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1

Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

It is interesting to note that as with almost all initial advances in the study of ferroelectric oxides the impetus for studies of relaxor ferroelectrics stemmed from early work on polycrystalline ceramic systems. In the case of the relaxor ferroelectrics, the advance originated from studies in Professor Smolensky's group at the Ioffe Institute in Leningrad (now St. Petersburg) on perovskite structure electroceramics of complex composition. Originally classified as ferroelectrics with diffuse phase transitions, it slowly became clear that the very high dielectric maximum being highly dispersive could not mark a classical ferroelectric phase transition. Now, following studies at Penn State University, the suggested designation as relaxor ferroelectrics has become internationally adopted. The name is nicely compact and does highlight two key features, the combination of massive dielectric relaxation with almost classical lower-temperature ferroelectric response.

Cross, L. E.

2

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

SciTech Connect

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

Faria, Luiz O.; Welter, Cezar; Moreira, Roberto L. [Centro de Desenvolvimento da Tecnologia Nuclear, C.P. 941, Belo Horizonte, 30123-970, Minas Gerais (Madagascar) (Brazil); Departamento de Fisica, UFMG, C.P. 702, Belo Horizonte, 30123-970 Minas Gerais (Madagascar) (Brazil)

2006-05-08

3

Electrocaloric effect in relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

4

Theory of Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

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

Guzman Verri, Gian Giacomo

5

Niobium doping effects and ferroelectric relaxor behavior of bismuth lantanium titanate  

Microsoft Academic Search

Ferroelectrics Bi3.25La0.75(Ti3?x\\u000a Nbx)O12 (BLTN, x = 0? 0.1) solid solution systems were prepared, and Nb doping effects and relaxor behaviors were investigated. The\\u000a BLTN single phases were confirmed by XRD. The phase transition temperature decreased as the Nb content increased, and the\\u000a corresponding dielectric constant maximum broadened. The temperature T\\u000a m of the dielectric maximum depended on frequency and increased,

Jin Soo Kim; Min Su Jang; Ill Won Kim; Kwang Sei Lee

2006-01-01

6

Effects of ordering degree on the dielectric and ferroelectric behaviors of relaxor ferroelectric Pb(Sc1/2Nb1/2)O3 ceramics  

NASA Astrophysics Data System (ADS)

Relaxor ferroelectric Pb(Sc0.5Nb0.5)O3 ceramics were synthesized by a modified solid oxide reaction method. The x-ray diffraction and Raman scattering analysis affirmed that annealing dominated the ordering degree of PSN samples. The measurements on dielectric response and ferroelectric behavior indicate the prominent impact of the ordering degree. The dielectric response of a relaxor ferroelectric is determined by the growing and freezing behaviors of the polar regions, which is correlated with the ordering degree. In addition, the behavior of the ferroelectric phase transition was controlled by the lattice distortion in ordered domain due to the displacement of Pb and ferroelectrically active Nb cations in the PSN lattice.

Zhu, Mankang; Chen, Chuan; Tang, Jianlan; Hou, Yudong; Wang, Hao; Yan, Hui; Zhang, Weihong; Chen, Jian; Zhang, Wenjun

2008-04-01

7

Investigation of relaxors that transform spontaneously into ferroelectrics  

Microsoft Academic Search

B-site disordered Pb(Sc½Ta½)O3 and Pb(Sc½Nb½)O3 can be prepared in a controlled manner to show (a) relaxor behavior and (b) relaxor that undergoes a first order ferroelectric phase transition at zero-bias field. The latter case is a first demonstration of a spontaneous transformation from relaxor to ferroelectric state. TEM, DSC and dielectric and electric characterization techniques are used to investigate this

F. Chu; I. M. Reaney; N. Setter

1994-01-01

8

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

9

Normal and Relaxor Behaviors of Ferroelectric P(VDF-TrFE) Copolymers  

Microsoft Academic Search

Structural and dielectric techniques were used to investigate semi-crystalline ferroelectric P(VDF-TrFE) copolymers. These materials undergo normal diffuse phase transition without any relaxation character of the Curie temperatures. By submitting them to high doses of ?-irradiation we were able to destroy the stability of their ferroelectric domains, and thus, to induce the appearing of relaxor features. The irradiation provokes the appearing

C. Welter; L. O. Faria; R. L. Moreira

2003-01-01

10

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

11

Bi:SrTiO3: A quantum ferroelectric and a relaxor  

NASA Astrophysics Data System (ADS)

Quantum ferroelectric and ferroelectric relaxor behavior has been found in (Sr1-1.5xBix)TiO3. For x<=0.0267, the quantum ferroelectric relationship T?m~(x-xc)1/2 holds with xc~0.0005, and obvious hysteresis loops were observed. The polarization relaxation shows critical slowing down. At high Bi concentration, a crossover from quantum ferroelectric to relaxor behavior occurred. The coexistence of ferroelectric and relaxor behavior in Bi:SrTiO3 was attributed to a ferroelectric domain state induced by random fields.

Ang, Chen; Yu, Zhi; Vilarinho, P. M.; Baptista, J. L.

1998-04-01

12

Relaxor Ferroelectric Polymers–Fundamentals and Applications  

Microsoft Academic Search

We present recent studies in the fundamentals and applications of the relaxor ferroelectric polymers, i.e., Poly(vinylidene fluoride-trifluroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE) terpolymers and high energy electron irradiated P(VDF-TrFE) copolymers. We show that the dynamic processes in these relaxor ferroelectric polymers are very similar to these observed in various polar-glasses. We further show that the large and reversible polarization change in these polymers leads

Qin Chen; Kailiang Ren; Baojin Chu; Yiming Liu; Q. M. Zhang; Vid. Bobnar; A. Levstik

2007-01-01

13

Tunability and ferroelectric relaxor properties of bismuth strontium titanate ceramics  

NASA Astrophysics Data System (ADS)

A systemic study was performed on bismuth strontium titanate (Sr1-1.5xBixTiO3, 0.04<=x<=0.25) ceramics. Dielectric properties were measured from 83 to 373 K at different frequencies. A transformation from relaxor ferroelectrics to relaxor behavior was observed when x>0.10. Both diffuseness and relaxation degree increase as x rises. Tunability was found to increase with increasing x value until 0.07, and then decrease when Bi3+ content increases. Meanwhile, their figures of merit (defined as tunability/loss) shows a maximum at x=0.12. The change from relaxor ferroelectrics into relaxor behavior has a positive impact on the tunability of bismuth strontium titanate system.

Chen, Wei; Yao, Xi; Wei, Xiaoyong

2007-04-01

14

Advances in relaxor ferroelectric terpolymer: New applications  

Microsoft Academic Search

r Abstract-It has been found that by introducing defects into the P(VDF-TrFE) copolymers, it is possible to convert the polymer from a normal ferroelectric to a relaxor ferroelectric. A new class of ferroelectric polymers, i.e., the terpolymers of P(VDF-TrFE­ CFE) or of P(VDF- TrFE-CTFE), was developed from the normal ferroelectric PVDF-TrFE polymer by employing proper defect modifications which eliminate detrimental

Francois Bauer; Jean Fabien Capsal; Quentin Larcher; F. Domingues Dos Santos

2011-01-01

15

Broadband Brillouin scattering of relaxor ferroelectric crystals  

NASA Astrophysics Data System (ADS)

The dynamical properties of relaxor ferroelectrics have been studied by broadband Brillouin scattering. In 0.65PMN-PT an intense central peak (CP) was observed in a wide temperature range below about 250°C. The relaxation time determined from CP shows slowing down above the cubic to tetragonal transition temperature Tct=158°C. Under the assumption that the origin of CP is the dynamical behavior of polar micro regions, this behavior was well reproduced by the extended superparaelectric model above Tct. The intense CP of uniaxial relaxor 0.61SBN with the dielectric maximum temperature Tm=70°C was also observed in a wide temperature range below about Tc+400°C. The anisotropy of CP intensity indicates that CP of 0.61SBN is originated mainly from fluctuating polar clusters along the c-axis. However, the slowing down of the relaxation time determined from CP stopped at about Tm+100°C. This fact may indicate growing interaction between PMRs in 0.61SBN. .

Kojima, Seiji; Jiang, Fuming

2001-08-01

16

Vogel-Fulcher freezing in relaxor ferroelectrics  

SciTech Connect

A physical mechanism for the freezing of polar nanoregions (PNRs) in relaxor ferroelectrics is presented. Assuming that the activation energy for the reorientation of a cluster of PNRs scales with the mean volume of the cluster, the characteristic relaxation time {tau} is found to diverge as the cluster volume reaches the percolation limit. Applying the mean field theory of continuum percolation, the familiar Vogel-Fulcher equation for the temperature dependence of {tau} is derived.

Pirc, R.; Blinc, R. [Jozef Stefan Institute, P.O. Box 3000, 1001 Ljubljana (Slovenia)

2007-07-01

17

Brillouin Scattering Study on Polycrystalline Relaxor Ferroelectrics  

Microsoft Academic Search

Brillouin spectra of Pb(Yb1\\/2Nb1\\/2)O3(PYN)-based relaxor ferroelectric ceramics were measured using a conventional tandem Fabry-Perot interferometer. The measured spectra were composed of a strong elastic peak and a broad doublet with a sharp cutoff at the high-frequency side. The broad doublet was attributed to the distributed Brillouin shift of the longitudinal acoustic mode owing to the scattering events at all scattering

Jae-Hyeon Ko; Do Han Kim; Seiji Kojima; Jai-Hyun Kim; Woong Kil Choo

2003-01-01

18

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

19

Pressure as a Probe of the Physics of Relaxor Ferroelectrics  

SciTech Connect

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

Samara, George A.

1999-08-09

20

Brillouin Scattering Study on Polycrystalline Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

Brillouin spectra of Pb(Yb1/2Nb1/2)O3(PYN)-based relaxor ferroelectric ceramics were measured using a conventional tandem Fabry-Perot interferometer. The measured spectra were composed of a strong elastic peak and a broad doublet with a sharp cutoff at the high-frequency side. The broad doublet was attributed to the distributed Brillouin shift of the longitudinal acoustic mode owing to the scattering events at all scattering angles from 0° to 180° which is due to multiple reflections and refractions. From the sharp high-frequency cutoff of this band, which corresponds to the largest Brillouin shift of the backward scattering geometry, the average longitudinal sound velocities were estimated to be 4.22-4.33 km/s for PYN-based relaxor ceramics. The present results imply that Brillouin spectroscopy can be used to derive elastic properties of not only single crystals but also ceramic samples in the gigahertz range, which will be very important for high-frequency applications.

Ko, Jae-Hyeon; Kim, Do Han; Kojima, Seiji; Kim, Jai-Hyun; Choo, Woong Kil

2003-05-01

21

A multi-Debye relaxation model for relaxor ferroelectrics showing diffuse phase transition  

NASA Astrophysics Data System (ADS)

The relaxor ferroelectrics showing diffuse phase transition (DPT) are promising materials for multilayer ceramic capacitors because of their high dielectric permittivity in the vicinity of the so called DPT. This physical parameter is also important in the fine piezoelectric, pyroelectric and electro optic performance of relaxor ferroelectrics. The dielectric behavior of these materials shows that the ferroelectric-paraelectric transition is diffuse. Also, there is a frequency dispersion of the real and imaginary parts of the dielectric permittivity and a deviation from the Curie-Weiss law. Many models have been developed to explain this phenomenon, but the exact mechanism associated to this dielectric behavior has not been established yet. This paper presents an analysis of the dielectric behavior in PLZT ferroelectric ceramics by using a new multi-Debye relaxation model, which does not make assumptions that involve the microstructure or possible correlation mechanisms.

Peláiz-Barranco, A.; García-Zaldívar, O.; Calderón-Piñar, F.; López-Noda, R.; Fuentes Betancourt, J.

2005-07-01

22

Pulsed laser deposition of perovskite relaxor ferroelectric thin films  

Microsoft Academic Search

Structural, dielectric and ferroelectric properties of thin films of La-doped lead zirconate titanate (PLZT) and sodium bismuth titanate–barium titanate (NBT–BT) perovskite relaxor ferroelectric have been investigated. PLZT films were deposited on Pt\\/Si substrates in oxygen atmosphere by pulsed laser deposition (PLD) and radio frequency (RF) discharge-assisted PLD, using sintered targets with different La content and Zr\\/Ti ratio, near or at

N. Scarisoreanu; M. Dinescu; F. Craciun; P. Verardi; A. Moldovan; A. Purice; C. Galassi

2006-01-01

24

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

25

Recent progress in relaxor ferroelectrics with perovskite structure  

Microsoft Academic Search

Relaxor ferroelectrics were discovered almost 50 years ago among the complex oxides with perovskite structure. In recent years\\u000a this field of research has experienced a revival of interest. In this paper we review the progress achieved. We consider the\\u000a crystal structure including quenched compositional disorder and polar nanoregions (PNR), the phase transitions including compositional\\u000a order-disorder transition, transition to nonergodic (probably

A. A. Bokov; Z.-G. Ye

2006-01-01

26

Mesoscopic cell structure of relaxor ferroelectrics at morphotropic phase boundary  

NASA Astrophysics Data System (ADS)

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

Ahn, Sang-Jin; Kim, Jong-Jean

2003-03-01

27

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

NASA Astrophysics Data System (ADS)

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

Grinberg, Ilya

2012-02-01

28

Ferroelectric Relaxor Terpolymers: Properties and Potential Applications  

Microsoft Academic Search

Ferroelectric materials are intrinsically multifunctional and have found a broad range of applications. A new class of semicrystalline terpolymers comprising vinylidene fluoride (VDF), trifluoroethylene (TrFE), and 1,1-chlorofluoroethylene (CFE), were prepared at the Institut Franco-Allem and de Recherches in Saint-Louis (ISL) via a suspension polymerization process. Relevant studies and results show that this class of electroactive polymers offers unique properties in

Francois Bauer; Qiming Zhang; Eric Fousson

2006-01-01

29

Ferroelectric Relaxor Terpolymers: Properties and Potential Applications  

Microsoft Academic Search

Ferroelectric materials are intrinsically multifunctional and have found a broad range of applications. A new class of semicrystalline terpolymers comprising vinylidene fluoride (VDF), trifluoroefhylene (TrFE), and 1,1-chlorofluoroefhylene (CFE), were prepared at the Institut Franco-Allemand de Recherches in Saint-Louis (ISL) via a suspension polymerization process. Relevant studies and results show that this class of electroactive polymers offers unique properties in comparison

Franvois Bauer; Qiming Zhang; E. Fousson

2006-01-01

30

Temperature, frequency and bias-field co-dependence of the electrostrictive relaxor ferroelectric lead magnesium niobate-lead titinate  

NASA Astrophysics Data System (ADS)

Fundamental to the design of intelligent material systems and structures are the realization of attributes of the constitutive materials - the sensors and actuators - and the ability to model the characteristics of these transducers. In this paper, electromechanical behaviors of the electrostrictive relaxor ferroelectric lead magnesium niobate-lead titinate (PMN-PT) are phenomenologically modeled. The dependencies of PMN-PT electromechanical transduction on temperature and frequency, characteristics of relaxor ferroelectrics, and on applied direct-current electric field, an attribute of electrostrictors which enables tunable transduction sensitivities, are modeled with respect to electrical, sensing, and actuation properties. The objective for this research is to mathematically represent the behaviors of PMN-PT sensors and actuators with respect to temperature, frequency, and bias field for practical application to mechanical and control design.

Namboodri, Chet G., Jr.

1993-04-01

31

Production and characterisation of composite relaxor ferroelectric multi-layer structures  

Microsoft Academic Search

The drive for miniaturisation of passive capacitor and filter devices requires dielectric materials with higher relative permittivities than can be attained using normal ferroelectrics. Relaxor ferroelectrics possess the required high relative permittivities but are incapable of being chemically doped to give a temperature stable capacitance. Work is presented detailing the design and development of a new class of temperature stable

Andrew. W Tavernor; Hui-Ping S Li; Ronald Stevens

1999-01-01

32

Biferroic relaxors  

NASA Astrophysics Data System (ADS)

Epitaxial biferroic relaxors of formula Pb[(Zr0.53Ti0.47)0.4(Fe0.67W0.33)0.6]O3 (PZTFW) were grown by pulsed laser deposition (PLD) techniques. Raman spectra revealed a global Fm3m symmetry with two high-frequency A1g modes that imply the existence of polar nano-regions (PNRs). Near room temperature, frequency-dependent dielectric patterns follow Vogel-Fulcher (VF) relation that implies relaxor ferroelectric phase, however, a frequency-dependent, high-temperature, Maxwell-Wagner space charge-based phase transition was also noticed. A large and irreversible magnetization with a sharp cusp in zero-field-cooled (ZFC) magnetization with low ZFC magnetic field advocates Heisenberg spin-glass behavior. Observation of slim ferroelectric hysteresis below the freezing temperature (Tf), PNRs, and spin glass confirms biferroic-relaxor nature.

Kumar, Ashok; Scott, J. F.; Katiyar, R. S.

2011-07-01

33

Nanostructure, defect chemistry and properties of relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

This research focused on cation ordering, defect chemistry, and dielectric properties of the BaTiO3-Ba(Zn(1/3)Nb(2/3))O3 (BZN) system. The latter compound was chosen as an analog of the PbO-based relaxor ferroelectrics to avoid the severe experimental restrictions caused by the volatility and reducibility of PbO. Two types of ordering of the Zn and Nb content of BZN were observed: a 1:1 (alternate layer) type that represents a local compositional change and charge imbalance that restricts the size of ordered domains, and a 1:2 type that is consistent with the composition of BZN. The effects of the Zn/Nb ratio and doping on the type and extent of ordering were determined. The defect chemistry of BZN is closely related to that of BaTiO3, which has been well-characterized. The material usually contains a large concentration of extrinsic oxygen vacancies because of compositional variations and ZnO loss. Mass-action expressions and thermodynamic parameters of the oxidation and reduction reactions, and of the band gap were determined. The proposed defect model is in excellent quantitative agreement with the experimental observations. The evolution of dielectric properties was studied as the Ti content of BaTiO3 was gradually replaced by Zn(1/3)Nb(2/3).

Harmer, M. P.; Smyth, D. M.

1992-02-01

34

Phase Diagram of Magnetically Ordered Relaxor Ferroelectric Pb(Fe_2\\/3W_1\\/3)O3 and PbTiO3 (PFW-PT)  

Microsoft Academic Search

Complex perovskite Pb(Fe_2\\/3W_1\\/3)O3 (PFW) shows typical relaxor ferroelectric behavior and magnetic ordering [1]. It has been known as a promising material for multilayer ceramics capacitor. When it forms a multi-component system with other ferroelectrics, the materials exhibit excellent multi-functional properties due to an improvement of dielectric properties, a higher Curie temperature, as well as a low firing temperature [2]. In

Li Feng; Zuo Guang Ye

2001-01-01

35

Electrostrictive and relaxor ferroelectric behavior in BiAlO3-modified BaTiO3 lead-free ceramics  

NASA Astrophysics Data System (ADS)

The crystal structure of (1-x)BaTiO3-xBiAlO3 (x = 0, 0.02, 0.05, 0.08, and 0.1) ceramics was determined using X-ray diffraction and Raman spectroscopy at room temperature, which revealed a phase transition from tetragonal to rhombohedral with increasing x. The dielectric properties were studied as a function of temperature at different frequencies, which indicated that the phase transition temperature (Tm) decreased with increasing x. The relaxor behavior was observed by frequency and temperature dependent dielectric permittivity. The Lorenz-type quadratic law was used to characterize the dielectric permittivity peaks near Tm of high-temperature slopes at 1 MHz. The temperatures Tm of dielectric permittivity peaks fit very well with the Vogel-Fulcher law in x = 0.05 and x = 0.1. The polarization hysteresis loops and electrostrictive were displayed at room temperature. The sample for x = 0.1 exhibits a slim loop with negligible hysteresis and a subtle linear feature, which is a promising transducer material for use as an active element.

Zheng, Shaoying; Odendo, Erika; Liu, Laijun; Shi, Danping; Huang, Yanming; Fan, Longlong; Chen, Jun; Fang, Liang; Elouadi, Brahim

2013-03-01

36

Distribution function of the random field and polar properties of the relaxor ferroelectric films  

Microsoft Academic Search

The model for calculation of relaxor ferroelectrics thin films properties is\\u000aproposed. The basis of the model is the theory of random field. This field is\\u000aoriginated from the chemical disorder allowing for influence of the film\\u000asurfaces, which destroys the polar long-range order and transform it into mixed\\u000astate of ferroelectric glass (FG) or dipole glass (DG). The spatial

E. A. Eliseev; M. D. Glinchuk

2004-01-01

37

Correlations between curie temperature, relaxation frequency and chemical bonding in relaxor ferroelectric materials  

Microsoft Academic Search

Correlations between Curie temperature, relaxation frequency and chemical bonding have been evidenced in ABO3 type ferroelectric perovskites. This approach is extended to Pb(B, B')O3 type relaxor ferroelectric materials for which a high frequency relaxation has been recently observed. A study of relaxation frequency—chemical bonding relations using Extended Hückel theory is proposed. The influence of the covalency of oxygen — cation

C. Elissalde; A. Villesuzanne; J. Ravez; M. Pouchard

1997-01-01

38

MPB design and crystal growth of PMN–PT–PZ relaxor ferroelectrics  

Microsoft Academic Search

Rhombohedral–tetragonal ferroelectric structural phase transition temperature (TR?T), far below the Curie temperature (Tc) in lead magnesium niobate–lead titanate (PMN–PT) relaxor ferroelectric single crystal, heavily restricts its further applications either as a sensor or transducer. To overcome this shortcoming, lead zirconate (PZ) was introduced into the PMN–PT pseudo-binary system to increase TR?T via the morphotropic phase boundary (MPB) composition design and

Qiang Li; Yiling Zhang; Zhiguo Xia; Xiangcheng Chu

2011-01-01

39

Ferroelectric to relaxor crossover and dielectric phase diagram in the BaTiO3-BaSnO3 system  

NASA Astrophysics Data System (ADS)

The (1-x)BaTiO3-xBaSnO3 (0<=x<=0.30) perovskite solid solution ceramics were prepared by solid state reaction and studied by dielectric spectroscopy. The complex dielectric permittivity was measured as a function of frequency (0.1 Hz-100 kHz) in the temperature (T) range of 123-573 K. The transition from the high-temperature paraelectric state where the dielectric constant obeys the Curie-Weiss law to the ergodic cluster state is found to occur at the same temperature of 485 K in all the compositions of x>=0.04 and at lower temperatures in those with a smaller x. For 0<=x<=xc=0.19, the temperature of the dielectric peak Tm, corresponding to the diffuse transition from the ergodic polar cluster state to the ferroelectric state, decreases with increasing x and does not depend on frequency. The diffuseness of the peak gradually increases. For x>xc, the permittivity exhibits relaxor behavior with the frequency-dependent Tm satisfying the Vogel-Fulcher law. The temperature variation of the permittivity on the high-temperature slope of the peak (T>Tm) is characterized by the characteristic Lorenz-type quadratic law for relaxors, with the diffuseness increasing with the increase of x. The mechanisms of the dielectric response in different parts of the phase diagram are discussed. In particular, the crossover from diffuse ferroelectric phase transition to relaxor ferroelectric behavior is attributed to the appearance at x>xc of the additional dielectric contribution arising from the flipping of the local polarization of the polar clusters. The temperature-composition phase diagram of the Ba(Ti1-xSnx)O3 system has been established, which delimits the paraelectric, ergodic polar cluster, nonergodic ferroelectric, and relaxor phases (states) and indicates the crossover from ferroelectric to relaxor behavior at x=xc.

Lei, C.; Bokov, A. A.; Ye, Z.-G.

2007-04-01

40

Modeling of enhanced electrocaloric effect above the Curie temperature in relaxor ferroelectrics  

Microsoft Academic Search

The electrocaloric (EC) effect offers promise as a means to realize solid-state refrigeration, which requires EC materials possessing a pronounced pyroelectric effect over a broad temperature range. Pauli’s master equation is adopted to investigate the recently observed phenomenon of enhanced EC effect above the Curie temperature in relaxor ferroelectrics. The proposed approach allows the EC coefficient to be determined within

Y. P. Shi; A. K. Soh

2011-01-01

41

Behavior of optical phonons near the diffuse phase transition in relaxor ferroelectric PbMg{sub 1/3}Ta{sub 2/3}O{sub 3}  

SciTech Connect

Raman scattering in relaxor ferroelectric PbMg{sub 1/3}Ta{sub 2/3}O{sub 3} (PMT) was investigated in the single-crystalline form in the temperature range of 20-295 K. An anomalous temperature dependence of the integrated intensity and the Raman line contours were found at the diffuse phase transition. A correlation between the anomalies in the integrated intensities and the dispersion of the dielectric response was observed. The distortions of Raman lines with decreasing temperature are discussed.

Lushnikov, S.; Gvasaliya, S.; Katiyar, R.S. [Ioffe Physical Technical Institute, 26 Politekhnicheskaya, 194021 St. Petersburg (Russian Federation); Laboratory for Neutron Scattering, ETHZ and Paul-Scherrer Institut, CH-5232 Villigen PSI (Switzerland); University of Puerto Rico, P. O. Box 23343, San Juan (Puerto Rico)

2004-11-01

42

Ferroelectric-to-relaxor crossover and oxygen vacancy hopping in the compositionally disordered perovskites KTa1-xNbxO3:Ca  

NASA Astrophysics Data System (ADS)

It is shown that lattice disorder induced by Nb and Ca substitution has a strong influence on the dielectric and relaxational properties of KTaO3. Both substituents are believed to occupy off-center positions at the Ta site, and the difference in valence between the Ca2+ and Ta5+ ions leads to the formation of oxygen vacancies (VO). Specifically, for a KTa1-xNbxO3:Ca crystal with x=0.023 and with a 0.055 at. % Ca doping, we observe (i) a ferroelectric transition at atmospheric pressure (1 bar); (ii) a large enhancement of the transition temperature by Ca doping; (iii) a pressure-induced crossover from ferroelectric-to-relaxor behavior; (iv) the impending vanishing of the relaxor phase at high pressure; (v) the reorientation of the Ca-oxygen vacancy (Ca:VO) pair defect; and (vi) the variation of the energetics and dynamics of this reorientation with pressure. Most of these effects are associated with Nb- and Ca-induced dipolar entities and appear to be general features of soft mode ferroelectrics with random-site polar nanodomains. The ferroelectric-to-relaxor crossover can be understood in terms of a large decrease with pressure in the correlation length among polar nanodomains-a unique property of soft ferroelectric mode systems.

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

2000-02-01

43

Grain size dependence of relaxor behavior in CaCu3Ti4O12 ceramics  

Microsoft Academic Search

The dielectric properties show a typical ferroelectric relaxor behavior in CaCu3Ti4O12 ceramics with different grain sizes in the temperature range of 400-600 K. The relaxation strength and the frequency dispersion increase with grain size decreasing, which can be due to the different stresses in grains with different sizes. These variations have been confirmed by the modified Curie-Weiss law. The results

Hongtao Yu; Hanxing Liu; Hua Hao; Liling Guo; Chengjun Jin; Zhiyong Yu; Minghe Cao

2007-01-01

44

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

45

High-temperature structural transformations in the relaxor ferroelectrics PbSc0.5Ta0.5O3 and Pb0.78Ba0.22Sc0.5Ta0.5O3  

Microsoft Academic Search

Temperature-driven structural transformations in Pb-based perovskite-type relaxors are studied by using polarized Raman spectroscopy, high-resolution powder, and synchrotron single-crystal x-ray diffraction applied to PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST). The two compounds were chosen as model systems because PST is a relaxor that exhibits ferroelectric long-range order on cooling, whereas PBST shows canonical relaxor behavior. The temperature evolution of phonon anomalies

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

2008-01-01

46

Monte Carlo simulations for describing the ferroelectric-relaxor crossover in BaTiO3-based solid solutions  

NASA Astrophysics Data System (ADS)

The properties induced by the M4 + addition (M = Zr, Sn, Hf) in BaMxTi1 - xO3 solid solutions have been described on the basis of a 2D Ising-like network and Monte Carlo calculations, in which BaMO3 randomly distributed unit cells were considered as being non-ferroelectric. The polarization versus temperature dependences when increasing the M4 + concentration (x) showed a continuous reduction of the remanent polarization and of the critical temperature corresponding to the ferroelectric-paraelectric transition and a modification from a first-order to a second-order phase transition with a broad temperature range for which the transition takes place, as commonly reported for relaxors. The model also describes the system's tendency to reduce the polar clusters' average size while increasing their stability in time at higher temperatures above the Curie range, when a ferroelectric-relaxor crossover is induced by increasing the substitution (x). The equilibrium micropolar states during the polarization reversal process while describing the P(E) loops were comparatively monitored for the ferroelectric (x = 0) and relaxor (x = 0.3) states. Polarization reversal in relaxor compositions proceeds by the growth of several nucleated domains (the 'labyrinthine domain pattern') instead of the large scale domain formation typical for the ferroelectric state. The spatial and temporal evolution of the polar clusters in BaMxTi1 - xO3 solid solutions at various x has also been described by the correlation length and correlation time. As expected for the ferroelectric-relaxor crossover characterized by a progressive increasing degree of disorder, local fluctuations cause a reducing correlation time when the substitution degree increases, at a given temperature. The correlation time around the Curie temperature increases, reflecting the increasing stability in time of some polar nanoregions in relaxors in comparison with ferroelectrics, which was experimentally proved in various types of relaxors.

Padurariu, Leontin; Enachescu, Cristian; Mitoseriu, Liliana

2011-08-01

47

Monte Carlo simulations for describing the ferroelectric-relaxor crossover in BaTiO?-based solid solutions.  

PubMed

The properties induced by the M(4+) addition (M = Zr, Sn, Hf) in BaM(x)Ti(1-x)O(3) solid solutions have been described on the basis of a 2D Ising-like network and Monte Carlo calculations, in which BaMO(3) randomly distributed unit cells were considered as being non-ferroelectric. The polarization versus temperature dependences when increasing the M(4+) concentration (x) showed a continuous reduction of the remanent polarization and of the critical temperature corresponding to the ferroelectric-paraelectric transition and a modification from a first-order to a second-order phase transition with a broad temperature range for which the transition takes place, as commonly reported for relaxors. The model also describes the system's tendency to reduce the polar clusters' average size while increasing their stability in time at higher temperatures above the Curie range, when a ferroelectric-relaxor crossover is induced by increasing the substitution (x). The equilibrium micropolar states during the polarization reversal process while describing the P(E) loops were comparatively monitored for the ferroelectric (x = 0) and relaxor (x = 0.3) states. Polarization reversal in relaxor compositions proceeds by the growth of several nucleated domains (the 'labyrinthine domain pattern') instead of the large scale domain formation typical for the ferroelectric state. The spatial and temporal evolution of the polar clusters in BaM(x)Ti(1-x)O(3) solid solutions at various x has also been described by the correlation length and correlation time. As expected for the ferroelectric-relaxor crossover characterized by a progressive increasing degree of disorder, local fluctuations cause a reducing correlation time when the substitution degree increases, at a given temperature. The correlation time around the Curie temperature increases, reflecting the increasing stability in time of some polar nanoregions in relaxors in comparison with ferroelectrics, which was experimentally proved in various types of relaxors. PMID:21785183

Padurariu, Leontin; Enachescu, Cristian; Mitoseriu, Liliana

2011-07-25

48

Polar nanodomains and local ferroelectric phenomena in relaxor lead lanthanum zirconate titanate ceramics  

SciTech Connect

Transparent Pb{sub 0.9125}La{sub 0.0975}(Zr{sub 0.65}Ti{sub 0.35}){sub 0.976}O{sub 3} ceramics (conventionally abbreviated as PLZT 9.75/65/35) is a typical relaxor characterized by the absence of the ferroelectric order at the macroscopic scale. In this letter, we report on the observation of complex polar structures on the surface of this material via piezoresponse force microscopy (PFM). The irregular polarization patterns are associated with the formation of a glassy state, where random electric fields destroy the long-range ferroelectric order. The measure of the disorder, the correlation length of {approx}50 nm, was directly deduced from the PFM images. Local poling of relaxor ceramics resulted in the formation of a stable micron-size domain that could be continuously switched under varying dc bias (local relaxor-ferroelectric phase transition). Fractal analysis was applied to analyze the origin of local order in PLZT.

Shvartsman, V.V.; Kholkin, A.L.; Orlova, A.; Kiselev, D.; Bogomolov, A.A.; Sternberg, A. [Department of Ceramics and Glass Engineering and Center for Research in Ceramic and Composite Materials (CICECO), University of Aveiro, 3810-193 Aveiro (Portugal); Department of Physics, Tver State University, 170000 Tver (Russian Federation); Institute of Solid State Physics, University of Latvia, LV-1063 Riga (Latvia)

2005-05-16

49

Fracture of ferroelectric and relaxor electro-ceramics: influence of electric field 1 1 Work begun during a post doctoral appointment at the University of California, Santa Barbara  

Microsoft Academic Search

Crack growth is studied in a ferroelectric and a relaxor composition of lead lanthanum zirconate titanate (PLZT) ceramic using Vicker’s indentations with electric field. The polarized ferroelectric composition displays excess crack growth perpendicular to the polarization direction. This excess crack growth is increased by an electric field in the polarization direction. The relaxor composition does not display this excess crack

Christopher S. Lynch

1998-01-01

50

Thickness Dependent Properties of Relaxor-PbTiO3 Ferroelectrics for Ultrasonic Transducers  

PubMed Central

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

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

2011-01-01

51

Electrocaloric Effect In Relaxor Ferroelectric Ceramics and Single Crystals  

Microsoft Academic Search

In the last two decades, the electrocaloric (EC) effect which is associated to the temperature (¿) dependence of the macroscopic polarization P(E,¿) under electric field E has been spasmodically studied in ferroelectric materials in order to find an alternative to the classical refrigeration devices using freon. Basically, large electrocaloric temperature variation ¿¿ originates from electric field-induced phase transition at the

Gael Sebald; Benoit Guiffard; Laurence Seveyrat; Abdelmjid Benayad; Laurent Lebrun; Sebastien Pruvost; Daniel Guyomar

2006-01-01

52

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

Microsoft Academic Search

The electro-optic (E-O) effects of the relaxor ferroelectric materials, Lead Magnesium Niobate-Lead Titanate Pb(Mg 1\\/3Nb2\\/3)O3- PbTiO3 (PMN-PT) single crystals and poly(vinylidene fluoride-trifluoroethylene) [P( VDF-TrFE)] based polymers, are investigated here. The tetragonal 0.62PMN-0.38PT single crystals poled along the direction (the spontaneous polarization direction) have a stable single domain and show high transparency from the visible to Near-IR range. Using the Mach-Zender

Daeyong Jeong

2004-01-01

53

Field Effect on Displacive First-Order Transition in Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

As preliminaries of a microscopic theory for displacive phase transition, the first-order transition is investigated within a phenomenological study that provides a good explanation of experimental results on the electric field dependence and pressure effect in relaxor ferroelectrics. The morphotropic phase boundary (MPB) region in mixed perovskite oxides is described in the same phase diagram corresponding to individual perovskite oxides with successive phase transitions. On the basis of the calculated field-dependent phase transitions, the origin of the MPB is examined in comparison with that in the case of BaTiO3 with the first-order displacive transition.

Matsushita, Eiko; Sugiyama, Kouichi; Nozawa, Kazuki

2012-09-01

54

Persistence and memory of polar nanoregions in a ferroelectric relaxor under an electric field  

NASA Astrophysics Data System (ADS)

The response of polar nanoregions (PNR) in the ferroelectric relaxor Pb[(Zn1/3Nb2/3)0.92Ti0.08]O3 subject to a [111]-oriented electric field has been studied by neutron diffuse scattering. Contrary to classical expectations, the diffuse scattering associated with the PNR persists, and is even partially enhanced, after field cooling. The effect of the external electric field is retained by the PNR after the field is removed. The “memory” of the applied field reappears even after heating the system above the Curie temperature TC and cooling in zero field.

Xu, Guangyong; Gehring, P. M.; Shirane, G.

2005-12-01

55

Electrocaloric Effect In Relaxor Ferroelectric Ceramics and Single Crystals  

Microsoft Academic Search

In the last two decades, the electrocaloric (EC) effect which is associated to the temperature (thetas) dependence of the macroscopic polarization P(E,thetas) under electric field E has been spasmodically studied in ferroelectric materials in order to find an alternative to the classical refrigeration devices using freon. Basically, large electrocaloric temperature variation Deltathetas originates from electric field-induced phase transition at the

G. Sebald; B. Guiffard; L. Seveyrat; A. Benayad

2006-01-01

56

Relaxor Behavior and Morphotropic Phase Boundary in a Simple Model  

NASA Astrophysics Data System (ADS)

A simple model to reproduce the strong enhancement of the dielectric response near the morphotropic phase boundary (MPB) is proposed. This model consists of a long-range dipole--dipole interaction and compositional chemical disorder incorporated by the variation in lengths of dipole moments. By applying a Monte Carlo simulation, we show that a ferroelectric boundary phase appears between an antiferroelectric phase and a relaxor ferroelectric phase at an optimal strength of randomness. In the boundary phase, the ferroelectric domain becomes extremely large and flexible to external electric fields, leading to a huge dielectric response. This observation indicates that the huge dielectric response near the MPB originates from local polarization rotation under the suppression of anisotropy by phase competition.

Tomita, Yusuke; Kato, Takeo

2013-06-01

57

Electric-field-induced and spontaneous relaxor-ferroelectric phase transitions in (Na1/2Bi1/2)1 - xBaxTiO3  

NASA Astrophysics Data System (ADS)

Complex dielectric susceptibility was used to investigate the relaxor properties and the ferroelectric phase transitions in (Na1/2Bi1/2)1 - xBaxTiO3 (0 <= x <= 0.08) ceramics. XRD was used to characterize the ground states of poled and unpoled samples. Dielectric susceptibility vs. temperature studies allowed to obtain the relaxor properties and to identify the electric field-induced phase transitions in the morphotropic phase boundary (MPB) compositions (0.06 < x < 0.08) and the spontaneous relaxor-ferroelectric phase transitions in the rhombohedral compositions (x < 0.06). The frequency dispersion of the dielectric maximum at Tm was observed for all compositions, although of decreased extension for lower x. The relaxor properties have been analysed with Vogel-Fulcher law. The activation energy and attempt frequency for the MPB compositions are similar to those of classical relaxors like Pb(Mg1/3Nb2/3)O3, while for rhombohedral compositions, they are similar to relaxor ferroelectrics with spontaneous relaxor-ferroelectric phase transitions, like Pb(Sc1/2Nb1/2)O3. A relationship has been found between the relaxor dispersion degree and the hysteresis of the ferroelectric transition.

Craciun, F.; Galassi, C.; Birjega, R.

2012-12-01

58

Pressure-Induced Ferroelectric-to-Relaxor Crossover in PSN and Isomorphs  

NASA Astrophysics Data System (ADS)

We discuss the influences of pressure (P) and bias field on the dielectric properties and phase behavior of a single crystal of the chemically-disordered ABB'O3 perovskite Pb(Sc0.5Nb0.5)O3 or PSN. On cooling from high temperatures (T), PSN first enters a relaxor (R) state and then spontaneously transforms to a ferroelectric (FE) phase at a temperature Tc substantially below the maximum in the dielectric susceptibility. The R state indicates the presence of polar nanoregions, arising from the B-site chemical disorder, that increase in size with decreasing T. At ambient P, these regions grow to macroscopic size, leading to a first-order FE transition at Tc. Hydrostatic P offers a unique method to systematically decrease the dielectric polarizability of PSN by reducing the unit cell volume and, hence, increasing the frequency of the soft transverse optic phonon modes. As P increases, the size of the polar regions decreases, enhancing the R state at the expense of the FE phase. It appears that the FE phase vanishes somewhat above the highest P reached in the experiments, making the R state the ground state of the crystal at reduced volume. This suggests a T-P phase diagram with a Tc(P) phase line that terminates between 10 and 15 kbar in a manner akin to a critical point; however, in the case of PSN this feature represents a FE-to-R crossover. In contrast, a biasing electric field favors the FE phase over the R state, and the data indicate that the R state vanishes above 5 kV/cm. Additional insight is provided by comparison to dielectric results on isomorphous Pb(Sc0.5Ta0.5)O3 in both its compositionally ordered and disordered forms.

Venturini, Eugene

2006-03-01

59

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

60

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

61

Strong variation of electrostrictive coupling near an intermediate temperature of relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

A sudden increase in the electrostrictive coefficient Q13 when temperature decreases is seen in three different types of ferroelectric relaxors (PLZT 9/65/35, PLZT 22/20/80, and PMN-PT) starting from ˜50K above the dielectric permittivity maximum temperature, Tm . The temperature dependence is attributed to the softening of the quasilocal mode occurring near dopants or charge-transfer sites. The steep increase when the temperature decreases could be related to the transition of polar nanoregions from dynamic to quasistatic regime, which introduces an intermediate temperature scale T? [W. Dmowski, S. B. Vakhrushev, I.-K. Jeong, M. P. Hehlen, F. Trouw, and T. Egami, Phys. Rev. Lett. 100, 137602 (2008); B. Dkhil, P. Gemeiner, A. Al-Barakaty, L. Bellaiche, E. Dul’kin, E. Mojaev, and M. Roth, Phys. Rev. B 80, 064103 (2009)], besides Burns temperature TB and freezing temperature Tf . Possible consequences for nonequilibrium phenomena, including high-temperature memory found in relaxors, are conjectured.

Craciun, F.

2010-05-01

62

Pyroelectric energy conversion using PLZT ceramics and the ferroelectric-ergodic relaxor phase transition  

NASA Astrophysics Data System (ADS)

This paper is concerned with direct conversion of waste heat into electricity by executing the Olsen cycle on lead lanthanum zirconate titanate (PLZT) ceramics undergoing a relaxor-ferroelectric phase transition. The Olsen cycle consists of two isothermal and two isoelectric field processes. First, the temperature-dependent dielectric properties were measured for x/65/35 PLZT. The polarization transition temperature of x/65/35 PLZT was found to decrease from 240 to 10?°C as x increased from 5 to 10 mol%. This suggests that the different compositions should be operated over different temperature ranges for maximum thermal to electrical energy conversion. The energy and power densities generated by the Olsen cycle using x/65/35 PLZT samples were measured by successively dipping the samples in isothermal dielectric oil baths. Large energy and power densities were obtained when the samples underwent the ergodic relaxor-ferroelectric phase transition. A maximum energy density of 1014 J l-1 per cycle was obtained with a 190 ?m thick 7/65/35 PLZT sample cycled at 0.026 Hz between 30 and 200?°C and between 0.2 and 7.0 MV m-1. To the best of our knowledge, this is the largest pyroelectric energy density ever demonstrated experimentally with ceramics, single crystals, or polymers. A maximum power density of 48 W l-1 was achieved using a 200 ?m thick 6/65/35 PLZT sample for temperatures between 40 and 210?°C and electric fields between 0 and 8.5 MV m-1 at a frequency of 0.060 Hz. The maximum applied electric field and temperature swings of these materials were physically limited by dielectric breakdown and thermomechanical stress.

Lee, Felix Y.; Ryul Jo, Hwan; Lynch, Christopher S.; Pilon, Laurent

2013-02-01

63

Pulsed laser deposition of relaxor ferroelectric lead magnesium niobate-lead titanate thin films and heterostructures  

NASA Astrophysics Data System (ADS)

Since their discovery several decades ago, relaxor ferroelectrics (RFE) (1- x)Pb(Mg1/3Nb2/3)O3- xPbTiO3 (PMN-PT), engineered near the morphotropic phase boundary (x = 0.3), have raised tremendous interest in the ferroelectric community, due to their broad ferroelectric transition, enormous dielectric constant, high piezoelectric coefficients and exceptional electromechanical coupling factors. However, these attractive qualities were demonstrated mainly by PMN-PT single crystals and ceramics and scarcely at all by PMN-PT thin films. This thesis addresses critical issues of the pulsed laser deposition growth of high quality epitaxial 0.70PMN-0.30PT thin films and heterostructures, for potential ferroelectric and piezoelectric thin film applications. A review of relaxor ferroelectrics in terms of general characteristics, crystallographic structure, models and synthesis with a special emphasis on 0.70PMN-0.30PT solid solutions is presented, including current issues of the Pulsed Laser Deposition (PLD) method, highlighting particular problems of lead-compound synthesis. The development of two pulsed laser deposition systems, two six target carousels, a target motion amplifier, an inverse position arm sputtering system, one He-Ne laser alignment system and one shadow mask set are described. These systems have been used for the growth of epitaxial RFE PMN-PT thin films and heterostructures. The main issues regarding the growth of pure perovskite phase single crystal PMN-PT/(001)SrTiO3 thin films and PMN-PT/SrRuO3/(001)SrTiO 3 heterostructures by PLD, the optimized deposition parameter space for in-situ growth, and the structural and chemical characterization of high quality PMN-PT thin films and heterostructures are addressed. Epitaxial PMN-PT thin films and heterostructures of unprecedented quality, resembling that of bulk single crystals are reported, and the thickness dependences of the strain state and crystalline quality are established. A film-growth, self-regulatory mechanism was found to adjust the non-stoichiometric atomic flux coming from the off-stoichiometric PMN-PT targets to form the perovskite phase when lower deposition rates were used. Laser instabilities and their impact upon the films reproducibility are discussed. Dielectric and piezoelectric measurements performed on PMN-PT thin films, together with the factors that influence these measurements, are presented. The thickness dependences of dielectric and ferroelectric parameters is reported. Annealing treatments in high oxygen pressure are shown to improve film dielectric and ferroelectric properties. Thicker films demonstrate the highest room temperature dielectric constants (? = 12000) and ferroelectric properties (remnant polarization Pr = 20 ?C/cm2, coercive field EC = 10 KV/cm, saturation polarization PS = 38 ?C/cm2, saturation field ES = 30 KV/cm) ever reported for a PMN- PT film, regardless of the deposition method involved. The piezoelectric charge coefficient at high fields is found to be d33 = 30 pm/V.

Lavric, Dan Silviu

64

High-temperature structural transformations in the relaxor ferroelectrics PbSc{sub 0.5}Ta{sub 0.5}O and Pb{sub 0.78}Ba{sub 0.22}Sc{sub 0.5}Ta{sub 0.5}O  

Microsoft Academic Search

Temperature-driven structural transformations in Pb-based perovskite-type relaxors are studied by using polarized Raman spectroscopy, high-resolution powder, and synchrotron single-crystal x-ray diffraction applied to PbSc{sub 0.5}Ta{sub 0.5}O (PST) and Pb{sub 0.78}Ba{sub 0.22}Sc{sub 0.5}Ta{sub 0.5}O (PBST). The two compounds were chosen as model systems because PST is a relaxor that exhibits ferroelectric long-range order on cooling, whereas PBST shows canonical relaxor behavior.

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

2008-01-01

65

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

66

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

67

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

NASA Astrophysics Data System (ADS)

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

Ramam, K.; Luis, S. H.

2006-07-01

68

High-temperature structural transformations in the relaxor ferroelectrics PbSc0.5Ta0.5O3 and Pb0.78Ba0.22Sc0.5Ta0.5O3  

NASA Astrophysics Data System (ADS)

Temperature-driven structural transformations in Pb-based perovskite-type relaxors are studied by using polarized Raman spectroscopy, high-resolution powder, and synchrotron single-crystal x-ray diffraction applied to PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST). The two compounds were chosen as model systems because PST is a relaxor that exhibits ferroelectric long-range order on cooling, whereas PBST shows canonical relaxor behavior. The temperature evolution of phonon anomalies and the pseudocubic unit-cell parameter for both PST and PBST reveals the existence of a characteristic temperature T? between the Burns temperature TB and the temperature of the dielectric-permittivity maximum Tm . T? is associated with the coupling of initially nucleated small polar clusters and their aggregation into larger polar clusters. The temperature range between TB and T? is characterized by a coupling between adjacent off-centered BO6 octahedra to form initial polar clusters, while the range between T? and Tm is characterized by a coupling between off-centered B cations from adjacent polar clusters. Off-centered Pb atoms exist even above the Burns temperature and their length of coherence governs the coupling between polar regions comprising B -cation off-center shifts and, consequently, directs the formation of the ferroelectric state to a normal, long-range ordered or nonergodic relaxor state.

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

2008-05-01

69

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

SciTech Connect

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

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

2011-01-01

70

High temperature lead-free relaxor ferroelectric: Intergrowth Aurivillius phase BaBi{sub 2}Nb{sub 2}O{sub 9}-Bi{sub 4}Ti{sub 3}O{sub 12} ceramics  

SciTech Connect

Intergrowth BaBi{sub 2}Nb{sub 2}O{sub 9}-Bi{sub 4}Ti{sub 3}O{sub 12} (BaBi{sub 6}Ti{sub 3}Nb{sub 2}O{sub 21}) Aurivillius phase ceramic has been found to be a relaxor ferroelectric (RFE) with the highest reported temperature of the maximum of the dielectric permittivity (T{sub m}) of all of the known RFE systems. Dielectric characterization revealed that it has two dielectric anomalies. The first one is a frequency independent broad dielectric constant peak at {approx}280 deg. C, while the second anomaly shows relaxor behavior at 636 deg. C (100 kHz). There is obvious frequency dispersion of dielectric response at room temperature, which is in agreement with dielectric properties of a typical relaxor. Ferroelectric hysteresis loops and a measurable value of piezoelectric constant d{sub 33} confirmed the ferroelectric nature of BaBi{sub 6}Ti{sub 3}Nb{sub 2}O{sub 21} ceramics. The piezoelectric response remained even after annealing at temperatures above 636 deg. C.

Zhang Hongtao [School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS (United Kingdom); Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Yan Haixue; Reece, Michael J. [School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS (United Kingdom); Nanoforce Technology Ltd., London E1 4NS (United Kingdom)

2010-05-15

71

Stress-mediated magnetoelectric memory effect with uni-axial TbCo2/FeCo multilayer on 011-cut PMN-PT ferroelectric relaxor  

NASA Astrophysics Data System (ADS)

We present here the implementation of a magnetoelectric memory with a voltage driven writing method using a ferroelectric relaxor substrate. The memory point consists of a magnetoelastic element in which two orthogonal stable magnetic states are defined by combining uni-axial anisotropy together with a magnetic polarization in the hard axis direction. Using a ferroelectric relaxor substrate, an anisotropic stress is created in the magnetic element when applying a voltage across electrodes. Because of the inverse magnetostrictive effect, the effective anisotropy of the magnetic element is controlled by the applied voltage and used to switch magnetization from one state to the other.

Dusch, Yannick; Tiercelin, Nicolas; Klimov, Alexey; Giordano, Stefano; Preobrazhensky, Vladimir; Pernod, Philippe

2013-05-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

73

Evolution of nanodomains during the electric-field-induced relaxor to normal ferroelectric phase transition in a Sc-doped Pb(Mg1/3Nb2/3)O3 ceramic  

NASA Astrophysics Data System (ADS)

Sc doping in Pb(Mg1/3Nb2/3)O3 enhances the B-site 1:1 cation order significantly but promotes the ferroelectric polar order moderately. At low doping levels, the electrical polar domains remain at the nanometer scale and the relaxor ferroelectric behavior is preserved. A normal ferroelectric state can be triggered with electric fields from the relaxor state at lower temperatures. This electric-field-induced phase transition process was directly observed with an in situ transmission electron microscopy technique in a 4 at. % Sc-doped Pb(Mg1/3Nb2/3)O3 polycrystalline ceramic under different conditions. It was found that the phase transition started at the grain boundary and took two steps to complete: The gradual coalescence of the polar nanodomains and the abrupt formation of the long-range ferroelectric domains. During the growth of the polar nanodomains, the morphology of the cation ordered chemical domains does not change. Furthermore, these chemical domains seem to have no strong resistance to the growth of polar domains in Sc-doped Pb(Mg1/3Nb2/3)O3.

Qu, W.; Zhao, X.; Tan, X.

2007-10-01

74

Physical Chemistry of the PbO-MgO-Nb2O5-TiO2 System for Ferroelectric Relaxors.  

National Technical Information Service (NTIS)

This project was devoted to evaluating the phase chemistry and thermochemistry of the quaternary lead-magnesium-niobium titanate system (PbO- MgO-Nb2O5-TiO2). It is technologically relevant to the development of ferroelectric relaxors with the perovskite ...

W. T. Petuskey

2004-01-01

75

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

76

Novel electro-strain-effect in La-doped Pb(Zr,Ti)O3 relaxor ferroelectrics  

Microsoft Academic Search

Lanthanum doped lead zirconate titanate [(Pb,La)(Zr,Ti)O3] transparent ceramics show relaxor behavior when the content of Lanthanum is 4-14% and molar ratio of Zr\\/Ti is 65\\/35. They were known as important electro-optical materials, but few researches had been focused on their electromechanical behavior. In the present work, we report a large recoverable electrostrain of about 0.2% at 1.0 kV\\/mm in (Pb,La)

L. X. Zhang; X. Ren; Y. Wang; X. Q. Ke; X. D. Ding; J. Sun

2009-01-01

77

Structural phase transitions in the relaxor ferroelectric Pb{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18}  

SciTech Connect

The relaxor ferroelectric Pb{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18} has been studied by Rietveld refinement of powder neutron diffraction data collected at temperatures of 100, 250 and 400 deg. C. Our refinements are compatible with the 'average' crystal structure of Pb{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18} undergoing the phase transition sequence F2mm->I4mm->I4/mmm as a function of increasing temperature, with the latter phase being observed above the known ferroelectric Curie temperature, T{sub m}, and the intermediate phase consistent with a previously observed dielectric anomaly around 207 deg. C. The results are, however, in conflict with both observation of a symmetry lowering (to space group B2eb) in the lowest temperature phase, observed by electron diffraction, and also with electrical property measurements, which suggest both a- and c-axis polarisation up to T{sub m}. Nevertheless, these crystallographic results are consistent with the observation of relaxor behaviour in this material, and underline the importance of considering 'long-range' versus 'local' structural effects in relaxor materials. - Abstract: A powder neutron diffraction study suggests that the relaxor ferroelectric Pb{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18} undergoes the phase transition sequence F2mm-I4mm-I4/mmm with increasing temperature. Display Omitted

Goff, Richard J. [EaStChem, School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST (United Kingdom); Lightfoot, Philip, E-mail: pl@st-and.ac.u [EaStChem, School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST (United Kingdom)

2009-10-15

78

X-ray Intensity Fluctuation Spectroscopy Using Nanofocused Hard X-rays: Its Application to Study of Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

The use of a combination of coherent X-rays from a third-generation synchrotron light source and ultraprecise Kirkpatrick-Baez mirrors enables us to apply nanofocused hard X-rays in solid-state physics. We developed an apparatus for X-ray intensity fluctuation spectroscopy using the nanofocused hard X-rays and applied it to the study of relaxor ferroelectrics. We have successfully detected a large and slow intensity fluctuation of scattered X-rays above cubic-to-tetragonal phase transition temperature with a characteristic time scale on the order of 10 s. We speculated that the intensity fluctuation originates from domain number fluctuation, which is directly related to the dielectric response, particularly the frequency dispersion.

Kenji Ohwada,; Kazumichi Namikawa,; Susumu Shimomura,; Hironori Nakao,; Hidekazu Mimura,; Kazuto Yamauchi,; Mitsuyoshi Matsushita,; Jun'ichiro Mizuki,

2010-02-01

79

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

80

Phonon mode and phase transition behaviors of (1-x)PbSc1/2Ta1/2O3-xPbHfO3 relaxor ferroelectric ceramics determined by temperature-dependent Raman spectra  

NASA Astrophysics Data System (ADS)

The composition dependence of phase transition temperature in (1-x)PbSc1/2Ta1/2O3-xPbHfO3 (PSTH) ceramics (0<=x<=0.2) has been investigated by Raman spectra. From the typical phonon mode variations, the PSTH ceramics unambiguously undergoes three structural transformations with increasing the temperature from 82 to 673 K. It was found that the F2g phonon mode disappears above the Curie temperature. Moreover, the PSTH ceramics exhibited the paraelectric to ferroelectric phase transitions at 287, 293, 313, 320, and 330 K with the composition. The phenomena can be ascribed to the enhanced length of Pb-O-Ta bonds induced by the incorporation of Hf4+ ions.

Zhang, W. J.; Li, W. W.; Chen, X. G.; Hu, Z. G.; Liu, W.; Wang, G. S.; Dong, X. L.; Chu, J. H.

2011-07-01

81

Temperature-dependent dielectric nonlinearity of relaxor ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 thin films  

NASA Astrophysics Data System (ADS)

Rayleigh analysis has been used to investigate the temperature dependence of the dielectric response of relaxor ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 films grown on platinized silicon substrates by chemical solution deposition. The irreversible contribution to dielectric permittivity maximizes at 50 °C and decreases with further temperature increase; while the intrinsic/reversible contribution is weakly dependent on temperature. The relaxor ferroelectric transition temperature Tm increases from 160 °C to 172 °C when the frequency increases from 1 kHz to 100 kHz. The dielectric nonlinearity decreases with temperature: falling from 0.012 cm/kV at room temperature to 0.005 cm/kV at 225 °C in tests at 1 kHz.

Ma, Beihai; Hu, Zhongqiang; Liu, Shanshan; Tong, Sheng; Narayanan, Manoj; Koritala, Rachel E.; Balachandran, Uthamalingam

2013-05-01

82

Analysis of polarization behavior in relaxation of BaTiO?-based ferroelectrics using wideband dielectric spectroscopy.  

PubMed

Wideband dielectric spectra from the kilohertz to terahertz range are discussed for BaTiO?-based ferroelectrics. Ceramics of BaTiO? (BT), Ba(0.6)Sr(0.4)TiO? (BST-0.6), and BaZr(0.25)Ti(0.75)O? (BZT-0.25) were selected as normal ferroelectrics, ferroelectrics with diffuse phase transition (DPT ferroelectrics), and relaxor ferroelectrics, respectively. The variation of ionic polarization in both BT and BST-0.6 ceramics with temperature could be explained by the softening of the soft phonon mode. In BZT-0.25, a permittivity anomaly at the dielectric maximum temperature (T(m)) at low frequencies is not attributed to the softening of the soft phonon mode, but originates from the permittivity derived from the dipole polarization (?(dipole)). Relaxor behavior in BZT-0.25 is derived from the increase in the depression of ?(dipole) on cooling across the T(m) with increasing frequency. In dipole polarization, BT, BST- 0.6, and BZT-0.25 all exhibited a similar tendency of ?(dipole) above the Curie temperature (T(c)) and T(m). However, behavior of ?(dipole) below the T(c) can be explained by the ferroelectric domains in BT, whereas the variation of ?(dipole) below the Tm could be explained by growth process of polar nanoregions (PNRs) in BST-0.6 and BZT-0.25. Regarding this, BT can be distinguished from BST-0.6 and BZT-0.25. Relaxation in BT could be interpreted as successive change in polarization mechanism from normal ferroelectrics to relaxor ferroelectrics via DPT ferroelectrics. PMID:20889394

Teranishi, Takashi; Hoshina, Takuya; Takeda, Hiroaki; Tsurumi, Takaaki

2010-10-01

83

Mode coupling and polar nanoregions in the relaxor ferroelectric Pb(Mg1\\/3Nb2\\/3)O3  

Microsoft Academic Search

We present a quantitative analysis of the phonon line shapes obtained by neutron inelastic scattering methods in the relaxor ferroelectric Pb(Mg1\\/3Nb2\\/3)O3 (PMN). Differences in the shapes and apparent positions of the transverse acoustic- (TA) and transverse optic- (TO) phonon peaks measured in the (300) and (200) Brillouin zones at 690 K are well described by a simple model that couples

S. Wakimoto; C. Stock; Z.-G. Ye; W. Chen; P. M. Gehring; G. Shirane

2002-01-01

84

Optical properties of epitaxial relaxor ferroelectric PbSc0.5Nb0.5O3 films  

NASA Astrophysics Data System (ADS)

The optical properties of epitaxial perovskite-structure relaxor ferroelectric PbSc0.5Nb0.5O3 thin films are studied in broad spectral and temperature ranges by variable-angle spectroscopic ellipsometry. The films possess a metrically tetragonal crystal structure with a biaxial in-plane compressive strain of 0.1%-0.8%. The optical constants of the films with thickness of 10-50 nm are determined accurately using the advanced ellipsometry technique. The dramatic changes in the spectra of the dielectric functions and the absorption coefficient are found under various strain conditions. The characteristic energies of the spectra, including the bandgaps, vary by 0.1-0.5 eV. A frustration of the ferroelectric phase transition is evidenced by thermo-optical studies. A complex relationship between strain, polarization, and optical properties is discussed in terms of possible ionic displacements in metrically tetragonal PbSc0.5Nb0.5O3 films.

Lynnyk, A.; Chvostova, D.; Pacherova, O.; Kocourek, T.; Jelinek, M.; Dejneka, A.; Tyunina, M.

2013-09-01

85

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

86

Low-temperature dielectric behavior of BiFeO3-modified CaTiO3 incipient ferroelectric ceramics  

NASA Astrophysics Data System (ADS)

CaTiO3 incipient ferroelectric ceramics have been modified by introducing BiFeO3. The single-phase (Ca1-yBiy)(Ti1-yFey)O3 solid solutions in space group Pbnm at room temperature are obtained for y <= 0.7. An obvious relaxor dielectric peak is induced in the present ceramics, and the peak temperature Tm increases with increasing y, where the dielectric constant as function of temperature can be well fitted with Barrett equation. The monotonic increase of T1 and T0 and decrease of (T1 - 2T0) in Barrett equation with increasing y suggest an approximation to the ferroelectric behavior, where the ferroelectric ordering becomes stronger compared with the quantum fluctuations. That is, the ferroelectric transition can be induced by introducing BiFeO3 in CaTiO3 incipient ferroelectric ceramics.

Qing Wang, Qing; Jian Zhao, Hong; Ming Chen, Xiang

2012-06-01

87

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

88

Ferroelectric to relaxor crossover and dielectric phase diagram in the BaTiO3-BaSnO3 system  

Microsoft Academic Search

The (1-x)BaTiO3-xBaSnO3 (0<=x=0.04 and at lower temperatures in those with a smaller x. For 0<=x<=xc=0.19, the temperature of the dielectric peak Tm, corresponding to the diffuse transition from the ergodic polar cluster state to the ferroelectric state, decreases with increasing x and does not depend on frequency. The diffuseness of the peak gradually increases. For x>xc, the permittivity exhibits relaxor

C. Lei; A. A. Bokov; Z.-G. Ye

2007-01-01

89

Relaxor ferroelectric and photocatalytic behaviour of Ba 0.785Bi 0.127Y 0.017TiO 3 composition  

Microsoft Academic Search

The composition of Ba0.785Bi0.127Y0.017TiO3 (BaBiYTiO) belongs to the BaTiO3–Bi2O3–Y2O3 system. A dielectric study on ceramics performed at temperatures in the range (77K–500K) and frequency (102–2×105Hz) revealed ferroelectric relaxor behaviour with a phase transition close to room temperature. The conductivity of BaBiYTiO obeys to an Arrhenius-type law with activation energy equals to 0.21eV, in conformity with a small polaron hopping where

A. Kerfah; K. Taïbi; S. Omeiri; M. Trari

2011-01-01

90

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

SciTech Connect

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

Tong, S.; Narayanan, M.; Ma, B.; Koritala, R. E.; Liu, S.; Balachandran, U.; Shi, D. (Energy Systems); ( MSD); (Univ. of Cincinnati)

2011-02-01

91

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

92

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

93

Origin of high-temperature relaxor-like behavior in CaCu3Ti4O12  

NASA Astrophysics Data System (ADS)

The relaxor-like behavior in CaCu3Ti4O12 was investigated in details. The dielectric anomaly was found to be an extrinsic phenomenon related to oxygen vacancy. Annealing treatments in N2 and O2 atmospheres revealed that the relaxor-like behavior is composed of two types of relaxations with close relaxation parameters. Impedance analysis showed that the relaxations appearing in the low- and high-temperature wings of the anomaly are related to the dipolar and Maxwell-Wagner (MW) relaxation, respectively. Both relaxations are induced by the hopping motions of confined carriers related to single-ionized oxygen vacancies, and they are intimately linked with each other. The relaxor-like anomaly is attributed to the combining effect of these two relaxations, i.e., the dipolar relaxation first creates a steplike increase followed by a rapid decrease in dielectric constant caused by the MW relaxation, thereby, giving rise to the relaxor-like behavior.

Wang, Chun-Chang; Zhang, Mei-Ni; Xu, Ke-Biao; Wang, Guo-Jing

2012-08-01

94

Relaxor- and phase-transition-like behaviors in ZnO single crystals at high temperatures  

NASA Astrophysics Data System (ADS)

We herein reported the dielectric properties of ZnO single crystals, and three dielectric anomalies were found. The first anomaly shows a relaxor-like behavior. It is composed of two oxygen-vacancy-related relaxation processes: a dipolar relaxation related to the hopping motions of single-ionized oxygen vacancies and a Maxwell-Wagner relaxation as the defects were blocked by the interfaces of sample/electrode contacts. The second anomaly behaves as a phase-transition-like behavior. It is ascribed to the distribution state transition for oxygen vacancies from static disorder to dynamic disorder. The third anomaly exhibits a relaxor-like behavior. It is an artificial effect caused by negative capacitance.

Liu, L. N.; Wang, C. C.; Lei, C. M.; Li, T.; Wang, G. J.; Sun, X. H.; Wang, J.; Huang, S. G.; Li, Y. D.; Wang, H.

2013-03-01

95

Field-induced orientational percolation to a ferroelectric phase in relaxor Pb(In1/2Nb1/2)1-xTixO3  

NASA Astrophysics Data System (ADS)

This work presents direct observations of orientational percolation and depolarization in a (001)-cut relaxor Pb(In1/2Nb1/2)0.70Ti0.30O3 (PINT30%) crystal by means of dielectric permittivity, depolarization current, domain structure, and hysteresis loop. Electric (E) -field poling induced a 10-300?m size orientational percolation transition in the matrix. The percolation breaks down at depolarization temperature Td?395K , which is ˜20-40K higher than in rhombohedral Pb(Mg1/3Nb2/3)1-xTixO3 . Near 420K , the remaining polarization disappears, and the full relaxor-type dielectric dispersion due to polar nanoclusters reappears, and remains evident up to the Burns temperature TB?520K . Under E=40kV/cm at room temperature, small regions of [001] tetragonal domains appeared, but most of the crystal exhibited field-induced percolation rhombohedral and monoclinic microdomains embedded randomly in the matrix. This work suggests that this relaxor ferroelectric consists of two components (spherical glassy matrix and polar nanoclusters) as proposed for Pb(Mg1/3Nb2/3)O3 by Blinc [Phys. Rev. Lett. 91, 247601 (2003)].

Tu, C.-S.; Chien, R. R.; Hung, C.-M.; Schmidt, V. Hugo; Wang, F.-T.; Tseng, C.-T.

2007-06-01

96

Brillouin and dielectric studies of the phase transition in the relaxor ferroelectric Pb(Ni1/3Nb2/3)O3  

NASA Astrophysics Data System (ADS)

Brillouin scattering has been performed on the relaxor ferroelectric Pb(Ni1/3Nb2/3)O3 (PNN) from 80 to 450 K across its Curie temperature. A diffuse phase transition from the paraelectric to ferroelectric phase, associated with a broad phonon frequency dip and a damping maximum, is observed around 200 K. A relaxation mode in the form of a broad Rayleigh wing, whose frequency is strongly temperature dependent above 190 K, is observed and analyzed based on a modified superparaelectric model. Dielectric studies of PNN have also been carried out at several measurement frequencies. The relation between the measurement frequency and the dielectric maximum temperature was analyzed on a modified Vogel-Fulcher model.

Fan, H. J.; Kuok, M. H.; Ng, S. C.; Yasuda, N.; Ohwa, H.; Iwata, M.; Orihara, H.; Ishibashi, Y.

2002-02-01

97

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

2013-02-14

98

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

99

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

SciTech Connect

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

Liu Yun [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia); Withers, Ray L. [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)], E-mail: withers@rsc.anu.edu.au; Wei Xiaoyong [Electronic Materials Research Laboratory (EMRL), Xi'an Jiaotong University, Xi'an (China); Fitz Gerald, John D. [Research School of Earth Sciences, Australian National University, Canberra, ACT 0200 (Australia)

2007-03-15

100

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

Microsoft Academic Search

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

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

2009-01-01

101

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

102

Fabrication and characterization of relaxor ferroelectric PbFe1/2Ta1/2O3 thin film: A comparison with ceramics  

NASA Astrophysics Data System (ADS)

Highly oriented Pb(Fe1/2Ta1/2)O3 (PFT) film is fabricated on conducting La0.67Sr0.33CoO3 coated (100) MgO substrate using pulsed laser deposition technique. The x-ray diffraction pattern shows single phase compound having preferential orientation along (100) plane. Surface topography of the film indicates homogeneous distribution of grains with an average grain size ~55 nm. Broad dielectric dispersion, high dielectric diffusivity, and moderate dielectric loss are observed in the vicinity of wide range of temperatures and frequencies. A reasonably good shift in dielectric maximum temperature (~30 K) is observed from 1 to 500 kHz suggests relaxor nature of film in this frequency range. At the same time, diffuse dielectric dispersion is seen above 500 kHz indicating diffuse ferroelectric phase transition. Dielectric data fallows the nonlinear Vogel-Fulcher relation below 500 kHz applied frequency which support the relaxor nature of PFT film. The ferroelectric hysteresis loop and butterfly loop show well defined saturated loop below freezing temperature (Tf) (~150 K). A large shift in dielectric maximum temperature (Tm), i.e., around 75 K is observed compared to bulk counterpart that may be due to misfit strain across substrate-bottom electrode-film interface and in plane compressive strain in the film.

Martínez v, R.; Kumar, Ashok; Sanchez, Dilsom A.; Palai, R.; Katiyar, R. S.

2010-10-01

103

Relaxor ferroelectricity and the freezing of short-range polar order in magnetite  

NASA Astrophysics Data System (ADS)

A thorough investigation of single-crystalline magnetite using broadband dielectric spectroscopy and other methods provides evidence for relaxorlike polar order in Fe3O4. We find long-range ferroelectric order to be impeded by the continuous freezing of polar degrees of freedom and the formation of a tunneling-dominated glasslike state at low temperatures. This also explains the lack of clear evidence for a noncentrosymmetric crystal structure below the Verwey transition. Within the framework of recent models assuming an intimate relation of charge and polar order, the charge order, too, can be speculated to be of short-range type only and to be dominated by tunneling at low temperatures.

Schrettle, F.; Krohns, S.; Lunkenheimer, P.; Brabers, V. A. M.; Loidl, A.

2011-05-01

104

Chemical order and local structure of the lead-free relaxor ferroelectric NaBiTiO3  

NASA Astrophysics Data System (ADS)

The A-site mixed perovskite sodium bismuth titanate (NaBi)TiO3 (NBT) is investigated by means of first-principles calculations based on density functional theory. By studying different geometries with varying occupations of the A-site, the influence of chemical order on the thermodynamic stability and local structure is explored. We find that the hybridization of Bi 6sp with O 2p-states leads to stereochemically active Bi3 lone pairs and increases the stability of structures with high Bi concentrations in {001}-planes. This goes along with displacive disorder on the oxygen sublattice, which up to now has been neglected in experimental studies. The calculated ordering energies are, however, small as compared to the thermal energy and therefore only short-range chemical order can be expected in experiments. Thus, it is conceivable that chemically ordered local areas can act as nucleation sites for polar nano-regions, which would explain the experimentally observed relaxor behavior of NBT.

Gröting, Melanie; Hayn, Silke; Albe, Karsten

2011-08-01

105

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

NASA Astrophysics Data System (ADS)

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

Vierheilig, Albert A.

106

Structured diffuse scattering and polar nano-regions in the Ba(Ti1-xSnx)O3 relaxor ferroelectric system  

NASA Astrophysics Data System (ADS)

The observation via electron diffraction of relatively sharp G±{001}* sheets of diffuse intensity arising from the large amplitude excitation of inherently polar, transverse optical modes of distortion in Ba(Ti1-xSnx)O3 (BTS), 0.1?x?0.5, samples, both at room temperature as well as liquid nitrogen temperature, shows that the polar nano-regions (PNRs) in these relaxor ferroelectric materials correspond to the same highly anisotropic <001> chain dipoles as are characteristic of the normal ferroelectric end member BaTiO3 itself. The correlation length along the chain of these 1-d PNRs can, in principle, be determined from the width of the observed {001}* diffuse sheets in reciprocal space and is estimated to be at least 5 nm even for the higher x samples. The distribution of the substitutional Sn ions thus appears to have only a minor effect upon the correlation length along the <001> chain dipole directions. It is suggested that the role of the dopant Sn ions is not to directly induce PNRs but rather to set up random local strain fields preventing the condensation of long wavelength homogeneous strain distortions of the unit cell thereby suppressing transverse correlations of the <001> chain dipoles and the development of long-range ordered ferroelectric state/s.

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

2007-03-01

107

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

108

Thermodynamics of Stress and Electric Field Induced Phase Transition in Relaxor Ferroelectric Crystals  

Microsoft Academic Search

A thermodynamics based analysis of measured material behavior in (110) orientated (PMN-32%PT) and (PZN-4.5%PT) crystals under combined stress, electric field and temperature loading leads to a determination of the relative energy levels of phases. The approach is to perform path integrals to determine external work done by electrical and mechanical loads at constant temperature and to remove the effect of

Tieqi Liu; Christopher S. Lynch; Elizabeth A. Mclaughlin

2007-01-01

109

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

SciTech Connect

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

Groeting, Melanie, E-mail: groeting@mm.tu-darmstadt.de [Fachgebiet Materialmodellierung, Institut fuer Materialwissenschaft, TU Darmstadt, Petersenstr. 32, 64287 Darmstadt (Germany); Hayn, Silke, E-mail: shayn@mm.tu-darmstadt.de [Fachgebiet Materialmodellierung, Institut fuer Materialwissenschaft, TU Darmstadt, Petersenstr. 32, 64287 Darmstadt (Germany); Albe, Karsten, E-mail: albe@mm.tu-darmstadt.de [Fachgebiet Materialmodellierung, Institut fuer Materialwissenschaft, TU Darmstadt, Petersenstr. 32, 64287 Darmstadt (Germany)

2011-08-15

110

Strontium-induced ferroelectriclike relaxor behavior in Bi-based pyrochlores  

NASA Astrophysics Data System (ADS)

The dielectric properties of stoichiometric dense ceramics (Bi1.5Zn0.5-xSrx)(Ti1.5Nb0.5)O7 (BZSTN, x=0-0.5) have been investigated as a function of temperature and frequency. A significant relaxation behavior at about 250 °C is induced when moderate Sr2+ is substituted with Zn2+ in Bi1.5Zn0.5Ti1.5Nb0.5O7 (BZTN) ceramics. The observation of hysteretic behavior in the P versus E curves shows the existence of a polar state. The ferroelectriclike relaxor behavior arises mainly from the dynamic response of the micropolar clusters, which exist in the off-center ions doped paraelectric. The ultrahigh permittivity of 245 at ambient temperature could be very promising for integrated capacitors and microwave resonators.

Du, Huiling; Shi, Xiang

2010-08-01

111

Relaxor behavior and dielectric relaxation in Pb(Ba1/3Nb2/3)O3: A phase pure new relaxor material  

NASA Astrophysics Data System (ADS)

Pb(Ba1/3Nb2/3)O3 was prepared by two steps solid state reaction route. Material stabilized in orthorhombic perovskite phase with lattice constants a=4.0849(3) A?, b=11.8469(4) A?, and c=10.6818(9) A?. The scanning electron micrograph exhibits heterogeneous grain distribution with average grain size of 1-3 ?m. Temperature dependent dielectric constant exhibits a broad peak at 316 K (?m=2250) that shows frequency dependent shifts toward higher temperature-typical relaxor behavior. Modified Curie-Weiss law is used to fit the dielectric data that exhibits almost complete diffuse phase transition characteristics. The dielectric relaxation obeys the Vogel-Fulcher relationship with the freezing temperature 286 K. In addition to relaxation observed due to transformation of the material into ergodic relaxor phase below Burn temperature, significant dielectric dispersion is observed in low frequency regime in both components of dielectric response and a small dielectric relaxation peak is observed in the temperature range (423-598 K) that is associated with defect related hopping process. Cole-Cole plots indicate polydispersive nature of this dielectric relaxation; the relaxation distribution increasing with temperature.

Bajpai, P. K.; Pastor, Mukul; Singh, K. N.

2011-01-01

112

Relaxor ferro- and paraelectricity in anisotropically strained SrTiO3 films  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

113

Electrical Properties of Lead-Free Relaxor Ferroelectric Solid Solution Single Crystal (Na1/2Bi1/2)TiO3-BaTiO3 Grown by Bridgman Method  

NASA Astrophysics Data System (ADS)

Lead-free relaxor ferroelectric solid solution single crystals of (Na1/2Bi1/2)TiO3-BaTiO3 (NBT-BT) grown by the Bridgman method without the flux of Bi2O3 and Na2O have good optical quality and electrical properties. It was found that their transition from the rhombohedral phase to the tetragonal phase occurs at about 250 °C, accompanied by isotropization. Moreover, the domain wall structure changes with heating, and dielectric dispersion gradually disappears at 250 °C. Relative permittivity increases with further heating and shows a peak at Ta of 340 °C with the appearance of brightness in a polarizing microscope, accompanied by a small frequency dispersion in \\tan?. Polarization-electric field (P-E) hysteresis loops reveal a narrow shape without saturation with increasing electric field due to random fields based on defects at A-sites in perovskite compounds. Strain (S) versus electric field curves under bipolar fields reveal a slightly piezoelectric behavior without polarization reversal. The value of d33 (Smax/Emax) was estimated to be about 250 pm/V at room temperature.

Yasuda, Naohiko; Hashimoto, Shinji; Ohwa, Hidehiro; Sakurada, Osamu; Fujita, Kazuhiko; Yamashita, Yohachi; Iwata, Makoto; Ishibashi, Yoshihiro

2009-09-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

115

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

116

Mechanical stress modified ferroelectric aging behavior  

NASA Astrophysics Data System (ADS)

Mechanical stress effect on aging behavior of Bi3.25La0.75Ti3O12 (BLT) and PbZr0.53Ti0.47O3 (PZT) films was investigated. It is found that the remnant polarization decreases with time while the coercive field increases in stress-free BLT films. For unconfined PZT films, both the remnant polarization and the coercive field decrease as time elapses. The applied tensile stress weakens the aging of remnant polarization of BLT films but strengthens the aging of coercive field, while the applied tensile stress possesses opposite effect. In contrary, the applied compressive stress simultaneously improves the aging behavior of both remnant polarization and coercive field of PZT films. Mechanical-stress-induced variation of domain wall mobility in different materials was suggested as the possible origin of these observations. This work indicates that the aging behavior modification using stress could be realized, and it is helpful for promoting the reliability of ferroelectric films for industrial applications.

Xu, Tingting; Kan, Yi; Jin, Yaming; Sun, Hui; Du, Yingchao; Wu, Xiumei; Bo, Huifeng; Cai, Wei; Huang, Fengzhen; Lu, Xiaomei; Zhu, Jinsong

2013-05-01

117

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

118

Relaxor fluorinated polymers: novel applications and recent developments  

Microsoft Academic Search

It has been found that by introducing defects into the P(VDF-TrFE) copolymers, it is possible to convert the polymer from a normal ferroelectric to a relaxor ferroelectric. A new class of ferroelectric polymers, i.e., the terpolymers of P(VDF-TrFE-CFE) or of P(VDF-TrFE- CTFE), was developed from the normal ferroelectric PVDF-TrFE polymer by employing proper defect modifications which eliminate detrimental effects associated

Francois Bauer

2010-01-01

119

Relaxor behavior of PbxBi4Ti3+xO12+3x (x=2,3) Aurivillius ceramics  

NASA Astrophysics Data System (ADS)

The relaxor response of the PbxBi4Ti3+xO12+3x (x=2,3) Aurivillius ceramics is reported. The relaxor behavior appears with an increase of the symmetry in the ab plane of the structure and a decrease of the transition temperature. By the application of a bias field on nonpoled samples, it is possible to induce the piezoelectric response. The piezoelectric coefficient in the planar mode of -72 pC/N was measured at 210 °C for Pb2Bi4Ti5O18 ceramic disks. These results represent a step in the search of high-temperature piezoelectric ceramics.

Fernández, J. F.; Caballero, A. C.; Villegas, M.; de Frutos, J.; Lascano, L.

2002-12-01

120

Investigation of ferroelectric behavior in electroactive polymer systems  

Microsoft Academic Search

Ferroelectric behavior has been investigated in newly synthesized electroactive cyanopolymer systems. These systems are chemical analogs to the well known ferroelectric polymer poly(vinylidene fluoride), PVDF, and its copolymers with trifluoroethylene, P(VDF-TrFE). Various chemical groups have been used to replace the electronegative fluorine and electropositive hydrogen atoms found in PVDF. This substitution maintains the polar nature of the all-trans conformation while

Matt Poulsen

2007-01-01

121

Dipole glass behavior in ferroelectric pyridinium periodate  

NASA Astrophysics Data System (ADS)

Detailed investigations have been performed on the dielectric behavior in polycrystalline pyridinium periodate C5NH6IO4 at temperatures 100K?T?340K and frequencies 10Hz???105Hz. A remarkable dielectric relaxation is clearly observed at temperatures below 250 K. The frequency dependence of the dielectric constant is analysed by use of a sum of two kinds of relaxation process with different strength. The relaxation time for the dominant relaxation process obeys the Arrhenius law with the activation energy E=3869±15K and the pre-exponential factor ?0=3.3×10-12s. The dominant one is regarded as clear evidence of the dipole glass state in C5NH6IO4. Its origin is thought to be the coupled reorientation of the pyridinium cation and the IO4 anion. The overall temperature dependence of the relaxation time for the other weak relaxation process shows a quite different pattern which can hardly be described by the Arrhenius law. The weak one is considered to originate from the ferroelectric domain wall motion.

Shin, H. K.

2013-03-01

122

Broadband gigahertz dynamics of relaxor ferroelectric Pb(Sc1/2Nb1/2)O3-xPbTiO3 single crystal probed by Brillouin scattering  

NASA Astrophysics Data System (ADS)

The broadband gigahertz dynamics of a relaxor ferroelectric crystal 0.70Pb(Sc1/2Nb1/2)O3-0.30PbTiO3 with a composition close to the starting point of the morphotropic phase boundary is studied by Brillouin scattering. The significant anomaly of the longitudinal acoustic (LA) mode is observed in the vicinity of the Curie temperature, TC = 500 K. Upon cooling, it starts below the Burns temperature, TB = 670 K, due to the interaction between the LA mode and dynamic polar nanoregions (PNRs). The broad central peak (CP) clearly appears below TB, and its intensity becomes a maximum at TC. The relaxation time, ?CP, determined from the CP width, shows the typical critical slowing down of the order-disorder phase transition in the vicinity of TC. The size of a dynamic PNR significantly increases below the intermediate temperature, T* = 562 K.

Kojima, S.; Tsukada, S.; Hidaka, Y.; Bokov, A. A.; Ye, Z.-G.

2011-04-01

123

Experimental Study of Polarization Clusters in 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 Relaxor Ferroelectrics by means of Synchrotron Radiation X-ray Diffraction  

SciTech Connect

X-ray diffraction has been conducted to study the microscopic-scale structures for 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 relaxor ferroelectrics in a high external DC field during phase transition. Clear quasi-periodic structures were observed along <111> and <1-11> directions near Tc induced by the high external DC field. The formation of these periodic structures are interpreted as a type of Coulomb interaction among adjacent polar clusters. The cluster size was estimated to be 17nm. It was also found that the dominating interaction direction among clusters (periodic direction) were changeable among <111> and <1-11> as temperature changed.

Guo Zhi; Tai Renzhong; Xu Hongjie [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800 (China); Gao Chen; Pan Guoqiang; Hu Chuansheng; Fan Rong; Li Ruipeng [National Synchrotron Radiation Laboratory, University of Sciences and Technology of China, Hefei 230029 (China); Luo Haosu; Lin Di [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Dingxi road 1295, Shanghai 200050 (China); Namikawa, Kazumichi [Department of Physics, Tokyo Gakugei University, 4-1-1 Nukui-Kita Machi, Kogannei-Shi, Tokyo 184-8501 (Japan)

2007-01-19

124

High acousto-optic and electro-optic effects in relaxor ferroelectric single crystals and related device development  

NASA Astrophysics Data System (ADS)

The electro-optic and acousto-optic effects of Lead Zinc Niobate-Lead Titanate (1-x)Pb(Zn1/3, Nb2/3)O3-(x)PbTiO 3 (PZN-PT), and Lead Magnesium Niobate-Lead Titanate (1-x)Pb(Mg 1/3, Nb2/3)O3-(x)PbTiO3 (PMN-PT) single crystals are new materials investigated for high performance piezoelectrics. Based on their extraordinary electromechanical properties and associated structure information, it is likely to also find the phase transition related high optical modulation ability in these crystals. In order to better understand the underlying nature of their phase transition behaviors, materials have been examined on their dielectric and piezoelectric properties. In order to verify their optical properties, the characterization methods for electro-optic and acousto- optic effects are presented in detail. The measurement results show these new materials have both high electro- optic and acousto-optic coefficients. Using a phenomenology theory, the temperature independent electro-optic coefficients and relationship among acousto-optic coefficients are explained. To fully demonstrate both excellent electromechanical and optical performances in these materials, a new ultrasonic transducer design is proposed with piezoelectric effect as transmitter and optical Fabry-Perot etalon as receiver. In order to realize nontuning interferometric measurement, a quadrature detection method is developed. Experimental results on the single element transducer demonstrate the feasibility of this new type of transducer. Conclusion and proposals for further work are presented.

Lu, Yu

125

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

126

Domain structures and dielectric properties resulting from tweed precursors of relaxor ferroelectric solid-solution single-crystal 24Pb(In1/2Nb1/2)O3-46Pb (Mg1/3Nb2/3)O3-30PbTio3.  

PubMed

The domain structures of poled and depoled lead-based relaxor ferroelectric solid-solution single-crystal 24Pb(In(1/2)Nb(1/2))O(3)-46Pb (Mg(1/3)Nb(2/3))O(3)-30PbTio(3) are studied by polarized light microscopy, piezoresponse force microscopy (PFM), scanning electron microscopy (SEM), and dielectric spectroscopy. The domain structures in the nonergodic relaxor state are found by PFM to consist of tweed structures resulting from random fields from the competition between ferroelectric and antiferroelectric distortion, and planar defects found by SEM are treated as dislocations associated with strain accommodation, resulting in superior piezoelectric properties. This domain structure is found to be connected with hierarchical domain structures. PMID:23007761

Yasuda, Naohiko; Nur Hidayah, Z A; Ohwa, Hidehiro; Tachi, Yoshihito; Yamashita, Yohachi

2012-09-01

127

Auxetic behavior under electrical loads in an induced ferroelectric phase  

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

128

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

130

Locating the normal to relaxor phase boundary in Ba(Ti{sub 1-x}Hf{sub x})O{sub 3} ceramics  

SciTech Connect

In this article, we report our studies on the relaxor behavior of Ba(Ti{sub 1-x}Hf{sub x})O{sub 3} ceramics, made with close compositions between 0.20 {<=} x {<=} 0.30, to locate the hafnium concentration boundary for the normal to relaxor crossover. X-ray diffraction followed by Rietveld refinement shows the occurrence of single-phase cubic structure for the synthesized Ba(Ti{sub 1-x}Hf{sub x})O{sub 3} ceramics. Temperature and frequency dependence of the real ({epsilon}') and imaginary ({epsilon}'') parts of the dielectric permittivity has been studied in the temperature range of 90-350 K at frequencies of 0.1, 1, 10, and 100 kHz. A diffuse phase transition accompanying frequency dispersion is observed in the permittivity versus temperature plots revealing the occurrence of relaxor ferroelectric behavior. The T{sub m} verses Hf concentration plot shows a discontinuous jump and change in the slope at x = 0.23. Quantitative characterization based on phenomenological models has also been presented. The plausible mechanism of the relaxor behavior has been discussed. Substitution of Hf{sup 4+} for Ti{sup 4+} in BaTiO{sub 3} reduces the long-range polar ordering yielding a diffuse ferroelectric phase transition.

Anwar, Shahid [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India)], E-mail: shahidanwr@gmail.com; Sagdeo, P.R. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India); Lalla, N.P. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India)], E-mail: nplalla@csr.ernet.in

2008-07-01

131

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

Microsoft Academic Search

Ba1-xCaxTiO3 thin films (x=0.05 to 0.17) were deposited on Pt-coated Si substrates using a pulsed excimer laser ablation technique. X-ray diffraction and scanning electron microscope studies of the Ba1-xCaxTiO3 targets exhibit a polycrystalline nature and thin films also show the same but with a significant orientation along the (111) direction. Secondary ion mass spectrometer analysis reveals the presence of a

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

2003-01-01

132

Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics.  

PubMed

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

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

2010-04-05

133

Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics  

PubMed Central

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

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

2010-01-01

134

The effect of ac field amplitude on the relaxor behaviors in Langmuir-Blodgett terpolymer films  

NASA Astrophysics Data System (ADS)

The ac field (Eac) amplitude dependence of dielectric response has been investigated for poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) relaxor terpolymer films. The frequency dependence of the temperature of the permittivity maximum Tm can be well described by the Vogel-Fulcher relation for Eac in the range from 1.33 to 80 MV/m. Tm remains nearly constant at an Eac level lower than 13.3 MV/m, and starts decreasing with Eac increases further. The two parameters fitting to the Vogel-Fulcher relation, freezing temperature Tf and activation energy Ea, vary little for Eac below 26.7 MV/m and then Tf decreases, while Ea increases for higher Eac level.

Meng, X. J.; Wang, J. L.; Xu, H. S.; Sun, J. L.; Chu, J. H.

2009-12-01

135

Memristive behaviors of LiNbO3 ferroelectric diodes  

NASA Astrophysics Data System (ADS)

Memristive systems are expected to lead to analog computers that process information the way the human brain does. In this work, memristive behaviors have been revealed in ferroelectric diodes employing LiNbO3. The conduction states in such diodes can be continually modulated by the successive voltage sweeps, which is essentially based on electron tunneling through a thin residual barrier. The role of oxygen vacancies in such memristive behaviors is also discussed.

Li, Haitao; Xia, Yidong; Xu, Bo; Guo, Hongxuan; Yin, Jiang; Liu, Zhiguo

2010-07-01

136

Rescaled temperature dependence of dielectric behavior of ferroelectric polymer composites  

Microsoft Academic Search

Rescaled temperature dependence of dielectric behavior of ferroelectric polyvinylidene fluoride (PVDF) filled with electroactive ceramic particles of rocksalt-type Li and Ti codoped NiO (LTNO) was studied at wide frequency ranges. Dielectric behavior of the flexible PVDF-LTNO composites with LTNO filler at the volumetric function of 0.3 exhibits a dielectric constant value, ?~50 at broad temperature range (290-360 K), and the

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

2005-01-01

137

Dielectric Behavior of KNO3 in Its Ferroelectric Phase III  

Microsoft Academic Search

The dielectric behavior of KNO3 crystal was investigated. Mainly in its ferroelectric phase III, which appears in the temperature range of about 125˜115°C on cooling, the D-E hysteresis loop along the c axis was observed by the usual Sawyer-Tower method using the 50 c\\/s ac electric field, the pyroelectric current in this direction was measured by the usual galvanometer method

Shozo Sawada; Shoichiro Nomura; Yohko Asao

1961-01-01

138

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

NASA Astrophysics Data System (ADS)

This thesis extends the investigations on perovskite solid solutions based on PbTiO3-Bi(Me',Me")O3 (Me' = Sc3+, Zn2+, Mg2+, Ni2+, In3+ , Fe3+, etc. and Me" = Ti4+, Nb 5+, W6+) systems. The ferroelectric transition temperature (TC) behavior was considered in the tetragonal phase region of the PbTiO 3-Bi(Me',Me")O3 systems. Trends in the TC compositional dependence exhibited three main cases: case 1, a continued increase in transition temperature above the end-member PbTiO3 (495°C); case 2, an increase and then decrease of the transition temperature; and case 3, a continuous decrease in the transition temperature with Bi(Me',Me")O 3 additions. New relaxor materials were developed from the PbTiO3-Bi(Me',Me")O 3 solid solutions; specifically, the Bi(Mg3/4W1/4)O 3-PbTiO3 (BMW-PT) binary solid solution and BiScO3-Pb(Mg 1/3Nb2/3)O3-PbTiO3 (BS-PMN-PT) ternary solid solution were investigated. Permittivity, polarization and pyroelectric measurements were performed on BMW-PT and BS-PMN-PT compositions with respect to temperature with characteristic relaxor behavior observed. The complex solid solution BMW-PT exhibited a morphotropic phase boundary at ˜48 mol% PbTiO3 with a corresponding TC of 205°C. On further structural analysis with diffraction contrast transmission electron microscopy along with x-ray diffraction, evidence of B-site ordering was observed. The BS-PMN-PT proved to be a model system with high temperature relaxor properties of Tmax ˜ 250°C to 300°C and ?max ˜ 14,000 to 17,000 at 1 kHz. The deviation temperature, TD, or temperature of the onset of local spontaneous polarization, was determined by thermal strain measurement and high temperature dielectric measurement to be approximately 600°C; up to 250°C higher than any reported value for relaxor ferroelectrics. The frequency dependence of the temperature of the permittivity maximum was found to follow the Vogel-Fulcher relationship, with an activation energy (EA) of ˜0.1 eV, and a freezing temperature (Tf) of ˜150°C. Static and in-situ transmission electron microscopy investigations of the BS-PMN-PT compositions demonstrated a frustrated microstructure of nanometer scale regions and were used to establish structure-property relationships with different electric field and thermal histories. A comparative study of the key relaxor parameters, EA, T f, and TD was tabulated with previously investigated relaxor ferroelectrics. These parameters were found to scale relative to other lead-based perovskite relaxor ferroelectric compounds and solid solutions, with the BS-PMN-PT ternary system exhibiting the highest temperature behavior. Finally, to demonstrate one possible application area for these materials, multilayer ceramic capacitor devices were designed for operation at 300°C and up to 10 kHz. The voltage saturation was found to be extremely encouraging at 300°C with observed changes in capacitance (˜3%) on the application of 10 kV/cm. The insulation resistivity followed an Arrhenius behavior and at 300°C was ˜1010 O-cm. Weibull statistics were used to estimate a characteristic breakdown field at 300°C for the BS-PMN-PT multilayer capacitors of ˜40 kV/cm. Current-voltage measurements were performed to voltages up to breakdown and exhibited Ohmic behavior, indicating intrinsically controlled conduction. Highly accelerated life time tests were performed on BS-PMN-PT capacitors. It was observed that silver migration from termination electrodes caused premature failure at elevated temperature.

Stringer, Craig J.

139

Phase diagram and skin effect of the relaxor ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3+xPbTiO3  

NASA Astrophysics Data System (ADS)

We revisit the phase diagram of the relaxor ferroelectric PMN-xPT using neutron powder diffraction to test suggestions that defects in the oxygen stoichiometry and/or strain affect the ground state crystal structure. Two identical sets of PMN-xPT powders were prepared with x=0.10, 0.20, 0.30, and 0.40. One set was annealed in air at 873K for 2h. For a given composition and temperature the same structural phase is observed in each set, thus indicating that the effects of strain and oxygen vacancies are minimal. But the distortions measured in the annealed samples are consistently smaller than those in the as-grown samples. In addition, the average grain size of the annealed samples is approximately twice that of the as-grown samples (1.2±0.6 microns vs 0.6±0.3 microns). This result is consistent with a skin effect in which Ti-poor bulk crystals show significantly smaller distortions than do powders of the same composition. The diffraction patterns for both the as-grown and annealed samples with compositions x=0.10 and x=0.20 are best refined using the monoclinic Cm space group, which agrees with recent speculation by Singh et al., Phys. Rev. B 74, 024101 (2006).

Gehring, Peter; Phelan, Daniel; Rodriguez, Efrain; Ye, Zuo-Guang

2012-02-01

140

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

141

Relaxor fluorinated polymers: novel applications and recent developments  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

142

Electrical switching behavior from all-polymer-based system of semiconductor/ferroelectrics/semiconductor  

NASA Astrophysics Data System (ADS)

Ferroelectricity is attractive in data storage application as the polarizations can be used as binary levels. However, conductivity and ferroelectricity cannot be tuned independently in inorganic materials, thus two-terminal resistive memories with ferroelectrics are yet to be achieved. Here, we present an all-polymer-based system of semiconductor/ferroelectrics/semiconductor. Electrical switching behavior, which is critical to resistive memories, is observed. The mechanism of the conduction transition is attributed to the transmission probability of charge carriers tuned by electrical polarization. The importance of polarization in controlling the charge transport deserves further investigation for the realization and optimization of the two-terminal resistive memories with ferroelectrics.

Li, Yun; Liu, Chuan; Pan, Lijia; Pu, Lin; Sirringhaus, Henning; Shi, Yi

2011-04-01

143

Polar Nanoregions and Relaxors: How Nanoscale Disorder Leads to Enormous Electromechanical Response (438th Brookhaven Lecture)  

SciTech Connect

Relaxors is the name given to a special class of materials called relaxor ferroelectrics. Xu will describe a series of experiments done by BNL researchers with collaborators from Stony Brook University, Johns Hopkins University, and the National Institute of Standards and Technology, to discover why relaxors have such an exceptional electromechanical response. The explanation is dependent on "polar nanoregions" -- tiny, nanometer-scale regions within the relaxors. The team established a link between polar nanoregions and the relaxors' ability to deform in response to an electric field, or to have a pulse of electric current induced by a deforming physical force. This understanding promises to lead to more improvements to relaxor materials for an even greater variety of applications.

Xu, Guangyong (Condensed Matter Physics and Materials Science Dept)

2008-07-16

144

Relaxor-based solid solutions for piezoelectric and electrostrictive applications  

Microsoft Academic Search

This thesis explores the dielectric, piezoelectric, and electrostrictive properties of a number of relaxor ferroelectric-based solid solution systems. The components of these solid solution systems have a variety of characteristics ranging from normal- to relaxor- to anti-ferroelectric. Some of the relaxor end-members investigated were Pb(In1\\/2Nb1\\/2)O3 [PIN], Pb(In1\\/2Ta1\\/2)O3 [PIT], Pb(Sc 1\\/2Nb1\\/2)O3 [PSN], Pb(Ni1\\/3Nb 2\\/3)O3 [PNN], Pb(Mg1\\/3Nb2\\/3)O 3 [PMN], and Pb(Zn1\\/3Nb2\\/3)O3 [PZN].

Edward F. Alberta

2003-01-01

145

The structural origin of the antiferroelectric properties and relaxor behavior of Na0.5Bi0.5TiO3  

NASA Astrophysics Data System (ADS)

This work presents a study of Na0.5Bi0.5TiO3 (NBT) by transmission electron microscopy in the 20-370 °C temperature range. A new orthorhombic intermediate phase between the rhombohedral and the tetragonal phases is proposed to account for the occurrence of 12(oee) superstructure spots. The phase transition from the rhombohedral to the orthorhombic phase occurs via a modulated phase formed by rhombohedral blocks and orthorhombic sheets. It is shown that these latter represent rhombohedral (0 1 0) twin planes. The modulated phase is proposed to explain the antiferroelectric and relaxor behaviors of NBT.

Dorcet, V.; Trolliard, G.; Boullay, P.

2009-06-01

146

Polymer Alignment Behavior with Molecular Switching of Ferroelectric Liquid Crystal  

NASA Astrophysics Data System (ADS)

This paper describes the molecular alignment behavior of polymer networks with switching of a ferroelectric liquid crystal (FLC) in a molecularly aligned FLC/polymer composite film. The polymer alignment in the composite film, which was slowly formed by photopolymerization-induced phase separation of a heated nematic-phase solution of FLC and monomers, was observed by polarization Raman spectral microscopy. Raman peak intensities originating from the polymers were changed with those from the FLC, when the applied voltage polarity was changed. The trace patterns of the Raman peak intensity with in-plane rotation of the composite film indicated that the formed flexible polymers can follow FLC molecular switching.

Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

2007-01-01

147

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

2011-08-30

148

Crystallization Behaviors of Ferroelectric and Piezoelectric Materials  

NASA Astrophysics Data System (ADS)

Crystallization represents a kind of phase transition, which can be regarded as a process related to bond formation and breaking. According to the chemical bonding characteristics of constituent atoms, the ideal morphology of LiNbO3 crystals has been successfully predicted by using the chemical bonding theory, which consists well with our experimental results. Some observations concerning the morphology evolution of KH2PO4 (KDP), NH4H2PO4 (ADP) and ZnO crystals can also be kinetically simulated by the present theory. The obtained results indicate that the microscopic constituent chemical bonds can help us to comprehensively understand the crystallization mechanism on the basis of quantitative calculations of growth rate in different crystal faces. The chemical bonding theory builds up a link between the crystallographic structure, growth morphology and microscopic chemical bonds of crystal materials, which provides us a useful microscopic tool to quantitatively understand single crystal growth behaviors.

Zhao, Xu; Sun, Congting; Si, Yunfei; Liu, Meinan; Xue, Dongfeng

149

Rescaled temperature dependence of dielectric behavior of ferroelectric polymer composites  

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

150

Electro-optic measurements of the ferroelectric-paraelectric boundary in Ba{sub 1-x}Sr{sub x}TiO{sub 3} materials chips  

SciTech Connect

The combinatorial material chip strategy is used to study the ferroelectric-paraelectric phase boundary of the Ba{sub 1-x}Sr{sub x}TiO{sub 3} thin film system. The electro-optic (EO) effect at different compositions is measured using a modified direct-current/alternating-current birefringence EO measurement technique. We find that Ba{sub 1-x}Sr{sub x}TiO{sub 3} thin films exhibit relaxor like behavior with diffused ferroelectric domains existing well past the previously defined ferroelectric-paraelectric boundary (x>0.3). (c) 2000 American Institute of Physics.

Li, Jingwei [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Duewer, Fred [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Gao, Chen [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Chang, Hauyee [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Xiang, X.-D. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Lu, Yalin [NZ Applied Technologies, Corp., Woburn, Massachusetts 01801 (United States)

2000-02-07

151

Abnormal dynamic behavior in a ferroelectric bilayer film  

NASA Astrophysics Data System (ADS)

Based on the Landau–Khalatnikov equation of motion, the switching dynamic behavior (including switching time, hysteresis loop and remanent polarization) of a ferroelectric bilayer film with surface transition layer within each constituent thin film and an interfacial coupling between two thin films has been first studied. The results show that the serious lag phenomenon of the hysteresis loop of the bilayer film occurs due to the strong strength of the interfacial coupling. It is interesting to note that there is a critical point, which is an equilibrium point of two contrary actions of the surface transition layer and interfacial coupling. The abnormal behavior of the switching time and remanent polarization in the bilayer film is attributed to the competition of the surface transition layer and interfacial coupling.

Cui, Lian; Han, Zhiyou; Xu, Quan; Gao, Yukai; Li, Ruiying; Ren, Yandong; Lü, Tianquan

2013-10-01

152

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

NASA Astrophysics Data System (ADS)

Besides characteristic dielectric relaxations, relaxor ferroelectrics have also been shown to exhibit strong resonances. These resonances are related to the ubiquitous presence of polar nanodomains in relaxors in their ``paraelectric'' phase below a certain temperature T*. In the relaxor K1-xLixTaO3 (KLT), the dielectric spectrum reveals pairs of coupled resonances with a Fano-type line shape that evolves dramatically with temperature. At higher temperature, the line shape reflects the close interplay between relaxations and resonances. Near the phase transition, it reveals the existence of coherent heterophase fluctuations. KLT provides a good example of the multiscale dynamics (from nano to macro) that is intrinsic to relaxors.

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

2013-03-01

153

Micromechanical theory of the nonlinear behavior of ferroelectric ceramics  

NASA Astrophysics Data System (ADS)

Ferroelectric and ferroelastic switching cause ferroelectric ceramics to depolarize and deform when subjected to excessive electric field or stress. Switching is the source of the classic butterfly shaped strain vs. electric field hysteresis loops and the corresponding electric displacement vs. electric field loops. It is also the source of a stress-strain curve with linear elastic behavior at low stress, non-linear switching strain at intermediate stress, and linear elastic behavior at high stress. In this work, a series of experiments on lead lanthanum zirconate titanate are modeled with a computer simulation of the ceramic microstructure. The polarization and strain for an individual grain are predicted from the imposed electric field and stress through a Preisach hysteresis model. The response of the bulk ceramic to applied loads is predicted by averaging the response of individual grains that are considered to be statistically random in orientation. The random orientation yields essential non-linear behavior of the observed strain and electric displacement hysteresis loops and the non-linear stress- strain curve for the polycrystalline ceramic. The linear piezoelectric effect opens up a butterfly shape to the strain vs. electric field hysteresis loop but the model fails to predict the observed effect of 90 degree(s) switching. The grain to grain residual stress and residual polarization are estimated from inclusion calculations. These are both a function of the remanent strain and remanent polarization of the ceramic. This constraint opposed switching but has little effect on the butterfly shape in the strain vs. electric field hysteresis loop.

Lynch, Christopher S.; Hwang, Stephen C.; McMeeking, Robert M.

1995-02-01

154

Effect of Hydrostatic Pressure on the Dielectric Behavior of Polymer Relaxors  

Microsoft Academic Search

Dielectric response of P(VDF\\/TrFE)(50\\/50) copolymer irradiated with 1 MeV electrons was studied under hydrostatic pressure. Pressure results in a nonlinear shift of the dielectric anomaly towards higher temperatures with the initial slope of the temperature of maximum losses dTm\\/dp = 142 K\\/GPa. The contribution of polar clusters to the pressure behavior of the dielectric response is discussed.

B. HILCZER; E. MARKIEWICZ; C Z. PAWLACZYK; M. SZAFRA?SKI; A. HILCZER

2004-01-01

155

Mesoscale Domains and Nature of the Relaxor State by Piezoresponse Force Microscopy  

NASA Astrophysics Data System (ADS)

Ferroelectric relaxors continue to be one of the most mysterious solid-state materials. Since their discovery by Smolenskii and coworkers, there have been many attempts to understand the properties of these materials, which are exotic, yet useful for applications. On the basis of the numerous experimental data, several theories have been established, but none of them can explain all the properties of relaxors. The recent advent of piezoresponse force microscopy (PFM) has allowed for polarization mapping on the surface of relaxors with subnanometer resolution. This development thus leads to the question of whether the polar nanoregions that contribute to diffuse X-ray scattering and a range of macroscopic properties can be visualized. This review summarizes recent advancements in the application of PFM to a number of ferroelectric relaxors and provides a tentative explanation of the peculiar polarization distributions related to the intriguing physical phenomena in these materials.

Shvartsman, V. V.; Dkhil, B.; Kholkin, A. L.

2013-07-01

156

Influence of silver migration on dielectric properties and reliability of relaxor based MLCCs  

Microsoft Academic Search

In order to study the micro-mechanism of silver migration which influences the reliability of relaxor based multilayer ceramic capacitors (MLCCs), micro-silver-doped PMN-PZN based relaxor ferroelectric ceramics were investigated for their microstructural and dielectric properties. SEM observations showed that the microstructure near the interface of MLCCs was greatly changed by the action of the inner silver\\/palladium electrode. The results indicate that

Ruzhong Zuo; Longtu Li; Zhilun Gui

2000-01-01

157

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

SciTech Connect

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

Maier, B. J.; Welsch, A.-M.; Mihailova, B.; Paulmann, C.; Bismayer, U. [Department Geowissenschaften, Universitaet Hamburg, Grindelallee 48, D-20146 Hamburg (Germany); Angel, R. J.; Zhao, J. [Virginia Tech Crystallography Laboratory, Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24060 (United States); Engel, J. M. [Institut fuer Werkstoffwissenschaften, Technische Universitaet Dresden, Helmholtzstr. 7, D-01069 Dresden (Germany); Schmitt, L. A. [Materials Science Structure Research, Universitaet Darmstadt, Petersenstr. 23, D-64287 Darmstadt (Germany); Gospodinov, M. [Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chausse 72, 1784 Sofia (Bulgaria); Friedrich, A. [Institut fuer Geowissenschaften, Goethe-Universitaet, Altenhoeferallee 1, D-60438 Frankfurt am Main (Germany)

2010-05-01

158

Incipient ferroelectrics: Anomalous T1 behaviors and their rotor interpretation  

NASA Astrophysics Data System (ADS)

The quantum temperature (denoted by T1) behaviors of three typical incipient ferroelectrics, SrTiO3, KTaO3 and CaTiO3, are studied. This quantity is argued to serve fundamentally in identifying the nature of the local mode responsible for the dielectric responses. Our main findings are as follows. For all compounds, T1 saturates at low temperatures. For CaTiO3, T1 monotonically increases with temperature and no clear saturation is discernible at high temperatures. For KTaO3, similar behaviors are observed but with a little twist: a dip shows up around 35 K, above which T1 increases but below it T1 decreases with temperature. Although it is hardly seeable in this compound, this dip might mark a transition, whose nature is unclear for the moment. In parallel with KTiO3, SrTiO3 also has a dip, which is much stronger and broader. It happens around 105 K, at which the famous anti-ferrodistortive (AFD) transition occurs. Were it not for this dip, T1 would drop to zero in SrTiO3 at low temperatures and the ferroelectric (FE) transition would take place. The dip halts the drop and makes T1 rise up to a value that is enough to stabilize the FE instability. In this respect, the dip is essential in preventing the FE transition in SrTiO3. Since the dip and the AFD transition occur at roughly the same temperature, we attempt to ascribe the former to the latter. This ascription is compatible with previous work [A. Yamanaka, M. Kataoka, Y. Inaba, K. Inoue, B. Hehlen, E. Courtens, Europhys. Lett., 50:(2000) 688]. To interpret the T1 behaviors, we utilize an anisotropic rotor model, according to which the local variable is supposed to move on a non-uniform sphere. By tuning the anisotropy parameter, ?, qualitative agreement can be achieved. Especially, a single ??100 can fit the T1 of CaTiO3 over the entire temperature range under consideration, whereas the fitting for KTaO3 requires two different ?, namely, ??260 above the dip temperature and ??40 below it. Analogously, two ? are also required for SrTiO3. Below the dip temperature, a very good fitting can be obtained with ??40. We did not try to fit the high temperature data of SrTiO3, because the data in this range are scarce and inaccurate. Nevertheless, we believe that a different and bigger ? should be at work, considering the case with KTaO3. Assuming the AFD transition as the cause of the dip in SrTiO3, we may claim that, the true role of the AFD transition in stabilizing the FE instability is to reduce the ? and then enhance quantum fluctuations. The quantum temperature (T1) behaviors of three incipient ferroelectrics are investigated. A broad dip is found around 105 K in T1 with strontium titanate (ST). This dip is argued to be subsequent to the anti-ferrodistortive transition in ST.An anisotropic rotor model is forwarded to explain such dip phenomena. This model also applies to other two compounds and comparison with experiments is made.

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

2012-01-01

159

Ferroelectric behavior in vinylidene fluoride-tetrafluoroethylene copolymers  

Microsoft Academic Search

Ferroelectric properties have been studied for copolymers of vinylidene fluoride (VDF) and tetrafluoroethylene (TeFE) with different TeFE content of 17 to 30 mol%. The Curie transition in the copolymers was considerably influenced by annealing as well as poling in preparation of specimens. The polarization reversal and the ferroelectric hysteresis were observed using 10 mHz high voltage triangular wave. A large

Y. Murata; N. Koizumi

1989-01-01

160

Synthesis and Dielectric Study of NBT- BSN: a Lead Free Relaxor Materials  

NASA Astrophysics Data System (ADS)

Solid solutions of (1-x)(Na0.5 Bi0.5TiO3)--x(BaSnO3) (x = 0, 0.15, 0.20, 0.25) are successfully synthesized using conventional solid state reaction route. Formation of solid solutions is confirmed by x-ray diffraction technique. NBT stabilizes in hexagonal structural form whereas the other end member of solid solution BSN stabilizes in cubic structure. Lattice parameters (a, b) and the unit cell volume increase, whereas c-parameter decreases with increasing BSN composition. The temperature dependent dielectric constant and dc conductivity also show anomalies at phase transition and show ferroelectric relaxor behavior. Modified Curie-Weiss law is used to fit the dielectric data that exhibits almost complete diffusion phase transition characteristics.

Kumar, Nitin; Singh, K. N.; Bajpai, P. K.

2011-11-01

161

Piezoelectric properties of sol-gel-derived ferroelectric and antiferroelectric thin layers  

SciTech Connect

The piezoelectric properties of ferroelectric and antiferroelectric thin layers were investigated by interferometry as a function of frequency and dc electric bias. Materials included: a ferroelectric lead zirconate titanate (PZT) with a Zr/Ti ratio of 53/47; a relaxor ferroelectric La-modified PZT with a Zr/Ti ratio of 70/30 and a La content of 7.8 at. %; and antiferroelectric lead zirconate. The hysteretic behavior of the piezoelectric coefficient due to polarization reversal was also studied. The layers were prepared by a sol-gel method, and were found to have properties similar to bulk ceramics. Significant strain levels could be achieved in the materials due to the relatively high electric strengths supported in thin-layer form. Polarization was found to be completely switchable between forward and reverse directions; however, the strain levels generated by switching were found to be inequivalent. In addition, pronounced piezoelectric relaxations and strong piezoelectric losses were observed.

Li, J.; Viehland, D.D.; Tani, T.; Lakeman, C.D.E.; Payne, D.A. (Department of Materials Science and Engineering, Materials Research Laboratory and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States))

1994-01-01

162

Dielectric maximum temperature non-monotonic behavior in unaxial Sr0.75Ba0.25Nb2O6 relaxor seen via acoustic emission  

NASA Astrophysics Data System (ADS)

[100] oriented Sr0.75Ba0.25Nb2O6 relaxor crystals have been studied by means of acoustic emission (AE) over a wide 20-400 °C temperature range. Both the Burns temperature, Td = 350 °C, and the intermediate temperature, T* = 183°C, and the susceptibility maximum temperature, Tm (59 °C on heating and 47 °C on cooling), have been successfully detected. Dependent upon the external electric field, the Tm exhibits a local minimum near 0.25 kV/cm accompanied by pronounced AE maximum in a manner which had recently been detected in Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 by Dul'kin et al. [Appl. Phys. Lett. 94, 252904 (2009)] and in Pb(Sc1/2Ta1/2)O3 by Dul'kin et al. [Phys. Rev. B 82, 180101(R) (2010)], whereas the T* increases monotonically, similar to that which had recently been revealed in BaTiO3 by Dul'kin et al. [Appl. Phys. Lett. 97, 032903 (2010)] with a rate of 7.5 K cm/kV. An observed Tm behavior is discussed from the point of view of the existence of the random electric field components along the [100] direction in Sr0.75Ba0.25Nb2O6 crystals.

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

2011-08-01

163

Ferroelectric Tunnel Junctions: Resistive Switching Behavior by Scanning Probe Microscopy  

Microsoft Academic Search

In this work, we demonstrate the reproducible tunneling electroresistance effect in ultrathin epitaxial ferroelectric heterostructures by means of scanning probe microscopy techniques. Ultrathin films of barium titanate (in the range from 2 nm to 10 nm) with microscopically patterned SrRuO3 top electrodes have been grown on the SrRuO3\\/SrTiO3 substrates by atomic-layer-controlled pulsed-laser deposition. Imaging and control of polarization state in

A. Stamm; H. Lu; D. Wu; Y. Wang; D. Felker; M. Rzchowski; H. W. Jang; C. W. Bark; C.-B. Eom; E. Y. Tsymbal; A. Gruverman

2010-01-01

164

Effect of Annealing on the Ferroelectric Behavior of Nylon 7 and Nylon 11.  

National Technical Information Service (NTIS)

We have recently discovered that melt quenched and cold- drawn nylon 11 films exhibit very clear ferroelectric hysteresis behavior. In the present study, a remanent polarization as high as 86 mC/m2 has been found in nylon 7 samples; this is significantly ...

B. A. Newman J. I. Scheinbeim J. W. Lee Y. Takase

1991-01-01

165

Effects of surface tension and axis stress on piezoelectric behaviors of ferroelectric nanowires  

Microsoft Academic Search

The effects of surface tension and axis stress on piezoelectric behaviors of ferroelectric nanowires with radius polarization were investigated by the time-dependent Ginzburg-Landau theory. When surface tension increases, both of coercive field and remnant strain decrease. The larger the surface tension is, the more they decrease. The axis compressive stress enhances the coercive field and remnant strain, while the axis

Y. Q. Chen; Y. F. En; Y. Huang; X. D. Kong; X. J. Zheng; Y. D. Lu

2011-01-01

166

From incipient ferroelectricity in CaTiO3 to real ferroelectricity in Ca1-xPbxTiO3 solid solutions  

Microsoft Academic Search

Dielectric spectra of ceramic samples of Ca1-xPbxTiO3 (0less-than-or-equal]x[less-than-or-equal0.4) solid solutions were studied at frequencies between 10 Hz and 1 MHz in a temperature range of 4.2-300 K. A ferroelectric phase transition was observed at x=0.3 with transformation to a relaxor type behavior at x>0.3. The transition temperature Tc follows a linear dependence Tc[is proportional to](x-xc) with xc=0.28 contrary to a

V. V. Lemanov; A. V. Sotnikov; E. P. Smirnova; M. Weihnacht

2002-01-01

167

Dielectric relaxation and conductivity behavior in modified lead titanate ferroelectric ceramics  

NASA Astrophysics Data System (ADS)

The frequency and temperature dielectric response and the electrical conductivity behavior around the ferroelectric-paraelectric phase transition temperature are studied in the ferroelectric ceramic system (Pb0.88Sm0.08)(Ti1-xMnx)O3, with x = 0,1,3 at.%. The contribution of the conductive processes to the dielectric relaxation for the studied frequency range is discussed considering the oxygen vacancies as the most mobile ionic defects in perovskites, whose concentration seems to increase with the manganese content. The relaxation processes below the transition temperature are associated with the decay of the polarization in the oxygen-defect-related dipoles due to their hopping conduction. Above the ferroelectric-paraelectric phase transition temperature, the electrical conduction is governed by the thermal excitation of carriers from oxygen vacancies; the relaxation processes are associated with ionic dipoles distorted by the oxygen vacancies.

Peláiz-Barranco, A.; González Abreu, Y.; López-Noda, R.

2008-12-01

168

A phase-field study on the hysteresis behaviors and domain patterns of nanocrystalline ferroelectric polycrystals  

NASA Astrophysics Data System (ADS)

The overall hysteresis behavior of nanocrystalline ferroelectric polycrystals demonstrates unique characteristics against conventional ferroelectric ceramics. The existence of low-permittivity paraelectric grain boundary and its influence to the microstructure of grains can be a key factor leading to such characteristics, especially the grain size-dependent properties. A two dimensional (2D) polycrystalline phase-field model, which distinguishes the grain boundary from the ferroelectric grain, has been developed to investigate the microstructural evolution and hysteresis behavior of nanocrystalline barium titanate (BaTiO3) polycrystals. The results show apparent grain-size dependence on the hysteresis and noticeable vortex polarization structure that dominates the grains as the grain size reduces to tens of nanometers. By studying the hysteresis and domain patterns, it is observed that the grain size-dependent properties are significantly attributed to the grain boundary in two ways: the ``dilution effect'' due to its low permittivity and paraelectric property that are intensified with increased volume concentration, and the extrinsic effect due to the existence of depolarization field, leading to the superparaelectric domain structure. We conclude that this grain-size dependent microstructural mechanism can well explain various experimentally observed properties of nano-grained ferroelectric polycrystals.

Liu, Ning; Su, Yu; Weng, George J.

2013-05-01

169

Ferroelectric Tunnel Junctions: Resistive Switching Behavior by Scanning Probe Microscopy  

NASA Astrophysics Data System (ADS)

In this work, we demonstrate the reproducible tunneling electroresistance effect in ultrathin epitaxial ferroelectric heterostructures by means of scanning probe microscopy techniques. Ultrathin films of barium titanate (in the range from 2 nm to 10 nm) with microscopically patterned SrRuO3 top electrodes have been grown on the SrRuO3/SrTiO3 substrates by atomic-layer-controlled pulsed-laser deposition. Imaging and control of polarization state in SrRuO3/BaTiO3/SrRuO3 and BaTiO3/SrRuO3 heterostructures have been performed via Piezoresponse Force Microscopy (PFM) along with conductance measurements by Conducting Atomic Force Microscopy (C-AFM). The selected locations have been probed by performing the local I-V measurements using a fixed tip. In parallel, at the same locations local PFM hysteresis loops have been measured. The obtained results show a change in resistance by about two orders of magnitude upon polarization reversal on a lateral scale of 20 nm at room temperature. These results are promising for employing ferroelectric tunnel junctions in non-volatile memory and logic devices.

Stamm, A.; Lu, H.; Wu, D.; Wang, Y.; Felker, D.; Rzchowski, M.; Jang, H. W.; Bark, C. W.; Eom, C.-B.; Tsymbal, E. Y.; Gruverman, A.

2010-03-01

170

Fabrication and characterization of relaxor-ferroelectric 0.55Pb(Ni1/3Nb2/3)O3-0.45Pb(Zr0.3Ti0.7)O3 ceramics with sintering aid  

NASA Astrophysics Data System (ADS)

A traditional solid-state sintering method was used to fabricate 0.55Pb(Ni1/3Nb2/3)O3-0.45Pb(Zr0.3Ti0.7)O3 (0.55PNN-0.45PZT) relaxor-ferroelectric ceramics with CuO as sintering aid. The influence of xCuO additions (x=0.0, 0.2, 0.4, 0.6, 0.8 wt.%) on the microstructure and electrical properties of the 0.55PNN-0.45PZT ceramics was investigated. X-ray diffraction patterns demonstrated that all specimens formed a typical perovskite structure with pseudo-cubic phase. Cu2+ ions entered into the B sites in ABO3 structure for the PNN-PZT solid solution ceramics. The additions of CuO improved the sinterability of the 0.55PNN-0.45PZT ceramics. The grain size and density of these specimens increased slightly with increasing amounts of CuO addition. The specimen with 0.4 wt.% CuO addition achieves the maximum value of density ?~8108 kg/m3. Meanwhile, the piezoelectric, dielectric and ferroelectric properties also enhanced significantly with increasing amount of CuO addition. Excellent properties, d33~777 pC/N, kp~55%, ?1 r~7365, tan?~2.9%, pr~18.86 ?C/cm2, and Ec~3.52 kV/cm were obtained for the 0.55PNN-0.45PZT ceramics with 0.4 wt.% CuO addition sintered at 1125°C for 2 h.

Du, Jianzhou; Qiu, Jinhao; Zhu, Kongjun; Ji, Hongli; Chen, Yuansheng

2011-11-01

171

Temperature-dependent Raman scattering and multiple phase coexistence in relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals  

NASA Astrophysics Data System (ADS)

We report direct observation for the structural transformations of relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals with the aid of temperature-dependent polarized Raman scattering and X-ray diffraction. The cubic to tetragonal phase transition is observed at 460 K and tetragonal to rhombohedral structural transformation takes place at 390 K, which are consistent with the results determined by dielectric spectroscopy. In addition to two well-known phase transitions above room temperature, anomalous structure deformations involving octahedral rotations and tilting angle of polarization can be found around 200 K. A comparison of experimental results with the Devonshire expansion of the free energy by Vanderbilt et al. [Phys. Rev. B 63, 094108 (2001)] allows us to elucidate the peculiar characteristic as the variation of volume fractions among coexistence of three phases, including a first-order phase transition between the orthorhombic and rhombohedral phases and a second-order phase transition between the monoclinic and orthorhombic ones at low temperature.

Zhu, J. J.; Jiang, K.; Xu, G. S.; Hu, Z. G.; Li, Y. W.; Zhu, Z. Q.; Chu, J. H.

2013-10-01

172

Phase diagram and ferroelectric behaviors of BaTiO3 nanowires  

NASA Astrophysics Data System (ADS)

A modified Landau-Ginzburg-Devonshire theory is developed to investigate the ``diameter-temperature'' phase diagram and the ferroelectric behaviors of BaTiO3 nanowires. Four phases, such as the Cubic phase, the Tetragonallike phase, the Orthorhombic phase, and the Monoclinic phase, are obtained. The ferroelectric phase transition temperatures are all depressed as the diameter decreases. A temperature-dependent critical diameter below which the polarization disappears is 0.8 nm at 0 K. Moreover, the magnitude and the direction of the polarization are strongly dependent on the diameter as well as the dielectric behaviors. Therefore, it can generate a specific direction of the polarization by controlling the diameter of the nanowires which may optimize the physical properties.

Qiu, J. H.; Ding, J. N.; Yuan, N. Y.; Cao, H. X.; Wang, X. Q.; Zhou, Y.

2011-03-01

173

Incipient piezoelectrics and electrostriction behavior in Sn-doped Bi1/2(Na0.82K0.18)1/2TiO3 lead-free ceramics  

NASA Astrophysics Data System (ADS)

Dielectric, ferroelectric, piezoelectric, and strain properties of lead-free Sn-doped Bi1/2(Na0.82K0.18)1/2TiO3 (BNKT) were investigated. A crossover from a nonergodic relaxor to an ergodic relaxor state at room temperature, accompanied by a giant electric-field-induced strain, was observed at 5 at. % Sn doping. Switching dynamics monitored during a bipolar poling cycle manifested that the observed giant strain originates from incipient piezoelectricity. When Sn doping level reached 8 at. %, BNKT exhibited an electrostrictive behavior with a highly temperature-insensitive electrostrictive coefficient of Q11 = 0.023 m4 C-2.

Han, Hyoung-Su; Jo, Wook; Kang, Jin-Kyu; Ahn, Chang-Won; Won Kim, Ill; Ahn, Kyoung-Kwan; Lee, Jae-Shin

2013-04-01

174

High-temperature ferroelectric behaviors of poly(vinylidene fluoride-trifluoroethylene) copolymer ultrathin films with electroactive interlayers  

NASA Astrophysics Data System (ADS)

The high-temperature ferroelectric behaviors for poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer ultrathin films with electroactive interlayers have been studied. The different electroactive polymers, commercial poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonic) acid (PEDOT-PSSH), in situ synthesized PEDOT-PSSH with high PEDOT ratio and poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonic) ammonia (PEDOT-PSSNH4), are used as the interlayer between P(VDF-TrFE) and metal electrodes. It is found that the ferroelectric properties at high temperature are strongly dependent on the interlayer and the faster degradation occurs on the sample with the interlayer which has enough protons as compensating charges. Further analysis on the polarization response behaviors and capacitance shows that the high-temperature ferroelectric properties are more closely associated with the compensating charges in interlayer than the ferroelectric film itself, illustrating the importance of the appropriate interlayer materials.

Hou, Ying; Zhang, Xiuli; Zhang, Yuan; Xu, Guoqiang; Xu, Haisheng

2012-03-01

175

The pyroelectric behavior of lead free ferroelectric ceramics in thermally stimulated depolarization current measurements  

NASA Astrophysics Data System (ADS)

The present paper shows a detailed analysis on the thermally stimulated processes in barium modified SrBi2Nb2O9 ferroelectric bi-layered perovskite, which is one of the most promising candidates for non-volatile random access memory applications because of its excellent fatigue-resistant properties. A numerical method is used to separate the real pyroelectric current from the other thermally stimulated processes. A discharge due to the space-charge injected during the poling process, the pyroelectric response, and a conductive process are discussed in a wide temperature range from ferroelectric to paraelectric phase. The pyroelectric response is separated from the other components to evaluate the polarization behavior and some pyroelectric parameters. The remanent polarization, the pyroelectric coefficient, and the merit figure are evaluated, which show good results.

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

2012-06-01

176

Phase diagram of polar states in doped ferroelectric systems  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2001-05-01

178

Structure and Relaxor Behaviour of Ba2+ Substituted NBT Ceramics  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

179

LETTER TO THE EDITOR: Structural, optical and dielectric properties of relaxor-ferroelectric Pb0.78Ba0.22Sc0.5Ta0.5O3  

NASA Astrophysics Data System (ADS)

We report on the synthesis of a new relaxor compound with chemical formula Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST). Single crystals were obtained by the high-temperature solution growth method. The structure of the new compound is of double-perovskite type with face-centred cubic symmetry at room temperature. The frequency dependence of the dielectric constant of PBST shows a strong dielectric dispersion in a wide temperature range and a dielectric-constant maximum near 200 K at 10 kHz. The local atomic environment was probed by Raman scattering and optical absorption spectroscopy. The results show that the incorporation of Ba deforms the BO6 octahedra adjoining the BaO12-polyhedra along the \\langle 111\\rangle direction and shortens the Pb-O bond lengths next to the BaO12-polyhedra within the {111} planes. The random substitution of Ba for Pb leads to a wider distribution in the size and shape of the ferroic species in PBST compared to stoichiometric PbSc0.5Ta0.5O3. The addition of Ba shifts the optical absorption edge to lower energies and gives rise to extra absorption peaks at 460 and 730 nm. The latter peak is related to polar atomic rearrangements in the vicinity of the Ba ions embedded into the PbSc0.5Ta0.5O3 matrix.

Marinova, V.; Mihailova, B.; Malcherek, T.; Paulmann, C.; Lengyel, K.; Kovacs, L.; Veleva, M.; Gospodinov, M.; Güttler, B.; Stosch, R.; Bismayer, U.

2006-08-01

180

Elastic responses to different electric-field directions in relaxor ferroelectric Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 single crystals  

NASA Astrophysics Data System (ADS)

Micro-Brillouin scattering was applied to relaxor-based complex perovskite Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZN-9% PT) single crystals during a polarization switching under two different electric-field directions along <111> and <101>. Brillouin spectra consisted of one longitudinal and two transverse acoustic modes, and the Brillouin shift and the full width at half maximum of these modes showed clear changes near the coercive field (Ec) where the polarization reversal occurred. In particular, the lowest transverse mode was the most sensitive to Ec. In the case of <111>-poled crystals the Brillouin spectrum exhibited an asymmetric shape in a narrow electric-field range near Ec due to a coupling between the lowest transverse mode and a central peak. In the case of <101>-poled crystals, the lowest transverse mode showed an abrupt softening at Ec and a slow recovery to the initial value upon further increasing the electric field. This may indicate the appearance of the monoclinic symmetry where the polarization can rotate freely toward the orthorhombic phase in the MB plane under the electric field along the <101> direction. The observation of no changes in the Brillouin spectra with decreasing the electric field seems to indicate that the PZN-9% PT crystal, poled under the field along <101>, does not become rhombohedral, but remains in the induced orthorhombic phase upon the removal of the field.

Ko, Jae-Hyeon; Kim, Do Han; Kojima, Seiji

2003-09-01

181

Origin of the ``Waterfall'' Effect in Phonon Dispersion of Relaxor Perovskites  

Microsoft Academic Search

We have undertaken an inelastic neutron scattering study of the perovskite relaxor ferroelectric Pb(Zn1\\/3Nb2\\/3)O3 with 8% PbTiO3 (PZN-8%PT) in order to elucidate the origin of the previously reported unusual kink on the low frequency transverse phonon dispersion curve (known as the ``waterfall effect''). We show that its position (qwf) depends on the choice of the Brillouin zone and that the

J. Hlinka; S. Kamba; J. Petzelt; J. Kulda; C. A. Randall; S. J. Zhang

2003-01-01

182

Improved ferroelectric behavior in (110) oriented BiFeO3 thin films  

NASA Astrophysics Data System (ADS)

Multiferroic BiFeO3 thin films were grown on LaNiO3-buffered Pt/TiO2/SiO2/Si substrates by off-axis radio frequency magnetic sputtering, where (110) oriented texture was obtained. The LaNiO3 buffer layer promoted the growth of BiFeO3 film, resulting in a dense texture and columnar growth of BiFeO3 thin films. The BiFeO3 thin film exhibits 2Pr~145.8 ?C/cm2 and 2Ec~573.5 kV/cm, together with a very low dielectric loss (0.80% at 10 kHz) and an almost fatigue-free behavior at 500 kHz up to 1010 switching cycles. The 2Pr value is comparable to the reported value of the BiFeO3 deposited on the SrTiO3(110) substrate. While a weak ferromagnetism is demonstrated for the multiferroic thin film at room temperature, the low leakage current and high (110) orientation contribute toward the improved ferroelectric behavior. The BFO thin film with a giant remanent polarization and a fatigue-free behavior promises a candidate material for high-temperature ferroelectric random access memory.

Wu, Jiagang; Wang, John

2010-02-01

183

The role of tetragonal side morphotropic phase boundary in modified relaxor-PbTiO3 crystals for high power transducer applications  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

184

Nanoscale studies of switching behavior of ferroelectric thin films by using piezoresponse force microscopy  

Microsoft Academic Search

The work presented in this dissertation is focused on the study of ferroelectric thin films using the method of Piezo-response Force Microscopy (PFM) with several modifications specific to ferroelectrics. In this research, the main motivation is the study of polarization-reversal mechanisms for different sizes of very small-scale (0.5-5 mum size) ferroelectric capacitors in possible applications to ferroelectric random-access-memory devices (FeRAM).

Dong Wu

2009-01-01

185

Thermal and Electric Field Hysteresis Effects in Structuraly Disordered Ferroelectric Materials  

Microsoft Academic Search

Thermal and electric field hysteresis effects near the ferroelectric transition were studied by a high resolution calorimetry and dielectric spectroscopy in several solid and soft disordered ferroelectrics such as perovskite relaxors and P(VDF-TrFE)-based ferroelectric polymers, respectively. Significant thermal hysteresis effects were observed in PMN-PT and SBN crystals as well as in P(VDF-TrFE) polymers reminiscent of the supercooling effect in glassy

Z. Kutnjak

2010-01-01

186

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

SciTech Connect

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

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

1998-03-10

187

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

188

KTa0.6Nb0.4O3 ferroelectric thin film behavior at microwave frequencies for tunable applications.  

PubMed

In this study about the relationships between structural and microwave electrical properties of KTa(1-x)NbxO3 (KTN) ferroelectric materials, a KTN thin film was deposited on different substrates to investigate how KTN growth affects the microwave behavior. Interdigital capacitors and stubs were made on these films through a simple engraving process. Microwave measurements under a static electric field showed the importance of the substrate on the circuit behavior and, notably, on the tuning factor. PMID:17186908

Laur, Vincent; Rousseau, Anthony; Tanné, Gérard; Laurent, Paul; Députier, Stéphanie; Guilloux-Viry, Maryline; Huret, Fabrice

2006-12-01

189

Influence of cycling electric polarization on multiferroic behaviors in heterostructural films composed of ferroelectric and ferromagnetic oxides  

NASA Astrophysics Data System (ADS)

The CoFe2O4/Pb(Zr0.52Ti0.48)O3 bilayer films were prepared by a sol-gel process, and the influence of cycling electric polarization on the multiferroic behaviors of the bilayer films was studied. The ferroelectric polarization hysteresis loops under various choices of magnetic bias were measured by an integrating current method. The results showed that after undergoing cycling electric polarization the ferroelectric polarization of the bilayer films enhanced and the suppression of ferroelectric polarization by external magnetic bias remarkably weakened. Based on the measurements of activation energy and leakage current, we confirmed that the oxygen vacancy migration in the bilayer films occurred during cycling electric polarization. Furthermore, we analyzed the mechanism of the influence of cycling electric polarization on the multiferroic behaviors of the bilayer films and attributed it to the oxygen vacancy migration, which could cause a part of ferroelectric domains to be unpinned from the oxygen vacancies and become more active under electric field and magnetic bias.

Li, Zi-Wei; Zhou, Ming-Xiu; Chen, Bo; Wan, Jian-Guo; Liu, Jun-Ming; Wang, Guang-Hou

2013-11-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

191

Device modeling of ferroelectric capacitors  

Microsoft Academic Search

A physically based methodology is developed for modeling the behavior of electrical circuits containing nonideal ferroelectric capacitors. The methodology is illustrated by modeling the discrete ferroelectric capacitor as a stacked dielectric structure, with switching ferroelectric and nonswitching dielectric layers. Electrical properties of a modified Sawyer–Tower circuit are predicted by the model. Distortions of hysteresis loops due to resistive losses as

S. L. Miller; R. D. Nasby; J. R. Schwank; M. S. Rodgers; P. V. Dressendorfer

1990-01-01

192

Device modeling of ferroelectric capacitors  

Microsoft Academic Search

A physically based methodology is developed for modeling the behavior of electrical circuits containing nonideal ferroelectric capacitors. The methodology is illustrated by modeling the discrete ferroelectric capacitor as a stacked dielectric structure, with switching ferroelectric and nonswitching dielectric layers. Electrical properties of a modified Sawyer--Tower circuit are predicted by the model. Distortions of hysteresis loops due to resistive losses as

S. L. Miller; R. D. Nasby; J. R. Schwank; M. S. Rodgers; P. V. Dressendorfer

1990-01-01

193

Enhanced flexoelectric effect in a non-ferroelectric composite  

NASA Astrophysics Data System (ADS)

Direct flexoelectric effect was investigated in a non-ferroelectric composite (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7/Ag (BZN/Ag) where the structure symmetry permits no macro-piezoelectricity. The flexoelectric coefficient of the BZN/Ag composite approaches 0.17 ?C/m at room temperature. This value is 3-4 orders of magnitude higher than those of common dielectrics. Our research confirms the existence of flexoelectric effect in insulated non-ferroelectric materials except for ferroelectric relaxors.

Li, Yong; Shu, Longlong; Zhou, Yongcun; Guo, Jing; Xiang, Feng; He, Li; Wang, Hong

2013-09-01

194

Acoustic Mode Behavior in Ferroelectric Phase Transition of Li Doped ZnO Semiconductor and its Photoinduced Effect  

Microsoft Academic Search

Acoustic phonon behavior and photoexcited effect in Li-doped ZnO ceramics were investigated at around the ferroelectric phase transition point Tc = 350 K by Brillouin scattering using a Sandercock-type tandem Fabry-Perot interferometer. The temperature dependence of Brillouin scattering spectra was obtained from 300 K to 500 K through Tc. A bunch of longitudinal-acoustic (LA) phonons did not show any anomaly

Daisuke Kagami; Masaki Takesada; Akira Onodera; Hiroyasu Satoh

2011-01-01

195

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

NASA Astrophysics Data System (ADS)

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

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

2000-03-01

196

Investigation into the dielectric behavior of ferroelectric superlattices formed by pulsed laser deposition  

Microsoft Academic Search

In an attempt to reproduce the functional properties associated with relaxor electroceramics, pulsed laser deposition has been used to fabricate thin-film capacitor structures in which the dielectric layer is composed of a superlattice of Ba0.8Sr0.2TiO3 and Ba0.2Sr0.8TiO3. The properties of the capacitors were investigated as a function of superlattice periodicity. The dielectric constant was enhanced at stacking periodicities of a

D. O'Neill; R. M. Bowman; J. M. Gregg

2000-01-01

197

Dielectric response of polymer relaxors  

Microsoft Academic Search

Dielectric response of vinylidene fluoride type ferroelectric polymers is dominated by that of segmental motions in the amorphous\\u000a phase in temperature range 200–300 K and contributions related to the local mode and ferroelectric-paraelectric transition\\u000a in the crystalline phase of the polymer at higher temperatures. Diffuse and frequency-dependent dielectric anomaly observed\\u000a in fast electron irradiated polyvinylidene fluoride-trifluoroethylene P(VDF\\/TrFE) has been related

Bo?ena Hilczer; Hilary Smogór; Janina Goslar

198

Dielectric response of polymer relaxors  

Microsoft Academic Search

Dielectric response of vinylidene fluoride type ferroelectric polymers is dominated by that of segmental motions in the amorphous\\u000a phase in temperature range 200–300 K and contributions related to the local mode and ferroelectric–paraelectric transition\\u000a in the crystalline phase of the polymer at higher temperatures. Diffuse and frequency-dependent dielectric anomaly observed\\u000a in fast electron irradiated polyvinylidene fluoride-trifluoroethylene P(VDF\\/TrFE) has been related to

Bozena Hilczer; Hilary Smogór; Janina Goslar

2006-01-01

199

Pb(Mg 1\\/3 Nb 2\\/3 )O 3 and (1 ? x )Pb(Mg 1\\/3 Nb 2\\/3 )O 3 ? x PbTiO 3 Relaxor Ferroelectric Thick Films: Processing and Electrical Characterization  

Microsoft Academic Search

The lead magnesium niobate [Pb(Mg1\\/3Nb2\\/3)O3 or PMN], and its solid solutions with lead titanate (PbTiO3 or PT), are of great interest because of their high electromechanical properties. At large PMN content, these materials exhibit relaxor characteristics with large electrostrictive strains and a large permittivity, while compositions near the morphotropic phase boundary present very interesting piezoelectric properties. So far, properties of

S. Gentil; D. Damjanovic; N. Setter

2004-01-01

200

Coupled short-range ferroelectric and magnetic order in PbFe1/2Nb1/2O3  

NASA Astrophysics Data System (ADS)

A neutron scattering investigation of the magnetoelectric coupling in PbFe1/2Nb1/2O3 has been undertaken. Ferroelectric order occurs below 400 K, as evidenced by the softening with temperature and subsequent recovery of the zone center transverse optic phonon mode energy (??0). Over the same temperature range, magnetic correlations become resolution limited on a terahertz energy scale. In contrast to the behavior of nonmagnetic disordered ferroelectrics [namely Pb(Mg,Zn)1/3Nb2/3O3], we report the observation of a strong deviation from linearity in the temperature dependence of (??0)2. This deviation is compensated by a corresponding change in the energy scale of the magnetic excitations, as probed through the first moment of the inelastic response. The coupling between the short-range ferroelectric and antiferromagnetic correlations is consistent with calculations showing that the ferroelectricity is driven by the displacement of the body-centered iron site, illustrating the multiferroic nature of magnetic-lead-based relaxors in the dynamical regime.

Stock, C.; Dunsiger, S. R.; Mole, R. A.; Li, X.; Luo, H.

2013-09-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

202

Photocathodic behavior of ferroelectric Pb(Zr,Ti)O(3) films decorated with silver nanoparticles.  

PubMed

ITO/Pb(Zr,Ti)O(3) contacts and Ag nanoparticles were used to construct a novel ferroelectric film photocathode exhibiting a stable short-circuit photocurrent of 110 ?A cm(-2) and an open-circuit voltage of 0.76 V under 100 mW cm(-2) Xe-lamp illumination and zero-bias versus SCE. PMID:23535610

Wang, Chunyan; Cao, Dawei; Zheng, Fengang; Dong, Wen; Fang, Liang; Su, Xiaodong; Shen, Mingrong

2013-03-28

203

Enhancement of dielectric and ferroelectric properties in ferroelectric superlattices  

Microsoft Academic Search

I studied theoretically the enhancement of remanent polarization and dielectric permittivity of interfacial-coupled ferroelectric superlattices based on the Landau–Ginzburg theory. Our model adopts the Landau–Khalatnikov equation to describe hysteresis behavior and takes the time-dependent space-charge-limited conductivity into account to investigate the ferroelectric and dielectric properties of ferroelectric superlattices. The results are in good agreement with recent experimental observations on the

Y. Zhou

2010-01-01

204

Compositional engineering of BaTiO3/(Ba,Sr)TiO3 ferroelectric superlattices  

NASA Astrophysics Data System (ADS)

Epitaxial strain is one of the major factors influencing physical properties of artificial superlattice (SL) structures. One way to control the local stress in epitaxial films is altering the lattice parameters by doping. Superlattices of BT/Ba(1-x)SrxTiO3 (BT/BST) with x = (0, 0.3, 0.4, 0.5, 0.6, 0.7, 1) with a modulation period of about 80-90 A? were grown on La0.67Sr0.33MnO3 coated (100) MgO substrates by pulsed laser deposition technique. The modulated structure of the thin films was confirmed by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The increase in Sr concentration in BST layers of the SLs results in an increase in in-plane (a) and out-plane (c) compressive/tensile misfit strains in the BT/BST layers, respectively. The highest value of the dielectric constant was obtained for BT/Ba0.3Sr0.7TiO3 (BT/BST3070) and BT/Ba0.7Sr0.3TiO3 (BT/BST7030) SLs. Slim, asymmetric, but well-saturated ferroelectric hysteresis loops were observed in all SLs. Additionally, BT/BST SLs exhibited exceptionally high electric field stress sustainability over a wide range of frequency (10 kHz) and temperature (80-350 K). Temperature-dependent dielectric and ferroelectric properties show a ferroelectric relaxor behavior when the Sr content is increased in the BST layer of the SLs. Analysis of polarization versus temperature data using Landau-Devonshire theory suggests a second-order ferroelectric phase transition in these SLs. This structure can therefore be attractive in the design of a new kind of dielectric device capable in both high power and high energy density applications.

Ortega, N.; Kumar, Ashok; Resto, Oscar; Maslova, O. A.; Yuzyuk, Yu. I.; Scott, J. F.; Katiyar, Ram S.

2013-09-01

205

Rayleigh type behavior of the Young's modulus of unpoled ferroelectric ceramics and its dependence on temperature  

NASA Astrophysics Data System (ADS)

The dependence on stress of the low frequency Young's modulus and mechanical losses of unpoled ferroelectric ceramics has been studied as a function of temperature. The Young's modulus of unpoled Pb(Zr,Ti)O3 (PZT) showed a Rayleigh type dependence, analogous to the one already described for the longitudinal piezoelectric coefficient. This has been associated to ferroelectric/ferroelastic domain wall movements across, and their pinning/depinning on, randomly distributed defects. The Rayleigh coefficient was found to increase with temperature. The activation energy of the Rayleigh process was obtained, which must be related to the pinning energy. The Young's modulus of Mn doped 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 showed no stress dependence.

Algueró, M.; Jiménez, B.; Pardo, L.

2003-09-01

206

Energy principle and nonlinear electric–mechanical behavior of ferroelectric ceramics  

Microsoft Academic Search

Summary  Many experimental observations have shown that a single domain in a ferroelectric material switches by progressive movement\\u000a of domain walls, driven by a combination of electric field and stress. The mechanism of the domain switch involves the following\\u000a steps: initially, the domain has a uniform spontaneous polarization; new domains with the reverse polarization direction nucleate,\\u000a mainly at the surface, and

F. Liu; H. J. Li; T. C. Wang

2008-01-01

207

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

Microsoft Academic Search

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

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

2005-01-01

208

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

Microsoft Academic Search

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 mum nominal radius. It was found that the

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

2005-01-01

209

Ferroelectric properties of vinylidene fluoride copolymers  

Microsoft Academic Search

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

Takeo Furukawa

1989-01-01

210

Non-Debye dielectric dispersion of barium titanate stannate in the relaxor and diffuse phase-transition state  

NASA Astrophysics Data System (ADS)

Frequency dependence Tm(f ) of the permittivity maximum temperature observed in BaTi1-xSnx03, x=0.2 (BTS20), confirms that this composition is close above threshold xc for relaxor behavior in BTS. The low-frequency permittivity carries a ln(1/f )-frequency dependence in the vicinity of Tm, both for x=0.2 and x=0.125relaxor state of BTS.

Mueller, V.; Beige, H.; Abicht, H.-P.

2004-02-01

211

Fabrication of lithium-doped zinc oxide film by anodic oxidation and its ferroelectric behavior  

SciTech Connect

A lithium-doped zinc oxide (ZnO) film was obtained by the anodic oxidation of a zinc sheet in a lithium hydroxide (LiOH) solution under an external DC voltage. The formation of the ZnO film on the surface of the Zn sheet is attributed to two simultaneous processes: the electrochemical oxidation of Zn to ZnO, and the chemical dissolution of ZnO. It was also confirmed that Li element was successfully introduced into the lattice of the ZnO film. The curves of the polarization versus applied field were measured to be hysteresis loops, suggesting ferroelectricity of the Li-doped ZnO film. The remanent polarization and the coercive field of the film were measured to be 4.7 x 10{sup -3} C m{sup -2} and 1.2 x 10{sup 7} V m{sup -1}, respectively. This ferroelectricity is believed to be the result of the occupation of off-centered positions in oxygen tetrahedra by the Li{sup +} ions.

Yu Ligang [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Zhang Gengmin [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China)], E-mail: zgmin@pku.edu.cn; Zhao Xingyu; Guo Dengzhu [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China)

2009-03-05

212

Characterization of local piezoelectric behavior of ferroelectric GeTe and Ge2Sb2Te5 thin films  

NASA Astrophysics Data System (ADS)

We studied the ferroelectric properties of GeTe and Ge2Sb2Te5 thin films through the analysis of capacitance-temperature, contact resonance piezoresponse force, resonance tracking piezoresponse force, and switching piezoresponse force microscopy measurements. These alloys are non-typical ferroelectric materials with low electrical resistivity, which makes their ferroelectric properties difficult to investigate by other conventional techniques. On the basis of measurement values of the Curie temperature, ferroelectric domain structure, piezoelectric coefficient d33, and coercive voltage were obtained. For the first time, hysteresis loops, and switching effects of domains under electrical field were observed in chalcogenide materials.

Gervacio-Arciniega, J. J.; Prokhorov, E.; Espinoza-Beltrán, F. J.; Trapaga, G.

2012-09-01

213

Ferroelectric polymers  

Microsoft Academic Search

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

R. G. Kepler; R. A. Anderson

1992-01-01

214

X-ray Study of the Ferroelectric [Ba0.6Sr0.4] [(YTa)0.03Ti0.94]O3  

SciTech Connect

We have studied the system [Ba{sub 0.6}Sr{sub 0.4}] [(YTa){sub 0.03}Ti{sub 0.94}]O{sub 3}, as produced using two different sintering temperatures. It was shown by others that for a sample sintered at 1550 {sup o}C the material is a relaxor, whereas for the same composition produced with sintering temperature of 1600 {sup o}C the sample is a normal ferroelectric. We have employed analysis of x-ray diffraction peak broadening, Ti K edge x ray near edge spectroscopy, and extended x-ray absorption edge fine structure spectroscopy of Ta and Y sites in our study. We find that the 1550 {sup o}C sinter sample has over double the lattice strain as does the 1600 {sup o}C sample. For the lower temperature sinter material, both Ta and Y go to sites substitutional for Ti in the lattice, with a significant expansion (contraction) of the local perovskite structure about Y (Ta) dopants. Thus, with only three percent B site addition of Y and Ta dopants, there is a strain associated relaxor behavior produced in a bulk sample. For the higher temperature sinter specimen, there is a marked change in the average Y environment relative to the lower temperature sinter sample.

Shanthakumar,P.; Balasubramanian, M.; Pease, D.; Frenkel, A.; Potrepka, D.; Kraizman, V.; Budnick, J.; Hines, W.

2006-01-01

215

Pressure-induced changes in the dielectric response of polymer relaxors  

SciTech Connect

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

Hilczer, B. [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznan (Poland); Szafranski, M.; Hilczer, A. [Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland)

2012-01-30

216

KTa\\/sub 0.6\\/Nb\\/sub 0.4\\/O\\/sub 3\\/ ferroelectric thin film behavior at microwave frequencies for tunable applications  

Microsoft Academic Search

In this study about the relationships between structural and microwave electrical properties of KTa1-xNbxO3 (KTN) ferroelectric materials, a KTN thin film was deposited on different substrates to investigate how KTN growth affects the microwave behavior. Interdigital capacitors and stubs were made on these films through a simple engraving process. Microwave measurements under a static electric field showed the importance of

Vincent Laur; Anthony Rousseau; Gerard Tanne; Paul Laurent; Stephanie Deputier; Maryline Guilloux-Viry; Fabrice Huret

2006-01-01

217

Fatigue and ferroelectric behavior of La and Zn comodified BiFeO3 thin films  

NASA Astrophysics Data System (ADS)

Bi0.90La0.10Fe0.95Zn0.05O3 (BLFZO) thin films were grown directly on Pt/TiO2/SiO2/Si(100) substrates without any buffer layer by off-axis radio frequency sputtering. The BLFZO thin film deposited at 580 °C possesses a single-phase purity, while those deposited at other temperatures exhibit a varying amount of second phases, indicating that the deposition temperature plays a critical role in the phase development of BLFZO thin films. Although La and Zn cosubstitutions lower the Curie temperature (Tc) of BiFeO3 thin films, the resulting Tc value (~630 °C) is still much higher as compared to other lead-based or lead-free ferroelectric thin films. The BLFZO thin film exhibits a remanent polarization of 2Pr~131.7 ?C/cm2 and a coercive field of 2Ec~496 kV/cm, in association with the improvement in electrical resistance. On the basis of the studies for frequency (1 kHz~1 MHz) and driving field (0.8Ec~2.0Ec) dependences, the BLFZO thin film demonstrates the desired fatigue endurance and weak frequency and driving field dependence. La and Zn cosubstitutions are shown to contribute toward the high remanent polarization and fatigue endurance.

Wu, Jiagang; Wang, John

2010-07-01

218

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

SciTech Connect

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

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

2009-07-15

219

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

220

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

221

Magnetic properties and dielectric behavior in ferrite/ferroelectric particulate composites  

NASA Astrophysics Data System (ADS)

Particulate composites of ferrite and ferroelectric phases having the general formula (x)BaTiO3+(1 x)Ni0.92Co0.03Cu0.05Fe2O4 (where x is mole fraction of components that varies as 0.85, 0.70 and 0.55) were prepared by conventional double-sintering ceramic method. The presence of constituent phases was confirmed by X-ray diffraction (XRD) technique. The average grain size was determined by using scanning electron micrographs. The variation of dielectric constant and tan ? with frequency in the range 20 Hz 1 MHz was studied. The variation of loss tangent (tan ?) and dielectric constant with temperature at fixed frequencies of 1 kHz, 10 kHz, 100 kHz and 1 MHz was also studied. The saturation magnetization (Ms) and magnetic moment (?B in Bohr magnetons) are reported for all composites. The static magnetoelectric (ME) voltage coefficient was measured as a function of intensity of applied DC magnetic field. The changes were observed in dielectric properties as well as in ME output with variation in molar fraction of constituent phases. A maximum ME conversion factor of 538.59 ?V/cm G was observed for the composites with 70% BaTiO3+30% Ni0.92Co0.03Cu0.05Fe2O4. The present ME composites may be useful in preparing devices such as magnetic sensors and cables, etc.

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

2007-04-01

222

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

SciTech Connect

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

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

2001-06-18

223

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

224

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  

NASA Astrophysics Data System (ADS)

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 ?c (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 (?c = 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 (?c = 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 V? 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.

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

2013-07-01

225

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

2013-01-02

226

Universal properties of ferroelectric domains.  

PubMed

Based on the Ginzburg-Landau approach, we generalize the Kittel theory and derive the interpolation formula for the temperature evolution of a multidomain polarization profile P(x,z). We resolve the long-standing problem of the near-surface polarization behavior in ferroelectric domains and demonstrate polarization vanishing instead of the usually assumed fractal domain branching. We propose an effective scaling approach to compare the properties of different domain-containing ferroelectric plates and films. PMID:19392481

Luk'yanchuk, Igor A; Lahoche, Laurent; Sené, Anaïs

2009-04-09

227

Precursor dynamics in the ferroelectric phase transition of barium titanate single crystals studied by Brillouin light scattering  

NASA Astrophysics Data System (ADS)

The acoustic anomalies and precursor dynamics of high-quality barium titanate single crystals were investigated by Brillouin light scattering and the birefringence measurements in the paraelectric phase above the cubic-to-tetragonal ferroelectric phase transition temperature (Tc). Two elastic stiffness coefficients C11 and C44, the related sound velocities, and their absorption coefficients were determined from Tc to 400?C for the first time. The longitudinal acoustic (LA) mode showed a substantial softening over a wide temperature range above Tc which was accompanied by a remarkable increase in the acoustic damping as well as growth of central peaks. The broad central peak (CP) exhibited a two-mode and one-mode behavior in the paraelectric and ferroelectric phase, respectively, which was consistent with recent far-infrared reflectivity measurements and first-principle-based calculations [Ponomareva , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.77.012102 77, 012102 (2008)]. The acoustic anomalies and CP behavior were correlated with the anomalous birefringence, piezoelectric effect, and the deviation of the Curie-Weiss law observed from the same crystal. This strongly indicates similarity between the dynamics of polar clusters in typical ferroelectrics and the dynamics of polar nanoregions in relaxors, consistent with recent acoustic emission measurements [Dul’kin , Appl. Phys. Lett.APPLAB0003-695110.1063/1.3464968 97, 032903 (2010)]. The relaxation times estimated from the central peak and the LA mode anomalies exhibited similar temperature dependences with comparable orders of magnitude, indicating that the polarization fluctuations due to the precursor polar clusters couples to the LA mode through density fluctuations. All these anomalies share common microscopic origin, correlated Ti off-centered motions forming polar clusters having local symmetry breaking in the paraelectric phase. The existence of the polar clusters were directly evidenced by the temperature evolution of the precise birefringence map. The narrow central peak within ±5 GHz proposed before was not confirmed to exist in the present study.

Ko, Jae-Hyeon; Kim, Tae Hyun; Roleder, K.; Rytz, D.; Kojima, Seiji

2011-09-01

228

Resistive switching via the converse magnetoelectric effect in ferromagnetic multilayers on ferroelectric substrates.  

PubMed

A voltage-controlled resistive switching is predicted for ferromagnetic multilayers and spin valves mechanically coupled to a ferroelectric substrate. The switching between low- and high-resistance states results from the strain-driven magnetization reorientations by about 90°, which are shown to occur in ferromagnetic layers with a high magnetostriction and weak cubic magnetocrystalline anisotropy. Such reorientations, not requiring external magnetic fields, can be realized experimentally by applying moderate electric field to a thick substrate (bulk or membrane type) made of a relaxor ferroelectric having ultrahigh piezoelectric coefficients. The proposed multiferroic hybrids exhibiting giant magnetoresistance may be employed as electric-write nonvolatile magnetic memory cells with nondestructive readout. PMID:21030777

Pertsev, N A; Kohlstedt, H

2010-10-29

229

Resistive switching via the converse magnetoelectric effect in ferromagnetic multilayers on ferroelectric substrates  

NASA Astrophysics Data System (ADS)

A voltage-controlled resistive switching is predicted for ferromagnetic multilayers and spin valves mechanically coupled to a ferroelectric substrate. The switching between low- and high-resistance states results from the strain-driven magnetization reorientations by about 90°, which are shown to occur in ferromagnetic layers with a high magnetostriction and weak cubic magnetocrystalline anisotropy. Such reorientations, not requiring external magnetic fields, can be realized experimentally by applying moderate electric field to a thick substrate (bulk or membrane type) made of a relaxor ferroelectric having ultrahigh piezoelectric coefficients. The proposed multiferroic hybrids exhibiting giant magnetoresistance may be employed as electric-write nonvolatile magnetic memory cells with nondestructive readout.

Pertsev, N. A.; Kohlstedt, H.

2010-11-01

230

Critical behavior near the Lifshitz point in Sn(2)P(2)(S(1 - x)Se(x))(6) ferroelectric semiconductors from thermal diffusivity measurements.  

PubMed

The thermal diffusivity of the ferroelectric family Sn(2)P(2)(Se(x)S(1 - x))(6) (0 ? x ? 1) has been measured by a high-resolution ac photopyroelectric technique, using single crystals, with the aim of studying the evolution of the ferroelectric transition with Se doping. Its change from second order character to first order while passing the Lifshitz point (x approximately 0.28) has been evaluated, as well as the splitting of the transition at high Se concentrations. The critical behavior of the ferroelectric transition in terms of the different universality classes and their underlying physical dominant effects (tricriticality, long-range dipole interactions, Lifshitz point) has been discussed using thermal diffusivity measurements in the very close vicinity of the critical temperature. This study reveals that for Se concentrations around the Lifshitz point, long-range dipole interactions do not play a significant role and that the critical parameters are close to those predicted for the Lifshitz universality class. PMID:21406848

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

2010-12-16

231

Ferroelectric Phase Transitions in Small Particles and Local Regions  

NASA Astrophysics Data System (ADS)

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.

Levanyuk, A. P.; Blinc, R.

2013-08-01

232

X-ray study of the ferroelectric [Ba{sub 0.6}Sr{sub 0.4}] [(YTa){sub 0.03}Ti{sub 0.94}]0[sub 3}.  

SciTech Connect

We have studied the system [Ba{sub 0.6}Sr{sub 0.4}] [(YTa){sub 0.03}Ti{sub 0.94}]O{sub 3}, as produced using two different sintering temperatures. It was shown by others that for a sample sintered at 1550 C the material is a relaxor, whereas for the same composition produced with sintering temperature of 1600 C the sample is a normal ferroelectric. We have employed analysis of x-ray diffraction peak broadening, Ti K edge x ray near edge spectroscopy, and extended x-ray absorption edge fine structure spectroscopy of Ta and Y sites in our study. We find that the 1550 C sinter sample has over double the lattice strain as does the 1600 C sample. For the lower temperature sinter material, both Ta and Y go to sites substitutional for Ti in the lattice, with a significant expansion (contraction) of the local perovskite structure about Y (Ta) dopants. Thus, with only three percent B site addition of Y and Ta dopants, there is a strain associated relaxor behavior produced in a bulk sample. For the higher temperature sinter specimen, there is a marked change in the average Y environment relative to the lower temperature sinter sample.

Shanthakumar, P.; Balasubramanian, M.; Pease, D.M.; Frenkel, A.I.; Potrepka, D.M.; Kraizman, V.; Budnick, J.; Hines, W.A.; X-Ray Science Division; Univ. of Conn.; Yeshiva Univ.; U.S. Army Research Lab.; Restov State Univ.

2006-01-01

233

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

234

Ferroelectric tunnel memristor.  

PubMed

Strong interest in resistive switching phenomena is driven by a possibility to develop electronic devices with novel functional properties not available in conventional systems. Bistable resistive devices are characterized by two resistance states that can be switched by an external voltage. Recently, memristors-electric circuit elements with continuously tunable resistive behavior-have emerged as a new paradigm for nonvolatile memories and adaptive electronic circuit elements. Employment of memristors can radically enhance the computational power and energy efficiency of electronic systems. Most of the existing memristor prototypes involve transition metal oxide resistive layers where conductive filaments formation and/or the interface contact resistance control the memristive behavior. In this paper, we demonstrate a new type of memristor that is based on a ferroelectric tunnel junction, where the tunneling conductance can be tuned in an analogous manner by several orders of magnitude by both the amplitude and the duration of the applied voltage. The ferroelectric tunnel memristors exhibit a reversible hysteretic nonvolatile resistive switching with a resistance ratio of up to 10(5) % at room temperature. The observed memristive behavior is attributed to the field-induced charge redistribution at the ferroelectric/electrode interface, resulting in the modulation of the interface barrier height. PMID:23039785

Kim, D J; Lu, H; Ryu, S; Bark, C-W; Eom, C-B; Tsymbal, E Y; Gruverman, A

2012-10-11

235

Ferroelectric switchable behavior through fast reversible de/adsorption of water spirals in a chiral 3D metal-organic framework.  

PubMed

A polar homochiral 3D MOF [{Co2(L)(bpe)(H2O)}·5H2O]n constructed with cobalt(II) and a new ligand N-(1,3-dicarboxy-5-benzyl)-carboxymethylglycine (H4L) accommodates ordered helical water streams in its helical grooves. It provides the first example of switchable ferroelectric and optical behavior through two-step reversible single-crystal to single-crystal transformation (SCSC) upon desorption/adsorption of water spirals and coordinated water molecules, respectively. PMID:23829317

Dong, Xi-Yan; Li, Bo; Ma, Bin-Bin; Li, Shi-Jun; Dong, Ming-Ming; Zhu, Yan-Yan; Zang, Shuang-Quan; Song, You; Hou, Hong-Wei; Mak, Thomas C W

2013-07-05

236

In-situ TEM investigation of the phase transitions in perovskite ferroelectrics  

NASA Astrophysics Data System (ADS)

Ferroelectrics are important materials displaying outstanding dielectric, piezoelectric, and ferroelectric properties and are widely used in capacitors, transducers, actuators, filters, sensors, and random access memories. Direct observation of the dynamic process of thermal and/or electric field-induced phase transitions in ferroelectrics is of great importance in understanding the underlying mechanisms of their peculiar properties. In this work, thermal and electric field in-situ TEM techniques were used to study the dynamic process of antiferroelectric to normal ferroelectric, normal ferroelectric to normal ferroelectric as well as relaxor ferroelectric to normal ferroelectric phase transitions. A thermal in-situ TEM technique was used to study the antiferroelectric to normal ferroelectric phase transition in 0.98PbZrO 3-0.02Pb(Ni1/3Nb2/3)O3 ceramics during heating. The low temperature antiferroelectric phase and intermediate ferroelectric phase are characterized by the 1/4{110}c-type and the 1/2{110}c-type superlattice diffractions, respectively. An incommensurate phase with 1/6.48{110}c satellite diffractions was revealed to exist within a narrow temperature range of 3°C between the antiferroelectric and ferroelectric phases presumably as a result of the competition between two these two types of ordering. The ferroelectric phase is special not only because of its frequency dependence, but also because of its checkerboard type domain morphology. Electric field in-situ TEM and thermal in-situ TEM techniques are used separately to study the FERL ? FERH phase transition in Pb0.99[(Zr0.95Ti 0.05)0.982Nb0.018]O3 ceramics. There appear to be different ferroelectric domains associated with the 1/2{111} c-type superlattice diffraction spots. These two types of domains respond to temperature increase independently. Under the conditions used in this study (thin TEM specimen and field close to <011>c), external electric fields favor the FERH over the FERL phase at room temperature. A cryo electric field in-situ TEM technique was used to study the relaxor ferroelectric to normal ferroelectric phase transition in 0.92Pb(Mg1/3Nb2/3)O3-0.08Pb(Sc 1/2Nb1/2)O3 ceramics. The dynamic phase transition process was observed under TEM for the first time. It is revealed that the electric field-induced relaxor to normal ferroelectric phase transition initiates at grain boundaries. The transition involves the gradual coalescence of polar nanoregions and the successive abrupt formation of large ferroelectric domains. The formed domain/phase walls are roughly along {110} planes. The morphology of the cation ordered domains does not change under applied electric fields. Furthermore, no evidence for strong interactions of these chemical domains with the induced large ferroelectric domains is found in the Sc-doped PMN ceramic.

Qu, Weiguo

237

Grain-size effects on the ferroelectric behavior of dense nanocrystalline BaTiO3 ceramics  

Microsoft Academic Search

A progressive reduction of tetragonal distortion, heat of transition, Curie temperature, and relative dielectric constant has been observed on dense BaTiO3 ceramics with grain size decreasing from 1200 to 50nm . The correlations between grain size, extent of tetragonal distortion, and ferroelectric properties strongly support the existence of an intrinsic size effect. From the experimental trends the critical size for

Zhe Zhao; Vincenzo Buscaglia; Massimo Viviani; Maria Teresa Buscaglia; Liliana Mitoseriu; Andrea Testino; Mats Nygren; Mats Johnsson; Paolo Nanni

2004-01-01

238

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

NASA Astrophysics Data System (ADS)

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

Tirupathi, Patri; Chandra, Amreesh

2013-09-01

239

Ferroelectric behaviors and charge carriers in Nd-doped Bi{sub 4}Ti{sub 3}O{sub 12} thin films  

SciTech Connect

Nd-doped Bi{sub 4}Ti{sub 3}O{sub 12} thin films (Bi{sub 3.25}Nd{sub 0.85}){sub 4}Ti{sub 3}O{sub 12}, of layered perovskite structure were synthesized by rf sputtering, followed by postannealing at 600-700 deg. C. They show enhanced ferroelectricity with rising postannealing temperature in the range of 650-750 deg. C. When annealed at 700 deg. C, a remanent polarization 2P{sub r} of 25.2 {mu}C/cm{sup 2} and a coercive field E{sub c} of 87.2 kV/cm were measured at 9 V, together with an almost fatigue-free behavior up to 1.4x10{sup 10} switching cycles. Their ferroelectric, dielectric, and ac conductivity properties over the temperature range from 25 to 300 deg. C were studied over the frequency range of 0.1-1 MHz. Space-charge relaxation by oxygen vacancies was shown to play an important role in determining the dielectric and conductivity behaviors of Nd-doped Bi{sub 4}Ti{sub 3}O{sub 12} thin films.

Gao, X.S.; Xue, J.M.; Wang, J. [Department of Materials Science, Faculty of Science, National University of Singapore, Singapore 119260 (Singapore)

2005-02-01

240

Electrical Properties of Barium and Zirconium Modified NBT Ferroelectric Ceramics  

SciTech Connect

Recently a new wave of interest has risen on relaxor ferroelectrics with complex perovskite structure due to their wide use in fabrication of multilayer ceramic capacitors, electrostrictive actuators, and electromechanical transducers. The polycrystalline 0.93(Bi{sub 0.5}Na{sub 0.5})Ba{sub 0.07}Z{sub 0.04}T{sub 0.96}O{sub 3}(0.07BNBZT) ceramic material, which is in the vicinity of the morphotropic phase boundary (MPB) has been prepared by using high temperature solid state reaction method. The tolerance factor has been estimated and found to be 0.815. XRD analysis revealed a rhombohedral perovskite type structure. SEM micrographs showed highly dense grains with rectangular shape. The average grain size is found to be 1.51{mu}m. Dielectric studies in the material ha indicated relaxor behaviour with diffuse phase transition. High value of {epsilon}{sub m}>1958 is found at 1kHz, Tm (phase transition temperature) 335 deg. C, The diffuseness parameter was established to be 1.60 revealing the relaxor behaviour. Further, to confirm the relaxor behaviour in the material, Vogel-Fulcher (V-F) relation has been used. Estimated V-F parameters are found to be T{sub f} = 138 deg. C, E{sub a} = 0.080 eV and {nu}{sub o} = 2.32x10{sup 8} Hz. Cole-Cole analysis has shown a non-Debye type relaxation in the system. Conductivity studies in the material obeyed the Jonscher's power law in frequency range of (45Hz-5MHz) and temperature range of (35 deg. C - 600 deg. C). The electric conduction in the system may be due to hopping/mobility/ transportation of charge carriers.

Rao, K. Sambasiva; Tilak, B.; Swathi, A.; Workineh, Haileeyesus [Department of Physics, Andhra University, Visakhapatnam-530003 (India); Rajulu, K. Ch. Varada [Indian Plywood Industries Research and Training Institute (IPIRTI), Bangalore (India)

2011-11-22

241

Characteristic temperatures and field effect in KTa1-x NbxO3 relaxor crystals seen via acoustic emission  

NASA Astrophysics Data System (ADS)

[100]-oriented KTa1-xNbxO3 (x=0.32) relaxor ferroelectric crystals have been studied by acoustic emission (AE) count rate dot N in the temperature range from 200?K to 700?K. Burns temperature Td=620?K (dot N = 1.7 -1) and intermediate temperature T*=310?K (dot N = 3.1 -1) as well as both the tetragonal-cubic TT-C=259?K (dot N = 4.0 -1) and orthorhombic-tetragonal TO-T=243?K (dot N = 5.0 -1) phase transition temperatures have been clearly detected. T* is found to be influenced by an external DC electric field E: T* essentially decreases with a slope of approximately -?60?K·cm/kV accompanied with weakening in dot N, as E enhances. The mechanisms of abnormal T*(E) and dot N(T) dependences are discussed.

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

2012-03-01

242

Proton glass behavior and hopping conductivity in solid solutions of antiferroelectric betaine phosphate and ferroelectric betaine phosphite  

Microsoft Academic Search

Measurements of the dielectric permittivity are reported for solid solutions of antiferroelectric betaine phosphate and ferroelectric betaine phosphite at frequencies 10-2 HzTc the dielectric response is

S. L. Hutton; I. Fehst; R. Böhmer; M. Braune; B. Mertz; P. Lunkenheimer; A. Loidl

1991-01-01

243

A dual-phase homogenization theory for the hysteresis and butterfly-shaped behavior of ferroelectric single crystals  

Microsoft Academic Search

Based on the mechanism of domain switch and a micromechanics-based thermodynamic approach, a dual-phase homogenization theory is developed to calculate the hysteresis loops of ferroelectric single crystals. Unlike the classical phenomenological theories, this dual-phase model is capable of delivering the evolution of new domain concentration, and it further indicates that the driving force for domain switch under a pure electric

N. Srivastava; G. J. Weng

2006-01-01

244

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

Microsoft Academic Search

Since its introduction in the 90's, the first-principles effective-Hamiltonian method has been successfully used to simulate temperature-driven phenomena in increasingly complex ferroelectrics, from classic compound BaTiO3 to multiferroic BiFeO3. Currently, the emergence of nano-structured materials -- e.g., in the form of ultra-thin films or short-period superlattices -- poses new challenges to the simulations, and the development of predictive models seems

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

2011-01-01

245

Ion Implantation in Perovskite Type Ferroelectrics.  

National Technical Information Service (NTIS)

The object of this work was to study ion implantation in perovskite ferroelectrics and to investigate the conductive behavior of implanted layers. Implantation experiments were carried out on strontium titanate, barium titanate (single crystal and ceramic...

R. Gerson

1979-01-01

246

Ferroelectricity in strain-free SrTiO3 thin films.  

PubMed

Biaxial strain is known to induce ferroelectricity in thin films of nominally nonferroelectric materials such as SrTiO3. By a direct comparison of the strained and strain-free SrTiO3 films using dielectric, ferroelectric, Raman, nonlinear optical and nanoscale piezoelectric property measurements, we conclude that all SrTiO3 films and bulk crystals are relaxor ferroelectrics, and the role of strain is to stabilize longer-range correlation of preexisting nanopolar regions, likely originating from minute amounts of unintentional Sr deficiency in nominally stoichiometric samples. These findings highlight the sensitive role of stoichiometry when exploring strain and epitaxy-induced electronic phenomena in oxide films, heterostructures, and interfaces. PMID:20866998

Jang, H W; Kumar, A; Denev, S; Biegalski, M D; Maksymovych, P; Bark, C W; Nelson, C T; Folkman, C M; Baek, S H; Balke, N; Brooks, C M; Tenne, D A; Schlom, D G; Chen, L Q; Pan, X Q; Kalinin, S V; Gopalan, V; Eom, C B

2010-05-13

247

Device modeling of ferroelectric capacitors  

SciTech Connect

A physically based methodology is developed for modeling the behavior of electrical circuits containing nonideal ferroelectric capacitors. The methodology is illustrated by modeling the discrete ferroelectric capacitor as a stacked dielectric structure, with switching ferroelectric and nonswitching dielectric layers. Electrical properties of a modified Sawyer--Tower circuit are predicted by the model. Distortions of hysteresis loops due to resistive losses as a function of input signal frequency are accurately predicted by the model. The effect of signal amplitude variations predicted by the model also agree with experimental data. The model is used as a diagnostic tool to demonstrate that cycling degradation, at least for the sample investigated, cannot be modeled by the formation of nonswitching dielectric layer(s) or the formation of conductive regions near the electrodes, but is consistent with a spatially uniform reduction in the number of switching dipoles.

Miller, S.L.; Nasby, R.D.; Schwank, J.R.; Rodgers, M.S.; Dressendorfer, P.V. (Division 2144, Sandia National Laboratories, Albuquerque, NM (USA))

1990-12-15

248

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

249

Ferroelectric aging behaviors of BaTi0.995Mn0.005O3 ceramics: grain size effects  

NASA Astrophysics Data System (ADS)

We report the ferroelectric aging effect of dense BaTi0.995Mn0.005O3 ceramics with grain size varying from 2000 nm to 150 nm. Given the identical aging process, it is revealed that the significant aging effect with clear double-hysteresis loop, observed in coarse-grain sample, is substantially suppressed with decreasing grain size. This suppression can be attributed to the reduction of tetragonal distortion and the grain boundary barrier effect in fine-grain sample. Consequently, the weak thermodynamic driving force and the limited kinetic migration are unfavorable to a reversible domain switching, resulting in a normal hysteresis loop in small grained samples.

Guo, Y. Y.; Yan, Z. B.; Zhang, N.; Cheng, W. W.; Liu, J.-M.

2012-04-01

250

Evidence for anisotropic polar nanoregions in relaxor Pb(Mg1/3Nb2/3)O3: A neutron study of the elastic constants and anomalous TA phonon damping in PMN  

NASA Astrophysics Data System (ADS)

We use neutron inelastic scattering to characterize the acoustic phonons in the relaxor Pb(Mg1/3Nb2/3)O3 (PMN) and demonstrate the presence of a highly anisotropic damping mechanism that is directly related to short-range polar correlations. For a large range of temperatures above Tc˜210 K, where dynamic, short-range polar correlations are present, acoustic phonons propagating along [11¯0] and polarized along [110] (TA2 phonons) are overdamped and softened across most of the Brillouin zone. By contrast, acoustic phonons propagating along [100] and polarized along [001] (TA1 phonons) are overdamped and softened for a more limited range of wave vectors q. The anisotropy and temperature dependence of the acoustic phonon energy linewidth ? are directly correlated with neutron diffuse scattering cross section, indicating that polar nanoregions are the cause of the anomalous behavior. The damping and softening vanish for q?0, i.e., for long-wavelength acoustic phonons near the zone center, which supports the notion that the anomalous damping is a result of the coupling between the relaxational component of the diffuse scattering and the harmonic TA phonons. Therefore, these effects are not due to large changes in the elastic constants with temperature because the elastic constants correspond to the long-wavelength limit. We compare the elastic constants we measure to those from Brillouin scattering experiments and to values reported for pure PbTiO3. We show that while the values of C44 are quite similar, those for C11 and C12 are significantly less in PMN and result in a softening of (C11-C12) over PbTiO3. The elastic constants also show an increased elastic anisotropy [2C44/(C11-C12)] in PMN versus that in PbTiO3. These results are suggestive of an instability to TA2 acoustic fluctuations in PMN and other relaxor ferroelectrics. We discuss our results in the context of the current debate over the “waterfall” effect and show that they are inconsistent with acoustic-optic phonon coupling or other models that invoke the presence of a second, low-energy optic mode.

Stock, C.; Gehring, P. M.; Hiraka, H.; Swainson, I.; Xu, Guangyong; Ye, Z.-G.; Luo, H.; Li, J.-F.; Viehland, D.

2012-09-01

251

Field Induced Evolution of Nanoscale Structures in Relaxor PLZT Ceramics  

Microsoft Academic Search

The kinetics of the nanoscale structures under application of bipolar and unipolar ac field was investigated by recording of the switching charge in wide temperature and field range in hot-pressed relaxor PLZT ceramics. Original analysis of the switching charge data was based on the consideration of the field induced transformation as an evolution of the nanoscale domain structure with nanoscale

V. Y. A. SHUR; E. L. Rumyantsev; G. G. Lomakin; O. V. Yakutova; D. V. Pelegov; A. Sternberg; M. Kosec

2005-01-01

252

Ferroelectric properties of nanocrystalline barium titanate ceramics  

NASA Astrophysics Data System (ADS)

Dense nanocrystalline BaTiO3 ceramics with the average grain size of 20 nm obtained by spark plasma sintering were investigated. The dielectric data show a ferroelectric to paraelectric phase transition with a maximum permittivity of ~930 at 115 °C and at 1 kHz. The polarization-reversal characteristics and the local ferroelectric switching behavior were measured; the typical piezoelectric hysteresis loops were recorded. The present results provide experimental evidence, indicating that if a critical grain size exists for ferroelectricity it is less than 20 nm for polycrystalline BaTiO3 ceramics.

Deng, Xiangyun; Wang, Xiaohui; Wen, Hai; Chen, Liangliang; Chen, Lei; Li, Longtu

2006-06-01

253

Giant Electrocaloric Effect in Ferroelectric Polymers with Great Impact on Energy and Environment  

NASA Astrophysics Data System (ADS)

Refrigeration and air conditioning overall consume around 20% of the energy budget in developed countries which necessitates a search for new approaches to increase the energy efficiency of these cooling technologies. Cooling technologies based on the electrocaloric effect (ECE) hold great potential and promise in realizing these goals. The electrocaloric effect (ECE) refers to the change in temperature and/or entropy of a dielectric material by an applied voltage. Recently, a class of P(VDF-TrFE) based ferroelectric polymers have been discovered that provide a giant electrocaloric effect with an adiabatic temperature change of ?T ˜ 20 K and an isothermal entropy change ?S > 90 J/kgK at room temperature. This talk will review the earlier works in the ECE, as well as present the basic materials considerations and experimental results of the ECE in both normal and relaxor ferroelectric polymers. It will be shown he relaxor ferroelectric polymer displays a nearly flat ECE response over a broad temperature range, which is very attractive for practical cooling device applications Furthermore, we will present our recent investigation, exploiting the giant ECE in these polymers for cooling devices with compact size, high cooling power and efficiency.

Li, Xinyu; Qian, Xiaoshi; Gu, Haiming; Lu, Shengguo; Zhang, Qiming

2012-02-01

254

A classroom experiment to demonstrate ferroelectric hysteresis  

NASA Astrophysics Data System (ADS)

We have developed a classroom experiment suitable for undergraduate students in which they fabricate a ferroelectric capacitor from potassium nitrate and then observe the electrical behavior as the film is cooled through its transition temperature. The experiment can be carried out using a capacitance bridge that is simple to construct and inexpensive. The experiment gives students a hands-on experience with ferroelectric phenomena, a subject of considerable interest from both a fundamental and a technological standpoint.

Dawber, M.; Farnan, I.; Scott, J. F.

2003-08-01

256

Temporal and Spatial Behavior of the Field-Induced Transition between Antiferroelectric and Ferroelectric Phases in Chiral Smectics  

Microsoft Academic Search

Optical transmittance change and stroboscopic micrographs have been obtained in homogeneously aligned thin cells of S-MHPOBC, C8H17O-\\\\includegraphics{dummy.eps}---\\\\includegraphics{dummy.eps}-COO-\\\\includegraphics{dummy.eps}-COO-*CH(CH3)C6H13, and R-TFMNPOBC, C8H17O-\\\\includegraphics{dummy.eps}---\\\\includegraphics{dummy.eps}-COO-\\\\includegraphics{dummy.eps}-COO-*CH(CF3)C8H17, by varying the initial applied DC voltage stepwise into the final one across the threshold. There exist two components, fast and slow, in the transmittance change due to the phase transition from antiferroelectric SmCA* to ferroelectric SmC*. The fast component

Masahiro Johno; Keizou Itoh; Ji Lee; Yukio Ouchi; Hideo Takezoe; Atsuo Fukuda; Tomoya Kitazume

1990-01-01

257

Ferroelectrics for semiconductor devices  

NASA Astrophysics Data System (ADS)

The technology for the implementation of the integration of thin film ferroelectrics with silicon processing for various devices is described, and factors affecting the integration of ferroelectric films with semiconductor processing are discussed. Consideration is also given to film properties, the properties of electrode materials and structures, and the phenomena of ferroelectric fatigue and aging. Particular attention is given to the nonmemory device application of ferroelectrics.

Sayer, M.; Wu, Z.; Vasant Kumar, C. V. R.; Amm, D. T.; Griswold, E. M.

1992-11-01

258

A Continuum Theory of Deformable, Semiconducting Ferroelectrics  

NASA Astrophysics Data System (ADS)

Ferroelectric solids, especially ferroelectric perovskites, are widely used as sensors, actuators, filters, memory devices, and optical components. While these have traditionally been treated as insulators, they are in reality wide-band-gap semiconductors. This semiconducting behavior affects the microstructures or domain patterns of the ferroelectric material and the interaction of ferroelectrics with electrodes, and is affected significantly by defects and dopants. In this paper, we develop a continuum theory of deformable, semiconducting ferroelectrics. A key idea is to introduce space charges and dopant density as field (state) variables in addition to polarization and deformation. We demonstrate the theory by studying oxygen vacancies in barium titanate. We find the formation of depletion layers, regions of depleted electrons, and a large electric field at the ferroelectric-electrode boundary. We also find the formation of a charge double layer and a large electric field across 90° domain walls but not across 180° domain walls. We show that these internal electric fields can give rise to a redistribution or forced diffusion of oxygen vacancies, which provides a mechanism for aging of ferroelectric materials.

Xiao, Yu; Bhattacharya, Kaushik

2008-07-01

259

Modeling ferroelectric capacitor switching using a parallel-elements model  

Microsoft Academic Search

The charge-voltage (Q-V) relationship of ferroelectric capacitors experiencing arbitrary applied voltages is investigated both theoretically and experimentally. The complex behavior and history dependence of a ferroelectric capacitor in response to arbitrary voltage patterns can be well described by a parallel-elements model. This approach not only describes all of the major properties of ferroelectric hysteresis but is also very easy to

Bo Jiang; Jack C. Lee; Peter Zurcher; Robert E. Jones Jr

1997-01-01

260

Competing antiferroelectric and ferroelectric interactions in NaNbO{sub 3}: Neutron diffraction and theoretical studies  

SciTech Connect

Neutron diffraction studies using powder samples have been used to understand the complex sequence of low temperature phase transitions of NaNbO{sub 3} in the temperature range from 12 to 350 K. Detailed Rietveld analysis of the diffraction data reveals that the antiferroelectric to ferroelectric phase transition occurs on cooling around 73 K, while the reverse ferroelectric to antiferroelectric transition occurs on heating at 245 K. However, the former transformation is not complete until it reaches 12 K and there is unambiguous evidence for the presence of the ferroelectric R3c phase coexisting with an antiferroelectic phase (Pbcm) over a wide range of temperatures. The coexisting phases and reported anomalous smearing of the dielectric response akin to dipole glasses and relaxors observed in the same temperature range are consistent with competing ferroelectric and antiferroelectric interactions in NaNbO{sub 3}. We have carried out theoretical lattice dynamical calculations which reveal that the free energies of the antiferroelectric Pbcm and ferroelectric R3c phases are nearly identical over a wide range of temperature. The small energy difference between the two phases is of interest as it explains the observed coexistence of these phases over a wide range of temperature. The computed double well depths and energy barriers from paraelectric Pm3m to antiferroelectric Pbcm and ferroelectric R3c phases in NaNbO{sub 3} are also quite similar, although the ferroelectric R3c phase has a slightly lower energy.

Mishra, S. K.; Choudhury, N.; Chaplot, S. L.; Krishna, P. S. R.; Mittal, R. [Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2007-07-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

262

The effects of nonhydrostatic compression and applied electric field on the electromechanical behavior of poled lead zirconate titanate 95\\/5-2Nb ceramic during the ferroelectric to antiferroelectric polymorphic transformation  

Microsoft Academic Search

We conducted hydrostatic compression and constant-stress-difference experiments, with and without an applied electric field, on poled, niobium-doped lead zirconate titanate ceramic. The objective was to quantify the effects of nonhydrostatic stress and electric field bias on electromechanical behavior of the ceramic during the ferroelectric, rhombohedral antiferroelectric, orthorhombic phase transformation. Increasing stress difference (shear stress) decreases the mean stress at which

D. M. Zeuch; D. J. Holcomb

1999-01-01

263

Ferroelectricity in hafnium oxide thin films  

NASA Astrophysics Data System (ADS)

We report that crystalline phases with ferroelectric behavior can be formed in thin films of SiO2 doped hafnium oxide. Films with a thickness of 10 nm and with less than 4 mol. % of SiO2 crystallize in a monoclinic/tetragonal phase mixture. We observed that the formation of the monoclinic phase is inhibited if crystallization occurs under mechanical encapsulation and an orthorhombic phase is obtained. This phase shows a distinct piezoelectric response, while polarization measurements exhibit a remanent polarization above 10 ?C/cm2 at a coercive field of 1 MV/cm, suggesting that this phase is ferroelectric. Ferroelectric hafnium oxide is ideally suited for ferroelectric field effect transistors and capacitors due to its excellent compatibility to silicon technology.

Böscke, T. S.; Müller, J.; Bräuhaus, D.; Schröder, U.; Böttger, U.

2011-09-01

264

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

NASA Astrophysics Data System (ADS)

We report neutron diffuse scattering measurements on the lead-free relaxors Na1/2Bi1/2TiO3 (NBT) and NBT doped with 5.6% BaTiO3, a composition that is located close to the morphotropic phase boundary. The diffuse scattering in NBT appears on cooling near 700 K, which coincides with the temperature at which the dielectric constant deviates from Curie-Weiss behavior. Strong, anisotropic diffuse scattering intensity is observed near the (100), (110), (200), (220), and (210) Bragg peaks. The reciprocal space distribution of the diffuse scattering is consistent with the presence of competing rhombohedral and tetragonal short-range structural correlations. Doping NBT with 5.6% BaTiO3 reduces the correlation length associated with the tetragonal order by a factor of 10 while simultaneously enhancing the piezoelectric properties.

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

2013-03-01

265

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>R_{c}), the phase transition is into a vortex state while for Rrelaxors. PMID:24033071

Levanyuk, A P; Blinc, R

2013-08-27

266

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

267

Low-temperature thermal properties of ferroelectrics  

Microsoft Academic Search

Through measurements of the low-temperature thermal conductivity and specific heat, we show that two classes of ferroelectrics can be distinguished. One class exhibits behavior typical of crystalline solids and the other displays behavior identical to that seen in structural glasses. We correlate these observations with measurements of the dielectric constant and optic index of refraction in the vicinity of the

J. J. de Yoreo; R. O. Pohl; Gerald Burns

1985-01-01

268

Coexistence of antiferromagnetic and spin cluster glass order in the magnetoelectric relaxor multiferroic PbFe 0.5 Nb 0.5 O3.  

PubMed

The coexistence of cluster glass with long-range antiferromagnetic order in the relaxor ferroelectric PbFe 0.5 Nb 0.5 O3 is elucidated. While the transition at T(N) = 153 K on the infinite antiferromagnetic cluster induces 3m symmetry with large EH2 magnetoelectric response, the disconnected subspace of isolated Fe3+ ions and finite clusters accommodates the cluster glass below T(g) = 10.6 K with field-induced m' symmetry and EH-type magnetoelectric response. Critical slowing-down, memory and rejuvenation after aging, occurrence of a de Almeida-Thouless phase line, and stretched exponential relaxation of remanence corroborate the glass nature. PMID:21231620

Kleemann, W; Shvartsman, V V; Borisov, P; Kania, A

2010-12-13

269

Dielectric and ferroelectric behaviors of BaTiO3-(K1/4Bi3/4)(Mg1/4Ti3/4)O3 ceramics  

NASA Astrophysics Data System (ADS)

Perovskite ferroelectric ceramics of (1-x)BaTiO3-x(K1/4Bi3/4)(Mg1/4Ti3/4)O3 [(1-x)BT-xKBMT, x=0.06, 0.1, and 0.14] were synthesized via solid-state reaction method. Dielectric constant maximum ?m of BT-KBMT ceramics declines with KBMT content. V(T) peak temperature Tm (402 K) is close to Tc (403 K) of the parent BT for composition 0.94BT-0.06KBMT, and decreases to 382 K for 0.9BT-0.1KBMT. Dielectric behaviors of the two compositions exhibit features of ferroelectrics with diffuse phase transition. A high-field linear polarization behavior was observed in the two compositions around temperature range of the V(T) peak summit. V(T) peak of 0.86BT-0.14KBMT is saddle-backed. The high turning temperature Tm1 fixes around 384 K, and is the Burns temperature TB of the composition. The low turning point Tm2 is 326 K at 100 Hz and highly frequency dependent. The dielectric anomaly of 0.86BT-0.14KBMT around Tm2 is associated with diffuse transitions from ferroelectric macrodomains to microdomains, polar nanoregions and paraelectric states.

Lu, Bin; Wang, Xiaoli; Shi, Jing

2011-01-01

270

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

Microsoft Academic Search

A monoclinic phase is evidenced between rhombohedral and cubic phases in a ?111?-cut single crystal PMN-33%PT from polarizing microscope observation of domain structures. Some rules for interpreting these observations for various cuts are reviewed, to illustrate how particular cuts are useful for distinguishing among particular types of phases and domains. Near 360 K the structure begins to distort from the

V. Hugo Schmidt; R. Chien; I.-C. Shih; Chi-Shun Tu

2003-01-01

271

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

Microsoft Academic Search

A monoclinic phase is evidenced between rhombohedral and cubic phases in a -cut single crystal PMN-33%PT from polarizing microscope observation of domain structures. Some rules for interpreting these observations for various cuts are reviewed, to illustrate how particular cuts are useful for distinguishing among particular types of phases and domains. Near 360 K the structure begins to distort from the

V. Hugo Schmidt; R. Chien; I.-C. Shih; Chi-Shun Tu

2003-01-01

272

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

NASA Astrophysics Data System (ADS)

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

Sebald, Gael; Pruvost, Sebastien; Guyomar, Daniel

2008-02-01

273

Electric-field-, temperature-, and stress-induced phase transitions in relaxor ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

Electric-field-induced phase transitions have been evidenced by macroscopic strain measurements at temperatures between 25°C and 100°C in [001]C -poled (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3[(PMN-xPT);x=0.25,0.305,0.31] and (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3[(PZN-xPT);x=0.05,0.065,0.085] single crystals. Such measurements provide a convenient way of ascertaining thermal and electrical phase stabilities over a range of compositions and give direct evidence for first-order phase transitions. A pseudorhombohedral (MA) -pseudo-orthorhombic (MC) -tetragonal (T) polarization rotation path is evidenced by two first-order-like, hysteretic discontinuities in strain within the same unipolar electric field cycle for PZN-5PT, PMN-30.5PT, and PMN-31PT whereas, in PMN-25PT, a single first-order-like MA-T transition is observed. This agrees well with in situ structural studies reported elsewhere. Electric-field-temperature (E-T) phase diagrams are constructed showing general trends for MA , MC , and T phase stabilities for varying temperatures and electric fields in poled samples over the given range of compositions. The complex question of whether the MA and MC states constitute true phases, or rather piezoelectrically distorted versions of their rhombohedral (R) and orthorhombic (O) parents, is discussed. Finally, stress-induced phase transitions are evidenced in [001]C -poled PZN-4.5PT by application of a moderate compressive stress (<100MPa) both along and perpendicularly to the poling direction (longitudinal and transverse modes, respectively). The rotation path is likely R-MB-O , via a first-order, hysteretic rotation within the MB monoclinic plane. The results are presented alongside a thorough review of previously reported electric-field-induced and stress-induced phase transitions in PMN-xPT and PZN-xPT .

Davis, Matthew; Damjanovic, Dragan; Setter, Nava

2006-01-01

274

Perovskite ferroelectric nanomaterials.  

PubMed

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. PMID:23912964

Nuraje, Nurxat; Su, Kai

2013-08-05

275

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

276

Diodelike and resistive hysteresis behavior of heterolayered BiFeO3/ZnO ferroelectric thin films  

NASA Astrophysics Data System (ADS)

BiFeO3/ZnO, ZnO/BiFeO3, BiFeO3/ZnO/BiFeO3, and ZnO/BiFeO3/ZnO thin film heterostructures were deposited on SrRuO3/Pt(111)/TiO2/SiO2/Si(100) substrates by off-axis radio frequency sputtering. Their diodelike and resistive hysteresis behavior are dependent on the combination sequence of the constituent layers in the heterostructures. Both the diodelike and resistive hysteresis behavior were clearly observed in BiFeO3/ZnO and ZnO/BiFeO3. The phenomena became more apparent with rising temperature. The behavior arises from the interface formed between BiFeO3 and ZnO. As expected, the diodelike and resistive hysteresis behavior are weakened and almost disappeared in the case of BiFeO3/ZnO/BiFeO3 and ZnO/BiFeO3/ZnO, where the two interfaces are equal and opposite to each other. The interface-limited Fowler-Nordheim tunneling in the high electric field region is demonstrated to involve in the formation of resistive hysteresis.

Wu, Jiagang; Wang, John

2010-11-01

277

Ferroelectric Schottky diode behavior from a SrRuO3-Pb(Zr0.2Ti0.8)O3-Ta structure  

NASA Astrophysics Data System (ADS)

A single ferroelectric Schottky diode was obtained on a SrRuO3-Pb(Zr0.2Ti0.8)O3-Ta (SRO-PZT20/80-Ta) structure in which the SRO-PZT20/80 interface is the rectifying contact and the PZT20/80-Ta interface behaves as a quasiohmic contact. Both the capacitance-voltage (C-V) and the current-voltage (I-V) characteristics show the memory effect due to the ferroelectric polarization. However, retention studies had revealed that only the “down” orientation of ferroelectric polarization is stable in time (polarization oriented from top to bottom contact). The analysis of the experimental results suggests that the PZT20/80 is n type and that the stable orientation of polarization is related to the presence of a depletion region at the SRO-PZT20/80 Schottky interface.

Pintilie, Lucian; Stancu, Viorica; Trupina, L.; Pintilie, Ioana

2010-08-01

278

Diodelike and resistive hysteresis behavior of heterolayered BiFeO3\\/ZnO ferroelectric thin films  

Microsoft Academic Search

BiFeO3\\/ZnO, ZnO\\/BiFeO3, BiFeO3\\/ZnO\\/BiFeO3, and ZnO\\/BiFeO3\\/ZnO thin film heterostructures were deposited on SrRuO3\\/Pt(111)\\/TiO2\\/SiO2\\/Si(100) substrates by off-axis radio frequency sputtering. Their diodelike and resistive hysteresis behavior are dependent on the combination sequence of the constituent layers in the heterostructures. Both the diodelike and resistive hysteresis behavior were clearly observed in BiFeO3\\/ZnO and ZnO\\/BiFeO3. The phenomena became more apparent with rising temperature. The

Jiagang Wu; John Wang

2010-01-01

279

Magnetoelectric effects in oxide magnetic tunnel junctions with ferroelectric barriers  

NASA Astrophysics Data System (ADS)

Functional properties of magnetic tunnel junction can be enhanced by employing a ferroelectric material as the barrier layer. We report on La0.7Sr0.3MnO3(LSMO)/BaTiO3(BTO)/LSMO magnetic tunnel junctions(MTJ) with BTO ferroelectric tunnel barrier. Switching BTO ferroelectric polarization influences the tunneling magnetoresistance (TMR) achieving two different r resistance states for each magnetic state (parallel or antiparallel) of the magnetization of the electrodes . The voltage dependence of the differential conductance obtained from IV curves displays oscillations whose period depends on the BTO electric polarization. This unusual behavior could be related to the presence of an induced magnetic moment in BTO ferroelectric barrier detected by XMCD measurements. These results reveal that spin polarization, and its tunneling conductance can be electrically tuned through reversal of the ferroelectric polarization of the barrier.

Tornos, Javier; Liu, Y. H.; Te Velthuis, S. G. E.; Fitzsimmons, M. R.; Rivera, A.; Lopez Anton, R.; Sanchez Santolino, G.; Varela Del Arco, M.; Nemes, N. M.; Pennycook, S. J.; Sefrioui, Z.; Yebra, C. Leon; Santamaria, J.

2013-03-01

280

Mechanically-induced resistive switching in ferroelectric tunnel junctions.  

PubMed

Recent advances in atomic-precision processing of oxide ferroelectrics-materials with a stable polarization that can be switched by an external electric field-have generated considerable interest due to rich physics associated with their fundamental properties and high potential for application in devices with enhanced functionality. One of the particularly promising phenomena is the tunneling electroresistance (TER) effect-polarization-dependent bistable resistance behavior of ferroelectric tunnel junctions (FTJ). Conventionally, the application of an electric field above the coercive field of the ferroelectric barrier is required to observe this phenomenon. Here, we report a mechanically induced TER effect in ultrathin ferroelectric films of BaTiO(3) facilitated by a large strain gradient induced by a tip of a scanning probe microscope (SPM). The obtained results represent a new paradigm for voltage-free control of electronic properties of nanoscale ferroelectrics and, more generally, complex oxide materials. PMID:23181389

Lu, H; Kim, D J; Bark, C-W; Ryu, S; Eom, C B; Tsymbal, E Y; Gruverman, A

2012-11-26

281

Ion implantation in perovskite type ferroelectrics  

Microsoft Academic Search

The object of this work was to study ion implantation in perovskite ferroelectrics and to investigate the conductive behavior of implanted layers. Implantation experiments were carried out on strontium titanate, barium titanate (single crystal and ceramic), titanium dioxide (rutile), lithium niobate, and lithium tantalate. Ion beams attempted were H(-), B(-), C(-), N(-), Fe(-), Ar(-), As(-), Ta(-), and Nb(--). In general

R. Gerson

1979-01-01

282

Negative longitudinal electrostriction in polycrystalline ferroelectrics: a nonlinear approach  

NASA Astrophysics Data System (ADS)

The longitudinal strains ?3 of initially unpoled polycrystalline (ceramic) ferroelectrics having different composition were measured as a function of the electric field strength E. The electric field dependences of the longitudinal piezoelectric coefficients d33(E) and longitudinal electrostriction coefficients M33(E) were calculated from the virgin ?3(E) curves and analysed. It was shown that taking into account the polarization nonlinearity (that is, the dependence of dielectric susceptibility on E) leads to nonmonotonic field dependences d33(E) and M33(E). In a nonlinear system, the electrostrictive effect is due not only to polarization but also to the dependence of dielectric susceptibility on the electric field strength. The large magnitude of the dielectric susceptibility of soft and relaxor ferroelectric ceramics is responsible for the giant electrostriction being positive in low electric fields and negative in strong ones. The possibility of giant negative electrostriction existing has been found for the first time. In strong electric fields, the strain gain has a limitation because of the competition between the positive contribution of the piezoelectric effect and the negative contribution of electrostriction to the strain.

Turik, A. V.; Yesis, A. A.; Reznitchenko, L. A.

2006-05-01

283

Effects of criticality and disorder on piezoelectric properties of ferroelectrics  

NASA Astrophysics Data System (ADS)

The piezoelectric response of BaTiO3 is studied in the vicinity of the cubic to tetragonal phase transition, as a function of temperature and the applied electric field in the polar direction. We also investigate the influence of disorder. In the clean limit we obtain the divergence of the piezoelectric tensor at the critical point. The effect of a small amount of disorder is to translate the critical point in the temperature-electric field phase diagram. For large values of the disorder, the paraelectric to ferroelectric phase transition becomes diffuse but a maximum of the piezoelectric tensor is still obtained even though the divergence of the piezoelectric response is lost. These results are in agreement with experimental observations for the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3. We use a Ginzburg-Landau model which explicitly includes the coupling of the polarization to the strain, the electrostatic interaction between polarizations, and a quenched random compressional stress field generated by point defects. The strain field and its associated elastic energy are written in terms of the stress field and the electric polarization by energy minimization subject to elastic compatibility.

Porta, Marcel; Lookman, Turab; Saxena, Avadh

2010-09-01

284

Statistical mechanical origin of hysteresis in ferroelectrics  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

285

Soft phonon columns on the edge of the Brillouin zone in the relaxor PbMg1/3Nb2/3O3  

NASA Astrophysics Data System (ADS)

We report lattice-dynamical measurements, made using neutron inelastic-scattering methods, of the relaxor perovskite PbMg1/3Nb2/3O3 (PMN) at momentum transfers near the edge of the Brillouin zone. Unusual “columns” of phonon scattering that are localized in momentum, but extended in energy, are seen at both high-symmetry points along the zone edge: Q?R={(1)/(2),(1)/(2),(1)/(2)} and Q?M={(1)/(2),(1)/(2),0} . These columns soften at ˜400K which is similar to the onset temperature of the zone-center diffuse scattering, indicating a competition between ferroelectric and antiferroelectric distortions. We propose a model for the atomic displacements associated with these phonon modes that is based on a combination of structure factors and group theoretical analysis. This analysis suggests that the scattering is not from tilt modes (rotational modes of oxygen octahedra), but from zone-boundary optic modes that are associated with the displacement of Pb2+ and O2- ions. Whereas similar columns of scattering have been reported in metallic and (less commonly) molecular systems, they are unusual in insulating materials, particularly in ferroelectrics; therefore, the physical origin of this inelastic feature in PMN is unknown. We speculate that the underlying disorder contributes to this unique anomaly.

Swainson, I. P.; Stock, C.; Gehring, P. M.; Xu, Guangyong; Hirota, K.; Qiu, Y.; Luo, H.; Zhao, X.; Li, J.-F.; Viehland, D.

2009-06-01

286

Soft Phonon Columns on the Edge of the Brillouin Zone in the Relaxor PbMg1/3Nb2/3O3  

SciTech Connect

We report lattice-dynamical measurements, made using neutron inelastic-scattering methods, of the relaxor perovskite PbMg{sub 1/3}Nb{sub 2/3}O{sub 3} (PMN) at momentum transfers near the edge of the Brillouin zone. Unusual 'columns' of phonon scattering that are localized in momentum, but extended in energy, are seen at both high-symmetry points along the zone edge: Q{sub R}={l_brace}1/2,1/2,1/2{r_brace} and Q{sub M}={l_brace}1/2,1/2,0{r_brace}. These columns soften at {approx}400 K which is similar to the onset temperature of the zone-center diffuse scattering, indicating a competition between ferroelectric and antiferroelectric distortions. We propose a model for the atomic displacements associated with these phonon modes that is based on a combination of structure factors and group theoretical analysis. This analysis suggests that the scattering is not from tilt modes (rotational modes of oxygen octahedra), but from zone-boundary optic modes that are associated with the displacement of Pb{sup 2+} and O{sup 2-} ions. Whereas similar columns of scattering have been reported in metallic and (less commonly) molecular systems, they are unusual in insulating materials, particularly in ferroelectrics; therefore, the physical origin of this inelastic feature in PMN is unknown. We speculate that the underlying disorder contributes to this unique anomaly.

Swainson, I.P.; Xu, G.; Stock, C.; Gehring, P.M.; Hirota, K.; Qiu, Y.; Luo, H.; Zhao, X.; Li, J.-F.; Viehland, D.

2009-06-01

287

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

288

Dielectric characteristics of the relaxor state of the perovskite ceramics 0.9(Na1 - x K x Bi)1/2TiO3-0.1Bi(ZnTi)1/2O3 near the morphotropic phase boundary  

NASA Astrophysics Data System (ADS)

X-ray diffraction investigations have revealed that, in the system of solid solutions 0.9(Na1 - x K x Bi)1/2TiO3-0.1Bi(ZnTi)1/2O3, there is a morphotropic phase boundary in the potassium concentration range of x ? 0.25, which separates the regions of compositions with rhombohedral ( R3 c) and tetragonal ( P4 mm) structures. It has been shown that, in the vicinity of this boundary, ceramic samples of the studied system exhibit properties of relaxor ferroelectrics. The results of the investigation into the dielectric properties of relaxor ceramics of the composition x = 0.3 with the use of the impedance spectra measured in the frequency range from 25 to 106 Hz at temperatures from 100 to 900 K have been presented. It has been found that, in the temperature region of the existence of the relaxor state lying below the temperature corresponding to the maximum of the real part of the permittivity ( T' m = 550 K), the dielectric polarization is determined by the sum of the contributions from the matrix and dipole clusters. The temperature dependence of the contribution from the clusters, which is determined by the kinetics of their formation and freezing, is characterized by a curve with the maximum at approximately 400 K. The process of freezing of dipole clusters occurs over an extended temperature range of more than 200 K.

Olekhnovich, N. M.; Pushkarev, A. V.; Radyush, Yu. V.

2013-10-01

289

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

2013-05-30

290

Structural study on ferroelectric phase transition of vinylidene fluoride-trifluoroethylene copolymers (III) dependence of transitional behavior on VDF molar content  

Microsoft Academic Search

Structural changes occurring in the ferroelectric phase transition of vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymers with the various VDF molar contents have been investigated by means of X-ray diffraction and infrared spectroscopic methods. The phase transition occurs among three crystal phases of the low-temperature (regular all-trans conformation), the high-temperature (gauche conformation with a large rotational motion), and the cooled phases (disordered trans

K. Tashiro; K. Takano; M. Kobayashi; Y. Chatani; H. Tadokoro

1984-01-01

291

Ferroelectric and Antiferroelectric Liquid Crystals  

Microsoft Academic Search

Ferroelectric liquid crystals have been a major research topic since 30 years. However, when it comes to liquid crystals, the term “ferroelectric” is strongly ambiguous and frequently not only leads to confusion and misunderstanding but also obscures the basic concepts.The property of ferroelectricity in liquid crystals was first claimed in 1975. Five years later so-called surface-stabilized ferroelectric liquid crystals were

SVEN T. LAGERWALL

2004-01-01

292

Physics of the ferroelectric nonvolatile memory field effect transistor  

SciTech Connect

The operation of the ferroelectric nonvolatile memory field effect transistor is theoretically examined extensively for the first time. The ferroelectric transistor device properties are derived by combining the silicon charge-sheet model of metal-oxide-semiconductor field-effect transistor device operation with Maxwell's first equation which describes the properties of the ferroelectric film. The model we present describes ferroelectric transistor {ital I}-{ital V} and {ital C}-{ital V} behavior when time-dependent voltages are applied which result in hysteresis due to ferroelectric switching. The theoretical results provide unique insight into the effects of geometrical and material parameters on the electrical properties of the transistor. These parameters include the ferroelectric spontaneous and remanent polarization, the coercive field, and dielectric layer thicknesses. We have found that the conventional concept of threshold voltage is no longer useful, and that increasing the spontaneous polarization has only a minor impact on memory operation due to reverse dipole switching of the ferroelectric layer. The application of the model to optimize design and fabrication parameters is illustrated with a virtual prototyping example. The model is also used to develop a practical testing methodology for this unique device.

Miller, S.L.; McWhorter, P.J. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1992-12-15

293

Influence of zirconium substitution on dielectric, ferroelectric and field-induced strain behaviors of lead-free 0.99[Bi1/2(Na0.82K0.18)1/2(Ti1- x Zr x )O3]-0.01LiSbO3 ceramics  

NASA Astrophysics Data System (ADS)

The Crystal structure, dielectric, ferroelectric and field-induced strain behaviors of lead-free 0.99[Bi1/2(Na0.82K0.18)1/2(Ti1- x Zr x )O3]-0.01LiSbO3 (BNKTZ-LS) ceramics were investigated in the composition range x = 0 - 0.040. XRD patterns revealed the formation of a pure perovskite phase with no apparent structural phase transition. The temperature-dependent dielectric peaks of the BNKTZ-LS ceramics broadened and the ferroelectric polarizations decreased with increasing Zr concentration. Ferroelectric and bipolar field induced-strain curves indicated a disruption of ferroelectric order upon Zr addition into the BNKT-LS ceramics. This destabilization of the ferroelectric order was accompanied by an enhanced field-induced strain. A high field-induced strain ( S = 0.30%) with a normalized strain ( d*33 = S max / E max = 500 pm/V) was observed at an applied electric field of 6 kV/mm at x = 0.020.

Zaman, A.; Iqbal, Y.; Hussain, A.; Ryu, G. H.; Song, T. K.; Kim, M. H.; Kim, W. J.

2012-09-01

294

Ferroelectric random access memories.  

PubMed

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

Ishiwara, Hiroshi

2012-10-01

295

Transmission electron microscopy of second-phase particles in Pb(Sc 1\\/2 Ta 1\\/2 )O 3 Ferroelectric ceramics  

Microsoft Academic Search

Pb-rich second-phase particles in perovskite-structured Pb(Sc1\\/2Ta1\\/2)O3 (PST) ferroelectric ceramic relaxors have been investigated using transmission electron microscopy. The second-phase particles were observed to exhibit a range of morphologies which included spheroidal inclusions, plate-like precipitates and intergranular films. Moiré fringes and lattice images have been used to identify various non-perovskite phases. It is deduced that excess PbO, which is used to

K. Z. Baba-Kishi; I. M. Reaney; D. J. Barber

1990-01-01

296

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

297

A Investigation of the Dielectric and Hysteresis Properties of Plzt Ferroelectric and Multilayer Composite Thin Films.  

NASA Astrophysics Data System (ADS)

The dielectric and hysteresis properties of ferroelectric and multilayer composite thin films were investigated. PLZT ferroelectrics were produced in bulk ceramic and thin film form from the same acetate precursor solutions in order to compare their electrical and physical properties. Bulk ceramics were hot pressed from chemically coprecipitated powders, and thin films were fabricated by spin and dip coating on Ag and Pt-coated Si substrates. Internal film stress from thermal expansion mismatch between films and substrates was found to contribute to differences in electrical properties and Curie temperatures between the thin film and bulk materials as were interface layer effects, grain size and mechanical clamping from the substrates. Rapid thermal processing (RTP) of PLZT thin films using an automated spin coat reactor was found to improve thin film dielectric and hysteresis properties as well as enhance perovskite phase formation, induce preferred (110) and (111) orientations, decrease grain size and increase microstructural uniformity. RTP films were compared with manually spin coated thin films with conventional furnace pyrolysis (CFP) in order to isolate the effects of heating rate from deposition technique. Heating rates of at least 70^circC per second were obtained by RTP versus 35^circC per second for CFP. The development of composite thin films further optimized PLZT thin film properties. Improved antiferroelectric -to-ferroelectric domain switching with decreased ferroelectric coercive field, increased induced polarization with decreased coercivity and polarization remanence for relaxor-type composites and increased hysteresis loop squareness for ferroelectric memory materials were among the advances compared with films of homogeneous PLZT composition. Experimental dielectric and hysteresis properties were described by a series capacitor model consisting of the linear and nonlinear properties of the individual composite components.

Dausch, David Edward

1995-01-01

298

Ferroelectric optical image comparator  

DOEpatents

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

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

1989-08-30

299

A ferroelectric memristor.  

PubMed

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

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

2012-09-16

300

A ferroelectric memristor  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

301

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

302

On the Development of Multiaxial Phenomenological Constitutive Laws for Ferroelectric Ceramics  

Microsoft Academic Search

Multiaxial constitutive laws for ferroelectric ceramics that include hysteresis, rate dependence, saturation, and are capable of simulating nonproportional loading are needed for stress analysis and reliable design of smart structures. The relationship between constitutive behavior of ferroelectric ceramics and phenomena that occur across multiple length scales is reviewed. A framework for the development of phenomenological constitutive laws at the macroscopic

Christopher S. Lynch

1998-01-01

303

Effects of silver incorporation on the dielectric and ferroelectric properties of PMN–PNN–PZT ceramics  

Microsoft Academic Search

The effects of silver addition on the sintering behavior, the dielectric, and ferroelectric properties of PMN–PNN–PZT piezoelectric ceramics for multilayer piezoelectric transformers were investigated. A small amount of silver promoted the sintering, but with more silver the density of the samples decreased. The silver incorporation affected the dielectric and ferroelectric properties of the samples. The dielectric constant presented an interesting

Ruzhong Zuo; Longtu Li; Xiaobing Hu; Zhilun Gui

2001-01-01

304

Ferroelectricity from magnetic order  

Microsoft Academic Search

Magnetic insulators with competing exchange interactions can give rise to strong fluctuations and qualitatively new ground states. The proximity of such systems to quantum critical points can lead to strong cross-coupling between magnetic long-range order and the chemical lattice. Case in point is a new class of multiferroic materials in which the magnetic and ferroelectric order parameters are directly coupled,

Michel Kenzelmann

2009-01-01

305

Interatomic Potentials: Ferroelectrics  

Microsoft Academic Search

Ferroelectric perovskites are important in many areas of modern technology including memories, sensors and electronic applications, and are of fundamental scientific interest. The fascinating feature of perovskites is that they exhibit a wide variety of structural phase transitions. Generically these compounds have a chemical formula ABO3, where A is a monovalent or divalent cation and B, a transition metal cation;

Marcelo Sepliarsky; Marcelo G. Stachiotti; Simon R. Phillpot

2005-01-01

306

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

PubMed

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

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

2012-02-21

307

Dynamic Local Distortions in Ferroelectrics  

NASA Astrophysics Data System (ADS)

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

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

1998-03-01

308

Monte Carlo simulation on rotation of ferroelectric polarization by rotating magnetic field in conical-spin-ordered multiferroics  

Microsoft Academic Search

To understand the rotation phenomenon of ferroelectric polarization (P) controlled by a magnetic field (h), which is currently of great interest in experiments, the variation of the magnetic and ferroelectric behaviors under rotating h are investigated by Monte Carlo simulation on a three-dimensional spinel lattice with classical Heisenberg spins. The anisotropic behaviors are observed for the different paths in which

Xiaoyan Yao; Qichang Li

2009-01-01

309

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

310

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

311

New Ferroelectric Aminoguanidinium Hexafluorozirconate  

Microsoft Academic Search

Satisfaction of structural criteria led to the prediction that anhydrous aminoguanidinium hexafluorozirconate CN_4H_8ZrF6 is a new ferroelectric. Calorimetric and dielectric permittivity measurements reveal a highly-reproducible anomaly at the Curie temperature Tc = 383(1) K. The heat capacity undergoes an entropy change of 0.7(1) J mol-1 K-1 at Tc as the relative permittivity increases sharply by nearly an order of magnitude.

Matt Bauer; Darin Arbogast; Craig Gallagher; Jim Christie; David Pugmire; Brian Paulsen; Charles Ross; Panos Photinos; Roger Nielson; Sidney C. Abrahams

2000-01-01

312

Ferroelectric electron beam sources  

SciTech Connect

Ferroelectric materials offer the possibility of compact electron sources, with modest requirements to initiate the emission process. We are studying such sources as possible injectors for microwave generation. The source consists of a polarized ferroelectric ceramic disk with silver electrodes coated on both faces. The front electrode consists of a periodic grid created by etching the silver to expose a line pattern of ceramic. This electrode functions as the cathode in a planar diode geometry with an accelerating gap adjustable from 0.1 to 5 cm. A rapid change in the polarization state of the ceramic is achieved by applying a 1{endash}2 kV, 150 ns pulse between the electrodes of the ferroelectric. Early work used a coaxial cable to maintain an anode potential of up to 1 kV across the A{endash}K gap. The emitted electron current was measured as a function of the gap spacing and the anode potential. The current varies linearly with the anode voltage, up to 1 kV, for gaps {much_gt}10 mm, and typically exceeds the Child-Langmuir current density by at least two orders of magnitude. Current densities in excess of 70 A/cm{sup 2} have been measured. More recent work has used a 300 ns pulse forming network to apply a potential of up to 15 kV at the anode. Results of emittance and scaling measurements under these conditions are reported. {copyright} 1995 {ital American Institute of Physics}.

Flechtner, D.; Flechtner, D.; Ivers, J.D.; Kerslick, G.S.; Nation, J.A.; Schaechter, L.; Zhang, G. [Laboratory of Plasma Studies and School of Electrical Engineering, Cornell University, Ithaca, New York 14853 (United States)

1995-06-01

313

Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites  

NASA Astrophysics Data System (ADS)

Particulate composites of ferrite and ferroelectric phases with xNiFe2O4 (NF) and (1 - x)Pb0.988(Zr0.52Ti0.48)0.976Nb0.024O3 (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 °C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.

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

2013-02-01

314

Ferroelectric Based Technologies for Accelerators  

Microsoft Academic Search

Ferroelectrics have unique intrinsic properties that make them extremely attractive for high-energy accelerator applications. Low loss ferroelectric materials can be used as key elements in RF tuning and phase shifting components to provide fast, electronic control. These devices are under development for different accelerator applications for the X, Ka and L-frequency bands. The exact design of these devices depends on

A. Kanareykin; E. Nenasheva; S. Kazakov; A. Kozyrev; A. Tagantsev; V. Yakovlev; C. Jing

2009-01-01

315

Piezoelectricity, ferroelectricity, and crystal structure  

Microsoft Academic Search

By visualizing polar crystals as a network of permanent dipole moments, the piezo- and ferroelectric properties of dielectrics may be derived from the standpoint of molecular symmetry. This approach is used to clarify the relation between the sphalerite and wurtzite structures, the ferroelectric feedback effect in barium titanate, aspects of domain formation, and the interrelationship between ferro and piezoelectricity.

A. von Hippel

1952-01-01

316

Ferroelectricity in Ultrathin Perovskite Films  

Microsoft Academic Search

Understanding the suppression of ferroelectricity in perovskite thin films is a fundamental issue that has remained unresolved for decades. We report a synchrotron x-ray study of lead titanate as a function of temperature and film thickness for films as thin as a single unit cell. At room temperature, the ferroelectric phase is stable for thicknesses down to 3 unit cells

Dillon D. Fong; G. Brian Stephenson; Stephen K. Streiffer; Jeffrey A. Eastman; Orlando Auciello; Paul H. Fuoss; Carol Thompson

2004-01-01

317

Plasma etch processing of advanced ferroelectric devices  

Microsoft Academic Search

Ferroelectric structures are being used in SRAM devices and are migrating to DRAM devices. A DRAM cell size can be dramatically reduced by employing ferroelectric structures in place of the current silicon oxide capacitor structures. A 5? DRAM cell capacitor can be reduced in size by a factor of 20 using a ferroelectric structure.The current technology used to etch ferroelectric

Alferd Cofer; Paritosh Rajora; Steve Deornellas; Doug Keil

1997-01-01

318

CMOS Equivalent Model of Ferroelectric RAM  

Microsoft Academic Search

The current research work in the paper is the representation of FRAM (Ferroelectric Random Access Memory) as an equivalent Model of Ferroelectric memory cell in Spice Tool. This Equivalent CMOS based model is designed to work at par with the behaviour working of the FRAM. The crux of the design of ferroelectric capacitor in the Ferroelectric Random Access Memory lies

Parvinder S. Sandhu; Iqbaldeep Kaur; Amit Verma; Birinderjit S. Kalyan; Jagdeep Kaur; Sanyam Anand

2010-01-01

319

Effects of doping on ferroelectric properties and leakage current behavior of KNN-LT-LS thin films on SrTiO3 substrate  

NASA Astrophysics Data System (ADS)

We report the effects of Ba, Ti, and Mn dopants on ferroelectric polarization and leakage current of (K0.44Na0.52Li0.04)(Nb0.84Ta0.1Sb0.06)O3 (KNN-LT-LS) thin films deposited by pulsed laser deposition. It is shown that donor dopants such as Ba2+, which increased the resistivity in bulk KNN-LT-LS, had an opposite effect in the thin film. Ti4+ as an acceptor B-site dopant reduces the leakage current by an order of magnitude, while the polarization values showed a slight degradation. Mn4+, however, was found to effectively suppress the leakage current by over two orders of magnitude while enhancing the polarization, with 15 and 23 ?C/cm2 remanent and saturated polarization, whose values are ~70% and 82% of the reported values for bulk composition. This phenomenon has been associated with the dual effect of Mn4+ in KNN-LT-LS thin film, by substituting both A- and B-site cations. A detailed description on how each dopant affects the concentrations of vacancies in the lattice is presented. Mn-doped KNN-LT-LS thin films are shown to be a promising candidate for lead-free thin films and applications.

Abazari, M.; Safari, A.

2009-05-01

320

Octahedral rotation-induced ferroelectricity in cation ordered perovskites.  

PubMed

Electronic structure calculations based on density functional theory have uncovered a novel mechanism for inducing ferroelectric polarizations in cation ordered perovskites. We outline a materials selection strategy for designing this behavior. The guidelines are based on the octahedral rotations found in the two constituent oxides and the way the perovskite building blocks are interwoven to form the superlattice. PMID:22488734

Rondinelli, James M; Fennie, Craig J

2012-04-17

321

Coulomb-driven cluster-glass behavior in Mn-intercalated Ti1+yS2  

NASA Astrophysics Data System (ADS)

We have investigated the low-temperature spin-glasslike phase in the intercalated transition-metal dichalcogenide Mn0.09Ti1.1S2. A departure from Curie-Weiss behavior in the paramagnetic regime indicated the formation of small ferromagnetically correlated clusters. The Vogel-Fulcher law provided an excellent description of relaxation times in the vicinity of the transition, showing that the glasslike phase occurs due to interaction between the clusters. Cole-Cole plots for data close to the transition were linear, which is consistent with a simple exponential distribution of cluster sizes. A Monte Carlo simulation of the dichalcogenide system, including excess self-intercalated Ti ions, gave an exponential cluster-size distribution for a relatively narrow range of concentration values of Mn and Ti ions, values that were consistent with those of the Mn0.09Ti1.1S2 sample. Strong commonality in the relaxation behavior with certain ferroelectric relaxor systems suggests underlying similarity in the microscopic structure of the clusters in both systems, which may be chainlike or quasi-one-dimensional.

Shand, P. M.; Meyer, A. L.; Streicher, M.; Wilson, A.; Rash, T.; Roth, M. W.; Kidd, T. E.; Strauss, L. H.

2012-04-01

322

Diffuse phase transition and dielectric tunability of Ba(Zr y Ti 1? y )O 3 relaxor ferroelectric ceramics  

Microsoft Academic Search

Barium zirconate titanate Ba(ZryTi1?y)O3 (BZT, y=0.2, 0.25, 0.30, 0.35) ceramics have been prepared by a sol–gel process. The temperature dependence of dielectric permittivity of the ceramics has been investigated. The results show that the phase transition temperature TC (or Tm) is suppressed with increasing Zr content. The degree of diffuseness of the phase transition is more pronounced for higher Zr

X. G. Tang; K.-H. Chew; H. L. W. Chan

2004-01-01

323

Temperature dependence of the direct piezoelectric effect in relaxor-ferroelectric single crystals: Intrinsic and extrinsic contributions  

NASA Astrophysics Data System (ADS)

The direct piezoelectric response d33 of [001]C-poled 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3 [PZN-4.5PT] and 0.98Pb(Zn1/3Nb2/3)O3-0.08PbTiO3 [PZN-8PT] has been investigated as a function of temperature upon heating above 40 °C to the paraelectric phase. Using a Rayleigh-law based analysis, it is shown that both the reversible/intrinsic and irreversible (extrinsic) contributions to the response increase in both compositions as the phase transition to a tetragonal phase is approached. The latter is likely due to an increased domain wall mobility close to the first order transition temperature, which also gives rise to an increased frequency dispersion. Large reversible direct piezoelectric responses d33>1600pm/V are observed for both compositions, which increase dramatically close to the transition temperature. Most importantly, the reversible contribution is always much larger than the irreversible part in the low temperature, domain-engineered phase, the latter accounting for around 20% of the response in PZN-8PT, at 40 °C, and 5% in PZN-4.5PT. The importance of this result to the validity of the adaptive phase model is discussed.

Davis, Matthew; Damjanovic, Dragan; Setter, Nava

2006-10-01

324

Energy harvesting by nonlinear capacitance variation for a relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer  

NASA Astrophysics Data System (ADS)

The present letter describes the investigation of the electrostatic energy harvesting through nonlinear capacitance variation caused by changes in temperature for a poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) [P(VDF-TrFE-CFE)] terpolymer. Owing to the electric tunability of the terpolymer, the harvested energy can-using an Ericsson cycle-be simulated from permittivity under a dc electric field. When going from 25 to 0 °C, it was found, from simulation, that the harvested energy increased up to 240 mJ/cm3 when raising the electric field at 80 kV/mm. Experimental measurement was also carried out, thus confirming the feasibility of electrostatic energy harvesting through low temperature Ericsson cycle.

Zhu, H.; Pruvost, S.; Cottinet, P. J.; Guyomar, D.

2011-05-01

325

LETTER TO THE EDITOR: Absence of true critical exponents in relaxor ferroelectrics: the case for nanodomain freezing  

NASA Astrophysics Data System (ADS)

Scott's (2006 J. Phys.: Condens. Matter 18 7123) recent review of Kleemann et al' s (2002 Europhys. Lett. 57 14) critical exponents of strontium barium niobate is shown to be misled by erroneous input parameters. Although the observed set of exponents reflects, indeed, the absence of true three-dimensional (3D) random-field Ising model critical behaviour, it cannot be compatible with the proposed domain wall model in d = 2.5 dimensions or with Levanyuk and Sigov's (1988 Defects and Structural Phase Transitions (London: Gordon and Breach)) defect model. As was argued independently by Kleemann et al (2006 Phys. Rev. Lett. 97 065702), it is rather in agreement with the pure two-dimensional (2D) Ising model.

Kleemann, Wolfgang

2006-10-01

326

LETTER TO THE EDITOR: Absence of true critical exponents in relaxor ferroelectrics: the case for nanodomain freezing  

Microsoft Academic Search

Scott's (2006 J. Phys.: Condens. Matter 18 7123) recent review of Kleemann et al' s (2002 Europhys. Lett. 57 14) critical exponents of strontium barium niobate is shown to be misled by erroneous input parameters. Although the observed set of exponents reflects, indeed, the absence of true three-dimensional (3D) random-field Ising model critical behaviour, it cannot be compatible with the

Wolfgang Kleemann

2006-01-01

327

Magnetic-field dependence of the ferroelectric polarization and spin-lattice coupling in multiferroic MnWO4  

NASA Astrophysics Data System (ADS)

The magnetic-field dependence of the ferroelectric polarization and the spin-lattice coupling in multiferroic MnWO4 have been investigated. The ferroelectric transition from the low temperature paraelectric phase occurs when the magnetic field is applied along the a , c , and the spin easy axes. The ferroelectric polarization in the magnetic field along the a and the c axis shows a contrasting behavior depending on the field direction, possibly reflecting the relative configuration between the crystallographic axis and the magnetic principal axis in the ac plane. Incommensurate lattice modulation observed in the ferroelectric spiral-spin phase confirms the existence of spin-lattice coupling in MnWO4 . The lattice modulation indicates that the ferroelectric AF2 phase also takes the incommensurate magnetic structure in a magnetic field. In the high-field phase, which appears in high magnetic fields above 12T along the easy axis, the magnetic-field-induced ferroelectric polarization disappeared.

Taniguchi, K.; Abe, N.; Sagayama, H.; Ohtani, S.; Takenobu, T.; Iwasa, Y.; Arima, T.

2008-02-01

328

Ferroelectricity in one unit-cell period oxide superlattices  

NASA Astrophysics Data System (ADS)

We present electric properties of one unit-cell period superlattices composed of CaTiO3 (CTO), SrTiO3 (STO), and BaTiO3 (BTO) perovskites, in which the structural symmetry and lattice misfit strain can be systematically varied without changing the chemical valence states. The one unit-cell period CTO/BTO, BTO/STO, and CTO/STO superlattices were grown by high oxygen pressure pulsed laser deposition on atomically flat SrRuO3 conducting oxide grown on STO (001) substrates. CTO/BTO and BTO/STO showed ferroelectricity in room temperature, while CTO/STO showed paraelectric behavior. Such spontaneous electric polarization was an unexpected result, because all TiO6 octahedron was not in the same structural condition with ferroelectric BTO, but was sandwiched by CaO (SrO) and BaO layers in these superlattices. By performing first principle calculations, ferroelectric ground states can be found in the distorted TiO6. Moreover, the ferroelectricity was described as the collective displacement of the titanium-oxygen-titanium ions, which is different from that of bulk ferroelectric material.

Noh, T. W.; Lee, J. H.; Lee, H. N.

2005-03-01

329

Ferroelectric Based Technologies for Accelerators  

NASA Astrophysics Data System (ADS)

Ferroelectrics have unique intrinsic properties that make them extremely attractive for high-energy accelerator applications. Low loss ferroelectric materials can be used as key elements in RF tuning and phase shifting components to provide fast, electronic control. These devices are under development for different accelerator applications for the X, Ka and L-frequency bands. The exact design of these devices depends on the electrical parameters of the particular ferroelectric material to be used-its dielectric constant, loss tangent and tunability. BST based ferroelectric-oxide compounds have been found to be suitable materials for a fast electrically-controlled tuners. We present recent results on the development of BST based ferroelectric compositions synthesized for use in high power technology components. The BST(M) ferroelectrics have been tested using both transverse and parallel dc bias fields to control the permittivity. Fast switching of a newly developed material has been shown and the feasibility of using of ferroelectric-based accelerator components in vacuum and in air has been demonstrated.

Kanareykin, A.; Nenasheva, E.; Kazakov, S.; Kozyrev, A.; Tagantsev, A.; Yakovlev, V.; Jing, C.

2009-01-01

330

Ferroelectric Based Technologies for Accelerators  

SciTech Connect

Ferroelectrics have unique intrinsic properties that make them extremely attractive for high-energy accelerator applications. Low loss ferroelectric materials can be used as key elements in RF tuning and phase shifting components to provide fast, electronic control. These devices are under development for different accelerator applications for the X, Ka and L-frequency bands. The exact design of these devices depends on the electrical parameters of the particular ferroelectric material to be used--its dielectric constant, loss tangent and tunability. BST based ferroelectric-oxide compounds have been found to be suitable materials for a fast electrically-controlled tuners. We present recent results on the development of BST based ferroelectric compositions synthesized for use in high power technology components. The BST(M) ferroelectrics have been tested using both transverse and parallel dc bias fields to control the permittivity. Fast switching of a newly developed material has been shown and the feasibility of using of ferroelectric-based accelerator components in vacuum and in air has been demonstrated.

Kanareykin, A.; Jing, C. [Euclid Techlabs LLC, Rockville, MD 20850 (United States); Nenasheva, E. [Ceramics Co. Ltd, St. Petersburg 194223 (Russian Federation); Kazakov, S. [KEK Tsukuba, 305-0801 Japan/Omega-P Inc., New Haven, CT 06511 (United States); Kozyrev, A. [St. Petersburg Electrical Engineering University, St. Petersburg 197376 (Russian Federation); Tagantsev, A. [EPFL, 1015 Lausanne (Switzerland); Yakovlev, V. [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)

2009-01-22

331

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 \\ehr 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

332

The effects of nonhydrostatic compression and applied electric field on the electromechanical behavior of poled lead zirconate titanate 95/5-2Nb ceramic during the ferroelectric to antiferroelectric polymorphic transformation  

SciTech Connect

We conducted hydrostatic compression and constant-stress-difference experiments, with and without an applied electric field, on poled, niobium-doped lead zirconate titanate ceramic. The objective was to quantify the effects of nonhydrostatic stress and electric field bias on electromechanical behavior of the ceramic during the ferroelectric, rhombohedral {r_arrow} antiferroelectric, orthorhombic phase transformation. Increasing stress difference (shear stress) decreases the mean stress at which the transformation occurs. Increasing shear stress also retards the rate of transformation, causing reductions in both the rate of charge release and peak voltage attained during depoling. Application of the electric field bias slightly increases the transformation pressure for poled ceramic. Previously, we showed that under nonhydrostatic stress, the transformation took place in {ital unpoled} ceramic when the maximum compressive stress equalled the hydrostatic pressure at which the transformation would otherwise occur. This simple stress criterion does not apply to poled ceramic. However, poled material has a preferred crystallographic orientation and mechanical anisotropy, whereas unpoled ceramic is isotropic. We present a qualitative model for the transformation under nonhydrostatic stress-related to that anisotropy, which resolves these seemingly disparate observations. {copyright} {ital 1999 Materials Research Society.}

Zeuch, D.M.; Holcomb, D.J. [Geomechanics Department 6117, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] Montgomery, S.T. [Integrated Product Development Department 1567, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

1999-05-01

333

Multigap Semiconducting ferroelectric perovskites  

NASA Astrophysics Data System (ADS)

The energy conversion efficiency of a solar cell is directly related to the band gap of the material. By doping ferroelectric perovskites with Bi^5+ on the B-site, we propose low band-gap materials suitable for bulk photovoltaic effect and related solar applications.Our DFT calculations indicate that the low-lying 6s empty states of the electronegative Bi atom produce empty isolated bands in the gap of the parent materials, effectively lowering the band gap by 1˜2eV in various perovskites. Ferroelectricity (and therefore inversion symmetry breaking) weakens but survives upon doping, which enables the ``shift current'' mechanism for photocurrent generation, while the decreased band gap helps absorb low energy photons in the visible range. Furthermore, the existence of multiple band gaps allows for solar conversion devices with efficiency beyond the traditional Shockly-Queisser limit, in which successive photon excitations result in carriers with higher energy than a single-step excitation would achieve.

Jiang, Lai; Grinberg, Ilya; Wang, Fenggong; Davies, Peter; Rappe, Andrew

2013-03-01

334

Ferroelectric Thin Films for Electronic Applications  

NASA Astrophysics Data System (ADS)

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

Udayakumar, K. R.

335

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

SciTech Connect

The temperature evolution of the nanoscale structure of PbSc{sub 0.5}Nb{sub 0.5}O{sub 3} (PSN) and (Pb,A{sup ''})Sc{sub 0.5}Nb{sub 0.5}O{sub 3}, (A{sup ''}=Ba,Bi) is analyzed by applying synchrotron single-crystal and high-resolution powder x-ray diffraction as well as polarized Raman spectroscopy. The study compares the effect of incorporation of two-valent cations with isotropic electron structure (Ba{sup 2+}) and three-valent cations with stereochemically active lone pairs (Bi{sup 3+}) on the structure of Pb-based perovskite-type relaxor ferroelectrics. The results reveal that the violation of the host system of cations with lone-pair electrons (Pb{sup 2+}), i.e., the reduction in ferroic species with coherent off-centered Pb atoms, is the major factor for the suppression of long-range ferroelectric ordering at low temperatures. The local charge imbalance associated with A site chemical disorder has negligible impact on the development of ferroelectric order if the second type of A-positioned cations also forms lone-pair electrons. The substitution of Bi{sup 3+} for Pb{sup 2+} even enhances the cubic-to-ferroelectric transformation processes in PSN and results in a structural state consisting of abundant ferroelectric domains, which are large enough to be identified by polarized Raman spectroscopy as crystalline, but with an average size close to the intrinsic detection limit of synchrotron single-crystal x-ray diffraction.

Maier, B.; Mihailova, B.; Paulmann, C.; Bismayer, U. [Mineralogisch-Petrographisches Institut, Universitaet Hamburg, Grindelallee 48, D-20146 Hamburg (Germany); Ihringer, J. [Institut fuer Angewandte Physik, Universitaet Tuebingen, Auf der Morgenstelle 10, 72076 Tuebingen (Germany); Gospodinov, M. [Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chausse 72, 1784 Sofia (Bulgaria); Stosch, R.; Guettler, B. [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)

2009-06-01

336

Fracture mechanics of ferroelectric ceramics  

NASA Astrophysics Data System (ADS)

The reliable operation of smart devices and structures depends on the integrity of the materials chosen for sensor and actuator components. Though piezoelectric ceramics rank among the most common transducer materials, their mechanical reliability has yet to be characterized adequately. The difficulty stems from a basic discrepancy between theoretical predictions and empirical observations of their fracture behavior. For instance, experiments conducted on transversely isotropic piezoceramics with cracks normal to the poling axis show an odd functional dependence between the failure load and the applied electric field, but the linear fracture analysis indicates an even relation. In tests performed on unpoled ferroelectric ceramics, an applied voltage appears to promote cracking, while the linear theory predicts no such effect. In an effort to reconcile theory with experience, we present two physics-based models for the polarization switching and saturation that dominate material nonlinearity in these ceramics. In the first, we separate the length scales of the electrical yielding zone and the fracture process zone, and represent the electrical nonlinearity using discrete dipoles superimposed on a homogeneous piezoelectric medium. The multiscale framework reveals a singularity conversion, from apparent electromechanical intensities at the global level to purely mechanical effective opening forces in the local view. By restricting the nonlinearity to a plane passing through the crack front, we derive a closed-form expression for the driving force in terms of the local stress intensities. The resulting fracture criterion is independent of the microstructural parameters, and it predicts a dependence of critical stress on electric field that qualitatively matches the empirically observed trends. In the second model, we remove the geometrical restrictions on the nonlinear region, and include the effects of the transformation strains induced by polarization switching. Local domain interactions are simulated using combinations of electric dipoles and force couples affixed to an isotropic background medium, and domain orientations are changed when an electromechanical energy threshold is exceeded. The model successfully reproduces the hysteresis and butterfly loops typically measured in ferroelectric ceramics. Furthermore, our simulations predict an influence of near-tip domains on crack-opening stresses that explains the effect of voltage on apparent strength reported in experiments.

Fulton, Chandler Chang-Il

337

Ferroelectric polarization in the magnetic world  

NASA Astrophysics Data System (ADS)

Switchable spontaneous polarization in ferroelectrics is produced by a structural distortion of a high-symmetry reference phase which lowers the symmetry to a polar space group. Under certain conditions, this structural distortion and symmetry breaking can also induce ferromagnetism and other changes, such as a metal-insulator transition, allowing the possibility of electric and magnetic field control. In this talk, I will present first-principles illustrations of specific materials realizations of the rich variety of this behavior in magnetic perovskite oxides, identified using a database of first-principles calculations of the full phonon dispersions of a range of magnetic perovskites, including the d3 compounds SrMnO3and SrCaO3, the d5 compounds BiFeO3, and the series SrMO3 (M= V, Cr, Mn, Fe, Co). First, I will discuss an epitaxial-strain-induced multiferroic phase produced by large spin-phonon coupling in SrMnO3 [1]. Then, I will turn to colossal magnetoresistance based on a ferromagnetic- metal/antiferromagnetic-ferroelectric phase boundary with epitaxial strain in SrCoO3, which exhibits typical ferromagnetic metallic character in room-temperature but with a large spin-phonon coupling by which antiferromagnetic ordering favors a polar distortion. Lastly, I will discuss the identification of perovskite superlattice systems in which the symmetry lowering produced layer-by-layer ordering produces a phase with ferroelectrically-induced weak ferromagnetism. I will present first-principles calculations demonstrating these behaviors in BaMnO3/SrMnO3 superlattices and other systems which could provide robust experimental realizations. [4pt] [1] J. H. Lee and K. M. Rabe, "Epitaxial-strain-induced multiferroicity in SrMnO3 from first principles," Phys. Rev. Lett. 104, 207204 (2010)

Lee, Jun Hee

2011-03-01

338

Relaxor Dielectric Materials for Multilayer Ceramic Capacitor in High-Temperature Applications  

Microsoft Academic Search

A relaxor ceramic dielectric based on the (Pb, Ba)[(Zn1\\/3Nb2\\/3)(Mg1\\/3Nb2\\/3)Ti]O3 system has been developed for multilayer ceramic capacitors (MLC) in high-temperature applications. This dielectric material is designed to exhibit a capacitance peak value at around 60° C, which is a typical temperature inside a switching mode power supply (SMPS). An MLC fabricated using this new dielectric and fired at 1050° C

Yohachi Yamashita; Hideyuki Kanai; Osamu Furukawa; Kouichi Hasegawa; Satoshi Mukaeda; Kiyoji Handa

1995-01-01

339

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

340

Transparent Ferroelectric Glass-Ceramics  

Microsoft Academic Search

In recent years, there has been a resurgence of interest in transparent ferroelectric glass-ceramics (TFGCs), which are a special class of glass-ceramic composites that combine the low cost of fabrication and forming of transparent glass with the superior nonlinear optical and electro-optical properties of ferroelectric crystals. In this paper, we present a review of the current status, focusing on the

H. JAIN

2004-01-01

341

Fresnoite: A new ferroelectric mineral  

Microsoft Academic Search

Fresnoite, Ba2TiOSi2O7, has been predicted structurally to be a new ferroelectric. Detection of both ac and dc dielectric hysteresis verifies the prediction. The spontaneous polarization Ps estimated from the hysteresis at 1.2 MV m-1 ac is ~0.2 C m-2 at 295 K, comparable with the minimum Ps observed in one-dimensional ferroelectrics. A reproducible calorimetric anomaly with entropy change 0.19(3) J

M. C. Foster; D. J. Arbogast; R. M. Nielson; P. Photinos; S. C. Abrahams

1999-01-01

342

Monte Carlo simulation of ferroelectric domain structure: Electrostatic and elastic strain energy contributions  

SciTech Connect

A lattice-Monte Carlo approach was developed to simulate ferroelectric domain behavior. The model utilizes a Hamiltonian for the total energy that includes electrostatic terms (involving dipole-dipole interactions, local polarization gradients, and applied electric field), and elastic strain energy. The contributions of these energy components to the domain structure and to the overall applied field response of the system were examined. In general, the model exhibited domain structure characteristics consistent with those observed in a tetragonally distorted ferroelectric. Good qualitative agreement between the appearance of simulated electrical hysteresis loops and those characteristic of real ferroelectric materials was found.

POTTER JR.,BARRETT G.; TUTTLE,BRUCE A.; TIKARE,VEENA

2000-04-04

343

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

344

Monte Carlo Simulation of Ferroelectric Domain Structure and Applied Field Response in Two Dimensions  

SciTech Connect

A 2-D, lattice-Monte Carlo approach was developed to simulate ferroelectric domain structure. The model currently utilizes a Hamiltonian for the total energy based only upon electrostatic terms involving dipole-dipole interactions, local polarization gradients and the influence of applied electric fields. The impact of boundary conditions on the domain configurations obtained was also examined. In general, the model exhibits domain structure characteristics consistent with those observed in a tetragonally distorted ferroelectric. The model was also extended to enable the simulation of ferroelectric hysteresis behavior. Simulated hysteresis loops were found to be very similar in appearance to those observed experimentally in actual materials. This qualitative agreement between the simulated hysteresis loop characteristics and real ferroelectric behavior was also confirmed in simulations run over a range of simulation temperatures and applied field frequencies.

Potter, Jr., B.G.; Tikare, V.; Tuttle, B.A.

1999-06-30

345

Effective Conductivity due to Continuous Polarization Reorientation in Fluid Ferroelectrics  

NASA Astrophysics Data System (ADS)

In crystal ferroelectrics, the macroscopic polarization density P is stabilized to a set of discrete orientations by the underlying lattice, and ferroelectricity characterized by field-induced switching of P between these stable states. Fluid ferroelectrics exhibit P with no energy barriers to its reorientation. As a result, P can respond to applied electric field in a continuous fashion. We show here that, due to the reorientation of P, an otherwise insulating fluid ferroelectric behaves electrically as a resistive medium, with conductivity in the semiconducting range. Measurements of cell dynamics are reported for the SmAPF material W623, a bent-core liquid crystal (LC) with large macroscopic polarization that we find to exhibit nearly ideal field-induced block polarization reorientation. We have investigated theoretically the dynamic behavior of block polarization in the SmAPF phase, finding that a reorienting LC polarization block behaves electrically as a resistor. Experimental studies of W623 confirm this behavior, revealing the low resistance of the block-reorienting LC and the corresponding characteristic flat-topped step in the current response.

Maclennan, Joseph; Shen, Yongqiang; Gong, Tao; Shao, Renfan; Korblova, Eva; Walba, David; Clark, Noel

2012-02-01

346

Local surface potential distribution and its relaxation in ferroelectric poly(vinylidenefluoride-co-trifluoroethylene) thin films  

NASA Astrophysics Data System (ADS)

Local surface potential distributions and their relaxation behavior in ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) thin films were investigated using Kelvin-probe force microscopy. All surface potentials were negative regardless of the sign of the applied voltage because of the intrinsic negative charges that originated from the self-aligned region of dipoles at the ferroelectric/electrode interface. Importantly, the intrinsic charges would have a remarkable influence on the reliability of written data.

Choi, Hyunwoo; Hong, Jongin; No, Kwangsoo

2012-07-01

347

Ferroelectric Tape Recording and Reproducing Processes.  

National Technical Information Service (NTIS)

The development in recent years of ferroelectric materials suggests the possibility of a new method of tape recording. It is the purpose of the study to investigate this possibility. After a theoretical discussion of ferroelectricity, and of tape recordin...

T. S. Yu

1964-01-01

348

Transparent ferroelectric ceramics PbMg1/3Nb2/3O3- xPbZr0.53Ti0.47O3: Dielectric and electro-optical properties  

NASA Astrophysics Data System (ADS)

Lanthanum-free high-transparency ferroelectric ceramics PbMg1/3Nb2/3O3- xPbZr0.53Ti0.47O3 (PMN- xPZT) have been prepared for the first time by a two-stage sintering method. The dielectric and electro-optical properties of the PMN- xPZT ceramics of different compositions, with the values of x both far from the morphotropic phase boundary ( x = 10, 16, 23%) and close to it ( x = 33%), have been studied. It has been shown that, in compositions lying closer to the morphotropic phase boundary ( x = 23 and 33%), one observes, with no electric field applied, a first-order phase transition to a macrodomain ferroelectric phase, whereas the compositions far from the boundary ( x = 10, 16%) persist in the relaxor cubic phase down to the low-temperature domain. It has been found that, in the ceramic with x = 33%, the quadratic electro-optical coefficients have at high temperatures ( T > 340 K) the largest value among the relaxor systems, which expands the temperature interval of applicability of these solid solutions in industry.

Kamzina, L. S.; Ruan, Wei; Li, Guorong; Zeng, Jiangtao

2012-10-01

349

Effect of Ferroelectric Polarization Domain Structure on Electronic Transport Property of Ferroelectric\\/ZnO Heterostructure  

Microsoft Academic Search

To discuss the effect of the ferroelectric domain structure on the electronic transport property in the channel of a ferroelectric gate thin film transistor, the electrical property of the ferroelectric gate stack structure of an organic ferroelectric copolymer of vinylidenefluoride and tetrafluoroethylene [P(VDF--TeFE)] and ZnO was investigated. Unlike the gate stack structure using a paraelectric layer, ferroelectrics possibly affect the

Hiroaki Yamada; Tadahiro Fukushima; Takeshi Yoshimura; Norifumi Fujimura

2011-01-01

350

Hysteretic resistance concepts in ferroelectric thin films  

Microsoft Academic Search

Hysteretic resistance effects based on a correlation between ferroelectric polarization and conductivity might become of particular interest for nonvolatile memory applications, because they are not subject to the scaling restrictions of charge based memories such as the ferroelectric random access memory. Two basic concepts, a metal-ferroelectric-metal structure and a metal-ferroelectric-semiconductor structure are discussed in the literature. This contribution discusses the

René Meyer; Rainer Waser

2006-01-01

351

Thin-film ferroelectric microwave devices  

Microsoft Academic Search

When an electric field is applied to a ferroelectric material, the microwave permittivity undergoes a substantial change. This change in permittivity can be utilized in microwave devices to produce frequency-agile functions. This paper is a comprehensive review of the work on ferroelectric materials; this includes models of the ferroelectric permittivity and loss tangent, as well as methods of measurement of

M. J. Lancaster; J. Powell; A. Porch

1998-01-01

352

Nature of Ferroelectricity in KNO3  

Microsoft Academic Search

The lattice parameters of KNO3 were measured in the temperature region of the ferroelectric transition. The changes in the lattice parameters as the crystal undergoes the paraelectric-to-ferroelectric transition have been interpreted as being due to the electrostriction effect. The dielectric constants and losses along the ferroelectric axis have been measured in the audio, megacycle, and microwave frequency regions. The occurrence

Arthur Chen; Fred Chernow

1967-01-01

353

Analyses and syntheses of ferroelectric refrigeration ceramics  

Microsoft Academic Search

Cryogenic refrigeration could be realized by using the electrocaloric effect (i. e. inverse pyroelectric effect) of ferroelectric materials. Recent progresses implied that ferroelectric refrigeration may be a possible new technique of cryogenic refrigeration operated near room temperature. The analyses and syntheses of ferroelectric refrigeration ceramics of PMN-PT system are presented in this paper

D. Q. Xiao; B. Yang; S. Q. Peng; Y. C. Wang; J. G. Zhu

1997-01-01

354

Improper ferroelectricity in perovskite oxide artificial superlattices  

Microsoft Academic Search

Ferroelectric thin films and superlattices are currently the subject of intensive research because of the interest they raise for technological applications and also because their properties are of fundamental scientific importance. Ferroelectric superlattices allow the tuning of the ferroelectric properties while maintaining perfect crystal structure and a coherent strain, even throughout relatively thick samples. This tuning is achieved in practice

Matthew Dawber; Celine Lichtensteiger; Patrick Hermet; Stefano Gariglio; Jean-Marc Triscone; Philippe Ghosez

2008-01-01

355

Inorganic ceramic\\/polymer ferroelectric composite electrets  

Microsoft Academic Search

Ferroelectric composites are now an established alternative to conventional ferroelectric ceramic materials and to the more recently discovered ferroelectric polymers. These materials due to their unique blending of polymetric properties of mechanical flexibility, formability and low cost with high electro-active properties have been been suggested to be a viable alternative both in piezoelectric and pyroelectric transducer applications. This review is

C. J. Dias; D. K. Das-Gupta

1996-01-01

356

Multiferroic composite ferroelectric-ferromagnetic films  

NASA Astrophysics Data System (ADS)

Multiferroic behavior was confirmed for epitaxial composite ferroelectric-ferromagnetic heterostructures, using a ferromagnetic crystal as both substrate and straining medium. Heterostructures having 2-2 connectivity (plane-on-plane) were fabricated by chemical solution deposition of Pb(Zr0.3,Ti0.7)O3 (PZT) thin films on La1.2Sr1.8Mn2O7 (LSMO) single crystal substrates. Magnetostriction (0.13%) of the substrate at its transition temperature (~105 K) induces an abrupt 7.3% increase in switchable polarization of the PZT. This confirmation of elastic coupling induced by the onset of ferromagnetism is a first step toward fabricating such structures for study of the interrelationship of their magnetic and electrical field-dependent behaviors.

Zurbuchen, M. A.; Wu, T.; Saha, S.; Mitchell, J.; Streiffer, S. K.

2005-12-01

357

Recent Development in Polymer Ferroelectric Field Effect Transistor Memory  

Microsoft Academic Search

The article presents the recent research development in polymer ferroelectric non-volatile memory. A brief overview is given of the history of ferroelectric memory and device architectures based on inorganic ferroelectric materials. Particular emphasis is made on device elements such as metal\\/ferroelectric\\/metal type capacitor, metal- ferroelectric-insulator-semiconductor (MFIS) and ferroelectric field effect transistor (FeFET) with ferroelectric poly(vinylidene fluoride) (PVDF) and its copolymers

Youn Jung Park; Hee June Jeong; Jiyoun Chang; Seok Ju Kang

2008-01-01

358

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

359

Ferroelectric gated electrical transport in CdS nanotetrapods.  

PubMed

Complex nanostructures such as branched semiconductor nanotetrapods are promising building blocks for next-generation nanoelectronics. Here we report on the electrical transport properties of individual CdS tetrapods in a field effect transistor (FET) configuration with a ferroelectric Ba(0.7)Sr(0.3)TiO(3) film as high-k, switchable gate dielectric. A cryogenic four-probe scanning tunneling microscopy (STM) is used to probe the electrical transport through individual nanotetrapods at different temperatures. A p-type field effect is observed at room temperature, owing to the enhanced gate capacitance coupling. And the reversible remnant polarization of the ferroelectric gate dielectric leads to a well-defined nonvolatile memory effect. The field effect is shown to originate from the channel tuning in the arm/core/arm junctions of nanotetrapods. At low temperature (8.5 K), the nanotetrapod devices exhibit a ferroelectric-modulated single-electron transistor (SET) behavior. The results illustrate how the characteristics of a ferroelectric such as switchable polarization and high dielectric constant can be exploited to control the functionality of individual three-dimensional nanoarchitectures. PMID:21513340

Fu, Wangyang; Qin, Shengyong; Liu, Lei; Kim, Tae-Hwan; Hellstrom, Sondra; Wang, Wenlong; Liang, Wenjie; Bai, Xuedong; Li, An-Ping; Wang, Enge

2011-04-22

360

Effects of Ca-substitution on structural, dielectric, and ferroelectric properties of Ba5SmTi3Nb7O30 tungsten bronze ceramics  

NASA Astrophysics Data System (ADS)

Effects of Ca-substitution on the crystal structure and dielectric properties were investigated for Ba5SmTi3Nb7O30 tungsten bronze ceramics. The tetragonal tungsten bronze structure in space group P4bm was determined in Ba4CaSmTi3Nb7O30 ceramics, which was the same for Ba5SmTi3Nb7O30. The c-axis off center displacement in both B1 and B2-sites for Ba5SmTi3Nb7O30 was slightly larger than that in BaCaSmTi3Nb7O30, while the distortion of Ti/Nb(2)O6 octahedra in Ba4CaSmTi3Nb7O30 was obviously suppressed compared with that in Ba5SmTi3Nb7O30. Though there were also two dielectric anomalies observed in Ba4CaSmTi3Nb7O30, the relaxor ferroelectric nature was changed to the normal ferroelectric one, and both the endothermal peak in differential scanning calorimetry curve and the significant thermal hysteresis of the phase transition confirmed the first order ferroelectric transition. These results indicated that the ferroelectric nature of Ba4CaSmTi3Nb7O30 was more close to that in Ba4Sm2Ti4Nb6O30, and it could be concluded that the ferroelectric nature in filled tungsten bronze ceramics was primarily dominated by the A-site occupation rather than B-site occupation.

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

2012-07-01

361

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

2012-06-01

362

Nanoscale ferroelectric tunnel junctions based on ultrathin BaTiO3 film and Ag nanoelectrodes  

NASA Astrophysics Data System (ADS)

In this work, Ag nanoisland electrodes (nanoelectrodes) have been deposited on top of ultrathin ferroelectric BaTiO3 (BTO) films to form a nanoscale metal-ferroelectric-metal tunnel junction by integrating growth techniques of nanocluster beam source and laser-molecular beam epitaxy. The ultrathin BTO films (~3 nm thick) exhibit both apparent ferroelectric polarization reversal and ferroelectric tunneling related resistive switching behaviors. The introducing of Ag nanoislands (~20 nm in diameter) as top electrode substantially enhances the tunneling current and alters the symmetry of I-V hysteresis curves. The enhanced tunneling current is likely due to the reduction in tunneling barrier height and an increase in effective tunneling area by Ag nano-electrodes, while the improved symmetric in I-V curve may be attributed to the variation of electrode-oxide contact geometry.

Gao, X. S.; Liu, J. M.; Au, K.; Dai, J. Y.

2012-10-01

363

Nondispersive dielectric component of ferroelectric thin films in the frequency range of 10-1-106 Hz  

NASA Astrophysics Data System (ADS)

We show that there exists a nondispersive (or elastic) capacitance component Cnon which is independent of frequency f, ac amplitude VOSC, and dc bias voltage Vdc, in the frequency range of 0.063 Hz-1 MHz. It can be separated from the total capacitance Ct of ferroelectric thin films by using either the C(Vdc,f)-C[Vdc,f(r)](VOSC=const) or C(f,VOSC)-C[f,VOSC(r)](Vdc=const) plot, where f(r) and VOSC(r) are the referenced frequency and ac amplitude, respectively. Our results suggest that the dispersive and nondispersive capacitance components may originate from different dielectric relaxation mechanisms. The extracted nondispersive Cnon can be a useful physical parameter in evaluating maximum dielectric tunability for the phase-shift application of ferroelectric thin films in microwave devices and characterizing phase-transition temperature in a multilayered 0.2Pb(Zn1/3Nb2/3)O3-0.8BaTiO3/Pb(Mg1/3Nb2/3)O3 relaxor.

Jiang, A. Q.; Chu, D. P.; Migliorato, P.; Kijima, T.; Natori, E.; Shimoda, T.

2005-07-01

364

Leakage current behavior in lead-free ferroelectric (K,Na)NbO3-LiTaO3-LiSbO3 thin films  

NASA Astrophysics Data System (ADS)

Conduction mechanisms in epitaxial (001)-oriented pure and 1 mol % Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.1,Sb0.06)O3 (KNN-LT-LS) thin films on SrTiO3 substrate were investigated. Temperature dependence of leakage current density was measured as a function of applied electric field in the range of 200-380 K. It was shown that the different transport mechanisms dominate in pure and Mn-doped thin films. In pure (KNN-LT-LS) thin films, Poole-Frenkel emission was found to be responsible for the leakage, while Schottky emission was the dominant mechanism in Mn-doped thin films at higher electric fields. This is a remarkable yet clear indication of effect of 1 mol % Mn on the resistive behavior of such thin films.

Abazari, M.; Safari, A.

2010-12-01

365

Some Studies on Ferroelectricity in KNO3 and Related Compounds  

Microsoft Academic Search

(NH4)xK1-xNO3 mixed crystals have been found to show ferroelectricity for a wide range of concentration. Dielectric measurements and infrared absorption studies were carried out. The librational behaviors of the NO3 radical about the 3-fold axis and the axes perpendicular to the 3-fold axis were analysed. The librational frequency and the mean declination angle of the radical were estimated. The Lorentz

Taketoshi Yanagi

1965-01-01

366

Holographic diffraction gratings using polymer-dispersed ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

By controlling the morphology of holographic polymer-dispersed ferroelectric liquid crystals (FLCs), highly aligned FLC domains are obtained for diffractive optical applications. Rapid, thresholdless switching is observed for various grating pitch sizes between ˜3 and ˜12 ?m. A simple phenomenological model is presented encompassing a distribution of domain sizes and an effective field that stabilizes the FLC domains to reflect the observed thresholdless switching and optical behavior.

Woltman, Scott J.; Eakin, James N.; Crawford, Gregory P.; Žumer, Slobodan

2006-11-01

367

Dielectric enhancement and Maxwell-Wagner effects in ferroelectric superlattice structures  

NASA Astrophysics Data System (ADS)

In an attempt to reproduce the functional properties associated with relaxor electroceramics, pulsed laser deposition has been used to fabricate thin-film capacitor structures in which the dielectric layer is composed of a superlattice of Ba0.8Sr0.2TiO3 and Ba0.2Sr0.8TiO3. The properties of the capacitors were investigated as a function of superlattice periodicity. The dielectric constant was significantly enhanced at stacking periodicities of a few unit cells, consistent with relaxor behavior. However, enhancement in dielectric constant was generally associated with high dielectric loss. Analysis of the imaginary permittivity as a function of frequency shows that fine-scale superlattices conform to Maxwell-Wagner behavior. This suggests that the observed enhancement of the real part of the dielectric constant is an artifact produced by carrier migration to interfaces within the dielectric. A comparison of this data with that already published on dielectric superlattices suggests that previous claims of an enhancement in dielectric constant may also be attributed to the Maxwell-Wagner effect.

O'Neill, D.; Bowman, R. M.; Gregg, J. M.

2000-09-01

368

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

369

Relaxation model for ferroelectric capacitors  

Microsoft Academic Search

A ferroelectric capacitor with non saturated polarization state loses its polarisation depending on its previous polarization history in two different ways. Relaxation measures have been performed using SBT capacitors. They show a differrence in polarization relaxation of up to 60% after 100 Ps, depending on the applied voltage sequence. To our knowledge this phenomena has not been observed. In this

G. Le Grand de Mercey; O. Kowarik

2001-01-01

370

Lattice viscosity of displacive ferroelectric crystals  

NASA Astrophysics Data System (ADS)

With the aid of the double-time thermal Green's-function method and the correlation function formula, the lattice viscosity of a displacive-type ferroelectric crystal in the paraelectric phase is theoretically investigated from a modification of the Silverman and Joseph Hamiltonian considering dominant third- and fourth-order anharmonic terms in the lattice potential energy. It is shown that the total viscosity can be separated into two terms arising from acoustical and optical phonons, which for a small half-width of phonons reduce to the form similar to that propounded by Rice. The temperature dependence of the viscosity is discussed. In the vicinity of the Curie temperature, the viscosity shows an anomalous temperature behavior due to a soft mode, in agreement with experimental investigations.

Goyal, V. K.; Sharma, P. K.

1981-02-01

371

Response Surface Methodology Study of Ferroelectric Memory Devices.  

National Technical Information Service (NTIS)

Fatigue in ferroelectric memory devices was studied. The application of fatigue pulses to a ferroelectric sample was controlled by the RT-66 Ferroelectric Tester, a variation of the Sawyer-Tower circuit. The RT-66 also controlled data collection following...

K. C. Smith

1992-01-01

372

Self-Accommodation of Ionic Size-Effect Atomic Displacements in Antiferroelectric Order in Relaxor Lead Scandium Niobate  

Microsoft Academic Search

Local antiferroelectric order of lattice distortion caused by an ionic size difference has been discovered in relaxor lead scandium niobate, Pb\\\\(Sc 1\\/2Nb 1\\/2\\\\)O 3, using an x-ray diffuse scattering technique. This ordering nature is thought to produce a glassy motion of ions in response to an applied electric field.

Naohisa Takesue; Yasuhiko Fujii; Masaki Ichihara; Haydn Chen

1999-01-01

373

Current status of ferroelectric-gate Si transistors and challenge to ferroelectric-gate CNT transistors  

Microsoft Academic Search

Current status of ferroelectric-gate FETs (field effect transistors) is reviewed. First, characteristics of Si FETs with MFIS (metal–ferroelectric–insulator–semiconductor) gate structures are discussed. It has been shown that the data retention characteristics of ferroelectric-gate FETs are much improved by use of HfO2-based buffer layers which are inserted between the ferroelectric-gate film and Si substrate for preventing inter-diffusion of constituent elements. Then,

Hiroshi Ishiwara

2009-01-01

374

Supramolecular bola-like ferroelectric: 4-methoxyanilinium tetrafluoroborate-18-crown-6.  

PubMed

Molecular motion is one of the structural foundations for the development of functional molecular materials such as artificial motors and molecular ferroelectrics. Herein, we show that pendulum-like motion of the terminal group of a molecule causes a ferroelectric phase transition. Complex 4-methoxyanilinium tetrafluoroborate-18-crown-6 ([C(7)H(10)NO(18-crown-6)](+)[BF(4)](-), 1) shows a second-order ferroelectric phase transition at 127 K, together with an abrupt dielectric anomaly, Debye-type relaxation behavior, and the symmetry breaking confirmed by temperature dependence of second harmonic generation effect. The origin of the polarization is due to the order-disorder transition of the pendulum-like motions of the terminal para-methyl group of the 4-methoxyanilinium guest cation; that is, the freezing of pendulum motion at low temperature forces significant orientational motions of the guest molecules and thus induces the formation of the ferroelectric phase. The supramolecular bola-like ferroelectric is distinct from the precedent ferroelectrics and will open a new avenue for the design of polar functional materials. PMID:21744841

Fu, Da-Wei; Zhang, Wen; Cai, Hong-Ling; Zhang, Yi; Ge, Jia-Zhen; Xiong, Ren-Gen; Huang, Songping D

2011-07-25

375

Origin of piezoelectric response under a biased scanning probe microscopy tip across a 180? ferroelectric domain wall  

NASA Astrophysics Data System (ADS)

The piezoelectric response of a material under a nanoscale biased tip scanned across a sample in piezoelectric force microscopy (PFM) provides insight into the structure and dynamics of domain walls in ferroelectrics. While the vertical displacements of the tip under piezoelectric deformations of the sample have been reasonably explained, the origin of the lateral twisting of the tip remains unclear. This poses a serious problem when combining vertical and lateral signals to create vector PFM maps of polarization distribution in ferroelectrics. Using a combination of finite element modeling and analytical theory, and by comparison with prior experimental work across a single antiparallel domain wall on the (0001) surface of LiNbO3, we unequivocally show that the lateral signal originates from a shear displacement of the surface. We show that there are two types of lateral signals, one arising from the d15 shear deformation, and the other from the d22 lateral deformation. The vertical PFM signal surprisingly shows equal contributions from the d33 (leading to normal displacements) and d15 (leading to shear displacement) coefficients. We also show that an averaging of the PFM signal over a finite contact area of the tip, as experimentally observed, is essential to understanding the line shape of the PFM responses across the wall. After clarifying the origin of the nanoscale PFM signals, we conclude that, in general, a vertical signal does not automatically indicate a polarization component out of the surface, while a lateral signal does not automatically indicate an in-plane polarization component. Without a detailed theory or simulation especially in materials with nanoscale domain structures, ferroelectric relaxors, and morphotropic compositions, such assumptions may lead to incorrect domain and wall interpretations. The proposed model and numerical simulation method could be applied to all piezoelectric materials.

Lei, Shiming; Eliseev, Eugene A.; Morozovska, Anna N.; Haislmaier, Ryan C.; Lummen, Tom T. A.; Cao, W.; Kalinin, Sergei V.; Gopalan, Venkatraman

2012-10-01

376

Terahertz plasmonics in ferroelectric-gated graphene  

NASA Astrophysics Data System (ADS)

Inspired by recent advancement of ferroelectric-gated memories and transistors, we propose a design of ferroelectric-gated nanoplasmonic devices based on graphene sheets clamped in ferroelectric crystals. We show that the two-dimensional plasmons in graphene can strongly couple with the phonon-polaritons in ferroelectrics, leading to characteristic modal wavelength of the order of 100-200 nm at low temperature and low-THz frequencies albeit with an appreciable dissipation. By patterning the ferroelectrics into different domains, one can produce compact on-chip plasmonic waveguides, which exhibit negligible crosstalk even at 20 nm separation distance. Harnessing the memory effect of ferroelectrics, low-power operation can be achieved on these plasmonic waveguides.

Jin, Dafei; Kumar, Anshuman; Hung Fung, Kin; Xu, Jun; Fang, Nicholas X.

2013-05-01

377

Re-entrant ferroelectricity and the multiferroic phase diagram of Mn1-xFexWO4  

NASA Astrophysics Data System (ADS)

We report the discovery of re-entrant ferroelectricity in the phase diagram of multiferroic Fe-substituted MnWO4. At zero magnetic field (H) the spin-spiral ferroelectric (FE) state is completely suppressed at Fe substitutions (x) exceeding 0.04. For x<0.04 a zero-field ferroelectric phase exists in a narrow temperature (T) range. This phase shows a re-entrant behavior at lower T above a critical magnetic field. The re-entrant FE transition is explored by polarization, dielectric constant, and magnetization measurements. The complete multiferroic x-T-H phase diagram of Mn1-xFexWO4 is derived.

Chaudhury, R. P.; Lorenz, B.; Wang, Y. Q.; Sun, Y. Y.; Chu, C. W.

2009-03-01

378

Structural, Dielectric, Piezoelectric and Ferroelectric Characterization of NBT-BT Lead-Free Piezoelectric Ceramics  

NASA Astrophysics Data System (ADS)

Lead free piezoelectric 0.94(Na0.5Bi0.5)TiO3-0.06BaTiO3 (NBT-BT) ceramics were synthesized in MPB composition by conventional solid state reaction method. The crystalline nature of NBT-BT ceramic was studied by XRD and the size of the grains are determined by SEM. The X- ray diffraction results reveal that Ba2+ diffuse into the Na0.5 Bi0.5TiO3 lattices to form a solid solution with a pure perovskite structure. Because of the strong ferroelectricity and MPB, the ceramics exhibit high piezoelectric properties: d33 = 206 pC/N. Td (depolarization temperature) and Tm (temperature at with the dielectric constant epsilonr reaches a maximum) were observed through the phase transition in dielectric studies. In addition, the prepared ceramic exhibits relaxor characteristic, which probably results from the cation disordering in the 12fold coordination sites. Pr and Ec of the prepared ceramics were determined from the P-E hysteresis loop.

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

2013-05-01

379

Electromigration of microspheres in ferroelectric smectic liquid crystals  

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

380

The influence of notches on domain dynamics in ferroelectric nanowires  

NASA Astrophysics Data System (ADS)

The extent to which notches inhibit axial switching of polarization in ferroelectric nanowires was investigated by monitoring the switching behavior of single crystal BaTiO3 wires before and after patterning triangular notches along their lengths. Static zero-field domain patterns suggested a strong domain-notch interaction, implying that notches should act as pinning sites for domain wall propagation. Surprisingly though, notches appeared to assist, rather than inhibit, polar switching. The origin of this effect was rationalized using finite element modeling of the electric field distribution along the notched wire; it was found that the air gap associated with the notch acted to enhance the local field, both in the air, and in the adjacent region of the ferroelectric. It seems that this local field enhancement outweighs any pinning interactions.

McMillen, M.; McQuaid, R. G. P.; Haire, S. C.; McLaughlin, C. D.; Chang, L. W.; Schilling, A.; Gregg, J. M.

2010-01-01

381

Domain engineered ferroelectric energy harvesters on a substrate  

NASA Astrophysics Data System (ADS)

Phase-field modeling is used to study the domain evolution of nano-scaled ferroelectric devices influenced by the mechanical strain of an underlying substrate. The investigations focus on the design of the energy harvesting systems to convert mechanical into electrical energy. Mechanical energy is provided by an alternating in-plane strain in the substrate through bending or unidirectional stretching. Additionally, lattice mismatch between the substrate and the ferroelectric material induces epitaxial strain and controls the polarization behavior within the system. Further, electrical boundary conditions are used to stabilize the domain topology. Finite element simulations are employed to explore the performance of the engineered domain topologies in delivering electrical charge from mechanical deformation.

Münch, I.; Krauß, M.; Landis, C. M.; Huber, J. E.

2011-05-01

382

Fast Switching Ferroelectric Materials for Accelerator Applications  

Microsoft Academic Search

Fast switching (<10 nsec) measurement results on the recently developed BST(M) (barium strontium titanium oxide composition with magnesium-based additions) ferroelectric materials are presented. These materials can be used as the basis for new advanced technology components suitable for high-gradient accelerators. A ferroelectric ceramic has an electric field-dependent dielectric permittivity that can be altered by applying a bias voltage. Ferroelectric materials

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

2006-01-01

383

Application of ferroelectrics in phase shifter design  

Microsoft Academic Search

The theoretical aspects of the design of optimal construction of microwave ferroelectric phase-shifter are discussed. The 30 GHz phase-shifter based on grounded coplanar waveguide with layered structure is under investigation. As a result expressions to determine the optimal construction of CPW ferroelectric phase-shifter and the suitable composition of ferroelectric film are derived. Continuous 0-360 degree phase shift and maximum insertion

A. Kozyrev; V. Osadchy; A. Pavlov; L. Sengupta

2000-01-01

384

Ferroelectricity: From organic conductors to conducting polymers  

NASA Astrophysics Data System (ADS)

We compare the ferroelectricity for two families of synthetic conductors: the experimentally found ferroelectricity in organic crystal like (TMTTF)2X and a plausilble ferroelectricity in specially designed polyene chains. The difference of the polymer with respect to the organic conductor is the reverse of the build-in (now the sites) and spontaneous (now the bonds) effects of dimerizations. The theory predicts the existence of solitons (dimerization kinks) with non-integer variable charges, both with and without the spin. With today's understanding, we see them as walls separating domains with opposite electric polarization. Their physics will serve to relate transient ferroelectric processes and the visible range optics.

Kirova, N.; Brazovskii, S.

2009-03-01

385

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

386

Artificial ferroelectricity in perovskite superlattices  

SciTech Connect

Artificial superlattices of SrZrO{sub 3}(SZO)/SrTiO{sub 3}(STO) were fabricated by molecular-beam epitaxy. Lattice parameters showed that the lattice distortion (c/a ratio) attained a maximum value in the [(SZO){sub 10}/(STO){sub 10}]{sub 4} superlattice. Dielectric relaxation was observed in the [(SZO){sub 1}/(STO){sub 1}]{sub 40} and [(SZO){sub 10}/(STO){sub 10}]{sub 4} superlattices in the low frequency domain. Dielectric permittivity of the SZO/STO superlattices was over 10 000 at 110 MHz. The SZO/STO superlattices showed clear Q-V hysteresis curves, which indicated that ferroelectricity was induced artificially in the superlattices in spite of the paraelectric nature of SZO and STO. The origin of the ferroelectricity was related to the anisotropic lattice distortion in the superlattice structure.

Tsurumi, Takaaki; Harigai, Takakiyo; Tanaka, Daisuke; Nam, Song-Min; Kakemoto, Hirofumi; Wada, Satoshi; Saito, Keisuke [Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552 (Japan)

2004-11-22

387

Ferromagnetism and ferroelectric properties of (Mn, Li) co-doped ZnO nanorods arrays deposited by electrodeposition  

Microsoft Academic Search

One dimensional (Mn, Li) co-doped ZnO nanorods have been prepared using electrodeposition method at constant current mode. Room temperature ferromagnetism and ferroelectricity were found coexisted in the co-doped ZnO nanorods and the underlying mechanism were discussed. The origin of the ferroelectric behavior could be explained on the basis of the ionic radii difference between the Zn2+ (0.74Å) and the dopants

C. W. Zou; L. X. Shao; L. P. Guo; D. J. Fu; T. W. Kang

2011-01-01

388

Ferromagnetism and ferroelectric properties of (Mn, Li) co-doped ZnO nanorods arrays deposited by electrodeposition  

Microsoft Academic Search

One dimensional (Mn, Li) co-doped ZnO nanorods have been prepared using electrodeposition method at constant current mode. Room temperature ferromagnetism and ferroelectricity were found coexisted in the co-doped ZnO nanorods and the underlying mechanism were discussed. The origin of the ferroelectric behavior could be explained on the basis of the ionic radii difference between the Zn 2+ (0.74 Å) and

C. W. Zou; L. X. Shao; L. P. Guo; D. J. Fu; T. W. Kang

2011-01-01

389

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

Microsoft Academic Search

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

M. Narayanan; S. Tong; B. Ma; S. Liu; U. Balachandran

2012-01-01

390

Dielectric response in ferroelectric superlattices.  

SciTech Connect

The dielectric response of a ferroelectric multilayer, having a designed heterogeneity, has been studied near its phase transition range by use of the Landau-Ginzburg theory. The coherent lattice coupling between ultrathin layers can be significantly strong, resulting in a broad phase transition of the superlattice system as a whole. The thickness of layers and their spatial distribution hold the keys for enhancing dielectric properties in a broad temperature range.

Li, S.; Eastman, J. A.; Vetrone, J. M.; Newnham, R. E.; Cross, L. E.; Materials Science Division; Pennsylvania State Univ.

1997-01-01

391

The Hysteretic Ferroelectric Tunnel FET  

Microsoft Academic Search

We present the fabrication and the electrical characterization of ferroelectric tunnel FETs (Fe-TFETs). This novel family of hysteretic switches combines the low subthreshold power of band-to-band tunneling devices with the retention characteristics of Fe gate stacks, offering some interesting features for future one-transistor (1T) memory cells. We report Ion\\/Ioff larger than 105 and Ioff on the order of 100 fA\\/?m

Adrian M. Ionescu; Livio Lattanzio; Giovanni A. Salvatore; L. De Michielis; Kathy Boucart; Didier Bouvet

2010-01-01

392

Terahertz response of ferroelectric nanofibers.  

PubMed

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

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

2011-11-01

393

A concept of ferroelectric microparticle propulsion thruster  

SciTech Connect

A space propulsion concept using charged ferroelectric microparticles as a propellant is suggested. The measured ferroelectric plasma source thrust, produced mainly by microparticles emission, reaches {approx}9x10{sup -4} N. The obtained trajectories of microparticles demonstrate that the majority of the microparticles are positively charged, which permits further improvement of the thruster.

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

2008-02-25

394

Phase Transitions in Ferroelectric and Antiferroelectric Crystals  

Microsoft Academic Search

Group theory is applied to phase transitions in ferroelectric and antiferroelectric crystals. The procedure is given to derive for a paraelectric crystal with a given space group all possible ferroelectric states which can exist for arbitrarily small values of the polarization. A knowledge of the space groups of the crystal above and below the transition point makes it possible to

C. Haas

1965-01-01

395

Ferroelectric Particles in Liquid Crystals: Recent Frontiers  

Microsoft Academic Search

In this article we describe electro-optical properties of recently discovered ferroelectric particles\\/liquid crystal colloids. We show that the presence of ferroelectric particles in a liquid crystal changes its birefringence and dielectric anisotropy. In contrast to the traditional time consuming and expensive chemical synthetic methods, this method to create liquid crystals with enhanced properties is relatively simple and has a great

Anatoliy Glushchenko; Chae Il Cheon; John West; Fenghua Li; Ebru Büyüktanir; Yuri Reznikov; Alexander Buchnev

2006-01-01

396

Observation of Ferroelectric Domain Structure in TGS  

Microsoft Academic Search

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

N. Nakatani

2011-01-01

397

A polycrystal hysteresis model for ferroelectric ceramics  

Microsoft Academic Search

Most key elements of ferroelectric properties are defined through the hysteresis loops. For a ferroelectric ceramic, its loop is contributed collectively by its constituent grains, each having its own hysteresis loop when the ceramic polycrystal is under a cyclic electric field. In this paper, we propose a polycrystal hysteresis model so that the hysteresis loop of a ceramic can be

Y. Su; G. J. Weng

2006-01-01

398

Single point diamond turning of ferroelectric materials  

Microsoft Academic Search

One of the most important ferroelectric ceramics materials used in a wide range of applications is the lead zirconate titanate solid solution series (PZT). The possibility of machining brittle materials using single point diamond turning in a ‘ductile mode’ has been investigated by many researchers in recent years. The ability to machine ferroelectrics in a ductile manner and by so

Paulo A. Beltrão; Anthony E. Gee; John Corbett; Roger W. Whatmore; Christopher A. Goat; Susan A. Impey

1999-01-01

399

Single point diamond machining of ferroelectric materials  

Microsoft Academic Search

One of the most important ferroelectric ceramic materials used in a wide range of applications is the lead zirconate titanate solid solution series (PZT). The ability to machine ferroelectrics in a ductile manner and by so doing reduce sub-surface damage, could eliminate the need for subsequent lapping and polishing and thus reduce production costs. Fracture mechanics techniques were used to

Anthony E Gee; John Corbett; Roger W Whatmore; Christopher A Goat; Susan A Impey

1999-01-01

400

Why ferroelectric polyvinylidene fluoride is special  

Microsoft Academic Search

Ferroelectric polymers entail a number of constraints, which together limit the useful compositional variations. These constraints include the following: a stable molecular dipole moment, compact crystal structure, conformational flexibility, and minimal steric hindrance. They are well satisfied by the prototype ferroelectric polymer, polyvinylidene fluoride, and yet almost every other conceivable molecular structure is limited by comparison.

Matthew Poulsen; Stephen Ducharme

2010-01-01

401

Domain-switching embedded nonlinear electromechanical finite element method for ferroelectric ceramics  

Microsoft Academic Search

To simulate the nonlinear behavior of ferroelectric structures and devices under non-uniform electromechanical loadings, a\\u000a domain-switching embedded electromechanical finite element method is developed in this paper. Following continuum assumption,\\u000a the electromechanical behavior of each representative material point can be obtained by averaging the behavior of the local\\u000a corresponding microstructure, e.g. 42 domains used in this work. A new Double Gibbs

Bin Liu; Daining Fang

2011-01-01

402

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

403

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

NASA Astrophysics Data System (ADS)

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

Picozzi, Silvia; Yamauchi, Kunihiko; Sergienko, Ivan A.; Sen, Cengiz; Sanyal, Biplab; Dagotto, Elbio

2008-10-01

404

In-plane and out-of-plane ferroelectric instabilities in epitaxial SrTiO3 films.  

PubMed

The in-plane and out-of-plane ferroelectric instabilities in compressed (100)-epitaxial SrTiO3 films were examined by infrared reflection spectroscopy. The strongly stiffened in-plane soft mode frequency softened very slowly on cooling. On the other hand, the silent mode appeared at around 150 K, indicating an out-of-plane ferroelectric transition. This behavior points to a split of in-plane and out-of-plane ferroelectric instability temperatures due to the lowered symmetry of the SrTiO3 lattice caused by mechanical misfit strain. Infrared spectroscopy provides a possibility to detect such an effect in the strained epitaxial ferroelectric films. PMID:16712197

Yamada, T; Petzelt, J; Tagantsev, A K; Denisov, S; Noujni, D; Petrov, P K; Mackova, A; Fujito, K; Kiguchi, T; Shinozaki, K; Mizutani, N; Sherman, V O; Muralt, P; Setter, N

2006-04-19

405

A cohesive model of fatigue of ferroelectric materials under electro-mechanical cyclic loading  

Microsoft Academic Search

A cohesive fatigue-crack nucleation and growth model for ferroelectric materials under electro-mechanical loading is presented. The central feature of the model is a hysteretic cohesive law which couples the mechanical and electrical fields. This law can be used in conjunction with general constitutive relations of bulk behavior, possibly including domain switching, in order to predict fatigue crack growth under arbitrary

Irene Arias; Santiago Serebrinsky; Michael Ortiz

2004-01-01

406

Complex notation for the dielectric response of ferroelectric materials beyond the small sinusoidal fields  

Microsoft Academic Search

For the polarization response beyond the small field range, Rayleigh's law has been introduced in the past to describe the field-dependent behavior (with loss) of ferroelectric materials with some success. We examine the relationship between Rayleigh's law and the complex dielectric constant notation that has been used widely in the scientific and engineering community; and we show that a modified

Xin Zhou; Baojin Chu; Qiming M. Zhang

2006-01-01

407

Self-Accommodation of Ionic Size-Effect Atomic Displacements in Antiferroelectric Order in Relaxor Lead Scandium Niobate  

SciTech Connect

Local antiferroelectric order of lattice distortion caused by an ionic size difference has been discovered in relaxor lead scandium niobate, Pb(Sc{sub 1/2}Nb{sub 1/2})O{sub 3} , using an x-ray diffuse scattering technique. This ordering nature is thought to produce a glassy motion of ions in response to an applied electric field. {copyright} {ital 1999} {ital The American Physical Society}

Takesue, N.; Fujii, Y. [Neutron Scattering Laboratory, Institute for Solid State Physics, The University of Tokyo, 106-1 Shirakata, Tokai, Ibaraki 319-1106 (Japan); Ichihara, M. [Materials Design and Characterization Laboratories, Institute for Solid State Physics, The University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106-8666 (Japan); Chen, H. [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green Street, Urbana, Illinois 61801 (United States)

1999-05-01

408

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

409

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

SciTech Connect

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

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

2010-11-17

410

Interface-induced polarization and inhibition of ferroelectricity in Epitaxial SrTiO3/Si.  

SciTech Connect

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

Kolpak, A.M.; Walker, F.J.; Reiner, J.W.; Segal, Y.; Su, D.; Sawicki, M.S.; Broadbridge, C.C.; Zhang, Z.; Zhu, Y.; Ahn, C.H.; Ismail-Beigi, S. (X-Ray Science Division); (Yale Univ.); (Brookhaven National Laboratory); (Southern Connecticut State University)

2010-11-19

411

Finite curvature-mediated ferroelectricity.  

PubMed

We demonstrate that ferroelectric (FE) polarizations oriented along the finite thickness direction in ultrathin films are enhanced by the introduction of extreme curvature, thereby suppressing the finite-size-driven evolution of the FE phase transition temperature T(C). The measured responses within individual nanoshells possess magnitudes nearly three times that for their planar counterparts while exhibiting finite curvature-dependent offsets in FE switching hystereses. In stark contrast to the expected scaling of a depression of T(C) with inverse thickness, results based on modified Landau-Ginzburg model calculations indicate geometric curvature-driven polarization gradients in ultrathin films result in significant increases in T(C). PMID:20067286

Nonnenmann, Stephen S; Leaffer, Oren D; Gallo, Eric M; Coster, Michael T; Spanier, Jonathan E

2010-02-10

412

Gamma Ray Irradiation Effects on the Ferroelectric and Piezoelectric Properties of Barium Titanate Ceramics  

NASA Astrophysics Data System (ADS)

The effect of heavy dose gamma ray irradiation on the ferroelectric and piezoelectric properties of barium titanate (BaTiO3) ceramics has been investigated. It is found that on irradiation the ferroelectric property decreases and polarization behavior shows double loop hysteresis. The piezoelectric properties including piezoelectric charge constant ( d 33), electromechanical coupling coefficient ( K p), and electrostrictive strain also decreases. The most probable reason for decreased ferroelectric and piezoelectric properties may be the occurrence of random local strain upon irradiation. The phase transition temperature from ferroelectric to paraelectric decreases and degree of diffuseness increases on irradiation. The thermoluminescence (TL) glow curve showed a peak at 226 °C showing that irradiated BaTiO3 has TL properties. Presence of TL clearly indicates that gamma ray irradiation causes trapped holes and electrons and these trapped charges are released at temperature higher than 226 °C. The creation of trapped holes and electrons effected the microstrain of BaTiO3 ceramic leading to change in the ferroelectric and piezoelectric properties of BaTiO3 ceramic.

Medhi, Nirmali; Nath, A. K.

2013-09-01

413

Nanoscale Electromechanics of Ferroelectric and Biological Systems: A New Dimension in Scanning Probe Microscopy  

SciTech Connect

Functionality of biological and inorganic systems ranging from nonvolatile computer memories and microelectromechanical systems to electromotor proteins and cellular membranes is ultimately based on the intricate coupling between electrical and mechanical phenomena. In the past decade, piezoresponse force microscopy (PFM) has been established as a powerful tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric and piezoelectric materials. Here, we give an overview of the fundamental image formation mechanism in PFM and summarize recent theoretical and technological advances. In particular, we show that the signal formation in PFM is complementary to that in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) techniques, and we discuss the implications. We also consider the prospect of extending PFM beyond ferroelectric characterization for quantitative probing of electromechanical behavior in molecular and biological systems and high-resolution probing of static and dynamic polarization switching processes in low-dimensional ferroelectric materials and heterostructures.

Kalinin, Sergei V [ORNL; Rodriguez, Brian J [ORNL; Jesse, Stephen [ORNL; Karapetian, Edgar [ORNL; Mirman, B [Suffolk University, Boston; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine

2007-01-01

414

Structural, electronic, and ferroelectric properties of compressed CdPbO3 polymorphs.  

PubMed

By means of first-principles calculations based on density functional theory (DFT) and hybrid functional, we studied the structural, electronic, and ferroelectric properties of the two recently synthesized high-pressure perovskite-type (orthorhombic, space group Pnma) and LiNbO(3)-type (rhombohedral, space group R3c) polymorphs of CdPbO(3). Besides providing structural and electronic results in good agreement with available experiments, our results are able to correctly describe the pressure-induced Pnma ? R3c structural phase transition and most importantly predict the realization of proper ferroelectric behavior in LiNbO(3)-type CdPbO(3) with an electric polarization of 52.3 ?C/cm(2). The proper covalent interaction mechanism driving the ferroelectric transition is discussed and explained in terms of the analysis of Born effective charges, potential-energy surfaces, charge density isosurfaces, and electric localization function. PMID:23301906

Xu, Yuanhui; Hao, Xianfeng; Franchini, Cesare; Gao, Faming

2013-01-09

415

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

416

Space charge effect in ultrathin ferroelectric films  

NASA Astrophysics Data System (ADS)

Space charge influence on the depolarization field becomes pronounced in nano-scale ferroelectric films in static state. We have studied theoretically the ferroelectric, dielectric, and piezoelectric properties of ultrathin ferroelectric films with the consideration of influence from space charges, surface, incomplete screening, and misfit strain. It is found that space charges accumulated near the surface of the film can modify the depolarization field, which results an enhancement of the polarization in ultrathin films and a persisting polarization even below the critical thickness. The singularities of the dielectric constant and piezoelectric coefficient were all being rounded near the critical thickness.

Lu, Xiaoyan; Cao, Wenwu; Li, Hui

2012-04-01

417

Theoretical study of ferroelectric potassium nitrate  

NASA Astrophysics Data System (ADS)

We present a detailed study of the structural behavior and polarization reversal mechanism in phase III of KNO3 , an unusual ferroelectric material in which the nitrate groups rotate during polarization reversal. This material was one of several studied in a previous work [O. Diéguez and D. Vanderbilt, Phys. Rev. Lett. 96, 056401 (2006)] where methods were described for computing curves of energy versus electric polarization. In the present work, we extend and systematize the previous first-principles calculations on KNO3 and analyze in detail a two-parameter model in which the energy of the system is written as a low-order expansion in the polarization and the nitrate group orientation. We confirm that this model reproduces the first-principles results for KNO3 very well and construct its parameter-space phase diagram, describing regions where unusual triple-well potentials appear. We also present first-principles calculations of KNO3 under pressure, finding that its energy-versus-polarization curves change character by developing a first-derivative discontinuity at zero polarization.

Diéguez, Oswaldo; Vanderbilt, David

2007-10-01

418

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

PubMed

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

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

2013-08-28

419

Improper Ferroelectricity: A Theoretical and Experimental Investigation.  

National Technical Information Service (NTIS)

A combined theoretical and experimental study has been made of the origins and properties of the improper ferroelectricity associated with structural modulations of non-zero wavelengths. Two classes of materials have been studied: rare earth molybdates (s...

J. R. Hardy F. G. Ullman

1984-01-01

420

Interface control of bulk ferroelectric polarization  

SciTech Connect

The control of material interfaces at the atomic level has led to no- vel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we em- ploy a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite un- derlayers extends the generality of this phenomenon.

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

2012-01-01

421

Ferroelectric-Gated Terahertz Plasmonics on Graphene  

NASA Astrophysics Data System (ADS)

Inspired by recent advancement of low-power ferroelectic-gated memories and transistors, we propose a design of ferroelectic-gated nanoplasmonic devices based on graphene sheets clamped in ferroelectric crystals. We show that the two-dimensional plasmons in graphene strongly couple with the phonon-polaritons in ferroelectrics at terahertz frequencies, leading to characteristic modal wavelength of the order of 100--200 nm at only 3--4 THz. By patterning the ferroelectrics into different domains, one can produce compact on-chip plasmonic waveguides, which exhibit negligible crosstalk even at 50 nm separation distance. Harnessing the memory effect of ferroelectrics, low-power electro-optical switching can be achieved on these plasmonic waveguides.

Jin, Dafei; Kumar, Anshuman; Fung, Kin Hung; Xu, Jun; Fang, Nicholas

2013-03-01

422

Tunnel electroresistance in ferroelectric tunnel junctions  

NASA Astrophysics Data System (ADS)

In tunnel junctions with a ferroelectric barrier, large resistance changes can arise upon switching the ferroelectric polarization direction. This tunnel electroresistance (TER) effect has recently been observed by scanning probe techniques on electrode/barrier bilayers (e.g. LSMO/BaTiO3), yielding giant TER values in the 50000% range at room temperature. Beside their fundamental interest to elucidate the interplay between electrostatic effects, changes in the interfacial density of states, piezoelectricity and quantum-mechanical tunneling, ferroelectric tunnel junctions undoubtedly present a great potential for application as memory devices with simple, non-destructive readout and low-power write operations. We will present our progress towards the realization of solid-state ferroelectric tunnel junctions and discuss their potential as next-generation non-volatile memories.

Chanthbouala, A.; Crassous, A.; Garcia, V.; Bouzehouane, K.; Fusil, S.; Grollier, J.; Deranlot, C.; Moya, X.; Mathur, N.; Bibes, M.; Barthelemy, A.

2011-03-01

423

Polarity control of carrier injection at ferroelectric/metal interfaces for electrically switchable diode and photovoltaic effects  

NASA Astrophysics Data System (ADS)

We investigated a switchable ferroelectric diode effect and its physical mechanism in Pt/BiFeO3/SrRuO3 thin-film capacitors. Our results of electrical measurements support that, near the Pt/BiFeO3 interface of as-grown samples, a defective layer (possibly an oxygen-vacancy-rich layer) becomes formed and disturbs carrier injection. We therefore used an electrical training process to obtain ferroelectric control of the diode polarity where, by changing the polarization direction using an external bias, we could switch the transport characteristics between forward and reverse diodes. Our system is characterized with a rectangular polarization-hysteresis loop with which we confirmed that the diode-polarity switching occurred at the ferroelectric coercive voltage. Moreover, we observed a simultaneous switching of the diode polarity and the associated photovoltaic response dependent on the ferroelectric domain configurations. Our detailed study suggests that the polarization charge can affect the Schottky barrier at the ferroelectric/metal interfaces, resulting in a modulation of the interfacial carrier injection. The amount of polarization-modulated carrier injection can affect the transition voltage value at which a space-charge-limited bulk current-voltage (J-V) behavior is changed from Ohmic (i.e., J ? V) to nonlinear (i.e., J ? Vn with n ? 2). This combination of bulk conduction and polarization-modulated carrier injection explains the detailed physical mechanism underlying the switchable diode effect in ferroelectric capacitors.

Lee, D.; Baek, S. H.; Kim, T. H.; Yoon, J.-G.; Folkman, C. M.; Eom, C. B.; Noh, T. W.

2011-09-01

424

Pentacene Field-Effect Transistor with Ferroelectric Gate Insulator as Maxwell-Wagner Effect Element  

Microsoft Academic Search

The behavior of charges in pentacene field-effect transistors (FETs) with a ferroelectric gate insulator [copolymer of vinylidene fluoride and tetrafluoroethylene, i.e., P(VDF-TeFE)] was investigated. Two peaks appeared in the Igs-Vgs characteristics at Vds = 0 V. Analyzing the behavior of the charges in the pentacene FETs revealed that the first peak appearing at the lower Vgs is ascribed to the

Ryousuke Tamura; Shuhei Yoshita; Eunju Lim; Takaaki Manaka; Mitsumasa Iwamoto

2008-01-01

425

Electron beam generation using a ferroelectric cathode  

Microsoft Academic Search

Data is presented on the production of electron beams from a ferroelectric cathode at voltages of order 0.5 MV and current densities of order 100 A\\/cm2. In comparison with data at lower voltages, the beam current scales as the three-halves-power of the voltage. An interpretation of the voltage dependent scaling, based on the coupling of electrostatic energy from the ferroelectric

Jim D. Ivers; Donald Flechtner; Czeslaw Golkowski; Guozhi Liu; John A. Nation; L. Schaechter

1999-01-01

426

Fast Switching Ferroelectric Materials for Accelerator Applications  

SciTech Connect

Fast switching (<10 nsec) measurement results on the recently developed BST(M) (barium strontium titanium oxide composition with magnesium-based additions) ferroelectric materials are presented. These materials can be used as the basis for new advanced technology components suitable for high-gradient accelerators. A ferroelectric ceramic has an electric field-dependent dielectric permittivity that can be altered by applying a bias voltage. Ferroelectric materials offer significant benefits for linear collider applications, in particular, for switching and control elements where a very short response time of <10 nsec is required. The measurement results presented here show that the new BST(M) ceramic exhibits a high tunability factor: a bias field of 40-50 kV/cm reduces the permittivity by a factor of 1.3-1.5. The recently developed technology of gold biasing contact deposition on large diameter (110 cm) thin wall ferroelectric rings allowed {approx}few nsec switching times in witness sample experiments. The ferroelectric rings can be used at high pulsed power (tens of megawatts) for X-band components as well as at high average power in the range of a few kilowatts for the L-band phase-shifter, under development for optimization of the ILC rf coupling. Accelerator applications include fast active X-band and Ka-band high-power ferroelectric switches, high-power X-band and L-band phase shifters, and tunable dielectric-loaded accelerating structures.

Kanareykin, A.; Schoessow, P. [Euclid Techlabs LLC, Solon, OH 44139 (United States); Nenasheva, E. [Ceramics Co. Ltd, St.Petersburg 194223 (Russian Federation); Yakovlev, V. [Omega-P Inc., New Haven, CT 06511 (United States); Dedyk, A.; Karmanenko, S.; Kozyrev, A.; Osadchy, V.; Kosmin, D.; Semenov, A. [St. Petersburg Electrical Engineering University, St. Petersburg 197376 (Russian Federation)

2006-11-27

427

Ferroelectric memristor based on Pt/BiFeO3/Nb-doped SrTiO3 heterostructure  

NASA Astrophysics Data System (ADS)

We report a continuously tunable resistive switching behavior in Pt/BiFeO3/Nb-doped SrTiO3 heterostructure for ferroelectric memristor application. The resistance of this memristor can be tuned up to 5 × 105% by applying voltage pulses at room temperature, which exhibits excellent retention and anti-fatigue characteristics. The observed memristive behavior is attributed to the modulation effect of the ferroelectric polarization reversal on the width of depletion region and the height of potential barrier of the p-n junction formed at the BiFeO3/Nb-doped SrTiO3 interface.

Hu, Zhongqiang; Li, Qian; Li, Meiya; Wang, Qiangwen; Zhu, Yongdan; Liu, Xiaolian; Zhao, Xingzhong; Liu, Yun; Dong, Shuxiang

2013-03-01

428

Processing of patterned ferroelectric capacitors  

NASA Astrophysics Data System (ADS)

Processing steps are described in detail for a procedure to fabricate sol-gel-derived lead-zirconate-titanate (PZT) ferroelectric thin-film capacitors in a manner compatible with processed complementary metal-oxide-semiconductor (CMOS) integrated-circuit wafers. The intended purpose of this work is to fabricate nonvolatile-element memory test structures for electrical and radiation characterization studies. A number of critical processing issues dealing with the etching of the PZT films and the deposition and definition of the top and bottom platinum electrodes were addressed and suitable solutions found during the course of this work. Using the procedures described herein, we fabricated working PZT capacitors and evaluated them electrically.

Rod, Bernard J.

1992-09-01

429

The shift of Curie temperature and evolution of ferroelectric domain in ferroelectric crystals  

Microsoft Academic Search

A micromechanics-based thermodynamic model for the phase transition of ferroelectric crystals is developed and, with it, the shift of Curie temperature and evolution of ferroelectric phase upon cooling are examined. This approach differs from the classical phenomenological one in that the evolution of new domain concentration can be predicted. We start out by formulating the Gibbs free energy of a

Y. Su; G. J. Weng

2005-01-01

430

Ferroelectric Phase Transitions from First Principles  

NASA Astrophysics Data System (ADS)

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

Rabe, Karin M.

1997-03-01

431

Domain switching in nanometer scale in Bismuth-based relaxor solid solution  

NASA Astrophysics Data System (ADS)

Microscopic piezoresponse force microscopy observation in 0.9967(Na1/2Bi1/2)TiO3(NBT)-0.0033BaTiO3(BT) rhombohedral (001) plate reveals two kinds of piezoresponse images, one with domain switching characterized with superior piezoresponsibility and the other without one, whereas macroscopic observation reveals non-switching of domain. Such microscopic remarkable difference of domain switching depends on coercive field caused by localized nucleation of domains with reversed polarization. Such coercive fields depend on relaxor states induced by random fields due to built-in charge disorder resulting from lattice defects at A-site and oxygen vacancies in ABO3 perovskite. The random fields based on lattice defects on {110} plane lower activation barrier for domain switching, leading to nucleation and growth of domains, while for non-switching of domains, oxygen vacancies on {110} and/or {001} plane play a role as clamping center for restriction of domain switching.

Yasuda, Naohiko; Takahashi, Natsumi; Hidayah, Nur; Ohwa, Hidehiro; Sakurada, Osamu; Tachi, Yoshihito; Fujita, Kazuhiko; Yamashita, Yohachi; Iwata, Makoto; Terauchi, Hikaru; Ishibashi, Yoshihiro

2011-09-01