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1

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

NASA Astrophysics Data System (ADS)

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

Shekhar Pandey, Chandra; Schreuer, Jürgen; Burianek, Manfred; Mühlberg, Manfred

2013-01-01

2

Theory of Relaxor Ferroelectric Electrocalorics  

NASA Astrophysics Data System (ADS)

Conventional perovskite ferroelectrics are the material of choice in many modern day technologies such as capacitive energy storage devices, infrared sensors, and random access memories. Conventional ferroelectrics, however, have not been exploited in cooling applications mainly because their narrow region of critical fluctuations of polarization results in a small electrocaloric effect (a few miliKelvin per volt). Relaxor ferroelectrics, on the other hand, exhibit a broad region of critical fluctuations which makes them promising candidates for large electrocalorics. In this talk, we present a theoretical study of electrocalorics in relaxor ferroelectrics. We compute isothermal changes in entropy and adiabatic changes in temperature within a model of polarizable unit cells with local short-range forces, dipolar forces, and compositional disorder.

Guzman-Verri, Gian; Littlewood, Peter

2013-03-01

3

Mechanical flexible and electric fatigue resistant behavior of relaxor ferroelectric terpolymer  

NASA Astrophysics Data System (ADS)

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

Fang, Fei; Yang, Wei; Yang, Wen

2009-08-01

4

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

5

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

SciTech Connect

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

Gallagher, John A.; Lynch, Christopher S., E-mail: cslynch@seas.ucla.edu [Department of Mechanical and Aerospace Engineering, University of California Los Angeles, 420 Westwood Plaza, Los Angeles, California 90095 (United States); Tian, Jian [H. C. Materials Corporation, 479 Quadrangle Dr., Suite-E, Bolingbrook, Illinois 60440 (United States)

2014-08-04

6

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

7

Role of template layer on microstructure, phase formation and polarization behavior of ferroelectric relaxor thin films  

NASA Astrophysics Data System (ADS)

(1-x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 (PMNPT) a relaxor ferroelectric has gained attention due to its interesting physical properties both in the bulk and thin film forms from a technological and fundamental point of view. The PMNPT solid solution at the morphotropic phase boundary composition has superior properties and is potentially used as an electrostrictive actuator, sensor, and in MEMS applications. Deposition of phase pure PMNPT thin films on bare platinized silicon wafers has been an impossible task so far. In this study the role of the LSCO template on the phase formation and the influence of platinum surface on the same have been studied. It was observed that formation of hillocks in Pt coated silicon wafers is associated with an ATG type of instability while roughening through strain relaxation. The hillocks formation was observed only on the troughs of the strain waves on the surface of Pt. The nucleation and growth of the PMNPT films were analyzed using AFM studies and the nucleation nucleates only at the tips of the hillocks and grows along the same direction with a new nucleus adjacent to the first one. A wavy pattern of PMNPT nuclei was observed and later the lateral growth of the islands takes place to cover the surface and minimizes the roughness to 2 nm. Hence, a template layer with a minimum of 40 nm is required to have a complete coverage with a roughness of less than 2 nm. The chemical states of the PMNPT films grown with and without the template layer were analyzed using x-ray photoelectron spectrum. The XPS spectrum of PMNPT deposited on a Pt surface exhibited a reduced oxidation state of niobium ions and a metallic state of Pb at the initial stage of the growth, which effectively destabilizes the perovskite phase of PMNPT in which the charge states and the ordering of Nb and Mg are more crucial to have a stable perovskite structure.

Ranjith, R.; Chaudhuri, Ayan Roy; Krupanidhi, S. B.; Victor, P.

2007-05-01

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

Development of “fragility” in relaxor ferroelectrics  

SciTech Connect

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

Wang, Yi-zhen, E-mail: wangyizhen80@gmail.com [College of Physics and Electronic Engineering, Hainan Normal University, Haikou 571158 (China); Bioengineering Program and Mechanical Engineering and Mechanics Department, Lehigh University, 19 Memorial Drive West, Bethlehem, Pennsylvania 18015 (United States); State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Chen, Lan; Xiong, Xiao-min; Zhang, Jin-xiu [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Wang, Hai-yan [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Guangzhou Institute of Measurement and Testing Technology, Guangzhou 510663 (China); Frank Zhang, X. [Bioengineering Program and Mechanical Engineering and Mechanics Department, Lehigh University, 19 Memorial Drive West, Bethlehem, Pennsylvania 18015 (United States); Fu, Jun [College of Physics and Electronic Engineering, Hainan Normal University, Haikou 571158 (China)

2014-02-07

10

Polarization dynamics and formation of polar nanoregions in relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

Polarization dynamics and formation of polar nanoregions (PNR) in relaxor ferroelectrics is considered within a model of interacting short range polar clusters formed by off-center ions in highly polarizable materials. The model is applicable on the mesoscopic level and takes explicitly into account the distribution of cluster relaxation times and the existence of quenched random fields which control the size of PNR. Using self-consistent random field theory and continuous time random walk approximation, a relationship is established between the average polarization dynamics contributing to the low frequency dielectric response, and the local polarization dynamics determining NMR spin lattice relaxation time [Blinc , Phys. Rev. B 63, 024104 (2001); Cordero , ibid. 71, 094112 (2005)]. The lengthscale of PNR estimated from the obtained universal relationship between the parameters of the soft mode dispersion curve and the static dielectric permittivity is in agreement with the experiment [Vakhrushev , Physica B 156-157, 90 (1989)]. The predicted proportionality, between the intensity of diffuse neutron scattering from dynamic PNR and square of PNR correlation length, which has been recently a subject of controversy, is also in agreement with experiment by Vakhrushev Therefore, we conclude that the model captures essential features of the static and dynamic behavior of relaxor ferroelectrics, and could be used for the characterization of new relaxor materials.

Vugmeister, B. E.

2006-05-01

11

Surface Domain Structures and Mesoscopic Phase Transition in Relaxor Ferroelectrics  

SciTech Connect

Relaxor ferroelectrics are a prototypical example of ferroic systems in which interplay between atomic disorder and order parameters gives rise to emergence of unusual properties, including non-exponential relaxations, memory effects, polarization rotations, and broad spectrum of bias- and temperatureinduced phase transitions. Despite more than 40 years of extensive research following the original discovery of ferroelectric relaxors by the Smolensky group, the most basic aspect of these materials the existence and nature of order parameter has not been understood thoroughly. Using extensive imaging and spectroscopic studies by variable-temperature and time resolved piezoresponse force microscopy, we fi nd that the observed mesoscopic behavior is consistent with the presence of two effective order parameters describing dynamic and static parts of polarization, respectively. The static component gives rise to rich spatially ordered systems on the 100 nm length scales, and are only weakly responsive to electric fi eld. The surface of relaxors undergoes a mesoscopic symmetry breaking leading to the freezing of polarization fl uctuations and shift of corresponding transition temperature.

Kholkin, Andrei [University of Aveiro, Portugal; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine; Kiselev, Dmitri [University of Aveiro, Portugal; Akhremitchev, Dr. Boris B. [Duke University; Bdikin, Igor [University of Aveiro, Portugal; Rodriguez, Brian J [ORNL; Wu, P [Pennsylvania State University; Bokov, Alexei A. [Simon Fraser University, Canada; Ye, Z.-G. [Simon Fraser University, Canada; Dkhil, Brahim [Ecole Centrale Paris; Chen, Long-Qing [Pennsylvania State University; Kosec, Marija [Jozef Stefan Institute, Slovenia; Kalinin, Sergei V [ORNL

2011-01-01

12

Anomalous elastic behavior of relaxor ferroelectric Ca0.28Ba0.72Nb2O6:Ce studied by resonant ultrasound spectroscopy  

NASA Astrophysics Data System (ADS)

Elastic behavior of tetragonal tungsten bronze uniaxial relaxor ferroelectric cerium doped Ca0.28Ba0.72Nb2O6 single crystal was investigated employing resonant ultrasound spectroscopy in the temperature range from room temperature up to 1323 K. Doping of cerium lowers the phase transition temperature Tc and Burns temperature Tb significantly, however, intermediate characteristic temperature T* (between the Burns temperature Tb and the temperature of maximum dielectric permittivity Tm) remains same as for pure Ca0.28Ba0.72Nb2O6. All independent elastic constants evolved differently with temperature, reflecting their coupling to different types of the reorientational motion of the polar nanoregions through their interaction with the acoustic waves.

Shekhar Pandey, Chandra; Schreuer, Jürgen; Burianek, Manfred; Mühlberg, Manfred

2011-12-01

13

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

NASA Astrophysics Data System (ADS)

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

Pandey, Chandra Shekhar; Schreuer, Jürgen; Burianek, Manfred; Mühlberg, Manfred

2011-11-01

14

Evolution of dielectric and ferroelectric relaxor states in Al3+-doped BaTiO3  

NASA Astrophysics Data System (ADS)

In ferroelectric BaTiO3, we report the evolution of the Dielectric Relaxor and Ferroelectric Relaxor states as a function of B-site doped Al3+ concentration. The relaxor states occur after the paraelectric-ferroelectric phase transition upon cooling. Two different mechanisms are proposed; one based on migration of oxygen vacancies for symmetry-confirmation and the other based on disruption of long-range ferroelectric order by high concentrations of Al3+ ions at the B-site.

Vani, K.; Kumar, Viswanathan

2015-02-01

15

Tunability and relaxor properties of ferroelectric barium stannate titanate ceramics  

SciTech Connect

Barium stannate titanate [Ba(Sn{sub x}Ti{sub 1-x})O{sub 3}, x=0.1, 0.2, 0.3, and 0.4] ceramics were prepared using a conventional solid-state reaction process. Their dielectric properties were measured under direct current bias fields ranging from 0 to 2.5 kV/cm. A transformation from normal to relaxor ferroelectrics was observed when x{>=}0.3. Broken long-range order or 'dirty' ferroelectric domains and nanodomains were observed in Ba(Sn{sub 0.1}Ti{sub 0.9})O{sub 3} and Ba(Sn{sub 0.4}Ti{sub 0.6})O{sub 3} by transmission electron microscopy, respectively. Voltage driven tunability was found to decrease with increasing Sn content. The change from normal ferroelectric into relaxor ferroelectric had a negative impact on the tunability value of the materials.

Lu, S.G.; Xu, Z.K.; Chen, Haydn [Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong (China)

2004-11-29

16

Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics  

NASA Astrophysics Data System (ADS)

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

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

2004-11-01

17

Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics  

SciTech Connect

Several polycrystalline samples of bismuth layer-structured ferroelectrics (BLSF) family doped by lanthanum, Bi{sub 4-x}La{sub x}Ti{sub 3}O{sub 12}, SrBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15}, Sr{sub 2}Bi{sub 4-x}La{sub x}Ti{sub 5}O{sub 18}, and (Bi,La){sub 4}Ti{sub 3}O{sub 12}-Sr(Bi,La){sub 4}Ti{sub 4}O{sub 15}, were prepared by the traditional solid-state reaction method. Their ferroelectric and dielectric properties were investigated. The dielectric measurement data showed that the content of lanthanum determined the ferroelectric characteristics of the compounds. In each series samples, they behaved as normal ferroelectrics for small x, but all of them tended to become relaxors when x was increased. The critical value of the La content causing relaxor characteristics is different for the different BLSFs due to the difference of the number of strontium atoms in their crystal structures. The appearance of the relaxor behavior was attributed to a ferroelectric microdomain state induced by random fields.

Chen Xiaobing; Hui Rong; Zhu Jun; Lu Wangping; Mao Xiangyu [College of Physics Science and Technology, Yangzhou University, Yangzhou 225002 (China); National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210008 (China)

2004-11-15

18

Influencing dielectric properties of relaxor polymer system by blending vinylidene fluoride-trifluoroethylene-based terpolymer with a ferroelectric copolymer  

NASA Astrophysics Data System (ADS)

We report the influence of blending the poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer [P(VDF-TrFE-CFE), a member of the relaxor polymer family that exhibits fast response speeds, giant electrostriction, high electric energy density, and large electrocaloric effect] with the ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer [P(VDF-TrFE)] on its dielectric response. Although both components form separate crystalline phases, at low copolymer content, the P(VDF-TrFE-CFE)/P(VDF-TrFE) blends entirely exhibit a relaxorlike linear dielectric response, since the interfacial couplings to the bulky defects in the terpolymer convert the normal ferroelectric copolymer into a relaxor. On the other hand, the linear and particularly nonlinear dielectric experiments, i.e., temperature dependences of the second and the third harmonic dielectric response, clearly evidence that in blends with 20-50 wt. % of P(VDF-TrFE), the ferroelectric and relaxor states coexist. The nonlinear dielectric response further reveals the onset of ferroelectric behavior also in blends with low copolymer amount, due to a high VDF content in the terpolymer, which increases the ferroelectric interactions: While in relaxor polymers with lower VDF content, the third order nonlinear dielectric constant, in accordance with the theoretical predictions, exhibits solely positive values, here it changes sign even in the pure P(VDF-TrFE-CFE).

Casar, G.; Li, X.; Zhang, Q. M.; Bobnar, V.

2014-03-01

19

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

20

Transition of Modified Layered Structured Bismuth Titanate from Normal to Relaxor Ferroelectric State  

NASA Astrophysics Data System (ADS)

The Aurivillius-type compounds with generic formula SrxBi4-xNbxTi3-xO12 (with x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been synthesized to investigate the effect of Sr and Nb substitution on the bismuth titanate, by a conventional solid state technique. The phase formation of the compound was confirmed through XRD. The dielectric measurements were made at different constant frequencies of 10 kHz, 50 kHz, 100 kHz, 500 kHz and 1 MHz over a wide temperature range. The samples showed a transition from normal ferroelectric behavior to relaxor dielectric behavior with an increasing value of "x".

Siddeshwar, A.; Prasad, G.; Kumar, G. S.

21

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

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

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

24

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

25

Electric-field-induced local structural phenomena in Pb-based ABO3-type relaxor ferroelectrics.  

PubMed

Lead-based ABO3-type relaxors and related systems have numerous applications in modern technical devices because of their remarkably high dielectric permittivity and piezoelectric/electroelastic and electro-optic coefficients. However, lead is not desired from an environmental point of view, and to switch to alternative alkali-, Ba-, or Bi-based relaxor systems, one must understand in great detail the structural mesoscopic order and coupling processes responsible for the outstanding performance and multifunctionality of the exemplar Pb-based compounds. To elucidate the type of ferroic coupling, three relaxor compounds PbSc0.5Ta0.5O3 (PST), Pb0.78Ba0.22Sc0.5Ta0.5O3 (PST-Ba), and PbSc0.5Nb0.5O3 (PSN), were studied by polarized Raman scattering and acoustic emission at different temperatures and under an external electric field. The results reveal the coexistence of mesoscopic-scale ferroelectric and antiferroelectric coupling, which are predominantly related to B-site cations and A-site Pb cations, respectively. This suggests that the polar structural state of relaxors is frustrated ferrielectric. The presence of A-site cations with affinity to off-center is significant for the development of mesoscopic-scale antiferroelectric order coexisting with the mesoscopic-scale ferroelectric order. PMID:25585386

Mihailova, Boriana; Maier, Bernd J; Steilmann, Thomas; Dul'kin, Evgeniy; Roth, Michael

2015-01-01

26

Machining induced defects in Relaxor ferroelectric PMN-PT crystals  

Microsoft Academic Search

The superior piezoelectric and dielectric properties of the relaxor based piezoelectric single crystals (PMN-PT) render them as prime candidates for Navy sonar detectors as well as in broad band medical ultrasonic imaging devices. Production of phased array probes utilizing these types of high performance ceramics requires dicing these crystals to arrays with pitches of less than the desired wavelength, ranging

Cheng Deng

2010-01-01

27

Resonant ultrasonic spectroscopy of KTa1-xNbxO3 ferroelectric relaxor crystals  

SciTech Connect

The influence of the development of a ferroelectric state on the elastic properties of KTa1-xNbxO3 relaxor crystals is explored. The high sensitivity of all elements of the elastic stiffness tensor to the polar distortions and their reorientational dynamics is, however, individual for each particular element: c11 and c44 are pimarily influenced by the reorientational motion of these distortions between neighboring (111) directions; the c12 mostly depends on the reorientations between cubic face diagonal (111) directions. Consequently, the temperature behavior of c12 demonstrates different dependence on the Nb concentration than that of c11 and c44. While in the 1.2% Nb crystal all three elastic constants clearly show their softening with the appearance of the dynamic polar distortions; in the 16% crystal this effect is strong for c11 and c44, but negligible for c12. The curves of slowness and Young's modulus within (100) crystallographic plane are presented. The linear compressibility modulus is estimated. The value of the Debye temperature is estimated to be approximately 592 K.

Svitelskiy, O. [Florida State University; Headley, S. [Florida State University; Suslov, A. V. [Florida State University; Migliori, A. [Los Alamos National Laboratory (LANL); Yong, G. [Towson University, Maryland; Boatner, Lynn A [ORNL

2008-01-01

28

Dielectric properties and relaxor behavior of rare-earth (La, Sm, Eu, Dy, Y) substituted barium zirconium titanate ceramics  

SciTech Connect

Based on the Ti-vacancy defect compensation model (Ba{sub 1-x}Ln{sub x})Zr{sub 0.2}Ti{sub 0.8-x/4}O{sub 3} (Ln=La,Sm,Eu,Dy,Y) ceramics have been fabricated via the conventional solid-state reaction method. The microstructures, dielectric properties, and ferroelectric relaxor behavior of (Ba{sub 1-x}Ln{sub x})Zr{sub 0.2}Ti{sub 0.8-x/4}O{sub 3} ceramics have been investigated. The results indicate that rare-earth ions with various ionic radii enter the unit cell to substitute for A-site Ba{sup 2+} ions and inhibit the grain growth. The typical ferroelectric relaxor behavior is induced due to the rare-earth ions substitution. The diffuseness of the phase transition and the degree of ferroelectric relaxor behavior are enhanced, the T{sub C} is remarkably shifted to lower temperature, and the tunability is suppressed with the increase of x value and substituted ionic radius for (Ba{sub 1-x}Ln{sub x})Zr{sub 0.2}Ti{sub 0.8-x/4}O{sub 3} (x=0.005-0.04, Ln=La,Sm,Eu,Dy,Y) ceramics. Tunable ferroelectric materials with moderate dielectric constant and low dielectric loss can be obtained by manipulating the doping amount of suitable rare-earth ions.

Chou Xiujian; Zhai Jiwei; Jiang Haitao; Yao Xi [Functional Materials Research Laboratory, Tongji University, Siping Road 1239, Shanghai 200092 (China)

2007-10-15

29

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

30

Machining induced defects in Relaxor ferroelectric PMN-PT crystals  

NASA Astrophysics Data System (ADS)

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

Deng, Cheng

31

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

32

Evidence of local anisotropic strains in relaxor ferroelectrics below intermediate temperature T* detected by acoustic emission.  

PubMed

Oriented {100}-, {110}-, and {111}-cuts of Pb?.??)Ba?.??Sc?.?Ta?.?O? single crystals have been studied by means of the acoustic emission (AE) method during their thermal cycling in the temperature range of 300-600 K. For all crystal orientations pronounced AE signals have been detected near 490 K, which corresponds to the intermediate temperature T(*). However, the highest AE count rate has been detected from {110}-oriented cuts, revealing strong anisotropic coupling between the existing polar species that at T(*) merge into larger regions of polarization (PNRs). The temperature's hysteresis is revealed to be 15 K, indicating that the transformation processes at T(*) can be considered as local Martensitic-like ferroelectric transitions inside PNRs. The interplay between PNRs and ultrahigh local strains of perovskite-type relaxor ferroelectrics is discussed. PMID:21393735

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

2010-06-01

33

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

34

Change from 3D-Ising to Random Field-Ising-Model Criticality in a Uniaxial Relaxor Ferroelectric  

E-print Network

Change from 3D-Ising to Random Field-Ising-Model Criticality in a Uniaxial Relaxor Ferroelectric T piezoelectric sensors or actuators, where ceramics of lead zirconate titanate (PZT) or lead lanthanum zirconate titanate (PLZT) are extensively used [3], to optical applications like phase conjugated mirrors, where

Osnabrück, Universität

35

Ferroelectric relaxor behaviour and impedance spectroscopy of Bi2O3-doped barium zirconium titanate ceramics  

NASA Astrophysics Data System (ADS)

Bi2O3-doped barium zirconate titanate ceramics, Ba1-xBix(Zr0.05Ti0.95)O3, have been prepared by the conventional solid-state reaction method. The ferroelectric relaxor behaviour and dielectric properties have been investigated in detail. By XRD analysis, it is suggested that up to x = 0.04, Bi3+ substitutes A-site ion, and thereafter with higher Bi3+ content, it enters the B-site sub lattice. Substitution of Bi3+ ions induces ferroelectric relaxor behaviour and the degree of relaxation behaviour increases with bismuth concentration. The remanent polarization and strain behaviour show a slight increase with the substitution level. The degree of hysteresis (strain versus electric field) also reduces from 21.4% to 4.6% with bismuth substitution. Impedance measurements were made on the prepared sample over a wide range of temperatures (300-723 K) and frequencies (40 Hz-1 MHz), which show the presence of both bulk and grain boundary effects in the material. The bulk and grain boundary conductivities determined from impedance study indicate the Arrhenius-type thermally activated process. Impedance spectroscopy is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries to the complex impedance of a ceramic system, accurately estimating its electrical conductivity as well as its corresponding activation energies and drawing conclusions on its structural properties.

Mahajan, Sandeep; Thakur, O P; Bhattacharya, D K; Sreenivas, K

2009-03-01

36

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

PubMed

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

37

The structural state of lead-based relaxor ferroelectrics under pressure.  

PubMed

The exceptional properties of lead-based perovskite-type (ABO(3)) relaxor ferroelectrics are due to their structural inhomogeneities. At ambient conditions, the average structure is pseudocubic but rich in ferroic nanoregions too small to be directly studied by conventional diffraction analysis. However, combining in situ temperature and pressure diffraction and Raman scattering allows us to resolve the structural complexity of relaxors. Because of the different length and time scales of sensitivity, diffraction probes the long-range order, i.e., the structure averaged over time and space, whereas Raman spectroscopy can detect local structural deviations from the average structure via the anomalous Raman activity of the phonon modes that, when the symmetry of the average structure is considered, should not generate Raman peaks. Hence, the combined analysis of the long-range order induced at low temperatures or high pressures and of the phonon anomalies enhanced on temperature decrease or pressure increase can reveal the energetically preferred structural nanoclusters existing at ambient conditions. In this regard, high-pressure experiments are vital for understanding the nanoscale structure of relaxors. Using X-ray diffraction, neutron diffraction, and Raman scattering on stoichiometric and doped PbSc(0.5)Ta(0.5)O(3) and PbSc(0.5)Na(0.5)O(3), we demonstrate the existence of a pressure-induced cubic-to-rhombohedral continuous phase transition. The high-pressure structure has suppressed polar shifts of B-site cations, enhanced correlation of Pb-O ferroic species, and long-range ordered antiphase BO(6) octahedral tilts. The critical pressure is preceded by an intermediate pressure at which the coupling between off-centered Pb and B-cations is suppressed and octahedral tilting detectable by neutron diffraction is developed. PMID:21937324

Mihailova, Boriana; Angel, Ross J; Maier, Bernd J; Welsch, Anna-Maria; Zhao, Jing; Gospodinov, Marin; Bismayer, Ulrich

2011-09-01

38

Study of (Bi2O3)(BaxMo1-xO3) polycrystalline ceramic as relaxor ferroelectric  

NASA Astrophysics Data System (ADS)

Solid solutions of bismuth layered (Bi2O3)(BaxMo1-xO3) (0.2?x?0.8, x is in step of 0.2) ceramics were prepared by conventional solid-state reaction of the constitutive oxides at optimized temperatures with a view to study its electrical properties. Powder X-ray diffraction has been employed for physical characterization and an average grain size of ?16 to 22 nm was obtained. XRD study reveals the single phase structure of the samples. Dielectric properties such as dielectric constant (??), dielectric loss (tan?) and ac electrical conductivity (?ac) of the prepared ceramics sintered at various temperatures in the frequency range 101-107 Hz have been studied. A strong dispersion observed in the dielectric properties shows the relaxor type behavior of the ceramic. The presence of maxima in the dielectric permittivity spectra indicates the ferroelectric behavior of the samples. Impedance plots (Cole-Cole plots) at different frequencies and temperatures were used to analyze the electric behavior. The value of grain resistance increases with the increase in Ba ion concentration. The conductivity mechanism shows a frequency dependence, which can be ascribed to the space charge mainly due to the oxygen vacancies. The relaxation observed for the M? (?) or Z? (?) curves is correlated to both localized and long range conduction. A single ‘master curve’ for the normalized plots of all the modulus isotherms observed for a given composition indicates that the conductivity relaxation is temperature independent.

Singh, Paramjeet; Agarwal, Ashish; Sanghi, Sujata; Singh, Navneet; Khasa, Satish

2012-12-01

39

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

PubMed

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

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

2015-04-01

40

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

41

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

42

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

PubMed

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

Gallagher, John; Lynch, Christopher; Tian, Jian

2014-12-01

43

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

44

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

NASA Astrophysics Data System (ADS)

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

Pandey, Chandra Shekhar; Schreuer, Jürgen; Burianek, Manfred; Mühlberg, Manfred

2013-03-01

45

Relaxor ferroelectric-like high effective permittivity in leaky dielectrics/oxide semiconductors induced by electrode effects: A case study of CuO ceramics  

NASA Astrophysics Data System (ADS)

The electrical behavior of copper oxide (CuO) ceramics sintered at 920 °C has been characterized by a combination of fixed, radio frequency (rf) capacitance measurements, and impedance spectroscopy (IS). Fixed rf capacitance measurements on ceramics with sputtered Au electrodes revealed a temperature- and frequency-dependent high effective permittivity of ˜104 in the temperature range of 150-320 K. The response is similar to that observed for relaxor-ferroelectrics, however, the magnitude of the effect can be suppressed by thermal annealing of the ceramics with Au electrodes in air at 300 °C or by changing the work function of the electrode material by using In-Ga as opposed to Au. IS data analysis revealed the ceramics to be electrically heterogeneous semiconductors with a room temperature dc resistivity <104 ? cm, consisting of semiconducting grains with relative permittivity, ?r, <10 and slightly more resistive grain boundaries with "effective" permittivity, ?eff, of ˜110. Samples with Au electrodes exhibited an additional low frequency response with ?eff˜104. dc bias experiments showed the capacitance behavior of this additional response to obey the Mott-Schottky law and thus confirm it to be a non-Ohmic electrode contact. We conclude, therefore, that an electrode rather than a grain boundary effect is the primary source for the high effective permittivity in CuO ceramics, although the latter is also present and does give additional effective permittivity. This work demonstrates how an extrinsic effect associated with non-Ohmic electrode contacts can; (i) dominate the rf capacitance spectra of leaky dielectrics/oxide semiconductors over a wide temperature and frequency range; and, (ii) manifest a dielectric response more typically associated with relaxor-ferroelectrics.

Li, Ming; Feteira, Antonio; Sinclair, Derek C.

2009-06-01

46

Ferroelectric Behavior of Thiourea  

Microsoft Academic Search

The dielectric constant, and the ferroelectric, pyroelectric, and piezoelectric properties of thiourea crystals have been measured in the temperature range 90°K to 300°K. At least three dielectric anomalies are found at 169°K, 177°K, and 202°K, the lowest of these corresponding to a pronounced discontinuity. The crystals are ferroelectric in two regions, below 169°K and between 176°K and 180°K. Substitution of

G. J. Goldsmith; J. G. White

1959-01-01

47

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

48

Octahedral tilting in Pb-based relaxor ferroelectrics at high pressure.  

PubMed

We have employed a combination of powder neutron diffraction and single-crystal synchrotron X-ray diffraction to characterize the pressure-induced phase transitions that occur in the perovskite-type relaxor ferroelectric PbSc(0.5)Ta(0.5)O(3) (PST) and Pb(0.78)Ba(0.22)Sc(0.5)Ta(0.5)O(3) (PST-Ba). At ambient pressure the symmetry of the average structure for both compounds is Fm3m as a result of partial ordering of the Sc and Ta cations on the octahedral sites. At pressures above the phase transition both the neutron and X-ray diffraction patterns exhibit an increase in the intensities of h,k,l = all odd reflections and no appearance of additional Bragg reflections. Synchrotron single-crystal X-ray diffraction data show that the intensity of hhh peaks, h = 2n + 1, does not change with pressure. This indicates that the structural distortion arising from the phase transition has a glide-plane pseudo-symmetry along the 111 cubic directions. Rietveld refinement to the neutron powder data shows that the high-pressure phase has either R3c or R3 symmetry, depending on whether the presence of 1:1 octahedral cation ordering is neglected or taken into account, and comprises octahedral tilts of the type a(-)a(-)a(-) that continuously evolve with pressure. The cubic-to-rhombohedral transition is also marked by a large increase in the anisotropy of the displacement ellipsoids of the Pb cations, indicating larger displacements of Pb cations along the rhombohedral threefold axis rather than within the perpendicular plane. For PST the anisotropy of the Pb displacement parameters decreases at approximately 3 GPa above the phase-transition pressure. For both PST and PST-Ba the average magnitudes of Pb-cation displacements expressed in terms of isotropic displacement ellipsoids gradually decrease over the entire pressure range from ambient to 7.35 GPa. PMID:20484799

Maier, Bernd J; Angel, Ross J; Marshall, William G; Mihailova, Boriana; Paulmann, Carsten; Engel, Jens M; Gospodinov, Marin; Welsch, Anna-Maria; Petrova, Dimitrina; Bismayer, Ulrich

2010-06-01

49

Characterization of the electrocaloric effect and hysteresis loss in relaxor ferroelectric thin films under alternating current bias fields  

NASA Astrophysics Data System (ADS)

We report characterization and analysis of the frequency-dependent temperature responses in thin films exhibiting the electrocaloric (EC) effect under AC bias fields using a high-precision lock-in technique. The temperature response detected by an embedded thin-film resistance thermometer is analyzed using the steady-periodic solutions of a 3D heat conduction model to extract the equivalent volumetric heat sources/sinks, which represent the combined effects of electrocaloric cooling/heating and hysteresis loss. The dependence of the measured heat source strengths on the bias field frequency and amplitude is consistent with our model prediction and independently measured dielectric properties. The volumetric heating rate due to hysteresis loss is estimated to be as much as 15% of the EC heating/cooling rates for solution-cast relaxor ferroelectric polymer films studied here. Our experimental approach enables a systematic study of the electrocaloric performance of thin films and deleterious impact of hysteresis loss.

Jia, Yanbing; Ju, Y. Sungtaek

2014-06-01

50

High pressure Raman spectroscopic study on the relaxor ferroelectric PbSc(0.5)Nb(0.5)O(3).  

PubMed

The pressure evolution of the local structure and dynamics of polar nanoregions in PbSc(0.5)Nb(0.5)O(3) relaxor ferroelectric is analysed by Raman spectroscopy. The pressure dependence of phonon modes up to 10 GPa reveals three characteristic pressures related to changes in the local structure: near 2 GPa, at which ferroic ordering in the Pb system occurs; near 4 GPa, at which significant structural transformations, involving decoupling of Pb and B-cations in polar nanoclusters and suppression of the B-cation off-centring take place; and near 6 GPa, at which the system reaches a saturation state. The structural transformations observed in PbSc(0.5)Nb(0.5)O(3) are compared to those in PbSc(0.5)Ta(0.5)O(3) and other Pb-based perovskite-type relaxor ferroelectrics. PMID:21825597

Welsch, A-M; Mihailova, B; Gospodinov, M; Stosch, R; Güttler, B; Bismayer, U

2009-06-10

51

Electrocaloric effect: relaxor ferroelectric-based electrocaloric polymer nanocomposites with a broad operating temperature range and high cooling energy (adv. Mater. 13/2015).  

PubMed

The electrocaloric effect (ECE) refers to field-induced reversible temperature changes of a polarizable material and can form the basis for the next-generation refrigeration technologies that are environmentally friendly and highly efficient. The synergistic combination of relaxor ferroelectric polymers and fillers leads to significantly enhanced ECE and very high cooling efficiencies over a broad temperature range at and near room temperature, as described by Z. Zhang, Q. Wang, and co-workers on page 2236. PMID:25845458

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

2015-04-01

52

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

53

Evolution of structure, dielectric properties, and re-entrant relaxor behavior in Ba5LaxSm1-xTi3Nb7O30 (x = 0.1, 0.25, 0.5) tungsten bronze ceramics  

NASA Astrophysics Data System (ADS)

The effects of A site occupation on the structure, dielectric, and re-entrant relaxor behaviors were studied for Ba5LaxSm1-xTi3Nb7O30 (x = 0.1, 0.25, 0.5) tungsten bronze ceramics. The tetragonal tungsten bronze structure in space group P4bm was indicated for all compositions. The dielectric and ferroelectric properties were investigated over a broad temperature range. For all compositions, broad permittivity peaks with strong frequency dispersion were observed, where the peak points well fitted the Vogel-Fulcher relationship. The temperature dependency of ferroelectric hysteresis loops indicated the re-entrant relaxor behavior for all compositions: both the maximum and remanent polarization tended to decrease and vanish at low temperatures. In Ba5LaxSm1-xTi3Nb7O30, the re-entrant temperature (Tr) decreased with La-substitution, and the reduced remanent polarization at Tr (PTr) was determined. It seemed that the A1 site cation substitution exerted direct effects on the long-range ferroelectric order, and then the re-entrant relaxor behavior.

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

2013-07-01

54

Chemical approach to neutral ionic valence instability, quantum phase transition, and relaxor ferroelectricity in organic charge-transfer complexes  

NASA Astrophysics Data System (ADS)

Neutral-ionic (NI) phase transition is a reversible switching of organic charge-transfer complexes between distinct valence states by external stimuli. This phase transformation in the low-dimensional system is demonstrated to provide a variety of novel dielectric, structural, and electronic properties. Importantly, ionization of the electron donor-acceptor pairs is usually accompanied by a ferroelectric or antiferroelectric order of the molecular lattice, leading to huge dielectric response near the transition point. Although these characteristics are potentially useful for future electronic and optical applications, the thermally accessible NI transition (TINIT) is still an extremely rare case. The TINIT compounds including some new materials are overviewed in order to provide convenient guides to their design and experimental identifications. The phase transition and dielectric properties can be closely controlled in various ways depending on chemical and physical modifications of the crystals. Among them, a quantum phase transition and relaxor ferroelectricity, both of which are currently attracting subjects from both scientific and practical perspectives, are highlighted as the first achievements in organic charge-transfer complexes.

Horiuchi, Sachio; Kumai, Reiji; Okimoto, Yoichi; Tokura, Yoshinori

2006-06-01

55

Bulk relaxor ferroelectric ceramics as a working body for an electrocaloric cooling device  

NASA Astrophysics Data System (ADS)

The electrocaloric effect (ECE), i.e., the conversion of the electric into the thermal energy has recently become of great importance for development of a new generation of cooling technologies. Here, we explore utilization of [Pb(Mg1/3Nb2/3)O3]0.9[PbTiO3]0.1 (PMN-10PT) relaxor ceramics as active elements of the heat regenerator in an ECE cooling device. We show that the PMN-10PT relaxor ceramic exhibits a relatively large electrocaloric change of temperature ?TEC > 1 K at room temperature. The experimental testing of the cooling device demonstrates the efficient regeneration and establishment of the temperature span between the hot and the cold sides of the regenerator, exceeding several times the ?TEC within a single PMN-10PT ceramic plate.

Plaznik, Uroš; Kitanovski, Andrej; Roži?, Brigita; Mali?, Barbara; Urši?, Hana; Drnovšek, Silvo; Cilenšek, Jena; Vrabelj, Marko; Poredoš, Alojz; Kutnjak, Zdravko

2015-01-01

56

Relaxor properties of lanthanum-doped bismuth layer-structured ferroelectrics  

Microsoft Academic Search

Several polycrystalline samples of bismuth layer-structured ferroelectrics (BLSF) family doped by lanthanum, Bi4-xLaxTi3O12, SrBi4-xLaxTi4O15, Sr2Bi4-xLaxTi5O18, and (Bi,La)4Ti3O12-Sr(Bi,La)4Ti4O15, were prepared by the traditional solid-state reaction method. Their ferroelectric and dielectric properties were investigated. The dielectric measurement data showed that the content of lanthanum determined the ferroelectric characteristics of the compounds. In each series samples, they behaved as normal ferroelectrics for small

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

2004-01-01

57

Blockage of domain growth by nanoscale heterogeneities in a relaxor ferroelectric Sr0.61Ba0.39Nb2O6  

NASA Astrophysics Data System (ADS)

The growth of localized subsurface domains in a relaxor ferroelectric Sr0.61Ba0.39Nb2O6 is studied using the technique of piezoresponse force microscopy (PFM). Ferroelectric domains are created by applying moderate voltages of 10-50 V to the conductive tip of a scanning force microscope brought into contact with a nonpolar face of a Sr0.61Ba0.39Nb2O6 crystal. PFM images of written domains are acquired and analyzed quantitatively to determine the domain length along the polar axis and its width in the transverse direction. The dependences of domain sizes on the applied voltage, pulse duration, and the time passed after completion of the voltage pulse are reported and analyzed theoretically. It is shown that the observed kinetics of domain growth can be explained by the creep of domain boundaries occurring in the presence of random electric fields inherent in Sr0.61Ba0.39Nb2O6. The comparison of measured domain sizes with their equilibrium values calculated with the aid of the thermodynamic theory demonstrates that the growth of subsurface domains in Sr0.61Ba0.39Nb2O6 is blocked by nanoscale heterogeneities characteristic of this relaxor ferroelectric. These results may have important implications for the development of nonlinear optical devices based on nanoheterogeneous ferroelectrics.

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

2015-01-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

59

BaTiO3 based relaxor ferroelectric epitaxial thin-films for high-temperature operational capacitors  

NASA Astrophysics Data System (ADS)

The epitaxial growth of 0.6[BaTiO3]–0.4[Bi(Mg2/3Nb1/3)O3] (BT–BMN) relaxor ferroelectric thin-films on (100) Nb doped SrTiO3 substrates has been achieved and the structure is investigated for high-temperature capacitor applications. The post growth annealing decreases the oxygen vacancy and other defects in BT–BMN films, resulting in the enhancement of dielectric constant. An insertion of intermediate SrRuO3 layers as an electrode instead of Pt, sandwiching the film, is found to be more effective in enhancing the dielectric constant. A very high dielectric constant exceeding 400 was achieved from high-temperature annealed film and the film showed an excellent dielectric constant stability of below 11% in the temperature range of 80–400 °C. This will enable smaller, high-temperature tolerant, monolithically integrated thin-film capacitors on power semiconductor devices.

Kumaragurubaran, Somu; Nagata, Takahiro; Takahashi, Kenichiro; Ri, Sung-Gi; Tsunekawa, Yoshifumi; Suzuki, Setsu; Chikyow, Toyohiro

2015-04-01

60

Two-component Model of the Neutron Diffuse Scattering in the Relaxor Ferroelectric PZN-4.5%PT  

SciTech Connect

We report measurements of the neutron diffuse scattering in a single crystal of the relaxor ferroelectric material 95.5% Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}-4.5%PbTiO{sub 3}. Our results suggest that the nanometer scale structure in this compound exhibits both <100> and <110> polarizations, which contribute to different portions of the total diffuse scattering intensity. These contributions can be distinguished by the differing responses to an electric field applied along [001]. While diffuse scattering intensities associated with <110> (T2-type) polarizations show little to no change in a [001] field, those associated with <100> (T1-type) polarizations are partially suppressed by the field at temperatures below the Curie temperature T{sub C} {approx} 475 K. Neutron spin-echo measurements show that the diffuse scattering at (0.05,0,1) is largely dynamic at high temperature and gradually freezes on cooling, becoming mostly static at 200 K.

Xu, Z.; Wen, J.; Xu, G.; Stock, C.; Gardner, J.S.; Gehring, P.M.

2010-10-28

61

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

62

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

PubMed

The pressure-induced phase transition sequence in PbSc(0.5)Ta(0.5)O(3) (PST) and PbSc(0.5)Nb(0.5)O(3) (PSN) heavily doped with homo- and heterovalent cations on the A- or B-site of the perovskite-type structure (ABO(3)) was analysed by in situ synchrotron x-ray diffraction and Raman spectroscopy up to pressures of 25 GPa. We focused on the structural phenomena occurring above the first pressure-induced phase transition at p(c1) from a relaxor state to a non-polar rhombohedral phase with antiphase tilting of the BO(6) octahedra. The samples studied were PST doped with Nb(5+) and Sn(4+) on the B-site, PST doped with Ba(2+) and La(3+) on the A-site and PSN doped with Sr(2+) and La(3+) on the A-site. All of them exhibit a second pressure-induced phase transition at p(c2), similar to pure PST and PSN. The second transition involves the development of either order of antiparallel Pb(2+) displacements and complementary a(+)b(-)b(-) octahedral tilts, or a(-)b(-)b(-) (0 ? a < b) tilting alone. As in pure PST and PSN, the second phase transition is preceded by the occurrence of unequal octahedral tilts on the local scale. The substitution of Nb(5+) for Ta(5+) as well as the coupled substitution of Sn(4+) for Sc(3+) + Ta(5+) on the octahedral B sites increases the second critical pressure. The doping by Nb(5+) also reduces the length of coherence of antipolar Pb(2+) order developed at p(c2). The isovalent substitution of the larger Ba(2+) for Pb(2+) on the A-site suppresses the antipolar Pb(2+) order due to the induced local elastic stresses and thus significantly increases p(c2). The substitution of smaller cations for Pb(2+) on the A-site generally favours the development of long-range order of antiparallel Pb(2+) displacements because of the chemically enhanced a(-)a(-)a(-) octahedral tilts. However, this ordering is less when the dopant is aliovalent, due to the charge imbalance on the A-site. For all of the relaxors studied here, the dynamic compressibility estimated from the pressure derivative of the wavenumber of the soft mode associated with the first phase transition is larger in the pressure interval between p(c1) and p(c2) than above p(c2). The dynamic compressibility of the phase above p(c2) decreases if the antipolar Pb(2+) order is disturbed. PMID:23411463

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

2013-03-20

63

Glasslike behaviour in the relaxor ferroelectric 0.6 Pb(? - 0.4 Pb(?  

Microsoft Academic Search

Studies have been conducted on the ferroelectric properties of 0022-3727\\/32\\/4\\/020\\/img3-0022-3727\\/32\\/4\\/020\\/img4, a solid solution of the antiferroelectric oxides 0022-3727\\/32\\/4\\/020\\/img5 and 0022-3727\\/32\\/4\\/020\\/img6. X-ray diffraction shows that at room temperature this solid solution has a tetragonal perovskite crystal structure. Evidence for a diffuse phase transition in this material is provided from measurements of the dielectric and piezoelectric properties and the form of the

Yung Park; Kevin M. Knowles

1999-01-01

64

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

PubMed

1- x - y)BiFeO3-x(K0.5Bi0.5)TiO3-yPbTiO3 (BFKBT- PT) piezoelectric ceramics were investigated across the compositional space and contrasted against the xBiFeO3- (1-x)(K0.5Bi0.5)TiO3 (BF-KBT) system, whereby a range of relaxor-like/ferroelectric behavior was observed. Structural and piezoelectric properties were closely related to the PbTiO3 concentration; below a critical concentration, relaxor-like behavior was identified. The mechanisms governing the piezoelectric behavior were investigated with structural, electrical, and imaging techniques. X-ray diffraction established that longrange non-centrosymmetric crystallographic order was evident above a critical PbTiO3 concentration, y > 0.1125. Commensurate with the structural analysis, electric-field-induced strain responses showed electrostrictive behavior in the PbTiO3-reduced compositions, with increased piezoelectric switching in PbTiO3-rich compositions. Positive-up-negative-down (PUND) analysis was used to confirm electric-field-induced polarization measurements, elucidating that the addition of PbTiO3 increased the switchable polarization and ferroelectric ordering. Piezoresponse force microscopy (PFM) of the BF-KBT-PT system exhibited typical domain patterns above a critical PbTiO3 threshold, with no ferroelectric domains observed in the BF-KBT system in the pseudocubic region. Doping of BiFeO3-PbTiO3 has been unsuccessful in the search for hightemperature materials that offer satisfactory piezoelectric properties; however, this system demonstrates that the partial substitution of alternative end-members can be an effective method. The partial substitution of PbTiO3 into BF-KBT enables long-range non-centrosymmetric crystallographic order, resulting in increased polar order and TC, compared with the pseudocubic region. The search for novel high-temperature piezoelectric ceramics can therefore exploit the accommodating nature of the perovskite family, which allows significant variance in chemical and physical characters in the exploration of new solid-solutions. PMID:25585388

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

2015-01-01

65

High energy-storage performance in Pb0.91La0.09(Ti0.65Zr0.35)O3 relaxor ferroelectric thin films  

NASA Astrophysics Data System (ADS)

In this work, 1-?m-thick relaxor ferroelectric (FE) films with a typical composition of Pb0.91La0.09(Ti0.65Zr0.35)O3 (PLZT 9/65/35) were successfully deposited on platinum-buffered silicon substrates via a sol-gel technique. The microstructure, electrical properties, and energy-storage performance of the obtained thin films were investigated in detail. X-ray diffraction (XRD) analysis and field-emission scanning electron microscopy pictures indicated that the crystallized thin films showed a random orientation with uniform and dense microstructure. Electrical measurements illustrated that the relaxor FE thin films had a considerable capacitance density of 925 nF/cm2 at 1 MHz and a higher critical breakdown field of 2177 kV/cm. As a result, a large recoverable energy-storage density of 28.7 J/cm3 was obtained in the thin films at room temperature. Moreover, good charge-discharge endurance was also realized in the FE films, confirmed by the repeated polarization-electric field loops.

Hao, Xihong; Wang, Ying; Yang, Jichun; An, Shengli; Xu, Jinbao

2012-12-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

67

Electrocaloric properties in relaxor ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 system  

NASA Astrophysics Data System (ADS)

The electrocaloric effect (ECE) in the Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) solid solution system was investigated by means of detailed direct temperature measurements as a function of temperature, composition, and electric field. The (1-x)PMN-xPT ceramics of compositions 0 ? x ? 0.3 were fabricated by the columbite route. In opposite to conventional ferroelectrics, the maximum of electrocaloric effect was found to shift from the proximity of depolarization/Curie temperature to higher temperatures above a certain composition-dependent electric field strengths. Especially, the compositions with low PT content showed a broadened temperature range of electrocaloric effect. With increasing PbTiO3 concentration, the magnitude of ?T increased, and the temperature dependence of the maximum ECE response gradually developed towards a more pronounced anomaly typical for conventional ferroelectrics. The arising high temperature electrocaloric effect in the ergodic relaxor phase was attributed to the contribution from polar nanoregions. All the compositions studied showed the highest electrocaloric activity just above the depolarization/Curie temperature close to the possible critical point, as recently predicted and observed for some compositions. The magnitude of the maximum electrocaloric temperature change was in the range of ?T = 0.77-1.55 °C under an electric field strength of 50 kV/cm.

Peräntie, J.; Tailor, H. N.; Hagberg, J.; Jantunen, H.; Ye, Z.-G.

2013-11-01

68

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

NASA Astrophysics Data System (ADS)

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

Liu, Yunying; Hao, Xihong; An, Shengli

2013-11-01

69

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; Leão, Juscelino; Long, Xifa; Xie, Yujuan; Bokov, Alexei A.; Ye, Zuo-Guang; Ganesh, Panchapakesan; Gehring, Peter M.

2014-01-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

71

The effect of defect field on dielectric ageing of lead magnesium niobate-lead titanate relaxor ferroelectrics  

Microsoft Academic Search

The ageing effect on the temperature dependence of the dielectric permittivity and loss angle tangent was examined for Pb(Mg1\\/3Nb2\\/3)0.9Ti0.1O3 and 0.1 wt% MnO- Pb(Mg1\\/3Nb2\\/3)0.95Ti0.05O3 ceramics. A Debye-like dielectric relaxation process was clearly observed in the higher temperature range for the latter composition, but not for the former. It is stressed that the metastability of the ferroelectric domain structure is due

Huiqing Fan; Litong Zhang; Liangying Zhang; Xi Yao

2000-01-01

72

Room temperature giant electrocaloric properties of relaxor ferroelectric 0.93PMN-0.07PT thin film  

NASA Astrophysics Data System (ADS)

In this paper, 0.93PMN-0.07PT thin film shows a giant electrocaloric effect at room temperature. At electric field shift of 723 kV/cm, the peak value of ?S of 0.93PMN-0.07PT thin film is 13.05 J/K.kg. The largest change (12.24 °C in 15.18 V, i.e. 0.8 K/V) at TC = 27 °C is more than the previous results obtained in giant electrocaloric PbZr0.95Ti0.05O3 films near the ferroelectric Curie temperature of 222°C (12 K in 25 V, i.e. 0.48 K/V) [A.S. Mischenko, et.al. Science 311, 1270 (2006)].

Hamad, Mahmoud A.

2013-03-01

73

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

74

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

SciTech Connect

Aging of piezoelectric properties was investigated in lead-free (1???x)(Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-xBaTiO{sub 3} doped with 1at.?% Fe. The relaxor character of the un-poled material prevents macroscopic aging effects, while in the field-induced ferroelectric phase aging phenomena are similar to those found in lead zirconate titanate or barium titanate. Most prominent aging effects are the development of an internal bias field and the decrease of switchable polarization. These effects are temperature activated, and can be explained in the framework of defect complex reorientation. This picture is further supported by electron paramagnetic resonance spectra indicating the existence of (Fe{sub Ti}{sup ?}?V{sub O}{sup ••}){sup •} defect complexes in the Fe-doped material.

Sapper, Eva; Dittmer, Robert; Rödel, Jürgen [Materials Science Department, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Damjanovic, Dragan [Ceramics Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne 1015 (Switzerland); Erdem, Emre [Institute of Physical Chemistry I, Universität Freiburg, 79104 Freiburg (Germany); Keeble, David J. [Division of Electronic Engineering and Physics, University of Dundee, Dundee DD1 4HN (United Kingdom); Jo, Wook [School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798 (Korea, Republic of); Granzow, Torsten [Centre de Recherche Public—Gabriel Lippmann, L-4422 Belvaux (Luxembourg)

2014-09-14

75

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

76

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

PubMed

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

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

2014-04-30

77

Linear electro-optic properties of relaxor-based ferroelectric 0.24Pb(In1/2Nb1/2)O3-(0.76-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single  

E-print Network

for electro-optic modulation applications. VC 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4811811] I relaxor-based ferroelectric single crystals (1 � x � y)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3) O3-xPbTiO3 (PIN and applications in ultrasonic transducers and actuators.3­8 It has been reported that the ternary PIN

Cao, Wenwu

78

Acoustic evidence of distinctive temperatures in relaxor-multiferroics  

NASA Astrophysics Data System (ADS)

We present an acoustic study of relaxor ferroelectrics with magnetic ordering PbFexB1-xO3 (B = Nb, Ta, W) in the wide temperature range from 100 to 750 K as well as relaxor PbMg1/3Nb2/3O3 at temperatures from 300 to 750 K. The longitudinal and transverse acoustic wave velocity and attenuation have been measured by the ultrasonic pulse-echo technique at frequencies of 5 and 10 MHz. The strong anomalies observed in the longitudinal sound velocity and attenuation versus temperature are correlated with a temperature range of the coexistence of relaxor ferroelectric and antiferromagnetic states. Attenuation peaks have been observed at distinctive temperatures for relaxors, i.e., at TB (Burns temperature) and T* (an additional distinctive temperature). Fluctuations of the polar nanoregion boundaries are considered as the source of the acoustic anomalies.

Smirnova, E.; Sotnikov, A.; Ktitorov, S.; Zaitseva, N.; Schmidt, H.; Weihnacht, M.

2014-02-01

79

Behavior of highly deformable relaxor-ferroelectric-based ceramics in an electric field  

NASA Astrophysics Data System (ADS)

The deformation characteristics of multicomponent barium-doped piezoelectric ceramics mPbMg1/3Nb2/3O3- n PbNi1/3Nb2/3O3- y PbZn1/3Nb2/3O3- x PbTiO3 are studied in electric fields E = 0-12 kV/cm. Anomalies are detected in the dependences of elastic strain ?3 and piezoelectric modulus d {33/eff} on the external dc electric field. The history of the materials is shown to affect the change of piezoelectric modulus d {33/eff} in an electric field. The revealed dependences are used to propose a method to increase the efficiency of operation of piezoelectric actuators.

Talanov, M. V.; Reznichenko, L. A.

2013-10-01

80

The ferroelectric phase transition in lithium tantalate single crystals: A composition-dependence study  

NASA Astrophysics Data System (ADS)

The dielectric behavior of lithium tantalate (LT) single crystals has been investigated in the vicinity of the ferroelectric phase transition for nonstoichiometric and near-stoichiometric compositions. Fitting of the experimental data to a modified Curie-Weiss equation indicates the occurrence of a mildly relaxor-ferroelectric-like phase transition in congruent LT single crystals (with the Curie-Weiss exponent ? having a value 1.2, rather than the value unity for a regular ferroelectric). As the Li concentration of these crystals approaches the stoichiometric value, the phase transition gets sharper, indicative of an increasing amount of long-range ordering. The bulk concentration of cation vacancies has also been estimated.

Bhaumik, Indranil; Ganesamoorthy, S.; Bhatt, R.; Karnal, A. K.; Wadhawan, V. K.; Gupta, P. K.; Kitamura, K.; Takekawa, S.; Nakamura, M.

2008-01-01

81

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

SciTech Connect

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

Matsuura, M.; Hirota, K. [Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581 (Japan); Gehring, P. M. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8562 (United States); Ye, Z.-G.; Chen, W. [Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6 (Canada); Shirane, G. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

2006-10-01

82

Superspin glass phase and hierarchy of interactions in multiferroic PbFe1/2Sb1/2O3: an analog of ferroelectric relaxors?  

NASA Astrophysics Data System (ADS)

We have fabricated new perovskite multiferroic PbFe1/2Sb1/2O3 with a high degree (up to 0.9) of chemical ordering and unexpectedly high-temperature magnetic relaxor properties, which can barely be described within concepts of conventional spin glass physics. Notably, we found that the field-temperature phase diagram of this material, in the extremely wide temperature interval, contains the de Almeida-Thouless-type critical line, which has been the subject of long debates regarding its possible experimental realization. We explain our findings by the creation, at high temperatures of not less than 250 K, of giant superspins (SSs), owing, curiously enough, to the antiferromagnetic superexchange interaction. We show that these SSs are capable of strong high-temperature magnetic relaxation in the relaxor phase, down to about 150 K, where they transform into a SS glass phase. On further cooling, the material experiences another striking transition, this time, into an ordinary (single-spin) antiferromagnetic phase. We comprehensively analyze the above complex physical picture in terms of three complimentary theoretical approaches. Namely, the ab initio calculations elucidate the microscopic mechanism of giant SS formation, the high-temperature expansion accounts for the morphology of these clusters, and the random field approach provides the description of disorder-related characteristics.

Laguta, V. V.; Stephanovich, V. A.; Savinov, M.; Marysko, M.; Kuzian, R. O.; Kondakova, I. V.; Olekhnovich, N. M.; Pushkarev, A. V.; Radyush, Yu V.; Raevski, I. P.; Raevskaya, S. I.; Prosandeev, S. A.

2014-11-01

83

Elastic and anelastic relaxations in the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3: II. Strain-order parameter coupling and dynamic softening mechanisms.  

PubMed

Elastic and anelastic behaviour of single crystal and ceramic samples of Pb(Mg(1/3)Nb(2/3))O(3) has been investigated at frequencies of ~0.1-1.2 MHz through the temperature interval 10-800 K by resonant ultrasound spectroscopy (RUS). Comparison with data from the literature shows that softening of the shear modulus between the Burns temperature and the freezing interval is independent of frequency. The softening is attributed to coupling between acoustic modes and the relaxation mode(s) responsible for central peaks in Raman and neutron scattering spectra below the Burns temperature, and can be described with Vogel-Fulcher parameters. Shear elastic compliance and dielectric permittivity show similar patterns of temperature dependence through the freezing interval, demonstrating strong coupling between ferroelectric polarization and strain such that the response to applied stress is more or less the same as the response to an applied electric field, with a frequency dependence consistent with Vogel-Fulcher-like freezing in both cases. Differences in detail show, however, that shearing induces flipping between different twin orientations, in comparison with the influence of an electric field, which induces 180° flipping: the activation energy barrier for the former appears to be higher than for the latter. Below the freezing interval, the anelastic loss also has a similar pattern of evolution to the dielectric loss, signifying again that essentially the same mechanism is involved in the freezing process. Overall softening at low temperatures is attributed to the contributions of strain relaxations due to coupling with the local ferroelectric order parameter and of coupling between acoustic modes and continuing relaxational modes of the polar nanostructure. Dissipation is attributed to movement of boundaries between PNRs or between correlated clusters of PNRs. Overall, strain coupling is fundamental to the development of the characteristic strain, dielectric and elastic properties of relaxors. PMID:22186067

Carpenter, M A; Bryson, J F J; Catalan, G; Zhang, S J; Donnelly, N J

2012-02-01

84

Raman scattering study on relaxor ferroelectric Pb(In1/2Nb1/2)-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals  

NASA Astrophysics Data System (ADS)

The vibrational property of relaxor ferroelectric Pb(In1/2Nb1/2)-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals was investigated by using Raman scattering. The angular dependences of two Raman bands, one located at ˜50 cm-1 and the other at ˜560 cm-1, were investigated in the paraelectric phase where no Raman bands are allowed in the average symmetry. The angular variation of the Raman intensity of the strong low-frequency mode at ˜50 cm-1 was compatible with the F 2 g mode of symmetry, indicating that this mode could be attributed to the 1:1 chemical order at the B-site in PIN-PMN-PT. The high-frequency Raman mode at ˜560 cm-1 exhibited an intensity modulation consistent with the rhombohedral R3 m symmetry, suggesting that this mode was related to polar nanoregions. The intensity ratio of the depolarized to the polarized component of this high-frequency mode showed an abrupt change when PIN-PMN-PT underwent a structural phase transition into the rhombohedral phase.

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

2014-10-01

85

Ferroelectric behavior in bismuth ferrite thin films of different thickness.  

PubMed

The ferroelectric behavior of BiFeO(3) thin films is modified by changing the film thicknesses, where the BiFeO(3) thin films with different thicknesses were grown on SrRuO(3)/Pt/TiO(2)/SiO(2)/Si(100) substrates by radio frequency sputtering. The mixture of (110) and (111) orientations is induced for all BiFeO(3) thin films regardless of their thicknesses, together with the columnar structure and the dense microstructure. Their dielectric behavior is almost independent of the film thickness where all thin films have a low dielectric loss. A giant remanent polarization of 2P(r) ? 156.6-188.8 ?C/cm(2) is induced for the BiFeO(3) thin films in the thickness range of 190-600 nm. As a result, it is an effective way to improve the ferroelectric behavior of the BiFeO(3) thin film by tailoring the film thickness. PMID:21861505

Wu, Jiagang; Wang, John; Xiao, Dingquan; Zhu, Jianguo

2011-09-01

86

In situ high-temperature high-pressure Raman spectroscopy on single-crystal relaxor ferroelectrics PbSc(1/2)Ta(1/2)O3 and PbSc(1/2)Nb(1/2)O3.  

PubMed

The effect of temperature on the pressure-induced structural changes in perovskite-type (ABO3) relaxor ferroelectrics is studied by in situ high-temperature high-pressure Raman spectroscopy on single crystals of PbSc1/2Ta1/2O3 (PST) and PbSc1/2Nb1/2O3 (PSN), which allowed us to elucidate the interplay between the polar and antiferrodistortive order coexisting on the mesoscopic scale at ambient conditions. High-pressure experiments were carried out at elevated temperatures below and above the characteristic intermediate temperature T*. The results were compared with those obtained at room temperature, which for PST is just above the paraelectric-ferroelectric phase transition TC, whereas for PSN is below TC. It is shown that the first critical pressure pc1, at which a transition from a relaxor to a non-polar rhombohedral state with antiphase octahedral tilt ordering occurs, decreases at elevated temperatures due to the weakening of the polar coupling, which in turn facilitates the evolution of the preexisting medium-range antiferrodistortive order into a long-range order. The critical pressure pc2 of the second phase transition, involving a change in the type of the antiferrodistortive order, is not affected by temperature, i.e. it is independent of the state of polar coupling and is mainly related to the initial correlation length of antiferrodistortive order. The strong influence of temperature on pc1, which occurs only when the mesoscopic polar order is suppressed, emphasizes the importance of coexisting ferroelectric and antiferrodistortive coupling for the occurrence of the relaxor states. PMID:23515250

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

2013-04-17

87

A NEW MICROSCOPIC MECHANISM FOR FATIGUE BEHAVIOR IN BISMUTH LAYER STRUCTURE FERROELECTRICS  

Microsoft Academic Search

Systemic transmission electron microscopy investigations have been performed on bismuth layer structure ferroelectrics (BLSFs). Ferroelectric domains concluding 90° domain and 180° domain, and antiphase boundary were observed in dark field images and the characters for the 90° domain walls are summarized. We found that the fatigue behaviors of BLSFs show an obvious correlation with the morphology of the 90° domain

D. SU; WEI. LI; J. S. ZHU; Y. N. WANG

2006-01-01

88

Study of the Hysteretic Behavior in Polymer-Stabilized Ferroelectric Liquid Crystal System  

Microsoft Academic Search

We have studied the hysteresis-free switching behaviors of a polymer-stabilized ferroelectric liquid crystal (PSFLC) as well as a pure ferroelectric liquid crystal (FLC) system and found that they coincided with the model suggested by Blinov et al. [Phys. Rev. E 66 (2002) 021701] The hysteresis inversion frequency was promoted to up to 7000 Hz by connecting an external capacitor and

Ji-Hoon Lee; Tong-Kun Lim

2005-01-01

89

Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions Unraveling Relaxor Phase Transitions by  

E-print Network

Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions Unraveling Relaxor 2009 WILLIAMSBURG WORKSHOP ON FUNDAMENTAL PHYSICS OF FERROELECTRICS #12;Introduction Strontium Barium ferroelectrics Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions SBN ­ SrxBa1-xNb2O6

Osnabrück, Universität

90

High-resolution structure studies and magnetoelectric coupling of relaxor multiferroic Pb (F e0.5N b0.5) O3  

NASA Astrophysics Data System (ADS)

Pb (F e0.5N b0.5) O3 (PFN), one of the few relaxor multiferroic systems, has a G -type antiferromagnetic transition at TN=143 K and a ferroelectric transition at TC=385 K . By using high-resolution neutron-diffraction experiments and a total scattering technique, we paint a comprehensive picture of the long- and short-range structures of PFN: (i) a clear sign of short-range structural correlation above TC, (ii) no sign of the negative thermal expansion behavior reported in a previous study, and (iii) clearest evidence thus far of magnetoelectric coupling below TN. We conclude that at the heart of the unusual relaxor multiferroic behavior lies the disorder between Fe3 + and Nb5 + atoms. We argue that this disorder gives rise to short-range structural correlations arising from O disorder in addition to Pb displacement.

Sim, Hasung; Peets, Darren C.; Lee, Sanghyun; Lee, Seongsu; Kamiyama, T.; Ikeda, K.; Otomo, T.; Cheong, S.-W.; Park, Je-Geun

2014-12-01

91

The effect of polar nanoregions on electromechanical properties of relaxor-PbTiO3 crystals: Extracting from electric-field-induced polarization and strain behaviors  

NASA Astrophysics Data System (ADS)

The electric-field-induced polarization and strain of Pb(Mg1/3Nb2/3)O3 (PMN) and Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 (PMN-0.27PT) crystals were investigated at temperatures above their respective maximum permittivity temperatures Tm, where the macro-polarizations vanish while polar nanoregions (PNRs) still persist. The local structure of PNRs was proved to be of rhombohedral phase in PMN, while the local phase was unstable for PMN-0.27PT, leading to the isotropic spontaneous polarization of PNRs and strong anisotropic electric-field-induced strain. The electrostrictive coefficient Q33 was determined as functions of temperature and E-field, with 50% increment over temperature range of 20 ˜120 °C for PMN, being attributed to the decrease of spontaneous polarization of PNRs with increasing temperature. The results presented in this paper indicate that the local structure and spontaneous polarization of PNRs play important roles on electromechanical properties of relaxor ferroelectrics.

Li, Fei; Xu, Zhuo; Zhang, Shujun

2014-09-01

92

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

93

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

94

Manganese incorporation into ferroelectric lead titanate  

Microsoft Academic Search

Substitution with 3d magnetic transition elements in ABO 3 ferroelectric perovskite host media is widely utilized to produce relaxor ferroelectrics. Many resulting solid solutions exhibit magnetoelectric properties affected by concentration levels of the introduced magnetic ions. For conventional material preparation techniques such as firing of mechanically mixed oxides, incorporation is often limited by 5 mol% concentration level. Doping at higher

Stanislav Stoupin

2007-01-01

95

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

96

The intermediate temperature T* revealed in relaxor polymers  

NASA Astrophysics Data System (ADS)

The temperature dependence of the dielectric and optical properties, crystal structure, and infrared spectra of the relaxor poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) terpolymer films obtained from Langmuir-Blodgett method have been comprehensively investigated. All the results suggest that there exists a peculiar point at ˜370 K, which is attributed to the intermediate temperature T* recently discovered in inorganic relaxors. Here, T* results from the change in the growth rate of the trans gauche T3GT3G' chain conformations with temperature, which is similar to the transformation from dynamic to static behavior of the so-called polar nano-regions in inorganic relaxors.

Liu, B. L.; Tian, B. B.; Geiger, S.; Hu, Z. G.; Zhao, X. L.; Zou, Y. H.; Wang, J. L.; Sun, J. L.; Sun, S.; Dkhil, B.; Meng, X. J.; Chu, J. H.

2014-06-01

97

The extrinsic nature of nonlinear behavior observed in lead zirconate titanate ferroelectric ceramic  

E-print Network

. Studies on barium~ titanate, BaTi03, and lead zir- conate titanate (PZT), Pb(Zr,Tit --x)O3,8 showThe extrinsic nature of nonlinear behavior observed in lead zirconate titanate ferroelectric February 1991) The nonlinear electric and electromechanical responses of lead zirconate titanate Pb

Cao, Wenwu

98

Study of the Hysteretic Behavior in Polymer-Stabilized Ferroelectric Liquid Crystal System  

NASA Astrophysics Data System (ADS)

We have studied the hysteresis-free switching behaviors of a polymer-stabilized ferroelectric liquid crystal (PSFLC) as well as a pure ferroelectric liquid crystal (FLC) system and found that they coincided with the model suggested by Blinov et al. [Phys. Rev. E 66 (2002) 021701] The hysteresis inversion frequency was promoted to up to 7000 Hz by connecting an external capacitor and resistor in series. In addition, the influence of temperature on the hysteresis-free switching of the cell could be optimized.

Lee, Ji-Hoon; Lim, Tong-Kun

2005-08-01

99

Ferroelectric-like behavior in nonpolar cellular electrets  

NASA Astrophysics Data System (ADS)

Cellular space-charge electrets have emerged as a new class of materials for electromechanical devices, offering a huge potential for applications in noise reduction or cancellation, non-intrusive surveillance, advanced monitoring in health care, as well as in non-destructive testing. Here we report on piezoelectric responses in sandwich structures of two dielectric films separated by an air-gap of a few micrometer thickness. The sandwich structure is charged by dielectric barrier microdischarges within the air-gap. Wide ranging similarities to ferroelectric materials are demonstrated, like hysteresis loops in the dielectric and electromechanical properties versus applied voltage. Applications may emerge in electrostatic microelectromechanical devices.

Lindner, Michael; Bauer-Gogonea, Simona; Bauer, Siegfried

2003-03-01

100

Anisotropic behavior of water in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

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.

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

2010-05-01

101

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

SciTech Connect

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

Kumar, Nitish, E-mail: nitishkumar.iitk@gmail.com; Ansell, Troy Y.; Cann, David P. [Materials Science, School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, Oregon 97331 (United States)

2014-04-21

102

Contrast in ultrathin film ferroelectric behavior between air and vacuum environments  

NASA Astrophysics Data System (ADS)

At nanoscale dimensions, ferroelectric properties of oxide materials are dominated by depolarizing effects which depend strongly on the electrostatic screening at the interfaces and the environment. Oxide surfaces readily react with adsorbed molecules that may chemically or electronically alter the ferroelectric behavior. We have examined ultrathin (5-20 nm) BiFeO3 thin films grown on SrTiO3(110) using ultra-high vacuum Piezoresponse Force Microscopy. All the films reveal a characteristic behavior trend that in air the films are uniformly polarized, while multiple domains are observed in vacuum. The monodomain to polydomain transition occurs via either annealing in oxygen or simple evacuation, which suggests that molecules may be weakly adsorbed on the surface. Local ferroelectric switching behavior has also been compared for vacuum and ambient environments on the same substrate. Measurements were made at the Center for Nanophase Materials Sciences, sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. DOE.

Baddorf, A. P.; Maksymovych, P.; Kalinin, S. V.; Ramesh, R.

2008-03-01

103

Strain effect on ferroelectric behaviors of BaTiO3 nanowires: a molecular dynamics study.  

PubMed

In this paper, a molecular dynamics method is utilized to investigate the strain effect on the polarization distribution, piezoelectric coefficient, and hysteresis behaviors of BaTiO(3) nanowires. The axial polarization changes almost linearly with the strain over a relatively large range, and the ferroelectricity vanishes under a critical compressive strain. With the nanowire becoming thicker, the piezoelectric coefficient increases, and approaches its counterpart for bulk material when the diameter is larger than 2.4 nm. It is also revealed that a pre-tension strain can induce the emergence of a stepwise hysteresis loop while a pre-compression strain can lead to the disappearance of the stepwise shape. Furthermore, the strain effect and size effect are found to play some equivalent roles in the ferroelectric properties of BaTiO(3) nanowires. PMID:19946153

Zhang, Yihui; Hong, Jiawang; Liu, Bin; Fang, Daining

2010-01-01

104

Strain effect on ferroelectric behaviors of BaTiO3 nanowires: a molecular dynamics study  

NASA Astrophysics Data System (ADS)

In this paper, a molecular dynamics method is utilized to investigate the strain effect on the polarization distribution, piezoelectric coefficient, and hysteresis behaviors of BaTiO3 nanowires. The axial polarization changes almost linearly with the strain over a relatively large range, and the ferroelectricity vanishes under a critical compressive strain. With the nanowire becoming thicker, the piezoelectric coefficient increases, and approaches its counterpart for bulk material when the diameter is larger than 2.4 nm. It is also revealed that a pre-tension strain can induce the emergence of a stepwise hysteresis loop while a pre-compression strain can lead to the disappearance of the stepwise shape. Furthermore, the strain effect and size effect are found to play some equivalent roles in the ferroelectric properties of BaTiO3 nanowires.

Zhang, Yihui; Hong, Jiawang; Liu, Bin; Fang, Daining

2010-01-01

105

Size-dependent ferroelectric behaviors of BaTiO3 nanowires  

NASA Astrophysics Data System (ADS)

Landau-Ginsburg-Devonshire theory is introduced to investigate the size-dependent ferroelectric properties of BaTiO3 nanowires, with the consideration of polarization orienting along the radial direction. It is shown that the Curie temperature, mean polarization, and area enclosed by hysteresis loop decrease with the reducing diameter of the nanowire. However, this size effect becomes obvious only when the diameter is below 20nm. Above this, the ferroelectric behaviors of nanowires are almost the same as those of bulk materials. Furthermore, there exists a temperature-dependent critical diameter for BaTiO3 nanowire below which the hysteresis loops vanish and it is 3.6nm at room temperature.

Hong, Jiawang; Fang, Daining

2008-01-01

106

J. Am. Ceram. Soc., 80 [6] 146268 (1997) Domain-Related Phase Transitionlike Behavior in Lead Zinc Niobate  

E-print Network

J. Am. Ceram. Soc., 80 [6] 1462­68 (1997) Domain-Related Phase Transitionlike Behavior in Lead Zinc observed by severalThe relaxor ferroelectric lead zinc niobate (Pb(Zn1/3Nb2/3)O3) methods, such as optical LEAD zinc niobate, Pb(Zn1/3Nb2/3)O3 (PZN), single crystals Single crystals of PZN were grown using

Cao, Wenwu

107

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

SciTech Connect

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

Wen, Zheng [College of Physics, Qingdao University, Qingdao 266071 (China); National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China and Department of Materials Science and Engineering, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093 (China); Wu, Di, E-mail: diwu@nju.edu.cn; Li, Aidong [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China and Department of Materials Science and Engineering, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093 (China)

2014-08-04

108

Ferroic nanoclusters in relaxors: the effect of oxygen vacancies.  

PubMed

Single crystals of PbSc(0.5)Ta(0.5)O(3) with suppressed and enhanced oxygen deficiencies and different degrees of long-range B-site ordering were studied by Raman spectroscopy in order to clarify the significance of the different factors for the formation and growth of ferroic clusters in relaxors. It is shown that the presence of oxygen vacancies impacts more strongly on the incipient ferroic clustering than the degree of long-range B-site ordering. The oxygen deficiency hinders the formation of ferroelectric crystalline-type nanoregions, regardless of the presence/absence of long-range B(')/B('')-ordered regions. The low degree of defects in the O system enhances the long-range ferroelectric ordering, even in entirely B-site-disordered materials. PMID:21694063

Mihailova, B; Gospodinov, M; Güttler, B; Petrova, D; Stosch, R; Bismayer, U

2007-06-20

109

Interpretation of the odd-even behavior for the emergence of ferroelectricity and antiferroelectricity in bent-core mesogens  

NASA Astrophysics Data System (ADS)

Simple theoretical interpretation has been made on the previously reported odd-even behavior of the emergence of ferroelectricity and antiferroelectricity in homologous series of bent-core mesogens with the same chiral end chains (S,S) ; compounds with even and odd carbon numbers (including oxygen) exhibit ferroelectric and antiferroelectric B2 phases, respectively. The odd-even behavior was confirmed in newly synthesized racemic compounds with chiral end chains of R and S forms (R,S) together with (R,R) and (S,S) forms. According to our theoretical interpretation, ferroelectricity should be more stable in (R,S) compounds than in (S,S) compounds. Actually, the transition temperature from the isotropic phase to the Sm-CP phase was higher and the temperature range of the B2 phase was broader in the (R,S) compound than in the (S,S) compound.

Nishida, Koushi; ?epi?, Mojca; Kim, Won Jeon; Lee, Seng Kue; Heo, Sung; Lee, Jong Gun; Takanishi, Yoichi; Ishikawa, Ken; Kang, Kyung-Tae; Watanabe, Junji; Takezoe, Hideo

2006-08-01

110

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

Microsoft Academic Search

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

Nevin P. Sherlock

2010-01-01

111

The persistence of ferroelectric distortions in electron-doped BaTiO3: microscopic origins and critical behavior  

NASA Astrophysics Data System (ADS)

To explore possible novel applications of the prototypical ferroelectric oxides we perform theoretical studies of electron-doping in BaTiO3. The presence of conduction electrons in a ferroelectric opens the possibility of bi-stable behavior directly in a conducting material which may lead to new functionalities. It is known, however, that conduction electrons screen the long range Coulomb interactions responsible for polar instabilities. Interestingly though, our first-principle density functional calculations reveal that ferroelectric distortions can persist in electron-doped BaTiO3 up to 0.01 e/unit cell, consistent with experimental results [1], suggesting that ferroelectricity and conductivity can coexist. To elucidate the competition between the long range Coulomb interactions and the short range bonding effects we have developed an adequate electrostatic model. Using this model, we reproduce the polarization vs. doping behavior obtained from first-principles and derive an analytical expression for the critical doping above which ferroelectric distortions disappear. [1] T. Kolodiazhnyi et al, Phys. Rev. Lett. 104, 147602 (2010).

Wang, Yong; Burton, John; Jaswal, Sitaram; Tsymbal, Evgeny

2012-02-01

112

Enhanced ferroelectric and ferromagnetic properties in lead-free multilayer composite films based on ferroelectric (Bi0.5Na0.5)0.945Ba0.055TiO3 and multiferroic BiFeO3  

NASA Astrophysics Data System (ADS)

The study of the functional properties of the multilayer composite films of ferroelectric (Bi0.5Na0.5)0.945Ba0.055TiO3 (BNBT) and multiferroic BiFeO3 (BF) obtained by chemical solution deposition has been performed in this work. First, it has been observed a significant improvement of the remnant polarization of the multilayer composite with respect to the single phase film of BNBT: Pr = 32 ?C × cm-2, which is comparable with the values reported for bulk BNBT. This is a consequence of the stabilization of the ferroelectric domains of BNBT, although the relaxor character is still present. The leakage currents, which prevent the full exploitation of the properties of BF films, are reduced thanks to the combination with insulator BNBT layers. Besides, the magnetic behavior shows values of remnant magnetization at room temperature that makes this multilayer composites promising for multiferroic applications.

Perez-Rivero, A.; Ricote, J.; Bretos, I.; García-Hernández, M.; Calzada, M. L.; Jiménez, R.

2015-02-01

113

Characterization and polymerization behavior of polymer-stabilized ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

Recently, the development and application of polymer/liquid crystal (LC) composites have become an area of great interest in LC research. One class of these materials, namely polymer stabilized ferroelectric liquid crystals (PSFLCs), shows great promise in improving upon existing ferroelectric liquid crystal (FLC) technology. Introduction of a polymer into an FLC increases the inherent mechanical strength, but may also detrimentally affect the desirable electro-optic properties. This work focuses on understanding the process of PSFLC formation, and in so doing, builds a foundation to allow for performance optimization by selecting appropriate polymeric materials and polymerization conditions. An integral part of this formation process lies in the polymerization itself. The effects of liquid crystalline order on the polymerization were investigated by monitoring the polymerization using differential scanning calorimetry. The reaction kinetics and mechanisms were examined for a variety of monomers polymerized at different temperatures corresponding to the various LC phases of the FLC. Interestingly, as the polymerization temperature decreased and the liquid crystalline order of the medium increased, a dramatic increase in polymerization rate was observed. This rate acceleration was seen in polymerizations of a number of monomers with different chemical structures and in a variety of different smectic LC materials. For some systems the rate increase was driven by a decrease in the termination rate, whereas in other polymerizations increases in both the apparent termination and propagation rates were observed. By using X-ray diffraction as well as polarized infra-red spectroscopy, the role of monomer segregation in the mechanisms driving these reaction behaviors was explored. These techniques demonstrated that some monomers segregated between the smectic layers, whereas others appeared to mimic the liquid crystals and segregate in the layers. Both types of segregation acted to reduce the reaction volume, thereby increasing the concentration of double bonds. Taking this segregation behavior into account, the polymerization behavior of certain monomer/FLC systems was also modeled. Additionally, the electro-optic properties and optical characteristics were examined for PSFLCs formed with different polymers and under different polymerization conditions. Both ferroelectric polarization and optical response time depended heavily on the type of polymer as well as the temperature at which the monomer was polymerized. Although these properties exhibited by the PSFLC materials were typically much different than those of the neat FLC, by selecting appropriate monomer systems and polymerization conditions, the electro-optic characteristics were optimized and values very close to those exhibited in the FLC were achieved.

Guymon, Clair Allan

1997-11-01

114

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

PubMed

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

Graetsch, Heribert A; Pandey, Chandra Shehkar; Schreuer, Jürgen; Burianek, Manfred; Mühlberg, Manfred

2014-08-01

115

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

116

Modern Physics of Ferroelectrics: Essential Background  

Microsoft Academic Search

\\u000a Principles of ferroelectricity and information about ferroelectric materials and\\u000a their applications are reviewed. The characterization of ferroelectric behavior through\\u000a measurement of electrical hysteresis is discussed in detail. The main families of\\u000a ferroelectric oxides, including perovskite compounds and solid solutions, lithium\\u000a niobate, layered oxides, magnetic ferroelectric oxides, and electronic ferroelectrics are\\u000a presented and their crystal structures and polarizations given. The effects

Karin M. Rabe; Matthew Dawber; Céline Lichtensteiger; Charles Ahn; Jean-Marc Triscone

117

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

118

Relaxor-PT Single crystals: Observations and Developments  

PubMed Central

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

Zhang, Shujun; Shrout, Thomas R.

2011-01-01

119

Ferroelectric Transition and Curie—Weiss Behavior in Some Filled Tungsten Bronze Ceramics  

NASA Astrophysics Data System (ADS)

Ferroelectric transitions in filled tungsten bronze ceramics Sr4R2Ti4Nb6O30, Sr5RTi3Nb7O30 (R=La, Nb, Sm & Eu) and Ba4Nd2Ti4Nb6O30 are investigated with differential scanning calorimetry (DSC) and the Curie—Weiss law fitting to the dielectric constant. The magnitude of the Curie-Weiss constant C ~ 105 suggests displacement-type ferroelectric transition in the present compounds. The large ?T difference between dielectric maximum temperature Tm and Curie—Weiss temperature T0) values indicate the difficult formation of ferroelectric domains or polar nanoregions in the present compounds and also the characteristics of the first order ferroelectric transition. Three categories are suggested for the ferroelectric transition in the above tungsten bronzes. The ferroelectric transition exhibits large thermal hysteresis. According to the DSC results, gradual recovery of the endothermic peak occurs after aging at temperature below the Curie point, indicating the gradual stability of the ferroelectric phase after cooling from the high-temperature para-electric phase. The relationship between the Curie—Weiss law fitting parameters and the nature of the ferroelectric transition is modified for the filled tungsten bronzes.

Zhu, Xiao-Li; Chen, Xiang-Ming

2014-01-01

120

Characterization and polymerization behavior of polymer-stabilized ferroelectric liquid crystals  

Microsoft Academic Search

Recently, the development and application of polymer\\/liquid crystal (LC) composites have become an area of great interest in LC research. One class of these materials, namely polymer stabilized ferroelectric liquid crystals (PSFLCs), shows great promise in improving upon existing ferroelectric liquid crystal (FLC) technology. Introduction of a polymer into an FLC increases the inherent mechanical strength, but may also detrimentally

Clair Allan Guymon

1997-01-01

121

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

122

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

123

Magnetoelectric relaxor A. Levstik,a  

E-print Network

Magnetoelectric relaxor A. Levstik,a V. Bobnar, C. Filipic, J. Holc, M. Kosec, and R. Blinc Jozef is a magnetoelectric relaxor which shows broad and frequency dependent maxima both in the electric as well by a significant magnetic anomaly demonstrating magnetoelectric coupling. Thus, a magnetoelectric effect

Bobnar, Vid

124

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

125

Contribution of oxygen vacancies to the ferroelectric behavior of Hf0.5Zr0.5O2 thin films  

NASA Astrophysics Data System (ADS)

The ferroelectric properties of the (Hf0.5Zr0.5)O2 films on Pt/Ti/SiO2/Si substrate are investigated. It is found that the films crystallized by annealing in O2 and N2 atmospheres have similar crystal structures as well as remanent polarization and coercive fields. Weak temperature and frequency dependences of the ferroelectric properties indicate that the hysteretic behavior in HfO2-based films originates not from the mobile defects but rather from the lattice ionic displacement, as is the case of the typical ferroelectric materials.

Shimizu, Takao; Yokouchi, Tatsuhiko; Oikawa, Takahiro; Shiraishi, Takahisa; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Gruverman, Alexei; Funakubo, Hiroshi

2015-03-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2004-04-01

127

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

Microsoft Academic Search

Relaxor ferroelectric ceramic materials have attracted considerable attentions due to their high dielectric constants and superior piezoelectric properties. Since such properties are associated with single perovskite phase, the synthesis process is of utmost importance. The traditional solid-state reaction encounters difficulties in eliminating pyrochlore phases. To synthesize pyrochlore-free Pb-based relaxors, other methods have been proposed including the columbite route, the chemical

Yin Ye

2010-01-01

128

From spin induced ferroelectricity to spin and dipolar glass in a triangular lattice: The CuCr{sub 1?x}V{sub x}O{sub 2} (0?x?0.5) delafossite  

SciTech Connect

The change from antiferromagnetism induced ferroelectricity to spin glass ferroelectric relaxor has been studied along the CuCr{sub 1?x}V{sub x}O{sub 2} (0?x?0.5) solid solution of polycrystalline samples. As x increases from CuCrO{sub 2} (x=0) to CuCr{sub 0.82}V{sub 0.18}O{sub 2}, it is found that the Néel temperature decreases from ?24 K down to ?13 K. This progressive weakening of the antiferromagnetism of CuCrO{sub 2} induces a rapid decrease of the spin induced ferroelectricity with polarization values going from ?44 ?C/m{sup 2} down to ?1.5 ?C/m{sup 2} 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. - Graphical abstract: The P(T) curves evidencing the aging effect on polarization in CuCr{sub 0.5}V{sub 0.5}O{sub 2}: E=135 kV/m is applied during cooling at different temperatures. The P values and the inflection point of the transition depend on the poling temperature suggesting a relaxor behaviour. This effect related to the spin glass state is not observed for the lowest vanadium content. - Highlights: • Samples of the CuCr{sub 1?x}V{sub x}O{sub 2} series have been studied. • The V content increase induces a change from antiferromagnetism to spin glass. • A behavior characterisitic of a spin and dipole glass is demonstrated. • The ferroelectricity is shown to go from spin induced to relaxor. • Competing magnetic interactions are efficient way to generate multiglass state.

Kumar, S.; Singh, K. [Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France); Miclau, M. [Analysis and Characterization Department, National Institute for R and D in Electrochemistry and Condensed Matter, Timisoara 30024 (Romania); Simon, Ch.; Martin, C. [Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France); Maignan, A., E-mail: antoine.maignan@ensicaen.fr [Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France)

2013-07-15

129

Ferroelectric Behavior in Polyamides of m-Xylylenediamine and Dicarboxylic Acids  

NASA Astrophysics Data System (ADS)

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

Murata, Yukinobu; Tsunashima, Kenji; Koizumi, Naokazu

1995-12-01

130

Dielectric and Mössbauer studies of ferroelectric and magnetic phase transitions in A-site and B-site substituted multiferroic PbFe0.5Nb0.5O3.  

PubMed

In the present study, we diluted either A- or B- sublattice of perovskite multiferroic PbFe(0.5)Nb(0.5)O(3) (PFN) and studied the changes of the magnetic and ferroelectric phase transition temperatures and dielectric properties caused by such dilution. Dielectric studies of PFN single crystals show that, in contrast to the commonly adopted view, the ferroelectric phase transition in PFN is non-diffused and the relaxor-like behavior usually observed in ceramic samples has an extrinsic nature. A-site substitutions (Ba, Ca) lead to the smearing of the permittivity-temperature maximum, lowering its maximum temperature, T(m) and inducing relaxor behavior. B-site diluting of PFN by Ti increases T(m) and only slightly affects the permittivity maximum diffuseness. Both A-site and B-site substitutions in PFN lead to lowering of its Neel temperature, T(N). However, above a certain compositional threshold, fast lowering of T(N) stops and a new magnetic state with comparatively high (~50K) transition temperature becomes stable in a rather wide compositional range. PMID:23007753

Raevski, Igor P; Kubrin, Stanislav P; Raevskaya, Svetlana I; Prosandeev, Sergey A; Malitskaya, Maria A; Titov, Victor V; Sarychev, Dmitry A; Blazhevich, Aleksei V; Zakharchenko, Irina N

2012-09-01

131

A TemperatureDependent Hysteresis Model for Relaxor Ferroelectrics  

E-print Network

with temperature, actuators reach an equilibrium temperature when heat dissipation due to conduction, convection and radiation balances the internal heat generated by the ceramic. The final equilibrium temperature depends

132

Focused ion beam fabricated bragg grating filters in relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the fabrication and characterization of optical waveguide Bragg filters in ion-implanted PMN-32PT [68Pb (Mg 1/3Nb 2/3)-32PbTiO 3] single crystal substrates. PMN-32PT posses exceptionally high piezoelectric and electro-optic properties and has immediate applications in on-chip optical circuitry. We use commercial modeling programs to design the waveguide filter and fabricate the device using ion-implantation and nano-fabrication techniques. First, slab waveguides are created in <001> mirror polished substrates through He + ion-implantation process. He + implantation creates an optical barrier with reduced refractive index. Second, ridge waveguides on the slab are fabricated through standard photolithography and dry etching techniques. Third, Periodic refractive index modulation (grating) on the top of the ridge waveguide is achieved through Focused Ion Beam [FIB] milling which is controlled by Nanometer Pattern Generation System [NPGS]. Photonic bandgaps are observed in 1480-1580 nm wavelength range in these filters. The experimental data shows excellent agreement with the theory.

Vanga, Raghav; Huang, Xiaoyue; Zhou, Ziyou

2012-02-01

133

Pyroelectric behavior and thermally stimulated processes in niobium modified lead zirconate titanate ferroelectric ceramics  

NASA Astrophysics Data System (ADS)

The thermally stimulated processes in niobium modified lead zirconate titanate ferroelectric system are analyzed from the thermally stimulated depolarization current. Different theoretical models are considered to evaluate the i-T experimental data. The results are associated with the space charge, the pyroelectric response, and the electrical conduction mechanism related to the oxygen vacancies. The results for the pyroelectric contribution are discussed considering the niobium concentration.

Peláiz-Barranco, A.; Garcia-Wong, A. C.; González-Abreu, Y.; Guerra, J. D. S.

2013-01-01

134

Aging behavior in single-domain Mn-doped BaTiO3 crystals: Implication for a unified microscopic explanation of ferroelectric aging  

NASA Astrophysics Data System (ADS)

The change of ferroelectric, dielectric, and piezoelectric properties with time, the ferroelectric aging phenomena, has been observed in most ferroelectrics. Phenomenologically, aging can be attributed to the gradual stabilization of ferroelectric domains by defects, but the microscopic origin of the domain stabilization has remained controversial. It is unclear whether the domain stabilization is a boundary effect (caused by domain-wall-pinning) or a volume effect (stabilization of the whole domain). In the present paper, we made a single-domain (domain-wall-free) Mn-doped BaTiO3 single crystal and studied the aging behavior of its hysteresis loop. We found that after aging, the single-domain sample shows a significant increase in the coercive field, clearly indicating a strong stabilization of the single domain. Furthermore, the sample exhibits an abnormal double hysteresis loop, which corresponds to an interesting reversible domain switching process. These are direct evidence for the stabilization of single domain by aging. Our results preclude any explanation by the domain-wall-pinning effect and strongly suggest that the volume effect is the governing mechanism for the aging in hysteresis loop. We further show that the microscopic origin of the volume effect comes naturally from a general symmetry-conforming property of point defects. Such a microscopic mechanism can explain not only the aging in hysteresis loop (large signal aging) but also the aging in dielectric and piezoelectric constants (small signal aging), thus providing a unified microscopic explanation for all kinds of ferroelectric aging.

Zhang, Lixue; Ren, Xiaobing

2006-03-01

135

Ferroelectric Pump  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

136

Piezoelectric activity in Perovskite ferroelectric crystals.  

PubMed

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

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

2015-01-01

137

Molecular dynamics investigations on the size-dependent ferroelectric behavior of BaTiO3 nanowires.  

PubMed

Validated by ab initio simulations on the spontaneous polarization, the molecular dynamics method is used to investigate the size effect on the polarization distribution, hysteresis behaviors and Curie temperatures of BaTiO3 nanowires. A quasi-axisymmetric radial distribution of polarization in the cross-section plane is disclosed. It is also found that there exist three typical polarization distribution scenarios for different wire diameters, and thus two critical diameters can be identified. Moreover, unusual stepwise hysteresis loops, and core-shell polarization structures with opposite polarization directions at the outer and inner regions of the nanowire are revealed in our simulations. This study on the atomic level polarization evolution may help us to understand the ferroelectric properties of nanowires. PMID:19738302

Zhang, Yihui; Hong, Jiawang; Liu, Bin; Fang, Daining

2009-10-01

138

Molecular dynamics investigations on the size-dependent ferroelectric behavior of BaTiO3 nanowires  

NASA Astrophysics Data System (ADS)

Validated by ab initio simulations on the spontaneous polarization, the molecular dynamics method is used to investigate the size effect on the polarization distribution, hysteresis behaviors and Curie temperatures of BaTiO3 nanowires. A quasi-axisymmetric radial distribution of polarization in the cross-section plane is disclosed. It is also found that there exist three typical polarization distribution scenarios for different wire diameters, and thus two critical diameters can be identified. Moreover, unusual stepwise hysteresis loops, and core-shell polarization structures with opposite polarization directions at the outer and inner regions of the nanowire are revealed in our simulations. This study on the atomic level polarization evolution may help us to understand the ferroelectric properties of nanowires.

Zhang, Yihui; Hong, Jiawang; Liu, Bin; Fang, Daining

2009-10-01

139

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

140

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

141

Critical behavior in the heat capacity of ferroelectric TGS, TGSe, and TGFB  

NASA Astrophysics Data System (ADS)

Measurements of the heat capacity were carried out on triglycine sulfate (TGS), triglycine selenate (TGSe,) and triglycine fluoberyllate (TGFB) with an AC calorimetry technique to clarify their critical nature near the ferroelectric phase transition point. An anomalous heat capacity with logarithmic temperature dependence was found in all of the three crystals in a temperature range T-Tc less than 10-20 K above Tc. The relation between this anomaly and the quality of sample was studied by examining crystals of different growth conditions. The effect of gamma-ray irradiation on this anomaly was also examined. From such studies the observed logarithmic anomaly was ascribed to critical fluctuation. The data are analyzed with a theory for an Ising-dipole system taking into account the effect of fluctuation to the first order. The observed heat capacity anomaly both above and below Tc is fitted satisfactorily with reasonable values of parameters.

Ema, K.

1983-08-01

142

Dielectric relaxor behaviors and tunability of (1- x)Ba(Zr0.2Ti0.8)O3- x(Ba0.7Ca0.3)TiO3 thin films fabricated by sol-gel method  

NASA Astrophysics Data System (ADS)

Temperature dependence of dielectric properties of (1- x)Ba(Zr0.2Ti0.8)O3- x(Ba0.7Ca0.3)TiO3 ( x=0.15, 0.30, and 0.50) (BZT- xBCT) thin films prepared by a sol-gel method has been investigated. The results show that there is a broad dielectric maximum near T m and the diffuse parameter ? is close to 2, indicating a nearly complete diffuse phase transition in BZT- xBCT thin films. The dielectric relaxor behaviors of the thin films well follow Vogel-Fulcher relation. The thin films show a high dielectric tunability up to 65 %, with a small variation in the temperature range from 248.15 to 373.15 K. This study indicates that the thin films, especially for x=0.50, are promising candidates for tunable device applications with good temperature stability.

Lin, Yanting; Qin, Ni; Wu, Guangheng; Sa, Tongliang; Bao, Dinghua

2012-11-01

143

Ferroelectricity in Si-doped HfO2 revealed: a binary lead-free ferroelectric.  

PubMed

Static domain structures and polarization dynamics of silicon doped HfO2 are explored. The evolution of ferroelectricity as a function of Si-doping level driving the transition from paraelectricity via ferroelectricity to antiferroelectricity is investigated. Ferroelectric and antiferroelectric properties can be observed locally on the pristine, poled and electroded surfaces, providing conclusive evidence to intrinsic ferroic behavior. PMID:25352107

Martin, Dominik; Müller, Johannes; Schenk, Tony; Arruda, Thomas M; Kumar, Amit; Strelcov, Evgheni; Yurchuk, Ekaterina; Müller, Stefan; Pohl, Darius; Schröder, Uwe; Kalinin, Sergei V; Mikolajick, Thomas

2014-12-23

144

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

NASA Astrophysics Data System (ADS)

Bismuth-doped barium titanate ceramics with the general formula Ba1-x Bi2x/3TiO3 (x = 0.0, 0.01, 0.025, 0.05) have been prepared by the solid state reaction technique. The phase formation and structural property of all compositions have been studied by x-ray diffraction (XRD) pattern and Rietveld refinement. XRD pattern reports the single phase tetragonal crystal system with space group of P4mm. All compositions have been sintered at 1100°C in a microwave furnace for 30 min. The variation of dielectric constant with respect to temperature and frequency was studied and it was found that the dielectric constant decreases whereas transition temperature increased with the increase in Bi content. The diffusivity parameter was calculated by the modified Curie-Weiss law and the diffusivity increased with the increase in Bi content. The ferroelectric property was studied by the P-E hysteresis loop and it was observed that the saturation polarization decreased, but the coercive field increased with Bi content. The optical band gap was calculated from UV-Visible spectroscopy and found to decrease with Bi content.

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

2014-12-01

145

La3Ni2SbO9: a relaxor ferromagnet.  

PubMed

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

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

2013-06-01

146

Supramolecular ferroelectrics  

NASA Astrophysics Data System (ADS)

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

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

2015-04-01

147

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

NASA Astrophysics Data System (ADS)

Transparent glasses in the system (100-x) Li2B4O7-xSrBi2Ta2O9 (0?x?20) were fabricated via a splat-quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses. X-ray powder diffraction and transmission electron microscopic studies confirmed the amorphous nature of the as-quenched and crystallinity (40 nm) in the heat-treated (glass-ceramic) samples. The dielectric constant (?r) of the glass-ceramic composite (x=20, heat treated at 773 K/8 h) was in between that of the parent host glass (Li2B4O7) and strontium bismuth tantalate ceramics in the frequency range 100 Hz-40 MHz at 300 K. These exhibited intense second-harmonic generation and a ferroelectric hysteritic behavior (P vs E loops) at 300 K. The coercive field (Ec) and the remnant polarization (Pr) were 1053 V/cm and 0.483 ?C/cm2, respectively.

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

2001-06-01

148

Large electrocaloric effect in ferroelectric polymers near room temperature.  

PubMed

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

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

2008-08-01

149

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

NASA Astrophysics Data System (ADS)

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 ?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 deff 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.

2005-04-01

150

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

151

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

PubMed

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

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

2013-02-13

152

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

153

Effect of radiation-induced defects on the dielectric response of lead scandoniobate ferroelectric ceramics  

Microsoft Academic Search

The effect of ionizing gamma irradiation on the frequency and temperature dependences of the permittivity ?’(T) for lead scandoniobate relaxor (disordered) ferroelectric ceramics before and after thermal annealing was investigated by\\u000a low-and infralow-frequency dielectric spectroscopy. It was demonstrated that the irradiation leads to a shift in the temperatures\\u000a of the maxima in the dependence ?’(T) and the temperatures of the

A. V. Sopit; A. I. Burkhanov; A. Sternberg

2006-01-01

154

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

155

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

NASA Astrophysics Data System (ADS)

Ferroelectrics are important materials due to their extensive technological applications, such as non-volatile memories, field-effect transistors, ferroelectric tunneling junctions, dielectric capacitors, piezoelectric transducers, sensors and actuators. As is well known, the outstanding dielectric, piezoelectric, and ferroelectric properties of these functional oxides originate from their ferroelectric domain arrangements and the corresponding evolution under external stimuli (e.g. electric field, stress, and temperature). Electric field has been known as the most efficient stimulus to manipulate the ferroelectric domains through polarization switching and alignment. Therefore, direct observation of the dynamic process of electric field-induced domain evolution and crystal structure transformation is of significant importance to understand the microstructural mechanisms for the functional properties of ferroelectrics. In this dissertation, electric field in situ transmission electron microscopy (TEM) technique was employed to monitor the real-time evolution of the domain morphology and crystal structure during various electrical processes: (1) the initial poling process, (2) the electric field reversal process, and (3) the electrical cycling process. Two types of perovskite-structured ceramics, normal ferroelectrics and relaxor ferroelectrics, were used for this investigation. In addition to providing the microscopic insight for some well-accepted phase transformation rules, discoveries of some new or even unexpected physical phenomena were also demonstrated. For the initial poling process, microstructural origins for the piezoelectricity development in the three most promising lead-free piezoceramic systems were investigated. For the non-ergodic relaxor ferroelectric compositions ( x = 6% - 9%) in the (1-x)(Bi1/2Na 1/2)TiO3-xBaTiO3 system, well-developed piezoelectricity was realized at poling fields far below the coercive field and phase transition field. Such an unusual behavior is attributed to the electric field-induced irreversible P4bm nanodomains coalescence into thin lamellar domains prior to the phase transition. In the (K0.5 Na0.5)NbO3-based ceramics, as demonstrated by an archetypical polymorphic phase boundary (PPB) composition of 0.948(K 0.5Na0.5)NbO3-0.052LiSbO3, the origin of the excellent piezoelectric performance is due to a tilted monoclinic phase that emerges from the tetragonal and orthorhombic PPB at the poling fields beyond 14 kV/cm. This monoclinic phase, as manifested by the appearance of blotchy domains and 1/2{oeo} superlattice diffraction spots, was determined to possess a Pm symmetry with a 0b+c0 oxygen octahedra tilting and antiparallel cation displacements. For the PPB composition of x = 0.5 in the (1-x)Ba(Zr0.2Ti0.8 )O3-x(Ba0.7Ca0.3)TiO 3 solid solution system, the original multi-domain state was found to transform into a unique single-domain state with orthorhombic symmetry at very moderate poling fields of 3 6 kV/cm. This single-domain state is suggested to be primarily responsible for the observed large piezoelectricity due to its significant elastic softening. In the electrical reversal process, a highly unusual phenomenon of electric field-induced ferroelectric-to-relaxor phase transition was directly observed in a lead-free composition of [(Bi1/2Na1/2)0.95 Ba0.05]0.98La0.02TiO3. It is manifested by the disruption of large ferroelectric domains with long range polar order into polar nanodomains with short range orders when the polarity of electric field is reversed. This observation was further rationalized by a phenomenological model that takes the large difference in kinetics between the phase transition and the polarization reversal processes into account. During the electrical cycling process, the microstructural mechanisms for electric fatigue behaviors of two ceramics were investigated. In 0.7Pb(Mg 1/3Nb2/3)O3-0.3PbTiO3, the frozen domain configuration after 103 cycles is responsible for the pronounced functionality degradation. Both seed inhibition and domain wall pinning mech

Guo, Hanzheng

156

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

157

Ferroelectric precursor behavior of highly cation-ordered PbSc0.5Ta0.5O3 detected by acoustic emission: Tweed and polar nanoregions  

NASA Astrophysics Data System (ADS)

Highly ordered ferroelectric PbSc0.5Ta0.5O3 crystals were studied by acoustic emission over a wide temperature range. Acoustic emission was found at three characteristic temperatures: 330, 409, and ?600 K, which are close to those, known from the same disordered crystals, containing polar nanoregions. The microstructure in our crystals contains structural "tweed" rather than nanoregions. The coincidence of acoustic emission temperatures points towards a close structural relationship between nanoregions and "tweed." Under electric field, these temperatures shift similar to "critical end point" behavior. The obtained data prove that acoustic emission detects signals in a wider parameter space than previously expected.

Dul'kin, Evgeniy; Salje, Ekhard K. H.; Aktas, Oktay; Whatmore, Roger W.; Roth, Michael

2014-11-01

158

Ferroelectric and piezoelectric behaviors of individual single crystalline BaTiO3 nanowire under direct axial electric biasing  

NASA Astrophysics Data System (ADS)

A method, which is especially useful for the study of ferroelectric nanowire with piezoresponse force microscopy (PFM), was developed. In this method electric bias is directly applied on the axial direction of nanowire. The axial poling and switching of single crystalline BaTiO3 nanowire were realized, and hysteresis loop and shear piezoresponse were acquired with PFM operated in lateral mode. The study demonstrated the ferroelectric nature of the nanowire and the need of a significantly higher poling electric field to reach polarization saturation in nanowire than that in bulk BaTiO3 crystal.

Wang, Zhaoyu; Suryavanshi, Abhijit P.; Yu, Min-Feng

2006-08-01

159

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

PubMed

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

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

2015-02-01

160

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

161

Temperature-dependent coherent oscillation in photorefractive relaxor strontium barium  

E-print Network

Temperature-dependent coherent oscillation in photorefractive relaxor strontium barium niobate M of the photorefractive light-induced scattering (beam fanning) in Sr0.61Ba0.39Nb2O6 (strontium barium niobate) doped

Osnabrück, Universität

162

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

Microsoft Academic Search

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

T. Lahiri; T. Pal Majumder

2011-01-01

163

Linear electro-optic properties of relaxor-based ferroelectric 0.24Pb(In1/2Nb1/2)O3-(0.76?-?x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals.  

PubMed

Linear electro-optic properties of 0.24Pb(In1/2Nb1/2)O3-(0.76?-?x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals, with compositions in the rhombohedral, morphotropic phase boundary (MPB) and tetragonal phases, have been investigated. Very large effective electro-optic coefficient [Formula: see text] (204?pm/V) was observed in a crystal with the MPB composition when it is poled along [001]. The rhombohedral phase (x?=?0.27 and 0.30) single crystals poled along [111] direction and tetragonal phase (x?=?0.39) single crystal poled along [001] direction are in single domain, and their electro-optic coefficients ([Formula: see text]?=?76, 94, and 43?pm/V for the crystals with x?=?0.27, 0.30, and 0.39, respectively) were found to be much higher than that of traditional electro-optic single crystal LiNbO3 ([Formula: see text]?=?19.9?pm/V). The electro-optic coefficients of the single crystal in the rhombohedral phase have excellent temperature stability in the experimental temperature range of 10-40?°C. The half-wave voltage [Formula: see text] was calculated to be much lower (less than 1000?V) than that of LiNbO3 single crystal (2800?V). These superior properties make the ternary relaxor-PT single crystals very promising for electro-optic modulation applications. PMID:23922449

Wu, Fengmin; Yang, Bin; Sun, Enwei; Liu, Gang; Tian, Hao; Cao, Wenwu

2013-07-14

164

Domains in Ferroelectric Nanostructures  

NASA Astrophysics Data System (ADS)

Ferroelectric materials have great potential in influencing the future of small scale electronics. At a basic level, this is because ferroelectric surfaces are charged, and so interact strongly with charge-carrying metals and semiconductors - the building blocks for all electronic systems. Since the electrical polarity of the ferroelectric can be reversed, surfaces can both attract and repel charges in nearby materials, and can thereby exert complete control over both charge distribution and movement. It should be no surprise, therefore, that microelectronics industries have already looked very seriously at harnessing ferroelectric materials in a variety of applications, from solid state memory chips (FeRAMs) to field effect transistors (FeFETs). In all such applications, switching the direction of the polarity of the ferroelectric is a key aspect of functional behavior. The mechanism for switching involves the field-induced nucleation and growth of domains. Domain coarsening, through domain wall propagation, eventually causes the entire ferroelectric to switch its polar direction. It is thus the existence and behavior of domains that determine the switching response, and ultimately the performance of the ferroelectric device. A major issue, associated with the integration of ferroelectrics into microelectronic devices, has been that the fundamental properties associated with ferroelectrics, when in bulk form, appear to change quite dramatically and unpredictably when at the nanoscale: new modes of behaviour, and different functional characteristics from those seen in bulk appear. For domains, in particular, the proximity of surfaces and boundaries have a dramatic effect: surface tension and depolarizing fields both serve to increase the equilibrium density of domains, such that minor changes in scale or morphology can have major ramifications for domain redistribution. Given the importance of domains in dictating the overall switching characteristics of a device, the need to fully understand how size and morphology affect domain behaviour in small scale ferroelectrics is obvious. In this talk, observations from a programme of study examining domains in meso and nano-scale BaTiO3 shapes, that have been cut directly from bulk single crystal using focused ion beam milling, will be presented. In general, the equilibrium static domain configurations that occur appear to be the result of a simultaneous desire to minimize both the macroscopic strain and depolarizing fields developed on cooling through the Curie Temperature. While such governing factors might be obvious, the specific patterns that result as a function of morphology are often non-intuitive, and a series of images of domains in nanodots, rods and wires will be presented and rationalised. In addition, the nature in which morphological factors influence domain dynamics during switching will be discussed, with particular focus on axial switching in nanowires, and the manner in which local surface perturbations (such as notches and antinotches) affect domain wall propagation. In collaboration with Alina Schilling, Li-Wu Chang, Mark McMillen, Raymond McQuaid, and Leo McGilly, Queen's University Belfast; Gustau Catalan, Universitat Autonoma de Barcelona; and James Scott, University of Cambridge.

Gregg, Marty

2010-03-01

165

Magnetite (Fe3O4): a new variant of relaxor multiferroic?  

NASA Astrophysics Data System (ADS)

The electric polarization, dielectric permittivity, magnetoelectric effect, heat capacity, magnetization and ac susceptibility of magnetite films and polycrystals were investigated. The electric polarization of magnetite films with saturation values between 4 and 8 µC cm-2 was found to vanish between 32 and 38 K, but in polycrystals no phase transition was detected in this range by heat capacity. Both types of samples showed magnetoelectric effects at low temperatures below a frequency-dependent crossover. This is interpreted as arising from multiferroic relaxor behavior.

Ziese, M.; Esquinazi, P. D.; Pantel, D.; Alexe, M.; Nemes, N. M.; Garcia-Hernández, M.

2012-02-01

166

Magnetite (Fe3O4): a new variant of relaxor multiferroic?  

PubMed

The electric polarization, dielectric permittivity, magnetoelectric effect, heat capacity, magnetization and ac susceptibility of magnetite films and polycrystals were investigated. The electric polarization of magnetite films with saturation values between 4 and 8 ?C cm(-2) was found to vanish between 32 and 38 K, but in polycrystals no phase transition was detected in this range by heat capacity. Both types of samples showed magnetoelectric effects at low temperatures below a frequency-dependent crossover. This is interpreted as arising from multiferroic relaxor behavior. PMID:22314835

Ziese, M; Esquinazi, P D; Pantel, D; Alexe, M; Nemes, N M; Garcia-Hernández, M

2012-02-29

167

Charge Trapping in Ferroelectric Polymers  

Microsoft Academic Search

Experimental results are presented on anomalous behavior of absorption currents in PVDF during the stepwise increase of the voltage applied through a corona. These results, supplemented with the dynamics of the time constant of the electret potential decay are consistent with a hypothesis assuming deep trapping of the charge carriers during the polarization buildup in ferroelectric polymers. Model calculations are

A. F. Butenko

2009-01-01

168

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

SciTech Connect

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

Puli, Venkata Sreenivas, E-mail: pvsri123@gmail.com [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States); Martinez, R.; Kumar, Ashok [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States)] [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States); Scott, J.F. [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States) [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States); Cavendish Laboratory, Dept. Physics, University of Cambridge, Cambridge CB0 3HE (United Kingdom); Katiyar, Ram S., E-mail: rkatiyar@uprrp.edu [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States)

2011-12-15

169

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

170

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

171

Failure behavior of Pb(Zr0.95Ti0.05)O3 ferroelectric ceramics under shock compression  

NASA Astrophysics Data System (ADS)

PZT 95/5 ferroelectric ceramics have been used in shock-driven pulsed-power supplies for many years; their mechanical failure under shock compression plays an important role in dielectric breakdown. Shock experiments have been conducted to understand such failure by measuring the velocity of the free surface or the PZT/sapphire interface. Results confirm that delayed failure exists in PZT 95/5 before dynamic yielding at 2.4 GPa; multipoint measurements indicate that the failure layer in PZT 95/5 was not a plane but a rough front. The delay time and velocity of this layer had been determined by measuring samples of varying thicknesses at fixed pressure; results indicate that this velocity is the same as the shock-wave speed and the delay time decreases with increasing shock stress. At a shock stress of 4.9 GPa, the delay time falls to zero and a ramp wave is observed. This kind of failure is a new phenomenon in electric breakdown of PZT 95/5 under shock compression.

Zhang, Fuping; He, Hongliang; Liu, Gaomin; Liu, Yusheng; Yu, Yin; Wang, Yonggang

2013-05-01

172

Impedance Measurements on a and B Site Modified Bismuth Layered Structure Ferroelectric Ceramics  

NASA Astrophysics Data System (ADS)

A and B site modified new bismuth layered structure ferroelectric ceramics of the Aurivillius family were prepared by the solid-state route. Impedance measurements were performed on these samples to understand the relaxation effects in the frequency range of 100 Hz to 1 MHz. From the detailed impedance and modulus spectroscopic analysis, it is found that the aliovalent modified B-site enhances the relaxor-like nature, compared to A-site substitution. These results were corroborated with ac-conductivity transport analysis. In this connection, a defect formula is also proposed. The results are discussed.

Prasad, N. V.; Karmakar, S.; Gupta, S. M.

173

Relaxor characteristics at the interfaces of NdMnO3\\/SrMnO3\\/LaMnO3 superlattices  

Microsoft Academic Search

We have investigated the magnetic properties of transition-metal oxide superlattices with broken inversion symmetry composed of three different antiferromagnetic insulators, [NdMnO3\\/SrMnO3\\/LaMnO3] . In the superlattices studied here, we identify the emergence of a relaxor, glassylike behavior below TSG=36K . Our results offer the possibility to study and utilize magnetically metastable devices confined at nanoscale interfaces.

Jiwon Seo; Bach T. Phan; Jochen Stahn; Jaichan Lee; Christos Panagopoulos

2010-01-01

174

Relaxor characteristics at the interfaces of NdMnO3/SrMnO3/LaMnO3 superlattices  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of transition-metal oxide superlattices with broken inversion symmetry composed of three different antiferromagnetic insulators, [NdMnO3/SrMnO3/LaMnO3] . In the superlattices studied here, we identify the emergence of a relaxor, glassylike behavior below TSG=36K . Our results offer the possibility to study and utilize magnetically metastable devices confined at nanoscale interfaces.

Seo, Jiwon; Phan, Bach T.; Stahn, Jochen; Lee, Jaichan; Panagopoulos, Christos

2010-10-01

175

Ferroelectric Materials: Ferroelectric Kinetics Computer Lab  

NSDL National Science Digital Library

The discussion on phase field modeling and conserved order-disorder transformations is extended to phase transformations for non-conserved order parameters. As an enabling application, a one-parameter two-dimensional ferroelectric material is described. The Allen-Cahn equation is presented. This lab is intended to complement the "Ferroelectric Materials: An Introduction" lecture.

García, R. Edwin

2008-08-25

176

Ferroelectric polymer nanostructures: fabrication, structural characteristics and performance under confinement.  

PubMed

Ferroelectric polymers have recently attracted tremendous research interest due to their potential application in various emerging flexible devices. Nanostructured ferroelectric polymer materials, such as nanorods, nanotube, and nanowires, are essential for miniaturization of the relevant electronic components. More importantly, their improved sensitivity and functionality may be used to enhance the performance of existing devices or to develop and design new devices. In this article, the recently developed methods for fabricating ferroelectric polymer nanostructures are briefly reviewed. In particular, the distinct crystallization behaviors confined at the nanometer scale, the nanoconfinement induced structural change, their influence on the physical properties of the ferroelectric polymer nanostructures, and the possible underlying mechanisms are discussed. PMID:24749475

Guo, Dong; Zeng, Fei; Dkhil, Brahim

2014-02-01

177

Pulse-loaded ferroelectric nanowire as an alternating current source.  

PubMed

The behavior of an uniaxially pulse-loaded ferroelectric nanowire is simulated using a Landau-Ginzburg type thermodynamic model. Our results show that under a load of suitable magnitude and frequency, an appropriately dimensioned ferroelectric nanowire can produce a sizable alternating current voltage, sufficient for applications as a nanopower source for energy harvesting, or as an effective nanomechanical sensor. PMID:18781805

Zheng, Yue; Woo, C H; Wang, B

2008-10-01

178

Internal field and thermally stimulated effect in ferroelectric odd nylons  

Microsoft Academic Search

An unusual ferroelectric behavior of nylon 11 has been observed at high temperature. The very large value of the remnant polarization shows that the dipole in the amorphous regions of the semi-crystalline odd nylons could have an important contribution to the ferroelectric polarization. The homocharge and heterocharge are related with the applied electric field. The spectra of thermally stimulated depolarization

Zicai Liang; Bo Jiang; Wenqing Chen

1996-01-01

179

The effective pyroelectric and thermal expansion coefficients of ferroelectric ceramics  

E-print Network

The effective pyroelectric and thermal expansion coefficients of ferroelectric ceramics JiangYu Li ceramics in terms of their microstructural information. The overall behaviors of ferroelectric ceramics be induced in an originally isotropic, thus non-pyroelectric ceramic composed of randomly oriented

Li, Jiangyu

180

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

SciTech Connect

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

Zhu, J. J.; Zhang, J. Z.; Chu, J. H. [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Xu, G. S. [R and D Center of Synthetic Crystals, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhang, X. L.; Hu, Z. G. [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China)

2014-03-31

181

Possible ferroelectricity in perovskite oxynitride SrTaO2N epitaxial thin films  

PubMed Central

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

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

2014-01-01

182

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

183

Perovskite ferroelectric nanomaterials  

NASA Astrophysics Data System (ADS)

In this review, the main concept of ferroelectricity of perovskite oxides and related materials at nanometer scale and existing difficulties in the synthesis of those nanocrystals are discussed. Important effects, such as depolarization field and size effect, on the existence of ferroelectricity in perovskite nanocrystals are deliberated. In the discussion of modeling works, different theoretical calculations are pinpointed focusing on their studies of lattice dynamics, phase transitions, new origin of ferroelectricity in nanostructures, etc. As the major part of this review, recent research progress in the facile synthesis, characterization and various applications of perovskite ferroelectric nanomaterials, such as BaTiO3, PbTiO3, PbZrO3, and BiFeO3, are also scrutinized. Perspectives concerning the future direction of ferroelectric nanomaterials research and its potential applications in renewable energy, etc., are presented. This review provides an overview in this area and guidance for further studies in perovskite ferroelectric nanomaterials and their applications.In this review, the main concept of ferroelectricity of perovskite oxides and related materials at nanometer scale and existing difficulties in the synthesis of those nanocrystals are discussed. Important effects, such as depolarization field and size effect, on the existence of ferroelectricity in perovskite nanocrystals are deliberated. In the discussion of modeling works, different theoretical calculations are pinpointed focusing on their studies of lattice dynamics, phase transitions, new origin of ferroelectricity in nanostructures, etc. As the major part of this review, recent research progress in the facile synthesis, characterization and various applications of perovskite ferroelectric nanomaterials, such as BaTiO3, PbTiO3, PbZrO3, and BiFeO3, are also scrutinized. Perspectives concerning the future direction of ferroelectric nanomaterials research and its potential applications in renewable energy, etc., are presented. This review provides an overview in this area and guidance for further studies in perovskite ferroelectric nanomaterials and their applications. The authors declare no competing financial interests.

Nuraje, Nurxat; Su, Kai

2013-09-01

184

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.

2010-06-01

185

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

NASA Astrophysics Data System (ADS)

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

Tong, Sheng

186

Surface layer in relaxor ferroelectric PZN-4.5%PT single crystals  

NASA Astrophysics Data System (ADS)

The origin of the extremely broad peak at the lower 2? side of the main (002) rhombohedral x-ray peak in an unpoled (001)-cut Pb(Zn1/3Nb2/3)0.955Ti0.045O3 (PZN-4.5%PT) single crystal has been examined. This peak, located at about 2?˜43°-44°, was absent on fractured surfaces of the crystal but reappeared when the fractured surfaces were polished mechanically. High-resolution synchrotron x-ray mesh scans revealed that the as-polished surface was covered with a "deformed layer" of heavily stressed rhombohedral phase of monoclinic symmetry having its c axis lying perpendicular to the surface. This deformed phase can be structurally likened to one full of "incipient monoclinic nuclei/phases," which are microscopic in size and subject to intense compression in the plane of the surface. With a given polishing direction, this surface layer showed parallel domain patterns when viewed under the polarized light microscope. This surface layer could be largely eliminated by appropriate poling at 0.7-1.5 kV/mm at room temperature but became resistant to poling after annealing.

Chang, W. S.; Shanthi, M.; Rajan, K. K.; Lim, L. C.; Wang, F. T.; Tseng, C. T.; Tu, C. S.; Yang, Ping; Moser, H. O.

2007-06-01

187

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

E-print Network

the 4mm tetragonal (T), mm2 orthorhombic (O), and 3m rhombohedral (R) phases, or from one domain type face of the cube. The triangles at its corners represent four R-phase P directions, and the circles

188

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

189

Effect of Tantalum on Ferroelectric Phase Transition Behavior of SrBi4Ti4O15 Sintered Discs  

NASA Astrophysics Data System (ADS)

Tantalum modified strontium bismuth titanate ceramic discs with general formula SrBi4Ti(4-5x)Ta4xO15 with x = 0, 0.1, 0.2 and 0.3 have been prepared through solid state reaction method. The samples are poled and dielectric constant, loss and AC conductivity measurements are done in the temperature region (30-600°C). Ta5+ doping brought out interesting changes in dielectric phase transition behavior of the samples. Dielectric loss and conductivity measurements indicate the presence of charged defects. The results indicate changes in the distortion of the lattice. The distortion is calculated from the changes in the Curie temperature. AC conductivity results are understood in terms of the unoccupied sites and oxygen vacancies that are present in the samples.

Madhavi, K.; Kumar, G. S.; Prasad, G.

190

Ferroelectric Materials: An Introduction  

NSDL National Science Digital Library

The discussion on phase field modeling and conserved order-disorder transformations is extended to phase transformations for non-conserved order parameters. The Allen-Cahn equation is presented. This lecture is intended to prepare students for the "Ferroelectric Materials: Ferroelectric Kinetics Computer Lab."

García, R. Edwin

2008-08-25

191

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

192

Four switching categories of ferroelectrics  

NASA Astrophysics Data System (ADS)

We classify the switching kinetics of ferroelectrics including both epitaxial/polycrystalline thin films and single-crystalline/ceramic bulks at various applied fields into four categories, depending on whether the depolarization field and/or the polarization reversal induced by the switching promotion effect between adjacent parts can be neglected. We show that our statistical model developed very recently [X. J. Lou, J. Phys.: Condens. Matter 21, 012207 (2009)] in its generalized form applies to all these four categories. Finally, we make the comparison between our model and the conventional Kolmogorov-Avrami-Ishibashi model and discuss the behavior of the switching currents for different n.

Lou, X. J.

2009-05-01

193

Ferroelectric switching of elastin  

PubMed Central

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

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

2014-01-01

194

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

195

Dielectric Characteristics in BiFeO3-Modified SrTiO3 Incipient Ferroelectric Ceramics  

NASA Astrophysics Data System (ADS)

We investigate the dielectric and ferroelectric properties of Sr1?xBixTi1?xFexO3 solid solutions (x = 0, 0.05, 0.1, 0.15 and 0.2) together with their structures. Through the analysis of Rietveld refinement of powder x-ray diffraction, a cubic structure in space group Pm3¯m is determined for all the compositions. An obvious dielectric relaxation peak differing from SrTiO3 is observed in the present ceramics. The peak temperature Tm increases with increasing x, and it approaches room temperature at x = 0.2. The Vogel—Fulcher law and Curie—Weiss law fittings further confirm the relaxor ferroelectricity in the present ceramics.

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

2015-02-01

196

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

197

Phase transition hysteresis and anomalous Curie-Weiss behavior of ferroelectric tetragonal tungsten bronzes Ba2RETi2Nb3O15:RE=Nd,Sm  

NASA Astrophysics Data System (ADS)

The ferroelectric tetragonal tungsten bronze (TTB) phases, Ba2RETi2Nb3O15:RE=Nd,Sm, were prepared by low temperature solvothermal synthesis. The permittivity versus temperature data of sintered ceramics show two unusual features: first, a hysteresis of 50-100 °C between values of the Curie temperature Tc on heat-cool cycles and second: a huge depression in the Curie-Weiss temperature T0. Both effects are attributed to the complex nature of their TTB-related crystal structures with different superstructures above and below Tc and the difficulty in nucleating ferroelectric domains on cooling through Tc. Several factors may contribute to the latter difficulty: first, the structures contain two sets of crystallographic sites for the "active" Ti, Nb ions; second, the distribution of Ti and Nb over these two sets of sites is not random but partially ordered; and third, below Tc a weak commensurate superstructure perpendicular to the polar c&barbelow; axis is present, but above Tc a weak incommensurate superstructure in a similar orientation is present. Hence the formation of the ferroelectric structure on cooling requires both nucleation of polar domains involving two sets of cation sites and structural change from an incommensurate to a commensurate supercell.

Prades, Marta; Beltrán, Héctor; Masó, Nahum; Cordoncillo, Eloisa; West, Anthony R.

2008-11-01

198

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

199

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

200

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

SciTech Connect

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

Ou, Xin; Xu, Bo, E-mail: xubonju@gmail.com; Yin, Qiaonan; Xia, Yidong; Yin, Jiang; Liu, Zhiguo [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China)] [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Gong, Changjie; Lan, Xuexin [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)] [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)

2014-05-15

201

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

NASA Astrophysics Data System (ADS)

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 BaTiO3 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 (TNI) and from nematic to smectic-A phase (TNA) 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 TNI and almost unchanged TNA 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.

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

2012-02-01

202

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

203

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

204

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

205

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

206

Depolarization field effect on dielectric and piezoelectric properties of particulate ferroelectric ceramic-polymer composites  

NASA Astrophysics Data System (ADS)

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

Ma, Fengde D.; Wang, Yu U.

2015-03-01

207

Applications of modern ferroelectrics.  

PubMed

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

Scott, J F

2007-02-16

208

Applications of Modern Ferroelectrics  

NASA Astrophysics Data System (ADS)

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

Scott, J. F.

2007-02-01

209

Geometric ferroelectricity in fluoroperovskites  

NASA Astrophysics Data System (ADS)

We used first-principles calculations to investigate the existence and origin of the ferroelectric instability in the ABF3 fluoroperovskites. While the ground states of most ABF3 compounds are paraelectric (Pnma phase), we find that many fluoroperovskites have a ferroelectric instability in their high-symmetry cubic structure that is of similar amplitude to that commonly found in oxide perovskites. In contrast to the oxides, however, the fluorides have nominal Born effective charges, indicating a different mechanism for the instability. We show that the instability originates from ionic size effects, and is therefore in most cases largely insensitive to pressure and strain, again in contrast to the oxide perovskites. An exception is NaMnF3, where coherent epitaxial strain matching to a substrate with equal in-plane lattice constants destabilizes the bulk Pnma structure, leading to a ferroelectric, and indeed multiferroic, ground state with an unusual polarization/strain response.

Garcia-Castro, A. C.; Spaldin, Nicola A.; Romero, A. H.; Bousquet, E.

2014-03-01

210

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

SciTech Connect

We report the results of neutron elastic scattering measurements between -250oC and 620oC on the lead-free relaxor Na1/2Bi1/2TiO3 (NBT). Strong, anisotropic, elastic diffuse scattering intensity decorates the (100), (110), (111), (200), (220), and (210) Bragg peaks at room temperature. The wavevector dependence of this diffuse scattering is compared to that in the lead-based relaxor PbMg1/3Nb2/3O3 (PMN) to determine if any features might be common to relaxors. Prominent ridges in the elastic diffuse scattering intensity contours that extend along <110> are seen that exhibit the same zone dependence as those observed in PMN and other lead-based relaxors. These ridges disappear gradually on heating above the cubic-to-tetragonal phase transition temperature TCT = 523oC, which is also near the temperature at which the dielectric permittivity begins to deviate from Curie-Weiss behavior. We thus identify the <110>-oriented ridges as a relaxor-specific property. The diffuse scattering contours also display narrower ridges oriented along <100> that are consistent with the x-ray results of Kreisel et al. (2003); these vanish below 320oC indicating that they have a different physical origin. The <100>-oriented ridges are not observed in PMN. We observe no equivalent relaxor-specific elastic diffuse scattering from the homovalent relaxor analogues K0.95Li0.05TiO3 (A-site disordered) and KTa0.95Nb0.05O3 (B-site disordered). This suggests that the <110>-oriented diffuse scattering ridges are correlated with the presence of strong random electric fields and invites a reassessment of what defines the relaxor phase. We find that doping NBT with 5.6% BaTiO3, a composition close to the morphotropic phase boundary with enhanced piezoelectric properties, increases the room temperature correlation length along [1 1 0] from 40 to 60 while doubling the associated integrated diffuse scattering. Similar behavior was reported by Matsuura et al. (2006) for compositions of PMN doped with PbTiO3. Finally, we comment on the recent observation of monoclinicity in NBT at room temperature by placing a strict bound on the strength of the ( ) superlattice reflection associated with the Cc space group based on the atomic coordinates published in the x-ray study by Aksel et al. (2011) for NBT. We argue that a skin effect, analogous to that reported in the relaxors PZN and PMN-10%PT, can reconcile our single-crystal data with the powder data of Aksel et al. We believe this represents the first evidence of the relaxor skin effect in a lead-free relaxor.

Ge, Wenwei [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Devreugd, Christopher [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Phelan, Daniel [National Institute of Standards and Technology (NIST), Gaithersburg, MD] [National Institute of Standards and Technology (NIST), Gaithersburg, MD; Zhang, Qinjui [Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS)] [Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS); Muhtar, Aheart [Carnegie Institution of Washington] [Carnegie Institution of Washington; Li, Jiefang [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Luo, Haosu [Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS)] [Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS); Boatner, Lynn A [ORNL] [ORNL; Viehland, Dwight [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Gehring, P. M. [National Institute of Standards and Technology (NIST)] [National Institute of Standards and Technology (NIST)

2013-01-01

211

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

SciTech Connect

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

Li, Yuanyuan; Li, Qiang, E-mail: qiangli@mail.tsinghua.edu.cn; Yan, Qingfeng; Gao, Jinghan; Zhuo, Fangping [Department of Chemistry, Tsinghua University, Beijing 100084 (China); Cao, Wenwu [Condensed Matter Science and Technology Institute, Harbin Institute of Technology, Harbin, Heilongjiang 150080 (China); Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Xi, Xiaoqing; Zhang, Yiling; Chu, Xiangcheng [State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084 (China)

2014-02-03

212

High permittivity 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 relaxor thin films for high-value, wide-temperature capacitor applications  

NASA Astrophysics Data System (ADS)

High permittivity 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMNT) relaxor thin films with a nearly pure perovskite structure as well as a dense and uniform microstructure have been prepared on Pb(Zr,Ti)O3-buffered platinized silicon substrates by sol-gel method. Interestingly, the PMNT thin film exhibits high dielectric permittivity, ?r ˜ 1200, and high dielectric tunability, ˜70% under a moderate E = 333 kV/cm, over a wide temperature range. These results are explained in terms of a relaxor behavior of the PMNT film. Moreover, the leakage current density of the PMNT thin film is reasonably low, roughly 5.2 × 10-6 A/cm2 at an electric field intensity of 400 kV/cm. As the dc electric field increases, the leakage current mechanism is transformed from ohmic law to Fowler-Nordheim tunneling mechanism. All the results obtained indicate that the PMNT relaxor thin film is a good candidate for high-value, wide-temperature capacitor applications.

Zhu, Xiaohong; Defaÿ, Emmanuel; Le Rhun, Gwenaël; Aïd, Marc; Xu, Yunhui; Zhang, Qiang; Xiao, Yunjun; Gao, Haobin; Liang, Dayun; Zhu, Jiliang; Zhu, Jianguo; Xiao, Dingquan

2012-09-01

213

Study of physical properties of integrated ferroelectric/ferromagnetic heterostructures  

SciTech Connect

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

Martinez, R.; Kumar, A. [Department of Physics, University of Puerto Rico, Puerto Rico 00931-3343 (United States); Palai, R.; Katiyar, R. S. [Department of Physics, University of Puerto Rico, Puerto Rico 00931-3343 (United States); Institute for Functional Nanomaterials, University of Puerto Rico, Puerto Rico 00931-3343 (United States); Scott, J. F. [Cavendish Laboratory, Department of Physics, Cambridge University, Cambridge CB3 0HE (United Kingdom)

2010-06-15

214

Domain switching of fatigued ferroelectric thin films  

SciTech Connect

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

Tak Lim, Yun [Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Yeog Son, Jong, E-mail: jyson@khu.ac.kr, E-mail: hoponpop@ulsan.ac.kr [Department of Applied Physics, College of Applied Science, Kyung Hee University, Suwon 446-701 (Korea, Republic of); Shin, Young-Han, E-mail: jyson@khu.ac.kr, E-mail: hoponpop@ulsan.ac.kr [Department of Physics and EHSRC, University of Ulsan, Ulsan 680-749 (Korea, Republic of)

2014-05-12

215

Molecular ferroelectrics: where electronics meet biology.  

PubMed

In the last several years, we have witnessed significant advances in molecular ferroelectrics, with the 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 an overview of the fundamentals of ferroelectricity. The latest developments 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 described. PMID:24018952

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

2013-12-28

216

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

217

Ferroelectric control of magnetic anisotropy.  

PubMed

We demonstrate unambiguous evidence of the electric field control of magnetic anisotropy in a wedge-shaped Co film of varying thickness. A copolymer ferroelectric of 70% vinylidene fluoride with 30% trifluoroethylene, P(VDF-TrFE) overlays the Co wedge, providing a large switchable electric field. As the ferroelectric polarization is switched from up to down, the magnetic anisotropy of the Co films changes by as much as 50%. At the lowest Co thickness the magnetic anisotropy switches from out-of-plane to in-plane as the ferroelectric polarization changes from up to down, enabling us to rotate the magnetization through a large angle at constant magnetic field merely by switching the ferroelectric polarization. The large mismatch in the stiffness coefficients between the polymer ferroelectric and metallic ferromagnet excludes typical magnetoelectric strain coupling; rather, the magnetic changes arise from the large electric field at the ferroelectric/ferromagnet interface. PMID:21823660

Mardana, A; Ducharme, Stephen; Adenwalla, S

2011-09-14

218

Kinetics of nucleation of the ferroelectric transitions in PbMg1/3Nb2/3O3 and PbMg1/3Nb2/3O3-12%PbTiO3  

NASA Astrophysics Data System (ADS)

The nucleation kinetics of the formation of ordered ferroelectric phases from the glassy relaxor states of PbMg1/3Nb2/3O3 (PMN) and of solid solutions of PMN and PbTiO3 is investigated. A delay time, dependent on field and temperature, is found to precede a rather rapid establishment of macroscopic polarization. The qualitative form of the temperature dependence follows prior theory for the lag preceding homogeneous nucleation of a crystal from a glass. However, the increase of the lag time as the "melting" line is approached from below is stronger than expected.

Colla, Eugene V.; Jeliazkov, Jeliazko R.; Weissman, M. B.; Viehland, D. D.; Ye, Zuo-Gang

2014-07-01

219

Semiconductor/relaxor 0-3 type composites without thermal depolarization in Bi0.5Na0.5TiO3-based lead-free piezoceramics.  

PubMed

Commercial lead-based piezoelectric materials raised worldwide environmental concerns in the past decade. Bi0.5Na0.5TiO3-based solid solution is among the most promising lead-free piezoelectric candidates; however, depolarization of these solid solutions is a longstanding obstacle for their practical applications. Here we use a strategy to defer the thermal depolarization, even render depolarization-free Bi0.5Na0.5TiO3-based 0-3-type composites. This is achieved by introducing semiconducting ZnO particles into the relaxor ferroelectric 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 matrix. The depolarization temperature increases with increasing ZnO concentration until depolarization disappears at 30 mol% ZnO. The semiconducting nature of ZnO provides charges to partially compensate the ferroelectric depolarization field. These results not only pave the way for applications of Bi0.5Na0.5TiO3-based piezoceramics, but also have great impact on the understanding of the mechanism of depolarization so as to provide a new design to optimize the performance of lead-free piezoelectrics. PMID:25790446

Zhang, Ji; Pan, Zhao; Guo, Fei-Fei; Liu, Wen-Chao; Ning, Huanpo; Chen, Y B; Lu, Ming-Hui; Yang, Bin; Chen, Jun; Zhang, Shan-Tao; Xing, Xianran; Rödel, Jürgen; Cao, Wenwu; Chen, Yan-Feng

2015-01-01

220

The dielectric relaxation behavior of (Na0.82K0.18)0.5Bi0.5TiO3 ferroelectric thin film  

NASA Astrophysics Data System (ADS)

(Na1-xKx)0.5Bi0.5TiO3 (NBT-KBT-100 x) thin films were deposited on Pt/Ti/SiO2/Si(100) by metal organic decomposition, and the effects of potassium content (x = 0.15, 0.18, 0.20, 0.25) on ferroelectric, piezoelectric, dielectric properties of the thin films, and the temperature dependence of dielectric permittivity of NBT-KBT-18 thin film were investigated in detail. NBT-KBT-18 thin film is of the largest effective piezoelectric coefficient d33eff, remnant polarization 2Pr, spontaneous polarization 2 Ps, dielectric constant ?r, and the lowest dielectric loss among the thin films. The dielectric constants decrease steeply with the increase of frequency, and there are a series of resonance peaks with Debye-like relaxation. In dielectric temperature spectra, two abnormal peaks corresponding to depolarization temperature and Curie temperature are at the range of 75-90 °C and 295-320 °C, and they are associated with the phase transitions. Based on the dielectric relaxation theory, Debye-like relaxation and diffused phase transition/frequency dispersion are interpreted by space charge polarization and polar nanoregions. Because of the centrosymmetric paraelectric phase, the 2 Ps and ?r of NBT-KBT-100 x thin film are responsible for the d33eff according to phenomenological equation. The improved d33eff may make NBT-KBT-18 thin film a promising candidate for piezoelectric thin film devices, and the enhanced Curie temperature will offer useful guidelines of safe working temperature for potential application in micro-electro-mechanical system.

Dong, H.; Zheng, X. J.; Li, W.; Gong, Y. Q.; Peng, J. F.; Zhu, Z.

2011-12-01

221

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

222

Characterization of a Common-Source Amplifier Using Ferroelectric Transistors  

NASA Technical Reports Server (NTRS)

This paper presents empirical data that was collected through experiments using a FeFET in the established common-source amplifier circuit. The unique behavior of the FeFET lends itself to interesting and useful operation in this widely used common-source amplifier. The paper examines the effect of using a ferroelectric transistor for the amplifier. It also examines the effects of varying load resistance, biasing, and input voltages on the output signal and gives several examples of the output of the amplifier for a given input. The difference between a commonsource amplifier using a ferroelectric transistor and that using a MOSFET is addressed.

Hunt, Mitchell; Sayyah, Rana; MacLeond, Todd C.; Ho, Pat D.

2010-01-01

223

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

NASA Astrophysics Data System (ADS)

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 ACr2O4 polycrystalline samples (A=Ni, Fe, Co). The presence of a Jahn-Teller cation such as Ni2+ at the A site is shown to yield larger polarization values. In the delafossites, substitution by V3+ at the Cr or Fe site in CuCrO2 (CuFeO2) 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.

Maignan, A.; Martin, C.; Singh, K.; Simon, Ch.; Lebedev, O. I.; Turner, S.

2012-11-01

224

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

SciTech Connect

NaNbO{sub 3} thin films have been grown under anisotropic biaxial strain on several oxide substrates by liquid-delivery spin metalorganic chemical vapor deposition. Compressive lattice strain of different magnitude, induced by the deposition of NaNbO{sub 3} films with varying film thickness on NdGaO{sub 3} single crystalline substrates, leads to modifications of film orientation and phase symmetry, which are similar to the phase transitions in Pb-containing oxides near the morphotropic phase boundary. Piezoresponse force microscopy measurements exhibit large out-of-plane polarization components, but no distinctive domain structure, while C-V measurements indicate relaxor properties in these films. When tensile strain is provoked by the epitaxial growth on DyScO{sub 3}, TbScO{sub 3}, and GdScO{sub 3} single crystalline substrates, NaNbO{sub 3} films behave rather like a normal ferroelectric. The application of these rare-earth scandate substrates yields well-ordered ferroelectric stripe domains of the type a{sub 1}/a{sub 2} with coherent domain walls aligned along the [001] substrate direction as long as the films are fully strained. With increasing plastic lattice relaxation, initially, a 2D domain pattern with still exclusively in-plane electric polarization, and finally, domains with in-plane and out-of-plane polar components evolve.

Schwarzkopf, J., E-mail: jutta.schwarzkopf@ikz-berlin.de; Braun, D.; Schmidbauer, M.; Duk, A. [Leibniz-Institute for Crystal Growth, Max-Born-Str. 2, 12489 Berlin (Germany); Wördenweber, R. [Forschungszentrum Jülich, Peter Grünberg Institute, Jülich (Germany)

2014-05-28

225

RELAXATIONAL PROPERTIES OF LAYERED FERROELECTRICS CaBi1.5 La0.5Nb2O9  

Microsoft Academic Search

CaBi1.5La0.5Nb2O9 ceramics were prepared by a conventional solid-state reaction method. Their structure and dielectric properties were investigated. X-ray diffraction analysis indicated that single phase layered perovskites were obtained. Dielectric studies demonstrated that CaBi1.5La0.5Nb2O9 is characteristic of relaxor ferroelectrics. The dielectric relaxation of CaBi1.5La0.5Nb2O9 was modeled using the Vögel-Fulcher relationship, and the dielectric relaxation in CaBi1.5La0.5Nb2O9 is found to be analogous

SHIMING HUANG; MU GU; XIAOLIN LIU; BO LIU; CHEN NI

2008-01-01

226

Electron emission from ferroelectrics  

NASA Astrophysics Data System (ADS)

Ferroelectric emission (FE) was discovered at CERN in 1988. However, a diverse array of results and explanations concerning FE have appeared. This dissertation focused on understanding the influence of material properties and external parameters on this complex process. The sample preparation, pulse generator and other experimental techniques are described. Plasma emission (PE), FE and mixed PE and FE were observed and described. The field enhancement at the electrode-dielectric-vacuum triple point was suggested to be the basis for PE. An apparent delay time, instability, visible light generation and strong electrode erosion are features of PE. Comparatively, FE does not require an extraction field, exhibits no apparent delay time and a relatively stable emission, and generates either no or a very weak light signal. A direct relationship between the switching current and emission current exists for the FE. Different FE characteristics of antiferroelectric PLZT 2/95/5, "normal" ferroelectric PLZT 8/65/35 and nonferroelectric PLZT 15/65/35 were described. The strong relationship between the emission and switching current was demonstrated. Repeatable emission is exhibited by 2/95/5, which can also be pulsed at high frequency due to its fast antiferroelectric <=> ferroelectric phase transition. The strong degradation of FE from 8/65/35 was attributed to decrease in the remanent polarization. While no emission signal was detected from 15/65/35, which can be interpreted as an additional evidence that electron emission from the above two PLZT was indeed FE process. Based on the field and domain switching distribution model, sample geometry effect on FE was predicted, and verified using the results from different groups. Electron emission energy distribution of PLZT 8/65/35 showed a very narrow energy distribution (FWHM ? 10 eV to 20 eV), and the emission energy was on the order of the applied pulse potential. The possible application of FE for emissive flat panel displays was discussed compared to the mature technology based on field emitters.

Zhang, Weiming

227

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

228

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

229

Conductivity and interfacial charge induced phenomena in ferroelectric films and composites  

NASA Astrophysics Data System (ADS)

Ferroelectric materials are polar dielectrics which normally possess small but finite electrical conductivity. We believe that conductivity in ferroelectrics can induce new phenomena or modify known physical phenomena, which may be difficult to understand if the materials are regarded as perfectly insulating. In this thesis, some "anomalous" phenomena are investigated for which the origins are still under debate in literature, and we suggest that these may very well be manifestations of electrical conduction and electric charges. Ferroelectric systems of interest to this investigation include composites and films. Electrical conductivity in ferroelectric composites allows free charge to accumulate at the matrix-inclusion interfaces. We focus on the role of interfacial charge at such interfaces in ferroelectric 0--3 composites (normally, ferroelectric ceramic inclusions dispersed in polymer matrices) in the interpretation of their peculiar experimental results. The effect of interfacial charge on the piezoelectric properties of ferroelectric 0--3 composites and the effect of electrical conductivity on their dielectric and piezoelectric properties are also investigated. Our previously developed model has been extended to include the additional contribution from the deformation of the inclusion particles (for discussing the effect of interfacial charge) due to the applied stresses in piezoelectric measurements, and for discussing the effect of conductivity to include its contribution as well as the frequency of measurement. Phenomena induced by electrical conductivity in other ferroelectric systems have also been studied. We consider the effects of electrical conductivity on the dynamic polarization behavior of ferroelectric films. Using a parallelogram-like P-E hysteresis model for the film material, explicit expressions are obtained for describing the D-E loops of ferroelectric films as would be measured from a Sawyer-Tower circuit which originally assumes the measured sample is insulating. The calculation shows that resistive losses inflate the ferroelectric loop to a varying extent. Theoretical simulations have also been performed to study the anomalously large polarization shift behavior in compositionally graded ferroelectric films and the bias field dependent dielectricity of ferroelectric thin films. The model is capable of modeling saturated and unsaturated hysteresis behavior under arbitrary fields. (Abstract shortened by UMI.)

Wong, Chung Kwan

2005-11-01

230

Ferroelectrics in uncooled thermal imaging  

NASA Astrophysics Data System (ADS)

Uncooled Thermal Imaging (TI) in the UK involves large arrays of ferroelectric bolometer elements, at a pitch of from 100 micrometer down to 40 micrometer. A Hybrid Array Technology, exploiting the pyroelectric property of ferroelectric ceramic materials for the bolometer elements, has produced a range of successful solder bump bonded 2-D arrays. However, in innovative technologies under research, direct deposition of the ferroelectric material as a thin film onto suitable thermal microstructures on the silicon readout IC will provide substantial reductions in costs as well as improved performance. A route has been defined for this Integrated Array Technology, leading to performance enhancements by a factor of three over the Hybrids. In achieving the performance, the optimized ferroelectric signal readout, signal conditioning and processing architectures perfected for the Hybrid Arrays will be retained. Microscan mechanisms, readily incorporated in the IR chopped format used with ferroelectric imaging, have been demonstrated for the Hybrids, and will be even more closely matched to the improved thermal diffusion MTF of the Integrated devices. The ferroelectric capacitative detector filters the high frequencies, limiting noise bandwidths for very large arrays, and with microscan technology added, the ferroelectric arrays retain their potential to provide high quality IR imaging at very large equivalent array sizes.

Watton, Rex; Manning, Paul A.

1998-10-01

231

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

232

Glasses with ferroelectric phases  

NASA Astrophysics Data System (ADS)

Glasses ceramics, with ferroelectric phases embedded in the glass matrix, were prepared by the melt- quenching through heat-treatments (HT) of silicate, borate and phosphate glasses. Some glasses were heat-treated with the application of an external electric field (TET). The structure and morphology of the samples were studied by X-ray powder diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The dielectric properties, in function of frequency and temperature, were studied and discussed through a three serial of a resistance in parallel with a constant phase element (CPE), two related with the sample surfaces and one with the bulk material, showing that the bulk has the major contribution for the dielectrical characteristics. The temperature dependence of the dc electrical conductivity (?dc), the thermally stimulated depolarization current (TSDC), and the ac conductivity (?ac), measured at 1 kHz, were used to characterize the samples. The structure, the dielectric properties and the electrical conductivity reflect the important role carried out by the base glass the heat-treatment and the electric field during the HT and the ferroelectric phases in the properties of glass-ceramics.

Valente, M. A.; Graça, M. P. F.

2009-07-01

233

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

234

Striking similarity of ferroelectric aging effect in tetragonal, orthorhombic and rhombohedral crystal structures  

NASA Astrophysics Data System (ADS)

A series of Mn-doped alkaline niobate-based and lead zirconic titanate ferroelectrics that possess tetragonal, orthorhombic, and rhombohedral perovskite structures was fabricated, and the aging behavior of their hysteresis loop and electrostrain was studied. We found that after aging, all the samples showed a similar double hysteresis loop and large recoverable electrostrain behavior, regardless of their crystal structure and of their ionic species. The striking similarity of the aging effect in different ferroelectric phases suggests that there exists a common physical origin of aging in ferroelectric perovskites. Based on a symmetry-conforming short-range ordering mechanism of point defects, we provided a unified microscopic explanation for the aging effect in the tetragonal, orthorhombic, and rhombohedral ferroelectrics.

Feng, Zuyong; Ren, Xiaobing

2008-04-01

235

Advanced fabrication and characterization of epitaxial ferroelectric thin films and multilayers.  

PubMed

Understanding the behavior of ferroelectrics on the nanoscale level requires the production of materials of the highest quality and advanced characterization techniques for probing the fascinating properties of these systems with reduced dimensions. Here we give an overview of our recent achievements in this area, which includes the detailed study of the suppression of ferroelectricity in PbTiO3 thin films, the fabrication of PbTiO3/SrTiO3 superlattices in which ferroelectricity shows some surprising behavior, and finally the manipulation of nanoscale ferroelectric domains using the atomic force microscope which leads to the precise analysis of domain wall creep and roughness in Pb(Zr,Ti)O3 thin films. PMID:17186905

Dawber, Matthew; Lichtensteiger, Céline; Paruch, Patrycja; Triscone, Jean-Marc

2006-12-01

236

Relaxor-PbTiO3 Single Crystals for Various Applications  

PubMed Central

Piezoelectric materials lie at the heart of electromechanical devices. Applications include actuators, ultrasonic imaging, high intensity focused ultrasound, underwater ultrasound, nondestructive evaluation transducer, pressure sensors, and accelerometers, to name a few. In this work, the advantages and disadvantages of relaxor-PbTiO3-based single crystals are discussed, based on the requirements (figure of merit) of various applications, with emphasis on recent developments of the shear properties of single crystals as a function of temperature and applied fields. PMID:25004527

Zhang, Shujun; Li, Fei; Luo, Jun; Sahul, Raffi; Shrout, Thomas R.

2014-01-01

237

Ferroelectric capacitor with reduced imprint  

DOEpatents

An improved ferroelectric capacitor exhibiting reduced imprint effects in comparison to prior art capacitors. A capacitor according to the present invention includes top and bottom electrodes and a ferroelectric layer sandwiched between the top and bottom electrodes, the ferroelectric layer comprising a perovskite structure of the chemical composition ABO.sub.3 wherein the B-site comprises first and second elements and a dopant element that has an oxidation state greater than +4. The concentration of the dopant is sufficient to reduce shifts in the coercive voltage of the capacitor with time. In the preferred embodiment of the present invention, the ferroelectric element comprises Pb in the A-site, and the first and second elements are Zr and Ti, respectively. The preferred dopant is chosen from the group consisting of Niobium, Tantalum, and Tungsten. In the preferred embodiment of the present invention, the dopant occupies between 1 and 8% of the B-sites.

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

1997-01-01

238

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

239

Ferroelectric infrared detector and method  

DOEpatents

An apparatus and method are provided for sensing infrared radiation. The apparatus includes a sensor element that is positioned in a magnetic field during operation to ensure a .lamda. shaped relationship between specific heat and temperature adjacent the Curie temperature of the ferroelectric material comprising the sensor element. The apparatus is operated by inducing a magnetic field on the ferroelectric material to reduce surface charge on the element during its operation.

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

2010-03-30

240

Programmable ferroelectric tunnel memristor  

NASA Astrophysics Data System (ADS)

We report an analogously programmable memristor based on genuine electronic resistive switching combining ferroelectric switching and electron tunneling. The tunnel current through an 8 unit cell thick epitaxial Pb(Zr[0.2]Ti[0.8])O[3] film sandwiched between La[0.7]Sr[0.3]MnO[3] and cobalt electrodes obeys the Kolmogorov-Avrami-Ishibashi model for bidimensional growth with a characteristic switching time in the order of 10^-7 seconds. The analytical description of switching kinetics allows us to develop a characteristic transfer function that has only one parameter viz. the characteristic switching time and fully predicts the resistive states of this type of memristor.

Quindeau, Andy; Hesse, Dietrich; Alexe, Marin

2014-02-01

241

Block copolymer/ferroelectric nanoparticle nanocomposites  

E-print Network

surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes or similar to one of the blocks in the BCP for the surface functionalization of NPs.12 Barium titanate (Ba

Lin, Zhiqun

242

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

243

Improved Ferroelectric Memories With Nondestructive Readout  

NASA Technical Reports Server (NTRS)

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

Thakoor, Sarita; Thakoor, Anil P.

1994-01-01

244

Lead Titanate Based Ferroelectric Superlattices with Conventional and Novel Dielectric Components  

NASA Astrophysics Data System (ADS)

Within the family of oxide materials which have a perovskite structure there are many different types of materials: ferroelectrics, metals, ferromagnets and antiferromagnets, superconductors, and dielectric insulators. Ferroelectric materials are those with a switchable, spontaneous electric polarization and by combining them with other perovskite oxides in a superlattice structure, the properties of the system can be tailored by exploiting competition between the interacting properties of the constituent materials. In ferroelectric/dielectric superlattices important structural and functional properties of the system can be tailored by the relative thicknesses of the ferroelectric and non-ferroelectric layers. In PbTiO3/SrTiO 3 superlattice SrTiO3, an insulator, plays the role of a conventional dielectric. Ferroelectric stripe domains in this system were investigated and it was found that the domain periodicity as a function of PbTiO3 layer thickness displays a scaling relation which raises interesting questions about the Kittel Scaling law as applied to ferroelectric superlattices. In addition to the static properties of the domains the evolution of domain structure under electric field was studied by time-resolved x-ray studies at the APS. A second system, PbTiO3/SrRuO3, uses SrRuO 3, which is normally metallic in bulk but displays insulating behavior in the ultrathin limit, as a novel dielectric component to create superlattices that display an out-of-plane ferroelectric polarization. The incorporation of SrRuO3 also breaks inversion symmetry at the interface between the two materials, which affects the ferroelectric double-well energy potential and the system's dielectric properties. The transport properties of this system are also of interest, with anisotropic conductivity and resonant tunneling between layers. This was investigated by electrical measurements and photoemission studies performed at NSLS U13.

Callori, Sara Jane

245

Optimization of Ferroelectric Ceramics by Design at the Microstructure Level  

SciTech Connect

Ferroelectric materials show remarkable physical behaviors that make them essential for many devices and have been extensively studied for their applications of nonvolatile random access memory (NvRAM) and high-speed random access memories. Although ferroelectric ceramics (polycrystals) present ease in manufacture and in compositional modifications and represent the widest application area of materials, computational and theoretical studies are sparse owing to many reasons including the large number of constituent atoms. Macroscopic properties of ferroelectric polycrystals are dominated by the inhomogeneities at the crystallographic domain/grain level. Orientation of grains/domains is critical to the electromechanical response of the single crystalline and polycrystalline materials. Polycrystalline materials have the potential of exhibiting better performance at a macroscopic scale by design of the domain/grain configuration at the domain-size scale. This suggests that piezoelectric properties can be optimized by a proper choice of the parameters which control the distribution of grain orientations. Nevertheless, this choice is complicated and it is impossible to analyze all possible combinations of the distribution parameters or the angles themselves. Hence we have implemented the stochastic optimization technique of simulated annealing combined with the homogenization for the optimization problem. The mathematical homogenization theory of a piezoelectric medium is implemented in the finite element method (FEM) by solving the coupled equilibrium electrical and mechanical fields. This implementation enables the study of the dependence of the macroscopic electromechanical properties of a typical crystalline and polycrystalline ferroelectric ceramic on the grain orientation.

Jayachandran, K. P.; Guedes, J. M.; Rodrigues, H. C. [IDMEC-IST, Technical University of Lisbon, Mechanical Engineering, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)

2010-05-21

246

Compact modelling of ferroelectric tunnel memristor and its use for neuromorphic simulation  

NASA Astrophysics Data System (ADS)

Ferroelectric tunnel memristor (FTM) was recently discovered. Its resistance can be continuously tuned by controlling the growth of domain in ferroelectric tunnel barrier. Experiments show its large OFF/ON resistance ratio (>102) and high operation speed (˜10 ns), providing great potential to build up multi-level storage and neuromorphic circuits. However, the corresponding electrical model for circuit simulation is still lacking. In this Letter, we developed a compact model for a voltage-controlled ferroelectric tunnel memristor based on experimental results and ferroelectric switching dynamics. The memristive behavior of this model was demonstrated by resistance measurements as a function of the amplitude and duration of programming voltage pulses, and the accuracy was validated by the relative good agreement between simulation results and experimental measurement. Our model was used to simulate a FTM-based spike-timing dependent plasticity circuit to show its use in neuromorphic circuits.

Wang, Zhaohao; Zhao, Weisheng; Kang, Wang; Zhang, Yue; Klein, Jacques-Olivier; Ravelosona, Dafiné; Chappert, Claude

2014-02-01

247

Defect-mediated polarization switching in ferroelectrics and related materials: from mesoscopic mechanisms to atomistic control  

SciTech Connect

The plethora of lattice and electronic behaviors in ferroelectric and multiferroic materials and heterostructures opens vistas into novel physical phenomena including magnetoelectric coupling and ferroelectric tunneling. The development of new classes of electronic, energy-storage, and information-technology devices depends critically on understanding and controlling field-induced polarization switching. Polarization reversal is controlled by defects that determine activation energy, critical switching bias, and the selection between thermodynamically equivalent polarization states in multiaxial ferroelectrics. Understanding and controlling defect functionality in ferroelectric materials is as critical to the future of oxide electronics and solid-state electrochemistry as defects in semiconductors are for semiconductor electronics. Here, recent advances in understanding the defect-mediated switching mechanisms, enabled by recent advances in electron and scanning probe microscopy, are discussed. The synergy between local probes and structural methods offers a pathway to decipher deterministic polarization switching mechanisms on the level of a single atomically defined defect.

Kalinin, Sergei V [ORNL; Rodriguez, Brian J [ORNL; Baddorf, Arthur P [ORNL; Balke, Nina [ORNL; Borisevich, Albina Y [ORNL; Chang, Hye Jung [ORNL; Chen, Long-Qing [Pennsylvania State University; Jesse, Stephen [ORNL; Maksymovych, Petro [ORNL; Nikiforov, Maxim [ORNL; Pennycook, Stephen J [ORNL

2010-01-01

248

Dual nature of the ferroelectric and metallic state in LiOsO3  

NASA Astrophysics Data System (ADS)

Using density functional theory we investigate the lattice instability and electronic structure of recently discovered ferroelectric metal LiOsO3. We show that the ferroelectric-like lattice instability is related to the Li-O distortion modes while the Os-O displacements change the d -p hybridization as in common ferroelectric insulators. Within the manifold of the d orbitals, a dual behavior emerges. In the ferroelectric transition the empty eg orbitals change their hybridization with the oxygen p orbitals, while the t2 g orbitals are responsible for the metallic response. Interestingly, these orbitals are nominally half filled by three electrons, a configuration which suffers from strong correlation effects even for moderate values of the screened Coulomb interaction.

Giovannetti, Gianluca; Capone, Massimo

2014-11-01

249

Molecular Orientation Dynamics of Polymer-Stabilized Ferroelectric Liquid Crystals  

Microsoft Academic Search

The dynamic behavior of ferroelectric liquid crystal molecules can be studied in terms of the phase difference angle and the angle of the relative amplitude ratio of elliptically polarized light, measured by time-resolved transmission ellipsometry. It has been known that the phase difference angle and the angle of the relative amplitude ratio indicate qualitatively the out-of-plane and in-plane molecular rotations

Hirokazu Furue; Mizuho Gonda; Jun Hatano

2005-01-01

250

Ferroelectric memory based on nanostructures.  

PubMed

In the past decades, ferroelectric materials have attracted wide attention due to their applications in nonvolatile memory devices (NVMDs) rendered by the electrically switchable spontaneous polarizations. Furthermore, the combination of ferroelectric and nanomaterials opens a new route to fabricating a nanoscale memory device with ultrahigh memory integration, which greatly eases the ever increasing scaling and economic challenges encountered in the traditional semiconductor industry. In this review, we summarize the recent development of the nonvolatile ferroelectric field effect transistor (FeFET) memory devices based on nanostructures. The operating principles of FeFET are introduced first, followed by the discussion of the real FeFET memory nanodevices based on oxide nanowires, nanoparticles, semiconductor nanotetrapods, carbon nanotubes, and graphene. Finally, we present the opportunities and challenges in nanomemory devices and our views on the future prospects of NVMDs. PMID:22655750

Liu, Xingqiang; Liu, Yueli; Chen, Wen; Li, Jinchai; Liao, Lei

2012-01-01

251

Ferroelectric memory based on nanostructures  

PubMed Central

In the past decades, ferroelectric materials have attracted wide attention due to their applications in nonvolatile memory devices (NVMDs) rendered by the electrically switchable spontaneous polarizations. Furthermore, the combination of ferroelectric and nanomaterials opens a new route to fabricating a nanoscale memory device with ultrahigh memory integration, which greatly eases the ever increasing scaling and economic challenges encountered in the traditional semiconductor industry. In this review, we summarize the recent development of the nonvolatile ferroelectric field effect transistor (FeFET) memory devices based on nanostructures. The operating principles of FeFET are introduced first, followed by the discussion of the real FeFET memory nanodevices based on oxide nanowires, nanoparticles, semiconductor nanotetrapods, carbon nanotubes, and graphene. Finally, we present the opportunities and challenges in nanomemory devices and our views on the future prospects of NVMDs. PMID:22655750

2012-01-01

252

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

253

Temperature dependence scaling behavior of the dynamic hysteresis in 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 ferroelectric ceramics  

NASA Astrophysics Data System (ADS)

Temperature dependent dynamic hysteresis of 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 (BNT-BT-ST) bulk ferroelectric ceramic was systematically studied. The scaling relations were estimated for corrective electric field ({{E}c}), remnant polarization ({{P}r}) and hysteresis loop area ?ft( ?ft< A \\right> \\right) as a function of temperature ?ft( T \\right). It was observed that {{E}c}\\propto {{T}-0.6396}, {{P}r}\\propto {{T}-0.6849} and ?ft< A \\right> \\propto {{T}-0.6446} for a constant magnitude of electric field ?ft( E \\right). To understand the domain dynamics, back-switching polarization as a function of T is also predicted. The relation between back-switching polarization and temperature is estimated by well described Arrhenius law to evaluate the average activation energy. It also depends on the applied electric field; the relation fits well to a simple exponential decay function. The saturation polarization as a function of T was also evaluated to estimate the electrocaloric effect. It was found that electrocaloric effect and heat extract capacity in BNT-BT-ST ceramic is of a similar order to that observed in most other lead-free bulk ferroelectric ceramics. It can be said that BNT-BT-ST is also a promising material for solid state refrigeration. These results can be helpful to understand the temperature dependent hysteresis behavior and polarization switching in lead-free ferroelectric ceramics.

Patel, Satyanarayan; Chauhan, Aditi; Chauhan, Aditya; Vaish, Rahul

2015-03-01

254

Recent patents on perovskite ferroelectric nanostructures.  

PubMed

Ferroelectric oxide materials with a perovskite structure have promising applications in electronic devices such as random access memories, sensors, actuators, infrared detectors, and so on. Recent advances in science and technology of ferroelectrics have resulted in the feature sizes of ferroelectric-based electronic devices entering into nanoscale dimensions. At nanoscale perovskite ferroelectric materials exhibit a pronounced size effect manifesting itself in a significant deviation of the properties of low-dimensional structures from the bulk and film counterparts. One-dimensional perovskite ferroelectric nanotube/nanowire systems, offer fundamental scientific opportunities for investigating the intrinsic size effects in ferroelectrics. In the past several years, much progress has been made both in fabrication and physical property testing of perovskite ferroelectric nanostructures. In the first part of this paper, the recent patents and literatures for fabricating ferroelectric nanowires, nanorods, nanotubes, and nanorings with promising features, are reviewed. The second part deals with the recent advances on the physical property testing of perovskite ferroelectric nanostructures. The third part summarizes the recently patents and literatures about the microstructural characterizations of perovskite ferroelectric nanostructures, to improve their crystalline quality, morphology and uniformity. Finally, we conclude this review with personal perspectives towards the potential future developments of perovskite ferroelectric nanostructures. PMID:19149754

Zhu, Xinhua

2009-01-01

255

Terahertz sensing using ferroelectric nanowires.  

PubMed

Molecular dynamics simulations are used to study the interaction of ferroelectric nanowires with terahertz (THz) Gaussian-shaped pulses of electric field. The computational data indicate the existence of two interaction scenarios that are associated with 'lossless' and dissipative, or 'lossy', interaction mechanisms. A thermodynamical approach is used to analyze the computational data for a wide range of THz pulses. The analysis establishes the foundation for understanding the nanowires' response to the THz pulses and reveals the potential of ferroelectric nanowires to function as nanoscale sensors of THz radiation. Various aspects of this THz nanosensing are analyzed and discussed. PMID:23299283

Herchig, R; Schultz, Kimberly; McCash, Kevin; Ponomareva, I

2013-02-01

256

Ferroelectric Fluid Flow Control Valve  

NASA Technical Reports Server (NTRS)

An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.

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

1999-01-01

257

Coupling of Magnetic and Ferroelectric Order Parameters in Improper Ferroelectrics  

NASA Astrophysics Data System (ADS)

This talk concerns systems for which the onset of incommensurate magnetic order induces ferroelectricity. I review how Landau theory [1,2] provided a convenient phenomenological explanation of this phenomenon. In the simplest and most frequent scenario, as the temperature is lowered, one first induces collinear incommensurate magetic order. At a lower temperature transition, transverse magnetic components appear and these two different symmetry magnetic order parameters combine to induce ferroelectricity via a trilinear magnetoelectric coupling. I will present several examples of this mechanism, subsequently discussed by Mostovoy[3] within a model of spiral magnetic order. Landau theory also explains [4] a contrasting scenario in which ferroelectric and magnetic can order within a single phase transition as in RbFe(MoO4)2, whose magnetic spiral contradicts the Mostovoy construction, but which Kaplan[5] has subsequently shown to be consistent with a more complete symmetry analysis of microscopic interactions. Other more exotic higher order magnetoelectric couplings, not easily accessible to an analysis of microscopic interactions, are also possible, especially in the presence of nonuniform magnetic order. I close with a few remarks on microscopic models for magnetically induced ferroelectricity. [4pt] [1] G. Lawes et al. PRL 95, 087205 (2005).[2] M. Kenzelmann et al., PRL 95, 087206 (2005).[3] Mostotovy, PRL 96, 067201 (2006).[4] M. Kenzelmann et al., PRL 98, 267205 (2007).[5] T. Kaplan et al, PRB 83, 174432 (2011)

Harris, A. Brooks

2013-03-01

258

Atomic Polarization and Local Reactivity on Ferroelectric Surfaces: Ferroelectric Nanolithography  

Microsoft Academic Search

In order to realize the potential inherent in nanodevices, methods of assembling a wide range of dissimilar elements, connecting the resulting complex structures, and integrating them into systems must be developed. There is a need control structural elements with diverse properties, locating them in pre defined positions. We report here a novel approach that controls local reactivity of ferroelectric surfaces

Dawn Bonnell

2004-01-01

259

Relaxor-like dielectric response of spin liquid CuCrO{sub 2}  

SciTech Connect

Broadband dielectric analysis (10{sup ?2}-10{sup 7} Hz) of layered triangular lattice CuCrO{sub 2} is performed (123 K - 473 K) and analyzed in connection with recently observed spin frustration in this multiferroic [M. Poienar et al. Phys. Rev. B 81, 104411, (2010); M. Frontzek et al. Phys. Rev. B 84, 094448, (2011)]. Most unexpectedly, this well known delafossite has found to have nontrivial charge degrees of freedom, being characterized by a relaxor-like dielectric relaxation around 375 K with FWHM of ?100K. The result strongly suggests the existence of intermolecular Coulomb interaction between charge disproportionation induced electric dipoles.

Mazumder, N., E-mail: nileshmazumder@gmail.com; Roy, R. [Physics Department, Jadavpur University, Kolkata-700032 (India); Ghorai, U. K.; Saha, S. [School of Materials Science and Nanotechnology, Jadavpur University, Kolkata-700032 (India); Chattopadhyay, K. K., E-mail: kalyan-chattopadhyay@yahoo.com [Physics Department, Jadavpur University, Kolkata-700032, India and School of Materials Science and Nanotechnology, Jadavpur University, Kolkata-700032 (India)

2014-04-24

260

Strong coupling of ferroelectricity and magnetism in the hexagonal ferrites  

NASA Astrophysics Data System (ADS)

During the last decade one of the most extensively studied class of multiferroics has been the hexagonal rare-earth manganites RMnO3 where R=Dy-Lu, Y, Sc. These compounds exhibit antiferromagnetic (AFM) order with a Néel temperature TN 100 K. In addition, they are improper ferroelectrics (TC> 1200K) driven a by zone-tripling structural distortion associated with a buckling of the R-planes and a rotation of the oxygen trigonal bipyramids. The improper nature of the transition is responsible for the fascinating, topologically protected trimer-domains. Even though magnetism and ferroelectricity in these materials are not intrinsically coupled, there is a non-trivial interaction between the structural and magnetic domain walls. In contrast to the manganites, the ground state structure of the rare-earth ferrites RFeO3 is the orthorhombic perovskite. Recently, however, thin films of RFeO3 have been epitaxially stabilized in the hexagonal rare-earth manganite structure. This development has triggered several new studies of these hexagonal ferrite systems. Similar to manganites, ferrites exhibit ferroelectricity above room temperature and crystallize in P63cm polar structure but conflicting results have been reported as to the origin of ferroelectricity in these materials. Unlike the manganites, recent neutron diffraction measurements suggest a considerably high AFM ordering temperature, TN=440 K. Additionally there is an indication of a second temperature, TwFM˜100K, at which weak ferromagnetism has been observed. In this work my collaborators (Alex Wysocki and Craig J. Fennie) and I address the nature of ferroelectricity and magnetic order in the RFeO3 systems from first-principles. We elucidate the origin of ferroelectricity in the rare-earth ferrites and provide many useful insights into their magnetic behavior, which we will show is fundamentally different than that observed in the manganites. Combining first-principles calculations with a detailed modeling of the magnetic structure we will also show how this difference leads to an interplay between ferroelectricity and magnetism in the ferrites. This strong coupling, absent in the hexagonal manganites, manifests itself in a nontrivial way that may be useful for voltage controlled magnetic functionalities.

Das, Hena

2013-03-01

261

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

SciTech Connect

Memory and switching devices acquired new materials which exhibit ferroelectric and ferromagnetic order simultaneously. We reported multiferroic behavior in Zn{sub 1?y}Li{sub y}O(0.00?y?0.10) nanoparticles. The analysis of transmission electron micrographs confirmed the hexagonal morphology and wurtzite crystalline structure. We investigated p-type conductivity in doped samples and measured hole carriers in range 2.4?×?10{sup 17}/cc to 7.3?×?10{sup 17}/cc for different Li contents. We found that hole carriers are responsible for long range order ferromagnetic coupling in Li doped samples. Room temperature ferroelectric hysteresis loops were observed in 8% and 10% Li doped samples. We demonstrated ferroelectric coercivity (remnant polarization) 2.5?kV/cm (0.11 ?C/cm{sup 2}) and 2.8?kV/cm (0.15 ?C/cm{sup 2}) for y?=?0.08 and y?=?0.10 samples. We propose that the mechanism of Li induced ferroelectricity in ZnO is due to indirect dipole interaction via hole carriers. We investigated that if the sample has hole carriers ?5.3?×?10{sup 17}/cc, they can mediate the ferroelectricity. Ferroelectric and ferromagnetic measurements showed that higher electric polarization and larger magnetic moment is attained when the hole concentration is larger and vice versa. Our results confirmed the hole dependent coexistence of ferromagnetic and ferroelectric behavior at room temperature, which provide potential applications for switchable and memory devices.

Awan, Saif Ullah, E-mail: saifullah@comsats.edu.pk, E-mail: ullahphy@gmail.com [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan); Hasanain, S. K. [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Anjum, D. H. [Advanced Nanofabrication, Imaging and Characterization Core Lab (ANIC), King Abdullah University of Science and Technology (KAUST), Thuwal, Makkah 23599-6900 (Saudi Arabia); Awan, M. S. [Center for Micro and Nano Devices, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan); Shah, Saqlain A. [Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195 (United States)

2014-10-28

262

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

263

Ionic field effect and memristive phenomena in single-point ferroelectric domain switching  

SciTech Connect

Electric field induced polarization switching underpins most functional applications of ferroelectric materials in information technology, materials science, and optoelectronics. In the last 20 years, much attention has been focused on the switching of individual domains using scanning probe microscopy, both as model of ferroelectric data storage and approach to explore fundamental physics of ferroelectric switching. The classical picture of tip induced switching includes formation of cylindrical domain oriented along the tip field, with the domain size is largely determined by the tip-induced field distribution and domain wall motion kinetics. The polarization screening is recognized as a necessary precondition to the stability of ferroelectric phase; however, screening processes are generally considered to be uniformly efficient and not leading to changes in switching behavior. Here, we demonstrate that single-point tip-induced polarization switching can give rise to a surprisingly broad range of domain morphologies, including radial and angular instabilities. These behaviors are traced to the surface screening charge dynamics, which in some cases can even give rise to anomalous switching against the electric field (ionic field effect). The implications of these behaviors for ferroelectric materials and devices are discussed.

Ievlev, Anton [ORNL] [ORNL; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine] [National Academy of Science of Ukraine, Kiev, Ukraine; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine] [National Academy of Science of Ukraine, Kiev, Ukraine; Shur, Vladimir Ya. [Ural Federal University, Russia] [Ural Federal University, Russia; Kalinin, Sergei V [ORNL] [ORNL

2014-01-01

264

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

SciTech Connect

Surface acoustic wave devices are extensively used in contemporary wireless communication devices. We used atomic force microscopy to form periodic macroscopic ferroelectric domains in sol-gel deposited lead zirconate titanate, where each ferroelectric domain is composed of many crystallites, each of which contains many microscopic ferroelastic domains. We examined the electro-acoustic characteristics of the apparatus and found a resonator behavior similar to that of an equivalent surface or bulk acoustic wave device. We show that the operational frequency of the device can be tailored by altering the periodicity of the engineered domains and demonstrate high-frequency filter behavior (>8?GHz), allowing low-cost programmable high-frequency resonators.

Ivry, Yachin, E-mail: ivry@mit.edu, E-mail: cd229@eng.cam.ac.uk; Wang, Nan; Durkan, Colm, E-mail: ivry@mit.edu, E-mail: cd229@eng.cam.ac.uk [Nanoscience Centre, University of Cambridge, 11 JJ Thomson Avenue, Cambridge CB3 0FF (United Kingdom)

2014-03-31

265

NEW LEAD-FREE PEROVSKITE RELAXOR CERAMICS DERIVED FROM BaTiO3 AND CONTAINING SCANDIUM  

E-print Network

NEW LEAD-FREE PEROVSKITE RELAXOR CERAMICS DERIVED FROM BaTiO3 AND CONTAINING SCANDIUM ANNIE SIMON-ray diffraction and dielectric characterizations. Dielectric measurements performed on ceramics with 0 x 0 therefore been performed in detail on ceramics with BaTiO3-derived compositions.2-23 Thanks to frequency

Boyer, Edmond

266

Ferroelectric studies of excessive Sm{sup 3+} containing perovskite PZT and pyrochlore biphase ceramics  

SciTech Connect

Polycrystalline samples of Sm{sup 3+} modified Pb{sub 1?x} Sm{sub 2x/3} (Zr{sub 0.6}Ti{sub 0.4}) O{sub 3} (PSZT) ceramics (where x = 0.1, 0.2, 0.3, 0.4) have been prepared by a high energy ball milling technique, followed by calcination at 950°C and sintering at 1150°C. As x is increased more than 0.1 mole%, considerable secondary phase has been formed. This phase has been identified as pyrochlore Sm{sub 2}Ti{sub 2}O{sub 7} from its X-ray diffraction (XRD) peaks. The XRD studies also indicate that the perovskte phases of the present systems undergo a dopant induced phase transformation from rhombohedral to tetragonal strucure. All the samples exhibit diffuse but non-relaxor type ferroelectric phase transition. The results of dielectric and hysteresis studies of these materials are presented.

Babu, T. Anil; Sastry, D. L., E-mail: dl-sastry@yahoo.com [Physics Department, Andhra University, Visakhapatnam - 530 003, AP (India); Ramesh, K. V. [Department of Engineering Physics, GITAM University, Visakhapatnam - 530 045, AP (India); Reddy, V. Raghavendra [UGC-DAE Consortium for Scientific Research, University Campus, Indore-452017, MP (India)

2014-04-24

267

New Ferroelectrics for Naval SONAR and Modeling of Nanoscale Ferroelectric Nonvolatile Memory Materials  

E-print Network

New Ferroelectrics for Naval SONAR and Modeling of Nanoscale Ferroelectric Nonvolatile Memory Navigation and Ranging (SONAR). At the nanoscale, our quantum-mechanical studies show that ferroelectricity with high piezoelectric response are of particular interest as they may be employed as sensors in SONAR

Rappe, Andrew M.

268

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

NASA Astrophysics Data System (ADS)

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

Ye, Yin

269

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

270

Switchable diode effect in ferroelectric thin film: High dependence on poling process and temperature  

NASA Astrophysics Data System (ADS)

Pb(Zr0.53Ti0.47)O3 (PZT) thin film was fabricated on Pt/Ti/SiO2/Si substrate by chemical solution deposition method. Our results show a very great switchable ferroelectric diode effect (SFDE) in Pt-PZT-Au structure, which is more obvious and controllable than that in other ferroelectric thin films. The electrical conduction exhibits high rectifying behavior after pre-poling and the polarity of ferroelectric diode can be switched by changing the orientation of polarization in ferroelectric thin film. Our results also indicate that the SFDE in PZT film is highly dependent on remanent polarization and temperature. With the increase of remanent polarization, the forward current of bistable rectifying behavior observably reduces. Therefore, our measurement indicated that the biggest rectification ratio can reach about 220, which is found in 250K after +10V poling. By analyzing the conduction data, it is found that the dominant conduction mechanism of the SFDE in this sample is due to the space-charge-limited bulk conduction (SCLC), and Schottky emission (SE) may play subordinate role in forward bias voltage. Our observation demonstrates that SFDE may be general characteristic in ferroelectrics as long as proper electrodes chosen.

Li, Z. X.; Liu, X. L.; Chen, W. J.; Zhang, X. Y.; Wang, Ying; Xiong, W. M.; Zheng, Yue

2014-12-01

271

Dielectric behaviors of lead zirconate titanate ceramics with coplanar electrodes  

Microsoft Academic Search

This paper reports on the dielectric behaviors of lead zirconate titanate (PZT) capacitors with coplanar electrodes. Usually a ferroelectric device has a metal-ferroelectric-metal configuration (parallel plate capacitor); when both the electrodes are on one side of a ceramic to form a coplanar capacitor, different dielectric behaviors will be anticipated because of the change in the distribution of the test field

Y Wang; Y. L Cheng; Y. W Zhang; H. L. W Chan; C. L Choy

2003-01-01

272

Ferroelectric Stirling-Cycle Refrigerator  

NASA Technical Reports Server (NTRS)

A Stirling-cycle refrigerator has a three-pump configuration and pumping sequence, in which one pump serves as a compressor. one pump serves as an expander, and one pump serves as a displacer. The pumps are ferroelectrically actuated diaphragm pumps which are coordinated by synchronizing the ferroelectric-actuator voltages in such a way that the net effect of the displacer is to reduce the deleterious effect of dead space; that is, to circulate a greater fraction of the working fluid through the heat exchangers than would be possible by use of the compressor and expander alone. In addition. the displacer can be controlled separately to make the flow of working fluid in the heat exchangers turbulent (to increase the rate of transfer of heat at the cost of greater resistance to flow) or laminar (to decrease the resistance to flow at the cost of a lower heat-transfer rate).

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

1999-01-01

273

Ferroelectric and Antiferromagnetic Domain Wall  

Microsoft Academic Search

It has been experimentally confirmed that the ferroelectric (FEL) and antiferromagnetic (AFM) order-parameter in hexagonal YMnO3 are coupled at the FEL domain boundary. A microscopic model for this clamping of the two order-parameters is proposed. The clamping can be understood as due to the change of exchange integrals induced by the spin-orbit interaction and low symmetry field within the FEL

Eiichi Hanamura; Yukito Tanabe

2003-01-01

274

High Temperature Ferroelectrics for Actuators: Recent Developments and Challenges  

NASA Technical Reports Server (NTRS)

A variety of piezoelectric applications have been driving the research in development of new high temperature ferroelectrics; ranging from broader markets such as fuel and gas modulation and deep well oil drilling to very specific applications such as thermoacoustic engines and ultrasonic drilling on the surface of Venus. The focus has been mostly on increasing the Curie temperature. However, greater challenges for high temperature ferroelectrics limit the operating temperature to levels much below the Curie temperature. These include enhanced loss tangent and dc conductivity at high fields as well as depoling due to thermally activated domain rotation. The initial work by Eitel et al. [Jpn. J. Appl. Phys., 40 [10, Part 1] 59996002 (2001)] increased interest in investigation of Bismuth containing perovskites in solid solution with lead titanate. Issues that arise vary from solubility limits to increased tetragonality; the former one prohibits processing of morphotropic phase boundary, while the latter one impedes thorough poling of the polycrystalline ceramics. This talk will summarize recent advances in development of high temperature piezoelectrics and provide information about challenges encountered as well as the approaches taken to improve the high temperature behavior of ferroelectrics with a focus on applications that employ the converse piezoelectric effect.

Sehirlioglu, Alp; Kowalski, Benjamin

2014-01-01

275

The Improper Ferroelectric Phase Transition of Magnesium-Chloride Boracite  

NASA Astrophysics Data System (ADS)

Laser Raman backscattering has been used to determine the Raman scattering strength as a function of temperature, in the ferroelectric phase of magnesium-chloride (Mg-Cl) boracite. Raman spectroscopy looks directly at the optical phonon responsible for the ferroelectric phase transition, at 142 cm('-1). Ferroelectricity may be explained by the Landau theory of second order phase transitions. The thermodynamic Gibbs potential is assumed to be expandable in terms of the phase transition's order parameter. Within this context there are two models, one proposed by V. Dvorak and another by A. Levanyuk, to explain the coupled (improper) phase transition of boracite. Dvorak takes the primary order parameter to be the lattice distorting mode, while Levanyuk assigns the polar mode as the order parameter. Both models adequately predict dielectric susceptibility vs. temperature. It is shown here how to calculate, for any coupled phase transition, the dielectric susceptibility, oscillator strength, spontaneous polarization, and polarization-optic coefficient. The polarization-optic coefficient is necessary to calculate the total Raman scattering strength. An expression is developed where the scattering strength is written as a combination of derivatives of the Gibbs potential and the Bose population factor. The models of Levanyuk and Dvorak are computer simulated and predict very different behavior of the scattering strength. The Dvorak model predicts a strong divergence in the intensity of Raman scattering at the critical temperature. The results of experiment do not show such a divergence and therefore confirm the Levanyuk model.

Arakelian, Henry Edward

276

ARTICLES--Outstanding Meeting Papers Domain switch toughening in polycrystalline ferroelectrics  

E-print Network

Jianxin Wang and Chad M. Landisa) Department of Mechanical Engineering and Materials Science, Rice the material behavior of the ferroelectric ceramic. The constitutive law is then implemented within the finite This paper was presented at the Spring meeting of the Materials Research Society on March 29, 2005 in San

277

On the role of charge injection and trapping in stability of polarization in ferroelectric polymers  

Microsoft Academic Search

The experimental results are presented on anomalous behavior of absorption currents in PVDF during the stepwise increase of the voltage applied through a corona. These results, supplemented with the dynamics of the time constant of the electret potential decay, are consistent with a hypothesis assuming a deep trapping of the charge carriers during the polarization buildup in ferroelectric polymers. The

S. Fedosov; A. Sergeeva

1994-01-01

278

Domain switching in polycrystalline ferroelectric ceramics  

E-print Network

ARTICLES Domain switching in polycrystalline ferroelectric ceramics J. Y. LI1, R. C. ROGAN2,3, E:10.1038/nmat1485 Ferroelectric ceramics are widely used as sensors and actuators for their electro collective process in commercially used polycrystalline ceramics that are agglomerations of a very large

Li, Jiangyu

279

Graded ferroelectric capacitors with robust temperature characteristics  

Microsoft Academic Search

Ferroelectric thin films offer the possibility of engineering the dielectric response for tunable components in frequency-agile rf and microwave devices. However, this approach often leads to an undesired temperature sensitivity. Compositionally graded ferroelectric films have been explored as a means of redressing this sensitivity, but experimental observations vary depending on geometry and other details. In this paper, we present a

Mohamed Y. El-Naggar; Kaushik Dayal; David G. Goodwin; Kaushik Bhattacharya

2006-01-01

280

Ferroelectric translational antiphase boundaries in nonpolar materials  

PubMed Central

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

281

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

282

Ferroelectric Liquid Crystal Conglomerates DAVID M. WALBA  

E-print Network

Chapter 8 Ferroelectric Liquid Crystal Conglomerates DAVID M. WALBA University of Colorado, Boulder 5.1 Crystal Conglomerates 5.2 Spontaneous Reflection Symmetry Breaking in Liquid Crystals 6 Chiral-471-05497-6 Copyright 2003 John Wiley & Sons, Inc. 457 #12;458 FERROELECTRIC LIQUID CRYSTAL CONGLOMERATES ferro-, pyro

Walba, David

283

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

284

Novel complex phenomena in ferroelectric nanocomposites.  

PubMed

A first-principles-based effective Hamiltonian is used to investigate finite-temperature properties of ferroelectric nanocomposites made of periodic arrays of ferroelectric nanowires embedded in a matrix formed by another ferroelectric material. Novel transitions and features related to flux-closure configurations are found. Examples include (i) a vortex core transition, that is characterized by the change of the vortex cores from being axisymmetric to exhibiting a 'broken symmetry'; (ii) translational mode of the vortex cores; (iii) striking zigzag dipolar chains along the vortex core axis; and (iv) phase-locking of ferroelectric vortices accompanied by ferroelectric antivortices. These complex phenomena are all found to coexist with a spontaneous electrical polarization aligned along the normal of the plane containing the vortices. PMID:22968903

Louis, Lydie; Kornev, Igor; Geneste, Grégory; Dkhil, Brahim; Bellaiche, L

2012-10-10

285

Pressure tuned ferroelectric reentrance in nano-BaTiO{sub 3} ceramics  

SciTech Connect

In nano-grain BaTiO{sub 3} ceramics, internal compressive stresses make the cubic phase more stable, while internal shear stresses stabilize rhombohedral and orthorhombic phases. The competition between internal compressive stresses and internal shear stresses gives a ferroelectric to paraelectric to ferroelectric reentrance phenomenon as a function of grain size. The pressure can be a tuning factor of reentrance behavior by controlling the interactions between external hydrostatic pressure and internal compressive stresses. These experimental phenomena can be well described by a modified Ginzburg-Landau-Devonshire thermodynamic theory.

Zhu, J. L.; Lin, S.; Feng, S. M.; Wang, L. J.; Liu, Q. Q.; Jin, C. Q. [Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Wang, X. H.; Zhong, C. F.; Li, L. T. [Department of Materials Sciences, Tsinghua University, Beijing 100084 (China); Cao, Wenwu [Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2012-12-15

286

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

287

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

288

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

289

Thin layer composite unimorph ferroelectric driver and sensor  

NASA Astrophysics Data System (ADS)

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.; Bryant, Robert G.; Fox, Robert L.; Jalink, Antony, Jr.; Rohrbach, Wayne W.; Simpson, Joycelyn O.

1995-04-01

290

Low temperature dependent ferroelectric resistive switching in epitaxial BiFeO3 films  

NASA Astrophysics Data System (ADS)

The ferroelectric switchable diode induced resistive switching behavior at low temperature has been investigated in the epitaxial BiFeO3 (BFO) thin films. The switchable diode can be tuned using a higher voltage at low temperatures. The diode barrier is determined to be ˜0.55 eV at the interface between BFO and electrode. The resistive switchable barrier with respect to the ferroelectric domain switching has been systematically characterized at various low temperatures. The temperature dependent conduction and leakage mechanisms have also been identified. These results can advance our understanding of resistive switching based on ferroelectric switchable diode at low working temperatures and potentially extend the applications of memristor to a larger temperature scale.

Yan, F.; Xing, G. Z.; Li, L.

2014-03-01

291

Ferroelectricity-induced effects in interaction and self-organization of inclusions in smectic membranes  

NASA Astrophysics Data System (ADS)

Our experiments reveal that breaking of chiral symmetry in smectic membranes leads to a dramatic modification of the collective behavior of inclusions. We investigated nematic and cholesteric droplets, respectively, in nonpolar membranes formed by the racemic mixture and in ferroelectric ones formed by the chiral isomer. Inclusions in nonpolar and polar membranes induce substantially different elastic deformation of the c-director field: quadrupolar symmetry and dipolar symmetry, respectively. Interaction between inclusions related with deformation of the c-director field leads to self-organization of inclusions into linear chains in ferroelectric membranes and into clusters in nonpolar membranes. The experiments suggest that polarization-induced charges play a substantial role in self-organization processes in ferroelectric membranes.

Dolganov, P. V.; Nguyen, H. T.; Joly, G.; Dolganov, V. K.; Cluzeau, P.

2006-10-01

292

Universal Ferroelectric Switching Dynamics of Vinylidene Fluoride-trifluoroethylene Copolymer Films  

PubMed Central

In this work, switching dynamics of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films are investigated over unprecedentedly wide ranges of temperature and electric field. Remarkably, domain switching of copolymer films obeys well the classical domain nucleation and growth model although the origin of ferroelectricity in organic ferroelectric materials inherently differs from the inorganic counterparts. A lower coercivity limit of 50?MV/m and 180° domain wall energy of 60?mJ/m2 are determined for P(VDF-TrFE) films. Furthermore, we discover in copolymer films an anomalous temperature-dependent crossover behavior between two power-law scaling regimes of frequency-dependent coercivity, which is attributed to the transition between flow and creep motions of domain walls. Our observations shed new light on the switching dynamics of semi-crystalline ferroelectric polymers, and such understandings are critical for realizing their reliable applications. PMID:24759786

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

2014-01-01

293

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

NASA Astrophysics Data System (ADS)

Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1-xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of ˜1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.

Vasudevan, R. K.; Bogle, K. A.; Kumar, A.; Jesse, S.; Magaraggia, R.; Stamps, R.; Ogale, S. B.; Potdar, H. S.; Nagarajan, V.

2011-12-01

294

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

295

Calligraphic Poling of Ferroelectric Material  

NASA Technical Reports Server (NTRS)

Calligraphic poling is a technique for generating an arbitrary, possibly complex pattern of localized reversal in the direction of permanent polarization in a wafer of LiNbO3 or other ferroelectric material. The technique is so named because it involves a writing process in which a sharp electrode tip is moved across a surface of the wafer to expose the wafer to a polarizing electric field in the desired pattern. The technique is implemented by use of an apparatus, denoted a calligraphic poling machine (CPM), that includes the electrode and other components as described in more detail below.

Mohageg, Makan; Strekalov, Dmitry; Savchenkov, Anatoliy; Matsko, Adrey; Maleki, Lute; Iltchenko, Vladimir

2007-01-01

296

One-dimensional nanostructures of ferroelectric perovskites.  

PubMed

Nanorods, nanowires, and nanotubes of ferroelectric perovskites have recently been studied with increasing intensity due to their potential use in non-volatile ferroelectric random access memory, nano-electromechanical systems, energy-harvesting devices, advanced sensors, and in photocatalysis. This Review summarizes the current status of these 1D nanostructures and gives a critical overview of synthesis routes with emphasis on chemical methods. The ferroelectric and piezoelectric properties of the 1D nanostructures are discussed and possible applications are highlighted. Finally, prospects for future research within this field are outlined. PMID:21796684

Rørvik, Per Martin; Grande, Tor; Einarsrud, Mari-Ann

2011-09-15

297

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

298

Static Characteristics of the Ferroelectric Transistor Inverter  

NASA Technical Reports Server (NTRS)

The inverter is one of the most fundamental building blocks of digital logic, and it can be used as the foundation for understanding more complex logic gates and circuits. This paper presents the characteristics of an inverter circuit using a ferroelectric field-effect transistor. The voltage transfer characteristics are analyzed with respect to varying parameters such as supply voltage, input voltage, and load resistance. The effects of the ferroelectric layer between the gate and semiconductor are examined, and comparisons are made between the inverters using ferroelectric transistors and those using traditional MOSFETs.

Mitchell, Cody; Laws, crystal; MacLeond, Todd C.; Ho, Fat D.

2010-01-01

299

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

300

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

301

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

302

Negative capacitance in a ferroelectric capacitor.  

PubMed

The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time--in exactly the opposite direction to which voltage for a regular capacitor should change. Analysis of this 'inductance'-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications. PMID:25502099

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

2015-02-01

303

Negative capacitance in a ferroelectric capacitor  

NASA Astrophysics Data System (ADS)

The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time—in exactly the opposite direction to which voltage for a regular capacitor should change. Analysis of this ‘inductance’-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications.

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

2015-02-01

304

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

305

Ferroelectric control of orbital occupancy in manganites  

NASA Astrophysics Data System (ADS)

Recent successful fabrication of epitaxial and coherent ferroelectric/manganite interfaces makes it possible to dynamically control charge and spin in manganites [1]. We demonstrate with ab initio calculations that in this system, d-orbital occupancies of the interfacial Mn atom can also be modulated by flipping the ferroelectric polarization (i.e. flippable orbital polarization). The underlying mechanism is the structural distortions of the oxygen octahedron and the Mn atom inside induced by the ferroelectric polarization. The in-plane orbital dx^2-y^2 is stablized by rumpling in MnO2 layers, while the Jahn-Teller distortion (c/a>1) favors the out-of-plane orbital d3z^2-r^2. This ferroelectric control of orbital occupancy serves as a new approach separate from strain for engineering orbital orderings in transition metal oxides. [4pt] [1] C.A.F.Vaz et al., Phys. Rev. Lett. 104, 127202 (2010)

Chen, Hanghui; Ismail-Beigi, Sohrab

2012-02-01

306

Interface control of bulk ferroelectric polarization  

PubMed Central

The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon. PMID:22647612

Yu, P.; Luo, W.; Yi, D.; Zhang, J. X.; Rossell, M. D.; Yang, C.-H.; You, L.; Singh-Bhalla, G.; Yang, S. Y.; He, Q.; Ramasse, Q. M.; Erni, R.; Martin, L. W.; Chu, Y. H.; Pantelides, S. T.; Pennycook, S. J.; Ramesh, R.

2012-01-01

307

Ferroelectric and ferromagnetic properties in BaTiO{sub 3} thin films on Si (100)  

SciTech Connect

In this paper, we report on the epitaxial integration of room temperature lead-free ferroelectric BaTiO{sub 3} thin (?1050?nm) films on Si (100) substrates by pulsed laser deposition technique through a domain matching epitaxy paradigm. We employed MgO and TiN as buffer layers to create BaTiO{sub 3}/SrRuO{sub 3}/MgO/TiN/Si (100) heterostructures. C-axis oriented and cube-on-cube epitaxial BaTiO{sub 3} is formed on Si (100) as evidenced by the in-plane and out-of-plane x-ray diffraction, and transmission electron microscopy. X-ray photoemission spectroscopic measurements show that Ti is in 4(+) state. Polarization hysteresis measurements together with Raman spectroscopy and temperature-dependent x-ray diffraction confirm the room temperature ferroelectric nature of BaTiO{sub 3}. Furthermore, laser irradiation of BaTiO{sub 3} thin film is found to induce ferromagnetic-like behavior but affects adversely the ferroelectric characteristics. Laser irradiation induced ferromagnetic properties seem to originate from the creation of oxygen vacancies, whereas the pristine BaTiO{sub 3} shows diamagnetic behavior, as expected. This work has opened up the route for the integration of room temperature lead-free ferroelectric functional oxides on a silicon platform.

Singamaneni, Srinivasa Rao, E-mail: ssingam@ncsu.edu; Prater, John T. [Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Punugupati, Sandhyarani; Hunte, Frank; Narayan, Jagdish [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

2014-09-07

308

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.

309

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

2014-11-12

310

Polymer-stabilized ferroelectric liquid crystals  

Microsoft Academic Search

Polymer-stabilized ferroelectric liquid crystal (PSFLCs) are made by photopolymerizing a small amount of reactive mesogenic monomer on a quasi-bookshelf texture of ferroelectric liquid crystals (FLCs). We observed the templated submicron-scaled polymer fibrils from the two- dimensionally ordered host. The polymer fibrils capture the orientation of the host with thin polymer fibrils interweaving the smectic layers that act as additional surfaces

Soonnam Lee; S. Suresh; Liang-Chy Chien

2002-01-01

311

Temperature-dependent fatigue rate in ferroelectric Bi3.25La0.75Ti3O12 thin films  

Microsoft Academic Search

Bismuth-layer structured ferroelectric (BLSF) thin films with a composition of Bi3.25La0.75Ti3O12 were prepared by an acetic-acid based sol-gel route. The ferroelectric, dielectric, and fatigue characteristics of the films over a wide temperature range from 300 K to 100 K were analyzed by using a computerized measurement system. The fatigue characteristic of the film was improved with decreasing temperature. This behavior

J.-Y. Hwang; S.-A. Lee; S.-Y. Jeong; C.-R. Cho

2006-01-01

312

Temperature-dependent fatigue rate in ferroelectric Bi3.25La0.75Ti3O12 thin films  

Microsoft Academic Search

Bismuth-layer–structured ferroelectric (BLSF) thin films with a composition of Bi3.25La0.75Ti3O12 were prepared by an acetic-acid–based sol-gel route. The ferroelectric, dielectric, and fatigue characteristics of the films over a wide temperature range from 300 K to 100 K were analyzed by using a computerized measurement system. The fatigue characteristic of the film was improved with decreasing temperature. This behavior is attributed

J.-Y. Hwang; S.-A. Lee; S.-Y. Jeong; C.-R. Cho

2006-01-01

313

Ferroelectric vortices from atomistic simulations  

NASA Astrophysics Data System (ADS)

In 2004, the use of a first-principles-based effective Hamiltonian [1] led to the prediction of a novel structure in zero-dimensional ferroelectrics, in which the electric dipoles organize themselves to form a vortex [2]. Such structure exhibits the so-called spontaneous toroidal moment, rather than the spontaneous polarization, as its order parameter [2]. Subsequently, various original phenomena, all related to vortices, were predicted in ferroelectric nanostructures. Examples of such phenomena are: (i) the existence of a new order parameter, denoted as the hypertoroidal moment, that is associated with many complex dipolar structures (such as double-vortex states) [3]; (ii) the possible control of single and double vortex states by electric fields, via the formation of original intermediate states [4-8]; (iii) the discovery of a new class of quantum materials (denoted as incipient ferrotoroidics), for which zero-point vibrations wash out the vortex state and yield a complex local structure [9]; (iv) the existence of chiral patterns of oxygen octahedral tiltings that originate from the coupling of these tiltings with the ferroelectric vortices [10]. The purpose of this talk is to discuss some of these striking phenomena, as well as, to reveal others (if time allows). These studies are done in collaboration with A.R. Akbarzadeh, H. Fu, I. Kornev, I. Naumov, I. Ponomareva, S. Prosandeev, Wei Ren and D. Sichuga. [4pt] [1] L. Bellaiche, A. Garcia and D. Vanderbilt, Phys. Rev. Lett. 84, 5427 (2000). [0pt] [2] Ivan I. Naumov, L. Bellaiche and Huaxiang Fu, Nature (London) 432, 737 (2004). [0pt] [3] S. Prosandeev and L. Bellaiche, Phys. Rev. B 77, 060101(R) (2008). [0pt] [4] S. Prosandeev, I. Ponomareva, I. Kornev, I. Naumov and L. Bellaiche, Phys. Rev. Lett. 96, 237601 (2006). [0pt] [5] I. Naumov and H. Fu, Phys. Rev. Lett. 98, 077603 (2007). [0pt] [6] S. Prosandeev and L. Bellaiche, Phys. Rev. Lett. 101, 097203 (2008). [0pt] [7] S. Prosandeev, I. Ponomareva, I. Kornev, and L. Bellaiche, Phys. Rev. Lett. 100, 047201 (2008). [0pt] [8] I. Naumov and H. Fu, Phys. Rev. Lett. 101, 197601 (2008). [0pt] [9] S. Prosandeev, A. R. Akbarzadeh and L. Bellaiche, Phys. Rev. Lett. 102, 257601(2009). [0pt] [10] David Sichuga, Wei Ren, Sergey Prosandeev, and L. Bellaiche, Phys. Rev. Lett. 104, 207603 (2010).

Bellaiche, Laurent

2011-03-01

314

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

SciTech Connect

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(Zr{sub 0.5}Ti{sub 0.5})O{sub 3}?FeGaB and BaTiO{sub 3}?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. [Laboratoire Structures, Propriétés et Modélisation des Solides, UMR CNRS—École Centrale Paris, 92295 Châtenay-Malabry (France); Kohlstedt, H. [Nanoelektronik, Technische Fakultät, Christian-Albrechts-Universität zu Kiel, D-24143 Kiel (Germany); Pertsev, N. A., E-mail: pertsev.domain@mail.ioffe.ru [A. F. Ioffe Physical-Technical Institute and St. Petersburg State Polytechnical University, St. Petersburg, 194021 and 195251 (Russian Federation)

2014-09-21

315

PREFACE: 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity and 9th International Conference on Functional Materials and Nanotechnologies (RCBJSF–2014–FM&NT)  

NASA Astrophysics Data System (ADS)

The joint International Symposium RCBJSF–2014–FM&NT successfully has united two international events – 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity (RCBJSF-12) and 9th International Conference Functional Materials and Nanotechnologies (FM&NT-2014). The RCBJSF symposium is a continuation of series of meetings on ferroelectricity, the first of which took place in Novosibirsk (USSR) in 1976. FM&NT conferences started in 2006 and have been organized by Institute of Solid State Physics, University of Latvia in Riga. In 2012 the International program committee decided to transform this conference into a traveling Baltic State conference and the FM&NT-2013 was organized by the Institute of Physics, University of Tartu, Estonia. In 2014 the joint international symposium RCBJSF–2014–FM&NT was organized by the Institute of Solid State Physics, University of Latvia and was part of Riga – 2014, the European Capital of Culture event. The purpose of the joint Symposium was to bring together scientists, students and high-level experts in solid state physics, materials science, engineering and related disciplines. The number of the registered participants from 26 countries was over 350. During the Symposium 128 high quality scientific talks (5 plenary, 42 invited, 81 oral) and over 215 posters were presented. All presentations were divided into 4 parallel sessions according to 4 main topics of the Symposium: Ferroelectricity, including ferroelectrics and multiferroics, pyroelectrics, piezoelectrics and actuators, integrated ferroelectrics, relaxors, phase transitions and critical phenomena. Multifunctional Materials, including theory, multiscale and multiphenomenal material modeling and simulation, advanced inorganic, organic and hybrid materials. Nanotechnologies, including progressive methods, technologies and design for production, investigation of nano- particles, composites, structures, thin films and coatings. Energy, including perspective materials and technologies for renewable and hydrogen energy, fuel cells, photovoltaics, LEDs, OLEDs. Based on these reports, 48 papers are included in this volume of IOP Conference Series: Materials Science and Engineering. Additional information about RCBJSF–2014–FM&NT is available at the homepage http://www.fmnt.lu.lv. The Organizing Committee would like to thank all the speakers, contributors, session chairs, referees and other involved staff for their efforts in making the RCBJSF–2014–FM&NT successful. Sincerely, organizers of the event Andris Sternberg Liga Grinberga Anatolijs Sarakovskis Martins Rutkis

Sternberg, Andris; Grinberga, Liga; Sarakovskis, Anatolijs; Rutkis, Martins

2015-03-01

316

Ferroelectricity in free niobium clusters.  

PubMed

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

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

2003-05-23

317

Infrared and Far-Infrared Studies of Boracite Improper Ferroelectrics.  

NASA Astrophysics Data System (ADS)

The infrared and far-infrared reflectances (20 -4000 cm('-1)) of single crystal nickel bromine and copper chlorine boracites have been measured in the ferroelectric and paraelectric phases. Kramers-Kronig analysis and four -parameter oscillator fits were performed to obtain the dielectric function. The spectral features of the boracites above 200 cm('-1) are found to be very similar and can be associated with the internal vibrational modes of the boron-oxygen framework. In the ferroelectric phase, an anomalous increase of the linewidth of a low-frequency band in the Ni-Br boracite is observed near the transition temperature. A similar temperature dependence is also seen in the linewidth of the anti-symmetric stretch mode of the BO(,3) group in both boracites. This behavior is interpreted as the result of an enhanced coupling to a low-frequency soft mode. We have identified the band near 138 cm('-1) in the Ellc spectra of the Ni-Br boracite with the infrared active A(,1) soft mode predicted in Dvorak's theory. The corresponding A(,1) soft mode is not observed in the unpolarized spectra of the Cu-Cl boracite. In the paraelectric of the Ni-Br boracite, we have observed the appearance of a relaxation-like mode at frequencies below (TURN)100 cm('-1). Furthermore, comparison of our values of the static dielectric constants calculated from the Lyydane-Sachs-Teller relation with those obtained from capacitance measurements shows that (epsilon)(cap) of both boracites in the paraelectric phase is (TURN)1.5 -2.0 times larger than (epsilon)(LST). These observations suggest that the microscopic origin of the improper ferroelectric phase transition in these materials is both of an order -disorder and displacive nature.

Moopenn, Alexander W.

318

Ferroelectric order in individual nanometre-scale crystals.  

PubMed

Ferroelectricity in finite-dimensional systems continues to arouse interest, motivated by predictions of vortex polarization states and the utility of ferroelectric nanomaterials in memory devices, actuators and other applications. Critical to these areas of research are the nanoscale polarization structure and scaling limit of ferroelectric order, which are determined here in individual nanocrystals comprising a single ferroelectric domain. Maps of ferroelectric structural distortions obtained from aberration-corrected transmission electron microscopy, combined with holographic polarization imaging, indicate the persistence of a linearly ordered and monodomain polarization state at nanometre dimensions. Room-temperature polarization switching is demonstrated down to ~5?nm dimensions. Ferroelectric coherence is facilitated in part by control of particle morphology, which along with electrostatic boundary conditions is found to determine the spatial extent of cooperative ferroelectric distortions. This work points the way to multi-Tbit/in(2) memories and provides a glimpse of the structural and electrical manifestations of ferroelectricity down to its ultimate limits. PMID:22772655

Polking, Mark J; Han, Myung-Geun; Yourdkhani, Amin; Petkov, Valeri; Kisielowski, Christian F; Volkov, Vyacheslav V; Zhu, Yimei; Caruntu, Gabriel; Alivisatos, A Paul; Ramesh, Ramamoorthy

2012-08-01

319

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

320

Development and characterization of a ferroelectric non-volatile memory for flexible electronics  

NASA Astrophysics Data System (ADS)

Flexible electronics have received significant attention recently because of the potential applications in displays, sensors, radio frequency identification (RFID) tags and other integrated circuits. Electrically addressable non-volatile memory is a key component for these applications. The major challenges are to fabricate the memory at a low temperature compatible with plastic substrates while maintaining good device reliability, by being compatible with process as needed to integrate with other electronic components for system-on-chip applications. In this work, ferroelectric capacitors fabricated at low temperature were developed. Based on that, a ferroelectric random access memory (FRAM) for flexible electronics was developed and characterized. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer was used as a ferroelectric material and a photolithographic process was developed to fabricate ferroelectric capacitors. Different characterization methods including atomic force microscopy, x-ray diffraction and Fourier-transform infrared reflection-absorption spectroscopy were used to study the material properties of the P(VDF-TrFE) film. The material properties were correlated with the electrical characteristics of the ferroelectric capacitors. To understand the polarization switching behavior of the P(VDF-TrFE) ferroelectric capacitors, a Nucleation-Limited-Switching (NLS) model was used to study the switching kinetics. The switching kinetics were characterized over the temperature range from -60 °C to 100 °C. Fatigue characteristics were studied at different electrical stress voltages and frequencies to evaluate the reliability of the ferroelectric capacitor. The degradation mechanism is attributed to the increase of the activation field and the suppression of the switchable polarization. To develop a FRAM circuit for flexible electronics, an n-channel thin film transistor (TFT) based on CdS as the semiconductor was integrated with a P(VDF-TrFE) ferroelectric capacitor for a one-transistor-one-capacitor (1T1C) memory cell. The 1T1C devices were fabricated at low temperature and demonstrated a memory window (DeltaVBL) of 2.3 V and 3.5 V, depending on the device dimensions. Next, FRAM arrays (4-bit, 16-bit and 64-bit) based on the two-transistor-two-capacitor (2T2C) memory cell architecture were designed and fabricated using a photolithographic process with 9 masks. The fabricated FRAM arrays were packaged in 28-pin ceramic packages. The read/write schemes were developed and the FRAM arrays show successful program and erase with a memory window of approximately 1 V at the output of the sense amplifier.

Mao, Duo

321

Silver-modified nanosized ferroelectrics as a novel photocatalyst.  

PubMed

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

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

2015-01-14

322

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

NASA Astrophysics Data System (ADS)

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

Zhou, Xiaolan

323

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

NASA Astrophysics Data System (ADS)

Cellular electrets polymer is a new ferroelectret material exhibiting large piezoelectricity and has attracted considerable attentions in researches and industries. Property characterization is very important for this material and current investigations are mostly on macroscopic properties. In this work, we conduct nanoscale piezoelectric and ferroelectric characterizations of cellular polypropylene (PP) films using piezoresponse force microscopy (PFM). First, both the single-frequency PFM and dual-frequency resonance-tracking PFM testings were conducted on the cellular PP film. The localized piezoelectric constant d33 is estimated to be 7-11pC/N by correcting the resonance magnification with quality factor and it is about one order lower than the macroscopic value. Next, using the switching spectroscopy PFM (SS-PFM), we studied polarization switching behavior of the cellular PP films. Results show that it exhibits the typical ferroelectric-like phase hysteresis loops and butterfly-shaped amplitude loops, which is similar to that of a poly(vinylidene fluoride) (PVDF) ferroelectric polymer film. However, both the phase and amplitude loops of the PP film are intensively asymmetric, which is thought to be caused by the nonzero remnant polarization after poling. Then, the D-E hysteresis loops of both the cellular PP film and PVDF film were measured by using the same wave form as that used in the SS-PFM, and the results show significant differences. Finally, we suggest that the ferroelectric-like behavior of cellular electrets films should be distinguished from that of typical ferroelectrics, both macroscopically and microscopically.

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

2014-08-01

324

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

SciTech Connect

Cellular electrets polymer is a new ferroelectret material exhibiting large piezoelectricity and has attracted considerable attentions in researches and industries. Property characterization is very important for this material and current investigations are mostly on macroscopic properties. In this work, we conduct nanoscale piezoelectric and ferroelectric characterizations of cellular polypropylene (PP) films using piezoresponse force microscopy (PFM). First, both the single-frequency PFM and dual-frequency resonance-tracking PFM testings were conducted on the cellular PP film. The localized piezoelectric constant d{sub 33} is estimated to be 7–11pC/N by correcting the resonance magnification with quality factor and it is about one order lower than the macroscopic value. Next, using the switching spectroscopy PFM (SS-PFM), we studied polarization switching behavior of the cellular PP films. Results show that it exhibits the typical ferroelectric-like phase hysteresis loops and butterfly-shaped amplitude loops, which is similar to that of a poly(vinylidene fluoride) (PVDF) ferroelectric polymer film. However, both the phase and amplitude loops of the PP film are intensively asymmetric, which is thought to be caused by the nonzero remnant polarization after poling. Then, the D-E hysteresis loops of both the cellular PP film and PVDF film were measured by using the same wave form as that used in the SS-PFM, and the results show significant differences. Finally, we suggest that the ferroelectric-like behavior of cellular electrets films should be distinguished from that of typical ferroelectrics, both macroscopically and microscopically.

Miao, Hongchen; Sun, Yao; Zhou, Xilong; Li, Yingwei [LTCS and Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); Li, Faxin, E-mail: lifaxin@pku.edu.cn [LTCS and Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); HEDPS and Center for Applied Physics and Technology, Peking University, Beijing (China)

2014-08-14

325

Ferroelectric Thin-Film Capacitors As Ultraviolet Detectors  

NASA Technical Reports Server (NTRS)

Advantages include rapid response, solar blindness, and relative invulnerability to ionizing radiation. Ferroelectric capacitor made to function as photovoltaic detector of ultraviolet photons by making one of its electrodes semitransparent. Photovoltaic effect exploited more fully by making Schottky barrier at illuminated semitransparent-electrode/ferroelectric interface taller than Schottky barrier at other electrode/ferroelectric interface.

Thakoor, Sarita

1995-01-01

326

Quantum jump and “kaizen” toward commercialization of ferroelectric ULSI memories  

Microsoft Academic Search

With the invention of BLSF (Bismuth Layer-Structured Ferroelectric), Ferroelectrics has changed from research topics to development theme. A number of challenges yet to be made for realistic Ferro-electric products to come to marketplace are discussed. Potential and promising market will be embedded applications as the first commercial product.

Hideya Esaki

1997-01-01

327

Ferroelectric sources and their application to pulsed power: a review  

Microsoft Academic Search

We present in this review an account of recent research into the use of ferroelectrics as electron beam sources for pulsed power applications. The work is reviewed according to the ferroelectric material used and the switching process employed. Most of the current research uses PLZT or PZT, which can be ferroelectric, antiferroelectric, or paraelectric depending on the stoichiometry. Switching is

Charles B. Fleddermann; John A. Nation

1997-01-01

328

Behaviorism  

ERIC Educational Resources Information Center

Early forms of psychology assumed that mental life was the appropriate subject matter for psychology, and introspection was an appropriate method to engage that subject matter. In 1913, John B. Watson proposed an alternative: classical S-R behaviorism. According to Watson, behavior was a subject matter in its own right, to be studied by the…

Moore, J.

2011-01-01

329

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

330

Onset of ferrielectricity and the hidden nature of nanoscale polarization in ferroelectric thin films  

NASA Astrophysics Data System (ADS)

Using calculations from first principles we have elucidated the nanoscale organization and local polarization in ferroelectric thin films between metallic contacts. We discovered a ferrielectric pattern of polarization in what was originally thought to be a simple ferroelectric domain. Applying the layer polarization concept (Wu et al., Phys. Rev. Lett. 97, 107602 (2006)), we analyzed the polarization profile for different film thicknesses. The results (M. Nunez and M. B. Nardelli, Phys. Rev. Letters, to be published) unveil a peculiar spatial pattern where individual atomic layers acquire uncompensated opposing dipoles in what was originally thought to be a simple ferroelectric domain. This ferrielectric behavior arises as consequence of the complex energetic competition between the interface effects, the depolarization field, and the mutual interaction of the layer dipoles. Morover, as the thickness of the film is varied, we show that the system undergoes a ferroelectric-to-ferrielectric phase transition at a critical thickness. These results are interpreted using a simple classical model where the interface effects are explicitly taken into account. We propose a method in order to carefully tune the spatial polarization pattern of the film (M. Nunez and M. B. Nardelli, Appl. Phys. Lett. 92, 1 (2008)).

Nunez, Matias; Buongiorno Nardelli, Marco

2008-10-01

331

A pair of dinuclear Re(i) enantiomers: synthesis, crystal structures, chiroptical and ferroelectric properties.  

PubMed

The reaction of enantiomeric bis-bidentate bridging ligands (+)/(-)-2,5-bis(4,5-pinene-2-pyridyl)pyrazine (LS/LR) with [Re(CO)5Cl] yielded a pair of dinuclear Re(i) enantiomers formulated as [Re2(LS/LR)(CO)6Cl2]·4CH2Cl2 ( and , the isomers containing the respective LR and LS ligands). They were characterized by elemental analyses, IR spectra and X-ray crystallography. Circular dichroism spectra verified their chiroptical activities and enantiomeric nature. The measurements of second harmonic generation (SHG) and ferroelectric properties showed that displays a nonlinear optical (NLO) activity and ferroelectricity with a remnant polarization (Pr) of 1.6 ?C cm(-2) under an applied field of 7.3 kV cm(-1) at room temperature. and represent the first example of polynuclear Re(i) complexes with ferroelectric properties. Notably, the Pr value is much larger than that of the reported mononuclear chiral Re(i) analogue. In particular, unlike mononuclear Re(i) complexes of the type [Re(CO)3(N^N)(X)] (N^N = diimine and X = halide), which usually exhibit an intense emission in the visible range, and do not show any detectable emission at any temperature range and the reason for the nonluminescence of and was further elucidated in this work. Moreover, our research results also elucidated that Re nuclearity has a great influence on not only the emitting properties but also on ferroelectric behavior. PMID:25623284

Li, Xi-Li; Zhang, Zhiqiang; Zhang, Xue-Li; Kang, Jia-Long; Wang, Ai-Ling; Zhou, Liming; Fang, Shaoming

2015-02-17

332

Ferroelectric switching in Bi4Ti3O12 nanorods.  

PubMed

We report the piezoelectric and ferroelectric properties of individual one-dimensional objects made of Bi(4)Ti(3)O(12) (BiT). The nanorods and nanowires investigated in this study were fabricated by a two-step process: 1) preparation of reactive templates using hydrothermal-like synthesis and colloidal chemistry and 2) transformation of the reactive templates in Bi(4)Ti(3)O(12) by solid-state reaction, overcoming the morphological instability problem of 1-D templates. Using piezoresponse force microscopy (PFM) with both out-of-plane and in-plane detection capability, we show that both types of objects exhibit strong piezoelectric activity and good switching ferroelectric behavior. Analysis of the PFM hysteresis loops obtained revealed that the coercive voltage of the in-plane PFM signal can be either equal to or different from that of the out-of-plane response. We associate these situations with two types of polarization switching mechanisms: direct 180° switching, and via rotation of polarization, resulting from the independent switching of the components along the a- and ccrystallographic axes. In a few instances, we observe a negative piezoelectric coefficient, which we explain by the specific shape of the piezoelectric surface of Bi(4)Ti(3)O(12). PMID:23007759

Azodi, Mehrnoosh; Harnagea, Catalin; Buscaglia, Vincenzo; Buscaglia, Maria Theresa; Nanni, Paolo; Rosei, Federico; Pignolet, Alain

2012-09-01

333

Properties of ferroelectric polymers under high pressure and shock loading  

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 CH 2?CF 2 and copolymers PVDF with C 2F 3H. The effects of frequency, temperature and hydrostatic pressure on the dielectric properties, molecular relaxations, and phase transitions of PVDF and a copolymer with 30% trifluoroethylene will be discussed. Pressure causes large slowing down of the ? molecular relaxations as well as large increases in the ferroelectric transition temperatures and melting points, but the magnitudes of the effects are different for the different "transitions". A unique application of these polymers as time-resolved dynamic stress gauges based on PVDF studies under very high pressure shock compression is discussed. In particular piezoelectric response of shock compressed PVDF film prepared with attention to mechanical and electrical processing exhibits precise, well defined reproducible behavior to 35 GPa. P(VDF-TrFE) copolymers exhibit unique piezoelectric properties over a wide range of temperature depending on the compositions. Under high shock pressure loading, unique piezoelectric response is also observed. The first record of detonation profile is presented. Results of PVDF shock sensors subjected to X-ray deposition and to neutron fluence above 10 13 n/cm 2 while stressed at a peak level of 2 GPa will be also discussed.

Bauer, F.

1995-11-01

334

Stable ferroelectric liquid crystals derived from salicylaldimine-core.  

PubMed

Five pairs of enantiomers derived from salicylaldimine-core have been prepared by condensing (R)- or (S)-4-(octan-2-yloxy)anilines with 4-formyl-3-hydroxyphenyl 4-(n-alkoxy)benzoates. They have been designed to probe the correlation between molecular structure and mesomorphism, and especially to provide stable mesogens having potential for applications in ferroelectric liquid crystal devices. Thus, they have been substituted with a chiral tail at one end and by n-alkoxy chains of varying length at the other terminal. A detailed study confirms an indistinguishable behavior of all ten mesogens exhibiting an enantiotropic chiral smectic C (SmC*) phase besides blue phase (BP) and chiral nematic (N*) phase. The SmC* phase occurring over a 50-70 °C thermal width shows ferroelectric switching with spontaneous polarization (Ps) value crossing over 100 nC/cm(2). Circular dichroism spectroscopic study of the mesophases confirms the chromophores of the molecules being in the macroscopic chiral (helical) environment. PMID:25734233

Veerabhadraswamy, Bhyranalyar N; Rao, D S Shankar; Yelamaggad, Channabasaveshwar V

2015-03-26

335

Low-symmetry phases in ferroelectric nanowires.  

PubMed

Ferroelectric nanostructures have recently attracted much attention due to the quest of miniaturizing devices and discovering novel phenomena. In particular, studies conducted on two-dimensional and zero-dimensional ferroelectrics have revealed original properties and their dependences on mechanical and electrical boundary conditions. Meanwhile, researches aimed at discovering and understanding properties of one-dimensional ferroelectric nanostructures are scarce. The determination of the structural phase and of the direction of the polarization in one-dimensional ferroelectrics is of technological importance, since, e.g., a low-symmetry phase in which the polarization lies away from a highly symmetric direction typically generates phenomenal dielectric and electromechanical responses. Here, we investigate the phase transition sequence of nanowires made of KNbO(3) and BaTiO(3) perovskites, by combining X-ray diffraction, Raman spectroscopy, and first-principles-based calculations. We provide evidence of a previously unreported ferroelectric ground state of monoclinic symmetry and the tuning of the polarization's direction by varying factors inherent to the nanoscale. PMID:20230042

Louis, L; Gemeiner, P; Ponomareva, I; Bellaiche, L; Geneste, G; Ma, W; Setter, N; Dkhil, B

2010-04-14

336

Raman study of the improper ferroelectric phase transition in iron iodine boracite  

NASA Technical Reports Server (NTRS)

The reduction in the dielectric anomaly near the phase transition temperature in improper ferroelectrics suggests that this behavior may be exploited to significantly enhance the figure-of-merit for pyroelectric infrared detection. This reduction is associated with a decoupling of the thermal and dielectric responses which, in turn, reflects the unusual nature of the lattice instability at the phase transition. In order to elucidate the characteristics of the phonon behavior connected with the lattice instability, Raman scattering of Fe3B7O13I has been examined in both the paraelectric and ferroelectric phases. The results of this study as well as results from earlier measurements on other boracites, provides insight into the nature of the mode softening.

Kim, Q.; Somoano, R. B.

1981-01-01

337

Misfit strain dependence of ferroelectric and piezoelectric properties of clamped (001) epitaxial Pb(Zr0.52,Ti0.48)O3 thin films  

NASA Astrophysics Data System (ADS)

A study on the effects of the residual strain in Pb(Zr0.52Ti0.48)O3 (PZT) thin films on the ferroelectric and piezoelectric properties is presented. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched between SrRuO3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinations by pulsed laser deposition. Compressive or tensile strain caused by the difference in thermal expansion of the PZT film and substrate influences the ferroelectric and piezoelectric properties. All the PZT stacks show ferroelectric and piezoelectric behavior that is consistent with the theoretical model for strained thin films in the ferroelectric r-phase. We conclude that clamped (001) oriented Pb(Zr0.52Ti0.48)O3 thin films strained by the substrate always show rotation of the polarization vector.

Nguyen, Minh D.; Dekkers, Matthijn; Houwman, Evert; Steenwelle, Ruud; Wan, Xin; Roelofs, Andreas; Schmitz-Kempen, Thorsten; Rijnders, Guus

2011-12-01

338

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

339

Ferroelectric Field Effect Transistor Model Using Partitioned Ferroelectric Layer and Partial Polarization  

NASA Technical Reports Server (NTRS)

A model of an n-channel ferroelectric field effect transistor has been developed based on both theoretical and empirical data. The model is based on an existing model that incorporates partitioning of the ferroelectric layer to calculate the polarization within the ferroelectric material. The model incorporates several new aspects that are useful to the user. It takes into account the effect of a non-saturating gate voltage only partially polarizing the ferroelectric material based on the existing remnant polarization. The model also incorporates the decay of the remnant polarization based on the time history of the FFET. A gate pulse of a specific voltage; will not put the ferroelectric material into a single amount of polarization for that voltage, but instead vary with previous state of the material and the time since the last change to the gate voltage. The model also utilizes data from FFETs made from different types of ferroelectric materials to allow the user just to input the material being used and not recreate the entire model. The model also allows the user to input the quality of the ferroelectric material being used. The ferroelectric material quality can go from a theoretical perfect material with little loss and no decay to a less than perfect material with remnant losses and decay. This model is designed to be used by people who need to predict the external characteristics of a FFET before the time and expense of design and fabrication. It also allows the parametric evaluation of quality of the ferroelectric film on the overall performance of the transistor.

MacLeod, Todd C.; Ho, Fat D.

2004-01-01

340

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

341

Diisopropylammonium bromide is a high-temperature molecular ferroelectric crystal.  

PubMed

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

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

2013-01-25

342

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

343

Uncooled monolithic ferroelectric IRFPA technology  

NASA Astrophysics Data System (ADS)

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

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

1998-10-01

344

Terahertz Frequency Dynamics of Ferroelectric Nanowires  

NASA Astrophysics Data System (ADS)

A thorough understanding of ferroelectric nanostructures is imperative considering their utility in creating nanoscale devices for the technology of the future. One such ferroelectric nanostructure which may prove useful in the design of nanosensors is the nanowire. We report our study on ferroelectric nanowires of Pb(Zr0.4Ti0.6)O3 alloy done using classic molecular dynamics with first-principle-based effective Hamiltonian[1] and Evans-Hoover thermostat. We found that 1) the polarization of such nanowires can be reversed and 2) that the nanowires temperature can be controlled by the application of a terahertz electric field pulse. The dependence of these properties on the frequency, width, and amplitude of the pulse is explored and discussed in addition to a possible energy dissipation mechanism. [1] L. Bellaiche et al, Phys. Rev. Lett. 8, 5427 (2000).

Herchig, Ryan; Schultz, Kimberly; McCash, Kevin; Ponomareva, Inna

2012-02-01

345

Electronic ferroelectricity in molecular organic crystals  

NASA Astrophysics Data System (ADS)

Electronic ferroelectricity in molecular organic crystals is reviewed from a theoretical perspective. In particular, we focus on the charge-driven-type electronic ferroelectricity where electronic charge order without inversion symmetry induces a spontaneous electric polarization in quarter-filling systems. Two necessary conditions to realize this type of ferroelectricity are the dimer-type lattice structure and alternate electronic charge alignments. Some prototypical organic compounds are introduced. In particular, ?-type BEDT-TTF organic salts, which are termed the dimer-Mott insulating systems, are focused on. Recent developments in the theoretical researches for dielectric and magnetodielectric properties, a collective dipole excitation and a possibility of superconductivity induced by polar charge fluctuation are reviewed. Some perspectives are presented.

Ishihara, Sumio

2014-12-01

346

Vortex Domains in Ferroelectric Nano-Structures  

NASA Astrophysics Data System (ADS)

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

Scott, James F.

2011-03-01

347

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

348

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

349

Modified Johnson model for ferroelectric lead lanthanum zirconate titanate at very high fields and below Curie temperature.  

SciTech Connect

A modified Johnson model is proposed to describe the nonlinear field dependence of the dielectric constant ({var_epsilon}-E loop) in ferroelectric materials below the Curie temperature. This model describes the characteristic ferroelectric 'butterfly' shape observed in typical {var_epsilon}-E loops. The predicted nonlinear behavior agreed well with the measured values in both the low- and high-field regions for lead lanthanum zirconate titanate films. The proposed model was also validated at different temperatures below the ferroelectric-to-paraelectric Curie point. The anharmonic coefficient in the model decreased from 6.142 x 10{sup -19} cm{sup 2}/V{sup 2} to 2.039 x 10{sup -19} cm{sup 2}/V{sup 2} when the temperature increased from 25 C to 250 C.

Narayanan, M.; Tong, S.; Ma, B.; Liu, S.; Balachandran, U. (Energy Systems)

2012-01-01

350

Static ferroelectric memory transistor having improved data retention  

DOEpatents

An improved ferroelectric FET structure in which the ferroelectric layer is doped to reduce retention loss. A ferroelectric FET according to the present invention includes a semiconductor layer having first and second contacts thereon, the first and second contacts being separated from one another. The ferroelectric FET also includes a bottom electrode and a ferroelectric layer which is sandwiched between the semiconductor layer and the bottom electrode. The ferroelectric layer is constructed from a perovskite structure of the chemical composition ABO.sub.3 wherein the B site comprises first and second elements and a dopant element that has an oxidation state greater than +4 in sufficient concentration to impede shifts in the resistance measured between the first and second contacts with time. The ferroelectric FET structure preferably comprises Pb in the A-site. The first and second elements are preferably Zr and Ti, respectively. The preferred B-site dopants are Niobium, Tantalum, and Tungsten at concentrations between 1% and 8%.

Evans, Jr., Joseph T. (13609 Verbena Pl., N.E., Albuquerque, NM 87112); Warren, William L. (7716 Wm. Moyers Ave., NE., Albuquerque, NM 87112); Tuttle, Bruce A. (12808 Lillian Pl., NE., Albuquerque, NM 87112)

1996-01-01

351

Probing nanoscale ferroelectricity by ultraviolet Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Conventional vibrational spectroscopies operating in visible and infrared range fail to measure the phonon spectra of nanoscale ferroelectric structures because of extremely weak signals and the overwhelming substrate contribution. In this talk, application of ultraviolet (UV) Raman spectroscopy for studies of lattice dynamics and ferroelectric phase transitions in nanoscale ferroelectrics will be presented. We demonstrate that UV Raman spectroscopy is an effective technique allowing the observation of phonons and determination of the ferroelectric phase transition temperature (Tc) in nanoscale ferroelectrics, specifically, BaTiO3/SrTiO3 superlattices having the ferroelectric BaTiO3 layers as thin as 1 unit cell, and single BaTiO3 layers as thin as 4 nm. BaTiO3/SrTiO3 superlattices and ultrathin BaTiO3 films studied were grown by molecular beam epitaxy on SrTiO3 as well as GdScO3 and DyScO3 substrates. Excellent epitaxial quality and atomically abrupt interfaces are evidenced by X-ray diffraction and high resolution transmission electron microscopy. UV Raman results show that one-unit-cell thick BaTiO3 layers in BaTiO3/SrTiO3 superlattices are ferroelectric with the Tc as high as 250 K, and induce the polarization in much thicker SrTiO3 layers adjacent to them. The Tc in superlattices was tuned by hundreds of degrees from ˜170 to 650 K by varying the thicknesses of BaTiO3 and SrTiO3 layers. Using scandate substrates enables growth of superlattices with systematically changed coherent strain, thus allowing studying the stress effect on the ferroelectric phase transitions. UV Raman data are supported by the thermodynamic calculations of polarization in superlattices as a function of temperature. The work was done in collaboration with A. Soukiassian, W. Tian, D.G. Schlom, Y.L. Li, L.-Q. Chen, X.X. Xi (Pennsylvania State University), A. Bruchhausen, A. Fainstein (Centro Atomico Bariloche & Instituto Balseiro, Argentina), R. S. Katiyar (University of Puerto Rico), A. Cantarero (University of Valencia, Spain), K.J. Choi, D.M. Kim, C.-B. Eom (University of Wisconsin), H.P. Sun, X.Q. Pan (University of Michigan), S.M. Nakhmanson; K.M. Rabe (Rutgers University), Q.X. Jia (Los Alamos National Laboratory)

Tenne, Dmitri

2007-03-01

352

Switching Characteristics of Ferroelectric Transistor Inverters  

NASA Technical Reports Server (NTRS)

This paper presents the switching characteristics of an inverter circuit using a ferroelectric field effect transistor, FeFET. The propagation delay time characteristics, phl and plh are presented along with the output voltage rise and fall times, rise and fall. The propagation delay is the time-delay between the V50% transitions of the input and output voltages. The rise and fall times are the times required for the output voltages to transition between the voltage levels V10% and V90%. Comparisons are made between the MOSFET inverter and the ferroelectric transistor inverter.

Laws, Crystal; Mitchell, Coey; MacLeod, Todd C.; Ho, Fat D.

2010-01-01

353

Anomalously thick domain walls in ferroelectrics  

NASA Astrophysics Data System (ADS)

Using the Landau theory we demonstrate the possibility of unusual, anomalously thick ferroelectric domain walls, where the order parameter rotates with a nearly constant modulus as in ferromagnets. The effect occurs in 90? charged domain walls and is associated with the easy polarization rotation near the morphotropic phase boundary. This magneticlike profile is unique to charged domain walls due to the availability of free charges which screen the depolarizing field resulting from polarization rotation. In contrast to previously known thick ferroelectric domain walls, the large thickness of 90? charged domain walls near the morphotropic boundary is predicted for a wide temperature interval. This property may be favorable for potential applications.

Yudin, P. V.; Gureev, M. Y.; Sluka, T.; Tagantsev, A. K.; Setter, N.

2015-02-01

354

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

355

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

356

Electrically modulated photoluminescence in ferroelectric liquid crystal  

E-print Network

Electrical modulation and switching of photoluminescence (PL) have been demonstrated in pure deformed helix ferroelectric liquid crystal (DHFLC) material. The PL intensity increases and peak position shifts towards lower wavelength above a threshold voltage which continues up to a saturation voltage. This is attributed to the helix unwinding phenomenon in the DHFLC on the application of an electric field. Moreover, the PL intensity could be switched between high intensity (field-on) and low intensity (field-off) positions. These studies would add a new dimension to ferroelectric liquid crystal's application in the area of optical devices.

Prasun Ganguly; T. Joshi; S. Singh; D. Haranath; A. M. Biradar

2012-12-28

357

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

358

Ferroelectric Material Application: Modeling Ferroelectric Field Effect Transistor Characteristics from Micro to Nano  

NASA Technical Reports Server (NTRS)

All present ferroelectric transistors have been made on the micrometer scale. Existing models of these devices do not take into account effects of nanoscale ferroelectric transistors. Understanding the characteristics of these nanoscale devices is important in developing a strategy for building and using future devices. This paper takes an existing microscale ferroelectric field effect transistor (FFET) model and adds effects that become important at a nanoscale level, including electron velocity saturation and direct tunneling. The new model analyzed FFETs ranging in length from 40,000 nanometers to 4 nanometers and ferroelectric thickness form 200 nanometers to 1 nanometer. The results show that FFETs can operate on the nanoscale but have some undesirable characteristics at very small dimensions.

MacLeod, Todd, C.; Ho, Fat Duen

2006-01-01

359

Ferroelectric phase transition in RbH2PO4: Picosecond time-resolved impulsive stimulated Brillouin scattering experiments  

NASA Astrophysics Data System (ADS)

The anomalous acoustic behavior of rubidium dihydrogen phosphate near its ferroelectric phase transition was studied using ``impulsive'' stimulated Brillouin scattering with several scattering angles between 5.05° and 32.2°. The C66 shear elastic stiffness constant in the high-temperature phase showed elastic Curie-Weiss behavior, as expected on the basis of mean-field (MF) theory of the phase transition. Logarithmic corrections to MF behavior, suggested by other reports, were not observed to within 0.01 K of Tc. The p66 photoelastic constant also showed MF behavior. The polarization relaxation-time divergence was consistent with Landau-Khalatnikov theory, i.e., ?~(T-T0)-1 over a substantial temperature range. Our observations are in agreement with those made on other KDP-family crystals, and with theoretical expectations for uniaxial ferroelectrics which are also ferroelastic in the low-temperature phase.

Cheng, Lap-Tak; Nelson, Keith A.

1988-03-01

360

Structure dependence of ferroelectric properties of bismuth layer-structured ferroelectric single crystals  

Microsoft Academic Search

Ferroelectric properties along the a(b) axis and c axis in single crystals of various bismuth layer-structured ferroelectrics (BLSFs) were investigated. By measuring saturated P-E hysteresis curves of BLSFs, values of the saturated remanent polarization and the coercive electric field were found to be related to the Curie temperature and the number of BO6 octahedra (m) between bismuth layers, respectively, along

Hiroshi Irie; Masaru Miyayama; Tetsuichi Kudo

2001-01-01

361

Direct observations of polarization reversal process in ferroelectric thin films using high speed piezoresponse force microscopy  

NASA Astrophysics Data System (ADS)

Ferroelectric thin films have been widely implicated for use in future ultra-high-density memory devices, using atomic force microscopy (AFM) related techniques for the read/write operations of ferroelectric memory media where formation of a single domain structure with a defined polarization direction acts as a distinct memory bit. Therefore, it is important to understand the mechanisms and kinetics involved in the polarization switching process, which includes the nucleation and growth of ferroelectric domains at the nanoscale. In recent years, the piezoresponse force microscopy (PFM) technique has been widely been used to image, characterize and modify the domain structures in ferroelectric films with this spatial resolution. However, operating speeds for PFM (and AFM in general) remain a continuing limitation for imaging dynamic processes such as domain switching and read/write operations. A simple method to increase PFM characterization speeds by several orders of magnitude is presented here based on standard commercial equipment and AFM probes. Essentially, an AC voltage at a high resonance frequency is applied to a conducting AFM tip, which is in contact with a ferroelectric surface. The tip is rapidly rastered across a surface without force feedback, while the amplitude and phase of the high frequency resonances are detected with a lock-in amplifier. Although the topography is not reliably recorded, stable contrast related to ferroelectric properties is accurately mapped due to the relative insensitivity of many dynamic AFM contrast mechanisms to variations in repulsive contact forces. Images with nanoscale contrast of ferroelectric domains are presented, acquired at complete frame rates as low as 6 seconds per 256x256 pixel image. The mechanism and kinetics involved in the dynamic domain switching process of PZT thin films are therefore uniquely presented with nanoscale and nanosecond resolution. It was found that domain dynamics processes are governed by the spatial distribution of inhomogeneities present in the film. This allowed a spatially resolved analysis of nucleation and growth kinetics based on tracking thousands of individual domain locations, areas, nucleation times, and growth rates. Finally, an exponential behavior is observed for individual domain growth, and inversely for nucleation time, as a function of electric field.

Premnath, Ramesh Nath

362

Density fluctuations and phase transitions of ferroelectric polymer nanowires.  

PubMed

Phase transitions of polymeric materials are accompanied by changes in density as a function of temperature. Being able to measure these changes in polymeric systems in one, two or three dimensions on the nanoscopic length-scale is a challenge, but it would provide a simple route to assess phase transitions in nanoscopically confined systems. It is shown that the measurement of the dielectric permittivity in the high frequency limit (in spectral regions not affected by dielectric dispersions) offers an effective and very sensitive means to assess density fluctuations, and hence phase transitions, in nanoscopic systems. The sensitivity of this approach is demonstrated by assessing the phase transition behavior of ferroelectric polymer nanowires confined within alumina membranes. No significant shifts in the Curie transition are observed down to pore diameters as small as 15 nm. PMID:20665753

Serghei, Anatoli; Lutkenhaus, Jodie L; Miranda, Daniel F; McEnnis, Kathleen; Kremer, Friedrich; Russell, Thomas P

2010-08-16

363

A surface-layer model of ferroelectric nanowire  

NASA Astrophysics Data System (ADS)

In this paper, a surface-layer model is established to study the axial polarization distributions and critical diameters of nanowires with different surface compositions. Analytical solutions are obtained based on this model, which are validated by the ab initio results for small-size nanowires and can also predict the behaviors of large-size specimen. Compared to the traditional Landau-Ginzburg-Devonshire theory using an extrapolation length, the present model describes more microstructure information of the surface-layer, and is thus capable of characterizing the influences of different surface compositions. Furthermore, this model may shed insight into the mechanisms of the size effect and polarization distribution patterns in nanoscale ferroelectrics.

Zhang, Yihui; Hong, Jiawang; Liu, Bin; Fang, Daining

2010-12-01

364

Properties of ferroelectric/ferromagnetic thin film heterostructures  

SciTech Connect

Ferroelectric/ferromagnetic thin film heterostructures, SrBi{sub 2}Ta{sub 2}O{sub 9}/BaFe{sub 12}O{sub 19} (SBT/BaM), were grown on platinum-coated Si substrates using metal-organic decomposition. X-ray diffraction patterns confirmed that the heterostructures contain only SBT and BaM phases. The microwave properties of these heterostructures were studied using a broadband ferromagnetic resonance (FMR) spectrometer from 35 to 60 GHz, which allowed us to determine gyromagnetic ratio and effective anisotropy field. The FMR linewidth is as low as140 Oe at 58 GHz. In addition, measurements of the effective permittivity of the heterostructures were carried out as a function of bias electric field. All heterostructures exhibit hysteretic behavior of the effective permittivity. These properties indicate that such heterostructures have potential for application in dual electric and magnetic field tunable resonators, filters, and phase shifters.

Chen, Daming, E-mail: chendaming1986@gmail.com [Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, 1420 Austin Bluffs Pkwy, Colorado Springs, Colorado 80918 (United States); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054 Sichuan (China); Harward, Ian; Linderman, Katie; Economou, Evangelos; Celinski, Zbigniew [Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, 1420 Austin Bluffs Pkwy, Colorado Springs, Colorado 80918 (United States); Nie, Yan [Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, 1420 Austin Bluffs Pkwy, Colorado Springs, Colorado 80918 (United States); School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074 (China)

2014-05-07

365

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

366

Soft memory in a ferroelectric nanoparticle-doped liquid crystal.  

PubMed

A small quantity of BaTiO(3) 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. PMID:25353490

Basu, Rajratan

2014-02-01

367

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

368

Aging effect in paraelectric state of ferroelectrics: Implication for a microscopic explanation of ferroelectric deaging  

NASA Astrophysics Data System (ADS)

Most ferroelectric materials exhibit aging effect (a time-dependent change in physical properties) in their ferroelectric state; however, aging is not reported to exist in the paraelectric state. In this letter we report the existence of a "paraelectric aging effect" in Mn-doped (Ba0.80Sr0.20)TiO3 ceramics. We found that when the paraelectric state is formed from an aged ferroelectric state through a reverse ferroelectric transition, the paraelectric state shows a gradual increase in the dielectric permittivity and decrease in dielectric loss with time. Such paraelectric aging effect exists only in acceptor-doped samples, not in undoped samples. The kinetics of the paraelectric aging follows a simple relaxation function with activation energy of 0.43 eV. Our results suggest that the paraelectric aging stems from the migration of oxygen vacancies, being the same as the case of ferroelectric aging. We show that such a migration is driven by a symmetry-conforming short-range ordering tendency of point defects. Such a microscopic mechanism also provides a microscopic explanation for the well-observed "ferroelectric deaging effect."

Xue, Dezhen; Gao, Jinghui; Zhang, Lixue; Bao, Huixin; Liu, Wenfeng; Zhou, Chao; Ren, Xiaobing

2009-02-01

369

Theory of ferroelectric polymer-ceramic composites  

Microsoft Academic Search

A model is proposed to establish the relevant constitutional parameters of ferroelectric composite materials such as shape, composition, and connectivity which determine the piezoelectric, dielectric, and elastic properties of the composite. A proper Monte Carlo method is used to calculate the active volumetric fraction of ceramic. An equivalent circuit is proposed to calculate the effective dielectric constant. The effective medium

Habtamu Zewdie; F. Brouers

1990-01-01

370

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.

371

Local polarization dynamics in ferroelectric materials  

NASA Astrophysics Data System (ADS)

Ferroelectrics and multiferroics have recently emerged as perspective materials for information technology and data storage applications. The combination of extremely narrow domain wall width and the capability to manipulate polarization by electric field opens the pathway toward ultrahigh (>10 TBit inch-2) storage densities and small (sub-10 nm) feature sizes. The coupling between polarization and chemical and transport properties enables applications in ferroelectric lithography and electroresistive devices. The progress in these applications, as well as fundamental studies of polarization dynamics and the role of defects and disorder on domain nucleation and wall motion, requires the capability to probe these effects on the nanometer scale. In this review, we summarize the recent progress in applications of piezoresponse force microscopy (PFM) for imaging, manipulation and spectroscopy of ferroelectric switching processes. We briefly introduce the principles and relevant instrumental aspects of PFM, with special emphasis on resolution and information limits. The local imaging studies of domain dynamics, including local switching and relaxation accessed through imaging experiments and spectroscopic studies of polarization switching, are discussed in detail. Finally, we review the recent progress on understanding and exploiting photochemical processes on ferroelectric surfaces, the role of surface adsorbates, and imaging and switching in liquids. Beyond classical applications, probing local bias-induced transition dynamics by PFM opens the pathway to studies of the influence of a single defect on electrochemical and solid state processes, thus providing model systems for batteries, fuel cells and supercapacitor applications.

Kalinin, Sergei V.; Morozovska, Anna N.; Qing Chen, Long; Rodriguez, Brian J.

2010-05-01

372

Graded Ferroelectric Capacitors with Robust Temperature Characteristics  

Microsoft Academic Search

the possibility of engineering a high dielectric response for tunable components in frequency-agile RF and microwave devices. However, this approach often leads to an undesired temperature sensitivity. Compositionally graded ferroelectric films have been explored as a means of redressing this sensitivity, but experimental observations vary depending on geometry and other details. In this paper, we present a continuum model to

Mohamed Y. El-Naggar; Kaushik Dayal; David G. Goodwin; Kaushik Bhattacharya

2006-01-01

373

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

374

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

375

Ferroelectric polarization reversal via successive ferroelastic transitions.  

PubMed

Switchable polarization makes ferroelectrics a critical component in memories, actuators and electro-optic devices, and potential candidates for nanoelectronics. Although many studies of ferroelectric switching have been undertaken, much remains to be understood about switching in complex domain structures and in devices. In this work, a combination of thin-film epitaxy, macro- and nanoscale property and switching characterization, and molecular dynamics simulations are used to elucidate the nature of switching in PbZr(0.2)Ti(0.8)O3 thin films. Differences are demonstrated between (001)-/(101)- and (111)-oriented films, with the latter exhibiting complex, nanotwinned ferroelectric domain structures with high densities of 90° domain walls and considerably broadened switching characteristics. Molecular dynamics simulations predict both 180° (for (001)-/(101)-oriented films) and 90° multi-step switching (for (111)-oriented films) and these processes are subsequently observed in stroboscopic piezoresponse force microscopy. These results have implications for our understanding of ferroelectric switching and offer opportunities to change domain reversal speed. PMID:25344784

Xu, Ruijuan; Liu, Shi; Grinberg, Ilya; Karthik, J; Damodaran, Anoop R; Rappe, Andrew M; Martin, Lane W

2015-01-01

376

Ferroelectric Devices Emit Charged Particles and Radiation  

NASA Technical Reports Server (NTRS)

Devices called solid-state ferroelectric- based sources (SSFBSs) are under development as sources of electrons, ions, ultraviolet light, and x-rays for diverse applications in characterization and processing of materials. Whereas heretofore it has been necessary to use a different device to generate each of the aforementioned species of charged particles or radiation, a single SSFBS can be configured and operated to selectively generate any of the species as needed using a single source. Relative to comparable prior sources based, variously, on field emission, thermionic emission, and gaseous discharge plasmas, SSFBSs demand less power, and are compact and lightweight. An SSFBS exploits the unique physical characteristics of a ferroelectric material in the presence of a high-frequency pulsed electric field. The basic building block of an SSFBS is a ferroelectric cathode -- a ferroelectric wafer with a solid electrode covering its rear face and a grid electrode on its front face (see figure). The application of a voltage pulse -- typically having amplitude of several kilovolts and duration of several nanoseconds -- causes dense surface plasma to form near the grid wires on the front surface.

Bar-Cohen, Yoseph; Sherrit, Stewart; Bao, Xiaoqi; Felsteiner, Joshua; Karsik, Yakov

2005-01-01

377

Ferroelectric control of a Mott insulator  

PubMed Central

The electric field control of functional properties is an important goal in oxide-based electronics. To endow devices with memory, ferroelectric gating is interesting, but usually weak compared to volatile electrolyte gating. Here, we report a very large ferroelectric field-effect in perovskite heterostructures combining the Mott insulator CaMnO3 and the ferroelectric BiFeO3 in its “supertetragonal” phase. Upon polarization reversal of the BiFeO3 gate, the CaMnO3 channel resistance shows a fourfold variation around room temperature, and a tenfold change at ~200 K. This is accompanied by a carrier density modulation exceeding one order of magnitude. We have analyzed the results for various CaMnO3 thicknesses and explain them by the electrostatic doping of the CaMnO3 layer and the presence of a fixed dipole at the CaMnO3/BiFeO3 interface. Our results suggest the relevance of ferroelectric gates to control orbital- or spin-ordered phases, ubiquitous in Mott systems, and pave the way toward efficient Mott-tronics devices. PMID:24089020

Yamada, Hiroyuki; Marinova, Maya; Altuntas, Philippe; Crassous, Arnaud; Bégon-Lours, Laura; Fusil, Stéphane; Jacquet, Eric; Garcia, Vincent; Bouzehouane, Karim; Gloter, Alexandre; Villegas, Javier E.; Barthélémy, Agnès; Bibes, Manuel

2013-01-01

378

Thermotropic phase boundaries in classic ferroelectrics.  

PubMed

High-performance piezoelectrics are lead-based solid solutions that exhibit a so-called morphotropic phase boundary, which separates two competing phases as a function of chemical composition; as a consequence, an intermediate low-symmetry phase with a strong piezoelectric effect arises. In search for environmentally sustainable lead-free alternatives that exhibit analogous characteristics, we use a network of competing domains to create similar conditions across thermal inter-ferroelectric transitions in simple, lead-free ferroelectrics such as BaTiO3 and KNbO3. Here we report the experimental observation of thermotropic phase boundaries in these classic ferroelectrics, through direct imaging of low-symmetry intermediate phases that exhibit large enhancements in the existing nonlinear optical and piezoelectric property coefficients. Furthermore, the symmetry lowering in these phases allows for new property coefficients that exceed all the existing coefficients in both parent phases. Discovering the thermotropic nature of thermal phase transitions in simple ferroelectrics thus presents unique opportunities for the design of 'green' high-performance materials. PMID:24445840

Lummen, Tom T A; Gu, Yijia; Wang, Jianjun; Lei, Shiming; Xue, Fei; Kumar, Amit; Barnes, Andrew T; Barnes, Eftihia; Denev, Sava; Belianinov, Alex; Holt, Martin; Morozovska, Anna N; Kalinin, Sergei V; Chen, Long-Qing; Gopalan, Venkatraman

2014-01-01

379

Thermotropic phase boundaries in classic ferroelectrics  

NASA Astrophysics Data System (ADS)

High-performance piezoelectrics are lead-based solid solutions that exhibit a so-called morphotropic phase boundary, which separates two competing phases as a function of chemical composition; as a consequence, an intermediate low-symmetry phase with a strong piezoelectric effect arises. In search for environmentally sustainable lead-free alternatives that exhibit analogous characteristics, we use a network of competing domains to create similar conditions across thermal inter-ferroelectric transitions in simple, lead-free ferroelectrics such as BaTiO3 and KNbO3. Here we report the experimental observation of thermotropic phase boundaries in these classic ferroelectrics, through direct imaging of low-symmetry intermediate phases that exhibit large enhancements in the existing nonlinear optical and piezoelectric property coefficients. Furthermore, the symmetry lowering in these phases allows for new property coefficients that exceed all the existing coefficients in both parent phases. Discovering the thermotropic nature of thermal phase transitions in simple ferroelectrics thus presents unique opportunities for the design of ‘green’ high-performance materials.

Lummen, Tom T. A.; Gu, Yijia; Wang, Jianjun; Lei, Shiming; Xue, Fei; Kumar, Amit; Barnes, Andrew T.; Barnes, Eftihia; Denev, Sava; Belianinov, Alex; Holt, Martin; Morozovska, Anna N.; Kalinin, Sergei V.; Chen, Long-Qing; Gopalan, Venkatraman

2014-01-01

380

Ferroelectric polarization reversal via successive ferroelastic transitions  

NASA Astrophysics Data System (ADS)

Switchable polarization makes ferroelectrics a critical component in memories, actuators and electro-optic devices, and potential candidates for nanoelectronics. Although many studies of ferroelectric switching have been undertaken, much remains to be understood about switching in complex domain structures and in devices. In this work, a combination of thin-film epitaxy, macro- and nanoscale property and switching characterization, and molecular dynamics simulations are used to elucidate the nature of switching in PbZr0.2Ti0.8O3 thin films. Differences are demonstrated between (001)-/(101)- and (111)-oriented films, with the latter exhibiting complex, nanotwinned ferroelectric domain structures with high densities of 90° domain walls and considerably broadened switching characteristics. Molecular dynamics simulations predict both 180° (for (001)-/(101)-oriented films) and 90° multi-step switching (for (111)-oriented films) and these processes are subsequently observed in stroboscopic piezoresponse force microscopy. These results have implications for our understanding of ferroelectric switching and offer opportunities to change domain reversal speed.

Xu, Ruijuan; Liu, Shi; Grinberg, Ilya; Karthik, J.; Damodaran, Anoop R.; Rappe, Andrew M.; Martin, Lane W.

2015-01-01

381

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

382

Inductive crystallization effect of atomic-layer-deposited Hf0.5Zr0.5O2 films for ferroelectric application  

NASA Astrophysics Data System (ADS)

Ferroelectric Hf x Zr1- x O2 thin films are considered promising candidates for future lead-free CMOS-compatible ferroelectric memory application. The inductive crystallization behaviors and the ferroelectric performance of Hf0.5Zr0.5O2 thin films prepared by atomic layer deposition were investigated. Inductive crystallization can be induced by the film growth condition and appropriate top electrode selection. In this work, a Ni/Hf0.5Zr0.5O2/Ru/Si stack annealed at 550°C for 30 s in N2 ambient after the Ni top electrode has been deposited was manufactured, and it shows the best ferroelectric hysteresis loop in the dielectric thickness of 25 nm, with a remanent polarization value of 6 ?C/cm2 and a coercive field strength of 2.4 MV/cm measured at 10 kHz. Endurance, retention, and domain switching current characteristics were evaluated well for potential application in the field of ferroelectric field effect transistor (FeFET) and nonvolatile ferroelectric memories (FeRAM).

Zhang, Xun; Chen, Lin; Sun, Qing-Qing; Wang, Lu-Hao; Zhou, Peng; Lu, Hong-Liang; Wang, Peng-Fei; Ding, Shi-Jin; Zhang, David Wei

2015-01-01

383

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

384

Modeling ferroelectric permittivity dependence on electric field and estimation of the intrinsic and extrinsic contributions  

NASA Astrophysics Data System (ADS)

The nonlinear dependence of the dielectric permittivity on electric field ?(E) is modeled by the relationship ?(E) = ?00 + 1/(? + ? Eeff2), where Eeff = E + ? P(E). Using an appropriate mathematical representation of the polarization loop P(E), it is possible to describe correctly the hysteretic behavior of the curve ?(E). This model allows the separation of the intrinsic and extrinsic contributions to the dielectric response from the experimental measurement of ?(E). The model is validated for PZT and PLZT ferroelectric thin films. It is shown that the polarization hysteresis loop can be reconstructed from the curve ?(E), which can be very useful for separating polarization current from leakage current in ferroelectric samples.

Placeres-Jiménez, R.; Rino, J. P.; Eiras, J. A.

2015-01-01

385

Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions  

NASA Astrophysics Data System (ADS)

Based on model calculations we predict electric-field control of the spin-transfer torque (STT) in magnetic tunnel junctions with ferroelectric barriers. We demonstrate that the bias dependence of the in-plane T? and out-of-plane T? components of the STT can be dramatically modified by the ferroelectric polarization. In particular, the magnitude of the STT can be enhanced or suppressed by switching the polarization direction and in some cases the sign of STT can be toggled. The underlying mechanism is the combination of polarization-induced symmetry breaking and the interplay of the bias-induced and polarization-induced spin-dependent screening giving rise to a rich behavior of the electrostatic potential energy profile. These properties could lead to enhanced switching efficiency in STT-based devices and open a new avenue for applications of multiferroic devices.

Useinov, Artur; Kalitsov, Alan; Velev, Julian; Kioussis, Nicholas

2015-03-01

386

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

PubMed

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. PMID:24953042

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

2014-08-01

387

The effects of layering in ferroelectric Si-doped HfO{sub 2} thin films  

SciTech Connect

Atomic layer deposited Si-doped HfO{sub 2} thin films approximately 10?nm thick are deposited with various Si-dopant concentrations and distributions. The ferroelectric behavior of the HfO{sub 2} thin films are shown to be dependent on both the Si mol. % and the distribution of Si-dopants. Metal-ferroelectric-insulator-semiconductor capacitors are shown to exhibit a tunable remanent polarization through the adjustment of the Si-dopant distribution at a constant Si concentration. Inhomogeneous layering of Si-dopants within the thin films effectively lowers the remanent polarization. A pinched hysteresis loop is observed for higher Si-dopant concentrations and found to be dependent on the Si layering distribution.

Lomenzo, Patrick D.; Nishida, Toshikazu, E-mail: nishida@ufl.edu [Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida 32611 (United States); Takmeel, Qanit; Moghaddam, Saeed [Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States); Zhou, Chuanzhen; Liu, Yang; Fancher, Chris M.; Jones, Jacob L. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27696-7907 (United States)

2014-08-18

388

New classes of piezoelectrics, ferroelectrics, and antiferroelectrics by first-principles high-throughput materials design  

NASA Astrophysics Data System (ADS)

Functional materials, such as piezoelectrics, ferroelectrics, and antiferroelectrics, exhibit large changes with applied fields and stresses. This behavior enables their incorporation into a wide variety of devices in technological fields such as energy conversion/storage and information processing/storage. Discovery of functional materials with improved performance or even new types of responses is thus not only a scientific challenge, but can have major impacts on society. In this talk I will review our efforts to uncover new families of functional materials using a combined crystallographic database/high-throughput first-principles approach. I will describe our work on the design and discovery of thousands of new functional materials, specifically the LiAlSi family as piezoelectrics, the LiGaGe family as ferroelectrics, and the MgSrSi family as antiferroelectrics.

Bennett, Joseph

2013-03-01

389

Ferroelectric liquid crystal waveguide modulators  

NASA Astrophysics Data System (ADS)

Liquid crystals (LCs) possess effective electro-optic coefficients orders of magnitude larger than other materials used in integrated optics such as lithium niobate or poled polymers. In addition, the relatively simple fabrication of huge arrays of LC-based devices has made them the technology of choice in the flat panel display market. When nematic LC displays were introduced in the 1970's, researchers investigated waveguiding in these material, but found they scattered light too strongly to be of practical use. In 1980, the surface stabilized ferroelectric liquid crystal (FLC) display element was introduced, which used the smectic C liquid crystalline state. The smectic state has a higher degree of ordering than the nematic state, and therefore exhibits far less scattering loss. However, in stark contrast to the large volume of nematic waveguiding research performed following the introduction of the nematic based displays, there have been relatively few studies of FLC waveguides. This research described an FLC cladded waveguide as well as an FLC film waveguide. The performance of these two structures was calculated, and it was shown that the switching effect of the FLC film waveguide is greater but more sensitive to FLC defects. Several different modulator configurations are described and their performance is modeled theoretically. These configurations include Mach-Zehnder and directional couplers, a cut-off modulator, a deflection modulator, and a prism/total internal reflection modulator. Coupling light into a liquid crystal waveguide is complicated by the thick substrates and covers required to mechanically support the liquid film. Techniques for coupling light into the waveguide are described including techniques that directly excite the mode in the waveguide, and indirect techniques that first excite a mode in an intermediary waveguide (such as a polymer waveguide or an optical fiber), then transfer power to the FLC film. An experimental FLC waveguide modulator was designed and built. It was found that these devices require virtually defect-free uniform alignments because defects in the FLC cause significant scattering. Finally, the surface mode which propagates at the interface including an anisotropic material (like FLCs) was investigated and possible implications to FLC waveguides was discussed.

Walker, David Brian

390

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

391

Ferroelectric domain wall motion induced by polarized light  

NASA Astrophysics Data System (ADS)

Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light.

Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F.

2015-03-01

392

Ferroelectric domain wall motion induced by polarized light.  

PubMed

Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F

2015-01-01

393

Ferroelectric domain wall motion induced by polarized light  

PubMed Central

Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F.

2015-01-01

394

Molecule-displacive ferroelectricity in organic supramolecular solids  

NASA Astrophysics Data System (ADS)

Ferroelectricity is essential to many forms of current technology, ranging from sensors and actuators to optical or memory devices. In this circumstance, organic ferroelectrics are of particular importance because of their potential application in tomorrow's organic devices, and several pure organic ferroelectrics have been recently developed. However, some problems, such as current leakage and/or low working frequencies, make their application prospects especially for ferroelectric memory (FeRAM) not clear. Here, we describe the molecule-displacive ferroelectricity of supramolecular adducts of tartaric acid and 1,4-diazabicyclo[2.2.2]octane N,N'-dioxide. The adducts show large spontaneous polarization, high rectangularity of the ferroelectric hysteresis loops even at high operation frequency (10 kHz), and high performance in polarization switching up to 1 × 106 times without showing fatigue. It opens great perspectives in terms of applications, especially in organic FeRAM.

Ye, Heng-Yun; Zhang, Yi; Noro, Shin-Ichiro; Kubo, Kazuya; Yoshitake, Masashi; Liu, Zun-Qi; Cai, Hong-Ling; Fu, Da-Wei; Yoshikawa, Hirofumi; Awaga, Kunio; Xiong, Ren-Gen; Nakamura, Takayoshi

2013-07-01

395

The origin of ferroelectricity in magnetoelectric YMnO3  

Microsoft Academic Search

Understanding the ferroelectrocity in magnetic ferroelectric oxides is of both fundamental and technological importance. Here, we identify the nature of the ferroelectric phase transition in the hexagonal manganite, YMnO3, using a combination of single-crystal X-ray diffraction, thorough structure analysis and first-principles density-functional calculations. The ferroelectric phase is characterized by a buckling of the layered MnO5 polyhedra, accompanied by displacements of

Bas B. Van Aken; Thomas T. M. Palstra; Alessio Filippetti; Nicola A. Spaldin

2004-01-01

396

Ferroelectric mesoscopic structures by room-temperature PLD  

NASA Astrophysics Data System (ADS)

Usually ferroelectric thin films are deposited by pulsed laser deposition (PLD) at elevated substrate temperatures, in order to obtain a good crystalline quality. Here we report the fabrication of ferroelectric BaTiO3 and BiFeO3 structures by room-temperature PLD combined with post-deposition annealing, and their ferroelectric characterization. A method to control the position of the deposited structures is also presented.

Harnagea, C.; Cojocaru, C. V.; Gautreau, O.; Rosei, F.; Pignolet, A.

2007-04-01

397

Stochastic ferroelectric switching of lead zirconate titanate thin films  

NASA Astrophysics Data System (ADS)

We investigate the repolarization phenomenon in a ferroelectric film. Our ferroelectric sample was lead zirconate titanate (PZT) obtained by sol-gel synthesis and deposited by spin coating on ITO/glass substrate. A series of repolarizations were induced in the ferroelectric film by applying a triangular wave and the current peaks related to the switchings of the ferroelectric domains were acquired for statistical analyses. It is shown that the dynamics and statistics of polarization switchings are well simulated by a simple mean-field model in which a double-well, asymmetric potential is included to describe the asymmetry at the PZT-ITO interface.

Marino, S.; Lepreti, F.; Carbone, V.; Scaramuzza, N.

2010-04-01

398

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

399

Relaxation of ferroelectric thin films of diisopropylammonium perchlorate.  

PubMed

Molecular ferroelectric thin films are highly desirable for their easy and environmentally friendly processing, light weight, and mechanical flexibility. A thin film of diisopropylammonium perchlorate (DIPAP) processed by a spin-coating method shows a good roughness and textured structure with (101) orientation in the ferroelectric phase with a space group of P1. Simultaneously, the thin film shows ferroelectricity and ferroelectric relaxivity above room temperature, which is completely different from crystals. These properties make DIPAP a candidate in sensing, data storage, electro-optics, and molecular/flexible electronics. PMID:25583685

Zhu, Jiansheng; Gao, Kaige; Xiao, Shuyu; Qiu, Xiangbiao; Cai, Hong-Ling; Wu, X S

2015-02-14

400

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

401

Block copolymer/ferroelectric nanoparticle nanocomposites  

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available: Summary of data for star-like PAA-b-PS, 1H-NMR, XRD, EDS, TGA, TEM and AFM images. See DOI: 10.1039/c3nr03036a

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

2013-08-01

402

Glucose Suppresses Biological Ferroelectricity in Aortic Elastin  

NASA Astrophysics Data System (ADS)

Elastin is an intriguing extracellular matrix protein present in all connective tissues of vertebrates, rendering essential elasticity to connective tissues subjected to repeated physiological stresses. Using piezoresponse force microscopy, we show that the polarity of aortic elastin is switchable by an electrical field, which may be associated with the recently discovered biological ferroelectricity in the aorta. More interestingly, it is discovered that the switching in aortic elastin is largely suppressed by glucose treatment, which appears to freeze the internal asymmetric polar structures of elastin, making it much harder to switch, or suppressing the switching completely. Such loss of ferroelectricity could have important physiological and pathological implications from aging to arteriosclerosis that are closely related to glycation of elastin.

Liu, Yuanming; Wang, Yunjie; Chow, Ming-Jay; Chen, Nataly Q.; Ma, Feiyue; Zhang, Yanhang; Li, Jiangyu

2013-04-01

403

Fast Ferroelectric L-band Tuner  

SciTech Connect

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. [High Energy Accelerator Research Organization (KEK), Tsukua, 305-0801 (Japan); Omega-P, Inc., New Haven, CT 06511 (United States); Yakovlev, V. P. [Omega-P, Inc., New Haven, CT 06511 (United States); Hirshfield, J. L. [Omega-P, Inc., New Haven, CT 06511 (United States); Yale University, Physics Department, New Haven, CT 06520 (United States); Kanareykin, A. D. [Euclid TechLabs, LLC, Solon, OH 44139 (United States); Nenasheva, E. A. [Ceramics, Ltd, St. Petersburg 194223 (Russian Federation)

2006-11-27

404

Micromachined high frequency ferroelectric sonar transducers  

Microsoft Academic Search

Millimeter-sized ferroelectric monomorph sonar transducers have been built using sol-gel PZT on micromachined silicon wafers. First generation transducer arrays with diaphragms varying in size from 0.2 to 2 mm were tested. Second generation 8×8 arrays have also been built and tested in water in the frequency range of 0.3 to 2 MHz. Improvements to the sol-gel process have yielded high-quality,

J. J. Bernstein; S. L. Finberg; K. Houston; L. C. Niles; H. D. Chen; L. E. Cross; K. K. Li; K. Udayakumar

1997-01-01

405

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

406

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

407

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

408

Flat panel ferroelectric electron emission display system  

DOEpatents

A device is disclosed 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. 6 figs.

Sampayan, S.E.; Orvis, W.J.; Caporaso, G.J.; Wieskamp, T.F.

1996-04-16

409

Ferroelectric domain inversion: The role of humidity  

NASA Astrophysics Data System (ADS)

The authors report on the effect of ambient humidity on domain inversion in ferroelectrics using atomic force microscopy. It is shown that the size of single domains inverted under low humidity in stoichiometric lithium tantalate single crystals is much smaller relative to ambient conditions. These differences are due to the much smaller tip-sample capacitance under low humidity. This phenomenon paves the way for the use of atomic force microscopy to tailor various nanodomain configurations for nonlinear optical applications.

Dahan, D.; Molotskii, M.; Rosenman, G.; Rosenwaks, Y.

2006-10-01

410

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

411

Piezoelectricity and Ferroelectricity in one dimensional nanowires  

NASA Astrophysics Data System (ADS)

Two recent studies, one by Mele and Král on the theoretical study of the polarization and piezoelectricity of BN nanotube and another by Yun et al. on the experimental study of the synthesis and the ferroelectric property of BaTiO3 single crystalline nanowire, showed exciting results for such piezoelectric/ferroelectric nanomaterials being used for studying low dimensional piezoelectricity and ferroelectricity at the nanoscale. These two nanomaterials represent two unique material nanosystems. BN nanotube is layered and uniquely tubular in structure and has chiral symmetry variations; and BaTiO3 nanowire is a crystalline and one dimensional solid. In this study, we report our recent results on the synthesis of BaTiO3 nanowires having diameters of as small as 6 nm, and the piezoelectric characterization of such nanowires; we also present our systematic study of the mechanics and the piezoelectric property of individual BN nanotubes, using our recently developed advanced nanomanipulation tools integrated with various microscopes.

Wang, Zhaoyu; Suryavanshi, Abhijit; Wen, Jianguo; Yu, Min-Feng

2004-03-01

412

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

413

Ferroelectric tunnel junctions with graphene electrodes  

NASA Astrophysics Data System (ADS)

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 × 105%. 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.

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

2014-11-01

414

WFL: Microwave Applications of Thin Ferroelectric Films  

NASA Technical Reports Server (NTRS)

We have developed a family of tunable microwave circuits, operating from X- through Ka-band, based on laser ablated BaxSr1-xTiO films on lanthanum aluminate and magnesium oxide substrates. Circuits include voltage controlled oscillators, filters, phase shifters and antennas. A review of the basic theory of operation of these devices will be presented along with measured performance. Emphasis has been on low-loss phase shifters to enable a new phased array architecture. The critical role of phase shifter loss and transient response in reflectarray antennas will be discussed. The Ferroelectric Reflectarray Critical Components Space Experiment was launched on the penultimate Space Shuttle, STS-134, in May of 2011. It included a bank of ferroelectric phase shifters with two different stoichiometries as well as ancillary electronics. The experiment package and status will be reported. In addition, unusual results of a Van der Pauw measurement involving a ferroelectric film grown on buffered high resisitivity silicon will be discussed.

Romanofsky, Robert

2013-01-01

415

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

416

Enhanced ferroelectric loop asymmetry of lead zirconate titanate thin films under nanoindentation  

NASA Astrophysics Data System (ADS)

The effect of mechanical stress on the local switching behavior and hysteresis properties of Pb(Zr ,Ti)O3 and Mn-doped Pb(Zr ,Ti)O3 ferroelectric thin films has been studied using spherical nanoindentation. A conductive WC-Co cermet indenter tip of 500?m nominal radius was employed in a modified nanoindentation system to allow the simultaneous application of driving voltage and mechanical loading, and consequently to collect the ferroelectric charge developed on thin films without a top electrode. Instrumented progressive indentation caused an enhancement of hysteresis loop deformations. The charge released versus applied voltage (Q-V) hysteresis loops gradually shifted along the voltage axis with increasing indentation force. Also, an enhanced vertical shift and hysteresis gap of the Q-V loops was observed. The parameter of horizontal loop asymmetry (? ) increased almost linearly with the force by an increment of about (0.4-0.5)×10-3/100mN with a 50V peak drive voltage and a 50Hz sinusoidal wave form. The effect of nanoindentation on polarization reversal in thin ferroelectric films is suggested to result from a variation in residual stress state, asymmetric distribution of charged defects, and asymmetric lattice distortion produced by the inhomogeneous indentation stress field.

Koval, V.; Reece, M. J.; Bushby, A. J.

2007-01-01

417

Nanoscale ferroelectric and piezoelectric properties of Sb2S3 nanowire arrays.  

PubMed

We report the first observation of piezoelectricity and ferroelectricity in individual Sb(2)S(3) nanowires embedded in anodic alumina templates. Switching spectroscopy-piezoresponse force microscopy (SS-PFM) measurements demonstrate that individual, c-axis-oriented Sb(2)S(3) nanowires exhibit ferroelectric as well as piezoelectric switching behavior. Sb(2)S(3) nanowires with nominal diameters of 200 and 100 nm showed d(33(eff)) values around 2 pm V(-1), while the piezo coefficient obtained for 50 nm diameter nanowires was relatively low at around 0.8 pm V(-1). A spontaneous polarization (P(s)) of approximately 1.8 ?C cm(-2) was observed in the 200 and 100 nm Sb(2)S(3) nanowires, which is a 100% enhancement when compared to bulk Sb(2)S(3) and is probably due to the defect-free, single-crystalline nature of the nanowires synthesized. The 180° ferroelectric monodomains observed in Sb(2)S(3) nanowires were due to uniform polarization alignment along the polar c-axis. PMID:22268546

Varghese, Justin; Barth, Sven; Keeney, Lynette; Whatmore, Roger W; Holmes, Justin D

2012-02-01

418

Ferroelectricity in hexagonal YFeO3 film at room temperature  

NASA Astrophysics Data System (ADS)

In this paper we report the leakage current, ferroelectric and piezoelectric properties of the YFeO3 film with hexagonal structure, which was fabricated on Si(111) substrate by a simple sol-gel method. The leakage current test shows good characteristics as the leakage current density is 5.4×10?6 A/cm2 under 5 V. The dominant leakage mechanism is found to be an Ohmic behavior at low electric field and space-charge-limited conduction at high electric field region. The P–E measurements show ferroelectric hysteresis loops with small remnant polarization and coercive field at room temperature. The distinct and switchable domain structures on the nanometer scale are observed by piezoresponse force microscopy, which testifies to the ferroelectricity of the YFeO3 film further. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471301, 61078057, 51202195, and 511172183), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20126102110045), and the NPU Foundation for Fundamental Research (Grant Nos. JC201155, JC201271, and JC20120246).

Zhang, Run-Lan; Chen, Chang-Le; Zhang, Yun-Jie; Xing, Hui; Dong, Xiang-Lei; Jin, Ke-Xin

2015-01-01

419

Electronic and magnetic structures of the ferroelectric compound PbBaFe2O5  

NASA Astrophysics Data System (ADS)

By using first-principles electronic and magnetic as well as ferroelectric property calculations on the ferroelectric compound PbBaFe2O5 , we find that the ground states of the two PbBaFe2O5 phases, the space group I m m a and P n m a phases, exhibit an antiferromagnetic structure with a propagation vector [0 ,1/2 ,1/2 ] state and the magnetic moment of 3.99 ?B on Fe atoms, which are in good agreement with neutron diffraction experiments. In addition, we find that this magnetic ordering state is an insulating state with an energy gap of 2.24 (2.62) eV for the I m m a (P n m a ) phase. These findings can be tested by future optical measurements. Furthermore, the parameters of magnetic exchange coupling are also evaluated to illustrate the nature of frustrated magnetic behaviors based on the localized Heisenberg model. Finally, we discuss whether the presence of an improper geometric spin frustration causes the appearance of ferroelectricity.

Li, Wei; Xu, Xuguang; Wei, Xin-Yuan; Mu, Gang; Ting, C. S.; Chen, Yan

2015-02-01

420

Large electrostrain in poled and aged acceptor-doped ferroelectric ceramics via reversible domain switching  

NASA Astrophysics Data System (ADS)

The electrostrain behavior through reversible domain switching in aged acceptor-doped ferroelectric ceramics has been widely investigated in the past decade. However, previous works were focused on unpoled ceramics, which could only utilize part of domains to exchange nonequal crystalline axis to generate strain under external electric field. In this paper, we proposed an effective method: (1) Initially, the acceptor-doped ceramics should be poled. (2) Then, the ceramics need to be aged for enough time. (3) Finally, the applied electric field should be perpendicular to the poling direction. Our method can utilize more domains to exchange nonequal crystalline axis to contribute to electrostrain in comparison with unpoled ceramics reported in the literature. According to our method, the unipolar electrostrain of 1.5 mol. % Fe-doped (Pb,Ba,Sr)(Zr,Ti)O3 ceramics in this work could reach 0.33%, which was 3.75 times larger than that of unpoled one at 3.0 kV mm-1. Meanwhile, the normalized strain d33* could reach nearly 1100 pm V-1 which was one of the highest values reported in ferroelectric ceramics. Additionally, the ceramics displayed interesting double or slim P-E (polarization-electric field) hysteresis loops at various electric fields. Our work provides a general method via reversible domain switching in aged acceptor-doped ferroelectric ceramics to obtain large electrostrain for high-displacement actuator applications.

Zhao, Xiaobo; Liang, Ruihong; Zhang, Wenbin; Wang, Genshui; Dong, Xianlin

2014-12-01

421

Ferroelectric glycine silver nitrate: a single-crystal neutron diffraction study.  

PubMed

Protonated crystals of glycine silver nitrate (C4H10Ag2N4O10) undergo a displacive kind of structural phase transition to a ferroelectric phase at 218?K. Glycine silver nitrate (GSN) is a light-sensitive crystal. Single-crystal X-ray diffraction investigations are difficult to perform on these crystals due to the problem of crystal deterioration on prolonged exposure to X-rays. To circumvent this problem, single-crystal neutron diffraction investigations were performed. We report here the crystal structure of GSN in a ferroelectric phase. The final R value for the refined structure at 150?K is 0.059. A comparison of the low-temperature structure with the room-temperature structure throws some light on the mechanism of the structural phase change in this crystal. We have attempted to explain the structural transition in GSN within the framework of the vibronic theory of ferroelectricity, suggesting that the second-order Jahn-Teller (pseudo-Jahn-Teller) behavior of the Ag(+) ion in GSN leads to structural distortion at low temperature (218?K). PMID:24253085

Choudhury, R R; Chitra, R; Aliouane, N; Schefer, J

2013-12-01

422

Fabrication of Glassy and Crystalline Ferroelectric Oxide by Containerless Processing  

NASA Astrophysics Data System (ADS)

1. Instruction Much effort has been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic effects. However, they require a higher cooling rate than glass formed by conventional techniques. Therefore, only amorphous thin-films have been formed, using rapid quenching with a cooling rate >105 K/s. The containerless processing is an attractive synthesis technique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable phase and glassy material. Recently a new ferroelectric materiel, monoclinic BaTi2 O5 , with Currie temperature as 747 K was reported. In this study, we fabricated a bulk BaTi2 O5 glass from melt using containerless processing to study the phase relations and ferroelectric properties of BaTi2 O5 . To our knowledge, this was the first time that a bulk glass of ferroelectric material was fabricated from melt without adding any network-forming oxide. 2. Experiments BaTi2 O5 sphere glass with 2mm diameter was fabricated using containerless processing in an Aerodynamic Levitation Furnace (ALF). The containerless processing allowed the melt to achieve deep undercooling for glass forming. High purity commercial BaTiO3 and TiO2 powders were mixed with a mole ratio of 1:1 and compressed into rods and then sintered at 1427 K for 10 h. Bulk samples with a mass of about 20 mg were cut from the rod, levitated with the ALF, and then melted by a CO2 laser beam. After quenching with a cooling rate of about 1000 K/s, 2 mm diameter sphere glass could be obtained. To analyze the glass structure, a high-energy x-ray diffraction experiment was performed using an incident photon energy of 113.5 keV at the high-energy x-ray diffraction beamline BL04B2 of SPring-8, with a two-axis diffractometer for the disordered materials. The glass-transition behavior was studied by Differential Scanning Calorimetry (DSC) with a heating rate of 10 K/min from room temperature to 1600 K. The structure changes during heating were characterized by powder x-ray diffraction in the temperature range from room temperature to 1100 K. For electrical property measurements, we cut and ground the samples into disks of 0.3 to 0.4 mm thickness and measured the dielectric constant and impedance from room temperature to 1123 K at a heating rate of 3 K/s using Ag electrodes. 3. Results Above the glass transition temperature (972 K), three successive phase transitions, from glass to a metastable ?-phase at 972 K, then to a metastable ?-phase at 1038 K, and finally to a stable monoclinic ?-phase above 1100 K, were observed. At the crystallization temperature of ?-phase, the permittivity jumped instantaneously by more than one order of magnitude, reaching a peak of 1.4 x 107 . This interesting phenomenon, occurring near the crystallization temperature, has important technical implications for obtaining an excellent dielectric glassceramics through controlled crystallization of BaTi2 O5 glass 504b030414000600080000002100828abc13fa0000001c020000130000005b436f6e74656e745f54797065735d2e78

Yoda, Shinichi

423

Charge Trapping in Ferroelectric Polymers  

Microsoft Academic Search

Experimental results are presented on anomalous behavior of absorption\\u000acurrents in PVDF during the stepwise increase of the voltage applied through a\\u000acorona. These results, supplemented with the dynamics of the time constant of\\u000athe electret potential decay are consistent with a hypothesis assuming deep\\u000atrapping of the charge carriers during the polarization buildup in\\u000aferroelectric polymers. Model calculations are

A. F. Butenko

2009-01-01

424

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

425

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