Science.gov

Sample records for ferroelectric single crystal

  1. Ferroelectric polarization reversal in single crystals

    NASA Technical Reports Server (NTRS)

    Stadler, Henry L.

    1992-01-01

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

  2. Imaging linear polarimetry using a single ferroelectric liquid crystal modulator.

    PubMed

    Gendre, Luc; Foulonneau, Alban; Bigué, Laurent

    2010-09-01

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

  3. 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.

  4. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    PubMed

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the VG sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics. PMID:26487348

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

    SciTech Connect

    Murugan, G. Senthil Ramasamy, P.

    2014-04-24

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

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

    NASA Astrophysics Data System (ADS)

    Murugan, G. Senthil; Ramasamy, P.

    2014-04-01

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

  7. Giant Electro-Mechanical Energy Conversion in [011] cut Relaxor Ferroelectric Single Crystals

    NASA Astrophysics Data System (ADS)

    Finkel, Peter; Dong, Wen; Lynch, Chris; Amin, Ahmed

    2012-02-01

    Giant electro-mechanical energy conversion is demonstrated under a ferroelectric/ferroelectric phase transformation in [011] cut and poled lead titanate-based relaxor perovskite morphotropic single crystals. It is found that under mechanical pre-stress, a relatively small oscillatory stress drives the material reversibly between rhombohedral and orthorhombic phases with a remarkably high polarization and strain jumps induced at zero bias electric field and room temperature. The measured electrical output per cycle is more than an order of magnitude larger than that reported for linear piezoelectric materials. Ideal thermodynamic cycles are presented for this electro-mechanical energy conversion followed by a presentation and discussion of the experimental data.

  8. Giant electro-mechanical energy conversion in [011] cut ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Dong, Wen D.; Finkel, Peter; Amin, Ahmed; Lynch, Christopher S.

    2012-01-01

    Giant electro-mechanical energy conversion is demonstrated under a ferroelectric/ferroelectric phase transformation in [011] cut and poled lead titanate-based relaxor perovskite morphotropic single crystals. It is found that under mechanical pre-stress, a relatively small oscillatory stress drives the material reversibly between rhombohedral and orthorhombic phases with a remarkably high polarization and strain jump induced at zero bias electric field and room temperature. The measured electrical output per cycle is more than an order of magnitude larger than that reported for linear piezoelectric materials. Ideal thermodynamic cycles are presented for this electro-mechanical energy conversion followed by a presentation and discussion of the experimental data.

  9. 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.; Jayavel, R.

    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.

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

    PubMed Central

    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

  11. 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

  12. Ferroelectric-like transition on a hygroscopic barium thiourea chloride single crystal

    NASA Astrophysics Data System (ADS)

    Raju, S.; Muralidharan, R.; Krishnan, H.

    2015-04-01

    Barium thiourea chloride (BTC) single crystals were grown by slow evaporation of aqueous solution. The X-ray and spectral studies confirmed the formation of the title compound. Thermal studies carried out using differential scanning calorimetry (DSC) showed the presence of both the adsorbed and absorbed water in the grown crystal, which can be identified through the peaks around temperatures 80C and 130C. The dielectric constant against temperature curve for different frequencies showed concomitant anomaly around the temperature region of 80C to 120C similar to a ferroelectric phase transition. We infer that this peak is due to the removal of water and not due to ferroelectric transition and care should be taken while measuring and interpreting dielectric properties of similar hygroscopic crystals containing volatile compounds.

  13. Origin of ultrahigh piezoelectric activity of [001]-oriented ferroelectric single crystals at the morphotropic phase boundary

    NASA Astrophysics Data System (ADS)

    Ke, X. Q.; Wang, D.; Wang, Y.

    2016-01-01

    The physical origin of the ultrahigh piezoelectricity of [001]-oriented ferroelectric single crystals at the morphotropic phase boundary (MPB) is investigated via computer simulations using the phase field method. A wide composition range is explored and the existence of a monoclinic phase at the MPB is considered. The relative contributions from polarization rotation and domain wall motion are discriminated. The domain structures, hysteresis and hysteresis-free strain-electric field curves, and change of d33 as a function of composition for poled samples near the MPB predicted by the simulations are all in agreement with experimental observations. It is found that under small polarization anisotropy the ultrahigh piezoelectricity of [001]-oriented ferroelectric single crystals at the MPB originates mainly from polarization rotation. Although domain wall motion also takes place for poled samples with monoclinic nanodomain structures and contributes to the hysteresis, its contribution to the ultrahigh piezoelectricity is insignificant.

  14. Ferroelectric liquid crystal display

    NASA Technical Reports Server (NTRS)

    York, Paul K. (Inventor)

    1977-01-01

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

  15. Slow relaxation of piezoelectric response in CdZnTe ferroelectric semiconductor single crystals

    NASA Astrophysics Data System (ADS)

    Ke, Shanming; Huang, Haitao; Wang, Tao; Fan, Huiqing; Jie, Waiqi; Chan, H. L. W.

    2007-10-01

    The piezoelectric response in Cd0.9Zn0.1Te (CZT) semiconductor single crystals has been investigated by analyzing room temperature impedance spectra. The polarization is significantly influenced by light illumination. A slow relaxation process of the piezoelectric response has been observed with a relaxation time of 37s, which is comparable to the discharge current results. The frequencies for piezoelectric resonance and antiresonance can be tuned to lower values when a bias field is applied and can be recovered when the bias field is removed. These phenomena may be universal for ferroelectric semiconductors and can be explained by a slow relaxation model in dielectrics.

  16. Optical, Dielectric and Ferroelectric Properties of LaCrO3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Matam, Mahesh Kumar; Ye, Zuo Guang

    2001-03-01

    Perovskite LaCrO3 crystallizes in an orthorhombic structure, which is used in various applications as an electrode material due to its p-type semicondutivity. LaCrO3 shows an antiferromagnetic behavior up to a Neel temperature TN = 258 K, and supposedly also exhibit ferroelectricity. However, the dielectric and ferroelectric properties have not been characterized thoroughly. This situation is mainly due to the difficulties encountered both in the ceramics sintering and the crystal growth of LaCrO3 due to its highly refractory character, which has also limited certain applications. In this work, single crystals of LaCrO3 have been successfully grown using a complex flux of Bi_2O3 and B_2O3 by slow cooling. Crystals thus obtained are transparent, green and of 0.75 x 0.5 x 0.1 mm size. Dielectric measurements carried out at various frequencies show an anomaly, pointing to a phase transition around TC = 350 ^oC. A large increase in dissipation factor (tan?) is observed just above the phase transition, which is attributed to an increase in conductivity. A partially saturated hysteresis loop is displayed, indicating the presence of ferroelectric behavior. Studies by Polarized Light Microscopy reveal the ferroelastic domain structures. Temperature dependence of domain structures and birefrengence shows the phase transition at TC around 350 ^oC accompanied by a significant change in domain structure, which is consistent with measurements. With its multi-ferroic properties confirmed, LaCrO3 could become a potentially magnetoelectric material.

  17. Giant photovoltaic effect of ferroelectric domain walls in perovskite single crystals

    PubMed Central

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

    2015-01-01

    The photovoltaic (PV) effect in polar materials offers great potential for light-energy conversion that generates a voltage beyond the bandgap limit of present semiconductor-based solar cells. Ferroelectrics have received renewed attention because of the ability to deliver a high voltage in the presence of ferroelastic domain walls (DWs). In recent years, there has been considerable debate over the impact of the DWs on the PV effects, owing to lack of information on the bulk PV tensor of host ferroelectrics. In this article, we provide the first direct evidence of an unusually large PV response induced by ferroelastic DWs—termed ‘DW’-PV effect. The precise estimation of the bulk PV tensor in single crystals of barium titanate enables us to quantify the giant PV effect driven by 90° DWs. We show that the DW-PV effect arises from an effective electric field consisting of a potential step and a local PV component in the 90° DW region. This work offers a starting point for further investigation into the DW-PV effect of alternative systems and opens a reliable route for enhancing the PV properties in ferroelectrics based on the engineering of domain structures in either bulk or thin-film form. PMID:26443381

  18. Giant photovoltaic effect of ferroelectric domain walls in perovskite single crystals.

    PubMed

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

    2015-01-01

    The photovoltaic (PV) effect in polar materials offers great potential for light-energy conversion that generates a voltage beyond the bandgap limit of present semiconductor-based solar cells. Ferroelectrics have received renewed attention because of the ability to deliver a high voltage in the presence of ferroelastic domain walls (DWs). In recent years, there has been considerable debate over the impact of the DWs on the PV effects, owing to lack of information on the bulk PV tensor of host ferroelectrics. In this article, we provide the first direct evidence of an unusually large PV response induced by ferroelastic DWs-termed 'DW'-PV effect. The precise estimation of the bulk PV tensor in single crystals of barium titanate enables us to quantify the giant PV effect driven by 90 DWs. We show that the DW-PV effect arises from an effective electric field consisting of a potential step and a local PV component in the 90 DW region. This work offers a starting point for further investigation into the DW-PV effect of alternative systems and opens a reliable route for enhancing the PV properties in ferroelectrics based on the engineering of domain structures in either bulk or thin-film form. PMID:26443381

  19. Giant photovoltaic effect of ferroelectric domain walls in perovskite single crystals

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    The photovoltaic (PV) effect in polar materials offers great potential for light-energy conversion that generates a voltage beyond the bandgap limit of present semiconductor-based solar cells. Ferroelectrics have received renewed attention because of the ability to deliver a high voltage in the presence of ferroelastic domain walls (DWs). In recent years, there has been considerable debate over the impact of the DWs on the PV effects, owing to lack of information on the bulk PV tensor of host ferroelectrics. In this article, we provide the first direct evidence of an unusually large PV response induced by ferroelastic DWstermed DW-PV effect. The precise estimation of the bulk PV tensor in single crystals of barium titanate enables us to quantify the giant PV effect driven by 90 DWs. We show that the DW-PV effect arises from an effective electric field consisting of a potential step and a local PV component in the 90 DW region. This work offers a starting point for further investigation into the DW-PV effect of alternative systems and opens a reliable route for enhancing the PV properties in ferroelectrics based on the engineering of domain structures in either bulk or thin-film form.

  20. Millimeter-Wave Dielectric Properties of Single Crystal Ferroelectric and Dielectric Materials

    SciTech Connect

    McCloy, John S.; Korolev, Konstantin A.; Li, Zijing; Afsar, Mohammed N.; Sundaram, S. K.

    2011-01-03

    Transmittance measurements on various single crystal ferroelectric materials over a broad millimeter-wave frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been determined in the millimeter wave region for the first time. The measurements have been employed using a free-space quasi-optical millimeter-wave spectrometer equipped with a set of high power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 - 120 GHz. The uncertainties and possible sources of instrumentation and measurement errors related to the free-space millimeter-wave technique are discussed. This work has demonstrated that precise MMW permittivities can be obtained even on small thin crystals using the BWO quasi-optical approach.

  1. Anomalous Phase Diagram of Ferroelectric (Ba,Ca)TiO3 Single Crystals with Giant Electromechanical Response

    NASA Astrophysics Data System (ADS)

    Fu, Desheng; Itoh, Mitsuru; Koshihara, Shin-Ya; Kosugi, Taichi; Tsuneyuki, Shinji

    2008-06-01

    We report the anomalous phase evolution in ferroelectric single crystals Ba1-xCaxTiO3 (0.02ferroelectric phase transition. In addition, large electromechanical responses in this class of crystals are also demonstrated. Our results indicate that an effective approach to control the ferroelectricity of perovskite oxide can be realized not only by the covalency between A site atom and oxygen but also by the substitution of A site with small ions with off-centering nature. Theoretical calculations support the idea that the off-center displacements of the smaller Ca ions in the Ba-site play an important role in the exotic natures of Ba1-xCaxTiO3.

  2. Millimeter-wave dielectric properties of single-crystal ferroelectric and dielectric materials.

    PubMed

    McCloy, John S; Korolev, Konstantin A; Li, Zijing; Afsar, Mohammed N; Sundaram, Shanmugavelayutham K

    2011-01-01

    Transmittance measurements on various single crystal ferroelectric and dielectric materials, BaTiO(3), SrTiO(3), LiNbO(3), LiTaO(3), (PbMg(1/3)Nb(2/3)O(3))0.73-(PbTiO(3))0.27, LaAlO(3), and Bi(4)Ge(3)O(12), over a broad millimeter-wave (MMW) frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been measured in the MMW region using high-power sources for the first time, using a free-space, quasi-optical MMW spectrometer equipped with high-power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 to 120 and 180 to 260 GHz. These results are compared with MMW permittivity of these materials obtained by other methods as well as to RF, microwave, and optical frequency permittivities for all the materials tested. The effects of both crystallographic orientation and quality of the surface polishing of the crystals have been examined. Uncertainties and possible sources of instrumentation and measurement errors related to the freespace MMW technique are discussed. This work demonstrates that precise MMW permittivity data can be obtained even on relatively small and thin crystals of different surface conditions and orientations using the high-power BWO-based quasioptical approach. PMID:21244971

  3. Partially transformed relaxor ferroelectric single crystals with distributed phase transformation behavior

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.

    2015-11-01

    Relaxor ferroelectric single crystals such as PMN-PT and PIN-PMN-PT undergo field driven phase transformations when electrically or mechanically loaded in crystallographic directions that provide a positive driving force for the transformation. The observed behavior in certain compositions is a phase transformation distributed over a range of fields without a distinct forward or reverse coercive field. This work focuses on the material behavior that is observed when the crystals are loaded sufficiently to drive a partial transformation and then unloaded, as might occur when driving a transducer to achieve high power levels. Distributed transformations have been modeled using a normal distribution of transformation thresholds. A set of experiments was conducted to characterize the hysteresis loops that occur with the partial transformations. In this work the normal distribution model is extended to include the partial transformations that occur when the field is reversed before the transformation is complete. The resulting hysteresis loops produced by the model are in good agreement with the experimental results.

  4. 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

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

    PubMed Central

    Sun, Enwei; Cao, Wenwu

    2014-01-01

    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-xTixO3 (PZT) ceramics, the piezoelectric coefficient d33 is increased by a factor of 5 and the electromechanical coupling factor k33 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

  6. Electromechanical behavior of relaxor ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Liu, Tieqi

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

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

    SciTech Connect

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

    1993-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  9. Bulk crystal growth, optical, mechanical and ferroelectric properties of new semiorganic nonlinear optical and piezoelectric Lithium nitrate monohydrate oxalate single crystal

    NASA Astrophysics Data System (ADS)

    Dalal, Jyoti; Kumar, Binay

    2016-01-01

    New semiorganic nonlinear optical single crystals of Lithium nitrate oxalate monohydrate (LNO) were grown by slow evaporation solution technique. Single crystal X-ray diffraction study indicated that LNO crystal belongs to the triclinic system with space group P1. Various functional groups present in the material were identified by FTIR and Raman analysis. UV-vis study showed the high transparency of crystals with a wide band gap 5.01 eV. Various Optical constants i.e. Urbach energy (Eu), extinction coefficient (K), refractive index, optical conductivity, electric susceptibility with real and imaginary parts of dielectric constant were calculated using the transmittance data which have applications in optoelectronic devices. A sharp emission peak was found at 438 nm in photoluminescence measurement, which revealed suitability of crystal for fabricating violet lasers. In dielectric studies, a peak has been observed at 33 C which is due to ferroelectric to paraelectric phase transition. Piezoelectric charge coefficients (d33 = 9.2 pC/N and g33) have been calculated, which make it a suitable for piezoelectric devices applications. In ferroelectric studies, a saturated loop was found in which the values of coercive field and remnant polarization were found to be 2.18 kV/cm and 0.39 ?C/cm2, respectively. Thermal behavior was studied by TGA and DSC studies. The relative SHG efficiency of LNO was found to be 1.2 times that of KDP crystal. In microhardness study, Meyer's index value was found to be 1.78 which revealed its soft nature. These optical, dielectric, piezoelectric, ferroelectric, mechanical and non-linear optical properties of grown crystal establish the usefulness of this material for optoelectronics, non-volatile memory and piezoelectric devices applications.

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

    SciTech Connect

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

    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 PE 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.

  11. Investigations on ferroelectric PMN-PT and PZN-PT single crystals ability for power or resonant actuators.

    PubMed

    Lebrun, L; Sebald, G; Guiffard, B; Richard, C; Guyomar, D; Pleska, E

    2004-04-01

    Ferroelectric single crystals of PZN-PT and PMN-PT exhibit outstanding properties: high charge coefficient (dij), high coupling factor (kij) and high strain levels under DC fields. Besides, their mechanical quality factor is believed to be low. Their usefulness for non-resonant or large bandwidth transducers has therefore been previously investigated. However, few studies have been devoted to the dielectric and mechanical losses of single crystals and to their stability under high levels of excitations (electric fields, temperature and mechanical stress). A knowledge and understanding of such performances is needed to determine whether single crystals are suitable materials for power or resonant transducers. In this work, losses and non-linearity versus external excitations are investigated. Dielectric losses and mechanical losses are measured versus electric field for different compositions, orientations. The evolution of d33 and epsilonT33 are obtained versus electric field and temperature for the longitudinal mode. Strain and hysteresis versus sweep mode (up and down) are measured near the resonance frequency using a laser Doppler vibrometer. PMID:15047336

  12. 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.; Tian, Jian

    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.

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

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.; Tian, Jian; Lynch, Christopher S.

    2014-08-01

    The large field behavior of [011]C cut relaxor ferroelectric lead indium niobate-lead magnesium niobate-lead titanate, xPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3, single crystals was experimentally characterized in the piezoelectric d322-mode configuration under combined mechanical, electrical, and thermal loading. Increasing the concentration of lead indium niobate and decreasing the concentration of lead titanate in compositions near the morphotropic phase boundary resulted in a decrease of mechanical compliance, dielectric permittivity, and piezoelectric coefficients as well as a shift from a continuous to a discontinuous transformation.

  14. 180 domain structure and its evolution in Ca0.28Ba0.72Nb2O6 ferroelectric single crystals of tungsten bronzes structure

    NASA Astrophysics Data System (ADS)

    Lu, C. J.; Nie, C. J.; Duan, X. F.; Li, J. Q.; Zhang, H. J.; Wang, J. Y.

    2006-05-01

    Ferroelectric domain structure and its evolution in uniaxial relaxor Ca0.28Ba0.72Nb2O6 single crystals were investigated using transmission electron microscopy. It was found that there exists a high density of 180 domain walls in the crystals. The domains appear predominantly spike shaped along the polar axis and have a typical diameter of 50-500nm. Domain wall motion was occasionally induced by electron beam irradiation. Macrodomains-to-microdomains switching has been observed corresponding to the normal-to-relaxor ferroelectrics transition during an in situ heating experiments. At temperature just below ferroelectric phase transition temperature TC, zero-field-cooled needlelike nanodomains were also observed.

  15. Energy harvesting based on FE-FE transition in ferroelectric single crystals.

    PubMed

    Guyomar, Daniel; Pruvost, Sebastien; Sebald, Gael

    2008-02-01

    The pyroelectric properties of Pb(Zn(1/3)Nb(2/3))(0955)Ti(0.045)O(3) single crystals versus an electric field have been studied for energy harvesting in this paper. Two thermodynamic cycles (Stirling and Ericsson) were used for this purpose. By applying an electric field, a FE-FE transition was induced, abruptly increasing the polarization. This transition minimized the supplied energy and improved the harvested energy. By discharging the single crystal at a higher temperature, a gain of 1100% was obtained with the Stirling cycle at 1 kV/mm (gain is defined as harvested energy divided by supplied energy). The study revealed that Stirling cycles are more interesting for low electric fields. Based on experimental results, simulations were carried out to estimate energy harvesting in high electric fields to evaluate the performances of thin samples (single crystals or oriented thin films). At high electric fields, both cycles gave almost the same energy harvesting, but Ericsson cycles were more appropriate to control the voltage on the sample. The simulation led to a harvested energy of 500 mJ/g for an applied electric field equal to 50 kV/mm. The efficiency with respect to Carnot was raised 20%. PMID:18334334

  16. Ferroelectric domain structures in <001>-oriented K{sub 0.15}Na{sub 0.85}NbO{sub 3} lead-free single crystal

    SciTech Connect

    Chen, Yan; Wong, Chi-Man; Yau, Hei-Man; Dai, Jiyan; Deng, Hao; Luo, Haosu; Wang, Danyang; Yan, Zhibo; Chan, Helen L. W.

    2015-03-15

    In this work, ferroelectric domain structures of <001 >-oriented K{sub 0.15}Na{sub 0.85}NbO{sub 3} single crystal are characterized. Transmission electron microscopy (TEM) observation revealed high-density of laminate domain structures in the crystal and the lattices of the neighboring domains are found to be twisted in a small angle. Superlattice diffraction spots of 1/2 (eeo) and 1/2 (ooe) in electron diffraction patterns are observed in the crystal, revealing the a{sup +}a{sup +}c{sup −} tilting of oxygen octahedral in the perovskite structure. The piezoresponse of domains and in-situ poling responses of K{sub 0.15}Na{sub 0.85}NbO{sub 3} crystal are observed by piezoresponse force microscopy (PFM), and the results assure its good ferroelectric properties.

  17. Switching ferroelectric domain configurations using both electric and magnetic fields in Pb(Zr,Ti)O3Pb(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)O3Pb(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

  18. High pressure single crystal x-ray and neutron powder diffraction study of the ferroelectricparaelectric phase transition in PbTiO3

    NASA Astrophysics Data System (ADS)

    Al-Zein, A.; Bouvier, P.; Kania, A.; Levelut, C.; Hehlen, B.; Nassif, V.; Hansen, T. C.; Fertey, P.; Haines, J.; Rouquette, J.

    2015-12-01

    The results obtained by high pressure neutron powder diffraction and single-crystal x-ray diffraction for the P4mmPm \\bar{3} m phase transition in the prototype ferroelectric perovskite lead titanate are shown. Neutron diffraction is found to be strongly sensitive to the dipolar moment in the PbTiO3 unit cell due to the gradual reduction of the displacement of the Ti and O atoms from centrosymmetric positions in the cubic perovskite structure which exhibits anti-phase scattering of Pb, Ti and O atoms. From applying both techniques, the anomalously high DebyeWaller factor for the lead atoms confirms the disordered character of the cubic phase. High pressure single crystal x-ray diffraction also perfectly describes the ferroelectricparaelectric transition and will be the technique of choice to solve higher pressure structures for PbTiO3.

  19. Fabrication of graphene field-effect transistor on top of ferroelectric single-crystal substrate

    NASA Astrophysics Data System (ADS)

    Park, Nahee; Kang, Haeyong; Lee, Yourack; Kim, Jeong-Gyun; Kim, Joong-Gyu; Yun, Yoojoo; Park, Jeongmin; Kim, Taesoo; Kim, Jung Ho; Jin, Youngjo; Shin, Yong Seon; Lee, Young Hee; Suh, Dongseok

    2015-03-01

    In the analysis of Graphene field-effect transistor, the substrate material which has the direct contact with Graphene layer plays an important in the device performance. In this presentation, we have tested PMN-PT(i.e.(1-x)Pb(Mg1/3Nb2/3) O3-xPbTiO3) substrate as a gate dielectric of Graphene field-effect transistor. Unlike the case of previously used substrates such as silicon oxide or hexagonal Boron-Nitride(h-BN), the PMN-PT substrate can induce giant amount of surface charge that is directly injected to the attached Graphene layer due to its ferroelectric property. And the hysteresis of polarization versus electric field of PMN-PT can cause the device to show the ferroelectric nonvolatile memory operation. We had successfully fabricated Graphene field-effect transistor using the mechanically exfoliated Graphene layer transferred on the PMN-PT(001) substrate. Unlike the case of mechanical exfoliation on the surface of silicon-oxide or the Poly(methyl methacrylate) (PMMA), the weak adhesion properties between graphene and PMNPT required the pretreatment on PMMA before the exfoliation process. The device performance is analyzed in terms of the effect of ferro- and piezo-electric effect of PMNPT substrate.

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

    NASA Astrophysics Data System (ADS)

    Pandey, Chandra Shekhar; Schreuer, Jrgen; Burianek, Manfred; Mhlberg, Manfred

    2011-11-01

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

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

    PubMed

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

    2015-01-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  4. Stability of nano-scale ferroelectric domains in a LiNbO3 single crystal: The role of surface energy and polar molecule adsorption

    NASA Astrophysics Data System (ADS)

    Sun, X.; Su, Y. J.; Li, X.; Gao, K. W.; Qiao, L. J.

    2012-05-01

    The stability of nano-scale ferroelectric domains in a LiNbO3 single crystal under varied atmospheric humidity levels was studied using piezoelectric force microscopy. Experimental results showed that the nano-scale domains fabricated by the tip field of the atomic force microscope changed as the environmental humidity changed; the c- domains expanded or shrank with increases or decreases in the environmental humidity (that is, with the amount of adsorbed H2O molecules on the domain surface), while the c+ domains transformed in the opposite sense. The surface energy of the domains is responsible for these transformations.

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

    SciTech Connect

    Li, Yuanyuan; Li, Qiang Yan, Qingfeng; Gao, Jinghan; Zhuo, Fangping; Cao, Wenwu; Xi, Xiaoqing; Zhang, Yiling; Chu, Xiangcheng

    2014-02-03

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

  6. Ferroelectric and dielectric properties of Ca0.28Ba0.72Nb2O6 single crystals of tungsten bronzes structure

    NASA Astrophysics Data System (ADS)

    Qi, Y. J.; Lu, C. J.; Zhu, J.; Chen, X. B.; Song, H. L.; Zhang, H. J.; Xu, X. G.

    2005-08-01

    Large Ca0.28Ba0.72Nb2O6 (CBN-28) single crystals exhibit saturated ferroelectric hysteresis loops under an electric field of 115kV/cm along the [001] direction. Their spontaneous polarization, remanent polarization and coercive field are 35.3?C/cm2, 32.2?C/cm2, and 38.1kV/cm, respectively. The dielectric constant and dielectric loss tan? of the crystals are 195 and 0.32 at 10 kHz, respectively. A diffused dielectric anomaly with relaxor characteristic was observed in the range of 325-500 C at low frequencies, while the CBN-28 crystals experienced a first-order normal-relaxor ferroelectric phase transition around 252 C on heating. A broad dielectric loss peak appears around 120 C and it is interpreted in terms of the migration of oxygen vacancies. The conductance activation energy was determined to be 1.33 eV in the high temperature regime (500-560 C).

  7. Microdomain dynamics in single-crystal BaTi O3 during paraelectric-ferroelectric phase transition measured with time-of-flight neutron scattering

    NASA Astrophysics Data System (ADS)

    Pramanick, A.; Wang, X. P.; Hoffmann, C.; Diallo, S. O.; Jrgensen, M. R. V.; Wang, X.-L.

    2015-11-01

    Microscopic polar clusters can play an important role in the phase transition of ferroelectric perovskite oxides such as BaTi O3 , which have shown coexistence of both displacive and order-disorder dynamics, although their topological and dynamical characteristics are yet to be clarified. Here, we report sharp increases in the widths and intensities of Bragg peaks from a BaTi O3 single crystal, which are measured in situ during heating and cooling within a few degrees of its phase transition temperature TC, using the neutron time-of-flight Laue technique. Most significantly sharper and stronger increases in peak widths and peak intensities were found to occur during cooling compared to that during heating through TC. A closer examination of the Bragg peaks revealed their elongated shapes in both the paraelectric and ferroelectric phases, the analysis of which indicated the presence of microdomains that have correlated <111 > -type polarization vectors within the {110}-type crystallographic planes. No significant increase in the average size of the microdomains (10 nm ) near TC could be observed from diffraction measurements, which is also consistent with small changes in the relaxation times for motion of Ti ions measured with quasielastic neutron scattering. The current observations do not indicate that the paraelectric-ferroelectric phase transition in BaTi O3 is primarily caused by an increase in the size of the microscopic polar clusters or critical slowing down of Ti ionic motion. The sharp and strong increases in peak widths and peak intensities during cooling through TC are explained as a result of microstrains that are developed at microdomain interfaces during paraelectric-ferroelectric phase transition.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  9. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    In this work, a large size lead-free piezoelectric single crystal, (K,Na,Li)(Nb,Ta,Sb)O3 (KNLNTS) with the dimensions of 8.58.513.5 mm3 was successfully grown by the top-seeded solution growth method. This KNLNTS single crystal with high compositional homogeneity is in the tetragonal phase at room temperature. The Curie temperature TC of the tetragonal-cubic phase transition temperature is 210 C. The piezoelectric coefficients and electromechanical coupling factors of the [001]C oriented KNLNTS single crystal are d33=172.55 pC/N, d31=-71.90 pC/N, k31=0.327, k33=0.523, and kt=0.541. In addition, the crystal shows good thermal stability so that it can be used for making high temperature electromechanical devices.

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

    NASA Astrophysics Data System (ADS)

    Finkel, Peter; Amin, Ahmed; Dong, Wen

    2013-03-01

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

  13. Incommensurate modulation structure in ferroelectric Ca0.28Ba0.72Nb2O6 single crystals of tungsten bronze structure

    NASA Astrophysics Data System (ADS)

    Lu, C. J.; Qi, Y. J.; Li, J. Q.; Zhang, H. J.; Wang, J. Y.

    2006-11-01

    Incommensurate modulation structure in uniaxial relaxor ferroelectric Ca0.28Ba0.72Nb2O6 single crystals was investigated using transmission electron microscopy (TEM). The wave-modulation vector can be expressed as q =(1/2)c*+(1+?)(a*-b*)/4, where the incommensurability parameter ? was determined to be about 0.09 from [110] diffraction pattern. High-resolution TEM observations along [110] zone provided direct evidence of the incommensurate superstructure. Structural modulation was also evident by high-resolution TEM images through [001] zone, where a sinusoidal variation along [110] and [110] was identified. The incommensurate superlattice structure is caused by the uniform mixing of slabs of two orthorhombic cells.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  15. Ferroelectric, Thermal, and Magnetic Characteristics of Praseodymium Malonate Hexahydrate Crystals

    NASA Astrophysics Data System (ADS)

    Ahmad, Nazir; Ahmad, M. M.; Kotru, P. N.

    2016-01-01

    Gel-grown single crystals of [Pr2(C3H2O4)3(H2O)6] exhibit remarkably flat habit faces, the most predominant being {110}. High-resolution x-ray diffraction analysis showed that the crystals are free from structural grain boundaries, which is the key requirement for single crystals for use in the microelectronics industry to serve as low-dielectric-constant ferroelectric material. The dielectric behavior recorded on {110} planes of single crystals shows that the crystal is ferroelectric with transition temperature T c = 135°C, which differs from the Curie-Weiss temperature T 0 by 2°C (T 0 < T c). Material in pellet form is shown to exhibit slightly different dielectric behavior. Polarization versus electric field confirms the ferroelectric behavior of the material. The dielectric behavior is also supported by the results of thermal studies, viz. thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The magnetic susceptibility and magnetic moment are calculated to be 30.045 × 10-6 emu and 3.092 BM, respectively.

  16. Phase-field modeling of ferroelectric to paraelectric phase boundary structures in single-crystal barium titanate

    NASA Astrophysics Data System (ADS)

    Woldman, Alexandra Y.; Landis, Chad M.

    2016-03-01

    Ferroelectric perovskite materials have been shown to exhibit a large electrocaloric effect near phase transitions. We develop a computational model based on a phase-field approach to characterize the structure of ferroelectric to paraelectric phase boundaries for planar configurations under generalized plane strain with temperatures near the Curie temperature. A nonlinear finite element method is used to solve for the phase boundary structure of a representative unit cell with a 180° ferroelectric laminate for a range of domain widths. The temperature at which the phase boundary can be found increases with domain width, approaching the Curie temperature asymptotically. The excess free energy density per unit area of the boundary increases with domain width. As expected, closure domains form between the ferroelectric and paraelectric phase, and the shape of the closure domains evolves from triangular to needle-shaped as the domain width increases. The entropy jump across the phase boundary is quantified and is shown to increase with domain width as well. A planar configuration with a 90° ferroelectric laminate is investigated, but shown to be physically unlikely due to the high stress levels required to achieve strain compatibility between the phases. Possible three-dimensional structures of the ferroelectric–paraelectric phase boundary are also discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Torres, Mara; Ricote, Jess; Amorn, Harvey; Jaafar, Miriam; Holgado, Susana; Piqueras, Juan; Asenjo, Agustina; Garca-Hernndez, Mar; Alguer, Miguel

    2011-12-01

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

  19. Optical bandgap and phase transition in relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals: An inherent relationship

    NASA Astrophysics Data System (ADS)

    Zhang, X. L.; Hu, Z. G.; Xu, G. S.; Zhu, J. J.; Li, Y. W.; Zhu, Z. Q.; Chu, J. H.

    2013-07-01

    We report band to band transition behaviors of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) single crystals derived from temperature-dependent spectral transmittance. A typical bandgap formula with the temperature and composition (8 K≤Texp≤453 K, 0.1≤x≤0.4) has been presented. Moreover, the phase diagram of PMN-xPT crystals can be well proposed, which is based on the bandgap variations and can be explained by electronic structure evolution. It reveals an intrinsic relationship between fundamental bandgap and phase transition of PMN-xPT single crystals, which pioneers an effective methodology to explore the phase transition of ferroelectric oxides.

  20. Crystal growth and dynamic ferroelectric hysteresis scaling behavior of molecular ferroelectric diisopropylammonium bromide

    NASA Astrophysics Data System (ADS)

    Jiang, Chunli; Lin, Hechun; Luo, Chunhua; Zhang, Yuanyuan; Yang, Jing; Peng, Hui; Duan, Chun-Gang

    2016-03-01

    The molecular ferroelectric, diisopropylammonium bromide (DIPAB) crystal with P21 phase is successfully prepared in an anhydrous environment at room temperature. The results illustrate that the water in the solvent / environment plays a key role in the phase of DIPAB single crystal during crystallization process. The scaling behavior of the dynamic hysteresis of DIPAB crystal is also investigated. The scaling relations of hysteresis area(A) against frequency (f) and applied electric field amplitude (E0) can be expressed with A ∝ f - 0 . 17E01 in the f-region I (30-6.6 Hz), A ∝ f 0 . 045E00.92 in the f-region II (200-50 Hz) and A ∝ f - 0 . 41E02 in the f-region III (500-250 Hz). This three-stage behavior between the loop area A and frequency is ascribed to the coexistence of order-disorder and displacive characters in the ferroelectric transition characters in such molecular ferroelectrics.

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

    SciTech Connect

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

    2011-12-31

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

  2. Super-crystals in composite ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pierangeli, D.; Ferraro, M.; di Mei, F.; di Domenico, G.; de Oliveira, C. E. M.; Agranat, A. J.; Delre, E.

    2016-02-01

    As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium-lithium-tantalate-niobate with micrometric lattice constant, 104 times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies.

  3. Super-crystals in composite ferroelectrics.

    PubMed

    Pierangeli, D; Ferraro, M; Di Mei, F; Di Domenico, G; de Oliveira, C E M; Agranat, A J; DelRe, E

    2016-01-01

    As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium-lithium-tantalate-niobate with micrometric lattice constant, 10(4) times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies. PMID:26907725

  4. Super-crystals in composite ferroelectrics

    PubMed Central

    Pierangeli, D.; Ferraro, M.; Di Mei, F.; Di Domenico, G.; de Oliveira, C. E. M.; Agranat, A. J.; DelRe, E.

    2016-01-01

    As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium–lithium–tantalate–niobate with micrometric lattice constant, 104 times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies. PMID:26907725

  5. Growth and characterization of piezo-/ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3-Bi(Zn1/2Ti1/2)O3 ternary single crystals

    NASA Astrophysics Data System (ADS)

    Belan, Reagan A.; Tailor, Hamel N.; Long, Xifa; Bokov, Alexei A.; Ye, Zuo-Guang

    2011-03-01

    In order to develop new piezo-/ferroelectric materials, single crystals of the Pb(Mg1/3Nb2/3)O3-PbTiO3-Bi(Zn1/2Ti1/2)O3 [PMN-PT-BZT] ternary complex perovskite system has been grown by a high temperature solution method using the mixture of PbO and H3BO3 as flux (in a molar ratio of 4:2) with an optimum flux:charge molar ratio of 6:1. It is found that the addition of BZT into the relaxor ferroelectric PMN-PT system reduces the number of spontaneous nucleations, resulting in large single crystals (5 mm×5 mm×14 mm) of good quality. The grown crystals exhibit a pseudo-cubic morphology and show evidence of two-dimensional growth mechanism. Examination by polarized light microscopy (PLM) reveals the formation of striation, which can be reduced by changing the growth conditions. The domain structure and phase transition of the PMN-PT-BZT crystals are investigated by PLM. The temperature and frequency dependences of the dielectric permittivity of the grown crystals show typical relaxor ferroelectric behavior, with the frequency dependence of the temperature of maximum permittivity (Tmax) following the Vogel-Fulcher law. The ferroelectric property is displayed in the crystals with a remnant polarization, Pr=21 μC/cm2 and a coercive field, EC=3.5 kV/cm. The piezoelectric coefficient, d33, is found to be 825 pC/N, a value much higher than that of the ternary ceramics.

  6. Piezoelectric activity in Perovskite ferroelectric crystals.

    PubMed

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

    2015-01-01

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

  7. Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering

    NASA Astrophysics Data System (ADS)

    Shin, Seonhyeop; Ko, Jae-Hyeon; Tsukada, Shinya; Akishige, Yukikuni; Roleder, Krystian; Rytz, Daniel

    2015-05-01

    The elastic properties of KF-substituted perovskite lead titanate (PbTiO3) were investigated by dielectric measurements and Brillouin light scattering. The ferroelectric phase transition occurred at substantially lower temperature due to KF substitution, which was attributed to the modification of the covalency in Pb-O and Ti-O bonds. The longitudinal acoustic (LA) mode of KF-substituted PbTiO3 showed a frequency softening in the paraelectric phase, which was accompanied by increasing acoustic damping. This indicated that polarization fluctuations responsible for the acoustic anomalies were enhanced by KF substitution.

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

    SciTech Connect

    Gao, W.L.; Zhang, H.J.; Xia, S.Q.; Huang, B.B.; Liu, D.; Wang, J.Y.; Jiang, M.H.; Zheng, L.M.; Wang, J.F.; Lu, C.J.

    2010-09-15

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

  9. Diisopropylammonium bromide is a high-temperature molecular ferroelectric crystal.

    PubMed

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

    2013-01-25

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

  10. Ferroelectric Liquid Crystals In Aerodynamic Testing

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Holmes, Harlan K.

    1994-01-01

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

  11. Fast Optical Switches Using Ferroelectric Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Le Pesant, Jean-Pierre; Galvan, Jean-Marc; Le Barny, Pierre

    1989-01-01

    The discovery of ferroelectricity in smectic C liquid crystals, in 1975, has introduced a new electrooptic effect, driven by linear coupling between the permanent electric polarization of chiral smectic C molecules and the addressing electric field. Ferroelectric liquid crystals allow a reduction of at least 3 orders of magnitude of the switching time with respect to conventional twisted nematics, and yield permanent stable states used for memory effects (surface stabilization for small thickness cells and AC stabilization for small and medium thickness cells). All this has open the way to new and faster devices ranging from highly multiplexed displays to optical shutters. The authors describe the present trends in material synthesis, molecular anchoring and device fabrication. New mixtures have been prepared at Thomson-CSF and other laboratories which yield low viscosity materials by using high polarity chiral molecules as dopants. Response times of less than 40 μs have already been obtained and lower ones are forseable. Small pitch (less than 50 μm) optical shutters will be described and applications such like light modulators and line printers will be discussed.

  12. Topology and temperature dependence of the diffuse X-ray scattering in Na0.5Bi0.5TiO3 ferroelectric single crystals

    PubMed Central

    Gorfman, Semn; Keeble, Dean S.; Bombardi, Alessandro; Thomas, Pam A.

    2015-01-01

    The results of high-resolution measurements of the diffuse X-ray scattering produced by a perovskite-based Na0.5Bi0.5TiO3 ferroelectric single crystal between 40 and 620?K are reported. The study was designed as an attempt to resolve numerous controversies regarding the average structure of Na0.5Bi0.5TiO3, such as the mechanism of the phase transitions between the tetragonal, P4bm, and rhombohedral | monoclinic, R3c?|?Cc, space groups and the correlation between structural changes and macroscopic physical properties. The starting point was to search for any transformations of structural disorder in the temperature range of thermal depoling (420480?K), where the average structure is known to remain unchanged. The intensity distribution around the {032} pseudocubic reflection was collected using a PILATUS 100K detector at the I16 beamline of the Diamond Light Source (UK). The data revealed previously unknown features of the diffuse scattering, including a system of dual asymmetric L-shaped diffuse scattering streaks. The topology, temperature dependence, and relationship between Bragg and diffuse intensities suggest the presence of complex microstructure in the low-temperature R3c?|?Cc phase. This microstructure may be formed by the persistence of the higher-temperature P4bm phase, built into a lower-temperature R3c?|?Cc matrix, accompanied by the related long-range strain fields. Finally, it is shown that a correlation between the temperature dependence of the X-ray scattering features and the temperature regime of thermal depoling is present. PMID:26877721

  13. Microstructure and enhanced in-plane ferroelectricity of Ba0.7Sr0.3TiO3 thin films grown on MgAl2O4 (001) single-crystal substrate

    NASA Astrophysics Data System (ADS)

    Zhou, X. Y.; Heindl, T.; Pang, G. K. H.; Miao, J.; Zheng, R. K.; Chan, H. L. W.; Choy, C. L.; Wang, Y.

    2006-12-01

    The microstructure and in-plane dielectric and ferroelectric properties of highly oriented Ba0.7Sr0.3TiO3 (BST) thin film grown on MgAl2O4 (001) single-crystal substrate through pulsed laser deposition were investigated. X-ray diffraction measurements indicated that BST had a distorted lattice with a tetragonality a /c=1.012. The cross-sectional observation under transmission electron microscope revealed that, while most of BST grains grew epitaxially on MgAl2O4, the film also contained a noticeable amount of misoriented grains and dislocations. The electrical measurements indicated that the film had a shifted Curie temperature (TC=78C ) and an enhanced in-plane ferroelectricity (remnant polarization Pr=7.1?C/cm2) when compared with BST ceramic (TC?33C and Pr?0).

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

    SciTech Connect

    Matsumoto, Takao; Okamoto, Masakuni

    2011-01-01

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

  15. Structure and properties of Bi(Zn0.5Ti0.5)O3- Pb(Zr(1-x)Ti(x))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(Zr(1-x)Ti(x))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 T(C) 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 μC/cm(2) and a coercive field E(C) of 22.1 kV/cm. PMID:26067036

  16. Growth, dielectric, ferroelectric and optical properties of Ca 0.28Ba 0.72Nb 2O 6 single crystals

    NASA Astrophysics Data System (ADS)

    Song, Hualong; Zhang, Huaijin; Jiang, Quanzhong; Xu, Xiangang; Lu, Chaojing; Hu, Xiaobo; Wang, Jiyang; Jiang, Minhua

    2006-05-01

    Calcium barium niobate Ca 0.28Ba 0.72Nb 2O 6 (CBN-28) crystals were grown by the Czochralski method. The effective segregation coefficients of Ca, Ba, Na elements in CBN-28 crystal growth were measured, and the rocking curve from 0 0 2 reflection of CBN-28 wafer was also measured by the high-resolution X-ray diffractometer D5005, and the full-width at half-maximum value was measured to be 70.6?. The measured dependence of dielectric constants on temperature showed the Curie temperature of the CBN-28 crystals is between 246.8 and 260 C. Typical polarization-electric field ( P- E) hysteresis loops were measured at room temperature. Ferroelectric 180 domains were observed by scanning electron microscopy (SEM) on the etched (0 0 1) surface of the CBN-28 crystals. The transmittance of [0 0 1]-oriented CBN-28 crystals was measured and the result shows that optical properties of CBN-28 crystal are almost the same as those of SBN for wavelengths between 2500 and 7500 nm.

  17. Chiralization and ferroelectric state induction in nanostructured liquid crystals

    NASA Astrophysics Data System (ADS)

    Katranchev, B.; Petrov, M.; Rafailov, P. M.; Todorov, N.

    2016-02-01

    The liquid crystals (LC), due to their naturally high bulk ordering, strong birefringence and easy electrooptical driving, serve as matrix in the nanocomposites doped with non-mesogenic or mesogenic nanoparticles. The nanocomposite's structural units exhibit very complex molecular form indicating the strength and the intermolecular interaction between the matrix and dopant's molecules. Hydrogen bonds are of particular significance for the formation of the nanocomposite structural units, since the symmetry of the LC nanocomposite could be controlled and controllably decreased due to the acceptor-donor interaction between the dimeric matrix and the dopants. As a result, the LC nanocomposite can reach the lowest symmetry, known as triclinic - C1. Using the LC p,n-alkyloxybensoic acids (nOBA) in form of hydrogen-bonded dimers as matrix and non-mesogenics - single walls carbon nanotubes (SWCNT), perfluorooctanoic acid (PFOA), 4-hydrooxypiridin (HOPY) or mesogen - cholesteryl benzoate (ChB) as dopants and choosing optimal concentrations (where the typical LC state was preserved), we obtained nanocomopsites 7OBA/SWCNT, 7OBA/PFOA, 9OBA/HOPY and 8OBA/ChB. We indicate two forms of ferroelectricity in the studied nanocomposites: developable ferroelectricity, characteristic for the 9OBA/HOPY, 7OBA/PFOA compounds and developed ferroelectricity characteristic for 8OBA/SWCNT, 8OBA/ChB.

  18. A theory of double hysteresis for ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Srivastava, N.; Weng, G. J.

    2006-03-01

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

  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; Zhuang, Jian; Wu, Xiaoqing; Ren, Wei; Ye, Zuo-Guang

    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 μC/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. Phononic Crystal Tunable via Ferroelectric Phase Transition

    NASA Astrophysics Data System (ADS)

    Xu, Chaowei; Cai, Feiyan; Xie, Shuhong; Li, Fei; Sun, Rong; Fu, Xianzhu; Xiong, Rengen; Zhang, Yi; Zheng, Hairong; Li, Jiangyu

    2015-09-01

    Phononic crystals (PCs) consisting of periodic materials with different acoustic properties have potential applications in functional devices. To realize more smart functions, it is desirable to actively control the properties of PCs on demand, ideally within the same fabricated system. Here, we report a tunable PC made of Ba0.7Sr0.3Ti O3 (BST) ceramics, wherein a 20-K temperature change near room temperature results in a 20% frequency shift in the transmission spectra induced by a ferroelectric phase transition. The tunability phenomenon is attributed to the structure-induced resonant excitation of A0 and A1 Lamb modes that exist intrinsically in the uniform BST plate, while these Lamb modes are sensitive to the elastic properties of the plate and can be modulated by temperature in a BST plate around the Curie temperature. The study finds opportunities for creating tunable PCs and enables smart temperature-tuned devices such as the Lamb wave filter or sensor.

  1. Dynamic response of polar nanoregions under an electric field in a paraelectric KTa0.61Nb0.39O3 single crystal near the para-ferroelectric phase boundary

    NASA Astrophysics Data System (ADS)

    Tian, Hao; Yao, Bo; Wang, Lei; Tan, Peng; Meng, Xiangda; Shi, Guang; Zhou, Zhongxiang

    2015-09-01

    The dynamic response of polar nanoregions under an AC electric field was investigated by measuring the frequency dependence of the quadratic electro-optic (QEO) effect in a paraelectric KTa0.61Nb0.39O3 single crystal near the para-ferroelectric phase boundary (0?C?crystal was attributed to the dynamic rearrangement of polar nanoregions and its anomalous distortion can be explained by considering the asymmetric distribution of polar nanoregions.

  2. 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. Prakasam, M.; Viraphong, O.; Maglione, M.; Shimamura, K.

    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)

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Optimal properties like piezoelectricity can be found in polarizable materials for which the structure changes sharply under small composition variations in the vicinity of their morphotropic phase boundary or the triple point in their isobaric temperature-composition phase diagram. In the latter, lead-free (Ba0.850Ca0.150)(Ti0.900Zr0.100)O3 ceramics exhibit outstanding piezoelectric coefficients. For the first time, we report the growth of piezoelectric lead-free single crystals in the BaTiO3-BaZrO3-CaTiO3 pseudo-ternary system. The stoichiometry control in the CaO-BaO-TiO2-ZrO2 solid solution led to single crystals with various compositions ranging from (Ba0.857Ca0.143)(Ti0.928Zr0.072)O3 to (Ba0.953Ca0.047)(Ti0.427Zr0.573)O3. We evidenced a continuous cross-over from a ferroelectric state at high titanium content to a relaxor one on increasing the zirconium content. Such a property tuning is rather seldom observed in lead-free ferroelectrics and confirms what was already reported for ceramics. Single crystal with (Ba0.838Ca0.162)(Ti0.854Zr0.146)O3 composition, which has been grown and oriented along [001] crystallographic direction, displayed electromechanical coefficients d31 and k31 of 93 pC.N-1 and 0.18, respectively, near the room temperature (T = 305 K).

  4. 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.

  5. Optical recording using a photochromic ferroelectric liquid crystal

    SciTech Connect

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

    2001-06-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  7. Electric-field-controlled interface strain coupling and non-volatile resistance switching of La{sub 1-x}Ba{sub x}MnO₃ 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; Wang, Yu

    2014-09-21

    We have fabricated magnetoelectric heterostructures by growing ferromagnetic La{sub 1-x}Ba{sub x}MnO₃ (x=0.2, 0.4) thin films on (001)-, (110)-, and (111)-oriented 0.31Pb(In{sub 1/2}Nb{sub 1/2})O₃-0.35Pb(Mg{sub 1/3}Nb{sub 1/2})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 [(ΔR/R){sub 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.

  8. 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.

  9. Pressure-induced transitions in ferroelectric single-crystal PbZr0.54Ti0.46O3

    NASA Astrophysics Data System (ADS)

    Ahart, Muhtar; Cohen, R. E.; Hemley, Russell J.

    2014-03-01

    Ceramics of PbZr(1 - x)TixO3 (PZT) are widely used in many modern electromechanical transducers. Because single crystals of these materials are difficult to grow, many intrinsic physical properties have not been well understood. Recent breakthroughs in the growth of PZT single crystals have allowed us to study their fundamental physical properties. Here, we study the pressure induced phase transitions in PbZr0.54Ti0.46O3 single crystal by means of combined high-pressure Raman scattering and x-ray diffraction. Our Raman results indicate that the structural transition at 3 GPa is driven by soft optical phonons, and is accompanied by the appearance of a sharp peak near 370 cm-1 above 3 GPa. We also observe a new structural transition occurring above 27 GPa associated with a drastic change of the Raman spectrum. The pressure evolution of the diffraction patterns for PbZr0.54Ti0.46O3 show obvious splitting above 27 GPa, particularly for the pseudo-cubic [111] and [220] diffraction peaks, the results indicate a lowering symmetry transition in PbZr0.54Ti0.46O3. We propose that the second transition is from rhombohedral to orthorhombic induced by a pressure above 27 GPa. This work in supported by the Carnegie/Department of Energy Alliance Center (CDAC, DE-FC03-03NA00144).

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

    SciTech Connect

    Das, Abhijit; Department of Physics, Gauhati University, Guwahati 781014, Assam ; Boruah, Bosanta R.

    2014-04-15

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

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

    SciTech Connect

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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  13. Dynamic response of polar nanoregions under an electric field in a paraelectric KTa0.61Nb0.39O3 single crystal near the para-ferroelectric phase boundary.

    PubMed

    Tian, Hao; Yao, Bo; Wang, Lei; Tan, Peng; Meng, Xiangda; Shi, Guang; Zhou, Zhongxiang

    2015-01-01

    The dynamic response of polar nanoregions under an AC electric field was investigated by measuring the frequency dependence of the quadratic electro-optic (QEO) effect in a paraelectric KTa0.61Nb0.39O3 single crystal near the para-ferroelectric phase boundary (0?C?crystal was attributed to the dynamic rearrangement of polar nanoregions and its anomalous distortion can be explained by considering the asymmetric distribution of polar nanoregions. PMID:26334181

  14. Dynamic response of polar nanoregions under an electric field in a paraelectric KTa0.61Nb0.39O3 single crystal near the para-ferroelectric phase boundary

    PubMed Central

    Tian, Hao; Yao, Bo; Wang, Lei; Tan, Peng; Meng, Xiangda; Shi, Guang; Zhou, Zhongxiang

    2015-01-01

    The dynamic response of polar nanoregions under an AC electric field was investigated by measuring the frequency dependence of the quadratic electro-optic (QEO) effect in a paraelectric KTa0.61Nb0.39O3 single crystal near the para-ferroelectric phase boundary (0?C?crystal was attributed to the dynamic rearrangement of polar nanoregions and its anomalous distortion can be explained by considering the asymmetric distribution of polar nanoregions. PMID:26334181

  15. Electromigration of microspheres in ferroelectric smectic liquid crystals.

    PubMed

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

    2007-08-01

    When an electric field is applied to microspheres which are dispersed in a ferroelectric smectic liquid crystal, particle translation along the smectic layer plane, i.e., in a direction nearly perpendicular to that of the director, can be observed. Under certain electric field conditions the translation is shown to be linear in time. We have determined the stability regime of linear particle displacement in the parameter space of amplitude and frequency for various applied wave forms. This regime enlarges for increasing electric field amplitude and frequency, with a threshold behavior observed for small parameters. The upper stability boundary is related to the reciprocal ferroelectric switching time. The microspheres translational velocity is independent of the applied electric field amplitude, but increases linearly with applied frequency. The microsphere velocity also increases with increasing temperature, which is indicative of the respective decrease in liquid crystal viscosity. Possible mechanisms of electric-field-induced particle motion are discussed. PMID:17930054

  16. Criticality of bistability phenomenon in deformed helix ferroelectric liquid crystal

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  17. Smectic layer rotation by dc field in ferroelectric liquid crystal

    NASA Astrophysics Data System (ADS)

    Nakayama, K.; Ozaki, M.; Yoshino, K.

    1997-04-01

    The smectic layer rotation of a ferroelectric liquid crystal (FLC) has been investigated by applying a dc electric field. The smectic layer of FLC doped with a small amount of an ionic impurity can be rotated around the axis perpendicular to the glass plates upon application of dc voltage. This smectic layer rotation is interpreted in terms of the electrohydrodynamic flow due to an ionic impurity.

  18. 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

  19. Ferroelectric polymers

    SciTech Connect

    Lovinger, A.J.

    1983-06-10

    Piezoelectricity and pyroelectricity, traditionally encountered in certain single crystals and ceramics, have now also been documented in a number of polymers. Recently, one such polymer - poly(vinylidene fluoride) - and some of its copolymers have been shown to be ferroelectric as well. The extraordinary molecular and supermolecular structural requirements for ferroelectric behavior in polymers are discussed in detail, with particular emphasis on poly(vinylidene fluoride). Piezoelectric, pyroelectric, and ferroelectric properties are also briefly reviewed, as are some promising applications of such polymers. 8 figures, 1 table.

  20. Acceptor-oxygen vacancy defect dipoles and fully coordinated defect centers in a ferroelectric perovskite lattice: Electron paramagnetic resonance analysis of Mn2+ in single crystal BaTiO3

    NASA Astrophysics Data System (ADS)

    Maier, R. A.; Pomorski, T. A.; Lenahan, P. M.; Randall, C. A.

    2015-10-01

    Defect dipoles are significant point defects in perovskite oxides as a result of their impact on oxygen vacancy dynamics. Electron paramagnetic resonance (EPR) was used to investigate the local defect structure of single crystal BaTiO3 doped with manganese. These results, along with a re-analysis of literature data, do not support the conclusion that transition metal-oxygen vacancy nearest neighbor defect dipoles ( M nT i ? - VO ) in ferroelectric BaTiO3 are majority defect centers as previously reported. Local symmetry analysis of the zero-field splitting term of the spin Hamiltonian supports the assignment of fully coordinated defect centers as opposed to defect dipoles for resonance signals at geff 2. A newly discovered defect center with g? 6 is observed in the manganese doped system, and it is argued that this defect center belongs to an associated defect complex or defect dipole. This newly reported strong axial defect center, however, is present in small, minor concentrations compared to the well-known Mn2+ center with zero-field splitting of D 645 MHz. In regard to relative concentration, it is concluded that the dominant point defect related to the Mn2+ ion doped in BaTiO3 corresponds to B-site substitution with six nearest neighbor anions in octahedral coordination.

  1. Optical evidences for an intermediate phase in relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolong; Zhang, Jinzhong; Xu, Guisheng; Jiang, Kai; Hu, Zhigao; Chu, Junhao

    2016-02-01

    The mechanism of low-temperature structural transformation and evolution of polar nano-structures in relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-xPbTiO3 (x = 0.33, 0.35, and 0.42) single crystals have been investigated with the aid of temperature dependent low-wavenumber Raman scattering (LWRS) and photoluminescence (PL) spectra. The E(TO1) phonon mode reveals the characteristic relaxational polarization fluctuations associated with the reorientation of either polar nano-regions or polar nano-domains. It was found that these mechanisms are not independent and they can be ascribed to the phonon localization. In addition, a short-range monoclinic phase (Mc) can be found below 250 K in the tetragonal phase region by LWRS, which is always associated with the morphotropic phase boundary (MPB) and excellent electromechanical properties. It is interesting that PL spectra confirm these results. The present work indicates that external field modulation and change of composition can result in the monoclinic phase and co-existence of multi-phase.

  2. Refractive index, band gap energy, dielectric constant and polarizability calculations of ferroelectric Ethylenediaminium Tetrachlorozincate crystal

    NASA Astrophysics Data System (ADS)

    Kalyanaraman, S.; Shajinshinu, P. M.; . Vijayalakshmi, S.

    2015-11-01

    Single crystal of Ethylenediaminium Tetrachlorozincate has been grown by slow evaporation method. The single crystal XRD study confirms the orthorhombic structure of the crystal. The presence of functional group vibrations are ascertained through FTIR and Raman studies. In optical studies, the insulating behaviour of the material is established by Tauc plot. The refractive index and the real dielectric constant of the crystal are calculated. The electronic polarizability in the high frequency optical region is also calculated from the dielectric constant values by using the Clausius-Mossotti equation. The large value of dielectric constant is identified through dielectric studies and it points to the ferroelectric behaviour of the material. Further an experimental study confirms the ferroelectric behaviour of the material. The total polarizability of the crystal owing to the space charge, dipole, ionic and electronic polarizability contributions is obtained experimentally, and it matches well with the theoretically obtained value from Penn analysis. Further, Plasmon energy and Fermi energy of the material are also calculated using Penn analysis.

  3. Structural and electronic properties of Diisopropylammonium bromide molecular ferroelectric crystal

    NASA Astrophysics Data System (ADS)

    Alsaad, A.; Qattan, I. A.; Ahmad, A. A.; Al-Aqtash, N.; Sabirianov, R. F.

    2015-10-01

    We report the results of ab-initio calculations based on Generalized Gradient Approximation (GGA) and hybrid functional (HSE06) of electronic band structure, density of states and partial density of states to get a deep insight into structural and electronic properties of P21 ferroelectric phase of Diisopropylammonium Bromide molecular crystal (DIPAB). We found that the optical band gap of the polar phase of DIPAB is ∼ 5 eV confirming it as a good dielectric. Examination of the density of states and partial density of states reveal that the valence band maximum is mainly composed of bromine 4p orbitals and the conduction band minimum is dominated by carbon 2p, carbon 2s, and nitrogen 2s orbitals. A unique aspect of P21 ferroelectric phase is the permanent dipole within the material. We found that P21 DIPAB has a spontaneous polarization of 22.64 consistent with recent findings which make it good candidate for the creation of ferroelectric tunneling junctions (FTJs) which have the potential to be used as memory devices.

  4. Energy principle of ferroelectric ceramics and single domain mechanical model

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Li, Haijun; Wang, T. C.

    2007-10-01

    Many physical experiments have shown that the domain switching in a ferroelectric material is a complicated evolution process of the domain wall with the variation of stress and electric field. According to this mechanism, the volume fraction of the domain switching is introduced in the constitutive law of ferroelectric ceramic and used to study the nonlinear constitutive behavior of ferroelectric body in this paper. The principle of stationary total energy is put forward in which the basic unknown quantities are the displacement u i , electric displacement D i and volume fraction ρ I of the domain switching for the variant I. Mechanical field equation and a new domain switching criterion are obtained from the principle of stationary total energy. The domain switching criterion proposed in this paper is an expansion and development of the energy criterion. On the basis of the domain switching criterion, a set of linear algebraic equations for the volume fraction ρ I of domain switching is obtained, in which the coefficients of the linear algebraic equations only contain the unknown strain and electric fields. Then a single domain mechanical model is proposed in this paper. The poled ferroelectric specimen is considered as a transversely isotropic single domain. By using the partial experimental results, the hardening relation between the driving force of domain switching and the volume fraction of domain switching can be calibrated. Then the electromechanical response can be calculated on the basis of the calibrated hardening relation. The results involve the electric butterfly shaped curves of axial strain versus axial electric field, the hysteresis loops of electric displacement versus electric filed and the evolution process of the domain switching in the ferroelectric specimens under uniaxial coupled stress and electric field loading. The present theoretic prediction agrees reasonably with the experimental results given by Lynch.

  5. Single Crystal Membranes

    NASA Technical Reports Server (NTRS)

    Stormont, R. W.; Morrison, A.

    1974-01-01

    Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

  6. 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; Wade, Scott; Frohnhaus, Jakob; Soergel, Elisabeth

    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.

  7. Understanding single-crystal superalloys

    NASA Technical Reports Server (NTRS)

    Dreshfield, Robert L.

    1986-01-01

    The unique properties of single crystals are considered. The anisotropic properties of single crystals, and the relation between crystal orientation and the fatigue life and slip systems of the crystals are examined. The effect of raft formation on the creep-rupture life of the crystals is studied. Proposed research on the properties of and new applications for single crystals is discussed.

  8. 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)].

  9. 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.

  10. 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.

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

    SciTech Connect

    Kaznacheev, A. V.; Pozhidaev, E. P.

    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).

  12. Single crystal functional oxides on silicon

    PubMed Central

    Bakaul, Saidur Rahman; Serrao, Claudy Rayan; Lee, Michelle; Yeung, Chun Wing; Sarker, Asis; Hsu, Shang-Lin; Yadav, Ajay Kumar; Dedon, Liv; You, Long; Khan, Asif Islam; Clarkson, James David; Hu, Chenming; Ramesh, Ramamoorthy; Salahuddin, Sayeef

    2016-01-01

    Single-crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism and so on that have the potential for completely new electronic applications. Direct synthesis of such oxides on silicon remains challenging because of the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. Here we report integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature. In a field-effect transistor using a transferred lead zirconate titanate layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single-crystal functional oxides on-demand on silicon. PMID:26853112

  13. Single crystal functional oxides on silicon.

    PubMed

    Bakaul, Saidur Rahman; Serrao, Claudy Rayan; Lee, Michelle; Yeung, Chun Wing; Sarker, Asis; Hsu, Shang-Lin; Yadav, Ajay Kumar; Dedon, Liv; You, Long; Khan, Asif Islam; Clarkson, James David; Hu, Chenming; Ramesh, Ramamoorthy; Salahuddin, Sayeef

    2016-01-01

    Single-crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism and so on that have the potential for completely new electronic applications. Direct synthesis of such oxides on silicon remains challenging because of the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. Here we report integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature. In a field-effect transistor using a transferred lead zirconate titanate layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single-crystal functional oxides on-demand on silicon. PMID:26853112

  14. Note: High-power piezoelectric transformer fabricated with ternary relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Ma, Chuanguo; Wang, Feifei; Liu, Bao; Chen, Jianwei; Luo, Haosu; Wang, Tao; Shi, Wangzhou

    2016-03-01

    A plate-shaped piezoelectric transformer was designed and fabricated using ternary relaxor ferroelectric single crystal Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbTiO3. Both the input and output sections utilized the transverse-extensional vibration mode. The frequency and load dependences of the electrical properties for the proposed transformer were systematically studied. Results indicated that under a matching load resistance of 14.9 kΩ, a maximum output power of 2.56 W was obtained with the temperature rise less than 5 °C. The corresponding power density reached up to 50 W/cm3. This ternary single-crystal transformer had potential applications in compact-size converters requiring high power density.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  16. Optical interband transitions in [111] poled relaxor-based ferroelectric 0.24Pb(In1/2Nb1/2)O3(0.76 ? x)Pb(Mg1/3Nb2/3)O3xPbTiO3 single crystal

    PubMed Central

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

    2013-01-01

    Optical transmission spectra of single crystal 0.24Pb(In1/2Nb1/2)O3(0.76 ? x)Pb(Mg1/3Nb2/3)O3xPbTiO3 (x = 0.27, 0.33) were measured in the pseudo-cubic crystallographic directions [111] and [112?]. Ferroelectric domain structures were observed in order to explain the difference of transmittance for the two composition crystals. Wavelength dependence of the absorption coefficients was measured and the optical energy band gaps were calculated for both direct and indirect transitions, which are Egd = 3.093.18 eV and Egi = 2.892.96 eV, respectively, and the phonon energy is Ep = 0.070.08 eV. The transmission spectra were explained by the refractive indices and extinction coefficients measured by spectroscopic ellipsometry. PMID:25170190

  17. Free energies of ferroelectric crystals from a microscopic approach

    NASA Astrophysics Data System (ADS)

    Geneste, Grgory

    2010-04-01

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

  18. Growth, structural phase transition and ferroelectric properties of Pb[(Zn 1/3Nb 2/3) 0.91 Ti 0.09]O 3 single crystals

    NASA Astrophysics Data System (ADS)

    Bubesh Babu, J.; Madeswaran, G.; Prakash, Chandra; Dhanasekaran, R.

    2006-07-01

    Growth of PZNT (91/9) single crystals at morphotropic phase boundary has been carried out by flux and flux Bridgman methods. Effects of multinucleation on morphology and effect of PbO evaporation on crystal growth are discussed. The grown crystals were cut along (0 0 1) direction and crystals were poled at the rate of 1 kV/mm. The slow scan X-ray diffraction results of the oriented crystals show a structural phase transition on poling. The phase transition has been studied with slow scan X-ray diffraction pattern for powdered Pb(Zn 1/3Nb 2/3)O 3-PbTiO 3 (PZN-PT) crystal and (0 0 1) oriented single crystal which shows the existence of stressed phases and trapped phases in both cases. Further the grown PZN-PT single crystals have been subjected to compositional studies. Electrical characterizations such as hysteresis measurement, strain measurement and piezoelectric measurement were carried out and the results are discussed in detail.

  19. Flexo- and piezo-electric polarization of smectic layers in ferroelectric and antiferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Kuczyński, W.; Hoffmann, J.; Dardas, D.; Nowicka, K.; Bielejewska, N.

    2015-11-01

    In this paper, we report on how flexoelectric and piezoelectric polarization components can be determined by a method based on simultaneous studies of dielectric and electrooptic properties of the chiral smectic liquid crystal in the regime of weak electric fields. As a rule, the measurements of spontaneous polarization are performed using switching experiments. The polarization measured in this way is not complete—it contains the piezoelectric component only. However, the knowledge of the entire local polarization of a single smectic layer is of great importance—it is necessary for correct determination of some material parameters, for instance elastic constants. Our experiments performed in a helical smectic mixture demonstrated that flexoelectric contribution to the local spontaneous polarization is significant in both ferroelectric and antiferroelectric phases. In the antiferroelectric phase, the flexoelectric polarization is less due to higher helical pitch.

  20. Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review

    PubMed Central

    Zhang, Shujun; Li, Fei; Jiang, Xiaoning; Kim, Jinwook; Luo, Jun; Geng, Xuecang

    2014-01-01

    Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials’ behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor-PT crystals are summarized to guide on-going and future research in the development of relaxor-PT crystals for the next generation electroacoustic transducers. PMID:25530641

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

    NASA Astrophysics Data System (ADS)

    Bose, Tushar Kanti; Saha, Jayashree

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  3. 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.

  4. 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

  5. Quantum ferroelectricity in charge-transfer complex crystals

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  6. 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

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

    NASA Astrophysics Data System (ADS)

    Pter, .; Hajdara, I.; Szaller, Zs.; Lengyel, K.; Kovcs, L.

    2013-05-01

    Ferroelectric K3Li2Nb5O15 (KLN-1) crystals have been grown by the top-seeded solution growth method from pure, Na+, Rb+ and Cs+ doped melt. The impact of alkali additives was assessed all over the entire pulling range by investigating the variation of the structural and physical properties by using spectroscopic and dielectric methods. The incorporation of alkali homologs has been correlated with their ionic radii: Na+ ions were found to enter both Li and K sites with high segregation coefficient (k1.6), Rb+ ions were detected only at K sites (k0.34) and Cs+ ions practically did not incorporate into the lattice (k0.12). Alkali additives have been found to play a dual role in the growth process by affecting the crystallization temperature and promoting the K and Li site occupancy. By decreasing the crystallization temperature the Cs2O additive reduced the concentration both of the antisite Nb ions at Li site and that of alkali vacancies; therefore it can be considered as a promising fluxing agent in the growth of KLN crystals.

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

    NASA Astrophysics Data System (ADS)

    Stojanovi?, Maja; Obadovi?, Dusanka .; Bubnov, Alexej; Hamplov, Vera; Ka?par, Miroslav

    2007-04-01

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

  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. Highly polarized single-c-domain single-crystal Pb(Mn,Nb)O(3)-PZT thin films.

    PubMed

    Wasa, Kiyotaka; Adachi, Hideaki; Nishida, Ken; Yamamoto, Takashi; Matsushima, Tomoaki; Kanno, Isaku; Kotera, Hidetoshi

    2012-01-01

    In-plane unstrained single-c-domain/single-crystal thin films of PZT-based ternary ferroelectric perovskite, ?Pb(Mn,Nb)O3-(1 - ?)PZT, were grown on SrRuO(3)/Pt/MgO substrates using magnetron sputtering followed by quenching. The sputtered unstrained thin films exhibit unique ferroelectric properties: high coercive field, Ec > 180 kV/cm, large remanent polarization, P(r) = 100 ?C/cm(2), small relative dielectric constants, ?* = 100 to 150, high Curie temperature, Tc = ~600 C, and bulk-like large transverse piezoelectric constants, e31,f = -12.0 C/m(2) for PZT(48/52) at ? = 0.06. The unstrained thin films are an ideal structure to extract the bulk ferroelectric properties. Their micro-structures and ferroelectric properties are discussed in relation to the potential applications for piezoelectric MEMS. PMID:22293730

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

    PubMed

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

    2008-06-01

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

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan

    2014-09-01

    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 π-π 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.

  14. 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.

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

    SciTech Connect

    Basu, Rajratan

    2014-09-15

    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 π–π 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  17. Effect of Reoriented Nanodomains on Crystal Structure and Piezoelectric Properties of Polycrystalline Ferroelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Fan, Qiaolan; Zeng, Weidong; Zhou, Changrong; Cen, Zhenyong; Yuan, Changlai; Xiao, Jianrong; Ma, Jiafeng

    2015-10-01

    It has been widely accepted that electric fields induce a reversible structural phase transition and thus yield giant piezoelectric responses in ferroelectric ceramics. Based on detailed measurements of polycrystalline (Li0.5Nd0.5)2+-modified 0.95Bi0.5Na0.5TiO3-0.05BaTiO3 ceramics, we demonstrate in this study that coherent diffraction from nanodomains in ferroelectric ceramics masks the real crystal structure. The observed electric-field-induced phase transformation behavior is a consequence of relaxor-to-ferroelectric transformation caused by changes in the coherence length of the nanodomains. A driving mechanism of the structure-property relationship in which high piezoelectric properties originate from correlated ordering of nanodomains during poling is proposed.

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

    NASA Astrophysics Data System (ADS)

    Garca-Gutirrez, Mari-Cruz; Linares, Amelia; Martn-Fabiani, Ignacio; Hernndez, Jaime J.; Soccio, Michelina; Rueda, Daniel R.; Ezquerra, Tiberio A.; Reynolds, Michael

    2013-06-01

    The successful development of ferroelectric polymer devices depends on the effective fabrication of polar ferroelectric crystalline nanostructures. We demonstrate, by scanning X-ray microdiffraction using synchrotron light, the heterogeneous character of high aspect ratio one-dimensional nanoarrays of poly(vinylidene fluoride-co-trifluoroethylene) copolymers supported by a residual polymer film. They were prepared by melt and solution template wetting, using porous anodic aluminum oxide as a template. The spatial evolution of different polymorphs from the mixture of paraelectric and ferroelectric crystal forms (residual film) to the pure ferroelectric form (nanoarray) is evidenced for the samples prepared by solution wetting. However, for samples prepared by melt wetting the ferroelectric phase is exclusively obtained in both the residual film and nanoarray. The crystal nuclei formed in the polymer film connected to the nanoarray play a key role in determining the formation of a crystallinity distribution gradient, where the crystallinity decreases along the first 5-10 microns in the nanorods reaching a steady value afterwards. The minimum decrease in crystallinity is revealed for samples prepared by melt wetting. The results reported in this work endeavour to enhance the understanding of crystallization under confinement for ferroelectric copolymers and reveal the parameters for improving the ferroelectric character of polymer nanostructures.The successful development of ferroelectric polymer devices depends on the effective fabrication of polar ferroelectric crystalline nanostructures. We demonstrate, by scanning X-ray microdiffraction using synchrotron light, the heterogeneous character of high aspect ratio one-dimensional nanoarrays of poly(vinylidene fluoride-co-trifluoroethylene) copolymers supported by a residual polymer film. They were prepared by melt and solution template wetting, using porous anodic aluminum oxide as a template. The spatial evolution of different polymorphs from the mixture of paraelectric and ferroelectric crystal forms (residual film) to the pure ferroelectric form (nanoarray) is evidenced for the samples prepared by solution wetting. However, for samples prepared by melt wetting the ferroelectric phase is exclusively obtained in both the residual film and nanoarray. The crystal nuclei formed in the polymer film connected to the nanoarray play a key role in determining the formation of a crystallinity distribution gradient, where the crystallinity decreases along the first 5-10 microns in the nanorods reaching a steady value afterwards. The minimum decrease in crystallinity is revealed for samples prepared by melt wetting. The results reported in this work endeavour to enhance the understanding of crystallization under confinement for ferroelectric copolymers and reveal the parameters for improving the ferroelectric character of polymer nanostructures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00516j

  19. Crystal growth of alkali metal ion doped potassium niobate fiber single crystals

    NASA Astrophysics Data System (ADS)

    Kimura, H.; Tanahashi, R.; Zhao, H. Y.; Maiwa, K.; Cheng, Z. X.; Wang, X. L.

    2010-05-01

    Alkali metal (Na, Rb or Cs) ion doped KNbO 3 fiber single crystals are grown using an original pulling down method, to improve their composition change during a crystal growth, by means of co-doping of small ionic size Na and large ionic size Rb or Cs into KNbO 3. In spite of the co-doping, single crystals can be grown with orthorhombic single-phase at room temperature, as well as pure KNbO 3. Their electric properties, such as impedance, are changed depending on the doping ions. Na and Rb co-doped KNbO 3 is promising Pb free ferroelectric and piezoelectric crystals.

  20. 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.

  1. Second optical harmonic near the surface of ferroelectric photonic crystals and photon traps

    NASA Astrophysics Data System (ADS)

    Voinov, Yu. P.; Gorelik, V. S.; Zaitsev, K. I.; Zlobina, L. I.; Sverbil', P. P.; Yurchenko, S. O.

    2015-03-01

    This paper reports on the results of experimental investigations of the generation of the second optical harmonic localized in a thin subsurface layer of ferroelectric photonic crystals and photon traps. To excite the second optical harmonic, a KGW: Yb solid-state pulsed-periodic laser generating the radiation with a wavelength of 1026 nm in a form of pulses 10-13 s long with a repetition frequency of 200 kHz at the average power of 0.1-3.5 W and power density of 109-1012 W/cm2 in a spot less than 100 ?m in diameter focused near the surface was used. Ferroelectrics, notably, barium titanate or sodium nitrite, were introduced into the pores between SiO2 nanoglobules. It is established that the maximal conversion efficiency of the exciting radiation into the second optical harmonic was several percents. The generation characteristics of the second optical harmonic near the surface of photonic crystals filled with ferroelectrics are compared with the generation of the second optical harmonic in ferroelectric photon traps of barium titanate ceramics and sodium nitrite microcrystals.

  2. 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

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

    SciTech Connect

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

    2014-12-31

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

  4. Losses in Ferroelectric Materials

    PubMed Central

    Liu, Gang; Zhang, Shujun; Jiang, Wenhua; Cao, Wenwu

    2015-01-01

    Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate-lead titanate and lead zinc niobate-lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy loss mechanisms are discussed in terms of compositions, crystal structures, temperature, domain configurations, domain sizes and grain boundaries. The intrinsic and extrinsic contributions to the total energy dissipation are quantified. In domain engineered ferroelectric single crystals and ceramics, polarization rotations, domain wall motions and mechanical wave scatterings at grain boundaries are believed to control the mechanical quality factors of piezoelectric resonators. We show that a thorough understanding on the kinetic processes is critical in analyzing energy loss behavior and other time-dependent properties in ferroelectric materials. At the end of the review, existing challenges in the study and control of losses in ferroelectric materials are analyzed, and future perspective in resolving these issues is discussed. PMID:25814784

  5. Ferroelectric BaTiO3 phase of orthorhombic crystal structure contained in nanoparticles

    NASA Astrophysics Data System (ADS)

    Ram, S.; Jana, A.; Kundu, T. K.

    2007-09-01

    Ferroelectric BaTiO3 phase of a Pnma orthorhombic crystal structure is synthesized from a chemical method using a polymer complex of Ba2+ and Ti4+ with polyvinyl alcohol (PVA). After burning out the polymer at temperature as high as 550 C in air for 2 h results in an average 15 nm crystallite BaTiO3 size, with lattice parameters a =0.6435 nm, b =0.5306 nm, c =0.8854 nm, and density 5.124 g/cm3. The relationship between dielectric constant ?r and temperature showed a single Curie transition temperature TC=131 C, with as large a ?r value as 263 at TC. A low value of dissipation factor tan ?, as small as 0.033 at room temperature (frequency f =1 kHz), with good insulating properties made the sample promising for use in uncooled infrared detectors and thermal imaging applications. The ?r value is nearly independent of f value up to 100 kHz. A spectrum of sharp EPR signals of g values 2.21 to 1.88 characterizes three major kinds of VBa-, VTi3-, and Ti3+-Vo2+ paramagnetic species present in the imperfections.

  6. Pressure-induced phase transitions of perovskite ferroelectric crystals: comparison of hydrostatic and 1D compression pressure

    NASA Astrophysics Data System (ADS)

    Gao, Junjie; Xie, Long; Zhang, Hao; Yu, Jidong; Wang, Ganghua; Liu, Gaomin; Gu, Yanqin; He, Hongliang; Bai, Jingsong

    2015-11-01

    The effects of hydrostatic and one-dimensional (1D) compression pressure on the phase transition of perovskite ferroelectric crystal were comparably investigated via the measurement of polarization P r with respect to applied pressure and the Landau-Devonshire (LD) phenomenological approach. The results showed that hydrostatic pressure can induce ferroelectric-to-paraelectric phase transition, while 1D compression can stablize the ferroelectric phase. This phenomenon was very different from the phase transitions of metal crystals, such as iron. In the framework of LD phenomenological theory, this phenomenon is believed to be associated with the strong anisotropy and electromechanical coupling which exists in ferroelectrics under high pressure. On the other hand, the piezoelectric stress coefficient e 31 and piezoelectric strain coefficient d h for PIN-PMN-PT crystal were obtained as??-2.9 C m-2 and 80 pC N-1, respectively.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    SciTech Connect

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

    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.

  9. Nondestructive imaging and characterization of ferroelectric domains in periodically poled crystals

    NASA Astrophysics Data System (ADS)

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

    1998-06-01

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

  10. Photonic band gap structure for a ferroelectric photonic crystal at microwave frequencies.

    PubMed

    King, Tzu-Chyang; Chen, De-Xin; Lin, Wei-Cheng; Wu, Chien-Jang

    2015-10-10

    In this work, the photonic band gap (PBG) structure in a one-dimensional ferroelectric photonic crystal (PC) is theoretically investigated. We consider a PC, air/(AB)N/air, in which layer A is a dielectric of MgO and layer B is taken to be a ferroelectric of Ba0.55Sr0.45TiO3 (BSTO). With an extremely high value in the dielectric constant in BSTO, the calculated photonic band structure at microwave frequencies exhibits some interesting features that are significantly different from those in a usual dielectric-dielectric PC. First, the photonic transmission band consists of multiple and nearly discrete transmission peaks. Second, the calculated bandwidth of the PBG is nearly unchanged as the angle of incidence varies in the TE wave. The bandwidth will slightly reduce for the TM mode. Thus, a wide omnidirectional PBG can be obtained. Additionally, the effect of the thickness of the ferroelectric layer on the PBG is much more pronounced compared to the dielectric layer thickness. That is, the increase of ferroelectric thickness can significantly decrease the PBG bandwidth. PMID:26479812

  11. Femtosecond wavevector overtone spectroscopy of anharmonic lattice dynamics in ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Brennan, Ciaran Joseph

    Impulse Stimulated Raman Scattering (ISRS) is a useful technique for characterizing the soft optic modes that are responsible for the polar distortion in ferroelectric crystals. ISRS provides an impulse force to the selected mode at a specific wavevector, and the subsequent oscillations and damping of the mode can be observed. Previous researchers have used this technique to measure the wavevector-dependent frequency and damping of optic phonons and phonon-polaritons in a variety of ferroelectric crystals. The recent development of powerful amplified Ti:sapphire femtosecond lasers opens the possibility that the impulse force applied to the ferroelectric soft mode is so large that the resultant ionic excursions will sample the anharmonic portions of the potential energy surface for the soft mode. This would, in principle, allow the experimental measurement of the potential energy surface by carefully characterizing the anharmonic content of the ISRS signals. This information would give insight into the causal mechanism for the phenomenon of ferroelectricity. Measurements of anharmonic phonon-polaritons in ferroelectric crystals have been performed using Wavevector Overtone Spectroscopy (WOS), a refinement of the impulsive stimulated Raman scattering (ISRS) technique. Numerical simulations suggest that harmonics of the polariton wavevector, rather than harmonics of the polariton frequency, are the key signatures of lattice anharmonicity in a time resolved grating experiment. The predicted signals at the wavevector overtones were observed up to the 5th order in LiTaO3, providing strong evidence of anharmonicity of the phonon-polariton response. Further evidence for anharmonicity comes from ISRS measurements at the fundamental wavevector and measurements of diffraction efficiency. The ISRS data shows non-sinusoidal response with a rich overtone spectrum, while the diffraction efficiency measurements reveal ionic displacements of about 1% of the ferroelectric distortion. These measurements provide a confirmation of the anharmonicity in the large-amplitude phonon-polariton response created by the intense light field of the amplified femtosecond laser. It is possible to extract a potential energy surface for the phonon-polariton from the anharmonic coefficients when measured over a range of experimental wavevectors. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139- 4307. Ph. 617-253-5668; Fax 617-253-1690.)

  12. 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.

  13. Development of single crystal membranes

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Zribi, Olena; Garbovskiy, Yuriy; Glushchenko, Anatoliy

    2014-12-01

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

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

    SciTech Connect

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2002-08-01

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

  18. Direct pulse technique for spontaneous polarization dynamics and molecular reorientation processes in ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Bawa, S. S.; Biradar, A. M.; Saxena, K.; Chandra, Subhas

    1988-09-01

    A method has been devised for studying the spontaneous polarization, dynamics of polarization reversal, and the molecular reorientation processes that occur in the bulk and surfaces of ferroelectric liquid crystals. These studies have been carried out by analyzing the current response to triangular- and square-wave forms. The current response to a triangular wave yields the spontaneous polarization by conveniently subtracting the background contribution due to the conductive and capacitive currents. Molecular reorientation processes which take place within the bulk and the boundary surface layer can be studied by the appearance of polarization current peaks on the triangular-wave response. The dynamics of polarization reversal between bistable states and of the polarization change between the zero-field relaxed state and either of the saturation remanent polarization states have been studied by applying ``symmetric'' and ``asymmetric'' square waves. The technique can also be successfully applied to solid ferroelectrics for studying the spontaneous polarization and the domain dynamics during switching.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  20. Mechanism of Helix Unwinding in the Ferroelectric Liquid Crystal Phase of Compounds Which Display an Antiferro - Ferri - Ferroelectric Sequence

    NASA Astrophysics Data System (ADS)

    Pavel, J.; Gisse, P.; Nguyen, H. T.; Martinot-Lagarde, Ph.

    1995-03-01

    The behaviour of planar samples of an antiferroelectric liquid crystal under DC electric field has been studied through observations with a polarizing microscope. In the ferroelectric phase the dechiralization lines have not been observed under a vanishing electric field. They appeared with the increasing field. To explain that effect, we show by analysing the anchoring energy, that the structure of the planar helicoidal SmC^* sample can exist with π-disclinations on the glass surfaces. The behaviour of such samples under an electric field is also discussed. Nous avons étudié le comportement des lignes de “déchiralisation” observées en microscopie optique polarisante sur des échantillons en géométrie planaire, d'un cristal liquide antiferroélectrique sous l'action d'un champ électrique continu. Dans la phase ferroélectrique, ces lignes de “déchiralisation” ne sont pas observées à champ nul, mais apparaissent à faible champ. Pour l'expliquer, nous avons montré en analysant les énergies d'ancrages des molécules, que des “π- disinclinaisons” de surface avec un ancrage antiferroélectrique du coeur des défauts peuvent exister dans la phase SmC^*.

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

    NASA Astrophysics Data System (ADS)

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

    2004-04-01

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

  2. Polarization-shielded V-shaped ferroelectric liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Mochizuki, Akihiro

    2004-05-01

    A unique electro-optical behavior in the "chiral smectic C phase" liquid crystal cell is introduced in conjunction with possible interpretation of the specific molecular initial alignment. This cell shows continuous gray shades capability with keeping fast optical response such as less than 100 ms at room temperature. This gray shade has hysteresis-free, which suggests possible shielding of spontaneous polarization in the cell. Asymmetrical optical response between rise and decay profiles with very small temperature dependence strongly suggests the shielding of polarization in the cell. Therefore, this particular cell may be called as the polarization shielded smectic liquid crystal display or the PSS-LCD. The unique electro-optical response phenomena and their interpretation are discussed here.

  3. Investigation of specific features of the lattice dynamics and the ferroelectric transition in perovskite crystals

    SciTech Connect

    Maksimov, E. G.; Matsko, N. L.

    2009-03-15

    The specific features of diffuse X-ray scattering in BaTiO{sub 3}, KNbO{sub 3}, and PbTiP{sub 3} perovskite crystals have been investigated. The former two perovskite compounds in cubic, tetragonal, and orthorhombic phases exhibit anomalous sheets due to diffuse X-ray scattering, whereas no similar sheets are observed in the case of diffuse X-ray scattering in PbTiO{sub 3}. For these compounds, the phonon spectra are calculated in the quasi-harmonic approximation within the polarizable-shell model, and the mechanism of stabilization of the soft mode above the temperature of the phase transition to the ferroelectric state is considered. It is demonstrated that, in the cubic phase of BaTiO{sub 3} and KNbO{sub 3} crystals, there exist quasi-one-dimensional 'soft' modes of vibrations of ions in M-O-M-O- chains, where M = Ti or Nb. In PbTiO{sub 3}, this feature of the soft mode has not been revealed. The pair correlation functions of simultaneous atomic displacements in BaTiO{sub 3}, KNbO{sub 3}, and PbTiO{sub 3} are determined and used to calculate the intensity of diffuse X-ray scattering. The results obtained are in good agreement with experimental data. This is a strong argument in support of the hypothesis that the specific features of diffuse scattering are associated with the existence of quasi-one-dimensional correlations of atomic displacements in the soft optical mode and that the ferroelectric transition in perovskites is a displacive ferroelectric phase transition. The possible influence of the specific features revealed in the phonon spectra of the perovskite crystals on the processes of nuclear magnetic resonance and X-ray absorption (extended X-ray absorption fine structure spectra) is briefly discussed.

  4. Influence of annealing temperature on the crystallization and ferroelectricity of perovskite CH3NH3PbI3 film

    NASA Astrophysics Data System (ADS)

    Wang, Fangfang; Meng, Dechao; Li, Xiaoning; Zhu, Zhu; Fu, Zhengping; Lu, Yalin

    2015-12-01

    Organometal halide perovskite materials are emerging as solar cell materials, but the understanding of its performance is not yet enough, especially in its ferroelectricity which is important for the separation of photo-generated carriers. In this paper, we report investigations on influences of annealing temperature on the ferroelectricity of solution-processed methylammonium lead triiodide (CH3NH3PbI3) thin film. It is found that annealing temperature has significant effect on the crystallinity and the crystal size, which further affects the ferroelectricity and the luminescence property. It indicates that the crystallization degree of the thin film and the uniformity of crystal growth are gradually getting better, and the phase contrast of positive polarization areas and negative polarization areas are gradually strengthened.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  6. Theoretical study of ferroelectrics and dielectrics properties of novel pyroelectricc material triglycine sulphate crystal

    NASA Astrophysics Data System (ADS)

    Upadhyay, Trilok Chandra; Sharma, Sandeep

    2011-11-01

    An extended two sublattice pseudospin lattice coupled mode model of Chaudhuri et al [Phys.Rev.338 (1988) 689] by adding third and fourth-order phonon anharmonic interactions terms is considered for triglycine sulphate (CH2NH2COOH)3H2SO4 crystal and its isomorphs. With the help of double-time temperature dependent Green's function method, expressions for shift,width, soft mode frequency, dielectric constant and loss tangent are derived. By fitting model values in the theoritical expressions, temperature dependence of soft mode frequency, dielectric constant and loss tangent are calculated. The theoretical results compare well with experimental results of Aravazhi et al [Ferroelectrics200 (1997) 279.

  7. 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).

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

    NASA Astrophysics Data System (ADS)

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

    1983-10-01

    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 line. Moreover, the experiment with pulsed triangular waves clearly reveals no existence of the threshold voltage for deforming the helix and some characteristic properties of the dynamic reaction of the helix to the field applied.

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

    SciTech Connect

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

    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.

  10. 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 ?50C 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

  11. Electric-field-induced weakly chaotic transients in ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Śliwa, I.; JeŻewski, W.; Kuczyński, W.

    2016-01-01

    Nonlinear dynamics induced in surface stabilized ferroelectric liquid crystals by strong alternating external electric fields is studied both theoretically and experimentally. As has already been shown, molecular reorientations induced by sufficiently strong fields of high-enough frequencies can reveal a long transient behavior that has a weakly chaotic character. The resulting complex dynamics of ferroelectric liquid crystals can be considered not only as a consequence of irregular motions of particular molecules but also as a repercussion of a surface-enforced partial decorrelation of nonlinear molecular motions within smectic layers. To achieve more insight into the nature of this phenomenon and to show that the underlying complex field-induced behavior of smectic liquid crystals is not exceptional, ranges of system parameters for which the chaotic behavior occurs are determined. It is proved that there exists a large enough set of initial phase trajectory points, for which weakly chaotic long-time transitory phenomena occur, and, thereby, it is demonstrated that such a chaotic behavior can be regarded as being typical for strongly field-driven thin liquid crystal systems. Additionally, the influence of low-amplitude random noise on the duration of the transient processes is numerically studied. The strongly nonlinear contribution to the electro-optic response, experimentally determined for liquid crystal samples at frequencies lower than the actual field frequency, is also analyzed for long-time signal sequences. Using a statistical approach to distinguish numerically response signals of samples from noise generated by measuring devices, it is shown that the distribution of sample signals distinctly differs from the device noise. This evidently corroborates the occurrence of the nonlinear low-frequency effect, found earlier for different surface stabilized liquid crystal samples.

  12. Supramolecular ferroelectrics

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  14. Relaxor-PT single crystals: observations and developments.

    PubMed

    Zhang, Shujun; Shrout, Thomas

    2010-10-01

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

  15. A phenomenological thermodynamic potential for BaTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Li, Y. L.; Cross, L. E.; Chen, L. Q.

    2005-09-01

    A phenomenological thermodynamic potential was constructed based on the properties of bulk BaTiO3 single crystals. An eighth-order polynomial of Landau-Devonshire expansion was employed. It reproduces bulk properties including the three possible ferroelectric transition temperatures and their dependence on electric fields, as well as the dielectric and piezoelectric constants. Different from the existing thermodynamic potential, it is applicable to predicting the ferroelectric phase transitions and properties of BaTiO3 thin films under large compressive biaxial strains.

  16. 8 MeV electron irradiation effect on the dielectric and optical properties of iminodiacetic acid doped ferroelectric triglycine sulphate crystals

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

  17. Light modulation in planar aligned short-pitch deformed-helix ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Kotova, Svetlana P.; Samagin, Sergey A.; Pozhidaev, Evgeny P.; Kiselev, Alexei D.

    2015-12-01

    We study both experimentally and theoretically modulation of light in a planar aligned deformed-helix ferroelectric liquid crystal (DHFLC) cell with subwavelength helix pitch, which is also known as a short-pitch DHFLC. In our experiments, the azimuthal angle of the in-plane optical axis and electrically controlled parts of the principal in-plane refractive indices are measured as a function of voltage applied across the cell. Theoretical results giving the effective optical tensor of a short-pitch DHFLC expressed in terms of the smectic tilt angle and the refractive indices of the ferroelectric liquid crystal (FLC) are used to fit the experimental data. The optical anisotropy of the FLC material is found to be weakly biaxial. For both the transmissive and reflective modes, the results of fitting are applied to model the phase and amplitude modulation of light in the DHFLC cell. We demonstrate that if the thickness of the DHFLC layer is about 50 μ m , the detrimental effect of field-induced rotation of the in-plane optical axes on the characteristics of an axicon designed using the DHFLC spatial light modulator in the reflective mode is negligible.

  18. Effects of crystallization conditions on dielectric and ferroelectric properties of PZT thin films

    NASA Astrophysics Data System (ADS)

    Arajo, E. B.; Eiras, J. A.

    2003-08-01

    This paper reports studies on dielectric and ferroelectric properties of lead zirconate titanate (PZT) thin films crystallized by conventional thermal annealing (CTA) and rapid thermal annealing (RTA) in air, oxygen and nitrogen atmospheres to better understand, control and optimize these properties. The dielectric constant (varepsilon) and dissipation factor (tan delta) values, at a frequency of 100 kHz, for film crystallized in air by CTA process, were 358 and 0.039, respectively. Considering the same frequency for film crystallized in air by RTA, these values were 611 and 0.026, respectively. The different dielectric values were justified by a space-charge or interfacial polarization in films, often characterized as Maxwell-Wagner type. This effect was also responsible to dispersion at frequencies above 1 MHz in film crystallized in air by CTA process and film crystallized by RTA in oxygen atmosphere. The film crystallized by RTA under nitrogen atmosphere presented an evident dispersion at frequencies around 100 Hz, characterized by an increase in both varepsilon and tan delta. This dispersion was attributed to conductivity effects. The remanent polarization (Pr) and coercive field (Ec) were also obtained for all films. Films obtained from RTA in air presented higher Pr (17.8 muC cm-2) than film crystallized from CTA (7.8 muC cm-2). As a function of the crystallization atmospheres, films crystallized by RTA in air and nitrogen presented essentially the same Pr values (around 18 muC cm-2) but the Pr (3.9 muC cm-2) obtained from film crystallized under oxygen atmosphere was profoundly influenced.

  19. 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.

  20. Piezoelectric and pyroelectric properties of ferroelectric glass-ceramics

    NASA Astrophysics Data System (ADS)

    Wu, Mian-Xue; Zhu, Pei-nan

    1985-05-01

    In this paper we report the ferroelectric glass-ceramics possessing both piezoelectric and pyroelectric properties. The properties can be comparable to those of corresponding ceramics or single crystals.

  1. Ideal energy harvesting cycle using a phase transformation in ferroelectric crystals

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  2. 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< 19CSmC*89C SmA* 108C 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 s at ambient temperature.

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

    SciTech Connect

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

    2013-08-28

    The impact of UV laser irradiation on the distribution of lithium ions in ferroelectric lithium niobate single crystals has been numerically modelled. Strongly absorbed UV radiation at wavelengths of 244305 nm produces steep temperature gradients which cause lithium ions to migrate and result in a local variation of the lithium concentration. In addition to the diffusion, here the pyroelectric effect is also taken into account which predicts a complex distribution of lithium concentration along the c-axis of the crystal: two separated lithium deficient regions on the surface and in depth. The modelling on the local lithium concentration and the subsequent variation of the coercive field are used to explain experimental results on the domain inversion of such UV treated lithium niobate crystals.

  4. 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.

  5. Induction of ferroelectricity in the B2 phase of a liquid crystal composed of achiral bent-core molecules

    NASA Astrophysics Data System (ADS)

    Etxebarria, J.; Folcia, C. L.; Ortega, J.; Ros, M. B.

    2003-04-01

    We report the observation of a transition from the antiferroelectric B2 phase to a ferroelectric phase in a liquid crystal composed of achiral bent-core (banana-shaped) molecules. The transition is induced by an electric field of magnitude larger than the switching threshold and is not reversible, i.e., the original B2 phase does not reappear upon field removal. The transformation is accompanied by a dramatic texture change, resulting in an almost optically isotropic structure in the absence of field. The ferroelectric character assigned to the structure is based on the electro-optic behavior of the material and on previously reported dielectric measurements. A short-pitch smectic-C*-type structure is proposed for the ferroelectric phase.

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

    SciTech Connect

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

    2014-07-21

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

  7. Performance of ferroelectric liquid crystal spatial light modulators for polarization and color diffractive elements

    NASA Astrophysics Data System (ADS)

    Moreno, Ignacio; Garca-Martnez, P.; Snchez-Lpez, M. M.; Martnez-Garca, A.; Martnez, J. L.

    2009-08-01

    In this work we applied a ferroelectric liquid crystal on silicon (FLCoS) display for implementing monochrome and color diffractive optical elements (DOE). We first apply a reverse engineering process specifically adapted to characterize the optical parameters of a commercial FLCoS display, specifically the phase shift and the tilt angle. We then analyze the performance of the device for implementing a binary polarization diffraction grating (PDG), and how it adopts the form of either a binary amplitude grating or a binary phase grating as particular cases when the polarization states emerging from the display are projected to an analyzer. As a final experiment, we have applied the FLCoS display to generate RGB improved dynamic color binary-phase Fourier computer-generated holograms (CGHs). We have electronically synchronized the properly scaled image addressed to the display with a color filter wheel with RGB filters. Experimental results show an excellent chromatic compensation of the color image reconstruction.

  8. Time evolution photoluminescence studies of quantum dot doped ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Hanaoka, Y.

    2009-06-01

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

  10. Alumina nanoparticles find an application to reduce the ionic effects of ferroelectric liquid crystal

    NASA Astrophysics Data System (ADS)

    Joshi, T.; Prakash, J.; Kumar, A.; Gangwar, J.; Srivastava, A. K.; Singh, S.; Biradar, A. M.

    2011-08-01

    We observed that the doping of alumina nanoparticles (AL-NPs) has suppressed the undesired ionic effect in ferroelectric liquid crystals (FLCs). The pure and AL-NPs doped FLC cells were analysed by means of dielectric spectroscopy and electrical resistivity/conductivity measurements. Dielectric loss spectra confirmed the disappearance of the low-frequency relaxation peak, which appears due to the presence of ionic impurities in the FLC materials. The reduction of ionic effects has been attributed to the strong adsorption of ionic impurities on the surface of AL-NPs. The adsorption capability of AL-NPs has been studied with both the size and their concentration in FLC material. This study would be helpful to minimize the undesired ionic effects of LC-based display devices.

  11. Fast switchable ferroelectric liquid crystal gratings with two electro-optical modes

    NASA Astrophysics Data System (ADS)

    Ma, Ying; Wang, Xiaoqian; Srivastava, A. K.; Chigrinov, V. G.; Kwok, H.-S.

    2016-03-01

    In this article, we reveal a theoretical and experimental illustration of the Ferroelectric liquid crystal (FLC) grating fabricated by mean of patterned alignment based on photo-alignment. The complexity related to the mismatching of the predefined alignment domains on the top and bottom substrate has been avoided by incorporating only one side photo aligned substrate while the other substrate does not have any alignment layer. Depending on the easy axis in the said alignment domains and the azimuth plane of the impinging polarized light, the diffracting element can be tuned in two modes i.e. DIFF/OFF switchable and DIFF/TRANS switchable modes, which can be applied to different applications. The diffraction profile has been illustrated theoretically that fits well with the experimental finding and thus the proposed diffraction elements with fast response time and high diffraction efficiency could find application in many modern devices.

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

    NASA Astrophysics Data System (ADS)

    Bailey, Jeremy; Kedziora-Chudczer, Lucyna; Cotton, Daniel V.; Bott, Kimberly; Hough, J. H.; Lucas, P. W.

    2015-05-01

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

  13. Effect of polymeric nanoparticles on dielectric and electro-optical properties of ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Silotia, P.; Biradar, A. M.

    2010-07-01

    It has been observed that the polymeric nanoparticles, copolymer of polybenzene and anthracene (PBA NPs), can induce a homeotropic (HMT) alignment in various ferroelectric liquid crystal (FLC) mixtures. The HMT alignment of various FLCs is attributable to the fact that the anthracene molecules favor an upright orientation (with a little tilt) on the surfaces of indium tin oxide and this upright orientation of anthracene molecules works as a template to align FLC molecules homeotropically. It has been concluded that the addition of ˜0.5 wt % of PBA NPs is enough to induce a HMT alignment in a FLC material Felix 17/100. The influence of the PBA NPs concentrations on the transition temperature, physical constants (such as spontaneous polarization, rotational viscosity, and response time) and dielectric relaxation processes of FLC material (Felix 17/100) has also been investigated.

  14. Manifestation of quantum disordered wave functions with weak localization from conical second harmonic generation in ferroelectric crystal

    NASA Astrophysics Data System (ADS)

    Yu, H. H.; Zhang, H. J.; Wang, Z. P.; Xu, H. H.; Wang, Y. C.; Wang, J. Y.; Petrov, V.

    2012-02-01

    The spatial structure of two-dimensional quantum disordered wave functions with weak localization (WL) is experimentally observed using a calcium barium niobate Ca0.28Ba0.72Nb2O6 (CBN-28) ferroelectric crystal illuminated by a pulsed laser beam. Non-collinear phase-matching in CBN-28 produces conical second harmonic pattern in the far-field. The probability density distribution of the experimental near-field pattern agrees very well with the theoretical predictions. The localization degree, within the error limits, is the same at different transverse positions due to the periodicity of the crystal and the eigenfunctions are degenerated. We conclude that a ferroelectric crystal represents an ideal model system for investigation of WL.

  15. Experimental Demonstration of Hybrid Improper Ferroelectric in the Layered Ruddlesden-Popper Compounds

    NASA Astrophysics Data System (ADS)

    Oh, Yoon Seok

    2015-03-01

    Geometric ferroelectrics are called as improper ferroelectrics where geometric structural constraints, rather than typical cation-anion paring, induce proper ferroelectric polarization. Hybrid improper ferroelectricity, one kind of geometric ferroelectricity, results from the combination of two or more of non-ferroelectric structural order parameters. In recent, hybrid improper ferroelectricity has been theoretically predicted in ordered perovskites and the Ruddlesden-Popper compounds. However, the ferroelectricity of these compounds has never been experimentally confirmed and even their polar nature has been under debate. In this talk, we report our experimental results of exploring switchable electric polarization and domain structures in the single crystals of the n = 2 layered Ruddlesden-Popper compounds. In collaboration with Xuan Luo, Laboratory for Pohang Emergent Materials, Postech; Fei-Ting Huang, Department of Physics & Astronomy, Rutgers University; Yazhong Wang, Department of Physics & Astronomy, Rutgers University; and Sang-Wook Cheong, Department of Physics & Astronomy, Rutgers University.

  16. Nonlinear pyroelectric energy harvesting from relaxor single crystals.

    PubMed

    Khodayari, Akram; Pruvost, Sebastien; Sebald, Gael; Guyomar, Daniel; Mohammadi, Saber

    2009-04-01

    Energy harvesting from temperature variations in a Pb(Zn(1/3)Nb(2/3))(0.955)Ti(0.045)O(3) single crystal was studied and evaluated using the Ericsson thermodynamic cycle. The efficiency of this cycle related to Carnot cycle is 100 times higher than direct pyroelectric energy harvesting, and it can be as high as 5.5% for a 10 degrees C temperature variation and 2 kV/mm electric field. The amount of harvested energy for a 60 degrees C temperature variation and 2 kV/mm electric field is 242.7 mJ x cm(-3). The influence of ferroelectric phase transitions on the energy harvesting performance is discussed and illustrated with experimental results. PMID:19406698

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

    PubMed

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

    2015-02-01

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

  18. Textures and free energies in free-standing thin films of ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Bong

    The textures and free energies of islands; resulting from heterogeneous nucleation on a freely suspended thin film of ferroelectric liquid crystals, are studied in the 2 dimensional (2D) limit. The free standing film is prepared by drawing the material over a hole in a thin metal foil or a thin cover glass, and then submicron particles are blown into the film to create islands. An energetic argument is described for the equilibrium size of the islands; which usually undergo textural transformations before reaching equilibrium. To understand transformations of textures, a linear stability analysis is employed for their stability, which predicts a phase diagram for the island. The analysis is based on the molecular configurations and boundary conditions determined by optical experiments. The electrostatic interaction of the polarization charges in the islands, due to the ferroelectricity of the material, is considered. In order to explain our observations, in which the behavior of the textural transformations dependent on the magnitude of the spontaneous polarization, we show how the electrostatic energy, screened by impurity ions dissolved in the material, can lead to an increased effective bend elastic constant in the long wave limit in 2D. The measurement of 2pi disclination walls formed by an external electric field is carried out to determine the ratio of the bend elastic constant to the spontaneous polarization and qualitatively to show the existence of the screening effect. To complete the study of the electrostatic interaction, we develop the theory for dynamics of the director coupled to free ions in 2D and perform a dynamic light scattering experiment as well, through which the 2D screening length can be determined. Finally the experimental results are compared with the theoretical analysis.

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

    NASA Astrophysics Data System (ADS)

    Suewattana, Malliga

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

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

    SciTech Connect

    Kitamura, Naoto; Mizoguchi, Takuma; Itoh, Takanori; Idemoto, Yasushi

    2014-02-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-05-01

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

  2. Nonlinear optical properties of a channel waveguide produced with crosslinkable ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Fazio, V. S. U.; Lagerwall, S. T.; Zauls, V.; Schrader, S.; Busson, P.; Hult, A.; Motschmann, H.

    2000-11-01

    A binary mixture of ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The FLCs possess two important functionalities: a chromophore with a high hyperpolarizability ? and photoreactive groups. The smectic liquid crystal is aligned in layers parallel to the glass plates in a sandwich geometry. This alignment offers several advantages, such as that moderate electric fields are sufficient to achieve a high degree of polar order. The arrangement was then permanently fixed by photopolymerization which yielded a polar network possessing a high thermal and mechanical stability which did not show any sign of degradation within the monitored period of several months. The linear and nonlinear optical properties have been measured and all four independent components of the nonlinear susceptibility tensor overline d have been determined. The off-resonant d-coefficients are remarkably high and comparable to those of the best known inorganic materials. The alignment led to an inherent channel waveguide for p-polarized light without additional preparation steps. The photopolymerization did not induce scattering sites in the waveguide and the normalized losses were less than 2 dB/cm. The material offers a great potential for the design of nonlinear optical devices such as frequency doublers of low-power laser diodes.

  3. Ferroelectric domain wall motion induced by polarized light

    PubMed Central

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernndez, 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

  4. Ferroelectric domain wall motion induced by polarized light.

    PubMed

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernndez, 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. Single crystals for welding research

    SciTech Connect

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

    1991-01-01

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

  6. Ames Lab 101: Single Crystal Growth

    SciTech Connect

    Schlagel, Deborah

    2013-09-27

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

  7. Ames Lab 101: Single Crystal Growth

    ScienceCinema

    Schlagel, Deborah

    2014-06-04

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

  8. Ultratough single crystal boron-doped diamond

    DOEpatents

    Hemley, Russell J [Carnegie Inst. for Science, Washington, DC ; Mao, Ho-Kwang [Carnegie Inst. for Science, Washington, DC ; Yan, Chih-Shiue [Carnegie Inst. for Science, Washington, DC ; Liang, Qi [Carnegie Inst. for Science, Washington, DC

    2015-05-05

    The invention relates to a single crystal boron doped CVD diamond that has a toughness of at least about 22 MPa m.sup.1/2. The invention further relates to a method of manufacturing single crystal boron doped CVD diamond. The growth rate of the diamond can be from about 20-100 .mu.m/h.

  9. Method of making single crystal fibers

    NASA Technical Reports Server (NTRS)

    Westfall, Leonard J. (inventor)

    1990-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2000-03-01

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

  11. Local environment of optically active Nd3+ ions in the ultratransparent BaMgF4 ferroelectric crystal

    NASA Astrophysics Data System (ADS)

    Muoz-Santiuste, J. E.; Loro, H.; Marino, R.; Goldner, Ph.; Vasyliev, V.; Vllora, E. G.; Shimamura, K.; Molina, P.; Ramrez, M. O.; Baus, L. E.

    2012-05-01

    A comprehensive study of the site location of Nd3+ ions in the BaMgF4 ultratransparent ferroelectric crystal is presented. By combining different low-temperature optical spectroscopies and electron paramagnetic resonance, the crystal field energy levels of Nd3+ ions and the gyromagnetic factors are experimentally determined. These results are employed to perform the crystal field analysis of Nd3+ ions considering a Cs point symmetry. The crystal field calculation yields a small root-mean-square deviation of 18 cm-1 and reveals a large crystal field strength (621 cm-1), verifying the assignment of the Ba2+ cationic site as the location for Nd3+ ions in this fluoride host. The results suggest a slight displacement of Nd3+ from the barium regular site with a rearrangement of the fluorine ions around it. The work gives a deep insight into the properties of the Nd3+-doped BaMgF4 crystal, a ferroelectric widely ultra-transparent material with potential applications as optical device operating in the Vacuum Ultraviolet-Ultraviolet and midinfrared spectral regions.

  12. Synthesis, properties, and structure of potassium titanyl phosphate single crystals doped with chromium

    NASA Astrophysics Data System (ADS)

    Orlova, E. I.; Kharitonova, E. P.; Novikova, N. E.; Sorokina, N. I.; Voronkova, V. I.

    2015-11-01

    Chromium-doped potassium titanyl phosphate single crystals have been synthesized and their physical properties have been studied. Doping with chromium barely affects the temperature of the ferroelectric phase transition but significantly reduces conductivity (by almost two orders of magnitude). A precise Xray diffraction study of K1.00Cr0.02Ti0.98OPO4 and K0.996Cr0.005Ti0.995OPO4 crystals has shown that chromium atoms are located near sites of titanium atoms.

  13. Crystal orientation dependent optical transmittance and band gap of Na0.5Bi0.5TiO3-BaTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    He, Chongjun; Deng, Chenguang; Wang, Jiming; Gu, Xiaorong; Wu, Tong; Zhu, Kongjun; Liu, Youwen

    2016-02-01

    Optical transmittance spectra of lead-free ferroelectric (1-x)Na0.5Bi0.5TiO3-xBaTiO3 (NBT-xBT) single crystals poled along different directions have been studied comprehensively. After poled along [001] direction, the transmittance of tetragonal NBT-8%BT crystal is about 70%, which is much higher than that of NBT-2%BT crystal with rhombohedral structure and NBT-5%BT crystal with morphotropic phase boundary (MPB) composition. However, after poled [111] direction, the transmittance of tetragonal NBT-8%BT crystal is the smallest among them. These properties are manifest in view of the crystal structure. Both direct and indirect optical energy band gaps, as well phonon energies were obtained from absorption coefficient spectra by Tauc equations. The band gaps of [001]-poled NBT-xBT crystals increase with BT content, yet the [111]-poled crystals have opposite trends.

  14. Single Crystal Sapphire Optical Fiber Sensor Instrumentation

    SciTech Connect

    Anbo Wang; Russell May; Gary R. Pickrell

    2000-10-28

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

  15. Fabrication of Defect-Free Ferroelectric Liquid Crystal Displays Using Photoalignment and Their Electrooptic Performance

    NASA Astrophysics Data System (ADS)

    Kurihara, Ryuji; Furue, Hirokazu; Takahashi, Taiju; Yamashita, Tomo-o; Xu, Jun; Kobayashi, Shunsuke

    2001-07-01

    A photoalignment technique has been utilized for fabricating zigzag-defect-free ferroelectric liquid crystal displays (FLCDs) using polyimide RN-1199, -1286, -1266 (Nissan Chem. Ind.) and adopting oblique irradiation of unpolarized UV light. A rubbing technique was also utilized for comparison. It is shown that among these polyimide materials, RN-1199 is the best for fabricating defect-free cells with C-1 uniform states, but RN-1286 requires low energy to produce a photoaligned FLC phase. We have conducted an analytical investigation to clarify the conditions for obtaining zigzag-defect-free C-1 states, and it is theoretically shown that zigzag-defect-free C-1 state is obtained using a low azimuthal anchoring energy at a low pretilt angle, while a zigzag-defect-free C-2 state is obtained by increasing azimuthal anchoring energy above a critical value, also at a low pretilt angle. The estimated critical value of the azimuthal anchoring energy at which a transition from the C-1 state to the C-2 state occurs is 310-6 J/m2 for the FLC material FELIX M4654/100 (Clariant) used in this research; this value is shown to fall in a favorable range which is measured in an independent experiment.

  16. 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.

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

    PubMed

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

    2006-11-20

    A polarimeter to be mounted on the Yunnan solar tower is described. It features the ability to simultaneously measure the magnetic fields of the solar photosphere and chromosphere by analyzing the Stokes spectra of those magnetosensitive lines forming in the two regions with very high efficiency of polarization measurement. The polarimeter consists of two ferroelectric liquid crystals and one lambda/4 wave plate before a polarizing beam splitter. The achromatism of the design is emphasized to get the maximum combination efficiency over a spectral range from 5000 to 6000 A. For the used solar absorption lines MgI517.27, FeI525.06, FeI630.15, and FeI630.25 nm, the design gives theoretical efficiencies of polarization measurements, which are 0.999, 1.0, 0.943, and 0.943, respectively. A comparison with other reference polarimeters, such as the Synoptic Optical Long-term Investigation of the Sun, the Tenerife infrared polarimeter, and the La Palma Stokes Polarimeter, is carried out. PMID:17086251

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

    NASA Astrophysics Data System (ADS)

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

    2006-11-01

    A polarimeter to be mounted on the Yunnan solar tower is described. It features the ability to simultaneously measure the magnetic fields of the solar photosphere and chromosphere by analyzing the Stokes spectra of those magnetosensitive lines forming in the two regions with very high efficiency of polarization measurement. The polarimeter consists of two ferroelectric liquid crystals and one ?/4 wave plate before a polarizing beam splitter. The achromatism of the design is emphasized to get the maximum combination efficiency over a spectral range from 5000 to 6000 . For the used solar absorption lines MgI517.27, FeI525.06, FeI630.15, and FeI630.25 nm, the design gives theoretical efficiencies of polarization measurements, which are 0.999, 1.0, 0.943, and 0.943, respectively. A comparison with other reference polarimeters, such as the Synoptic Optical Long-term Investigation of the Sun, the Tenerife infrared polarimeter, and the La Palma Stokes Polarimeter, is carried out.

  19. Defects in the reduced rutile single crystal

    NASA Astrophysics Data System (ADS)

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

    2001-09-01

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

  20. Ultrathin single crystal diamond nanomechanical dome resonators.

    PubMed

    Zalalutdinov, Maxim K; Ray, Matthew P; Photiadis, Douglas M; Robinson, Jeremy T; Baldwin, Jeffrey W; Butler, James E; Feygelson, Tatyana I; Pate, Bradford B; Houston, Brian H

    2011-10-12

    We present the first nanomechanical resonators microfabricated in single-crystal diamond. Shell-type resonators only 70 nm thick, the thinnest single crystal diamond structures produced to date, demonstrate a high-quality factor (Q ? 1000 at room temperature, Q ? 20?000 at 10 K) at radio frequencies (50-600 MHz). Quality factor dependence on temperature and frequency suggests an extrinsic origin to the dominant dissipation mechanism and methods to further enhance resonator performance. PMID:21913676

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  2. 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.

  3. 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.

  4. Size effects of 109 domain walls in rhombohedral barium titanate single crystalsA molecular statics analysis

    NASA Astrophysics Data System (ADS)

    Endres, Florian; Steinmann, Paul

    2016-01-01

    Ferroelectric functional materials are of great interest in science and technology due to their electromechanically coupled material properties. Therefore, ferroelectrics, such as barium titanate, are modeled and simulated at the continuum scale as well as at the atomistic scale. Due to recent advancements in related manufacturing technologies the modeling and simulation of smart materials at the nanometer length scale is getting more important not only to predict but also fundamentally understand the complex material behavior of such materials. In this study, we analyze the size effects of 109 nanodomain walls in ferroelectric barium titanate single crystals in the rhombohedral phase using a recently proposed extended molecular statics algorithm. We study the impact of domain thicknesses on the spontaneous polarization, the coercive field, and the lattice constants. Moreover, we discuss how the electromechanical coupling of an applied electric field and the introduced strain in the converse piezoelectric effect is affected by the thickness of nanodomains.

  5. Single Crystals Grown Under Unconstrained Conditions

    NASA Astrophysics Data System (ADS)

    Sunagawa, Ichiro

    Based on detailed investigations on morphology (evolution and variation in external forms), surface microtopography of crystal faces (spirals and etch figures), internal morphology (growth sectors, growth banding and associated impurity partitioning) and perfection (dislocations and other lattice defects) in single crystals, we can deduce how and by what mechanism the crystal grew and experienced fluctuation in growth parameters through its growth and post-growth history under unconstrained condition. The information is useful not only in finding appropriate way to growing highly perfect and homogeneous single crystals, but also in deciphering letters sent from the depth of the Earth and the Space. It is also useful in discriminating synthetic from natural gemstones. In this chapter, available methods to obtain molecular information are briefly summarized, and actual examples to demonstrate the importance of this type of investigations are selected from both natural minerals (diamond, quartz, hematite, corundum, beryl, phlogopite) and synthetic crystals (SiC, diamond, corundum, beryl).

  6. Magnetodielectric Effects and Transport Study in LuFe2O4 Single Crystal

    NASA Astrophysics Data System (ADS)

    Jang, Tae Hwan; Park, Sang Youn; Lee, Hai Joon; Kang, Sun Hee; Koo, Tae Yeong; Kim, Sung Baek; Kim, Ill Won; Jeong, Yoon Hee; Cheong, Sang Wook

    2008-03-01

    Magnetic, dielectric, and magnetodielectric properties of geometrically frustrated mixed valance LuFe2O4 single crystal are discussed to clarify the charge order based ferroelectricity and its coupling with magnetism. From the magnetization and dielectric constant measurement, a new anomalous temperature point TN'(160 K) in both magnetization and dielectric constant versus temperature curve below the ferrimagnetic transition temperature TN(225 K) has been observed. The sign of magnetodielectric effect (MDE) also changes from positive T > TN' into negative T < TN'. No field hysteresis in positive MDE temperature region was found. However a large hysteretic behavior in negative MDE below TN' with the same magnetic coercive field measured in M (H) curve was observed. This indicates a strong coupling between magnetism and ferroelectricity in the charge and spin frustrated ferrimagnetic LuFe2O4 system.

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

    PubMed

    Martnez, Jos Luis; Martnez-Garca, Antonio; Moreno, Ignacio

    2009-02-10

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

  8. Fatigue hardening in niobium single crystals.

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  9. Chiral photonic crystal fibers with single mode and single polarization

    NASA Astrophysics Data System (ADS)

    Li, She; Li, Junqing

    2015-12-01

    Chiral photonic crystal fiber (PCF) with a solid core is numerically investigated by a modified chiral plane-wave expansion method. The effects of structural parameters and chirality strength are analyzed on single-polarization single-mode range and polarization states of guided modes. The simulation demonstrates that the chiral photonic crystal fiber compared to its achiral counterpart possesses another single-circular-polarization operation range, which is located in the short-wavelength region. The original single-polarization operation range in the long-wavelength region extends to the short wavelength caused by introducing chirality. Then this range becomes a broadened one with elliptical polarization from linear polarization. With increase of chirality, the two single-polarization single-mode ranges may fuse together. By optimizing the structure, an ultra-wide single-circular-polarization operation range from 0.5 ?m to 1.67 ?m for chiral PCF can be realized with moderate chirality strength.

  10. Interfacial Interactions, Director Configurations and Layer Structures of Surface Stabilized Ferroelectric Liquid Crystals.

    NASA Astrophysics Data System (ADS)

    Zhuang, Zhiming

    1991-02-01

    When sandwiched in a micron thick gap between flat solid substrates, ferroelectric liquid crystals (FLCs) can exhibit a variety of surface stabilized states of different molecular orientations. This orientational bistability, along with fast switching (microseconds) in response to external electric field, make the surface stabilized FLC (SSFLC) one of the most promising electrooptic devices. The physical properties as well as the potential technical applications of SSFLCs strongly depend on the surface interactions, layer structure, and molecular orientations in the SSFLC cells, facts that provided the motivations for the work presented in this thesis described briefly in the following paragraph. We first characterized the polarization space charge effects of FLCs and applied the results to geometries of practical interest. This is of current importance because of the increasing availability of high polarization FLC materials. We then carried out a polarized light microspectrophotometry study on SSFLC cells prepared with surface treatments which promote both planar and non-planar molecular alignment at the bounding plates. The measured spectra were compared with the numerical solution of Maxwell's equations in inhomogeneous anisotropic dielectric medium based on our model of the layer and molecular orientation structure in SSFLC cells. The results revealed the origin of differences in domain shape as well as contrast in the SSFLC switching process. We noticed a exact optical symmetry during the spectral studies which provided crucial evidence for the aforementioned model. Additionally we investigated the surface molecular orientation directly via depolarized total internal reflection (TIR) and found out a surprising plastic orientational effect at FLC-polymer interface. The TIR results were also interpreted using the numerical solutions of the Maxwell's equations. Finally we developed a three dimensional model explaining the newly observed layer defects in SSFLC cells, the mountain defects, whose formation indicates that the chevron layer structure is not necessarily a stable structure.

  11. Ultrathin single crystal ZnS nanowires.

    PubMed

    Zhang, Yejun; Xu, Huarui; Wang, Qiangbin

    2010-12-21

    A facile synthesis of ultrathin single crystal ZnS nanowires with an average diameter of 4.4 nm in high yield (close to 100%) was firstly reported through the pyrolysis of a single-source precursor (zinc diethyldithiocarbamate). The obtained ultrathin ZnS nanowires exhibit good optical properties and hold promise for future applications in nanodevices. PMID:21052583

  12. 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

  13. 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.

  14. 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 550C for 30s 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 25nm, with a remanent polarization value of 6 ?C/cm(2) and a coercive field strength of 2.4 MV/cm measured at 10kHz. 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

  15. Single crystal growth of the tetragonal tungsten bronze Ca xBa 1- xNb 2O 6 ( x=0.28; CBN-28)

    NASA Astrophysics Data System (ADS)

    Eer, M.; Burianek, M.; Klimm, D.; Mhlberg, M.

    2002-04-01

    The material group of the tetragonal tungsten bronzes (TTBs) is very attractive due to its outstanding ferroelectric properties. Herein we report attempts to grow single crystals of calcium barium niobate (CBN) that until now was only known as ceramic samples. The single crystal growth of CBN could be realized in two different ways. In a first step a high-temperature tetraborate flux was applied to prepare small crystals for phase analysis. Then, for the first time large single crystals of Ca 0.28Ba 0.72Nb 2O 6 (CBN-28) with dimensions up to 5 cm length were grown by using the Czochralski method. CBN-28 shows a ferroelectric phase transition at about 280C (detected by dielectric and thermal expansion measurements) that is about 200C higher than the transition temperature of the widely investigated TTB Sr 0.60Ba 0.40Nb 2O 6 (SBN-60).

  16. Domain wall nucleation by impurity ions in KNbO3 single crystals

    NASA Astrophysics Data System (ADS)

    Ingle, S. G.; Dutta, H. S.; David, A. P.

    1988-11-01

    It has been shown theoretically as well as experimentally that microwalls with linear dimensions of the order of 10-6-10-8 m can be nucleated in KNbO3 single crystals under the influence of the electric dc fields applied externally at the sites of the impurity ions. The critical field for nucleation is found to be about 8103 V m-1. Since such low fields already exist in crystals at the nonferroelectric to ferroelectric phase transition, the mechanism is expected to be operative at that time, and a photographic evidence of it is also obtained. A model has been developed to explain the nucleation. Employing thermodynamic considerations, expressions have been derived for the critical length of the domain wall nucleated, and the activation energy of nucleation, both for 60 and 90 walls. The photomicrographs obtained after applying the dc fields show microwalls nucleated at the impurity sites, with their linear dimensions of the order given by the theory. Many other aspects of the domain wall nucleation have been made clear by the photomicrographs. Particularly, it has been found that the microwalls move after nucleation to lie linearly to reduce the strain energy of the crystal. The microwalls are not pinned at the impurities, and extend themselves so that they meet each other end to end, producing a continuous wall. It is possible to distinquish these microwalls from the microwalls nucleated by the dislocation loops. The expression for the activation energy of nucleation is also verified experimentally. It is suggested that the mechanism of domain wall nucleation can occur in other ferroelectric crystals also, and shown that the memory of domain walls, commonly observed in ferroelectrics, can be readily attributed to the impurity ions present in the crystals, and the phenomenon of domain wall nucleation operative at their sites.

  17. Neutron detection with single crystal organic scintillators

    SciTech Connect

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

    2009-07-15

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

  18. Oxygen Incorporation in Rubrene Single Crystals

    PubMed Central

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

    2014-01-01

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

  19. Domains in Ferroelectric Nanostructures

    NASA Astrophysics Data System (ADS)

    Gregg, Marty

    2010-03-01

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

  20. 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.

  1. Magnetoelasticity of Fe-Si single crystals

    SciTech Connect

    Xing, Q; Wu, D.; Lograsso, T. A.

    2010-04-20

    The tetragonal magnetostriction constant, (3/2){lambda}{sub 100}, of Fe-Si single crystals was measured and was found to be structure dependent. Similar to that of Fe-Ge single crystals, (3/2){lambda}{sub 100} is positive in the single phase A2 regime, becomes negative in the single phase D0{sub 3} regime, and changes from positive to negative between the two regimes. Short-range order in the A2 regime decreases the magnetostriction prior to the onset of long range order. In the single phase regions of both A2 and D0{sub 3}, thermal history does not show any obvious effect on the magnetostriction, contrary to that found for Fe-Ga alloys. However, in the regions of phase mixture involving A2, B2, and D0{sub 3} phases, quenching pushes the change in magnetostriction from positive to negative to higher Si contents.

  2. Crystal growth and characterization of MnTe single crystals

    NASA Astrophysics Data System (ADS)

    de Melo, O.; Leccabue, F.; Pelosi, C.; Sagredo, V.; Chourio, M.; Martin, J.; Bocelli, G.; Calestani, G.

    1991-03-01

    The growth of MnTe single crystals by means of a chemical transport technique using iodine as a transport agent is reported. A detailed thermodynamical study of MnTe-I 2 system has been undertaken in order to define the best growth conditions. Moreover, structural, magnetic and electrical properties are reported and discussed.

  3. 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

  4. First Single-Crystal Mullite Fibers

    NASA Technical Reports Server (NTRS)

    1997-01-01

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

  5. Strong influence of non-ideality of electrodes on stability of single domain state in ferroelectric-paraelectric superlattices

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    We study the phase stabilities with respect to small perturbations in ferroelectric-paraelectric superlattices and show that nature of the electrodes characterized by a deviation from the ideal behavior strongly influences the possibility to obtain single-domain state in ferroelectric-paraelectric superlattices. To demonstrate this, we analyze the limit of stability of the paraelectric and the single domain state in ferroelectric-paraelectric superlattices in contact with top and bottom electrodes with finite screening lengths. The combined analytical and numerical analyses of one bilayer and two bilayer systems are carried out using the Landau-Ginzburg-Devonshire formalism and equations of electrostatics. The BaTiO3/SrTiO3 system was considered as an example. Unlike the case of ideal electrodes where the stability limits are independent of the system size, the stability analysis in a multilayer with real electrodes should take into account explicitly the number of the repeating units that makes the algebra very cumbersome, forcing us to consider systems with one and two bilayer stacks only. Extrapolating the difference between the two systems to the cases of many repeating units gives us the possibility to make qualitative but feasible predictions related to those with many repeating units. We observe that in systems with nearly equal thicknesses of the ferroelectric and paraelectric layers, the electrodes with realistic screening lengths lead to dramatic widening of the parametric region where the single-domain state is absolutely unstable expelling the single-domain state to unphysical layer thicknesses and temperatures. This region grows when one goes from a single bilayer to two bilayer system, implying that obtaining a single domain state becomes even less feasible in systems with many bilayers. When electrode properties approach that of ideal in addition to increasing the volume fraction of the ferroelectric component, the effect of growth of the region of absolute instability of the single domain state may remain very strong for relatively thin repeating units (a few nanometers). This tendency will continue with increasing the number of the repeating units.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    PubMed

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

    2014-08-01

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

  8. Inkjet printing of single-crystal films

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  9. Inkjet printing of single-crystal films.

    PubMed

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

    2011-07-21

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

  10. Charge transport in single crystal organic semiconductors

    NASA Astrophysics Data System (ADS)

    Xie, Wei

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

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

    SciTech Connect

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

    2013-11-28

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

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

    NASA Astrophysics Data System (ADS)

    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.

  13. 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

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

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

  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. 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.

  17. Growth of single-crystal gallium nitride

    NASA Technical Reports Server (NTRS)

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

    1970-01-01

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

  18. Pyroelectric performances of rhombohedral 0.42Pb(In?/?)Nb?/?)O?-0.3Pb(Mg?/?Nb?/?)O?-0.28PbTiO? single crystals.

    PubMed

    Liu, Linhua; Wu, Xiao; Zhao, Xiangyong; Feng, Xiqi; Jing, Weiping; Luo, Haosu

    2010-10-01

    Relaxor-based ferroelectric single crystals xPb(In?/?)Nb?/?)O?-yPb(Mg?/?Nb?/?)O?-(1-x-y)PbTiO? {PIMNT [100x/100y/100(1-x-y)]} have been grown by a modified Bridgman technique. The as-grown PIMNT (42/30/28) crystal with rhombohedral perovskite-type structure shows higher Curie temperature TC ~ 187 C, and higher ferroelectric rhombohedral-to-tetragonal phase transition temperature TRT ~ 152 C, both about 50 C higher than those found for 0.71Pb(In?/?)Nb?/?)O?-0.3Pb(Mg?/?Nb?/?)O?-0.29PbTiO? crystals. Moreover, as a core parameter of pyroelectric material, the detectivity figures-of-merit of PIMNT (42/30/28) crystal are higher than other typical relaxor-based ferroelectric crystals, which primarily stems from the lower dielectric loss, making it promising candidate for infrared detector applications. PMID:20889399

  19. Single crystal tungsten kinetic energy penetrators

    SciTech Connect

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

    1992-05-01

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

  20. Single crystal tungsten kinetic energy penetrators

    SciTech Connect

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

    1992-05-01

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

  1. Multiple single-crystal-to-single-crystal guest exchange in a dynamic 1D coordination polymer.

    PubMed

    Mart-Rujas, Javier; Bonafede, Simone; Tushi, Dorearta; Cametti, Massimo

    2015-08-11

    A novel 1D coordination polymer that dynamically expands or shrinks upon the uptake of vapours of volatile small chlorinated molecules, such as 1,2-dichloroethane (DCE), dichloromethane (DCM) and trichloromethane (TCM), is reported. This system is robust enough to withstand multiple guest exchange via single-crystal-to-single-crystal transformation, as proved by (1)H-NMR and X-ray diffraction. The single crystal of guest-free, host framework, stable at 400 K, can also be obtained. PMID:26097909

  2. Crystal structure and morphology of syndiotactic polypropylene single crystals

    SciTech Connect

    Bu, J.Z.; Cheng, S.Z.D.

    1996-12-31

    In the past several years there have been an increased interest in the crystal structure and morphology of s-PP due to the new development of homogeneous metallocene catalysts which can produce s-PP having a high stereoregularity. In this research, the crystal structure and morphology of s-PP single crystals grown from the melt were investigated. A series of ten fractions of s-PP was studied with different molecular weights ranging from 10,300 to 234,000 (g/mol). These fractions all possess narrow molecular weight distributions (around 1.1-1.2) and high syndiotacticities ([r]{approximately}95%). The main techniques employed including transmission electron microscopy (TEM), atomic force microscopy (AFM), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS).

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  4. Tunable dielectric properties of KTaO3 single crystals in the terahertz range

    NASA Astrophysics Data System (ADS)

    Skoromets, V.; Kadlec, C.; N?mec, H.; Fattakhova-Rohlfing, D.; Kuel, P.

    2016-02-01

    Electric-field tunability of the dielectric properties of potassium tantalate single crystal was studied by terahertz spectroscopy in a broad temperature range (40250?K). Complex-valued terahertz transmission spectra of samples were measured with an external electric field perpendicular to the sample surface and parallel to the terahertz wave-vector. We found that the ferroelectric soft mode hardening is fully responsible for the observed electric-field-induced changes in the spectra and no signature of a central mode was detected. We determined the anharmonic properties of the soft-mode potential in the mean field approximation. The observed behavior was compared with that previously reported for SrTiO3 single crystals.

  5. Experimental Investigation of Orthoenstatite Single Crystal Rheology

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Dhar, Romit

    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 composition. It is demonstrated that significant power can be harvested using unimorph structures from an acoustic field at resonance. Passive circuit components were used for output circuit with a resistive load in series with a tunable inductor. A tuning capacitor connected in parallel to the device further increased the power output by matching the impedance of the unimorph. The power harvested can be either used directly for running low-power devices or can be stored in a rechargeable battery. A comparison of the performance of PMN-PT and PZT unimorphs at the resonance of the coupled structure under identical excitation conditions was done. For a certain optimized thickness ratio and circuit parameters, the single crystal PMN-PT unimorph generated 30 mW of power while a PZT unimorph generated 7.5 mW at resonance and room temperature. The harvested output power from the single crystal PMN-PT unimorphs depends on several material properties, physical and ambient parameters and an effort has been made to study their effect on the performance. A self-seeding high pressure Bridgman (HPB) technique was used to grow the PMN-PT single crystal ingots in a cost-effective way in our laboratories. Several techniques of material processing were developed to fabricate the PMN-PT single crystal unimorphs from as grown bulk ingots. This growth technique produced good quality single crystals for our experiments, with a k33 = 0.91 for a <001> oriented bar.

  7. A double-mode piezoelectric single-crystal ultrasonic micro-actuator.

    PubMed

    Guo, Mingsen; Dong, Shuxiang; Ren, Bo; Luo, Haosu

    2010-11-01

    Ternary Pb(In(1/2)Nb(1/2))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) single crystals with higher coercive field (E(C) ~9 kV/cm) and higher ferroelectric-transition temperature (T(R-T) = 108C) were grown, and correspondingly, a double-mode piezoelectric ultrasonic micro-actuator made of PIN-PMN-PT crystal brick (5 x 1.5 x 1.32 mm) and operated in the first longitudinal and the second bending modes was developed. The ferroelectric, dielectric, electromechanical, and resonance displacement properties of the micro-actuator were characterized for miniature linear piezo-motor applications. The longitudinal displacement of the actuator is ~0.11 ?m (with an applied voltage of 5 V), which is comparable to that of a multilayer piezoelectric-ceramic actuator of the same size. This crystal micro-actuator was successfully used to drive a slider moving linearly. PMID:21041147

  8. 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.

  9. SSME single crystal turbine blade dynamics

    NASA Technical Reports Server (NTRS)

    Moss, Larry A.; Smith, Todd E.

    1987-01-01

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

  10. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  11. Shock Hugoniot of Single Crystal Copper

    SciTech Connect

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

    2009-08-28

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

  12. 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.

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

    SciTech Connect

    Vasudevan, Rama K; Bogle, K A; Kumar, Amit; Jesse, Stephen; Magaraggia, R; Stamps, R; Ogale, S; Potdar, H S

    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.

  14. Single-crystal gallium nitride nanotubes.

    PubMed

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

    2003-04-10

    Since the discovery of carbon nanotubes in 1991 (ref. 1), there have been significant research efforts to synthesize nanometre-scale tubular forms of various solids. The formation of tubular nanostructure generally requires a layered or anisotropic crystal structure. There are reports of nanotubes made from silica, alumina, silicon and metals that do not have a layered crystal structure; they are synthesized by using carbon nanotubes and porous membranes as templates, or by thin-film rolling. These nanotubes, however, are either amorphous, polycrystalline or exist only in ultrahigh vacuum. The growth of single-crystal semiconductor hollow nanotubes would be advantageous in potential nanoscale electronics, optoelectronics and biochemical-sensing applications. Here we report an 'epitaxial casting' approach for the synthesis of single-crystal GaN nanotubes with inner diameters of 30-200 nm and wall thicknesses of 5-50 nm. Hexagonal ZnO nanowires were used as templates for the epitaxial overgrowth of thin GaN layers in a chemical vapour deposition system. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. This templating process should be applicable to many other semiconductor systems. PMID:12686996

  15. Single-Crystal Diamond Nanobeam Waveguide Optomechanics

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Single-crystal diamond optomechanical devices have the potential to enable fundamental studies and technologies coupling mechanical vibrations to both light and electronic quantum systems. Here, we demonstrate a single-crystal diamond optomechanical system and show that it allows excitation of diamond mechanical resonances into self-oscillations with amplitude >200 nm . The resulting internal stress field is predicted to allow driving of electron spin transitions of diamond nitrogen-vacancy centers. The mechanical resonances have a quality factor >7 105 and can be tuned via nonlinear frequency renormalization, while the optomechanical interface has a 150 nm bandwidth and 9.5 fm /?{Hz } sensitivity. In combination, these features make this system a promising platform for interfacing light, nanomechanics, and electron spins.

  16. Biomineralization of nanoscale single crystal hydroxyapatite.

    PubMed

    Omokanwaye, Tiffany; Wilson, Otto C; Gugssa, Ayelle; Anderson, Winston

    2015-11-01

    The chemical and physical characteristics of nanocrystalline hydroxyapatite particles which formed during the subcutaneous implantation of crab shell in Sprague-Dawley rats were studied using selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The initial SAED characterization evidence indicated the presence of an amorphous calcium phosphate phase. The electron dense nanophase particles which formed in the wound healing zone displayed broad diffuse rings which usually indicate a low crystalline order or amorphous phase. High resolution transmission electron microscopy (HRTEM) revealed that these mineralized regions contained discrete single crystal particles less than 5nm in size. Micrographs taken at successively higher magnifications revealed very small nanoparticles with a hexagonal arrangement of ion channels with characteristic spacing of 0.54nm and 0.23nm. This study revealed that single crystal hydroxyapatite nanoparticles consisting of only a few unit cells formed via a biomineralization directed process. PMID:26249568

  17. Optimizing Scale Adhesion on Single Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Pint, Bruce A.

    2000-01-01

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

  18. Macrodeformation Twins in Single-Crystal Aluminum.

    PubMed

    Zhao, F; Wang, L; Fan, D; Bie, B X; Zhou, X M; Suo, T; Li, Y L; Chen, M W; Liu, C L; Qi, M L; Zhu, M H; Luo, S N

    2016-02-19

    Deformation twinning in pure aluminum has been considered to be a unique property of nanostructured aluminum. A lingering mystery is whether deformation twinning occurs in coarse-grained or single-crystal aluminum at scales beyond nanotwins. Here, we present the first experimental demonstration of macrodeformation twins in single-crystal aluminum formed under an ultrahigh strain rate (∼10^{6}  s^{-1}) and large shear strain (200%) via dynamic equal channel angular pressing. Large-scale molecular dynamics simulations suggest that the frustration of subsonic dislocation motion leads to transonic deformation twinning. Deformation twinning is rooted in the rate dependences of dislocation motion and twinning, which are coupled, complementary processes during severe plastic deformation under ultrahigh strain rates. PMID:26943543

  19. Macrodeformation Twins in Single-Crystal Aluminum

    NASA Astrophysics Data System (ADS)

    Zhao, F.; Wang, L.; Fan, D.; Bie, B. X.; Zhou, X. M.; Suo, T.; Li, Y. L.; Chen, M. W.; Liu, C. L.; Qi, M. L.; Zhu, M. H.; Luo, S. N.

    2016-02-01

    Deformation twinning in pure aluminum has been considered to be a unique property of nanostructured aluminum. A lingering mystery is whether deformation twinning occurs in coarse-grained or single-crystal aluminum at scales beyond nanotwins. Here, we present the first experimental demonstration of macrodeformation twins in single-crystal aluminum formed under an ultrahigh strain rate (˜106 s-1 ) and large shear strain (200%) via dynamic equal channel angular pressing. Large-scale molecular dynamics simulations suggest that the frustration of subsonic dislocation motion leads to transonic deformation twinning. Deformation twinning is rooted in the rate dependences of dislocation motion and twinning, which are coupled, complementary processes during severe plastic deformation under ultrahigh strain rates.

  20. Ionic diffusion in single crystals of vermiculite

    SciTech Connect

    Maraqah, H.R.

    1993-01-01

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

  1. Flexible single-crystal silicon nanomembrane photonic crystal cavity.

    PubMed

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

    2014-12-23

    Flexible inorganic electronic devices promise numerous applications, especially in fields that could not be covered satisfactorily by conventional rigid devices. Benefits on a similar scale are also foreseeable for silicon photonic components. However, the difficulty in transferring intricate silicon photonic devices has deterred widespread development. In this paper, we demonstrate a flexible single-crystal silicon nanomembrane photonic crystal microcavity through a bonding and substrate removal approach. The transferred cavity shows a quality factor of 2.210(4) and could be bent to a curvature of 5 mm radius without deteriorating the performance compared to its counterparts on rigid substrates. A thorough characterization of the device reveals that the resonant wavelength is a linear function of the bending-induced strain. The device also shows a curvature-independent sensitivity to the ambient index variation. PMID:25409282

  2. Exfoliation of graphene oxide and its application in improving the electro-optical response of ferroelectric liquid crystal

    NASA Astrophysics Data System (ADS)

    Kumar, Veeresh; Kumar, Ajay; Bhandari, Shruti; Biradar, A. M.; Reddy, G. B.; Pasricha, Renu

    2015-09-01

    Near complete exfoliation and reduction of lyophilized graphene oxide (GO) has been carried out at temperature as low as 400 C. The structural characterizations of the reduced GO have been performed using X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy techniques. The morphological studies were carried out using scanning electron microscopy. The synthesized GO finds an application in improving the switching performance of a liquid crystal (LC) mixture by remarkably modifying the physical properties, such as spontaneous polarization and rotational viscosity of the ferroelectric LC (FLC) material which in turn resulted into faster response of the FLC. The present study explores the possibility of low temperature thermal reduction of GO along with its application in improving the properties of LC based display systems.

  3. The ferroelectric phase transition of calcium barium niobate: experimental evidence of Smolenskii's model for diffuse phase transitions?

    NASA Astrophysics Data System (ADS)

    Heine, Urs; Voelker, Uwe; Betzler, Klaus; Burianek, Manfred; Muehlberg, Manfred

    2009-08-01

    We present investigations on temperature-dependent changes in the size distribution of ferroelectric domains in single crystals of the novel tungsten bronze type calcium barium niobate (CBN). Since its congruently melting composition has a relatively high ferroelectric phase transition temperature of about 265 C, CBN can be considered as an interesting material for various future applications. Using k-space spectroscopy, both unpoled polydomain crystals and crystals poled at room temperature have been investigated in the vicinity of the ferroelectric phase transition. In unpoled CBN, an intermixture of domain-size dependent phase transitions has been observed, which can be described with the model for diffuse phase transitions established by Smolenskii.

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

    PubMed

    Krishnan, Baiju P; Sureshan, Kana M

    2015-02-01

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

  5. Perpetually self-propelling chiral single crystals.

    PubMed

    Panda, Manas K; Run?evski, Tom?e; Husain, Ahmad; Dinnebier, Robert E; Naumov, Pan?e

    2015-02-11

    When heated, single crystals of enantiomerically pure D- and L-pyroglutamic acid (PGA) are capable of recurring self-actuation due to rapid release of latent strain during a structural phase transition, while the racemate is mechanically inactive. Contrary to other thermosalient materials, where the effect is accompanied by crystal explosion due to ejection of debris or splintering, the chiral PGA crystals respond to internal strain with unprecedented robustness and can be actuated repeatedly without deterioration. It is demonstrated that this superelasticity is attained due to the low-dimensional hydrogen-bonding network which effectively accrues internal strain to elicit propulsion solely by elastic deformation without disintegration. One of the two polymorphs (?) associated with the thermosalient phase transition undergoes biaxial negative thermal expansion (?a = -54.8(8) 10(-6) K(-1), ?c = -3.62(8) 10(-6) K(-1)) and exceptionally large uniaxial thermal expansion (?b = 303(1) 10(-6) K(-1)). This second example of a thermosalient solid with anomalous expansion indicates that the thermosalient effect can be expected for first-order phase transitions in soft crystals devoid of an extended 3D hydrogen-bonding network that undergo strongly anisotropic thermal expansion around the phase transition. PMID:25581716

  6. Curved Ferroelectric Liquid Crystal Matrix Displays Driven by Field-Sequential-Color and Active-Matrix Techniques

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Sato, Hiroto; Murashige, Takeshi; Fujisaki, Yoshihide; Kurita, Taiichiro; Furukawa, Tadahiro; Sato, Fumio

    This paper describes a curved field-sequential-color matrix display using fast-response ferroelectric liquid crystal. Black matrix and transparent electrode patterns were formed on a thin plastic substrate by a transfer method from a glass substrate. While a composite film of liquid crystal and micro-polymers of walls and fibers was formed between the flexible substrates by printing, laminating and curing processes of a solution of monomers and liquid crystal, the mechanical stability was enhanced by use of multi-functional monomers to form large display panels. The image pixels of the matrix panel were driven by an active matrix scheme using an external switch transistor array at a frequency of 180 Hz for intermittent three-primary-color backlight illumination. The flexible A4-paper-sized color display with 24 16 pixels and 60 Hz field frequency was demonstrated by illuminating it with sequential three-primary-color lights from light-emitting diodes of the backlight. Our display system is useful in various information displays because of its freedom of setting and location.

  7. Dielectric/piezoelectric properties and temperature dependence of domain structure evolution in lead free (KNa)NbO single crystal

    NASA Astrophysics Data System (ADS)

    Lin, Dabin; Li, Zhenrong; Zhang, Shujun; Xu, Zhuo; Yao, Xi

    2009-10-01

    (K 0.5Na 0.5)NbO 3 (KNN) single crystals were grown using a high temperature flux method. The dielectric permittivity was measured as a function of temperature for [001]-oriented KNN single crystals. The ferroelectric phase transition temperatures, including the rhombohedral-orthorhombic T, orthorhombic-tetragonal T and tetragonal-cubic TC were found to be located at -149 ∘C, 205 ∘C and 393 ∘C, respectively. The domain structure evolution with an increasing temperature in [001]-oriented KNN single crystal was observed using polarized light microscopy (PLM), where three distinguished changes of the domain structures were found to occur at -150 ∘C, 213 ∘C and 400 ∘C, corresponding to the three phase transition temperatures.

  8. Sponge-like nanoporous single crystals of gold

    NASA Astrophysics Data System (ADS)

    Khristosov, Maria Koifman; Bloch, Leonid; Burghammer, Manfred; Kauffmann, Yaron; Katsman, Alex; Pokroy, Boaz

    2015-11-01

    Single crystals in nature often demonstrate fascinating intricate porous morphologies rather than classical faceted surfaces. We attempt to grow such crystals, drawing inspiration from biogenic porous single crystals. Here we show that nanoporous single crystals of gold can be grown with no need for any elaborate fabrication steps. These crystals are found to grow following solidification of a eutectic composition melt that forms as a result of the dewetting of nanometric thin films. We also present a kinetic model that shows how this nano-porous single-crystalline structure can be obtained, and which allows the potential size of the porous single crystal to be predicted. Retaining their single-crystalline nature is due to the fact that the full crystallization process is faster than the average period between two subsequent nucleation events. Our findings clearly demonstrate that it is possible to form single-crystalline nano porous metal crystals in a controlled manner.

  9. Sponge-like nanoporous single crystals of gold.

    PubMed

    Khristosov, Maria Koifman; Bloch, Leonid; Burghammer, Manfred; Kauffmann, Yaron; Katsman, Alex; Pokroy, Boaz

    2015-01-01

    Single crystals in nature often demonstrate fascinating intricate porous morphologies rather than classical faceted surfaces. We attempt to grow such crystals, drawing inspiration from biogenic porous single crystals. Here we show that nanoporous single crystals of gold can be grown with no need for any elaborate fabrication steps. These crystals are found to grow following solidification of a eutectic composition melt that forms as a result of the dewetting of nanometric thin films. We also present a kinetic model that shows how this nano-porous single-crystalline structure can be obtained, and which allows the potential size of the porous single crystal to be predicted. Retaining their single-crystalline nature is due to the fact that the full crystallization process is faster than the average period between two subsequent nucleation events. Our findings clearly demonstrate that it is possible to form single-crystalline nano porous metal crystals in a controlled manner. PMID:26554856

  10. Crystal structure, dielectric, ferroelectric and energy storage properties of La-doped BaTiO3 semiconducting ceramics

    NASA Astrophysics Data System (ADS)

    Puli, Venkata Sreenivas; Li, Patrick; Adireddy, Shiva; Chrisey, Douglas B.

    2015-09-01

    Polycrystalline La-doped BaTiO3 (Ba(1-x)Lax TiO3) [x=0,0.0005,0.001,0.003] ceramics (denoted as BTO,BLT1,BLT2,BLT3) were synthesized by conventional solid-state reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. XRD and Raman spectra revealed single-phase tetragonal perovskite crystalline structure. Well-saturated polarization-electric field (P-E) hysteresis loops were observed with the measurement frequency of 50 Hz at room temperature and confirmed ferroelectric nature of these ceramics and a high recoverable electrical energy storage density of 0.350 J/cm3 with energy efficiency (n)9%, which is useful in energy storage capacitor applications. Dielectric studies revealed anomalies around 415-420 K and near the Curie temperature. The latter is attributed to the ferroelectric to paraelectric phase transition. Better dielectric performances were obtained for La-doped samples sintered at 1350C for 4 h. Grain growth is inhibited with lanthanum (La) incorporation into the BTO lattice. Room temperature semiconducting behavior with positive temperature coefficient of resistivity (PTCR) behavior at TC is attributed to electron compensation mechanism.

  11. Frequency Dependent Polarization Reversal and the Response Time of Ferroelectric Liquid Crystal by Triangular Wave Method

    NASA Astrophysics Data System (ADS)

    Bawa, S. S.; Biradar, A. M.; Chandra, Subhas

    1986-06-01

    Dynamic processes of molecular reorientation of thin (10 ?m) well aligned film of ferroelectric smectic C (DOBAMBC) have been studied with a triangular wave by observing a current signal due to polarization realignment at different frequencies. The peak due to polarization reversal shifts along the abscissa axis with the increase in frequency of the triangular pulses. The peak originates from both a surface and interior molecular reorientation, switches amongst uniform up(UU)?ftrightarrowtwisted(TI)?ftrightarrowuniform down(UD) states and shifts due to their composite response time. The method also provides an estimate for the response time by comparing the occurrence of the peak at two known frequencies.

  12. Bridgman growth of paratellurite single crystals

    NASA Astrophysics Data System (ADS)

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

    2004-09-01

    The growth of paratellurite single crystals by the vertical-gradient freezing technique is reported for the first time. Boules of 120 mm long and 25 mm in diameter were obtained under a temperature gradient of 10C cm-1 and translation rates lower than 0.6 mm h-1. The spatial distribution of defects along the growth axis reveals a continuous evolution of the free convective fluid-flow regime as growth proceeds. Gas bubbles and dark inclusions rejected to the periphery in the upper part of the crystal are observed to lay preferentially in (1 0 0), (0 0 1), (1 1 bar 0) and (1 1 2) crystallographic planes. Among them, SEM and microprobe analyses evidenced the presence of metallic platinum, while micro-Raman experiments allowed to assess oxygen as being actually the gas content of occluded bubbles, originated at the crucible wall through Pt-induced dissociation of Te-O bonds.

  13. ?-Lead tellurite from single-crystal data

    PubMed Central

    Zavodnik, Valery E.; Ivanov, Sergey A.; Stash, Adam I.

    2008-01-01

    The crystal structure of the title compound, ?-PbTeO3 (PTO), has been reported previously by Mariolacos [Anz. Oesterr. Akad. Wiss. Math. Naturwiss. Kl. (1969), 106, 128130], refined on powder data. The current determination at room temperature from data obtained from single crystals grown by the Czochralski method shows a significant improvement in the precision of the geometric parameters when all atoms have been refined anisotropically. The selection of a centrosymmetric (C2/c) structure model was confirmed by the second harmonic generation test. The asymmetric unit contains three formula units. The structure of PTO is built up of three types of distorted [PbOx] polyhedra (x = 7 and 9) which share their O atoms with TeO3 pyramidal units. These main anionic polyhedra are responsible for establishing the two types of tunnel required for the stereochemical activity of the lone pairs of the Pb2+ and Te4+ cations. PMID:21201834

  14. Crystal ion slicing of single-crystal magnetic garnet films

    NASA Astrophysics Data System (ADS)

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

    1998-06-01

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

  15. Single crystal to single crystal polymerization of a columnar assembled diacetylene macrocycle

    NASA Astrophysics Data System (ADS)

    Xu, Weiwei

    Organic tubular materials have attracted lots of attentions for their potential applications as nanoscale fluidic transport systems, specific ion sensors, molecular sieves and confined molecular reaction containers. While conjugated polymers, due to delocalized Pi electrons, exhibit interesting solar cells and sensors applications. In this thesis, we developed a conjugated polymer which combines the attributes of conjugated polymers with tubular materials, which should have great potential to work as a sensing material. We reproduced and scaled-up the synthesis of a polymerizable macrocycle 1 that contains two rigidly separated diacetylene units. We found that, through hydrogen bonding, 1 can assemble into columnar crystals and can be polymerized under a single crystal to single crystal transformation process to afford porous polydiacetylene (PDA) crystals. We studied the assembly of the macrocycles 1 under different conditions to give three different crystalline forms and micro-phase crystals, and also investigated their subsequent polymerizations. The macrocycle assembly and polymerized materials were characterized by a variety of technique. Since the gas adsorption measurement exhibited PDA crystals still retained its porosity and the polymer should have ability to uptake suitable guest molecules, therefore the absorption of iodine for PDA crystals was investigated as well.

  16. Chemical vapor deposition of graphene single crystals.

    PubMed

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

    2014-04-15

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Choudhury, Rajul Ranjan; Chitra, R.

    2009-08-01

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

  19. Growth and dielectric parameters of DGS single crystal

    NASA Astrophysics Data System (ADS)

    Patel, Vimal; Vyas, S. M.; Patel, Piyush; Jani, M. P.; Pavagadhi, Himanshu

    2015-08-01

    Anhydrous Diglycine sulfate single crystals have been grown from the aqueous solutions, which is made from the glycerin and sulfuric acid at room temperature with pH values. This grown crystal now used to study some optical and dielectric properties. i.e. refractive index, density, molar refraction, Polarizability and Molar Polarization. These all parameter provides information about the DGS single crystals, which is used in various processes of dielectric presentation of DGS single crystals.

  20. Fabrication of crystals from single metal atoms

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  1. Fabrication of crystals from single metal atoms

    PubMed Central

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

    2014-01-01

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

  2. 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.

  3. 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.

  4. Magnetic anisotropy in pyroxene single crystals

    NASA Astrophysics Data System (ADS)

    Biedermann, Andrea Regina; Hirt, Ann Marie; Pettke, Thomas; Bender Koch, Christian

    2014-05-01

    Anisotropy of magnetic susceptibility (AMS) is often used as a proxy for the mineral fabric in a rock. This requires understanding the intrinsic magnetic anisotropy of the minerals that define the rock fabric. With their prismatic habit, pyroxenes describe the texture in mafic and ultramafic rocks. Magnetic anisotropy in pyroxene crystals often arises from both paramagnetic and ferromagnetic components that can be separated from high-field magnetic data. The paramagnetic component is related to the silicate lattice, whereas the ferromagnetic part arises from the magnetic properties of ferromagnetic inclusions that were further characterized by isothermal remanent magnetization measurements. These inclusions often have needle-like habit and are located on the well-defined cleavage planes within the pyroxenes. We characterize low-field and high-field AMS in pyroxene single crystals of diverse orthopyroxene and clinopyroxene minerals. In addition to the magnetic measurements, we analyzed their chemical composition and Fe2+/Fe3+ distribution. The anisotropy arising from inclusions in some augite crystals displays consistent principal susceptibility directions, whereas no preferred orientation is found in other crystals. The principal susceptibilities of the paramagnetic component can be related to the crystal lattice, with the intermediate susceptibility parallel to the b-axis, and minimum and maximum in the a-c-plane for diopside, augite and spodumene. The degree of anisotropy increases with iron concentration. Aegirine shows a different behavior; not only is its maximum susceptibility parallel to the c-axis, but the anisotropy degree is also lower in relation to its iron concentration. This possibly relates to a predominance of Fe3+ in aegirine, whereas Fe2+ is dominant in the other minerals. In orthopyroxene, the maximum susceptibility is parallel to the c-axis and the minimum is parallel to b. The degree of anisotropy increases linearly with iron concentration. The difference in principal directions between clino- and orthopyroxene reflects their different crystal structure; in clinopyroxene, iron mainly occupies M1 sites, whereas it prefers the distorted M2 sites in orthopyroxene. The difference in anisotropy degree between aegirine and the other clinopyroxenes suggests that Fe2+ causes a stronger anisotropy than Fe3+. Thus, the magnetic anisotropy in pyroxenes is mainly dominated by the concentration, oxidation state and site occupancy of iron. The results from this study are important when interpreting magnetic fabrics in ultramafic rocks that contain both olivine and pyroxenes.

  5. Photorefractive properties of tungsten bronze ferroelectric lead barium niobate (Pb1-xBaxNb2O6) crystals

    NASA Astrophysics Data System (ADS)

    Lee, Myeongkyu; Feigelson, Robert S.; Liu, Alice; Hesselink, Lambertus

    1998-06-01

    Lead barium niobate (Pb1-xBaxNb2O6) is a very promising material for photorefractive applications in that it has a high ferroelectric-to-paraelectric transition temperature (300-500 C depending on composition) and simultaneously can have large electro-optic coefficients, because of the nearly vertical morphotropic phase boundary (MPB) near 1-x=0.63. Pb1-xBaxNb2O6 crystals have been grown by the vertical Bridgman method for near-MPB compositions (0.5<1-x<0.6), and their photorefractive properties were investigated by the two wave mixing experiments. Material properties such as composition and absorption coefficient varied along the growth direction because of the incongruent charge composition and the nonuniform distribution of impurities. A maximum diffraction efficiency of 50% at ?=514.5 nm was observed in a 3.2 mm thick nominally undoped as-grown crystal. The photorefractive sensitivity increased as the wavelength decreased. The gain coefficient also increased with decreasing wavelength, changing from 0.5 cm-1 at ?=633 nm to above 8 cm-1 at ?=465 nm.

  6. Constitutive modeling for single crystal superalloys

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  7. Phase transition peculiarities in LAMOX single crystals

    NASA Astrophysics Data System (ADS)

    Voronkova, V. I.; Kharitonova, E. P.; Krasilnikova, A. E.; Kononkova, N. N.

    2008-05-01

    The series of oxide-ion-conducting La2Mo2O9 single crystals, undoped and doped with Ca, Bi, W, Nb, Zn and V (LAMOX), was grown by the flux method in the system La2O3-MoO3, which has allowed us to use polarization microscopy for the identification of phases. Phase transition peculiarities in the LAMOX family have been studied by polarization microscopy and calorimetry. The results demonstrate that both the monoclinic phase (α), which is stable at room temperature, and the metastable cubic phase (βms), or a mixture of these phases, may exist at room temperature, depending on the post-growth cooling rate and the nature of the dopant at low doping level. On heating, all of the quenched crystals undergo \\beta_{\\mathrm {ms}} \\to \\alpha (450 °C) and \\alpha \\to \\beta (500-560 °C) phase transitions (where β designates the stable cubic phase). At heavy doping levels, the high-temperature transition is suppressed and the crystals (La2Mo1.95V0.05Oy, La2Mo1.84W0.16Oy in our case) are found in the cubic state. The thermal peak near 450 °C at high doping level is not associated with a \\beta_{\\mathrm {ms}} \\to \\alpha transition and may be the result of defect association/dissociation in the cubic crystals. The thermal history, nature of the dopant and doping level are shown to influence the phase transition sequence and type.

  8. Polarization tomography of residual stresses in trigonal single crystals

    NASA Astrophysics Data System (ADS)

    Puro, A. E.; Karov, D. D.

    2015-11-01

    A way to determine residual stresses in cylindrical trigonal single crystals the optical axis of which is directed along the crystal axis is proposed. It is assumed that the residual deformation tensor is of thermal character and is characterized by fictive temperature. The measurements are performed in the middle part of a single crystal the length of which is much larger than its diameter; therefore, the stresses in this part do not vary along the single crystal axis. The reconstruction of stresses is based on determining characteristic parameters of polarized light by use of the tomographic method in the plane orthogonal to the single crystal axis.

  9. Phase equilibria, crystal growth and characterization of the novel ferroelectric tungsten bronzes CaxBa1-xNb2O6 (CBN) and CaxSryBa1-x-yNb2O6 (CSBN)

    NASA Astrophysics Data System (ADS)

    Muehlberg, M.; Burianek, M.; Joschko, B.; Klimm, D.; Danilewsky, A.; Gelissen, M.; Bayarjargal, L.; Grler, G. P.; Hildmann, B. O.

    2008-04-01

    Phase diagram analyses and crystal growth experiments of the novel ferroelectric tetragonal tungsten bronzes CaxBa1-xNb2O6 (calcium barium niobate, CBN) and CaxSryBaNb2O6 (calcium strontium barium niobate, CSBN) were performed in this study. The quasi-binary phase diagram BaNb2O6-CaNb2O6 was found to be similar to the related system BaNb2O6-SrNb2O6, but with a remarkably reduced existence region. In the quasi-ternary phase diagram CaNb2O6-SrNb2O6-BaNb2O6 the stability field of CaxSryBaNb2O6 mixed crystals was determined by X-ray powder diffraction of sintered and annealed samples. Large, transparent, and nearly colorless CBN and CSBN single crystals of high quality were grown by the Czochralski method. The dislocation network structure of the core region in the as-grown crystals was analyzed by X-ray topography employing white beam synchrotron radiation. Precise measurements of the refractive index dispersion showed a composition dependance only for the extraordinary beam. The Curie temperature of the ferroelectric phase transition {4}/{m}mm?4mm determinated by calorimetric measurements exhibited a clear composition dependance. It is expected that in the complete mixed crystal system CaxSryBaNb2O6 the Curie temperature could be varied between about 80C for strontium barium niobate with xSr=0.61 and about 300C for CBN with xCa?0.20, the lowest possible Ca content.

  10. 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.

  11. 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.

  12. Solar cell structure incorporating a novel single crystal silicon material

    DOEpatents

    Pankove, Jacques I.; Wu, Chung P.

    1983-01-01

    A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

  13. Accelerated domain switching speed in single-crystal LiNbO{sub 3} thin films

    SciTech Connect

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

    2015-03-14

    By using ionic implantation and wafer bonding technologies, we peeled off a single-crystal LiNbO{sub 3} thin film in the atomic-layer smoothness from the surface of a bulk Z-cut LiNbO{sub 3} 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.

  14. High-Temperature Electromechanical Characterization of AlN Single Crystals.

    PubMed

    Kim, Taeyang; Kim, Jinwook; Dalmau, Rafael; Schlesser, Raoul; Preble, Edward; Jiang, Xiaoning

    2015-10-01

    Hexagonal AlN is a non-ferroelectric material and does not have any phase transition up to its melting point (>2000C), which indicates the potential use of AlN for high-temperature sensing. In this work, the elastic, dielectric, and piezoelectric constants of AlN single crystals were investigated at elevated temperatures up to 1000C by the resonance method. We used resonators of five different modes to obtain a complete set of material constants of AlN single crystals. The electrical resistivity of AlN at elevated temperature (1000C) was found to be greater than 5 10(10) ? cm. The resonance frequency of the resonators, which was mainly determined by the elastic compliances, decreased linearly with increasing temperature, and was characterized by a relatively low temperature coefficient of frequency, in the range of -20 to -36 ppm/C. For all the investigated resonator modes, the elastic constants and the electromechanical coupling factors exhibited excellent temperature stability, with small variations over the full temperature range, <11.2% and <17%, respectively. Of particular significance is that due to the pyroelectricity of AlN, both the dielectric and the piezoelectric constants had high thermal resistivity even at extreme high temperature (1000C). Therefore, high electrical resistivity, temperature independence of electromechanical properties, as well as high thermal resistivity of the elastic, dielectric, and piezoelectric properties, suggest that AlN single crystals are a promising candidate for high-temperature piezoelectric sensing applications. PMID:26759848

  15. Quantum criticality in a uniaxial organic ferroelectric

    NASA Astrophysics Data System (ADS)

    Rowley, S. E.; Hadjimichael, M.; Ali, M. N.; Durmaz, Y. C.; Lashley, J. C.; Cava, R. J.; Scott, J. F.

    2015-10-01

    Tris-sarcosine calcium chloride (TSCC) is a highly uniaxial ferroelectric with a Curie temperature of approximately 130 K. By suppressing ferroelectricity with bromine substitution on the chlorine sites, pure single crystals were tuned through a ferroelectric quantum phase transition. The resulting quantum critical regime was investigated in detail and was found to persist up to temperatures of at least 30-40 K. The nature of long-range dipole interactions in uniaxial materials, which lead to non-analytical terms in the free-energy expansion in the polarization, predict a dielectric susceptibility varying as 1/T 3close to the quantum critical point. Rather than this, we find that the dielectric susceptibility varies as 1/T 2 as expected and observed in better known multi-axial systems. We explain this result by identifying the ultra-weak nature of the dipole moments in the TSCC family of crystals. Interestingly, we observe a shallow minimum in the inverse dielectric function at low temperatures close to the quantum critical point in paraelectric samples that may be attributed to the coupling of quantum polarization and strain fields. Finally, we present results of the heat capacity and electro-caloric effect and explain how the time dependence of the polarization in ferroelectrics and paraelectrics should be considered when making quantitative estimates of temperature changes induced by applied electric fields.

  16. Single crystal fiber for laser sources

    NASA Astrophysics Data System (ADS)

    Dlen, Xavier; Aubourg, Adrien; Deyra, Loc.; Lesparre, Fabien; Martial, Igor; Didierjean, Julien; Balembois, Franois; 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).

  17. Mechanical properties of single crystal YAg

    SciTech Connect

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

    2004-08-02

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  19. 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.

  20. Low-cobalt single crystal Rene 150

    NASA Technical Reports Server (NTRS)

    Scheuermann, C. M.

    1982-01-01

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

  1. Stress- Corrosion cracking of copper single crystals

    NASA Astrophysics Data System (ADS)

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

    1984-10-01

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

  2. Transient thermoelectric effect in bismuth single crystals

    NASA Astrophysics Data System (ADS)

    Sasaki, M.; Tai, G. X.; Inoue, M.; Bidadi, H.

    1994-05-01

    The photo-induced transient thermoelectric effect (TTE) has been measured for bismuth single crystals along nearly the X and Y axes over the temperature range 6-300 K and time range 50 ns-2 ms. The decay curves of the TTE voltages are characterized by multiple relaxation processes for thermal diffusions of photogenerated electrons and holes. From the analysis of the relaxation times, we have evaluated the carrier mobilities and their effective masses of each carrier pocket at the L and T points based on the existing band model; in particular, we have found an additional hole pocket at the L point lying below the Fermi energy. This TTE technique is shown to be useful for understanding electronic properties of a multicarrier system.

  3. 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.

  4. Computer simulation of channeling in single crystals

    NASA Astrophysics Data System (ADS)

    Smulders, P. J. M.; Boerma, D. O.

    1987-12-01

    A Monte Carlo program for the calculation of channeling phenomena is described. The program combines the binary collision model and the multistring approximation. The energy loss due to electronic excitation is taken into account, with the use of the model of Dettmann and Robinson for the inner-shell electrons and the theory of Pines for valence electrons. The output of the Monte Carlo program may be used for the determination of the impurity sites in single crystals, via a set of auxiliary programs, that enable that calculation of the impurity yield and the analysis of experimental channeling dips. As an application, the site determination of iodine in silicon is described. Another application is the simulation of RBS spectra of planar channeling ions. Simulated and experimental spectra are compared for 1 MeV ions in the (110), (111) and (100) planes of silicon. A reasonable agreement was found. The possible causes of the remaining deviations are discussed.

  5. Piezomagnetism of FeSe single crystals

    NASA Astrophysics Data System (ADS)

    Fil, V. D.; Fil, D. V.; Zhekov, K. R.; Gaydamak, T. N.; Zvyagina, G. A.; Bilich, I. V.; Chareev, D. A.; Vasiliev, A. N.

    2013-08-01

    The acoustic-electric transformation in high-quality FeSe single crystals is studied. In zero magnetic field we observe an abnormally strong electromagnetic radiation induced by a transverse elastic wave. Usually a radiation of such intensity and polarization is observed only in metals subjected to a high magnetic field (the radiation is caused by the Hall current). We argue that in FeSe in zero magnetic field it is caused by the piezomagnetic effect which is most probably of dynamical origin. We find that the piezomagnetism survives under the transition from the normal to superconducting state. In the superconducting state the electromagnetic signal decreases with decreasing temperature that is connected with the change in the London penetration depth.

  6. Single-crystal AlN nanonecklaces

    NASA Astrophysics Data System (ADS)

    Wang, Huatao; Xie, Zhipeng; Wang, Yiguang; Yang, Weiyou; Zeng, Qingfeng; Xing, Feng; An, Linan

    2009-01-01

    Distinct single-crystal aluminum nitride nanonecklaces with uniform \\{10\\bar {1}1\\} faceted beads are synthesized via catalyst-assisted nitriding of Al. The detailed morphology and structure of the nanonecklaces have been characterized. The growth process has been investigated by comparing the products obtained at different synthesis times. The results reveal that the formation of the nanonecklaces is via a process consisting of facet formation and bead unification. The formation of the \\{10\\bar {1}1\\} facets is due to the presence of a liquid phase that lowers the surface tension of otherwise high-energy \\{10\\bar {1}1\\} planes. The bead unification is driven by minimizing the energy contributed by surface energy and electrostatic energy. The unique morphology of the nanonecklaces could be useful for studying fundamental physical phenomena and fabricating nanodevices.

  7. Electrical switching in cadmium boracite single crystals

    NASA Technical Reports Server (NTRS)

    Takahashi, T.; Yamada, O.

    1981-01-01

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

  8. Method of Making Lightweight, Single Crystal Mirror

    NASA Technical Reports Server (NTRS)

    Bly, Vincent T. (Inventor)

    2015-01-01

    A method of making a mirror from a single crystal blank may include fine grinding top and bottom surfaces of the blank to be parallel. The blank may then be heat treated to near its melting temperature. An optical surface may be created on an optical side of the blank. A protector may be bonded to the optical surface. With the protector in place, the blank may be light weighted by grinding a non-optical surface of the blank using computer controlled grinding. The light weighting may include creating a structure having a substantially minimum mass necessary to maintain distortion of the mirror within a preset limit. A damaged layer of the non-optical surface caused by light weighting may be removed with an isotropic etch and/or repaired by heat treatment. If an oxide layer is present, the entire blank may then be etched using, for example, hydrofluoric acid. A reflecting coating may be deposited on the optical surface.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  11. Mechanical Behavior and Processing of DS and Single Crystal Superalloys

    NASA Astrophysics Data System (ADS)

    Khan, T.; Caron, P.; Nakagawa, Y. G.

    1986-07-01

    This article examines mechanical anisotropy of single crystals, cold work induced surface recrystallization on directionally solidified (DS) materials, and the effect of temperature gradient in a DS furnace on the fatigue strength of single crystals. It draws attention to the highly anisotropic creep behavior of some modern single crystal alloys showing, in particular, extremely poor creep resistance in the <111> orientation. Effects of surface recrystallization on the creep strength are evaluated. The present work incites further investigation on heat treatments and alloy chemistry modifications in order to reduce the effect of mechanical anisotropy. Great care should be taken during the "mechanical" handling of DS or single crystal components to avoid surface recrystallization. HIP'ing or high gradient solidification are shown to be two possible ways for enhancing the durability and the fatigue strength of single crystal superalloys. In certain liquid fuel rocket engine applications, where hydrogen embrittlement of single crystal turbopump blades can be of concern, both these techniques can be useful.

  12. Piezoelectric single crystals for ultrasonic transducers in biomedical applications

    PubMed Central

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

    2014-01-01

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

  13. Terahertz response of ferroelectric nanofibers.

    PubMed

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

    2011-11-01

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

  14. Three-dimensional single crystal silicon micromachining

    NASA Astrophysics Data System (ADS)

    Hofmann, Wolfgang Maximilian Josef

    1999-11-01

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

  15. Probing on phase dependent luminescent properties of Al2O3 nanowires for their performance in ferroelectric liquid crystal

    NASA Astrophysics Data System (ADS)

    Gangwar, Jitendra; Chandran, Achu; Joshi, Tilak; Verma, Rajni; Biradar, Ashok M.; Kant Tripathi, Surya; Gupta, Bipin Kumar; Srivastava, Avanish Kumar

    2015-07-01

    Herein, we have investigated the various characteristics of two structurally different phases of Al2O3 nanowires: (i) ?-Al2O3 (cubic) and (ii) ?-Al2O3 (monoclinic). These nanowires were synthesized via hydrothermal treatment followed by calcination. The structural and luminescent properties were analyzed by scanning electron microscopy, high-resolution transmission electron microscopy and time-resolved photoluminescence spectroscopy. A plausible formation mechanism was proposed on the basis of experimental observations and analysis. These nanowires of both phases exhibit blue emission at ?466 nm (2.65 eV) upon 253 nm UV excitation wavelength. The time-resolved photoluminescence spectroscopy indicated that the decay time (?) of ?-Al2O3 nanowires (? = 273 picoseconds) is longer than that of ?-Al2O3 nanowires (? = 198 picoseconds). Moreover, these Al2O3 nanowires were dispersed in ferroelectric liquid crystal (FLC) to observe their effect on the electro-optical characteristics. The electro-optical response of the composite devices showed faster electro-optical response, thereby suggesting potential applications in electro-optical shutters and modulators.

  16. 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.

  17. 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

  18. Electro-Optical Properties of Ferroelectric Liquid Crystals with a Sulfinate Group as Unique Source of Chirality

    NASA Astrophysics Data System (ADS)

    Zoubair Cherkaoui, Mohammed; Nicoud, Jean-François; Galerne, Yves; Guillon, Daniel

    1995-09-01

    In this communication, we present the first electro-optical measurements performed on ferroelectric liquid crystals materials based on molecules containing a sulfinate group as the unique chiral source. Spontaneous polarization, response time to the applied electric field and tilt angle of the molecules as a function of temperature are reported for two representative molecules of the whole series. It is also shown the existence of a significant electroclinic effect in the smectic A phase. Dans cette communication, nous rapportons les premières mesures électro-optiques sur des cristaux liquides ferroélectriques obtenus à partir de molécules contenant un groupe sulfinate comme centre unique de chiralité. Sont présentés la polarisation spontanée, le temps de réponse au champ électrique appliqué et l'angle d'inclinaison des molécules en fonction de la température pour deux molécules typiques de la série homologue. Il est aussi mis en évidence un fort effet électroclinique dans la phase smectique A.

  19. Ultratough CVD single crystal diamond and three dimensional growth thereof

    DOEpatents

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

    2009-09-29

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

  20. Formation of unusual nonferroic domains in TeO2 single crystals under external electric field

    NASA Astrophysics Data System (ADS)

    Kovalchuk, M. V.; Blagov, A. E.; Kulikov, A. G.; Marchenkov, N. V.; Pisarevsky, Yu. V.

    2014-11-01

    The formation of unusual slowly relaxing domains under an external dc electric field has been revealed in paratellurite (TeO2) crystals. These domains differ from those arising in ferroics (ferromagnets, ferroelectrics, ferroelastics, etc.). The effect is characterized by the existence of a threshold field strength (at which domains begin to be formed) and long equilibrium settling times (up to a few hours, depending on the electric field strength). A crystal returns to the initial single-domain state also after a few hours after the field is switched off. High-resolution triple-crystal X-ray diffractometry has revealed that domains retaining the paraelastic tetragonal phase rotate with respect to each other in space without changing their lattice parameter. The domain sizes are 2-4 mm, depending on the field strength. Currently, the exact mechanisms of domain formation are unclear. Possible reasons for the formation of these defects and an analogy of the observed effects with the behavior of liquid crystals under electric field are discussed.

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

    DOEpatents

    Todt, Volker; Miller, Dean J.; Shi, Donglu; Sengupta, Suvankar

    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.

  2. Study of temperature-dependent Raman spectroscopy and electrical properties in [001]-oriented 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3-Mn single crystals

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Fang, Bijun; Deng, Ji; Yan, Hong; Deng, Hao; Yue, Qingwen; Ding, Jianning; Zhao, Xiangyong; Luo, Haosu

    2016-01-01

    In this work, the temperature-dependent Raman spectra and electrical properties of the [001]-oriented 0.5 mol. % Mn-doped 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3-Mn (PIMNT-Mn) single crystals were investigated. All the unpoled and poled PIMNT-Mn single crystals experience a ferroelectric tetragonal phase to paraelectric cubic phase transition (FET-PC) around 183 °C (TC), which exhibits a second-order transition behavior. Whereas, the poled PIMNT-Mn single crystals exhibit another two dielectric anomalies around 130 °C (TRM) and 148 °C (TMT), in which the ferroelectric rhombohedral phase to ferroelectric monoclinic phase (FER-FEM) and the ferroelectric monoclinic phase to ferroelectric tetragonal phase (FEM-FET) transitions take place, respectively. Both the two ferroelectric phase transitions exhibit a first-order transition behavior. The discontinuous change of the phase degree (θ) and frequencies (fr and fa) around TRM suggest the occurrence of the FER-FEM phase transition in the poled PIMNT-Mn single crystals. The narrowing of the 510 cm-1 and 582 cm-1 Raman modes around the TRM, TMT, and TC temperatures shown in the temperature-dependent Raman spectra suggests their increased ordering of the local structure. The intensity ratio of I272 cm-1/I801 cm-1 increases obviously around the phase transition temperatures (TRM, TMT, and TC), indicating the reduction of the long-range order. The anomalous broadening of the 272 cm-1 Raman mode around the TRM, TMT, and TC temperatures indicates the occurrence of the successive ferroelectric phase transitions (FER-FEM, FEM-FET, and FET-PC) with increasing temperature in the poled PIMNT-Mn single crystals.

  3. Investigation on Growth and Surface Analysis of DAST Single Crystals

    SciTech Connect

    Thomas, Tina; Vijay, R. Jerald; Gunaseelan, R.; Sagayaraj, P.

    2011-07-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  5. Stress dependence of thermally driven pyroelectric charge release during FER-FEO phase transformations in [011] cut relaxor ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Dong, Wen D.; Finkel, Peter; Amin, Ahmed; Lynch, Christopher S.

    2012-06-01

    The stress dependence of thermally driven polarization change is reported for a ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut and poled Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT). A jump in polarization and strain is associated with a phase transformation of the ferroelectric material. The phase transformation temperature can be tuned, over a broad temperature range, through the application of bias stress. This phenomenon has applications in the field of energy harvesting and thermal sensing.

  6. Oxygen diffusion in single crystal barium titanate.

    PubMed

    Kessel, Markus; De Souza, Roger A; Martin, Manfred

    2015-05-21

    Oxygen diffusion in cubic, nominally undoped, (100) oriented BaTiO3 single crystals has been studied by means of (18)O2/(16)O2 isotope exchange annealing and subsequent determination of the isotope profiles in the solid by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Experiments were carried out as a function of temperature 973 < T/K < 1173, at an oxygen activity of aO2 = 0.200, and as a function of oxygen activity 0.009 < aO2 < 0.900 at T = 1073 K. The oxygen isotope profiles comprise two parts: slow diffusion through a space-charge zone at the surface depleted of oxygen vacancies followed by faster diffusion in a homogeneous bulk phase. The entire isotope profile can be described by a single solution to the diffusion equation involving only three fitting parameters: the surface exchange coefficient ks*, the space-charge potential ?0 and the bulk diffusion coefficient D*(?). Analysis of the temperature and oxygen activity dependencies of D*(?) and ?0 yields a consistent picture of both the bulk and the interfacial defect chemistry of BaTiO3. Values of the oxygen vacancy diffusion coefficient DV extracted from measured D*(?) data are compared with literature data; consequently a global expression for the vacancy diffusivity in BaTiO3 for the temperature range 466 < T/K < 1273 is obtained, with an activation enthalpy of vacancy migration, ?Hmig,V = (0.70 0.04) eV. PMID:25899818

  7. Investigation about relationships between the symmetries of ferroelectric crystal Ca0.28Ba0.72Nb2O6 and second-harmonic patterns

    NASA Astrophysics Data System (ADS)

    Xu, Tianxiang; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

    2015-08-01

    The broadband quasi-phase matching (QPM) process in a uniaxial ferroelectric crystal Ca0.28Ba0.72Nb2O6 (CBN-28) was demonstrated with the second-harmonic wavelength range from 450 nm to 650 nm, and the relationship between the symmetries of CBN-28 and the second-harmonic patterns was experimentally and theoretically investigated based on the random anti-parallel domains in the crystal and QPM conditions. The dependences of frequency-doubled patterns on the wavelength and anisotropy of the nonlinear crystal were also studied, and the frequency-doubled photons were found to be trapped on circles. By analyzing the light-matter interacting Hamiltonians, the trapping force for second-harmonic photons was found to be centripetal and tunable by the fundamental lasers, and the variation tendencies of the rotational velocity of second-harmonic generation photons could also be predicated. The results indicate that the CBN-28 ferroelectric crystal is a promising nonlinear optical material for the generation of broadband frequency-doubled waves, and the analysis on centripetal force based on the interaction Hamiltonians may provide a novel recognition for the investigation of QPM process to be further studied.

  8. 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.

  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. Advanced single crystal for SSME turbopumps

    NASA Technical Reports Server (NTRS)

    Fritzemeier, L. G.

    1989-01-01

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

  11. A Quick Method for Determining the Density of Single Crystals.

    ERIC Educational Resources Information Center

    Roman, Pascual; Gutierrez-Zorrilla, Juan M.

    1985-01-01

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

  12. Full field electron spectromicroscopy applied to ferroelectric materials

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  13. 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.

  14. Reshock and release response of aluminum single crystal

    NASA Astrophysics Data System (ADS)

    Huang, H.; Asay, J. R.

    2007-03-01

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

  15. 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.

  16. Growth and characterization of undoped and Mn doped lead-free piezoelectric NBTKBT single crystals

    SciTech Connect

    Babu, G. Anandha; Subramaniyan, Raja R.; Bhaumik, Indranil; Ganesamoorthy, S.; Ramasamy, P.; Gupta, P.K.

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  18. 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.

  19. Method for harvesting single crystals from a peritectic melt

    DOEpatents

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

    1996-01-01

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

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

    DOEpatents

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

    1996-01-01

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

  1. 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.

  2. 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.

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

    PubMed

    Li, Changsheng; Shen, Xiaoli; Zeng, Rong

    2013-11-01

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

  4. 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)

  5. A Single Crystal Niobium RF Cavity of the TESLA Shape

    SciTech Connect

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

    2007-08-09

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

  6. A Single Crystal Niobium RF Cavity of the TESLA Shape

    SciTech Connect

    W. Singer; X. Singer; P. Kneisel

    2007-09-01

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

  7. Growing Single Crystals of Compound Semiconductors

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J.; Lehoczky, Sandor L.; Frazier, Donald O.

    1987-01-01

    Defect reduced by preventing melt/furnace contact and suppressing convention. Large crystals of compound semiconductors with few defects grown by proposed new method. Such materials as gallium arsenide and cadmium telluride produced, with quality suitable for very-large-scale integrated circuits or for large focal-plane arrays of photodetectors. Method used on small scale in Earth gravity, but needs microgravity to provide crystals large enough for industrial use.

  8. Single-drop optimization of protein crystallization.

    PubMed

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

    2012-08-01

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

  9. Single-drop optimization of protein crystallization

    PubMed Central

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

    2012-01-01

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

  10. 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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  12. High quality factor single-crystal diamond mechanical resonators

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  13. Potassium-Sodium Niobate Single Crystals and Electric Properties

    NASA Astrophysics Data System (ADS)

    Kimura, H.; Tanahashi, R.; Maiwa, K.; Baba, H.; Cheng, Z. X.; Wang, X. L.

    Potassium-sodium-rubidium niobate single crystals are grown using an original pulling down method, to improve their composition change during a crystal growth, by means of co-doping of small ionic size sodium and large ionic size rubidium into potassium niobate. Even by the co-doping, single crystals can be grown with orthorhombic single-phase at room temperature, as well as pure potassium niobate. Their electric properties, such as the dielectric constant and the impedance, are changed depending on the doping ions.

  14. Halide electrodeposition on single-crystal electrodes

    NASA Astrophysics Data System (ADS)

    Mitchell, Steven James

    2001-07-01

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

  15. 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.

  16. Single crystal Processing and magnetic properties of gadolinium nickel

    SciTech Connect

    Shreve, Andrew John

    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.

  17. 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

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

    SciTech Connect

    Siva Sankari, R.; Perumal, Rajesh Narayana

    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.

  19. The growth of multicomponent oxide single crystals by Stepanov's technique

    NASA Astrophysics Data System (ADS)

    Ivleva, L. I.; Kuzminov, Iu. S.; Osiko, V. V.; Polozkov, N. M.

    1987-03-01

    Single crystals of LiNbO3, Sr(x)Ba(1-x)Nb2O6, Ca3(VO4), Bi12SiO20, Bi12GeO20, Bi4Ge3O12 and Nd3Ga5O12 were grown in an apparatus using RF heating of platinum crucibles in air. Stepanov's technique made it possible to increase by several times the rates of solidification needed to obtain optically homogeneous single crystals. Optimum crystallographic directions of pulling were experimentally determined for crystals from various symmetry groups. The shape of a growing crystal was related to the structural defects according to the Curie principle. The experimental data provided support for the growth of profiled multicomponent single crystals.

  20. Three-Dimensional Conformation of Folded Polymers in Single Crystals

    NASA Astrophysics Data System (ADS)

    Hong, You-lee; Yuan, Shichen; Li, Zhen; Ke, Yutian; Nozaki, Koji; Miyoshi, Toshikazu

    2015-10-01

    The chain-folding mechanism and structure of semicrystalline polymers have long been controversial. Solid-state NMR was applied to determine the chain trajectory of 13C CH3 -labeled isotactic poly(1-butene) (i PB 1 ) in form III chiral single crystals blended with nonlabeled i PB 1 crystallized in dilute solutions under low supercooling. An advanced 13C - 13C double-quantum NMR technique probing the spatial proximity pattern of labeled 13C nuclei revealed that the chains adopt a three-dimensional (3D) conformation in single crystals. The determined results indicate a two-step crystallization process of (i) cluster formation via self-folding in the precrystallization stage and (ii) deposition of the nanoclusters as a building block at the growth front in single crystals.

  1. Pulse shape discrimination with new single crystal organic scintillators

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

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

  2. 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 1200C. 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.

  3. Double hydrogen bonded ferroelectric liquid crystals: A study of field induced transition (FiT)

    NASA Astrophysics Data System (ADS)

    Vijayakumar, V. N.; Madhu Mohan, M. L. N.

    2009-12-01

    A novel series of chiral hydrogen bonded liquid crystals have been isolated. Hydrogen bond was formed between chiral nonmesogen ingredient levo tartaric acid and mesogenic p-n-alkoxybenzoic acids. Phase diagram was constructed from the transition temperatures obtained by DSC and polarizing optical microscopic (POM) studies. Thermal and electrical properties exhibited by three complexes namely LTA+8BA, LTA+7BA and LTA+5BA were discussed. Salient feature of the present work was the observation of a reentrant smectic ordering in LTA+8BA complex designated as C r? phase. This reentrant phenomenon was confirmed by DSC thermograms, optical textures of POM and temperature variation of capacitance and dielectric loss studies. Tilt angle was measured in smectic C ? and reentrant smectic C r? phases. Another interesting feature of the present investigation was the observation of a field induced transition (FiT) in the LTA+ nBA homologous series. Three threshold field values were noticed which give rise to two new phases (E 1 and E 2) induced by electric field and on further enhancement of the applied field the mesogen behaves like an optical shutter. FiT is reversible in the sense that when applied field is removed the original texture was restored.

  4. Investigation of the optical response of photonic crystal nanocavities in ferroelectric oxide thin film

    NASA Astrophysics Data System (ADS)

    Lin, Pao Tai; Russin, William A.; Joshi-Imre, Alexandra; Ocola, Leonidas E.; Wessels, B. W.

    2015-10-01

    The optical properties of BaTiO3 two dimensional photonic crystal (PhC) nanocavities were investigated. Two types of nanocavities consisting of dopants and vacancies with PhC periodicities ranging from 200 to 550 nm were evaluated. The images from laser scanning confocal microscopy show the optical scattering of the PhC cavities is highly wavelength dependent. An optical intensity reversal is observed when the wavelength of probe light shifts by 29 nm. Meanwhile, intensity contrast between the nanocavity and its adjacent PhCs is enhanced as the PhC periodicity becomes shorter than the probe wavelength. To determine the photonic band structures fluorescence from dye covered PhCs were imaged and analyzed. A strong enhancement of fluorescence is observed for the PhC with a period of 200 nm. Upon comparison to the 2D finite difference time domain calculations, the enhancement is attributed to strong light localization within the PhC nanocavity. As a result, the in-plane lightwave propagation is prohibited that results in an increase in the vertical light scattering.

  5. Designed three-dimensional freestanding single-crystal carbon architectures.

    PubMed

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

    2014-11-25

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

  6. Study of single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  7. Effect of gamma ray irradiation on sodium borate single crystals

    NASA Astrophysics Data System (ADS)

    Kalidasan, M.; Asokan, K.; Baskar, K.; Dhanasekaran, R.

    2015-12-01

    In this work, the effects of 5 kGy, 10 kGy and 20 kGy doses of gamma ray irradiation on sodium borate, Na2[B4O5(OH)4](H2O)8 single crystals have been studied. Initially these crystals were grown by solution growth technique and identified as monoclinic using X-ray diffraction analysis. X-ray rocking curves confirm the formation of crystalline defects due to gamma rays in sodium borate single crystals. The electron paramagnetic resonance spectra have been recorded to identify the radicals created due to gamma ray irradiation in sodium borate single crystals. The thermoluminescence glow curves due to the defects created by gamma rays in this crystal have been observed and their kinetic parameters were calculated using Chen's peak shape method. The optical absorption increases and photoluminescence spectral intensity decreases for 5 kGy and 20 kGy doses gamma ray irradiated crystals compared to pristine and 10 kGy dose irradiated one. The effect of various doses of gamma rays on vibrational modes of the sodium borate single crystals was studied using FT-Raman and ATR-FTIR spectral analysis. The dielectric permittivity, conductance and dielectric loss versus frequency graphs of these crystals have been analyzed to know the effect of gamma ray irradiation on these parameters.

  8. 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.

  9. On the deformation mechanisms in single crystal Hadfield manganese steels

    SciTech Connect

    Karaman, I.; Sehitoglu, H.; Gall, K.; Chumlyakov, Y.I.

    1998-02-13

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

  10. 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.

  11. Some Properties Of Synthetic Single Crystal And Thin Film Diamonds

    NASA Astrophysics Data System (ADS)

    Yazu, Shuji; Sato, Shuichi; Fujimori, Naoji

    1989-01-01

    Large synthetic diamond single crystals, in sizes up to 1.4 ct, are produced on 4 commercial basis for some industrial application fields by Sumitomo Electric. The crystals are yellow colored type Ib stones which contain lower amounts of nitrogen (up to about 100 ppm) dispersed through the crystal structure in the form of singly substituting atoms. The impurity controlled type lb crystals have the highest thermal conductivity which is equivalent to that of pure type IIa crystals. Optical and thermal properties of diamond crystals are strongly affected by dispersed impurities. We studied the kinds of dispersed impurities and amounts of those impurity atoms in our synthesized crystals by SIMS. A relation of the thermal conductivities and the nitrogen concentrations of the crystals was examined. The state of nitrogen impurity in the crystals could be transformed by electron irradiation and subsequent high temperature annealing. The reaction rates for the transformation Ib nitrogen to type IaA aggregates and differences in crystal growth sectors have been studied. Vapor phase deposited diamond films are hopeful candidates for optical application of diamond. Preliminary spectroscopic analysis has been done for the free standing polycrystalline films.

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

    SciTech Connect

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

    2015-05-04

    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.

  13. Inhomogeneities in single crystals of cuprate oxide superconductors

    NASA Technical Reports Server (NTRS)

    Moorjani, K.; Bohandy, J.; Kim, B. F.; Adrian, F. J.

    1991-01-01

    The next stage in the evolution of experimental research on the high temperature superconductors will require high quality single crystals and epitaxially grown crystalline films. However, inhomogeneities and other defects are not uncommon in single crystals of cuprate oxide superconductors, so a corollary requirement will be a reliable method for judging the quality of these materials. The application of magnetically modulated resistance methods in this task is briefly described and illustrated.

  14. 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.

  15. Single femtosecond laser pulse-single crystal formation of glycine at the solution surface

    NASA Astrophysics Data System (ADS)

    Liu, Tsung-Han; Uwada, Takayuki; Sugiyama, Teruki; Usman, Anwar; Hosokawa, Yoichiroh; Masuhara, Hiroshi; Chiang, Ting-Wei; Chen, Chun-Jung

    2013-03-01

    We demonstrate femtosecond laser-induced crystallization of glycine from its supersaturated solution depending on laser tunable parameters (pulse energy and repetition rate) and focal position, and examine the crystallization probability, crystal morphology, and crystal polymorph. The generation of cavitation bubble through multiphoton absorption of water depends on input laser pulse energy and repetition rate, which strongly determine morphology and number of the obtained crystals. Significant increase in the crystallization probability is observed by irradiating the femtosecond laser pulses to the air/solution interface, and single pulse-induced single crystal formation is successfully achieved. The crystallization mechanism is discussed in view of inhomogeneous mechanical stress induced by cavitation bubble generation and molecular assembly characteristics of the surface.

  16. Synthesis, crystal growth and characterization of an organic material: 2-Aminopyridinium succinate succinic acid single crystal.

    PubMed

    Magesh, M; Bhagavannarayana, G; Ramasamy, P

    2015-11-01

    The 2-aminopyridinium succinate succinic acid (2APS) single crystal was synthesized and grown by slow evaporation method. The crystal structure has been confirmed by powder X-ray diffraction as well as single crystal X-ray diffraction analysis. The crystal perfection has been evaluated by high resolution X-ray diffraction (HRXRD). The grown crystal is transparent in the visible and near infrared region. The optical absorption edge was found to be 348 nm. The fluorescence study was carried out by spectrofluorophotometer. The thermal stability of grown crystal was analyzed by thermal gravimetric and differential thermal gravimetric (TG-DTA) analysis. Vicker's hardness study carried out at room temperature shows increased hardness while increasing the load. Laser damage threshold value was determined by Nd:YAG laser operating at 1064 nm. The grown 2APS crystal was characterized by etching studies using water as etchant. PMID:26099828

  17. Growth technology of piezoelectric langasite single crystal

    NASA Astrophysics Data System (ADS)

    Uda, Satoshi; Wang, Shou-Qi; Konishi, Nozomi; Inaba, Hitoshi; Harada, Jiro

    2005-02-01

    Although langasite (La 3Ga 5SiO 14) is an incongruent material, it can directly grow from the "pseudo-congruent melt" via the Czochralski method using a langasite seed crystal when the appropriate supercooling is provided. This may be explained by the extension of the univariant line of langasite+liquid into the primary phase field of Ga-containing lanthanum silicate. Free energies serving to solute transport, growth kinetics, surface creation and defect generation are summed up to be the total supercooling necessary for growth which may be larger for the formation of Ga-containing lanthanum silicate and smaller for langasite than the actual supercooling. The growth technology of 4-in-size crystal along [0 1 1 1] is optimized by understanding (i) the importance of the prior annealing of the melt to acquire the suitable supercooling for growth, (ii) the transform of the unstable growth interface, (0 1 1 1), into the complex of more stable principal planes, and (iii) the necessity of the accurate evaluation method to examine the homogeneity of the grown crystal. Issues of (i) and (ii) are interrelated. Physical crystal properties at high temperature are also demonstrated.

  18. Synthetic Superconductivity in Single-Layer Crystals

    NASA Astrophysics Data System (ADS)

    Levitov, Leonid; Borgnia, Dan; Lee, Patrick

    2015-03-01

    Electronic states in atomically thin 2D crystals are fully exposed and can couple to extrinsic degrees of freedom via long-range Coulomb interactions. Novel many-body effects in such systems can be engineered by embedding them in a polar environment. Superconducting pairing interaction induced in this way can enhance the intrinsic electron-phonon pairing mechanism. We take on this notion, which was around since the 60's (''excitonic superconductivity''), and consider synthetic superconductivity (SSC) induced in 2D crystals by a polar environment. One interesting aspect of this scenario is that Coulomb repulsion acts as superconductivity friend rather than a foe. Such repulsion-to-attraction transmutation allows to access strong-coupling superconductivity regime even when intrinsic pairing interaction is weak. We analyze pairing interaction in 2D crystals placed atop a highly polarizable dielectric with dispersive permittivity ? (?) and predict that by optimizing system parameters a substantial enhancement can be achieved. We also argue that the SSC mechanism can be responsible, at least in part, for 100 K superconductivity recently observed in FeSe monolayers grown on SrTiO3 substrate, with Tc more than 10 times larger than in bulk 3D FeSe crystals, arxiv:1406.3435.

  19. Top-Seeded Solution Growth of Pb[(Zn1/3Nb2/3)0.93Ti0.07]O3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Karaki, Tomoaki; Nakamoto, Maki; Adachi, Masatoshi

    2002-11-01

    Top-seeded solution growth (TSSG) of relaxor-based ferroelectric single crystal Pb[(Zn1/3Nb2/3)0.93Ti0.07]O3 (PZNT93/7) was investigated. PbO and PbO+B2O3 were used as fluxes. The solution compositions were (PZNT93/7)/PbO]=70/30 wt% and (PZNT93/7)/PbO/B2O3=70/29/1 wt%. A platinum stick, PZNT93/7 single crystal and Pb[(Mg1/3Nb2/3)0.65Ti0.35]O3 (PMNT65/35) single crystal were used as seeds. The addition of B2O3 was used to lower the growth temperature and reduce the rate of PbO evaporation. Crystals grown inside the melting solution had a pure perovskite structure and their Curie temperature was 168C, corresponding to PZNT93/7 composition. However, it was found that the perovskite crystals decomposed little by little from the crystal surface to undesirable pyrochlore after being pulled out of the melt and exposed to air during the growth. Crystals grown at the melt surface were originally of pyrochlore structure. The investigated results revealed the possibility of growing these single crystals by a continually charged TSSG technique.

  20. SINGLE CRYSTAL NIOBIUM TUBES FOR PARTICLE COLLIDERS ACCELERATOR CAVITIES

    SciTech Connect

    MURPHY, JAMES E

    2013-02-28

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

  1. Differences between individual ZSM-5 crystals in forming hollow single crystals and mesopores during base leaching.

    PubMed

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

    2015-04-13

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

  2. 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.

  3. An analytical model for porous single crystals with ellipsoidal voids

    NASA Astrophysics Data System (ADS)

    Mbiakop, A.; Constantinescu, A.; Danas, K.

    2015-11-01

    A rate-(in)dependent constitutive model for porous single crystals with arbitrary crystal anisotropy (e.g., FCC, BCC, HCP, etc.) containing general ellipsoidal voids is developed. The proposed model, denoted as modified variational model (MVAR), is based on the nonlinear variational homogenization method, which makes use of a linear comparison porous material to estimate the response of the nonlinear porous single crystal. Periodic multi-void finite element simulations are used in order to validate the MVAR for a large number of parameters including cubic (FCC, BCC) and hexagonal (HCP) crystal anisotropy, various creep exponents (i.e., nonlinearity), several stress triaxiality ratios, general void shapes and orientations and various porosity levels. The MVAR model, which involves a priori no calibration parameters, is found to be in good agreement with the finite element results for all cases considered in the rate-dependent context. The model is then used in a predictive manner to investigate the complex response of porous single crystals in several cases with strong coupling between the anisotropy of the crystal and the (morphological) anisotropy induced by the shape and orientation of the voids. Finally, a simple way of calibrating the MVAR with just two adjustable parameters is depicted in the rate-independent context so that an excellent agreement with the FE simulation results is obtained. In this last case, this proposed model can be thought as a generalization of the Gurson model in the context of porous single crystals and general ellipsoidal void shapes and orientations.

  4. 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.

  5. 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.

  6. Direct observation of interlocked domain walls and topological four-state vortex-like domain patterns in multiferroic YMnO{sub 3} single crystal

    SciTech Connect

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

    2015-03-16

    Using the advanced spherical aberration-corrected high angle annular dark field scanning transmission electron microscope imaging techniques, we investigated atomic-scale structural features of domain walls and domain patterns in YMnO{sub 3} single crystal. Three different types of interlocked ferroelectric-antiphase domain walls and two abnormal topological four-state vortex-like domain patterns are identified. Each ferroelectric domain wall is accompanied by a translation vector, i.e., 1/6[210] or ?1/6[210], demonstrating its interlocked nature. Different from the four-state vortex domain patterns caused by a partial edge dislocation, two four-state vortex-like domain configurations have been obtained at atomic level. These observed phenomena can further extend our understanding of the fascinating vortex domain patterns in multiferroic hexagonal rare-earth manganites.

  7. 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.

  8. 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.

  9. Selective Metal Cation Capture by Soft Anionic Metal-Organic Frameworks via Drastic Single-Crystal-to-Single-Crystal Transformations

    SciTech Connect

    Tian, Jian; Saraf, Laxmikant V.; Schwenzer, Birgit; Taylor, S. M.; Brechin, Euan K.; Liu, Jun; Dalgarno, S. J.; Thallapally, Praveen K.

    2012-05-25

    Flexible anionic metal-organic frameworks transform to neutral heterobimetallic systems via single-crystal-to-single-crystal processes invoked by cation insertion. These transformations are directed by cooperative bond breakage and formation, resulting in expansion or contraction of the 3D framework by up to 33% due to the flexible nature of the organic linker. These MOFs displays highly selective uptake of divalent transition metal cations (Co2+ and Ni2+ for example) over alkali metal cations (Li+ and Na+).

  10. Metal-center exchange of tetrahedral cages: single crystal to single crystal and spin-crossover properties.

    PubMed

    Zhang, Feng-Li; Chen, Jia-Qian; Qin, Long-Fang; Tian, Lei; Li, Zaijun; Ren, Xuehong; Gu, Zhi-Guo

    2016-04-01

    An effective single crystal to single crystal transformation from a tetrahedral Ni cage to an FeNi cage was demonstrated. The iron(ii) centers of the FeNi cage can be induced to display spin crossover behaviors with an increasing amount of Fe(ii) ions. The SCSC metal-center exchange provides a powerful approach to modify solid magnetic properties. PMID:26955799

  11. Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot.

    PubMed

    Bouwes Bavinck, Maaike; Jns, Klaus D; Zieli?ski, Michal; Patriarche, Gilles; Harmand, Jean-Christophe; Akopian, Nika; Zwiller, Val

    2016-02-10

    We report the first comprehensive experimental and theoretical study of the optical properties of single crystal phase quantum dots in InP nanowires. Crystal phase quantum dots are defined by a transition in the crystallographic lattice between zinc blende and wurtzite segments and therefore offer unprecedented potential to be controlled with atomic layer accuracy without random alloying. We show for the first time that crystal phase quantum dots are a source of pure single-photons and cascaded photon-pairs from type II transitions with excellent optical properties in terms of intensity and line width. We notice that the emission spectra consist often of two peaks close in energy, which we explain with a comprehensive theory showing that the symmetry of the system plays a crucial role for the hole levels forming hybridized orbitals. Our results state that crystal phase quantum dots have promising quantum optical properties for single photon application and quantum optics. PMID:26806321

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  14. 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.; Xu, G. S.; Zhang, X. L.; Hu, Z. G.

    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}?=?3.173.18?eV, E{sub a}?=?3.413.61?eV, and E{sub b}?=?4.744.81?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.

  15. Organic single crystal transistor characteristics of single-crystal phase pentacene grown by ionic liquid-assisted vacuum deposition

    NASA Astrophysics Data System (ADS)

    Takeyama, Yoko; Ono, Shimpei; Matsumoto, Yuji

    2012-08-01

    Organic transistor characteristics of single-crystal phase pentacene were investigated. Ionic liquids (ILs) were used as not only a gate dielectric material in the transistors but also a crystallization solvent in vacuum deposition of pentacene. The crystal sizes reached 200 ?m and their surface exhibits a molecularly step-and-terrace structure. There was no sign of IL molecules inside the crystal, and the impurity level of 6,13-pentacenequinone was also reduced. The average value of the field-effect mobility was not so inferior to those for the conventional pentacene single crystals, and the highest value exceeded 5 cm2/Vs, with the on/off current ratio of 104.

  16. Creep of CoO single crystals.

    NASA Technical Reports Server (NTRS)

    Clauer, A. H.; Seltzer, M. S.; Wilcox, B. A.

    1971-01-01

    The crystals were creep tested in compression over ranges of temperature, stress, and oxygen pressure. The creep curves were S-shaped, and only the inflection creep rate was analyzed. A formula is presented for the inflection creep rate in the range from 1000 to 1200 C, 850 to 1700 psi, and 0.001 to 1 atm oxygen. Slip was found to occur on two orthogonal slip systems. The presence of subboundaries was observed by optical and transmission electron microscopy. It is suggested that the creep rate is controlled by oxygen diffusion.

  17. Growth and properties of InP single crystals

    NASA Astrophysics Data System (ADS)

    Dun-fu, Fang; Xiang-xi, Wang; Yong-quan, Xu; Li-tong, Tan

    1984-04-01

    InP single crystals with various dopants including S, Sn, Zn and Fe have been grown successfully by the Czochralski method under high pressure with liquid encapsulation. It is found that by carefully adjusting the thermal symmetry of the heating field and by further improving the quality of the polycrystals and by dehydrating B 2O 3, twin-free InP crystals can be obtained even with a shoulder angle of up to 54, and defects caused by thermal decomposition appear on the surface of the crystals during pulling. Furthermore, a comparison of the crystal perfection and uniformity between S-doped and Sn-doped InP crystals shows that the quality of the former is better than that of the latter. Dislocation-free Zn-doped p-InP single crystals without precipitates have also been easily obtained when the carrier concentration is greater than 210 18 cm -3 and the diameter less than 30 mm. By controlling the iron content, semi-insulating thermally stable single crystals of InP doped with ?0.03 wt% of Fe without precipitates and with a homogeneous resistivity can be produced.

  18. 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

  19. 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.

  20. Single crystal growth and characterization of holmium tartrate trihydrate

    NASA Astrophysics Data System (ADS)

    Want, Basharat; Ahmad, Farooq; Kotru, P. N.

    2007-02-01

    The growth of holmium tartrate trihydrate (HTT) single crystals is achieved in organic (agar-agar) as well as in inorganic (silica) gels by single gel diffusion method. Results of the study on nucleation kinetics of crystals grown in silica gel are described. The crystals exhibit the morphological form of a tetragonal dipyramidal class with {0 0 1} and {1 1 1} as dominant faces. Elemental and thermogravimetric analysis (TGA) supplemented by energy dispersive analysis of X-rays (EDAX) support the suggested chemical formula of the grown crystals to be [Ho (C 4H 4O 6) (C 4H 5O 6)3H 2O]. Single crystal X-ray diffraction (XRD) studies indicate that the crystals belong to tetragonal system with the cell parameters a=5.97 , c=36.09 , bearing the space group P4 1. Fourier transform infrared (FT-IR) spectroscopic study indicates the presence of tartrate ligands and suggests that one of the tartrate ions is singly ionized. TGA suggests that the material is thermally stable up to 220 C.

  1. Enhancing the Mechanical Properties of Single-Crystal CVD Diamond

    SciTech Connect

    Liang, Q.; Yan, C; Meng, Y; Lai, J; Krasnicki, S; Mao, H; Hemley, R

    2009-01-01

    Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness ({approx}78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

  2. Low-cost single-crystal turbine blades, volume 2

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Dennis, R. E.; Heath, B. R.

    1984-01-01

    The overall objectives of Project 3 were to develop the exothermic casting process to produce uncooled single-crystal (SC) HP turbine blades in MAR-M 247 and higher strength derivative alloys and to validate the materials process and components through extensive mechanical property testing, rig testing, and 200 hours of endurance engine testing. These Program objectives were achieved. The exothermic casting process was successfully developed into a low-cost nonproperietary method for producing single-crystal castings. Single-crystal MAR-M 247 and two derivatives DS alloys developed during this project, NASAIR 100 and SC Alloy 3, were fully characterized through mechanical property testing. SC MAR-M 247 shows no significant improvement in strength over directionally solidified (DS) MAR-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. Firtree testing, holography, and strain-gauge rig testing were used to determine the effects of the anisotropic characteristics of single-crystal materials. No undesirable characteristics were found. In general, the single-crystal material behaved similarly to DS MAR-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined. These blades were successfully engine-tested.

  3. Ferroelectricity induced by ferriaxial crystal rotation and spin helicity in a B -site-ordered double-perovskite multiferroic In2NiMnO6

    NASA Astrophysics Data System (ADS)

    Terada, Noriki; Khalyavin, Dmitry D.; Manuel, Pascal; Yi, Wei; Suzuki, Hiroyuki S.; Tsujii, Naohito; Imanaka, Yasutaka; Belik, Alexei A.

    2015-03-01

    We have performed dielectric measurements and neutron diffraction experiments on the double perovskite In2NiMnO6 . A ferroelectric polarization, P ?30 ? C /m2, is observed in a polycrystalline sample below TN= 26 K where a magnetic phase transition occurs. The neutron diffraction experiment demonstrates that a complex noncollinear magnetic structure with "cycloidal" and "proper screw" components appears below TN, which has the incommensurate propagation vector k =(ka,0 ,kc;ka?0.274 ,kc?-0.0893 ) . The established magnetic point group 21' implies that the macroscopic ferroelectric polarization is along the monoclinic b axis. Recent theories based on the inverse Dzyaloshinskii-Moriya effect allow us to specify two distinct contributions to the polarization of In2NiMnO6 . One of them is associated with the cycloidal component, p1?ri j(SiSj)? , and the other with the proper screw component, p2?[ri j.(SiSj)||] A . The latter is explained by coupling between spin helicity and "ferriaxial" crystal rotation with macroscopic ferroaxial vector A , characteristic of the B -site ordered perovskite systems with out-of-plane octahedral tilting.

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

    SciTech Connect

    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.

  5. Single-Crystal Structure of a Covalent Organic Framework

    SciTech Connect

    Zhang, YB; Su, J; Furukawa, H; Yun, YF; Gandara, F; Duong, A; Zou, XD; Yaghi, OM

    2013-11-06

    The crystal structure of a new covalent organic framework, termed COF-320, is determined by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepared by an imine condensation of tetra-(4-anilyl)methane and 4,4'-biphenyldialdehyde in 1,4-dioxane at 120 degrees C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m(2)/g and a methane total uptake of 15.0 wt % (176 cm(3)/cm(3)) at 25 degrees C and 80 bar. The successful determination of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chemistry.

  6. Irradiation effects on ammonium penta borate (APB) single crystals

    NASA Astrophysics Data System (ADS)

    Prabha, K.; Babu, M. Ramesh; Prabhukanthan, P.; Chen, H.; Chen, X. L.; Sagayaraj, P.

    2015-02-01

    Single crystals of ammonium penta borate (APB) were irradiated with 120 MeV Ag9+ swift heavy ions (SHI) of fluence 11013 ions/cm2. The UV-visible spectrum of irradiated crystal shows slight shift in the absorption edge and it also indicates the non uniformity in its absorbance level. An attempt was made to explain the surface damage caused due to SHI irradiation using AFM and SEM images.

  7. Growth and characterization of lithium yttrium borate single crystals

    SciTech Connect

    Singh, A. K.; Singh, S. G.; Tyagi, M.; Desai, D. G.; Sen, Shashwati

    2014-04-24

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

  8. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  9. 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.

  10. CuInP?S? Room Temperature Layered Ferroelectric.

    PubMed

    Belianinov, A; He, Q; Dziaugys, A; Maksymovych, P; Eliseev, E; Borisevich, A; Morozovska, A; Banys, J; Vysochanskii, Y; Kalinin, S V

    2015-06-10

    We explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP2S6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleaved bulk surfaces, whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V-likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. The existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing "graphene family". PMID:25932503

  11. Synthesis and properties of erbium oxide single crystals

    SciTech Connect

    Petrovic, J.J.; Romero, R.S.; Mendoza, D.; Kukla, A.M.; Hoover, R.C.; McClellan, K.J.

    1999-04-01

    Erbium oxide (Er{sub 2}O{sub 3}, erbia) is a highly stable cubic rare earth oxide with a high melting point of 2,430 C. Because of this, it may have potential applications where high temperature stability and corrosion resistance are required. However, relatively little is known about the properties of this oxide ceramic. The authors have employed a xenon optical floating zone unit with a temperature capability of 3,000 C to grow high quality single crystals of erbia. The conditions for single crystal growth of erbia have been established. The mechanical properties of erbia single crystals have been initially examined using microhardness indentation as a function of temperature.

  12. Internal Hydrogen-induced Embrittlement in Iron Single Crystals

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Sheng

    A thermodynamic model for internal hydrogen-induced embrittlement (HIE) in single crystals is proposed. The model is based on the assumption that the ductile versus brittle transition is controlled by the competition between dislocation emission from the crack tip and cleavage decohesion of the lattice. Embrittlement in single crystals is induced by segregation of hydrogen in solid solution to the crack tip and/or the fracture surfaces during separation, which reduces the cohesive energy of the lattice. This process will occur when the mobility of hydrogen atoms is high so that a surface excess of hydrogen can be built up during separation. The model predictions for hydrogen induced cleavage in iron single crystals are presented.

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

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

    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 to judge the preference or not for the nucleation of deformation twins and stacking faults in various face-centered-cubic metals in terms of the critical stress for dislocation glide or twinning by considering the intrinsic factors, such as stacking fault energy, crystallographic orientation, and grain size. The new finding of deformation induced microtwins and stacking faults in aluminum single crystal and the proposed model should be of interest to a broad community.

  14. Elastic constants of single crystal Hastelloy X at elevated temperatures

    SciTech Connect

    Canistraro, H.A.; Jordan, E.H.; Shi Shixiang; Favrow, L.H.; Reed, F.A.

    1998-07-01

    An acoustic time of flight technique is described in detail for measuring the elastic constants of cubic single crystals that allows for the constants to be determined at elevated temperature. Although the overall technique is not new, various aspects of the present work may prove extremely useful to others interested in finding these values, especially for aerospace materials applications. Elastic constants were determined for the nickel based alloy, Hastelloy X from room temperature to 1,000 C. Accurate elastic constants were needed as part of an effort to predict both polycrystal mechanical properties and the nature of grain induced heterogeneous mechanical response. The increased accuracy of the acoustically determined constants resulted in up to a 15% change in the predicted stresses in individual grains. These results indicate that the use of elastic single crystal constants of pure nickel as an approximation for the constants of gas turbine single crystal alloys, which is often done today, is inaccurate.

  15. 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.

  16. 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.

  17. 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.

  18. Crystal growth and characterization of semiorganic single crystals of L-histidine family for NLO applications

    NASA Astrophysics Data System (ADS)

    Anandan, Pandurangan; Jayavel, Ramasamy

    2011-05-01

    Single crystals of L-histidine hydrochloride monohydrate and tartaric acid mixed L-histidine hydrochloride monohydrate have been grown by slow evaporation solution growth technique from appropriate mixtures of respective chemicals. Single crystal and powder X-ray diffraction analyses, Fourier transform infrared, nuclear magnetic resonance spectral analysis, thermo-gravimetric (TG), differential thermal analysis (DTA) have been employed to characterize the as-grown crystals. It is observed to be a wide transparency window for both the crystals from 300 to 1000 nm, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics have been studied using Q switched Nd: YAG laser ( ?=1064 nm). The second harmonic generation conversion efficiency of the grown crystal shows the suitability for frequency conversion applications.

  19. 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.

  20. 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.

  1. Effect of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes on electro-optical and dielectric properties of a ferroelectric liquid crystal.

    PubMed

    Ghosh, S; Nayek, P; Roy, S K; Gangopadhyay, R; Rahaman Molla, M; Majumder, T P

    2011-04-01

    A detailed comparative study of the dielectric and electro-optical properties of a ferroelectric liquid crystal (FLC) and FLC after having doped with conducting polymer Poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes is done. The electro-optic study reveals a lower electrical response time, rotational viscosity and spontaneous polarization in the FLC/PEDOT nanocomposite system. By fitting the capacitance with voltage in a Preisach model, four dipolar species in both FLC and composites system have been obtained. The orientation of the four dipolar species in the composites system is such that the effective dipole moment in the transverse direction of the FLC molecule is less than that in FLC compound. PMID:21476135

  2. Preparation of single-crystal copper ferrite nanorods and nanodisks

    SciTech Connect

    Du Jimin; Liu Zhimin . E-mail: liuzm@iccas.ac.cn; Wu Weize; Li Zhonghao; Han Buxing . E-mail: hanbx@iccas.ac.cn; Huang Ying

    2005-06-15

    This article, for the first time, reports the preparation of single-crystal copper ferrite nanorods and nanodisks. Using amorphous copper ferrite nanoparticles synthesized by reverse micelle as reaction precursor, single-crystal copper ferrite nanorods were synthesized via hydrothermal method in the presence of surfactant polyethylene glycol (PEG), however, copper ferrite nanodisks were prepared through the same procedures except the surfactant PEG. The resulting nanomaterials have been characterized by powder X-ray diffraction (XRD), selected electron area diffraction (SEAD), and transmission electron microscopy (TEM). The bulk composition of the samples was determined by means of X-ray photoelectron spectroscopy (XPS)

  3. How a silver dendritic mesocrystal converts to a single crystal

    SciTech Connect

    Fang, J.; Ding, B.; Song, X.; Han, Y.

    2008-05-02

    In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the transformation, there is a crystallographic fusion process, dominated by oriented attachment mechanism. Ostwald ripening also plays an important role in forming smooth surface and regular shape of the final nanocrystal.

  4. 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.

  5. 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.

  6. Performance of a Single-Crystal Diamond-Pixel Telescope

    NASA Astrophysics Data System (ADS)

    Hits, Dmitry; Schnetzer, Steve; Stone, Robert; Bartz, Ed; Doroshenko, John; Halyo, Valerie; Harrop, Bert; Hunt, Adam; Marlow, Dan; Johns, Will; Bugg, William; Hollingsworth, Matt; Spanier, Stefan; Hall-Wilton, Richard; Ryjov, Vladimir; Pernicka, Manfred

    2010-02-01

    We will present the results of a test beam study of a single-crystal, diamond, pixel telescope. This telescope is a prototype for a dedicated luminosity monitor for CMS. The telescope has three equally-spaced planes with a total length of 7.5 cm. Each plane consists of a single-crystal CVD diamond with an active area of 4mm x 4mm bump-bonded to a PSI46v2 pixel readout chip. The study was carried out in a high energy pion beam at the CERN SPS. We will present results on the performance of the telescope including occupancy, efficiency, pulse height distributions and tracking. )

  7. Crystal growth and spectral studies of nonlinear optical ?-glycine single crystal grown from phosphoric acid

    NASA Astrophysics Data System (ADS)

    Parimaladevi, R.; Sekar, C.

    2010-09-01

    Single crystals of the organic nonlinear material ?-glycine have been grown in the presence of phosphoric acid by slow-evaporation method. The crystal structure is confirmed by X-ray powder diffraction method. The thermal stability and decomposition of the sample have been studied by thermal analysis. The result shows that the transition temperature, i.e. transition from ?- to ?-glycine is enhanced from 165 C to 191 C. The modes of vibrations of different molecular groups present in glycine have been identified by spectral analyses. The transmittance spectrum of ?-glycine crystal shows that the lower UV cut-off wavelength lies at 230 nm. Second harmonic generation (SHG) conversion efficiency has been estimated as 125 mV and the output power by the crystal was 1.3 times that of potassium dihydrogen phosphate (KDP) crystal. The dielectric and microhardness measurements have been carried out on the ?-glycine crystal.

  8. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  9. Quantum properties of charged ferroelectric domain walls

    NASA Astrophysics Data System (ADS)

    Sturman, B.; Podivilov, E.; Stepanov, M.; Tagantsev, A.; Setter, N.

    2015-12-01

    We consider the properties of charged domain walls in ferroelectrics as a quantum problem. This includes determination of self-consistent attracting 1D potential for compensating charge carriers, the number and positions of discrete energy levels in this potential, dependencies on the ferroelectric characteristics, as well as the spatial structure and formation energy of the wall. Our description is based on the Hartree and Thomas-Fermi methods and Landau theory for the ferroelectric transitions. Changeover from a few to many quantum levels (with the electron binding energies ˜1 eV) is controlled by a single characteristic parameter. The quantum models well describe the core of the wall, whose width is typically ˜10 nm. Additionally, the walls possess pronounced long-range tails which are due to trap recharging. For the trap concentration Nt=(1017-1018) cm-3 , the tail length ℓ is of the μ m scale. On the distances much larger than ℓ the walls are electrically uncoupled from each other and the crystal faces.

  10. Small- and strong-signal dielectric response in a single-crystal film of partially deuterated betaine phosphite

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Lemanov, V. V.

    2011-06-01

    Poly- and single-crystal films of betaine phosphite deuterated to 20% have been grown by evaporation on NdGaO3 (001) substrates with a preliminarily deposited planar interdigital structure of electrodes. The small-signal dielectric response in the 0.1-100.0-kHz frequency range has revealed a strong anomaly in capacitance upon the transition of the films to the ferroelectric state. Application of a bias field brings about suppression and a slight shift of the dielectric anomaly toward higher temperatures. The strong-signal dielectric response has been studied by the Sawyer-Tower method over the frequency range 0.06-3.00 kHz both in the para- and ferroelectric phases. In contrast to the case of a plane-parallel capacitor, in the planar structure studied, the dielectric hysteresis loops exhibit a very small coercivity at low frequencies, which grows with increasing frequency. This difference should be assigned to different domain structures formed in a planeparallel capacitor and in a planar structure in a saturating field. The growth of hysteresis with increasing frequency in a planar structure is considered to be associated with the domain wall motion.

  11. Nanocharacterization of the negative stiffness of ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Alipour Skandani, A.; Ctvrtlik, R.; Al-Haik, M.

    2014-08-01

    Phase changing materials such as ferroelectric materials could exhibit negative stiffness under certain thermomechanical environments. This negative stiffness is embodied by a deflection along the opposite direction of the applied load. So far negative stiffness materials were investigated with the specific morphology of embedded inclusions in stiff matrices then the resulting composite is studied to measure the behavior of each constituent indirectly. In this study, a modified nonisothermal nanoindentation method is developed to measure the negative stiffness of triglycine sulfate single crystal directly. This in-situ method is intended to first demonstrate the feasibility of detecting the negative stiffness via nanoindentation and nanocreep of a ferroelectric material at its Curie point and then to quantify the negative stiffness without the need for embedding the crystal within a stiffer matrix.

  12. Near-field resonance shifts of ferroelectric barium titanate domains upon low-temperature phase transition

    SciTech Connect

    Dring, Jonathan; Ribbeck, Hans-Georg von; Kehr, Susanne C.; Eng, Lukas M.; Fehrenbacher, Markus

    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.

  13. Origin of the enhanced piezoelectric thermal stability in BiScO3-PbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Kong, Lingping; Liu, Gang; Zhang, Shujun; Yang, Wenge

    2015-06-01

    BiScO3-PbTiO3 single crystals were reported to possess high piezoelectric coefficient of 1200 pC/N and Curie temperature of >400 C, exhibiting excellent thermal stability of properties up to 350 C. However, the origin of the thermal stability is yet unclear. In this research, high resolution synchrotron-based technique was used to study the temperature driven structural evolution in BiScO3-PbTiO3 system, where two competing symmetries and local distortion were observed, accounting for the high piezoelectric activity. A strong correlation between thermal stability of structure and temperature-dependent properties was established, which will benefit the design of ferroelectric materials with broad temperature usage range.

  14. Ultrasonic characterization of single crystal langatate

    NASA Astrophysics Data System (ADS)

    Sturtevant, Blake T.

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

  15. 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.

  16. Recent developments in high curie temperature perovskite single crystals.

    PubMed

    Zhang, Shujun; Randall, Clive A; Shrout, Thomas R

    2005-04-01

    The temperature behavior of various relaxor-PT piezoelectric single crystals was investigated. Owing to a strongly curved morphotropic phase boundary, the usage temperature of these perovskite single crystals is limited by TR-T--the rhombohedral to tetragonal phase transformation temperature--which occurs a significantly lower temperatures than the Curie temperature Tc. Attempts to modify the temperature usage range of Pb(Zn1/3Nb2/3)O3--PbTiO3 (PZNT) and Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMNT) rhombohedral crystals (Tx to approximately 150-170 degrees C, TR-T to approximately 60-120 degrees C) using minor dopant modifications were limited, with little success. Of significant potential are crystals near the mor photropic phase boundary in the Pb(Yb1/2Nb1/2)O3-PbTiO3 (PYNT) system, with a Tc > 330 degrees C, even thoug TR-T was found to be only half that value at approximately 160 degrees C. Single crystals in the novel BiScO3-PbTiO3 system offer significantly higher Tcs > 400 degrees C, while exhibiting electromechanical coupling coefficients k33 > 90% being nearly constant till the TR-T temperature around 350 degrees C, which greatly increases the temperature range for transducer applications. PMID:16060503

  17. Green planting nanostructured single crystal silver

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

    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

  19. Mesoscale flux-closure domain formation in single-crystal BaTiO3

    PubMed Central

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

    2011-01-01

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

  20. 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.

  1. 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(ɛ-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.

  2. 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.

  3. Micro-Structuring and Ferroelectric Domain Engineering of Single Crystal Lithium Niobate

    NASA Astrophysics Data System (ADS)

    Mailis, S.; Sones, C. L.; Eason, R. W.

    The ability to microstructure specific materials is always associated with the ability to selectively remove material over small scale-lengths. Localized etching whether it is chemical or physical, wet or dry, parallel or sequential is central to every modern microstructuring method. For example a beam of accelerated ions is scanned on the surface of interest removing material along its trajectory. Alternatively the surface is prepared/treated in a manner that changes its "quality" locally making it more susceptible or more resistive to a particular etching agent. The whole surface is subsequently exposed to the etching agent which can be a uniform accelerated ion beam, a laser beam or an acid. The etching agent preferentially attacks the pre-treated (or the untreated) portion of the surface removing material.

  4. 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.

  5. The viscoplastic behavior of Hastelloy-X single crystal

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  6. Characterization of hydrogen embrittlement in nickel base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Chene, J.; Baker, C. L.; Bernstein, I. M.; Williams, J. C.

    1986-01-01

    In order to study the role of CMSX2 single crystal microstructure on the combined stress-hydrogen environment effects, hydrogen was introduced by cathodic charging. Concentration measurements were carried out to investigate the dependence of hydrogen solubility and trapping on microstructure. Mechanical properties were measured at room temperature on smooth tensile specimens as a function of heat treatment, crystal orientation and H charging conditions. SEM and TEM allow to study H induced cracks initiation and propagation. A large amount of hydrogen can be dissolved and trapped in CMSX2 single crystals when exposed to a high hydrogen fugacity environment. The strong H trapping evidenced in voids explains the predominant role of these defects as crack initiation sites. The strong detrimental effect of hydrogen on the material tenacity is discussed.

  7. Single crystal plasticity with bend-twist modes

    NASA Astrophysics Data System (ADS)

    Elkhodary, Khalil I.; Bakr, Mohamed A.

    2015-06-01

    In this work a formulation is proposed and computationally implemented for rate dependent single crystal plasticity, which incorporates plastic bend-twist modes that arise from dislocation density based poly-slip mechanisms. The formulation makes use of higher order continuum theory and may be viewed as a generalized micromechanics model. The formulation is then linked to the burgers and Nye tensors, showing how their material rates are derivable from a newly proposed third-rank tensor ?p, which incorporates a crystallographic description of bend-twist plasticity through selectable slip-system level constitutive laws. A simple three-dimensional explicit finite element implementation is outlined and employed in three simulations: (a) bi-crystal bending; (b) tension on a notched single crystal; and (c) the large compression of a microstructure to induce the plastic buckling of secondary phases. All simulation are transient, for computational expediency. The results shed light on the physics resulting from dynamic inhomogeneous plastic deformation.

  8. Growth of hafnium dioxide-based single crystals

    SciTech Connect

    Voronov, V.V.; Lavrishchev, S.V.; Markov, N.I.; Miftyakhetdinova, N.R.; Osiko, V.V.; Tatarintsev, V.M.; Zufarov, M.A.

    1986-03-01

    This paper considers the induction melting of hafnium dioxide with rare earth oxide mixtures, and studies defects in resulting hafnium dioxide single crystals stabilized by the oxides of scandium, yttrium, neodymium, gadolinium, terbium, erbium, and ytterbium at concentrations between 1 and 33 mole %. Crystallization of solid solutions occurs in the systems HfO/sub 2/Ln/sub 2/O/sub 3/. For the HfO/sub 2/-Er/sub 2/O/sub 3/ system, single crystals grow at 11-33 mole %, for HfO/sub 2/-Tb/sub 2/O/sub 3/ at 10-20 mole % and for HfO/sub 3/Sc/sub 2/O/sub 3/ (Nd/sub 2/O/sub 3/) at 10 mole % rare-earth oxide.

  9. Deformation of single crystal Hadfield steel by twinning and slip

    SciTech Connect

    Karaman, I.; Sehitoglu, H.; Gall, K.; Chumlyakov, Y.I.; Maier, H.J.

    2000-04-03

    The stress-strain behavior of Hadfield steel (Fe, 12.34 Mn, 1.03 C, in wt%) single crystals was studied for selected crystallographic orientations ([{bar 1}11 ], [001] and [{bar 1}23]) under tension and compression. The overall stress-strain response was strongly dependent on the crystallographic orientation and applied stress direction. Transmission electron microscopy and in situ optical microscopy demonstrated that twinning is the dominant deformation mechanism in [{bar 1}11] crystals subjected to tension, and [001] crystals subjected to compression at the onset of inelastic deformation. In the orientations that experience twinning, the activation of multiple twinning systems produces a higher strain-hardening coefficient than observed in typical f.c.c. alloys. Based on these experimental observations, a model is presented that predicts the orientation and stress direction effects on the critical stress for initiating twinning. The model incorporates the role of local pile-up stresses, stacking fault energy, the influence of the applied stress on the separation of partial dislocations, and the increase in the friction stress due to a high solute concentration. On the other hand, multiple slip was determined to be the dominant deformation mechanism in [{bar 1}11] crystals subjected to compression, and [001] crystals deformed under tension. Furthermore, the [{bar 1}23] crystals experience single slip in both tension and compression with planar type dislocations. Using electron back-scattered diffraction patterns, macroscopic shear bands (MSBs) were identified with a misorientation of 9 {degree} in the compressed [{bar 1}11] single crystals at strains as low as 1%.

  10. A Study of Single Crystal Fatigue Failure Criteria

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  11. Area detectors in single-crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    McIntyre, Garry J.

    2015-12-01

    The introduction of area detectors has brought about a gentle revolution in the routine application of single-crystal neutron diffractometry. Implemented first for macromolecular crystallography, electronic detectors subsequently gradually spread to chemical and physics-oriented crystallography at steady-state sources. The volumetric surveying of reciprocal space implicit in the Laue technique has required area detectors right from the start, whether using film and more recently image plates and CCD-based detectors at reactors, or scintillation detectors at spallation sources. Wide-angle volumetric data collection has extended application of neutron single-crystal diffractometry to chemical structures, sample volumes, and physical phenomena previously deemed impossible. More than 30 of the dedicated single-crystal neutron diffractometers at steady-state reactor and neutron spallation sources worldwide and accessible via peer-review proposal mechanisms are currently equipped with area detectors. Here we review the historical development of the various types of area detectors used for single crystals, discuss experimental aspects peculiar to experiments with such detectors, highlight the scientific fields where the use of area detectors has had a special impact, and forecast future developments in hardware, implementation, and software.

  12. Reliability analysis of single crystal NiAl turbine blades

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  13. Low-cost single-crystal turbine blades, volume 1

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    The exothermic casting process was successfully developed into a low cost nonproprietary method for producing single crystal (SC) castings. Casting yields were lower than expected, on the order of 20 percent, but it is felt that the casting yield could be significantly improved with minor modifications to the process. Single crystal Mar-M 247 and two derivative SC alloys were developed. NASAIR 100 and SC Alloy 3 were fully characterized through mechanical property testing. SC Mar-M 247 shows no significant improvement in strength over directionally solidified (DS) Mar-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. The 1000 hr/238 MPa (20 ksi) stress rupture capability compared to DS Mar-M 247 was improved over 28 C. Firtree testing, holography, and strain gauge rig testing were used to evaluate the effects of the anisotropic characteristics of single crystal materials. In general, the single crystal material behaved similarly to DS Mar-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined.

  14. 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.

  15. 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.

  16. Some Debye temperatures from single-crystal elastic constant data

    USGS Publications Warehouse

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

    1966-01-01

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

  17. Dynamic actuation of single-crystal diamond nanobeams

    NASA Astrophysics Data System (ADS)

    Sohn, Young-Ik; Burek, Michael J.; Kara, Vural; Kearns, Ryan; Lon?ar, Marko

    2015-12-01

    We show the dielectrophoretic actuation of single-crystal diamond nanomechanical devices. Gradient radio-frequency electromagnetic forces are used to achieve actuation of both cantilever and doubly clamped beam structures, with operation frequencies ranging from a few MHz to 50 MHz. Frequency tuning and parametric actuation are also studied.

  18. Low temperature magnetic transitions of single crystal HoBi

    SciTech Connect

    Fente, A.; Suderow, H.; Vieira, S.; Nemes, N. M.; Garcia-Hernandez, M.; Budko, Sergei L.; Canfield, Paul C.

    2013-09-04

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

  19. Coarsening model of cavity nucleation and thin film delamination from single-crystal BaTiO3 with proton implantation

    NASA Astrophysics Data System (ADS)

    Hong, Jung-Wuk; Pyeon, Jae-Ho; Tedesco, Joseph W.; Park, Young-Bae

    2007-06-01

    The layer splitting mechanism of a proton implanted single crystal ferroelectric BaTiO3 thin film layer from its bulk BaTiO3 substrate has been investigated. The single crystal BaTiO3 thin film layer splits as the hydrogen gas diffuses and the internal cavity pressure increases. Ripening mechanism driven by the pressurized hydrogen in the implantation-induced damage zone makes coarsening of the cavities and causes the delamination of the thin layer during the annealing. A unique criterion relation of blister nucleation and evolution has been derived and a simplified debonding criterion is proposed in terms of dimensionless parameters based on the force equilibrium condition. A numerical simulation of two-bubble evolution and delamination of thin film is performed using a finite element method.

  20. Local control of magnetic anisotropy in transcritical permalloy thin films using ferroelectric BaTiO3 domains

    NASA Astrophysics Data System (ADS)

    Fackler, Sean W.; Donahue, Michael J.; Gao, Tieren; Nero, Paris N. A.; Cheong, Sang-Wook; Cumings, John; Takeuchi, Ichiro

    2014-11-01

    We investigated the local coupling between dense magnetic stripe domains in transcritical permalloy (tPy) thin films and ferroelectric domains of BaTiO3 single crystals in a tPy/BaTiO3 heterostructure. Two distinct changes in the magnetic stripe domains of tPy were observed from the magnetic force microscopy images after cooling the heterostructure from above the ferroelectric Curie temperature of BaTiO3 (120 C) to room temperature. First, an abrupt break in the magnetic stripe domain direction was found at the ferroelectric a-c-domain boundaries due to an induced change in in-plane magnetic anisotropy. Second, the magnetic stripe domain period increased when coupled to a ferroelectric a-domain due to a change in out-of-plane magnetic anisotropy. Micromagnetic simulations reveal that local magnetic anisotropy energy from inverse magnetostriction is conserved between in-plane and out-of-plane components.

  1. Novel single-mode and polarization maintaining photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Yin, Aihan; Xiong, Lei

    2014-11-01

    In this paper, we present and propose a novel structure for improved birefringence and single-mode propagation condition photonic crystal fiber (PCF) in a broad range of wavelength. The birefringence of the fundamental mode and single mode property in such a PCF is numerically estimated by employing full vector finite element method (FVFEM) and anisotropic perfectly matched layers (APML). The simulation results illustrate that we can achieve a high birefringence and perfect single-mode condition by employing silica-filled into one-line elliptical air holes parallel to x-axis and rotated by an angle. Obviously, the proposed PCF is quite useful for optical devices.

  2. 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.

  3. Single crystal diamond probes for atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Tuyakova, F. T.; Obraztsova, E. A.; Klinov, D. V.; Ismagilov, R. R.

    2014-07-01

    Results obtained in the development and testing of high-strength, chemically inert, and sharply pointed single crystal diamond probes for atomic-force microscopy are presented. The probes were fabricated on the basis of pyramidal diamond single crystals produced by selective oxidation of polycrystalline films grown by chemical vapor deposition. A procedure was developed for attachment of single needles to cantilevers of silicon probes. A transmission electron microscope was used to find that the apical angle of the pyramidal diamond crystallites is about 10 and the radius of curvature of the apex of the diamond crystallite is 2-10 nm. It is shown for the example of two test samples (graphite surface and DNA molecules) that the diamond probes can be effectively used in atomic-force microscopy and make it possible to improve the image quality compared with standard silicon probes.

  4. ESR and Microwave Absorption in Boron Doped Diamond Single Crystals

    NASA Astrophysics Data System (ADS)

    Timms, Christopher

    2015-03-01

    Superconductivity has been reportedly found in boron-doped diamond. Most research to date has only studied superconductivity in polycrystalline and thin film boron-diamonds, as opposed to a single crystal. In fact, only one other group has examined a macro scale boron-doped diamond crystal. Our group has successfully grown large single crystals by using the High Temperature High Pressure method (HTHP) and observed a transition to metallic and superconducting states for high B concentrations. For the present, we are studying BDD crystal using Electron Spin Resonance. We conducted our ESR analysis over a range of temperatures (2K to 300K) and found several types of signals, proving the existence of charge carriers with spin 1/2 in BDD. Moreover, we have found that with increasing B concentrations, from n ~ 1018 cm-3 to n of over 1020 cm-3, the ESR signal changes from that of localized spins to the Dysonian shape of free carriers. The low magnetic field microwave absorption has also been studied in BDD samples at various B concentrations and the clear transition to superconducting state has been found below Tc that ranges from 2K to 4 K depending on concentration and quality of crystal. Sergey Polyakov, Victor Denisov, Vladimir Blank, Ray Baughman, Anvar Zakhidov.

  5. New perspectives for ferroelectric LC-polymers

    SciTech Connect

    Brehmer, M.; Gebhard, E.; Wittig, T.

    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.

  6. Single crystal structure analysis of a single Sm2Fe17N3 particle

    NASA Astrophysics Data System (ADS)

    Inami, Nobuhito; Takeichi, Yasuo; Ueno, Tetsuro; Saito, Kotaro; Sagayama, Ryoko; Kumai, Reiji; Ono, Kanta

    2014-05-01

    We performed single crystal structure analysis of Sm2Fe17N3 using X-ray diffraction. A pick-up system combined with a micromanipulation tool driven by piezoelectric actuators and a microgripper was used. A single Sm2Fe17Nx particle with the diameter of about 20 μm was picked up, and X-ray diffraction was measured using an X-ray diffractometer at the synchrotron radiation beamline at the Photon Factory, KEK. Single crystal structure analysis of a Sm2Fe17N3 particle was performed and the structure was successfully determined from X-ray diffraction patterns. The space group and the lattice constants were determined to be R-3m (#166) a = b = 8.7206 Å and c = 12.6345 Å, respectively. Atomic positions of Sm and Fe atoms were accurately determined by single crystal structure analysis of only one particle.

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

    SciTech Connect

    Yang, Qian; Department of Chemistry, Tianjin Key Lab on Metal and Molecule-based Material Chemistry, Nankai University, Tianjin 300071 ; Zhao, Jiong-Peng; Liu, Zhong-Yi

    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.

  8. 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.

  9. Domain wall conductivity in semiconducting hexagonal ferroelectric TbMnO3 thin films

    NASA Astrophysics Data System (ADS)

    Kim, D. J.; Connell, J. G.; Seo, S. S. A.; Gruverman, A.

    2016-04-01

    Although enhanced conductivity of ferroelectric domain boundaries has been found in BiFeO3 and Pb(Zr,Ti)O3 films as well as hexagonal rare-earth manganite single crystals, the mechanism of the domain wall conductivity is still under debate. Using conductive atomic force microscopy, we observe enhanced conductance at the electrically-neutral domain walls in semiconducting hexagonal ferroelectric TbMnO3 thin films where the structure and polarization direction are strongly constrained along the c-axis. This result indicates that domain wall conductivity in ferroelectric rare-earth manganites is not limited to charged domain walls. We show that the observed conductivity in the TbMnO3 films is governed by a single conduction mechanism, namely, the back-to-back Schottky diodes tuned by the segregation of defects.

  10. Domain wall conductivity in semiconducting hexagonal ferroelectric TbMnO3 thin films.

    PubMed

    Kim, D J; Connell, J G; Seo, S S A; Gruverman, A

    2016-04-15

    Although enhanced conductivity of ferroelectric domain boundaries has been found in BiFeO3 and Pb(Zr,Ti)O3 films as well as hexagonal rare-earth manganite single crystals, the mechanism of the domain wall conductivity is still under debate. Using conductive atomic force microscopy, we observe enhanced conductance at the electrically-neutral domain walls in semiconducting hexagonal ferroelectric TbMnO3 thin films where the structure and polarization direction are strongly constrained along the c-axis. This result indicates that domain wall conductivity in ferroelectric rare-earth manganites is not limited to charged domain walls. We show that the observed conductivity in the TbMnO3 films is governed by a single conduction mechanism, namely, the back-to-back Schottky diodes tuned by the segregation of defects. PMID:26933770

  11. 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.

  12. Crystal structure, physical properties and superconductivity in AxFe2Se2 single crystals

    NASA Astrophysics Data System (ADS)

    Luo, X. G.; Wang, X. F.; Ying, J. J.; Yan, Y. J.; Li, Z. Y.; Zhang, M.; Wang, A. F.; Cheng, P.; Xiang, Z. J.; Ye, G. J.; Liu, R. H.; Chen, X. H.

    2011-05-01

    We studied the correlation among structure, transport properties and superconductivity in different AxFe2Se2 single crystals (A=K, Rb and Cs). Two sets of (00l) reflections are observed in the x-ray single-crystal diffraction patterns, and they arise from the intrinsic inhomogeneous distribution of the intercalated alkali atoms. The occurrence of superconductivity is closely related to the c-axis lattice constant, and the A content is crucial to superconductivity. The hump observed in resistivity seems to be irrelevant to the superconductivity. There exist many deficiencies within the FeSe layers in AxFe2Se2, although their Tc does not change so much. In this sense, superconductivity is robust to the vacancies within the FeSe layers. Very high resistivity in the normal state should be ascribed to such defects in the conducting FeSe layers. AxFe2Se2 (A=K, Rb and Cs) single crystals show the same susceptibility behavior in the normal state, and no anomaly is observed in susceptibility at the hump temperature in resistivity. The clear jump in specific heat for RbxFe2Se2 and KxFe2Se2 single crystals indicates the good bulk superconductivity of these crystals.

  13. Growth and electrical properties of mercury indium telluride single crystals

    SciTech Connect

    Wang Linghang Dong Yangchun; Jie Wanqi

    2007-11-06

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

  14. Structural and thermal properties of MnSi single crystal

    NASA Astrophysics Data System (ADS)

    Tite, T.; Shu, G. J.; Chou, F. C.; Chang, Y.-M.

    2010-07-01

    Polarized Raman spectroscopy of MnSi single crystal was carried out to characterize its phonons, crystal structure, and thermal stability. The Raman spectra show correct Raman selection rules and consistence with those of the other transition metal silicide compounds. The MnSi thermal stability and phase transformation is investigated by monitoring the evolution of Raman spectrum as a function of the laser intensity, in which three compositions, MnSi, MnSiO3, and Mn5Si3, can be identified. The involved oxidation reaction is then proposed and verified by performing the thermogravimetric and x-ray diffraction analysis.

  15. Antifreeze glycopeptide adsorption on single crystal ice surfaces using ellipsometry

    PubMed Central

    Wilson, P. W.; Beaglehole, D.; DeVries, A. L.

    1993-01-01

    Antarctic fishes synthesise antifreeze proteins which can effectively inhibit the growth of ice crystals. The mechanism relies on adsorption of these proteins to the ice surface. Ellipsometry has been used to quantify glycopeptide antifreeze adsorption to the basal and prism faces of single ice crystals. The rate of accumulation was determined as a function of time and at concentrations between 0.0005 and 1.2 mg/ml. Estimates of packing density at saturation coverage have been made for the basal and prism faces. PMID:19431902

  16. Simulation of isotope effects in single crystal sputtering

    NASA Astrophysics Data System (ADS)

    Shulga, V. I.

    Sputtering of isotopic (001), (011), and (111) Mo single crystals with 0.15-10 keV Ar ions at low fluences has been studied by means of computer simulation. Attention was given to the dependence of the preferential emission of light isotopes on ion energy and direction of incidence. It has been shown that the enrichment in light isotopes results mainly from a high contribution to sputtering of recoils of low generations which, in turn, correlates very closely with the crystal transparaency and accompanying channeling effects. At glancing incidence, the preferential emission of light isotopes is strongly affected by the surface channeling of bombarding particles.

  17. Heavy ion passive dosimetry with silver halide single crystals

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  18. A design for single-polarization single-mode photonic crystal fiber with rectangular lattice

    NASA Astrophysics Data System (ADS)

    Zhang, Wan; Li, Shu-guang; Bao, Ya-jie; Fan, Zhen-kai; An, Guo-wen

    2016-01-01

    A design for single-polarization single-mode photonic crystal fiber with rectangular lattice is proposed in this paper. The proposed fiber is studied by the full vector finite element method with perfectly matched layers. The single-polarization single-mode operation region of the fiber is achieved in a certain wavelength range with low confinement loss include the wavelength of 1.55 μm. The loss of one polarization is 0.124 dB/km at the wavelength of 1.55 μm and the confinement loss of the other one polarization is very high which can not ensure the transmission in the fiber. The single-polarization single-mode photonic crystal fiber is desirable for some polarization-sensitive applications such as high-power fiber lasers, fiber optic gyroscopes, current sensors and optical coherent communication systems.

  19. 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.

  20. A high performance triboelectric nanogenerator for self-powered non-volatile ferroelectric transistor memory

    NASA Astrophysics Data System (ADS)

    Fang, Huajing; Li, Qiang; He, Wenhui; Li, Jing; Xue, Qingtang; Xu, Chao; Zhang, Lijing; Ren, Tianling; Dong, Guifang; Chan, H. L. W.; Dai, Jiyan; Yan, Qingfeng

    2015-10-01

    We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 103. More importantly, we demonstrate the feasibility to switch the polarization state of this FET gate insulator, namely the stored information, by finger tapping the TENG with a designed circuit. These results may open up a novel application of TENGs in the field of self-powered memory systems.We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 103. More importantly, we demonstrate the feasibility to switch the polarization state of this FET gate insulator, namely the stored information, by finger tapping the TENG with a designed circuit. These results may open up a novel application of TENGs in the field of self-powered memory systems. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05098g