Sample records for ferroelectric single crystal

  1. Single crystal ternary oxide ferroelectric integration with Silicon

    NASA Astrophysics Data System (ADS)

    Bakaul, Saidur; Serrao, Claudy; Youun, Long; Khan, Asif; Salahuddin, Sayeef

    2015-03-01

    Integrating single crystal, ternary oxide ferroelectric thin film with Silicon or other arbitrary substrates has been a holy grail for the researchers since the inception of microelectronics industry. The key motivation is that adding ferroelectric materials to existing electronic devices could bring into new functionality, physics and performance improvement such as non-volatility of information, negative capacitance effect and lowering sub-threshold swing of field effect transistor (FET) below 60 mV/decade in FET [Salahuddin, S, Datta, S. Nano Lett. 8, 405(2008)]. However, fabrication of single crystal ferroelectric thin film demands stringent conditions such as lattice matched single crystal substrate and high processing temperature which are incompatible with Silicon. Here we report on successful integration of PbZr0.2Ti0.8O3 in single crystal form with by using a layer transfer method. The lattice structure, surface morphology, piezoelectric coefficient d33, dielectric constant, ferroelectric domain switching and spontaneous and remnant polarization of the transferred PZT are as good as these characteristics of the best PZT films grown by pulsed laser deposition on lattice matched oxide substrates. We also demonstrate Si based, FE gate controlled FET devices.

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

    NASA Astrophysics Data System (ADS)

    Goyal, Amit; Shin, Junsoo

    2010-03-01

    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 polycrystalline, lead-based compounds on flexible, polycrystalline, copper foils. However, randomly oriented polycrystalline films have a large suppression of ferroelectric properties. In this work we have fabricated single-crystal-like, epitaxial lead-free ferroelectric thin films (BaTiO3 and BiFeO3) on metallic Ni-alloy substrates via pulsed laser deposition. The textures, the microstructure of ferroelectric domains and switching of the local polarization, and the macroscopic polarization hysteresis of the samples were characterized using a 4-circle X-ray diffractometer, piezoresponse force microscopy and spectroscopy and a ferroelectric tester. The performance values obtained are comparable to that reported for ferroelectric films on single crystal substrates..

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

    Microsoft Academic Search

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

    2011-01-01

    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

  4. Ferroelectric properties of tungsten bronze lead barium niobate (PBN) single crystals

    Microsoft Academic Search

    T. R. Shrout; L. E. Cross; D. A. Hukin

    1982-01-01

    A ferroelectric tungsten bronze single crystal of Pb0.33Ba0.70Nb2O6 was grown from a melt using the Czochralski technique. The crystal belongs to the tetragonal point group 4mm with the spontaneous polarization parallel to the ‘c’ axis. The room temperature lattice parameters were a = 12.50 Å and c = 3.995 Å. The spontaneous polarization was found to be 0.40 C\\/m°C. The

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

    SciTech Connect

    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

    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.

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

    PubMed

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

    2014-01-01

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

  7. EPR study of Cu 2+ ions in ferroelectric Rb 2ZnCl 4 single crystals

    NASA Astrophysics Data System (ADS)

    Grecu, N. M.; Lazar, D. P.; Nistor, S. V.; Stefan, M.

    1994-02-01

    EPR spectra attributed to Cu 2+ paramagnetic ions have been observed below T = 130K, in the low-temperature ferroelectric phase of as grown Rb 2ZnCl 4 single crystals doped in the melt with CuCl 2. Their concentration is strongly increased by subsequent X- or ?-ray irradiation at room temperature. The analysis of the EPR spectra shows the Cu 2+ ion to be situated at the distorted, tetrahedrally coordinated Zn 2+ sites.

  8. Landau Theory of Phase Transition in Ferroelectric Vinylidene Fluoride/Trifluoroethylene Copolymer Single Crystals: Hysteresis Loop

    NASA Astrophysics Data System (ADS)

    Iwata, Makoto; Ishibashi, Yoshihiro

    2005-09-01

    Ferroelectric hysteresis loops in vinylidene fluoride/trifluoroethylene, P[VDF/TrFE], copolymer single crystals are discussed on the basis of the Landau-type free energy function with the anisotropy parameter ?2. It was found that the coercive field strongly depends on the value of ?2, and decreases as ?2=0 is approached, because the Landau-type free energy function becomes isotropic in the order parameter space. We successfully reproduced the p-E hysteresis loop with a square shape and a small coercive field in P[VDF/TrFE] on the basis of the Landau theory with the anisotropy parameter ?2.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Shujun; Li, Fei

    2012-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Harker, John Chamberlain

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

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

    PubMed

    Sun, Enwei; Cao, Wenwu

    2014-08-01

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

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

    PubMed

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

    2014-04-23

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

  14. Oxygen Stability and Leakage Current Mechanism in Ferroelectric La-Substituted Bi4Ti3O12 Single Crystals

    Microsoft Academic Search

    Yuji Noguchi; Masayuki Soga; Masatake Takahashi; Masaru Miyayama

    2005-01-01

    We have investigated the effects of La substitution on the oxygen stability, defects, leakage current and polarization properties in ferroelectric bismuth titanate (Bi4Ti3O12) by measuring the properties of single crystals and by ab initio electronic structure calculations. It is shown that electron holes arising from the incorporation of oxygen at oxygen vacancies act as detrimental carriers for leakage current at

  15. Electric field control of magnetism and ferroelectricity in single crystals of multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Kiryukhin, Valery

    2009-03-01

    BiFeO3 is a room-temperature multiferroic combining large electric polarization (P) with long-wavelength spiral magnetic order. Significant efforts have been devoted to studies of thin- film BiFeO3 model multiferroic devices, and local control of magnetization by an electric field has been demonstrated recently. However, the extant thin films consist of a poorly controlled patchwork of ferroelastic domains severely impeding experimental work. We report growth of mm-sized single crystals consisting of a single ferroelectric (FE) domain. Switching between two (out of 8) unique directions of P by an electric field is demonstrated. Magnetic moments are strongly coupled to the lattice, and rotate together with P when the field is applied. Electric field can be used to control the populations of the 3 equivalent magnetic domains with different directions of the spiral wave vector. In particular, a FE monodomain with a single-wave-vector magnetic spiral can be prepared. The spiral has the same helicity in the entire sample. All these effects are reversible. Thus, electric field can be used to control the ferroelectric and magnetic states, and even the magnetic helicity of the sample. This level of control, so far unachievable in thin films, makes single- crystal BiFeO3 a promising object for investigation of physics of magnetoelectric coupling in multiferroics, as well as for model multiferroic device research.

  16. Oxygen-vacancy-induced 90° -domain clamping in ferroelectric Bi4Ti3O12 single crystals

    NASA Astrophysics Data System (ADS)

    Kitanaka, Yuuki; Noguchi, Yuji; Miyayama, Masaru

    2010-03-01

    We have investigated domain clamping in ferroelectric single crystals of Bi4Ti3O12 (BiT) and (Bi3.6La0.4)Ti3O12 (BLT) using polarization measurements along the a(b) axis and piezoresponse force microscopy (PFM). PFM observations reveal that 90° domains are clamped during polarization switching. The crystals of BiT with less oxygen vacancies and BLT exhibited a low volume fraction of the clamped 90° domains. Polarization measurements demonstrate that the clamping of 90° domains decreases the remanent polarization in BiT crystals. These experimental results and ab initio calculations show that an attractive interaction between 90° -domain walls and oxygen vacancies is the main origin of the clamping of 90° domains.

  17. Piezoelectric and ferroelectric properties of lead-free niobium-rich potassium lithium tantalate niobate single crystals

    SciTech Connect

    Li, Jun, E-mail: lijuna@hit.edu.cn [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Li, Yang [Department of chemistry, Harbin Institute of Technology, Harbin 150001 (China); Zhou, Zhongxiang [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Guo, Ruyan; Bhalla, Amar S. [Multifunctional Electronic Materials and Device Research Lab, Department of Electrical and Computer Engineering, The University of Texas at San Antonio, San Antonio 78249 (United States)

    2014-01-01

    Graphical abstract: - Highlights: • Lead-free K{sub 0.95}Li{sub 0.05}Ta{sub 1?x}Nb{sub x}O{sub 3} single crystals were grown using the top-seeded melt growth method. • The piezoelectric and ferroelectric properties of as-grown crystals were systematically investigated. • The piezoelectric properties are very attractive, e.g. for x = 0.60 composition, k{sub t} ? 70%, k{sub 31} ? 70%, k{sub 33} ? 77%, d{sub 31} ? 230 pC/N, d{sub 33} ? 600 pC/N. • The coercive fields of P–E hysteresis loops are quite small, about or less than 1 kV/mm. - Abstract: Lead-free potassium lithium tantalate niobate single crystals with the composition of K{sub 0.95}Li{sub 0.05}Ta{sub 1?x}Nb{sub x}O{sub 3} (abbreviated as KLTN, x = 0.51, 0.60, 0.69, 0.78) were grown using the top-seeded melt growth method. Their piezoelectric and ferroelectric properties in as-grown crystals have been systematically investigated. The phase transitions and Curie temperatures were determined from dielectric and pyroelectric measurements. Piezoelectric coefficients and electromechanical coupling factors in thickness mode, length-extensional mode and longitudinal mode were obtained. The piezoelectric properties are very attractive, e.g. for x = 0.60 composition, k{sub t} ? 70%, k{sub 31} ? 70%, k{sub 33} ? 77%, d{sub 31} ? 230 pC/N, d{sub 33} ? 600 pC/N are comparable to the lead-based PZT composition. The polarization versus electric field hysteresis loops show saturated shapes. In short, lead-free niobium-rich KLTN system possesses comparable properties to those in important lead-based piezoelectric material nowadays.

  18. Polarization fatigue in Pb(Zn1/3Nb2/3)O3-PbTiO3 ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Ozgul, Metin; Takemura, Koichi; Trolier-McKinstry, Susan; Randall, Clive A.

    2001-05-01

    Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) single crystal ferroelectrics have been studied to determine the relative rates of polarization fatigue. It was recently found that ferroelectrics with the rhombohedral phase in the PZN-PT solid solution have essentially no polarization fatigue in the [001]C directions (all of the orientations in this article will be given in terms of the prototype cubic (m3m) axes, denoted by the subscript C). In this study, we expand upon this observation to correlate fatigue rates more completely with respect to composition, orientation, temperature, and electric field strength. It is inferred that an engineered domain state in relaxor based ferroelectric crystals with the spontaneous polarization inclined to the normal of the electrode is associated with negligible or no fatigue at room temperature. However, if thermal history, temperature, or field strength induces a phase transition that produces a polarization parallel to the normal of electrode, these orientations fatigue. The relative fatigue rates are also studied as a function of temperature. In directions, such as [111]C in the ferroelectric rhombohedral phase, the polarization fatigues at room temperature, but as temperature is increased the fatigue rate systematically decreases. This is explained in terms of a thermally activated process that limits the net fatigue rate of ferroelectrics. In summary, this article gives information on the polarization states and orientation that control fatigue in ferroelectric crystals with a relaxor end member.

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

    SciTech Connect

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

    2014-08-04

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

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

    Microsoft Academic Search

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

    2011-01-01

    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

  1. Correlation between number of ferroelectric variants and coercive field of lead ziconate titanate single crystals

    E-print Network

    Chen, Long-Qing

    , and electrostatics. While the values of coercive fields predicted from the phenomenological thermodynamic theory. Theoretically, the coercive field calculated from a phenomenological thermodynamic theory assuming a perfect crystal with a single domain corresponds to the criti- cal field that drives a homogeneously polarized

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

    PubMed Central

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

    2014-01-01

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

  3. Dielectric dispersion of ferroelectric ceramics and single crystals at microwave frequencies

    Microsoft Academic Search

    G. Arlt; U. Böttger; S. Witte

    1994-01-01

    The dielectric constant of ferroelectric ceramics shows strong Debye-like relaxation at GHz frequencies. This relaxation is caused by sound generation inside the crystallites. The ferroelastic domain walls which vibrate in the electric ac field are very effective shear wave transducers. The shear wave emission has a maximum when the wavelength of the sound wave is comparable to the width of

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

    Microsoft Academic Search

    Matthew Davis; Dragan Damjanovic; Nava Setter

    2006-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    1998-04-01

    Using selective chemical etching, scanning electron microscope (SEM) and wave dispersive X-ray (WDX) microanalysis we showed that the ferroelectric domain walls coincide with the maxima and minima Nd-impurity modulation in a periodically poled Nd : Mg : LiNbO 3 crystal grown by the Czochralski method along the normal to the (0 1 1¯ 2) face. Asymmetric form of the Nd-modulation produces nonequal positive and negative domains for one period. Variations of instantaneous rate of growth were estimated for facet and nonfacet crystal region in the framework of Burton-Prim-Slichter theory.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  7. Single-crystal-like, c-axis oriented BaTiO3 thin films with high-performance on flexible metal templates for ferroelectric applications

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

    Epitaxial, c-axis oriented BaTiO3 thin films were deposited using pulsed laser ablation on flexible, polycrystalline Ni alloy tape with biaxially textured oxide buffer multilayers. The high quality of epitaxial BaTiO3 thin films with P4mm group symmetry was confirmed by x-ray diffraction. The microscopic ferroelectric domain structure and the piezoelectric domain switching in these films were confirmed via spatially resolved piezoresponse mapping and local hysteresis loops. Macroscopic measurements demonstrate that the films have well-saturated hysteresis loops with a high remanent polarization of ˜11.5 ?C/cm2. Such high-quality, single-crystal-like BaTiO3 films on low-cost, polycrystalline, flexible Ni alloy substrates are attractive for applications in flexible lead-free ferroelectric devices.

  8. Ferroelectric Liquid Crystal Conglomerates DAVID M. WALBA

    E-print Network

    Walba, David

    Liquid Crystals from Achiral Molecules: Banana Phases 6.1 Bilayer Smectics and First Achiral Antiferroelectric LC 6.2 Bent-Core Mesogens 6.3 Matsunaga Diesters 6.4 Banana Mania 6.5 B4 Phase 6.6 B2 Phase.10 Ferroelectric Banana by Design 6.11 Ferroelectric "Macroscopic Racemate" from Unichiral Mesogen 7 Conclusion

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  10. High-Performance Ferroelectric Bi4Ti3O12 Single Crystals Grown by Top-Seeded Solution Growth Method under High-Pressure Oxygen Atmosphere

    NASA Astrophysics Data System (ADS)

    Kitanaka, Yuuki; Noguchi, Yuji; Miyayama, Masaru

    2010-09-01

    The top-seeded solution growth (TSSG) method under high oxygen pressure (PO2 ) atmosphere has been developed to obtain large high-performance single crystals of ferroelectric Bi4Ti3O12. Crystals grown at 960 °C at a PO2 of 0.9 MPa exhibited well-saturated hysteresis with a remanent polarization of 48 µC/cm2 and a coercive field of 29 kV/cm. The results of piezoresponse force microscopy indicate that polarization switching is accomplished throughout the crystals. Electric-field-induced strain measurements along the a axis yield a piezoelectric constant d11* of 37 pm/V for Bi4Ti3O12.

  11. Optical spectroscopy of a chromium doped (CH 3) 2NH 2Al(SO 4) 2·6H 2O single crystal in the ferroelectric phase

    NASA Astrophysics Data System (ADS)

    Ryba-Romanowski, W.; Go?ab; , S.; Pisarski, W. A.; Podsiad?a, D.; Czapla, Z.

    1997-01-01

    The chromium doped (CH 3) 2NH 2Al(SO 4) 2·6H 2O crystal was obtained from solution by a slow evaporaion method at 303 K and investigated in the ferroelectric phase below 150 K using optical spectroscopy. It was found that the Cr 3+ ions in the crystal are situated in a strong crystal field in which the 2E state is the lowest. A single narrow R line associated with the 2E- 4A 2 phosphorescence indicates an undistorted octahedral Cr 3+ site in the host lattice. The O?H bonds in the first coordination sphere induce efficient nonradiative transitions from the 2E emitting state and the Cr 3+ emission is completely quenched at temperatures above 150 K.

  12. Direct laser-writing of ferroelectric single-crystal waveguide architectures in glass for 3D integrated optics

    PubMed Central

    Stone, Adam; Jain, Himanshu; Dierolf, Volkmar; Sakakura, Masaaki; Shimotsuma, Yasuhiko; Miura, Kiyotaka; Hirao, Kazuyuki; Lapointe, Jerome; Kashyap, Raman

    2015-01-01

    Direct three-dimensional laser writing of amorphous waveguides inside glass has been studied intensely as an attractive route for fabricating photonic integrated circuits. However, achieving essential nonlinear-optic functionality in such devices will also require the ability to create high-quality single-crystal waveguides. Femtosecond laser irradiation is capable of crystallizing glass in 3D, but producing optical-quality single-crystal structures suitable for waveguiding poses unique challenges that are unprecedented in the field of crystal growth. In this work, we use a high angular-resolution electron diffraction method to obtain the first conclusive confirmation that uniform single crystals can be grown inside glass by femtosecond laser writing under optimized conditions. We confirm waveguiding capability and present the first quantitative measurement of power transmission through a laser-written crystal-in-glass waveguide, yielding loss of 2.64?dB/cm at 1530?nm. We demonstrate uniformity of the crystal cross-section down the length of the waveguide and quantify its birefringence. Finally, as a proof-of-concept for patterning more complex device geometries, we demonstrate the use of dynamic phase modulation to grow symmetric crystal junctions with single-pass writing. PMID:25988599

  13. Nickel nanoparticles doped ferroelectric liquid crystal composites

    NASA Astrophysics Data System (ADS)

    Neeraj; Raina, K. K.

    2013-01-01

    With the advance of nanoparticles-liquid crystal composites, it became increasingly interesting to measure the various physical parameters, preferably near the transition temperature. In this research work, fine nickel nanoparticles with 2-8 nm size distribution were synthesized by chemical reduction of nickel hydrazine complex in aqueous solution at 60 °C. A small concentration of 0.5 wt.% of nickel nanoparticles dispersed in a novel ferroelectric liquid crystal mixture showed improved transmittance and fast switching response. Moreover, nickel addition indicates a slight increase in the conductivity of the ferroelectric sample. These studies indicate the occurrence of strong dipole interactions between metallic nanoparticles and ferroelectric liquid crystal molecules in the presence of applied electric field.

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

    PubMed

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

    2010-06-01

    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

  15. Anomalous variations in elastic properties of lead zirconate niobate-lead titanate single crystals in the vicinity of its ferroelectric phase transition

    NASA Astrophysics Data System (ADS)

    Shabbir, G.; Kojima, S.

    2014-03-01

    The acoustic phonon mode anomalies in the paraelectric phase of tetragonal and rhombohedral (1 - x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 single crystals were systematically investigated by Brillouin light scattering measurements. The inverse relaxation time in the paraelectric phase of both crystals showed a stretched-type slowing-down temperature dependence approaching the structural phase transition temperature (T_{\\text{C}}) instead of a normal critical slowing-down. The observed anomalous part of the elastic constant (c_{11}) in the paraelectric phase of the tetragonal crystal in the vicinity of T_{\\text{C}} , exhibited a log(T-T_{0}/T_{0}) -type dependence in the temperature range from T_{\\text{C}} to \\sim T_{\\text{C}}+80\\ ^\\circ \\text{C} . On the other hand, the elastic constant of the rhombohedral ferroelectric crystal exhibited a deviation from such a temperature dependence. This was attributed to the interaction of acoustic phonon modes with strong polarization fluctuations and elastic deformation arising from the complex dynamics of polar nanoregions.

  16. Domain structure evolution and fatigue cracking of <001>-oriented [Pb(Mg1/3Nb2/3)O3]0.67(PbTiO3)0.33 ferroelectric single crystals under cyclic electric loading

    NASA Astrophysics Data System (ADS)

    Fang, F.; Yang, W.; Zhang, F. C.; Qing, H.

    2007-08-01

    The authors report on the electrically induced fatigue cracking and phase transition behavior for ?001?-oriented [Pb(Mg1/3Nb2/3)O3]0.67(PbTiO3)0.33 (PMN-PT 67/33) ferroelectric single crystals under cyclic electric field. For crystals with initial cracks, crack growth and deviation are associated with the transition from the rhombohedral to the tetragonal phase, even though the peak value of the applied cyclic electric field is below the coercive field (Ec). For crystals without initial cracks, numerous microcracks are developed in the crystal as a result of 71° domain switching.

  17. Interplay of ferroelectricity and single electron tunneling

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  18. Impact of Defect Control on the Polarization Properties in Bi4Ti3O12 Ferroelectric Single Crystals

    Microsoft Academic Search

    Yuji Noguchi; Takahiro Matsumoto; Masaru Miyayama

    2005-01-01

    We have investigated the defect structure in bismuth titanate (Bi4Ti3O12) through high-temperature neutron powder diffraction analysis and ab-initio electronic structure calculations. It is shown that the vacancies of Bi and oxide ions are created preferentially in the perovskite layers rather than in the Bi2O2 layers. Measurements of the leakage-current properties of the single crystals demonstrate that electron holes arising from

  19. Novel ferroelectric single crystals of Bi(Zn{sub 1/2}Ti{sub 1/2})O{sub 3}-PbZrO{sub 3}-PbTiO{sub 3} ternary solid solution

    SciTech Connect

    Wang, Bixia; Xie, Yujuan [Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Zhuang, Jian [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049 (China); Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Wu, Xiaoqing; Ren, Wei [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049 (China); Ye, Zuo-Guang, E-mail: zye@sfu.ca [Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049 (China)

    2014-02-28

    Ferroelectric single crystals of a new lead-reduced Bi(Zn{sub 1/2}Ti{sub 1/2})O{sub 3}-PbZrO{sub 3}-PbTiO{sub 3} (BZT-PZ-PT) ternary solid solution system have been grown for the first time by three different methods, namely high temperature solution growth (HTSG, or flux method), top-cooled solution growth (TCSG), and top-seeded solution growth (TSSG). The chemical and thermodynamic parameters, including the flux concentration, the soaking temperature and the cooling rate, have been optimized, leading to the growth of good quality BZT-PZ-PT crystals of pseudo-cubic morphology. A large size crystal of the dimensions of 2?×?2?×?0.5 cm{sup 3} has been obtained by the TSSG technique. The crystal structure is analyzed by means of X-ray powder diffraction. The highest ferroelectric Curie temperature T{sub C} of the grown crystals is found to be 320?°C by means of dielectric measurements. A remnant polarization of 32??C/cm{sup 2} is displayed with a coercive field of 15.4?kV/cm. The high T{sub C} and large coercive field of the BZT-PZ-PT single crystal make this material a promising candidate for applications in high power electromechanical transducers that can operate in a wider temperature range and at high fields.

  20. Permissible symmetries of multi-domain configurations in perovskite ferroelectric crystals

    E-print Network

    Cao, Wenwu

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

  1. Structure and properties of Bi(Zn0.5Ti0.5)O3- Pb(Zr1-?Ti?)O3 ferroelectric single crystals grown by a top-seeded solution growth technique.

    PubMed

    Wang, Bixia; Wu, Xiaoqing; Ren, Wei; Ye, Zuo-Guang

    2015-06-01

    Bi(Zn0.5Ti0.5)O3 (BZT)-modified Pb(Zr1-?Ti?)O3 (PZT) single crystals have been grown using a top-seeded solution growth technique and characterized by various methods. The crystal structure is found to be rhombohedral by means of X-ray powder diffraction. The composition and homogeneity of the as-grown single crystals are studied by laser ablation inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. The domain structure of a (001)cub platelet is investigated by polarized light microscopy (PLM), which confirms the rhombohedral symmetry. The paraelectric-to-ferroelectric phase transition temperature TC is found to be 313°C with the absence of rhombohedral-tetragonal phase transition. The ferroelectric properties of the ternary crystals are enhanced by the BZT substitution with a remanent polarization of 28 ?C/cm(2) and a coercive field EC of 22.1 kV/cm. PMID:26067036

  2. Effects of electron irradiation on the ferroelectric 180° in-plane nanostripe domain structure in a thin film prepared from a bulk single crystal of BaTiO3 by focused ion beam

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takao; Okamoto, Masakuni

    2011-01-01

    Effects of electron irradiation on the ferroelectric 180° in-plane nanostripe domain structure in a thin film prepared from a bulk single crystal of BaTiO3 by focused ion beam were studied. The domain structure transformed into a characteristic 90° in-plane nanostripe domain structure under intense electron irradiation. In particular, an unconventional triangular 90° 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.

  3. Modeling phonon-polariton generation and control in ferroelectric crystals

    E-print Network

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  5. A programmable ferroelectric single electron transistor Vijay Narayanan,2

    E-print Network

    Yener, Aylin

    #12;A programmable ferroelectric single electron transistor Lu Liu,1 Vijay Narayanan,2 and Suman as a suitable candidate for implementing logic with these single electron transistors (SETs).2 Due online 6 February 2013) We experimentally demonstrate a programmable ferroelectric single electron

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

    SciTech Connect

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

    2014-04-14

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

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

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

    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.

  8. A Mesoscopic Electromechanical Theory of Ferroelectric Films and Ceramics

    E-print Network

    Bhattacharya, Kaushik

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

  9. Thermally tunable ferroelectric thin film photonic crystals.

    SciTech Connect

    Lin, P. T.; Wessels, B. W.; Imre, A.; Ocola, L. E.; Northwestern Univ.

    2008-01-01

    Thermally tunable PhCs are fabricated from ferroelectric thin films. Photonic band structure and temperature dependent diffraction are calculated by FDTD. 50% intensity modulation is demonstrated experimentally. This device has potential in active ultra-compact optical circuits.

  10. Optical model of transient light scattering in ferroelectric liquid crystals

    SciTech Connect

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

    2009-03-15

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

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

    E-print Network

    Cao, Wenwu

    the PLZST single crystal a promising candidate for thermal switch and actuator application. VC 2014 AIP, Harbin Institute of Technology, Harbin, Heilongjiang 150080, China 3 Materials Research Institute Publishing LLC. [http://dx.doi.org/10.1063/1.4864317] Antiferroelectric (AFE) materials, in contrast to ferro

  12. CRYSTAL CHEMISTRY OF PEROVSKITE-LIKE LAYER-TYPE FERROELECTRICS

    E-print Network

    Paris-Sud XI, Université de

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

  13. RADIATION DAMAGE EFFECTS IN FERROELECTRIC LiTaO3 SINGLE C. J. WETTELAND, K. E. SICKAFUS, V. GOPALAN, J.N. MITCHELL, T. HARTMANN,

    E-print Network

    Gopalan, Venkatraman

    RADIATION DAMAGE EFFECTS IN FERROELECTRIC LiTaO3 SINGLE CRYSTALS C. J. WETTELAND, K. E. SICKAFUS, V-cut lithium tantalate (LiTaO3) ferroelectric single crystals were irradiated with 200 keV Art ions. LiTaO3 of a LiTaO3 crystal at an irradiation temperature of -120K. This represents a rather exceptional

  14. Electric-field-controlled interface strain coupling and non-volatile resistance switching of La{sub 1-x}Ba{sub x}MnO? thin films epitaxially grown on relaxor-based ferroelectric single crystals

    SciTech Connect

    Zheng, Ming; Zhu, Qiu-Xiang; Li, Xue-Yan; Yang, Ming-Min; Li, Xiao-Min; Shi, Xun; Luo, Hao-Su; Zheng, Ren-Kui, E-mail: zrk@ustc.edu [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Wang, Yu [Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong (China)

    2014-09-21

    We have fabricated magnetoelectric heterostructures by growing ferromagnetic La{sub 1-x}Ba{sub x}MnO? (x=0.2, 0.4) thin films on (001)-, (110)-, and (111)-oriented 0.31Pb(In{sub 1/2}Nb{sub 1/2})O?-0.35Pb(Mg{sub 1/3}Nb{sub 1/2})O?-0.34PbTiO? (PINT) ferroelectric single-crystal substrates. Upon poling along the [001], [110], or [111] crystal direction, the electric-field-induced non-180° domain switching gives rise to a decrease in the resistance and an enhancement of the metal-to-insulator transition temperature TC of the films. By taking advantage of the 180° ferroelectric domain switching, we identify that such changes in the resistance and TC are caused by domain switching-induced strain but not domain switching-induced accumulation or depletion of charge carriers at the interface. Further, we found that the domain switching-induced strain effects can be efficiently controlled by a magnetic field, mediated by the electronic phase separation. Moreover, we determined the evolution of the strength of the electronic phase separation against temperature and magnetic field by recording the strain-tunability of the resistance [(?R/R){sub strain}] under magnetic fields. Additionally, opposing effects of domain switching-induced strain on ferromagnetism above and below 197 K for the La?.?Ba?.?MnO? film and 150 K for the La?.?Ba?.?MnO? film, respectively, were observed and explained by the magnetoelastic effect through adjusting the magnetic anisotropy. Finally, using the reversible ferroelastic domain switching of the PINT, we realized non-volatile resistance switching of the films at room temperature, implying potential applications of the magnetoelectric heterostructure in non-volatile memory devices.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  16. Ga-substitution-induced single ferroelectric phase in multiferroic CuFeO2

    NASA Astrophysics Data System (ADS)

    Terada, N.; Nakajima, T.; Mitsuda, S.; Kitazawa, H.; Kaneko, K.; Metoki, N.

    2008-07-01

    We have succeeded in realizing a single ferroelectric phase in CuFe0.963Ga0.037O2 by substituting nonmagnetic Ga3+ for Fe3+ sites in CuFeO2 . Ferroelectric polarization P in CuFe0.963Ga0.037O2 is observed below 7.5 K, and has the relatively large value of ˜250?C/m2 , which is comparable to P=300˜400?C/m2 in the magnetic-field-induced ferroelectric phase of CuFeO2 . In neutron-diffraction measurements, a single magnetic diffraction peak with an incommensurate wave number was observed below 7.5 K in CuFe0.963Ga0.037O2 , indicating that the ferroelectric-incommensurate (FEIC) phase is realized as a single phase. Therefore, CuFe0.963Ga0.037O2 with a single FEIC phase is strongly expected to provide the best opportunity to investigate unresolved problems regarding the ferroelectric mechanism in CuFeO2 . In this paper, we report measurements of magnetic susceptibility, specific heat, pyroelectric, dielectric constant, and neutron diffraction of a single crystal of CuFe0.963Ga0.037O2 .

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

    SciTech Connect

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

    2014-07-28

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

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

    NASA Astrophysics Data System (ADS)

    Kikuta, Toshio; Yamazaki, Toshinari; Nakatani, Noriyuki

    2010-12-01

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

  19. Photo-aligned ferroelectric liquid crystals in microchannels.

    PubMed

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

    2014-08-15

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

  20. Dispersion and distribution of optical index of refraction in ferroelectric relaxor crystal

    NASA Astrophysics Data System (ADS)

    Li, Chunlai

    This thesis deals with the optical properties of relaxor ferroelectrics with nano/micro polar regions, including their optical frequency dispersion near phase transition, thermo-optical properties, and transmission spectrum analysis. The essential objectives of this thesis work are to deepen the understanding on diffuse phase transition of relaxor ferroelectrics and to obtain practical data for potential optical application from technically important ferroelectrics crystals PBN and PZN-PT. Temperature dependent birefringence and optical refractive indices of PBN (Pb1-xBaxNb2O6) crystal (1-x=0.57) were measured in several optical wavelengths (lambda= 694nm, 633nm, 535nm, and 450nm) to understand the optical frequency dependency of ferroelectric phase transitions in relaxor ferroelectric crystals of tungsten bronze structure. Local polarization is verified to be dynamically activated by thermal process and probed effectively by suitable wavelength of light. An optical isotropic point, as a function of temperature and light frequency, is reported at which the crystal's standing birefringence is fully compensated by polarization. A modified single oscillator model is used to calculate the index of refraction in the ferroelectric phase. The deviation temperature from the single oscillator model is reported to be significantly marking the crossover from macroscopic to microscopic polarization. A new parameter, optical Curie temperature region, defined by the temperature difference between the well known Burns temperature and the deviation temperature (from the single oscillator model for index of refraction) is explored for its significance in depolarization behavior of the micro- to nano-polar regions of the ferroelectric relaxor. Temperature dependent optical indices of refraction of PZN-0.12PT (1-x)PbZn 1/3Nb2/3O3-xPbTiO3, x=0.12, were also studied with emphasis on poling effect. The refractive index n3 decreases as a result of [001] poling. Temperature dependent effective energy of dispersion oscillator E0 and dispersion energy Ed were calculated using single oscillator model and found that E0 and Ed increased by 32% and 60% after [001] poling, respectively. Birefringence of poled PZN-0.12PT also was measured with several frequencies and varying temperature. The polarization derived from refractive index and birefringence were consistent with each other. The remnant polarization was increased by approximately 30% as a result of [001] poling. Transmission spectrum of PZN-0.12PT was measured from near UV to IR for both poled sample and unpoled sample. Transmission was improved significantly after poling. By analyzing the transmission spectrum in the visible range, optical band gap and lattice phonon were determined. The existence of hydrogen in PZN-0.12PT single crystal grown by flux method was postulated based on evidence obtained by FTIR. For accurate and fast birefringence measurement, which is of fundamental importance to device design, quality control, and various sensing functions, a two-dimensional birefringence profiling and analysis system was designed and implemented successfully. Jones matrices of two and three 90° domains are derived and conclude that odd number of stacked 90° domains can be treated as a single 90° domain while even number of stacked 90° domains can be treated as two 90° domains. By rotating analyzer method a test experiment using voltage controllable liquid crystal as sample is demonstrated.

  1. Direct evidence of ferroelastic participation in 180° polarization switching and fatigue for 111 oriented rhombohedral ferroelectric 0.955 Pb(Zn1/3Nb2/3)O3:0.045 PbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Zhu, Wenyi; Cross, L. Eric

    2004-03-01

    Direct elastic deformation measurements taken during polarization reversal in 111 oriented 0.955 Pb(Zn1/3Nb2/3)O3-0.045 PbTiO3 single crystals confirm the observation by W. Cao [Ferroelectrics 290, 107 (2003)] that a ferroelastic reorientation of the domain polarization vectors is involved, and the observed strain changes are consistent with the model he proposed. First cycle nonrecoverable fatigue occurring in our crystals and the associated changes of shape in polarization and strain hysteresis are suggested to be due to microcracking associated with the large very rapid strain changes associate with the ferroelastic switching mode.

  2. Theory of layer structure in ferroelectric liquid crystal devices in applied electric fields M. B. Hamaneh,1

    E-print Network

    Taylor, Philip L.

    Theory of layer structure in ferroelectric liquid crystal devices in applied electric fields M. B sta- bilized ferroelectric liquid crystal SSFLC devices, and in such cases is known as high-field energy of a ferroelectric liquid crystal formed by cooling a sample from the smectic-A phase between

  3. Ferroelectric order in highly disordered molecular-ionic crystals

    NASA Astrophysics Data System (ADS)

    Paja?, Zdzis?aw; Czarnecki, Piotr; Szafra?ska, Barbara; Ma?uszy?ska, Hanna; Fojud, Zbigniew

    2004-04-01

    The ordering of the anionic sublattice at the coexisting high orientational disorder of the cationic sublattice produces spontaneous polarization in imidazolium tetrafluoroborate [C3N2H5]+[BF4]-. This ferroelectric crystal exhibits the Curie point at 297.0 K and undergoes two other polymorphic phase transitions at 213.6 and 187.8 K. In spite of its pentagonal ring the dynamically disordered polar cation is localized at a special position on the threefold axis of the highly symmetrical rhombohedral unit cell. Thus it does not contribute immediately to the spontaneous polarization which originates predominantly from the behavior of the distorted tetrahedral fluoroborate anion.

  4. Quantitative calculation of spontaneous polarization in ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Terzis, Andreas F.; Photinos, Demetri J.; Samulski, Edward T.

    1997-09-01

    We compute the spontaneous polarization, P, exhibited by a class of ferroelectric liquid crystals (FLCs) with systematically varying structures in an effort to critically test a recently proposed model [D. J. Photinos and E. T. Samulski, Science 270, 783 (1995)] which implies that polarity is indigenous to tilted smectic phases. We evaluate the first and second rank segmental order parameters of the FLC compounds by taking into account the essential features of molec-ular structure and conformation subjected to the general stratification constraints in the model smectic FLC. The results compare favorably with available experimental values of P and bond order parameters obtained from NMR measurements.

  5. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    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.

  6. Crystal Growth, Dielectric and Polarization Reversal Properties of Bi4Ti3O12 Single Crystal

    Microsoft Academic Search

    Yoichiro Masuda; Hiroshi Masumoto; Akira Baba; Takashi Goto; Toshio Hirai

    1992-01-01

    A Bi2O3-TiO2 phase diagram was determined using differential thermal analysis (DTA) apparatus. Bi4Ti3O12 (BIT) micalike single crystals grown by a flux method were clear and slightly grayish in color. Ferroelectric and dielectric properties of BIT crystals were observed from measurements of electric displacement vs electric field hysteresis loops and the dielectric constant. Also, the polarization switching characteristics of BIT crystals

  7. A 256 × 256 SRAM-XOR pixel ferroelectric liquid crystal over silicon spatial light modulator

    NASA Astrophysics Data System (ADS)

    Burns, D. C.; Underwood, I.; Gourlay, J.; O'Hara, A.; Vass, D. G.

    1995-02-01

    An electronically addressed spatial light modulator is introduced. It is based on the hybrid technology of ferroelectric liquid crystal over silicon, and comprises an array of 256 × 256 pixels operating at a charge balanced frame rate of up to 2.1 kHz. The pixel circuit, incorporating a static random access memory latch and an exclusive-OR gate, has significant performance advantages over the single transistor design used elsewhere. The silicon backplane has also been used to help develop post-processing planarisation techniques for high fill-factor (84%), optically flat electrode mirrors.

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

    SciTech Connect

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

    2013-09-30

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

  9. Magnetically induced ferroelectricity in single crystalline Lu2CoMnO6

    NASA Astrophysics Data System (ADS)

    Chikara, Shalinee; Singleton, John; Choi, Hwan Young; Lee, Nara; Choi, Young J.; Zapf, Vivien

    2015-03-01

    We present pulsed-magnetic-field measurements on Lu2CoMnO6 single crystals. We are able to resolve electric polarization in single crystals for the first time. The bulk hysteretic magnetization couples to the electric polarization resulting in coupled, hysteretic, multiferroic behavior. The alternating S = 3 / 2 Co2+ and Mn4+ ions sit in a corner-sharing octahedral oxygen environment. The Co-Mn-Co-Mn spins order in an up-up-down-down (uudd) arrangement along the c - axis. The ferroelectricity was believed to originate from the exchange striction due to the uudd spin arrangement. However, recent dielectric measurements suggest polarization along the b - not the c - axis. Our results confirm that ferroelectricity is indeed observed along the b - axis and not along the uudd spin-ordering direction. This indicates a different origin for the multiferroic behavior. The frustrated spin system displays an incommensurate long-wavelength modulation that may play a role in inducing ferroelectricity.

  10. Nuclear Quadrupole Spin-Lattice Relaxation and Critical Dynamics of Ferroelectric Crystals

    Microsoft Academic Search

    G. Bonera; F. Borsa; A. Rigamonti

    1970-01-01

    The effect on the nuclear spin-lattice relaxation of the anomalous temperature dependence of generalized unstable lattice modes near the ferroelectric transition is investigated both theoretically and experimentally. Expressions for the relaxation rate near Tc are derived for typical cases of critical dynamics of ferroelectric crystals. For the case of undamped soft-phonon modes it is shown that, on the basis of

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

    NASA Astrophysics Data System (ADS)

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

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

  12. A theory of triple hysteresis in ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Weng, George J.

    2009-10-01

    In the vicinity of the transition temperature between two ferroelectric states, a ferroelectric crystal could exhibit a triple hysteresis under an ac field. For a BaTiO3 with the "c-plate" configuration slightly below this temperature, the middle loop is caused by the 0°?180° domain switch in the orthorhombic phase, whereas the upper and lower loops are the result of orthorhombic-to-tetragonal phase transition, and vice versa. In this article we first develop a micromechanics-based thermodynamic model to determine the thermodynamic driving force for phase transition and for domain switch as a function of electric field and temperature, and in the latter case, further supplement it with a kinetic equation and a homogenization scheme. The dependence of dielectric constant of the orthorhombic and tetragonal phases on temperature and electric field are also established. The developed theory is then applied to calculate the triple hysteresis loops of BaTiO3 at several levels of temperature. The calculated results for the triple loops, and for the variation of dielectric constant, are found to be in full accord with the test data of Huibregtse and Young [Phys. Rev. 103, 1705 (1956)].

  13. Arnold Schwarzenegger SINGLE CRYSTAL SILICON

    E-print Network

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

  14. Anchoring energy and orientational elasticity of a ferroelectric liquid crystal

    SciTech Connect

    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

    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).

  15. Temperature Dependent Energy Loss of Protons in Barium Titanate Single Crystals

    Microsoft Academic Search

    Khadke Uday Kumar; B. R. Kerur; S. M. Hanagodimath; M. T. Lagare; D. K. Avasthi; A. Mandal

    2005-01-01

    The energy loss of 25 MeV protons in ferroelectric Barium Titanate [BT] single crystals was measured as a function of the temperature of BT with an accuracy of 0.06%. When the protons traversed the crystal along the ferroelectric axis energy loss showed broad fluctuations with a peak-to-peak variation of 5% from the value at room temperature and the energy losses

  16. LIQUID CRYSTALS, 2003, VOL. 30, NO. 1, 8186 Use of a gelator in a ferroelectric liquid crystal

    E-print Network

    Zhao, Yue

    LIQUID CRYSTALS, 2003, VOL. 30, NO. 1, 81­86 Use of a gelator in a ferroelectric liquid crystal September 2002) A new azobenzene-containing gelator for liquid crystals, AG2, was synthesized and used, the aggregation of AG2 occurs in the lower temperature SmA or SmC* phases, and the gelator molecules self

  17. Elastic behavior of PbTiO{sub 3} crystals near ferroelectric phase transition

    SciTech Connect

    Dul`kin, E.A. [Rostov State Univ., Rostov-na-Donu (Russian Federation)

    1995-03-01

    Domain structures arising in multiaxial ferroelectric crystals below the Curie point (T{sub c}) are generally a superposition of the 180{degrees} ferroelectric domains and 180{degrees} mechanical domains (twins). The latter domains are characterized by spontaneous strains directed along different crystallographic axes and form the so called ferroelastic phase within the crystal bulk. The twins in the ferroelectric phase are packed in such a way that the net strain (taking into account the sign of strain in each domain) vanishes in the crystals. The simplest example of such packing has the phase divided into 90{degrees} twins. In this case, the spontaneous strain along the axis normal to the twinning plane is lacking in the crystals. The 90{degrees} twins are typical of perovskite crystals. Therefore, this paper deals with PbTiO{sub 3} crystals. 7 refs., 2 figs.

  18. Neutron Scattering Study of Single Crystal PZT

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Coleman, David Anthony

    2002-08-01

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

  20. 8 MeV electron irradiation effect on the dielectric and optical properties of iminodiacetic acid doped ferroelectric triglycine sulphate crystals

    Microsoft Academic Search

    Chitharanjan Rai; Ganesh Sanjeev; S. M. Dharmaprakash

    2010-01-01

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

  1. Lithium niobate single-crystal and photo-functional device

    DOEpatents

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

    2001-01-01

    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.

  2. Orientation dependence of piezoelectric properties of single domain 0.67Pb,,Mg13Nb23...O3 0.33PbTiO3 crystals

    E-print Network

    Cao, Wenwu

    ­PT ferroelectric single crystals has improved drastically since 1996,1­4 and several complete data sets of PZN Pb(ZrxTi1 x)O3 ceramics, which have been dominating piezoelectric applica- tions for more than 40 structure with crystal symmetry m3¯m. It transforms to ferroelectric rhombohedral phase with 3m symmetry

  3. Ferroelectric domain reversal in congruent LiTaO3 crystals at elevated temperatures

    E-print Network

    Gopalan, Venkatraman

    Ferroelectric domain reversal in congruent LiTaO3 crystals at elevated temperatures Charles C in congruent LiTaO3 crystals with an increase in temperature from 22 to 250 °C. This is accompanied) and lithium tantalate (LiTaO3) into diverse shapes such as gratings, lenses, and prisms has become the basis

  4. Unique single-domain state in a polycrystalline ferroelectric ceramic

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  5. Polarized Raman scattering of multiferroic BiFeO3 single domian crystal and thin film

    Microsoft Academic Search

    R. Palai; H. S. Schmid; R. S. Katiyar

    2008-01-01

    We report the investigation of polarized Raman spectroscopy of multiferroic bismuth ferrite BiFeO3, using a ferroelectric\\/ferroelastic single domain crystal with an as-grown pseudo-cubic (pc) (100)pc surface and (001)pc thin film, grown by pulsed laser deposition. The polarized Raman spectra of the single crystal taken at different crystallographic orientations, agree with the rhombohedral crystal structure with C3v point group, whereas the

  6. Ferroelectric domain wall injection.

    PubMed

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

    2014-01-15

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

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

    PubMed

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

    2012-08-28

    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

  8. Measurements on ferroelectric liquid-crystal spatial light modulators: contrast ratio and speed

    NASA Astrophysics Data System (ADS)

    Collings, N.; Gourlay, J.; Vass, D. G.; Stace, C.; Proudley, G. M.; White, H. J.

    1995-09-01

    The contrast ratio and the speed of a 16 \\times 16 electrically addressed spatial light modulator, composed of a ferroelectric liquid-crystal layer on top of a VLSI silicon backplane, are measured with different methods but consistent results. The results are presented and compared with recently reported results on a similar spatial light modulator [Appl. Opt. 33, 2775 (1994)].

  9. Surface charge regulation of osteogenic differentiation of mesenchymal stem cell on polarized ferroelectric crystal substrate.

    PubMed

    Li, Jianhua; Mou, Xiaoning; Qiu, Jichuan; Wang, Shu; Wang, Dongzhou; Sun, Dehui; Guo, Weibo; Li, Deshuai; Kumar, Anil; Yang, Xuebin; Li, Aixue; Liu, Hong

    2015-05-01

    Polarized ferroelectric crystal lithium niobate wafers with different cuts are selected to offer differently charged surfaces. By induction of the mesenchymal stem cells differentiation into osteoblasts on different charged surfaces, the specific osteogenic-associated markers are assessed and the results illustrate that the positively charged wafer surface enhances rBMMSCs osteogenic differentiation. PMID:25663267

  10. Direct Method with Triangular Waves for Measuring Spontaneous Polarization in Ferroelectric Liquid Crystals

    Microsoft Academic Search

    Keita Miyasato; Shigeharu Abe; Hideo Takezoe; Atsuo Fukuda; Eiichi Kuze

    1983-01-01

    It is proposed to apply the direct measurement of spontaneous polarization using triangular waves to ferroelectric liquid crystals. The use of the triangular waves allows us to easily subtract the background contribution due to the conductive and the capacitive current and to accurately determine the spontaneous polarization, since a bump due to the polarization realignment appears on a straight base

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

    Microsoft Academic Search

    Fedor V. Podgornov; Anna V. Ryzhkova; Wolfgang Haase

    2010-01-01

    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

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

    E-print Network

    Zhao, Yue

    cell whose bulk alignment is induced by rubbed surfaces.4 Alignment has always been an important issuePhotoinduced Alignment of Ferroelectric Liquid Crystals Using Azobenzene Polymer Networks to induce and stabilize a bulk alignment of FLC. Photoinduced reorientation of the FLC can also be achieved

  13. Plasma crystallization of polymer-ferroelectric\\/piezoelectric ceramic composites and their piezoelectric properties

    Microsoft Academic Search

    M. A. Kurbanov; I. S. Sultanakhmedova; É. A. Kerimov; Kh. S. Aliev; G. G. Aliev; G. M. Geidarov

    2009-01-01

    The crystallization of ``polymer-ferroelectric\\/piezoelectric ceramic'' composites under the action of an electric discharge plasma and temperature is investigated. It is shown that this process results in strong oxidation of polymer chains. The oxidation of polymer chains is accompanied by an enhancement of interfacial interactions and an increase in the concentration of charge localization centers or the number of local levels

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

    Microsoft Academic Search

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

    2008-01-01

    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

  15. Longitudinal and transverse pyroelectric effects in a chiral ferroelectric liquid crystal

    NASA Astrophysics Data System (ADS)

    Yablonskii, S. V.; Bondarchuk, V. V.; Soto-Bustamante, E. A.; Romero-Hasler, P. N.; Ozaki, M.; Yoshino, K.

    2015-04-01

    In this study, we compare the results of experimental investigations of longitudinal and transverse pyroelectric effects in a chiral ferroelectric crystal. In a transverse geometry, we studied freely suspended liquid-crystal films. In both geometries, samples exhibited bistability, demonstrating stable pyroelectric signals of different polarities at zero voltage. It is shown that a bistable cell based on a freely suspended film requires 40 times less energy expenditures as compared to the conventional sandwich-type cell.

  16. Quantum ferroelectricity in charge-transfer complex crystals

    PubMed Central

    Horiuchi, Sachio; Kobayashi, Kensuke; Kumai, Reiji; Minami, Nao; Kagawa, Fumitaka; Tokura, Yoshinori

    2015-01-01

    Quantum phase transition achieved by fine tuning the continuous phase transition down to zero kelvin is a challenge for solid state science. Critical phenomena distinct from the effects of thermal fluctuations can materialize when the electronic, structural or magnetic long-range order is perturbed by quantum fluctuations between degenerate ground states. Here we have developed chemically pure tetrahalo-p-benzoquinones of n iodine and 4–n bromine substituents (QBr4–nIn, n=0–4) to search for ferroelectric charge-transfer complexes with tetrathiafulvalene (TTF). Among them, TTF–QBr2I2 exhibits a ferroelectric neutral–ionic phase transition, which is continuously controlled over a wide temperature range from near-zero kelvin to room temperature under hydrostatic pressure. Quantum critical behaviour is accompanied by a much larger permittivity than those of other neutral–ionic transition compounds, such as well-known ferroelectric complex of TTF–QCl4 and quantum antiferroelectric of dimethyl–TTF–QBr4. By contrast, TTF–QBr3I complex, another member of this compound family, shows complete suppression of the ferroelectric spin-Peierls-type phase transition. PMID:26076656

  17. A colloid of ferroelectric nanoparticles in a cholesteric liquid crystal

    Microsoft Academic Search

    O. Kurochkin; O. Buchnev; A. Iljin; S. K. Park; S. B. Kwon; O. Grabar; Yu Reznikov

    2009-01-01

    The introduction of a minor quantity of ferroelectric nanoparticles into a cholesteric mixture causes a 45% decrease of the driving voltage with both the optical cell quality and the director field in the cell remaining undisturbed. The drop of the driving voltage results from a more than twofold increase of the effective dielectric anisotropy of the nematic matrix, which is

  18. Quantum ferroelectricity in charge-transfer complex crystals.

    PubMed

    Horiuchi, Sachio; Kobayashi, Kensuke; Kumai, Reiji; Minami, Nao; Kagawa, Fumitaka; Tokura, Yoshinori

    2015-01-01

    Quantum phase transition achieved by fine tuning the continuous phase transition down to zero kelvin is a challenge for solid state science. Critical phenomena distinct from the effects of thermal fluctuations can materialize when the electronic, structural or magnetic long-range order is perturbed by quantum fluctuations between degenerate ground states. Here we have developed chemically pure tetrahalo-p-benzoquinones of n iodine and 4-n bromine substituents (QBr4-nIn, n=0-4) to search for ferroelectric charge-transfer complexes with tetrathiafulvalene (TTF). Among them, TTF-QBr2I2 exhibits a ferroelectric neutral-ionic phase transition, which is continuously controlled over a wide temperature range from near-zero kelvin to room temperature under hydrostatic pressure. Quantum critical behaviour is accompanied by a much larger permittivity than those of other neutral-ionic transition compounds, such as well-known ferroelectric complex of TTF-QCl4 and quantum antiferroelectric of dimethyl-TTF-QBr4. By contrast, TTF-QBr3I complex, another member of this compound family, shows complete suppression of the ferroelectric spin-Peierls-type phase transition. PMID:26076656

  19. Electro-optic and dielectric studies of silica nanoparticle doped ferroelectric liquid crystal in SmC* phase

    Microsoft Academic Search

    A. Chaudhary; P. Malik; R. Mehra; K. K. Raina

    2011-01-01

    We present the results based on the electro-optic and dielectric properties of silica nanoparticle (SNP) doped ferroelectric liquid crystal (FLC) in SmC* phase. Switching time, spontaneous polarization and rotational viscosity decreases with increase in the silica concentration. An improvement in switching time after doping the silica nanoparticle is due to enhancement in anchoring energy exist between silica nanoparticle and ferroelectric

  20. Electro-optic and dielectric studies of silica nanoparticle doped ferroelectric liquid crystal in SmC* phase

    Microsoft Academic Search

    A. Chaudhary; P. Malik; R. Mehra; K. K. Raina

    2012-01-01

    We present the results based on the electro-optic and dielectric properties of silica nanoparticle (SNP) doped ferroelectric liquid crystal (FLC) in SmC* phase. Switching time, spontaneous polarization and rotational viscosity decreases with increase in the silica concentration. An improvement in switching time after doping the silica nanoparticle is due to enhancement in anchoring energy exist between silica nanoparticle and ferroelectric

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

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan

    2015-03-01

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

  2. Low Frequency Magnetoelectric Interactions in Single Crystal YIG\\/PMN-PT Bilayers

    Microsoft Academic Search

    C. P. Devreugd; G. Srinivasan; J. V. Mantese

    2004-01-01

    This work is concerned with magnetoelectric (ME) coupling in novel layered ferromagnetic-ferroelectric composites. The heterostructures are capable of electric-to-magnetic field conversion that is mediated by mechanical stress [1]. We recently developed a theoretical model for low frequency effects that predicts an order of magnitude enhancement in ME coupling in single crystals compared to polycrystalline samples [2]. Use of single crystals

  3. Single crystal PMN-PT\\/Epoxy 1-3 composite for energy-harvesting application

    Microsoft Academic Search

    Kailiang Ren; Yiming Liu; Xuecang Geng; Heath F. Hofmann; Qiming M. Zhang

    2006-01-01

    One key parameter in using electroactive materials to harvest electric energy from mechanical sources is the energy conversion efficiency. Recently, it was shown that, in the relaxor ferroelectric PMN-PT single crystals, a very high longitudinal electromechanical coupling factor (>90%) can be obtained. This paper investigates energy harvesting using 1-3 composites of PMN-PT single crystals in a soft epoxy matrix. It

  4. Growth and optimization of piezoelectric single crystal transducers for energy harvesting from acoustic sources

    Microsoft Academic Search

    Romit Dhar

    2009-01-01

    Low power requirements of modern sensors and electronics have led to the examination of the feasibility of several energy harvesting schemes. This thesis describes the fabrication and performance of an acoustic energy harvester with single crystal piezoelectric unimorph. The unimorphs were fabricated from single crystal relaxor ferroelectric (1-x)PMN - xPT grown with x = 0.3 and 0.32 as the starting

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

    Microsoft Academic Search

    Seishiro Ide; Kentaro Kobari; Toshihiro Tsuji; Kazushi Yamanaka

    2007-01-01

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

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

    E-print Network

    and Zhiwen Yin Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, People been measured as a function of temperature in relaxor-based ferroelectric single crystals (PbMg1/3Nb2 cluster induced by an external electric field. PMN-34%PT exhibits a nearly normal ferroelectric phase

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

    NASA Astrophysics Data System (ADS)

    Lebedev, A. I.

    2010-07-01

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

  8. Full determination of single ferroelectric nanocrystal orientation by Pockels electro-optic microscopy.

    PubMed

    Trinh, Duc Thien; Mayer, Ludovic; Hajj, Bassam; Lautru, Joseph; Zyss, Joseph; Shynkar, Vasyl

    2015-04-10

    We present a nanoscale electro-optic imaging method allowing access to the phase response, which is not amenable to classical second-harmonic generation microscopy. This approach is used to infer the vectorial orientation of single domain ferroelectric nanocrystals, based on polarization-resolved Pockels microscopy. The electro-optic phase response of KTP nanoparticles yields the full orientation in the laboratory frame of randomly dispersed single nanoparticles, together with their electric polarization dipole. The complete vector determination of the dipole orientation is a prerequisite to important applications including ferroelectric nanodomain orientation, membrane potential imaging, and rotational dynamics of single biomolecules. PMID:25967332

  9. Iminodiacetic acid doped ferroelectric triglycine sulphate crystal: Crystal growth and characterization

    Microsoft Academic Search

    Chitharanjan Rai; B. Narayana Moolya; S. M. Dharmaprakash

    2011-01-01

    Single crystals of iminodiacetic acid (HN(CH2COOH)2) doped triglycine sulphate (IDATGS) crystals have been grown from aqueous solution containing 1–10mol% of iminodiacetic acid at constant temperature by slow evaporation technique. The effects of different amounts of doping entities on the growth habit have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters.

  10. Novel Ferroelectric Liquid Crystal Mode for Active Matrix Liquid Crystal Display Using Cholesteric Chiral Smectic C Phase Transition Material

    Microsoft Academic Search

    Yasufumi Asao; Takeshi Togano; Masahiro Terada; Takashi Moriyama; Shinichi Nakamura; Jun Iba

    1999-01-01

    We propose a novel ferroelectric liquid crystal (FLC) mode which is capable of gray-scale display with an active device such as a thin-film transistor (TFT). This technology is based on the monostable FLC mode, which is obtained from a material with cholesteric chiral smectic C (Ch SmC*) phase transition sequences and by applying a low DC voltage only near the

  11. Real-Time Optical Aberration Correction with a Ferroelectric Liquid-Crystal Spatial Light Modulator

    NASA Astrophysics Data System (ADS)

    Birch, Philip M.; Gourlay, James; Love, Gordon D.; Purvis, Alan

    1998-04-01

    Real-time correction of an optically aberrated wave front by use of a 10 10 ferroelectric liquid-crystal spatial light modulator as the correction device and a point-diffraction interferometer as the wave-front sensor is demonstrated. This type of interferometer requires no reference arm and so can be used, in theory, in an astronomical adaptive-optics system. We discuss some of the unusual features of the point-diffraction interferometer for wave-front sensing.

  12. Plasma crystallization of polymer-ferroelectric\\/piezoelectric ceramic composites and their piezoelectric properties

    Microsoft Academic Search

    M. A. Kurbanov; I. S. Sultanakhmedova; É. A. Kerimov; Kh. S. Aliev; G. G. Aliev; G. M. Ge?darov

    2009-01-01

    The crystallization of “polymer-ferroelectric\\/piezoelectric ceramic” composites under the action of an electric discharge\\u000a plasma and temperature is investigated. It is shown that this process results in strong oxidation of polymer chains. The oxidation\\u000a of polymer chains is accompanied by an enhancement of interfacial interactions and an increase in the concentration of charge\\u000a localization centers or the number of local levels

  13. Ferroelectric-like response from the surface of SrTiO? crystals at high temperatures

    SciTech Connect

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

    2014-09-14

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

  14. Single Crystal Surfaces

    NASA Astrophysics Data System (ADS)

    Aguilar-Santillan, Joaquin

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  16. Aging and memory effect in magnetoelectric gallium ferrite single crystals

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    E-print Network

    Cao, Wenwu

    %PT ferroelectric single crystals poled along 111 c has been analyzed theoretically. We found. doi:10.1063/1.3271775 Relaxor-based ferroelectric single crystals 0.67Pb Mn1/3Nb2/3 O3-0.33PbTiO3 PMN that of the best modi- fied Pb ZrxTi1-x O3 PZT ceramics. PMN-33%PT crystals are now commercially available

  19. In-situ monitoring of periodic domain formation in ferroelectric crystals

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

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

  20. Critical Property in Relaxor-PbTiO(3) Single Crystals --- Shear Piezoelectric Response.

    PubMed

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

    2011-06-01

    The shear piezoelectric behavior in relaxor-PbTiO(3) (PT) single crystals is investigated in regard to crystal phase. High levels of shear piezoelectric activity, d(15) or d(24) >2000 pC N(-1), has been observed for single domain rhombohedral (R), orthorhombic (O) and tetragonal (T) relaxor-PT crystals. The high piezoelectric response is attributed to a flattening of the Gibbs free energy at compositions proximate to the morphotropic phase boundaries, where the polarization rotation is easy with applying perpendicular electric field. The shear piezoelectric behavior of pervoskite ferroelectric crystals was discussed with respect to ferroelectric-ferroelectric phase transitions and dc bias field using phenomenological approach. The relationship between single domain shear piezoelectric response and piezoelectric activities in domain engineered configurations were given in this paper. From an application viewpoint, the temperature and ac field drive stability for shear piezoelectric responses are investigated. A temperature independent shear piezoelectric response (d(24), in the range of -50°C to O-T phase transition temperature) is thermodynamically expected and experimentally confirmed in orthorhombic relaxor-PT crystals; relatively high ac field drive stability (5 kV cm(-1)) is obtained in manganese modified relaxor-PT crystals. For all thickness shear vibration modes, the mechanical quality factor Qs are less than 50, corresponding to the facilitated polarization rotation. PMID:21960942

  1. Critical Property in Relaxor-PbTiO3 Single Crystals --- Shear Piezoelectric Response

    PubMed Central

    Xu, Zhuo; Wei, Xiaoyong; Shrout, Thomas R.

    2011-01-01

    The shear piezoelectric behavior in relaxor-PbTiO3 (PT) single crystals is investigated in regard to crystal phase. High levels of shear piezoelectric activity, d15 or d24 >2000 pC N?1, has been observed for single domain rhombohedral (R), orthorhombic (O) and tetragonal (T) relaxor-PT crystals. The high piezoelectric response is attributed to a flattening of the Gibbs free energy at compositions proximate to the morphotropic phase boundaries, where the polarization rotation is easy with applying perpendicular electric field. The shear piezoelectric behavior of pervoskite ferroelectric crystals was discussed with respect to ferroelectric-ferroelectric phase transitions and dc bias field using phenomenological approach. The relationship between single domain shear piezoelectric response and piezoelectric activities in domain engineered configurations were given in this paper. From an application viewpoint, the temperature and ac field drive stability for shear piezoelectric responses are investigated. A temperature independent shear piezoelectric response (d24, in the range of ?50°C to O-T phase transition temperature) is thermodynamically expected and experimentally confirmed in orthorhombic relaxor-PT crystals; relatively high ac field drive stability (5 kV cm?1) is obtained in manganese modified relaxor-PT crystals. For all thickness shear vibration modes, the mechanical quality factor Qs are less than 50, corresponding to the facilitated polarization rotation. PMID:21960942

  2. Enhancement of the electromechanical response in ferroelectric ceramics by design

    E-print Network

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

    2010-01-01

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

  3. Piezoelectric and pyroelectric coefficients for ferroelectric crystals with polarizable molecules

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  4. Boundary layer elasto-optic switching in ferroelectric liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.

    1992-01-01

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

  5. Ellipsometric structural studies of ground state synclinic and anticlinic ferroelectric liquid crystal films*

    NASA Astrophysics Data System (ADS)

    Olson, D. A.; Johnson, P. M.; Pankratz, S.; Cady, A.; Huang, C. C.; Bahr, Ch.; Goodby, J. W.

    2000-03-01

    A novel ellipsometric technique is used to resolve details of the surface induced molecular tilt structures in freestanding liquid crystal films above the SmA-SmC* transition with electric fields that range from 0 to 300V/cm. Below a critical field, either a synclinic or anticlinic surface structure may be present depending on the compound characteristics. Compounds with relatively large ferroelectric polarizations enter an anticlinic state with no applied field. Above a critical field the film changes from anticlinic to synclinic. Compounds with relatively small ferroelectric polarization go into a synclinic state with no applied field; a large applied field may cause these compounds to switch to an anticlinic state. Ellipsometric parameters are measured at a variety of structural orientations. * NSF DMR97-03898

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

    E-print Network

    Gopalan, Venkatraman

    for vertical and lateral piezoelectric force microscopy PFM profiles of a single ferroelectric domain wall. 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

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

    E-print Network

    Chen, Long-Qing

    -out schemes (6, 7). Applications of ferroelectric and multiferroic materials in nanoscale devices necessitate in multiferroic BiFeO3 is studied on a single-domain level by using piezoresponse force spectroscopy. Variation ordering in multiferroic ma- terials and self-assembled nanostructures has recently propelled

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

    SciTech Connect

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  10. Scanning Nonlinear Dielectric Microscopy Nano-Science and Technology for Next Generation High Density Ferroelectric Data Storage

    NASA Astrophysics Data System (ADS)

    Tanaka, Kenkou; Kurihashi, Yuichi; Uda, Tomoya; Daimon, Yasuhiro; Odagawa, Nozomi; Hirose, Ryusuke; Hiranaga, Yoshiomi; Cho, Yasuo

    2008-05-01

    An investigation of ultrahigh-density ferroelectric data storage based on scanning nonlinear dielectric microscopy (SNDM) is described. To obtain fundamental knowledge of high-density ferroelectric data storage, several studies of nanodomain formation in a congruent lithium tantalate single crystal were conducted. This paper is a summary report consisting of the most recent experimental data from investigations of ferroelectric high density data storage.

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

    NASA Astrophysics Data System (ADS)

    Podgornov, Fedor V.; Ryzhkova, Anna V.; Haase, Wolfgang

    2010-11-01

    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.

  12. Plasma crystallization of polymer-ferroelectric/piezoelectric ceramic composites and their piezoelectric properties

    NASA Astrophysics Data System (ADS)

    Kurbanov, M. A.; Sultanakhmedova, I. S.; Kerimov, É. A.; Aliev, Kh. S.; Aliev, G. G.; Ge?darov, G. M.

    2009-06-01

    The crystallization of “polymer-ferroelectric/piezoelectric ceramic” composites under the action of an electric discharge plasma and temperature is investigated. It is shown that this process results in strong oxidation of polymer chains. The oxidation of polymer chains is accompanied by an enhancement of interfacial interactions and an increase in the concentration of charge localization centers or the number of local levels in the quasi-band gap of the polymer phase, which upon polarization leads to an increase in interfacial charges. These charges and oxidation of polymer chains favor the effective polarization of piezoelectric phase domains and, hence, an increase in the piezoelectric parameters of the composite.

  13. Helix unwinding in ferroelectric liquid crystals induced by tilted electric field

    NASA Astrophysics Data System (ADS)

    Nail, G. Migranov; Aleksey, A. Kudreyko

    2015-07-01

    Helix unwinding in ferroelectric liquid crystals induced by an electric field is theoretically studied on the basis of the continuum theory. By applying a weak electric field tilted to the smectic layers, the contribution of the dielectric interaction energy density to the total free energy density is increased. Approximation methods are used to calculate the free energy for different tilt angles between the electric field and the smectic layers. The obtained results suggest selecting the optimal number of pitches in the film that matches to the minimum of the free energy. Project supported by the Russian Foundation for Basic Research (RFBR) (Grant No. 14-02-97026).

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

    SciTech Connect

    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

    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.

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

    PubMed

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

    2009-07-01

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

  16. Direct and simultaneous observation of ferroelectric and magnetic domains

    Microsoft Academic Search

    H. Z. Song; Y. X. Li; K. Y. Zhao; H. R. Zeng; S. X. Hui; G. R. Li; Q. R. Yin

    2009-01-01

    The ferroelectric\\/magnetic domain structure in a magnetoelectric binding BaTiO3\\/Fe81Ga19 and the ferroelectric\\/crystallographic domain structure in a magnetoelectric binding PMN-34PT\\/Mn50Ni28Ga22 were observed successfully by scanning electron acoustic microscopy (SEAM). Both the stripe ferroelectric domains in single crystals and the stripe magnetic domains in polycrystalline grains are obtained simultaneously, which exhibits that the scanning electron acoustic microscopy is a unique imaging technique.

  17. Chiral selectivity of improper ferroelectricity in single-wall PbTiO3 nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Xu, Tao; Shimada, Takahiro; Wang, Xiaoyuan; Zhang, Tong-Yi; Kitamura, Takayuki

    2014-04-01

    Full density functional theory calculations successfully demonstrate that a remarkable spontaneous polarization can stably exist in extremely thin PbTiO3 single-wall nanotubes (PTO-SWNTs) folded from (110) nanosheets with a specific chirality of (m, 0), whereas ferroelectricity is absent from nanotubes with other chiralities and from the unfolded thin films. In other words, there is chiral selectivity of ferroelectricity. The chirality of the ferroelectric (FE) nanotubes plays a variety of significant roles in (i) the stabilization of a low-energy single-wall tubular structure, (ii) the emergence of antiferrodistortive (AFD) distortion hidden in the PbTiO3 bulk, and (iii) the strong coupling between FE and emergent AFD distortions. The direct FE-AFD coupling stabilizes the remarkable FE distortion in these ultrathin nanotubes through tilting of oxygen octahedra, suggesting improper ferroelectricity. The existence of a large spontaneous polarization suggests that PTO-SWNTs hold promise for applications in advanced sensors and nanoscale energy-harvesting devices.

  18. Single Crystals of Single-Walled Carbon Nanotubes Formed by

    E-print Network

    Gimzewski, James

    -assembly of single crystals of single-walled carbon nano- tubes (SWCNTs) using thermolysis of nano of carbon nanotube fabrication is to form large uniform and ordered nano- and microstructuresSingle Crystals of Single-Walled Carbon Nanotubes Formed by Self-Assembly R. R. Schlittler,1 J. W

  19. Comment on "Single Crystals of Single-Walled Carbon Nanotubes

    E-print Network

    Kono, Junichiro

    et al. (1) reported the production of single crystals of single-walled carbon nano- tubes (SWCNTsComment on "Single Crystals of Single-Walled Carbon Nanotubes Formed by Self-Assembly" Schlittler) by the thermolysis of nano- patterned structures of alternating layers of C60 and nickel. Electron diffraction, high

  20. Electric field effects on the phase transitions in 001-oriented ,,1x...Pb,,Mg13Nb23...O3-xPbTiO3 single crystals with compositions near the morphotropic phase boundary

    E-print Network

    Cao, Wenwu

    this shift under 1 kV dc bias along 001 . A transition between the normal ferroelectric and relaxor states of the frequency dispersion at a lower temperature. This relaxor-ferroelectric transition was found to be thermally-PT ceramics, which may not be applicable to single crystals due to the fact that many properties are highly

  1. High strength single crystal superalloys

    SciTech Connect

    Chin, S.; Duhl, D.N.

    1990-03-13

    This patent describes an alloy composition suitable for casting into a single crystal nickel base superalloy article. It comprises, on a weight percent basis, 4-5.5 Cr, 7.5-12 Co, 1.5-2.5 Mo, 1-6 W, 2-4 Re, 4.5-5.5 Al, 0.5-1.5 Ti, 8-12 Ta, 0-1 V, 0-0.5 Hf, 0.0-0.01 B, 0.0-0.2 Cb, 0.0-0.05 C, 0.0-0.01 Zr, with the balance nickel.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  3. Feature article Novel polymer ferroelectric behavior via crystal isomorphism and the

    E-print Network

    Taylor, Philip L.

    ] behavior in ceramics, RFE and double-hysteresis-loop (DHL) behavior in crystalline ferroelectric polymers behavior is observed. Obviously, the physics for ferroelectric polymers is different from that for ceramics nonlinear dielectric properties Different from ceramic ferroelectrics, ferroelectric (FE) polymers represent

  4. Cascaded electro-optic scanning of laser light over large angles using domain microengineered ferroelectrics

    E-print Network

    Gopalan, Venkatraman

    in a single crystal wafer of ferroelectric LiTaO3 . By operating the device using a specially designed to a maximum of 10°­15° as demonstrated in LiTaO3 .9 In this letter, we propose and demonstrate the con- cept,10 In a uniaxial ferroelectric crystal such as LiNbO3 or LiTaO3 with its ferroelectric polarization Ps along

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

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.

    1991-01-01

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

  6. Polarization elasticity in a ferroelectric smectic liquid crystal film

    NASA Astrophysics Data System (ADS)

    Zhu, Chenhui; Pattanaporkratana, Apichart; Maclennan, Joseph; Link, Darren; Pang, Jinzhong; Clark, Noel

    2014-03-01

    Topological +1 and -1 point defects were induced in freely suspended smectic-C crystal films by quickly bending the film by air pressure so that the film momentarily enters SmA phase and relaxes back to the SmC phase. The symmetry breaking in this process spontaneously generates many pairs of topological point defects in the film. We report that the molecular organization of -1 defects is drastically different in high polarization smectic-C films from that in achiral or racemic smectic-C films. Such -1 defect structure can be tuned by ion concentration in the materials, and the enantiomeric excess in the mixture of left-hand and right hand chiral smectic-C. This novel behavior can be understood by considering both an effective increase in Frank elastic constants due to polarization splay and the electrostatic interaction between spatial charges generated by polarization splay which is geometrically enforced in -1 defect. Results on the annihilation of +1 and -1 defect pairs will also be presented. Funding provided by MRSEC Grant No. NSF DMR 0820579. DMR 0820579

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

    Microsoft Academic Search

    Guntis Liberts; Girts Ivanovs; Vilnis Dimza; Edmunds Tamanis

    2005-01-01

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

  8. Electrical Conduction Mechanism in Bi4Ti3O12 Single Crystal

    Microsoft Academic Search

    Masatake Takahashi; Yuji Noguchi; Masaru Miyayama

    2002-01-01

    To reveal the influence of lattice defects on electrical conduction of bismuth titanate (Bi4Ti3O12: BIT), one of the bismuth layer structured ferroelectrics, changes in lattice parameters and weight by high-temperature annealing and the dependence of conductivity on oxygen partial pressure (Po2) were examined for BIT powders and single crystals, respectively. Decrease in lattice parameters and weight loss by annealing suggested

  9. Precise determination of phonon constants in lead-free monoclinic (K0.5Na0.5)NbO3 single crystals

    NASA Astrophysics Data System (ADS)

    Asif Rafiq, Muhammad; Supancic, Peter; Elisabete Costa, M.; Vilarinho, Paula M.; Deluca, Marco

    2014-01-01

    A polarized Raman analysis of ferroelectric (K0.5Na0.5)NbO3 (KNN) single crystals is presented. The Raman modes of KNN single crystals are assigned to the monoclinic symmetry. Angular-dependent intensities of A', A?, and mixed A' + A? phonons have been theoretically calculated and compared with the experimental data, allowing the precise determination of the Raman tensor coefficients for (non-leaking) modes in single-domain monoclinic KNN. This study is the basis for non-destructive assessments of domain distribution by Raman spectroscopy in KNN-based lead-free ferroelectrics.

  10. Writing and probing light-induced waveguides thanks to an endlessly single-mode photonic crystal fiber.

    PubMed

    Huy, Kien Phan; Safioui, Jassem; Guichardaz, Blandine; Devaux, Fabrice; Chauvet, Mathieu

    2012-07-01

    We demonstrate writing and probing of light-induced waveguides in photorefractive bulk LiNbO3 crystal using an endlessly single-mode photonic crystal fiber. The optical waveguides are written at visible wavelengths by slightly raising the ferroelectric crystal temperature to benefit from the pyroelectric-driven photorefractive effect and the guiding properties are investigated at telecom wavelengths using the same photonic crystal fiber. End butt coupling with this photonic crystal fiber enables writing and probing of optical waveguides due to the self-alignment properties of spatial solitons. PMID:22772107

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    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.

  12. 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)

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

    2013-07-01

    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.

  13. Growth of single crystal diamond

    NASA Astrophysics Data System (ADS)

    Regmi, Murari

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

  14. Formulation of a room temperature ferroelectric liquid crystal mixture with sub-millisecond switching time

    NASA Astrophysics Data System (ADS)

    Debnath, A.; Sinha, D.; Mandal, P. K.; Dabrowski, R.

    2015-06-01

    Ferroelectric liquid crystal (FLC) based display devices show faster response compared to nematic LC based devices. Since pure FLC compounds are high temperature LCs and do not possess optimum parameters necessary for display devices, a room temperature FLC mixture has been formulated, first time by any Indian group. The mixture is prepared by doping an appropriate chiral compound in a four-component LC based achiral host mixture. Resulting mixture was characterized using optical polarizing microscopy, frequency domain dielectric spectroscopy and electro-optic methods. It shows very wide range ferroelectric SmC* phase followed by paraelectric SmA* phase (Cr< 19°CSmC*89°C SmA* 108°C I) which would facilitate attaining book shelf geometry alignment in display devices. Dielectric spectroscopy study reveals Goldstone (in kHz region) and soft mode (in hundred kHz region) relaxations in SmC* and SmA* phases respectively. The mixture possesses moderate tilt angle (34.5° - 13°), low viscosity (0.9 - 0.05 N.s.m-2) and moderately high spontaneous polarization (112 - 36 nC.cm-2) which decrease with temperature. These result in very fast switching, slowest response time being 475 µs at ambient temperature.

  15. Electronic conduction through single crystals of polyethylene 

    E-print Network

    Samson, Gerald Maurice

    1966-01-01

    la-slier growths by crystallizing the polymer from dilute solutions in benzene and xylene. Since that tine, solut'on-grown lamellar single crystals have been identified for a rumber of other polymers. 5 All solution-grown polymer single crystals... lower . e""perctures thc a?-'or contribu ion . o che current is probably "eld omission (tunneling). Solution-grown single crystals we c deposi lcd upon s. microscope slide coated w' th a thin layer of otal, which served as o. . c electrode. he counter...

  16. Bragg reflector waveguide array with ferroelectric liquid crystal cladding for optical tunable wavelength filters

    NASA Astrophysics Data System (ADS)

    Nakatsuhara, Katsumi; Kato, Akifumi; Hayama, Yoshiki

    2014-08-01

    A tunable wavelength filter array is proposed, which consists of a 1 × 6 multimode interferometer silicon waveguide splitter and Bragg reflector waveguides with ferroelectric liquid crystal (FLC) cladding. The transmission characteristics of the proposed device were reported, which were theoretically and experimentally obtained. Different operating wavelengths were obtained by using different waveguide widths with the same grating period. The stop bandwidth we obtained with a sampled grating was narrower than that in conventional uniform grating structures. Bistable tuning operation with a 0.8 nm shift in wavelength characteristics, which had six different Bragg wavelengths, was demonstrated. The distribution of the optical axis in the FLC cladding layer was also measured using a system for birefringence measurements.

  17. Optically switchable grating based on dye-doped ferroelectric liquid crystal with high efficiency.

    PubMed

    Kim, Jiyoon; Suh, Jeng-Hun; Lee, Bo-Yeon; Kim, Se-Um; Lee, Sin-Doo

    2015-05-18

    We demonstrate an all-optically switchable ferroelectric liquid crystal (FLC) grating constructed in an alternating binary configuration with different optical properties from domain to domain. A dye-doped FLC is uniformly aligned in one type of domains whereas it is infiltrated into the photo-polymerized networks of reactive mesogens in the other. Compared to conventional nematic LC cases, our FLC grating allows more efficient all-optical modulation and faster diffraction switching between the 0th and the 1st orders in subsecond since the optical response associated with the dye molecules in the layered state is less hindered than in the orientationally ordered state. Our dye-doped FLC grating with periodically infiltrated structures will be useful for designing a new class of all-optically switching systems. PMID:26074517

  18. Micro-patterned photo-aligned ferroelectric liquid crystal Fresnel zone lens.

    PubMed

    Srivastava, A K; Wang, X; Gong, S Q; Shen, D; Lu, Y Q; Chigrinov, V G; Kwok, H S

    2015-04-15

    In this Letter, we disclose a fast switchable Fresnel zone lens (FZL) by confining the ferroelectric liquid crystals (FLCs) in multiple microscopically defined photo-aligned alignment domains. The photo-alignment (PA) offers good control on the anchoring energy (W) by mean of irradiation doses (ID) and thus excellent alignment for FLCs. Two operational modes of the FLCFZL, i.e., FOCUS/OFF and FOCUS/DEFOCUS, were demonstrated. The proposed diffracting element provides fast response time, high diffraction efficiency (?), with saturated electro-optical (EO) operations up to high frequency (?2??kHz). Thus, the proposed FLCFZLs with simple fabrication open several opportunities to improve the quality of existing devices and to find new applications. PMID:25872037

  19. Single crystal PMN-PT/epoxy 1-3 composite for energy-harvesting application.

    PubMed

    Ren, Kailiang; Liu, Yiming; Geng, Xuecang; Hofmann, Heath F; Zhang, Qiming M

    2006-03-01

    One key parameter in using electroactive materials to harvest electric energy from mechanical sources is the energy conversion efficiency. Recently, it was shown that, in the relaxor ferroelectric PMN-PT single crystals, a very high longitudinal electromechanical coupling factor (>90%) can be obtained. This paper investigates energy harvesting using 1-3 composites of PMN-PT single crystals in a soft epoxy matrix. It is shown that 1-3 composites enable the single crystals operating in the longitudinal mode to achieve high efficiency for energy harvesting, and the soft-polymer, matrix-supported single-crystal rods maintain high mechanical integrity under different external loads. For comparison, 1-3 composites with piezoceramic PZT also are investigated in energy-harvesting applications, and the results show that the high coupling factor of single crystal PMN-PT 1-3 composites leads to much higher electric energy output for similar mechanical energy input. The harvested energy density of 1-3 composite with single crystal (22.1 mW/cm3 under a stress of 40.4 MPa) is about twice of that harvested with PZT ceramic 1-3 composite (12 mW/cm3 under a stress of 39 MPa). At a higher stress level, the harvested-energy density of 1-3 PMN-PT single crystal composite can reach 96 mW/cm3. PMID:16555772

  20. Ferroelectric-gated terahertz plasmonics on graphene

    E-print Network

    Jin, Dafei

    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 ...

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

    Microsoft Academic Search

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

    2011-01-01

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

  2. Improved ferroelectric and pyroelectric parameters in iminodiacetic acid doped TGS crystal

    Microsoft Academic Search

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

    2010-01-01

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

  3. Ferroelastic and ferroelectric phase transition in a molecular crystal : tanane 1. Neutron and Brillouin scattering studies of the acoustic and pseudo-spin

    E-print Network

    Paris-Sud XI, Université de

    coefficients, elastic constants, ...). A phase change in a pure molecular crystal may also induce dielectric phase transitions in molecular crystals [1]. A number of those include a change in molecular dynamics1375 Ferroelastic and ferroelectric phase transition in a molecular crystal : tanane 1. Neutron

  4. Ferroelectric domain wall motion induced by polarized light.

    PubMed

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

    2015-01-01

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

  5. Ferroelectric domain wall motion induced by polarized light

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  7. Growth of Sillenite-Structure Single Crystals

    Microsoft Academic Search

    V. M. Skorikov; Yu. F. Kargin; A. V. Egorysheva; V. V. Volkov; M. Gospodinov

    2005-01-01

    The main processes for preparing bulk single crystals and films of photorefractive and piezoelectric Bi12MxO20±? (M = Group II–VIII elements) sillenite compounds are considered. Experimental data are summarized on the crystal growth of\\u000a Bi12MxO20±? from the melt and under hydrothermal conditions, and the key morphological features of sillenites are analyzed. Various types\\u000a of macroscopic growth defects in sillenite-type crystals are

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

    Microsoft Academic Search

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

    2004-01-01

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

  9. The Remanent Magnetization of Haematite Single Crystals

    Microsoft Academic Search

    T. E. Gallon

    1968-01-01

    The variation of the remanent magnetization with temperature of several synthetic and natural single crystals of haematite has been measured in the temperature range 60 to -90 ^circC. Particular attention was given to the measurement of the remanence at temperatures close to the transition temperature. The remanent magnetization of the synthetic crystals showed a sharp reduction over a narrow temperature

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

    PubMed

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

    2002-02-01

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

  11. VOLUME 84, NUMBER 25 P H Y S I C A L R E V I E W L E T T E R S 19 JUNE 2000 Crossover from Glassy to Inhomogeneous-Ferroelectric Nonlinear Dielectric Response

    E-print Network

    Pirc, Rasa

    to Inhomogeneous-Ferroelectric Nonlinear Dielectric Response in Relaxor Ferroelectrics Vid Bobnar, Zdravko Kutnjak single crystal and in 9 65 35 PLZT ceramics has been determined by measuring the first and third harmonic to a spherical glass, while above the critical field a transition into a ferroelectric state occurs. PACS numbers

  12. Ferromagnetic Resonance Absorption in Magnetite Single Crystals

    Microsoft Academic Search

    L. R. Bickford

    1950-01-01

    The microwave resonance absorption technique, at both 1.25 and 3.3 cm wave-lengths, was used to study the ferromagnetic crystalline anisotropy characteristics and g-factor of magnetite Fe3O4. The experiments were performed on single crystals, both synthetic and natural, from room temperature to -195°C. Depending upon the temperature, magnetite single crystals were found to have magnetic anisotropy characteristics similar to those of

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    Since SrTiO3 has a high dielectric constant, it is used as a substrate for a large number of complex physical systems for electrical characterization. Since SrTiO3 crystals are known to be non-ferroelectric/non-piezoelectric at room temperature and above, SrTiO3 has been believed to be a good choice as a substrate/base material for PFM (Piezoresponse Force Microscopy) on novel systems at room temperature. In this paper, from PFM-like measurement using an atomic force microscope on bare crystals of (110) SrTiO3 we show that ferroelectric and piezoelectric-like response may originate from bare SrTiO3 at remarkably high temperatures up to 420 K. Electrical domain writing and erasing are also possible using a scanning probe tip on the surface of SrTiO3 crystals. This observation indicates that the role of the electrical response of SrTiO3 needs to be revisited in the systems where signature of ferroelectricity/piezoelectricity has been previously observed with SrTiO3 as a substrate/base material.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  15. A comparison of single crystal versus ceramic piezoelectric materials for acoustic applications

    NASA Astrophysics Data System (ADS)

    Tressler, James F.

    2003-04-01

    For nearly fifty years, piezoelectric ceramics (primarily from the PZT family) have been the materials of choice as the active elements in sound projectors and receivers, medical ultrasound probes, etc. There is currently great interest in the materials community in the use of newly discovered single crystal relaxor ferroelectric materials as a replacement in applications that currently utilize piezoelectric ceramics. The salient features of single crystal piezoelectrics are strains an order of magnitude larger than are achievable in PZT and electromechanical coupling coefficients on the order of 90 percent. This presentation will provide a more thorough comparison of the physical and piezoelectric properties of single crystal piezoelectrics versus conventional PZT piezoceramics. This will hopefully provide the transducer designer with a better understanding of the pros and cons in the use of single crystals. In addition, a brief review of single crystal synthesis procedures will be described. Finally, some acoustic devices utilizing both single crystals and piezoceramics will be compared. [Work supported by DARPA and ONR Code 321-TS.

  16. Enhancement of Ferroelectricity in Strained BaTiO3 Thin Films

    Microsoft Academic Search

    K. J. Choi; M. Biegalski; Y. L. Li; A. Sharan; J. Schubert; R. Uecker; P. Reiche; Y. B. Chen; X. Q. Pan; V. Gopalan; L.-Q. Chen; D. G. Schlom; C. B. Eom

    2004-01-01

    Biaxial compressive strain has been used to markedly enhance the ferroelectric properties of BaTiO3 thin films. This strain, imposed by coherent epitaxy, can result in a ferroelectric transition temperature nearly 500°C higher and a remanent polarization at least 250% higher than bulk BaTiO3 single crystals. This work demonstrates a route to a lead-free ferroelectric for nonvolatile memories and electro-optic devices.

  17. Enhancement of ferroelectricity in strained BaTiO3 thin films.

    PubMed

    Choi, K J; Biegalski, M; Li, Y L; Sharan, A; Schubert, J; Uecker, R; Reiche, P; Chen, Y B; Pan, X Q; Gopalan, V; Chen, L-Q; Schlom, D G; Eom, C B

    2004-11-01

    Biaxial compressive strain has been used to markedly enhance the ferroelectric properties of BaTiO3 thin films. This strain, imposed by coherent epitaxy, can result in a ferroelectric transition temperature nearly 500 degrees C higher and a remanent polarization at least 250% higher than bulk BaTiO3 single crystals. This work demonstrates a route to a lead-free ferroelectric for nonvolatile memories and electro-optic devices. PMID:15528439

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

    NASA Astrophysics Data System (ADS)

    Gehring, Peter

    2011-03-01

    The outstanding piezoelectric properties of PbZr 1-x Ti x O3 (PZT) perovskite ceramics have long been exploited in numerous device applications, making PZT arguably the most technologically important ferroelectric material in use today. Efforts to understand the piezoelectric mechanism have inspired a plethora of structural studies spanning decades, but solving the PZT phase diagram has proven to be famously problematic because single crystals have not been available save for Zr- and Ti-rich compositions that lie very near the end members PbZr O3 and PbTi O3 , where the piezoelectricity is weakest. Thus, whereas PZT has been the subject of thousands of powder and ceramic investigations, no consensus regarding the crystal structures of PZT exists. We report the first neutron diffraction study of single-crystal PZT with compositions x = 0.325 and 0.460. Our data refute the thesis that the ferroelectric phases of PZT within this composition range, all of which are highly piezoelectric, are purely monoclinic (Cc or Cm). The broadening of certain Bragg peaks can be interpreted in terms of coexisting rhombohedral and monoclinic domains, whereby monoclinic order is enhanced by Ti-doping. This is consistent with the theoretical proposal that the tendency to form macroscopic monoclinic phases facilitates the mechanism of polarization rotation by reducing the energy required to reorient the electric polarization. Dispersions of the lowest energy TO and TA phonon modes were measured on a single crystal of PZT with x = 0.325 in the paraelectric phase at 650 K. The TO mode energy drops at small wave-vectors suggesting that it is a soft mode associated with the ferroelectric phase transition at 590 K. Evidence of a second soft-mode, corresponding to a phase transition at 370 K at the R-point, is provided based on the redistribution of spectral weight as a function of temperature.

  19. Liquid crystal deposition on poled, single crystalline lithium niobate

    NASA Astrophysics Data System (ADS)

    Bharath, S. C.; Pimputkar, K. R.; Pronschinske, A. M.; Pearl, T. P.

    2008-01-01

    For the purpose of elucidating the mechanisms for molecular organization at poled ferroelectric surfaces, single crystalline lithium niobate (LN), 'Z-cut' along the (0 0 0 1) plane, has been prepared and characterized and subsequently exposed to liquid crystal molecules. As a model system we chose to study the anchoring of 4- n-octyl-4'-cyanobiphenyl (8CB) to LN. Liquid crystalline films are of interest because of their useful electronic and optical properties as well as chemical sensing attributes. Low-energy electron diffraction (LEED), atomic force microscopy (AFM), surface contact angle measurements (CA), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface of lithium niobate as well as the nature of 8CB films grown on the surface. Atomically flat LN surfaces were prepared as a support for monolayer thick, 8CB molecular domains. 8CB liquid crystal molecules were deposited by an ambient vaporization technique and the films were analyzed using XPS and CA. Understanding electrostatic anchoring mechanisms and thin film organization for this molecule on uniformly poled surfaces allows for a fuller appreciation of how molecular deposition of other polarizable molecules on periodically poled and patterned poled lithium niobate surfaces would occur.

  20. Cutting fluid study for single crystal silicon

    Microsoft Academic Search

    Chargin

    1998-01-01

    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

  1. Characterization of zinc selenide single crystals

    NASA Technical Reports Server (NTRS)

    Gerhardt, Rosario A.

    1996-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

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

    PubMed

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

    2007-06-01

    We study both theoretically and experimentally switching dynamics in asymmetric surface stabilized ferroelectric liquid crystal cells where the bounding surfaces are treated differently to produce asymmetry in their anchoring properties. Our electro-optic measurements of the switching voltage thresholds, V+ and -V{-}, that are determined by the peaks of the reversal polarization current reveal the frequency dependent shift of the hysteresis loop, V{+}-V{-}. We examine the predictions of the uniform dynamic model with the anchoring energy taken into account. It is found that the asymmetry effects are dominated by the polar contribution to the anchoring energy. Frequency dependence of the voltage thresholds is studied by analyzing the properties of time-periodic solutions to the dynamic equation (cycles). For this purpose, we apply the method linking the cycles and the fixed points of the composition of two parametrized half-period mappings for the approximate model. It is found that the cycles are unstable and can only be formed if the driving frequency is lower than its critical value. The polar anchoring parameter is estimated by making a comparison between the results of modeling and the experimental data for the shift vs frequency curve. PMID:17677282

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

    E-print Network

    Cao, Wenwu

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    Microsoft Academic Search

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

    2003-01-01

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

  7. Vibrational study of CsH2PO4 and CsD2PO4 single crystals

    Microsoft Academic Search

    B. Marchon; A. Novak

    1983-01-01

    The infrared and Raman spectra of disordered paraelectric and ordered ferroelectric phases of CsH2PO4 and CsD2PO4 single crystals have been investigated at various temperatures in the 4000–10 and 4000–0 cm?1 range, respectively. An assignment of lattice and internal vibrations in terms of symmetry species and approximate type of motion is given. Most of the external vibrations of the paraelectric phase

  8. Ferromagnetic Resonance in Manganese Ferrite Single Crystals

    Microsoft Academic Search

    P. E. Tannenwald

    1955-01-01

    The microwave properties of two types of manganese ferrite single crystals have been investigated by means of the ferromagnetic resonance phenomenon from 300°K to 4.2°K and at 24 000, 9100, 5600, and 2800 Mc\\/sec. The low resistivity of one of the crystals, believed to be related to the presence of divalent iron, led to significantly different microwave behavior. Resonance lines

  9. Single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  10. Intrinsic aspect of V-shaped switching in ferroelectric liquid crystals: biaxial anchoring arising from peculiar short axis biasing in the molecular rotation around the long axis.

    PubMed

    Hayashi, Naoki; Kato, Tatsuhisa; Ando, Tomohiro; Fukuda, Atsuo; Kawada, Sachiko; Kondoh, Shinya

    2003-07-01

    To clarify the intrinsic aspect of practically usable thresholdless V-shaped switching in ferroelectric liquid crystals, we have observed textures and measured polarized Raman scattering as well as optical transmittance in a thin homogeneous cell of a single compound by applying an electric field. The results indicate that the so-called surface stabilized ferroelectric states are destabilized, and that there exist rather stable two domains with broad and narrow molecular orientational distributions, both of which show the almost ideal V-shaped switching with considerably low transmittance at the tip of the V. We have concluded that the main cause of the V-shaped switching is the biaxial anchoring on the substrates coated with polyimide, which makes the most polarizable short axis normal to the substrates. It is in competition with the ordinary anchoring that favors the director parallel to the substrates, when the material has such a bulk intrinsic property that this short axis is parallel to the tilt plane. The competition makes the total anchoring energy almost independent of the azimuthal angle and gives rise to the V-shaped switching. PMID:12935157

  11. Self-diffusion in ?-Zr single crystals

    NASA Astrophysics Data System (ADS)

    Lubbehusen, M.; Vieregge, K.; Hood, G. M.; Mehrer, H.; Herzig, Chr.

    1991-06-01

    Self-diffusion in ?-Zr single crystals has been measured in the temperature interval 871-1074 K. The results, extrapolated, are consistent with single crystal self-diffusion data from an early study in which measurements were reported for one temperature, 1124 K. The composite data, within the scatter of the measurements, display non-linear Arrhenius behaviour, with the effective activation enthalpy increasing with decreasing temperature. This behaviour parallels that found in a recent investigation of self-diffusion in ?-Zr single crystals: except at the low temperature limit, the present diffusion coefficients are systematically higher than those of the previous work. The last aspect, in combination with the higher Fe content of the Zr used here, supports a current view that the unusual Arrhenius behaviour reflects an extrinsic diffusion process dominated by the presence (as an impurity) of Fe.

  12. Graphene single crystals: size and morphology engineering.

    PubMed

    Geng, Dechao; Wang, Huaping; Yu, Gui

    2015-05-13

    Recently developed chemical vapor deposition (CVD) is considered as an effective way to large-area and high-quality graphene preparation due to its ultra-low cost, high controllability, and high scalability. However, CVD-grown graphene film is polycrystalline, and composed of numerous grains separated by grain boundaries, which are detrimental to graphene-based electronics. Intensive investigations have been inspired on the controlled growth of graphene single crystals with the absence of intrinsic defects. As the two most concerned parameters, the size and morphology serve critical roles in affecting properties and understanding the growth mechanism of graphene crystals. Therefore, a precise tuning of the size and morphology will be of great significance in scale-up graphene production and wide applications. Here, recent advances in the synthesis of graphene single crystals on both metals and dielectric substrates by the CVD method are discussed. The review mainly covers the size and morphology engineering of graphene single crystals. Furthermore, recent progress in the growth mechanism and device applications of graphene single crystals are presented. Finally, the opportunities and challenges are discussed. PMID:25809643

  13. Strong ferromagnetic-dielectric coupling in multiferroic Lu2CoMnO6 single crystals

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  14. Millimeter Wave Studies of Analogs to Optical Phenomena in Ferroelectric Crystals and Artificial Kerr Media.

    NASA Astrophysics Data System (ADS)

    Bobbs, Bradley Lance

    Refractive, absorptive, electrooptical, and nonlinear optical phenomena have traditionally been associated with visible light, but can readily be extended to include analogs for millimeter wave radiation. Studies of such analog phenomena can reveal material properties with remarkable enhancements over corresponding properties in the visible spectrum. This is particularly true for materials grown or developed specifically for millimeter wave applications. One class of materials investigated was tungsten bronze ferroelectric crystals. Indices of absorption and refraction of Sr_{rm x} Ba_{rm 1-x}Nb _2O_6 and Ba_{rm 2-x}Sr _{rm x}K_ {rm1-y}Na_{ rm y}Nb_5O _{15} at millimeter wave frequencies between 55 and 110 GHz and temperatures between 20 and 300K were derived from measurements of transmittance spectra containing Fabry-Perot fringes produced by crystal surface reflections. The anisotropies observed in both indices at these frequencies are huge compared with those at optical frequencies. Absorption in both materials decreases markedly upon cooling, but only for incident waves polarized along the crystal polar axis. Measurements of linear electrooptic modulation show this effect to be quite large at 300 K, but indicate a significant reduction upon cooling. An artificial Kerr medium consisting of a suspension of short graphite fibers was shown to provide an effective means for observing nonlinear millimeter wave interactions. Using a 18 GHz pump beam with up to 20 W continuous power, changes in the 94 GHz refractive index were measured by interferometry. The induced birefringence and anisotropic absorption indicate an alignment of the fibers with the electric field of the pump beam. The resulting nonlinear refractive index is predicted to be of sufficient magnitude to demonstrate millimeter wave bistability and phase conjugation by degenerate four-wave mixing. Although theoretical model fits to the experimental results show a reasonable degree of success, they also indicate some serious shortcomings. A number of key experiments are proposed for further investigations which may resolve questions raised by this study.

  15. Vibrational spectra and the ferroelectric phase transition of colemanite

    NASA Astrophysics Data System (ADS)

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

    1990-06-01

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

  16. Endlessly single-mode photonic crystal fiber.

    PubMed

    Birks, T A; Knight, J C; Russell, P S

    1997-07-01

    We made an all-silica optical fiber by embedding a central core in a two-dimensional photonic crystal with a micrometer-spaced hexagonal array of air holes. An effective-index model confirms that such a fiber can be single mode for any wavelength. Its useful single-mode range within the transparency window of silica, although wide, is ultimately bounded by a bend-loss edge at short wavelengths as well as at long wavelengths. PMID:18185719

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

    PubMed

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

    2015-01-01

    Ferroelectric Hf x Zr1-x O2 thin films are considered promising candidates for future lead-free CMOS-compatible ferroelectric memory application. The inductive crystallization behaviors and the ferroelectric performance of Hf0.5Zr0.5O2 thin films prepared by atomic layer deposition were investigated. Inductive crystallization can be induced by the film growth condition and appropriate top electrode selection. In this work, a Ni/Hf0.5Zr0.5O2/Ru/Si stack annealed at 550°C for 30 s in N2 ambient after the Ni top electrode has been deposited was manufactured, and it shows the best ferroelectric hysteresis loop in the dielectric thickness of 25 nm, with a remanent polarization value of 6 ?C/cm(2) and a coercive field strength of 2.4 MV/cm measured at 10 kHz. Endurance, retention, and domain switching current characteristics were evaluated well for potential application in the field of ferroelectric field effect transistor (FeFET) and nonvolatile ferroelectric memories (FeRAM). PMID:25852322

  18. Microhardness studies of sulfamic acid single crystal

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  19. Fracture in single crystal NiTi

    Microsoft Academic Search

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

    2008-01-01

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

  20. MAGNETIC PROPERTIES OF DYSPROSIUM SINGLE CRYSTALS

    Microsoft Academic Search

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

    1958-01-01

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

  1. Molecular ferroelectrics: where electronics meet biology

    PubMed Central

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1988-01-01

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

  3. Single-polarization single-mode photonic crystal fibers

    Microsoft Academic Search

    Kunimasa Saitoh; Masanori Koshiba

    2003-01-01

    A new structure of single-polarization single-mode (SPSM) photonic crystal fiber (PCF) is proposed and analyzed by using a full-vector finite element method with anisotropic perfectly matched layers. From the numerical results it is confirmed that the proposed fiber is low-loss SPSM-PCF within the wavelengths ranging from 1.48 to 1.6 ?m, where only the slow-axis mode exists and the confinement loss

  4. Brillouin scattering study of elastic properties in ferroelectric copolymer single-crystalline films.

    PubMed

    Otani, L; Yoshihara, A; Ohigashi, H

    2001-11-01

    The in-plane elastic properties of as-grown random copolymer poly (vinylidene fluoride-trifluoroethylene) single-crystalline films with 75/25 molecular ratio have been studied by Brillouin light scattering up to approximately 140 degrees C from room temperature, covering the D6h-C2v ferroelectric phase transition at approximately 126 degrees C. The in-plane longitudinal acoustic (LA) phonons propagating parallel and perpendicular to the polymer chains were examined. In spite of the strongly first-order nature of the phase transition, both LA velocities exhibit only a broad down step in the temperature range between approximately 100 degrees C and approximately 130 degrees C, depending on the propagation direction, with increasing temperature. The LA phonon width perpendicular to the polymer chains increases with increasing temperature, and exhibits a broad maximum centered at approximately 120 degrees C. On the other hand, the LA phonon width along the polymer-chain axis is much wider than the width perpendicular to the polymer chains, and continues to increase even in the paraelectric phase. Treating the E(u) symmetry electric polarizations (Px,P(y)) of the D6h point group as the macroscopic order parameter, a Laudau free energy was developed to discuss the elastic properties. Using the free energy, we found that the elastic anomalies expected through the electrostrictive couplings between the order parameter and the elastic strains are strongly suppressed by the intrinsic electrical nature of the ferroelectric polymer. For both LA phonons, the temperature development of the phonon frequency and width can be reasonably reproduced by the Cole-Davidson relaxation model for the velocity dispersion with an exponent of betaCD=0.4. The relaxation time was found to obey the Arrhenius law tau=tau(0) exp(DeltaE/k(B)T) with DeltaE=0.55+/-0.01 eV and tau(0)=(4.0+/-0.6)x10(-18) s. At 24.0 degrees C in the ferroelectric phase, the in-plane phonon width anisotropy can be reasonably described by gammaB(straight theta)/2pi=0.18+0.72 sin4 straight theta for the LA phonon and gammaB(straight theta)/2pi=0.02+0.095 sin2 2straight theta for the transverse acoustic phonon, where the phonon propagation angle straight theta is measured from the perpendicular direction with respect to the polymer-chain axis. The straight theta dependence is strongly related to the one-dimensional freedom constrained in each copolymer chain. PMID:11735955

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

    E-print Network

    Gopalan, Venkatraman

    NbO3 and lithium tantalate LiTaO3 , and their manipulation into diverse shapes on vari- ous length in a single crystal of LiNbO3 or LiTaO3 by external electric fields, one observes a variety of naturally. The stoichiometric crystals of both LiNbO3 and LiTaO3 exhibit six-sided polygonal shapes, with domain walls parallel

  6. Lightweight optical mirrors formed in single crystal substrate

    NASA Technical Reports Server (NTRS)

    Bly, Vincent T. (Inventor)

    2006-01-01

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

  7. Optical studies of anthracene single crystals

    NASA Astrophysics Data System (ADS)

    Jiang, Yuhong; Delong, Matthew; Vardeny, Z. Valy

    2001-03-01

    Recently the polyacene crystals such as pentacene, tetracene and anthracene have attracted great interest both in research and applications. These ultra-pure molecular crystals are very promising materials for FETs, organic photovoltaic diodes, LEDs and lasing. High purity anthracene crystal have been grown by physical vapor transport. High photo luminecense (PL) quantum efficiency(over 20%) was observed in these pure anthracene single crystals. The PL excitation spectrum closely follows the absorption spectrum consistent with Kasha¡¦s rule. Photo induced absorption (PA) spectroscopy showed a very small signal for the pure anthracene single crystals, indicating high purity and very few defects. By intentionally introducing defects, the PA increased substantially. Two PA bands at around 1.1eV & 1.5eV and a strong photo bleaching(PB) band due to defects were observed. Also I2 doped crystal was achieved by entraining I2 vapor in the Ar transport gas. Where doping induced IRAV absorption bands appeared in the infrared range. Compared with the difficulty of doping pure anthracene in either iodine vapor or iodine hexanes solution, doping the crystals during the growth process is an efficient way of obtaining charge carriers in the crystals.A series of substituted poly(p-phenylene-ethynylene) [PPEs] were synthesized where the substituents dibutyl(a), dioctyl(b), ditetradecyl(c), di-2-ethylhexyl(d), and di-2-cyclohexylethyl(e) were placed on the 2,5 positions of the phenyl rings. Side groups (a), (b), and (c) are linear chains with increasing length, whereas (d) is branched side chain and (e) is a bulky side chain. The photoinduced absorption (PA) spectroscopy has been applied to investigate the properties of the photoexcitations in these polymer films. The PA spectra of PPE(a) and PPE(b) show a low energy band at ca 850cm-1 and 1000cm-1, respectively. We assigned this PA as due to delocalized polaron excitations, indicating that these PPE polymers self-assembled into two-dimensional lamellae structure, similar to those that have been observed in thin films of regio-regular poly-3-hexythiophene.The low energy PA bands of PPE(c),PPE(d) and PPE(e) are at higher energies, suggesting a decrease in the polaron delocalization as the size of the side group increases. In the visible spectral range the PA spectra of PPE(a) and PPE(b) are also quite similar, showing bands at ca 2.0eV and 2.5eV, respectively.Optical studies of anthracene single crystals

  8. Ferroelectric mobile water.

    PubMed

    Nakamura, Yoshimichi; Ohno, Takahisa

    2011-01-21

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

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

    NASA Astrophysics Data System (ADS)

    Louchev, Oleg A.; Hatano, Hideki; Saito, Norihito; Wada, Satoshi; Kitamura, Kenji

    2013-11-01

    Using our experimental data for ns pulsed second harmonic generation (SHG) by periodically poled stoichiometric LiTaO3 (PPSLT) crystals, we consider in detail the mechanism underlying laser-induced damage in ferroelectric crystals. This mechanism involves generation and heating of free electrons, providing an effective kinetic pathway for electric breakdown and crystal damage in ns pulsed operation via combined two-photon absorption (TPA) and induced pyroelectric field. In particular, a temperature increase in the lattice of ?1 K induced initially by ns SHG and TPA at the rear of operating PPSLT crystal is found to induce a gradient of spontaneous polarization generating a pyroelectric field of ?10 kV/cm, accelerating free electrons generated by TPA to an energy of ?10 eV, followed by impact ionization and crystal damage. Under the damage threshold for ns operation, the impact ionization does not lead to the avalanche-like increase of free electron density, in contrast to the case of shorter ps and fs pulses. However, the total number of collisions by free electrons, ?1018 cm-3 (generated during the pulse and accelerated to the energy of ?10 eV), can produce widespread structural defects, which by entrapping electrons dramatically increase linear absorption for both harmonics in subsequent pulses, creating a positive feedback for crystal lattice heating, pyroelectric field and crystal damage. Under pulse repetition, defect generation starting from the rear of the crystal can propagate towards its center and front side producing damage tracks along the laser beam and stopping SHG. Theoretical analysis leads to numerical estimates and analytical approximation for the threshold laser fluence for onset of this damage mechanism, which agree well with our (i) experiments for the input 1064 nm radiation in 6.8 kHz pulsed SHG by PPSLT crystal, (ii) pulsed low frequency 532 nm radiation transmission experiments, and also (iii) with the data published for other nonlinear crystals and operated wavelengths.

  10. SSME single-crystal turbine blade dynamics

    NASA Technical Reports Server (NTRS)

    Moss, Larry A.

    1988-01-01

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

  11. The Creep of Single Crystals of Aluminum

    NASA Technical Reports Server (NTRS)

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

    1953-01-01

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

  12. Growth of Sr/sub x/Ba/sub 1-x/Nb/sub 2/O/sub 6/ single crystal fibers

    SciTech Connect

    Yamamoto, J.K.; Bhalla, A.S. (Pennsylvania State Univ., University Park, PA (USA). Materials Research Lab.)

    1989-06-01

    The growth of tungsten bronze Sr/sub x/Ba/sub 1-x/Nb/sub 2/O/sub 6/ (x=0.5, 0.61) single crystals have been achieved using a laser heated pedestal growth (LPHG) technique. The crystals were grown from ceramic rods and were approximately 500 {mu}m in diameter. The growth direction was parallel to the c-axis. Preliminary electrical measurements indicate that the crystals are ferroelectric and optical observations show that these crystals appear to be striation free.

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

    PubMed Central

    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

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

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

    PubMed

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

    2002-11-01

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

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

    PubMed

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  17. Q-1 of forsterite single crystals

    Microsoft Academic Search

    Y. Gueguen; M. Darot; P. Mazot; J. Woirgard

    1989-01-01

    Internal friction (Q-1) experiments have been performed on synthetic forsterite single crystals in order to investigate the role of temperature, frequency and dislocation density on the Q-1 factor. Data have been obtained for both deformed and undeformed specimens over a frequency range from 10 to 10-4 Hz at 15, 1000, 1200 and 1400°C. Measurements were done using a torsional pendulum

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

    Microsoft Academic Search

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

    1993-01-01

    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

  19. High speed analogue autocorrelation for PIV transparency analysis using a ferroelectric liquid crystal spatial light modulator

    Microsoft Academic Search

    Z. Q. Mao; N. A. Halliwell; J. M. Coupland

    1996-01-01

    This paper describes a novel automated high-speed optical autocorrelation system for particle image velocimetry (PIV) analysis. In this system, a bistable ferroelectric optically addressed spatial light modulator (BOASLM) is used for real time optical autocorrelation. Input data from a PIV transparency is scanned into the system by utilising two scanning mirrors and the output autocorrelation signals are detected with a

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

    E-print Network

    Meyer, Robert B.

    Dynamics of the molecular orientation field coupled to ions in two-dimensional ferroelectric liquid, they determined the ratio of the bend Kb or splay Ks elastic constant to the corresponding vis- cous coefficients b, s and the bend elastic constant to the square of the spontaneous polarization P0 in the free

  1. Single crystal formation in micro/nano-confined domains by melt-mediated crystallization without seeds

    NASA Astrophysics Data System (ADS)

    Pan, Heng; Shou, Wan

    2015-06-01

    Using molecular dynamics (MD) simulation, we study the characteristics of unseeded crystallization within nano/microscale confining domains. It is demonstrated that unseeded crystallization can yield single crystal domains facilitated by the confinement effects. The stochastic nature of this process and the mechanisms leading to single crystal formation are revealed. A phenomenological model has been developed and tailored by MD simulations, which was applied to quantitatively evaluate the effects of domain size and processing laser pulse width on single crystal formation.

  2. Magnetoelectric emission in rare-earth doped ferroelectric crystals La2Ti2O7:R3+ ( R=Er , Eu, and Nd)

    NASA Astrophysics Data System (ADS)

    Shimada, Y.; Kiyama, H.; Tokura, Y.

    2007-06-01

    The optical magnetoelectric (OME) effect, i.e., the change of optical response on the reversal of light propagation vector (k) , has been investigated for the emission of rare earth R3+ ion ( R=Nd , Eu, Er) doped in a ferroelectric La2Ti2O7 single crystal under magnetic field (H) . The symmetry condition for the appearance of the OME effect for H?k was confirmed by varying the relative angle between the electric polarization and magnetic field. Another tensor component of the second-order magnetolectric tensor ?ijk for H?k , i.e., the magnetochiral effect, is allowed in the Faraday configuration but found to be small compared with the OME effect in the Voigt configuration. The importance of the spin-orbit coupling, the magnetic dipole transition, and the noncentrosymmetric crystal structure is discussed as the origin of the OME effect on the basis of the observed signal magnitude depending on the species of the rare-earth ion and its optical transition moment.

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

    PubMed

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

    2009-03-20

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

  4. Roflumilast - A reversible single-crystal to single-crystal phase transition at 50 °C

    NASA Astrophysics Data System (ADS)

    Viertelhaus, Martin; Holst, Hans Christof; Volz, Jürgen; Hummel, Rolf-Peter

    2013-01-01

    Roflumilast is a selective phosphodiesterase type 4 inhibitor and is marketed under the brand names Daxas®, Daliresp® and Libertec®. A phase transition of the drug substance roflumilast was observed at 50 °C. The low temperature form, the high temperature form and the phase transition were characterised by differential scanning calorimetry, variable temperature powder X-ray diffraction and single crystal X-ray diffraction, Raman spectroscopy and solid state NMR spectroscopy. The phase transition of roflumilast at 50 °C is completely reversible, the high temperature form cannot be stabilised by quench cooling and the phase transition does not influence the quality of the active pharmaceutical ingredient (API) and the drug product. It was observed to be a single crystal to single crystal phase transition.

  5. Inelastic deformation in shocked sapphire single crystals

    NASA Astrophysics Data System (ADS)

    Fuller, H. D.; Winey, J. M.; Gupta, Y. M.

    2013-06-01

    To gain insight into orientation-dependent inelastic deformation of shocked sapphire (?-Al2O3) single crystals, resolved shear stresses, applicable for various dislocation slip and twinning systems, were determined for shock compression along different crystal orientations. Results from our anisotropic wave propagation analysis provide an explanation for why the measured elastic limit of shocked r-cut sapphire is lower, compared to c-cut and a-cut sapphire: Shock wave compression of r-cut sapphire favors activation of basal slip and basal twinning. In contrast, shock wave compression of c-cut and a-cut sapphire favors rhombohedral twinning and prismatic slip, respectively. Also, basal slip and/or basal twinning may be important for understanding why r-cut sapphire shocked beyond the elastic limit loses optical transparency gradually, when compared to c-cut and a-cut sapphire.

  6. Influence of temperature on the optical properties of zinc tris-thiourea sulfate (ZTS) single crystal

    NASA Astrophysics Data System (ADS)

    Abdulwahab, A. M.

    2012-12-01

    Single crystal of zinc tris-thiourea sulfate (ZTS) was synthesized and grown by the slow evaporation technique at 315 K. The effect of temperature on the optical properties of ZTS crystal was studied in the temperature range 293-338 K. This range involves the first-order phase transition temperature from ferroelectric to paraelectric phase (323 K). At room temperature (293 K), the optical transmittance (T) has high values in the completely visible wavelength range. The cut off wavelength equals to 278.5 nm at room temperature. By increasing temperature, the optical transmittance decreases, however the cut off shifts to higher wavelengths. These changes have different rates in the two phases (ferroelectric and paraelectric). Analysis reveals that the type of transition is the direct allowed one. The optical energy gap (Eg) has the value of 3.89 eV at room temperature. This value decreases linearly with increasing temperature by different rates in the two phases. In the region of the absorption edge, the absorption coefficient obeys Urbach's rule, and Urbach parameters were calculated. The Urbach tail energy (Ee), which equals to 1.024 eV at room temperature, increases linearly with increasing temperature. This change has different rates in the two phases. At room temperature, the steepness parameter (?) has the value of 24.697 × 10-3. It decreases linearly with increasing [1/(Temp.)2] by different rates in the two phases. For all studied parameters, the temperature dependence relations change considerably while passing through 323 K. This anomalous behavior confirms that the transition from ferroelectric to paraelectric phase occurs at this temperature.

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

    NASA Astrophysics Data System (ADS)

    Machida, Mitsuo; Yagi, Toshirou

    1988-04-01

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

  8. Conduction mechanism of single-crystal alumina

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  9. Triplet exciton dynamics in rubrene single crystals

    NASA Astrophysics Data System (ADS)

    Ryasnyanskiy, Aleksandr; Biaggio, Ivan

    2011-11-01

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

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

    Microsoft Academic Search

    Jun Kuwata; Kenji Uchino; Shoichiro Nomura

    1982-01-01

    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

  11. Solid-state 93Nb MAS NMR studies of single crystal Pb(Mg1\\/3Nb2\\/3)O3, (PMN) and Pb(Zn1\\/3Nb2\\/3)O3, (PZN) and related lead titanate solid-solution relaxor ferroelectrics

    Microsoft Academic Search

    John J. Fitzgerald; Jiong Huang; Jay S. Shore

    1999-01-01

    Solid-state 93Nb MAS NMR spectra measured at 14.1 Tesla of single crystal Pb(Mg1\\/3Nb2\\/3 (PMN), Pb(Zn1\\/3Nb2\\/3)O3 (PZN), 0.93 PMN\\/0.07 PT, and 0.92 PZN\\/0.08 PT, and polycrystalline PMN and 0.90 PMN\\/0.10 PT materials have two major resonances due to the central transition (+l\\/2?-l\\/2), a sharp peak at ?-900 ppm, and a broad resonance centered near -980 ppm. The sharp 93Nb signal has

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

    E-print Network

    Kiselev, Alexei D

    2014-01-01

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

  13. SAW propagation in the two domain states of ferroelectric LiNbO3 crystal

    Microsoft Academic Search

    Jaroslav Nosek

    2004-01-01

    We propose a new geometry of ferroelectric LiNbO3 domain systems, which may be useful for SAW applications. Since two domain states of this material differ in elastic coefficients and in signs of piezoelectric constants, different domain geometry influencing the propagation of SAW can be considered. Here we wish to point out that even a simple system of two domains D1

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

    PubMed

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

    2015-03-01

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

  15. Cutting fluid study for single crystal silicon

    SciTech Connect

    Chargin, D.

    1998-05-05

    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.

  16. Biaxial constitutive equation development for single crystals

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1984-01-01

    Current gas turbine engines utilize large single crystal superalloy components in the hot section. Structural analysis of these components requires a valid stress strain temperature constitutive equation. The goal of the program described is to create one or more models and verify these models. A constitutive equation based on an assumed slip behavior of a single slip system was formulated, programmed, and debugged. Specifically, the basic theory for a model based on aggravating slip behavior on individual slip systems was formulated and programmed and some simulations were run using assumed values of constants. In addition, a formulation allowing strain controlled simulations was completed. An approach to structural analysis of the specimen was developed. This approach uses long tube consistancy conditions and finite elements specially formulated to take advantage of the symmetry of 100 oriented specimens.

  17. Single crystal diamond nanobeam waveguide optomechanics

    E-print Network

    Behzad Khanaliloo; Harishankar Jayakumar; Aaron C. Hryciw; David P. Lake; Hamidreza Kaviani; Paul E. Barclay

    2015-04-28

    Optomechanical devices sensitively transduce and actuate motion of nanomechanical structures using light. Single--crystal diamond promises to improve the performance of optomechanical devices, while also providing opportunities to interface nanomechanics with diamond color center spins and related quantum technologies. Here we demonstrate dissipative waveguide--optomechanical coupling exceeding 35 GHz/nm to diamond nanobeams supporting both optical waveguide modes and mechanical resonances, and use this optomechanical coupling to measure nanobeam displacement with a sensitivity of $9.5$ fm/$\\sqrt{\\text{Hz}}$ and optical bandwidth $>150$nm. The nanobeams are fabricated from bulk optical grade single--crystal diamond using a scalable undercut etching process, and support mechanical resonances with quality factor $2.5 \\times 10^5$ at room temperature, and $7.2 \\times 10^5$ in cryogenic conditions (5K). Mechanical self--oscillations, resulting from interplay between photothermal and optomechanical effects, are observed with amplitude exceeding 200 nm for sub-$\\mu$W absorbed optical power, demonstrating the potential for optomechanical excitation and manipulation of diamond nanomechanical structures.

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

    SciTech Connect

    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

    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.

  19. Growth and properties of PMN-PT single crystals

    NASA Astrophysics Data System (ADS)

    Jiang, X.; Tang, F.; Wang, J. T.; Chen, T.-P.

    2001-11-01

    Piezoelectric single crystals of Pb(Mg 1/3Nb 2/3)O 3-PbTiO 3 (PMN-PT) show superior properties to piezoelectric ceramics and piezoelectric films in device applications. However, the applications of PMN-PT single crystals are limited by the lack of a simple and reproducible fabrication technique. By studying the effect of fabrication condition on the growth of PMN-PT single crystals in the flux method, we successfully obtained PMN-PT single crystals. The size of the obtained crystals varied from 1 to 4 mm, mostly showing regular cubic shape. X-ray diffraction technique identified the crystal phase was PMN-PT. Electron diffraction spectroscope analysis indicated that the composition of the single crystals was closed to the designed solid solution. The (0 0 1) single crystals showed a dielectric constant peak of 15,200 at 42°C. The crystals had a remnant polarization 16 ?c/cm 2, a spontaneous polarization 22.1 ?c/cm 2, and a coercive field 2.55 kV/cm. Our measurement indicated the temperature dependence and frequency dependence of the dielectric constant and dielectric loss of PMN-PT single crystals. The results will be a great help for the applications of PMN-PT single crystals.

  20. Phase transformation via a monoclinic phase in relaxor-based ferroelectric crystal ,,PbMg13Nb23O3...1x,,PbTiO3...x

    E-print Network

    Phase transformation via a monoclinic phase in relaxor-based ferroelectric crystal ,,PbMg1Õ3Nb2Õ3O3.020102 PACS number s : 77.80.Dj, 77.80.Bh Relaxor-based ferroelectric FE crystals (PbMg1/3Nb2/3O3)1 x(PbTiO3)x rotation from 111 to 001 will be largely cancelled in randomly oriented ceramics.14 These phenomena open

  1. Accelerated domain switching speed in single-crystal LiNbO3 thin films

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Meng, X. J.; Geng, D. Q.; Jiang, A. Q.

    2015-03-01

    By using ionic implantation and wafer bonding technologies, we peeled off a single-crystal LiNbO3 thin film in the atomic-layer smoothness from the surface of a bulk Z-cut LiNbO3 single crystal. X-ray diffraction patterns showed only (00l) orientation of the film. From positive-up-negative-down pulse characterization, we measured domain switching current transients under various short-pulse voltages, where we observed domain switching currents to occur separately at time after initial capacitor charging currents. This is similar to early observations in bulk ferroelectric single crystals, where apparent positive/negative coercive fields of domain switching determined from polarization-electric field hysteresis loops always equal maximum/minimum applied fields. However, after pulse stressing of the film for more than 1000 cycles, the domain switching speed is accelerated, where domain switching current overlaps with the initial capacitor charging current with a well-defined coercive field independent of the applied-field strength. Finally, we simulated the whole domain switching current transients with the assumption of the resistance degradation across interfacial passive layers between the film and electrodes.

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

    SciTech Connect

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

    2011-01-01

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

  3. Growing single crystals in silica gel

    NASA Technical Reports Server (NTRS)

    Rubin, B.

    1970-01-01

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

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

    PubMed Central

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

    2013-01-01

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

  5. Experimental dynamic metamorphism of mineral single crystals

    USGS Publications Warehouse

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

    1993-01-01

    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.

  6. Unidirectional crystallization of large diameter benzophenone single crystal from solution at ambient temperature

    Microsoft Academic Search

    K. Sankaranarayanan; P. Ramasamy

    2006-01-01

    Oriented organic crystals along prerequisite direction are very important in terms of reducing loss of material and cost during nonlinear optical device fabrication. In this paper, “uniaxially solution-crystallization method” [K. Sankaranarayanan, J. Crystal Growth 284 (2005) 203] was elaborated and usefulness of this method has been demonstrated by growing ?110? oriented, 60mm diameter, benzophenone single crystal ingot out of xylene

  7. Rainbow Radiating Single-Crystal Ag Nanowire Nanoantenna Taejoon Kang,

    E-print Network

    Kim, Bongsoo

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

  8. Single crystal fiber for laser sources

    NASA Astrophysics Data System (ADS)

    Délen, Xavier; Aubourg, Adrien; Deyra, Loïc.; Lesparre, Fabien; Martial, Igor; Didierjean, Julien; Balembois, François; Georges, Patrick

    2015-02-01

    Single crystal fiber (SCF) is a hybrid laser architecture between conventional bulk laser crystals and active optical fibers allowing higher average powers than with conventional crystals and higher energy than with fibers in pulsed regime. The pump beam delivered by a fiber-coupled laser diode is confined by the guiding capacity of the SCF whereas the signal beam is in free propagation. In this paper, we study the pump guiding in the SCF and give an overview of the results obtained using SCF gain modules in laser oscillators and amplifiers. We report about up to 500 ?J nanosecond pulses at the output of a passively Q-switched Er:YAG SCF oscillator at 1617 nm. High power experiments with Yb:YAG allowed to demonstrate up to 250 W out of a multimode oscillator. High power 946 nm Nd:YAG SCF Q-switched oscillators followed by second and fourth harmonic generation in the blue and the UV is also presented with an average power up to 3.4 W at 473 nm and 600 mW at 236.5 nm. At 1064 nm, we obtain up to 3 mJ with a nearly fundamental mode beam in sub-nanosecond regime with a micro-chip laser amplified in a Nd:YAG SCF. Yb:YAG SCF amplifiers are used to amplify fiber based sources limited by non-linearities such as Stimulated Brillouin Scattering with a narrow linewidth laser and Self Phase Modulation with a femtosecond source. Using chirped pulse amplification, 380 fs pulses are obtained with an energy of 1 mJ and an excellent beam quality (M2<1.1).

  9. Aging characteristics of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals with different crystal orientations

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Wu, Dun; Fang, Bijun; Ding, Jianning; Li, Xiaobing; Zhao, Xiangyong; Luo, Haosu; Ko, Jae-Hyeon; Ahn, Chang Won

    2015-06-01

    In this work, the time and temperature dependence of the piezoelectric and ferroelectric properties of the 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (0.7PMN-0.3PT) single crystals were investigated in order to search for an effective method to improve their properties further. The piezoelectric properties of the [001]-, [110]- and [111]-oriented 0.7PMN-0.3PT single crystals exhibit excellent time stability during the 2-month room-temperature aging process. The re-poling process leads to the improvement of piezoelectric constant d 33 for the [001]-, [110]- and [111]-oriented 0.7PMN-0.3PT single crystals, while the values of electromechanical coupling coefficient k t change little. During the thermal aging, the values of the measured d 33, calculated converse piezoelectric constant , maximum strain S max% and longitudinal electrostrictive coefficient Q of the [001]-, [110]- and [111]-oriented crystal plates increase gradually before the ferroelectric phase transition temperatures ( T FPT, T R-M, T R-O and T R-T) and then decline continuously. The increase in these values before the T FPT is a result of the phase instability. In general, the [001]- and [110]-oriented 0.7PMN-0.3PT single crystals exhibit large piezoelectricity, excellent time stability and relatively high thermal stability between 20 and 80 °C, which is favorable to the piezoelectric applications.

  10. Hydroxyl concentration in orthoclase single crystals

    NASA Astrophysics Data System (ADS)

    Wang, Z.-C.; Dresen, G.; Andrut, M.

    Hydroxyl concentrations in natural orthoclase single crystals have been studied by combining high pressure and high temperature annealing experiments with Fourier Transform Infrared Spectroscopy (FTIR). Crystals (rectangular wafers) with large (100), (010) and (001) faces were hydrothemally annealed at T=800°-1200 °C, P=50-300MPa and constant oxygen fugacities set by Cu/CuO, Ni/NiO and Fe/FeO buffers for t=1-168 hours in either a cold-seal hydrothermal apparatus or a gas-medium high-temperature and high-pressure apparatus. A broad absorbance band centered near 3450 cm-1 and sharp peaks at 3431 cm-1, 3500-3550 cm-1 and 3650 cm-1 were observed. Hydroxyl concentrations from 50-70 H/106 Si (T=800 °C and P=50MPa) to 1500 H/106 Si (T=1200 °C and P=300MPa) were obtained by integrating the absorption bands in the range from 3700 cm-1 to 3000 cm-1. The FTIR-spectra suggest the presence of molecular water combined with different types of hydrogen-associated point defects.

  11. Fracture in single crystal NiTi

    NASA Astrophysics Data System (ADS)

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

    This paper presents an investigation of the pseudoelastic transformation of two crystallographic orientations of a single crystal NiTi shape memory alloy (SMA). Both uniaxial tension and notched tension samples are considered with the tensile axes along the [1 0 0] and [1 1 1] directions. The phase transformation is observed using optical techniques in situ. For the uniaxial tension samples, martensite plates and Lüders-band structures are observed. For the notched samples, transformation structures in the [1 0 0] sample appeared predominantly on the sides of the notch and crack tip with stable crack propagation. In the [1 1 1] notched samples transformation occurs directly ahead of the notch and unstable crack propagation is observed. An available work criterion is used to predict the location of the transformation, with good agreement to the experimental observations. The different fracture behavior of the two notched sample orientations is explained utilizing the available work calculations.

  12. Hydrogen Annealing Of Single-Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Schaeffer, John C.; Murphy, Wendy

    1995-01-01

    Annealing at temperature equal to or greater than 2,200 degrees F in atmosphere of hydrogen found to increase ability of single-crystal superalloys to resist oxidation when subsequently exposed to oxidizing atmospheres at temperatures almost as high. Supperalloys in question are principal constituents of hot-stage airfoils (blades) in aircraft and ground-based turbine engines; also used in other high-temperature applications like chemical-processing plants, coal-gasification plants, petrochemical refineries, and boilers. Hydrogen anneal provides resistance to oxidation without decreasing fatigue strength and without need for coating or reactive sulfur-gettering constituents. In comparison with coating, hydrogen annealing costs less. Benefits extend to stainless steels, nickel/chromium, and nickel-base alloys, subject to same scale-adhesion and oxidation-resistance considerations, except that scale is chromia instead of alumina.

  13. Vibration-assisted machining of single crystal

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  14. Constitutive modeling for single crystal superalloys

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  15. Diffusion of Ti in ?-Zr single crystals

    NASA Astrophysics Data System (ADS)

    Hood, G. M.; Zou, H.; Schultz, R. J.; Bromley, E. H.; Jackman, J. A.

    1994-12-01

    Ti diffusion coefficients ( D) have been measured in nominally pure ?-Zr single crystals (773-1124 K) in directions both parallel ( Dpa) and perpendicular ( Dpe, few data) to the c-axis: tracer techniques and secondary ion mass spectrometry were used to determine the diffusion profiles. The results show a temperature dependence which may be interpreted in terms of two regions of diffusion behaviour. Above 1035 K, region I, diffusion conforms to the expectations of intrinsic behaviour with normal Arrhenius law constants: Dpa = 1.7 × 10 -3exp(-2.93 ± 0.08 eV/kT) m 2/s. Below 1035 K, region II, D' s appear to be enhanced with respect to an extrapolation of region I behaviour.

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

    E-print Network

    Gopalan, Venkatraman

    in ferroelectrics such as lithium niobate LiNbO3 and lithium tantalate LiTaO3 . Of these, the most common domain walls is a funda- mental property of interest. However, recent studies of LiNbO3 and LiTaO3

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

    Microsoft Academic Search

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

    2004-01-01

    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

  18. Polymer single crystal membranes from curved liquid/liquid interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Li, Christopher; Soft Matter Research Group Team

    2014-03-01

    The weak mechanical properties of the current available vesicles such as liposomes, polymersomes, colloidosomes limit their applications for targeting delivery of drugs/genes. Recently, we developed an emulsion-crystallization method to grow polymer curved single crystals. Using polyethylene and poly(l-lactic acid)as the model systems, enclosed or partially open polymer single crystals have been obtained. Electron diffraction and XRD results confirmed their crystalline structure. The single crystal hollow sphere is structurally close to polymersomes, but with thinner wall and higher modulus.

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

    DOEpatents

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

    1998-01-01

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

  20. Deformation Induced Microtwins and Stacking Faults in Aluminum Single Crystal

    Microsoft Academic Search

    W. Z. Han; G. M. Cheng; S. D. Wu; Z. F. Zhang

    2008-01-01

    Microtwins and stacking faults in plastically deformed aluminum single crystal were successfully observed by high-resolution transmission electron microscope. The occurrence of these microtwins and stacking faults is directly related to the specially designed crystallographic orientation, because they were not observed in pure aluminum single crystal or polycrystal before. Based on the new finding above, we propose a universal dislocation-based model

  1. Mercuric iodide single crystals for nuclear radiation detectors

    Microsoft Academic Search

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

    1996-01-01

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

  2. Mercuric iodide single crystal for nuclear radiation detectors

    Microsoft Academic Search

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

    1995-01-01

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

  3. Crack tip deformation fields in ductile single crystals

    Microsoft Academic Search

    Jeffrey W. Kysar; Clyde L. Briant

    2002-01-01

    Crack tip deformation fields in ductile single crystal media are studied experimentally. The crack, located between two single crystals of aluminum joined by a thin ductile interlayer of tin, is introduced via selective chemical etching and can be considered “sharp”; the material surrounding the tip is fully annealed. After a Mode I loading is applied, the specimen is sectioned and

  4. Mercuric iodide single crystals for nuclear radiation detectors

    SciTech Connect

    Li, W.; Li, Z.; Zhu, S.; Yin, S.; Zhao, B.; Chen, G. [Sichuan Univ., Chengdu (China). Material Science Dept.; Yin, S. [Univ. of Southern California, Los Angeles, CA (United States). Physics Dept.; Yuan, H.; Xu, H. [Deyang Mercuric Iodide Single Crystal Plant, Sichuan (China)

    1996-06-01

    Large size HgI{sub 2} single crystals were grown using the Modified Temperature Oscillation Method (MTOM) with low dislocation densities in a relatively stable temperature environment. Radiation detectors were fabricated from the single crystals which showed good energy resolution with small polarization. Applications have been found in geological explorations, marine mineral analysis, environment pollution monitoring, industrial material quality assurance, and space explorations.

  5. Semiconductor single crystal external ring resonator cavity laser and gyroscope

    SciTech Connect

    Spitzer, M.P.

    1993-08-31

    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.

  6. Fatigue behavior of a single crystal nickel-base superalloy

    SciTech Connect

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

    1995-06-15

    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.

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

    E-print Network

    Arie, Ady

    - dimensional and two-dimensional were fabricated in several FE crystals.11 As an example two-dimensional strip of backward-propagating frequency converters in- clude backward propagating frequency doublers, and mirror study of domain re- versal in RbTiOPO4 RTP FE crystals using the scanning tip of the HVAFM. It is shown

  8. Studies of the Mechanism of a Single-Crystal-to-Single-Crystal Reversible Dehydration of a Copper Carboxylate Framework

    E-print Network

    . Single crystals kept under vacuum at different temperatures (room temperature, 65 °C, and 105 °C) remain are reversible evidenced by the structural studies of the dehydrated single crystals after exposure to humid air. Magnetic measurements showed antiferromagnetic coupling between the Cu2+ ions. Homometallic ferrimagnetism

  9. Microscale Laser Peen Forming of Single Crystal

    SciTech Connect

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

    2008-01-01

    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.

  10. Growth and characterization of undoped and Mn doped lead-free piezoelectric NBT–KBT single crystals

    SciTech Connect

    Babu, G. Anandha, E-mail: anandcgc@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Subramaniyan, Raja R. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Bhaumik, Indranil [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Ganesamoorthy, S. [X-ray Scattering and Crystal Growth Section, Condensed Matter Physics Division, Materials Science Group, IGCAR, Kalpakkam 603102 (India); Ramasamy, P. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Gupta, P.K. [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India)

    2014-05-01

    Highlights: • Single crystals of undoped and Mn doped NKBT crystals are grown by spontaneous nucleation. • Temperature and frequency dependent dielectric constant and loss are measured. • Dielectric constant has increased and the loss has reduced on Mn doped NKBT. • Concentration of oxygen vacancies has been reduced in Mn doped NKBT. • The activation energy for undoped and Mn doped NKBT are calculated. - Abstract: Lead-free piezoelectric single crystals of undoped and 1 wt% Mn doped 0.80 Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}–0.20 K{sub 0.5}Bi{sub 0.5}TiO{sub 3} (NKBT) was grown using self-flux. Powder X-ray diffraction analysis revealed that the grown crystals belong to tetragonal system at room temperature. The lattice strain was calculated from Williamson Hall relation for undoped and Mn doped NKBT crystals. A significant change is observed in dielectric behavior of Mn doped NKBT when compared to undoped sample. The diffuseness increased substantially on Mn doped NKBT which masked the ferroelectric to antiferroelectric transition in the dielectric constant plot. The AC impedance study revealed that the conduction is governed by the singly ionized oxygen vacancy. Further, the decrease in the conductivity on Mn doping suggests that Mn replaces the Bi vacancy, which reduces the oxygen vacancy.

  11. Prospects for the synthesis of large single-crystal diamonds

    NASA Astrophysics Data System (ADS)

    Khmelnitskiy, R. A.

    2015-02-01

    The unique properties of diamond have stimulated the study of and search for its applications in many fields, including optics, optoelectronics, electronics, biology, and electrochemistry. Whereas chemical vapor deposition allows the growth of polycrystalline diamond plates more than 200 mm in diameter, most current diamond application technologies require large-size (25 mm and more) single-crystal diamond substrates or films suitable for the photolithography process. This is quite a challenge, because the largest diamond crystals currently available are 10 mm or less in size. This review examines three promising approaches to fabricating large-size diamond single crystals: growing large-size single crystals, the deposition of heteroepitaxial diamond films on single-crystal substrates, and the preparation of composite diamond substrates.

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

    NASA Astrophysics Data System (ADS)

    Kiselev, Alexei D.; Chigrinov, Vladimir G.

    2014-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    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.

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

    PubMed

    Kiselev, Alexei D; Chigrinov, Vladimir G

    2014-10-01

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

  15. Polarization switching detection method using a ferroelectric liquid crystal for dichroic atomic vapor laser lock frequency stabilization techniques.

    PubMed

    Dudzik, Grzegorz; Rzepka, Janusz; Abramski, Krzysztof M

    2015-04-01

    We present a concept of the polarization switching detection method implemented for frequency-stabilized lasers, called the polarization switching dichroic atomic vapor laser lock (PSDAVLL) technique. It is a combination of the well-known dichroic atomic vapor laser lock method for laser frequency stabilization with a synchronous detection system based on the surface-stabilized ferroelectric liquid crystal (SSFLC).The SSFLC is a polarization switch and quarter wave-plate component. This technique provides a 9.6 dB better dynamic range ratio (DNR) than the well-known two-photodiode detection configuration known as the balanced polarimeter. This paper describes the proposed method used practically in the VCSEL laser frequency stabilization system. The applied PSDAVLL method has allowed us to obtain a frequency stability of 2.7×10-9 and a reproducibility of 1.2×10-8, with a DNR of detected signals of around 81 dB. It has been shown that PSDAVLL might be successfully used as a method for spectra-stable laser sources. PMID:25967193

  16. Method for harvesting single crystals from a peritectic melt

    DOEpatents

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

    1996-08-27

    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.

  17. Ferroelectric thin films fabricated by sol-gel technique

    Microsoft Academic Search

    Yuhuan Xu

    2001-01-01

    This paper reviews our studies of sol-gel processes for some of ferroelectric thin films, including PZT, PLZT, BaTiO3, LiNbO 3, KNbO3, and Sr0.6Ba0.4Nb 2O6, etc. Different microstructures, such as epitaxial (single crystal-like), polycrystalline, and amorphous films, which depend on the sol-gel processing, were studied. Some interested phenomena including thickness effect, interface effect, ferroelectric-like property of amorphous, second harmonic generation, electro-optical

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

    NASA Technical Reports Server (NTRS)

    Lal, R. B.

    1979-01-01

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

  19. Crystallization phase diagram, the growth of large single crystals of bovine ?-Lactoglobulin A

    NASA Astrophysics Data System (ADS)

    Yagi, D.; Ohnishi, Y.; Tanaka, I.; Niimura, N.

    2010-11-01

    A crystallization phase diagram defining the meta-stable region of bovine ?-lactoglobulin A (?-Lg) was firstly determined by a dialysis method. We have succeeded in growing a large single crystal of ?-Lg by selecting a crystal grown in this "meta-stable region" method described in the present paper. The quality of protein crystals was characterized quantitatively via rapid X-ray data collections, followed by the use of Wilson plots to analyze their resulting average B-factors.

  20. Single crystal Processing and magnetic properties of gadolinium nickel

    SciTech Connect

    Shreve, Andrew John [Ames Laboratory

    2012-11-02

    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.

  1. Ferroelectric Pump

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    2000-01-01

    A ferroelectric pump has one or more variable volume pumping chambers internal to a housing. Each chamber has at least one wall comprising a dome shaped internally prestressed ferroelectric actuator having a curvature and a dome height that varies with an electric voltage applied between an inside and outside surface of the actuator. A pumped medium flows into and out of each pumping chamber in response to displacement of the ferroelectric actuator. The ferroelectric actuator is mounted within each wall and isolates each ferroelectric actuator from the pumped medium, supplies a path for voltage to be applied to each ferroelectric actuator, and provides for positive containment of each ferroelectric actuator while allowing displacement of the entirety of each ferroelectric actuator in response to the applied voltage.

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

    PubMed

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

    2015-01-25

    The organic material 4-dimethylaminobenzaldehyde single crystals were grown by slow evaporation technique. The grown crystal was confirmed by the single crystal and powder X-ray diffraction analyses. The functional groups of the crystal have been identified from the Fourier Transform Infrared (FTIR) and FT-Raman studies. The optical property of the grown crystal was analyzed by UV-Vis-NIR and photoluminescence (PL) spectral measurements. The thermal behavior of the grown crystal was analyzed by thermogravimetric (TG) and differential thermal analyses (DTA). Dielectric measurements were carried out with different frequencies by using parallel plate capacitor method. The third order nonlinear optical properties of 4-dimethylaminobenzaldehyde was measured by the Z-scan technique using 532 nm diode pumped continuous wave (CW) Nd:YAG laser. PMID:25168233

  3. Growth and characterization of diammonium copper disulphate hexahydrate single crystal

    SciTech Connect

    Siva Sankari, R. [Department of Physics, Agni College of Technology, Thalambur, Chennai 603103 (India); Perumal, Rajesh Narayana, E-mail: r.shankarisai@gmail.com [Department of Physics, SSN College of Engineering, Kalavakkam, Chennai 603110 (India)

    2014-03-01

    Graphical abstract: Diammonium copper disulphate hexahydrate (DACS) is one of the most promising inorganic dielectric crystals with exceptional mechanical properties. Good quality crystals of DACS were grown by using solution method in a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis were performed for the crystal. Several solid state physical parameters have been determined for the grown crystals. The dielectric constant and the dielectric loss and AC conductivity of the grown crystal were studied as a function of frequency and temperature has been calculated and plotted. - Highlights: • Diammonium copper disulphate is grown for the first time and CCDC number obtained. • Thermal analysis is done to see the stability range of the crystals. • Band gap and UV cut off wavelength of the crystal are determined to be 2.4 eV and 472.86 nm, respectively. • Dielectric constant, dielectric loss and AC conductivity are plotted as a function of applied field. - Abstract: Diammonium copper disulphate hexahydrate is one of the most promising inorganic crystals with exceptional dielectric properties. A good quality crystal was harvested in a 30-day period using solution growth method. The grown crystal was subjected to various characterization techniques like single crystal X-ray diffraction analysis, thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis. Unit cell dimensions of the grown crystal have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Thermal stability of the samples was checked by TG/DTA studies. Band gap of the crystal was calculated. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. AC conductivity was plotted as a function of temperature.

  4. Growing intermetallic single crystals using in situ decanting

    SciTech Connect

    Petrovic, Cedomir; Canfield, Paul; Mellen, Jonathan

    2012-05-16

    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.

  5. Organic ferroelectrics

    Microsoft Academic Search

    Sachio Horiuchi; Yoshinori Tokura

    2008-01-01

    Ferroelectricity results from one of the most representative phase transitions in solids, and is widely used for technical applications. However, observations of ferroelectricity in organic solids have until recently been limited to well-known polymer ferroelectrics and only a few low-molecular-mass compounds. Whereas the traditional use of dipolar molecules has hardly succeeded in producing ferroelectricity in general, here we review advances

  6. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  7. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  8. Growth of large single crystals of the orthorhombic paracetamol

    NASA Astrophysics Data System (ADS)

    Mikhailenko, M. A.

    2004-05-01

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

  9. The Bauschinger effect in cyclically deformed niobium single crystals

    Microsoft Academic Search

    M. Anglada; F. Guiu

    1988-01-01

    The Bauschinger effect has been studied in niobium single crystals cyclically deformed to saturation at small strain amplitudes and at different temperatures. The parameters used to characterize the Bauschinger effect have been measured from the saturation hysteresis loops. The fatigued work-hardened crystals have been modelled as a composite consisting of a hard deformable phase (the regions of high dislocation density)

  10. Synthesis and characterization of single-crystal indium nitride nanowires

    E-print Network

    Zhou, Chongwu

    Synthesis and characterization of single-crystal indium nitride nanowires Tao Tang, Song Han, Wu semiconducting III-V nitrides have long been viewed as promising materials for electronic and optoelectronic

  11. Deformation mechanisms in tungsten single crystals in ballistic impact experiments

    NASA Astrophysics Data System (ADS)

    Bruchey, W. J., Jr.; Herring, R. N.; Kingman, P. W.; Horwath, E. J.

    1993-05-01

    The performance of tungsten single crystals in ballistic impact varies strongly as a function of crystallographic orientation. The deformation structure of recovered single crystal rods fired in ballistic environments has been characterized by optical microscopy, SEM and TEM, and x-ray diffraction. The observed microstructures are varied and provide substantial insights into the factors governing the penetration and flow behavior under ballistic conditions. Crystallographic orientation influences the potential for developing shear which enhances material flow, and this enhancement ultimately maximizes the energy available for target penetration. Microstructural analysis elucidates the various mechanisms occuring during the flow process for single crystals of high-symmetry orientations, and suggests possible analogies between the penetration behavior of the tungsten single crystals and other materials.

  12. Constitutive modeling of creep of single crystal superalloys

    E-print Network

    Prasad, Sharat Chand

    2006-10-30

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

  13. Electromechanical response to white noise excitation in a ferroelectric liquid crystal

    E-print Network

    Boyer, Edmond

    (EM) coupling in a chiral liquid crystal was first investigated under a white electrical excitation, magnetic response [5]. We suggest to apply this method to study electric and mechanical properties du type bruit blanc. La réponse mécanique du système a été détectée dans le domaine de fréquence 0

  14. A high frequency polarization intensity electrooptic modulator in BSTN ferroelectric crystal

    E-print Network

    Wilson, Erik James

    1996-01-01

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

  15. Electrically and Optically Controlled Light Modulation and Color Switching Using Helix Distortion of Ferroelectric Liquid Crystals

    Microsoft Academic Search

    I. Abdulhalim; G. Moddel

    1991-01-01

    The electro-optic effect associated with the helix distortion of chiral smectic C (SmC*) liquid crystals and its application to light modulation are investigated. Optically and electrically addressed spatial light modulators based on this effect are demonstrated. They exhibit an analog response, response times as short as 100 ?s, good contrast ratio and resolution, and color switching capability. The analog response

  16. The Growth of Large Single Crystals.

    ERIC Educational Resources Information Center

    Baer, Carl D.

    1990-01-01

    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)

  17. Microwave absorption in single crystals of lanthanum aluminate

    Microsoft Academic Search

    Claudio Zuccaro; Michael Winter; Norbert Klein; Knut Urban

    1997-01-01

    A very sensitive dielectric resonator technique is employed to measure loss tangent tan ? and relative permittivity &egr;r of lanthanum aluminate (LaAlO3) single crystals at 4–300 K and 4–12 GHz. A variety of single crystals grown by different techniques and purchased from different suppliers are considered. For T>150 K the loss tangent tan ? is almost sample independent with linear

  18. Microwave dielectric properties of lanthanum aluminate ceramics and single crystal

    Microsoft Academic Search

    T. Shimada; Ken-ich Kakimoto; Hitoshi Ohsato

    2005-01-01

    Single crystal and ceramics of LaAlO3 were prepared by a Czochralski method and conventional solid phase reaction, respectively, using high purity reagents. Far infrared reflectivity spectra for single crystals and ceramics of LaAlO3 were measured and eigenfrequencies and damping constants of transverse and longitudinal optical modes were evaluated in order to discuss variations in the dielectric properties. The observed reflectivity

  19. Aspects of single crystal and thin film high field electroluminescence

    Microsoft Academic Search

    Michael Joseph Robert Swift

    1989-01-01

    Electro-optical investigations of unimplanted and ion implanted ZnS and ZnSe direct current electroluminescent (DCEL) devices under reverse bias have enabled advances to be made in understanding some of the physical processes which govern the behavior of such devices. The three types of devices studied were ZnS thin films, ZnS single crystal diodes and ZnSe single crystal diodes. For reasons discussed

  20. Synthesis and Single-Crystal Growth of Ca

    SciTech Connect

    Nakatsuji, Satoru; Maeno, Yoshiteru

    2001-01-01

    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.

  1. Dislocation structures in single-crystal tungsten and tungsten alloys

    Microsoft Academic Search

    Joseph R. Stephens

    1970-01-01

    Deformation of tungsten single crystals as a function of strain, temperature, and alloying was studied by transmission electron\\u000a microscopy. Single crystals oriented for (?101)[lll] slip were grown by electron beam zone refining. Compression specimens\\u000a of tungsten, W-l and 3 pct Re and W-l and 3 pct Ta were deformed to 2 pct strain at 150°, 300°, and 590°K (0.04, 0.08,

  2. Dislocation structures in single-crystal tungsten and tungsten alloys

    Microsoft Academic Search

    Joseph R. Stephens

    1970-01-01

    Deformation of tungsten single crystals as a function of strain, temperature, and alloying was studied by transmission electron microscopy. Single crystals oriented for (-101)[lll] slip were grown by electron beam zone refining. Compression specimens of tungsten, W-l and 3 pct Re and W-l and 3 pct Ta were deformed to 2 pct strain at 150°, 300°, and 590°K (0.04, 0.08,

  3. A phenomenological thermodynamic potential for BaTiO3 single crystals Department of Materials Science and Engineering, The Pennsylvania State University, University Park,

    E-print Network

    Chen, Long-Qing

    Institute of Physics. DOI: 10.1063/1.2042528 I. INTRODUCTION Ferroelectric BaTiO3 ceramics and single-Devonshire expansion was employed. It reproduces bulk properties including the three possible ferroelectric transition. Different from the existing thermodynamic potential, it is applicable to predicting the ferroelectric phase

  4. Effect of crystal and crucible rotations on the interface shape of Czochralski grown silicon single crystals

    NASA Astrophysics Data System (ADS)

    Asadi Noghabi, Omidreza; M'Hamdi, Mohammed; Jomâa, Moez

    2011-03-01

    A set of global heat transfer simulations in Czochralski (Cz) furnace for producing silicon single crystals have been performed to investigate the effect of crystal and crucible rotations on melt convection and crystal/melt interface shape. The 2D axisymmetric simulations are carried out taking into account radiative and conductive heat transfers between furnace components, melt convection including thermocapillary forces (Marangoni) and gas flow. Melt flow pattern and temperature distribution have been studied for several combinations of crystal and crucible rotations and for different crystal heights. The result shows that crystal/melt interface shape and melt flow regime are strongly sensitive to the rate of rotations of both crystal and crucible. Interfaces with low deflection can be achieved for certain combinations of crystal and crucible rotation rates.

  5. Tip-induced domain growth on the non-polar cuts of lithium niobate single-crystals

    NASA Astrophysics Data System (ADS)

    Alikin, D. O.; Ievlev, A. V.; Turygin, A. P.; Lobov, A. I.; Kalinin, S. V.; Shur, V. Ya.

    2015-05-01

    Currently, ferroelectric materials with designed domain structures are considered as a perspective material for new generation of photonic, data storage, and data processing devices. Application of external electric field is the most convenient way of the domain structure formation. Lots of papers are devoted to the investigation of domain kinetics on polar surface of crystals while the forward growth remains one of the most mysterious stages due to lack of experimental methods allowing to study it. Here, we performed tip-induced polarization reversal on X- and Y-non-polar cuts in single-crystal of congruent lithium niobate which allows us to study the forward growth with high spatial resolution. The revealed difference in the shape and length of domains induced on X- and Y-cuts is beyond previously developed theoretical approaches used for the theoretical consideration of the domains growth at non-polar ferroelectric surfaces. To explain experimental results, we used kinetic approach with anisotropy of screening efficiency along different crystallographic directions.

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

    DOEpatents

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

    1998-07-07

    A method of fabricating bulk YBa{sub 2}Cu{sub 3}O{sub x} where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa{sub 2}Cu{sub 3}O{sub x} are heated in the presence of a Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y} seed crystal to a temperature sufficient to form a liquid phase in the YBa{sub 2}Cu{sub 3}O{sub x} while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa{sub 2}Cu{sub 3}O{sub x} material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material. 7 figs.

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

    NASA Technical Reports Server (NTRS)

    Vandenberg, Lodewijk

    1992-01-01

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

  8. Growth and properties of benzil doped benzimidazole (BMZ) single crystals

    SciTech Connect

    Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Sukumar, M. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)] [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Vasudevan, V. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India) [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Shakir, Mohd. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)] [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)] [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Bhagavannarayana, G. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)] [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)

    2010-09-15

    In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure and doped benzimidazole crystals measured using Kurtz powder test.

  9. Growth and characterization of biadmixtured TGS single crystals

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    Single crystals of triglycine sulfate (TGS) with L-glutamine and L-methionine were grown in aqueous solutions by a slow cooling method. The grown crystals were subjected to single crystal and powder X-ray diffraction studies to identify the morphology and the structure. FTIR and UV-visible spectra reveal the functional group identification and optical property of the grown crystals. The dielectric studies were carried out to identify the phase transition temperature and to find the dielectric constant. Microhardness studies have been carried out to assess the mechanical property. P- E hysteresis studies were carried out to find the values of spontaneous polarization and coercive field for doped TGS crystals.

  10. Anisotropy of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  11. Fatigue Failure Criteria for Single Crystal Nickel Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.

    1999-01-01

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

  12. Measurement of single crystal surface parameters

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  13. Growth and characterization of ? and ?-glycine single crystals

    NASA Astrophysics Data System (ADS)

    Srinivasan, T. P.; Indirajith, R.; Gopalakrishnan, R.

    2011-03-01

    Single crystals of ?- and ?-glycine were grown by the slow evaporation solution growth method using deionised water as solvent. The ?-glycine was transformed to ?-glycine by addition of KNO3 as additive and both the forms of glycine single crystals were grown and the characteristic properties were studied and compared. From the single crystal XRD analysis the grown ?- and ?-glycine crystals are confirmed. The presence of the functional groups of ?- and ?-glycine was analyzed from the recorded FT-IR spectrum. The optical transmission was ascertained from UV-vis-NIR spectrum. The lower cut-off wavelengths of ?- and ?-glycine are 292 and 272 nm, respectively. The second harmonic generation relative efficiency was measured by the Kurtz and Perry powder technique. Group theoretical analysis predicts 120 vibrational optical modes in ?-glycine and 90 vibrational optical modes in ?-glycine. The TGA, DTA and dielectric studies were carried out to explore information about thermal and dielectric behavior, respectively, for ?- and ?-glycine.

  14. VGF growth of germanium single crystals without crucible contact

    NASA Astrophysics Data System (ADS)

    Langheinrich, D.; Pätzold, O.; Raabe, L.; Stelter, M.

    2010-08-01

    Experimental results on the vertical gradient freeze growth of germanium single crystals without crucible contact are presented. Two different approaches to establish a stable pressure difference necessary for avoiding the contact between crystal and crucible on solidification are described. Germanium crystals with a diameter of up to 3 in were grown almost without contact to the crucible wall. The effect of detachment is discussed with respect to the microscopical surface roughness and dislocation density of the grown crystals. In comparison to conventionally grown reference crystals the structural perfection of the detached-grown crystals is found to be much higher which can be attributed to the reduced thermal and thermo-mechanical stress in growth without wall contact.

  15. Preparation of bead metal single crystals by electron beam heating

    NASA Astrophysics Data System (ADS)

    Voigtländer, Bert; Linke, Udo; Stollwerk, H.; Brona, J.

    2005-11-01

    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, Pd80Pt20, 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.

  16. Crystal growth of lanthanum calcium borate (LCB) single crystals from melt and its characterization

    NASA Astrophysics Data System (ADS)

    Senthi lkumar, M.; Kalidasan, M.; Sugan; Dhanasekaran, R.

    2013-01-01

    Non-linear optical lanthanum calcium borate (LCB) single crystals were grown by the melt growth method using the Czohralski technique. The polycrystalline LCB compound is synthesized using the solid state reaction method. The grown crystals were characterized by XRD, EDAX, DTA, HRXRD, specific heat, dielectric and NLO studies. The powder XRD pattern revealed the formation of LCB compound and the lattice parameters of the grown crystals were identified through single crystal XRD studies. The melting point of the LCB compound is analyzed by the DTA measurements. Good crystalline nature of the grown crystal is observed from HRXRD analysis. Specific heat measurements in the temperature range 50-550 °C are carried out for the as grown crystal samples. The results obtained by the dielectric and NLO studies are also presented.

  17. Optical spectroscopy of chromium doped (CH 3) 2NH 2X(SO 4) 2·6H 2O (X=Al, Ga) single crystals

    NASA Astrophysics Data System (ADS)

    Ryba-Romanowski, W.; Go?ab, S.; Dominiak-Dzik, G.; Pisarski, W. A.; Podsiad?a, D.; Czapla, Z.

    1998-09-01

    Chromium doped (CH 3) 2NH 2Al(SO 4) 2·6H 2O (DMAAlS) and (CH 3) 2NH 2Ga(SO 4) 2·6H 2O (DMAGaS) single crystals were grown and investigated using the methods of optical spectroscopy. It was found that the Cr 3+ ions in the two crystals are situated in a strong crystal field in which the 2E state is the lowest. The single narrow R-line associated with the 2E- 4A 2 phosphorescence of Cr 3+ in DMAAlS in a ferroelectric phase indicates an undistorted octahedral site, whereas important distortion of O h symmetry and structural disorder was inferred from spectral data obtained with DMAGaS:Cr 3+ in a low temperature phase. Results of optical investigation are discussed taking into account the structural data.

  18. Ferroelectricity in ultrathin perovskite films

    Microsoft Academic Search

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

    2004-01-01

    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

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

    NASA Technical Reports Server (NTRS)

    Arakere, N. K.; Swanson, G.

    2002-01-01

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

  20. Experiences in Large Grain-Single Crystal Cavity Fabrication

    Microsoft Academic Search

    Michael Pekeler; Johannes Schwellenbach; Marco Tradt

    2007-01-01

    At ACCEL instruments several single cell and 9-cell cavities have been produced out of large grain niobium sheets from different suppliers. The fabrication experience and difference to the production out of fine grain niobium sheets will be described. In addition two cavities were produced using single crystal niobium sheets. The final cavities showed no grain boundaries at all in the

  1. Electrochemical Growth of Single-Crystal Metal Nanowires via a

    E-print Network

    physical properties and potential applications as interconnects in future generations of nanometer the electro- chemical growth of copper single-crystal wires in polycar- bonate and anodic alumina membranes. The diameters of these wires range from micrometers down to nanometers (70 nm). Similarly, Pb, Bi, and Ag single

  2. Method of making macrocrystalline or single crystal semiconductor material

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  3. ''6-Degrees of Freedom'' Single Crystal Plasticity Experiments

    SciTech Connect

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

    2003-05-21

    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.

  4. Dynamical Dielectric Properties of Ferroelectric Pyridinium Perchlorate and Pyridinium Fluoroborate Crystals

    NASA Astrophysics Data System (ADS)

    Deguchi, Kiyoshi

    2008-02-01

    The complex dielectric constants of pyridinium perchlorate C5NH6\\cdotClO4 (PyClO4) and pyridinium fluoroborate C5NH6\\cdotBF4 (PyBF4) were measured in a frequency range from 45 MHz to 20 GHz. Typical dielectric relaxations were observed in both crystals. The activation energies for the reorientational motions of pyridinium cations were determined. It was found that the high-frequency dielectric constant \\varepsilon? in the Cole-Cole arc law shows small but distinct anomalies at the transition temperatures of PyClO4 and PyBF4. The origin of the anomalies in \\varepsilon? may be attributed to the polarization of ClO4 and BF4 anions that are distorted from a regular tetrahedron.

  5. Raman spectra of deuteriated taurine single crystals

    NASA Astrophysics Data System (ADS)

    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

    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.

  6. Shock Driven Twinning in Tantalum Single Crystals

    SciTech Connect

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

    2009-07-20

    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.

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

    Microsoft Academic Search

    Dapeng Chen

    2008-01-01

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

  8. Roles of microcracking and phase transition on electric fatigue for [001]-oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Fang, F.; Yang, W.; Luo, X.

    2009-11-01

    Microstructure and polarization degradation are observed under cyclic electric loadings for [001]-oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals. Microcracking and phase transition are found to bear effect for polarization degradation. Upon cyclic electric loading with a comparatively low field magnitude, phase transition does not occur but the propagation of microcracks significantly reduces the polarization. When electric loading is cycled under a high field magnitude, the single crystal transforms from a rhombohedral phase to a monoclinic one. Both microcracking and phase transition hinder ferroelectric domain switching and reduce the number of electric dipoles that may switch under cyclic electric field. The phase transition degrades the polarization to a greater degree than the microcracks. The results imply that the polydomain state of a ferroelectric rhombohedral phase enhances the electromechanical properties.

  9. Physical mechanism for orientation dependence of ferroelectric fatigue in Pb(Zn1/3Nb2/3)O3-5% PbTiO3 crystals

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Kun; Yi, Jae Yun; Hong, Kug-Sun

    2004-12-01

    The underlying phenomenology of the crystallographic orientation dependence on ferroelectric fatigue behavior was investigated in rhombohedral Pb(Zn1/3Nb2/3)O3-5%PbTiO3 (PZN-5PT) crystals. It was recently found that an electric field (E field) application along the ?001? direction of PZN-5PT crystal did not induce the fatigue to 105cycles of bipolar electric field cycling (switching), while the ferroelectric fatigue became evident from 103cycles of polarization switching along the ?111? direction. In this study, the dependence of ferroelectric fatigue on the crystal orientation is explained by changes in internal stress, switching mechanisms, and domain configuration. The magnitude of the in-plane tensile strain was a maximum during a domain switching in ?111? oriented crystals, resulting in the suppressed motion of domain boundaries in ?111? oriented crystals. In addition to the stress, differences in domain switching mechanisms and domain boundary density for ?001? and ?111? oriented crystals contributed to the orientation dependence of ferroelectric fatigue. Sideways domain growth became dominant and domain width increased when the E field was applied along the ?111? direction. Sideways domain growth of ?111? oriented crystal swept oxygen vacancies of the domains during the consecutive switching process, leading to the effective accumulation of oxygen vacancies at the domain boundaries. Smaller domain boundary densities found in ?111? oriented crystals, in comparison to ?100? oriented crystals, also contributed to the increase in the density of accumulated oxygen vacancies at domain boundaries after sweeping oxygen vacancies of the domains, due to the impact of increased E-field cycling and cumulative switching. High in-plane tensile stress and a high concentration of oxygen vacancies at the domain boundaries due to sideways growth and small domain boundary density were suggested to pin the movement of domain boundaries and enhance the fatigue in ?111? oriented crystals.

  10. Method for harvesting rare earth barium copper oxide single crystals

    DOEpatents

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

    1996-04-02

    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.

  11. Modelling of Heat Transfer in Single Crystal Growth

    E-print Network

    Zhmakin, Alexander I

    2014-01-01

    An attempt is made to review the heat transfer and the related problems encountered in the simulation of single crystal growth. The peculiarities of conductive, convective and radiative heat transfer in the different melt, solution, and vapour growth methods are discussed. The importance of the adequate description of the optical crystal properties (semitransparency, specular reflecting surfaces) and their effect on the heat transfer is stresses. Treatment of the unknown phase boundary fluid/crystal as well as problems related to the assessment of the quality of the grown crystals (composition, thermal stresses, point defects, disclocations etc.) and their coupling to the heat transfer/fluid flow problems is considered. Differences between the crystal growth simulation codes intended for the research and for the industrial applications are indicated. The problems of the code verification and validation are discussed; a brief review of the experimental techniques for the study of heat transfer and flow structu...

  12. Anomalous electro-optic effect in Sr0.6Ba0.4Nb2O6 single crystals and its application in two-dimensional laser scanning

    E-print Network

    Gopalan, Venkatraman

    single crystal for vertical scanning; full scan angle of 0.79° 0.07° and lithium tantalate (LiTaO3 in the ferroelectric materials, such as LiNbO3 and LiTaO3 , by selectively inverting do- mains by 180° using external for vertical scanning in tandem with a conventional LiTaO3 scanner for horizontal scanning to demonstrate a two

  13. Q-switching with single crystal photo-elastic modulators

    Microsoft Academic Search

    F. Bammer; R. Petkovsek

    2010-01-01

    An overview is given about experiments with a new method for Q-switching lasers at a constant pulse repetition frequency. It uses inside the laser resonator a Single Crystal Photo-Elastic Modulator (SCPEM). This consists of one piezo-electric crystal electrically excited on a mechanical resonance frequency. In resonance mechanical stresses are induced that lead via the photo-elastic effect to a strongly modulated

  14. Orientation effects in nanoindentation of single crystal copper

    Microsoft Academic Search

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

    2008-01-01

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

  15. Sound velocity and dynamic elastic constants of lysozyme single crystals

    Microsoft Academic Search

    M. Tachibana; K. Kojima; R. Ikuyama; Y. Kobayashi; M. Ataka

    2000-01-01

    We have succeeded in the first measurement of the sound velocity of lysozyme single crystals using an ultrasonic pulse-echo method. The sound velocity along the [110] crystallographic direction in the tetragonal crystals is obtained to be 1817 m\\/s in the solution with pH 4.3 at 20°C. The corresponding elastic constant C11+C66 is evaluated to be approximately 3.99 GPa. Assuming the

  16. Effect of Crystal Orientation on Analysis of Single-Crystal, Nickel-Based Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Swanson, G. R.; Arakere, N. K.

    2000-01-01

    High-cycle fatigue-induced failures in turbine and turbopump blades is a pervasive problem. Single-crystal nickel turbine blades are used because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant and complicating factor. A fatigue failure criterion based on the maximum shear stress amplitude on the 24 octahedral and 6 cube slip systems is presented for single-crystal nickel superalloys (FCC crystal). This criterion greatly reduces the scatter in uniaxial fatigue data for PWA 1493 at 1,200 F in air. Additionally, single-crystal turbine blades used in the Space Shuttle main engine high pressure fuel turbopump/alternate turbopump are modeled using a three-dimensional finite element (FE) model. This model accounts for material orthotrophy and crystal orientation. Fatigue life of the blade tip is computed using FE stress results and the failure criterion that was developed. Stress analysis results in the blade attachment region are also presented. Results demonstrate that control of crystallographic orientation has the potential to significantly increase a component's resistance to fatigue crack growth without adding additional weight or cost.

  17. Plane wave simulation of elastic-viscoplastic single crystals

    NASA Astrophysics Data System (ADS)

    Lloyd, J. T.; Clayton, J. D.; Austin, R. A.; McDowell, D. L.

    2014-09-01

    Despite the large amount of research that has been performed to quantify the high strain rate response of Aluminum, few studies have addressed effects of crystal orientation and subsequent crystal-level microstructure evolution on its high strain rate response. To study orientation effects in single crystal Al, both a constitutive model and novel numerical method have been developed. A plane wave formulation is developed so that materials undergoing anisotropic viscoplastic deformation can be modeled in a thermodynamically consistent framework. Then, a recently developed high strain rate viscoplastic model is extended to include single crystal effects by incorporating higher order crystal-based thermoelasticity, anisotropic plasticity kinetics, and distinguishing influences of forest and parallel dislocation densities. Steady propagating shock waves are simulated for [100], [110], and [111] oriented single crystals and compared to existing experimental wave profile and strength measurements. Finally, influences of initial orientation and peak pressure ranging from 0 to 30 GPa are quantified. Results indicate that orientation plays a significant role in dictating the high rate response of both the wave profile and the resultant microstructure evolution of Al. The plane wave formulation can be used to evaluate microstructure-sensitive constitutive relations in a computationally efficient framework.

  18. Growth and characterization of 4-methyl benzene sulfonamide single crystals

    NASA Astrophysics Data System (ADS)

    Thirumalaiselvam, B.; Kanagadurai, R.; Jayaraman, D.; Natarajan, V.

    2014-11-01

    Single crystals of 4-methyl benzene sulfonamide (4MBS) were successfully grown from aqueous solution by low temperature solution growth technique. The grown crystal was characterized by single crystal XRD and powder XRD methods to obtain the lattice parameters and the diffraction planes of the crystal. UV-vis-NIR absorption spectrum was used to measure the range of optical transmittance and optical band gap energy. The optical transmission range was measured as 250-1200 nm. FTIR spectral studies were carried out to identify the presence of functional groups in the grown crystal. The thermal behavior of the crystal was investigated from thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC) study. The absence of SHG was noticed by Kurtz and Perry powder technique. The third order NLO behavior of the material was confirmed by measuring the nonlinear optical properties using Z-scan technique and it was found that the crystal is capable of exhibiting saturation absorption and self-defocusing performance.

  19. The Load Capability of Piezoelectric Single Crystal Actuators

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  20. The Load Capability of Piezoelectric Single Crystal Actuators

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  1. Ballistic penetration phenomenology of high symmetry single crystals

    NASA Astrophysics Data System (ADS)

    Kingman, Pat W.; Herring, Rodney A.

    1995-02-01

    The ballistic performance of tungsten single crystal penetrators is known to be a function of crystallographic symmetry. The macroscopic deformation geometry of both single crystal and polycrystal tungsten penetrators is a continuous eversion of the rod into a hollow tube. The differences in energy partitioning leading to these variations in ballistic performance must therefore be accounted for by detailed material deformation processes governed by crystallographic orientation. Inferences about these processes have been drawn from microstructural characterization of recovered penetrators. Residual penetrators of both 011 and 111 orientations were found to have repeatedly deformed and recrystalized, but the actual operative processes led to quite different macrostructures, microstructures, and penetration depths. The 001 orientation deformed by a unique process which allowed very efficient deformation, resulting in maximum penetration depth. These single crystal experiments demonstrate the critical role of detailed deformation processes in determining the final penetration depths even when similar macroscopic material flow geometry occurs.

  2. Single Crystal Synthesis and STM Studies of High Temperature Superconductors

    NASA Technical Reports Server (NTRS)

    Barrientos, Alfonso

    1997-01-01

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

  3. Enhanced performance configuration for fast-switching deformed helix ferroelectric liquid crystal continuous tunable Lyot filter.

    PubMed

    Tam, A M W; Qi, G; Srivastava, A K; Wang, X Q; Fan, F; Chigrinov, V G; Kwok, H S

    2014-06-10

    In this paper, we present a novel design configuration of double DHFLC wave plate continuous tunable Lyot filter, which exhibits a rapid response time of 185 ?s, while the high-contrast ratio between the passband and stop band is maintained throughout a wide tunable range. A DHFLC tunable filter with a high-contrast ratio is attractive for realizing high-speed optical processing devices, such as multispectral and hyperspectral imaging systems, real-time remote sensing, field sequential color display, and wavelength demultiplexing in the metro network. In this work, an experimental prototype for a single-stage DHFLC Lyot filter of this design has been fabricated using photoalignment technology. We have demonstrated that the filter has a continuous tunable range of 30 nm for a blue wavelength, 45 nm for a green wavelength, and more than 50 nm for a red wavelength when the applied voltage gradually increases from 0 to 8 V. Within this tunable range, the contrast ratio of the proposed double wave plate configuration is maintained above 20 with small deviation in the transmittance level. Simulation and experimental results showed the proposed double DHFLC wave plate configuration enhances the contrast ratio of the tunable filter and, thus, increases the tunable range of the filter when compared with the Lyot filter using a single DHFLC wave plate. Moreover, we have proposed a polarization insensitive configuration for which the efficiency of the existing prototype can theoretically be doubled by the use of polarization beam splitters. PMID:24921146

  4. Anisotropy of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    The influence of orientation on the tensile and stress rupture behavior of 52 Mar-M247 single crystals was studied. Tensile tests were performed at temperatures between 23 and 1093 C; stress rupture behavior was examined between 760 and 1038 C. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factor contours for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The tensile properties correlated well with the appropriate Schmid factor contours. The stress rupture lives at lower testing temperatures were greatly influenced by the lattice rotations required to produce cross slip. A unified analysis was attained for the stress rupture life data generated for the Mar-M247 single crystals at 760 and 774 C under a stress of 724 MPa and the data reported for Mar-M200 single crystals tested at 760 C under a stress of 689 MPa. Based on this analysis, the stereographic triangle was divided into several regions which were rank ordered according to stress rupture life for this temperature regime.

  5. Single-Crystal Epitaxial Thin Films of the Isotropic Metallic Oxides Sr1-xCaxRuO3 (0 le x le 1).

    PubMed

    Eom, C B; Cava, R J; Fleming, R M; Phillips, J M; Vandover, R B; Marshall, J H; Hsu, J W; Krajewski, J J; Peck, W F

    1992-12-11

    Single-crystal epitaxial thin films of the isotropic metallic oxides Sr1-xCaxRuO(3) (0 ferroelectric, magneto-optic, and electro-optic devices. PMID:17831659

  6. Epitaxial Pb(Zr0.53Ti0.47)O3\\/LaNiO3 heterostructures on single crystal substrates

    Microsoft Academic Search

    Tao Yu; Yan-Feng Chen; Zhi-Guo Liu; Si-Bei Xiong; Li Sun; Xiao-Yuan Chen; Lian-Je Shi; Nai-Ben Ming

    1996-01-01

    Epitaxial near-stoichiometric ferroelectric Pb(Zr0.53Ti0.47)O3 thin films were fabricated on epitaxial metallic LaNiO3 electrodes deposited on (001) SrTiO3 and (001) LaAlO3 single crystal substrates by pulsed laser ablation. The P–E hysteresis loop of PZT in the trilayer of Ag\\/PZT\\/LNO\\/STO was measured using the Sawyer–Tower circuit. The remnant polarization Pr and coercive field Ec at room temperature were 30 ?C\\/cm2 and 69.3

  7. Lead pyrovanadate single crystal as a new SRS material

    SciTech Connect

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

    2011-02-28

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

  8. Apparatus And Method For Producing Single Crystal Metallic Objects

    DOEpatents

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

    2006-03-14

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

  9. Shock wave compression of single-crystal forsterite

    Microsoft Academic Search

    Ian Jackson; Thomas J. Ahrens

    1979-01-01

    Hugoniot equation of state measurements have been performed on pure synthetic single-crystal forsterite (Mg2SiO4) in the pressure range 70-160 GPa (0.7-1.6 Mbar). These and earlier data for polycrystalline forsterite are compared with theoretical Hugoniots for the assemblages 2MgO (rocksalt) +SiO2 (stishovite) and MgO (rocksalt) +MgSiO3 (perovskite). The densities attained by single-crystal forsterite at pressures in excess of 120 GPa are

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

    PubMed

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

    2013-05-14

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  12. Regularities of recrystallization in rolled Zr single crystals

    NASA Astrophysics Data System (ADS)

    Isaenkova, M.; Perlovich, Yu; Fesenko, V.; Krymskaya, O.; Krapivka, N.; Thu, S. S.

    2015-04-01

    Experiments by rolled single crystals give a more visible conception of the operating mechanisms of plastic deformation and the following recrystallization, than experiments by polycrystals. Studies by usage of X-ray diffraction methods were conducted by Zr single crystals. It was revealed, that regions of the ?-Zr matrix, deformed mainly by twinning, are characterized with decreased tendency to recrystallization. Orientations of recrystallized ?-Zr grains correspond to “slopes” of maxima in the rolling texture, where the level of crystalline lattice distortion is maximal and the number of recrystallization nuclei is most of all.

  13. Growth, mechanical, thermal and dielectric properties of pure and doped KHP single crystal

    NASA Astrophysics Data System (ADS)

    M, Lakshmipriya.; Babu, D. Rajan; Vizhi, R. Ezhil

    2015-06-01

    L-Arginine doped potassium hydrogen phthalate and L-Histidine doped potassium hydrogen phthalate single crystals were grown by slow evaporation method at room temperature. The grown crystal crystallizes in orthorhombic system which is confirmed by single crystal XRD analysis. The grown crystals are subjected to thermal, mechanical and dielectric analysis.

  14. High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization.

    PubMed

    Saidaminov, Makhsud I; Abdelhady, Ahmed L; Murali, Banavoth; Alarousu, Erkki; Burlakov, Victor M; Peng, Wei; Dursun, Ibrahim; Wang, Lingfei; He, Yao; Maculan, Giacomo; Goriely, Alain; Wu, Tom; Mohammed, Omar F; Bakr, Osman M

    2015-01-01

    Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3(+), X=Br(-) or I(-)) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at elevated temperatures. The crystals can be both size- and shape-controlled by manipulating the different crystallization parameters. Despite the rapidity of the method, the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPbX3 reported to date. The phenomenon of inverse or retrograde solubility and its correlated inverse temperature crystallization strategy present a major step forward for advancing the field on perovskite crystallization. PMID:26145157

  15. Melting of Dust Crystals by Single Particles

    SciTech Connect

    Ivanov, Yuriy; Melzer, Andre [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet Greifswald, 17489 Greifswald (Germany)

    2005-10-31

    The melting transition of 2D finite dust clusters has been investigated. Therefore, a single dust particle was placed in a plane below the actual cluster plane. With reducing the gas pressure and with increase of the plasma power an instability due to the non-reciprocal attraction of the lower dust particle was excited that heats the cluster layer. The novel method of singular value decomposition (SVD) has been applied for the analysis of the cluster dynamics during melting.

  16. Exploiting polymer single crystals to assemble and functionalize nanomaterials

    NASA Astrophysics Data System (ADS)

    Li, Bing

    Nanomaterials are fundamental building blocks for nanoscience and nanotechnology. They can generally be categorized into three classes: zero-dimensional (0D) (e.g. nanoparticles), one-dimensional (1D) (e.g. carbon nanotubes) and two-dimensional (2D) (e.g. thin films) nanomaterials. Assembly of nanomaterials is the key step to transfer their fascinating mechanical, electronic and optical properties from nano- to micro- or macro-scale. Among all types of assemblies, assembling across different nanomaterial classes is of particular interest. For example, assembling 0D nanoparticles with 1D nanotubes or 2D thin films. These assembled structures have the advantage of possessing properties from both classes of nanomaterials. Functionalization of nanomaterials is important from both scientific and technological points of view. A newly developed field of functionalization is called "patchy particles". Multiple types of functional molecules form different domains on particle surface. Each domain contains only one type of functional molecules. These domains are called patches. These patchy particles are advanced building blocks, which may assemble into useful complex structures. In this thesis, polymer single crystals are exploited to assemble and functionalize nanomaterials. Polymer single crystals have a lamellar structure. Since the thickness of these lamellae is ˜10 nm, polymer single crystals are introduced as a new type of 2D nanomaterials. Different from the traditional 2D nanomaterials such as Langmuir-Blodgett films, self-assembled monolayers and thin films made by Layer-by-Layer technique, these polymer single crystals are free-standing, which means no substrate is needed. Furthermore, the surface of these polymer single crystals can be readily functionalized by crystallizing end-functionalized polymers. Based on the studied polymers, this thesis is divided into two parts. The first part is focused on single crystals of poly(ethylene oxide) (PEO). Thiol-terminated PEO is used to make functional lamellar single crystals. Assembling 0D nanoparticles with these 2D lamellae leads to nanoparticles sheets with three different structures: monolayer, bilayer and sandwich. Furthermore, by assembling nanoparticles during crystallization of PEO, nanoparticle sheets with frame-like patterns are obtained. The morphology of these frames can be readily controlled by tuning experimental parameters. Finally, as nanoparticles sheets form, patchy nanoparticles are produced as well. Structures like "bilines" and nanowires are formed by self-assembly of these patchy nanoparticles. The second part deals with single crystals of polyethylene-block -poly(ethylene oxide) (PE-b-PEO). Single crystals of PE-b-PEO are used to functionalize carbon nanotubes and assemble nanoparticles with these nanotubes. Alternating patterns are formed on carbon nanotube surface by thin film crystallization of PE-b-PEO. As a result, the surface of a carbon nanotube is uniformly divided into many sub-10 nm pieces along the tube axis. This functionalization opens the door to periodical functionalization of carbon nanotubes at nanoscale. By employing thiol-terminated PE-b-PEO, thiol groups are introduced to the alternating patterns. These periodically functionalized 1D carbon nanotubes are used to assemble 0D nanoparticles into periodical parallel nanoparticle chains.

  17. Ellipsometric monitoring of molecular evolution in freely suspended films of M12\\/10 ferroelectric liquid crystal

    Microsoft Academic Search

    E. G. Bortchagovsky; A. Deineka; M. Glogarová; V. Hamplová; L. Jastrab??k; M. Kašpar

    2004-01-01

    This work is devoted to the ellipsometric investigation of the evolution of the molecular order in free standing films of the ferroelectric liquid crystalline compound M12\\/10 after its alignment by electric field. Creation of pronounced oscillations of anisotropic properties of films was found and monitored over a scale of hours. These oscillations are explained as the mutual precession of molecular

  18. Experiences in Large Grain-Single Crystal Cavity Fabrication

    SciTech Connect

    Pekeler, Michael; Schwellenbach, Johannes; Tradt, Marco [ACCEL Instruments GmbH, Friedrich-Ebert-Str. 1, D-51429 Bergisch Gladbach (Germany)

    2007-08-09

    At ACCEL instruments several single cell and 9-cell cavities have been produced out of large grain niobium sheets from different suppliers. The fabrication experience and difference to the production out of fine grain niobium sheets will be described. In addition two cavities were produced using single crystal niobium sheets. The final cavities showed no grain boundaries at all in the cavity cell, even not in the electron beam welding seam.

  19. Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Swanson, Gregory

    2000-01-01

    Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal nickel base turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. High Cycle Fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. Furthermore, crystallographic crack growth on octahedral planes under fretting induced mixed mode loading can be an order of magnitude faster than under pure mode I loading. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate Advanced High Pressure Fuel Turbo Pump (HPFTP/AT) for the Space Shuttle Main Engine (SSME). Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale 3D finite element (FE) model capable of accounting for contact friction, material orthotrophy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation, Stress results are used to discuss fretting fatigue failure analysis of SSME blades. Attachment stresses are seen to reach peak values at locations where fretting cracks have been observed. Fretting stresses at the attachment region are seen to vary significantly as a function of crystal orientation. Attempts to adapt techniques used for estimating fatigue life in the airfoil region, for life calculations in the attachment region, are presented. An effective model for predicting crystallographic crack initiation under mixed mode loading is required for life prediction under fretting action.

  20. Polymer single crystal membrane from liquid/liquid interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Li, Christopher; Soft Matter Research Group-Drexel University Team

    2013-03-01

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

  1. Microhardness studies of vapour grown tin (II) sulfide single crystals

    NASA Astrophysics Data System (ADS)

    Hegde, S. S.; Kunjomana, A. G.; Ramesh, K.

    2015-06-01

    Earth abundant tin sulfide (SnS) has attracted considerable attention as a possible absorber material for low-cost solar cells due to its favourable optoelectronic properties. Single crystals of SnS were grown by physical vapour deposition (PVD) technique. Microindentation studies were carried out on the cleaved surfaces of the crystals to understand their mechanical behaviour. Microhardness increased initially with the load, giving sharp maximum at 15 g. Quenching effect has increased the microhardness, while annealing reduced the microhardness of grown crystals. The hardness values of as-grown, annealed and quenched samples at 15 g load are computed to be 99.69, 44.52 and 106.29 kg/mm2 respectively. The microhardness of PVD grown crystals are high compared to CdTe, a leading low-cost PV material. The as-grown faces are found to be fracture resistant.

  2. Macroscale Janus polymer single crystal film and its wettability analysis

    NASA Astrophysics Data System (ADS)

    Qi, Hao; Wang, Wenda; Zhou, Tian; Li, Christopher

    2014-03-01

    Liquid-liquid interface between two immiscible solvents is crucial to studying amphiphile and colloidal self-assembly. It can also guide chain folding during the crystallization process. In this presentation, we show that crystallization of dicarboxy end functionalized poly(?-caprolactone) at water/pentyl acetate interface result in millimeter scale, uniform polymer single crystal (PSC) film. Due to the asymmetric nature at the liquid-liquid interface, the PSC film exhibit Janus property - a hydrophobic side and a hydrophilic side, which is confirmed by in-situ nano-condensation experiment using an environmental scanning electron microscope. The thickness of the PSC film changes with different polymer solution concentration, revealing a surface tension dominated crystallization process.

  3. Influence of N-H-O hydrogen bonds on the structure and properties of (K1-x(NH4)xH2PO4) proton glasses: a single crystal neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Ranjan Choudhury, Rajul; Chitra, R.

    2013-02-01

    It has been known for quite some time now that proton dynamics plays a key role in the structural ferroelectric (FE)/antiferroelectric (AFE) phase transition in the crystals belonging to the potassium dihydrogen phosphate crystal family. Mixed crystals belonging to this family having the composition M1-x(NW4)xW2AO4, where M = K, Rb, Cs, W = H, D, and A = P, As, exhibit proton glass behavior due to frustration between FE and AFE ordering; these proton glasses do not undergo any structural phase change but retain their room temperature structure down to very low temperatures. Single crystal neutron diffraction investigations of four mixed crystals with composition (K1-x(NH4)xH2PO4), where x = 0.0, 0.29, 0.67 1.0, were undertaken with the intention to investigate the effect of the local structural deviations on the overall average structure of the crystals and correlate these structural changes to the presence or absence of a structural phase transition in these crystals. Hydrogen bonding is shown to play a key role in the changing nature of the mixed crystals as the composition varies from the potassium rich ferroelectric region to the proton glass region to the ammonium rich antiferroelectric region.

  4. Magnetothermal properties of single crystal dysprosium

    NASA Astrophysics Data System (ADS)

    Chernyshov, A. S.; Tishin, A. M.; Gschneidner, K. A.; Pecharsky, A. O.; Pecharsky, V. K.; Lograsso, T. A.

    2002-05-01

    The magnetocaloric properties (the adiabatic temperature change) of the high purity single crystalline dysprosium have been measured directly over the temperature range from 78 to 220 K in magnetic fields from 0 to 14 kOe applied along the easy magnetization direction (a-axis). These results are in good to excellent agreement, except for two regions (105 to 127 K, and 179 to 182 K), with the previous magnetocaloric effect data reported on lower purity dysprosium samples. The magnetic phase diagram of Dy has been refined based on the results of these measurements and two new high magnetic field phases have been identified.

  5. Electronic conduction through single crystals of polyethylene

    E-print Network

    Samson, Gerald Maurice

    1966-01-01

    ELECTRORIC CO:iC' CTIOE?TEROUCH Sl". , GLE C OISTf~S OF POL" IZLELE A Thesis Gerald Mauri co Samson Submitted to the Graduate College of' the Texas AcM University in partial Wlfillment of' the requirements f' or the degree of' MASTER OF SCIENCE... talc o Polyot! ylone . -y, i'oo Gerald !':cur"' co Samson Directed by: Zr. Joe S. The predominant conduction mechani m through single cryo' mls op polyethylene is shown to be Schott!cy ( hernal) oui "sion . or tompora- o tu. es - bove 0 C. . "or...

  6. Monte Carlo simulations of single crystals from polymer solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Jianing; Muthukumar, M.

    2007-06-01

    A novel "anisotropic aggregation" model is proposed to simulate nucleation and growth of polymer single crystals as functions of temperature and polymer concentration in dilute solutions. Prefolded chains in a dilute solution are assumed to aggregate at a seed nucleus with an anisotropic interaction by a reversible adsorption/desorption mechanism, with temperature, concentration, and seed size being the control variables. The Monte Carlo results of this model resolve the long-standing dilemma regarding the kinetic and thermal roughenings, by producing a rough-flat-rough transition in the crystal morphology with increasing temperature. It is found that the crystal growth rate varies nonlinearly with temperature and concentration without any marked transitions among any regimes of polymer crystallization kinetics. The induction time increases with decreasing the seed nucleus size, increasing temperature, or decreasing concentration. The apparent critical nucleus size is found to increase exponentially with increasing temperature or decreasing concentration, leading to a critical nucleus diagram composed in the temperature-concentration plane with three regions of different nucleation barriers: no growth, nucleation and growth, and spontaneous growth. Melting temperatures as functions of the crystal size, heating rate, and concentration are also reported. The present model, falling in the same category of small molecular crystallization with anisotropic interactions, captures most of the phenomenology of polymer crystallization in dilute solutions.

  7. Monte Carlo simulations of single crystals from polymer solutions.

    PubMed

    Zhang, Jianing; Muthukumar, M

    2007-06-21

    A novel "anisotropic aggregation" model is proposed to simulate nucleation and growth of polymer single crystals as functions of temperature and polymer concentration in dilute solutions. Prefolded chains in a dilute solution are assumed to aggregate at a seed nucleus with an anisotropic interaction by a reversible adsorption/desorption mechanism, with temperature, concentration, and seed size being the control variables. The Monte Carlo results of this model resolve the long-standing dilemma regarding the kinetic and thermal roughenings, by producing a rough-flat-rough transition in the crystal morphology with increasing temperature. It is found that the crystal growth rate varies nonlinearly with temperature and concentration without any marked transitions among any regimes of polymer crystallization kinetics. The induction time increases with decreasing the seed nucleus size, increasing temperature, or decreasing concentration. The apparent critical nucleus size is found to increase exponentially with increasing temperature or decreasing concentration, leading to a critical nucleus diagram composed in the temperature-concentration plane with three regions of different nucleation barriers: no growth, nucleation and growth, and spontaneous growth. Melting temperatures as functions of the crystal size, heating rate, and concentration are also reported. The present model, falling in the same category of small molecular crystallization with anisotropic interactions, captures most of the phenomenology of polymer crystallization in dilute solutions. PMID:17600443

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

    SciTech Connect

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

    2014-03-31

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

  9. Pulsed electron beam irradiation of vanadium single crystals

    Microsoft Academic Search

    J. M. Lombaard; O. Meyer

    1983-01-01

    The damage produced by pulsed electron beam irradiation of vanadium single crystals has been studied by the channeling technique and by thin film X-ray analysis. A surface disorder peak and a small dechanneling component was produced by applying electron energy densities below the melting threshold. The structure of the surface disorder was microcrystalline or amorphous and the dechanneling component could

  10. Unified constitutive model for single crystal deformation behavior with applications

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  11. Oriented Co Nanoparticles in a Single-Crystal Alumina Matrix

    Microsoft Academic Search

    L. A. Boatner; C. W. White; T. E. Haynes; J. R. Thompson; K. D. Sorge; J. D. Budai; A. Meldrum

    2003-01-01

    Crystallographically oriented nanoparticles of Co can be formed in a single-crystal alumina host by employing ion implantation combined with thermal processing. Depending on the Co implantation and thermal processing conditions, Co particles can be created that are either almost pure hexagonal or pure cubic phase precipitates. The hexagonal Co particles are oriented with their six-fold axis parallel to the alumina

  12. Halide adsorption on single-crystal silver substrates: dynamic

    E-print Network

    Rikvold, Per Arne

    · Investigated validity of lattice-gas approach * Justified for well-localized adsorption sites · Tested MarkovHalide adsorption on single-crystal silver substrates: dynamic simulations and ab initio density State University Supported by US NSF #12;How good is lattice-gas approximation? Using 2D corrugation

  13. Transverse Mode Multi-Resonant Single Crystal Transducer

    NASA Technical Reports Server (NTRS)

    Snook, Kevin A. (Inventor); Liang, Yu (Inventor); Luo, Jun (Inventor); Hackenberger, Wesley S. (Inventor); Sahul, Raffi (Inventor)

    2015-01-01

    A transducer is disclosed that includes a multiply resonant composite, the composite having a resonator bar of a piezoelectric single crystal configured in a d(sub 32) transverse length-extensional resonance mode having a crystallographic orientation set such that the thickness axis is in the (110) family and resonance direction is the (001) family.

  14. Creep, plasticity, and fatigue of single crystal superalloy

    Microsoft Academic Search

    Alexander Staroselsky; Brice N. Cassenti

    2011-01-01

    Single crystal components in gas turbine engines are subject to such extreme temperatures and stresses that life prediction becomes highly inaccurate resulting in components that can only be shown to meet their requirements through experience. Reliable life prediction methodologies are required both for design and life management. In order to address this issue we have developed a thermo-viscoplastic constitutive model

  15. Ultrabroadband single crystal composite transducers for underwater ultrasound

    Microsoft Academic Search

    S. Cochran; M. Parker; P. Marin-Franch

    2005-01-01

    Through the use of complex piezoelectric structures, it is possible to obtain resonant harmonics not observed in the usual odd- harmonic response of a conventional structure. When combined with inherently broadband components, such as composites made with PMN- PT single crystal material, this permits the realisation of ultrabroadband devices. In the work reported here, results from modelling indicate that a

  16. Direct Bonding of LiTaO3 Single Crystals

    Microsoft Academic Search

    Yoshihiro Tomita; Masato Sugimoto; Kazuo Eda; Tetsuyuki Okano

    1994-01-01

    A new fabrication method for combining lithium tantalate single crystals by direct bonding without using bonding agents has been developed. The bonded interface was found to be very uniform, and bonding on an atomic scale was achieved in spite of a relatively low heat-treatment temperature of 350°C. This method is very promising for realizing new stacked structures and new fabrication

  17. Quantum Nernst effect in a bismuth single crystal

    Microsoft Academic Search

    Mari Matsuo; Akira Endo; Naomichi Hatano; Hiroaki Nakamura; Ryoen Shirasaki; K. Sugihara

    2009-01-01

    We calculate the phonon-drag contribution to the transverse (Nernst) thermoelectric power Syx in a bismuth single crystal subjected to a quantizing magnetic field. The calculated heights of the Nernst peaks originating from the hole Landau levels and their temperature dependence reproduce the right order of magnitude for those of the pronounced magneto-oscillations recently reported by Behnia [Phys. Rev. Lett. 98,

  18. The Reactive Activity and Selectivity of Platinum Single Crystal Surfaces

    Microsoft Academic Search

    Jianhua Wang

    1994-01-01

    Alcohol, methylamine, acetylene, and ethyl iodide decomposition on platinum single crystal surfaces have been investigated in this thesis work. The objective of this research is to examine factors affecting surface reaction pathways and the rate of the reaction. Alcohol conversion on transition metals has been studied for many years. The importance of this research is to find new ways to

  19. Amplified Ferrimagnetic Echoes in Single Crystal-Polycrystal YIG Composites

    Microsoft Academic Search

    D. E. Kaplan; W. I. Dobrov; G. F. Herrmann

    1972-01-01

    To clarify the conditions for generation of amplified Hahn-type echoes in ferrimagnets, experiments were conducted with composite samples formed by imbedding single crystal YIG wafers at various positions at and near the end of a poly crystalline YIG bar of similar cross section and 4?M value. The poly crystalline component provided the internal field and field gradient needed for echo

  20. Growth of large single crystals of MgO

    SciTech Connect

    Boatner, L.A. [Oak Ridge National Lab., TN (United States); Urbanik, M. [Commercial Crystal Laboratories, Inc., Naples, FL (United States)

    1997-06-12

    The progressive identification of new high-technology applications and requirements for MgO single crystals in the commercial realm, as well as in DOE and other government-agency project areas, has resulted in an increased demand and international market for this material. Specifically, the demand for MgO crystals in large sizes and quantities is presently increasing due to existing and developing applications that include: (a) MgO substrates for the formation of electro-optic thin films and devices, (b) epitaxial substrates for high-temperature thin-film superconducting devices MgO optical components - including high-temperature windows, lenses, and prisms, and (d) specialty MgO crucibles and evaporation sources for thin-film production. In the course of CRADA ORNL92-0091, carried out with Commercial Crystal Laboratories of Naples, Florida as the commercial participant, we have made major progress in increasing the size of single crystals of MgO produced by means of the submerged-arc-fusion technique-thereby increasing the commercial utility of this material. Prior to the accomplishments realized in the course of this CRADA, the only commercially available single crystals of MgO were produced in Japan, Israel, and Russia. The results achieved in the course of CRADA ORNL92-0091 have now led to the establishment of a domestic commercial source of MgO single-crystal substrates and components, and the U.S. is no longer totally dependent on foreign sources of this increasingly important material.

  1. Journal of Crystal Growth 271 (2004) 128133 Growth of strontium barium niobate

    E-print Network

    Osnabrück, Universität

    2004-01-01

    Journal of Crystal Growth 271 (2004) 128­133 Growth of strontium barium niobate: the liquidus. Czochralski method; A2. Growth from the melt; A2. Single crystal growth; B1. Niobates; B2. Ferroelectric;crystal growth at such a composition is greatly facilitated, practically all publications up to now deal

  2. Ferroelectric phase transition in the whitlockite-type Ca 9Fe(PO 4) 7; crystal structure of the paraelectric phase at 923 K

    NASA Astrophysics Data System (ADS)

    Lazoryak, Bogdan I.; Morozov, Vladimir A.; Belik, Alexei A.; Stefanovich, Sergey Yu.; Grebenev, Vadim V.; Leonidov, Il'ya A.; Mitberg, Edward B.; Davydov, Sergey A.; Lebedev, Oleg I.; Van Tendeloo, Gustaaf

    2004-02-01

    A newly discovered phase transition in Ca 9Fe(PO 4) 7 is studied by high-temperature X-ray powder diffraction (XRD) and electron diffraction (ED), high-resolution electron microscopy, second-harmonic generation (SHG), differential scanning calorimetry, dielectric and electrical conductivity measurements. The phase transition temperature, Tc, is 890±10 K. Dielectric measurements reveal the ferroelectric nature of the phase transition. A spontaneous polarization of about 2-3 ?C cm -2 is estimated from SHG. The phase transition from a polar ferroelectric form ? (space group R3 c), to a centrosymmetric paraelectric form ?' (space group R overline3c ), is reversible and of first order. The evolution of the crystal structure and lattice parameters is studied by high-temperature XRD and ED. The structural parameters of ?'-Ca 9Fe(PO 4) 7 are refined by the Rietveld method from XRD data at 923 K in the space group R overline3c ( Z=6) with lattice parameters a=10.3878(2) Å and c=37.8387(4) Å ( Rwp=1.48% and RI=2.16%). Both ?- and ?'-Ca 9Fe(PO 4) 7 are related to the whitlockite-type structure. The ?? ?' phase transition in Ca 9Fe(PO 4) 7 is accompanied by a disordering of the Ca 2+ ions at the Ca3 sites and orientational disordering of the P1O 4 tetrahedra.

  3. Near-field resonance shifts of ferroelectric barium titanate domains upon low-temperature phase transition

    SciTech Connect

    Döring, Jonathan; Ribbeck, Hans-Georg von; Kehr, Susanne C.; Eng, Lukas M. [Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, D-01069 Dresden (Germany); Fehrenbacher, Markus [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, D-01328 Dresden (Germany)

    2014-08-04

    Scattering scanning near-field optical microscopy (s-SNOM) has been established as an excellent tool to probe domains in ferroelectric crystals at room temperature. Here, we apply the s-SNOM possibilities to quantify low-temperature phase transitions in barium titanate single crystals by both temperature-dependent resonance spectroscopy and domain distribution imaging. The orthorhombic-to-tetragonal structural phase transition at 263?K manifests in a change of the spatial arrangement of ferroelectric domains as probed with a tunable free-electron laser. More intriguingly, the domain distribution unravels non-favored domain configurations upon sample recovery to room temperature as explainable by increased sample disorder. Ferroelectric domains and topographic influences are clearly deconvolved even at low temperatures, since complementing our s-SNOM nano-spectroscopy with piezoresponse force microscopy and topographic imaging using one and the same atomic force microscope and tip.

  4. A Model for Simulating Polarization Switching and AF-F Phase Changes in Ferroelectric Ceramics

    Microsoft Academic Search

    W. Chen; C. S. Lynch

    1998-01-01

    A computational micromechanics model for polycrystalline ferroelectric ceramics developed by Chen and Lynch (1997) is modified and applied to the simulation of ferroelectric and ferroelastic switching of the tetragonal and the rhombohedral crystal structures, and to antiferroelectric to ferroelectric phase changes. Interactions between different grains in the ceramic are considered. Two switching criteria are used, one for ferroelectric switching and

  5. Analytical model of the ferroelectric radiation detector

    Microsoft Academic Search

    J. T. Klopcic; D. L. Swanson

    1973-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  7. Microwave Induced Direct Bonding of Single Crystal Silicon Wafers

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  8. Transport and magnetic properties of Fe2VAl single crystal

    NASA Astrophysics Data System (ADS)

    Ishikawa, F.; Fukuda, K.; Kawase, N.; Mochigi, M.; Yamada, Yuh; Matsushita, A.

    We prepared single crystals of Fe1.95V1.05Al, Fe1.98V1.02Al, Fe2VAl, Fe2.02V0.98Al and Fe2.05V0.95Al by the conventional Czochralski pulling method in a tetra-arc furnace. The magnetization along the [1 0 0] direction was measured using a SQUID magnetometer. The Fe2VAl sample showed the smallest value of magnetization among the samples. The magnetization of the single crystalline sample was smaller than that of the polycrystalline sample with the same composition. These results for the single crystal suggest that the Fe2VAl has the lower concentration of magnetic antisite defects. The Seebeck coefficients were measured in the temperature range from 10 to 300 K. Fe2VAl showed the largest absolute value of the Seebeck coefficient S among the present samples, about |S|=180 ?V/K.

  9. Optical properties of anhydrous copper(II) formate single crystal

    NASA Astrophysics Data System (ADS)

    Narsimlu, N.; Sivarama Sastry, G.

    1996-12-01

    Infrared (IR) (450-4500 cm -1) spectroscopy, electron paramagnetic resonance (EPR) and optical absorption (52 631-3225 cm -1) studies of anhydrous copper(II) formate single crystal have been carried out at 300 K. The IR spectrum of Cu(COOH) 2 single crystal shows four strong absorption bands at 3199, 1569, 1363 and 833 cm -1 which are attributed to the stretching and bending vibrations between the formate ion atoms. Analysis of EPR spectra using crystal field theory reveals that the Jahn-Teller active copper(II) ion is present in a tetragonally elongated square pyramidal site. The optical absorption in the UV and visible region is characterized by a charge transfer band, and a cubic field splitting of 3 d energy level of Cu 2+ ion. In addition, in the near infrared region eight absorption peaks are recorded. These transitions in the near infrared are assigned variously to the d- d transitions of copper(II) ion between the admixtured quantized energy levels of copper and oxygen orbitals, to the transitions arising out of the Hubbard energy gap of the crystal, and to the Fermi energy gap of the crystal, respectively. Finally the weak absorptions that are recorded are attributed to the linear combinations of the IR bands.

  10. Structure and mechanical properties of biogenic single calcite crystals

    NASA Astrophysics Data System (ADS)

    Aizenberg, Joanna; Weiner, Steve; Addadi, Lia

    2000-03-01

    Composite materials, in which the organic host is stiffened by guest crystalline particles, are widely used in nature (bones, teeth, mollusk shells) and are produced synthetically by man (fiber-reinforced composites). Organisms also produce a different type of composite in which the host is a single crystal and the guests are macromolecules occluded in an orderly fashion within the crystal. The best-studied examples, to date, are skeletal elements composed of a single calcite crystal. These skeletons have unique mechanical properties, and fracture with a glassy conchoidal surface, which is quite different from the smooth planar cleavage of pure calcite. The specific positions of macromolecules in calcite crystals were identified by in vitro crystallization experiments and synchrotron X-ray studies. We show that the occluded macromolecules introduced specifically along crystallographic planes that are oblique to the cleavage planes of calcite strengthen the material against failure by both absorbing and deviating the advancing cracks. These novel, "reverse" fiber-reinforced, composites may be just one example of strategies used in nature for producing materials with improved properties.

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

    SciTech Connect

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

    2012-12-15

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

  12. Phase transition behavior and defect chemistry of [001]-oriented 0.15Pb(In1/2Nb1/2)O3-0.57Pb(Mg1/3Nb2/3)O3-0.28PbTiO3-Mn single crystals

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Fang, Bijun; Deng, Ji; Deng, Hao; Yan, Hong; Yue, Qingwen; Chen, Jianwei; Li, Xiaobing; Ding, Jianning; Zhao, Xiangyong; Luo, Haosu

    2015-06-01

    The ferroelectric single crystals 0.5 mol. % Mn-doped 0.15Pb(In1/2Nb1/2)O3-0.57Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PIMNT-Mn) with rhombohedral perovskite structure were grown by a modified Bridgman method. Dielectric performance analysis reveals that the as-grown PIMNT-Mn single crystals exhibit complex dielectric behavior after polarization, in which the dielectric constant depends on frequency apparently around the ferroelectric phase transition temperatures TR-M and Tm. The temperature and electric-field induced ferroelectric phase transitions were investigated by the temperature dependent unipolar strain curves. The electric-field induced discontinuous ferroelectric phase transitions at elevated temperatures exhibit first-order like phase transition character. The converse piezoelectric constant (d33), maximum strain value (Smax%), and longitudinal electrostrictive coefficient (Q) increase considerably when the temperature approaches the ferroelectric phase transition temperatures TR-M and TM-T. The complex impedance curves (Z?-Z') present typical semicircle shapes from 425 °C to 550 °C. The activation energy calculated by the Arrhenius law is 0.86 eV, indicating that the high-temperature conduction mechanism is dominated by the extrinsically formed oxygen vacancies.

  13. Subsurface Stress Fields In Single Crystal (Anisotropic) Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Knudsen, Erik C.; Duke, Greg; Battista, Gilda; Swanson, Greg

    2004-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is , presented, for evaluating the subsurface stresses in the elastic half-space, using a complex potential method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis. Effects of crystal orientation on stress response and fatigue life are examined.

  14. Giant Enhancement of Ferroelectricity in Strained BaTiO3 Thin Films

    NASA Astrophysics Data System (ADS)

    Eom, Chang-Beom

    2005-03-01

    Epitaxial thin films often have quite different properties than bulk single crystals due to epitaxial and thermal strains arising from substrate constraints. This offers the opportunity to modify ferroelectric properties by heteroepitaxy and strain engineering. Biaxial compressive strain has been used to dramatically enhance the ferroelectric properties of BaTiO3 thin films on (110) GdScO3 and (110) DyScO3 substrates [1]. This strain, imposed by commensurate epitaxy, can result in a ferroelectric transition temperature (Tc) nearly 500 C higher and a remanent polarization (Pr) at least 250% higher than bulk BaTiO3 single crystals. This is the largest increase in Tc ever reported for a ferroelectric, and it is consistent with thermodynamic prediction. This work demonstrates a route to a lead-free ferroelectric for non-volatile memories and electro-optic devices, and is a general means for achieving extraordinary physical properties in thin films through strain engineering. [1] K. J. Choi et al. SCIENCE, 306, 1005 (2004). This work has been done in collaboration with K. J. Choi, M. Biegalski, Y. L. Li, A. Sharan, J. Schubert, R. Uecker, P. Reiche, Y. B. Chen, X. Q. Pan, V. Gopalan, L.-Q. Chen, D. G. Schlom.

  15. Subsurface Stress Fields in FCC Single Crystal Anisotropic Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Knudsen, Erik; Swanson, Gregory R.; Duke, Gregory; Ham-Battista, Gilda

    2004-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent high cycle fatigue (HCF) failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and non-crystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is presented for evaluating the subsurface stresses in the elastic half-space, based on the adaptation of a stress function method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis (FEA). Effects of crystal orientation on stress response and fatigue life are examined. Obtaining accurate subsurface stress results for anisotropic single crystal contact problems require extremely refined three-dimensional (3-D) finite element grids, especially in the edge of contact region. Obtaining resolved shear stresses (RSS) on the principal slip planes also involves considerable post-processing work. For these reasons it is very advantageous to develop analytical solution schemes for subsurface stresses, whenever possible.

  16. K(0.46)Na(0.54)NbO3 ferroelectric ceramics: chemical synthesis, electro-mechanical characteristics, local crystal chemistry and elastic anomalies.

    PubMed

    Yi, Zhiguo; Liu, Yun; Carpenter, Michael A; Schiemer, Jason; Withers, Ray L

    2011-05-14

    K(0.46)Na(0.54)NbO(3) ceramics have been fabricated via a chemical synthesis route. It was found that 500 °C heat treatment is sufficient to crystallize the niobate powder and the ceramic sintered at 1080 °C in air shows good ferroelectric and piezoelectric properties (P(r) ~ 15 ?C cm(-2), d(33) ~ 120 pC N(-1)). Electron diffraction patterns not only determine the space group symmetry of Pcm2(1) for the first time, but also reveal structural disorder in K(0.46)Na(0.54)NbO(3), and 1-D correlated strings of Nb-O atomic displacements are suggested to account for the polar behaviour. Elastic constants such as the bulk and shear moduli as well as their evolution with temperature were also measured using the resonant ultrasound spectroscopy method. PMID:21451881

  17. Journal of Crystal Growth 304 (2007) 114117 Single crystal growth of YbRh2Si2 using Zn flux

    E-print Network

    Broholm, Collin Leslie

    2007-01-01

    Journal of Crystal Growth 304 (2007) 114­117 Single crystal growth of YbRh2Si2 using Zn flux-temperature solution technique, using Zn flux and followed by a decanting process. As opposed from the crystals growth: A1. Growth from high-temperature solutions; A1. Single crystal; B2. YbRh2Si2 1. Introduction YbRh2Si

  18. Photoluminescence of Neutron-Irradiated LiF Single Crystals

    NASA Astrophysics Data System (ADS)

    Jonane, I.; Podins, A.; Ivanova, A.

    2010-01-01

    In 1980, a single LiF crystal was irradiated by thermal neutrons up to the exposition dose 1019 n/cm2 at the Salaspils nuclear reactor. The crystal has been kept at room temperature for 29 years. Samples in size of 5×4×1 mm3 were cut from the crystal and some of them annealed at 920 K for 30 min. To study photoluminescence, measurements with a confocal laser scanning microscope Leica TCS SP5 were performed, during which 3D-defects of size of ~1?m3 were revealed. Photoluminescence was observed in the red spectral region with the peak of ~ 655 nm when excited with an argon laser (? = 458 nm).

  19. Synthesis, crystal structure and EPR spectra of tetraaquabis(methylisonicotinate) copper(II) disaccharinate single crystal

    NASA Astrophysics Data System (ADS)

    Çelik, Yunus; Bozkurt, Esat; Uçar, ?brahim; Karabulut, Bünyamin

    2011-10-01

    The crystal structure of the [Cu(mein)2(H2O)4]·(sac)2 complex (mein: methylisonicotinate, sac: saccharine) was investigated by single crystal X-ray diffraction technique. The vibrational spectrum was also discussed in relation with the other compounds containing methylisonicotinate and saccharinate complexes. The EPR spectra of [Cu(mein)2(H2O)4]·(sac)2 single crystal have been studied in the temperature range between 113 and 300 K in three mutually perpendicular planes and exhibit two sets of four hyperfine lines of Cu2+ ion. The ground state wave function of the Cu2+ ion is an admixture of dx2-y2 and dz2 states.

  20. Single crystal growth, crystal structure characterization and magnetic properties of UCo0.5Sb2

    SciTech Connect

    Bukowski, Z. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland)]. E-mail: bukowski@int.pan.wroc.pl; Tran, V.H. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland); Stepien-Damm, J. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland); Troc, R. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland)

    2004-11-01

    Single crystals of uranium intermetallic compound UCo0.5Sb2 were grown by means of the antimony-flux technique. The characterization of the samples has been carried out utilizing single crystal X-ray diffraction and magnetization measurements. UCo0.5Sb2 is found to crystallize in the tetragonal HfCuSi2-type structure, space group P4/nmm with Z=2 formula units per cell, and the lattice parameters a=0.4300(1) and c=0.8958(2)nm. The refinement of the occupancy parameters and the energy dispersive X-ray analysis have indicated a distinct deficiency on the cobalt sites. The results of magnetization measurements showed that UCo0.5Sb2 orders ferromagnetically below 65K with a huge magnetocrystalline anisotropy with the c direction being the easy magnetization axis.

  1. Crystal growth and characterization of CuI single crystals by solvent evaporation technique

    SciTech Connect

    Gu, Mu, E-mail: mgu@tongji.edu.cn [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Department of Physics, Tongji University, No. 1239 Siping Road, Yangpu District, Shanghai 200092 (China)] [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Department of Physics, Tongji University, No. 1239 Siping Road, Yangpu District, Shanghai 200092 (China); Gao, Pan; Liu, Xiao-Lin; Huang, Shi-Ming; Liu, Bo; Ni, Chen [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Department of Physics, Tongji University, No. 1239 Siping Road, Yangpu District, Shanghai 200092 (China)] [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Department of Physics, Tongji University, No. 1239 Siping Road, Yangpu District, Shanghai 200092 (China); Xu, Rong-Kun; Ning, Jia-min [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)] [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2010-05-15

    Cuprous iodide (CuI) crystals are grown by slow evaporation technique in three different solvents. Large CuI single crystals with dimensions of 7.5 mm x 5 mm x 3 mm are obtained in pure acetonitrile solvent at 40 {sup o}C. The as-grown crystals are analyzed by X-ray diffraction, energy-dispersive X-ray analysis, differential scanning calorimetry, current-voltage characteristic and photoluminescence spectrum. The results show that the CuI crystal has the zinc-blende structure with no secondary phase. The elemental Cu/I ratio is 1.09:1. The melting point of the crystal is 875 K and two phase transitions occur from room temperature to its melting point. The electrical conductivity of CuI platelet crystal is in the range of 1.11-2.38 {Omega}{sup -1} cm{sup -1}. Under ultraviolet excitation, the CuI crystals exhibit three emission bands with peak positions at 426, 529 and 671 nm. The nature of the luminescence is discussed.

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

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Swanson, Gregory R.

    2000-01-01

    High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine engines is a pervasive problem affecting a wide range of components and materials. HCF is currently the primary cause of component failures in gas turbine aircraft engines. Turbine blades in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys. Single-crystal Nickel-base superalloys were developed to provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys previously used in the production of turbine blades and vanes. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. PWA1493, identical to PWA1480, but with tighter chemical constituent control, is used in the NASA SSME (Space Shuttle Main Engine) alternate turbopump, a liquid hydrogen fueled rocket engine. Objectives for this paper are motivated by the need for developing failure criteria and fatigue life evaluation procedures for high temperature single crystal components, using available fatigue data and finite element modeling of turbine blades. Using the FE (finite element) stress analysis results and the fatigue life relations developed, the effect of variation of primary and secondary crystal orientations on life is determined, at critical blade locations. The most advantageous crystal orientation for a given blade design is determined. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to optimize blade design by increasing its resistance to fatigue crack growth without adding additional weight or cost.

  3. Electron paramagnetic resonance characterization of gamma irradiation damage centers in S-butyrylthiocholine iodide single crystal

    Microsoft Academic Search

    Betül Çali?kan; Mehmet Çivi; Mehmet Birey

    2007-01-01

    Radiation-induced S-butyrylthiocholine Iodide (SBTCI) (C9H20INOS) single crystals have been ana-lysed as results from the use of electron paramagnetic resonance (EPR) spectroscopy. SBTCI single crystals were irradiated with Co–? rays at 296 K and their EPR spectrum was studied as a function of temperature. The single crystals have been investigated between 120 and 445 K. The single crystal spectra were taken at 5°

  4. Laser radiation frequency doubling in a single-crystal fibre based on a stoichiometric LiNbO3 crystal

    NASA Astrophysics Data System (ADS)

    Kashin, V. V.; Nikolaev, D. A.; Rusanov, S. Ya; Tsvetkov, V. B.

    2015-01-01

    We demonstrate the employment of single-crystal optical fibres based on lithium niobate for doubling the laser radiation frequency. The measured characteristics of the fibre confirm its high quality and spatial homogeneity. Parameters of the frequency doublers for neodymium laser radiation (? = 1 mm) based on fibre and bulk single crystals are compared. Single crystals are grown by the method of laser-heated pedestal growing with heating by radiation of a CO2 laser (LHPG-method).

  5. Single crystal electrical resistivity of magnetite under high pressure

    NASA Astrophysics Data System (ADS)

    Muramatsu, Takaki; Helmuth Berger Collaboration; Lev V Gasparov Collaboration; Viktor V. Struzhkin Collaboration; Russell J. Hemley Collaboration

    2015-03-01

    Magnetite (Fe3O4), the oldest known magnetic mineral has the cubic inversed spinel structure at ambient pressure and temperature. It shows a metal to insulator transition (Verway transition) at about 125 K as temperature decreases at ambient pressure. Under high pressure the Verwey transition is suppressed down to 0 K and above 25 GPa magnetite undergoes a structural transformation to high pressure phase. These behaviors have been intensively examined by various experimental means and computational calculations for decades. However only the limited number of the electrical resistivity measurements on single crystal magnetite under pressure have been performed at the moment. We performed high pressure and low temperature experiments by means of the electrical resistivity on single crystal magnetite to examine Verwey transition under pressure and a structural transformation from cubic spinel phase to high pressure phase. We report the results of the temperature dependence of the electrical resistivity in the pressure range from ambient pressure to more than 50 GPa.

  6. Ferromagnetic Ordering in Carbon Nanotubes, Incorporated in Diamond Single Crystals

    E-print Network

    Dmitri Yerchuck; Vyacheslav Stelmakh; Alla Dovlatova; Yauhen Yerchak; Andrey Alexandrov

    2013-06-02

    The physical origin of the mechanism of the formation of ferromagnetic ordering in carbon nanotubes (NTs), produced by high energy ion beam modification of diamond single crystals in $\\langle{110}\\rangle$ and $\\langle{111}\\rangle$ directions has been found. It is concluded from analysis of experimental results on ferromagnetic spin wave resonance observed, that the only $\\pi$-electronic subsystem of given NTs is responsible for the appearance of ferromagnetism. It is determined by asymmetry in spin density distribution in Su-Schrieffer-Heeger (SSH) topological soliton lattice. The formation of SSH topological soliton lattice is considered in the frames of generalized SSH-model of organic conductors, in which $\\pi$-electronic subsystem is represented being to be 1D quantum Fermi liquid. The phenomenon of formation of uncompensated antiferromagnetic ordering coexisting with superconductivity at room temperature in carbon nanotubes, produced by high energy ion beam modification of diamond single crystals in $\\langle{100}\\rangle$ direction is argued.

  7. Plastic Deformation of Aluminum Single Crystals at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

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

    1956-01-01

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

  8. Challenges for Single-crystal (SX) Crack Cladding

    NASA Astrophysics Data System (ADS)

    Rottwinkel, Boris; Schweitzer, Luiz; Noelke, Christian; Kaierle, Stefan; Wesling, Volker

    The formation of cracks in single-crystal (SX) turbine blades is a common problem for aero-engines. If cracks are located under the tip-area, the blade-repair is not possible. Anew method to repair these cracks is to clad with single-crystal-technology.To reduce the loss of material and working time,notches are used to remove the affected crack zone. The usednotch geometries must be weldable and also permit the material solidification in the same oriented plane as the original microstructure. For that, a thermal gradient has to be introduced in order to guide the grain growth. The process characteristics of laser cladding, such as small local heat input and controlled material supply, make it an efficient process to fill the notch. However, there are challenges to achieve a SX structure without cracks and pores. The unstable energy distribution may result in a polycrystalline structure. Current achievements and further challenges are presented in this paper.

  9. Dynamic gas-inclusion in a single crystal.

    PubMed

    Takamizawa, Satoshi

    2015-06-01

    In solid-state science, most changing phenomena have been mysterious. Furthermore, the changes in chemical composition should be added to mere physical changes to also cover the chemical changes. Here, the first success in characterizing the nature of gas inclusion in a single crystal is reported. The gas inclusion process has been thoroughly investigated by in?situ optical microscopy, single-crystal X-ray diffraction analyses, and gas adsorption measurements. The results demonstrated an inclusion action of a first-order transition behavior induced by a critical concentration on the phase boundary. The transfer of phase boundary and included gas are strongly related. This relationship can generate the dynamic features hidden in the inclusion phenomena, which can lead to the guest capturing and transfer mechanism that can apply to spatiotemporal inclusion applications by using host solids. PMID:25925283

  10. Ultrafast dynamics of excitons in tetracene single crystals

    NASA Astrophysics Data System (ADS)

    Birech, Zephania; Schwoerer, Markus; Schmeiler, Teresa; Pflaum, Jens; Schwoerer, Heinrich

    2014-03-01

    Ultrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states Sn on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S1 on a 40 ps timescale. The high energy Davydov component of the S1 exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale.

  11. Ultrafast dynamics of excitons in tetracene single crystals.

    PubMed

    Birech, Zephania; Schwoerer, Markus; Schmeiler, Teresa; Pflaum, Jens; Schwoerer, Heinrich

    2014-03-21

    Ultrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states S(n) on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S1 on a 40 ps timescale. The high energy Davydov component of the S1 exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale. PMID:24655187

  12. Ultrafast dynamics of excitons in tetracene single crystals

    SciTech Connect

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

    2014-03-21

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

  13. Constitutive modeling of superalloy single crystals with verification testing

    NASA Technical Reports Server (NTRS)

    Jordan, Eric; Walker, Kevin P.

    1985-01-01

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

  14. Properties of salt-grown uranium single crystals.

    SciTech Connect

    Cooley, J. C. (Jason C.); Hanrahan, R. J. (Robert J.); Hults, W. L. (William L.); Lashley, J. C. (Jason C.); Manley, M. E. (Michael E.); Mielke, C. H. (Charles H.); Smith, J. L. (James L.); Thoma, D. J. (Dan J.); Clark, R. G. (Robert G.); Hamilton, A. R.; O'Brien, J. L. (Jeremy L.); Gay, E. C. (Eddie C.); Lumpkin, N. E.; McPheeters, C. C. (Charles C.); Willit, J.; Schmiedeshoff, G. M. (George M.); Touton, S. (Sharon); Woodfield, B. F. (Brian F.); Lang, B. E. (Brian E.); Boerio-Goates, Juliana

    2001-01-01

    Recently single crystals of {alpha}-uranium were grown from a liquid salt bath. The electrical, magnetic and thermal properties of these crystals have been surveyed. The ratio of the room temperature resistivity of these crystals to the saturation value at low temperature is three times larger than any previously reported demonstrating that the crystals are of higher purity and quality than those in past work. The resistive signatures of the CDW transitions at 43, 37 and 22 K are obvious to the naked eye. The transition at 22 K exhibits temperature hysteresis that increases with magnetic field. In addition the superconducting transition temperature from resistivity is 820 mK and the critical field is 80 mT. Contrary to earlier work where the Debye temperature ranged from 186 to 218 K, the Debye temperature extracted from the heat capacity is 254 K in good agreement with the predicted value of 250 K. Magnetoresistance, Hall effect and magnetic susceptibility measurements are underway. In time, measurements made on these crystals may help us to understand the origin of superconductivity and its relation to the CDW transitions in pure uranium.

  15. Growth of single-crystalline Bi6FeCoTi3O18 thin films and their magnetic–ferroelectric properties

    NASA Astrophysics Data System (ADS)

    Yun, Yu; Zhai, Xiaofang; Ma, Chao; Huang, Haoliang; Meng, Dechao; Cui, Zhangzhang; Wang, Jianlin; Fu, Zhengping; Peng, Ranran; Brown, Gail J.; Lu, Yalin

    2015-05-01

    High-quality single-crystalline thin films of n = 5 (n denotes the period of the Aurivillius structure) multiferroic Aurivillius oxides were obtained by determining and applying an optimal growth temperature of 605 °C and oxygen pressure of 20 Pa using pulsed laser deposition. The optimal growth ranges were narrower than 30 °C for the temperature and 10 Pa for the pressure. The optimized thin films exhibited obvious ferroelectric polarization switching in the out-of-plane direction as well as weak ferromagnetism with a saturation magnetization of less than 10 emu/cm3.

  16. Neutron Detectors Based Upon Artificial Single Crystal Diamond

    Microsoft Academic Search

    Maurizio Angelone; Giulio Aielli; Salvatore Almaviva; Roberto Cardarelli; Daniele Lattanzi; Marco Marinelli; Enrico Milani; Giuseppe Prestopino; Mario Pillon; Rinaldo Santonico; Aldo Tucciarone; Claudio Verona; Gianluca Verona-Rinati

    2009-01-01

    This paper reports about state-of-the-art artificial Single Crystal Diamond (SCD) neutron detectors based on a multilayered structure and grown by chemical vapour deposition (CVD) technique. Multilayered SCD detectors covered with a thin layer of 6LiF allow the simultaneous detection of both slow and fast neutrons and can operate in pulse and current mode. These detectors can also be produced with

  17. Stress induced transformations in Beta III Ti alloy single crystals

    Microsoft Academic Search

    J. A. Roberson; S. Fujishiro; V. S. Arunachalam; C. M. Sargent

    1974-01-01

    A combination of X-ray metallographic and transmission electron microscopy techniques have been used to investigate deformation\\u000a modes and deformation products in Beta III Ti alloy single crystals. Crystallographic slip was observed on {110}, {112} and\\u000a {113} planes. Twinning occurred on {ll2}, {332} and {2, 4.8, 4.8} planes. A martensitic transformation of the type proposed\\u000a by Blackburn and Feeney1 took place;

  18. Pockels effect in yttrium aluminum borate single crystals

    Microsoft Academic Search

    A. H. Reshak; A. Majchrowski; W. Imiolek

    2008-01-01

    Experimental measurements of linear electro-optical coefficients are reported for YAl3(BO3)4 (YAB) single crystals for the two principal tensor components xyz and yyy at the wavelength of a CW semiconducting GaAlAs laser emitting at 1040 nm. We have found the values of the Pockels coefficients\\u000a to be equal to 0.21 ± 0.06 and 0.56 ± 0.08 pm\\/V for 123 and 222

  19. Converting Ceria Polyhedral Nanoparticles into Single-Crystal Nanospheres

    Microsoft Academic Search

    Xiangdong Feng; Dean C. Sayle; Zhong Lin Wang; M. Sharon Paras; Brian Santora; Anthony C. Sutorik; Thi X. T. Sayle; Yi Yang; Yong Ding; Xudong Wang; Yie-Shein Her

    2006-01-01

    Ceria nanoparticles are one of the key abrasive materials for chemical-mechanical planarization of advanced integrated circuits. However, ceria nanoparticles synthesized by existing techniques are irregularly faceted, and they scratch the silicon wafers and increase defect concentrations. We developed an approach for large-scale synthesis of single-crystal ceria nanospheres that can reduce the polishing defects by 80% and increase the silica removal

  20. Constitutive modelling of single crystal and directionally solidified superalloys

    NASA Technical Reports Server (NTRS)

    Walker, Kevin P.; Jordan, Eric H.

    1987-01-01

    Successful attempts were made to model the deformation behavior of nickel base superalloys to be used in gas turbine engines based on both a macroscopic constitutive model and a micromechanical formulation based on crystallographic slip theory. These models were programmed as FORTRAN subroutines, are currently being used to simulate thermomechanical loading predictions expected at the fatigue critical locations on a single crystal turbine blade. Such analyses form a natural precursor to the application of life prediction methods to gas turbine airfoils.

  1. The kinetics of hydrogen diffusion in single crystal orthopyroxene

    Microsoft Academic Search

    Susan Jean Carpenter

    2003-01-01

    The kinetics of hydrogen diffusion in single crystals of orthopyroxene were investigated parallel to the [100], [010] and [001] crystallographic directions during dehydration and hydrogenation. The two groups of samples investigated spanned a range of metal composition, most notably iron, 4.5--8.5 wt % FeO, and aluminum, 2.1--3.5 wt % Al2O3; the aluminum was bound in both regular metal sites (AlVI)

  2. Nonpercolative metal-insulator transition in VO2 single crystals

    Microsoft Academic Search

    Bongjin Simon Mun; Kai Chen; Joonseok Yoon; Catherine Dejoie; Nobumichi Tamura; Martin Kunz; Zhi Liu; Michael E. Grass; Sung-Kwan Mo; Changwoo Park; Y. Yvette Lee; Honglyoul Ju

    2011-01-01

    Detailed temperature-dependent transport, optical microscopy, and synchrotron-based polychromatic x-ray microdiffraction measurements have been carried out in the vicinity of the metal-insulator transition (MIT) temperature of VO2 single crystals. The formation and propagation of a real-space phase boundary along the rutile c axis is monitored during the transition. Pure metallic rutile R, as well as insulating monoclinic M1 phases, is observed

  3. Electron spectroscopy of single crystal and polycrystalline cerium oxide surfaces

    Microsoft Academic Search

    D. R Mullins; S. H Overbury; D. R Huntley

    1998-01-01

    Valence band photoemission (XPS), valence band electron energy loss spectroscopy (EELS), Ce3d and 4d XPS, O1s XPS and O1s X-ray absorption (XAS) have been investigated for oxidized and sputtered single crystal CeO2 films and for oxidized Ce foil. Features were identified that distinguish between the Ce4+ or Ce3+ oxidation states. Ce4+ was identified by the highest binding energy peaks in

  4. Cascaded fourth-harmonic generation in a single nonlinear crystal

    Microsoft Academic Search

    Rosen Ivanov; Solomon Saltiel

    2005-01-01

    We investigate theoretically the process of phase-matched fourth-harmonic generation in a single quadratic crystal. In the case of a plane-wave fundamental or weak focusing, the results have an analytical form. The optimal focusing position of the fundamental beam depends on the values of the mismatches for each of the two steps of the second-order cascading: doubling of the fundamental frequency

  5. Low temperature strengthening in niobium-hydrogen single crystals

    Microsoft Academic Search

    K. V. Ravi; R. Gibala

    1971-01-01

    The mechanical behavior of high purity niobium and niobium-hydrogen single crystals at temperatures in the range 77? to 380?K\\u000a was investigated. Thermally activated hardening by hydrogen in solution is appreciable at temperatures ?150?K. However, hydride\\u000a precipitation occurs at these temperatures, can be strain-induced during mechanical testing, and accounts for the largest\\u000a part of the decrease in ductility in alloys with

  6. Elastic and Piezoelectric Coefficients of Single-Crystal Barium Titanate

    Microsoft Academic Search

    Don Berlincourt; Hans Jaffe

    1958-01-01

    Mechanical resonance and antiresonance frequencies were measured on barium titanate single-crystal elements maintained under electric dc bias from -50°C to +150°C. A complete set of elastic, piezoelectric, and dielectric constants of the tetragonal modification at 25°C is obtained. The elastic compliances show substantial deviation from cubic symmetry. Measurements in the orthorhombic state show longitudinal compliance four times higher than in

  7. High-temperature creep of forsterite single crystals

    Microsoft Academic Search

    Michel Darot; Yves Gueguen

    1981-01-01

    Creep of forsterite single crystals has been studied with respect to the orientation of the differential stress. Three orientations have been investigated: [110]c, [101]c, and [011]c. Specimens were deformed at high temperature (T?1400°C) and moderate stresses (5 < sigma<110 MPa) in a load creep apparatus at room pressure and under controlled atmosphere. Assuming Assuming, that the creep law has the

  8. Growth of niobium oxide films on single-crystal silicon

    Microsoft Academic Search

    V. A. Logacheva; N. A. Divakova; Yu. A. Tikhonova; E. A. Dolgopolova; A. M. Khoviv

    2007-01-01

    200-nm-thick niobium films grown on single-crystal silicon wafers by magnetron sputtering have been oxidized by annealing\\u000a in flowing oxygen. X-ray diffraction examination revealed the metal-like phase Nb6O in the as-deposited films. Annealing in flowing oxygen for 1 h led to the formation of tetragonal NbO2 at 570 K and hexagonal Nb2O5 at temperatures above 770 K. The grain size and

  9. Internal friction measurement in high purity tungsten single crystal

    NASA Technical Reports Server (NTRS)

    Rieu, G. E.

    1974-01-01

    Internal friction peaks observed after small deformation in high purity tungsten single crystals between liquid helium temperature and 800 K in the frequency range 30-50 KHz, are studied as a function of orientation. An orientation effect is observed in the internal friction spectra due to the creation of internal stresses. The elementary processes related to these peaks are discussed in terms of kink generation and geometric kink motion on screw and edge dislocations in an internal stress field.

  10. Electrical transport properties of CuS single crystals

    Microsoft Academic Search

    A Casaca; E B Lopes; A P Gonçalves; M Almeida

    2012-01-01

    Electrical resistivity, transverse magnetoresistance and thermoelectric power measurements were performed on CuS high quality single crystals in the range 1.2–300 K and under fields of up to 16 T. The zero field resistivity data are well described below 55 K by a quasi-2D model, consistent with a carrier confinement at lower temperatures, before the transition to the superconducting state. The

  11. Dielectric Breakdown of Single-Crystal Strontium Titanate

    Microsoft Academic Search

    Harrison H. Barrett

    1964-01-01

    Measurements of the intrinsic dielectric breakdown strength of single-crystal strontium titanate over a temperature range from ?195° to +100°C and under both pulse and dc conditions are described; dc breakdown at +100°C is thermal in origin. At room temperature and at ?40°C the breakdown strength is independent of duration of applied field and of sample configuration and hence may properly

  12. Hydrogen embrittlement in single- and poly-crystal niobium

    Microsoft Academic Search

    M. M. Farahani; F. Attia; K. Salama

    1981-01-01

    The effects of hydrogen on the yielding and the ductility of niobium have been studied in the temperature range between 373\\u000a and 78 K. Tensile tests were undertaken on single- and poly-crystal specimens containing hydrogen ranging between 30 and 230\\u000a ppm wt. at a strain rate of 1.7 X 10-4 s-1. The fracture surfaces of specimens tested were also examined

  13. Hydrogen embrittlement in single- and poly-crystal niobium

    Microsoft Academic Search

    M. M. Farahani

    1980-01-01

    The effect of dissolved hydrogen on the yielding and the ductility of both poly- and single-crystal niobium was studied in the temperature range between 78 and 373 K. Tensile tests were carried out on niobium specimens containing hydrogen ranging between 30 and 230 ppm wt., at a strain rate of 1.7 x 10 to the -4 power\\/sec. The fracture surfaces

  14. A piezoelectric single-crystal ultrasonic microactuator for driving optics

    Microsoft Academic Search

    Mingsen Guo; Shuxiang Dong; Bo Ren; Haosu Luo

    2011-01-01

    At the millimeter scale, the motions or force outputs generated by conventional piezoelectric, magnetostrictive, photostrictive, or electromagnetic actuators are very limited. Here, we report a piezoelectric ultrasonic microactuator (size: 1.5 x 1.5 x 5 mm, weight: 0.1 g) made of PIN-PMN-PT single crystal. The actuator converts its high-frequency microscopic displacements (nanometer to micrometer scale) into a macroscopic, centimeter-scale linear movement

  15. A study of single crystal zirconia implanted with platinum ions

    Microsoft Academic Search

    D.-Z. Xie; D.-Z. Zhu; D.-X. Cao; Z.-Y. Zhou

    1997-01-01

    Single crystal samples of (100) oriented cubic (yttria stabilized zirconia)(YSZ) were implanted with 105 and 160 keV platinum ions, using a metal vapor vacuum are (MEVVA) high current ion implanter, to nominal doses of 2 × 1016 ions\\/cm2 and 5 × 1016 ions\\/cm2, respectively, at room temperature (RT). The implanted samples were annealed isothermally in air ambient at 850°C and

  16. A study of single crystal zirconia implanted with platinum ions

    Microsoft Academic Search

    Dong-zhu Xie; De-zhang Zhu; De-xin Cao; Zhu-yao Zhou

    1997-01-01

    Single crystal samples of ?1 0 0? oriented cubic (yttria stabilized zirconia) (YSZ) were implanted with 105 and 160 keV platinum ions, using a metal vapor vacuum arc (MEVVA) high current ion implanter, to nominal doses of 2 × 1016ions\\/cm2 and 5 × 1016ions\\/cm2, respectively, at room temperature (RT). The implanted samples were annealed isothermally in air ambient at 850°C

  17. Amplified Ferrimagnetic Echoes in Single Crystal-Polycrystal YIG Composites

    Microsoft Academic Search

    D. E. Kaplan; W. I. Dobrov; G. F. Herrmann

    1972-01-01

    To clarify the conditions for generation of amplified Hahn-type echoes in ferrimagnets, experiments were conducted with composite samples formed by imbedding single crystal YIG wafers at various positions at and near the end of a poly crystalline YIG bar of similar cross section and 4piM value. The poly crystalline component provided the internal field and field gradient needed for echo

  18. Single crystal silicon as a low-temperature structural material

    NASA Astrophysics Data System (ADS)

    Roach, P. R.

    1984-07-01

    In neutron scattering applications, it is frequently desirable to construct a sample container from a material that is strong but has very little neutron absorption of scattering. Single crystal silicon is very good by these criteria but it is difficult to work with because of its brittleness. A technique for gluing silicon was developed that yields high strength joints at low temperatures and allows very compact designs for sample containers.

  19. Shock compression and spallation of single crystal tantalum Sheng-Nian Luo

    E-print Network

    Goddard III, William A.

    Shock compression and spallation of single crystal tantalum Sheng-Nian Luo Citation: AIP Conf. Proc://proceedings.aip.org/about/rights_permissions #12;SHOCK COMPRESSION AND SPALLATION OF SINGLE CRYSTAL TANTALUM Q. An, R. Ravelo, T. C. Germann, W. Z present molecular dynamics simulations of shock-induced plasticity and spall damage in single crystal Ta

  20. NUMERICAL SIMULATIONS OF CRACK TIP STRESS-STRAIN FIELDS IN SINGLE CRYSTAL NICKEL-BASE SUPERALLOYS

    E-print Network

    Paris-Sud XI, Université de

    NUMERICAL SIMULATIONS OF CRACK TIP STRESS-STRAIN FIELDS IN SINGLE CRYSTAL NICKEL-BASE SUPERALLOYS propagation model based on local approach to fracture. 1 INTRODUCTION Single crystal Nickel-base superalloys and turbine performances. In some temperature ranges, single crystal Nickel-base superalloys are prone

  1. A LIFETIME PREDICTION MODEL FOR SINGLE CRYSTAL SUPERALLOYS SUBJECTED TO THERMOMECHANICAL

    E-print Network

    Paris-Sud XI, Université de

    of nickel based single crystal superalloys. These materials are optimized for creep resistance but are proneA LIFETIME PREDICTION MODEL FOR SINGLE CRYSTAL SUPERALLOYS SUBJECTED TO THERMOMECHANICAL CREEP for Single Crystal Superalloys operated at high temperatures and subjected to creep, fatigue and oxidation

  2. Method for thermal processing alumina-enriched spinel single crystals

    DOEpatents

    Jantzen, C.M.

    1995-05-09

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly. 12 figs.

  3. Oxygen tracer diffusion in single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Cawley, James D.; Halloran, John W.; Cooper, Alfred R.

    1991-01-01

    Oxygen tracer diffusion coefficients are determined in single-crystal alumina samples with differing dopant levels using the gas-exchange technique. The diffusion direction is parallel to the c-axis and the ambient PO2 is 1 atm (100,000 Pa) for all experiments except a single run with a low PO2, approximately 10 to the -15th atm (10 to the -10th Pa) produced by a CO/CO2 mixture. The diffusion is insensitive to both impurities and ambient PO2. The insensitivities are discussed in terms of point-defect clustering. Prior tracer studies are compared and discussed.

  4. Large single-crystal monolayer graphene by decomposition of methanol

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, Gouri; Adams, Paul M.; Stapleton, Andrew D.; Muller, Heinrich G.; Foran, Brendan J.

    2011-10-01

    We present a novel method for the synthesis of monolayer graphene with large single-crystal domains extending over 10-30 ?m2, produced by the decomposition of methanol on Cu in a single process step, in a flow of pure Ar gas, without H2. Eliminating H2 as a process gas offers increased safety and greatly facilitates fabrication scaling. The graphene grain size and orientation were characterized by selected area electron diffraction in transmission electron microscopy. Based on analyses of effluents from the furnace during the synthesis, a possible mechanism for graphene formation from methanol, involving carbon monoxide as an intermediate, is proposed.

  5. Method for thermal processing alumina-enriched spinel single crystals

    DOEpatents

    Jantzen, Carol M. (Aiken, SC)

    1995-01-01

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly.

  6. Diamond turning of Si and Ge single crystals

    SciTech Connect

    Blake, P.; Scattergood, R.O.

    1988-12-01

    Single-point diamond turning studies have been completed on Si and Ge crystals. A new process model was developed for diamond turning which is based on a critical depth of cut for plastic flow-to-brittle fracture transitions. This concept, when combined with the actual machining geometry for single-point turning, predicts that {open_quotes}ductile{close_quotes} machining is a combined action of plasticity and fracture. Interrupted cutting experiments also provide a meant to directly measure the critical depth parameter for given machining conditions.

  7. Modeling single-crystal microstructure evolution due to shock loading

    NASA Astrophysics Data System (ADS)

    Lloyd, J. T.; Clayton, J. D.; Austin, R. A.; McDowell, D. L.

    2014-05-01

    An existing high strain rate viscoplastic (HSRVP) model is extended to address single-crystal anisotropic, elastic-plastic material response and is implemented into a steady plastic wave formulation in the weak shock regime. The single-crystal HSRVP model tracks the nucleation, multiplication, annihilation, and trapping of dislocations, as well as thermally activated and phonon drag limited glide kinetics. The steady plastic wave formulation is used to model the elastic-plastic response with respect to a propagating longitudinal wave, and assumes that the magnitudes of quasi-transverse waves are negligible. This steady wave analysis does not require specification of artificial viscosity, which can give rise to spurious dissipative effects. The constitutive model and its numerical implementation are applied to single-crystal pure Al and results are compared with existing experimental data. Dislocation density evolution, lattice reorientation, and macroscopic velocity-time histories are tracked for different initial orientations subjected to varying peak shock pressures. Results suggest that initial material orientation can significantly influence microstructure evolution, which can be captured using the modified Taylor factor.

  8. Hydrogen embrittlement in single- and poly-crystal niobium

    SciTech Connect

    Farahani, M.M.

    1980-01-01

    The effect of dissolved hydrogen on the yielding and the ductility of, both poly- and single-crystal, niobium have been studied in the temperature range between 78 and 373 K. Tensile tests were carried out on niobium specimens containing hydrogen ranging between 30 and 230 ppM wt, at a strain rate of 1.7 x 10/sup -4/ sec/sup -1/. The fracture surfaces of specimens tested were also examined by means of a scanning electron microscope (S.E.M.). These studies were undertaken with the ultimate goal of determining the roles of hydrogen concentration, grain boundaries, and temperature in the embrittlement and fracture process of a representative of group VA metals. The results obtained show that the addition of 30, 80, and 130 ppM wt H has no significant effect on the yield stress of either single- or poly-crystal niobium over the entire range of temperature studied. Addition of 230 ppM wt H to single crystal niobium, however, is found to have a strengthening effect in the temperature range where hydrogen is in solid solution. At lower temperatures, where the hydride phase is to be formed, no increase in the yield stress by hydrogen is observed. The addition of hydrogen strongly influences the temperature dependence of ductility of niobium.

  9. Interfacial dislocation motion and interactions in single-crystal superalloys

    SciTech Connect

    Liu, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Raabe, D. [Max Planck Inst. fur Eisenforshung. Dusseldorf (Germany); Roters, F. [Max Planck Inst. fur Eisenforshung. Dusseldorf (Germany); Arsenlis, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-10-01

    The early stage of high-temperature low-stress creep in single-crystal superalloys is characterized by the rapid development of interfacial dislocation networks. Although interfacial motion and dynamic recovery of these dislocation networks have long been expected to control the subsequent creep behavior, direct observation and hence in-depth understanding of such processes has not been achieved. Incorporating recent developments of discrete dislocation dynamics models, we simulate interfacial dislocation motion in the channel structures of single-crystal superalloys, and investigate how interfacial dislocation motion and dynamic recovery are affected by interfacial dislocation interactions and lattice misfit. Different types of dislocation interactions are considered: self, collinear, coplanar, Lomer junction, glissile junction, and Hirth junction. The simulation results show that strong dynamic recovery occurs due to the short-range reactions of collinear annihilation and Lomer junction formation. The misfit stress is found to induce and accelerate dynamic recovery of interfacial dislocation networks involving self-interaction and Hirth junction formation, but slow down the steady interfacial motion of coplanar and glissile junction forming dislocation networks. The insights gained from these simulations on high-temperature low-stress creep of single-crystal superalloys are also discussed.

  10. Subsurface Stress Fields in Single Crystal (Anisotropic) Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.

    2003-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and fatigue stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. Techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts are presented in this report. Figure 1 shows typical damper contact locations in a turbine blade. The subsurface stress results are used for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades.

  11. Segregation effects in Fe microalloyed NiAl single crystals

    SciTech Connect

    Vaerst, G.; Loeser, W.; Leonhardt, M.; Oswald, S. [Inst. fur Festkoerper- und Werkstofforschung Dresden (Germany)] [Inst. fur Festkoerper- und Werkstofforschung Dresden (Germany)

    1995-10-15

    The low density, excellent oxidation resistance and high thermal conductivity of the intermetallic phase NiAl compared to conventional nickel-based superalloys make NiAl based materials suitable for gas turbine applications. The lack of room-temperature ductility has been one of the barriers which hamper the technical use of the new material. Recently, a significant enhancement of room temperature tensile ductility up to 6% of soft <110> oriented NiAl single crystalline samples by microalloying with Fe, Ga or Mo was reported, compared with {approximately} 1 to 2% of binary stoichiometric NiAl. Dopant elements can display a rather inhomogeneous distribution along the crystal due to the redistribution of solute during directional solidification. Furthermore, the solute pile-up ahead of the smooth solidification front may lead to a morphological instability and to a transition from the single crystalline to a cellular/dendritic solidification mode. The scope of this paper is, therefore, to investigate the Fe distribution along the directionally solidified NiAl(Fe) crystals and possible transitions in microstructure, in order to reveal limitations for microalloying and to find out appropriate levels of dopant concentration and process parameters for homogeneously microalloyed NiAl single crystals.

  12. Formation of nanodomain ensembles during polarization reversal in Sr0.61Ba0.39Nb2O6: Ce single crystals

    NASA Astrophysics Data System (ADS)

    Shur, V. Ya.; Shikhova, V. A.; Pelegov, D. V.; Ievlev, A. V.; Ivleva, L. I.

    2011-11-01

    The results of the study of nano- and microdomain structure evolution in single crystals of relaxor ferroelectric strontium barium niobate Sr0.61Ba0.39Nb2O6 doped by cerium are presented. It was shown that the initial nanodomain structure represents a self-similar three-dimensional maze. The fractal dimension and average period were revealed. It was demonstrated that application of series of alternating electric field pulses makes it possible to produce a single-domain state in the surface layer. The features of the growth and "merging," as well as the shape of ensembles of isolated nanodomains formed during switching from the single-domain state, were investigated. The formation of the nanodomain ensembles was considered as a result of the self-organized discrete switching controlled by determined nucleation.

  13. Atomic force microscopy of insulin single crystals: direct visualization of molecules and crystal growth.

    PubMed Central

    Yip, C M; Ward, M D

    1996-01-01

    Atomic force microscopy performed on single crystals of three different polymorphs of bovine insulin revealed molecularly smooth (001) layers separated by steps whose heights reflect the dimensions of a single insulin hexamer. Whereas contact mode imaging caused etching that prevented molecular-scale resolution, tapping mode imaging in solution provided molecular-scale contrast that enabled determination of lattice parameters and polymorph identification while simultaneously enabling real-time examination of growth modes and assessment of crystal quality. Crystallization proceeds layer by layer, a process in which the protein molecules assemble homoepitaxially with nearly perfect orientational and translational commensurism. Tapping mode imaging also revealed insulin aggregates attached to the (001) faces, their incorporation into growing terraces, and their role in defect formation. These observations demonstrate that tapping mode imaging is ideal for real-time in situ investigation of the crystallization of soft protein crystals of relatively small proteins such as insulin, which cannot withstand the lateral shear forces exerted by the scanning probe in conventional imaging modes. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 PMID:8842243

  14. Interaction of Terahertz Radiation with Ferroelectrics

    Microsoft Academic Search

    Keith Nelson

    2007-01-01

    Ferroelectric crystals have long been used as acoustic transducers and receivers. An extensive toolset has been developed for MHz-frequency acoustic wave generation, control, guidance, and readout. In recent years, an analogous toolset has been developed for terahertz wave transduction and detection. Femtosecond optical pulses irradiate ferroelectric crystals to generate responses in the 0.1-5 THz frequency range that are admixtures of

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

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

    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 phase cannot be explained by a dynamics of only protons. This requires, instead, collective displacements within clusters that include also the heavier ions. These tunneling clusters can explain the recent evidence of tunneling obtained from Compton scattering measurements. The sole effect of mass change upon deuteration is not sufficient to explain the huge isotope effect. Instead, we find that structural modifications deeply connected with the chemistry of the H bonds produce a feedback effect on tunneling that strongly enhances the phenomenon. The resulting influence of the geometric changes on the isotope effect agrees with experimental data from neutron scattering. Calculations under pressure allowed us to analyze the issue of universality in the disappearance of ferroelectricity upon compression. Compressing DKDP so that the distance between the two peaks in the deuteron distribution is the same as for protons in KDP, corresponds to a modification of the underlying double-well potential, which becomes 23meV shallower. This energy difference is what is required to modify the O?O distance in such a way as to have the same distribution for protons and deuterons. At the high pressures required experimentally, the above feedback mechanism is crucial to explain the magnitude of the geometrical effect.

  16. New perspectives for ferroelectric LC-polymers

    SciTech Connect

    Brehmer, M.; Gebhard, E.; Wittig, T. [Univ. Mainz (Germany)

    1996-10-01

    LC-Elastomers prepared from ferroelectric LC-polymers are interesting materials for two reasons. From a materials point of view they are interesting because of their ferroelectric, piezoelectric and pyrroelectric properties. From a scientific point of view they are fascinating because they allow us to study the interplay of electric and mechanical forces in a rubbery material The coupling between the director reorientation and the network can be modified by crosslinking at the end of the mesogens or in the range of the polymer chains . In the last case the coupling is minimal. Besides the planar orientation in SSFLC-cells, free standing films offer the possibility of a homeotropic alignment of smectic liquid crystals ferroelectric LC elastomers of a different topology can be obtained by mixing a low molar mass or an oligomeric ferroelectric LC with a bifunctional crosslinkable: liquid crystal and performing photochemically a crosslinking reaction in one switching state of the smectic C* phase. As a result non crosslinkable ferroelectric LC will form micro-droplets surrounded by a densely crosslinked network, which is formed by the crosslinked non-ferroelectric liquid crystals. This gives a two phasic Volume or Network Stabilized Ferroelectric Liquid Crystal.

  17. Design of a single-polarization single-mode photonic crystal fiber double-core coupler

    Microsoft Academic Search

    Jianfeng Li; Kailiang Duan; Yishan Wang; Xiangjie Cao; Yongkang Guo; Xiangdi Lin

    2009-01-01

    A simple single-polarization single-mode (SPSM) photonic crystal fiber (PCF) coupler with two cores is introduced. The full-vector finite-element method (FEM) is applied to analyze the modal interference phenomenon of the even and odd modes of two orthogonal polarizations and the power propagation within the two cores. Meanwhile, the SPSM coupling wavelength range and its corresponding coupling length for different structure

  18. Design of Wideband Single-Polarization Single-Mode Photonic Crystal Fiber

    Microsoft Academic Search

    Fangdi Zhang; Min Zhang; Xiaoyi Liu; Peida Ye

    2007-01-01

    The present paper proposes a novel design for achieving single-polarization single-mode (SPSM) operation in photonic crystal fiber (PCF), using a rectangular-lattice PCF with two lines of three central air holes enlarged. The proposed PCF that is composed entirely of silica material is modeled by a full-vector finite element method with anisotropic perfectly matched layers. The position of the region of

  19. Single-domain-like behavior in a 3-mm natural single crystal of magnetite

    Microsoft Academic Search

    Özden Özdemir; David J. Dunlop

    1998-01-01

    We have observed single-domain (SD) like behavior in a 3-mm natural single crystal of magnetite following low-temperature demagnetization (LTD), which consists of zero-field cycling through the Verwey transition to erase remanence carried by pinned domain walls. We compared stepwise alternating field (AF) and thermal demagnetization curves of 1-mT total thermoremanent magnetization (TRM), 1-mT partial TRM (pTRM) acquired between the Curie

  20. Impact of oxygen ambient on ferroelectric properties of polar-axis-oriented CaBi4Ti4O15 films

    Microsoft Academic Search

    Kazumi Kato; Kiyotaka Tanaka; Kazuyuki Suzuki; Tatsuo Kimura; Kaori Nishizawa; Takeshi Miki

    2005-01-01

    Polar-axis oriented CaBi4Ti4O15 (CBTi144) films were fabricated on Pt foils using a complex metal alkoxide solution. The oxygen ambient during crystallization of the films impacted the crystal perfection, crystallite size, and the ferroelectric properties. The 500 mm thick film crystallized in oxygen flow had single columnar structure and in-plane grain size of about 200 nm. The Scherrer's crystallite diameter was

  1. Standard Reference Material (SRM 1990) for Single Crystal Diffractometer Alignment

    USGS Publications Warehouse

    Wong-Ng, W.; Siegrist, T.; DeTitta, G.T.; Finger, L.W.; Evans, H.T., Jr.; Gabe, E.J.; Enright, G.D.; Armstrong, J.T.; Levenson, M.; Cook, L.P.; Hubbard, C.R.

    2001-01-01

    An international project was successfully completed which involved two major undertakings: (1) a round-robin to demonstrate the viability of the selected standard and (2) the certification of the lattice parameters of the SRM 1990, a Standard Reference Material?? for single crystal diffractometer alignment. This SRM is a set of ???3500 units of Cr-doped Al2O3, or ruby spheres [(0 420.011 mole fraction % Cr (expanded uncertainty)]. The round-robin consisted of determination of lattice parameters of a pair of crystals' the ruby sphere as a standard, and a zeolite reference to serve as an unknown. Fifty pairs of crystals were dispatched from Hauptman-Woodward Medical Research Institute to volunteers in x-ray laboratories world-wide. A total of 45 sets of data was received from 32 laboratories. The mean unit cell parameters of the ruby spheres was found to be a=4.7608 A?? ?? 0.0062 A??, and c=12.9979 A?? ?? 0.020 A?? (95 % intervals of the laboratory means). The source of errors of outlier data was identified. The SRM project involved the certification of lattice parameters using four well-aligned single crystal diffractometers at (Bell Laboratories) Lucent Technologies and at NRC of Canada (39 ruby spheres), the quantification of the Cr content using a combined microprobe and SEM/EDS technique, and the evaluation of the mosaicity of the ruby spheres using a double-crystal spectrometry method. A confirmation of the lattice parameters was also conducted using a Guinier-Ha??gg camera. Systematic corrections of thermal expansion and refraction corrections were applied. These rubies_ are rhombohedral, with space group R3c. The certified mean unit cell parameters are a=4.76080 ?? 0.00029 A??, and c=12 99568 A?? ?? 0.00087 A?? (expanded uncertainty). These certified lattice parameters fall well within the results of those obtained from the international round-robin study. The Guinier-Ha??gg transmission measurements on five samples of powdered rubies (a=4.7610 A?? ?? 0.0013 A??, and c=12.9954 A?? ?? 0.0034 A??) agreed well with the values obtained from the single crystal spheres.

  2. New Techniques in Characterization of Ferroelectric Materials

    NASA Technical Reports Server (NTRS)

    Sehirlioglu, Alp

    2008-01-01

    Two new techniques have been developed to characterize Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) based ferroelectric single crystals: (i) electro-thermal imaging, and (ii) single crystal x-ray diffraction in the transmission mode. (i) Electro-thermal imaging is a remote sensing technique that can detect the polarization direction and poling state of a whole crystal slice. This imaging technique utilizes an IR camera to determine the field induced temperature change and does not require any special or destructive sample preparation. In the resulting images it is possible to distinguish regions of 180 deg domains. This powerful technique can be used remotely during poling to determine the poling state of the crystal to avoid over-poling that can result in inferior properties and/or cracking of the crystals. Electro-thermal imaging produced the first direct observations of polarization rotation. Under bipolar field, the domains near the corners were the first to switch direction. As the field increased above the coercive field, domains at the center part of the crystals switched direction. (ii) X-ray diffraction in the transmission mode has long been used in structure determination of organic crystals and proteins; however, it is not used much to characterize inorganic systems. 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals were examined by this XRD technique for the first time, and a never-before-seen super-lattice was revealed with a doubling of the unit cell in all three directions, giving a cell volume eight times that of a traditional perovskite unit cell. The significance of the super-lattice peaks increased with poling, indicating a structural contribution to ordering. Lack of such observations by electron diffraction in the transmission electron microscope examinations suggests the presence of a bulk effect.

  3. ESR Study on Irradiated Ascorbic Acid Single Crystal

    NASA Astrophysics Data System (ADS)

    Tuner, H.; Korkmaz, M.

    2007-04-01

    Food irradiation is a ``cold'' process for preserving food and has been established as a safe and effective method of food processing and preservation after more than five decades of research and development. The small temperature increase, absence of residue and effectiveness of treatment of pre-packed food are the main advantages. In food industry, ascorbic acid and its derivatives are frequently used as antioxidant agents. However, irradiation is expected to produces changes in the molecules of food components and of course in the molecules of the agents added as preservation agents such as ascorbic acid. These changes in the molecular structures could cause decreases in the antioxidant actions of these agents. Therefore, the radiation resistance of these agents must be known to determine the amount of radiation dose to be delivered. Electron spin resonance (ESR) is one of the leading methods for identification of intermediates produced after irradiation. ESR spectrum of irradiated solid powder of ascorbic acid is fairly complex and determinations of involved radical species are difficult. In the present work, single crystals of ascorbic acid irradiated by gamma radiation are used to determine molecular structures of radiation induced radicalic species and four radicalic species related in pair with P21 crystal symmetry are found to be responsible from experimental ESR spectrum of gamma irradiated single crystal of ascorbic acid.

  4. Strength anomaly in B2 FeAl single crystals

    SciTech Connect

    Yoshimi, K.; Hanada, S.; Yoo, M.H. [Oak Ridge National Lab., TN (United States); Matsumoto, N. [Tohoku Univ. (Japan). Graduate School

    1994-12-31

    Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). The orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.

  5. Plastic deformation of Ni{sub 3}Nb single crystals

    SciTech Connect

    Hagihara, Kouji; Nakano, Takayoshi; Umakoshi, Yukichi

    1999-07-01

    Temperature dependence of yield stress and operative slip system in Ni{sub 3}Nb single crystals with the D0{sub a} structure was investigated in comparison with that in an analogous L1{sub 2} structure. Compression tests were performed at temperatures between 20 C and 1,200 C for specimens with loading axes perpendicular to (110), (331) and (270). (010)[100] slip was operative for three orientations, while (010)[001] slip for (331) and {l{underscore}brace}211{r{underscore}brace}{lt}{bar 1}{bar 0} 7 13{gt} twin for (270) orientations were observed, depending on deformation temperature. The critical resolved shear stress (CRSS) for the (010)[100] slip anomaly increased with increasing temperature showing a maximum peak between 400 C and 800 C depending on crystal orientation. The CRSS showed orientation dependence and no significant strain rate dependence in the temperature range for anomalous strengthening. The [100] dislocations with a screw character were aligned on the straight when the anomalous strengthening occurred. The anomalous strengthening mechanism for (010)[100] slip in Ni{sub 3}Nb single crystals is discussed on the basis of a cross slip model which has been widely accepted for some L1{sub 2}-type compounds.

  6. CdSe nanoparticles dispersed in ferroelectric smectic liquid crystals: effects upon the smectic order and the smectic-A to chiral smectic-C phase transition.

    PubMed

    Thanassoulas, Angelos; Karatairi, Eva; Cordoyiannis, George; Kutnjak, Zdravko; Tzitzios, Vassilios; Lelidis, Ioannis; Nounesis, George

    2013-09-01

    Spherical CdSe nanoparticles, surface-treated with oleylamine and tri-octylphosphine, dispersed in ferroelectric liquid crystals, can efficiently target disclination lines, substantially altering the macroscopic properties of the host compound. Here we present an ac calorimetry and x-ray diffraction study demonstrating that for a large range of nanoparticle concentrations the smectic-A layer thickness increases monotonically. This provides evidence for enhanced accumulation of nanoparticles at the smectic layers. Our results for the Smectic-A (SmA) to chiral smectic-C (SmC) phase transition of the liquid crystal S-(+)4-(2'-methylbutyl)phenyl-4'-n-octylbiphenyl-4-carboxylate (CE8) reveal that the character of the transition is profoundly changed as a function of the nanoparticle concentration. Large transition temperature shifts are recorded. Moreover, the heat-capacity peaks exhibit a crossover trend to a step-like anomaly. This behavior may be linked to the weakening of the SmA and SmC order parameter coupling responsible for the observed near-tricritical, mean-field character of the transition in bulk CE8. At lower temperatures, the presence of nanoparticles disrupts the phase sequence involving the tilted hexatic phases most likely by obstructing the establishment of long-range bond-orientational order. PMID:24125282

  7. Electronic properties of graphene-single crystal diamond heterostructures

    SciTech Connect

    Zhao, Fang; Thuong Nguyen, Thuong; Golsharifi, Mohammad; Amakubo, Suguru; Jackman, Richard B., E-mail: r.jackman@ucl.ac.uk [London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH (United Kingdom); Loh, K. P. [Department of Chemistry, National University of Singapore, 3 Science Drive, Singapore 117543 (Singapore)

    2013-08-07

    Single crystal diamond has been used as a substrate to support single layer graphene grown by chemical vapor deposition methods. It is possible to chemically functionalise the diamond surface, and in the present case H-, F-, O-, and N-group have been purposefully added prior to graphene deposition. The electronic properties of the resultant heterostructures vary strongly; a p-type layer with good mobility and a band gap of ?0.7?eV is created when H-terminated diamond layers are used, whilst a layer with more metallic-like character (high carrier density and low carrier mobility) arises when N(O)-terminations are introduced. Since it is relatively easy to pattern these functional groups on the diamond surface, this suggests that this approach may offer an exciting route to 2D device structures on single layer graphene sheets.

  8. Single crystal growth and mechanical properties of MoSi2 and WSi2

    Microsoft Academic Search

    T. Hirano; M. Nakamura; K. Kimura; Y. Umakoshi

    1991-01-01

    A floating zone (FZ) furnace was modified into a high vacuum type furnace in order to grow high-purity single crystals of MoSi2 and WSi2. The impurity levels of the grown MoSi2 single crystals were very low and the residual resistivity ratio was large, indicating that the grown crystals were of good quality. Compression tests of MoSi2 and WSi2 single crystals

  9. Optical Properties of a Piezoelectric Ta2O5 Single Crystal Film

    Microsoft Academic Search

    Yasuhiko Nakagawa; Isao Morita; Masashi Takahashi; Shoji Kakio

    2007-01-01

    Following the production of a uniaxially oriented Ta2O5 thin film on a single crystal substrate (X-cut LiTaO3) by RF sputtering, a Ta2O5 single-crystal film was created using linear rapid thermal annealing. Then the reflection high-energy electron diffraction (RHEED) pattern and X-ray diffraction pattern of the Ta2O5 single-crystal film were measured to examine its crystallization level. A refractive index tensor was

  10. A measurement of the temperature dependence of the absorption edge of single crystals, using polarized light 

    E-print Network

    Dunham, Robert Latham

    1964-01-01

    ~ ~ ~ ~ ~ . . ~ ~ ~ ~ ~ 24 4 Absorption of Iodine Single Crystals ~ ~ . . ~ ~ . ~ ~ 25 5 Absorption of Cadmium Sulfide Single Crystals ~ ~ 26 INTRODUCTION The objective of this particular research is to determine the absorption edge of single, molecular crystals... in the attempt to determine the absorption edge of the crystal for temperatures varying from SO'K to room temperature Principal drawbacks in the study of iodine are its physical and chemical properties. Its high vapor pressure, even at room temperature...

  11. Crystal structures of carbonates up to Mbar pressures determined by single crystal synchrotron radiation diffraction

    NASA Astrophysics Data System (ADS)

    Merlini, M.

    2013-12-01

    The recent improvements at synchrotron beamlines, currently allow single crystal diffraction experiments at extreme pressures and temperatures [1,2] on very small single crystal domains. We successfully applied such technique to determine the crystal structure adopted by carbonates at mantle pressures. The knowledge of carbon-bearing phases is in fact fundamental for any quantitative modelling of global carbon cycle. The major technical difficulty arises after first order transitions or decomposition reactions, since original crystal (apx. 10x10x5 ?m3) is transformed in much smaller crystalline domains often with random orientation. The use of 3D reciprocal space visualization software and the improved resolution of new generation flat panel detectors, however, allow both identification and integration of each single crystal domain, with suitable accuracy for ab-initio structure solution, performed with direct and charge-flipping methods and successive structure refinements. The results obtained on carbonates, indicate two major crystal-chemistry trends established at high pressures. The CO32- units, planar and parallel in ambient pressure calcite and dolomite structures, becomes non parallel in calcite- and dolomite-II and III phases, allowing more flexibility in the structures with possibility to accommodate strain arising from different cation sizes (Ca and Mg in particular). Dolomite-III is therefore also observed to be thermodynamically stable at lower mantle pressures and temperatures, differently from dolomite, which undergoes decomposition into pure end-members in upper mantle. At higher pressure, towards Mbar (lowermost mantle and D'' region) in agreement with theoretical calculations [3,4] and other experimental results [5], carbon coordination transform into 4-fold CO4 units, with different polymerisation in the structure depending on carbonate composition. The second important crystal chemistry feature detected is related to Fe2+ in Fe-bearing magnesite, which spontaneously oxidises at HP/HT, forming Fe3+ carbonates, Fe3+ oxides and reduced carbon (diamonds). Single crystal diffraction approach allowed full structure determination of these phases, yielding to the discovery of few unpredicted structures, such as Mg2Fe2C4O13 and Fe13O19, which can be well reproduced in different experiments. Mg2Fe2C4O13 carbonate present truncated chain C4O13 groups, and Fe13O19 oxide, whose stoichiometry is intermediate between magnetite and hematite, is a one-layer structure, with features encountered in superconducting materials. The results fully support the ideas of unexpected complexities in the mineralogy of the lowermost mantle, and single crystal technique, once properly optimized in ad-hoc synchrotron beamlines, is fundamental for extracting accurate structural information, otherwise rarely accessible with other experimental techniques. References: [1] Merlini M., Hanfland M. (2013). Single crystal diffraction at Mbar conditions by synchrotron radiation. High Pressure Research, in press. [2] Dubrovinsky et al., (2010). High Pressure Research, 30, 620-633. [3] Arapan et al. (1997). Phys. Rev. Lett., 98, 268501. [4] Oganov et al. (2008) EPSL, 273, 38-47. [5] Boulard et al. (2011) PNAS, 108, 5184-5187.

  12. Quantitative layer analysis of single crystal surfaces by LEIS

    NASA Astrophysics Data System (ADS)

    Beikler, Robert; Taglauer, Edmund

    2002-06-01

    The quantitative interpretation of energy and angle resolved low-energy ion scattering intensity distributions is achieved by comparing the experimental results with those from numerical simulations using the MARLOWE code with extensions for layer selective analysis. The example used is the CuAu(1 0 0) alloy crystal surface. For adequate analysis the potential parameter (i.e. the screening length) has to be calibrated. This is done by using elemental single crystal standards. Anisotropic thermal vibrations are taken into account in correspondence with published Debye temperature values. Neutralization effects are found to be of minor importance for Na + and He + scattering from CuAu. A quantitative analysis of the first and second layer composition of CuAu(1 0 0) as a function of temperature could thus be obtained, the results being in good agreement with theoretical predictions.

  13. Multiband Effects on -FeSe single crystals

    SciTech Connect

    Petrovic C.; Lei, H.; Graf, D.; Hu, R.; Ryu, H.; Choi, E.S.; Tozer, S.W.

    2012-03-01

    We present the upper critical fields {mu}{sub 0}H{sub c2}(T) and Hall effect in {beta}-FeSe single crystals. The {mu}{sub 0}H{sub c2}(T) increases as the temperature is lowered for fields applied parallel and perpendicular to (101), the natural growth facet of the crystal. The {mu}{sub 0}H{sub c2}(T) for both field directions and the anisotropy at low temperature increase under pressure. Hole carriers are dominant at high magnetic fields. However, the contribution of electron-type carriers is significant at low fields and low temperature. Our results show that multiband effects dominate {mu}{sub 0}H{sub c2}(T) and electronic transport in the normal state.

  14. Conoscopic study of strontium-barium niobate single crystals

    NASA Astrophysics Data System (ADS)

    Kolesnikov, Aleksandr; Grechishkin, Rostislav; Malyshkina, Olga; Malyshkin, Yury; Dec, Jan; ?ukasiewicz, Tadeusz; Ivanova, Aleksandra

    2013-12-01

    Optically transparent single crystals of strontium-barium niobate, SrxBa1-xNb2O6, of different compositions (x = 0.26...0.7) were examined with the aid of conoscopic light interference figures. A regular change of the isochrome concentric ring number and diameters consistent with the temperature variation of the value of birefringence is demonstrated by direct observations of polar cuts of optically uniaxial samples. Anomalous violations of the conventional (uniaxial) interference patterns occur occasionaly in some samples being indicative of the existence of biaxial trait in their behaviour even though no voltage is applied. These features may depend on annealing treatments at elevated temperatures. The results of the study show that conoscopic images may serve as a sensitive indicator of the structural state of SBN crystals related to the effects of stress-induced change of optical anisotropy and temperature dependent birefringence parameters.

  15. Crystal oscillators using negative voltage gain, single pole response amplifiers

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L. (Inventor)

    1989-01-01

    A simple and inexpensive crystal oscillator is provided which employs negative voltage gain, single pole response amplifiers. The amplifiers may include such configurations as gate inverters, operational amplifiers and conventional bipolar transistor amplifiers, all of which operate at a frequency which is on the roll-off portion of their gain versus frequency curve. Several amplifier feedback circuit variations are employed to set desired bias levels and to allow the oscillator to operate at the crystal's fundamental frequency or at an overtone of the fundamental frequency. The oscillator is made less expensive than comparable oscillators by employing relatively low frequency amplifiers and operating them at roll-off, at frequencies beyond which they are customarily used. Simplicity is provided because operation at roll-off eliminates components ordinarily required in similar circuits to provide sufficient phase-shift in the feedback circuitry for oscillation to occur.

  16. The Thermoanalysis of Metal Single Crystals and a New Thermoelectric Effect of Bismuth Crystals Grown in Magnetic Fields

    Microsoft Academic Search

    Alexander Goetz; Maurice F. Hasler

    1930-01-01

    Part I. The Thermoanalysis of Bi Single Crystals Production of crystals.-Crystals of Bi of any desired orientation were grown by the method of Goetz, one half of each normally, the other half within a transversal magnetic field. The orientations, predetermined by a seed crystal, were not affected by this process. Two methods of growth-the continuous and the discontinuous-were used. The

  17. Single Crystal Structure Determination of Alumina to 1 Mbar

    NASA Astrophysics Data System (ADS)

    Dong, H.; Zhang, L.; Prakapenka, V.; Mao, H.

    2014-12-01

    Aluminum oxide (Al2O3) is an important ceramic material and a major oxide in the earth. Additionally, alumina is a widely used pressure standard in static high-pressure experiments (Cr3+-bearing corundum, ruby). The changes of its crystal structure with pressure (P) and temperature (T) are important for its applications and understanding its physical properties in the deep Earth. There have been numerous reports on the high P-T polymorphs of alumina. Previous theoretical calculations and experiments suggest that the crystal structure of Al2O3 evolves greatly at high P-T. In this study, we used the newly developed multigrain crystallography method combined with single-crystal x-ray diffraction analysis technique for the structure determination of alumina at high P-T to provide single-crystal structure refinement for high-pressure phases of Al2O3. Alumina powder was mixed with ~10% Pt and Ne was used as both pressure transmitting media and thermal insulating layers during laser-heating. Coarse-grained aggregates of Al2O3 were synthesized in a laser-heated diamond anvil cell. The structure change of Al2O3 was monitored by in situ x-ray diffraction at ~1 Mbar and 2700 K. The results allow us to distinguish the structural differences between the Rh2O3 (II) structure (space group Pbcn) and perovskite structure (space group Pbnm) for the first high-pressure phase of Al2O3. More detailed results will be discussed in the later work.

  18. Bending behavior of a flexible single crystal nanomembrane photonic crystal cavity

    NASA Astrophysics Data System (ADS)

    Xu, Xiaochuan; Subbaraman, Harish; Chen, Ray T.

    2015-02-01

    In this paper, we present experimental and theoretical studies on the bending induced resonance shift of a photonic crystal cavity. The photonic crystal devices are fabricated on a 2cm x 2cm large-area single crystal SiNM which is transferred defect-freely onto a Kapton substrate with an SU-8 bottom cladding. Photonic crystal tapers are implemented at the strip-photonic crystal waveguide interfaces, which lowers the coupling loss and enables operation closer to the band edge. Subwavelength grating (SWG) couplers are employed at the input and output of the device in order to enable device characterization. The device is mounted on the two jaws of a caliper and it can be buckled up and down through sliding one of the jaws. The bending radius at the top of the curvature can be estimated with the length of the specimen and the distance between the two jaws. A minimum bending radius of 5 mm is achieved. Finite element method (FEM) is used to simulate the deformation and the strain of the nanomembrane. The results are used as the input of finite difference time-domain (FDTD) simulation. The analysis shows that the strain sensitivities are 0.673 pm/??, 0.656 pm/??, 0.588 pm/??, and 0.591 pm/??, for longitudinal face-out, longitudinal face-in, transverse face-out, and transverse face-in bending, respectively.

  19. Thermal neutron dosimeter by synthetic single crystal diamond devices.

    PubMed

    Almaviva, S; Marinelli, Marco; Milani, E; Prestopino, G; Tucciarone, A; Verona, C; Verona-Rinati, G; Angelone, M; Pillon, M

    2009-07-01

    We report on a new solid state dosimeter based on chemical vapor deposition (CVD) single crystal diamond fabricated at Roma "Tor Vergata" University laboratories. The dosimeter has been specifically designed for direct neutron dose measurements in boron neutron capture therapy (BNCT). The response to thermal neutrons of the proposed diamond dosimeter is directly due to (10)B and, therefore, the dosimeter response is directly proportional to the boron absorbed doses in BNCT. Two single crystal diamond detectors are fabricated in a p-type/intrinsic/metal configuration and are sandwiched together with a boron containing layer in between the metallic contacts (see Fig.1). Neutron irradiations were performed at the Frascati Neutron Generator (FNG) using the 2.5 MeV neutrons produced through the D(d,n)(3)He fusion reaction. Thermal neutrons were then produced by slowing down the 2.5 MeV neutrons using a cylindrical polymethylmethacrylate (PMMA) moderator. The diamond dosimeter was placed in the center of the moderator. The products of (10)B(n,alpha)Li nuclear reaction were collected simultaneously giving rise to a single peak. Stable performance, high reproducibility, high efficiency and good linearity were observed. PMID:19375336

  20. Growth of High Quality A N Single Crystals and Their Optical Properties

    E-print Network

    Nabben, Reinhard

    Growth of High Quality A N Single Crystals and Their Optical Properties M. strassburgl, J a two-step growth process in a TaN crucible. Crystal defects and the effect of incorporated impurities,2,3]. Hence, the growth and crystal quality opiimhtion of buk AiN crystals is of primary importance

  1. Single crystal NMR studies of high temperature superconductors

    SciTech Connect

    Pennington, C.H.; Durand, D.J.; Zax, D.B.; Slichter, C.P.; Rice, J.P.; Bukowski, E.D.; Ginsberg, D.M.

    1989-01-01

    The authors report Cu NMR studies in the normal state of a single crystal of the T/sub c/ = 90 K superconductor YBa/sub 2/Cu/sub 3/O/sub 7/minus/delta/. The authors have measured the magnetic shift tensor, the electric field gradient tensor, the nuclear spin-lattice relaxation rate tensor, and the time dependence and functional form of the transverse decay. From these data they obtain information about the charge state and magnetic state of the Cu atoms, and the existence and size of the electronic exchange coupling between spins of adjacent Cu atoms. 18 refs., 3 figs., 2 tabs.

  2. Thin single-crystal Ge layers on 2? Si substrates

    NASA Astrophysics Data System (ADS)

    Shengurov, V. G.; Denisov, S. A.; Chalkov, V. Yu.; Buzynin, Yu. N.; Drozdov, M. N.; Buzynin, A. N.; Yunin, P. A.

    2015-01-01

    Conditions for preparing thin homogeneous mirror-smooth Ge layers on 2? Si substrates by hot wire chemical vapor-phase deposition have been determined. Ge layers 200 nm thick have a structure of epitaxial mosaic single crystal with almost completely relaxed elastic stresses. The X-ray diffraction rocking curve half-width is less than 6'. The density of grown-in dislocations in Ge layers is in the range of (3-6) × 105 cm-2, and the rms surface roughness does not exceed 0.8 nm.

  3. Polarization-dependent exciton dynamics in tetracene single crystals.

    PubMed

    Zhang, Bo; Zhang, Chunfeng; Xu, Yanqing; Wang, Rui; He, Bin; Liu, Yunlong; Zhang, Shimeng; Wang, Xiaoyong; Xiao, Min

    2014-12-28

    We conduct polarization-dependent ultrafast spectroscopy to study the dynamics of singlet fission (SF) in tetracene single crystals. The spectrotemporal species for singlet and triplet excitons in transient absorption spectra are found to be strongly dependent on probe polarization. By carefully analyzing the polarization dependence, the signals contributed by different transitions related to singlet excitons have been disentangled, which is further applied to construct the correlation between dynamics of singlet and triplet excitons. The anisotropy of exciton dynamics provides an alternative approach to tackle the long-standing challenge in understanding the mechanism of singlet fission in organic semiconductors. PMID:25554147

  4. Polarization-dependent exciton dynamics in tetracene single crystals

    E-print Network

    Zhang, Bo; Xu, Yanqing; Wang, Rui; He, Bin; Liu, Yunlong; Zhang, Shimeng; Wang, Xiaoyong; Xiao, Min

    2014-01-01

    We conduct polarization-dependent ultrafast spectroscopy to study the dynamics of singlet fission in tetracene single crystals. The spectrotemporal species for singlet and triplet excitons in transient absorption spectra are found to be strongly dependent on probe polarization. By carefully analyzing the polarization dependence, the signals contributed by different transitions related to singlet excitons have been disentangled, which is further applied to construct the correlation between dynamics of singlet and triplet excitons. The anisotropy of exciton dynamics provides an alternative approach to tackle the long-standing challenge in understanding the mechanism of singlet fission in organic semiconductors.

  5. Polarization-dependent exciton dynamics in tetracene single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Zhang, Chunfeng; Xu, Yanqing; Wang, Rui; He, Bin; Liu, Yunlong; Zhang, Shimeng; Wang, Xiaoyong; Xiao, Min

    2014-12-01

    We conduct polarization-dependent ultrafast spectroscopy to study the dynamics of singlet fission (SF) in tetracene single crystals. The spectrotemporal species for singlet and triplet excitons in transient absorption spectra are found to be strongly dependent on probe polarization. By carefully analyzing the polarization dependence, the signals contributed by different transitions related to singlet excitons have been disentangled, which is further applied to construct the correlation between dynamics of singlet and triplet excitons. The anisotropy of exciton dynamics provides an alternative approach to tackle the long-standing challenge in understanding the mechanism of singlet fission in organic semiconductors.

  6. EPR studies of gamma-irradiated taurine single crystals

    NASA Astrophysics Data System (ADS)

    Bulut, A.; Karabulut, B.; Tapramaz, R.; Köksal, F.

    2000-04-01

    An EPR study of gamma-irradiated taurine [C 2H 7NO 3S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32?O -2 and 33?O -2 radicals. The hyperfine values of 33?O -2 radical were used to obtain O-S-O bond angle for both sites.

  7. Characterization of defects in ?-Ga2O3 single crystals

    NASA Astrophysics Data System (ADS)

    Nakai, Katsuhiko; Nagai, Tetsuya; Noami, Kengo; Futagi, Toshiro

    2015-05-01

    We have investigated defects in beta-type gallium oxide (?-Ga2O3) single crystals by X-ray topography, selective etching, and transmission electron microscopy. Two types of defects, namely, dislocations and nanopipes, were found. Dislocations are screw dislocations with Burgers vector parallel to [010]. The majority of them lie on (\\bar{2}01) and (001). Nanopipes are hollow pipes of 0.1 µm diameter and of at least 15 µm length elongated along [010]. No strain field was found around them. From the observation results, we have discussed the formation mechanisms of these defects.

  8. Coherent Josephson phase qubit with a single crystal silicon capacitor

    NASA Astrophysics Data System (ADS)

    Patel, U.; Gao, Y.; Hover, D.; Ribeill, G. J.; Sendelbach, S.; McDermott, R.

    2013-01-01

    We have incorporated a single crystal silicon shunt capacitor into a Josephson phase qubit. The capacitor is derived from a commercial silicon-on-insulator wafer. Bosch reactive ion etching is used to create a suspended silicon membrane; subsequent metallization on both sides is used to form the capacitor. The superior dielectric loss of the crystalline silicon leads to a significant increase in qubit energy relaxation times. T1 times up to 1.6 ?s were measured, more than a factor of two greater than those seen in amorphous phase qubits. The design is readily scalable to larger integrated circuits incorporating multiple qubits and resonators.

  9. Raman Investigations of Rare Earth Arsenate Single Crystals

    SciTech Connect

    Barros, G [Universidade Federal do Ceara, Ceara, Brazil; Santos, C. C. [Universidade Federal do Ceara, Ceara, Brazil; Ayala, A. P. [Universidade Federal do Ceara, Ceara, Brazil; Guedes, I. [Universidade Federal do Ceara, Ceara, Brazil; Boatner, Lynn A [ORNL; Loong, C. K. [Sun Yat-Sen University, Guangzhou, China

    2010-01-01

    Polarized Raman Spectroscopy was used to investigate the room-temperature phonon characteristics of a series of rare-earth arsenate (REAsO4, RE = Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu) single crystals. The Raman data were interpreted in a systematic manner based on the known tetragonal zircon structure of these compounds, and assignments and correlations were made for the observed bands. We found that the wavenumber of the internal modes of the AsO4 tetrahedron increased with increasing atomic number, and for three out of four lattice wavenumbers observed, this tendency was not nearly so marked as in the case of the internal mode wavenumber.

  10. Two-Photon Absorption Spectrum of a Single Crystal Cyanine-like Honghua Hu,

    E-print Network

    Van Stryland, Eric

    Two-Photon Absorption Spectrum of a Single Crystal Cyanine-like Dye Honghua Hu, Dmitry A. Fishman Vegas, New Mexico 87701, United States *S Supporting Information ABSTRACT: The two-photon absorption (2PA) spectrum of an organic single crystal is reported. The crystal is grown by self

  11. Growth of Nd2TiO5 single crystal using optical floating zone technique

    NASA Astrophysics Data System (ADS)

    Murugesan, G.; Nithya, R.; Kalainathan, S.; Ravindran, T. R.

    2015-06-01

    Single crystals of Nd2TiO5 were grown using Optical Floating zone technique in oxygen atmosphere by spontaneous nucleation. Powder X-ray diffraction pattern showed that the grown single crystal is of homogeneous composition. Laue diffraction was recorded in both transmission and backscattering geometries to check the crystal quality. Vibrational properties were analyzed using Raman measurements.

  12. Orientation dependence of plastic deformation in nickel-based single crystal superalloys: Discretecontinuous model simulations

    E-print Network

    Devincre, Benoit

    Orientation dependence of plastic deformation in nickel-based single crystal superalloys: Discrete of single-crystal nickel-based superalloys is simulated. At 1123 K, two uniaxial tensile loading cases crystals of nickel-based superalloys are specifically developed for high-temperature applications [1

  13. Smectic-C* liquid crystals with six-layer periodicity appearing between the ferroelectric and antiferroelectric chiral smectic phases.

    PubMed

    Takanishi, Yoichi; Nishiyama, Isa; Yamamoto, Jun; Ohtsuka, Youko; Iida, Atsuo

    2013-05-01

    We found a subphase with a six-layer periodicity which appears between the ferroelectric SmC(*) and the antiferroelectric SmC(A)(*)(q(T) = 0) phases. The six-layer periodic structure is directly determined by the microbeam resonant x-ray scattering measurement. Furthermore, considering the dielectric constants, this phase was found to be ferrielectric, assigned as SmC(A)(*)(q(T) = 2/3). This subphase indicates the importance of the competition between the ferro- and the antiferroelectric phases and, in that point, it is essentially different from the previously observed six-layer phase. The relation between current theories and our present experimental results has been studied and discussed. PMID:23767473

  14. Observation of Ferroelectricity in a Confined Crystallite Using Electron Backscattered Diffraction and Piezoresponse Force Microscopy

    SciTech Connect

    Gupta, P. [Lehigh University, Bethlehem, PA; Jain, H. [Lehigh University, Bethlehem, PA; Williams, D. B. [Lehigh University, Bethlehem, PA; Kalinin, Sergei V [ORNL; Shin, Junsoo [ORNL; Jesse, Stephen [ORNL; Baddorf, Arthur P [ORNL

    2005-01-01

    LaBGeO{sub 5} is a model transparent ferroelectric glass-ceramic (TFGC) material, developed as an inexpensive alternative to single-crystal nonlinear optical materials. The optical activity of the TFGC originates from the ferroelectric phase which remains under a hydrostatic pressure exerted by the surrounding glass matrix. A combination of two techniques, electron-backscattered diffraction (EBSD) and piezoresponse force microscopy (PFM), is employed to monitor the development of the ferroelectric phase. A method is proposed to theoretically construct PFM amplitude maps from EBSD orientation maps. The theoretical vertical piezoresponse map is compared with the experimental piezoresponse map from PFM. A good correlation between the theoretical and experimental maps is observed.

  15. Investigation of the multiscale constitutive behavior of ferroelectric materials using advanced diffraction techniques

    NASA Astrophysics Data System (ADS)

    Rogan, Robert C.

    Ferroelectric ceramics are widely used in a diverse set of devices including sensors, actuators, and transducers. The technological importance of ferroelectrics originates from their large electromechanical coupling. Ferroelectric materials exhibit a complicated behavior in response to both electrical and mechanical loads which produce large internal stresses that eventually lead to failure. Efforts to model and predict the behavior of ferroelectrics have been hindered by the lack of suitable constitutive relations that accurately describe the electromechanical response of these materials. While many measurements have been conducted on the macroscopic response of single-crystals or polycrystals, multiaxial (and multiscale) data about the in situ internal strain and texture response of these materials is lacking; this information is critical to the development of accurate models, and diffraction techniques which directly measure internal crystal strains and material texture are aptly suited to supply it. A neutron diffraction technique was employed which allowed for the simultaneous measurement of material texture and lattice strains in directions parallel and transverse to an applied mechanical load. By comparing the behaviors of single-phase tetragonal, single-phase rhombohedral, and dual-phase morphotropic compositions, information concerning mechanics of average macroscopic behavior was inferred. In an effort to probe more of the multiaxial constitutive behavior, a high-energy X-ray diffraction technique was employed. Using transmission geometry and a 2-D image plate detector, 36 different directions of sample behavior were measured simultaneously. Polychromatic scanning X-ray microdiffraction was used to investigate the microscale three-dimensional strain tensor in single-crystals. One investigation yielded the first ever direct measurement of the tri-axial strain fields associated with single domain walls in ferroelectrics. The second investigation recorded the domain switching mechanisms activated to accommodate indentation-induced fracture stresses. Finally, 3-D XRD was used to probe the mesoscale constitutive behavior of single, embedded grains of BaTiO3 within a polycrystalline matrix. The experimental methods described in this thesis provide access to two-dimensional and three-dimensional multiaxial constitutive strain behavior in ferroelectrics for each of the microscopic , mesoscopic, and macroscopic length scales. Results from each of these length scales will provide critical data for models attempting to accurately describe the behavior of ferroelectric materials.

  16. Synthesis, crystal growth, structural, thermal, optical and mechanical properties of solution grown 4-methylpyridinium 4-hydroxybenzoate single crystal.

    PubMed

    Sudhahar, S; Krishna Kumar, M; Sornamurthy, B M; Mohan Kumar, R

    2014-01-24

    Organic nonlinear optical material, 4-methylpyridinium 4-hydroxybenzoate (4MPHB) was synthesized and single crystal was grown by slow evaporation solution growth method. Single crystal and powder X-ray diffraction analyses confirm the structure and crystalline perfection of 4MPHB crystal. Infrared, Raman and NMR spectroscopy techniques were used to elucidate the functional groups present in the compound. TG-DTA analysis was carried out in nitrogen atmosphere to study the decomposition stages, endothermic and exothermic reactions. UV-visible and Photoluminescence spectra were recorded for the grown crystal to estimate the transmittance and band gap energy respectively. Linear refractive index, birefringence, and SHG efficiency of the grown crystal were studied. Laser induced surface damage threshold and mechanical properties of grown crystal were studied to assess the suitability of the grown crystals for device applications. PMID:24184578

  17. Pockels effect in yttrium aluminum borate single crystals

    NASA Astrophysics Data System (ADS)

    Reshak, A. H.; Majchrowski, A.; Imiolek, W.

    2008-10-01

    Experimental measurements of linear electro-optical coefficients are reported for YAl3(BO3)4 (YAB) single crystals for the two principal tensor components xyz and yyy at the wavelength of a CW semiconducting GaAlAs laser emitting at 1040 nm. We have found the values of the Pockels coefficients to be equal to 0.21 ± 0.06 and 0.56 ± 0.08 pm/V for 123 and 222 Pockels components, respectively. Additional measurements performed for the thin-cut samples with the thickness varying within the 100 500 ?m have confirmed the values of the corresponding parameters. We have eliminated a contribution of the piezooptical coefficients as well as for other disturbing factors. We have established that the crystals with a different number of defects do not show any differences, which indicate the principal role of the borate clusters on the observed effects. The temperature changes are very low (due to a low ionic contribution), and do not exceed 5 6%, which indicates the low contribution of the electron-phonon to the Pockels effect. Because the YAB crystals possess a very large photothermal damage (more than 15 GW/cm2) and are only slightly temperature dependent. Hence, they may be proposed as promising materials for high-power laser electro-optic modulators.

  18. Plastic anisotropy in MoSi{sub 2} single crystals

    SciTech Connect

    Mitchell, T.E.; Maloy, S.A.

    1993-05-01

    Single crystals Of MoSi{sub 2} are an order of magnitude stronger when compressed along [001] than along any other orientation. This is because the easy slip systems, <101><100> and <110><111>, have a zero Schmid factor acting on them so that harder slip systems are forced into operation. We find that [001] crystals compressed at 1OOO{degree}C yield by slip on <103><331>. TEM shows that the 1/2<331> dislocations tend to decompose into 1/2<111> and <110> dislocations. This decomposition process apparently inhibits the mobility of 1/2<331> dislocations at higher temperatures and another system, <101><1ll>, becomes operative at 1300{degree}C and above. [021] crystals have been tested for comparison and are found to yield at much lower stresses on the easy systems. In the design of advanced high temperature structural materials based on MOSi{sub 2}, the large plastic anisotropy should be used to advantage.

  19. Strong Interplay between Ferroelectric and Magnetic Orders in Novel Complex Oxides

    NASA Astrophysics Data System (ADS)

    Lee, Nara

    Multiferroics, where ferroelectric and magnetic orders are concurrently present, reveal new physical properties due to the strong interplay between the dual order parameters. The emergence of the unprecedented cross-coupling effects in such materials has offered a new vein of essential understanding of correlated spin and lattice degrees of freedom and the related macroscopic phenomena, and has invigorated the application in future generations of novel devices. Recently, the enhanced coupling has been discovered in the new class of materials called spin-driven ferroelectrics in which ferroelectric order originates from the exchange striction of special types of magnetic orders with broken inversion symmetry. However, the driven ferroelectric polarization appears to be minuscule, compared with that of the typical ferroelectrics. Thus, one of the demanding challenges of the multiferroics research is finding systems or ways to escalate the magnitude of polarization. Herein, we present discoveries of new multiferroics which exhibit giant ferroelectricity due to the new exchange striction mechanism through rare-earth and transition-metal ions and their strong tunability of polarization by applying magnetic fields. (1) New multiferroic of single-crystalline orthorhombic HoMnO 3 was, for the first time, grown by the flux method. The crystals with incommensurate E-type magnetic structure exhibit much large ferroelectric polarization with the direction along the c-axis, completely different from the theoretical predictions. From the analysis, the polarization can be described by the new emerging mechanism of Ho-Mn exchange striction. (3) Tunable giant ferroelecric polarization in the multiferroic GdMn 2O5 has been demonstrated. The ferroelectric polarization in this compound is found to be the largest and be varied repeatedly with the largest change by applying external magnetic fields among the spin-driven ferroelectrics known to date. In addition, contrary to the known origin for ferroelectricity in REMn2O5 (RE=rare earth ions), the Mn-Mn exchange striction mechanism, the complete magnetic structure constructed by the x-ray resonant scattering experiment clarify that the giant ferroelectricity in GdMn2O5 results mainly from the Gd-Mn symmetric exchange striction.

  20. Constitutive relations of ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Su, Yu

    The objective of this thesis is to obtain a better understanding on the fundamental constitutive behavior of ferroelectric ceramics based on the physics of phase transition, micromechanics of heterogeneous materials, and principles of irreversible thermodynamics. Within this framework, a self-consistent model is developed to investigate the electromechanical responses of ferroelectric polycrystals under temperature change and electromechanical loading. Cooling of a paraelectric crystal below its curie temperature Tc would result in spontaneous polarization, whereas electromechanical loading on a poled crystal could lead to domain switch. Domain growth and reorientation inside ferroelectric crystals are studied in light of these phase transition and domain switch. In this process, the change of the effective elastic, dielectric and piezoelectric constants during the evolution of microstructures are examined. In addition, hysteresis loops for the electric displacement and other related phenomena are computed under cyclic electric load. On top of all methods implemented in this work, the kinetic equation derived from the irreversible thermodynamics is the key to study the domain evolution in ferroelectric crystals. The kinetic relation not only governs the growth of new domain in a ferroelectric crystal, but it also determines the onset of phase transition. This characteristic is used to study the effect of hydrostatic pressure on the shift of Curie temperature of a ferroelectric crystal. Based on the derived expressions, it is observed that the deriving force can increase or decrease upon applied hydrostatic mechanical loading, depending on the change of electromechanical moduli, eigenstrain and electro-polarization. Several typical cases are computed and it is found that the change of the electromechanical moduli during phase transformation plays the key role in the shift of Curie temperature. Since ferroelectric ceramics are in a polycrystal form, a self-consistent model is used to examine the issues involved. In this model, each grain is represented by a spherical inclusion embedded in an infinitely extended piezoelectric matrix, and the inclusion further possesses an eigenstrain and eigen polarization. Secant relations between the polycrystal-matrix and the embedded inclusion are established by extending Hill's [1] incremental relations. An iterative computational program is developed for this self-consistent model.