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1

Ferroelectric polarization reversal in single crystals  

NASA Technical Reports Server (NTRS)

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

Stadler, Henry L.

1992-01-01

2

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

Microsoft Academic Search

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

Hiroshi Irie; Masaru Miyayama; Tetsuichi Kudo

2001-01-01

3

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. PMID:23226595

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

2012-01-01

4

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

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

5

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

NASA Astrophysics Data System (ADS)

Ferroelectric properties along the a(b) axis and c axis in single crystals of various bismuth layer-structured ferroelectrics (BLSFs) were investigated. By measuring saturated P-E hysteresis curves of BLSFs, values of the saturated remanent polarization and the coercive electric field were found to be related to the Curie temperature and the number of BO6 octahedra (m) between bismuth layers, respectively, along the a(b) axis. The saturated remanent polarization was larger in the BLSF with a higher Curie temperature. This is attributed to a large atomic displacement accompanied by a high Curie temperature. In contrast, the saturated coercive electric field was smaller in the BLSF with a larger number of m. This phenomenon is assumed to be caused by the decrease in the strain energy of the octahedra from the bismuth layer, which leads to an easy movement of the octahedral cations in the direction of an applied external electric field. Along the c axis, the BLSFs with an odd number of m had the same relationship, that is, the saturated remanent polarization was larger with the high Curie temperature, and the saturated coercive field was smaller with the large m number. However, no remanent polarization was confirmed in the BLSFs with an even number of m.

Irie, Hiroshi; Miyayama, Masaru; Kudo, Tetsuichi

2001-10-01

6

Nucleation kinetics and growth aspects of glycine phosphite ferroelectric single crystals  

Microsoft Academic Search

The nucleation parameters of glycine phosphite (GPI) ferroelectric single crystal were estimated in an aqueous solution using the classical homogeneous nucleation theory. The solubility, metastable zonewidth and induction period were determined experimentally by employing gravimetric, polythermal and isothermal method respectively. The interfacial energy was determined using the induction period values and the same was used for the further evaluation of

R. Perumal; S. Moorthy Babu

2011-01-01

7

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

PubMed

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

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

2013-12-01

8

Mechanical confinement for tuning ferroelectric response in PMN-PT single crystal  

NASA Astrophysics Data System (ADS)

Ferroelectrics form an important class of materials and are employed for a variety of applications. However, specific applications dictate the need of tailored ferroelectric response. This creates a requirement to obtain ferroelectric materials with tunable properties. Generally, chemical modifications or domain engineering are employed to this effect. This study attempts to shed light on the use of compressive pre-stresses for tuning and enhancing the ferroelectric properties. For the purpose, polarization versus electric field hysteresis data for 68Pb(Mn1/3Nb2/3)O3-32PbTiO3 (PMN-PT) single crystals were obtained as a function of uniaxial compressive stresses and operating temperatures. These data were utilized to investigate the effects of mechanical confinement for four individual case studies of electrocaloric effect, electrical energy storage, pyroelectric, and piezoelectric effect. A significant improvement was obtained for all case studies. The adiabatic temperature change was improved by ?80% (28 MPa, 353 K); energy storage density increased by a factor of five (28 MPa, 353 K); pyroelectric figure of merits improved by an order of magnitude (21 MPa) and the piezoelectric coefficient was tailored (variable stress). The results offer promising insight into the use of directional confinement for improving application specific ferroelectric properties in PMN-PT single crystal.

Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

2015-02-01

9

Strontium–barium niobate single crystals, growth and ferroelectric properties  

Microsoft Academic Search

Single crystals of strontium–barium niobate SrxBa1?xNb2O6 (SBN) undoped and doped with Ce or Cr were grown by the Czochralski method. The inductive heating system was used. In order to improve conditions of growth, a crucible-base cooling was introduced. Single crystals of the following nominal compositions have been obtained: Sr0.4Ba0.6Nb2O6, Sr0.5Ba0.5Nb2O6, Sr0.61Ba0.39Nb2O6 (congruent melting) and Sr0.75Ba0.25Nb2O6, designated hereafter as SBN40, SBN50,

T. Lukasiewicz; M. A. Swirkowicz; J. Dec; W. Hofman; W. Szyrski

2008-01-01

10

Pyroelectric, ferroelectric, dielectric and thermal properties of Mn 3B 7O 13Br single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of Mn 3B 7O 13Br (Mn?Br) boracite were studied between 300 and 550 K by means of thermal, dielectric, pyroelectric and ferroelectric characterization, under simultaneous visual control of the ferroelectric/ferroelastic domain state of the samples. We observe an unusual change of sign of the pyroelectric coefficient in Mn?Br at about 440 K which can be an indication of the existence of a new phase transition in this compound. A preliminary DSC study seems to confirm the presence of such a transition.

Campa-Molina, J.; Castellanos-Guzmán, A. G.; Bárcena-Soto, M.; Reyes-Gómez, J.

1994-03-01

11

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

PubMed

Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60%) near the morphotropic phase boundary (MPB). Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc) and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed. PMID:25076222

Chen, Yan; Lam, Kwok-Ho; Zhou, Dan; Yue, Qingwen; Yu, Yanxiong; Wu, Jinchuan; Qiu, Weibao; Sun, Lei; Zhang, Chao; Luo, Haosu; Chan, Helen L W; Dai, Jiyan

2014-01-01

12

Ferroelectric liquid crystal display  

NASA Technical Reports Server (NTRS)

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

York, Paul K. (Inventor)

1977-01-01

13

The effect of antinotches on domain wall mobility in single crystal ferroelectric nanowires.  

PubMed

Changes in domain wall mobility, caused by the presence of antinotches in single crystal BaTiO(3) nanowires, have been investigated. While antinotches appeared to cause a slight broadening in the distribution of switching events, observed as a function of applied electric field (inferred from capacitance-voltage measurements), the effect was often subtle. Greater clarity of information was obtained from Rayleigh analysis of the capacitance variation with ac field amplitude. Here the magnitude of the domain wall mobility parameter (alpha) associated with irreversible wall movements was found to be reduced by the presence of antinotches--an effect which became more noticeable on heating toward the Curie temperature. The reduction in this domain wall mobility was contrasted with the noticeable enhancement found previously in ferroelectric wires with notches. Finite element modeling of the electric field, developed in the nanowires during switching, revealed regions of increased and decreased local field at the center of the notch and antinotch structures, respectively; the absolute magnitude of field enhancement in the notch centers was considerably greater than the field reduction in the center of the antinotches and this was commensurate with the manner in, and degree to, which domain wall mobility appeared to be affected. We therefore conclude that the main mechanism by which morphology alters the irreversible component of the domain wall mobility in ferroelectric wire structures is via the manner in which morphological variations alter the spatial distribution of the electric field. PMID:20715806

McQuaid, R G P; Chang, L-W; Gregg, J M

2010-09-01

14

Elastic and Piezoelectric Properties of High-Quality Ferroelectric Bi4Ti3O12 Single Crystals  

NASA Astrophysics Data System (ADS)

Piezoelectric properties of ferroelectric Bi4Ti3O12 (BiT) single crystals have been investigated by a resonance-antiresonance method. Large and high-quality single crystals of BiT were obtained via top-seeded solution growth under a high oxygen pressure of 0.9 MPa. The elastic and piezoelectric constants in the (11), (12), (13), and (26) modes for BiT single crystals have been determined for the first time. It is shown that BiT has a large d26 constant of 79 pC/N and a large k26 factor of 40%, indicating that BiT is a promising ferroelectric material for application to shear-mode piezoelectric devices.

Kitanaka, Yuuki; Noguchi, Yuji; Miyayama, Masaru; Kagawa, Yutaka

2012-09-01

15

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

PubMed

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

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

2014-04-23

16

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

17

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

SciTech Connect

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

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

2014-08-04

18

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

NASA Astrophysics Data System (ADS)

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

Zhang, Lixue; Ren, Xiaobing

2006-03-01

19

Ferroelectric Liquid Crystal Conglomerates DAVID M. WALBA  

E-print Network

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

Walba, David

20

Switching ferroelectric domain configurations using both electric and magnetic fields in Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 single-crystal lamellae  

PubMed Central

Thin single-crystal lamellae cut from Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 ceramic samples have been integrated into simple coplanar capacitor devices. The influence of applied electric and magnetic fields on ferroelectric domain configurations has been mapped, using piezoresponse force microscopy. The extent to which magnetic fields alter the ferroelectric domains was found to be strongly history dependent: after switching had been induced by applying electric fields, the susceptibility of the domains to change under a magnetic field (the effective magnetoelectric coupling parameter) was large. Such large, magnetic field-induced changes resulted in a remanent domain state very similar to the remanent state induced by an electric field. Subsequent magnetic field reversal induced more modest ferroelectric switching. PMID:24421376

Evans, D. M.; Schilling, A.; Kumar, Ashok; Sanchez, D.; Ortega, N.; Katiyar, R. S.; Scott, J. F.; Gregg, J. M.

2014-01-01

21

Switching ferroelectric domain configurations using both electric and magnetic fields in Pb(Zr,Ti)O3-Pb(Fe,Ta)O3 single-crystal lamellae.  

PubMed

Thin single-crystal lamellae cut from Pb(Zr,Ti)O3-Pb(Fe,Ta)O3 ceramic samples have been integrated into simple coplanar capacitor devices. The influence of applied electric and magnetic fields on ferroelectric domain configurations has been mapped, using piezoresponse force microscopy. The extent to which magnetic fields alter the ferroelectric domains was found to be strongly history dependent: after switching had been induced by applying electric fields, the susceptibility of the domains to change under a magnetic field (the effective magnetoelectric coupling parameter) was large. Such large, magnetic field-induced changes resulted in a remanent domain state very similar to the remanent state induced by an electric field. Subsequent magnetic field reversal induced more modest ferroelectric switching. PMID:24421376

Evans, D M; Schilling, A; Kumar, Ashok; Sanchez, D; Ortega, N; Katiyar, R S; Scott, J F; Gregg, J M

2014-02-28

22

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

23

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

24

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

25

Ferroelectric, piezoelectric, and optical properties of SrTeO3 single crystals and phase-transition points in the solid-solution systems  

Microsoft Academic Search

Temperature dependences of dielectric, ferroelectric, elastic, piezoelectric, and optical properties of a new ferroelectric crystal, SrTeO3, have been measured. Ferroelectricity in this crystal is confined to the temperature range between 312 and 485°C. All the measured constants exhibit abrupt changes at 312°C, which shows the phase transition at this temperature to be of the first order. The electromechanical coupling factors

Tomoaki Yamada; Hiroshi Iwasaki

1973-01-01

26

Phase transitions and thermal-stress-induced structural changes in a ferroelectric Pb(Zr0.80Ti0.20)O3 single crystal.  

PubMed

A single crystal of lead-zirconate-titanate, composition Pb(Zr0.80Ti0.20)O3, was studied by polarized-Raman scattering as a function of temperature. Raman spectra reveal that the local structure deviates from the average structure in both ferroelectric and paraelectric phases. We show that the crystal possesses several, inequivalent complex domain boundaries which show no sign of instability even 200 K above the ferroelectric-to-paraelectric phase transition temperature TC. Two types of boundaries are addressed. The first boundary was formed between ferroelectric domains below TC. This boundary remained stable up to the highest measurement temperatures, and stabilized the domains so that they had the same orientation after repeated heating and cooling cycles. These domains transformed normally to the cubic paraelectric phase. Another type of boundary was formed at 673 K and exhibited no signs of instability up to 923 K. The boundary formation was reversible: it formed and vanished between 573 and 673 K during heating and cooling, respectively. A model in which the crystal is divided into thin slices with different Zr/Ti ratios is proposed. The physical mechanism behind the thermal-stress-induced structural changes is related to the different thermal expansion of the slices, which forces the domain to grow similarly after each heating and cooling cycle. The results are interesting for non-volatile memory development, as it implies that the original ferroelectric state can be restored after the material has been transformed to the paraelectric phase. It also suggests that a low-symmetry structure, stable up to high temperatures, can be prepared through controlled deposition of layers with desired compositions. PMID:25531118

Frantti, J; Fujioka, Y; Puretzky, A; Xie, Y; Ye, Z-G; Parish, C; Glazer, A M

2015-01-21

27

Phase transitions and thermal-stress-induced structural changes in a ferroelectric Pb(Zr0.80Ti0.20)O3 single crystal  

NASA Astrophysics Data System (ADS)

A single crystal of lead-zirconate-titanate, composition Pb(Zr0.80Ti0.20)O3, was studied by polarized-Raman scattering as a function of temperature. Raman spectra reveal that the local structure deviates from the average structure in both ferroelectric and paraelectric phases. We show that the crystal possesses several, inequivalent complex domain boundaries which show no sign of instability even 200 K above the ferroelectric-to-paraelectric phase transition temperature TC. Two types of boundaries are addressed. The first boundary was formed between ferroelectric domains below TC. This boundary remained stable up to the highest measurement temperatures, and stabilized the domains so that they had the same orientation after repeated heating and cooling cycles. These domains transformed normally to the cubic paraelectric phase. Another type of boundary was formed at 673 K and exhibited no signs of instability up to 923 K. The boundary formation was reversible: it formed and vanished between 573 and 673 K during heating and cooling, respectively. A model in which the crystal is divided into thin slices with different Zr/Ti ratios is proposed. The physical mechanism behind the thermal-stress-induced structural changes is related to the different thermal expansion of the slices, which forces the domain to grow similarly after each heating and cooling cycle. The results are interesting for non-volatile memory development, as it implies that the original ferroelectric state can be restored after the material has been transformed to the paraelectric phase. It also suggests that a low-symmetry structure, stable up to high temperatures, can be prepared through controlled deposition of layers with desired compositions.

Frantti, J.; Fujioka, Y.; Puretzky, A.; Xie, Y.; Ye, Z.-G.; Parish, C.; Glazer, A. M.

2015-01-01

28

Polymer-stabilized ferroelectric liquid crystals  

Microsoft Academic Search

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

Soonnam Lee; S. Suresh; Liang-Chy Chien

2002-01-01

29

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

SciTech Connect

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

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

2014-02-03

30

Structure and electrical properties of Na1/2Bi1/2TiO3-xK1/2Bi1/2TiO3 lead-free ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

Dielectric, ferroelectric and piezoelectric properties of lead-free Na1/2Bi1/2TiO3-xK1/2Bi1/2TiO3 (NBT-xKBT) ferroelectric single crystals were characterized systematically. With increasing KBT concentration, the remanent polarization and coercive electric field decrease, while the piezoelectric constant and the electromechanical coupling coefficient increase. The evolution of average and local structures as a function of temperature and composition was investigated using in-situ X-ray diffraction and Raman spectroscopy. The structure/property relationship of NBT-xKBT single crystals was discussed in detail.

Zhang, Haiwu; Chen, Chao; Zhao, Xiangyong; Deng, Hao; Ren, Bo; Li, Xiaobing; Luo, Haosu; Li, Shundao

2015-01-01

31

Growth and characterization of lead-free ferroelectric (K,Na,Li)(Nb,Ta,Sb)O3 single crystal  

NASA Astrophysics Data System (ADS)

In this work, a large size lead-free piezoelectric single crystal, (K,Na,Li)(Nb,Ta,Sb)O3 (KNLNTS) with the dimensions of 8.5×8.5×13.5 mm3 was successfully grown by the top-seeded solution growth method. This KNLNTS single crystal with high compositional homogeneity is in the tetragonal phase at room temperature. The Curie temperature TC of the tetragonal-cubic phase transition temperature is 210 °C. The piezoelectric coefficients and electromechanical coupling factors of the [001]C oriented KNLNTS single crystal are d33=172.55 pC/N, d31=-71.90 pC/N, k31=0.327, k33=0.523, and kt=0.541. In addition, the crystal shows good thermal stability so that it can be used for making high temperature electromechanical devices.

Wang, Junjun; Zheng, Limei; Yang, Bin; Wang, Rui; Huo, Xiaoqing; Sang, Shijing; Wu, Jie; Chang, Yunfei; Ning, Huanpo; Lv, Tianquan; Cao, Wenwu

2015-01-01

32

Ferroelectric liquid crystal waveguide modulators  

NASA Astrophysics Data System (ADS)

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

Walker, David Brian

33

Electrically modulated photoluminescence in ferroelectric liquid crystal  

E-print Network

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

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

2012-12-28

34

Synchrotron radiation analyses of domain switching behaviors for ferroelectric BaTiO3 single crystals under electric fields  

NASA Astrophysics Data System (ADS)

The domain structures and their dynamics of BaTiO3 single crystals under in-situ electric fields along the <101> direction were investigated by using synchrotron radiation single-crystal X-ray diffractions. Diffraction patterns clearly show the presence of a 90° domain structure in <101>-poled crystals. The linear characteristics of the strain and the polarization with respect to unipolar electric fields along the <101> direction suggest that the 90° domain structures established by poling treatments are not changed by applying electric fields. The diffraction analysis, however, provides direct evidence for a reversible change in the volume fractions of two kinds of 90° domains under unipolar in-situ electric fields.

Ishikawa, Shotaro; Kitanaka, Yuuki; Oguchi, Takeshi; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

2013-04-01

35

Numerical Calculation of SAW Propagation Properties at the x-Cut of Ferroelectric PMN-33%PT Single Crystals  

E-print Network

, such as medical imag- ing transducers, ultrasonic transducers, piezoelectric actuators, etc.[18-20] Relaxor is a kind of material with a low phase velocity and high electrome- chanical coupling coefficient, and the single crystal possesses some cuts with zero power flow angle. The results are based on the material

Cao, Wenwu

36

Electronic ferroelectricity in molecular organic crystals  

NASA Astrophysics Data System (ADS)

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

Ishihara, Sumio

2014-12-01

37

Spontaneous Ferroelectric Order in a Bent-Core Smectic Liquid Crystal of Fluid Orthorhombic Layers  

SciTech Connect

Macroscopic polarization density, characteristic of ferroelectric phases, is stabilized by dipolar intermolecular interactions. These are weakened as materials become more fluid and of higher symmetry, limiting ferroelectricity to crystals and to smectic liquid crystal stackings of fluid layers. We report the SmAP{sub F}, the smectic of fluid polar orthorhombic layers that order into a three-dimensional ferroelectric state, the highest-symmetry layered ferroelectric possible and the highest-symmetry ferroelectric material found to date. Its bent-core molecular design employs a single flexible tail that stabilizes layers with untilted molecules and in-plane polar ordering, evident in monolayer-thick freely suspended films. Electro-optic response reveals the three-dimensional orthorhombic ferroelectric structure, stabilized by silane molecular terminations that promote parallel alignment of the molecular dipoles in adjacent layers.

R Reddy; C Zhu; R Shao; E Korblova; T Gong; Y Shen; M Glaser; J Maclennan; D Walba; N Clark

2011-12-31

38

Effect of doping with Nd{sup 3+} ions on the structural and ferroelectric properties of Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} single crystal  

SciTech Connect

The crystal structure of Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} (CBN-28) crystal with Nd-doping has been determined from X-ray single crystal diffraction data, in the tetragonal system with space group P4bm and the following parameters: a = b = 12.458 A, c = 3.954 A, V = 613.688 A{sup 3}, and Z = 5. X-ray diffraction results on a Nd-doped CBN-28 single crystal also have demonstrated that Nd{sup 3+} and Ca{sup 2+} occupy the same site in the crystal structure. Dielectric and ferroelectric measurements have been performed. Transition from ferroelectric to paraelectric at around 223 {sup o}C has been observed. The Nd-doped crystal has a lower Curie temperature (T{sub m}) than that of undoped CBN-28 crystal. The spontaneous polarization (P{sub s}) and coercive electric field (E{sub c}) also decrease compared with their values in the undoped CBN-28 crystal.

Gao, W.L. [State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, 27 South Shanda Road, Jinan, Shandong 250100 (China)] [State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, 27 South Shanda Road, Jinan, Shandong 250100 (China); Zhang, H.J., E-mail: huaijinzhang@sdu.edu.cn [State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, 27 South Shanda Road, Jinan, Shandong 250100 (China); Xia, S.Q.; Huang, B.B.; Liu, D.; Wang, J.Y.; Jiang, M.H. [State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, 27 South Shanda Road, Jinan, Shandong 250100 (China)] [State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, 27 South Shanda Road, Jinan, Shandong 250100 (China); Zheng, L.M.; Wang, J.F. [School of Physics, Shandong University, Jinan 250100 (China)] [School of Physics, Shandong University, Jinan 250100 (China); Lu, C.J. [Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)] [Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)

2010-09-15

39

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

40

Piezoelectric activity in Perovskite ferroelectric crystals.  

PubMed

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

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

2015-01-01

41

Diisopropylammonium bromide is a high-temperature molecular ferroelectric crystal.  

PubMed

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

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

2013-01-25

42

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

43

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

44

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

45

Hysteresis effects in x-irradiated KH2PO4, KD2PO4, and RbH2PO4 ferroelectric single crystals observed with electron-spin resonance  

NASA Astrophysics Data System (ADS)

Hysteresis curves were plotted from the ESR spectra of selected x-irradiated potassium dihydrogen phosphate (KDP) type ferroelectric single crystals. The data for the loops were obtained by measuring the difference in intensity of appropriate lines in the ESR spectra of the radicals formed by x irradiation in KH2PO4, KD2PO4, and RbH2PO4. Coercive field values at 90 K varied from 8 to kV/cm. These results are compared to coercive field values reported by other workers for x-irradiated KH2PO4 doped with selenium and arsenic ions.

Truesdale, Roger D.; Farach, Horacio A.; Poole, Charles P., Jr.

1980-07-01

46

Deformed helix ferroelectric liquid crystal display: A new electrooptic mode in ferroelectric chiral smectic C liquid crystals  

Microsoft Academic Search

A new electrooptic mode of operation of ferroelectric chiral smectic C liquid crystal displays (LCDs) is proposed and demonstrated. The effect, which is called the deformed helical ferroelectric (DHF) effect, is based on the deformation of the helical structure by weak electric fields. In the unbiased device the smectic layers are arranged in the bookshelf geometry with the helix axis

L. A. Beresnev; V. G. Chigrinov; D. I. Dergachev; E. P. Poshidaev; J. Fünfschilling; M. Schadt

1989-01-01

47

Response Time of Polymer-Stabilized Ferroelectric Liquid Crystals  

Microsoft Academic Search

Polymer-stabilized ferroelectric liquid crystals (PSFLCs), in which a photocurable mesogenic monomer is doped into a ferroelectric liquid crystal and a UV photocure is carried out in the SmC* phase under the application of a bipolar AC electric field, show the monostable V-shaped electrooptical characteristics. In this research, we investigate the dependence of the molecular reorientational motion on the photocuring condition

Hiroki Tsuda; Nobuaki Waki; Hirokazu Furue

2008-01-01

48

Polymer-Stabilized Ferroelectric Liquid Crystals Photocured at Nematic Phase  

Microsoft Academic Search

Polymer-stabilized ferroelectric liquid crystals (PSFLCs), in which a photocurable mesogenic monomer is doped into a ferroelectric liquid crystal and a UV photocure is carried out in the SmA or the SmC* phase under the application of a bipolar AC electric field, show the monostable and V-shaped electrooptical characteristics, and thus are expected to be a newly developed materials for LC

Hideo Takahashi; Akihito Yokote; Hirokazu Furue

2009-01-01

49

Dynamic amplification of light signals in photorefractive ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

The photorefractive effect in ferroelectric liquid crystalline mixtures containing photoconductive chiral compounds was investigated. Ter-thiophene compounds with chiral structures were chosen as the photoconductive chiral compounds, and they were mixed with an achiral smectic C liquid crystal. The mixtures exhibit the ferroelectric chiral smectic C phase. The photorefractivity of the mixtures was investigated by two-beam coupling experiments. It was found that the ferroelectric liquid crystals containing the photoconductive chiral compound exhibit a large gain coefficient of over 1200 cm-1 and a fast response time of 1 ms. Real-time dynamic amplification of an optical image signal of over 30 fps using the photorefractive ferroelectric liquid crystal was demonstrated.

Sasaki, Takeo; Naka, Yumiko

2014-10-01

50

Are hydrogen-bonded charge transfer crystals room temperature ferroelectrics?  

PubMed

We present a theoretical investigation of the anomalous ferroelectricity of mixed-stack charge transfer molecular crystals, based on the Peierls-Hubbard model, and first-principles calculations for its parametrization. This approach is first validated by reproducing the temperature-induced transition and the electronic polarization of TTF-CA, and then applied to a novel series of hydrogen-bonded crystals, for which room temperature ferroelectricity has recently been claimed. Our analysis shows that the hydrogen-bonded systems present a very low degree of charge transfer and hence support a very small polarization. A critical reexamination of experimental data supports our findings, shedding doubts on the ferroelectricity of these systems. More generally, our modeling allows the rationalization of general features of the ferroelectric transition in charge transfer crystals and suggests design principles for materials optimization. PMID:25526158

D'Avino, Gabriele; Verstraete, Matthieu J

2014-12-01

51

Are Hydrogen-Bonded Charge Transfer Crystals Room Temperature Ferroelectrics?  

NASA Astrophysics Data System (ADS)

We present a theoretical investigation of the anomalous ferroelectricity of mixed-stack charge transfer molecular crystals, based on the Peierls-Hubbard model, and first-principles calculations for its parametrization. This approach is first validated by reproducing the temperature-induced transition and the electronic polarization of TTF-CA, and then applied to a novel series of hydrogen-bonded crystals, for which room temperature ferroelectricity has recently been claimed. Our analysis shows that the hydrogen-bonded systems present a very low degree of charge transfer and hence support a very small polarization. A critical reexamination of experimental data supports our findings, shedding doubts on the ferroelectricity of these systems. More generally, our modeling allows the rationalization of general features of the ferroelectric transition in charge transfer crystals and suggests design principles for materials optimization.

D'Avino, Gabriele; Verstraete, Matthieu J.

2014-12-01

52

Study of ferroelectric-paraelectric phase transition of RbH2AsO4 single crystals by 87Rb NMR relaxation time measurements  

NASA Astrophysics Data System (ADS)

The temperature dependences of the resonance frequency, line width, and spin-lattice relaxation time T1 of the ferroelectric and paraelectric phases of RbH2AsO4 crystals are investigated. The 87Rb NMR line at the phase transition temperature TC (=110 K) splits into two lines, which indicates the occurrence of phase transition from tetragonal to orthorhombic phase. In addition, T1 for the 87Rb nucleus undergoes remarkable changes near TC, which indicates drastic alterations of the spin dynamics at TC. At TC, changes occur in the resonance frequency and T1, which are related to variations in the symmetry of the environments of the 87Rb ions.

Lim, Ae Ran; Kim, Changsoo; Lee, SangGap; Lee, Kwang-Sei

2014-01-01

53

Spontaneous magnetization and magnetic susceptibility of a ferroelectric/ferromagnetic/ferroelastic single domain crystal of nickel bromine boracite Ni 3B 7O 13Br  

NASA Astrophysics Data System (ADS)

Using a SQUID magnetometer, the magnetic field-induced magnetization has been measured on a ferroelastically `poled' orthorhombic ferroelectric/ferroelastic single domain of Ni 3B 7O 13Br. Measurements were performed along the three principal orthorhombic crystallographic axis directions at 0.5, 1.0, 3.0, and 5.0 kOe in the range 4-40 K, and at 10 kOe in the range 4-300 K. The corresponding magnetic susceptibilities have been derived. The sequence of magnetic phases at low temperature, their magnetic point groups and transition temperatures Tc1=30 K and Tc2=21 K have been confirmed: mm21'? Tc1?m'm2'? Tc2?1. In the weakly ferromagnetic/ferroelectric/ferroelastic orthorhombic phase with Shubnikov-Heesch point group m'm2' in the range 21 K< T<30 K, the spontaneous magnetization vector Ms lies along the orthorhombic b0-axis, with a value of Ms=0.71 emu/g at 25 K. In the triclinic phase with point group 1, below Tc2=21 K, Ms assumes a temperature-dependent crystallographic general direction lying nearly in the pseudo-orthorhombic (0 0 1) 0-plane, for example at 5 K with a value of Ms=(2.7 a0+1.76 b0+0.34 c0) emu/g.

Mao, Shao-Yu; Schmid, Hans; Triscone, Gilles; Muller, Jean

1999-04-01

54

Ferroelectricity in antiferroelectric NaNbO3 crystal.  

PubMed

Sodium niobate (NaNbO3, or NNO) is known to be antiferroelectric at temperatures between 45 and 753 K. Here we show experimentally the presence of the ferroelectric phase at temperatures between 100 and 830 K in the NNO crystals obtained by top-seeded solution growth. The ferroelectric phase and new phase transitions are evidenced using a combination of thermo-optical studies by variable angle spectroscopic ellipsometry, Raman spectroscopy analysis, and photoelectron emission microscopy. The possibility for strain-induced ferroelectricity in NNO is suggested. PMID:24594846

Tyunina, M; Dejneka, A; Rytz, D; Gregora, I; Borodavka, F; Vondracek, M; Honolka, J

2014-03-26

55

Strongly nonlinear dynamics of ferroelectric liquid crystals.  

PubMed

Molecular reorientation processes induced in thin ferroelectric liquid crystal systems by strong alternating external electric fields are studied both by solving numerically the equation of reorientation motion of molecules and by measuring the electro-optic response of thin samples. It is shown that the occurrence of a wide band in nonlinear response spectra above the Goldstone-mode frequency is a consequence of complex partially uncorrelated molecular reorientations enforced within smectic layers by sufficiently high fields of high enough frequencies. Such nonlinear reorientational motions of molecules are argued to have a character of weakly chaotic long-lasting transients, related to almost periodic modulations of the amplitude of rotational oscillations performed by molecules with the field frequency. These modulations have been numerically proved to proceed with lower frequencies than the field frequency and with space-dependent depths of temporal changes. The occurrence of the modulations has experimentally been confirmed by registering distinct contributions to electro-optic response spectra at frequencies less than the running frequency of the applied electric field. PMID:23306447

Je?ewski, W; Sliwa, I; Kuczy?ski, W

2013-01-01

56

Growth and characterization of ferroelectric SrBi 2 Ta 2 O 9 single crystals via high-temperature self-flux solution method  

Microsoft Academic Search

SrBi2Ta2O9 (SBT) single crystals were produced by the high-temperature self-flux solution method using a Bi2O3 flux modified with B2O3. The processing conditions were optimized to obtain large and translucent SBT crystals with a layered habit and typical dimensions\\u000a of approximately 7 5 0.2 mm. X-ray diffraction and x-ray topography measurements revealed that the major faces of the\\u000a crystals with natural

H. Amorín; I. K. Bdikin; A. L. Kholkin; M. E. V. Costa

2006-01-01

57

ORIGINAL ARTICLE Single ferroelectric-domain photovoltaic switch based  

E-print Network

ORIGINAL ARTICLE Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells Ji general implications for the design rules of ferroelectric photovoltaic cells, which can be tuned serves as a basis for solid-state memory. This phenomenon can also yield an interesting photovoltaic

Jo, Moon-Ho

58

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

59

NONLINEAR OPTICS: Ferroelectric phase transitions and properties of nonlinear optical crystals of KTiOPO4 and its analogs  

NASA Astrophysics Data System (ADS)

Single crystals of new efficient nonlinear optical compounds KTiOPO4 (KTP), RbTiOPO4 (RTP), and TlTiOPO4 (TTP) were grown from molten solutions and some characteristics of their physical properties were investigated. The temperature dependences of the intensity of the second harmonic of laser radiation generated in these crystals and of their permittivities revealed a second-order ferroelectric phase transition at temperatures 934 °C (KTP), 789 °C (RTP), and 581 °C (TTP). Moreover, these crystals exhibited an anomalously high ionic electrical conductivity. The ferroelectricity and the conductivity could affect significantly nonlinear optical characteristics of these crystals.

Voronkova, V. I.; Stefanovich, S. Yu; Yanovski?, V. K.

1988-04-01

60

Ferroelectric Liquid Crystals For Second Order Nonlinear Optics  

Microsoft Academic Search

Main-chain ferroelectric liquid crystal polymers (FLCPs) and oligomers are of interest as precursors to free standing glassy fibers with the FLCP static structure. In particular, a supermolecular structure where the polar axis is oriented normal to the fiber axis may be of utility for frequency mixing applications. We report herein the synthesis of just such a main- chain FLCP wherein

David M. Walba; Lei Xiao; Patrick Keller; Renfan Shao; Darren Link; Noel A. Clark

1999-01-01

61

Influence of chirality on phase transitions in ferroelectric liquid crystals  

Microsoft Academic Search

The transition temperatures between various smectic liquid crystal phases are determined as a function of the enantiomeric excess for three different chiralracemic systems (i.e. binary mixtures consisting of a chiral enantiomer and its racemate). It is shown that transitions involving a ferroelectric phase occur in the chiral compounds at higher temperatures compared to their racemates, the temperature shift being proportional

Ch. Bahr; G. Heppke; B. Sabaschus

1991-01-01

62

Electric-field-controlled interface strain coupling and non-volatile resistance switching of La1-xBaxMnO3 thin films epitaxially grown on relaxor-based ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

We have fabricated magnetoelectric heterostructures by growing ferromagnetic La1-xBaxMnO3 (x = 0.2, 0.4) thin films on (001)-, (110)-, and (111)-oriented 0.31Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb1/2)O3-0.34PbTiO3 (PINT) ferroelectric single-crystal substrates. Upon poling along the [001], [110], or [111] crystal direction, the electric-field-induced non-180° domain switching gives rise to a decrease in the resistance and an enhancement of the metal-to-insulator transition temperature TC of the films. By taking advantage of the 180° ferroelectric domain switching, we identify that such changes in the resistance and TC are caused by domain switching-induced strain but not domain switching-induced accumulation or depletion of charge carriers at the interface. Further, we found that the domain switching-induced strain effects can be efficiently controlled by a magnetic field, mediated by the electronic phase separation. Moreover, we determined the evolution of the strength of the electronic phase separation against temperature and magnetic field by recording the strain-tunability of the resistance [(?R/R)strain] under magnetic fields. Additionally, opposing effects of domain switching-induced strain on ferromagnetism above and below 197 K for the La0.8Ba0.2MnO3 film and 150 K for the La0.6Ba0.4MnO3 film, respectively, were observed and explained by the magnetoelastic effect through adjusting the magnetic anisotropy. Finally, using the reversible ferroelastic domain switching of the PINT, we realized non-volatile resistance switching of the films at room temperature, implying potential applications of the magnetoelectric heterostructure in non-volatile memory devices.

Zheng, Ming; Zhu, Qiu-Xiang; Li, Xue-Yan; Yang, Ming-Min; Wang, Yu; Li, Xiao-Min; Shi, Xun; Luo, Hao-Su; Zheng, Ren-Kui

2014-09-01

63

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

SciTech Connect

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 [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India) [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India); Department of Physics, Gauhati University, Guwahati 781014, Assam (India); Boruah, Bosanta R., E-mail: brboruah@iitg.ernet.in [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India)

2014-04-15

64

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

65

Nanodomain engineering in RbTiOPO4 ferroelectric crystals  

Microsoft Academic Search

A high voltage atomic force microscope has been applied for tailoring strip-like nanodomains in RbTiOPO4 ferroelectric crystal. Highly anisotropic nanodomain propagation has been observed owing to the difference in lattice constants along the principal axes of the RbTiOPO4 crystal. Studying the influence of the applied high voltage, and tip velocity on the domain strips has allowed us to fabricate fine

G. Rosenman; P. Urenski; A. Agronin; A. Arie; Y. Rosenwaks

2003-01-01

66

Visualization of ferroelectric domains in a hydrogen-bonded molecular crystal using emission of terahertz radiation  

SciTech Connect

Using a terahertz-radiation imaging, visualizations of ferroelectric domains were made in a room-temperature organic ferroelectric, croconic acid. In as-grown crystals, observed are ferroelectric domains with sizes larger than 50-?m square, which are separated by both 180° and tail-to-tail domain walls (DWs). By applying an electric field along c axis (the polarization direction), a pair of 180° DWs is generated and an each 180° DW oppositely propagates along a axis, resulting in a single domain. By cyclic applications of electric fields, a pair of 180° DWs repeatedly emerges, while no tail-to-tail DWs appear. We discuss the usefulness of the terahertz-radiation imaging as well as the observed unique DW dynamics.

Sotome, M.; Kida, N., E-mail: kida@k.u-tokyo.ac.jp; Okamoto, H. [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwa-no-ha, Chiba 277-8561 (Japan); Horiuchi, S. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 102-0076 (Japan)

2014-07-28

67

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 P2? 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

68

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

69

Frederiks transition in ferroelectric liquid-crystal nanosuspensions  

NASA Astrophysics Data System (ADS)

We construct a theoretical model of the dielectric properties of a ferroelectric LC nanosuspension (FLCNS), using a generalized Maxwell-Garnett picture. The theory supposes that an FLCNS may as a first approximation be considered as a complex homogeneous dielectric ceramic, thus neglecting positional correlations of the colloidal particles. The FLCNS then consists of an anisotropic matrix with a very low concentration (<1% by volume) of impurity particles. The impurity particles possess both shape and dielectric anisotropy, as well as a permanent electric polarization and strong liquid-crystal director anchoring on the particle surface. We show that the effective dielectric properties for capacitance properties and for effective liquid-crystal free energies do not coincide. We calculate the effect of doping a liquid crystal with ferroelectric impurities on the Frederiks transition. The theory takes account of inclusion shape, dielectric susceptibility, and local field effects. We neglect the possibility of dielectric particle chaining, which appears experimentally not to occur in general. Our calculations suggest, in qualitative agreement with experiment, that doping a nematic liquid crystal with ferroelectric particles, even at very low particle concentration, can in some cases significantly decrease the electric Frederiks threshold field.

Shelestiuk, Sergii M.; Reshetnyak, Victor Yu.; Sluckin, Timothy J.

2011-04-01

70

Fatigue effect in ferroelectric crystals: Growth of the frozen domains  

NASA Astrophysics Data System (ADS)

The model of the fatigue effect during cyclic switching caused by growth of the frozen domain area with charged domain walls has been proposed. It was claimed on the basis of the previous experimental results that for switching in increasing field the frozen domain area started to grow at the given sub-threshold field value and stopped at the threshold field. The influence of the shape and frequency of the field pulses used for cyclic switching has been considered. The uniaxial ferroelectric stoichiometric lithium tantalate single crystals produced by vapor transport equilibration with record low value of coercive field have been chosen as a model material for experimental verification of the model. The formation of the charged domain walls as a result of cyclic switching has been revealed by analysis of the domain images obtained by optical and Raman confocal microscopy. It has been shown that the fatigue degree is equal to the fraction of the frozen domain area. The experimental dependence of the switched charge on the cycle number has been successfully fitted by modified Kolmogorov-Avrami formula. The experimentally observed frequency independence of fatigue profile for rectangular pulses and frequency dependence for triangular pulses has been explained by proposed model.

Shur, V. Ya.; Akhmatkhanov, A. R.; Baturin, I. S.

2012-06-01

71

Piezoelectric and flexoelectric effects in ferroelectric liquid crystals.  

PubMed

Flexoelectric and piezoelectric effects in ferroelectric liquid crystals (FLCs) have been studied. It is shown that nonlinear electromechanical coupling is determined by a local flexoelectric effect. Dependence of the parameters of nonlinearity of the flexoelectric effect on the parameter of phase transition from a paraelectric phase to a polar phase has been studied. Dependencies of flexoelectric and piezoelectric coefficients on the frequency of the mechanical vibrations have been studied. PMID:23030931

Popova, E V; Kopeychenko, E I; Krivoshey, A I; Vashchenko, V V; Fedoryako, A P

2012-09-01

72

Reorientational Motion of Polymer-Stabilized Ferroelectric Liquid Crystals  

Microsoft Academic Search

A polymer-stabilized ferroelectric liquid crystals (PSFLCs), in which photocurable mesogenic monomers are doped into an FLC and then a UV photocure is carried out in the SmC* phase under the application of a bipolar AC electric field, can exhibits monostable and V-shaped electrooptical characteristics. In this research, the time-resolved ellipsometry is applied to the PSFLCs, and we investigate the dependence

Hirokazu Furue; Hiroaki Tsuda; Kohei Yagihara

2009-01-01

73

Molecular Orientation Dynamics of Polymer-Stabilized Ferroelectric Liquid Crystals  

Microsoft Academic Search

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

Hirokazu Furue; Mizuho Gonda; Jun Hatano

2005-01-01

74

Dielectric spectroscopy of Polymer Stabilised Ferroelectric Liquid Crystals  

Microsoft Academic Search

Dielectric measurements were carried out in the frequency range from 20Hz to 500kHz on Polymer Stabilised Ferroelectric Liquid\\u000a Crystals (PSFLCs). Polymerisation in the Smectic A* (Sm A*) and the Smectic C* (Sm C*) phase at equal polymer concentration\\u000a results in a dielectric strength which is nearly twice the value in the latter case. An increase of the polymer concentration\\u000a results

S. Kaur; I. Dierking; H. F. Gleeson

2009-01-01

75

Photoinduced Alignment of Ferroelectric Liquid Crystals Using Azobenzene Polymer Networks of Chiral Polyacrylates and  

E-print Network

Photoinduced Alignment of Ferroelectric Liquid Crystals Using Azobenzene Polymer Networks of Chiral the alignment of FLC. Introduction Polymer-stabilized liquid crystals (PSLC) refer to low- molar-mass liquid ferroelectric liquid crystal (FLC) host. With two of the monomers, thermally induced radical polymerization

Zhao, Yue

76

High-speed infrared phase modulators using short helical pitch ferroelectric liquid crystals  

E-print Network

using a polymer- dispersed liquid crystal," Appl. Phys. Lett. 86, 141110 (2005). 3. S. T. Wu and D. KHigh-speed infrared phase modulators using short helical pitch ferroelectric liquid crystals Ju: A fast phase modulator based on ferroelectric liquid crystal (FLC) is demonstrated and its performances

Wu, Shin-Tson

77

Voltage-variable microwave delay line using ferroelectric liquid crystal with aligned submicron polymer fibers  

Microsoft Academic Search

This letter describes a variable microwave delay line that uses a thick ferroelectric liquid crystal film stabilized by aligned polymer fibers of submicron diameter. The delay line consists of a microstrip transmission line with a 50-mum-thick liquid crystal film as the dielectric material. The conical axis of the helical alignment of the ferroelectric liquid crystal molecules can be anchored in

Hideo Fujikake; Takao Kuki; Hirokazu Kamoda; Fumio Sato; Toshihiro Nomoto

2003-01-01

78

Measurement of the thermal expansion coefficients of ferroelectric crystals by a moire interferometer  

E-print Network

Measurement of the thermal expansion coefficients of ferroelectric crystals by a moire Flegrei 34, 80078 Pozzuoli (NA), Italy b LENS, European Laboratory for Non-linear Spectroscopy, Via Campi to measure the thermal expansion of two ferroelectric crystals, LiNbO3 and KTiOPO4. The crystal samples

Arie, Ady

79

Nanodomain engineering in RbTiOPO4 ferroelectric crystals G. Rosenman,a)  

E-print Network

Nanodomain engineering in RbTiOPO4 ferroelectric crystals G. Rosenman,a) P. Urenski, A. Agronin, A microscope has been applied for tailoring strip-like nanodomains in RbTiOPO4 ferroelectric crystal. Highly the principal axes of the RbTiOPO4 crystal. Studying the influence of the applied high voltage, and tip velocity

Arie, Ady

80

Characterization and polymerization behavior of polymer-stabilized ferroelectric liquid crystals  

Microsoft Academic Search

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

Clair Allan Guymon

1997-01-01

81

Nanodomain engineering in RbTiOPO4 ferroelectric crystals  

NASA Astrophysics Data System (ADS)

A high voltage atomic force microscope has been applied for tailoring strip-like nanodomains in RbTiOPO4 ferroelectric crystal. Highly anisotropic nanodomain propagation has been observed owing to the difference in lattice constants along the principal axes of the RbTiOPO4 crystal. Studying the influence of the applied high voltage, and tip velocity on the domain strips has allowed us to fabricate fine nanodomain gratings, which is useful for backward-propagating quasi-phase-matched frequency conversion.

Rosenman, G.; Urenski, P.; Agronin, A.; Arie, A.; Rosenwaks, Y.

2003-06-01

82

Photo-aligned ferroelectric liquid crystals in microchannels.  

PubMed

In this Letter we disclose a method to realize a good alignment of ferroelectric liquid crystals (FLCs) in microchannels, based on photo-alignment. The sulfonic azo dye used in our research offers variable anchoring energy depending on the irradiation energy and thus provides good control on the FLC alignment in microchannels. The good FLC alignment has been observed only when anchoring energy normalized to the capillary diameter is less than the elastic energy of the FLC helix. The same approach can also be used for the different microstructures viz. photonic crystal fibers, microwaveguides, etc. which gives an opportunity for designing a photonic devices based on FLC. PMID:25121847

Budaszewski, Daniel; Srivastava, Abhishek K; Tam, Alwin M W; Wolinski, Tomasz R; Chigrinov, Vladimir G; Kwok, Hoi-Sing

2014-08-15

83

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

84

Comments on the paper “Studies on growth and characterization of a novel nonlinear optical and ferroelectric material - N,N-dimethylurea picrate single crystal  

NASA Astrophysics Data System (ADS)

The authors of the title paper (J. Cryst. Growth 393 (2014) 7-12) report to have grown a novel organic nonlinear optical (NLO) crystal namely N,N-dimethylurea picrate (NNDMP) by the slow evaporation technique using dimethylformamide (DMF) as solvent. Many points of criticism, concerning the characterization of this so called NNDMP crystal, are highlighted in this comment to prove that NNDMP is not a novel NLO crystal.

Srinivasan, Bikshandarkoil R.; Naik, Suvidha G.; Dhavskar, Kiran

2015-01-01

85

Photoinduced Alignment of Ferroelectric Liquid Crystals Using Azobenzene Polymer Networks of Polyethers and Polyepoxides  

E-print Network

Photoinduced Alignment of Ferroelectric Liquid Crystals Using Azobenzene Polymer Networks moiety were synthesized and used to investigate the photoalignment of a ferroelectric liquid crystal (FLC or polyepoxide network for the commanding effect on the FLC alignment. Introduction In polymer-stabilized liquid

Zhao, Yue

86

Self-Restoration by Smectic Layer Structures of Monostable Ferroelectric Liquid Crystal in Flexible Devices  

Microsoft Academic Search

In this paper, we discuss a self-restoration phenomenon affecting smectic layer deformation and molecular alignment in monostable ferroelectric liquid crystals used for flexible displays. First, the mechanical stability of tilted `bookshelf' structures of smectic layers anchored on substrates using alignment layers was examined by precisely shearing two substrates. The microscopic texture of a monostable ferroelectric liquid crystal showed tolerance to

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

2004-01-01

87

Rigid Formation of Aligned Polymer Fiber Network in Ferroelectric Liquid Crystal  

Microsoft Academic Search

A rigid polymer fiber network for fastening two substrates and anchoring a ferroelectric liquid crystal alignment was formed, for the first time, by rapidly polymerizing aligned high-concentration acrylate monomers. The µm-size polymer fibers segregated from a nematic solution of the monomers and the ferroelectric liquid crystal under high temperature and strong ultraviolet light irradiation are oriented in the rubbing direction

Hideo Fujikake; Tahito Aida; Jun Yonai; Hiroshi Kikuchi; Masahiro Kawakita; Kuniharu Takizawa

1999-01-01

88

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

Microsoft Academic Search

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

Ji-Hoon Lee; Tong-Kun Lim

2005-01-01

89

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

2009-12-01

90

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

91

NONLINEAR OPTICS: Ferroelectric phase transitions and properties of nonlinear optical crystals of KTiOPO4 and its analogs  

Microsoft Academic Search

Single crystals of new efficient nonlinear optical compounds KTiOPO4 (KTP), RbTiOPO4 (RTP), and TlTiOPO4 (TTP) were grown from molten solutions and some characteristics of their physical properties were investigated. The temperature dependences of the intensity of the second harmonic of laser radiation generated in these crystals and of their permittivities revealed a second-order ferroelectric phase transition at temperatures 934 °C

V. I. Voronkova; S. Yu Stefanovich; V. K. Yanovskii

1988-01-01

92

Gyroid Single Crystal Diffraction  

NASA Astrophysics Data System (ADS)

A “single crystal” of a block copolymer / homopolymer blend with the Gyroid morphology was obtained by slow solvent casting. The block copolymer was an I2S2 star shaped block copolymer, which has two polystyrene arms and two polyisoprene arms connected at a single junction point. The homopolymer was low MW polyisoprene. The sample was studied by SAXS and TEM. SAXS of this sample produced single crystal diffraction patterns of several different zones with as many as 128 diffraction peaks in a single diffraction pattern, and 148 total unique diffraction peaks. Analysis of this data provides the most unambiguous proof to date of the Ia3d symmetry and Gyroid structure.

Yang, L.; Hong, S.; Gido, S. P.; Uhrig, D.; Mays, J. W.

2001-03-01

93

Triboelectric activation of ferroelectric liquid crystal memory devices  

NASA Astrophysics Data System (ADS)

The switching of ferroelectric liquid crystal (FLC) memory device is achieved by triboelectric effect of externally connected insulator to the sample through a conductor. The positive and negative charges are induced by triboelectrification of polymers, depending on the nature of materials, and utilized to get the bright and dark states of the FLC memory device. These switching states are analyzed by electro-optical studies. This technique of polarization switching proves to be powerful for FLC devices exhibiting long-term memory. The charges, developed on the electrodes by this nonconventional technique, generate enough potential to switch the FLC molecules in memory state.

Choudhary, A.; Joshi, T.; Biradar, A. M.

2010-09-01

94

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. PMID:21516190

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

95

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

PubMed

Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (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 (k(33)> 90%) and piezoelectric coefficients (d(33)~1500pC/N), when compared to their binary counterpart Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3). 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 d(33), 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. PMID:21516190

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

2011-03-01

96

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

97

Solvent-induced single-crystal-to-single-crystal transformation in multifunctional chiral dysprosium(III) compounds.  

PubMed

Two new enantiomeric ionic chiral dysprosium(III) compounds were designed and synthesized. These compounds show simultaneously the optical activity, ferroelectric effects, nonlinear-optical effects, and slow magnetic relaxation behavior. More interestingly, these compounds exhibit reversible single-crystal-to-single-crystal transformations associated with the release or absorption of solvent molecules. The structure transformations are accompanied by distinct changes in the physical properties. PMID:22862848

Liu, Jian; Zhang, Xiao-Peng; Wu, Tao; Ma, Bin-Bin; Wang, Tian-Wei; Li, Cheng-Hui; Li, Yi-Zhi; You, Xiao-Zeng

2012-08-20

98

Theory of nanoparticles doped in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

We developed a theory for the statistical mechanics of nanoparticles doped in ferroelectric liquid crystals (FLC). The presence of nanoparticles in FLC medium creates strong local fields that produce large alignment effects over the distribution of the nanosuspensions. Considering these local field effects, we presented a modified Landau free energy to calculate the electro-optic properties of the system. Then, we investigated the response of the nanoparticles doped FLC to an applied electric field. The variations in the polarization and the tilt angle show marked differences with the pure FLC medium. The rotational viscosity of the system is also calculated with its possible variation in temperature and applied field. Then, we conjectured on the possibility of shift in transition temperature, which is supposed to be induced by an electrostatic interaction between the nanoparticles and the liquid crystal molecules. Finally, strong experimental evidence is presented in favor of our results emerged from this theoretical model.

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

2013-02-01

99

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

100

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

101

Ferroelectric domains in KTiOPO4 and RbTiOPO4 crystals  

NASA Astrophysics Data System (ADS)

Ferroelectric domains in KTiOPO4 and RbTiOPO4 crystals are identified by using the methods of chemical etching and scanning electron microscopy. Both methods indicate, with a high degree of reliability, that some of the above crystals partition into 180-degree ferroelectric domains, although such partitioning is not generally characteristic of crystals of this group due to their high electrical conductivity. Details of the experimental procedures used are presented.

Voronkova, V. I.; Gvozdover, R. S.; Ianovskii, V. K.

1987-08-01

102

Ferroelectric domains in KTiOPO4 and RbTiOPO4 crystals  

Microsoft Academic Search

Ferroelectric domains in KTiOPO4 and RbTiOPO4 crystals are identified by using the methods of chemical etching and scanning electron microscopy. Both methods indicate, with a high degree of reliability, that some of the above crystals partition into 180-degree ferroelectric domains, although such partitioning is not generally characteristic of crystals of this group due to their high electrical conductivity. Details of

V. I. Voronkova; R. S. Gvozdover; V. K. Ianovskii

1987-01-01

103

Calorimetric investigation of the ferroelectric overline43m-mm2 phase transition in boracite crystals  

NASA Astrophysics Data System (ADS)

The isobaric molar heat capacity of Cr?Cl, Fe?I, Cu?Cl, Ni?Br and Zn?Br boracite at the ferroelectric overline43m-mm2 phase transition is reported. The magnitude of the rise in Cp at the transition, and the large upper bound values of ?H and ?S prove that the phase transition is first order. The values of ?H follow the trend Zn?Br ? Ni?Br > Cr?Cl ? Cu?Cl > Fe?I reflecting possible structural dissimilarities amongst the boracites. Thermal annealing of single crystal boracite samples of Ni?Br and Cr?Cl is found to remove multiple peaking of the heat capacity at the transition resulting in single peak heat capacity curves. The multiple peaking is thought to arise from internal stresses within the crystal.

Delfino, M.; Loiacono, G. M.; Smith, W. A.; Gentile, P. S.

1980-06-01

104

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

PubMed

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

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

2009-02-01

105

Stable ferroelectric liquid crystals derived from salicylaldimine-core.  

PubMed

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

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

2015-03-26

106

Arnold Schwarzenegger SINGLE CRYSTAL SILICON  

E-print Network

Arnold Schwarzenegger Governor SINGLE CRYSTAL SILICON SHEET GROWTH Prepared For: California Energy CRYSTAL SILICON SHEET GROWTH EISG AWARDEE ENERGY MATERIALS RESEARCH 132 Chalmers Drive Rochester Hills, MI

107

Ferroelectric phase transitions and the properties of nonlinear optical KTiOPO4 crystals and their analogs  

NASA Astrophysics Data System (ADS)

Solution-melt growth techniques were used to grow single crystals of the nonlinear optical compounds KTiOPO4 (KTP), RbTiOPO4 (RTP), and TlTiOPO4 (TTP), and several features of these compounds' physical properties are studied. Measurements of the temperature dependences of intensive SHG under laser exposure and of the permittivity show that these crystals undergo ferroelectric phase transitions of the second kind at temperatures of 934 C, 789 C, and 581 C for KTP, RTP and TTP, respectively. In addition, they display an anomalously high ionic conductance. The ferroelectric phase transition and high ionic conductance can both substantially affect the nonlinear optical characteristics of the crystals.

Voronkova, V. I.; Stefanovich, S. Iu.; Ianovskii, V. K.

1988-04-01

108

Electro-Optical Studies in a Ferroelectric Liquid Crystal Mixture  

NASA Astrophysics Data System (ADS)

Symmetric square and triangular wave pulses have been applied across planar cells of different thickness to a ferroelectric liquid crystal mixture in the SmC* phase. Dynamic processes of molecular reorientation associated with the helix unwinding and winding by applying bias (-10V -0V - +10V) and taking micrographs simultaneously have been studied. The spontaneous polarization (PS), response time (?R) and torsional viscosity (?) have been studied as a function of temperature, sample thickness and bias voltage. PS follows the relation PS = Po(Tc - T)?. ? obeys the Arrhenius relation from 35°C to 60°C with an activation energy of 0.89 eV for 5.0 ?m sample thickness. The surface switching in the thin cell is more dominant due to the strong surface pinning effect.

Singh, Rajbir; Raina, K. K.

2013-07-01

109

Anisotropic behavior of water in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

110

Soft memory in a ferroelectric nanoparticle-doped liquid crystal.  

PubMed

A small quantity of BaTiO(3) ferroelectric nanoparticles (FNP) was doped in a liquid crystal (LC), and the LC + FNP hybrid was found to exhibit a nonvolatile electromechanical memory effect in the isotropic phase. The permanent dipole moment of the FNPs causes the LC molecule to form short-range pseudonematic domains surrounding the FNPs. The FNP-induced short-range orders become more prominent in the isotropic phase when the global nematic order is absent. These short-range domains, being anisotropic in nature, interact with an external electric field, exhibiting a Fréedericksz-type transition. When the field is turned off, these domains stay oriented, showing a hysteresis effect due to the absence of any long-range order and restoring forces in the isotropic phase. The hysteresis graph for this memory effect shows a significant pretransitional behavior on approaching the nematic phase from the isotropic phase. PMID:25353490

Basu, Rajratan

2014-02-01

111

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

112

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

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

113

Enhanced ferroelectric properties and thermal stability of nonstoichiometric 0.92(Na{sub 0.5}Bi{sub 0.5})TiO{sub 3}-0.08(K{sub 0.5}Bi{sub 0.5})TiO{sub 3} single crystals  

SciTech Connect

Bi deficient, Mn doped 0.92(Na{sub 0.5}Bi{sub 0.5})TiO{sub 3}-0.08(K{sub 0.5}Bi{sub 0.5})TiO{sub 3} 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, E-mail: zhw3789@sina.com, E-mail: hsluo@mail.sic.ac.cn; Chen, Chao; Deng, Hao; Li, Long [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800 (China) [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, Xiangyong; Lin, Di; Li, Xiaobing; Ren, Bo; Luo, Haosu, E-mail: zhw3789@sina.com, E-mail: hsluo@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800 (China)] [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800 (China); Yan, Jun [Shibei Power Supply Branch, Shanghai Municipal Electric Power Company, Shanghai 200072 (China)] [Shibei Power Supply Branch, Shanghai Municipal Electric Power Company, Shanghai 200072 (China)

2013-11-18

114

Preliminary Study of Field Sequential Fullcolor Liquid Crystal Display using Polymer Stabilized Ferroelectric Liquid Crystal Display  

Microsoft Academic Search

Using a side-chain mesogenic polymer stabilized ferroelectric liquid crystal display (PS-FLCD) cell together with a two-dimensional array of red, green and blue light-emitting diodes (LEDs) as a modulated back light unit, we constructed a field sequential fullcolor (FSC) LCD. The PS-FLCD used in this research exhibits a high contrast ratio (230:1) with thresholdless monostability, grayscale capability, and a fast response

Taiju Takahashi; Hirokazu Furue; Masahiro Shikada; Noriyuki Matsuda; Tomohiro Miyama; Shunsuke Kobayashi

1999-01-01

115

Machining induced defects in Relaxor ferroelectric PMN-PT crystals  

Microsoft Academic Search

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

Cheng Deng

2010-01-01

116

A New Design of Optical Configuration of Transflective Liquid Crystal Displays using Antiferroelectric Liquid Crystals and Frustelectric Ferroelectric Liquid Crystals  

Microsoft Academic Search

We propose an optical configuration of transflective antiferroelectric liquid crystal (AFLC) and frustelectric ferroelectric liquid crystal (FR-FLC) display modes using a half-wave LC cell in which the in-plane tilt angle is 22.5°. It is composed of two polarizers, an AFLC or FR-FLC cell, two achromatic quarter-wave films, and a transflective film layer. In the case of using it in the

Won Sang Park; Sung-Chul Kim; Seo Hern Lee; Yong Suk Hwang; Gi-dong Lee; Tae-Hoon Yoon; Jae Chang Kim

2001-01-01

117

Design of a polarized head-mounted projection display using ferroelectric liquid-crystal-on-silicon  

E-print Network

have much higher optical efficiency than a transmissive-type liquid crystal display (LCD) and helpDesign of a polarized head-mounted projection display using ferroelectric liquid-crystal liquid-crystal-on-silicon (FLCOS) microdisplays. In addition to higher resolution, the FLCOS displays

Hua, Hong

118

Physical properties and alignment of a polymer-monomer ferroelectric liquid crystal mixture  

E-print Network

355 Physical properties and alignment of a polymer-monomer ferroelectric liquid crystal mixture D weight liquid crystals, normal to the rubbing direction at low polymer concentra- tions. The aligned with respect to their thermodynamic and physical properties. These polymer liquid crystals include mesogenic

Paris-Sud XI, Université de

119

Fundamental display properties of flexible devices containing polymer-stabilized ferroelectric liquid crystal between plastic substrates  

Microsoft Academic Search

We describe several fundamental display properties of a flexible ferroelectric liquid crystal device containing polymer fibers between thin plastic substrates. The composite film of liquid crystal and polymer was created from a solution of liquid crystal and monomer materials between the plastic substrates under ultraviolet light irradiation. The dynamic electrooptic response to analog voltage pulses was examined with an incidence

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

2002-01-01

120

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

121

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

122

Ultrafast polarization response of an optically trapped single ferroelectric nanowire.  

PubMed

One-dimensional potassium niobate nanowires are of interest as building blocks in integrated piezoelectric devices, exhibiting large nonlinear optical and piezoelectric responses. Here we present femtosecond measurements of light-induced polarization dynamics within an optically trapped ferroelectric nanowire, using the second-order nonlinear susceptibility as a real-time structural probe. Large amplitude, reversible modulations of the nonlinear susceptibility are observed within single nanowires at megahertz repetition rates, developing on few-picosecond time-scales, associated with anomalous coupling of light into the nanowire. PMID:25051318

Nah, Sanghee; Kuo, Yi-Hong; Chen, Frank; Park, Joonsuk; Sinclair, Robert; Lindenberg, Aaron M

2014-08-13

123

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

124

Polymer-stabilized ferroelectric liquid crystal for flexible displays using plastic substrates  

Microsoft Academic Search

We have developed a ferroelectric liquid crystal device with a novel structure containing a polymer fiber network for flexible lightweight displays using thin plastic substrates. The aligned polymer fibers of sub-micrometers -diameter were formed under ultraviolet light irradiation in a heated nematic- phase solution consisting of liquid crystal and monofunctional acrylate monomer. The rigid polymer network was found to adhere

Hideo Fujikake; Takeshi Murashige; Hiroto Sato; Yoshiki Iino; Hiroshi Kikuchi; Masahiro Kawakita; Yuzuru Tsuchiya

2001-01-01

125

The Influence of Alkyl Spacer on Helical Structure of Polymer-Stabilized Ferroelectric Liquid Crystals  

Microsoft Academic Search

Polymer stabilization is a technique for stabilizing a liquid crystal molecular orientation. The effect of polymer stabilization on the helical structure of FLCs can be analyzed by the observation of the conoscopic figures of polymer-stabilized ferroelectric liquid crystals (PSFLCs) obtained from the computer simulation and the experiment. In this study, we investigate the conoscopic figures of PSFLCs fabricated using a

Nozomi Higuchi; Kentaro Okazoe; Hirokazu Furue

2009-01-01

126

Unique single-domain state in a polycrystalline ferroelectric ceramic  

NASA Astrophysics Data System (ADS)

Non-180° ferroelectric domains are also ferroelastic domains; their existence in polycrystalline materials is to relieve internal stresses generated during solid-solid phase transitions and minimize the elastic distortion energy. Therefore, grains with random orientations in polycrystalline ceramics are always occupied by many domains, especially in the regions close to grain boundaries. In this Rapid Communication, we report the observation of a single-domain state in a BaTiO3-based polycrystalline ceramic at intermediate poling electric fields with in situ transmission electron microscopy. The grains in the virgin ceramic and under high poling fields are found multidomained. The unique single-domain state is believed to be responsible for the ultrahigh piezoelectric property observed in this lead-free composition and is suggested to be of orthorhombic symmetry for its exceptionally low elastic modulus.

Guo, Hanzheng; Zhou, Chao; Ren, Xiaobing; Tan, Xiaoli

2014-03-01

127

Guided Wave Propagation in a Gold Electrode Film on a Pb(Mg1/3Nb2/3)O3?33%PbTiO3 Ferroelectric Single Crystal Substrate  

NASA Astrophysics Data System (ADS)

Dispersion relations of Love mode acoustic guided waves propagation in Pb(Mg1/3Nb2/3)O3?33%PbTiO3 (PMN-0.33 PT) single crystal with a gold electrode film are calculated. There is no cross coupling among Love wave modes, which is conducive to eliminating the cross interference between modes. The general formula is derived to precisely measure the thickness of the electrode. More acoustic energy would be concentrated inside the electrode with the increase of film thickness for a given frequency. Compared with the PZT-5 ceramic, [001]c poled PMN-33%PT single crystal has a slower attenuation of the amplitude of the acoustic guided wave. Therefore, single crystal is extremely suitable for making low loss acoustic wave devices with a high operating frequency.

Huang, Nai-Xing; LÜ, Tian-Quan; Zhang, Rui; Wang, Yu-Ling; Cao, Wen-Wu

2014-10-01

128

Single-crystal barium titanate thin films by ion slicing T. Izuhara,a)  

E-print Network

Single-crystal barium titanate thin films by ion slicing T. Izuhara,a) I.-L. Gheorma, and R. M, D.C. 20052 Received 19 September 2002; accepted 3 December 2002 Thin barium titanate films, 0.5­8 m.1063/1.1540727 Barium titanate, BaTiO3 BTO , is a ferroelectric crystal whose outstanding electrical and optical

Reeves, Mark E.

129

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

130

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

PubMed

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. PMID:25353817

Bose, Tushar Kanti; Saha, Jayashree

2014-05-01

131

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

132

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

NASA Astrophysics Data System (ADS)

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

Feng, Zuyong; Ren, Xiaobing

2008-04-01

133

Ferroelectric crystals for the low-voltage operation of surface dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharges (DBD) are commonly used to generate surface plasmas in atmospheric conditions due to their broad operational scope. Yet, high input voltages are typically required to breakdown atmospheric air. Ferroelectric crystals, however, can be used in place of dielectrics in order to reduce the driving voltage required to generate a DBD. Ferroelectrics are unique in that they have spontaneous polarizations that can be reversed by an applied electric field and also typically have very large relative permittivities. By using a ferroelectric with a large permittivity and small coercive fields, the applied voltage required to generate a discharge was reduced to <600 V in atmospheric air, and a visible glow and current filaments consistent with polarization switching were observed. Analysis of the discharge showed that the onset voltage follows a power law relation with its capacitance. Furthermore, poling the ferroelectric with a large DC voltage before use also reduced the onset voltage of the discharge.

Johnson, Michael J.; Go, David B.

2014-12-01

134

Free-Standing Polymer-Stabilized Ferroelectric Liquid Crystal Film: Chemical Study of Phase Separation  

Microsoft Academic Search

This paper describes a chemical study of a new free-standing ferroelectric liquid crystal film containing a rigid fiber network polymer formed by photopolymerization-induced phase separation. The liquid crystal and acrylate polymer separated from a homogeneous solution were individually dissolved by different solvents, and examined by high-performance liquid chromatography and gel permeation chromatography, respectively. The liquid crystal component segregated from the

Hideo Fujikake; Jun Yonai; Hiroto Sato; Yuzuru Tsuchiya; Hiroshi Kikuchi; Yoshiki Iino; Masahiro Kawakita; Kuniharu Takizawa

2001-01-01

135

High-resolution display using a laser-addressed ferroelectric liquid-crystal light valve  

NASA Astrophysics Data System (ADS)

The laser-addressed ferroelectric liquid crystal light valve (FLCLV) consists of metal-insulator-semiconductor (MIS) photoconductive sensor and ferroelectric liquid crystal (FLC). It has a high resolving power of 50 1p/mm for laser pulse recording and 130 1p/mm for 2-dimensional image recording. The multibeam laser scanning method is applied in this display system, which achieves high writing speed (0.5 s/frame) and high resolution (1500 X 1600 pixels--higher than that of HDTV.

Nakajima, Hajime; Kisaki, Jyunko; Tahata, Shin; Horikawa, Tsuyoshi; Nishi, Kazuro

1991-08-01

136

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

NASA Astrophysics Data System (ADS)

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

Lee, Ji-Hoon; Lim, Tong-Kun

2005-08-01

137

Electric-field-induced spin flop in BiFeO3 single crystals at room temperature.  

PubMed

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 argue here that the coupling between the two orders may be stronger in the bulk than in thin films where the cycloid is absent. PMID:18643458

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

2008-06-01

138

Ferroelectric domain wall injection.  

PubMed

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

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

2014-01-15

139

Machining induced defects in Relaxor ferroelectric PMN-PT crystals  

NASA Astrophysics Data System (ADS)

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

Deng, Cheng

140

Photoreduction of SERS-active metallic nanostructures on chemically patterned ferroelectric crystals.  

PubMed

Photodeposition of metallic nanostructures onto ferroelectric surfaces is typically based on patterning local surface reactivity via electric field poling. Here, we demonstrate metal deposition onto substrates which have been chemically patterned via proton exchange (i.e., without polarization reversal). The chemical patterning provides the ability to tailor the electrostatic fields near the surface of lithium niobate crystals, and these engineered fields are used to fabricate metallic nanostructures. The effect of the proton exchange process on the piezoelectric and electrostatic properties of the surface is characterized using voltage-modulated atomic force microscopy techniques, which, combined with modeling of the electric fields at the surface of the crystal, reveal that the deposition occurs preferentially along the boundary between ferroelectric and proton-exchanged regions. The metallic nanostructures have been further functionalized with a target probe molecule, 4-aminothiophenol, from which surface-enhanced Raman scattering (SERS) signal is detected, demonstrating the suitability of chemically patterned ferroelectrics as SERS-active templates. PMID:22775541

Carville, N Craig; Manzo, Michele; Damm, Signe; Castiella, Marion; Collins, Liam; Denning, Denise; Weber, Stefan A L; Gallo, Katia; Rice, James H; Rodriguez, Brian J

2012-08-28

141

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

142

Main-Chain Ferroelectric Liquid Crystal Polymers for Electronic Nonlinear Optics Applications 1  

Microsoft Academic Search

We report the synthesis of organic polymer optical fibers with the following interesting supermolecular stereochemistry: 1) A thermodynamically stable macroscopic polar axis oriented approximately normal to the fiber axis; and 2) A nonlinear optical (NLO) chromophore oriented along the polar axis. Such a polymer fiber has been created using a main-chain ferroelectric liquid crystal polymer (FLCP) frozen in the glassy

David M. Walba; Lei Xiao; Eva Korblova; Patrick Keller; Richard Shoemaker; Michi Nakata; Renfan Shao; Darren R. Link; David A. Coleman; Noel A. Clark

2004-01-01

143

Thermal Shock Tolerance of Ferroelectric Liquid Crystal Stabilized by Aligned Polymer Fibers  

Microsoft Academic Search

In this paper, we report the marked enhancement of thermal shock tolerance of smectic layer structures of ferroelectric liquid crystal stabilized by aligned fine polymer fibers, which were formed by photopolymerization-induced phase separation. It was found that a smectic layer structure with such polymer fibers, which are aligned perpendicular to the smectic layer, generates no zigzag defects even after the

Hideo Fujikake; Takeshi Murashige; Hiroto Sato; Yoshihide Fujisaki; Masahiro Kawakita; Hiroshi Kikuchi; Taiichiro Kurita

2003-01-01

144

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

Microsoft Academic Search

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

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

2006-01-01

145

Flexible Display Technologies Using Ferroelectric Liquid Crystal: Low Driving-Voltage Panel Fabrication  

Microsoft Academic Search

We have reduced driving voltage of a flexible ferroelectric liquid crystal panel with polymer fibers and walls fastening two thin plastic substrates. The saturation voltage in the monostable V-shaped electrooptic property was decreased at several V, by dispersing fine sparse polymer fibers with small monomer concentration and by forming rigid polymer walls with strong ultraviolet light irradiation. The formation process

Hideo Fujikake; Hiroto Sato

2008-01-01

146

Electromechanical response to white noise excitation in a ferroelectric liquid crystal  

E-print Network

783 Electromechanical response to white noise excitation in a ferroelectric liquid crystal G. Por possible to use white noise excitation as an input signal. By measuring the time response of the system to the white noise, one can estimate the transfer function (by using for example Fast Fourier Transformation

Boyer, Edmond

147

The Effect of Polymer Doping on the Formation of Helical Structure in Ferroelectric Liquid Crystals  

Microsoft Academic Search

The effect of polymer stabilization on the helical structure of ferroelectric liquid crystal (FLC) and the deformation of the helical structure under the application of an electric field has not been cleared. In this study, conoscope observations for polymer-stabilized (PS) FLCs were performed, and we try to examine the polymer anchoring strength from the comparison between the experimental and the

Takayuki Inoue; Nozomi Higuchi; Hirokazu Furue

2008-01-01

148

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

149

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

150

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

151

Effects of graphene on electro-optic switching and spontaneous polarization of a ferroelectric liquid crystal  

SciTech Connect

A small quantity of graphene flakes was doped in a ferroelectric liquid crystal (FLC), and the field-induced ferroelectric electro-optic switching was found to be significantly faster in the FLC + graphene hybrid than that of the pure FLC. Further studies revealed that the suspended graphene flakes enhanced the FLC's spontaneous polarization by improving smectic-C ordering resulting from the ?–? electron stacking, and reduced rotation viscosity by trapping some of the free ions of the FLC media. These effects coherently impacted the FLC-switching phenomenon, enabling the FLC molecules to switch faster on reversing an external electric field.

Basu, Rajratan, E-mail: basu@usna.edu [Department of Physics, Soft-matter and Nanomaterials Laboratory, The United States Naval Academy, Annapolis, Maryland 21402 (United States)

2014-09-15

152

Structure and energetics of a ferroelectric organic crystal of phenazine and chloranilic acid  

NASA Astrophysics Data System (ADS)

We report first-principles calculations for a ferroelectric organic crystal of phenazine and chloranilic acid molecules. Weak intermolecular interactions are properly treated by using a second version of the van der Waals density functional known as vdW-DF2 [K. Lee , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.82.081101 82, 081101 (2010)]. Lattice constants, total energies, spontaneous electric polarizations, phonon modes and frequencies, and the energy barrier of proton transfer are calculated and compared with PBE and experiments whenever possible. We show that the donation of one proton from a chloranilic acid molecule to a neighboring phenazine molecule is energetically favorable. This proton transfer is the key structural change that breaks the centrosymmetry and leads to the ferroelectric structure. However, there is no unstable phonon associated with the proton transfer, and an energy barrier of 8 meV is found between the paraelectric and ferroelectric states.

Lee, Kyuho; Kolb, Brian; Thonhauser, T.; Vanderbilt, David; Langreth, David C.

2012-09-01

153

Polarization switching using single-walled carbon nanotubes grown on epitaxial ferroelectric thin films  

NASA Astrophysics Data System (ADS)

We have directly grown single-walled carbon nanotubes on epitaxial BaTiO3 thin films, fabricating prototype carbon nanotube-ferroelectric devices. We demonstrate polarization switching using the nanotube as a local electric field source and compare the results to switching with an atomic force microscopy tip. The observed variation of domain growth rates in the two cases agrees with the changes in electric field intensity at the ferroelectric surface.

Paruch, P.; Posadas, A.-B.; Dawber, M.; Ahn, C. H.; McEuen, P. L.

2008-09-01

154

Ultrasonic Atomic Force Microscopy of Domain Structure in Lead Magnesium Niobate-Lead Titanate Single Crystal Using a Surface Electrode Pair  

Microsoft Academic Search

In order to improve the ferroelectric properties of films for ferroelectric memories or relaxor single crystals for actuators, it is necessary to observe domain structures on the nanoscale. We propose an approach to observing three-dimensional (3D) domain structures by ultrasonic atomic force microscopy (UAFM) with a subsurface observation capability. Moreover, it is sometimes necessary to observe the motion of the

Seishiro Ide; Kentaro Kobari; Toshihiro Tsuji; Kazushi Yamanaka

2007-01-01

155

A multistep single-crystal-to-single-crystal bromodiacetylene dimerization.  

PubMed

Packing constraints and precise placement of functional groups are the reason that organic molecules in the crystalline state often display unusual physical or chemical properties not observed in solution. Here we report a single-crystal-to-single-crystal dimerization of a bromodiacetylene that involves unusually large atom displacements as well as the cleavage and formation of several bonds. Density functional theory computations support a mechanism in which the dimerization is initiated by a [2 + 1] photocycloaddition favoured by the nature of carbon-carbon short contacts in the crystal structure. The reaction proceeded up to the theoretical degree of conversion without loss of crystallinity, and it was also performed on a preparative scale with good yield. Moreover, it represents the first synthetic pathway to (E)-1,2-dibromo-1,2-diethynylethenes, which could serve as synthetic intermediates for the preparation of molecular carbon scaffolds. Our findings both extend the scope of single-crystal-to-single-crystal reactions and highlight their potential as a synthetic tool for complex transformations. PMID:23511422

Hoheisel, Tobias N; Schrettl, Stephen; Marty, Roman; Todorova, Tanya K; Corminboeuf, Clémence; Sienkiewicz, Andrzej; Scopelliti, Rosario; Schweizer, W Bernd; Frauenrath, Holger

2013-04-01

156

Effects of Nano-Particle Doping on the Physical Properties of Ferroelectric Liquid Crystals  

NASA Astrophysics Data System (ADS)

Ferroelectric liquid crystals (FLCs) are special class of lamellar crystal materials. They are used as optical materials in several display devices. The fast switching responses have made them best suited over conventional nematic and chiral nematic systems. Electro-optic studies have been carried out on silica nano-particles (SiO2) dispersed FLC mixture in planer aligned sample cells. The effect of temperature and bias field on the switching characteristics of FLC composites were studied and compared. These studies suggest high contrast over undoped system. Our results indicate that the doped FLC composites are promising materials for electro-optical and liquid crystal display (LCD) devices.

Neeraj, Neeraj; Raina, K. K.

2011-12-01

157

Growth and piezoelectric properties of ferroelectric Bi 2 WO 6 mono-domain crystals  

Microsoft Academic Search

A mono-domain crystal of Bismuth tungstate Bi2WO6, one of the bismuth layered structure ferroelectric (BLSF) compounds, is synthesized by a slow cooling method using lithium tetra-borate as the flux below the Curie temperature of 940 °C. Fifteen of seventeen independent tensor components of dielectric constant ?ij\\/?0, piezoelectric constant dij and elastic compliance sij are determined. The dielectric constants, ?ij\\/?0, were about

Hiroaki Takeda; Joong Sang Han; Masaya Nishida; Tadashi Shiosaki; Takuya Hoshina; Takaaki Tsurumi

2010-01-01

158

Enhanced orientational Kerr effect in vertically aligned deformed helix ferroelectric liquid crystals.  

PubMed

We disclose the vertically aligned deformed helix ferroelectric liquid crystal whose Kerr constant (Kkerr?130??nm/V2 at ?=543??nm) is around one order of magnitude higher than any other value previously reported for liquid crystalline structures. Under certain conditions, the phase modulation with ellipticity less than 0.05 over the range of continuous and hysteresis-free electric adjustment of the phase shift from zero to 2? has been obtained at subkilohertz frequency. PMID:24978232

Pozhidaev, Evgeny P; Srivastava, Abhishek Kumar; Kiselev, Alexei D; Chigrinov, Vladimir G; Vashchenko, Valery V; Krivoshey, Alexander I; Minchenko, Maxim V; Kwok, Hoi-Sing

2014-05-15

159

Electro-Optical Properties of Polymer-Stabilized Ferroelectric Liquid Crystal  

Microsoft Academic Search

We report electro-optical studies of polymer-stabilized ferroelectric liquid crystals (PSFLCs). PSFLCs are made by photopolymerizing 3% reactive mesogenic monomer using the quasi bookshelf texture of a FLC as a template. We observe the formation of nano-scaled polymer fibrils templated by the two dimensionally ordered host. The polymer fibrils capture the orientation of the host; locate between smectic layers with thinner

S. Suresh; L.-C. Chien

2003-01-01

160

Models of Molecular Alignment Structure in Polymer-Stabilized Ferroelectric Liquid Crystals  

Microsoft Academic Search

The electrooptical (EO) characteristics of polymer-stabilized ferroelectric liquid crystals (PSFLCs), which are fabricated by UV photocure of doped monoacrylates with mesogenic side chains at a temperature where the LC medium is in the SmC* phase under the simultaneous application of a bipolar square-pulsed AC electric field, depend on the polymer density. The PSFLC with low concentration of polymer exhibits a

Hirokazu Furue; Taiju Takahashi; Shunsuke Kobayashi; Hiroshi Yokoyama

2002-01-01

161

Electro-optic properties of thiol-ene polymer stabilized ferroelectric liquid crystals  

Microsoft Academic Search

Electro-optic properties of polymer stabilized ferroelectric liquid crystal (PSFLC) systems are examined as a function of varying concentrations of either a linear or crosslinked thiol-ene polymer. The thiol-ene method of polymer stabilization is a drastic change from previous studies designed to avert the problem of polymer phase separation. FLC rise time and tilt angle measurements were used to determine the

Eric R. Beckel; Neil B. Cramer; Adam W. Harant

2003-01-01

162

Molecular Reorientational Motion of a Polymer-Stabilized Ferroelectric Liquid Crystal  

Microsoft Academic Search

The polymer-stabilized ferroelectric liquid crystals (PS-FLC) exhibit monostable and asymmetric electrooptical characteristics with grayscale capability without a threshold. The reorientational motion of FLC molecules can be investigated in terms of two independent optical parameters: the phase difference angle and the angle of the relative amplitude ratio measured with time-resolved ellipsometry. In this study, the time-resolved ellipsometry is applied to the

Hirokazu Furue; Yoshiro Hiyama; Jun Hatano

2007-01-01

163

Effect of Polymer Stabilization on Molecular Reorientational Motion of Ferroelectric Liquid Crystals  

Microsoft Academic Search

The polymer-stabilized ferroelectric liquid crystals (PSFLC) exhibit monostable electrooptical characteristics having grayscale capability without a threshold. The reorientational motion of FLC molecules can be investigated in terms of two independent optical parameters: the phase difference angle and the angle of the relative amplitude ratio measured with time-resolved ellipsometry. In this study, the time-resolved ellipsometry is applied to the PSFLCs, and

Hirokazu Furue; Yoshiro Hiyama; Jun Hatano

2007-01-01

164

Measurement of Polymer Stabilization Strength in Polymer-Stabilized Ferroelectric Liquid Crystals  

Microsoft Academic Search

We have analyzed the effect of polymer stabilization on the helical structure of FLCs, such as polymer stabilization strength and molecular-alignment-structural deformation, by the conoscopic figures of polymer-stabilized ferroelectric liquid crystals (PSFLCs) observed from computer simulation and experiment. In this study, we research the conoscopic figures and the polymer stabilization strength of PSFLCs fabricated using a new FLC material and

Hirokazu Furue; Kentaro Okazoe; Masahiro Saito

2010-01-01

165

Crystal ball single event display  

SciTech Connect

The Single Event Display (SED) is a routine that is designed to provide information graphically about a triggered event within the Crystal Ball. The SED is written entirely in FORTRAN and uses the CERN-based HICZ graphing package. The primary display shows the amount of energy deposited in each of the NaI crystals on a Mercator-like projection of the crystals. Ten different shades and colors correspond to varying amounts of energy deposited within a crystal. Information about energy clusters is displayed on the crystal map by outlining in red the thirteen (or twelve) crystals contained within a cluster and assigning each cluster a number. Additional information about energy clusters is provided in a series of boxes containing useful data about the energy distribution among the crystals within the cluster. Other information shown on the event display include the event trigger type and data about {pi}{sup o}`s and {eta}`s formed from pairs of clusters as found by the analyzer. A description of the major features is given, along with some information on how to install the SED into the analyzer.

Grosnick, D.; Gibson, A. [Valparaiso Univ., IN (United States). Dept. of Physics and Astronomy; Allgower, C. [Argonne National Lab., IL (United States). High Energy Physics Div.; Alyea, J. [Valparaiso Univ., IN (United States). Dept. of Physics and Astronomy]|[Argonne National Lab., IL (United States). High Energy Physics Div.

1997-10-15

166

Memory effect in a ferroelectric single-electron transistor: Violation of conductance periodicity in the gate voltage  

NASA Astrophysics Data System (ADS)

A fundamental property of most single-electron devices with a quasicontinuous quasiparticle spectrum on an island is the periodicity of their transport characteristics in a gate voltage. This property is robust even with respect to placing ferroelectric insulators in the source and drain tunnel junctions. We show that placing a ferroelectric insulator inside the gate capacitance breaks this periodicity. The current-voltage characteristics of this single-electron transistor strongly depends on the ferroelectric polarization and shows a giant memory effect even for negligible ferroelectric hysteresis making this device promising for memory applications.

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

2014-11-01

167

Switching of ferroelectric liquid crystal doped with cetyltrimethylammonium bromide-assisted CdS nanostructures.  

PubMed

Large scale high yield cadmium sulfide (CdS) nanowires with uniform diameter were synthesized using a rapid and simple solvo-chemical and hydrothermal route assisted by the surfactant cetyltrimethylammonium bromide (CTAB). Unique CdS nanowires of different morphologies could be selectively produced by only varying the concentration of CTAB in the reaction system with cadmium acetate, sulfur powder and ethylenediamine. We obtained CdS nanowires with diameters of 64-65 nm and lengths of up to several micrometers. A comparative study of the optical properties of ferroelectric liquid crystal (FLC) Felix-017/100 doped with 1% of CdS nanowires was performed. Response times of the order of from 160 to 180 ?s, rotational viscosities of the order of from 5000 to 3000 mN s m(-2) and polarizations of the order of from 10 to 70 nC cm(-2) were measured. We also observed an anti-ferroelectric to ferroelectric transition for CdS doped FLC instead of the ferroelectric to paraelectric transition for pure FLC. PMID:23459239

Pal, Kaushik; Maiti, Uday Narayan; Majumder, Tapas Pal; Debnath, Subhas Chandra; Ghosh, Sharmistha; Roy, Subir Kumar; Otón, José Manuel

2013-03-29

168

Aging and memory effect in magnetoelectric gallium ferrite single crystals  

NASA Astrophysics Data System (ADS)

Here, we present a time and temperature dependent magnetization study to understand the spin dynamics in flux grown single crystals of gallium ferrite (GaFeO3), a known magnetoelectric, ferroelectric and ferrimagnet. Results of the magnetic measurements conducted in the field-cooled (FC) and zero-field-cooled (ZFC) protocols in the heating and cooling cycles were reminiscent of a "memory" effect. Subsequent time dependent magnetic relaxation measurements carried out in ZFC mode at 30 K with an intermittent cooling to 20 K in the presence of a small field show that the magnetization in the final wait period tends to follow its initial state which was present before the cooling break taken at 20 K. These observations provide an unambiguous evidence of single crystal gallium ferrite having a spin glass like phase.

Singh, Vijay; Mukherjee, Somdutta; Mitra, Chiranjib; Garg, Ashish; Gupta, Rajeev

2015-02-01

169

Thermal Shock Tolerance of Ferroelectric Liquid Crystal Stabilized by Aligned Polymer Fibers  

NASA Astrophysics Data System (ADS)

In this paper, we report the marked enhancement of thermal shock tolerance of smectic layer structures of ferroelectric liquid crystal stabilized by aligned fine polymer fibers, which were formed by photopolymerization-induced phase separation. It was found that a smectic layer structure with such polymer fibers, which are aligned perpendicular to the smectic layer, generates no zigzag defects even after the composite film is cooled to -15°C, which is lower than the chiral smectic C-to-crystal phase-transition temperature, or heated to 100°C, which is above the chiral nematic-to-isotropic phase-transition temperature.

Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Fujisaki, Yoshihide; Kawakita, Masahiro; Kikuchi, Hiroshi; Kurita, Taiichiro

2003-02-01

170

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

171

Speckle noise suppression using a helix-free ferroelectric liquid crystal cell  

NASA Astrophysics Data System (ADS)

We have studied the method for suppressing speckle noise in patterns produced by a laser based on a fast-response electro-optical cell with a ferroelectric liquid crystal (FLC) in which helicoid is absent, i.e., compensated for. The character of smectic layer deformation in an electric field is considered along with the mechanism of spatially inhomogeneous phase modulation of a laser beam passing through the cell which is accompanied by the destruction of phase relations in the beam. Advantages of a helix-free FLC cell are pointed out as compared to helical crystal cells studied previously.

Andreev, A. L.; Andreeva, T. B.; Kompanets, I. N.; Zalyapin, N. V.

2014-12-01

172

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

173

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=548K 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˜210pC/N and low dielectric constant have lead to a very large value of piezoelectric voltage constant g33˜53.9×10-3Vm/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

174

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

175

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

176

Relaxor-PT Single crystals: Observations and Developments  

PubMed Central

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

Zhang, Shujun; Shrout, Thomas R.

2011-01-01

177

Non linear dielectric spectroscopy: a method to determine physical parameters of ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

This paper concerns non linear dielectric spectroscopy in the SmC* phase of a ferroelectric liquid crystal. The experimental set-up and the procedure used to determine non linear permittivities are described. The results are discussed on the basis of the model proposed by Kimura et al. [Y. Kimura, S. Hara, R. Hayakawa, Phys. Rev. E 62, R5907 (2000); Y. Kimura, S. Hara, R. Hayakawa, Ferroelectrics 245, 61 (2000)]. A good agreement is obtained between the measurements and the theoretical predictions for ?*3,3 and ?*5,5 non linear permittivities. Some physical parameters of the material like the polarization, the rotational viscosity and the elastic term are determined. The polarization is found similar to this obtained with classical triangular wave method.

Leblond, J. M.; Douali, R.; Legrand, C.; Dabrowski, R.

2006-11-01

178

Photon tunnelling microscopy of polyethylene single crystals  

E-print Network

Photon tunnelling microscopy of polyethylene single crystals Mohan Srinivasarao* and Richard S:photon tunnellingmicroscopy;single crystals; polyethylene) INTRODUCTION The study of morphology of polymers is an area

Srinivasarao, Mohan

179

One-dimensional ferroelectric monodomain formation in single crystalline BaTiO3 nanowire  

NASA Astrophysics Data System (ADS)

The authors report the existence of one-dimensional and stable formation of ferroelectric monodomain in single crystalline BaTiO3 nanowire. Piezoresponse force microscopy operated in both vertical and lateral modes showed ferroelectric polarization switching along the axial (lateral) direction of nanowire, while the polarization along the transversal (vertical) direction was strongly suppressed. Such a one-dimensional polarization formation was also found to be highly stable and nonretentive in that switched polarization spontaneously returned to its original orientation at the instant of removing the applied poling voltage.

Wang, Zhaoyu; Hu, Jie; Yu, Min-Feng

2006-12-01

180

Nanoscale Calorimetry of Isolated Polyethylene Single Crystals  

E-print Network

Nanoscale Calorimetry of Isolated Polyethylene Single Crystals A. T. KWAN, M. YU. EFREMOV, E. A-film differential scanning calorimetry to investigate the melt- ing of isolated polyethylene single crystals of lamellar single crystals of polyethylene (PE). We obtain thickness, diffraction, and calorimetry data

Allen, Leslie H.

181

The phase transitions of ferroelectric Sr2Ta2O7 crystals by MDSC, Brillouin and dielectric spectroscopy  

NASA Astrophysics Data System (ADS)

The structural phase transitions of Sr2Ta2O7 single crystals have been studied by the modulated temperature differential scanning calorimetry (MDSC), Brillouin scattering and dielectric spectroscopy. The specific heat (Cp) was measured over a wide temperature range from -150°C to 25°C and from 100°C to 210°C. The Cp curve showed an anomaly at To = 166.7°C, indicating the phase transition Cmcm rarr P21/m. The transition enthalpy DgrH, the transition entropy DgrS and specific heat jump DgrCp at To were estimated to be 0.465 J g-1, 1.01 mJ g-1 K-1 and 9.78 mJ g-1 K-1, respectively. The Cp anomaly associated with the ferroelectric phase transition at Tc = -107°C has not been detected. However, both Brillouin and dielectric data showed the anomalies corresponding to the ferroelectric phase transition from P21/m to P21.

Hushur, A.; Shabbir, G.; Ko, J.-H.; Kojima, S.

2004-04-01

182

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

SciTech Connect

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

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

2014-01-01

183

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

184

Electrical Freedericksz transitions in nematic liquid crystals containing ferroelectric nanoparticles  

NASA Astrophysics Data System (ADS)

A new theoretical approach was elaborated to explain the contradictions reported in many papers about the electric threshold for Freedericksz transition in nematic liquid crystal (NLC) with ferroparticles additives. The free energy density of the mixture was estimated and the contributions of the interaction energy of NLC molecules with ferroparticles surface were calculated. Experimental results for 5CB-BaTiO3 mixture are given.

Cîrtoaje, Cristina; Petrescu, Emil; Stoian, Victor

2015-03-01

185

Programmable ZnO nanowire transistors using switchable polarization of ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

We demonstrate modulations of electrical conductance and hysteresis behavior in ZnO nanowire transistors via electrically polarized switching of ferroelectric liquid crystal (FLC). After coating a nanowire channel in the transistors with FLCs, we observed large increases in channel conductance and hysteresis width, and a strong dependence of hysteresis loops on the polarization states associated with the orientation of electric dipole moments along the direction of the gate electric field. Furthermore, the reversible switching and retention characteristics provide the feasibility of creating a hybrid system with switch and memory functions.

Hong, Woong-Ki; Inn Sohn, Jung; Cha, SeungNam; Min Kim, Jong; Park, Jong-Bae; Seok Choi, Su; Coles, Harry J.; Welland, Mark E.

2013-02-01

186

Topographic Confinement of a Ferroelectric Liquid Crystal for Highly Efficient Tunable Electrooptic Effect with Reduced Threshold  

NASA Astrophysics Data System (ADS)

We report a highly efficient linear electrooptic (EO) effect of a tight-pitch ferroelectric liquid crystal (FLC) in a microchannel architecture where the FLC molecules are vertically aligned on the surrounding surfaces. Due to the topographic confinement in a large surface-to-volume configuration, the competing anchoring forces exerted by the lateral walls and the substrates impose directly the restrictions on the deformations of the smectic layers and the molecular director. The observed EO effect should be directly applicable for diverse optical devices requiring fast response, high optical modulation, and high subthreshold slope at a reduced operation voltage.

Na, Jun-Hee; Kim, Jiyoon; Choi, Yoonseuk; Lee, Sin-Doo

2013-05-01

187

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

188

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

189

Crystal growth and structure-property relationships for ferroelectric strontium bismuth tantalate  

NASA Astrophysics Data System (ADS)

This thesis reports on the crystal growth of SrBi2Ta 2O9 ISBN, the measurements of intrinsic properties and the determination of structure-property relationships. Data are reported for the first time for the spontaneous polarization, dielectric anisotropy, electric resistivity, elastic coefficients, piezoelectric activity, heat capacity, and thermal expansion. Details are reported for the high-temperature solution growth of SBT from a Bi2O3 self-flux. Sizable single crystals (up to 6 x 2 x 1.7 mm3) were grown. High resolution TEM imaging verified the basic layer structure, and occasionally identified defects including stacking faults in the SBT structure. The crystal structure was determined by x-ray diffraction. The refinement was consistent with ion exchange between Bi and Sr sites. A theoretical value for the spontaneous polarization was calculated from ionic displacements in the refined structure, and found to be in excellent agreement with experimental data (17 muC/cm2). Well-saturated ferroelectric hysteresis loops were observed for the first time in this thesis for SBT single crystals, from which the spontaneous polarization was obtained. Dielectric constant values were determined along the three principal directions, and were at room temperature Ka = 300, Kb = 186, and Kc = 93. The temperature dependence of their anisotropy was also investigated, with a strong anomaly at a lower transition temperature of ˜300°C. In addition, the electrical resistivity was also determined for the three principal directions. The value along c (rhoc = 3.6 x 1014 ·CM) was more than an order of magnitude greater than along the other two principal directions (rhoa = 1.4 x 1013 ·cm and rhob = 2.2 x 1013 ·cm). The full tensors of elastic and piezoelectric coefficients were obtained by Brillouin scattering method. The piezoelectric coefficients for SBT are weak (e.g., d11˜24 pC/N), and should not give rise to any significant strain on switching PS. Two phase transformations were identified. The higher-temperature phase transformation (˜580°C) was attributed to a tetragonal-orthorhombic transformation on cooling (4/mmm?2mmm). The lower-temperature phase transformation (˜305°C) was identified to be within the same point group (2mm) and the same Aizu species. Raman spectroscopy as a function of temperature identified a soft mode with A1 symmetry which disappeared at the lower-transition temperature on heating. Raman data suggest a structural change with a lower transition from A21am to F2mm on heating. Thermal analysis indicated the latent heat of transformation was small. Thermal properties including thermal expansion coefficient and heat capacity were also determined. Discoveries in this thesis suggest that Sr and Bi exchange between the layers and compensated doping, and the weak piezoelectric properties, are the major mechanisms by which SBT shows excellent resistance to fatigue.

Lu, Xinliang

2000-10-01

190

Dielectric properties and phase transition of zinc tris(thiourea) sulfate single crystal  

NASA Astrophysics Data System (ADS)

The dielectric properties and the ferroelectric to paraelectric phase transition of zinc tris(thiourea) sulfate (ZTS) single crystal have been investigated in a wide range of temperatures and frequencies. In the lower frequency region the real part of dielectric permittivity of the ZTS crystal shows a sudden increase at 323 K. Prominent first-order ferroelectric to paraelectric phase transition at 323 K has been observed in the plot of dielectric permittivity versus temperature at different frequencies. It has been observed that the phase transition occurs in ZTS crystal with a low degree of disorder. Surprisingly, it has been observed for ZTS that the value of the dielectric permittivity is only about 10 at high frequencies and is found to increase to 50 at low frequencies. Dielectric loss has higher values in the paraelectric region.

Moitra, S.; Bhattacharya, S.; Kar, T.; Ghosh, A.

2008-09-01

191

Orthorhombic phase of nickel bromine boracite Ni3B7O13Br: Room temperature ferroelectric-ferroelastic crystal structure  

NASA Astrophysics Data System (ADS)

Nickel bromine boracite Ni3B7O13Br is a fully coupled ferroelectric-ferroelastic crystal with a Curie temperature of 398 K that crystallizes in the orthorhombic system with space group Pca21 and four formula units per unit cell. The lattice constants at 298 K are a = 8.5218±0.0002, b = 8.5127±0.0002, and c = 12.0408±0.0002 Å. The integrated intensities of 11 682 reflections were measured with an Enraf-Nonius CAD-4 diffractometer using monochromatic Mo K? radiation and a small single-domain crystal. The crystal structure was refined by the method of least squares, using the coordinates of isomorphous Mg3B7O13Cl as the initial model, with 1531 symmetry-independent Fmeas. The final agreement factor is 0.0492, based on anisotropic thermal vibrations for all atoms. Six independent boron atoms form tetrahedra with nearest-neighbor oxygen atoms at an average B-O distance of 1.478 Å. The remaining B(3) is 0.140 Å from a plane formed by three oxygen atoms, wth average B-O = 1.378 Å, and is 2.198 Å from a fourth oxygen. Each Ni has four O neighbors at 2.024 Å, one Br at 2.667 Å, and a more distant Br at 3.370 Å, on average. Two ferroelectric-ferroelastic tranformation mechanisms are applicable, each fully coupled. In the first, the sense of the spontaneous polarization is reversed as the spontaneous strain is reoriented: it has a magnitude calculated to be about 0.9×10-2 C m-2, based on a point charge model. The largest atomic displacement in this transformation is 0.72 Å for a Ni2+ ion: All other displacements are less than 0.5 Å. In the second mechanism, the spontaneous polarization is rotated through 90° as the spontaneous strain is also reoriented: it has a calculated magnitude of 2.6×10-2 C m-2. The largest corresponding atomic displacement is 0.60 Å for a Ni2+ ion. As-grown crystals could be only partially detwinned in an electric or a stress field. Ni3B7O13Br is closely isomorphous with Mg3B7O13Cl, the largest difference between coordinates of corresponding atoms being only 0.175 Å, with an average difference of 0.055 Å.

Abrahams, S. C.; Bernstein, J. L.; Svensson, C.

1981-08-01

192

Titania single crystals with a curved surface  

NASA Astrophysics Data System (ADS)

Owing to its scientific and technological importance, crystallization as a ubiquitous phenomenon has been widely studied over centuries. Well-developed single crystals are generally enclosed by regular flat facets spontaneously to form polyhedral morphologies because of the well-known self-confinement principle for crystal growth. However, in nature, complex single crystalline calcitic skeleton of biological organisms generally has a curved external surface formed by specific interactions between organic moieties and biocompatible minerals. Here we show a new class of crystal surface of TiO2, which is enclosed by quasi continuous high-index microfacets and thus has a unique truncated biconic morphology. Such single crystals may open a new direction for crystal growth study since, in principle, crystal growth rates of all facets between two normal {101} and {011} crystal surfaces are almost identical. In other words, the facet with continuous Miller index can exist because of the continuous curvature on the crystal surface.

Yang, Shuang; Yang, Bing Xing; Wu, Long; Li, Yu Hang; Liu, Porun; Zhao, Huijun; Yu, Yan Yan; Gong, Xue Qing; Yang, Hua Gui

2014-11-01

193

Protein single crystal growth under microgravity  

NASA Astrophysics Data System (ADS)

Crystal growth conditions for proteins under microgravity were investigated with two model compounds (?-galactosidase and lysozyme). The single crystals obtained have been found to be significantly larger than those prepared in the same environment on earth.

Littke, Walter; John, Christina

1986-08-01

194

Microscopic interpretation of sign reversal in the electrocaloric effect in a ferroelectric PbMg1/3Nb2/3O3-30PbTiO3 single crystal  

NASA Astrophysics Data System (ADS)

With increasing temperature, PbMg1/3Nb2/3O3-30PbTiO3 (PMN-30PT) crystals change from pseudo-rhombohedral to tetragonal to cubic phases. In addition to the usual positive electrocaloric effect (ECE), a negative ECE, whose origin is uncertain, is observed. Here, these two types of the ECE contributions in PbMg1/3Nb2/3O3-30PbTiO3 crystals are modelled theoretically using a one dimensional statistical mechanical lattice model, which is solved by an exact matrix method. The quasi one-dimensional model reproduces the trends in the experimental behaviour and attributes the electrocaloric sign reversal to free energy changes induced by the electric field.

Axelsson, A.-K.; Le Goupil, F.; Dunne, L. J.; Manos, G.; Valant, M.; Alford, N. McN.

2013-03-01

195

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

196

Supramolecular ferroelectrics  

NASA Astrophysics Data System (ADS)

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

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

2015-04-01

197

Growth and piezoelectric properties of ferroelectric BiWO mono-domain crystals  

NASA Astrophysics Data System (ADS)

A mono-domain crystal of Bismuth tungstate Bi 2WO 6, one of the bismuth layered structure ferroelectric (BLSF) compounds, is synthesized by a slow cooling method using lithium tetra-borate as the flux below the Curie temperature of 940 °C. Fifteen of seventeen independent tensor components of dielectric constant ?/?0, piezoelectric constant d and elastic compliance s are determined. The dielectric constants, ?/?0, were about 100, 70 and 70 for ij=11, 22 and 33 and the piezoelectric constants, d31 and d33 were -17 and 27 pC/N, respectively. These characteristics are consistent with those of BLSF grain-oriented ceramics. The resonance response revealed that the BWO crystals maintained the piezoelectricity up to 400 °C.

Takeda, Hiroaki; Han, Joong Sang; Nishida, Masaya; Shiosaki, Tadashi; Hoshina, Takuya; Tsurumi, Takaaki

2010-05-01

198

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

199

Thermo-Optical Investigation of Sodium-Bismuth Titanate Single Crystal and PLZT Ceramics  

Microsoft Academic Search

Thermal lensing in relaxor type ferroelectrics as a function of temperature has been investigated by using pulse\\/probe method. Enhanced thermo-optical (TO) properties had been observed in 3d elements (Cu, Co) doped PLZT ceramics and in sodium-bismuth titanate single crystals near phase transitions (PT). Comparison of TO signals for several doped PLZT materials reveals that 0.5 wt.% Cu doping is responsible

Guntis Liberts; Girts Ivanovs; Vilnis Dimza; Edmunds Tamanis

2005-01-01

200

Electronic Structure of KH2PO4 Single Crystal Studied by Soft-X-Ray Spectroscopy  

Microsoft Academic Search

The problem of resolving molecular components of the electronic structure of KH2PO4 single crystal with respect to its chemical and orbital character has been approached by X-ray absorption spectroscopy (XAS) and soft X-ray emission spectroscopy (SXES). XAS around K-absorption edge of O atom was carried out in order to the existence of relation between the electronic structure and ferroelectric phase

Tetsuya Nishina; Tohru Higuchi; Eisuke Magome; Poul Olade Velasco; Jeng Long Chen; Wang Li Yang; Jinghua Guo; Masanori Fukunaga; Masaru Komukae

2011-01-01

201

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

202

Blue SHG enhancement by silver nanocubes photochemically prepared on a RbTiOPO4 ferroelectric crystal.  

PubMed

Silver nanocubes with low size dispersion have been selectively photo-deposited on the positive surface of a periodically poled RbTiOPO4 ferroelectric crystal. The obtained nanocubes show preferential orientations with respect to the substrate suggesting epitaxial growth. The plasmonic resonances supported by the nanocubes are exploited to enhance blue SHG at the domain walls. PMID:25123401

Sánchez-García, Laura; Ramírez, Mariola O; Molina, Pablo; Gallego-Gómez, Francisco; Mateos, Luis; Yraola, Eduardo; Carvajal, Joan J; Aguiló, Magdalena; Díaz, Francesc; de Las Heras, Carmen; Bausá, Luisa E

2014-10-01

203

Alignment of ferroelectric liquid crystal on surface SiO2 films on oblique ion beam deposition  

E-print Network

Ferroelectric liquid crystals (FLC) have a tre- mendous potential for production of fast switching electro properties of the thin SiO2 layer using 2D Fourier transform analysis of the AFM pictures are pre- sented source with the racetrack shape of the discharge area. It generates two sheet-like fluxes of Ar+ ions

204

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

Microsoft Academic Search

It was clearly indicative that the polymer chains make a tremendous interaction with the tilt angle in case of a polymer stabilized ferroelectric liquid crystal (PSFLC). After suitable consideration of such interaction, we expanded the Landau free energy for a PSFLC system. We theoretically demonstrated the effect of free volumes, which expected to create bulk self-energy, on the physical functionalities

T. Lahiri; T. Pal Majumder

2011-01-01

205

Characterization and polymerization behavior of polymer-stabilized ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

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

Guymon, Clair Allan

1997-11-01

206

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

NASA Astrophysics Data System (ADS)

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.; Daniell, G. J.; Steigerwald, H.; Soergel, E.; Mailis, S.

2013-08-01

207

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

208

Ideal energy harvesting cycle using a phase transformation in ferroelectric crystals  

NASA Astrophysics Data System (ADS)

A near ideal mechanical-to-electrical energy harvesting cycle that takes advantage of a stress driven ferroelectric–ferroelectric phase transformation was demonstrated in ?ft[ 011 \\right] oriented Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT). The cycle involves loading and unloading the material between two compressive stress loads under open-circuit conditions. The compressive stress loads exceed the coercive stresses required to drive the forward and reverse phase transformation; however, open-circuit conditions result in the surface charge on the electrodes producing an electric field that hinders the phase transformation. The crystal is then discharged through a shunt resistor at constant stress. The phase transformation takes place during the discharge and results in a charge output that is significantly greater than that of a linear piezoelectric material. An output electrical energy density of 6.22 kJ m?3 per cycle was demonstrated for a stress loading interval from ?14 to ?25 MPa and the peak efficiency was measured to be 36% for a stress loading interval of ?16.5 to ?22.5 MPa. Although electrical output increases with the stress loading interval, charge leakage at high electric fields occurred for large stress intervals. This placed a limit on the maximum energy density achievable.

Dong, Wen D.; Gallagher, John A.; Lynch, Christopher S.

2014-12-01

209

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

210

Growth of high temperature superconducting single crystals  

Microsoft Academic Search

YBa2-xSrxCu3O7-y and YBa2Cu3O7 high-Tc superconducting single crystal up to 2.5×2×1 mm having orthorhombic lattices and transition temperatures of 84 and 94 K, respectively, have been grown. Conductivity anisotropy has been confirmed. The grown single crystals exhibit superconducting properties even without additional thermal treatment.

A. P. Voronov; V. M. Dmitriev; M. B. Kosmyna; S. F. Prokopovich; V. P. Seminozhenko

1988-01-01

211

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

212

Ultraprecision diamond turning of aluminium single crystals  

Microsoft Academic Search

Ultraprecision diamond turning is an important technology to generate a high surface finish in precision components and optics. In this paper, the diamond turning of aluminium single crystal rods with crystallographic axes normal to , and is analysed. The effect of the crystallographic anisotropy on the machining of these single crystals is investigated in the light of the mechanics of

S. To; W. B. Lee; C. Y. Chan

1997-01-01

213

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

214

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

215

Banded Structure and Domain Arrangements in PbTiO3 Single Crystals  

NASA Astrophysics Data System (ADS)

In the present work we report the ferroelectric domain arrangements and characteristics of banded structures observed in flux-grown PbTiO3 single crystals. Investigations of etched crystals indicate that most of the specimens show banded structures which may correspond to surface relief characteristics of as-grown crystals. Banded structures, which are different from domain structures, possess structural characteristics similar to those of martensite variants in various alloys and ceramics. The stresses produced during transformation were relieved by the formation of the banded structures and the 90° domain structures, suggesting that the band structures and 90° domains are the products of self-accommodation in as-grown PbTiO3 crystals during the cubic/tetragonal (C/T) transformation. Image characteristics imply that banded-structure-induced domain intersections may store high strain energy in lead titanate crystals and therefore hinder polarization switching of the crystals.

Chou, Chen-Chia; Chen, Cheng-Sao

1998-09-01

216

Protein Single Crystal Growth under Microgravity  

NASA Astrophysics Data System (ADS)

The preparation of suitably large protein single crystals is essentially the rate-determining step of protein x-ray structure determinations. Attempts to produce single crystals with two model compounds--? -galactosidase and lysozyme--under conditions of microgravity were successful. Crystals formed by salting out from solutions kept free of convection were 27 and 1000 times larger in volume, respectively, than those produced in the same apparatus but exposed to terrestrial gravitation.

Littke, Walter; John, Christina

1984-07-01

217

Well aligned half-V ferroelectric liquid crystal in asymmetrical surface polarity controlled alignment cells  

NASA Astrophysics Data System (ADS)

Ferroelectric liquid crystals (FLCs) were known to possess fast response time under 1 ms. The low contrast ratio yielding from defect alignment, however, limited their display application. Based on FLC elastic free energy, the asymmetrical surface polarity controlled alignment was able to suppress the horizontal chevron defects in a half Vshaped switching FLC cell. It is due to the FLC's spontaneous polarization (Ps) pointed to one direction inducing by the opposite surface polarity in asymmetrical hybrid cell. The experimental approach of different alignment materials and different strengths of surface anchoring energies were evaluated in this study. The highest contrast ratio of 780:1 at saturation voltage under 5 V was obtained. The asymmetrical surface polarity controlled alignment technique provided a promising FLC well alignment and fast switching result for TFT-LCD application.

Chen, Huang-Ming Philip; Lin, Chi-Wen

2010-08-01

218

Polarization-gratings approach to deformed-helix ferroelectric liquid crystals with subwavelength pitch  

NASA Astrophysics Data System (ADS)

Electro-optical properties of deformed helix ferroelectric liquid crystal (DHFLC) cells are studied by using a general theoretical approach to polarization gratings in which the transmission and reflection matrices of diffraction orders are explicitly related to the evolution operator of equations for the Floquet harmonics. In the short-pitch approximation, a DHFLC cell is shown to be optically equivalent to a uniformly anisotropic biaxial layer where one of the optical axes is normal to the bounding surfaces. For in-plane anisotropy, orientation of the optical axes and birefringence are both determined by the voltage applied across the cell and represent the parameters that govern the transmittance of normally incident light passing through crossed polarizers. We calculate the transmittance as a function of the electric field and compare the computed curves with the experimental data. The theoretical and experimental results are found to be in good agreement.

Kiselev, Alexei D.; Pozhidaev, Eugene P.; Chigrinov, Vladimir G.; Kwok, Hoi-Sing

2011-03-01

219

A high-sensitivity polarimeter using a ferro-electric liquid crystal modulator  

E-print Network

We describe the HIgh Precision Polarimetric Instrument (HIPPI), a polarimeter built at UNSW Australia and used on the Anglo-Australian Telescope (AAT). HIPPI is an aperture polarimeter using a ferro-electric liquid crystal modulator. HIPPI measures the linear polarization of starlight with a sensitivity in fractional polarization of ~4 x 10$^{-6}$ on low polarization objects and a precision of better than 0.01% on highly polarized stars. The detectors have a high dynamic range allowing observations of the brightest stars in the sky as well as much fainter objects. The telescope polarization of the AAT is found to be 48 $\\pm$ 5 x 10$^{-6}$ in the g' band.

Bailey, Jeremy; Cotton, Daniel; Bott, Kimberly; Hough, J H; Lucas, P W

2015-01-01

220

Effect of cadmium selenide quantum dots on the dielectric and physical parameters of ferroelectric liquid crystal  

SciTech Connect

The effect of cadmium selenide quantum dots (CdSe QDs) on the dielectric relaxation and material constants of a ferroelectric liquid crystal (FLC) has been investigated. Along with the characteristic Goldstone mode, a new relaxation mode has been induced in the FLC material due to the presence of CdSe QDs. This new relaxation mode is strongly dependent on the concentration of CdSe QDs but is found to be independent of the external bias voltage and temperature. The material constants have also been modified remarkably due to the presence of CdSe QDs. The appearance of this new relaxation phenomenon has been attributed to the concentration dependent interaction between CdSe QDs and FLC molecules.

Singh, D. P.; Gupta, S. K.; Manohar, R., E-mail: rajiv.manohar@gmail.com [Liquid Crystal Research Lab, Physics Department, University of Lucknow, Lucknow-226007 (India); Varia, M. C.; Kumar, S. [Soft Condensed Matter Laboratory, Raman Research Institute, C. V. Raman Avenue, Sadashivnagar, Bangalore 560080 (India); Kumar, A. [Department of Physics, Deshbandhu College, Delhi University, Delhi-110019 (India)

2014-07-21

221

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

222

Use of ferroelectric liquid crystal panels to control state and degree of polarization in light beams.  

PubMed

We propose a new technique that is able to generate a light beam with a controlled state of polarization (SoP) and a customized degree of polarization (DoP). The technique relies on the fact that effective depolarization can be achieved by temporally averaging a time-dependent SoP. Our proposed setup is based on a ferroelectric liquid crystal panel of retardance ?/2, with a fast polarization switching capability (33 Hz). A mathematical basis describing the experiment is given. In addition, simulation data is discussed, showing the possibility of generating any SoP with full control of the DoP. Finally, to prove the potential of the invention proposed, experimental results are provided as well, reaching an experimental minimum DoP of 0.14. PMID:24487892

Peinado, Alba; Lizana, Angel; Campos, Juan

2014-02-01

223

Models of Molecular Alignment Structure in Polymer-Stabilized Ferroelectric Liquid Crystals  

NASA Astrophysics Data System (ADS)

The electrooptical (EO) characteristics of polymer-stabilized ferroelectric liquid crystals (PSFLCs), which are fabricated by UV photocure of doped monoacrylates with mesogenic side chains at a temperature where the LC medium is in the SmC* phase under the simultaneous application of a bipolar square-pulsed AC electric field, depend on the polymer density. The PSFLC with low concentration of polymer exhibits a bistable EO performance accompanied by microsized domain switching. On the other hand, the PSFLC with high concentration of polymer exhibits a monostable V-shaped EO performance without a threshold. We propose a model to explain the effect of polymer density on the molecular alignment structure of the PSFLC by investigating theoretically the free energy.

Furue, Hirokazu; Takahashi, Taiju; Kobayashi, Shunsuke; Yokoyama, Hiroshi

2002-11-01

224

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.

2012-04-01

225

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

226

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

227

Molecular Alignment Structure and Switching of a Ferroelectric Liquid Crystal Stabilized by a Polymer Network Created in the SmA Phase  

Microsoft Academic Search

In order to realize monostability in surface-stabilized ferroelectric liquid crystals, polymer stabilization techniques have been proposed, and the polymer-stabilized ferroelectric liquid crystals (PSFLCs), which is fabricated by UV photocure of doped photocurable mesogenic monomers at a temperature where the FLC medium is in the SmA phase, has been reported to show V-shaped electrooptical characteristics. However, the reason why the monostable

Hirokazu Furue; Yukio Koizumi; Jun Hatano; Hiroshi Yokoyama

2005-01-01

228

Improved ferroelectric and pyroelectric parameters in iminodiacetic acid doped TGS crystal  

Microsoft Academic Search

Single crystals of Iminodiacetic acid (HN(CH2COOH)2) doped Triglycine sulphate (IDATGS) has been grown from aqueous solution at constant temperature by slow evaporation technique. The concentration of the dopant in the TGS solution was 2mol%. The X-ray diffraction analysis indicates that there is significant change in the lattice parameters compared to pure TGS crystal. The IDATGS crystal has larger transition temperature

Chitharanjan Rai; K. Sreenivas; S. M. Dharmaprakash

2010-01-01

229

Synthesis and properties of zirconium-doped RbTiOPO 4 single crystals  

Microsoft Academic Search

Single crystals of the solid solutions RbTi1 ? x\\u000a Zr\\u000a x\\u000a OPO4 (0.015 x < 0.034) were grown and their physical properties were studied. In the presence of zirconium in the crystals with the maximum\\u000a content x = 0.034, the ferroelectric phase transition and the high-temperature transition from the orthorhombic to the cubic phase\\u000a are shifted to lower temperatures by

E. I. Agapova; V. I. Voronkova; E. P. Kharitonova; I. N. Leont’eva; S. Yu. Stefanovich; N. I. Sorokina; A. P. Dudka; O. A. Alekseeva; N. N. Kononkova

2008-01-01

230

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

231

Synthesis and properties of zirconium-doped RbTiOPO4 single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of the solid solutions RbTi1 - x Zr x OPO4 (0.015 < x < 0.034) were grown and their physical properties were studied. In the presence of zirconium in the crystals with the maximum content x = 0.034, the ferroelectric phase transition and the high-temperature transition from the orthorhombic to the cubic phase are shifted to lower temperatures by 100 and 50°C, respectively. In the temperature range from 700°C to room temperature, the conductivity of doped crystals decreases compared to that of the undoped crystals. It is of particular interest that the intensity of the second-harmonic generation of the doped crystals is substantially higher than that of RbTiOPO4.

Agapova, E. I.; Voronkova, V. I.; Kharitonova, E. P.; Leont'eva, I. N.; Stefanovich, S. Yu.; Sorokina, N. I.; Dudka, A. P.; Alekseeva, O. A.; Kononkova, N. N.

2008-03-01

232

Local Weak Ferromagnetism in Single-Crystalline Ferroelectric BiFeO3  

NASA Astrophysics Data System (ADS)

Polarized small-angle neutron scattering studies of single-crystalline multiferroic BiFeO3 reveal a long-wavelength spin density wave generated by ˜1° spin canting of the spins out of the rotation plane of the antiferromagnetic cycloidal order. This signifies weak ferromagnetism within mesoscopic regions of dimension 0.03 microns along [11¯0], to several microns along [111], confirming a long-standing theoretical prediction. The average local magnetization is 0.06?B/Fe. Our results provide an indication of the intrinsic macroscopic magnetization to be expected in ferroelectric BiFeO3 thin films under strain, where the magnetic cycloid is suppressed.

Ramazanoglu, M.; Laver, M.; Ratcliff, W., II; Watson, S. M.; Chen, W. C.; Jackson, A.; Kothapalli, K.; Lee, Seongsu; Cheong, S.-W.; Kiryukhin, V.

2011-11-01

233

Local weak ferromagnetism in single-crystalline ferroelectric BiFeO3.  

PubMed

Polarized small-angle neutron scattering studies of single-crystalline multiferroic BiFeO(3) reveal a long-wavelength spin density wave generated by ?1° spin canting of the spins out of the rotation plane of the antiferromagnetic cycloidal order. This signifies weak ferromagnetism within mesoscopic regions of dimension 0.03 microns along [110], to several microns along [111], confirming a long-standing theoretical prediction. The average local magnetization is 0.06 ?(B)/Fe. Our results provide an indication of the intrinsic macroscopic magnetization to be expected in ferroelectric BiFeO(3) thin films under strain, where the magnetic cycloid is suppressed. PMID:22181767

Ramazanoglu, M; Laver, M; Ratcliff, W; Watson, S M; Chen, W C; Jackson, A; Kothapalli, K; Lee, Seongsu; Cheong, S-W; Kiryukhin, V

2011-11-11

234

Defects in the reduced rutile single crystal  

NASA Astrophysics Data System (ADS)

In this paper, the UV-VIS optical absorption spectra of oxidized and reduced rutile single crystals are measured by means of spectrophotometer and two absorption peaks around 430 and 730 nm are found. These spectral data are analyzed by using the crystal field theory. Based on these studies, we suggest that the reduced crystal contain the defect center [Ti 3+-O v], with the oxygen vacancy (O v) on one of the nearest neighbor sites of the central Ti 3+ ion.

Lu, Tie-Cheng; Wu, Shao-Yi; Lin, Li-Bin; Zheng, Wen-Chen

2001-09-01

235

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 ?R 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 ?R(V) hysteresis loops are specifically examined. Static mapping related to ?R(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

236

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

PubMed

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

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

2015-02-01

237

Ferroelectric domain wall motion induced by polarized light  

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

238

Ferroelectric domain wall motion induced by polarized light.  

PubMed

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

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

2015-01-01

239

Ferroelectric domain wall motion induced by polarized light  

PubMed Central

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

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

2015-01-01

240

Ferroelectric C* phase induced in a nematic liquid crystal matrix by a chiral non-mesogenic dopant  

NASA Astrophysics Data System (ADS)

We report on a ferroelectric chiral smectic C (C*) phase obtained in a mixture of a nematic liquid crystal (NLC) and a chiral nonmesogenic dopant. The existence of C* phase was proven by calorimetric, dielectric and optical measurements, and also by X-rays analysis. The smectic C* which is obtained in such a way can flow, allowing to restore the ferroelectric liquid crystal layer structure in the electro-optical cells after action of the mechanical stress, as it happens with the cells filled with NLC. The proposed method of obtaining smectic C* material allows us to create innovative electro-optical cell combining the advantages of NLC (mechanical resilience) and smectic C* (high switching speed).

Pozhidaev, E. P.; Torgova, S. I.; Barbashov, V. A.; Minchenko, M. V.; Sulyanov, S. N.; Dorovatovskii, P. V.; Ostrovskii, B. I.; Strigazzi, A.

2015-02-01

241

Monte Carlo simulations of ferroelectric crystal growth and molecular electronic structure of atoms and molecules  

NASA Astrophysics Data System (ADS)

In this thesis, we explore two stochastic techniques to study properties of materials in realistic systems. Specifically, the kinetic Monte Carlo (KMC) method is utilized to study the crystal growth process of ferroelectric materials and the quantum Monte Carlo (QMC) approach is used to investigate the ground state properties of atoms and molecules. In the growth simulations, we study the growth rates and chemical ordering of ferroelectric alloys using an electrostatic model with long-range Coulomb interactions. Crystal growth is characterized by thermodynamic processes involving adsorption and evaporation, with solid-on-solid restrictions and excluding diffusion. A KMC algorithm is formulated to simulate this model efficiently in the presence of long-range interactions. The growth process is simulated as a function of temperature, chemical composition, and substrate orientation. We carried out the simulations on two heterovalent binaries, those of the NaCl and the Ba(Mg1/3Nb2/3))O3(BMN) structures. Compared to the simple rocksalt ordered structures, ordered BMN grows only at very low temperatures and only under finely tuned conditions. For materials with tetravalent compositions, such as (1-x)Ba(Mg 1/3Nb2/3))O3 + x BaZrO3 (BMN-BZ), the model does not incorporate tetravalent ions at low-temperature, exhibiting a phase-separated ground state instead. At higher temperatures, tetravalent ions can be incorporated, but the resulting crystals show no chemical ordering in the absence of diffusive mechanisms. In the second part of the thesis, we present results from an auxiliary field quantum Monte Carlo (AFQMC) study of ground state properties, in particular dissociation and ionization energy, of second-row atoms and molecules. The method projects the many-body ground state from a trial wavefunction by random walks in the space of Slater determinants. The Hubbard-Stratonovich transformation is employed to decouple the Coulomb interaction between electrons. A trial wave function is used in the approximation to control the "phase problem". We also carry out Hartree-Fock (HF) and Density Functional Theory (DFT) calculations for comparison to AFQMC results and to serve as starting wavefunctions for our AFQMC calculations. Results of dissociation energy are in excellent agreement with experimental values. Ionization energy errors are somewhat larger than those of other methods. We conclude with a discussion of several possible sources of error as well as a direction for the improvement.

Suewattana, Malliga

242

Ferroelectric performances and crystal structures of (Pb, La)(Zr, Ti, Nb)O{sub 3}  

SciTech Connect

In this study, we focused on Nb and La substituted Pb(Zr, Ti)O{sub 3}: i.e., (Pb, La)(Zr, Ti, Nb)O{sub 3}. As for the samples, dependences of ferroelectric properties on La and Nb compositions were examined. In addition, the crystal structures were analyzed by the Rietveld method, and then a relationship between the metal compositions and the crystal structures were discussed. From P–E hysteresis loop measurements, it was found that the remanant polarization of Pb(Zr, Ti)O{sub 3} was increased by both the La and Nb substitutions although the heavy substitution of La had an undesirable effect. It was also indicated that the Curie temperature decreased with increasing La content. The Rietveld analysis using synchrotron X-ray diffraction patterns demonstrated that the structure distortion was relaxed by the La and Nb substitutions. Such a change in the crystals was well consistent with the harmful effects on the Curie temperature and the remanent polarization by the heavy La substitution. - Graphical abstract: Rietveld refinement pattern of 2 mol% PbSiO{sub 3}-added Pb{sub 0.95}La{sub 0.05}Zr{sub 0.50}Ti{sub 0.45}Nb{sub 0.05}O{sub 3} (synchrotron X-ray diffraction). Display Omitted - Highlights: • (Pb,La)(Zr,Ti,Nb)O{sub 3} were successfully synthesized. • Remanant polarization of Pb(Zr,Ti)O{sub 3} was improved by substitutions of La and Nb. • Crystal structures of (Pb,La)(Zr,Ti,Nb)O{sub 3} were refined and the distortions were estimated.

Kitamura, Naoto [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan); Division of Ecosystem Research, Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan); Mizoguchi, Takuma [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan); Itoh, Takanori [AGC Seimi Chemical Co., Ltd., 3-2-10 Chigasaki-City, Kanagawa 253-8585 (Japan); Idemoto, Yasushi, E-mail: idemoto@rs.noda.tus.ac.jp [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan); Division of Ecosystem Research, Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)

2014-02-15

243

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

PubMed

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

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

2013-07-14

244

Improved Equivalent Circuit Model for V-Shaped, Thresholdless Switching Ferroelectric Liquid Crystals  

NASA Astrophysics Data System (ADS)

For V-shaped, thresholdless switching ferroelectric liquid crystals (FLCs), the impedance divider induced by the multilayer structure of FLC cells and the drive circuit play an important role in switching characteristics. In this paper, an equivalent circuit model that can be applied to conventional circuit simulators is proposed for the optical response prediction and drive circuit optimization of V-shaped FLCs. The model is improved from the original model of Moore and Travis; however, the impedance divider is taken into account, and both polar and nonpolar surface anchoring energies are considered to make the model more preferable. The model is then utilized to investigate thresholdless switching characteristics. Simulation results show that the hysteresis inversion frequency fi increases more than one thousand fold with the drive circuit and then decreases with REXT following the relation log fi = -alog REXT + b, and a (b) increases from 0.43 to 0.46 (2.46 to 2.66) as the amplitude of triangular voltage increases from 4 to 10 V, agreeing with experimental results. Also, the same optical transmissions are plotted as different coordinates, as a function of voltage dropping on liquid crystal layer and of drive voltage, and the results show that genuine V-shaped switching is only observed when the transmission is plotted as a function of drive voltage, coinciding with the model suggested by Blinov et al.

Wang, Meng-yao; Pan, Wei; Luo, Bin; Zhang, Wei-li; Zou, Xi-hua

2008-05-01

245

Relationship between the nonlinear ferroelectric and liquid crystal models for microtubules  

NASA Astrophysics Data System (ADS)

Microtubules (MTs), which are the main components of the cytoskeleton, are important in a variety of cellular activities, but some physical properties underlying the most important features of their behavior are still lacking satisfactory explanation. One of the essential enigmas regarding the energy balance in MTs is the hydrolysis of the exchangable guanosine 5'-triphosphate bound to the ? monomer of the molecule. The energy released in the hydrolysis process amounts to 6.25×10-20 J and has been the subject of many attempts to answer the questions of its utilization. Earlier, we put forward a hypothesis that this energy can cause a local conformational distortion of the dimer. This distortion should have nonlinear character and could lead to the formation of a traveling kink soliton. In this paper we use the formalism of the liquid crystal theory to consider the nonlinear dynamics of MTs. We demonstrate that this new model is formally equivalent to our earlier ferroelectric model which was widely exploited in an attempt to elucidate some important dynamical activities in MTs. We also study the stability of kink solitons against small perturbations and their unusual mutual interactions as well as the interactions with structural inhomogenities of MTs. Our new approach based on liquid crystal properties of microtubules has been recently corroborated by new insights gained from the electrostatic properties of tubulin and microtubules.

Satari?, M. V.; Tuszy?ski, J. A.

2003-01-01

246

Control of the Anisotropic Phase Separation and the Electro-Optical Stability of Ferroelectric Liquid Crystal-Photopolymer Composites  

Microsoft Academic Search

The criteria for controlling the anisotropic phase separation process in ferroelectric liquid crystal (FLC)-photopolymer mixtures are presented. Depending on the FLC composition and the irradiated intensity of the ultraviolet light, one of the polymer-dispersed, anisotropic phase separated (PS), and polymer-network structures is found to be energetically favored to form it from the FLC-photopolymer mixture. In contrast to a surface-stabilized FLC

Jae-Hong Park; Won-Je Lee; Jae-Hoon Kim; Sin-Doo Lee

2003-01-01

247

Ferroelectric-like response from the surface of SrTiO{sub 3} crystals at high temperatures  

SciTech Connect

Since SrTiO{sub 3} has a high dielectric constant, it is used as a substrate for a large number of complex physical systems for electrical characterization. Since SrTiO{sub 3} crystals are known to be non-ferroelectric/non-piezoelectric at room temperature and above, SrTiO{sub 3} has been believed to be a good choice as a substrate/base material for PFM (Piezoresponse Force Microscopy) on novel systems at room temperature. In this paper, from PFM-like measurement using an atomic force microscope on bare crystals of (110) SrTiO{sub 3} we show that ferroelectric and piezoelectric-like response may originate from bare SrTiO{sub 3} at remarkably high temperatures up to 420?K. Electrical domain writing and erasing are also possible using a scanning probe tip on the surface of SrTiO{sub 3} crystals. This observation indicates that the role of the electrical response of SrTiO{sub 3} needs to be revisited in the systems where signature of ferroelectricity/piezoelectricity has been previously observed with SrTiO{sub 3} as a substrate/base material.

Jyotsna, Shubhra; Arora, Ashima; Sekhon, Jagmeet S.; Sheet, Goutam, E-mail: goutam@iisermohali.ac.in [Department of Physical Sciences, Indian Institute of Science Education and Research Mohali (IISER M), Sector 81, S. A. S. Nagar, Manauli PO 140306 (India)

2014-09-14

248

Photomodulation of the spontaneous polarization of ferroelectric liquid crystals using chiral thioindigo dopants  

NASA Astrophysics Data System (ADS)

Ferroelectric liquid crystals (FLC) are chiral smectic C (S C*) phases that exhibit a spontaneous polarization (Ps). This permanent dipole moment is a macroscopic manifestation of molecular chirality. Between crossed polarizers, a FLC becomes a light valve by switching the orientation of Ps using an applied electric field. Due to the bistability exhibited by FLC light valves, any digital information written in such devices is kept for an indefinite period of time in the absence of the electrical field. The switching of the orientation of Ps can also be achieved optically if the FLC media is photoresponsive. Thus, an erasable optical memory device can be developed. Optically addressed FLC light valves have been developed based on the photomodulation of Ps via the so-called photomechanical effect, which works on the principle of destabilizing the FLC phase using azobenzene dopants that absorb in the UV region of the spectrum. In the work described here in, we propose the following approach: to photomodulate the spontaneous polarization of a ferroelectric liquid crystal by modulating the transverse dipole moment of a chiral thioindigo dopant. This dopant undergoes a reversible cis-trans isomerization when irradiated in the visible range of the spectrum, and maintains a rod-like shape in both isomeric forms. In the first part of the project, we synthesized a series of 6,6-dialkoxythioindigo dopants and tested their solubility properties in a variety of S C and nematic liquid crystals. Based on these results, we synthesized the first chiral thioindigo dopant (R,R)-1a with improved solubility in S C hosts. This compound was doped in a phenyl benzoate S C* host to induce a ferroelectric S C* phase and irradiated to cause trans-cis photoisomerization, which resulted in negligible photomodulation of Ps due to the absence of steric coupling between the thioindigo core and the chiral side-chains.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) In order to harness the transversal dipole modulation of the core towards Ps modulation, we synthesized a second generation of chiral thioindigo dopants with additional polar substituents at the 5,5' positions, e.g. (R,R)-1b, -1c, which provide the necessary steric coupling with the chiral side-chains. As a dopant in a S C host, R,R)-1b caused Ps to increase by ca. 85% upon trans-cis photoisomerization at 514 nm, while (R,R)-1c caused Ps to increase by ca. 300% upon trans-cis photoisomerization at 532 nm. Control experiments showed that Ps photomodulation is achieved without destabilization of the S C layers. The prototype of a FLC optical switch based on photoinduced Ps sign reversal using dopant (R,R)-1c has been built and tested.

Dinescu, Liviu

249

Tuning the functional properties of PMN-PT single crystals via doping and thermoelectrical treatments  

NASA Astrophysics Data System (ADS)

Single crystals based on solid solutions of lead-magnesium-niobate (PMN) and lead titanate (PT) have emerged as highly promising multifunctional systems combining piezoelectric, pyroelectric, and electro-optic properties that surpass by far those of the best known lead-zirkonium-titanate ceramics. In this paper we present new findings on how the phase transition temperature and the dielectric and ferroelectric properties can be tuned depending on crystal composition, orientation, and thermoelectrical treatment. Mn-doped and pure 0.72PbMg1/3Nb2/3O3-0.28PbTiO3 (0.72PMN-0.28PT) single crystals with ?111? and ?001? orientations were investigated. A special attention was devoted to field cooling (FC), i.e., cooling under electric field from different temperatures. The results illustrate different findings that were not reported before: the Curie temperature, i.e., ferroelectric-paraelectric transition temperature, is enhanced after field cooling of the Mn-doped, ?001?-oriented crystal while such a shift is not observed in the ?111?-oriented and the non-doped crystals. In addition, substantial polarization suppression occurs in the Mn-doped crystals upon FC from high temperature regardless of orientation. Based on piezoforce microscopy of the domain structure that shows suppression of domain growth following field cooling from 200 °C, we propose a mechanism for polarization suppression based on domain pinning by charged defects. The practical importance of our results lies in showing the opportunity offered by a proper choice of crystal composition and poling conditions for tuning the functional properties of PMN-PT single crystals for a specific application. This should contribute to the understanding of their properties towards advanced sensor and transducers devices.

Luo, Laihui; Dietze, Matthias; Solterbeck, Claus-Henning; Luo, Haosu; Es-Souni, Mohammed

2013-12-01

250

High-Tc/high-coupling relaxed PZT-based single crystal thin films  

NASA Astrophysics Data System (ADS)

Pb(Zr,Ti)O3 (PZT)-based ferroelectric ceramics exhibit high piezoelectricity, however, their Curie temperature (Tc) values are not so high, i.e., Tc < 400 °C. PZT-based piezoelectric thin films with higher Tc would be beneficial for improved micro actuators, sensors, memories, and piezoelectric micro-electro mechanical systems. In-plane biaxial strained PZT thin films in a laminated composite structure are known to exhibit enhanced Tc; however, the thickness of PZT-based thin films is limited to below a critical thickness typically <50 nm. The Tc of relaxed PZT-based thin films with thicknesses greater than the critical thickness is the same as bulk Tc. However, a sort of relaxed PZT-based single-crystal thin films exhibit extraordinary high Tc, Tc = ˜600 °C. In addition, the films show extremely low dielectric constant, ?/?o ˜ 100 with high coupling factor, kt ˜ 0.7, and large remnant polarization, Pr ˜ 100 ?C/cm2. These exotic properties would result from the single-domain/single-crystal structure. The enhanced Tc is possibly caused by the highly stable interface between the PZT-based thin films and substrates. Their ferroelectric performances are beyond those of conventional PZT. The high-Tc/high-coupling performances are demonstrated, and the possible mechanisms of the high Tc behavior in relaxed PZT-based single-crystal thin films are discussed.

Wasa, K.; Matsushima, T.; Adachi, H.; Matsunaga, T.; Yanagitani, T.; Yamamoto, T.

2015-03-01

251

Fatigue hardening in niobium single crystals.  

NASA Technical Reports Server (NTRS)

Nb single crystals of various orientations were cyclically deformed in tension-compression under strain control. At low strain amplitudes all crystals oriented for single slip and some oriented for multiple slip showed a two stage hardening. When present, the first stage was characterized with almost no cyclic work hardening. The rate of hardening in the second stage increased with strain amplitude and the amount of secondary slip. In crystals oriented for single slip kink bands developed on their side faces during rapid hardening stage which resulted in considerable amount of asterism in Laue spots. A cyclic stress-strain curve independent of prior history was found to exist which was also independent of crystal orientation. Furthermore, this curve differed only slightly from that of polycrystalline Nb obtained from data in literature.

Doner, M.; Diprimio, J. C.; Salkovitz, E. I.

1973-01-01

252

Anisotropic Shock Propagation in Single Crystals  

SciTech Connect

Most single-crystal shock experiments have been performed in high-symmetry directions while the nature of shock propagation in low-symmetry directions remains relatively unstudied. It is well known that small-amplitude, linear acoustic waves propagating in low-symmetry directions can focus and/or form caustics (Wolfe, 1995). In this report we provide evidence for similar focusing behavior in nonlinear (shock) waves propagating in single crystals of silicon and diamond. Using intense lasers, we have driven non-planar (divergent geometry) shock waves through single-crystals of silicon or diamond and into an isotropic backing plate. On recovery of the backing plates we observe a depression showing evidence of anisotropic plastic strain with well-defined crystallographic registration. We observe 4-, 2-, and 3-fold symmetric impressions for [100], [110], and [111] oriented crystals respectively.

Eggert, J; Hicks, D; Celliers, P; Bradley, D; Cox, J; Unites, W; Collins, G; McWilliams, R; Jeanloz, R; Bruygoo, S; Loubeyre, P

2005-05-26

253

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

254

Magnetic field tuning of polaron losses in Fe doped BaTiO3 single crystals.  

PubMed

Artificial tuning of dielectric parameters can result from interface conductivity in polycrystalline materials. In ferroelectric single crystals, it has already been shown that ferroelectric domain walls can be the source of such artificial coupling. We show here that low-temperature dielectric losses can be tuned by a dc magnetic field. Since such losses were previously ascribed to polaron relaxation we suggest this results from the interaction of hopping polarons with the magnetic field. The fact that this loss alteration has no counterpart in the real part of the dielectric permittivity confirms that no interface is involved in this purely dynamical effect. The contribution of mobile charges hopping among Fe-related centers was confirmed by ESR spectroscopy, showing a maximum intensity at ca T ~ 40 K. PMID:22951582

Theerthan, R Anand; Artemenko, Alla; Maglione, Mario

2012-10-10

255

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

256

Characterization of zinc selenide single crystals  

NASA Technical Reports Server (NTRS)

ZnSe single crystals of high quality and low impurity levels are desired for use as substrates in optoelectronic devices. This is especially true when the device requires the formation of homoepitaxial layers. While ZnSe is commercially available, it is at present extremely expensive due to the difficulty of growing single crystal boules with low impurity content and the resultant low yields. Many researchers have found it necessary to heat treat the crystals in liquid Zn in order to remove the impurities, lower the resistivity and activate the photoluminescence at room temperature. The physical vapor transport method (PVT) has been successfully used at MSFC to grow many single crystals of II-VI semiconducting materials including ZnSe. The main goal at NASA has been to try to establish the effect of gravity on the growth parameters. To this effect, crystals have been grown vertically upwards or horizontally. Both (111) and (110) oriented ZnSe crystals have been obtained via unseeded PVT growth. Preliminary characterization of the horizontally grown crystals has revealed that Cu is a major impurity and that the low temperature photoluminescence spectra is dominated by the copper peak. The ratio of the copper peak to the free exciton peak is being used to determine variations in composition throughout the crystal. It was the intent of this project to map the copper composition of various crystals via photoluminescence first, then measure their electrical resistivity and capacitance as a function of frequency before proceeding with a heat treatment designed to remove the copper impurities. However, equipment difficulties with the photoluminescence set up, having to establish a procedure for measuring the electrical properties of the as-grown crystals and time limitations made us re-evaluate the project goals. Vertically grown samples designated as ZnSe-25 were chosen to be measured electrically since they were not expected to show as much variation in their composition through their cross-section as the horizontally grown samples.

Gerhardt, Rosario A.

1996-01-01

257

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

258

Development of single crystal filaments. Final report  

SciTech Connect

The program just completed addresses a route to a more efficient longer-lasting electric light bulb filament. All current filaments for light bulbs are metallic in nature. They are subject to embrittlement with age (large grain growth) and relatively high vapor pressures which limits their operating temperature. There is evidence which suggests advantages to using high temperature refractory single crystal fibers as a filament for a light bulb. These refractory materials may include materials such as hafnium or tantalum carbide which have melting points about 500{degrees}C higher than tungsten. Another advantage is that single crystal fibers have a very high degree of crystalline perfection with very few voids and dislocations. Without these imperfections, the atomic mobility at high temperatures is highly restricted. Thus single crystal fibers are very stable at high temperature and will last longer. The efficiencies result from running these single crystal ceramic fiber filaments at higher temperatures and the higher emissivity of the carbide filaments compared to tungsten. The amount of visible light is proportional to the 4the power of the temperature thus a 500{degrees}C higher operating give about a 3-fold increase in radiation in the visible range. The program accomplishments can be summarized as follows: (1) Single crystal fibers of JfC sufficient crystal quality for light bulb filament applications were made. (2) The HfC fiber furnace growth chamber, power control and data collection system was developed for the laboratory scale plant. (3) method for mounting and apparatuses for testing the single crystal fiber filaments were developed and built.

Milewski, J.V.; Shoultz, R.A.; Bourque-McConnell, M.M.

1995-04-01

259

Monolithic electronic devices based on domain wall motion in a ferroelectric crystal  

Microsoft Academic Search

Ferroelectric domain wall motion can provide the basis for monolithic electronic devices which are able to gate, amplify, perform digital logic, read out permanent analog messages, provide digital shift register storage, and scan optical images. No use of ferroelectric coercivity is made in these devices. Most of the functions have been experimentally demonstrated in simple form. The basic operating principles

J. M. Geary

1979-01-01

260

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

261

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

262

Optimization and tolerance analysis of a polarimeter with ferroelectric liquid crystals.  

PubMed

We present the design of Stokes and Mueller polarimeters based on ferroelectric liquid crystal (FLC) panels. The instrument is complete and takes time-sequential measurements. A FLC device is modeled as a uniaxial birefringent waveplate with two stable optical axis orientations switchable by a squared electrical signal. The optical parameters of the LC device (retardance and the two stable orientations of the fast axis) are calibrated. Then the orientations of the optical elements of the setup are optimized in order to minimize the propagation of the noise. We also provide a tolerance study to achieve 2% accuracy for the Stokes vector and Mueller matrix metrology. These analyses are conducted as a function of the incident state of polarization and of the Mueller matrix to be measured, respectively. The optimized system is implemented and calibrated in the laboratory. We evaluate its repeatability over 24 h of operation, and the dependence with the temperature is discussed. In addition, we include a study related to the speed of taking the measurements. Finally, we provide some experimental measurements of different Stokes vectors and Mueller matrices, validating the proposed prototypes. PMID:23938428

Peinado, Alba; Lizana, Angel; Campos, Juan

2013-08-10

263

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

264

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

265

A ferroelectrically switchable columnar liquid crystal phase with achiral molecules: superstructures and properties of liquid crystalline ureas.  

PubMed

Novel columnar liquid crystalline compounds N,N'-bis(3,4,5-trialkoxylphenyl)ureas 1a-c (R = n-C(8)H(17), n-C(12)H(25), and n-C(16)H(33)) were synthesized, and their phase transitions were measured by differential scanning calorimetery. The superstructures were investigated by X-ray diffraction, polarized light optical microscopy, and IR spectroscopy. The compounds exhibited both rectangular and hexagonal columnar phases in which the urea molecules in each column were stacked in one direction with strong hydrogen bonds. To confirm the ferroelectric switching, optoelectronic experiments were carried out, and the hexagonal columnar phases of 1b and 1c gave a sharp peak of spontaneous polarization in response to an applied triangular wave electric field (0.1-18 Hz). This is the first example of ferroelectrically switchable columnar liquid crystal phases generated by achiral molecules. PMID:15725011

Kishikawa, Keiki; Nakahara, Shoichiro; Nishikawa, Yohei; Kohmoto, Shigeo; Yamamoto, Makoto

2005-03-01

266

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

267

Growth of high-quality hexagonal ErMnO3 single crystals by the pressurized floating-zone method  

NASA Astrophysics Data System (ADS)

Hexagonal manganites are among the most intensively studied multiferroics, exhibit unusual geometrically driven ferroelectricity and magnetoelectric couplings, and form domains and domain walls with intriguing functional properties. In order to study these electronic correlation phenomena and develop a comprehensive understanding about the underlying physics, the availability of high-quality single-crystals is crucial. In particular, different members of the RMnO3 (R=Sc, Y, In, Dy to Lu) family require different growth condition in order to achieve stoichiometric single-phase crystals. Here, we report on the growth of high-quality ErMnO3 single crystals with dimensions of 5 mm in diameter and up to 60 mm in length using the pressurized floating-zone technique. We present Laue diffraction, piezoresponse force microscopy, and conductive atomic force microscopy data, reflecting the quality of our single crystals regarding the structure, as well as electronic properties on the level of domains and domain walls.

Yan, Z.; Meier, D.; Schaab, J.; Ramesh, R.; Samulon, E.; Bourret, E.

2015-01-01

268

Modern Physics of Ferroelectrics: Essential Background  

Microsoft Academic Search

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

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

269

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

NASA Astrophysics Data System (ADS)

By dynamic light scattering we studied the temperature dependence of scattered intensities and relaxation rates for pure twist and pure bend modes in a colloidal system of BaTiO3 single domain nanoparticles and liquid crystal octylcyanobiphenyl (8CB) close to the nematic to smectic-A phase transition. From the experiments we obtained the critical exponents for the smectic correlation lengths, which in suspensions differ from the values for pure 8CB. The phase transition temperatures from isotropic to nematic phase (TNI) and from nematic to smectic-A phase (TNA) are both affected by the presence of the particles in two ways. The electric field around the ferroelectric particles increases the transition temperatures, whereas the disorder and probably also the excess of the surfactant cause a decrease of the transition temperatures compared to pure 8CB. The net effect is lower TNI and almost unchanged TNA in suspensions. After prolonged exposure to the external field the ferroelectric particles irreversibly aggregate, which results in the decrease of the internal electric field and, consequently, in the decrease of both transition temperatures.

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

2012-02-01

270

An ultrahigh vacuum single crystal adsorption microcalorimeter  

NASA Astrophysics Data System (ADS)

The design of an ultrahigh vacuum microcalorimeter enabling calorimetric heats of adsorption to be obtained on single crystal surfaces as a detailed function of coverage is discussed. The system comprises a pulsed supersonic molecular beam source, an ultrathin metal single crystal, and remote infrared temperature sensing. Sticking probabilities and coverages are determined pulsewise by the King and Wells method, and heat capacity calibrations are conducted in situ by laser beam pulsing. Results for CO and O2 on Ni{110} demonstrate excellent sensitivity to adsorption of ˜10-13 moles of gas (˜0.01 monolayer). The heat capacity of the calorimeter is 4.2 ?J K-1.

Borroni-Bird, C. E.; King, D. A.

1991-09-01

271

The stabilization of a single domain in free-standing ferroelectric nanocrystals.  

PubMed

High resolution electron microscopy, electron diffraction and electron holography were used to study individual free-standing ? 30 nm barium titanate nanocrystals. Large unidirectional variations in the tetragonal distortion were mapped across the smaller nanocrystals, peaking to anomalously large values of up to 4% at the centers of the nanocrystals. This indicated that the nanocrystals consist of highly strained single ferroelectric domains. Simulations using an effective Hamiltonian for modeling a nanocrystal under a small depolarizing field and negative pressure qualitatively confirm this picture. These simulations, along with the development of a phenomenological model, show that the tetragonal distortion variation is a combined effect of: (i) electrostrictive coupling between the spontaneous polarization and strain inside the nanocrystal, and (ii) a surface-induced effective stress existing inside the nanodot. As a result, a 'strain skin layer', having a smaller tetragonal distortion relative to the core of the nanocrystal, is created. PMID:24594615

Szwarcman, Daniel; Prosandeev, S; Louis, Lydie; Berger, Shlomo; Rosenberg, Yuri; Lereah, Yossi; Bellaiche, L; Markovich, Gil

2014-03-26

272

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

273

Microhardness studies of sulfamic acid single crystal  

NASA Astrophysics Data System (ADS)

Vicker's microhardness study of (100), (010) and (001) faces of a non-linear optical crystal sulfamic acid have been reported. Single crystals of sulfamic acid have been grown by slow evaporation method. The load dependence of the Vickers microhardness of sulfamic acid crystal were investigated and analyzed from the stand point of various theoretical models. Crystal samples in a, b and c-axes exhibit reverse indentation effect which is best described by Meyer's law, Hays-Kendall's approach and proportional specimen resistance (PSR) models. The negative values of load dependent quantities in Hays-Kendall's approach and PSR model suggest that the origin of indentation size effect is associated with the process of relaxation of indentation stresses.

Santhosh Kumar, A.; Joseph, Cyriac; Paulose, Reshmi; R, Rajesh; Joseph, Georgekutty; Louis, Godfrey

2015-02-01

274

Single crystal articles having reduced anisotropy  

SciTech Connect

This paper describes a method of modifying the nickel base superalloy composition Ni-5Co-10Cr-4W-5Al-1.5Ti-12Ta such that single crystal castings made therefrom have reduced anisotropy. It comprises: adding an effective amount of hafnium to the alloy composition.

Shah, D.M.; Duhl, D.N.

1990-04-10

275

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

NASA Astrophysics Data System (ADS)

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

Lahiri, T.; Majumder, T. Pal

2011-06-01

276

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

277

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

278

Design, optimization and realization of a ferroelectric liquid crystal based Mueller matrix ellipsometer using a genetic algorithm  

NASA Astrophysics Data System (ADS)

The design of broad-band polarimeters with high performance is challenging due to the wavelength dependence of optical components. An efficient Genetic Algorithm (GA) computer code was recently developed in order to design and re-optimize complete broadband Stokes polarimeters and Mueller matrix ellipsometers (MME). Our results are improvements of previous patented designs based on two and three ferroelectric liquid crystals (FLC), and are suited for broad-band hyperspectral imaging, or multichannel spectroscopy applications. We have realized and implemented one design using two FLCs and compare the spectral range and precision with previous designs.

Aas, Lars Martin S.; Skåre, Daniel G.; Ellingsen, Pål G.; Letnes, Paul Anton; Kildemo, Morten

2014-11-01

279

Control of the Anisotropic Phase Separation and the Electro-Optical Stability of Ferroelectric Liquid Crystal-Photopolymer Composites  

NASA Astrophysics Data System (ADS)

The criteria for controlling the anisotropic phase separation process in ferroelectric liquid crystal (FLC)-photopolymer mixtures are presented. Depending on the FLC composition and the irradiated intensity of the ultraviolet light, one of the polymer-dispersed, anisotropic phase separated (PS), and polymer-network structures is found to be energetically favored to form it from the FLC-photopolymer mixture. In contrast to a surface-stabilized FLC cell, no broken layers and defects are observed under an external mechanical or a thermal shock exerted on the PSFLC cell and thus the electro-optical stability is obtained.

Park, Jae-Hong; Lee, Won-Je; Kim, Jae-Hoon; Lee, Sin-Doo

2003-10-01

280

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

281

Molecular ferroelectrics: where electronics meet biology.  

PubMed

In the last several years, we have witnessed significant advances in molecular ferroelectrics, with the ferroelectric properties of molecular crystals approaching those of barium titanate. In addition, ferroelectricity has been observed in biological systems, filling an important missing link in bioelectric phenomena. In this perspective, we will present short historical notes on ferroelectrics, followed by an overview of the fundamentals of ferroelectricity. The latest developments in molecular ferroelectrics and biological ferroelectricity will then be highlighted, and their implications and potential applications will be discussed. We close by noting molecular ferroelectric as an exciting frontier between electronics and biology, and a number of challenges ahead are also described. PMID:24018952

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

2013-12-28

282

Molecular ferroelectrics: where electronics meet biology  

PubMed Central

In the last several years, we have witnessed significant advances in molecular ferroelectrics, with ferroelectric properties of molecular crystals approaching those of barium titanate. In addition, ferroelectricity has been observed in biological systems, filling an important missing link in bioelectric phenomena. In this perspective, we will present short historical notes on ferroelectrics, followed by overview on the fundamentals of ferroelectricity. Latest development in molecular ferroelectrics and biological ferroelectricity will then be highlighted, and their implications and potential applications will be discussed. We close by noting molecular ferroelectric as an exciting frontier between electronics and biology, and a number of challenges ahead are also noted. PMID:24018952

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

2013-01-01

283

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

284

Transverse acoustic actuation of Ni-Mn-Ga single crystals  

E-print Network

Two methods for the transverse acoustic actuation of {110}-cut Ni-Mn-Ga single crystals are discussed. In this actuation mode, crystals are used that have the {110}- type twinning planes parallel to the base of the crystal. ...

Simon, Jesse Matthew

2007-01-01

285

Nanoscale probing and photonic applications of ferroelectric domain walls  

NASA Astrophysics Data System (ADS)

Ferroelectrics are a versatile solid-state platform for a new generation of micro- and nanophotonic applications. Conventional integrated optics has often treated the phenomenon of ferroelectric domains and domain walls more as a nuisance rather than an asset. Ironically, domain walls can be immensely valuable in realizing a wide variety of new functionalities such as laser scanning, dynamic focusing, frequency conversion, beam shaping, waveguiding, high-speed modulation, and photonic crystal structures. All of these functions can be realized by shaping ferroelectric domain walls into arbitrary shapes on micro to nanoscale dimensions. Domain walls, however, have a mind of their own when it comes to shaping them. This thesis will focus on the fundamental domain switching characteristics under the uniform electrical fields, and local electromechanical response across the single ferroelectric domain wall in ferroelectric crystals lithium niobate, lithium tantalate and strontium barium niobate. The local electromechanical response across the single was modeled using finite element method to better understand the fundamentals of piezoelectric force microscopy in order to quantitatively interpret the measured material properties. The influence of stoichiometry on domain dynamics on macroscale and on local electromechanical properties on nanoscale was studied. The challenges in shaping ferroelectric domain are discussed and the examples of optical devices such as optical switch and optical beam deflector based on ferroelectric domain walls are presented.

Tian, Lili

286

SSME single-crystal turbine blade dynamics  

NASA Technical Reports Server (NTRS)

A study was performrd 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 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 base. Crystal axis orientation optimization indicated that the third mode interference will exist in any SC orientation.

Moss, Larry A.

1988-01-01

287

Shock Hugoniot of Single Crystal Copper  

SciTech Connect

The shock Hugoniot of single crystal copper is reported for stresses below 66 GPa. Symmetric impact experiments were used to measure the Hugoniots of three different crystal orientations of copper, [100], [110], [111]. The photonic doppler velocimetry (PDV) diagnostic was adapted into a very high precision time of arrival detector for these experiments. The measured Hugoniots along all three crystal directions were nearly identical to the experimental Hugoniot for polycrystalline Cu. The predicted orientation dependence of the Hugoniot from MD calculations was not observed. At the lowest stresses, the sound speed in Cu was extracted from the PDV data. The measured sound speeds are in agreement with values calculated from the elastic constants for Cu.

Chau, R; Stolken, J; Asoka-Kumar, P; Kumar, M; Holmes, N C

2009-08-28

288

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

289

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

NASA Astrophysics Data System (ADS)

Using our experimental data for ns pulsed second harmonic generation (SHG) by periodically poled stoichiometric LiTaO3 (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, ?1018 cm-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.; Hatano, Hideki; Saito, Norihito; Wada, Satoshi; Kitamura, Kenji

2013-11-01

290

Single crystal growth of SiC and electronic devices  

Microsoft Academic Search

Single crystal growth of silicon carbide (Sic) and application to electronic devices are reviewed. In the crystal growth, bulk and homoepitaxial growth are picked up, and crystal quality and electrical properties are described. For electronic devices, various device processes are argued. Power devices based on Sic are stressed in this review.Bulk single crystals of SiC can be grown by a

Akira Itoh; Hiroyuki Matsunami

1997-01-01

291

Dielectric, electro-optical, and photoluminescence characteristics of ferroelectric liquid crystals on a graphene-coated indium tin oxide substrate.  

PubMed

Multilayer graphene was deposited on indium tin oxide (ITO) -coated glass plates and characterized by suitable techniques. A liquid crystal sample cell was designed using graphene deposited ITO glass plates without any additional treatment for alignment. Ferroelectric liquid crystal (FLC) material was filled in the sample cell. The effect of multilayer graphene on the characteristics of FLC material was investigated. The extremely high relative permittivity of pristine graphene and charge transfer between graphene and FLC material were consequences of the enormous increase in relative permittivity for the graphene-FLC (GFLC) system as compared to pure FLC. The presence of multilayer graphene suppresses the ionic impurities, comprised in the FLC material at lower frequencies. The ionic charge annihilation mechanism might be responsible for the reduction of ionic impurities. The presence of graphene reduces the net ferroelectricity and results in a change in the spontaneous polarization of pure FLC. Rotational viscosity of the GFLC system also decreases due to the strong ?-? interaction between the FLC molecule and multilayer graphene. The photoluminescence of the GFLC system is blueshifted as compared to pure FLC, which is due to the coupling of energy released in the process of charge annihilation and photon emission. PMID:25215743

Singh, Dharmendra Pratap; Gupta, Swadesh Kumar; Vimal, Tripti; Manohar, Rajiv

2014-08-01

292

Domains in Ferroelectric Nanostructures  

NASA Astrophysics Data System (ADS)

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

Gregg, Marty

2010-03-01

293

Optimizing Scale Adhesion on Single Crystal Superalloys  

NASA Technical Reports Server (NTRS)

To improve scale adhesion, single crystal superalloys have been desulfurized to levels below 1 ppmw by hydrogen annealing. A transition to fully adherent behavior has been shown to occur at a sulfur level of about 0.2 ppmw, as demonstrated for PWA 1480, PWA 1484, and Rene N5 single crystal superalloys in 1100-1150 C cyclic oxidation tests up to 2000 h. Small additions of yttrium (15 ppmw) also have been effective in producing adhesion for sulfur contents of about 5 ppmw. Thus the critical Y/S ratio required for adhesion was on the order of 3-to-1 by weight (1-to-1 atomic), in agreement with values estimated from solubility products for yttrium sulfides. While hydrogen annealing greatly improved an undoped alloy, yielding <= 0.01 ppmw S, it also produced benefits for Y-doped alloys without measurably reducing the sulfur content.

Smialek, James L.; Pint, Bruce A.

2000-01-01

294

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

295

Ferroelectric domain engineering using atomic force microscopy tip arrays in the domain breakdown regime  

Microsoft Academic Search

One of the main obstacles to ultrahigh-density scanning probe ferroelectric-based devices is the writing speed of the device when using a single tip. We report here on the application of atomic force microscopy tip arrays for nanodomain engineering in ferroelectric crystals under the domain breakdown conditions. Using a multiple-tip array, it is shown that domain writing in 200-mum-thick RbTiOPO4 crystals

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

2005-01-01

296

Single crystal growth of organic photoconductors: phthalocyanine  

Microsoft Academic Search

An effective method of growing single crystals of organic photoconductors such as phthalocyanine in the presence of doping\\u000a impurity such as iodine by vacuum sublimation is discussed in this paper. This method is very useful especially when an organic\\u000a material does not have a melting point but decomposes above a particular temperature. So far, doping has been done by exposing

Francis P Xavier; George J Goldsmith

1996-01-01

297

New application of terahertz time-domain spectrometry (THz-TDS) to the phonon-polariton observation on ferroelectric crystals.  

PubMed

A new instrument for terahertz time-domain spectroscopy (THz-TDS) has been developed. It consists of a composite THz-TDS system and a high throughput (Martin-Puplett) interferometer. The instrument is for use in the qualitative study of optoelectronic constants of materials. The spectral transmission intensity and phase shift related to phonon-polariton dispersion have been measured between 100 cm(-1) and 3 cm(-1) on ferroelectric crystals of industrial interest. These include bismuth titanate Bi4Ti3O12 (a key material for FeRAM), lithium niobate LiNbO3 (a typical nonlinear crystal for parametric oscillator applications) and lithium heptagermanate Li2Ge7O15 for surface elastic wave filter applications. The complex dielectric constants are well reproduced by the phonon-polariton dispersion relation based on the Kurosawa formula. The instrument details and phonon-polariton dispersion results are described. PMID:12452567

Nishizawa, Seizi; Tsumura, Naoki; Kitahara, Hideaki; Wada Takeda, Mitsuo; Kojima, Seiji

2002-11-01

298

Experimental demonstration of hybrid improper ferroelectricity and the presence of abundant charged walls in (Ca,Sr)3Ti2O7 crystals  

NASA Astrophysics Data System (ADS)

On the basis of successful first-principles predictions of new functional ferroelectric materials, a number of new ferroelectrics have been experimentally discovered. Using trilinear coupling of two types of octahedron rotation, hybrid improper ferroelectricity has been theoretically predicted in ordered perovskites and the Ruddlesden–Popper compounds (Ca3Ti2O7, Ca3Mn2O7 and (Ca/Sr/Ba)3(Sn/Zr/Ge)2O7). However, the ferroelectricity of these compounds has never been experimentally confirmed and even their polar nature has been under debate. Here we provide the first experimental demonstration of room-temperature switchable polarization in bulk crystals of Ca3Ti2O7, as well as Sr-doped Ca3Ti2O7. Furthermore, (Ca, Sr)3Ti2O7 is found to exhibit an intriguing ferroelectric domain structure resulting from orthorhombic twins and (switchable) planar polarization. The planar domain structure accompanies abundant charged domain walls with conducting head-to-head and insulating tail-to-tail configurations, which exhibit a conduction difference of two orders of magnitude. These discoveries provide new research opportunities, not only for new stable ferroelectrics of Ruddlesden–Popper compounds, but also for meandering conducting domain walls formed by planar polarization.

Oh, Yoon Seok; Luo, Xuan; Huang, Fei-Ting; Wang, Yazhong; Cheong, Sang-Wook

2015-04-01

299

Experimental demonstration of hybrid improper ferroelectricity and the presence of abundant charged walls in (Ca,Sr)3Ti2O7 crystals.  

PubMed

On the basis of successful first-principles predictions of new functional ferroelectric materials, a number of new ferroelectrics have been experimentally discovered. Using trilinear coupling of two types of octahedron rotation, hybrid improper ferroelectricity has been theoretically predicted in ordered perovskites and the Ruddlesden-Popper compounds (Ca3Ti2O7, Ca3Mn2O7 and (Ca/Sr/Ba)3(Sn/Zr/Ge)2O7). However, the ferroelectricity of these compounds has never been experimentally confirmed and even their polar nature has been under debate. Here we provide the first experimental demonstration of room-temperature switchable polarization in bulk crystals of Ca3Ti2O7, as well as Sr-doped Ca3Ti2O7. Furthermore, (Ca, Sr)3Ti2O7 is found to exhibit an intriguing ferroelectric domain structure resulting from orthorhombic twins and (switchable) planar polarization. The planar domain structure accompanies abundant charged domain walls with conducting head-to-head and insulating tail-to-tail configurations, which exhibit a conduction difference of two orders of magnitude. These discoveries provide new research opportunities, not only for new stable ferroelectrics of Ruddlesden-Popper compounds, but also for meandering conducting domain walls formed by planar polarization. PMID:25581628

Oh, Yoon Seok; Luo, Xuan; Huang, Fei-Ting; Wang, Yazhong; Cheong, Sang-Wook

2015-04-01

300

A nanoporous two-dimensional polymer by single-crystal-to-single-crystal photopolymerization  

NASA Astrophysics Data System (ADS)

In contrast to the wide number and variety of available synthetic routes to conventional linear polymers, the synthesis of two-dimensional polymers and unambiguous proof of their structure remains a challenge. Two-dimensional polymers—single-layered polymers that form a tiling network in exactly two dimensions—have potential for use in nanoporous membranes and other applications. Here, we report the preparation of a fluorinated hydrocarbon two-dimensional polymer that can be exfoliated into single sheets, and its characterization by high-resolution single-crystal X-ray diffraction analysis. The procedure involves three steps: preorganization in a lamellar crystal of a rigid monomer bearing three photoreactive arms, photopolymerization of the crystalline monomers by [4?+?4] cycloaddition, and isolation of individual two-dimensional polymer sheets. This polymer is a molecularly thin (~1?nm) material that combines precisely defined monodisperse pores of ~9?Å with a high pore density of 3.3?×?1013 pores?cm-2. Atomic-resolution single-crystal X-ray structures of the monomer, an intermediate dimer and the final crystalline two-dimensional polymer were obtained and prove the single-crystal-to-single-crystal nature and molecular precision of the two-dimensional photopolymerization.

Kissel, Patrick; Murray, Daniel J.; Wulftange, William J.; Catalano, Vincent J.; King, Benjamin T.

2014-09-01

301

Polarized Raman study on phase transitions in 0.24Pb(In1/2Nb1/2)O30.43Pb(Mg1/3Nb2/3)O30.33PbTiO3 single crystal  

E-print Network

spectroscopy was performed to investigate the local lattice structure and phase transi- tions of unpoled 0.24Pb spectroscopy is a convenient microprobe to study the local lattice structure and phase transitions single crystals. The giant electromechanical response of relaxor-based ferroelectric single crystals has

Cao, Wenwu

302

A spontaneous single-crystal-to-single-crystal polymorphic transition involving major packing changes.  

PubMed

4,6-O-Benzylidene-?-d-galactosyl azide crystallizes into two morphologically distinct polymorphs depending on the solvent. While the ? form appeared as thick rods and crystallized in P21 space group (monoclinic) with a single molecule in the asymmetric unit, the ? form appeared as thin fibers and crystallized in P1 space group (triclinic) with six molecules in the asymmetric unit. Both the polymorphs appeared to melt at the same temperature. Differential scanning calorimetry analysis revealed that polymorph ? irreversibly undergoes endothermic transition to polymorph ? much before its melting point, which accounts for their apparently same melting points. Variable temperature powder X-ray diffraction (PXRD) experiments provided additional proof for the polymorphic transition. Single-crystal XRD analyses revealed that ? to ? transition occurs in a single-crystal-to-single-crystal (SCSC) fashion not only under thermal activation but also spontaneously at room temperature. The SCSC nature of this transition is surprising in light of the large structural differences between these polymorphs. Polarized light microscopy experiments not only proved the SCSC nature of the transition but also suggested nucleation and growth mechanism for the transition. PMID:25585170

Krishnan, Baiju P; Sureshan, Kana M

2015-02-01

303

Laser-induced nondestructive patterning of a thin ferroelectric polymer film with controlled crystals using Ge8Sb2Te11 alloy layer for nonvolatile memory.  

PubMed

We present a simple but robust nondestructive process for fabricating micropatterns of thin ferroelectric polymer films with controlled crystals. Our method is based on utilization of localized heat arising from thin Ge(8)Sb(2)Te(11) (GST) alloy layer upon exposure of 650 nm laser. The heat was generated on GST layer within a few hundred of nanosecond exposure and subsequently transferred to a thin poly(vinylidene fluoride-co-trifluoroethylene) film deposited on GST layer. By controlling exposure time and power of the scanned laser, ferroelectric patterns of one or two microns in size are fabricated with various shape. In the micropatterned regions, ferroelectric polymer crystals were efficiently controlled in both degree of the crystallinity and the molecular orientations. Nonvolatile memory devices with laser scanned ferroelectric polymer layers exhibited excellent device performance of large remnant polarization, ON/OFF current ratio and data retention. The results are comparable with devices containing ferroelectric films thermally annealed at least for 2 h, making our process extremely efficient for saving time. Furthermore, our approach can be conveniently combined with a number of other functional organic materials for the future electronic applications. PMID:25127181

Bae, Insung; Kim, Richard Hahnkee; Hwang, Sun Kak; Kang, Seok Ju; Park, Cheolmin

2014-09-10

304

Experimental evidence of soft mode in the smectic C(?)(*) phase of chiral ferroelectric liquid crystals.  

PubMed

Dielectric properties of chiral smectic liquid crystals characterised by the occurrence of the C(?)(*) phase were investigated in the frequency range 10 Hz-1 MHz. In the range of existence of this phase the observed relaxation spectrum is composed of two kinds of mode, and not of a single one, as commonly thought. Phase modes of the Goldstone type coexist in it with an amplitude type soft mode. The share of the soft mode in the global value of electric permittivity ? can be dominant and attain 90%. A possible explanation for that effect is sought in the similarity to chiral phases of the de Vries type. PMID:25249040

Hoffmann, Jerzy; Nowicka, Kamila; Kuczy?ski, Wojciech; Bielejewska, Natalia

2014-11-14

305

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

PubMed

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

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

2015-02-17

306

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

Microsoft Academic Search

Summary 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

J. CANET-FERRER; L. MARTÍN-CARRÓN; J. MARTÍNEZ-PASTOR; J. L. VALDÉS; A. PEÑA; J. J. CARVAJAL; F. DIAZ

2007-01-01

307

Molecular theory of proper ferroelectricity in bent-core liquid crystals.  

PubMed

Antiferro- and ferro-electric ordering has been discovered in orthogonal smectic phases composed of nonchiral bent-core molecules. These systems are the only proper fluid ferroelectrics confirmed experimentally so far. We consider a molecular theory of proper ferroelectric ordering in isotropic, nematic and smectic A phases and conclude that the delicate balance between the tendencies for local parallel and antiparallel ordering of molecular electric and steric dipoles is strongly shifted in restricted geometries. This is a reason why dipolar ordering is more likely to occur within a smectic layer. We derive model interaction potentials for polar bent-core molecules and present the results of the mean-field theory of ferroelectric ordering in the orthogonal smectic phase taking into account also the molecular biaxiality. Order parameter profiles have been calculated numerically and phase diagrams are presented which enable one to analyze the relative importance of dipole-dipole interaction and intermolecular attraction modulated by polar bent-core molecular shape. PMID:25209336

Osipov, M A; Pajak, G

2014-09-01

308

Computational modeling of domain wall interactions with dislocations in ferroelectric crystals  

E-print Network

-linear dielectric, piezoelectric and elastic properties of ferroelectrics. In this context, defects such as oxygen are computed. The presented numer- ical results are compared with the findings reported for charged defects and it is shown that non-charged defects, such as dislocations, can also interact strongly with domain walls

309

Ferroelectric domain inversion: The role of humidity  

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

310

Ferroelectric Behavior of Thiourea  

Microsoft Academic Search

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

G. J. Goldsmith; J. G. White

1959-01-01

311

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

312

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

313

X-Ray Characterization and Domain Structure of High-Quality SrBi2Ta2O9 Single-Crystals Grown by Self-Flux Solution Method  

Microsoft Academic Search

High-quality SrBi2Ta2O9 single crystals were grown by self-flux solution method. According to x-ray topography the crystals with layered habitus and typical dimensions up to ? 7 × 5 × 0.05 mm show perfect (001)-orientation with the edges directed along [110] axes. The quality of the crystals was also confirmed by high-field measurements, which did not detect any ferroelectric hysteresis along

HARVEY AMORÍN; IGOR K. BDIKIN; VLADIMIR V. SHVARTSMAN; M. ELISABETE V. COSTA; ANDREI L. KHOLKIN

2004-01-01

314

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

315

Chemical vapor deposition of graphene single crystals.  

PubMed

As a two-dimensional (2D) sp(2)-bonded carbon allotrope, graphene has attracted enormous interest over the past decade due to its unique properties, such as ultrahigh electron mobility, uniform broadband optical absorption and high tensile strength. In the initial research, graphene was isolated from natural graphite, and limited to small sizes and low yields. Recently developed chemical vapor deposition (CVD) techniques have emerged as an important method for the scalable production of large-size and high-quality graphene for various applications. However, CVD-derived graphene is polycrystalline and demonstrates degraded properties induced by grain boundaries. Thus, the next critical step of graphene growth relies on the synthesis of large graphene single crystals. In this Account, we first discuss graphene grain boundaries and their influence on graphene's properties. Mechanical and electrical behaviors of CVD-derived polycrystalline graphene are greatly reduced when compared to that of exfoliated graphene. We then review four representative pathways of pretreating Cu substrates to make millimeter-sized monolayer graphene grains: electrochemical polishing and high-pressure annealing of Cu substrate, adding of additional Cu enclosures, melting and resolidfying Cu substrates, and oxygen-rich Cu substrates. Due to these pretreatments, the nucleation site density on Cu substrates is greatly reduced, resulting in hexagonal-shaped graphene grains that show increased grain domain size and comparable electrical properties as to exfoliated graphene. Also, the properties of graphene can be engineered by its shape, thickness and spatial structure. Thus, we further discuss recently developed methods of making graphene grains with special spatial structures, including snowflakes, six-lobed flowers, pyramids and hexagonal graphene onion rings. The fundamental growth mechanism and practical applications of these well-shaped graphene structures should be interesting topics and deserves more attention in the near future. Following that, recent efforts in fabricating large single-crystal monolayer graphene on other metal substrates, including Ni, Pt, and Ru, are also described. The differences in growth conditions reveal different growth mechanisms on these metals. Another key challenge for graphene growth is to make graphene single crystals on insulating substrates, such as h-BN, SiO2, and ceramic. The recently developed plasma-enhanced CVD method can be used to directly synthesize graphene single crystals on h-BN substrates and is described in this Account as well. To summarize, recent research in synthesizing millimeter-sized monolayer graphene grains with different pretreatments, graphene grain shapes, metal catalysts, and substrates is reviewed. Although great advancements have been achieved in CVD synthesis of graphene single crystals, potential challenges still exist, such as the growth of wafer-sized graphene single crystals to further facilitate the fabrication of graphene-based devices, as well as a deeper understanding of graphene growth mechanisms and growth dynamics in order to make graphene grains with precisely controlled thicknesses and spatial structures. PMID:24527957

Yan, Zheng; Peng, Zhiwei; Tour, James M

2014-04-15

316

A Neutron Study of the Structure and Lattice Dynamics of Single Crystal PZT  

NASA Astrophysics Data System (ADS)

The outstanding piezoelectric properties of PbZr1-xTixO3 (PZT) perovskite ceramics have long been exploited in numerous device applications, making PZT arguably the most technologically important ferroelectric material in use today. Efforts to understand the piezoelectric mechanism have inspired a plethora of structural studies spanning decades, but solving the PZT phase diagram has proven to be famously problematic because single crystals have not been available save for Zr- and Ti-rich compositions that lie very near the end members PbZrO3 and PbTiO3, where the piezoelectricity is weakest. Thus, whereas PZT has been the subject of thousands of powder and ceramic investigations, no consensus regarding the crystal structures of PZT exists. We report the first neutron diffraction study of single-crystal PZT with compositions x = 0.325 and 0.460 [1]. Our data refute the thesis that the ferroelectric phases of PZT within this composition range, all of which are highly piezoelectric, are purely monoclinic (Cc or Cm). The broadening of certain Bragg peaks can be interpreted in terms of coexisting rhombohedral and monoclinic domains, whereby monoclinic order is enhanced by Ti-doping. This is consistent with the theoretical proposal that the tendency to form macroscopic monoclinic phases facilitates the mechanism of polarization rotation by reducing the energy required to reorient the electric polarization. Dispersions of the lowest energy TO and TA phonon modes were measured on a single crystal of PZT with x = 0.325 in the paraelectric phase at 650 K [2]. The TO mode energy drops at small wave-vectors suggesting that it is a soft mode associated with the ferroelectric phase transition at 590 K. Evidence of a second soft-mode, corresponding to a phase transition at 370 K at the R-point, is provided based on the redistribution of spectral weight as a function of temperature. [4pt] [1] D. Phelan et al., Phys. Rev. Lett. 105, 207601 (2010). [0pt] [2] D. Phelan et al., submitted.

Gehring, Peter

2011-03-01

317

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

318

Growth rate study of canavalin single crystals  

NASA Technical Reports Server (NTRS)

The dependence on supersaturation of the growth rate of single crystals of the protein canavalin is studied. In the supersaturation ranges studied, the rate-limiting step for growth is best described by a screw dislocation mechanism associated with interface attachment kinetics. Using a ln-ln plot, the growth-rate data is found to fit a predictive relationship of the form G = 0.012 x the supersaturation to the 6.66, which, together with the solubility curves, allows the growth rate to be estimated under a variety of conditions.

Demattei, R. C.; Feigelson, R. S.

1989-01-01

319

Triplet exciton dynamics in rubrene single crystals  

NASA Astrophysics Data System (ADS)

The decay of the photoluminescence excited in rubrene single crystals by picosecond pulses is measured over 7 orders of magnitude and more than 4 time decades. We identify the typical decay dynamics due to triplet-triplet interaction. We show that singlet exciton fission and triplet fusion quantum yields in rubrene are both very large, and we directly determine a triplet exciton lifetime of 100±20 ?s, which explains the delayed buildup of a large photocurrent that has been reported earlier for low excitation densities.

Ryasnyanskiy, Aleksandr; Biaggio, Ivan

2011-11-01

320

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

321

Crystal Structure of Deuterated Dicalcium Strontium Propionate, Ca2Sr(C2D5CO2)6 in the Paraelectric and Ferroelectric Phases  

NASA Astrophysics Data System (ADS)

The absolute crystal structure of the deuterated dicalcium strontium propionate (DDSP) has been determined by the X-ray diffraction with a four-circle automatic diffractometer at three temperatures in each of the paraelectric and ferroelectric phases. The space group is determined to be D44-P41212 or D48-P43212 in the paraelectric phase with the R-factors less than 3% and to be C42-P41 or C44-P43 in the ferroelectric phase with the R-factors less than 5%. The molecular structure of the deuterated propionates is also elucidated and compared with that of the nondeuterated one. The comparison confirms the structure quite similar to each other, indicating no isotope effect on the molecular structure. The disordered arrangement of the propionate molecules on (001) plane is observed in the ferroelectric phase similarly to the nondeuterated DSP.

Machida, Mitsuo; Yagi, Toshirou

1988-04-01

322

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

323

Electron Optical Studies of Barium Titanate Single Crystal Films  

Microsoft Academic Search

Thin single crystal films of barium titanate prepared by chemical thinning of single crystal plates are studied by transmission electron microscopy and electron diffraction. The films as thin as 1000 Å are found to have the same lattice parameters as the bulk crystals, giving no evidence for the existence of the anomalous surface layer proposed by Känzig et al. The

Michiyoshi Tanaka; Goro Honjo

1964-01-01

324

Cutting fluid study for single crystal silicon  

SciTech Connect

An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions showed promise for further research, as they yielded the best combination of reduced tool wear and good surface finish in the ductile regime. Negative rake tools were verified to improve the surface finish, but the negative rake tools used in the experiments also showed much higher wear than conventional 0{degree} rake tools. Effects of crystallographic orientation on SPDT, such as star patterns of fracture damage forming near the center of the samples, were observed to decrease with lower feedrates. Silicon chips were observed and photographed, indicative of a ductile materials removal process.

Chargin, D.

1998-05-05

325

Fabrication of crystals from single metal atoms  

NASA Astrophysics Data System (ADS)

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, 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.

2014-05-01

326

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. 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

327

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

328

Orientational Kerr effect and phase modulation of light in deformed-helix ferroelectric liquid crystals with subwavelength pitch.  

PubMed

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. PMID:23767555

Pozhidaev, Evgeny P; Kiselev, Alexei D; Srivastava, Abhishek Kumar; Chigrinov, Vladimir G; Kwok, Hoi-Sing; Minchenko, Maxim V

2013-05-01

329

Polarization gratings in the short-pitch approximation: electro-optics of deformed helix ferroelectric liquid crystals  

E-print Network

Electro-optical properties of deformed helix ferroelectric liquid crystal (DHFLC) cells are studied by using a general theoretical approach to polarization gratings in which the transmission and reflection matrices of diffraction orders are explicitly related to the evolution operator of equations for the Floquet harmonics. In the short-pitch approximation, a DHFLC cell is shown to be optically equivalent to a uniformly anisotropic biaxial layer where one of the optical axes is normal to the substrates. For in-plane anisotropy, orientation of the optical axes and birefringence are both determined by the voltage applied across the cell and represent the parameters that govern the transmittance of normally incident light passing through crossed polarizers. We calculate the transmittance as a function of the applied voltage and compare the computed curves with the experimental data. The theoretical and experimental results are found to be in good agreement.

Alexei D. Kiselev; Eugene P. Pozhidaev; Vladimir G. Chigrinov; Hoi-Sing Kwok

2010-11-19

330

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

PubMed

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

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

2013-05-01

331

Irradiation growth of zirconium single crystals  

NASA Astrophysics Data System (ADS)

Irradiation growth of zirconium single crystals has been studied during neutron irradiation at 353 K and 553 K at fluences up to 2× 10 25 n/m 2. The results may be summarized as follows: (a) there was an expansion parallel to the a-axis and a c-axis contraction; (b) the growth strains were small (~10 -4), (c) growth saturated at fluences less than ~5× 10 24 n/m 2, (d) the growth behaviour was only weakly dependent on temperature for the range studied, (e) there was a calculated volume increase of the same order as the growth strain, and (f) single crystals prepared from stock of iodide and zone-refined purity showed similar growth behaviour at 553 K. The a-axis expansion is attributed to the annihilation of an excess of interstitials at < a>-type dislocations and interstitial loops. The c-axis contraction may be caused by: (1) elastic relaxation around vacancies or small vacancy clusters, (2) non-linear elastic effects at the dislocation cores of small < a>-type loops, or (3) sub-microscopic vacancy loops with < c>-component Burgers vectors. Comparison with data from polycrystalline zirconium confirms that grain boundaries can play an important role in the irradiation growth of zirconium.

Carpenter, G. J. C.; Murgatroyd, R. A.; Rogerson, A.; Watters, J. F.

1981-10-01

332

Orientation dependence of electrocaloric effects in Pb(Zn1/3Nb2/3)-PbTiO3 single crystals  

NASA Astrophysics Data System (ADS)

Electrocaloric effects of (001), (011) and (111) oriented single crystals have been thoroughly investigated to study the ferroelectric-ferroelectric (FE-FE) phase transition induced isothermal entropy changes in 0.94Pb(Zn1/3Nb2/3)O3-0.06PbTiO3 (PZN-PT) material. The results showed that the PZN-PT crystals oriented in (111) direction exhibit ˜ 38% higher electrocaloric cooling values near lower critical phase transitions from rhombohedral (R) to tetragonal (T) phases in PZN-PT crystals, compared to those oriented in (011) direction. Though (111) samples display higher cooling values, (011) samples showed broader cooling curves due to their easily switchable characteristics between R and T phases.

Chukka, Rami; Vandrangi, Suresh; Chen, Zuhuang; You, Lu; Wang, Junling; Yang, Ping; Chen, Lang

2013-07-01

333

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

334

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

335

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

336

Wavelength dependence of refractive index in lead-free Na0.5Bi0.5TiO3-BaTiO3 single crystals  

NASA Astrophysics Data System (ADS)

Refractive indices of (1-x)Na0.5Bi0.5TiO3-xBaTiO3 (NBT-xBT, x = 0, 0.06 and 0.08) single crystals were measured at room temperature after poled along pseudo-cubic crystallographic direction [0 0 1]. The refractive indices decrease dramatically when the wavelength increases for all crystals. At the same wavelength, refractive indices of NBT-xBT single crystals decrease with increasing BT content. Sellmeier dispersion equations were obtained by least square fitting, which can be used to calculate the refractive indices in low absorption wavelength range. Parameters connected to the energy band structure were determined by fitting single-oscillator dispersion equation. Similar to most oxygen-octahedral ferroelectrics, NBT-xBT crystals have the same dispersion behavior described by the refractive-index dispersion parameter. Dispersion energies take on covalent crystal values.

He, Chongjun; Yi, Xiujie; Wu, Tong; Wang, Jiming; Zhu, Kongjun; Liu, Youwen

2014-10-01

337

Growing single crystals in silica gel  

NASA Technical Reports Server (NTRS)

Two types of chemical reactions for crystal growing are discussed. The first is a metathetical reaction to produce calcium tartrate tetrahydrate crystals, the second is a decomplexation reaction to produce cuprous chloride crystals.

Rubin, B.

1970-01-01

338

Experimental dynamic metamorphism of mineral single crystals  

USGS Publications Warehouse

This paper is a review of some of the rich and varied interactions between non-hydrostatic stress and phase transformations or mineral reactions, drawn mainly from results of experiments done on mineral single crystals in our laboratory or our co-authors. The state of stress and inelastic deformation can enter explicitly into the equilibrium phase relations and kinetics of mineral reactions. Alternatively, phase transformations can have prominent effects on theology and on the nature of inelastic deformation. Our examples represent five types of structural phase changes, each of which is distinguished by particular mechanical effects. In increasing structural complexity, these include: (1) displacive phase transformations involving no bond-breaking, which may produce anomalous brittle behavior. A primary example is the a-?? quartz transition which shows anomalously low fracture strength and tertiary creep behavior near the transition temperature; (2) martensitic-like transformations involving transformation strains dominated by shear deformation. Examples include the orthoenstatite ??? clinoenstatite and w u ??rtzite ??? sphalerite transformations; (3) coherent exsolution or precipitation of a mineral solute from a supersaturated solid-solution, with anisotropy of precipitation and creep rates produced under nonhydrostatic stress. Examples include exsolution of corundum from MgO ?? nAl2O3 spinels and Ca-clinopyroxene from orthopyroxene; (4) order-disorder transformations that are believed to cause anomalous plastic yield strengthening, such as MgO - nAl2O3 spinels; and (5) near-surface devolatilization of hydrous silicate single-crystals that produces a fundamental brittleness thought to be connected with dehydration at microcracks at temperatures well below nominal macroscopic dehydration temperatures. As none of these interactions between single-crystal phase transformations and non-hydrostatic stress is understood in detail, this paper serves as a challenge to field structural geologists to test whether interactions of these types occur in nature, and to theoreticians to reach a deeper understanding of the complex relations between phase transformations, the local state of stress and associated deformation and deformation rates. ?? 1993.

Kirby, S.H.; Stern, L.A.

1993-01-01

339

Experimental dynamic metamorphism of mineral single crystals  

NASA Astrophysics Data System (ADS)

This paper is a review of some of the rich and varied interactions between non-hydrostatic stress and phase transformations or mineral reactions, drawn mainly from results of experiments done on mineral single crystals in our laboratory or our co-authors. The state of stress and inelastic deformation can enter explicitly into the equilibrium phase relations and kinetics of mineral reactions. Alternatively, phase transformations can have prominent effects on theology and on the nature of inelastic deformation. Our examples represent five types of structural phase changes, each of which is distinguished by particular mechanical effects. In increasing structural complexity, these include: (1) displacive phase transformations involving no bond-breaking, which may produce anomalous brittle behavior. A primary example is the a- ? quartz transition which shows anomalously low fracture strength and tertiary creep behavior near the transition temperature; (2) martensitic-like transformations involving transformation strains dominated by shear deformation. Examples include the orthoenstatite ? clinoenstatite and w ürtzite ? sphalerite transformations; (3) coherent exsolution or precipitation of a mineral solute from a supersaturated solid-solution, with anisotropy of precipitation and creep rates produced under nonhydrostatic stress. Examples include exsolution of corundum from MgO · nAl 2O 3 spinels and Ca-clinopyroxene from orthopyroxene; (4) order-disorder transformations that are believed to cause anomalous plastic yield strengthening, such as MgO - nAl2O3 spinels; and (5) near-surface devolatilization of hydrous silicate single-crystals that produces a fundamental brittleness thought to be connected with dehydration at microcracks at temperatures well below nominal macroscopic dehydration temperatures. As none of these interactions between single-crystal phase transformations and non-hydrostatic stress is understood in detail, this paper serves as a challenge to field structural geologists to test whether interactions of these types occur in nature, and to theoreticians to reach a deeper understanding of the complex relations between phase transformations, the local state of stress and associated deformation and deformation rates.

Kirby, Stephen H.; Stern, Laura A.

1993-09-01

340

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. PMID:24145958

Masuno, Atsunobu; Moriyoshi, Chikako; Mizoguchi, Teruyasu; Okajima, Toshihiro; Kuroiwa, Yoshihiro; Arai, Yasutomo; Yu, Jianding; Inoue, Hiroyuki; Watanabe, Yasuhiro

2013-01-01

341

Mechanical properties of single crystal YAg  

SciTech Connect

YAg, a rare earth-precious metal 'line compound', is one member of the family of B2 rare earth intermetallic compounds that exhibit high ductilities. Tensile tests of polycrystalline YAg specimens have produced elongations as high as 27% before failure. In the present work, single crystal specimens of YAg with the B2, CsCl-type crystal structure were tensile tested at room temperature. Specimens with a tensile axis orientation of [0 1 1-bar] displayed slip lines on the specimen faces corresponding to slip on the {l_brace}1 1 0{r_brace}<0 1 0> with a critical resolved shear stress of 13 MPa. A specimen with a tensile axis orientation of [1 0 0] showed no slip lines and began to crack at a stress of 300 MPa. The test specimens also displayed some slip lines whose position corresponded to slip on the {l_brace}1 0 0{r_brace}<0 1 0>; these slip lines were found near intersections of {l_brace}1 1 0{r_brace}<0 1 0> slip lines, which suggests that the {l_brace}1 0 0{r_brace}<0 1 0> may be a secondary slip system in YAg. Transmission electron microscope (TEM) examination of the crystals was performed after tensile testing and the dislocations observed were analyzed by g {center_dot} b=0 out of contrast analysis. This TEM analysis indicated that the predominant Burgers vector for the dislocations present was <1 1 1> with some <0 1 1> dislocations also being observed. This finding is inconsistent with the <0 1 0> slip direction determined by slip line analysis, and possible explanations for this surprising finding are presented.

Russell, A.M.; Zhang, Z.; Lograsso, T.A.; Lo, C.C.H.; Pecharsky, A.O.; Morris, J.R.; Ye, Y.; Gschneidner, K.A.; Slager, A.J

2004-08-02

342

Investigation of ferroelectric materials with scanning microwave microscope  

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

343

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

344

Dynamic characteristics of single crystal SSME blades  

NASA Technical Reports Server (NTRS)

The Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) blades are currently manufactured using a directionally solidified (DS) material, MAR-M-246+Hf. However, a necessity to reduce the occurrence of fatigue cracking within the DS blades has lead to an interest in the use of a single crystal (SC) material, PWA-1480. A study was initiated to determine the dynamic characteristics of the HPFTP blades made of SC material and find possible critical engine order excitations. This study examined both the first and second stage drive turbine blades of the HPFTP. The dynamic characterization was done analytically as well as experimentally. The analytical study examined the SC first stage HPFTP blade dynamic characteristics under typical operating conditions. The blades were analyzed using MSC/NASTRAN and a finite element model. Two operating conditions, 27500 RPM and 35000 RPM, were investigated.

Moss, L. A.; Smith, T. E.

1987-01-01

345

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

346

Thermal debracketing of single crystal sapphire brackets.  

PubMed

Because of their optical clarity, single crystal sapphire brackets provide an esthetic advantage over many other types of orthodontic brackets. However, debonding of these brackets has caused iatrogenic damage to enamel. Thermal debonding has been proposed for use in removing sapphire brackets without causing damage to teeth. This study determined the temperature required at the enamel/resin interface to thermally debond sapphire brackets from etched bovine enamel using 23 different commercially available orthodontic resins and one experimental product. The results indicate a wide range of debonding temperatures for the various resins. As a group, the powder-liquid materials had a statistically lower debonding temperature than the two-paste, the no-mix products, or the light-cured materials, for which the temperatures were all similar. This paper presents relative information a clinician can use in selecting an orthodontic bonding resin to minimize thermal damage to the teeth while debonding sapphire brackets. PMID:1554162

Rueggeberg, F A; Lockwood, P E

1992-01-01

347

Low-cobalt single crystal Rene 150  

NASA Technical Reports Server (NTRS)

The effects of cobalt content on a single crystal version of the advanced, high gamma prime content turbine airfoil alloy Rene 150 were investigated. Cobalt contents under investigation include 12 wt.% (composition level of Rene 150), 6 wt.%, and 0 wt.%. Preliminary test results are presented and compared with the properties of standard DS Rene 150. DTA results indicate that the liquidus goes through a maximum of about 1435 C near 6 wt.% Co. The solidus remains essentially constant at 1390 C with decreasing Co content. The gamma prime solvus appears to go through a minimum of about 1235 C near 6 wt.% Co content. Preliminary as-cast tensile and stress rupture results are presented along with heat treat schedules and future test plans.

Scheuermann, C. M.

1982-01-01

348

Electrical switching in cadmium boracite single crystals  

NASA Astrophysics Data System (ADS)

Cadmium boracite single crystals at high temperatures ( 300 C) were found to exhibit a reversible electric field-induced transition between a highly insulative and a conductive state. The switching threshold is smaller than a few volts for an electrode spacing of a few tenth of a millimeter corresponding to an electric field of 100 to 1000 V/cm. This is much smaller than the dielectric break-down field for an insulator such as boracite. The insulative state reappears after voltage removal. A pulse technique revealed two different types of switching. Unstable switching occurs when the pulse voltage slightly exceeds the switching threshold and is characterized by a pre-switching delay and also a residual current after voltage pulse removal. A stable type of switching occurs when the voltage becomes sufficiently high. Possible device applications of this switching phenomenon are discussed.

Takahashi, T.; Yamada, O.

349

Electrical switching in cadmium boracite single crystals  

NASA Technical Reports Server (NTRS)

Cadmium boracite single crystals at high temperatures ( 300 C) were found to exhibit a reversible electric field-induced transition between a highly insulative and a conductive state. The switching threshold is smaller than a few volts for an electrode spacing of a few tenth of a millimeter corresponding to an electric field of 100 to 1000 V/cm. This is much smaller than the dielectric break-down field for an insulator such as boracite. The insulative state reappears after voltage removal. A pulse technique revealed two different types of switching. Unstable switching occurs when the pulse voltage slightly exceeds the switching threshold and is characterized by a pre-switching delay and also a residual current after voltage pulse removal. A stable type of switching occurs when the voltage becomes sufficiently high. Possible device applications of this switching phenomenon are discussed.

Takahashi, T.; Yamada, O.

1981-01-01

350

Rainbow Radiating Single-Crystal Ag Nanowire Nanoantenna Taejoon Kang,  

E-print Network

Rainbow Radiating Single-Crystal Ag Nanowire Nanoantenna Taejoon Kang, Wonjun Choi, Ilsun Yoon rainbow antenna radiation in the Fresnel region. Detailed antenna radiation properties, such as radiating

Kim, Bongsoo

351

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

PubMed

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

Gallagher, John; Lynch, Christopher; Tian, Jian

2014-12-01

352

Free space adaptive optical interconnect at 1.25 Gb\\/s, with beam steering using a ferroelectric liquid-crystal SLM  

Microsoft Academic Search

A free space adaptive optical interconnect is reported, in which an optically modulated channel from a vertical-cavity surface-emitting laser at 1.25 Gb\\/s is steered using reconfigurable binary phase gratings displayed on a ferroelectric liquid crystal on silicon (LCOS) spatial light modulator (SLM), to correct for misalignment. The optical system, and addressing scheme to maintain a transparent optical path, is described.

Charley J. Henderson; Diego Gil Leyva; Timothy D. Wilkinson

2006-01-01

353

New Fluorinated Terphenyl Isothiocyanate Liquid Crystal Single Compounds and Mixtures  

E-print Network

New Fluorinated Terphenyl Isothiocyanate Liquid Crystal Single Compounds and Mixtures Amanda Parish fluorinated NCS terphenyl single compounds and mixtures based solely on laterally fluorinated aromatic rigid) alignment interfaces [14]. The high melting temperature can be combated through the lateral fluorination

Wu, Shin-Tson

354

Thermally Triggered Solid-State Single-Crystal-to-Single-Crystal Structural Transformation Accompanies Property Changes.  

PubMed

The 1D complex [(CuL0.5 H2 O)?H2 O]n (1) (H4 L=2,2'-bipyridine-3,3',6,6'-tetracarboxylic acid) undergoes an irreversible thermally triggered single-crystal-to-single-crystal (SCSC) transformation to produce the 3D anhydrous complex [CuL0.5 ]n (2). This SCSC structural transformation was confirmed by single-crystal X-ray diffraction analysis, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD) patterns, variable-temperature powder X-ray diffraction (VT-PXRD) patterns, and IR spectroscopy. Structural analyses reveal that in complex 2, though the initial 1D chain is still retained as in complex 1, accompanied with the Cu-bound H2 O removed and new O(carboxyl)?Cu bond forming, the coordination geometries around the Cu(II) ions vary from a distorted trigonal bipyramid to a distorted square pyramid. With the drastic structural transition, significant property changes are observed. Magnetic analyses show prominent changes from antiferromagnetism to weak ferromagnetism due to the new formed Cu1-O-C-O-Cu4 bridge. The catalytic results demonstrate that, even though both solid-state materials present high catalytic activity for the synthesis of 2-imidazolines derivatives and can be reused, the activation temperature of complex 1 is higher than that of complex 2. In addition, a possible pathway for the SCSC structural transformations is proposed. PMID:25663637

Li, Quan-Quan; Ren, Chun-Yan; Huang, Yang-Yang; Li, Jian-Li; Liu, Ping; Liu, Bin; Liu, Yang; Wang, Yao-Yu

2015-03-16

355

Single crystal growth and characterization of the nonlinear optical crystal l-arginine hydrofluoride  

Microsoft Academic Search

In this communication, single crystal growth of the nonlinear optical crystal l-arginine hydrofluoride C6H14N4O2. HF (here after abbreviated as LAHF) of dimensions up to 20×15×3mm3 is reported. Crystals have been grown by the temperature lowering method and also by slow evaporation method at constant temperature 30°C from its aqueous solution with pH at 2.2. As-grown single crystals were then characterized

Tanusri Pal; Tanusree Kar

2002-01-01

356

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

E-print Network

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

Cao, Wenwu

357

Flux growth of high-homogeneity PMN PT single crystals and their property characterization  

NASA Astrophysics Data System (ADS)

The effects of B 2O 3 addition to the PbO flux for growing Pb(Mg 1/3Nb 2/3)O 3- yPbTiO 3 (PMN- yPT) single crystals, where y=0.28-0.34, have been investigated. The results show that the amount of B 2O 3 in the PbO flux is crucial in altering the chemistry of the high-temperature solution and determining the quality of the ensuing crystals. With optimum amounts of B 2O 3 in the PbO flux, inclusion-free high-uniformity PMN-PT single crystals have been successfully grown. The typical size of the crystals obtained is about 25-35 mm in edge length. Ferroelectric transition temperature, Tc, distribution measurements reveal that the bottom half of the grown crystals, i.e., the portion adjacent to the nucleation site, shows good compositional uniformity, with ?T?±3.0 °C. The PT content of this uniform composition portion is typically 2 mol% smaller than that in the initial charge, indicating that the composition of the actual flux is PbO+ z(B 2O 3+ ?PT), where ? depends on the amount of B 2O 3 in the flux. Electrical poling studies reveal that while crystals of PMN-(31-32)%PT ( T=140-145 °C) composition are susceptible to overpoling, both PMN-28%PT ( T=125 °C) and PMN-30%PT ( T=135 °C) crystals show good resistance to overpoling. Of the latter two, PMN-30%PT exhibits better dielectric and piezoelectric properties with K=7500-9000, k33=2200-2500 pC/N, d31=1100-1400 pC/N. The various electromechanical coupling factors are relatively insensitive to poling conditions and crystal composition, with k33=0.90-0.94, k31=0.48-0.55 and kt=0.58-0.62 for PMN-(28-32)%PT. The results show that flux-grown PMN-PT single crystals exhibit superior dielectric and piezoelectric properties in comparison to their melt-grown counterparts, possibly due to a lower concentration of defects in flux-grown crystals.

Lim, L. C.; Shanthi, M.; Rajan, K. K.; Lim, C. Y. H.

2005-09-01

358

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

359

Crucibleless crystal growth and Radioluminescence study of calcium tungstate single crystal fiber  

NASA Astrophysics Data System (ADS)

In this article, single phase and high optical quality scheelite calcium tungstate single crystal fibers were grown by using the crucibleless laser heated pedestal growth technique. The as-synthesized calcium tungstate powders used for shaping seed and feed rods were investigated by X-ray diffraction technique. As-grown crystals were studied by Raman spectroscopy and Radioluminescence measurements. The results indicate that in both two cases, calcined powder and single crystal fiber, only the expected scheelite CaWO4 phase was observed. It was verified large homogeneity in the crystal composition, without the presence of secondary phases. The Radioluminescence spectra of the as-grown single crystal fibers are in agreement with that present in Literature for bulk single crystals, presented a single emission band centered at 420 nm when irradiated with ?-rays.

Silva, M. S.; Jesus, L. M.; Barbosa, L. B.; Ardila, D. R.; Andreeta, J. P.; Silva, R. S.

2014-11-01

360

Fast-Response Single Cell Gap Transflective Liquid Crystal Displays  

Microsoft Academic Search

A single cell gap transflective liquid crystal display (TR-LCD) using dual fringing field switching mode is proposed, in which a positive dielectric anisotropy liquid crystal is vertically aligned and driven by fringing fields from both substrates. By optimizing the electrode width and gap of the transmissive and reflective regions, this TR-LCD exhibits a fast response time, high optical efficiency, single

Meizi Jiao; Shin-Tson Wu; Wing-Kit Choi

2009-01-01

361

Mercuric iodide single crystals for nuclear radiation detectors  

Microsoft Academic Search

Large size HgI2 single crystals were grown using the modified temperature oscillation method with low dislocation densities in a relatively stable temperature environment. Radiation detectors were fabricated from the single crystals which showed good energy resolution with small polarization

Weitang Li; Zhenghui Li; Shifu Zhu; Shujun Yin; Beijun Zhao; Guanxiong Chen; Shi Yin; Hong Yuan; Huapeng Xu

1996-01-01

362

Mercuric iodide single crystal for nuclear radiation detectors  

Microsoft Academic Search

Large size HgI2 single crystals are grown using the modified temperature oscillation method with low dislocation densities in a relatively stable temperature environment. Radiation detectors are fabricated from the single crystals which show good energy resolution with small polarization

Weitang Li; Zhenghui Li; Shifu Zhu; Shujun Yin; Beijun Zhao; Guanxiong Chen; Shi Yin; Hong Yuan; Huapeng Xu

1995-01-01

363

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

364

Novel biphenyl-substituted 1,2,4-oxadiazole ferroelectric liquid crystals: synthesis and characterization  

PubMed Central

Summary Two novel series of unsymmetrically substituted 1,2,4-oxadiazole viz., R.Ox.C*Cn compounds are synthesized and characterized. An optically active, (S)-(+)-methyl 3-hydroxy-2-methylpropionate is used to introduce a chiral center in the molecule. A biphenyl moiety prepared by Suzuki coupling reaction is directly attached to the oxadiazole core at C-5 position. Investigations for the phase behavior revealed that the series with a benzyl group on one end of the oxadiazole core exhibits an 1D orthogonal smectic-A phase while the second series with dodecyl flexible end chain shows orthogonal smectic-A and tilted chiral smectic-C (SmC*) phases over a wide range of temperatures. The smectic-C phase exhibits ferroelectric (FE) polarization switching. The mesomorphic thermal stabilities of these compounds are discussed in the domain of the symmetry and the flexibility of the alkyloxy end chain length attached to the chiral center.

Subrao, Mahabaleshwara; Potukuchi, Dakshina Murthy; Sharada Ramachandra, Girish; Bhagavath, Poornima; Bhat, Sangeetha G

2015-01-01

365

Origin of ferroelectric phase transition in SbSClxI1-x mixed crystals  

NASA Astrophysics Data System (ADS)

The measurements of SbSClxI1-x(x = 0.2) temperature dependent capacitance were carried out. The temperature of ferroelectric phase transition TC ?340 K was measured experimentally. TC of SbSClxI1-x was calculated theoretically in anharmonic and harmonic approximations. TC was calculated in anharmonic approximation using temperature dependence of mean potential energy of Sb atoms as a function of the soft B1u symmetry normal coordinate along c(z)-axis. Moreover, TC was calculated in harmonic approximation using temperature dependence of vibrational thermodynamic functions (Helmholc free energy). TC dependence from unit cell parameters a, b and from mixture composition x was carried out.

Audzijonis, A.; Žigas, L.; Sereika, R.; Žaltauskas, R.

2014-08-01

366

Tensor tomography of residual stresses of hexagonal single crystals  

NASA Astrophysics Data System (ADS)

A method for determining residual stresses in elongated transparent blanks of hexagonal single crystals the optical axis of which is directed along the crystal is proposed. It is assumed that the residual deformation tensor is of thermal character and is characterized by a fictitious temperature. Characteristic parameters of polarized light have been measured by the tomographic method in the plane orthogonal to the single crystal axis.

Puro, A. E.

2014-09-01

367

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

368

Semiconductor single crystal external ring resonator cavity laser and gyroscope  

SciTech Connect

A ring laser is described comprising: a semiconductor single crystal external ring resonator cavity having a plurality of reflecting surfaces defined by the planes of the crystal and establishing a closed optical path; and a discrete laser medium disposed in said semiconductor single crystal external ring resonator cavity for generating coherent light in said cavity, wherein said resonator cavity is decoupled from the laser medium.

Spitzer, M.P.

1993-08-31

369

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

370

Fatigue behavior of a single crystal nickel-base superalloy  

SciTech Connect

Many investigations indicate that high cycle fatigue cracks, in general, initiate at pores, inclusions, and grain boundaries in materials. The fatigue strength limit of a single crystal superalloy increases markedly compared to that of a conventional cast alloy, because the number of pores and inclusions in a single crystal superalloy are less than those of both conventionally cast and directionally solidified superalloys. Also, grain boundaries are eliminated in the single crystal superalloy. The fatigue fracture of a single crystal superalloy usually appears to be brittle. Therefore, it is necessary to study the micro-fracture mechanism. This paper presents an investigation of the fracture characteristics and micro-mechanism of fracture in a single crystal superalloy during high cycle fatigue.

Zhang, J.H.; Xu, Y.B.; Wang, Z.G.; Hu, Z.Q. [Academy of Sciences, Shenyang (China). State Key Lab. for Fatigue and Fracture of Materials] [Academy of Sciences, Shenyang (China). State Key Lab. for Fatigue and Fracture of Materials

1995-06-15

371

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

372

High-temperature and pressure-induced ferroelectricity in hydrogen-bonded supramolecular crystals of anilic acids and 2,3-di(2-pyridinyl)pyrazine.  

PubMed

Cocrystallization of anilic acids (H2xa) and 2,3-di(2-pyridinyl)pyrazine (dppz) affords a variety of molecular geometries, including hydrogen-bonding and supramolecular structures. Proton-transferred 1:1 salts of [H-dppz][Hca] and [H-dppz][Hba] (H2ca = chloranilic acid, H2ba = bromanilic acid) were found to host room-temperature ferroelectricity with a spontaneous polarization of 3-4 ?C/cm(2) along the hydrogen-bonded chains. Compared with the Curie points of other supramolecular ferroelectrics, those of the salts are relatively high (402 K and >420 K, respectively) because of the elongated hydrogen bonds, which stabilize the proton-ordered state against thermal agitation. In addition to the ferroelectric black (?) form, dppz and H2ba gave two different crystal forms with a 2:3 ratio: the brown ? form of [H(1.5)-dppz]2[Hba]3 and the brownish-red ? form of [H-dppz]2[Hba]2[H2ba]. Mixed solutions of dppz with the less acidic fluoranilic acid (H2fa) exhibit valence instability; the H2fa molecules remain mostly neutral in absolute ethanol, whereas methanol (MeOH) solution apparently increases the deprotonated Hfa(-) content. Crystallizations of these solutions gave a neutral [dppz][H2fa] cocrystal and ionic [H-dppz(+)][Hfa(-)]·MeOH salt, respectively. The ferroelectricity induced by a modest hydrostatic pressure corroborates the conclusion that the ionic state with a dipolar [H-dppz(+)][Hfa(-)] chain is energetically close to the nonpolar neutral ground state of the [dppz][H2fa] crystal. PMID:23448384

Horiuchi, Sachio; Kumai, Reiji; Tokura, Yoshinori

2013-03-20

373

New ferroelectric compound SrTeO3  

Microsoft Academic Search

A synthetic compound SrTeO3 was discovered to exhibit ferroelectricity in the temperature range between 312 and 485°C. Small single crystals could be grown by the Kyropoulos method. The crystal belongs to the monoclinic system and its space group is C2? c ? C2 h6 at room temperature. A pronounced dielectric anomaly was observed along the b axis at 485°C. The

Tomoaki Yamada; Hiroshi Iwasaki

1972-01-01

374

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

375

Nano and micro reoriented domains and their relation with the crystal structure in the new ferroelectric boracite Zn3B7O13Br  

NASA Astrophysics Data System (ADS)

A new zinc brome boracite Zn3B7O13Br has been grown by a chemical transport reaction in closed quartz ampoules at 920 K. The crystal structure was characterized by Rietveld refinement. Ferroelectric nano and micro reorientable domains were found in this material using polarizing optical microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Chemical analysis was performed with x-ray energy dispersive spectroscopy (EDX). In the crystal, a new structure transition at 586 K from orthorhombic (Pca 21) to cubic cell (F\\overline 4 3c ) has been found. This transition was corroborated by differential scanning calorimetry (DSC).

Campa-Molina, J.; Ulloa-Godínez, S.; Barrera, A.; Bucio, L.; Mata, J.

2006-05-01

376

Luminescence and scintillation properties of Y 3 A l5 O 12 :Ce single crystals and single-crystal films  

Microsoft Academic Search

Luminescence and scintillation properties of Y3Al5O12:Ce single crystals grown from the melt by the Czochralski and horizontal directed crystallization methods in various gas\\u000a media and Y3Al5O12:Ce single-crystal films grown by liquid-phase epitaxy from a melt solution based on a PbO-B2O3 flux have been comparatively analyzed. The strong dependence of scintillation properties of Y3Al5O12:Ce single crystals on their growth conditions and

Yu. V. Zorenko; V. P. Savchin; V. I. Gorbenko; T. I. Voznyak; T. E. Zorenko; V. M. Puzikov; A. Ya. Dan’ko; S. V. Nizhankovskii

2011-01-01

377

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

378

Crystal Growth and Characterization of (Bi0.5Na0.5)TiO3--BaTiO3 Single Crystals Obtained by a Top-Seeded Solution Growth Method under High-Pressure Oxygen Atmosphere  

Microsoft Academic Search

A single crystal of ferroelectric 0.88(Bi,Na)TiO3--0.12BaTiO3 (BNT--BT) solid solution with tetragonal P4mm structure was grown by a top-seeded solution growth (TSSG) method at a high oxygen pressure (PO\\\\scale70%2) of 0.9 MPa. The crystals exhibited a large remanent polarization (Pr) of 54 muC\\/cm2, which leads to a spontaneous polarization estimated to be 54 muC\\/cm2. The large Pr compared with that of

Hiroaki Onozuka; Yuuki Kitanaka; Yuji Noguchi; Masaru Miyayama

2011-01-01

379

New Configuration of a Transflective Liquid Crystal Display Having a Single Cell Gap and a Single Liquid Crystal Mode  

Microsoft Academic Search

We report on a new tranflective liquid crystal display (LCD) mode having a single cell gap and a single LC mode. For this display mode, a low twisted nematic liquid crystal cell, having the twist angle of 60°, is used for both transmissive and reflective applications. The measured electro-optic characteristics of our transflective cell agree well with numerical simulation results.

Jinyool Kim; Dong-Woo Kim; Chang-Jae Yu; Sin-Doo Lee

2004-01-01

380

Study of single crystals of metal solid solutions  

NASA Technical Reports Server (NTRS)

The growth of single crystals of relatively high melting point metals such as silver, copper, gold, and their alloys was investigated. The purpose was to develop background information necessary to support a space flight experiment and to generate ground based data for comparison. The ground based data, when compared to the data from space grown crystals, are intended to identify any effects which zero-gravity might have on the basic process of single crystal growth of these metals. The ultimate purposes of the complete investigation are to: (1) determine specific metals and alloys to be investigated; (2) grow single metal crystals in a terrestrial laboratory; (3) determine crystal characteristics, properties, and growth parameters that will be effected by zero-gravity; (4) evaluate terrestrially grown crystals; (5) grow single metal crystals in a space laboratory such as Skylab; (6) evaluate the space grown crystals; (7) compare for zero-gravity effects of crystal characteristics, properties, and parameters; and (8) make a recommendation as to production of these crystals as a routine space manufacturing proceses.

Doty, J. P.; Reising, J. A.

1973-01-01

381

Crystal Structure of A-amylose: a Revisit from Synchrotron Microdiffraction Analysis of Single Crystals  

E-print Network

1 Crystal Structure of A-amylose: a Revisit from Synchrotron Microdiffraction Analysis of Single;2 Abstract The three-dimensional structure of A-amylose crystals, as a model of the crystal domains of A the resolution of important new fine details. These include a distortion of the amylose double helices resulting

Paris-Sud XI, Université de

382

Hard Polarized Photon Emission in Single Crystals by High Energy Electrons for Planar Crystal Orientations  

E-print Network

The radiation emission spectra of polarized photons emitted from charge particle in single crystal are obtained in semiclassical theory in Baer-Katkov-Strakhovenko approximation for planar crystal orientation. The range of applicability of this approximation is estimated by comparing the results with calculations in exact semiclassical theory. Optimal crystal orientations for producing unpolarized and polarized photon beams are also founded.

S. M. Darbinian; N. L. Ter-Isaakian

1999-09-07

383

Physicochemical principles of high-temperature crystallization and single crystal growth methods  

Microsoft Academic Search

The mechanisms of crystal growth are reviewed, with attention given to the physicochemical reactions taking place in the melt near the phase boundary; phenomena determining physical and chemical kinetics directly at the growth front; solid-phase processes occurring within the crystal. Methods for growing refractory single crystals are discussed with particular reference to the Verneuil method, zone melting, Czhochralskii growth, horizontal

Kh. S. Bagdasarov

1987-01-01

384

Observation of ferroelectric domains in bismuth-layer-structured ferroelectrics using Raman spectroscopy  

Microsoft Academic Search

Raman spectroscopy has been used to investigate the domain structures in bismuth-layered-structured ferroelectrics (BLSFs). In Bi4Ti3O12 single crystal, the lowest frequency mode (soft mode) at ?30cm?1 appears exclusively for the xx polarization configuration (x?polar axis). We found that the polarization dependence of the Raman signal exhibits spatial symmetries that reflect the presence of different domain variants present in Bi4Ti3O12. This

Minoru Osada; Masaru Tada; Masato Kakihana; Yuji Noguchi; Masaru Miyayama

2005-01-01

385

Remarkable optics of short-pitch deformed helix ferroelectric liquid crystals: symmetries, exceptional points and polarization-resolved angular patterns  

E-print Network

In order to explore electric-field-induced transformations of polarization singularities in the polarization-resolved angular (conoscopic) patterns emerging after deformed helix ferroelectric liquid crystal (DHFLC) cells with subwavelength helix pitch, we combine the transfer matrix formalism with the results for the effective dielectric tensor of biaxial FLCs evaluated using an improved technique of averaging over distorted helical structures. Within the framework of the transfer matrix method, we deduce a number of symmetry relations and show that the symmetry axis of L lines (curves of linear polarization) is directed along the major in-plane optical axis which rotates under the action of the electric field. When the angle between this axis and the polarization plane of incident linearly polarized light is above its critical value, the C points (points of circular polarization) appear in the form of symmetrically arranged chains of densely packed star-monstar pairs. We also emphasize the role of phase singularities of a different kind and discuss the enhanced electro-optic response of DHFLCs near the exceptional point where the condition of zero-field isotropy is fulfilled.

Alexei D. Kiselev; Vladimir G. Chigrinov

2014-07-14

386

Optics of short-pitch deformed-helix ferroelectric liquid crystals: Symmetries, exceptional points, and polarization-resolved angular patterns  

NASA Astrophysics Data System (ADS)

In order to explore electric-field-induced transformations of polarization singularities in the polarization-resolved angular (conoscopic) patterns emerging after deformed-helix ferroelectric liquid crystal (DHFLC) cells with subwavelength helix pitch, we combine the transfer matrix formalism with the results for the effective dielectric tensor of biaxial FLCs evaluated using an improved technique of averaging over distorted helical structures. Within the framework of the transfer matrix method, we deduce a number of symmetry relations and show that the symmetry axis of L lines (curves of linear polarization) is directed along the major in-plane optical axis which rotates under the action of the electric field. When the angle between this axis and the polarization plane of incident linearly polarized light is above its critical value, the C points (points of circular polarization) appear in the form of symmetrically arranged chains of densely packed star-monstar pairs. We also emphasize the role of phase singularities of a different kind and discuss the enhanced electro-optic response of DHFLCs near the exceptional point where the condition of zero-field isotropy is fulfilled.

Kiselev, Alexei D.; Chigrinov, Vladimir G.

2014-10-01

387

Optics of short-pitch deformed-helix ferroelectric liquid crystals: symmetries, exceptional points, and polarization-resolved angular patterns.  

PubMed

In order to explore electric-field-induced transformations of polarization singularities in the polarization-resolved angular (conoscopic) patterns emerging after deformed-helix ferroelectric liquid crystal (DHFLC) cells with subwavelength helix pitch, we combine the transfer matrix formalism with the results for the effective dielectric tensor of biaxial FLCs evaluated using an improved technique of averaging over distorted helical structures. Within the framework of the transfer matrix method, we deduce a number of symmetry relations and show that the symmetry axis of L lines (curves of linear polarization) is directed along the major in-plane optical axis which rotates under the action of the electric field. When the angle between this axis and the polarization plane of incident linearly polarized light is above its critical value, the C points (points of circular polarization) appear in the form of symmetrically arranged chains of densely packed star-monstar pairs. We also emphasize the role of phase singularities of a different kind and discuss the enhanced electro-optic response of DHFLCs near the exceptional point where the condition of zero-field isotropy is fulfilled. PMID:25375512

Kiselev, Alexei D; Chigrinov, Vladimir G

2014-10-01

388

Method for harvesting single crystals from a peritectic melt  

DOEpatents

A method of preparing single crystals. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals unmelted, allowing the wicking away of the peritectic liquid.

Todt, Volker R. (Lemont, IL); Sengupta, Suvankar (Columbus, OH); Shi, Donglu (Cincinnati, OH)

1996-01-01

389

Method for harvesting rare earth barium copper oxide single crystals  

DOEpatents

A method of preparing high temperature superconductor single crystals. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid.

Todt, Volker R. (Lemont, IL); Sengupta, Suvankar (Columbus, OH); Shi, Donglu (Cincinnati, OH)

1996-01-01

390

Structure of the RbTi 0.98 Zr 0.02 OPO 4 single crystal at temperatures of 293 and 105 K  

Microsoft Academic Search

This paper reports on the results of precision X-ray structural investigations of a RbTi0.98Zr0.02OPO4 single crystal at temperatures of 293 and 105 K. It is established that the observed decrease in the temperature of the ferroelectric\\u000a phase transition in RbTiOPO4 crystals doped with zirconium is associated with the increase in the Rb-O bond lengths. The structural factors responsible\\u000a for the

O. A. Alekseeva; A. P. Dudka; N. E. Novikova; N. I. Sorokina; E. I. Agapova; V. I. Voronkova

2008-01-01

391

Ion crystal transducer for strong coupling between single ions and single photons  

E-print Network

A new approach for realization of a quantum interface between single photons and single ions in an ion crystal is proposed and analyzed. In our approach the coupling between a single photon and a single ion is enhanced via the collective degrees of freedom of the ion crystal. Applications including single-photon generation, a memory for a quantum repeater, and a deterministic photon-photon, photon-phonon, or photon-ion entangler are discussed.

L. Lamata; D. R. Leibrandt; I. L. Chuang; J. I. Cirac; M. D. Lukin; V. Vuletic; S. F. Yelin

2011-07-11

392

A Single Crystal Niobium RF Cavity of the TESLA Shape  

NASA Astrophysics Data System (ADS)

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 without destruction of the single crystal. A prototype single crystal single cell cavity was build. An accelerating gradient of 37.5 MV/m was reached after approximately 110 ?m of Buffered Chemical Polishing (BCP) and in situ baking at 120°C for 6 hrs with a quality factor exceeding 2×1010 at 1.8 K. The developed fabrication method can be extended to fabrication of multi cell cavities.

Singer, W.; Singer, X.; Kneisel, P.

2007-08-01

393

A study of crystal growth by solution technique. [triglycine sulfate single crystals  

NASA Technical Reports Server (NTRS)

The advantages and mechanisms of crystal growth from solution are discussed as well as the effects of impurity adsorption on the kinetics of crystal growth. Uncertainities regarding crystal growth in a low gravity environment are examined. Single crystals of triglycine sulfate were grown using a low temperature solution technique. Small components were assembled and fabricated for future space flights. A space processing experiment proposal accepted by NASA for the Spacelab-3 mission is included.

Lal, R. B.

1979-01-01

394

High quality factor single-crystal diamond mechanical resonators  

NASA Astrophysics Data System (ADS)

Single-crystal diamond is a promising material for microelectromechanical systems (MEMs) because of its low mechanical loss, compatibility with extreme environments, and built-in interface to high-quality spin centers. But its use has been limited by challenges in processing and growth. We demonstrate a wafer bonding-based technique to form diamond on insulator, from which we make single-crystal diamond micromechanical resonators with mechanical quality factors as high as 338 000 at room temperature. Variable temperature measurements down to 10 K reveal a nonmonotonic dependence of quality factor on temperature. These resonators enable integration of single-crystal diamond into MEMs technology for classical and quantum applications.

Ovartchaiyapong, P.; Pascal, L. M. A.; Myers, B. A.; Lauria, P.; Bleszynski Jayich, A. C.

2012-10-01

395

Crystal growth and characterization of monometallic NLO single crystals of Cd(IO 3) 2  

Microsoft Academic Search

This work aims to study the growth and physicochemical properties of second-order nonlinear optical active inorganic crystal of cadmium iodate (CDI). Efforts have been made to grow an improved size single crystal of CDI by the slow-cooling technique. The XRD data of CDI are determined by single-crystal XRD analysis. CDI is further characterized by UV–vis–NIR spectroscopy, TGA, dielectric, ac conductivity,

S. M. Ravi Kumar; N. Melikechi; S. Selvakumar; P. Sagayaraj

2009-01-01

396

Single crystal Processing and magnetic properties of gadolinium nickel  

SciTech Connect

GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd{sub 2}O{sub 3} W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

Shreve, Andrew John [Ames Laboratory

2012-11-02

397

Stability of Detached Grown Germanium Single Crystals  

NASA Technical Reports Server (NTRS)

Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years, especially under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 micrometers, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5 mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 micrometers. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be discussed in detail.

Schweizer, M.; Volz, M. P.; Cobb, S. D.; Vujisic, L.; Szofran, F. R.; Rose, M. Franklin (Technical Monitor)

2001-01-01

398

Stability of Detached Grown Germanium Single Crystals  

NASA Technical Reports Server (NTRS)

Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years especially, under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 microns, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 microns. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be discussed in detail.

Schweizer, M.; Volz, M. P.; Cobb, S. D.; Motakef, S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)

2002-01-01

399

Growth and characterization of organic material 4-dimethylaminobenzaldehyde single crystal  

NASA Astrophysics Data System (ADS)

The organic material 4-dimethylaminobenzaldehyde single crystals were grown by slow evaporation technique. The grown crystal was confirmed by the single crystal and powder X-ray diffraction analyses. The functional groups of the crystal have been identified from the Fourier Transform Infrared (FTIR) and FT-Raman studies. The optical property of the grown crystal was analyzed by UV-Vis-NIR and photoluminescence (PL) spectral measurements. The thermal behavior of the grown crystal was analyzed by thermogravimetric (TG) and differential thermal analyses (DTA). Dielectric measurements were carried out with different frequencies by using parallel plate capacitor method. The third order nonlinear optical properties of 4-dimethylaminobenzaldehyde was measured by the Z-scan technique using 532 nm diode pumped continuous wave (CW) Nd:YAG laser.

Jebin, R. P.; Suthan, T.; Rajesh, N. P.; Vinitha, G.; Madhusoodhanan, U.

2015-01-01

400

Growth and characterization of ammonium acid phthalate single crystals  

NASA Astrophysics Data System (ADS)

Ammonium acid phthalate (AAP) has been synthesized and single crystals were grown by slow evaporation solution growth technique. The unit cell parameters were confirmed by single crystal X-ray diffraction analysis and it belongs to orthorhombic system with the space group of Pcab. The high resolution X-ray diffraction studies revealed the crystalline perfection of the grown crystal. The various functional groups of AAP were identified by FT-IR and Raman spectral analyses. Thermal stability of the grown crystals was studied by TGA/DTA. The optical properties of the grown crystals were analyzed by UV-Vis-NIR and photoluminescence spectral studies. The mechanical property of the grown crystal was studied by Vickers microhardness measurement. The growth features of AAP were analyzed by chemical etching.

Arunkumar, A.; Ramasamy, P.

2013-04-01

401

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

402

Growing intermetallic single crystals using in situ decanting  

SciTech Connect

High temperature metallic solution growth is one of the most successful and versatile methods for single crystal growth, and is particularly suited for exploratory synthesis. The method commonly utilizes a centrifuge at room temperature and is very successful for the synthesis of single crystal phases that can be decanted from the liquid below the melting point of the silica ampoule. In this paper, we demonstrate the extension of this method that enables single crystal growth and flux decanting inside the furnace at temperatures above 1200°C. This not only extends the number of available metallic solvents that can be used in exploratory crystal growth but also can be particularly well suited for crystals that have a rather narrow exposed solidification surface in the equilibrium alloy phase diagram.

Petrovic, Cedomir; Canfield, Paul; Mellen, Jonathan

2012-05-16

403

Modified triglycine sulphate (TGS) single crystals for pyroelectric infrared detector applications  

NASA Technical Reports Server (NTRS)

Effects of caesium and cerium, L-alanine, and caesium plus L-alanine impurities on ferroelectric and pyroelectric properties of TGS crystals are investigated. Dielectric constant and loss, pyroelectric coefficient, spontaneous polarization, and coercive field measurements of these modified crystals, as a function of temperature, are reported. Caesium and cerium did not affect the electrical properties of TGS crystals significantly, whereas L-alanine- and, especially, Cs + L-alanine-doped TGS crystals exhibited promising improvements in pyroelectric properties, up to 48 C, as compared to pure TGS crystals.

Banan, M.; Lal, R. B.; Batra, Ashok

1992-01-01

404

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

NASA Astrophysics Data System (ADS)

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

Sherlock, Nevin P.

2010-06-01

405

Large Single Crystal growth of Bi2212 superconducting oxide  

Microsoft Academic Search

A floating zone method was used to study the effects of the growth velocity and starting composition of the feed rod on the crystal growth behaviour of Bi-2212 superconducting materials. It shows that a necessary condition for large single crystal growth is that the solid-liquid interface of a rod maintains a planar interface during crystal growth. The planar solid-liquid interface

Genda Gu; Gangyong Xu; John Tranquada

2006-01-01

406

On the growth of calcium tartrate tetrahydrate single crystals  

Microsoft Academic Search

Calcium tartrate single crystals were grown using silica gel as the growth medium. Calcium formate mixed with formic acid\\u000a was taken as the supernatant solution. It was observed that the nucleation density was reduced and the size of the crystals\\u000a was improved to a large extent compared to the conventional way of growing calcium tartrate crystals with calcium chloride.\\u000a The

X. Sahaya Shajan; C. Mahadevan

2004-01-01

407

Designed three-dimensional freestanding single-crystal carbon architectures.  

PubMed

Single-crystal carbon nanomaterials have led to great advances in nanotechnology. The first single-crystal carbon nanomaterial, fullerene, was fabricated in a zero-dimensional form. One-dimensional carbon nanotubes and two-dimensional graphene have since followed and continue to provide further impetus to this field. In this study, we fabricated designed three-dimensional (3D) single-crystal carbon architectures by using silicon carbide templates. For this method, a designed 3D SiC structure was transformed into a 3D freestanding single-crystal carbon structure that retained the original SiC structure by performing a simple single-step thermal process. The SiC structure inside the 3D carbon structure is self-etched, which results in a 3D freestanding carbon structure. The 3D carbon structure is a single crystal with the same hexagonal close-packed structure as graphene. The size of the carbon structures can be controlled from the nanoscale to the microscale, and arrays of these structures can be scaled up to the wafer scale. The 3D freestanding carbon structures were found to be mechanically stable even after repeated loading. The relationship between the reversible mechanical deformation of a carbon structure and its electrical conductance was also investigated. Our method of fabricating designed 3D freestanding single-crystal graphene architectures opens up prospects in the field of single-crystal carbon nanomaterials and paves the way for the development of 3D single-crystal carbon devices. PMID:25329767

Park, Ji-Hoon; Cho, Dae-Hyun; Moon, Youngkwon; Shin, Ha-Chul; Ahn, Sung-Joon; Kwak, Sang Kyu; Shin, Hyeon-Jin; Lee, Changgu; Ahn, Joung Real

2014-11-25

408

Single-drop optimization of protein crystallization  

PubMed Central

A completely new crystal-growth device has been developed that permits charting a course across the phase diagram to produce crystalline samples optimized for diffraction experiments. The utility of the device is demonstrated for the production of crystals for the traditional X-ray diffraction data-collection experiment, of microcrystals optimal for data-collection experiments at a modern microbeam insertion-device synchrotron beamline and of nanocrystals required for data collection on an X-ray laser beamline. PMID:22869140

Meyer, Arne; Dierks, Karsten; Hilterhaus, Dierk; Klupsch, Thomas; Mühlig, Peter; Kleesiek, Jens; Schöpflin, Robert; Einspahr, Howard; Hilgenfeld, Rolf; Betzel, Christian

2012-01-01

409

Single-drop optimization of protein crystallization.  

PubMed

A completely new crystal-growth device has been developed that permits charting a course across the phase diagram to produce crystalline samples optimized for diffraction experiments. The utility of the device is demonstrated for the production of crystals for the traditional X-ray diffraction data-collection experiment, of microcrystals optimal for data-collection experiments at a modern microbeam insertion-device synchrotron beamline and of nanocrystals required for data collection on an X-ray laser beamline. PMID:22869140

Meyer, Arne; Dierks, Karsten; Hilterhaus, Dierk; Klupsch, Thomas; Mühlig, Peter; Kleesiek, Jens; Schöpflin, Robert; Einspahr, Howard; Hilgenfeld, Rolf; Betzel, Christian

2012-08-01

410

Halide electrodeposition on single-crystal electrodes  

NASA Astrophysics Data System (ADS)

In this dissertation, we investigate in depth by computational and theoretical methods the processes and behavior of submonolayer electrochemical deposition of Br onto single-crystal Ag(100) electrodes. Although this system has little direct industrial application, it provides a test bed for developing theoretical and computational techniques which can be used to study systems of more applied interest. Br electrodeposited onto a Ag(100) substrate at room temperature displays a disordered phase at low electrochemical potentials. At higher electrochemical potentials, the adlayer undergoes a disorder-order phase transition to a c(2 x 2) ordered phase. The phase transition, the equilibrium properties of the adlayer, and the dynamics of the ordering and disordering processes are studied by a variety computational techniques, including static and dynamic lattice-gas models, an off-lattice equilibrium model, and Langevin simulations. Using a two-dimensional lattice-gas approximation for the adlayer, Monte Carlo simulations are used to explore the equilibrium properties of the Br adlayer under different values of the electrochemical potential. The model predicts the existence of low-temperature phases which are not stable at room temperature. The effects of these low-temperature phases on the room-temperature properties of the adlayer are discussed. Starting from the lattice-gas model developed for equilibrium simulations, a dynamic Monte Carlo simulation program is constructed, and the phase-ordering, disordering, and hysteresis behaviors are studied. The phase-ordering process is in the dynamic universality class known as Model A (Lifshitz-Allen-Cahn dynamics), but the disordering behavior is not as easily classified. Dynamic simulations of cyclic-voltammetry experiments show hysteresis due to kinetic limitations associated with the ordering and disordering processes. To further investigate the properties of the adlayer, the lattice-gas approximation was relaxed and replaced by a corrugation-potential approximation. Within this two-dimensional off-lattice model, the equilibrium properties were found to be similar to those of the lattice-gas model. However, the off-lattice model obviously allows calculations of additional quantities, such as the average lateral displacement from the adsorption site. Langevin dynamic simulations of the off-lattice model were also performed to test the validity of the assumptions used in the dynamic Monte Carlo simulations. However, these dynamic simulations were far too computationally intensive to allow off-lattice simulations of the ordering, disordering, and hysteresis behaviors. As a first step towards developing accelerated simulation methods for off-lattice simulations, we construct an advanced dynamic algorithm for continuum spin systems.

Mitchell, Steven James

2001-07-01

411

Brittlestar-Inspired Microlens Arrays Made of Calcite Single Crystals.  

PubMed

Unique concave microlens arrays (MLAs) made of calcite single crystals with tunable crystal orientations can be readily fabricated by template-assisted epitaxial growth in solution without additives under ambient conditions. While the non-birefringent calcite (001) MLA showed excellent imaging performance like brittlestar's microlens arrays, the birefringent calcite (104) MLA exhibited remarkable polarization-dependent optical properties. PMID:25366272

Ye, Xiaozhou; Zhang, Fei; Ma, Yurong; Qi, Limin

2014-11-01

412

Electron-hole fluid in ZnSe single crystals  

NASA Astrophysics Data System (ADS)

Recombination emission and light amplification spectra were obtained for cubic single crystals of ZnSe under intense optical excitation. Experimental results point to the existence of electron-hole plasma droplets in the semiconductor crystals. Electron-hole droplet parameters are examined; reasons for distortions of equilibrium electron and hole concentrations in droplets and of droplet binding energy are discussed.

Baltrameiunas, R.; Kuokshtis, E.

1980-10-01

413

Numerical simulation of single crystal growth by submerged heater method  

Microsoft Academic Search

A novel method of crystal growth which utilizes an axial submerged heater is proposed and numerically simulated. Single crystals should be grown by directional solidification in vertical bottom seeded crucibles. Submerged in the melt, the heater supplies the heat axially downward, enclosing and stratifying a small active portion of the melt.

Aleksandar G. Ostrogorsky

1990-01-01

414

EURODISPLAY 2002 137 7-4: Alignment of Ferroelectric Liquid Crystals with Photoanisotropic  

E-print Network

with mechanical damage of the surface are produced in this case, which has to be completely avoided for the new gap (less than 2µm) which provides the best optical transmission of the cells [1]. Moreover, as we,4]. A hybrid of linearly photopolymerized photoalignment (LPP) with liquid crystal polymer (LCP) layers

415

A high frequency polarization intensity electrooptic modulator in BSTN ferroelectric crystal  

E-print Network

than those of LiNbOq and LiTaOs. Relevant characteristic properties of two particular tungsten bronze crystals, SBN:60 (Strontium Barium Niobate) and BSTN (Barium Strontium Titanium Niobate), are compared with LiNb03 and LiTaOq in Table I...

Wilson, Erik James

1996-01-01

416

Diluted ferroelectric suspension of Sn2P2S6 nanoparticles in nematic liquid crystal  

Microsoft Academic Search

Long-range forces between ultra-fine particles imbedded in liquid crystal (LC) matrices result in intriguing colloids. Embedded inorganic particles in LC contribute to the properties of the LC matrix. For example, doping of a LC with ferromagnetic particles resulted in a strong enhancement of magnetic properties of the LC. Large (>>µm) colloidal particles form defects in LC matrices due to strong

Olexander Buchnev; Anatoliy V. Glushchenko; Yurii Reznikov; Victor Y. Reshetnyak; Olexander Tereshchenko; John L. West

2003-01-01

417

Synthesis and physical characterization of thermoelectric single crystals  

E-print Network

There is much current interest in thermoelectric devices for sustainable energy. This thesis describes a research project on the synthesis and physical characterization of thermoelectric single crystals. 1In?Se?-[delta] ...

Porras Pérez Guerrero, Juan Pablo

2012-01-01

418

On the deformation mechanisms in single crystal Hadfield manganese steels  

SciTech Connect

Austenitic manganese steel, so called Hadfield manganese steel, is frequently used in mining and railroad frog applications requiring excessive deformation and wear resistance. Its work hardening ability is still not completely understood. Previous studies attributed the work-hardening characteristics of this material to dynamic strain aging or an imperfect deformation twin, a so-called pseudotwin. Unfortunately, these previous studies have all focused on polycrystalline Hadfield steels. To properly study the mechanisms of deformation in the absence of grain boundary or texture effects, single crystal specimens are required. The purpose of this work is the following: (1) observe the inelastic stress-strain behavior of Hadfield single crystals in orientations where twinning and slip are individually dominating or when they are competing deformation mechanisms; and (2) determine the microyield points of Hadfield single crystals and use micro-mechanical modeling to predict the stress-strain response of a single crystal undergoing micro-twinning.

Karaman, I.; Sehitoglu, H.; Gall, K. [Univ. of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering] [Univ. of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering; Chumlyakov, Y.I. [Siberian Physical and Technical Inst., Tomsk (Russian Federation). Physics of Plasticity and Strength of Materials Lab.] [Siberian Physical and Technical Inst., Tomsk (Russian Federation). Physics of Plasticity and Strength of Materials Lab.

1998-02-13

419

Electrical and Optical Properties of Porphyrin Single Crystals  

Microsoft Academic Search

In this work, we investigate the transport and optical properties of single crystal 5,10,15,20-tetrakis (4-N-ethylpyridyl) porphyrin salts, [H2TEPyP·4I]. The electrical conductivity exhibits high anisotropy, in that the conductivity along the stacking column, which is equal to 3.2 × 10?· cm, is three orders of magnitude larger than that perpendicular to the stacking column. The absorption spectra of the single crystals

Y. C. Chen; M. W. Lee; L. L. Li; K. J. Lin

2008-01-01

420

Synthesis and Single-Crystal Growth of Ca  

SciTech Connect

For the study of the quasi-two-dimensional Mott transition system Ca{sub 2-x}Sr{sub x}RuO{sub 4}, we have succeeded in synthesizing polycrystalline samples and also growing single crystals by a floating-zone method. Details of the preparations for the entire solution range are described. The structural, transport, and magnetic properties of both polycrystalline and single-crystal samples are fully in agreement.

Nakatsuji, Satoru; Maeno, Yoshiteru

2001-01-01

421

Optical characteristics of anisotropic CdP2 single crystals  

NASA Astrophysics Data System (ADS)

The refined results of the specified dispersion of refractive indexes, birefringence, optical activity of anisotropic (beta) -CdP2 single crystals and the components of both the gyration tensor G33 and the optical activity tensor (gamma) 123 in a wide spectral band of polarized light under normal conditions are presented. The influence of temperature and radiation intensity of neodymium and ruby lasers on these characteristics of CdP2 single crystals is studied and analyzed.

Borshch, Volodymyr V.; Gnatyuk, Volodymyr A.; Kovalenko, S. A.; Kuzmenko, M. G.; Yarernko, R. V.

2001-05-01

422

Bulk GaN single-crystals growth  

Microsoft Academic Search

Gallium nitride powder was prepared from gallium and ammonia at temperatures of 1000–1200°C. Parameters of the crystallographic lattice as well as photoluminescence and Raman spectra were determined for the obtained powder. As a result of GaN powder sublimation, GaN single crystals of 3×2×0.2mm were received, at temperatures 1200–1250°C. Single crystals of gallium nitride were also synthesised in a reaction of

Grzegorz Kamler; Janusz Zachara; S?awomir Podsiad?o; Leszek Adamowicz; Wojciech G?bicki

2000-01-01

423

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{minus}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. 7 figs.

Todt, V.; Miller, D.J.; Shi, D.; Sengupta, S.

1998-07-07

424

Differences Between Individual ZSM-5 Crystals in Forming Hollow Single Crystals and Mesopores During Base Leaching.  

PubMed

After base treatment of ZSM-5 crystals below 100?nm in size, TEM shows hollow single crystals with a 10?nm shell. SEM images confirm that the shell is well- preserved even after prolonged treatment. Determination of the Si/Al ratios with AAS and XPS in combination with argon sputtering reveals aluminum zoning of the parent zeolite, and the total pore volume increases in the first two hours of base treatment. In corresponding TEM images, the amount of hollow crystals are observed to increase during the first two hours of base treatment, and intact crystals are visible even after 10?h of leaching; these observations indicate different dissolution rates between individual crystals. TEM of large, commercially available ZSM-5 crystals shows inhomogeneous distribution of mesopores among different crystals, which points to the existence of structural differences between individual crystals. Only tetrahedrally coordinated aluminum is detected with (27) Al MAS NMR after the base leaching of nano-sized ZSM-5. PMID:25720305

Fodor, Daniel; Krumeich, Frank; Hauert, Roland; van Bokhoven, Jeroen A

2015-04-13

425

Crystal Structure and the Paraelectric-to-Ferroelectric Phase Transition of Nanoscale BaTiO3  

E-print Network

the paraelectric-to-ferroelectric phase transition of various sizes of nanocrystalline barium titanate (BaTiO3 of the distortions, which is decreased in the smaller particles. Introduction Barium titanate (BaTiO3

426

Vapor crystal growth studies of single crystals of mercuric iodide (3-IML-1)  

NASA Technical Reports Server (NTRS)

A single crystal of mercuric iodide (HgI2) will be grown during the International Microgravity Lab. (IML-1) mission. The crystal growth process takes place by sublimation of HgI2 from an aggregate of purified material, transport of the molecules in the vapor from the source to the crystal, and condensation on the crystal surface. The objectives of the experiment are as follow: to grow a high quality crystal of HgI2 of sufficient size so that its properties can be extensively analyzed; and to study the vapor transport process, specifically the rate of diffusion transport at greatly reduced gravity where convection is minimized.

Vandenberg, Lodewijk

1992-01-01

427

Measurement of single crystal surface parameters  

NASA Technical Reports Server (NTRS)

The sticking coefficient and thermal desorption spectra of Cs from the (110) plane of W was investigated. A sticking coefficient of unity for the monolayer region was measured for T 250 K. Several distinct binding states were observed in the thermal desorption spectrum. Work function and electron reflection measurements were made on the (110) and (100) crystal faces of Mo. Both LEED and Auger were used to determine the orientation and cleanliness of the crystal surfaces. The work function values obtained for the (110) and (100) planes of Mo were 4.92 and 4.18 eV respectively.

Swanson, L. W.; Bell, A. E.; Strayer, R. W.

1972-01-01

428

Growth of single crystals by vapor transport  

NASA Technical Reports Server (NTRS)

The primary objectives of the program were to establish basic vapor transport and crystal growth properties and to determine thermodynamic, kinetic and structural parameters relevant to chemical vapor transport systems for different classes of materials. An important aspect of these studies was the observation of the effects of gravity-caused convection on the mass transport rate and crystal morphology. These objectives were accomplished through extensive vapor transport, thermochemical and structural studies on selected Mn-chalcogenides, II-VI and IV-VI compounds.

Wiedemeier, H.

1978-01-01

429

Optical and photoelectrochemical study of WTe2 single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of Tungsten Ditelluride (WTe2) having a layered structure grown by chemical vapor transport method using iodine as the transporting agent are studied here. The optical response of these crystals has been obtained by UV-Vis-NIR spectroscopy at room temperature. Results of optical spectra have been analyzed on the basis of three dimensional models. Photoelectrochemical (PEC) characterization of WTe 2 single crystals have been carried out. Photo response measurements were obtained at different intensities of light source to illuminate the photoanode. The effect of intensity in the efficiency of PEC solar cell has been studied. The implications of the results have been discussed.

Desai, P. F.; Patel, D. D.; Bhavsar, D. N.; Jani, A. R.

2013-06-01

430

CeSi 2? ? single crystals: growth features and properties  

Microsoft Academic Search

Single crystals of CeSix (x=1.79–1.85) with an orthorhombic structure have been grown by floating zone methods both with RF induction and optical heating at feed rod compositions CeSiy (y=1.76–1.89). High-perfection single crystals were achieved for a narrow composition interval y=1.81–1.82. A slight axial segregation of Si in the crystal and 2nd phase inclusions of Si (y>1.82) and of CeSi (y<1.80),

D. Souptel; G. Behr; W. Löser; A. Teresiak; S. Drotziger; C. Pfleiderer

2004-01-01

431

Anisotropy of nickel-base superalloy single crystals  

NASA Technical Reports Server (NTRS)

The effects of crystal orientation on the mechanical properties of single crystals of the nickel-based superalloy Mar-M247 are investigated. Tensile tests at temperatures from 23 to 1093 C and stress rupture tests at temperatures from 760 to 1038 C were performed for 52 single crystals at various orientations. During tensile testing between 23 and 760 C, single crystals with high Schmid factors were found to be favorably oriented for slip and to exhibit lower strength and higher ductility than those with low Schmid factors. Crystals which required large rotations to become oriented for cross slip were observed to have the shortest stress rupture lives at 760 C, while those which required little or no rotation had the longest lives. In addition, stereographic triangles obtained for Mar-M247 and Mar-M200 single crystals reveal that crystals with orientations near the -111 had the highest lives, those near the 001 had high lives, and those near the 011 had low lives.

Mackay, R. A.; Maier, R. D.; Dreshfield, R. L.

1980-01-01

432

Fatigue Failure Criteria for Single Crystal Nickel Superalloys  

NASA Technical Reports Server (NTRS)

High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine and rocket engine turbopump blades is a pervasive problem. Single crystal turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry and NASA because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the pan geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades is complicated to predict due to the material orthotropy and variations in crystal orientations. A fatigue failure criteria based on the maximum shear stress amplitude [delta t max] on the 30 slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criteria reduces the scatter in uniaxial LCF test data, for four different specimen orientations, for PWA 1484 at 1200 F in air, quite well. A power law curve fit of the failure parameter, delta t max, vs. cycles to failure is presented.

Arakere, Nagaraj K.

1999-01-01

433

Elastic Moduli, Pressure Derivatives, and Temperature Derivatives of Single-Crystal Olivine and Single-Crystal Forsterite  

Microsoft Academic Search

Ultrasonic wave velocities in single-crystal forsteritc (F) and single-crystal olivine (0) have been measured as a function of pressure and of temperature near ambient conditions. Shear and longitudinal velocities were measured in eighteen independent modes, so that each of the nine elastic constants could be calculated by at least two independent equations. The adiabatic stiffness constants c{j (in Mb), their

Mineo Kumazawa; Orson L. Anderson

1969-01-01

434

Crystallization and electrical characteristics of ferroelectric Bi3.15Nd0.85Ti3O12 thin films prepared by a sol gel process  

Microsoft Academic Search

Ferroelectric Bi3.15Nd0.85Ti3O12 (BNdT) thin films were deposited on Pt\\/Ti\\/SiO2\\/Si substrates using a sol gel process and Bi(NO3)3 was used as one of starting materials. Upon heating the major weight loss of the wet films occurred below 320 °C and nitrogen was almost completely removed at 650 °C. The films began to crystallize around 520 °C. The films annealed at 750

Y. Qiao; C. J. Lu; Y. J. Qi; Y. H. Zhou

2008-01-01

435

Transitions between paraelectric and ferroelectric phases of bent-core smectic liquid crystals in the bulk and in thin freely suspended films.  

PubMed

We report on the contrasting phase behavior of a bent-core liquid crystal with a large opening angle between the mesogenic units in the bulk and in freely suspended films. Second-harmonic generation experiments and direct observation of director inversion walls in films in an applied electric field reveal that the nonpolar smectic C phase observed in bulk samples becomes a ferroelectric "banana" phase in films, showing that a mesogen with a small steric moment can give a phase with polar order in freely suspended films even when the corresponding bulk phase is paraelectric. PMID:23214799

Eremin, Alexey; Floegel, Martin; Kornek, Ulrike; Stern, Stephan; Stannarius, Ralf; Nádasi, Hajnalka; Weissflog, Wolfgang; Zhu, Chenhui; Shen, Yongqiang; Park, Cheol Soo; Maclennan, Joseph; Clark, Noel

2012-11-01

436

Crystal growth, structural and optical characterization of a semi-organic single crystal for frequency conversionapplications  

NASA Astrophysics Data System (ADS)

Single crystals of semi-organic L-histidine hydrobromide have been grown by slow evaporation technique from a mixture of L-histidine and hydrobromic acid in aqueous solution at ambient temperature. From high-resolution X-ray diffraction analysis, the crystalline perfection of the grown crystal has been studied. Single crystal X-ray diffraction analyses, Nuclear Magnetic Resonance spectral analysis, Thermo-Gravimetry (TG), Differential Thermal Analysis (DTA) and hardness test have been employed to characterize the as-grown crystals. The UV cutoff wavelength of the grown crystal is below 300 nm and has a wide transparency window, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics have been studied using Q switched Nd:YAG laser ( ?=1064 nm). The second harmonic generation conversion efficiency of the grown crystals confirms their suitability for frequency conversion applications.

Anandan, P.; Parthipan, G.; Saravanan, T.; Mohan Kumar, R.; Bhagavannarayana, G.; Jayavel, R.

2010-12-01

437

Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys  

NASA Technical Reports Server (NTRS)

High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297 finite element model runs. Fatigue lives at critical points in the blade are computed using finite element stress results and the failure criterion developed. Stress analysis results in the blade attachment region are also presented. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to significantly increase a component S resistance to fatigue crack growth with- out adding additional weight or cost. [DOI: 10.1115/1.1413767

Arakere, N. K.; Swanson, G.

2002-01-01

438

SINGLE CRYSTAL NIOBIUM TUBES FOR PARTICLE COLLIDERS ACCELERATOR CAVITIES  

SciTech Connect

The objective of this research project is to produce single crystal niobium (Nb) tubes for use as particle accelerator cavities for the Fermi laboratory’s International Linear Collider project. Single crystal Nb tubes may have superior performance compared to a polycrystalline tubes because the absence of grain boundaries may permit the use of higher accelerating voltages. In addition, Nb tubes that are subjected to the high temperature, high vacuum crystallization process are very pure and well annealed. Any impurity with a significantly higher vapor pressure than Nb should be decreased by the relatively long exposure at high temperature to the high vacuum environment. After application of the single crystal process, the surfaces of the Nb tubes are bright and shiny, and the tube resembles an electro polished Nb tube. For these reasons, there is interest in single crystal Nb tubes and in a process that will produce single crystal tubes. To convert a polycrystalline niobium tube into a single crystal, the tube is heated to within a few hundred ?C of the melting temperature of niobium, which is 2477 ?C. RF heating is used to rapidly heat the tube in a narrow zone and after reaching the operating temperature, the hot zone is slowly passed along the length of the tube. For crystallization tests with Nb tubes, the traverse rate was in the range of 1-10 cm per hour. All the crystallization tests in this study were performed in a water-cooled, stainless steel chamber under a vacuum of 5 x10-6 torr or better. In earliest tests of the single crystal growth process, the Nb tubes had an OD of 1.9 cm and a wall thickness of 0.15 mm. With these relatively small Nb tubes, the single crystal process was always successful in producing single crystal tubes. In these early tests, the operating temperature was normally maintained at 2200 ?C, and the traverse rate was 5 cm per hour. In the next test series, the Nb tube size was increased to 3.8 cm OD and the wall thickness was increased 0.18 mm and eventually to 0.21 mm. Again, with these larger tubes, single crystal tubes were usually produced by the crystallization process. The power supply was generally operated at full output during these tests, and the traverse rate was 5 cm per hour. In a few tests, the traverse rate was increased to 10 cm per hour, and at the faster traverse rate, single crystal growth was not achieved. In these tests with a faster traverse rate, it was thought that the tube was not heated to a high enough temperature to achieve single crystal growth. In the next series of tests, the tube OD was unchanged at 3.8 cm and the wall thickness was increased to 0.30 mm. The increased wall thickness made it difficult to reach an operating temperature above 2,000 ?C, and although the single crystal process caused a large increase in the crystal grains, no single crystal tubes were produced. It was assumed that the operating temperature in these tests was not high enough to achieve single crystal growth. In FY 2012, a larger power supply was purchased and installed. With the new power supply, temperatures above the melting point of Nb were easily obtained regardless of the tube thickness. A series of crystallization tests was initiated to determine if indeed the operating temperature of the previous tests was too low to achieve single crystal growth. For these tests, the Nb tube OD remained at 3.8 cm and the wall thickness was 0.30 mm. The first test had an operating temperature of 2,000 ?C. and the operating temperature was increased by 50 ?C increments for each successive test. The final test was very near the Nb melting temperature, and indeed, the Nb tube eventually melted in the center of the tube. These tests showed that higher temperatures did yield larger grain sizes if the traverse rate was held constant at 5 cm per hour, but no single crystal tubes were produced even at the highest operating temperature. In addition, slowing the traverse rate to as low as 1 cm per hour did not yield a single crystal tube regardless of operating temperature. At this time, it

MURPHY, JAMES E [University of Nevada, Reno] [University of Nevada, Reno

2013-02-28

439

Single Crystal Growth of Se-Te Alloys onto Tellurium from the Melts  

Microsoft Academic Search

The method to obtain single crystals of Se-Te alloys is developed. In this method, it is possible to grow a single crystal of an alloy from the melt, using a single crystal of tellurium as a seed for a Bridgmanlike method. The crystal is grown epitaxially onto tellurium. The obtained crystals is homogeneous except the layer of a few mm

Tadashi Shiosaki; Akira Kawabata

1971-01-01

440

THE PALEOMAGNETISM OF SINGLE SILICATE CRYSTALS: RECORDING GEOMAGNETIC FIELD  

E-print Network

THE PALEOMAGNETISM OF SINGLE SILICATE CRYSTALS: RECORDING GEOMAGNETIC FIELD STRENGTH DURING MIXED of the geomagnetic reversal chronology of the last 160 million years are well established. The relationship between of in situ and laboratory-induced alteration. Here we review an alternative approach. Single plagioclase

Jellinek, Mark

441

Direct observation of interlocked domain walls and topological four-state vortex-like domain patterns in multiferroic YMnO3 single crystal  

NASA Astrophysics Data System (ADS)

Using the advanced spherical aberration-corrected high angle annular dark field scanning transmission electron microscope imaging techniques, we investigated atomic-scale structural features of domain walls and domain patterns in YMnO3 single crystal. Three different types of interlocked ferroelectric-antiphase domain walls and two abnormal topological four-state vortex-like domain patterns are identified. Each ferroelectric domain wall is accompanied by a translation vector, i.e., 1/6[210] or -1/6[210], demonstrating its interlocked nature. Different from the four-state vortex domain patterns caused by a partial edge dislocation, two four-state vortex-like domain configurations have been obtained at atomic level. These observed phenomena can further extend our understanding of the fascinating vortex domain patterns in multiferroic hexagonal rare-earth manganites.

Tian, Lei; Wang, Yumei; Ge, Binghui; Zhang, Xiangqun; Zhang, Zhihua

2015-03-01

442

Raman spectra of deuteriated taurine single crystals  

NASA Astrophysics Data System (ADS)

The polarized Raman spectra of partially deuteriated taurine [(ND 3+) 0.65(NH 3+) 0.35(CH 2) 2SO 3-] crystals from x( zz) x and x( zy) x scattering geometries of the A g and B g irreducible representations of the factor group C 2h are reported. The temperature-dependent Raman spectra of partially deuteriated taurine do not reveal any evidence of the structural phase transition undergone by normal taurine at about 250 K, but an anomaly observed in the 180 cm -1 band at ˜120 K implies a different dynamic for this band (which is involved in a pressure-induced phase transition) in the deuteriated crystal.

Souza, J. M. de; Lima, R. J. C.; Freire, P. T. C.; Sasaki, J. M.; Melo, F. E. A.; Filho, J. Mendes; Jones, Derry W.

2005-05-01

443

The phase transitions of ferroelectric Sr2Ta2O7 crystals by MDSC, Brillouin and dielectric spectroscopy  

Microsoft Academic Search

The structural phase transitions of Sr2Ta2O7 single crystals have been studied by the modulated temperature differential scanning calorimetry (MDSC), Brillouin scattering and dielectric spectroscopy. The specific heat (Cp) was measured over a wide temperature range from -150°C to 25°C and from 100°C to 210°C. The Cp curve showed an anomaly at To = 166.7°C, indicating the phase transition Cmcm rarr

A. Hushur; G. Shabbir; J.-H. Ko; S. Kojima

2004-01-01

444

Stress-induced single-polarization single-transverse mode photonic crystal fiber with low nonlinearity  

Microsoft Academic Search

We report on the design of a single-polarization single-transverse mode large mode area photonic crystal fiber. By including index-matched stress applying elements in the photonic cladding an ultra-broadband single polarization window is obtained while a large mode field area of ~700 mum is maintained. Based on that design, an Yb-doped double-clad photonic crystal fiber is realized that combines low nonlinearity

T. Schreiber; F. Röser; O. Schmidt; J. Limpert; R. Iliew; F. Lederer; A. Petersson; C. Jacobsen; K. P. Hansen; J. Broeng; A. Tünnermann

2005-01-01

445

Structure of the RbTi0.98Zr0.02OPO4 single crystal at temperatures of 293 and 105 K  

NASA Astrophysics Data System (ADS)

This paper reports on the results of precision X-ray structural investigations of a RbTi0.98Zr0.02OPO4 single crystal at temperatures of 293 and 105 K. It is established that the observed decrease in the temperature of the ferroelectric phase transition in RbTiOPO4 crystals doped with zirconium is associated with the increase in the Rb-O bond lengths. The structural factors responsible for the decrease in the electrical conductivity in these crystals are revealed. An analysis is made of the structure of the helical channels which in crystals of this family are considered to be a decisive factor for the manifestation of superionic conduction. It is shown that, in structures of the KTiOPO4 (KTP) type, the migration of ions in channels is most hindered inside the cavities.

Alekseeva, O. A.; Dudka, A. P.; Novikova, N. E.; Sorokina, N. I.; Agapova, E. I.; Voronkova, V. I.

2008-07-01

446

Atomic beam scattering from single crystal surfaces  

NASA Astrophysics Data System (ADS)

Application of atom-scattering to a variety of surface problems is expanding rapidly, owing in large part to the extreme surface- sensitivity of this probe. Helium is particularly useful because of its low mass and chemical inertness. Beams with velocity spreads of less than one percent and wavelength of the order of one Angstrom can be formed by nozzle expansion. The scattered flux from a clean, well-ordered crystal surface contains elastic and inelastic, coherent and incoherent, components. The coherent elastic component (i.e., the specular and diffracted beams) contains information about the crystallographic structure of the outer- most atomic layer of the crystal and about the interaction potential between the crystal and the scattered particle. The latter manifests itself in the form of resonances between the incoming free-particle state, and the two-dimensional Bloch states bound in the potential well at the surface. Elastic scattering theory has reached the point where the resonance signatures in the various diffracted beams can be predicted accurately. Crystallographic information resides in the diffracted beam intensities. Theoretical interpretation is less well advanced, though some progress has been made with “hard-wall” models. Experimental studies of reconstructed surfaces and chemisorbed overlayers appear very promising. In inelastic scattering, energy resolution has been achieved by both time-of-flight and diffraction methods. High-resolution studies on alkali halide surfaces have led to experimental determination of Rayleighwave dispersion relations over the full Brillouin zone. Preliminary results have also been obtained on some metals.

Frankl, Daniel R.

447

Crystal rotation in Cu single crystal micropillars: In situ Laue and electron backscatter diffraction  

Microsoft Academic Search

In situ microdiffraction experiments were conducted on focused ion beam machined single crystal Cu pillars oriented for double slip. During deformation, the crystal undergoes lattice rotation on both the primary and critical slip system. In spite of the initial homogeneous microstructure of the Cu pillar, rotation sets in already at yield and is more important at the top of the

R. Maaß; S. van Petegem; D. Grolimund; H. van Swygenhoven; D. Kiener; G. Dehm

2008-01-01

448

Method of making macrocrystalline or single crystal semiconductor material  

NASA Technical Reports Server (NTRS)

A macrocrystalline or single crystal semiconductive material is formed from a primary substrate including a single crystal or several very large crystals of a relatively low melting material. This primary substrate is deposited on a base such as steel or ceramic, and it may be formed from such metals as zinc, cadmium, germanium, aluminum, tin, lead, copper, brass, magnesium silicide, or magnesium stannide. These materials generally have a melting point below about 1000 C and form on the base crystals the size of fingernails or greater. The primary substrate has an epitaxial relationship with a subsequently applied layer of material, and because of this epitaxial relationship, the material deposited on the primary substrate will have essentially the same crystal size as the crystals in the primary substrate. If required, successive layers are formed, each of a material which has an epitaxial relationship with the previously deposited layer, until a layer is formed which has an epitaxial relationship with the semiconductive material. This layer is referred to as the epitaxial substrate, and its crystals serve as sites for the growth of large crystals of semiconductive material. The primary substrate is passivated to remove or otherwise convert it into a stable or nonreactive state prior to deposition of the seconductive material.

Shlichta, P. J. (inventor); Holliday, R. J. (inventor)

1986-01-01

449

Crystal growth, magnetism, transport and superconductivity of two dimensional sodium cobalt oxide single crystals  

Microsoft Academic Search

The objective of this work was to study the single crystal growth of NaxCoO2 by the optical floating zone technique and the intrinsic properties of the high quality single crystal samples thus produced. The properties of the superconductors derived from it will also be reported. This thesis, after a literature review on the NaxCoO2 family and the superconductors derived from

Dapeng Chen

2008-01-01

450

Phase diagram of ( 1 -x )PbMg1/3Nb2/3 O3-x P b TiO3 single crystals  

NASA Astrophysics Data System (ADS)

Experimental results indicated that the Rhombohedral (R) phase, Tetragonal (T) phase, Cubic (C) phase, and the Monoclinic (MC) phase are the stable phases in ferroelectric (1 -x )P b M g1 /3N b2 /3O3-x P b TiO3 single crystals. The Monoclinic MC phase, around the morphotropic phase boundary, was observed in a composition region (0.31 < x < 0.37) between the rhombohedral and tetragonal phase. However, the recent theory poses a challenge in explaining the "temperature-composition" phase diagram completely. Here, an eighth-order expansion of Landau-Dovenshire theory is constructed to investigate the phase transition properties of (1 -x )P b M g1 /3N b2 /3O3-x P b TiO3 single crystals. A full phase diagram is obtained in phenomenological parameter space which is in good accordance with experimental observation. The ferroelectric, dielectric, and piezoelectric properties are calculated in (1 -x )P b M g1 /3N b2 /3O3-x P b TiO3 single crystals with different compositions.

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

2015-02-01

451

Picosecond blue-light-induced infrared absorption in single-domain and periodically poled ferroelectrics  

NASA Astrophysics Data System (ADS)

Picosecond blue-light-induced infrared absorption is investigated in bulk and periodically poled ferroelectrics known to have high photorefractive resistance (KTiOPO4, MgO-doped congruent LiNbO3, MgO-doped stoichiometric LiNbO3, MgO-doped stoichiometric LiTaO3, and KNbO3). KNbO3 and MgO-doped congruent and stoichiometric LiNbO3 show the lowest susceptibility to induced absorption. Periodic poling slightly increases the susceptibility to the induced absorption in all materials but most noticeably in KTiOPO4, MgO-doped stoichiometric LiTaO3, and KNbO3. Different dynamics of induced absorption are investigated. Relatively high thresholds for induced absorption were observed in MgO-doped stoichiometric LiTaO3 and KNbO3. By increasing the peak power intensity of blue light, the induced absorption for LiNbO3, KTiOPO4, and KNbO3 are saturated, while in MgO-doped stoichiometric LiTaO3, the induced absorption increases almost linearly with the blue peak intensity. The low susceptibility to induced absorption observed in KNbO3 corroborates well with the earlier proposed existence of very shallow traps close to the valence band.

Hirohashi, J.; Pasiskevicius, V.; Wang, S.; Laurell, F.

2007-02-01

452

Low-cost single-crystal turbine blades, volume 2  

NASA Technical Reports Server (NTRS)

The overall objectives of Project 3 were to develop the exothermic casting process to produce uncooled single-crystal (SC) HP turbine blades in MAR-M 247 and higher strength derivative alloys and to validate the materials process and components through extensive mechanical property testing, rig testing, and 200 hours of endurance engine testing. These Program objectives were achieved. The exothermic casting process was successfully developed into a low-cost nonproperietary method for producing single-crystal castings. Single-crystal MAR-M 247 and two derivatives DS alloys developed during this project, NASAIR 100 and SC Alloy 3, were fully characterized through mechanical property testing. SC MAR-M 247 shows no significant improvement in strength over directionally solidified (DS) MAR-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. Firtree testing, holography, and strain-gauge rig testing were used to determine the effects of the anisotropic characteristics of single-crystal materials. No undesirable characteristics were found. In general, the single-crystal material behaved similarly to DS MAR-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined. These blades were successfully engine-tested.

Strangman, T. E.; Dennis, R. E.; Heath, B. R.

1984-01-01

453

Method for harvesting rare earth barium copper oxide single crystals  

DOEpatents

A method of preparing high temperature superconductor single crystals is disclosed. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid. 2 figs.

Todt, V.R.; Sengupta, S.; Shi, D.

1996-04-02

454

A 1.0V power supply, 9.5GByte\\/sec write speed, Single-Cell Self-Boost program scheme for Ferroelectric NAND Flash SSD  

Microsoft Academic Search

A Single-Cell Self-Boost (SCSB) program scheme is proposed to achieve a 1.0V power supply operation in Ferroelectric (Fe-) NAND flash memories. In the proposed SCSB sc