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Sample records for crystal structure-ionic conductivity

  1. New ferroelastic K2Sr(MoO4)2: Synthesis, phase transitions, crystal and domain structures, ionic conductivity

    NASA Astrophysics Data System (ADS)

    Tsyrenova, Galina D.; Pavlova, Erzhena T.; Solodovnikov, Sergey F.; Popova, Nadezhda N.; Kardash, Tatyana Yu.; Stefanovich, Sergey Yu.; Gudkova, Irina A.; Solodovnikova, Zoya A.; Lazoryak, Bogdan I.

    2016-05-01

    K2Sr(MoO4)2 crystals were synthesized and their properties examined. The distortive polymorphic transformations at 421 K (α (LT)→ β(MT)) and 744 K (β(MT)→γ (HT)) of K2Sr(MoO4)2 were studied. It has been shown that the transitions go in sequence from the high-temperature palmierite K2Pb(SO4)2-type γ-phase (R 3 bar m) to an intermediate β-phase with a probable incommensurate structure and then to a low-temperature α-phase. Domain structures peculiarities in ferroelastic α-K2Sr(MoO4)2 have been investigated. The electrical conductivity of K2Sr(MoO4)2 rises tenfold in the vicinity of the phase transition at 744 K that may be associated with a change conductivity path from quasi-one-dimensional to two-dimensional. The crystal structure of the α-phase (sp. gr. C2/c, e=14.318(3) Å, b=5.9337(12) Å, c=10.422(2) Å, β=105.83(3)°, Z=4, R=0.0219) is similar to that of α-Pb3(PO4)2. Sr-atoms are mainly located at site with the coordination number CN=8 (a tetragonal antiprism with bond lengths of 2.578(2)-2.789(2) Å) and K atoms are located at site with CN=9+1.

  2. Structure, ionic Conductivity and mobile Carrier Density in Fast Ionic Conducting Chalcogenide Glasses

    SciTech Connect

    Wenlong Yao

    2006-12-12

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M{sub 2}S + (0.1 Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2}) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2} was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M{sub 2}S + (0.1Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2}) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na{sub 2}S + B{sub 2}S{sub 3} (x {le} 0.2) glasses by neutron and synchrotron x-ray diffraction. Similar results were obtained both in neutron and synchrotron x

  3. Liquid crystal-templated conducting organic polymers

    DOEpatents

    Stupp, Samuel I.; Hulvat, James F.

    2004-01-20

    A method of preparing a conductive polymeric film, includes providing a liquid crystal phase comprising a plurality of hydrophobic cores, the phase on a substrate, introducing a hydrophobic component to the phase, the component a conductive polymer precursor, and applying an electric potential across the liquid crystal phase, the potential sufficient to polymerize the said precursor.

  4. Thermal conductivity of garnet laser crystals

    NASA Astrophysics Data System (ADS)

    Wang, B. S.; Jiang, H. H.; Zhang, Q. L.; Yin, S. T.

    2008-03-01

    The thermal conductivities of nine different synthetic garnet laser crystals at various temperatures, range from 273 to 393 K have been investigated by instantaneous measurement method. The results show that the thermal conductivity of each crystal decreases exponentially with the temperature increasing. It is notable that, different host crystals, such as YAG, GGG, and GSGG have different thermal conductivity, which is attributed to the crucial influence of crystal structure and composition on the absolute value of their thermal conductivity. Moreover, with respect to the same host crystals, the impurity scattering also results in the change of their thermal conductivities. This is because that a higher concentration of doped ions leads to a more phonon scattering modes, which results in a shorter mean free path of the phonons and a lower thermal conductivity. In addition, different host crystals have various dependences of thermal conductivity on dopant concentration. This works provides reliable and useful information for designing high power, high quality, and high stability laser devices.

  5. Thermal conductivity of synthetic garnet laser crystals

    NASA Astrophysics Data System (ADS)

    Wang, B. S.; Jiang, H. H.; Zhang, Q. L.; Yin, S. T.

    2007-07-01

    The thermal conductivities of nine different synthetic garnet laser crystals at various temperatures, range from 273 to 393K have been investigated by instantaneous measurement method. The results show that the thermal conductivity of each crystal decreases exponentially with the temperature increasing. It is notable that, different host crystals, such as YAG, GGG, and GSGG have different thermal conductivity, which is attributed to the crucial influence of crystal structure and composition on the absolute value of their thermal conductivity. Moreover, with respect to the same host crystals, the impurity scattering also results in the change of their thermal conductivities. This is because that a higher concentration of doped ions leads to a more phonon scattering modes, which results in a shorter mean free path of the phonons and a lower thermal conductivity. In addition, different host crystals have various dependences of thermal conductivity on dopant concentration. This works provides reliable and useful information for designing high power, high quality, and high stability laser devices.

  6. Thermal conductivity behavior of superatom molecular crystals

    NASA Astrophysics Data System (ADS)

    Ong, Wee-Liat; O'Brien, Evan; Dougherty, Patrick; Epstein, Jillian; Higgs, C. Fred; McGaughey, Alan; Roy, Xavier; Malen, Jonathan

    The room temperature thermal conductivity of several superatom molecular crystals (SMCs) are measured and found to be below 0.3 W/mK. The trend of room temperature thermal conductivity of the different crystals agree well with their sound speeds obtained independently using nano-indentation. These crystals, however, can exhibit non-crystalline thermal conductivity behavior depending on their constituent elements. A superatom is a cluster of atoms that acts as a stable entity [e.g., fullerenes (C60)]. By careful mixing and assembling these nano-sized superatoms, the resulting superatom-assembled materials hold promises for improving various technological devices. Organic-inorganic superatoms can assemble into unary SMCs or co-crystallized with C60 superatoms into binary SMCs. Thermal transport is of considerable interest with possible new physics in these hierarchically atomic precise crystals in the low temperature regime. The thermal conductivity of the SMCs are measured using the frequency domain thermoreflectance setup. Unary SMCs exhibit an almost invariant thermal conductivity down to a temperature of 150 K. Binary SMCs, however, can either show a crystalline-like increase or an amorphous-like decrease with decreasing temperature.

  7. Phonon heat conduction in layered anisotropic crystals

    NASA Astrophysics Data System (ADS)

    Minnich, A. J.

    2015-02-01

    The thermal properties of anisotropic crystals are of both fundamental and practical interest, but transport phenomena in anisotropic materials such as graphite remain poorly understood because solutions of the Boltzmann equation often assume isotropy. Here, we extend an analytic solution of the transient, frequency-dependent Boltzmann equation to highly anisotropic solids and examine its predictions for graphite. We show that this simple model predicts key results, such as long c -axis phonon mean free paths and a negative correlation of cross-plane thermal conductivity with in-plane group velocity, that were previously observed with computationally expensive molecular-dynamics simulations. Further, using our analytic solution, we demonstrate a method to reconstruct the anisotropic mean free path spectrum of crystals with arbitrary dispersion relations without any prior knowledge of their harmonic or anharmonic properties using observations of quasiballistic heat conduction. These results provide a useful analytic framework to understand thermal transport in anisotropic crystals.

  8. Conduction mechanism of single-crystal alumina

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  9. Highly anisotropic conductivity in organosiloxane liquid crystals

    NASA Astrophysics Data System (ADS)

    Gardiner, D. J.; Coles, H. J.

    2006-12-01

    In this paper, we present the conductivity and dielectric characterization of three homologous series of smectic A siloxane containing liquid crystals. The materials studied include one monomesogenic series, which consists of a 4-(ω-alkyloxy)-4'-cyanobiphenyl unit terminated by pentamethyldisiloxane, and two bimesogenic series, which consist of twin 4-(ω-alkyloxy)-4'-cyanobiphenyls joined via tetramethyldisiloxane or decamethylpentasiloxane. All of the compounds exhibit wide temperature range enantiotropic smectic A phases; the effect of the siloxane moiety is to suppress nematic morphology even in the short chain homologs. We find that these compounds exhibit a highly anisotropic conductivity: the value perpendicular to the director is to up to 200 times that parallel to the director. For the nonsiloxane analog 4-(ω-octyl)-4'-cyanobiphenyl (8CB), this value is approximately 2. It is also found that the dielectric anisotropy is reduced significantly; a typical value is ˜1 compared to 8.4 for 8CB. We propose that the origin of these unusual properties is in the smectic structure; the microphase separation of the bulky, globular siloxane moieties into liquidlike regions severely inhibits the mobility parallel to the director and across the smectic layers. Further, the inclusion of this unit acts to increase the antiparallel correlations of molecular dipoles in the aromatic and alkyloxy sublayers, reducing the dielectric anisotropy significantly compared to nonsiloxane analogs. The highly anisotropic conductivity suggests that these materials are particularly suitable for application in electro-optic effects which exploit this property, e.g., the bistable electro-optic effect in smectic A liquid crystals.

  10. Thermal Conductivity and Liquid Crystal Thermometers.

    ERIC Educational Resources Information Center

    Edge, R. D., Ed.

    1993-01-01

    Describes using stock liquid crystal postcards as inexpensive classroom thermometers. Also suggests using these postcards as a good visual temperature indicator for classroom demonstrations such as temperature gradients. One such activity is provided. (MVL)

  11. Ionic conductivity of imidazole-functionalized liquid crystal mesogens

    NASA Astrophysics Data System (ADS)

    Roddecha, Supacharee; Anthamatten, Mitchell

    2012-02-01

    Imidazole has been investigated as a novel anhydrous proton conducting functional group that could enable higher temperature operation (> 120 ^oC) of polymer electrolyte fuel cells. Its amphoteric behavior can support Grotthuss-like proton transport; however molecular mobility and a high concentration of imidazole groups are needed to achieve high ionic conductivity. Our hypothesis is that liquid crystal ordering, particularly in layered smectic phase, can facilitate formation of 2D proton transport and promote proton conductivity. We have designed and synthesized two imidazole-terminated liquid crystal mesogens, and the ionic conductivities in the liquid crystalline and isotropic states have been measured. Here we report on synthesis and characterization of diacylhydrazine liquid crystals bearing imidazole terminal groups. The proton conductivity of products is compared to pure liquid imidazole and to liquid crystal mesogens without imidazole groups.

  12. Electrical conductivity of Cs2CuCl4 crystals

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.

    2016-05-01

    The electrical conductivity of Cs2CuCl4 single crystals, synthesized by crystallization from aqueous solutions in the CsCl-CuCl2-H2O system, has been investigated. The temperature dependence of the electrical conductivity of crystals in a temperature range of 338-584 K exhibits no anomalies. The electrical transfer activation enthalpy is Δ H σ = 0.72 ± 0.05 eV and the conductivity is σ = 3 × 10-4 S/cm at 584 K. The most likely carriers in Cs2CuCl4 are Cs+ cations, which transfer electric charge according to the vacancy mechanism.

  13. Reduction of Thermal Conductivity by Nanoscale 3D Phononic Crystal

    PubMed Central

    Yang, Lina; Yang, Nuo; Li, Baowen

    2013-01-01

    We studied how the period length and the mass ratio affect the thermal conductivity of isotopic nanoscale three-dimensional (3D) phononic crystal of Si. Simulation results by equilibrium molecular dynamics show isotopic nanoscale 3D phononic crystals can significantly reduce the thermal conductivity of bulk Si at high temperature (1000 K), which leads to a larger ZT than unity. The thermal conductivity decreases as the period length and mass ratio increases. The phonon dispersion curves show an obvious decrease of group velocities in 3D phononic crystals. The phonon's localization and band gap is also clearly observed in spectra of normalized inverse participation ratio in nanoscale 3D phononic crystal. PMID:23378898

  14. Reduction of thermal conductivity by nanoscale 3D phononic crystal.

    PubMed

    Yang, Lina; Yang, Nuo; Li, Baowen

    2013-01-01

    We studied how the period length and the mass ratio affect the thermal conductivity of isotopic nanoscale three-dimensional (3D) phononic crystal of Si. Simulation results by equilibrium molecular dynamics show isotopic nanoscale 3D phononic crystals can significantly reduce the thermal conductivity of bulk Si at high temperature (1000 K), which leads to a larger ZT than unity. The thermal conductivity decreases as the period length and mass ratio increases. The phonon dispersion curves show an obvious decrease of group velocities in 3D phononic crystals. The phonon's localization and band gap is also clearly observed in spectra of normalized inverse participation ratio in nanoscale 3D phononic crystal. PMID:23378898

  15. Remarkable reduction of thermal conductivity in phosphorene phononic crystal

    NASA Astrophysics Data System (ADS)

    Xu, Wen; Zhang, Gang

    2016-05-01

    Phosphorene has received much attention due to its interesting physical and chemical properties, and its potential applications such as thermoelectricity. In thermoelectric applications, low thermal conductivity is essential for achieving a high figure of merit. In this work, we propose to reduce the thermal conductivity of phosphorene by adopting the phononic crystal structure, phosphorene nanomesh. With equilibrium molecular dynamics simulations, we find that the thermal conductivity is remarkably reduced in the phononic crystal. Our analysis shows that the reduction is due to the depressed phonon group velocities induced by Brillouin zone folding, and the reduced phonon lifetimes in the phononic crystal. Interestingly, it is found that the anisotropy ratio of thermal conductivity could be tuned by the ‘non-square’ pores in the phononic crystal, as the phonon group velocities in the direction with larger projection of pores is more severely suppressed, leading to greater reduction of thermal conductivity in this direction. Our work provides deep insight into thermal transport in phononic crystals and proposes a new strategy to reduce the thermal conductivity of monolayer phosphorene.

  16. Remarkable reduction of thermal conductivity in phosphorene phononic crystal.

    PubMed

    Xu, Wen; Zhang, Gang

    2016-05-01

    Phosphorene has received much attention due to its interesting physical and chemical properties, and its potential applications such as thermoelectricity. In thermoelectric applications, low thermal conductivity is essential for achieving a high figure of merit. In this work, we propose to reduce the thermal conductivity of phosphorene by adopting the phononic crystal structure, phosphorene nanomesh. With equilibrium molecular dynamics simulations, we find that the thermal conductivity is remarkably reduced in the phononic crystal. Our analysis shows that the reduction is due to the depressed phonon group velocities induced by Brillouin zone folding, and the reduced phonon lifetimes in the phononic crystal. Interestingly, it is found that the anisotropy ratio of thermal conductivity could be tuned by the 'non-square' pores in the phononic crystal, as the phonon group velocities in the direction with larger projection of pores is more severely suppressed, leading to greater reduction of thermal conductivity in this direction. Our work provides deep insight into thermal transport in phononic crystals and proposes a new strategy to reduce the thermal conductivity of monolayer phosphorene. PMID:27033566

  17. Calculation of the lattice thermal conductivity in granular crystals

    SciTech Connect

    Kazan, M.; Volz, S.

    2014-02-21

    This paper provides a general model for the lattice thermal conductivity in granular crystals. The key development presented in this model is that the contribution of surface phonons to the thermal conductivity and the interplay between phonon anharmonic scattering and phonon scattering by boundaries are considered explicitly. Exact Boltzmann equation including spatial dependence of phonon distribution function is solved to yield expressions for the rates at which phonons scatter by the grain boundaries in the presence of intrinsic phonon scattering mechanisms. The intrinsic phonon scattering rates are calculated from Fermi's golden rule, and the vibration parameters of the model are derived as functions of temperature and crystallographic directions by using a lattice dynamics approach. The accuracy of the model is demonstrated with reference to experimental measurements regarding the effects of surface orientation and isotope composition on the thermal conductivity in single crystals, and the effect of grains size and shape on the thermal conductivity tensor in granular crystals.

  18. ac conductance of surface layer in lithium tetraborate single crystals

    NASA Astrophysics Data System (ADS)

    Kim, Chung-Sik; Park, Jong-Ho; Moon, Byung Kee; Seo, Hyo-Jin; Choi, Byung-Chun; Hwang, Yoon-Hwae; Kim, Hyung Kook; Kim, Jung Nam

    2003-12-01

    ac conductance for the electrode effect in Li2B4O7 single crystal was investigated by use of a coplanar electrode applied on the surface of a (001) plate. A coplanar electrode in this material more clearly shows conduction of the electrode effect than a conventional parallel planar electrode. The electrode effect in ac conductance is likely to be controlled by the surface layer, which is a poorly conductive depletion layer possibly filled with vacancies of lithium ions. We found that the surface layer is not locally distributed near the electrodes, but, rather, on the broad area of the surface (001) plane of the material. So we conclude that the electrode effect in ac conduction of Li2B4O7 single crystal is mainly due to the poor conductive surface layer distributed over the whole surface of the (001) plane and is not a secondary phase formed by reaction with the electrode material.

  19. Engineering thermal conductance using a two-dimensional phononic crystal

    PubMed Central

    Zen, Nobuyuki; Puurtinen, Tuomas A.; Isotalo, Tero J.; Chaudhuri, Saumyadip; Maasilta, Ilari J.

    2014-01-01

    Controlling thermal transport has become relevant in recent years. Traditionally, this control has been achieved by tuning the scattering of phonons by including various types of scattering centres in the material (nanoparticles, impurities, etc). Here we take another approach and demonstrate that one can also use coherent band structure effects to control phonon thermal conductance, with the help of periodically nanostructured phononic crystals. We perform the experiments at low temperatures below 1 K, which not only leads to negligible bulk phonon scattering, but also increases the wavelength of the dominant thermal phonons by more than two orders of magnitude compared to room temperature. Thus, phononic crystals with lattice constants ≥1 μm are shown to strongly reduce the thermal conduction. The observed effect is in quantitative agreement with the theoretical calculation presented, which accurately determined the ballistic thermal conductance in a phononic crystal device. PMID:24647049

  20. Low Frequency Thermal Conductivity in Micro Phononic Crystals

    NASA Astrophysics Data System (ADS)

    Anjos, Virgilio; Arantes, Alison

    2015-03-01

    We study theoretically the cumulative thermal conductivity of a micro phononic crystal at low temperature regime. The phononic crystal considered presents carbon microtubes inclusions arranged periodically in a two-dimensional square lattice embebed in soft elastic matrix. Moderate and high impedance mismatch are considered concerning the material composition. The low frequency phonon spectra (up to tens of GHz) are obtained solving the generalized wave equation for inhomogeneous media within the Plane Wave Expansion method. We consider low temperatures in order to increase the participation of GHz thermal phonons. We observed suppression in the cumulative thermal conductivity at the band gap region and thus a reduction of thermal conductivity of the phononic crystal when compared with the bulk matrix. The authors would like to thank the Brazilian agencies, National Council of Technological and Scientific Development (CNPq), Foundation for Research Support of Minas Gerais (FAPEMIG) and CAPES for their support.

  1. Limits to Fourier theory in high thermal conductivity single crystals

    NASA Astrophysics Data System (ADS)

    Wilson, R. B.; Cahill, David G.

    2015-11-01

    We report the results of time-domain thermoreflectance (TDTR) experiments that examine the ability of Fourier theory to predict the thermal response in single crystals when heater dimensions are small. We performed TDTR measurements on Al-coated diamond, 6H-SiC, GaP, Ge, MgO, GaAs, and GaSb single crystals with a wide range of laser spot size radii, 0.7 μm < w 0 < 12 μm. When the laser spot-size is large, w 0 ≈ 12 μm, TDTR data for all crystals are in agreement with predictions of Fourier theory with bulk thermal conductivity values. When the laser spot-size is small, w 0 < 2 μm, there are significant differences between the predictions of Fourier theory and TDTR data for all crystals except MgO.

  2. Photon assisted hopping conduction mechanism in Tl2SSe crystals

    NASA Astrophysics Data System (ADS)

    Qasrawi, A. F.; Ziqan, Abdelhalim M.; Jazzar, Suha Kh.; Gasanly, N. M.

    2015-02-01

    In this article, the powder X-ray diffraction data and the dark and the photo-excited electrical conduction parameters of Tl2SSe crystal are reported. The dark and photon excited electrical conduction in the tetragonal crystal are found to be dominated by thermionic emission assisted variable range hopping conduction (VRH). The dark Mott's VRH parameters representing by the degree of disorder (To), the density of localized states near the Fermi level (N (EF)), the average hopping range (R) and average hopping energy (W) exhibited wide tunability via incremental photon intensity. Particularly, while the dark values of T0 , W and R significantly decreased from 2.32 ×108 to 1.52 ×105 K, 114 to 18.25 meV and from 66.15 to 10.58 A°, respectively, the values of N (EF) increased from 7.23 ×1018 to 1.10 ×1022cm-3 /eV when the crystal was photo-excited with a 53.6 mW/cm2 light intensity. These variations in the hopping parameters via photon excitations are promisig for using the crystal in the fabrication of well controlled, widely tunable, low energy consuming and highly efficient electronic devices.

  3. Explosive crystallization in thin amorphous layers on heat conducting substratesa)

    NASA Astrophysics Data System (ADS)

    Buchner, Christoph; Schneider, Wilhelm

    2015-06-01

    A model for explosive crystallization in a thin amorphous layer on a heat conducting substrate is presented. For the thin layer, the energy equation is used in a one-dimensional approximation. Heat conduction into the substrate and thermal contact resistance at the interface between layer and substrate are taken into account. Four rate equations are used to describe the kinetics of the homogeneous amorphous-crystalline transition. The whole process is examined as a plane wave of invariant shape in a moving frame of reference. Heat conduction in the substrate is described by introducing a continuous distribution of moving heat sources at the interface. This gives an integral representation for the temperature in the substrate in terms of the unknown source distribution. The integral term implies that there is a non-local influence of the temperature distribution in the layer on the heat loss. A coupled system of an integro-differential equation and four ordinary differential equations is obtained and solved numerically. The propagation velocity of the wave is obtained as an eigenvalue of the system of equations. Varying a non-dimensional heat loss parameter, a critical value is found beyond which no crystallization wave of invariant shape is possible. This can also be interpreted as a certain minimum layer thickness. Temperature and crystallinity distributions are shown for some interesting configurations. Predictions of crystallization-wave velocities and minimum layer thicknesses are compared with experimental values for explosive crystallization in germanium.

  4. Coherent thermal conductance of 1-D photonic crystals

    NASA Astrophysics Data System (ADS)

    Tschikin, Maria; Ben-Abdallah, Philippe; Biehs, Svend-Age

    2012-10-01

    We present an exact calculation of coherent thermal conductance in 1-D multilayer photonic crystals using the S-matrix method. In particular, we study the thermal conductance in a bilayer structure of Si/vacuum or Al2O3/vacuum slabs by means of the exact radiative heat flux expression. Based on the results obtained for the Al2O3/vacuum structure we show by comparison with previous works that the material losses and (localized) surface modes supported by the inner layers play a fundamental role and cannot be omitted in the definition of thermal conductance. Our results could have significant implications in the conception of efficient thermal barriers.

  5. Photoinduced extrinsic electrical conduction of nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Dedov, O. V.; Krivoschekov, V. A.

    1996-05-01

    During recent years the interest in media with strong nonlinear response is growing. These media allow the user to observe different nonlinear optic effects using small intensities of light. It is well known that liquid crystals are rather promising media for this research. This paper is devoted to the experimental research of the photoinduced conduction of a mixture of a nematic liquid crystal and a dye. Dependence of the conduction on the intensity of light was studied for different concentrations of a dye added to the nematic crystal. Also the problem of the optimum type of a dye for observing the photorefractive nonlinearity using Ar+- ion laser was considered. We made the experiments using the following available laser dyes: rhodamine '6G,' rhodamine 'G,' rhodamine 'C' and two ocsasine-type dyes also. The mixture of the nematic crystal 5CB and a dye was placed in a cell of 100 micrometer width, with the plates filmed with the transparent electrodes of SnO2. The dc voltage on the order of magnitude 1 V was applied to decrease the influence of the cell capacity on the conduction measurements of the samples. We used the light of two wavelengths: lambda1 equals 488 nm, lambda2 equals 514.5 nm. The best dyes for these wavelengths were the rhodamine- type dyes. Taking the other two dyes we observed much smaller effect of influence of the laser radiation on conduction of the samples. Maybe the reason was that the pump wavelength of ocsasine dyes is too far way from the wavelength of the radiation used. So the optimum dye must have the wavelength of the pump near to the wavelength used. Using rhodamine 'C' we obtained the dependencies of the induced conduction on laser light intensity for three different concentrations of the dye.

  6. Electrochemical growth of linear conducting crystals in microgravity

    NASA Technical Reports Server (NTRS)

    Cronise, Raymond J., IV

    1988-01-01

    Much attention has been given to the synthesis of linear conducting materials. These inorganic, organic, and polymeric materials have some very interesting electrical and optical properties, including low temperature superconductivity. Because of the anisotropic nature of these compounds, impurities and defects strongly influences the unique physical properties of such crystals. Investigations have demonstrated that electrochemical growth has provided the most reproducible and purest crystals. Space, specifically microgravity, eliminates phenomena such as buoyancy driven convection, and could permit formation of crystals many times purer than the ones grown to date. Several different linear conductors were flown on Get Away Special G-007 on board the Space Shuttle Columbia, STS 61-C, the first of a series of Project Explorer payloads. These compounds were grown by electrochemical methods, and the growth was monitored by photographs taken throughout the mission. Due to some thermal problems, no crystals of appreciable size were grown. The experimental results will be incorporated into improvements for the next 2 missions of Project Explorer. The results and conclusions of the first mission are discussed.

  7. Electrical conduction in nanodomains in congruent lithium tantalate single crystal

    SciTech Connect

    Cho, Yasuo

    2014-01-27

    The electrical current flow behavior was investigated for nanodomains formed in a thin congruent lithium tantalate (LiTaO{sub 3}) single-crystal plate. When the nanodomains were relatively large, with diameters of about 100 nm, current flow was detected along the domain wall. However, when they were about 40 nm or smaller, the current flowed through the entire nanodomain. Schottky-like rectifying behavior was observed. Unlike the case of LiNbO{sub 3}, optical illumination was not required for current conduction in LiTaO{sub 3}. A clear temperature dependence of the current was found indicating that the conduction mechanism for nanodomains in LiTaO{sub 3} may involve thermally activated carrier hopping.

  8. Lithium-cation conductivity and crystal structure of lithium diphosphate

    SciTech Connect

    Voronin, V.I.; Sherstobitova, E.A.; Blatov, V.A.; Shekhtman, G.Sh.

    2014-03-15

    The electrical conductivity of lithium diphosphate Li{sub 4}P{sub 2}O{sub 7} has been measured and jump-like increasing of ionic conductivity at 913 K has been found. The crystal structure of Li{sub 4}P{sub 2}O{sub 7} has been refined using high temperature neutron diffraction at 300–1050 K. At 913 K low temperature triclinic form of Li{sub 4}P{sub 2}O{sub 7} transforms into high temperature monoclinic one, space group P2{sub 1}/n, a=8.8261(4) Å, b=5.2028(4) Å, c=13.3119(2) Å, β=104.372(6)°. The migration maps of Li{sup +} cations based on experimental data implemented into program package TOPOS have been explored. It was found that lithium cations in both low- and high temperature forms of Li{sub 4}P{sub 2}O{sub 7} migrate in three dimensions. Cross sections of the migrations channels extend as the temperature rises, but at the phase transition point have a sharp growth showing a strong “crystal structure – ion conductivity” correlation. -- Graphical abstract: Crystal structure of Li{sub 4}P{sub 2}O{sub 7} at 950 K. Red balls represent oxygen atoms; black lines show Li{sup +} ion migration channels in the layers perpendicular to [001] direction. Highlights: • Structure of Li{sub 4}P{sub 2}O{sub 7} has been refined using high temperature neutron diffraction. • At 913 K triclinic form of Li{sub 4}P{sub 2}O{sub 7} transforms into high temperature monoclinic one. • The migration maps of Li{sup +} implemented into program package TOPOS have been explored. • Cross sections of the migrations channels at the phase transition have a sharp growth.

  9. Conductivity of boules of single crystal sodium beta-alumina

    NASA Technical Reports Server (NTRS)

    Fielder, W. L.; Kautz, H. E.; Fordyce, J. S.; Singer, J.

    1974-01-01

    The ionic and electrochemical polarization characteristics of two boules of single crystal sodium beta-alumina (Na2O.8Al2O3), 2 cm in diameter, were investigated over the range of 25 to 300 C using 2- and 4-probe ac and dc techniques with reversible and ion-blocking electrodes. Textural (or internal) polarization at 27 C was present only in boule 1 which cleaved easily. Interfacial polarization, using solid sodium electrodes, was present at 27 C in the 2-probe conductivities for both boules. Cleaning with liquid sodium at 300 C reduced its magnitude, but some interfacial polarization was still present in the 2-probe conductivities for boule 2 below about 140 C. Above 140 C, with liquid sodium electrodes, the 2-probe conductivities, essentially polarization-free, were given by KT = 3300 exp(-3650/RT). The conductivity of boule 2 at 180 C remained essentially constant with increasing current density up to about 140 milliamps per square centimeter.

  10. Proton Conduction and Defect Studies in Acceptor - Potassium Tantalate Crystals.

    NASA Astrophysics Data System (ADS)

    Lee, Wing Kit

    The protonic transport properties of the cubic perovskite structured crystal KTaO(,3) doped with transition metal ions (Fe('3+), Cu('2+), etc.) are studied. These dopants substitute for the Ta('5+) ions and require oxygen vacancies for charge compensation. Protons are introduced by annealing the doped crystals in water vapor. A sharp IR peak at 3472 cm('-1) is observed at room temperature. This OH('-) band can be removed by vacuum annealing. Undoped crystals are not susceptible to H('+) incorporation. A reaction is proposed for the incorporation of H('+): H(,2)O + V(,o) (--->) O(,o)('x) + 2H(.). A saturation content of H('+) is always attained which is independent of both pH(,2)O and annealing temperature. Impendence analysis is employed to obtain the bulk electrical conductivity, (sigma). The (sigma) of H('+) charged samples is an order of magnitude higher than that without H('+). The activation energy for conduction, E(,H), for H('+) charged samples is close to 1.05 eV, irrespective of nature of dopants. A rough monotonic relation between (sigma) and (alpha)(,OH), the IR absorption coefficient, is observed. Conductivity calculated from diffusion data is in rough agreement with the measured (sigma). In addi- tion, the protonic transport number is found to be almost unity in an electrochemical cell experiment. The position of the IR peak is the same for different dopants, suggesting no association between dopant and H('+). The presence of an EPR axial spectrum in H('+) free Fe-doped samples and its conversion to a cubic spectrum after charging with H('+) favors the suggestion that H('+) dissociates from dopants. No dielectric relaxa- tion peak related to H('+) is ever observed. E(,H) thus corresponds to migrational energy only. The migration of the proton is probably just the jump of H('+) between neighboring O('2-) ions in the direction of O-H vibration. The isotope effect on (sigma) is also studied when H('+) is replaced entirely by D('+). The result is non

  11. Effect of crystal orientation on conductivity and electron mobility in single-crystal alumina

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    The electrical conductivity of high-purity, single-crystal alumina is determined parallel to and perpendicular to the c-axis. The mean conductivity of four samples of each orientation is a factor 3.3 higher parallel to the c-axis than perpendicular to it. The conductivity as a function of temperature is attributed to extrinsic electron conduction at temperatures from 400 to 900 C, and intrinsic semiconduction at temperatures from 900 to 1300 C. In the high-temperature regime, the slope on all eight specimens is 4.7 +/- 0.1 eV. Hence, the thermal bandgap at O K is 9.4 +/- 0.2 eV.

  12. Polaron conductivity mechanism in potassium acid phthalate crystal: AC-conductivity investigation

    NASA Astrophysics Data System (ADS)

    Filipič, Cene; Levstik, Iva; Levstik, Adrijan; Hadži, Dušan

    2016-08-01

    The complex dielectric constant, \\varepsilon *(ν ,T), of potassium acid phthalate monocrystal (KAP) was investigated over the broad frequency and temperature range. While the imaginary part of dielectric constant ε‧‧(ν) increases rapidly with increasing temperature in the studied temperature range, the real part of dielectric constant ε‧(ν) increases only at high temperatures; there is almost no change of ε‧(ν) below 200 K. Both values of ε‧ and ε‧‧ are frequency dependent; the values increase with decreasing frequencies. At temperatures below 450 K the ac electrical conductivity and dielectric constant follow simultaneously the universal dielectric response (UDR). The analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for small polarons revealed that this mechanism governs the charge transport in KAP crystal in the studied temperature range.

  13. Possible enhancement of physical properties of nematic liquid crystals by doping of conducting polymer nanofibres

    NASA Astrophysics Data System (ADS)

    Manda, R.; Dasari, V.; Sathyanarayana, P.; Rasna, M. V.; Paik, P.; Dhara, Surajit

    2013-09-01

    We report on the preparation and physical characterization of the colloidal suspension of conducting polyaniline (PANI) nanofibres and a nematic liquid crystal (5CB). The ac electrical conductivity anisotropy increases significantly and the rotational viscosity decreases with increasing wt. % of PANI nanofibres, while other physical properties such as birefringence, dielectric anisotropy, splay, and bend elastic constants are changed moderately. The high conductivity anisotropy of liquid crystal nano-composites is very useful for magnetically steered liquid crystal-nanofibre switch.

  14. Catalytic synthesis of metal crystals using conductive polymers

    DOEpatents

    Wang, Hsing-Lin; Li, Wenguang

    2008-01-15

    A method of forming metal nanoparticles using a polymer colloid that includes at least one conductive polymer and at least one polyelectrolyte. Metal ions are reduced in water by the conductive polymer to produce the nanoparticles, which may be then incorporated in the colloidal structure to form a colloid composite. The method can also be used to separate selected metal ions from aqueous solutions.

  15. Mesoscale conductivity and scaling function in aggregates of cubic, trigonal, hexagonal, and tetragonal crystals

    NASA Astrophysics Data System (ADS)

    Ranganathan, Shivakumar I.; Ostoja-Starzewski, Martin

    2008-06-01

    The framework of stochastic mechanics is used to obtain scale-dependent bounds on the thermal conductivity of random polycrystals. This is done with the help of a scaling function that enables one to define the mesoscale that separates the effective, macroscopic conductivity from the realization-dependent microscale conductivity. We demonstrate that the scaling function depends upon the single-crystal anisotropy measure (k) and the mesoscale (δ) for aggregates made up of cubic, trigonal, hexagonal, and tetragonal single crystals. The proposed methodology unifies the treatment of a variety of crystals over different length scales. Finally, we develop a methodology to construct a material selection diagram in the (k-δ) space.

  16. Mechanical tension and electrical conductivity of liquid crystal filaments

    NASA Astrophysics Data System (ADS)

    Kress, Oliver H.

    During the NSF funded IRES internship at the Otto-von-Geuricke Univeristy in Magdeburg, Germany, I studied the optical properties and mechanical behavior in the form of line tension of bent-core liquid crystal fiber bundles and verified previously published tension values and temperature dependent behavior. Then, carbon nanotubes were added and it as found that the tension in the fibers decreased by a factor of two instead of increasing as was hoped. A new device for pulling fibers and measuring tension by deflection due to the adhesion of glass beads was built at the LCI. The device was meant to improve upon the device used at O.v.G. Improvements included a smaller heating chamber with better insulation, temperature control, large viewing windows, more stable mounting interface, easier disassembly and the option to quickly modify the device in order to perform a variety of other experiments such as observing behavior due to acoustic driving (based on previous literature), observing optical behavior under a polarizing microscope and introducing probes to measure the electrical properties of fibers. The platform remains modular and makes the addition of new components for carrying out new experiments very simple and straightforward. The addition of carbon nanotubes has scattered results regarding the modulation of fiber tension. It seems that the addition of CNTs to BLC1571 may slightly be decreasing tension while the addition to BLC1688 may be increasing it. In both mesogens, 10wt% CNT yielded the highest tension value above the theoretical surface tension contribution. A reversal of temperature dependence was observed for fibers containing CNT; their tension increased with temperature instead of decreased. A driving rod attached to a speaker was used to acoustically drive a filament of pure BLC1571 in an attempt to replicate the tension values in a different way. The movement of the fiber and the driving rod were captured using a high-speed camera and MATLAB code

  17. Enhancing proton conduction via doping of supramolecular liquid crystals (4-alkoxybenzoic acids) with imidazole

    NASA Astrophysics Data System (ADS)

    Liang, Ting; Wu, Yong; Tan, Shuai; Yang, Xiaohui; Wei, Bingzhuo

    2015-09-01

    Enhancing proton conduction via doping was first achieved in hydrogen-bonded liquid crystals consisting of benzoic acids. Supramolecular liquid crystals formed by pure 4-alkoxybenzoic acids (nAOBA, n = 8, 10, 12) exhibited the maximum proton conductivity of 5.0 × 10-8 S cm-1. Doping of nAOBA with 25 mol% imidazole (Im0.25) had little impact on mesomorphism but increased proton conductivities by at least 3 orders of magnitude. The liquid crystals formed by nAOBA-Im0.25 exhibited the maximum proton conductivity of 1.9 × 10-4 S cm-1. It was proposed that structure diffusion of imidazole bridged interdimer proton transfer to form continuous conducting pathways in mesomorphic nAOBA-Im0.25.

  18. Switchable photoluminescence liquid crystal coated bacterial cellulose films with conductive response.

    PubMed

    Tercjak, Agnieszka; Gutierrez, Junkal; Barud, Hernane S; Ribeiro, Sidney J L

    2016-06-01

    Three different low molecular weight nematic liquid crystals (LCs) were used to impregnate bacterial cellulose (BC) film. This simple fabrication pathway allows to obtain highly transparent BC based films. The coating of BC film with different liquid crystals changed transmittance spectra in ultraviolet-visible region and allows to design UVC and UVB shielding materials. Atomic force microscopy results confirmed that liquid crystals coated BC films maintain highly interconnected three-dimensional network characteristic of BC film and simultaneously, transversal cross-section scanning electron microscopy images indicated penetration of liquid crystals through the three-dimensional network of BC nanofibers. Investigated BC films maintain nematic liquid crystal properties being switchable photoluminiscence as a function of temperature during repeatable heating/cooling cycles. Conductive response of the liquid crystal coated BC films was proved by tunneling atomic force microscopy measurement. Moreover, liquid crystal coated BC films maintain thermal stability and mechanical properties of the BC film. Designed thermoresponsive materials possessed interesting optical and conductive properties opening a novel simple pathway of fabrication liquid crystal coated BC films with tuneable properties. PMID:27083359

  19. Phononic Thermal Conduction Engineering for Bolometers: From Phononic Crystals to Radial Casimir Limit

    NASA Astrophysics Data System (ADS)

    Maasilta, I. J.; Puurtinen, T. A.; Tian, Y.; Geng, Z.

    2016-07-01

    We discuss two alternative and complementary means of controlling radial phonon conduction for bolometers in two dimensions: by using phononic crystals or by roughening the surface of the membranes (Casimir limit). For phononic crystals, we present new experiments with a modified geometry and a larger hole periodicity than before, achieving a low thermal conductance {˜ }2 pW/K at 150 mK. Calculations in the Casimir limit, on the other hand, show that for small detector dimensions thermal conductance below 1 fW/K seems achievable.

  20. Conductive Hybrid Crystal Composed from Polyoxomolybdate and Deprotonatable Ionic-Liquid Surfactant.

    PubMed

    Kobayashi, Jun; Kawahara, Ryosuke; Uchida, Sayaka; Koguchi, Shinichi; Ito, Takeru

    2016-01-01

    A polyoxomolybdate inorganic-organic hybrid crystal was synthesized with deprotonatable ionic-liquid surfactant. 1-dodecylimidazolium cation was employed for its synthesis. The hybrid crystal contained δ-type octamolybdate (Mo₈) isomer, and possessed alternate stacking of Mo₈ monolayers and interdigitated surfactant bilayers. The crystal structure was compared with polyoxomolybdate hybrid crystals comprising 1-dodecyl-3-methylimidazolium surfactant, which preferred β-type Mo₈ isomer. The less bulky hydrophilic moiety of the 1-dodecylimidazolium interacted with the δ-Mo₈ anion by N-H···O hydrogen bonds, which presumably induced the formation of the δ-Mo₈ anion. Anhydrous conductivity of the hybrid crystal was estimated to be 5.5 × 10(-6) S·cm(-1) at 443 K by alternating current (AC) impedance spectroscopy. PMID:27347926

  1. Conductive Hybrid Crystal Composed from Polyoxomolybdate and Deprotonatable Ionic-Liquid Surfactant

    PubMed Central

    Kobayashi, Jun; Kawahara, Ryosuke; Uchida, Sayaka; Koguchi, Shinichi; Ito, Takeru

    2016-01-01

    A polyoxomolybdate inorganic-organic hybrid crystal was synthesized with deprotonatable ionic-liquid surfactant. 1-dodecylimidazolium cation was employed for its synthesis. The hybrid crystal contained δ-type octamolybdate (Mo8) isomer, and possessed alternate stacking of Mo8 monolayers and interdigitated surfactant bilayers. The crystal structure was compared with polyoxomolybdate hybrid crystals comprising 1-dodecyl-3-methylimidazolium surfactant, which preferred β-type Mo8 isomer. The less bulky hydrophilic moiety of the 1-dodecylimidazolium interacted with the δ-Mo8 anion by N–H···O hydrogen bonds, which presumably induced the formation of the δ-Mo8 anion. Anhydrous conductivity of the hybrid crystal was estimated to be 5.5 × 10−6 S·cm−1 at 443 K by alternating current (AC) impedance spectroscopy. PMID:27347926

  2. Supramolecular rotators of (aniliniums)([18]crown-6) in electrically conducting [Ni(dmit)2] crystals.

    PubMed

    Hoshino, Norihisa; Yoshii, Yuuya; Aonuma, Masaki; Kubo, Kazuya; Nakamura, Takayoshi; Akutagawa, Tomoyuki

    2012-12-01

    Supramolecular assemblies of anilinium (Ani(+)) and fluoroanilinium derivatives (FAni(+)) with [18]crown-6 were introduced into electrically conducting [Ni(dmit)(2)] crystals (dmit(2-) is 2-thioxo-1,3-dithiole-4,5-dithiolate). The crystal structures, electrical conductivities, and magnetic susceptibilities of four new crystals of (Ani(+))([18]crown-6)[Ni(dmit)(2)](3) (1), (o-FAni(+))([18]crown-6)[Ni(dmit)(2)](3) (2), (m-FAni(+))([18]crown-6)[Ni(dmit)(2)](3) (3), and (p-FAni(+))([18]crown-6)[Ni(dmit)(2)](3) (4) were examined from the viewpoint of dynamic supramolecular rotator structures within the crystals. The crystal structures, electrical conduction, and magnetic properties were classified into group-I (crystals 1 and 4) and group-II (crystals 2 and 3). The hydrogen-bonding interaction between -NH(3)(+) and the oxygen atoms of [18]crown-6 formed the stand-up configuration of rotator-stator structures of (Ani(+))([18]crown-6) and (FAni(+))([18]crown-6) supramolecules. The potential energy barriers for the 2-fold flip-flop motion of phenyl- and p-fluorophenyl-rings in crystals 1 and 4 had a relatively small magnitude of ∼150 kJ mol(-1), suggesting that rotations of Ani(+) and p-FAni(+) cations around the C-NH(3)(+) axis occurred in the crystals. In contrast, a large magnitude of the potential energy barriers for the rotations of o-FAni(+) and m-FAni(+) cations in crystals 2 and 3 (>600 kJ mol(-1)) resulted in static supramolecular cationic structures. The cation:anion ratio of 1:3 in these crystals yielded a trimer π-stack of [Ni(dmit)(2)] with a semiconductor-like temperature dependence. The magnetic susceptibilities of the static crystals 2 and 3 were reproduced by the one-dimensional antiferromagnetic linear Heisenberg chain through the one-dimensional linear trimer arrangement. The magnetic susceptibilities of dynamic crystals 1 and 4 enhanced electron delocalization through the intratrimer and intertrimer interactions within the trimer stack, where the

  3. Ionic conductivity of ScF3 single crystals (ReO3 type)

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.; Karimov, D. N.; Grebenev, V. V.; Sobolev, B. P.

    2016-03-01

    Electrical conductivity σ of ScF3 single crystals (sp. gr. Pmoverline 3 m, ReO3 structure type) has been studied by impedance spectroscopy and compared with the electrical conductivity of rare earth HoF3 (β-YF3 type) and LaF3 (tysonite type) trifluorides. ScF3 crystals obtained by Bridgman directional solidification have ionic conductivity σ = 4 × 10-8 S/cm at 673 K. It is smaller than the σ values for LaF3 (sp. gr. Poverline 3 c1) and HoF3 (sp. gr. Pnma) single crystals by a factor of 104-105. The low conductivity of ScF3 crystals is due to the weak coordinating ability (coordination number CN = 6) and low electronic polarizability (α cat = 1.1 Å3) of Sc3+ ions. Mobile V F + vacancies and less mobile interstitial V i - ions (defects are formed according to the Frenkel mechanism) are involved in the ion transport. HoF3 and LaF3 single crystals have a high coordinating ability (CN = 9 for Ho3+ and CN = 11 for La3+) and a high electronic polarizability of cations (α cat = 1.6-1.9 Å3 for Ho3+ and α cat = 2.2 Å3 for La3+). Only mobile V F + vacancies (defects are formed according to the Schottky mechanism) are involved in ion transport.

  4. Low-temperature conductivity in CuGaS{sub 2} single crystals

    SciTech Connect

    Abdullaev, N. A. Aliguliyeva, Kh. V.; Aliyeva, L. N.; Qasimoglu, I.; Kerimova, T. G.

    2015-04-15

    CuGaS{sub 2} single crystals are grown by the Bridgman-Stockbarger method. X-ray diffraction and Raman studies are performed. It is shown that the conductivity at low temperatures has an activation mechanism: in the range of 100–300 K, impurity conduction with an acceptor activation energy of 12 meV dominates; at temperatures below 100 K, Mott conductivity, i.e., so-called hopping conductivity with a variable hop length prevails. The density of localized states and the average carrier hop length are estimated.

  5. From crystal to glass-like thermal conductivity in crystalline minerals.

    PubMed

    Bouyrie, Y; Candolfi, C; Pailhès, S; Koza, M M; Malaman, B; Dauscher, A; Tobola, J; Boisron, O; Saviot, L; Lenoir, B

    2015-08-14

    The ability of some materials with a perfectly ordered crystal structure to mimic the heat conduction of amorphous solids is a remarkable physical property that finds applications in numerous areas of materials science, for example, in the search for more efficient thermoelectric materials that enable to directly convert heat into electricity. Here, we unveil the mechanism in which glass-like thermal conductivity emerges in tetrahedrites, a family of natural minerals extensively studied in geology and, more recently, in thermoelectricity. By investigating the lattice dynamics of two tetrahedrites of very close compositions (Cu12Sb2Te2S13 and Cu10Te4S13) but with opposite glasslike and crystal thermal transport by means of powder and single-crystal inelastic neutron scattering, we demonstrate that the former originates from the peculiar chemical environment of the copper atoms giving rise to a strongly anharmonic excess of vibrational states. PMID:26109211

  6. Surface conductivity of the single crystal aluminum oxide in vacuum and caesium vapors

    SciTech Connect

    Vasilchenko, A.V.; Izhvanov, O.L.

    1996-03-01

    Results of measurements of surface conductivity of single-crystal aluminum oxide samples in vacuum and cesium vapors at T=620{endash}830 K and P{sub Cs}=0.13{endash}2 Pa are shown in the paper. Analysis of caesium vapor influence is carried out and ultimate characteristics of samples conductivity under operation conditions in thermionic nuclear power system (NPP) TFE are estimated. {copyright} {ital 1996 American Institute of Physics.}

  7. Heat, Light, and Videotapes: Experiments in Heat Conduction Using Liquid Crystal Film.

    ERIC Educational Resources Information Center

    Bacon, Michael E.; And Others

    1995-01-01

    Presents a range of experiments in heat conduction suitable for upper-level undergraduate laboratories that make use of heat sensitive liquid crystal film to measure temperature contours. Includes experiments mathematically described by Laplace's equation, experiments theoretically described by Poisson's equation, and experiments that involve…

  8. Anisotropy of thermal conductivities in non- and Mg-doped near-stoichiometric LiTaO 3 crystals

    NASA Astrophysics Data System (ADS)

    Nakamura, Masaru; Takekawa, Shunji; Kitamura, Kenji

    2010-09-01

    We investigated the thermal conductivities of non-doped near-stoichiometric LiTaO 3 (SLT) and Mg (1 mol%)-doped near-stoichiometric LiTaO 3 (Mg:SLT) crystals along the X-, Y-, and Z-axes at room temperature. Those of non-doped congruent LiTaO 3 (CLT) crystal along the same axes were also estimated to investigate the effect of non-stoichiometric defects. The thermal conductivities were determined by measuring the thermal diffusivity using a laser-flash method and measuring the specific heat using a differential scanning calorimeter. Anisotropy of the thermal conductivities was found for all three crystals. That is, the thermal conductivities along the X-axis were the same as those along the Y-axis and less than those along the Z-axis. The thermal conductivities of the SLT crystal were the highest and were twice those of the CLT crystal. The thermal conductivities of the Mg:SLT crystal were slightly lower than those of the SLT crystal apparently due to the Mg-doping. We also investigated the effect of the difference in domain structure on thermal conductivity using as-grown Mg:SLT crystal with randomly distributed multi-domains and found that it did not affect the thermal conductivity along any axis. These findings regarding thermal conductivity should be useful for designing high-power laser applications using SLT and Mg:SLT crystals.

  9. RAPID COMMUNICATION: Simultaneous determination of anisotropic thermal conductivities of liquid crystals by means of a photothermal self-diffracting technique

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Shibata, Kazuaki

    2000-11-01

    Anisotropic thermal conductivities of liquid crystals were simultaneously determined by means of a photothermal self-diffracting technique. A single-mode laser beam with Gaussian profile excited refractive index distribution due to the photothermal effect in homogeneously-aligned liquid-crystal films. The refractive index distribution, which is affected by thermal conductivities of liquid crystals, transformed the incident Gaussian beam. The laser beam was self-diffracted and thermal conductivities of liquid crystals were determined by characterizing the beam profile by both Kirchhoff's diffraction theory and heat conduction analysis.

  10. Thermal conductivity of heavily doped bulk crystals GaN:O. Free carriers contribution

    NASA Astrophysics Data System (ADS)

    Jeżowski, A.; Churiukova, O.; Mucha, J.; Suski, T.; Obukhov, I. A.; Danilchenko, B. A.

    2015-08-01

    Here we report the results of an experimental study of the thermal conductivity of GaN crystals doped by oxygen with concentrations of 4 × 1016, 2.6 × 1018 and 1.1 × 1020 cm-3, carried out in the temperature interval 7-318 K. We observed the highest thermal conductivity ever reported for GaN, 269 Wm-1 K-1 at 300 K, in the sample with the lowest oxygen content. This result is explained by the renormalization of GaN elastic constants, caused by the effect of spontaneous polarization. Results were analyzed using the Callaway model. The contribution of phonon scattering by free carriers in doped GaN crystals was considered for the first time. We show that free electrons reduce the thermal conductivity by up to 32%-42% at 300 K for a sample with a 1.1 × 1020 cm-3 of oxygen concentration.

  11. Discontinuous anchoring transition and photothermal switching in composites of liquid crystals and conducting polymer nanofibers

    NASA Astrophysics Data System (ADS)

    Rasna, M. V.; Zuhail, K. P.; Manda, R.; Paik, P.; Haase, W.; Dhara, Surajit

    2014-05-01

    We prepared nanocomposites of a nematic liquid crystal and nanofibers of a conducting polymer (polyaniline). All the nanocomposites exhibit a discontinuous surface anchoring transition from planar to homeotropic in the nematic phase on a perfluoropolymer coated surface with a thermal hysteresis (≈5.3∘C). We observe a relatively large bistable conductivity and demonstrate a light driven switching of conductivity and dielectric constant in dye doped nanocomposites in the thermal hysteresis (bistable) region. The experimental results have been explained based on the reorientation of the nanofibers driven by the anchoring transition of the nematic liquid crystal. We show a significant enhancement of the bistable temperature range (≈13∘C) by an appropriate choice of compound in the binary system.

  12. Dielectric and conducting behavior of gadolinium-terbium fumarate heptahydrate crystals

    NASA Astrophysics Data System (ADS)

    Shah, M. D.; Want, B.

    2015-07-01

    Gadolinium-terbium fumarate heptahydrate crystals were grown in silica gel by using single gel diffusion technique. The crystals were characterized by different physico-chemical techniques of characterization. Powder X-ray diffraction results showed that the grown material is purely crystalline in nature. Elemental analyses suggested the chemical formula of the compound to be Gd Tb (C4H2O4)3ṡ7H2O. Energy dispersive X-ray analysis confirmed the presence of Gd and Tb in the title compound. The dielectric and conductivity studies of the grown compound were carried as function of frequency of applied field and the temperature. The grown material showed a dielectric anomaly which was correlated with its thermal behavior. The ac conductivity of the material showed Jonscher's power law behavior: σ(ω)=σo+Aωs, with a temperature-dependent power exponent s(<1). The conductivity was found to be a function of temperature and frequency.

  13. Extreme low thermal conductivity in nanoscale 3D Si phononic crystal with spherical pores.

    PubMed

    Yang, Lina; Yang, Nuo; Li, Baowen

    2014-01-01

    In this work, we propose a nanoscale three-dimensional (3D) Si phononic crystal (PnC) with spherical pores, which can reduce the thermal conductivity of bulk Si by a factor up to 10,000 times at room temperature. Thermal conductivity of Si PnCs depends on the porosity, for example, the thermal conductivity of Si PnCs with porosity 50% is 300 times smaller than that of bulk Si. The phonon participation ratio spectra demonstrate that more phonons are localized as the porosity increases. The thermal conductivity is insensitive to the temperature changes from room temperature to 1100 K. The extreme-low thermal conductivity could lead to a larger value of ZT than unity as the periodic structure affects very little the electric conductivity. PMID:24559126

  14. Highly conducting crystals based on single-component gold complexes with extended-TTF dithiolate ligands.

    PubMed

    Suzuki, Wakako; Fujiwara, Emiko; Kobayashi, Akiko; Fujishiro, Yuichi; Nishibori, Eiji; Takata, Masaki; Sakata, Makoto; Fujiwara, Hideki; Kobayashi, Hayao

    2003-02-12

    Highly conducting crystals based on single-component gold complexes with extended-TTF dithiolate ligands [Au(dmdt)(2)](0+) (1) and [Au(tmdt)(2)](0+) (2) were prepared (dmdt = dimethyltetrathiafulvalenedithiolate and tmdt = trimethylenetetrathiafulvalenedithiolate). On the basis of the synchrotron radiation powder diffraction data, the MEM electron density of 2 was successfully obtained. The conductivities of compacted powder samples of 1 and 2 at room temperature were 12 and 15 S cm(-1), respectively. Pauli-like susceptibility of 1 suggested the system to be essentially metallic at least above 50 K, while 2 showed a magnetic transition around 100 K without loss of its high conductivity. PMID:12568602

  15. Influence of purity of NdF3 single crystals on their ionic conductivity

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.; Zhmurova, Z. I.; Krivandina, E. A.; Sobolev, B. P.

    2012-05-01

    Single crystals of the NdF3 superionic conductor have been grown by the Bridgman method from a melt in a helium atmosphere using a fluorinating PbF2 agent. Commercial NdF3 reagents of special purity grade, reagent grade, and pure grade are used. It is found that the ionic conductivity σ of the crystals depends considerably on the purity grade of the starting substances: at 200°C σ = 1.4 × 10-, 3 × 10-4, and 8 × 10-4 S/cm for reagents of special purity grade, reagent grade, and pure grade, respectively.

  16. Glass Formation of a Coordination Polymer Crystal for Enhanced Proton Conductivity and Material Flexibility.

    PubMed

    Chen, Wenqian; Horike, Satoshi; Umeyama, Daiki; Ogiwara, Naoki; Itakura, Tomoya; Tassel, Cédric; Goto, Yoshihiro; Kageyama, Hiroshi; Kitagawa, Susumu

    2016-04-18

    The glassy state of a two-dimensional (2D) Cd(2+) coordination polymer crystal was prepared by a solvent-free mechanical milling process. The glassy state retains the 2D structure of the crystalline material, albeit with significant distortion, as characterized by synchrotron X-ray analyses and solid-state multinuclear NMR spectroscopy. It transforms to its original crystal structure upon heating. Thus, reversible crystal-to-glass transformation is possible using our new processes. The glass state displays superior properties compared to the crystalline state; specifically, it shows anhydrous proton conductivity and a dielectric constant two orders of magnitude greater than the crystalline material. It also shows material flexibility and transparency. PMID:26990042

  17. Data Mining-Aided Crystal Engineering for the Design of Transparent Conducting Oxides: Preprint

    SciTech Connect

    Suh, C.; Kim, K.; Berry, J. J.; Lee, J.; Jones, W. B.

    2010-12-01

    The purpose of this paper is to accelerate the pace of material discovery processes by systematically visualizing the huge search space that conventionally needs to be explored. To this end, we demonstrate not only the use of empirical- or crystal chemistry-based physical intuition for decision-making, but also to utilize knowledge-based data mining methodologies in the context of finding p-type delafossite transparent conducting oxides (TCOs). We report on examples using high-dimensional visualizations such as radial visualization combined with machine learning algorithms such as k-nearest neighbor algorithm (k-NN) to better define and visualize the search space (i.e. structure maps) of functional materials design. The vital role of search space generated from these approaches is discussed in the context of crystal chemistry of delafossite crystal structure.

  18. Linked reactivity at mineral-water interfaces through bulk crystal conduction.

    PubMed

    Yanina, Svetlana V; Rosso, Kevin M

    2008-04-11

    The semiconducting properties of a wide range of minerals are often ignored in the study of their interfacial geochemical behavior. We show that surface-specific charge density accumulation reactions combined with bulk charge carrier diffusivity create conditions under which interfacial electron transfer reactions at one surface couple with those at another via current flow through the crystal bulk. Specifically, we observed that a chemically induced surface potential gradient across hematite (alpha-Fe2O3) crystals is sufficiently high and the bulk electrical resistivity sufficiently low that dissolution of edge surfaces is linked to simultaneous growth of the crystallographically distinct (001) basal plane. The apparent importance of bulk crystal conduction is likely to be generalizable to a host of naturally abundant semiconducting minerals playing varied key roles in soils, sediments, and the atmosphere. PMID:18323417

  19. Organic single-crystal surface-induced polymerization of conducting polypyrroles.

    PubMed

    Jeon, Sang Soo; Park, Jun Kyu; Yoon, Chong Seung; Im, Seung Soon

    2009-10-01

    Polypyrrole hexagonal microplates (PHMs) (50-100 microm long, 10-20 microm wide, and 0.8-1.2 microm thick) with a quasicrystalline structure and high electrical conductivity (up to 400 S/cm) are simply fabricated using single crystals of 4-sulfobenzoic acid monopotassium salt (KSBA) in aqueous medium. Moreover, the fabrication process described here differs strikingly from traditional methods, such as template-free, soft template, and hard template methods. Synthetic time-resolved polypyrrole (PPy) morphology dynamics reveals that the fabrication process of PHMs composed of PPy nanostructures combines a shape-copying process for forming a PPy preform that imitates the shape of a KSBA single crystal and the self-assembly process of PPys on the preform. The PHMs exhibit the improved pi-stacking and bipolaron structure. The strong pi-stacks among PPy rings of bipolaron structures lead to a high quasicrystalline structural order and the metallic conduction. Other single organic crystals that can act as dopants could also be grown using this approach, which will also enable the fabrication of complex micro/nanostructures on organic single crystals. PMID:19681625

  20. Pressure tuning of the thermal conductivity of the layered muscovite crystal

    SciTech Connect

    Hsieh, Wen-Pin; Chen, Bin; Li, Jie; Keblinski, Pawel; Cahill, David G.

    2010-01-12

    The physics of heat conduction in layered, anisotropic crystals is probed by measurements of the cross-plane elastic constant C{sub 33} and thermal conductivity {Lambda} of muscovite mica as a function of hydrostatic pressure. Picosecond interferometry and time-domain thermoreflectance provide high-precision measurements of C{sub 33} and {Lambda}, respectively, of micron-sized samples within a diamond-anvil cell; {Lambda} changes from the anomalously low value of 0.46 W m{sup -1} K{sup -1} at ambient pressure to a value more typical of oxides crystals with large unit cells, 6.6 W m{sup -1} K{sup -1}, at P = 24 GPa. Most of the pressure dependence of {Lambda} can be accounted for by the pressure dependence of the cross-plane sound velocities.

  1. Conductive and dielectric defects, and anisotropic and isotropic turbulence in liquid crystals: Electric power fluctuation measurements

    NASA Astrophysics Data System (ADS)

    Tóth-Katona, Tibor; Gleeson, James T.

    2004-01-01

    Fluctuations of the injected electric power during electroconvection (EHC) of liquid crystals are reported in both the conductive and the dielectric regime of convection. The amplitude and the frequency of the fluctuations, as well as the probability density functions have been compared in these two regimes and substantial differences have been found both in defect turbulence of EHC and at the DSM1→DSM2 transition.

  2. Diversity of surface conduction in pyrite FeS2 single crystals

    NASA Astrophysics Data System (ADS)

    Leighton, Chris; Walter, Jeff; Zhang, Xin; Mork, Frazier; Hool, Ryan; Manno, Mike; Aydil, Eray

    Pyrite FeS2 has long been recognized as an attractive material for solar cells because of its high absorptivity, potential low cost, high abundance, and low toxicity. Despite having appropriate band gap (0.95 eV) and minority carrier diffusion length (100-1000 nm), low open circuit voltages (Voc <= 0.1 V) have plagued FeS2-based cells. Surface conduction has been proposed as a contributing factor for the low Voc, particularly a p-type surface inversion layer on n-type crystals. Here we report a detailed electronic transport study of a large number of well-characterized CVT-grown n-FeS2 single crystals. Abundant evidence of surface conduction is found from the T dependence of resistivity, resistance anisotropy, low T behavior at the 2D quantum resistance, thickness dependence, and the influence of contact metal work function. However, striking diversity in this surface conduction is found, even in nominally identical crystals at similar doping. The results cannot be understood by surface inversion alone, pointing to as yet uncontrolled surface factors. Work supported by NSF.

  3. The temperature dependence of the heat conductivity of a liquid crystal studied by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Sarman, Sten; Laaksonen, Aatto

    2010-01-01

    The temperature dependence of the heat conductivity has been obtained for a liquid crystal model based on the Gay-Berne fluid, from the isotropic phase at high temperatures through the nematic phase to the smectic A phase at low temperatures. The ratio of the parallel and the perpendicular components of the heat conductivity is about 2.5:1 in the nematic phase, which is similar to that of real systems. Both Green-Kubo methods and nonequilibrium molecular dynamics methods have been applied and the results agree within in a relative error of a couple of percent, but the latter method is much more efficient.

  4. Real-time crystallization in fluorinated parylene probed by conductivity spectra

    NASA Astrophysics Data System (ADS)

    Khazaka, R.; Locatelli, M. L.; Diaham, S.; Tenailleau, C.; Kumar, R.

    2014-03-01

    Dielectric relaxation spectroscopy experiments were performed at high temperature on fluorinated parylene films during the occurrence of the isothermal crystalline phase transition. For this polymer, since the difference between the glass transition temperature (Tg) and the phase transition temperature (Tc) is very strong (Tc ≥ 4Tg), segmental and dipolar relaxation usually used to probe the crystallization are not shown in the experiment frequency window (10-1 to 106 Hz) during the crystallization. The charge diffusion becomes the only electrical marker that allows probing the phase transition. During the transition phase, a continuous decrease of about two orders of magnitude is observed in the conductivity values below an offset frequency (fc) with a tendency to stabilization after 600 min. Below the offset frequency, the decrease of the normalized conductivity to the initial value as function of time is frequency independent. The same behavior is also observed for the fc values that decrease from 160 Hz to about 20 Hz. Above the offset frequency, the electronic hopping mechanism is also affected by the phase transition and the power law exponent (n) of the AC conductivity shows a variation from 0.7 to 0.95 during the first 600 min that tend to stabilize thereafter. Accordingly, three parameters (n, fc, and AC conductivity values for frequencies below fc) extracted from the AC conductivity spectra in different frequency windows seem suitable to probe the crystalline phase transition.

  5. Self-assembling of molecular nanowires for enhancing the conducting properties of discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Park, Ji Hyun; Kim, Kyung Ho; Takanishi, Yoichi; Yamamoto, Jun; Park, Yung Woo; Kim, Youn Sang; Scalia, Giusy

    2015-08-01

    The self-organization of discotic liquid crystal molecules in columns has enormous interest for soft nanoelectronic applications. A great advantage of discotic liquid crystal is that defects can be self-annealed in contrast to typical organic materials. Through the overlap of molecular orbitals, the aromatic cores assemble into long range ordered one-dimensional structures. Very thin structured films can be obtained by spin-coating from solution and the resulting morphologies are strongly dependent on the interaction between discotics and solvent molecules. Toluene produces films formed by very long nanowires, spontaneously aligned along a common direction and over fairly large areas. These nanostructured films are a result of the interplay between liquid crystal self-organization and solvent driven assembly. The ordered nanowire structures exhibit improvement in the electrical properties compared to misaligned structures and even to pristine HAT5, deposited without the aid of solvent. In this study we show that the toluene-based deposition of discotic liquid crystals is advantageous because it allows a uniform coverage of the substrate, unlike pristine HAT5 but also thanks to the type of induced structures exhibiting one order of magnitude higher conductivity, in the aligned nanowire films, compared to bare HAT5 ones.

  6. Kinetic of crystallization and electrical conductance of Ge 5As 38Te 57 amorphous chalcogenide alloy

    NASA Astrophysics Data System (ADS)

    Elshafie, A.; Abdel-All, A.

    1999-07-01

    DTA measurements were made on Ge 5As 38Te 57 amorphous chalcogenide alloy. The glass transition temperature ( Tg), the first exothermic peak ( Tc1) and the second exothermic peak ( Tc2) were found to increase as the heating rate increases. The kinetic parameters were evaluated from the DTA curves and related to the crystallization mechanism where both the bulk and surface cyrstallization were considered. The crystal nucleation and growth of Ge 5As 38Te 57 glass were studied by three simple methods, and the average activation energy of nucleation was found to be 31.74 kcal/mol. The apparent activation energies for crystallization were estimated to be 59.7 and 42.6 kcal/mol for the 1st and 2nd peak, respectively. X-ray analysis for samples, isothermally annealed at temperatures higher than the glass transition and crystallization temperatures indicates that phases of Te and As 2Te 3 were nucleated and grown. The activation energy of conduction as well as the disordered enegy were also calculated.

  7. Magnetic detonation structure in crystals of nanomagnets controlled by thermal conduction and volume viscosity

    NASA Astrophysics Data System (ADS)

    Jukimenko, O.; Modestov, M.; Marklund, M.; Bychkov, V.

    2015-03-01

    Experimentally detected ultrafast spin avalanches spreading in crystals of molecular (nano)magnets [Decelle et al., Phys. Rev. Lett. 102, 027203 (2009), 10.1103/PhysRevLett.102.027203] have recently been explained in terms of magnetic detonation [Modestov et al., Phys. Rev. Lett. 107, 207208 (2011), 10.1103/PhysRevLett.107.207208]. Here magnetic detonation structure is investigated by taking into account transport processes of the crystals such as thermal conduction and volume viscosity. The transport processes result in smooth profiles of the most important thermodynamical crystal parameters, temperature, density, and pressure, all over the magnetic detonation front, including the leading shock, which is one of the key regions of magnetic detonation. In the case of zero volume viscosity, thermal conduction leads to an isothermal discontinuity instead of the shock, for which temperature is continuous while density and pressure experience jump. It is also demonstrated that the thickness of the magnetic detonation front may be controlled by applying the transverse-magnetic field, which is important for possible experimental observations of magnetic detonation.

  8. Vertically Conductive Single-Crystal SiC-Based Bragg Reflector Grown on Si Wafer

    PubMed Central

    Massoubre, David; Wang, Li; Hold, Leonie; Fernandes, Alanna; Chai, Jessica; Dimitrijev, Sima; Iacopi, Alan

    2015-01-01

    Single-crystal silicon carbide (SiC) thin-films on silicon (Si) were used for the fabrication and characterization of electrically conductive distributed Bragg reflectors (DBRs) on 100 mm Si wafers. The DBRs, each composed of 3 alternating layers of SiC and Al(Ga)N grown on Si substrates, show high wafer uniformity with a typical maximum reflectance of 54% in the blue spectrum and a stopband (at 80% maximum reflectance) as large as 100 nm. Furthermore, high vertical electrical conduction is also demonstrated resulting to a density of current exceeding 70 A/cm2 above 1.5 V. Such SiC/III-N DBRs with high thermal and electrical conductivities could be used as pseudo-substrate to enhance the efficiency of SiC-based and GaN-based optoelectronic devices on large Si wafers. PMID:26601894

  9. Manipulating the temperature dependence of the thermal conductivity of graphene phononic crystal

    NASA Astrophysics Data System (ADS)

    Hu, Shiqian; An, Meng; Yang, Nuo; Li, Baowen

    2016-07-01

    By using non-equilibrium molecular dynamics simulations, modulating the temperature dependence of thermal conductivity of graphene phononic crystals (GPnCs) is investigated. It is found that the temperature dependence of thermal conductivity of GPnCs follows ∼T ‑α behavior. The power exponents (α) can be efficiently tuned by changing the characteristic size of GPnCs. The phonon participation ratio spectra and dispersion relation reveal that the long-range phonon modes are more affected in GPnCs with larger holes (L 0). Our results suggest that constructing GPnCs is an effective method to manipulate the temperature dependence of thermal conductivity of graphene, which would be beneficial for developing GPnC-based thermal management and signal processing devices.

  10. Vertically Conductive Single-Crystal SiC-Based Bragg Reflector Grown on Si Wafer.

    PubMed

    Massoubre, David; Wang, Li; Hold, Leonie; Fernandes, Alanna; Chai, Jessica; Dimitrijev, Sima; Iacopi, Alan

    2015-01-01

    Single-crystal silicon carbide (SiC) thin-films on silicon (Si) were used for the fabrication and characterization of electrically conductive distributed Bragg reflectors (DBRs) on 100 mm Si wafers. The DBRs, each composed of 3 alternating layers of SiC and Al(Ga)N grown on Si substrates, show high wafer uniformity with a typical maximum reflectance of 54% in the blue spectrum and a stopband (at 80% maximum reflectance) as large as 100 nm. Furthermore, high vertical electrical conduction is also demonstrated resulting to a density of current exceeding 70 A/cm(2) above 1.5 V. Such SiC/III-N DBRs with high thermal and electrical conductivities could be used as pseudo-substrate to enhance the efficiency of SiC-based and GaN-based optoelectronic devices on large Si wafers. PMID:26601894

  11. Vertically Conductive Single-Crystal SiC-Based Bragg Reflector Grown on Si Wafer

    NASA Astrophysics Data System (ADS)

    Massoubre, David; Wang, Li; Hold, Leonie; Fernandes, Alanna; Chai, Jessica; Dimitrijev, Sima; Iacopi, Alan

    2015-11-01

    Single-crystal silicon carbide (SiC) thin-films on silicon (Si) were used for the fabrication and characterization of electrically conductive distributed Bragg reflectors (DBRs) on 100 mm Si wafers. The DBRs, each composed of 3 alternating layers of SiC and Al(Ga)N grown on Si substrates, show high wafer uniformity with a typical maximum reflectance of 54% in the blue spectrum and a stopband (at 80% maximum reflectance) as large as 100 nm. Furthermore, high vertical electrical conduction is also demonstrated resulting to a density of current exceeding 70 A/cm2 above 1.5 V. Such SiC/III-N DBRs with high thermal and electrical conductivities could be used as pseudo-substrate to enhance the efficiency of SiC-based and GaN-based optoelectronic devices on large Si wafers.

  12. Manipulating the temperature dependence of the thermal conductivity of graphene phononic crystal.

    PubMed

    Hu, Shiqian; An, Meng; Yang, Nuo; Li, Baowen

    2016-07-01

    By using non-equilibrium molecular dynamics simulations, modulating the temperature dependence of thermal conductivity of graphene phononic crystals (GPnCs) is investigated. It is found that the temperature dependence of thermal conductivity of GPnCs follows ∼T (-α) behavior. The power exponents (α) can be efficiently tuned by changing the characteristic size of GPnCs. The phonon participation ratio spectra and dispersion relation reveal that the long-range phonon modes are more affected in GPnCs with larger holes (L 0). Our results suggest that constructing GPnCs is an effective method to manipulate the temperature dependence of thermal conductivity of graphene, which would be beneficial for developing GPnC-based thermal management and signal processing devices. PMID:27196392

  13. Purification and crystallization of the cystic fibrosis transmembrane conductance regulator (CFTR).

    PubMed

    Rosenberg, Mark F; Kamis, Alhaji Bukar; Aleksandrov, Luba A; Ford, Robert C; Riordan, John R

    2004-09-10

    The cystic fibrosis transmembrane conductance regulator (CFTR) is a membrane protein that is mutated in patients suffering from cystic fibrosis. Here we report the purification and first crystallization of wild-type human CFTR. Functional characterization of the material showed it to be highly active. Electron crystallography of negatively stained two-dimensional crystals of CFTR has revealed the overall architecture of this channel for two different conformational states. These show a strong structural homology to two conformational states of another eukaryotic ATP-binding cassette transporter, P-glycoprotein. In contrast to P-glycoprotein, however, both conformational states can be observed in the presence of a nucleotide, which may be related to the role of CFTR as an ion channel rather than a transporter. The hypothesis that the two conformations could represent the "open" and "closed" states of the channel is considered. PMID:15247233

  14. 2-Hydroxy-4-methylbenzenesulfonic acid dihydrate: Crystal structure, vibrational spectra, proton conductivity, and thermal stability

    NASA Astrophysics Data System (ADS)

    Pisareva, A. V.; Shilov, G. V.; Karelin, A. I.; Dobrovolsky, Yu. A.; Pisarev, R. V.

    2010-03-01

    The crystal and molecular structure of 2-hydroxy4-methylbenzenesulfonic acid dihydrate C6H3(CH3)(OHSO- 3 H5O2 + (I) was studied by X-ray diffraction and vibrational spectroscopy. The compound crystallized in the monoclinic crystal system; crystal data: a=10.853(2) Å, b=7.937(2) Å, c=12.732(3) Å, β=112.13(3)°, V=1015.9(4)Å3,Z=4,dcalc=1.466g/cm3,spacegroupP21/c,Rf=0.0486,GOOF=1.161.The S-O distances in the sulfonate group differed substantially (S1-O2 1.439(2) Å, S1-O3 1.455(2) Å, and S1-O4 1.464(2) Å. The symmetry of the H5O2 cation decreased due to proton displacement toward one of the two water molecules. XRD data on the asymmetry of H5O2 were confirmed by IR and Raman spectral data. The strong triplet at 2900, 3166, 3377 cm-1 in the IR spectrum of I corresponds to different types of H-bond and shifted to 2185, 2363, 2553 cm-1 after deuteration. The proton conductivity of the compound was measured by impedance spectroscopy: 6 × 10-7 S/cm at 298 K (32 rel %), E act=0.4±0.01 eV. The conductivity increased to 10-3 S/cm, Eact=0.1 eV when ambient humidity increased to 60 rel %.

  15. Mechanism of the Reduced Thermal Conductivity of Fishbone-Type Si Phononic Crystal Nanostructures

    NASA Astrophysics Data System (ADS)

    Nomura, M.; Maire, J.

    2015-06-01

    The mechanism of the reduced thermal conductivity of fishbone-type phononic crystal (PnC) nanostructures, in which ballistic phonon transport is dominant, was investigated with consideration of both the wave and particle nature of phonons. Phononic band diagrams were calculated for an Si nanowire and a fishbone-type PnC structure with a period of 100 nm, and a clear reduction of the group velocity of phonons, because of a zone-folding effect, was shown. Air-suspended Si nanowires and fishbone-type PnC structures were fabricated by electron beam (EB) lithography, and their thermal conductivities were measured by use of the originally developed micro time-domain thermoreflectance method. The PnC structure had a much lower thermal conductivity. We measured the thermal conductivity of a variety of PnC structures with different fin widths to investigate the mechanism of the reduced thermal conductivity observed. The result indicates that the increase of the phonon traveling distance. as a result of the fins, also results in reduced thermal conductivity.

  16. Mechanism of the Reduced Thermal Conductivity of Fishbone-Type Si Phononic Crystal Nanostructures

    NASA Astrophysics Data System (ADS)

    Nomura, M.; Maire, J.

    2014-09-01

    The mechanism of the reduced thermal conductivity of fishbone-type phononic crystal (PnC) nanostructures, in which ballistic phonon transport is dominant, was investigated with consideration of both the wave and particle nature of phonons. Phononic band diagrams were calculated for an Si nanowire and a fishbone-type PnC structure with a period of 100 nm, and a clear reduction of the group velocity of phonons, because of a zone-folding effect, was shown. Air-suspended Si nanowires and fishbone-type PnC structures were fabricated by electron beam (EB) lithography, and their thermal conductivities were measured by use of the originally developed micro time-domain thermoreflectance method. The PnC structure had a much lower thermal conductivity. We measured the thermal conductivity of a variety of PnC structures with different fin widths to investigate the mechanism of the reduced thermal conductivity observed. The result indicates that the increase of the phonon traveling distance. as a result of the fins, also results in reduced thermal conductivity.

  17. Enhancing ionic conductivity of bulk single-crystal yttria-stabilized zirconia by tailoring dopant distribution

    SciTech Connect

    Lee, E.; Prinz, F. B.; Cai, W.

    2011-02-11

    We present an ab initio–based kinetic Monte Carlo model for ionic conductivity in single-crystal yttria-stabilized zirconia. Ionic interactions are taken into account by combining density functional theory calculations and the cluster expansion method and are found to be essential in reproducing the effective activation energy observed in experiments. The model predicts that the effective energy barrier can be reduced by 0.15–0.25 eV by arranging the dopant ions into a superlattice.

  18. Electrically tunable liquid-crystal wave plate using quadripolar electrode configuration and transparent conductive polymer layers.

    PubMed

    Fraval, Nicolas; Joffre, Pascal; Formont, Stéphane; Chazelas, Jean

    2009-10-01

    We present the realization of an electrically tunable wave plate, which uses a nematic liquid-crystal (LC) phase retarder that allows fast and continuous control of the polarization state. This device is built using a quadripolar electrode design and transparent conductive polymer layers in order to obtain a uniform electric field distribution in the interelectrode area. With this realization, we obtain a high degree of control of the orientation of the electric field and, consequently, of the LC director. Indeed, this modulator outperforms classical bipolar LC cells in both optical path variation (>4 microm) and LC rotation speed (0.4 degrees/micros). PMID:19798369

  19. Real-time crystallization in fluorinated parylene probed by conductivity spectra

    SciTech Connect

    Khazaka, R. Diaham, S.; Locatelli, M. L.; Tenailleau, C.

    2014-03-17

    Dielectric relaxation spectroscopy experiments were performed at high temperature on fluorinated parylene films during the occurrence of the isothermal crystalline phase transition. For this polymer, since the difference between the glass transition temperature (T{sub g}) and the phase transition temperature (T{sub c}) is very strong (T{sub c} ≥ 4T{sub g}), segmental and dipolar relaxation usually used to probe the crystallization are not shown in the experiment frequency window (10{sup −1} to 10{sup 6} Hz) during the crystallization. The charge diffusion becomes the only electrical marker that allows probing the phase transition. During the transition phase, a continuous decrease of about two orders of magnitude is observed in the conductivity values below an offset frequency (f{sub c}) with a tendency to stabilization after 600 min. Below the offset frequency, the decrease of the normalized conductivity to the initial value as function of time is frequency independent. The same behavior is also observed for the f{sub c} values that decrease from 160 Hz to about 20 Hz. Above the offset frequency, the electronic hopping mechanism is also affected by the phase transition and the power law exponent (n) of the AC conductivity shows a variation from 0.7 to 0.95 during the first 600 min that tend to stabilize thereafter. Accordingly, three parameters (n, f{sub c}, and AC conductivity values for frequencies below f{sub c}) extracted from the AC conductivity spectra in different frequency windows seem suitable to probe the crystalline phase transition.

  20. Thermal conductivity of Glycerol's liquid, glass, and crystal states, glass-liquid-glass transition, and crystallization at high pressures

    NASA Astrophysics Data System (ADS)

    Andersson, Ove; Johari, G. P.

    2016-02-01

    To investigate the effects of local density fluctuations on phonon propagation in a hydrogen bonded structure, we studied the thermal conductivity κ of the crystal, liquid, and glassy states of pure glycerol as a function of the temperature, T, and the pressure, p. We find that the following: (i) κcrystal is 3.6-times the κliquid value at 140 K at 0.1 MPa and 2.2-times at 290 K, and it varies with T according to 138 × T-0.95; (ii) the ratio κliquid (p)/κliquid (0.1 MPa) is 1.45 GPa-1 at 280 K, which, unexpectedly, is about the same as κcrystal (p)/κcrystal (0.1 MPa) of 1.42 GPa-1 at 298 K; (iii) κglass is relatively insensitive to T but sensitive to the applied p (1.38 GPa-1 at 150 K); (iv) κglass-T plots show an enhanced, pressure-dependent peak-like feature, which is due to the glass to liquid transition on heating; (v) continuous heating cold-crystallizes ultraviscous glycerol under pressure, at a higher T when p is high; and (vi) glycerol formed by cooling at a high p and then measured at a low p has a significantly higher κ than the glass formed by cooling at a low p. On heating at a fixed low p, its κ decreases before its glass-liquid transition range at that p is reached. We attribute this effect to thermally assisted loss of the configurational and vibrational instabilities of a glass formed at high p and recovered at low p, which is different from the usual glass-aging effect. While the heat capacity, entropy, and volume of glycerol crystal are less than those for its glass and liquid, κcrystal of glycerol, like its elastic modulus and refractive index, is higher. We discuss these findings in terms of the role of fluctuations in local density and structure, and the relations between κ and the thermodynamic quantities.

  1. Pulsed-laser crystallized highly conductive boron-doped microcrystalline silicon

    SciTech Connect

    Nebel, C.E.; Dahlheimer, B.; Karrer, U.; Stutzmann, M.

    1997-07-01

    The preparation of seed lattices, using three interfering beams (TIB) from a pulsed Nd:YAG laser in a-Si layers of 100 to 400 nm thickness is introduced and applied for seeded laser or thermally induced crystallization of a-Si on Corning 7059 glass. The structural and electronic properties of the {micro}c-Si layers are investigated by X-ray, electron- and atomic force microscopy, Hall and conductivity measurements. In highly boron-doped {micro}c-Si, grains up to 1.3 {micro}m in diameter are detected, giving rise to conductivities of {approx}2,000 S/cm and hole mobilities of {approx}10 cm{sup 2}/Vs.

  2. Crystal structure and ion conducting properties of La5NbMo2O16

    NASA Astrophysics Data System (ADS)

    Vu, T. D.; Krichen, F.; Barre, M.; Busselez, R.; Adil, K.; Jouanneaux, A.; Suard, E.; Goutenoire, F.

    2016-05-01

    The new compound La5NbMo2O16 with high ionic conduction has been discovered during the study of the ternary phase diagram of La2O3-MoO3-Nb2O5. The material crystallizes in the cubic space group Pn 3 bar n (no 222) with the unit cell parameter a=11.2250(1) Å. La5NbMo2O16 is a new analogue of the R5Mo3O16 series (R=Pr, Nd). The structure was refined from a combined data X-ray and neutron powder diffraction. The ionic conductivity of the compound is then measured on sintered pellets, by means of complex impedance spectroscopy.

  3. Surface electrical conductivity of single crystal spinel in cesium vapor. Final report

    SciTech Connect

    Agnew, P.; Ing, J.L.

    1995-04-02

    The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose of investigating the degradation of TFE electrical insulators. The major emphasis of this research has been on the interactions of oxide ceramics with cesium (Cs) vapor, and the resurfacing decrease of surface resistivity. Previous work has studied the surface electrical conductivity of sapphire exposed to Cs. In this report the authors describe the results of an experimental investigation of the surface electrical conductivity of single crystal magnesium aluminate spinel at temperatures ranging from 573K to 923K, in the presence of cesium vapor at pressures up to 1 Torr. The interest in spinel has arisen in view of its apparent resistance to radiation damage.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  5. Point defect distribution in high-mobility conductive SrTiO{sub 3} crystals

    SciTech Connect

    Gentils, A.; Copie, O.; Bibes, M.; Bouzehouane, K.; Jacquet, E.; Carretero, C.; Barthelemy, A.; Fortuna, F.; Basletic, M.; Tafra, E.; Hamzic, A.

    2010-04-01

    We have carried out positron-annihilation spectroscopy to characterize the spatial distribution and the nature of vacancy defects in insulating as-received as well as in reduced SrTiO{sub 3} substrates exhibiting high-mobility conduction. The substrates were reduced either by ion etching the substrate surfaces or by doping with vacancies during thin-film deposition at low pressure and high temperature. We show that Ti vacancies are native defects homogeneously distributed in as-received substrates. In contrast, the dominant vacancy defects are the same both in ion etched crystals and substrates reduced during the film growth, and they consist of nonhomogeneous distributions of cation-oxygen vacancy complexes. Their spatial extension is tuned from a few microns in ion-etched samples to the whole substrate in specimens reduced during film deposition. Our results shed light on the transport mechanisms of conductive SrTiO{sub 3} crystals and on strategies for defect-engineered oxide quantum wells, wires, and dots.

  6. Thermal conductivity of Zn, Pr and Tb doped YBCO single crystals: Theory and experiment

    SciTech Connect

    Henning, P.F.; Cao, G.; Crow, J.E.

    1995-08-01

    The thermal conductivity K(T) vs temperature has been measured for (Y,Pr)Ba{sub 2}Cu{sub 3}O{sub 7}, (Y,Tb)Ba{sub 2}Cu{sub 3}O{sub 7} and YBa{sub 2}(Cu,Zn){sub 3}O{sub 7} single crystals from 10{le}T{le}280K. For YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO), a strong enhancement in K(T) is observed for T{le}T{sub c} with a peak in K(T) at approximately T{approx}T{sub c}/2 with a sharp change in slope of K(T) at T{sub c}. These results are similar to those reported previously. For the selectively doped YBCO, the peak in K(T) is shifted to lower temperatures and occurs at T{approx}20K independent of T{sub c} and the impurity concentration. In addition, the sharp change in slope of K(T) at T{sub c} is not apparent for the doped crystals. These results are discussed along with a theoretical model for electronic conduction including both impurity and inelastic scattering from spin fluctuations.

  7. Influence of composition nonstoichiometry on the electrical conductivity of LiNaGe4O9 crystals

    NASA Astrophysics Data System (ADS)

    Volnyanskii, M. D.; Trubitsyn, M. P.; Bibikova, O. A.

    2014-06-01

    The electrical conductivity σ of Li2 - x Na x Ge4O9 ( x = 1, 0.5, 0.2) crystals in an alternating-current electric field has been investigated at a frequency of 1 kHz in the temperature range of 300-800 K. A considerable anisotropy of the electrical conductivity has been revealed for crystals with a sodium concentration x = 1 at T > 500 K. It has been shown that the electrical conductivity σ along certain crystallographic directions increases by more than three orders of magnitude with a change in the sodium concentration from x = 1 to x = 0.2. The results have been discussed taking into account the specific features of the structure of the crystals under investigation. Presumably, the major charge carriers are interstitial Li ions migrating along channels of the framework structure of the Li2 - x Na x Ge4O9 crystals.

  8. Drude-type conductivity of charged sphere colloidal crystals: density and temperature dependence.

    PubMed

    Medebach, Martin; Jordán, Raquel Chuliá; Reiber, Holger; Schöpe, Hans-Joachim; Biehl, Ralf; Evers, Martin; Hessinger, Dirk; Olah, Julianna; Palberg, Thomas; Schönberger, Ernest; Wette, Patrick

    2005-09-01

    We report on extensive measurements in the low-frequency limit of the ac conductivity of colloidal fluids and crystals formed from charged colloidal spheres suspended in de-ionized water. Temperature was varied in a range of 5 degrees C < Theta < 35 degrees C and the particle number density n between 0.2 and 25 microm(-3) for the larger, respectively, 2.75 and 210 microm(-3) for the smaller of two investigated species. At fixed Theta the conductivity increased linearly with increasing n without any significant change at the fluid-solid phase boundary. At fixed n it increased with increasing Theta and the increase was more pronounced for larger n. Lacking a rigorous electrohydrodynamic treatment for counterion-dominated systems we describe our data with a simple model relating to Drude's theory of metal conductivity. The key parameter is an effectively transported particle charge or valence Z(*). All temperature dependencies other than that of Z(*) were taken from literature. Within experimental resolution Z(*) was found to be independent of n irrespective of the suspension structure. Interestingly, Z(*) decreases with temperature in near quantitative agreement with numerical calculations. PMID:16178620

  9. High conductance 2D transport around the Hall mobility peak in electrolyte-gated rubrene crystals.

    PubMed

    Xie, Wei; Wang, Shun; Zhang, Xin; Leighton, C; Frisbie, C Daniel

    2014-12-12

    We report the observation of the Hall effect at hole densities up to 6×10¹³ cm⁻² (0.3  holes/molecule) on the surface of electrolyte-gated rubrene crystals. The perplexing peak in the conductance as a function of gate voltage is confirmed to result from a maximum in mobility, which reaches 4  cm² V⁻¹ s⁻¹ at 2.5×10¹³ cm⁻². Measurements to liquid helium temperatures reveal that this peak is markedly asymmetric, with bandlike and hopping-type transport occurring on the low density side, while unconventional, likely electrostatic-disorder-affected transport dominates the high density side. Most significantly, near the mobility peak the temperature coefficient of the resistance remains positive to as low as 120 K, the low temperature resistance becomes weakly temperature dependent, and the conductance reaches within a factor of 2 of e²/h, revealing conduction unprecedentedly close to a two-dimensional metallic state. PMID:25541790

  10. Geometric treatment of conduction electron scattering by crystal lattice strains and dislocations

    SciTech Connect

    Viswanathan, Koushik; Chandrasekar, Srinivasan

    2014-12-28

    The problem of conduction electron scattering by inhomogeneous crystal lattice strains is addressed using a tight-binding formalism and the differential geometric treatment of deformations in solids. In this approach, the relative positions of neighboring atoms in a strained lattice are naturally taken into account, even in the presence of crystal dislocations, resulting in a fully covariant Schrödinger equation in the continuum limit. Unlike previous work, the developed formalism is applicable to cases involving purely elastic strains as well as discrete and continuous distributions of dislocations—in the latter two cases, it clearly demarcates the effects of the dislocation strain field and core. It also differentiates between elastic and plastic strain contributions, respectively. The electrical resistivity due to the strain field of edge dislocations is then evaluated and the resulting numerical estimate for Cu shows good agreement with reported experimental values. This indicates that the electrical resistivity of edge dislocations in metals is not entirely due to the core, contrary to current models. Application to the study of strain effects in constrained quantum systems is also discussed.

  11. Rubrene crystal field-effect mobility modulation via conducting channel wrinkling

    PubMed Central

    Reyes-Martinez, Marcos A.; Crosby, Alfred J.; Briseno, Alejandro L.

    2015-01-01

    With the impending surge of flexible organic electronic technologies, it has become essential to understand how mechanical deformation affects the electrical performance of organic thin-film devices. Organic single crystals are ideal for the systematic study of strain effects on electrical properties without being concerned about grain boundaries and other defects. Here we investigate how the deformation affects the field-effect mobility of single crystals of the benchmark semiconductor rubrene. The wrinkling instability is used to apply local strains of different magnitudes along the conducting channel in field-effect transistors. We discover that the mobility changes as dictated by the net strain at the dielectric/semiconductor interface. We propose a model based on the plate bending theory to quantify the net strain in wrinkled transistors and predict the change in mobility. These contributions represent a significant step forward in structure–function relationships in organic semiconductors, critical for the development of the next generation of flexible electronic devices. PMID:25939864

  12. Rubrene crystal field-effect mobility modulation via conducting channel wrinkling.

    PubMed

    Reyes-Martinez, Marcos A; Crosby, Alfred J; Briseno, Alejandro L

    2015-01-01

    With the impending surge of flexible organic electronic technologies, it has become essential to understand how mechanical deformation affects the electrical performance of organic thin-film devices. Organic single crystals are ideal for the systematic study of strain effects on electrical properties without being concerned about grain boundaries and other defects. Here we investigate how the deformation affects the field-effect mobility of single crystals of the benchmark semiconductor rubrene. The wrinkling instability is used to apply local strains of different magnitudes along the conducting channel in field-effect transistors. We discover that the mobility changes as dictated by the net strain at the dielectric/semiconductor interface. We propose a model based on the plate bending theory to quantify the net strain in wrinkled transistors and predict the change in mobility. These contributions represent a significant step forward in structure-function relationships in organic semiconductors, critical for the development of the next generation of flexible electronic devices. PMID:25939864

  13. Crystal structure of human aquaporin 4 at 1.8 Å and its mechanism of conductance

    PubMed Central

    Ho, Joseph D.; Yeh, Ronald; Sandstrom, Andrew; Chorny, Ilya; Harries, William E. C.; Robbins, Rebecca A.; Miercke, Larry J. W.; Stroud, Robert M.

    2009-01-01

    Aquaporin (AQP) 4 is the predominant water channel in the mammalian brain, abundantly expressed in the blood–brain and brain–cerebrospinal fluid interfaces of glial cells. Its function in cerebral water balance has implications in neuropathological disorders, including brain edema, stroke, and head injuries. The 1.8-Å crystal structure reveals the molecular basis for the water selectivity of the channel. Unlike the case in the structures of water-selective AQPs AqpZ and AQP1, the asparagines of the 2 Asn-Pro-Ala motifs do not hydrogen bond to the same water molecule; instead, they bond to 2 different water molecules in the center of the channel. Molecular dynamics simulations were performed to ask how this observation bears on the proposed mechanisms for how AQPs remain totally insulating to any proton conductance while maintaining a single file of hydrogen bonded water molecules throughout the channel. PMID:19383790

  14. Crystal structure of human aquaporin 4 at 1.8 A and its mechanism of conductance.

    PubMed

    Ho, Joseph D; Yeh, Ronald; Sandstrom, Andrew; Chorny, Ilya; Harries, William E C; Robbins, Rebecca A; Miercke, Larry J W; Stroud, Robert M

    2009-05-01

    Aquaporin (AQP) 4 is the predominant water channel in the mammalian brain, abundantly expressed in the blood-brain and brain-cerebrospinal fluid interfaces of glial cells. Its function in cerebral water balance has implications in neuropathological disorders, including brain edema, stroke, and head injuries. The 1.8-A crystal structure reveals the molecular basis for the water selectivity of the channel. Unlike the case in the structures of water-selective AQPs AqpZ and AQP1, the asparagines of the 2 Asn-Pro-Ala motifs do not hydrogen bond to the same water molecule; instead, they bond to 2 different water molecules in the center of the channel. Molecular dynamics simulations were performed to ask how this observation bears on the proposed mechanisms for how AQPs remain totally insulating to any proton conductance while maintaining a single file of hydrogen bonded water molecules throughout the channel. PMID:19383790

  15. Fluctuation conductivity of oxygen underdoped YBa2Cu3O7-δ single crystals

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Khadzhai, G. Ya.; Goulatis, I. L.; Chroneos, A.

    2014-03-01

    The electrical resistance in the range of ТC-300 K in the layer planes of YВа2Сu3О7-δ single crystals with a range of oxygen deficiency (providing a range of TC from 78 to 92 K) was investigated. The experimental data is approximated by an expression that accounts for the scattering of electrons on phonons, as well as on defects and the fluctuation conductivity in a 3-D model of the Aslamazov-Larkin theory. According to this approximation, depending upon the oxygen deficiency, the Debye temperature varies from 245 to 400 K, coherence length ξС(0)≈0.5 Å.

  16. The role of temperature on dielectric relaxation and conductivity mechanism of dark conglomerate liquid crystal phase

    NASA Astrophysics Data System (ADS)

    Yildiz, Alptekin; Canli, Nimet Yilmaz; Özdemir, Zeynep Güven; Ocak, Hale; Eran, Belkız Bilgin; Okutan, Mustafa

    2016-03-01

    In this study, dielectric properties and ac conductivity mechanism of the bent-core liquid crystal 3‧-{4-[4-(3,7-Dimethyloctyloxy)benzoyloxy]benzoyloxy}-4-{4-[4-[6-(1,1,3,3,5,5,5-heptamethyltrisiloxan-1yl)hex-1-yloxy]benzoyloxy]benzoyloxy}biphenyl (DBB) have been analyzed by impedance spectroscopy measurements at different temperatures. According to the polarizing microscopy results, DBB liquid crystal compound exhibits a dark conglomerate mesophase (DC[*] phase) which can be identified by the occurrence of a conglomerate of domains with opposite chirality. The chiral domains of this low-birefringent mesophase become more visible by rotating the polarizer. The variation of the real (ε‧) and imaginary (ε″) parts of dielectric constant with angular frequency and Cole-Cole curves of DBB have been analyzed. The fitting results for dispersion curves at different temperatures revealed that DBB system exhibits nearly Debye-type relaxation except for 125 °C. Moreover, it has been determined that while the relaxation frequencies shift to higher frequencies as the temperature increases from 25 °C to 125 °C, the peak intensities remarkably decrease with increasing temperature. According to Cole-Cole plot and phase angle versus frequency curve, it has been determined that DBB LC may have a possibility of utilizing as a super-capacitor at room temperature. Furthermore, it has been found that the conductivity mechanism of the DBB alters from Correlated Barrier Hoping (CBH) model to Quantum Tunneling Model (QMT) with in increasing temperature at high frequency region. In terms of CBH model, optical band gaps at 25 °C and 75 °C temperatures have also been calculated. Finally, activation energies for some selected angular frequencies have also been calculated.

  17. Single-Crystal X-ray Structures of conductive π-Stacking Dimers of Tetrakis(alkylthio)benzene Radical Cations.

    PubMed

    Chen, Xiaoyu; Gao, Feng; Yang, Wuqin

    2016-01-01

    Salts containing radical cations of 1,2,4,5-tetrakis(isopropylthio)benzene (TPB) and 1,2,4,5-tetrakis(ethylthio) benzene (TEB) have been successfully synthesized with . These newly synthesized salts have been characterized by UV-Vis absorption, EPR spectroscopy, conductivity measurement, single crystal X-ray diffraction analysis as well as DFT calculation. This study raises the first crystal structure of conductive π-stacking radical cation with single phenyl ring and reveals their conductivity has relationship with the stack structure which affected by the substituent. PMID:27403720

  18. Single-Crystal X-ray Structures of conductive π-Stacking Dimers of Tetrakis(alkylthio)benzene Radical Cations

    PubMed Central

    Chen, Xiaoyu; Gao, Feng; Yang, Wuqin

    2016-01-01

    Salts containing radical cations of 1,2,4,5-tetrakis(isopropylthio)benzene (TPB) and 1,2,4,5-tetrakis(ethylthio) benzene (TEB) have been successfully synthesized with . These newly synthesized salts have been characterized by UV-Vis absorption, EPR spectroscopy, conductivity measurement, single crystal X-ray diffraction analysis as well as DFT calculation. This study raises the first crystal structure of conductive π-stacking radical cation with single phenyl ring and reveals their conductivity has relationship with the stack structure which affected by the substituent. PMID:27403720

  19. Single-Crystal X-ray Structures of conductive π-Stacking Dimers of Tetrakis(alkylthio)benzene Radical Cations

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoyu; Gao, Feng; Yang, Wuqin

    2016-07-01

    Salts containing radical cations of 1,2,4,5-tetrakis(isopropylthio)benzene (TPB) and 1,2,4,5-tetrakis(ethylthio) benzene (TEB) have been successfully synthesized with . These newly synthesized salts have been characterized by UV-Vis absorption, EPR spectroscopy, conductivity measurement, single crystal X-ray diffraction analysis as well as DFT calculation. This study raises the first crystal structure of conductive π-stacking radical cation with single phenyl ring and reveals their conductivity has relationship with the stack structure which affected by the substituent.

  20. Electrical conduction mechanisms in PbSe and PbS nano crystals 3D matrix layer

    NASA Astrophysics Data System (ADS)

    Arbell, Matan; Hechster, Elad; Sarusi, Gabby

    2016-02-01

    A simulation study and measurements of the electrical conductance in a PbSe and PbS spherical Nano-crystal 3D matrix layer was carried out focusing on its dependences of Nano-crystal size distribution and size gradient along the layer thickness (z-direction). The study suggests a new concept of conductance enhancement by utilizing a size gradient along the layer thickness from mono-layer to the next mono-layer of the Nano-crystals, in order to create a gradient of the energy levels and thus improve directional conductance in this direction. A Monte Carlo simulation of the charge carriers path along the layer thickness of the Nano-crystals 3D matrix using the Miller-Abrahams hopping model was performed. We then compared the conductance characteristics of the gradual size 3D matrix layer to a constant-sized 3D matrix layer that was used as a reference in the simulation. The numerical calculations provided us with insights into the actual conductance mechanism of the PbSe and PbS Nano-crystals 3D matrix and explained the discrepancies in actual conductance and the variability in measured mobilities published in the literature. It is found that the mobility and thus conductance are dependent on a critical electrical field generated between two adjacent nano-crystals. Our model explains the conductance dependents on the: Cathode-Anode distance, the distance between the adjacent nano-crystals in the 3D matrix layer and the size distribution along the current direction. Part of the model (current-voltage dependence) was validated using a current-voltage measurements taken on a constant size normal distribution nano-crystals PbS layer (330nm thick) compared with the predicted I-V curves. It is shown that under a threshold bias, the current is very low, while after above a threshold bias the conductance is significantly increased due to increase of hopping probability. Once reaching the maximum probability the current tend to level-off reaching the maximal conductance

  1. Fergusonite-type CeNbO{sub 4+δ}: Single crystal growth, symmetry revision and conductivity

    SciTech Connect

    Bayliss, Ryan D.; Pramana, Stevin S.; An, Tao; Wei, Fengxia; Kloc, Christian L.; White, Andrew J.P.; Skinner, Stephen J.; White, Timothy J.; Baikie, Tom

    2013-08-15

    Large fergusonite-type (ABO{sub 4}, A=Ce, B=Nb) oxide crystals, a prototype electrolyte composition for solid oxide fuel cells (SOFC), were prepared for the first time in a floating zone mirror furnace under air or argon atmospheres. While CeNbO{sub 4} grown in air contained CeNbO{sub 4.08} as a minor impurity that compromised structural analysis, the argon atmosphere yielded a single phase crystal of monoclinic CeNbO{sub 4}, as confirmed by selected area electron diffraction, powder and single crystal X-ray diffraction. The structure was determined in the standard space group setting C12/c1 (No. 15), rather than the commonly adopted I12/a1. AC impedance spectroscopy conducted under argon found that stoichiometric CeNbO{sub 4} single crystals showed lower conductivity compared to CeNbO{sub 4+δ} confirming interstitial oxygen can penetrate through fergusonite and is responsible for the higher conductivity associated with these oxides. - Graphical abstract: Large fergusonite-type CeNbO{sub 4} crystals were prepared for the first time in a floating zone mirror furnace. Crystal growth in an argon atmosphere yielded a single phase monoclinic CeNbO4, as confirmed by selected area electron diffraction, powder and single crystal X-ray diffraction. The structure was determined in the standard space group setting C12/c1 (No. 15), rather than the commonly adopted I12/a1. AC impedance spectroscopy found CeNbO{sub 4} single crystals showed lower conductivity compared to CeNbO{sub 4+δ} confirming interstitial oxygen can penetrate through fergusonite and is responsible for the higher conductivity associated with these oxides. Highlights: • Preparation of single crystals of CeNbO{sub 4} using a floating zone mirror furnace. • Correction to the crystal symmetry of the monoclinic form of CeNbO{sub 4}. • Report the conductivity of a single crystal of CeNbO{sub 4}.

  2. Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals

    NASA Astrophysics Data System (ADS)

    Zhao, Li-Dong; Lo, Shih-Han; Zhang, Yongsheng; Sun, Hui; Tan, Gangjian; Uher, Ctirad; Wolverton, C.; Dravid, Vinayak P.; Kanatzidis, Mercouri G.

    2014-04-01

    The thermoelectric effect enables direct and reversible conversion between thermal and electrical energy, and provides a viable route for power generation from waste heat. The efficiency of thermoelectric materials is dictated by the dimensionless figure of merit, ZT (where Z is the figure of merit and T is absolute temperature), which governs the Carnot efficiency for heat conversion. Enhancements above the generally high threshold value of 2.5 have important implications for commercial deployment, especially for compounds free of Pb and Te. Here we report an unprecedented ZT of 2.6 +/- 0.3 at 923 K, realized in SnSe single crystals measured along the b axis of the room-temperature orthorhombic unit cell. This material also shows a high ZT of 2.3 +/- 0.3 along the c axis but a significantly reduced ZT of 0.8 +/- 0.2 along the a axis. We attribute the remarkably high ZT along the b axis to the intrinsically ultralow lattice thermal conductivity in SnSe. The layered structure of SnSe derives from a distorted rock-salt structure, and features anomalously high Grüneisen parameters, which reflect the anharmonic and anisotropic bonding. We attribute the exceptionally low lattice thermal conductivity (0.23 +/- 0.03 W m-1 K-1 at 973 K) in SnSe to the anharmonicity. These findings highlight alternative strategies to nanostructuring for achieving high thermoelectric performance.

  3. Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals.

    PubMed

    Zhao, Li-Dong; Lo, Shih-Han; Zhang, Yongsheng; Sun, Hui; Tan, Gangjian; Uher, Ctirad; Wolverton, C; Dravid, Vinayak P; Kanatzidis, Mercouri G

    2014-04-17

    The thermoelectric effect enables direct and reversible conversion between thermal and electrical energy, and provides a viable route for power generation from waste heat. The efficiency of thermoelectric materials is dictated by the dimensionless figure of merit, ZT (where Z is the figure of merit and T is absolute temperature), which governs the Carnot efficiency for heat conversion. Enhancements above the generally high threshold value of 2.5 have important implications for commercial deployment, especially for compounds free of Pb and Te. Here we report an unprecedented ZT of 2.6 ± 0.3 at 923 K, realized in SnSe single crystals measured along the b axis of the room-temperature orthorhombic unit cell. This material also shows a high ZT of 2.3 ± 0.3 along the c axis but a significantly reduced ZT of 0.8 ± 0.2 along the a axis. We attribute the remarkably high ZT along the b axis to the intrinsically ultralow lattice thermal conductivity in SnSe. The layered structure of SnSe derives from a distorted rock-salt structure, and features anomalously high Grüneisen parameters, which reflect the anharmonic and anisotropic bonding. We attribute the exceptionally low lattice thermal conductivity (0.23 ± 0.03 W m(-1) K(-1) at 973 K) in SnSe to the anharmonicity. These findings highlight alternative strategies to nanostructuring for achieving high thermoelectric performance. PMID:24740068

  4. Thermomechanical coupling, heat conduction and director rotation in cholesteric liquid crystals studied by molecular dynamics simulation.

    PubMed

    Sarman, Sten; Laaksonen, Aatto

    2013-03-14

    The lack of a centre of inversion in a cholesteric liquid crystal allows linear cross couplings between thermodynamic forces and fluxes that are polar vectors and pseudovectors, respectively. This makes it possible for a temperature gradient parallel to the cholesteric axis to induce a torque that rotates the director, a phenomenon known as the Lehmann effect or thermomechanical coupling. The converse is also possible: a torque applied parallel to the cholesteric axis rotates the director and drives a heat flow. In order to study this phenomenon, nonequilibrium molecular dynamics simulation algorithms and Green-Kubo relations evaluated by equilibrium molecular dynamics simulation have been used to calculate the Leslie coefficient, i.e. the cross coupling coefficient between the temperature gradient and the director angular velocity, for a model system composed of soft prolate ellipsoids of revolution interacting via the Gay-Berne potential augmented by a chiral interaction potential causing the formation of a cholesteric phase. It is found that the Leslie coefficient is two orders of magnitudes smaller than other transport coefficients such as the heat conductivity and the twist viscosity, so that very long simulations are required to evaluate it. The Leslie coefficient decreases with the pitch but it has not been possible to determine the exact functional dependence of this coefficient on the pitch. Since very long simulations have been performed to evaluate the Leslie coefficient, very accurate values have been obtained for the twist viscosity and the heat conductivity as a by-product and it is found that they are very similar to the values of the corresponding quantities in the achiral nematic phase that arises when the pitch goes to infinity. PMID:23223192

  5. Piezoresistivity and electro-thermomechanical degradation of a conducting layer of nanoparticles integrated at the liquid crystal elastomer surface.

    PubMed

    Chambers, Martin; Zalar, Boštjan; Remškar, Maja; Finkelmann, Heino; Zumer, Slobodan

    2008-04-16

    When a liquid crystal elastomer (LCE) is reprocessed with conducting nanosized particles a conducting layer can be formed at the LCE surfaces. Here, two different LCE materials and two different conducting carbon particles were used. These four reprocessed LCEs were investigated when subject to a thermal phase transition and mechanical extension. Here it is shown that the resistance change with strain ('piezoresistivity') for these reprocessed LCEs can be described through lattice percolation and geometrical changes in the LCE shape. The mechanisms and rate of degradation are also described for the conducting layer as a function of the number of electro-thermomechanical strain cycles performed. PMID:21825613

  6. Ionic conductivity of single crystals of sodium aluminium germanate Na8Al6Ge6O24(OH)2

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.

    2015-09-01

    The electrical conductivity of single crystals of sodium aluminium germanate Na8Al6Ge6O24(OH)2 (cubic system, sp. gr. ), which is a germanium analog of sodalite, has been studied in the temperature range of 468‒758 K. Na8Al6Ge6O24(OH)2 crystals are obtained by hydrothermal synthesis (temperature in the dissolution zone 573‒673 K, temperature gradient ~1.5 K/cm). NaAlO2 and GeO2В oxides are used as starting reagents; NaOH hydroxide serves as a solvent. The ionic conductivity of Na8Al6Ge6O24(OH)2 crystals is 2 × 10-4 S/cm (at 758 K); the activation energy of ionic transfer is 0.46 ± 0.03 eV.

  7. Analysis of the nature of electrical conductivity in nominally undoped LiNbO{sub 3} crystals

    SciTech Connect

    Pritulenko, A. S. Yatsenko, A. V.; Yevdokimov, S. V.

    2015-03-15

    The temperature dependence of electrical conductivity and admittance of two nominally undoped lithium niobate crystals of congruent composition has been investigated in the temperature range of 293–450 K and simulated in the range of 350–700 K. It is shown that the ion conductivity at T < 450 K is mainly determined by OH{sup −} groups; however, some other mechanisms may manifest themselves at higher temperatures; a likely one is diffusion of oxygen vacancies, which leads to an increase in the “averaged” conductivity activation energy.

  8. Thermal diffusivity of Zn1-xBexSe crystals and it's correlation with electrical conductivity and optical absorption spectra

    NASA Astrophysics Data System (ADS)

    Bodzenta, J.; Firszt, F.; Kaźmierczak-Bałata, A.; Pyka, M.; Szperlich, P.; Szydłowski, M.; Zakrzewski, J.

    2008-01-01

    This article presents results obtained for mixed crystal of Zn{1-x}Be{x}Se. Samples with different Be contents were examined to determine their thermal, optical and electrical properties. The influence of composition of investigated mixed crystals on the value of thermal diffusivity, electrical resistivity and energy gap was checked. An interesting problem is a correlation between thermal properties and other physical parameters. In this work possible correlations between the thermal diffusivity and either the optical band gap determined from photothermal spectra or electrical conductivity are studied. The current investigation is a part of research projects: BK-269/RMF-1/2006 and 1 P03B 092 27.

  9. Trivalent aluminum ion conducting characteristics in Al{sub 2}(WO{sub 4}){sub 3} single crystals

    SciTech Connect

    Imanaka, N.; Tamura, S.; Hiraiwa, M.; Adachi, G.; Dabkowska, H.; Dabkowski, A.; Greedan, J.E.

    1998-09-01

    Single crystals of the trivalent Al{sup 3+} ion conductor Al{sub 2}(WO{sub 4}){sub 3} were grown by the Czochralski (CZ) method. The ionic conductivity in the a-, b-, and c-axis directions was determined and Al{sup 3+} ion conduction in the direction of the b-axis was concluded to be the most suitable pathway for ion migration in the tungstate grains. The ionic conductivities in the a- and c-axis directions were 0.3 and 10{sup {minus}2} times lower than the conductivity in the b-axis. Consistent with this observation, the lowest activation energy (E{sub a}) for Al{sup 3+} ion migration was obtained for the b-axis direction. The E{sub a} of the conductivity in the direction of the c-axis was almost comparable to that of the polycrystalline samples and the E{sub a} of the Al{sup 3+} ionic conduction in the grains of this material was explicitly verified to be controlled by the Al{sup 3+} ionic migration in the c-axis direction. The Al{sup 3+} ion conductivity of the polycrystalline sample was higher in the higher temperature region, indicating that the conductivity in the grain boundaries enhances the total Al{sup 3+} ion conductivity to a considerable extent. From the oxygen pressure dependencies of the electrical conductivity and the polarization behavior, the single crystals were demonstrated to be pure Al{sup 3+} ionic conductors showing an anisotropic ion conducting behavior.

  10. Unipolar conductivity of SrTiO3 crystals with light-induced drop in electrical resistance

    NASA Astrophysics Data System (ADS)

    Shablaev, S. I.; Grachev, A. I.

    2016-05-01

    This paper reports on the results of the experimental investigation of unipolar (diode) current-voltage characteristics of local regions in high-resistance SrTiO3 crystals that experienced a light-induced drop in electrical resistance. This behavior has been explained by the influence exerted on the electrical conductivity by the irradiated region in the Schottky barrier of one of the contacts. The ideality factor of the Schottky barrier has been determined and the barrier height for a number of regions has been estimated from measurements of the forward branch of the current-voltage characteristics. An analysis of the specific features in the behavior of the reverse branch of the current-voltage characteristics has revealed that, in the SrTiO3 crystals with p-type conductivity, the resistance switching occurs through a pure electronic mechanism, in contrast to models based on electrochemical processes, in particular, the migration of oxygen vacancies.

  11. Strong tendency of homeotropic alignment and anisotropic lithium ion conductivity of sulfonate functionalized zwitterionic imidazolium ionic liquid crystals.

    PubMed

    Rondla, Rohini; Lin, Joseph C Y; Yang, C T; Lin, Ivan J B

    2013-09-17

    Here, we report the first attempt to investigate the liquid crystal (LC) behavior of SO3(-) functionalized imidazolium zwitterionic (SO3(-)ImZI) salts, which display homeotropic alignment on a glass slide without the aid of any aligning approach. Doping lithium salt to ImZI salts lowers the melting temperatures and raises the clearing temperatures substantially to form room temperature ImZILCs. Excellent anisotropic lithium ion conductivity is achieved; which is strengthened by their tendency for homeotropic alignment. PMID:24010889

  12. Dual-barrel conductance micropipet as a new approach to the study of ionic crystal dissolution kinetics.

    PubMed

    Kinnear, Sophie L; McKelvey, Kim; Snowden, Michael E; Peruffo, Massimo; Colburn, Alex W; Unwin, Patrick R

    2013-12-17

    A new approach to the study of ionic crystal dissolution kinetics is described, based on the use of a dual-barrel theta conductance micropipet. The solution in the pipet is undersaturated with respect to the crystal of interest, and when the meniscus at the end of the micropipet makes contact with a selected region of the crystal surface, dissolution occurs causing the solution composition to change. This is observed, with better than 1 ms time resolution, as a change in the ion conductance current, measured across a potential bias between an electrode in each barrel of the pipet. Key attributes of this new technique are: (i) dissolution can be targeted at a single crystal surface; (ii) multiple measurements can be made quickly and easily by moving the pipet to a new location on the surface; (iii) materials with a wide range of kinetics and solubilities are open to study because the duration of dissolution is controlled by the meniscus contact time; (iv) fast kinetics are readily amenable to study because of the intrinsically high mass transport rates within tapered micropipets; (v) the experimental geometry is well-defined, permitting finite element method modeling to allow quantitative analysis of experimental data. Herein, we study the dissolution of NaCl as an example system, with dissolution induced for just a few milliseconds, and estimate a first-order heterogeneous rate constant of 7.5 (±2.5) × 10(-5) cm s(-1) (equivalent surface dissolution flux ca. 0.5 μmol cm(-2) s(-1) into a completely undersaturated solution). Ionic crystals form a huge class of materials whose dissolution properties are of considerable interest, and we thus anticipate that this new localized microscale surface approach will have considerable applicability in the future. PMID:24224979

  13. Temperature-dependent thermal conductivity in Mg-doped and undoped β-Ga2O3 bulk-crystals

    NASA Astrophysics Data System (ADS)

    Handwerg, M.; Mitdank, R.; Galazka, Z.; Fischer, S. F.

    2015-02-01

    For β -G{{a}2}{{O}3}, only little information exists concerning the thermal properties, especially the thermal conductivity λ. Here, the thermal conductivity is measured by applying the electrical 3ω-method on Czochralski-grown β -G{{a}2}{{O}3} bulk crystals, which have a thickness of 200 μ m and 800 μ m. At room temperature (RT), the thermal conductivity along the [100]-direction in Mg-doped electrical insulating and undoped semiconducting β -G{{a}2}{{O}3} is confirmed as 13+/- 1 W{{m}-1}{{K}-1} for both crystals. The thermal conductivity increases for decreasing temperature down from 25 K to λ (25\\K)=(5.3+/- 0.6)\\cdot {{10}2} W{{m}-1}{{K}-1}. The phonon contribution of λ dominates over the electron contribution below RT. The observed function λ (T) is in accord with phonon-phonon-Umklapp scattering and the Debye model for the specific heat at T≳ 90 K which is about 0.1 times the Debye temperature {{θ }D}. Here, a detailed discussion of the phonon-phonon-Umklapp scattering for T\\lt {{θ }D} is carried out. The influence of point defect scattering is considered for T\\lt 100 K.

  14. FORTRAN 77 programs for conductive cooling of dikes with temperature-dependent thermal properties and heat of crystallization

    USGS Publications Warehouse

    Delaney, P.T.

    1988-01-01

    Temperature histories obtained from transient heat-conduction theory are applicable to most dikes despite potential complicating effects related to magma flow during emplacement, groundwater circulation, and metamorphic reaction during cooling. Here. machine-independent FORTRAN 77 programs are presented to calculate temperatures in and around dikes as they cool conductively. Analytical solutions can treat thermal-property contrasts between the dike and host rocks, but cannot address the release of magmatic heat of crystallization after the early stages of cooling or the appreciable temperature dependence of thermal conductivity and diffusivity displayed by most rock types. Numerical solutions can incorporate these additional factors. The heat of crystallization can raise the initial temperature at the dike contact, ??c1, about 100??C above that which would be estimated if it were neglected, and can decrease the rate at which the front of solidified magma moves to the dike center by a factor of as much as three. Thermal conductivity and diffusivity of rocks increase with decreasing temperature and, at low temperatures, these properties increase more if the rocks are saturated with water. Models that treat these temperature dependencies yield estimates of ??c1 that are as much as 75??C beneath those which would be predicted if they were neglected. ?? 1988.

  15. Transition from semiconducting to metallic-like conducting and weak antilocalization effect in single crystals of LuPtSb

    SciTech Connect

    Hou, Zhipeng; Wang, Yue; Xu, Guizhou; Zhang, Xiaoming; Liu, Enke; Xi, Xuekui; Wang, Wenhong Wu, Guangheng; Wang, Wenquan; Liu, Zhongyuan

    2015-03-09

    High quality half-Heusler single crystals of LuPtSb have been synthesized by a Pb flux method. The temperature dependent resistivity and Hall effects indicate that the LuPtSb crystal is a p-type gapless semiconductor showing a transition from semiconducting to metallic conducting at 150 K. Moreover, a weakly temperature-dependent positive magnetoresistance (MR) as large as 109% and high carrier mobility up to 2950 cm{sup 2}/V s are experimentally observed at temperatures below 150 K. The low-field MR data show evidence for weak antilocalization (WAL) effect at temperatures even up to 150 K. Analysis of the temperature and angle dependent magnetoconductance manifests that the WAL effect originates from the bulk contribution owing to the strong spin-orbital coupling.

  16. Hierarchical self-assembly of hexagonal single-crystal nanosheets into 3D layered superlattices with high conductivity.

    PubMed

    Tao, Yulun; Shen, Yuhua; Yang, Liangbao; Han, Bin; Huang, Fangzhi; Li, Shikuo; Chu, Zhuwang; Xie, Anjian

    2012-06-21

    While the number of man-made nano superstructures realized by self-assembly is growing in recent years, assemblies of conductive polymer nanocrystals, especially for superlattices, are still a significant challenge, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we firstly report a facile and general route to a new generation of 3D layered superlattices of polyaniline doped with CSA (PANI-CSA) and show how PANI crystallize and self-assemble, in a suitable single solution environment. In cyclohexane, 1D amorphous nanofibers transformed to 1D nanorods as building blocks, and then to 2D single-crystal nanosheets with a hexagonal phase, and lastly to 3D ordered layered superlattices with the narrowest polydispersity value (M(w)/M(n) = 1.47). Remarkably, all the instructions for the hierarchical self-assembly are encoded in the layered shape in other non-polar solvents (hexane, octane) and their conductivity in the π-π stacking direction is improved to about 50 S cm(-1), which is even higher than that of the highest previously reported value (16 S cm(-1)). The method used in this study is greatly expected to be readily scalable to produce superlattices of conductive polymers with high quality and low cost. PMID:22609947

  17. Ionic conductivity in gem-quality single-crystal alkali feldspar from the Eifel: temperature, orientation and composition dependence

    NASA Astrophysics Data System (ADS)

    El Maanaoui, Hamid; Wilangowski, Fabian; Maheshwari, Aditya; Wiemhöfer, Hans-Dieter; Abart, Rainer; Stolwijk, Nicolaas A.

    2016-05-01

    We measured the ion conductivity of single-crystal alkali feldspar originating from two different locations in the Eifel/Germany, named Volkesfeld and Rockeskyller sanidine and having potassium site fractions C_K of 0.83 and 0.71, respectively. The dc conductivities resulting from electrochemical impedance spectroscopy over the temperature range of 300-900°C show a weak composition dependence but pronounced differences between the b-direction [perp (010)] and c^{*}-direction [perp (001)] of the monoclinic feldspar structure. Conductivity activation energies obtained from the observed linear Arrhenius plots are close to 1.2 eV in all cases, which is closely similar to the activation energies of the ^{22}Na tracer diffusivity in the same crystals. Taking into account literature data on K tracer diffusion and diffusion correlation effects, the present results point to a predominance of the interstitialcy mechanism over the vacancy mechanism in mass and charge transport on the alkali sublattice in potassium-rich alkali feldspar.

  18. Reverse ultrasonic changes of electrical conductivity in CdTe:Cl crystals

    NASA Astrophysics Data System (ADS)

    Olikh, Ya. M.; Tymochko, M. D.

    2016-07-01

    Acousto-stimulated changes of electrical conductivity in low ohmic resistance n-type CdTe:Cl monocrystals are reversible and can be seen only during the ultrasonic influence. For the first time the long-term relaxation processes of the conductivity σ(t) at ultrasound-on as well as at ultrasound-off have been found out. The relaxation σ(t) is not monotonous generally, but, at least, has two stages. Acousto-active metastable defects are resposible for "instant" jump-like changes of the temperature dependence of conductivity σ(t). The acousto-stimulated diffusion processes where the defining role belongs to dislocations, are responsible for long-term relaxation the temperature dependence of conductivity σ(t). The main rebuilding process at ultrasound-on consists of the transformation of the charged acceptor complex into a neutral one.

  19. Origin of mineralogical zoning in an intermediate subvolcanic pluton by crystal settling and conductive cooling

    SciTech Connect

    Hildebrand, R.S.

    1985-01-01

    The Rainy Lake Intrusive Complex is one of nine sheet-like intermediate plutons that are compositionally, temporally, and spatially linked to andesitic stratovolcanoes in the western Great Bear Magmatic Zone, an early Proterozoic continental magmatic arc. The pluton, exposed in oblique cross section, has a flat roof and is 1.5 km thick by 12 km long. The observed distribution of plagioclase phenocrysts in the body closely resembles the sinusoidal olivine distribution patterns found in lava lakes and some mafic sills. The shape of the curve indicates that the volume fraction plagioclase phenocrysts in the pluton at the time of intrusion ranged for 10% near the roof to 50% near the base. Calculations indicate that the plagioclase phenocrysts were denser than the surrounding melt. The effects of different crystal concentrations on the viscosity, and hence settling velocities, were computed as a function of height in the pluton; settling velocities ranged, at the time of intrusion, from 160 meters per year near the top to less than 1 meter per year near the base. The observed sinusoidal distribution curve for plagioclase can be explained by the interplay between crystal settling and the solidification of the pluton from the top downwards and the bottom upwards. This suggests that whole body convection did not play a major role in the cooling of the pluton.

  20. Large Scale Laser Crystallization of Solution-based Alumina-doped Zinc Oxide (AZO) Nanoinks for Highly Transparent Conductive Electrode

    NASA Astrophysics Data System (ADS)

    Nian, Qiong; Callahan, Michael; Saei, Mojib; Look, David; Efstathiadis, Harry; Bailey, John; Cheng, Gary J.

    2015-10-01

    A new method combining aqueous solution printing with UV Laser crystallization (UVLC) and post annealing is developed to deposit highly transparent and conductive Aluminum doped Zinc Oxide (AZO) films. This technique is able to rapidly produce large area AZO films with better structural and optoelectronic properties than most high vacuum deposition, suggesting a potential large-scale manufacturing technique. The optoelectronic performance improvement attributes to UVLC and forming gas annealing (FMG) induced grain boundary density decrease and electron traps passivation at grain boundaries. The physical model and computational simulation developed in this work could be applied to thermal treatment of many other metal oxide films.

  1. Large Scale Laser Crystallization of Solution-based Alumina-doped Zinc Oxide (AZO) Nanoinks for Highly Transparent Conductive Electrode

    PubMed Central

    Nian, Qiong; Callahan, Michael; Saei, Mojib; Look, David; Efstathiadis, Harry; Bailey, John; Cheng, Gary J.

    2015-01-01

    A new method combining aqueous solution printing with UV Laser crystallization (UVLC) and post annealing is developed to deposit highly transparent and conductive Aluminum doped Zinc Oxide (AZO) films. This technique is able to rapidly produce large area AZO films with better structural and optoelectronic properties than most high vacuum deposition, suggesting a potential large-scale manufacturing technique. The optoelectronic performance improvement attributes to UVLC and forming gas annealing (FMG) induced grain boundary density decrease and electron traps passivation at grain boundaries. The physical model and computational simulation developed in this work could be applied to thermal treatment of many other metal oxide films. PMID:26515670

  2. Large Scale Laser Crystallization of Solution-based Alumina-doped Zinc Oxide (AZO) Nanoinks for Highly Transparent Conductive Electrode.

    PubMed

    Nian, Qiong; Callahan, Michael; Saei, Mojib; Look, David; Efstathiadis, Harry; Bailey, John; Cheng, Gary J

    2015-01-01

    A new method combining aqueous solution printing with UV Laser crystallization (UVLC) and post annealing is developed to deposit highly transparent and conductive Aluminum doped Zinc Oxide (AZO) films. This technique is able to rapidly produce large area AZO films with better structural and optoelectronic properties than most high vacuum deposition, suggesting a potential large-scale manufacturing technique. The optoelectronic performance improvement attributes to UVLC and forming gas annealing (FMG) induced grain boundary density decrease and electron traps passivation at grain boundaries. The physical model and computational simulation developed in this work could be applied to thermal treatment of many other metal oxide films. PMID:26515670

  3. A non-immersed induction conductivity system for controlling supersaturation in corrosive media: the case of gibbsite crystals agglomeration in Bayer liquors

    NASA Astrophysics Data System (ADS)

    Seyssiecq, I.; Veesler, S.; Boistelle, R.

    1996-11-01

    Agglomeration of gibbsite Al(OH) 3 crystallites is an important stage of the Bayer process, aiming at increasing the initial size of the particles. In the present work, a semi-continuous crystallizer working at constant and imposed supersaturation, and equipped with an automatic withdrawal system was developed to study the agglomeration of gibbsite crystals in supersaturated Bayer liquors. The liquor conductivity was measured using an induction conductivity system placed around the crystallizer, the conductivity regulation being used to work at constant supersaturation. Using this system allowed one to work with both a small crystallizer and a highly corrosive and abrasive suspension of gibbsite in a five molar caustic soda solution at 70°C. Analyses of the withdrawals were carried out with an Elzone particle counter, in order to draw {N(t)}/{N(0) = f(t)} plots, representing the decrease of crystal number with time, due to agglomeration.

  4. Quantum transport in strongly disordered crystals: Electrical conductivity with large negative vertex corrections

    NASA Astrophysics Data System (ADS)

    Janiš, Václav; Pokorný, Vladislav

    2012-12-01

    We propose a renormalization scheme of the Kubo formula for the electrical conductivity with multiple backscatterings contributing to the electron-hole irreducible vertex derived from the asymptotic limit to high spatial dimensions. We use this vertex to represent the two-particle Green function via a symmetrized Bethe-Salpeter equation in momentum space. We further utilize the dominance of a pole in the irreducible vertex to an approximate diagonalization of the Bethe-Salpeter equation and a non-perturbative representation of the electron-hole correlation function. The latter function is then used to derive a compact representation for the electrical conductivity at zero temperature without the necessity to evaluate separately the Drude term and vertex corrections. The electrical conductivity calculated in this way remains nonnegative also in the strongly disordered regime where the localization effects become significant and the negative vertex corrections in the standard Kubo formula overweight the Drude term.

  5. Hydrogen bonding-assisted thermal conduction in β-sheet crystals of spider silk protein

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Chen, Teli; Ban, Heng; Liu, Ling

    2014-06-01

    Using atomistic simulations, we demonstrate that β-sheet, an essential component of spider silk protein, has a thermal conductivity 1-2 orders of magnitude higher than that of some other protein structures reported in the literature. In contrast to several other nanostructured materials of similar bundled/layered structures (e.g. few-layer graphene and bundled carbon nanotubes), the β-sheet is found to uniquely feature enhanced thermal conductivity with an increased number of constituting units, i.e. β-strands. Phonon analysis identifies inter-β-strand hydrogen bonding as the main contributor to the intriguing phenomenon, which prominently influences the state of phonons in both low- and high-frequency regimes. A thermal resistance model further verifies the critical role of hydrogen bonding in thermal conduction through β-sheet structures.Using atomistic simulations, we demonstrate that β-sheet, an essential component of spider silk protein, has a thermal conductivity 1-2 orders of magnitude higher than that of some other protein structures reported in the literature. In contrast to several other nanostructured materials of similar bundled/layered structures (e.g. few-layer graphene and bundled carbon nanotubes), the β-sheet is found to uniquely feature enhanced thermal conductivity with an increased number of constituting units, i.e. β-strands. Phonon analysis identifies inter-β-strand hydrogen bonding as the main contributor to the intriguing phenomenon, which prominently influences the state of phonons in both low- and high-frequency regimes. A thermal resistance model further verifies the critical role of hydrogen bonding in thermal conduction through β-sheet structures. Electronic supplementary information (ESI) available: Structure of the β-sheets, computational model, determination of area and temperature gradient, and additional phonon DOS results. See DOI: 10.1039/c4nr01195c

  6. Reciprocated suppression of polymer crystallization toward improved solid polymer electrolytes: Higher ion conductivity and tunable mechanical properties

    SciTech Connect

    Bi, Sheng; Sun, Che-Nan; Zawodzinski, Thomas A.; Ren, Fei; Keum, Jong Kahk; Ahn, Suk-Kyun; Li, Dawen; Chen, Jihua

    2015-08-06

    Solid polymer electrolytes based on lithium bis(trifluoromethanesulfonyl) imide and polymer matrix were extensively studied in the past due to their excellent potential in a broad range of energy related applications. Poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) are among the most examined polymer candidates as solid polymer electrolyte matrix. In this paper, we study the effect of reciprocated suppression of polymer crystallization in PVDF/PEO binary matrix on ion transport and mechanical properties of the resultant solid polymer electrolytes. With electron and X-ray diffractions as well as energy filtered transmission electron microscopy, we identify and examine the appropriate blending composition that is responsible for the diminishment of both PVDF and PEO crystallites. Laslty, a three-fold conductivity enhancement is achieved along with a highly tunable elastic modulus ranging from 20 to 200 MPa, which is expected to contribute toward future designs of solid polymer electrolytes with high room-temperature ion conductivities and mechanical flexibility.

  7. Conducting glasses recovered from thin film transistor liquid crystal display wastes for dye-sensitized solar cell cathodes.

    PubMed

    Chen, C-C; Chang, F-C; Peng, C Y; Wang, H Paul

    2015-01-01

    Transparent conductive glasses such as thin film transistor (TFT) array and colour filter glasses were recovered from the TFT-liquid crystal display panel wastes by dismantling and sonic cleaning. Noble metals (i.e. platinum (Pt)) and indium tin oxide (ITO) are generally used in the cathode of a dye-sensitized solar cell (DSSC). To reduce the DSSC cost, Pt was replaced with nano nickel-encapsulated carbon-shell (Ni@C) nanoparticles, which were prepared by carbonization of Ni²⁺-β-cyclodextrin at 673 K for 2 h. The recovered conductive glasses were used in the DSSC electrodes in the substitution of relatively expensive ITO. Interestingly, the efficiency of the DSSC having the Ni@C-coated cathode is as high as 2.54%. Moreover, the cost of the DSSC using the recovered materials can be reduced by at least 24%. PMID:25399759

  8. Crystal structure, phase, and electrical conductivity of nanocrystalline W₀.₉₅Ti(₀.₀₅)O₃ thin films.

    PubMed

    Kalidindi, N R; Manciu, F S; Ramana, C V

    2011-03-01

    W(0.95)Ti(0.05)O(3) films were fabricated using sputter-deposition onto Si(100) wafers in by varying the growth temperature from room temperature (RT) to 500 °C. X-ray diffraction (XRD), high-resolution scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDS), and Raman spectroscopy (RS) were performed to investigate the effect of temperature on the growth behavior, crystal structure, texturing, surface morphology, and chemical bonding of W(0.95)Ti(0.5)O(3) films. The results indicate that the effect of temperature is significant on the growth and microstructure of W(0.95)Ti(0.05)O(3) films. XRD results indicate that the effect of Ti is remarkable on the crystallization of WO(3). W(0)(.95)Ti(0.05)O(3) films grown at temperatures <300 °C are amorphous compared to pure WO(3) crystalline films crystallizing at 200 °C. Phase transformation is induced in W(0)(.95)Ti(0.05)O(3) resulting in tetragonal structure at ≥300 °C. The structural changes were also reflected in the intensities of -W-O-W- vibrational modes in RS measurements. The SEM imaging analysis indicates that the phase transformations are accompanied by a characteristic change in surface morphology. Room temperature electrical conductivity of W(0.95)Ti(0.05)O(3) films increases from 0.63 to 27 (Ω m)(-1) with increasing temperature from RT to 400 °C due to improved structural order. Electrical conductivity exhibit a decrease at 500 °C (7.4 (Ω m)(-1)) due to disordering induced by Ti segregation, which is confirmed by XRD and RS measurements. PMID:21323357

  9. Coupled effects of conduction in the crystal and thermo-solutal convection in a rectangular inclined enclosure

    NASA Technical Reports Server (NTRS)

    Mennetrier, Christophe; Duval, Walter M. B.

    1990-01-01

    To date modeling of crystal growth of optoelectronic materials using Physical Vapor Transport has been limited to the study of the fluid phase. To achieve it, the equations of coupled heat, mass and momentum transfer in the gas have to be solved. The first objective of this study is to examine the effect of heat conduction in the crystal on the fluid flow in the neighborhood of the interface. Heat transfer boundary conditions on both interfaces were modified to take into account the additional heat flux between gas and solid. It is proved that heat conduction does not affect the fluid flow. In the presence of gravity, density gradients in the fluid phase generate convection responsible for the problem of a nonplanar growth of the interface. The second objective is to study systematically under one-g the different possible flows in order to solve this problem. Depending on the parameters, a diffusive mode and three convective modes (thermal, solutal and thermo-solutal) are observed. The competition between thermal and solutal convections leads to a mathematical condition which can be used to achieve a planar growth. It is proven that, under the physical conditions chosen, this mathematical condition cannot be thermodynamically satisfied.

  10. Electrical conductivity and asymmetric material changes upon irradiation of Mg-doped lithium niobate crystals with low-mass, high-energy ions

    SciTech Connect

    Jentjens, L.; Raeth, N. L.; Peithmann, K.; Maier, K.

    2011-06-15

    Radiation damage in magnesium-doped lithium niobate crystals, created by low-mass, high-energy ions which have transmitted the entire crystal thickness, leads to an enhanced electrical dark conductivity as well as an enhanced photoconductivity. Experimental results on the electrical properties after ion exposure are given, and an asymmetric dependence of the conductivity as well as refractive index changes on the irradiation geometry with respect to the ferroelectric axis is revealed.

  11. Hydrogen centers and the conductivity of In2O3 single crystals

    DOE PAGESBeta

    Yin, Weikai; Smithe, Kirby; Weiser, Philip; Stavola, Michael; Fowler, W. Beall; Boatner, Lynn A.; Pearton, Stephen J.; Hays, David C.; Koch, Sandro G.

    2015-02-24

    A series of infrared absorption experiments and complementary theory have been performed in order to determine the properties of OH and OD centers in In2O3 single crystals. Annealing In2O3 samples in H2 or D2 at temperatures near 450°C produces an n-type layer ≈0.06mm thick with an n-type doping of 1.6×1019 cm-3. The resulting free-carrier absorption is correlated with an OH center with a vibrational frequency of 3306 cm-1 that we associate with interstitial H+. Additional O-H (O-D) vibrational lines are assigned to metastable configurations of the interstitial H+(D+) center and complexes of H (D) with In vacancies. In addition, unlikemore » other oxides studied recently where H trapped at an oxygen vacancy is the dominant shallow donor (ZnO and SnO2, for example), interstitial H+ is found to be the dominant H-related shallow donor in In2O3.« less

  12. Thermal and Electrical Conduction of Single-crystal Bi2Te3 Nanostructures grown using a one step process

    PubMed Central

    Park, Dambi; Park, Sungjin; Jeong, Kwangsik; Jeong, Hong-Sik; Song, Jea Yong; Cho, Mann–Ho

    2016-01-01

    Single-crystal Bi2Te3 nanowires (NWs) and nanoribbons (NRs) were synthesized by a vapor-liquid-solid (VLS) method from Bi2Te3 powder. To investigate the thermal properties of the Bi2Te3 nanostructure, a nondestructive technique based on temperature dependent Raman mapping was carried out. The Raman peaks were red shifted with increasing temperature. In addition, the fraction of the laser power absorbed inside the Bi2Te3 nanostructures was estimated by optical simulation and used to calculate the thermal conductivity value (κ). The thermal conductivity value obtained for the Bi2Te3 NW and NR was 1.47 Wm−1K−1 and 1.81 Wm−1K−1 at 300 K, respectively. The electrical conductivity of the Bi2Te3 nanostructure was also measured. In particular, an excellent electrical conductivity value of 1.22 * 103 Ω−1 cm−1 was obtained for the Bi2Te3 NW at 300 K. This result can be attributed to topological insulator surface states. As a result of our study, the figure of merit (ZT) for the Bi2Te3 NW and NR can be significantly improved. PMID:26750563

  13. The heat conductivity of liquid crystal phases of a soft ellipsoid string-fluid evaluated by molecular dynamics simulation.

    PubMed

    Sarman, Sten; Laaksonen, Aatto

    2011-04-01

    We have applied a nonequilibrium molecular dynamics heat flow algorithm to calculate the heat conductivity of a molecular model system, which forms uniaxial and biaxial nematic liquid crystals. The model system consists of a soft ellipsoid string-fluid where the ellipsoids interact according to a repulsive version of the Gay-Berne potential. On compression, this system forms discotic or calamitic uniaxial nematic phases depending on the dimensions of the molecules, and on further compression a biaxial nematic phase is formed. In the discotic nematic phase, the heat conductivity has two components, one parallel and one perpendicular to the director, where the last mentioned component is the largest one. This order of magnitudes is reversed in the calamitic nematic phase. In the biaxial nematic phase there are three components of the heat conductivity, one in the direction around which the long axes of the molecules are oriented, this is the largest component, another one in the direction around which the normals of the broadsides of the molecules are oriented, this is the smallest component, and one in the direction perpendicular to these two directions with a magnitude in between those of the first mentioned components. The relative magnitudes of the components of the heat conductivity span a fairly wide interval so it should be possible to use the model to parameterise experimental data. PMID:21336361

  14. Hierarchical self-assembly of hexagonal single-crystal nanosheets into 3D layered superlattices with high conductivity

    NASA Astrophysics Data System (ADS)

    Tao, Yulun; Shen, Yuhua; Yang, Liangbao; Han, Bin; Huang, Fangzhi; Li, Shikuo; Chu, Zhuwang; Xie, Anjian

    2012-05-01

    While the number of man-made nano superstructures realized by self-assembly is growing in recent years, assemblies of conductive polymer nanocrystals, especially for superlattices, are still a significant challenge, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we firstly report a facile and general route to a new generation of 3D layered superlattices of polyaniline doped with CSA (PANI-CSA) and show how PANI crystallize and self-assemble, in a suitable single solution environment. In cyclohexane, 1D amorphous nanofibers transformed to 1D nanorods as building blocks, and then to 2D single-crystal nanosheets with a hexagonal phase, and lastly to 3D ordered layered superlattices with the narrowest polydispersity value (Mw/Mn = 1.47). Remarkably, all the instructions for the hierarchical self-assembly are encoded in the layered shape in other non-polar solvents (hexane, octane) and their conductivity in the π-π stacking direction is improved to about 50 S cm-1, which is even higher than that of the highest previously reported value (16 S cm-1). The method used in this study is greatly expected to be readily scalable to produce superlattices of conductive polymers with high quality and low cost.While the number of man-made nano superstructures realized by self-assembly is growing in recent years, assemblies of conductive polymer nanocrystals, especially for superlattices, are still a significant challenge, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we firstly report a facile and general route to a new generation of 3D layered superlattices of polyaniline doped with CSA (PANI-CSA) and show how PANI crystallize and

  15. Electrically continuous graphene from single crystal copper verified by terahertz conductance spectroscopy and micro four-point probe.

    PubMed

    Buron, Jonas D; Pizzocchero, Filippo; Jessen, Bjarke S; Booth, Timothy J; Nielsen, Peter F; Hansen, Ole; Hilke, Michael; Whiteway, Eric; Jepsen, Peter U; Bøggild, Peter; Petersen, Dirch H

    2014-11-12

    The electrical performance of graphene synthesized by chemical vapor deposition and transferred to insulating surfaces may be compromised by extended defects, including for instance grain boundaries, cracks, wrinkles, and tears. In this study, we experimentally investigate and compare the nano- and microscale electrical continuity of single layer graphene grown on centimeter-sized single crystal copper with that of previously studied graphene films, grown on commercially available copper foil, after transfer to SiO2 surfaces. The electrical continuity of the graphene films is analyzed using two noninvasive conductance characterization methods: ultrabroadband terahertz time-domain spectroscopy and micro four-point probe, which probe the electrical properties of the graphene film on different length scales, 100 nm and 10 μm, respectively. Ultrabroadband terahertz time-domain spectroscopy allows for measurement of the complex conductance response in the frequency range 1-15 terahertz, covering the entire intraband conductance spectrum, and reveals that the conductance response for the graphene grown on single crystalline copper intimately follows the Drude model for a barrier-free conductor. In contrast, the graphene grown on commercial copper foil shows a distinctly non-Drude conductance spectrum that is better described by the Drude-Smith model, which incorporates the effect of preferential carrier backscattering associated with extended, electronic barriers with a typical separation on the order of 100 nm. Micro four-point probe resistance values measured on graphene grown on single crystalline copper in two different voltage-current configurations show close agreement with the expected distributions for a continuous 2D conductor, in contrast with previous observations on graphene grown on commercial copper foil. The terahertz and micro four-point probe conductance values of the graphene grown on single crystalline copper shows a close to unity correlation, in

  16. Ordered structures in proton conducting membranes from supramolecular liquid crystal polymers.

    PubMed

    Every, Hayley A; Mendes, Eduardo; Picken, Stephen J

    2006-11-30

    Highly sulfonated forms of poly(p-phenylene terephthalamide) (PPTA) have been prepared in three different molecular configurations; sulfonated diamine form (S-PPTA), sulfonated terephthalic acid form (S-invert-PPTA), and the bi-sulfonated form (S2-PPTA). All three polymers are water soluble to a certain degree and films were cast from solution for S-PPTA and S-invert-PPTA. S-PPTA films absorb less water than S-invert-PPTA (under controlled humidity conditions) and consequently, the conductivity for this polymer is also slightly lower. Although the conductivities are comparable to Nafion (of the order of 10(-2) to 10(-1) Scm(-1)), proton mobility is more restricted. X-ray diffraction showed that the rigid molecules are aligned in opposite directions for the two polymer films, being homeotropic in S-PPTA films and planar for S-invert-PPTA. SEM analysis demonstrated layering in the same direction as the alignment of the polymer chains. The variation in the polymer alignment is most likely the result of the differences in the solution properties and the film forming process. It is possible, however, that this alignment could be exploited to enhance proton transport and thus these films are of interest for fuel cell membranes. PMID:17125333

  17. Crystal Structure and Ionic Conductivity of Three Polymorphic Phases of Rubidium Trefluoromethyl Sulfonate, RbSO3CF3

    SciTech Connect

    Hildebrandt,L.; Dinnebier, R.; Jansen, M.

    2006-01-01

    The crystal structures of three polymorphic phases of rubidium trifluoromethyl sulfonate (RbSO{sub 3}CF{sub 3}, rubidium 'triflate') were solved from X-ray powder diffraction data. At room temperature, rubidium triflate crystallizes in the monoclinic space group Cm with lattice parameters of a = 19.9611(5) Angstroms, b = 23.4913(7) Angstroms, c = 5.1514(2) Angstroms, = 102.758(2); Z = 16. At T = 321 K, a first-order phase transition occurs toward a monoclinic phase in space group P2{sub 1} with lattice parameters at T = 344 K of a = 10.3434(5) Angstroms, b = 5.8283(3) Angstroms, c = 5.1982(3) Angstroms, = 104.278(6); Z = (2). At T = 461 K, another phase transition, this time of second order, occurs toward an orthorhombic phase in space group Cmcm with lattice parameters at T = 510 K of a = 5.3069(2) Angstroms, b = 20.2423(10) Angstroms, c = 5.9479(2) Angstroms; Z = 4. As a common feature within all three crystal structures of rubidium triflate, the triflate anions are arranged in double layers with the lipophilic CF{sub 3} groups facing each other. The rubidium ions are located between the SO{sub 3} groups. The general packing is similar to the packing in cesium triflate. Rubidium triflate can be classified as a solid electrolyte with a specific ionic conductivity of = 9.89 x 10{sup -9} S/cm at T = 384 K and = 3.84 x 10{sup -6} S/cm at T = 481 K.

  18. On the growth of conductive aluminum doped zinc oxide on 001 strontium titanate single crystals

    NASA Astrophysics Data System (ADS)

    Trinca, L. M.; Galca, A. C.; Aldica, G.; Radu, R.; Mercioniu, I.; Pintilie, L.

    2016-02-01

    Aluminum doped zinc oxide (AZO) thin films were obtained by pulsed laser deposition on (001) SrTiO3 (STO) on a range of substrate temperatures during ablation between 300 °C and 600 °C. A hexagonal system lying on a cubic one should be difficult to be obtained in epitaxial form. The geometrical selection of the AZO growth on (001) STO is not giving a unique preferential orientation. Two orientations, c-axis (along [001]) and 110, have been observed experimentally with different ratios at different substrate temperature. Discussions are made with respect to the temperature dependence of lattice mismatch between the two cases and the cubic surface of the substrate, and to the substrate surface morphology and terminating atomic layer composition. The 110 AZO is the main phase at deposition temperature of 550 °C, while for other substrate temperatures the 001 is the preferential orientation. The conductive character of 110 AZO thin film have been inferred from both ellipsometry spectra and current-voltage measurements. Excepting the samples deposited at 300 °C, the lowest resistivity is recorded for the samples with 110 AZO as the main phase.

  19. Selectively transparent and conducting photonic crystal rear-contacts for thin-film silicon-based building integrated photovoltaics

    NASA Astrophysics Data System (ADS)

    O'Brien, P. G.; Chutinan, A.; Mahtani, P.; Leong, K.; Ozin, G. A.; Kherani, N. P.

    2011-08-01

    Wave-optics analysis is performed to show that selectively transparent and conducting photonic crystals (STCPCs) can be utilized as rear contacts to enhance the performance of building-integrated photovoltaics (BIPV). For instance, the current generated in an a-Si:H cell with an STCPC functioning as its rear contact is comparable to that of a similar cell with an optimized ZnO/Ag rear contact. However, the solar lumens (~3.5 klm/m2) and power (~430W/m2) transmitted through the cell with the STCPC rear contact can potentially provide indoor heating and lighting, respectively. Moreover, experimental results show that STCPC rear contacts could be used to control the color temperature of light transmitted through BIPV panels.

  20. Electron scattering in the Δ{sub 1} model of the conduction band of germanium single crystals

    SciTech Connect

    Luniov, S. V. Burban, O. V.; Nazarchuk, P. F.

    2015-05-15

    Electron scattering in the possible Δ{sub 1} models of the conduction band in germanium crystals formed by hydrostatic or uniaxial pressure is investigated. On the basis of the theory of anisotropic scattering, the temperature dependences of the anisotropy parameter of the relaxation times and electron mobility for these models under conditions of scattering at impurity ions, as well as at acoustic and intervalley phonons are obtained. Analysis of the temperature dependences indicates that, in the temperature range of 77–300 K, intervalley scattering becomes substantial. Only for the Δ{sub 1} model formed by uniaxial pressure along the crystallographic direction [100], the electron scattering at intervalley phonons, which correspond to the g transitions, is minor with respect to scattering at acoustic phonons (the intravalley scattering) and impurity ions.

  1. Selectively transparent and conducting photonic crystal rear-contacts for thin-film silicon-based building integrated photovoltaics.

    PubMed

    O'Brien, P G; Chutinan, A; Mahtani, P; Leong, K; Ozin, G A; Kherani, N P

    2011-08-29

    Wave-optics analysis is performed to show that selectively transparent and conducting photonic crystals (STCPCs) can be utilized as rear contacts to enhance the performance of building-integrated photovoltaics (BIPV). For instance, the current generated in an a-Si:H cell with an STCPC functioning as its rear contact is comparable to that of a similar cell with an optimized ZnO/Ag rear contact. However, the solar lumens (~3.5 klm/m2) and power (~430W/m2) transmitted through the cell with the STCPC rear contact can potentially provide indoor heating and lighting, respectively. Moreover, experimental results show that STCPC rear contacts could be used to control the color temperature of light transmitted through BIPV panels. PMID:21935064

  2. See-through amorphous silicon solar cells with selectively transparent and conducting photonic crystal back reflectors for building integrated photovoltaics

    SciTech Connect

    Yang, Yang; O’Brien, Paul G.; Ozin, Geoffrey A. E-mail: kherani@ecf.utoronto.ca; Kherani, Nazir P. E-mail: kherani@ecf.utoronto.ca

    2013-11-25

    Thin semi-transparent hydrogenated amorphous silicon (a-Si:H) solar cells with selectively transparent and conducting photonic crystal (STCPC) back-reflectors are demonstrated. Short circuit current density of a 135 nm thick a-Si:H cell with a given STCPC back-reflector is enhanced by as much as 23% in comparison to a reference cell with an ITO film functioning as its rear contact. Concurrently, solar irradiance of 295 W/m{sup 2} and illuminance of 3480 lux are transmitted through the cell with a given STCPC back reflector under AM1.5 Global tilt illumination, indicating its utility as a source of space heating and lighting, respectively, in building integrated photovoltaic applications.

  3. Coupled theoretical interpretation and experimental investigation of the lattice thermal conductivity of Bi2Te3 single crystal

    NASA Astrophysics Data System (ADS)

    Jacquot, A.; Bayer, B.; Winkler, M.; Jaegle, M.

    2012-06-01

    An essential challenge in thermoelectric material research is the selection of materials having potentially a high figure-of-merit and their improvement by the reduction of their lattice thermal conductivity. In the present article the Debye model is modified for the calculation of the lattice thermal conductivity and used to gain insight into the anisotropy of single crystalline bismuth telluride (Bi2Te3). In this article the minimum wavelength of phonons that moved, which is closely related to the concept of cutoff frequency, is not taken twice the atoms separation. The Debye temperature is in fact not used to estimate the cutoff frequencies of the phonons that carry heat. The cutoff frequencies are defined in this work by setting an upper limit to the energy of acoustic phonons using the complete dispersion relations. Our work indicates that the cutoff frequencies of acoustic phonons are anisotropic in Bi2Te3. The anisotropy of the thermal conductivity is surprisingly found to be unrelated to the anisotropy of the sound velocities that are calculated as a function of the tensor of the elastic constants. The sound velocity is in fact almost isotropic when the longitudinal and two transversal waves are added together. In addition it is suggested that the relaxation time is also a function of the cutoff frequencies and that this may counterbalance the anisotropy arising from the variation of the number of acoustic phonons traveling in various directions. Finally, the anisotropy of the thermal conductivity of Bi2Te3 single crystal is found to be mostly related to the Grüneisen's constant if the main scattering mechanism is a phonon-phonon interaction.

  4. Reciprocated suppression of polymer crystallization toward improved solid polymer electrolytes: Higher ion conductivity and tunable mechanical properties

    DOE PAGESBeta

    Bi, Sheng; Sun, Che-Nan; Zawodzinski, Thomas A.; Ren, Fei; Keum, Jong Kahk; Ahn, Suk-Kyun; Li, Dawen; Chen, Jihua

    2015-08-06

    Solid polymer electrolytes based on lithium bis(trifluoromethanesulfonyl) imide and polymer matrix were extensively studied in the past due to their excellent potential in a broad range of energy related applications. Poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) are among the most examined polymer candidates as solid polymer electrolyte matrix. In this paper, we study the effect of reciprocated suppression of polymer crystallization in PVDF/PEO binary matrix on ion transport and mechanical properties of the resultant solid polymer electrolytes. With electron and X-ray diffractions as well as energy filtered transmission electron microscopy, we identify and examine the appropriate blending composition thatmore » is responsible for the diminishment of both PVDF and PEO crystallites. Laslty, a three-fold conductivity enhancement is achieved along with a highly tunable elastic modulus ranging from 20 to 200 MPa, which is expected to contribute toward future designs of solid polymer electrolytes with high room-temperature ion conductivities and mechanical flexibility.« less

  5. Anomalous enhancement of proton conductivity for water molecular clusters stabilized in interstitial spaces of porous molecular crystals.

    PubMed

    Tadokoro, Makoto; Ohhata, Yuki; Shimazaki, Yuriko; Ishimaru, Shin'ichi; Yamada, Teppei; Nagao, Yuki; Sugaya, Tomoaki; Isoda, Kyosuke; Suzuki, Yuta; Kitagawa, Hiroshi; Matsui, Hiroshi

    2014-10-13

    In an investigation into the proton conductivity of crystallized water clusters confined within low-dimensional nanoporous materials, we have found that water-stable nanoporous crystals are formed by complementary hydrogen bonding between [Co(III) (H2 bim)3 ](3+) (H2 bim: 2,2'-biimidazole) and TATC(3-) (1,3,5- tricarboxyl-2,4,6-triazinate); the O atoms in the -COO(-) groups of TATC(3-) in the porous outer wall are strongly hydrogen bonded with H2 O, forming two types of WMCs (water molecular clusters): a spirocyclic tetramer chain (SCTC) that forms infinite open 1D channels, and an isolated cyclic tetramer (ICT) present in the void space. The ICT is constructed from four H2 O molecules as a novel C2 -type WMC, which are hydrogen bonded with four-, three-, and two-coordination spheres, respectively. The largest structural fluctuation is observed at elevated temperatures from the two-coordinated H2 O molecules, which begin to rapidly and isotropically fluctuate on heating. This behavior can be rationalized by a simple model for the elucidation of pre-melting phenomena, similar to those in ice surfaces as the temperature increases. Moreover, high proton conductivity of SCTCs (ca. 10(-5) S cm(-1) at 300 K with an activation energy of 0.30 eV) through a proton-hole mechanism was observed for pellet samples using the alternating impedance method. The proton conductivity exhibits a slight enhancement of about 0.1×10(-5) S cm(-1) at 274 K due to a structural transition upon approaching this temperature that elongates the unit cell along the b-axis. The proton-transfer route can be predicted in WMCs, as O(4) of an H2 O molecule at the center of an SCTC shows a motion that rotates the dipole in the b-axis direction, but not the c-axis; the thermal ellipsoids of O(4) based on anisotropic temperature factors obtained by X-ray crystallography reflect a structural fluctuation along the b-axis direction induced by [Co(III) (H2 bim)3 ](3+) . PMID:25186220

  6. A thiophene-containing compound as a matrix for matrix-assisted laser desorption/ ionization mass spectrometry and the electrical conductivity of matrix crystals.

    PubMed

    Yasuda, Akikazu; Ishimaru, Takayuki; Nishihara, Shogo; Sakai, Masamichi; Kawasaki, Hideya; Arakawa, Ryuichi; Shigeri, Yasushi

    2013-01-01

    The electrical conductivity of the matrix crystal might be a new factor to enhance matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sensitivity. In MALDI-MS, several compounds are used as a standard matrix. Utilization of such compounds is based on an a posteriori approach, but there is no theoretical guidance for selecting a matrix. In an attempt to further understand performance in MALDI-MS, we utilized peptide detection for random screening of a chemical library (12,383 compounds) for compounds with matrix functions in MALDI-MS. A lot of thiophene compounds were found to be a matrix, in which 2-[5-(2,4-dichlorobenzoyl)-2-thienyl] acetic acid (DCBTA) provided an important clue to measure the electrical conductivity of the matrix crystal, because the structure of DCBTA is analogous to conductive polymers and organic solar cells. Most of the crystals of standard matrices, such as alpha-cyano-4-hydroxycinnamic acid (CHCA), 3,5-dimethoxy-4-hydroxycinnamic acid [sinapinic acid, (SA)], and DCBTA showed electrical conductivity, whereas the conductivity of crystal was not observed in 2,5-dihydroxybenzoic acid (2,5-DHB). On the other hand, super-DHB using 2-hydroxy-5-methoxybenzoic acid [5-methoxysalicylic acid, (MSA)] as an additive to 2,5-DHB, improved the electrical conductivity of the crystal, that followed the enhancement of peak intensity in MS spectrum. These observations might indicate that the electrical conductivity of matrix crystals is a key consideration in obtaining efficient MALDI performance. PMID:23841223

  7. Growth of MgF2 optical crystals and their ionic conductivity in the as-grown state and after partial pyrohydrolysis

    NASA Astrophysics Data System (ADS)

    Karimov, D. N.; Sorokin, N. I.; Chernov, S. P.; Sobolev, B. P.

    2014-11-01

    MgF2 single crystals have been grown from melt by the Bridgman technique in a fluorinating atmosphere. To control the presence of oxygen impurity, it was first suggested to measure the ionic conductivity in MgF2 crystals by impedance spectroscopy. The characteristics of ionic conductivity of " as grown" (i.e., without thermal treatment) crystals and crystals obtained by commercial vacuum technology practically coincide: the volume conductivity σv = 1.4 × 10-7 S/cm at 773 K and the ion-transport activation energy E a = 1.40 ± 0.05 eV. Annealing MgF2 crystals during electrophysical studies upon heating from 293 to 823 K in vacuum (residual pressure ˜1 Pa) for 4 h led to their partial pyrohydrolisis. The influence of this thermal treatment of MgF2 crystals on their optical transmission is studied in the wavelength range of 115-300 nm.

  8. Temperature Distribution in a Gaussian End-Pumped Nonlinear KTP Crystal: the Temperature Dependence of Thermal Conductivity and Radiation Boundary Condition

    NASA Astrophysics Data System (ADS)

    Sabaeian, Mohammad; Jalil-Abadi, Fatemeh Sedaghat; Rezaee, Mostafa Mohammad; Motazedian, Alireza; Shahzadeh, Mohammadreza

    2015-02-01

    The presence of a temperature-dependent thermal conductivity and the heat radiation boundary condition in the diffusion-type heat equation driven by a Gaussian source make it impossible to find an analytical solution for temperature distribution in the solid-state laser media. In this work, a temperature distribution for a solid-state end-pumped KTP (KTiOPO4) crystal under a Gaussian continuous wave as a heat source is reported. More precisely, the effects of considering the temperature-dependent nature of the thermal conductivity of the KTP crystal and the heat radiation from the end faces of the crystal, in addition to heat convection, which are usually ignored, were studied. It was shown that considering the temperature dependence of thermal conductivity leads to significantly different results compared to constant thermal conductivity case. In addition, it was shown that the radiation can be influential for crystals with large surfaces from which the radiation can occur. Making the crystal thinner, the radiation impact becomes negligible and can be ignored.

  9. Dramatically Different Conductivity Properties of Metal-Organic Framework Polymorphs of Tl(TCNQ): An Unexpected Room-Temperature Crystal-to-Crystal Phase Transition

    SciTech Connect

    Avendano, Carolina; Zhang, Zhongyue; Ota, Akira; Zhao, Hanhua; Dunbar, Kim R

    2012-02-07

    Tl(TCNQ) polymorphs with very different charge-transport properties have been isolated, one of which undergoes a remarkable crystal-to-crystal phase transition to the second phase when exposed to ambient water vapor (see picture; TCNQ=tetracyanoquinodimethane).

  10. Probing the lower limit of lattice thermal conductivity in an ordered extended solid: Gd117Co56Sn112, a phonon glass-electron crystal system.

    PubMed

    Schmitt, Devin C; Haldolaarachchige, Neel; Xiong, Yimin; Young, David P; Jin, Rongying; Chan, Julia Y

    2012-04-01

    The discovery of novel materials with low thermal conductivity is paramount to improving the efficiency of thermoelectric devices. As lattice thermal conductivity is inversely linked to unit cell complexity, we set out to synthesize a highly complex crystalline material with glasslike thermal conductivity. Here we present the structure, transport properties, heat capacity, and magnetization of single-crystal Gd(117)Co(56)Sn(112), a complex material with a primitive unit cell volume of ~6858 Å(3) and ~285 atoms per primitive unit cell (1140 atoms per face-centered cubic unit cell). The room temperature lattice thermal conductivity of this material is κ(L) = 0.28 W/(m·K) and represents one of the lowest ever reported for a nonglassy or nonionically conducting bulk solid. Furthermore, this material exhibits low resistivity at room temperature, and thus represents a true physical system that approaches the ideal phonon glass-electron crystal. PMID:22375963

  11. Cobalt-doped Bi{sub 26}Mo{sub 10}O{sub 69}: Crystal structure and conductivity

    SciTech Connect

    Mikhailovskaya, Z.A.; Buyanova, E.S.; Petrova, S.A.; Morozova, M.V.; Zhukovskiy, V.M.; Zakharov, R.G.; Tarakina, N.V.; Berger, I.F.

    2013-08-15

    A series of cobalt-doped bismuth molybdates were synthesized and investigated using X-ray powder diffraction, transmission electron microscopy and impedance spectroscopy. The ranges of solid solution were determined. Two new compounds, Bi{sub 1−x}Co{sub x}[Bi{sub 12}O{sub 14}]Mo{sub 5}O{sub 34.5±δ} (x=0.2) and Bi[Bi{sub 12}O{sub 14}]Mo{sub 5−y}Co{sub y}O{sub 34.5±δ} (y=0.2), which crystallise in monoclinic unit cells have been examined in detail by diffraction methods. Impedance spectroscopy measurements show that the studied materials are good ionic conductors with conductivity values about 5×10{sup −3} S×cm{sup −1} at 973 K and 1.7×10{sup −4} S×cm{sup −1} at 623 K, which are similar to conductivity values of yttrium substituted zirconia and (YSZ) gadolinium doped ceria (CGO). - Graphical abstract: Measured and calculated diffraction spectra for Bi{sub 12.8}Co{sub 0.2}Mo{sub 5}O{sub 34±δ} and projection of the Bi{sub 12.8}Co{sub 0.2}Mo{sub 5}O{sub 34±δ} crystal structure onto the ac plane. Highlights: • The limit of the Bi{sub 1−x}Co{sub x}[Bi{sub 12}O{sub 14}]Mo{sub 5}O{sub 34.5±δ} homogeneity range is equal to x=0.2. • The limit of the Bi[Bi{sub 12}O{sub 14}]Mo{sub 5−y}Co{sub y}O{sub 34.5±δ} homogeneity range is equal to y=0.2. • Solid solutions have monoclinic symmetry. No phase transition is observed. • The conductivity at 700° for y=0.2 solid solutions is equal to −lg σ, S×cm{sup −1}=2.23. • The conductivity at 350° for y=0.2 solid solutions is equal to −lg σ, S×cm{sup −1}=3.74.

  12. Silver transfer in proustite Ag{sub 3}AsS{sub 3} at high temperatures: Conductivity and single-crystal X-ray studies

    SciTech Connect

    Gagor, Anna Pawlowski, Antoni; Pietraszko, Adam

    2009-03-15

    Single crystals of proustite Ag{sub 3}AsS{sub 3} have been characterised by impedance spectroscopy and single-crystal X-ray diffraction in the temperature ranges of 295-543 and 295-695 K, respectively. An analysis of the one-particle potential of silver atoms shows that in the whole measuring temperature range defects in the silver substructure play a major role in the conduction mechanism. Furthermore, the silver transfer is equally probable within silver chains and spirals, as well as between chains and spirals. The trigonal R3c room temperature phase does not change until the decomposition of the crystal. The electric anomaly of the first-order character which appears near 502 K is related to an increase in the electronic component of the total conductivity resulting from Ag{sub 2}S deposition at the sample surface. - Joint probability density function map of silver atoms at T=695 K.

  13. Electrical conduction mechanism in La3Ta0.5Ga5.3Al0.2O14 single crystals.

    PubMed

    Yaokawa, Ritsuko; Aota, Katsumi; Uda, Satoshi

    2013-12-14

    The electrical conduction mechanism in La3Ta0.5Ga5.3Al0.2O14 (LTGA) single crystals was studied by nonstoichiometric defect formation during crystal growth. Since stoichiometric LTGA is not congruent, the single crystal grown from the stoichiometric melt was Ta-poor and Al-rich, where Al atoms were substituted not only in Ga sites but also in Ta sites. The population of the substitutional Al in Ta sites increased with increasing oxygen partial pressure during growth (growth-pO2) in the range from 0.01 to 1 atm. Below 600 °C, substitutional Al atoms in Ta sites were ionized to yield holes, and thus the electrical conductivity of the LTGA crystal depended on temperature and the growth-pO2. The dependence of the electrical conductivity on the growth-pO2 decreased as temperature increased. The temperature rise increases ionic conductivity, for which the dominant carriers are oxygen defects formed by the anion Frenkel reaction. PMID:24396153

  14. Correction: Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials.

    PubMed

    Muñoz Rojo, Miguel; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2015-03-01

    Correction for 'Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials' by Miguel Muñoz Rojo et al., Nanoscale, 2014, 6, 7858-7865. PMID:25668105

  15. Highly controllable and stable quantized conductance and resistive switching mechanism in single-crystal TiO2 resistive memory on silicon.

    PubMed

    Hu, Chengqing; McDaniel, Martin D; Posadas, Agham; Demkov, Alexander A; Ekerdt, John G; Yu, Edward T

    2014-08-13

    TiO2 is being widely explored as an active resistive switching (RS) material for resistive random access memory. We report a detailed analysis of the RS characteristics of single-crystal anatase-TiO2 thin films epitaxially grown on silicon by atomic layer deposition. We demonstrate that although the valence change mechanism is responsible for the observed RS, single-crystal anatase-TiO2 thin films show electrical characteristics that are very different from the usual switching behaviors observed for polycrystalline or amorphous TiO2 and instead very similar to those found in electrochemical metallization memory. In addition, we demonstrate highly stable and reproducible quantized conductance that is well controlled by application of a compliance current and that suggests the localized formation of conducting Magnéli-like nanophases. The quantized conductance observed results in multiple well-defined resistance states suitable for implementation of multilevel memory cells. PMID:25072099

  16. Crystal structure, NMR study, dielectric relaxation and AC conductivity of a new compound [Cd3(SCN)2Br6(C2H9N2)2]n

    NASA Astrophysics Data System (ADS)

    Saidi, K.; Kamoun, S.; Ayedi, H. Ferid; Arous, M.

    2013-11-01

    The crystal structure, the 13C NMR spectroscopy and the complex impedance have been carried out on [Cd3(SCN)2Br6(C2H9N2)2]n. Crystal structure shows a 2D polymeric network built up of two crystallographically independent cadmium atoms with two different octahedral coordinations. This compound exhibits a phase transition at (T=355±2 K) which has been characterized by differential scanning calorimetry (DSC), X-rays powder diffraction, AC conductivity and dielectric measurements. Examination of 13C CP/MAS line shapes shows indirect spin-spin coupling (14N and 13C) with a dipolar coupling constant of 1339 Hz. The AC conductivity of this compound has been carried out in the temperature range 325-376 K and the frequency range from 10-2 Hz to 10 MHz. The impedance data were well fitted to two equivalent electrical circuits. The results of the modulus study reveal the presence of two distinct relaxation processes. One, at low frequency side, is thermally activated due to the ionic conduction of the crystal and the other, at higher frequency side, gradually disappears when temperature reaches 355 K which is attributed to the localized dipoles in the crystal. Moreover, the temperature dependence of DC-conductivity in both phases follows the Arrhenius law and the frequency dependence of σ(ω,T) follows Jonscher's universal law. The near values of activation energies obtained from the conductivity data and impedance confirm that the transport is through the ion hopping mechanism.

  17. Electrical and Optical Properties of Index-Matched Transparent Conducting Oxide Layers for Liquid Crystal on Si Projection Displays

    NASA Astrophysics Data System (ADS)

    Park, Cheol Young; Choi, Bum Ho; Lee, Jong Ho

    2013-06-01

    In this study, the characteristics of several kinds of index-matched transparent conducting oxide layers (TCO) were investigated for applications to liquid crystals on silicon (LCoS) projection displays. The purpose of exploring the characteristics of these materials is to find alternatives to currently used index-matched indium-doped tin oxide (ITO) layers, since index-matched ITO suffers from high production costs and materials shortages. Based on zinc oxide (ZnO) TCO layers, metal dopants such as Al, In, or Ga were added to improve the optical and electrical properties; 15 nm thick ZnO, aluminum-doped ZnO (AZO), indium-gallium-doped ZnO (IGZO), indium-doped ZnO (IZO), and gallium-doped ZnO (GZO) layers were sputtered on glass substrates using radio frequency (RF) and direct current (DC) magnetron sputtering. The measured transparency in the visible radiation range was above 94% for all prepared index-matched TCO layers. Among them, the transparency of AZO layers was the highest, reaching 97.5%. The sheet resistance of the TCO layers was around 100 Ω cm-2, with 82.6 Ω cm-2 being the lowest measured value obtained from a 15 nm thick AZO layer. Furthermore, the sheet resistance uniformity measured by samples with an area of 200×200 mm2 was below 5%. Atomic force microscopy measurement results show that the root-mean-square surface roughness values were lower than 0.01 nm in ZnO and AZO, and 0.128 and 0.261 in IGZO and GZO, respectively. The contact angle, which is another key factor in index-matched TCO-coated substrates, was around 25°, which meets the requirements for LCoS projection display panels. Among the tested TCO layers, AZO exhibited superior characteristics in terms of optical and electrical properties. Therefore, AZO represents an alternative to currently used index-matched ITO layers in LCoS projection displays.

  18. Ultraviolet laser crystallized ZnO:Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency

    SciTech Connect

    Nian, Qiong; Zhang, Martin Y.; Schwartz, Bradley D.; Cheng, Gary J.

    2014-05-19

    One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that UVLC dramatically improves the electron mobility, while the carrier concentration decreases which in turn simultaneously increases conductivity and transparency. AZO films under optimized UVLC achieve the highest electron mobility of 79 cm{sup 2}/V s at a low carrier concentration of 7.9 × 10{sup +19} cm{sup −3}. This is realized by a laser crystallization induced decrease of both grain boundary density and electron trap density at grain boundaries. The infrared (IR) to mid-IR range transmittance spectrum shows UVLC significantly enhances the AZO film transparency without compromising conductivity.

  19. An efficient light trapping scheme based on textured conductive photonic crystal back reflector for performance improvement of amorphous silicon solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Peizhuan; Hou, Guofu; Fan, QiHua; Huang, Qian; Zhao, Jing; Zhang, Jianjun; Ni, Jian; Zhang, Xiaodan; Zhao, Ying

    2014-08-01

    An efficient light trapping scheme named as textured conductive photonic crystal (TCPC) has been proposed and then applied as a back-reflector (BR) in n-i-p hydrogenated amorphous silicon (a-Si:H) solar cell. This TCPC BR combined a flat one-dimensional photonic crystal and a randomly textured surface of chemically etched ZnO:Al. Total efficiency enhancement was obtained thanks to the sufficient conductivity, high reflectivity and strong light scattering of the TCPC BR. Unwanted intrinsic losses of surface plasmon modes are avoided. An initial efficiency of 9.66% for a-Si:H solar cell was obtained with short-circuit current density of 14.74 mA/cm2, fill factor of 70.3%, and open-circuit voltage of 0.932 V.

  20. An efficient light trapping scheme based on textured conductive photonic crystal back reflector for performance improvement of amorphous silicon solar cells

    SciTech Connect

    Chen, Peizhuan; Hou, Guofu Huang, Qian; Zhao, Jing; Zhang, Jianjun Ni, Jian; Zhang, Xiaodan; Zhao, Ying; Fan, QiHua

    2014-08-18

    An efficient light trapping scheme named as textured conductive photonic crystal (TCPC) has been proposed and then applied as a back-reflector (BR) in n-i-p hydrogenated amorphous silicon (a-Si:H) solar cell. This TCPC BR combined a flat one-dimensional photonic crystal and a randomly textured surface of chemically etched ZnO:Al. Total efficiency enhancement was obtained thanks to the sufficient conductivity, high reflectivity and strong light scattering of the TCPC BR. Unwanted intrinsic losses of surface plasmon modes are avoided. An initial efficiency of 9.66% for a-Si:H solar cell was obtained with short-circuit current density of 14.74 mA/cm{sup 2}, fill factor of 70.3%, and open-circuit voltage of 0.932 V.

  1. Ionic conductivity of alkaline (Li 2O, Na 2O) and alkaline-earth (BaO) borates in crystallization (vitrification) region

    NASA Astrophysics Data System (ADS)

    Solntsev, V. P.; Davydov, A. V.

    2011-11-01

    In this paper we report the existence of abnormal behavior of electric properties of alkaline (Li 2O,Na 2O) and alkaline-earth (BaO) borate in the melt—a crystal (glass) transition region. Results of measurement of conductivity in the mentioned interval evidence the existence of a strong variation of electric properties depending on the concentration of alkaline and alkaline-earth ions. The reasons of such behavior are discussed.

  2. Investigation of laser-fired point contacts on KOH structured laser-crystallized silicon by conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Gref, Orman; Weizman, Moshe; Rhein, Holger; Gabriel, Onno; Gernert, Ulrich; Schlatmann, Rutger; Boit, Christian; Friedrich, Felice

    2016-06-01

    A conductive atomic force microscope is used to study the local topography and conductivity of laser-fired aluminum contacts on KOH-structured multicrystalline silicon surfaces. A significant increase in conductivity is observed in the laser-affected area. The area size and spatial uniformity of this enhanced conductivity depends on the laser energy fluence. The laser-affected area shows three ring-shaped regimes of different conductance depending on the local aluminum and oxygen concentration. Finally, it was found that the topographic surface structure determined by the silicon grain orientation does not significantly affect the laser-firing process.

  3. A molecular dynamics study of the effect of thermal boundary conductance on thermal transport of ideal crystal of n-alkanes with different number of carbon atoms

    NASA Astrophysics Data System (ADS)

    Rastgarkafshgarkolaei, Rouzbeh; Zeng, Yi; Khodadadi, J. M.

    2016-05-01

    Phase change materials such as n-alkanes that exhibit desirable characteristics such as high latent heat, chemical stability, and negligible supercooling are widely used in thermal energy storage applications. However, n-alkanes have the drawback of low thermal conductivity values. The low thermal conductivity of n-alkanes is linked to formation of randomly oriented nano-domains of molecules in their solid structure that is responsible for excessive phonon scattering at the grain boundaries. Thus, understanding the thermal boundary conductance at the grain boundaries can be crucial for improving the effectiveness of thermal storage systems. The concept of the ideal crystal is proposed in this paper, which describes a simplified model such that all the nano-domains of long-chain n-alkanes are artificially aligned perfectly in one direction. In order to study thermal transport of the ideal crystal of long-chain n-alkanes, four (4) systems (C20H42, C24H50, C26H54, and C30H62) are investigated by the molecular dynamics simulations. Thermal boundary conductance between the layers of ideal crystals is determined using both non-equilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) simulations. Both NEMD and EMD simulations exhibit no significant change in thermal conductance with the molecular length. However, the values obtained from the EMD simulations are less than the values from NEMD simulations with the ratio being nearly three (3) in most cases. This difference is due to the nature of EMD simulations where all the phonons are assumed to be in equilibrium at the interface. Thermal conductivity of the n-alkanes in three structures including liquid, solid, and ideal crystal is investigated utilizing NEMD simulations. Our results exhibit a very slight rise in thermal conductivity values as the number of carbon atoms of the chain increases. The key understanding is that thermal transport can be significantly altered by how the molecules and the

  4. The crystal structure, thermal behaviour and ionic conductivity of a novel lithium gadolinium polyphosphate LiGd(PO{sub 3}){sub 4}

    SciTech Connect

    Ettis, Hasna; Naili, Houcine . E-mail: houcine_naili@yahoo.com; Mhiri, Tahar

    2006-10-15

    Crystal structure and ionic conductivity of lithium gadolinium polyphosphate, LiGd(PO{sub 3}){sub 4}, were investigated. Single crystals of the title compound have been grown by a flux technique. The structure of this novel phosphate was determined by single crystal X-ray diffraction techniques. LiGd(PO{sub 3}){sub 4} is isotypic with LiNd(PO{sub 3}){sub 4}. It crystallizes in the monoclinic space group C2/c with the unit cell parameters a=16.386(2), b=7.059(3), c=9.677(2) A, {beta}=126.12(1){sup o}, V=904.2(4) A{sup 3} and Z=4. The structure refined from 967 independent reflections leads to R {sub 1}=0.0167 and wR {sub 2}=0.0458. The lattice of LiGd(PO{sub 3}){sub 4} is built of twisted zig-zag chains running along with the b direction and make up of PO{sub 4} tetrahedra sharing two corners, connected to the GdO{sub 8} and LiO{sub 4} polyhedra by common oxygen atoms to form a three-dimensional framework. Differential and thermogravimetric thermal analysis are given. The thermal curve of this compound was recorded and interpreted in agreement with impedance measurements. The ionic conductivity has been measured on pellet of the polycrystalline powder and evaluated as a function of temperature. This phase showed the conductivity of 2x10{sup -6} and 2x10{sup -4} {omega}{sup -1} cm{sup -1} at 682 and 951 K, respectively. - Graphical abstract: The structural arrangement of LiGd(PO{sub 3}){sub 4} viewed in the (0 1 0) plane.

  5. Pattern Formation in a Nematic Liquid Crystal Mixture with Negative Anisotropy of the Electric Conductivity-A Long-Known System with "Inverse" Light Scattering Revisited.

    PubMed

    Zhang, Bingru; Kitzerow, Heinz

    2016-07-14

    Pattern formation in binary calamitic liquid crystal mixtures with positive dielectric anisotropy and negative conductivity anisotropy, which attracted attention owing to field-induced light scattering under unusual conditions many years ago, is reinvestigated in the conductive regime. Homeotropic cells with these mixtures exhibit a direct transition to isotropic electroconvection, while planar cells show a Fréedericksz transition to the quasi-homeotropic state and subsequent electroconvection at higher voltages. A temperature-induced change from normal and oblique convection rolls to longitudinal rolls reveals a transition from standard electroconvection to nonstandard electroconvection, which can be attributed to a sign inversion of the conductivity anisotropy. In summary, this system shows an unusually large variety of patterns and effects, which were observed and theoretically considered more recently in other systems of quite different types. PMID:27347852

  6. Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials.

    PubMed

    Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2014-07-21

    To date, there is no experimental characterization of thermal conductivity of semiconductor polymeric individual nanowires embedded in a matrix. This work reports on scanning thermal microscopy measurements in a 3ω configuration to determine how the thermal conductivity of individual nanowires made of a model conjugated polymer (P3HT) is modified when decreasing their diameters. We observe a reduction of thermal conductivity, from λNW = 2.29 ± 0.15 W K(-1) m(-1) to λNW = 0.5 ± 0.24 W K(-1) m(-1), when the diameter of nanowires is reduced from 350 nm to 120 nm, which correlates with the polymer crystal orientation measured by WAXS. Through this work, the foundations for future polymer thermal transport engineering are presented. PMID:24933655

  7. Evidence of conduction-electron shielding of the crystal electric field of Tb sub x Gd sub 1 minus x Al sub 2 intermetallics

    SciTech Connect

    del Moral, A.; Joven, E. Instituto de Ciencio de Materiales de Aragon, Universidad de Zaragoza, Consejo Superior de Investigaciones Cientificas, Zaragoza )

    1990-12-01

    A comparison of the values obtained for the {ital B}{sub 4} crystal-electric-field (CEF) parameter in the series of cubic intermetallics Tb{sub {ital x}}Gd{sub 1{minus}{ital x}}Al{sub 2} with a model which predicts a dependence of {ital B}{sub 4} on the density of states with {ital d} character at the Fermi level, allows us to demonstrate directly the shielding effect of the conduction electrons on the CEF produced by the lattice of tripositive rare-earth and Al ions.

  8. Synthesis, Crystal Structures and Physical Properties of TTF-Based Conducting Charge Transfer Salts with Anions Containing Selenocyanate Ligands

    NASA Astrophysics Data System (ADS)

    Turner, Scott S.; Le Pévelen, Delphine; Day, Peter; Prout, Keith

    2002-11-01

    Three new charge transfer salts of tetrathiafulvalene (TTF)-based donors with selenocyanate-metal complex anions have been synthesized. The salts have been characterized as BEDT-TTF 4[Cr(NCSe) 6]·CH 2Cl 2, II, TTF 3[Cr(NCSe) 4phen] 2, III and BEDT-TTF 2[Cr(NCSe) 4phen]·CH 2Cl 2, IV, where phen=1,10'-phenanthroline and BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene. At 120 K, II crystallizes in the P2 1/ m space group with a= 10.454(1), b= 31.990(1), c= 12.339(1) Å, β= 113.163(2)°, V= 3793.8Å 3, Z= 4 and at 240 K in the same space group with a= 10.530(1), b=32.122(1), c= 12.396(1) Å, β=113.186(3)°, V=3854.2 Å 3, Z=4. At 240 K III crystallizes in the C2/ c space group, a=38.9272(5), b=11.2992(1), c=15.2540(3) Å, β=106.8877(6)°, V=6420.1 Å 3, Z=8. The structure of IV has been solved in the Poverline1 space group with a=8.7629(3), b=11.7977(4), c=26.6031(9), α=81.697(2), β=87.858(3), γ=74.8471(14), V=2626.8 Å 3, Z=2. All of the salts have numerous S·Se close atomic contacts between donors and acceptors but there is no magnetic exchange between ions, as previously seen in closely related salts such as TTF[Cr(NCS) 4phen] and (donor)[ M(NCS) 4(isoquinoline) 2], where M=Cr, Fe and donor=TTF, BEDT-TTF or TMTTF (tetramethyltetrathiafulvalene). Indeed, II and IV are paramagnetic semiconductors whereas III is a paramagnetic insulator. The absence of long-range magnetic order is discussed in terms of structure-function relations since there are no π-stacking interactions between donor and acceptor, which are seen in all of the bulk magnets of this type where the donor spin is magnetically coupled to the anion. The synthesis and crystal structure of the starting material, [(C 4H 9) 4N] 3[Cr(NCSe) 6], I, is also reported; it crystallizes in the Poverline1 space group with a=12.220(1), b=12.814(1), c=13.008(1) Å, α=99.608(6), β=114.028(5), γ=92.637(6)°, V=1819.5 Å 3, Z=2.

  9. Conductivity of laser printed copper structures limited by nano-crystal grain size and amorphous metal droplet shell

    NASA Astrophysics Data System (ADS)

    Winter, Shoshana; Zenou, Michael; Kotler, Zvi

    2016-04-01

    We present a study of the morphology and electrical properties of copper structures which are printed by laser induced forward transfer from bulk copper. The percentage of voids and the oxidation levels are too low to account for the high resistivities (~4 to 14 times the resistivity of bulk monocrystalline copper) of these structures. Transmission electron microscope (TEM) images of slices cut from the printed areas using a focused ion beam (FIB) show nano-sized crystal structures with grain sizes that are smaller than the electron free path length. Scattering from such grain boundaries causes a significant increase in the resistivity and can explain the measured resistivities of the structures. The TEM images also show a nano-amorphous layer (~5 nm) at the droplet boundaries which also contributes to the overall resistivity. Such morphological characteristics are best explained by the ultrafast cooling rate of the molten copper droplets during printing.

  10. Encapsulating Mobile Proton Carriers into Structural Defects in Coordination Polymer Crystals: High Anhydrous Proton Conduction and Fuel Cell Application.

    PubMed

    Inukai, Munehiro; Horike, Satoshi; Itakura, Tomoya; Shinozaki, Ryota; Ogiwara, Naoki; Umeyama, Daiki; Nagarkar, Sanjog; Nishiyama, Yusuke; Malon, Michal; Hayashi, Akari; Ohhara, Takashi; Kiyanagi, Ryoji; Kitagawa, Susumu

    2016-07-13

    We describe the encapsulation of mobile proton carriers into defect sites in nonporous coordination polymers (CPs). The proton carriers were encapsulated with high mobility and provided high proton conductivity at 150 °C under anhydrous conditions. The high proton conductivity and nonporous nature of the CP allowed its application as an electrolyte in a fuel cell. The defects and mobile proton carriers were investigated using solid-state NMR, XAFS, XRD, and ICP-AES/EA. On the basis of these analyses, we concluded that the defect sites provide space for mobile uncoordinated H3PO4, H2PO4(-), and H2O. These mobile carriers play a key role in expanding the proton-hopping path and promoting the mobility of protons in the coordination framework, leading to high proton conductivity and fuel cell power generation. PMID:27324658

  11. Effects of the amino acid sequence on thermal conduction through β-sheet crystals of natural silk protein.

    PubMed

    Zhang, Lin; Bai, Zhitong; Ban, Heng; Liu, Ling

    2015-11-21

    Recent experiments have discovered very different thermal conductivities between the spider silk and the silkworm silk. Decoding the molecular mechanisms underpinning the distinct thermal properties may guide the rational design of synthetic silk materials and other biomaterials for multifunctionality and tunable properties. However, such an understanding is lacking, mainly due to the complex structure and phonon physics associated with the silk materials. Here, using non-equilibrium molecular dynamics, we demonstrate that the amino acid sequence plays a key role in the thermal conduction process through β-sheets, essential building blocks of natural silks and a variety of other biomaterials. Three representative β-sheet types, i.e. poly-A, poly-(GA), and poly-G, are shown to have distinct structural features and phonon dynamics leading to different thermal conductivities. A fundamental understanding of the sequence effects may stimulate the design and engineering of polymers and biopolymers for desired thermal properties. PMID:26455593

  12. Electrical conductivity of vacuum deposited films and crystals of redox-isomeric о-semiquinonato cobalt complexes

    NASA Astrophysics Data System (ADS)

    Lukyanov, A. Yu.; Bubnov, M. P.; Skorodumova, N. A.; Travkin, V. V.; Pakhomov, G. L.; Korolyov, S. A.; Yunin, P. A.; Cherkasov, V. K.

    2015-10-01

    A study of the temperature dependences of electrical conductivity of crystalline and thin-film samples of о-semiquinonato complexes of cobalt (2,2‧-bpy)Co(3,6-DBSQ)2 (complex 1) and (1,10-phen)Co(3,6-DBSQ)2 (complex 2) is reported; where 3,6-DBSQ is 3,6-di-tert-butyl-benzoquinone-1,2. It was shown that the electrical conductivity of samples having amorphous, polycrystalline and monocrystalline structure depends on temperature in the range 150-400 K in a different way. The abrupt drop of conductivity (up to 10% per a degree) was observed in crystalline samples in the region of phase transition (270-310 K for complex 1 and 140-230 K for complex 2). It makes such materials promising for design of uncooled matrix bolometers.

  13. The behavior of thermal conductivity in the chaotic phase of [N(CH{sub 3}){sub 4}]{sub 2}ZnCl{sub 4} crystal

    SciTech Connect

    Sveleba, S. A. Karpa, I. V.; Kunyo, I. M.; Semotyuk, O. V.; Katerynchuk, I. M.; Phitsych, E. I.; Pankivskyi, Yu. I.

    2010-07-15

    A thermal investigation of the modulated structure dynamics at the transition between metastable states in the incommensurate phase of [N(CH{sub 3}){sub 4}]{sub 2}ZnCl{sub 4} crystal have been performed. It is established that the anomalous behavior of the thermal conductivity in the absence of a defect-density wave is due to the inelastic scattering of thermal phonons from critical phonons of the soft optical branch. In the presence of a defect-density wave, the anomalous increase in thermal conductivity is caused by the existence of a chaotic phase and is related to the contribution that soft optical phonons make to the heat transfer due to the increase in their group velocity.

  14. Ionic conductivity of crystallization products of Ba1- x Yb x F2 + x melts ( x = 0.1, 0.2, 0.25)

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.; Sul'yanova, E. A.; Sobolev, B. P.

    2016-05-01

    The ionic conductivity σ of the crystallization products of Ba1 - x Yb x F2 + x melts with 10, 20 and 25 mol % YbF3 has been studied. A Ba0.9Yb0.1F2.1 sample is a solid solution with the CaF2 structure type, sp. gr. Fmoverline 3 m. A Ba0.8Yb0.2F2.2 sample contains two cubic forms with sp. gr. Fmoverline 3 m and Pmoverline 3 m. The σ values for Ba0.9Yb0.1F2.1 and Ba0.8Yb0.2F2.2 coincide and are equal to 3 × 10-5 S/cm at 500 K. A Ba0.75Yb0.25F2.25 sample is heterogeneous, despite its monolithic nature and transparency. A greater part of its volume has a cubic lattice with sp. gr. Pmoverline 3 m, while the smaller part is a phase crystallizing in the orthorhombic system. A change of composition from x = 0.2 to 0.25 leads to a change in the symmetry group and type of the cluster defects in the Ba1 - x Yb x F2 + x phase. The sp. gr. Fmoverline 3 m is replaced by the sp. gr. Pmoverline 3 m, and octahedral‒cubic {Ba8Yb6F69} clusters are transformed into "inverse" octahedral‒cubic {Yb8Ba6F71} clusters. These changes in the defect structure lead to an increase in conductivity by a factor of about 100. The fluorine-ionic conductivity of Ba0.75Yb0.25F2.25 is 2.5 × 10-3 S/cm at 500 K. This value exceeds the conductivity of Ba0.69La0.31F2.31 crystal by a factor of 15 (Ba0.69La0.31F2.31 has the best conducting properties among the fluorite phases of the Ba1 - x R x F2 + x family, for which σ was found to increase with a decrease in the atomic number of rare earth element (REE)).

  15. Thermal Conductivity of Ultrahigh Molecular Weight Polyethylene Crystal: Defect Effect Uncovered by 0 K Limit Phonon Diffusion.

    PubMed

    Liu, Jing; Xu, Zaoli; Cheng, Zhe; Xu, Shen; Wang, Xinwei

    2015-12-16

    Crystalline ultrahigh molecular weight polyethylene (UHMWPE) has the highest reported thermal conductivity at room temperature: 104 W/(m·K), while theoretical predictions proposed an even higher value of 300 W/(m·K). Defects and amorphous fraction in practical UHMWPE fibers significantly reduces the thermal conductivity from the ideal value. Although the amorphous effect can be readily analyzed based on the effective medium theory, the defect effects are poorly understood. This work reports on the temperature-dependent behavior (down to 22 K) of thermal diffusivity and conductivity of UHMWPE fibers in anticipation of observing the reduction in phonon density and scattering rate against temperature and of freezing out high-momentum phonons to clearly observe the defect effects. By studying the temperature-dependent behavior of thermal reffusivity (Θ, inverse of thermal diffusivity) of UHMWPE fibers, we are able to quantify the defect effects on thermal conductivity. After taking out the amorphous region's effect, the residual thermal reffusivities (Θ0) for the studied two samples at the 0 K limit are determined as 3.45 × 10(4) and 2.95 × 10(4) s/m(2), respectively. For rare-/no-defects crystalline materials, Θ0 should be close to zero at the 0 K limit. The defect-induced low-momentum phonon mean free paths are determined as 8.06 and 9.42 nm for the two samples. They are smaller than the crystallite size in the (002) direction (19.7 nm) determined by X-ray diffraction. This strongly demonstrates the diffuse phonon scattering at the grain boundaries. The grain boundary thermal conductance (G) can be evaluated as G ≈ βρc(p)v with sound accuracy. At room temperature, G is around 3.73 GW/(m(2)·K) for S2, comparable to that of interfaces with tight atomic bonding. PMID:26593380

  16. Anisotropy of electrical conductivity in dc due to intrinsic defect formation in α-Al2O3 single crystal implanted with Mg ions

    NASA Astrophysics Data System (ADS)

    Tardío, M.; Egaña, A.; Ramírez, R.; Muñoz-Santiuste, J. E.; Alves, E.

    2016-07-01

    The electrical conductivity in α-Al2O3 single crystals implanted with Mg ions in two different crystalline orientations, parallel and perpendicular to c axis, was investigated. The samples were implanted at room temperature with energies of 50 and 100 keV and fluences of 1 × 1015, 5 × 1015 and 5 × 1016 ions/cm2. Optical characterization reveals slight differences in the absorption bands at 6.0 and 4.2 eV, attributed to F type centers and Mie scattering from Mg precipitates, respectively. DC electrical measurements using the four and two-point probe methods, between 295 and 490 K, were used to characterize the electrical conductivity of the implanted area (Meshakim and Tanabe, 2001). Measurements in this temperature range indicate that: (1) the electrical conductivity is thermally activated independently of crystallographic orientation, (2) resistance values in the implanted region decrease with fluence levels, and (3) the I-V characteristic of electrical contacts in samples with perpendicular c axis orientation is clearly ohmic, whereas contacts are blocking in samples with parallel c axis. When thin layers are sequentially removed from the implanted region by immersing the sample in a hot solution of nitric and fluorhydric acids the electrical resistance increases until reaching the values of non-implanted crystal (Jheeta et al., 2006). We conclude that the enhancement in conductivity observed in the implanted regions is related to the intrinsic defects created by the implantation rather than to the implanted Mg ions (da Silva et al., 2002; Tardío et al., 2001; Tardío et al., 2008).

  17. Synthesis crystal structure and ionic conductivity of Ca 0.5Bi 3V 2O 10 and Sr 0.5Bi 3V 2O 10

    NASA Astrophysics Data System (ADS)

    Porob, Digamber G.; Guru Row, T. N.

    2004-12-01

    Two new compounds Ca 0.5Bi 3V 2O 10 and Sr 0.5Bi 3V 2O 10 have been synthesized in the ternary system: MO-Bi 2O 3-V 2O 5 system ( M=M 2+). The crystal structure of Sr 0.5Bi 3V 2O 10 has been determined from single crystal X-ray diffraction data, space group P1¯ and Z=2, with cell parameters a=7.1453(3) Å, b=7.8921(3) Å, c=9.3297(3) Å, α=106.444(2)°, β=94.088(2)°, γ=112.445(2)°, V=456.72(4) Å 3. Ca 0.5Bi 3V 2O 10 is isostructural with Sr 0.5Bi 3V 2O 10, with, a=7.0810(2) Å, b=7.8447(2) Å, c=9.3607(2) Å, α=106.202(1)°, β=94.572(1)°, γ=112.659(1)°, V=450.38(2) Å 3 and its structure has been refined by Rietveld method using powder X-ray data. The crystal structure consists of infinite chains of (Bi 2O 2) along c-axis formed by linkage of BiO 8 and BiO 6 polyhedra interconnected by MO 8 polyhedra forming 2D layers in ac plane. The vanadate tetrahedra are sandwiched between these layers. Conductivity measurements give a maximum conductivity value of 4.54×10 -5 and 3.63×10 -5 S cm -1 for Ca 0.5Bi 3V 2O 10 and Sr 0.5Bi 3V 2O 10, respectively at 725 °C.

  18. Hydrogen centers and the conductivity of In2O3 single crystals

    SciTech Connect

    Yin, Weikai; Smithe, Kirby; Weiser, Philip; Stavola, Michael; Fowler, W. Beall; Boatner, Lynn A.; Pearton, Stephen J.; Hays, David C.; Koch, Sandro G.

    2015-02-24

    A series of infrared absorption experiments and complementary theory have been performed in order to determine the properties of OH and OD centers in In2O3 single crystals. Annealing In2O3 samples in H2 or D2 at temperatures near 450°C produces an n-type layer ≈0.06mm thick with an n-type doping of 1.6×1019 cm-3. The resulting free-carrier absorption is correlated with an OH center with a vibrational frequency of 3306 cm-1 that we associate with interstitial H+. Additional O-H (O-D) vibrational lines are assigned to metastable configurations of the interstitial H+(D+) center and complexes of H (D) with In vacancies. In addition, unlike other oxides studied recently where H trapped at an oxygen vacancy is the dominant shallow donor (ZnO and SnO2, for example), interstitial H+ is found to be the dominant H-related shallow donor in In2O3.

  19. Revealing surface oxidation on the organic semi-conducting single crystal rubrene with time of flight secondary ion mass spectroscopy.

    PubMed

    Thompson, Robert J; Fearn, Sarah; Tan, Ke Jie; Cramer, Hans George; Kloc, Christian L; Curson, Neil J; Mitrofanov, Oleg

    2013-04-14

    To address the question of surface oxidation in organic electronics the chemical composition at the surface of single crystalline rubrene is spatially profiled and analyzed using Time of Flight - Secondary Ion Mass Spectroscopy (ToF-SIMS). It is seen that a uniform oxide (C42H28O) covers the surface while there is an increased concentration of peroxide (C42H28O2) located at crystallographic defects. By analyzing the effects of different primary ions, temperature and sputtering agents the technique of ToF-SIMS is developed as a valuable tool for the study of chemical composition variance both at and below the surface of organic single crystals. The primary ion beams C60(3+) and Bi3(+) are found to be most appropriate for mass spectroscopy and spatial profiling respectively. Depth profiling of the material is successfully undertaken maintaining the molecular integrity to a depth of ~5 μm using an Ar cluster ion source as the sputtering agent. PMID:23455651

  20. Relationship between changes in the crystal lattice strain and thermal conductivity of high burnup UO 2 pellets

    NASA Astrophysics Data System (ADS)

    Amaya, Masaki; Nakamura, Jinichi; Fuketa, Toyoshi; Kosaka, Yuji

    2010-01-01

    Two kinds of disk-shaped UO 2 samples (4 mm in diameter and 1 mm in thickness) were irradiated in a test reactor up to about 60 and 130 GWd/t, respectively. The microstructures of the samples were investigated by means of optical microscopy, scanning electron microscopy/ electron probe micro-analysis (SEM/EPMA) and micro-X-ray diffractometry. The measured lattice parameters tended to be considerably smaller than the reported values, and the typical cauliflower structure which is often observed in high burnup fuel pellet is hardly seen in these samples. Thermal diffusivities of the samples were also measured by using a laser flash method, and their thermal conductivities were evaluated by multiplying the heat capacity of unirradiated UO 2 and sample densities. While the thermal conductivities of sample 2 showed recovery after being annealed at 1500 K, those of sample 4 were not clearly observed even after being annealed at 1500 K. These trends suggest that the amount of accumulated irradiation-induced defects depends on the irradiation condition of each sample. From the comparison of the changes in the lattice parameter and strain energy density before and after the thermal diffusivity measurements, it is likely that the thermal conductivity recovery in the temperature region from 1200 to 1500 K is related to the migration of dislocation.

  1. Experimental determination of single-crystal halite thermal conductivity, diffusivity and specific heat from -75°C to 300°C

    DOE PAGESBeta

    Urquhart, Alexander; Bauer, Stephen

    2015-05-19

    The thermal properties of halite have broad practical importance, from design and long-term modeling of nuclear waste repositories to analysis and performance assessment of underground natural gas, petroleum and air storage facilities. Using a computer-controlled transient plane source method, single-crystal halite thermal conductivity, thermal diffusivity and specific heat were measured from -75°C to 300°C. These measurements reproduce historical high-temperature experiments and extend the lower temperature extreme into cryogenic conditions. Measurements were taken in 25-degree increments from -75°C to 300°C. Over this temperature range, thermal conductivity decreases by a factor of 3.7, from 9.975 to 2.699 W/mK , and thermal diffusivitymore » decreases by a factor of 3.6, from 5.032 to 1.396 mm²/s. Specific heat does not appear to be temperature dependent, remaining near 2.0 MJ/m³K at all temperatures. This work is intended to develop and expand the existing dataset of halite thermal properties, which are of particular value in defining the parameters of salt storage thermophysical models. The work was motivated by a need for thermal conductivity values in a mixture theory model used to determine bulk thermal conductivity of reconsolidating crushed salt.« less

  2. Experimental determination of single-crystal halite thermal conductivity, diffusivity and specific heat from -75°C to 300°C

    SciTech Connect

    Urquhart, Alexander; Bauer, Stephen

    2015-05-19

    The thermal properties of halite have broad practical importance, from design and long-term modeling of nuclear waste repositories to analysis and performance assessment of underground natural gas, petroleum and air storage facilities. Using a computer-controlled transient plane source method, single-crystal halite thermal conductivity, thermal diffusivity and specific heat were measured from -75°C to 300°C. These measurements reproduce historical high-temperature experiments and extend the lower temperature extreme into cryogenic conditions. Measurements were taken in 25-degree increments from -75°C to 300°C. Over this temperature range, thermal conductivity decreases by a factor of 3.7, from 9.975 to 2.699 W/mK , and thermal diffusivity decreases by a factor of 3.6, from 5.032 to 1.396 mm²/s. Specific heat does not appear to be temperature dependent, remaining near 2.0 MJ/m³K at all temperatures. This work is intended to develop and expand the existing dataset of halite thermal properties, which are of particular value in defining the parameters of salt storage thermophysical models. The work was motivated by a need for thermal conductivity values in a mixture theory model used to determine bulk thermal conductivity of reconsolidating crushed salt.

  3. Hydrogen-bond-dynamics-based switching of conductivity and magnetism: a phase transition caused by deuterium and electron transfer in a hydrogen-bonded purely organic conductor crystal.

    PubMed

    Ueda, Akira; Yamada, Shota; Isono, Takayuki; Kamo, Hiromichi; Nakao, Akiko; Kumai, Reiji; Nakao, Hironori; Murakami, Youichi; Yamamoto, Kaoru; Nishio, Yutaka; Mori, Hatsumi

    2014-08-27

    A hydrogen bond (H-bond) is one of the most fundamental and important noncovalent interactions in chemistry, biology, physics, and all other molecular sciences. Especially, the dynamics of a proton or a hydrogen atom in the H-bond has attracted increasing attention, because it plays a crucial role in (bio)chemical reactions and some physical properties, such as dielectricity and proton conductivity. Here we report unprecedented H-bond-dynamics-based switching of electrical conductivity and magnetism in a H-bonded purely organic conductor crystal, κ-D3(Cat-EDT-TTF)2 (abbreviated as κ-D). This novel crystal κ-D, a deuterated analogue of κ-H3(Cat-EDT-TTF)2 (abbreviated as κ-H), is composed only of a H-bonded molecular unit, in which two crystallographically equivalent catechol-fused ethylenedithiotetrathiafulvalene (Cat-EDT-TTF) skeletons with a +0.5 charge are linked by a symmetric anionic [O···D···O](-1)-type strong H-bond. Although the deuterated and parent hydrogen systems, κ-D and κ-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only κ-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1). The X-ray crystal structure analysis demonstrates that this dramatic switching of the electronic structure and physical properties originates from deuterium transfer or displacement within the H-bond accompanied by electron transfer between the Cat-EDT-TTF π-systems, proving that the H-bonded deuterium dynamics and the conducting TTF π-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in κ-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve. PMID:25127315

  4. Superconducting energy gap and normal state conductivity of a single domain Y sub 1 Ba sub 2 Cu sub 3 O sub 7 crystal

    SciTech Connect

    Schlesinger, Z.; Collins, R.T.; Holtzberg, F.; Feild, C.; Blanton, S.H. . Thomas J. Watson Research Center); Welp, U. Argonne National Lab., IL ); Crabtree, G.W.; Fang, Y. ); Liu, J.Z. . Dept. of Physics)

    1990-09-01

    Using polarized reflectivity measurements of single domain crystals, we are able to distinguish chain and plane contributions to the infrared conductivity of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7}. A substantial chain contribution to {sigma}({omega}) persisting to low frequency and temperature is observed. For the intrinsic conductivity of the CuO{sub 2} planes a superconducting energy gap of 500 cm{sup {minus}1} (2{Delta}/k{Tc} {approx equal} 8) is evident in the infrared data, while the normal state conductivity drops much more slowly with {omega} than the ordinary Drude form, and can be described in terms of a scattering rate {Dirac h}/{tau}* {approximately} kT + {Dirac h}{omega} at low frequency. The former result (2{Delta}/k{Tc} {approx equal} 8) suggests substantial suppression of {Tc}; the latter, that Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} is not ordinary Fermi liquid. 26 refs., 4 figs.

  5. Crystal structure and AC conductivity mechanism of [N(C3H7)4]2CoCl4 compound

    NASA Astrophysics Data System (ADS)

    Moutia, N.; Oueslati, A.; Ben Gzaiel, M.; Khirouni, K.

    2016-09-01

    We found that the new organic-inorganic compound [N(C3H7)4]2 CoCl4, crystallizes at room temperature in the centrosymmetric monoclinic system with P21/c space group. The atomic arrangement can be described by an alternation of organic and organic-inorganic layers parallel to the (001) plan. Indeed, the differential scanning calorimetry (DSC) studies indicate a presence of three order-disorder phase transitions located at 332, 376 and 441 K. Furthermore, the conductivity was measured in the frequency range from 200 MHz to 5 MHz and temperatures between 318 K and 428 K using impedance spectroscopy. Analysis of the AC conductivity experimental data obtained, and the frequency exponent s with theoretical models reveals that the correlated barrier hopping (CBH) model is the appropriate mechanism for conduction in the title compound. The analysis of the dielectric constants ε ‧ and ε ″ versus temperature, at several frequencies, shows a distribution of relaxation times. This relaxation is probably due to the reorientational dynamics of [N(C3H7)4]+ cations.

  6. Crystal structure, NMR study, dc-conductivity and dielectric relaxation studies of a new compound [C2H10N2]Cd(SCN)2Cl2

    NASA Astrophysics Data System (ADS)

    Saidi, K.; Kamoun, S.; Ayedi, H. F.; Gargouri, M.

    2012-06-01

    The crystal structure, the solid NMR spectroscopy and the complex impedance study have been carried out on [C2H10N2]CdCl2(SCN)2. Characterization by single crystal X-ray crystallography shows that the cadmium atoms have à 2N2S2Cl hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The cadmium atoms are bridged by two thiocyanate ions generating 1-D polymeric-chains. These chains are themselves interconnected by means of N-H…Cl(NCS) hydrogen bonds originating from the organic cation [(NH3)2(CH2)2]2+. 111Cd isotropic chemical shifts span a range of 268ppm. The cadmium atom exhibits multiplets that result from 111Cd-14N spin-spin coupling. Examination of 111Cd and 13C MAS line shapes shows direct measurement of the indirect spin-spin coupling constant 2J(111Cd, 14N) = 105Hz and the dipolar coupling constant of 1381Hz . Impedance spectroscopy measurements of [C2H10N2]CdCl2(SCN)2 have been studied from 209Hz to 5 MHz over the temperature range 300-370 K. The Cole-Cole (Z" versus Z') plots are fitted to two equivalent circuits models. The formalism of complex permittivity and impedance were employed to analyze the experimental data. The dc conductivity follows the Arrhenius relation with an activation energy Ea = 0.54 (3) eV.

  7. Influence of gas atmosphere and temperature on the conductivity and the photoconductivity of a TiO2 single crystal in the surface region.

    PubMed

    Amade, R; Heitjans, P; Indris, S; Finger, M; Haeger, A; Hesse, D

    2006-02-14

    The electrical photoconductivity and conductivity at (and near) the surface of a TiO(2) single crystal (rutile) was studied in a range of temperatures between 300 and 573 K and under different ambient gases (oxygen and nitrogen) by means of impedance spectroscopy. The long times required (many hours) to reach steady state photoconductivity can be explained by the reduction of the material upon illumination. At about 475 K a maximum is observed in the equilibrium photoconductivity and a minimum in the rate constants of the rise and decay after switching on and off, respectively, the light. After switching off the light a fast decay takes place during the first milliseconds followed by a slow exponential decay. The first one is related to recombination through defects, while the latter is due to re-oxidation processes of the material. The results are correlated with measurements of photocatalytic activity. PMID:16482319

  8. Selectively Transparent and Conducting Photonic Crystals and their Potential to Enhance the Performance of Thin-Film Silicon-Based Photovoltaics and Other Optoelectronic Devices

    NASA Astrophysics Data System (ADS)

    O'Brien, Paul G.

    2011-12-01

    The byproducts of human engineered energy production are increasing atmospheric CO2 concentrations well above their natural levels and accompanied continual decline in the natural reserves of fossil fuels necessitates the development of green energy alternatives. Solar energy is attractive because it is abundant, can be produced in remote locations and consumed on site. Specifically, thin-film silicon-based photovoltaic (PV) solar cells have numerous inherent advantages including their availability, non-toxicity, and they are relatively inexpensive. However, their low-cost and electrical performance depends on reducing their thickness to as great an extent as possible. This is problematic because their thickness is much less than their absorption length. Consequently, enhanced light trapping schemes must be incorporated into these devices. Herein, a transparent and conducting photonic crystal (PC) intermediate reflector (IR), integrated into the rear side of the cell and serving the dual function as a back-reflector and a spectral splitter, is identified as a promising method of boosting the performance of thin-film silicon-based PV. To this end a novel class of PCs, namely selectively transparent and conducting photonic crystals (STCPC), is invented. These STCPCs are a significant advance over existing 1D PCs because they combine intense wavelength selective broadband reflectance with the transmissive and conductive properties of sputtered ITO. For example, STCPCs are made to exhibit Bragg-reflectance peaks in the visible spectrum of 95% reflectivity and have a full width at half maximum that is greater than 200nm. At the same time, the average transmittance of these STCPCs is greater than 80% over the visible spectrum that is outside their stop-gap. Using wave-optics analysis, it is shown that STCPC intermediate reflectors increase the current generated in micromorph cells by 18%. In comparison, the more conventional IR comprised of a single homogeneous

  9. Single-scan measurement of conductance of a quartz crystal microbalance array coupled with resonant markers for biosensing in liquid phase

    NASA Astrophysics Data System (ADS)

    Hsiao, Hsien-Yi; Chen, Richie L. C.; Cheng, Tzong-Jih

    2009-04-01

    This work presents a method for sensing the viscoelastic property of liquid/solid interface using a quartz crystal microbalance (QCM) array. Each sensor in a QCM array has a unique resonant frequency and can be identified by a single-scan measurement of admittance (or impedance). The resonant frequency encoding at each sensor in an array was realized by connecting a capacitor with a known capacitance, called a resonant marker, to the sensor in series. Changes in the resonant frequency of all sensors in an array can be determined using an impedance analyzer and a program that determines the frequencies at which the conductance is at a local maximum. The sensing method allows every sensor output (resonant frequency) to be obtained without the use of time-consuming multiplexed hardware and software. Adsorptions of biomolecules by multiple sensor are monitored in the liquid phase to demonstrate the feasibility of frequency encoding using resonant markers and the single-scan measurement of conductance of a QCM array.

  10. Transparent conductive ZnInSnO-Ag-ZnInSnO multilayer films for polymer dispersed liquid-crystal based smart windows

    NASA Astrophysics Data System (ADS)

    Kim, Eun Mi; Choi, In-Seok; Oh, Jeong-Pyo; Kim, Young-Baek; Lee, Jong-Ho; Choi, Yong-Sung; Cho, Jung-Dae; Kim, Yang-Bae; Heo, Gi-Seok

    2014-09-01

    Multilayer transparent films with electrical resistances lower than those in conventionally used transparent conductive electrodes were prepared at room temperature on glass substrates in an RF/DC magnetron sputtering system. The multilayer structure of the films consisted of three layers, ZnInSnO (ZITO)-Ag-ZITO. The optical and electrical properties of the multilayer structures were investigated with respect to the thickness of each ZITO-Ag-ZITO layer. Transparent conductive films with a sheet resistance of 9.4 Ω/square and an average transmittance of 92% at 550 nm were obtained at the following thicknesses of the glass substrate: ZITO (100 nm)-Ag (8 nm)-ZITO (42 nm). The surface roughness (RRMS) of the obtained ZITO-Ag-ZITO multilayer films was below 0.8 nm. Overall, the properties of the ZITO-Ag-ZITO multilayer films were comparable or superior to those of other multilayers such as InSnO (ITO)-Ag-ITO and InZnO (IZO)-Ag-IZO. The deposited ZITO single layer and ZITO-Ag-ZITO multilayer films were used in the fabrication of polymer-dispersed liquid-crystal (PDLC)-based smart windows. The ZITO-Ag-ZITO multilayer-based smart windows exhibited a lower operating voltage (16 V) and a higher cutoff rate of infrared light than ITO or ZITO-based smart windows 20-26 V. However, they showed a lower PDLC-ON transmittance than ITO-based smart windows.

  11. Single-scan measurement of conductance of a quartz crystal microbalance array coupled with resonant markers for biosensing in liquid phase

    SciTech Connect

    Hsiao, Hsien-Yi; Chen, Richie L. C.; Cheng, Tzong-Jih

    2009-04-15

    This work presents a method for sensing the viscoelastic property of liquid/solid interface using a quartz crystal microbalance (QCM) array. Each sensor in a QCM array has a unique resonant frequency and can be identified by a single-scan measurement of admittance (or impedance). The resonant frequency encoding at each sensor in an array was realized by connecting a capacitor with a known capacitance, called a resonant marker, to the sensor in series. Changes in the resonant frequency of all sensors in an array can be determined using an impedance analyzer and a program that determines the frequencies at which the conductance is at a local maximum. The sensing method allows every sensor output (resonant frequency) to be obtained without the use of time-consuming multiplexed hardware and software. Adsorptions of biomolecules by multiple sensor are monitored in the liquid phase to demonstrate the feasibility of frequency encoding using resonant markers and the single-scan measurement of conductance of a QCM array.

  12. Comments on the paper: 'Optical reflectance, optical refractive index and optical conductivity measurements of nonlinear optics for L-aspartic acid nickel chloride single crystal'

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bikshandarkoil R.; Naik, Suvidha G.; Dhavskar, Kiran T.

    2016-02-01

    We argue that the 'L-aspartic acid nickel chloride' crystal reported by the authors of the title paper (Optics Communications, 291 (2013) 304-308) is actually the well-known diaqua(L-aspartato)nickel(II) hydrate crystal.

  13. Synthesis, crystal structure, phase transition and electrical conduction mechanism of the new [(C3H7)4N]2MnCl4 compound

    NASA Astrophysics Data System (ADS)

    Gzaiel, M. Ben; Oueslati, A.; Hlel, F.; Gargouri, M.

    2016-09-01

    Bis tetrapropylammonium tetrchloro-monganete has been synthesized and characterized by X-ray, differential scanning calorimetry, vibrational spectroscopy and impedance spectroscopy. At room temperature, the latter is crystallized in the monoclinic phase, with P2/c space group. The projection of atomic arrangement along b axis shows that all nitrogen atoms are disposed linearly along [001] direction. Differential scanning calorimetry (DSC) disclosed three order-disorder phase transitions at T1=333 K, T2=356 K and T3=379 K. Besides, impedance measurements indicate that the electrical and dielectric properties are strongly dependent on both temperature and frequency. Nyquist plots (Z″ versus Z‧) show that the conductivity behavior is accurately represented by an equivalent circuit model which consists of a series combination of grains interior and grains boundary. The evolution of the dielectric constant as a function of temperature shows a distribution of relaxation times which is probably due to the reorientational dynamics of alkyl chains. On the other hand, the dependency of m(T) with temperature has been discussed in terms of the correlated barrier hopping (CBH) model in phase (I and IV). The quantum mechanical tunneling (QMT) model describes the second phase (II), whereas the third one (III) is characterized by the non-overlapping small Polaron tunneling (NSPT) model.

  14. The effect of salt on ion adsorption on a SiOx alignment film and reduced conductivity of a liquid crystal host

    NASA Astrophysics Data System (ADS)

    Huang, Yi; Bhowmik, Achintya; Bos, Philip J.

    2012-01-01

    It is shown that the addition of salt to liquid crystal cells, using a SiOx alignment layer, can actually reduce the ion concentration. This seeming contradiction may be explained by the ability of salt to complex with water and to aid the drying of the liquid crystal material. The results show a pathway to purifying liquid crystal devices to the extent needed for low-power low-refresh rate displays for e-book applications.

  15. Electrical conduction mechanism in La{sub 3}Ta{sub 0.5}Ga{sub 5.3}Al{sub 0.2}O{sub 14} single crystals

    SciTech Connect

    Yaokawa, Ritsuko Aota, Katsumi; Uda, Satoshi

    2013-12-14

    The electrical conduction mechanism in La{sub 3}Ta{sub 0.5}Ga{sub 5.3}Al{sub 0.2}O{sub 14} (LTGA) single crystals was studied by nonstoichiometric defect formation during crystal growth. Since stoichiometric LTGA is not congruent, the single crystal grown from the stoichiometric melt was Ta-poor and Al-rich, where Al atoms were substituted not only in Ga sites but also in Ta sites. The population of the substitutional Al in Ta sites increased with increasing oxygen partial pressure during growth (growth-pO{sub 2}) in the range from 0.01 to 1 atm. Below 600 °C, substitutional Al atoms in Ta sites were ionized to yield holes, and thus the electrical conductivity of the LTGA crystal depended on temperature and the growth-pO{sub 2}. The dependence of the electrical conductivity on the growth-pO{sub 2} decreased as temperature increased. The temperature rise increases ionic conductivity, for which the dominant carriers are oxygen defects formed by the anion Frenkel reaction.

  16. Nonstoichiometry in inorganic fluorides: 2. Ionic conductivity of nonstoichiometric M 1 - x R xF2 + x and R 1 - y M yF3 - y crystals ( M = Ca, Sr, Ba; R are rare earth elements)

    NASA Astrophysics Data System (ADS)

    Sobolev, B. P.; Sorokin, N. I.

    2014-11-01

    The peak manifestation of nonstoichiometry in fluoride systems in the number of phases with valuable properties and wide homogeneity ranges is 45 MF2- RF3 systems, where M = Ca, Sr, Ba and R are 15 rare earth elements from La to Lu and Y (with Pm and Sc excluded). A deviation from stoichiometry in crystals of the M 1 - x R xF2 + x (CaF2 fluorite type) and R 1 - y M yF3 - y (LaF3 tysonite type) phases is responsible for the fluorine superionic conductivity σ. The range of variation in σ with changes in the qualitative ( M, R) and quantitative ( x, y) compositions in both structure types is very wide. The σ value changes by a factor of 108 in the M 1 - x R xF2 + x phases (at 500 K) and by a factor of 106 in the R 1 - y M yF3 - y phases (at 293 K). Changing compositions, one can also obtain crystals with σ values large enough for their use as fluorine-conducting solid electrolytes. Phases promising for solid electrolytes were revealed in the MFm- RFn systems ( m < n ≤ 4), which were studied within the program of searching for new multicomponent fluoride materials at the Institute of Crystallography, Russian Academy of Sciences (IC RAS). Superionic conductivity is one of the peak manifestations of the influence of defect structure of nonstoichiometric crystals on their properties. The subject of this review is the results of the studies performed at the IC RAS on the ionic conductivity of single crystals of the M 1 - x R xF2 + x and R 1 - y M yF3 - y nonstoichiometric phases.

  17. Sealing behaviour and hall conductivity of mixed-state hall effect in heavy-ion irradiated YBa{sub 2}Cu{sub 3}O{sub 7} crystals

    SciTech Connect

    Kim, D.H.; Shim, S.Y. |; Kang, W.N.

    1995-12-31

    The Hall effect ({rho}{sub xy}) and longitudinal resistivity ({rho}{sub xx}) measured in YBa{sub 2}Cu{sub 3}O{sub 7} crystals before and after the irradiation of Sn and Xe ions. We found a clear evidence that the strong pinning induced by the columnar defects not only modifies the scaling behavior between the Hall resistivity {rho}{sub xy} and longitudinal resistivity {rho}{sub xx} but also affects the temperature dependence of the Hall conductivity. For the irradiated crystals with columnar defects, the scaling exponent {beta} of {rho}{sub xy} = A{rho}{sub xx}{sup {beta}} was found to be {beta} = 1.55 {+-} 0.1, whereas {beta} of the unirradiated one was larger than 1.8. In case of the Hall conductivity, the pinning strength dependence was also observed. The Hall conductivity after irradiation exhibited a clear deviation from that of the unirradiated crystal at low temperatures. These results are in a good agreement with the work by Wang et al. in which pinning plays an important role.

  18. Growth and defect structure of CdF{sub 2} crystal and nonstoichiometric Cd{sub 1-x}R{sub x}F{sub 2+x} phases (R are rare earth elements and in): 6. Growth and ionic conductivity of Cd{sub 0.904}In{sub 0.096}F{sub 2.096} single crystal

    SciTech Connect

    Sorokin, N. I. Sul'yanova, E. A.; Buchinskaya, I. I.; Artyukhov, A. A.; Sobolev, B. P.

    2013-07-15

    Cd{sub 0.904}In{sub 0.096}F{sub 2.096} crystals with fluorite-type defect structures have been grown from melt in a fluorinating atmosphere by the Bridgman method, and their ionic conductivity is investigated. The fluorine-ion transport activation enthalpy in Cd{sub 0.904}In{sub 0.096}F{sub 2.096} ({Delta}H = 0.68 eV) is much smaller than the corresponding characteristic of the crystals belonging to the isoconcentration series Cd{sub 0.9}R{sub 0.1}F{sub 2.1}, R = La-Lu, Y ({Delta}H = 0.8-0.9 eV). The ionic conductivity of Cd{sub 0.904}In{sub 0.096}F{sub 2.096} is {sigma} = 2 Multiplication-Sign 10{sup -4} S/cm (at 467 K); this value exceeds the conductivity of the CdF{sub 2} crystal matrix and the highest conductivity Cd{sub 0.9}R{sub 0.1}F{sub 2.1} crystals with rare earth elements by factors of 3 Multiplication-Sign 10{sup 3} and {approx}10, respectively. Nonstoichiometric crystals of solid electrolyte Cd{sub 1-x}In{sub x}F{sub 2+x} have the highest conductivity out of all studied electrolytes based on the CdF{sub 2} matrix.

  19. Conducting a thermal conductivity survey

    NASA Technical Reports Server (NTRS)

    Allen, P. B.

    1985-01-01

    A physically transparent approximate theory of phonon decay rates is presented starting from a pair potential model of the interatomic forces in an insulator or semiconductor. The theory applies in the classical regime and relates the 3-phonon decay rate to the third derivative of the pair potential. Phonon dispersion relations do not need to be calculated, as sum rules relate all the needed quantities directly to the pair potential. The Brillouin zone averaged phonon lifetime turns out to involve a dimensionless measure of the anharmonicity multiplied by an effective density of states for 3-phonon decay. Results are given for rare gas and alkali halide crystals. For rare gases, the results are in good agreement with more elaborate perturbation calculations. Comparison to experimental data on phonon linewidths and thermal conductivity are made.

  20. Apparatus for mounting crystal

    DOEpatents

    Longeway, Paul A.

    1985-01-01

    A thickness monitor useful in deposition or etching reactor systems comprising a crystal-controlled oscillator in which the crystal is deposited or etched to change the frequency of the oscillator. The crystal rests within a thermally conductive metallic housing and arranged to be temperature controlled. Electrode contacts are made to the surface primarily by gravity force such that the crystal is substantially free of stress otherwise induced by high temperature.

  1. Phononic crystal devices

    DOEpatents

    El-Kady, Ihab F.; Olsson, Roy H.

    2012-01-10

    Phononic crystals that have the ability to modify and control the thermal black body phonon distribution and the phonon component of heat transport in a solid. In particular, the thermal conductivity and heat capacity can be modified by altering the phonon density of states in a phononic crystal. The present invention is directed to phononic crystal devices and materials such as radio frequency (RF) tags powered from ambient heat, dielectrics with extremely low thermal conductivity, thermoelectric materials with a higher ratio of electrical-to-thermal conductivity, materials with phononically engineered heat capacity, phononic crystal waveguides that enable accelerated cooling, and a variety of low temperature application devices.

  2. Implanted Si atoms shifting between Ga sites and As sites by thermal stress in conductive-layer GaAs crystals on semi-insulating substrates

    NASA Astrophysics Data System (ADS)

    Saito, Yasuyuki

    1992-04-01

    Large (0.8 V order) discrepancies of threshold voltage Vth between the predicted Vth values by the Lindhard-Scharff-Schio/tt Gaussian approximate calculation and the Vth of the tungsten nitride (WNx) self-alignment (SA) gate GaAs metal-semiconductor field-effect transistors (MESFETs) were observed. These discrepancies were confirmed by the comparison of the Vth of the WNx-SA-gate MESFETs and the Vth of the (N+: high carrier concentration layers self-aligned of source-drain electrodes)-less conventional MESFETs on 2-in.-diam semi-insulating substrates from liquid-encapsulated-Czochralski-technique-grown <100> boules. The discrepancy was also analyzed by the capacitance-voltage (C-V) measurement of large-diameter (440 μm) Schottky diodes which were built into the MESFET arrays. It was found that for obtained SA-process carrier depth profiles (Si, 150 keV, 3×1012 cm-2) the carrier concentration at a depth of 0.25 μm decreased from 5.3×1016 to 2.0×1016 cm-3, but, on the other hand, the peak carrier concentration slightly decreased from 12.8×1016 to 12.4×1016 cm-3. By the calculation for Vth on the basis of the actual C-V carrier depth profiles, it was found that the carrier concentration decrease was comparable to the Vth variation (0.8 V). Furthermore, the Vth variation of the shallow channel implantation (50 keV) was comparable to that of the deep channel implantation (150 keV). As a result of the experiment and analysis, it was found that the large Vth variation for the SA N+ process was caused by reoccupation (Ga sites to As sites) of implanted Si atoms in the channel active-layer crystal by tensile stress formed by the thermal-expansion coefficient difference between chemical-vapor deposition (CVD) phosphosilicate glass (or CVD SiO2) film and (100) GaAs substrate crystal. The Si atom reoccupation quantity was, for the first time, explained by the Si atom compensation ratio equation as a function of the bond length (Si-As and Si-Ga) variation, an equation

  3. Super-fast switching of liquid crystals sandwiched between highly conductive graphene oxide/dimethyl sulfate doped PEDOT:PSS composite layers

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Zhang, Yifan; Oh, Byeong-Yun; Seo, Dae-Shik; Li, Xiangdan

    2016-05-01

    Graphene oxide (GO)-doped dimethyl sulfate (DMS)/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) superconductive alignment layer, aligning liquid crystals (LCs) with super switching and non-residual direct current (non-residual DC) performance, is presented in this manuscript. Doping of GO increased the pristine polar energy of a thin composite layer as well as the corresponding anchoring energy of the LCs sandwiched between these thin layers but only slightly affected the thin layers' morphology. When rubbed GO/DMS/PEDOT:PSS composite layers were used as alignment layers, a homogeneous alignment of nematic LCs was observed with competitive optoelectrical switching properties and non-residual DC performance because of the enhanced field effect and charge transport induced by the doped GO.

  4. Liquid crystal self-assembly of halloysite nanotubes in ionic liquids: a novel soft nanocomposite ionogel electrolyte with high anisotropic ionic conductivity and thermal stability

    NASA Astrophysics Data System (ADS)

    Zhao, Ningning; Liu, Yulin; Zhao, Xiaomeng; Song, Hongzan

    2016-01-01

    We report a novel class of liquid crystalline (LC) nanohybrid ionogels fabricated via self-assembly of natural halloysite nanotubes (HNTs) in ionic liquids (ILs). The obtained ionogels are very stable and nonvolatile and show LC phases over a wide temperature range. Remarkably, the nanocomposite ionogels exhibit high anisotropic ionic conductivity after shear, and their room temperature ionic conductivity can reach 3.8 × 10-3 S cm-1 for aligned nanotubes perpendicular to the electrode even when the HNTs content increases to 40 wt%, which is 380 times higher than that obtained for aligned nanotubes parallel to the electrode, which is 1.0 × 10-5 S cm-1. Crucially, the obtained LC nanocomposite ionogels have very high thermal stability, which can sustain 400 °C thermal treatment. The findings will promote the development of novel nanocomposite ionogel electrolytes with faster ion transport and larger anisotropic conductivity.We report a novel class of liquid crystalline (LC) nanohybrid ionogels fabricated via self-assembly of natural halloysite nanotubes (HNTs) in ionic liquids (ILs). The obtained ionogels are very stable and nonvolatile and show LC phases over a wide temperature range. Remarkably, the nanocomposite ionogels exhibit high anisotropic ionic conductivity after shear, and their room temperature ionic conductivity can reach 3.8 × 10-3 S cm-1 for aligned nanotubes perpendicular to the electrode even when the HNTs content increases to 40 wt%, which is 380 times higher than that obtained for aligned nanotubes parallel to the electrode, which is 1.0 × 10-5 S cm-1. Crucially, the obtained LC nanocomposite ionogels have very high thermal stability, which can sustain 400 °C thermal treatment. The findings will promote the development of novel nanocomposite ionogel electrolytes with faster ion transport and larger anisotropic conductivity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06888f

  5. Coupled theoretical interpretation and experimental investigation of the anisotropy of the lattice thermal conductivity of Bi{sub 2}Te{sub 3} single crystal

    SciTech Connect

    Jacquot, A.; Bayer, B.; Winkler, M.; Boettner, H.; Jaegle, M.

    2012-09-15

    The Debye model is modified for the calculation of the lattice thermal conductivity and used to gain insight into the anisotropy of Bi{sub 2}Te{sub 3}. In this work, the Debye temperature is not used to estimate the cutoff frequencies of the phonons that carry heat. The cutoff frequencies are defined by setting an upper limit to the energy of acoustic phonons using the complete dispersion relations. The anisotropy of the thermal conductivity is found to be unrelated to the anisotropy of the sound velocities. It is found that the sound velocity is almost isotropic when the longitudinal and two transversal waves are added together. In addition the relaxation time must be a function of the cutoff frequencies and counterbalances the anisotropy arising from the variation of the number of acoustic phonons traveling in various directions. It is concluded that the anisotropy of the thermal conductivity is mostly related to the Grueneisen's constant. - Graphical abstract: Dispersion relations of Bi{sub 2}Te{sub 3} along c-axis. The cutoff frequencies are found to be anisotropic and are defined exactly in this article where the acoustic branch crosses the optical branch. This affects both the number of phonons that carry heat in a given direction and the number of phonons that can scatter them. This is decisive for understanding the lattice thermal conductivity. Highlights: Black-Right-Pointing-Pointer Prediction of the anisotropy of the lattice thermal conductivity. Black-Right-Pointing-Pointer Provide a definition of the cutoff frequencies that makes sense. Black-Right-Pointing-Pointer Reduction of the number of frees parameter in phenomenological model. Black-Right-Pointing-Pointer Prediction that the anisotropy is a function of the scattering mechanism. Black-Right-Pointing-Pointer Means of experimental verification of theory.

  6. Sputtering characteristics, crystal structures, and transparent conductive properties of TiOxNy films deposited on α-Al2O3(0 0 0 1) and glass substrates

    NASA Astrophysics Data System (ADS)

    Akazawa, Housei

    2012-12-01

    Adding N2 gas during reactive sputtering of a Ti target prevented the target surface from being severely poisoned by oxygen atoms and sustained a high deposition rate for titanium oxynitride films under metal-mode-like sputtering conditions. With progress in the degree of oxidization, films deposited onto a glass substrate varied from TiO1-xNx having a face-centered cubic (fcc) structure to TiO2-xNx having an anatase structure. Titanium oxynitride films deposited on an Al2O3(0 0 0 1) substrate were epitaxial with major orientations toward the (1 1 1) and (2 0 0) directions for fcc-TiO1-xNx and (1 1 2) for anatase-TiO2-xNx. Intermediately oxidized films between TiO1-xNx and TiO2-xNx were amorphous on the glass substrate but crystallized into a Magneli phase, TinO(N)2n-1, on the Al2O3(0 0 0 1) substrate. Partially substituting oxygen in TiO2 with nitrogen as well as continuously irradiating the growing film surface with a Xe plasma stream preferentially formed anatase rather than rutile. However, the occupation of anion sites with enough oxygen rather than nitrogen was the required condition for anatase crystals to form. The transparent conductive properties of epitaxial TiO2-xNx films on Al2O3(0 0 0 1) were superior to those of microcrystalline films on the glass substrate. Since resistivity and optical transmittance of TiOxNy films vary continuously with changing N2 flow rate, their transparent conductive properties can be controlled more easily than TiOx. Nb5+ ions could be doped as donors in TiO2-xNx anatase crystals.

  7. Photo-controllable thermal diffusivity and thermal conductivity driven by the orientation change of nematic liquid crystal with azo-dendrimers

    NASA Astrophysics Data System (ADS)

    Ryu, Meguya; Takezoe, Hideo; Haba, Osamu; Yonetake, Koichiro; Morikawa, Junko

    2015-11-01

    We measured the temperature dependences of anisotropic thermal properties, i.e., thermal diffusivity, thermal effusivity, thermal conductivity, and heat capacity per unit volume, of a nematogen 4'-n-pentyloxybiphenyl-4-carbonitrile (5OCB) containing a small amount (0.02 wt. %) of dendritic azobenzene derivatives (azo-dendrimer), using a temperature wave method. The azo-dendrimers spontaneously adsorb on cell surfaces and act as a command surface, i.e., photo-induced planar/homeotropic alignment by ultraviolet/visible light illumination. By using this effect, we demonstrated thermal property changes except for the heat capacity by almost two times within a few tens of seconds. The phenomenon can be applied to a sheet with photo-controllable thermal diffusivity or thermal conductivity.

  8. Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage.

    PubMed

    Wang, Bo; Liu, Anmin; Abdulla, Wael Al; Wang, Dianlong; Zhao, X S

    2015-05-21

    Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a "platelet-on-sheet" LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (∼56 mA h g(-1) at 60 C) and long life cycling stability (∼87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (∼98% capacity retention over 1000 cycles at 10 C). PMID:25908535

  9. Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Liu, Anmin; Abdulla, Wael Al; Wang, Dianlong; Zhao, X. S.

    2015-05-01

    Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a ``platelet-on-sheet'' LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (~56 mA h g-1 at 60 C) and long life cycling stability (~87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (~98% capacity retention over 1000 cycles at 10 C).Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a ``platelet-on-sheet'' LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (~56 mA h g-1 at 60 C) and long life cycling stability (~87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples

  10. Synthesis, crystal structure and mono-dimensional thallium ion conduction of TlFe{sub 0.22}Al{sub 0.78}As{sub 2}O{sub 7}

    SciTech Connect

    Ouerfelli, Najoua; Guesmi, Abderrahmen Mazza, Daniele; Madani, Adel; Zid, Mohamed Faouzi; Driss, Ahmed

    2007-04-15

    A new solid solution TlFe{sub 0.22}Al{sub 0.78}As{sub 2}O{sub 7} has been synthesized by a solid-state reaction. The structure of the title compound has been determined from a single-crystal X-ray diffraction and refined to final values of the reliability factors: R(F {sup 2})=0.030 and wR(F {sup 2})=0.081 for 1343 independent reflections with I>2{sigma}(I). It crystallizes in the triclinic space group P-1, with a=6.296(2) A, b=6.397(2) A, c=8.242(2) A, {alpha}=96.74(2){sup o}, {beta}=103.78(2){sup o}, {gamma}=102.99(3){sup o}, V=309.0(2) A{sup 3} and Z=2. The structure can be described as a three-dimensional framework containing (Fe/Al)O{sub 6} octahedra connected through As{sub 2}O{sub 7} groups. The metallic units and diarsenate groups share oxygen corners to form a three-dimensional framework with interconnected tunnels parallel to the a, b and c directions, where Tl{sup +} cations are located. The ionic conductivity measurements are performed on pellets of the polycrystalline powder. At 683 K, The conductivity value is 5.23x10{sup -6} S cm{sup -1} and the ionic jump activation energy is 0.656 eV. The bond valence analysis reveals that the ionic conductivity is ensured by Tl{sup +} along the [001] direction. - Graphical abstract: Optimized trajectory for Tl(1)-Tl(2) jump.

  11. Mean carrier transport properties and charge collection dynamics of single-crystal, natural type IIa diamonds from ion-induced conductivity measurements

    SciTech Connect

    Han, S.S.

    1993-09-01

    Ion-induced conductivity has been used to investigate the detector characteristics of diamond detectors. Both integrated-charge, and time-resolved current measurements were performed to examine the mean carrier transport properties of diamond and the dynamics of charge collection under highly-localized and high-density excitation conditions. The integrated-charge measurements were conducted with a standard pulse-counting system with {sup 241}Am radioactivity as the excitation source for the detectors. The time-resolved current measurements were performed using a 70 GHz random sampling oscilloscope with the detectors incorporated into high-speed microstrip transmission lines and the excitation source for these measurements was an ion beam of either 5-MeV He{sup +} or 10-MeV Si{sup 3+}. The detectors used in both experiments can be described as metal-semiconductor-metal (MSM) devices where a volume of the detector material is sandwiched between two metal plates. A charge collection model was developed to interpret the integrated-charge measurements which enabled estimation of the energy required to produce an electron-hole pair ({epsilon}{sub di}) and the mean carrier transport properties in diamond, such as carrier mobility and lifetime, and the behavior of the electrical contacts to diamond.

  12. High frequency cut-off in 1/f conductivity noise of hole-doped La1‑x Ca x MnO3 manganite single crystals

    NASA Astrophysics Data System (ADS)

    Przybytek, Jacek; Fink-Finowicki, Jan; Puźniak, Roman; Jung, Grzegorz

    2016-05-01

    High frequency bias and temperature-dependent Lorentzian cut-off has been observed in the 1/f spectra of the conductivity fluctuations in low hole-doped ferromagnetic insulating La1‑x Ca x MnO3 manganite at low temperatures. The cut-off frequency depends on dc current bias and temperature. The high frequency cut-off has been tentatively associated with intrinsic limits of the appearance of 1/f noise in the hopping regime of the Coulomb glass state. The assumption is validated by the fact that the Efros–Shklovskii temperature {{T}\\text{ES}} , estimated from the fit of the model to the experimentally measured temperature dependence of the cut-off frequency, has the same value as the temperature {{T}\\text{ES}} evaluated independently from the temperature dependence of the resistivity in the corresponding temperature range.

  13. Single crystals of the fluorite nonstoichiometric phase Eu{sub 0.916}{sup 2+}Eu{sub 0.084}{sup 3+}F{sub 2.084} (conductivity, transmission, and hardness)

    SciTech Connect

    Sobolev, B. P. Turkina, T. M.; Sorokin, N. I.; Karimov, D. N.; Komar'kova, O. N.; Sulyanova, E. A.

    2010-07-15

    The nonstoichiometric phase EuF{sub 2+x} has been obtained via the partial reduction of EuF{sub 3} by elementary Si at 900-1100 deg. C. Eu{sub 0.916}{sup 2+}Eu{sub 0.084}{sup 3+}F{sub 2.084} (EuF{sub 2.084}) single crystals have been grown from melt by the Bridgman method in a fluorinating atmosphere. These crystals belong to the CaF{sub 2} structure type (sp. gr. Fm3-barm) with the cubic lattice parameter a = 5.8287(2) A, are transparent in the spectral range of 0.5-11.3 {mu}m, and have microhardness H{sub {mu}} = 3.12 {+-} 0.13 GPa and ionic conductivity {sigma} = 1.4 x 10{sup -5} S/cm at 400 deg. C with the ion transport activation energy E{sub a} = 1.10 {+-} 0.05 eV. The physicochemical characteristics of the fluorite phases in the EuF{sub 2} - EuF{sub 3} systems are similar to those of the phases in the SrF{sub 2} - EuF{sub 3} and SrF{sub 2} - GdF{sub 3} systems due to the similar lattice parameters of the EuF{sub 2} and SrF{sub 2} components. Europium difluoride supplements the list of fluorite components MF{sub 2} (M = Ca, Sr, Ba, Cd, Pb), which are crystal matrices for nonstoichiometric (nanostructured) fluoride materials M{sub 1-x}R{sub x}F{sub 2+x} (R are rare earth elements).

  14. Crystal structure of new Li + ion conducting perovskites: Li 2 xCa 0.5- xTaO 3 and Li 0.2[Ca 1- ySr y] 0.4TaO 3

    NASA Astrophysics Data System (ADS)

    Pham, Quoc Nghi; Crosnier-Lopez, Marie-Pierre; Le Berre, Françoise; Fauth, François; Fourquet, Jean-Louis

    2004-09-01

    Two new solid solutions—Li 2 xCa 0.5- xTaO 3 (0.05⩽ x⩽0.25) and Li 0.2[Ca 1- ySr y] 0.4TaO 3 (0< y⩽0.15)—based on the A defective ABO 3 perovskite structural type, are synthesized. The crystal structures of these Li + ion conducting compounds are solved from synchrotron radiation and conventional X-ray powder diffraction data. The unit cells exhibit a classical orthorhombic distortion of the cubic perovskite model (space group Pnma No. 62) with parameters close to 2a p, 2 ap, 2a p ( ap, primitive cubic cell parameter). The distortion of the cubic aristotype arises from the three tilts system a+b-b- of the TaO 6 octahedra. For the same lithium content ( x=0.10), the Sr 2+ substitution to Ca 2+ is found to enhance the electrical conductivity by quasi-one order of magnitude (at 200 °C, bulk dc conductivity values are close to 2.3×10 -6 and 1.1×10 -5 S cm -1 for Li 0.2Ca 0.4TaO 3 and Li 0.2[Ca 0.9Sr 0.1] 0.4TaO 3, respectively).

  15. Crystal structure and ion conductivity of a new mixed-anion phosphate LiMg3(PO4)P2O7

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Chul; Lee, Mi-Sun; Kang, Jinyeong; Kim, Young-Il; Kim, Seung-Joo

    2015-05-01

    A new lithium-containing phosphate, LiMg3(PO4)P2O7, was prepared by a solid-state reaction, and it was characterized by an ab initio structure determination method on the basis of synchrotron powder X-ray diffraction data. LiMg3(PO4)P2O7 was found to be orthorhombic (space group Pnma) with lattice parameters a=9.0387(1) Å, b=10.6072(1) Å, c=8.3065(1) Å, and V=796.39(1) Å3. The structure features infinite [Mg3O10]∞ layers that are parallel to the bc plane and that are interconnected along the a axis by PO4 and P2O7 groups. The [Mg3O10]∞ layer contains Mg3O14 trimers that are formed by three edge-shared MgO6 octahedra. The PO4 and P2O7 groups are located alternatively between [Mg3O10]∞ layers. This gives rise to a three-dimensional framework that contains large tunnels along the directions [1 0 0] and [0 1 0]; the Li+ ions are stabilized in these tunnels. AC impedance spectroscopy shows that LiMg3(PO4)P2O7 has an ionic conductivity of 3.40×10-5 S cm-1 at 769 K, with an activation energy of 1.17 eV.

  16. Crystal Structure of the Cystic Fibrosis Transmembrane Conductance Regulator Inhibitory Factor Cif Reveals Novel Active-Site Features of an Epoxide Hydrolase Virulence Factor

    SciTech Connect

    Bahl, C.; Morisseau, C; Bomberger, J; Stanton, B; Hammock, B; O' Toole, G; Madden, D

    2010-01-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) inhibitory factor (Cif) is a virulence factor secreted by Pseudomonas aeruginosa that reduces the quantity of CFTR in the apical membrane of human airway epithelial cells. Initial sequence analysis suggested that Cif is an epoxide hydrolase (EH), but its sequence violates two strictly conserved EH motifs and also is compatible with other {alpha}/{beta} hydrolase family members with diverse substrate specificities. To investigate the mechanistic basis of Cif activity, we have determined its structure at 1.8-{angstrom} resolution by X-ray crystallography. The catalytic triad consists of residues Asp129, His297, and Glu153, which are conserved across the family of EHs. At other positions, sequence deviations from canonical EH active-site motifs are stereochemically conservative. Furthermore, detailed enzymatic analysis confirms that Cif catalyzes the hydrolysis of epoxide compounds, with specific activity against both epibromohydrin and cis-stilbene oxide, but with a relatively narrow range of substrate selectivity. Although closely related to two other classes of {alpha}/{beta} hydrolase in both sequence and structure, Cif does not exhibit activity as either a haloacetate dehalogenase or a haloalkane dehalogenase. A reassessment of the structural and functional consequences of the H269A mutation suggests that Cif's effect on host-cell CFTR expression requires the hydrolysis of an extended endogenous epoxide substrate.

  17. Conduction mechanism in highly doped β-Ga2O3(\\bar{2}01) single crystals grown by edge-defined film-fed growth method and their Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Oishi, Toshiyuki; Harada, Kazuya; Koga, Yuta; Kasu, Makoto

    2016-03-01

    Edge-defined fed-grown (\\bar{2}01) β-Ga2O3 single crystals with high electron concentration of 3.9 × 1018 cm-3 at 300 K were characterized by Hall effect measurement, and Schottky barrier diodes have been demonstrated. Electron mobility was as high as 74 cm2/(V·s) at 300 K regardless of the high doping concentration. The electron concentration did not change substantially in the low temperature below 160 K. This properties can be explained by the two-band model due to the inter-band conduction. On the Schottky barrier diodes, the rectification characteristics were clearly observed, and the current density of 96.8 A/cm2 at the forward voltage of 1.6 V was obtained.

  18. First-Principles Characterization of the Unknown Crystal Structure and Ionic Conductivity of Li7P2S8I as a Solid Electrolyte for High-Voltage Li Ion Batteries.

    PubMed

    Kang, Joonhee; Han, Byungchan

    2016-07-21

    Using first-principles density functional theory calculations and ab initio molecular dynamics (AIMD) simulations, we demonstrate the crystal structure of the Li7P2S8I (LPSI) and Li ionic conductivity at room temperature with its atomic-level mechanism. By successively applying three rigorous conceptual approaches, we identify that the LPSI has a similar symmetry class as Li10GeP2S12 (LGPS) material and estimate the Li ionic conductivity to be 0.3 mS cm(-1) with an activation energy of 0.20 eV, similar to the experimental value of 0.63 mS cm(-1). Iodine ions provide an additional path for Li ion diffusion, but a strong Li-I attractive interaction degrades the Li ionic transport. Calculated density of states (DOS) for LPSI indicate that electrochemical instability can be substantially improved by incorporating iodine at the Li metallic anode via forming a LiI compound. Our methods propose the computational design concept for a sulfide-based solid electrolyte with heteroatom doping for high-voltage Li ion batteries. PMID:27345207

  19. Visible light absorbance enhanced by nitrogen embedded in the surface layer of Mn-doped sodium niobate crystals, detected by ultra violet - visible spectroscopy, x-ray photoelectron spectroscopy, and electric conductivity tests

    NASA Astrophysics Data System (ADS)

    Molak, A.; Pilch, M.

    2016-05-01

    Sodium niobate crystals doped with manganese ions, Na(NbMn)O3, were annealed in a nitrogen N2 flow at 600, 670, and 930 K. It was verified that simultaneous doping with Mn ions and annealing in nitrogen enhanced the photocatalytic features of sodium niobate. The transmission in the ultraviolet-visible range was measured at room temperature. The absorbance edge is in the range from 3.4 to 2.3 eV. The optical band gap Egap = 1.2-1.3 eV was evaluated using the Tauc relation. Crystals annealed at 670 K and 930 K exhibited an additional shift of the absorption edge of ˜20-40 nm toward longer wavelengths. The optical energy gap narrowed as a result of the superimposed effect of Mn and N co-doping. The x-ray photoelectron spectroscopy test showed that N ions incorporated into the surface layer. The valence band consisted of O 2p states hybridized with Nb 4d, Mn 3d, and N 2s states. The disorder detected in the surroundings of Nb and O ions decreased due to annealing. The binding energy of oxygen ions situated within the surface layer was EB ≈ 531 eV. The other contributions were assigned to molecular contamination. The contribution centered at 535.5 eV vanished after annealing at 600 K and 670 K. The contribution centered at 534 eV vanished after annealing at 930 K. The N2 annealing partly removed carbonates from the surfaces of the samples. In the 480-950 K range, the electric conductivity activation energy, Ea = 0.7-1.2 eV, was comparable with the optical Egap. The electric permittivity showed dispersion in the 0.1-800 kHz range that corresponds to the occurrence of defects.

  20. Minimizing radiation damage in nonlinear optical crystals

    DOEpatents

    Cooke, D.W.; Bennett, B.L.; Cockroft, N.J.

    1998-09-08

    Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal. 5 figs.

  1. Minimizing radiation damage in nonlinear optical crystals

    DOEpatents

    Cooke, D. Wayne; Bennett, Bryan L.; Cockroft, Nigel J.

    1998-01-01

    Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal.

  2. Crystal structure and ion conductivity of a new mixed-anion phosphate LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7}

    SciTech Connect

    Kim, Sung-Chul; Lee, Mi-Sun; Kang, Jinyeong; Kim, Young-Il; Kim, Seung-Joo

    2015-05-15

    A new lithium-containing phosphate, LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7}, was prepared by a solid-state reaction, and it was characterized by an ab initio structure determination method on the basis of synchrotron powder X-ray diffraction data. LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} was found to be orthorhombic (space group Pnma) with lattice parameters a=9.0387(1) Å, b=10.6072(1) Å, c=8.3065(1) Å, and V=796.39(1) Å{sup 3}. The structure features infinite [Mg{sub 3}O{sub 10}]{sub ∞} layers that are parallel to the bc plane and that are interconnected along the a axis by PO{sub 4} and P{sub 2}O{sub 7} groups. The [Mg{sub 3}O{sub 10}]{sub ∞} layer contains Mg{sub 3}O{sub 14} trimers that are formed by three edge-shared MgO{sub 6} octahedra. The PO{sub 4} and P{sub 2}O{sub 7} groups are located alternatively between [Mg{sub 3}O{sub 10}]{sub ∞} layers. This gives rise to a three-dimensional framework that contains large tunnels along the directions [1 0 0] and [0 1 0]; the Li{sup +} ions are stabilized in these tunnels. AC impedance spectroscopy shows that LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} has an ionic conductivity of 3.40×10{sup −5} S cm{sup −1} at 769 K, with an activation energy of 1.17 eV. - Graphical abstract: Polyhedral view of LiMg3(PO4)P2O7. Li+ ions are represented by orange spheres, MgO6 groups by octahedra, and PO4 groups by tetrahedra. - Highlights: • New compound LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} is reported. • The crystal structure is investigated by synchrotron XRD analysis. • The structure features [Mg{sub 3}O{sub 10}]{sub ∞} layers with interconnecting PO{sub 4} and P{sub 2}O{sub 7} groups. • Correlation between the crystal structure and ionic conductivity is discussed.

  3. Crystal Creations.

    ERIC Educational Resources Information Center

    Whipple, Nona; Whitmore, Sherry

    1989-01-01

    Presents a many-faceted learning approach to the study of crystals. Provides instructions for performing activities including crystal growth and patterns, creating miniature simulations of crystal-containing rock formations, charcoal and sponge gardens, and snowflakes. (RT)

  4. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Allen, Philip B.

    1979-01-01

    Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)

  5. Fluctuation-induced in-plane conductivity, magnetoconductivity, and diamagnetism of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} single crystals in weak magnetic fields

    SciTech Connect

    Pomar, A.; Ramallo, M.V.; Mosqueira, J.; Torron, C.; Vidal, F.

    1996-09-01

    We report detailed experimental results on the fluctuation-induced in-plane conductivity {Delta}{sigma}{sub {ital ab}}, magnetoconductivity {Delta}{tilde {sigma}}{sub {ital ab}}, and diamagnetism {Delta}{chi}{sub {ital ab}}, of high-quality Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} crystals. The data were obtained with magnetic fields {ital H} applied perpendicularly to the superconducting (CuO{sub 2}) planes and up to {mu}{sub 0}{ital H}=5 T, which not too close to the transition [for reduced temperatures {var_epsilon}{equivalent_to}({ital T}{minus}{ital T}{sub {ital C}0})/{ital T}{sub {ital C}0}{approx_gt}10{sup {minus}2}] may be considered in the weak magnetic field limit. In the mean field region (MFR) above the transition, these data are analyzed in terms of thermal fluctuations of the superconducting order parameter amplitude (OPF), on the grounds of the existing theoretical approaches for layered superconductors that take into account the presence of two superconducting layers in the layer periodicity length, {ital s}, which for these compounds is equal to one-half the crystallographic unit-cell length in the {ital c} direction. These results show that, due to its strong {var_epsilon} dependence, {Delta}{tilde {sigma}}{sub {ital ab}} is dramatically affected by the presence of small {ital T}{sub {ital C}} inhomogeneities, associated with small oxygen content inhomogeneities uniformly distributed in the crystals. These inhomogeneity effects are taken into account, consistently with our {Delta}{sigma}{sub {ital ab}} and {Delta}{chi}{sub {ital ab}} results, by using an effective medium approach proposed by Maza and Vidal. In this way, the amplitude and the {var_epsilon} behavior of the three observables studied here are explained in terms of the direct OPF effects, at a quantitative level, confirming then the absence of appreciable indirect contributions [as, for instance, the Maki-Thompson and the density-of-states (DOS) terms]. (Abstract Truncated)

  6. Thermal evolution of the crystal structure of proton conducting BaCe0.8Y0.2O3-δ from high-resolution neutron diffraction in dry and humid atmosphere.

    PubMed

    Eriksson Andersson, Annika K; Selbach, Sverre M; Grande, Tor; Knee, Christopher S

    2015-06-21

    The crystal structure of the proton conducting perovskite BaCe(0.8)Y(0.2)O(3-δ) (BCY20) has been studied via high-resolution in situ neutron diffraction performed in controlled dry and humid (heavy water) oxygen flow. Two phase transitions, cubic Pm3[combining macron]m→R3[combining macron]c (775 °C)→Imma (250 °C) were observed on cooling from 1000 °C in dry O(2). A significant shift of the phase stability fields was observed on cooling in wet oxygen (pD(2)O ≈ 0.2 atm) with the R3[combining macron]c structure stabilised at 900 °C, and the R3[combining macron]c→Imma transition occurring at 675 °C. On cooling below 400 °C a monoclinic, I2/m, phase started to appear. The structural dependence on hydration level is primarily due to the de-stabilisation of the correlated, octahedra tilts as a consequence of structural relaxation around the oxygen vacancies present in the non-hydrated phase. The tendency of hydrated BaCe(0.8)Y(0.2)O(3-δ) to show octahedral tilting is also found to be enhanced, indicating that the deuteronic (protonic) defects influence the crystal structure, possibly via hydrogen bonding. Stabilisation of the monoclinic I2/m phase is attributed to the structural effect of deuterons that is inferred to increase on cooling as deuterons localise to a greater extent. Changing from wet oxidising (O(2) + D2O(g)) to wet reducing (5% H2 in Ar + D2O(g)) atmosphere did not influence the structure or the phase stability, indicating that Ce(4+) was not reduced under the present conditions. Based on the observed cell volume expansion protonic defects are present in the material at 900 °C at a D(2)O partial pressure of ∼0.2 atm. The origin of the chemical expansion is explained by the effective size of the oxygen vacancy being significantly smaller than the [OD] defect. Rietveld analysis has been used to locate possible sites for the deuterons in the high temperature, R3[combining macron]c and Imma, phases that are most relevant for proton transport

  7. Dynamic telerobotic control of crystallization experiments

    NASA Technical Reports Server (NTRS)

    Ward, K. B.; Zuk, W. M.; Perozzo, M. A.; Walker, M. A.; Birnbaum, G. I.; Kung, W.; Cavaliere, A.; Uffen, D. R.; Scholaert, H.

    1992-01-01

    A dynamically controlled system has been used to prepare crystals of lysozyme. The temperature of the crystallization chamber was adjusted based upon a scintillation signal used to detect the degree of nucleation and incipient crystal growth. Experiments conducted in one country were controlled and monitored by researchers in another, providing the first demonstration of telerobotic control of a protein crystallization experiment.

  8. Conduct disorder

    MedlinePlus

    Disruptive behavior - child; Impulse control problem - child ... Conduct disorder has been linked to: Child abuse Drug or alcohol abuse in the parents Family conflicts Genetic defects Poverty The diagnosis is more common among boys. It is ...

  9. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Hershey, David R.; Sand, Susan

    1993-01-01

    Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)

  10. Low thermal conductivity oxides

    SciTech Connect

    Pan, Wei; Phillpot, Simon R.; Wan, Chunlei; Chernatynskiy, Aleksandr; Qu, Zhixue

    2012-10-09

    Oxides hold great promise as new and improved materials for thermal-barrier coating applications. The rich variety of structures and compositions of the materials in this class, and the ease with which they can be doped, allow the exploration of various mechanisms for lowering thermal conductivity. In this article, we review recent progress in identifying specific oxides with low thermal conductivity from both theoretical and experimental perspectives. We explore the mechanisms of lowering thermal conductivity, such as introducing structural/chemical disorder, increasing material density, increasing the number of atoms in the primitive cell, and exploiting the structural anisotropy. We conclude that further systematic exploration of oxide crystal structures and chemistries are likely to result in even further improved thermal-barrier coatings.

  11. Crystal Systems.

    ERIC Educational Resources Information Center

    Schomaker, Verner; Lingafelter, E. C.

    1985-01-01

    Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

  12. Appropriate Conduct

    ERIC Educational Resources Information Center

    Di Lullo, Louis

    2004-01-01

    Many years ago when the author assumed the role of assistant principal for school climate, discipline, and attendance, he inherited many school policies and guidelines that were outdated, unfair, and without merit in the current school climate. Because the school conduct code had not been revised since the school opened in 1960, many of the…

  13. Conducting Meetings.

    ERIC Educational Resources Information Center

    United Tribes Educational Technical Center, Bismarck, ND.

    Written for anyone interested in what makes a meeting run smoothly (and what doesn't), the guide for conducting meetings is divided into the following sections: the chairperson (his/her responsibilities, preparing an agenda, organizing discussions); the meeting (quorums, discussions, points of order, and clarification); the motion (making the…

  14. The Effect of Ionic Liquids on Protein Crystallization and X-ray Diffraction Resolution

    SciTech Connect

    Judge, Russell A.; Takahashi, Sumiko; Longenecker, Kenton L.; Fry, Elizabeth H.; Abad-Zapatero, Cele; Chiu, Mark L.

    2009-09-08

    Ionic liquids exhibit a variety of properties that make them attractive solvents for biomaterials. Given the potential for productive interaction between ionic liquids and biological macromolecules, we investigated the use of ionic liquids as precipitating agents and additives for protein crystallization for six model proteins (lysozyme, catalase, myoglobin, trypsin, glucose isomerase, and xylanase). The ionic liquids produced changes in crystal morphology and mediated significant increases in crystal size in some cases. Crystals grown using ionic liquids as precipitating agents or as additives provided X-ray diffraction resolution similar to or better than that obtained without ionic liquids. Based upon the experiments performed with model proteins, the ionic liquids were used as additives for the crystallization of the poorly diffracting monoclonal antibody 106.3 Fab in complex with the B-type natriuretic peptide (5-13). The ionic liquids improved the crystallization behavior and provided improved diffraction resulting in the determination of the structure. Ionic liquids should be considered as useful additives for the crystallization of other proteins.

  15. Electrodeless conductivity.

    PubMed

    Light, T S; McHale, E J; Fletcher, K S

    1989-01-01

    Electrodeless conductivity is a technique for measuring the concentration of electrolytes in solution and utilizes a probe consisting of two toroids in close proximity, both of which are immersed in the solution. In special cases, the toroids may be mounted externally on insulated pipes carrying the solution. One toroid radiates an alternating electric field in the audiofrequency range and the other acts as a receiver to pick up the small current induced by the ions moving in a conducting loop of solution. Coatings which would foul contacting electrodes, such as suspensions, precipitates or oil, have little or no effect. Applications are chiefly to continuous measurement in the chemical processing industries, including pulp and paper, mining and heavy chemical production. The principles and practical details of the method are reviewed and cell-diameter, wall, and temperature effects are discussed. PMID:18964695

  16. Heat conduction

    SciTech Connect

    Lilley, D.G.

    1987-01-01

    Analytical and numerical methods, including both finite difference and finite element techniques, are presented with applications to heat conduction problems. Numerical and analytical methods are integrated throughout the text and a variety of complexities are thoroughly treated with many problems, solutions and computer programs. This book is presented as a fundamental course suitable for senior undergraduate and first year graduate students, with end-of-chapter problems and answers included. Sample case studies and suggested projects are included.

  17. Conduction apraxia.

    PubMed

    Ochipa, C; Rothi, L J; Heilman, K M

    1994-10-01

    A left hemisphere damaged patient with ideomotor apraxia is described, whose performance on pantomime to verbal command was superior to pantomime imitation. His reception of these same gestures (gesture naming) was spared. This syndrome has been named conduction apraxia. To account for this selective impaired performance on gesture imitation, a separation of the representations for gesture production and reception is proposed and a non-lexical gesture processing route for gesture imitation is suggested. PMID:7931387

  18. Monomial Crystals and Partition Crystals

    NASA Astrophysics Data System (ADS)

    Tingley, Peter

    2010-04-01

    Recently Fayers introduced a large family of combinatorial realizations of the fundamental crystal B(Λ0) for ^sln, where the vertices are indexed by certain partitions. He showed that special cases of this construction agree with the Misra-Miwa realization and with Berg's ladder crystal. Here we show that another special case is naturally isomorphic to a realization using Nakajima's monomial crystal.

  19. Electrical Conductivity in Transition Metals

    ERIC Educational Resources Information Center

    Talbot, Christopher; Vickneson, Kishanda

    2013-01-01

    The aim of this "Science Note" is to describe how to test the electron-sea model to determine whether it accurately predicts relative electrical conductivity for first-row transition metals. In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalised valence…

  20. Conductivity Probe

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Thermal and Electrical Conductivity Probe (TECP) for NASA's Phoenix Mars Lander took measurements in Martian soil and in the air.

    The needles on the end of the instrument were inserted into the Martian soil, allowing TECP to measure the propagation of both thermal and electrical energy. TECP also measured the humidity in the surrounding air.

    The needles on the probe are 15 millimeters (0.6 inch) long.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  1. Lysozyme Crystal

    NASA Technical Reports Server (NTRS)

    2004-01-01

    To the crystallographer, this may not be a diamond but it is just as priceless. A Lysozyme crystal grown in orbit looks great under a microscope, but the real test is X-ray crystallography. The colors are caused by polarizing filters. Proteins can form crystals generated by rows and columns of molecules that form up like soldiers on a parade ground. Shining X-rays through a crystal will produce a pattern of dots that can be decoded to reveal the arrangement of the atoms in the molecules making up the crystal. Like the troops in formation, uniformity and order are everything in X-ray crystallography. X-rays have much shorter wavelengths than visible light, so the best looking crystals under the microscope won't necessarily pass muster under the X-rays. In order to have crystals to use for X-ray diffraction studies, crystals need to be fairly large and well ordered. Scientists also need lots of crystals since exposure to air, the process of X-raying them, and other factors destroy them. Growing protein crystals in space has yielded striking results. Lysozyme's structure is well known and it has become a standard in many crystallization studies on Earth and in space.

  2. Thermoelectricity in liquid crystals

    NASA Astrophysics Data System (ADS)

    Mohd Said, Suhana; Nordin, Abdul Rahman; Abdullah, Norbani; Balamurugan, S.

    2015-09-01

    The thermoelectric effect, also known as the Seebeck effect, describes the conversion of a temperature gradient into electricity. A Figure of Merit (ZT) is used to describe the thermoelectric ability of a material. It is directly dependent on its Seebeck coefficient and electrical conductivity, and inversely dependent on its thermal conductivity. There is usually a compromise between these parameters, which limit the performance of thermoelectric materials. The current achievement for ZT~2.2 falls short of the expected threshold of ZT=3 to allow its viability in commercial applications. In recent times, advances in organic thermoelectrics been significant, improving by over 3 orders of magnitude over a period of about 10 years. Liquid crystals are newly investigated as candidate thermoelectric materials, given their low thermal conductivity, inherent ordering, and in some cases, reasonable electrical conductivity. In this work the thermoelectric behaviour of a discotic liquid crystal, is discussed. The DLC was filled into cells coated with a charge injector, and an alignment of the columnar axis perpendicular to the substrate was allowed to form. This thermoelectric behavior can be correlated to the order-disorder transition. A reasonable thermoelectric power in the liquid crystal temperature regime was noted. In summary, thermoelectric liquid crystals may have the potential to be utilised in flexible devices, as a standalone power source.

  3. RNA Crystallization

    NASA Technical Reports Server (NTRS)

    Golden, Barbara L.; Kundrot, Craig E.

    2003-01-01

    RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

  4. Protein Crystallization

    NASA Technical Reports Server (NTRS)

    Chernov, Alexander A.

    2005-01-01

    Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

  5. Computational crystallization.

    PubMed

    Altan, Irem; Charbonneau, Patrick; Snell, Edward H

    2016-07-15

    Crystallization is a key step in macromolecular structure determination by crystallography. While a robust theoretical treatment of the process is available, due to the complexity of the system, the experimental process is still largely one of trial and error. In this article, efforts in the field are discussed together with a theoretical underpinning using a solubility phase diagram. Prior knowledge has been used to develop tools that computationally predict the crystallization outcome and define mutational approaches that enhance the likelihood of crystallization. For the most part these tools are based on binary outcomes (crystal or no crystal), and the full information contained in an assembly of crystallization screening experiments is lost. The potential of this additional information is illustrated by examples where new biological knowledge can be obtained and where a target can be sub-categorized to predict which class of reagents provides the crystallization driving force. Computational analysis of crystallization requires complete and correctly formatted data. While massive crystallization screening efforts are under way, the data available from many of these studies are sparse. The potential for this data and the steps needed to realize this potential are discussed. PMID:26792536

  6. Crystal Chemistry of Melanite Garnet

    NASA Technical Reports Server (NTRS)

    Nguyen, Dawn Marie

    1999-01-01

    This original project resulted in a detailed crystal chemical data map of a titanium rich garnet (melanite) suite that originates from the Crowsnest Volcanics of Alberta Canada. Garnet is typically present during the partial melting of the earth's mantle to produce basalt. Prior studies conducted at Youngstown State University have yielded questions as to the crystal structure of the melanite. In the Studies conducted at Youngstown State University, through the use of single crystal x-ray diffraction, the c-axis appears to be distorted creating a tetragonal crystal instead of the typical cubic crystal of garnets. The micro probe was used on the same suite of titanium rich garnets as used in the single crystal x-ray diffraction. The combination of the single crystal x-ray research and the detailed microprobe research will allow us to determine the exact crystal chemical structure of the melanite garnet. The crystal chemical data was gathered through the utilization of the SX100 Electron Probe Micro Analyzer. Determination of the exact chemical nature may prove useful in modeling the ultramafic source rock responsible for the formation of the titanium rich lunar basalts.

  7. Crystal growth of a series of lithium garnets Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd): Structural properties, Alexandrite effect and unusual ionic conductivity

    SciTech Connect

    Roof, Irina P.; Smith, Mark D.; Cussen, Edmund J.; Loye, Hans-Conrad zur

    2009-02-15

    We report the single crystal structures of a series of lanthanide containing tantalates, Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd) that were obtained out of a reactive lithium hydroxide flux. The structures of Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} were determined by single crystal X-ray diffraction, where the Li{sup +} positions and Li{sup +} site occupancies were fixed based on previously reported neutron diffraction data for isostructural compounds. All three oxides crystallize in the cubic space group Ia3-bard (No. 230) with lattice parameters a=12.7735(1), 12.6527(1), and 12.5967(1) A for La{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, Pr{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, and Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, respectively. A UV-Vis diffuse reflectance spectrum of Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} was collected to explain its unusual Alexandrite-like optical behavior. To evaluate the transport properties of Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, the impedance data were collected in air in the temperature range 300{<=}T(deg. C){<=}500. - Graphical abstract: Crystal structure of garnets Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd). TaO{sub 6} polyhedra are shown in yellow and Ln{sup 3+} are shown as light blue spheres. Octahedrally and tetrahedrally coordinated Li{sup +} ions are shown in green and brown, respectively. Oxygen atoms are omitted for clarity.

  8. Crystal Structure of Garnet-Related Li-Ion Conductor Li7–3xGaxLa3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    PubMed Central

    2016-01-01

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga3+ shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li7–3xGaxLa3Zr2O12 with x > 0.07 crystallizes in the acentric cubic space group I-43d. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga3+. 7Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space group I-43d compared to space group Ia-3d. Despite all efforts undertaken to reveal structure–property relationships for this class of materials, this study highlights the potential for new discoveries. PMID:27019548

  9. Crystal growth of a series of lithium garnets Ln3Li 5Ta 2O 12 ( Ln=La, Pr, Nd): Structural properties, Alexandrite effect and unusual ionic conductivity

    NASA Astrophysics Data System (ADS)

    Roof, Irina P.; Smith, Mark D.; Cussen, Edmund J.; zur Loye, Hans-Conrad

    2009-02-01

    We report the single crystal structures of a series of lanthanide containing tantalates, Ln3Li 5Ta 2O 12 ( Ln=La, Pr, Nd) that were obtained out of a reactive lithium hydroxide flux. The structures of Ln3Li 5Ta 2O 12 were determined by single crystal X-ray diffraction, where the Li + positions and Li + site occupancies were fixed based on previously reported neutron diffraction data for isostructural compounds. All three oxides crystallize in the cubic space group Ia3¯d (No. 230) with lattice parameters a=12.7735(1), 12.6527(1), and 12.5967(1) Å for La 3Li 5Ta 2O 12, Pr 3Li 5Ta 2O 12, and Nd 3Li 5Ta 2O 12, respectively. A UV-Vis diffuse reflectance spectrum of Nd 3Li 5Ta 2O 12 was collected to explain its unusual Alexandrite-like optical behavior. To evaluate the transport properties of Nd 3Li 5Ta 2O 12, the impedance data were collected in air in the temperature range 300⩽ T(°C)⩽500.

  10. Pressure sensor using liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S. (Inventor); Holmes, Harlan K. (Inventor)

    1994-01-01

    A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially.