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1

Domain Engineered Relaxor Ferroelectric Single Crystals  

NASA Astrophysics Data System (ADS)

Single crystal relaxor ferroelectric materials exhibit extraordinary electromechanical properties. They are being applied in high performance sensors, actuators, and transducers. Field induced polarization switching and phase transitions of these crystals lead to complex nonlinear behavior. In recent years experimental investigations have been conducted to characterize the polarization switching and phase transition behavior as a function of crystallographic orientation, temperature, electric field, and stress. The results give insight into the mechanism underlying the observed large field hysteretic behavior. This review article describes the observed behavior and presents results of multiscale modeling that predicts the macroscopic behavior from the single domain single crystal behavior and evolution of crystal variants at the microscale.

Liu, T.; Lynch, C. S.

2006-08-01

2

A model for Large Electrostrictive Actuation in Ferroelectric Single Crystals  

E-print Network

1 A model for Large Electrostrictive Actuation in Ferroelectric Single Crystals D. Shilo1 , E will allow larger strains at lower mechanical loads. Keywords: Ferroelectrics; Actuation; Electromechanical Institute of Technology, Pasadena, CA 91125, USA A new mode of large electrostrictive actuation, based on 90

Bhattacharya, Kaushik

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

Effective symmetry and physical properties of twinned perovskite ferroelectric single crystals  

E-print Network

Effective symmetry and physical properties of twinned perovskite ferroelectric single crystals Jirí properties of twinned ferroelectric crystals with perovskite structure were analyzed. The twins or twinbands perovskite structure. When a single fer- roelectric crystal is poled along [001] of the cubic coor- dinates

Cao, Wenwu

5

Epitaxial Liftoff for Fully Single Crystal Ferroelectric Thin Films  

NASA Astrophysics Data System (ADS)

High-frequency signal transmission demands in RF and microwave systems, such as electronic phased-array radar and scanning antennas, call for innovative approaches in materials technology. Outstanding issues in such systems are the fabrication of low-loss, highly tunable capacitive elements made of thin-film ferroelecrics. This program used a new epitaxial liftoff technique developed at Columbia University to reduce high-quality, single-crystal films of ferroelectrics such as strontium titanate (ST), potassium tantalate, KTaO3 and potassium tantalate niobate (KTN) for use in microwave devices.

Osgood, Richard M., Jr.; Levy, Miguel; Bakhru, Hassaram; Cross, Eric

2002-08-01

6

Relaxor-based ferroelectric single crystals for electromechanical actuators  

Microsoft Academic Search

The piezoelectric properties of relaxor based ferroelectric single crystals, such as Pb(Zn1\\/3Nb2\\/3)O3 - PbTiO3 (PZN-PT) and Pb(Mg1\\/3Nb2\\/3)O3 - PbTiO3 (PMN- PT) were investigated for electromechanical actuators. In contrast to polycrystalline materials such as Pb(Zr,Ti)O3 (PZT's), morphotropic phase boundary compositions were not essential for high piezoelectric strain. Piezoelectric coefficients (d33's) > 2500 pC\\/N and subsequent strain levels up to > 0.6%

Seung Eek Park; Venkata Vedula; Ming Jen Pan; Wesley S. Hackenberger; Patrick Pertsch; Thomas R. Shrout

1998-01-01

7

Relaxor based ferroelectric single crystals for electro-mechanical actuators  

Microsoft Academic Search

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

S.-E. Park; Thomas R. Shrout

1997-01-01

8

Relaxor-based ferroelectric single crystals for electromechanical actuators  

NASA Astrophysics Data System (ADS)

The piezoelectric properties of relaxor based ferroelectric single crystals, such as Pb(Zn1/3Nb2/3)O3 - PbTiO3 (PZN-PT) and Pb(Mg1/3Nb2/3)O3 - PbTiO3 (PMN- PT) were investigated for electromechanical actuators. In contrast to polycrystalline materials such as Pb(Zr,Ti)O3 (PZT's), morphotropic phase boundary compositions were not essential for high piezoelectric strain. Piezoelectric coefficients (d33's) > 2500 pC/N and subsequent strain levels up to > 0.6% with minimal hysteresis were observed. Crystallographically, high strains are achieved for <001> oriented rhombohedral crystals, though <111> is the polar direction. Ultrahigh strain levels up to 1.7%, an order of magnitude larger than those available from conventional piezoelectric and electrostrictive ceramics could be achieved, being related to an E-field induced phase transformation. Strain vs. E-field behavior under external stress was also much superior to that of conventional piezoelectric ceramics. High electromechanical coupling (k33) > 90% and low dielectric loss <1%, along with large strain make these crystals promising candidates for high performance solid state actuators.

Park, Seung Eek E.; Vedula, Venkata; Pan, Ming-Jen; Hackenberger, Wesley S.; Pertsch, Patrick; Shrout, Thomas R.

1998-07-01

9

Ferroelectric studies on amino acids mixed TGSP single crystals  

Microsoft Academic Search

Amino acids mixed TGS crystals are of interest due to their high pyroelectric coefficient and low dielectric constant. Partial substitution of phosphate has resulted in triglycine sulpho-phosphate (TGSP), a mixed crystal with improved pyroelectric figure of merit. In order to study the effect of amino acids on the ferroelectric properties of TGSP, we have substituted l-alanine (ATGSP), l-valine (VTGSP), l-asparagine

G. Arunmozhi; R. Jayavel; C. Subramanian

1998-01-01

10

Dielectric and ferroelectric properties of phosphoric acid doped triglycine sulfate single crystals  

Microsoft Academic Search

Single crystals of triglycine sulfate (TGS) grown with 25–50 mol% phosphoric acid dopant in solution were investigated for their dielectric, ferroelectric and mechanical hardness properties. A 25 mol% of H3PO4 in solution yielded crystals with a large area in the ac plane without any seed crystal. The room temperature (300 K) dielectric constant (??) and tan? in the frequency range

Aparna Saxena; Vinay Gupta; K. Sreenivas

2001-01-01

11

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

SciTech Connect

Polar organic nonlinear optical material, L-tartaric acid single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study indicates that the grown crystal crystallized in monoclinic system with space group P2{sub 1}. Crystalline perfection of the crystal has been evaluated by high resolution X-ray diffraction technique and it reveals that the crystal quality is good and free from structural grain boundaries. Mechanical stability of the crystal has been analyzed by Vickers microhardness measurement and it exhibits reverse indentation size effect. Piezoelectric d{sub 33} co-efficient for the crystal has been examined and its value is 47 pC/N. The ferroelectric behaviour of the crystal was analyzed by polarization-electric field hysteresis loop measurement.

Murugan, G. Senthil, E-mail: nanosen@gmail.com; Ramasamy, P., E-mail: nanosen@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam, Tamilnadu - 603110 (India)

2014-04-24

12

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

NASA Astrophysics Data System (ADS)

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

Murugan, G. Senthil; Ramasamy, P.

2014-04-01

13

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

14

Multiferroic oxides: Growth of single crystals and investigation of their magnetic, dielectric and ferroelectric properties  

NASA Astrophysics Data System (ADS)

In this talk, special emphasis will be placed on the crystal growth of various oxides by the floating zone technique using optical furnaces. Oxides such as the RMnO3 compounds exhibit a strong coupling between the magnetic and dielectric properties and some of them exhibit multiferroic behavior. LuFe2O4 is another example of a multiferroic crystal, but in this system, the observed ferroelectric polarisation arises due to the charge ordering and electron correlation effects as opposed to the normally observed polarisation due to ionic displacements. In order to understand the emergence of multiferroic behaviour in the RMnO3 compounds, we have produced single crystals of several pure and substituted RMnO3 compounds and investigated the effects of lattice modulations on the magnetic and dielectric properties. The crystal growth of the LuFe2O4 multiferroic compounds and the investigation of the magnetic, dielectric and ferroelectric properties of these crystals will also be presented.

Balakrishnan, Geetha

2013-02-01

15

High performance ferroelectric relaxor-PbTiO3 single crystals: Status and perspective  

NASA Astrophysics Data System (ADS)

Ferroelectrics are essential components in a wide range of applications, including ultrasonic transducers, sensors, and actuators. In the single crystal form, relaxor-PbTiO3 (PT) piezoelectric materials have been extensively studied due to their ultrahigh piezoelectric and electromechanical properties. In this article, a perspective and future development of relaxor-PT crystals are given. Initially, various techniques for the growth of relaxor-PT crystals are reviewed, with crystals up to 100 mm in diameter and 200 mm in length being readily achievable using the Bridgman technique. Second, the characterizations of dielectric and electromechanical properties are surveyed. Boundary conditions, including temperature, electric field, and stress, are discussed in relation to device limitations. Third, the physical origins of the high piezoelectric properties and unique loss characteristics in relaxor-PT crystals are discussed with respect to their crystal structure, phase, engineered domain configuration, macrosymmetry, and domain size. Finally, relaxor-PT single crystals are reviewed with respect to specific applications and contrasted to conventional piezoelectric ceramics.

Zhang, Shujun; Li, Fei

2012-02-01

16

Measurements of the microhardness and compression testing of ferroelectric lead nitrate phosphate single crystals  

Microsoft Academic Search

Ferroelectric crystals of lead nitrate phosphate (LNP) have been grown employing the controlled reaction between lead nitrate\\u000a and orthophosphoric acid. The microhardness of LNP crystals has been determined. The effect of annealing and quenching on\\u000a the mechanical properties of these crystals has been studied.

C C Desai; M S V Ramana

1987-01-01

17

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

Microsoft Academic Search

Effect of amino acids (l-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in

C. M. Raghavan; R. Sankar; R. Mohan Kumar; R. Jayavel

2008-01-01

18

Ferroelectric and Antiferroelectric Liquid Crystals  

Microsoft Academic Search

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

SVEN T. LAGERWALL

2004-01-01

19

Ferroelectric domain switching in tri-glycine sulphate and barium-titanate bulk single crystals by scanning force microscopy  

NASA Astrophysics Data System (ADS)

Direct writing of ferroelectric domains into tri-glycine sulphate and barium-titanate single crystals by scanning force microscopy is demonstrated. Oppositely polarized domains were created by choosing an adequate polarity for the d.c. voltage applied to the conductive tip: a positive voltage bias applied to the tip results in the polarization pointing into the crystal, and vice versa. The direct writing of lines and dots measuring less than 500 nm in width is demonstrated. Any structure written by this method is imaged with the same tip, now biased with an a.c. voltage. Image contrast results from both Maxwell stress and the piezoelectric response of the ferroelectric sample.

Eng, L. M.; Abplanalp, M.; Günter, P.

20

Ferroelectric Liquid Crystals  

Microsoft Academic Search

The main advances in the field of bulk ferroelectric liquid crystals since 1984 are reviewed. Recent experiments have shown that the molecular tilt and the in-plane spontaneous polarization are not strictly proportional to each other as assumed before. Microscopic experiments such as NMR and NQR have further allowed for a determination of the basic order parameters as a function of

Robert Blinc; Cene Filipi?; Adrijan Levstik; BošTjan Žekš; T. Carlsson

1987-01-01

21

Investigation of dielectric, piezoelectric and ferroelectric properties of b-axis grown triglycine sulphate single crystal  

NASA Astrophysics Data System (ADS)

Large single crystal of triglycine sulphate (dimension 100 mm along monoclinic b-axis and 15 mm in diameter) was grown using the unidirectional solution growth technique. The X-ray diffraction studies confirmed the growth/long axis to be b-axis (polar axis). The dielectric studies were carried out at various temperatures to establish the phase transition temperature. The frequency response of the dielectric constant, dielectric loss and impedance of the crystal along the growth axis, was monitored. These are typically characterized by strong resonance peaks in the kHz region. The piezoelectric coefficients like stiffness constant ( C), elastic coefficient ( S), electromechanical coupling coefficient ( k) and d 31 were calculated using the resonance-antiresonance method. Polarization ( P)-Electric field ( E) hysteresis loops were recorded at various temperatures to find the temperature-dependent spontaneous polarization of the grown crystal. The pyroelectric coefficients were determined from the pyroelectric current measurement by the Byer and Roundy method. The ferroelectric domain patterns were recorded on (010) plane using scanning electron microscopy and optical microscopy.

Justin Raj, C.; Kundu, Swarup; Varma, K. B. R.

2011-12-01

22

Ultrahigh strain and piezoelectric behavior in relaxor based ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

The piezoelectric properties of relaxor based ferroelectric single crystals, such as Pb(Zn1/3Nb2/3)O3-PbTiO3 and Pb(Mg1/3Nb2/3)O3-PbTiO3 were investigated for electromechanical actuators. In contrast to polycrystalline materials such as Pb(Zr,Ti)O3, morphotropic phase boundary compositions were not essential for high piezoelectric strain. Piezoelectric coefficients (d33's)>2500 pC/N and subsequent strain levels up to >0.6% with minimal hysteresis were observed. Crystallographically, high strains are achieved for <001> oriented rhombohedral crystals, although <111> is the polar direction. Ultrahigh strain levels up to 1.7%, an order of magnitude larger than those available from conventional piezoelectric and electrostrictive ceramics, could be achieved being related to an E-field induced phase transformation. High electromechanical coupling (k33)>90% and low dielectric loss <1%, along with large strain make these crystals promising candidates for high performance solid state actuators.

Park, Seung-Eek; Shrout, Thomas R.

1997-08-01

23

Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications.  

PubMed

In the past decade, domain engineered relaxor-PT ferroelectric single crystals, including (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) and (1-x-y)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT), with compositions near the morphotropic phase boundary (MPB) have triggered a revolution in electromechanical devices owing to their giant piezoelectric properties and ultra-high electromechanical coupling factors. Compared to traditional PbZr1-x Ti x O3 (PZT) ceramics, the piezoelectric coefficient d 33 is increased by a factor of 5 and the electromechanical coupling factor k 33 is increased from < 70% to > 90%. Many emerging rich physical phenomena, such as charged domain walls, multi-phase coexistence, domain pattern symmetries, etc., have posed challenging fundamental questions for scientists. The superior electromechanical properties of these domain engineered single crystals have prompted the design of a new generation electromechanical devices, including sensors, transducers, actuators and other electromechanical devices, with greatly improved performance. It took less than 7 years from the discovery of larger size PMN-PT single crystals to the commercial production of the high-end ultrasonic imaging probe "PureWave". The speed of development is unprecedented, and the research collaboration between academia and industrial engineers on this topic is truly intriguing. It is also exciting to see that these relaxor-PT single crystals are being used to replace traditional PZT piezoceramics in many new fields outside of medical imaging. The new ternary PIN-PMN-PT single crystals, particularly the ones with Mn-doping, have laid a solid foundation for innovations in high power acoustic projectors and ultrasonic motors, hinting another revolution in underwater SONARs and miniature actuation devices. This article intends to provide a comprehensive review on the development of relaxor-PT single crystals, spanning material discovery, crystal growth techniques, domain engineering concept, and full-matrix property characterization all the way to device innovations. It outlines a truly encouraging story in materials science in the modern era. All key references are provided and 30 complete sets of material parameters for different types of relaxor-PT single crystals are listed in the Appendix. It is the intension of this review article to serve as a resource for those who are interested in basic research and practical applications of these relaxor-PT single crystals. In addition, possible mechanisms of giant piezoelectric properties in these domain-engineered relaxor-PT systems will be discussed based on contributions from polarization rotation and charged domain walls. PMID:25061239

Sun, Enwei; Cao, Wenwu

2014-08-01

24

Electric field induced metastable ferroelectric phase and its behavior in (Pb, La)(Zr, Sn, Ti)O3 antiferroelectric single crystal near morphotropic  

E-print Network

Electric field induced metastable ferroelectric phase and its behavior in (Pb, La)(Zr, Sn, Ti)O3-ray diffraction analysis and electrical properties reveal coexistence of antiferroelectric/ferroelectric (FE the PLZST single crystal a promising candidate for thermal switch and actuator application. VC 2014 AIP

Cao, Wenwu

25

Surface morphology, chemical contrast, and ferroelectric domains in TGS bulk single crystals differentiated with UHV non-contact force microscopy  

NASA Astrophysics Data System (ADS)

Ferroelectric bulk single crystals of tri-glycine sulphate (TGS) have been investigated in ultra-high vacuum (UHV) using dynamic force microscopy (DFM) in the non-contact (nc) mode. Both chemical contrast from different sub-unit cell cleavage steps, and ferroelectric domains were differentiated by recording the variation in interaction force affecting the excitation amplitude Aexc applied to the piezo shaker in constant amplitude DFM. No chemical difference was found for steps measuring half the unit cell height b, in contrast to b/4—steps where sulphate ions change the local short-range chemical forces. By varying the bias voltage applied to the TGS counter electrode, the sign of bound surface charge within each ferroelectric domain was determined. Domain walls separating regions with antiparallel polarisation vectors are resolved down to a 9 nm domain wall width. Furthermore, we achieved atomic resolution with nc-DFM on cleaved TGS samples indicating the monoclinic unit cell at the ferroelectric sample surface with a=1.0±0.05 nm, c=0.55±0.05 nm, and ?=107±3°.

Eng, L. M.; Bammerlin, M.; Loppacher, Ch; Guggisberg, M.; Bennewitz, R.; Lüthi, R.; Meyer, E.; Güntherodt, H.-J.

1999-02-01

26

Electromechanical behavior of relaxor ferroelectric crystals  

NASA Astrophysics Data System (ADS)

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

Liu, Tieqi

27

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

NASA Astrophysics Data System (ADS)

The large field behavior of [011]C cut relaxor ferroelectric lead indium niobate-lead magnesium niobate-lead titanate, xPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3, single crystals was experimentally characterized in the piezoelectric d322-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.; Tian, Jian; Lynch, Christopher S.

2014-08-01

28

Domain Motion of Ferroelectricity of Bi2SrTa2O9 Single Crystals under an AC-Voltage Electric Field  

Microsoft Academic Search

A novel phenomenon, which increases the remanent polarization of Bi2SrTa2O9 single crystals, a promising candidate for ferroelectric random access memories (FeRAM), has been identified. The single crystals, grown in vapor phases using the self-flux method, have a composition characterized asBixSryTa2O9 (x=2.08±0.09, y=1.04±0.06). Incontrast to BixSryTa2O9 (x=1.91±0.05, y=1.27±0.08) single crystals grown by the self-flux method, the coercive field of the present

Akio Machida; Naomi Nagasawa; Takaaki Ami; Masayuki Suzuki

1999-01-01

29

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

30

Theory of magnetoelectric effects at magnetoacoustic resonance in single-crystal ferromagnetic-ferroelectric heterostructures  

NASA Astrophysics Data System (ADS)

A theoretical model that predicts very strong magnetoelectric (ME) interactions at magnetoacoustic resonance (MAR) in single-crystal ferrite-piezoelectric bilayer is discussed. In such bilayers, the ME interactions are mediated by mechanical strain. We considered ME coupling at the coincidence of electromechanical resonance for the electrical subsystem and ferromagnetic resonance for the ferrite. The theory predicts efficient transfer of energy between phonons, spin waves, and electric and magnetic fields at MAR. Ultrahigh ME coefficients, on the order of 80-480V/cmOe at 5-10GHz , are expected for nickel ferrite-lead zirconate titanate (PZT) and yttrium-iron garnet-PZT bilayers. The phenomenon is also of importance for the realization of multifunctional ME nanosensors/transducers operating at microwave frequencies.

Bichurin, M. I.; Petrov, V. M.; Ryabkov, O. V.; Averkin, S. V.; Srinivasan, G.

2005-08-01

31

Ferroelectric Liquid Crystal Chemistry: Cyanohydrin Ether and Cyanoalkyl Ferroelectric Liquid Crystals; Synthesis and Liquid Crystal Properties  

Microsoft Academic Search

From simple symmetry arguments it can be predicted that tilted chiral smectic liquid crystals should exhibit ferroelectric polarization. While these predictions are found to hold true, the symmetry arguments do not lead insight into the molecular origins of this phenomena. Such insight is necessary to allow the directed design of new high-performance ferroelectric liquid crystal materials is to be achieved.

Kirk Frederick Eidman

1988-01-01

32

Effect of field driven phase transformations on the loss tangent of relaxor ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

The effect of a bias stress induced phase transformation on the large field dielectric loss in [001] cut and poled single crystal stack actuators of (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT, x = 32) was experimentally characterized. Dielectric loss was observed to increase with compressive preload and electric field amplitude. The dielectric loss was determined by measuring the area within electric displacement vs. electric field hysteresis loops and the measured area was expressed in terms of an effective loss tangent. This approach matches the measured area within the hysteresis loop to an equivalent area ellipse in which the electric displacement lags the electric field by an amount, delta, under sinusoidal loading. The results collapse the measured loss as a function of bias stress and electric field amplitude reasonably close to a single curve. The measured dielectric loss behavior was attributed to the compressive stress preload driving a partial phase transformation from rhombohedral to orthorhombic and the electric field driving the reverse phase transformation from the stress induced orthorhombic phase to the zero stress rhombohedral phase. When the compressive bias stress partially or fully drives this phase transformation, the dielectric loss under unipolar electric field loading increases. This work is focused on quasi-static measurements. The large field dielectric loss is anticipated to be a function of frequency and temperature.

Gallagher, John A.; Liu, Tieqi; Lynch, Christopher S.

2013-02-01

33

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

34

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

35

Kinetics of etching of dislocations in ferroelectric lead hydrogen phosphate and lead nitrate phosphate single crystals  

Microsoft Academic Search

The principle behind the selection of etchants and the mechanism of their action are poorly understood in spite of many attempts made by Gilman and Johnston in LiF [1], Thyagarajan and Urusovskaya in CSI [2] and Baranoya and Nadgornyi in NaC1 [3] ionic crystals. Having chosen the proper etchants, it naturally becomes interesting to investigate the kinetics of etching for

C. C. Desai; M. S. V. Ramana; M. J. Shukla

1990-01-01

36

A relaxor ferroelectric single crystal cut resulting in large d312 and zero d311 for a shear mode accelerometer and related applications  

NASA Astrophysics Data System (ADS)

Relaxor ferroelectric single crystals exhibit anisotropic piezoelectric behavior. This enables the use of a combination of crystal cut and poling to obtain piezoelectric properties optimized for certain applications. This work describes a crystal cut that is optimized for applications where a strong face shear mode d312 coupling is desired with a zero d311 or zero d322 piezoelectric coefficient. Such a crystal cut enables the production of stack actuators in a long bar shape with the electric field perpendicular to the bar length. These bars can be cantilevered with a mass at the end to produce a highly sensitive shear mode accelerometer. The zero value of d311 or d322 eliminates a possible extensional mode coupling along the length of the bar. Only one of d311 or d322 can be made equal to zero, the other having a negative value.

Goljahi, S.; Gallagher, J.; Zhang, S. J.; Luo, J.; Sahul, R.; Hackenberger, W.; Lynch, C. S.

2012-05-01

37

Local Electromechanical Response at a Single Ferroelectric Domain Wall in Lithium Niobate  

E-print Network

Local Electromechanical Response at a Single Ferroelectric Domain Wall in Lithium Niobate DAVID A electromechanical response across a single ferroelectric domain wall in congruent lithium niobate at room in the crystal, which interact with the domain wall. I. INTRODUCTION FERROELECTRIC lithium niobate and lithium

Gopalan, Venkatraman

38

Photorefractive effect in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

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

Sasaki, Takeo; Naka, Yumiko

2014-03-01

39

Photoluminescence and electrical properties of Eu-doped (Na0.5Bi0.5)TiO3 ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

Eu3+-doped Na0.5Bi0.5TiO3 (Eu:NBT) single crystals were grown by a top-seeded solution growth method. Photoluminescence emission and excitation spectra of Eu:NBT were investigated. The two transitions in 7F0 ? 5D0 excitation spectra reveal that Eu3+ ions were incorporated into two adjacent crystallographic sites in NBT, i.e., Bi3+ and Na+ sites. The former has a symmetrical surrounding, while the later has a disordered environment, which was confirmed by decay curve measurements. The dielectric dispersion behavior was depressed and the piezoelectric and ferroelectric properties were improved after Eu doping.

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

2014-02-01

40

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

41

Electric field induced metastable ferroelectric phase and its behavior in (Pb, La)(Zr, Sn, Ti)O3 antiferroelectric single crystal near morphotropic phase boundary  

NASA Astrophysics Data System (ADS)

Antiferroelectric (AFE) (Pb, La)(Zr, Sn, Ti)O3 (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; Cao, Wenwu; Li, Qiang; Yan, Qingfeng; Gao, Jinghan; Zhuo, Fangping; Xi, Xiaoqing; Zhang, Yiling; Chu, Xiangcheng

2014-02-01

42

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

43

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

44

Bipolar electro-caloric effect in SrxBa(1-x)Nb2O6 lead-free ferroelectric single crystal  

NASA Astrophysics Data System (ADS)

Here we report the anomalous electro-caloric effect (ECE) observed in lead-free SrxBa(1-x)Nb2O6 (x=0.50 , 0.61 and 0.75) ferroelectric single crystals. Temperature-dependent hysteresis measurement revealed that the spontaneous polarization of SrxBa(1-x)Nb2O6 single crystals with all the compositions under investigation decreases with a decrease in the temperature below the temperature of the dielectric maxima (T_{\\max}) . As a consequence, these crystals exhibited negative electro-caloric effect at lower temperature along with the usual positive ECE above T_{\\max} . The EC coefficient (\\xi) obtained near T_{\\max} is 0.21, 0.43 and 0.28 K mm/kV for x=0.50 , 0.61 and 0.75 samples, respectively. The maximum values of \\xi in the negative ECE region are -1.4, -0.81 and -0.44\\ \\text{K mm/kV} for 50SBN, 61SBN and 75SBN, respectively.

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

2014-08-01

45

Generalized Landau model of ferroelectric liquid crystals  

Microsoft Academic Search

Using a generalized Landau type of free-energy density, we develop a theoretical model which, in a unified way, describes the general features of the tilt, polarization, pitch, dielectric susceptibility, and heat capacity of ferroelectric liquid crystals. Rewriting the equations into dimensionless form, we show that six parameters are needed in order to account properly for the temperature dependence of the

T. Carlsson; B. Zeks; A. Levstik; C. Filipic; I. Levstik; R. Blinc

1987-01-01

46

Ferroelectric behaviour of triglycine sulphate crystals containing low concentrations of metal ions near the transition temperature  

Microsoft Academic Search

Several ferroelectric properties of triglycine sulphate single crystals both pure and with different doping substitutions in the structure have been studied in the vicinity of the critical point Tc. The parameters engaged in the statistical dipolar theory of ferroelectrics are derived, from dielectric constant and hysteresis loop measurements, allowing a distinction between atomic and dipolar polarisation. The numerical values of

M. A. Gaffar; A. A. El-Fadl; S. A. Mansour

1989-01-01

47

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

48

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

49

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

50

Permissible symmetries of multi-domain configurations in perovskite ferroelectric crystals  

E-print Network

Permissible symmetries of multi-domain configurations in perovskite ferroelectric crystals Jiri through domain engineering are specified for perovskite ferroelectric crystals having tetragonal walls . Many useful ferroelectric materials have the so-called perovskite structure, which contains

Cao, Wenwu

51

Diisopropylammonium Bromide Is a High-Temperature Molecular Ferroelectric Crystal  

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

52

Ferroelectric order in individual nanometre-scale crystals  

NASA Astrophysics Data System (ADS)

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/in2 memories and provides a glimpse of the structural and electrical manifestations of ferroelectricity down to its ultimate limits.

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

2012-08-01

53

Growth and ferroelectric properties of l-, d-, and dl-methionine-doped triglycine sulfate crystals  

Microsoft Academic Search

Single crystals of triglycine sulfate (TGS) doped with l-, d-, and dl-methionine have been prepared. Doping effects on the crystal morphology, the ferroelectric domain structure, and the generation of internal bias field Eb were investigated. These effects were compared with each other and also compared with those of alanine-doped crystals. Though l-methionine-doped crystals show the asymmetric morphology analogous to l-alanine-doped

Toshio Kikuta; Toshinari Yamazaki; Noriyuki Nakatani

2010-01-01

54

Modeling and simulation of switchings in ferroelectric liquid crystals.  

E-print Network

of liquid crystals confined between two plates, and study properties of the ..... this case, application of an applied field parallel to x?axis causes a reorientation of ..... of ferroelectric solids, particularly materials in the perovskite family, although ...

2009-12-09

55

Anisotropy of ferroelectric behavior of (1 - x)Bi1/2Na1/2TiO3-xBaTiO3 single crystals across the morphotropic phase boundary  

NASA Astrophysics Data System (ADS)

(1 - x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-100xBT) single crystals with three different compositions of x = 0.036, 0.065, and 0.088, covering the rhombohedral to predominantly tetragonal region of the phase diagram and encompassing the morphotropic phase boundary (MPB), were grown by top-seeded solution growth. Dielectric and ferroelectric measurements were performed on samples with different orientations with respect to the crystallographic axes. While the results complied with the current understanding of the crystallographic structure, no enhancement of electromechanical properties based on transient polarization rotation was observed. This clearly sets BNT-100xBT apart from other relaxor ferroelectric systems with a rhombohedral-tetragonal MPB such as (1 - x) Pb(Mg1/3Nb2/3)O3-xPbTiO3. An anomaly was observed in the poling behavior of the strain in <001> oriented BNT-100xBT in the immediate vicinity of the MPB with x = 0.065, resulting in a giant small-signal piezoelectric coefficient d33 of 4600 pm/V. This effect is hypothesized to be due to an irreversible phase change from rhombohedral polar nanoregions to tetragonal ferroelectric microdomains.

Schneider, D.; Jo, Wook; Rödel, J.; Rytz, D.; Granzow, T.

2014-07-01

56

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

57

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

58

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

NASA Astrophysics Data System (ADS)

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

Asaji, Tetsuo; Gotoh, Kazuma; Watanabe, Jun

2006-06-01

59

ORIGINAL ARTICLE Single ferroelectric-domain photovoltaic switch based  

E-print Network

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

Jo, Moon-Ho

60

Continuous cross-over from ferroelectric to relaxor state and piezoelectric properties of BaTiO{sub 3}-BaZrO{sub 3}-CaTiO{sub 3} single crystals  

SciTech Connect

Optimal properties like piezoelectricity can be found in polarizable materials for which the structure changes sharply under small composition variations in the vicinity of their morphotropic phase boundary or the triple point in their isobaric temperature-composition phase diagram. In the latter, lead-free (Ba{sub 0.850}Ca{sub 0.150})(Ti{sub 0.900}Zr{sub 0.100})O{sub 3} ceramics exhibit outstanding piezoelectric coefficients. For the first time, we report the growth of piezoelectric lead-free single crystals in the BaTiO{sub 3}-BaZrO{sub 3}-CaTiO{sub 3} pseudo-ternary system. The stoichiometry control in the CaO-BaO-TiO{sub 2}-ZrO{sub 2} solid solution led to single crystals with various compositions ranging from (Ba{sub 0.857}Ca{sub 0.143})(Ti{sub 0.928}Zr{sub 0.072})O{sub 3} to (Ba{sub 0.953}Ca{sub 0.047})(Ti{sub 0.427}Zr{sub 0.573})O{sub 3}. We evidenced a continuous cross-over from a ferroelectric state at high titanium content to a relaxor one on increasing the zirconium content. Such a property tuning is rather seldom observed in lead-free ferroelectrics and confirms what was already reported for ceramics. Single crystal with (Ba{sub 0.838}Ca{sub 0.162})(Ti{sub 0.854}Zr{sub 0.146})O{sub 3} composition, which has been grown and oriented along [001] crystallographic direction, displayed electromechanical coefficients d{sub 31} and k{sub 31} of 93 pC.N{sup ?1} and 0.18, respectively, near the room temperature (T?=?305?K)

Benabdallah, F.; Veber, P., E-mail: veber@icmcb-bordeaux.cnrs.fr; Prakasam, M.; Viraphong, O.; Maglione, M. [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Université Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Shimamura, K. [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2014-04-14

61

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

62

Research on TGS single crystal growth with modulated structure  

NASA Astrophysics Data System (ADS)

The experimental results of TGS crystal growth with modulated structure (periodic laminar of ferroelectric domains) is briefly discussed in this paper. The method used here is to add some DL-alanine additive in the solution of TGS and to apply the electric field during crystal growth, the direction of which is periodically varied. By using this method, TGS single crystals containing a nearly regular and flat periodic laminar structure of ferroelectric domains have been fabricated.

Wang, Wenshan; Qi, Ming

1986-12-01

63

EVIDENCE OF TWO NEW ORDERED SMECTIC PHASES IN FERROELECTRIC LIQUID CRYSTALS  

E-print Network

548 EVIDENCE OF TWO NEW ORDERED SMECTIC PHASES IN FERROELECTRIC LIQUID CRYSTALS J. DOUCET, P of ferroelectricity in liquid crystals was given by R. B. Meyer et al. in 1975 [1]. The authors studied a chiral ferroelectric liquid crystals have been synthetized [3] ; some of them exhibit an ordered smectic phase

Boyer, Edmond

64

Dielectric relaxation in a ferroelectric liquid crystal (*) Ph. Martinot-Lagarde and G. Durand  

E-print Network

269 Dielectric relaxation in a ferroelectric liquid crystal (*) Ph. Martinot-Lagarde and G. Durand transverse A.C. electric field on a ferroelectric liquid crystal close to its transition temperature Tc. - Ferroelectric liquid crystals possess in their ordered C* phase an increase of the transverse dielectric

Boyer, Edmond

65

Optical recording using a photochromic ferroelectric liquid crystal  

SciTech Connect

The direction of molecular switching, i.e., the sign of the electro-optic response, in ferroelectric liquid crystals depends on the polarity of the applied electric field as well as on the sign of the spontaneous polarization. Light-induced switching of the molecules by ultraviolet light was found in a photochromic ferroelectric liquid crystal at fixed field polarity. A high contrast image was recorded whose contrast could easily be inverted by reversing the field polarity. Moreover, in the presence of bistable boundary conditions, the optically recorded image can be stored after removal of the electric field. The effect of light-assisted switching in the photochromic ferroelectric liquid crystal seems to be promising for applications such as optical recording, all-optical switches, and image storage. {copyright} 2001 American Institute of Physics.

Komitov, L.; Tsutsumi, O.; Ruslim, C.; Ikeda, T.; Ichimura, K.; Yoshino, K.

2001-06-15

66

Design of a polarimeter with two ferroelectric liquid crystal panels  

NASA Astrophysics Data System (ADS)

We present a Stokes polarimeter based on two ferroelectric liquid crystal monopixel panels. This architecture presents advantages associated to dynamic polarimeters and also, allows very fast polarization measurements. A ferroelectric liquid crystal panel can be modeled as a waveplate with a constant retardance and, with two possible orientations for its fast axis when a bipolar electrical sign is addressed. We have calibrated the optical features of our ferroelectric liquid crystal panels: retardance and rotation of the optical axis. In addition, we have carried out an optimization of the orientation of these panels in the setup in order to obtain a minimum condition number of our polarimeter and so, minimize the propagation of noise. Afterwards, we have conducted a tolerance analysis of the elements involved in the setup, focusing for a 2% of accuracy in the Stokes vectors measurements. Then, an experimental calibration is carried out and several measurements are taken in order to analyze its performance.

Peinado, Alba; Lizana, Angel; Campos, Juan

2013-09-01

67

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

68

Liquid crystal photonics: optical switching and image storage using nematic liquid crystals and ferroelectric liquid crystals  

Microsoft Academic Search

Manipulation of light by light as a stimulus by the use of liquid-crystalline materials was explored, which was aimed at optical switching, optical image storage and optical display. Two types of the liquid-crystalline materials are used: nematic liquid crystals and ferroelectric liquid (FLCs). Several kinds of optical switching and image storage systems were demonstrated by means of photochromic molecules and

Atsushi Shishido; Osamu Tsutsumi; Akihiko Kanazawa; Takeshi Shiono; Tomiki Ikeda

1997-01-01

69

Rotational viscosities in ferroelectric liquid crystal SCE9  

Microsoft Academic Search

From the measurements of the soft mode frequency and the dielectric strength and of the electroclinic effect close to the chiral smectic C - smectic A transition in ferroelectric liquid crystal SCE9 we show that the rotational viscosities associated with the soft mode and the Goldstone mode are equal at Tc, in agreement with symmetry predictions.

A. Levstik; Z. Kutnjak; C. Filipi?; B. žekš

1992-01-01

70

CRYSTAL CHEMISTRY OF PEROVSKITE-LIKE LAYER-TYPE FERROELECTRICS  

E-print Network

CRYSTAL CHEMISTRY OF PEROVSKITE-LIKE LAYER-TYPE FERROELECTRICS I. H. ISMAILZADE The Institute. S. R. Rbum6. -Le nombre m de couches monooctatdriquesdans lesempilementsdu type perovskite depend presente note. Abstract. -The number of monooctahedral layers in the perovskite-likepackage m depends

Paris-Sud XI, Université de

71

Director reorientation dynamics in chevron ferroelectric liquid crystal cells  

Microsoft Academic Search

We present sample numerical solutions of the equation of motion that governs the dynamics of molecular orientation in ferroelectric liquid crystal cells with chevron layer structure. We show that the chevron structure significantly influences the director field, the chevron interface providing surface stabilization on a plane interior to the FLC layer. Assuming non-polar nematic-like elasticity in the vicinity of the

J. E. Maclennan; M. A. Handschy; N. A. Clark

1990-01-01

72

Image shifting for PIV using birefringent and ferroelectric liquid crystals  

Microsoft Academic Search

This paper discusses a new implementation of electrooptical image shifting, used to resolve directional ambiguity in particle image velocimetry (PIV) measurements. The setup uses a ferroelectric liquid crystal (FLC) as a polarization rotator and a birefringent calcite plate as a shifter. The system can be used with non-polarized light sources and fluorescent particles. The minimum shifting time (pulse separation) is

L. Bertuccioli; S. Gopalan; J. Katz

1996-01-01

73

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

74

Electromigration of microspheres in ferroelectric smectic liquid crystals  

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

75

Electro-Optics Effect in Periodically Domain-Inverted Ferroelectrics Crystals: Principles and Applications  

Microsoft Academic Search

Ferroelectric crystals are important materials in many applications. Since the invention of laser and proposal of the so-called\\u000a quasi-phase matching technique, periodically domain-inverted ferroelectrics crystals with modulated second-order nonlinear\\u000a susceptibility are widely used in frequency conversion application such as optical parametric oscillation (OPO), second harmonic\\u000a generation (SHG), and so on. In periodically domain-inverted ferroelectrics crystals, besides the nonlinear optical coefficients,

J. Shi; X. Chen

76

Stressed states in domain switching of ferroelectric liquid crystal devices  

Microsoft Academic Search

In this paper we show that the director profile of a low pre-tilt surface stabilized ferroelectric liquid crystal passes through quasi-static stressed states during domain switching under direct drive conditions. Using polarized stroboscopic microscopy, we have observed two quasi-static transmission levels during a domain switching transition from dark to light. This is a result of the directors reorienting into stressed

D. C. Ulrich; S. J. Elston

1994-01-01

77

FERROELECTRIC LIQUTD CRYSTALS R. B. MEYER (*), L. LIBERT, L. STRZELECKI and P. KELLER  

E-print Network

cinnamate are described, demonstrating that chiral smectic C and H liquid crystals are ferroelectric. Some show by symmetry that smectic C and H liquid crystals composed of chiral molecules must have a sponta of the unusual properties of these fluid ferroelectrics are discussed. In a smectic C liquid crystal, rod

Boyer, Edmond

78

Growth and ferroelectric properties of L-, D-, and DL-methionine-doped triglycine sulfate crystals  

NASA Astrophysics Data System (ADS)

Single crystals of triglycine sulfate (TGS) doped with L-, D-, and DL-methionine have been prepared. Doping effects on the crystal morphology, the ferroelectric domain structure, and the generation of internal bias field Eb were investigated. These effects were compared with each other and also compared with those of alanine-doped crystals. Though L-methionine-doped crystals show the asymmetric morphology analogous to L-alanine-doped crystals, these two crystals are distinct from each other in their domain structure and the generation of Eb. It was ascertained that the asymmetry caused by L- and D-methionine are mutually reversed in the b-axis. For the doping of racemic mixture DL-methionine, we could recognize the overlap of doping effects caused by the both enantiomers of methionine.

Kikuta, Toshio; Yamazaki, Toshinari; Nakatani, Noriyuki

2010-12-01

79

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

NASA Astrophysics Data System (ADS)

Pure and dye doped (0.1 and 0.2 mol%) Triglycine Sulfate (TGS) single crystals were grown by slow evaporation technique. A pyramidal coloring pattern, along with XRD and FT-IR studies confirmed the dye doping. Decrease in dielectric constant and increase in Curie temperature (Tc) were observed with increasing doping concentration. Low absorption cut off (231 nm) and high optical transparency (>90%) resulting in large band gap was observed in UV-VIS studies. In addition, strong hyper-luminescent emission bands at 350 and 375 nm were observed in which the relative intensity were found to be reversed as a result of doping. In P-E hysteresis loop studies, a higher curie temperature and an improved and more uniform figure of merit over a large region of the ferroelectric phase were observed. The improved dielectric, optical and ferroelectric/pyroelectric properties make the dye doped TGS crystals better candidate for various opto- and piezo-electronics applications.

Sinha, Nidhi; Goel, Neeti; Singh, B. K.; Gupta, M. K.; Kumar, Binay

2012-06-01

80

Characteristic Pressure Dependence of Spontaneous Polarization in Ferroelectric Liquid Crystal  

NASA Astrophysics Data System (ADS)

The spontaneous polarization and rotational viscosity of the c-director of the ferroelectric liquid crystal 4'-octyloxy-biphenyl-4-carboxylic acid 4-(1-methyl-heptyloxy)-phenyl ester at various pressures were investigated. Spontaneous polarization as a function of T-TCA( p) decreased markedly when pressure was changed from 0.1 to 20 MPa and was independent of pressure as pressure was further increased. Rotational viscosity decreased when pressure was applied. These results suggest that the conformation of liquid crystal molecules changes at pressures below 20 MPa.

Uehara, Hiroyuki

2008-09-01

81

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

82

Investigation of domain structure of TGS single crystal after a transverse electric field by piezoresponse force microscopy  

Microsoft Academic Search

An investigation of the influence of electric field transverse to the ferroelectric axis bHOP and parallel to cHOP axis of triglycine sulfate (TGS) single crystal on ferroelectric domain structure was performed by piezoresponse force microscopy. To check if the applied electric field changed the dielectric properties and ferroelectric domain structure the hysteresis loop measurements were carried out as well as

K. ?wikiel; D. Kajewski

2010-01-01

83

Ferroelectric Materials  

NASA Astrophysics Data System (ADS)

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

Whatmore, Roger

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

Interdigitated single crystal piezoelectric actuator  

NASA Astrophysics Data System (ADS)

Piezoelectric actuators are used as critical units or elements of various electromechanical systems. In this paper, we propose a novel piezoelectric actuator cantilever with double interdigitated electrode patterns. We investigate the possibility of both flexural and longitudinal actuation capabilities of the double interdigitated electrode patterns applied on a piezoelectric cantilever structure. This monomorph structure has the interdigitated electrode patterns top and bottom. The structure also uses single-crystal relaxor ferroelectric material. We separately pattern interdigitated electrodes on the top and bottom surfaces of a PMN-PT single crystal cantilever beam. The interdigitated electrode design on a surface of the cantilever beam results in an electric field gradient. This results in a flapping actuation. Previously, we showed that the vertical field component induced by the interdigitated electrode is dominant over the horizontal component under input bias voltage, and generates subsequent contraction of the surface along the axial direction after poling. In this paper, we show that a contraction on the top surface and an elongation on the bottom leads to upward bending motion because of the differential contraction along the thickness induced by the interdigitated electrode pattern. Similarly, an equivalent elongation on the top and bottom surfaces is shown to lead to longitudinal motion in the double interdigitated electrode sample.

Hong, Yong K.; Moon, Kee S.

2005-12-01

86

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

87

Optic mode determination of the relaxed state configuration in a ferroelectric liquid crystal cell  

Microsoft Academic Search

Here the method of propagation of optic modes to examine the alignment in a ferroelectric liquid crystal layer is fully discussed. A sample geometry which allows the excitation of optic modes in a ferroelectric liquid crystal cell is presented and the data obtained in terms of reflectivity. The data are analysed by modelling the expected reflectivity from such a cell

S. J. Elston

1991-01-01

88

Flexoelectric effects in ferroelectric liquid crystals ? Ph. Martinot-Lagarde and G. Durand  

E-print Network

L-43 Flexoelectric effects in ferroelectric liquid crystals ? Ph. Martinot-Lagarde and G. Durand* liquid crystal does not contribute at all to the static dielectric constant in the ferroelectric phase la polarisation spontanée électrique des cristaux liquides smectique C* ne joue aucun rôle dans la

Boyer, Edmond

89

Crystal growth and dielectric, mechanical, electrical and ferroelectric characterization of n-bromo succinimide doped triglycine sulphate crystals  

NASA Astrophysics Data System (ADS)

Single crystals of triglycine sulphate (TGS) doped with n-bromo succinimide (NBS) were grown at ambient temperature by the slow evaporation technique. An aqueous solution containing 1-20 mol% of n-bromo succinimide as dopant was used for the growth of NBSTGS crystals. The incorporation of NBS in TGS crystals has been qualitatively confirmed by FTIR spectral data. The effect of the dopant on morphology and crystal properties was investigated. The cell parameters of the doped crystal were determined by the powder X-ray diffraction technique. The dielectric constant of NBS doped TGS crystal was calculated along the ferroelectric direction over the temperature range of 30-60 °C. The dielectric constant of NBSTGS crystals decrease with the increase in NBS concentration and considerable shift in the phase transition temperature ( TC) towards the higher temperature observed. Pyroelectric studies on doped TGS were carried out to determine the pyroelectric coefficient. The emergence of internal bias field due to doping was studied by collecting P- E hysteresis data. Temperature dependence of DC conductivity of the doped crystals was studied and gradual increase in the conductivity with the increase of dopant concentration was observed. The activation energy (? E) calculated was found to be lower in both the ferroelectric and the paraelectric phases for doped crystals compared to that of pure TGS. The micro-hardness studies were carried out at room temperature on thin plates cut perpendicular to the b-axis. Less doped TGS crystals show higher hardness values compared to pure TGS. Piezoelectric measurements were also carried out on 010 plates of doped TGS crystals at room temperature.

Rai, Chitharanjan; Byrappa, K.; Dharmaprakash, S. M.

2011-09-01

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

Microwave Frequency Ferroelectric Domain Imaging of Deuterated Triglycine Sulfate Crystals  

NASA Astrophysics Data System (ADS)

We have used a near-field scanning microwave microscope(D. E. Steinhauer, C. P. Vlahacos, F. C. Wellstood, Steven M. Anlage, C. Canedy, R. Ramesh, A. Stanishevsky, and J. Melngailis, "Quantitative Imaging of Dielectric Permittivity and Tunability with a Near-Field Scanning Microwave Microscope," Rev. Sci. Instrum. 71), 2751-2758 (2000). to image domain structure and quantitatively measure dielectric permittivity and nonlinearity in ferroelectric crystals at 8.1 GHz with a spatial resolution of 1 ?m. We imaged ferroelectric domains in periodically-poled LiNbO_3, BaTiO_3, and deuterated triglycine sulfate (DTGS) with a signal-to-noise ratio of 7. Measurement of the permittivity and nonlinearity of DTGS in the temperature range 300--400 K shows a peak at the Curie temperature, TC ? 340 K, as well as reasonable agreement with thermodynamic theory. In addition, the domain growth relaxation time shows a minimum near T_C. We observe coarsening of ferroelectric domains in DTGS after a temperature quench from 360 K to 330 K, and evaluate the structure factor.

Steinhauer, David E.; Anlage, Steven M.

2001-03-01

92

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

93

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

94

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

SciTech Connect

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

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

2012-06-15

95

Anomalous Behaviour of the Spontaneous Polarization of Ferroelectric, SmC* Liquid Crystals  

Microsoft Academic Search

A generalized, dimensionless Landau model of the ferroelectric, SmC* phase is presented. The equations governing the tilt, polarization and pitch of ferroelectric, SmC* liquid crystals are given. It is shown that the solutions of these equations agree with available experimental data. It is also shown that the introduction of a biquadratic coupling between tilt and polarization in the Landau expansion

B. Žekš; T. Carlsson; C. Filipi?; A. Levstik

1987-01-01

96

Time-Resolved, Electric-Field-Induced Domain Switching and Strain in Ferroelectric Ceramics and Crystals  

NASA Astrophysics Data System (ADS)

Ferroelectric materials are used in a variety of applications including diagnostic and therapeutic ultrasound, sonar, vibration and displacement sensors, and non-volatile random access memory. The electromechanical response in ferroelectric materials is comprised of both intrinsic (piezoelectric lattice strain) and extrinsic (e.g., domain wall motion) components that are expressed as characteristic changes in the diffraction pattern. By applying slow, step-wise changes in the electric field, prior quasi-dynamic diffraction measurements have demonstrated both lattice strains and non-180 ? domain switching at fields exceeding the macroscopically defined coercive field. However, the loading conditions which most replicate real device operation involve dynamic actuation with sub-coercive, cyclic electric fields. At these operating conditions, extrinsic irreversibilities lead to hysteresis, frequency dispersion and nonlinearity of macroscopic properties. Observation of strain and domain switching at these cyclic loading conditions is an area in which we have reported recent advances using stroboscopic techniques. This chapter highlights the electric-field-induced lattice strain and kinetics of domain switching in a number of materials including technologically-relevant lead zirconate titanate (PZT) ceramics and relaxor single crystals. An outlook on the continuing use of time-resolved diffraction techniques in the characterization of ferroelectric materials is also discussed.

Jones, Jacob L.; Nino, Juan C.; Pramanick, Abhijit; Daniels, John E.

97

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

98

Anchoring energy and orientational elasticity of a ferroelectric liquid crystal  

SciTech Connect

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

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

2012-06-15

99

A ferro-electric liquid crystal polarization controlled switch for WDM applications  

Microsoft Academic Search

A broadband switching using an optical switch with ferro-electric liquid crystal polarization control devices is demonstrated. The device could be available for a broadband and polarization independent switch in wavelength division multiplexing systems.

K. Nakatsuhara; T. Yamada; T. Nakagami

2003-01-01

100

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

NASA Astrophysics Data System (ADS)

The research on ferroelectric materials-mostly inorganic compounds or organic polymers-is increasingly motivated by both basic scientific concerns and the potential for practical applications in electronics and optics. Ferroelectricity in organic solids would be important for the development of all-organic electronic and photonic devices. The conventional approach to making organic ferroelectrics is based on the use of polar molecules. Here we report that through supramolecular assembly of nonpolar conjugated molecules, a remarkable ferroelectric response can be obtained in co-crystals of low-molecular-weight organic compounds. Co-crystals of phenazine and chloranilic acid reveal large spontaneous polarization and sizable room-temperature dielectric constants exceeding 100. The present findings provide an approach to making potentially useful organic ferroelectric materials.

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

2005-02-01

101

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

PubMed

The research on ferroelectric materials-mostly inorganic compounds or organic polymers-is increasingly motivated by both basic scientific concerns and the potential for practical applications in electronics and optics. Ferroelectricity in organic solids would be important for the development of all-organic electronic and photonic devices. The conventional approach to making organic ferroelectrics is based on the use of polar molecules. Here we report that through supramolecular assembly of nonpolar conjugated molecules, a remarkable ferroelectric response can be obtained in co-crystals of low-molecular-weight organic compounds. Co-crystals of phenazine and chloranilic acid reveal large spontaneous polarization and sizable room-temperature dielectric constants exceeding 100. The present findings provide an approach to making potentially useful organic ferroelectric materials. PMID:15665837

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

2005-02-01

102

In-situ monitoring of periodic domain formation in ferroelectric crystals  

Microsoft Academic Search

Ferroelectric crystals, such as lithium niobate (LN) and lithium tantalate, find many photonic applications including the fabrication of periodically poled crystals for nonlinear frequency generation by quasi-phase-matching (QPM). All of the phenomena used in those devices depend on the existence and kinetics of the domain structure. As a consequence, the ability to micro-engineer ferroelectric domains is central to all of

Simonetta Grilli; Melania Paturzo; Lisa Miccio; Pietro Ferraro

2007-01-01

103

Temperature and frequency dependent dielectric behavior of lead potassium niobate single crystal  

E-print Network

of the pyroelectric current The pyroelectric charge as a function of temperature in BaTiOs single crystal Temperature dependence of the pyroelectric current in Colemanite crystal Real permittivity vs temperature of PKN single crystal at 50Hz, 500Hz, 10KHz, 85KHz... for various potential applications, such as laser modulators, pyroelectric and infrared detectors, SAW device substrate material, optoelectronics device material, and other ferroelectric based devices. Single crystals having TB a The Journal of Applied...

Hossain, Akram

2012-06-07

104

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

105

Anchoring strength of a nematic liquid crystal on a ferroelectric crystal M. Glogarova (1) and G. Durand (2)  

E-print Network

1575 Anchoring strength of a nematic liquid crystal on a ferroelectric crystal interface M Abstracts 61.30 1. Introduction. Anchoring properties of nematic liquid crystals on solid surfaces possess an intrinsic bulk polarity, which could enhance the natural polarity of a solid-liquid interface

Boyer, Edmond

106

Scanning tunnelling microscopic study of the interfacial order in a ferroelectric liquid crystal  

Microsoft Academic Search

We present scanning tunnelling microscopy images of a ferroelectric liquid crystal in its chiral smectic C phase. These images show evidence of pronounced interaction between the adjacent lateral dipoles located near the chiral centres of neighbouring molecules. The two dimensional structure at the graphite—liquid crystal interface is found to be highly ordered. Features of this crystal-like order are the pronounced

S. L. Brandow; J. A. Harrison; D. P. Dilella; R. J. Colton; S. Pfeiffer; R. Shashidhar

1993-01-01

107

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

108

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

109

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

110

The optical tensor configuration in a surface stabilized ferroelectric liquid crystal determined by using half leaky guided modes  

Microsoft Academic Search

The optic tensor configuration in a surface stabilized ferroelectric liquid crystal cell is investigated using optical excitation of half leaky guided modes. A thin ferroelectric liquid crystal layer is confined between a high index pyramid, with an index greater than the maximum of the liquid crystal, and a glass substrate having an index less than the minimum of the liquid

Fuzi Yang; J. R. Sambles

1993-01-01

111

Neutron Scattering Study of Single Crystal PZT  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

112

Model For The Molecular Origins Of The Polarization In Ferroelectric Liquid Crystals  

NASA Astrophysics Data System (ADS)

A ferroelectric polarization P (permanent, spontaneous electric dipole moment) is predicted for certain non-racemic liquid crystals based upon simple symmetry arguments. The magnitude of this polarization is a major factor in determining the eletro-optic response times achievable in ferroelectric liquid crystal (FLC) spatial light modulators. While the symmetry arguments are compelling, insight into the actual molecular origins of P is necessary if new materials with high polarization and fast electro-optic response are to be designed in a directed way. Based upon the concept that ferroelectricity in FLCs is a manifestation of a novel form of molecular recognition occurring in the FLC phase, we have developed a simple stereochemical model for P in principle allowing prediction of the sign (handedness) and magnitude of the polarization for specific compounds. The design, synthesis and ferroelectric properties of new materials will be described in the context of this model.

Walba, David M.; Clark, Noel A.

1988-02-01

113

8 MeV electron irradiation effect on the dielectric and optical properties of iminodiacetic acid doped ferroelectric triglycine sulphate crystals  

Microsoft Academic Search

Single crystal of iminodiacetic acid (5mol%) doped Tri Glycine Sulphate (IDATGS) was grown by slow evaporation from its aqueous solution at constant temperature, using solution growth method. The dielectric constant (??) and pyroelectric current (IP) were measured over the temperature range of 30–60°C in the ferroelectric direction. The measured values of ?? and IP were found to be smaller compared

Chitharanjan Rai; Ganesh Sanjeev; S. M. Dharmaprakash

2010-01-01

114

Dielectric relaxation in chevron surface stabilized ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

The dielectric response of surface stabilized ferroelectric liquid crystals with chevron layer structure is studied within low and intermediate frequency ranges, characteristic for collective molecular excitations. By analytically solving the dynamic equation for collective molecular fluctuations under a weak alternating electric field, it is demonstrated that chevron cells stabilized by both nonpolar and polar surface interactions undergo at medium frequencies two Debye relaxation processes, connected with two chevron slabs, on opposite sides of the interface plane. This result is confirmed, experimentally, making use of the electro-optic technique. Based on qualitative arguments supported by microscopic observations of zigzag defects at different frequencies and amplitudes of the external electric field, it is shown that, at low frequencies, the electro-optic response of chevron samples is determined by three kinds of motions of zigzag walls. The first two dynamic categories are related to collective relaxation processes at weak fields, within smectic A layers forming zigzag walls, and drift or creep motions of thick walls occurring at stronger field amplitudes. Dynamic processes of the third kind correspond to sliding of zigzag walls, which appear at yet stronger field amplitudes, but below the switching threshold.

Je?ewski, W.; Kuczy?ski, W.; Hoffmann, J.

2006-06-01

115

Measurement of the refractive indices of a ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

Optical excitation of half-leaky guided modes has been used to determine the refractive indices of a ferroelectric liquid crystal (Merck-SCE13) in a homeotropically aligned state. The uniform homeotropic alignment is realized, with no surface treatment, by the application of an in-plane dc electric field. This applied field, of the order of 5×105 V m-1 is sufficient to fully unwind the S*c helix giving a uniformly tilted homeotropic monodomain for optical characterization. Analytic and numerical modeling results indicate that, for a slab with its optic axis tilted in a plane orthogonal to the plane of incidence, two distinct critical angles appear in the half-leaky guided mode response. These independently relate simply to the ordinary and extraordinary refractive indices of the S*c material. By fitting theoretical angle dependent reflectivities to those recorded experimentally the two refractive indices have been obtained for a range of temperatures in both the S*c and SA phases.

Yang, Fuzi; Sambles, J. R.; Bradberry, G. W.

1995-08-01

116

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

117

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

118

Terahertz radiation by optical rectification in a hydrogen-bonded organic molecular ferroelectric crystal, 2-phenylmalondialdehyde  

E-print Network

Terahertz radiation by optical rectification has been observed at room temperature in a hydrogen-bonded organic molecular ferroelectric crystal, 2-phenyl malondialdehyde (PhMDA). The radiated electromagnetic wave consisted of a single-cycle terahertz pulse with a temporal width of $\\sim$ 0.5 ps. The terahertz radiation amplitude divided by the sample thickness in PhMDA was nearly equivalent to that in a typical terahertz wave emitter ZnTe. This is attributable to a long coherence length in the range of 130 $\\sim$ 800 $\\mu$m for the terahertz radiation from PhMDA. We also discussed the possibility of PhMDA as a terahertz wave emitter in terms of the phase-matching condition.

Guan, W; Sotome, M; Kinoshita, Y; Takeda, R; Inoue, A; Horiuchi, S; Okamoto, H

2014-01-01

119

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

120

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

121

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.

122

LETTER TO THE EDITOR: High-precision 31P chemical shift measurements on KH2PO4-type crystals: role of electronic instability in the ferroelectric transition mechanism  

NASA Astrophysics Data System (ADS)

The mechanism of the ferroelectric transition in KH2PO4-type crystals has been probed using magic angle spinning 31P NMR on single crystals. The higher resolution thus obtained has enabled us to detect a marked change in the 31P isotropic chemical shift around the transition temperature Tc, with a clear jump at Tc. These results are interpreted as evidence that the transition involves a displacive component with electronic instabilities playing a role in the driving mechanism.

Bussmann-Holder, Annette; Dalal, Naresh; Fu, Riqiang; Migoni, Ricardo

2001-03-01

123

Influence of alignment layer thickness on ferroelectric liquid-crystal structure  

NASA Astrophysics Data System (ADS)

We have investigated the influence of the thickness of polyvinyl alcohol alignment layer on azimuthal anchoring of ferroelectric liquid crystals by measuring the azimuthal angle of the chevron C2 structure. By varying not only the alignment but also the ferroelectric liquid-crystal layer thickness, we also studied the influence of the ions screening the polarization charge on the chevron layer structure. A simple model describing the free enthalpy of the system was used to calculate the anchoring coefficient from the azimuthal angle of the structure.

Petkovšek, Rok; ?opi?, Martin; Pirš, Janez

2006-02-01

124

A Mesoscopic Electromechanical Theory of Ferroelectric Films and Ceramics  

E-print Network

actuation strains in ferroelectric single crystals through polarization rotation [1, 2] , or by domainA Mesoscopic Electromechanical Theory of Ferroelectric Films and Ceramics Jiangyu Li and Kaushik the effective electromechanical behavior of ferroelectric ceramics and thin films. This paper specifically

Bhattacharya, Kaushik

125

Phenomenological theory of a single domain wall in uniaxial trigonal ferroelectrics: Lithium niobate and lithium tantalate  

E-print Network

Phenomenological theory of a single domain wall in uniaxial trigonal ferroelectrics: Lithium niobate and lithium tantalate David A. Scrymgeour and Venkatraman Gopalan Department of Materials Science, lithium niobate and lithium tantalate. The contributions to the domain- wall energy from polarization

Gopalan, Venkatraman

126

Synthesis of layer-structured ferroelectric Bi 3NbTiO 9 plate-like seed crystals  

Microsoft Academic Search

Pure bismuth layer-structured ferroelectric Bi3NbTiO9 plate-like seed crystals are synthesized by molten-salt method in NaCl–KCl flux using Bi3NbTiO9 precursor from precipitation. Single phase Bi3NbTiO9 powder is obtained in NaCl–KCl flux at 700 °C for only 0.5 h, which is 200 °C lower than the formation temperature of pure Bi3NbTiO9 Aurivillius phase without chloride salts. The Bi3NbTiO9 platelet synthesized at 900

Ping-Hua Xiang; Yoshiaki Kinemuchi; Koji Watari

2005-01-01

127

Surface acoustic wave propagation properties in 0.67Pb,,Mg1/3Nb2/3...O3-0.33PbTiO3 single crystal  

E-print Network

%PT ferroelectric single crystals poled along 111 c has been analyzed theoretically. We found. doi:10.1063/1.3271775 Relaxor-based ferroelectric single crystals 0.67Pb Mn1/3Nb2/3 O3-0.33PbTiO3 PMN electromechanical devices, actuators, ultra- sonic motors, wideband medical ultrasonic transducers, etc.5 Surface

Cao, Wenwu

128

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

Microsoft Academic Search

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

D. S. Parmar

1991-01-01

129

Two Dimensional Modelling of Domain Nucleation and Growth in Surface Stabilised Ferroelectric Liquid Crystals  

Microsoft Academic Search

In surface stabilised ferroelectric liquid crystal (SSFLC) cells driven by low voltages, typically below 10V, it is observed that domains of the switched state nucleate and grow, merging to fill the cell. A model of domain nucleation in SSFLCs is proposed, which considers a nucleation site as a local absence of the chevron interface torque. The model is implemented in

S. McCrea; P. Migliorato; S. J. Elston

1995-01-01

130

Time-resolved switching analysis of a ferroelectric liquid crystal by Snapshot Mueller Matrix Polarimetry  

E-print Network

1 Time-resolved switching analysis of a ferroelectric liquid crystal by Snapshot Mueller Matrix *Corresponding author: matthieu.dubreuil@univ-brest.fr An experimental snapshot Mueller Matrix polarimeter based of America. OCIS codes: 120.5410, 160.3710, 230.5440, 260.5430. Mueller matrix (MM) polarimetry is usually

Paris-Sud XI, Université de

131

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

Microsoft Academic Search

The specific features of the ferroelectric behavior of triglycine sulfate crystals with a nonuniform distribution of chromium impurities are analyzed. It is demonstrated that the dielectric hysteresis loops of the samples exhibit large shifts both along the polarization and electric field directions. The results obtained are well explained within the phenomenological approach with due regard for the gradient term in

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

2008-01-01

132

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

133

Ferroelectric liquid crystal device based photonic controllers for microwave antenna arrays  

Microsoft Academic Search

For the first time, this dissertation proposes, studies, analyzes, and experimentally demonstrates the use of ferroelectric liquid crystal (FLC) technology for wideband phased array control applications. FLC devices are used as polarization switches in photonic delay lines (PDLs) to control and process optical signals that drive the elements of a phased array antenna (PAA). The use of photonics for PAA

Nicholas Madamopoulos

1998-01-01

134

Hydrogen-induced degradation in strontium titanate single crystals  

NASA Astrophysics Data System (ADS)

Hydrogen-induced degradation in strontium titanate single crystals was studied through an electrochemical hydrogen charging process, in which the silver electrodes of the crystals were made a cathode in 0.01 M NaOH solution to evolve hydrogen by electrolysis of water. After the process, the resistance of the crystals was decreased by more than one order of magnitude, the dielectric loss was obviously increased, and the capacitance became more dependent on frequency. It is proposed that atomic hydrogen generated by electrolysis of water diffuses into the crystals and exists as a charged interstitial impurity donating electrons to the conduction band of the crystals. Attention should be paid to this hydrogen-induced degradation when the reliability of perovskite-type ferroelectric devices and components is studied.

Chen, W. P.; Dai, J. Y.; Wang, Y.; Lai-Wah Chan, H.

2005-08-01

135

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

136

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

137

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

138

Thermodynamic Model of Ferroelectric Chiral Smectic C* Liquid Crystals  

Microsoft Academic Search

A thermodynamic model of the ferroelectric SmC* phase, based on an extended Landau expansion of the free-energy density, is presented. We discuss how the signs of the parameters entering the model are depending on whether the pitch of the helix is right-handed or left-handed and whether the compound is of the (+) or (-) type in regard to the sign

T. Carlsson; B. žekš; C. Filipi?; A. Levstik; R. Blinc

1988-01-01

139

Electromagnetic generation of longitudinal ultrasound in YBa2Cu3O7 single crystals  

NASA Astrophysics Data System (ADS)

Experimental observations of longitudinal ultrasound generation are reported for YBa2Cu3O7 single crystal specimens (1 x 1 x 0,15 cu mm) placed in a variable electric field normal to the specimen surface. No external magnetic field was applied to the specimens in the experiments. The observed phenomenon is believed to be related to the volume and surface piezoelectric properties of the single crystal, which may be associated with ferroelectric phase transitions.

Khizhnyi, V. I.; Ganapol'Skii, E. M.; Koroliuk, A. P.; Bondarenko, A. V.; Obolenskii, M. A.

1991-12-01

140

Microstructure and properties of single crystal BaTiO3 thin films synthesized by ion implantation-induced layer transfer  

E-print Network

extensively reported. Single crystal ferroelectric thin films can be used in applications such as actuator Institute of Physics. [DOI: 10.1063/1.1773373] Ferroelectric thin films have been widely explored, and have promise for high work/volume mechanical actuators in microelectromechanical systems (MEMS

Atwater, Harry

141

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

142

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

143

Ground state and properties of ferroelectric superlattices based on crystals of the perovskite family  

NASA Astrophysics Data System (ADS)

The crystal structure of the ground state of ten free-standing ferroelectric superlattices based on crystals with the perovskite structure (BaTiO3/SrTiO3, PbTiO3/SrTiO3, PbTiO3/PbZrO3, SrZrO3/SrTiO3, PbZrO3/BaZrO3, BaTiO3/BaZrO3, PbTiO3/BaTiO3, BaTiO3/CaTiO3, KNbO3/KTaO3, and KNbO3/NaNbO3) was calculated from first principles within the density functional theory taking into account criteria for stability of the structures with respect to acoustic and optical distortions. It was shown that the ground state in all the considered superlattices corresponds to the ferroelectric phase. It was found that the polarization vector has a tendency toward a tilt to the plane of the superlattice layers, which makes it possible to decrease the electrostatic and elastic energy in the superlattices consisting of materials with different ferroelectric properties. The importance of the inclusion of structural distortions due to unstable phonons at the Brillouin zone boundary, which, in a number of cases, lead to significant changes in ferroelectric and dielectric properties of the superlattices, was demonstrated.

Lebedev, A. I.

2010-07-01

144

Radiation Damage Effects in Ferroelectric Triglycine Sulfate  

Microsoft Academic Search

Peculiar changes in the ferroelectric hysteresis loops of single crystals of triglycine sulfate result when the crystals are subjected to ionizing radiations (x-rays and electrons). Fully polarized crystals develop hysteresis loops biased along the field axis while partially polarized crystals develop double-loop patterns, each subsidiary loop being biased to the same extent but in opposite directions. The biased loops retain

A. G. Chynoweth

1959-01-01

145

Dielectric and elastic properties of 0.70Pb(Mg1/3Nb2/3) O30.30PbTiO3 single crystal and their electric-field dependence  

E-print Network

field corresponding to an electric-induced ferroelectric phase transition. At 360 K, the PMN­0.3PT domain wall contributions. Introduction Relaxor-based ferroelectric single crystals, such as (1 - x) Pb crystals excellent components for the actuators, ultrasonic motors, and wideband medical ultrasonic

Cao, Wenwu

146

Water-soluble ferroelectric crystals with inhomogeneous impurity distribution  

Microsoft Academic Search

Stabilization of the unipolar state via the formation of inhomogeneous impurity distribution in crystal bulk is considered.\\u000a Possible growth of crystals with stable characteristics is demonstrated on triglycine sulfate (TGS) crystals with a regular\\u000a inhomogeneous impurity distribution. The properties of TGS crystals with an inhomogeneous distribution of chromium ions grown\\u000a above and below the Curie temperature T\\u000a C are studied.

V. N. Shut; I. F. Kashevich; B. E. Watts

2004-01-01

147

Role of electrostatics in the texture of islands in free standing ferroelectric liquid crystal films  

E-print Network

Curved textures of ferroelectric smectic C* liquid crystals produce space charge when they involve divergence of the spontaneous polarization field. Impurity ions can partially screen this space charge, reducing long range interactions to local ones. Through studies of the textures of islands on very thin free-standing smectic films, we see evidence of this effect, in which materials with a large spontaneous polarization have static structures described by a large effective bend elastic constant. To address this issue, we calculated the electrostatic free energy of a free standing film of ferroelectric liquid crystal, showing how the screened coulomb interaction contributes a term to the effective bend elastic constant, in the static long wavelength limit. We report experiments which support the main features of this model.

Jong-Bong Lee; Robert A. Pelcovits; Robert B. Meyer

2007-08-16

148

Hysteresis-free electro-optical switching in conductive ferroelectric liquid crystals: experiments and modelling  

Microsoft Academic Search

The hysteresis-free electro-optical switching, or so-called V-shaped, regime has been studied in a commercial ferroelectric liquid crystal (FLC) mixture having a smectic C* phase with a very small value of spontaneous polarization. The FLC was introduced into commercial EHC cells with thin aligning layers. In such cells V-shaped switching could be observed only at very low frequencies, less than 1?Hz.

S. P. Palto; F. V. Podgornov; H. Moritake; W. Haase

2004-01-01

149

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

Microsoft Academic Search

The specific features of the ferroelectric behavior of triglycine sulfate crystals with a nonuniform distribution of chromium\\u000a impurities are analyzed. It is demonstrated that the dielectric hysteresis loops of the samples exhibit large shifts both\\u000a along the polarization and electric field directions. The results obtained are well explained within the phenomenological\\u000a approach with due regard for the gradient term in

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

2008-01-01

150

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

151

dc field effect on stability of piezoelectric PZN-0.06PT single crystals under compressive stress  

Microsoft Academic Search

A reversible elastic instability was observed in PZN-0.06PT high coupling single crystals when subjected to uniaxial compressions similar to those used in sound projectors. The strain magnitude at the onset of the instability supported a free energy prediction of a ferroelectric rhombohedral (FR)-ferroelectric orthorhombic (FO) phase transition. The thermal response of the normalized phase transition strain is in a good

Chiaki Okawara; Ahmed Amin

2009-01-01

152

Nondestructive imaging and characterization of ferroelectric domains in periodically poled crystals  

NASA Astrophysics Data System (ADS)

We report the nondestructive investigation and visualization of periodically poled domains in ferroelectric potassium titanyl phosphate (KTP) crystals using polarization sensitive scanning force microscopy (SFM). Applying an alternating voltage technique to SFM allows ferroelectric domain wall resolution beyond 100 nm. Image contrast between KTP and Rb doped KTP, i.e., rubidium titanyl phosphate (RTP) regions arises from the differential piezoelectric response. We find the polarization vectors in both KTP and RTP to be aligned parallel to the negative z axes as deduced (a) when comparing our data with a ferroelectric reference sample, i.e., tri-glycine sulfate (b) from comparison of nanoscale hysteresis loops recorded on KTP and RTP, and (c) from direct domain switching in KTP applying very high electric fields between tip and counter electrode. The latter experiments show that nanoscale ferroelectric domains in KTP switch from the negative to the positive z-axes alignment for electric fields stronger than 750 V/cm. Nevertheless, spontaneous backswitching is observed after a couple of minutes.

Eng, L. M.; Güntherodt, H.-J.; Rosenman, G.; Skliar, A.; Oron, M.; Katz, M.; Eger, D.

1998-06-01

153

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

154

Cooperative phenomena in crystals containing off-center ions-dipole glass and ferroelectricity  

NASA Astrophysics Data System (ADS)

The current state of experimental and theoretical research into cooperative phenomena in crystals containing off-center ions is reviewed. This field has attracted considerable attention in recent years because of the general interest in disordered systems, including spin glasses of which dipole glass is the electric analog. The properties of dipole glass in alkali halide crystals containing off-center ions are discussed. Experimental studies performed over the last few years have shown that off-center ions can induce the ferroelectric phase transition in highly-polarizable crystals. The physical nature and the theory of the phenomenon are examined, and the physical properties of crystals exhibiting this induced phase transition are discussed. Possible lines of future research into cooperative phenomena in crystals containing off-center ions are reviewed.

Vugmeister, B. E.; Glinchuk, M. D.

1985-07-01

155

Compositional dependence of single-crystal PMN-xPT phase transformations  

NASA Astrophysics Data System (ADS)

Relaxor ferroelectric single crystals produce extraordinary strain levels in response to electric field, but the response is highly dependent on temperature and bias stress. This behavior must be well characterized for the successful development of actuation and sensor applications. This paper presents the results of experimental characterization of <001> oriented single crystal PMN-xPT (x = 0.27 and 0.29) is presented for combined electrical and mechanical loading at various temperatures. These data are contrasted with previously reported constitutive behavior of <001> single crystal PMN-xPT with different compositions. The effects of composition on the phase transformation behavior and linear material properties are compared and discussed.

Webber, Kyle G.; Lynch, Christopher S.

2008-03-01

156

In-situ monitoring of periodic domain formation in ferroelectric crystals  

NASA Astrophysics Data System (ADS)

Ferroelectric crystals, such as lithium niobate (LN) and lithium tantalate, find many photonic applications including the fabrication of periodically poled crystals for nonlinear frequency generation by quasi-phase-matching (QPM). All of the phenomena used in those devices depend on the existence and kinetics of the domain structure. As a consequence, the ability to micro-engineer ferroelectric domains is central to all of these applications and thus techniques for visualizing domain structure and dynamics are important. Recently a digital holography (DH) based technique has been proposed by the authors to visualize the free evolution of reversing domains in ferroelectric substrates during electric field poling. A fundamental step forward has been achieved in this work, where the technique has been applied to resist patterned samples under different voltage waveforms and resist conditions in order to characterize the dynamics of the periodic poling in presence of a resist grating. The results show that this technique can be used as a valid and reliable alternative tool to monitor online the periodic poling of ferroelectric crystals by a non-invasive in-situ procedure, avoiding both the critical control of the poling current and the post-poling etching process. The imaging of the resist grating and of the reversed domain regions can be discriminated accurately by using the qualitative and quantitative information provided by the amplitude and phase shift images, respectively. Moreover the technique allows to investigate systematically and, most important, in-situ the influence of different features on the poling behaviour, such as the poling waveform, the resist grating geometry, the patterned z face, the resist properties. The movies of the periodic poling dynamics are presented and discussed.

Grilli, Simonetta; Paturzo, Melania; Miccio, Lisa; Ferraro, Pietro

2007-06-01

157

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

158

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

159

Hydrogen-related dynamic dielectric behavior of barium titanate single crystals  

NASA Astrophysics Data System (ADS)

Barium titanate single crystals had been placed in 0.01M NaOH solution to deposit hydrogen on their electrodes through the electrolysis of water. Two kinds of time-dependent changes in dielectric properties of the single crystals were observed: One occurred in the course of hydrogen deposition and the other lasted for a long period of time after the deposition. The diffusion of hydrogen and in and out of the single crystals may be the cause for the changes. This hydrogen-related dynamic dielectric behavior clearly shows that hydrogen is an important mobile ion other than oxygen vacancy in perovskite-type lattice. Extra attention should be paid to the role of hydrogen in time-dependent property changes, including resistance degradation and ferroelectric aging, of perovskite-type ferroelectric titanates.

Chen, W. P.; Wang, Y.; Chan, H. L. W.; Luo, H. S.

2006-05-01

160

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

161

Enhancement of the electromechanical response in ferroelectric ceramics by design  

E-print Network

It is demonstrated based on continuum mechanics modeling and simulation that it is possible to obtain polycrystalline ceramic ferroelectric materials which beggars single crystals in electromechanical properties. The local inhomogeneities at the ferroelectric domain-scale level due to spontaneous polarization and the underlying anisotropy are taken into consideration in the framework of mathematical homogenization of physical properties in ferroelectric materials. The intrinsic randomness of the spatial distribution of polarization is shown to be judiciously employed for the design of better polycrystalline ferroelectrics. The noncollinear rotation of the net polarization-vectors embedded in crystallites of the ceramic ferroelectrics is demonstrated to play the key role in the enhancement of physical properties.

Jayachandran, K P; Rodrigues, H C; 10.1063/1.3089216

2010-01-01

162

Coupled director and polarization fluctuations in suspensions of ferroelectric nanoparticles in nematic liquid crystals  

NASA Astrophysics Data System (ADS)

In colloidal suspensions of nanosized ferroelectric particles and nematic liquid crystals a large increase in the isotropic-nematic transition temperature has been observed recently. By dynamic light scattering we measured the relaxation rate of the nematic director fluctuations in colloidal systems with BaTiO3 and Sn2P2S6 particles. A substantial increase in the bend-mode relaxation rate, attributed to an increase in the bend elastic constant, is observed. A mode with relaxation rate around 200000s-1 , independent of the scattering vector, is also observed. We propose that it represents the out-of-phase motion of the nematic director and average direction of the spontaneous polarization of the ferroelectric particles. No translation motion is observed, indicating that the particles may form chains.

?opi?, Martin; Mertelj, Alenka; Buchnev, Olexandr; Reznikov, Yuri

2007-07-01

163

Ferroelectric-chiral-antiferroelectric-racemic liquid crystal phase transition of bent-shape molecules  

NASA Astrophysics Data System (ADS)

Detailed dielectric, polarization current, electro-optical, and textural observations are reported on an asymmetric banana-shaped compound 1,3-biphenylene-bis[4-(3-fluoro-4-octyloxyphenyliminomethyl)benzoate]. The material possesses a chiral-ferroelectric-racemic-antiferroelectric phase transition. Our studies reveal that the higher temperature ferroelectric phase has a polar double-tilted smectic structure, where both the molecular plane and the long axis are tilted with respect to the layer normal. Accordingly, it has a chiral triclinic structure with an out-of-plane polarization component. The lower temperature phase has a monoclinic symmetry, which is higher than that of the higher temperature phase. To our knowledge, among liquid crystals such situations were previously observed only in reentrant phases.

Rauch, S.; Bault, P.; Sawade, H.; Heppke, G.; Nair, G. G.; Jákli, A.

2002-08-01

164

Relaxor-PT single crystals: observations and developments.  

PubMed

Relaxor-PT based ferroelectric single crystals Pb(Zn?/?)Nb(?/?)O?-PbTiO? (PZNT) and Pb(Mg?/?)Nb(?/?)O?-PbTiO? (PMNT) offer high performance with ultra-high electromechanical coupling factors k?? > 0.9 and piezoelectric coefficients d??s > 1500 pC/N. However, the usage temperature range of these perovskite single crystals is limited by T(RT)-the rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature T(C), a consequence of curved morphotropic phase boundaries (MPBs). Furthermore, these <001>-oriented crystals exhibit low mechanical quality Q and coercive fields, restricting their usage in high-power applications. In this survey, recent developments on binary and ternary perovskite relaxor-PT crystal systems are reviewed with respect to their temperature usage range. General trends of dielectric and piezoelectric properties of relaxor-PT crystal systems are discussed in relation to their respective T(C)/T(RT). In addition, two approaches have been implemented to improve mechanical Q, including acceptor dopants, analogous to hard polycrystalline ceramics, and anisotropic domain engineering, enabling low-loss crystals with high coupling for high-power applications. PMID:20889397

Zhang, Shujun; Shrout, Thomas

2010-10-01

165

Ferroelectric liquid crystals: The 2004 Benjamin Franklin Medal in Physics presented to Robert B. Meyer of Brandeis University  

Microsoft Academic Search

In a theoretical examination of the structures of liquid crystal phases, Robert B. Meyer in 1975 creatively utilized symmetry arguments to predict that tilted, layered liquid crystal phases of chiral molecules are ferroelectric. He then engaged the help of organic chemists to synthesize a compound that might possess such a phase, and once the material was in his hands, Meyer

Peter J. Collings

2005-01-01

166

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

167

Growth of Various Amino-Acid-Doped Triglycine Sulfate Crystals and Their Ferroelectric Properties  

Microsoft Academic Search

Single crystals of triglycine sulfate (TGS) were grown from solutions containing 10 mol% of L-alpha-alanine, DL-alpha-alanine, sarcosine, L-serine or L-valine. The crystal form, domain structure and internal bias field Eb of these crystals were investigated. The crystal form and macroscopic distribution of Eb in crystals doped with L-alpha-alanine and L-serine show polar symmetry 2, and those in crystals with DL-alpha-alanine

Noriyuki Nakatani

1993-01-01

168

Ferroelectric and electromechanical property characterization of single Pb(ZrTi)O3 fiber resonator  

Microsoft Academic Search

Piezoelectric fibers and fiber composites have attracted much attention for anisotropic sensing and actuation applications in recent year. Complete property characterization for piezoelectric fibers is essential for material and device design and fabrication. In this work, ferroelectric and electromechanical properties of single piezoelectric Pb(ZrTi)O3 (PZT) fiber were characterized by polarization-electric field hysteresis loop measurement using single PZT fiber\\/polymer 1-3 composite

Chengliang Sun; Lifeng Qin; Hao Xue; Zhaoxian Xiong; Qing-Ming Wang

2010-01-01

169

Ferroelectric properties of TGS crystals grown under an intense DC electric field  

NASA Astrophysics Data System (ADS)

The application of electric field during crystal growth modifies the ferroelectric properties of triglycine sulphate (TGS) crystals. Scanning electron microscopic examination of freshly cleaved (0 1 0) surface shows the presence of some domains tilted with respect to the c-axis. It is suggested that the cause of the onset of domains misaligned with the c-axis is the partial pinning by the field of the rotation of the NH 3+ group of the glycine I molecule. The modified domains originate a decrease of the dielectric values, a reduced spontaneous polarization and an increase of the relaxation times. Crystals of TGS grown under field remain in a stable state with modified properties as long as they are not subjected to intense AC fields or annealed above the Curie temperature for more than two cycles.

Arunmozhi, G.; Gomes, E. de M.; Ribeiro, J. L.

2003-01-01

170

Free alignment defect, low driving voltage of half-V ferroelectric liquid crystal device  

NASA Astrophysics Data System (ADS)

The horizontal chevron alignment defect in half-V mode ferroelectric liquid crystal (FLC) cell can be reduced by asymmetrical alignment hybrid cell. The low free energy level generated from the interaction between spontaneous polarization and opposite polar alignment surfaces was found. As a result, uniformly aligned FLC cell can be achieved without applied external voltage. The R3206 FLC material is applied as model compound. The contrast ratio of R3206-70 is greatly enhanced from 76 to 780 with 1.0 ms response time under 5 V.

Chen, Huang-Ming P.; Lin, Chi-Wen

2009-08-01

171

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

SciTech Connect

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

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

2010-11-22

172

Hysteresis curves for ferroelectric crystals in a varying external field. Relaxation model  

NASA Astrophysics Data System (ADS)

We propose a description of switching in ferroelectric crystals using the equations of relaxation processes taking into account the action of a varying external electric field. Exact analytic solutions to these equations are obtained for an arbitrary dependence of the relaxation time on the external field and an arbitrary time dependence of the external field. The resultant solution forms the basis of numerical analysis of coupling between the frequency of the sinusoidal external field and the shape of the hysteresis curves. The results of calculations are in qualitative agreement with experimental data.

Zakharov, A. Yu.; Bichurin, M. I.; Yan, Y.; Priya, S.

2014-08-01

173

8 MeV electron irradiation effect on the dielectric and optical properties of iminodiacetic acid doped ferroelectric triglycine sulphate crystals  

NASA Astrophysics Data System (ADS)

Single crystal of iminodiacetic acid (5 mol%) doped Tri Glycine Sulphate (IDATGS) was grown by slow evaporation from its aqueous solution at constant temperature, using solution growth method. The dielectric constant ( ?') and pyroelectric current ( I P) were measured over the temperature range of 30-60 °C in the ferroelectric direction. The measured values of ?' and I P were found to be smaller compared to pure triglycine sulphate (TGS) crystal parameters. But increased transition temperature was observed for doped crystals. Curie Weiss constants C P and C f in the paraelectric and ferroelectric phases were also determined. The doped crystal was irradiated with graded dosages from 5 to 80 kGy of electron beam from 8 MeV Microtron at room temperature and radiation effects on optical and dielectric properties were studied. The UV-Vis absorption spectrum indicates that the UV lower cutoff shifts towards the higher wavelength region (red shift) and the optical band gap is found to be decreasing with the increase of electron dose. It is also observed that the electron irradiation effects in pure and doped TGS were found to be long lasting. The dielectric study shows that there is a gradual reduction in dielectric constant at T C and shifting of Curie temperature towards lower temperature region with the increase in electron radiation dose. The material figures of merit were found increased after the crystal was irradiated. Induced changes in the physical and optical properties due to irradiation may help one to tailor the device quality and characteristics.

Rai, Chitharanjan; Sanjeev, Ganesh; Dharmaprakash, S. M.

2010-08-01

174

Nanostructured Calcite Single Crystals with Gyroid Morphologies  

E-print Network

Nanostructured Calcite Single Crystals with Gyroid Morphologies By Alexander S. Finnemore, Maik R of which has a complex, sponge-like structure, and yet is a single crystal of calcite.[2] In contrast calcite crystals. Biologically controlled mineralization depends on the interplay between a number

Steiner, Ullrich

175

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

176

Optimization of piezoelectric properties for 001c poled 0.94Pb,,Zn1/3Nb2/3...O30.06PbTiO3 single crystals  

E-print Network

devel- oped in recent years for obtaining enhanced piezoelectric properties in ferroelectric materials, broadband transducers, and large dis- placement actuators.1,2 However, the macroscopic properties It should be noted that the properties of ferroelectric single crystals are sensitive to the poling

Cao, Wenwu

177

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

178

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

179

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

NASA Astrophysics Data System (ADS)

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.

1991-02-01

180

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

181

Growth of ZnSe single crystals  

Microsoft Academic Search

The growth conditions of ZnSe single crystals were investigated by chemical vapor transport (CVT) and physical vapor transport (PVT) methods. The growth temperatures were about 850°C (CVT) and 1100°C (PVT). Single crystals of 18–20mm diameter, 30mm long and orange colored were grown. The homogeneity of crystals was measured. The etch pit density of good crystals is in the range of

C. S Fang; Q. T Gu; J. Q Wei; Q. W Pan; W Shi; J. Y Wang

2000-01-01

182

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

E-print Network

switching in ferroelectric single crystals J.H. Yena , Y.C. Shua,Ã?, J. Shiehb , J.H. Yehb a Institute and experimental studies developed to investigate the switching behavior of ferroelectric single crystals experiments. It is found that depolarization has a non-trivial influence on attainable actuation strains. r

Shu, Yi-Chung

183

C N.M.R. and N N.Q.R. in ferroelectric liquid crystals Polar versus quadrupolar ordering  

Microsoft Academic Search

C nuclear magnetic resonance and N nuclear quadrupole resonance spectra of ferroelectric smectic C*liquid crystals and their non-chiral analogues allow for a microscopic determination of the polar and quadrupolar (or bipolar) biasing of rotation around the long molecular axis as well as for a determination of the anisotropy in the fluctuations of this axis. The results show that the microscopic

R. Blinc; J. Dolinšek; M. Luzar; J. Seliger

1988-01-01

184

Reconfigurable wavelength add-drop filtering based on a Banyan network topology and ferroelectric liquid crystal fiber-optic switches  

Microsoft Academic Search

This paper presents a modular optical implementation of a Banyan network by using the physical flexibility of the optical fiber to form the interconnections between compact switching stages based on bulk polarization optics. Specifically, these switching stages use total internal reflection (TIR) prisms with ferroelectric liquid crystal (FLC) polarization rotators to form compact modules. Using this Banyan network implementation, a

Nabeel A. Riza; Shifu Yuan

1999-01-01

185

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

Microsoft Academic Search

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

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

2000-01-01

186

Piezoelectric anisotropy - phase transition relations in perovskite single crystals  

Microsoft Academic Search

The orientation dependence of the longitudinal piezoelectric coefficient is investigated as a function of temperature in BaTiO3 and PbTiO3 crystals using Landau-Ginsburg-Devonshire theory. We show that a presence of the ferroelectric - ferroelectric phase transitions in BaTiO3 leads to an enhanced piezoelectric longitudinal response along nonpolar directions. The reason for this is the abrupt increase of the shear piezoelectric coefficients

Marko Budimir; Dragan Damjanovic; Nava Setter

2004-01-01

187

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

NASA Astrophysics Data System (ADS)

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).

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

2014-07-01

188

Lattice dynamics and the ferroelectric and antiferrodistorsive instabilities in a bulk crystal and thin films of SrZrO3  

NASA Astrophysics Data System (ADS)

The lattice dynamics and energies of phases related to antiferrodistorsive and ferroelectric distortions of bulk crystals and thin films of the SrZrO3 crystal have been calculated within the framework of the ab initio model of an ionic crystal. In the case of a bulk crystal, it has been found that the most energetically favorable phases are related to antiferrodistorsive lattice distortions. Ferroelectricity in the SrZrO3 crystal is suppressed by structural lattice distortions. In the case of thin films, it has been found that the ferroelectric instability is retained after the "rotation" of the oxygen octahedron and the film remains polar both in the case of a free surface and with the inclusion of the SrTiO3 substrate in the calculation. The spontaneous polarization of thin films of different thicknesses in the ferroelectric phase has been calculated.

Zhandun, V. S.; Zinenko, V. I.

2012-07-01

189

Optical studies of anthracene single crystals  

Microsoft Academic Search

Recently the polyacene crystals such as pentacene, tetracene and anthracene have attracted great interest both in research and applications. These ultra-pure molecular crystals are very promising materials for FETs, organic photovoltaic diodes, LEDs and lasing. High purity anthracene crystal have been grown by physical vapor transport. High photo luminecense (PL) quantum efficiency(over 20%) was observed in these pure anthracene single

Yuhong Jiang; Matthew Delong; Z. Valy Vardeny

2001-01-01

190

Complete set of material properties of single domain 0.24Pb(In1/2Nb1/2) O3-0.49Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystal and the orientation effects  

E-print Network

Institute of Physics. [doi:10.1063/1.3615684] Multidomain relaxor-based ferroelectric single crystals, (1-x, and may lead to revolutionary changes in next generation sensors, actuators, and other electromechanical-based ferroelectric ternary xPb(In1/ 2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 (PIN-PMN- PT) single crystal system

Cao, Wenwu

191

Inkjet printing of single-crystal films  

Microsoft Academic Search

The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by

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

2011-01-01

192

Method of making single crystal fibers  

NASA Technical Reports Server (NTRS)

Single crystal fibers are made from miniature extruded ceramic feed rods. A decomposable binder is mixed with powders to inform a slurry which is extruded into a small rod which may be sintered, either in air or in vacuum, or it may be used in the extruded and dried condition. A pair of laser beams focuses onto the tip of the rod to melt it thereby forming a liquid portion. A single crystal seed fiber of the same material as the feed rod contacts this liquid portion to establish a zone of liquid material between the feed rod and the single crystal seed fiber. The feed rod and the single crystal feed fiber are moved at a predetermined speed to solidify the molten zone onto the seed fiber while simultaneously melting additional feed rod. In this manner a single crystal fiber is formed from the liquid portion.

Westfall, Leonard J. (inventor)

1990-01-01

193

Organic single-crystal complementary inverter  

NASA Astrophysics Data System (ADS)

The authors demonstrate the operation of an organic single-crystal complementary circuit in the form of a simple inverter. The device is constructed from a high mobility p-type organic single-crystal transistor of tetramethylpentacene (TMPC) and a n-type single-crystal transistor of N ,N'-di[2,4-difluorophenyl]-3,4,9,10-perylenetetracarboxylic diimide (PTCDI). Field-effect mobilities of up to 1.0cm2/Vs are reported for TMPC devices, while a mobility of 0.006cm2/Vs is reported for a n-type PTCDI single-crystal device. Considering that organic single-crystal inverters have not yet been explored, they are representative of potential candidates for use in high-performance complementary circuits.

Briseno, Alejandro L.; Tseng, Ricky J.; Li, Sheng-Han; Chu, Chih-Wei; Yang, Yang; Falcao, Eduardo H. L.; Wudl, Fred; Ling, Mang-Mang; Chen, Hong Zheng; Bao, Zhenan; Meng, Hong; Kloc, Christian

2006-11-01

194

Expanding Applications of the Polarimeters with Ferroelectric Liquid Crystals and their Calibration  

NASA Astrophysics Data System (ADS)

We are carrying out regular solar observations in the Fe 6303 and the H? lines by polarimeters with ferroelectric liquid crystals (FLCs), and they realized the polarimetry with very high sensitivity. On the basis of this success, we are now extending the polarimetry with the FLC polarimeters to various types of observations. To make such `transplant' easy, the following design principles are adopted: - Portable design of the polarimeter - independent from the specific telescope system and optics. - Standardized, easy-to-do calibration procedure. Our polarimeters can be installed into various systems easily, and they achieve the same high sensitivity as the existing successful system even in a short-term experimental observation. Here we present various new observations with the FLC polarimeters, which we are carrying out/planning now, and we show examples of the calibration parameters for the FLC polarimeters, which help to obtain the high-precision polarization data.

Hanaoka, Y.

2009-06-01

195

Influence of Fabrication Conditions on Monostability of Polymer-Stabilized Ferroelectric Liquid Crystals  

NASA Astrophysics Data System (ADS)

Polymer-stabilized ferroelectric liquid crystals (PS-FLCs) photocured in the SmA phase can show monostable V-shaped electrooptical characteristics. In this study, we have researched the influence of the fabrication conditions such as polymer concentration, cell gap, and alignment film materials on the monostable electrooptical characteristics of PS-FLCs. As a result, it is confirmed that the monostable capability strongly depends on the polymer concentration. However, the driving voltage increases as the polymer concentration increases. Therefore, to fabricate practicable PS-FLC devices, it is important to investigate the effects of other factors on the monostable capability. From the investigation of the influence of the cell gap and the alignment film materials on the monostable capability of PS-FLCs, it is concluded that the surface anchoring of the alignment film strongly influences the monostable characteristics of PS-FLCs photocured in the SmA phase.

Furue, Hirokazu; Amano, Mana; Shime, Tsubasa; Horiguchi, Toshiki; Oka, Shinichiro; Komura, Shinichi; Kobayashi, Shunsuke

2013-09-01

196

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

197

Crystal growth and dielectric, mechanical, electrical and ferroelectric characterization of n-bromo succinimide doped triglycine sulphate crystals  

Microsoft Academic Search

Single crystals of triglycine sulphate (TGS) doped with n-bromo succinimide (NBS) were grown at ambient temperature by the slow evaporation technique. An aqueous solution containing 1–20mol% of n-bromo succinimide as dopant was used for the growth of NBSTGS crystals. The incorporation of NBS in TGS crystals has been qualitatively confirmed by FTIR spectral data. The effect of the dopant on

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

2011-01-01

198

Stabilization of metastable ferroelectric Ba?-xCaxTi?O? by breaking Ca-site selectivity via crystallization from glass.  

PubMed

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

199

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

200

Phase transitions in potassium ammonium dihydrogen phosphate single crystals  

NASA Astrophysics Data System (ADS)

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

Bromberek, Marek

201

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

202

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

203

High-authority telescoping actuators with single-crystal piezoelectric materials  

NASA Astrophysics Data System (ADS)

The displacement output of the telescoping actuators, as developed in the NRL, depend on the material properties. Recently developed relaxor ferroelectric materials, with compositions near the morphotropic phase boundary and in single crystal forms, show high strain output capability and high coupling coefficients. These materials, when design into devices, would provide high performance, in terms of displacement output, and high transduction efficiency. We have utilized one of these single crystal materials, namely, lead zinc niobate-lead titanate, PZN-PT, for the construction of the NRL telescoping actuators. The evaluation of the piezoelectric performance of these single crystal-based telescoping actuators showed much higher displacement outputs than that for the ones previously made with polycrystalline PZT ceramics.

Wu, Carl C.; Lewis, David, III; Park, Seung Eek E.

2000-06-01

204

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

205

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

NASA Astrophysics Data System (ADS)

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

Rudiak, V. M.

1983-04-01

206

Ferroelectric and electromechanical property characterization of single Pb(ZrTi)O3 fiber resonator  

NASA Astrophysics Data System (ADS)

Piezoelectric fibers and fiber composites have attracted much attention for anisotropic sensing and actuation applications in recent year. Complete property characterization for piezoelectric fibers is essential for material and device design and fabrication. In this work, ferroelectric and electromechanical properties of single piezoelectric Pb(ZrTi)O3 (PZT) fiber were characterized by polarization-electric field hysteresis loop measurement using single PZT fiber/polymer 1-3 composite approach, and by direct measurement of the complex impedance spectrum of single PZT fiber resonator. A normalized electrical impedance spectrum method developed recently was used to determine the complex piezoelectric, elastic, and dielectric coefficients, mechanical quality factor and electromechanical coefficient from the complex electrical impedance-frequency spectrum measurement. The results were compared with those determined by the IEEE standard method for the pure length extensional resonator. The permittivity of PZT fiber was found larger than PZT bulk materials, which was attributed for the core-shell structure of the fibers.

Sun, Chengliang; Qin, Lifeng; Xue, Hao; Xiong, Zhaoxian; Wang, Qing-Ming

2010-01-01

207

Visible polarized light transmission spectroscopy of the electro-optic switching behaviour of surface stabilized ferroelectric liquid crystal cells  

Microsoft Academic Search

We present in this paper an experimental and theoretical modelling study of the switching characteristics and electro-optic behaviour of chevron surface stabilized ferroelectric liquid crystal cells with planar (low pre-tilt) and non-planar (high pre-tilt) surface conditions. The visible polarized light transmission spectra were taken of the cells with glass plates coated with films of either rubbed polymer or obliquely evaporated

Zhiming Zhuang; Noel A. Clark; Joseph E. Maclennan

1991-01-01

208

Thermal fluctuation effects in ferroelectric liquid-crystal polarization reversal: Light scattering from a transient domain-wall foam  

Microsoft Academic Search

Thermal orientation fluctuations of the director field during electric-field-induced polarization reversal in ferroelectric liquid crystals lead to the nondeterministic formation of a transient domain-wall foam that strongly scatters light. This foam comprises domains of molecules that have reoriented locally in the same sense on the smectic-C tilt cone and are separated from one another by 2pi inversion walls. The dynamics

Joseph E. Maclennan; Noel A. Clark

1991-01-01

209

Ferroelectric-like response from the surface of SrTiO3 crystals at high temperatures  

NASA Astrophysics Data System (ADS)

Since SrTiO3 has a high dielectric constant, it is used as a substrate for a large number of complex physical systems for electrical characterization. Since SrTiO3 crystals are known to be non-ferroelectric/non-piezoelectric at room temperature and above, SrTiO3 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) SrTiO3 we show that ferroelectric and piezoelectric-like response may originate from bare SrTiO3 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 SrTiO3 crystals. This observation indicates that the role of the electrical response of SrTiO3 needs to be revisited in the systems where signature of ferroelectricity/piezoelectricity has been previously observed with SrTiO3 as a substrate/base material.

Jyotsna, Shubhra; Arora, Ashima; Sekhon, Jagmeet S.; Sheet, Goutam

2014-09-01

210

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

211

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

212

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

213

Allowed mesoscopic point group symmetries in domain average engineering of perovskite ferroelectric crystals  

E-print Network

Allowed mesoscopic point group symmetries in domain average engineering of perovskite ferroelectric average engineering in proper ferroelectric systems arising from the cubic Pm3¯m symmetry perovskite­4 Both solid solution systems have a perovskite structure. Poling along one of the pseudocubic axes

Cao, Wenwu

214

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

215

Broadband single-polarization photonic crystal fiber  

Microsoft Academic Search

We demonstrate a single-mode photonic crystal fiber that supports only one polarization state in a 220-nm-broad spectral region centered at 727 nm. The fiber has a mode-field diameter of 15.5 mum and background losses of <15 dB\\/km in the single-polarization region. To our knowledge, these are the broadest bandwidth and the largest mode size yet reported for a single-polarization fiber.

J. R. Folkenberg; M. D. Nielsen; C. Jakobsen

2005-01-01

216

Oxygen Incorporation in Rubrene Single Crystals  

PubMed Central

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

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

2014-01-01

217

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

218

Neutron detection with single crystal organic scintillators  

NASA Astrophysics Data System (ADS)

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, Natalia P.; Newby, Jason; Hamel, Sebastien; Carman, Leslie; Faust, Michelle; Lordi, Vincenzo; Cherepy, Nerine J.; Stoeffl, Wolfgang; Payne, Stephen A.

2009-08-01

219

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

E-print Network

that the monoclinic­tetragonal (M­T) phase transition of the ternary relaxor- based ferroelectric single crystal 0. Introduction Relaxor-based ternary ferroelectric single crystals (1�x�y)Pb (In1/2Nb1/2)O3­yPb(Mg1/3Nb2/3)O3­x properties and their potential applications in ultrasonic transducers and actuators [1­6]. It was reported

Cao, Wenwu

220

Elastic, piezoelectric, and dielectric properties of multidomain 0.67Pb,,Mg13Nb23...O3 0.33PbTiO3 single crystals  

E-print Network

Relaxor based ferroelectric single crystal systems, Pb Zn1/3Nb2/3 O3­PbTiO3 PZN­PT and Pb Mg1/3Nb2/3 O3 transducers with superior broadband characteristics, large strain actuators, and many other electromechanical

Cao, Wenwu

221

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

222

Giant electro-optic effect of PMN-33%PT single crystals under proper AC electric field bias  

NASA Astrophysics Data System (ADS)

In this paper, electro-optic properties of 0.67Pb(Mg1/3Nb2/3)03-0.33PbTiO3 (PMN-33%PT) single crystals under proper AC bias are reported. It is found that PMN-33%PT has an extremely large linear electro-optic coefficient, r33 ~9800 pm/V under proper AC bias. Besides this huge electro-optic coefficient, PMN-33%PT crystals also have very good optical quality and the random scatterings caused by the multiple domains can be totally removed by the AC bias. Furthermore, unlike KTN, PMN-PT has a much higher phase transition temperature (~175°C), which is sufficiently away from the room temperature so that a good thermal stability can be achieved. The combinations of giant electro-optic coefficient, good optical quality, and high thermal stability may make PMN-33%PT the best electro-optic material among all electro-optic crystals developed so far, which could revolutionize applications of electro-optic crystals to telecommunications, medical imaging, et al. This research may also help to understand the mechanism underlying the ultrahigh performance of this new generation of single crystal materials (e.g., PZN-PT, PMN-PT) via the interaction between crystal internal structures and external AC electric field, which may stimulate further interest in the fundamental theory of ferroelectrices under changing electric field that could direct improving the quality of existing ferroelectric crystals and developing new ferroelectric crystals.

Yin, Shizhuo; Wu, Juntao; Zhan, Chun; Luo, Claire

2003-10-01

223

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

224

First Single-Crystal Mullite Fibers  

NASA Technical Reports Server (NTRS)

Ceramic-matrix composites strengthened by suitable fiber additions are being developed for high-temperature use, particularly for aerospace applications. New oxide-based fibers, such as mullite, are particularly desirable because of their resistance to high-temperature oxidative environments. Mullite is a candidate material in both fiber and matrix form. The primary objective of this work was to determine the growth characteristics of single-crystal mullite fibers produced by the laser-heated floating zone method. Directionally solidified fibers with nominal mullite compositions of 3Al2O3 2SiO2 were grown by the laser-heated floating zone method at the NASA Lewis Research Center. SEM analysis revealed that the single-crystal fibers grown in this study were strongly faceted and that the facets act as critical flaws, limiting fiber strength. The average fiber tensile strength is 1.15 GPa at room temperature. The mullite fibers exhibit superior strength retention (80 percent of their room temperature tensile strength at 1450 C). Examined by transmission electron microscopy, these mullite single crystals are free of dislocations, low-angle boundaries, and voids. In addition, they show a high degree of oxygen vacancy ordering. High-resolution digital images from an optical microscope furnish evidence of the formation of a liquid-liquid miscibility gap during crystal growth. These images represent the first experimental evidence of liquid immiscibility for these compositions and temperatures. Continuing investigation with controlled seeding of mullite single crystals is planned.

1997-01-01

225

Investigations on the electrical and mechanical properties of triglycine sulphate single crystals modified with some rare earth metal ions  

Microsoft Academic Search

Single crystals of triglycine sulphate (TGS) modified with La3+, Ce3+ and Nd3+ have been grown from aqueous solutions by low-temperature solution growth method. The effect of rare earth ion dopants (La, Ce and Nd) on the ferroelectric properties of TGS is reported. Dielectric constant and dielectric loss have been measured for different frequencies. Dielectric measurements revealed that the dielectric constant

R Muralidharan; R Mohankumar; R Dhanasekaran; A. K Tirupathi; R Jayavel; P Ramasamy

2003-01-01

226

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

227

Inkjet printing of single-crystal films  

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

228

Surface flatness of polished metal single crystals  

SciTech Connect

The Fizeau interference has been utilized to measure the flatness of a metal single crystal after grinding and polishing by standard techniques. It is postulated that deviations from flatness are due to distortions of flexible abrasive substrates during the grinding step. {copyright} {ital 1996 American Vacuum Society}

Tripa, C.E.; Yates, J.T. Jr. [Surface Science Center, Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)] [Surface Science Center, Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

1996-07-01

229

MAGNETIC PROPERTIES OF DYSPROSIUM SINGLE CRYSTALS  

Microsoft Academic Search

Single crystals of metallic dysprosium have been grown by the Bridgman ; method and their magnetic properties have been determined in different ; crystallographic directions of the hexagonal close-packed structure. Below the ; Neel point of 178.5 deg K the individual magnetic moments are aligned ; perpendicular to the c\\/sub o\\/ axis. The moments are aligned in an ; antiferromagnetic

D. R. Behrendt; S. Legvold; F. H. Speddin

1958-01-01

230

Single-crystal ruby fiber temperature sensor  

Microsoft Academic Search

Single-crystal ruby fibers with nominal diameters in the range from 80 to 500?m and lengths up to 170mm have been produced using the laser heated miniature pedestal growth technique. These fibers were tested for use as the basis of fiber optic temperature sensors. Characterization of the fiber fluorescence properties and comparison to bulk samples together with their high melting point

H. C Seat; J. H Sharp; Z. Y Zhang; K. T. V. Grattan

2002-01-01

231

Guided wave propagation in 0.67Pb,,Mg1/3Nb2/3...O30.33PbTiO3 single crystal plate poled along 001c  

E-print Network

-x Pb Zn1/3Nb2/3 O3­xPbTiO3 PZN-PT and 1 -x Pb Mg1/3Nb2/3 O3­xPbTiO3 PMN-PT ferroelectric single devices, including piezoelec- tric transducers, actuators, piezoelectric ultrasonic motors, etc. Some crystal is in the ferroelectric phase at room temperature with rhombohedral 3m symmetry. When being poled

Cao, Wenwu

232

Dielectric method for determining the rotational viscosity in thick samples of ferroelectric chiral smectic-C* liquid crystals  

Microsoft Academic Search

An alternative method, based on dielectric measurements on thick samples, for determining the Goldstone-mode rotational viscosity and the twist elastic constant of ferroelectric, chiral smectic-C* liquid crystals is presented. By the use of this method the temperature dependence of these quantities for p-decyloxibenzilidine-p'-amino-1-methylpropyl-cinamate (DOBA-1-MPC) and p-n-decyloxybenzylidine-p-amino-2-methyl-butyl-cinamate (DOBAMBC) has been determined. An Arrhenius-type behavior of the Goldstone-mode rotational viscosity was obtained

A. Levstik; Z. Kutnjak; C. Filipi; I. Levstik; Z. Bregar; B. Zeks; T. Carlsson

1990-01-01

233

Determination of Chevron Direction and Sign of the Boat-Shaped Disclination in Surface-Stabilized Ferroelectric Liquid Crystals  

NASA Astrophysics Data System (ADS)

On the basis of a smectic layer bend (chevron) structure confirmed recently, the absolute configuration of a zigzag defect and a boat-shaped disclination loop were investigated in surface-stabilized ferroelectric liquid crystal (SSFLC) cells. Comparing the color of the SSFLC state stabilized by a lateral electric field with the color calculated by a suitable model, the following configurations were clarified: 1) the apices of lightning and the thick lines of hairpin zigzag defects correspond to ?l*?g and ?g*?l, respectively, and 2) the bow and the stern of boat-shaped domains correspond to +2? and -2? wedge disclinations, respectively.

Hiji, Naoki; Ouchi, Yukio; Takezoe, Hideo; Fukuda, Atsuo

1988-01-01

234

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

235

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

236

Temperature change effect on BaTiO3 single crystal surface potential around domain walls  

NASA Astrophysics Data System (ADS)

Temperature dependence of the surface potential distribution on the BaTiO3 (0 0 1) single crystal ferroelectric domain walls was investigated by the scanning Kelvin probe microscopy. After decreasing the single crystal temperature below the Curie point (TC), high potential (?600 mV) stripes were immediately observed near the 90° a-c domain wall surface. The potential stripes were not stable and decayed with time. The adjacent c domain surface screening charges and their mobility play a dominant role in this experiment. The corrugation topography at the 90° a-c domain wall acts as a natural charge trap and should not be neglected. Besides, the polarization and the strain variations across the wall induce large physical changes of the material.

He, D. Y.; Xing, X. R.; Qiao, L. J.; Volinsky, Alex A.

2014-08-01

237

Lightweight optical mirrors formed in single crystal substrate  

NASA Technical Reports Server (NTRS)

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

Bly, Vincent T. (Inventor)

2006-01-01

238

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

PubMed Central

Ferroelectric domain nucleation and growth in multiferroic BiFeO3 is studied on a single-domain level by using piezoresponse force spectroscopy. Variation of local electromechanical response with dc tip bias is used to determine the size of the domain formed below the conductive scanning probe tip. The domain parameters are calculated self-consistently from the decoupled Green function theory by using tip geometry determined from the domain wall profile. The critical parameters of the nucleating domain and the activation energy for nucleation are determined. The switching mechanism is modeled by using the phase-field method, and comparison with experimental results shows that the nucleation biases are within a factor of ?2 of the intrinsic thermodynamic limit. The role of atomic-scale defects and long-range elastic fields on nucleation bias lowering is discussed. These measurements open a pathway for quantitative studies of the role of a single defect on kinetics and thermodynamics of first order bias-induced phase transitions and electrochemical reactions. PMID:18077335

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

2007-01-01

239

Growth and characterization of rare earths doped triglycine sulfate crystals  

Microsoft Academic Search

Ferroelectric triglycine sulfate (TGS) single crystals have been grown by a temperature-lowering technique from the aqueous solution by doping with samarium sulfate, ytterbium sulfate and terbium sulfate in the ferroelectric phase. The effects of these different dopants on the morphology, growth and various properties such as dielectric, pyroelectric and piezoelectric of doped TGS crystals have been investigated. The decrease in

A. K. Batra; Padmaja Guggilla; Dewanna Cunningham; M. D. Aggarwal; R. B. Lal

2006-01-01

240

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

241

SSME single crystal turbine blade dynamics  

NASA Technical Reports Server (NTRS)

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

Moss, Larry A.; Smith, Todd E.

1987-01-01

242

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

243

Growth of Solid Solution Single Crystals  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

244

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

245

Time-resolved infrared spectroscopy of molecule/binding site reorientation during ferroelectric liquid crystal electro-optic switching  

PubMed

Polarized Fourier transform infrared (IR) absorption is used to probe molecular conformation in a ferroelectric liquid crystal during the large-scale collective reorientation induced by external applied electric field. Spectra of planar-aligned cells of the ferroelectric liquid crystal (FLC) W314 ((S)-4(')-(decyloxy)4-[(1-methylheptyl)oxy]-2-nitrophenyl-[1, 1'-biphenyl]-4-carboxylic acid ester) are measured as functions of IR polarizer orientation and time following the reversal of the electric field applied to the FLC. The time evolution of the dichroism of the absorbance due to the specific molecular vibration modes, particularly from the biphenyl core and alkyl tail, is observed. Static IR dichroism experiments show a W314 IR dichroism structure in which the principal axis of the dielectric tensor from molecular core vibrations are tilted further from the smectic layer normal than those of the tail. This structure indicates that the effective binding site in which the molecules are confined in the Sm-C phase has, on average, a "zig-zag" shape. The dynamic experiments show that this zig-zag binding site structure is rigidly maintained while the molecular axis rotates about the layer normal during field-induced switching. PMID:11089063

Jang; Park; Clark

2000-10-01

246

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

247

Pyroelectroluminescence of barium beta borate single crystals  

Microsoft Academic Search

Investigations were made of the pyroluminescence properties of barium beta borate single crystals. The measurements were made\\u000a at air pressures of 1–10 Pa and temperatures of 80–400 K. Luminescence was observed as isolated flashes over the entire range\\u000a of experimental conditions. It was observed that the light flashes coincided with the pyrocurrent oscillations.

V. T. Adamiv; Ya. V. Burak; M. R. Panasyuk; I. M. Teslyuk

1998-01-01

248

Single crystal silicon micro-actuators  

Microsoft Academic Search

A novel process suitable for fabricating single-crystal silicon microactuators is described. The process utilizes boron-diffused silicon etch stop to define the silicon microstructure thickness and a dry etch process to form narrow and deep trenches, followed by a silicon-to-glass bonding step and subsequent unmasked wafer dissolution. For rotational microactuators, polysilicon trench filling and sacrificial layer patterning are added to define

K. Suzuki

1990-01-01

249

Ionic diffusion in single crystals of vermiculite  

SciTech Connect

Novel guest-host compounds, based on single crystal vermiculite, were synthesized by diffusive techniques through a new hydrogen vermiculite. Single crystals were chosen because of the ease of characterization. An investigation of the ion transport properties of these single crystals was done to determine the mechanism of conductivity including the predominant charge carrier. Measurements of the ionic conductivity using impedance spectroscopy and X-ray lattice parameters of the ion-exchanged samples strongly suggest that the native cations and not protons are the major current carriers. Single crystals of hydrogen vermiculite were synthesized at room temperature by ion exchange from sodium-vermiculite using 1 molar acetic acid for a one week. Subsequent ion exchange with other cations was found to be much enhanced. Thus transition metals were exchanged in about a week in contrast to the need of several months using previous methods. The ionic conductivity of hydrogen vermiculite was measured and shown to be much lower than that of many other monovalent cations in the same host lattice. Its enthalpy of motion is also much lower. These marked differences suggest that protonic species do not play a significant role in charge transport in these layered materials. These materials were characterized by x-ray powder diffraction, thermogravimetric analysis and acid-base titration. Hydrogen-vermiculite was found to react with organic bases, like methylamine, ethylamine, n-butylamine, n-hexylamine, n-octylamine, n-decylamine, aniline, acrylamide, methacrylaminde, urea, 1,10phenanthroline, and 1,1phenanthroline ferrous sulfate complex, to undergo ion exchange with metal cations like sodium, zinc, copper(II) ions and polymerization reactions could be performed in the galleries of the structure like pyrrole and aniline. Its behavior was compared with that of powdered montmorillonite.

Maraqah, H.R.

1993-01-01

250

Crack Growth in Single-Crystal Silicon  

NASA Technical Reports Server (NTRS)

Report describes experiments on crack growth in single-crystal silicon at room temperature in air. Crack growth in (111) cleavage plane of wafers, 50 by 100 by 0.76 mm in dimension, cut from Czochralski singlecrystal silicon studied by double-torsion load-relaxation method and by acoustic-emission measurements. Scanning electron microscopy and X-ray topography also employed. Results aid in design and fabrication of silicon photovoltaic and microelectronic devices.

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

1986-01-01

251

Characterization of Defects in PTerphenyl Single Crystals  

Microsoft Academic Search

White Beam Synchrotron X-ray Topography has been used to characterize defects in solution-grown p-terphenyl single crystals. Defects observed include growth dislocations, mechanically introduced dislocations, macroscopic twins, twin lamellae, and dislocations emitted from twin boundaries. Line direction and Burgers Vector analysis of the growth and mechanically introduced dislocations, using projective geometry calculations and g. b analysis, respectively, are presented, along with

Michael Dudley; Rosemarie Disalvo; Shang-Yun Hou; Bruce M. Foxman; William Jones

1992-01-01

252

Flexible single-crystal silicon nanomembrane photonic crystal cavity.  

PubMed

Flexible inorganic electronic devices promise numerous applications, especially in fields that could not be covered satisfactorily by conventional rigid devices. Benefits on a similar scale are also foreseeable for silicon photonic components. However, the difficulty in transferring intricate silicon photonic devices has deterred widespread development. In this paper, we demonstrate a flexible single-crystal silicon nanomembrane photonic crystal microcavity through a bonding and substrate removal approach. The transferred cavity shows a quality factor of 2.2 × 10(4) and could be bent to a curvature of 5 mm radius without deteriorating the performance compared to its counterparts on rigid substrates. A thorough characterization of the device reveals that the resonant wavelength is a linear function of the bending-induced strain. The device also shows a curvature-independent sensitivity to the ambient index variation. PMID:25409282

Xu, Xiaochuan; Subbaraman, Harish; Chakravarty, Swapnajit; Hosseini, Amir; Covey, John; Yu, Yalin; Kwong, David; Zhang, Yang; Lai, Wei-Cheng; Zou, Yi; Lu, Nanshu; Chen, Ray T

2014-12-23

253

Director orientation in chevron surface-stabilized ferroelectric liquid crystal cells. Verification of orientational binding at the chevron interface using visible polarized light transmission spectroscopy  

Microsoft Academic Search

We present results of theoretical modelling and experimental study of director distributions and the associated optical properties of chevron surface stabilized ferroelectric liquid crystal (SSFLC) cells. Chevron cells are modelled as being two stacked FLC slabs, described by distinct orientation distributions of the director [ncirc]-polarization P([ncirc] – P) couple. In each slab the [ncirc] – P distribution is governed by

J. E. Maclennan; N. A. Clark; M. A. Handschy; M. R. Meadows

1990-01-01

254

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

255

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

256

Guest exchange through single crystal-single crystal transformations in a flexible hydrogen-bonded framework.  

PubMed

A molecular framework based on guanidinium cations and 1,2,4,5-tetra(4-sulfonatophenyl)benzene (TSPB), an aromatic tetrasulfonate with nominal 2-fold and mirror symmetry, exhibits three crystallographically unique one-dimensional channels as a consequence of molecular symmetry and complementary hydrogen bonding between the guanidinium (G) ions and the sulfonate (S) groups of TSPB. Unlike previous GS frameworks, this new topology is sufficiently flexible to permit reversible release and adsorption of guest molecules in large single crystals through a cyclic shrinkage and expansion of the channels with retention of single crystallinity, as verified by single crystal X-ray diffraction. Moreover, the G4TSPB framework permits guest exchange between various guest molecules through SCSCTs as well as exchange discrimination based on the size and character of the three different channels. The exchange of guest molecules during single crystal-single crystal transformations (SCSCT), a rare occurrence for hydrogen-bonded frameworks, is rather fast, with diffusivities of approximately 10(-6) cm(2) s(-1). Rapid diffusion in the two channels having cross sections sufficient to accommodate two guest molecules can be explained by two-way or ring diffusion, most likely vacancy assisted. Surprisingly, rapid guest exchange also is observed in a smaller channel having a cross-section that accommodates only one guest molecule, which can only be explained by guest-assisted single-file unidirectional diffusion. Several single crystals of inclusion compounds can be realized only through guest exchange in the intact framework, suggesting an approach to the synthesis of single crystalline inclusion compounds that otherwise cannot be attained through direct crystallization methods. PMID:25248132

Xiao, Wenchang; Hu, Chunhua; Ward, Michael D

2014-10-01

257

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

E-print Network

Design of a polarized head-mounted projection display using ferroelectric liquid 2008 It has been a common problem in optical see-through head-mounted displays that the displayed image- gravated in head-mounted projection displays in which multiple beam splitting and low retroreflectance

Hua, Hong

258

The origin of ferroelectricity in magnetoelectric YMnO3.  

PubMed

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

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

2004-03-01

259

Effect of a single dislocation in a heterostructure layer on the local polarization of a ferroelectric layer.  

PubMed

We study, on an atomic scale, the influence of a single dislocation in a SrTiO3 sublayer on the local ferroelectric polarization of the neighboring ferroelectric PbZr0.2Ti0.8O3 (PZT) sublayer in an epitaxial SrTiO3/PbZr0.2Ti0.8O3/SrTiO3 three-layer heterostructure. The strain field of the dislocation in the SrTiO3 layer propagates across the interface into the PZT layer and leads to a strong variation of the c-lattice parameter of the PZT layer. Accompanying a strong reduction of the c-lattice parameter, the off-center displacements of the Zr/Ti atoms away from the center of the oxygen octahedra are also strongly decreased, resulting in a decrease of the local spontaneous polarization by up to 48%. PMID:19392236

Jia, C L; Mi, S B; Urban, K; Vrejoiu, I; Alexe, M; Hesse, D

2009-03-20

260

Oriented single-crystal-to-single-crystal phase transition with dramatic changes in the dimensions of crystals.  

PubMed

We report here a new polymorph of cocrystal CuQ2-TCNQ that shows an oriented single-crystal-to-single-crystal phase transition along its a-axis at ambient conditions. Upon mechanical stimulation, it converts into another polymorph accompanied by almost doubling its length and halving its thickness. Our crystallographic studies indicate the dramatic changes in crystal dimensions resulted from the prominent changes of molecular stacking patterns. A reasonable mechanism for the phenomenon was proposed on the basis of the structural, microscopic, and thermal analysis. PMID:24372005

Liu, Guangfeng; Liu, Jie; Liu, Yang; Tao, Xutang

2014-01-15

261

Orientation dependence of the properties of PZN-4.5%PT relaxor single crystals  

NASA Astrophysics Data System (ADS)

Relaxor ferroelectric PZN-xPT and PMN-xPT single crystals exhibit excellent electromechanical coupling properties that depend on crystallographic orientations. In this study compressive stress and electric field were applied to relaxor single crystals [Pb(Zn1/3Nb2/3)O3]0.955-[PbTiO3]0.045 (PZN-4.5%PT) in a series of crystal orientations between <001> and <111>, and the corresponding strain and electric displacement were measured. It was found that as the angle of the orientation cut is rotated from <001> to <111>, the piezoelectric coefficient d33 drops and hysteresis increases dramatically. A crystal variant based approach was used to model the piezoelectric coefficients and remnant electric displacement. The bipolar electro-mechanical response of these crystals is presented. Observed hysteresis and nonlinear phenomena related to polarization reorientation and phase transitions is discussed. In actuator design and performance control, these results give a guideline regarding appropriate external fields in order to prevent depolarization, heat generation and damage.

Liu, T.; Lynch, C. S.

2005-05-01

262

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-sized single crystals. The resulting datasets allowed a determination of the structure with conventional X

Paris-Sud XI, Université de

263

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

264

Phase transition in sarcosine phosphite single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of sarcosine phosphite (SarcH3PO3) have been grown. The amino acid sarcosine is an isomer of the protein amino acid alanine. Both amino acids are described by the same chemical formula but have different structures; or, more specifically, in contrast to the alanine molecule, the sarcosine molecule has a symmetric structure. It has been found that the sarcosine phosphite compound undergoes a structural phase transition at a temperature of approximately 200 K. This result has demonstrated that compounds of achiral amino acids are more susceptible to structural phase transitions.

Lemanov, V. V.; Popov, S. N.; Pankova, G. A.

2011-06-01

265

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

266

Conduction mechanism of single-crystal alumina  

NASA Technical Reports Server (NTRS)

The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

1992-01-01

267

Polarization switching in ferroelectric crystals with defects charged under photo- or UV-excitation  

NASA Astrophysics Data System (ADS)

We have proposed the phenomenological description of dielectric hysteresis loops in ferroelectric semiconductors with impurity centers charged under photo- or UV excitation. Exactly we have modified Landau-Ginsburg approach and shown that the macroscopic state of the aforementioned inhomogeneous system can be described by three coupled equations for three order parameters. Both the experimentally observed coercive field values well below the thermodynamic one and the various hysteresis loop deformations (constricted and double loops) have been obtained in the framework of our model.

Morozovska, Anna N.

2005-11-01

268

Properties of salt-grown uranium single crystals  

Microsoft Academic Search

Recently single crystals of -uranium were grown from a liquid salt bath. The electrical, magnetic and thermal properties of these crystals have been surveyed. The ratio of the room temperature resistivity of these crystals to the saturation value at low temperature is three times larger than any previously reported demonstrating that the crystals are of higher purity and quality than

J. C. Cooley; R. J. Hanrahan; W. L. Hults; J. C. Lashley; M. E. Manley; C. H. Mielke; J. L. Smith; D. J. Thoma; R. G. Clark; A. R. Hamilton; J. L. OBrien; E. C. Gay; N. E. Lumpkin; C. C. McPheeters; J. Willit; G. M. Schmiedeshoff; S. Touton; B. F. Woodfield; B. E. Lang; Juliana Boerio-Goates

2001-01-01

269

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

270

Single-crystal fiber optics: a review  

NASA Astrophysics Data System (ADS)

Single-crystal (SC) fiber optics have been grown for many years for use as passive fibers for the delivery of IR laser radiation and as active fibers useful as minirod lasers. Most of the early work on SC fiber optics involved the growth of unclad sapphire fibers for the transmission of Er:YAG laser radiation at 2.94 ?m. More recently there has been a renewed interest in rare-earth (RE) doped oxide crystal fibers for use as high power fiber lasers. By analogy with RE doped-bulk laser crystals it is expected that pure YAG and other crystalline SC fibers should be capable of transmitting extremely high laser energies. SC oxide fibers have some distinct advantages over conventional glass fibers including higher thermal conductivity and low stimulated Brillouin scattering (SBS) gain coefficients. The latter can limit the ultimate power output of glass fiber lasers. To date most of the investigators have used the technique of Laser Heated Pedestal Growth (LHPG) to grow unclad SC fibers with diameters ranging from 30 to 350 ?m and in lengths as long as 5 m. The loss for SC sapphire fibers at 2.94 ?m has been measured as low as 0.3 dB/m. In this review we discuss the technique of LHPG, the various SC fiber optics that have been grown for both active and passive applications, and methods that may be used to clad the fibers.

Harrington, James A.

2014-02-01

271

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

272

Ultrahigh-quality silicon carbide single crystals.  

PubMed

Silicon carbide (SiC) has a range of useful physical, mechanical and electronic properties that make it a promising material for next-generation electronic devices. Careful consideration of the thermal conditions in which SiC [0001] is grown has resulted in improvements in crystal diameter and quality: the quantity of macroscopic defects such as hollow core dislocations (micropipes), inclusions, small-angle boundaries and long-range lattice warp has been reduced. But some macroscopic defects (about 1-10 cm(-2)) and a large density of elementary dislocations (approximately 10(4) cm(-2)), such as edge, basal plane and screw dislocations, remain within the crystal, and have so far prevented the realization of high-efficiency, reliable electronic devices in SiC (refs 12-16). Here we report a method, inspired by the dislocation structure of SiC grown perpendicular to the c-axis (a-face growth), to reduce the number of dislocations in SiC single crystals by two to three orders of magnitude, rendering them virtually dislocation-free. These substrates will promote the development of high-power SiC devices and reduce energy losses of the resulting electrical systems. PMID:15329716

Nakamura, Daisuke; Gunjishima, Itaru; Yamaguchi, Satoshi; Ito, Tadashi; Okamoto, Atsuto; Kondo, Hiroyuki; Onda, Shoichi; Takatori, Kazumasa

2004-08-26

273

Synthesis and characterization of superconducting single-crystal Sn nanowires  

E-print Network

June 2003 Single-crystal superconducting tin nanowires with diameters of 40­160 nm have been prepared was attributed by the authors to be related to the ``poor crystal structure;'' that is, a lacking of electronSynthesis and characterization of superconducting single-crystal Sn nanowires Mingliang Tian

274

Structural origin for the change of the order of ferroelectric phase transition in triglycine sulfate/selenate systems  

NASA Astrophysics Data System (ADS)

Crystal structures of triglycine selenate (TGSe) and triglycine sulfate (TGS) obtained from single crystal neutron diffraction are compared. The double well single cell local potential experienced by the non-planar amino group of one of the three glycine ions (GI) of these two isostructural crystals is obtained using their crystal structure. It is suggested that the change in the nature of the ferroelectric phase transition as one goes from TGS to TGSe is due to the increase in the zero point energy resulting due to the change in the shape and height of the double well local potential of these crystals. Substitution of a selenate ion (SeO42-) in TGSe by a sulfate ion (SO42-) is considered as a source of an effective chemical pressure that can be utilized to tune the ferroelectric phase boundary in these crystals. The influence of alanine substitution on the ferroelectric phase transition in these crystals is investigated using differential scanning calorimetry.

Choudhury, Rajul Ranjan; Chitra, R.

2009-08-01

275

Piezoelectric single crystals for ultrasonic transducers in biomedical applications.  

PubMed

Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state-of-art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN-PT and PIN-PMN-PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single-element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed. PMID:25386032

Zhou, Qifa; Lam, Kwok Ho; Zheng, Hairong; Qiu, Weibao; Shung, K Kirk

2014-10-01

276

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

277

Growth and characterization of biadmixtured TGS single crystals  

Microsoft Academic Search

Single crystals of triglycine sulfate (TGS) with l-glutamine and l-methionine were grown in aqueous solutions by a slow cooling method. The grown crystals were subjected to single crystal and powder X-ray diffraction studies to identify the morphology and the structure. FTIR and UV–visible spectra reveal the functional group identification and optical property of the grown crystals. The dielectric studies were

T. Bharthasarathi; V. Siva Shankar; R. Jayavel; P. Murugakoothan

2009-01-01

278

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

279

Ion Crystal Transducer for Strong Coupling between Single Ions and Single Photons  

E-print Network

A new approach for the 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 ...

Lamata, L.

280

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

281

Smart ferroelectric materials for sensors and mechatronic device applications  

Microsoft Academic Search

Ferroelectric single crystals, ceramics, polymers and composites can convert changes in mechanical and thermal energies into electrical signals as well as exhibiting the converse effect. This dual functional ability enables them to sense changes in their environment and actuate a desired response, which allow them to be regarded as smart (or intelligent) materials. The present paper reviews the piezoelectric and

H. L. W. Chan

1999-01-01

282

Ferroelectricity, Domain Structure, and Phase Transitions of Barium Titanate  

Microsoft Academic Search

A summarizing account is given of the research on barium titanate in progress at the Laboratory for Insulation Research at M. I. T. since 1943. The investigations have led to an understanding of the mechanism of ferroelectricity in the titanates and to discoveries such as the piezoelectric effect in the ceramics and the domain structure of the single crystals of

A. von Hippel

1950-01-01

283

Exchange coupling with the multiferroic compound BiFeO3 in antiferromagnetic multidomain films and single-domain crystals  

NASA Astrophysics Data System (ADS)

The exchange coupling observed between a soft ferromagnetic layer and the antiferromagnetic multiferroic compound BiFeO3 (BFO) is investigated. Results obtained on BFO ferroelectric and antiferromagnetic multidomain films and monodomain single crystals are compared. A significant interface coupling occurs in the two systems whose anisotropy however differs significantly. In thin film based heterostructures, the measured twofold anisotropy of the FM layer imposed by the magnetic field during deposition is well accounted for using a double macrospin model describing the role of uncompensated spins, pinned or reversible, in the vicinity of the interface. In contrast, no macroscopic bias is observed in thin films deposited on BFO single crystals where the anisotropy direction is imposed by the underlying antiferromagnetic structure. This highlights the fundamental difference between exchange coupling with a single domain antiferromagnet and with a much more magnetically disordered multidomain state.

Lebeugle, D.; Mougin, A.; Viret, M.; Colson, D.; Allibe, J.; Béa, H.; Jacquet, E.; Deranlot, C.; Bibes, M.; Barthélémy, A.

2010-04-01

284

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

285

Constitutive modeling for single crystal superalloys  

NASA Technical Reports Server (NTRS)

A crystallographic approach to constitutive modeling of single crystal superalloys is discussed. The approach is based on identifying the active slip planes and slip directions. The shear stresses are computed on each of the slip planes from applied stress components. The slip rate is then computed on each slip system and the microscopic inelastic strain rates are the sum of the slip in the individual slip systems. The constitutive model was implemented in a finite element code using twenty noted isoparametric solid elements. Constants were determined for octahedral and cube slip systems. These constants were then used to predict tension-compression asymmetry and fatigue loops. Other data was used to model the tensile and creep response.

Stouffer, Donald C.; Dame, L. Thomas; Jayaraman, N.

1985-01-01

286

Magnetoplasticity and diffusion in silicon single crystals  

SciTech Connect

The effect of static magnetic fields on the dynamics of surface dislocation segments, as well as the diffusion mobility of a dopant in silicon single crystals, has been analyzed. It has been experimentally found that the preliminary treatment of p-type silicon plates (the dopant is boron with a concentration of 10{sup 16} cm{sup -3}) in the static magnetic field (B = 1 T, a treatment time of 30 min) leads to an increase in the mobility of surface dislocation segments. The characteristic times of observed changes (about 80 h) and the threshold dopant concentration (10{sub 15} cm{sup -3}) below which the magneto-optical effect in silicon is not fixed have been determined. It has been found that diffusion processes in dislocation-free silicon are magnetically sensitive: the phosphorus diffusion depth in p-type silicon that is preliminarily aged in the static magnetic field increases (by approximately 20%) compared to the reference samples.

Skvortsov, A. A., E-mail: SkvortsovAA2009@yandex.ru; Karizin, A. V. [Moscow State Technical University 'MAMI' (Russian Federation)

2012-01-15

287

Vibration-assisted machining of single crystal  

NASA Astrophysics Data System (ADS)

Vibration-assisted machining offers a solution to expanding needs for improved machining, especially where accuracy and precision are of importance, such as in micromachining of single crystals of metals and alloys. Crystallographic anisotropy plays a crucial role in determining on overall response to machining. In this study, we intend to address the matter of ultra-precision machining of material at the micron scale using computational modelling. A hybrid modelling approach is implemented that combines two discrete schemes: smoothed particle hydrodynamics and continuum finite elements. The model is implemented in a commercial software ABAQUS/Explicit employing a user-defined subroutine (VUMAT) and used to elucidate the effect of crystallographic anisotropy on a response of face centred cubic (f.c.c.) metals to machining.

Zahedi, S. A.; Roy, A.; Silberschmidt, V. V.

2013-07-01

288

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

289

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

290

FAST TRACK COMMUNICATION: Evolution of piezoelectric resonance in switching current of 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 ferroelectric single crystal excited by a stepwise electric field  

NASA Astrophysics Data System (ADS)

Piezoelectric resonance current and switching current of 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMT-32%PT) single crystal were investigated by a stepwise electric field. As the reversely applied field increased from the coercive field to higher levels, high frequency resonance current always existed while the low frequency resonance current was replaced by a peak in the switching current gradually. This phenomenon is discussed based on a domain reversal process. The maximum switching current observed in switching current is fitted well using the equation proposed by Merz. This indicates that domain wall growth, instead of domain nucleation, plays an important role in that process.

Jin, Li; Yao, Xi; Wei, Xiaoyong

2008-10-01

291

Ferroelectric properties of doped triglycine sulfate crystals grown at negative temperatures  

Microsoft Academic Search

The effect of Cr3+ impurity ions on the dielectric and pyroelectric properties of triglycine sulfate crystals grown at temperatures below 0°C is studied. The Curie temperature T C of the chromium-containing crystals is 0.2-0.4°C lower than that of the impurity-free crystals grown at conventional temperatures. A stable reproducibility of the results of the pyroelectric measurements for the crystals studied is

S. D. Milovidova; N. G. Babicheva; O. V. Rogazinskaya; A. S. Sidorkin

2009-01-01

292

Ferroelectric properties of doped triglycine sulfate crystals grown at negative temperatures  

Microsoft Academic Search

The effect of Cr3+ impurity ions on the dielectric and pyroelectric properties of triglycine sulfate crystals grown at temperatures below 0°C\\u000a is studied. The Curie temperature T\\u000a C of the chromium-containing crystals is 0.2–0.4°C lower than that of the impurity-free crystals grown at conventional temperatures.\\u000a A stable reproducibility of the results of the pyroelectric measurements for the crystals studied is

S. D. Milovidova; N. G. Babicheva; O. V. Rogazinskaya; A. S. Sidorkin

2009-01-01

293

Unusual glass-like systems – relaxation dynamics of Cu + ions in ferroelectric KTN crystals  

Microsoft Academic Search

We present a broadband dielectric spectroscopy study of potassium tantalate niobate (KTN) crystals, doped with varying amounts of Cu ions. The dielectric landscape in frequency and temperature is rich, with multiple processes in different temperature phases of the crystals. Of particular interest are the processes resulting from Cu and Nb ions in the paraelectric phase of the crystal and from

P. Ben Ishai; C. E. M. de Oliveira; Y. Ryabov; A. J. Agranat; Yu. Feldman

2005-01-01

294

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

PubMed

It has been a common problem in optical see-through head-mounted displays that the displayed image lacks brightness and contrast compared with the direct view of a real-world scene. This problem is aggravated in head-mounted projection displays in which multiple beam splitting and low retroreflectance of a typical retroreflective projection screen yield low luminous transfer efficiency. To address this problem, we recently proposed a polarized head-mounted projection display (p-HMPD) design where the polarization states of the light are deliberately manipulated to maximize the luminous transfer efficiency. We report the design of a compact p-HMPD prototype system using a pair of high-resolution ferroelectric liquid-crystal-on-silicon (FLCOS) microdisplays. In addition to higher resolution, the FLCOS displays have much higher optical efficiency than a transmissive-type liquid crystal display (LCD) and help to further improve the overall light efficiency and image quality. We detail the design of a compact illumination unit for the FLCOS microdisplay, also commonly referred to as the light engine, and a projection lens, both of which are key parts of the p-HMPD system. The performances of the light engine and projection lens are analyzed in detail. Finally, we present the design of a compact p-HMPD prototype using the custom-designed light engine and projection optics. PMID:18493297

Zhang, Rui; Hua, Hong

2008-05-20

295

Crystallization of single phase (K, Na)clinoptilolite  

Microsoft Academic Search

A single phase (K, Na)-clinoptilolite was hydrothermally crystallized without seed crystals from a reactant mixture of (K, Na)-aluminosilicate gel slurry through homogeneous mixing at 150 °C for 144 h. Compositions of the reactant mixtures and reaction temperatures to obtain the clinoptilolite were restricted within narrow limits in the case of syntheses without seed crystals, while the compositions and temperatures were

Shigeo Satokawa; Keiji Itabashi

1997-01-01

296

Investigation on Growth and Surface Analysis of DAST Single Crystals  

SciTech Connect

We have explored the growth of bulk size N, N-dimethylamino-N'-methylstilbazolium p-toluenesulphonate (DAST) using slope nucleation method. The grown crystal was characterized by single crystal X-ray diffraction (XRD), and CHN analyses. The surface morphology of the crystal was analyzed using Scanning electron microscopy (SEM).

Thomas, Tina; Vijay, R. Jerald; Gunaseelan, R.; Sagayaraj, P. [Department of Physics, Loyola College, Chennai - 600 034 (India)

2011-07-15

297

High-pressure studies of ferroelectric phases related to the earth and planetary interiors  

Microsoft Academic Search

Dielectric property measurements to 5.5 GPa have been conducted on single crystals and polycrystalline aggregates of several ferroelectrics (BaTiO3, Pb(Zr, Ti)O3, triglycine sulfate, Rochelle salt) for the purpose of determining the effects of high-pressure constraints on the overall behavior of ferroelectrics (FE) of both the perovskite 'soft-mode' and hydrogen-bonded types. It is found that dielectric hysteresis is possible in FE

G. W. Timco; H. H. Schloessin

1978-01-01

298

Ferroelectric Domain Structure and Internal Bias Field in DL-alpha-Alanine-Doped Triglycine Sulfate  

Microsoft Academic Search

Single crystals of ferroelectric triglycine sulfate (TGS) have been grown from solutions containing 10 and 30 mol% of DL-alpha-alanine. Crystal form, domain structure and distribution of internal bias field Eb in these DL-alpha-alanine-doped triglycine sulfate: (DLATGS) crystals were investigated. Although the crystal form is influenced by the doping, it shows the symmetry of 2\\/m similar to pure TGS. The intensity

Noriyuki Nakatani

1991-01-01

299

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

300

Anisotropy of transient photoconductivity in functionalized pentacene single crystals  

E-print Network

to their potential applications in thin film transis- tors, organic light-emitting diodes, solar cells, etc.1 Thin single crystal platelets and polycrystalline thin films are par- ticularly interesting for applicationsAnisotropy of transient photoconductivity in functionalized pentacene single crystals O

Ostroverkhova, Oksana

301

Deformation-Free Single-Crystal Nanohelixes of Polar Nanowires  

E-print Network

Deformation-Free Single-Crystal Nanohelixes of Polar Nanowires Rusen Yang, Yong Ding, and Zhong Lin, deformation-free, single-crystal nanohelixes/nanosprings of piezoelectric ZnO are reported. The nanohelixes observed for carbon nanotubes,1 SiC2 and amorphous silicon carbide.3 The carbon coils are created due

Wang, Zhong L.

302

Precipitation of Copper Silicide in Voids in Silicon Single Crystals  

E-print Network

Precipitation of Copper Silicide in Voids in Silicon Single Crystals A thesis presented by Cheng Spaepen Cheng-Yen Wen Precipitation of Copper Silicide in Voids in Silicon Single Crystals Abstract precipitates have filled the open volume. For implementation of this method, precipitation of the Cu silicide

303

The growth technology for 300 mm single crystal silicon  

Microsoft Academic Search

The fabrication technique for 300 mm silicon single crystals and wafers is the central topic of silicon material research recently. The study on the growth technique of 300 mm silicon ingots has been developed in our institute since 1997. The research mainly focuses on the following aspects: (1) process conditions for fabrication of the dislocation-free silicon single crystal; (2) oxygen

H Tu; Q Zhou; G Zhang; J Wang; Q Chang; F Qin; F Fang; Z Wu; G Wan

2001-01-01

304

Single crystal silicon rotary microactuator for hard disk drive  

Microsoft Academic Search

A single crystal silicon rotary microactuator for hard disk drives (HDD) is described in this paper. The microactuator is mounted between the slider and suspension and drives the slider on which a magnetic head element is attached. The microactuator has electrically isolated microstructures with an aspect ratio 20:1 directly processed from a single crystal silicon substrate. It consists of a

J. Q. Mou; Y. Lu; J. P. Yang; Q. H. Li

2003-01-01

305

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

306

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

307

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

308

Microscale Laser Peen Forming of Single Crystal  

SciTech Connect

As the result of quickly increased requirement in many industrial products resulting from microtechnology, laser thermal microforming and microsurface treatment [microscale laser shock peening (?LSP)] have been well studied. By combining the beneficial effects of these two processes with a controlled bending deformation, microscale laser peen forming (?LPF) attracts more attention recently since it not only improves the fatigue life of the material but also shapes microscale metallic parts at the same time. In the present study, ?LSP of single crystal aluminum was presented to study anisotropic material response. Local plastic deformation was characterized by lattice rotation measured through electron backscatter diffraction. Residual stress distributions of both sides of a peened sample, characterized by x-ray microdiffraction, were compared with the results obtained from finite element method simulation. ?LPF anisotropic behavior was investigated in three effective slip systems via both the anisotropic slip line theory and numerical method. Also, the work hardening effect resulted from self-hardening, and latent hardening was analyzed through comparing the results with and without considering hardening.

Wang,Y.; Fan, Y.; Kysar, J.; Vukelic, S.; Yao, Y.

2008-01-01

309

Advanced single crystal for SSME turbopumps  

NASA Technical Reports Server (NTRS)

The objective of this program was to evaluate the influence of high thermal gradient casting, hot isostatic pressing (HIP) and alternate heat treatments on the microstructure and mechanical properties of a single crystal nickel base superalloy. The alloy chosen for the study was PWA 1480, a well characterized, commercial alloy which had previously been chosen as a candidate for the Space Shuttle Main Engine high pressure turbopump turbine blades. Microstructural characterization evaluated the influence of casting thermal gradient on dendrite arm spacing, casting porosity distribution and alloy homogeneity. Hot isostatic pressing was evaluated as a means of eliminating porosity as a preferred fatigue crack initiation site. The alternate heat treatment was chosen to improve hydrogen environment embrittlement resistance and for potential fatigue life improvement. Mechanical property evaluation was aimed primarily at determining improvements in low cycle and high cycle fatigue life due to the advanced processing methods. Statistically significant numbers of tests were conducted to quantitatively demonstrate life differences. High thermal gradient casting improves as-cast homogeneity, which facilitates solution heat treatment of PWA 1480 and provides a decrease in internal pore size, leading to increases in low cycle and high cycle fatigue lives.

Fritzemeier, L. G.

1989-01-01

310

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

E-print Network

%) single crystal grown by the modified Bridgman method with Pb(Mg1/3Nb2/3)0.71Ti0.29O3 (PMNT29%) seed29% seed crystal, exhibits higher piezoelectric constant d33 (O2000 pC/N) and electromechanical PINT35% (starting composition) single crystal grown with PMNT33% seed crystal, also shows high

311

Single crystal to single crystal transformation and hydrogen-atom transfer upon oxidation of a cerium coordination compound.  

PubMed

Trivalent and tetravalent cerium compounds of the octamethyltetraazaannulene (H2omtaa) ligand have been synthesized. Electrochemical analysis shows a strong thermodynamic preference for the formal cerium(IV) oxidation state. Oxidation of the cerium(III) congener Ce(Homtaa)(omtaa) occurs by hydrogen-atom transfer that includes a single crystal to single crystal transformation upon exposure to an ambient atmosphere. PMID:23534677

Williams, Ursula J; Mahoney, Brian D; Lewis, Andrew J; DeGregorio, Patrick T; Carroll, Patrick J; Schelter, Eric J

2013-04-15

312

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

313

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

Microsoft Academic Search

Effect of caesium and cerium,l-alanine and caesium +l-alanine impurities are investigated on ferroelectric and pyroelectric properties of TGS crystals. 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, whereasl-alanine- and, especially, Cs +l-alanine-doped

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

1992-01-01

314

High cycle fatigue crack initiation in single crystals and polycrystals  

NASA Astrophysics Data System (ADS)

The objective of this research is to analyze the high-cycle fatigue crack initiation in both monocrystalline and polycrystalline ductile metals. Persistent slip bands have been observed in both single crystals and polycrystals in numerous high-cycle fatigue tests. Extrusions and intrusions at the free surface of fatigued specimens are the favorable sites for fatigue crack initiation. In the present study, the micromechanic theory of high-cycle fatigue crack initiation, proposed by Lin and Ito, is extended to include the crystal anisotropic effect on the growth of extrusions in polycrystals and to study the high-cycle fatigue deformation in single crystals. Previous studies based on Lin and Ito model mainly concerned the fatigue crack initiation in aluminum and its alloys. The elastic anisotropy of individual crystals is insignificant and was accordingly neglected. However, the anisotropy of the elastic constants of some other metallic crystals, such as titanium and some intermetallic compounds, is not negligible. In this study, the effect of crystal anisotropy is considered by using Eshelby's equivalent inclusion method. The polycrystal of Nisb3Al intermetallic compound is analyzed for studying the effect on fatigue crack initiation. The model of fatigue crack initiation of polycrystals is applied to analyze the fatigue deformation in single crystals. The residual stress field in a single crystal is calculated by using a superposition method. The fatigue deformation of single crystals under the constant plastic strain amplitude control is investigated.

Teng, Ningjun

315

Grooving wear of single-crystal tungsten carbide  

Microsoft Academic Search

The anisotropic nature of tungsten carbide (WC) single crystals has been evaluated in single-tip scratch testing and in multiple-tip abrasion. The single-tip grooves were made with a Vickers diamond indenter and the abrasion tests were performed with diamond and silica grits. All tests were performed on both the prism and basal planes of the WC crystals. A polycrystalline binderless carbide

H Engqvist; S Ederyd; N Axén; S Hogmark

1999-01-01

316

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

317

Experimental study of the dynamic behaviour of twisted ferroelectric liquid crystal samples using snap-shot Mueller matrix polarimetry  

NASA Astrophysics Data System (ADS)

The full-optical set-up snap-shot Mueller matrix polarimeter (SMMP) is used to measure the channelled spectrum I?(?) related to a twisted ferroelectric liquid crystal (TwFLC) studied here with this technique. The samples were preliminarily exposed to a high-amplitude/low-frequency rectangular voltage before all the optical measurements. This voltage applied permits one to work in the specific stripe regime. From the channelled spectrum recorded I?(?), the different Mueller matrix (MM) can be obtained: the depolarization matrix, the retardance matrix and the diattenuation matrix. Several scalar polarimetric parameters are extracted from these MM, and especially ?R(t), ?R(t) and R(t). These relevant scalar coefficients, calculated from the retardance matrix, are used to determine the three hysteresis loops ?R(V), ?R(V) and R(V). We define ? as the difference of angle between the two rubbing directions of the two symmetrical (top and bottom) substrates and we examine how the hysteresis loops obtained are modified with the value of the geometrical externally controllable parameter ?, for angles between ? = 0° and ? = 90°. The key characteristics of the hysteresis loops and the evolution of these key values with ? are detailed.

Babilotte, P.; Silva, V. N. H.; Dubreuil, M.; Rivet, S.; Le Jeune, B.; Dupont, L.

2013-03-01

318

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

319

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

2011-02-21

320

Characteristic temperatures of PbFe1/2Nb1/2O3 ferroelectrics crystals seen via acoustic emission  

NASA Astrophysics Data System (ADS)

PbFe1/2Nb1/2O3 ferroelectrics crystals have been investigated using an acoustic emission. All the characteristic points have been detected: the Néel antiferromagnetic-paramagnetic phase transition at 158.6 K, both the rhombohedral-tetragonal at 363-348 K and tetragonal-cubic at 382-365 K structural phase transitions, the intermediate temperature T* at 431-427.5 K and the Burns temperature T d, extending through 564-603 K. It is shown that a dielectric response is unable to locate the T d correctly, but both the thermal expansion and acoustic emission are able. Acoustic emission is found to be more powerful for T* than for T d, which is usually observed in some well known relaxor ferroelectrics. Such a phenomenon is discussed from a viewpoint of dynamics of polar nanoregions.

Dul'kin, E.; Kania, A.; Roth, M.

2014-03-01

321

Single-crystal gallium nitride nanotubes  

Microsoft Academic Search

Since the discovery of carbon nanotubes in 1991 (ref. 1), there have been significant research efforts to synthesize nanometre-scale tubular forms of various solids. The formation of tubular nanostructure generally requires a layered or anisotropic crystal structure. There are reports of nanotubes made from silica, alumina, silicon and metals that do not have a layered crystal structure; they are synthesized

Joshua Goldberger; Rongrui He; Yanfeng Zhang; Sangkwon Lee; Haoquan Yan; Heon-Jin Choi; Peidong Yang

2003-01-01

322

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

323

Constricted hysteresis loops in Fe and Ni single crystals  

NASA Astrophysics Data System (ADS)

Magnetic hysteresis loops reflect the variety of magnetic domain structures and have been considered to have normal rectangular or leaf-like shapes in standard ferromagnets such as Fe and Ni metals. We report on observations of constricted hysteresis loops in Fe and Ni single crystals with very low defect densities. The constricted loops were observed below T=150 K and in a medium temperature range from 150 to 430 K in Fe and Ni single crystals, respectively. These constricted loops disappear by weak plastic deformation for both single crystals. The origin of constricted hysteresis loops was explained by eddy current effects under less domain wall pinning due to dislocations.

Takahashi, Seiki; Kobayashi, Satoru; Shishido, Toetsu

2010-11-01

324

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

325

Hole mobility in organic single crystals measured by a ``flip-crystal'' field-effect technique  

Microsoft Academic Search

We report on single crystal high mobility organic field-effect transistors prepared on prefabricated substrates using a ``flip-crystal'' approach. This method minimizes crystal handling and avoids direct processing of the crystal that may degrade the field-effect transistors' electrical characteristics. A chemical treatment process for the substrate ensures a reproducible device quality. With limited purification of the starting materials, hole mobilities of

C. Goldmann; S. Haas; C. Krellner; K. P. Pernstich; D. J. Gundlach; B. Batlogg

2004-01-01

326

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

327

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

328

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

329

Growth and characterization of organic material 4-dimethylaminobenzaldehyde single crystal.  

PubMed

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. PMID:25168233

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

2015-01-25

330

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

331

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

332

Transverse polarization reversal in the triglycine sulphate ferroelectric  

NASA Astrophysics Data System (ADS)

A single triglycine sulphate (TGS) crystal was initially transversely polarized in a prolonged constant electric field not parallel to the ferroelectric b-axis. Afterwards, the reversal process of c component of polarization (in the Hoshino-Okaya-Pepi?sky co-ordinate system) was investigated experimentally. It was shown that a time period of the order of 100 h is required for the transverse polarization of the order of 0.01 C/m 2 to be reversed in the transverse electric field E? c, where ? E??180 kV/m. Quasi-pyroelectric properties in the c-axis direction of the crystal could be modified by such a field, formerly applied to the crystal. Hence, at the time of heating the sample, various temperature dependencies of a depolarizing current of both signs could be observed for the same crystal along the direction perpendicular to the ferroelectric b-axis.

Fugiel, B.

2007-04-01

333

Testing of new ferroelectric elements custom engineered for explosively driven ferroelectric applications  

Microsoft Academic Search

Explosively driven ferroelectric generators (FEGs) are reliable, compact, high voltage sources that utilize high pressures to liberate charge trapped in the crystal structure of ferroelectric materials. For the active ferroelectric element most FEG designs use commercial lead zirconate-titanate (PZT) compositions designed for either precision actuators or naval sonar transducers. However, the material properties that are important in FEG applications are

S. L. Holt; J. T. Krile; D. J. Hemmert; W. S. Hackenberger; E. F. Alberta; J. W. Walter; J. C. Dickens; L. L. Altgilbers; A. H. Stults

2007-01-01

334

Testing of New Ferroelectric Elements Custom Engineered for Explosively Driven Ferroelectric Generator Applications  

Microsoft Academic Search

Summary form only given. Explosively driven ferroelectric generators (FEGs) are reliable, compact, high voltage sources that utilize high pressures to liberate charge trapped in the crystal structure of ferroelectric materials. For the active ferroelectric element most FEG designs use commercial lead zirconate-titanate (PZT) compositions designed for either precision actuators or naval sonar transducers. However, the material properties that are important

S. L. Holt; J. T. Krile; D. J. Hemmert; W. S. Hackenberger; E. F. Alberta; J. W. Walter; J. C. Dickens; L. L. Altgilbers; A. H. Stults

2007-01-01

335

The Growth of Large Single Crystals.  

ERIC Educational Resources Information Center

Presented is an experiment which demonstrates principles of experimental design, solubility, and crystal growth and structure. Materials, procedures and results are discussed. Suggestions for adapting this activity to the high school laboratory are provided. (CW)

Baer, Carl D.

1990-01-01

336

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

337

Growth of Zinc Oxide Single Crystals by Vapor Phase Reaction  

Microsoft Academic Search

ZnO single crystals are grown by vapor phase reaction with ZnI2 source. When the growth region is maintained between 1150°C and 1200°C, crystals grow by oxidation, and between 970°C and 1020°C, by hydrolysis. Crystals are mainly needles 15 mm in length or plates 8 mm2 in area. Patterns suggesting their growth mechanisms are observed in their microphotographs. The present experiments

Masami Hirose

1971-01-01

338

Characterization of phosphoric acid doped TGS single crystals  

Microsoft Academic Search

Single crystals of phosphoric acid (H3PO4) doped triglycine sulfate (TGSP) are grown from aqueous solution containing 10–50mol% of H3PO4. Large sized crystals of dimension (70mm×40mm×25mm) suitable for IR detector applications are obtained with 20mol% of H3PO4. They exhibit elongated domains, and the domain density is higher than in undoped TGS crystals. FT-IR analysis indicates the presence of both zwitter and

Aparna Saxena; Vinay Gupta; K. Sreenivas

2004-01-01

339

X-ray topographic examination of large paraffin single crystals  

Microsoft Academic Search

The internal microstructure of large melt-grown paraffin (n-eicosane, C20H42) single crystals was examined by the Lang x-ray diffraction projection topographic technique. Crystal selection was facilitated by use of an electro-optical system which permitted instantaneous display of Laue transmission x-ray diffraction patterns on a television monitor. The crystals were oriented and topographic diffraction planes were selected by the use of a

Robert E. Green; Edward N. Farabaugh; John M. Crissman

1975-01-01

340

Growth and polytypism of single crystals of cadmium bromide  

NASA Astrophysics Data System (ADS)

Single crystals of cadmium bromide have been grown by Bridgman-Stockbarger technique and their polytypism studied by X-ray diffraction. Oscillation photographs obtained from several different regions of the crystals have revealed the occurrence of only the small-period polytype 6R in the crystals. The results have been compared with those reported earlier for the isostructural compounds CdI 2 and PbI 2.

Chaudhary, S. K.; Trigunayat, G. C.

1985-12-01

341

Silicon Backplane Ferroelectric Liquid Crystal Spatial Light Modulator for Uses Within an Optical Telecommunications Environment  

Microsoft Academic Search

Liquid crystal on silicon (LCOS) devices are ideal for uses as miniature light modulating elements. They can replace either transmissive LC (TFT) micro-displays or micro-mechanical MEMS and have been extensively used in display applications 1. Pioneering works have proposed adapting them to implement optical communication functions such as optical spatial switches 2, 3. For the first time to our knowledge,

K. Heggarty; B. Fracasso; C. Letort; J. L. de Bougrenet de la Tocnaye; M. Birch; D. Krüerke

2004-01-01

342

A high frequency polarization intensity electrooptic modulator in BSTN ferroelectric crystal  

E-print Network

device is a high electrooptic coefficient. This allows the optical signal to be manipulated with a low electrical voltage. A material that has a higher electrooptic coefficient than the commercially used LiNbO3 and LiTaO3 is the tungsten bronze crystal...

Wilson, Erik James

2012-06-07

343

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

NASA Astrophysics Data System (ADS)

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

1992-05-01

344

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

345

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

346

Study of single crystals of metal solid solutions  

NASA Technical Reports Server (NTRS)

The parameters and requirements for growing single crystals of relatively high melting point metals in a zero gravity environment are studied. The crystal growth of metals such as silver, copper, gold, and alloys with a melting point between 900-1100 C is examined.

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

1973-01-01

347

Growth of large single crystals of the orthorhombic paracetamol  

NASA Astrophysics Data System (ADS)

A new procedure for the growth of large (cm-range) single crystals of the metastable orthorhombic (s.g. Pcab) polymorph of paracetamol is described. The crystals were grown by very slow cooling of hot water solutions under the conditions, when the multiple nucleation was prevented. The samples were characterized by DSC and X-ray diffraction.

Mikhailenko, M. A.

2004-05-01

348

Hertzian Fracture in Single Crystals with the Diamond Structure  

Microsoft Academic Search

Extension of an earlier theory of Hertzian fracture in brittle isotropic materials is here made to include the case of brittle single crystals, with particular reference to crystals having the diamond structure. A detailed description is first given of the inhomogeneous stress field in a flat, elastic specimen loaded normally with a hard sphere. The geometry of cracks growing in

B. R. Lawn

1968-01-01

349

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

350

Single crystal orientation effects in shock initiation of PETN explosive  

SciTech Connect

Over the past nine years in Los Alamos we have studied shock initiation of detonation in single crystals of PETN explosive. We have demonstrated the effects of point defects and crystal orientation on shock sensitivity. Here we report recent work on orientation effects and anomalous detonation in <110> orientation at 4 GPa. 5 refs.

Dick, J.J.

1988-01-01

351

Constitutive modeling of creep of single crystal superalloys  

E-print Network

In this work, a constitutive theory is developed, within the context of continuum mechanics, to describe the creep deformation of single crystal superalloys. The con- stitutive model that is developed here is based on the fact that as bodies deform...

Prasad, Sharat Chand

2006-10-30

352

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

353

Growth and properties of shaped single crystals of lithium fluoride  

NASA Astrophysics Data System (ADS)

Shaped single crystals of lithium fluoride have been produced by the Stepanov method using shapers which are wetted and unwetted by the melt. Dislocation structure, porosity, optical properties, ion conductivity, and distribution of magnesium impurities have been studied.

Antonov, P. I.; Krymov, V. M.; Hartmann, E.

1990-07-01

354

Emission of multiple types of radiation using a miniature ferroelectric-based single source  

NASA Astrophysics Data System (ADS)

NASA exploration missions are increasingly seeking to determine existence of past or present life, detect water and examine the mineralogy of various planets in the solar system. Determination of the surface and bulk properties of selected samples currently requires multiple analytical instruments, each with an independent type of radiation source. Using multitude of instruments requires high power, mass and volume resulting in high cost and complexity. Recently, the authors developed a ferroelectric based radiation source, which they named Ferrosource, that was demonstrated to emit five radiation types enabling a new generation of compact, low power, low mass multifunctional NDE analytical instruments. The emitted radiation types include visible light, ultraviolet, X-ray, as well as electron and ion beams. These radiation types are already in use in a multitude of instruments for detecting water, performing mineralogical/chemical analysis and for identifying biological markers. This ferroelectric-based source consists of a disk having a continuous ground electrode on one side and a grid-shaped cathode on the other side. This source is placed in a vacuum tube and is used to generate plasma by switching high voltage pulses and the plasma is harnessed to generate the radiation. To make the source more practical and applicable for NASA missions it was miniaturized by about 50 times the original chamber volume and efforts were made to increase its efficiency to compensate for the size reduction. A series of experiments were performed to demonstrate the capability of the developed miniature source. The source, the experiments, and the test results will be described and discussed in this paper.

Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; Bao, Xiaoqi; Sherrit, Stewart; Badescu, Mircea

2007-04-01

355

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

NASA Astrophysics Data System (ADS)

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 3D domain structures under an electric field. We propose for this case a method of applying an electric field using a surface electrode pair (SEP) in the observation plane of UAFM. When applying a field to a lead magnesium niobate-lead titanate [0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3: PMN-PT] single crystal, reversible domain switching was observed at low fields, and irreversible switching with domain boundary (DB) motion was observed at high fields. In the latter case, the growth of the domain was observed with the subsurface DB motion. A SEP and UAFM are thus proved useful in evaluating the motion of domain structures in ferroelectrics.

Ide, Seishiro; Kobari, Kentaro; Tsuji, Toshihiro; Yamanaka, Kazushi

2007-07-01

356

Magnetic properties of Gd doped Y and Sc single crystals  

Microsoft Academic Search

Magnetization measurements on 5 and 15% ScGd single crystals show typical spin glass like behaviour for fields parallel and perpendicular to the c axis of the hexagonal structure. In contrast for1, 2 and 3% Gd doped in Y single crystals there is a cusp in the susceptibility but no irreversibility below the temperature of the cusp. Spin-flop like transitions in

R. Wendler; P. Pureur; A. Fert; K. Baberschke

1984-01-01

357

Melt growth of high purity cadmium bromide single crystals  

NASA Astrophysics Data System (ADS)

The earlier attempts to grow pure single crystals of cadmium bromide by zone-melting have proved difficult due to the very high vapour pressure of the compound. The problem has been successfully overcome now by suitably employing the method of vertical zone-refining, which has helped to reduce the loss of material by evaporation to just 3%. Highly pure single crystals have been grown and results of their preliminary X-ray diffraction analysis have been briefly reported.

Singh, Kulvinder; Trigunayat, G. C.

1989-10-01

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{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

359

As75 and Cs133 Quadrupole Interactions in Ferroelectric CsH2AsO4  

Microsoft Academic Search

Quadrupole coupling parameters of As75 and Cs133 have been studied in a single crystal of CsH2AsO4 (ferroelectric Curie point Tc{=}143°K). As75 resonance could not be observed below 153°K. The temperature coefficient of As75 quadrupole coupling constant exhibits an anomalous behaviour. Cs133 resonance was seen in the ferroelectric phase also. The average of the two EFG tensors corresponding to the two

L. C. Gupta

1969-01-01

360

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

361

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

362

Polaronic Effects in Ferroelectrics  

Microsoft Academic Search

We studied polaronic effects due to the interaction of an electron with optical phonons in ferroelectric materials with a layered crystal structure. We evaluated the polaron self-energy part using the effective T-matrix approach. It has been shown that transition from the large radius polaron to the small radius polaron is controlled by the interlayer interaction or interlayer spacing. We have

Y. M. Malozovsky; J. D. Fan; D. Bagayoko; J. T. Wang

2000-01-01

363

Catalyzed growth of doped TGS single crystals for infrared applications  

NASA Astrophysics Data System (ADS)

Single crystals of triglycine sulphate (TGS) doped with Pr3+ Sm3+, Pd2+, Co2+, Pt4+ and PO43- with L-alanin were grown from aqueous solutions by means of the slow cooling method. Surface morphology, domain structure and P-E hysteresis loops have been investigated. The model of catalyzed growth of {001}and{101}crystal pyramids on the basis of metal-glycine complexes has been suggested. We have found on the basis of experimental results that TGS single crystals doped with Pt4+ and L-alanin are excellent materials for construction of infrared detectors.

Novotny, Jan; Zelinka, J.; Podvalova, Z.

2002-03-01

364

Hydroxyethylammonium maleate (HEAM) single crystal for optical limiting applications  

NASA Astrophysics Data System (ADS)

A novel hydroxyethylammonium maleate single crystal was grown by slow evaporation solution method for the first time. The structure of the title compound is determined by single crystal X-ray diffraction. The linear optical properties were studied using ultraviolet-visible and photoluminescence spectroscopy. The third-order nonlinear optical property of title compound was studied by Z-scan technique to determine its nonlinear absorption and nonlinear refraction. Thermal property was studied by thermogravimetry, differential thermal analysis and differential scanning calorimetric analyses. The mechanical stability of the material was studied by Vickers microhardness tester. Further, etching study was done to examine the defects in the crystal.

Sudharsana, N.; Hamad, S.; Venugopal Rao, S.; Krishnakumar, V.; Nagalakshmi, R.

2015-02-01

365

Investigation of localized deformation in NiAl single crystals  

SciTech Connect

Deformation of NiAl single crystals was studied using finite element analysis to investigate the modes of localized deformation. Constitutive parameters and hardening characteristics of the active slip systems were estimated by comparing numerical simulation results with experimental results. Deformation of tensile specimens of NiAl single crystal was simulated when loaded along different crystal orientations to understand the deformation mechanism that results in various localized modes of deformation. In particular, the formation of shear bands and kink bands was studied and the material and geometric characteristics that influence the formation of such localization were investigated.

Kumar, A.V.; Yang, Culho; Seelam, V.B.R. [Univ. of Florida, Gainesville, FL (United States). Dept. of Mechanical Engineering

1998-07-01

366

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

367

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

368

Crystal structure, spectral, thermal and dielectric studies of a new zinc benzoate single crystal  

NASA Astrophysics Data System (ADS)

Single crystals of zinc benzoate with a novel structure were grown in gel media. Sodium metasilicate of gel density 1.04 g/cc at pH 6 was employed to yield transparent single crystals. The crystal structure of the compound was ascertained by single crystal X-ray diffractometry. It was noted that the crystal belongs to monoclinic system with space group P21/c with unit cell parameters a = 10.669(1) Å, b = 12.995(5) Å, c = 19.119(3) Å, and ? = 94.926(3)°. The crystal was seen to possess a linear polymeric structure along b-axis; with no presence of coordinated or lattice water. CHN analysis established the stoichiometric composition of the crystal. The existence of functional groups present in the single crystal system was confirmed by FT-IR studies. The thermal characteristic of the sample was analysed by TGA-DTA techniques, and the sample was found to be thermally stable up to 280 °C. The kinetic and thermodynamic parameters were also determined. UV-Vis spectroscopy corroborated the transparency of the crystal and revealed the optical band gap to be 4 eV. Dielectric studies showed decrease in the dielectric constant of the sample with increase in frequency.

Bijini, B. R.; Prasanna, S.; Deepa, M.; Nair, C. M. K.; Rajendra Babu, K.

2012-11-01

369

Ferroelectricity in ultrathin perovskite films  

Microsoft Academic Search

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

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

2004-01-01

370

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

371

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

372

Shock Driven Twinning in Tantalum Single Crystals  

SciTech Connect

Recovery based observations of high pressure material behavior generated under high explosively driven flyer based loading conditions are reported. Two shock pressures, 25, and 55 GPa and four orientations {l_brace}(100), (110), (111), (123){r_brace} were considered. Recovered material was characterized using electron backscatter diffraction along with a limited amount of transmission electron microscopy to assess the occurrence of twinning under each test condition. Material recovered from 25 GPa had a very small fraction of twinning for the (100), (110), and (111) oriented crystals while a more noticeable fraction of the (123) oriented crystal was twinned. Material recovered from 55 GPa showed little twinning for (100) orientation slightly more for the (111) orientation and a large area fraction for the (123) orientation. The EBSD and TEM observations of the underlying deformation substructure are rationalized by comparing with previous static and dynamic results.

McNaney, J M; HSUING, L M; Barton, N R; Kumar, M

2009-07-20

373

Scintillation Properties of Praseodymium Activated Single Crystals  

Microsoft Academic Search

Scintillation properties of LuAG:Pr grown by Furukawa Co. Ltd., Japan, have been studied. The best crystals display light outputs up to 19000 ph\\/MeV and an energy resolution of 4.6% at 662 keV. The scintillation yield is found to be a function of size and temperature of the sample; it can be enhanced by 40% upon heating to 450 K. Radioluminescence

Winicjusz Drozdowski; Pieter Dorenbos; J. T. M. de Haas; R. Drozdowska; A. Owens; K. Kamada; K. Tsutsumi; Y. Usuki; T. Yanagida; A. Yoshikawa

2008-01-01

374

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

375

''6-Degrees of Freedom'' Single Crystal Plasticity Experiments  

SciTech Connect

A deformation experiment has been developed specifically for the purpose of validation of dislocation dynamics simulations of plastic flow up to strains on the order of 1% [1]. The experiment has been designed so that a compressive uniaxial stress field is essentially super imposed on the test sample, and the crystal is free to deform with 3 orthogonal translation directions, and 3 rotation/tilt axes of freedom and has been given the name ''6-degrees of freedom'' (6DOF) experiment. The rotation, tilt and translation of the crystal are monitored by 5 laser displacement gages and 3 extensometers. Experiments are being performed on high purity Mo single crystals orientated for ''single slip''. All of the experiments are performed in pairs, with one test sample having highly polished surfaces for optical light and AFM slip-trace analyses, and the other having 4 strain gage rosettes mounted on the sides for measurement of the bi-axial surface strains during testing. All of the experimental data is used together to determine the slip activity of the orientated single crystal during deformation. Experimental results on high-purity Mo single crystals are presented. The results of these experiments show that slip behavior is in substantial deviation from the expected ''Schmid'' behavior. These experimental results bring into question some of the fundamental assumptions used in both the construction of crystal plasticity constitutive relationships and rules for dislocation mobility use in 3-D dislocation dynamics simulations.

Lassila, D H; Florando, J N; LeBlanc, M M; Arsenlis, T; Rhee, M

2003-05-21

376

Crystal Structure, Physical Properties, and Electrochemistry of Copper Substituted LiFePO4 Single Crystals  

E-print Network

indicate that the dark brown color originates from interionic d-d transitions. A part of the lithium ions phosphate, with the olivine structure, has been synthesized hydrothermally as dark-brown single crystals

Ceder, Gerbrand

377

Relaxor ferroelectric behavior in Ca-doped TbMnO3  

NASA Astrophysics Data System (ADS)

We have studied the effect of Ca-doping in single-crystal Tb1-xCaxMnO3(x?0.1) on the crystal and magnetic structure, magnetocapacitance, and electric polarization. For low doping (x=0.05) , the presence of Mn4+ ions gives rise to a state with behavior resembling that of a relaxor ferroelectric. The coherence length of the Mn magnetic spin spiral is reduced, while the Mn-modulation wave vector is unchanged. For doping larger than 5%, the ferroelectric state is suppressed, which we ascribe to breakdown of the spiral magnetic structure.

Mufti, N.; Nugroho, A. A.; Blake, G. R.; Palstra, T. T. M.

2008-07-01

378

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

379

Ferroelectric Nanowires  

Microsoft Academic Search

\\u000a Ferroelectric materials are compounds that exhibit a spontaneous electric polarization that can be reoriented by an external\\u000a electric field [1, 2]. Over the last decade, these materials, especially the ferroelectric oxides, have received considerable attention because\\u000a of the fundamental interest in their properties and their potential for a variety of technical applications. The ferroelectric\\u000a oxides typically exhibit a host of

Jonathan E. Spanier; Jeffrey J. Urban; Lian Ouyang; Wan Soo Yun; Hongkun Park

380

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

381

Isotropic behavior of an anisotropic material: single crystal silicon  

NASA Astrophysics Data System (ADS)

Zero defect single crystal silicon (Single-Crystal Si), with its diamond cubic crystal structure, is completely isotropic in most properties important for advanced aerospace systems. This paper will identify behavior of the three most dominant planes of the Single-Crystal Si cube (110), (100) and (111). For example, thermal and optical properties are completely isotropic for any given plane. The elastic and mechanical properties however are direction dependent. But we show through finite element analysis that in spite of this, near-isotropic behavior can be achieved with component designs that utilize the optimum elastic modulus in directions with the highest loads. Using glass frit bonding to assemble these planes is the only bonding agent that doesn't degrade the performance of Single-Crystal Si. The most significant anisotropic property of Single-Crystal Si is the Young's modulus of elasticity. Literature values vary substantially around a value of 145 GPa. The truth is that while the maximum modulus is 185 GPa, the most useful <110< crystallographic direction has a high 169 GPa, still higher than that of many materials such as aluminum and invar. And since Poisson's ratio in this direction is an extremely low 0.064, distortion in the plane normal to the load is insignificant. While the minimum modulus is 130 GPa, a calculated average value is close to the optimum at approximately 160 GPa. The minimum modulus is therefore almost irrelevant. The (111) plane, referred to as the natural cleave plane survives impact that would overload the (110) and/or (100) plane due to its superior density. While mechanical properties vary from plane to plane each plane is uniform and response is predictable. Understanding the Single-Crystal Si diamond cube provides a design and manufacture path for building lightweight Single-Crystal Si systems with near-isotropic response to loads. It is clear then that near-isotropic elastic behavior is achievable in Single-Crystal Si components and will provide subsecond thermal equilibrium and sub-micron creep.

McCarter, Douglas R.; Paquin, Roger A.

2013-09-01

382

Smectic Liquid Crystal Polarization Interference Filters  

Microsoft Academic Search

Surface stabilized smectic liquid crystal devices can be used in a wide variety of optical filters for providing very rapid discrete, and continuous tunability. One such example, analyzed here, is the discrete switching Ferroelectric Liquid Crystal Polarization Interference Filter (FLCPIF). This filter is implemented using binary swiching surface stabilized FLC's and linear polarizers. A single-stage FLCPIF is analyzed, and the

Gary Sharp; Kristina Johnson; Dave Doroski; Jay Stockley; Chan Oh; Wilbur Kaye; Bob Obremski

1992-01-01

383

TGS single crystals doped by Pd(II) ions  

NASA Astrophysics Data System (ADS)

Single crystals of triglycine sulphate (TGS) doped with Pd(II) were grown from aqueous solutions by means of the slow cooling method. Concentration of the doping compound PdSO 4 in the growth solutions varied from 0.3 to 5 mol%. Morphology, domain structure and P- E hysteresis loops have been investigated. The effect of the dopant on the crystal growth velocity is explained on the basis of the notion of an activated Pd(II)-glycine complex.

Novotný, J.; Prokopová, L.; Mi?ka, Z.

2001-06-01

384

Pyroelectric properties of phosphoric acid-doped TGS single crystals  

Microsoft Academic Search

Pyroelectric properties of phosphoric acid (H3PO4)-doped triglycine sulfate (TGSP) single crystals grown from solutions containing 0.1-0.5 mol of H3PO4 have been studied. Incorporation of H3PO4 into the crystal lattice is found to induce an internal bias field (Eb) and is observed through the presence of a sustained polarization and pyroelectricity beyond the transition temperature. The internal bias field has been

Aparna Saxena; M. Fahim; Vinay Gupta; K. Sreenivas

2003-01-01

385

Low temperature pyroelectric properties of modified TGS single crystals  

Microsoft Academic Search

Pyroelectric and dielectric properties of three different single crystals in the triglycine sulphate (TGS) family have been studied in the temperature range from 20K to room temperature. These crystals are: (1) unmodified TGS; (2) TGS with L-alanine doping and partial substitution of (PO4) for (SO4), abbreviated as ATGSP; (3) TGS with L-alanine doping and partial substitution of (AsO4) for (SO4)

Zhang Peilin; Zhong Weilie; Fang Changshui; Zhao Huansui; Li Cuiping

1990-01-01

386

Growth and characterization of lithium yttrium borate single crystals  

SciTech Connect

Single crystals of 0.1% Ce doped Li{sub 6}Y(BO{sub 3}){sub 3} have been grown using the Czochralski technique. The photoluminescence study of these crystals shows a broad emission at ? 420 nm corresponding to Ce{sub 3+} emission from 5d?4f energy levels. The decay profile of this emission shows a fast response of ? 28 ns which is highly desirable for detector applications.

Singh, A. K.; Singh, S. G.; Tyagi, M.; Desai, D. G.; Sen, Shashwati [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai- 400085 (India)

2014-04-24

387

Orientation effects in nanoindentation of single crystal copper  

Microsoft Academic Search

Numerical simulations and experimental results of nanoindentation on single crystal copper in three crystallographic orientations [(100), (011) and (111)] using a spherical indenter (3.4?m radius) were reported. The simulations were conducted using a commercial finite element code (ABAQUS) with a user-defined subroutine (VUMAT) that incorporates large deformation crystal plasticity constitutive model. This model can take full account of the crystallographic

Y. Liu; S. Varghese; J. Ma; M. Yoshino; H. Lu; R. Komanduri

2008-01-01

388

Growth Defect Studies in SiC Single Crystals  

Microsoft Academic Search

Growth defects in vapor grown 6H-SiC single crystals have been studied using a combination of techniques, including: synchrotron white beam x-ray topography (SWBXT), conventional optical microscopy, fluorescence microscopy, and epi-fluorescence laser scanning confocal microscopy (LSCM). These studies of crystal sections cut both parallel and perpendicular to the [0001] growth axis focused on growth dislocations of screw character running approximately parallel

Michael Dudley; William M. Vetter

1996-01-01

389

Nucleation kinetics, growth and studies of ?-alanine single crystals  

NASA Astrophysics Data System (ADS)

Solubility and metastable zone width for the re-crystallized salt of ?-alanine was determined. Induction period measurement for the selected supersaturation ratios at room temperature (31 °C) was carried out for supersaturated aqueous solutions of ?-alanine and it is noticed that induction period decreases with increase of supersaturation ratio. The nucleation parameters such as Gibbs free energy change, radius and number of molecules of the critical nucleus, interfacial tension and the nucleation rate have been evaluated by classical nucleation theory. Single crystals of ?-alanine were grown using the optimized nucleation parameters by solution method and grown crystals have been subjected to various studies like XRD studies, FTIR, optical, thermal and SHG studies.

Shanthi, D.; Selvarajan, P.; HemaDurga, K. K.; Lincy Mary Ponmani, S.

2013-06-01

390

Polymer single crystal meets nanoparticle, toward ordered hybrid materials  

NASA Astrophysics Data System (ADS)

Judiciously selected polymer single crystal (PSC) systems can interplay with 1-D and 0-D nanoparticles, forming ordered hybrid structures. In this presentation, I will first focus on patterning PSCs on individual carbon nanotubes (CNT). Using both controlled solution crystallization, thin film crystallization and physical vapor deposition methods, CNTs were periodically decorated with PSCs, resulting in nano hybrid shish-kebab (NHSK) structures. Because the polymer kebabs can be easily removed, these unique NHSKs can serve as templates to fabricate a variety of CNTs-containing hybrid materials with controlled pattering on the CNT surface. Sub-20 nanometer alternating patterning was achieved by using crystalline block copolymers. The mechanism was attributed to the crystallization induced block copolymer phase separation. This pattern was successfully used to template nanoparticles (NP) pattering on CNTs. In the second part of the talk, I will discuss fabricating Janus NPs and patterning these NPs using PSCs. Single crystals of thiol-terminated polyethylene oxide (PEO) were incubated in a gold sol. Au-S bonds were formed between the AuNPs and the PEO single crystal surfaces. The inter-particle spacing was controlled by PEO molecular weights, the incubation time, and the annealing temperatures after incubation. The planar geometry of the PSCs led to Janus NP formation. A series of NP dimers, trimers and tetramers were synthesized. NP nanowires were also fabricated. We anticipate that this observation could lead to controlled synthesis of artificial molecules and NP chains for a variety of optical, electronic, and biomedical applications.

Li, Christopher

2009-03-01

391

The Load Capability of Piezoelectric Single Crystal Actuators  

NASA Technical Reports Server (NTRS)

Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

2006-01-01

392

The Load Capability of Piezoelectric Single Crystal Actuators  

NASA Technical Reports Server (NTRS)

Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

2007-01-01

393

Single Crystal Synthesis and STM Studies of High Temperature Superconductors  

NASA Technical Reports Server (NTRS)

This is a final report for the work initiated in September of 1994 under the grant NAG8-1085 - NASA/OMU, on the fabrication of bulk and single crystal synthesis, specific heat measuring and STM studies of high temperature superconductors. Efforts were made to fabricate bulk and single crystals of mercury based superconducting material. A systematic thermal analysis on the precursors for the corresponding oxides and carbonates were carried out to synthesized bulk samples. Bulk material was used as seed in an attempt to grow single crystals by a two-step self flux process. On the other hand bulk samples were characterized by x-ray diffraction, electrical resistivity and magnetic susceptibility, We studied the specific heat behavior in the range from 80 to 300 K. Some preliminary attempts were made to study the atomic morphology of our samples. As part of our efforts we built an ac susceptibility apparatus for measuring the transition temperature of our sintered samples.

Barrientos, Alfonso

1997-01-01

394

Constitutive modelling of single crystal and directionally solidified superalloys  

NASA Technical Reports Server (NTRS)

The trend towards improved engine efficiency and durability places increasing demands on materials that operate in the hot section of the gas turbine engine. These demands are being met by new coatings and materials such as single crystal and directionally solidified nickel-base superalloys which have greater creep/fatigue resistance at elevated temperatures and reduced susceptibility to grain boundary creep, corrosion and oxidation than conventionally cast alloys. Work carried out as part of a research program aimed at the development of constitutive equations to describe the elevated temperature stress-strain-time behavior of single crystal and directionally solidified turbine blade superalloys is discussed. The program involves both development of suitable constitutive models and their verification through elevated temperature tension-torsion testing of single crystals of PWA 1480.

Jordan, E. H.; Walker, K. P.

1986-01-01

395

Mechanical properties of hydroxyapatite single crystals from nanoindentation data  

PubMed Central

In this paper we compute elasto-plastic properties of hydroxyapatite single crystals from nanindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young’s modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals. PMID:21262492

Zamiri, A.; De, S.

2011-01-01

396

Single-crystal neutron diffraction investigation on crystals belonging to the langasite family: a comparative study.  

PubMed

Crystals of the langasite family are of interest as they are piezoelectric in different devices. The properties of these classes of crystals can be modified within certain limits by isomorphous substitution. Single-crystal neutron diffraction studies were carried out for LGT (La(3)Ga(5.5)Ta(0.5)O(14)), LGST (La(3)Ga(5.25)Ta(0.25)Si(0.5)O(14)) and LGZrT (La(3)Ga(5.25)Ta(0.25)Zr(0.5)O(14)) as the neutron study gives a better average picture of the crystal properties over a macroscopic region of the grown crystal. The effect of small substitutions at various sites on the piezoelectric properties of the crystal was studied. PMID:20841917

Chitra, R; Choudhury, R R

2010-10-01

397

Complete sets of elastic, dielectric, and piezoelectric properties of [001]-poled Pb(Zn1/3Nb2/3)O3-(6-7)%PbTiO3 single crystals of [110]-length cut  

NASA Astrophysics Data System (ADS)

[001]-poled relaxor based ferroelectric Pb(Zn1/3Nb2/3)O3-(6-7)%PbTiO3 single crystals of [110]-length cut exhibit k31?0.85 and very high d31/s11E value. They are promising materials for sensors and actuators comprising an elastic substrate such as a metal shim or support, especially under dynamic loading conditions. In this work, the full sets of elastic, dielectric, and piezoelectric properties of [110]L×[001]T(P ) single crystal are determined by means of the resonant technique. The obtained property matrix can be readily used for device design and simulation purposes.

Shukla, Rahul; Rajan, Kalidindi Kotam; Gandhi, Prasanna; Lim, Leong-Chew

2008-05-01

398

Lead pyrovanadate single crystal as a new SRS material  

SciTech Connect

Lead pyrovanadate Pb{sub 2}V{sub 2}O{sub 7} single crystals of optical quality suitable for laser experiments are obtained. Vibrational modes are identified based on the analysis of the polarised Raman spectra of the single crystals. The main parameters (width at half maximum, peak and integral intensities) of the spectral lines most promising for SRS conversion in this material are estimated. These parameters are compared with the corresponding parameters of the most frequently used lines of known Raman materials: yttrium and gadolinium vanadates, potassium and lead tungstates, and lead molybdate. (active media)

Basiev, Tasoltan T; Voronko, Yu K; Maslov, Vladislav A; Sobol, A A; Shukshin, V E [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2011-02-28

399

Two-photon-induced singlet fission in rubrene single crystal.  

PubMed

The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet fission from the two-photon excited states. The TPA absorption coefficient of rubrene single crystal is 52 cm?GW at 740 nm, as obtained from Z-scan measurements. Quantum chemical calculations based on time-dependent density functional theory support our experimental data. PMID:23676057

Ma, Lin; Galstyan, Gegham; Zhang, Keke; Kloc, Christian; Sun, Handong; Soci, Cesare; Michel-Beyerle, Maria E; Gurzadyan, Gagik G

2013-05-14

400

Two-photon-induced singlet fission in rubrene single crystal  

NASA Astrophysics Data System (ADS)

The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet fission from the two-photon excited states. The TPA absorption coefficient of rubrene single crystal is 52 cm/GW at 740 nm, as obtained from Z-scan measurements. Quantum chemical calculations based on time-dependent density functional theory support our experimental data.

Ma, Lin; Galstyan, Gegham; Zhang, Keke; Kloc, Christian; Sun, Handong; Soci, Cesare; Michel-Beyerle, Maria E.; Gurzadyan, Gagik G.

2013-05-01

401

Apparatus And Method For Producing Single Crystal Metallic Objects  

DOEpatents

A mold is provided for enabling casting of single crystal metallic articles including a part-defining cavity, a sorter passage positioned vertically beneath and in fluid communication with the part-defining cavity, and a seed cavity positioned vertically beneath and in fluid communication with the sorter passage. The sorter passage includes a shape suitable for encouraging a single crystal structure in solidifying molten metal. Additionally, a portion of the mold between the sorter passage and the part-defining cavity includes a notch for facilitating breakage of a cast article proximate the notch during thermal stress build-up, so as to prevent mold breakage or the inclusion of part defects.

Huang, Shyh-Chin (Latham, NY); Gigliotti, Jr., Michael Francis X. (Scotia, NY); Rutkowski, Stephen Francis (Duanesburg, NY); Petterson, Roger John (Fultonville, NY); Svec, Paul Steven (Scotia, NY)

2006-03-14

402

Growth of single-crystal diamonds in microwave plasma  

NASA Astrophysics Data System (ADS)

A microwave plasma (2.45 GHz) was used for depositing single crystal diamond layers at the deposition rate up to 40 ?m/h in hydrogen-methane mixtures on the substrates from natural and synthetic diamond with the (100) deposition surface and with the size up to 5 × 5 mm. The structure and the defect-impurity composition of the fabricated single crystals with the thickness up to 600 ?m have been investigated using Raman spectroscopy, photoluminescence spectroscopy, cathode luminescence spectroscopy, and electron and optical microscopy. A high quality and purity of the diamond layers deposited from a plasma was confirmed.

Bolshakov, A. P.; Ralchenko, V. G.; Polskiy, A. V.; Konov, V. I.; Ashkinazi, E. E.; Khomich, A. A.; Sharonov, G. V.; Khmelnitsky, R. A.; Zavedeev, E. V.; Khomich, A. V.; Sovyk, D. N.

2012-12-01

403

Synthesis of Large Single Crystals of LaMnPO  

NASA Astrophysics Data System (ADS)

The compound LaMnPO is isostructural with LaFeAsO, a recently discovered high-temperature superconductor, but optical spectroscopy and transport measurements of this compound have been heretofore limited by small crystal size. Accordingly, crystal syntheses from Sn, Pb and molten salt fluxes (including NaCl/KCl, LiCl/NaCl, KCl, CaCl2, BaCl2/CaCl2 and KCl/CaCl2) were investigated. Fluorine doping was explored; concentrations less than 30 at.% (nominal) had no effect on crystal size; concentrations greater than 40 at.% (nominal) did not yield crystals. Once growth parameters were optimized, the crystals grew in a flat rectangular shape with black luster; their composition was verified with powder and single crystal x-ray diffraction. Successful growths yielded crystals with dimensions up to 3.2 mm by 1 mm by 10 ?m, a significant improvement upon previously reported growths in the literature. These large crystals enabled our group to perform a wide range of experiments that were previously restricted to polycrystalline materials. It may be feasible to extend these methods to the synthesis of similar compounds.

Smith, Greg; Simonson, Jack; Marques, Carlos; Leyva, Victor; Aronson, Meigan

2011-03-01

404

Transverse polarization reversal in the triglycine sulphate ferroelectric  

Microsoft Academic Search

A single triglycine sulphate (TGS) crystal was initially transversely polarized in a prolonged constant electric field not parallel to the ferroelectric b-axis. Afterwards, the reversal process of c component of polarization (in the Hoshino–Okaya–Pepi?sky co-ordinate system) was investigated experimentally. It was shown that a time period of the order of 100h is required for the transverse polarization of the order

B. Fugiel

2007-01-01

405

Investigation of ferroelectricity and piezoelectricity in ferroelectric thin film capacitors using synchrotron x-ray microdiffraction  

Microsoft Academic Search

Ferroelectric materials have a wide range of applications in nonvolatile memory devices, sensors, and actuators due to their properties such as remnant polarization and piezoelectricity. It is necessary to investigate those properties to understand physical phenomena in ferroelectric materials and to have better device performance. Since ferroelectricity and piezoelectricity are directly related to structure at the scale of a single

Dal-Hyun Do

2006-01-01

406

Growth of Solid Solution Single Crystals  

NASA Technical Reports Server (NTRS)

The solidification of a solid solution semiconductor, having a wide separation between liquidus and serious has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; mercury cadmium telluride with 80.0 mole percent of HgTe and 84.8 mole percent respectively. These alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed of residual acceleration effects. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system by a previously processed sample, the sample was not received until May 1998, and the preliminary analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. Early results are indicating that the sample may not accomplish the desired objectives. As with the USMP-2 mission, the results of the ground based experiments were compared with the crystal grown in orbit under microgravity conditions. On the earth, it has been demonstrated that the application of the magnetic field leads to a significant reduction in fluid flow, with improved homogeneity of composition. The field strength required to suppress flow increases with diameter of the material. The 8 mm diameter sample used here was less than the upper diameter limit for a ST magnet. The configuration for USMP-4 was changed so that the material was seeded and other processing techniques were also modified. It was decided to examine the effects of a strong magnetic field under the modified configuration and parameters. A further change from USMP-2 was that a different composition of material was grown, namely with 0.152 mole fraction of cadmium telluride rather than the 0.200 of the USMP-2 experiment. The objective was to grow highly homogeneous, low defect density material of a composition at which the conduction band and the valence band of the material impinge against each other. As indicated, the furnace was contaminated during the mission. As a result of solid debris remaining in the furnace bore, the cartridge in this experiment, denoted as SL1-417, was significantly bent during the insertion phase. During translation the cartridge scraped against the plate which isolates the hot and cold zones of the furnace. Thermocouples indicated that a thermal assymetry resulted. The scraping in the slow translation or crystal growth part of the processing was not smooth and it is probable that the jitter was sufficient to give rise to convection in the melt. Early measurements of composition from the surface of the sample have shown that the composition varies in an oscillatory manner.

Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.; Watring, D. A.

1999-01-01

407

Relaxor single crystals in the (Bi1/2Na1/2)1-xBaxZryTi1-yO3 system exhibiting high electrostrictive strain  

NASA Astrophysics Data System (ADS)

Single crystals have been grown in the (Bi1/2Na1/2)1-xBaxZryTi1-yO3 perovskite system by a self-flux method over the range of compositions y=0.04 and x=0.06-0.012. Rhombohedral (x?0.08) and tetragonal phase (x?0.09) crystals have been obtained that do not show polarization or field-induced strain hysteresis characteristics of a ferroelectric. However, a frequency-dispersive dielectric response characteristic of a relaxor ferroelectric, and predominantly electrostrictive actuation, is observed across the range of compositions tested, with Q11=(2.8-3.3)×10-2m4/C2. Due to induced polarizations that do not saturate at fields beyond 50 kV/cm, high electrostrictive strains are obtained. Rhombohedral phase crystals exhibit d33 up to 1180 pC/N and strains of S3=0.3% before electrical breakdown, while tetragonal phase crystals exhibit d33 up to 2000 pC/N and S3 up to 0.45% strain. These crystals show the highest electrostrictive strains yet reported for an inorganic compound. The unusually high electrostriction is discussed in relation to an energy landscape that allows ferroelastic and ferroelectric distortions to be simultaneously accessible at the nanometer scale.

Sheets, Sossity A.; Soukhojak, Andrey N.; Ohashi, Naoki; Chiang, Yet-Ming

2001-11-01

408

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

SciTech Connect

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

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

2014-03-31

409

Growth of Solid Solution Single Crystals  

NASA Technical Reports Server (NTRS)

The solidification of a solid solution semiconductor, having a wide separation between liquidus and solidus has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; with 80.0 mole percent of HgTe and 84.8 mole percent of HgTe respectively, the remainder being cadmium telluride. Such alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed correlating composition variations to measured residual acceleration. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system, analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. The results indicate that the sample did accomplish the desired objectives.

Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.

2001-01-01

410

A single crystal multiple-wavelength electro-optic modulator  

Microsoft Academic Search

A new multi-wavelength low voltage electro-optic modulator has been constructed using the r41coefficient in a single crystal of ADP. It is intended for use in multi-color laser display and recording systems employing a single source such as a krypton-ion laser. The modulator accepts a coaxial mixed wavelength beam and separates the colors using a set of direct view spectroscopic prisms.

J. Schlafer; V. J. Fowler

1971-01-01

411

Engineering chromium related single photon emitters in single crystal diamond  

E-print Network

Color centers in diamond as single photon emitters, are leading candidates for future quantum devices due to their room temperature operation and photostability. The recently discovered chromium related centers are particularly attractive since they possess narrow bandwidth emission and a very short lifetime. In this paper we investigate the fabrication methodologies to engineer these centers in monolithic diamond. We show that the emitters can be successfully fabricated by ion implantation of chromium in conjunction with oxygen or sulfur. Furthermore, our results indicate that the background nitrogen concentration is an important parameter, which governs the probability of success to generate these centers.

I Aharonovich; S Castelletto; B C Johnson; J C McCallum; S Prawer

2010-09-29

412

Engineering chromium related single photon emitters in single crystal diamond  

E-print Network

Color centers in diamond as single photon emitters, are leading candidates for future quantum devices due to their room temperature operation and photostability. The recently discovered chromium related centers are particularly attractive since they possess narrow bandwidth emission and a very short lifetime. In this paper we investigate the fabrication methodologies to engineer these centers in monolithic diamond. We show that the emitters can be successfully fabricated by ion implantation of chromium in conjunction with oxygen or sulfur. Furthermore, our results indicate that the background nitrogen concentration is an important parameter, which governs the probability of success to generate these centers.

Aharonovich, I; Johnson, B C; McCallum, J C; Prawer, S

2010-01-01

413

Thermal exfoliation and crystallographic transformation of single-crystal metal oxides induced by He-ion implantation  

NASA Astrophysics Data System (ADS)

We report on the thermal exfoliation of 7 ?m thick films from 3.8 MeV He ion-implanted single-crystal 0.955 Pb(Zn1/3Nb2/3)O3-0.045 PbTiO3 [(PZN-PT) with 4.5% PT] by rapid thermal processing. Comparison with z-cut LiNbO3 shows a significantly higher exfoliation threshold temperature in PZN-PT for the same implantation conditions. Unusually large strains in the through-implanted layer are induced in the relaxor ferroelectric PZN-PT upon ion implantation leading to a crystallographic phase transformation in that material that is not observed in LiNbO3. Depth profile analysis of the refractive index shows a much larger refractive index modulation due to nuclear collisions than in LiNbO3. The higher exfoliation temperature observed for PZN-PT, despite a larger impact of the ion implantation on material structure, suggests that the electronic polarizability and elastic response of relaxor ferroelectrics near the morphotropic phase boundary have a significant impact on the crack propagation process responsible for thermally induced exfoliation.

Moran, P. D.; Levy, M.

2003-09-01

414

Polymer single crystal membrane from liquid/liquid interface  

NASA Astrophysics Data System (ADS)

Vesicles, mimicking the structure of cell membrane at the molecular scale, are small membrane-enclosed sacks that can store or transport substances. The weak mechanical properties and the nature of environment-sensitivity of the current available vesicles: liposomes, polymersomes, colloidsomes limit their applications as an excellent candidate for targeting delivery of drugs/genes in biomedical engineering and treatment. Recently, we developed an emulsion-based method to grow curved polymer single crystals. Varying the polymer concentration and/or the emulsification conditions (such as surfactant concentration, water-oil volume ratio), curved crystals with different sizes and different openness could be obtained. This growing process was attributed to polymer crystal growth along the liquid/liquid interface. In addition, the liquid/liquid interfacial crystal growth is promising for synthesis of enclosed hollow sphere.

Wang, Wenda; Li, Christopher

2013-03-01

415

The viscoplastic behavior of Hastelloy-X single crystal  

NASA Technical Reports Server (NTRS)

A viscoplastic constitutive model for simulating the behavior of Hastelloy-X single crystal material was derived based on crystallographic slip theory. To determine the appropriate constitutive model constants and to test the predictions of the model, tests on Hastelloy-X crystals were carried out, including the rate sensitivity, cyclic hardening, nonproportional hardening, relaxation, and strain rate dip tests. It was found necessary to include cube slip in the model in order to correlate the uniaxial behavior of the single crystal, to incorporate the interaction effects in both the hardening and the dynamic recovery evolution equations for the drag stress, and to successfully capture correct strain rate sensitivity under biaxial tension-torsion loading conditions.

Jordan, Eric H.; Shi, Shixiang; Walker, Kevin P.

1993-01-01

416

Ultrasonic characterization of single crystal langatate  

NASA Astrophysics Data System (ADS)

Langatate (LGT), a synthetic piezoelectric crystal with chemical composition La3Ga5.5Ta0.5O14, has recently received significant interest in the sensor and frequency control communities as a possible alternative to quartz owing to its higher piezoelectric coupling, structural stability up to 1400°C and presence of temperature compensated acoustic wave (AW) orientations. With these exciting properties, LGT is expected to find applications in AW sensor, timing, and frequency control. This thesis focuses on the characterization of the acoustic wave material properties of LGT up to 120°C. Such a characterization is critical for the design and fabrication of LGT acoustic wave devices. The elastic and piezoelectric constants were determined through measurements of bulk acoustic wave phase velocities by two independent methods, the pulse echo overlap technique and a combined resonance technique. The extracted constants and temperature coefficients enabled the identification of a range of particularly interesting LGT surface acoustic wave (SAW) orientations with Euler angles (90°, 23°, 118-124°) that exhibits predicted electromechanical coupling up to 0.7% and reduced or zero temperature coefficient of delay (TCD). The consistency of the determined constants and temperature coefficients was established using SAW measurements of seven crystallographic orientations at temperatures ranging up to 120°C. Measured SAW phase velocities and TCDs were found to be in agreement with predictions based on the determined constants. Two of the seven SAW orientations exhibited temperature compensation within 40°C of room temperature, agreeing with predictions. Deposition of SiAlON films on top of LGT SAW devices for surface protection in chemically and mechanically harsh environments was also investigated. SiAlON films deposited by reactive RF magnetron co-sputtering of Al and Si targets were controlled to within a few percent for film thickness and composition. SiAlON thin film clastic constants were extracted using differential SAW delay line methods and were found to be: C11,s = 160 +/- 30 GPa and C44,s = 55 +/- 5 GPa. SiAlON films up to 800 nm in thickness were shown to have no measurable effect on the TCD of LGT SAW delay lines.

Sturtevant, Blake T.

417

A Study of Single Crystal Fatigue Failure Criteria  

NASA Technical Reports Server (NTRS)

This paper presents the results of a study whose objective was to study the applicability of different failure equations in modeling low cycle fatigue (LCF) test data for single crystal test specimens. A total of four failure criteria were considered in this study. One of the failure equations was developed by Pratt & Whitney and is based on normal and shear strains on the primary crystallographic slip planes of the single crystal material. Other failure equations considered are based on isotropic criteria. Because these failure equations were originally developed for isotropic materials such as structural steel, they were modified to be applicable to the single crystal slip systems of the LCF specimen material. By observing how closely the various equations were able to reduce the scatter in the LCF test data, the applicability of those equations in modeling the LCF test data was assessed. It is desired to subsequently use the failure equation with the highest correlation in the development of a new single crystal failure criterion for the Alternative Turbopump Development (ATD) for the space shuttle main engine (SSME) High Pressure Fuel Turbopump (HPFTP).

Sayyah, Tarek; Swanson, Gregory R.; Schonberg, William P.

2000-01-01

418

Unified constitutive model for single crystal deformation behavior with applications  

NASA Technical Reports Server (NTRS)

Single crystal materials are being used in gas turbine airfoils and are candidates for other hot section components because of their increased temperature capabilities and resistance to thermal fatigue. Development of a constitutive model which assesses the inelastic behavior of these materials has been studied in 2 NASA programs: Life Prediction and Constitutive Models for Engine Hot Section Anisotropic Materials and Biaxial Constitutive Equation Development for Single Crystals. The model has been fit to a large body of constitutive data for single crystal PWA 1480 material. The model uses a unified approach for computing total inelastic strains (creep plus plasticity) on crystallographic slip systems reproducing observed directional and strain rate effects as a natural consequence of the summed slip system quantities. The model includes several of the effects that have been reported to influence deformation in single crystal materials, such as shear stress, latent hardening, and cross slip. The model is operational in a commercial Finite Element code and is being installed in a Boundary Element Method code.

Walker, K. P.; Meyer, T. G.; Jordan, E. H.

1988-01-01

419

Reliability analysis of single crystal NiAl turbine blades  

NASA Technical Reports Server (NTRS)

As part of a co-operative agreement with General Electric Aircraft Engines (GEAE), NASA LeRC is modifying and validating the Ceramic Analysis and Reliability Evaluation of Structures algorithm for use in design of components made of high strength NiAl based intermetallic materials. NiAl single crystal alloys are being actively investigated by GEAE as a replacement for Ni-based single crystal superalloys for use in high pressure turbine blades and vanes. The driving force for this research lies in the numerous property advantages offered by NiAl alloys over their superalloy counterparts. These include a reduction of density by as much as a third without significantly sacrificing strength, higher melting point, greater thermal conductivity, better oxidation resistance, and a better response to thermal barrier coatings. The current drawback to high strength NiAl single crystals is their limited ductility. Consequently, significant efforts including the work agreement with GEAE are underway to develop testing and design methodologies for these materials. The approach to validation and component analysis involves the following steps: determination of the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; measurement of the failure strength envelope of the material; coding of statistically based reliability models; verification of the code and model; and modeling of turbine blades and vanes for rig testing.

Salem, Jonathan; Noebe, Ronald; Wheeler, Donald R.; Holland, Fred; Palko, Joseph; Duffy, Stephen; Wright, P. Kennard

1995-01-01

420

Intrinsic electron and hole defects in stabilized zirconia single crystals  

Microsoft Academic Search

Intrinsic defects have been produced in yttria- and calcia-stabilized zirconia (YSZ or CaSZ) single crystals either by x irradiation at 300 and 77 K or by thermochemical reduction at 1370, 1670, and 1870 K. The spectroscopic properties of the defects have been studied by electron paramagnetic resonance (EPR), optical absorption, and photoemission techniques. Their thermal stability and bleaching characteristics have

V. M. Orera; R. I. Merino; Y. Chen; R. Cases; P. J. Alonso

1990-01-01

421

Pyroelectric properties of the modified triglycine sulphate (TGS) single crystals  

Microsoft Academic Search

Several doping substitutions (Li, Mn, D, P, As) in the TGS structure have been studied and the pyroelectric and dielectric properties measured. In the case of TGS single crystals modified by partial substitution of (P04 and (As04) groups for the (S04). higher pyroelectric coefficients and an enhancement of the pyroelectric material figure of merit (p\\/K) > 2 x TGS have

A. S. Bhalla; C. S. Fang; L. E. Cross; Yao Xi

1984-01-01

422

Growth of single crystals of bismuth sulpho iodide in gel  

Microsoft Academic Search

Single crystals of bismuth sulpho iodide have been grown in sodium silicate gel at room temperature by diffusing suitable reactants. In the first batch of experiments 3 to 7 g solution of BiCl3 was diffused into the gel containing 10 to 15% KI. Platelets of dimensions upto 5 mm were obtained in a period of 30 days. When thiourea of

R. Roop Kumar; G. Raman; F. D. Gnanam

1989-01-01

423

High definition TV projection via single crystal faceplate technology  

NASA Astrophysics Data System (ADS)

Single crystal phosphor faceplates are epitaxial phosphors grown on crystalline substrates with the advantages of high light output, resolution, and extended operational life. Single crystal phosphor faceplate industrial technology in the United States is capable of providing a faceplate appropriate to the projection industry of up to four (4) inches in diameter. Projection systems incorporating cathode ray tubes utilizing single crystal phosphor faceplates will produce 1500 lumens of white light with 1000 lines of resolution, non-interlaced. This 1500 lumen projection system will meet all of the currently specified luminance and resolution requirements of Visual Display systems for flight simulators. Significant logistic advantages accrue from the introduction of single crystal phosphor faceplate CRT's. Specifically, the full performance life of a CRT is expected to increase by a factor of five (5); ie, from 2000 to 10,000 hours of operation. There will be attendant reductions in maintenance time, spare CRT requirements, system down time, etc. The increased brightness of the projection system will allow use of lower gain, lower cost simulator screen material. Further, picture performance characteristics will be more balanced across the full simulator.

Kindl, H. J.; St. John, Thomas

1993-03-01

424

Temperature Dependence of Plastic Deformation in White Tin Single Crystals  

Microsoft Academic Search

Tensile experiments have been carried out over a wide range of temperatures on single crystals of high-purity white tin with low dislocation density. From the observations of slip lines it is found that different slip systems are activated for different temperature regions and for different orientations of specimens. By deformation with the (100)[010] slip system the cell structure is formed

Muneo Nagasaka

1989-01-01

425

Studies on Slip in Fe2%V Alloy Single Crystals  

Microsoft Academic Search

In an attempt to measure the critical resolved shear stress for slip of bcc metals, Fe-2%V single crystals were compressed along [110] direction, constraining the side faces, (001) and (00\\\\bar{1}), with a pair of fixed walls. Under these conditions, all slips are geometrically expected to be suppressed, and consequently [100] or [010] slip will be activated. Electron microscope study on

Shin Takeuchi

1969-01-01

426

Low temperature magnetic transitions of single crystal HoBi  

SciTech Connect

We present resistivity, specific heat and magnetization measurements in high quality single crystals of HoBi, with a residual resistivity ratio of 126. We find, from the temperature and field dependence of the magnetization, an antiferromagnetic transition at 5.7 K, which evolves, under magnetic fields, into a series of up to five metamagnetic phases.

Fente, A. [Universidad Autonoma de Madrid; Suderow, H. [Universidad Autonoma de Madrid; Vieira, S. [Universidad Autonoma de Madrid; Nemes, N. M. [Instituto de Ciencia de Materiales de Madrid; Garcia-Hernandez, M. [Instituto de Ciencia de Materiales de Madrid; Budko, Sergei L. [Ames Laboratory; Canfield, Paul C. [Ames Laboratory

2013-09-04

427

Optical waveguides of single-crystal garnet films  

NASA Astrophysics Data System (ADS)

We report light-wave propagation experiments in single-crystal epitaxially grown garnet films. The discussion includes refractive index and lattice constant considerations for various garnets, and also the use of iron garnet films on gallium garnet substrates as magneto-optical waveguides useful in integrated optics.

Tien, P. K.; Martin, R. J.; Blank, S. L.; Wemple, S. H.; Varnerin, L. J.

1972-09-01

428

Numerical aperture of single-mode photonic crystal fibers  

Microsoft Academic Search

We consider the problem of radiation into free space from the end-facet of a single-mode photonic crystal fiber (PCF). We calculate the numerical aperture NA = sin ? from the half-divergence angle ? ? tan-1 (?\\/??) with ??2 being the effective area of the mode in the PCF. For the fiber first presented by Knight et al. (1996), we find

Niels Asger Mortensen; Jacob Riis Folken; Peter M. W. Skovgaard; Jes Broeng

2002-01-01

429

Low-cost single-crystal turbine blades, volume 1  

NASA Technical Reports Server (NTRS)

The exothermic casting process was successfully developed into a low cost nonproprietary method for producing single crystal (SC) castings. Casting yields were lower than expected, on the order of 20 percent, but it is felt that the casting yield could be significantly improved with minor modifications to the process. Single crystal Mar-M 247 and two derivative SC alloys were developed. 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. The 1000 hr/238 MPa (20 ksi) stress rupture capability compared to DS Mar-M 247 was improved over 28 C. Firtree testing, holography, and strain gauge rig testing were used to evaluate the effects of the anisotropic characteristics of single crystal materials. 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.

Strangman, T. E.; Heath, B.; Fujii, M.

1983-01-01

430

Some Debye temperatures from single-crystal elastic constant data  

USGS Publications Warehouse

The mean velocity of sound has been calculated for 14 crystalline solids by using the best recent values of their single-crystal elastic stiffness constants. These mean sound velocities have been used to obtain the elastic Debye temperatures ??De for these materials. Models of the three wave velocity surfaces for calcite are illustrated. ?? 1966 The American Institute of Physics.

Robie, R.A.; Edwards, J.L.

1966-01-01

431

Pathways towards ferroelectricity in hafnia  

NASA Astrophysics Data System (ADS)

The question of whether one can systematically identify (previously unknown) ferroelectric phases of a given material is addressed, taking hafnia (HfO2) as an example. Low free energy phases at various pressures and temperatures are identified using a first-principles based structure search algorithm. Ferroelectric phases are then recognized by exploiting group theoretical principles for the symmetry-allowed displacive transitions between nonpolar and polar phases. Two orthorhombic polar phases occurring in space groups Pca21 and Pmn21 are singled out as the most viable ferroelectric phases of hafnia, as they display low free energies (relative to known nonpolar phases), and substantial switchable spontaneous electric polarization. These results provide an explanation for the recently observed surprising ferroelectric behavior of hafnia, and reveal pathways for stabilizing ferroelectric phases of hafnia as well as other compounds.

Huan, Tran Doan; Sharma, Vinit; Rossetti, George A.; Ramprasad, Rampi

2014-08-01

432

Crystal growth and electrical properties of Pb(Yb 1/2Nb 1/2)O 3-PbTiO 3 perovskite single crystals  

NASA Astrophysics Data System (ADS)

Pb(Yb 1/2Nb 1/2)O 3-PbTiO 3 (PYNT) single crystals were firstly grown using the high temperature solution method. Based on X-ray powder diffraction and thermal behavior of polycrystalline material, issues of perovskite instability were revealed. Barium additions were used to aid in the stabilization of the perovskite rhombohedral phase. The Curie temperature of PYNT (60/40) was found to vary from 244°C to 268°C, the characteristic of relaxor ferroelectric with the temperature of dielectric maximum increasing with increasing frequencies. Electrical properties of PYNT (60/40) investigated along <0 0 1>, <0 1 1>, and <1 1 1> pseudo-cubic directions, revealed remnant polarizations (Pr) of 26.5, 27.6 and 41.6 ?C/cm 2, respectively, while the coercive fields ( Ec) were 10.1, 9.4, and 11.5 kV/cm. The piezoelectric coefficient ( d33) of <0 0 1> oriented samples was found to be ˜1200 pC/N, with a strain reaching 0.54% at 100 kV/cm. The large piezoelectric coefficient, coercive field, and high Tc (>250°C) make PYNT single crystals promising candidates for high temperature and high performance solid-state actuators and transducers.

Zhang, Shujun; Rehrig, Paul W.; Randall, Clive; Shrout, Thomas R.

2002-01-01

433

Mesoscale flux-closure domain formation in single-crystal BaTiO3  

PubMed Central

Over 60 years ago, Charles Kittel predicted that quadrant domains should spontaneously form in small ferromagnetic platelets. He expected that the direction of magnetization within each quadrant should lie parallel to the platelet surface, minimizing demagnetizing fields,and that magnetic moments should be configured into an overall closed loop, or flux-closure arrangement. Although now a ubiquitous observation in ferromagnets, obvious flux-closure patterns have been somewhat elusive in ferroelectric materials. This is despite the analogous behaviour between these two ferroic subgroups and the recent prediction of dipole closure states by atomistic simulations research. Here we show Piezoresponse Force Microscopy images of mesoscopic dipole closure patterns in free-standing, single-crystal lamellae of BaTiO3. Formation of these patterns is a dynamical process resulting from system relaxation after the BaTiO3 has been poled with a uniform electric field. The flux-closure states are composed of shape conserving 90° stripe domains which minimize disclination stresses. PMID:21792183

McQuaid, R.G.P.; McGilly, L.J.; Sharma, P.; Gruverman, A.; Gregg, J.M.

2011-01-01

434

Green “planting” nanostructured single crystal silver  

PubMed Central

Design and fabrication of noble metal nanocrystals have attracted much attention due to their wide applications in catalysis, optical detection and biomedicine. However, it still remains a challenge to scale-up the production in a high-quality, low-cost and eco-friendly way. Here we show that single crystalline silver nanobelts grow abundantly on the surface of biomass-derived monolithic activated carbon (MAC), using [Ag(NH3)2]NO3 aqueous solution only. By varying the [Ag(NH3)2]NO3 concentration, silver nanoplates or nanoflowers can also be selectively obtained. The silver growth was illustrated using a galvanic-cell mechanism. The lowering of cell potential via using [Ag(NH3)2]+ precursor, together with the AgCl crystalline seed initiation, and the releasing of OH? in the reaction process, create a stable environment for the self-compensatory growth of silver nanocrystals. Our work revealed the great versatility of a new type of template-directed galvanic-cell reaction for the controlled growth of noble metal nanocrystals. PMID:23515002

Zhao, Hong; Wang, Fei; Ning, Yuesheng; Zhao, Binyuan; Yin, Fujun; Lai, Yijian; Zheng, Junwei; Hu, Xiaobin; Fan, Tongxiang; Tang, Jianguo; Zhang, Di; Hu, Keao

2013-01-01

435

X-ray crystal spectroscopy with stationary-state single-crystal utilizing Laue diffraction  

Microsoft Academic Search

A new type of x-ray crystal spectrometry has been designed to characterize a hard x-ray spectrum of each pulse emission from a laser-induced plasma x-ray source. Utilizing the Laue diffraction and a two-dimensional detector, it makes possible the measurement of diffracted monochromatic x rays without any time difference using a single crystal in a stationary state. Thus, a hard x-ray

Kazumasa Honda; Tadayuki Ohchi; Isao Kojima; Shigeki Hayashi

2001-01-01

436

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

437

Microwave Induced Direct Bonding of Single Crystal Silicon Wafers  

NASA Technical Reports Server (NTRS)

We have heated polished doped single-crystal silicon wafers in a single mode microwave cavity to temperatures where surface to surface bonding occurred. The absorption of microwaves and heating of the wafers is attributed to the inclusion of n-type or p-type impurities into these substrates. A cylindrical cavity TM (sub 010) standing wave mode was used to irradiate samples of various geometry's at positions of high magnetic field. This process was conducted in vacuum to exclude plasma effects. This initial study suggests that the inclusion of impurities in single crystal silicon significantly improved its microwave absorption (loss factor) to a point where heating silicon wafers directly can be accomplished in minimal time. Bonding of these substrates, however, occurs only at points of intimate surface to surface contact. The inclusion of a thin metallic layer on the surfaces enhances the bonding process.

Budraa, N. K.; Jackson, H. W.; Barmatz, M.

1999-01-01

438

Ultralarge negative dispersion single-polarization photonic crystal fiber  

NASA Astrophysics Data System (ADS)

The concept of employing a central air hole in the core is exploited to obtain an ultralarge negative dispersion photonic crystal fiber (PCF) over the wavelength range of 1350 to 1650 nm. The results show that the fiber may exhibit an average dispersion well over -500 ps/nm-km with a flattened dispersion profile. It is also found that the fiber shows a high birefringence in the order of 10-2 over the entire wavelength bands of interest. The endlessly single-mode behavior of PCFs is utilized to ensure the single modedness of the proposed fiber. Also, the technique of liquid crystal infiltration is exploited to suppress one of the two orthogonal modes of the fundamental mode. Along with the single-polarization behavior, the fiber shows an even more negative dispersion profile with less dispersion variation.

Islam, Md. Asiful; Alam, M. Shah

2014-09-01

439

Giant room-temperature barocaloric effect and pressure-mediated electrocaloric effect in BaTiO{sub 3} single crystal  

SciTech Connect

Barocaloric effect in BaTiO{sub 3} 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 LiNbO{sub 3}. We believe that our findings could open a potential route by combining the barocaloric effect and pressure-mediated electrocaloric effect in BaTiO{sub 3} single crystal for cooling devices.

Liu, Yang [Laboratoire Structures, Propriétés et Modélisation des Solides, UMR 8580 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, Châtenay-Malabry Cedex 92295 (France); Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049 (China); Wei, Jie [Laboratoire Structures, Propriétés et Modélisation des Solides, UMR 8580 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, Châtenay-Malabry Cedex 92295 (France); Electronic Materials Research Laboratory, Key Laboratory of Ministry of Education, Xi'an Jiaotong University, Xi'an 710049 (China); Janolin, Pierre-Eymeric; Infante, Ingrid C.; Dkhil, Brahim, E-mail: brahim.dkhil@ecp.fr, E-mail: xlou03@mail.xjtu.edu.cn [Laboratoire Structures, Propriétés et Modélisation des Solides, UMR 8580 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, Châtenay-Malabry Cedex 92295 (France); Lou, Xiaojie, E-mail: brahim.dkhil@ecp.fr, E-mail: xlou03@mail.xjtu.edu.cn [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049 (China)

2014-04-21

440

Shock wave-induced phase transition in RDX single crystals.  

PubMed

The real-time, molecular-level response of oriented single crystals of hexahydro-1,3,5-trinitro-s-triazine (RDX) to shock compression was examined using Raman spectroscopy. Single crystals of [111], [210], or [100] orientation were shocked under stepwise loading to peak stresses from 3.0 to 5.5 GPa. Two types of measurements were performed: (i) high-resolution Raman spectroscopy to probe the material at peak stress and (ii) time-resolved Raman spectroscopy to monitor the evolution of molecular changes as the shock wave reverberated through the material. The frequency shift of the CH stretching modes under shock loading appeared to be similar for all three crystal orientations below 3.5 GPa. Significant spectral changes were observed in crystals shocked above 4.5 GPa. These changes were similar to those observed in static pressure measurements, indicating the occurrence of the alpha-gamma phase transition in shocked RDX crystals. No apparent orientation dependence in the molecular response of RDX to shock compression up to 5.5 GPa was observed. The phase transition had an incubation time of approximately 100 ns when RDX was shocked to 5.5 GPa peak stress. The observation of the alpha-gamma phase transition under shock wave loading is briefly discussed in connection with the onset of chemical decomposition in shocked RDX. PMID:17718475

Patterson, James E; Dreger, Zbigniew A; Gupta, Yogendra M

2007-09-20

441

Is the methanation reaction over Ru single crystals structure dependent?  

PubMed

The influence of monoatomic steps and defects on the methanation reaction over ruthenium has been investigated. The experiments are performed on a Ru(0 1 54) ruthenium single crystal, which contains one monoatomic step atom for each 27 terrace atoms. The methanation activity is measured at one bar of hydrogen and CO in a high pressure cell, which enables simultaneous measurements of the local reactivity of the well defined single crystal surface and the global reactivity of the entire crystal and its auxiliary support. By adding sulfur we observe that the measured activity from the well defined stepped front-side of the crystal is poisoned faster than the entire crystal containing more defects. We also observe that additional sputtering of the well-defined front-side increases the reactivity measured on the surface. Based on this, we conclude that the methanation reaction takes place on undercoordinated sites, such as steps and kinks, and that the methanation reaction is extremely structure dependent. Simulations of the flow, temperature, and product distributions in the high pressure cell are furthermore presented as supplementary information. PMID:21258708

Vendelbo, Søren B; Johansson, Martin; Nielsen, Jane H; Chorkendorff, Ib

2011-03-14

442

Growth and characterization of terbium fumarate heptahydrate single crystals  

NASA Astrophysics Data System (ADS)

The growth of terbium fumarate heptahydrate single crystals was achieved by single gel diffusion technique using silica gel as a medium of growth. The effect of various growth parameters on the nucleation rate of these crystals was studied. The crystals were characterized by different physico-chemical techniques of characterization. Powder X-ray diffraction pattern showed that terbium fumarate is a crystalline compound. Fourier transform infrared spectroscopy was performed for the identification of water and other functional groups present in the compound. UV-vis and photoluminescence spectrophotometric experiments were carried out to study the optical properties of the grown crystals. Elemental analysis suggested the chemical formula of the crystals to be Tb2(C4H2O4)3·7H2O. The presence of seven molecules of water was also supported by the thermogravimetric analysis. The hydrated compound was found to be thermally stable upto a temperature of about 110 °C and its anhydrous form up to the temperature of 410 °C. The thermal decomposition of the compound in the nitrogen atmosphere leads to the formation of terbium oxide as the final product. An attempt was made to relate the experimental results with the classical nucleation theory.

Want, B.; Shah, M. D.

2014-03-01

443

EPR observations of trivalent titanium in orthophosphate single crystals  

SciTech Connect

The ground state spectroscopic properties of the 3d/sup 1/ electronic configuration ion Ti/sup 3 +/ have been investigated using EPR spectroscopy. Trivalent titanium was incorporated as a dilute impurity in single crystals of the tetragonal, zircon-structure hosts ScPO/sub 4/, YPO/sub 4/, and LuPO/sub 4/. The EPR spectrum of Ti/sup 3 +/ was observed in the as-grown orthophosphate crystals, and low temperature irradiations were not required to produce the trivalent state. The EPR results show that Ti/sup 3 +/ occupies a substitutional cation site in the host orthophosphate single crystals. Axial spin-Hamiltonian parameters were determined at 77 K, and these results are compared to those obtained previously for the 4d/sup 1/ and 5d/sup 1/ configuration ions Zr/sup 3 +/ and Hf /sup 3 +/ in the same host crystals. Titanium-doped orthophosphate crystals containing isotopically enriched /sup 47/Ti or /sup 49/Ti were also grown and employed in determinations of the hyperfine parameters. The g-values observed here for Ti/sup 3 +/, and determined previously for Zr/sup 3 +/ and Hf /sup 3 +/ are not accounted for by the published second-order expressions indicating that additional coupling mechanisms are operative.

Abraham, M.M.; Boatner, L.A.; Aronson, M.A.

1986-07-01

444

Single crystal to single crystal transition in (10, 3)-d framework with pyrazine-2-carboxylate ligand: Synthesis, structures and magnetism  

SciTech Connect

Assembling of pyrazine-2-carboxylate (Pzc) acid with nickel chlorine under solvothermal condition with MeOH as solvent gave a porous complex 1 {l_brace}[Ni(Pzc)ClH{sub 2}O]{center_dot}MeOH{r_brace}{sub n} with 1D channels. In 1 the ligands and metal ions are connected by three of each other and a rare (10,3)-d topology net is gained. The MeOH molecules filled in the 1D channels as guests. It is interesting that 1 undergoes a single-crystal-to-single-crystal transformation to another complex 2 when the guest MeOH molecules in the channels are exchanged by water molecules. Magnetic study indicates anti-ferromagnetic couplings exist in the two complexes and the guest exchange in the complex has little influence on the magnetism. - Graphical abstract: A porous complex 1 with rare (10,3)-d net was gained, and 1 underwent a single-crystal-to-single-crystal transformation to another phase 2. Highlights: Black-Right-Pointing-Pointer New (10,3)-d net was obtained with pyrazine-2-carboxylate ligands as a triangular node. Black-Right-Pointing-Pointer The complex 1 has a 1D channel filled with methanol molecules as guests. Black-Right-Pointing-Pointer 1 could undergo SCSC structural transition to 2 after guests exchanged. Black-Right-Pointing-Pointer Antiferromagnetic interactions were found in 1 and 2.

Yang, Qian [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China) [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Department of Chemistry, Tianjin Key Lab on Metal and Molecule-based Material Chemistry, Nankai University, Tianjin 300071 (China); Zhao, Jiong-Peng, E-mail: horryzhao@yahoo.com [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)] [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Liu, Zhong-Yi [College of Chemistry, Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Tianjin Normal University, Tianjin 300387 (China)] [College of Chemistry, Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Tianjin Normal University, Tianjin 300387 (China)

2012-12-15

445

Single crystal growth, crystal structure and characterization of a novel crystal: L-arginine 4-nitrophenolate 4-nitrophenol dehydrate (LAPP)  

NASA Astrophysics Data System (ADS)

A novel organic crystal, L-arginine 4-nitrophenolate 4-nitrophenol dehydrate (LAPP), synthesized and grown from aqueous solution, is presented. X-ray single diffraction shows that LAPP belongs to the monoclinic crystallographic system with space group P2 1. FT-IR and UV/vis/NIR transmission spectra have been employed to characterize the crystal. The computational calculation based on the density functional theory at the B3LYP/6-31G (d, p) level has been used to compute the first-order hyperpolarizability of LAPP relating to different molecular models. The morphology, nonlinear characteristic and thermal stability of the crystal have also been investigated.

Wang, L. N.; Wang, X. Q.; Zhang, G. H.; Liu, X. T.; Sun, Z. H.; Sun, G. H.; Wang, L.; Yu, W. T.; Xu, D.

2011-07-01

446

Analytical model of the ferroelectric radiation detector  

Microsoft Academic Search

As part of the Defense Nuclear Agency project Jl1 AAXPX231 to study the ; behavior of the ferroelectric radiation detector, an analytical model of the ; energy balance within a ferroelectric crystal has been developed. This model ; relates ionic spacing and charges to macroscopic quantities such as the ; pyroelectric and piezoelectric coefficients. Although a highly simplified model, ;

J. T. Klopcic; D. L. Swanson

1973-01-01

447

Single crystal growth and anisotropic crystal-fluid interfacial free energy in soft colloidal systems.  

PubMed

We measure the anisotropy of the crystal-fluid interfacial free energy in soft colloidal systems. A temperature gradient is used to direct crystal nucleation and control the growth of large single crystals in order to achieve well-equilibrated crystal-fluid interfaces. Confocal microscopy is used to follow both the growth process and the equilibrium crystal-fluid interface at the particle scale: heterogeneous crystal nucleation, the advancing interface, and the stationary equilibrium interface. We use the measured growth velocity to determine the chemical potential difference between crystal and fluid phases. Well-equilibrated, large crystal-fluid interfaces are then used to determine the interfacial free energy and its anisotropy directly from thermally excited interface fluctuations. We find that while the measured average interfacial free energy is in good agreement with values found in simulations, the anisotropy is significantly larger than simulation values. Finally, we investigate the effect of impurities on the advancing interface. We determine the critical force needed to overcome impurity particles from the local interface curvature. PMID:21867183

Nguyen, Van Duc; Hu, Zhibing; Schall, Peter

2011-07-01

448

Growth and electrical properties of mercury indium telluride single crystals  

SciTech Connect

A novel photoelectronic single crystal, mercury indium telluride (MIT), has been successfully grown by using vertical Bridgman method (VB). The crystallinity, thermal and electrical properties of the MIT crystal were investigated. The results of X-ray rocking curve show that the as-grown MIT crystal has good crystal quality with the FWHM on (3 1 1) face of about 173 in. DSC measurement reveals that the Hg element is easy to solely evaporate from the compound when the temperature is higher than 387.9 deg. C in the open system. Hall measurements at room temperature show that the resistivity, carrier density and mobility of the MIT crystal were 4.79 x 10{sup 2} {omega} cm, 2.83 x 10{sup 13} cm{sup -3} and 4.60 x 10{sup 2} cm{sup 2} V{sup -1} s{sup -1}, respectively. The reduction of carrier mobility and the increase of the resistivity are related to the adding of In{sub 2}Te{sub 3} into HgTe, which changes the energy band structure of the crystal.

Wang Linghang [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072 (China)], E-mail: uswlh@yahoo.com.cn; Dong Yangchun; Jie Wanqi [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072 (China)

2007-11-06

449

Single-crystal CsBr infrared fibers  

NASA Astrophysics Data System (ADS)

A study of the crystal growth, optical losses, and mechanical behavior of single-crystal CsBr infrared fibers is presented. The fibers were grown with a modified pull down technique and showed total losses in the range 2-5 dB/m at 10.6 microns, as well as excess scattering loss from surface imperfections such as growth striations, subgrain boundaries, and flaws. The main absorption loss at the CO2 wavelength is attributed to SO4(2-) ions contained in the raw materials. Because of their yield strength in addition to their flexibility, the (001)-oriented fibers are considered the best mechanically.

Mimura, Y.; Okamura, Y.; Ota, C.

1982-08-01

450

Spatial Coherence Preservation By Synthetic Single Diamond Crystals  

SciTech Connect

The degree of spatial coherence after x-ray diffraction by synthetic single diamond crystals was investigated. The coherence preservation was measured by means of the Talbot effect for x-rays at the optics beamline BM5 at the ESRF. The (111)- and (100)- oriented specimens of type Ib and IIa were grown by De Beers. To establish a correlation between the coherence degradation and the surface quality, 3D surface topography was measured with an optical interferometric profiler and an AFM. Likewise, to pinpoint the relationship with crystalline quality, the samples were characterized by means of double crystal x-ray diffractometry with microscopic resolution.

Hoszowska, J.; Freund, A. K.; Guigay, J.-P.; Rommeveaux, A. [European Synchrotron Radiation Facility, 6 Jules Horowitz, F-38043 Grenoble (France)

2004-05-12

451

Heavy ion passive dosimetry with silver halide single crystals  

NASA Technical Reports Server (NTRS)

A method of detecting radiation damage tracks due to heavy particles in large single crystals of the silver halides is described. The tracks, when made visible with a simple electrical apparatus, appear similar to tracks in emulsions. The properties of the crystals, the technique of printing out the tracks, and evidence concerning the threshold energy for registering particles indicates that this method may find application in heavy ion dosimetry. The method has been found to be sensitive to stopping He nuclei and relativistic M group cosmic rays. Some impurities strongly influence the printout of the tracks, and the effects of these impurities are discussed.

Childs, C. B.; Parnell, T. A.

1972-01-01

452

Electron Paramagnetic Resonance of Yb3+ in Scheelite Single Crystals  

Microsoft Academic Search

The electron paramagnetic resonance spectra of the ground state of trivalent ytterbium have been observed in eight single crystals with scheelite structure at 4.2°K and X band frequencies. The crystals used were CdMoO4, CaWO4, CaMoO4, SrWO4, SrMoO4, PbWO4, PbMoO4, and BaWO4. The tetragonal spectra for Yb171, Yb173, and the even isotopes of ytterbium were best fitted with an axial spin

J. P. Sattler; J. Nemarich

1970-01-01

453

Submicrometer Single Crystal Diffractometry for Highly Accurate Structure Determination  

NASA Astrophysics Data System (ADS)

Submicrometer single crystal diffractometry for highly accurate structure determination was developed using the extremely stable and highly brilliant synchrotron radiation from SPring-8. This was achieved using a microbeam focusing system and the submicrometer precision low-eccentric goniometer system. We demonstrated the structure analyses with 2×2×2 ?m3 cytidine, 600×600×300 nm3 BaTiO3, and 1×1×1 ?m3 silicon. The observed structure factors of the silicon crystal were in agreement with the structure factors determined by the Pendellösung method and do not require absorption and extinction corrections.

Yasuda, Nobuhiro; Fukuyama, Yoshimitsu; Toriumi, Koshiro; Kimura, Shigeru; Takata, Masaki

2010-06-01

454

Submicrometer Single Crystal Diffractometry for Highly Accurate Structure Determination  

SciTech Connect

Submicrometer single crystal diffractometry for highly accurate structure determination was developed using the extremely stable and highly brilliant synchrotron radiation from SPring-8. This was achieved using a microbeam focusing system and the submicrometer precision low-eccentric goniometer system. We demonstrated the structure analyses with 2x2x2 {mu}m{sup 3} cytidine, 600x600x300 nm{sup 3} BaTiO{sub 3}, and 1x1x1 {mu}m{sup 3} silicon. The observed structure factors of the silicon crystal were in agreement with the structure factors determined by the Pendelloesung method and do not require absorption and extinction corrections.

Yasuda, Nobuhiro; Fukuyama, Yoshimitsu; Kimura, Shigeru [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Sayo, Hyogo 679-5198 (Japan); Japan Science and Technology Agency, CREST, 5, Sanbancho, Chiyoda, Tokyo 102-0075 (Japan); Toriumi, Koshiro [Japan Science and Technology Agency, CREST, 5, Sanbancho, Chiyoda, Tokyo 102-0075 (Japan); University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo 678-1297 (Japan); Takata, Masaki [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Sayo, Hyogo 679-5198 (Japan); Japan Science and Technology Agency, CREST, 5, Sanbancho, Chiyoda, Tokyo 102-0075 (Japan); RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Sayo, Hyogo 679-5148 (Japan)

2010-06-23

455

First principles study on the ferroelectricity of the perovskite ABO3 ferroelectrics  

NASA Astrophysics Data System (ADS)

In order to understand well the different ferroelectric behaviour of quantum paraelectrics and ferroelectrics and the origin of the ferroelectricity of the solid solution KTa0.5Nb0.5O3(KTN), we calculated the electronic structure of CaTiO3, BaTiO3 and KTN by first principles calculation. From total energy analysis, it is shown that, with increasing cell volume, the crystals (CaTiO3, SrTiO3) will have a ferroelectric instability. For BaTiO3, the ferroelectricity will disappear as the cell volume is decreased. From the density of states analysis, it is shown that the hybridization between B d and O p is very important for the ferroelectric stability of ABO3 perovskite ferroelectrics. This is consistent with the analysis of band structure.

Wang, Yuan-Xu; Zhong, Wei-Lie; Wang, Chun-Lei; Zhang, Pei-Lin; Su, Xuan-Tao

2002-07-01

456

Ferroelectric memories  

Microsoft Academic Search

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

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

1989-01-01

457

Ferroelectric Materials  

Microsoft Academic Search

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

Roger Whatmore

2007-01-01

458

Nucleation kinetics, growth and studies of ?-alanine single crystals.  

PubMed

Solubility and metastable zone width for the re-crystallized salt of ?-alanine was determined. Induction period measurement for the selected supersaturation ratios at room temperature (31 °C) was carried out for supersaturated aqueous solutions of ?-alanine and it is noticed that induction period decreases with increase of supersaturation ratio. The nucleation parameters such as Gibbs free energy change, radius and number of molecules of the critical nucleus, interfacial tension and the nucleation rate have been evaluated by classical nucleation theory. Single crystals of ?-alanine were grown using the optimized nucleation parameters by solution method and grown crystals have been subjected to various studies like XRD studies, FTIR, optical, thermal and SHG studies. PMID:23548638

Shanthi, D; Selvarajan, P; HemaDurga, K K; Lincy Mary Ponmani, S

2013-06-01

459

Investigation on the growth kinetics of KDP:LAP and TGS:LAP single crystals  

Microsoft Academic Search

Potassium dihydrogen phosphate KDP; (KH2PO4) and triglycine sulfate TGS; (CH2NH2COOH.H2SO4), are extensively studied ferroelectric materials, and find wide applications in electrooptic and infrared detecting devices respectively. L-arginine phosphate monohydrate (C6H14N4O2H3PO4.H2O), abbreviated as LAP, is a highly transparent monoclinic crystal with attractive properties for efficient frequency conversion of infrared lasers. Effects of doping KDP and TGS crystals with LAP are investigated.

A. K. Batra; J. Stephens; K. Bhat; M. D. Aggarwal; Burl H. Peterson; Michael Curley; R. B. Lal

2005-01-01

460

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

Microsoft Academic Search

Optically transparent single crystals of Cu2+ and Zn2+ doped potassium acid phthalate (KAP) were grown in aqueous solution by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis confirmed the changes in the lattice parameters of the doped crystals. The presence of functional groups in the crystal lattice has been determined qualitatively by Fourier transform infrared (FTIR) analysis.

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

2010-01-01

461

Determining thermodynamic properties of molecular interactions from single crystal studies.  

PubMed

The concept of single crystals of macromolecules as thermodynamic systems is not a common one. However, it should be possible to derive thermodynamic properties from single crystal structures, if the process of crystallization follows thermodynamic rules. We review here an example of how the stabilizing potentials of molecular interactions can be measured from studying the properties of DNA crystals. In this example, we describe an assay based on the four-stranded DNA junction to determine the stabilizing potentials of halogen bonds, a class of electrostatic interactions, analogous to hydrogen bonds, that are becoming increasing recognized as important for conferring specificity in protein-ligand complexes. The system demonstrates how crystallographic studies, when coupled with calorimetric methods, allow the geometries at the atomic level to be directly correlated with the stabilizing energies of molecular interactions. The approach can be generally applied to study the effects of DNA sequence and modifications of the thermodynamic stability of the Holliday junction and, by inference, on recombination and recombination dependent processes. PMID:23933330

Vander Zanden, Crystal M; Carter, Megan; Ho, Pui Shing

2013-11-01

462

Ultrafast dynamics of excitons in tetracene single crystals  

SciTech Connect

Ultrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states S{sub n} on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S{sub 1} on a 40 ps timescale. The high energy Davydov component of the S{sub 1} exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale.

Birech, Zephania; Schwoerer, Heinrich, E-mail: heso@sun.ac.za [Laser Research Institute, Stellenbosch University, Stellenbosch 7600 (South Africa)] [Laser Research Institute, Stellenbosch University, Stellenbosch 7600 (South Africa); Schwoerer, Markus [Department of Physics, University of Bayreuth, Bayreuth (Germany)] [Department of Physics, University of Bayreuth, Bayreuth (Germany); Schmeiler, Teresa; Pflaum, Jens [Experimental Physics VI, University of Würzburg and Bavarian Center for Applied Energy Research, Würzburg (Germany)] [Experimental Physics VI, University of Würzburg and Bavarian Center for Applied Energy Research, Würzburg (Germany)

2014-03-21

463

Constitutive modeling of superalloy single crystals with verification testing  

NASA Technical Reports Server (NTRS)

The goal is the development of constitutive equations to describe the elevated temperature stress-strain behavior of single crystal turbine blade alloys. The program includes both the development of a suitable model and verification of the model through elevated temperature-torsion testing. A constitutive model is derived from postulated constitutive behavior on individual crystallographic slip systems. The behavior of the entire single crystal is then arrived at by summing up the slip on all the operative crystallographic slip systems. This type of formulation has a number of important advantages, including the prediction orientation dependence and the ability to directly represent the constitutive behavior in terms which metallurgists use in describing the micromechanisms. Here, the model is briefly described, followed by the experimental set-up and some experimental findings to date.

Jordan, Eric; Walker, Kevin P.

1985-01-01

464

Plastic Deformation of Aluminum Single Crystals at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

This report describes the results of a comprehensive study of plastic deformation of aluminum single crystals over a wide range of temperatures. The results of constant-stress creep tests have been reported for the temperature range from 400 degrees to 900 degrees F. For these tests, a new capacitance-type extensometer was designed. This unit has a range of 0.30 inch over which the sensitivity is very nearly linear and can be varied from as low a sensitivity as is desired to a maximum of 20 microinches per millivolt with good stability. Experiments were carried out to investigate the effect of small amounts of prestraining, by two different methods, on the creep and tensile properties of these aluminum single crystals. From observations it has been concluded that plastic deformation takes place predominantly by slip which is accompanied by the mechanisms of kinking and polygonization.

Johnson, R D; Young, A P; Schwope, A D

1956-01-01

465

Synthesis and characterization of single-crystal strontium hexaboride nanowires.  

PubMed

Catalyst-assisted growth of single-crystal strontium hexaboride (SrB6) nanowires was achieved by pyrolysis of diborane (B2H6) over SrO powders at 760-800 degrees C and 400 mTorr in a quartz tube furnace. Raman spectra demonstrate that the nanowires are SrB6, and transmission electron microscopy along with selected area diffraction indicate that the nanowires consist of single crystals with a preferred [001] growth direction. Electron energy loss data combined with the TEM images indicate that the nanowires consist of crystalline SrB 6 cores with a thin (1 to 2 nm) amorphous oxide shell. The nanowires have diameters of 10-50 nm and lengths of 1-10 microm. PMID:18950235

Jash, Panchatapa; Nicholls, Alan W; Ruoff, Rodney S; Trenary, Michael

2008-11-01

466

Flextensional Single Crystal Piezoelectric Actuators for Membrane Deformable Mirrors  

NASA Technical Reports Server (NTRS)

Large aperture and light weight space telescopes requires adaptive optics with deformable mirrors capable of large amplitude aberration corrections at a broad temperature range for space applications including NASA missions such as SAFIR, TPF, Con-X, etc. The single crystal piezoelectric actuators produced at TRS offer large stroke, low hysteresis, and an excellent cryogenic strain response. Specifically, the recently developed low profile, low voltage flextensional single crystal piezoelectric actuators with dimensions of 18 x 5 x 1 mm showed stroke larger than 95 microns under 300 V. Furthermore, flextensional actuator retained approx. 40-50% of its room temperature strain at liquid Nitrogen environment. In this paper, ATILA FEM design of flextensional actuators, actuator fabrication, and characterization results will be presented for the future work on membrane deformable mirror.

Jiang, Xiaoning; Sahul, Raffi; Hackenberger, Wesley S.

2006-01-01

467

A piezoelectric single-crystal ultrasonic microactuator for driving optics.  

PubMed

At the millimeter scale, the motions or force out puts generated by conventional piezoelectric, magnetostrictive, photostrictive, or electromagnetic actuators are very limited. Here, we report a piezoelectric ultrasonic microactuator (size: 1.5 × 1.5 × 5 mm, weight: 0.1 g) made of PIN-PMN-PT single crystal. The actuator converts its high-frequency microscopic displacements (nanometer to micrometer scale) into a macro scopic, centimeter-scale linear movement of a slider via frictional force, resulting in a speed up to 50 mm/s and a ve