. The output photoresponse, which may be a photocurrent or photo-emf, is a function of the product of the remanent polarization from a previously applied polarization voltage and the incident light intensity. The cell is useful for analog and digital data storage as well as opto-electric computing. The optical read operation is non-destructive of the remanent polarization. The cell provides a method for computing the product of stored data and incident optical data by applying an electrical signal to store data by polarizing the thin film ferroelectric material, and then applying an intensity modulated optical signal incident onto the thin film material to generate a photoresponse therein related to the product of the electrical and optical signals.

Thakoor, Sarita (Inventor); Thakoor, Anilkumar P. (Inventor)

1993-01-01

344

Multiscaling analysis of ferroelectric domain wall roughness.  

PubMed

Using multiscaling analysis, we compare the characteristic roughening of ferroelectric domain walls in Pb(Zr0.2Ti0.8)O3 thin films with numerical simulations of weakly pinned one-dimensional interfaces. Although at length scales up to L(MA)?5???m the ferroelectric domain walls behave similarly to the numerical interfaces, showing a simple monoaffine scaling (with a well-defined roughness exponent ?), we demonstrate more complex scaling at higher length scales, making the walls globally multiaffine (varying ? at different observation length scales). The dominant contributions to this multiaffine scaling appear to be very localized variations in the disorder potential, possibly related to dislocation defects present in the substrate. PMID:23083287

Guyonnet, J; Agoritsas, E; Bustingorry, S; Giamarchi, T; Paruch, P

2012-10-01

345

Fast Ferroelectric L-band Tuner  

NASA Astrophysics Data System (ADS)

Description is given of a preliminary conceptual design for a tuner that employs a new ferroelectric ceramic that allows fast changes in coupling between the SRF acceleration structure of a linac and the external RF feeding line. The switching time of this device is in the range of a few microseconds. Utilization of this tuner is predicted to decrease Ohmic losses in the acceleration structure and thereby to reduce the power consumption of the linac. Using parameters of the TESLA-800 collider as an example, it is shown that it may be possible to reduce the ac mains power consumption by 12 MW, or about by 10%. The design of the tuner that is described allows reduced pulsed and average heating of the ferroelectric ceramics.

Kazakov, S. Yu.; Yakovlev, V. P.; Hirshfield, J. L.; Kanareykin, A. D.; Nenasheva, E. A.

2006-11-01

346

Electrically induced mechanical precompression of ferroelectric plates  

DOEpatents

A method of electrically inducing mechanical precompression of a ferroelectric plate covered with electrodes utilizes the change in strains of the plate as functions of applied electric field. A first field polarizes and laterally shrinks the entire plate. An outer portion of the electrodes are removed, and an opposite field partially depolarizes and expands the central portion of the plate against the shrunk outer portion.

Chen, Peter J. (Albuquerque, NM)

1987-01-01

347

High pressure applications of ferroelectric polymers  

Microsoft Academic Search

Ferroelectric polymers are the most recent class piezoelectric and pyroelectric materials developed. The most common piezoelectric polymers are PVDF, based on the monomer CH2-CF2 and copolymers PVDF with C2F3H. Techniques to process PVDF and P(VDF-TrFE) copolymers such that their physical properties exhibit reproducibility approaching that of piezoelectric single crystals are presented. Instrinsic piezoelectric properties of such materials are presented in

F. Bauer

1994-01-01

348

High pressure applications of ferroelectric polymers  

Microsoft Academic Search

Ferroelectric polymers are the most recent class piezoelectric and pyroelectric materials developed. The most common piezoelectric polymers are PVDF, based on the monomer CH2-CF2 and copolymers PVDF with C2F3H. Under high hydrostatic pressure, piezoelectric polymers exhibit well defined piezoelectric response. Piezoelectric response of shock compressed PVDF film prepared with attention to mechanical and electrical processing exhibits precise, well defined reproducible

F. Bauer

1994-01-01

349

Block copolymer/ferroelectric nanoparticle nanocomposites.  

PubMed

Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites. PMID:23900588

Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

2013-09-21

350

Electrically induced mechanical precompression of ferroelectric plates  

DOEpatents

A method of electrically inducing mechanical precompression of ferroelectric plate covered with electrodes utilizes the change in strains of the plate as functions of applied electric field. A first field polarizes and laterally shrinks the entire plate. An outer portion of the electrodes are removed, and an opposite field partially depolarizes and expands the central portion of the plate against the shrunk outer portion. 2 figs.

Chen, P.J.

1987-03-02

351

Sideways dynamics of ferroelectric domain walls  

NASA Astrophysics Data System (ADS)

Characteristic features of the sideways motion of domain walls in ferroelectrics are considered. The proposed model for calculating the mobility of domain walls for this type of motion is based on the approaches developed by D. G. Sannikov and M. A. Collins et al. We examine the dynamics of domain walls in the vicinity of second-order phase transitions. The calculated domain wall mobility is in agreement with experiment in Pb 5Ge 3O 11, Pb 5-xBa xGe 3O 11, Rochelle salt, gadolinium molybdate, terbium molybdate, triglycine sulphate, and barium titanate. It is shown that the velocity of domain walls is proportional to the difference between the applied field and a threshold field. Good agreement with experiments in a number of ferromagnets and ferroelectrics is obtained in this aspect. The coupling of the spontaneous polarization to the strain is shown to induce propagation of solitary stress waves during the domain wall motion in ferroelectrics. We analyse some properties of stress wave propagation within the framework of the suggested model as well the elastic, electrostrictive and piezoelectric effects on the domain wall motion. The contribution of inertia to the velocity of domain walls is calculated. The domain wall mass for 180° walls in barium titanate estimated in the framework of the model is in accordance with its known value. Magnetic-field-induced motion of ferroelectric domain walls is considered. The finite-size effect on the mobility of domain walls is calculated. The mobility exhibits a critical increase when the sample thickness decreases. This behaviour is similar to the temperature growth of the mobility in the vicinity of the second-order phase transition temperature obtained in this model.

Bakaleinikov, L.; Gordon, A.

2007-01-01

352

Flat panel ferroelectric electron emission display system  

DOEpatents

A device which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density.

Sampayan, Stephen E. (Manteca, CA); Orvis, William J. (Livermore, CA); Caporaso, George J. (Livermore, CA); Wieskamp, Ted F. (Livermore, CA)

1996-01-01

353

Tunable Metallic Conductivity in Ferroelectric Nanodomains  

NASA Astrophysics Data System (ADS)

Domain wall conductivity in ferroelectric and multiferroic oxides is an essential example of new electronic properties created by topological defects. So far electron transport through domain walls in canonical BiFeO3 and PbZr0.2Ti0.8O3 (PZT) ferroelectrics has been dominated by thermally activated hopping, concealing the enabling physics and limiting potential applications. We will present a pioneering observation of metallic conductivity in nanoscale ferroelectric domains in PZT, that unambiguously identifies a new conduction channel created through the bulk of the oxide film [1]. From a corollary theoretical analysis, we conclude that metallic conductance is enabled by the interplay of charging and flexoelectric effects at tilted and curved walls of the nanodomain. Furthermore, both type and density of carriers can be tuned by manipulation of the order parameter. Thus, a new family of electronic properties may be found in multiferroic and topologically nanostructured complex oxides. [1] Maksymovych et al, Nano Lett. in review (2011). Research conducted at the Center for Nanophase Materials Sciences, sponsored by BES, U. S. DOE.

Maksymovych, P.; Morozovska, A. N.; Yu, P.; Eliseev, E. A.; Chu, Y.-H.; Ramesh, R.; Baddorf, A. P.; Kalinin, S. V.

2012-02-01

354

X-ray catastrophe focusing with ferroelectrics  

NASA Astrophysics Data System (ADS)

Familiar ripple patterns reflected from water waves and the characteristic cusp of light seen in the bottom of a coffee cup are examples of “catastrophe” optics, where focusing occurs without need for highly engineered optical elements; catastrophe theory provides the mathematical tools needed to describe the stability and topology of the caustics that produce these effects. We have discovered catastrophe focusing in the diffraction of hard x-rays from crystalline wafers of ferroelectric lithium niobate, by diffracting monochromated synchrotron undulator radiation from surface planes while applying a voltage across the thin crystal. The presence of anti-phase ferroelectric domains causes a rippling of the surface that produces focusing at an x-ray CCD camera a half meter away. The catastrophe focusing pattern can be uniquely controlled by the applied voltage. These results suggest possible applications of catastrophe optics to x-ray microfocusing, and to the use of voltage-controlled patterned ferroelectrics as a new concept in x-ray optical devices.

Durbin, Stephen; Jach, Terrence; Kim, Sungwon; Gopalan, Venkatraman

2006-03-01

355

Domains in multiferroics with magnetically induced ferroelectricity  

NASA Astrophysics Data System (ADS)

Two types of multiferroics are distinguished. In the split-order-parameter multiferroics magnetic and ferroelectric order evolve independently while in the joint-order-parameter multiferroics the emergence of the spontaneous polarization is a direct consequence of the magnetic order. The latter type is particularly interesting because of the inherent giant magnetoelectric effects. In the joint-order-parameter multiferroics any magnetoelectric interaction is, at its root, an interaction of its magnetic and ferroelectric domains. Yet, very little is known about the topology of these domains. In my talk I will discuss the domain topology and its magnetoelectric manipulation in a variety of joint-order-parameter multiferroics: MnWO4, RMn2O5, RMnO3, CuO, CuCrO2. Domains are resolved by optical second harmonic generation. Two types of unusual and fundamentally different domains will be distinguished: (i) hybrid-multiferroic domains in which hallmarks of magnetic and ferroelectric domains are inseparably entangled; (ii) incommensurate translation domains whose walls correspond to discontinuities in the incommensurate magnetic wave vector.

Fiebig, Manfred

2010-03-01

356

Scanning resistive probe microscopy: Imaging ferroelectric domains  

NASA Astrophysics Data System (ADS)

We report a resistive probe that detects electric field by field-induced resistance changes in a small resistive region at the apex of the tip and demonstrate a method of imaging ferroelectric domains at high speed, which is named scanning resistive probe microscopy (SRPM). We designed and fabricated the probe by self-aligning process that readily implemented the resistive region at the tip apex. In order to measure the field sensitivity, we contacted the probe with a thermally oxidized silicon sample and detected a 0.3% resistance change per volt applied to the sample. We obtained domain images of freshly cleaved triglycine sulfate (TGS) single crystal by contact mode SRPM. The operating voltage of the probe was 4 V and the scan rate and size were 2 Hz and 40×40 ?m2, respectively. We controlled the polarization of Pb(Zr0.4Ti0.6)O3 (PZT) by applying voltage between the resistive tip and the bottom electrode of PZT, and acquired the domain images with the same tip at 2 Hz scan rate. By controlling and detecting the ferroelectric domains without an additional signal modulating system, we verified that the resistive probe could detect the ferroelectric domain at high speed and be used as a read/write head of a probe data storage system.

Park, Hongsik; Jung, Juhwan; Min, Dong-Ki; Kim, Sungdong; Hong, Seungbum; Shin, Hyunjung

2004-03-01

357

Ferroelectric-carbon nanotube memory devices  

NASA Astrophysics Data System (ADS)

One-dimensional ferroelectric nanostructures, carbon nanotubes (CNT) and CNT-inorganic oxides have recently been studied due to their potential applications for microelectronics. Here, we report coating of a registered array of aligned multi-wall carbon nanotubes (MWCNT) grown on silicon substrates by functional ferroelectric Pb(Zr,Ti)O3 (PZT) which produces structures suitable for commercial prototype memories. Microstructural analysis reveals the crystalline nature of PZT with small nanocrystals aligned in different directions. First-order Raman modes of MWCNT and PZT/MWCNT/n-Si show the high structural quality of CNT before and after PZT deposition at elevated temperature. PZT exists mostly in the monoclinic Cc/Cm phase, which is the origin of the high piezoelectric response in the system. Low-loss square piezoelectric hysteresis obtained for the 3D bottom-up structure confirms the switchability of the device. Current-voltage mapping of the device by conducting atomic force microscopy (c-AFM) indicates very low transient current. Fabrication and functional properties of these hybrid ferroelectric-carbon nanotubes is the first step towards miniaturization for future nanotechnology sensors, actuators, transducers and memory devices.

Kumar, Ashok; Shivareddy, Sai G.; Correa, Margarita; Resto, Oscar; Choi, Youngjin; Cole, Matthew T.; Katiyar, Ram S.; Scott, James F.; Amaratunga, Gehan A. J.; Lu, Haidong; Gruverman, Alexei

2012-04-01

358

Ferroelectric-carbon nanotube memory devices.  

PubMed

One-dimensional ferroelectric nanostructures, carbon nanotubes (CNT) and CNT-inorganic oxides have recently been studied due to their potential applications for microelectronics. Here, we report coating of a registered array of aligned multi-wall carbon nanotubes (MWCNT) grown on silicon substrates by functional ferroelectric Pb(Zr,Ti)O3 (PZT) which produces structures suitable for commercial prototype memories. Microstructural analysis reveals the crystalline nature of PZT with small nanocrystals aligned in different directions. First-order Raman modes of MWCNT and PZT/MWCNT/n-Si show the high structural quality of CNT before and after PZT deposition at elevated temperature. PZT exists mostly in the monoclinic Cc/Cm phase, which is the origin of the high piezoelectric response in the system. Low-loss square piezoelectric hysteresis obtained for the 3D bottom-up structure confirms the switchability of the device. Current-voltage mapping of the device by conducting atomic force microscopy (c-AFM) indicates very low transient current. Fabrication and functional properties of these hybrid ferroelectric-carbon nanotubes is the first step towards miniaturization for future nanotechnology sensors, actuators, transducers and memory devices. PMID:22460805

Kumar, Ashok; Shivareddy, Sai G; Correa, Margarita; Resto, Oscar; Choi, Youngjin; Cole, Matthew T; Katiyar, Ram S; Scott, James F; Amaratunga, Gehan A J; Lu, Haidong; Gruverman, Alexei

2012-04-27

359

Ferroelectricity with Ferromagnetic Moment in Orthoferrites  

NASA Astrophysics Data System (ADS)

Exotic multiferroics with gigantic magnetoelectric (ME) coupling have recently been attracting broad interests from the viewpoints of both fundamental physics and possible technological application to next-generation spintronic devices. To attain a strong ME coupling, it would be preferable that the ferroelectric order is induced by the magnetic order. Nevertheless, the magnetically induced ferroelectric state with the spontaneous ferromagnetic moment is still quite rare apart from a few conical-spin multiferroics. To further explore multiferroic materials with both the strong ME coupling and spontaneous magnetization, we focused on materials with magnetic structures other than conical structure. In this talk we present that the most orthodox perovskite ferrite systems DyFeO3 and GdFeO3 have ``ferromagnetic-ferroelectric,'' i.e., genuinely multiferroic states in which weak ferromagnetic moment is induced by Dzyaloshinskii-Moriya interaction working on Fe spins and electric polarization originates from the striction due to symmetric exchange interaction between Fe and Dy (Gd) spins [1] [2]. Both materials showed large electric polarization (>0.1 ?C/cm^2) and strong ME coupling. In addition, we succeeded in mutual control of magnetization and polarization with electric- and magnetic-fields in GdFeO3, and attributed the controllability to novel, composite domain wall structure. [4pt] [1] Y. Tokunaga et al., Phys. Rev. Lett. 101, 097205 (2008). [0pt] [2] Y. Tokunaga et al., Nature Mater. 8, 558 (2009).

Tokunaga, Yusuke

2010-03-01

360

Ferroelectric domain dynamics under an external field  

NASA Astrophysics Data System (ADS)

Ferroelectric oxides with the perovskite structure are promising materials for nonvolatile random access computer memories. PbZr1-xTixO3 is currently used for this purpose. In these materials, storage of a bit involves the reorientation of polarization, or the movement of a ferroelectric domain wall. However, the intrinsic properties of the polarization reversal process of ferroelectrics at the microscopic level still have not been revealed, either by experiments or computations. In this talk, I will show how this problem can be studied with a multi-scale approach. First, an interatomic potential is parameterized to first-principles calculations, and molecular dynamics (MD) simulations are performed. Second, stochastic Monte Carlo simulations are conducted, with nucleation and growth rates extracted from the MD simulations. For PbTiO3, we find that while the overall domain-wall speed from our calculation is in good agreement with the recent experiments, the size of the critical nucleus is much smaller than predicted from the Miller-Weinreich model. We think that this discrepancy can be explained by a diffuse-boundary model and by the fact that the overall wall motion is controlled by both the nucleation and growth processes.

Rappe, Andrew; Shin, Young-Han; Grinberg, Ilya; Chen, I.-Wei

2007-03-01

361

Influence of ferroelectric polarization on magnetic anisotropy  

NASA Astrophysics Data System (ADS)

Thin film heterostructures of transition metal ferromagnets (FM) and polymer ferroelectrics (FE) are investigated to look for changes in the magnetic anisotropy of the FM layer that occur on switching the FE polarization (with an ensuing change in the electric field direction).[1] Samples of [Glass/ Pd (50 nm)/Co wedge (0.9-2.6nm)/ferroelectric P(VDF-TrFE) (53 nm)/Al (30nm)] are deposited via sputtering or evaporation for the metallic layers and via Langmuir-Schaefer deposition for the polymer ferroelectric. [2] Magnetic and FE properties have been characterized using the Magneto-Optical Kerr Effect (MOKE) and the pyroelectric effect. Polar and longitudinal MOKE loops are measured across the Co wedge for both positive and negative FE polarization and the difference in the two MOKE loops is ascribed to the changes in the magnetic anisotropy of the FM layer. [3] These changes are most apparent in the region where the Co undergoes a transition from in-plane to out-of-plane anisotropy. This research is supported by the NSF MRSEC through Grant No. DMR- 0820521 1. Chun-Gang Duan et al, Appl. Phys. Lett. 92, 122905 (2008) 2. A. V. Bune, et al, Nature (London) 391, 874 (1998) 3. P. F. Carcia, J.Appl. Phys. 63, 5066 (1988)

Mardana, A.; Ducharme, S.; Adenwalla, S.

2010-03-01

362

Ferroelectric tunnel junctions with graphene electrodes.  

PubMed

Polarization-driven resistive switching in ferroelectric tunnel junctions (FTJs)-structures composed of two electrodes separated by an ultrathin ferroelectric barrier-offers new physics and materials functionalities, as well as exciting opportunities for the next generation of non-volatile memories and logic devices. Performance of FTJs is highly sensitive to the electrical boundary conditions, which can be controlled by electrode material and/or interface engineering. Here, we demonstrate the use of graphene as electrodes in FTJs that allows control of interface properties for significant enhancement of device performance. Ferroelectric polarization stability and resistive switching are strongly affected by a molecular layer at the graphene/BaTiO3 interface. For the FTJ with the interfacial ammonia layer we find an enhanced tunnelling electroresistance (TER) effect of 6 × 10(5)%. The obtained results demonstrate a new approach based on using graphene electrodes for interface-facilitated polarization stability and enhancement of the TER effect, which can be exploited in the FTJ-based devices. PMID:25417720

Lu, H; Lipatov, A; Ryu, S; Kim, D J; Lee, H; Zhuravlev, M Y; Eom, C B; Tsymbal, E Y; Sinitskii, A; Gruverman, A

2014-01-01

363

Reliability study of tunable ferroelectric capacitors  

NASA Astrophysics Data System (ADS)

In this paper, the reliability of tunable ferroelectric thin film capacitors has been addressed. The long term stability of tunable capacitors based on Ba0.3Sr0.7TiO3 films deposited by chemical solution deposition onto an alumina substrate was investigated by monitoring their tunable performance as a function of the number of ON-OFF switching cycles and as a function of time. The conditions of civil aeronautic applications were chosen to plan the lifetime experiments. More than 300×106 of switching cycles with an amplitude of 150 V and frequency of 1 kHz were successfully applied to the investigated capacitors without damaging them. Moreover, no degradation in the C-V characteristic was observed after the application of 150 V dc voltage during 15 h. Additionally, the effect of illumination of the ferroelectric film by ultraviolet light on the tunable performance of the capacitors has been investigated. A positive effect of such illumination on the C-V characteristics of ferroelectric capacitor has been found.

Sherman, Vladimir O.; Czarnecki, Piotr; De Wolf, Ingrid; Yamada, Tomoaki; Setter, Nava; Malic, Barbara; Vukadinovic, Miso; Kosec, Marija

2008-09-01

364

Influence of step heights and terrace lengths of bottom electrodes on structural and ferroelectric properties of BiFeO3 thin films  

NASA Astrophysics Data System (ADS)

The ferroelastic domain structures of epitaxial ferroelectric thin films are critical to control the ferroelectric properties. We have already demonstrated the selection of ferroelastic domain structure variants in epitaxial BiFeO3 films and consequently significant improvement in ferroelectric switching behavior and leakage current by employing miscut in cubic (001) SrTiO3 substrates. We have also observed significant step bunching in the SrRuO3 bottom electrode and BiFeO3 thin films on high miscut substrates resulting in significant surface roughness. In particular, the formation of step bunching causes different step heights and terrace lengths which can affect the growth behaviors of subsequent epitaxial films. We have studied the influence of step bunching of SrRuO3 bottom electrodes on structural and ferroelectric properties of BiFeO3 thin films grown on SrRuO3 bottom electrodes by sputtering. We have varied the step heights and terrace lengths of SrRuO3 bottom electrodes on 0.2^o miscut (001) SrTiO3 substrates by controlling of the growth conditions such as laser energy and pulse frequency in pulsed laser deposition. We will discuss the relationship between underlying step structures and the ferroelectric properties of epitaxial BiFeO3 films.

Park, Jae-Wan; Baek, Seung-Hyub; Eom, Chang-Beom

2009-03-01

365

Patterned Ferroelectric Films for Tunable Microwave Devices  

NASA Technical Reports Server (NTRS)

Tunable microwave devices based on metal terminals connected by thin ferroelectric films can be made to perform better by patterning the films to include suitably dimensioned, positioned, and oriented constrictions. The patterns can be formed during fabrication by means of selective etching processes. If the width of the ferroelectric film in such a device is reduced at one or more locations, then both the microwave field and any applied DC bias (tuning) electric field become concentrated at those locations. The magnitudes of both the permittivity and the dielectric loss of a ferroelectric material are reduced by application of a DC field. Because the concentration of the DC field in the constriction(s) magnifies the permittivity- and loss-reducing effects of the applied DC voltage, the permittivity and dielectric loss in the constriction(s) are smaller in the constriction(s) than they are in the wider parts of the ferroelectric film. Furthermore, inasmuch as displacement current must flow through either the constriction(s) or the low-loss dielectric substrate, the net effect of the constriction(s) is equivalent to that of incorporating one or more low-loss, low-permittivity region(s) in series with the high-loss, high-permittivity regions. In a series circuit, the properties of the low-capacitance series element (in this case, the constriction) dominate the overall performance. Concomitantly, the capacitance between the metal terminals is reduced. By making the capacitance between the metal terminals small but tunable, a constriction increases the upper limit of the frequency range amenable to ferroelectric tuning. The present patterning concept is expected to be most advantageous for devices and circuits that must operate at frequencies from about 4 to about 60 GHz. A constriction can be designed such that the magnitude of the microwave electric field and the effective width of the region occupied by the microwave electric field become functions of the applied DC electric field, so that tunability is enhanced. It should even be possible to design the constriction to obtain a specific tuning-versus-voltage profile.

Miranda, Felix A.; Mueller, Carl H.

2008-01-01

366

Dielectric, piezoelectric, and ferroelectric properties of lanthanum-modified PZTFN ceramics  

NASA Astrophysics Data System (ADS)

Specimens of Pb1-1.5 x La x (Zr0.53Ti0.47)1- y- z Fe y Nb z O3 ( x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01) (PZTFN) ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal (space group P4 mm) and rhombohedral (space group R3 c) phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that La doping inhibits grain growth. Doping of La into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hysteresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response at x ? 0.012, which corresponds to the morphotropic phase boundary (MPB).

Kumar, Arvind; Mishra, S. K.

2014-10-01

367

Radiospectroscopic studies of ferroelectric triglycine sulphate-like crystals  

Microsoft Academic Search

The possibility of using radio and microwave spectroscopy to study intermolecular interactions in ferroelectrics of the TGS family will be presented.Ferroelectric crystals (TGSe, TGS and TGFB) doped with Cr3+ chromium ions were investigated by epr as a function of temperature. The fine structure parameter D of the epr spectra near Tc is closely related to the macroscopic deformation measured by

J. Stankowski

1978-01-01

368

Hydrogen induced degradation phenomena of PZT ferroelectric capacitors  

Microsoft Academic Search

During the CMOS process, ferroelectric capacitors show degraded ferroelectric properties due to a process involving hydrogen. When hydrogen diffuses in PZT thin films through noble metal electrodes (such as Pt, Ir), XRD data indicate a change of lattice parameters and XPS spectra exhibit a change in the Pb-O bonding in the crystalline perovskite phase. In particular, the variation of lattice

June-Mo Koo; TaeHo Kini; Jiyoung Kim

2000-01-01

369

Influences of hydrogen damages in ferroelectric thin film capacitors  

Microsoft Academic Search

During the CMOS process, ferroelectric capacitors show degraded ferroelectric properties due to a hydrogen involving process. When hydrogen diffused in PZT thin films through noble metal electrodes (such as Pt, Ir), XRD data indicate a change of lattice parameters and XPS spectra exhibit a change of Pb-O bond in crystalline perovskite phase. Especially, the variation of lattice parameter of PZT

June-Mo Koo; Hyung-Seob Min; Wonhee Lee; Jae-Gab Lee; Jiyoung Kim; Jin-Ho Ahn

2001-01-01

370

Dielectric response of a uniaxial ferroelectric in a magnetic field  

NASA Astrophysics Data System (ADS)

Change in the dielectric response of a uniaxial ferroelectric in a static magnetic field has been detected. The effect has been observed in a polydomain ferroelectric crystal and is likely attributed to the action of the magnetic field on the domain wall pinning centers.

Yakushkin, E. D.

2014-06-01

371

A Mesoscopic Electromechanical Theory of Ferroelectric Films and Ceramics  

E-print Network

actuation strains in ferroelectric single crystals through polarization rotation [1, 2] , or by domain as the energetic cost of forming domain walls. The second term W is the stored energy density (Landau energyA Mesoscopic Electromechanical Theory of Ferroelectric Films and Ceramics Jiangyu Li and Kaushik

Bhattacharya, Kaushik

372

Influence of interfacial dislocations on hysteresis loops of ferroelectric films  

E-print Network

of domains with reversed polariza- tion, and domain wall mobility.3­9 Defects such as disloca- tions, space transition tem- peratures and domain structures in ferroelectric films and superlattices.20­22 It has also transition temperature and leads to the preferen- tial formation of ferroelectric domains around misfit

Chen, Long-Qing

373

Ferroelectric domain imaging by defect-luminescence microscopy V. Dierolfa)  

E-print Network

Ferroelectric domain imaging by defect-luminescence microscopy V. Dierolfa) and C. Sandmann the domain inversion process in ferroelectric LiNbO3 crystals, we investigated the optical properties of intentionally introduced Er3 defect complexes across a 180° domain wall produced at room temperature by electric

Gopalan, Venkatraman

374

Domain Wall Geometry Controls Conduction in Ferroelectrics R. K. Vasudevan,  

E-print Network

Domain Wall Geometry Controls Conduction in Ferroelectrics R. K. Vasudevan, A. N. Morozovska, E. A the properties at the individual wall level. For ferroelectrics, Guro et al.20 predicted that charged domains 37831, United States *S Supporting Information ABSTRACT: A new paradigm of domain wall nanoelectronics

Chen, Long-Qing

375

Investigation of Ferroelectric Domain Walls by Raman Spectroscopy  

Microsoft Academic Search

Ferroelectric materials are characterized by an intrinsic spontaneous electric dipole moment that can be manipulated by the application of an electric field. Regions inside the crystal, known as domains, can have the spontaneous dipole moments oriented in a different direction than the surrounding crystal. Due to favorable piezoelectric, pyroelectric, electro-optic, and nonlinear optical properties, ferroelectric materials are attractive for commercial

Gregory A. Stone

2010-01-01

376

Ferroelectrics, 290: 107114, 2003 Copyright c Taylor & Francis Inc.  

E-print Network

- ways through the motion of 180 domain walls to complete the polarization On leave from Department in ferroelectric community [3]. However, because the formation of 180 domains involves little strain, it is hard ask is: If this 180 -domain mediated switching mechanism is universally true for all ferroelectric ma

Cao, Wenwu

377

Ferroelectric domains and polar clusters in disordered structures  

Microsoft Academic Search

Known experimental facts concerning ferroelectric phase transitions in disordered clusters are discussed in terms of phenomenological kinetik theory. Depending on the values of several parameters, one of the following three alternatives may be observed. a) Randomly oriented nanoclusters of the ferroelectric short-range order make their appearance in paraelectric matrix in a wide temperature range. Under cooling the size of the

Alexey A. Bokov

1997-01-01

378

Ferroelectric thin films: Review of materials, properties, and applications  

Microsoft Academic Search

An overview of the state of art in ferroelectric thin films is presented. First, we review applications: microsystems' applications, applications in high frequency electronics, and memories based on ferroelectric materials. The second section deals with materials, structure (domains, in particular), and size effects. Properties of thin films that are important for applications are then addressed: polarization reversal and properties related

N. Setter; D. Damjanovic; L. Eng; G. Fox; S. Gevorgian; S. Hong; A. Kingon; H. Kohlstedt; N. Y. Park; G. B. Stephenson; I. Stolitchnov; A. K. Taganstev; D. V. Taylor; T. Yamada; S. Streiffer

2006-01-01

379

Atomic-level simulation of ferroelectricity in oxide materials  

Microsoft Academic Search

Recent work on using atomic-level simulation methods to study the ferroelectric properties of oxide materials is reviewed. In particular, it is illustrated how such methods can provide insights into the physical properties of a wide range of ferroelectric oxide materials inaccessible by other means. Approaches for further improvements in materials fidelity and increased range of applicability are discussed.

M. Sepliarsky; A. Asthagiri; S. R. Phillpot; M. G. Stachiotti; R. L. Migoni

2005-01-01

380

Atomic-level simulation of ferroelectricity in oxide materials  

Microsoft Academic Search

Recent work on using atomic-level simulation methods to study the ferroelectric properties of oxide materials is reviewed. In partic- ular, it is illustrated how such methods can provide insights into the physical properties of a wide range of ferroelectric oxide materials inaccessible by other means. Approaches for further improvements in materials fidelity and increased range of applicability are discussed. 2006

M. Sepliarsky; A. Asthagiri; S. R. Phillpot; M. G. Stachiotti; R. L. Migoni

2006-01-01

381

Electrical domain morphologies in compositionally graded ferroelectric films  

Microsoft Academic Search

We present a nonlinear thermodynamic formalism coupled with an electrostatic analysis of uniaxial n-layered compositionally graded heteroepitaxial ferroelectric films and extend this formalism to continuously graded ferroelectric films. We show that the domain morphology and its subsequent evolution in the presence of an electric field are determined by the spontaneous polarisation of the film induced through the compositional grading. The

M B Okatan; A L Roytburd; V Nagarajan; S P Alpay

2012-01-01

382

Standardized ferroelectric capacitor test methodology for nonvolatile semiconductor memory applications  

Microsoft Academic Search

The use of integrated ferroelectric capacitors as nonvolatile memory elements in semiconductor memory designs imposes additional electrical performance requirements on the capacitor which are not normally characterized in ferroelectric materials research. This paper will describe those requirements and present a suggested set of testing procedures we have developed for their standardized measurement. The most significant property for memory design is

Steve Bernacki; Larry Jack; Yanina Kisler; Steve Collins; S. D. Bernstein; Rob Hallock; Bruce Armstrong; Jerry Shaw; Joe Evans; Bruce Tuttle; Bill Hammetter; Steve Rogers; Bob Nasby; Jack Henderson; Joe Benedetto; Randy Moore; Cpt Robert Pugh; Al Fennelly

1993-01-01

383

Future Development of Dense Ferroelectric Memories for Space Applications  

NASA Technical Reports Server (NTRS)

The availability of high density, radiation tolerant, nonvolatile memories is critical for space applications. Ferroelectric memories, when fabricated with radiation hardened complementary metal oxide semiconductors (CMOS), can be manufactured and packaged to provide high density replacements for Flash memory, which is not radiation tolerant. Previous work showed ferroelectric memory cells to be resistant to single event upsets and proton irradiation, and ferroelectric storage capacitors to be resistant to neutron exposure. In addition to radiation hardness, the fast programming times, virtually unlimited endurance, and low voltage, low power operation make ferroelectric memories ideal for space missions. Previously, a commercial double level metal 64-kilobit ferroelectric memory was presented. Although the capabilities of radiation hardened wafer fabrication facilities lag behind those of the most modern commercial wafer fabrication facilities, several paths to achieving radiation tolerant, dense ferroelectric memories are emerging. Both short and long term solutions are presented in this paper. Although worldwide major semiconductor companies are introducing commercial ferroelectric memories, funding limitations must be overcome to proceed with the development of high density, radiation tolerant ferroelectric memories.

Philpy, Stephen C.; Derbenwick, Gary F.

2001-01-01

384

ORIGINAL ARTICLE Single ferroelectric-domain photovoltaic switch based  

E-print Network

ORIGINAL ARTICLE Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells Ji serves as a basis for solid-state memory. This phenomenon can also yield an interesting photovoltaic imposed by the ferroelectric polarization vectors. Here, we demonstrate a single-domain photovoltaic

Jo, Moon-Ho

385

The influence of 180 ferroelectric domain wall width on the threshold field for wall motion  

E-print Network

The influence of 180° ferroelectric domain wall width on the threshold field for wall motion Samrat° ferroelectric walls that are a unit cell wide 0.5 nm , real walls in ferroelectrics have been reported and lithium tantalate LiTaO3 ferroelectrics, we show that the wall width at surfaces can vary considerably

Chen, Long-Qing

386

Phase-field model for epitaxial ferroelectric and magnetic nanocomposite thin films  

E-print Network

energy, ferroelectric bulk free energy, ferroelectric domain wall energy, electrostatic energy films. The model can simultaneously take into account the ferroelectric and magnetic domain structuresPhase-field model for epitaxial ferroelectric and magnetic nanocomposite thin films J. X. Zhang,a Y

Chen, Long-Qing

387

Insulating interlocked ferroelectric and structural antiphase domain walls in multiferroic YMnO3  

Microsoft Academic Search

Hexagonal YMnO3 shows a unique improper ferroelectricity induced by structural trimerization. Extensive research on this system is primarily due to its candidacy for ferroelectric memory as well as the intriguing coexistence of ferroelectricity and magnetism. Despite this research, the true ferroelectric domain structure and its relationship with structural domains have never been revealed. Using transmission electron microscopy and conductive atomic

T. Choi; Y. Horibe; H. T. Yi; Y. J. Choi; Weida Wu; S.-W. Cheong

2010-01-01

388

Atomic-scale mapping of dipole frustration at 90? charged domain walls in ferroelectric PbTiO3 films  

PubMed Central

The atomic-scale structural and electric parameters of the 90° domain-walls in tetragonal ferroelectrics are of technological importance for exploring the ferroelectric switching behaviors and various domain-wall-related novel functions. We have grown epitaxial PbTiO3/SrTiO3 multilayer films in which the electric dipoles at 90° domain-walls of ferroelectric PbTiO3 are characterized by means of aberration-corrected scanning transmission electron microscopy. Besides the well-accepted head-to-tail 90° uncharged domain-walls, we have identified not only head-to-head positively charged but also tail-to-tail negatively charged domain-walls. The widths, polarization distributions, and strains across these charged domain-walls are mapped quantitatively at atomic scale, where remarkable difference between these domain-walls is presented. This study is expected to provide fundamental information for understanding numerous novel domain-wall phenomena in ferroelectrics. PMID:24534846

Tang, Y. L.; Zhu, Y. L.; Wang, Y. J.; Wang, W. Y.; Xu, Y. B.; Ren, W. J.; Zhang, Z. D.; Ma, X. L.

2014-01-01

389

Hydrogen-bonded ferroelectrics based on metal-organic coordination.  

PubMed

Metal-organic coordination (MOC)-type ferroelectrics, cobalt(II) (R)-2-methylpiperazine (MPPA) trichloride [Co(II)Cl(3)(H-MPPA)], was constructed through hydrogen bonds. It is a good ferroelectric candidate with a P(s) = 6.8 microC.cm(-2) as high as almost twice that of triglycine sulfate (P(s) = 3.5 microC.cm(-2)) and significantly larger than that of KH(2)PO(4) at the low-temperature ferroelectric phase Fdd2. [Co(II)Cl(3)(H-MPPA)] is the first example of ferroelectric MOC that can really reach the spontaneous polarization status and opens up a new avenue to explore novel MOC-based ferroelectrics. PMID:19128170

Ye, Heng-Yun; Fu, Da-Wei; Zhang, Yi; Zhang, Wen; Xiong, Ren-Gen; Huang, Songping D

2009-01-14

390

Semiconductor clathrates with a periodically modulated topology of a host ferroelectric liquid crystal in thermal, magnetic, and light-wave fields  

NASA Astrophysics Data System (ADS)

The characteristics of gallium selenide with a ferroelectric liquid crystal in between its layers are studied. The liquid crystal consists of an achiral smectic (a derivative of phenyl benzoate) and a chiral component. The frequency behavior of the specific impedance, permittivity, and loss tangent at different temperatures, in a magnetic field, and under illumination are found.

Bishchaniuk, T. M.; Grygorchak, I. I.; Fechan, A. V.; Ivashchyshyn, F. O.

2014-07-01

391

Page 260, AIP Conference Proceedings, Fundamental physics of Ferroelectrics 2002. Real-Time Studies of Strains at Ferroelectric  

E-print Network

of Strains at Ferroelectric Domain walls under an Applied Field Terrence Jach(a) , Sungwon Kim(b) , Steven of visualizing domain wall strains in congruent ferroelectric crystals such as LiNbO3 with Bragg x-ray topography. With the application of an electric field, we observe unexpected domain wall deformations. Piezoelectric strains

Gopalan, Venkatraman

392

Ferroelectric opening switches for large-scale pulsed power drivers.  

SciTech Connect

Fast electrical energy storage or Voltage-Driven Technology (VDT) has dominated fast, high-voltage pulsed power systems for the past six decades. Fast magnetic energy storage or Current-Driven Technology (CDT) is characterized by 10,000 X higher energy density than VDT and has a great number of other substantial advantages, but it has all but been neglected for all of these decades. The uniform explanation for neglect of CDT technology is invariably that the industry has never been able to make an effective opening switch, which is essential for the use of CDT. Most approaches to opening switches have involved plasma of one sort or another. On a large scale, gaseous plasmas have been used as a conductor to bridge the switch electrodes that provides an opening function when the current wave front propagates through to the output end of the plasma and fully magnetizes the plasma - this is called a Plasma Opening Switch (POS). Opening can be triggered in a POS using a magnetic field to push the plasma out of the A-K gap - this is called a Magnetically Controlled Plasma Opening Switch (MCPOS). On a small scale, depletion of electron plasmas in semiconductor devices is used to affect opening switch behavior, but these devices are relatively low voltage and low current compared to the hundreds of kilo-volts and tens of kilo-amperes of interest to pulsed power. This work is an investigation into an entirely new approach to opening switch technology that utilizes new materials in new ways. The new materials are Ferroelectrics and using them as an opening switch is a stark contrast to their traditional applications in optics and transducer applications. Emphasis is on use of high performance ferroelectrics with the objective of developing an opening switch that would be suitable for large scale pulsed power applications. Over the course of exploring this new ground, we have discovered new behaviors and properties of these materials that were here to fore unknown. Some of these unexpected discoveries have lead to new research directions to address challenges.

Brennecka, Geoffrey L.; Rudys, Joseph Matthew; Reed, Kim Warren; Pena, Gary Edward; Tuttle, Bruce Andrew; Glover, Steven Frank

2009-11-01

393

Development of the instrumentation for studing the properties of ferroelectric materials with a special emphasis on potassium tantalate niobate  

E-print Network

with loss 14 16 18 A lossy dielectric 18 12 14 Modified Sawyer-Tower circuit . Dielectric constant measurement setup Dielectric constant measurement setup for different frequencies . 22 24 25 15 Pyroelectric measurement setup 28 16... MEASUREMENT TECHNIQUES A. Polarization Measurement A circuit designed by Sawyer-Tower[16] and later modified by Sinha [16] is used for observing hysteresis behavior in ferroelectric samples. A schematic representation of the circuit is shown in figure 12...

Kallur, Venugopal A.

2012-06-07

394

Structural, Dielectric and Electron Transport Properties of LaFeO3 Substituted (PbBa)TiO3 Ferroelectrics  

Microsoft Academic Search

The paper reports investigations of structural properties, IR absorption, relative permittivity, pyroelectric coefficient and electrical conductivity of LaFeO3 substituted (Pb0.5Ba0.5)TiO3 ceramics.The observations of XRD, show that the crystal structure is tetragonal. The variation of ? with T show a characteristic behavior of ferroelectric systems. Here the Curie point Tc decreases with increasing level of substitution. Further, the Curie Point does

N. T. Padal; S. A. Pawar; Y. D. Kolekar; S. V. Kulkarni; P. B. Joshi

2005-01-01

395

Stress-induced phase transition in ferroelectric domain walls of BaTiO3  

Microsoft Academic Search

The seminal paper by Zhirnov (1958 Zh. Eksp. Teor. Fiz.35 1175–80) explained why the structure of domain walls in ferroelectrics and ferromagnets is drastically different. Here we show that the antiparallel ferroelectric walls in rhombohedral ferroelectric BaTiO3 can be switched between the Ising-like state (typical for ferroelectrics) and a Bloch-like state (unusual for ferroelectric walls but typical for magnetic ones).

V Stepkova; P Marton; J Hlinka

2012-01-01

396

Electron emission from ferroelectrics - a review  

NASA Astrophysics Data System (ADS)

The strong pulsed emission of electrons from the surface of ferroelectric (FE) materials was discovered at CERN in 1987. Since then many aspects and properties of the method of generation and propagation of electron beams from FE have been studied experimentally. The method is based on macroscopic charge separation and self-emission of electrons under the influence of their own space-charge fields. Hence, this type of emission is not limited by the Langmuir-Child law as are conventional emission methods. Charge separation and electron emission can be achieved by rapid switching of the spontaneous, ferroelectric polarization. Polarization switching may be induced by application of electrical-field or mechanical-pressure pulses, as well as by thermal heating or laser illumination of the ferroelectric emitter. At higher emission intensities plasma formation assists the FE emission and leads to a strong growth of emitted current amplitude, which is no longer limited by the FE material and the surface properties. The most attractive features of FE emission are robustness and ease of manipulation of the emitter cathodes which can be transported through atmospheric air and used without any problems in vacuum, low-pressure gas or plasma environments. Large-area arrangements of multiple emitters, switched in interleaved mode, can produce electron beams of any shape, current amplitude or time structure. The successful application of FE emission in accelerator technology has been demonstrated experimentally in several cases, e.g. for triggering high-power gas switches, for photocathodes in electron guns, and for electron-beam generators intended to generate, neutralize and enhance ion beams in ion sources and ion linacs. Other applications can be envisaged in microwave power generators and in the fields of electronics and vacuum microelectronics.

Riege, H.

1994-02-01

397

Radiation-damage-assisted ferroelectric domain structuring in magnesium-doped lithium niobate  

NASA Astrophysics Data System (ADS)

Irradiation of 5% magnesium-doped lithium niobate crystals (LiNbO3:Mg) with high-energy, low-mass 3He ions, which are transmitted through the crystal, changes the domain reversal properties of the material. This enables easier domain engineering compared to non-irradiated material and assists the formation of small-sized periodically poled domains in LiNbO3:Mg. Periodic domain structures exhibiting a width of ?520 nm are obtained in radiation-damaged sections of the crystals. The ferroelectric poling behavior between irradiated and non-treated material is compared.

Jentjens, L.; Peithmann, K.; Maier, K.; Steigerwald, H.; Jungk, T.

2009-06-01

398

Ferroelectric properties of triglycine sulfate crystals with a nonuniform distribution of chromium impurities  

NASA Astrophysics Data System (ADS)

The specific features of the ferroelectric behavior of triglycine sulfate crystals with a nonuniform distribution of chromium impurities are analyzed. It is demonstrated that the dielectric hysteresis loops of the samples exhibit large shifts both along the polarization and electric field directions. The results obtained are well explained within the phenomenological approach with due regard for the gradient term in the expansion of the free energy. It is established that the unipolarity coefficient and the pyroelectric signal of nonuniform crystals remain virtually unchanged in multiple heating-cooling cycles.

Shut, V. N.; Kashevich, I. F.; Syrtsov, S. R.

2008-01-01

399

Ferroelectric triglycine sulphate crystals with a profile distribution of chromium impurity  

NASA Astrophysics Data System (ADS)

Some features of the ferroelectric behavior of triglycine sulphate crystals with a nonuniform distribution of chromium impurity have been considered. The dielectric hysteresis loop of the samples is characterized by a large shift along both the polarization axis and the electric field direction. The results are explained well within the phenomenological approach with allowance for the gradient term in the expansion of free energy. It is established that the unipolarity coefficient and pyroelectric signal of inhomogeneous crystals barely changes during multiple heating-cooling cycles.

Shut, V. N.; Kashevich, I. F.; Syrtsov, S. R.; Shnaídshteín, I. V.

2010-05-01

400

Phase-transitions in Langmuir-Blodgett and cast films of a ferroelectric liquid crystal.  

PubMed

Langmuir-Blodgett films and cast films of a ferroelectric liquid crystal of sec-butyl-6-(4-(nonyloxy)benzoyloxy)-2-naphthoate have been fabricated. Their thermal behavior was investigated using infrared spectroscopy at elevated temperature combined with principal component analysis. The result shows a new phase transition from smectic A to nematic phase, compared to the phase sequence obtained by polarizing optical microscopy. Another solid transition of different isomeric crystals was also found, which was confirmed by calorimetric measurement. PMID:17625316

Wen, Zi; Jiang, Qing; DU, Yiping; Ozaki, Yukihiro

2007-07-01

401

X-ray diffraction study of ferroelectric and antiferroelectric liquid crystal mixtures exhibiting de Vries SmA?-SmC? transitions.  

PubMed

In this Rapid Communication, results on smectic layer thickness, using synchrotron radiation x-ray diffraction, for different mixtures of ferroelectric and antiferroelectric liquid crystals are given. We find that with an increased ferroelectric component in the mixtures, the layer shrinkage at the de Vries SmA?-SmC? transition increases. This observation can be used to explain our previously observed behaviors [U. Manna, J.-K. Song, Yu. P. Panarin, A. Fukuda, and J. K. Vij, Phys. Rev. E 77, 041707 (2008)] that the soft-mode dielectric strength decreases, the Landau coefficient increases, and the Curie-Weiss temperature range decreases with increased ferroelectric component in the mixture exhibiting de Vries SmA?-SmC? transition. PMID:20866175

Manna, U; Richardson, R M; Fukuda, Atsuo; Vij, J K

2010-05-01

402

X-ray linear dichroism dependence on ferroelectric polarization.  

PubMed

X-ray absorption spectroscopy and photoemission electron microscopy are techniques commonly used to determine the magnetic properties of thin films, crystals, and heterostructures. Recently, these methods have been used in the study of magnetoelectrics and multiferroics. The analysis of such materials has been compromised by the presence of multiple order parameters and the lack of information on how to separate these coupled properties. In this work, we shed light on the manifestation of dichroism from ferroelectric polarization and atomic structure using photoemission electron microscopy and x-ray absorption spectroscopy. Linear dichroism arising from the ferroelectric order in the PbZr0:2Ti0:8O3 thin films was studied as a function of incident x-ray polarization and geometry to unambiguously determine the angular dependence of the ferroelectric contribution to the dichroism. These measurements allow us to examine the contribution of surface charges and ferroelectric polarization as potential mechanisms for linear dichroism. The x-ray linear dichroism from ferroelectric order revealed an angular dependence based on the angle between the ferroelectric polarization direction and the x-ray polarization axis, allowing a formula for linear dichroism in ferroelectric samples to be defined. PMID:22627181

Polisetty, S; Zhou, J; Karthik, J; Damodaran, A R; Chen, D; Scholl, A; Martin, L W; Holcomb, M

2012-06-20

403

Nanopolar reorientation in ferroelectric thin films  

NASA Astrophysics Data System (ADS)

The influence of varying oxygen pressure P(O2) during the growth of Ba0.4Sr0.6TiO3 thin films is investigated using dielectric and local optical probes. A transition from in-plane to out-of-plane ferroelectricity is observed with increasing P(O2). Signatures of in-plane and out-of-plane ferroelectricity are identified using dielectric response and time-resolved confocal scanning optical microscopy (TRCSOM). At the crossover pressure between in-plane and out-of-plane polarization (Pc=85 mTorr), TRCSOM measurements reveal a soft, highly dispersive out-of-plane polarization that reorients in plane under modest applied electric fields. At higher deposition pressures, the out-of-plane polarization is hardened and is less dispersive at microwave frequencies, and the dielectric tuning is suppressed. Nanopolar reorientation is believed to be responsible for the marked increase in dielectric tuning at P(O2)=Pc.

Hubert, C.; Levy, J.; Rivkin, T. V.; Carlson, C.; Parilla, P. A.; Perkins, J. D.; Ginley, D. S.

2001-09-01

404

Interaction of ferroelectric twins with grain boundaries  

SciTech Connect

Experimental investigations suggest that microcracking may be the major cause for the commonly-encountered degradation of ferroelectric actuators, namely electric fatigue. The present analysis, based upon the lattice distortions occurring during the formation of electric twins, indicates that intersections of domain walls with grain boundaries are likely to be origins of microcracks because of the concentrations of stress and electric fields arising due to the incompatibility of the lattice distortions with the grain boundary constraints. This further motivated an asymptotic analysis on the stress and electric field concentrations near intersections of domain walls with grain boundaries. This analysis is carried out within a framework of electrostatics for deformable continua. Assuming that the electromechanical state in each of the ferroelectric domains is slightly distorted from one of the natural states of the crystal, the authors developed a piecewise linearized model for which concentrations of stress and electric fields correspond to singularities of these fields. The asymptotic analysis concludes that both the stress and electric fields exhibit a power-law singularity. Several examples indicate that the order of singularity depends upon the crystal orientation and the orientations of the domain walls with respect to the grain boundary which they intersect. The work presented here is a summary of the author`s investigation on this subject in collaboration with Y. Zhang in 1994.

Jiang, Q. [Univ. of Nebraska, Lincoln, NE (United States)

1995-12-31

405

Ferroelectric Liquid Crystals In Aerodynamic Testing  

NASA Technical Reports Server (NTRS)

The process of simultaneous optical visualization and quantitative measurement of aerodynamic boundary layer parameters requires new concepts, materials and utilization methods. Measurement of shear stress in terms of the transmitted or the reflected light intensity from an aligned ferroelectric liquid crystal (FLC) thin (approx. 1 micron) film deposited on a glass substrate has been the first step in this direction. In this paper, recent progress in utilization of FLC thin films for skin friction measurement and for studying the state of the boundary layer in a wind tunnel environment is reviewed. The switching characteristics of FLCs have been used to measure pressure from the newly devised system of partially exposed polymer dispersed ferroelectric liquid crystals (PEPDFLCs). In this configuration, a PEPDFLC thin film (approx. 10-25 microns) is sandwiched between two transparent conducting electrodes, one a rigid surface and the other a flexible sheet such as polyvinylidene fluoride or mylar. The switching characteristics of the film are a function of the pressure applied to the flexible transparent electrode and a predetermined bias voltage across the two electrodes. The results, considering the dielectrics of composite media, are discussed.

Parmar, Devendra S.; Holmes, Harlan K.

1994-01-01

406

Improper ferroelectricity: A theoretical and experimental investigation  

NASA Astrophysics Data System (ADS)

A combined theoretical and experimental study has been made of the origins and properties of the improper ferroelectricity associated with structural modulations of non-zero wavelengths. Two classes of materials have been studied: rare earth molybdates (specifically, gadolinium molybdate: GMO), and potassium selenate and its isomorphs. In the former, the modulation is produced by a zone boundary phonon instability, and in the latter by the instability of a phonon of wave vector approximately two-thirds of the way to the zone-boundary. In the second case the initial result is a modulated structure whose repeat distance is not a rational multiple of the basic lattice repeat distance. This result is a modulated polarization which, when the basic modulation locks in to a rational multiple of the lattice spacing, becomes uniform, and improper ferroelectricity results. The origins of these effects have been elucidated by theoretical studies, initially semi-empirical, but subsequently from first-principles. These complemented the experimental work, which primarily used inelastic light scattering, uniaxial stress, and hydrostatic pressure, to probe the balance between the interionic forces through the effects on the phonons and dielectric properties.

Hardy, J. R.; Ullman, F. G.

1984-02-01

407

Anisotropic conductance at improper ferroelectric domain walls.  

PubMed

Transition metal oxides hold great potential for the development of new device paradigms because of the field-tunable functionalities driven by their strong electronic correlations, combined with their earth abundance and environmental friendliness. Recently, the interfaces between transition-metal oxides have revealed striking phenomena, such as insulator-metal transitions, magnetism, magnetoresistance and superconductivity. Such oxide interfaces are usually produced by sophisticated layer-by-layer growth techniques, which can yield high-quality, epitaxial interfaces with almost monolayer control of atomic positions. The resulting interfaces, however, are fixed in space by the arrangement of the atoms. Here we demonstrate a route to overcoming this geometric limitation. We show that the electrical conductance at the interfacial ferroelectric domain walls in hexagonal ErMnO(3) is a continuous function of the domain wall orientation, with a range of an order of magnitude. We explain the observed behaviour using first-principles density functional and phenomenological theories, and relate it to the unexpected stability of head-to-head and tail-to-tail domain walls in ErMnO(3) and related hexagonal manganites. As the domain wall orientation in ferroelectrics is tunable using modest external electric fields, our finding opens a degree of freedom that is not accessible to spatially fixed interfaces. PMID:22367003

Meier, D; Seidel, J; Cano, A; Delaney, K; Kumagai, Y; Mostovoy, M; Spaldin, N A; Ramesh, R; Fiebig, M

2012-04-01

408

Strain-induced ferroelectricity in simple rocksalt binary oxides.  

PubMed

Using first-principles density functional calculations, we show that ferroelectricity can be induced in simple alkaline-earth-metal binary oxides such as barium oxide (BaO) using appropriate epitaxial strains. Going beyond the fundamental discovery, we highlight that the functional properties (polarization, dielectric constant, and piezoelectric response) of such strained binary oxides are comparable in magnitude to those of typical ferroelectric perovskite oxides, making them of direct interest for applications. Finally, we show that magnetic binary oxides such as EuO, with the same rocksalt structure, behave similarly to the alkaline-earth-metal oxides, suggesting a route to new multiferroics combining ferroelectric and magnetic properties. PMID:20366683

Bousquet, Eric; Spaldin, Nicola A; Ghosez, Philippe

2010-01-22

409

Ferroelectric control of magnetism and transport in oxide heterostructures  

NASA Astrophysics Data System (ADS)

Magnetism and transport are two key functional ingredients in modern electronic devices. In oxide heterostructures, ferroelectricity can provide a new route to control these two properties via electrical operations, which is scientifically interesting and technologically important. In this brief review, we will introduce recent progresses on this fast developing research field. Several subtopics will be covered. First, the ferroelectric polarization tuning of interfacial magnetism will be introduced, which includes the tuning of magnetization, easy axis, magnetic phases, as well as exchange bias. Second, the ferroelectric polarization tuning of transverse and tunneling transport will be reviewed.

Huang, Xin; Dong, Shuai

2014-09-01

410

Phase diagrams of single-domain ferroelectric-dielectric superlattices  

NASA Astrophysics Data System (ADS)

Using the thermodynamic theory, the authors developed misfit strain-temperature phase diagrams of single-domain ferroelectric-dielectric superlattices grown on cubic substrates. Owing to internal electric fields appearing in such multilayers, the superlattice diagrams are expected to be very different from phase maps of homogeneous ferroelectric films. The calculations show, however, that this electrostatic effect does not change relative positions of phase transition lines. It only shifts the diagram as a whole along the line separating stability ranges of paraelectric phase and in-plane polarization state. The magnitude of this shift is governed by the capacitance of dielectric layer and the thickness of ferroelectric one.

Urtiev, F. A.; Kukhar, V. G.; Pertsev, N. A.

2007-06-01

411

An unusual route to polarization reversal in ferroelectric ultrathin nanowires  

NASA Astrophysics Data System (ADS)

Ferroelectric nanowires are promising candidates for miniaturized ferroelectric devices. Some potential nanoscale applications of the nanowires, such as ultra high density ferroelectric memory, utilize their reversible polarization. To meet the ever increasing demand for low energy consumption, it is extremely desirable to reduce the operational fields associated with polarization reversal. In this Letter, we use first-principles-based simulations to explore an unusual route to polarization reversal that utilizes a combination of relatively low bias field and THz pulsed radiation. Such an approach allows for lower operational fields and may lead to other potential applications such as THz radiation sensing and remote switches.

Herchig, R.; Chang, Ch.-M.; Mani, B. K.; Ponomareva, I.

2014-07-01

412

Linear scanning array with bulk ferroelectric-integrated feed network.  

PubMed

Variable ferroelectric delay line technology has been utilized to implement a proof-of-concept, continuous scanning, ferroelectric integrated phased array antenna system. S21 phase shifts of up to 157 degrees have been achieved from the phase shifter itself via analogous variation of a DC bias. When integrated into a phased array, beam scanning of at least +/-12 degrees is achieved prior to any optimization. Some of the key material requirements, fabrication procedures, characterization, and assembly of the ferroelectric material will be revealed. The design, integration, and performance of the array system using such phased shifters will be presented. PMID:12046931

Teo, Peng-Thian; Jose, Kollakompil A; Wang, Ya-Jun; Lee, Ching-Kwang; Varadan, Vijay K

2002-05-01

413

The transverse field effect in the triglycine sulphate ferroelectric  

NASA Astrophysics Data System (ADS)

The thermodynamic state of a triglycine sulphate crystal, previously exposed to an electric field parallel to the non-ferroelectric c-axis, has been investigated. The frozen ferroelectric c-domains have been observed by a liquid crystal technique and under the scanning electron microscope. Pyroelectric properties and polarization in the non-ferroelectric direction have been investigated. Regions of dipoles that are strongly correlated along the c-direction as well as the clamping of the b-polarization switching have been found to be accompanied by permanent transverse polarization.

Fugiel, B.; ?wikiel, K.; Serwecinski, W.

2002-11-01

414

Electrical properties of ferroelectric liquid crystals during thermal phase transition  

NASA Astrophysics Data System (ADS)

The ferroelectric properties of ferroelectric liquid crystals (FLCs) during thermal phase transition in the surface-stabilized ferroelectric liquid crystal (SSFLC) cells were examined. The coercive electric field (Ec) and remanent polarization (Pr) changed with increasing temperature. These temperature-dependent variations of Ec and Pr were in agreement with the differential scanning calorimetry results. Moreover, the fatigue characteristic of the SSFLC cells was examined. No polarized fatigue was observed after 1 × 106 cycles of polarization switching, because FLCs may have the self-repair property for structural and interfacial defects.

Morimoto, Masahiro; Sakaki, Yosuke; Koshiba, Yasuko; Misaki, Masahiro; Ueda, Yasukiyo; Ishida, Kenji

2014-01-01

415

Ferroelectric films of deuterated glycine phosphite: Structure and dielectric properties  

NASA Astrophysics Data System (ADS)

Polycrystalline textured films of deuterated glycine phosphite consisting of single-crystal blocks with lateral dimensions ˜(50-100) ?m and a thickness d ˜ (1-5) ?m have been grown by evaporation on NdGaO3(100) and ?-Al2O3 substrates with preliminarily deposited interdigitated electrodes, as well as on Al substrates. The c* ( Z) crystallographic axis in the blocks is normal to the film plane, and the a ( X) axis and the polar axis b ( Y) are oriented in the film plane. The temperature dependences of the capacitance of the structures measured with the interdigitated electrode system reveal a strong dielectric anomaly at the film transition to the ferroelectric state. The phase transition temperature T c depends on the degree of deuteration D of the glycine phosphite. The maximum value T c = 275 K obtained in the structures studied corresponds to a degree of deuteration of the glycine phosphite D ˜ 50%. The frequency behavior of the dielectric hysteresis loops in glycine phosphite films differs radically from that of the previously studied films of deuterated betaine phosphite, which evidences that polarization switching in these structures proceeds by different mechanisms. It has been that application of a dc bias to the electrodes changes the shape of the dielectric hysteresis loops and shifts them along the electric field axis. The shift of the loops depends on the sign, magnitude, and time of application of the bias. Possible mechanisms underlying the induced unipolarity are discussed.

Balashova, E. V.; Krichevtsov, B. B.; Svinarev, F. B.; Lemanov, V. V.

2013-05-01

416

Extremely high tunability and low loss in nanoscaffold ferroelectric films.  

PubMed

There are numerous radio frequency and microwave device applications which require materials with high electrical tunability and low dielectric loss. For phased array antenna applications there is also a need for materials which can operate above room temperature and which have a low temperature coefficient of capacitance. We have created a nanoscaffold composite ferroelectric material containing Ba(0.6)Sr(0.4)TiO(3) and Sm(2)O(3) which has a very high tunability which scales inversely with loss. This behavior is opposite to what has been demonstrated in any previous report. Furthermore, the materials operate from room temperature to above 150 °C, while maintaining high tunability and low temperature coefficient of tunability. This new paradigm in dielectric property control comes about because of a vertical strain control mechanism which leads to high tetragonality (c/a ratio of 1.0126) in the BSTO. Tunability values of 75% (200 kV/cm field) were achieved at room temperature in micrometer thick films, the value remaining to >50% at 160 °C. Low dielectric loss values of <0.01 were also achieved, significantly lower than reference pure films. PMID:22830673

Lee, OonJew; Harrington, Sophie A; Kursumovic, Ahmed; Defay, Emmanuel; Wang, Haiyan; Bi, Zhenxing; Tsai, Chen-Fong; Yan, Li; Jia, Quanxi; MacManus-Driscoll, Judith L

2012-08-01

417

Irradiation effects on domain dynamics in ferroelectric glycine phosphite  

SciTech Connect

The effect of x-ray irradiation on polarization switching properties of a glycine phosphite (GPI) single crystal is investigated using the Merz technique. GPI undergoes a paraelectric to ferroelectric phase transition at 224.7 K. Switching studies were performed in the temperature range of 173-221 K with the applied field varying from 1.1 to 4.9 kV/cm. X-ray irradiation causes an increase in the threshold field below which switching could not occur. The activation energy for the domain wall motion is found to increase with irradiation from 0.12 eV for a pristine sample to 0.34 eV after irradiating it for 20 min. The temperature dependence of domain wall mobility shows an unusual behavior with the radiation dosage. The calculated domain wall mobility increases with the exposure time, which is contrary to expectation. This apparent increase in mobility with exposure time is attributed to the creation of a large number of radiation induced defects, identified as PO{sub 3}{sup 2-} radicals, resulting in the loss of effective switchable volume of the sample.

Vanishri, S.; Reddy, J. N. Babu; Bhat, H. L. [Department of Physics, Indian Institute of Science, Bangalore-560012 (India)

2007-03-01

418

Stability of electrodeless ferroelectric domains near a ferroelectric/dielectric interface  

SciTech Connect

The stability of an electrodeless near-surface ferroelectric domain, such as the one written by the tip of an atomic-force microscope, is considered. The analysis takes into account the domain-wall energy, depolarization energy, and coercive field. The domain is found unstable unless the surface charge is compensated, which was experimentally verified. A high-dielectric substrate is found to stabilize the domain while a low-dielectric substrate has the opposite effect. {copyright} 2001 American Institute of Physics.

Li, X.; Mamchik, A.; Chen, I.-W.

2001-08-06

419

Shock-induced electrical conductivity in some ferroelectrics  

Microsoft Academic Search

This paper gives the results of measurement of shock-induced electrical conductivity in ferroelectrics: PKR-1 lead zirconate-titanate\\u000a piezoceramic, deuterated triglycerine sulphate single crystal, and polymer polyvinylidene fluoride.

V. A. Bragunets; V. G. Simakov; V. A. Borisenok; S. V. Borisenok; V. A. Kruchinin

2010-01-01

420

Stress effects in ferroelectric perovskite thin-films  

Microsoft Academic Search

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 (\\

Ricardo Johann Zednik

2008-01-01

421

Investigation of ferroelectric materials with scanning microwave microscope  

NASA Astrophysics Data System (ADS)

By using scanning microwave microscope (SMM), we investigated dielectric properties of ferroelectric materials in high frequency regime (1.5GHz). Our SMM had the capability to measure a complex dielectric constant of the samples from the shift of resonant frequency (fr) and Q value of the probing resonator. In order to obtain non-linear dielectric constants of the ferroelectric samples, we applied oscillating electric field perpendicular to the sample and measured the 1^st order derivative of the resonant frequency of the resonator (dfr/dE) with respect to the applied field. In this way we could image the ferroelectric domain and the domain boundary structure of the triglycine sulfate single crystal using the dfr/dE and the fr signal, respectively. Moreover we observed the ferroelectric responses from the tunable dielectric Ba0.6Sr0.4TiO3 thin film under the additional DC voltage bias to the film.

Park, Jewook; Cho, Jonghoon; Lee, Sangyun; Char, Kookrin

2006-03-01

422

Performance of thin-film ferroelectric capacitors for EMC decoupling.  

PubMed

This paper studied the effects of thin-film ferroelectrics as decoupling capacitors for electromagnetic compatibility applications. The impedance and insertion loss of PZT capacitors were measured and compared with the results from commercial off-the-shelf capacitors. An equivalent circuit model was extracted from the experimental results, and a considerable series resistance was found to exist in ferroelectric capacitors. This resistance gives rise to the observed performance difference around series resonance between ferroelectric PZT capacitors and normal capacitors. Measurements on paraelectric (Ba,Sr)TiO(3)-based integrated varactors do not show this significant resistance. Some analyses were made to investigate the mechanisms, and it was found that it can be due to the hysteresis in the ferroelectric thin films. PMID:19126480

Li, Huadong; Subramanyam, Guru

2008-12-01

423

Polarization control of electron tunneling into ferroelectric surfaces.  

PubMed

We demonstrate a highly reproducible control of local electron transport through a ferroelectric oxide via its spontaneous polarization. Electrons are injected from the tip of an atomic force microscope into a thin film of lead-zirconate titanate, Pb(Zr0.2Ti0.8)O3, in the regime of electron tunneling assisted by a high electric field (Fowler-Nordheim tunneling). The tunneling current exhibits a pronounced hysteresis with abrupt switching events that coincide, within experimental resolution, with the local switching of ferroelectric polarization. The large spontaneous polarization of the PZT film results in up to 500-fold amplification of the tunneling current upon ferroelectric switching. The magnitude of the effect is subject to electrostatic control via ferroelectric switching, suggesting possible applications in ultrahigh-density data storage and spintronics. PMID:19520954

Maksymovych, Peter; Jesse, Stephen; Yu, Pu; Ramesh, Ramamoorthy; Baddorf, Arthur P; Kalinin, Sergei V

2009-06-12

424

Modeling phonon-polariton generation and control in ferroelectric crystals  

E-print Network

In this thesis, we present simulations, using Finite Element Method (FEM), of phonon-polariton generation and coherent control in ferroelectric crystals LiNbO? and LiTaO? through nonlinear electro-optic interactions with ...

Chen, Zhao, S.M. Massachusetts Institute of Technology

2009-01-01

425

Thermal-to-electric energy conversion using ferroelectric film capacitors  

NASA Astrophysics Data System (ADS)

The capacitive ferroelectric thermoelectric converter harvesting electrical energy through non-linear capacitance variation caused by changes in temperature is analyzed. The ferroelectric material used was the thin (0.5 ?m) Ba0.3Sr0.7TiO3 film. On the basis of experimental dependencies of the ferroelectric film permittivity on temperature ranging from 100 K to 350 K under different electric fields up to 80 V/?m, the optimum values of operating temperatures and electric field for the energy harvesting optimization were determined. For the temperature oscillations of ±15 K around room temperature and electric field about 40 V/?m, the harvested energy was estimated as 30 mJ/cm3. It is shown that the use of thin ferroelectric films for rapid capacitance variation versus temperature and microelectromechanical systems for fast temperature modulations may be a relevant solution for creation of small power scale generators for portable electronics.

Kozyrev, A. B.; Platonov, R. A.; Soldatenkov, O. I.

2014-10-01

426

Ferroelectricity in low-symmetry biaxial nematic liquid crystals.  

PubMed

Order parameters and phenomenological theory for both high- and low-symmetry biaxial nematic phases are presented and it is predicted that the chiral low-symmetry biaxial phase must be ferroelectric. This conclusion is based on general symmetry arguments and on the results of the Landau-de Gennes theory. The microscopic mechanism of the ferroelectric ordering in this chiral biaxial phase is illustrated using a simple molecular model based on dispersion interactions between biaxial molecules of low symmetry. Similar to the chiral smectic C* phase, the ferroelectricity in the chiral biaxial nematic phase is improper, i.e., polarization is not a primary order parameter and is not determined by dipolar interactions. Ferroelectric ordering in biaxial nematics may be found, in principle, in materials composed of chiral analogues of the tetrapod molecules which are known to exhibit biaxial phases. PMID:21386515

Osipov, Mikhail A; Gorkunov, Maxim V

2010-09-15

427

Fast Ferroelectric L-Band Tuner for ILC Cavities  

SciTech Connect

Design, analysis, and low-power tests are described on a 1.3 GHz ferroelectric tuner that could find application in the International Linear Collider or in Project X at Fermi National Accelerator Laboratory. The tuner configuration utilizes a three-deck sandwich imbedded in a WR-650 waveguide, in which ferroelectric bars are clamped between conducting plates that allow the tuning bias voltage to be applied. Use of a reduced one-third structure allowed tests of critical parameters of the configuration, including phase shift, loss, and switching speed. Issues that were revealed that require improvement include reducing loss tangent in the ferroelectric material, development of a reliable means of brazing ferroelectric elements to copper parts of the tuner, and simplification of the mechanical design of the configuration.

Hirshfield, Jay L

2010-03-15

428

Figures of merit for ferroelectric electron emission cathodes  

NASA Astrophysics Data System (ADS)

Pyroelectrically induced electron emission from different ferroelectric single crystals and ceramics is studied. It is observed that (Pb,La)(Zr,Ti)O3 ceramics generate rather low ferroelectric electron emission (FEE) current compared with single crystals such as triglycine sulphate and lithium niobate. Figures of merit for FEE cathodes in the pyroelectric excitation mode are derived. It is shown that a physical origin and consequently figures of merit are quite different for FEE cathodes and conventional field electron cathodes.

Shur, D.; Rosenman, G.

1996-09-01

429

Threshold fields for antiparallel ferroelectric domain wall motion  

Microsoft Academic Search

While an ideal antiparallel ferroelectric wall is considered a unit cell in width (~0.5nm), we show using phase field modeling that the threshold field for moving this wall dramatically drops by 2-3 orders of magnitude if the wall were diffuse by only ~2-3nm. Since antiparallel domain walls are symmetry allowed in all ferroelectrics, and since domain wall broadening on nanometer

Samrat Choudhury; Yulan Li; Nozomi Odagawa; Aravind Vasudevarao; L. Tian; Pavel Capek; Volkmar Dierolf; Anna N. Morozovska; Eugene A. Eliseev; Long-qing Chen; Yasuo Cho; Sergei Kalinin; Venkatraman Gopalan

2008-01-01

430

Nanoscale piezoelectric response across a single antiparallel ferroelectric domain wall  

Microsoft Academic Search

Experiments and three-dimensional numerical modeling of nanoscale piezoelectric response across a single domain wall in ferroelectric lithium niobate are presented. Surprising asymmetry in the local electromechanical response across a single antiparallel ferroelectric domain wall is reported. Piezoelectric force microscopy is used to investigate both the in-plane and out-of- plane electromechanical signals around domain walls in congruent and near-stoichiometric lithium niobate.

David A. Scrymgeour; Venkatraman Gopalan

2005-01-01

431

Imaging of ferroelectric domain walls by force microscopy  

Microsoft Academic Search

We have imaged ferroelectric domain walls in the ferroelectric-ferroelastic material Gd2(Mo)3 using force microscopy. By using a mode of imaging developed for the detection of static surface charge, the force gradient due to the polarization charge at the sample surface was imaged. The signal was seen to change sign at the domain wall, consistent with the reversal in sign of

F. Saurenbach; B. D. Terris

1990-01-01

432

Atomic structure of ferroelectric domain walls, free surfaces and steps  

Microsoft Academic Search

The goal of this thesis is to develop a general framework for lattice statics analysis of defects in ferroelectric Perovskites. The techniques presented here are general and can be easily applied to other systems as well. We present all the calculations and numerical examples for two technologically important ferroelectric materials, namely, PbTiO3 and BaTiO3. We use shell potentials, that are

Arash Yavari

2004-01-01

433

Direct observations of retention failure in ferroelectric memories.  

PubMed

Nonvolatile ferroelectric random-access memory uses ferroelectric thin films to save a polar state written by an electric field that is retained when the field is removed. After switching, the high energy of the domain walls separating regions of unlike polarization can drive backswitching resulting in a loss of switched domain volume, or in the case of very small domains, complete retention loss. PMID:22331626

Gao, Peng; Nelson, Christopher T; Jokisaari, Jacob R; Zhang, Yi; Baek, Seung-Hyub; Bark, Chung Wung; Wang, Enge; Liu, Yuanming; Li, Jiangyu; Eom, Chang-Beom; Pan, Xiaoqing

2012-02-21

434

Electric Control of Spin Helicity in a Magnetic Ferroelectric  

SciTech Connect

Magnetic ferroelectrics or multiferroics, which are currently extensively explored, may provide a good arena to realize a novel magnetoelectric function. Here we demonstrate the genuine electric control of the spiral magnetic structure in one such magnetic ferroelectric, TbMnO{sub 3}. A spin-polarized neutron scattering experiment clearly shows that the spin helicity, clockwise or counterclockwise, is controlled by the direction of spontaneous polarization and hence by the polarity of the small electric field applied on cooling.

Yamasaki, Y.; Goto, T. [Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan); Sagayama, H. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Matsuura, M.; Hirota, K. [Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581 (Japan); Arima, T. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Spin Superstructure Project, ERATO, Japan Science and Technology Agency, Tsukuba 305-8562 (Japan); Tokura, Y. [Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan); Spin Superstructure Project, ERATO, Japan Science and Technology Agency, Tsukuba 305-8562 (Japan); Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562 (Japan)

2007-04-06

435

Pyroelectric Response and Conduction Mechanism in Highly Crystallized Ferroelectric Sr3(VO4)2 Ceramic  

NASA Astrophysics Data System (ADS)

We present a study on the ferroelectric phase transition, pyroelectric properties, and conduction mechanism of highly crystallized strontium orthovanadate (Sr3V2O8) ceramic, prepared by a solid-state reaction technique. X-ray diffraction studies show the formation of a single-phase compound in trigonal crystal system. Detailed studies of dielectric parameters (? r and tan ?) of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency. An anomaly in ? r suggests the possible existence of a ferroelectric-paraelectric phase transition of diffuse type in the material, which is confirmed by electric polarization and pyroelectric studies. The low dielectric loss and moderate relative permittivity make this material (with suitable modifications) a potential candidate for use in microwave applications. The low leakage current and negative temperature coefficient of resistance (NTCR) behavior of the sample have been verified from J-E plots. The nature of the variation of the direct-current (DC) conductivity with temperature confirms the Arrhenius and NTCR behavior of the material.

Pati, Biswajit; Choudhary, R. N. P.; Das, Piyush R.

2014-10-01

436

Chemical solution growth of ferroelectric oxide thin films and nanostructures.  

PubMed

Chemical solution deposition (CSD) provides a low-cost, versatile approach for processing of thin and ultrathin ferroelectric films, as well as short and high aspect ratio ferroelectric nanostructures. This review discusses the state of the art in the processing of ferroelectric oxide thin films and nanostructures by CSD, with special emphasis on nucleation and growth phenomena. The effects of choice of precursor solution, substrate and bottom electrode stack, and thermal treatment conditions on the nucleation and growth are examined. Furthermore, methods to control ferroelectric thin film's microstructure, including phase content, texture, grain size and chemical homogeneity, are reviewed. Lastly, current CSD-based methods for processing of ferroelectric oxide nanostructures are presented with special consideration of the structural development, as well as advantages and shortcomings associated with each method. Lead zirconate-titanate, Pb(ZrxTi1-x)O3 (PZT), and barium titanate, BaTiO3 (BT), are used throughout the discussion, as specific examples for CSD processing of perovskite ferroelectrics. PMID:24121276

Bassiri-Gharb, Nazanin; Bastani, Yaser; Bernal, Ashley

2014-04-01

437

Columnar liquid crystal as a unique ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

A recently discovered ferroelectric columnar liquid crystal (LC) is reviewed. Particular attention is paid to differentiate it from conventional ferroelectric LCs such as the smectic-C*-type and bent-core LCs from the symmetry point of view. After reviewing ferroelectric smectic LCs (FSLCs), a ferroelectric columnar LC (FCLC) is introduced as a unique ferroelectric LC. FSLCs have a polarization parallel to the layer plane and have arbitrariness in the polarization direction within the two-dimensional plane. Hence surface constraints are generally indispensable for fixing the polarization direction. In contrast, FCLC has an Ising polarization along the column axis, which is very stable once poling is performed and convertible by applying an opposite electric field. In this sense, FCLC is the first genuine ferroelectric LC. Poling and switching can be achieved using spin-coated FCLC films with an open surface as well as conventional sandwich cells. Hence the FCLCs are more suitable for applications such as piezoelectric devices and ultrahigh-density memory devices, whereas only an application to fast display devices is proposed for FSLCs.

Araoka, Fumito; Takezoe, Hideo

2014-01-01

438

Total Refraction of P-Polarized Light at the Boundary of 90°-Domains in the Ferroelectric Crystal  

NASA Astrophysics Data System (ADS)

A 90°-domain structure was fabricated using electrical poling in ferroelectric birefringent KNbO3 crystal. The refraction and reflection characteristics of the light at the boundary of the 90°-domain structure were investigated, and the novel behavior of total refraction (no reflection) has been found for the P-polarized light throughout the entire range of incident angle (0??? 90°). Strong refraction of the light was observed after it exited from the crystal output surface at the incidence parallel to the domain boundary. These behaviors were explained analytically.

Shichijyo, Shiro; Hirohashi, Junji; Kamio, Hiroyuki; Yamada, Kazuhiro

2004-06-01

439

Mechanical switching of ferro-electric rubber  

E-print Network

At the A to C transition, smectic elastomers have recently been observed to undergo $\\sim$35% spontaneous shear strains. We first explicitly describe how strains of up to twice this value could be mechanically or electrically induced in Sm-$C$ elastomers by rotation of the director on a cone around the layer normal at various elastic costs depending on constraints. Secondly, for typical sample geometries, we give the various microstructures in Sm-$C$ akin to those seen in nematic elastomers under distortions with constraints. It is possible to give explicit results for the nature of the textures. Chiral Sm-$C$ elastomers are ferro-electric. We calculate how the polarization could be mechanically reversed by large, hard or soft strains of the rubber, depending upon sample geometry.

J. M. Adams; M. Warner

2008-12-09

440

Vortex polarization states in nanoscale ferroelectric arrays.  

PubMed

Two-dimensional arrays of ferroelectric lead zirconate titanate (PZT) nanodots were fabricated using pulsed laser deposition through ultrathin anodic aluminum oxide membrane stencil masks. The static distribution of polarization configurations was investigated using in- and out-of-plane piezoresponse force microscopy (PFM). The observed presence of an in-plane polarization component in nominally (001) oriented PZT suggests the existence of a significant deviation from the regular tetragonal structure that allows the formation of complex core-polarization states. Core-polarization states may indicate the presence of quasi-toroidal polarization ordering. The experimental results are compared with a theoretical model to determine the fingerprint of a vortex polarization state in PFM. PMID:19191502

Rodriguez, B J; Gao, X S; Liu, L F; Lee, W; Naumov, I I; Bratkovsky, A M; Hesse, D; Alexe, M

2009-03-01