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1

Ferroelectric polarization reversal in single crystals  

NASA Technical Reports Server (NTRS)

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

Stadler, Henry L.

1992-01-01

2

Imaging linear polarimetry using a single ferroelectric liquid crystal modulator.  

PubMed

In the field of polarimetry, ferroelectric liquid crystal cells are mostly used as bistable polarization rotators suitable to analyze crossed polarizations. This paper shows that, provided such a cell is used at its nominal wavelength and correctly driven, its behavior is close to that of a tunable half-wave plate, and it can be used with much benefit in lightweight imaging polarimetric setups. A partial Stokes polarimeter using a single digital video camera and a single ferroelectric liquid crystal modulator is designed and implemented for linear polarization analysis. Polarization azimuthal angle and degree of linear polarization are available at 150 frames per second with a good accuracy. PMID:20820209

Gendre, Luc; Foulonneau, Alban; Bigué, Laurent

2010-09-01

3

Strain incompatibility and residual strains in ferroelectric single crystals.  

PubMed

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 BaTiO(3) 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

Orientation dependence of electromechanical properties of relaxor based ferroelectric single crystals  

E-print Network

extrinsic domain and domain wall contributions. For [011]c poled multi- domain crystals, the intrinsicOrientation dependence of electromechanical properties of relaxor based ferroelectric single of electromechan- ical properties of relaxor based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3­(6­7)%PbTiO3

Cao, Wenwu

5

Ferroelectricity in single crystal InMnO3  

NASA Astrophysics Data System (ADS)

Single crystal synthesis, structure, electric polarization, and heat capacity measurements on hexagonal InMnO3 show that this small R ion in the RMnO3 series is ferroelectric (space group P63cm). Structural analysis of this system reveals a high degree of order within the MnO5 polyhedra but significant distortions in the R-O bond distributions compared to the previously studied materials. Point-charge estimates of the electric polarization yield an electrical polarization of ˜7.8 ?C/cm2, 26% larger than the well-studied YMnO3 system. This system with enhanced room temperature polarization values may serve as a possible replacement for YMnO3 in device applications.

Yu, T.; Gao, P.; Wu, T.; Tyson, T. A.; Lalancette, R.

2013-04-01

6

A model for Large Electrostrictive Actuation in Ferroelectric Single Crystals  

E-print Network

° domain switching in ferroelectric crystals subjected to combined electromechanical loading, has recently a reasonable arrangement of domain walls and formulating equations of motion for these walls. The model by domain walls. The strain and the polarization jump across the domain wall, but in a compatible manner

Bhattacharya, Kaushik

7

Effective symmetry and physical properties of twinned perovskite ferroelectric single crystals  

E-print Network

symmetry is in general different from the microscopic symmetry of the crystal when it is not in a single crystal symmetry belongs to the rhombohedral 3m with dipoles formed in 111 family of the parent cubicEffective symmetry and physical properties of twinned perovskite ferroelectric single crystals Jirí

Cao, Wenwu

8

Orientation dependence of electromechanical properties of relaxor based ferroelectric single crystals  

E-print Network

wall contributions. For [011]c poled multi- domain crystals, the intrinsic orientation effect enhancesOrientation dependence of electromechanical properties of relaxor based ferroelectric single of relaxor based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3­(6­7)%PbTiO3 and Pb(Mg1/3Nb2/3)O3­ 33%PbTiO3

Cao, Wenwu

9

Simple macroscopic model of pyroelectric phenomenon in TGS single crystals in ferroelectric phase  

NASA Astrophysics Data System (ADS)

A simple mathematical model of pyroelectric phenomena, for ideal ferroelectrics, is presented. Material constants for triglycine sulphate (TGS) are used to verify the model. The results of simulations were compared with the temperature characteristics of the pyroelectric coefficient measured for a TGS ferroelectric sample. Single crystal growth and preparation of samples and experimental procedure are also presented. The relatively good conformity of the model calculations with the measurements allow us to expect further useful application of the model in future work on ferroelectric single crystals.

Trybus, M.; Proszak, W.; Wo?, B.

2009-09-01

10

Optical properties of microstructures in ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

It is well known that domain structures are very common in ferroelectric crystals such as BaTiO3, and KNbO3 due to the phase transitions when cooling down from the melting temperature in the growth process. In this dissertation, the formations and properties of different types of domains in perovskite type ferroelectric crystals are summarized. It is very difficult to completely eliminate these domains during the growth process. On the other hand, however, the complex domain structures are very unique characteristic properties that belong to ferroelectric crystals such as Fe: KNbO3 and other similar crystals which have excellent photorefractive and other properties. Study of domain structures is very important not only for eliminating them, but also for the implication of possible future applications (13,31,37). We have observed the 'comb' and 'grid' spatial structures as well as domain reversals on the growth surfaces of an iron-doped potassium niobate crystal. We did complete studies on these phenomena by using different means, such as metallurgical microscopy, surface profile measurement, and scanning electron microscopy. By analyzing these 'comb' and 'grid' structures and the surrounding physical conditions, we proved that the combination of 90o and 180o ferroelectric domains can generate certain uniform two dimensional or even possibly three dimensional microstructures. We also demonstrated that under certain conditions, the process can be synthetically achieved. In order to study these microstructures, we developed the Laser Assisted Micro-Manipulation Platform (LAMP) in our laboratory. By using this platform, not only did we gained understanding about these microstructures, but we were also able to generate laser induced optical index changes in the form of ferroelectric domain-type formation in a multiple-beam writing process. This writing process is totally reversible by an optical erasing process. The later study showed that the process is also reversible by an electrical poling process combined with optical means. The optical indices in neighboring areas are clearly distinguishable and the boundaries have very high contrast. By using the charge carrier exchange and dopant ion redistribution mechanisms, we have demonstrated that iron dopants played a significant role in forming this optically induced domains.

Lu, Zheng

1997-09-01

11

The birefringence spectroscopic studies on ferroelectric glycine phosphite (GPI) single crystals  

NASA Astrophysics Data System (ADS)

The ferroelectric glycine phosphite single crystals have been grown from aqueous solution by both conventional and Sankaranarayanan-Ramasamy methods. The modified channelled spectrum method has been adopted for spectral dependence of optical birefringence studies over the wavelength range of 480-620 nm, which show that both the crystals exhibit relatively high birefringence values. The photoluminescence excitation studies were carried out for the grown crystals in a wide wavelength range between 300 nm and 600 nm at 224 K. The crystals were also subjected to scanning electron microscopy analysis in order to determine the ferroelectric domain pattern configuration.

Bhoopathi, G.; Jayaramakrishnan, V.; Ravikumar, K.; Prasanyaa, T.; Karthikeyan, S.

2013-01-01

12

Ferroelectric domain phenomena and microdomain engineering in BaMgF 4 single crystal  

Microsoft Academic Search

Ferroelectric domain phenomena and periodic domain patterning of orthorhombic as-grown BaMgF4 single crystal were investigated in the present study. An isolated ferroelectric domain shows a hexagonal form and exhibits a high domain-wall anisotropy. Periodic domain patterning was demonstrated on the polar surface by a periodic macropoling technique. In-plane polarization switching-induced microdomain patterning was tailored by the lateral component of the

H. R. Zeng; K. Shimamura; C. V. Kannan; E. A. G. Villora; S. Takekawa; K. Kitamura

2006-01-01

13

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

Microsoft Academic Search

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

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

2011-01-01

14

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

15

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

NASA Astrophysics Data System (ADS)

We present a switchable grating based on chiral single walled carbon nano-tube (SWCNT) doped ferroelectric liquid crystals (FLCs). The presence of SWCNTs improves the diffraction profile of the pure FLC. The diffraction efficiency, i.e., the ratio of intensities of first order and zero order maxima is more than 100% for the higher concentration of SWCNTs in pure FLC. This phenomenon has been explained by the decrease in ferroelectric domain periodicity, due to the doping of SWCNTs in pure FLC, and optical activity of the chiral SWCNTs. These gratings with very high diffraction efficiency may find application in many devices.

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

2011-11-01

16

High Performance Relaxor-Based Ferroelectric Single Crystals for Ultrasonic Transducer Applications  

PubMed Central

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

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

2014-01-01

17

Photocurrent Characteristics of Mn-Doped Barium Titanate Ferroelectric Single Crystals  

NASA Astrophysics Data System (ADS)

We investigated the photocurrent characteristics of ferroelectric single crystals of nondoped barium titanate (BT) and Mn-doped barium titanate (Mn-BT). The introduction of 90° domain structures into the BT crystals markedly increased the photocurrent, which suggests that the separation of photoinduced carriers is significantly enhanced around 90° domain walls (DWs). The Mn doping led to a drastic increase in photocurrent, with a photon energy less than the band gap. Density functional theory calculations show that the large photocurrent observed for the Mn-BT crystals originates from the electron excitation from the O 2p valence band to the Mn eg defect level followed by carrier (hole) injection.

Inoue, Ryotaro; Ishikawa, Shotaro; Kitanaka, Yuuki; Oguchi, Takeshi; Noguchi, Yuji; Miyayama, Masaru

2013-09-01

18

Thickness of 90° ferroelectric domain walls in (Ba,Pb)TiO3 single crystals  

Microsoft Academic Search

90° ferroelectric domain boundaries were observed by direct transmission electron microscopy in single crystals of pure BaTiO3 and (Ba,Pb)TiO3 solid solutions. Domain-wall thickness measurements were made from electron image plates by a densitometer-trace-curve-fitting technique. Boundary widths varied from 50 to 150 Å. These results are compared with theoretical estimates of 90° domain-wall thicknesses and correlated with the relative purity levels

M. D. Dennis; R. C. Bradt

1974-01-01

19

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

20

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

NASA Astrophysics Data System (ADS)

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

Harker, John Chamberlain

21

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

22

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

PubMed

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

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

2010-09-01

23

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

24

Studies of the effects of ion irradiation on ferroelectric domains of triglycine sulfate single crystals on a nanometer scale  

NASA Astrophysics Data System (ADS)

The effects of low dose (10 9/cm 2) ion irradiation on the ferroelectric domains and on the ferroelectric?paraelectric phase transition of triglycine sulfate (TGS) single crystals has been studied by using variable temperature dynamic contact electrostatic force microscopy. The evolution with temperature of ferroelectric domains of virgin and ion irradiated samples was observed in situ. In general, the phase transition of ion unirradiated samples is similar to that of virgin samples, which can be well described by Landau's mean field theory. However, on ion irradiated samples, there is a strong asymmetry of spontaneous polarization P for positive and negative domains. This asymmetry is due to the defects produced by ion implantation.

Xie, Z.; Luo, E. Z.; Xu, J. B.; An, J.; Sundaravel, B.; Wilson, I. H.; Wang, Z. Y.; Chen, X. L.; Zhao, L. H.

2003-03-01

25

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

PubMed

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

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

2010-02-11

26

Synchrotron white-beam X-ray topography of ferroelectric domains in a BaTiO3 single crystal  

Microsoft Academic Search

Ferroelectric domains and strains in a barium titanate (BaTiO3) single crystal, grown by the top-seeded solution growth technique, have been investigated by synchrotron white-beam X-ray topography (SWBXT) and optical microscopy. Conventional radiation X-ray topography studies in this system had previously been hampered by the presence of internal strain fields which made it difficult to observe the overall domain structures. SWBXT

Bong Mo Park; Su Jin Chung; Hyung Soon Kim; Weimin Si; Michael Dudley

1997-01-01

27

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

PubMed

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

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

2014-04-23

28

Magnetic field induced ferroelectricity in copper doped CdI2 single crystals  

Microsoft Academic Search

We have discovered a new type of ferroelectricity in highly anisotropic CdI2 layered crystals doped with copper. A spontaneous electric polarization is created in result of interaction between long-range interlayer polar acoustical vibrations and magnetically oriented copper ions. The phenomenon is strongly enhanced after applying external magnetic field at liquid helium temperatures. The strongest effect has been observed in the

I. V. Kityk; S. A. Pyroha; T. Mydlarz; J. Kasperczyk; M. Czerwi?ski

1998-01-01

29

`Comment on `A novel experimental method: Electrochemical detection of phase transition in ferroelectric single crystals', Chem. Phys. Lett. 384 (2004) 262 by K. Gatner and R. Jakubas'  

NASA Astrophysics Data System (ADS)

The electrochemical method presented by us has been used for the first time to study the phase transition in ionic, nonmetallic ferroelectric single crystals. Our experimental results were obtained for the crystals grown in the Faculty of Chemistry, University of Wroc?aw.

?wikiel, K.; Matlak, M.

2007-04-01

30

Studies on conventional and Sankaranarayanan-Ramasamy (SR) method grown ferroelectric glycine phosphite (GPI) single crystals  

NASA Astrophysics Data System (ADS)

Transparent single crystals of glycine phosphite were grown by Sankaranarayanan-Ramasamy (SR) method and conventional slow evaporation solution technique (SEST) which had the sizes of 100 mm in length, 30 mm diameter and 10×11×8 mm 3. The conventional slow evaporation and Sankaranarayanan-Ramasamy method grown glycine phosphite single crystals were characterized using laser damage threshold, chemical etching, Vickers microhardness, UV-vis-NIR and dielectric analysis. The laser damage threshold value was higher in SR method grown GPI crystal as against conventional method grown crystal. The SR method grown GPI has higher hardness and also higher transmittance compared to conventional method grown crystal. The chemical etching and dielectric loss measurements indicate that the crystal grown by SR method has low density of defects and low value of dielectric loss compared to conventional method grown GPI crystal.

Senthil Pandian, M.; Pattanaboonmee, N.; Ramasamy, P.; Manyum, P.

2011-01-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

32

Ultrasonic study of the elastic and nonlinear acoustic properties of single-crystal triglycine sulphate in the ferroelectric and paraelectric phases  

Microsoft Academic Search

An experimental ultrasonic study has been made of the elastic and nonlinear acoustic behaviour of single-crystal triglycine sulphate (TGS) in both the ferroelectric and paraelectric phases. The ultrasonic wave velocities for 12 modes of vibration propagated along the [100], [010], [001] and [101] directions have been measured as functions of temperature in the range 293-338 K, which covers the Curie

G. A. Saunders; A. Dunk; M. Cankurtaran

2000-01-01

33

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

SciTech Connect

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

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

2008-06-15

34

Single crystal thin films of conductive oxides SrRuO3 and ferroelectric heterostructures  

Microsoft Academic Search

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

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

1998-01-01

35

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

PubMed

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

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

2014-02-28

36

Correlation between impurity distribution and location of ferroelectric domain walls in Nd : Mg : LiNbO 3 single crystal  

Microsoft Academic Search

Using selective chemical etching, scanning electron microscope (SEM) and wave dispersive X-ray (WDX) microanalysis we showed that the ferroelectric domain walls coincide with the maxima and minima Nd-impurity modulation in a periodically poled Nd:Mg:LiNbO3 crystal grown by the Czochralski method along the normal to the (011?2) face. Asymmetric form of the Nd-modulation produces nonequal positive and negative domains for one

I. I Naumova; N. F Evlanova; S. A Blokhin; S. V Lavrishchev

1998-01-01

37

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 the microscopic single domain crystal symmetry. Such engineered domain structures in certain ferroelectric the domain wall, since it usually appears as a planar structure along particular crystallographic orienta

Cao, Wenwu

38

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

SciTech Connect

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

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

1995-04-01

39

Ferroelectric liquid crystal optical interconnect switching systems  

Microsoft Academic Search

This grant explored the possible use of ferroelectric liquid crystals (FLC's) in the reamization of photonic switching fabrics. Problems addressed included device fabrication, switch architectures, and switch performance. Experimental versions of most architectures were constructed. The aim of the contract was to develop techniques for using ferroelectric liquid crystals (FLC's) for novel photonic switching architectures. Initial work was devoted to

Joseph W. Goodman

1993-01-01

40

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

41

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

42

Tuning the ferroelectric state in multiferroic TbMnO3 single crystal by a trapped-charge-induced internal electric field  

NASA Astrophysics Data System (ADS)

The pyroelectric current effects in multiferroic TbMnO3 single crystal are reinvestigated in a wide temperature range. We report a pyroelectric current peak occurring around T = 107 K, which is much higher than the magnetic phase transition temperatures, after poling the sample from T ? 60 K to low temperatures, and we attribute it to the thermal release of trapped-charges in TbMnO3. We also show that the trapped-charges form a strong internal electric field that remarkably controls the ferroelectric polarization state induced by the cycloidal Mn3+ spins at lower temperature.

Zou, Tao; Dun, Zhiling; Cao, Huibo; Zhu, Mengze; Zhou, Haidong; Ke, Xianglin

2014-09-01

43

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

44

The effect of mechanical strains on the ferroelectric and dielectric properties of a model single crystal Phase field simulation  

E-print Network

-dipole­dipole-electric and -elastic interactions into account. The evolution of the ferroelectric domain structure is simulated-water environments, etc. Mechanical loads and/ or constraints may cause lattice distortion, domain wall motion, and changes in the domain structure [1] and thus shift the paraelectric/ferroelectric phase transition

Chen, Long-Qing

45

Precursor polar clusters in the paraelectric phase of ferroelectric Ba?.??Ca?.??TiO? single crystals studied by Brillouin light scattering.  

PubMed

A strong relaxation mode was observed in the gigahertz frequency window in the paraelectric phase of Ba?.??Ca?.??TiO? single crystals by using Brillouin light scattering. The appearance and growth of this relaxation mode were accompanied by substantial softening of the longitudinal acoustic mode as well as a remarkable increase in the hypersonic damping. Similar to BaTiO?, the temperature dependence of the relaxation time of Ba?.??Ca?.??TiO? displayed a slowing-down behavior near the Curie temperature, indicating the order-disorder nature of the paraelectric-ferroelectric phase transition in this substance. The dynamics of precursor polar clusters observed in this work was discussed in relation with recent theoretical studies and found to be consistent with their predictions. PMID:21393751

Kim, Tae Hyun; Kojima, Seiji; Park, Kibog; Kim, Sung Baek; Ko, Jae-Hyeon

2010-06-01

46

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

SciTech Connect

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

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

2006-05-15

47

Spontaneous ferroelectric-ferroelectric phase transitions and giant electro-mechanical energy conversion in [011] cut relaxor ferroelectric crystals  

NASA Astrophysics Data System (ADS)

We report on giant electro-mechanical energy conversion is demonstrated under a ferroelectric/ferroelectric phase transformation in [011] cut and poled lead titanate-based relaxor perovskite morphotropic Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT). single crystals. It is found that under mechanical pre-stress, a relatively small oscillatory stress drives the material reversibly between rhombohedral and orthorhombic phases with a remarkably high polarization and strain jumps induced at zero bias electric field and room temperature. The measured electrical output per cycle is more than an order of magnitude larger than that reported for linear piezoelectric materials. Ideal thermodynamic cycles are presented for this electro-mechanical energy conversion followed by a presentation and discussion of the experimental data. The stress dependence of thermally driven polarization change is reported for a ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut and poled. A giant jump in polarization and strain is associated with the phase transformation of the ferroelectric material. The phase transition temperature can be tuned, over a broad temperature range, through the application of bias stress. This phenomenon results in a new approach to applications in the field of energy harvesting

Finkel, Peter; Amin, Ahmed; Dong, Wen

2013-03-01

48

FERROELECTRIC LIQUID CRYSTAL GLASSES FOR AMBLYOPIA RESEARCH  

Microsoft Academic Search

Ferroelectric Liquid Crystal (FLC) filters offer the speed of electronic light shutters and the vibration free operation. These characteristics make them ideal for applications requiring short exposure times and minimal blur, offering switching times of 0.0002 of a second. FLC filters can be used as the optical shutters for machine vision purposes, also in vision research. On the basis of

SERGEJS FOMINS; MARIS OZOLINSH; GUNTA KRUMINA; VARIS KARITANS

2008-01-01

49

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

50

Modeling of elastic nonlinearities in ferroelectric materials including nonlinear losses: application to nonlinear resonance mode of relaxors single crystals.  

PubMed

(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) and (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) single crystals are considered to behave like soft Pb(Zr,Ti)O3 (PZT) ceramics because of their small mechanical quality factor Qm and poor stability under external disturbances (Qm > 500-1000 for hard PZT ceramic, and Qm < 100 for soft PZT and PMN-PT and PZN-PT single crystals). At weak signal excitation of the first resonance mode, the displacement at the end of a lateral bar is proportional to the Q31d31 figure of merit that is very close to that found for hard PZT. Indeed the very large piezoelectric coefficient compensates the low Qm. But increasing alternating current (AC) field results in the appearance of strong non-linearities through a shift of the resonance frequency and jumps phenomenon observed on increasing and decreasing frequency sweep. It is shown in this paper that these nonlinearities are due to the nonlinear elastic compliance that can be modeled by a third order development of the constitutive piezoelectric equations. Experiments on PMN-PT and PZN-PT single crystals are used for comparison with the model to show the viability of the approach. Both the frequency shift and jumps phenomenon are simulated with a very good agreement with experimental results. The importance is also shown of losses associated with the third order term responsible for the large decrease of the mechanical quality factor for high strain levels. Thus, the nonlinear losses are related to the hysteresis of domain wall motion when subjected to large displacements. PMID:16060508

Sebald, Gaël; Lebrun, Laurent; Guyomar, Daniel

2005-04-01

51

Spontaneous ferroelectric order in a bent-core smectic liquid crystal of fluid orthorhombic layers.  

PubMed

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(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. PMID:21454782

Reddy, R Amaranatha; Zhu, Chenhui; Shao, Renfan; Korblova, Eva; Gong, Tao; Shen, Yongqiang; Garcia, Edgardo; Glaser, Matthew A; Maclennan, Joseph E; Walba, David M; Clark, Noel A

2011-04-01

52

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

53

Ferroelectric liquid crystal optical interconnect switching systems  

NASA Astrophysics Data System (ADS)

This grant explored the possible use of ferroelectric liquid crystals (FLC's) in the reamization of photonic switching fabrics. Problems addressed included device fabrication, switch architectures, and switch performance. Experimental versions of most architectures were constructed. The aim of the contract was to develop techniques for using ferroelectric liquid crystals (FLC's) for novel photonic switching architectures. Initial work was devoted to mastering the technology of making FLC polarization rotation shutters, which formed the basis for the switching architecture work to follow. Much of this work was performed using the facilities of Stanford's Center for Integrated Systems. We were able to build such shutters with respectable properties, including reasonable uniformity, insertion losses of the order X dB, and extinction ratios of the order of Y db. Switching speeds observed were on the order of ZZZ. Having mastered the basic shutter technology, we moved on to employing such shutters in novel architectures.

Goodman, Joseph W.

1993-02-01

54

Ferroelectricity in liquid crystals probed by second harmonic generation  

Microsoft Academic Search

Summary form only given. Ferroelectric liquid crystals (FLC) attract significant attention as promising materials for different applications and rare examples of two-dimensional (2D) ferroelectrics. It has been shown previously that a nonlinear optical probe of second harmonic generation (SHG) can be applied to study the structure and switching behaviour of FLC. In this study, ferroelectric properties and switching behaviour of

Yu. G. Fokin; T. V. Murzina; O. A. Aktsipetrov; S. Soria; G. Marowsky

2002-01-01

55

Direct observation of ferroelectric domains created by Wigner crystallization of electrons in ?-[bis(ethylenedithio)tetrathiafulvalene]2I3  

NASA Astrophysics Data System (ADS)

The organic conductor ?-[bis(ethylenedithio)tetrathiafulvalene]2I3 undergoes a ferroelectric transition due to the Wigner-crystal-like charge ordering. The present paper reports the direct observation of 180° polar domains growing in the ferroelectric phase by means of optical second-harmonic generation interferometry. Mapping observation of the nonlinear optical interference revealed the development of large polar domains, illustrating a strong tendency of single-domain growth in the ferroelectric compound. The domain structures were varied when the crystal was annealed above the transition temperature and recooled into the ferroelectric phase. The variation indicates the mobile nature of the domains in the ferroelectric organic conductor.

Yamamoto, Kaoru; Kowalska, Aneta Aniela; Yakushi, Kyuya

2010-03-01

56

Columnar liquid crystal as a unique ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

A recently discovered ferroelectric columnar liquid crystal (LC) is reviewed. Particular attention is paid to differentiate it from conventional ferroelectric LCs such as the smectic-C*-type and bent-core LCs from the symmetry point of view. After reviewing ferroelectric smectic LCs (FSLCs), a ferroelectric columnar LC (FCLC) is introduced as a unique ferroelectric LC. FSLCs have a polarization parallel to the layer plane and have arbitrariness in the polarization direction within the two-dimensional plane. Hence surface constraints are generally indispensable for fixing the polarization direction. In contrast, FCLC has an Ising polarization along the column axis, which is very stable once poling is performed and convertible by applying an opposite electric field. In this sense, FCLC is the first genuine ferroelectric LC. Poling and switching can be achieved using spin-coated FCLC films with an open surface as well as conventional sandwich cells. Hence the FCLCs are more suitable for applications such as piezoelectric devices and ultrahigh-density memory devices, whereas only an application to fast display devices is proposed for FSLCs.

Araoka, Fumito; Takezoe, Hideo

2014-01-01

57

Novel ferroelectric single crystals of Bi(Zn1/2Ti1/2)O3-PbZrO3-PbTiO3 ternary solid solution  

NASA Astrophysics Data System (ADS)

Ferroelectric single crystals of a new lead-reduced Bi(Zn1/2Ti1/2)O3-PbZrO3-PbTiO3 (BZT-PZ-PT) ternary solid solution system have been grown for the first time by three different methods, namely high temperature solution growth (HTSG, or flux method), top-cooled solution growth (TCSG), and top-seeded solution growth (TSSG). The chemical and thermodynamic parameters, including the flux concentration, the soaking temperature and the cooling rate, have been optimized, leading to the growth of good quality BZT-PZ-PT crystals of pseudo-cubic morphology. A large size crystal of the dimensions of 2 × 2 × 0.5 cm3 has been obtained by the TSSG technique. The crystal structure is analyzed by means of X-ray powder diffraction. The highest ferroelectric Curie temperature TC of the grown crystals is found to be 320 °C by means of dielectric measurements. A remnant polarization of 32 ?C/cm2 is displayed with a coercive field of 15.4 kV/cm. The high TC and large coercive field of the BZT-PZ-PT single crystal make this material a promising candidate for applications in high power electromechanical transducers that can operate in a wider temperature range and at high fields.

Wang, Bixia; Xie, Yujuan; Zhuang, Jian; Wu, Xiaoqing; Ren, Wei; Ye, Zuo-Guang

2014-02-01

58

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

E-print Network

Polarization Rotation and Monoclinic Phase in Relaxor Ferroelectric PMN-PT Crystal V. Hugo Schmidt. A monoclinic phase is evidenced between rhombohedral and cubic phases in a -cut single crystal PMN-33%PT#-type). However, the present -cut crystal seems to disfavor the tetragonal phase and persists

59

Investigation of ferroelectric liquid crystal orientation in the silica microcapillaries  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

60

Ferroelectric Liquid Crystals In Aerodynamic Testing  

NASA Technical Reports Server (NTRS)

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

Parmar, Devendra S.; Holmes, Harlan K.

1994-01-01

61

Radiospectroscopic studies of ferroelectric triglycine sulphate-like crystals  

Microsoft Academic Search

The possibility of using radio and microwave spectroscopy to study intermolecular interactions in ferroelectrics of the TGS family will be presented.Ferroelectric crystals (TGSe, TGS and TGFB) doped with Cr3+ chromium ions were investigated by epr as a function of temperature. The fine structure parameter D of the epr spectra near Tc is closely related to the macroscopic deformation measured by

J. Stankowski

1978-01-01

62

Optically rewritable ferroelectric liquid-crystal grating  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

63

Optical interband transitions in relaxor-based ferroelectric 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 single crystal  

NASA Astrophysics Data System (ADS)

The optical transmission spectrum of [111]c poled relaxor-based ferroelectric single crystal 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 (PZN-0.07PT) was measured in the range of ultraviolet to near infrared. The optical absorption edge has been determined and the wavelength dependence of the absorption coefficient was calculated. The direct energy gap Egd=3.144 eV, indirect energy gap Egi=2.915 eV, and phonon energy Ep=0.097 eV (or 782 cm-1) were determined based on the theory of band to band transitions. It was also confirmed by Raman spectra that the indirect transition for the [111]c poled PZN-0.07PT single crystal is mainly due to the contribution of 780 cm-1 phonon corresponding to the Nb-O-Zn bond stretching mode.

Sun, Enwei; Zhang, Rui; Wang, Zhu; Xu, Dapeng; Li, Liang; Cao, Wenwu

2010-06-01

64

Modeling phonon-polariton generation and control in ferroelectric crystals  

E-print Network

In this thesis, we present simulations, using Finite Element Method (FEM), of phonon-polariton generation and coherent control in ferroelectric crystals LiNbO? and LiTaO? through nonlinear electro-optic interactions with ...

Chen, Zhao, S.M. Massachusetts Institute of Technology

2009-01-01

65

Asymmetric Freedericksz transitions from symmetric liquid crystal cells doped with harvested ferroelectric nanoparticles.  

PubMed

The electrical Freedericksz transition characteristics of planar aligned liquid crystal cells doped with harvested single ferroelectric domain 9 nm nanoparticles of BaTiO(3) have been measured. We demonstrate for the first time that the electrical pre-history of the cells imparts significant polarity sensitivity to the Freedericksz characteristics. The presence of harvested single domain ferroelectric nanoparticles enables cells to be programmably semi-permanently polarized. This reduces or increases the Freedericksz transition threshold by 0.8 V, depending on the polarity of the applied voltage, giving a net 1.6 V Freedericksz threshold asymmetry for 8 mum thick cells filled with TL205 liquid crystal. PMID:20721121

Cook, G; Reshetnyak, V Yu; Ziolo, R F; Basun, S A; Banerjee, P P; Evans, D R

2010-08-01

66

Electrical properties of ferroelectric liquid crystals during thermal phase transition  

NASA Astrophysics Data System (ADS)

The ferroelectric properties of ferroelectric liquid crystals (FLCs) during thermal phase transition in the surface-stabilized ferroelectric liquid crystal (SSFLC) cells were examined. The coercive electric field (Ec) and remanent polarization (Pr) changed with increasing temperature. These temperature-dependent variations of Ec and Pr were in agreement with the differential scanning calorimetry results. Moreover, the fatigue characteristic of the SSFLC cells was examined. No polarized fatigue was observed after 1 × 106 cycles of polarization switching, because FLCs may have the self-repair property for structural and interfacial defects.

Morimoto, Masahiro; Sakaki, Yosuke; Koshiba, Yasuko; Misaki, Masahiro; Ueda, Yasukiyo; Ishida, Kenji

2014-01-01

67

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

68

Continuous cross-over from ferroelectric to relaxor state and piezoelectric properties of BaTiO3-BaZrO3-CaTiO3 single crystals  

NASA Astrophysics Data System (ADS)

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 (Ba0.850Ca0.150)(Ti0.900Zr0.100)O3 ceramics exhibit outstanding piezoelectric coefficients. For the first time, we report the growth of piezoelectric lead-free single crystals in the BaTiO3-BaZrO3-CaTiO3 pseudo-ternary system. The stoichiometry control in the CaO-BaO-TiO2-ZrO2 solid solution led to single crystals with various compositions ranging from (Ba0.857Ca0.143)(Ti0.928Zr0.072)O3 to (Ba0.953Ca0.047)(Ti0.427Zr0.573)O3. 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 (Ba0.838Ca0.162)(Ti0.854Zr0.146)O3 composition, which has been grown and oriented along [001] crystallographic direction, displayed electromechanical coefficients d31 and k31 of 93 pC.N-1 and 0.18, respectively, near the room temperature (T = 305 K).

Benabdallah, F.; Veber, P.; Prakasam, M.; Viraphong, O.; Shimamura, K.; Maglione, M.

2014-04-01

69

Electronic electrooptic effects in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

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

Rickard, Malcolm J.

70

Strongly nonlinear dynamics of ferroelectric liquid crystals.  

PubMed

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

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

2013-01-01

71

Theory of ferroelectric nanoparticles in nematic liquid crystals.  

PubMed

Recent experiments have reported that ferroelectric nanoparticles have drastic effects on nematic liquid crystals-increasing the isotropic-nematic transition temperature by about 5 K, and greatly increasing the sensitivity to applied electric fields. To understand these effects, we develop a theory for the statistical mechanics of ferroelectric nanoparticles in liquid crystals. This theory predicts the enhancements of liquid-crystal properties, in good agreement with experiments. These predictions apply even when electrostatic interactions are partially screened by moderate concentrations of ions. PMID:19518997

Lopatina, Lena M; Selinger, Jonathan V

2009-05-15

72

Observation of piezoelectric resonance in time domain transient current of ferroelectric ceramics and crystals  

Microsoft Academic Search

An abnormal resonance behavior was observed from the transient current in the time domain for both ferroelectric ceramics and single crystals excited with a stepwise electric field. The phenomenon can be accounted for as piezoelectric resonance. Corresponding resonant peaks in the frequency spectrum of impedance verified the piezoelectric origin of the abnormal resonance. Using a RLC series equivalent circuit of

Li Jin; Xi Yao; Xiaoyong Wei; Zengzhe Xi

2005-01-01

73

Structure and switching dynamics in ferroelectric crystal and liquid crystal thin films  

NASA Astrophysics Data System (ADS)

The structure and switching dynamics of ferroelectric solid state and liquid crystal thin films were investigated experimentally using x-ray scattering, dielectric measurements, and optical microspectroscopy. Crystalline piezoelectric ferroelectric films, formed by sol-gel and sputter deposition, were developed and analyzed for application as high speed nonvolatile memories. Ferroelectric liquid crystal devices were studied for application as fast electro-optic light valves in spatial light modulator applications. A novel thermo-optical effect in ferroelectric lead magnesium niobate suitable for use in pressure sensing applications was discovered.

Clark, Noel A.; Scott, James F.

1993-03-01

74

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

75

Surface-charge layers on ferroelectric KNbO3 crystals  

Microsoft Academic Search

The nature of surface-charge layers is studied, with the help of AF electro-luminescence (EL), in single crystals of ferroelectric KNbO3. The variation of EL output with the applied potential and its frequency suggests that the crystal surface has a domain reversal charge layer. The origin and growth of EL pulses reveal a non-uniform charge density on these layers. The observation

A G Katpatal; K G Deshmukh

1972-01-01

76

Local electromechanical response at a single ferroelectric domain wall in lithium niobate  

Microsoft Academic Search

We report the presence of an unexpected asymmetry in the local electromechanical response across a single ferroelectric domain\\u000a wall in congruent lithium niobate at room temperature. We provide evidence that this is related to the presence of nonstoichiometric\\u000a defects in the crystal, which interact with the domain wall.

David A. Scrymgeour; Venkatraman Gopalan

2004-01-01

77

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

78

Nanoscale piezoelectric response across a single antiparallel ferroelectric domain wall  

Microsoft Academic Search

Experiments and three-dimensional numerical modeling of nanoscale piezoelectric response across a single domain wall in ferroelectric lithium niobate are presented. Surprising asymmetry in the local electromechanical response across a single antiparallel ferroelectric domain wall is reported. Piezoelectric force microscopy is used to investigate both the in-plane and out-of- plane electromechanical signals around domain walls in congruent and near-stoichiometric lithium niobate.

David A. Scrymgeour; Venkatraman Gopalan

2005-01-01

79

Growth and characterization of L-tryptophan-doped ferroelectric TGS crystals  

NASA Astrophysics Data System (ADS)

Single crystals of L-tryptophan-doped triglycine sulphate (LTTGS) were grown by the low-temperature solution method. The effects of dopant on morphological changes were observed on the grown crystals. The grown crystals were characterized using powder X-ray diffraction (XRD), which shows that the LTTGS crystals are of monoclinic system. The presence of L-tryptophan in TGS was estimated qualitatively by Fourier transform infrared (FTIR) analysis. Microhardness studies carried out using Leitz Weitzler hardness tester at room temperature. The hysteresis studies were also carried out to understand the ferroelectric properties.

Jayalakshmi, D.; Kumar, J.

2008-04-01

80

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

NASA Astrophysics Data System (ADS)

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

Das, Abhijit; Boruah, Bosanta R.

2014-04-01

81

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

PubMed

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

Das, Abhijit; Boruah, Bosanta R

2014-04-01

82

Phase diagrams of single-domain ferroelectric-dielectric superlattices  

NASA Astrophysics Data System (ADS)

Using the thermodynamic theory, the authors developed misfit strain-temperature phase diagrams of single-domain ferroelectric-dielectric superlattices grown on cubic substrates. Owing to internal electric fields appearing in such multilayers, the superlattice diagrams are expected to be very different from phase maps of homogeneous ferroelectric films. The calculations show, however, that this electrostatic effect does not change relative positions of phase transition lines. It only shifts the diagram as a whole along the line separating stability ranges of paraelectric phase and in-plane polarization state. The magnitude of this shift is governed by the capacitance of dielectric layer and the thickness of ferroelectric one.

Urtiev, F. A.; Kukhar, V. G.; Pertsev, N. A.

2007-06-01

83

Journal of Crystal Growth 292 (2006) 395398 Direct observation of ferroelectric domains and phases in (0 0 1)-cut  

E-print Network

Journal of Crystal Growth 292 (2006) 395­398 Direct observation of ferroelectric domains and phases in (0 0 1)-cut Pb(Mg1/3Nb2/3)1�xTixO3 single crystals under electric-field poling R.R. Chiena,�, V. Hugo.33O3 (PMNT33%) single crystal has been performed by polarizing microscopy. A hysteresis loop

84

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

NASA Astrophysics Data System (ADS)

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

Sotome, M.; Kida, N.; Horiuchi, S.; Okamoto, H.

2014-07-01

85

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

PubMed

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

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

2009-03-20

86

Frederiks transition in ferroelectric liquid-crystal nanosuspensions  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

87

Frederiks transition in ferroelectric liquid-crystal nanosuspensions.  

PubMed

We construct a theoretical model of the dielectric properties of a ferroelectric LC nanosuspension (FLCNS), using a generalized Maxwell-Garnett picture. The theory supposes that an FLCNS may as a first approximation be considered as a complex homogeneous dielectric ceramic, thus neglecting positional correlations of the colloidal particles. The FLCNS then consists of an anisotropic matrix with a very low concentration (<1% by volume) of impurity particles. The impurity particles possess both shape and dielectric anisotropy, as well as a permanent electric polarization and strong liquid-crystal director anchoring on the particle surface. We show that the effective dielectric properties for capacitance properties and for effective liquid-crystal free energies do not coincide. We calculate the effect of doping a liquid crystal with ferroelectric impurities on the Frederiks transition. The theory takes account of inclusion shape, dielectric susceptibility, and local field effects. We neglect the possibility of dielectric particle chaining, which appears experimentally not to occur in general. Our calculations suggest, in qualitative agreement with experiment, that doping a nematic liquid crystal with ferroelectric particles, even at very low particle concentration, can in some cases significantly decrease the electric Frederiks threshold field. PMID:21599184

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

2011-04-01

88

Fatigue effect in ferroelectric crystals: Growth of the frozen domains  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

89

Electromigration of microspheres in ferroelectric smectic liquid crystals.  

PubMed

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. PMID:17930054

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

2007-08-01

90

Piezoelectric and flexoelectric effects in ferroelectric liquid crystals.  

PubMed

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

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

2012-09-01

91

Computational modeling of domain wall interactions with dislocations in ferroelectric crystals  

E-print Network

Computational modeling of domain wall interactions with dislocations in ferroelectric crystals framework to investigate the interactions between domain walls and arrays of dislocations in ferroelectric of ferroelectric behavior since they interact with domain walls at submicron scales. For example, Yang et al. (1999

92

Single crystal magnets  

NASA Astrophysics Data System (ADS)

Single crystals of the Fe-Cr-Co alloys without and with 3% Mo were prepared by a recrystallization process. The microstructures and the magnetic properties of <100>, <110>, and <111> single crystals were investigated after the heat treatment in the ridge region of the miscibility gap. The magnetic properties of the Fe-22 Cr-17 Co ridge single crystals were not affected very much by the crystal orientation. However, the Fe-23 Cr-20 Co-3 Mo alloys show the crystal orientation dependence of the magnetic properties. The single crystal alloys are aged in a magnetic field, the direction of which is varied around <100> axes. The magnetic properties are measured parallel to the applied field directions and are summarized in view of deviated angle from a <100> axis. The greater the deviation of the applied field direction from a <100> axis, the poorer are the magnetic properties of the Mo single crystal alloy. The best magnetic properties are achieved with Fe-22 Cr-18.5 Co-3 Mo <100> ridge single crystal as Br=1.58 T (15.8 kG), bHc=72.8 kA/m (910 Oe), and (BH)max=91.2 kJ/m3 (11.4 MGOe), which is the highest energy product reported for the Fe-Cr-Co magnet family.

Ikuta, N.; Okada, M.; Homma, M.; Minowa, T.

1983-09-01

93

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

E-print Network

Measurement of the thermal expansion coefficients of ferroelectric crystals by a moire to measure the thermal expansion of two ferroelectric crystals, LiNbO3 and KTiOPO4. The crystal samples interferometer. The thermal expansion of all the three axes of congruent LiNbO3 and of x and y axes of the flux

Arie, Ady

94

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

95

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

96

Wavelength and bandwidth tunable photonic stopband of ferroelectric liquid crystals.  

PubMed

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

Ozaki, Ryotaro; Moritake, Hiroshi

2012-03-12

97

1. Innovative Relaxor-Based PiezoCrystals: Phase Diagrams, Crystal Growth, Domain Structures and Electric Properties. 2. Piezo- and Ferroelectric Materials Based on Morphotropic Phase Boundary Synthesis, Characterization and Structure - Property Relations.  

National Technical Information Service (NTIS)

This final technical report is on the research work carried out in the area of design, synthesis and characterization of novel piezo- and ferroelectric materials, especially in the form of single crystals, with a view to developing new materials resources...

Z. G. Ye

2006-01-01

98

Continuum analysis of the nucleus growth of reverse domains in large ferroelectric crystals  

NASA Astrophysics Data System (ADS)

Polarization reversal in ferroelectrics arises due to domain nucleation and domain wall motion. The nucleation of reverse domains at crystal boundaries is the fundamental initiation process observed in single crystals. The classical continuum approach by Landauer determines an insurmountable energy barrier to extrinsic domain nucleation. We rediscuss the continuum approach. Predetermined surface states are found to be a misleading concept. Alternate energy contributions, for example, due to a dead layer or due to charge injection as well as reduced domain wall energy and anisotropy of domain wall energy, have to be included into a convincing picture of domain nucleation.

Neumeister, Peter; Balke, Herbert; Lupascu, Doru C.

2009-04-01

99

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

100

Faster and highly luminescent ferroelectric liquid crystal doped with ferroelectric BaTiO3 nanoparticles  

NASA Astrophysics Data System (ADS)

The results pertaining to faster electro-optic response time and improved photoluminescence (PL) of BaTiO3 nanoparticles (BT NPs) doped ferroelectric liquid crystal (FLC) are presented. The observed increase (˜2 fold) in PL intensity and simultaneous reduction of response time have been achieved for an optimal BT NPs doping of 0.2 wt. %. These are attributed to the large dipole moment of BT that couples effectively with that of FLC molecules. These studies would provide benchmark for realization of high luminescent FLC devices that are faster in response.

Ganguly, Prasun; Kumar, A.; Tripathi, Shashank; Haranath, D.; Biradar, A. M.

2013-06-01

101

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

102

Nanoscale piezoelectric response across a single antiparallel ferroelectric domain wall David A. Scrymgeour* and Venkatraman Gopalan  

E-print Network

Nanoscale piezoelectric response across a single antiparallel ferroelectric domain wall David A-dimensional numerical modeling of nanoscale piezoelectric response across a single domain wall in ferroelectric lithium antiparallel ferroelectric domain wall is reported. Piezoelectric force microscopy is used to investigate both

Gopalan, Venkatraman

103

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

104

Dielectric spectroscopy of Polymer Stabilised Ferroelectric Liquid Crystals.  

PubMed

Dielectric measurements were carried out in the frequency range from 20 Hz to 500 kHz on Polymer Stabilised Ferroelectric Liquid Crystals (PSFLCs). Polymerisation in the Smectic A* (Sm A*) and the Smectic C* (Sm C*) phase at equal polymer concentration results in a dielectric strength which is nearly twice the value in the latter case. An increase of the polymer concentration results in a decrease of the dielectric strength and an increase in relaxation frequency. The textural morphology and transmission intensity due to the residual birefringence of the polymer network in the isotropic phase, revealed a correlation between the interactions of the liquid crystal molecules with the polymer network. Results for polymerizing in the tilted Sm C* phase with a large bias field are also reported which show that the structure of the phase in which the system was polymerised affects the dielectric properties. The observed differences in dielectric behaviour can be explained by the polymer network morphology formed due to the interplay of phase and temperature on the stabilised ferroelectric liquid crystal materials. PMID:19821129

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

2009-11-01

105

Domain Configuration and Ferroelectric Related Properties of the (110)cub Cuts of Relaxor-Based Pb(Mg1\\/3Nb2\\/3)O3-PbTiO3 Single Crystals  

Microsoft Academic Search

Domain configuration and ferroelectric related properties of Pb(Mg1\\/3Nb2\\/3)O3-PbTiO3 were investigated as a function of applied electric field for the (110)cub cuts. It was found that a single domain orthorhombic state could be achieved by applying an electric field along the direction cub, but the state after removing the electric field strongly depends on the composition and electric field. A qualitative

Yiping Guo; Haosu Luo; Tianhou He; Haiqing Xu; Zhiwen Yin

2002-01-01

106

The phenomenon of nanomaterial induced photoluminescence in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

Most of ferroelectric liquid crystals (FLCs) show no photoluminescence (PL). But when, Cu doped ZnO (Cu-ZnO) nanoparticles (NPs) are dispersed in FLC, it shows an induced photoluminescence. This induced phenomenon of PL strongly depends on the concentration of the dopant NPs. The Cu-ZnO-FLC composite system has shown two distinct emission peaks near 400 nm and 650 nm that correspond to the violet and red emission respectively. The characteristic features of both the emission peaks suggest their different source of origins. The aspects related to induced PL and its applications have been discussed in the present investigation.

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

2013-06-01

107

Solitary wave propagation in surface stabilized ferroelectric liquid crystal cells  

NASA Astrophysics Data System (ADS)

Solitary wave propagation in surface stabilized ferroelectric liquid crystal cells controlled by surface anchoring of the alignment layers is investigated for different conditions of alignment on the two opposite surfaces. We show that the critical field Ec, where the speed of the solitary wave becomes zero, is finite for asymmetric alignment on two surfaces. We also show that the polar anchoring energy difference (?wp) between the alignment layers can be calculated by measuring Ec, and this depends on the rubbing condition and the material of the alignment layer.

Song, Jang-Kun; Sufin, M. J.; Vij, J. K.

2008-02-01

108

Photoelastic and electro-optic effects : study of PMN-29%PT single crystals.  

E-print Network

??Relaxor ferroelectrics PMN-PT single crystals exhibit extra-high dielectric and piezoelectric properties compared with conventional piezoelectric ceramics. They are becoming widely used in high performance electromechanical… (more)

Di, Na (1977 - )

2010-01-01

109

Plastic deformation of LiNbO3 single crystals E. Fries (*) and A. Pter (**)  

E-print Network

. Abstract. 2014 High temperature (> 0.8 TM) plastic deformation of ferroelectric monodomain LiNbO3 of the present work is to examine the high temperature plastic deformation in air of LiNb03in the ferroelectric of perfect single crystals ; nowadays they are grown by the Czochralski technique [2]. It is a high

Boyer, Edmond

110

Effect of the intrinsic width on the piezoelectric force microscopy of a single ferroelectric domain wall  

E-print Network

Intrinsic domain wall width is a fundamental parameter that reflects bulk ferroelectric properties for vertical and lateral piezoelectric force microscopy PFM profiles of a single ferroelectric domain wall to interpret the experi- mental results of the PFM image of a ferroelectric domain wall with "sharp" tips

Gopalan, Venkatraman

111

Effect of the intrinsic width on the piezoelectric force microscopy of a single ferroelectric domain wall  

Microsoft Academic Search

Intrinsic domain wall width is a fundamental parameter that reflects bulk ferroelectric properties and governs the performance of ferroelectric memory devices. We present closed-form analytical expressions for vertical and lateral piezoelectric force microscopy (PFM) profiles of a single ferroelectric domain wall for the conical and disk models of the tip, beyond point charge and sphere approximations. The analysis takes into

Anna N. Morozovska; Eugene A. Eliseev; George S. Svechnikov; Venkatraman Gopalan; Sergei V. Kalinin

2008-01-01

112

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

SciTech Connect

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

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

2013-09-30

113

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

PubMed

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

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

2009-02-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

115

EVIDENCE OF TWO NEW ORDERED SMECTIC PHASES IN FERROELECTRIC LIQUID CRYSTALS  

E-print Network

two new ordered smectic phases which appear at lower temperature than the ferroelectric Sm C* phase the other one, which appears when increasing the temperature, shows only a two-dimensional order548 EVIDENCE OF TWO NEW ORDERED SMECTIC PHASES IN FERROELECTRIC LIQUID CRYSTALS J. DOUCET, P

Boyer, Edmond

116

Electro-Optical Studies in a Ferroelectric Liquid Crystal Mixture  

NASA Astrophysics Data System (ADS)

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

Singh, Rajbir; Raina, K. K.

2013-07-01

117

Soft memory in a ferroelectric nanoparticle-doped liquid crystal  

NASA Astrophysics Data System (ADS)

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

Basu, Rajratan

2014-02-01

118

Anisotropic behavior of water in ferroelectric liquid crystals.  

PubMed

The outcome of water addition in ferroelectric liquid crystal (FLC) has been investigated in uniform and defect-free homogeneous and homeotropically aligned monodomain sample cells from electro-optical and dielectric spectroscopic measurements. The lagging in optical response between nonconducting (spatially variable switching) and conducting (conventional switching) portions of water added FLC sample cell has been observed by frequency-dependent electro-optical studies. The bias-dependent water related new relaxation peak near the conventional Goldstone mode relaxation process has been observed only in the homogeneous alignment and not in the homeotropic one. Further, the significant increment in dielectric anisotropy as well as faster diffusion of water along long molecular axis than short molecular axis has also been monitored. These studies strongly suggest that the distribution of water is anisotropic in FLC medium and could be the reason for new relaxation peak in the water added FLC sample. PMID:20866247

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

2010-05-01

119

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

SciTech Connect

Bi deficient, Mn doped 0.92(Na{sub 0.5}Bi{sub 0.5})TiO{sub 3}-0.08(K{sub 0.5}Bi{sub 0.5})TiO{sub 3} single crystals were grown by carefully controlled top-seeded solution growth method. Local structures were investigated by transmission electron microscopy. The site occupation and valence state of manganese were characterized by electron paramagnetic resonance spectrum. The leakage current density in the as-grown single crystals is effectively depressed. The introduced defect complexes suppress the temperature induced phase transformation, increasing the depolarization temperature (165?°C) and thermal stability of ferroelectric properties.

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

2013-11-18

120

Real-time holographic vibrometry with a ferroelectric liquid-crystal spatial light modulator.  

PubMed

A fast ferroelectric liquid-crystal spatial light modulator, originally developed for optical computing, has found a new application in vibrometry. A new scheme of vibration-synchronized double-exposure holographic interferometry is proposed that makes full use of the speed of the ferroelectric liquid-crystal spatial light modulator. Preliminary experiments were performed that demonstrate virtually continuous real-time vibrometric data acquisition. PMID:18301587

Sano, M; Takeda, M; Fukushima, S; Kurokawa, T

1998-11-10

121

Mapping of domain structure in Barium Titanate single crystals by synchrotron x-ray topography  

Microsoft Academic Search

Imaging of domains is a key step in understanding the microstructure and hence the properties of ferroelectric single crystals. This understanding is essential for exploiting engineered domain configurations to achieve enhanced performance. In this paper, single crystals of Barium Titanate are observed by reflection topography using unfocussed monochromatic synchrotron X-ray light. A 10 x 10 mm polished surface of an

Prashant R. Potnis; John E. Huber; John P. Sutter; Felix Hofmann; Brian Abbey; Alexander M. Korsunsky

2010-01-01

122

Ferroelectric domain reversal in congruent LiTaO3 crystals at elevated temperatures  

E-print Network

Ferroelectric domain reversal in congruent LiTaO3 crystals at elevated temperatures Charles C in congruent LiTaO3 crystals with an increase in temperature from 22 to 250 °C. This is accompaniedV/ mm . The temperature range of 25­200 °C is therefore par- ticularly interesting since many crystal

Gopalan, Venkatraman

123

Monte Carlo Simulations of Spontaneous Ferroelectric Order in Discotic Liquid Crystals  

NASA Astrophysics Data System (ADS)

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

Bose, Tushar Kanti; Saha, Jayashree

2013-06-01

124

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

PubMed

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

Bose, Tushar Kanti; Saha, Jayashree

2013-06-28

125

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

126

Optical interband transitions in [111] poled relaxor-based ferroelectric 0.24Pb(In1/2Nb1/2)O3-(0.76 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystal  

PubMed Central

Optical transmission spectra of single crystal 0.24Pb(In1/2Nb1/2)O3–(0.76 ? x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (x = 0.27, 0.33) were measured in the pseudo-cubic crystallographic directions [111] and [112?]. Ferroelectric domain structures were observed in order to explain the difference of transmittance for the two composition crystals. Wavelength dependence of the absorption coefficients was measured and the optical energy band gaps were calculated for both direct and indirect transitions, which are Egd = 3.09–3.18 eV and Egi = 2.89–2.96 eV, respectively, and the phonon energy is Ep = 0.07–0.08 eV. The transmission spectra were explained by the refractive indices and extinction coefficients measured by spectroscopic ellipsometry. PMID:25170190

Wu, Fengmin; Yang, Bin; Sun, Enwei; Wang, Zhu; Yin, Yongqi; Pei, Yanbo; Yang, Wenlong

2013-01-01

127

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

E-print Network

Dielectric and optical behaviors in relaxor ferroelectric Pb(In1/2Nb1/2)1KxTixO3 crystal C.-S. Tu a%) single crystal grown by the modified Bridgman method with Pb(Mg1/3Nb2/3)0.71Ti0.29O3 (PMNT29%) seed crystal. A diffused phase transition was observed in the temperature region of w430­460 K with strong

128

Ultrashort single-shot pulse characterization with high spatial resolution using localized nonlinearities in ferroelectric domain walls  

Microsoft Academic Search

Second-order nonlinearities localized in the regions adjacent to the ferroelectric domain wall in KTiOPO4 are used to realize a single-shot noncollinear frequency-resolved optical gating arrangement for ultrashort pulse characterization with high spatial resolution. Cerenkov phase matching is utilized to achieve spectral dispersion and makes the same nonlinear crystal applicable over wide spectral ranges from the visible to the mid-infrared.

S. J. Holmgren; C. Canalias; V. Pasiskevicius

2007-01-01

129

Ultrashort single-shot pulse characterization with high spatial resolution using localized nonlinearities in ferroelectric domain walls.  

PubMed

Second-order nonlinearities localized in the regions adjacent to the ferroelectric domain wall in KTiOPO(4) are used to realize a single-shot noncollinear frequency-resolved optical gating arrangement for ultrashort pulse characterization with high spatial resolution. Cerenkov phase matching is utilized to achieve spectral dispersion and makes the same nonlinear crystal applicable over wide spectral ranges from the visible to the mid-infrared. PMID:17546183

Holmgren, S J; Canalias, C; Pasiskevicius, V

2007-06-01

130

Effects of the spontaneous polarization on the structural and dynamic properties of ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

The creation, nearly 30 years ago, of chiral tilted smectic liquid crystals produced spontaneous polar order in a fluid for the first time. Unlike solid-state ferrolectrics in which the polarization is restricted by the symmetry of a crystal lattice, ferroelectric smectics can freely orient in two dimensions. Consequently, the liquid crystal polarization is extremely sensitive to interactions with external boundaries, electric field, and its own intrisic polarity. Optical and x-ray techniques have been used to study these interactions in the following three cases. Total Internal Reflection is used to probe the molecular organization at the interface between a solid substrate and a tilted chiral smectic liquid crystal at temperatures in the vicinity of the bulk antiferroelectric-ferroelectric phase transition. Optical reflectivity data are interpreted using an exact analytical solution of a real model for ferroelectric order at the surface. We discuss the conditions for polar order at the surface, and then demonstrate that in the mixture T3, ferroelectric surface order is expelled below the bulk ferroelectric-antiferroelectric transition. The continuously reorientable (XY-like) ferroelectric polarization density of a chiral smectic liquid crystal is shown experimentally to produce nearly complete screening of the applied electric field in an appropriate cell geometry. This screening, combined with the expulsion of polarization charge for large polarization materials, leads to semiconducting electrical behavior of the otherwise insulating liquid crystal and electrostatic control of the orientation of a uniform optic axis/polarization field. Finally, we determine the structure of an achiral ferroelectric liquid crystal in which the polarization spontaneously produces a periodically splayed structure. The structure of the smectic layers is determined by x-ray diffraction and the molecular order within the layers is deduced from polarized optical microscopy observations. On the basis of the x-ray measurements, we are able to differentiate between two optically-similar phases.

Coleman, David Anthony

2002-08-01

131

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

132

Electro-optical Characteristics of Ferroelectric Liquid Crystal Embedded in Photonic Crystal Fiber  

NASA Astrophysics Data System (ADS)

The confinement of liquid crystals in a small space induces interesting phenomena that deviate from the bulk properties. We report on the electro-optical properties of ferroelectric liquid crystals (FLCs) confined in transparent photonic crystal fibers (PCFs). A PCF has a large number of cylindrical air holes of micrometer size and they are filled with FLCs. Optical measurements indicate that the directors are parallel to the axis of PCF and the layers are inclined relative to the cylindrical wall with the tilt angle of SmC*. The electro-optical response depends on the surface condition and shows the unusual double hysteresis loop. We discuss the possible configuration of director arrangement and the electro-optical properties of FLC on the basis of a simple model.

Yu, Jeong-Seon; Yu, Jong Sung; Kim, Jong-Hyun

2013-05-01

133

Ferroelectric columnar liquid crystal featuring confined polar groups within core-shell architecture.  

PubMed

Ferroelectric liquid crystals are materials that have a remnant and electrically invertible polar order. Columnar liquid crystals with a ferroelectric nature have potential use in ultrahigh-density memory devices, if electrical polarization occurs along the columnar axis. However, columnar liquid crystals having an axial nonzero polarization at zero electric field and its electrical invertibility have not been demonstrated. Here, we report a ferroelectric response for a columnar liquid crystal adopting a core-shell architecture that accommodates an array of polar cyano groups confined by a hydrogen-bonded amide network with an optimal strength. Under an applied electric field, both columns and core cyano groups align unidirectionally, thereby developing an extremely large macroscopic remnant polarization. PMID:22499944

Miyajima, Daigo; Araoka, Fumito; Takezoe, Hideo; Kim, Jungeun; Kato, Kenichi; Takata, Masaki; Aida, Takuzo

2012-04-13

134

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

E-print Network

Intrinsic single-domain switching in ferroelectric materials on a nearly ideal surface S. V, TN, October 2, 2007 (received for review July 6, 2007) Ferroelectric domain nucleation and growth the decoupled Green function theory by using tip geometry determined from the domain wall profile. The critical

Chen, Long-Qing

135

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

136

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

NASA Astrophysics Data System (ADS)

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 ˜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 130-800 µm 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, Wenguang; Kida, Noriaki; Sotome, Masato; Kinoshita, Yuto; Takeda, Ryotaro; Inoue, Akito; Horiuchi, Sachio; Okamoto, Hiroshi

2014-09-01

137

Ferroelectricity in low-symmetry biaxial nematic liquid crystals.  

PubMed

Order parameters and phenomenological theory for both high- and low-symmetry biaxial nematic phases are presented and it is predicted that the chiral low-symmetry biaxial phase must be ferroelectric. This conclusion is based on general symmetry arguments and on the results of the Landau-de Gennes theory. The microscopic mechanism of the ferroelectric ordering in this chiral biaxial phase is illustrated using a simple molecular model based on dispersion interactions between biaxial molecules of low symmetry. Similar to the chiral smectic C* phase, the ferroelectricity in the chiral biaxial nematic phase is improper, i.e., polarization is not a primary order parameter and is not determined by dipolar interactions. Ferroelectric ordering in biaxial nematics may be found, in principle, in materials composed of chiral analogues of the tetrapod molecules which are known to exhibit biaxial phases. PMID:21386515

Osipov, Mikhail A; Gorkunov, Maxim V

2010-09-15

138

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

NASA Astrophysics Data System (ADS)

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

Bose, Tushar Kanti; Saha, Jayashree

2014-05-01

139

Probing the material properties and phase transitions of ferroelectric liquid crystals by determination of the Landau potential.  

PubMed

The full Landau potential of several, widely varying ferroelectric liquid-crystalline materials has been experimentally determined. Tilt angle and polarisation data is analysed across the SmA to SmC transition for varying applied electric-field amplitudes, allowing the determination of all the coefficients of the generalised Landau model of ferroelectric liquid crystals. The materials investigated encompass different materials, including low-polarisation mixtures to high-polarisation single-component materials. The materials also possess a variation in the order of the SmA to SmC phase transition from strongly first order to strongly second order. The effects of both the polarisation and order of phase transition of the system are discussed with respect to the various terms of the generalised Landau model. Further, the mechanisms behind the difference between a first- and second-order phase transition are discussed with respect to the Landau potential and the second Landau coefficient b . PMID:18425407

Archer, P; Dierking, I; Görtz, V; Goodby, J W

2008-04-01

140

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

141

Electro-optical investigations of holographic-polymer-dispersed ferroelectric liquid crystals.  

PubMed

Uniform alignment of ferroelectric liquid-crystal domains encapsulated by a polymer binder was established through a holographic exposure process. The refractive index modulation in these thin films is modeled as a phase grating that can be electrically addressed to erase the optical diffractive properties. A phenomenological model is developed to take into account a distribution of domain sizes and an effective field that stabilizes the ferroelectric liquid-crystal domains. A diffraction model successfully predicts changes in normalized intensities for first-order diffraction with applied field. These gratings demonstrate microsecond-scale response and relaxation times for various grating pitch sizes between approximately 3 and approximately 12 microm. PMID:18059932

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

2007-12-01

142

Photorefractive effect in ferroelectric liquid crystals containing oligo-thiophene chiral compounds  

NASA Astrophysics Data System (ADS)

The photorefractive effect in photoconductive ferroelectric liquid crystals (FLCs) that contain oligo-thiophene chiral compounds was investigated. Ter-thiophene and quarto-thiophene compounds with chiral structures were chosen as the photoconductive chiral compounds and mixed with an achiral smectic C liquid crystal. The mixtures exhibit the ferroelectric chiral smectic C phase. The photorefractivity of the mixtures was investigated by two-beam coupling experiments. It was found that the FLCs containing the photoconductive chiral compound exhibit a large gain coefficient of over 990 cm-1 and a fast response time of 1.7 ms.

Sasaki, Takeo; Ikegami, Masashi; Kajikawa, Satoshi; Naka, Yumiko

2013-09-01

143

A molecular dynamics study of ferroelectric nanoparticles immersed in a nematic liquid crystal.  

PubMed

A large number of interesting phenomena related to the insertion of colloidal particles in liquid crystals (LC) have recently been reported. Here, we investigate effects caused by the addition of spherically shaped ferroelectric nanoparticles to a nematic liquid crystal. Using molecular dynamics (MD) simulations, the density of LC molecules, the orientational order parameter, and the polar and azimuthal angle profiles are calculated as functions of the distance to the center of the immersed nanoparticle for different temperatures of the system. We observe that the assembly of ferroelectric nanoparticles enhances the nematic order in the LC medium changing many properties of its host above the nematic-isotropic transition temperature T (*) (NI) . PMID:20101517

Pereira, M S S; Canabarro, A A; de Oliveira, I N; Lyra, M L; Mirantsev, L V

2010-01-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

145

High-pressure investigations of a ferroelectric liquid crystal exhibiting a trend reversal in the thermal variation of polarization.  

PubMed

In contrast to the exhaustive measurements of various properties of ferroelectric liquid crystals at atmospheric pressure, only a few studies exist at high pressure. Here we report the isobaric thermal variation of spontaneous polarization (P(s)), coercive voltage (U(xc)), and rotational viscosity (?(?)) of a ferroelectric liquid crystal (10PPBN4) as a function of applied pressure. The material having a high value of P(s) exhibits a trend reversal: as the temperature is lowered below the transition from the smectic A to the smectic C* (ferroelectric) phase, P(s) increases to begin with but after reaching a maximum decreases with further decrease in temperature. Interestingly, the trend reversal feature becomes more dominant as the pressure is increased. Further, at a fixed reduced temperature with respect to the transition, all three parameters P(s), U(xc), and ?(?) decrease with pressure. We show that the data can be well described by a model developed for materials exhibiting a sign reversal in P(s). The single characteristic parameter of the model, viz., the ratio of the inversion temperature (at which P(s) changes sign), to the transition temperature, is seen to increase with pressure, corroborating predominance of trend reversal at elevated pressures observed experimentally. PMID:21809816

Bapat, Prasad N; Shankar Rao, D S; Krishna Prasad, S; Naciri, Jawad; Ratna, B R

2011-09-01

146

Ferroelectric domain wall injection.  

PubMed

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

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

2014-01-15

147

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

148

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

PubMed

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

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

2013-08-01

149

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

Microsoft Academic Search

We have investigated photoinduced redistribution of metal nanoparticles, placed on the surface of the ferroelectric photorefractive crystal during recording of dynamic holograms. Motivations for this study were improvement of sensitivity for recording of dynamic holographic gratings, for application in nondestructive testing of materials. The home- made biosynthesized gold and silver colloidal solutions were spread as a thin layer on the

N. Kukhtarev; T. Kukhtareva; J. Wang

2011-01-01

150

Thermal expansion of triglycine fluoroberyllate crystals near the ferroelectric transition point  

Microsoft Academic Search

Here we consider the coefficients of thermal expansion for various crystallographic directions during the transition from the ferroelectric state to the paraelectric one. The measurements were made by dilatometry over the range 120 to 100~ The expansion of the specimens was recorded to 0.1 #m. The specimens were cut from large crystals grown from aqueous solutions by temperature reduction. The

T. A. Zarembovskaya; V. M. Varikash; P. A. Pupkevich

1972-01-01

151

Fast electro-optical mode in photo-aligned reflective deformed helix ferroelectric liquid crystal cells.  

PubMed

The electro-optical behavior of deformed helix ferroelectric liquid crystal in reflective mode is described in this paper. The electrically controlled reflectance has been measured at subkilohertz driving voltage frequency for different polarizations of the incident light and compared quite successfully with the simulation results. PMID:22739902

Guo, Qi; Brodzeli, Zourab; Pozhidaev, Eugene P; Fan, Fan; Chigrinov, Vladimir G; Kwok, Hoi Sing; Silvestri, Leonardo; Ladouceur, Francois

2012-06-15

152

Multiwall carbon nanotubes doped ferroelectric liquid crystal composites: A study of modified electrical behavior  

NASA Astrophysics Data System (ADS)

We systematically investigated the role of carbon nanotubes and their nature of interaction with the high polarization ferroelectric liquid crystal molecules that causes a change in the dynamic behavior of the liquid crystals. The carbon nanotubes were functionalized with carboxyl group (-COOH) before dispersion in order to enhance their stability in the liquid crystal medium. For the systematic investigation of a non linear behavior of dispersed composite systems, results for various physical properties were determined by thermal, morphological and dielectric studies in the planer aligned 5 ?m thickness cells. An effort has also gone into detail to investigate these properties with varying concentration (0.02 wt%, 0.05 wt% and 0.1 wt%) of multiwall carbon nanotubes. The various carbon nanotubes doped ferroelectric liquid crystal thin film composites have shown enhanced dielectric strength and dielectric permittivity values as compared to the undoped sample.

Neeraj; Raina, K. K.

2014-02-01

153

Confinement-Induced Orientational Order in a Ferroelectric Liquid Crystal Containing Dispersed Aerosils  

Microsoft Academic Search

The study of the smectic-A to chiral smectic-C* phase transition of the liquid crystal S-(+)-[4-(2'-methyl butyl) phenyl 4'-n-octylbiphenyl-4-carboxylate] (CE8) containing dispersed hydrophilic aerosils reveals novel properties, important to understanding quenched disorder and confinement in ferroelectric liquid crystals. Smectic layer compression leads to a distribution of transition temperatures inducing smearing of the macroscopic data across the transition. A pronounced confinement-induced pretransitional

George Cordoyiannis; George Nounesis; Vid Bobnar; Samo Kralj; Zdravko Kutnjak

2005-01-01

154

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

Microsoft Academic Search

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

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

2008-01-01

155

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

NASA Astrophysics Data System (ADS)

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

2014-09-01

156

Development of single crystal membranes  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

157

Memory effect in the triglycine sulphate crystal polarized not parallel to the ferroelectric axis  

NASA Astrophysics Data System (ADS)

The experimental results concerning the electric susceptibility ?22 of the triglycine sulphate (TGS) crystal polarized not parallel to the ferroelectric axis at different temperatures have been shown. The process of partial rejuvenation in the ferroelectric phase has been presented. It has been found that the temperature changes of the slope s=d?22-1/dT correspond to step-wise changes of a pyroelectric coefficient p=d P/d T ( P= P2, P3), where P2 and P3 are the longitudinal and transverse polarizations, respectively. An interpretation of temperature dependences of P2 and P3 as well as ?22 of the triglycine sulphate ferroelectric previously exposed to a prolonged transverse electric field has been proposed. It has been concluded that the number of elementary cells containing molecules in metastable states depends on temperature in such a way that some kind of memory effect can be observed.

Fugiel, B.

2006-02-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

159

The elastic and piezoelectric properties of tungsten bronze ferroelectric crystals ,,Sr0.7Ba0.3...2NaNb5O15 and ,,Sr0.3Ba0.7...2NaNb5O15  

E-print Network

The elastic and piezoelectric properties of tungsten bronze ferroelectric crystals ,,Sr0.7Ba0 and piezoelectric constants of tungsten bronze ferroelectric crystals Sr0.7Ba0.3 2NaNb5O15 SBNN70 and Sr0.3Ba0.7 2Na that these single crystals have larger dielectric constant and good piezoelectric property compared to other known

Cao, Wenwu

160

Pressure-induced crossover from long-to-short-range order in Pb,,Zn13Nb23...O30.905,,PbTiO3...0.095 single crystal  

E-print Network

...0.095 single crystal G. A. Samaraa) and E. L. Venturini Sandia National Laboratories, Albuquerque, New Mexico normal ferroelectric­to­relaxor behavior has been observed in single crystal Pb Zn1/3Nb2/3 O3 0.905 Pb with single crystals. Numerous attempts, extending over several decades, to grow PZT crystals of suitable size

161

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

PubMed

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. PMID:17677078

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

2007-05-01

162

Dynamics of the molecular orientation field coupled to ions in two-dimensional ferroelectric liquid crystals.  

PubMed

Molecular orientation fluctuations in ferroelectric smectic liquid crystals produce space charges, due to the divergence of the spontaneous polarization. These space charges interact with mobile ions, so that one must consider the coupled dynamics of the orientation and ionic degrees of freedom. Previous theory and light scattering experiments on thin free-standing films of ferroelectric liquid crystals have not included this coupling, possibly invalidating their quantitative conclusions. We consider the most important case of very slow ionic dynamics, compared to rapid orientational fluctuations, and focus on the use of a short electric field pulse to quench orientational fluctuations. We find that the resulting change in scattered light intensity must include a term due to the quasistatic ionic configuration, which has previously been ignored. In addition to developing the general theory, we present a simple model to demonstrate the role of this added term. PMID:17930051

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

2007-08-01

163

Time-resolved switching analysis of a ferroelectric liquid crystal by snapshot Mueller matrix polarimetry.  

PubMed

An experimental snapshot Mueller matrix polarimeter based on wavelength polarization coding is used to get a time-resolved description of electric-field-induced fast transition within a ferroelectric liquid-crystal cell. The parameters extracted from experimental Mueller matrices are linked to the molecule director distribution to further determine the average trajectory and the collective behavior of these molecules while they switch over to another state. PMID:20364203

Dubreuil, Matthieu; Rivet, Sylvain; Le Jeune, Bernard; Dupont, Laurent

2010-04-01

164

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

165

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

PubMed

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

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

2013-03-29

166

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

167

Piezoelectric anisotropy of KNbO3 single crystal  

SciTech Connect

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

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

2010-11-01

168

Ferroelectric domains inside thick crystals of KNbO3  

Microsoft Academic Search

The domain structures inside the thick crystals of KNbO3 have been revealed using a liquid polishing agent to remove layers of crystals by dissolution without introducing any stress. It is found that entirely new structures unrelated to those on the original surface exist inside. A method has been suggested to analyse complicated domain patterns simply by viewing under a metallurgical

R H Kulkarni; R M Chaudhari; S G Ingle

1973-01-01

169

Reflection from gold-coated deformed-helix ferroelectric liquid crystal cells: theory and experiment  

NASA Astrophysics Data System (ADS)

Liquid crystal (LC) cells can be used in conjunction with optical fibres to develop cheap and efficient sensors, such as voltage sensors or hydrophones. In this paper we apply an effective tensor model to describe reflection from gold-coated deformed-helix ferroelectric liquid crystal (DHFLC) cells. We show that, depending on the polarisation of the incident light, it is possible to obtain a linear electro-optical response to the voltage applied to the cell. Theoretical results are compared with experimental results yielding accurate agreement.

Silvestri, Leonardo; Brodzeli, Zourab; Ladouceur, Francois; Michie, Andrew; Chigrinov, Vladimir G.; Guo, Grace Qi; Pozhidaev, Eugene P.; Kiselev, Alexei D.

2012-02-01

170

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

NASA Astrophysics Data System (ADS)

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 the expansion of the free energy. It is established that the unipolarity coefficient and the pyroelectric signal of nonuniform crystals remain virtually unchanged in multiple heating-cooling cycles.

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

2008-01-01

171

Ferroelectric triglycine sulphate crystals with a profile distribution of chromium impurity  

NASA Astrophysics Data System (ADS)

Some features of the ferroelectric behavior of triglycine sulphate crystals with a nonuniform distribution of chromium impurity have been considered. The dielectric hysteresis loop of the samples is characterized by a large shift along both the polarization axis and the electric field direction. The results are explained well within the phenomenological approach with allowance for the gradient term in the expansion of free energy. It is established that the unipolarity coefficient and pyroelectric signal of inhomogeneous crystals barely changes during multiple heating-cooling cycles.

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

2010-05-01

172

Phase-transitions in Langmuir-Blodgett and cast films of a ferroelectric liquid crystal.  

PubMed

Langmuir-Blodgett films and cast films of a ferroelectric liquid crystal of sec-butyl-6-(4-(nonyloxy)benzoyloxy)-2-naphthoate have been fabricated. Their thermal behavior was investigated using infrared spectroscopy at elevated temperature combined with principal component analysis. The result shows a new phase transition from smectic A to nematic phase, compared to the phase sequence obtained by polarizing optical microscopy. Another solid transition of different isomeric crystals was also found, which was confirmed by calorimetric measurement. PMID:17625316

Wen, Zi; Jiang, Qing; DU, Yiping; Ozaki, Yukihiro

2007-07-01

173

Solitons induced by alternating electric fields in surface-stabilized ferroelectric liquid crystals.  

PubMed

Propagation of solitary waves activated in thin ferroelectric liquid crystal cells under external, sinusoidally alternating electric fields is investigated using the electro-optic technique. It is shown that solitons give contributions only to the loss component of the response spectrum, within rather narrow ranges of frequencies and in sufficiently strong fields. The limit frequency, at which the amplitude of the velocity of the solitary waves is greatest, is found to be related to material constants of liquid crystals. Measuring this threshold frequency provides the capability to determine the elastic constant of surface stabilized liquid crystalline materials in the bookshelf or chevron layer geometries. PMID:21599223

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

2011-04-01

174

Nanoscale Calorimetry of Isolated Polyethylene Single Crystals  

E-print Network

Nanoscale Calorimetry of Isolated Polyethylene Single Crystals A. T. KWAN, M. YU. EFREMOV, E. A-film differential scanning calorimetry to investigate the melt- ing of isolated polyethylene single crystals: microelectromechanical systems; calorimetry; nanocalorimetry; polyeth- ylene single crystals; melting INTRODUCTION We

Allen, Leslie H.

175

Photon tunnelling microscopy of polyethylene single crystals  

E-print Network

Photon tunnelling microscopy of polyethylene single crystals Mohan Srinivasarao* and Richard S polyethylenesinglecrystals, providing a topographical map ofthe single-crystal surface.Tunnelling increases exponentially:photon tunnellingmicroscopy;single crystals; polyethylene) INTRODUCTION The study of morphology of polymers is an area

Srinivasarao, Mohan

176

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

177

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

178

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

Microsoft Academic Search

We have made a direct optical observation of pinning and bowing of a single 180° ferroelectric domain wall under a uniform applied electric field using a collection mode near-field scanning optical microscope. The domain wall is observed to curve between the pinning defects, with a radius of curvature determined by the material parameters and the applied electric field. The change

T. J. Yang; U. Mohideen; V. Gopalan; P. J. Swart

1999-01-01

179

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

Microsoft Academic Search

We have made a direct optical observation of pinning and bowing of a single 180° ferroelectric domain wall under a uniform applied electric field using a collection mode near-field scanning optical microscope. The domain wall is observed to curve between the pinning defects, with a radius of curvature determined by the material parameters and the applied electric field. The change

T. J. Yang; Venkatraman Gopalan; P. J. Swart; U. Mohideen

1999-01-01

180

Collective rotations of ferroelectric liquid crystals at the air/water interface.  

PubMed

We study the Langmuir monolayers of four different ferroelectric liquid crystals on water surface. Two of them are attached to water surface by their polar groups, and the chiral groups, at the opposite ends of the elongated molecules, remain well above the interface. The other two ferroelectrics have both groups (polar and chiral) at close proximity, and therefore the chiral group is also attached to the surface or even submerged in water. We demonstrate that only when the chiral group of the ferroelectric liquid crystal in Langmuir monolayer is not attached to the interface and stays in the air does the system exhibit the collective rotations induced by evaporation of water (described for the first time by: Tabe, Y.; Yokoyama, H. Nat. Mater. 2003, 2, 806). The isotherms of surface pressure and surface potential versus molecular area of four compounds were measured with simultaneous observations using Brewster angle microscopy. Experimental data of the compression isotherms are described with a van der Waals model with very good accuracy, and the fitted parameters were used for calculations of compressibility coefficients for different phases found in the compounds under investigations. The ability of the two compounds for rotation and the disability of the two others is discussed in a context of thermodynamic properties of the monolayers. PMID:18826262

Milczarczyk-Piwowarczyk, Patrycja; Zywoci?ski, Andrzej; Noworyta, Krzysztof; Ho?yst, Robert

2008-11-01

181

Single-step colloidal processing of stable aqueous dispersions of ferroelectric nanoparticles for biomedical imaging  

NASA Astrophysics Data System (ADS)

The biomedical applications of ferroelectric nanoparticles rely on the production of stable aqueous colloids. We report an implementation of the high energy ball milling method to produce and disperse ultrafine BaTiO3 nanoparticles in an aqueous media in a single step. This technique is low-cost, environmentally friendly and has the capability to control nanoparticle size and functionality with milling parameters. As a result, ultrafine nanoparticles with sizes as small as 6 nm can be produced. These nanoparticles maintain ferroelectricity and can be used as second harmonic generating nanoprobes for biomedical imaging. This technique can be generalized to produce aqueous nanoparticle colloids of other imaging materials.

Zribi, Olena; Garbovskiy, Yuriy; Glushchenko, Anatoliy

2014-12-01

182

Effect of the intrinsic width on the piezoelectric force microscopy of a single ferroelectric domain wall  

SciTech Connect

Intrinsic domain wall width is a fundamental parameter that reflects bulk ferroelectric properties and governs the performance of ferroelectric memory devices. We present closed-form analytical expressions for vertical and lateral piezoelectric force microscopy PFM profiles of a single ferroelectric domain wall for the conical and disk models of the tip, beyond point charge and sphere approximations. The analysis takes into account the finite intrinsic width of the domain wall and dielectric anisotropy of the material. These analytical expressions provide insight into the mechanisms of PFM image formation and can be used for a quantitative analysis of the PFM domain wall profiles. The PFM profile of a realistic domain wall is shown to be the convolution of its intrinsic profile and the resolution function of PFM.

Morozovska, Anna N [Institute for Problems of Materials Science, NAS of Ukraine; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Svechnikov, S. V. [National Academy of Science of Ukraine, Kiev, Ukraine; Gopalana, V. [Pennsylvania State University; Kalinin, Sergei V [ORNL

2008-01-01

183

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

PubMed

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 200000 s(-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. PMID:17677466

Copic, Martin; Mertelj, Alenka; Buchnev, Olexandr; Reznikov, Yuri

2007-07-01

184

Acoustic attenuation in ferroelectric Sn2P2S6 crystals  

NASA Astrophysics Data System (ADS)

The temperature and frequency dependencies of sound attenuation for the proper uniaxial ferroelectric Sn2P2S6, which has a strong nonlinear interaction of the polar soft optic and fully symmetrical optic modes that is related to the triple well potential, were studied by Brillouin spectroscopy. It was found that the sound velocity anomaly is described in the Landau-Khalatnikov approximation with one relaxation time. For explanation of the observed temperature and frequency dependencies of the sound attenuation in the ferroelectrric phase, the accounting of several relaxation times is needed and, for quantitative calculations, the mode Gruneisen coefficients are more appropriate as interacting parameters than are the electrostrictive coefficients. Relaxational sound attenuation by domain walls also appears in the ferroelectric phase of Sn2P2S6 crystals.

Kohutych, Anton A.; Yevych, Ruslan M.; Perechinskii, Sergij I.; Vysochanskii, Yulian M.

2010-12-01

185

Scanning probe microscopy applied to the study of domains and domain walls in a ferroelectric KNbO3 crystal  

Microsoft Academic Search

A commercial Atomic Force Microscope (AFM) and a semi-home made Scanning Near-Field Optical Microscope (SNOM) have been used to characterize electrically, topographically and optically the domain walls among natural ferroelectric domains in a KNbO3 crystal. The AFM measurements have been performed with a metallic coated tip in order to detect electrostatic forces between the polarization field at the ferroelectric surface

J. CANET-FERRER; J. L. VALDÉS

186

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

187

Landau model for polymer-stabilized ferroelectric liquid crystals: experiment and theory.  

PubMed

The interaction between a phase separated polymer network and a liquid crystal was studied across the smectic-A* (Sm-A*) to smectic-C* (Sm-C*) phase transition of a polymer-stabilized ferroelectric liquid crystal polymerized in the Sm-A* phase. Using precise measurements of the tilt angle and the spontaneous polarization as functions of the external electric field and polymer concentration, the effective coefficients of the Landau expansion of the free energy of the Sm-C* phase have been determined experimentally. The observed polymer concentration dependence of the Landau expansion coefficients is explained using a more general theoretical model which incorporates the effect of polymer networks on the local liquid crystal director configuration. In particular, using experimental estimates of the penetration depth of the polymer network into the liquid crystal, it is shown that the b coefficient calculated from the Landau model increases with polymer concentration, evidencing the relationship determined experimentally. PMID:19113139

Archer, Paul; Dierking, Ingo; Osipov, Mikhail

2008-11-01

188

Orientation of the Ferroelectric Domain Wall in Triglycine Sulfate Crystals  

Microsoft Academic Search

The domain wall energy as a function of wall orientation in triglycine sulfate (TGS) crystals has been calculated on the basis of the Zhirnov-type continuum theory. Contrary to the Fousek's misleading conclusion [Japan. J. appl. Phys. 6 (1967) 950.], the isotropic treatment of the correlation-energy coefficient kappa gives an inadequate result to explain the observed wall orientation which is nearly

Jun Hatano; Fujio Suda; Hideo Futama

1976-01-01

189

Elastic, dielectric, and piezoelectric constants of Pb,,In1/2Nb1/2...O3Pb,,Mg1/3Nb2/3...O3PbTiO3 single crystal poled  

E-print Network

resonance and ultra- sonic methods. The PIN-PMN-PT ternary relaxor based ferroelectric single crystal has single crystal poled along 011c Enwei Sun,1,2 Shujun Zhang,2 Jun Luo,3 Thomas R. Shrout,2 and Wenwu Cao1 Received 30 May 2010; accepted 29 June 2010; published online 20 July 2010 Ternary single crystals xPb In1

Cao, Wenwu

190

Experimental study of internal fields and movement of single ferroelectric domain walls  

Microsoft Academic Search

We have made a direct and submicron scale measurement of the strain, internal electric field of single 180° domain walls in ferroelectric LiTaO3 using a collection mode Near-Field Scanning Optical Microscope. We unambiguously identify single domain walls by simultaneously recording nanometer scale topographic and optical images. The birefringence at the domain wall is used in the optical imaging. From the

T. J. Yang; V. Gopalan; P. Swart; U. Mohideen

2000-01-01

191

Elastic stability of high coupling ternary single crystals  

NASA Astrophysics Data System (ADS)

A sub-hertz harmonic force was used to investigate the elastic response of ternary (1-y-x)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT) single crystal with compositions (x = 0.30 and x = 0.33) near the Morphotropic Phase Boundary (MPB) under isothermal and zero-field conditions. The observed instability under mechanical compression is attributable to a ferroelectric rhombohedral FR-ferroelectric orthorhombic FO phase transformation. The associated strain is a function of proximity to MPB and is consistent with the prediction of the classical Devonshire theory. Isothermal resonance-antiresonance frequency sweeps versus temperature revealed a non-vertical MPB with (?TRT/?x)<0, where TRT is the rhombohedral-tetragonal transition temperature. These results provide insights into the role of PT content on the stability of PIN-PMN-PT crystals used for electromechanical devices and sound projectors.

Finkel, Peter; Murphy, Colin J.; Stace, Joseph; Bussmann, Konrad; Heitmann, Adam; Amin, Ahmed

2013-05-01

192

Voltage sensor based on Deformed Helix Ferroelectric Liquid Crystal  

NASA Astrophysics Data System (ADS)

In this paper we propose a new approach to fibre optic voltage sensors via voltage-controlled Liquid Crystals (LC), which would allow direct measurement of up to 400 kV/m electric fields at multiple points. In addition, a novel polarization independent fibre optic sensor configuration is presented that exhibits a linear electro-optic (EO) response to variations of the electrical field under test.

Brodzeli, Zourab; Ladouceur, Francois; Silvestri, Leonardo; Phung, Toan; Michie, Andrew; Chigrinov, Vladimir; Guo, Grace Qi; Pozhidaev, Eugene P.; Kiselev, Alexei D.

2012-02-01

193

Ferroelectric polymer nano-flake crystal: Effect of counter charge  

Microsoft Academic Search

Recently, we have shown that crystalline two monolayer thick free standing film, ldquonano-flakerdquo, of polar phase of poly(vinylidene fluoride) grows intrinsically off substrate in vacuum under depolarization field neutralizing condition by use of a molecular dynamics simulation method [1]. The nucleation and growth of the ldquonano-flakerdquo crystal is achieved only for the depolarization field neutralizing condition. Here, we discuss the

Nobuyuki Takahashi; Masamichi Hikosaka

2008-01-01

194

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

195

Maier-Saupe-type theory of ferroelectric nanoparticles in nematic liquid crystals.  

PubMed

Several experiments have reported that ferroelectric nanoparticles have drastic effects on nematic liquid crystals-increasing the isotropic-nematic transition temperature by about 5 K, and greatly increasing the sensitivity to applied electric fields. In a recent paper [Lopatina and Selinger, Phys. Rev. Lett. 102, 197802 (2009)], we modeled these effects through a Landau theory, based on coupled orientational order parameters for the liquid crystal and the nanoparticles. This model has one important limitation: Like all Landau theories, it involves an expansion of the free energy in powers of the order parameters, and hence it overestimates the order parameters that occur in the low-temperature phase. For that reason, we now develop a new Maier-Saupe-type model, which explicitly shows the low-temperature saturation of the order parameters. This model reduces to the Landau theory in the limit of high temperature or weak coupling, but shows different behavior in the opposite limit. We compare these calculations with experimental results on ferroelectric nanoparticles in liquid crystals. PMID:22181153

Lopatina, Lena M; Selinger, Jonathan V

2011-10-01

196

Titania single crystals with a curved surface.  

PubMed

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. PMID:25373513

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

2014-01-01

197

Classification of laminate domain patterns in ferroelectrics  

NASA Astrophysics Data System (ADS)

Ferroelectric crystals are known to adopt low-energy, compatible domain configurations. Observations show that these configurations are commonly multirank laminate patterns. In this work, a method to classify and enumerate the laminate domain patterns that can form is presented. The criteria of exact compatibility for laminates structures in a ferroelectric single crystal are used to find all the rank-2 arrangements of domains in the polar tetragonal crystal system. Surprisingly, only eight distinct rank-2 laminate patterns that satisfy compatibility conditions at all domain walls are found. These patterns are classified and correlated with observations of domains in single crystals, showing good agreement.

Tsou, N. T.; Potnis, P. R.; Huber, J. E.

2011-05-01

198

Effects of ferroelectric nanoparticles on ion transport in a liquid crystal  

NASA Astrophysics Data System (ADS)

A small quantity of BaTiO3 ferroelectric nanoparticles (FNPs) of 50 nm diameter was doped in a nematic liquid crystal (LC), and the free ion concentration was found to be significantly reduced in the LC + FNP hybrid compared to that of the pure LC. The strong electric fields, due to the permanent dipole moment of the FNPs, trapped some mobile ions, reducing the free ion concentration in the LC media. The reduction of free ions was found to have coherent impacts on the LC's conductivity, rotational viscosity, and electric field-induced nematic switching.

Basu, Rajratan; Garvey, Alfred

2014-10-01

199

Surface-stabilized ferroelectric liquid-crystal diffraction gratings with micrometer-scale pitches.  

PubMed

The first-order diffraction efficiency eta1 of surface-stabilized ferroelectric liquid-crystal (SSFLC) phase gratings is calculated for device thicknesses in the range d = 1 to 5 microm and for pitches p of 5 to 20 microm assuming incident light at 633 nm. The peak value of eta1 as a function of d has negligible dependence on the incoming polarization when p = 20 microm. For smaller pitch values the peak value of eta1 decreases and becomes increasingly dependent on the orientation of the incoming polarization owing to the influence of the domain walls that occur between the SSFLC pixels. PMID:15495418

Brown, Carl V; Kriezis, Emmanouil E

2004-10-01

200

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

SciTech Connect

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

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

2007-03-15

201

Memory effect in weakly anchored surfaces of deformed helix ferroelectric liquid crystals.  

PubMed

A wide-range memory effect in deformed helix ferroelectric liquid crystals (DHFLCs) has been investigated by electro-optical and textural methods. A comparative study has been performed on strongly and weakly anchored surfaces of DHFLC cells. The saturation voltage has been compared in both types of cells by studying the variation of tilt angle and spontaneous polarization with applied voltage. The long-lasting memory effect has been observed in untreated (weakly anchored) cells. It has been proposed that perfect memory in DHFLC cells without any surface treatment is due to the possibility of the absence of depolarization and ionic charges over the surfaces of the cells. PMID:18850852

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

2008-08-01

202

Topological ferroelectric bistability in a polarization-modulated orthogonal smectic liquid crystal.  

PubMed

We report a bent-core liquid crystal (LC) compound exhibiting two fluid smectic phases in which two-dimensional, polar, orthorhombic layers order into three-dimensional ferroelectric states. The lower-temperature phase has a uniform polarization field which responds in an analog fashion to applied electric field. The higher-temperature phase is a new smectic state with periodic undulation of the polarization, structurally modulated layers, and a bistable response to applied electric field which originates in the periodically splay-modulated bulk of the LC rather than by surface stabilization at the cell boundaries. PMID:22545731

Zhu, Chenhui; Shao, Renfan; Reddy, R Amaranatha; Chen, Dong; Shen, Yongqiang; Gong, Tao; Glaser, Matthew A; Korblova, Eva; Rudquist, Per; Maclennan, Joseph E; Walba, David M; Clark, Noel A

2012-06-13

203

Optimization of alignment quality of ferroelectric liquid crystals by controlling anchoring energy  

NASA Astrophysics Data System (ADS)

Photoalignment allows precise control of anchoring energy, which enables the optimization of the alignment quality of ferroelectric liquid crystal (FLC) devices. Thus, the accurate measurement of the anchoring energy coefficient of the alignment layer in the FLC regime is critical. However, the methods proposed to date have several limitations and are not useful for FLC cells with a helical structure. In this paper, a method based on the evaluation of the optical relaxation time is proposed. The method is valid for both helical and helix-free FLC cells. The optimal anchoring energy to achieve the best alignment quality of FLCs is also investigated.

Guo, Qi; Srivastava, Abhishek K.; Pozhidaev, Evgeny P.; Chigrinov, Vladimir G.; Kwok, Hoi-Sing

2014-02-01

204

Effect of carbon nanotubes on response time of ferroelectric liquid crystals.  

PubMed

We present the results of the fast electro-optic response of multiwalled carbon nanotubes (MWCNTs)-doped deformed helix ferroelectric liquid crystal (DHFLC). The fastening of the response in MWCNTs-doped DHFLC has been attributed to the decrease in rotational viscosity and increase in anchoring energy. The decrease in the former is due to the experience of the torque both by MWCNTs and DHFLC and perturbation of order parameter of the DHFLC while the increase in the latter is due to the pi-pi electrons stacking between the MWCNTs, DHFLC molecules, and alignment layers. The increase in conductance in doped cells has also been observed. PMID:19658752

Prakash, J; Choudhary, A; Mehta, D S; Biradar, A M

2009-07-01

205

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

NASA Astrophysics Data System (ADS)

We disclose the vertically aligned deformed helix ferroelectric liquid crystal (VADHFLC) whose Kerr constant ($K_{\\mathrm{kerr}}\\approx 130$~nm/V$^2$ at $\\lambda=543$~nm) is 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$\\pi$ have been obtained at sub-kilohertz frequency.

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

2014-05-01

206

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

208

Dielectric relaxation of a ferroelectric liquid crystal showing anomalous behaviour due to polarization inversion  

NASA Astrophysics Data System (ADS)

The present study reports the dielectric study of a ferroelectric liquid crystal (FLC) material Felix 016/030 showing anomalous dielectric behaviour. This anomalous behaviour is explained on the basis of a model of dynamically fluctuating mixture of two interconvertible conformers, whose relative density changes with temperature. We have observed Goldstone mode of dielectric relaxation in the frequency range covered. The experimental results have been corrected for low and high frequency range and used to determine dielectric permittivity. The anomalous behaviour of dielectric permittivity has also been verified by discussing the temperature dependence behaviour of PS/Sin ? term where Ps is spontaneous polarization of the sample.

Misra, Abhishek Kumar; Pandey, Kamal Kr; Tripathi, Pankaj Kr; Manohar, Rajiv

2013-06-01

209

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

210

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

PubMed

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

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

2005-12-12

211

Electrochromism accompanying ferroelectric domain inversion in congruent RuO2:LiNbO3 crystal  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

212

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

213

Growth of single crystal diamond  

NASA Astrophysics Data System (ADS)

The subject of the research presented in this dissertation is the growth of single crystal diamond by microwave plasma chemical vapor deposition (CVD). Both heteroepitaxial and homoepitaxial growth methods have been examined, with emphasis on producing large diamond crystals of high structural and chemical perfection. By heteroepitaxy, epitaxial growth on a foreign substrate, diamond was grown on (001) Ir thin-film epitaxial buffer layers deposited on (001) strontium titanate (SrTiO3) by DC magnetron sputtering. To nucleate diamond on Ir, the Ir surface was bombarded with low energy ions extracted from the hydrocarbon plasma, a process known as DC biasing or bias-enhanced nucleation. Since this critical process is poorly understood, attention was paid to the spatial and temporal evolution of the Ir surface during the bias treatment. It was discovered that the biased Ir surface is etched on a surprisingly short time scale during which highly correlated nanopillars, 3-4 nm in height with mean separation 15 nm, emerge. The etching process is spatially non-uniform, propagating from substrate center to substrate edge in minutes. Diamond grew on Ir without an intervening phase. Lattice images revealed that interfacial strain from the 7% Ir-diamond lattice mismatch is largely relieved by misfit dislocations within 1 nm of the interface. It is suggested that the high nucleation density obtained with specific bias conditions is associated with the roughened Ir surface. To grow heteroepitaxial diamond as thick films, a two-step growth method was explored. This process involved the transfer of a thin heteroepitaxial diamond film, still attached to a substrate, to a second reactor where high growth rate conditions were possible. Characterization of films grown by this approach showed that the resulting diamond had much lower levels of internal strain, suggesting that the process could be used to grow diamond crystals of structural quality similar to natural diamond. In homoepitaxy, epitaxial growth on a substrate of the same material, diamond was deposited by CVD directly onto high-pressure, high-temperature Type Ib diamond substrates. Methods for removing substrate surface damage, as well as other imperfections, were devised by use of plasma etching. The characteristics and statistics of pits formed during etching were studied. Diamond growth methods were developed with the aim of minimizing the formation of various structural and chemical defects. To accomplish this, several growth parameters were varied, including substrate temperature, feed gas concentration, growth rate, substrate surface, microwave power, and reactor geometry. Regions of parameter space were found in which the diamond (001) surface remained smooth during growth, and complete suppression of instabilities that create hillocks or non-epitaxial crystallites was demonstrated. A great deal of information was obtained by interrupting growth, removing the crystal from the reactor for optical inspection, and then resuming the process with no apparent negative effects. Diamond crystals were grown on 3 x 3 mm2 substrates with thicknesses greater than 0.5 mm. The chemical purity of the crystals was such that it was impossible to observe signatures of substitutional nitrogen at the ppm level.

Regmi, Murari

214

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

E-print Network

domain wall contributions. Introduction Relaxor-based ferroelectric single crystals, such as (1 - x) Pb field corresponding to an electric-induced ferroelectric phase transition. At 360 K, the PMN­0.3PT and mechani- cal loss factors are observed in mono-domain state, which indicates that losses mainly come from

Cao, Wenwu

215

Barkhausen jumps in the motion of a single ferroelectric domain wall  

Microsoft Academic Search

It is shown that the motion of a domain wall in the improper ferroelectric-ferroelastic gadolinium molybdate Gd2(MoO4)3 demonstrates a self-organized critical behavior under polarization reversal. Barkhausen pulses are measured experimentally\\u000a during the jumpwise motion of a single plane domain wall in monocrystalline plates with artificial pinning centers of the\\u000a “field inhomogeneity” type.

V. Ya. Shur; V. L. Kozhevnikov; D. V. Pelegov; E. V. Nikolaeva; E. I. Shishkin

2001-01-01

216

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

217

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

PubMed

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

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

2007-05-01

218

Observation of localized domain reversal of iron-doped potassium niobate (Fe: KNbO3) single crystal  

Microsoft Academic Search

Localized reversal of patterns formed by ferroelectric domains on the naturally grown surface in an iron-doped potassium niobate (Fe: KNbO3) single crystal has been observed. Surface-profile measurement, scanning electronic microscopy, and the metalomicroscopy methods were used to verify the observation. The mechanism of forming this domain structure is discussed.

Zheng Lu; Min Xiao

1994-01-01

219

Observation of localized domain reversal of iron-doped potassium niobate (Fe: KNbO3) single crystal  

NASA Astrophysics Data System (ADS)

Localized reversal of patterns formed by ferroelectric domains on the naturally grown surface in an iron-doped potassium niobate (Fe: KNbO3) single crystal has been observed. Surface-profile measurement, scanning electronic microscopy, and the metalomicroscopy methods were used to verify the observation. The mechanism of forming this domain structure is discussed.

Lu, Zheng; Xiao, Min

1994-10-01

220

High-Resolution Calorimetric Study of Pb(Mg1/3Nb2/3)O3 Single Crystal  

NASA Astrophysics Data System (ADS)

Motivated by the long-standing unresolved enigma of the relaxor ferroelectric ground state, we performed a high-resolution heat capacity and polarization study of the field-induced phase transition in the relaxor ferroelectric single crystal Pb(Mg1/3Nb2/3)O3 (PMN) oriented along the [110] direction. We show that the discontinuous evolution of polarization as a function of the electric field or temperature is a consequence of a true first order transition from a glassy to ferroelectric state, which is accompanied by an excess heat capacity anomaly and released latent heat. We also find that in a zero field there is no ferroelectric phase transition in bulk PMN at any temperature, indicating that the nonergodic dipolar glass phase persists down to the lowest temperatures.

Novak, Nikola; Pirc, Raša; Wencka, Magdalena; Kutnjak, Zdravko

2012-07-01

221

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

222

Shock-induced electrical conductivity in some ferroelectrics  

Microsoft Academic Search

This paper gives the results of measurement of shock-induced electrical conductivity in ferroelectrics: PKR-1 lead zirconate-titanate\\u000a piezoceramic, deuterated triglycerine sulphate single crystal, and polymer polyvinylidene fluoride.

V. A. Bragunets; V. G. Simakov; V. A. Borisenok; S. V. Borisenok; V. A. Kruchinin

2010-01-01

223

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 domain as the energetic cost of forming domain walls. The second term W is the stored energy density (Landau energyA Mesoscopic Electromechanical Theory of Ferroelectric Films and Ceramics Jiangyu Li and Kaushik

Bhattacharya, Kaushik

224

Observation of Structural Phase Transition in Ferroelectric Crystals Using Green Fluorescence Protein  

NASA Astrophysics Data System (ADS)

The Green Fluorescence Protein (GFP) of the jellyfish Aequorea Victoria has attracted widespread interest as a biomolecular marker. It has created many applications in a variety of systems ranging from cell biology to biomedicine. One important application of GFP fluorescence is the detection of structural transitions in biomolecules.In order to examine the sensitivity of the protein fluorescence to structural changes, we sequestered GFP in ferroelectric crystals such as Triglycine sulfate (TGS) and Rochelle salt (RS). TGS has a second order phase transition at 49 C while RS has two phase transitions at -18 and +24 C. The peak of the fluorescence spectrum changes from 510 nm in solution to 470 nm in the crystal indicating a shift of the two absorption bands in the protein upon crystallization. The fluorescence intensity of GFP in TGS decreases as the temperature of the crystal approaches T_C, while its spectrum in RS shows complex changes with temperature. The changes in the time-resolved data are similar to that of the steady state data. Our data show that the onset of structural phase transition in these crystals is clearly detectable from the spectral changes of this chromophore. Other applications of this protein in time-resolved solid state dynamics will be discussed.

Sedarous, Salah; Wessels, William

1998-03-01

225

Ames Lab 101: Single Crystal Growth  

SciTech Connect

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

Schlagel, Deborah

2013-09-27

226

Ames Lab 101: Single Crystal Growth  

ScienceCinema

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

Schlagel, Deborah

2014-06-04

227

Single crystals for welding research  

SciTech Connect

Most welds last for many years, but a few fail after a relatively short time. Knowing the reasons why welds fail is important because cracks in welds can threaten the safety of people in buildings, airplanes, ships, automobiles, and power plants. Bad welds can lead to costly, extended shutdowns of industrial facilities such as petroleum refineries. Thus, research on this very important fabrication technology is critical to the multibillion-dollar welding industry. Research at ORNL and elsewhere strives to determine the structural features that make some welds strong and others weak. The goals are to find cost-effective ways to characterize the structure and strength of a new weld, correctly predict whether it will last a long time, and determine the welding conditions most likely to produce high-quality welds. There is more to welding than meets the eye. The cracks that make welds fail result from the complexities of microstructures formed during welding. Thus weld microstructure is linked to weld properties such as mechanical strength. As the hot weld material cools from a liquid into a solid, the crystalline grains grow at different speeds and in different directions, forming a new microstructure. By using single crystals rather than polycrystalline alloys to study different weld microstructures, scientists at ORNL have developed a way to predict more accurately the microstructures of various welds. The results could guide welders in providing the right conditions (correct welding speed, heat input, and weld thickness) for producing safer, higher-quality, and longer-lasting welds.

David, S.A.; Boatner, L.A.

1991-01-01

228

Blue SHG Enhancement by Silver Nanocubes Photochemically Prepared on a RbTiOPO4 Ferroelectric Crystal.  

PubMed

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

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

2014-10-01

229

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

230

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

231

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

PubMed

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

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

2014-01-01

232

Figures of merit for ferroelectric electron emission cathodes  

NASA Astrophysics Data System (ADS)

Pyroelectrically induced electron emission from different ferroelectric single crystals and ceramics is studied. It is observed that (Pb,La)(Zr,Ti)O3 ceramics generate rather low ferroelectric electron emission (FEE) current compared with single crystals such as triglycine sulphate and lithium niobate. Figures of merit for FEE cathodes in the pyroelectric excitation mode are derived. It is shown that a physical origin and consequently figures of merit are quite different for FEE cathodes and conventional field electron cathodes.

Shur, D.; Rosenman, G.

1996-09-01

233

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

SciTech Connect

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

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

2013-08-28

234

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

E-print Network

is achieved using multirank laminates. It offers an advantage of specifying different types of domain wall 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

Shu, Yi-Chung

235

Midinfrared modulation through the use of field-induced scattering in ferroelectric liquid crystals.  

PubMed

The feasibility of the use of modulation devices based on field-induced transient scattering in ferroelectric liquid crystals (LC) to replace mechanical choppers used in uncooled infrared-imaging systems was investigated. Devices fabricated with ITO-coated ZnSe substrates and a ferroelectric LC path length of 25 µm were able to modulate optical radiation by transient forward scattering at rates approaching 20 kHz. Through the use of a commercial arbitrary waveform generator and associated PC-based software, drive waveforms were developed that produced a variable, square-wave optical-modulation pattern by the extension of the duration of the scattering state to periods ranging from hundreds of microseconds to milliseconds. The ability of these extended-scattering-mode (ESM) devices to modulate radiation in both the visible and midinfrared regions was verified in a simple experiment through the use of a Fourier-transform infrared spectrometer, in which an unoptimized ESM device displayed a 40% modulation dep th for IR radiation in the 8-12-µm region. PMID:21060525

Marshall, K L; Jacobs, S D; Miller, J E

1995-10-10

236

Propagation of quasilongitudinal ultrasonic waves in the ferroelectric plane of TGS crystals  

NASA Astrophysics Data System (ADS)

The velocity of quasilongitudinal ultrasonic waves in ferroelectric triglycine sulphate crystals was measured for 12 different directions of its propagation in the plane (010) for temperatures ranging from 273 to 343 K. Applying Christoffel's equation, six components of the elastic stiffness tensor describing the wave propagation and their temperature changes in the range studied were computed. Deviations of the normal vibration vector and the group velocity vector from the wave propagation vector were calculated, too. The wave was found to be “pure” for the directions close to the crystallographic axes a and c in the Hoshino system. Moreover, for the direction where the piezoelectric coefficient value was equal to zero, an additional minimum of deviation was observed. This value decreases with the temperature increase and, at the temperature (355±2)K, it is expected to run to zero. The anisotropy of the wave velocity changes at the transition from ferroelectric to paraelectric phase was determined. These changes were found to be equal to zero for the propagation directions making angles of -65° and +55° with the axis [001].

Tylczy?ski, Z.

1981-12-01

237

Ferroelectric ordering in chiral smectic-C* liquid crystals determined by nonchiral intermolecular interactions.  

PubMed

General microscopic mechanism of ferroelectric ordering in chiral smectic-C* liquid crystals is considered. It is shown that if the mesogenic molecules have a sufficiently low symmetry, the spontaneous polarization is proportional to one of the biaxial vector order parameters of the smectic-C phase. This order parameter may be determined by intermolecular interactions which are not sensitive to molecular chirality. At the same time, the polarization is also proportional to a pseudoscalar parameter which vanishes if the molecules are nonchiral. The general statistical theory of ferroelectric ordering is illustrated by two particular models. The first model is based on electrostatic quadrupole-quadrupole interactions, and it enables one to obtain explicit analytical expressions for the spontaneous polarization. In the second model, the molecular chirality and polarity are determined by a pair of off-center nonparallel dipoles. For this case, the spontaneous polarization is calculated numerically as a function of temperature. The theory provides a more general interpretation of the previous approaches including the classical Boulder model. PMID:18517400

Osipov, M A; Gorkunov, M V

2008-03-01

238

Dielectric, hypersonic, and domain anomalies of ,,PbMg13Nb23O3...1x,,PbTiO3...x single crystals  

E-print Network

Dielectric, hypersonic, and domain anomalies of ,,PbMg1Ã?3Nb2Ã?3O3...1Ã?x,,PbTiO3...x single crystals been measured as a function of temperature in relaxor-based ferroelectric single crystals (PbMg1/3Nb2 increases, the PMN-24%PT crystal gradually develops cubic regions and is fully converted into the cubic

239

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

240

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

NASA Astrophysics Data System (ADS)

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

Singh, D. P.; Gupta, S. K.; Manohar, R.; Varia, M. C.; Kumar, S.; Kumar, A.

2014-07-01

241

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

242

Fabrication of vertical alignment in ferroelectric liquid crystals for display application  

NASA Astrophysics Data System (ADS)

In this study, we focus on vertical alignment ferroelectric liquid crystals (VA-FLCs), because an FLC display with a high contrast ratio is expected. In the VA, although the normal of smectic layers is vertical to the substrate surface, the director of FLC molecules must tilt to the substrate surface at the tilt angle of FLC molecules. Thus, it is usually difficult to obtain a uniform VA in FLCs. We determine the optimum conditions for the fabrication of VA-FLC cells in terms of the tilt angle of FLC molecules, the anchoring strength of the alignment film, and the cell gap. Results indicate that the FLC with a small tilt angle tends to form good VA, which can be obtained by utilizing alignment films with high surface anchoring strengths. Good VA strongly depends on the cell gap.

Furue, Hirokazu; Horiguchi, Toshiki; Yamamichi, Miyuki; Oka, Shinichiro; Komura, Shinichi; Kobayashi, Shunsuke

2014-09-01

243

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

244

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

PubMed

Electro-optical properties of deformed helix ferroelectric liquid crystal (DHFLC) cells are studied by using a general theoretical approach to polarization gratings in which the transmission and reflection matrices of diffraction orders are explicitly related to the evolution operator of equations for the Floquet harmonics. In the short-pitch approximation, a DHFLC cell is shown to be optically equivalent to a uniformly anisotropic biaxial layer where one of the optical axes is normal to the bounding surfaces. For in-plane anisotropy, orientation of the optical axes and birefringence are both determined by the voltage applied across the cell and represent the parameters that govern the transmittance of normally incident light passing through crossed polarizers. We calculate the transmittance as a function of the electric field and compare the computed curves with the experimental data. The theoretical and experimental results are found to be in good agreement. PMID:21517514

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

2011-03-01

245

Orientational order of a ferroelectric liquid crystal with small layer contraction.  

PubMed

We present spectroscopic and optical studies of a non-layer-shrinkage ferroelectric liquid crystal DSiKN65. The orientational order parameters S, measured with respect to the smectic layer normal using IR spectroscopy on a sample aligned homeotropically, does not exhibit any significant variation between the smectic-A? and smectic-C? phases. In contrast the birefringence of a planar homogenous sample abruptly increases at the smectic-A? to smectic-C? transition. This suggests a general increase in the orientational order, which can be described by the orientational order parameters S' defined with respect to the director. Simultaneous increase of S' and the director tilt ? may explain the low shrinkage of smectic layers, which is consistent with recent theoretical models describing the smectic-A? to smectic-C? transition for such materials. PMID:21230086

Korlacki, Rafa?; Panov, Vitaly P; Fukuda, Atsuo; Vij, Jagdish K; Spillmann, Christopher M; Naciri, Jawad

2010-09-01

246

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

PubMed

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

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

2014-02-01

247

Time evolution photoluminescence studies of quantum dot doped ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

Time evolution photoluminescence (PL) studies of ferroelectric liquid crystal (FLC) mixtures doped with different concentrations of ZnS and CdS quantum dots (QDs) are carried out. Remarkable enhancement in the PL intensity and a significant shift in the emission band of FLC materials are observed by doping with a suitable amount of QDs. The modifications in the PL behaviour of the QD/FLC composites are found to depend strongly on time, and also on the QD/FLC mixtures themselves. The enhancement in the PL intensity of the FLC materials is attributed to the additive combination of the emissions from FLCs and QDs and the highly scattering phase of the FLC materials used. The shifting of the emission band and reduction in the PL intensity of the QD/FLC composites could be attributed to the oxidation of QDs. The observed results would be helpful in selecting QD/FLC composites to observe stable and enhanced PL from composites.

Kumar, A.; Tripathi, S.; Deshmukh, A. D.; Haranath, D.; Singh, P.; Biradar, A. M.

2013-05-01

248

Bending Tolerance of Ferroelectric Liquid Crystal with Polymer Walls Fastening Plastic Substrates  

NASA Astrophysics Data System (ADS)

We studied ferroelectric liquid crystal (LC) deformation in a flexible display device using thin plastic substrates supported by polymer walls. During direct microscope observation of the bent device, no disorder of LC alignment was recognized with LC material flow, which was induced by the thickness change of the LC layer. From the estimated deformation of the bent LC layer (curvature radius: 10 mm) between the extendable substrates, the difference in length between the outer and inner planes of the LC layer was evaluated at only 50 nm, which was extremely small compared with the polymer wall interval (250 ?m). The extendable thin substrate is useful for enhancement of the bending tolerance of flexible devices.

Sato, Hiroto; Fujikake, Hideo; Kikuchi, Hiroshi; Kurita, Taiichiro

2003-05-01

249

Single Crystal Sapphire Optical Fiber Sensor Instrumentation  

SciTech Connect

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

Anbo Wang; Russell May; Gary R. Pickrell

2000-10-28

250

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

NASA Astrophysics Data System (ADS)

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

Ghoddoussi, Farhad

251

Photoelectrical properties of TlGaSe2 single crystals  

NASA Astrophysics Data System (ADS)

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

Ozdemir, Selahattin; Bucurgat, Mahmut

2014-07-01

252

Electrical Properties of Black Phosphorus Single Crystals  

Microsoft Academic Search

Large single crystals of black phosphorus have been grown under high pressure, and by using the crystals, the Hall measurements have been done in a range from 4.2 K to 550 K. All the undoped samples have exhibited p-type conduction, while we have succeeded in obtaining n-type crystals by doping Te impurity. The effective acceptor concentrations NA-ND of the p-type

Yuichi Akahama; Shoichi Endo; Shin-ichiro Narita

1983-01-01

253

Sublimation Kinetics of Zinc Single Crystals.  

National Technical Information Service (NTIS)

The kinetics of the free surface sublimation of zinc single crystals were investigated using the torsion-Langmuir technique in conjunction with optical and electron microscopes. Sublimation from cleaved surfaces took place in two distinct stages, a stage ...

R. W. Mar

1968-01-01

254

Dipole spring ferroelectrics in superlattice SrTiO3/BaTiO3 thin films exhibiting constricted hysteresis loops  

E-print Network

Institute of Physics. Related Articles Coexistence of ferroelectric vortex domains and charged domain walls-scale ferroelectric domains in a LiNbO3 single crystal: The role of surface energy and polar molecule adsorption JDipole spring ferroelectrics in superlattice SrTiO3/BaTiO3 thin films exhibiting constricted

Chen, Long-Qing

255

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

SciTech Connect

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

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

1999-05-01

256

Crystal orientation dependency of ferroelectric property in rhombohedral Pb(Zr,Ti)O3 films  

NASA Astrophysics Data System (ADS)

Ferroelectric properties were investigated for (100), (110), and (111)-single-oriented rhombohedral Pb(Zr0.65Ti0.35)O3 films. Saturation polarization, Psat, was changed by the simple tilting angle of the polar axis from the film surface normal. On the other hand, (100)- and (11\\bar{1})/(111)-oriented films prepared on (100) Si substrates showed similar Psat values due to the coexistence of (11\\bar{1}) orientation. The coercive field, Ec, of rhombohedral Pb(Zr0.65Ti0.35)O3 films was lower than that of tetragonal Pb(Zr0.4Ti0.6)O3 films. (100)-oriented rhombohedral films with SrRuO3 electrodes did not show noticeable degradation in polarization up to 1010 switching cycles. These results show that (100)-oriented rhombohedral Pb(ZrxTi1-x)O3 film is available to realize the low voltage operated ferroelectric random access memory instead of the present tetragonal Pb(ZrxTi1-x)O3 films.

Ehara, Yoshitaka; Utsugi, Satoru; Oikawa, Takahiro; Yamada, Tomoaki; Funakubo, Hiroshi

2014-01-01

257

Influence of crystal orientation on ECAP of aluminum single crystals  

Microsoft Academic Search

A single crystal of high purity aluminum, oriented with the {111} slip plane and the ?110? slip direction rotated by 20° in a clockwise sense from the theoretical shear plane and the shear direction, was processed by equal-channel angular pressing (ECAP) through a single pass. This configuration was designated the 20° orientation and the results are compared with earlier data

Yukihide Fukuda; Keiichiro Oh-ishi; Minoru Furukawa; Zenji Horita; Terence G. Langdon

2006-01-01

258

Linear and non-linear dielectric properties of a short-pitch ferroelectric liquid crystal stabilized by a polymer network.  

PubMed

Linear and non-linear dielectric measurements were carried out on a ferroelectric liquid crystal stabilized by an anisotropic polymer network. The polymerization process was achieved at room temperature. It was performed from an achiral monomer in the ferroelectric chiral smectic C phase, exhibiting a very short helical pitch and a large polarization. The linear and non-linear dielectric spectroscopy were also completed by textural morphology as well as structural and ferroelectric characterizations. All these measurements were carried out on a pure ferroelectric liquid crystal material and on composite films containing two polymer concentrations. The increase of the polymer network density leads to a decrease of the dielectric strength determined in the linear and non-linear dielectric spectroscopy. The complementarity between the linear and non-linear dielectric measurements and their confrontation with a theoretical model allowed the simultaneous determination of some physical parameters such as macroscopic polarization, rotational viscosity and twist elastic energy. We also discuss the effect of the polymer network density on the obtained physical parameters. PMID:21107879

Cherfi, Y; Hemine, J; Douali, R; Beldjoudi, N; Ismaili, M; Leblond, J M; Legrand, C; Daoudi, A

2010-12-01

259

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

Microsoft Academic Search

This paper demonstrates the possibility of inducing an antiferroelectric phase from an intrinsically ferroelectric phase-only liquid crystal by doping with linear-shaped molecules, thus separating the neighboring smectic layers of the ferroelectric liquid crystal from each other. Such an intrinsically impossible process is, in fact, shown to be quite possible due to its entropy-related origin. When the temperature of the doped

Ji-Hoon Lee; Tong-Kun Lim

2005-01-01

260

Computation of high-stability DC balancing scheme for ferroelectric liquid crystal on silicon holograms using graphics processing units.  

PubMed

Spatial light modulators based around liquid crystal on silicon have found use in a variety of telecommunications applications, including the optimization of multimode fibers, free-space communications, and wavelength selective switching. Ferroelectric liquid crystals are attractive in these areas due to their fast switching times and high phase stability, but the necessity for the liquid crystal to spend equal time in each of its two possible states is an issue of practical concern. Using the highly parallel nature of a graphics processing unit architecture, it is possible to calculate DC balancing schemes of exceptional quality and stability. PMID:21499344

Carpenter, Joel; Wilkinson, Timothy D

2011-04-15

261

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

262

V -shaped switching ferroelectric liquid crystal structure stabilized by dielectric surface layers.  

PubMed

The " V -shaped switching" mode in high polarization ferroelectric liquid crystals was studied with the aim of stabilizing the monostable bookshelf structure with the spontaneous polarization parallel to the glass plates. The director field in such cells was confirmed to be sensitive to both the liquid crystal properties and the cell parameters. In cells with only polyimide alignment layers, hysteresis free switching was never obtained, with bistable and asymmetric monostable structures compromising the zero-field dark state and preventing an ideal, hysteresis-free analog response. By incorporating a SiO(2) layer between the ITO electrode and the polyimide, the undesired states were suppressed and essentially hysteresis-free switching was obtained for driving frequencies in the range 0.2-200 Hz . Cells rubbed only on one side give more uniform alignment than cells rubbed on both sides but their inherent asymmetry shifts the long-term dark state away from 0 V and causes the response to gray level voltage modulation to be slightly asymmetric. The formation of different types of states as a function of the values of the surface parameters, and the observed stabilization of the V -shaped switching structure by the dielectric surface layers, are in good agreement with an earlier analysis by Copic [Phys. Rev. E 65, 021701 (2002)]. PMID:18517406

Hammarquist, A; D'Havé, K; Matuszczyk, M; Clark, N A; Maclennan, J E; Rudquist, P

2008-03-01

263

Structure and dynamics of ferroelectric liquid crystal cells exhibiting thresholdless switching.  

PubMed

Surface-stabilized ferroelectric liquid crystal cells are usually bistable, with the spontaneous polarization either up or down, perpendicular to the plane of the cell. In materials with high spontaneous polarization the polarization charge self-interaction leads to a monostable structure that exhibits a thresholdless, "V-shaped" switching of the optical response to an applied voltage. With a model that includes the electrostatic self-energy of the spontaneous polarization, we examine the transition from bistablity to monostability as a function of the polar and nonpolar anchoring energies, the liquid crystal elasticity, and the thickness of the alignment layers. Two bistable and one monostable structures are possible. The bistable state is only obtained when the thickness of the insulating alignment layer and the polar anchoring energy are small, or when the spontaneous polarization is small. From linear stability analysis we get analytical expressions for the limits of stability of the structures. Numerical calculations show that in some ranges of the parameters two structures can coexist. We also present the calculation of the polarization fluctuation modes. The lowest one becomes soft at the continuous transitions among the structures and at the limits of stability. PMID:11863546

Copic, Martin; Maclennan, Joseph E; Clark, Noel A

2002-02-01

264

Enhancement of electro-optic stability in the vertical configuration of a deformed-helix ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

We propose a reliable vertical configuration of a deformed-helix ferroelectric liquid crystal (DHFLC) mode in a transverse electrode structure by introducing reactive mesogens (RMs) into the DHFLC material. Polymerized RMs remember the direction of the DHFLC molecules in the absence of an applied voltage and suppress the bending and breaking of the smectic layer under a strong electric field. In this DHFLC mode with polymerized RMs, reliable switching characteristics are obtained in the vertical configuration.

Hwang, Jeoung-Yeon; Lee, You-Jin; Cho, Chuhyun; Heo, Jeong Uk; Baek, Ji-Ho; Kim, Youngsik; Kim, Jae-Hoon; Yu, Chang-Jae

2013-04-01

265

Dynamics of Ferroelectric Domain Walls  

Microsoft Academic Search

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

Volkmar Mueller

2001-01-01

266

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

267

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

268

Oxygen Incorporation in Rubrene Single Crystals  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

269

Remarkable structural diversity and single-crystal-to-single-crystal transformations in sulfone functionalized lanthanide MOFs  

SciTech Connect

We report the formation of novel open framework lanthanide (La, Ce, Pr and Dy) MOFs using the ligand 4,4{prime}-bibenzoic acid-2,2{prime}-sulfone. In the case of Ce and Pr, an unprecedented single-crystal-to-single-crystal transformation at room temperature was discovered.

Neofotistou, Eleftheria; Malliakas, Christos D.; Trikalitis, Pantelis N. (NWU); (Crete)

2010-04-13

270

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

271

Helical Single Crystals Grown in Confined Space  

NASA Astrophysics Data System (ADS)

We report here the formation and growth process of the double-twist PET(R*-9) helical single crystals. It has been observed that the population of helical crystals increases with increasing the thickness of the thin films. In addition to the crystallization temperature effect, the pitch lengths along both the long and short twist axes also change with thin film thickness, which is attributed to the substrate confinement effect on the thin film samples. The early stage of the helical crystals has been studied using solvent washing experiments. It has been found that the morphology is a saddle-like shape. Nucleation starts at the center of the flat-on part, and growth directions include both along the long and short axes of the crystals. Coexistence of the flat-elongated and helical forms will also be discussed.

Li, Christopher; Cheng, Stephen; Zhang, John; Harris, Frank; Chien, Liang-Chy; Lotz, Bernard

2001-03-01

272

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

PubMed

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

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

2012-10-10

273

Photoluminescence quenching in oligothiophene single crystal  

Microsoft Academic Search

A single crystal of stereo-regularly substituted dihexylsexithiophene (DH6T) was synthesized. The transient photoluminescence decay curve of the crystal was non-exponential as in amorphous polythiophene. This non-exponential decay curve could be successfully described by stretched exponential decay kinetics, which represent the exciton diffusing to the one-dimensionally dispersed quenching centers. The generation of radical species by photoirradiation was confirmed by light-induced ESR

Tadatake Sato; Mamoru Fujitsuka; Motoo Shiro; Kazuyoshi Tanaka

1998-01-01

274

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

275

Total Refraction of P-Polarized Light at the Boundary of 90°-Domains in the Ferroelectric Crystal  

NASA Astrophysics Data System (ADS)

A 90°-domain structure was fabricated using electrical poling in ferroelectric birefringent KNbO3 crystal. The refraction and reflection characteristics of the light at the boundary of the 90°-domain structure were investigated, and the novel behavior of total refraction (no reflection) has been found for the P-polarized light throughout the entire range of incident angle (0??? 90°). Strong refraction of the light was observed after it exited from the crystal output surface at the incidence parallel to the domain boundary. These behaviors were explained analytically.

Shichijyo, Shiro; Hirohashi, Junji; Kamio, Hiroyuki; Yamada, Kazuhiro

2004-06-01

276

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

277

Surface viscoelastic properties of spread ferroelectric liquid crystal monolayer on air-water interface  

NASA Astrophysics Data System (ADS)

Ferroelectric Liquid crystal having Smectic C* phase at room temperature was capable of forming Langmuir monolayer due to presence of both hydrophilic and hydrophobic groups in it. Surface viscoelasticity properties of FLC monolayer spread on water surface had been determined by dynamic oscillation method and discussed as a function of surface pressure. Dynamic viscoelastic properties such as G (Elastic modulus), G' (storage (elastic) modulus), G' (Loss (viscous) modulus) and phase change with sinusoidal oscillation had been measured at phase changing surface pressure values. As monolayer was becoming condensed, increasing trend was observed in G' values while G' was decreasing. At higher frequencies, viscous modulus G' had negative values. This relaxation phenomenon was probably caused by conformational rearrangements that acted to fluidize monolayer. Phase change tan ? was positive, response in surface pressure was ahead of the de-formation in area and the monolayer had positive dilatational viscosity. Phase change tan ? was negative, response in surface pressure was hysteretic to the deformation in area, and negative dilatational viscosity had been observed. Studies of monolayer in barrier oscillating mode provided us the surface pressure which was most suitable for Langmuir Blodgett monolayer deposition.

Kaur, Ramneek; Bhullar, Gurpreet Kaur; Raina, K. K.

2013-06-01

278

Investigations on ferroelectric liquid crystal by high resolution TEM and solid state 13C NMR.  

PubMed

In order to investigate the structural and dynamical properties of ferroelectric liquid crystal (FLC) in different phases a model compound [4-(3)-(S)-methyl-2-(S)-chloropentanoyloxy)]-4'-nonyloxy-biphenyl (3M2CPNOB) is synthesized. High resolution transmission electron microscopy (HR-TEM) is applied to observe the morphology of 3M2CPNOB and temperature-dependent solid state (13)C NMR to record (13)C chemical shifts at different phases. A liquid nitrogen quenching method is used to maintain the conformation of the mesophases for HR-TEM experiments. TEM images show that all the smectic A (SmA), smectic C* (SmC*) and crystalline phases have lamellar morphology. The interplanar distances in the crystalline phase are smaller than those in SmA and SmC* phases because of denser arrangement of the molecules. Both (13)C chemical shifts and line shape vary with different phases. The experimental results suggest that SmC* phase as an intermediate occurs in the anisotropy transition process from SmA to crystalline phase, the helical structure of the SmC* phase unwinds in the magnetic field and the conformations of the SmA and isotropic phase are very similar. PMID:21967597

Zhao, Yongxia; Yang, Yanqin; Xu, Jingwei; Yang, Wei; Zhou, Yunchun; Jiang, Zijiang; Ge, Xin

2011-11-17

279

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

PubMed

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

Peinado, Alba; Lizana, Angel; Campos, Juan

2013-08-10

280

Ferroelectric response in an achiral non-symmetric bent liquid crystal:C12C10  

NASA Astrophysics Data System (ADS)

An achiral Non-Symmetric Bent Liquid Crystal (BLC) with a Oxadiazole based hetero cyclic central moiety, abbreviated as C12C10 viz., dodecyl[4-{5-(4?-decyloxy)biphenyl-4-yl}-1,2,4-oxadiazol-3-yl]benzoate, exhibiting FerroElectric (FE) response is reported. Product is confirmed by 1H NMR, 13C NMR and elemental analysis. Characterization of BLC phases is carried out by Polarized Optical Microscopy (POM), Differential Scanning Calorimetry (DSC), Spontaneous Polarization (PS) and Low Frequency (10 Hz-10 MHz) Dielectric Relaxation studies. C12C10 exhibits enantiotropic LC SmA, FE B2, SmG, SmE phase variance. I-SmA, B2-SmG and SmG-SmE transitions are of first order nature. FE B2 phases exhibits a moderate PS of 80 nC cm-2. B2 phase exhibits Curie-Weiss behavior to confirm FE nature. Off-centered low frequency (KHz) dispersion infers a scissor mode and a high frequency (MHz) mode to reflect the distinct time-scale response. Dielectric Dispersion is relatively susceptible in lower frequency KHz region. Arrhenius shift in Relaxation Frequency (fR) infers higher activation energy (Ea) in non-FE phases for HF mode and lower value for KHz mode. Trends of fR, dielectric strength ??, ?-parameter and Ea are discussed in view of the data reported in other LC compounds.

Subrahmanyam, S. V.; Chalapathi, P. V.; Mahabaleshwara, S.; Srinivasulu, M.; George, A. K.; Potukuchi, D. M.

2014-10-01

281

Switching dynamics of surface stabilized ferroelectric liquid crystal cells: effects of anchoring energy asymmetry  

E-print Network

We study both theoretically and experimentally switching dynamics in surface stabilized ferroelectric liquid crystal cells with asymmetric boundary conditions. In these cells the bounding surfaces are treated differently to produce asymmetry in their anchoring properties. Our electro-optic measurements of the switching voltage thresholds that are determined by the peaks of the reversal polarization current reveal the frequency dependent shift of the hysteresis loop. We examine the predictions of the uniform dynamical model with the anchoring energy taken into account. It is found that the asymmetry effects are dominated by the polar contribution to the anchoring energy. Frequency dependence of the voltage thresholds is studied by analyzing the properties of time-periodic solutions to the dynamical equation (cycles). For this purpose, we apply the method that uses the parameterized half-period mappings for the approximate model and relate the cycles to the fixed points of the composition of two half-period mappings. The cycles are found to be unstable and can only be formed when the driving frequency is lower than its critical value. The polar anchoring parameter is estimated by making a comparison between the results of modelling and the experimental data for the shift vs frequency curve. For a double-well potential considered as a deformation of the Rapini-Papoular potential, the branch of stable cycles emerges in the low frequency region separated by the gap from the high frequency interval for unstable cycles.

Alexei D. Kiselev; Vladimir G. Chigrinov; Eugene P. Pozhidaev

2006-09-12

282

Charge transport in single crystal organic semiconductors  

NASA Astrophysics Data System (ADS)

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

Xie, Wei

283

Mapping of domain structure in Barium Titanate single crystals by synchrotron x-ray topography  

NASA Astrophysics Data System (ADS)

Imaging of domains is a key step in understanding the microstructure and hence the properties of ferroelectric single crystals. This understanding is essential for exploiting engineered domain configurations to achieve enhanced performance. In this paper, single crystals of Barium Titanate are observed by reflection topography using unfocussed monochromatic synchrotron X-ray light. A 10 x 10 mm polished surface of an unpoled crystal was mapped to form a composite image, indicating a fine structure of a- and c-domains. By making use of the angular separation of the diffracted reflections and specimen rocking, the relative tilts between adjacent domains about two orthogonal axes were found. Angular resolution better than 0.1mrad in tilt measurements allowed the local elastic curvature of lattice planes to be observed. The resulting composite images show well defined boundaries between regions of distinct microstructure, and give an indication of the proportion of the domain types present. Over large regions of the crystal the domain structure was finer than the X-ray camera resolution of 6.5?m AFM and SEM imaging of domains was then used to confirm the typical domain spacing. The results are interpreted in the context of models of compatible microstructure in tetragonal crystals using microscopy of etched crystals to assist the interpretation. The technique shows promise for mapping fine microstructure in single crystals, through the use of high resolution X-ray cameras, and is successful in revealing lattice orientation information that is not normally available in optical or AFM measurements.

Potnis, Prashant R.; Huber, John E.; Sutter, John P.; Hofmann, Felix; Abbey, Brian; Korsunsky, Alexander M.

2010-04-01

284

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

285

Growth of single-crystal gallium nitride  

NASA Technical Reports Server (NTRS)

Use of ultrahigh purity ammonia prevents oxygen contamination of GaN during growth, making it possible to grow the GaN at temperatures as high as 825 degrees C, at which point single crystal wafers are deposited on /0001/-oriented sapphire surfaces.

Clough, R.; Richman, D.; Tietjen, J.

1970-01-01

286

Magnetic Properties of Single Crystal Nickel Nanowires  

NASA Astrophysics Data System (ADS)

Toward the goal of understanding magnetism in confined dimensions, we have synthesized Nickel nanowires (NWs) by chemical vapor deposition and characterized their magnetic properties. By tuning chemical vapor deposition synthesis parameters, we can controllably synthesize a variety of morphologically dissimilar Ni products onto untreated amorphous SiO2||Si substrates [1]. These structures include polycrystalline core-shell NWs, single-crystal cubes, in-plane wires, and vertically-oriented single crystal arrays. To probe the magnetic properties of individual NWs, we combined magneto-transport, XPEEM, and magnetic modeling. For polycrystalline NWs, the magnetic properties are dominated by shape anisotropy. However, for single-crystal NWs, there is a competition between the shape anisotropy along the (001) direction and magneto-crystalline anisotropy along the (111) direction. This gives rise to complex magnetic stripe domain patterns along the wires, interesting magneto-transport properties, and novel reversal modes not typically observed in magnetic wires. [4pt] [1] K.T. Chan, J.J. Kan, E.E. Fullerton, et al., "Oriented Growth of Single-Crystal Ni Nanowires onto Amorphous SiO2," Nano Letters, Oct. 2010

Kan, Jimmy; Chan, Keith; Shipton, Erik; Fullerton, Eric

2011-03-01

287

Stress Corrosion cracking of copper single crystals  

Microsoft Academic Search

Constant extension rate tests have been carried out on copper single crystals in a sodium nitrite solution, using an applied potential to accelerate the cracking. Crack velocities up to 30 nm per second were obtained at 30 °C. The stress-corrosion fracture surfaces are cleavage-like, with curved striations parallel to the crack front. If the dynamic straining is stopped, the cracks

K. Sieradzki; R. L. Sabatini; R. C. Newman

1984-01-01

288

Multiferroicity in spin ice Ho2Ti2O7: An investigation on single crystals  

NASA Astrophysics Data System (ADS)

The single crystals of rare-earth titanate pyrochlore compound Ho2Ti2O7 are grown and their multiferroicity along the [110] and [111] directions is investigated. The ferroelectricity below ˜28 K, with a polarization of ˜2.50 ?C/m2 along the ?111? direction at 2 K, qualitatively fitting with the theoretical scenario proposed by Khomskii (Nat. Commun. 3, 904 (2012)), is revealed. The magnetoelectric responses along both the [110] and [111] directions are observed, but different underlying mechanisms associated with the specific spin configurations are suggested.

Liu, D.; Lin, L.; Liu, M. F.; Yan, Z. B.; Dong, S.; Liu, J.-M.

2013-05-01

289

Strong ferromagnetic-dielectric coupling in multiferroic Lu2CoMnO6 single crystals  

NASA Astrophysics Data System (ADS)

We have grown single crystals of multiferroic double-perovskite Lu2CoMnO6 and studied the directional dependence of their magnetic and dielectric properties. The ferromagnetic order emerges below TC ? 48 K along the crystallographic c axis. Dielectric anomaly arises along the b axis at TC, contrary to the polycrystalline work suggesting ferroelectricity along the c axis. Through the strongly coupled ferromagnetic and dielectric states, the highly non-linear variation of both dielectric constant and magnetization was achieved in application of magnetic fields. This concurrent tunability provides an efficient route to manipulation of multiple order parameters in multiferroics.

Lee, N.; Choi, H. Y.; Jo, Y. J.; Seo, M. S.; Park, S. Y.; Choi, Y. J.

2014-03-01

290

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

291

Near-field second-harmonic imaging of ferroelectric domain structure of YMnO3  

Microsoft Academic Search

Ferroelectrics have attracted much recent interest for applications in, e.g., data storage devices. The ferroelectric domain formation and order in a single crystal is the result of a subtle interplay between electric field and the elastic and domain wall energies to minimize the total free energy of the system. This makes the prediction of domain size and shape a priori

C. C. Neacsu; B. B. van Aken; M. Fiebig; M. B. Raschke

2007-01-01

292

Critical slowing down and elastic anomaly of uniaxial ferroelectric Ca0.28Ba0.72Nb2O6 crystals with tungsten bronze structure  

NASA Astrophysics Data System (ADS)

The ferroelectric phase transition of uniaxial Ca0.28Ba0.72Nb2O6 single crystals with a moderate effective charge disorder was investigated by Brillouin scattering to clarify the dynamic properties. In the tetragonal paraelectric phase a remarkable softening of the sound velocity of the longitudinal acoustic mode and a significant increase in the sound attenuation were observed close to the Curie temperature TC=527K. The intermediate temperature T* ˜640K and the Burns temperature TB ˜790K were determined from the temperature variation in the sound attenuation. The intense broad central peak (CP) caused by polarization and strain fluctuations due to polar nanoregions was clearly observed in the vicinity of TC. The relaxation time determined by the CP width clearly shows critical slowing down towards TC, reflecting a weakly first-order phase transition under weak random fields.

Suzuki, K.; Matsumoto, K.; Dec, J.; ?ukasiewicz, T.; Kleemann, W.; Kojima, S.

2014-08-01

293

Wavelength-compensated color Fourier diffractive optical elements using a ferroelectric liquid crystal on silicon display and a color-filter wheel.  

PubMed

In this work we describe the experimental realization of a simple scheme capable of implementing RGB improved dynamic color binary-phase Fourier computer-generated holograms (CGHs) by means of a single ferroelectric liquid crystal on silicon (FLCOS) display and an electronically controlled color-filter wheel. Tricolor multiwavelength illumination is achieved by aligning an Ar-Kr laser (wavelengths lambda(B)=488 nm and lambda(G)=568 nm) and a He-Ne laser ((R)=633 nm). Chromatic compensation is achieved by synchronizing a time sequence of properly scaled CGHs displayed on the FLCOS display with the corresponding filter from the color wheel. Quality CGHs are designed for each color component by using an optimized iterative Fourier transform algorithm applied to a phase-only modulation display. As a result, we present excellent experimental results on the reconstruction of these time-multiplexed wavelength-compensated diffractive optical elements and color CGHs. PMID:19209203

Martínez, José Luis; Martínez-García, Antonio; Moreno, Ignacio

2009-02-10

294

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

PubMed

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

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

2012-02-01

295

Crystal ion slicing of single-crystal magnetic garnet films  

Microsoft Academic Search

Epitaxial liftoff has been used for achieving heterogeneous integration of many III-V and elemental semiconductor systems. However, it has been heretofore impossible to integrate devices of many other important material systems. A good example of this problem has been the integration of single-crystal transition metal oxides on semiconductor platforms, a system needed for on-chip thin film optical isolators. We report

M. Levy; R. M. Osgood; A. Kumar; H. Bakhru

1998-01-01

296

Experimental Investigation of Orthoenstatite Single Crystal Rheology  

NASA Astrophysics Data System (ADS)

The plasticity of enstatite, upper mantle second most abundant mineral, is still poorly constrained, mostly because of its high-temperature (T) transformation into proto- and clino-enstatite at low pressure (P). Mackwell (1991, GRL, 18, 2027) reports a pioneer study of protoenstatite (Pbcn) single-crystal rheology, but the results do not directly apply to the orthorhombic (Pbca) mantle phase. Ohuchi et al. (2011, Contri. Mineral. Petrol , 161, 961) carried out deformation experiments at P=1.3 GPa on oriented orthoenstatite crystals, investigating the activity of [001](100) and [001](010) dislocation slip systems; they report the first rheological laws for orthoenstatite crystals. However, strain and stress were indirectly constrained in their experiments, which questioned whether steady state conditions of deformation were achieved. Also, data reported for [001](100) slip system were obtained after specimens had transformed by twinning into clinoenstatite. We report here new data from deformation experiments carried out at high T and P ranging from 3.5 to 6.2 GPa on natural Fe-bearing enstatite single crystals, using the Deformation-DIA apparatus (D-DIA) that equipped the X17B2 beamline of the NSLS (NY, USA). The applied stress and specimen strain rates were measured in situ by X-ray diffraction and imaging techniques (e.g., Raterron & Merkel, 2009, J. Sync. Rad., 16, 748; Raterron et al., 2013, Rev. Sci. Instr., 84, 043906). Three specimen orientations were tested: i) with the compression direction along [101]c crystallographic direction, which forms a 45° angle with both [100] and [001] axes, to investigate [001](100) slip-system activity; ii) along [011]c direction to investigate [001](010) system activity; iii) and along enstatite [125] axis, to activate both slip systems together. Crystals were deformed two by two, to compare slip system activities, or against enstatite aggregates or orientated olivine crystals of known rheology for comparison. Run products microstructures were investigated by transmission electron microscopy. Despite a significant hardening with P, enstatite [001](100) slip system is found to be the easiest system at mantle P and T. Furthermore, orthoenstatite crystals exhibit a higher sensitivity to stress than olivine crystals, i.e. a higher n exponent in classical power laws. At the low stress level prevailing in the Earth mantle, enstatite crystals are thus harder than olivine crystals.

fraysse, G.; Girard, J.; Holyoke, C. W.; Raterron, P.

2013-12-01

297

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

298

The Creep of Single Crystals of Aluminum  

NASA Technical Reports Server (NTRS)

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

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

1953-01-01

299

Polar structures in binary mixtures of bent-core liquid crystals showing ferroelectric and antiferroelectric B2 phases.  

PubMed

We have studied the polar structures in the binary mixtures of bent-core liquid crystals P-n-O-PIMB(n-2)*-(n-4)O showing the ferroelectric smectic- CAPF (Sm-CAPF) (n=8 and 10) and antiferroelectric Sm-CSPA (n=9) B2 phase. Although the polar structure of the one-to-one mixture is governed by the compound with longer end chains, it is much more complicated in the mixtures with slightly less fraction of compounds with longer end chains. Even if the mixtures show the antiferroelectric phase before field application, the ferroelectric domains remain once the field is applied and coexist with the antiferroelectric domains. The coexistence structure was modeled by comparing the microscope real image with that of second-harmonic generation. The fraction of the ferroelectric domains is larger at higher temperature region of the B2 phase and decreases with decreasing temperature. The stable phase structures were discussed based on the phenomenological theory. We suggest that the coupling energy of the layer chirality is higher than the energies of the orientation correlations of tilts and polarizations between adjacent layers. PMID:17930258

Niigawa, Yuya; Nishida, Koushi; Kim, Won Jeon; Lee, Seng Kue; Heo, Sung; Lee, Jong Gun; Araoka, Fumito; Takanishi, Yoichi; Ishikawa, Ken; Kang, Kyung-Tae; Cepic, Mojca; Takezoe, Hideo

2007-09-01

300

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

NASA Astrophysics Data System (ADS)

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

Lahiri, T.; Majumder, T. Pal

2011-06-01

301

Transverse acoustic actuation of Ni-Mn-Ga single crystals  

E-print Network

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

Simon, Jesse Matthew

2007-01-01

302

Nanoscale polarization switching at a single 180^o ferroelectric domain wall  

Microsoft Academic Search

Domain wall motion in ferroelectric materials is strongly affected by lattice, surface and defect pinning effects. A variant of Piezoresponse Force Microscopy (PFM) called Switching Spectroscopy PFM (SSPFM) is ideally suited to probe the local domain switching near ferroelectric domain walls and study domain dynamics and polarization switching on the nanoscale. In the vicinity of the biased probe tip, the

Venkatraman Gopalan; Vasudeva Rao Aravind; Samrat Choudhury; Yulan Li; Katyayani Seal; Anna Morozovska; Eugene Eliseev; Long-Qing Chen; Andrew Rappe; Simon Phillpot; Sergei Kalinin

2010-01-01

303

Single-crystal gallium nitride nanotubes  

NASA Astrophysics Data System (ADS)

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 by using carbon nanotubes and porous membranes as templates, or by thin-film rolling. These nanotubes, however, are either amorphous, polycrystalline or exist only in ultrahigh vacuum. The growth of single-crystal semiconductor hollow nanotubes would be advantageous in potential nanoscale electronics, optoelectronics and biochemical-sensing applications. Here we report an `epitaxial casting' approach for the synthesis of single-crystal GaN nanotubes with inner diameters of 30-200nm and wall thicknesses of 5-50nm. Hexagonal ZnO nanowires were used as templates for the epitaxial overgrowth of thin GaN layers in a chemical vapour deposition system. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. This templating process should be applicable to many other semiconductor systems.

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

2003-04-01

304

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

PubMed

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

Nakatsuhara, Katsumi; Kato, Akifumi; Hayama, Yoshiki

2014-04-21

305

Double pass, common path method for arbitrary polarization control using a ferroelectric liquid crystal spatial light modulator.  

PubMed

We present a method for arbitrary control of the polarization of a light beam. Our method uses two holograms on a binary ferroelectric liquid crystal spatial light modulator (FLCSLM), and so has the potential to allow polarization state switching at kilohertz rates. Unlike previous methods that achieve polarization control using FLCSLMs, our method is common path and requires only the simplest optical components. For this reason, the method is very easy to setup, align, and maintain. In addition, it has the ability to modulate unpolarized input light. We demonstrate the formation of radially, azimuthally, and circularly polarized beams by imaging their focal spots formed at low numerical aperture. PMID:23546237

Clegg, James H; Neil, Mark A A

2013-04-01

306

Ferromagnetic Resonance of Single-Crystal Gadolinium  

Microsoft Academic Search

Gadolinium metal is a system of relative simplicity as far as exchange interactions and ionic states are concerned. The 8S7?2 state of Gd3+ is consistent with the observed 7?b?atom and the moment contributing f electrons are most likely exchange coupled via conduction electrons. The present work concerns the measurement of the ferromagnetic resonance behavior of a single crystal at frequencies

T. W. Moore; D. S. Rodbell

1964-01-01

307

Amplified spontaneous emission in quaterthiophene single crystals  

Microsoft Academic Search

The authors demonstrate amplified spontaneous emission (ASE) from quaterthiophene single crystals and study its behavior at low temperature. The room temperature photoluminescence exhibits line narrowing (spectral width down to 10 nm) at 553 nm for excitation fluence larger than 1 mJ cm-2. At low temperature (10 K), ASE is observed from two vibronic transitions at 510 nm (0-1) and 553

Marco Polo; Andrea Camposeo; Silvia Tavazzi; Luisa Raimondo; Peter Spearman; Antonio Papagni; Roberto Cingolani; Dario Pisignano

2008-01-01

308

Stress Corrosion cracking of copper single crystals  

Microsoft Academic Search

Constant extension rate tests have been carried out on copper single crystals in a sodium nitrite solution, using an applied\\u000a potential to accelerate the cracking. Crack velocities up to 30 nm per second were obtained at 30 ?C. The stress-corrosion\\u000a fracture surfaces are cleavage-like, with curved striations parallel to the crack front. If the dynamic straining is stopped,\\u000a the cracks

K. Sieradzki; R. L. Sabatini; R. C. Newman

1984-01-01

309

Nanopolar structure in SrxBa1-xNb2O6 single crystals tuned by Sr\\/Ba ratio and investigated by piezoelectric force microscopy  

Microsoft Academic Search

Complex as-grown nanodomain patterns are studied with piezoresponse force microscopy in SrxBa1-xNb2O6 single crystals at variant Sr\\/Ba molar ratios, 0.4<=x<=0.75 . They reflect random-field Ising model (RFIM) ferroelectricity, which crosses over into relaxor behavior at increasing x . This is explained by an increase of the polar disorder within the open tungsten-bronze crystal structure giving rise to enhanced quenched random

Vladimir V. Shvartsman; Wolfgang Kleemann; Tadeusz Lukasiewicz; Jan Dec

2008-01-01

310

Single crystal diamond detector for radiotherapy  

NASA Astrophysics Data System (ADS)

The new generation of synthetic diamonds grown as a CVD single crystal on a high pressure high temperature substrate offers a wide range of applications. In particular, because of the near tissue equivalence and its small size (good spatial resolution), CVD single crystal diamond finds applicability in radiotherapy as a dosemeter of ionizing radiation. In this paper we report the electrical and dosimetric properties of a new diamond detector which was fabricated at IFJ based on a single crystal detector-grade CVD diamond provided with a novel contact metallization. Diamond properties were assessed at IFJ using a Theratron 680E therapeutic 60Co gamma rays unit and at COOK with 6 and 18 MV x-rays Varian Clinac CL2300 C/D accelerator. The new dosemeter showed high electric and dosimetric performances: low value of dark current, high current at the level of some nanoamperes during irradiation, very fast dynamic response with a rise time amounting to parts of a second, good stability and repeatability of the current and linearity of the detector signal at different dose and dose rate levels typically applied in radiotherapy. The results confirm the potential applicability of diamond material as a dosemeter for applications in radiotherapy.

Schirru, F.; Kisielewicz, K.; Nowak, T.; Marczewska, B.

2010-07-01

311

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

PubMed

Ferroelectric domain nucleation and growth in multiferroic BiFeO(3) 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 approximately 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

2007-12-18

312

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

313

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

PubMed

In contrast to the wide number and variety of available synthetic routes to conventional linear polymers, the synthesis of two-dimensional polymers and unambiguous proof of their structure remains a challenge. Two-dimensional polymers-single-layered polymers that form a tiling network in exactly two dimensions-have potential for use in nanoporous membranes and other applications. Here, we report the preparation of a fluorinated hydrocarbon two-dimensional polymer that can be exfoliated into single sheets, and its characterization by high-resolution single-crystal X-ray diffraction analysis. The procedure involves three steps: preorganization in a lamellar crystal of a rigid monomer bearing three photoreactive arms, photopolymerization of the crystalline monomers by [4?+?4] cycloaddition, and isolation of individual two-dimensional polymer sheets. This polymer is a molecularly thin (~1?nm) material that combines precisely defined monodisperse pores of ~9?Å with a high pore density of 3.3?×?10(13) pores?cm(-2). Atomic-resolution single-crystal X-ray structures of the monomer, an intermediate dimer and the final crystalline two-dimensional polymer were obtained and prove the single-crystal-to-single-crystal nature and molecular precision of the two-dimensional photopolymerization. PMID:25143211

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

2014-09-01

314

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

315

VOLUME 82, NUMBER 20 P H Y S I C A L R E V I E W L E T T E R S 17 MAY 1999 Direct Observation of Pinning and Bowing of a Single Ferroelectric Domain Wall  

E-print Network

of Pinning and Bowing of a Single Ferroelectric Domain Wall T. J. Yang,1 Venkatraman Gopalan,2 P. J. Swart,3± ferroelectric domain wall under a uniform applied electric field using a collection mode near-field scanning.g., in ferromagnetic and ferroelectric based memory devices). In these materials, domain wall movement can result

Gopalan, Venkatraman

316

Chapter III: Catalytic Activation of CO Over Single Crystals  

E-print Network

1 Chapter III: Catalytic Activation of CO Over Single Crystals José A. Rodriguez and D. Wayne Introduction III.2 Methanation of CO on Single Crystal Surfaces III.2.1 CO methanation on clean metal single crystals. III.2.1.1 Monometallic surfaces A. Ni(100) and Ni(111) B. Ru(110) and Ru(001) C. W(110) D. Rh(111

Goodman, Wayne

317

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

318

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

SciTech Connect

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

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

2013-11-28

319

Evaluation of Ferroelectric Properties of Piezoelectric Ceramics Based on Crystallographic Homogenization Method and Crystal Orientation Analysis by SEM·EBSD Technique  

NASA Astrophysics Data System (ADS)

Macroscopic ferroelectric properties of piezoelectric polycrystals are strongly affected by microscopic inhomogeneous crystal structure. In our previous study, a multi-scale finite element method based on crystallographic homogenization method has been developed to estimate macroscopic properties considering microscopic crystal morphology. In this paper, the crystal orientation distribution of polycrystalline barium titanate has been measured by SEM·EBSD technique, and the measured crystal orientation distribution has been introduced to the microscopic finite element model. As the prediction of macroscopic properties depends on the sampling conditions of the measured crystal orientations, the effects of number of sampling points and sampling area have been investigated. As a result, the effective sampling conditions have been clarified to estimate macroscopic ferroelectric properties.

Uetsuji, Yasutomo; Yoshida, Toshihiro; Yamakawa, Takayuki; Tsuchiya, Kazuyoshi; Ueda, Sei; Nakamachi, Eiji

320

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

321

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

PubMed

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

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

2014-08-01

322

Crystal ion slicing of single-crystal magnetic garnet films  

NASA Astrophysics Data System (ADS)

Epitaxial liftoff has been used for achieving heterogeneous integration of many III-V and elemental semiconductor systems. However, it has been heretofore impossible to integrate devices of many other important material systems. A good example of this problem has been the integration of single-crystal transition metal oxides on semiconductor platforms, a system needed for on-chip thin film optical isolators. We report here an implementation of epitaxial liftoff in magnetic garnets. Deep ion implantation is used to create a buried sacrificial layer in single-crystal yttrium iron garnet (YIG) and bismuth-substituted YIG (Bi-YIG) epitaxial layers grown on gadolinium gallium garnet (GGG). The damage generated by the implantation induces a large etch selectivity between the sacrificial layer and the rest of the garnet. Ten-micron-thick films have been lifted off from the original GGG substrates by etching in phosphoric acid. Millimeter-size pieces of excellent quality have been transferred to the silicon and gallium arsenide substrates. Study of the magnetic domain structure in the detached epilayers by Faraday contrast shows no changes in film anisotropy. Optical insertion loss measurements are also presented.

Levy, M.; Osgood, R. M.; Kumar, A.; Bakhru, H.

1998-06-01

323

Piezo-optical and electro-optical behaviour of nematic liquid crystals dispersed in a ferroelectric copolymer matrix  

NASA Astrophysics Data System (ADS)

Polymer-dispersed liquid crystals (PDLCs) are composite materials that consist of micrometre-sized liquid-crystal (LC) droplets embedded in a polymer matrix. From ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and a nematic LC, PDLC films containing 10 and 60 wt% LC were prepared, and their electro-optical and piezo-optical behaviour was investigated. The electric field that is generated by the application of mechanical stress leads to changes in the transmittance of the PDLC film through a combination of piezoelectric and electro-optical effects. Such a piezo-optical PDLC material may be useful, e.g., in sensing and visualization applications.

Meena Ganesan, Lakshmi; Wirges, Werner; Mellinger, Axel; Gerhard, Reimund

2010-01-01

324

The crystal structure of Cd2Nb2O7: symmetry mode analysis of the ferroelectric phase  

NASA Astrophysics Data System (ADS)

The crystal structure of the ferroelectric Cd2Nb2O7 (CNO) has been determined down to T = 98 K using synchrotron radiation. Low temperature structure refinement is conducted in space group Ima 2, starting from the crystal structure previously determined by ab initio methods. Symmetry mode analysis indicates that the primary order parameter is of T2u symmetry with the largest displacement amplitude at the Nb(2) position. The associated phase transition temperature is obtained as Tc = 194 K by extrapolation. Long exposure x-ray diffraction scans confirm the presence of anisotropic diffuse scattering intensity in layers normal to lang110rangcub over the entire temperature range. The diffuse scattering intensity significantly decays below T = 198 K. The refined thermal parameters indicate that the disorder responsible for the diffuse scattering is primarily associated with Nb.

Malcherek, T.; Bismayer, U.; Paulmann, C.

2010-05-01

325

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

326

Quantitative ferroelectric characterization of single submicron grains in Bi-layered perovskite thin films  

Microsoft Academic Search

The local polarization state and the electromechanical properties of ferroelectric thin films can be probed via the converse piezoelectric effect using scanning force microscopy (SFM) combined with a lock-in technique. This method, denominated as piezoresponse SFM, was used to characterize at the nanoscale level ferroelectric SrBi2Ta2O9 and Bi4Ti3O12 thin films, grown by pulsed laser deposition. Two types of samples were

C. Harnagea; A. Pignolet; M. Alexe; D. Hesse; U. Gösele

2000-01-01

327

Strain-gradient-induced polarization in SrTiO3 single crystals.  

PubMed

Piezoelectricity is inherent only in noncentrosymmetric materials, but a piezoelectric response can also be obtained in centrosymmetric crystals if subjected to inhomogeneous deformation. This phenomenon, known as flexoelectricity, can significantly affect the functional properties of insulators, particularly thin films of high permittivity materials. We have measured strain-gradient-induced polarization in single crystals of paraelectric SrTiO3 as a function of temperature and orientation down to and below the 105 K phase transition. Estimates were obtained for all the components of the flexoelectric tensor, and calculations based on these indicate that local polarization around defects in SrTiO3 may exceed the largest ferroelectric polarizations. A sign reversal of the flexoelectric response detected below the phase transition suggests that the ferroelastic domain walls of SrTiO3 may be polar. PMID:17995293

Zubko, P; Catalan, G; Buckley, A; Welche, P R L; Scott, J F

2007-10-19

328

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

329

Experimental evidence of soft mode in the smectic C phase of chiral ferroelectric liquid crystals.  

PubMed

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

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

2014-11-14

330

ARTICLES: Thermooptic data storage in the chiral ferroelectric smectic C* phase of liquid crystals  

Microsoft Academic Search

A study was made of the use of a smectic phase (chiral ferroelectric smectic C*) in thermooptic pulsed recording and recall of optical data. Methods were developed for preparing oriented textures of the smectic C* and the scattering indicatrices of the investigated mixture were obtained for coherent and noncoherent illumination. The parameters of planar capillaries filled with the smectic C*

A. N. Nesrullaev; A. Z. Rabinovich; Anatolii S. Sonin; E. B. Shelemin

1980-01-01

331

On Atomic Displacements in 90° Ferroelectric Domain Walls of Tetragonal BaTiO3 Crystals  

Microsoft Academic Search

The displacement field of atoms in 90° ferroelectric domain walls of tetragonal BaTiO3 is examined by symmetry analysis. Results illustrate advantages and limitations of this approach and demonstrate microscopic features of unusual asymmetric and irreversible domain walls.

V. JANOVEC; M. GROCKÝ; V. KOPSKÝ; Z. KLUIBER

2004-01-01

332

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

PubMed

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

Osipov, M A; Pajak, G

2014-09-01

333

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 Ge8Sb2Te11 (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

334

Thermodynamic forces in single crystals with dislocations  

NASA Astrophysics Data System (ADS)

A simple model for the evolution of macroscopic dislocation regions in a single crystal is presented. This model relies on maximal dissipation principle within Kröner's geometric description of the dislocated crystal. Mathematical methods and tools from shape optimization theory provide equilibrium relations at the dislocation front, similarly to previous work achieved on damage modelling (J Comput Phys 33(16):5010-5044, 2011). The deformation state variable is the incompatible strain as related to the dislocation density tensor by a relation involving the Ricci curvature of the crystal underlying elastic metric. The time evolution of the model variables follows from a novel interpretation of the Einstein-Hilbert flow in terms of dislocation microstructure energy. This flow is interpreted as the dissipation of non-conservative dislocations, due to the climb mechanism, modelled by an average effect of mesoscopic dislocations moving normal to their glide planes by adding or removing points defects. The model equations are a fourth-order tensor parabolic equation involving the operator "incompatibility," here appearing as a tensorial counterpart of the scalar Laplacian. This work encompasses and generalizes results previously announced (C R Acad Sci Paris Ser I 349:923-927, 2011), with in addition a series of physical interpretations to give a meaning to the newly introduced concepts.

Van Goethem, Nicolas

2014-06-01

335

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

336

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

337

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

338

Fabrication of crystals from single metal atoms.  

PubMed

Metal nanocrystals offer new concepts for the design of nanodevices with a range of potential applications. Currently the formation of metal nanocrystals cannot be controlled at the level of individual atoms. Here we describe a new general method for the fabrication of multi-heteroatom-doped graphitic matrices decorated with very small, ångström-sized, three-dimensional (3D)-metal crystals of defined size. We irradiate boron-rich precious-metal-encapsulated self-spreading polymer micelles with electrons and produce, in real time, a doped graphitic support on which individual osmium atoms hop and migrate to form 3D-nanocrystals, as small as 15 Å in diameter, within 1 h. Crystal growth can be observed, quantified and controlled in real time. We also synthesize the first examples of mixed ruthenium-osmium 3D-nanocrystals. This technology not only allows the production of ångström-sized homo- and hetero-crystals, but also provides new experimental insight into the dynamics of nanocrystals and pathways for their assembly from single atoms. PMID:24861089

Barry, Nicolas P E; Pitto-Barry, Anaïs; Sanchez, Ana M; Dove, Andrew P; Procter, Richard J; Soldevila-Barreda, Joan J; Kirby, Nigel; Hands-Portman, Ian; Smith, Corinne J; O'Reilly, Rachel K; Beanland, Richard; Sadler, Peter J

2014-01-01

339

Constitutive modeling for single crystal superalloys  

NASA Technical Reports Server (NTRS)

The inelastic response of single crystal gamma/gamma prime superalloys is quite different from the behavior of polycrystalline nickel base superalloys. Upto a critical temperature the yield stress of single crystal alloys is a function of the material orientation relative to the direction of the applied stress and the material exhibits significant tension/compression asymmetry. This behavior is primarily due to slip on the octahedral slip system. Above the critical temperature there is a sharp drop in the yield stress, cube slip becomes more predominant and the tension/compression asymmetry is reduced. Similar orientation and tension/compression asymmetry is observed in creep and secondary creep above the critical temperature is inferred to occur by octahedral slip. There are two exceptions to this behavior. First, loading near the (111) orientation exhibits cube slip at all temperatures, and; second, loading near the (001) orientation produces only octahedral slip at all temperatures. The constitutive model is based on separating the total global strain into elastic and inelastic components. This model is developed and briefly discussed.

Stouffer, D. C.; Jayaraman, N.; Sheh, M.; Alden, D.

1986-01-01

340

Employing a cylindrical single crystal in gas-surface dynamics  

Microsoft Academic Search

We describe the use of a polished, hollow cylindrical nickel single crystal to study effects of step edges on adsorption and desorption of gas phase molecules. The crystal is held in an ultra-high vacuum apparatus by a crystal holder that provides axial rotation about a [100] direction, and a crystal temperature range of 89 to 1100 K. A microchannel plate-based

C. Hahn; J. Shan; Y. Liu; O. Berg; A. W. Kleijn; L. B. F. Juurlink

2012-01-01

341

Spatiotemporal growth of faceted and curved single crystals  

PubMed

The spatiotemporal growth of single crystals in a crystalline polymer has been investigated theoretically based on a nonconserved time dependent Ginzburg-Landau equation (known as TDGL model A). In the description of the total free energy, a double-well local free energy density signifying metastability of crystal ordering is combined with a nonlocal free energy term representing an interface gradient. The resulting nonlinear reaction diffusion equation after renormalization possesses a solitary wave property. Two-dimensional numerical calculations were performed to elucidate the faceted single crystal growth including square, rectangular, diamond-shaped, and curved single crystals. A three-dimensional simulation was also undertaken for the emergence of diamond-shaped single crystals in polyethylene. Of particular importance is that the model field parameters can be linked directly to the material parameters of polyethylene single crystals. Simulation with various elements of the interface gradient coefficient tensor captures various topologies of polymer single crystals. PMID:11088211

Kyu; Mehta; Chiu

2000-04-01

342

Conformational changes at mesophase transitions in a ferroelectric liquid crystal by comparative DFT computational and (13)C NMR study.  

PubMed

In this work, we report a detailed investigation on both the conformational and the orientational ordering properties of a ferroelectric liquid crystal mesogen, namely, M10/**, through the combination of high resolution solid state (13)C NMR and density functional theory (DFT) computational methods. The trends of the observed (13)C chemical shift in the blue, cholesteric, and ferroelectric SmC* phases of M10/** were analyzed in terms of conformational changes occurring in the flexible parts of the molecule. In particular, we focused on the aliphatic alpha methylenoxy carbons because of their high sensitivity to mesophase environment, as evidenced by experimental (13)C chemical shift anisotropy (CSA). DFT computation of the chemical shift tensors as a function of geometrical parameters, such as dihedral angles, put in evidence significant changes in the average conformation at the mesophase transitions. The conformations predicted by DFT have been validated by comparing the calculated (13)C chemical shifts with those experimentally observed for the alkoxylic carbons, whose relative orientation plays a key role in establishing the overall conformation of the molecule in each liquid crystalline phase. Furthermore, the orientational order parameters of the relevant flexible fragments were calculated and found to be in good agreement with those characterizing similar systems, thus validating our approach. PMID:20701374

Marini, Alberto; Domenici, Valentina

2010-08-19

343

ORIGINAL PAPER Strength of single-crystal orthopyroxene under lithospheric  

E-print Network

ORIGINAL PAPER Strength of single-crystal orthopyroxene under lithospheric conditions Tomohiro sin- gle crystals was investigated via shear deformation exper- iments under lithospheric conditions under the lithospheric conditions suggesting that orthopyroxene may reduce the strength

344

Experimental dynamic metamorphism of mineral single crystals  

USGS Publications Warehouse

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

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

1993-01-01

345

Dynamic mechanism of the ferroelectric to antiferroelectric phase transition in chiral smectic liquid crystals.  

PubMed

The temperature-induced phase transition between the chiral smectic phases, antiferroelectric (smectic-C(A)*) and ferroelectric (smectic-C*), is found to occur through solitary wave propagation. We measure the free energy, which shows a double well shape in the entire SmC(A)* temperature range and the global minimum is found to shift from the antiferroelectric order to the ferroelectric order at the transition temperature. However, any significant supercooling is not observed and the transition cannot be described by the first order Landau-de Gennes theory, where the double well potential exists only in a narrow range of temperatures. This implies that the SmC(A)*-SmC* transition can occur only nonhomogeneously through the solitary wave propagation which overcomes the high energy barrier between the two minima. PMID:18851661

Song, Jang-Kun; Fukuda, Atsuo; Vij, J K

2008-08-29

346

Numerical Evaluation of Strain Rate Effect on Mechanical and Electromechanical Coupling Responses in BaTiO3 Single-Crystal Nanofilm  

NASA Astrophysics Data System (ADS)

The mechanical and electromechanical coupling responses of a ferroelectric single-crystal nanofilm under displacement loading at different strain rates have been simulated using the molecular dynamics method based on the shell model. While the linear stress-strain relation is independent of the strain rate, strong strain rate dependence is exhibited in the electromechanical coupling response for strain rates between 0 ns-1 and 0.5 ns-1. There is an approximate semilogarithmic linear relationship between the polarization stability strain and the strain rate. With increasing strain rate, local 180° domain switches take place sequentially from inside to outside in the stable domain structure evolution, and the number of domain walls increases. However, after the strain rate exceeds 0.5 ns-1, it has almost no effect on the?domain structure. This work is helpful for improving ferroelectric device design and expanding ferroelectric application fields.

Tian, Xiao Bao; Yang, Xin Hua; Cao, Wei Zhong

2014-02-01

347

Halide electroadsorption on single crystal surfaces  

SciTech Connect

The structure and phase behavior of halides have been investigated on single crystals of Ag and Au using synchrotron x-ray scattering techniques. The adlayer coverages are potential dependent. For all halides studied the authors found that with increasing potential, at a critical potential, a disordered adlayer transforms into an ordered structure. Often these ordered phases are incommensurate and exhibit potential-dependent lateral separations (electrocompression). The authors have analyzed the electrocompression in terms of a model which includes lateral interactions and partial charge. A continuous compression is not observed for Br on Ag(100). Rather, they find that the adsorption is site-specific (lattice gas) in both the ordered and disordered phases. The coverage increases with increasing potential and at a critical potential the disordered phase transforms to a well-ordered commensurate structure.

Ocko, B.M. [Brookhaven National Lab., Upton, NY (United States). Dept. of Physics; Wandlowski, T. [Univ. of Ulm (Germany). Dept. of Electrochemistry

1997-07-01

348

Multiphonon relaxation in YVO4 single crystals  

NASA Astrophysics Data System (ADS)

Multiphonon relaxation rates were measured for 13 different energy levels of various rare-earth ions in YVO4 single crystals at 77 K. Dependence of the multiphonon relaxation rate on the energy gap that separates each emitting multiplet from the one lying just below it was investigated over the range from 980 to 5200 cm-1. A significant change in gap dependence was observed for energy gaps smaller than about 2500 cm-1, in agreement with previous observations and with theoretical investigations. An extreme nonradiative transition rate of 1.1×1011 s-1 (?=9 ps), corresponding to a 980 cm-1 energy gap, was deduced from homogeneous absorption linewidth measurements at 1.5 K.

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

2000-02-01

349

Stress- Corrosion cracking of copper single crystals  

NASA Astrophysics Data System (ADS)

Constant extension rate tests have been carried out on copper single crystals in a sodium nitrite solution, using an applied potential to accelerate the cracking. Crack velocities up to 30 nm per second were obtained at 30 °C. The stress-corrosion fracture surfaces are cleavage-like, with curved striations parallel to the crack front. If the dynamic straining is stopped, the cracks apparently stop growing within about 20 /?m. The steps between adjacent flat facets are more energy-absorbing than in a-brass, providing a possible explanation for the importance of dynamic strain. Simultaneous acoustic emission and electrochemical current transients have been measured, and suggest that cracking proceeds by discontinuous cleavage.

Sieradzki, K.; Sabatini, R. L.; Newman, R. C.

1984-10-01

350

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

PubMed

In this Rapid Communication, results on smectic layer thickness, using synchrotron radiation x-ray diffraction, for different mixtures of ferroelectric and antiferroelectric liquid crystals are given. We find that with an increased ferroelectric component in the mixtures, the layer shrinkage at the de Vries SmA?-SmC? transition increases. This observation can be used to explain our previously observed behaviors [U. Manna, J.-K. Song, Yu. P. Panarin, A. Fukuda, and J. K. Vij, Phys. Rev. E 77, 041707 (2008)] that the soft-mode dielectric strength decreases, the Landau coefficient increases, and the Curie-Weiss temperature range decreases with increased ferroelectric component in the mixture exhibiting de Vries SmA?-SmC? transition. PMID:20866175

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

2010-05-01

351

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 sing...

Kiselev, Alexei D

2014-01-01

352

Thresholdless, hysteresis-free, V-shaped, electro-optical switching for a ferroelectric liquid crystal cell.  

PubMed

A ferroelectric liquid crystal (FLC) cell can be modeled as a combination of capacitors and resistors. In accordance with the properties of the FLC cell, external electric elements, such as capacitors and resistors, are usually connected to achieve a V-shaped performance at a driving inversion frequency fi. However, the inversion frequency is strongly dependent on the external electric elements and the applied voltage. In this paper, the relation between the inversion frequency and the applied voltage is discussed. Additionally, the inversion frequency is found to be approximately proportional to (ReqCeq)(-0.52), where Req and Ceq are equivalent resistance and capacitance, respectively. Based on the above properties, a useful driving scheme is proposed to achieve thresholdless, hysteresis-free, V-shaped characteristics for FLC cells at a driving frequency of 100 Hz. The driving scheme can be applied to fast-response FLC display. PMID:15324077

Tzeng, Shwu-Yun Tsay; Lin, T Y; Huang, R H; Wu, Jin-Jei; Wu, Shune-Long

2004-07-01

353

Nature of smectic A*-C* phase transitions in a series of ferroelectric liquid crystals with little smectic layer shrinkage.  

PubMed

The smectic layer spacing of two homologous series of ferroelectric liquid crystal compounds was characterized by small-angle x-ray diffraction and different degrees of smectic layer shrinkage on cooling from the SmA* into the SmC* phase were observed. The smectic A*-smectic C* phase transition was further studied by measuring the thermal and electric field effects on the optical tilt angle and the electric polarization. With decreasing length of the alkyl terminal chain the phase transition changes from tricritical exhibiting high layer shrinkage to a pure second-order transition with almost no layer shrinkage. This is explained by the increased one-dimensional translational order of the smectic layers, which seems to promote the "de Vries"-type [Mol. Cryst. Liq. Cryst. 41, 27 (1977)] smectic A*-C* phase transition with no or little layer shrinkage. PMID:17302502

Bezner, Samuel; Krueger, Michael; Hamplová, Vera; Glogarová, Milada; Giesselmann, Frank

2007-02-01

354

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

PubMed

We study both theoretically and experimentally the electro-optical properties of vertically aligned deformed helix ferroelectric liquid crystals (VADHFLC) with subwavelength pitch that are governed by the electrically induced optical biaxiality of the smectic helical structure. The key theoretical result is that the principal refractive indices of homogenized VADHFLC cells exhibit the quadratic nonlinearity and such behavior might be interpreted as an orientational Kerr effect caused by the electric-field-induced orientational distortions of the FLC helix. In our experiments, it has been observed that, for sufficiently weak electric fields, the magnitude of biaxiality is proportional to the square of electric field in good agreement with our theoretical results for the effective dielectric tensor of VADHFLCs. Under certain conditions, the 2? phase modulation of light, which is caused by one of the induced refractive indices, is observed without changes in ellipticity of incident light. PMID:23767555

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

2013-05-01

355

Electro-optical and dielectric characterizations of the Goldstone mode relaxation in ferroelectric chiral smectic C liquid crystals.  

PubMed

We report structural (helical pitch), electro-optical (tilt angle and spontaneous polarization) and dielectric (Goldstone mode) investigations of ferroelectric liquid crystals (FLCs) exhibiting the chiral smectic C phase (SmC(*)). All these characterizations were performed on two pure FLCs showing the SmC(*)-SmA-N(*) phase sequence and having small pitch, high spontaneous polarization and a large relaxation frequency. We have determined the Goldstone rotational viscosity and the twist elastic constant in the SmC(*) phase from the helical pitch, tilt angle, polarization, dielectric strength experimental data and from the relaxation frequency of the Goldstone-mode relaxation. An Arrhenius-type behaviour of the Goldstone rotational viscosity was obtained and the corresponding activation energies were evaluated. PMID:21483074

Hemine, J; Legrand, C; Daoudi, A; Isaert, N; Kaaouachi, A El; Nguyen, H T

2007-07-25

356

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

NASA Astrophysics Data System (ADS)

We study both theoretically and experimentally the electro-optical properties of vertically aligned deformed helix ferroelectric liquid crystals (VADHFLC) with subwavelength pitch that are governed by the electrically induced optical biaxiality of the smectic helical structure. The key theoretical result is that the principal refractive indices of homogenized VADHFLC cells exhibit the quadratic nonlinearity and such behavior might be interpreted as an orientational Kerr effect caused by the electric-field-induced orientational distortions of the FLC helix. In our experiments, it has been observed that, for sufficiently weak electric fields, the magnitude of biaxiality is proportional to the square of electric field in good agreement with our theoretical results for the effective dielectric tensor of VADHFLCs. Under certain conditions, the 2? phase modulation of light, which is caused by one of the induced refractive indices, is observed without changes in ellipticity of incident light.

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

2013-05-01

357

Effect of cadmium telluride quantum dots on the dielectric and electro-optical properties of ferroelectric liquid crystals.  

PubMed

We present here the dielectric and electro-optical studies of cadmium telluride quantum dots (CdTe QDs) doped ferroelectric liquid crystals (FLCs). It has been observed that the doping of CdTe QDs not only induced a pronounced memory effect but also affected the physical parameters of FLC material (LAHS19). The modifications in the physical parameters and memory effect of LAHS19 are found to depend on the concentration ratio of CdTe QDs. The lower concentration of CdTe QDs (1-3 wt%) enhanced the values of spontaneous polarization and rotational viscosity of LAHS19 material but did not favor the memory effect, whereas a higher concentration of CdTe QDs (>5 wt%) degraded the alignment of LAHS19 material. The doping of ?5 wt% of CdTe QDs is found to be the most suitable for achieving good memory effect without significantly affecting the material parameters. PMID:21599187

Kumar, A; Biradar, A M

2011-04-01

358

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

PubMed

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

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

2013-05-01

359

TOPICAL REVIEW: Organic field-effect transistors using single crystals  

Microsoft Academic Search

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of

Tatsuo Hasegawa; Jun Takeya

2009-01-01

360

Dielectric and Piezoelectric Properties of 0.91Pb(Zn1\\/3Nb2\\/3)O3-0.09PbTiO3 Single Crystals  

Microsoft Academic Search

The dielectric, piezoelectric and elastic properties of 0.91Pb(Zn1\\/3Nb2\\/3)O3-0.09PbTiO3 single crystals have been investigated as functions of temperature and applied electric field. Two multiple phase transitions at 68°C and 178°C, the crystal changing from the rhombohedral ferroelectric phase to tetragonal ferroelectric and then to cubic paraelectric, have been observed. Both the transitions are of first-order, but both are slightly diffused. Significant

Jun Kuwata; Kenji Uchino; Shoichiro Nomura

1982-01-01

361

Low-frequency-dependent electro-optic properties of potassium lithium tantalate niobate single crystals  

NASA Astrophysics Data System (ADS)

A series of lead-free ferroelectric potassium lithium tantalate niobate K0.95Li0.05Ta1-xNbxO3 (x = 0.78, 0.69, 0.60, 0.52) single crystals were grown using the top-seeded melt growth method. The low-frequency-dependent linear electro-optic properties of K0.95Li0.05Ta1-xNbxO3 single crystals in the tetragonal state were investigated using the Senarmont method, autoscanning Mach-Zehnder interferometer technique and AC measurement method at room temperature. The electro-optic measurements were taken with continuous low frequency (from 1 kHz to 100 kHz) of a sinusoidal electric field, and large electro-optic responses were observed. For every component, the values of the electro-optic coefficients ?33, ?13 and ?c decrease with the increase of frequency. However, the ?51 shows low sensitivity to the change of frequency. ?33, ?13 and ?c increase with tantalum content, but ?51 decreases with the increase of tantalum content. The electro-optic properties of high-optical-quality K0.95Li0.05Ta1-xNbxO3 single crystals forecast their outstanding potential in various electro-optic applications.

Li, Yang; Li, Jun; Zhou, Zhongxiang; Guo, Ruyan; Bhalla, Amar S.

2013-05-01

362

Three-dimensional single crystal silicon micromachining  

NASA Astrophysics Data System (ADS)

A monolithic, multiple-level (ML), single-crystal-silicon (SCS) micromachining process called SCREAM3D has been developed. The high-aspect-ratio (HAR) levels are self-aligned and are fabricated from a single substrate by deep etching. Anisotropic reactive ion etching of silicon has been studied in detail and new recipes for the vertical etch and release of HAR ML structures have been developed. The SCREAM3D levels are electrically isolated from the substrate and one another using a novel ML isolation scheme, which requires only a single lithography and metallization step, regardless of the number of levels. Two- and three-level SCREAM3D devices have been fabricated. They demonstrate three device concepts: ML microelectromechanical systems (MEMS), micromachined electron gun arrays (MEGA) and ML actuators for out-of-plane deflection. ML MEMS consist of several suspended levels moving relative to each other. They can be coupled mechanically and/or electrically. One example is a novel clamp-alignment device which uses the relative translation of two initially self-aligned apertures to grip and align an external component (such as an optical fiber) to the wafer. MEGA is a multiple-beam architecture to increase the throughput of electron beam lithography. MEGA is an array of identical electron sources, consisting of silicon field emitters with integrated electrostatic lenses. The parallel operation of a large number (N = 10,000) of sources is required to increase the total current and throughput (60 8"-wafers/hour) of the system while maintaining standard single-beam parameters (10nA, 20MHz exposure rate) and limiting charge-interaction effects. ML actuators have been studied by numerical simulation. All four designs outperform comparable single-level actuators: the generated force is up to five times larger, and the range of motion up to ten times greater. Two of the ML designs operate bi-directionally and one design can be used to form a bi-stable system. Several of the actuators have been integrated with torsional and z-motion-stages and experimentally characterized using laser vibrometry. SCREAM3D extends SCS bulk-micromachining to multiple-level structures. The self-aligned, high-aspect-ratio levels allow the implementation of more efficient device designs and novel ML device concepts. Complex actuators, generating larger forces in reduced chip area, can be fabricated and entire microinstruments can be integrated on a single wafer.

Hofmann, Wolfgang Maximilian Josef

1999-11-01

363

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

364

Temperature gradient transport growth of potassium tantalate niobate, KTa??xNbxO?, single crystals  

E-print Network

of crystal no. 2 . 39 CHAPTER I INTRODUCTION A. TECHNICAL BACKGROUND OF FERROELECTRIC MATERIALS Within the past 50 years many of the fundamental relationships between the structural elements of ferroelectric materials and their properties have been...), and ammonium dihydrogen phosphate (NH4H2P04) until a breakthrough occurred in t945. In an effort to find new dielectrics with superior properties to replace the commonly used mica, ceramics of barium titanate, BaTIOs were processed. Quite unexpectedly...

Goeking, Kent Wayne

2012-06-07

365

P-185 / L. Tan P-185: Single Cell Gap Single Mode Transflective Liquid Crystal Display  

E-print Network

P-185 / L. Tan P-185: Single Cell Gap Single Mode Transflective Liquid Crystal Display with High Kong Abstract A transflective liquid crystal display with single cell gap single mode structure of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Hong

366

Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals  

DOEpatents

A method of fabricating bulk YBa.sub.2 Cu.sub.3 O.sub.x where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa.sub.2 Cu.sub.3 O.sub.x are heated in the presence of a Nd.sub.1+x Ba.sub.2-x Cu.sub.3 O.sub.y seed crystal to a temperature sufficient to form a liquid phase in the YBa.sub.2 Cu.sub.3 O.sub.x while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa.sub.2 Cu.sub.3 O.sub.x material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material.

Todt, Volker (Lemont, IL); Miller, Dean J. (Darien, IL); Shi, Donglu (Oak Park, OH); Sengupta, Suvankar (Columbus, OH)

1998-01-01

367

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

368

Effect of strain and deadlayer on the polarization switching of ferroelectric Jie Wang, Yifan Xia, Long-Qing Chen, and San-Qiang Shi  

E-print Network

surface domain nucleation in a ferroelectric under an electrically charged tip J. Appl. Phys. 111, 014106 (2012) Polarization reversal and jump-like domain wall motion in stoichiometric LiTaO3 produced by vapor J. Appl. Phys. 110, 114106 (2011) Single walled carbon nano-tube, ferroelectric liquid crystal

Chen, Long-Qing

369

Stabilization of metastable ferroelectric Ba1?xCaxTi2O5 by breaking Ca-site selectivity via crystallization from glass  

PubMed Central

The thermal stability and dielectric and structural properties of ferroelectric Ba1?xCaxTi2O5 (0 ? x ? 0.30) prepared by crystallization from glass are investigated. The Ba1?xCaxTi2O5 compounds with x < 0.10 are thermally stable phases, while those with x ? 0.10 are metastable phases. The ferroelectric transition temperature drastically decreases from 470 to 220°C with increasing x. Crystal structure analyses reveal that one of two possible Ba sites is occupied by Ca in the stable phase region, while Ca-site selectivity is broken in the metastable phase region. The Ca-site selectivity introduces local distortion and makes the crystal lattice unstable. However, the local distortion is suppressed by the occupancy of Ca into both Ba sites. Accordingly, the metastable ferroelectric phase can be obtained beyond the substitution limit of Ca by crystallization from the glassy state. The stabilization mechanism provides possible wide control of the functionality of materials by expanding the composition range. PMID:24145958

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

2013-01-01

370

Characterization and growth of magnesium diboride single crystals  

Microsoft Academic Search

Single crystals of magnesium diboride with maximum dimension of 200×200×60?m3 have been successfully grown from copper flux in iron capsules. MgB2 crystallized separately in a system with the composition Mg40Cu40B20, and large single crystals were grown. Crystals grow together in the system with the composition Mg35Cu40B25, and MgB4 is found in this system due to excess B content. MgB2 crystallizes

Z. X. Cheng; X. L. Wang; A. V. Pan; H. L. Liu; S. X. Dou

2004-01-01

371

Fractoemission from cyclotrimethylenetrinitramine (RDX) explosive single crystals  

NASA Astrophysics Data System (ADS)

Production-grade Class D and laboratory-grown cyclotrimethylenetrinitramine (RDX) explosive crystals were fractured in a vacuum (10-5 Pa) while viewed by particle detectors biased to separate positive and negative charge. Fracture was achieved by compressive loading (both production and laboratory crystals) and by three-point bending (laboratory crystals only). ``Cleavage''-type fracture resulted for several crystals subjected to three-point bending and yielded a sharp emission peak followed by rapid decay. Longer and more intense emission was observed for a few crystals broken in flexure which may correspond to more ``energetic'' fracture. Multiple fracture, involving surface frictional grinding, occurred for crystals that were compressed; in this case, relatively intense emission resulted which continued for several minutes after fracturing the crystals. These results are discussed in terms of possible mechanisms.

Dickinson, J. T.; Miles, M. H.; Elban, W. L.; Rosemeier, R. G.

1984-06-01

372

Growth and preparation of lead-potassium-niobate (PKN) single crystals specimens  

NASA Astrophysics Data System (ADS)

Lead-potassium-niobate, Pb2KNb5O15 (PKN) is a member of the family of tungsten-bronze materials of the type A6B10O30. It is both ferroelastic and ferroelectric and it can be considered as a pseudo-binary compound represented by 2PbNb2O6.KNbO3. Its piezoelectric and electromechanical properties make it the leading substrate material for the fabrication of temperature compensated surface-acoustic-wave (SAW) devices. However, it is very difficult to synthesize PKN as a large, crack-free and chemically homogeneous single crystal. This report deals primarily with the problems encountered in crystal growth of PKN and suggests means to circumvent them. Furthermore, it describes two new methods - top seeded and solution growth - to synthesize crack-free, stoichiometrically uniform large single crystals of the compound. Also the results of PKN characterization by means of X-ray diffraction and dielectric, optical and electrical conductivity measurements are presented and discussed here.

Pandey, R. K.

1982-12-01

373

Chemical Solution Routes to Single-Crystal Thin Films  

Microsoft Academic Search

Epitaxial thin films of inorganic single crystals can be grown on single-crystal substrates with a variety of different solution chemistries. This review emphasizes chemical solution deposition, in which a solution is used to deposit a layer of precursor molecules that decompose to low-density, polycrystalline films during heating. Ways to control film cracking during deposition and heat treatment and why many

F. F. Lange

1996-01-01

374

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

375

A Quick Method for Determining the Density of Single Crystals.  

ERIC Educational Resources Information Center

Shows how the Archimedes method is used to determine the density of a single crystal of ammonium oxalate monohydrate. Also shows how to calculate the density of other chemicals when they are available as single crystals. Experimental procedures and materials needed are included. (JN)

Roman, Pascual; Gutierrez-Zorrilla, Juan M.

1985-01-01

376

A Multivariant model for single crystal shape memory alloy behavior  

Microsoft Academic Search

A general 3-D multivariant model based on thermodynamics and micromechanics for single crystal shape memory alloy (SMA) behavior is presented. This model is based on the habit plane and transformation directions for the variants of martensite in a given material. From this information, the single crystal behavior of the material to temperature and mechanical loads is derived using the concept

Miinshiou Huang; L. C. Brinson

1998-01-01

377

Ferroelectric properties of doped triglycine sulfate crystals grown at negative temperatures  

NASA Astrophysics Data System (ADS)

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 established, which indicates that the polar state in crystals is stabilized by growth defects.

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

2009-07-01

378

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

379

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

380

A continuum analysis of charge induced ferroelectric domain wall motions  

Microsoft Academic Search

A continuum model is presented for the motion of a domain wall in a plane 90°-domain configuration subjected to an isolated extrinsic charge near the surface of a ferroelectric single crystal. Local pinning is postulated for the kinetic law. Before the appearance of the extrinsic charge, all polarization surface charges are taken to be neutralized by environmental charges. The domain

H. Kessler; H. Balke

2006-01-01

381

Investigation of ferroelectric materials with scanning microwave microscope  

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

382

Temperature-induced sign reversal of biaxiality observed by conoscopy in some ferroelectric Sm-C* liquid crystals.  

PubMed

We have studied various ferroelectric liquid crystals to find the average molecular direction of the shortest axis in the perfectly unwound state by using tilted conoscopic measurements. We find that there exist two types of temperature dependencies of the biaxiality. Some materials exhibit increasing biaxiality while others show decreasing biaxiality with increasing temperature. The former shows a temperature-induced sign reversal of biaxiality. Three different physical mechanisms are identified as responsible for the emergence of biaxiality: (i) anisotropic fluctuations of the long molecular axis, (ii) a biased rotation around the long axis, and (iii) the local field effect. By means of a simple theoretical investigation, we conclude that these two types of trends are due mainly to the opposite signs of the biaxial order parameter C , which represents the second mechanism: the biased rotation around the long axis. This means that the central phenyl planes of molecules belonging to materials having biaxiality that increases with temperature are oriented on the average parallel to the tilt plane (the shortest index of refraction axis normal to the tilt plane), and, on the contrary, in those of the others molecules are oriented perpendicular to the tilt plane (the shortest index of refraction axis lying in the tilt plane). Thus, the direction of the phenyl ring plane of the liquid crystal molecules determines the different temperature dependencies of the biaxiality. It is also shown that the phenomenon of sign reversal of the biaxiality is due to the competitive contributions of the first and second physical mechanisms. PMID:17677473

Song, Jang-Kun; Chandani, A D L; Fukuda, Atsuo; Vij, J K; Kobayashi, Ichiro; Emelyanenko, A V

2007-07-01

383

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

384

Cleavage oriented iron single crystal fracture toughness  

NASA Astrophysics Data System (ADS)

Fundamental understanding of atomic level mechanisms controlling cleavage fracture in bcc metals, and the corresponding brittle to ductile transition (BDT) has been a long sought, 'grand challenge' of science. This is particularly true for the BDT in Fe, which is among vital elements that underpin our technological civilization. A key obstacle to developing an understanding of the BDT in Fe is the absence of a reliable database on the temperature dependence of toughness in Fe. In ferritic alloys, the micro-arrest toughness of ferrite, Kmu(T), is hypothesized to control macroscopic cleavage. As a surrogate for Kmu(T), special techniques were developed to measure the arrest toughness, Ka(T), for cleavage oriented, Fe single crystals. Further, the mechanisms controlling cleavage and the BDT should be reflected in the loading rate dependence of static-dynamic initiation toughness, K Ic and KId. Thus KIc/d(T) were also measured for K-rate from 10-1 to 104 MPa?m/s. These studies led to the following conclusions: (1) Ka is semi-brittle, increasing from an average of ? 3.5 MPa?m at -196°C to ? 9 MPa?m at 0°C. (2) The (100) Ka are similar in the [010] and [011] and orientations, but cleavage does not occur on (110) planes. (3) The Ka for unalloyed Fe is about 150°C lower than that for Fe-3wt%Si, suggesting that equivalent Ka may occur at equivalent lattice sigmay. (4) Higher K-rate shift K Ic/d(T) curves to higher T. (5) The shifts of the KIc/d(T) and Ka(T) curves can be understood and modeled based on dislocation dynamics concepts for the glide of screw dislocations with a stress (and T) controlled activation energy, Ea, with a maximum value of about ? 0.5 eV. (6) This Ea is consistent with a double kink nucleation mechanism. Etch pit, slip trace and ledge patterns on side, fracture and sectioned surfaces of the crystals were characterized to study dislocation activity associated with cleavage and the BDT. The results showed extensive dislocation activity on {110}<111> and {211}<111> slip systems. Consistent with its semi-brittle nature, there is evidence of significant dislocation glide and multiplication during cleavage, perhaps associated with pre-existing dislocations.

Hribernik, Michael Louis

385

High pressure applications of ferroelectric polymers  

Microsoft Academic Search

Ferroelectric polymers are the most recent class piezoelectric and pyroelectric materials developed. The most common piezoelectric polymers are PVDF, based on the monomer CH2-CF2 and copolymers PVDF with C2F3H. Techniques to process PVDF and P(VDF-TrFE) copolymers such that their physical properties exhibit reproducibility approaching that of piezoelectric single crystals are presented. Instrinsic piezoelectric properties of such materials are presented in

F. Bauer

1994-01-01

386

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

Microsoft Academic Search

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

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

2006-01-01

387

Method for harvesting rare earth barium copper oxide single crystals  

DOEpatents

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

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

1996-01-01

388

Method for harvesting single crystals from a peritectic melt  

DOEpatents

A method of preparing 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, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals unmelted, allowing the wicking away of the peritectic liquid. 2 figs.

Todt, V.R.; Sengupta, S.; Shi, D.

1996-08-27

389

Method for harvesting single crystals from a peritectic melt  

DOEpatents

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

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

1996-01-01

390

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

391

A Single Crystal Niobium RF Cavity of the TESLA Shape  

SciTech Connect

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material without destruction of the single crystal. A prototype single crystal single cell cavity was build. An accelerating gradient of 37.5 MV/m was reached after approximately 110 {mu}m of Buffered Chemical Polishing (BCP) and in situ baking at 120 deg. C for 6 hrs with a quality factor exceeding 2x1010 at 1.8 K. The developed fabrication method can be extended to fabrication of multi cell cavities.

Singer, W.; Singer, X.; Kneisel, P. [DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

2007-08-09

392

A Single Crystal Niobium RF Cavity of the TESLA Shape  

SciTech Connect

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material without destruction of the single crystal. A prototype single crystal single cell cavity was built. An accelerating gradient of 37.5 MV/m was reached after approximately 110 mu-m of Buffered Chanical Polishing (BCP) and in situ baking at 120°C for 6 hrs with a quality factor exceeding 2x1010 at 1.8 K. The developed fabrication method can be extended to fabrication of multi cell cavities.

W. Singer; X. Singer; P. Kneisel

2007-09-01

393

Giant Enhancement of Ferroelectricity in Strained BaTiO3 Thin Films  

Microsoft Academic Search

Epitaxial thin films often have quite different properties than bulk single crystals due to epitaxial and thermal strains arising from substrate constraints. This offers the opportunity to modify ferroelectric properties by heteroepitaxy and strain engineering. Biaxial compressive strain has been used to dramatically enhance the ferroelectric properties of BaTiO3 thin films on (110) GdScO3 and (110) DyScO3 substrates [1]. This

Chang-Beom Eom

2005-01-01

394

Electromechanical properties of tetragonal Pb(In1?2Nb1?2)O3-Pb(Mg1?3Nb2?3)O3-PbTiO3 ferroelectric crystals  

PubMed Central

The ferroelectric, dielectric, elastic, piezoelectric, and electromechanical properties of tetragonal Pb(In1?2Nb1?2)O3?Pb(Mg1?3Nb2?3)O3?PbTiO3 (PIN–PMN–PT) crystals were investigated. The single domain piezoelectric coefficients d33, d15, and d31 were found to be 530, 2350, and ?200 pC?N, respectively, with electromechanical coupling factors k33, k15, and k31 being on the order of 0.84, 0.85, and 0.58. The mechanical quality factor Q for longitudinal mode was found to be >700, with high coercive field (Ec) being on the order of 10 kV?cm. The temperature and dc bias electric-field characteristics of single domain tetragonal PIN–PMN–PT crystals were also investigated. In contrast to [001] oriented domain engineered rhombohedral crystals, tetragonal PIN–PMN–PT crystals exhibited broader temperature usage range and higher thermal?electric field stability, with improved coercive field and mechanical quality factor. PMID:20368987

Li, Fei; Zhang, Shujun; Xu, Zhuo; Wei, Xiaoyong; Luo, Jun; Shrout, Thomas R.

2010-01-01

395

Dielectric and baric characteristics of TlS single crystal  

NASA Astrophysics Data System (ADS)

The investigation of the frequency dependences of the dielectric coefficients and ac-conductivity of the TlS single crystals made it possible to elucidate the nature of dielectric loss and the charge transfer mechanism. Moreover, we evaluated the density and energy spread of localized states near the Fermi level, the average hopping time and the average hopping length. It was shown that the dc-conductivity of the TlS single crystals can be controlled by varying the hydrostatic pressure. This has opened up possibilities for using TlS single crystals as active elements of pressure detectors.

Mustafaeva, S. N.; Asadov, M. M.; Ismailov, A. A.

2014-11-01

396

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

397

Effect of the compressive stress on both polarization rotation and phase transitions in PMN-30%PT single crystal  

NASA Astrophysics Data System (ADS)

In this paper, we have investigated the dependence of both the electromechanical effect and the electrostriction on the compressive stress in PMN-30%PT single crystal on the basis of single domain polarization rotation model. In the model, the electroelastic energy induced by the compressive stress is taken into account. The results have demonstrated that the compressive stress can lead to a significant change in the initial polarization state in the crystal. The reason lies in the stress induced anisotropy which is the coupling between the compressive stress and the electrostrictive coefficients. Thus, the initial polarization state in single crystal is determined by the combination of both electrocrystalline anisotropy and the stress induced anisotropy. The compressive stress along the [100] axis can make the polarization in the crystal be perpendicular to the stress direction, and make it difficult to be polarized to the saturation. This model is useful for better understanding both the polarization rotation and electromechanical effect in ferroelectric crystals with the compressive stress present.

Zhang, Hui

2014-05-01

398

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

399

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

400

Compact, high power, energy efficient transmit systems for UUVs using single crystal transducers  

NASA Astrophysics Data System (ADS)

UUVs are currently being designed to perform a multiplitude of tasks in ocean exploration and Naval warfighting. Many of these tasks require the use of active acoustic projectors, and many may require the UUV to operate independently for hours, days, or even weeks. In order for a UUV to be as versatile as possible, its active transmit system must be versatile as well, implying that broad acoustic bandwidths are a must. However, due to size and battery life limitations, this broadband system must also be compact and energy efficient. By virtue of their extraordinary material properties, ferroelectric single crystals are the ideal transduction material for developing such broadband systems. The effect of their high coupling factor on transmit systems shall be illustrated by showing the dramatic impact on amplifier size, power factor, and acoustic response that is possible using these materials. In particular, a transducer built with these materials can be well matched to the power amplifier, i.e., 80% or more of the amplifier power reaches the transducer, over decades of frequency. Measured results from several prototype single crystal transducers shall be presented to demonstrate that the theoretical gains are actually realizable in practical devices. [Work sponsored by DARPA.

Robinson, Harold

2001-05-01

401

Local properties of the surface layer(s) of BiFeO3 single crystals  

NASA Astrophysics Data System (ADS)

The surface of BiFeO3 single crystals has been characterized at the local level using several AFM-based techniques. We have observed the presence of two different epilayers showing electrical and mechanical properties different from those of the bulk: a ferroelectrically "dead" outer skin of 5 nm sitting upon a subsurface layer that displays an extremely fine pattern of hierarchical self-ordered nanodomains. Based on the size of the nanodomains and applying a Kittel-like analysis, we argue that the nanotwinned region should be confined in a layer less than a micron deep. The superficial phase transition at T* = 275 °C is restricted to the outer skin layer (the "dead" layer), while the nanotwinned layer is insensitive to this transition. In view of the photovoltaic properties and spin-dependent transport of domain walls in BiFeO3, the existence of nanodomains (and thus a high density of domain walls) in bulk single crystals is likely to be relevant for understanding their functional properties.

Domingo, Neus; Narvaez, Jackeline; Alexe, Marin; Catalan, Gustau

2013-05-01

402

Molecular models for ferroelectric liquid crystals with conventional and anomalously weak layer contraction.  

PubMed

A molecular theory of the ferroelectric smectic C* phase has been developed using the simple model of a chiral molecule composed of a uniaxial core and a pair of off-center nonparallel dipoles which determine molecular chirality and polarity. The interaction between uniaxial cores is modeled by a rather general effective potential which can be used to describe smectic materials with both conventional and anomalously weak layer contraction in the smectic C* phase. Spontaneous polarization, tilt, and layer spacing are calculated numerically as functions of temperature, and it is shown that the variation of the polarization generally deviates from that of the tilt angle. It is shown that this deviation is more pronounced in smectic materials tilting with low layer contraction which corresponds to existing experimental data. The model has been used to reproduce qualitatively the experimental data for polarization, tilt and layer spacing for two similar mixtures exhibiting conventional and anomalously weak layer contraction. The polarization and the tilt are also calculated in the case when the smectic A-smectic C* transition is characterized by the biaxial primary order parameter. PMID:19230116

Osipov, M A; Gorkunov, M V; Gleeson, H F; Jaradat, S

2008-08-01

403

Magnetic and magnetoelectric properties of Ba2-xSrxNi2Fe12O22 single crystals with Y-type hexaferrite structure  

NASA Astrophysics Data System (ADS)

We studied the magnetic and magnetoelectric properties of Ba2-xSrxNi2Fe12O22 single crystals over a wide composition range (0 ? x ? 1.5). All the crystals show a ferrimagnetic order at around 660 K. While a Sr-free crystal is simply ferrimagnetic down to the lowest temperature, a transition from the ferrimagnetic into a screw magnetic ordered state was observed at temperatures below 300 K in Sr-substituted crystals. The transition temperature monotonically increases with increasing Sr content, meaning that the screw ordered state is stabilized by the Sr-substitution. By applying a magnetic field perpendicular to the hexagonal c axis, the samples showing the ground-state screw order undergo successive metamagnetic transitions and exhibit magnetically induced ferroelectricity in some of the intermediate magnetic phases. In an intermediate magnetic phase, the largest electric polarization emerges (2 × 102 ?C/m2 for x = 1.5 crystal), i.e., magnetoelectric effect. The evolution of the magnetic structures related to the magnetoelectric effect in x = 1.5 crystal was clarified by means of in-field neutron diffraction measurements. Though the magnetoelectric effect in the as-grown crystal was measurable only below ˜100 K due to its low resistivity, a post-annealing drastically enhances the resistivity and allows us to observe the magnetically induced ferroelectricity up to ˜175 K.

Hiraoka, Yuji; Nakamura, Hiroyuki; Soda, Minoru; Wakabayashi, Yusuke; Kimura, Tsuyoshi

2011-08-01

404

Time-resolved infrared spectroscopic study of the switching dynamics of a surface-stabilized ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

The orientation dynamics of a ferroelectric liquid crystal with a naphthalene ring (FLC-3) during the electric-field-induced switching between two surface-stabilized states was investigated by means of time-resolved Fourier-transform infrared spectroscopy. Time-resolved infrared spectra of the planar-aligned cell of FLC-3 were measured as a function of the polarization angle ranging from 0° to 180° under a rectangular electric field +/-40 V with a 5-kHz repetition rate in the smectic-C* (Sm-C*) phase at 137 °C. From these spectra details about the mutual arrangement of different molecular segments at all the delay times in the Sm-C* phase were derived. It was found that the C=O group in the core moiety exhibits a dynamical behavior different from that in the chiral moiety during the electric-field-induced switching between the two surface-stabilized states. The most important finding in the present study is that during the electric-field-induced switching the FLC molecule not only rotates around the layer normal, but also revolves around its own long axis. Furthermore, time-resolved infrared spectroscopy revealed that each group in the core moiety passes almost simultaneously through the projection of the layer normal in the cell window during the dynamic switching.

Zhao, J. G.; Yoshihara, T.; Siesler, H. W.; Ozaki, Y.

2002-02-01

405

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

406

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

407

X-Ray Study of Polygonization in Copper Single Crystals  

Microsoft Academic Search

Single crystals of electrolytic tough pitch copper and of high purity (99.999%) copper were deformed by bending. The substructure in the as-bent and annealed crystals was studied by means of sensitive x-ray techniques. It was found that regardless of purity, crystals of certain orientations in the as-bent condition do not have sub-boundaries detectable by the methods used. Polygonization took place

C. T. Wei; M. N. Parthasarathi; P. A. Beck

1957-01-01

408

Optical electric-field sensor based on angular optical bias using single ?-BaB2O4 crystal.  

PubMed

A novel optical electric-field sensor is proposed and demonstrated in experiment by use of a single beta barium borate (?-BaB2O4, BBO) crystal. The optical sensing unit is only composed of one BBO crystal and two polarizers. An optical phase bias of 0.5? is provided by using natural birefringence in the BBO crystal itself. A small angle (e.g., 0.6°) between the sensing light beam and principal axis of the crystal is required in order to produce the above optical bias. Thus the BBO crystal is used as the electric-field-sensing element and quarter waveplate. The ac electric field in the range of (1.4-703.2) kV/m has been measured with measurement sensitivity of 1.39 mV/(kV/m) and nonlinear error of 0.6%. Compared with lithium niobate crystal used as an electric-field sensor, main advantages of the BBO crystal include higher measurement sensitivity, compact configuration, and no ferroelectric ringing effect. PMID:24216661

Li, Changsheng; Shen, Xiaoli; Zeng, Rong

2013-11-01

409

Mesoporous silicon photonic crystal microparticles: towards single-cell optical  

E-print Network

Mesoporous silicon photonic crystal microparticles: towards single-cell optical biosensors Bin Guan such as the coupling of antibodies. The surface chemistry remained unchanged after sonication of the PSi to form PSi crystals, with complicated multilayer structures, to be produced. High- quality optical structures

Kilian, Kristopher A.

410

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

411

Electrochemistry of transition metal single crystals with well defined surfaces  

Microsoft Academic Search

The effect of extended defects of the surface of metallic single crystals on the electrochemical processes of dissolution and formation of a new phase has been analysed. Theoretical ideas on the rearrangement of a crystal surface (phase transitions of the second kind) during the adsorption of surface-active substances are presented. The reconstruction (faceting) of the surface under the influence of

Gennadii V. Khaldeev; T. A. Syur

1992-01-01

412

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

413

The Herbertsmithite Hamiltonian: ?SR measurements on single crystals  

E-print Network

We present transverse field muon spin rotation/relaxation measurements on single crystals of the spin-1/2 kagome antiferromagnet Herbertsmithite. We find that the spins are more easily polarized when the field is perpendicular ...

Ofer, Oren

414

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

415

Synthesis and physical characterization of thermoelectric single crystals  

E-print Network

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

Porras Pérez Guerrero, Juan Pablo

2012-01-01

416

Aluminium segregation of TiAl during single crystal growth  

SciTech Connect

{gamma}-TiAl single crystals have been successfully prepared by an induction-heated cold crucible Czochralski technique which offers more flexibility than vertical float zoning. Compositional analysis of the Czochralski grown single crystals indicates a homogeneous composition after initial transition; and the average composition is close to the peritectic composition. However, {gamma}-TiAl single crystals prepared by vertical float zoning show a small aluminium segregation profile along the growth direction; and the average composition of the as-grown crystals is close to that of the starting alloy. Compositional analysis further demonstrated the banded structure with alternative single {gamma}-phase and {alpha}{sub 2} + {gamma} lamellar regions in the vertical float zoned Ti-54 at.% Al.

Bi, Y.J.; Abell, J.S. [Univ. of Birmingham (United Kingdom). School of Metallurgy and Materials] [Univ. of Birmingham (United Kingdom). School of Metallurgy and Materials

1997-09-15

417

High polarization single dipole mode photonic crystal microlaser  

Microsoft Academic Search

A photonic crystal microlaser with elongate lattice was fabricated. Lasing action of single mode, y-dipole mode, was observed. With this mode, a high polarization extinction ratio of 51:1 was obtained.

Wei Chen; Mingxin Xing; Wenjun Zhou; Anjin Liu; Lianghui Chen; Wanhua Zheng

2009-01-01

418

Superconducting Proximity Effect in Single-Crystal Nanowires  

E-print Network

This dissertation describes experimental studies of the superconducting proximity effect in single-crystal Pb, Sn, and Zn nanowires of lengths up to 60 um, with both ends of the nanowires in contact with macroscopic electrodes that are either...

Liu, Haidong

2010-07-14

419

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

420

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

NASA Astrophysics Data System (ADS)

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

Sherlock, Nevin P.

421

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

422

Constitutive modeling of creep of single crystal superalloys  

E-print Network

of single crystal nickel based superalloys developed over last few decades. The second and third generation of superalloys are characterized by increasing concentration of Rhenium which improves creep and fatigue resistance. Fourth gener- ation superalloys... of single crystal nickel based superalloys developed over last few decades. The second and third generation of superalloys are characterized by increasing concentration of Rhenium which improves creep and fatigue resistance. Fourth gener- ation superalloys...

Prasad, Sharat Chand

2006-10-30

423

250 W single-crystal fiber Yb:YAG laser.  

PubMed

We demonstrate an Yb:YAG single-crystal fiber laser with 251 W output power in continuous-wave and an optical efficiency of 44%. This performance can be explained by the high overlap between pump and signal beams brought by the pump guiding and by the good thermal management provided by the single-crystal fiber geometry. The oscillator performance with a reflectivity of the output coupler as low as 20% also shows high potential for power amplification. PMID:22825171

Délen, Xavier; Piehler, Stefan; Didierjean, Julien; Aubry, Nicolas; Voss, Andreas; Ahmed, Marwan Abdou; Graf, Thomas; Balembois, Francois; Georges, Patrick

2012-07-15

424

Thermal and dielectric studies of nickel malonate dihydrate single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of nickel malonate dihydrate were grown by the gel technique, employing the single diffusion method. Thermal dehydration of the crystal was investigated by thermogravimetric and differential thermal analyses. The title compound exhibits a steady thermal behaviour at higher temperature range of 350-800 °C. The dielectric properties of the prepared sample were analyzed as a function of frequency in the range of 1 kHz-1 MHz and at temperatures between 40 and 140 °C.

Mathew, Varghese; Mathai, K. C.; Mahadeven, C. K.; Abraham, K. E.

2011-02-01

425

Forward diffracted parametric X radiation from a silicon single crystal  

NASA Astrophysics Data System (ADS)

Experiments were performed with the 855 MeV electron beam of the Mainz Microtron MAMI which focused on still open questions in the X-ray emission process upon traversal of ultra relativistic electrons through single crystals. To elucidate the quest of kinematical versus dynamical production of PXR the radiation from silicon single crystal targets, emitted close to the electron direction, has been studied. The observed interference structures show that PXR is produced in a dynamical process.

Backe, H.; Rueda, A.; Lauth, W.; Clawiter, N.; El-Ghazaly, M.; Kunz, P.; Weber, T.

2005-05-01

426

Annealing Effect on Photovoltages of Quartz Single Crystals  

Microsoft Academic Search

We investigate the photovoltaic effects of quartz single crystals annealed at high temperatures in ambient atmosphere. The open-circuit photovoltages and surface morphologies strongly depend on the heating treatments. When the annealing temperature increases from room temperature to 900°C, the rms roughness of quartz single crystal wafers increases from 0.207 to 1.011 nm. In addition, the photovoltages decrease from 1.994muV at

Lu Tian; Song-Qing Zhao; Kun Zhao

2010-01-01

427

Synthesis and Single-Crystal Growth of Ca  

SciTech Connect

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

Nakatsuji, Satoru; Maeno, Yoshiteru

2001-01-01

428

FAST TRACK COMMUNICATION: The effect of the ferroelectric domain walls in the scanning near field optical microscopy response of periodically poled Ba2NaNb5O15 and LiNbO3 crystals  

Microsoft Academic Search

A study of Ba2NaNb5O15 and LiNbO3 crystals with periodic ferroelectric domain structures using the scanning near field optical microscopy technique is reported. Optical contrast is observed in the regions of ferroelectric domain boundaries and it is analysed using beam propagation method modelling. This reveals that the optical contrast, a consequence of changes in the refractive index, is not due to

T. P. J. Han; F. Jaque; J. Lamela; D. Jaque; G. Lifante; F. Cusso; A. A. Kamiskii

2009-01-01

429

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

430

Single femtosecond laser pulse-single crystal formation of glycine at the solution surface  

NASA Astrophysics Data System (ADS)

We demonstrate femtosecond laser-induced crystallization of glycine from its supersaturated solution depending on laser tunable parameters (pulse energy and repetition rate) and focal position, and examine the crystallization probability, crystal morphology, and crystal polymorph. The generation of cavitation bubble through multiphoton absorption of water depends on input laser pulse energy and repetition rate, which strongly determine morphology and number of the obtained crystals. Significant increase in the crystallization probability is observed by irradiating the femtosecond laser pulses to the air/solution interface, and single pulse-induced single crystal formation is successfully achieved. The crystallization mechanism is discussed in view of inhomogeneous mechanical stress induced by cavitation bubble generation and molecular assembly characteristics of the surface.

Liu, Tsung-Han; Uwada, Takayuki; Sugiyama, Teruki; Usman, Anwar; Hosokawa, Yoichiroh; Masuhara, Hiroshi; Chiang, Ting-Wei; Chen, Chun-Jung

2013-03-01

431

Influence of heat treatment on crystallization of strontium barium niobate (SBN) ferroelectric thin films  

NASA Astrophysics Data System (ADS)

Strontium barium niobate (SBN) thin films of good quality were deposited on Si and Pt/Si substrates using a polymeric resin containing metallic ions. Using x-ray diffraction, the presence of SBN phase for films annealed at 600 °C and 700 °C for 1 hour was identified on both substrates. Films were also crystallized by rapid thermal annealing (RTA) at different temperatures and for different times, presenting good crystallization. Undesired phases such as SrNb2O6 and BaNb2O6 appear in films deposited on Si and Pt/Si substrates for films crystallized using a conventional furnace. However, using RTA these phases were eliminated for films annealed at 700 °C for 60 and 120 seconds.

Mendes, R. G.; Araújo, E. B.; Eiras, J. A.

1999-12-01

432

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

E-print Network

polariz- ation Ps is oriented from the surface toward the crystal, i.e. on negative domains, the nematic orientation homéotrope. La lame opposée donne dans un premier temps une orientation planaire, puis homéotrope'apparaît, ni d'une éventuelle polarisation de surface, ni du changement d'orientation des domaines

Boyer, Edmond

433

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

434

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.

2014-10-01

435

Growth, Crystal Structure, and Thermopower of Single Crystals of UNi 1.9Sn  

Microsoft Academic Search

We have grown single crystals of UNi1.9(1)Sn from a semi-levitated melt using the Kyropoulos technique. The crystal structure of UNi1.9(1)Sn was determined by single-crystal X-ray diffraction and refined to a residual value of R=0.0336. This compound crystallizes in the cubic MnCu2Al-type structure with the lattice parameter a=6.4633(4) Å. The temperature dependence of the thermoelectric power, different from that observed for

L. Shlyk; J. C. Waerenborgh; M. Almeida

2000-01-01

436

Solution Growth of Rubrene Single Crystals Using Various Organic Solvents  

NASA Astrophysics Data System (ADS)

To fabricate organic field-effect transistors (OFETs) with high carrier mobility, we attempted to grow 5,6,11,12-tetraphenylnaphthacene (rubrene) single crystals from solution and to improve their quality. Investigations into solvents in which rubrene was highly soluble proved that its solubility depended on the presence or absence of aromatic rings and chloro groups rather than on the polarity of the solvents. Rubrene crystals were grown from aromatic solvents, specifically from toluene, p-xylene, and aniline solvents, as well as from 1,2-dichloroethane (DCE) solvent. As a result, rubrene single crystals larger than 1 mm were obtained. Powder X-ray diffraction (XRD) analysis showed that the crystals obtained from the p-xylene and toluene solvents were rubrene, and 1H-nuclear magnetic resonance (1H-NMR) measurement proved that the crystals had not incorporated the solvent at the detection level. In addition, atomic force microscopy (AFM) confirmed that the rubrene crystals grown from the p-xylene and aniline solvents had flat faces and that the crystal from the p-xylene solvent had monomolecular steps on parts of the surfaces. Rubrene single crystal OFETs with graphite electrodes and parylene as an insulator showed carrier mobilities of ?0.75 cm2 V-1 s-1.

Matsukawa, Takeshi; Takahashi, Yoshinori; Tokiyama, Tsukasa; Sasai, Kenichi; Murai, Yusuke; Hirota, Nobuhiro; Tominari, Yukihiro; Mino, Norihisa; Yoshimura, Masashi; Abe, Masayuki; Takeya, Junichi; Kitaoka, Yasuo; Mori, Yusuke; Morita, Seizo; Sasaki, Takatomo

2008-12-01

437

Fabrication of Surface-Stabilized Ferroelectric Liquid Crystal Display with Stripe-Shaped Domain Structure  

E-print Network

DC voltage would cause concerns for long-term stability. Some methods have been proposed to eliminate liquid crystal (FLC) alignment by rubbing the polyimide films doped with silicon naphthalocyanine applications.1) However, technical issues on the zig-zag defects, mechanical stability and DC voltage balance

Wu, Shin-Tson

438

Growth and properties of benzil doped benzimidazole (BMZ) single crystals  

SciTech Connect

In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure and doped benzimidazole crystals measured using Kurtz powder test.

Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Sukumar, M. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)] [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Vasudevan, V. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India) [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Shakir, Mohd. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)] [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)] [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Bhagavannarayana, G. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)] [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)

2010-09-15

439

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

440

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

441

Coupling of magnetic field and lattice strain and its impact on electronic phase separation in La0.335Pr0.335Ca0.33MnO3/ferroelectric crystal heterostructures  

NASA Astrophysics Data System (ADS)

Phase-separated La0.335Pr0.335Ca0.33MnO3 films were epitaxially grown on (001)- and (111)-oriented ferroelectric single-crystal substrates. Upon poling along the [001] or [111] direction, dramatic decrease in resistance, up to 99.98%, and complete melting of the charge-ordered phase were observed, caused by poling-induced strain rather than accumulation of electrostatic charge at interface. Such poling-induced strain effects can be effectively tuned by a magnetic field and mediated by electronic phase separation. In particular, our findings show that the evolution of the strength of electronic phase separation against temperature and magnetic field can be determined by measuring the strain-tunability of resistance [(?R/R)strain] under magnetic fields.

Zheng, M.; Li, X. Y.; Yang, M. M.; Zhu, Q. X.; Wang, Y.; Li, X. M.; Shi, X.; Chan, H. L. W.; Li, X. G.; Luo, H. S.; Zheng, R. K.

2013-12-01

442

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

443

Photorefractive Properties of Stoichiometric Lithium Niobate Single Crystals  

SciTech Connect

The specific features of photorefractive light scattering in nominally pure stoichiometric (Li/Nb = 1) sin- gle crystals grown from a melt with 58.6 mol % Li{sub 2}O (LiNbO{sub 3}st) and in the stoichiometric single crystals grown from a melt of congruent composition in the presence of K{sub 2}O flux (LiNbO{sub 3}stK{sub 2}O) have been investi- gated. At an excitation power of 30 mW, LiNbO{sub 3}stK{sub 2}O single crystals are found to exhibit a stronger photo- refractive effect than LiNbO{sub 3}st single crystals.

Sidorov, N. V. [Russian Academy of Sciences, Institute of Chemistry and Technology of Rare Earth Elements and Mineral Raw Materials, Kola Scientific Center (Russian Federation); Antonycheva, E. A.; Syui, A. V. [Far Eastern State Transport University (Russian Federation); Palatnikov, M. N., E-mail: palat_mn@chemy.kolasc.net.ru [Russian Academy of Sciences, Institute of Chemistry and Technology of Rare Earth Elements and Mineral Raw Materials, Kola Scientific Center (Russian Federation)

2010-11-15

444

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

445

VGF growth of germanium single crystals without crucible contact  

NASA Astrophysics Data System (ADS)

Experimental results on the vertical gradient freeze growth of germanium single crystals without crucible contact are presented. Two different approaches to establish a stable pressure difference necessary for avoiding the contact between crystal and crucible on solidification are described. Germanium crystals with a diameter of up to 3 in were grown almost without contact to the crucible wall. The effect of detachment is discussed with respect to the microscopical surface roughness and dislocation density of the grown crystals. In comparison to conventionally grown reference crystals the structural perfection of the detached-grown crystals is found to be much higher which can be attributed to the reduced thermal and thermo-mechanical stress in growth without wall contact.

Langheinrich, D.; Pätzold, O.; Raabe, L.; Stelter, M.

2010-08-01

446

Surface conduction on insulating BaTiO3 crystal suggesting an intrinsic surface electron layer.  

PubMed

We report conduction measurements on the clean, free surface of transparent insulating BaTiO3 single crystals in high vacuum. We find that the insulating BaTiO3 crystals exhibit surface conductance that is dependent on the spontaneous polarization, whereas no conduction perpendicular to the surface is observed. The surface conduction shows semimetallic temperature dependence and persists down to at least 100 K. The observations suggest a two-dimensional electron on a clean, free ferroelectric surface that may be regarded as a ferroelectric metal. The results have important implications for understandings of the fundamental properties of ferroelectrics, the size effect, and ferroelectric devices. PMID:11177824

Watanabe, Y; Okano, M; Masuda, A

2001-01-01

447

A low-temperature crystallization path for device-quality ferroelectric films  

SciTech Connect

We show a path for low-temperature crystallization of device-quality solution-processed lead zirconate titanate films. The essential aspect of the path is to circumvent pyrochlore formation at around 300 deg. C during temperature increase up to 400 deg. C. By maintaining enough carbon via pyrolysis at 210 deg. C, well below the temperature for pyrochlore formation, Pb{sup 2+} can be reduced to Pb{sup 0}. This leads to the lack of Pb{sup 2+} in the film to suppress the development of pyrochlore, which accounts for the usual high-temperature conversion to perovskite. Films on metal, metal/oxide hybrid, and oxide bottom electrodes were successfully crystallized at 400-450 deg. C.

Li Jinwang; Trinh, Bui Nguyen Quoc; Miyasako, Takaaki;