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1

Strain incompatibility and residual strains in ferroelectric single crystals  

PubMed Central

Residual strains in ferroelectrics are known to adversely affect the material properties by aggravating crack growth and fatigue degradation. The primary cause for residual strains is strain incompatibility between different microstructural entities. For example, it was shown in polycrystalline ferroelectrics that residual strains are caused due to incompatibility between the electric-field-induced strains in grains with different crystallographic orientations. However, similar characterization of cause-effect in multidomain ferroelectric single crystals is lacking. In this article, we report on the development of plastic residual strains in [111]-oriented domain engineered BaTiO3 single crystals. These internal strains are created due to strain incompatibility across 90° domain walls between the differently oriented domains. The average residual strains over a large crystal volume measured by in situ neutron diffraction is comparable to previous X-ray measurements of localized strains near domain boundaries, but are an order of magnitude lower than electric-field-induced residual strains in polycrystalline ferroelectrics.

Pramanick, A.; Jones, J. L.; Tutuncu, G.; Ghosh, D.; Stoica, A. D.; An, K.

2012-01-01

2

Relaxor based ferroelectric single crystals for electro-mechanical actuators  

Microsoft Academic Search

The piezoelectric properties of relaxor based ferroelectric single crystals, such as Pb(Zn1\\/3Nb2\\/3)O3?PbTiO3 (PZN-PT) and Pb(Mg1\\/3Nb2\\/3)O3?PbTiO3 (PMN-PT) were investigated for electromechanical actuators. In contrast to polycrystalline materials such as Pb(Zr,Ti)O3 (PZTs), morphotropic phase boundary (MPB) compositions were not essential for high piezoelectric strain. Piezoelectric coefficients\\u000a (d33’s ) >2200 pC\\/N and subsequent strain levels up to >0.5% with minimal hysteresis were observed.

S.-E. Park; Thomas R. Shrout

1997-01-01

3

Ferroelectric domain periodicities in nanocolumns of single crystal barium titanate  

NASA Astrophysics Data System (ADS)

A focused ion beam microscope has been used to mill rectangular ``picture-frame'' shapes from single crystal barium titanate. The lengths of the sides of the picture frames were of the order of 3-5 ?m, while the side width and thickness dimensions were of the order of 100-500 nm. Such aspect ratios meant that each of the frame sides approximates to a column with rectangular cross section. Scanning transmission electron microsopy was used to characterize the ferroelectric domain configurations associated with these nanocolumns. It was found that conventional stripe domain patterns occurred in all cases, down to columnar cross-section sizes of the order of ~100×100 nm2. Despite the geometry of the columns rendering the ferroelectric as shape constrained in two dimensions, the domain periodicity was only noticeably sensitive to variations in the magnitude of one of those dimensions. Such observations were rationalized using arguments based on those used by Kittel [Phys. Rev. 70, 965 (1946)] and Mitsui and Furuichi [Phys. Rev. 90, 193 (1953)] for predicting the equilibrium domain periodicities in macroscopic slabs of ferroic material.

Schilling, A.; Bowman, R. M.; Gregg, J. M.; Catalan, G.; Scott, J. F.

2006-11-01

4

Study of ferroelectric domain structure of gash single crystals by scanning electron microscope  

Microsoft Academic Search

The domain structure of GASH single crystals is investigated by scanning electron microscopy. Ferroelectric domains are observed only outside a central hexagonal zone which the dimension varies, it is shown that the main polarity of trapeziums outside this hexagon is alternatively positive and negative. Inside each of these trapeziums, ferroelectric domains of opposite polarity are observed. With the electron beam,

Raymond Le Bihan; El Harbi Boudjema; Bozena Hilczer; Ludwik Szczesniak; Claus-Peter Mayer

1984-01-01

5

Ferroelectric domain structure of (CH3NH3)5Bi2Brll single crystals  

Microsoft Academic Search

Ferroelectric domain structure of (CH3, NH3)5 Bi2 Br11 single crystals was revealed using nematic liquid crystal decoration and scanning electron microscopy. The domain boundaries observed on the c-surface of the crystal were found to be parallel to the b-orthorhombic axis and this direction was found to be an easy direction of domain growth.

M. Po?omska; L. Szcze?niak; R. Jakubas; K.-P. Meyer; H. Blumtritt

1989-01-01

6

Single-crystal-like ferroelectric thin films on flexible, low-cost, polycrystalline, metal templates for ferroelectric applications  

Microsoft Academic Search

High quality thin ferroelectric thin films are required for fabrication of electronic devices such as nonvolatile random access memories. Typically, epitaxial films on various single crystal ceramic substrates have been used for such applications. However, such substrates have high cost, are inflexible and are available in very limited sizes. For these reasons, several groups have recently reported the fabrication of

Amit Goyal; Junsoo Shin

2010-01-01

7

Study on crack propagation in ferroelectric single crystal under electric loading  

Microsoft Academic Search

The crack propagation in ferroelectric single crystals subjected to electric fields was studied experimentally and theoretically. An in situ observation of crack propagation and domain switching near the crack tip in a poled PMN–PT62\\/38 single crystal was carried out using polarized optical microscopy. It was found that a pure negative electric field leads to a larger domain switching zone near

Y. Jiang; Y. Zhang; B. Liu; D. Fang

2009-01-01

8

Single walled carbon nano-tube, ferroelectric liquid crystal composites: Excellent diffractive tool  

Microsoft Academic Search

We present a switchable grating based on chiral single walled carbon nano-tube (SWCNT) doped ferroelectric liquid crystals (FLCs). The presence of SWCNTs improves the diffraction profile of the pure FLC. The diffraction efficiency, i.e., the ratio of intensities of first order and zero order maxima is more than 100% for the higher concentration of SWCNTs in pure FLC. This phenomenon

A. K. Srivastava; E. P. Pozhidaev; V. G. Chigrinov; R. Manohar

2011-01-01

9

Visualization of ferroelectric domains in bulk single crystals  

Microsoft Academic Search

In recent years ferroelectric domain patterning has become a popular topic of physical research because it enables photonic\\u000a applications as well as data storage. For generation of tailored domain structures and for further understanding of ferroelectricity,\\u000a a visualization of the domain patterns is required. A large number of imaging techniques have therefore been developed. This\\u000a review summarizes these techniques and

E. Soergel

2005-01-01

10

Standing wave electro-optic modulator by ferroelectric single crystal fiber in microwave cavity  

NASA Astrophysics Data System (ADS)

The application of ferroelectric crystals in light modulation has been of significant interests due to their exceptional electrical field sensitive optical properties or high electrooptic coefficients. Single crystal fibers of lithium niobate and strontium barium niobate grown by laser heated pedestal growth method are explored for optical pulse engineering (frequency shift, pulse compact, or pulse reshaping). The electrooptic behavior was investigated and compared in a microwave cavity of TE103 mode at 10GHz.

Huang, Chuanyong; Bhalla, Amar S.; Guo, Ruyan

2003-10-01

11

Investigation on crystalline perfection, mechanical, piezoelectric and ferroelectric properties of L-tartaric acid single crystal  

NASA Astrophysics Data System (ADS)

Polar organic nonlinear optical material, L-tartaric acid single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study indicates that the grown crystal crystallized in monoclinic system with space group P21. Crystalline perfection of the crystal has been evaluated by high resolution X-ray diffraction technique and it reveals that the crystal quality is good and free from structural grain boundaries. Mechanical stability of the crystal has been analyzed by Vickers microhardness measurement and it exhibits reverse indentation size effect. Piezoelectric d33 co-efficient for the crystal has been examined and its value is 47 pC/N. The ferroelectric behaviour of the crystal was analyzed by polarization-electric field hysteresis loop measurement.

Murugan, G. Senthil; Ramasamy, P.

2014-04-01

12

Effect of amino acid doping on the growth and ferroelectric properties of triglycine sulphate single crystals  

SciTech Connect

Effect of amino acids (L-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in the grown crystal. Morphology study reveals that amino acid doping induces faster growth rate along b-direction leading to a wide b-plane and hence suitable for pyroelectric detector applications. Ferroelectric domain structure has been studied by atomic force microscopy and hysteresis measurements reveal an increase of coercive field due to the formation of single domain pattern.

Raghavan, C.M.; Sankar, R.; Mohan Kumar, R. [Crystal Growth Centre, Anna University, Chennai 600 025 (India); Jayavel, R. [Crystal Growth Centre, Anna University, Chennai 600 025 (India)], E-mail: rjvel@annauniv.edu

2008-02-05

13

Stark effect of 14N NQR in single crystals of ferroelectric NaNO2  

Microsoft Academic Search

The effects of the external electric field on 14N nuclear quadrupole resonance (NQR) have been investigated in the ferroelectric phase of sodium nitrite (NaNO2) single crystals with either the single domain or the multidomain structure. NQR measurements of two resonance lines of n and n were made at 77 K under the external electric field up to 25 kV\\/cm. The

S. H. Choh; Y. J. Park; H. K. Kim; Y. M. Chang

1989-01-01

14

Frequency-dependent electrical properties of ferroelectric BaTi2O5 single crystal  

NASA Astrophysics Data System (ADS)

Analysis and modeling of impedance spectroscopy data of ferroelectric BaTi2O5 single crystal has been carried out at temperatures both below and above the ferroelectric Curie temperature, TC. The most appropriate equivalent circuit is found to consist of a parallel combination of a resistor (R), capacitor (C), and constant phase element (CPE). Below TC, the resistance R is too large to measure and the circuit simplifies to C-CPE. Above TC, R shows Arrhenius behavior with low values of conductivity, eg ~4×10-7 S cm-1 at 800 K and high activation energy, 1.13(2) eV, and represents a thermally activated dc hopping process associated with leakage transport of either electrons or holes through the crystal lattice. C is frequency-independent, passes through a maximum at the ferroelectric-paraelectric transition temperature, TC~475 °C, represents the limiting high frequency capacitance of the crystal and is attributed to the response of the individual dipoles that are responsible for the ferroelectricity. The A parameter of the CPE also passes through a maximum at TC, is not thermally activated in the same manner as R but shows similar temperature dependence to that of C. The physical origin of the CPE, with interlinked resistive and capacitive components, whose relative contributions are governed by the power law n parameter, may be associated with dipole-dipole interactions and reflect the time- and frequency-dependence of their cooperative nature.

Masó, Nahum; Yue, Xinyan; Goto, Takashi; West, Anthony R.

2011-01-01

15

Microwave electrooptic coefficient and modulation applications using ferroelectric single-crystal fibers  

NASA Astrophysics Data System (ADS)

Besides the well-known LiNbO3, ferroelectric strontium barium niobate (SBN) crystals are attractive for electrooptic modulation applications because of their high electrooptic coefficients and low half wave voltage. Their EO properties, typically obtained under low frequency electric field driving conditions, contain both primary and secondary contributions arising from electromechanical coupling. Single crystal fibers (Sr,Ba)Nb2O6 and LiNbO3 grown by laser heated pedestal growth method are investigated to explore the frequency dependence of electrooptic property both for mechanically stress-free crystals (low frequency) and at microwave driving frequency of 10GHz. An optical pulse can be up-tuned/down-tuned, squeezed/ expended in the range of GHz using a single piece of SBN crystal fiber under a moderate microwave field, controlled by the relative position of optical pulse traversing the crystal fiber to the microwave field. The effective microwave-photonic interactions demonstrated in ferroelectric SBN crystals provide a potential solution for the bandwidth definitions and wavelength tuning applications. The experimental configuration and the analysis are also of general significance in electrooptic property studies at microwave frequencies.

Huang, Chuanyong; Taylor, Jonathan; Liu, Hongbo; Bhalla, Amar; Guo, Ruyan

2006-09-01

16

Direct imaging of both ferroelectric and antiferromagnetic domains in multiferroic BiFeO{sub 3} single crystal using x-ray photoemission electron microscopy  

SciTech Connect

In this work, we propose to study the magnetic and ferroelectric configurations in ferroelectric multidomain BiFeO{sub 3} single crystals. Using x-ray (magnetic) linear dichroism in a photoemission electron microscope (X-PEEM), we are able to directly image both the antiferromagnetic and ferroelectric domains. We find that inside one single ferroelectric domain several antiferromagnetic domains coexist. This is different from what was observed on epitaxial thin films, where the ferroelectric domains perfectly match the antiferromagnetic ones, but also from previous neutron measurements on ferroelectric monodomain single-crystals for which one single antiferromagnetic domain was identified. This underlines the fundamental differences between thin films, bulk samples, and single versus ferroelectric multidomain samples.

Moubah, R.; Colson, D.; Viret, M. [Service de Physique de l'Etat Condense, URA CNRS 2464, CEA Saclay, 91191, Gif-sur-Yvette (France); Elzo, M. [Synchrotron Soleil, Saint-Aubin, 91192, Gif-sur-Yvette BP 48 (France); Institut Neel, CNRS/UJF, 38042, Grenoble (France); El Moussaoui, S. [Paul Scherrer Institut, Swiss Light Source, Villigen, CH-5232 (Switzerland); Jaouen, N.; Belkhou, R. [Synchrotron Soleil, Saint-Aubin, 91192, Gif-sur-Yvette BP 48 (France)

2012-01-23

17

Ferroelectric single crystal fibers for high frequency electrooptic modulation and optical frequency shift  

NASA Astrophysics Data System (ADS)

It is demonstrated in this thesis work that the pulse frequency and pulse profile of an optical wave propagating through an electrooptic single crystal fiber inside a microwave cavity are tuned or modulated by interaction with driving microwave field through nonlinear crystal medium. The approach provides a possible solution to the bandwidth demands and channel definition in optical communications systems. Ferroelectric crystals are of significant interests in electrooptic modulator devices due to their exceptionally high electrooptic coefficients. Ferroelectric single crystal fibers of strontium barium niobate (Sr0.61Ba0.39Nb2O6: SBN) grown by laser heated pedestal growth (LHPG) technique are employed to investigate the relevant properties and the characteristics of this bulk modulator in the microwave range. Grown from the congruent Sr0.61Ba0.39Nb2O 6 ceramics by LHPG, the phase component changing is monitored by XRD from ceramics to single crystal fibers. The corresponding dielectric properties are measured and compared with each other as function of temperature at low frequency range. Two dielectric anomalies are observed in dielectric spectroscopy at distinct temperature range and the mechanism is investigated to explain the difference of dielectric behavior. The dielectric property of SBN single crystal fiber is also measured at X band microwave frequency by perturbation method using the microwave resonant cavity. It is found that the dielectric constant is in the vicinity of ?r =40 (c-axis) in X band of microwave frequency and is relatively constant, deviating from the dramatic decrease trend of low frequency, and can be attributed to the combination of dipole reorientation and electronic polarizability at microwave frequency. The frequency dependent electrooptic (EO) coefficient of SBN crystal is investigated in this thesis using Senermont method at low frequency and a novel dynamic measurement at high frequency. The EO coefficient increases near the piezoelectric resonant frequency, which may be attributed to the harmonic contribution of piezoelectric resonances. The formula and new mechanism of measuring the EO coefficient at 10GHz is deduced and explored using a standing mode microwave cavity. It is found that SBN61 crystal possesses smaller electrooptic coefficient (r33 ˜200pm/V) at 10GHz compared to low frequency (rc ˜300pm/V) at 1kHz. This method can be easily extended to measure EO property at other frequency ranges using corresponsive cavity across the wide frequency scope without the requirement of electric contact on the specimen. Ferroelectric single SBN crystal fiber is evaluated for optical pulse engineering in terms of frequency shifting and pulse compression/expansion at microwave frequencies. The microwave-photonic interaction is investigated experimentally in a TE103 microwave cavity at 10GHz. The theoretical consideration and potential experimental solution in traveling wave mode are also studied in order to accumulate the modulating effect and to make full use of crystal length. It is shown that the frequency component of an optical pulse can be controlled effectively using the SBN single crystal in microwave cavity without the need of contact electrodes or any interruption to the optical system. The technique is of utility in several aspects of optical communications such as channel definition and security encoding of the signal, and of potential to a range of optoelectronic applications.

Huang, Chuanyong

18

Millimeter-Wave Dielectric Properties of Single Crystal Ferroelectric and Dielectric Materials  

SciTech Connect

Transmittance measurements on various single crystal ferroelectric materials over a broad millimeter-wave frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been determined in the millimeter wave region for the first time. The measurements have been employed using a free-space quasi-optical millimeter-wave spectrometer equipped with a set of high power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 - 120 GHz. The uncertainties and possible sources of instrumentation and measurement errors related to the free-space millimeter-wave technique are discussed. This work has demonstrated that precise MMW permittivities can be obtained even on small thin crystals using the BWO quasi-optical approach.

McCloy, John S.; Korolev, Konstantin A.; Li, Zijing; Afsar, Mohammed N.; Sundaram, S. K.

2011-01-03

19

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

20

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

NASA Astrophysics Data System (ADS)

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

Harker, John Chamberlain

21

Micro-/macro-responses of a ferroelectric single crystal with domain pinning and depinning by dislocations  

NASA Astrophysics Data System (ADS)

Phase field simulations are conducted to investigate the micro-structural signature and the macro-response of a ferroelectric single crystal with domain pinning and depinning phenomena by dislocation arrays. It is shown that due to the presence of the dislocation arrays, a domain with polarizations antiparallel to an applied field can survive under the small amplitude of applied field. The residual domain serves as a pre-existing nucleus during the following macroscopic switching via only domain wall motion. The pinned domain will be depinned when the external electric field amplitude exceeds a critical value, which highly depends on the dislocation spacing in the dislocation array. Due to the pinning and depinning effect, an asymmetric hysteresis loop of polarization versus electric field might appear when a bias field is applied.

Wu, H. H.; Wang, J.; Cao, S. G.; Chen, L. Q.; Zhang, T. Y.

2013-10-01

22

Millimeter-wave dielectric properties of single-crystal ferroelectric and dielectric materials.  

PubMed

Transmittance measurements on various single crystal ferroelectric and dielectric materials, BaTiO(3), SrTiO(3), LiNbO(3), LiTaO(3), (PbMg(1/3)Nb(2/3)O(3))0.73-(PbTiO(3))0.27, LaAlO(3), and Bi(4)Ge(3)O(12), over a broad millimeter-wave (MMW) frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been measured in the MMW region using high-power sources for the first time, using a free-space, quasi-optical MMW spectrometer equipped with high-power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 to 120 and 180 to 260 GHz. These results are compared with MMW permittivity of these materials obtained by other methods as well as to RF, microwave, and optical frequency permittivities for all the materials tested. The effects of both crystallographic orientation and quality of the surface polishing of the crystals have been examined. Uncertainties and possible sources of instrumentation and measurement errors related to the freespace MMW technique are discussed. This work demonstrates that precise MMW permittivity data can be obtained even on relatively small and thin crystals of different surface conditions and orientations using the high-power BWO-based quasioptical approach. PMID:21244971

McCloy, John S; Korolev, Konstantin A; Li, Zijing; Afsar, Mohammed N; Sundaram, Shanmugavelayutham K

2011-01-01

23

Ferroelectric domains and twinning in high-quality SrBi2Ta2O9 single crystals  

NASA Astrophysics Data System (ADS)

The domain structure of high-quality SrBi2Ta2O9 (SBT) single crystals is investigated by x-ray diffraction and piezoelectric force microscopy. Both ferroelectric 180° domains and ferroelastic 90° domains (twins) are revealed at room temperature. Remarkably, coexisting domains of two types form a well-defined ``herringbone'' structure with mostly flat 90° walls. Formation of the observed complex domain pattern is attributed to a two-stage process associated with the presence of separate ferroelastic and ferroelectric phase transitions in SBT.

Amorín, H.; Shvartsman, V. V.; Bdikin, I. K.; Costa, M. E. V.; Kholkin, A. L.; Pertsev, N. A.

2006-02-01

24

Above-room-temperature ferroelectricity in a single-component molecular crystal.  

PubMed

Ferroelectrics are electro-active materials that can store and switch their polarity (ferroelectricity), sense temperature changes (pyroelectricity), interchange electric and mechanical functions (piezoelectricity), and manipulate light (through optical nonlinearities and the electro-optic effect): all of these functions have practical applications. Topological switching of pi-conjugation in organic molecules, such as the keto-enol transformation, has long been anticipated as a means of realizing these phenomena in molecular assemblies and crystals. Croconic acid, an ingredient of black dyes, was recently found to have a hydrogen-bonded polar structure in a crystalline state. Here we demonstrate that application of an electric field can coherently align the molecular polarities in crystalline croconic acid, as indicated by an increase of optical second harmonic generation, and produce a well-defined polarization hysteresis at room temperature. To make this simple pentagonal molecule ferroelectric, we switched the pi-bond topology using synchronized proton transfer instead of rigid-body rotation. Of the organic ferroelectrics, this molecular crystal exhibits the highest spontaneous polarization ( approximately 20 muC cm(-2)) in spite of its small molecular size, which is in accord with first-principles electronic-structure calculations. Such high polarization, which persists up to 400 K, may find application in active capacitor and nonlinear optics elements in future organic electronics. PMID:20148035

Horiuchi, Sachio; Tokunaga, Yusuke; Giovannetti, Gianluca; Picozzi, Silvia; Itoh, Hirotake; Shimano, Ryo; Kumai, Reiji; Tokura, Yoshinori

2010-02-11

25

Comprehensive characterization of surface acoustic wave resonators using relaxor based ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

One-port surface acoustic wave resonators (SAW) were fabricated and characterized using Y-cut X propagating relaxor based ferroelectric single crystals of Pb(Mg1/3Nb2/3)O3-33%PbTiO3 and Pb(In1/3Nb2/3)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT). The experimental results demonstrated ultrahigh electromechanical coupling factor K2 of ~60% for shear horizontal SAW and a relatively strong spurious resonance due to the Rayleigh-type SAW which can be sufficiently suppressed with Au electrode of large thickness. Characteristics of temperature stability, sensitivity to DC bias voltage, and homogeneity for the two resonators were evaluated and compared. The results showed similar instability of domain structure, and PIN-PMN-PT resonators have better temperature stability, but inferior homogeneity compared to that of PMN-33%PT resonators.

Chen, Jing; Han, Tao; Ji, Xiaojun; Zhao, Xiangyong; Luo, Haosu

2013-07-01

26

Electromechanical behavior of relaxor ferroelectric crystals  

NASA Astrophysics Data System (ADS)

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

Liu, Tieqi

27

The Influence of Quantum Effects on the Ferroelectric Properties of TSCC-Type Single Crystals  

NASA Astrophysics Data System (ADS)

Experimental investigations on tris-sarcosine calcium chloride (TSCC)-type crystals reveal that pure TSCBr and TSCJ are quantum paraelectrics. Measurements of the concentration dependence of phase transition temperature and order parameter, of the pressure dependence of phase transition temperature and of the shift of permittivity peak due to an external electric field show a pronounced influence of quantum fluctuations on the behaviour of these crystals. Based on the model of coupled anharmonic oscillators it is possible to describe all essential ferroelectric properties of the crystal system using only few model parameters in consistent manner. The proposed model can be successfully applied to other quantum paraelectrics.Translated AbstractDer Einfluß von Quanteneffekten auf die Ferroelektrischen Eigenschaften von Kristallen vom TSCC-TypExperimentelle Untersuchungen an Kristallen vom Typ Trissarkosinkalziumchlorid (TSCC) zeigen, daß reines TSCBr und TSCJ Quantenparaelektrika sind. Messungen der Konzentrationsabhängigkeit der Phasenübergangstemperatur und des Ordnungsparameters, der Druckabhängigkeit der Phasenübergangstemperatur und des Maximums der DK unter der Einwirkung eines äußeren Feldes, weisen auf einen deutlichen Einfluß der Quantenfluktuationen auf das Verhalten dieser Kristalle hin. Basierend auf dem Modell gekoppelter anharmonischer Oszillatoren gelingt es, alle wesentlichen ferroelektrischen Eigenschaften des Kristallsystems mit Hilfe nur weniger Modellparameter in einheitlicher Weise zu beschreiben. Das vorgeschlagene Modell läßt sich mit Erfolg auf andere Quantenparaelektrika anwenden.

Windsch, W.; Braeter, H.

28

Complementary characterization techniques for identification of ferroelectric domains in KNbO{sub 3} single crystals  

SciTech Connect

KNbO{sub 3} single crystals are often utilized for their piezoelectric and optical properties. In this study the domain configurations in as-grown single crystals were investigated using reflected light microscopy, scanning electron microscopy and atomic force microscopy. Using atomic force microscopy it was possible to image the distortion induced on the crystal surface by the domain walls and to quantify the predicted angle between (001){sub pc} planes across these walls for the cases of both 90 deg. domain walls and S walls. These features can also be imaged using the other two techniques. This direct measurement of surface distortion verifies the geometrical model of domain structures, and suggests that any possible strain energy considerations are minor in predicting the surface topography in the material after phase changes from the growth temperature.

Bellou, A. [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, 99164 (United States); Bahr, D.F. [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, 99164 (United States)], E-mail: dbahr@wsu.edu

2008-06-15

29

Above-room-temperature ferroelectricity in a single-component molecular crystal  

Microsoft Academic Search

Ferroelectrics are electro-active materials that can store and switch their polarity (ferroelectricity), sense temperature changes (pyroelectricity), interchange electric and mechanical functions (piezoelectricity), and manipulate light (through optical nonlinearities and the electro-optic effect): all of these functions have practical applications. Topological switching of pi-conjugation in organic molecules, such as the keto-enol transformation, has long been anticipated as a means of realizing

Sachio Horiuchi; Yusuke Tokunaga; Gianluca Giovannetti; Silvia Picozzi; Hirotake Itoh; Ryo Shimano; Reiji Kumai; Yoshinori Tokura

2010-01-01

30

Enhancement of ferroelectric properties of Na1/2Bi1/2TiO3-BaTiO3 single crystals by Ce dopings  

NASA Astrophysics Data System (ADS)

Ferroelectric single crystal of Na1/2Bi1/2TiO3-BaTiO3 (NBT-BT) and Ce doped NBT-BT have been grown by flux technique. It is found that the addition of Ce plays a significant role in improving the ferroelectric properties of NBT-BT crystals, (i) by improving the value of the dielectric constant at room temperature and at Tm (the phase transition temperature between antiferroelectric and paraelectric phases with dielectric maximum), (ii) by increasing the depolarization temperature (Td) and Tm, (iii) by increasing the degree of diffuseness, and (iv) by increasing the remnant polarization (Pr) and coercive field (Ec). The reasons behind these enhancements of ferroelectric properties are discussed in detail.

Bubesh Babu, J.; He, Ming; Zhang, D. F.; Chen, X. L.; Dhanasekaran, R.

2007-03-01

31

Ferroelectric domain structures in PZN–8%PT single crystals studied by scanning force microscopy  

Microsoft Academic Search

Domain structures in unpoled PZN–8%PT single-crystal (001) plates have been investigated by scanning force microscopy in the piezoresponse mode, at room temperature. Regular fingerprint structure of nonferroelastic domains with antiparallel polarization (of typical width 1–2?m) has been observed. Compared to domain patterns usually observed in other materials, domains are rather diffuse, with irregular domain walls. The latter are preferably oriented

M. Abplanalp; D. Barosova; P. Bridenbaugh; J Erhart; J Fousek; P Günter; J Nosek; M Šulc

2001-01-01

32

Single crystal thin films of conductive oxides SrRuO3 and ferroelectric heterostructures  

Microsoft Academic Search

We have grown epitaxial thin films of the conductive oxide SrRuO3 with well controlled surface morphology and domain structure using vicinal (001) SrTiO3 substrates. Scanning tunneling microscopy and x-ray diffraction show that the SrRuO3 thin films on miscut (001) SrTiO3 substrates with miscut angle > 2° grow by step flow in one direction leading to single crystal films. In contrast,

Chang-Beom Eom; Rajesh A. Rao; Qing Gan; Kiyotaka Wasa; D. J. Werder

1998-01-01

33

Energy harvesting based on FE-FE transition in ferroelectric single crystals.  

PubMed

The pyroelectric properties of Pb(Zn(1/3)Nb(2/3))(0955)Ti(0.045)O(3) single crystals versus an electric field have been studied for energy harvesting in this paper. Two thermodynamic cycles (Stirling and Ericsson) were used for this purpose. By applying an electric field, a FE-FE transition was induced, abruptly increasing the polarization. This transition minimized the supplied energy and improved the harvested energy. By discharging the single crystal at a higher temperature, a gain of 1100% was obtained with the Stirling cycle at 1 kV/mm (gain is defined as harvested energy divided by supplied energy). The study revealed that Stirling cycles are more interesting for low electric fields. Based on experimental results, simulations were carried out to estimate energy harvesting in high electric fields to evaluate the performances of thin samples (single crystals or oriented thin films). At high electric fields, both cycles gave almost the same energy harvesting, but Ericsson cycles were more appropriate to control the voltage on the sample. The simulation led to a harvested energy of 500 mJ/g for an applied electric field equal to 50 kV/mm. The efficiency with respect to Carnot was raised 20%. PMID:18334334

Guyomar, Daniel; Pruvost, Sebastien; Sebald, Gael

2008-02-01

34

Spreading resistance microscopy of polycrystalline and single-crystal ferroelectric films  

NASA Astrophysics Data System (ADS)

Thin films based on lead zirconate titanate with stoichiometric composition near the morphotropic boundary have been studied using atomic-force microscopy methods. The dependence of the local conductivity on the local polarization direction has been observed for all samples, independently of substrate type, deposition method, and film thickness. It has been shown that the current response to the applied voltage exhibits a long current relaxation, about several tens of seconds, which is two to three orders of magnitude greater than the current relaxation time in an external circuit, associated with the ferroelectric domain switching. The conductivity features have been explained by recharging of traps localized at ferroelectric grain boundaries near electrodes and involved in polarization charge screening.

Gushchina, E. V.; Ankudinov, A. V.; Delimova, L. A.; Yuferev, V. S.; Grekhov, I. V.

2012-05-01

35

Domain switching and microcracking in ferroelectric single crystals and polycrystalline ceramics  

NASA Astrophysics Data System (ADS)

This study investigated the domain switching and the microcracking driven by contact forces, static electric fields and cyclic electric fields in a PZT ceramic and PMN-PT single crystals. Field-driven polarization switching was studied in a soft PZT ceramic by an in-situ transmission electron microscopy (TEM) technique. Responses of nanometer-sized domains to the first cycle of a bipolar field were recorded for the first time. Domain switching in PMN-PT single crystals was investigated by optical microscopy. The bipolar fields were found to drive the lamellar domains into complex mosaic patterns of domain zones with elastic distortion and electric charge at the zone boundaries. Contact force-driven 90° domain switching was studied by pressing a Vickers diamond indentor against the surface of a PMN-PT crystal. The stress-induced domain switching was confined to butterfly-shaped zones that extended preferentially along the <101> directions. Based on a critical shear stress criterion, a stress analysis was made to determine the conditions for the 90° domain switching. The field-driven in-situ TEM technique was applied to the study of domain boundary cracking in a 0.65PMN--0.35PT crystal. Fracture of the 90° domain wall was directly observed under both static and cyclic electric fields. The amplitude of the cyclic field required to cause the crack growth was much less than that of the static field. The mechanical energy produced due to the incompatible piezoelectric strain between neighboring domains was shown to be the driving force for the fracture. In polycrystalline piezoelectric ceramics, electric field-induced cracking occurred by intergranular fracture. The macroscopic path of the crack growth depended strongly upon the applied field and the poling direction. Analysis showed that cracks extended along the place of maximum normal strain. Mechanisms for the intergranular fracture were investigated by the in-situ TEM technique. During electrical cycling, transient dielectric breakdown and local melting in the amorphous grain boundary layers were the likely precursors to fracture. Assisted by the incompatible stresses, cavitation took place. The increase of the density and the linkage of these cavities weakened the grain boundary, leading to crack growth along the boundary.

Tan, Xiaoli

36

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

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

37

Ferroelectric domain structure of PbZr0.35Ti0.65O3 single crystals by piezoresponse force microscopy  

Microsoft Academic Search

Ti-rich PbZr1?xTixO3 (x = 0.65, PZT65) single crystals with the dimensions of 1 × 1 × 0.2 mm3 were grown by the self-flux method. Micron-sized ferroelectric domains were observed and characterized via piezoresponse force microscopy (PFM) and switching spectroscopy PFM. Both out-of-plane and in-plane components of polarization were obtained by detecting vertical and lateral vibrations of the PFM cantilever. The

I. K. Bdikin; J. A. Pe´rez; I. Coondoo; A. M. R. Senos; P. Q. Mantas; A. L. Kholkin

2011-01-01

38

Spatial inhomogeneity of ferroelectric domain structure in Pb(Mg 1\\/3Nb 2\\/3)O 3–30%PbTiO 3 single crystals  

Microsoft Academic Search

Piezoresponse force microscopy studies of domain structures have been performed on (001)-oriented Pb(Mg1\\/3Nb2\\/3)O3–30%PbTiO3 single crystals with a rhombohedral ferroelectric state. Regular (narrow strip-like) and irregular (fingerprint-like) domain patterns were clearly observed on the different surfaces of the unpoled samples. The results reveal that the random internal field due to nanoscale structure irregularity plays an important role in the spatial inhomogeneity

H. R. Zeng; H. F. Yu; R. Q. Chu; G. R. Li; H. S. Luo; Q. R. Yin

2005-01-01

39

Ferroelectric domain structure of PbZr0.35Ti0.65O3 single crystals by piezoresponse force microscopy  

Microsoft Academic Search

Ti-rich PbZr1-xTixO3 (x = 0.65, PZT65) single crystals with the dimensions of 1 × 1 × 0.2 mm3 were grown by the self-flux method. Micron-sized ferroelectric domains were observed and characterized via piezoresponse force microscopy (PFM) and switching spectroscopy PFM. Both out-of-plane and in-plane components of polarization were obtained by detecting vertical and lateral vibrations of the PFM cantilever. The

I. K. Bdikin; J. A. Pérez; I. Coondoo; A. M. R. Senos; P. Q. Mantas; A. L. Kholkin

2011-01-01

40

The growth striations and ferroelectric domain structures in Czochralski-grown LiNbO 3 single crystals  

Microsoft Academic Search

The rotational striations and power striations are studied in LiNbO3 crystals and one-to-one correspondence between the striations and temperature fluctuations is demonstrated. The ferroelectric domain structures related to the rotational striations and the power striations have been observed. The distribution of solute concentration in rotational striations is measured by means of energy dispersive X-ray analysis in the scanning electron microscope,

Nai-Ben Ming; Jing-Fen Hong; Duan Feng

1982-01-01

41

Dielectric dispersion of ferroelectric ceramics and single crystals by sound generation in piezoelectric domains  

SciTech Connect

Periodic domain configurations with alternating 180{degree} and 90{degree} domains are not completely mechanically clamped up to microwave frequencies. Above the acoustic resonance of the ferroelectric sample, therefore, the dielectric constant comprises contributions which can be attributed to the free dielectric constant. Up to microwave frequencies the domains are piezoelectrically active; they emit longitudinal and shear thickness waves into the surroundings which cause dielectric loss in the sample. The dielectric step from the free condition to the clamped condition at the relaxation frequency is on the order of {Delta}{var_epsilon} {approx} 10--100. This step is much smaller than the step caused by the emission of shear waves from 90{degree} domain walls.

Arlt, G.; Boettger, U.; Witte, S. [Aachen Univ. of Technology (Germany). Inst. fuer Werkstoffe der Elektrotechnik

1995-04-01

42

Single-Crystal-Like, c-axis Oriented BaTiO3 Thin Films with High-Performance on Flexible Metal Templates for Ferroelectric Applications  

SciTech Connect

Epitaxial, c-axis oriented BaTiO{sub 3} thin films were deposited using pulsed laser ablation on flexible, polycrystalline Ni alloy tape with biaxially textured oxide buffer multilayers. The high quality of epitaxial BaTiO{sub 3} thin films with P4mm group symmetry was confirmed by x-ray diffraction. The microscopic ferroelectric domain structure and the piezoelectric domain switching in these films were confirmed via spatially resolved piezoresponse mapping and local hysteresis loops. Macroscopic measurements demonstrate that the films have well-saturated hysteresis loops with a high remanent polarization of {approx} 11.5 {micro}C/cm{sup 2}. Such high-quality, single-crystal-like BaTiO{sub 3} films on low-cost, polycrystalline, flexible Ni alloy substrates are attractive for applications in flexible lead-free ferroelectric devices.

Shin, Junsoo [ORNL; Goyal, Amit [ORNL; Jesse, Stephen [ORNL; Kim, Dae Ho [ORNL

2009-01-01

43

Stability of perovskite-type clusters in melts for relaxor ferroelectric crystal growth  

Microsoft Academic Search

Relaxor ferroelectric single crystals with perovskite structure were novel materials which might revolutionize some applications\\u000a in medical ultrasonic imaging, telecommunication and ultrasonic devices. But during crystal growth and melt solidification,\\u000a pyrochlore-type phase presented now and then, which reduced the integrality and properties of ferroelectric single crystals.\\u000a This work dealt with the stability of perovskite-type clusters in melts for relaxor ferroelectric

Zengzhe Xi; Wei Long; Jiangnan Liu; Peng Liu; Zhenrong Li; Xi Yao

2009-01-01

44

Photorefractive effect in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

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

Sasaki, Takeo; Naka, Yumiko

2014-03-01

45

Ferroelectric Liquid Crystal Optical Interconnect Switching Systems.  

National Technical Information Service (NTIS)

This grant explored the possible use of ferroelectric liquid crystals (FLC's) in the reamization of photonic switching fabrics. Problems addressed included device fabrication, switch architectures, and switch performance. Experimental versions of most arc...

J. W. Goodman

1993-01-01

46

Ferroelectric properties of sol–gel deposited Pb(Zr,Ti)O 3\\/LaNiO 3 thin films on single crystal and platinized-Si substrates  

Microsoft Academic Search

Electrically conductive LaNiO3 (LNO) and ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films were deposited on single crystal (100)SrTiO3 (STO), (100)LaAlO3 (LAO), and Pt\\/Ti\\/SiO2\\/Si(100) substrates using solution deposition routes. X-ray diffraction and scanning electron microscopy were used to investigate the crystallinity and microstructure of the films. The surface bonding states of the PZT and LNO films were determined by X-ray photoelectron spectroscopy (XPS).

C. R. Cho; L. F. Francis; D. L. Polla

1999-01-01

47

Studies on growth and characterization of a novel nonlinear optical and ferroelectric material – N,N-dimethylurea picrate single crystal  

NASA Astrophysics Data System (ADS)

A novel organic nonlinear optical (NLO) material viz. N,N-dimethylurea picrate (NNDMP) was grown by the slow evaporation technique using N,N-dimethyl formamide as a solvent. The solubility of the grown sample has been estimated for various temperatures. The XRD study reveals that the grown crystal crystallizes in the monoclinic crystal system and the corresponding lattice parameters were determined. The relative second harmonic generation (SHG) efficiency of the NNDMP was found to be 1.045 times that of KDP by Kurtz–Perry powder technique. FTIR and FT-Raman spectral analyses explain the various functional groups present in the sample. The optical spectral analysis of the grown crystal has been performed by UV–vis–NIR spectroscopy and the band gap energy was found out. The thermogravimetric analysis and differential thermal analysis (TG/DTA) reveal that the NNDMP crystal is stable at up to 172 °C. A prominent first-order ferroelectric to paraelectric phase transition at 323 K has been observed and activation energy was determined for the AC conduction process in the sample.

Shanthi, A.; Krishnan, C.; Selvarajan, P.

2014-05-01

48

Effect of Poling Directions on the Electric-Field-Induced Fatigue Crack Growth in Barium Titanate Ferroelectric Single Crystals  

Microsoft Academic Search

Electric-field-induced crack growth under cyclic electric field was reported for BaTiO3 single crystals with different poling directions. Pre-existing cracks were introduced by Vicker's indent on the polished surfaces of the single crystals, and crack propagation was observed in-situ under cyclic electric field using a polarized optical microscope. For [001]-oriented BaTiO3Êsingle crystal, the applied cyclic electric field is perpendicular to the

F. Fang; Y. H. Li; W. Yang

2005-01-01

49

Ferroelectric poling and converse-piezoelectric-effect-induced strain effects in La0.7Ba0.3MnO3 thin films grown on ferroelectric single-crystal substrates  

NASA Astrophysics Data System (ADS)

Using ferroelectric 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystals as substrates, we studied the effects of the ferroelectric poling and the converse piezoelectric effect on the strain state, resistance, insulator-to-metal transition temperature (TC) , and magnetoresistance (MR) of La0.7Ba0.3MnO3 (LBMO) thin films. In situ x-ray diffraction measurements indicate that the ferroelectric poling (or the converse piezoelectric effect) induces a substantial reduction in the in-plane tensile strain in the LBMO film, giving rise to a decrease in the resistance and an increase in TC . The relative changes of the resistance and TC are proportional to the induced reduction in the in-plane tensile strain (??xx) in the film. The reduction in the in-plane tensile strain leads to opposite effects on MR below and above TC , namely, MR is reduced for TTC . We discuss these strain effects within the framework of the Jahn-Teller (JT) electron-lattice coupling and phase separation scenario that are relevant to the induced strain. Similar studies on CaMnO3 thin films, for which there is no JT distortion of MnO6 octahedra, show that the resistance of the films also decreases when the tensile strain is reduced, indicating that the resistance change arising from the reduction in Mn-O bond length dominates over that arising from the reduction in Mn-O-Mn bond angle.

Zheng, R. K.; Jiang, Y.; Wang, Y.; Chan, H. L. W.; Choy, C. L.; Luo, H. S.

2009-05-01

50

Interplay of ferroelectricity and single electron tunneling  

NASA Astrophysics Data System (ADS)

We investigate the interplay of ferroelectricity and quantum electron transport at the nanoscale in the regime of Coulomb blockade. Ferroelectric polarization in this case is no longer the external parameter but should be self-consistently calculated along with electron hopping probabilities leading to physical transport phenomena studied in this paper. These phenomena appear mostly due to effective screening of a grain electric field by ferroelectric environment rather than due to polarization dependent tunneling probabilities. At small bias voltages polarization can be switched by a single excess electron in the grain. In this case transport properties of a single electron transistor exhibit the instability (memory effect).

Fedorov, S. A.; Korolkov, A. E.; Chtchelkatchev, N. M.; Udalov, O. G.; Beloborodov, I. S.

2014-04-01

51

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

SciTech Connect

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

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

2006-05-15

52

Spin-driven ferroelectricity in ferroaxial crystals  

NASA Astrophysics Data System (ADS)

Spin-driven ferroelectricity in most non-collinear magnets, such as TbMnO3, is induced by the so-called inverse Dzyalonshinskii-Moriya mechanism and requires a cycloidal magnetic structure, an ordered magnetic state that is not truly chiral (or lacks helicity). Conversely, in a truly chiral magnetic state (proper helix), the pseudo-scalar helicity can not couple directly to the electric polarization, and therefore can't induce ferroelectric order. However, in systems of specific crystal symmetry, named here ``ferroaxials,'' the presence of collective structural rotations mediates an indirect coupling between magnetic helicity and ferroelectricity. I will review our recent experimental results for new compounds of this class, obtained by magnetic X-ray and neutron diffraction techniques, including a clear demonstration that the magnetic helicity can be controlled by an electric field.

Chapon, Laurent

2012-02-01

53

Multiferroic nanoparticulate thin film composites by Co implantation of ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal targets  

NASA Astrophysics Data System (ADS)

Two-phase magnetostrictive-piezoelectric thin film composites are key materials to the development of a range of potentially disruptive magnetoelectric technologies, such as electrical-writing magnetic-reading random access memories. However, multiferroic thin film composites prepared so far show neither magnetoelectric switching nor magnetoelectric responses comparable to those of related bulk ceramic materials and cermets. Here we show that ion implantation of magnetic species into ferroelectric single crystal targets can be an effective alternative means of obtaining nanoparticulate thin film composites of this type. Concept is proved by the implantation of Co into a Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal with ultrahigh piezoelectricity. Formation of an ensemble of ferromagnetic nanoparticles embedded in an amorphized layer within the ferroelectric crystal is clearly shown.

Torres, María; Ricote, Jesús; Amorín, Harvey; Jaafar, Miriam; Holgado, Susana; Piqueras, Juan; Asenjo, Agustina; García-Hernández, Mar; Algueró, Miguel

2011-12-01

54

Ferroelectric domain structure of [N(CH3)4]2 ZnC14 single crystals  

Microsoft Academic Search

Ferroelectric domain structure of tetramethylammonium zinc chloride was revealed in the temperature range 275. 8R-279. OK by means of scanning electron microscopy. The domain patterns of lamellar type were observed. The mean width of the domains at 276.1 K amounted to 10 ?m.

R. Le Bihan; D. Averty; B. Hilczer; L. Szczepanska

1989-01-01

55

Large electrostrictive actuation of barium titanate single crystals  

Microsoft Academic Search

An experimental investigation of the electromechanical behavior of single crystals of the ferroelectric perovskite barium titanate is presented. An experimental setup has been designed to investigate large strain actuation in single crystal ferroelectrics subjected to combined electrical and mechanical loading. Experiments have been performed on initially single domain crystals of barium titanate with (100) and (001) orientation at compressive stresses

E. Burcsu; G. Ravichandran; K. Bhattacharya

2004-01-01

56

High-speed switching of nanoscale ferroelectric domains in congruent single-crystal LiTaO3  

NASA Astrophysics Data System (ADS)

The nanodomain reversal characteristics of congruent LiTaO3 (CLT) single crystal are investigated. It is found that fast nanosecond domain switching can be achieved by reducing the sample thickness, even for CLT, which contains many Li vacancy defects that pin domain-wall movement. As an example, the authors obtain a polarization inverted domain dot with a radius of 7.9 nm by application of a 4 ns 10 V pulse. These results demonstrate that the speed of polarization reversal is closely related to the thickness of the medium.

Fujimoto, Kenjiro; Cho, Yasuo

2003-12-01

57

Growth and characterization of piezo-/ferroelectric Pb(Mg 1/3Nb 2/3)O 3-PbTiO 3-Bi(Zn 1/2Ti 1/2)O 3 ternary single crystals  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

58

Enhanced ferroelectric properties and thermal stability of nonstoichiometric 0.92(Na0.5Bi0.5)TiO3-0.08(K0.5Bi0.5)TiO3 single crystals  

NASA Astrophysics Data System (ADS)

Bi deficient, Mn doped 0.92(Na0.5Bi0.5)TiO3-0.08(K0.5Bi0.5)TiO3 single crystals were grown by carefully controlled top-seeded solution growth method. Local structures were investigated by transmission electron microscopy. The site occupation and valence state of manganese were characterized by electron paramagnetic resonance spectrum. The leakage current density in the as-grown single crystals is effectively depressed. The introduced defect complexes suppress the temperature induced phase transformation, increasing the depolarization temperature (165 °C) and thermal stability of ferroelectric properties.

Zhang, Haiwu; Chen, Chao; Zhao, Xiangyong; Deng, Hao; Li, Long; Lin, Di; Li, Xiaobing; Ren, Bo; Luo, Haosu; Yan, Jun

2013-11-01

59

Surface Acoustic Wave Propagation in Relaxor-Based Ferroelectric Single Crystals 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 Poled along [011]c  

NASA Astrophysics Data System (ADS)

Surface acoustic wave (SAW) propagation in relaxor-based ferroelectric single crystals 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 (PZN-7%PT) poled along [011]c has been analyzed theoretically. The results show that PZN-7%PT single crystals have excellent SAW properties, such as low phase velocities, very high electromechanical coupling coefficients and small power flow angles. It is also found that the SAW properties strongly depend on the propagation direction and the characteristic curves of SAW phase velocity, and the electromechanical coupling coefficients are symmetric with respect to ? = 90°. Considering all related factors, the X-cut PZN-7%PT single crystal has the best performance. Based on our results, the X-cut PZN-7%PT single crystals poled along [011]c are an excellent candidate for ultra-wide bandwidth low-frequency SAW devices.

Li, Xiu-Ming; Zhang, Rui; Huang, Nai-Xing; Lü, Tian-Quan; Cao, Wen-Wu

2012-02-01

60

A programmable ferroelectric single electron transistor  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a programmable ferroelectric single electron transistor using direct monolithic integration of a multi-gate III-V (In0.7Ga0.3As) quantum well field effect transistor with a composite ferroelectric (lead zirconium titanate) and high-k (hafnium dioxide) gate stack. A split gate electrode configuration allows electrical tuning of the tunnel barrier profile and reconfigurable programming of the device to operate in both classical and Coulomb blockade mode. The ferroelectric gate stack under the split gate electrode further allows non-volatile operation in both modes. This demonstration is a significant step towards realization of a non-volatile, programmable binary decision diagram logic circuit for ultra low power operation.

Liu, Lu; Narayanan, Vijay; Datta, Suman

2013-02-01

61

Investigation of ferroelectric liquid crystal orientation in the silica microcapillaries  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

62

Physical Properties of Ferroelectric Mixed Crystals  

NASA Astrophysics Data System (ADS)

The recent studies of the KH2PO4 family mixed crystals with long-range ferroelectric (FE) order and short-range glass order have been reviewed. In mixed crystals of KH2PO4 family FE or antiferroelectric (AFE) with intermediate mixing concentration, a competing interaction gives rise to a nonergodic proton glass (PG) similar to magnetic spin glass. To understand the phase diagram, we have investigated the phase near FE boundary and observed a coexistence of FE and PG in Rb1-x(NH4)xH2AsO4 and Rb1-x(NH4)xH2PO4 mixed crystals. The nonergodic behavior of the coexisting PG was investigated by the polarization as well as dielectric constant measurement. The remaining FE polarization and the low freezing temperature were discussed in terms of mean field model of dipole glass systems.

Kwun, Sook-Il; Noh, Keum Hwan

2001-04-01

63

Basic sputtering process and ferroelectric properties of single–domain single–crystal thin films of PbTiO3  

Microsoft Academic Search

Single c–domain single crystal PbTiO3 (PT) thin films were prepared by sputtering on both miscut (001)SrTiO3 (ST) and (110)SrRuO3\\/miscut (001)ST substrates with a miscut angle of 1.7°. Film thickness ranged from 5 nm to 250 nm. The film growth was governed by step-flow growth and the film surface was atomically flat. The lattice misfit strain induced during the film growth

Kiyotaka Wasa; Yoko Haneda; Toshifumi Sato; Hideaki Adachi; Isaku Kanno; Darrell G. Schlom; S. Trolier-Mckinstry; Qing Gan; Chang-Beom Eom

1998-01-01

64

Ferroelectric order in individual nanometre-scale crystals.  

PubMed

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

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

2012-08-01

65

Single ferroelectric and chiral magnetic domain of single-crystalline BiFeO3 in an electric field  

NASA Astrophysics Data System (ADS)

We report on polarized neutron-scattering and piezoresponse force microscopy studies of millimeter-sized single crystals of multiferroic BiFeO3 . The crystals, grown below the Curie temperature, consist of a single ferroelectric domain. Two unique electric polarization directions, as well as the populations of equivalent spiral magnetic domains, can be switched reversibly by an electric field. A ferroelectric monodomain with a single- q single-helicity spin spiral can be obtained. This level of control, so far unachievable in thin films, makes single-crystal BiFeO3 a promising object for multiferroics research.

Lee, Seongsu; Choi, Taekjib; Ratcliff, W., II; Erwin, R.; Cheong, S.-W.; Kiryukhin, V.

2008-09-01

66

Ferroelectric Domains in SrxBa1 ? xNb2O6 Single Crystals (0.4 ? × ? 0.75)  

Microsoft Academic Search

The crossover of single crystalline SrxBa1 ? xNb2O6 (SBN) from ferroelectric to relaxor behavior when increasing the Sr content from x = 0.4 to x = 0.75 is investigated by dielectric low-frequency susceptometry and scanning piezo-force microscopy. Increasing quenched random electric fields are conjectured to be responsible for the observed increasing dielectric polydispersivity and the growing fractality of the polar

Vladimir V. Shvartsman; Jan Dec; Seweryn Miga; Tadeusz ?ukasiewicz; Wolfgang Kleemann

2008-01-01

67

Ferroelectric Liquid Crystals In Aerodynamic Testing  

NASA Technical Reports Server (NTRS)

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

Parmar, Devendra S.; Holmes, Harlan K.

1994-01-01

68

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

69

Effects of electron irradiation on the ferroelectric 180 deg. in-plane nanostripe domain structure in a thin film prepared from a bulk single crystal of BaTiO{sub 3} by focused ion beam  

SciTech Connect

Effects of electron irradiation on the ferroelectric 180 deg. in-plane nanostripe domain structure in a thin film prepared from a bulk single crystal of BaTiO{sub 3} by focused ion beam were studied. The domain structure transformed into a characteristic 90 deg. in-plane nanostripe domain structure under intense electron irradiation. In particular, an unconventional triangular 90 deg. in-plane nanostripe domain structure was observed. Polarization analysis suggests the existence of an incomplete or half tetradomain vortex at the boundary of the triangular domain structure. Together with the help of phase-field simulations using time-dependent Ginzburg-Landau equations, it is suggested that such a domain structure is created by an anisotropic in-plane electric field, which is plausibly induced by an anisotropic interaction of the incident electron beam with the ferroelectric material.

Matsumoto, Takao [Central Research Laboratory, Hitachi, Ltd., 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo 185-8601 (Japan); Okamoto, Masakuni [Advanced Research Laboratory, Hitachi, Ltd., 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo 185-8601 (Japan)

2011-01-01

70

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

Microsoft Academic Search

The change of ferroelectric, dielectric, and piezoelectric properties with time, the ferroelectric aging phenomena, has been observed in most ferroelectrics. Phenomenologically, aging can be attributed to the gradual stabilization of ferroelectric domains by defects, but the microscopic origin of the domain stabilization has remained controversial. It is unclear whether the domain stabilization is a boundary effect (caused by domain-wall-pinning) or

Lixue Zhang; Xiaobing Ren

2006-01-01

71

Investigation of Ferroelectric Phase Transition in DMAAS Crystals: Neutron Diffraction, Neutron Spectroscopy, Theoretical Model  

Microsoft Academic Search

The aim of the present work is the comparative analysis of data of neutron diffraction investigation of DMAAS ((CH3)2NH2Al(SO4)2·6H2O) single crystals in paraelectric and ferroelectric phases at 293 and 135 K, neutron spectroscopy investigation of polycrystalline samples of DMAAS in a wide temperature range above and below the ferroelectric phase transition point and theoretical calculations with the purpose of ascertainment

V. Yu. Kazimirov; V. A. Sarin; M. B. Smirnov; L. A. Shuvalov

2004-01-01

72

Optically rewritable ferroelectric liquid-crystal grating  

NASA Astrophysics Data System (ADS)

This paper describes the fabrication procedure and optical characterization of ferroelectric liquid-crystal (FLC) gratings based on photo-alignment. The fabrication procedure includes only one side photo-alignment substrate, while the other substrate does not have any alignment layer. Both 1D and 2D gratings have been fabricated. The proposed diffraction element shows high diffraction efficiency ? 65% and fast response time of 50 ?s, which is much faster than the existing technologies. Such gratings can be operated with high frequency of around 2 kHz at the electric field of 6.67 V/?m. Moreover, the proposed grating can be erased and rewritten optically for different grating vector in simple steps. Therefore, with these advance features, such gratings have high potential to be applied in verity of devices and for the improvement of some important existing devices.

Ma, Y.; Sun, J.; Srivastava, A. K.; Guo, Q.; Chigrinov, V. G.; Kwok, H. S.

2013-04-01

73

Growth, dielectric, ferroelectric and optical properties of Ca 0.28Ba 0.72Nb 2O 6 single crystals  

NASA Astrophysics Data System (ADS)

Calcium barium niobate Ca 0.28Ba 0.72Nb 2O 6 (CBN-28) crystals were grown by the Czochralski method. The effective segregation coefficients of Ca, Ba, Na elements in CBN-28 crystal growth were measured, and the rocking curve from 0 0 2 reflection of CBN-28 wafer was also measured by the high-resolution X-ray diffractometer D5005, and the full-width at half-maximum value was measured to be 70.6?. The measured dependence of dielectric constants on temperature showed the Curie temperature of the CBN-28 crystals is between 246.8 and 260 °C. Typical polarization-electric field ( P- E) hysteresis loops were measured at room temperature. Ferroelectric 180° domains were observed by scanning electron microscopy (SEM) on the etched (0 0 1) surface of the CBN-28 crystals. The transmittance of [0 0 1]-oriented CBN-28 crystals was measured and the result shows that optical properties of CBN-28 crystal are almost the same as those of SBN for wavelengths between 2500 and 7500 nm.

Song, Hualong; Zhang, Huaijin; Jiang, Quanzhong; Xu, Xiangang; Lu, Chaojing; Hu, Xiaobo; Wang, Jiyang; Jiang, Minhua

2006-05-01

74

A theory of double hysteresis for ferroelectric crystals  

NASA Astrophysics Data System (ADS)

A ferroelectric crystal is known to exhibit the usual single hysteresis below its Curie point TC, but above this temperature its electric displacement D versus electric field E plot tends to form double loops. We first point out that there is a fundamental difference in the formation of double loops from the single one: the single loop is formed solely by polar reorientation, but in the double loops the right branch of its upper loop is formed by phase transition and only the left branch is formed by polar reorientation (the process is reversed for the lower loop). In this study we take the view that both cubic-->tetragonal phase transition and the polar reorientation of ferroelectric domain are thermodynamics-driving process and use this concept to develop a micromechanics-based thermodynamic model to simulate the double hysteresis behavior of the crystal. We first derive the thermodynamic driving force for both spontaneous polarization and domain switch at a given level of temperature, stress, electric field, and new domain concentration c1 and then establish the kinetic equations for domain growth. A dual-phase homogenization theory is then introduced to calculate the overall electric displacement and mechanical strain of the crystal. This approach differs from the classical Landau-Ginzburg-Devonshire theory in at least two significant aspects: (i) it is developed with a micromechanics-based thermodynamics principle, and (ii) it can provide the evolution of new domain concentration. The developed theory is applied to a BaTiO3 crystal. The calculated results show a single loop below its TC and double loops above it but with a diminishing width at higher temperature. Furthermore, the longitudinal strain ? vs E loop is found to exhibit the usual butterfly-shape relation below TC, but above it the loop shows a new, overlapping double-well picture. Good agreement with available test data is also observed.

Srivastava, N.; Weng, G. J.

2006-03-01

75

Characteristics of Localized Domains in Ferroelectric Crystals.  

National Technical Information Service (NTIS)

The characteristics of localized domains in a-domain and c-domain single crystals of barium titanate were investigated. Experimentally, the domains have been optically observed with a polarizing microscope. The domains and the surrounding strain patterns ...

M. M. Shabana

1965-01-01

76

Harvesting single ferroelectric domain stressed nanoparticles for optical and ferroic applications  

NASA Astrophysics Data System (ADS)

We describe techniques to selectively harvest single ferroelectric domain nanoparticles of BaTiO3 as small as 9 nm from a plethora of nanoparticles produced by mechanical grinding. High resolution transmission electron microscopy imaging shows the unidomain atomic structure of the nanoparticles and reveals compressive and tensile surface strains which are attributed to the preservation of ferroelectric behavior in these particles. We demonstrate the positive benefits of using harvested nanoparticles in disparate liquid crystal systems.

Cook, G.; Barnes, J. L.; Basun, S. A.; Evans, D. R.; Ziolo, R. F.; Ponce, A.; Reshetnyak, V. Yu.; Glushchenko, A.; Banerjee, P. P.

2010-09-01

77

Sketched ferroelectric single-electron transistor  

NASA Astrophysics Data System (ADS)

Oxide heterostructures formed from ultrathin layers of LaAlO3 grown on TiO2-terminated SrTiO3, combined with a reversible nanoscale patterning technique, provide a versatile platform for nanoscale control at the single-electron limit. Here we demonstrate the creation and characterization of "sketched" single-electron transistors made from ultrasmall (1-2 nm) quantum dots. Shell filling from N=0 up to N=2 electrons by single-electron tunneling is observed. Resonant tunneling can be controlled in a deterministic and non-volatile fashion by altering the ferroelectric polarization within the SrTiO3 tunnel barrier. These single-electron devices may find use as nanoscale hybrid piezoelectric/charge sensors, and as elemental building blocks for solid-state quantum computation and quantum simulation platforms.

Cheng, Guanglei; Siles, Pablo; Bi, Feng; Cen, Cheng; Bogorin, Daniela; Wung Bark, Chung; Folkman, Chad; Park, Jae-Wan; Eom, Chang-Beom; Medeiros-Ribeiro, Gilberto; Levy, Jeremy

2011-03-01

78

Nonvolatile polymer memory with nanoconfinement of ferroelectric crystals.  

PubMed

We demonstrate significantly improved performance of a nonvolatile polymeric ferroelectric field effect transistor (FeFET) memory using nanoscopic confinement of poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) within self-assembled organosilicate (OS) lamellae. Periodic OS lamellae with 30 nm in width and 50 nm in periodicity were templated using block copolymer self-assembly. Confined crystallization of PVDF-TrFE not only significantly reduces gate leakage current but also facilitates ferroelectric polarization switching. These benefits are due to the elimination of structural defects and the development of an effective PVDF-TrFE crystal orientation through nanoconfinement. A bottom gate FeFET fabricated using a single-crystalline triisopropylsilylethynyl pentacene channel and PVDF-TrFE/OS hybrid gate insulator shows characteristic source-drain current hysteresis that is fully saturated at a programming voltage of ±8 V with an ON/OFF current ratio and a data retention time of approximately 10(2) and 2 h, respectively. PMID:21114332

Kang, Seok Ju; Bae, Insung; Shin, Yu Jin; Park, Youn Jung; Huh, June; Park, Sang-Min; Kim, Ho-Cheol; Park, Cheolmin

2011-01-12

79

Single Crystals  

NASA Astrophysics Data System (ADS)

We have prepared single crystals of type-VIII clathrate Ba8Ga15.9- x In x Sn30.1 for x ? 0.60 by the Sn-flux method. As x is increased from 0 to 0.60, the lattice parameter increases by 0.2%, which is consistent with the larger covalent diameter for In than for Ga. The Seebeck coefficient ?, electrical resistivity ?, and thermal conductivity ? were measured in the temperature range from 300 K to 600 K. For all samples, ? is negative, indicating the dominant charge carriers are electrons. With increasing x from 0 to 0.20, ? and decrease by 50% and 30%, respectively. As a result, the lattice thermal conductivity at 300 K decreases from 0.58 W/Km to 0.41 W/Km, which is ascribed to enhancement of rattling of the guest atoms. It is found that the maximum of the dimensionless figure of merit ZT reaches 1.05 at 540 K for x = 0.20.

Chen, Yuexing; Du, Baoli; Kajisa, Kousuke; Takabatake, Toshiro

2014-06-01

80

Electronic electrooptic effects in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

There are a variety of potential applications in telecommunications and data processing for high-speed second-order nonlinear electronic electro-optic (EEO) switches in chip-based electronics. In these applications the ability to process optical materials and to integrate the electro-optical and electronic components are key issues that have led to the interest in and development of organic-based electro-optical materials. Ferroelectric liquid crystals (FLCs) have potential because they are intrinsically polar by symmetry, a result of their tilted chiral smectic structure, which puts chiral molecules in a monoclinic environment. The directed design of FLCs for second order NLO and EEO applications has evolved a systematic increase in their performance in recent years with electrooptic coefficients, r ˜ 3 pm/V, demonstrated in EEO devices and d ˜ 20 pm/V in NLO applications. The integration of FLCs with silicon-based electronics is a proven commercial technology, but to apply FLCs for EEO it is clear that LC materials with larger second-order nonlinear coefficients (susceptibilities) must be developed. In this dissertation EEO characteristics of FLCs are explored. Including bent-core molecules and materials for potential telecommunication use, probing the modulation of the refractive index for lambda = 1310 nm light induced by applied radio frequency (RF) electric field.

Rickard, Malcolm J.

81

35Cl NQR of an organic ferroelectric phenazine chloranilic acid co-crystal  

NASA Astrophysics Data System (ADS)

A ferroelectric transition of phenazine (Phz) chloranilic acid (H 2ca) co-crystal was studied by 35Cl nuclear quadrupole resonance (NQR). The single NQR line observed at 36.689 MHz at 295 K, split into a doublet below the ferroelectric transition temperature Tc=253 K in accord with the inversion-symmetry breaking at the H 2ca molecular center in the crystal. The continuous variation of the splitting-width through Tc suggests a second-order nature of this phase transition. The NQR frequency is consistent with the crystal structure in which the two acid hydrogen atoms of H 2ca remain as attached to the quinone molecules. The spin-lattice relaxation time T1 showed a decrease with decreasing temperature in the ferroelectric phase. This suggests the existence of a fast motion of nearby atomic group, which is a cause of electric field gradient fluctuation.

Asaji, Tetsuo; Gotoh, Kazuma; Watanabe, Jun

2006-06-01

82

Large strain transduction utilizing phase transition in relaxor-ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals  

NASA Astrophysics Data System (ADS)

In this work, we present experimental evidence that under relatively low level drive (<0.1 MV/m) the large strain (~0.5%) associated with ferroelectric rhombohedral FR-ferroelectric orthorhombic FO phase transition in domain engineered relaxor-ferroelectric single crystals under compressive stress and bias electric field can be captured. We have demonstrated this in mechanically confined ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals poised at the rhombohedral side of the morphotropic phase boundary. Experimental strain-field results, methods of mechanical confinement and drive, and a low frequency, compact, high source level sound projector design are presented. Transducers that operate on a large strain principle as a design rule will benefit from this development.

Finkel, Peter; Benjamin, Kim; Amin, Ahmed

2011-05-01

83

Nanoscale piezoelectric response across a single antiparallel ferroelectric domain wall  

NASA Astrophysics Data System (ADS)

Experiments and three-dimensional numerical modeling of nanoscale piezoelectric response across a single domain wall in ferroelectric lithium niobate are presented. Surprising asymmetry in the local electromechanical response across a single antiparallel ferroelectric domain wall is reported. Piezoelectric force microscopy is used to investigate both the in-plane and out-of- plane electromechanical signals around domain walls in congruent and near-stoichiometric lithium niobate. The observed asymmetry is shown to have a strong correlation to crystal stoichiometry, suggesting defect-domain-wall interactions. A defect-dipole model is proposed. The finite-element method is used to simulate the electromechanical processes at the wall and reconstruct the images. For the near-stoichiometric composition, good agreement is found in both form and magnitude. Some discrepancy remains between the experimental and modeling widths of the imaged effects across a wall. This is analyzed from the perspective of possible electrostatic contributions to the imaging process, as well as local changes in the material properties in the vicinity of the wall.

Scrymgeour, David A.; Gopalan, Venkatraman

2005-07-01

84

Optical model of transient light scattering in ferroelectric liquid crystals  

SciTech Connect

A static optical model is developed for the effect of field-induced transient scattering on coherent light transmission through ferroelectric liquid crystals. Scattering processes are described by introducing an optically anisotropic medium containing scatterers (transient domains). The results presented in the paper are obtained for a plane parallel layer of ferroelectric liquid crystals with a planar helicoidal structure under normal illumination with a linearly polarized plane wave. An analysis is presented of the coherent transmittance of the layer in static applied electric fields.

Loiko, V. A., E-mail: loiko@dragon.bas-net.by; Konkolovich, A. V.; Miskevich, A. A. [National Academy of Sciences of Belarus, Stepanov Institute of Physics (Belarus)

2009-03-15

85

Polymer Network Volume Stabilized Ferroelectric Liquid Crystal Displays  

Microsoft Academic Search

A ferroelectric liquid crystal (FLC) cell for flat panel displays with volume stabilized bistable states is described. Volume stabilization is achieved by the FLC\\/polymer gel dispersion which is prepared by polymerizing a FLC\\/polymer precursor solution in a suitably aligned FLC display cell. The volume stabilized LC cell gives mechanical stability to FLC displays with internal memory and provides for high

J. Pirš; R. Blinc; B. Marin; S. Pirs; J. W. Doane

1995-01-01

86

Dynamical, scattering and dielectric properties of ferroelectric crystals  

Microsoft Academic Search

A unified treatment is given of various properties of ferroelectric crystals in their non-polar phases, typified by BaTiO3, KH2PO4 and NaNO2. Certain relations are established between measurable dielectric and scattering properties. Critical scattering is discussed in terms of lattice dynamics.

W. Cochran

1969-01-01

87

Crystallization and Microstructural Control of Ferroelectric Thin-Films and Glass-Ceramics.  

National Technical Information Service (NTIS)

Research on solution-derived ferroelectric thin-films and melt-derived ferroelectric glass-ceramics was conducted in parallel with considerable overlap in the compositions studied and the evaluations of the crystallization behavior, microstructural develo...

M. J. Haun

1998-01-01

88

Crystallization and Microstructural Control of Ferroelectric Thin-Films and Glass-Ceramics.  

National Technical Information Service (NTIS)

Research on solution-derived ferroelectric thin-films and melt-derived ferroelectric glass-ceramics is being conducted in parallel with considerable overlap in the compositions studied and the evaluations of the crystallization behavior, microstructural d...

M. J. Haun

1993-01-01

89

Ferroelectric phases in a chiral bent-core smectic liquid crystal: Dielectric and optical second-harmonic generation measurements  

NASA Astrophysics Data System (ADS)

We report unambiguous evidence for ferroelectricity in a chiral bent-core liquid crystal. This evidence includes (i) a single current peak in the polarization reversal current, (ii) a strong dielectric response that is suppressed by applying a bias electric field, and (iii) strong optical second-harmonic generation in the absence of electric field even at normal incidence. We propose a phase structure that is anticlinic in tilt and ferroelectric in polar order, i.e., smectic-CAP*F.

Gorecka, E.; Pociecha, D.; Araoka, F.; Link, D. R.; Nakata, M.; Thisayukta, J.; Takanishi, Y.; Ishikawa, K.; Watanabe, J.; Takezoe, H.

2000-10-01

90

Note: Laser beam scanning using a ferroelectric liquid crystal spatial light modulator  

NASA Astrophysics Data System (ADS)

In this work we describe laser beam scanning using a ferroelectric liquid crystal spatial light modulator. Commercially available ferroelectric liquid crystal spatial light modulators are capable of displaying 85 colored images in 1 s using a time dithering technique. Each colored image, in fact, comprises 24 single bit (black and white) images displayed sequentially. We have used each single bit image to write a binary phase hologram. For a collimated laser beam incident on the hologram, one of the diffracted beams can be made to travel along a user defined direction. We have constructed a beam scanner employing the above arrangement and demonstrated its use to scan a single laser beam in a laser scanning optical sectioning microscope setup.

Das, Abhijit; Boruah, Bosanta R.

2014-04-01

91

Note: Laser beam scanning using a ferroelectric liquid crystal spatial light modulator.  

PubMed

In this work we describe laser beam scanning using a ferroelectric liquid crystal spatial light modulator. Commercially available ferroelectric liquid crystal spatial light modulators are capable of displaying 85 colored images in 1 s using a time dithering technique. Each colored image, in fact, comprises 24 single bit (black and white) images displayed sequentially. We have used each single bit image to write a binary phase hologram. For a collimated laser beam incident on the hologram, one of the diffracted beams can be made to travel along a user defined direction. We have constructed a beam scanner employing the above arrangement and demonstrated its use to scan a single laser beam in a laser scanning optical sectioning microscope setup. PMID:24784681

Das, Abhijit; Boruah, Bosanta R

2014-04-01

92

Design of ferroelectric organic molecular crystals with ultrahigh polarization.  

PubMed

Inspired by recent successful synthesis of room-temperature ferroelectric supramolecular charge-transfer complexes, i.e., tetrathiafulvalene (TTF)- and pyromellitic diimide (PMDI)-based crystals (Tayi et al. Nature 2012, 488, 485-489), three new ferroelectric two-component organic molecular crystals are designed based on the TTF and PMDI motifs and an extensive polymorph search. To achieve energetically favorable packing structures for the crystals, a newly developed computational approach that combines polymorph predictor with density functional theory (DFT) geometry optimization is employed. Tens of thousands of packing structures for the TTF- and PMDI-based crystals are first generated based on the limited number of asymmetric units in a unit cell as well as limited common symmetry groups for organocarbon crystals. Subsequent filtering of these packing structures by comparing with the reference structures yields dozens of promising crystal structures. Further DFT optimizations allow us to identify several highly stable packing structures that possess the space group of P21 as well as high to ultrahigh spontaneous polarizations (23-127 ?C/cm(2)) along the crystallographic b axis. These values are either comparable to or much higher than the computed value (25 ?C/cm(2)) or measured value (55 ?C/cm(2)) for the state-of-the-art organic supramolecular systems. The high polarization arises from the ionic displacement. We further construct surface models to derive the electric-field-switched low-symmetry structures of new TTF- and PMDI-based crystals. By comparing the high-symmetry and low-symmetry crystal structures, we find that the ferroelectric polarization of the crystals is very sensitive to atomic positions, and a small molecular displacement may result in relatively high polarizations along the a and c axes, polarity reversal, and/or electronic contribution to polarization. If these newly designed TTF- and PMDI-based crystals with high polarizations are confirmed by experiments, the computer-aided ferroelectric material design on the basis of hydrogen-bonded charge-transfer complexes with flexible electron-donor and acceptor molecules would be proven valuable for expediting the search of room-temperature "displasive-type" ferroelectric organic crystals. PMID:24717106

Chen, Shuang; Zeng, Xiao Cheng

2014-04-30

93

Nanosecond Switching of Nanoscale Ferroelectric Domains in Congruent Single-Crystal LiTaO3 Using Scanning Nonlinear Dielectric Microscopy  

NASA Astrophysics Data System (ADS)

The domain switching characteristics of a congruent LiTaO3 (CLT) single crystal are investigated mainly with respect to switching speed. It is found that fast nanosecond domain switching can be achieved by reducing the sample thickness, even for CLT, which has been thought to be unsuitable for high-speed switching. As an example, the authors successfully obtain a polarization inverted domain dot with a radius of 7.9 nm in a 60-nm-thick CLT plate by application of a 4 ns, 10 V pulse. These results demonstrate that the speed of polarization reversal is closely related to the thickness of the medium.

Fujimoto, Kenjiro; Cho, Yasuo

2004-05-01

94

Fast beam steering with a ferroelectric-liquid-crystal optical phased array.  

PubMed

We demonstrate fast, efficient beam steering using a single 1x32 analog ferroelectric liquid crystal (FLC) spatial light modulator. A high-tilt FLC material with 82 degrees optic-axis switching provides, in a reflective-mode device with a passive quarter-wave retarder between a half-wave FLC layer and a mirror, 91% of full 0-2pi phase modulation. Electronic drive based on applied charge gives 200 micros response-time analog modulation. PMID:19305470

Engström, David; O'Callaghan, Michael J; Walker, Chris; Handschy, Mark A

2009-03-20

95

Criticality of bistability phenomenon in deformed helix ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

The dynamics of bistability in deformed helix ferroelectric liquid crystal have been investigated by electro-optical method. The threshold value of the voltage required to switch the molecules of deformed helix ferroelectric liquid crystals (DHFLC) material has been studied by applying triangular wave pulse and texture observation under polarizing microscope. Two peaks have been observed in low and high frequency regimes on the application of triangular wave pulse to the sample. It has been proposed that the first peak is due to helix unwinding-winding process and the second is due to molecular reorientation process. The occurrence of double peak has been predicted to have close correlation with the observance of memory effect in DHFLC material, which is critically dependent on frequency and applied voltage, on the application of time delayed square wave pulse to the sample cell. The conditions for dynamic and static memory effects in DHFLC material have also been discussed in detail.

Prakash, J.; Mehta, D. S.; Choudhary, A.; Kaur, S.; Rathore, V.; Biradar, A. M.

2008-02-01

96

Dynamic Responses of Dispersed Ferroelectric Liquid Crystal Composite Materials  

Microsoft Academic Search

Dynamic responses of high polarization ferroelectric liquid crystal—multi walled carbon nanotubes composite material has been investigated in the wide frequency range (up to 1 MHZ). Permittivity increased by ?20% to 40% (50 Hz–1 kHz range) but at high frequency >2 kHz, it was independent of carbon nano-tube concentration. The increase in permittivity is attributed to strong anisotropic interactions which enhances

Neeraj; K. K. Raina

2011-01-01

97

Peculiarities of Dielectric Relaxation in DMAAS Ferroelectric Crystals  

Microsoft Academic Search

This paper presents the results of investigations of the dielectric properties of NH2(CH3)2Al(SO4)2x6H2O crystals performed in a wide frequency range. In particular, the temperature and frequency dependences of the dielectric permittivity were measured in the region of ferroelectric phase at different rates of temperature change. The thermal dipole relaxation with a critical slowing-down at Tc1 was observed at comparatively low

V. Kapustianik; Z. Czapla; R. Czukwinski

2000-01-01

98

EPR and NMR line shapes in disordered ferroelectric crystals  

Microsoft Academic Search

A theory is developed for the magnetic resonance line shape in disordered ferroelectric crystals. In a study of the random\\u000a fields responsible for inhomogeneous line broadening, nonlinear and spatial correlation effects are taken into account. It\\u000a is shown that homogeneous broadening depends on the temperature and on the magnitude and orientation of the external magnetic\\u000a field, as well as on

M. D. Glinchuk; I. V. Kondakova

1998-01-01

99

Polymer-stabilized ferroelectric liquid crystal for flexible displays  

Microsoft Academic Search

We developed a novel-structured ferroelectric liquid crystal (LC) device containing two fine polymer structures for a flexible moving-image display incorporating thin plastic film substrates. Aligned polymer fibers of sub-?m-diameter stabilize the LC alignment and create high-speed grayscale capability, while the polymer walls attach the two flexible plastic substrates and keep the gap between the substrates constant when the structure is

Hideo Fujikake; Hiroto Sato; Takashi Murashige

2004-01-01

100

Waveguide formation mechanism generated by double doping in ferroelectric crystals  

Microsoft Academic Search

Physical mechanisms causing the refractive index increase ?n in uniaxial oxidized ferroelectric crystals subjected to double doping are discussed. The analysis shows that the index changes of the two different dopants, ?nA and ?nB, are additive only if the corresponding changes of the spontaneous polarization are small. Ti indiffusion and proton exchange (TIPE) waveguides in LiNbO3 are considered as an

V. V. Atuchin; C. C. Ziling; I. Savatinova; M. N. Armenise; V. M. N. Passaro

1995-01-01

101

Glass-forming low-molecular-mass ferroelectric liquid crystals  

Microsoft Academic Search

For the first time, glass forming low molar mass liquid crystals were synthesized exhibiting ferroelectric properties. This goal was achieved using derivatives of 2,5-dihydroxybenzoic acid with lateral aromatic branches. Several of the compounds prepared show a glass transition near room temperature occurring either in the SmA or in the SmC* phase. In the SmC* phase high values of the spontaneous

J. Boemelburg; G. Heppke; K. Wuthe

1994-01-01

102

Growth and ferroelectric properties of Pb(Zr 0.52Ti 0.48)O 3 thin films crystallized on MgO single-crystal substrates by hot isostatic pressing  

NASA Astrophysics Data System (ADS)

Pb(Zr 0.52Ti 0.48)O 3 films with highly uniform c-axis orientation were fabricated on PbTiO 3 (PT) /Pt(1 0 0)/MgO(1 0 0) substrates from the amorphous state by hot isostatic pressing (HIP). The seven PZT films HIP-treated by single- and multi-step annealing indicated almost preferential (0 0 1) orientation with the degree of the c-axis orientation, ?=0.89-0.99. The PZT films treated according to a one-step (700 °C) annealing program had a good squareness of the hysteresis curves. The PZT capacitors with high initial pulse-derived switchable polarization ( Qsw) and a simple Pt/PZT/PT/Pt/MgO structure fabricated using an HIP technique a one-step (700 °C) annealing program can be expected as high endurance ferroelectric ones for FeRAM applications.

Kobune, Masafumi; Nishioka, Yusuke; Inoue, Tomoaki; Yazawa, Tetsuo

2005-02-01

103

Wavelength and bandwidth tunable photonic stopband of ferroelectric liquid crystals.  

PubMed

The chiral smectic C phase of ferroelectric liquid crystals (FLCs) has a self-assembling helical structure which is regarded as a one-dimensional pseudo-photonic crystal. It is well known that a stopband of a FLC can be tuned in wavelength domain by changing temperature or electric field. We here have demonstrated an FLC stopband with independently tunable wavelength and bandwidth by controlling temperature and incident angle. At highly oblique incidence, the stopband does not have polarization dependence. Furthermore, the bandwidth at highly oblique incidence is much wider than that at normal incidence. The mechanism of the tunable stopband is clarified by considering the reflection at oblique incidence. PMID:22418500

Ozaki, Ryotaro; Moritake, Hiroshi

2012-03-12

104

Effect of shear horizontal leaky surface acoustic wave on selectivity for ethanol decomposition of a copper thin-film catalyst deposited on a positively polarized ferroelectric LiTaO 3 single crystal  

NASA Astrophysics Data System (ADS)

The effect of dynamic surface lattice vibration on the selectivity of ethanol decomposition over a thin-film copper catalyst was studied by using a shear horizontal leaky surface acoustic wave (SH-LSAW) generated by radio frequency (RF) power on a positively polarized, 36° rotated, y-cut LiTaO 3 single crystal. The surface acoustic wave (SAW) caused a remarkably high enhancement of ethylene production but a small increase in acetaldehyde production, thus indicating the SAW's ability to dramatically change the selectivity. Laser Doppler measurements showed an irregular pattern of standing waves with different amplitudes up to 5 nm during SAW propagation. Contact potential difference measurements showed the generation of a negative voltage by the SAW propagation on the positively polarized ferroelectric surface. These changes are quite similar to those previously observed for a thickness-extensional mode resonance oscillation and are associated with the characteristic features of a leaky wave. Selective production of ethylene by the SAW is proposed to be related to the enhancement of the copper surface-oxygen atom interactions through dynamic lattice displacement.

Nishiyama, H.; Saito, N.; Yashima, T.; Sato, K.; Inoue, Y.

1999-06-01

105

Frequency dependent electro-optic property of SBN single crystal  

NASA Astrophysics Data System (ADS)

In electro-optic (EO) modulator devices ferroelectric crystals of strontium barium niobate (SBN) are attractive due to exceptional high EO coefficients and low half wave voltage. SBN single crystals grown by laser heated pedestal growth are investigated to explore frequency dependent EO property at low frequency and near resonant frequency range. The mechanism of its frequency dependence is discussed briefly.

Huang, Chuanyong; Fu, John; Liu, Hongbo; Liu, Yuexin; Gu, Man; Bhalla, Amar S.; Guo, Ruyan

2005-09-01

106

Barium strontium titanate ferroelectric tunable photonic and phononic crystals  

NASA Astrophysics Data System (ADS)

This thesis presents the results of theoretical simulations and experimental investigations on developing electro-optically tunable photonic crystals and thermally tunable phononic crystals based on the ferroelectric materials, Barium Strontium Titanate (Ba0.7Sr0.3TiO3, BST). One-dimensional photonic crystal (PC), consists of alternating Ba 0.7Sr0.3TiO3 and MgO layers, was fabricated using pulsed laser deposition. A photonic bandgap has been observed in the transmission measurement which is consistent with simulation using the plane wave expansion (PWE) method and the transfer matrix method. A 2-nm shift towards the longer wavelength is observed when a dc voltage of 240 V (corresponding to an electric field of about 12 MV/m) has been applied across the coplanar electrodes on the film surface. The experimental result suggests that the electric field induced change in the refractive index of Ba0.7Sr0.3TiO 3 is about 0.5%. Photonic bandstructures and photonic bandgap maps of two-dimensional (2D) Ba0.7Sr0.3TiO3-based photonic crystals with different cavity geometries (square or circular air rods) in square lattice were calculated using the PWE method. Bandgap features along different symmetry directions have also been compared. The appropriate geometry of a single-mode rib waveguide based on Ba 0.7Sr0.3TiO3 thin film was determined by applying the effective index method. A photonic crystal cavity embedded Ba0.7 Sr0.3TiO3 rib waveguide which functions as a tunable filter for lambda = 1550 nm was designed with the help of the finite-difference time-domain (FDTD) simulation. A 6-nm shift in the resonant peak for a 0.5% change in the refractive index of Ba0.7Sr0.3TiO 3 was illustrated in the simulation. Photonic crystal cavities were fabricated on a Ba0.7Sr0.3TiO3 rib waveguide by focused ion beam etching with satisfactory results. A drastic variation in the sound velocities was observed across the Curie temperature of Ba0.7Sr0.3TiO3 via the ultrasonic through-transmission technique. Phononic crystal composed of Ba0.7Sr 0.3TiO3 square rods in a matrix of epoxy were fabricated using the dice-and-fill method. The temperature dependence of the phononic bandgaps was characterized by the reflection spectra obtained using the ultrasonic pulse-echo technique. Thermal tuning of the phononic bandgap was observed and the results were in good agreement with the phononic bandstructure calculation by the PWE method.

Jim, Kwok Lung

107

Energy principle of ferroelectric ceramics and single domain mechanical model  

NASA Astrophysics Data System (ADS)

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

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

2007-10-01

108

Recent Developments on High Curie Temperature PIN-PMN-PT Ferroelectric Crystals  

PubMed Central

Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) ferroelectric crystals attracted extensive attentions in last couple years, due to their higher usage temperatures range (> 30°C) and coercive fields (~5kV/cm), meanwhile maintaining similar electromechanical couplings (k33> 90%) and piezoelectric coefficients (d33~1500pC/N), when compared to their binary counterpart Pb(Mg1/3Nb2/3)O3-PbTiO3. In this article, we reviewed recent developments on the PIN-PMN-PT single crystals, including the Bridgman crystal growth, dielectric, electromechanical, piezoelectric and ferroelectric behaviors as function of temperature and dc bias. Mechanical quality factor Q was studied as function of orientation and phase. Of particular interest is the dynamic strain, which related to the Q and d33, was found to be improved when compared to binary system, exhibiting the potential usage of PIN-PMN-PT in high power application. Furthermore, PIN-PMN-PT crystals exhibit improved thickness dependent properties, due to their small domain size, being on the order of 1?m. Finally, the manganese acceptor dopant in the ternary crystals was investigated and discussed briefly in this paper.

Zhang, Shujun; Li, Fei; Sherlock, Nevin P.; Luo, Jun; Lee, Hyeong Jae; Xia, Ru; Meyer, Richard J.; Hackenberger, Wesley; Shrout, Thomas R.

2011-01-01

109

Electric-Field-Induced Spin Flop in BiFeO3 Single Crystals at Room Temperature  

Microsoft Academic Search

Bismuth ferrite, BiFeO3, is the only known room-temperature magnetic ferroelectric material. We demonstrate here, using neutron scattering measurements in high quality single crystals, that the antiferromagnetic and ferroelectric order parameters are intimately coupled. Initially in a single ferroelectric state, our crystals have a canted antiferromagnetic structure describing a unique cycloid. Under electrical poling, polarization reorientation induces a spin flop. We

D. Lebeugle; D. Colson; A. Forget; M. Viret; A. M. Bataille; A. Gukasov

2008-01-01

110

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

111

Single Crystal Membranes  

NASA Technical Reports Server (NTRS)

Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

Stormont, R. W.; Morrison, A.

1974-01-01

112

Direct writing of ferroelectric domains on strontium barium niobate crystals using focused ultraviolet laser light  

SciTech Connect

We report ferroelectric domain inversion in strontium barium niobate (SBN) single crystals by irradiating the surface locally with a strongly focused ultraviolet (UV) laser beam. The generated domains are investigated using piezoresponse force microscopy. We propose a simple model that allows predicting the domain width as a function of the irradiation intensity, which indeed applies for both SBN and LiNbO{sub 3}. Evidently, though fundamentally different, the domain structure of both SBN and LiNbO{sub 3} can be engineered through similar UV irradiation.

Boes, Andreas; Crasto, Tristan; Steigerwald, Hendrik; Mitchell, Arnan [School of Electrical and Computer Engineering and ARC Center for Ultra-High Bandwidth Devices for Optical Systems (CUDOS), RMIT University, Melbourne, Victoria 3001 (Australia)] [School of Electrical and Computer Engineering and ARC Center for Ultra-High Bandwidth Devices for Optical Systems (CUDOS), RMIT University, Melbourne, Victoria 3001 (Australia); Wade, Scott [Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia)] [Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Frohnhaus, Jakob; Soergel, Elisabeth [Institute of Physics, University of Bonn, Wegelerstr. 8, 53115 Bonn (Germany)] [Institute of Physics, University of Bonn, Wegelerstr. 8, 53115 Bonn (Germany)

2013-09-30

113

Direct writing of ferroelectric domains on strontium barium niobate crystals using focused ultraviolet laser light  

NASA Astrophysics Data System (ADS)

We report ferroelectric domain inversion in strontium barium niobate (SBN) single crystals by irradiating the surface locally with a strongly focused ultraviolet (UV) laser beam. The generated domains are investigated using piezoresponse force microscopy. We propose a simple model that allows predicting the domain width as a function of the irradiation intensity, which indeed applies for both SBN and LiNbO3. Evidently, though fundamentally different, the domain structure of both SBN and LiNbO3 can be engineered through similar UV irradiation.

Boes, Andreas; Crasto, Tristan; Steigerwald, Hendrik; Wade, Scott; Frohnhaus, Jakob; Soergel, Elisabeth; Mitchell, Arnan

2013-09-01

114

Single Crystal Diamond Films.  

National Technical Information Service (NTIS)

Diamond films are important for radiation tolerant devices. However, fabrication of single crystal films has proven to be much more difficult than polycrystalline deposits. A novel deposition process is proposed which can be used to deposit diamond on a s...

S. N. Bunker R. Sahagian

1993-01-01

115

Enhancement in ferroelectric, pyroelectric and photoluminescence properties in dye doped TGS crystals  

SciTech Connect

Pure and dye doped (0.1 and 0.2 mol%) Triglycine Sulfate (TGS) single crystals were grown by slow evaporation technique. A pyramidal coloring pattern, along with XRD and FT-IR studies confirmed the dye doping. Decrease in dielectric constant and increase in Curie temperature (T{sub c}) were observed with increasing doping concentration. Low absorption cut off (231 nm) and high optical transparency (>90%) resulting in large band gap was observed in UV-VIS studies. In addition, strong hyper-luminescent emission bands at 350 and 375 nm were observed in which the relative intensity were found to be reversed as a result of doping. In P-E hysteresis loop studies, a higher curie temperature and an improved and more uniform figure of merit over a large region of the ferroelectric phase were observed. The improved dielectric, optical and ferroelectric/pyroelectric properties make the dye doped TGS crystals better candidate for various opto- and piezo-electronics applications. - Graphical abstract: Dye doping in TGS crystal resulted in hourglass morphology, increased hyper-luminescence intensity, improved T{sub c} and figure of merit. Highlights: Black-Right-Pointing-Pointer Amaranth dye doping in TGS crystals resulted in hourglass morphology. Black-Right-Pointing-Pointer Doping resulted in enhancement of Curie temperature from 49 to 53 Degree-Sign C. Black-Right-Pointing-Pointer Low cut off (230 nm) and wider transmittance window observed. Black-Right-Pointing-Pointer Strong hyper-luminescent emission bands at 350 and 375 nm were observed. Black-Right-Pointing-Pointer High and uniform figure of merit in ferroelectric phase was obtained.

Sinha, Nidhi [Department of Electronics, SGTB Khalsa College, University of Delhi, Delhi-110007 (India); Goel, Neeti; Singh, B.K.; Gupta, M.K. [Crystal Lab, Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Kumar, Binay, E-mail: bkumar@physics.du.ac.in [Crystal Lab, Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)

2012-06-15

116

SINGLE CRYSTAL NEUTRON DIFFRACTION.  

SciTech Connect

Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

KOETZLE,T.F.

2001-03-13

117

Soft memory in a ferroelectric nanoparticle-doped liquid crystal  

NASA Astrophysics Data System (ADS)

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

Basu, Rajratan

2014-02-01

118

V-shaped switching in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

We have studied the three-component liquid crystal mixture reported by Inui et al. to exhibit `thresholdless antiferroelectricity', as well as some other materials with the same V-shaped (linear) electro-optic switching behavior. We find that thresholdless behavior is obtained in the absence of antiferroelectricity. The characteristic response of these materials is due to the field-induced switching of a twisted smectic C* structure stabilized by strong polar surface interactions. The twist is confined to thin surface regions by polarization charge effects leaving the bulk of the cell uniform, which gives almost complete extinction at zero field. Model calculations of the electro-optic response are in good agreement with the experimental data. In sufficiently thin cells, such thresholdless switching can in fact be followed down to much lower temperatures, where the bulk would be antiferroelectric but the cell is maintained in the ferroelectric state by hysteresis.

Maclennan, Joseph E.; Rudquist, Per; Shao, Ren Fan; Link, Darren R.; Walba, David M.; Clark, Noel A.; Lagerwall, Sven T.

1999-10-01

119

Optical recording using smectic layer rotation in ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

Optical recording in a ferroelectric liquid crystal using smectic layer rotation induced by the application of asymmetric voltage pulses has been proposed. This recording method is based on the temperature dependence of the rotation rate and the fact that the rate in the smectic A (SmA) phase is considerably smaller than that in the chiral smectic C (SmC*) phase. The transition from the SmC* to the SmA phase can be induced by the photothermal effect. The application of asymmetric voltage pulses during partial laser irradiation results in the patterning of the layer alignment. This recording method can erase and invert the stored pattern and can handle gray-level patterns.

Nakayama, Keizo; Ohtsubo, Junji; Ozaki, Masanori; Yoshino, Katsumi

2002-04-01

120

Anchoring energy and orientational elasticity of a ferroelectric liquid crystal  

SciTech Connect

The dielectric susceptibility of a helix-free ferroelectric liquid crystal layer has been experimentally and theoretically studied as a function of the layer thickness. The investigation has been performed on the inner branch of the polarization hysteresis loop, in the region of a linear dependence of the polarization on the electric field. The experimental results are explained using the notion of effective layer thickness, which involves the characteristic distance {xi} over which the orienting effect of interfaces is operative. Comparison of the experimental data and theoretical results made it possible to estimate this distance as {xi} = 41 {mu}m and evaluate the anchoring energy (W = 2.8 Multiplication-Sign 10{sup -3}-1.1 Multiplication-Sign 10{sup -2} J/m{sup 2}) and the intralayer elastic constant (K Double-Prime Almost-Equal-To 1 Multiplication-Sign 10{sup -8}-3 Multiplication-Sign 10{sup -7} N).

Kaznacheev, A. V., E-mail: kazna@ineos.ac.ru [Russian Academy of Sciences, Nesmeyanov Institute of Organoelement Compounds (Russian Federation); Pozhidaev, E. P., E-mail: epozhidaev@mail.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

2012-06-15

121

Electro-Optic and Photorefractive Response of Liquid Crystals with Inorganic Ferroelectric Nanoparticles.  

National Technical Information Service (NTIS)

The project will focus on the implementation of nanoparticles in hybrid polymer-liquid crystal systems. In particular we will pursue the following tasks: 1. Preparing high optical quality suspensions of ferroelectric nanoparticles (LC DSFNP) in liquid cry...

M. Kaczmarek

2009-01-01

122

Characterization of lead-based relaxor ferroelectric crystals by acoustic emission  

NASA Astrophysics Data System (ADS)

The acoustic emission (AE) method is presented as a useful complementary tool for nondestructive characterization of selective relaxor ferroelectrics. Combined measurements of the dielectric permittivity and AE activity as a function of temperature and externally applied electric fields have been carried out using Pb(Mg 1/3Nb 2/3)O 3-33%PbTiO 3 (PMN-0.33PT) single crystals and Pb(Sc 0.5Ta 0.5)O 3 (PST) single crystals. Anomalous behavior in the electric field dependencies of the characteristic temperatures, T m (diffuse permittivity maximum in PMN-PT) and T n (formation of incommensurate antiferroelectric domains in PST), and the associated AE intensities has been observed. Both T m and T n exhibit minima coinciding with the AE activities maxima at critical values of the applied dc electric fields, 0.5 and 0.13 kV respectively. These phenomena are discussed mainly in terms of the interaction of the external field with the random electric fields originating from the polar nanoregions in relaxor ferroelectrics.

Roth, M.; Dul'kin, E.; Mojaev, E.; Tseitlin, M.

2011-12-01

123

Electro-optic properties of aligned polysiloxane dispersed ferroelectric liquid crystal composite thin films  

Microsoft Academic Search

Thin polymer dispersed ferroelectric liquid crystal (PDFLC) composite films were prepared using polydimethyl siloxanes of different viscosity grades and ferroelectric liquid crystal mixture (ZLI-3654) using solvent induced phase separation (SIPS) and polymer induced phase separation (PIPS) techniques simultaneously.The electro-optic properties of these films in aligned and unaligned configurations were measured. A comparison indicates that the performance of aligned PDFLCs is

G. Sumana; K. K. Raina

2005-01-01

124

Analysis of polarization switching in ferroelectric crystals in the injection mode  

SciTech Connect

We report on the results of experiments on polarization switching in a ferroelectric TGS crystal during injection of electron beams from a scanning electron microscope under a surface layer. A series of models reflecting the polarization switching dynamics of a ferroelectric crystal under the action of an injected charge is constructed. The implementation of these models is based on the principles of evolution of domain structures taking into account analysis of possible polarization switching mechanisms for ferroelectric samples. A mathematical model developed using these principles demonstrates qualitative similarity of model current pulses and those obtained experimentally in the injection mode.

Maslovskaya, A. G., E-mail: maslovskayaag@mail.ru; Kopylova, I. B. [Amur State University (Russian Federation)

2009-07-15

125

High power single crystal piezoelectric transformer  

US Patent & Trademark Office Database

A piezoelectric transformer includes a single crystal relaxor ferroelectric element poled along a [0 11] direction and selected from the group consisting of PZN-PT, PMN-PZT, PZN-PT and PMN-PT. The element has two opposed surfaces substantially perpendicular to the [0 11] direction with an input electrode and an output electrode positioned on one surface. The output electrode is isolated from electrical communication with the input electrode. A ground electrode is positioned on the second, opposed surface. Input electrical energy results in piezoelectric change in the element that is mechanically coupled through the element to generate piezoelectric output energy.

2013-03-12

126

Low Temperature Ferroelectric Polarization Reversal in X-Ray Irradiated Potassium-Deuterium - Potassium - Acid Mixed Crystals Monitored by Electron Spin Resonance of the Arsenic OXIDE(4-) Free Radical  

Microsoft Academic Search

The polarization reversal of a ferroelectric crystal has been monitored for the first time by the technique of electron spin resonance. This method was employed to study the reversal process in the ferroelectric crystal KD(,2)PO(,4) at low temperatures for a series of electric field strengths. The experiments utilized the AsO(,4)('4 -) free radical formed by x-ray irradiation of single crystals

Roger Dale Truesdale

1982-01-01

127

Monte Carlo Simulations of Spontaneous Ferroelectric Order in Discotic Liquid Crystals  

NASA Astrophysics Data System (ADS)

The demonstration of a spontaneous macroscopic ferroelectric order in liquid phases in the absence of any long-range positional order is considered as an outstanding problem of great fundamental and technological interest. We report here off-lattice Monte Carlo simulations of a system of polar achiral disklike ellipsoids which spontaneously exhibit a novel ferroelectric nematic phase which is a liquid in three dimensions, considering attractive-repulsive pair interaction suitable for the anisotropic particles. At lower temperature, the ferroelectric nematic phase condenses to a ferroelectric hexagonal columnar fluid with an axial macroscopic polarization. A spontaneous ferroelectric order of dipolar origin is established here for the first time in columnar liquid crystals. Our study demonstrates that simple dipolar interactions are indeed sufficient to produce a class of novel ferroelectric fluids of essential interest. The present work reveals the structure-property relationship of achieving long searched ferroelectric liquid crystal phases and transitions between them, and we hope these findings will help in future development of technologically important fluid ferroelectric materials.

Bose, Tushar Kanti; Saha, Jayashree

2013-06-01

128

Monte Carlo simulations of spontaneous ferroelectric order in discotic liquid crystals.  

PubMed

The demonstration of a spontaneous macroscopic ferroelectric order in liquid phases in the absence of any long-range positional order is considered as an outstanding problem of great fundamental and technological interest. We report here off-lattice Monte Carlo simulations of a system of polar achiral disklike ellipsoids which spontaneously exhibit a novel ferroelectric nematic phase which is a liquid in three dimensions, considering attractive-repulsive pair interaction suitable for the anisotropic particles. At lower temperature, the ferroelectric nematic phase condenses to a ferroelectric hexagonal columnar fluid with an axial macroscopic polarization. A spontaneous ferroelectric order of dipolar origin is established here for the first time in columnar liquid crystals. Our study demonstrates that simple dipolar interactions are indeed sufficient to produce a class of novel ferroelectric fluids of essential interest. The present work reveals the structure-property relationship of achieving long searched ferroelectric liquid crystal phases and transitions between them, and we hope these findings will help in future development of technologically important fluid ferroelectric materials. PMID:23848900

Bose, Tushar Kanti; Saha, Jayashree

2013-06-28

129

From nonpolar to ferroelectric crystal structure: the temperature-tuned growth of two guanidinium ethoxysulfonate polymorphs.  

PubMed

Guanidinium ethoxysulfonate, [C(NH2)3]+[C2H5O-SO3]-, was synthesized, and two polymorphs, both stable at normal conditions, were grown from an aqueous solution by only a slight change in the crystallization temperature. The nonpolar polymorph I is built of hydrogen-bonded bilayers, while the ferroelectric polymorph II consists of single-layers. The diversity in the crystals' architecture and properties originates from the excessive number of proton-acceptor sites. At 298 K, the structure of polymorph I is orthorhombic, space group Pbam, formed of supramolecular hydrogen-bonded sheets. Within such a sheet, the ethoxysulfonate anions assume alternately cis and trans conformations, both disordered at room temperature and at 150 K. The anisotropy of the crystal structure is mirrored by a strong anisotropy of its thermal expansion. Upon cooling at 120 K, the crystal undergoes a first-order order-disorder phase transition. The structure of polymorph II is also reinforced by the two-dimensional network of NH...O hydrogen bonds, but the supramolecular motif formed is different from that of polymorph I. The H-bonded strongly corrugated sheets are stacked, forming a densely packed single-layer structure. All the anions assume the same trans conformation. At 298 K, they are disordered between the two sites related by the mirror symmetry plane. The onset of ordering of the anions coincides with the Curie point at TC = 211 K, at which the dielectric constant exceeds 4000. The continuous paraelectric-ferroelectric phase transition is associated with the symmetry change Pnma --> Pna21. Despite the apparent order-disorder character of the transition, the transition mechanism also involves a substantial displacement of the ions and a rearrangement of the H-bonded network. PMID:18288830

Szafra?ski, Marek; Jarek, Marcin

2008-03-13

130

Piezoelectric properties of tetragonal single-domain Mn-doped NBT-6 %BT single crystals  

NASA Astrophysics Data System (ADS)

We report a study of properties of Mn-doped NBT-6 %BT single crystals. We show that tetragonal single-domain states can be stabilized by poling along a [001] direction. For carefully prepared crystals, the piezoelectric coefficient d_{33} can reach 570 pC/N. When poled along non-polar directions, the crystals exhibit ferroelectric domain structures consistent with tetragonal micron-sized domains, as revealed by optical observation and Raman spectroscopy. The multidomain crystals have lower d_{33} values, 225 and 130 pC/N for [011] and [111]-oriented crystals, respectively. This trend is commented on from a domain-engineering perspective.

Guennou, Mael; Savinov, Maxim; Drahokoupil, Jan; Luo, Haosu; Hlinka, Jirka

2013-11-01

131

SrxBa1-xNb2O6-delta Ferroelectric-thermoelectrics: Crystal anisotropy, conduction mechanism, and power factor  

Microsoft Academic Search

Nonstoichiometric tungsten bronze-structured ferroelectric SrxBa1-xNb2O6-delta (SBN) single crystals were found to be a promising n-type thermoelectric oxide. Thermopower anomalies were observed at the phase transition temperatures, depending on the degree of reduction as well as crystal anisotropy. Above 500 K, heavily reduced SBN crystals show high thermoelectric power factors (~20 muW\\/cm K2 at 516 K) with both thermopower and electrical

Soonil Lee; Rudeger H. T. Wilke; Susan Trolier-McKinstry; Shujun Zhang; Clive A. Randall

2010-01-01

132

Growth, structural phase transition and ferroelectric properties of Pb[(Zn 1/3Nb 2/3) 0.91 Ti 0.09]O 3 single crystals  

NASA Astrophysics Data System (ADS)

Growth of PZNT (91/9) single crystals at morphotropic phase boundary has been carried out by flux and flux Bridgman methods. Effects of multinucleation on morphology and effect of PbO evaporation on crystal growth are discussed. The grown crystals were cut along (0 0 1) direction and crystals were poled at the rate of 1 kV/mm. The slow scan X-ray diffraction results of the oriented crystals show a structural phase transition on poling. The phase transition has been studied with slow scan X-ray diffraction pattern for powdered Pb(Zn 1/3Nb 2/3)O 3-PbTiO 3 (PZN-PT) crystal and (0 0 1) oriented single crystal which shows the existence of stressed phases and trapped phases in both cases. Further the grown PZN-PT single crystals have been subjected to compositional studies. Electrical characterizations such as hysteresis measurement, strain measurement and piezoelectric measurement were carried out and the results are discussed in detail.

Bubesh Babu, J.; Madeswaran, G.; Prakash, Chandra; Dhanasekaran, R.

2006-07-01

133

Light Deflection from Ferroelectric Domain Structures in Congruent Lithium Tantalate Crystals  

Microsoft Academic Search

Congruently grown lithium tantalate crystals containing ferroelectric domain structures have been illuminated with ultraviolet light along the crystallographic c axis with simultaneous application of an external electric field. This gives rise to a star-shaped light diffraction pattern in the transmitted beam. The characteristics of this phenomenon are investigated and compared with those observed in lithium niobate crystals.

Manfred Müller; Elisabeth Soergel; Karsten Buse

2004-01-01

134

Electrooptical Switching of Ferroelectric Liquid Crystals in Electrically Distorted Chevron Structure  

Microsoft Academic Search

X-ray diffraction studies on the field induced distortion of the layer structure in ferroelectric liquid crystals are reported. Depending on the liquid crystal materials and alignment layers, electric fields produced reversible or irreversible distortions. Bistable electrooptical switching was observed only in the samples with the irreversibly distorted layer structure. Experimental results on the light transmissions indicated that a bookshelf-like structure

M. Isogai; M. Oh-e; T. Kitamura; A. Mukoh

1991-01-01

135

Synthesis and characterization of halogen-containing ferroelectric liquid crystals and side chain liquid crystalline polymers  

Microsoft Academic Search

A new series of ferroelectric liquid crystals and side chain liquid crystalline polymers based on halogen-containing chiral centres has been synthesized. Chemical structures were analysed by NMR. Liquid crystal phases were characterized by differential scanning calorimetry, optical polarizing microscopy, and X-ray diffractometry. The behaviour of the liquid crystalline phases was investigated as a function of spacer units and differing terminal

Ging-Ho Hsiue; Yi-An Sha; Shih-Jung Hsieh; Ru-Jong Jeng; Wen-Jang Kuo

2001-01-01

136

Light deflection from ferroelectric domain structures in congruent lithium tantalate crystals.  

PubMed

Congruently grown lithium tantalate crystals containing ferroelectric domain structures have been illuminated with ultraviolet light along the crystallographic c axis with simultaneous application of an external electric field. This gives rise to a star-shaped light diffraction pattern in the transmitted beam. The characteristics of this phenomenon are investigated and compared with those observed in lithium niobate crystals. PMID:15619847

Müller, Manfred; Soergel, Elisabeth; Buse, Karsten

2004-12-01

137

Neutron Scattering Study of Single Crystal PZT  

NASA Astrophysics Data System (ADS)

Single crystal specimens of the technologically important ferroelectric material Pb(Zr1-xTix)O3, or PZT, have only recently been grown for the first time at Simon Fraser University. We have characterized the transition temperatures, thermal expansion, and crystal structure of a PZT single crystal between 10 K and 670 K using neutron scattering methods. This crystal, which has a composition (x˜0.46) that lies close to the morphotropic phase boundary (MPB), exhibits a surprisingly large thermal expansion (˜ 10-3 1/K) that changes sign near 545 K, and a rhombohedral crystal structure at 30 K. In addition we observe an enormous relief of extinction beginning around 650 K, which was observed through the temperature dependence of the (200) Bragg peak. Neutron inelastic measurements are planned as are measurements under an applied electric field. This work was supported by the U. S. Office of Naval Research (Grant No. N00014-1-06-0166). All neutron measurements were performed at the NIST Center for Neutron Research.

Phelan, Daniel; Gehring, Peter; Ye, Zuo-Guang; Long, Xifa

2010-03-01

138

Ferroelectric order in liquid crystal phases of polar disk-shaped ellipsoids  

NASA Astrophysics Data System (ADS)

The demonstration of a spontaneous macroscopic ferroelectric order in liquid phases in the absence of any long range positional order is considered an outstanding problem of both fundamental and technological interest. Recently, we reported that a system of polar achiral disklike ellipsoids can spontaneously exhibit a long searched ferroelectric nematic phase and a ferroelectric columnar phase with strong axial polarization. The major role is played by the dipolar interactions. The model system of interest consists of attractive-repulsive Gay-Berne oblate ellipsoids embedded with two parallel point dipoles positioned symmetrically on the equatorial plane of the ellipsoids. In the present work, we investigate in detail the profound effects of changing the separation between the two symmetrically placed dipoles and the strength of the dipoles upon the existence of different ferroelectric discotic liquid crystal phases via extensive off-lattice N-P-T Monte Carlo simulations. Ferroelectric biaxial phases are exhibited in addition to the uniaxial ferroelectric fluids where the phase biaxiality results from the dipolar interactions. The structures of all the ferroelectric configurations of interest are presented in detail. Simple phase diagrams are determined which include different polar and apolar discotic fluids generated by the system.

Bose, Tushar Kanti; Saha, Jayashree

2014-05-01

139

Observation of stochastic resonance using an optically addressed amorphous silicon\\/ferroelectric liquid crystal spatial light modulator  

Microsoft Academic Search

The phenomenon of stochastic resonance is predicted and experimentally verified using an amorphous silicon\\/ferroelectric liquid crystal optically addressed spatial light modulator. We exploit the bistability of aligned ferroelectric liquid crystal for use as the nonlinear element with the noise induced switching intensity set by an optical beam. Readout of the bistable system is also optical. Our measurements show the characteristic

J. P Sharpe; N. Sungar; N. Macaria

1995-01-01

140

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

141

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

PubMed

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

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

2013-04-17

142

Chirping effect on electrooptic modulator SBN single-crystal fiber in microwave cavity  

NASA Astrophysics Data System (ADS)

A ferroelectric single crystal fiber placed inside a microwave cavity is designed to perform pulse uptuning, downtuning, or reshaping by utilizing chirping effects on optical pulses traversing through it. For electrooptic modulator devices ferroelectric crystal fibers are of significant interest due to their high electrooptic coefficients and near-circular cross-sectional waveguide configuration. Single crystal fibers of strontium barium niobate grown by the laser heated pedestal growth method are shown to have high sensitivity to microwave electromagnetic field. Quantitative exploration for the influence of chirping on the performance of this modulator in a microwave cavity waveguide is carried out and reported.

Huang, Chuanyong; Bhalla, Amar S.; Guo, Ruyan

2004-10-01

143

Ferroelectric Polarization Reversal in X-Ray Irradiated Deuterated Potassium Arsenate-Potassium Arsenate Mixed Crystals as Monitored by Electron Spin Resonance  

Microsoft Academic Search

The polarization reversal in the ferroelectric crystal KD_2PO_4 has been monitored by the technique of Electron Spin Resonance (ESR). The experiments employed the AsO _4^{4-} free radical formed by x-irradiation of single crystals of KD _2PO_4 that had been doped with 5 mole % of KH_2AsO _4. At temperatures below T_ {rm c} (223K), the lowest-field hyperfine component of the

Oscar Armando Lopez

1992-01-01

144

Lithium niobate single-crystal and photo-functional device  

DOEpatents

Provided are lithium niobate single-crystal that requires a low voltage of not larger than 10 kV/nm for its ferroelectric polarization inversion and of which the polarization can be periodically inverted with accuracy even at such a low voltage, and a photo-functional device comprising the crystal. The crystal has a molar fraction of Li.sub.2 O/(Nb.sub.2 O.sub.5 +Li.sub.2 O) of falling between 0.49 and 0.52. The photo-functional device can convert a laser ray being incident thereon.

Gopalan, Venkatraman (State College, PA); Mitchell, Terrence E. (Los Alamos, NM); Kitamura, Kenji (Tsukuba, JP); Furukawa, Yasunori (Tsukuba, JP)

2001-01-01

145

Single crystal cylinder transducers for sonar applications  

NASA Astrophysics Data System (ADS)

A segmented cylinder transducer constructed of single crystal lead magnesium niobate-lead titanate (PMN-PT) has been under development at NUWC and EDO Corporation for several years. The purpose of this development was to provide an extremely compact, high power broadband source. By virtue of their extraordinary material properties, ferroelectric single crystals are the ideal transduction material for developing such compact broadband systems. This presentation shall review the evolution of the transducer design as well as present the results of a successful in-water test conducted at NUWC in October of 2003. It shall be shown that design changes intended to eliminate spurious modes limiting the transducer bandwidth first observed in 2002 were successful, resulting in a transducer with a clean frequency response and an effective coupling factor of 0.85. The measured transducer admittance was in nearly exact agreement with theoretical predictions. The NUWC in-water tests demonstrated that the single crystal cylinder achieved an admittance bandwidth (based on the Stansfield criterion) of over 100%, while the tuned power factor was 0.8 or more over 2.5 octaves of frequency. Additionally, the transducer produced 12 dB higher source levels than a similarly sized PZT transducer. [Work sponsored by DARPA.

Robinson, Harold; Stevens, Gerald; Buffman, Martin; Powers, James

2005-04-01

146

Bioengineering single crystal growth.  

PubMed

Biomineralization is a "bottom-up" synthesis process that results in the formation of inorganic/organic nanocomposites with unrivaled control over structure, superior mechanical properties, adaptive response, and the capability of self-repair. While de novo design of such highly optimized materials may still be out of reach, engineering of the biosynthetic machinery may offer an alternative route to design advanced materials. Herein, we present an approach using micro-contact-printed lectins for patterning sea urchin embryo primary mesenchyme cells (PMCs) in vitro. We demonstrate not only that PMCs cultured on these substrates show attachment to wheat germ agglutinin and concanavalin A patterns but, more importantly, that the deposition and elongation of calcite spicules occurs cooperatively by multiple cells and in alignment with the printed pattern. This allows us to control the placement and orientation of smooth, cylindrical calcite single crystals where the crystallographic c-direction is parallel to the cylinder axis and the underlying line pattern. PMID:21265521

Wu, Ching-Hsuan; Park, Alexander; Joester, Derk

2011-02-16

147

High-optical-quality ferroelectric film wet-processed from a ferroelectric columnar liquid crystal as observed by non-linear-optical microscopy.  

PubMed

The self-organization of ferroelectric columnar liquid crystals (FCLCs) is demonstrated. Columnar order is spontaneously formed in thin films made by the wet-process due to its liquid crystallinity. Electric-field application results in high optical quality and uniform spontaneous polarization. Such good processability and controllability of the wet-processed FCLC films provide us with potential organic ferroelectric materials for device applications. PMID:23740767

Araoka, Fumito; Masuko, Shiori; Kogure, Akinori; Miyajima, Daigo; Aida, Takuzo; Takezoe, Hideo

2013-08-01

148

Highly polarized single-c-domain single-crystal Pb(Mn,Nb)O(3)-PZT thin films.  

PubMed

In-plane unstrained single-c-domain/single-crystal thin films of PZT-based ternary ferroelectric perovskite, ?Pb(Mn,Nb)O3-(1 - ?)PZT, were grown on SrRuO(3)/Pt/MgO substrates using magnetron sputtering followed by quenching. The sputtered unstrained thin films exhibit unique ferroelectric properties: high coercive field, Ec > 180 kV/cm, large remanent polarization, P(r) = 100 ?C/cm(2), small relative dielectric constants, ?* = 100 to 150, high Curie temperature, Tc = ~600 °C, and bulk-like large transverse piezoelectric constants, e31,f = -12.0 C/m(2) for PZT(48/52) at ? = 0.06. The unstrained thin films are an ideal structure to extract the bulk ferroelectric properties. Their micro-structures and ferroelectric properties are discussed in relation to the potential applications for piezoelectric MEMS. PMID:22293730

Wasa, Kiyotaka; Adachi, Hideaki; Nishida, Ken; Yamamoto, Takashi; Matsushima, Tomoaki; Kanno, Isaku; Kotera, Hidetoshi

2012-01-01

149

Performance of ferroelectric liquid crystal spatial light modulators for polarization and color diffractive elements  

Microsoft Academic Search

In this work we applied a ferroelectric liquid crystal on silicon (FLCoS) display for implementing monochrome and color diffractive optical elements (DOE). We first apply a reverse engineering process specifically adapted to characterize the optical parameters of a commercial FLCoS display, specifically the phase shift and the tilt angle. We then analyze the performance of the device for implementing a

Ignacio Moreno; P. García-Martínez; M. M. Sánchez-López; A. Martínez-García; J. L. Martínez

2009-01-01

150

Poincaré sphere analysis of a ferroelectric liquid crystal optical modulator: application to optimize the contrast ratio  

Microsoft Academic Search

The Poincaré sphere representation is used to analyze the polarization transformation achieved with a ferroelectric liquid crystal (FLC) optical modulator. This device acts as a switchable wave-plate, in which the orientation of the principal axes rotates under the action of an applied bipolar voltage. In the standard operational mode for intensity switching, the rotation angle of the principal axes is

M. M. Sánchez-López; P. García-Martínez; A. Martínez-García; I. Moreno

2009-01-01

151

Photorefractivity in ferroelectric liquid crystal composites containing electron donor and acceptor molecules.  

SciTech Connect

The first observation of photorefractivity in ferroelectric liquid crystals (FLCs) is reported here. Dopant chromophores chosen to optimize production of mobile ions and careful control of the wavevector and light polarization are believed to play a decisive role in the observed behavior. The Figure is a schematic illustration of the experimental geometry used.

Wiederrecht, G. P.; Yoon, B. A.; Wasielewski, M. R.; Chemistry; Northwestern Univ.

2000-10-16

152

Bistability and nonlinearity in optically addressed ferroelectric liquid-crystal spatial light modulators: applications to neurocomputing.  

PubMed

We report the characteristics of a truly bistable optically addressed ferroelectric liquid-crystal spatial light modulator that is capable of storing binary images. We show that, in addition to this bistability, a nonlinear response and gray scales can be observed under certain operating conditions. We then report on how these capabilities can be used in implementing optical neurocomputing architectures. PMID:20725369

Killinger, M; de Bougrenet de la Tocnaye, J L; Cambon, P; Chittick, R C; Crossland, W A

1992-07-10

153

Investigation of Terbium in the Ferroelectric Crystal, Gadolinium Molybdate, as a Potential Laser.  

National Technical Information Service (NTIS)

A preliminary non-stimulated study of the laser host combination Gd(2 - x)Tb(x)(MoO4)3 is made. The host material, gadolinium molybdate (GMO), is a ferroelectric/ferroelastic crystal. An investigation of temperature and external electric field affects on ...

J. E. Crouch

1976-01-01

154

Anomalous dielectric behavior of KH2PO4 type crystals in the ferroelectric phase  

Microsoft Academic Search

Experimental studies on the dielectric constants of KH2PO4 type ferroelectrics below the Curie temperature Tc are reviewed with special emphasis to the anomalously large dielectric constant and its abrupt decrease in the low temperature region called domain freezing. The origin of the large dielectric constant below Tc is explained in connection with the elastic softening in the multidomain crystals. The

Eiji Nakamura

1992-01-01

155

Dielectric properties versus sample thickness in KH2PO4 ferroelectric crystals  

Microsoft Academic Search

The dielectric constant ??c and the loss constant e“c of KDP crystals are measured in the ferroelectric phase versus the sample thickness t. It is experimentally demonstrated that the ??c values change with t and become maximum for t approximately equal to one half of the other sample dimensions (in a axes directions). Then, it is shown that the domain

J. Bornarel; B. Torche

1992-01-01

156

The Dielectric Relaxation after Polarization Reversal in the Ferroelectric Crystals of KH2PO4—Family  

Microsoft Academic Search

The relaxation of the domain structure of KH2PO4, CsH2PO4, and RbH2PO4 ferroelectric crystals was studied by means of measurements of time dependences of the low frequency dielectric permittivity. Non-equilibrium state of the domain structure was induced by polarization reversal under the ac electric field.

S. N. Drozhdin; B. I. Ogienko; O. M. Golitsyna; A. I. Nikishina; M. Diestelhorst

2007-01-01

157

A micro-electro-mechanical model for polarization switching of ferroelectric materials  

Microsoft Academic Search

Ferroelectric and ferroelastic switching are the major source of nonlinearity and hysteresis in ferroelectric materials subjected to high electric field or mechanical stress. A computational micromechanics model for polycrystalline ferroelectric ceramics is developed based on consideration of the constitutive behavior of single crystals. This model simulates the tetragonal and the rhombohedral crystal structures. Saturation of the linear piezoelectric effect is

W. Chen; C. S. Lynch

1998-01-01

158

Fabrication of waveguide with ferroelectric-domain structure on electro-optical crystal slice  

Microsoft Academic Search

Waveguide is the basic component of integrated optical device. In this work, we introduced a new method to realize switchable waveguide on electric-optical crystals slice. We wrote ferroelectric-domain-inversed pattern in LiNbO3 crystal slice. When we added external electric field on the slice, electric-optical effect operates and the refractive index difference appears in domain-inversed part and its surroundings. Under appropriate configuration,

Guoxin Cui; Yudong Li; Jing Chen; Hongbing Liu; Jingjun Xu; Qian Sun

2007-01-01

159

Crystal Structure and Ferroelectric Properties of Poly(vinylidene fluoride)Carbon nano tube Nanocomposite Film  

Microsoft Academic Search

We investigated the effect of carbon nanotube on the crystal structure and mechanical\\/ferroelectric\\/piezoelectric properties based on poly(vinylidene fluoride) (PVDF) and carbon nano tube (CNT) composite film. The composite films were prepared by solution blending method, and the films were formed by hot-pressing. The contents of CNT were from 0.001 wt.% to 1 wt.%. For inducing piezoelectric beta-crystal structure, the hot-pressed nano composite

Ji Seok Lee; Gwang Ho Kim; Woo Nyon Kim; Kyung Hwan Oh; Hyeong Tae Kim; Seung Sang Hwang; Soon Man Hong

2008-01-01

160

Polarization Raman Spectral Microscopy of Polymer Fibers Formed in Ferroelectric Liquid Crystal  

Microsoft Academic Search

This letter focuses on Raman spectral microscopy of polymer fiber networks, which are formed by the photopolymerization of liquid crystalline acrylate monomers in low-molecular-weight ferroelectric liquid crystal, using polarized infrared light to excite the polymer molecules. It was found that the tolane side-chain molecules of the polymer are significantly orientated with the liquid crystal alignment along the rubbing direction of

Hideo Fujikake; Takeshi Murashige; Hiroto Sato; Masahiro Kawakita; Hiroshi Kikuchi

2003-01-01

161

Effect of rare earth ions on the properties of glycine phosphite single crystals  

NASA Astrophysics Data System (ADS)

Optically transparent glycine phosphite (GPI) single crystals doped with rare earth metal ions (Ce, Nd and La) were grown from aqueous solution by employing the solvent evaporation and slow cooling methods. Co-ordination of dopants with GPI was confirmed by X-ray fluorescence spectroscopic analysis. Single crystal X-ray diffraction analysis was carried out to determine the lattice parameters and to analyze the structural morphology of GPI with dopants, which indicates that cell parameters of doped crystals were significantly varied with pure GPI. Crystalline perfection of doped GPI crystals was determined by high resolution X-ray diffraction analysis by means of full width at half maximum values. Influence of the dopants on the optical properties of the material was determined. Paraelectric to ferroelectric transition temperature (Tc) of doped GPI crystals were identified using differential scanning calorimetric measurements. Piezoelectric charge coefficient d33 was measured for pure and doped GPI crystals. Hysteresis (P-E) loop was traced for ferroelectric b-axis and (100) plane of pure and doped GPI crystals with different biasing field and ferroelectric parameters were calculated. Mechanical stability of crystals was determined by Vickers microhardness measurements; elastic stiffness constant 'C11' and yield strength '?y' were calculated from hardness values. Mechanical and ferroelectric properties of doped crystals were improved with doping of rare earth metals.

Senthilkumar, K.; Moorthy Babu, S.; Kumar, Binay; Bhagavannarayana, G.

2013-01-01

162

SrxBa1-xNb2O6-? Ferroelectric-thermoelectrics: Crystal anisotropy, conduction mechanism, and power factor  

NASA Astrophysics Data System (ADS)

Nonstoichiometric tungsten bronze-structured ferroelectric SrxBa1-xNb2O6-? (SBN) single crystals were found to be a promising n-type thermoelectric oxide. Thermopower anomalies were observed at the phase transition temperatures, depending on the degree of reduction as well as crystal anisotropy. Above 500 K, heavily reduced SBN crystals show high thermoelectric power factors (~20 ?W/cm K2 at 516 K) with both thermopower and electrical conductivity higher parallel to the c-axis. It is noted that the power factor increases with temperature due to the semiconducting behavior with high carrier concentration. The carrier transport mechanism also varies with the degree of reduction and temperature.

Lee, Soonil; Wilke, Rudeger H. T.; Trolier-McKinstry, Susan; Zhang, Shujun; Randall, Clive A.

2010-01-01

163

Pressure-Temperature Phase Diagram of Ferroelectric Pyridinium Tetrafluoroborate Crystal  

NASA Astrophysics Data System (ADS)

The dielectric constant of pyridinium tetrafluoroborate C5NH6\\cdotBF4 (PyBF4) was measured in the frequency range of 300 Hz to about 10 MHz under pressures up to about 1.5 GPa. The critical slowing down of the dielectric relaxation was observed at all pressures examined, the relaxation frequency of which becomes lower with increasing pressure. The pressure derivative of the transition temperature Tc1 between the paraelectric phase and the ferroelectric phase, (dTc1/d p)0, is about 120 K/GPa. This is very large compared with those of other typical order-disorder ferroelectrics. The p-T phase diagram was discussed on the basis of phenomenological theory.

Deguchi, Kiyoshi

2007-01-01

164

Synthesis and Mesomorphic Properties of Naphthyl Propionate Ferroelectric Liquid Crystals  

Microsoft Academic Search

Ferroelectric liquid crystalline compounds containing (2 S )-2-(6-hydroxy-2-naphthyl)propionic acid moiety were synthesized from ( S )-naproxen ( 1 ). Reactions of ( S )-naproxen chloride with alkanols (C 4 -C 6 ) in the presence of propylene oxide gave chiral esters 4 . Demethylation of 4 with dimethylsulfide-AlCl 3 produced naphthols 5 . Esterfication of naphthols 5 with 4-(4-alkoxyphenyl)benzoic acid

Kyung-Tae Kang; Chang Mo Kim; Seng Kue Lee; Myung Soo Shin; Kyung Uk Lee; Jong Gun Lee; Jin Wook Choi; Yong Bae Kim

2002-01-01

165

Effect of Ni doping on ferroelectric and dielectric properties of strontium barium niobate crystals  

NASA Astrophysics Data System (ADS)

The influence of Ni doping on the ferroelectric and dielectric properties have been examined in Sr0.61Ba0.39Nb2O6 (SBN:61) relaxor crystals. The dopants introduced into SBN:61 crystals promote the switching process by reducing the value of threshold nucleation field, and thus coercive field. We present real-time studies of domain nucleation and growth processes in doped SBN:61 by the nematic liquid crystal (NLC) decoration technique. The broad phase transition and low-frequency dielectric dispersion that are exhibited by doped SBN:61 samples have a strong link to the configuration of the ferroelectrics microdomains, which in turn is strongly determined by Ni ions concentration.

Matyjasek, K.; Wolska, K.; Kaczmarek, S. M.; Subocz, J.; Ivleva, L.

2012-01-01

166

Photoinduced electrokinetic redistribution of nano/microparticles during holographic grating recording in the ferroelectric crystal  

NASA Astrophysics Data System (ADS)

We have investigated photoinduced redistribution of metal nanoparticles, placed on the surface of the ferroelectric photorefractive crystal during recording of dynamic holograms. Motivations for this study were improvement of sensitivity for recording of dynamic holographic gratings, for application in nondestructive testing of materials. The home- made biosynthesized gold and silver colloidal solutions were spread as a thin layer on the ferroelectric photorefractive crystal surface. Holographic gratings were recorded in photorefractive crystal of Fe:LiNbO3(Fe:LN) by the HeNe laser (?=633nm) to avoid direct influence of laser light on nanoparticles. Photorefractive holographic grating initially recorded in the crystal volume produce spatially modulated electric field on the crystal surface. This field led to electrophoretic redistribution of the nanoparicles on the crystal surface that result also in additional contribution to the electric field pattern and also change diffraction efficiency of hologram. In addition, we have recorded holographic grating in Fe:LN placed in 5mm cuvette with silver nanoparticles nanofluid and observed nanoparticles distribution along grating line. We have calculated electrophoretic (EP) and dielectrophoretic (DEP) forces on the crystal surface with holographic photorefractive grating, recorded in the crystal. It is shown that longitudinal (along the crystal surface) components of the DEP-force can be described only with high-contrast approach.

Kukhtarev, N.; Kukhtareva, T.; Wang, J.

2011-09-01

167

Crystal growth of alkali metal ion doped potassium niobate fiber single crystals  

NASA Astrophysics Data System (ADS)

Alkali metal (Na, Rb or Cs) ion doped KNbO 3 fiber single crystals are grown using an original pulling down method, to improve their composition change during a crystal growth, by means of co-doping of small ionic size Na and large ionic size Rb or Cs into KNbO 3. In spite of the co-doping, single crystals can be grown with orthorhombic single-phase at room temperature, as well as pure KNbO 3. Their electric properties, such as impedance, are changed depending on the doping ions. Na and Rb co-doped KNbO 3 is promising Pb free ferroelectric and piezoelectric crystals.

Kimura, H.; Tanahashi, R.; Zhao, H. Y.; Maiwa, K.; Cheng, Z. X.; Wang, X. L.

2010-05-01

168

Observation of ferroelectric domain structures by secondary-electron microscopy in as-grown KTiOPO4 crystals  

Microsoft Academic Search

Ferroelectric domain structures of as-grown KTiOPO4 crystals are observed on polished polar surfaces by the scanning secondary-electron microscopy (SEM) method. The results demonstrate a different contrast origin for domain boundaries and domains themselves. It is shown that the electron-beam irradiation in SEM causes a local heating of the ferroelectric crystal. Detailed calculations of the effects involved allow to assume that

G. Rosenman; A. Skliar; I. Lareah; N. Angert; M. Tseitlin; M. Roth

1996-01-01

169

Effect of polymer viscosity on morphological and electro-optic properties of aligned polymer dispersed ferroelectric liquid crystal composite films  

Microsoft Academic Search

A room temperature ferroelectric liquid crystal mixture was dispersed in UV curable polymers of different viscosity in 30:70 wt\\/wt ratio. These polymer dispersed ferroelectric liquid crystal (PDFLC) composite films were prepared by polymerization induced phase separation technique. It was found that the polymer viscosity influences the droplet size and the electro-optic properties. The spontaneous polarization of PDFLC decreases with an

Praveen Malik; Jasjit K. Ahuja; K. K. Raina

2003-01-01

170

Second-harmonic parametric scattering in ferroelectric crystals with disordered nonlinear domain structures.  

PubMed

We study the second-harmonic (SH) parametric processes in unpoled crystals of Strontium Barium Niobate (SBN) with disordered structures of ferroelectric domains. Such crystals allow for the simultaneous phase matching of several second-order nonlinear processes. We analyze the polarization properties of these parametric processes using two types of generation schemes: quasi-collinear SH generation and transverse SH generation. From our experimental data we determine the ratio of d(32) and d(33) components of the second order susceptibility tensor and also the statistical properties of the random structure of the SBN crystal. PMID:19550873

Trull, Jose; Cojocaru, Crina; Fischer, Robert; Saltiel, Solomon M; Staliunas, Kestutis; Herrero, Ramon; Vilaseca, Ramon; N Neshev, Dragomir; Krolikowski, Wieslaw; Kivshar, Yuri S

2007-11-26

171

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

172

A computer study and photoelectric property analysis of potassium-doped lithium niobate single crystals.  

PubMed

First-principles theory was used to design a potassium-doped lithium niobate single crystal. The structural, electronic, optical and ferroelectric properties of the potassium-doped LiNbO3 single crystal model have been investigated using a generalized gradient approximation within density functional theory. It was found that substitution with potassium drastically changed the optical and electronic nature of the crystal and that the band gap slightly decreases. A series of LiNbO3 single crystals doped with x mol% K (x = 0, 3, 6, 9, 12 mol%) were successfully grown using the Czochralski method. The crystals were characterized using powder X-ray diffraction, UV-vis-infrared absorption spectroscopy and a ferroelectric property test. The experimental test results were consistent with the calculated predictions. PMID:23877369

Wang, Wei; Wang, Rui; Zhang, Wen; Xing, Lili; Xu, Yanling; Wu, Xiaohong

2013-09-14

173

Growth of single crystal diamond  

Microsoft Academic Search

The subject of the research presented in this dissertation is the growth of single crystal diamond by microwave plasma chemical vapor deposition (CVD). Both heteroepitaxial and homoepitaxial growth methods have been examined, with emphasis on producing large diamond crystals of high structural and chemical perfection. By heteroepitaxy, epitaxial growth on a foreign substrate, diamond was grown on (001) Ir thin-film

Murari Regmi

2007-01-01

174

Single Crystal Silicon Instrument Mirrors  

NASA Technical Reports Server (NTRS)

The goals for the fabrication of single crystal silicon instrument mirrors include the following: 1) Develop a process for fabricating lightweight mirrors from single crystal silicon (SCS); 2) Modest lightweighting: 3X to 4X less than equivalent solid mirror; 3) High surface quality, better than lambda/40 RMS @ 633nm; 4) Significantly less expensive than current technology; and 5) Negligible distortion when cooled to cryogenic temperatures.

Bly, Vince

2007-01-01

175

Ferroelectric BaTiO3 phase of orthorhombic crystal structure contained in nanoparticles  

NASA Astrophysics Data System (ADS)

Ferroelectric BaTiO3 phase of a Pnma orthorhombic crystal structure is synthesized from a chemical method using a polymer complex of Ba2+ and Ti4+ with polyvinyl alcohol (PVA). After burning out the polymer at temperature as high as 550 °C in air for 2 h results in an average 15 nm crystallite BaTiO3 size, with lattice parameters a=0.6435 nm, b=0.5306 nm, c=0.8854 nm, and density 5.124 g/cm3. The relationship between dielectric constant ?r and temperature showed a single Curie transition temperature TC=131 °C, with as large a Vr value as 263 at TC. A low value of dissipation factor tan ?, as small as 0.033 at room temperature (frequency f=1 kHz), with good insulating properties made the sample promising for use in uncooled infrared detectors and thermal imaging applications. The Vr value is nearly independent of f value up to 100 kHz. A spectrum of sharp EPR signals of g values 2.21 to 1.88 characterizes three major kinds of VBa-, VTi3-, and Ti3+-Vo2+ paramagnetic species present in the imperfections.

Ram, S.; Jana, A.; Kundu, T. K.

2007-09-01

176

Dielectric and spectral properties of DMAAS ferroelectric crystals doped with chromium  

Microsoft Academic Search

This paper presents the results of investigations of the dielectric and spectral properties of NH2(CH3)2Al(SO4)2 × 6 H2O crystals doped with chromium. In particular, it is shown that the dopant noticeably changes the temperature of ferroelectric phase transition and corresponding thermal dipole relaxation with a critical slowing-down at Tc1. The Cr3+ ions were used as a convenient probe for investigations

V. Kapustianik; Z. Czapla; R. Tchukvinskyi; A. Batiuk; Yu. Eliyachevskyy; Yu. Korchak; V. Rudyk

2004-01-01

177

A helix unwinding process in ferroelectric liquid crystals with fixed boundaries  

NASA Astrophysics Data System (ADS)

An appropriate Euler equation for the helix unwinding process in ferroelectric liquid crystals was solved under the condition of fixed boundaries. In order to solve the equation, a Taylor-series expansion and Newton's method, which is a numerical method for finding the root of an equation, were used. The unwinding process depends on the boundary condition, and the threshold to be unwounded disappears in the case of the fixed boundary.

Uto, Sadahito

2005-01-01

178

Temperature Dependence of Selective Reflection in Ferroelectric SmC* Liquid Crystal  

Microsoft Academic Search

The temperature dependences of the selective reflection in a ferroelectric SmC* liquid crystal (CS-1017) are measured accurately in homeotropically aligned cells for different cell thicknesses. For over-50 mum cell thickness, those are in good agreement. Especially for 205 mum cell thickness, the wavelength of the selective reflection decreases with temperature near the SmC*-SmA transition point. The results obtained are also

Masahiro Kawaida; Masahiro Nakagawa; Tadashi Akahane

1988-01-01

179

Synthesis of stable and low melting ferroelectric liquid crystals of the ester family  

Microsoft Academic Search

Three different series of chiral ester compounds, 4?-((S)2-methylbutyloxy)-phenyl 4-alkyloxybenzoates, 4?-((S)4-methylhexyloxy)phenyl 4-alkyloxybenzoates, and 4?-alkyloxyphenyl 4-((S)6-methyloctyloxy)benzoates, have been synthesized and their mesomorphism studied. Low melting compounds have been obtained, all showing a chiral smectic C phase in conjunction with various other mesophases, depending on the series. These new ferroelectric liquid crystals have a remarkable chemical stability.

Patrick Keller

1984-01-01

180

Electro-optical response of ferroelectric liquid crystal cells with photo-dimerization alignment layer  

Microsoft Academic Search

The electro-optical characteristics of ferroelectric liquid crystal (FLC) cells were investigated with a surface-stabilized alignment layer by a photo-dimerization method. The photo-dimerization was performed using a polarized UV light (PUVL) irradiation and monitored with an UV\\/Vis spectrophotometer. It was found that the photo-dimerization method required the lower energy in PUVL exposure energy consumption than a photo-degradation method did. The highest

Kyung-Soo Choi; Hyun-Wuk Kim; Jin-Yool Kim; Tae-Min Kim; Yong-Bae Kim; Jong-Duk Kim

2003-01-01

181

Effects of dichroic dye on the dielectric properties of ferroelectric liquid crystal mixture  

Microsoft Academic Search

The dielectric spectroscopy of the ferroelectric liquid crystal mixture FLC-6980 doped with a low concentration (~2% wt\\/wt) of anthraquinone dye has been studied. The complex permittivity has been measured in the frequency range 100 Hz to 1 MHz in SmC* and SmA phases. Dielectric increments and the relaxation frequencies at various temperatures have been evaluated. Our results indicate that the

K. K. Raina; Arvind K. Gathania; Buta Singh

1999-01-01

182

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

NASA Astrophysics Data System (ADS)

The broadband inelastic light scattering spectra of ternary Pb(In1/2Nb1/2)-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals were investigated as a function of temperature and crystal orientation by combining Raman and Brillouin spectroscopies. The angular dependence of the strong Raman peak located at ˜50 cm-1 was investigated at 300 °C. The intensity variation of this mode with rotation angle was compatible with the F2g mode of Fm3¯m symmetry, suggesting that this mode arises from the 1:1 chemical order at the B-site in this perovskite structure. The temperature evolution of the polar nanoregions was associated with the growth of two central peaks and the change in the intensity of some Raman peaks, which were known to be sensitive to the rhombohedral symmetry. Both relaxation processes exhibited partial slowing-down behaviors with a common critical temperature of ˜160 °C. Poling the crystal along the [001] direction induced abrupt changes in some of the Raman bands at the rhombohedral-tetragonal phase transition. On the other hand, the diffuse tetragonal-cubic phase transition was not affected by the poling process. This high-temperature phase transformation seems to be smeared out by the inherent disorder and strong random fields enhanced by the addition of Pb(In1/2Nb1/2) into Pb(Mg1/3Nb2/3)O3-PbTiO3.

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

2014-06-01

183

A rate-dependent thermo-electro-mechanical free energy model for perovskite type single crystals  

Microsoft Academic Search

The three-dimensional electro-mechanical free energy potential developed by Kim and Seelecke [S.J. Kim and S. Seelecke, A rate-dependent three-dimensional free energy model for ferroelectric single crystals, Int. J. Solids Struct. 44 (2007) 1196–1209] is generalized to model various thermal aspects of perovskite type single crystals. A total of seven energy potentials are described in the 10-dimensional space of electric displacement

Sang-Joo Kim

2007-01-01

184

Aligned single crystal boron nanowires  

Microsoft Academic Search

The well aligned boron nanowires (BNWs) with single crystalline structure were successfully prepared by using nanochannel-Al2O3 as a substrate and a chemical vapor deposition process. The diameter and length of BNWs were around of 40 nm and several micrometers, respectively. The formation of single crystal BNWs has been conceptually interpreted.

Q. Yang; J Sha; J Xu; Y. J Ji; X. Y Ma; J. J Niu; H. Q Hua; D. R Yang

2003-01-01

185

Topographic investigation of ferroelectric domain structures in periodically-poled lithium niobate crystals by a profilometer  

SciTech Connect

A topographic investigation of periodically poled lithium niobate (PPLN) crystals was performed by recording a map of the crystal surface after a selective etching process using a standard profilometer. A procedure to correct for the systematic error introduced by the finite size of the tip is discussed in detail so that the width of ferroelectric domains can be mapped with an estimated tolerance of about 3% along the whole length of the sample. The method is applied to a PPLN structure obtained by the Czochralski off-center technique.

Bazzan, M.; Argiolas, N.; Bernardi, A.; Mazzoldi, P.; Sada, C

2003-10-15

186

Structural, electronic and ferroelectric properties of croconic acid crystal: a DFT study.  

PubMed

The recent discovery of high polarization at room temperature in croconic acid crystals as large as 21 ?C cm(-2) [Horiuchi et al., Nature, 2010, 463, 789] has lead to renewed interest in organic ferroelectrics, a promising class of materials for future electronic devices. We present here an extended ab initio study of this molecular crystal, using different approximations for the exchange-correlation functionals, ranging from local and semi-local types to more sophisticated hybrid functionals and van der Waals corrected functionals. Furthermore, by using distortion mode analysis, we focus on the different contributions to the polarization and on their microscopic origins. PMID:23032103

Di Sante, Domenico; Stroppa, Alessandro; Picozzi, Silvia

2012-11-14

187

Synthesis and characterization of ferroelectric side chain liquid crystal polymers bearing banana-shaped chiral mesogens  

Microsoft Academic Search

A series of ferroelectric liquid crystal polymers having banana-shaped side chain mesogens were synthesized through photo-polymerization\\u000a of epoxide moiety. 2,5-disubstituted-thiophene sub-unit was used in synthesizing the banana-shaped monomers. These liquid\\u000a crystal compounds were characterized by NMR, differential scanning calorimetry (DSC) and optical polarized microscopy (POM).\\u000a Mesomorphism was investigated as a function of spacer units. All the synthesized low molar mass

Long-Hai Wu; Chwn-San Chu; N. Janarthanan; Chain-Shu Hsu

2000-01-01

188

Electro-optic tunable multi-channel filter in two-dimensional ferroelectric photonic crystals  

NASA Astrophysics Data System (ADS)

An electro-optic tunable multi-channel filter is presented, which is based on a two-dimensional ferroelectric photonic crystal made of barium titanate. The filtering properties of the photonic crystal filter can be tuned by an applied voltage or by adjusting the structural parameters. The channel shifts about 30 nm under excitation of an applied voltage of 54.8 V. The influences of the structural disorders caused by the perturbations in the radius or the position of air holes on the filtering properties are also analyzed.

Fu, Yulan; Zhang, Jiaxiang; Hu, Xiaoyong; Gong, Qihuang

2010-07-01

189

Piezoelectric and pyroelectric coefficients for ferroelectric crystals with polarizable molecules  

NASA Technical Reports Server (NTRS)

Expressions for piezoelectric and pyroelectric coefficients for a crystal of polarizable point dipoles are derived. The effect of crystal structure on the local electric field acting to polarize the molecules is included via the Lorentz-factor formalism. The derived expressions for the piezo- and pyroelectric coefficients are found to contain terms dependent on derivatives of the Lorentz factors. These terms reflect the changing of molecular dipole moments in response to the changing local electric field in the strained crystal. Inclusion of this effect results in predictions of coefficients substantially different from those obtained using the Lorentz field approximation.

Purvis, C. K.; Taylor, P. L.

1982-01-01

190

Development of single crystal membranes  

NASA Technical Reports Server (NTRS)

The design and construction of a high pressure crystal growth chamber was accomplished which would allow the growth of crystals under inert gas pressures of 2 MN/sq m (300 psi). A novel crystal growth technique called EFG was used to grow tubes and rods of the hollandite compounds, BaMgTi7O16, K2MgTi7O16, and tubes of sodium beta-alumina, sodium magnesium-alumina, and potassium beta-alumina. Rods and tubes grown are characterized using metallographic and X-ray diffraction techniques. The hollandite compounds are found to be two or three-phase, composed of coarse grained orientated crystallites. Single crystal c-axis tubes of sodium beta-alumina were grown from melts containing excess sodium oxide. Additional experiments demonstrated that crystals of magnesia doped beta-alumina and potassium beta-alumina also can be achieved by this EFG technique.

Stormont, R. W.; Cocks, F. H.

1972-01-01

191

Amplitude and phase fluctuation modes of a newly synthesized anti ferroelectric liquid crystal material 4F6Bi  

Microsoft Academic Search

Frequency and temperature dependent dielectric spectroscopy of a newly synthesized anti ferroelectric liquid crystal (AFLC) material namely “(S)-(+)-(1-methylheptyloxycarbonyl)phenyl 4?-(6-perfluoropentanoyloxyhex-1-oxy) biphenyl-4-carboxylate ((S) (4F6Bi))” has been carried out in the frequency range 1 Hz to 1 MHz under planar anchoring conditions of the molecules. 4F6Bi possesses paraelectric (SmA?), ferroelectrics (SmC?), and wide range anti ferroelectric (SmCA?) phases. The SmA? phase shows soft mode relaxation

Aanchal Dwivedi; R. Dhar; M. B. Pandey; I. M. L. Das; R. Dabrowski

2009-01-01

192

Mechanism of crystal-symmetry dependent deformation in ferroelectric ceramics: Experiments versus model  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the mechanism of crystal-symmetry dependent deformation in ferroelectrics both experimentally and theoretically. We fabricated three types of Pb(ZrxTi1-x)O3 ceramics including the tetragonal (PZT45/55), the rhombohedral (PZT60/40), and the morphotropic (PZT52/48), where the tetragonal and rhombohedral phases coexist. X-ray diffraction and piezoresponse force microscopy were performed to characterize the crystal structures and domain patterns. Deformation of both poled and unpoled PZT ceramics was tested under bipolar electric fields and uniaxial compression, respectively. It is found that in both loading cases, the deformation of the morphotropic PZT is obviously larger than that of the tetragonal and rhombohedral PZT. As to the latter two, the electric field induced strain in the tetragonal PZT is smaller than that in the rhombohedral PZT, while the compression induced strains show the opposite tendency. To explore the observed crystal-symmetry deformation mechanism, we employed a previously proposed optimization-based constrained domain-switching model to simulate the experimental results. Domain switching in this model is realized by an optimization process to minimize the free energy of each grain. The constraint from neighboring grains is considered in an Eshelby inclusion manner, which is inherently crystal-symmetry dependent. The simulation results fit well with our experimental results without any fitting parameters, which indicate that the constrained domain-switching is responsible for the crystal-symmetry dependent deformation mechanism in ferroelectric ceramics.

Li, Y. W.; Zhou, X. L.; Miao, H. C.; Cai, H. R.; Li, F. X.

2013-06-01

193

Boundary layer elasto-optic switching in ferroelectric liquid crystals  

NASA Technical Reports Server (NTRS)

The first experimental observation of a change in the director azimuthal angle due to applied shear stress is reported in a sample configuration involving a liquid-crystal-coated top surface exposed directly to gas flow. The electrooptic response caused by the shear stress is large, fast, and reversible. These findings are relevant to the use of liquid crystals in boundary layer investigations on wind tunnel models.

Parmar, D. S.

1992-01-01

194

Single Crystal Surfaces  

NASA Astrophysics Data System (ADS)

The present work studies (0001) Al2O3 and (111) Al2MgO4 wetting with pure molten Al by the sessile drop technique from 1073 K to 1473 K (800 °C to 1200 °C) under Ar at PO2 10-15 Pa. Al pure liquid wets a smooth and chemically homogeneous surface of an inert solid, the wetting driving force ( t, T) can be readily studied when surface solid roughness increases in the system. Both crystals planes (0001) Al2O3 and (111) Al2MgO4 have crystallographic surfaces with identical O-2 crystalline positions however considering Mg2+ content in Al2MgO4 structure may influence a reactive mode. Kinetic models results under similar experimental conditions show that Al wetting on (0001) Al2O3 is less reactive than (111) Al2MgO4, however at >1273 K (1000 °C) (0001) Al2O3 transformation occurs and a transition of wetting improves. The (111) Al2MgO4 and Al system promotes interface formations that slow its wetting process.

Aguilar-Santillan, Joaquin

2014-06-01

195

Optical correlator using very-large-scale integrated circuit/ferroelectric-liquid-crystal electrically addressed spatial light modulators  

NASA Technical Reports Server (NTRS)

The use of 2-kHz 64 x 64 very-large-scale integrated circuit/ferroelectric-liquid-crystal electrically addressed spatial light modulators as the input and filter planes of a VanderLugt-type optical correlator is discussed. Liquid-crystal layer thickness variations that are present in the devices are analyzed, and the effects on correlator performance are investigated through computer simulations. Experimental results from the very-large-scale-integrated / ferroelectric-liquid-crystal optical-correlator system are presented and are consistent with the level of performance predicted by the simulations.

Turner, Richard M.; Jared, David A.; Sharp, Gary D.; Johnson, Kristina M.

1993-01-01

196

Basic Studies on Templated Grain Growth of Relaxor Ferroelectric Crystals and Textured Ceramics.  

National Technical Information Service (NTIS)

Templated grain growth (TGG) enables the relatively low cost fabrication of textured ceramics with single crystal-like properties, as well as single crystals. The resulting ceramics show texture levels up to 90%, and significant enhancements in the piezoe...

G. L. Messing S. Trolier-McKinstry

2003-01-01

197

Fabrication of waveguide with ferroelectric-domain structure on electro-optical crystal slice  

NASA Astrophysics Data System (ADS)

Waveguide is the basic component of integrated optical device. In this work, we introduced a new method to realize switchable waveguide on electric-optical crystals slice. We wrote ferroelectric-domain-inversed pattern in LiNbO3 crystal slice. When we added external electric field on the slice, electric-optical effect operates and the refractive index difference appears in domain-inversed part and its surroundings. Under appropriate configuration, incident beam could be guided along the domain structure. We produced successfully waveguides with width from 10 to 100 ?m. Experimental results show that the capability of the waveguides inside LiNbO3 crystal slice could be adjusted by changing the external electric field on the crystal slice. Compared with other production method of waveguide such as ion diffusion, our method is more flexible and more suitable to produce design-free waveguide devices.

Cui, Guoxin; Li, Yudong; Chen, Jing; Liu, Hongbing; Xu, Jingjun; Sun, Qian

2007-12-01

198

Radiation Effects in DMAAS:Cr Ferroelectric Crystal  

Microsoft Academic Search

This paper presents the results of investigations of the radiation effects in NH 2 (CH 3 ) 2 Al(SO 4 ) 2 x6H 2 O crystals doped with chromium. On the basis of absorption spectroscopy and resonance Raman scattering study it has been shown that comparatively low doses of radiation first of all causes recharging of Cr 3+ on Cr

V. Kapustianik; Z. Czapla; Yu. Eliyachevskyy; Yu. Korchak; B. Kulyk; V. Rudyk

2002-01-01

199

Crystal Structure and Dielectric Properties of PZT Ferroelectric Ceramic Fibers  

Microsoft Academic Search

The crystal structures of PZT ceramic fibers with continuum spinning process were identified, showing a pure tetragonal phase of perovskite for the samples treated at around 900°C. The microstructures of the PZT fibers were observed, displaying relatively complex evolution with the increasing of temperature during heat treatment. With the increasing of frequency, the dielectric constants and loss tangents became smaller

Z. X. Xiong; J. Pan; H. Xue; M. F. Mai; H. Qiu; L. F. Chen

2010-01-01

200

Dielectric Properties in Ferroelectric Liquid Crystal Mixtures with Ultrashort Pitch  

Microsoft Academic Search

The dielectric propereties of smectic liquid crystal mixtures containing chiral dopants derived from trifluoromethylated pyranose were studied. In every mixture, a large dielectric response due to the Goldstone mode was observed, indicating the smectic C* phase, although two switching current peaks indicative of the smectic CA* phase were observed in the mixtures with high dopant ratios. With increasing the chiral

Masahito Zennyoji; Jun Yokoyama; Yoichi Takanishi; Ken Ishikawa; Hideo Takezoe; Keizo Itoh

1998-01-01

201

Phase transitions in ferroelectric-paraelectric superlattices: Stability of single domain state  

NASA Astrophysics Data System (ADS)

We studied stability of the single-domain state with respect to domain formation within Landau-Ginzburg-Devonshire theory for ferroelectric-paraelectric superlattices having equal layer thickness. Single-domain state is possible if dielectric constant of the paraelectric is larger than that of the ferroelectric for non-polar directions as in the BaTiO3/SrTiO3 system, which was taken as an example. Stability limit of the single-domain state is found as a function of temperature and layer thickness where we show a strong dependence of this limit on character of near-electrode regions, a point often overlooked. We also show that transition between single- and multi-domain states is discontinuous.

Levanyuk, A. P.; Misirlioglu, I. B.

2013-11-01

202

Adsorption on Single Crystal Planes.  

National Technical Information Service (NTIS)

A working instrument has been developed and tested for measuring work functions of perfect single crystal planes. The longstanding high work function value (6.0 eV) for emission from the (110) plane of tungsten was investigated using the new FN plus energ...

R. D. Young H. E. Clark

1967-01-01

203

The growth of SbSBr, SbSCI and SbSF single crystal in gel  

NASA Astrophysics Data System (ADS)

Antimony sulphobromide, antimony sulphochloride and antimony sulphofluoride single crystals have been grown in sodium silicate gel at room temperature. The conditions of the growth of these ferroelectric semiconducting crystals have been investigated. Chemical and X-ray diffraction studies have been made for identifying the grown crystals as SbSBr, SbSC1 and SbSF. These crystals are found to be orthorhombic with space group D 162h.

Raman, G.; Gnanam, F. D.; Ramasamy, P.

1986-06-01

204

Piezoelectric anisotropy of KNbO3 single crystal  

SciTech Connect

Orientation dependence of the longitudinal piezoelectric coefficients (d*{sub 33}) of a KNbO{sub 3} single crystal has been investigated as a function of temperature by using the Landau-Ginzburg-Devonshire thermodynamic phenomenological theory. It is shown that the maximum of d*{sub 33} is not always along the polarization direction of the ferroelectric phase. The enhancement of d*{sub 33} d along a nonpolar direction is attributed to the ferroelectric phase transition at which a polarization changes its direction. In the tetragonal phase, the maximum of d*{sub 33}{sup t} for the tetragonal phase at high temperatures is along the tetragonal polar direction and then changes its direction toward the polar direction of the orthorhombic phase when close to the tetragonal-orthorhombic phase transition point. The maximum of d*{sub 33}{sup o} of the orthorhombic phase depends on the competition of both high-temperature and low temperature ferroelectric phase transitions. In the rhombohedral phase, the maximum of d*{sub 33}{sup r} is relatively insensitive to temperature due to the absence of any further phase transitions in the low temperature regime. These results can be generalized to the phase transitions induced by external electric-field, pressure, and composition variations.

Liang, Linyun; Li, Yulan; Hu, Shenyang Y.; Chen, Long-Qing; Lu, Guang-Hong

2010-11-01

205

Piezoelectric properties of lithium modified silver niobate perovskite single crystals  

NASA Astrophysics Data System (ADS)

We report the growth and the piezoelectric properties of lead-free perovskite single crystals of Ag1-xLixNbO3. It possesses a rhombohedral structure with high ferroelectric phase transition (Tc=548 K for x=0.086) and large spontaneous polarization (Ps~40 ?C/cm2 for x=0.062) along the <111>c direction of pseudocubic perovskite structure for x>0.05-0.06. High quasistatic d33~210 pC/N and low dielectric constant have lead to a very large value of piezoelectric voltage constant g33~53.9×10-3 Vm/N for the <001>c-cut crystal of this simple perovskite. It has been shown that Li substitution might enhance the piezoelectric coefficient of the crystal. The excellent piezo-/ferroelectricity of this system are considered to be facilitated by the strong polarization nature of both Ag and Li in the perovskite structure. Our findings may stimulate further interests in the development of lead-free piezoelectrics.

Fu, Desheng; Endo, Makoto; Taniguchi, Hiroki; Taniyama, Tomoyasu; Koshihara, Shin-Ya; Itoh, Mitsuru

2008-04-01

206

Criterion for identification of ferroelectric domains in Tags crystals from Am images  

SciTech Connect

Criteria for identification of actual (dynamic) domains and morphologically similar domain 'memory' regions are proposed based on the study of various types of contrast of topographic atomic-force microscopy images of lens like regions on the polar surface of Tags crystals. Inaccuracy in identification may result in further errors in estimating the parameters of the domain structure. The images of ferroelectric domains in the spreading-resistance mode that indicate directly the presence of conductive properties of the domain walls have been obtained for the first time.

Gainutdinov, R. V., E-mail: alla@ns.crys.ras.ru; Belugina, N. V.; Tolstikhina, A. L.; Lysova, O. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2007-03-15

207

Highly promising electrooptic material: Distorted helix ferroelectric liquid crystal with a specific tilt angle  

NASA Astrophysics Data System (ADS)

Short pitch deformable helix ferroelectric liquid crystals are shown to become optically isotropic at certain critical tilt angle with an average dielectric constant (?1+?2+?3)/3. For uniaxial medium, this angle equals ?d=cos-1(1/3), and it depends weakly on the local biaxial anisotropy. The degeneracy is removed upon the application of a small electric field and the medium becomes optically biaxial. A high contrast fast electrooptic modulation and display devices can be built using such materials even when aligned in a multi-domain. For tilt angles very near the degeneracy angle, ultrasensitivity of the eigenaxes rotation to the applied field is found.

Abdulhalim, I.

2012-10-01

208

Influence of gold nanorods size on electro-optical and dielectric properties of ferroelectric liquid crystals  

SciTech Connect

The influence of the gold nanorods (GNRs) diameter on the electro-optic and dielectric properties of the ferroelectric liquid crystals (FLCs) was investigated. It was shown that dispersing of GNRs in FLCs could lead to an increase of the internal electric field inside the liquid crystalline layer. This effect results in a significant decrease of the switching time and the rotational viscosity of the FLC/GNRs nanodispersions independently on the GNRs diameter. Oppositely, the relaxation frequency and the dielectric strength of the Goldstone mode strongly depend on the GNRs diameter, which can be explained by the charge transfer between the GNRs and FLC molecules.

Podgornov, Fedor V.; Ryzhkova, Anna V. [Eduard-Zintl-Institute for Inorganic and Physical Chemistry, Darmstadt University of Technology, Petersenstr. 20, Darmstadt D-64287 (Germany); Department of Physics, Electrical Engineering Technologies Laboratory, South Ural State University, Lenin Ave. 76, Chelyabinsk 454080 (Russian Federation); Haase, Wolfgang [Eduard-Zintl-Institute for Inorganic and Physical Chemistry, Darmstadt University of Technology, Petersenstr. 20, Darmstadt D-64287 (Germany)

2010-11-22

209

Mechanism of homeotropic alignment of ferroelectric liquid crystals doped with ferro-fluid and applications  

NASA Astrophysics Data System (ADS)

We report homeotropic (HT) alignment of ferroelectric liquid crystal (FLC) doped with various concentrations of ferro-fluid (FF) without using any type of alignment layer. The FF induced HT alignment of FLC was found to be dependent on the doping concentration as revealed by optical micrographs, contact angle, and dielectric spectroscopy studies. Higher water contact angle of FF doped FLC films with respect to pure FLC film suggests higher surface energy of FF doped FLC than the surface energy of substrate. The physico-chemical mechanism together with steric model successfully explains the HT alignment of the studied FLC on the ITO substrate.

Joshi, Tilak; Singh, Shri; Choudhary, Amit; Pant, R. P.; Biradar, A. M.

2013-07-01

210

Crystallization mechanism and piezoelectric properties of solution-derived ferroelectric poly(vinylidene fluoride) thin films  

NASA Astrophysics Data System (ADS)

?-phase dominant poly(vinylidene fluoride) (PVDF) ferroelectric thin films were obtained on silicon substrates by spin coating the precursor solutions with addition of hydrate salt and drying at an elevated temperature. The remnant polarization of the dense ?-phase dominant PVDF thin film was 69.5 mC/m2. The apparent longitudinal piezoelectric coefficient d33 was -17.4 pm/V without taking into account the substrate clamping effect. It was suggested that the hydrate salt functioned as nucleation sites for the crystallization of PVDF molecules, and the intermolecular hydrogen bonding together with dipolar interactions promoted all-trans conformation and ?-phase formation.

He, Xujiang; Yao, Kui

2006-09-01

211

Domain structure in a micron-sized PbZr1-xTixO3 single crystal on a Ti substrate fabricated by hydrothermal synthesis  

Microsoft Academic Search

Hydrothermal synthesis is an attractive method for the deposition of ferroelectric thin films because it can realize a low processing temperature of 200 °C or less. In this study, micron-sized PbZr1-xTixO3 (PZT) single crystals and thin films were fabricated on a Ti substrate at 160 °C by hydrothermal synthesis. The ferroelectricity of the crystals was investigated using local piezoresponse hysteresis,

D. J. You; W. W. Jung; S. K. Choi; Yasuo Cho

2004-01-01

212

Domain structure in a micron-sized PbZr1?xTixO3 single crystal on a Ti substrate fabricated by hydrothermal synthesis  

Microsoft Academic Search

Hydrothermal synthesis is an attractive method for the deposition of ferroelectric thin films because it can realize a low processing temperature of 200 °C or less. In this study, micron-sized PbZr1?xTixO3 (PZT) single crystals and thin films were fabricated on a Ti substrate at 160 °C by hydrothermal synthesis. The ferroelectricity of the crystals was investigated using local piezoresponse hysteresis,

D. J. You; W. W. Jung; S. K. Choi; Yasuo Cho

2004-01-01

213

Electrochromism accompanying ferroelectric domain inversion in congruent RuO2:LiNbO3 crystal.  

PubMed

Electrochromic phenomena accompanying the ferroelectric domain inversion in congruent RuO2-doped z-cut LiNbO3 crystals at room temperature are observed in experiments. During the electric poling process, the electrochromism accompanies the ferroelectric domain inversion simultaneously in the same poled area. The electrochromism is completely reversible when the domain is inverted from the reverse direction. The influences of electric field and annealing conditions on domain inversion and electrochromism are also discussed. We propose the reasonable assumption that charge redistribution within the crystal structure caused by domain inversion is the source for electrochemically oxidation and reduction of Ru ion to produce the electrochromic effect. PMID:19503233

Zhi, Ya'nan; Liu, De'an; Zhou, Yu; Chai, Zhifang; Liu, Liren

2005-12-12

214

Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals  

NASA Technical Reports Server (NTRS)

Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.

Parmar, D. S.; Holmes, H. K.

1993-01-01

215

Relaxor-PT Single crystals: Observations and Developments  

PubMed Central

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

Zhang, Shujun; Shrout, Thomas R.

2011-01-01

216

Crystal growth and characterization of a perovskite derived ferroelectric compound: (Nd4Ca 2)Ti6O20  

Microsoft Academic Search

Crystals of the ferroelectric compound (Nd4Ca 2)Ti6O20 have been synthesized for the first time by flux method. The most suitable flux is PbO and the starting oxides were either reacted or unreacted stoichiometric mixtures. The crystals obtained were of good quality with dimensions of 10×1×1 mm. Crystallographic analyses performed on the crystals show that they are twinned, with monoclinic symmetry,

J. Ostorero; M. Nanot; F. Queyroux; J. C. Gilles; H. Makram

1983-01-01

217

Polarization rotation and phase transition in [100]-oriented PZN-PT single crystals determined by the electro-crystalline anisotropy  

NASA Astrophysics Data System (ADS)

We have investigated the polarization rotation and phase transition in [100]-oriented PZN-4.5%PT and PZN-8%PT single crystals on the basis of the single domain polarization rotation model. The dependence of both the polarization and the electrostrictive responses in ferroelectric crystals on the field at various temperatures has been numerically obtained. The numerical results have shown that both the polarization rotation and the phase transition are in nature determined by the electro-crystalline anisotropy constants. These constants are dependent on the composition of PZN-PT solution and ferroelectric properties of its components. Without considering the piezoelectric effect, the numerical results are in agreement with the experimental data. This paper is useful for better understanding of the polarization switching and the phase transition in ferroelectric crystals.

Zhang, Hui

2013-11-01

218

Ferroelectric Domain Structures in Epitaxial PZT Thin Films: A Review  

Microsoft Academic Search

Heteroepitaxial growth of thin films of non-cubic ferroelectric materials on cubic single crystal substrates inevitably accompanies twin domain formation. Since the presence of twin domains strongly affects on the ferroelectric properties, studies on the twinning phenomena are crucial for controlling their properties. Ferroelectric twin-domain formation in epitaxial Pb(Zr,Ti)O 3 thin films has been investigated by changing several processing parameters such

Kilho Lee; Kyeong Seok Lee; Yong Kwan Kim; Sunggi Baik

2002-01-01

219

The origin of ferroelectricity in magnetoelectric YMnO3  

Microsoft Academic Search

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

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

2004-01-01

220

Scanning probe microscopies applied to the study of the domain wall in a ferroelectric crystal.  

PubMed

Scanning near-field optical microscopy is capable of measuring the topography and optical signals at the same time. This fact makes this technique a valuable tool in the study of materials at nanometric scale and, in particular, of ferroelectric materials, as it permits the study of their domains structure without the need of chemical etching and, therefore, not damaging the surface (as will be demonstrated later). We have measured the scanning near-field optical microscopy transmission, as well as the topography, of an RbTiOPO(4) single crystalline slab, which exhibits two different of macroscopic ferroelectric domains. A chemical selective etching has been performed to distinguish between them, obtaining areas with a noticeable roughness (C(-) domain) in comparison with the original flat aspect of the other ones (C(+) domain). The effects of the selective chemical etching have been quantified in topographic images obtained by means of our fibre tip probe, and have been compared to topographic images obtained by Atomic Force Microscopy, with a better resolution. The near-field optical transmission images recorded have been obtained under different excitation wavelengths. These images are modulated by the light scattering due to the grains at the rough surface, which depends on the excitation wavelength used. In addition, they show a significant optical contrast due to the variations of the dielectric constant on the proximity of the ferroelectric domain wall. PMID:17444942

Canet-Ferrer, J; Martín-Carrón, L; Martínez-Pastor, J; Valdés, J L; Peña, A; Carvajal, J J; Diaz, F

2007-05-01

221

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

C. Annis

1992-01-01

222

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

D. P. DeLuca C. Annis

1993-01-01

223

An azo-bridged ferroelectric liquid crystal with highly enhanced second and third harmonic generation.  

PubMed

A laterally azo-bridged trimer ferroelectric liquid crystal (FLC) incorporating a strong chromophore along its polar axis was synthesized and characterized by polarized-light optical microscopy, differential scanning calorimetry, two-dimensional X-ray diffraction analysis, electro-optical measurements, and nonlinear optical (NLO) investigations. This mesogen exhibits a thermodynamically stable enantiotropic SmC* phase and a bistable ferroelectric switching in a surface stabilized cell with bookshelf geometry. It gives the resonance-enhanced d(22) coefficient of 28 pm V(-1) (? = 1.369 ?m) for second harmonic generation (SHG), the largest NLO susceptibility reported to date for all FLCs. At the same wavelength, a new type of helicoidal phase matching assisted by the helical SmC* structure was identified. When the second harmonic wavelength of 780 nm is far away from the resonance wavelength (?(max) = 572 nm), the d(22) coefficient is reduced to 6.8 pm V(-1) (? = 1.56 ?m). In addition to a strong SHG activity, the trimer also shows a strong third harmonic generation (THG) with an estimated third-order nonlinear susceptibility of ?((3)) = ~3 × 10(-11) esu (? = 1.56 ?m), among the largest ?((3)) value reported from THG measurements for liquid crystals. This work enables viable applications of FLCs in nonlinear optics and offers an innovative approach to develop new FLCs with larger NLO strength. PMID:22909407

Zhang, Yongqiang; Ortega, Josu; Baumeister, Ute; Folcia, César L; Sanz-Enguita, Gerardo; Walker, Christopher; Rodriguez-Conde, Sofía; Etxebarria, Jesus; O'Callaghan, Michael J; More, Kundalika

2012-10-01

224

Poisson–Boltzmann equation and electro-convective instability in ferroelectric liquid crystals: a mean-field approach  

NASA Astrophysics Data System (ADS)

Commercialization of ferroelectric liquid crystal displays (FLCDs) suffers from mechanical and electro-convective instabilities. Impurity ions play a pivotal role in the latter case, and therefore we developed a mean-field type model to understand the complex role of space charges, particularly ions in a ferroelectric liquid crystal. Considering an effective ion-chirality relation, we obtained a modified Poisson–Boltzmann equation for ions dissolved into a chiral solvent like the ferroelectric smectic phase. A nonuniform director profile induced by the mean electrostatic potential of the ions is then calculated by solving an Euler–Lagrange equation for a helically twisted smectic state. A combination of effects resulting from molecular chirality and an electrostatically driven twist created by the ions seems to produce this nonuniform fluctuation in the director orientation. Finally, both theoretical and experimental points of view are presented on the prediction of this mean-field model.

Lahiri, T.; Pal Majumder, T.; Ghosh, N. K.

2014-07-01

225

Single crystal growth of the tetragonal tungsten bronze Ca x Ba 1? x Nb 2O 6 ( x=0.28; CBN28)  

Microsoft Academic Search

The material group of the tetragonal tungsten bronzes (TTBs) is very attractive due to its outstanding ferroelectric properties. Herein we report attempts to grow single crystals of calcium barium niobate (CBN) that until now was only known as ceramic samples. The single crystal growth of CBN could be realized in two different ways. In a first step a high-temperature tetraborate

M. Eßer; M. Burianek; D. Klimm; M. Mühlberg

2002-01-01

226

Synthesis and Characterization of Novel Ferromagnetic, Ferroelectric, Single Phase and Composite Multiferroic Mesoporous Materials  

NASA Astrophysics Data System (ADS)

Mesoporous nanostructures offer facile routes to novel materials with interesting and often unparalleled properties. Ferrimagnetic, ferroelectric and multiferroic phases, the latter comprising materials that simultaneously possess multiple order parameters, are of great technological importance. Developments in our knowledge of and ability to produce new materials exploiting their properties could have fundamental impacts. Employing versatile solution phase chemistry techniques utilizing co-assembly between organic block co-polymers and inorganic metal precursors, we are able to produce 3-dimensional porous nano-structures in thin film format. Mesoporous frameworks comprising various magnetic ferrites are explored in chapters 2, 3 & 4. The crystal structure and nanoscale architecture for each material is thoroughly examined, and the effects of mesoporosity on the magnetic characteristics of the individual ferrites are determined. The ferrites investigated (MFe2O4,M=Co, Zn, Ni, Mg) are magnetostrictive as their magnet moments are subject to change upon straining of the crystal lattice. It was observed that the nano-scale architecture imparts novel strain states on to the polycrystalline phases and spin re-orientation of their magnetic moment results, emulating results that, previous to the finding in this study, were exclusive to epitaxial growth techniques. Furthermore, the presence of high surface area, resulting from mesoporosity, increases surface spin states drastically altering the magnetic functionality of porous ferrites versus their bulk counterparts. The effects of mesoporosity on piezoelectric materials was also investigated. Piezoelectrics comprise a fascinating class of materials that exhibit internal creation of charge upon the action of mechanical strain, the reverse of which is also true. Mesoporous piezoelectric phases were successfully prepared, and the effects of porosity on the ferroelectric order paramter were established. The presence of pores in the nano-scale architecture allows for flexibility of the framework, as such for a given external electric field mesoporous piezoelectric frameworks can reach greater strain states versus dense counterparts who are subject to adverse clamping effects due to their anchorage to the substrate. The last class of materials investigated in chapters 6 & 7 are multiferroics, which combine the two ferroic order parameters discussed in the first part of this dissertation. Bismuth ferrite, a single phase multiferroic, is prepared in both a dense and mesoporous thin film format and the effects of porosity are investigated. Results from SQuID and synchrotron X-ray scattering experiments reveal the mesoporous materials to be superior multiferroics. The ferromagnetic and magneto-electric coupling qualities of the mesoporous films are greater than films prepared with epitaxial lattice mismatch techniques. Additional to single phase, composite multiferroic materials are also investigated. The potential of creating composite multiferroics via the combination of evaporation-induced-self-assembly techniques, for the fabrication of porous frameworks, and atomic layer deposition, for the subsequent filling of the pores, is explored. Though still in its infancy, this approach already shows great promise. The success of pore filling is examined via X-ray photoelectron spectroscopy, X-ray diffraction and microscopy studies.

Quickel, Thomas Eugene

227

A novel boundary layer sensor utilizing domain switching in ferroelectric liquid crystals  

NASA Technical Reports Server (NTRS)

This paper describes the design and the principles of operation of a novel sensor for the optical detection of a shear stress field induced by air or gas flow on a rigid surface. The detection relies on the effects of shear-induced optical switching in ferroelectric liquid crystals. It is shown that the method overcomes many of the limitations of similar measuring techniques including those using cholesteric liquid crystals. The present method offers a preferred alternative for flow visualization and skin friction measurements in wind-tunnel experiments on laminar boundary layer transition investigations. A theoretical model for the optical response to shear stress is presented together with a schematic diagram of the experimental setup.

Parmar, D. S.

1991-01-01

228

Single Crystals (M = Fe, Co)  

NASA Astrophysics Data System (ADS)

FeGa3 and related compounds have been subjects of recent investigation for their interesting thermoelectric, electronic, and magnetic behaviors. Here, single crystals of FeGa3- y Ge y were grown by the self-flux technique with effective y = 0, 0.09(1), 0.11(1), and 0.17(1) in order to investigate the evolution of the diamagnetic semiconducting compound FeGa3 into a ferromagnetic metal, which occurs through the electron doping and band structure modifications that result from substitution of Ge for Ga. Heat capacity and magnetization measurements reveal non-Fermi liquid behavior in the vicinity of the transition from a paramagnetic to ferromagnetic ground state, suggesting the presence of a ferromagnetic quantum critical point (FMQCP). We also present the first results of hole doping in this system by the growth of FeGa3- y Zn y single crystals, and electron- and hole doping of the related compound CoGa3 by CoGa3- y Ge y and CoGa3- y Zn y crystal growths, aiming to search for further routes to band structure and charge carrier tuning, thermoelectric optimization, and quantum criticality in this family of compounds. The ability to tune the charge carrier type warrants further investigation of the MGa3 system's thermoelectric properties above room temperature.

Cabrera-Baez, M.; Magnavita, E. Thizay; Ribeiro, Raquel A.; Avila, Marcos A.

2014-06-01

229

A Method for Molecular Alignment of Ferroelectric Smectic Liquid Crystal: Combination of Metal Oxide Thin Film and Electric Field  

Microsoft Academic Search

A method for molecular alignment of a ferroelectric smectic liquid crystal is reported. Homeotropic alignment with a small angle of pretilt was obtained by surface treatment with oblique deposition of metal oxide, such as yttria and alumina. Furthermore, an electric field was applied during the cooling period from isotropic liquid to chiral smectic phase. Uniformly pretilted alignment could be obtained

Michio Kuwahara; Yasushi Kawata; Hiroyoshi Onnagawa; Kazuo Miyashita

1988-01-01

230

Effect of the Surface Anchoring Energy on the Electro-Optical Properties in Monostable Ferroelectric Liquid Crystal Display  

Microsoft Academic Search

Nine series of polyimides (PIs) were used to examine the correlation between the surface energy of the alignment layer and electro-optical properties of the continuous director rotation (CDR) ferroelectric liquid crystal (FLC). We found that both driving voltage and response time for CDR FLC were reduced due to the weak interaction between FLC and PI, when the anchoring energy of

Yu-Jin Kim; Kyu-Sik Kim; Yong Bae Kim

2002-01-01

231

Piezoelectric single crystal langatate and ferromagnetic composites: Studies on low-frequency and resonance magnetoelectric effects  

NASA Astrophysics Data System (ADS)

Mechanical strain mediated magnetoelectric (ME) effects are studied in bilayers and trilayers of piezoelectric single-crystal lanthanum gallium tantalate (LGT) and magnetostrictive permendur (P). The ME voltage coefficient ranges from 2.3 V/cm Oe at 20 Hz to 720 V/cm Oe at bending resonance and is higher by an order of magnitude than in composites with ferroelectric lead zirconate titanate or lead magnesium niobate-lead titanate. The low-frequency magnetic noise for P-LGT-P is a factor of 2-10 smaller than for ferroelectrics based composites. Langatate is free of ferroelectric hysteresis, pyroelectric effects, and phase transitions up to 1450 °C and is of interest for ultrasensitive, high temperature magnetic sensors.

Sreenivasulu, G.; Fetisov, L. Y.; Fetisov, Y. K.; Srinivasan, G.

2012-01-01

232

Fatigue effect in bulk ferroelectrics  

Microsoft Academic Search

We have used a kinetic approach to the fatigue phenomenon in ferroelectrics for the analysis of the evolution of switching current and strain hysteresis loops in bulk PZT ceramics and the switching current in PZN-PT single crystals during cyclic switching. It is proposed that fatigue is due to a redistribution of the local internal bias field during cycling (spatially non-uniform

Vladimir Y. Shur; Evgenii L. Rumyantsev; Ekaterina Nikolaeva; Eugene Shishkin; Ivan Baturin; Alevtina Shur; Doru C. Lupascu; Clive A. Randall; Metin Ozgul

2002-01-01

233

Effect of metallic dopants on potassium acid phthalate (KAP) single crystals  

NASA Astrophysics Data System (ADS)

Optically transparent single crystals of Cu 2+ and Zn 2+ doped potassium acid phthalate (KAP) were grown in aqueous solution by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis confirmed the changes in the lattice parameters of the doped crystals. The presence of functional groups in the crystal lattice has been determined qualitatively by Fourier transform infrared (FTIR) analysis. Optical absorption studies revealed that the doped crystals possess very low absorption in the entire visible region. The dielectric constant has been studied as a function of frequency for the doped crystals at temperatures viz., 328, 348, 368 K. Further the influence of metal dopants on the dielectric behaviour has been studied which clearly exhibited the ferroelectric properties of the crystal.

Chithambaram, V.; Jerome Das, S.; Arivudai Nambi, R.; Srinivasan, K.; Krishnan, S.

2010-06-01

234

Studies on various properties of pure and Li-doped Barium Hydrogen Phosphate (BHP) single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of pure and Li-doped barium hydrogen phosphate (BHP) were grown by solution method with gel technique. Various properties of the harvested crystals were studied by carrying out single crystal and powder XRD, FTIR, TG/DTA, microhardness and dielectric studies. Atomic absorption study was carried out for Li-doped BHP crystal to check the presence of Li dopants. Unit cell dimensions and diffracting planes of the grown crystals have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Density of the grown crystals was calculated using the XRD data. Thermal stability of the samples was checked by TG/DTA studies. Mechanical and dielectric characterizations of the harvested pure and Li-doped BHP crystals reveal the mechanical strength and ferroelectric transition. The observed results are reported and discussed.

Nallamuthu, D.; Selvarajan, P.; Freeda, T. H.

2010-12-01

235

{shape{In situ}} Observation of the Crystallization Process of Ferroelectric Thin Films by Raman Microspectroscopy  

NASA Astrophysics Data System (ADS)

Crystallization processes of ferroelectric strontium bismuth tantalate (SrBi2Ta2O9; SBT) films with a Bi-layered structure and lead zirconate titanate [Pb(Zr0.5Ti0.5)O3; PZT] films with a perovskite structure have been investigated by Raman microspectroscopy. Amorphous films were prepared by rf-magnetron sputtering at room temperature using nearly stoichiometric ceramic targets. In situ Raman observations were performed at intervals with increasing sample temperatures. Under a heating rate of 20°C/min, the SBT films began to crystallize at 710°C, and completed crystallization at 850°C. It was found that SBT film crystallization advanced rapidly in the temperature region from 750 to 800°C. Raman mapping measurements of the SBT films at room temperature after annealing at 700 and 800°C clearly indicated the nucleation and growth processes of the crystal grains, respectively. The Raman peaks of the PZT films, which were observed in situ in spite of the cubic symmetry at the annealing temperatures, showed perovskite structure formation at temperatures as low as 500°C.

Nomura, Kenji; Takeda, Yasutoshi; Maeda, Masunobu; Shibata, Noriyoshi

2000-09-01

236

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

PubMed

Electric field-induced polarization switching underpins most functional applications of ferroelectric materials in information technology, materials science and optoelectronics. Recently, much attention has been focused on the switching of individual domains using scanning probe microscopy. The classical picture of tip-induced switching, including formation of cylindrical domains with size, is largely determined by the field distribution and domain wall motion kinetics. The polarization screening is recognized as a necessary precondition to the stability of ferroelectric phase; however, screening processes are generally considered to be uniformly efficient and not leading to changes in switching behaviour. Here we demonstrate that single-point tip-induced polarization switching can give rise to a surprisingly broad range of domain morphologies, including radial and angular instabilities. These behaviours are traced to the surface screening charge dynamics, which in some cases can even give rise to anomalous switching against the electric field (ionic field effect). PMID:25066894

Ievlev, Anton V; Morozovska, Anna N; Eliseev, Eugene A; Shur, Vladimir Ya; Kalinin, Sergei V

2014-01-01

237

Crystal structures, phase transitions, and pressure-induced ferroelectricity in [C(NH2)3]5SO4(SO3-OC2H5)2F.  

PubMed

A guanidinium compound, [C(NH(2))(3)](5)SO(4)(SO(3)-OC(2)H(5))(2)F, with complex anionic sublattice has been synthesized and characterized by calorimetric and dielectric measurements at ambient and high hydrostatic pressures, as well as by single-crystal X-ray diffraction at varied temperatures. At room temperature, the crystal structure is orthorhombic, with the space group Pnma. In this phase, each of the two crystallographically nonequivalent ethoxysulfonate anions is disordered between two sites. On cooling, one of these anions starts to set in order at 228 K, where the crystal transforms in a continuous manner to the intermediate orthorhombic phase, with the space group P2(1)2(1)2(1). This transition belongs to the exceptionally rare pure gyrotropic phase transitions, the order parameter of which is described by the third-rank gyrotropic tensor. The ordering of the second ethoxysulfonate anion occurs suddenly at 187 K, inducing a first-order phase transition to the low-temperature phase of space group Pna2(1). The dissimilar response of both ethoxysulfonate anions to the temperature variation can be attributed to the different hydrogen bonding patterns they form with the cationic framework. Despite the polar symmetry, the low-temperature phase is not ferroelectric at ambient pressure, but it acquires ferroelectric features at elevated pressures above 140 MPa, as evidenced by the polarization reversal in an external electric field. The ferroelectric properties disappear on increasing pressure above 220 MPa, where the phase transition strongly modifying the crystal properties, but fully reversible, takes place. In the pressure-induced phase, a Debye-like dipolar relaxation process has been found and characterized as a function of pressure. The unusual properties of [C(NH(2))(3)](5)SO(4)(SO(3)-OC(2)H(5))(2)F under hydrostatic pressure have been summarized in the p-T phase diagram. PMID:21761883

Szafra?ski, Marek

2011-09-01

238

Pyroelectric field assisted ion migration induced by ultraviolet laser irradiation and its impact on ferroelectric domain inversion in lithium niobate crystals  

SciTech Connect

The impact of UV laser irradiation on the distribution of lithium ions in ferroelectric lithium niobate single crystals has been numerically modelled. Strongly absorbed UV radiation at wavelengths of 244–305 nm produces steep temperature gradients which cause lithium ions to migrate and result in a local variation of the lithium concentration. In addition to the diffusion, here the pyroelectric effect is also taken into account which predicts a complex distribution of lithium concentration along the c-axis of the crystal: two separated lithium deficient regions on the surface and in depth. The modelling on the local lithium concentration and the subsequent variation of the coercive field are used to explain experimental results on the domain inversion of such UV treated lithium niobate crystals.

Ying, C. Y. J.; Mailis, S. [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom)] [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Daniell, G. J. [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)] [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Steigerwald, H.; Soergel, E. [Institute of Physics, University of Bonn, Wegelerstrasse 8, 53115 Bonn (Germany)] [Institute of Physics, University of Bonn, Wegelerstrasse 8, 53115 Bonn (Germany)

2013-08-28

239

Effect of polymeric nanoparticles on dielectric and electro-optical properties of ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

It has been observed that the polymeric nanoparticles, copolymer of polybenzene and anthracene (PBA NPs), can induce a homeotropic (HMT) alignment in various ferroelectric liquid crystal (FLC) mixtures. The HMT alignment of various FLCs is attributable to the fact that the anthracene molecules favor an upright orientation (with a little tilt) on the surfaces of indium tin oxide and this upright orientation of anthracene molecules works as a template to align FLC molecules homeotropically. It has been concluded that the addition of ~0.5 wt % of PBA NPs is enough to induce a HMT alignment in a FLC material Felix 17/100. The influence of the PBA NPs concentrations on the transition temperature, physical constants (such as spontaneous polarization, rotational viscosity, and response time) and dielectric relaxation processes of FLC material (Felix 17/100) has also been investigated.

Kumar, A.; Silotia, P.; Biradar, A. M.

2010-07-01

240

Dispersions of multi-wall carbon nanotubes in ferroelectric liquid crystals.  

PubMed

The electro-optic and dielectric properties of ferroelectric liquid crystal-multi-wall carbon nanotube dispersions were investigated with respect to temperature and nanotube concentration. The main physical properties, such as tilt angle, spontaneous polarization, response time, viscosity, and Goldstone-mode relaxation strength and frequency were studied. While all dispersions exhibit the expected temperature dependencies of their physical properties, their dependence on nanotube concentration is still a controversial discussion in literature, with several contradicting reports. For increasing nanotube concentration we observed a decrease in tilt angle, but an increase in spontaneous polarisation, the latter explaining the enhancement of the bilinear coupling coefficient, and the dielectric relaxation strength. Despite the increase in polarization, the electro-optic response times slow down, which suggests an increase of rotational viscosity along the tilt cone. It is anticipated that the latter also accounts for the observed decrease of the Goldstone-mode relaxation frequency for increasing nanotube concentration. PMID:24532223

Yakemseva, M; Dierking, I; Kapernaum, N; Usoltseva, N; Giesselmann, F

2014-02-01

241

Beam steering experiment with two cascaded ferroelectric liquid-crystal spatial light modulators.  

PubMed

The design, construction, and evaluation of a laser beam steerer that uses two binary ferroelectric liquid-crystal (FLC) spatial light modulators (SLMs) operated in conjunction are presented. The system is characterized by having few components and is in principle lossless. Experimentally, a throughput of approximately 20% was achieved. The simple system design was achieved because of the high tilt angle FLC material used in the SLMs, which were specifically designed and manufactured for this study. By coherently imaging the first SLM onto the second SLM, pixel by pixel, we obtained an effective four-level phase structure with a phase step of 90 degrees. An appropriate alignment procedure is presented. The beam steering performance of the system is reported and analyzed. PMID:15015538

Engström, David; Hård, Sverker; Rudquist, Per; Dhavé, Koen; Matuszczyk, Tomasz; Skeren, Marek; Löfving, Björn

2004-03-01

242

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

Microsoft Academic Search

The high piezoelectric response of the ferroelectric relaxor (1 - x)Pb(Mg1\\/3Nb2\\/3)O3 - xPbTiO3 (PMNT) in single crystal form has generated significant interest in producing broad bandwidth SONAR systems. Both the piezoelectric coefficient (d33 > 2000 pC\\/N) and coupling coefficient (k33 > 0.90) are superior to those of conventional piezoelectric ceramics. Within the context of a high power acoustic projector, its

Nevin P. Sherlock

2010-01-01

243

Single crystal PZN\\/PT-polymer composites for ultrasound transducer applications  

Microsoft Academic Search

Single crystal relaxor ferroelectrics of PZN-8%PT were investigated for potential application in ultrasound transducers. The full set of electromechanical properties was determined using combined resonance and laser interferometry techniques. Ultra-high length extensional coupling (k33) of 0.94 was observed, a 25% increase over Navy Type VI PZT ceramics. The thickness extensional coupling (kt) of 0.48 was comparable to PZT compositions, and

Timothy Ritter; Xuecang Geng; K. Kirk Shung; P. D. Lopath; Seung-Eek Park; Thomas R. Shrout

2000-01-01

244

The temperature-electric field phase diagram of a ferroelectric smectic C* liquid crystal  

NASA Astrophysics Data System (ADS)

We have studied the temperature-electric field phase diagram of a ferroelectric smectic C* liquid crystal. We used 4-(2'methyl butyl) phenyl 4'-n-octylbiphenyl-4-carboxylate (CE8) as our ferroelectric liquid crystal material. Using extensive electro-optical measurements which included the direct observation of the sample under a polarizing microscope and also laser light diffraction from the helicoidal structure of the unwound smectic-C* phase, the entire temperature-electric field phase space for the smectic-C* phase was explored thoroughly. We looked for all possible phase transitions in the smectic-C* region. The character of the phase transitions, that is, whether they are first order (discontinuous) or second order (continuous), and also whether they are the instability or nucleation type was determined. Our results shows that the experimental phase diagram is incompatible with the existing theoretically predicted phase diagrams. The discrepancy is in both the shape and the nature of the phase boundary lines. Based on our experimental results we have proposed a new temperature-electric field phase diagram. We have proposed that it consists of two unwound smectic-C* phases, C¯1* (high temperature) and C¯2* (low temperature, high electric field), and a helicoidally modulated C* (low temperature, low electric field) phase as well. There are three phase boundary lines, each one separating two of the above three phases. The phase boundary lines between C*- C¯ 1* and C¯1*- C¯2* phases are second order and the phase boundary line between C*- C¯2* phases is first order. The two second order and one first order lines meet at a triple point that we tentatively have identified as a Lifshitz point.

Ghoddoussi, Farhad

245

Manifestation of quantum disordered wave functions with weak localization from conical second harmonic generation in ferroelectric crystal  

NASA Astrophysics Data System (ADS)

The spatial structure of two-dimensional quantum disordered wave functions with weak localization (WL) is experimentally observed using a calcium barium niobate Ca0.28Ba0.72Nb2O6 (CBN-28) ferroelectric crystal illuminated by a pulsed laser beam. Non-collinear phase-matching in CBN-28 produces conical second harmonic pattern in the far-field. The probability density distribution of the experimental near-field pattern agrees very well with the theoretical predictions. The localization degree, within the error limits, is the same at different transverse positions due to the periodicity of the crystal and the eigenfunctions are degenerated. We conclude that a ferroelectric crystal represents an ideal model system for investigation of WL.

Yu, H. H.; Zhang, H. J.; Wang, Z. P.; Xu, H. H.; Wang, Y. C.; Wang, J. Y.; Petrov, V.

2012-02-01

246

Vapor-Deposited Single-Crystal Germanium  

Microsoft Academic Search

Germanium layers have been formed on single-crystal Ge substrates by the thermal decomposition of GeI2. The single-crystal nature of the layers has been established by x-ray and electron diffraction examination and by electrical measurements. The deposition process is described briefly. The crystal growth rate varies with crystal direction, and under certain conditions Ge whiskers appear. The layers as deposited are

Ralph P. Ruth; John C. Marinace; W. C. Dunlap

1960-01-01

247

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

248

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

PubMed Central

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

2013-01-01

249

Distribution and formation mechanism of the domain structure in PMN 33% PT single crystals  

NASA Astrophysics Data System (ADS)

Domain structures investigation in (110)-oriented Pb(Mg1/3Nb2/3)O3-33% PbTiO3 (PMN-33% PT) single crystals has been performed by piezoresponse force microscopy. Submicron-sized fingerprint pattern and tweed pattern domains (TPDs) have been observed in large parallel domains with typical sizes of 20-30 µm. Based on the existence of gradual transition regions between fingerprint pattern domains and TPDs in the same large ferroelectric domain, the relationship between the two pattern domains is discussed and a possible formation mechanism of the domain structure in PMN-33% PT single crystal is proposed.

Yu, H. F.; Zeng, H. R.; Chu, R. Q.; Li, G. R.; Luo, H. S.; Xu, Z. K.; Yin, Q. R.

2004-10-01

250

Performance of Single Crystal Niobium Cavities  

Microsoft Academic Search

We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other

Peter Kneisel; Gianluigi Ciovati; Waldemar Singer; Xenia Singer; Detlef Reschke; A. Brinkmann

2008-01-01

251

Rapid crystallization of ferroelectric lead zirconate titanate thin films by microwave heating  

NASA Astrophysics Data System (ADS)

Pb(Zr0.52Ti0.48)O3 (PZT) thin films were coated onto Pt/Ti/SiO2/Si substrates by a sol-gel method and then crystallized by 2.45 GHz microwave irradiation in the magnetic field. The crystalline phases and microstructures as well as the electrical properties of the PZT films were investigated as a function of the annealing temperature from 550 to 750°C for 60 s. The crystallization behavior of the PZT films annealed at 650°C for different times were also investigated. X-ray diffraction and transmission electron microscopy reveal that the pyrochlore phase is formed initially but that it transforms into the perovskite phase very quickly. The ferroelectric and dielectric properties of the PZT films are correlated to the crystallization behavior. The annealing time to obtain perovskite PZT films with good electrical properties at 650°C is only 60 s, and is much shorter than that in conventional furnace annealing process. The reasons for the reduction of annealing time in the rapid microwave annealing process are also discussed.

Wang, X. W.; Wang, Z. J.; Zhu, M. W.; Zhang, Y. Q.; Zhang, Z. D.

2011-11-01

252

Resonant ultrasonic spectroscopy of KTa1-xNbxO3 ferroelectric relaxor crystals  

SciTech Connect

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

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

2008-01-01

253

The Growth of Single Crystals of Triglycine Sulfate  

NASA Astrophysics Data System (ADS)

An experiment in which the growth of the 001 and 010 faces of single crystals of triglycine sulfate is studied at temperatures below the ferroelectric transition temperature is described. Growth rates were measured under conditions of both natural convection and forced convection. Growth rate measurements at different solution velocities were used to determine the solution velocity at which the growth is dominated by surface processes. In order to obtain the activation energy for volume diffusion of TGS in water, the diffusion coefficient was measured at various temperatures and concentrations using the diaphragm cell method. Growth rate versus relative supersaturation data for the 001 face are interpreted in terms of the Burton, Cabrera and Frank surface diffusion model. The results are ascribed to the variation of the spontaneous polarization of TGS with temperature.

Reiss, Donald Andrew

254

Direct Observation of Pinning and Bowing of a Single Ferroelectric Domain Wall  

SciTech Connect

We have made a direct optical observation of pinning and bowing of a single 180{degree} ferroelectric domain wall under a uniform applied electric field using a collection mode near-field scanning optical microscope. The domain wall is observed to curve between the pinning defects, with a radius of curvature determined by the material parameters and the applied electric field. The change in birefringence with applied field is used to infer the orientation of the internal field at the domain wall. {copyright} {ital 1999} {ital The American Physical Society}

Yang, T.J.; Mohideen, U. [Department of Physics, University of California, Riverside, California 92521 (United States)] [Department of Physics, University of California, Riverside, California 92521 (United States); Gopalan, V. [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Swart, P.J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1999-05-01

255

Origin of low-frequency dielectric dispersion in KH2PO4 and RbH2PO4 ferroelectric crystals  

Microsoft Academic Search

We have measured the low-frequency dielectric dispersions in KH2PO4 and RbH2PO4 crystals. In the paraelectric phase both crystals were observed to be free of dielectric dispersion in the low-frequency region concerned. However, both of them exhibited the low-frequency dielectric dispersion in the ferroelectric phase. Our study of the temperature-dependent dielectric relaxation in the ferroelectric phase supports that the major part

Bog-Gi Kim; Jong-Jean Kim

1999-01-01

256

Nanoindentation of gold single crystals  

NASA Astrophysics Data System (ADS)

Nanoindentation is an increasingly used tool to investigate the mechanical properties of very small volumes of material. Gold single crystals were chosen as a model system for surface modification studies, because of the electrochemical advantages and the simple structure of the material. Experiments on these samples displayed a spectrum of residual deformation, with measured hardness values on the same surface differing by over a factor of two. The yield point also exhibited considerable variation, but the depth of penetration was independent of this elastic-plastic transition. The onset of plastic deformation in these tests is observed at stress levels on the order of the theoretical yield strength. There are a limited number of defects in a single crystal specimen of gold, especially on the length scale required to influence nearly every indentation experiment. A test matrix was designed to change the concentrations of possible defects in a sample (dislocations, vacancies, and structural features), by altering some of the surface preparation parameters. The results of these experiments were extremely consistent. Observed trends within the matrix, combined with the observations of reduced hardness and earlier plasticity when compared to the preliminary testing, indicate a decline in the structural continuity of the sample. This is surprising considering the extensive material removal and thermal history of some of these surfaces. There is no indication of a cause for the dramatic inconsistencies in mechanical properties observed in preliminary testing, but a consistent surface enables the study of intentional modifications. Changes in contact area that were undetectable in preliminary results now demonstrate predictable shifts in hardness values. The deposition of a single monolayer of gold oxide raised the average load at yield by a factor of three and increased the hardness by over 26%. Attributing this change to the oxide is corroborated by the reduction of hardness when the oxide is stripped. Similar behavior is observed when a lead monolayer is deposited and tested ex-situ. It is surprising that layers <0.5 nm in thickness would have such a dramatic influence on indentation tests at least 35 nm deep. This indicates that no surface layer can be ignored at this scale. These experiments demonstrate that there is still much to be learned about nanoscale deformation mechanisms.

McCann, Martha Mary

257

Dynamics of Ferroelectric Domain Walls  

Microsoft Academic Search

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

Volkmar Mueller

2001-01-01

258

Dielectric, Ferroelectric and Thermal Studies of Gel Grown Yttrium Tartrate (YT) Crystals  

Microsoft Academic Search

Yttrium tartrate (YT) single crystals have been grown by gel encapsulation technique. The crystallinity of the grown crystals was confirmed by XRD technique. The dielectric constant, dielectric loss and ac conductivity was measured as a function of frequency in the range 1 kHz to 1 MHz and temperature range of 30°C to 250°C. Dielectric studies shows two transition peaks at

Sanjay Kumar; B. Kaur; P. N. Kotru; K. K. Bamzai

2006-01-01

259

Dislocation Distribution in Deformed Copper Single Crystals.  

National Technical Information Service (NTIS)

Observations of dislocation distribution in copper single crystals oriented for single glide and deformed at low temperatures are described. In stage I the dislocation population consists mainly of bundles of long edge dislocations belonging to the primar...

Z. S. Basinski

1964-01-01

260

Twisted ferroelectric liquid crystals dynamic behaviour modification under electric field: A Mueller matrix polarimetry approach using birefringence  

NASA Astrophysics Data System (ADS)

A low frequency and high amplitude rectangular voltage V has been applied during different increased duration to Twisted Surface Stabilized Ferroelectric Liquid crystal (TwFLC) samples in which the alignment layers of the two substrates were rubbed along two different directions between 0° and 90°. The optical bistability properties have been evaluated using the specific Mueller Matrix formalism that allows a simultaneous access, through a single-shot measurement, to different polarimetric coefficients. In this new approach, the ellipticity ? and the azimuthal ?R polarimetric parameters, extracted from the birefringence Mueller Matrix MR will be considered in priority. Several significant parameters, such as the horizontal offset ?V, the degree of asymmetry DA, the characteristic area S of the hysteresis loop, are used to characterize the degradation observed into the hysteretic behaviour of the samples, for different values of ?, at different duration T of exposure to V, before reaching the so-called stripes regime, giving a new experimental point of view concerning the evolution of the dynamic properties of the samples studied. The ?R(V) and the ?(V) hysteresis loops are specifically examined. Static mapping related to ?(T) is given too. Among the different possible physical origins of the observed degradation, the in-plane anchoring energy contribution will be particularly examined, and a theoretical model is proposed that also gives access to different physical parameters, through a new approach.

Babilotte, P.; Nunes Henrique Silva, V.; Sathaye, K.; Dubreuil, M.; Rivet, S.; Dupont, L.; de Bougrenet de la Tocnaye, J. L.; Le Jeune, B.

2014-01-01

261

Chiral liquid crystals for ferroelectric, electroclinic, and antiferroelectric displays and photonic devices  

NASA Astrophysics Data System (ADS)

Ferroelectric and antiferroelectric liquid crystals have shown great promise for use in large area flat panel displays because of their fast switching and bistable operation. However, the commercialization of FLCDs and AFLCDs using surface stabilized geometries has not materialized for a number of reasons, most notably shock instability, the need to control the cell spacing of the display to between 1 and 2 micrometer, and competition from actively addressed nematic displays. Surface stabilized displays are nevertheless finding niche markets in areas such as spatial light modulators, microdisplays, and projection systems. Even though this is the present situation, it is clear that FLCs and AFLCs will be used advantageously in the future in active matrix configurations to give LCDs that operate at video-frame rates. Furthermore, there are many emerging uses for such materials in the areas of photonics and sensors e.g., novel switching and wavelength filtering components based on liquid crystal phase modulators and filters. There is also interest in utilizing LC technology in fiber optic networks, telecommunication transmission systems, interconnecting networks in large computers, optical image processors, and optically accessible electronic memory structures. All of these applications require fast switching materials that are stable and non-absorbent to light of various wavelengths.

Goodby, John W.; Toyne, Kenneth J.; Hird, Michael; Styring, Peter; Lewis, R. A.; Beer, Andreas; Dong, C. C.; Glendenning, M. E.; Jones, John C.; Lymer, K. P.; Slaney, Andrew J.; Minter, Victoria; Chan, L. K. M.

2000-03-01

262

Second-harmonic generation of blue light in LiNbO3 crystal with periodic ferroelectric domain structures  

Microsoft Academic Search

Optical pulse generation of blue light (430 and 435 nm) was demonstrated in a bulk yttrium-doped LiNbO3 crystal with periodic ferroelectric domain structures, under the condition of quasi-phase matching. Blue light output of 0.2 microJ energy was measured for input energy 5 microJ of fundamental wave in pulse operation. The average efficiency was 4.2 percent, and the maximal point pulse

Ya-Lin Lu; Lun Mao; Shi-De Cheng; Nai-Ben Ming; Yu-Tian Lu

1991-01-01

263

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

Microsoft Academic Search

The effect of oblique evaporation of SiO on the chevron structure and the switching behavior in a ferroelectric liquid crystal have been investigated by means of the X-ray diffraction and the stroboscopic micrographs. It is found experimentally that the chevron direction and the domain structure appearing during the switching are determined by the direction of incidence of evaporated SiO. On

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

1989-01-01

264

Photo-dimerization of a chalcone-based side chain polymer for the alignment of ferroelectric liquid crystals  

Microsoft Academic Search

The alignment and optical properties of ferroelectric liquid crystal cells, having alignment films of a chalcone-based side chain polymer treated by linearly polarized UV irradiation were investigated. The long absorption band of the UV\\/Vis spectra gradually decreased and the FTIR spectra shifted as the irradiation times increased, indicating that cyclo-addition and isomerization reactions of the chalcone-based side chains occurred. UV

Kyung-Soo Choi; Hyun-Wuk Kim; Yong-Bae Kim

2004-01-01

265

Confinement stabilises single crystal vaterite rods.  

PubMed

Single-crystals of vaterite, the least-stable anhydrous polymorph of CaCO3, are rare in biogenic and synthetic systems. We here describe the synthesis of high aspect ratio single crystal vaterite rods under additive-free conditions by precipitating CaCO3 within the cylindrical pores of track-etch membranes. PMID:24676457

Schenk, Anna S; Albarracin, Eduardo J; Kim, Yi-Yeoun; Ihli, Johannes; Meldrum, Fiona C

2014-04-01

266

Single crystal growth of actinide compounds  

Microsoft Academic Search

During recent years, the importance of solid state actinide research has been increasingly recognized. Further progress in actinide solid state physics depends on the availability of pure and perfect single crystals. Actinide compounds have large magnetic anisotropy with anisotropy fields of 8 × 107 A.m-1 or higher. Investigation of the mechanism responsible for such unique behaviour requires large single crystals

J. C. Spirlet; W. Müller; J. van Audenhove

1985-01-01

267

Ames Lab 101: Single Crystal Growth  

SciTech Connect

Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

Schlagel, Deborah

2013-09-27

268

Ames Lab 101: Single Crystal Growth  

ScienceCinema

Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

Schlagel, Deborah

2014-06-04

269

Ferroelectricity near room temperature in co-crystals of nonpolar organic molecules  

Microsoft Academic Search

The research on ferroelectric materials-mostly inorganic compounds or organic polymers-is increasingly motivated by both basic scientific concerns and the potential for practical applications in electronics and optics. Ferroelectricity in organic solids would be important for the development of all-organic electronic and photonic devices. The conventional approach to making organic ferroelectrics is based on the use of polar molecules. Here we

Sachio Horiuchi; Fumiyuki Ishii; Reiji Kumai; Yoichi Okimoto; Hiroaki Tachibana; Naoto Nagaosa; Yoshinori Tokura

2005-01-01

270

Temperature dependence dielectric behavior of Ge-doped lead scandium tantalate single crystals  

NASA Astrophysics Data System (ADS)

The doping of Pb2SeTaO6 with Ge ferroelectrics was produced by a high-temperature solution method. We measure dielectric constant, dielectric loss and conductivity in the temperature range -30°C to 200°C and frequency range 1 to 100 KHz. The value of dielectric constant of the Pb2SeTaO6 (PST) crystal remained the same after thermal annealing whereas they decreased after Ge doping in the phase transition temperature range of the PST single crystal. All samples were investigated for conductivity with increasing temperature.

Dixit, Chandra Kumar; Srivastava, Anil Kumar

2012-07-01

271

All-Union Conference on Ferroelectricity, 10th, Minsk, Belorussian SSR, September 19-23, 1982, Proceedings  

NASA Astrophysics Data System (ADS)

Topics discussed include the photovoltaic effect in piezoelectric and ferroelectric crystals; photogalvanic currents in reduced lithium tantalate crystals; the electrooptical effect in barium-strontium niobate crystals; the correlation of the electron spectra and temperatures of phase transformations in solid solutions based on barium titanates; the dynamics of ferroelectric and ferroelastic domains in NaH3 (SeO3) crystals in the biaxial ferroelectric phase; and the switching of ferroelectric domains in KFe (MoO4)2 and related crystals. Attention is also given to the piezooptical properties of triglycine sulfate (TGS) crystals doped with L-alpha-alanine, the effect of growth conditions on the polarization of TGS doped with L-alpha-alanine, the relaxation of the pyroelectric response of single crystals of TGS doped with metal ions, and dielectric-viscosity phenomena in ferroelectrics and ferroelastics. For individual items see A83-31302 to A83-31310

Rudiak, V. M.

1983-04-01

272

Fast near infra-red ferroelectric liquid crystal based Mueller matrix system for imaging and spectroscopy  

NASA Astrophysics Data System (ADS)

The science and optical engineering of imaging Mueller Matrix Ellipsometry (MME) and Spectroscopic MME is currently being revitalized based on an efficient optimal design method, and through the use of the so-called Eig envalue Calibration Technique (ECT). Through the ECT one may efficiently measure the details of the polarization state generator (PSG) matrix, and the polarization state analyzer (PSA) matrix, and hence avoid modeling of any unknown polarizing components in the system, and in particular the exact response of complex polarizing elements such as liquid crystal retarders. We here start up with presenting a detailed an alysis of the dynamic response of a near infrared Ferroelectric Liquid Crystal based Mueller matrix ellipsometer (NIR FLC- MME) [1] . A time dependent simulation model, using the measured time response of the individual FLCs, is used to describe the measured temporal response. Furthermore, the impulse response of the detector and the pre-amplifier is characterized and in cluded in the simulation model. The measured time dependent intensity response of the MME is well explained by simulations. A FLC based NIRMME system is here shown to be able to operate accurately at the maximum speed of approximately 16 ms per Mueller matrix measurement (steady state response). We demonstrate here time dependent Mueller Matrix measurements of a dynamically changing sample, with even down to 8 ms sampling time of each complete Mueller Matrix (with some loss of accuracy). We secondly briefly present the NIR-FLC- MME imaging system, and show applications to strain imaging of a crystal subjected to an external pressure. Furthermore, we present near-infra-red Mueller matrix images and corresponding polar decomposition images of thin slices of bio-tissue [2].

Kildemo, M.; Sandvik Aas, L. M.; Ellingsen, P. G.; Lindgren, M.

2010-06-01

273

Ferroelectric phase transitions and electromechanical properties of barium titanate and lead titanate crystals under uniaxial and shear stresses: a thermodynamic analysis  

NASA Astrophysics Data System (ADS)

Ferroelectric phase transitions and electromechanical properties of BaTiO3 (BT) and PbTiO3 (PT) crystals under uniaxial and shear stresses are investigated using the Landau-Devonshire phenomenological approach. The results show that (1) the Curie temperature of BT and PT crystals increases with increasing stress; (2) at room temperature, no ferroelectric-ferroelectric phase transition is induced by uniaxial stress along the [1?0?0]c direction for the PT crystal, while the orthorhombic phase is the ultimate stable state for BT and PT crystals under uniaxial stress along the [0?0?1]c direction and shear stress; (3) shear stress induces a temperature-independent morphotropic phase boundary in tetragonal phase BT and PT crystals; (4) the dielectric and piezoelectric properties are closely related to the phase transition induced by external stresses, where nonlinearity is observed owing to higher order terms of free energy.

Gao, Junjie; Li, Fei; Xu, Zhuo; Zhang, Chonghui; Liu, Yi; Liu, Gaomin; Zhang, Tao; He, Hongliang

2013-05-01

274

Photoelectrical properties of TlGaSe2 single crystals  

NASA Astrophysics Data System (ADS)

The spectral distribution of photocurrent (PC) of TlGaSe2 single crystals in the range of wavelengths between 500 nm and 700 nm possesses a single maximum at 2.04 eV corresponds to the direct energy band gap of this crystal. The PC is enhanced dramatically by pre-illuminations at low temperatures with band gap light. The temperature dependence of PC of the sample investigated in the temperature range from 80 K to 300 K at constant heating rate shows that the overlapping peaks in the PC spectrum are direct reflection of the Thermally Stimulated Current (TSC) associated with the several trapping levels. The PC response is strongly dependent on the degree of occupancy of traps. The wavelength at the maximum of the PC spectrum is found to be dependent on the wavelength scan direction being up or down. The ferroelectric phase transitions of TlGaSe2 are detected at ?108 K and ?118 K in the PC spectrum.

Ozdemir, Selahattin; Bucurgat, Mahmut

2014-07-01

275

Single crystal research — Crystal quality control — Industrial production  

Microsoft Academic Search

A summary is given of the tasks involved in improving crystal quality, their interrelations and the organizational framework\\u000a required for completing them. The possibilities inherent in single crystal research for the development of industrial products\\u000a are demonstrated.

R. Voszka

1985-01-01

276

Seeded Single Crystal Silicon Carbide Growth and Resulting Crystals.  

National Technical Information Service (NTIS)

A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system and in the absence of a solid silicon carbide source, by reducing the separation between a silicon carbide seed crystal and a seed holder u...

D. P. Malta H. M. Hobgood J. R. Jenny M. Brady S. G. Mueller

2005-01-01

277

Dynamics of Ferroelectric Domain Walls  

NASA Astrophysics Data System (ADS)

Dielectric data obtained in the ferroelectric phase of KH2PO4 and Rb2ZnCl4 single crystals as well as in PZT-ceramics are provided demonstrating qualitatively similar behavior in quite different ferroelectric systems. The peculiar low frequency dispersion, nonlinearity, dielectric loss and ageing phenomena, respectively, reflect the creep-like dynamics of highly susceptible domain walls. The significance of the domain wall-defect interaction becomes evident from the crucial influence of impurity type and concentration, respectively. The experimental results are discussed in terms of theoretical concepts developed for elastic interfaces in quenched disorder. The physical nature of the pinned elastic domain walls requires new approaches to characterize the properties of ferroelectric materials.

Mueller, Volkmar

278

Phase transitions in potassium ammonium dihydrogen phosphate single crystals  

NASA Astrophysics Data System (ADS)

An apparatus for growing single crystals from aqueous solution by the slow evaporation method was constructed. Mixed crystals of K1-x(NH 4)xH2PO4 (KADP) with (NH4)H 2PO4 (ADP) fractions of 0.021 and 0.12 were successfully grown. Their composition was determined by means of the x-ray powder diffraction method. This analysis also suggests that those crystals are a mixture of two phases even at room temperature. The details of the structure of the additional phase could not be determined. The dielectric constant epsilon of the mixed crystals as well as pure KH2PO4 (KDP) was measured along the polar axis in the temperature range from 20 K to 300 K. The frequency range of the applied electric field was from 100 Hz to 10 MHz. The data were analyzed by means of the standard Landau theory of phase transitions with coupling terms reflecting the interaction between the electric and elastic degrees of freedom. The temperature dependence of epsilon follows a typical Curie-Weiss behavior in the range of approximately 30 K aboveTc for all crystals studied. The value of the critical temperature decreases with increasing ammonium ion content in agreement with previously published results. The analysis of the frequency dependence of the dielectric susceptibility clearly indicates the existence of two dispersion processes: resonant and relaxational. The former is attributed to the piezoelectric activity of all the crystals studied. The latter is the result of the response of the permanent dipole moments present in ferroelectric crystals to the applied electric field. In the case of mixed crystals the relaxational dispersion is characterized by a distribution of relaxation times. Its mean relaxation time as well as its width increases with decreasing T. This is a typical behavior for mixed crystals for which the two end members of the solid solution in their pure form undergo ferroelectric and antiferroelectric phase transitions, respectively. This behavior is a result of competing long range interactions. New results for the temperature dependence of the CE66 and CE11 elastic constants of the crystals were obtained by means of the Brillouin spectroscopy. In addition to that the soft acoustic mode behaviour was also studied by means of the piezoelectric resonance method. Both of them gave qualitatively similar results which also correlate very well with the dielectric measurements. All major differences could be explained by assuming an inhomogeneous distribution of the ammonium ions in the KDP matrix. The Brillouin results were also analyzed by means of the Landau theory. It approximates very well the temperature dependence of the CE66 elastic constant in the paraelectric phase region for all crystals studied. The measured values of CE66 below Tc are in general lower than those predicted by the model. The greater the NH4 content the bigger the discrepancy. Moreover, the analysis of the temperature dependence of the CE66 elastic constant indicates the existence of a new phase in the mixed materials. Its stability region broadens with increasing NH4 concentration. For the crystal with the highest ammonium concentration studied it coincides with the dielectric plateau region between 70 K and 55 K. At temperatures below the plateau region the K0.88(NH4)0.12H 2PO4 sample scattered the laser light very strongly. This is most likely caused by defects and sample inhomogeneities but annealing the sample for two hours at 400 K does not result in any significant change.

Bromberek, Marek

279

Site-Selective Calcium Substitution in BaTi2O5: Effect on the Crystal Structure and the Ferroelectric Phase Transition  

NASA Astrophysics Data System (ADS)

The crystal structure and the ferroelectric phase transition are investigated in 4 mol % Ca-substituted BaTi2O5 synthesized by a containerless method. The synchrotron radiation powder diffraction reveals that the Ca ion prefers to settle at one of two crystallographically nonequivalent Ba sites surrounded by a rather distorted oxygen polyhedron. The crystal lattice is shrunk in the b-axis parallel to the spontaneous polarization in the ferroelectric phase by the substitution. The small amount of the Ca substitution suppresses the ferroelectric instability in BaTi2O5, and the ferroelectric phase transition temperature is significantly lowered by 40 K, which provides a great contrast with the case of Ca substitution in BaTiO3.

Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Masuno, Atsunobu; Inoue, Hiroyuki

2012-01-01

280

Inducing an antiferroelectric phase by segregating the layers of an intrinsically ferroelectric phase-only liquid crystal with linear-shaped molecules  

NASA Astrophysics Data System (ADS)

This paper demonstrates the possibility of inducing an antiferroelectric phase from an intrinsically ferroelectric phase-only liquid crystal by doping with linear-shaped molecules, thus separating the neighboring smectic layers of the ferroelectric liquid crystal from each other. Such an intrinsically impossible process is, in fact, shown to be quite possible due to its entropy-related origin. When the temperature of the doped cell is increased, the antiferroelectric phase reverts to the ferroelectric phase as the dopant molecules change position from interlayer space to intralayer space, a result that coincides with the sawtooth model suggested by Glaser and Clark [Phys. Rev. E 66, 021711 (2002)]. The macroscopic spontaneous polarization of the induced antiferroelectric phase (13.5 nC/cm2) is smaller than that of the ferroelectric phase (73.3 nC/cm2), which shows that the charge fluctuation is not the origin of the conversion.

Lee, Ji-Hoon; Lim, Tong-Kun

2005-11-01

281

Polarimeter with two ferroelectric liquid-crystal modulators attached to the Yunnan solar tower.  

PubMed

A polarimeter to be mounted on the Yunnan solar tower is described. It features the ability to simultaneously measure the magnetic fields of the solar photosphere and chromosphere by analyzing the Stokes spectra of those magnetosensitive lines forming in the two regions with very high efficiency of polarization measurement. The polarimeter consists of two ferroelectric liquid crystals and one lambda/4 wave plate before a polarizing beam splitter. The achromatism of the design is emphasized to get the maximum combination efficiency over a spectral range from 5000 to 6000 A. For the used solar absorption lines MgI517.27, FeI525.06, FeI630.15, and FeI630.25 nm, the design gives theoretical efficiencies of polarization measurements, which are 0.999, 1.0, 0.943, and 0.943, respectively. A comparison with other reference polarimeters, such as the Synoptic Optical Long-term Investigation of the Sun, the Tenerife infrared polarimeter, and the La Palma Stokes Polarimeter, is carried out. PMID:17086251

Xu, Chenglin; Qu, Zhongquan; Zhang, Xiaoyu; Jin, Chunlan; Yan, Xiaoli

2006-11-20

282

Sign inversion of the spontaneous polarization in a "de Vries"-type ferroelectric liquid crystal.  

PubMed

In contrast to common ferroelectric smectic C* liquid crystals, the siloxane-terminated smectic mesogen E6 is characterized by an unusual temperature variation of the spontaneous polarization. The polarization starts to grow from nearly zero despite the first-order SmA*-SmC* transition, and increases faster than linearly over a large temperature interval while the tilt angle rapidly saturates. To study this behavior in more detail, binary mixtures of different concentrations of E6 in the achiral SmC material C8Cl, which has a similar chemical structure, were investigated. Surprisingly, all mixtures show a temperature dependent polarization sign inversion, which shifts towards the SmC*-SmA* transition with increasing E6 concentration. For the pure E6 the inversion temperature meets the SmA*-SmC* phase transition temperature. In a second binary mixture with E6 and a conventional material C9-2PhP we found out, that the dependence of the inversion temperature on the concentration of E6 changes qualitatively when the nanosegregation is partially destroyed. A molecular theory of the polarization sign inversion in smectics C* with strong polar intermolecular interactions is developed which enables one to explain the concentration dependence of the inversion temperature in both mixtures. PMID:24668913

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

2014-05-19

283

Special phase matching of second-harmonic generation in helical ferroelectric liquid crystal cells  

NASA Astrophysics Data System (ADS)

The helical structures in ferroelectric liquid crystals can be utilized to realize a special phase matching for second-harmonic generation (SHG) when two counter fundamental waves propagate along the helical axis and the wavelength of SHG is near the photonic (selective reflection) band edge. On the basis of the exact theory [Drevensek-Olenik and Copic, Phys. Rev. E 56, 581 (1997)], a simple analytical description is derived and some characteristic features of the special phase matching are shown. (1) Special phase matching is definitely achieved under particular combinations of polarization. (2) The SH spectrum is related to a subsidiary oscillating structure in the selective reflection spectrum. The maximum SH intensity is realized at the first dip of the oscillation near one of the edges in the selective reflection band. (3) The thickness (d) dependence of the maximum SH intensity is d4 in thick cells, while it is d2 for conventional phase matching. (4) The linewidth for the SH peak is d-3 dependent, which is much narrower than in conventional phase matching.

Hoshi, Hajime; Chung, Doo-Han; Ishikawa, Ken; Takezoe, Hideo

2001-05-01

284

Distortion and unwinding of the helical structure in polymer-stabilized short-pitch ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

We report the effect of an anisotropic polymer network formed from an achiral photoreactive monomer in a short-pitch chiral SmC* phase on the distortion and the unwinding of the helical structure of the ferroelectric phase. The electro-optical behaviour and ferroelectric properties were experimentally determined for films containing various polymer concentrations. The critical field, Eu, for the transition from the distorted structure to the homogeneous state was measured as a function of polymer concentration. A linear increase of Eu versus polymer concentration was observed, showing that the helical structure of the short-pitch SmC* phase was stabilized by the polymer network. This behaviour was expected to be a consequence of the increase of the apparent elastic constants of the ferroelectric liquid crystal stabilized by the anisotropic polymer network films. The polymer network morphology was investigated using atomic-force microscopy, revealing a twisted structure of the polymer fibers. This twisted structure was transferred onto a polymer network during the polymerization process within a short-pitch SmC* phase. The increase of the apparent elasticity can then be interpreted by a strong interaction between polymer network and the liquid-crystal molecules. From our experimental data, the coupling coefficient, Wp, characterizing this interaction was evaluated for all studied polymer concentrations.

Petit, M.; Daoudi, A.; Ismaili, M.; Buisine, J. M.

2006-07-01

285

Single Crystal Sapphire Optical Fiber Sensor Instrumentation  

SciTech Connect

The goal of this 30 month program is to develop reliable accurate temperature sensors based on single crystal sapphire materials that can withstand the temperatures and corrosive agents present within the gasifier environment. The research for this reporting period has been segregated into two parallel paths--corrosion resistance measurements for single crystal sapphire fibers and investigation of single crystal sapphire sensor configurations. The ultimate goal of this phase one segment is to design, develop and demonstrate on a laboratory scale a suitable temperature measurement device that can be field tested in phase two of the program.

Anbo Wang; Russell May; Gary R. Pickrell

2000-10-28

286

Dielectric and Ferroelectric Studies on Gel Grown Samarium Tartrate (SmT) Crystals  

Microsoft Academic Search

Samarium tartrate (SmT) single crystals have been grown by gel encapsulation technique. The crystallinity of the grown crystals was confirmed by XRD technique. The dielectric constant, dielectric loss and ac conductivity was measured as a function of frequency in the range 5 kHz to 1 MHz and temperature range 20°C to 275°C. Dielectric studies show a transition peak at temperature

Sanjay Kumar; B. Kaur; P. N. Kotru; K. K. Bamzai

2007-01-01

287

Color Centers in Cesium Halide Single Crystals  

Microsoft Academic Search

Color centers have been investigated in the CsCl-type alkali halides. Cesium chloride, bromide, and iodide single crystals were grown from the melt and CsCl crystals also from solution. Coloration was produced by 130-kv x rays, 3.0-Mev electrons, and by electrolysis. In CsI coloration resulted from electrolysis only. The absorption of uncolored and colored crystals has been measured from 0.175 to

Peter Avakian; A. Smakula

1960-01-01

288

Study of the Ferroelectric Domain Structure and Phase Transitions by Confocal Scanning Optical Microscopy  

Microsoft Academic Search

Confocal scanning optical microscopy (CSOM) has been shown to be a promising method to investigate different properties of ferroelectric domain structures. It combines diffraction-limited spatial resolution with non-invasiveness and sensitivity of optical techniques. We have obtained optical and electrooptic images in ac modulation mode using model ferroelectrics systems, including both single crystals and thin films. The origin of CSOM contrast,

Oleg Tikhomirov; Jeremy Levy

2003-01-01

289

Crystal growth and high piezoelectric performance of 0.95Na0.5Bi0.5TiO3 0.05BaTiO3 lead-free ferroelectric materials  

Microsoft Academic Search

A large single crystal of 0.95Na0.5Bi0.5TiO3-0.05BaTiO3 (0.95NBT-0.05BT) with dimensions of 35 mm diameter × 10 mm length was grown by the top-seeded-solution growth method (TSSG). X-ray powder diffraction results indicate that the as-grown 0.95NBT-0.05BT crystal is of a perovskite structure and belongs to the rhombohedral system. The dielectric, ferroelectric and piezoelectric properties were investigated in detail. The room temperature dielectric

Wenwei Ge; Hong Liu; Xiangyong Zhao; Bijun Fang; Xiaobing Li; Feifei Wang; Dan Zhou; Ping Yu; Xiaoming Pan; Di Lin; Haosu Luo

2008-01-01

290

Neutron irradiation effects on YBCO single crystals.  

National Technical Information Service (NTIS)

Fast neutron irradiation of YBCO single crystals has proved to result in significant increases of magnetization hysteresis and consequently an enhancement of critical current densities. In addition, shifts of the irreversibility line have been observed. B...

F. M. Sauerzopf H. P. Wiesinger H. W. Weber G. W. Crabtree

1991-01-01

291

Molybdenum-Reinforced Aluminum Oxide Single Crystals.  

National Technical Information Service (NTIS)

Molybdenum wire-reinforced aluminum oxide single crystals have been fabricated by the heat exchanger method of seeded unidirectional solidification. No interfacial reaction products were observed and cathodoluminescent evaluation indicated a good diffusio...

J. W. McCauley F. Schmid D. J. Viechnicki

1979-01-01

292

Investigation of Growth of Electromagnetic Single Crystals.  

National Technical Information Service (NTIS)

Research was carried out on the growth of single crystals of plain and doped sapphire, ruby, spinel, yttrium oxide, magnesium titanate, yttrium iron garnet, beryl, cerium molybdate, lanthanum molybdate, sodium ferrite, and high melting fluorides. The meth...

C. M. Cobb J. A. Adamski E. B. Wallis

1964-01-01

293

Kinetics of ferroelectric domain structure: Retardation effects  

Microsoft Academic Search

We review the experimental and theoretical investigations of the kinetics of ferroelectric domain structure in single crystals and thin films. The significant influence of the retardation of screening process on the evolution of the domain structure is pointed out and is demonstrated in various experimental situations.

V. Ya. Shur; E. L. Rumyantsev

1997-01-01

294

Mechanistic study for heterogeneous product growth in topochemical single-crystal-to-single-crystal transformation  

Microsoft Academic Search

Kinetic evaluation for the solid-state reaction of 1,4-dithiin\\/anthracene mixed single crystal proved the mechanism of the anisotropic heterogeneous propagation during the single-crystal-to-single-crystal transformation. The number of hydrogen bonds in the reactive molecule is directly correlated with the activation energy for the reaction––the ‘chain’ character of solid-state propagation being triggered by the breaking of the C–H?O hydrogen bonds.

Jae Hong Kim; Jae Yun Jaung; Sung Hoon Jeong

2003-01-01

295

Linear analytical theory of a transformation from a single crystal A to another single crystal B  

Microsoft Academic Search

An isothermal phase transformation from a single crystal A to another single crystal B is theoretically investigated along preferred lines (Rosiwal's lines). It is supposed that the nuclei of the B-phase are Poisson distributed within the single crystal A. From these nuclei the B-grains grow instantaneously, equioriented, and in the form of cuboids with three different growth ratesvx,vy andvz. If

G. E. W. Schulze; H.-P. Wilbert

1987-01-01

296

Ferroelectric\\/superconductor heterostructures  

Microsoft Academic Search

This review covers the fabrication and characterization of ferroelectric\\/superconductor heterostructures such as Pb(ZrxTi1?x)O3\\/YBa2Cu3O7?? (YBCO), BaTiO3\\/YBCO and BaxSr1?xTiO3\\/YBCO etc. on various single crystal substrates. Pulsed laser deposition, laser molecular beam epitaxy, and magnetron-sputtering methods are compared. This report shows that pulsed laser deposition equipped with in situ reflection high-energy electron diffraction is a good method to control the growth mode of

Lin Li

2000-01-01

297

Transition metal complexes with oligopeptides: single crystals and crystal structures.  

PubMed

The coordination chemistry of short chain peptides with transition metals is described in terms of the available crystal structures. Despite their high interest as synthetic models for metalloproteins and as building blocks for molecular materials based on the tuneable properties of oligopeptides, single crystal X-ray diffraction studies are scarce. A perusal of the most relevant results in this field allows us to define the main characteristics of oligopeptide-metal interactions, the fundamental problems for the crystallization of these complexes, and some hints to identify future promising approaches to advance the development of metallopeptide chemistry. PMID:24874062

Lillo, Vanesa; Galán-Mascarós, José Ramón

2014-07-14

298

Thermal diffuse scattering in time-of-flight neutron diffraction studied on SBN single crystals  

NASA Astrophysics Data System (ADS)

At time-of-flight (TOF) diffractometer D N-2, installed at the pulsed reactor IBR-2 in Dubna, Sr(x)Ba(1-x)Nb2O6 mixed single crystals (SBN-x) of different compositions (0.50 less than x less than 0.75) were investigated between 15 and 773 K. The diffraction patterns were found to be strongly influenced by the thermal diffuse scattering (TDS). The appearance of the TDS from the long wavelength acoustic models of vibration in single crystals is characterized by the ratio of the velocity of sound to the velocity of neutron. Due to the nature of the TOF Laue diffraction technique used on D N-2, the TDS around Bragg peaks has rather a complex profile. An understanding of the TDS close to Bragg peaks is essential in allowing the extraction of the diffuse scattering occurring at the diffuse ferroelectric phase transition in SBN crystals.

Prokert, F.; Savenko, B. N.; Balagurov, A. M.

299

Performance of Single Crystal Niobium Cavities  

SciTech Connect

We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other cavities of the scaled "Low Loss" (LL) shape (two) and "High Gradient" (HG) shape (one) resonated at 2.3 GHz and were fabricated from "as received" single crystals, both from Heraeus and CBMM niobium. After appropriate surface treatments by buffered chemical polishing and electropolishing most cavities performed quite nicely and peak surface magnetic fields of ~ 160 mT or above corresponding to accelerating gradients between 38 MV/m and 45 MV/m were reached. This paper reports about the performance of these cavities.

Kneisel, Peter; Ciovati, Gianluigi; Singer, Waldemar; Singer, Xenia; Reschke, Detlef; Brinkmann, A.

2008-07-01

300

Nano-dimensional short pitch ferroelectric liquid crystal materials and devices with improved performance at oblique incidence  

NASA Astrophysics Data System (ADS)

Deformable Helix Ferroelectric Liquid Crystal (DHFLC) devices with nanodimensionally short pitch are examined for the purpose of applications in biomedical optical imaging. While nematic Liquid Crystal (NLC) devices have been used in our previous research as retarders, optical filters and polarization rotators and integrated into biomedical optical imaging systems, the current research is devoted to DHFLCs and to highlight the advantages that these devices can offer. Ferroelectric Liquid Crystal (FLC) devices are considerably faster than Nematic LC devices, the DHFLC sub group possesses other, more desired effects. The desired electro-optical response of the device is continuous, hysteretic-free and insensitive to the sign of the applied voltage. This can be achieved by using the DHFLC V-shaped switching effect which is observed when the helix pitch magnitude is shifted to nanoscale below 400nm (sub-wavelength) down to 150 nm. DHFLC cells with a sub-wavelength helix pitch have small light scattering in the visible spectral range when the applied voltage is below the critical level of the helix unwinding. Designs, experimental results and simulations are presented particularly for the reflectivity at oblique incidence showing some unique properties including polarization independent modulation, faster response and surface waves excitation.

Krupsky Reisman, Hadar; Pozhidaev, Evgeny P.; Torgova, Sofia I.; Abdulhalim, Ibrahim

2012-11-01

301

Two-dimensional ferroelectrics  

Microsoft Academic Search

The minimum size for a ferroelectric crystal has not been demonstrated experimentally because of difficulties in making thin films or small particles of sufficient quality. Langmuir-Blodgett deposition of crystalline films of vinylidene fluoride copolymers has produced high quality ferroelectric films as thin as 1 nm. These films permit the ultimate investigation of the finite-size effects on the atomic thickness scale

V. M. Fridkin; Stephen Ducharme; A. V. Bune; S. P. Palto; S. G. Yudin; L. M. Blinov

2000-01-01

302

Large second-order optical nonlinearity in a ferroelectric molecular crystal of croconic acid with strong intermolecular hydrogen bonds  

NASA Astrophysics Data System (ADS)

Linear and nonlinear optical responses in a molecular crystal, croconic acid, showing electronic-type ferroelectricity were studied by reflection and second harmonic generation spectroscopy. The second-order nonlinear susceptibility ?(2) was very large, exceeding 10-6 esu in the near-infrared region. The enhancement of ?(2) was attributed to the large dipole moment of the lowest ?-?* transition and the large difference between the molecular dipole moments for the ground state and the photoexcited state. We deduced the molecular orbitals (MOs) and dipole moments responsible for the large ?(2) by comparing the experimental optical parameters and MO calculation results based upon density functional theory.

Sawada, R.; Uemura, H.; Sotome, M.; Yada, H.; Kida, N.; Iwano, K.; Shimoi, Y.; Horiuchi, S.; Okamoto, H.

2013-04-01

303

Time-multiplexed optical Hadamard image transforms with ferroelectric-liquid-crystal-over-silicon spatial light modulators.  

PubMed

The Hadamard transform is an example of a matrix transform that allows images to be represented in terms of orthogonal basis functions with binary-valued matrix elements. Such basis functions can be displayed on binary amplitude modulating ferroelectric-liquid-crystal-over-silicon spatial light modulators, permitting novel, real-time, and high-speed implementation of the transform on incoherently illuminated input scenes. An example of an optical Hadamard transform performed in real time by using a spatial light modulator is described. To show the validity of this optical decomposition, we electronically reconstruct the transformation data for comparison with the original input scene. PMID:19823504

Gourlay, J; McOwan, P; Vass, D G; Underwood, I; Worboys, M

1993-10-15

304

Latching operation in a tunable wavelength filter using Si sampled grating waveguide with ferroelectric liquid crystal cladding.  

PubMed

A tunable wavelength filter fabricated with a latching function is proposed. The proposed tunable wavelength filter consists of a silicon sampled grating waveguide and ferro-electric liquid crystal (FLC) cladding. The sampled grating waveguide in a silicon-on-insulator (SOI) wafer achieved narrower stop bands than that with the conventional uniform grating structure. Enhanced wavelength shift was also obtained due to the increased effect in FLC by using a thinner silicon core. Bistable switching operation with the fabricated device, which was latching without state-sustaining power, was successfully demonstrated. Its switching and latching characteristics are also reported. PMID:24787847

Nakatsuhara, Katsumi; Kato, Akifumi; Hayama, Yoshiki

2014-04-21

305

Ferroelectric mobile water.  

PubMed

In molecular dynamics simulations single-domain ferroelectric water is produced under ordinary ambient conditions utilizing carbon nanotubes open to a water reservoir. This ferroelectric water diffuses while keeping its proton-ordered network intact. The mobile/immobile water transitions and the step-wise changes in net polarization of water are observed to occur spontaneously. The immobile water becomes mobile by transforming into the single-domain ferroelectric water. Our general notion of relating a more highly ordered structure with a lower temperature has so far restricted researchers' attention to very low temperatures when experimenting on proton-ordered phases of water. The present study improves our general understanding of water, considering that the term 'ferroelectric water' has so far practically stood for 'ferroelectric ice,' and that single-domain ferroelectric water has not been reported even for the ice nanotubes. PMID:21072393

Nakamura, Yoshimichi; Ohno, Takahisa

2011-01-21

306

Single crystal growth of the tetragonal tungsten bronze Ca xBa 1- xNb 2O 6 ( x=0.28; CBN-28)  

NASA Astrophysics Data System (ADS)

The material group of the tetragonal tungsten bronzes (TTBs) is very attractive due to its outstanding ferroelectric properties. Herein we report attempts to grow single crystals of calcium barium niobate (CBN) that until now was only known as ceramic samples. The single crystal growth of CBN could be realized in two different ways. In a first step a high-temperature tetraborate flux was applied to prepare small crystals for phase analysis. Then, for the first time large single crystals of Ca 0.28Ba 0.72Nb 2O 6 (CBN-28) with dimensions up to 5 cm length were grown by using the Czochralski method. CBN-28 shows a ferroelectric phase transition at about 280°C (detected by dielectric and thermal expansion measurements) that is about 200°C higher than the transition temperature of the widely investigated TTB Sr 0.60Ba 0.40Nb 2O 6 (SBN-60).

Eßer, M.; Burianek, M.; Klimm, D.; Mühlberg, M.

2002-04-01

307

Vibrational spectra and the ferroelectric phase transition of colemanite  

NASA Astrophysics Data System (ADS)

The infrared and far infrared (10 4000 cm-1) polarized, single crystal reflectivity of the calcium borate mineral colemanite, CaB3O4(OH)3·H2O, have been measured at room temperature and at several temperatures below the ferroelectric phase transition at approximately 270 K. Over the entire frequency range studied, only minor spectral changes are seen at the ferroelectric phase transition.

Gallup, R. F.; Coleman, L. B.

1990-06-01

308

Origin of low-frequency dielectric dispersion in KH2PO4 and RbH2PO4 ferroelectric crystals  

NASA Astrophysics Data System (ADS)

We have measured the low-frequency dielectric dispersions in KH2PO4 and RbH2PO4 crystals. In the paraelectric phase both crystals were observed to be free of dielectric dispersion in the low-frequency region concerned. However, both of them exhibited the low-frequency dielectric dispersion in the ferroelectric phase. Our study of the temperature-dependent dielectric relaxation in the ferroelectric phase supports that the major part of the low-frequency dielectric dispersion observed should be originated from the domain wall relaxations rather than the heat diffusion central peak of recent reports.

Kim, Bog-Gi; Kim, Jong-Jean

1999-06-01

309

Oxygen incorporation in rubrene single crystals.  

PubMed

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed. PMID:24786311

Mastrogiovanni, Daniel D T; Mayer, Jeff; Wan, Alan S; Vishnyakov, Aleksey; Neimark, Alexander V; Podzorov, Vitaly; Feldman, Leonard C; Garfunkel, Eric

2014-01-01

310

Oxygen Incorporation in Rubrene Single Crystals  

NASA Astrophysics Data System (ADS)

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed.

Mastrogiovanni, Daniel D. T.; Mayer, Jeff; Wan, Alan S.; Vishnyakov, Aleksey; Neimark, Alexander V.; Podzorov, Vitaly; Feldman, Leonard C.; Garfunkel, Eric

2014-05-01

311

Neutron detection with single crystal organic scintillators  

SciTech Connect

Detection of high-energy neutrons in the presence of gamma radiation background utilizes pulse-shape discrimination (PSD) phenomena in organics studied previously only with limited number of materials, mostly liquid scintillators and single crystal stilbene. The current paper presents the results obtained with broader varieties of luminescent organic single crystals. The studies involve experimental tools of crystal growth and material characterization in combination with the advanced computer modeling, with the final goal of better understanding the relevance between the nature of the organic materials and their PSD properties. Special consideration is given to the factors that may diminish or even completely obscure the PSD properties in scintillating crystals. Among such factors are molecular and crystallographic structures that determine exchange coupling and exciton mobility in organic materials and the impurity effect discussed on the examples of trans-stilbene, bibenzyl, 9,10-diphenylanthracene and diphenylacetylene.

Zaitseva, N; Newby, J; Hamel, S; Carman, L; Faust, M; Lordi, V; Cherepy, N; Stoeffl, W; Payne, S

2009-07-15

312

Oxygen Incorporation in Rubrene Single Crystals  

PubMed Central

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed.

Mastrogiovanni, Daniel D. T.; Mayer, Jeff; Wan, Alan S.; Vishnyakov, Aleksey; Neimark, Alexander V.; Podzorov, Vitaly; Feldman, Leonard C.; Garfunkel, Eric

2014-01-01

313

Fabrication of piezoelectric micro-cantilevers in domain-engineered LiNbO3 single crystals  

Microsoft Academic Search

We report on a novel route for fabrication of micro-cantilevers in ferroelectric single-crystal lithium niobate (LiNbO3). Using the sequential techniques of photolithographic patterning, electric field poling, direct bonding and domain-oriented differential etching, free-standing cantilevers of dimensions 50 mum × 50 mum × 5 mm in the x, z and y crystallographic directions, respectively, have been fabricated.

Collin Sones; Sakellaris Mailis; Vasilis Apostolopoulos; Ian E. Barry; Corin Gawith; Peter G. R. Smith; Robert W. Eason

2002-01-01

314

??-SnSb single crystals obtained by the method of inclined front crystallization  

Microsoft Academic Search

?? phase plates of single crystals of SnSb alloy were obtained by using a modification of the horizontal Bridgman method. It was ascertained that during crystallization the single crystals grow in the upper layer of the charge. It was found that the thickness of the single crystal (single crystal layer) and also its relative antimony content, depend on the growth

W. Bogdanowicz; Z. Bojarski

1995-01-01

315

Intrinsic single-domain switching in ferroelectric materials on a nearly ideal surface  

PubMed Central

Ferroelectric domain nucleation and growth in multiferroic BiFeO3 is studied on a single-domain level by using piezoresponse force spectroscopy. Variation of local electromechanical response with dc tip bias is used to determine the size of the domain formed below the conductive scanning probe tip. The domain parameters are calculated self-consistently from the decoupled Green function theory by using tip geometry determined from the domain wall profile. The critical parameters of the nucleating domain and the activation energy for nucleation are determined. The switching mechanism is modeled by using the phase-field method, and comparison with experimental results shows that the nucleation biases are within a factor of ?2 of the intrinsic thermodynamic limit. The role of atomic-scale defects and long-range elastic fields on nucleation bias lowering is discussed. These measurements open a pathway for quantitative studies of the role of a single defect on kinetics and thermodynamics of first order bias-induced phase transitions and electrochemical reactions.

Kalinin, S. V.; Rodriguez, B. J.; Jesse, S.; Chu, Y. H.; Zhao, T.; Ramesh, R.; Choudhury, S.; Chen, L. Q.; Eliseev, E. A.; Morozovska, A. N.

2007-01-01

316

Single-Crystal-to-Single-Crystal Transformations in One Dimensional Ag-Eu Helical System  

SciTech Connect

Single-crystal-to-single-crystal transformation of 1-D 4d-4f coordination polymers have been investigated for the first time. It displays high selectivity for Mg2+ and can be used as magnesium ion-selective luminescent probe. More importantly, we observed the transformation of meso-helical chain to rac-helical chain as a function of temperature.

Cai, Yue-Peng; Zhout, Xiu-Xia; Zhout, Zheng-Yuan; Zhu, Shi-Zheng; Thallapally, Praveen K.; Liu, Jun

2009-07-06

317

Self-diffusion in naphthalene single crystals  

Microsoft Academic Search

Studies of self-diffusion in pure single crystals of naphthalene have been carried out by a sectioning method, using a 14C labelled tracer. The effects of impurity content and pre-annealing upon the diffusion process “were examined. Diffusion coefficients are low compared to those found for other solid systems. In the best available crystals self-diffusion can be described by an equation D

J. N. Sherwood; D. J. White

1967-01-01

318

Visualization of a ferroelectric domain structure in the X cut of a LiNbO3 crystal using x-ray diffraction and topography  

Microsoft Academic Search

A ferroelectric domain structure formed in the X cut of a LiNbO3 crystal by aftergrowth thermoelectrical treatment was studied by x-ray diffraction and topography methods. An external electric field applied along the X axis to the crystal causes shift deformations due to the reverse piezoelectric effect, which permits visualization of domain structures in the X cut of a LiNbO3 crystal.

D. V. Roshchupkin; D. V. Irzhak; V. V. Antipov

2009-01-01

319

Single crystals of metal solid solutions  

NASA Technical Reports Server (NTRS)

The following definitions were sought in the research on single crystals of metal solid solutions: (1) the influence of convection and/or gravity present during crystallization on the substructure of a metal solid solution; (2) the influence of a magnetic field applied during crystallization on the substructure of a metal solid solution; and (3) requirements for a space flight experiment to verify the results. Growth conditions for the selected silver-zinc alloy system are described, along with pertinent technical and experimental details of the project.

Miller, J. F.; Austin, A. E.; Richard, N.; Griesenauer, N. M.; Moak, D. P.; Mehrabian, M. R.; Gelles, S. H.

1974-01-01

320

Ferroelectric Ba 0.6 Sr 0.4 TiO 3 Phase Shifters Under High Power Microwave  

Microsoft Academic Search

High power microwave properties of the ferroelectric phase shifters have been studied to reduce the effect of the nonlinear response of ferroelectrics under high power microwave with an applied dc bias field of 0 - 40 kV\\/cm. The Ba 0.6 Sr 0.4 TiO 3 ferroelectric films were prepared on (001) MgO single crystals by pulsed laser deposition. Coplanar waveguide (CPW)

Seung Eon Moon; Eun-Kyoung Kim; Su-Jae Lee; Seok-Kil Han; Kwang Yong Kang; Won-Jeong Kim

2002-01-01

321

Czochralski single crystal growth, modeling, and characterization of ilmenite  

Microsoft Academic Search

Ilmenite is a wide band gap material, and could be used for electronic applications. Since ilmenite is stoichiometric at its melting point, the single crystals are grown using Czochralski crystal growth method. Earlier research in ilmenite uses ceramic material, and smaller size single crystals. In this research large size single crystals of ilmenite are grown. To grow large size single

Jayakumar Muthusami

1998-01-01

322

Electronic Ferroelectricity in a Molecular Crystal with Large Polarization Directing Antiparallel to Ionic Displacement  

NASA Astrophysics Data System (ADS)

Ferroelectric polarization of 6.3?Ccm-2 is induced by the neutral-to-ionic transition, upon which nonpolar molecules of electron donor tetrathiafulvalene (TTF) and acceptor p-chloranil (CA) are incompletely ionized to ±0.60e and dimerized along the molecular stacking chain. We find that the ferroelectric properties are governed by intermolecular charge transfer rather than simple displacement of static point charge on molecules. The observed polarization and poling effect on the absolute structural configuration can be interpreted in terms of electronic ferroelectricity, which not only exhibits antiparallel polarity to the ionic displacement but also enhances the polarization more than 20 times that of the point-charge model.

Kobayashi, Kensuke; Horiuchi, Sachio; Kumai, Reiji; Kagawa, Fumitaka; Murakami, Youichi; Tokura, Yoshinori

2012-06-01

323

Electronic ferroelectricity in a molecular crystal with large polarization directing antiparallel to ionic displacement.  

PubMed

Ferroelectric polarization of 6.3???C?cm(-2) is induced by the neutral-to-ionic transition, upon which nonpolar molecules of electron donor tetrathiafulvalene (TTF) and acceptor p-chloranil (CA) are incompletely ionized to ±0.60e and dimerized along the molecular stacking chain. We find that the ferroelectric properties are governed by intermolecular charge transfer rather than simple displacement of static point charge on molecules. The observed polarization and poling effect on the absolute structural configuration can be interpreted in terms of electronic ferroelectricity, which not only exhibits antiparallel polarity to the ionic displacement but also enhances the polarization more than 20 times that of the point-charge model. PMID:23003988

Kobayashi, Kensuke; Horiuchi, Sachio; Kumai, Reiji; Kagawa, Fumitaka; Murakami, Youichi; Tokura, Yoshinori

2012-06-01

324

Single-Crystal Springs For Accelerometers  

NASA Technical Reports Server (NTRS)

Thermal noise reduced, enabling use of smaller proof masses. Spring-and-mass accelerometers in which springs made of single-crystal material being developed. In spring-and-mass accelerometer, proof mass attached to one end of spring, and acceleration of object at other end of spring measured in terms of deflection of spring, provided frequency spectrum of acceleration lies well below resonant frequency of spring-and-proof-mass system. Use of single-crystal spring materials instead of such polycrystalline spring materials as ordinary metals makes possible to construct highly sensitive accelerometers (including seismometers) with small proof masses.

Vanzandt, Thomas R.; Kaiser, William J.; Kenny, Thomas W.

1995-01-01

325

Crystal growth and characterization of new high Curie temperature (1? x)BiScO 3– xPbTiO 3 single crystals  

Microsoft Academic Search

Novel perovskite ferroelectric (1?x)BiScO3–xPbTiO3 single crystals with tetragonal phase were successfully grown by a conventional high-temperature solution method using a Pb3O4 and Bi2O3 flux. The typical crystal size was 2–15mm with rectangular shape and green\\/blue color. The dielectric constant (K) at room temperature was determined to be 400–550, decreasing to about 300 after the poling process. The Curie temperature of

Shujun Zhang; Laurent Lebrun; Sorah Rhee; Richard E Eitel; Clive A Randall; Thomas R Shrout

2002-01-01

326

Inkjet printing of single-crystal films  

NASA Astrophysics Data System (ADS)

The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. `Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4cm2V-1s-1. This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.

Minemawari, Hiromi; Yamada, Toshikazu; Matsui, Hiroyuki; Tsutsumi, Jun'ya; Haas, Simon; Chiba, Ryosuke; Kumai, Reiji; Hasegawa, Tatsuo

2011-07-01

327

Laser-induced breakdown and damage generation by nonlinear frequency conversion in ferroelectric crystals: Experiment and theory  

SciTech Connect

Using our experimental data for ns pulsed second harmonic generation (SHG) by periodically poled stoichiometric LiTaO{sub 3} (PPSLT) crystals, we consider in detail the mechanism underlying laser-induced damage in ferroelectric crystals. This mechanism involves generation and heating of free electrons, providing an effective kinetic pathway for electric breakdown and crystal damage in ns pulsed operation via combined two-photon absorption (TPA) and induced pyroelectric field. In particular, a temperature increase in the lattice of ?1 K induced initially by ns SHG and TPA at the rear of operating PPSLT crystal is found to induce a gradient of spontaneous polarization generating a pyroelectric field of ?10 kV/cm, accelerating free electrons generated by TPA to an energy of ?10 eV, followed by impact ionization and crystal damage. Under the damage threshold for ns operation, the impact ionization does not lead to the avalanche-like increase of free electron density, in contrast to the case of shorter ps and fs pulses. However, the total number of collisions by free electrons, ?10{sup 18} cm{sup ?3} (generated during the pulse and accelerated to the energy of ?10 eV), can produce widespread structural defects, which by entrapping electrons dramatically increase linear absorption for both harmonics in subsequent pulses, creating a positive feedback for crystal lattice heating, pyroelectric field and crystal damage. Under pulse repetition, defect generation starting from the rear of the crystal can propagate towards its center and front side producing damage tracks along the laser beam and stopping SHG. Theoretical analysis leads to numerical estimates and analytical approximation for the threshold laser fluence for onset of this damage mechanism, which agree well with our (i) experiments for the input 1064 nm radiation in 6.8 kHz pulsed SHG by PPSLT crystal, (ii) pulsed low frequency 532 nm radiation transmission experiments, and also (iii) with the data published for other nonlinear crystals and operated wavelengths.

Louchev, Oleg A.; Saito, Norihito; Wada, Satoshi [Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)] [Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Hatano, Hideki; Kitamura, Kenji [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2013-11-28

328

Detection of chiral perturbations in ferroelectric liquid crystals induced by an atropisomeric biphenyl dopant.  

PubMed

The atropisomeric dopant 2,2',6,6'-tetramethyl-3,3'-dinitro-4,4'-bis[(4-nonyloxybenzoyl)oxy]biphenyl (1) induces a ferroelectric SmC phase when doped into the SmC liquid crystal hosts 2-(4-butyloxyphenyl)-5-octyloxypyrimidine (PhP1) and (+/-)-4-[(4-methylhexyl)oxy]phenyl 4-decyloxybenzoate (PhB). The propensity of dopant 1 to induce a spontaneous polarization (polarization power) is much higher in PhP1 than in PhB (1555 nC/cm(2) vs <35 nC/cm(2)), which is attributed to a greater propensity of 1 to undergo chirality transfer via core-core interactions with PhP1. In previous work, we postulated that a chiral perturbation exerted by 1 in PhP1 amplifies the polarization power of the dopant by causing a chiral distortion of the mean field potential (binding site) constraining the dopant in the SmC host, as described by the Chirality Transfer Feedback (CTF) model. To test the validity of the CTF model, and to provide a more direct assessment of the chiral perturbation exerted by dopant 1 on surrounding host molecules, we measured the effect of 1 on the polarization power of other chiral dopants acting as probes. In one series of experiments, (S,S)-5-(2,3-difluorooctyl)-2-(4-octylphenyl)pyridine (MDW950) and (S)-4-(1-methylheptyloxy)phenyl 4-decyloxybenzoate (4), which mimic the structures of PhP1 and PhB, were used as probes. In another series of experiments, the atropisomeric dopant 2,2',3,3',6,6'-hexamethyl-4,4'-bis[(4-nonyloxybenzoyl)oxy]biphenyl (2) was used as probe in PhP1. The results of the probe experiments suggest that dopant 1 exerts a much stronger chiral perturbation in PhP1 than in PhB. More significantly, the results of experiments using 2 as probe show that the chiral perturbation exerted by 1 can amplify the polarization power of another atropisomeric dopant, thus providing the first experimental evidence of the CTF effect. PMID:12418905

Hartley, C Scott; Lazar, Carmen; Wand, Michael D; Lemieux, Robert P

2002-11-13

329

High frequency hysteresis-free switching in thin layers of smectic-C* ferroelectric liquid crystals.  

PubMed

The insulating layers used for the alignment of ferroelectric liquid crystals (FLC) in electro-optical cells usually have non-negligible thickness and their capacitance determines the type of the director switching caused by a triangular-form external voltage U(tr) . With decreasing frequency of U(tr) , the hysteresis in a switching direction changes from the normal to the abnormal one at a characteristic hysteresis inversion frequency f(i) . In the vicinity of f(i) , the electro-optical response is thresholdless and the optical transmission manifests the V -shape field dependence. The V -shape regime is very interesting for certain applications, in particular to microdisplays due to a possibility of the gray scale realization. However, f(i) has to be enhanced from the usually observed frequency of a few Hz up to the range of hundreds of Hz. To this effect, a special FLC material has been designed and its basic properties (tilt angle, spontaneous polarization, rotational viscosity, and electric conductivity) have been measured over the entire range of the smectic-C* phase. Upon variation of cell parameters (thickness of both the FLC and alignment layers), temperature, and external voltage, the frequency of the V -shape effect as high as 150-1000 Hz (in the temperature range 30-75 degrees C) has been found experimentally. The operating voltage remains lower than 8 V. A quantitative interpretation of these results has been done using the modeling procedure developed earlier [S.P. Palto, Cryst. Rep. 48, 124 (2003)]. The modeling has been performed with the experimental values of the FLC material and the cell parameters and has shown very good agreement with experiment. The key point of this approach is consideration of the internal voltage on the FLC layer, the sign, amplitude, and form of which differ from U(tr) . The results of the modeling allow further improvement of the performance of electro-optical FLC cells for high frequency V-shape effect. PMID:16089559

Blinov, L M; Palto, S P; Pozhidaev, E P; Bobylev, Yu P; Shoshin, V M; Andreev, A L; Podgornov, F V; Haase, W

2005-05-01

330

Real time observation of domain reversal in cerium-doped Sr0.61Ba0.39Nb2O6 single crystal fibers  

NASA Astrophysics Data System (ADS)

Domain configuration is of significant importance in utilizing ferroelectric single crystals such as strontium barium niobate (SBN) to design optoelectronic and nonlinear optical devices. This letter reports the real time observation of domain reversal in cerium doped SBN crystal fibers by electro-optic imaging microscopy. The SBN single crystal fibers studied were grown using the laser heated pedestal growth technique. The dynamic polarization switching behavior of SBN crystal fibers can be described as an antiparallel domain nucleation at low electric fields after a dormant period and a sideways growth of domain walls at higher electric field. These two different mechanisms result in the asymmetric current curve of domain switching dynamics.

Huang, C.; Bhalla, A.; Guo, R.

2006-11-01

331

Charge transport in single crystal organic semiconductors  

NASA Astrophysics Data System (ADS)

Organic electronics have engendered substantial interest in printable, flexible and large-area applications thanks to their low fabrication cost per unit area, chemical versatility and solution processability. Nevertheless, fundamental understanding of device physics and charge transport in organic semiconductors lag somewhat behind, partially due to ubiquitous defects and impurities in technologically useful organic thin films, formed either by vacuum deposition or solution process. In this context, single-crystalline organic semiconductors, or organic single crystals, have therefore provided the ideal system for transport studies. Organic single crystals are characterized by their high chemical purity and outstanding structural perfection, leading to significantly improved electrical properties compared with their thin-film counterparts. Importantly, the surfaces of the crystals are molecularly flat, an ideal condition for building field-effect transistors (FETs). Progress in organic single crystal FETs (SC-FETs) is tremendous during the past decade. Large mobilities ~ 1 - 10 cm2V-1s-1 have been achieved in several crystals, allowing a wide range of electrical, optical, mechanical, structural, and theoretical studies. Several challenges still remain, however, which are the motivation of this thesis. The first challenge is to delineate the crystal structure/electrical property relationship for development of high-performance organic semiconductors. This thesis demonstrates a full spectrum of studies spanning from chemical synthesis, single crystal structure determination, quantum-chemical calculation, SC-OFET fabrication, electrical measurement, photoelectron spectroscopy characterization and extensive device optimization in a series of new rubrene derivatives, motivated by the fact that rubrene is a benchmark semiconductor with record hole mobility ~ 20 cm2V-1s-1. With successful preservation of beneficial pi-stacking structures, these rubrene derivatives form high-quality single crystals and exhibit large ambipolar mobilities. Nevertheless, a gap remains between the theory-predicted properties and this preliminary result, which itself is another fundamental challenge. This is further addressed by appropriate device optimization, and in particular, contact engineering approach to improve the charge injection efficiencies. The outcome is not only the achievement of new record ambipolar mobilities in one of the derivatives, namely, 4.8 cm2V-1s-1 for holes and 4.2 cm2V-1s-1 for electrons, but also provides a comprehensive and rational pathway towards the realization of high-performance organic semiconductors. Efforts to achieve high mobility in other organic single crystals are also presented. The second challenge is tuning the transition of electronic ground states, i.e., semiconducting, metallic and superconducting, in organic single crystals. Despite an active research area since four decades ago, we aim to employ the electrostatic approach instead of chemical doping for reversible and systematic control of charge densities within the same crystal. The key material in this study is the high-capacitance electrolyte, such as ionic liquids (ILs), whose specific capacitance reaches ~ ?F/cm2, thus allowing accumulation of charge carrier above 1013 cm-2 when novel transport phenomena, such as insulator-metal transition and superconductivity, are likely to occur. This thesis addresses the electrical characterization, device physics and transport physics in electrolyte-gated single crystals, in the device architecture known as the electrical double layer transistor (EDLT). A detailed characterization scheme is first demonstrated for accurate determination of several key parameters, e.g., carrier mobility and charge density, in organic EDLTs. Further studies, combining both experiments and theories, are devoted to understanding the unusual charge density dependent channel conductivity and gate-to-channel capacitance behaviors. In addition, Hall effect and temperature-dependent measurements are employed for more in-depth unders

Xie, Wei

332

Kinetics of ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal  

NASA Astrophysics Data System (ADS)

Ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal has been studied by optical observation of the domain structure in low electric fields and switching current registration in high fields. We discuss investigations on the temporal behaviour of the electric polarization in static electric fields as well as polarization decay after removal of the electric field. The backswitching process appears to have a correlation to a defect-induced internal field in the crystal. For the interpretation of experimental data we utilize the classical nucleation and growth model of phase transformation (e.g. Avrami-Kolmogorov theory). An analysis assuming a statistical distribution of the characteristic domain growth times is proposed to explain and to find the functional form of the experimental data.

Rogowski, R. Z.; Matyjasek, K.; Jakubas, R.

2005-12-01

333

CVD-diamond single-crystal growth  

NASA Astrophysics Data System (ADS)

The synthesis of diamond volume crystals is of particular interest due to the material's outstanding physical and mechanical properties. Various techniques are pursued by numerous research groups. In hot-filament CVD (HF-CVD) we found a new process parameter window where the growth of single diamond volume crystals can be stabilized. These parameters are far beyond growth conditions for HF-CVD diamond coating processes. Extremely low methane content in the feed gas along with high substrate temperatures allows single diamond nuclei of a certain minimum size to grow stable. Crystals up to 100 ?m in diameter were successfully synthesized on ultrasonic pretreated substrates. They were characterized by SEM and Raman spectroscopy. A model for the observed exclusive growth of sufficiently large nuclei is presented. Based on well accepted diamond growth models, an advanced growth theory for the different morphologies and diamond qualities at the {1 0 0} and {1 1 1} faces of the crystals is postulated. The results give bases on which growing processes can be optimized and upscaled in order to evaluate the applicability of the method for single-crystal diamond growth.

Schwarz, S.; Rottmair, C.; Hirmke, J.; Rosiwal, S.; Singer, R. F.

2004-11-01

334

Giant pyroelectric coefficient determined from the frequency dependence of the pyroelectric signal generated by epitaxial Pb(Zr0.2Ti0.8)O3 layers grown on single crystal SrTiO3 substrates  

NASA Astrophysics Data System (ADS)

Epitaxial Pb(Zr0.2Ti0.8)O3 layers of good structural quality were grown on single crystal SrTiO3 substrates. The pyroelectric coefficient was estimated from the signal generated by the ferroelectric film working as a pyroelectric detector in the voltage mode, without pre-poling procedure. The obtained value is as high as 1.9 × 10-3 C/m2 K. The large value is attributed to the presence of 90° ferroelectric domains and to the compressive misfit strain, leading to an enhanced ferroelectric polarization.

Botea, M.; Iuga, A.; Pintilie, L.

2013-12-01

335

Ferroelectric phase transition in individual single-crystalline BaTiO3 nanowires.  

PubMed

We report scanned probe characterizations of the ferroelectric phase transition in individual barium titanate (BaTiO3) nanowires. Variable-temperature electrostatic force microscopy is used to manipulate, image, and evaluate the diameter-dependent stability of ferroelectric polarizations. These measurements show that the ferroelectric phase transition temperature (TC) is depressed as the nanowire diameter (dnw) decreases, following a 1/dnw scaling. The diameter at which TC falls below room temperature is determined to be approximately 3 nm, and extrapolation of the data indicates that nanowires with dnw as small as 0.8 nm can support ferroelectricity at lower temperatures. We also present density functional theory (DFT) calculations of bare and molecule-covered BaTiO3 surfaces. These calculations indicate that ferroelectricity in nanowires is stabilized by molecular adsorbates such as OH and carboxylates. These adsorbates are found to passivate polarization charge more effectively than metallic electrodes, explaining the observed stability of ferroelectricity in small-diameter BaTiO3 nanowires. PMID:16608274

Spanier, Jonathan E; Kolpak, Alexie M; Urban, Jeffrey J; Grinberg, Ilya; Ouyang, Lian; Yun, Wan Soo; Rappe, Andrew M; Park, Hongkun

2006-04-01

336

Scientific Review: The Single Crystal Diffractometer RESI  

Microsoft Academic Search

The single crystal diffractometer RESI (REciprocal Space Investigator) provides powerful techniques for structure research using thermal neutrons. With its unique setup of a kappa-goniometer and a neutron sensitive imaging plate, it is very well-suited for recording Bragg data, in particular, on samples with large unit cells, incommensurate structures, phase transitions, or dense patterns of reflections (quasicrystals). It is also designed

Björn Pedersen; Friedrich Frey; Wolfgang Scherer

2007-01-01

337

Multiphonon relaxation in YVO4 single crystals  

Microsoft Academic Search

Multiphonon relaxation rates were measured for 13 different energy levels of various rare-earth ions in YVO4 single crystals at 77 K. Dependence of the multiphonon relaxation rate on the energy gap that separates each emitting multiplet from the one lying just below it was investigated over the range from 980 to 5200 cm-1. A significant change in gap dependence was

F. S. Ermeneux; C. Goutaudier; R. Moncorgé; Y. Sun; R. L. Cone; E. Zannoni; E. Cavalli; M. Bettinelli

2000-01-01

338

Growth and Properties of Hydorxyapatite Single Crystals.  

National Technical Information Service (NTIS)

Four methods were attempted for the growth of large single crystals of hydroxyapatite: hydrothermal synthesis, growth in gels under hydrothermal conditions, growth in aqueous solution at 100C, and growth under conditions where the pH is controlled by the ...

J. F. Kirn H. Leidheiser

1967-01-01

339

Fracture in single crystal NiTi  

Microsoft Academic Search

This paper presents an investigation of the pseudoelastic transformation of two crystallographic orientations of a single crystal NiTi shape memory alloy (SMA). Both uniaxial tension and notched tension samples are considered with the tensile axes along the [100] and [111] directions. The phase transformation is observed using optical techniques in situ. For the uniaxial tension samples, martensite plates and Lüders-band

A. Creuziger; L. J. Bartol; K. Gall; W. C. Crone

2008-01-01

340

FERROELECTRIC SWITCHING LIQUID CRYSTAL POLYACRYLATES - THE CONTROL AND EFFECT OF MOLECULAR WEIGHT  

Microsoft Academic Search

The polymerisation of two liquid crystalline acrylate monomers is discussed with particular reference to control of the degree of polymerisation. Two series of liquid crystalline side chain polymers are produced, each with a broad smectic C phase and with a range of molecular weights. The electro-optic behaviour of the materials is discussed, and in one of the series ferroelectric response

Mark Verrall; David Beattie; David Coates; Ian Sage; Karl Lymer

1996-01-01

341

Domain Structures in Nano-Toroids and Ultra-Thin Single Crystals  

NASA Astrophysics Data System (ADS)

Rationalisation of the formation of domain structures, in ferroics of limited dimensions, has been a topic of interest since the 1940's [1], with early work, specifically in ferroelectrics, in the 1950's [2]. Experimental studies at that time primarily involved domain investigations using optical microscopy, on samples down to the order of hundreds of microns. More modern studies, extending domain research into the thin and ultrathin film regime [3], suggest that our understanding of certain aspects of domain behaviour remain relatively unchanged, despite the intervening decades. This might imply that reduction of scales into the nanometre range will not reveal anything new or interesting in ferroelectric domain research. In this talk, we hope to illustrate that this is not the case. We describe results from two recent research programmes on the characterisation of ferroelectric domain structures in single crystal BaTiO3 (BTO) using Scanning Transmission Electron Microscopy. In both studies sample preparation was performed using a Focused Ion Beam Microscope (FIB). In the first study, the domain periodicity has been measured as a function of thickness of parallel-walled BTO slabs from several hundred nanometres down to ˜50nm. Early work [2] suggested that the domain width should vary as the square root of slab thickness, and this is consistent with our data. However, we find, in plotting data from several works on different ferroelectric materials, with differing surface boundary conditions, across six decades in thickness, that all data lie on the same parent function, with the same constants of proportionality. This is totally unexpected, as the proportionality constants should be material and surface boundary state dependent. We suspect that this reveals fundamental aspects in the physics of ferroelectric domain formation that will be discussed. The second study was motivated by modelling done in 1994 by Gorbatsevich and Kopaev [4] and more recently by Fu and Bellaiche [5] and Naumov, Bellaiche and Fu [6]. Here, the influence of depolarization fields at ferroelectric surfaces were found to create polarization vortex structures when the ferroelectrics were sufficiently small. In toroidal shapes, Gorbatsevich and Kopaev even envisioned ordering of the vortices to produce nanoscale ferroelectric `solenoids'. We have used the FIB to make toroidal structures and have characterized their domain morphologies. At the time of writing, only conventional domain behaviour has been observed down to scales of the order of ˜100nm. However, results on smaller scales to be performed over the next few months will be described, as well as the novel imaging techniques we intend to use to probe for the ferroelectric vortices. [1] C. Kittel, Physical Review, 70, 965 (1946) [2] T. Mitsui and J. Furuichi, Physical Review, 90, 193 (1953) [3] S. K. Streiffer et al. Phys. Rev Lett. 89, 067601 (2002) [4] A. A. Gorbatsevich & Yu V. Kopaev, Ferroelectrics 161, 321 (1994) [5] I. Naumov et al. Nature 432, 737 (2004) [6] H. Fu and L. Bellaiche, Physical Review Letters, 91, 257601 (2003)

Gregg, Marty

2006-03-01

342

Single crystal tungsten kinetic energy penetrators  

SciTech Connect

We have explored the terminal ballistic performance of single crystal tungsten as a kinetic energy penetrator. Scientific speculation as to the anticipated penetration performance and nature of the interaction between such a kinetic energy penetrator and semi-infinite and spaced metallic targets has led us to perform laboratory scale experiments and metallographic examinations of post-impact penetrator materials. The single tungsten crystals were ground into kinetic energy penetrators with the [l angle]111[r angle] and [l angle]100[r angle] crystal direction being coincident with the axis of symmetry of the penetrators. The crystals were electro-polished to their final diameter. We, compared the terminal performance at current ordnance speeds of [l angle]111[r angle] single crystal tungsten to 90W-10 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against a spaced steel (triple) target at sixty-five degrees obliquity. We also compared the terminal performance of [l angle]100[r angle] and [l angle]111[r angle] single crystal tungsten with 90W-10 and 98W02 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against monolithic 4340 alloy steel (HRC = 36) at normal impact. We radiographed the penetrators during the interactions with the targets, we recovered portions of the penetrators after the ballistic experiments, and we conducted metallographic examinations of penetrator remnants. From the radiographic records and the metallographic examinations, we drew conclusions pertaining to insights into the terminal interactions of the penetrators with the targets and suggestions as to improved compositions of the cemented tungsten penetrators.

Cline, C.F.; Gogolewski, R.P.

1992-05-01

343

Single crystal tungsten kinetic energy penetrators  

SciTech Connect

We have explored the terminal ballistic performance of single crystal tungsten as a kinetic energy penetrator. Scientific speculation as to the anticipated penetration performance and nature of the interaction between such a kinetic energy penetrator and semi-infinite and spaced metallic targets has led us to perform laboratory scale experiments and metallographic examinations of post-impact penetrator materials. The single tungsten crystals were ground into kinetic energy penetrators with the {l_angle}111{r_angle} and {l_angle}100{r_angle} crystal direction being coincident with the axis of symmetry of the penetrators. The crystals were electro-polished to their final diameter. We, compared the terminal performance at current ordnance speeds of {l_angle}111{r_angle} single crystal tungsten to 90W-10 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against a spaced steel (triple) target at sixty-five degrees obliquity. We also compared the terminal performance of {l_angle}100{r_angle} and {l_angle}111{r_angle} single crystal tungsten with 90W-10 and 98W02 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against monolithic 4340 alloy steel (HRC = 36) at normal impact. We radiographed the penetrators during the interactions with the targets, we recovered portions of the penetrators after the ballistic experiments, and we conducted metallographic examinations of penetrator remnants. From the radiographic records and the metallographic examinations, we drew conclusions pertaining to insights into the terminal interactions of the penetrators with the targets and suggestions as to improved compositions of the cemented tungsten penetrators.

Cline, C.F.; Gogolewski, R.P.

1992-05-01

344

The origin of ferroelectricity in magnetoelectric YMnO3.  

PubMed

Understanding the ferroelectrocity in magnetic ferroelectric oxides is of both fundamental and technological importance. Here, we identify the nature of the ferroelectric phase transition in the hexagonal manganite, YMnO(3), using a combination of single-crystal X-ray diffraction, thorough structure analysis and first-principles density-functional calculations. The ferroelectric phase is characterized by a buckling of the layered MnO(5) polyhedra, accompanied by displacements of the Y ions, which lead to a net electric polarization. Our calculations show that the mechanism is driven entirely by electrostatic and size effects, rather than the usual changes in chemical bonding associated with ferroelectric phase transitions in perovskite oxides. As a result, the usual indicators of structural instability, such as anomalies in Born effective charges on the active ions, do not hold. In contrast to the chemically stabilized ferroelectrics, this mechanism for ferroelectricity permits the coexistence of magnetism and ferroelectricity, and so suggests an avenue for designing novel magnetic ferroelectrics. PMID:14991018

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

2004-03-01

345

Photoluminescence of C60 Single Crystals  

NASA Astrophysics Data System (ADS)

The photoluminescence (PL) spectra of C60 single crystals grown under double temperature gradient (DTG) and single temperature gradient (STG) techniques were investigated at room temperature. The results show that the PL emission intensity increases first and then decreases with increasing illuminated power density for the C60 single crystals grown by both DTG and STG techniques. Furthermore, one main peak with a shoulder peak can be clearly distinguished at low illumination, while only one main peak without the shoulder peak can be seen at high illumination. The main peak undergoes a continuous blue shift and broadening with the increase of illuminated power density. The difference of PL emission energy at the same illumination density of DTG and STG samples may correlated with the degree of both the orientational disorder of C60 molecule and lattice perfectness. The Laue diffraction patterns show that the DTG sample has stronger strains and poorer crystalline quality than the STG sample.

Li, Chaorong; Wang, Gang; Zhang, Jiaming; Mai, Zhenhong; Zhao, Tienan; Xu, Lu; Xie, Sishen

1995-05-01

346

Polar phonons in SO 2 single crystal  

NASA Astrophysics Data System (ADS)

The Raman spectrum of a single SO 2 crystal in various polarization geometries has been measured at 20 K and discussed in terms of LO and TO components of polar crystal modes. Lattice phonons have been assigned on the basis of their behaviour with polarization. Lattice dynamical calculations on both the internal and lattice phonons are in good agreement with experimental data. Using gas-phase transition dipole moments and a dipole—dipole intermolecular potential the angular dispersion of fundamental vibrons has been calculated. For lattice phonons, a combination of atom—atom and electrostatic potential reproduces not only the phonon frequencies but, for polar phonons, also their LO—TO splitting.

Tafi, A.; Procacci, P.; Castellucci, E.; Salvi, P. R.

1991-03-01

347

THERMAL STRESS ANALYSIS OF TETRAGONAL SINGLE CRYSTAL DURING GROWTH PROCESS : PMO SINGLE CRYSTAL  

Microsoft Academic Search

A three-dimensional finite element computer code was developed to deal with thermal stress analyses of tetragonal single crystals during the growth. They have the crystal anisotropy, so three-dimensional analysis is required for calculation of the thermal stress, even though they have axisymmetrical shapes. A tensor transformation technique was used to obtain the components of elastic constant matrix and thermal strain

N. Miyazaki; Y. Matsuura; D. Imahase

348

Ferroelectric Domain Structure of Na0.5K0.5NbO3 Crystal Grown by Floating Zone Method  

Microsoft Academic Search

The ferroelectric domain structures of orthorhombic Na0.5K0.5NbO3 (NKN) crystals grown by the floating zone method are characterized. Three types of laminar domain of 30-80, 10-15, and 5-10 mum in width were found in the crystal cut perpendicular to the growth direction. The thinnest laminar domains were observed between two different 90° domains. Raman spectroscopy confirmed that the NbO6 units of

Yumi Inagaki; Ken-ichi Kakimoto; Isao Kagomiya

2009-01-01

349

Growth of LiNbO3 crystal with periodic ferroelectric domain structure by current-induction and its acoustic application  

Microsoft Academic Search

In this report, Y-doped lithium niobate (LN) crystal with periodic ferroelectric domain structure (PFDS) was grown by the current-induction technique. The distribution of dopant (Y) along the growth direction was measured by an electron-probe microscopic analyzer. The periodic variation of the dielectric constant in the crystal was revealed by the light diffraction. When a radio-frequency electric field was applied, a

Zhiliang Wan; Yuanxin Xi; Quan Wang; Yanqing Lu; XY Zhu; Naiben Ming

2001-01-01

350

Lightweight optical mirrors formed in single crystal substrate  

NASA Technical Reports Server (NTRS)

This invention is directed to a process for manufacturing a lightweight mirror from a single crystal material, such as single crystal silicon. As a near perfect single crystal material, single crystal silicon has much lower internal stress than a conventional material. This means much less distortion of the optical surface during the light weighting process. After being ground and polished, a single crystal silicon mirror is light weighted by removing material from the back side using ultrasonic machining. After the light weighting process, the single crystal silicon mirror may be used as-is or further figured by conventional polishing or ion milling, depending on the application and the operating wavelength.

Bly, Vincent T. (Inventor)

2006-01-01

351

Laser-Induced Ferroelectric Structural Order in an Organic Charge-Transfer Crystal  

NASA Astrophysics Data System (ADS)

We report the direct observation by x-ray diffraction of a photoinduced paraelectric-to-ferroelectric structural phase transition using monochromatic 100-picosecond synchrotron pulses. It occurs in tetrathiafulvalene-p-chloranil, a charge-transfer molecular material in which electronic and structural changes are strongly coupled. An optical 300-femtosecond laser pulse switches the material from a neutral to an ionic state on a 500-picosecond time scale and, by virtue of intrinsic cooperativity, generates self-organized long-range structural order. The x-ray data indicate a macroscopic ferroelectric reorganization after the laser irradiation. Refinement of the structures before and after laser irradiation indicates structural changes at the molecular level.

Collet, Eric; Lemée-Cailleau, Marie-Hélène; Buron-Le Cointe, Marylise; Cailleau, Hervé; Wulff, Michael; Luty, Tadeusz; Koshihara, Shin-Ya; Meyer, Mathias; Toupet, Loic; Rabiller, Philippe; Techert, Simone

2003-04-01

352

Growth of Solid Solution Single Crystals  

NASA Technical Reports Server (NTRS)

The objective of the study is to establish the effects of processing semiconducting, solid solution, single crystals in a microgravity environment on the metallurgical, compositional, electrical, and optical characteristics of the crystals. The alloy system being investigated is the solid solution semiconductor Hg(1-x)Cd(x)Te, with x-values appropriate for infrared detector applications in the 8 to 14 mm wavelength region. Both melt and Te-solvent growth are being performed. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. The ground-based portion of the investigation also includes the evaluation of the relative effectiveness of stabilizing techniques, such as applied magnetic fields, for suppressing convective flow during the melt growth of the crystals.

Lehoczky, Sandor L.; Szofran, Frank R.; Gillies, Donald C.; Watring, Dale A.

1999-01-01

353

SSME single crystal turbine blade dynamics  

NASA Technical Reports Server (NTRS)

A study was performed to determine the dynamic characteristics of the Space Shuttle main engine high pressure fuel turbopump (HPFTP) blades made of single crystal (SC) material. The first and second stage drive turbine blades of HPFTP were examined. The nonrotating natural frequencies were determined experimentally and analytically. The experimental results of the SC second stage blade were used to verify the analytical procedures. The analytical study examined the SC first stage blade natural frequencies with respect to crystal orientation at typical operating conditions. The SC blade dynamic response was predicted to be less than the directionally solidified blade. Crystal axis orientation optimization indicated the third mode interference will exist in any SC orientation.

Moss, Larry A.; Smith, Todd E.

1987-01-01

354

The Creep of Single Crystals of Aluminum  

NASA Technical Reports Server (NTRS)

The creep of single crystals of high-purity aluminum was investigated in the range of temperatures from room temperature to 400 F and at resolved-shear-stress levels of 200, 300, and 400 psi. The tests were designed in an attempt to produce data regarding the relation between the rate of strain and the mechanism of deformation. The creep data are analyzed in terms of shear strain rate and the results are discussed with regard to existing creep theories. Stress-strain curves were determined for the crystals in tinsel and constant-load-rate tests in the same temperature range to supplement the study of plastic deformation by creep with information regarding the part played by crystal orientation, differences in strain markings, and other variables in plastic deformation.

Johnson, R D; Shober, F R; Schwope, A D

1953-01-01

355

Optical properties of some borate single crystals  

NASA Astrophysics Data System (ADS)

This paper describes efforts taken in Institute of Applied Physics and Institute of Electronic Materials Technology to obtain several single crystals from borate family, namely, CsLiB6)10, Ca4GdO(BO3)3, Li2B4O7, (beta) -BaB2O4, and Yal3(BO3)4, pure and doped with several ions. The main goal of this investigation was to develop technology of these new nonlinear optical materials to create possibility of their applications in higher harmonics generators and self- frequency doubling lasers. Depending on such properties of crystallized borate materials as incongruent melting or high temperature phase transitions, Czochralski technique or high temperature solution growth technique were used. The main aspects of crystallization of these materials as well as their optical properties are discussed.

Majchrowski, Andrzej; Lukasiewicz, Tadeusz; Mierczyk, Zygmunt; Malinowski, Michal

2001-08-01

356

Ferroelectric-Paraelectric Transition in BiFeO3: Crystal Structure of the Orthorhombic ? Phase  

Microsoft Academic Search

A detailed investigation using variable temperature powder neutron diffraction demonstrates that BiFeO3 undergoes a phase transition from the ferroelectric ? phase (rhombohedral, R3c) to a paraelectric ? phase (orthorhombic, Pbnm) between 820 oC and 830 oC. Co-existence of both phases over a finite temperature interval, together with abrupt changes in key structural parameters, confirm that the transition is first- order.

Donna C. Arnold; Kevin S. Knight; Finlay D. Morrison; Philip Lightfoot

2009-01-01

357

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

SciTech Connect

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

Vasudevan, Rama K [ORNL; Bogle, K A [University of New South Wales, Sydney, Australia; Kumar, Amit [ORNL; Jesse, Stephen [ORNL; Magaraggia, R [University of Glasgow; Stamps, R [University of Glasgow; Ogale, S [National Chemical Laboratory, India; Potdar, H S [National Chemical Laboratory, India

2011-01-01

358

Crack growth in single-crystal silicon  

NASA Technical Reports Server (NTRS)

Crack growth in single-crystal silicon at room temperature in air was evaluated by double torsion (DT) load-relaxation method and monitored by acoustic emission (AE) technique. Both DT and AE methods indicated lack of subcritical crack growth in silicon. At the critical stress intensity factor, the crack front was found to be jumping several times in a 'mirror' region and then followed by fast crack growth in a 'hackle' region. Hackle marks were found to be associated with plastic deformation at the tip of the fast moving crack. No dislocation etch pits were found in the 'mirror' region, in which crack growth may result from interatomic bonds broken at the crack tip under stress without any plastic deformation. Acoustic emission appears to be spontaneously generated from both interatomic bonds broken and dislocation generation at the moving crack tip during the crack growth in single-crystal silicon.

Chen, C. P.; Leipold, M. H.

1986-01-01

359

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

360

The ferroelectric phase transition of calcium barium niobate: experimental evidence of Smolenskii's model for diffuse phase transitions?  

NASA Astrophysics Data System (ADS)

We present investigations on temperature-dependent changes in the size distribution of ferroelectric domains in single crystals of the novel tungsten bronze type calcium barium niobate (CBN). Since its congruently melting composition has a relatively high ferroelectric phase transition temperature of about 265 °C, CBN can be considered as an interesting material for various future applications. Using k-space spectroscopy, both unpoled polydomain crystals and crystals poled at room temperature have been investigated in the vicinity of the ferroelectric phase transition. In unpoled CBN, an intermixture of domain-size dependent phase transitions has been observed, which can be described with the model for diffuse phase transitions established by Smolenskii.

Heine, Urs; Voelker, Uwe; Betzler, Klaus; Burianek, Manfred; Muehlberg, Manfred

2009-08-01

361

Bridgman growth of paratellurite single crystals  

Microsoft Academic Search

The growth of paratellurite single crystals by the vertical-gradient freezing technique is reported for the first time. Boules of 120mm long and 25mm in diameter were obtained under a temperature gradient of 10°Ccm?1 and translation rates lower than 0.6mmh?1. The spatial distribution of defects along the growth axis reveals a continuous evolution of the free convective fluid-flow regime as growth

P. Veber; J. Mangin; P. Strimer; P. Delarue; C. Josse; L. Saviot

2004-01-01

362

Crack Growth in Single-Crystal Silicon  

NASA Technical Reports Server (NTRS)

Report describes experiments on crack growth in single-crystal silicon at room temperature in air. Crack growth in (111) cleavage plane of wafers, 50 by 100 by 0.76 mm in dimension, cut from Czochralski singlecrystal silicon studied by double-torsion load-relaxation method and by acoustic-emission measurements. Scanning electron microscopy and X-ray topography also employed. Results aid in design and fabrication of silicon photovoltaic and microelectronic devices.

Chen, C. P.; Leipold, M. H.

1986-01-01

363

Q-1 of forsterite single crystals  

Microsoft Academic Search

Internal friction (Q-1) experiments have been performed on synthetic forsterite single crystals in order to investigate the role of temperature, frequency and dislocation density on the Q-1 factor. Data have been obtained for both deformed and undeformed specimens over a frequency range from 10 to 10-4 Hz at 15, 1000, 1200 and 1400°C. Measurements were done using a torsional pendulum

Y. Gueguen; M. Darot; P. Mazot; J. Woirgard

1989-01-01

364

Single crystal diffraction by synchrotron radiation  

SciTech Connect

The tunability and access to short wavelengths in combination with high intensity and the low divergence of the x-ray radiation produced by synchrotron storage rings opens up new and challenging fields for single crystal diffraction. These areas include microcrystal diffraction, studies of time-dependent phenomena, element selective diffraction, studies of materials under extreme conditions, solution of the crystallographic phase problem either by the use of the wavelength dependency of the anomalous scattering or by direct experimental determination of the phases. Single crystal diffraction from proteins and macromolecules using photographic film as a detection medium has already reached considerable maturity, but high-precision data collections using diffractometers at storage rings are still not routine because of the severe requirements for beam stability over extended periods of time. Development work at institutions such as the National Synchrotron Light Source, The Photon Factory, SSRL, CHESS, Hasylab and Daresbury, however, suggest that synchrotron single-crystal diffraction will become an essential part of the research at the synchrotron storage rings in the near future. 9 refs., 2 figs.

Kvick, A.

1988-01-01

365

Orientational Kerr effect and phase modulation of light in deformed-helix ferroelectric liquid crystals with subwavelength pitch  

NASA Astrophysics Data System (ADS)

We study both theoretically and experimentally the electro-optical properties of vertically aligned deformed helix ferroelectric liquid crystals (VADHFLC) with subwavelength pitch that are governed by the electrically induced optical biaxiality of the smectic helical structure. The key theoretical result is that the principal refractive indices of homogenized VADHFLC cells exhibit the quadratic nonlinearity and such behavior might be interpreted as an orientational Kerr effect caused by the electric-field-induced orientational distortions of the FLC helix. In our experiments, it has been observed that, for sufficiently weak electric fields, the magnitude of biaxiality is proportional to the square of electric field in good agreement with our theoretical results for the effective dielectric tensor of VADHFLCs. Under certain conditions, the 2? phase modulation of light, which is caused by one of the induced refractive indices, is observed without changes in ellipticity of incident light.

Pozhidaev, Evgeny P.; Kiselev, Alexei D.; Srivastava, Abhishek Kumar; Chigrinov, Vladimir G.; Kwok, Hoi-Sing; Minchenko, Maxim V.

2013-05-01

366

Fatigue In Single Crystal Nickel Superalloys Technical Progress Report.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

C. Annis

1992-01-01

367

Fatigue In Single Crystal Nickel Superalloys Technical Progress Report.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

C. Annis D. P. DeLuca

1993-01-01

368

Single Crystal Niobium RF Cavity of the TESLA Shape.  

National Technical Information Service (NTIS)

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without gra...

P. Kneisel W. Singer X. Singer

2007-01-01

369

Single Crystal Growth and Some Properties of Cd2Ti2O5F2 and CdTiO3  

Microsoft Academic Search

The pyrochlore-type compound Cd2Ti2O5F2 and the perovskite-type CdTiO3 were prepared by the reaction of CdF2 with TiO2 at high temperatures. The techniques used for the growth of single crystal are presented. A study was carried out the dielectric properties of single crystal specimens. No evidence for ferroelectricity in Cd2Ti2O5F2 was found, and the crystal seems to be paraelectric because of

Tokuko Sugai; Masanobu Wada

1979-01-01

370

Central peak in light scattering from the relaxor ferroelectric PbMg1\\/3Nb2\\/3O3  

Microsoft Academic Search

A model relaxor ferroelectric PbMg1\\/3Nb2\\/3O3 (PMN) in single-crystal form has been studied by Raman scattering with special attention to the low-frequency spectra in the vicinity of both the diffuse ferroelectric transition (~270 K) and the electric-field-induced ferroelectric transition (~200 K). In addition to the hard-mode features without any pronounced change, a broad central component has been observed and analyzed. This

I. G. Siny; S. G. Lushnikov; R. S. Katiyar; E. A. Rogacheva

1997-01-01

371

Unidirectional seeded single crystal growth from solution of benzophenone  

Microsoft Academic Search

A novel crystal growth method has been established for the growth of single crystal with selective orientation at room temperature. Using volatile solvent, the saturated solution containing the material to be crystallized was taken in an ampoule and allowed to crystallize by slow solvent evaporation assisted with a ring heater. The orientation of the growing crystal was imposed by means

K. Sankaranarayanan; P. Ramasamy

2005-01-01

372

Single crystal x-ray diffraction: optical and micro hardness studies on chalcone derivative single crystal  

NASA Astrophysics Data System (ADS)

1-(4-methylphenyl)-3-(4- N, N dimethyl amino phenyl)-2-propen-1-one, a chalcone derivative nonlinear optical material has been synthesized by standard method. FT-IR and NMR spectral studies have been performed to confirm the molecular structure of the synthesized compound. The single crystals up to a dimension of 13 x 9 x 3 mm3 were grown by slow evaporation method. The grown crystals were transparent in the entire visible region and absorbs in the UV-region. The refractive index has been measured using a He-Ne laser. The grown crystals have been subjected to single crystal X-ray diffraction studies to determine the crystal structure and hence the cell parameters of the crystal. From this study it is found that this compound crystallizes in orthorhombic system with a space group P212121 and corresponding lattice parameters are, a = 7.3610(13) Å, b = 11.651(2) Å, c = 17.6490(17) Å. The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for Photonic application. The micro hardness test on these crystals were carried out and the load dependence hardness was observed

Crasta, Vincent; Ravindrachary, V.; Bhajantri, R. F.; Naveen, S.; Shridar, M. A.; Shashidhara Prasad, J.

2005-08-01

373

Novel HDD-type SNDM ferroelectric data storage system aimed at high-speed data transfer with single probe operation.  

PubMed

In this study, several read/write tests were conducted using a novel ferroelectric data storage test system equipped with a spindle motor, targeted at high-speed data transfer using a single probe head. A periodically inverted signal can be read out correctly with a bit rate of 100 kbps using this test system, and 10 Mbps data transfer is also possible during writing operations. The effect of a dc-offset voltage applied to the writing waveform with high-speed probe scanning is discussed. In addition, a novel noncontact probe height control technique was adopted to solve the problem of tip abrasion. PMID:18276549

Hiranaga, Yoshiomi; Uda, Tomoya; Kurihashi, Yuichi; Tanaka, Kenkou; Cho, Yasuo

2007-12-01

374

?'-SnSb single crystals obtained by the method of inclined front crystallization  

NASA Astrophysics Data System (ADS)

?' phase plates of single crystals of SnSb alloy were obtained by using a modification of the horizontal Bridgman method. It was ascertained that during crystallization the single crystals grow in the upper layer of the charge. It was found that the thickness of the single crystal (single crystal layer) and also its relative antimony content, depend on the growth rate and on the angle of inclination of the crystallization front relative to the growth direction. A model proposed for the crystallization process permits the description of these relations obtained. This method for obtaining single crystals, the inclined front crystallization (IFC) method, offers new possibilities for control of chemical composition of plate single crystals of intermetallic phases, by varying the angle of inclination of the crystallization front.

Bogdanowicz, W.; Bojarski, Z.

1995-02-01

375

Study of ferroelectric domains structure on TGS crystals doped with L-? alanine  

Microsoft Academic Search

The domain structure of T.G.S. crystals doped with L-? alanine is investigated by scanning electron microscopy without metallization of the observed surface. Big zones observed in these crystals have, versus the voltage applied to the primary electron beam, a different contrast evolution from that we can observe for pure T. G. S. crystals. For domains obtained after heating the crystals

R. Le Bihan; G. Grandet

1981-01-01

376

Dye sensitization of single crystal semiconductor electrodes.  

PubMed

Even though investigations of dye-sensitized nanocrystalline semiconductors in solar cells has dominated research on dye-sensitized semiconductors over the past two decades, single crystal electrodes represent far simpler model systems for studying the sensitization process with a continuing train of studies dating back more than 40 years. Even today single crystal surfaces prove to be more controlled experimental models for the study of dye-sensitized semiconductors than the nanocrystalline substrates. This Account analyzes the scientific advances in the model sensitized single crystal systems that preceded the introduction of nanocrystalline semiconductor electrodes. It then follows the single crystal research to the present, illustrating both their striking simplicity of use and clarity of interpretation relative to nanocrystalline electrodes. Researchers have employed many electrochemical, photochemical, and scanning probe techniques for studying monolayer quantities of sensitizing dyes at specific crystallographic faces of different semiconductors. These methods include photochronocoulometry, electronic spectroscopy, and flash photolysis of dyes at potential-controlled semiconductor electrodes and the use of total internal reflection methods. In addition, we describe the preparation of surfaces of single crystal SnS(2) and TiO(2) electrodes to serve as reproducible model systems for charge separation at dye-sensitized solar cells. This process involves cleaving the SnS(2) electrodes and a photoelectrochemical surface treatment for TiO(2) that produces clean surfaces for sensitization (as verified by AFM) resulting in near unity yields for electron transfer from the molecular excited dyes into the conduction band. In recent experiments with ruthenium complexes at TiO(2) and with carboxylated cyanine dyes, we demonstrate the promise of this simple model for understanding dye-sensitized solar cells. In each of these systems, we can observe and analyze the complex photochemistry in a quantitative manner. Molecules of the well-known N3 ruthenium complex attach to four different crystallographic faces of anatase and rutile TiO(2) at different rates and to a different extent. With carboxylated cyanine dye sensitizers on these surfaces, molecular aggregation on the surface is a function of molecular structure and crystallographic face. In contrast with the N3 sensitizer these organic dyes undergo a photoinduced dimerization and desorption reaction when hydroquinone regenerators are present. With both classes of sensitizers, we demonstrate a new photochronocoulometric technique that quantifies the amount of attached dye on the electrode surface. We have completed initial experiments examining quantum dot sensitization of TiO(2) crystals, which could eventually lead to sensitizers with higher stability and absorption coefficients. Although these single crystal electrode models show promise for providing insights and predictive value in understanding the sensitization process, more sophisticated models will be needed to fully understand the charge transfer from the localized electronic states of the sensitizer to the extended states of the semiconductor. PMID:19924998

Spitler, Mark T; Parkinson, B A

2009-12-21

377

Influence of temperature on the optical properties of zinc tris-thiourea sulfate (ZTS) single crystal  

NASA Astrophysics Data System (ADS)

Single crystal of zinc tris-thiourea sulfate (ZTS) was synthesized and grown by the slow evaporation technique at 315 K. The effect of temperature on the optical properties of ZTS crystal was studied in the temperature range 293-338 K. This range involves the first-order phase transition temperature from ferroelectric to paraelectric phase (323 K). At room temperature (293 K), the optical transmittance (T) has high values in the completely visible wavelength range. The cut off wavelength equals to 278.5 nm at room temperature. By increasing temperature, the optical transmittance decreases, however the cut off shifts to higher wavelengths. These changes have different rates in the two phases (ferroelectric and paraelectric). Analysis reveals that the type of transition is the direct allowed one. The optical energy gap (Eg) has the value of 3.89 eV at room temperature. This value decreases linearly with increasing temperature by different rates in the two phases. In the region of the absorption edge, the absorption coefficient obeys Urbach's rule, and Urbach parameters were calculated. The Urbach tail energy (Ee), which equals to 1.024 eV at room temperature, increases linearly with increasing temperature. This change has different rates in the two phases. At room temperature, the steepness parameter (?) has the value of 24.697 × 10-3. It decreases linearly with increasing [1/(Temp.)2] by different rates in the two phases. For all studied parameters, the temperature dependence relations change considerably while passing through 323 K. This anomalous behavior confirms that the transition from ferroelectric to paraelectric phase occurs at this temperature.

Abdulwahab, A. M.

2012-12-01

378

Inelastic deformation in shocked sapphire single crystals  

NASA Astrophysics Data System (ADS)

To gain insight into orientation-dependent inelastic deformation of shocked sapphire (?-Al2O3) single crystals, resolved shear stresses, applicable for various dislocation slip and twinning systems, were determined for shock compression along different crystal orientations. Results from our anisotropic wave propagation analysis provide an explanation for why the measured elastic limit of shocked r-cut sapphire is lower, compared to c-cut and a-cut sapphire: Shock wave compression of r-cut sapphire favors activation of basal slip and basal twinning. In contrast, shock wave compression of c-cut and a-cut sapphire favors rhombohedral twinning and prismatic slip, respectively. Also, basal slip and/or basal twinning may be important for understanding why r-cut sapphire shocked beyond the elastic limit loses optical transparency gradually, when compared to c-cut and a-cut sapphire.

Fuller, H. D.; Winey, J. M.; Gupta, Y. M.

2013-06-01

379

Ferroelectric Properties and Second Harmonic Intensities of Stillwellite-Type (La,Ln)BGeO5 Crystallized Glasses  

NASA Astrophysics Data System (ADS)

Glasses with compositions corresponding to stillwellite-type (La,Ln)BGeO5 (Ln: Nd, Gd, Eu and Tm) crystalline phases have been prepared, and the effect of lanthanide substitutions on ferroelectric properties and second harmonic (SH) intensities of stillwellite-type crystalline phases formed by crystallization of glasses has been examined. The substitution of \\textit{Ln}3+ for La3+ ions in the LaBGeO5 phase has been confirmed from the results of X-ray diffraction (XRD) analysis and fluorescence spectra of Eu3+ ions. The substitution of \\textit{Ln}3+ for La3+ ions causes a decrease not only in the lattice constants but also in the a/c axis ratio. The amount of substitutions depends on the \\textit{Ln}3+ ionic radius. The Curie temperature of crystallized glasses increases almost linearly with decreasing mean ionic radius of lanthanides estimated from the composition of base glasses. A similar trend is observed in the SH intensity for crystallized glasses (powdered form), indicating the presence of a close relationship between Curie temperature and SH intensity. It is proposed from Raman spectra that the enhancement of SH intensities is caused by the change in the arrangements of BO4 and GeO4 tetrahedra in the (La,Ln)BGeO5 crystals due to the substitution of \\textit{Ln}3+ ions having stronger \\textit{Ln}3+-O bonds. A clear second harmonic generation is observed in transparent surface crystallized glasses of the Nd2O3- or Gd2O3-substituted system.

Takahashi, Yoshihiro; Iwasaki, Akihisa; Benino, Yasuhiko; Fujiwara, Takumi; Komatsu, Takayuki

2002-06-01

380

Oriented single-crystal-to-single-crystal phase transition with dramatic changes in the dimensions of crystals.  

PubMed

We report here a new polymorph of cocrystal CuQ2-TCNQ that shows an oriented single-crystal-to-single-crystal phase transition along its a-axis at ambient conditions. Upon mechanical stimulation, it converts into another polymorph accompanied by almost doubling its length and halving its thickness. Our crystallographic studies indicate the dramatic changes in crystal dimensions resulted from the prominent changes of molecular stacking patterns. A reasonable mechanism for the phenomenon was proposed on the basis of the structural, microscopic, and thermal analysis. PMID:24372005

Liu, Guangfeng; Liu, Jie; Liu, Yang; Tao, Xutang

2014-01-15

381

Single crystal to single crystal polymerization of a columnar assembled diacetylene macrocycle  

NASA Astrophysics Data System (ADS)

Organic tubular materials have attracted lots of attentions for their potential applications as nanoscale fluidic transport systems, specific ion sensors, molecular sieves and confined molecular reaction containers. While conjugated polymers, due to delocalized Pi electrons, exhibit interesting solar cells and sensors applications. In this thesis, we developed a conjugated polymer which combines the attributes of conjugated polymers with tubular materials, which should have great potential to work as a sensing material. We reproduced and scaled-up the synthesis of a polymerizable macrocycle 1 that contains two rigidly separated diacetylene units. We found that, through hydrogen bonding, 1 can assemble into columnar crystals and can be polymerized under a single crystal to single crystal transformation process to afford porous polydiacetylene (PDA) crystals. We studied the assembly of the macrocycles 1 under different conditions to give three different crystalline forms and micro-phase crystals, and also investigated their subsequent polymerizations. The macrocycle assembly and polymerized materials were characterized by a variety of technique. Since the gas adsorption measurement exhibited PDA crystals still retained its porosity and the polymer should have ability to uptake suitable guest molecules, therefore the absorption of iodine for PDA crystals was investigated as well.

Xu, Weiwei

382

Roflumilast - A reversible single-crystal to single-crystal phase transition at 50 °C  

NASA Astrophysics Data System (ADS)

Roflumilast is a selective phosphodiesterase type 4 inhibitor and is marketed under the brand names Daxas®, Daliresp® and Libertec®. A phase transition of the drug substance roflumilast was observed at 50 °C. The low temperature form, the high temperature form and the phase transition were characterised by differential scanning calorimetry, variable temperature powder X-ray diffraction and single crystal X-ray diffraction, Raman spectroscopy and solid state NMR spectroscopy. The phase transition of roflumilast at 50 °C is completely reversible, the high temperature form cannot be stabilised by quench cooling and the phase transition does not influence the quality of the active pharmaceutical ingredient (API) and the drug product. It was observed to be a single crystal to single crystal phase transition.

Viertelhaus, Martin; Holst, Hans Christof; Volz, Jürgen; Hummel, Rolf-Peter

2013-01-01

383

Stabilization of metastable ferroelectric Ba1?xCaxTi2O5 by breaking Ca-site selectivity via crystallization from glass  

PubMed Central

The thermal stability and dielectric and structural properties of ferroelectric Ba1?xCaxTi2O5 (0 ? x ? 0.30) prepared by crystallization from glass are investigated. The Ba1?xCaxTi2O5 compounds with x < 0.10 are thermally stable phases, while those with x ? 0.10 are metastable phases. The ferroelectric transition temperature drastically decreases from 470 to 220°C with increasing x. Crystal structure analyses reveal that one of two possible Ba sites is occupied by Ca in the stable phase region, while Ca-site selectivity is broken in the metastable phase region. The Ca-site selectivity introduces local distortion and makes the crystal lattice unstable. However, the local distortion is suppressed by the occupancy of Ca into both Ba sites. Accordingly, the metastable ferroelectric phase can be obtained beyond the substitution limit of Ca by crystallization from the glassy state. The stabilization mechanism provides possible wide control of the functionality of materials by expanding the composition range.

Masuno, Atsunobu; Moriyoshi, Chikako; Mizoguchi, Teruyasu; Okajima, Toshihiro; Kuroiwa, Yoshihiro; Arai, Yasutomo; Yu, Jianding; Inoue, Hiroyuki; Watanabe, Yasuhiro

2013-01-01

384

Metallisation of single crystal diamond radiation detectors  

NASA Astrophysics Data System (ADS)

Properties such as a large band gap, high thermal conductivity and resistance to radiation damage make diamond an extremely attractive candidate for detectors in next generation particle physics experiments. This paper presents our technique for metallisation of a single crystal diamond grown by chemical vapour deposition (CVD) for use as a radiation detector, suitable for operation in places such as the Large Hadron Collider. The front and back side of the diamond are metalised with aluminium and gold on top of titanium respectively, after which the diamond is mounted and read out via a charge sensitive preamplifier. The device is found to collect charge at an efficiency of 97%.

Ong, Lucas; Ganesan, Kumaravelu; Alves, Andrew; Barberio, Elisabetta

2012-10-01

385

Fabrication of single-crystal diamond microcomponents  

SciTech Connect

We have combined a technique for the lift-off of thin diamond films from a bulk diamond with a technique for engraving diamond with a focused excimer laser to produce free-standing single-crystal diamond microstructures. One microcomponent that has been produced is a 12 tooth gear [similar to]400 [mu]m in diameter and [similar to]13 [mu]m thick. Other microstructures have also been demonstrated, showing the versatility of this method. This process should be applicable to producing diamond microcomponents down to spatial dimensions (width and thickness) of a few micrometers.

Hunn, J.D.; Withrow, S.P.; White, C.W.; Clausing, R.E.; Heatherly, L. (Oak Ridge National Laboratory, Bldg 5500 MS-6376, Oak Ridge, Tennessee 37831-6376 (United States)); Christensen, C.P. (Potomac Photonics, Lanham, Maryland 20705 (United States))

1994-12-12

386

Conduction mechanism of single-crystal alumina  

NASA Technical Reports Server (NTRS)

The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

1992-01-01

387

Phase transition in sarcosine phosphite single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of sarcosine phosphite (SarcH3PO3) have been grown. The amino acid sarcosine is an isomer of the protein amino acid alanine. Both amino acids are described by the same chemical formula but have different structures; or, more specifically, in contrast to the alanine molecule, the sarcosine molecule has a symmetric structure. It has been found that the sarcosine phosphite compound undergoes a structural phase transition at a temperature of approximately 200 K. This result has demonstrated that compounds of achiral amino acids are more susceptible to structural phase transitions.

Lemanov, V. V.; Popov, S. N.; Pankova, G. A.

2011-06-01

388

Consequences of magnetoelectric interactions on ferroelectric domain structures  

Microsoft Academic Search

The standard lift mode of electrostatic force microscopy (EFM) has been utilized to study the influence of magnetoelectric (ME) effect on ferroelectric domain structures in a YIG-PZT bilayer. A PZT disk of thickness=250mum was bonded on to a (111) single crystal YIG on GGG substrates. Randomly oriented domains of PZT are observed in the absence of a dc magnetic filed

P. Mahanandia; A. S. Tatarenko; G. Srinivasan

2008-01-01

389

Quantitative nonlinear dielectric microscopy of periodically polarized ferroelectric domains  

SciTech Connect

A nonlinear dielectric scanning tip microwave near-field microscope capable of submicron quantitative imaging of nonlinear dielectric constant was developed. This nondestructive technique was used to image the nonlinear dielectric constant profiles of an yttrium-doped LiNbO{sub 3} single crystal with periodically polarized ferroelectric domains. {copyright} {ital 1998 American Institute of Physics.}

Gao, C.; Duewer, F.; Lu, Y.; Xiang, X. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

1998-08-01

390

Ferroelectric Perovskite X-Ray and Neutron Diffraction Study.  

National Technical Information Service (NTIS)

The atomic positions have been determined for ferroelectric BiFeO3 employing both X-ray single crystal and neutron powder diffraction. The oxygen atomic positions could be determined only by neutron diffraction and are interpreted as a rotation of rigid o...

C. Michel J. M. Moreau R. Gerson W. J. James

1970-01-01

391

Electrochemical Sc 2O 3 single crystal growth  

Microsoft Academic Search

Scandium oxide single crystals were successfully grown electrochemically by applying the Sc3+ ion-conducting Sc2(MoO4)3 solid electrolyte at 1223K. The single crystal growth can be regulated by the electrolysis condition, and the crystal size can be intentionally controlled by adjusting the electrolysis period. Although the single crystal growth of such refractory oxides as Sc2O3 is considerably difficult by the conventional thermal

Toshiyuki Masui; Young Woon Kim; Nobuhito Imanaka; Gin-ya Adachi

2004-01-01

392

Study of monoclinic-tetragonal-cubic phase transition in Pb(Zn1\\/3Nb2\\/3)O3-0.08PbTiO3 single crystals by micro-Raman spectroscopy  

Microsoft Academic Search

The relaxor ferroelectric Pb(Zn1\\/3Nb2\\/3)O3-0.08PbTiO3 (PZN-0.08PT) single crystal has been investigated using polarized micro-Raman scattering technique in a wide temperature range from -150 to 350 °C. Raman spectra of the crystal at temperatures lower than 90 °C show 11 modes over a frequency range of 100-1000 cm-1. There are 12 Raman active vibration modes in the monoclinic structure of relaxor ferroelectrics

Juan Cheng; Yang Yang; Yan-Hua Tong; Sheng-Bo Lu; Jing-Ya Sun; Ke Zhu; Yu-Long Liu; G. G. Siu; Z. K. Xu

2009-01-01

393

Growth of Oxalic Acid Single Crystals from Solution: Solvent Effects on Crystal Habit  

Microsoft Academic Search

Single crystals of oxalic acid dihydrate are difficult to grow from pure water solution, but good single crystals of the material may be obtained by growth from mixtures of acetone and water. The solvent markedly affects the crystal habit. Crystals grown in mixtures of acetone and water develop the prismatic habit, while those grown in water alone develop the tabular

John L. Torgesen; John Strassburger

1964-01-01

394

Exploratory crystal growth techniques in the search of new dielectrics and ferroelectrics  

Microsoft Academic Search

Exploratory crystal growth gives as fast as possible and as economically as possible first crystals for an assessment of chemical, structural and physical properties. The arsenal of the crystal grower is scanned and solution growth techniques are selected as first choice for exploratory growth. Equipment for obtaining rapidly the solubility data is described and the use of a modified temperature

H. Arend

1981-01-01

395

Single-crystal fiber optics: a review  

NASA Astrophysics Data System (ADS)

Single-crystal (SC) fiber optics have been grown for many years for use as passive fibers for the delivery of IR laser radiation and as active fibers useful as minirod lasers. Most of the early work on SC fiber optics involved the growth of unclad sapphire fibers for the transmission of Er:YAG laser radiation at 2.94 ?m. More recently there has been a renewed interest in rare-earth (RE) doped oxide crystal fibers for use as high power fiber lasers. By analogy with RE doped-bulk laser crystals it is expected that pure YAG and other crystalline SC fibers should be capable of transmitting extremely high laser energies. SC oxide fibers have some distinct advantages over conventional glass fibers including higher thermal conductivity and low stimulated Brillouin scattering (SBS) gain coefficients. The latter can limit the ultimate power output of glass fiber lasers. To date most of the investigators have used the technique of Laser Heated Pedestal Growth (LHPG) to grow unclad SC fibers with diameters ranging from 30 to 350 ?m and in lengths as long as 5 m. The loss for SC sapphire fibers at 2.94 ?m has been measured as low as 0.3 dB/m. In this review we discuss the technique of LHPG, the various SC fiber optics that have been grown for both active and passive applications, and methods that may be used to clad the fibers.

Harrington, James A.

2014-02-01

396

Fabrication of crystals from single metal atoms  

PubMed Central

Metal nanocrystals offer new concepts for the design of nanodevices with a range of potential applications. Currently the formation of metal nanocrystals cannot be controlled at the level of individual atoms. Here we describe a new general method for the fabrication of multi-heteroatom-doped graphitic matrices decorated with very small, ångström-sized, three-dimensional (3D)-metal crystals of defined size. We irradiate boron-rich precious-metal-encapsulated self-spreading polymer micelles with electrons and produce, in real time, a doped graphitic support on which individual osmium atoms hop and migrate to form 3D-nanocrystals, as small as 15?Å in diameter, within 1?h. Crystal growth can be observed, quantified and controlled in real time. We also synthesize the first examples of mixed ruthenium–osmium 3D-nanocrystals. This technology not only allows the production of ångström-sized homo- and hetero-crystals, but also provides new experimental insight into the dynamics of nanocrystals and pathways for their assembly from single atoms.

Barry, Nicolas P. E.; Pitto-Barry, Anais; Sanchez, Ana M.; Dove, Andrew P.; Procter, Richard J.; Soldevila-Barreda, Joan J.; Kirby, Nigel; Hands-Portman, Ian; Smith, Corinne J.; O'Reilly, Rachel K.; Beanland, Richard; Sadler, Peter J.

2014-01-01

397

Thermodynamic forces in single crystals with dislocations  

NASA Astrophysics Data System (ADS)

A simple model for the evolution of macroscopic dislocation regions in a single crystal is presented. This model relies on maximal dissipation principle within Kröner's geometric description of the dislocated crystal. Mathematical methods and tools from shape optimization theory provide equilibrium relations at the dislocation front, similarly to previous work achieved on damage modelling (J Comput Phys 33(16):5010-5044, 2011). The deformation state variable is the incompatible strain as related to the dislocation density tensor by a relation involving the Ricci curvature of the crystal underlying elastic metric. The time evolution of the model variables follows from a novel interpretation of the Einstein-Hilbert flow in terms of dislocation microstructure energy. This flow is interpreted as the dissipation of non-conservative dislocations, due to the climb mechanism, modelled by an average effect of mesoscopic dislocations moving normal to their glide planes by adding or removing points defects. The model equations are a fourth-order tensor parabolic equation involving the operator "incompatibility," here appearing as a tensorial counterpart of the scalar Laplacian. This work encompasses and generalizes results previously announced (C R Acad Sci Paris Ser I 349:923-927, 2011), with in addition a series of physical interpretations to give a meaning to the newly introduced concepts.

Van Goethem, Nicolas

2014-06-01

398

Fabrication of crystals from single metal atoms.  

PubMed

Metal nanocrystals offer new concepts for the design of nanodevices with a range of potential applications. Currently the formation of metal nanocrystals cannot be controlled at the level of individual atoms. Here we describe a new general method for the fabrication of multi-heteroatom-doped graphitic matrices decorated with very small, ångström-sized, three-dimensional (3D)-metal crystals of defined size. We irradiate boron-rich precious-metal-encapsulated self-spreading polymer micelles with electrons and produce, in real time, a doped graphitic support on which individual osmium atoms hop and migrate to form 3D-nanocrystals, as small as 15?Å in diameter, within 1?h. Crystal growth can be observed, quantified and controlled in real time. We also synthesize the first examples of mixed ruthenium-osmium 3D-nanocrystals. This technology not only allows the production of ångström-sized homo- and hetero-crystals, but also provides new experimental insight into the dynamics of nanocrystals and pathways for their assembly from single atoms. PMID:24861089

Barry, Nicolas P E; Pitto-Barry, Anaïs; Sanchez, Ana M; Dove, Andrew P; Procter, Richard J; Soldevila-Barreda, Joan J; Kirby, Nigel; Hands-Portman, Ian; Smith, Corinne J; O'Reilly, Rachel K; Beanland, Richard; Sadler, Peter J

2014-01-01

399

Fast and accurate shape measurement system utilizing the fringe projection method with a ferroelectric liquid-crystal-on-silicon microdisplay  

NASA Astrophysics Data System (ADS)

Fringe projection methods using the phase-shifting technique have the advantages of fast 3-D shape measurement and high accuracy. The performance of the fringe projection system, including image quality, nonlinearity of the projected intensity, stability, and switching time for multiple phase-shifted patterns, is essential for fast and accurate shape measurement. A fast and accurate measurement system using a ferroelectric liquid-crystal-on-silicon microdisplay and a high-powered light emitting diode light source is developed. Our results indicate that the nonlinearity of the projected intensity and the stability of the fringe projection were dramatically improved compared with an ordinary commercial liquid crystal display projector. The rapid measurement of the warpage distribution of a flip chip ball grid array electronic package was performed by using the developed system. Nine phase-shifted fringe images with a resolution of 1280×960 pixels were recorded in 1.6 s. In addition, the measurement results obtained by our system agreed well with the results obtained from a micrometer and laser focus sensor. The average error was 2.6 ?m, and the standard deviation was less than 10 ?m with a 6-mm measurement range.

Ri, Shien; Muramatsu, Takashi; Saka, Masumi; Tanaka, Hiroyuki

2012-08-01

400

EPR Studies of the Order-Disorder Phase Transition in DMAAS Crystal  

Microsoft Academic Search

X-band electron paramagnetic resonance (EPR) investigations of single crystals of Cr 3+ -doped dimethylammonium aluminium sulphate hexahydrate (DMAAS) are presented from 100 K to room temperature. The crystal undergoes a phase transition at 152 K from ferroelastic to ferroelectric phase. The spin Hamiltonian parameters have been determined for both phases. The spin Hamiltonian parameters in the ferroelectric phase are: g

R. Hrabanski; M. Janiec; M. Jackowska; V. Kapustianik

2003-01-01

401

Constitutive modeling for single crystal superalloys  

NASA Technical Reports Server (NTRS)

The inelastic response of single crystal gamma/gamma prime superalloys is quite different from the behavior of polycrystalline nickel base superalloys. Upto a critical temperature the yield stress of single crystal alloys is a function of the material orientation relative to the direction of the applied stress and the material exhibits significant tension/compression asymmetry. This behavior is primarily due to slip on the octahedral slip system. Above the critical temperature there is a sharp drop in the yield stress, cube slip becomes more predominant and the tension/compression asymmetry is reduced. Similar orientation and tension/compression asymmetry is observed in creep and secondary creep above the critical temperature is inferred to occur by octahedral slip. There are two exceptions to this behavior. First, loading near the (111) orientation exhibits cube slip at all temperatures, and; second, loading near the (001) orientation produces only octahedral slip at all temperatures. The constitutive model is based on separating the total global strain into elastic and inelastic components. This model is developed and briefly discussed.

Stouffer, D. C.; Jayaraman, N.; Sheh, M.; Alden, D.

1986-01-01

402

High-Energy Synchrotron X-Ray Diffraction for In Situ Diffuse Scattering Studies of Bulk Single Crystals  

NASA Astrophysics Data System (ADS)

High-energy synchrotron x-ray scattering offers a powerful technique for investigation of single-crystal material structures. Large, mm-sized crystals can be used, allowing complex in situ sample environments to be employed. Here, we demonstrate how this technique can be applied for the collection of single-crystal diffuse scattering volumes from the electro-active material 96%Bi0.5Na0.5TiO3-4%BaTiO3 while electric fields are applied in situ. The data obtained allow correlation of the atomic and nanoscale structures with the observed macroscopic electro-active properties of interest. This article presents a recent study relating the nanoscale stacking fault structure in BNT-BT to the relaxor-ferroelectric nature of the material [Daniels et al. in Appl. Phys. Lett. 98, 252904 (2011)], and extends this study with further experimental description and analysis.

Daniels, John E.; Jo, Wook; Donner, Wolfgang

2012-01-01

403

Field-Induced Alignment of Ferroelectric Liquid Crystal with the Phase Sequence of N*SmC* in an Uniform External Electric Field  

Microsoft Academic Search

We proposed a new field-induced alignment method for a ferroelectric liquid crystal (FLC) which exhibited chiral nematic (N*) to smectic C* (SmC*) phase transition. Homogeneous alignment for the FLC with the phase sequence of N*-SmC* can be obtained by applying an electric field to the cell at the temperature 2-3°C higher than the N*-SmC* phase transition temperature. Conventionally, the electric

Chang Ju Kim; Yu Jin Kim; Jong Min Wang; Kyu Sik Kim

2002-01-01

404

Phase equilibria, crystal growth and characterization of the novel ferroelectric tungsten bronzes CaxBa1-xNb2O6 (CBN) and CaxSryBa1-x-yNb2O6 (CSBN)  

NASA Astrophysics Data System (ADS)

Phase diagram analyses and crystal growth experiments of the novel ferroelectric tetragonal tungsten bronzes CaxBa1-xNb2O6 (calcium barium niobate, CBN) and CaxSryBaNb2O6 (calcium strontium barium niobate, CSBN) were performed in this study. The quasi-binary phase diagram BaNb2O6-CaNb2O6 was found to be similar to the related system BaNb2O6-SrNb2O6, but with a remarkably reduced existence region. In the quasi-ternary phase diagram CaNb2O6-SrNb2O6-BaNb2O6 the stability field of CaxSryBaNb2O6 mixed crystals was determined by X-ray powder diffraction of sintered and annealed samples. Large, transparent, and nearly colorless CBN and CSBN single crystals of high quality were grown by the Czochralski method. The dislocation network structure of the core region in the as-grown crystals was analyzed by X-ray topography employing white beam synchrotron radiation. Precise measurements of the refractive index dispersion showed a composition dependance only for the extraordinary beam. The Curie temperature of the ferroelectric phase transition {4}/{m}mm?4mm determinated by calorimetric measurements exhibited a clear composition dependance. It is expected that in the complete mixed crystal system CaxSryBaNb2O6 the Curie temperature could be varied between about 80C for strontium barium niobate with xSr=0.61 and about 300C for CBN with xCa?0.20, the lowest possible Ca content.

Muehlberg, M.; Burianek, M.; Joschko, B.; Klimm, D.; Danilewsky, A.; Gelissen, M.; Bayarjargal, L.; Görler, G. P.; Hildmann, B. O.

2008-04-01

405

Pulse shape discrimination with new single crystal organic scintillators  

Microsoft Academic Search

Pulse shape discrimination in organic single crystal and liquid scintillators provides a means of identifying fission energy neutrons with high specificity. We present the results of a broad survey of over one hundred single crystal organic scintillators produced from low-temperature solution growth technique. Each crystal was evaluated for light yield and pulse shape discrimination performance. The pulse shape dependence on

Jason Newby; Natalia Zaitseva; Stephen Payne; Nerine Cherepy; Leslie Carman; Giulia Hull

2009-01-01

406

Growth of strontium tartrate tetrahydrate single crystals in silica gels  

Microsoft Academic Search

Growth of single crystals of strontium tartrate tetrahydrate by controlled diffusion in silica gels has been narrated. In the field of material science, there is always a keen and competitive race to grow perfect single crystals with sufficient purity and perfection. Successful attempts to larger as well as more perfect crystals of SrTr are described in this paper and thus

A. R. Patel; S. K. Arora

1976-01-01

407

Single crystal alumina for dental implants and bone screws.  

PubMed

When ground to a suitable form, flexural strength of single crystal alumina (Al2O3) decreases to as low as one third the strength of the intact crystal. This flexural strength decrease is, however, recovered by chemical etching at a high temperature to eliminate surface defects caused by grinding. By using this strength recovery treatment, various types of single crystal implants with fine structure were able to be designed. Four kinds of single crystal bone screws and single crystal dental implants of screw and anchor type were designed. Flexural strength and impact strength of the implants were measured. PMID:7349666

Kawahara, H; Hirabayashi, M; Shikita, T

1980-09-01

408

Synthesis, properties, and structure of potassium titanyl phosphate single crystals doped with hafnium  

SciTech Connect

Single crystals of potassium titanyl phosphate doped with hafnium are grown by spontaneous flux crystallization. Their physical properties are studied, and the structure of three KTi{sub 1-x}Hf{sub x}OPO{sub 4} crystals (x = 0.01, 0.03, and 0.12) is determined. In the crystals studied, hafnium mostly occupies the second titanium position. The doping of KTP crystals with hafnium results in an elongation of K-O bonds in the potassium polyhedra and, as a consequence, in a considerable (by approximately 180 deg. C) decrease in the temperature of ferroelectric phase transition. The magnitude of anomalous permittivity substantially decreases. The electrical conduction in the specimens studied decreases by approximately half an order of magnitude in the low-temperature region but remains almost unchanged in the high-temperature region. Even at minor concentrations, the presence of a hafnium additive in the specimens considerably (by 35%) enhances the intensity of the second harmonic generation of laser radiation.

Orlova, E. I.; Kharitonova, E. P. [Moscow State University, Faculty of Physics (Russian Federation); Novikova, N. E., E-mail: natnov@ns.crys.ras.ru; Verin, I. A.; Alekseeva, O. A.; Sorokina, N. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Voronkova, V. I. [Moscow State University, Faculty of Physics (Russian Federation)

2010-05-15

409

Single event effect in a ferroelectric-gate field-effect transistor under heavy-ion irradiation  

NASA Astrophysics Data System (ADS)

The single event effect in ferroelectric-gate field-effect transistor (FeFET) under heavy ion irradiation is investigated in this paper. The simulation results show that the transient responses are much lower in a FeFET than in a conventional metal–oxide–semiconductor field-effect transistor (MOSFET) when the ion strikes the channel. The main reason is that the polarization-induced charges (the polarization direction here is away from the silicon surface) bring a negative surface potential which will affect the distribution of carriers and charge collection in different electrodes significantly. The simulation results are expected to explain that the FeFET has a relatively good immunity to single event effect.

Yan, Shao-An; Tang, Ming-Hua; Zhao, Wen; Guo, Hong-Xia; Zhang, Wan-Li; Xu, Xin-Yu; Wang, Xu-Dong; Ding, Hao; Chen, Jian-Wei; Li, Zheng; Zhou, Yi-Chun

2014-04-01

410

Solar cell structure incorporating a novel single crystal silicon material  

DOEpatents

A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

Pankove, Jacques I. (Princeton, NJ); Wu, Chung P. (Trenton, NJ)

1983-01-01

411

Mode Gruneisen Parameters for Single Crystal Al2O3.  

National Technical Information Service (NTIS)

Single crystal Al2O3 (sapphire or corundum), crystallizes in the trigonal lattice, point group 3m. Its thermodynamic properties have been extensively investigated over the last years. As the pressure derivatives of its elastic moduli have recently become ...

D. Gerlich

1969-01-01

412

Ferroelectric Pump  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

413

Hydrogen Annealing Of Single-Crystal Superalloys  

NASA Technical Reports Server (NTRS)

Annealing at temperature equal to or greater than 2,200 degrees F in atmosphere of hydrogen found to increase ability of single-crystal superalloys to resist oxidation when subsequently exposed to oxidizing atmospheres at temperatures almost as high. Supperalloys in question are principal constituents of hot-stage airfoils (blades) in aircraft and ground-based turbine engines; also used in other high-temperature applications like chemical-processing plants, coal-gasification plants, petrochemical refineries, and boilers. Hydrogen anneal provides resistance to oxidation without decreasing fatigue strength and without need for coating or reactive sulfur-gettering constituents. In comparison with coating, hydrogen annealing costs less. Benefits extend to stainless steels, nickel/chromium, and nickel-base alloys, subject to same scale-adhesion and oxidation-resistance considerations, except that scale is chromia instead of alumina.

Smialek, James L.; Schaeffer, John C.; Murphy, Wendy

1995-01-01

414

Magnetoplasticity and diffusion in silicon single crystals  

SciTech Connect

The effect of static magnetic fields on the dynamics of surface dislocation segments, as well as the diffusion mobility of a dopant in silicon single crystals, has been analyzed. It has been experimentally found that the preliminary treatment of p-type silicon plates (the dopant is boron with a concentration of 10{sup 16} cm{sup -3}) in the static magnetic field (B = 1 T, a treatment time of 30 min) leads to an increase in the mobility of surface dislocation segments. The characteristic times of observed changes (about 80 h) and the threshold dopant concentration (10{sub 15} cm{sup -3}) below which the magneto-optical effect in silicon is not fixed have been determined. It has been found that diffusion processes in dislocation-free silicon are magnetically sensitive: the phosphorus diffusion depth in p-type silicon that is preliminarily aged in the static magnetic field increases (by approximately 20%) compared to the reference samples.

Skvortsov, A. A., E-mail: SkvortsovAA2009@yandex.ru; Karizin, A. V. [Moscow State Technical University 'MAMI' (Russian Federation)

2012-01-15

415

Constitutive modeling for single crystal superalloys  

NASA Technical Reports Server (NTRS)

A crystallographic approach to constitutive modeling of single crystal superalloys is discussed. The approach is based on identifying the active slip planes and slip directions. The shear stresses are computed on each of the slip planes from applied stress components. The slip rate is then computed on each slip system and the microscopic inelastic strain rates are the sum of the slip in the individual slip systems. The constitutive model was implemented in a finite element code using twenty noted isoparametric solid elements. Constants were determined for octahedral and cube slip systems. These constants were then used to predict tension-compression asymmetry and fatigue loops. Other data was used to model the tensile and creep response.

Stouffer, Donald C.; Dame, L. Thomas; Jayaraman, N.

1985-01-01

416

Dielectric Dispersion in (CH3NH3)5Bi2X11 (X=Cl, Br) Single Crystals  

NASA Astrophysics Data System (ADS)

The temperature dependences of dielectric dispersion in (CH3NH3)5Bi2Cl11 and (CH3NH3)5Bi2Br11 single crystals, which undergo the para-ferroelectric phase transition (I?II) at 307 K and 311.5 K, respectively, were measured near the phase transition point in the frequency range from 1 MHz to 1 GHz. The dielectric dispersion exhibited was found to be of the Debye-type. The critical slowing down was observed near the phase transition point.

Iwata, Makoto; Ishibashi, Yoshihiro

1990-12-01

417

Ordered nano-scale domains in lithium niobate single crystals via phase-mask assisted all-optical poling  

NASA Astrophysics Data System (ADS)

We report the formation of directionally ordered nano-scale surface domains on the +z face of undoped congruent lithium niobate single crystals by using UV illumination through a phase mask of sub-micron periodicity with an energy fluence between ˜90 mJ/cm 2 and 150 mJ/cm 2 at ? = 266 nm. We clearly show here that the UV-induced surface ferroelectric domains only nucleate at and propagate along maxima of laser intensity. Although the domain line separation varies and is greater than 2 ?m for this set of experimental conditions, this enables a degree of control over the all-optical poling process.

Wellington, I. T.; Valdivia, C. E.; Sono, T. J.; Sones, C. L.; Mailis, S.; Eason, R. W.

2007-02-01

418

Organic ferroelectrics  

Microsoft Academic Search

Ferroelectricity results from one of the most representative phase transitions in solids, and is widely used for technical applications. However, observations of ferroelectricity in organic solids have until recently been limited to well-known polymer ferroelectrics and only a few low-molecular-mass compounds. Whereas the traditional use of dipolar molecules has hardly succeeded in producing ferroelectricity in general, here we review advances

Sachio Horiuchi; Yoshinori Tokura

2008-01-01

419

Irreversible alterations of ferroelectric domain structure in paramagnetic rare earth molybdates induced by a magnetic field  

Microsoft Academic Search

The effect of a magnetic field on the ferroelectric domain structure of single crystal samples of the metastable orthorhombic ferroelectric ferroelastic ?’-phase of Sm2(MoO4)3, Gd2(MoO4)3, Tb2(MoO4)3, and TbGd(MoO4)3 was investigated at 78 K in pulsed magnetic fields up to 100 kOe. It was shown that a magnetic field of certain orientation may change a ferroelectric domain structure in Tb2(MoO4)3 and

B. K. Ponomarev; S. A. Ivanov; B. S. Red’kin; V. N. Kurlov

1994-01-01

420

Acousto-domain interaction in ferroelectric lithium niobate  

NASA Astrophysics Data System (ADS)

First observation of the reorientation of ferroelectric domains in the lithium niobate single crystals induced by ultrasound is reported. This effect is detected from the samples, which are treated by megahertz frequency-range ultrasound with above certain threshold amplitude at room temperature. Acoustic strain amplitude causing the domain reorientation is of the order of E10-5. The effect is directly revealed by chemically etched crystal surfaces, and independently confirmed by the acoustically induced evolution of x-ray diffraction rocking curves and changes in acousto-electric properties of the lithium niobate crystals. The physical mechanism responsible for the interaction of the domains and ultrasound can be attributed to the mechanical stress and piezoelectric field produced by a piezo-active acoustic wave. A new effect of acousto-domain interaction in ferroelectric crystals might be taken into account for a wide variety of fundamental physical phenomena involving propagation of the acoustic waves in real crystals.

Ostrovskii, Igor V.; Borovoy, Mukola M.; Korotchenkov, Oleg O.; Nadtochii, Andrij B.; Chupryna, Roman G.

2001-05-01

421

Growth and studies of pure and potassium iodide-doped zinc tris-thiourea sulphate (ZTS) single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of pure and potassium iodide (KI)-doped Zinc Tris-thiourea Sulphate (ZTS) were grown from aqueous solutions by slow evaporation technique. The grown crystals have been subjected to single crystal X-ray diffraction to determine the unit cell dimensions. The grown crystals were also characterized by recording the powder X-ray diffraction patterns and by identifying the diffracting planes. The Fourier Transform Infrared (FT-IR) spectra have been recorded in the range 400-4500 cm -1. Second harmonic generation (SHG) for the materials of this work was confirmed using Nd:YAG laser. The UV-visible spectra show that the grown crystals have wide optical transparency in the entire visible region. The Thermogravimetric/Differential Thermal Analyses (TG/DTA) thermograms reveal that the materials have good thermal stability. Atomic absorption study reveals the presence of potassium in the doped f crystals. The electrical measurements were made in the temperature range 40-130 °C along c-direction of the grown crystals. The dielectric studies show that there may be a ferroelectric transition at 50 °C for both pure and KI-doped ZTS crystals. DC conductivity for both the samples is found to be increasing with increase in temperature. Activation energy values were also determined for both AC and DC conduction processes in the samples.

Krishnan, C.; Selvarajan, P.; Freeda, T. H.

2008-12-01

422

Single-Crystal Neutron Structural Analyses of Potassium Dihydrogen Phosphate and Potassium Dideuterium Phosphate  

NASA Astrophysics Data System (ADS)

Single-crystal neutron structural analyses have been performed on both potassium dihydrogen phosphate (KDP) and potassium dideuterium phosphate (DKDP) in order to discuss the isotope effect from structural viewpoints. The values of spontaneous polarization are calculated from the refined structural parameters by the point-charge method, and the calculated values are almost in good agreement with the experimental values of each compound. The temperature dependences of the anisotropic atomic displacement parameters U33's and positional shifts of potassium, phosphorus, oxygen, and hydrogen/deuterium atoms along the polar c-axis is compared between KDP and DKDP. It is concluded that the paraelectric-ferroelectric transitions are perfectly of the improper order--disorder type in both KDP and DKDP; the ordering of the hydrogen atom induces the spontaneous displacements of both potassium and phosphorus atoms. The interatomic distances and angles in the paraelectric and ferroelectric phases of KDP and DKDP are also investigated. From the result, all the structural differences seem to be caused by the difference in mass between protons and deuterons.

Miyoshi, Tatsuki; Mashiyama, Hiroyuki; Asahi, Takanao; Kimura, Hiroyuki; Noda, Yukio

2011-04-01

423

TOPICAL REVIEW: Organic field-effect transistors using single crystals  

Microsoft Academic Search

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of

Tatsuo Hasegawa; Jun Takeya

2009-01-01

424

Nanocomposite of semiconducting ferroelectric antimony sulphoiodide dots-doped glasses  

Microsoft Academic Search

Antimony sulphoiodide (SbSI) is a semiconducting ferroelectric crystal. The SbSI possesses attractive properties, such as high pizoelectric constant, very high dielectric permittivity, and high electro-optic coefficient, but it is very difficult to grow a single crystal with bigger size. Currently, a method for synthesis of SbSI by liquid reaction has been developed in our laboratory. Nanocomposites of SbSI dots in

Yuhuan Xu; F. Del Monte; J. D. Mackenzie; K. Namjoshi; P. Muggli; C. Joshi

1999-01-01

425

Ferroelectric Domain Structure and Internal Bias Field in DL-alpha-Alanine-Doped Triglycine Sulfate  

Microsoft Academic Search

Single crystals of ferroelectric triglycine sulfate (TGS) have been grown from solutions containing 10 and 30 mol% of DL-alpha-alanine. Crystal form, domain structure and distribution of internal bias field Eb in these DL-alpha-alanine-doped triglycine sulfate: (DLATGS) crystals were investigated. Although the crystal form is influenced by the doping, it shows the symmetry of 2\\/m similar to pure TGS. The intensity

Noriyuki Nakatani

1991-01-01

426

Study of ferroelectric domain structure on BaTiO3 crystals grown by pulling method  

Microsoft Academic Search

Domain structure of pulled barium titanate crystal is investigated by optical and scanning electron microscopy. Polished, as grown and cleaved surfaces are studied. Observations of the domain structure without etching are presented.

Raymond Le Bihan; Didier Beudon

1984-01-01

427

Micropatterning process of ferroelectric oxides by irradiation of an electron beam on metal naphthenate films  

Microsoft Academic Search

Fine micropatterns with linewidth of 0.35 ?m were fabricated by irradiation with an electron beam of metal naphthenate films, being precursors of ferroelectric oxides, and development with a solvent. Relatively large patterns were crystallized into the single phase Bi4Ti3O12 with c-axis orientation by successive heat-treatment at 800°C. Micropatterns with linewidth of 1 ?m were crystallized into single crystals and their

S. Okamura; Atsushi Kakimi; Yukie Yagi; Katsumi Mori; R. Tsukamoto

1994-01-01

428

Ultratough CVD single crystal diamond and three dimensional growth thereof  

DOEpatents

The invention relates to a single-crystal diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 30 MPa m.sup.1/2. The invention also relates to a method of producing a single-crystal diamond with a toughness of at least about 30 MPa m.sup.1/2. The invention further relates to a process for producing a single crystal CVD diamond in three dimensions on a single crystal diamond substrate.

Hemley, Russell J. (Washington, DC) [Washington, DC; Mao, Ho-kwang (Washington, DC) [Washington, DC; Yan, Chih-shiue (Washington, DC) [Washington, DC

2009-09-29

429

Formation of curved micrometer-sized single crystals.  

PubMed

Crystals in nature often demonstrate curved morphologies rather than classical faceted surfaces. Inspired by biogenic curved single crystals, we demonstrate that gold single crystals exhibiting curved surfaces can be grown with no need of any fabrication steps. These single crystals grow from the confined volume of a droplet of a eutectic composition melt that forms via the dewetting of nanometric thin films. We can control their curvature by controlling the environment in which the process is carried out, including several parameters, such as the contact angle and the curvature of the drops, by changing the surface tension of the liquid drop during crystal growth. Here we present an energetic model that explains this phenomenon and predicts why and under what conditions crystals will be forced to grow with the curvature of the microdroplet even though the energetic state of a curved single crystal is very high. PMID:24694217

Koifman Khristosov, Maria; Kabalah-Amitai, Lee; Burghammer, Manfred; Katsman, Alex; Pokroy, Boaz

2014-05-27

430

Investigation of single crystal silicates for blue tunable lasers  

NASA Astrophysics Data System (ADS)

The single crystal growth of rare earth silicates was investigated for the purpose of tunable laser hosts. Silicates of the type R2SiO5, where R = La, Gd, Y, Lu, were prepared from stoichiometric melts and doped with Ce(3+) activators. Seed crystals were obtained from crystallized melt sections or by growth on an iridium wire. These seeds were utilized in standard Czochralski type growth to obtain larger single crystals. Cathodoluminescence experiments on both powders and single crystals showed wavelength shifts with different rare earth ions. The Gd, Y, and mixed crystals of Gd-Y silicates gave good bright emission with Ce(3+). The emission is broad band and covers the wavelength range of 370 to 525 nm. The peak emission can be centered near 450 to 460 nm by other compositions. Larger single crystals for laser hosts are under development.

Belt, R. F.; Catalano, J. A.

1986-01-01

431

Reversible single-crystal-to-single-crystal photochemical formation and thermal cleavage of a cyclobutane ring.  

PubMed

A [2+2] cycloaddition reaction has been observed in a number of solids. The cyclobutane ring in a photodimerized material can be cleaved into olefins by UV light and heat. The high thermal stability of the metal-organic salt K2SDC (H2SDC = 4,4'-stilbenedicarboxylic acid) has been successfully utilized to investigate the reversible cleavage of a cyclobutane ring. The two polymorphs of K2SDC undergo reversible cyclobutane formation by UV light and cleavage by heat in cycles. Of these, one polymorph retains its single-crystal nature during the reversible processes. Polymorphs are known to show different physical properties and chemical reactivities. This work reveals that the retention of single-crystal nature is strongly associated with the packing of molecules, which is controlled by kinetics and thermodynamics. The photoemissive nature of the products makes this as a promising material for photoswitches and optical data storage devices. PMID:24459072

Kole, Goutam Kumar; Kojima, Tatsuhiro; Kawano, Masaki; Vittal, Jagadese J

2014-02-17

432

Growth of benzophenone single crystals from solution: A novel approach with 100% solute - crystal conversion efficiency  

Microsoft Academic Search

An unidirectional 60mm diameter benzophenone single crystal was successfully grown by utilizing a novel crystal growth method at room temperature. <110> oriented single crystal ingots were grown out of xylene as solvent and by fixing a seed at the bottom of the ampoule. The obtained benzophenone ingots with the sizes of 10mm, 25mm and 60mm diameter evident that ease in

K. Sankaranarayanan; P. Ramasamy

2006-01-01

433

Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals  

DOEpatents

A method of fabricating bulk YBa.sub.2 Cu.sub.3 O.sub.x where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa.sub.2 Cu.sub.3 O.sub.x are heated in the presence of a Nd.sub.1+x Ba.sub.2-x Cu.sub.3 O.sub.y seed crystal to a temperature sufficient to form a liquid phase in the YBa.sub.2 Cu.sub.3 O.sub.x while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa.sub.2 Cu.sub.3 O.sub.x material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material.

Todt, Volker (Lemont, IL); Miller, Dean J. (Darien, IL); Shi, Donglu (Oak Park, OH); Sengupta, Suvankar (Columbus, OH)

1998-01-01

434

Amorphouslike Density of Gap States in Single-Crystal Pentacene  

Microsoft Academic Search

We show that optical and electrical measurements on pentacene single crystals can be used to extract the density of states in the highest occupied molecular orbital lowest unoccupied molecular orbital band gap. It is found that these highly purified crystals possess band tails broader than those typically observed in inorganic amorphous solids. Results on field-effect transistors fabricated from similar crystals

Arthur Ramirez; David Lang; Xiaoliu Chi; Theo Siegrist; Mike Sergent

2004-01-01

435

Giant room-temperature barocaloric effect and pressure-mediated electrocaloric effect in BaTiO3 single crystal  

NASA Astrophysics Data System (ADS)

Barocaloric effect in BaTiO3 single crystal is studied by a thermodynamic phenomenological model. It is demonstrated that a giant barocaloric effect can be achieved near room temperature with an adiabatic temperature change of more than 3 K and a temperature span about 50 K. As expected, the electrocaloric peak can be shifted towards room temperature by pressure. However, a slight reduction of the electrocaloric peak is found in contrast to relaxor ferroelectrics and LiNbO3. We believe that our findings could open a potential route by combining the barocaloric effect and pressure-mediated electrocaloric effect in BaTiO3 single crystal for cooling devices.

Liu, Yang; Wei, Jie; Janolin, Pierre-Eymeric; Infante, Ingrid C.; Lou, Xiaojie; Dkhil, Brahim

2014-04-01

436

Microscale Laser Peen Forming of Single Crystal  

SciTech Connect

As the result of quickly increased requirement in many industrial products resulting from microtechnology, laser thermal microforming and microsurface treatment [microscale laser shock peening (?LSP)] have been well studied. By combining the beneficial effects of these two processes with a controlled bending deformation, microscale laser peen forming (?LPF) attracts more attention recently since it not only improves the fatigue life of the material but also shapes microscale metallic parts at the same time. In the present study, ?LSP of single crystal aluminum was presented to study anisotropic material response. Local plastic deformation was characterized by lattice rotation measured through electron backscatter diffraction. Residual stress distributions of both sides of a peened sample, characterized by x-ray microdiffraction, were compared with the results obtained from finite element method simulation. ?LPF anisotropic behavior was investigated in three effective slip systems via both the anisotropic slip line theory and numerical method. Also, the work hardening effect resulted from self-hardening, and latent hardening was analyzed through comparing the results with and without considering hardening.

Wang,Y.; Fan, Y.; Kysar, J.; Vukelic, S.; Yao, Y.

2008-01-01

437

Q-1 of forsterite single crystals  

NASA Astrophysics Data System (ADS)

Internal friction ( Q-1) experiments have been performed on synthetic forsterite single crystals in order to investigate the role of temperature, frequency and dislocation density on the Q-1 factor. Data have been obtained for both deformed and undeformed specimens over a frequency range from 10 to 10 -4 Hz at 15, 1000, 1200 and 1400°C. Measurements were done using a torsional pendulum operating in forced oscillations on specimens with dimensions of 20 mm × 5 mm × 1 mm. Samples were maintained in vacuum. Stress amplitudes were 0.1 MPa and strains 10 -6-10 -5. Pre-deformation experiments were creep tests performed at 1600°C and 20 MPa. The amount of strain was 10 -2. Dislocation microstructures were investigated by transmission electron microscopy. At room temperature, undeformed samples show low attenuation with no frequency dependence. At high temperature (1400°C), Q-1 increases up to 5 × 10 -2 for very low frequencies (10 -4 Hz). Deformed specimens show the same trend but there is a more pronounced increase in Q-1 with both frequency and temperature ( Q-1 = 2 × 10 -1, 10 -4 Hz at 1400°C). This high-temperature attenuation is the result of dislocation processes which are probably non-linear in the strain range explored by the present experiments ( ? > 10 -6). Non-linearity appears to be the best explanation for the disagreement between high Q-1 data reported in laboratory and low Q 1 data reported for the upper mantle.

Gueguen, Y.; Darot, M.; Mazot, P.; Woirgard, J.

1989-06-01

438

Preparation and morphology of pyramidal MFI single-crystal segments.  

PubMed

Single-crystal segments of tetra-n-propylammonium-templated Silicalite-1 and ZSM-5 were prepared by postsynthetic treatment of twinned MFI prisms. Microwave irradiation of the parent crystallites in alkaline solution containing hydrogen peroxide, followed by ultrasound treatment, led to disintegration of the zeolite prisms. The resulting wedge-shaped crystal segments proved to be single crystals of excellent crystallinity as shown by optical and X-ray investigations. The hydroxyl ions, compensating the positive charges of the tetrapropylammonium cations, were located by single-crystal structure refinement in template-containing Silicalite-1 and ZSM-5 but absent from the calcined samples. PMID:17988115

Schmidt, Wolfgang; Wilczok, Ursula; Weidenthaler, Claudia; Medenbach, Olaf; Goddard, Richard; Buth, Gernot; Cepak, Alexander

2007-12-01

439

Fabrication of polypyrrole nano-arrays in lysozyme single crystals  

NASA Astrophysics Data System (ADS)

A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals.A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals. Electronic supplementary information (ESI) available: Optical microscopy, SEM, TEM images, FTIR spectra and tables, conductivity plot. Experimental methods. See DOI: 10.1039/c2nr32413j

England, Matt W.; Lambert, Elizabeth M.; Li, Mei; Turyanska, Lyudmila; Patil, Avinash J.; Mann, Stephen

2012-10-01

440

Shear localization in dynamic deformation of copper single crystals  

Microsoft Academic Search

Dynamic deformation of copper single crystals, especially of fatigued copper single crystals with different orientations, was conducted on a split-Hopkinson pressure bar apparatus. The strain rates were in the range 2 - 9 × 103 s-1. After dynamic deformation, the adiabatic shear bands (ASBs) were examined in a light microscope and SEM. The width and spacing of ASBs formed under

S. X. Li; R. Q. Yang; J. W. Li; Z. F. Zhang

2006-01-01

441

Coefficients of thermal expansion for single crystal piezoelectric fiber composites  

Microsoft Academic Search

Piezoelectric fiber composites were developed to overcome drawbacks of typical monolithic piezoceramic (PZT) actuators. Although piezoelectric fiber composites had many improvements over the monolithic PZT, there are still improvements. Thus, the single crystal piezoelectric fiber composite actuator is proposed. Single crystal piezoelectric materials such as PMN-PT have larger piezoelectric strain constants, higher bandwidth and higher energy density than polycrystalline counterparts.

Jae-Sang Park; Ji-Hwan Kim

2007-01-01

442

Field Emission from Tungsten and Thoriated Tungsten Single Crystals  

Microsoft Academic Search

A reproducible time sequence of different pattern types has been found to appear in electron projector images of field emission from tungsten single crystals when the crystals are kept at temperatures above 1100°K. These pattern types, some of which have been observed before and attributed to migrations of surface tungsten atoms, can best be explained (with a single possible exception)

J. H. Daniel

1942-01-01

443

A Multivariant model for single crystal shape memory alloy behavior  

Microsoft Academic Search

A general 3-D multivariant model based on thermodynamics and micromechanics for single crystal shape memory alloy (SMA) behavior is presented. This model is based on the habit plane and transformation directions for the variants of martensite in a given material. From this information, the single crystal behavior of the material to temperature and mechanical loads is derived using the concept

Miinshiou Huang; L. C. Brinson

1998-01-01

444

Growth and Structure of Single-Crystal Films.  

National Technical Information Service (NTIS)

This research project was concerned with basic research on the growth and structure of single-crystal films of metals obtained by evaporation in ultra-high vaccum onto two types of substrates: mica and metal single-crystal films. The films were prepared i...

E. Grunbaum

1968-01-01

445

Preparation Techniques for Growth of Single Crystals of Nonmetallic Materials.  

National Technical Information Service (NTIS)

The report describes two techniques for growth of highpurity single crystals of nonmetallic materials using r-f induction-heating equipment in a frequency range of 5 to 100 Mc. One technique used for single-crystal growth was the Verneuil method using an ...

E. M. Clausen J. W. Rutter

1964-01-01

446

A Single Crystal Niobium RF Cavity of the TESLA Shape  

Microsoft Academic Search

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material

W. Singer; X. Singer; P. Kneisel

2007-01-01

447

A Quick Method for Determining the Density of Single Crystals.  

ERIC Educational Resources Information Center

Shows how the Archimedes method is used to determine the density of a single crystal of ammonium oxalate monohydrate. Also shows how to calculate the density of other chemicals when they are available as single crystals. Experimental procedures and materials needed are included. (JN)

Roman, Pascual; Gutierrez-Zorrilla, Juan M.

1985-01-01

448

Thermally induced single crystal to single crystal transformation leading to polymorphism  

NASA Astrophysics Data System (ADS)

The robust complex [La(1,10-phen)2(NO3)3] (1,10-phen = 1,10-phenanthroline) exhibits thermally induced single crystal to single crystal transformation from one polymorphic phase to another. The complex crystallizes in monoclinic C2/c space group with C2 molecular symmetry at 293 K while at 100 K it shows P21/c space group with C1 molecular symmetry. Supramolecular investigation shows that at 100 K the complex forms 2D achiral sheets whereas at 293 K forms two different homochiral 2D sheets. Low temperature DSC analysis indicates that this structural transformation occurs at 246 K and also this transformation is reversible in nature. We have shown that thermally induced coherent movement of ligands changes the molecular symmetry of the complex and leads to polymorphism. Photoluminescence property of complex has been studied in both solid state and in methanolic solution at room temperature. The effect of the presence low-lying LUMO orbital of ?-character in the complex is elucidated by theoretical calculation using DFT method.

Saha, Rajat; Biswas, Susobhan; Dey, Sanjoy Kumar; Sen, Arijit; Roy, Madhusudan; Steele, Ian M.; Dey, Kamalendu; Ghosh, Ashutosh; Kumar, Sanjay

2014-09-01

449

Thermally induced single crystal to single crystal transformation leading to polymorphism.  

PubMed

The robust complex [La(1,10-phen)2(NO3)3] (1,10-phen=1,10-phenanthroline) exhibits thermally induced single crystal to single crystal transformation from one polymorphic phase to another. The complex crystallizes in monoclinic C2/c space group with C2 molecular symmetry at 293K while at 100K it shows P21/c space group with C1 molecular symmetry. Supramolecular investigation shows that at 100K the complex forms 2D achiral sheets whereas at 293K forms two different homochiral 2D sheets. Low temperature DSC analysis indicates that this structural transformation occurs at 246K and also this transformation is reversible in nature. We have shown that thermally induced coherent movement of ligands changes the molecular symmetry of the complex and leads to polymorphism. Photoluminescence property of complex has been studied in both solid state and in methanolic solution at room temperature. The effect of the presence low-lying LUMO orbital of ?-character in the complex is elucidated by theoretical calculation using DFT method. PMID:24813281

Saha, Rajat; Biswas, Susobhan; Dey, Sanjoy Kumar; Sen, Arijit; Roy, Madhusudan; Steele, Ian M; Dey, Kamalendu; Ghosh, Ashutosh; Kumar, Sanjay

2014-09-15

450

Structural and spectroscopic studies on calcium succinate single crystals  

NASA Astrophysics Data System (ADS)

Calcium succinate crystals have been grown by gel aided solution growth technique. The structure of the crystal is solved by single crystal XRD analysis. The Crystal structure of the title compound is triclinic having space group P(1) Powder XRD studies confirmed the good crystalline nature of the sample. The different functional groups and their assigned vibrations are discussed by FT-IR and FT Raman spectroscopic studies.

Binitha, M. P.; Pradyumnan, P. P.

2014-04-01

451

Magnetic field controlled FZ single crystal growth of intermetallic compounds  

Microsoft Academic Search

Intermetallic rare-earth-transition-metal compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of bulk single crystals is very often unsuccessful due to an unfavorable solid–liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds.

R. Hermann; G. Behr; G. Gerbeth; J. Priede; H.-J. Uhlemann; F. Fischer; L. Schultz

2005-01-01

452

Ferroelectric smectic liquid crystals in the bent-core family: alignment for V-shaped analog switching  

NASA Astrophysics Data System (ADS)

Possible applications of the novel antiferroelectric/ferroelectric phases exhibited by achiral bent-core mesogens (termed banana phases, B phases, or bow- phases in the literature) are considered. Specifically, in a ferroelectric bow-phase, alignment such that the molecular bow plane of the bent mesogens is parallel to the substrates, anchoring the polarization parallel to the substrates, should afford an ideal geometry for analog `V- shaped switching' devices.

Walba, David M.; Korblova, Eva; Shao, Ren Fan; Maclennan, Joseph E.; Link, Darren R.; Clark, Noel A.

1999-10-01

453

A low-temperature crystallization path for device-quality ferroelectric films  

SciTech Connect

We show a path for low-temperature crystallization of device-quality solution-processed lead zirconate titanate films. The essential aspect of the path is to circumvent pyrochlore formation at around 300 deg. C during temperature increase up to 400 deg. C. By maintaining enough carbon via pyrolysis at 210 deg. C, well below the temperature for py