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1

Piezoelectric anisotropy of orthorhombic ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

In the frame of thermodynamic approach, it is shown that all the admissible values of the d33, d32, and d31 piezoelectric moduli of any orthorhombic (mm2) single crystal in the 3-dimensional (d33, d32, d31) space lie within a restricted area having the form of ellipsoid. The main parameters of this ellipsoid (the aspect ratios and the angles characterizing its orientation) depend only on the elastic constants of the crystal. Using the developed approach, the areas of the allowable values of piezoelectric moduli have been determined for six crystals: single-domain KNbO3 and 0.27Pb(In0.5Nb0.5)O3-0.40Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 crystals possessing true orthorhombic symmetry and four polydomain macroscopically pseudoorthorhombic crystals--tetragonal BaTiO3 and PbTiO3 crystals with laminate 90° domain structure as well as rhombohedral 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 and 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 crystals, poled along the [011] direction of the prototype cubic cell. Four crystals from this set possess negative values of the longitudinal Poisson's ratio and are thus partially auxetics.

Aleshin, V. I.; Raevski, I. P.

2013-06-01

2

Ferroelectric and piezoelectric behaviour of rhombohedral ferroelectric single crystal subjected to anisotropic poling  

Microsoft Academic Search

Anisotropic hysteresis and piezoelectric properties of a rhombohedral ferroelectric single crystal were studied in this paper using the phase field simulation method. Electric loading was applied along [0 0 1] and [1 1 1] directions separately. It was found that poling in the [0 0 1] direction resulted in a reduced hysteresis loop and an enhanced longitudinal piezoelectric coefficient. By

Y C Song; A K Soh; L Lu

2008-01-01

3

FAST TRACK COMMUNICATION: Ferroelectric and piezoelectric behaviour of rhombohedral ferroelectric single crystal subjected to anisotropic poling  

Microsoft Academic Search

Anisotropic hysteresis and piezoelectric properties of a rhombohedral ferroelectric single crystal were studied in this paper using the phase field simulation method. Electric loading was applied along [0 0 1] and [1 1 1] directions separately. It was found that poling in the [0 0 1] direction resulted in a reduced hysteresis loop and an enhanced longitudinal piezoelectric coefficient. By

Y. C. Song; A. K. Soh; L. Lu

2008-01-01

4

Ferroelectric domain periodicities in nanocolumns of single crystal barium titanate  

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

5

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

Microsoft Academic Search

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

Amit Goyal; Junsoo Shin

2010-01-01

6

Reversible electric field induced nonferroelectric to ferroelectric phase transition in single crystal nanorods of potassium nitrate  

NASA Astrophysics Data System (ADS)

Single-crystal rods of the ?-phase of potassium nitrate were grown with [010] uniform crystallographic orientation inside a matrix of aluminum oxide nanopores. The pores were prepared by anodization of polished aluminum substrates. The potassium nitrate single crystals were grown inside the pores from a supersaturated aqueous solution at various temperatures. Dielectric polarization measurements of the porous film filled with the potassium nitrate crystals show an electric field induced reversible transition from the nonferroelectric ?-phase to the ferroelectric ?-phase at about 200 kV/cm. The ferroelectric ?-phase has a coercive field of about 169 kV/cm and remnant polarization of about 0.216 ?C/cm2.

Yadlovker, Doron; Berger, Shlomo

2007-10-01

7

Electrical tuning of metastable dielectric constant of ferroelectric single crystals for low-power electronics  

NASA Astrophysics Data System (ADS)

Electrical control of the dielectric constant in (011) [Pb(Mg1/3Nb2/3)O3](1-x)-[PbTiO3]x (PMN-PT, x ~ 0.32) single crystal ferroelectric material is reported. It is demonstrated that the metastable dielectric constant value of (011) PMN-PT can be manipulated from approximately 3000 to 1000 by applying electric pulses of different amplitudes. These metastable properties are due to non-180° polarization reorientation within the ferroelectric crystals. Taking advantage of the tunable and metastable dielectric constant, a reconfigurable RC oscillator as well as a ferroelectric memory device is demonstrated. The reconfigurability of this ferroelectric capacitor and potential applications for low-power electronics are described.

Wu, Tao; Bao, Mingqiang; Bur, Alexandre; Kim, Hyungsuk K. D.; Mohanchandra, Kotekar P.; Lynch, Christopher S.; Carman, Gregory P.

2011-10-01

8

Epitaxial Liftoff for Fully Single-Crystal Ferroelectric Thin Films.  

National Technical Information Service (NTIS)

During the period covered by this report we initiated the application of crystal ion slicing to single crystal potassium tantalate and strontium titanate. Transport of ions in matter (TRIM) simulations and ion implantation at 3.8MeV and various dosages we...

R. M. Osgood M. Levy

1999-01-01

9

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

10

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

11

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

SciTech Connect

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

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

2008-02-05

12

Electrocaloric Effect In Relaxor Ferroelectric Ceramics and Single Crystals  

Microsoft Academic Search

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

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

2006-01-01

13

Electrocaloric Effect In Relaxor Ferroelectric Ceramics and Single Crystals  

Microsoft Academic Search

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

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

2006-01-01

14

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

SciTech Connect

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

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

2012-01-23

15

Ferroelectric and Antiferroelectric Liquid Crystals  

Microsoft Academic Search

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

SVEN T. LAGERWALL

2004-01-01

16

Ferroelectric lithium niobate. 3. Single crystal X-ray diffraction study at 24°C  

Microsoft Academic Search

A comprehensive X-ray study of lithium niobate at room temperature has been made, prompted by the recently discovered excellent nonlinear optical properties and unusual ferroelectric behavior of this crystal. Lithium niobate is rhombohedral with lattice constants (IH = 5~14829+0~00002, CH = 13.8631 kO.0004 A and space group R3c(Csvs), at 23°C. The crystal structure has been solved without reference to earlier

S. C. ABRAHAMS; J. M. REDDY; J. L. BERNSTEIN

1966-01-01

17

Optically isotropic and monoclinic ferroelectric phases in Pb(Zr1-xTix)O3 (PZT) single crystals near morphotropic phase boundary  

NASA Astrophysics Data System (ADS)

We report the finding of unusual scale-dependent symmetry below the ferroelectric Curie temperature in the perovskite Pb(Zr1-xTix)O3 single crystals of morphotropic phase boundary compositions. The crystals of tetragonal symmetry on submicrometer scale exhibit a macroscopic (optically determined) cubic symmetry. This peculiar optical isotropy is explained by the anomalously small size of tetragonal ferroelectric domains. Upon further cooling the crystals transform to the phase consisting of micrometer-sized domains of monoclinic symmetry.

Bokov, Alexei A.; Long, Xifa; Ye, Zuo-Guang

2010-05-01

18

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

19

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

Microsoft Academic Search

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

N. Srivastava; G. J. Weng

2006-01-01

20

Piezoelectricity, ferroelectricity, and crystal structure  

Microsoft Academic Search

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

A. von Hippel

1952-01-01

21

The elastic and electromechanical properties of BaTiO{sub 3} single crystal through the ferroelectric transition  

SciTech Connect

Using Brillouin scattering and impedance methods, the elastic, piezoelectric and dielectric properties have been determined for monodomain single crystal BaTiO{sub 3} from 23 to 160C. In the cubic phase (T> 130C) only the compressional elastic constant C{sub 11} exhibits partial softening of about 6% upon cooling. During the tetragonal to cubic phase transition, most elastic constants sow discontinuous changes; either stiffening or softening. These and other results are discussed in terms of precursive effects through the electromechanical interaction of the ferroelectric phase transformation.

Li, Z.; Grimsditch, M.; Chan, S.K.

1993-07-01

22

Growth and piezo-/ferroelectric properties of PIN-PMN-PT single crystals  

NASA Astrophysics Data System (ADS)

Ternary solid solution crystals of 0.19Pb(In1/2Nb1/2)O3- 0.46Pb(Mg1/3Nb2/3)O3- 0.35PbTiO3 [PIMNT(19/46/35)] with dimensions of 35 × 38 × 15 mm3 were grown by the top-seeded solution growth (TSSG) method. The dielectric, piezo- and ferroelectric properties of the grown crystals were characterized. The ternary piezocrystals exhibit a Curie temperature TC = 190 °C and a tetragonal-rhombohedral phase transition temperature TR-T = 130 °C, which are increased significantly compared with TC ~ 155 °C and TR-T ~ 80 °C of PMN-PT crystals. The dielectric constant (?') and dielectric loss tangent (tan ?) are 4300 and 0.40 at room temperature. The piezoelectric coefficient d33 is found to be 2380 pC/N. The longitudinal electromechanical coupling factor k33 reaches 90% at room temperature. A peak-to-peak bipolar strain value of 0.13% is obtained at E ~ +/- 14 kV/cm. The coercive field Ec and remanent polarization Pr are 5.50 kV/cm and 27.10 ?C/cm2, respectively, which are also improved from the vales of PMN-PT crystals.

Li, Xiuzhi; Wang, Zujian; He, Chao; Long, Xifa; Ye, Zuo-Guang

2012-02-01

23

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

24

Electrical breakdown in ferroelectric sodium nitrite crystals  

Microsoft Academic Search

The electric strength of sodium nitrite crystals is measured in the temperature range 125–205°C embracing the Curie ferroelectric transition temperature. Single constant-amplitude voltage pulses are used to initiate breakdown. Experimental values of breakdown strength are obtained for time delays to breakdown of 10 and 100 msec. Measurements of high-field electric conductivity are used to determine theoretical impulse thermal breakdown strengths

J. Fok; J. R. Hanscomb

1972-01-01

25

Phase Transitions in Ferroelectric and Antiferroelectric Crystals  

Microsoft Academic Search

Group theory is applied to phase transitions in ferroelectric and antiferroelectric crystals. The procedure is given to derive for a paraelectric crystal with a given space group all possible ferroelectric states which can exist for arbitrarily small values of the polarization. A knowledge of the space groups of the crystal above and below the transition point makes it possible to

C. Haas

1965-01-01

26

Ferroelectric Particles in Liquid Crystals: Recent Frontiers  

Microsoft Academic Search

In this article we describe electro-optical properties of recently discovered ferroelectric particles\\/liquid crystal colloids. We show that the presence of ferroelectric particles in a liquid crystal changes its birefringence and dielectric anisotropy. In contrast to the traditional time consuming and expensive chemical synthetic methods, this method to create liquid crystals with enhanced properties is relatively simple and has a great

Anatoliy Glushchenko; Chae Il Cheon; John West; Fenghua Li; Ebru Büyüktanir; Yuri Reznikov; Alexander Buchnev

2006-01-01

27

Spreading resistance microscopy of polycrystalline and single-crystal ferroelectric films  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

28

A rate-dependent two-dimensional free energy model for ferroelectric single crystals  

Microsoft Academic Search

The one-dimensional free energy model for ferroelectric materials developed by Smith et al. [29–31] is generalized to two\\u000a dimensions. The two-dimensional free energy potential proposed in this paper consists of four energy wells that correspond\\u000a to four variants of the material. The wells are separated by four saddle points, representing the barriers for 90°-switching\\u000a processes, and a local maximum, across

Stefan Seelecke; Sang-Joo Kim; Brian L. Ball; Ralph C. Smith

2005-01-01

29

Atomic structure of Cd{sub 1-x}Zn{sub x}Te solid solution single crystals and structural prerequisites of their ferroelectricity  

SciTech Connect

Precision X-ray structural investigation of Cd{sub 1-x}Zn{sub x}Te single crystals (x = 0.04, 0.10, 0.21, 0.30, 0.40) is performed at temperatures below and above the ferroelectric phase transition. The regularities associated with the increase in the concentration of Zn atoms in solid solutions are revealed. It is established that the unit cell parameter of the crystals varies according to the Vegard law. The thermal parameters of Te and Zn atoms are strongly overestimated within the model of a sphalerite-type average structure. It is found that the positions of the Zn cations are split and the anion sublattice is disordered in such a way that the Te anions are predominantly displaced along the threefold axes. The Zn atoms can serve as off-center impurities. This phenomenon offers strong possibilities for manifesting the ferroelectric properties in the solid solutions under investigation.

Rabadanov, M. Kh., E-mail: rab_mur@ns.crys.ras.ru; Simonov, V. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2006-10-15

30

Enhanced piezoelectric and ferroelectric properties in Mn-doped Na0.5Bi0.5TiO3-BaTiO3 single crystals  

NASA Astrophysics Data System (ADS)

High piezoelectric and ferroelectric properties have been found in Mn-doped Na0.5Bi0.5TiO3-BaTiO3 single crystals, which were grown by a top-seeded solution method. The electrical resistivity, dielectric constant, and ferroelectric and piezoelectric properties were all found to be notably enhanced by Mn. The piezoelectric constant d33 and electromechanical coupling coefficients kt and k31 were found to be as high as 483 pC/N, 0.56, and 0.40, respectively. These values are much higher than those previously reported for Pb-free piezoelectric crystals, demonstrating the real potential for alternative lead-free systems for sensor and piezoelectric applications.

Zhang, Qinhui; Zhang, Yaoyao; Wang, Feifei; Wang, Yaojin; Lin, Di; Zhao, Xiangyong; Luo, Haosu; Ge, Wenwei; Viehland, D.

2009-09-01

31

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

NASA Astrophysics Data System (ADS)

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

Davis, Matthew; Damjanovic, Dragan; Setter, Nava

2006-01-01

32

A theory of double hysteresis for ferroelectric crystals  

Microsoft Academic Search

A ferroelectric crystal is known to exhibit the usual single hysteresis below its Curie point TC, but above this temperature its electric displacement D versus electric field E plot tends to form double loops. We first point out that there is a fundamental difference in the formation of double loops from the single one: the single loop is formed solely

N. Srivastava; G. J. Weng

2006-01-01

33

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

Microsoft Academic Search

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

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

1990-01-01

34

Ferroelectricity in CaTiO3 Single Crystal Surfaces and Thin Films and Probed by Nonlinear Optics and Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Bulk CaTiO3 has a centrosymmetric point group and is not polar or ferroelectric. However, we present surprising results that show highly regular polar domains in single crystals of CaTiO3. Confocal Second Harmonic Generation (SHG) and Raman imaging studies were carried out on perovskite CaTiO3 crystal surfaces. They reveal large, crystallographic polar domains at room temperature, with in-plane polarization components delineated by twin walls. SHG analysis indicates that the highest symmetry of the polar surface is m (space group Pc) with polarization in the m plane. In addition, we present results of the polar domain structure imaged before and after the application of an external electric field. Finally, we present the SHG studies of CaTiO3 thin films grown using reactive Molecular Beam Epitaxy (MBE); these films are predicted by theory to be ferroelectric and are shown experimentally, both with SHG and in-plane dielectric measurements, to be ferroelectric for temperatures less than ˜150 K with group symmetry mm2.

Vlahos, Eftihia; Lummen, Tom; Haislmaier, Ryan; Denev, Sava; Brooks, Charles; Biegalski, Michael; Schlom, Darrell; Eklund, Carl-Johan; Rabe, Karin; Fennie, Craig; Gopalan, Venkatraman

2011-03-01

35

Elasticity and Polarizations in Ferroelectric Liquid Crystals  

Microsoft Academic Search

The effects of polarization on the elastic modulus in a ferroelectric liquid crystal and the ion-director coupling are studied in the thesis. A bend-type Goldstone mode in chiral smectic C liquid crystal results in a divergence of the polarization, thus a space charge. The energy cost associated with the space charge gives rise to a contribution to the effective bulk

Minhua Lu

1993-01-01

36

Single point diamond turning of ferroelectric materials  

Microsoft Academic Search

One of the most important ferroelectric ceramics materials used in a wide range of applications is the lead zirconate titanate solid solution series (PZT). The possibility of machining brittle materials using single point diamond turning in a ‘ductile mode’ has been investigated by many researchers in recent years. The ability to machine ferroelectrics in a ductile manner and by so

Paulo A. Beltrão; Anthony E. Gee; John Corbett; Roger W. Whatmore; Christopher A. Goat; Susan A. Impey

1999-01-01

37

Transferred hyperfine field of Rb2CoCl4 single crystals in the ferroelectric incommensurate normal phase by 87Rb NMR  

NASA Astrophysics Data System (ADS)

The molecular susceptibility and paramagnetic shift of Rb2CoCl4 single crystals grown using the slow evaporation method were measured, and from these experimental results we obtained the transferred hyperfine interaction due to the transfer of spin density from Co2+ ions to Rb+ ions. The transferred hyperfine field was obtained for the ferroelectric, incommensurate, and normal phases. In the case of Rb(I), the transferred hyperfine interaction decreases with increasing temperature in the incommensurate phase, and increases with increasing temperature in the normal phase. The value of Hhf in the incommensurate and normal phases increases abruptly with increasing temperature in the case of Rb(II). These results indicate that the effects due to the transfer of spin density from Co2+ ions to the Rb(I) and Rb(II) ions are large above Ti. In particular, the effect due to the transfer of spin density to Rb(II) ions in the normal phase is very large; the variations with temperature of the transferred hyperfine interactions of the Rb(I) and Rb(II) nuclei are more or less continuous in Tc1 and Ti, and are not affected by the ferroelectric incommensurate normal phase transitions.

Lim, Ae Ran; Bong, Pill Hoon; Jeong, Se-Young

2006-04-01

38

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

2010-05-20

39

Spatial light modulators using ferroelectric liquid crystal  

Microsoft Academic Search

Basic structures and functions of optically addressed spatial light modulators (SLMs) are discussed in the context of system applications. The most important functions imposed on spatial light modulators are those of image acceptance and transducers. SLMs using ferroelectric liquid crystal (FLC) satisfy essential requirements for high levels of resolution, sensitivity and response speed. We specifically surveyed the current performance of

T. Kurokawa; S. Fukushima

1992-01-01

40

A new method of growth ferroelectrics crystal  

Microsoft Academic Search

TGS crystals were grown from solution with ethyl alcohol additions. The TGS crystals weighed more than 100 grams.Ferroelectric hysteresis loop, dielectric and pyroelectric properties have been measured. The Curie temperature is 50.2°C. It is found that the properties of TGS grown by this method are similar to that grown by slowly lowering the temperature at constant supersaturation.An infrared detactor constructed

Deng Zhao-De

1981-01-01

41

Electrical and optical properties of Nd3+-doped Na0.5Bi0.5TiO3 ferroelectric single crystal  

NASA Astrophysics Data System (ADS)

Sodium bismuth titanate Na0.5Bi0.5TiO3 (NBT) single crystal doped with Nd3+ was grown by a top-seeded solution growth method. Powder x-ray diffraction revealed a pure perovskite structure with the rhombohedral phase. We found that the dielectric and ferroelectric properties were enhanced by the Nd3+ dopant. After poling along the [1?1?1] direction, transmittance was enhanced dramatically. The Sellmeier dispersion equation and energy band gaps were obtained. The absorption band around 808 nm has high full-width at half-maximum and large absorption cross-section, which is suitable for AlGaAs diode-laser pumping. A strong emission transition band of Nd3+ at around 1066 nm was observed; a long radiation lifetime 324 µs shows a low quenching effect. These results indicate that Nd3+-doped NBT crystal could be applied in photonic or integrated optoelectronic devices as a multi-functional crystal.

He, Chongjun; Zhang, Yungang; Sun, Liang; Wang, Jiming; Wu, Tong; Xu, Feng; Du, Chaoling; Zhu, Kongjun; Liu, Youwen

2013-06-01

42

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

NASA Astrophysics Data System (ADS)

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 SmAPF, 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.

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

43

Fabrication of ferroelectric liquid crystal devices  

Microsoft Academic Search

Electrically-controlled 64 X 64 ferroelectric liquid crystal spatial light modulators (FLC-SLMs) were fabricated with a quick response, high contrast ratio and good bistability at the resolution of 10 lmm. The special polymer films aligned SLMs have a quite long operation life. A 1.6 inch 64 X 80 FLC device for the display aim was fabricated, which e-o properties have been

Ke-Shu Xu; Ruibo Lu; Zhongjing Xing; Shuyan Zhan; Xiang Gu; Yandong Zhang

1999-01-01

44

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

NASA Astrophysics Data System (ADS)

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

Lu, Yu

45

Domain engineered switchable strain states in ferroelectric (011) [Pb(Mg1/3Nb2/3)O3](1-x)-[PbTiO3]x (PMN-PT, x~0.32) single crystals  

NASA Astrophysics Data System (ADS)

The ferroelectric properties of (011) [Pb(Mg1/3Nb2/3)O3](1-x)-[PbTiO3]x (PMN-PT, x~0.32) single crystals with focus on piezoelectric strain response were reported. Two giant reversible and stable remanent strain states and tunable remanent strain properties are achieved by properly reversing the electric field from the depolarized direction. The unique piezoelectric strain response, especially along the [100] direction, mainly stems from the non-180° ferroelectric polarization reorientation in the rhombohedral phase crystal structure. Such giant strain hysteresis with tunable remanent strain properties may be useful for magnetoelectric based memory devices as well as a potential candidate for other applications.

Wu, Tao; Zhao, Ping; Bao, Mingqiang; Bur, Alexandre; Hockel, Joshua L.; Wong, Kin; Mohanchandra, Kotekar P.; Lynch, Christopher S.; Carman, Gregory P.

2011-06-01

46

A programmable ferroelectric single electron transistor  

NASA Astrophysics Data System (ADS)

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

Liu, Lu; Narayanan, Vijay; Datta, Suman

2013-02-01

47

Microsphere Manipulation Using Ferroelectric Liquid Crystals  

NASA Astrophysics Data System (ADS)

We propose a strategy for a micromanipulation method using SSFLC (surface stabilized ferroelectric liquid crystals). By adjusting the frequency of the applied ac electric field, the surface layers that cannot follow an applied ac electric field are constructed in SSFLC. In addition, by applying a sawtooth wave voltage, net flow along the smectic layer is generated. The flow direction is reversed by changing the polarity of the sawtooth wave. Consequently, the particles dispersed in SSFLC can be driven bidirectionally along the smectic layer. The particle velocity depends on the temperature, amplitude, and frequency of the applied voltage.

Mieda, Yoshitaka; Furutani, Katsushi

2005-10-01

48

The shift of Curie temperature and evolution of ferroelectric domain in ferroelectric crystals  

Microsoft Academic Search

A micromechanics-based thermodynamic model for the phase transition of ferroelectric crystals is developed and, with it, the shift of Curie temperature and evolution of ferroelectric phase upon cooling are examined. This approach differs from the classical phenomenological one in that the evolution of new domain concentration can be predicted. We start out by formulating the Gibbs free energy of a

Y. Su; G. J. Weng

2005-01-01

49

Photorefractive effects in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

The photorefractive properties of SmC* phases are usually studied in samples which are not intrinsically photoconductive and in which light sensitization is achieved by doping. We propose two different approaches: the first one is the use of a liquid crystal which is intrinsically photoconducting and photorefractive without any doping. In this system a PR performance larger than what previously reported for doped systems was measured, as well as the amplitude of the photoinduced space-charge field. A further development of this research is the control of the polarization switching in a bistable surface-stabilized ferroelectric liquid crystal (SSFLC) device via a photorefractive (PR) mechanism. In this case, the space-charge field was generated on the surfaces of the SSFLC device, in two photoconducting layers coated on the sample substrates. The formation of a stable grating was observed.

Talarico, M.; Pucci, D.; Ghedini, M.; Termine, R.; Golemme, A.

2005-08-01

50

2-2 composites based on [011]-poled relaxor-ferroelectric single crystals: from the piezoelectric anisotropy to the hydrostatic response  

NASA Astrophysics Data System (ADS)

In this paper effect of the orientation of the main crystallographic axes on the piezoelectric anisotropy and hydrostatic parameters of 2-2 parallel-connected single crystal (SC) / auxetic polymer composites is analysed. SCs are chosen among the perovskite-type relaxor-ferroelectric solid solutions of (1 - x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 and xPb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-(1 - x - y)PbTiO3. The SC layers in a composite sample are poled along the perovskite unit-cell [011] direction and characterised by mm2 symmetry. The orientation of the main crystallographic axes in the SC layer is observed to strongly influence the effective piezoelectric coefficients d*3j, g*3j, squared figured of merit d*3j g*3j, electromechanical coupling factors k*3j (j = 1, 2 and 3), and hydrostatic analogs of these parameters of the 2-2 composite. A comparison of values of d*3j g*3j was first carried out at d*31 ? d*32 in a wide range of orientations and volume-fraction. Large values of the effective parameters and inequalities | d*33 / d*3f | > 5 and | k*33 / k*3f | > 5 (f = 1 and 2) are achieved at specific orientations of the main crystallographic axes due to the anisotropy of elastic and piezoelectric properties of the SC component. The use of an auxetic polyethylene with a negative Poisson's ratio leads to a significant increase in the hydrostatic parameters of the 2-2 composite. Particular advantages of the studied composites over the conventional ceramic / polymer composites are taken into account for transducer, hydroacoustic and energyharvesting applications.

Bowen, C. R.; Topolov, V. Y.; Betts, D. N.; Kim, H. A.

2013-05-01

51

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

SciTech Connect

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

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

2011-01-01

52

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

Microsoft Academic Search

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

Qiang Li; Yiling Zhang; Zhiguo Xia; Xiangcheng Chu

2011-01-01

53

Fabrication of ferroelectric liquid crystal devices  

NASA Astrophysics Data System (ADS)

Electrically-controlled 64 X 64 ferroelectric liquid crystal spatial light modulators (FLC-SLMs) were fabricated with a quick response, high contrast ratio and good bistability at the resolution of 10 lmm. The special polymer films aligned SLMs have a quite long operation life. A 1.6 inch 64 X 80 FLC device for the display aim was fabricated, which e-o properties have been improved by the modification of the aligning layers and a large area FLC alignment with uniformity can be obtained. A FLC light shutter at the aperture of 30 mm X 30 mm was also fabricated and used as a phase-sensitive image system for the investigation of fluorescence lifetime.

Xu, Ke-Shu; Lu, Ruibo; Xing, Zhongjing; Zhan, Shuyan; Gu, Xiang; Zhang, Yandong

1999-04-01

54

Lattice viscosity of displacive ferroelectric crystals  

NASA Astrophysics Data System (ADS)

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

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

1981-02-01

55

A theory of double hysteresis for ferroelectric crystals  

NASA Astrophysics Data System (ADS)

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

Srivastava, N.; Weng, G. J.

2006-03-01

56

Director Reorientation Dynamics in Chevron Ferroelectric Liquid Crystal Cells.  

National Technical Information Service (NTIS)

We present sample numerical solutions of the equation of motion that governs the dynamics of molecular orientation in ferroelectric liquid crystal cells with chevron layer structure. We show that the chevron structure significantly influences the director...

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

1990-01-01

57

Crystallization Behaviors of Ferroelectric and Piezoelectric Materials  

NASA Astrophysics Data System (ADS)

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

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

58

Optical recording using a photochromic ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

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

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

2001-06-01

59

Control of Alignment for Ferroelectric Liquid Crystal Display. Alignment of Ferroelectric Liquid Crystal by Oblique Evaporation Method.  

National Technical Information Service (NTIS)

The ferroelectric liquid crystal (FLC) has recently been the subject of attention for its fast response and memory effect. Different from the nematic liquid crystal, it has layered structure, so it has been considered to be difficult to obtain a uniform o...

T. Uemura N. Ohba N. Wakita H. Ohnishi I. Ota

1987-01-01

60

Polarization relaxation anisotropy in Pb(Zn1/3Nb2/3)O3-PbTiO3 single-crystal ferroelectrics as a function of fatigue history  

NASA Astrophysics Data System (ADS)

Polarization relaxation was studied in Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) single crystals that show fatigue anisotropy. To excite prepoled crystals, a modest dc voltage (<1/2 of the coercive field) was applied along the poling direction. Upon removal of the voltage, the polarization decay in the time domain was measured. Experimental data were modeled with a stretched exponential function. Stretching exponent (?) and characteristic time (?) constants for polarization relaxation were determined from data over four decades in the time domain at different stages of bipolar cycling. ? values after 101 cycles were 0.146+/-0.002 and 0.247+/-0.0004 in the <001> and <111> orientations, respectively. The ?<111> constant increased up to 0.453+/-0.104 after 105 cycles in <111> oriented crystals that show fatigue. However, much less change is observed in ?<001> as a function of cycling for <001> crystals. Characteristic time constants for relaxation (?) were calculated for <001> and <111> orientations as 0.401+/-0.048 s and 57.46+/-0.10 s, respectively. These results suggest a faster polarization relaxation in <001> than in the <111> orientation of rhombohedral PZN-PT ferroelectric crystals.

Ozgul, Metin; Furman, Eugene; Trolier-McKinstry, Susan; Randall, Clive A.

2004-03-01

61

Single point diamond machining of ferroelectric materials  

Microsoft Academic Search

One of the most important ferroelectric ceramic materials used in a wide range of applications is the lead zirconate titanate solid solution series (PZT). The ability to machine ferroelectrics in a ductile manner and by so doing reduce sub-surface damage, could eliminate the need for subsequent lapping and polishing and thus reduce production costs. Fracture mechanics techniques were used to

Anthony E Gee; John Corbett; Roger W Whatmore; Christopher A Goat; Susan A Impey

1999-01-01

62

Design of ferroelectric liquid crystals for microdisplay applications  

Microsoft Academic Search

In this paper, novel ferroelectric liquid crystals (FLC) incorporating silicon and fluorine into their structure have been designed and synthesized for microdisplay application. In addition a new class of de Vries bookshelf FLC materials and mixtures made from FLC has been described.

M. D. Wand; W. T. Thurmes; K. More; R. Vohra; X. Chen

2003-01-01

63

An improved SPICE model for ferroelectric liquid crystal microdisplays  

Microsoft Academic Search

This paper presents the development of SPICE equivalent circuits for the electrical and optical modelling of Ferroelectric Liquid Crystal (FLC) on silicon devices. An electro-optical model has been evaluated in a previous publication and although it can simulate the optical output from a display cell it does not accurately model the drive current required to switch the FLC material from

S. Smith; A. J. Walton; I. Underwood; C. Miremont; D. G. Vass; W. J. Hossack; M. Birch; A. Maartney; R. Nicol

2003-01-01

64

Field-induced domain interpenetration in tetragonal ferroelectric crystal  

Microsoft Academic Search

Ferroelectric domain structures of a -oriented lead magnesium niobate-lead titanate tetragonal crystal were examined under cyclic bipolar electric fields. Complex patterns of orthogonal domain strips were found to emerge from a simple structure of parallel strips of 90° domains. Near the boundary between the two orthogonal sets of the domain strips, domains were forced to intersect, creating charged domain walls

X. Tan; J. K. Shang

2004-01-01

65

Dipolar correlation times in ferroelectric HCL-DCL mixed crystals  

Microsoft Academic Search

Cl NQR relaxation measurements are used to derive the correlation times ? for the reorientation of both HCl and DCl dipoles in the ferroelectric phase of HCl-DCl mixed crystals. The ?'s for DCl are reasonably consistent with a theoretical picture based on a dynamical Ising model in a transverse field which includes damping in an heuristic way. For the HCl

M. Crowley; J. Brookeman; A. Rigamonti

1984-01-01

66

Microscopic calculations of ferroelectric instability in perovskite crystals  

Microsoft Academic Search

First-principles calculations are performed relating to the stability of a series of perovskite crystals with respect to transition\\u000a to the ferroelectric and the antiferroelectric state. The calculations employ the generalized Gordon-Kim method, in which\\u000a the total charge density of an ionic crystal is represented as a superposition of the densities of the individual ions. In\\u000a the spirit of the nonequilibrium

O. V. Ivanov; D. A. Shport; E. G. Maksimov

1998-01-01

67

On the equation of director motion in ferroelectric liquid crystals  

Microsoft Academic Search

In a one-dimensional situation of a liquid crystal sample between two electrodes perpendicular to thex-axis, it is thex-component of the electrical inductionDx and not the electrical fieldEx which is independent of thex-coordinate. In the present paper the equation of director motion is derived in a more precise way, and some applications for ferroelectric liquid crystals are discussed.WithFd the distortion energy

Herman J. Pauwels; Frank H. Cuypers

1991-01-01

68

Microwave frequency ferroelectric domain imaging of deuterated triglycine sulfate crystals  

NASA Astrophysics Data System (ADS)

We have used a near-field scanning microwave microscope to image domain structure and quantitatively measure dielectric permittivity and nonlinearity in ferroelectric crystals at 8.1 GHz with a spatial resolution of 1 ?m. We imaged ferroelectric domains in periodically poled LiNbO3, BaTiO3, and deuterated triglycine sulfate (DTGS) with a signal-to-noise ratio of 7. Measurement of the permittivity and nonlinearity of DTGS in the temperature range 300-400 K shows a peak at the Curie temperature, TC~340 K, as well as reasonable agreement with thermodynamic theory. In addition, the domain growth relaxation time shows a minimum near TC. We observe coarsening of ferroelectric domains in DTGS after a temperature quench from 360 to 330 K and evaluate the structure factor.

Steinhauer, D. E.; Anlage, Steven M.

2001-02-01

69

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

70

A fast and secure phase-multiplexing technique based on random speckles modulation in multimode ferroelectric single crystal fiber for volume holographic storage  

Microsoft Academic Search

In this paper, a new speckle based hologram multiplexing recording technique is proposed and tested. In this method, a multi-mode LiNbO3 single crystal fiber is employed to generate speckle patterns which are used as reference beams in hologram recording process. The speckle pattern generation can be precisely controlled by external E-field. Theoretically, this technique can generate thousands of decorrelated reference

Hongbo Liu; John Y. Fu; Man Gu; Amar S. Bhalla; Ruyan Guo

2006-01-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

72

Nanomaterials dispersed in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

Nanocomposites composed of a self prepared Ferroelectric Liquid Crystalline (FLC) matrix and different nanomaterials show pronounced reduction of important parameters like spontaneous polarization, switching time but no change of the tilt angle. As a typical subject silver nanoparticles where characterized. A pronounced increase of resistivity where described by comparing the pure FLC mixture with properties of FLC nanocomposites. Ion capturing due to silver particles has been discussed. Photoluminescence originated by the terphenyl compound and enhanced due to the Silver Surface Plasmon Resonance has been described.

Haase, W.; Lapanik, A.; Ottinger, M.

2011-09-01

73

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

2011-04-08

74

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

75

Multiferroic Behaviour in Mixtures of the Ferroelectric Liquid Crystal and Magnetic Nanoparticles  

Microsoft Academic Search

A dielectric spectroscopy, magnetic susceptibility and high resolution calorimetry have been carried out in the vicinity of the ferroelectric smectic C* phase of SCE9 ferroelectric liquid crystal (LC) mixtures with magnetic nanoparticles (NPs) to determine the impact of the magnetic nanoparticles on the Goldstone and soft mode and to study the disordering effects on the ferroelectric phase transition. It was

B. Roži?; M. Jagodi?; S. Gyergyek; M. Drofenik; S. Kralj; G. Cordoyiannis; Z. Kutnjak

2011-01-01

76

A fast and secure phase-multiplexing technique based on random speckles modulation in multimode ferroelectric single crystal fiber for volume holographic storage  

NASA Astrophysics Data System (ADS)

In this paper, a new speckle based hologram multiplexing recording technique is proposed and tested. In this method, a multi-mode LiNbO3 single crystal fiber is employed to generate speckle patterns which are used as reference beams in hologram recording process. The speckle pattern generation can be precisely controlled by external E-field. Theoretically, this technique can generate thousands of decorrelated reference beams at given practical constraints. Its storage capacity can be scaled up as material properties are improved, making it well adapted to new material development. A theoretical analysis and numerical simulation of speckle pattern generation are also presented in this paper.

Liu, Hongbo; Fu, John Y.; Gu, Man; Bhalla, Amar S.; Guo, Ruyan

2006-09-01

77

Electromigration of microspheres in ferroelectric smectic liquid crystals  

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

78

Criticality of bistability phenomenon in deformed helix ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

79

Holographic diffraction gratings using polymer-dispersed ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

80

Broadband Brillouin scattering of relaxor ferroelectric crystals  

NASA Astrophysics Data System (ADS)

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

Kojima, Seiji; Jiang, Fuming

2001-08-01

81

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

82

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

83

Photorefractive effects in ferroelectric liquid crystals  

Microsoft Academic Search

The photorefractive properties of SmC* phases are usually studied in samples which are not intrinsically photoconductive and in which light sensitization is achieved by doping. We propose two different approaches: the first one is the use of a liquid crystal which is intrinsically photoconducting and photorefractive without any doping. In this system a PR performance larger than what previously reported

M. Talarico; D. Pucci; M. Ghedini; R. Termine; A. Golemme

2005-01-01

84

Microwave Frequency Ferroelectric Domain Imaging of Deuterated Triglycine Sulfate Crystals  

NASA Astrophysics Data System (ADS)

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

Steinhauer, David E.; Anlage, Steven M.

2001-03-01

85

Barium strontium titanate ferroelectric tunable photonic and phononic crystals  

NASA Astrophysics Data System (ADS)

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

Jim, Kwok Lung

86

Polymer Alignment Behavior with Molecular Switching of Ferroelectric Liquid Crystal  

NASA Astrophysics Data System (ADS)

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

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

2007-01-01

87

Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants  

NASA Astrophysics Data System (ADS)

A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 °C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 ?m pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.

Chen, Huang-Ming Philip; Tsai, Yun-Yen; Lin, Chi-Wen; Shieh, Han-Ping David

2006-09-01

88

Single crystal faceplate evaluation  

NASA Astrophysics Data System (ADS)

The Naval Training Systems Center developed single crystal faceplates which held promise for providing a significantly improved life span over conventional power phosphor cathode ray tubes (CRT) while maintaining acceptable resolution and light output characteristics. Single crystal faceplates being evaluated are composed of yttrium aluminum garnet (YAG) with an epitaxial cerium phosphor layer grown on the YAG substrate producing a cathodoluminescent material (CE:YAG). The single crystal nature of these faceplates should allow higher resolution (no phosphor grains) and higher thermal conductivity.

Tucker, A. R.; Kindl, H. J.

1993-10-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

90

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

PubMed Central

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

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

2011-01-01

91

Optimization of optical switching with a ferroelectric liquid crystal modulator  

NASA Astrophysics Data System (ADS)

In this work we present a simple method for the characterization of a ferroelectric liquid crystal (FLC) optical modulator and the optimization of its contrast ratio. This device acts as switchable wave-plate, where the orientation of the principal axes rotates under the action of an applied bipolar voltage. It is designed to produce a binary intensity modulation when the phase shift introduced between the principal axes is equal to 180 degrees (half wave-plate). We present a simple technique to optimize its response when the phase shift differs from this ideal value, in order to produce a highly contrasted intensity modulation. The technique involves using elliptically polarized light and requires the use of an additional quarter wave-plate in front of the FLC modulator. We represent the polarization transformations on the Poincaré sphere to provide a physical explanation of the FLC optical performance, both in the standard operational mode as well as in the optimized configuration for non-ideal phase shifts. These situations are experimentally demonstrated using a commercially available ferroelectric liquid crystal cell and two He-Ne lasers with wavelengths of 543 nm and 633 nm respectively.

Sánchez-López, M. M.; García-Martínez, P.; Velásquez, P.; Moreno, I.

2007-09-01

92

Computer simulations of quasilattice models for novel ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

It has been suggested that ferroelectric smectic phases may be formed by ``fraternal-twin'' liquid-crystal molecules, consisting of two very different mesogens bonded together by an appropriate spacer [R. G. Petschek and K. M. Wiefling, Phys. Rev. Lett. 59, 343 (1987)]. We discuss the range in which these ferroelectric phases appear in a Monte Carlo simulation of a simple computer model for such mesogens. The mesogens consist of two identical flexible segments that are bonded to two rigid segments with very different lengths which, in turn, are bonded together by a flexible segment. In the computer model these monomers can move freely in one direction, but are constrained to lie on a hexagonal lattice of rods in the other two directions, roughly the packing expected in a smectic-B crystal. The flexible segments are modeled by springs, and there is an energy cost for the overlap of flexible and rigid segments on neighboring lattice rods. The region in which polar (flexible, short rigid, flexible, long rigid, flexible) smectic layers form will be discussed.

Perchak, Dennis R.; Petschek, Rolfe G.

1991-06-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

94

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

PubMed

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

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

2012-09-01

95

Growth and characterizations of lead-free ferroelectric KNN-based crystals  

NASA Astrophysics Data System (ADS)

We have grown by flux method centimeter-sized single crystals from pseudo-hexanary Li2O-Na2O-K2O-Nb2O5-Ta2O5-Sb2O3 system. Based on chemical analysis, crystals of compositions (Li0.023Na0.583K0.394)(Nb0.925Ta0.037Sb0.038)O3 and (Li0.034Na0.609K0.357)(Nb0.896Ta0.047Sb0.057)O3 were characterized by X-rays diffraction which revealed a tetragonal structure. The dielectric analysis confirmed that the ferroelectric behavior of these crystals is very sensitive to little changes in composition as previously observed on ceramics. Such high flexibility of the ferroelectric properties in crystals opens the way towards improved understanding of the relations between structure and polarization in solid solutions which may be an alternative to the lead-based materials.

Prakasam, Mythili; Veber, Philippe; Viraphong, Oudomsack; Etienne, Laetitia; Lahaye, Michel; Pechev, Stanislav; Lebraud, Eric; Shimamura, Kiyoshi; Maglione, Mario

2013-02-01

96

High-speed holographic optical tweezers using a ferroelectric liquid crystal microdisplay.  

PubMed

We demonstrate the advantages of a ferroelectric liquid crystal spatial light modulator for optical tweezer array applications. The fast switching speeds of the ferroelectric device (compared to conventional nematic systems) is shown to enable very rapid reconfiguration of trap geometries, controlled, high speed particle movement, and tweezer array multiplexing. PMID:19466092

Hossack, William; Theofanidou, Eirini; Crain, Jason; Heggarty, Kevin; Birch, Martin

2003-08-25

97

High-speed holographic optical tweezers using a ferroelectric liquid crystal microdisplay  

NASA Astrophysics Data System (ADS)

We demonstrate the advantages of a ferroelectric liquid crystal spatial light modulator for optical tweezer array applications. The fast switching speeds of the ferroelectric device (compared to conventional nematic systems) is shown to enable very rapid reconfiguration of trap geometries, controlled, high speed particle movement, and tweezer array multiplexing.

Hossack, William J.; Theofanidou, Eirini; Crain, Jason; Heggarty, Kevin; Birch, Martin

2003-08-01

98

Orientational Order-Magnetization Coupling in Mixtures of Magnetic Nanoparticles and the Ferroelectric Liquid Crystal  

Microsoft Academic Search

We have studied the ferroelectric SmC* phase of SCE9 ferroelectric liquid crystal (LC) mixtures with magnetic nanoparticles (NPs). The impact of the NPs on the Goldstone and soft mode dielectric response has been determined by the dielectric spectroscopy measurements. The possible indirect coupling between the magnetic moments and the electrical polarization has been verified by measuring the impact of the

B. Roži?; M. Jagodi?; S. Gyergyek; M. Drofenik; S. Kralj; G. Lahajnar; Z. Jagli?i?; Z. Kutnjak

2010-01-01

99

High-speed holographic optical tweezers using a ferroelectric liquid crystal microdisplay  

Microsoft Academic Search

We demonstrate the advantages of a ferroelectric liquid crystal spatial light modulator for optical tweezer array applications. The fast switching speeds of the ferroelectric device (compared to conventional nematic systems) is shown to enable very rapid reconfiguration of trap geometries, controlled, high speed particle movement, and tweezer array multiplexing.

William J. Hossack; Eirini Theofanidou; Jason Crain; Kevin Heggarty; Martin Birch

2003-01-01

100

Single event upset immunity of strontium bismuth tantalate ferroelectric memories  

SciTech Connect

An embedded 1Kbit non-volatile (NV) serial memory manufactured with strontium bismuth tantalate (SBT) ferroelectric (FE) technology was shown to be immune to effects of heavy ion irradiation. The memories did not lose any data in the non-volatile mode when exposed to xenon (maximum effective LET of 128 MeV-cm{sup 2}/mg and a total fluence of 1.5 x 10{sup 7} ions/cm{sup 2}). The ferroelectric memories also did not exhibit any loss in the ability to rewrite new data into the memory bits, indicating that no significant degradation of the FE dipoles occurred as a result of the heavy ion exposure. The fast read/write times of FE memories also means that single event gate rupture is unlikely to occur in this technology.

Benedetto, J.M.; Derbenwick, G.F.; Cuchiaro, J.D.

1999-12-01

101

SPICE modeling of ferroelectric liquid crystal on silicon microdisplays  

NASA Astrophysics Data System (ADS)

This paper presents the development of an electrical SPICE model of a Ferroelectric Liquid Crystal (FLC) on silicon microdisplay. Previous work has investigated the use of an electro-optical SPICE model to simulate the optical response of an FLC cell to a given electrical signal. However, the design of the backplane drive scheme for the display also requires an accurate model of the electrical load represented by an FLC cell. The model presented here provides a good fit to electrical measurement results and, in addition, can be combined with elements of the electro-optical model to allow the optical response of the cell to be modelled at the same time. This paper also presents results of charge collection current measurements which highlight the differences in the behavior of the cell when it is switched between positive and negative voltages and then in the other direction.

Smith, Stewart; Walton, Anthony J.; Underwood, Ian; Miremont, Christophe; Vass, David G.; Hossack, Will J.; Birch, Martin; Macartney, Andrew; Nicol, Robert

2003-11-01

102

Anchoring energy and orientational elasticity of a ferroelectric liquid crystal  

SciTech Connect

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

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

2012-06-15

103

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

National Technical Information Service (NTIS)

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

M. Kaczmarek

2009-01-01

104

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

105

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

Microsoft Academic Search

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

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

2001-01-01

106

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

Microsoft Academic Search

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

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

2002-01-01

107

Photorefractive and Raman light scattering in lithium niobate ferroelectric crystal  

NASA Astrophysics Data System (ADS)

Using the methods of photorefractive and Raman light scattering, we study subtle features of the structure of LiNbO3 single crystals with different Li/Nb ratios (pure and doped with nonphotorefractive cations) grown by different methods. We reveal that, upon the irradiation of a single crystal with visible laser light, locally fluctuating micro- and nanostructures are initially formed in it, with their physical parameters being different from the corresponding parameters of the single crystal in the absence of the photorefractive effect. Upon an increase in the irradiation intensity and in the course of time, more and more such micro-structures are formed, and they are transformed into static micro- and nanoformations, which are subsequently converted into a continuous laser track. The speckle structure of photorefractive scattering is studied in detail. We show that the photorefractive effect in single crystals of the stoichiometric composition is fairly strong for their use as materials for recording and storing information.

Sidorov, N. V.; Syuy, A. V.; Palatnikov, M. N.; Evstratova, D. V.; Mavrin, B. N.

2011-06-01

108

Single crystal diamond  

US Patent & Trademark Office Database

A single crystal diamond grown by vapor phase synthesis, wherein when one main surface is irradiated with a linearly polarized light considered to be the synthesis of two mutually perpendicular linearly polarized light beams, the phase difference between the two mutually perpendicular linearly polarized light beams exiting another main surface on the opposite side is, at a maximum, not more than 50 nm per 100 .mu.m of crystal thickness over the entire crystal. This single crystal diamond is of a large size and high quality unattainable up to now, and has characteristics that are extremely desirable in semiconductor device substrates and are applied to optical components of which low strain is required.

2009-11-10

109

Single crystals of chitosan.  

PubMed

Lamellar single crystals of chitosan were prepared at 125 degrees C by adding ammonia to a low DP fraction of chitosan dissolved in water. The crystals gave sharp electron diffraction diagrams which could be indexed in an orthorhombic P2(1)2(1)2(1) unit cell with a = 8.07 A, b = 8.44 A, c = 10.34 A. The unit cell contained two anti-parallel chitosan chains and no water molecules. It was found that cellulose microfibrils from Valonia ventricosa could act as nuclei for inducing the crystallization of chitosan on cellulose. This produced a shish-kebab morphology. PMID:2085494

Cartier, N; Domard, A; Chanzy, H

1990-10-01

110

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

111

Ferroelectric Liquid Crystal Chemistry: Studies Towards Development of a Model for the Molecular Origins of the Polarization in Ferroelectric Liquid Crystals.  

NASA Astrophysics Data System (ADS)

A ferroelectric polarization P is predicted for non-racemic tilted smectic liquid crystals based upon simple symmetry arguments. While such arguments are compelling, insight into the actual molecular origins of P is necessary if new materials with high polarization density are to be designed in a directed way. Such materials have utility in important new electro-optic devise applications. Based upon the concept that ferroelectricity in ferroelectric liquid crystals (FLCs) is a manifestation of a novel form of molecular recognition occurring in the LC phase, a simple stereochemical model for the ferroelectric polarization has been developed. Herein are presented the results of a critical test of this model. Thus, the series of enantiomerically enriched 4^' -decyloxyphenyl-4-(nonyl)benzoates substituted at carbons 1,2 and 3 of the nonyl grouping were synthesized. The substituents included fluoro-, chloro- and alkoxy substituents at C-1, and the trans-epoxide unit at C-2,3. Absolute configuration in the new materials was controlled by Sharpless asymmetric epoxidation chemistry, and by asymmetric reduction techniques. The new materials were characterized with respect to sign and magnitude of the ferroelectric polarization, and also the orientational viscosity and the electro-optic response times in the FLC phases. The results of these studies nicely confirm the basic tenets of the "bent cylinder binding site" model for the molecular origins of P. In addition, interesting new insights into some structural factors affecting viscosity and the electro-optic response times have been obtained.

Razavi, Homaune Azghadi

1988-12-01

112

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

Microsoft Academic Search

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

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

2010-01-01

113

Free energies of ferroelectric crystals from a microscopic approach  

NASA Astrophysics Data System (ADS)

The free energy of barium titanate is computed around the Curie temperature as a function of polarization P? from the first-principles derived Effective Hamiltonian of Zhong, Vanderbilt and Rabe [Phys. Rev. Lett. 73 (1994) 1861], through Molecular Dynamics simulations coupled to the method of the Thermodynamic Integration. The algorithms used to fix the temperature (Nosé-Hoover) and/or the pressure/stress (Parrinello-Rahman), combined with fixed-polarization molecular dynamics, allow to compute a Helmholtz free energy (fixed volume/strain) or a Gibbs free energy (fixed pressure/stress). The main feature of this approach is to calculate the gradient of the free energy in the 3-D space (P, P, P) from the thermal averages of the forces acting on the local modes, that are obtained by Molecular Dynamics under the constraint of fixed P?. This work extends the method presented in [Phys. Rev. B 79 (2009) 064101] to the calculation of the Gibbs free energy and presents new features about the computation of the free energy of ferroelectric crystals from a microscopic approach. A careful analysis of the states of constrained polarization is performed at T=280 K (?15-17 K below T) especially at low order parameter. These states are found reasonably homogeneous for small supercell size (L=12 and L=16), until inhomogeneous states are observed at low order parameter for large supercells (L=20). The effect of this evolution towards multidomain configurations on the mean force and free energy curves is shown. However, for reasonable supercell sizes (L=12), the free energy curves obtained are in very good agreement with phenomenological Landau potentials of the literature and the states of constrained polarization are homogeneous. Moreover, the free energy obtained is quite insensitive to the supercell size from L=12 to L=16 at T=280 K, suggesting that interfacial contributions, if any, are negligible at these sizes around T. The method allows a numerical estimation of the free energy barrier separating the paraelectric from the ferroelectric phase at T (?G?0.012-0.015 meV/5-atom cell). However, our tests evidence phase separation at low temperature and low order parameter, in agreement with the results of Tröster et al. [Phys. Rev. B 72 (2005) 094103]. Finally, the natural decomposition of the forces into onsite, short-range, dipole-dipole and elastic-local mode interaction allows to make the same decomposition of the free energy. Some parts of this decomposition can be directly calculated from the coefficients of the Effective Hamiltonian.

Geneste, Grégory

2010-04-01

114

Structural matching of ferroelectric domains and associated distortion in potassium titanyl phosphate crystals  

Microsoft Academic Search

The surface deformation and atomic-level distortions associated with crystal structural matching at ferroelectric inversion domain walls are investigated in periodically poled potassium titanyl phosphate (KTP) crystals. A deformation, of the order of 10-8 m in scale and having the periodicity of the domains, is observed at the surfaces by optical interferometry. It is discussed in terms of the piezoelectric effect.

P. Pernot-Rejmánková; P. A. Thomas; P. Cloetens; T. Lyford; J. Baruchel

2003-01-01

115

Fast-Switching Microwave Phase Shifter of Coplanar Waveguide Using Ferroelectric Liquid Crystal  

Microsoft Academic Search

The microwave variable phase shifter of a coplanar waveguide using ferroelectric liquid crystal with float electrodes, which are used for applying a dc voltage to a liquid crystal layer, is discussed. We confirmed the performance of the phase shifter in the frequency range from 10 to 30 GHz and found that phase shift is proportional to the frequency of the

Hiroshi Moritake; Satoshi Morita; Ryotaro Ozaki; Toshihisa Kamei; Yozo Utsumi

2007-01-01

116

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

117

Enhanced two-beam coupling in colloids of ferroelectric nanoparticles in liquid crystals  

NASA Astrophysics Data System (ADS)

We report on the first, to the best of our knowledge, studies of photorefraction in nematic liquid crystal (LC) doped with nanoferroelectric particles. We found the strong enhancement of two-beam coupling in the colloid of ferroelectric nanoparticles in LC. The effect originated from an increased birefringence of the colloid and a stronger LC reorientation torque. Our measurements allowed us to suggest that increased birefringence is caused by the contribution of polarizability anisotropy of the ferroelectric particles. Stronger reorientation torque is caused by the permanent dipole moment of the particles contributing to the dielectric anisotropy of the colloid ?acol. The enhancement of two-beam coupling in LCs by doping with ferroelectric nanoparticles at extremely small concentration shows the strong potential of ferroelectric nanoparticles for improving the optical response of LCs, especially for those materials where a method of chemical synthesis has reached its limit.

Buchnev, Oleksandr; Dyadyusha, Andriy; Kaczmarek, Malgosia; Reshetnyak, Victor; Reznikov, Yuriy

2007-07-01

118

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

119

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

PubMed

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

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

2012-07-16

120

Lithium niobate single-crystal and photo-functional device  

SciTech Connect

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

121

Fabrication of single crystal PZT thin films on glass substrates  

Microsoft Academic Search

We have successfully transferred heteroepitaxial Pb(Zr,Ti)O3 (PZT) thin films from MgO substrates on to glass substrates. The transferred PZT thin films exhibit single crystal structure with ferroelectric properties similar to the as-grown epitaxial films. The transferring process comprises coating of Cr-metallized surface of epitaxial PZT thin films, pressing and cementing the Cr-metallized surface on to the glass substrates by silicone

Kenichiro Terada; Takaaki Suzuki; Isaku Kanno; Hidetoshi Kotera

2007-01-01

122

Discrete phase model of domain walls in ferroelectric crystals  

NASA Astrophysics Data System (ADS)

A discrete phase model is used to simulate evolution of domain structures in ferroelectric materials. The discrete phase model balances the structural energy against local mechanical and electrical energies. Devonshire theory is used to model the structural energy while a finite element framework using scalar potential theory computes the local electric field and stress.

Dong, Wen; Pisani, David; Lynch, Christopher S.

2011-03-01

123

Dynamic Response of Surface-Stabilized Ferroelectric Liquid Crystals with Chevron Layer Structure  

Microsoft Academic Search

The dynamic response of surface-stabilized ferroelectric liquid crystals with chevron layer structure to a triangular wave voltage is studied based on the continuum theory. From systematic numerical calculations, the shape of polarization reversal current is found to be crucially affected by the surface-anchoring condition, and the frequency and the amplitude of applied voltages. The theoretical results are confirmed through comparison

Tadashi Akahane; Kazumasa Itoh; Norio Nihei

1993-01-01

124

X-ray and Dielectric Spectroscopy Studies Of Chiral Ferroelectric Liquid Crystals With Keto Group  

SciTech Connect

Series of ferroelectric liquid crystals with the keto group attached to the molecule core and one lactate group as the chiral centre have been studied by X-ray and dielectric spectroscopy. The thickness of smectic layers and the average distance between the long axes of neighboring molecules increases with increase of both chains.

Stojanovic, Maja; Obadovic, Dusanka Z. [Department of Physics, Faculty of Sciences, University of Novi Sad, Trg D. Obradovica 4, 21000 Novi Sad (Serbia); Bubnov, Alexej; Hamplova, Vera; Kaspar, Miroslav [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague (Czech Republic)

2007-04-23

125

Effective Dielectric Permittivity of Coplanar Waveguide Type Microwave Phase Shifter Using Ferroelectric Liquid Crystal  

Microsoft Academic Search

A coplanar waveguide type microwave phase shifter using ferroelectric liquid crystal is constructed and its fundamental characteristics are measured. An analysis procedure of the effective permittivity of the phase shifter is explained. The decrease of the width of the center conductor in the phase shifter leads the increase of the dielectric permittivity change, consequently increasing the phase shift. The distance

H. Moritake; R. Ozaki; T. Kamei; Y. Utsumi

2011-01-01

126

Ferro-electric Liquid Crystal Achromatic Phase Shifter for Broadband Interferometry  

NASA Astrophysics Data System (ADS)

Geometric phase shifting based on the Pancharatnam phase is in principle achromatic. Achromatic phase shifting techniques based on wave plates are relatively slow. We describe a system that produces high speed achromatic phase shifts, using a pair of ferro-electric liquid crystal devices and opens up new possibilities in broadband interferometry.

Roy, Maitreyee

2010-04-01

127

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

Microsoft Academic Search

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

Hiroto Sato; Hideo Fujikake; Hiroshi Kikuchi; Taiichiro Kurita

2003-01-01

128

A micromechanics-based thermodynamic model for the domain switch in ferroelectric crystals  

Microsoft Academic Search

In this work we take the view that domain switch in ferroelectric crystals is a thermodynamics-driven process. In this light we first consider the micromechanics of domain switch to derive the Gibbs free energy of the heterogeneous system and the corresponding thermodynamic driving force at a given level of switched domain concentration fp, applied stress ?ij, and applied electric field

W. F. Li; G. J. Weng

2004-01-01

129

Nonlinear optical anisotropy associated with polar ordering in ferroelectric liquid crystals  

Microsoft Academic Search

We have developed a new experimental method of measuring the second harmonic generation (SHG) from ferroelectric liquid crystals (FLCs). The measurements are made on a homogeneously aligned FLC cell at an oblique incidence to the surface normal as a function of the azimuthal angle of rotation. This method is simple and powerful to study both the molecular orientation and the

Moojong Lim; Ju-Hyun Lee; Jae-Hoon Kim; Sin-Doo Lee

1996-01-01

130

The role of alkali additives in the crystallization of ferroelectric potassium lithium niobate crystals  

NASA Astrophysics Data System (ADS)

Ferroelectric K3Li2Nb5O15 (KLN-1) crystals have been grown by the top-seeded solution growth method from pure, Na+, Rb+ and Cs+ doped melt. The impact of alkali additives was assessed all over the entire pulling range by investigating the variation of the structural and physical properties by using spectroscopic and dielectric methods. The incorporation of alkali homologs has been correlated with their ionic radii: Na+ ions were found to enter both Li and K sites with high segregation coefficient (k?1.6), Rb+ ions were detected only at K sites (k?0.34) and Cs+ ions practically did not incorporate into the lattice (k?0.12). Alkali additives have been found to play a dual role in the growth process by affecting the crystallization temperature and promoting the K and Li site occupancy. By decreasing the crystallization temperature the Cs2O additive reduced the concentration both of the antisite Nb ions at Li site and that of alkali vacancies; therefore it can be considered as a promising fluxing agent in the growth of KLN crystals.

Péter, Á.; Hajdara, I.; Szaller, Zs.; Lengyel, K.; Kovács, L.

2013-05-01

131

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

PubMed

Bismuth ferrite, BiFeO3, is the only known room-temperature magnetic ferroelectric material. We demonstrate here, using neutron scattering measurements in high quality single crystals, that the antiferromagnetic and ferroelectric order parameters are intimately coupled. Initially in a single ferroelectric state, our crystals have a canted antiferromagnetic structure describing a unique cycloid. Under electrical poling, polarization reorientation induces a spin flop. We argue here that the coupling between the two orders may be stronger in the bulk than in thin films where the cycloid is absent. PMID:18643458

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

2008-06-02

132

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

133

Thermal tuning of phononic bandstructure in ferroelectric ceramic/epoxy phononic crystal  

NASA Astrophysics Data System (ADS)

Thermal tuning of phononic bandgaps in megahertz range was demonstrated in ferroelectric ceramic-based phononic crystal structure. Temperature variation across ferroelectric phase transition, accompanied by substantial changes in acoustic velocities, leads to a shift in the phononic bandstructure of a two-dimensional (Ba,Sr)TiO3/epoxy composite sample over a range of 10 °C. Experimental results are supported by modelings based on plane-wave expansion calculations. The high tunability of phononic bandstructure is advantageous for active control of ultrasound transmissions.

Jim, K. L.; Leung, C. W.; Lau, S. T.; Choy, S. H.; Chan, H. L. W.

2009-05-01

134

Increased lateral dipole moment in the core region of potential ferroelectric liquid crystal molecules  

NASA Astrophysics Data System (ADS)

Visual displays, unlike audio systems, fall far short of human limits: orders of magnitude in information content separate what can be seen from what can be displayed. One technology employed for next-generation high-performance displays uses ferroelectric liquid crystals (FLCs), whose switching speed depends in part on the ferroelectric polarization of the active material, which itself arises from the lateral dipole moment of the constituent molecules. Several series of molecules based on the 2,3-dinitrophenyl moiety, which has a high lateral dipole moment, was conceived and prepared. Most of the new molecules did not exhibit any liquid crystal phases, but those that did had high polarization as expected. One such molecule, 2,3-Dinitro-4-(R)-(2-octyloxy)phenyl 4'-decyloxy-4-biphenylcarboxylate, had a polarization density of over 500 nC/cm2. Compounds with other core geometries, including phenyls, phenyl benzoates, biphenyls, and terphenyls, were prepared but failed to exhibit liquid crystal phases.

Tiemann, Bruce G.

2000-10-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2003-09-01

136

Ion Implantation in Perovskite Type Ferroelectrics.  

National Technical Information Service (NTIS)

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

R. Gerson

1979-01-01

137

Adaptive Beam Steering Implemented in a Ferroelectric Liquid-Crystal Spatial-Light-Modulator Free-Space, Fiber-Optic Switch  

Microsoft Academic Search

Active alignment of a 1 x 8 free-space optical switch was studied experimentally. Optical signals, carried on single-mode fibers, were switched by a ferroelectric liquid-crystal-on-silicon spatial light modulator. Continuous measurement of the in-coupled power to the fibers provided feedback for the switch control. The switch automatically located and locked to the output fibers. An advantage with adaptive switches of a

Mathias Johansson; Sverker Hård; Brian Robertson; Ilias Manolis; Timothy Wilkinson; William Crossland

2002-01-01

138

"Thresholdless" hysteresis-free switching as an apparent phenomenon of surface stabilized ferroelectric liquid crystal cells.  

PubMed

The thresholdless, hysteresis-free V-shape electro-optical switching in surface-stabilized ferroelectric liquid crystals, observed usually with a triangular voltage form, has been shown to be rather an apparent and not a real effect. Strictly speaking, it is observed only at one characteristic frequency f(i) and is accompanied by an inversion of the electro-optical hysteresis direction from the normal to the abnormal one. The switching of the director in a liquid crystal layer at f(i), in reality, has a threshold and a normal hysteresis. Even the optical transmittance shows a hysteresis at f(i) when it is plotted as a function of the voltage on the liquid crystal layer and not as a function of the total voltage on the liquid crystal cell which always includes the inner insulating layers. Due to these layers, a voltage divider is formed which includes the capacitance of the insulating layers and the dynamic impedance (capacitance and resistance) of the ferroelectric liquid crystal layer. The new explanation has been confirmed by experiments with different ferroelectric liquid crystal cells combined with external resistors and capacitors and by measurements of a strong dependence of f(i) on the liquid crystal resistance which was varied over three orders of magnitude. A theoretical analysis of the problem has also been made using certain approximations for material parameters and the space dependence of the sine form of the electric field in the liquid crystal layer. The conclusions are qualitatively consistent with the experimental results. Finally, the dynamic problem has been solved numerically by taking into account of all the relevant parameters (in the absence of flow and irregularities in the cell plane) and the obtained results are in excellent correspondence with the experiment. This has been demonstrated for sets of material and cell parameters providing the best V-shape performance. PMID:12241190

Blinov, L M; Pozhidaev, E P; Podgornov, F V; Pikin, S A; Palto, S P; Sinha, A; Yasuda, A; Hashimoto, S; Haase, W

2002-08-02

139

Optimization of the contrast ratio of a ferroelectric liquid crystal optical modulator  

NASA Astrophysics Data System (ADS)

In this work we present a simple method for the characterization of a ferroelectric liquid crystal (FLC) optical modulator and the optimization of its contrast ratio. This device acts as switchable wave-plate, where the orientations of the principal axes rotate under the action of a bipolar applied voltage. It is designed to produce a binary intensity modulation when the phase shift introduced between the principal axes is equal to ? radians. We present a simple technique to optimize its response when the phase shift differs from this ideal value, in order to produce a highly contrasted intensity modulation. The technique uses elliptically polarized light and requires the use of an additional quarter-wave-plate. This situation is experimentally demonstrated using a commercially available ferroelectric liquid crystal cell and two He-Ne lasers with wavelengths of 543 and 633 nm, respectively.

Martínez, Antonio; Beaudoin, Nicolas; Moreno, Ignacio; del Mar Sánchez-López, María; Velásquez, Pablo

2006-11-01

140

Ferroelectric liquid-crystal waveguide modulation based on a switchable uniaxial-uniaxial interface.  

PubMed

Liquid crystals have effective electro-optic coefficients that are orders of magnitude larger than other integrated optical materials such as lithium niobate. However, previous studies of liquid-crystal waveguides have mainly focused on nematic liquid crystals, which exhibit impractically large scattering losses as waveguides. Studies of smectic liquid crystals and liquid crystals under strong confinement suggest the losses in these materials may be more manageable. In this study, the possibility of using ferroelectric liquid crystals in active waveguide modulators is explored through the analysis of several modulator configurations: a cutoff modulator, a deflection modulator, and an input coupler. As a way to study these structures, a mode-matching technique was developed to analyze the effects of a discontinuity in a uniaxial slab waveguide whose optic axis is in the plane of the waveguide. The results from the mode-matching technique were compared with those from simple bulk models. The analysis shows that ferroelectric liquid-crystal modulators have many desirable performance characteristics and could form the basis for practical waveguide modulators. PMID:21085454

Walker, D B; Glytsis, E N; Gaylord, T K

1996-06-01

141

Smectic-C 'Chevron', a Planar Liquid-Crystal Defect: Implications for the Surface-Stabilized Ferroelectric Liquid-Crystal Geometry.  

National Technical Information Service (NTIS)

The recent discovery of chevron structured smectic-C (SC) layers in surface-stabilized ferroelectric liquid-crystal (SSFLC) cells enables the understanding of many commonly observed features of SSFLC director and layer structure. The full three-dimensiona...

N. A. Clark T. P. Rieker

1988-01-01

142

Understanding crystallization features of P(VDF-TrFE) copolymers under confinement to optimize ferroelectricity in nanostructures.  

PubMed

The successful development of ferroelectric polymer devices depends on the effective fabrication of polar ferroelectric crystalline nanostructures. We demonstrate, by scanning X-ray microdiffraction using synchrotron light, the heterogeneous character of high aspect ratio one-dimensional nanoarrays of poly(vinylidene fluoride-co-trifluoroethylene) copolymers supported by a residual polymer film. They were prepared by melt and solution template wetting, using porous anodic aluminum oxide as a template. The spatial evolution of different polymorphs from the mixture of paraelectric and ferroelectric crystal forms (residual film) to the pure ferroelectric form (nanoarray) is evidenced for the samples prepared by solution wetting. However, for samples prepared by melt wetting the ferroelectric phase is exclusively obtained in both the residual film and nanoarray. The crystal nuclei formed in the polymer film connected to the nanoarray play a key role in determining the formation of a crystallinity distribution gradient, where the crystallinity decreases along the first 5-10 microns in the nanorods reaching a steady value afterwards. The minimum decrease in crystallinity is revealed for samples prepared by melt wetting. The results reported in this work endeavour to enhance the understanding of crystallization under confinement for ferroelectric copolymers and reveal the parameters for improving the ferroelectric character of polymer nanostructures. PMID:23712559

García-Gutiérrez, Mari-Cruz; Linares, Amelia; Martín-Fabiani, Ignacio; Hernández, Jaime J; Soccio, Michelina; Rueda, Daniel R; Ezquerra, Tiberio A; Reynolds, Michael

2013-05-28

143

Electro-optic applications of ferroelectric liquid crystals to optical computing  

Microsoft Academic Search

The surface-stabilized ferroelectric liquid crystal (SSFLC) electro-optic device is superior in many regards to other available optical and electro-optical switching devices for optical computing applications requiring the parallel operation of a large number of elements. The SSFLC device's large interaction with light, stemming from its large permanent birefringence, allows individual electro-optic elements to be small in size and hence allows

M. A. Handschy; K. M. Johnson; G. Moddel; L. A. Pagano-Stauffer

1988-01-01

144

ZigZag Defects and Disclinations in the Surface-Stabilized Ferroelectric Liquid Crystals  

Microsoft Academic Search

Characteristic features of zig-zag defects and disclinations in surface-stabilized ferroelectric liquid crystal cells are presented. It is pointed out that there exist two kinds of zig-zag defects, i.e., a lightning type and a hairpin type, which appear alternatively along the smectic layer normal. This fact indicates that two types of mismatching of a layer bend structure cause two kinds of

Yukio Ouchi; Hideo Takano; Hideo Takezoe; Atsuo Fukuda

1988-01-01

145

Behaviour of Ionic Effects on Response Times of Surface Stabilized Ferroelectric Liquid Crystal Devices  

NASA Astrophysics Data System (ADS)

The response time measurements of a new room temperature ferroelectric liquid crystal have been done by using the field reversal method. The response time has been found to be frequency dependent and decreases considerably at frequencies above 10 kHz. The temperature dependence of response time showed the presence of ionic effects as is evident from the appearance of the second peak in the current response to an applied bipolar pulse.

Saxena, Kanchan; Bawa, S. S.; Biradar, A. M.; Chandra, Subhas; Rup, Raj

1990-10-01

146

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

147

Molecular Dynamics and Film Vibration Induced by Electric Field in Freely Suspended Ferroelectric Liquid Crystal Film  

NASA Astrophysics Data System (ADS)

We studied the molecular dynamics and film vibration in a freely suspended ferroelectric liquid crystal film in the smectic A (SmA) and chiral smectic C (SmC*) phases by monitoring the intensity change of the reflected light from the film surface. It was confirmed that the mechanisms of the film vibration are apparently different between in the SmA and SmC* phases.

Nakano, Kazuyuki; Ozaki, Masanori; Yoshino, Katsumi

2003-09-01

148

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

149

Nondestructive imaging and characterization of ferroelectric domains in periodically poled crystals  

NASA Astrophysics Data System (ADS)

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

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

1998-06-01

150

Growth of Zno Single Crystals.  

National Technical Information Service (NTIS)

Single crystals of ZnO have been grown by subliming both ZnS and ZnSe and reacting them with oxygen in an argon gas flow. Using ZnS as the starting material, both platelet- and prism-type ZnO crystals were grown. Prisms having a cross-sectional area in th...

Y. S. Park D. C. Reynolds

1966-01-01

151

Optical dispersion and interband transition in Na0.5Bi0.5TiO3-x%BaTiO3 lead-free relaxor ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

Optical properties of A-site disordered Na0.5Bi0.5TiO3-x%BaTiO3 (NBT-xBT) single crystals with three typical compositions were studied systematically. Refractive index as a function of wavelength was measured by Spectroscopic ellipsometry, and modified Sellmeier dispersion equations were obtained by the least square fitting. High optical transmittance (65%) over a wide transparent region (from 400 to 6000 nm) has been found in NBT-7.5BT, much higher than that of NBT and NBT-5BT. Optical band gap energies were calculated using the absorption coefficient through Tauc equation. With increasing BT content, refractive index and absorption coefficient decrease, while transmission and band gap energy increase.

Zhang, Haiwu; Zhang, Qinhui; Zhao, Xiangyong; Li, Xiaobing; Wang, Dong; Luo, Haosu

2013-05-01

152

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

NASA Astrophysics Data System (ADS)

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.

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

2011-04-01

153

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

SciTech Connect

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

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

2003-10-15

154

Fast-Switching Microwave Phase Shifter of Coplanar Waveguide Using Ferroelectric Liquid Crystal  

NASA Astrophysics Data System (ADS)

The microwave variable phase shifter of a coplanar waveguide using ferroelectric liquid crystal with float electrodes, which are used for applying a dc voltage to a liquid crystal layer, is discussed. We confirmed the performance of the phase shifter in the frequency range from 10 to 30 GHz and found that phase shift is proportional to the frequency of the microwave according to the theory. The measured phase shift increases with an increase in applied voltage. The response time of this phase shifter was less than 1 ms above 120 V and a very high speed variable phase shifter was achieved.

Moritake, Hiroshi; Morita, Satoshi; Ozaki, Ryotaro; Kamei, Toshihisa; Utsumi, Yozo

2007-06-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

156

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

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

157

Electro-optic and dynamic studies of biphenyl benzoate ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

We present electro-optic and dynamic properties on three homologous of biphenyl benzoate series of ferroelectric liquid crystals (FLCs) exhibiting the chiral smectic C phase (SmC*). The three compounds present high spontaneous polarization and show the SmC*-SmA*-N* phase sequence. Dielectric spectroscopy was used to provide the dynamics and dipolar ordering of the ferroelectric phase. The Goldstone relaxation mode was studied for sample cells on planar geometry without a DC bias voltage. The rotational viscosity corresponding to molecular motions in the SmC* phase was determined from dielectric measurements. The Arrhenius-type behavior of the rotational viscosity was found and the corresponding activation energies were evaluated.

Hemine, J.; Daoudi, A.; Legrand, C.; El Kaaouachi, A.; Nafidi, A.; Ismaili, M.; Isaert, N.; Nguyen, H. T.

2010-05-01

158

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

159

Effect of magnetic field and temperature on the ferroelectric loop in MnWO4  

NASA Astrophysics Data System (ADS)

The ferroelectric properties of MnWO4 single crystal have been investigated. Despite a relatively low remanent polarization, we show that the sample is ferroelectric. The shape of the ferroelectric loop of MnWO4 strongly depends on magnetic field and temperature. While its dependence does not directly correlate with the magnetocapacitance effect before the paraelectric transition, the effect of magnetic field on the ferroelectric polarization loop supports magnetoelectric coupling.

Kundys, Bohdan; Simon, Charles; Martin, Christine

2008-05-01

160

Pyroelectric and piezoelectric effects in single crystals of YBa2Cu3O(7-delta)  

SciTech Connect

The possibility of ferroelectric (or antiferroelectric) behavior in high-Tc materials is suggested by the well known tendency of the perovskite structure to distort and form such ordered phases. Moreover, the connection between incipient (anti)ferroelectricity and superconductivity has been made by a number of authors. However, the crystal structure of YBa2Cu3O7 as determined by X-ray and neutron diffraction measurements has been reported to be centrosymmetric and, therefore, not ferroelectric. In this paper, we report the observation of a transient voltage across the z-axis of a single crystal upon heating with thermal or laser pulses as well as a transient voltage across the z-axis resulting from the application of mechanical stress.

Mihailovic, D.; Heeger, A.J.

1990-01-01

161

Ferroelectricity and Isotope Effects in Hydrogen-Bonded KDP Crystals  

Microsoft Academic Search

Based on an accurate first principles description of the energetics in H-bonded potassium-dihydrogen-phosphate crystals, we conduct a first study of nuclear quantum effects and of the changes brought about by deuteration. Tunneling is allowed only for clusters involving correlated protons and heavy ion displacements, the main effect of deuteration being a depletion of the proton probability density at the O-H-O

S. Koval; J. Kohanoff; R. L. Migoni; E. Tosatti

2002-01-01

162

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

NASA Astrophysics Data System (ADS)

Ferroelectric domain structures of as-grown KTiOPO4 crystals are observed on polished polar surfaces by the scanning secondary-electron microscopy (SEM) method. The results demonstrate a different contrast origin for domain boundaries and domains themselves. It is shown that the electron-beam irradiation in SEM causes a local heating of the ferroelectric crystal. Detailed calculations of the effects involved allow to assume that pyroelectric potentials induced by heating are opposite in sign for C+ and C- domains which is the main reason for the domain contrast. Domain boundaries are revealed due to the converse piezoelectric effect and the corresponding crystal deformations of ferroelectric domains are induced by electron-beam charging.

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

1996-09-01

163

Mapping the Spatial Variation of Switching Properties within Single Ferroelectric Nanoparticle and Nanoparticle Arrays  

SciTech Connect

The spatial variability of polarization switching in ferroelectric lead zirconate-titanate nanoparticle arrays and within a single sub-100 nanometer nanoparticle is investigated by using switching spectroscopy piezoresponse force microscopy. Strong variations of switching properties within a single nanoparticle are observed and attributed to polarization pinning by geometric effects and interfacial dislocations. The spatial distributions of imprint bias and the thickness of the frozen polarization layer within the nanoparticle are reconstructed.

Rodriguez, Brian J [ORNL; Jesse, Stephen [ORNL; Alexe, M. [Max-Planck-Institut fur Mikrostrukturphysik, Germany; Kalinin, Sergei V [ORNL

2008-01-01

164

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

NASA Astrophysics Data System (ADS)

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.PRLTAO0031-900710.1103/PhysRevLett.102.197802 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.

Lopatina, Lena M.; Selinger, Jonathan V.

2011-10-01

165

Polarization rotation and field induced phase transition in PZN-4.5%PT single crystal  

NASA Astrophysics Data System (ADS)

We have investigated both the polarization rotations and the field induced phase transitions in [100], [110], and [111]-oriented PZN-4.5%PT single crystals on the basis of the single domain polarization rotation model. The dependence of the polarization, the electrostrictive response, and the lattice parameters in ferroelectric crystals on the field has been numerically obtained. The numerical results, in agreement with the experimental data, have shown that the polarization rotation is strongly dependent on the initial polarization state and polarization history in the single crystals, and the rhombohedral-monoclinic-tetragonal phase transitions occur for E//[100].

Zhang, Hui

2013-08-01

166

Fabrication of Defect-Free Ferroelectric Liquid Crystal Cells Using Alignment Films Rubbed in Antiparallel Direction  

NASA Astrophysics Data System (ADS)

The fabrication of operable surface-stabilized ferroelectric liquid crystals (SSFLCs) is often hampered by the occurrence of zigzag defects. In this study, we try to fabricate a defect-free SSFLC with antiparallel-rubbed films that exhibit different properties between two substrates for the energy condition in two types of chevron to be different. As a result, the occurrence of zigzag defects can be suppressed as the differences in anchoring strength and pretilt angle increase between two alignment films, and then in the case of the large differences in physical properties, zigzag defect-free SSFLCs can be obtained.

Furue, Hirokazu; Abe, Masamichi

2012-03-01

167

Formation of dynamic holograms based on spatial modulation of molecular motions of ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

The formation of dynamic holograms based on the spatial modulation of the molecular motions of ferroelectric liquid crystals (FLCs) was demonstrated. The consecutive rotational switching motion of FLC molecules under an alternating electric field was modulated by the photoinduced additional electric field built at the interference fringe. This spatially periodic difference in molecular motions of an FLC was confirmed to work as a diffraction grating. Since the motion-mode hologram is stable and the response is very fast when compared to photorefractive polymers, the motion-mode hologram appears to be promising for various photonic applications.

Sasaki, Takeo; Mochizuki, Oki; Nakazawa, Yukihito; Fukunaga, Godai; Nakamura, Tetsuya; Noborio, Kazunori

2004-08-01

168

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

169

Photomodulating the spontaneous polarization of a ferroelectric liquid crystal phase using chiral thioindigo dopants  

NASA Astrophysics Data System (ADS)

The chiral thioindigo dye (R,R)-5,5'-dinitro-6,6'-bis(2- octyloxy)thioindigo has been synthesized in optically active form and doped into a racemic SC liquid crystal host (xd equals 0.028) to induce a ferroelectric SC* phase. Irradiation of an aligned sample of this induced SC* phase at (lambda) greater than 450 nm produces a cis- enriched photostationary state of the dopant, and an increase in the spontaneous polarization of the SC* phase by a factor of 1.8. This modulation is reversible via thermal relaxation of the dopant to the trans-form.

Dinescu, Liviu; Lemieux, Robert P.

1997-04-01

170

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

SciTech Connect

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

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

2010-11-22

171

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

172

Ferroelectricity and Isotope Effects in Hydrogen-Bonded KDP Crystals  

NASA Astrophysics Data System (ADS)

Based on an accurate first principles description of the energetics in H-bonded potassium-dihydrogen-phosphate crystals, we conduct a first study of nuclear quantum effects and of the changes brought about by deuteration. Tunneling is allowed only for clusters involving correlated protons and heavy ion displacements, the main effect of deuteration being a depletion of the proton probability density at the O-H-O bridge center, which in turn weakens its proton-mediated covalent bonding. The ensuing lattice expansion couples self-consistently with the proton off-centering, thus explaining both the giant isotope effect and its close connection with geometrical effects.

Koval, S.; Kohanoff, J.; Migoni, R. L.; Tosatti, E.

2002-10-01

173

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

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

1991-01-01

174

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

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

1991-01-01

175

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

NASA Astrophysics Data System (ADS)

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

Lu, Xinliang

2000-10-01

176

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

2012-09-18

177

LARGE FIELD ELECTROMECHANICAL MEASUREMENT TECHNIQUES FOR FERROELECTRIC MATERIALS  

Microsoft Academic Search

Ferroelectric materials used in high power applications are subject to electric fields ? 2 MV\\/m and compressive stress preloads ?50 MPa. In 3-1 composites, the ferroelectric materials are driven in tension, which has necessitated development of large field characterization techniques for bulk ceramics, single crystals, and multilayer actuators. This paper describes techniques for compressive loading with electric field and temperature

C. S. LYNCH

2010-01-01

178

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

179

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

NASA Astrophysics Data System (ADS)

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

Quickel, Thomas Eugene

180

Guided Optical Waves in a Ferroelectric Liquid Crystal Layer: A Birefringence Analysis of Molecular Orientation on the Switching Process  

Microsoft Academic Search

Guided optical waves are very sensitive to the alteration of optical properties of dielectric media. In this report, we demonstrate the use of guided waves for studying dynamic behavior of ferroelectric liquid crystals. Propagating light in the anisotropic medium suffers a birefringent effect, which causes coupling of p- and s-polarized light. Theoretical calculations, based on the Maxwell equations, successfully describe

S. Ito; F. Kremer; T. Fischer; W. Knoll

1995-01-01

181

High-speed, low-power optical phase conjugation using a hybrid amorphous silicon/ferroelectric-liquid-crystal device.  

PubMed

Optical phase conjungation using an amorphous silicon/ferroelectric-liquid-crystal light modulator shows an optical response of 100 microsec with a diffraction efficiency of 8.5% for an incident optical intensity of 1 mW/cm(2). PMID:19771013

Johnson, K M; Mao, C C; Moddel, G; Handschy, M A; Arnett, K

1990-10-15

182

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

NASA Astrophysics Data System (ADS)

Hadamard transforms with a ferroelectric-liquid-crystal-over-silicon (FLCOS) spatial light modulator (SLM) has been described with application in optical-to-electronic information conversion. High resolution Hadamard transformation is possible in excess of TV frame rates, with basis functions generation on chip within a specially designed FLCOS SLM backplane device.

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

1993-10-01

183

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

Microsoft Academic Search

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

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

2004-01-01

184

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

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

C. Annis

1992-01-01

185

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

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

D. P. DeLuca C. Annis

1991-01-01

186

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

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

D. P. DeLuca C. Annis

1993-01-01

187

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

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

D. P. DeLuca C. Ann

1992-01-01

188

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

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

D. P. DeLuca C. Annis

1994-01-01

189

Adaptive Beam Steering Implemented in a Ferroelectric Liquid-Crystal Spatial-Light-Modulator Free-Space, Fiber-Optic Switch  

NASA Astrophysics Data System (ADS)

Active alignment of a 1 x 8 free-space optical switch was studied experimentally. Optical signals, carried on single-mode fibers, were switched by a ferroelectric liquid-crystal-on-silicon spatial light modulator. Continuous measurement of the in-coupled power to the fibers provided feedback for the switch control. The switch automatically located and locked to the output fibers. An advantage with adaptive switches of a similar kind is relaxed geometrical tolerances in the switch assembly. Further, such switches can adapt to possible geometrical changes and light wavelength drift during operation.

Johansson, Mathias; Hård, Sverker; Robertson, Brian; Manolis, Ilias; Wilkinson, Timothy; Crossland, William

2002-08-01

190

9Be Quadrupole Perturbed NMR Study of the Ferroelectric Transition in Deuterated Triglycine Fluoberyllate  

Microsoft Academic Search

The quadrupole perturbed magnetic resonance spectra of 9Be in a deuterated triglycine fluoberyllate single crystal have been studied as a function of temperature and crystal orientation, and the electric field gradient (EFG) tensors at the Be sites have been determined in the para- and in the ferroelectric phase. The data show that the main effect of the ferroelectric transition is

R. Blinc; J. Slak; J. Stepisnik

1971-01-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

192

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

193

First one-dimensional homochiral stairway-like Cu(II) chains: crystal structures, circular dichroism (CD) spectra, ferroelectricity and antiferromagnetic properties.  

PubMed

The reactions of enantiopure chiral ligands (+)/(?)-4,5-pinenepyridyl-2-pyrazine (LS/LR) with CuCl2·2H2O in CH3OH/CH2Cl2 solution led to the formations of one-dimensional homochiral enantiomeric pairs with the formula [Cu(LR/S)Cl2]n·2H2O (R-1 and S-1, the isomers containing the LR and LS ligands, respectively). The circular dichroism (CD) spectra verified their chiroptical activities and enantiomeric natures. Their structures have been determined by X-ray single-crystal analyses, showing stairway-like and mirror-symmetric features, which represent the first examples of homochiral metal complexes with stairway-like structures. The ferroelectric property measurement indicated that R-1 exhibits ferroelectricity with the remnant polarization (Pr) value of 0.02 ?C cm?2 under an applied electric field of 6.1 kV cm?1 at room temperature. The magnetic investigation of R-1 showed a weak intrachain antiferromagnetic coupling between Cu(II)–Cu(II) ions mediated by pyrazine, which can be interpreted by a spin-polarization mechanism. All these results suggested that R-1 and S-1 are potential multifunctional molecule-based materials combining optical activity, ferroelectricity and magnetism within one molecule. PMID:23391964

Li, Xi-Li; Chen, Chun-Lai; Han, Li-Feng; Liu, Cai-Ming; Song, You; Yang, Xiao-Gang; Fang, Shao-Ming

2013-04-14

194

Eight-level programmable binary optics system using cascaded ferroelectric liquid crystal spatial light modulators  

NASA Astrophysics Data System (ADS)

We present a novel method for producing arbitrary valued, binary phase-only modulation from a commercially available ferroelectric liquid crystal spatial light modulator (FLCSLM) used in conjunction with simple polarization components. Three such stages can be cascaded together in an instrument capable of producing up to eight discrete, equally spaced levels of phase modulation. By using 128 by 128 pixel FLCSLMs a reconfigurable, pixellated, eight-level, optical phase modulator has been constructed which we refer to here as a programmable phase transformer (PPT). We report on the near diffraction limited performance of such an instrument when stopped down to 64 by 64 pixels in producing simple diffraction patterns and when used to generate asymmetric spot arrays in the Fourier plane of a lens. We also discuss the limitations of the current system and the projected improvements that will result from current and future developments in device technology and modulation schemes.

Broomfield, Seth E.; Neil, Mark A.; Paige, Edward G.

1995-09-01

195

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

2010-09-17

196

Zig-Zag Defects and Disclinations in the Surface-Stabilized Ferroelectric Liquid Crystals  

NASA Astrophysics Data System (ADS)

Characteristic features of zig-zag defects and disclinations in surface-stabilized ferroelectric liquid crystal cells are presented. It is pointed out that there exist two kinds of zig-zag defects, i.e., a lightning type and a hairpin type, which appear alternatively along the smectic layer normal. This fact indicates that two types of mismatching of a layer bend structure cause two kinds of zig-zag defects. Switching between two twisted states occurs with the formation of internal boat-shaped disclination loops in relation to the zig-zag defects. The nucleation process of the boat-shaped domains is quite characteristic; the bows appear on each side of the bright hairpin-type lines, while the sterns appear on both sides of the dark lightning-type lines. A model structure is proposed in order to interpret the experimental observation around the zig-zag defect lines on the basis of disclination dynamics.

Ouchi, Yukio; Takano, Hideo; Takezoe, Hideo; Fukuda, Atsuo

1988-01-01

197

Mean-field coefficients and the electroclinic effect of a ferroelectric liquid crystal  

NASA Astrophysics Data System (ADS)

Experimental data on the temperature and electric field dependence of the tilt angle and the electroclinic effect of the smectic-C* (Sm-C*) and the smectic-A* (Sm-A*) phases are presented which have been obtained by electrooptical investigations on the ferroelectric liquid crystal mixture FLC 6430 from Hoffmann-La Roche, Basle, Switzerland. The data are analyzed according to the generalized Landau expansion and the results of a microscopic model for spontaneous polarization. The mean-field coefficients obtained from a fit of the Landau approach to the experimental data are discussed with respect to the electroclinic effect, the specific heat singularity, and the chirality. The results support the evidence of quadrupolar ordering and biquadratic coupling for the description of the Sm-C*-Sm-A* phase transition. The Landau model is extended to temperatures far below the phase transition.

Gießelmann, F.; Zugenmaier, P.

1995-08-01

198

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

199

Polarization inversion in a ferroelectric liquid crystal studied by 1H nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

A ferroelectric liquid crystal, S-2-methylbutyl 4-n-octanoyloxybiphenyl-4'-carboxylate, undergoing a characteristic polarization inversion, has been studied by 1H nuclear magnetic resonance (NMR). In addition to the discontinuities at the first-order isotropic and recrystallization phase transitions, the nuclear magnetic relaxation revealed a weak anomaly attributed to the soft mode at the Sm-A-Sm-C* liquid crystalline phase transition. Besides, the polarization inversion in the Sm-C* phase was manifested in the nuclear magnetic relaxation as well as in the NMR lineshape and in the temperature-dependent relative peak positions of the NMR line components, indicating that the polarization inversion is associated with a conformational transition.

Cha, J. K.; Lee, K. W.; Lee, Cheol Eui; Jin, J.-I.

2010-03-01

200

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

201

Physics of Heavily Implanted Single Crystal Complex Oxides  

NASA Astrophysics Data System (ADS)

Ion implantation is known to result in a significant amount of damage in solid single crystals. In this work a battery of material probes is used to study the effect of a very high-dose He implantation in ferroelectric lithium niobate (LiNbO3) and the implantation-induced formation of defects. In addition, the evolution of these defects with post-implantation annealing is examined. After irradiation, a high concentration of defects is found to collect and create a network of thick prismatic planar defects having typical dimensions of ˜1.5 microm and 200 nm parallel and perpendicular to the Z axis, respectively. Optical microscopy shows that there is strong temperature dependence for forming the network; the density of these defects reaches a maximum value for an annealing temperature of 250 °C. However, annealing to temperatures above 380 °C fully eliminates the defects. High-resolution TEM studies indicate that the defects are likely localized twinning and dislocation pileups due to plastic deformation of the lattice to relieve He-implantation-induced stress. During this deformation He accumulates at the twin boundaries. A second type of implantation induced defects is studied using room temperature, high- resolution electron microscopy; this study shows that implanted He in LiNbO3 nucleates and accumulates as bubbles. These He inclusions are at ˜20 GPa pressure and most probably in the solid phase. In addition, the energetically favored shape of the inclusions in their as-implanted form is spherical and not oblate; this spherical shape is due to the fact their diameter is below a critical radius for balancing the surface and elastics energies as predicted by elastic theory. When annealed, the characteristic length scale of the He inclusions increases, forming faceted bubbles. Annealing also causes the He inclusions to migrate and accumulate into strings due to the preferred {1014}-pyramidal-twinning planes. The ion implantation-induced defects are found to be useful for several microfabrication techniques, in particular we describe the use of these defects for ion slicing of single crystal thin films from bulk crystals and ferroelectric domain patterning by low voltage pulses applied to a scanning force microscope tip. The origin of the rate of anomalously high spatially selective etching of a buried heavily implanted region in complex oxides is found to be closely related to the implantation-induced defects. He+-ion implantation in single-crystal LiNbO3 samples followed by low-temperature anneal and wet etched results in an etch-rate enhancement of 104. This high rate selective etch is crucial for the Crystal Ion Slicing process, a novel technique to fabricate single crystal thin films by slicing them off a bulk crystal. Experiments, using time-resolved optical microscopy and proximal-probe microscopy, show that this enhancement arises from the more rapid etch-solution transport in the thick prismatic planar defect network formed in the implanted region after annealing. Ferroelectric domain patterns are generated in He-implanted single-crystal bulk wafers of LiNbO3 by means of low-voltage pulses applied to a scanning force microscope tip and investigated using piezoresponse force microscopy and selective etching. It is shown that high fluence implantation results in isolation of the near surface region, creating a free-standing-film-like behavior for the layer above the heavily implanted region. At low fluence the implantation damage allows low voltage poling, apparently by vacancy-induced dipole formation. In addition, electrostatic repulsion of the poling-induced buried charges from adjacent domains limits the domain size and depth; this effect results in a uniform domain structures and potentially enables large area nanodomains patterns to be written.

Ofan, Avishai

202

Director Orientation in Chevron Surface-Stabilized Ferroelectric Liquid Crystal Cells, Verification of Orientational Binding at the Chevron Interface Using Visible Polarized Light Transmission Spectroscopy.  

National Technical Information Service (NTIS)

Results are presented for theoretical modelling and experimental study of director distributions and the associated optical properties of chevron surface stabilized ferroelectric liquid crystal (SSFLC) cells. Chevron cells are modelled as being two stacke...

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

1990-01-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

204

Local weak ferromagnetism in single-crystalline ferroelectric BiFeO3.  

PubMed

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

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

2011-11-11

205

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

NASA Astrophysics Data System (ADS)

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

Suewattana, Malliga

206

Spectral Characterization of a Ferroelectric Liquid Crystal Modulator and Performance Optimization  

NASA Astrophysics Data System (ADS)

In this work we present a characterization of a ferroelectric liquid crystal modulator and its performance optimization as an optical switch. We present a procedure to characterize the orientation of the liquid crystal layer and its change with the applied voltage. Then we illuminate the modulator with white light and analyze the transmitted light with a portable spectro-photometer. The chromatic dispersion of the phase shift introduced by the modulator is obtained from the spectral intensity of the transmitted light. Then we apply this result to evaluate the response as an optical switch both for white light and monochromatic laser light with different wavelengths. We show that it is possible to optimize the response of the modulator for wavelengths that are far from the design wavelength. For that purpose a quarter wave-plate is placed in front of the modulator. In this configuration the modulator is illuminated with elliptically polarized light, being the polarization ellipse selected to produce at the exit two states as close as possible to be orthogonal.

Velásquez, Pablo; García, Pablo; Sánchez-Lopez, María M.; Moreno, Ignacio; Mateos, Felipe

2008-04-01

207

Optimization of ferroelectric liquid crystal optically addressed spatial light modulator performance  

NASA Astrophysics Data System (ADS)

The switching mechanisms of ferroelectric liquid crystal optically addressed spatial light modulators (OASLMs) using a photosensitive structure made of an intrinsic amorphous silicon layer sandwiched in between an indium tin oxide coated glass sheet and a reflective metal layer are reviewed. Devices based on photoconductor and photodiode layers are briefly reviewed and attention is focused on pixelated metal mirror devices, which offer fast switching and good optical characteristics with the same sensitivity range as the photodiode OASLMs. They are particularly suitable for high frame rate SLMs with intense read beams. Optimum drive conditions for this type of device are considered. An equivalent electrical circuit is proposed for the photosensitive structure and the voltage drop across the liquid crystal layer is investigated and related to the optical response of the device. Experimental work is carried out to demonstrate the validity of our equivalent circuit. We show that the synchronization of a light source with the case pulse enables the OASLM to work at frame rates of a few kilohertz. We also demonstrate that the exact synchronization of the write light source with the write pulse enhances the potential memory of the device.

Perennes, Frederic; Crossland, William A.

1997-08-01

208

Quantum tunneling effects in dipolar ferroelectrics: A nuclear-quadrupole-resonance study in HCl-DCl mixed crystals  

Microsoft Academic Search

Static and dynamical effects from a quantum tunneling contribution to the dipole reorientations in the ferroelectric phases of the mixed crystals HCl-DCl have been studied through 35Cl nuclearquadrupole-resonance pulse Fourier-transform measurements. Experimental data for the transition temperatures Tc and the local correlation times tau, of both the HCl and DCl dipoles, for several percentages of deuteration are analyzed in the

M. Crowley; J. Brookeman; A. Rigamonti

1983-01-01

209

Growth and concentration dependencies of rare-earth doped lithium niobate single crystals  

NASA Astrophysics Data System (ADS)

A series of lithium niobate LiNbO3 (LN) single crystals doped by rare-earth elements (Tm, Er, Dy, Tb, Gd, Pr) were grown under the same conditions by the Czochralski technique in a wide range of dopant concentrations. The distribution coefficients of rare-earth elements in the “crystal—melt” system of LN were determined at the beginning of the crystal growth. Their dependence on the dopant concentration in melt ranging from 0.1 to 3.5 wt% was investigated. Concentration dependences of physicochemical, ferroelectric and structural characteristics of doped LN single crystals were studied using X-ray diffraction, thermal analysis and Raman scattering measurements. A mechanism of rare-earth elements incorporation into the crystal lattice of LN was proposed for a wide range of dopant concentrations.

Palatnikov, M. N.; Biryukova, I. V.; Sidorov, N. V.; Denisov, A. V.; Kalinnikov, V. T.; Smith, P. G. R.; Shur, V. Ya.

2006-06-01

210

One-dimensional tunable ferroelectric photonic crystals based on Ba0.7Sr0.3TiO3/MgO multilayer thin films  

NASA Astrophysics Data System (ADS)

Tunable photonic crystals (PCs) have attracted much attention in the past decade because of their various applications, such as ultrafast optical filters and optical waveguides with add-drop functionalities. One way of achieving tunability is to make use of ferroelectric materials since the refractive index of ferroelectric materials can be electrically tuned through the electro-optic effect. In this paper, we present our work on developing a tunable one-dimensional (1D) PC based on a Ba0.7Sr0.3TiO3/MgO multilayer structure. The photonic band structures and band gap maps of the PC were calculated by using the plane-wave expansion (PWE) method. It is found that the gap center linearly shifts with the change in the refractive index of Ba0.7Sr0.3TiO3. A ferroelectric 1D PC consisting of a Ba0.7Sr0.3TiO3/MgO multilayer thin film was epitaxially deposited on a MgO (001) single-crystal substrate by pulsed laser deposition. A photonic band gap in the visible region is observed in the transmission spectrum of the multilayer thin film. The center wavelength of the band gap is ~464 nm, which agrees with the simulation results obtained by the transfer matrix method. The band gap can be tuned by applying an electric field E. The band gap shifts by about 2 nm when the thin film is subjected to a dc voltage of 240 V (E~12 MV/m). This shift corresponds to an ~0.5% change in the refractive index of the Ba0.7Sr0.3TiO3 layer, as calculated by the PWE method.

Jim, K. L.; Wang, D. Y.; Leung, C. W.; Choy, C. L.; Chan, H. L. W.

2008-04-01

211

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2000-03-01

213

Ultraprecision diamond turning of aluminium single crystals  

Microsoft Academic Search

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

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

1997-01-01

214

Protein Single Crystal Growth under Microgravity  

NASA Astrophysics Data System (ADS)

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

Littke, Walter; John, Christina

1984-07-01

215

Characterization of the dynamics of surface stabilized ferroelectric liquid crystal under electric field by full optical snapshot matrix Mueller polarimeter  

NASA Astrophysics Data System (ADS)

We investigated the layer dynamics of a conventional surface-stabilized ferroelectric liquid crystal (SSFLC) using a full-optical snapshot Mueller matrix polarimeter (SMMP) based on wavelength polarization coding. Time-resolved polarimetric measurements were performed with different SSFLC samples, and a strong correlation between the polarimetric parameters and the SSFLC under electric field at different exposure times was found. It has been shown that the SMMP polarimeter is able to determine the evolution of the trajectory of the liquid crystal director between the two addressed states, the reversible motion of the smectic layer while switching, as well as the irreversible transition from chevron to bookshelf texture.

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

2012-12-01

216

The self-biased heterojunction effect of ferroelectric thin film on silicon substrate  

Microsoft Academic Search

Several ferroelectric thin films with n-type or p-type conductivity, including undoped and doped lead zirconate titanate, barium titanate, strontium barium niobate, and potassium niobate, as well as lead barium niobate, were made on silicon single-crystal substrates by the sol-gel process. Self-biased heterojunction effects were observed in both p-ferroelectric thin film on n-silicon and n-ferroelectric thin film on p-silicon by the

Yuhuan Xu; Ching Jih Chen; Ren Xu; John D. Mackenzie

1990-01-01

217

Adhesion of single crystals on modified surfaces in crystallization fouling  

NASA Astrophysics Data System (ADS)

In crystallization fouling it has been observed that during a certain initial phase the fouling is formed by a non-uniform layer consisting of a population of single crystals. These single crystals are frequently formed by inverse soluble salts such as CaCO3. During heterogeneous nucleation and heterogeneous growth an interfacial area between the crystal and the heat transfer surface occurs. The development of this interfacial area is the reason for the adhesion of each single crystal and of all individual crystals, once a uniform layer has been built up. The emerging interfacial area is intrinsic to the heterogeneous nucleation of crystals and can be explained by the thermodynamic principle of the minimum of the Gibbs free energy. In this study CaCO3 crystals were grown heterogeneously on untreated and on modified surfaces inside a flow channel. An untreated stainless steel (AISI 304) surface was used as a reference. Following surface modifications were investigated: enameled and electropolished stainless steel as well as diamond-like-carbon based coatings on stainless steel substrate. The adhesion was measured through a novel measurement technique using a micromanipulator to shear off single crystals from the substrate which was fixed to a spring table inside a SEM.

Mayer, Moriz; Augustin, Wolfgang; Scholl, Stephan

2012-12-01

218

Thermal and optical properties of the ferroelectric (C3N2H5)5Bi2Cl11 crystal  

NASA Astrophysics Data System (ADS)

Thermal (specific heat) and optical (linear birefringence) studies were performed for a new ferroelectric crystal (C3N2H5)5Bi2Cl11. Two phase transitions were confirmed and described. The first-order paraelastic ferroelastic phase transition at 360 K was studied with a polarizing microscope. The continuous second-order phase transition at 165 K to the ferroelectric phase is described by the Landau model using specific heat and linear birefringence data. The Landau expansion coefficients B and C are of an order of magnitude higher than the closely related ferroelectric crystal; MAPCB — (CH3NH3)5Bi2Cl11. Thermal parameters (such as the excess enthalpy ?H and the excess entropy ?S) of the continuous transition were estimated and discussed. The ‘two-site’ model describing the motion of three of the five imidazolium cations, which is proposed from the structural studies, is fully confirmed by the data from the ac-calorimetric measurements.

Przes?awski, Janusz; Kosturek, Bogus?aw; Dacko, S?awomir; Jakubas, Ryszard

2007-06-01

219

New Pockels field sensor with ferroelectric liquid-crystal phase modulator  

NASA Astrophysics Data System (ADS)

A new optical field sensor for measuring the electric field close to an electrical discharge has been developed. The new system that uses both P- and S-polarized light-division and azimuth angle modulation methods has been devised and investigated. By using a ferroelectric liquid-crystal phase modulator instead of an azimuth angle modulator, it has been possible to eliminate noise from the optical field measurement system, specifically, the birefringence effects in a long optical fiber cable. The optical cable is used for connecting a Pockels field sensor located close to the discharge with the main system located at the ground. Furthermore, it has been possible to compensate for the sensitivity difference between two optical detectors for converting P- and S-polarized light waves to an electrical signal. From this, it is found that by using a light reflection technique, the measurable minimum field strength is reduced from 100 kV/m to 1.0 kV/m in the discharge region. If the smallest phase change in the system is set to be less than 10-3 [rad], the measurable minimum field strength is reduced to 0.1 kV/m. The possible use of the probe is also considered for checking for damage caused by cosmic rays to the insulating skin of a spacecraft.

Tada, K.; Tanaka, Y.; Takada, T.; Murooka, Y.

2003-05-01

220

Short-range ordering and freezing in a randomly mixed ferroelectric-antiferroelectric crystal  

Microsoft Academic Search

X-ray measurements on single-crystals of Rb1-x(NH4)xH2PO4 trace the development of a glasslike state. The absence of macroscopic crystal-symmetry change during freezing is confirmed, while diffuse scattering reveals the growth of very-short-range order. The latter coincides with a compressibility anomaly seen in Brillouin scattering and with dielectric effects suggesting freezing. The system is in many ways analogous to spin-glasses.

Eric Courtens; T. F. Rosenbaum; S. E. Nagler; P. M. Horn

1984-01-01

221

A nonvolatile memory device made of a ferroelectric polymer gate nanodot and a single-walled carbon nanotube.  

PubMed

We demonstrate a field-effect nonvolatile memory device made of a ferroelectric copolymer gate nanodot and a single-walled carbon nanotube (SW-CNT). A position-controlled dip-pen nanolithography was performed to deposit a poly(vinylidene fluoride-ran-trifluoroethylene) (PVDF-TrFE) nanodot onto the SW-CNT channel with both a source and drain for field-effect transistor (FET) function. PVDF-TrFE was chosen as a gate dielectric nanodot in order to efficiently exploit its bipolar chemical nature. A piezoelectric force microscopy study confirmed the canonical ferroelectric responses of the PVDF-TrFE nanodot fabricated at the center of the SW-CNT channel. The two distinct ferroelectric polarization states with the stable current retention and fatigue-resistant characteristics make the present PVDF-TrFE-based FET suitable for nonvolatile memory applications. PMID:21050014

Son, Jong Yeog; Ryu, Sangwoo; Park, Yoon-Cheol; Lim, Yun-Tak; Shin, Yun-Sok; Shin, Young-Han; Jang, Hyun Myung

2010-11-04

222

Photoemission from Germanium Single Crystals.  

National Technical Information Service (NTIS)

Studies of band structure of germanium by using photoemission have been reported recently by Donovan and Spicer and Donovan. Some new experimental results of electronic structures of simple crystal germanium are presented here. Principal results are as fo...

J. Matsuzaki

1970-01-01

223

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

224

Ion implantation in perovskite type ferroelectrics  

Microsoft Academic Search

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

R. Gerson

1979-01-01

225

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

PubMed

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

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

2012-02-21

226

Strategies for gallium removal after focused ion beam patterning of ferroelectric oxide nanostructures  

Microsoft Academic Search

As part of a study into the properties of ferroelectric single crystals at nanoscale dimensions, the effects that focused ion beam (FIB) processing can have, in terms of structural damage and ion implantation, on perovskite oxide materials has been examined, and a post-processing procedure developed to remove such effects. Single crystal material of the perovskite ferroelectric barium titanate (BaTiO3) has

A Schilling; T Adams; R M Bowman; J M Gregg

2007-01-01

227

Effect of swift heavy ion beam irradiation on the dielectric and ferroelectric properties of pure and cobalt doped TGS crystals  

NASA Astrophysics Data System (ADS)

Effect of swift heavy ion (100 MeV O7+ ion) beam irradiation on the temperature and frequency dependence of real (&z.epsiv;?) and imaginary (&z.epsiv;?) parts of dielectric permittivity in pure and Co2+ doped TGS crystals are analyzed. Irradiation with swift heavy ion beam changes the dielectric response considerably. Observed dielectric peak in irradiated crystals shifts towards lower temperature and broadens up; the reduction in peak value, shift in temperature and broadening changes systematically with fluence. The most interesting results of SHI irradiation are (i) the dielectric loss peak value (emax?) in all crystals is invariably less in comparison to the value in unirradiated crystals (ii) the minimum value of dielectric loss peak (emax?) occurs at different fluence in different crystals, and (iii) a second loss peak is observed below Tc in CTGS10 especially at higher fluence. It seems that irradiation creates/strengthens internal field in the crystals by orienting the domains through some mechanism that is not clear at present. The observed results could be explained if one presumes that irradiation annihilate the defects already present in the crystals by creating local charges and thermal gradient resulting into internal bias field. Ferroelectric hysteresis loops demonstrate the internal bias field developing in the SHI irradiated crystals. It is argued that SHI irradiation is a better alternate in comparison to cobalt doping in inhibiting dipolar switching in TGS crystal.

Bajpai, P. K.; Shah, Deepak; Kumar, Ravi

2012-01-01

228

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

229

FAST TRACK COMMUNICATION: Ferroelectricity in low-symmetry biaxial nematic liquid crystals  

NASA Astrophysics Data System (ADS)

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.

Osipov, Mikhail A.; Gorkunov, Maxim V.

2010-09-01

230

Crystallization and ferroelectric properties of lithium niobate powder obtained by the alkoxy method  

SciTech Connect

A detailed study is made of the formation of the ferroelectric properties of LiBbO/sub 3/ powders as the size of the crystallites and the perfection of their structure increase. The ferroelectric properties of finely dispersed powder was recorded by the method of generation of the second harmonic of laser radiation using a YAG:Nd laser with a wavelength of 1.06 ..mu..m. The ferroelectric properties of the LiNbO/sub 3/ powder form when the crystallites reach sizes of ca 0.01 ..mu..m during the process of heat treatment above 350 C. Short-time heat treatment of x-ray-amorphous KiNbO/sub 3/ powder at 700 C produces a monodispersed powder with crystallites 0.2-0.4 ..mu..m in size with completely formed structural and ferroelectric characteristics.

Leonov, A.P.; Kolganova, N.V.; Stefanovich, S.Y.; Turevskaya, E.P.; Turova, N.Y.; Yanovskaya, M.I.

1986-04-01

231

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

Microsoft Academic Search

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

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

2003-01-01

232

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

Microsoft Academic Search

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

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

2003-01-01

233

Optical Absorption of TNT Single Crystals.  

National Technical Information Service (NTIS)

A method for growing large area, thin, single crystal platelets of TNT is reported. The optical absorption properties of these crystals were studied, and dichroic behavior was observed. The absorption edge is approximately 3.1 eV and is tentatively assign...

A. C. Forsyth D. S. Downs

1973-01-01

234

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

2012-09-06

235

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

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

236

Single Crystal Diamond Nanomechanical Dome Resonator.  

National Technical Information Service (NTIS)

Superior mechanical and optical properties of single crystal (SC) diamond in combination with a chemically inert and bio-compatible surface enable the design and fabrication of novel nanoscale devices for sensing and signal processing applications. In thi...

B. B. Pate J. Yang J. E. Butler J. W. Baldwin M. K. Zalalutdinov

2008-01-01

237

Single Crystal NMR of High Temperature Superconductors  

Microsoft Academic Search

The author reports Cu NMR studies of the high temperature superconductor YBa_2Cu _3O_{7-delta } (T_{rm c} = 90K) using a 1 mg single crystal. Three types of measurements have been made for both the \\

Charles Holloway Pennington

1989-01-01

238

Computational Techniques in Single Crystal Mossbauer Spectroscopy.  

National Technical Information Service (NTIS)

The report summarizes some computational techniques which can be used to extract the effective field parameters from a given single crystal Mossbauer spectrum. The effective field parameters in this case are the effective electric field gradient and magne...

K. P. Singh G. R. Hoy

1969-01-01

239

Stability of tetragonal <0 0 1> oriented PZN-12PT single crystals  

NASA Astrophysics Data System (ADS)

The present paper reports on the synthesis and electromechanical characterization of tetragonal (1 - x)Pb(Zn1/3-Nb2/3)O3-xPbTiO3 (x = 12) single crystals as a function of various external disturbances. Tetragonal PZN-12PT single crystals were grown using the flux method. The set of piezoelectric coefficients in the lateral mode was measured. Samples with size of 10 × 2 × 1 mm3 were polled in the <0 0 1> and <1 1 0> crystallographic directions and were found to possess a high Curie temperature (>170 °C). Moreover, no ferroelectric-ferroelectric phase transition was observed for the positive temperatures, which expanded the usage range significantly. Tetragonal crystals were also found to have high coercive field, mechanical quality factors, and good optical properties, attracting much effort on the characterization of tetragonal PZN-12PT crystals. However, the most interesting properties in the lateral mode were obtained for <0 0 1>. Finally, the thermal stability and stress dependence were studied in order to determine the working conditions.

Touhtouh, S.; Hajjaji, A.; Boughaleb, Y.; Benkhouja, K.; Arbaoui, A.; Rguiti, M.; Guyomar, D.

2012-08-01

240

A variational model of ferroelectric rank-2 laminate domain structures  

Microsoft Academic Search

The equilibrium domain arrangements of ferroelectric single crystals are significantly affected by loads and boundary conditions. Domain structures evolve towards a minimum energy state. In this paper, a variational method, which minimizes a functional based on free energy and dissipation, is developed to model the evolution of several typical rank-2 laminate domain patterns in the tetragonal crystal system. Periodic laminates

N. T. Tsou; J. E. Huber

2010-01-01

241

Domains in Ferroelectric Nanostructures  

NASA Astrophysics Data System (ADS)

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

Gregg, Marty

2010-03-01

242

Fundamental Study on Ferroelectric Data Storage with the Density Above 1 Tbit\\/inch Using Congruent Lithium Tantalate  

Microsoft Academic Search

Ferroelectrics have created considerable interest as promising storage media. In this paper, an investigation for ultra high-density ferroelectric data storage based on scanning nonlinear dielectric microscopy (SNDM) was carried out. For the purpose of obtaining the fundamental knowledge of high-density ferroelectric data storage, several experiments of nano-domain formation in lithium tantalate (LiTaO3) single crystal were conducted. As a result, domain

YASUO CHO; YOSHIOMI HIRANAGA; KENJIRO FUJIMOTO; YASUO WAGATSUMA; ATSUSHI ONOE

2004-01-01

243

Cutting fluid study for single crystal silicon  

Microsoft Academic Search

An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions

Chargin

1998-01-01

244

Single crystal fibers for high power lasers  

NASA Astrophysics Data System (ADS)

In this paper, we present our recent results in developing cladded-single crystal fibers for high power single frequency fiber lasers significantly exceeding the capabilities of existing silica fiber based lasers. This fiber laser would not only exploit the advantages of crystals, namely their high temperature stability, high thermal conductivity, superior environmental ruggedness, high propensity for rare earth ion doping and low nonlinearity, but will also provide the benefits from an optical fiber geometry to enable better thermal management thereby enabling the potential for high laser power output in short lengths. Single crystal fiber cores with diameters as small as 35?m have been drawn using high purity rare earth doped ceramic or single crystal feed rods by Laser Heated Pedestal Growth (LHPG) process. The mechanical, optical and morphological properties of these fibers have been characterized. The fibers are very flexible and show good overall uniformity. We also measured the optical loss as well as the non-radiative loss of the doped crystal fibers and the results show that the fibers have excellent optical and morphological quality. The gain coefficient of the crystal fiber matches the low quantum defect laser model and it is a good indication of the high quality of the fibers.

Kim, W.; Florea, C.; Baker, C.; Gibson, D.; Shaw, L. B.; Bowman, S.; O'Connor, S.; Villalobos, G.; Bayya, S.; Aggarwal, I. D.; Sanghera, J. S.

2012-11-01

245

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

PubMed Central

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

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

2007-01-01

246

Crystal structure of ferroelectric Bi{sub 2}VO{sub 5.5}  

SciTech Connect

The structure of the {alpha}-phase of bismuth vanadate Bi{sub 2}VO{sub 5.5} has been determined using single crystal X-ray diffraction data in the space group Aba2. The refinement involves a well defined disorder at the vanadium site, which incorporates the features of the superlattice structure with vanadium tetrahedra and oxygen-deficient octahedra that is displaced about the twofold axis.

Sooryanarayana, K.; Guru Row, T.N.; Varma, K.B.R. [Indian Inst. of Science, Bangalore (India)

1997-12-01

247

Near-millimeter refractive indices, absorption coefficients, and electrooptic coefficients in ferroelectric and other crystals  

Microsoft Academic Search

We have used a Michelson interferometer operating in the power mode to measure the refractive indices and absorption coefficients over the near-millimeter-wave (NMMW) spectral region of single-crystal bismuth germanium oxide, bismuth silicon oxide, titanium dioxide, lithium niobate, lithium tantalate, and strontium titanate. The NMMW value of the electrooptic coefficient r33 for dc fields in lithium niobate was also measured.

P. S. Brody; J. P. Sattler; G. J. Simonis

1983-01-01

248

Investigations on electrocaloric properties of [111]-oriented 0.955PbZn1\\/3Nb2\\/3O3–0.045PbTiO3 single crystals  

Microsoft Academic Search

Under low electric fields, electrocaloric effects (ECEs) accompanied with the ferroelectric to paraelectric phase transition in ferroelectric [111]-oriented 0.955PbZn1\\/3Nb2\\/3O3–0.045PbTiO3 single crystals were simulated. The simulation predicted many interesting features of ECE, including the changes of entropy, heat capacity, and temperature due to different electric field shifts. A relative cooling and a refrigerant capacity due to applied electric field shift were

Mahmoud Aly Hamad

2012-01-01

249

Neutron detection with single crystal organic scintillators  

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

250

Neutron detection with single crystal organic scintillators  

SciTech Connect

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

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

2009-07-15

251

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

SciTech Connect

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

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

2009-07-06

252

Electroluminescence Studies in Pyrene Single Crystals  

Microsoft Academic Search

The observation of electroluminescence in pyrene single crystals is reported. Holes and electrons were introduced into the samples by contact injection using CuI and Na-Hg amalgam electrodes as hole and electron injectors, respectively. The radiation-recombination light intensity is found to be directly proportional to the current through the crystal. The yield for light emission is about 2 × 10 photons

J. Gonzalez Basurto; Z. Burshtein

1975-01-01

253

Single crystal NMR of high temperature superconductors  

Microsoft Academic Search

Cu NMR studies of the high temperature superconductor YBa2Cu3O(7-delta) (T sub c = 90 K) using a 1 mg single crystal is reported. Three types of measurements were made for both the plane and chain Cu crystallographic sites and with the static magnetic field placed successively along each of the three crystal axes a, b, and c: nuclear magnetic resonance

Charles Holloway Pennington

1989-01-01

254

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

255

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

Microsoft Academic Search

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

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

2002-01-01

256

The origin of ferroelectricity in magnetoelectric YMnO3.  

PubMed

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

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

2004-02-22

257

A Phenomenological Theory of Ferroelectric and Antiferroelectric Liquid Crystals Based on a Discrete Model  

Microsoft Academic Search

A discrete model of ferroelectric and antiferroelectric phases, which takes into account the molecular interactions up to the second-nearest neighbors, has been proposed. On the basis of the model the dispersion relation of normal modes and the temperature dependence of the helical pitch for four types of phase sequence are obtained. It is clarified that the experimentally observed phenomena such

Hongye Sun; Hiroshi Orihara; Yoshihiro Ishibashi

1993-01-01

258

Dilatometric Study on Monoclinic Crystals of Ferroelectric TGS Down to Cryogenic Temperature Region  

Microsoft Academic Search

We have further developed the clip-type strain gauge dilatometer in order to measure an angular deformation by applying the cosine theorem. In this research, not only a linear thermal expansion along three crystallographic axes but also a monoclinic angle ? of ferroelectric TGS in the monoclinic system were measured below 380 K down to the cryogenic temperature region. Each of

T. Yamaguchi; N. Nakatani; T. Kikuta; T. Kurihama; T. Mitsui; Y. Seimiya; S. Yoshizawa; F. Shimizu; M. Takashige

2006-01-01

259

Pulsed laser deposition (PLD) of ferroelectric thin films in conjunction with superconducting oxides  

Microsoft Academic Search

The possibility of combining ferroelectrics and superconductors has been of interest for use in memory storage devices. Additionally, superconductors offer crystal structures compatible to the epitaxial growth of the ferroelectric, Ba0.6Sr0.4TiO3 (BSTO), which is cubic at this stoichiometry. BSTO has a lattice constant of 3.94 Å as compared to the superconducting Pr2-x CexCuO4 tetragonal single crystal which also has a

S. Sengupta; L. C. Sengupta; W. Kosik

1994-01-01

260

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

NASA Astrophysics Data System (ADS)

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

Gregg, Marty

2006-03-01

261

Inkjet printing of single-crystal films.  

PubMed

The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. 'Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C(8)-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4?cm(2)?V(-1)?s(-1). This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications. PMID:21753752

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

2011-07-13

262

Growth and characterization of rare earths doped triglycine sulfate crystals  

Microsoft Academic Search

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

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

2006-01-01

263

Nano-turning of single crystal silicon  

Microsoft Academic Search

High-quality silicon surfaces have been obtained by single-point diamond turning. After the analysis of the turning mechanism, the relationship between the surface integrity and the turning parameters was studied in detail. Results from the mechanism were compared with turning tests on silicon using a commercially available single-crystal diamond tool with a rake angle of 0°. A novel technique was developed

F. Z Fang

1998-01-01

264

Three-dimensional single crystal silicon micromachining  

Microsoft Academic Search

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

Wolfgang Maximilian Josef Hofmann

1999-01-01

265

Anomalous domain inversion in LiNbO3 single crystals investigated by scanning probe microscopy  

NASA Astrophysics Data System (ADS)

Ferroelectric domains were written in lithium niobate (LiNbO3) single crystals by applying voltage pulses to the tip of a scanning force microscope. The generated domains are subsequently imaged by piezoresponse force microscopy. As it has been previously observed not only full domains but also doughnut-shaped ones arise from tip-based domain formation. In this contribution, we present our experiments which were carried out with 10-20 ?m thin LiNbO3 single crystals. We show that by choosing appropriate writing parameters, domains of predetermined shape (full or doughnut) can be reliably generated. In addition to the duration and the amplitude of the voltage pulse the moment of the retraction of the tip from the sample surface was found to be a crucial parameter for reproducible domain formation.

Lilienblum, M.; Soergel, E.

2011-09-01

266

Surface alignment of ferroelectric liquid crystals using polyimide, polyamide-imide and polyamide layers and their effect on pre-tilt angle  

Microsoft Academic Search

Fluoro and non-fluoro polymer alignment layers of high and low pre-tilt angle were developed for ferroelectric liquid crystal display devices to exploit the effect of rubbed polyimide, polyamide-imide and polyamide alignment layers on pre-tilt angle and other electro-optical properties. Fluorine containing polyimide and polyamide alignment control layers displayed high pre-tilt angle (< 10°) and good alignment of liquid crystal molecules

Y. S. Negi; Y. Suzuki; T. Hagiwara; I. Kawamura; N. Yamamoto; K. Mori; Y. Yamada; M. Kakimoto; Y. Imai

1993-01-01

267

Single Crystal Diffraction by Synchrotron Radiation.  

National Technical Information Service (NTIS)

The tunability and access to short wavelengths in combination with high intensity and the low divergence of the x-ray radiation produced by synchrotron storage rings opens up new and challenging fields for single crystal diffraction. These areas include m...

A. Kvick

1988-01-01

268

Development of single crystal filaments. Final report  

Microsoft Academic Search

The program just completed addresses a route to a more efficient longer-lasting electric light bulb filament. All current filaments for light bulbs are metallic in nature. They are subject to embrittlement with age (large grain growth) and relatively high vapor pressures which limits their operating temperature. There is evidence which suggests advantages to using high temperature refractory single crystal fibers

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

1995-01-01

269

Single crystal tungsten kinetic energy penetrators  

SciTech Connect

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

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

1992-05-01

270

Single crystal tungsten kinetic energy penetrators  

SciTech Connect

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

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

1992-05-01

271

Influence of crystallization on the spectral features of nano-sized ferroelectric barium strontium titanate (Ba0.7Sr0.3Tio3) thin films  

NASA Astrophysics Data System (ADS)

Ferroelectric barium strontium titanate (Ba0.7Sr0.3TiO3)(BST) thin films have been prepared from barium 2-ethylhexanoate [Ba[CH3(CH2)3CH(C2H5)CO2]2], strontium 2-ethylhexanoate [Sr[CH3(CH2)3CH(C2H5)CO2]2] and titanium(IV) isopropoxide [TiOCH(CH3)2]4 precursors using a modified sol gel technique. The precursor except [TiOCH(CH3)2]4 were synthesized in the laboratory. Transparent and crack-free films were fabricated on pre-cleaned quartz substrates by spin coating. The structural and optical properties of films annealed at different temperatures have been investigated. The as-fired films were found to be amorphous that crystallized to the tetragonal phase after annealing at 550 °C for 1 h in air. The lattice constants “a” and “c” were found to be 3.974 A and 3.990 A, respectively. The grain sizes of the films annealed at 450, 500 and 550 °C were found to be 30.8, 36.0 and 39.8 nm respectively. The amorphous film showed very high transparency (˜95%), which decreases slightly after crystallization (˜90%). The band gap and refractive index of the amorphous and crystalline films were estimated. The optical dispersion data are also analyzed in the light of the single oscillator model and are discussed.

Bobby Singh, S.; Sharma, H. B.; Sarma, H. N. K.; Phanjoubam, Sumitra

2008-08-01

272

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

2008-08-28

273

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

2010-05-28

274

Single-crystal disk drive miniactuators  

NASA Astrophysics Data System (ADS)

As hard disk drive areal densities increase at a compound annual growth rate (CAGR) of 60%, disk drives must position the head over increasingly small areas while moving more rapidly to reach the desired position. This results in an increase in vibration disturbance. To meet this demand, many hard disk drive manufactures have created prototype dual-stage actuators employing piezoelectric ceramics for the second stage. These are an attractive means of obtaining higher-bandwidth control due to the low inertia and size of the actuator element. As the technology improves, the next limiting factor will be the amount of displacement obtainable with traditional piezoceramic elements. Under the AXIS (Advanced Crystal Integrated System) Consortium program funded by DARPA, the application of PZN-PT single crystal piezoceramic as a second stage disk drive actuator was studied, based on the fact that the single crystal material provides larger stroke than its traditional PZT counterparts. The transverse (d31) strain of PZN-PT single crystal was measured to be about two times larger than that of PZT-5H ceramic. Both materials were integrated into a disk drive system and compared as second stage actuators. The methodologies used and the servo control techniques applied are also discussed in the paper.

Giovanardi, Marco; McKenney, Kevin; Rule, John A.; Yoshikawa, Shoko

2001-08-01

275

Ferroelectric Ultra High-Density Data Storage Based on Scanning Nonlinear Dielectric Microscopy  

Microsoft Academic Search

Nano-sized inverted domain dots in ferroelectric materials have potential application in ultrahigh-density rewritable data storage systems. Herein, a data storage system is presented based on scanning non-linear dielectric microscopy and a thin film of ferroelectric single-crystal lithium tantalite. Through domain engineering, we succeeded to form an smallest artificial nano-domain single dot of 5.1 nm in diameter and artificial nano-domain dot-array

Yasuo Cho; S. Hashimoto; N. Odagawa; K. Tanaka; Y. Hiranaga

2006-01-01

276

Phase-modulating bistable optically addressed spatial light modulators using wide-switching-angle ferroelectric liquid crystal layer  

NASA Astrophysics Data System (ADS)

We report the use of an experimental ferroelectric liquid crystal material called CDRR8 in bistable optically addressed spatial light modulators for both amplitude- and phase-modulating devices. First, the methods used to improve the alignment and obtain truly bistable switching with CDRR8 are described. The diffraction efficiency and switching characteristics of a bistable CDRR8 optically addressed spatial light modulator used as an amplitude-modulating device and then as a phase-modulating device for encoding high-resolution patterns are compared. The CDRR8 devices exhibit bistability when driven by alternating monopolar pulses. The results show that the use of a device as a phase-modulating rather than an amplitude-modulating device, increases the diffraction efficiency by 10 times. Resolution is better than 100 lp/mm, as measured by the fall in diffraction efficiency by 50% compared with the diffraction efficiency at low spatial frequencies.

Mias, Solon; Manolis, Ilias; Collings, Neil; Wilkinson, Timothy D.; Crossland, William A.

2005-01-01

277

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

2013-05-16

278

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

PubMed

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

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

2013-05-30

279

Growth of lead magnesium niobate-lead titanate single crystals by seeded polycrystal conversion  

NASA Astrophysics Data System (ADS)

Relaxor-based ferroelectric single crystals of Pb(Mg1/3Nb 2/3)O3-PbTiO3 [PMN-PT] have been produced via the Seeded Polycrystal Conversion [SPC] technique. Polycrystalline precursors of PMN-PT are converted to single crystals by inducing the boundary of a seed crystal to migrate through a polycrystalline matrix. The quality of PMN-PT single crystals grown by SPC is directly influenced by the microstructure of the polycrystalline precursor. The goal of this work was to examine the factors that controlled the final microstructure of the matrix and grown single crystals and to characterize their effects on properties. Sintering in oxygen was necessary to obtain fully dense matrix microstructures, which, in turn, produced pore-free single crystals. The primary role of oxygen was to remove insoluble gases before densification began, then to reduce the internal pressure by diffusing out and allowing the pores to close from pressures derived from their own curvatures. The presence of a PbO liquid phase assisted this process by enhancing the densification rate in the early stages of sintering. In contrast, fully-dense, hot-pressed samples of PMN-35PT with excess PbO underwent a de-densification process during the annealing treatments which was attributed to pore formation from internally evolved gases. Transparent single crystals with maximum strain values of 0.72% at 46 kV/cm, d33 ˜2180 pC/N, and a room temperature dielectric constant of ˜5300 were obtained for poled <001> oriented crystals of PMN-30mol.%PT. The dielectric behavior of {001} oriented single crystals was found to be highly dependent on the initial orientation of the seed crystal. For example, {111} seeded crystals grown in oxygen yielded Kmax values of ˜33000, while {001} seeded crystals grown in oxygen had Kmax values of ˜25000. In addition, the Tmax values were 3 to 5°C higher for crystals grown from {001} seeds, compared to {111} seeds.

Scotch, Adam Matthew

280

Study of defects in pentacene single crystals  

NASA Astrophysics Data System (ADS)

Our research focuses on the growth of the pentacene single crystals with a high degree of purity, and the investigation of their morphology and physical properties. We are able to reduce the number of traps by two orders of magnitude compared with conventional methods. This is reflected in the value of hole mobility of 35 cm2/Vs at room temperature increasing to 58 cm2/Vs at 225 K. These high mobilities result from a purification of the material, that consists of removal of 6,13-pentacenequinone, as the major impurity, using vacuum sublimation under a temperature gradient. We further study the influence of air exposure on the electronic properties of pentacene single crystals. Our observations show that gases can diffuse reversibly in/out the crystals, and influence the electronic properties. We discern two competing mechanisms that modulate the electronic transport. On the one hand stands the presence of water from ambient air that intercalates into the crystal lattice and forms trapping sites for injected charges. On the other hand, the presence of oxygen increases the hole conduction. The latter effect is enhanced by the presence of visible light.

Jurchescu, Oana D.

2005-03-01

281

Porosity evolution in a creeping single crystal  

NASA Astrophysics Data System (ADS)

Experimental observations on tensile specimens in Srivastava et al (2012 in preparation) indicated that the growth of initially present processing induced voids in a nickel-based single crystal superalloy played a significant role in limiting creep life. Also, creep tests on single crystal superalloy specimens typically show greater creep strain rates and/or reduced creep life for thinner specimens than predicted by current theories. In order to quantify the role of void growth in single crystals in creep loading, we have carried out three-dimensional finite deformation finite element analyses of unit cells containing a single initially spherical void. The materials are characterized by a rate-dependent crystal plasticity constitutive relation accounting for primary and secondary creep. Two types of imposed loading are considered: an applied true stress (force/unit current area) that is time independent; and an applied nominal stress (force/unit initial area) that is time independent. Isothermal conditions are assumed. The evolution of porosity is calculated for various values of stress triaxiality and of the Lode parameter. The evolution of porosity with time is sensitive to whether constant true stress or constant nominal stress loading is applied. However, the evolution of porosity with the overall unit cell strain is insensitive to the mode of loading. At high values of stress triaxiality, the response is essentially independent of the value of the Lode parameter. At sufficiently low values of the stress triaxiality, the porosity evolution depends on the value of the Lode parameter and void collapse can occur. Also, rather large stress concentrations can develop which could play a role in the observed thickness dependence.

Srivastava, A.; Needleman, A.

2012-04-01

282

Single Crystal Metals Encapsulated in Carbon Nanoparticles  

Microsoft Academic Search

Single-domain microcrystals of LaC_2 encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observed by high-resolution transmission electron microscopy and energy dispersive spectroscopy (EDS). EDS spectra show that La

Rodney S. Ruoff; Donald C. Lorents; Bryan Chan; Ripudaman Malhotra; Shekhar Subramoney

1993-01-01

283

The single crystal elastic moduli of neighborite  

Microsoft Academic Search

The adiabatic elastic moduli of a single crystal of Neighborite (NaMgF3perovskite) have been measured at ambient conditions using Brillouin spectroscopy. The adiabatic aggregate (Voight-Reuss-Hill) bulk modulus is K = 75.6 GPa, and shear modulus is µ = 46.7 GPa. The experimental results show the ratio of linear compressibilities ßb\\/ßa = 0.80 for neighborite. These ratios reflect the different amounts of

Yusheng Zhao; Donald J. Weidner

1993-01-01

284

Thermal properties of UO2 single crystal  

NASA Astrophysics Data System (ADS)

For decades UO2 has been the most widely studied actinide oxide because of its technological importance as fuel material for nuclear reactors. Therefore there is a large interest in understanding its thermal, transport and thermodynamic properties. We present recent experimental results for the thermal conductivity and thermal expansion of high quality UO2 single crystal, obtained for different crystallographic directions, and compare with results of molecular dynamics simulations. We will discuss the implications of this study.

Gofryk, K.; Du, S.; Andersson, A. D.; Stanek, C. R.; Schulze, R.; Safarik, D.; Mihaila, B.; Lashley, J. C.; Smith, J. L.

2013-03-01

285

Bridgman growth of paratellurite single crystals  

Microsoft Academic Search

The growth of paratellurite single crystals by the vertical-gradient freezing technique is reported for the first time. Boules of 120mm long and 25mm in diameter were obtained under a temperature gradient of 10°Ccm?1 and translation rates lower than 0.6mmh?1. The spatial distribution of defects along the growth axis reveals a continuous evolution of the free convective fluid-flow regime as growth

P. Veber; J. Mangin; P. Strimer; P. Delarue; C. Josse; L. Saviot

2004-01-01

286

Single crystal diffraction by synchrotron radiation  

SciTech Connect

The tunability and access to short wavelengths in combination with high intensity and the low divergence of the x-ray radiation produced by synchrotron storage rings opens up new and challenging fields for single crystal diffraction. These areas include microcrystal diffraction, studies of time-dependent phenomena, element selective diffraction, studies of materials under extreme conditions, solution of the crystallographic phase problem either by the use of the wavelength dependency of the anomalous scattering or by direct experimental determination of the phases. Single crystal diffraction from proteins and macromolecules using photographic film as a detection medium has already reached considerable maturity, but high-precision data collections using diffractometers at storage rings are still not routine because of the severe requirements for beam stability over extended periods of time. Development work at institutions such as the National Synchrotron Light Source, The Photon Factory, SSRL, CHESS, Hasylab and Daresbury, however, suggest that synchrotron single-crystal diffraction will become an essential part of the research at the synchrotron storage rings in the near future. 9 refs., 2 figs.

Kvick, A.

1988-01-01

287

Fatigue In Single Crystal Nickel Superalloys Technical Progress Report.  

National Technical Information Service (NTIS)

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

C. Annis

1992-01-01

288

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

NASA Astrophysics Data System (ADS)

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

Choudhury, Rajul Ranjan; Chitra, R.

2009-08-01

289

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

PubMed Central

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

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

2013-01-01

290

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

291

Single crystal x-ray diffraction: optical and micro hardness studies on chalcone derivative single crystal  

NASA Astrophysics Data System (ADS)

1-(4-methylphenyl)-3-(4- N, N dimethyl amino phenyl)-2-propen-1-one, a chalcone derivative nonlinear optical material has been synthesized by standard method. FT-IR and NMR spectral studies have been performed to confirm the molecular structure of the synthesized compound. The single crystals up to a dimension of 13 x 9 x 3 mm3 were grown by slow evaporation method. The grown crystals were transparent in the entire visible region and absorbs in the UV-region. The refractive index has been measured using a He-Ne laser. The grown crystals have been subjected to single crystal X-ray diffraction studies to determine the crystal structure and hence the cell parameters of the crystal. From this study it is found that this compound crystallizes in orthorhombic system with a space group P212121 and corresponding lattice parameters are, a = 7.3610(13) Å, b = 11.651(2) Å, c = 17.6490(17) Å. The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for Photonic application. The micro hardness test on these crystals were carried out and the load dependence hardness was observed

Crasta, Vincent; Ravindrachary, V.; Bhajantri, R. F.; Naveen, S.; Shridar, M. A.; Shashidhara Prasad, J.

2005-08-01

292

Fatigue behavior of a single crystal nickel-base superalloy  

Microsoft Academic Search

While the creep properties of single crystal nickel base superalloys are known to be superior to that of polycrystalline superalloys, the behavior of single crystals in low cycle fatigue (LCF) is less well understood. In this study the low cycle fatigue properties of an experimental single crystal nickel-based superalloy, Rene N4, were examined at 1400 F and 1800 F in

T. P. Gabb; J. Gayda; R. V. Miner

2008-01-01

293

Nature of Ferroelectricity in KNO3  

Microsoft Academic Search

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

Arthur Chen; Fred Chernow

1967-01-01

294

Improper ferroelectricity in perovskite oxide artificial superlattices  

Microsoft Academic Search

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

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

2008-01-01

295

Binary phase-only 1/f joint transform correlator using a ferroelectric liquid crystal spatial light modulator  

NASA Astrophysics Data System (ADS)

We present a new approach to implementing the joint transform correlator based on a single ferroelectric spatial light modulator used as a binary phase-only device. The correlator is a 1/f joint transform correlator that uses two passes through the optical system to generate the correlation peaks. The input scene and reference image are encoded with a checkerboard pattern to produce a spectrum with no zero order. The spectrum is then convolutionally binarized and replayed on the same spatial light modulator. Experimental results demonstrate strong correlation peaks, with the zero order in the correlation plane reduced to 6 dB below the correlation peaks. The correlator also demonstrates enhanced differentiation between closely correlated images.

Wilkinson, Timothy D.; Crossland, William A.; Kapsalis, V.

1999-02-01

296

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

297

Fast and accurate shape measurement system utilizing the fringe projection method with a ferroelectric liquid-crystal-on-silicon microdisplay  

NASA Astrophysics Data System (ADS)

Fringe projection methods using the phase-shifting technique have the advantages of fast 3-D shape measurement and high accuracy. The performance of the fringe projection system, including image quality, nonlinearity of the projected intensity, stability, and switching time for multiple phase-shifted patterns, is essential for fast and accurate shape measurement. A fast and accurate measurement system using a ferroelectric liquid-crystal-on-silicon microdisplay and a high-powered light emitting diode light source is developed. Our results indicate that the nonlinearity of the projected intensity and the stability of the fringe projection were dramatically improved compared with an ordinary commercial liquid crystal display projector. The rapid measurement of the warpage distribution of a flip chip ball grid array electronic package was performed by using the developed system. Nine phase-shifted fringe images with a resolution of 1280×960 pixels were recorded in 1.6 s. In addition, the measurement results obtained by our system agreed well with the results obtained from a micrometer and laser focus sensor. The average error was 2.6 ?m, and the standard deviation was less than 10 ?m with a 6-mm measurement range.

Ri, Shien; Muramatsu, Takashi; Saka, Masumi; Tanaka, Hiroyuki

2012-08-01

298

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

299

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

300

Optical characterization of organic semiconducting single crystals  

NASA Astrophysics Data System (ADS)

Over the last decade interest in the possibility of "plastic electronics," semi-conducting organic materials that hold the potential for display devices with improved characteristics, has increased. To date, the majority of research has focused on material development and device design. However, if scientists are able to understand the connection between the structural and electronic properties of molecules, they can tailor new compounds with desired physical characteristics. Optical characterization is the first step to understanding the structural properties of materials. This work focuses on characterizing single crystals of two specific molecules: alpha-hexathiophene and 5,6,11,12-tetraphenyl tetracene (rubrene). While there is plenty of information currently available in the literature about alpha-hexathiophene, the resonant Raman experiments I describe in Chapter 3 have uncovered the lowest experimentally-recorded excited electronic levels. I have tentatively identified these states as either a triplet Frenkel exciton or a bound singlet Frenkel exciton. Chapter 4 details how I used Raman, infrared and photoluminescence spectroscopy, as well as computer simulations, to characterize rubrene. Studies of tetracene single crystals helped guide the understanding of the structural and electronic properties of rubrene. Although all molecular crystals have low intermolecular coupling, my analysis showed that rubrene has particularly low coupling, even for a molecular crystal. This result goes against commonly held belief that the best molecules for "plastic electronic" devices should have strong pi-electron overlap. The temperature dependent photoluminescence spectrum clearly reveals emission from free carriers as well as free charge transfer excitons, free Frenkel excitons and deep impurity and defect levels.

Weinberg-Wolf, Jennifer

301

Robust ferroelectric state in multiferroic Mn1-xZnxWO4  

NASA Astrophysics Data System (ADS)

We report on the remarkably robust ferroelectric state in the multiferroic compound Mn1-xZnxWO4. Substitution of the magnetic Mn2+ with nonmagnetic Zn2+ reduces the magnetic exchange and provides control of the various magnetic and multiferroic states of MnWO4. Only 5% of Zn substitution results in complete suppression of the frustrated collinear (paraelectric) low-temperature phase. The helical magnetic and ferroelectric phase develops as the ground state. The multiferroic state is stable up to a high level of substitution of more than 50%. The magnetic, thermodynamic, and dielectric properties, as well as the ferroelectric polarization of single crystals of Mn1-xZnxWO4, are studied for different substitutions up to x=0.5. The magnetic phases have been identified in single-crystal neutron-scattering experiments. The ferroelectric polarization scales with the neutron intensity of the incommensurate peak of the helical phase.

Chaudhury, R. P.; Ye, F.; Fernandez-Baca, J. A.; Lorenz, B.; Wang, Y. Q.; Sun, Y. Y.; Mook, H. A.; Chu, C. W.

2011-01-01

302

Advanced piezoelectric single crystal based actuators  

Microsoft Academic Search

TRS is developing new actuators based on single crystal piezoelectric materials such as Pb(Zn1\\/3Nb2\\/3)1-xTixO3 (PZN-PT) and Pb(Mg1\\/3Nb2\\/3)x-1TixO3 (PMN-PT) which exhibit very high piezoelectric coefficients (d33 = 1800-2200 pC\\/N) and electromechanical coupling factors (k33 > 0.9), respectively, for a variety of applications, including active vibration damping, active flow control, high precision positioning, ultrasonic motors, deformable mirrors, and adaptive optics. The d32

Xiaoning Jiang; Paul W. Rehrig; Wesley S. Hackenberger; Edward Smith; Shuxiang Dong; Dwight Viehland; Jim Moore Jr.; Brian Patrick

2005-01-01

303

Fabrication of single-crystal diamond microcomponents  

SciTech Connect

We have combined a technique for the lift-off of thin diamond films from a bulk diamond with a technique for engraving diamond with a focused excimer laser to produce free-standing single-crystal diamond microstructures. One microcomponent that has been produced is a 12 tooth gear [similar to]400 [mu]m in diameter and [similar to]13 [mu]m thick. Other microstructures have also been demonstrated, showing the versatility of this method. This process should be applicable to producing diamond microcomponents down to spatial dimensions (width and thickness) of a few micrometers.

Hunn, J.D.; Withrow, S.P.; White, C.W.; Clausing, R.E.; Heatherly, L. (Oak Ridge National Laboratory, Bldg 5500 MS-6376, Oak Ridge, Tennessee 37831-6376 (United States)); Christensen, C.P. (Potomac Photonics, Lanham, Maryland 20705 (United States))

1994-12-12

304

Metallisation of single crystal diamond radiation detectors  

NASA Astrophysics Data System (ADS)

Properties such as a large band gap, high thermal conductivity and resistance to radiation damage make diamond an extremely attractive candidate for detectors in next generation particle physics experiments. This paper presents our technique for metallisation of a single crystal diamond grown by chemical vapour deposition (CVD) for use as a radiation detector, suitable for operation in places such as the Large Hadron Collider. The front and back side of the diamond are metalised with aluminium and gold on top of titanium respectively, after which the diamond is mounted and read out via a charge sensitive preamplifier. The device is found to collect charge at an efficiency of 97%.

Ong, Lucas; Ganesan, Kumaravelu; Alves, Andrew; Barberio, Elisabetta

2012-10-01

305

Characterisation of single-crystal mercuric iodide  

NASA Astrophysics Data System (ADS)

The mobility-lifetime product of electrons and holes in single-crystal mercuric iodide for detector applications was measured to be 4×10-5 and 3×10-5 cm2/V respectively. The charge carriers were optically induced by a near band gap excitation using a GaP (560nm) light emitting diode. Optical Deep Level Transient Spectrometry measurements of trapping states showed three dominant energy levels at 0.26, 0.8 and 1.4eV. There is little correlation between trapping levels reported in the literature.

Alexiev, D.; Dytlewski, N.; Reinhard, M. I.; Mo, L.

2004-01-01

306

Pressure-Induced Ferroelectricity in (NH4)3H(SO4)2  

Microsoft Academic Search

Dielectric properties of single crystals of (NH4)3H(SO4)2 were measured at various hydrostatic pressures up to about 8 kbar below room temperature. The broad peak of dielectric constant along the c*-direction which appears around -2.5°C at 1 atm becomes more and more prominent as pressure increases, and then a ferroelectric phase (Phase VI) develops above 4.9 kbar. Another ferroelectric phase (Phase

Kazuo Gesi

1976-01-01

307

Coupled Microstrip Line Ferroelectric Phase Shifter for Ka-Band Phased Array Antenna  

Microsoft Academic Search

This work presents the design, fabrication and microwave performance of coupled microstrip line phase shifter (CMPS) based on (Ba,Sr)TiO3 (BST) thin films for Ka-band phased array antenna. Ferroelectric BST thin films were deposited on MgO single crystal substrates by pulsed laser deposition. Because this CMPS design can bear the high dielectric constant of ferroelectric thin films at Ka-band, it has

HAN-CHEOL RYU; SEUNG EON MOON; SU-JAE LEE; MIN-HWAN KWAK; YOUNG-TAE KIM; KWANG-YONG KANG

2004-01-01

308

Ultrahigh-quality silicon carbide single crystals  

NASA Astrophysics Data System (ADS)

Silicon carbide (SiC) has a range of useful physical, mechanical and electronic properties that make it a promising material for next-generation electronic devices. Careful consideration of the thermal conditions in which SiC {0001} is grown has resulted in improvements in crystal diameter and quality: the quantity of macroscopic defects such as hollow core dislocations (micropipes), inclusions, small-angle boundaries and long-range lattice warp has been reduced. But some macroscopic defects (about 1-10cm-2) and a large density of elementary dislocations (~ 104cm-2), such as edge, basal plane and screw dislocations, remain within the crystal, and have so far prevented the realization of high-efficiency, reliable electronic devices in SiC (refs 12-16). Here we report a method, inspired by the dislocation structure of SiC grown perpendicular to the c-axis (a-face growth), to reduce the number of dislocations in SiC single crystals by two to three orders of magnitude, rendering them virtually dislocation-free. These substrates will promote the development of high-power SiC devices and reduce energy losses of the resulting electrical systems.

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

2004-08-01

309

Cutting fluid study for single crystal silicon  

SciTech Connect

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

Chargin, D.

1998-05-05

310

Single crystal NMR of high temperature superconductors  

SciTech Connect

Cu NMR studies of the high temperature superconductor YBa2Cu3O(7-delta) (T sub c = 90 K) using a 1 mg single crystal is reported. Three types of measurements were made for both the plane and chain Cu crystallographic sites and with the static magnetic field placed successively along each of the three crystal axes a, b, and c: nuclear magnetic resonance (NMR) lineshapes, spin-lattice relaxation, and transverse relaxation. From these measurements four NMR tensors are deduced: the magnetic shift tensor, the electric field gradient tensor, the spin-lattice relaxation rate tensor, and the transverse relaxation rate tensor. As a preliminary matter, the symmetries of the magnetic shift and electric field gradient tensors were used to assign the two families of NMR lines to their respective crystallographic sites. From an analysis of the electric field gradient tensors it is shown that both the plane and chain Cu have valences Cu(2+), giving a single hold in the Cu atomic d-shell. The spin-lattice relaxation rate and magnetic shift of the plane and chain Cu were analyzed; included were both analyses in which only normal state data were considered, and in which superconducting state measurements of magnetic shifts were considered as well. These analyses show that the plane Cu atom behaves very nearly as a local moment. The chain Cu is probably also in the local moment limit; however, its NMR properties are largely determined by its interaction with oxygen holes in the chain.

Pennington, C.H.

1989-01-01

311

Synthesis, properties, and structure of potassium titanyl phosphate single crystals doped with hafnium  

SciTech Connect

Single crystals of potassium titanyl phosphate doped with hafnium are grown by spontaneous flux crystallization. Their physical properties are studied, and the structure of three KTi{sub 1-x}Hf{sub x}OPO{sub 4} crystals (x = 0.01, 0.03, and 0.12) is determined. In the crystals studied, hafnium mostly occupies the second titanium position. The doping of KTP crystals with hafnium results in an elongation of K-O bonds in the potassium polyhedra and, as a consequence, in a considerable (by approximately 180 deg. C) decrease in the temperature of ferroelectric phase transition. The magnitude of anomalous permittivity substantially decreases. The electrical conduction in the specimens studied decreases by approximately half an order of magnitude in the low-temperature region but remains almost unchanged in the high-temperature region. Even at minor concentrations, the presence of a hafnium additive in the specimens considerably (by 35%) enhances the intensity of the second harmonic generation of laser radiation.

Orlova, E. I.; Kharitonova, E. P. [Moscow State University, Faculty of Physics (Russian Federation); Novikova, N. E., E-mail: natnov@ns.crys.ras.ru; Verin, I. A.; Alekseeva, O. A.; Sorokina, N. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Voronkova, V. I. [Moscow State University, Faculty of Physics (Russian Federation)

2010-05-15

312

Terahertz response of ferroelectric nanofibers.  

PubMed

Far-infrared optical and dielectric properties of ferroelectric SrTiO3 and BaTiO3 nanofibers, prepared by hydrothermal syntheses, were studied using terahertz time-domain spectroscopy. The power absorption, refractive index, and complex dielectric function were characterized in the frequency range from 0.2 to 1.0 THz. The measured results are well reproduced by theoretical fittings based on the dielectric models and the effective medium model. The study reveals that the low-frequency dielectric properties of the ferroelectric SrTiO3 nanofibers are associated with the lowest transverse optical (TO) soft mode TO1 at 2.70 THz (90.0 cm(-1)), and that of the ferroelectric BaTiO3 nanofibers are related to the lowest pair of transverse optical (TO) and longitudinal optical (LO) modes near 5.35 THz, which are both consistent with their bulk single-crystal and thin-film counterparts. PMID:22413261

Tian, Zhen; Xin, Kun; Wang, Mingwei; Han, Jiaguang; Wang, Haizhen; Tian, Z Ryan; Zhang, Weili

2011-11-01

313

Fredericksz Transition Threshold in Nematic Liquid Crystals Filled with Ferroelectric NanoParticles  

Microsoft Academic Search

A key liquid crystalline property for electro-optic applications is the Fredericksz threshold electric field. There has been recent experimental interest in liquid crystal-based colloidal suspensions in which the colloidal nanoparticles both possess a permanent electric polarization and provide strong director anchoring on the particle surface. Such suspensions are sometimes known as Filled Liquid Crystals. Our calculations suggest, in qualitative agreement

V. Yu. Reshetnyak; S. M. Shelestiuk; T. J. Sluckin

2006-01-01

314

Fast Visible-Near Infrared Filter Based on Ferroelectric Liquid Crystals  

Microsoft Academic Search

A conventional liquid crystal device consisting of two crossed polarizers and a liquid crystal cell displays a transmission in function of wavelength with different minima and maxima. By putting a number of these devices in series, with each step a different retardation (typically in each stage, the retardation doubles) a Lyot-Öhman filter can be fabricated (1-4). Such a multistage filter

D. P. Medialdea; J. Beeckman; T. Hui; R. Zmijan; K. Neyts

315

Preparation of ferrite single crystals by new floating zone technique  

Microsoft Academic Search

Single crystals of Ni ferrites and Ni-Zn ferrites having good uniformity were prepared by a new floating zone technique. In the preparation of the Ni-ferrite single crystal the initial molten zone was made from the material having a composition different from that of seed crystal. This made the composition of precipitate from molten zone the same as that of the

T. Akashi; K. Matumi; T. Okada; T. Mizutani

1969-01-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

317

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

318

Electric Conductivity of Ferroelectric Pb5Ge3O11  

Microsoft Academic Search

Electric conductivity of ferroelectric Pb5Ge3O11 single crystal was measured near the Curie point, thetaf{=}177°C. An a.c. method was adopted at very low frequency range of several Hz. At the low frequency limit the conductivity represents approximately the bulk d.c. conductivity. Near and above the Curie point, the crystal is semiconductive, sigma˜10-6 Omega-1m-1. Activation energies estimated from the conductivity data taken

Yoshihiro Goto; Etsuro Sawaguchi

1979-01-01

319

Implementation of colorless shutter-based free-space optical interconnections using ferroelectric liquid crystal spatial light modulators  

NASA Astrophysics Data System (ADS)

A shutter-based free-space optical switching core has been proposed as a promising technology for constructing Storage Area Networks (SANs) over an optical network. A vital component of this switch architecture is the use of a spatial light modulator (SLM) which can enhance the SANs performance. New optical materials are utilized to raise the switching speed and ferroelectric liquid crystals (FLCs) or transparent lanthanum-modified lead zirconate titanate (PLZT) used as an SLM have been compared. Both are capable of reaching the 3 usec target, by either raising the temperature or switching voltage, which is acceptable for SANs since the performance is dominated, not so much by switching speed, but more by reliable robust switching throughput. A six-by-six free-space 12-channel multi-mode fiber ribbon switch system using one fixed wavelength has been implemented. The objective of this paper is to demonstrate that multiwavelength operation based on the CWDM band in each fiber can be implemented on the same shutter-based free-space optical switching architecture using a FLC SLM.

Chou, H.-H.; Collings, N.; Wilkinson, T. D.; Zhang, F.; Crossland, W. A.

2007-10-01

320

Mode Gruneisen Parameters for Single Crystal Al2O3.  

National Technical Information Service (NTIS)

Single crystal Al2O3 (sapphire or corundum), crystallizes in the trigonal lattice, point group 3m. Its thermodynamic properties have been extensively investigated over the last years. As the pressure derivatives of its elastic moduli have recently become ...

D. Gerlich

1969-01-01

321

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

322

Mechanical properties of single crystal YAg  

SciTech Connect

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

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

2004-08-02

323

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

324

Stacking faults in fatigued titanium single crystals  

SciTech Connect

It is generally accepted that the mechanical behavior and interior dislocation substructure of metals and alloys are functions of the stacking fault energies (SFEs). The higher the SFE, the more difficult it is to split a dislocation into two partial dislocations separated by a stacking fault. Whereas materials with high SFE allow easy cross-slip of screw dislocations. Titanium is known to have a high SFE. Even though stacking faults in titanium have been observed experimentally, there is still doubt on them due to the high values of SFE. The purpose of the present study is to obtain further information on stacking faults in fatigued titanium single crystals and to discuss the relation between stacking fault and twinning.

Tan Xiaoli; Gu Haicheng [Xi`an Jiaotong Univ. (China). Research Inst. for Strength of Metals

1995-12-15

325

Magnetoplasticity and diffusion in silicon single crystals  

SciTech Connect

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

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

2012-01-15

326

2D Ligand ENDOR and TRIPLE resonance studies of Cu(II)-doped DTGS single crystals  

NASA Astrophysics Data System (ADS)

The deuteron hyperfine and quadrupole coupling tensors in the bis(glycinato)-Cu(II) ((ND2CH2COO)2Cu) complex in ferroelectric triglycine sulfate (DTGS) single crystals were measured by ENDOR spectroscopy. These data indicate that the molecular symmetry of the Cu complex is C1. From TRIPLE resonance experiments the signs of the isotropic coupling constants were determined. Structural information was obtained from the principal values of the quadrupole coupling tensors of the deuterium atoms and their direction cosines. Using the relationship between the deuterium quadrupole constant and ND bond lengths, the positions of the deuterons in bis(glycinato)-Cu(II) were estimated. The negative signs of the isotropic hyperfine coupling constants were explained by spin polarization of the deuteron 1s orbitals. The values of the anisotropic hyperfine coupling constants are discussed in the framework of conventional molecular-orbital theory and can be understood quite satisfactorily.

Bo¨Ttcher, R.; Heinhold, D.; Windsch, W.

1985-02-01

327

Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

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

Cross, L. E.

328

Study of monoclinic-tetragonal-cubic phase transition in Pb(Zn1/3Nb2/3)O3-0.08PbTiO3 single crystals by micro-Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-0.08PbTiO3 (PZN-0.08PT) single crystal has been investigated using polarized micro-Raman scattering technique in a wide temperature range from -150 to 350 °C. Raman spectra of the crystal at temperatures lower than 90 °C show 11 modes over a frequency range of 100-1000 cm-1. There are 12 Raman active vibration modes in the monoclinic structure of relaxor ferroelectrics according to the group theory analysis. Thus the structure of PZN-0.08PT single crystal at low temperatures is confirmed as monoclinic. Two structural phase transitions in the crystal were observed when the temperature was increasing. First, the monoclinic-tetragonal (M-T) phase transition happens at 90 °C. Second, the tetragonal-cubic (T-C) phase transition takes place at 170 °C.

Cheng, Juan; Yang, Yang; Tong, Yan-Hua; Lu, Sheng-Bo; Sun, Jing-Ya; Zhu, Ke; Liu, Yu-Long; Siu, G. G.; Xu, Z. K.

2009-03-01

329

Full field electron spectromicroscopy applied to ferroelectric materials  

NASA Astrophysics Data System (ADS)

The application of PhotoEmission Electron Microscopy (PEEM) and Low Energy Electron Microscopy (LEEM) techniques to the study of the electronic and chemical structures of ferroelectric materials is reviewed. Electron optics in both techniques gives spatial resolution of a few tens of nanometres. PEEM images photoelectrons, whereas LEEM images reflected and elastically backscattered electrons. Both PEEM and LEEM can be used in direct and reciprocal space imaging. Together, they provide access to surface charge, work function, topography, chemical mapping, surface crystallinity, and band structure. Examples of applications for the study of ferroelectric thin films and single crystals are presented.

Barrett, N.; Rault, J. E.; Wang, J. L.; Mathieu, C.; Locatelli, A.; Mentes, T. O.; Niño, M. A.; Fusil, S.; Bibes, M.; Barthélémy, A.; Sando, D.; Ren, W.; Prosandeev, S.; Bellaiche, L.; Vilquin, B.; Petraru, A.; Krug, I. P.; Schneider, C. M.

2013-05-01

330

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

331

Simulation of rolling behaviour of cubic oriented al single crystal with crystal plasticity FEM  

Microsoft Academic Search

The crystal plasticity finite element method (CPFEM), which incorporates the crystal plasticity constitutive law into the finite element method, has been used to investigate the rolling processes of the cubic oriented Al single crystal. The developed model has been validated by comparison with the experimental observations. The simulation results have shown that after rolling the crystal predominantly rotates around the

L. Y. Si; C. Lu; N. N. Huynh; A. K. Tieu; X. H. Liu

2008-01-01

332

Ultratough CVD single crystal diamond and three dimensional growth thereof  

DOEpatents

The invention relates to a single-crystal diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 30 MPa m.sup.1/2. The invention also relates to a method of producing a single-crystal diamond with a toughness of at least about 30 MPa m.sup.1/2. The invention further relates to a process for producing a single crystal CVD diamond in three dimensions on a single crystal diamond substrate.

Hemley, Russell J. (Washington, DC); Mao, Ho-kwang (Washington, DC); Yan, Chih-shiue (Washington, DC)

2009-09-29

333

Voltage-dependent domain evolution in La0.89Sr0.11MnO3 single crystals by Piezoresponse Force Microscopy  

NASA Astrophysics Data System (ADS)

Bias voltage dependent domain dynamics have been investigated on the surface of La0.89Sr0.11MnO3 (LSMO-0.11) single crystals by Piezoresponse Force Microscopy (PFM). The created domain size increases with both the amplitude and duration of the bias voltage pulse. It is observed that domain growth takes place following an activated process wherein the domain wall interacts with the defects (e.g. oxygen vacancies) resulting from the high electric field under the PFM tip. Fractal analysis, based on the interaction of the domain boundary with the defects, provides the Hausdorff fractal dimension value ˜1.3, lower than that usually observed for solid-state crystalline ferroelectrics indicating a smaller correlation length value for LSMO-0.11 crystal. These studies reveal a clear potential of LSMO for new memory devices based on ferroelectric-like domain states in manganites.

Panwar, Neeraj; Coondoo, Indrani; Kholkin, A. L.

2013-06-01

334

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

335

First-principles study of ferroelectricity and isotope effects in H-bonded K H2 P O4 crystals  

Microsoft Academic Search

By means of extensive first-principles calculations we studied the ferroelectric phase transition and the associated isotope effect in KH2PO4 (KDP). Our calculations revealed that the spontaneous polarization of the ferroelectric phase is due to electronic charge redistributions and ionic displacements which are a consequence of proton ordering, and not vice versa. The experimentally observed double-peaked proton distribution in the paraelectric

S. Koval; J. Kohanoff; J. A. Lasave; G. Colizzi; R. L. Migoni

2005-01-01

336

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

337

Crystal structures and ferroelectric properties of SrBi2Ta2O9 and Sr0.8Bi2.2Ta2O9  

NASA Astrophysics Data System (ADS)

Crystal structures of ferroelectric materials of stoichiometric SrBi2Ta2O9 (TC=300 °C) and Sr-deficient-and-Bi-excess Sr0.8Bi2.2Ta2O9 (TC=400 °C) were refined by neutron powder diffraction. Bi2O2 layer and TaO6 octahedra are considerably distorted and atomic displacements along the a axis cause ferroelectric spontaneous polarization. In Sr0.8Bi2.2Ta2O9, both Bi substitution and cation vacancies at the Sr site were revealed and a chemical composition of (Sr0.82Bi0.12)Bi2Ta2O9.0 was obtained. The calculated polarization of Sr0.8Bi2.2Ta2O9 is larger than that of the stoichiometric sample, which is consistent with observations of remanent polarization in thin-film capacitors. The Bi substitution and the cation vacancies at the Sr site enhance structural distortion in the TaO6 octahedra and lead to the larger ferroelectric spontaneous polarization and the higher Curie temperature.

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

1999-03-01

338

Electrooptical properties of the uniform chevron state of a ferroelectric smectic liquid crystal  

SciTech Connect

The influence of additives when introduced into the orienting agent on the orientation quality of the SmF phase of a liquid crystal (FLC) was studied. The conditions which allow bistable switching of the FLC with low spontaneous polarization P{sub s}(P{sub s} = 5 nCoul/cm{sup 2}) were determined. A model of smectic layers structure was suggested and the peculiarities of the optical transmission of thin chevron FLC cells were investigated. 8 figs., 5 refs.

Vorflusev, V.P.; Kosygina, M.A. [NIOPIK Research and Production Association of Organic Intermediaries and Dyes, Moscow (Russian Federation); Shoshin, V.M.; Bobylev, Y.P.

1995-12-31

339

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

Microsoft Academic Search

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

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

2007-01-01

340

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

Microsoft Academic Search

This thesis reports on the crystal growth of SrBi2Ta 2O9 ISBN, the measurements of intrinsic properties and the determination of structure-property relationships. Data are reported for the first time for the spontaneous polarization, dielectric anisotropy, electric resistivity, elastic coefficients, piezoelectric activity, heat capacity, and thermal expansion. Details are reported for the high-temperature solution growth of SBT from a Bi2O3 self-flux.

Xinliang Lu

2000-01-01

341

Visual and Quantitative Characterization of Ferroelectric Crystals and Related Domain Engineering Processes by Interferometric Techniques  

Microsoft Academic Search

Nonlinear crystals are, nowadays, key devices to build coherent sources emitting radiation from the UV to the IR spectral\\u000a range. Applications of nonlinear optics are primarily based on frequency conversion, through harmonic generation or sum and\\u000a difference frequency mixing. These nonlinear frequency conversion techniques make possible coherent light sources in spectral\\u000a regions where laser sources are limited, or do not

P. Ferraro; S. Grilli; M. Paturzo; S. De Nicola

342

Ferroelectricity in Ultrathin Perovskite Films  

Microsoft Academic Search

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

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

2004-01-01

343

Fabrication of polypyrrole nano-arrays in lysozyme single crystals  

NASA Astrophysics Data System (ADS)

A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals.A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals. Electronic supplementary information (ESI) available: Optical microscopy, SEM, TEM images, FTIR spectra and tables, conductivity plot. Experimental methods. See DOI: 10.1039/c2nr32413j

England, Matt W.; Lambert, Elizabeth M.; Li, Mei; Turyanska, Lyudmila; Patil, Avinash J.; Mann, Stephen

2012-10-01

344

Microscale Laser Peen Forming of Single Crystal  

SciTech Connect

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

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

2008-01-01

345

Bonding techniques for single crystal TFT AMLCDs  

NASA Astrophysics Data System (ADS)

Transmissive single crystal AMLCD light valves have recently drawn much attention for application in flat panel displays. The active matrix circuits are fabricated on SIMOX wafers and then transferred to glass. Circuit transfer consists in bonding a CMOS processed SIMOX wafer to a Pyrex glass substrate, thinning the SIMOX wafer and opening the contact pads. The pixel electrodes are made in polysilicon to allow standard CMOS processing. This paper discusses the transparency of the poly electrode and evaluates the potential of anodic bonding and adhesive bonding for circuit transfer. A major challenge for anodic bonding is the protection of the device dielectrics against the high voltages applied during bonding. A test chip was designed to investigate different ways of circumventing breakdown of the dielectrics. A method for adhesive bonding is discussed that assures good uniformity of the thickness of the epoxy layer and avoids the inclusion of air bubbles. It is demonstrated that the epoxies are resistant to the chemicals used for thinning the silicon substrate.

van der Groen, Sonja; Rosmeulen, Maarten; Jansen, Philippe; Deferm, Ludo; Baert, Kris

1996-09-01

346

High pressure synthesis of single crystals of ?-boron  

Microsoft Academic Search

A method of synthesis of single crystals of alfa-boron (?-B) is presented. ?-Boron has been crystallized from a boron–platinum melt at high pressures (6–11GPa) and high temperatures (1200–1600°C). The method is based on the high-pressure large volume (multi-anvil) press technique. An average size of the as-grown isometric crystals is 60–80?m in maximum dimension. A refinement of an accurate crystal structure

Gleb Parakhonskiy; Natalia Dubrovinskaia; Leonid Dubrovinsky; Swastik Mondal; Sander van Smaalen

2011-01-01

347

Anisotropy of Laser-Induced Bulk Damage of Single Crystals  

Microsoft Academic Search

The regularities of laser-induced damage of anisotropic materials, such as LiNbO3 and KDP dielectric single crystals, are experimentally studied. It is revealed that the shape of laser-induced damage in the dielectric crystals depends on the elastic symmetry of crystal and the propagation direction of the laser beam. When the beam propagates along the optic axis of crystals, the figures of

O. Krupych; Ya. Dyachok; I. Smaga; R. Vlokh

2007-01-01

348

Single crystal silicon rotary microactuator for hard disk drive  

Microsoft Academic Search

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

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

2003-01-01

349

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

350

Investigation of Advanced Processed Single-Crystal Turbine Blade Alloys.  

National Technical Information Service (NTIS)

This investigation studied the influence of thermal processing and microstructure on the mechanical properties of the single-crystal, nickel-based superalloys PWA 1482 and PWA 1484. The objective of the program was to develop an improved single-crystal tu...

B. J. Peters C. M. Biondo D. P. Deluca

1995-01-01

351

Fatigue behavior of a single crystal nickel-base superalloy  

Microsoft Academic Search

Many investigations indicate that high cycle fatigue cracks, in general, initiate at pores, inclusions, and grain boundaries in materials. The fatigue strength limit of a single crystal superalloy increases markedly compared to that of a conventional cast alloy, because the number of pores and inclusions in a single crystal superalloy are less than those of both conventionally cast and directionally

J. H. Zhang; Y. B. Xu; Z. G. Wang; Z. Q. Hu

1995-01-01

352

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

353

Fatigue behavior of a single crystal nickel-base superalloy  

SciTech Connect

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

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

1995-06-15

354

Reshock and release response of aluminum single crystal  

SciTech Connect

Reshock and release experiments were performed on single crystal aluminum along three orientations and on polycrystalline 1050 aluminum with 50 {mu}m grain size at shock stresses of 13 and 21 GPa to investigate the mechanisms for previously observed quasielastic recompression behavior. Particle velocity profiles obtained during reshocking both single crystals and polycrystalline aluminum from initial shock stresses of 13-21 GPa show similar quasielastic recompression behavior. Quasielastic release response is also observed in all single crystals, but the magnitude of the effect is crystal orientation dependent, with [111] and [110] exhibiting more ideal elastic-plastic release for unloading from the shocked state than for the [100] orientation and polycrystalline aluminum. The quasielastic response of 1050 aluminum is intermediate to that of the [100] and [111] orientations. Comparison of the wave profiles obtained for both unloading and reloading of single crystals and polycrystalline 1050 aluminum from shocked states suggests that the observed quasielastic response of polycrystalline aluminum results from the averaging response of single crystals for shock propagation along different orientations, and that the response of 1050 aluminum with large grain boundaries is not significantly different from the results obtained on single crystal aluminum. The yield strength of the single crystals and 1050 aluminum is found to increase with shock stress, which is consistent with previous results [H. Huang and I. R. Asay, J. Appl. Phys. 98, 033524 (2005)].

Huang, H.; Asay, J. R. [Institute for Shock Physics and Department of Physics, Washington State University, Pullman, Washington 99164-2816 (United States)

2007-03-15

355

Chemical doping-induced flop of ferroelectric polarization in multiferroic Mn0.9Co0.1WO4  

NASA Astrophysics Data System (ADS)

We studied the multiferroic properties of the incommensurate spiral phase of Mn1-xCoxWO4 using single-crystal neutron-diffraction and ferroelectric measurements. Whereas the rotational plane of the spin spiral is parallel to the b axis for x?0.05 , it flops by 90° for x=0.10 . As a result, the direction of the ferroelectric polarization also flops from the b to the a axis. These results show that the orientation of the ferroelectric polarization in MnWO4 can be controlled via chemical doping.

Song, Y.-S.; Yan, Li Qin; Lee, Bumsung; Chun, Sae Hwan; Kim, Kee Hoon; Kim, Sung Baek; Nogami, A.; Katsufuji, T.; Schefer, J.; Chung, J.-H.

2010-12-01

356

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

PubMed

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

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

2013-03-27

357

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

358

Ferroelectric polymers  

Microsoft Academic Search

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

R. G. Kepler; R. A. Anderson

1992-01-01

359

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

360

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

361

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

362

Guanidinium perchlorate ferroelectric crystal. Study of vibrational properties based on experimental measurements and theoretical calculations  

NASA Astrophysics Data System (ADS)

The infrared and Raman spectra of guanidinium perchlorate were measured at room temperature. The spectra are discussed with the framework of literature X-ray structure in relation to internal hydrogen bond network. For complete vibrational analysis the theoretical calculation of both infrared and Raman spectra in DFT approach were performed. The clear-cut assignment of observed bands was made on the basis of PED analysis. On the basis of theoretical studies the electrostatic charges and energies of HOMO and LUMO orbitals were obtained. Additionally the first order hyperpolarizability of investigated molecule was calculated. The obtained results are in good agreement with literature data, but according to performed calculation the specific damping of ? hyperpolarizability in unit cell (comparable with isolated molecule) is observed. To explain in detail phase transitions phenomena (at ca. 452 and 454 K) described in literature the temperature dependent infrared powder spectra were recorded. The temperature dependencies of bands position and intensities for titled crystal in the range 11-480 K are analyzed.

Drozd, M.; Dudzic, D.

2013-11-01

363

Phase transitions in the ferroelectric crystals [CH3NH3]5Bi2Cl11 and [CH3NH3]5Bi2Br11 studied by the nonlinear dielectric effect  

NASA Astrophysics Data System (ADS)

The real part of the complex electric permittivity at low frequencies and at several biasing fields (between 0 and 5×105V/m ) has been measured in ferroelectric crystals [CH3NH3]5Bi2Cl11 (MAPCB) and [CH3NH3]5Bi2Br11 (MAPBB) in the temperature range covering the temperature of the ferroelectric phase transitions. Comparative measurements for the known triglycine sulphate (NH2CH2COOH)3H2SO4 crystal have been used as a test of the validity and of possible errors in the determination of the ferroelectric equation of state by the method applied. The estimates of the critical parameters TC , ? , and ? then have been evaluated for MAPCB and MAPBB on the basis of the Widom-Griffiths scaling hypothesis. Complementary pyroelectric measurements of the spontaneous polarization providing the critical exponent ? are in accordance with the parameters obtained.

Szklarz, P.; Ga??zka, M.; Zieli?ski, P.; Bator, G.

2006-11-01

364

Transparent Ferroelectric Glass-Ceramics  

Microsoft Academic Search

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

H. JAIN

2004-01-01

365

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

366

Electromechanical properties and anisotropy of single- and multi-domain 0.72Pb(Mg1?3Nb2?3)O3-0.28PbTiO3 single crystals  

PubMed Central

Complete sets of elastic, piezoelectric, and dielectric constants of 0.72Pb(Mg1?3Nb2?3)O3-0.28PbTiO3 single crystal poled along [111]c (single domain) as well as non-polar axes [001]c and [011]c (multidomain) have been measured under natural conditions. These data allowed us to evaluate accurately the extrinsic contributions to the superior piezoelectric properties. Very large extrinsic contributions to the unusual anisotropies in multidomain crystals are confirmed. We found that the instability of domain structures is the origin of the low mechanical quality factor Q for the multidomain relaxor-based ferroelectric single crystals. Our results can provide useful guidance in future design of domain engineered materials.

Liu, Gang; Jiang, Wenhua; Zhu, Jiaqi; Cao, Wenwu

2011-01-01

367

Epitaxial electrodeposition of freestanding large area single crystal substrates  

SciTech Connect

The authors report on a method for producing freestanding single crystal metal films over large areas using electrodeposition and selective etching. The method can be turned into an inexpensive continuous process for making long ribbons or a large area of single crystal films. Results from a 5x5 mm{sup 2} Ni single crystal film using electron backscattering pattern pole figures and x-ray diffraction demonstrate that the quality of material produced is equivalent to the initial substrate without annealing or polishing.

Shin, Jae Wook; Standley, Adam; Chason, Eric [Brown University, Box D, Providence, Rhode Island 02912 (United States)

2007-06-25

368

Spherical Nb single crystals containerlessly grown by electrostatic levitation  

NASA Astrophysics Data System (ADS)

Spherical Nb (Tm=2750 K) single crystals were grown via containerless electrostatic levitation (ESL). Samples became spherical at melting in levitation and undercooled typically 300-450 K prior to nucleation. As-processed samples were still spherical without any macroscopic shape change by solidification showing a uniform dendritic surface morphology. Crystallographic {111} planes exposed in equilateral triangular shapes on the surface by preferential macroetching and spotty back-reflection Laue patterns confirm the single crystal nature of the ESL-processed Nb samples. No hysteresis in magnetization between zero field and field cooling also implies a clean defect-free condition of the spherical Nb single crystals.

Sung, Y. S.; Takeya, H.; Hirata, K.; Togano, K.

2003-05-01

369

Single crystal Processing and magnetic properties of gadolinium nickel  

SciTech Connect

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

Shreve, Andrew John [Ames Laboratory

2012-11-02

370

Pulse shape discrimination with new single crystal organic scintillators  

NASA Astrophysics Data System (ADS)

Pulse shape discrimination in organic single crystal and liquid scintillators provides a means of identifying fission energy neutrons with high specificity. We present the results of a broad survey of over one hundred single crystal organic scintillators produced from low-temperature solution growth technique. Each crystal was evaluated for light yield and pulse shape discrimination performance. The pulse shape dependence on excitations via a Compton electron from a gamma and a recoil proton from a fast neutron was measured using full waveform digitization. Several groups of compounds were compared in relation to molecular and crystallographic structures, crystal perfection, and the effect of impurities. New prospective materials offering neutron/gamma discrimination comparable or superior to stilbene will be presented. We also report on the growth of large single crystal lithium salicylate and other promising Li compounds which have sensitivity to lower energy neutrons via neutron capture on ^6Li and are separable from other excitations via pulse shape discrimination.

Newby, Jason; Zaitseva, Natalia; Payne, Stephen; Cherepy, Nerine; Carman, Leslie; Hull, Giulia

2009-10-01

371

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

372

Molecular Orientational Structures in Ferroelectric, Ferrielectric and Antiferroelectric Smectic Liquid Crystal Phases as Studied by Conoscope Observation  

Microsoft Academic Search

Molecular orientational structures in MHPOBC were studied by means of conoscope observation. Contrary to a ferroelectric response of the conoscope to an electric field in the smectic C* phase, the conoscopic figure in the antiferroelectric smectic CA* phase does not shift its center and is biaxial with its optic plane perpendicular to the field direction. This conoscope change is only

Ewa Gorecka; A. D. L. Chandani; Yukio Ouchi; Hideo Takezoe; Atsuo Fukuda

1990-01-01

373

LETTER TO THE EDITOR: Landau model for commensurate-commensurate phase transitions in uniaxial improper ferroelectric crystals  

Microsoft Academic Search

We propose the Landau model for lock-in phase transitions in uniaxially modulated improper ferroelectric incommensurate-commensurate systems of class I. It includes Umklapp terms of third and fourth order and secondary order parameters representing the local polarization. The corresponding phase diagram has the structure of a harmless staircase, with the allowed wave numbers obeying the Farey tree algorithm. Among the stable

M. Latkovic; A. Bjelis; V. Dananic

2000-01-01

374

A new route to grow single-crystal group III-V compound semiconductor nanostructures on non-single-crystal substrates  

Microsoft Academic Search

A new route to grow single-crystal semiconductor nanostructures is reviewed. Unlike conventional epitaxial growth of single-crystal semiconductor films, the proposed route for growing semiconductor nanostructures does not require a single-crystal semiconductor substrate. In the proposed route, instead of using single-crystal semiconductor substrates that are characterized by their long-range atomic order, a non-single-crystal template layer that possesses short-range atomic order prepared

Nobuhiko P. Kobayashi

2007-01-01

375

Adaptive ferroelectric states in systems with low domain wall energy: Tetragonal microdomains  

NASA Astrophysics Data System (ADS)

Ferroelectric and ferroelastic phases with very low domain wall energies have been shown to form miniaturized microdomain structures. A theory of an adaptive ferroelectric phase has been developed to predict the microdomain-averaged crystal lattice parameters of this structurally inhomogeneous state. The theory is an extension of conventional martensite theory, applied to ferroelectric systems with very low domain wall energies. The case of ferroelectric microdomains of tetragonal symmetry is considered. It is shown for such a case that a nanoscale coherent mixture of microdomains can be interpreted as an adaptive ferroelectric phase, whose microdomain-averaged crystal lattice is monoclinic. The crystal lattice parameters of this monoclinic phase are self-adjusting parameters, which minimize the transformation stress. Self-adjustment is achieved by application of the invariant plane strain to the parent cubic lattice, and the value of the self-adjusted parameters is a linear superposition of the lattice constants of the parent and product phases. Experimental investigations of Pb(Mg1/3Nb2/3)O3-PbTiO3 and Pb(Zn1/3Nb2/3)O3-PbTiO3 single crystals confirm many of the predictions of this theory.

Jin, Y. M.; Wang, Y. U.; Khachaturyan, A. G.; Li, J. F.; Viehland, D.

2003-09-01

376

Conformal Domain Miniaturization and Adaptive Monoclinic (Pseudo-orthorhombic) Ferroelectric States  

NASA Astrophysics Data System (ADS)

Ferroelectric and ferroelastic phases with very low domain wall energies have been shown to form miniaturized microdomain structures. A theory of an adaptive ferroelectric phase has been developed to predict the microdomain-averaged crystal lattice parameters of this structurally inhomogeneous state. The theory is an extension of conventional martensite theory, applied to ferroelectric systems with very low domain wall energies. The cases of ferroelectric microdomains of tetragonal (FEt) symmetry are considered. It is shown that a nano-scale coherent mixture of microdomains can be interpreted as an adaptive ferroelectric phase, whose microdomain-averaged crystal lattice is monoclinic. The crystal lattice parameters of this monoclinic phase are self-adjusting parameters, which minimize the transformation stress. Self-adjustment is achieved by application of the invariant plane strain (IPS) to the parent cubic lattice, and the value of the self-adjusted parameters constitutes a mixture of the lattice constants of the parent and product phases. Experimental investigations of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) single crystals confirm many of the predictions of this theory.

Jin, Y. M.; Wang, Yu; Khachaturyan, A. G.; Li, J. F.; Viehland, D.

2003-08-01

377

X-ray Study on the Disordered Structure above the Ferroelectric Curie Point in Potassium Nitrate  

Microsoft Academic Search

The disordered structure (phase I) above the ferroelectric Curie point (ca. 125°C) in KNO3 was studied by analysing X-ray diffuse scattering. The single crystal was prepared by slow cooling from the melt in a small glass tube which was mounted on the sample holder of a camera. The observed intensity distribution of the diffuse scattering in reciprocal space was characterized

Yasuhiro Shinnaka

1962-01-01

378

Microwave Phase Shifters Using Ferroelectric (Ba,Sr)TiO3 Films.  

National Technical Information Service (NTIS)

The ferroelectric (Ba(0.6)Sr(0.4)TiO3) (BST) films were prepared on (001) MgO single crystals by pulsed laser deposition. Coplanar waveguide (CPW) type phase shifters controlled by external dc bias field were fabricated on BST films using a 2 micrometers ...

E. Kim S. Lee S. Moon S. K. Han W. Kim

2003-01-01

379

Linear Compressibilities of Ii-Vi Compound Single Crystals.  

National Technical Information Service (NTIS)

The isothermal linear compressibilities of the II-VI compound single crystals, CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, and ZnTe were measured by an optical interferometer. The change in length of the crystals was obtained relative to iron under hydrostatic press...

D. W. Langer R. A. Montalvo

1970-01-01

380

EPR and Optical Absorption Studies of ?-irradiated Pyrene Single Crystals  

Microsoft Academic Search

Pyrene single crystals irradiated with ? rays at room temperature have been investigated by electron paramagnetic resonance and optical absorption experiments. EPR spectra exhibit a triplet characteristic and each line of the triplet shows characteristic features with rotations of the crystals in a magnetic field. From analyses of these spectra the presence of two kinds of hydrogen added pyrene radicals,

Tetsuya Kawakubo

1978-01-01

381

Dislocation Line Direction Determination in Pyrene Single Crystals  

Microsoft Academic Search

A new technique for the unambiguous determination of dislocation line directions in macroscopic single crystals is presented. The technique is based on analysis of the projected directions of the images of the dislocations on synchrotron white beam topographs. Calculation is carried out in a pseudo-cubic axis system which is related to the crystal axis system by a transformation matrix. Final

Ding Yuan; Michael Dudley

1992-01-01

382

Hertzian Fracture in Single Crystals with the Diamond Structure  

Microsoft Academic Search

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

B. R. Lawn

1968-01-01

383

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

384

Study of Single Crystals of Metal Solid Solutions.  

National Technical Information Service (NTIS)

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

J. A. Reising J. P. Doty

1973-01-01

385

Desorption of Oxygen from Virgin CDS Single Crystals.  

National Technical Information Service (NTIS)

Typical desorption data of amu 16 from virgin CdS single crystals is presented for two classes of crystals as determined by their electrical properties. Thermal desorption energies are found in the energy range of 0.87 eV to > with temperatures of maximum...

K. W. Boer R. Schubert C. Wright

1968-01-01

386

Domain growth kinetics in La0.89Sr0.11MnO3 single crystal studied by piezoresponse force microscopy  

NASA Astrophysics Data System (ADS)

Ferroelectric-like nanodomains have been written by applying voltage pulse of different durations to the surface of La0.89Sr0.11MnO3 manganite single crystals and subsequently examined by the piezoresponse force microscope (PFM) technique. The domain wall velocity was then calculated based on conventional PFM procedure. A transition from the non-activated to the activated type domain wall motion has been observed due to the inhomogeneous spatial variation of the tip-induced electric field. The maximum domain size that can develop in a non-activated motion process has been found to be ~170 nm. The formation of these ferroelectric-like nano domains at room temperature by PFM has been rationalized within phenomenological model based on Landau-Ginzburg formalism. Written domains are sufficiently stable and are attractive for device applications in nonvolatile random-access memories and development of metamaterials.

Panwar, Neeraj; Bdikin, Igor K.; Morozovska, Anna N.; Kholkin, Andrei L.

2012-09-01

387

Angular Variation of Coercivity in Orthoferrite Single Crystals.  

National Technical Information Service (NTIS)

The coercive force Hc as a function of the angle between the easy axis of magnetization and the external field was studied in orthoferrite single crystals using the vibrating sample technique. (Author)

S. Reich S. Shtrikman D. Treves

1964-01-01

388

Anthracene Fluorescence at Low Temperatures. II. Doped Single Crystals.  

National Technical Information Service (NTIS)

By the addition of dopants to single crystal anthracene it is shown that many of the fluorescence bands additional to exciton emission are due to traces of 2-methylanthracene. Other impurity bands, apparently arising from locally disorientated host molecu...

L. E. Lyons L. J. Warren

1972-01-01

389

Constitutive Modeling of Superalloy Single Crystals with Verification Testing.  

National Technical Information Service (NTIS)

The goal is the development of constitutive equations to describe the elevated temperature stress-strain behavior of single crystal turbine blade alloys. The program includes both the development of a suitable model and verification of the model through e...

E. Jordan K. P. Walker

1985-01-01

390

Planning Study for Preparation of Single Crystal Experiments.  

National Technical Information Service (NTIS)

In order to conceive suitable space experiments with single crystals their properties desired for technical applications must first be considered. By comparing the production possibilities, including their limitations in space and on earth, it is possible...

H. Weiss

1976-01-01

391

Toward, single molecule detection with photonic crystal microcavity biosensors  

Microsoft Academic Search

Time resolved biomolecular binding events were measured using photonic crystal microcavity resonators integrated with microfluidics. The optical field is confined to a volume of 33 times 10-18 liters, which enables monitoring of single binding events

L. W. Mirkarimi; S. Zlatanovic; S. Sigalas; M. A. Bynum; K. Robotti; E. Chow; A. Grot

2006-01-01

392

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

1997-09-15

393

Enhanced EPR Sensitivity from a Ferroelectric Cavity Insert  

Microsoft Academic Search

We report the development of a simple ferroelectric cavity insert that increases the electron paramagnetic resonance (EPR) sensitivity by an order of magnitude when a sample is placed within it. The insert is a hollow cylinder (length 4.8 mm, outside diameter 1.7 mm, inside diameter 0.6 mm) made from a single crystal of KTaO3, which has a dielectric constant of

Yuri E. Nesmelov; Jack T. Surek; David D. Thomas

2001-01-01

394

Single-crystal piezoceramic actuation for dynamic stall suppression  

Microsoft Academic Search

PZN-8%PT?111? —a new single-crystal piezoceramic is explored for its potential to torsionally actuate the existing structure utilizing the induced shear mechanism of piezoceramics. A model of the elastic rotor blade and piezoceramic actuator is developed using the Hamilton’s principle and the resulting equations are solved using the finite element method. Numerical results show that the single crystal material is able

D. Thakkar; R. Ganguli

2006-01-01

395

Electron Spin Resonance in an Irradiated Single Crystal of Dimethylglyoxime  

Microsoft Academic Search

The paramagnetic resonance of gamma-irradiated single crystals of dimethylglyoxime has been measured at 23 kMc\\/sec and 9 kMc\\/sec for various orientations of the crystal in the magnetic field. The resonance pattern was found to have a triplet structure caused by coupling to a single N14 nucleus. Both the nuclear coupling and the spectroscopic splitting factor were found to be anisotropic

Ichiro Miyagawa; Walter Gordy

1959-01-01

396

WELDING AND WELD REPAIR OF SINGLE CRYSTAL GAS TURBINE ALLOYS  

Microsoft Academic Search

The cost-effective commercial use of single crystal nickel-based superalloys for land-based turbine engine components such as blades and vanes requires that they can be repair welded to improve as-cast yields or to refurbish worn or failed components after intermediate service intervals. This program addresses this vital need by determining the welding behavior and weldability of single crystal nickel-based superalloys in

J. M. Vitek; S. A. David; S. S. Babu

397

How a silver dendritic mesocrystal converts to a single crystal  

Microsoft Academic Search

In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn\\/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the

Jixiang Fang; Bingjun Ding; Xiaoping Song; Yong Han

2008-01-01

398

Gradient-dependent deformation of two-phase single crystals  

Microsoft Academic Search

In this work, a gradient- and rate-dependent crystallographic formulation is proposed to investigate the macroscopic behaviour of two-phase single crystals. The slip-system-based constitutive formulation relies on strain-gradient concepts to account for the additional strengthening mechanism associated with the deformation gradients within a single crystal with a high volume fraction of dispersed inclusions. The resulting total slip resistance in each active

E. P. Busso; F. T. Meissonnier; N. P. O'Dowd

2000-01-01

399

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

400

Bithermal fatigue of a nickel-base superalloy single crystal  

Microsoft Academic Search

The thermomechanical fatigue behavior of a nickel-base superalloy single crystal was investigated using a bithermal test technique. The bithermal fatigue test was used as a simple alternative to the more complex thermomechanical fatigue test. Both in-phase and out-of-phase bithermal tests were performed on (100)-oriented coated and bare Rene N4 single crystals. In out-of-plane bithermal tests, the tensile and compressive halves

Verrilli

1988-01-01

401

Ferrite-ferroelectric hybrid wave phase shifters  

NASA Astrophysics Data System (ADS)

A dual, electric and magnetic field tunable microwave phase shifter based on the propagation of hybrid spin-electromagnetic waves in a ferrite-ferroelectric bilayer is discussed. The bilayer consists of a single-crystal yttrium iron garnet film and a ceramic barium strontium titanate slab. The electrical tunability of the differential phase shift ?? is achieved through the application of a voltage across barium strontium titanate. An insertion loss of 20 dB and a continuously variable ?? as high as 650° in the frequency range of 4.5-8 GHz are measured.

Ustinov, A. B.; Srinivasan, G.; Kalinikos, B. A.

2007-01-01

402

Single Crystal Growth of Photorefractive Sillenites.  

National Technical Information Service (NTIS)

The compounds, crystallized in the cubic form similar to sillenite structure, occur in a number of isomorphs. The well-known representatives of this family are bismuth germanium (BGO) and bismuth silicon oxides (BSo), both of which can be grown from their...

V. V. Volkov Y. F. Kargin V. M. Skorikov

1992-01-01

403

Single-helix crystal in atactic polypropylene  

NASA Astrophysics Data System (ADS)

The conformational arrangement of a locally stereoregular sequence of atactic polypropylene (aPP) was investigated via X-ray diffraction, thermal analysis, and infrared spectroscopy. Since the aPP used was an isotactic-rich sample, the X-ray diffraction pattern showed the typical profile of an ?-iPP (isotactic polypropylene) crystal, indicating that the crystal is constructed from locally stereoregular sequences. Even for a sample with low stereoregularity (meso pentad = 16%), small peaks due to ?-iPP crystals were observed. The melting temperature of aPP was reduced compared with an ?-iPP crystal. This corresponds to a shortening of the lamellar thickness. Helical units from chloroform insoluble and soluble fractions having meso pentads of 0.64 and 0.16, respectively, were composed of 3.5 and 1.2 repeating units, respectively. Such short conformational order was also confirmed by infrared spectroscopy. In general, a conformationally sensitive band is observed over a critical regular sequence (n). For the chloroform soluble fraction, a 977 cm-1 band for n = 5 was observed, but the typical 998 and 841 cm-1 bands for n = 11-12 and 13-15, respectively, were not observed. This signals that the regular conformation consists of 1-2 repeating units. It is concluded that a short conformational order (about 1-2 helical units) can construct the crystalline unit for aPP.

Nakaoki, Takahiko; Fukui, Daisuke

2013-11-01

404

Single Crystal Growth by Laser CVD.  

National Technical Information Service (NTIS)

CO2 gas lasers prove to be a superb heat source for use in various applications. Using the lasers, thin monocrystals with a diameter of less than 1 mm were grown. The processes are discussed for creation of the crystals, including a report on related work...

S. Hayashi

1988-01-01

405

Effect of Stress on CDS Single Crystals.  

National Technical Information Service (NTIS)

The electrical and luminescence properties of CdS crystals, which show the phenomenon of storage, were studied as a function of hydrostatic pressure and uniazial stress. In the excited state, uniaxial stress applied parallel to the c axis resulted in an i...

B. A. Kulp K. A. Gale

1966-01-01

406

Single crystals of single-walled carbon nanotubes formed by self-assembly.  

PubMed

We report the self-assembly of single crystals of single-walled carbon nanotubes (SWCNTs) using thermolysis of nano-patterned precursors. The synthesis of these perfectly ordered, single crystals of SWCNTs results in extended structures with dimension on the micrometer scale. Each crystal is composed of an ordered array of tubes with identical diameters and chirality, although these properties vary between crystals. The results show that SWCNTs can be produced as a perfect bulk material on the micrometer scale and point toward the synthesis of bulk macroscopic crystalline material. PMID:11292859

Schlittler, R R; Seo, J W; Gimzewski, J K; Durkan, C; Saifullah, M S; Welland, M E

2001-04-05

407

SCREAM I: A single mask, single-crystal silicon, reactive ion etching process for microelectromechanical structures  

Microsoft Academic Search

A single-crystal slhcon, high aspect ratlo, low-temperature process sequence for the fabrlcatlon of suspended rmcroelectromechamcal structures (MEMS) usmg a smgle hthography step and reactwe Ion etching (RIE) IS presented The process IS called SCRJZAM I (single-crystal reactwe etchmg and metalhzatmn) SCREAM I IS a bulk mlcromachmmg process that uses RIE of a s~hcon substrate to fabricate suspended movable smgle-crystal s&on

Kevin A. Shaw; Z. Lisa Zhang; Noel C. MacDonald

1994-01-01

408

Growth of Strontium Titanate Single Crystals from Molten Salts  

Microsoft Academic Search

Single crystals of strontium titanate (SrTiO3) were grown by flux method. The best results were obtained with KF-LiF and KF-K2MoO4 flux systems. Reasonably large single crystals were yielded from the solvent of KF-LiF systems and fine small crystals which were colorless, transparent and flawless were obtained from KF-K2MoO4 systems. The experiments were carried out by slow cooling method, temperature of

Tokuko Sugai; Shuzo Hasegawa; Gisaku Ohara

1968-01-01

409

Hydrothermal growth of carbonate-containing hydroxyapatite single crystals  

Microsoft Academic Search

Single crystals of carbonate-containing hydroxyapatite have been grown hydrothermally by gradually heating with a temperature gradient applied to the vessel, using CaHPO4, H2O and carbon dioxide as dry ice. The optimum conditions to obtain large single crystals are: CaHPO4, 10 g\\/l; final temperature gradient, 33.5°C\\/cm; heating rate, 0.005°C\\/min; and carbon dioxide, 55 g\\/l. The largest crystal obtained was 12 mm

Atsuo Ito; Satoshi Nakamura; Hideki Aoki; Masaru Akao; Kay Teraoka; Sadao Tsutsumi; Kazuo Onuma; Tetsuya Tateishi

1996-01-01

410

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

411

Ferroelectric memories  

Microsoft Academic Search

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

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

1989-01-01

412

Orthorhombic ferroelectric and ferroelastic Gd 2(MoO 4) 3 crystal — a new many-purposed nonlinear and optical material: efficient multiple stimulated Raman scattering and CW and tunable second harmonic generation  

Microsoft Academic Search

The nonlinear optical properties of a ferroelectric and ferroelastic ??-Gd2(MoO4)3 laser crystal-host were studied by second harmonic generation (SHG) and stimulated Raman scattering (SRS) experiments using different laser sources for excitation. It is shown that the investigated crystals are very attractive for SHG with IR CW lasers as well as for continuously tunable SHG under illumination with a femtosecond hyper-continuum

A. A. Kaminskii; A. V. Butashin; H.-J. Eichler; D. Grebe; R. Macdonald; K. Ueda; H. Nishioka; W. Odajima; M. Tateno; J. Song; M. Musha; S. N. Bagaev; A. A. Pavlyuk

1997-01-01

413

Why ferroelectric polyvinylidene fluoride is special  

Microsoft Academic Search

Ferroelectric polymers entail a number of constraints, which together limit the useful compositional variations. These constraints include the following: a stable molecular dipole moment, compact crystal structure, conformational flexibility, and minimal steric hindrance. They are well satisfied by the prototype ferroelectric polymer, polyvinylidene fluoride, and yet almost every other conceivable molecular structure is limited by comparison.

Matthew Poulsen; Stephen Ducharme

2010-01-01

414

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

415

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

416

Raman spectra of deuteriated taurine single crystals  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

417

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

418

Growth and characterization of pure and doped btzs single crystals  

NASA Astrophysics Data System (ADS)

The growth and characterization of pure and doped BTZS single crystals are discussed. In the present study powder X-Ray diffraction data of the grown crystal were recorded using BRUKER D8 Advance powder crystal X-ray diffractometer with 2.2 KW Cu anode ceramic X-ray tube. The various functional groups present in the grown crystals were identified and confirmed by recording the FTIR spectrum using BRUKER IFS-66V spectrophotometer by KBr Pellet Technique in the region 4000 â?? 400 cm The UV - Vis - NIR optical spectra of the crystals were recorded using the VARIAN CARY 5E model spectrophotometer. The degree of dopant inclusion was estimated by using Atomic Absorption Spectroscopy. The SHG efficiencies of the crystals were studied using Nd:YAG Q - switched laser.

Gunasekaran, Sethu; Venkatesan, Padmapriya

2012-05-01

419

Studies of single crystal organic scintillators for neutron detection  

NASA Astrophysics Data System (ADS)

Organic crystal scintillators have long been used for fission energy neutron detection and identification. The gamma/neutron separation techniques, known collectively as pulse shape discrimination (PSD), are based on the relative increase in delayed florescence for neutron excitations in comparison to that of gammas. We have conducted a broad survey of the PSD properties for over one hundred single crystal scintillators produced from solution growth techniques, including Li compounds which have sensitivity to lower energy neutrons via neutron capture on ^6Li. Crystal growth methods utilizing temperature reduction of super-saturated solutions have allowed us to produce large volume (> 100 cm^3) faceted organic crystal scintillators with neutron/gamma PSD comparable or superior to trans-stilbene for a subset of these materials. These results show good progress in overcoming the scalability issues of crystal scintillators for neutron detection. We present a survey of our recent results including mixed crystals of varying stilbene fraction.

Glenn, Andrew; Zaitseva, Natalia; Carman, Leslie; Payne, Stephen; Faust, Michelle; Cherepy, Nerine; Hamel, Sebastien; Newby, Jason

2010-11-01

420

Preparation of bead metal single crystals by electron beam heating  

SciTech Connect

For the fabrication of small metal bead crystals a gas flame is used to melt a wire forming a liquid droplet which solidifies upon cooling into a single crystal metal bead. Due to oxidation under ambient conditions bead crystals can be formed only from noble metals using this method. Here we describe a method how to fabricate bead crystals from a wide variety of metals and metal alloys (Cu, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, Pt, Au, PtPd, Pd{sub 80}Pt{sub 20}, PtRh, AuAg, and PtIr) by electron beam heating under vacuum conditions. Narrow x-ray diffraction peaks confirm a high crystal quality of the bead crystals.

Voigtlaender, Bert; Linke, Udo; Stollwerk, H.; Brona, J. [Institut fuer Schichten und Grenzflaechen ISG 3 and cni-Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Juelich, 52425 Juelich (Germany); Institut fuer Schichten und Grenzflaechen ISG 3 and cni-Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Juelich, 52425 Juelich, Germany and Institute of Experimental Physics, University of Wroclaw, pl. Maxa Borna 9, PL 50-204 Wroclaw (Poland)

2005-11-15

421

Ferroelectricity: From organic conductors to conducting polymers  

NASA Astrophysics Data System (ADS)

We compare the ferroelectricity for two families of synthetic conductors: the experimentally found ferroelectricity in organic crystal like (TMTTF)2X and a plausilble ferroelectricity in specially designed polyene chains. The difference of the polymer with respect to the organic conductor is the reverse of the build-in (now the sites) and spontaneous (now the bonds) effects of dimerizations. The theory predicts the existence of solitons (dimerization kinks) with non-integer variable charges, both with and without the spin. With today's understanding, we see them as walls separating domains with opposite electric polarization. Their physics will serve to relate transient ferroelectric processes and the visible range optics.

Kirova, N.; Brazovskii, S.

2009-03-01

422

Crystal growth and characterization of L-histidine hydrochloride monohydrate semiorganic nonlinear optical single crystals  

NASA Astrophysics Data System (ADS)

Nearly perfect single crystals of L-histidine hydrochloride monohydrate have been grown from the solution prepared from the mixture of L-histidine and hydrochloric acid using slow evaporation solution growth technique. Single crystal X-ray diffraction analysis, High resolution X-ray diffraction analysis, fourier transform infrared and FT-Raman analyzes were employed for structural characterization. Linear and nonlinear optical properties have been studied by UV-Vis transmission spectrum and Kurtz Perry technique respectively. The refractive index, redox behavior and hardness of the grown crystal have been found by suitable methods. Thermogravimetric, differential thermal analysis were employed to characterize the as-grown crystals. The second harmonic generation conversion efficiency of the grown crystal and other properties show the suitability of the grown crystal for frequency conversion applications.

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

2012-05-01

423

Effect of poling conditions on growth of calcium phosphate crystal in ferroelectric BaTiO 3 ceramics  

Microsoft Academic Search

Recently, ceramic materials have been given a lot of attention as candidates for implant materials, since they possess biologically favorable characteristics for osseointegration. Among them, BaTiO3 (BTO) ceramics are ferroelectric and piezoelectric after poling treatments. However, little or no information is available on the poling condition of BTO and their effect on calcium phosphate (CaP) formation. In this study, the

K. S. Hwang; J. E. Song; J. W. Jo; H. S. Yang; Y. J. Park; J. L. Ong; H. R. Rawls

2002-01-01

424

Effect of crystallization conditions on the shape of polymer single crystals: Experimental and theoretical approaches  

NASA Astrophysics Data System (ADS)

A modified system of Mansfield equations with different step propagation rates to the right and left was applied to describe the shape of solution-grown single crystals of long-chain alkanes with asymmetrically curved faces ?ub;110?ub;. Solution of this system of equations and simulation of the shape of single crystals of polyethylene, ?-polyvinylidene fluoride, and polyethylene oxide shows good agreement with the experimental data. Comparison of the simulated shapes and experimental micrographs makes it possible to determine the ratio of the intensity of secondary nucleation to the average propagation rate of the layer as well as the ratio of the rates of lateral steps to the right and left and to calculate the absolute values of the main crystallization parameters when the growth rates of single crystals in certain directions are known. It is shown that the asymmetry of the step propagation rate to the right and left is significant only for crystallization at very small supercoolings.

Shcherbina, M. A.; Chvalun, S. N.; Ungar, G.

2007-07-01

425

Solution-processed, Self-organized Organic Single Crystal Arrays with Controlled Crystal Orientation.  

PubMed

A facile solution process for the fabrication of organic single crystal semiconductor devices which meets the demand for low-cost and large-area fabrication of high performance electronic devices is demonstrated. In this paper, we develop a bottom-up method which enables direct formation of organic semiconductor single crystals at selected locations with desired orientations. Here oriented growth of one-dimensional organic crystals is achieved by using self-assembly of organic molecules as the driving force to align these crystals in patterned regions. Based upon the self-organized organic single crystals, we fabricate organic field effect transistor arrays which exhibit an average field-effect mobility of 1.1?cm(2)V(-1)s(-1). This method can be carried out under ambient atmosphere at room temperature, thus particularly promising for production of future plastic electronics. PMID:22563523

Kumatani, Akichika; Liu, Chuan; Li, Yun; Darmawan, Peter; Takimiya, Kazuo; Minari, Takeo; Tsukagoshi, Kazuhito

2012-05-03

426

Optical Spectroscopy of Single Pentacene Molecules in a Naphthalene Crystal  

Microsoft Academic Search

Dilute mixed molecular crystals of pentacene in naphthalene were prepared by cosublimation of the two compounds. Single pentacene molecules could be detected in the thin platelets by fluorescence excitation spectroscopy. By analyzing the exponential decay of the fluorescence intensity autocorrelation function for a single molecule in the microsecond time regime we could determine the population (k23) and depopulation (k31) rate

Susanne Kummer; Christoph Bräuchle; Thomas Basché

1996-01-01

427

Broadband single-polarization guidance in hybrid photonic crystal fibers.  

PubMed

We present hybrid photonic crystal fibers that provide broadband single-polarization guidance based on two different propagation mechanisms, namely, total internal reflection and the photonic bandgap effect. Experimental results demonstrate polarization dependent loss as high as 26.7 dB and the bandwidth of single-polarization behavior over 225 nm. PMID:21263477

Cerqueira S, Arismar; Lona, D G; de Oliveira, I; Hernandez-Figueroa, H E; Fragnito, H L

2011-01-15

428

Organic single crystal transistor characteristics of single-crystal phase pentacene grown by ionic liquid-assisted vacuum deposition  

NASA Astrophysics Data System (ADS)

Organic transistor characteristics of single-crystal phase pentacene were investigated. Ionic liquids (ILs) were used as not only a gate dielectric material in the transistors but also a crystallization solvent in vacuum deposition of pentacene. The crystal sizes reached 200 ?m and their surface exhibits a molecularly step-and-terrace structure. There was no sign of IL molecules inside the crystal, and the impurity level of 6,13-pentacenequinone was also reduced. The average value of the field-effect mobility was not so inferior to those for the conventional pentacene single crystals, and the highest value exceeded 5 cm2/Vs, with the on/off current ratio of 104.

Takeyama, Yoko; Ono, Shimpei; Matsumoto, Yuji

2012-08-01

429

Terahertz plasmonics in ferroelectric-gated graphene  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

430

Electro-caloric effect in 0.45BaZr0.2Ti0.8O3-0.55Ba0.7Ca0.3TiO3 single crystal  

NASA Astrophysics Data System (ADS)

Electro-caloric effect in 0.45BaZr0.2Ti0.8O3-0.55Ba0.7Ca0.3TiO3 single crystal has been investigated and electro-caloric coefficient of ~0.38 K mm/kV has been obtained near the tetragonal-to-cubic phase transition. The value obtained is significantly higher than that for the lead-free ferroelectric materials reported so far.

Singh, Gurvinderjit; Bhaumik, Indranil; Ganesamoorthy, S.; Bhatt, R.; Karnal, A. K.; Tiwari, V. S.; Gupta, P. K.

2013-02-01

431

Swimming photochromic azobenzene single crystals in triacrylate solution.  

PubMed

Self-motion of a growing single crystal of azobenzene chromophore in triacrylate solution (TA) is investigated in relation to the solid-liquid phase diagram bound by the solidus and liquidus lines. Upon thermal quenching from the isotropic melt to the crystal + liquid gap, various single crystals develop in a manner dependent on concentration and supercooling depth. During the crystal growth, TA solvent is rejected from the growing faceted fronts, enriching with TA in close proximity to the crystal-solution interface. The concentration gradient that formed as the result of TA expulsion induces convective flows in the solution and generates spatial variability of surface tension usually responsible for Marangoni effect. Either or both of these phenomena may have contributed to the observed self-motion including swimming, sinking, and floating of the azobenzene rhomboidal crystal in TA solution. A stationary rhomboidal crystal is also shown to swim upon irradiation with the UV light because of a mechanical torque generated by the trans-cis isomerization. Judging from the sinking or floating behavior of the azobenzene crystal, it may be inferred that the nucleation occurs at the solution-air interface. PMID:20491490

Milam, Kenneth; O'Malley, Garrett; Kim, Namil; Golovaty, Dmitry; Kyu, Thein

2010-06-17

432

Optical and structural properties of chalcone NLO single crystals  

NASA Astrophysics Data System (ADS)

Organic compound (E)-1-(4-methoxyphenyl)-3-(2,3,5-trichlorophenyl)prop-2-en-1-one [MPTCPP] with molecular formula C16H11Cl3O2 was synthesized using Claisen-Schmidt condensation reaction method. 1H NMR spectra was recorded to identify the various functional groups present in the compound and confirm the chemical structure. The single crystals were grown using slow evaporation solution growth technique. The UV-Visible spectrum study reveals that the crystal is transparent in the entire visible region and the absorption is observed at 364 nm. The Kurtz powder second harmonic generation (SHG) test shows that the MPTCPP is NLO active and its SHG efficiency is three times that of urea. Single crystal XRD study shows that the compound crystallizes in the monoclinic system with a space group Cc. The corresponding lattice parameters of the crystal are a = 28.215(5) Å, b = 3.9740(4) Å, c = 16.178(3) Å and V = 1503.0(4) Å3. The micro hardness test was carried out and the work hardening coefficient value (n) of the crystal was found to be 1.48. This indicates that the crystal is hard and is suitable for device application. The thermal study reveals that the thermal stability of the crystal is good.

Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Manjunath, H. R.; Karegouda, Prakash; Crasta, Vincent; Sridhar, M. A.

2011-11-01

433

Nuclear-magnetic-resonance interaction mechanism in Rb2CoCl4 single crystals with the electric magnetic type  

NASA Astrophysics Data System (ADS)

The 87Rb spin-lattice relaxation time of Rb2CoCl4 single crystals grown using the slow evaporation method was measured using nuclear magnetic resonance. The recovery trace for the central line of 87Rb with dominant magnetic relaxation cannot be represented with a single exponential function, but can be represented with a linear combination of two exponential functions. The change in the 87Rb spin-lattice relaxation rate near Tc1 corresponds to the ferroelectric to incommensurate phase transition. There is a weak anomalous contribution to T1, and this seems to be the only detectable influence of a structural phase transition. The temperature dependence of T1 -1 near Ti is more or less continuous and is not affected by the normal-incommensurate phase transition. For T>Ti, the spin-lattice relaxation rate is governed by molecular motion as described by the Bloembergen-Purcell-Pound theory. This behavior is different to that found for Rb in Rb2ZnCl4. The phase-transition temperatures of the Rb2CoCl4 and Rb2ZnCl4 single crystals are quite similar, but their phase-transition mechanisms are different. The nuclear-magnetic-resonance (NMR) interaction mechanism in Rb2ZnCl4 is well known to be of the electric quadrupolar type whereas in Rb2CoCl4 it is of magnetic origin. Therefore a completely different NMR behavior is obtained in the two crystals.

Lim, Ae Ran; Hong, Kwan Soo

2005-08-01

434

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

SciTech Connect

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

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

2003-05-21

435

Production of Unidirectionally Solidified Columnar Crystal and Single Crystal Superalloy Castings.  

National Technical Information Service (NTIS)

The material selection and casting as well as the properties and heat treatment practices of directionally solidified and single crystal superalloys have been reviewed. The presentation mainly concentrates on the turbine blade castings produced from the n...

J. E. Eklund

1992-01-01

436

Real-time velocity measurement by the use of a speckle-pattern correlation system that incorporates a ferroelectric liquid-crystal spatial light modulator.  

PubMed

We describe a technique for noncontact velocity measurement by using double-exposure speckle-pattern techniques with optical signal processing. The two speckle patterns are recorded on a ferroelectric liquid-crystal (FLC) spatial light modulator (SLM), which is a bistable optically addressed SLM, and the composite pattern is then analyzed by an optical system similar to a joint transform correlator, in which another FLC-SLM and a position-sensitive detector are used. We show that the performance of the system can be significantly improved by adjusting the time between exposures using a real-time feedback system that is based on the position of the correlation spot in the output plane. PMID:20885637

Kobayashi, Y; Takemori, T; Mukohzaka, N; Yoshida, N; Fukushima, S

1994-05-10

437

Phase coexistence and Mn-doping effect in lead-free ferroelectric (Na1/2Bi1/2)TiO3 crystals  

NASA Astrophysics Data System (ADS)

Phase transformations of (001)-cut (Na1/2Bi1/2)TiO3 (NBT) and 1 at. % Mn-doped NBT (Mn-NBT) crystals have been investigated by means of dielectric permittivity, conventional x-ray diffraction (XRD), and high-resolution synchrotron XRD and reciprocal space mapping. An R-R+T-T-C transition sequence was observed in NBT and Mn-NBT upon zero-field heating. R, T, and C are rhombohedral, tetragonal, and cubic phases, respectively. R+T represents that the ferroelastic T phase coexists with the ferroelectric R phase. The Mn dopant can enhance dielectric response and reduce the dielectric loss in the high-temperature region due to the increased degree of ordering.

Tu, C.-S.; Huang, S.-H.; Ku, C.-S.; Lee, H.-Y.; Chien, R. R.; Schmidt, V. H.; Luo, H.

2010-02-01

438

Effect of polymer networks on the smectic-C* phase of a ferroelectric liquid crystal: high-resolution x-ray studies.  

PubMed

High-resolution x-ray diffraction was used to investigate how polymer networks affect the tilt angle in the smectic-C* (SmC*) phase of the ferroelectric liquid crystal 4-[(S,S)-2,3-epoxyhexyloxy]-phenyl-4-(decyloxy)-benzoate (W46 or EPHDBPE). Blends comprising W46, a monomer, and a photoinitiator were prepared and photopolymerized at temperatures that correspond to isotropic and the SmC* phases of W46. When compared to the pure material, the tilt in the SmC* phase was found to decrease in both polymerized samples. The effect, however, is greater for the sample that was polymerized while it was in the SmC* phase. Also, the SmA*-SmC* transition in pure W46 is a weak first-order transition that becomes continuous if traces of polymer are added to W46. PMID:21797387

Singh, Upindranath

2011-06-22

439

Synthesis and Structure Characterization of Forsterite Single Crystal  

NASA Astrophysics Data System (ADS)

Forsterite (Mg2SiO4), the low-pressure polymorph of magnesium orthosilicate, is of great importance in the upper mantle due to its aboundance. Up to now, only powder samples of forsterite can be synthesized due to the difficulty of its crystal growth. Therefore, the exact crystal structure of forsterite is still an open question. The crystal structure of forsterite was firstly studied in 1926 by Brown and Bragg. Numerous experimental investigations have been performed in order to get the structure of the olivine group minerals at ambient conditions and a variety of temperature and pressures by using the advent of the computer, the single crystal diffractometer and the diamond cell. However, there are still considerable uncertaintes regarding the accuracy of its unit-cell parameter values. In this study, we synthesized for the first time high quality single crystals of forsterite using the Quickpress piston-cylinder apparatus. The single crystal of forsterite was synthesized by direct reaction of stoichiometric amounts of MgO and amorphous SiO2 (Alfa Aesar, 99.999%) in the presence of ~10-11 wt% distilled water at 2.0GPa, 1723 K for 12h. A colorless single crystal of Mg2SiO4 with size dimensions 0.16×0.11×0.04 mm was selected for single crystal X-ray diffraction analysis. The intensity data were collected with a Rigaku R-AXIS RAPID IP diffractometer by oscillation scans using graphite- monochromated Mo-K?0?6?0?6?7677?0?6?0?6?7699 radiation (?=0.71073 Å). Cell refinement and data reduction were accomplished with RAPID AUTO program. The crystal structure was solved by direct methods with the SHELXL crystallographic software package. Single crystal X-ray diffraction analysis shows a crystal structure of orthorhombic space group Pnma (No. 62) with a = 10.2073(11) Å, b = 5.9863(5) Å, c = 4.7611(4) Å and Z = 4. Our new data provides new constraints for theoretical investigations of the physical and chemistry properties and behaviors of forsterite under various pressures.

Wang, C.; Jin, S.; Wang, X.; Liu, X.; Fleet, M. E.; Jin, Z.

2006-12-01

440

Enhancing the Mechanical Properties of Single-Crystal CVD Diamond  

SciTech Connect

Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness ({approx}78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

Liang, Q.; Yan, C; Meng, Y; Lai, J; Krasnicki, S; Mao, H; Hemley, R

2009-01-01

441

Method for harvesting rare earth barium copper oxide single crystals  

DOEpatents

A method of preparing high temperature superconductor single crystals is disclosed. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid. 2 figs.

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

1996-04-02

442

Molecular dynamics simulation of shock melting of aluminum single crystal  

NASA Astrophysics Data System (ADS)

Molecular dynamics method in conjunction with multi-scale shock technique is employed to study the melting characteristics of aluminum single crystal under dynamic conditions. The simulated results show that a linear relationship exists between the shock wave velocity and particle velocity, in good agreement with the experimental data. Comparing the Lindemann melting curve with the two Hugoniot curves for the solid and liquid phases, the Hugoniot melting is found to begin at 93.6 GPa and end at 140 GPa, which is consistent with the theoretical calculations. The impact of crystal defects on the melting characteristics of aluminum single crystal is also studied, and the results indicate that the pressure and temperature increase slightly for the system experiencing the same dynamic loading due to the crystal defects.

Ju, Yuanyuan; Zhang, Qingming; Gong, Zizheng; Ji, Guangfu; Zhou, Lin

2013-09-01

443

Ferroelectric Phase Transition in (NH4)3H(SeO4)2  

Microsoft Academic Search

Dielectric properties of single crystal (NH4)3H(SeO4)2 were measured below room temperature. Two phase transitions were found at around +2°C and at -92°C. A lambda-type peak of the dielectric constant along the c-direction is found at -92°C, and the crystal shows ferroelectricity below the transition. The temperature dependence of the spontaneous polarization was measured by a pyroelectric method. The Curie temperature

Kazuo Gesi

1977-01-01

444

Isotropic behavior of an anisotropic material: single crystal silicon  

NASA Astrophysics Data System (ADS)

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

McCarter, Douglas R.; Paquin, Roger A.

2013-09-01

445

Doubling microsecond single pulses in a KTP crystal  

SciTech Connect

The 90{sup 0} phase-matching SHG is performed for microsecond single pulses from a Nd{sup 3+}:YAP laser in a KTP crystal with the 29% conversion efficiency. The 90{sup 0} phase-matching temperature is 54{sup 0}C. The crystal surface damage threshold measured without and with an antireflection coating was 107{+-}11 and 40{+-}4 J cm{sup -2}, respectively. (nonlinear optical phenomena)

Abrosimov, S A; Kochiev, D G [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Grechin, Sergei G [Scientific-Research Institute of Radioelectronics and Laser Technology at the N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Maklakova, N Yu; Semenenko, V N [Institute of Mineralogy and Petrography, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

2001-07-31

446

Acquisition of Single Crystal Growth and Characterization Equipment  

Microsoft Academic Search

Final Report for DOE Grant No. DE-FG02-04ER46178 'Acquisition of Single Crystal Growth and Characterization Equipment'. There is growing concern in the condensed matter community that the need for quality crystal growth and materials preparation laboratories is not being met in the United States. It has been suggested that there are too many researchers performing measurements on too few materials. As

M. Brian Maple; Diego A. Zocco

2008-01-01

447

Infrared Optical Properties of Single Crystals of Tellurium  

Microsoft Academic Search

The fundamental optical absorption and photoconductivity of single crystals of tellurium has been investigated. Tellurium crystals exhibit dichroism in the infrared, i.e., the absorption constant depends on the polarization of the incident radiation. At 300°K for radiation polarized perpendicular to the C axis the absorption edge, located by means of an arbitrary criterion, is at 3.82 microns (0.324 ev); for

Joseph J. Loferski

1954-01-01

448

Thermal properties of single-walled carbon nanotube crystal  

Microsoft Academic Search

In this work, the thermal properties of a single-walled carbon nanotube (SWCNT) crystal are studied. The thermal conductivity of the SWCNT crystal is found to have a linear dependence on temperature in the temperature range from 1.9 K to 100.0 K. In addition, a peak (658 W\\/mK) is found at a temperature of about 100.0 K. The thermal conductivity decreases

Li-Jun Hu; Ji Liu; Zheng Liu; Cai-Yu Qiu; Hai-Qing Zhou; Lian-Feng Sun

2011-01-01

449

Single crystal neutron diffraction study of sodium cyanide  

Microsoft Academic Search

The neutron diffraction pattern of a single crystal of cubic NaCN has been measured at 295°K. These data and earlier results for KCN at 180 and 295°K have been analyzed in terms of a model which expands the angular distribution of CN? orientations in symmetry-adapted spherical harmonics. From this analysis, the distributions of CN? in these crystals have been derived,

J. M. Rowe; D. G. Hinks; D. L. Price; S. Susman; J. J. Rush

1973-01-01

450

Thermal shock cracking of lithium niobate single crystal  

Microsoft Academic Search

The quantitative estimation of failure stress of a lithium niobate (LN) single crystal due to thermal shock was investigated.\\u000a Cylindrical test specimens were used in the thermal shock tests. The thermal stress of an LN test specimen under conditions\\u000a of thermal shock cracking was calculated from a computer program which takes account of the crystal anisotropy, using the\\u000a surface temperature

N. MIYAZAKI; A. HATTORI; H UCHIDA

1997-01-01

451

Single-point diamond turning of DAST crystals  

Microsoft Academic Search

Organic nonlinear optical crystal 4-dimethylamino-N-metyl-4-stilbazolium tosylate (DAST) can be used for new optical devices such as high frequency electro-optical sampling wavelength conversion, submillimeter wave generation, and terahertz-wave generation. The crystal is soft, brittle and hygroscopic so that it is very difficult to get optical surfaces by using conventional optical polishing process. This paper deals with single-point diamond turning for getting

Yoshiharu Namba; Masahiro Tsukahara; Atsuya Fushiki; Koji Suizu; Hiromasa Ito

2004-01-01

452

High Resolution Technique and Instrument for Measuring Lattice Parameters in Single Crystals.  

National Technical Information Service (NTIS)

A method of measuring the lattice parameter in an unknown single crystal by comparing its diffraction angle to a standard single crystal, on a double-crystal diffractometer is disclosed. The method comprises several steps including mounting the unknown an...

M. Fatemi

1990-01-01

453

Crystal growth and characterization of a semiorganic nonlinear optical single crystal of gamma glycine  

NASA Astrophysics Data System (ADS)

Gamma glycine has been successfully synthesized by taking glycine and potassium chloride and single crystals have been grown by solvent evaporation method for the first time. The grown single crystals have been analyzed with XRD, Fourier transform infrared (FTIR), and thermo gravimetric and differential thermal analyses (TG/DTA) measurements. Its mechanical behavior has been assessed by Vickers microhardness measurements. Its nonlinear optical property has been tested by Kurtz powder technique. Its optical behavior was examined by UV vis., and found that the crystal is transparent in the region between 240 and 1200 nm. Hence, it may be very much useful for the second harmonic generation (SHG) applications.

Prakash, J. Thomas Joseph; Kumararaman, S.

2008-11-01

454

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

455

Epitaxial Growth of WOx Nanorod on Single Crystal Tungsten Substrate  

NASA Astrophysics Data System (ADS)

Nanorods of substoichiometric tungsten oxide (WOx) were grown on single crystal tungsten substrate. The grown nanorods were investigated with scanning electron micrope and atomic force microscope. WOx nanorods were grown on W(001) in accordance with epitaxial relationship between WO3 crystals and W(001) surface. The results indicate that the WO3 crystals formed at the initial stage act as the nuclei of WOx nanorods. Nanorod growth of certain epitaxial directions can be selectively enhanced by choosing growth methods or choosing suitable crystallographic orientation of substrate surface.

Shingaya, Yoshitaka; Nakayama, Tomonobu

456

Polymer single crystal meets nanoparticle, toward ordered hybrid materials  

NASA Astrophysics Data System (ADS)

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

Li, Christopher

2009-03-01

457

Growth and characterization of single crystal of pentachloropyridine  

NASA Astrophysics Data System (ADS)

Bulk single crystals of pentachloropyridine (PCP) were grown by the Bridgman Stockbarger method. The single crystalline nature of the grown crystals was confirmed using powder X-ray diffraction (XRD) techniques. These were transparent in the 315 2000 nm range. The second harmonic generation (SHG) efficiency of polycrystalline materials using Kurtz powder technique was found to be twice that of the well-known organic nonlinear optical (NLO) material, urea. The mixing behavior of PCP with succinonitrile (SCN) and its effect on SHG and micro-hardness of PCP, along with the physicochemical properties of different compositions of PCP and SCN system were studied in detail. Bulk single crystals of the PCP solid solution containing 0.02 mole fraction of SCN have also been grown using the Bridgman Stockbarger technique.

Rai, R. N.; Varma, K. B. R.

2005-11-01

458

Synthesis and properties of erbium oxide single crystals  

SciTech Connect

Erbium oxide (Er{sub 2}O{sub 3}, erbia) is a highly stable cubic rare earth oxide with a high melting point of 2,430 C. Because of this, it may have potential applications where high temperature stability and corrosion resistance are required. However, relatively little is known about the properties of this oxide ceramic. The authors have employed a xenon optical floating zone unit with a temperature capability of 3,000 C to grow high quality single crystals of erbia. The conditions for single crystal growth of erbia have been established. The mechanical properties of erbia single crystals have been initially examined using microhardness indentation as a function of temperature.

Petrovic, J.J.; Romero, R.S.; Mendoza, D.; Kukla, A.M.; Hoover, R.C.; McClellan, K.J.

1999-04-01

459

All-glass endless single-mode photonic crystal fibers.  

PubMed

Endless single-mode fibers, which remain single mode over their entire range of guidance, are, to the best of our knowledge, the first reported unique application of photonic crystal fibers. These endless single-mode fibers are made by omitting a single air hole in a periodic array of small air holes in a background silica glass. The feasibility of all-glass endless single-mode photonic crystal fibers where the air holes are replaced by a glass with vanishingly small refractive index contrast relative to silica is first studied theoretically and then demonstrated experimentally. This new all-glass design enables not only ease and consistency of fabrication but also the convenience to be handled and spliced like conventional fibers. PMID:18978880

Dong, Liang; McKay, Hugh A; Fu, Libin

2008-11-01

460

Structural, spectral and mechanical studies of bimetallic crystal: cadmium manganese thiocyanate single crystals  

NASA Astrophysics Data System (ADS)

A nonlinear optical bimetallic thiocyanate complex crystal, cadmium manganese thiocyanate (CMTC) has been successfully synthesized. The growth of single crystals of cadmium manganese thiocyanate has been accomplished from aqueous solution using slow evaporation method. The presence of manganese and cadmium in the synthesized material was confirmed through energy dispersive spectrum (EDS) analysis. Structural analysis was carried out using powder X-ray diffractometer (PXRD) and crystalline perfection of the grown crystals was ascertained by high-resolution X-ray diffraction (HRXRD) analysis. Fourier transform infrared (FTIR) spectrum was taken to confirm the functional groups. The transmittance spectrum of the crystal in the UV-visible region has been recorded and the cutoff wavelength has been determined. The dielectric measurements for the crystals were performed for various frequencies and temperatures. The mechanical properties were evaluated by Vickers microhardness testing, which reveals hardness and stiffness constant of the crystals.

Manikandan, M.; Vijaya Prasath, G.; Bhagavannarayan, G.; Vijayan, N.; Mahalingam, T.; Ravi, G.

2012-09-01