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Sample records for crystal batio3 nanotube

  1. BaTiO3-based nanolayers and nanotubes: first-principles calculations.

    PubMed

    Evarestov, Robert A; Bandura, Andrei V; Kuruch, Dmitrii D

    2013-01-30

    The first-principles calculations using hybrid exchange-correlation functional and localized atomic basis set are performed for BaTiO(3) (BTO) nanolayers and nanotubes (NTs) with the structure optimization. Both the cubic and the ferroelectric BTO phases are used for the nanolayers and NTs modeling. It follows from the calculations that nanolayers of the different ferroelectric BTO phases have the practically identical surface energies and are more stable than nanolayers of the cubic phase. Thin nanosheets composed of three or more dense layers of (0 1 0) and (0 1 1[overline]) faces preserve the ferroelectric displacements inherent to the initial bulk phase. The structure and stability of BTO single-wall NTs depends on the original bulk crystal phase and a wall thickness. The majority of the considered NTs with the low formation and strain energies has the mirror plane perpendicular to the tube axis and therefore cannot exhibit ferroelectricity. The NTs folded from (0 1 1[overline]) layers may show antiferroelectric arrangement of Ti-O bonds. Comparison of stability of the BTO-based and SrTiO(3)-based NTs shows that the former are more stable than the latter.

  2. Nanostructural evolution of one-dimensional BaTiO3 structures by hydrothermal conversion of vertically aligned TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Muñoz-Tabares, J. A.; Bejtka, K.; Lamberti, A.; Garino, N.; Bianco, S.; Quaglio, M.; Pirri, C. F.; Chiodoni, A.

    2016-03-01

    The use of TiO2 nanotube (NT) arrays as templates for hydrothermal conversion of one-dimensional barium titanate (BaTiO3) structures is considered a promising synthesis approach, even though the formation mechanisms are not yet fully understood. Herein we report a nanostructural study by means of XRD and (HR)TEM of high aspect ratio TiO2-NTs hydrothermally converted into BaTiO3. The nanostructure shows two different and well-defined regions: at the top the conversion involves complete dissolution of NTs and subsequent precipitation of BaTiO3 crystals by homogeneous nucleation, followed by the growth of dendritic structures by aggregation and oriented attachment mechanisms. Instead, at the bottom, the low liquid/solid ratio, due to the limited amount of Ba solution that infiltrates the NTs, leads to the rapid crystallization of such a solution into BaTiO3, thus allowing the NTs to act as a template for the formation of highly oriented one-dimensional nanostructures. The in-depth analysis of the structural transformations that take place during the formation of the rod-like arrays of BaTiO3 could help elucidate the conversion mechanism, thus paving the way for the optimization of the synthesis process in view of new applications in energy harvesting devices, where easy and low temperature processing, controlled composition, morphology and functional properties are required.The use of TiO2 nanotube (NT) arrays as templates for hydrothermal conversion of one-dimensional barium titanate (BaTiO3) structures is considered a promising synthesis approach, even though the formation mechanisms are not yet fully understood. Herein we report a nanostructural study by means of XRD and (HR)TEM of high aspect ratio TiO2-NTs hydrothermally converted into BaTiO3. The nanostructure shows two different and well-defined regions: at the top the conversion involves complete dissolution of NTs and subsequent precipitation of BaTiO3 crystals by homogeneous nucleation, followed by the

  3. Strain of a BaTiO3 single crystal caused by the converse flexoelectric effect

    NASA Astrophysics Data System (ADS)

    Rumyantseva, E. D.; Zalesskii, V. G.

    2016-04-01

    The inhomogeneous strain induced by a homogeneous external electric field (the converse flexoelectric effect) has been studied in a thin BaTiO3 single crystal slab. The type of inhomogeneous strain (cylindrical and spherical bending) has been determined via the interference method, and its dependence on the applied filed is measured, as well. The influence of the domain structure on this effect has also been shown.

  4. Radiation effect on domain and defect structure of BaTiO3 crystals

    NASA Astrophysics Data System (ADS)

    Fesenko, Evgeni G.; Lisinska-Czekaj, Agata; Czekaj, Dionizy; Surowiak, Zygmunt

    2003-10-01

    BaTiO3 single crystals were obtained by Remeika-method from solutions of melted salts and oxides. Radioactive Co60 isotope was employed as a source of γ-radiation. Three different radiation doses were applied: 1.2 x 107 rad, 3.0 x 108 rad, and 1.3 x 107 rad. Temperature of single crystals during irradiation did not exceed 313 K. A few batches of crystals were subjected to irradiation, namely: single crystals with natural surface (after the crystal was grown), single crystals with the etched surface layer and single crystals which had been subjected to an influence of the strong direct and alternating electric fields before exposure. Both domain and defect structure of single crystals was investigated by the etching method, decorating method, optical microscopy and scanning electron microscopy. It has been found that irradiation causes destabilization of the domain walls of the head-to-head-type with a negative charge screening spontaneous polarization (Ps). The negative domains in a positive matrix, which did not grow through the whole crystal body, were found to decay under the influence of radiation. In a place previously occupied by decaying negative domains, defect clusters are observed. The investigations have shown that there is a close correlation between the domain structure and the defect structure of BaTiO3 crystals.

  5. Structural and magnetic studies of Co and Fe implanted BaTiO 3 crystals

    NASA Astrophysics Data System (ADS)

    Khalitov, N. I.; Khaibullin, R. I.; Valeev, V. F.; Dulov, E. N.; Ivoilov, N. G.; Tagirov, L. R.; Kazan, S.; Şale, A. G.; Mikailzade, F. A.

    2012-02-01

    Singly-charged Co or Fe ions with energy 40 keV were implanted into single-domain ferroelectric plates of barium titanate (BaTiO 3) with high fluences in the range of (0.5-1.5) × 10 17 ion/cm 2 to create new magnetoelectric materials. Scanning electron microscopy (SEM) and conversion electron Mössbauer spectroscopy (CEMS) studies have shown that high-fluence implantation with 3d-ions results in formation of cobalt or iron nanoparticles in the near-surface irradiated region of perovskite-type crystal. With increasing the fluence, the both Co- and Fe-implanted BaTiO 3 samples reveal at first superparamagnetic, and then ferromagnetic properties at room temperature. Analysis of magnetic hysteresis loops measured in the in-plane and out-of-plane geometries have shown that ferromagnetic BaTiO 3:Co(Fe) nanocomposite layers display the "easy plane" magnetic anisotropy similar to that found for thin granular magnetic films. Together with our previous observation of the magnetoelectric effect in these samples, our structural and magnetic investigations show that the ion implantation is suitable to synthesize the desired magnetoelectric nanocomposite materials.

  6. Fraunhofer diffraction to determine the twin angle in single-crystal BaTiO3.

    PubMed

    Melnichuk, Mike; Wood, Lowell T

    2003-08-01

    We present a new method for determining the electrically induced twin angle alpha of a (100) bulk single crystal of barium titanate (BaTiO3) using a nondestructive optical technique based on Fraunhofer diffraction. The technique required two steps that were performed simultaneously. First, we analyzed the diffracted light intensity captured with a line camera. Second, we measured the size of the diffracting element by analyzing images of crystal's surface taken with a CCD camera. The value obtained for the twin angle is 0.67 degrees +/- 0.05 degrees, which compares favorably with the theoretical value of 0.63 degrees.

  7. Electric-field-induced domain intersection in BaTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    He, Ming; Wang, Mengxia; Zhang, Zhihua

    2017-03-01

    Large-angle convergent beam electron diffraction was used to determine the directions of polarization vectors in a BaTiO3 single crystal. Domain intersections driven by an electric field were investigated by in situ transmission electron microscopy. The dark triangles observed in the domain intersection region can be accounted for by dislocations and the strain field. Domains nucleate at the domain tip depending on the dislocations and strain field to relieve the accumulated stress. Schematic representations of the intersecting domains and the microscopic structure are given, clarifying the special electric-field-induced domain structure.

  8. Composites of hybrids BaTiO3/carbon nanotubes/polyvinylidene fluoride with high dielectric properties

    NASA Astrophysics Data System (ADS)

    Fan, Benhui; Bai, Jinbo

    2015-11-01

    High dielectric composites were prepared based on polyvinylidene fluoride (PVDF) and hybrids BaTiO3-carbon nanotubes (H-BT-CNTs) with a special structure. The hybrids that BT was a core and CNTs grew outside were fabricated by chemical vapor deposition. Due to the special structure, composite’s dielectric permittivity reached 1777 at 100 Hz and 80 at 1 MHz, while loss tangent maintained as 6 at 100 Hz and 0.56 at 1 MHz, respectively. Moreover, dielectric permittivity and ac conductivity of composite were further enhanced after annealing process at moderate temperature. These improved properties were originated from the reformation of conductive network and BT-CNTs structure inside PVDF matrix.

  9. Interface charge behaviors of BaTiO3 film heterostructures with various crystal orientations

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Ouyang, Jun; Cheng, Hongbo; Yang, Qian; Kang, Limin; Zhang, Hua; Hu, Fangren

    2017-02-01

    Heteroepitaxial BaTiO3 ferroelectric films with (001), (110), and (111) orientations were grown on SrRuO3-buffered SrTiO3 substrates by magnetron sputtering. The leakage current and interface charge behaviors were systematically investigated. Without a discernible orientation-dependence behavior, the leakage current behaviors were all well described by a modified Schottky-contact model. On the basis of this theory, the interface charge state parameters, including dynamic dielectric constant, potential barriers, depletion layer width, effective space-charge density and hole concentration, and their evolution behaviors were analyzed in detail. They all exhibited anisotropic characteristics and were proved to be essentially attributed to the macrophysical properties of BaTiO3 film heterostructures.

  10. Growth and characterization of high-performance photorefractive BaTiO3 crystals

    NASA Technical Reports Server (NTRS)

    Warde, C.; Garrett, M. H.; Chang, J. Y.; Jenssen, H. P.; Tuller, H. L.

    1991-01-01

    Barium titanate has been used for many nonlinear optical applications primarily because it has high grain and high self-pumped phase conjugate reflectivities. However, barium titanate has had a relatively slow response time, and thus low sensitivity. Therefore, it has not been suited to real-time operations. In this report we will describe the modifications in crystal growth, doping, reduction, and poling that have produced barium titanate crystals with the fastest photorefractive response time reported to date, approximately 21 microseconds with a beam-coupling gain coefficient of 38.7 cm(exp -1) and the highest sensitivity reported to date of 3.44 cm(exp 3)/kJ. The sensitivity of these barium titanate crystals is comparable to or greater than other photorefractive oxides. We will show, for the first time, beam-coupling in barium titanate at video frame rates. We infer from response time measurements that barium titanate has a phonon limited mobility. Also, photorefractive response time measurements as a function of the crystallographic orientation and grating wave vector for our cobalt-doped oxygen reduced crystals indicate that their faster response time arise because of an increase in the free carrier lifetime.

  11. Sheets of Vertically Aligned BaTiO3 Nanotubes Reduce Cell Proliferation but Not Viability of NIH-3T3 Cells

    PubMed Central

    Giannini, Marianna; Giannaccini, Martina; Sibillano, Teresa; Giannini, Cinzia; Liu, Dun; Wang, Zhigang; Baù, Andrea; Dente, Luciana; Cuschieri, Alfred; Raffa, Vittoria

    2014-01-01

    All biomaterials initiate a tissue response when implanted in living tissues. Ultimately this reaction causes fibrous encapsulation and hence isolation of the material, leading to failure of the intended therapeutic effect of the implant. There has been extensive bioengineering research aimed at overcoming or delaying the onset of encapsulation. Nanotechnology has the potential to address this problem by virtue of the ability of some nanomaterials to modulate interactions with cells, thereby inducing specific biological responses to implanted foreign materials. To this effect in the present study, we have characterised the growth of fibroblasts on nano-structured sheets constituted by BaTiO3, a material extensively used in biomedical applications. We found that sheets of vertically aligned BaTiO3 nanotubes inhibit cell cycle progression - without impairing cell viability - of NIH-3T3 fibroblast cells. We postulate that the 3D organization of the material surface acts by increasing the availability of adhesion sites, promoting cell attachment and inhibition of cell proliferation. This finding could be of relevance for biomedical applications designed to prevent or minimize fibrous encasement by uncontrolled proliferation of fibroblastic cells with loss of material-tissue interface underpinning long-term function of implants. PMID:25506693

  12. Self-Pumped Phase-Conjugate Twyman-Green Interferometry Using a BaTiO3 Crystal

    DTIC Science & Technology

    1991-12-01

    mirrors without the need of additional high quality optics normally needed for this type of testing using conventional Twyman -Green interferometers ...conjugate interferometer is a highly sensitive test for collimation. vii SELF-PUMPED PHASE-CONJUGATE TWYMAN -GREEN INTERFEROMETRY USING A BaTiO 3...surfaces. Determining the quality of optical components by the use of interferometry was pioneered by Twyman in 1918, and the Twyman -Green interferometer

  13. Crystal structure and polarization hysteresis properties of ferroelectric BaTiO3 thin-film capacitors on (Ba,Sr)TiO3-buffered substrates

    NASA Astrophysics Data System (ADS)

    Maki, Hisashi; Noguchi, Yuji; Kutsuna, Kazutoshi; Matsuo, Hiroki; Kitanaka, Yuuki; Miyayama, Masaru

    2016-10-01

    Ferroelectric BaTiO3 (BT) thin-film capacitors with a buffer layer of (Ba1- x Sr x )TiO3 (BST) have been fabricated on (001) SrTiO3 (STO) single-crystal substrates by a pulsed laser deposition method, and the crystal structure and polarization hysteresis properties have been investigated. X-ray diffraction reciprocal space mapping shows that the BST buffer effectively reduces the misfit strain relaxation of the BT films on SrRuO3 (SRO) electrodes. The BT capacitor with the SRO electrodes on the BST (x = 0.3) buffer exhibits a well-saturated hysteresis loop with a remanent polarization of 29 µC/cm2. The hysteresis loop displays a shift toward a specific field direction, which is suggested to stem from the flexoelectric coupling between the out-of-plane polarization and the strain gradient adjacent to the bottom interface.

  14. One — dimensional laser beam steering using frequency detuning in two — wave mixing with a BaTiO 3 crystal

    NASA Astrophysics Data System (ADS)

    Dharmsaktu, K. S.; Joseph, Joby; Singh, Kehar

    2000-06-01

    We demonstrate a method of one-dimensional laser beam deflection using frequency detuning in two-wave mixing. Energy exchange between the interfering beams in a photo-refractive BaTiO 3 crystal has been used for deflection of a pump beam into predetermined probe beam directions. A one-dimensional array of several beams is generated from a single probe beam, employing a piezo-mirror and beam splitter combination. Probe beams so produced are detuned by exciting the piezo-mirror with a periodic near-saw-tooth voltage so as to produce running fringes. However, stable holographic gratings are recorded by matching the frequency of the probe beam with that of a pump beam reflected from another vibrating piezo-mirror, thereby controlling the direction of beam deflection.

  15. Non-isothermal crystallization kinetics of the BaTiO3-KNbO3-SiO2 glass

    NASA Astrophysics Data System (ADS)

    Yang, H. Y.; Yang, Y. S.; Choi, H. W.

    2015-04-01

    We have investigated the non-isothermal formation kinetics of nanocrystals from the BaTiO3-KNbO3-SiO2 (BKSO) glass at temperatures from room temperature to 800 °C. The thermal characteristics and the structural transformations of the BKSO glass have been studied by means of a differential thermal analysis and X-ray diffraction. The crystallization of BKSO glass is found to accompany a single-step occurrence of a tetragonal Ba3TiNb4O15 nanocrystal structure. During the crystallization, a nanocrystals with a size of ˜40 nm at the initial stage grow with increasing temperature and reach a size of ˜120 nm by the time the crystallization finishes. We use the non-isothermal model of Johnson-Mehl-Avrami-Kolmogorov to characterize the kinetics of the crystallization process for the BKSO glass. The Avrami exponent of 3.5 indicates that the crystallization mechanisms is an increasing nucleation rate with diffusion-controlled growth. In the view of applications, providing information on how to control the size of nanograins systematically by simply controlling the annealing temperature of the glass state, as described in this study, should be useful.

  16. Potential and piezoelectric response imaging of 180^o domain of atomically ordered clean surfaces of BaTiO3 single crystals in UHV

    NASA Astrophysics Data System (ADS)

    Watanabe, Yukio; Kaku, S.; Matsumoto, D.; Cheong, S. W.

    2009-03-01

    We report the electrostatic and piezoelectric properties of the clean, free surface of BaTiO3 single crystal in ultra high vacuum (UHV) The topographic imaging by AFM confirmed that the surface is atomically wellordered exhibiting clear one-lattice-height atomic steps. The amplitude and the phase image of piezoelectric response microscopy (PFM) identified 180^o domains. The electrostatic potential mapping by Kelvin force microscopy (KFM) of these domains revealed that the shapes of the domains agreed exactly with the PFM images, which confirms the correctness of the standard 180^o domain theory and disagrees with closure domains. However, the potential difference of upward and downward domain is approx. 0.1V, which is 100 times smaller than the value estimated by the standard theory. Similar measurements with changing temperature across Curie temperature show that this result cannot be explained by the compensation of the spontaneous polarization by contamination or oxygen deficiency or ionic conduction). The present results suggest that an intrinsic electrostatic shielding mechanism exists for 180^o domains, which is consistent with the reports of surface electron/hole layers [1]. [4pt] [1] Watanabe et al. PRL86332(2001);Ferroelectr.367, 23(2008) We acknowledge JSPS No.19340084.

  17. Structural Transformation of Hexagonal (0001)BaTiO3 Ceramics to Tetragonal (111)BaTiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Watanabe, Takayuki; Shimada, Mikio; Aiba, Toshiaki; Yabuta, Hisato; Miura, Kaoru; Oka, Kengo; Azuma, Masaki; Wada, Satoshi; Kumada, Nobuhiro

    2011-09-01

    A ceramic slurry that contains a 6H-type Ba(Ti0.95Mn0.05)O3 powder was casted into a plaster mold under 10 T magnetic field to form a green compact of (0001)-oriented Ba(Ti0.95Mn0.05)O3. After sintering the green compact at 1300 °C in air, it was confirmed that the (0001)-oriented 6H-type perovskite structure transformed to a (111)-oriented 3C-type perovskite structure. The structural transformation was again examined using hexagonal BaTiO3 prepared by reducing pseudo-cubic BaTiO3 powder in H2 atmosphere. In this case, the preferred (0001) orientation was not confirmed for the green compacts. After sintering the green compacts at 1300 °C in air, mixed crystal orientations of (100)/(001) and (111) were observed for the resultant tetragonal BaTiO3 ceramics. This (100)/(001) orientation was suppressed by annealing the hexagonal BaTiO3 powder at 1000 °C before slip-casting, leading to highly (111)-oriented ceramics. It was found that the green compacts of (0001)-oriented hexagonal BaTiO3 can transform into (111)-oriented tetragonal BaTiO3 ceramics, maintaining the macroscopic crystal orientations due to a similar atomic stacking along [0001] of 6H-type BaTiO3 and [111] of 3C-type BaTiO3.

  18. Electron-relaxation-mode interaction in BaTiO3:Nb

    NASA Astrophysics Data System (ADS)

    Maglione, M.; Belkaoumi, M.

    1992-02-01

    Dielectric relaxation was previously reported in BaTiO3 and BaTiO3:Fe single crystals at radio frequencies [M. Maglione et al., Phys. Rev. B 40, 11 441 (1989)]. We have measured the dielectric dispersion in four BaTiO3:Nb samples (xNb<0.3 at. %) as a function of frequency (10

  19. Pyroelectric response of spray-deposited BaTiO3 thin film

    NASA Astrophysics Data System (ADS)

    Peale, Robert E.; Oladeji, Isaiah O.; Smith, Evan M.; Vasilyev, Vladimir; Alhasan, Sarmad Fawzi Hamza; Abouelkhair, Hussain; Todorovski, Dalibor; Kimani, Martin; Cleary, Justin W.

    2016-09-01

    Pyroelectric photoresponse of aqueous spray deposited thin films containing BaTiO3 nano-crystals is reported. X-ray diffraction data indicate the presence of hexagonal BaTiO3 nano-crystals with 20 nm crystalline domains in a matrix of some as yet unidentified nano-crystalline material. When the film is annealed at 600 C, the X-ray pattern changes significantly and indicates a conversion to one of the non-hexagonal phases of BaTiO3 as well as a complete change in the matrix. With suitable amplifier, the measured photoresponse was 40V/W. Ferroelectric hysteresis on a film with significant presence of hexagonal BaTiO3 shows saturated polarization which is about 5-times smaller than for the bulk tetragonal phase. A potential application is a patternable infrared detector for photonic and plasmonic devices, such as chip-scale spectral sensors.

  20. First-principles calculations on the four phases of BaTiO3.

    PubMed

    Evarestov, Robert A; Bandura, Andrei V

    2012-04-30

    The calculations based on linear combination of atomic orbitals basis functions as implemented in CRYSTAL09 computer code have been performed for cubic, tetragonal, orthorhombic, and rhombohedral modifications of BaTiO(3) crystal. Structural and electronic properties as well as phonon frequencies were obtained using local density approximation, generalized gradient approximation, and hybrid exchange-correlation density functional theory (DFT) functionals for four stable phases of BaTiO(3). A comparison was made between the results of different DFT techniques. It is concluded that the hybrid PBE0 [J. P. Perdew, K. Burke, M. Ernzerhof, J. Chem. Phys. 1996, 105, 9982.] functional is able to predict correctly the structural stability and phonon properties both for cubic and ferroelectric phases of BaTiO(3). The comparative phonon symmetry analysis in BaTiO(3) four phases has been made basing on the site symmetry and irreducible representation indexes for the first time.

  1. Crystallization and electrical characteristics of 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 thin films under different annealing temperature and atmosphere.

    PubMed

    Diao, Chien-Chen; Yang, Cheng-Fu; Lin, Jing-Jenn

    2011-12-01

    0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 +1 wt% Bi2O3 (NBT-BT3) ceramic is used as target to deposit the NBT-BT3 thin films. The excess 1wt% Bi2O3 is used to compensate the vaporization of Bi2O3 during the sintering and annealing processes. NBT-BT3 thin films are successfully deposited using radio frequency (RF) magnetron sputter method and crystallized subsequently using a conventional furnace annealing (CFA) process. The annealed process is conducted in air and in oxygen atmosphere at temperatures ranging from 600-800 degrees C for 60 min. As compared with the as-deposited NBT-BT3 thin films, the CFA-treated process has improved the grain growth and crystallization. We will show that the annealing atmosphere is the more important parameter to influence the grain growth and crystallization of NBT-BT3 thin films than the annealing temperature. The influences of CFA-treated temperature and atmosphere on the electrical characteristics of NBT-BT3 thin films, including the polarization characteristics (Pr, Ps, and Ec values), the capacitance-voltage (C-V) curves, and the leakage current density-electric field (J-E) curves, are also investigated in this study.

  2. Electronic structures and abnormal phonon behaviors of cobalt-modified Na0.5Bi0.5TiO3-6%BaTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Huang, T.; Zhang, P.; Xu, L. P.; Chen, C.; Zhang, J. Z.; Hu, Z. G.; Luo, H. S.; Chu, J. H.

    2016-10-01

    Optical properties, electronic structures, and structural variations of x wt% cobalt (Co) doped Na0.5Bi0.5TiO3-6%BaTiO3 (x=0%, 0.5%, 0.8%) single crystals have been studied by temperature-dependent optical ellipsometry and Raman spectra from 250 to 650 K. Based on the temperature evolution of electronic transitions (Ecp1 and Ecp2) and the phonon modes involving Ti-O vibrations, two critical temperature points exhibit an increasing trend with Co dopants, which are related to structural variations for ferroelectric to anti-ferroelectric, and anti-ferroelectric to paraelectric transition, respectively. Additionally, distinguishing abnormal phonon behaviors can be observed from Raman spectra for the crystal of x=0.5% and 0.8%, which show reverse frequency shift of the modes involving Ti-O vibration. It can be ascribed to different relative concentration of Co2+ and Co3+ in the crystals, which has been confirmed by X-ray Photoelectron Spectroscopy data.

  3. Single crystalline BaTiO3 thin films synthesized using ion implantation induced layer transfer

    NASA Astrophysics Data System (ADS)

    Park, Young-Bae; Diest, Kenneth; Atwater, Harry A.

    2007-10-01

    Layer transfer of BaTiO3 thin films onto silicon-based substrates has been investigated. Hydrogen and helium ions were co-implanted to facilitate ion-implantation-induced layer transfer of films from BaTiO3 single crystals. From thermodynamic equilibrium calculations, we suggest that the dominant species during cavity nucleation and growth are H2, H+, H2O, Ba2+ and Ba-OH, and that the addition of hydrogen to the Ba-Ti-O system can effectively suppress volatile oxide formation during layer transfer and subsequent annealing. After ion implantation, BaTiO3 layers contain microstructural defects and hydrogen precipitates in the lattice, but after layer transfer, the single crystal is found to be stoichiometric. Using direct wafer bonding and layer splitting, single crystal BaTiO3 thin films were transferred onto amorphous Si3N4 and Pt substrates. Micro-Raman spectroscopy indicated that the density of defects generated by ion implantation in BaTiO3 can be significantly reduced during post-transfer annealing, returning the transferred layer to its single crystal state. Characterization using piezoresponse force microscopy shows that the layer transferred thin films are ferroelectric, with domain structures and piezoresponse characteristics similar to that of bulk crystals.

  4. Relaxation dynamics of lead-free (Na1/2Bi1/2)TiO3-BaTiO3 single crystals studied by Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Lee, Byoung Wan; Ko, Jae-Hyeon; Li, Xiaobing; Luo, Haosu

    2016-10-01

    The acoustic properties of 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 (NBT-0.05BT) single crystals were investigated in a hypersonic frequency range and compared to those of archetypal relaxor Pb(Mg1/3Nb2/3)O3 (PMN). Temperature dependences of the Brillouin frequency shift of the longitudinal acoustic (LA) mode, as well as its half width, of NBT-5%BT and PMN exhibited diffuse and broad anomalies over a wide temperature range, which were related to the softening of the sound velocity and substantial increase in the hypersonic damping toward the dielectric maximum temperature. These broad acoustic anomalies of unpoled NBT-0.05BT suggest the existence of noncentrosymmetric polar nanoregions in the paraelectric phase which do not evolve into a long-range ferroelectric order. The calculated relaxation times of NBT-0.05BT exhibited much longer values compared to those of PMN, which suggests that the size of polar nanoregions of NBT-0.05BT is larger than that of PMN.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  6. Crystal Growth and Electrical Properties of Lead-Free Piezoelectric Material (Na1/2Bi1/2)TiO3-BaTiO3

    NASA Astrophysics Data System (ADS)

    Hosono, Yasuharu; Harada, Kouichi; Yamashita, Yohachi

    2001-09-01

    Single crystals of lead-free piezoelectric material x(Na1/2Bi1/2)TiO3-yBaTiO3 (NBBT 100x/100y) have been successfully grown by the flux method and the Bridgman method. Using the flux method, crystals having an edge length of 2-8 mm were obtained using Bi2O3 flux with cooling from 1350°C to 800°C at a rate of 3.5°C/h. Using the Bridgman method, comparatively good crystal of 15 mm diameter and 50 mm length was obtained using Bi2O3 flux with the Pt crucible driven down through the heat zone at a speed of 1.0 mm/h. The resulting crystals showed single-phase perovskite structure. Inductively charged plasma (ICP) chemical analysis revealed that the composition of the pulverized powder of these crystals is NBBT 97/3, which is slightly different from the charged composition of NBBT 94/6. One of the single crystals grown by the Bridgman method showed a dielectric constant of 1230 at room temperature and a dielectric constant peak at 313°C.

  7. Eu-Doped BaTiO3 Powder and Film from Sol-Gel Process with Polyvinylpyrrolidone Additive

    PubMed Central

    García-Hernández, Margarita; García-Murillo, Antonieta; de J. Carrillo-Romo, Felipe; Jaramillo-Vigueras, David; Chadeyron, Geneviève; De la Rosa, Elder; Boyer, Damien

    2009-01-01

    Transparent BaTiO3:Eu3+ films were prepared via a sol-gel method and dip-coating technique, using barium acetate, titanium butoxide, and polyvinylpyrrolidone (PVP) as modifier viscosity. BaTiO3:Eu3+ films ~500 nm thick, crystallized after thermal treatment at 700 ºC. The powders revealed spherical and rod shape morphology. The optical quality of films showed a predominant band at 615 nm under 250 nm excitation. A preliminary luminescent test provided the properties of the Eu3+ doped BaTiO3. PMID:19865533

  8. Synthesis of transparent BaTiO3 nanoparticle/polymer composite film using DC field

    NASA Astrophysics Data System (ADS)

    Kondo, Yusuke; Okumura, Yasuko; Oi, Chifumi; Sakamoto, Wataru; Yogo, Toshinobu

    2008-10-01

    Transparent BaTiO3 nanoparticle/polymer composite films were synthesized from titanium-organic film and barium ion in aqueous solution under direct current (DC) field. Titanium-organic precursor was synthesized from titanium isopropoxide, acetylacetone and methacrylate derivative. The UV treatment was effective to increase the anti-solubility of the titanium-organic film during DC processing. BaTiO3 nanoparticles were crystallized in the precursor films on stainless substrates without high temperature process, as low as 40°C. The crystallite size of BaTiO3 increased with increasing reaction temperature from 40 to 50 °C at 3.0 V/cm. BaTiO3 nanoparticles also grew in size with increasing reaction time from 15 min to 45 min at 3.0 V/cm and 50 °C. Transparent BaTiO3 nanoparticle/polymer films were synthesized on stainless substrates at 3.0 V/cm and 50°C for 45 min.

  9. Carbon nanotubes as liquid crystals.

    PubMed

    Zhang, Shanju; Kumar, Satish

    2008-09-01

    Carbon nanotubes are the best of known materials with a combination of excellent mechanical, electronic, and thermal properties. To fully exploit individual nanotube properties for various applications, the grand challenge is to fabricate macroscopic ordered nanotube assemblies. Liquid-crystalline behavior of the nanotubes provides a unique opportunity toward reaching this challenge. In this Review, the recent developments in this area are critically reviewed by discussing the strategies for fabricating liquid-crystalline phases, addressing the solution properties of liquid-crystalline suspensions, and exploiting the practical techniques of liquid-crystal routes to prepare macroscopic nanotube fibers and films.

  10. Hydrothermal synthesis of BaTiO 3 nanoparticles using a supercritical continuous flow reaction system

    NASA Astrophysics Data System (ADS)

    Hayashi, Hiromichi; Noguchi, Takio; Islam, Nazrul M.; Hakuta, Yukiya; Imai, Yusuke; Ueno, Nobuhiko

    2010-06-01

    Highly crystalline BaTiO 3 nanoparticle was synthesized rapidly by hydrothermal reaction in supercritical water using a continuous flow reactor. The reactants of TiO 2 sol (or TiCl 4)/Ba(NO 3) 2 mixed solution and KOH solution were used as starting materials and that was heated quickly up to 400 °C under the pressure of 30 MPa for 8 ms as reaction time. The XRD results revealed that the crystal phase of the obtained particles was cubic BaTiO 3, indicating that the hydrothermal reaction in supercritical water was successfully proceeded under present reaction conditions. Primarily particle size of the BaTiO 3 nanoparticle was determined by means of BET surface area, as small as less than 10 nm with decreasing the reaction pH. In contrast, dispersed particle size in solution measured by DLS (dynamic light scattering) technique decreased from 260 to 90 nm with increasing the reactants concentration. Aggregation of BaTiO 3 nanoparticles might be depressed in the presence of coexisting nitrate anions.

  11. Microstructure evolution and electrical characterization of Lanthanum doped Barium Titanate (BaTiO3) ceramics

    NASA Astrophysics Data System (ADS)

    Billah, Masum; Ahmed, A.; Rahman, Md. Miftaur; Mahbub, Rubbayat; Gafur, M. A.; Bashar, M. Shahriar

    2016-07-01

    In the current work, we investigated the structural and dielectric properties of Lanthanum oxide (La2O3) doped Barium Titanate (BaTiO3) ceramics and established a correlation between them. Solid state sintering method was used to dope BaTiO3 with 0.3, 0.5 and 0.7 mole% La2O3 under different sintering parameters. The raw materials used were La2O3 nano powder of ~80nm grain size and 99.995% purity and BaTiO3 nano powder of 100nm grain size and 99.99% purity. Grain size distribution and morphology of fracture surface of sintered pellets were examined by Field Emission Scanning Electron Microscope and X-Ray Diffraction analysis was conducted to confirm the formation of desired crystal structure. The research result reveal that grain size and electrical properties of BaTiO3 ceramic significantly enhanced for small amount of doping (up to 0.5 mole% La2O3) and then decreased with increasing doping concentration. Desired grain growth (0.80-1.3 µm) and high densification (<90% theoretical density) were found by proper combination of temperature, sintering parameters and doping concentration. We found the resultant stable value of dielectric constant was 10000-12000 at 100-300 Hz in the temperature range of 30°-50° C for 0.5 mole% La2O3 with corresponding shift of curie temperature around 30° C. So overall this research showed that proper La3+ concentration can control the grain size, increase density, lower curie temperature and hence significantly improve the electrical properties of BaTiO3 ceramics.

  12. Engineered unique elastic modes at a BaTiO3/2x1-Ge(001) interface

    DOE PAGES

    Kumah, D. P.; Dogan, M.; Ngai, J. H.; ...

    2016-03-07

    Here, the strong interaction at an interface between a substrate and thin film leads to epitaxy and provides a means of inducing structural changes in the epitaxial film. These induced material phases often exhibit technologically relevant electronic, magnetic, and functional properties. The 2×1 surface of a Ge(001) substrate applies a unique type of epitaxial constraint on thin films of the perovskite oxide BaTiO3 where a change in bonding and symmetry at the interface leads to a non-bulk-like crystal structure of the BaTiO3. While the complex crystal structure is predicted using first-principles theory, it is further shown that the details ofmore » the structure are a consequence of hidden phases found in the bulk elastic response of the BaTiO3 induced by the symmetry of forces exerted by the germanium substrate.« less

  13. Complete set of material constants of 0.95(Na0.5Bi0.5)TiO3-0.05BaTiO3 lead-free piezoelectric single crystal and the delineation of extrinsic contributions

    NASA Astrophysics Data System (ADS)

    Zheng, Limei; Yi, Xiujie; Zhang, Shantao; Jiang, Wenhua; Yang, Bin; Zhang, Rui; Cao, Wenwu

    2013-09-01

    Lead-free piezoelectric single crystal 0.95(Na0.5Bi0.5)TiO3 (NBT)-0.05BaTiO3 was grown by top-seeded solution growth method, which has rhombohedral symmetry with composition near morphotropic phase boundary. Full set of dielectric, piezoelectric, and elastic constants for [001]c poled domain-engineered single crystal was determined. Excellent electromechanical properties and low dielectric loss (d33 = 360 pC/N, d31 = -113 pC/N, d15 = 162 pC/N, k33 = 0.720, kt = 0.540, and tan δ = 1.1%) make it a good candidate to replace lead-based piezoelectric materials. The depolarization temperature (Td = 135 °C) is the highest among all NBT-based materials and its electromechanical coupling properties are very stable below Td. Extrinsic contributions to piezoelectric properties were investigated by Rayleigh analysis.

  14. Nanotube networks in liquid crystals

    NASA Astrophysics Data System (ADS)

    Urbanski, Martin; Lagerwall, Jan Peter F.; Scalia, Giusy

    2016-03-01

    Liquid crystals (LCs) are very attractive hosts for the organization of anisotropic nanoparticles such as carbon nanotubes (CNTs) because of the macroscopic organization resulting in properties of nanoparticles manifest at a macroscopic scale. Different types of LCs have demonstrated the ability to organize nanotubes, showing the generality of the approach, i.e., that the liquid crystallinity per se is the driving factor for the organization. Compared to standard nanotube composites (e.g. with disordered polymer hosts) the introduction of carbon nanotubes into an LC allows not only the transfer of the outstanding CNT properties to the macroscopic phase, providing strength and conductivity, but these properties also become anisotropic, following the transfer of the orientational order from the LC to the CNTs. The LC molecular structure plays an important even if ancillary role since it enters in the surface interactions, fulfilling a mediating action between the particle and the bulk of the LC. Isolated nanotubes can be obtained by optimized dispersions at lower concentrations and this process requires the use or development of tailored strategies like using solvents or even another LC for pre-dispersing CNTs. Aggregates or networks can be observed in poor dispersions and at higher nanoparticle concentrations. In those, due to surface interactions, the LC behaviour can be strongly affected with changes in phase sequences or transition temperatures and the effect is expected to be more pronounced as the concentration of nanotubes increases. We present preliminary investigations and observations on nanotube - LC systems based on a smectic LC host.

  15. First-principles calculations on thermodynamic properties of BaTiO3 rhombohedral phase.

    PubMed

    Bandura, Andrei V; Evarestov, Robert A

    2012-07-05

    The calculations based on the linear combination of atomic orbitals have been performed for the low-temperature phase of BaTiO(3) crystal. Structural and electronic properties, as well as phonon frequencies were obtained using hybrid PBE0 exchange-correlation functional. The calculated frequencies and total energies at different volumes have been used to determine the equation of state and thermal contribution to the Helmholtz free energy within the quasiharmonic approximation. For the first time, the bulk modulus, volume thermal expansion coefficient, heat capacity, and Grüneisen parameters in BaTiO(3) rhombohedral phase have been estimated at zero pressure and temperatures form 0 to 200 K, based on the results of first-principles calculations. Empirical equation has been proposed to reproduce the temperature dependence of the calculated quantities. The agreement between the theoretical and experimental thermodynamic properties was found to be satisfactory.

  16. DFT study of Ag and La codoped BaTiO3

    NASA Astrophysics Data System (ADS)

    Maldonado, Frank; Stashans, Arvids

    2017-03-01

    Density functional theory and generalized gradient approximation including a Hubbard-like term was used in the present work to analyse structure as well as electronic and electrical properties of Ag and La codoped BaTiO3 material. Intrinsic oxygen vacancy defect has been taken into consideration throughout the calculations. Results on atomic shifts indicate the significance of Coulomb electrostatic interaction in finding equilibrium state of the system. It is shown that the n-type electrical conductivity should be expected as a result of codoping. Computed concentrations of free-carriers manifest the advantage of codoping procedure compared to the single impurity doping in the BaTiO3 crystal. It is also shown that oxygen vacancy alone can produce the n-type conductivity.

  17. Two-wave mixing and energy transfer in BaTiO3 application to laser beamsteering

    NASA Astrophysics Data System (ADS)

    Rak, D.; Ledoux, I.; Huignard, J. P.

    1984-03-01

    Energy transfer between the two recording beams in a BaTiO3 photorefractive crystal is analyzed as a function of the following parameters: incident beams ratio, spatial frequency, pump beam intensity. Exponential gain coefficients of approximately 20/cm are reached for optimized holographic recording conditions. Application of the energy transfer to a new method of laser beam deflection is proposed.

  18. High dielectric constant associated with the strain-induced phase transition of an ordered assembly of BaTiO3 nanocubes under three-dimensional clamping

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi; Mimura, Ken-ichi; Izu, Noriya; Kato, Kazumi

    2017-02-01

    Numerical calculations of the Gibbs function for an ordered assembly of BaTiO3 nanocubes (nanocrystals) under three-dimensional clamping have revealed that the phase transition from a tetragonal to cubic crystal structure can take place at room temperature at some misfit strain associated with a tilt angle of the attached nanocubes. The phase transition is second-order due to the three-dimensional clamping. Near and at the phase transition, the dielectric constant becomes extremely high owing to the second-order transition. This is considered to be the reason for the high dielectric constant of an assembly at room temperature, which has been experimentally observed. An ordered assembly of BaTiO3 nanocubes under rigid three-dimensional clamping is a completely different system from the normal nanocrystalline (polycrystalline) BaTiO3 ceramics under elastic clamping and from a BaTiO3 epitaxial thin film under two-dimensional clamping.

  19. Studies of local structural distortions in strained ultrathin BaTiO3 films using scanning transmission electron microscopy.

    PubMed

    Park, Daesung; Herpers, Anja; Menke, Tobias; Heidelmann, Markus; Houben, Lothar; Dittmann, Regina; Mayer, Joachim

    2014-06-01

    Ultrathin ferroelectric heterostructures (SrTiO3/BaTiO3/BaRuO3/SrRuO3) were studied by scanning transmission electron microscopy (STEM) in terms of structural distortions and atomic displacements. The TiO2-termination at the top interface of the BaTiO3 layer was changed into a BaO-termination by adding an additional BaRuO3 layer. High-angle annular dark-field (HAADF) imaging by aberration-corrected STEM revealed that an artificially introduced BaO-termination can be achieved by this interface engineering. By using fast sequential imaging and frame-by-frame drift correction, the effect of the specimen drift was significantly reduced and the signal-to-noise ratio of the HAADF images was improved. Thus, a quantitative analysis of the HAADF images was feasible, and an in-plane and out-of-plane lattice spacing of the BaTiO3 layer of 3.90 and 4.22 Å were determined. A 25 pm shift of the Ti columns from the center of the unit cell of BaTiO3 along the c-axis was observed. By spatially resolved electron energy-loss spectroscopy studies, a reduction of the crystal field splitting (CFS, ΔL3=1.93 eV) and an asymmetric broadening of the eg peak were observed in the BaTiO3 film. These results verify the presence of a ferroelectric polarization in the ultrathin BaTiO3 film.

  20. Ferroelectric control of magnetism in BaTiO3/Fe heterostructures

    NASA Astrophysics Data System (ADS)

    Sahoo, Sarbeswar; Polisetty, Srinivas; Duan, Chun Gang; Jaswal, Sitaram; Tsymbal, Evgeny; Binek, Christian

    2008-03-01

    Multiferroics can offer the possibility to manipulate the cross coupled order parameters by conjugate electric and magnetic fields. Switching off ferromagnetic order by an electric field for instance promises significant impact in the design of novel spintronic devices. Here we report on the reversible control of magnetism for a Fe thin film in proximity of a BaTiO3 single-crystal. Large magnetization changes emerge in response to ferroelectric switching and structural transitions of BaTiO3 controlled by applied electric fields and temperature, respectively.^ Interface strain coupling is the primary mechanism altering the induced magnetic anisotropy. As a result, coercivity changes up to 120% occur between the various structural states of BaTiO3. Up to 20% coercivity change is achieved via electrical control at room temperature. Our all solid state ferroelectric-ferromagnetic heterostructures open viable possibilities for new technological applications. ^S. Sahoo, S. Polisetty, C.-G. Duan, S. S. Jaswal, E. Y. Tsymbal, and Ch. Binek, Phys. Rev. B 76, 092108 (2007).

  1. Observation of self poling in BaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Lubomirsky, Igor; Chang, David T.; Stafsudd, Oscar M.

    1999-05-01

    The dependence of ferroelectric properties of sol-gel derived BaTiO3 thin (0.35 μm) films on various Si substrates was investigated. It was found that only films deposited on p+ Si (1020cm-3 B, 2% Ge) are (110) oriented and possess a few percent of the spontaneous polarization of single-crystal BaTiO3. The direction of polarization self restored after being reversed by external bias or heated above the Curie temperature. It was found that the pyroelectric coefficient was not zero above the Curie point, which indicated that the films are permanently subjected to an electric field, which originates from the contact potential between the film and the substrate. This conclusion was confirmed by surface photovoltage spectroscopy. Orientation of the films was attributed to the presence of Ge in the substrate, which decreased lattice mismatch between the (100) vector of the Si substrate and (110) vector of BaTiO3. The possibility of a paraelectric to ferroelectric transition driven by an electric field due to the contact potential difference must be taken into account for dynamic random access memory applications.

  2. Deposition barium titanate (BaTiO3) doped lanthanum with chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Iriani, Y.; Jamaludin, A.; Nurhadi, N.

    2016-11-01

    Deposition of Barium Titanate (BaTiO3) thin films used Chemical Solution Deposition (CSD) method and prepared with spin coater. BaTiO3 is doped with lanthanum, 1%, 2%, and 3%. The thermal process use annealing temperature 900°C and holding time for 3 hours. The result of characterization with x-ray diffraction (XRD) equipment show that the addition of La3+ doped on Barium Titanate caused the change of angle diffraction.The result of refine with GSAS software shows that lanthanum have been included in the structure of BaTiO3. Increasing mol dopant La3+ cause lattice parameter and crystal volume become smaller. Characterization result using Scanning Electron Microscopy (SEM) equipment show that grain size (grain size) become smaller with increasing mole dopant (x) La3+. The result of characterization using Sawyer Tower methods show that all the samples (Barium Titanante and Barium Titanate doped lanthanum) are ferroelectric material. Increasing of mole dopant La3+ cause smaller coercive field and remanent polarization increases.

  3. Structural evolution of BaTiO(3) nanocrystals synthesized at room temperature.

    PubMed

    Rabuffetti, Federico A; Brutchey, Richard L

    2012-06-06

    Sub-10 nm BaTiO(3) nanocrystals were synthesized at room temperature via the vapor diffusion sol-gel method, and their structural evolution during nucleation and growth stages was followed using a series of techniques that probe the atomic structure on different length and time scales. Special emphasis was placed on assessing the evolution of the local symmetry and structural coherence of the resulting nanocrystals, as these are the structural bases for cooperative properties such as ferroelectricity. Although the room-temperature crystal structure of the fully grown nanocrystals appears cubic to Rietveld analysis of synchrotron X-ray diffraction data, Raman spectroscopy and pair distribution function analysis demonstrate the presence of non-centrosymmetric regions arising from the off-centering of the titanium atoms. This finding demonstrates that accounting for diffuse scattering is critical when attempting the structural characterization of nanocrystals with X-ray diffraction. The local symmetry of acentric regions present in BaTiO(3) nanocrystals, particularly structural correlations within an individual unit cell and between two adjacent unit cells, is best described by a tetragonal P4mm space group. The orthorhombic Amm2 space group also provides an adequate description, suggesting both types of local symmetry can coexist at room temperature. The average magnitude of the local off-center displacements of the titanium atoms along the polar axis is comparable to that observed in bulk BaTiO(3), and their coherence length is on the order of 16 Å. The presence of local dipoles suggests that a large amount of macroscopic polarization can be achieved in nanocrystalline BaTiO(3) if the coherence of their ferroelectric coupling is further increased.

  4. Strain-induced magnetic domain wall control by voltage in hybrid piezoelectric BaTiO3 ferrimagnetic TbFe structures

    PubMed Central

    Rousseau, Olivier; Weil, Raphael; Rohart, Stanislas; Mougin, Alexandra

    2016-01-01

    This paper reports on the voltage dependence of the magnetization reversal of a thin amorphous ferromagnetic TbFe film grown on a ferroelectric and piezoelectric BaTiO3 single crystal. Magneto-optical measurements, at macroscopic scale or in a microscope, demonstrate how the ferroelectric BaTiO3 polarisation history influences the properties of the perpendicularly magnetized TbFe film. Unpolarised and twinned regions are obtained when the sample is zero voltage cooled whereas flat and saturated regions are obtained when the sample is voltage cooled through the ferroelectric ordering temperature of the BaTiO3 crystal, as supported by atomic force microscopy experiments. The two steps involved in the TbFe magnetization reversal, namely nucleation and propagation of magnetic domain walls, depend on the polarisation history. Nucleation is associated to coupling through strains with the piezoelectric BaTiO3 crystal and propagation to pinning with the ferroelastic surface patterns visible in the BaTiO3 topography. PMID:26987937

  5. Strain-induced magnetic domain wall control by voltage in hybrid piezoelectric BaTiO3 ferrimagnetic TbFe structures

    NASA Astrophysics Data System (ADS)

    Rousseau, Olivier; Weil, Raphael; Rohart, Stanislas; Mougin, Alexandra

    2016-03-01

    This paper reports on the voltage dependence of the magnetization reversal of a thin amorphous ferromagnetic TbFe film grown on a ferroelectric and piezoelectric BaTiO3 single crystal. Magneto-optical measurements, at macroscopic scale or in a microscope, demonstrate how the ferroelectric BaTiO3 polarisation history influences the properties of the perpendicularly magnetized TbFe film. Unpolarised and twinned regions are obtained when the sample is zero voltage cooled whereas flat and saturated regions are obtained when the sample is voltage cooled through the ferroelectric ordering temperature of the BaTiO3 crystal, as supported by atomic force microscopy experiments. The two steps involved in the TbFe magnetization reversal, namely nucleation and propagation of magnetic domain walls, depend on the polarisation history. Nucleation is associated to coupling through strains with the piezoelectric BaTiO3 crystal and propagation to pinning with the ferroelastic surface patterns visible in the BaTiO3 topography.

  6. Thin film processing of photorefractive BaTiO3

    NASA Technical Reports Server (NTRS)

    Schuster, Paul R.; Potember, Richard S.

    1991-01-01

    The principle objectives of this ongoing research involve the preparation and characterization of polycrystalline single-domain thin films of BaTiO3 for photorefractive applications. These films must be continuous, free of cracks, and of high optical quality. The two methods proposed are sputtering and sol-gel related processing.

  7. Intensity dependent absorption/transparency of a reducing BaTiO3

    NASA Astrophysics Data System (ADS)

    Chang, J. Y.; Garrett, M. H.; Jenssen, H. P.; Warde, C.

    1993-12-01

    We report intensity dependent absorption and transparency as a function of wavelength for barium titanate. The BaTiO3 crystal examined has an as-grown, light-blue color due to an absorption centered at 690 nm, and when reduced in a partial pressure of 10-15 atm of oxygen it has a yellow-orange color due to an absorption centered at 470 nm. Both energy levels are active in the reduced sample as revealed in the spectrum of the intensity dependent changes in absorption.

  8. Ferroelectric-like metallic state in electron doped BaTiO3

    PubMed Central

    Fujioka, J.; Doi, A.; Okuyama, D.; Morikawa, D.; Arima, T.; Okada, K. N.; Kaneko, Y.; Fukuda, T.; Uchiyama, H.; Ishikawa, D.; Baron, A. Q. R.; Kato, K.; Takata, M.; Tokura, Y.

    2015-01-01

    We report that a ferroelectric-like metallic state with reduced anisotropy of polarization is created by the doping of conduction electrons into BaTiO3, on the bases of x-ray/electron diffraction and infrared spectroscopic experiments. The crystal structure is heterogeneous in nanometer-scale, as enabled by the reduced polarization anisotropy. The enhanced infrared intensity of soft phonon along with the resistivity reduction suggests the presence of unusual electron-phonon coupling, which may be responsible for the emergent ferroelectric structure compatible with metallic state. PMID:26289749

  9. High Performance Flexible Piezoelectric Nanogenerators based on BaTiO3 Nanofibers in Different Alignment Modes.

    PubMed

    Yan, Jing; Jeong, Young Gyu

    2016-06-22

    Piezoelectric nanogenerators, harvesting energy from mechanical stimuli in our living environments, hold great promise to power sustainable self-sufficient micro/nanosystems and mobile/portable electronics. BaTiO3 as a lead-free material with high piezoelectric coefficient and dielectric constant has been widely examined to realize nanogenerators, capacitors, sensors, etc. In this study, polydimethylsiloxane (PDMS)-based flexible composites including BaTiO3 nanofibers with different alignment modes were manufactured and their piezoelectric performance was examined. For the study, BaTiO3 nanofibers were prepared by an electrospinning technique utilizing a sol-gel precursor and following calcination process, and they were then aligned vertically or horizontally or randomly in PDMS matrix-based nanogenerators. The morphological structures of BaTiO3 nanofibers and their nanogenerators were analyzed by using SEM images. The crystal structures of the nanogenerators before and after poling were characterized by X-ray diffraction. The dielectric and piezoelectric properties of the nanogenerators were investigated as a function of the nanofiber alignment mode. The nanogenerator with BaTiO3 nanofibers aligned vertically in the PDMS matrix sheet achieved high piezoelectric performance of an output power of 0.1841 μW with maximum voltage of 2.67 V and current of 261.40 nA under a low mechanical stress of 0.002 MPa, in addition to a high dielectric constant of 40.23 at 100 Hz. The harvested energy could thus power a commercial LED directly or be stored into capacitors after rectification.

  10. Epitaxial BaTiO3(100) films on Pt(100): a low-energy electron diffraction, scanning tunneling microscopy, and x-ray photoelectron spectroscopy study.

    PubMed

    Förster, Stefan; Huth, Michael; Schindler, Karl-Michael; Widdra, Wolf

    2011-09-14

    The growth of epitaxial ultrathin BaTiO(3) films on a Pt(100) substrate has been studied by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and x-ray photoelectron spectroscopy (XPS). The films have been prepared by radio-frequency-assisted magnetron sputter deposition at room temperature and develop a long-range order upon annealing at 900 K in O(2). By adjusting the Ar and O(2) partial pressures of the sputter gas, the stoichiometry was tuned to match that of a BaTiO(3)(100) single crystal as determined by XPS. STM reveals the growth of continuous BaTiO(3) films with unit cell high islands on top. With LEED already for monolayer thicknesses, the formation of a BaTiO(3)(100)-(1 × 1) structure has been observed. Films of 2-3 unit cell thickness show a brilliant (1 × 1) LEED pattern for which an extended set of LEED I-V data has been acquired. At temperatures above 1050 K the BaTiO(3) thin film starts to decay by formation of vacancy islands. In addition (4 × 4) and (3 × 3) surface reconstructions develop upon prolonged heating.

  11. Single-crystal gallium nitride nanotubes.

    PubMed

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

    2003-04-10

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

  12. Nanostructural evolution of one-dimensional BaTiO₃ structures by hydrothermal conversion of vertically aligned TiO₂ nanotubes.

    PubMed

    Muñoz-Tabares, J A; Bejtka, K; Lamberti, A; Garino, N; Bianco, S; Quaglio, M; Pirri, C F; Chiodoni, A

    2016-03-28

    The use of TiO2 nanotube (NT) arrays as templates for hydrothermal conversion of one-dimensional barium titanate (BaTiO3) structures is considered a promising synthesis approach, even though the formation mechanisms are not yet fully understood. Herein we report a nanostructural study by means of XRD and (HR)TEM of high aspect ratio TiO2-NTs hydrothermally converted into BaTiO3. The nanostructure shows two different and well-defined regions: at the top the conversion involves complete dissolution of NTs and subsequent precipitation of BaTiO3 crystals by homogeneous nucleation, followed by the growth of dendritic structures by aggregation and oriented attachment mechanisms. Instead, at the bottom, the low liquid/solid ratio, due to the limited amount of Ba solution that infiltrates the NTs, leads to the rapid crystallization of such a solution into BaTiO3, thus allowing the NTs to act as a template for the formation of highly oriented one-dimensional nanostructures. The in-depth analysis of the structural transformations that take place during the formation of the rod-like arrays of BaTiO3 could help elucidate the conversion mechanism, thus paving the way for the optimization of the synthesis process in view of new applications in energy harvesting devices, where easy and low temperature processing, controlled composition, morphology and functional properties are required.

  13. Surface reaction characteristics at low temperature synthesis BaTiO 3 particles by barium hydroxide aqueous solution and titanium tetraisopropoxide

    NASA Astrophysics Data System (ADS)

    Zeng, Min

    2011-05-01

    Well-crystallized cubic phase BaTiO 3 particles were prepared by heating the mixture of barium hydroxide aqueous solution and titania derived from the hydrolysis of titanium isopropoxide (TTIP) at 328 K, 348 K or 368 K for 24 h. The morphology and size of obtained particles depended on the reaction temperature and the Ba(OH) 2/TTIP molar ratio. By the direct hydrolytic reaction of titanium tetraisopropoxide, the high surface area titania (TiO 2) was obtained. The surface adsorption characteristics of the titania particles had been studied with different electric charges OH - ions or H + ions. The formation mechanism and kinetics of BaTiO 3 were examined by measuring the concentration of [Ba 2+] ions in the solution during the heating process. The experimental results showed that the heterogeneous nucleation of BaTiO 3 occurred on the titania surface, according to the Avrami's equation.

  14. Local control of magnetic anisotropy in transcritical permalloy thin films using ferroelectric BaTiO3 domains

    NASA Astrophysics Data System (ADS)

    Fackler, Sean W.; Donahue, Michael J.; Gao, Tieren; Nero, Paris N. A.; Cheong, Sang-Wook; Cumings, John; Takeuchi, Ichiro

    2014-11-01

    We investigated the local coupling between dense magnetic stripe domains in transcritical permalloy (tPy) thin films and ferroelectric domains of BaTiO3 single crystals in a tPy/BaTiO3 heterostructure. Two distinct changes in the magnetic stripe domains of tPy were observed from the magnetic force microscopy images after cooling the heterostructure from above the ferroelectric Curie temperature of BaTiO3 (120 °C) to room temperature. First, an abrupt break in the magnetic stripe domain direction was found at the ferroelectric a-c-domain boundaries due to an induced change in in-plane magnetic anisotropy. Second, the magnetic stripe domain period increased when coupled to a ferroelectric a-domain due to a change in out-of-plane magnetic anisotropy. Micromagnetic simulations reveal that local magnetic anisotropy energy from inverse magnetostriction is conserved between in-plane and out-of-plane components.

  15. Electrical and Optical Property of Ferroelectric BaTiO3:Eu

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon; Grichener, Alexander; Jensen, Jacob; Choi, Sang H.

    2005-01-01

    We studied various electrical and optical properties of Europium (1 atomic %) incorporated BaTiO3 film on n-Si(100) substrate. The thin film structure was analyzed by X-ray diffraction. Film thickness and optical refractive index were measured with an ellipsometer. P-E hysteresis measurement shows the remnant polarization of 37 micro C/sq cm in BaTiO3:Eu film. C-V measurements on the pure BaTiO3 film show recovery of capacitance across sweeping voltage ranges with a narrow transition zone due to the polarization change. On the other hand, C-V and I-V measurements on the BaTiO3:Eu film show that Europium incorporation increases positively charged states in the BaTiO3 layer such that BaTiO3:Eu/n-Si interface behaves like a leaky p-n junction.

  16. Enhancement of p-type conductivity in nanocrystalline BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Guo, Xin; Pithan, Christian; Ohly, Christian; Jia, Chun-Lin; Dornseiffer, Jügen; Haegel, Franz-Hubert; Waser, Rainer

    2005-02-01

    Undoped BaTiO3 ceramic samples with an average grain size of ˜35nm were prepared and the electrical properties investigated. The defect structure is dominated by acceptor impurities; therefore, the conductivity of nanocrystalline BaTiO3 is of p-type. Comparing with microcrystalline BaTiO3, the conductivity of nanocrystalline BaTiO3 is about 1 to 2 orders of magnitude higher and the activation energy remarkably lower, which is ascribed to a greatly reduced oxidation enthalpy in nanocrystalline BaTiO3 (˜0.3 versus ˜0.92eV for microcrystalline BaTiO3).

  17. Design and preparation of stress-free epitaxial BaTiO3 polydomain films by RF magnetron sputtering.

    PubMed

    Zhang, Wei; Yuan, Meiling; Wang, Xianyang; Pan, Wei; Wang, Chun-Ming; Ouyang, Jun

    2012-06-01

    Domain structures of BaTiO3 thick films grown on (100) SrTiO3 single-crystal substrates were engineered using an RF magnetron sputtering deposition process. By tuning the sputtering power and cooling rate and using an off-axis sputtering technique to prepare conducting perovskite oxide bottom electrode with heteroepitaxial quality, we have deposited epitaxial tetragonal single-domain and polydomain BaTiO3 films with a self-assembled three-domain architecture. The electrical properties and microstructure of the BaTiO3 films were characterized, and a c/a1/a2 cellular polydomain structure was clearly observed in as-grown films by optical microscopy. Such a polydomain structure was a consequence of a complete relaxation of misfit stresses of the film. Engineering of this self-assembled microstructure has great potential in providing large, field-tunable pyroelectric and electromechanical responses in next-generation microelectronic devices and micro-electro-mechanical systems (MEMS).

  18. Dimension effects on the dielectric properties of fine BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Hou, Zhi-Wen; Kang, Ai-Guo; Ma, Wei-Qing; Zhao, Xiao-Long

    2014-11-01

    It is found that the core-shell structured grains are easy to produce for fine grain doped BaTiO3 ceramics in the sintering process. We study the influence of the core-shell structure on the Curie—Weiss temperature and dielectric properties of BaTiO3 ceramics by using effective medium approximation (EMA). Considering the second approximation, the dielectric properties of fine grain doped BaTiO3 ceramics are consistent with experimental data.

  19. Thin film processing of photorefractive BaTiO3

    NASA Technical Reports Server (NTRS)

    Schuster, Paul R.

    1993-01-01

    During the period covered by this report, October 11, 1991 through October 10, 1992, the research has progressed in a number of different areas. The sol-gel technique was initially studied and experimentally evaluated for depositing films of BaTiO3. The difficulties with the precursors and the poor quality of the films deposited lead to the investigation of pulsed laser deposition as an alternative approach. The development of the pulsed laser deposition technique has resulted in continuous improvements to the quality of deposited films of BaTiO3. The initial depositions of BaTiO3 resulted in amorphous films, however, as the pulsed laser deposition technique continued to evolve, films were deposited in the polycrystalline state, then the textured polycrystalline state, and most recently heteroepitaxial films have also been successfully deposited on cubic (100) oriented SrTiO3 substrates. A technique for poling samples at room temperature and in air is also undergoing development with some very preliminary but positive results. The analytical techniques, which include x-ray diffraction, ferroelectric analysis, UV-Vis spectrophotometry, scanning electron microscopy with x-ray compositional analysis, optical and polarized light microscopy, and surface profilometry have been enhanced to allow for more detailed evaluation of the samples. In the area of optical characterization, a pulsed Nd:YAG laser has been incorporated into the experimental configuration. Now data can also be acquired within various temporal domains resulting in more detailed information on the optical response of the samples and on their photorefractive sensitivity. The recent establishment of collaborative efforts with two departments at Johns Hopkins University and the Army Research Lab at Fort Belvoir has also produced preliminary results using the metallo-organic decomposition technique as an alternative method for thin film processing of BaTiO3. RF and DC sputtering is another film deposition approach that should be initiated in the near future. Other techniques for optical characterization, which may even allow for intragrannular (within single grains) investigations, are also being considered.

  20. Stabilisation des phases monocristallines quadratique et cubique dans BaTiO3

    NASA Astrophysics Data System (ADS)

    Amami, J.; Goutaudier, C.; Trabelsi-Ayadi, M.; Boulon, G.

    2004-12-01

    Single crystals of Ba1-xYbxTiO3 and Ba1-xSrxTiO3 with tetragonal structure were grown by the floating zone (FZ) method using an LHPG (Laser Heated Pedestal Growth) technique. The grown crystals, typically 1 mm in diameter and 8 mm in length, were yellowish transparent. Substitution of more than 2.5 at % Sr for Ba in BaTiO3 and addition of 3 to 5 at % Ln (Ln= Yb, Eu), were effective in preventing the formation of the hexagonal phase. The Eu3+ emission spectra recorded at room temperature demonstrate a significant intensity enhancement of the 5D0 → 7F1 magnetic dipolar transition compared to the 5D0 → 7F2 electric dipolar transition. Les fibres monocristallines de Ba1-xYbxTiO3 et Ba1-xSrxTiO3 de structure quadratique ont été préparées par la méthode de la zone flottante (FZ) en utilisant la technique LHPG (Laser Heated Pedestal Growth). Les échantillons élaborés, de dimensions 1mm x 8 mm, sont jaunâtres et transparentes. La substitution du baryum par plus de 2,5 mol% de Sr dans BaTiO3 et le dopage de 3 à 5 mol% de Ln (Ln = Yb, Eu) évitent la formation de la phase hexagonale. Le spectre d’émission de Eu3+ enregistré à température ambiante montre le changement de structure traduit par la forte intensité de la transition dipolaire magnétique 5D0 → 7F1 comparée à celle de la transition dipolaire électrique 5D0 → 7F2.

  1. Effectiveness of BaTiO 3 dielectric patches on YBa 2 Cu 3 O 7 thin films for MEM switches

    DOE PAGES

    Vargas, J.; Hijazi, Y.; Noel, J.; ...

    2014-05-12

    A micro-electro-mechanical (MEM) switch built on a superconducting microstrip filter will be utilized to investigate BaTiO3 dielectric patches for functional switching points of contact. Actuation voltage resulting from the MEM switch provokes static friction between the bridge membrane and BaTiO3 insulation layer. Furthermore, the dielectric patch crystal structure and roughness affect the ability of repetitively switching cycles and lifetime. We performed a series of experiments using different deposition methods and RF magnetron sputtering was found to be the best deposition process for the BaTiO3 layer. The effect examination of surface morphology will be presented using characterization techniques as x-ray diffraction,more » SEM and AFM for an optimum switching device. The thin film is made of YBa2Cu3O7 deposited on LaAlO3 substrate by pulsed laser deposition. In our work, the dielectric material sputtering pressure is set at 9.5x10-6 Torr. The argon gas is released through a mass-flow controller to purge the system prior to deposition. RF power is 85 W at a distance of 9 cm. The behavior of Au membranes built on ultimate BaTiO3 patches will be shown as part of the results. These novel surface patterns will in turn be used in modelling other RF MEM switch devices such as distributed-satellite communication system operating at cryogenic temperatures.« less

  2. Effectiveness of BaTiO3 dielectric patches on YBa2Cu3O7 thin films for MEM switches

    DOE PAGES

    Vargas, J.; Hijazi, Y.; Noel, J.; ...

    2014-05-12

    A micro-electro-mechanical (MEM) switch built on a superconducting microstrip filter will be utilized to investigate BaTiO3 dielectric patches for functional switching points of contact. Actuation voltage resulting from the MEM switch provokes static friction between the bridge membrane and BaTiO3 insulation layer. Furthermore, the dielectric patch crystal structure and roughness affect the ability of repetitively switching cycles and lifetime. We performed a series of experiments using different deposition methods and RF magnetron sputtering was found to be the best deposition process for the BaTiO3 layer. The effect examination of surface morphology will be presented using characterization techniques as x-ray diffraction,more » SEM and AFM for an optimum switching device. The thin film is made of YBa2Cu3O7 deposited on LaAlO3 substrate by pulsed laser deposition. In our work, the dielectric material sputtering pressure is set at 9.5x10-6 Torr. The argon gas is released through a mass-flow controller to purge the system prior to deposition. RF power is 85 W at a distance of 9 cm. The behavior of Au membranes built on ultimate BaTiO3 patches will be shown as part of the results. These novel surface patterns will in turn be used in modelling other RF MEM switch devices such as distributed-satellite communication system operating at cryogenic temperatures.« less

  3. BaTiO3-Based Non-Reducible Low-Loss Dielectric Ceramics

    NASA Astrophysics Data System (ADS)

    Nakamura, Tomoyuki; Sano, Harunobu; Konoike, Takehiro; Tomono, Kunisaburo

    1999-09-01

    Dielectrics composed of BaTiO3-rare earth oxide-MgO havebeenstudied to design a non-reducible low-loss dielectricmaterial. Curie temperatures of dielectrics composed ofBaTiO3 Gd2O3 MgO were lowered by Gd2O3, which provided thedielectrics with low power loss. It was found that the addition ofBaZrO3 to BaTiO3 Gd2O3 MgO decreased the capacitance change withtemperature. Gd2O3 diffused easily into BaTiO3, but, it could noteasily diffuse into BaTiO3 to which BaZrO3 had been added. It wasconsidered that BaZrO3 prevented the Gd2O3 diffusion into BaTiO3,resulting the remains of ferroelectricity and reduced capacitancechange. Thus non-reducible and low power loss X7R dielectricceramics were developed.

  4. Direct writing of three-dimensional woodpile BaTiO3 structures

    NASA Astrophysics Data System (ADS)

    Li, Jijiao; Li, Bo; Wu, Hongya; Zhou, Ji

    2014-05-01

    Barium titanate (BaTiO3) woodpile structures with designed, three-dimensional (3D) geometry have been fabricated by direct-writing assembly techniques. Concentrated BaTiO3 inks with suitable rheological properties were prepared to enable the fabrication of the complex 3D structures. It was demonstrated that BaTiO3 inks with a total solids volume fraction of 0.41 are shear thinning and have a high storage modulus 1 × 105Pa with a yield stress of 300 Pa. Additionally, the woodpile lattice structures exhibited an excellent self-supporting feature.

  5. Consequences of Ca multisite occupation for the conducting properties of BaTiO3

    NASA Astrophysics Data System (ADS)

    Zulueta, Y. A.; Dawson, J. A.; Leyet, Y.; Anglada-Rivera, J.; Guerrero, F.; Silva, R. S.; Nguyen, Minh Tho

    2016-11-01

    In combination with the dielectric modulus formalism and theoretical calculations, a newly developed defect incorporation mode, which is a combination of the standard A- and B-site doping mechanisms, is used to explain the conducting properties in 5 mol% Ca-doped BaTiO3. Simulation results for Ca solution energies in the BaTiO3 lattice show that the new oxygen vacancy inducing mixed mode exhibits low defect energies. A reduction in dc conductivity compared with undoped BaTiO3 is witnessed for the incorporation of Ca. The conducting properties of 5 mol% Ca-doped BaTiO3 are analyzed using molecular dynamics and impedance spectroscopy. The ionic conductivity activation energies for each incorporation mode are calculated and good agreement with experimental data for oxygen migration is observed. The likely existence of the proposed defect configuration is also analyzed on the basis of these methods.

  6. Light Sensitive Lattice Defects In BaTiO3 Containing Fe

    NASA Astrophysics Data System (ADS)

    Possenriede, Ewald; Schirmer, Ortwin F.; Godefroy, Genevieve; Maillard, Alain

    1989-01-01

    Electron spin resonance spectra, which can consistently be explained by the models Fe4+ - Vo and Fe5+ - vBa, have been observed with BaTiO3 containing Fe. Also Fe3+ and - Fe3+ - Vo have been identified. All these centers as well as several unidentified ones are observed to change their charge states under illumination. They thus are possibly in involved in photorefractive processes in BaTiO3 containing Fe.

  7. Both High Reliability and Giant Electrocaloric Strength in BaTiO3 Ceramics

    PubMed Central

    Bai, Yang; Han, Xi; Zheng, Xiu-Cheng; Qiao, Lijie

    2013-01-01

    BaTiO3 has a giant electrocaloric strength, |ΔT|/|ΔE|, because of a large latent heat and a sharp phase transition. The electrocaloric strength of a new single crystal, as giant as 0.48 K·cm/kV, is twice larger than the previous best result, but it remarkably decreased to 0.18 K·cm/kV after several times of thermal cycles accompanied by alternating electric fields, because the field-induced phase transition and domain switching resulted in numerous defects such as microcracks. The ceramics prepared from nano-sized powders showed a high electrocaloric strength of 0.14 K·cm/kV, comparable to the single crystals experienced electrocaloric cycles, because of its unique microstructure after proper sintering process. Moreover, its properties did not change under the combined effects of thermal cycles and alternating electric fields, i.e. it has both large electrocaloric effect and good reliability, which are desirable for practical applications. PMID:24100662

  8. Atomistic description for temperature-driven phase transitions in BaTiO3

    NASA Astrophysics Data System (ADS)

    Qi, Y.; Liu, S.; Grinberg, I.; Rappe, A. M.

    2016-10-01

    Barium titanate (BaTiO3) is a prototypical ferroelectric perovskite that undergoes the rhombohedral-orthorhombic-tetragonal-cubic phase transitions as the temperature increases. In this paper, we develop a classical interatomic potential for BaTiO3 within the framework of the bond-valence theory. The force field is parametrized from first-principles results, enabling accurate large-scale molecular dynamics (MD) simulations at finite temperatures. Our model potential for BaTiO3 reproduces the temperature-driven phase transitions in isobaric-isothermal ensemble (N P T ) MD simulations. This potential allows for the analysis of BaTiO3 structures with atomic resolution. By analyzing the local displacements of Ti atoms, we demonstrate that the phase transitions of BaTiO3 exhibit a mix of order-disorder and displacive characters. Besides, from a detailed observation of structural dynamics during phase transition, we discover that the global phase transition is associated with changes in the equilibrium value and fluctuations of each polarization component, including the ones already averaging to zero, Contrary to the conventional understanding that temperature increase generally causes bond-softening transition, the x -polarization component (the one which is polar in both the orthorhombic and the tetragonal phases) exhibits a bond-hardening character during the orthorhombic-to-tetragonal transition. These results provide further insight about the temperature-driven phase transitions in BaTiO3.

  9. cc domains with intrinsic screening and absence of closure domains in atomically ordered BaTiO3 in UHV

    NASA Astrophysics Data System (ADS)

    Watanabe, Y.; Kaku, S.; Nakamura, K.

    2010-03-01

    cc domains have been observed in ordinary environments, where extraneous screening hampers rigorous comparison with theories. Indeed, recent theories predict closure domains in the absence of extraneous screening. Therefore, we performed simultaneous topographic, electrostatic and piezoelectric imaging of atomically clean, free surface of BaTiO3 single crystal by AFM operated in ultra high vacuum (UHV).footnotetextS. Kaku et al., J.Kor.Phys.Soc.55,799(2009) BaTiO3 surface retains stoichiometry in UHV because of the absence of volatile elements (Pb, Bi, Li) and low TC The surface cleanness is confirmed by the detection of chemical bonding. Three imaging methods verified the assignment of ac and cc domains, which is consistent with conventional theory and experiments. These ac and cc domains change reversibly by weak electric field of 2kV/cm at RT. In addition, the temperature dependence of the domains agrees with convention theories. These observations prove the absence of dominating control of defects and impurities on the observed domains. The sole deviation is the reduction of the potential difference to 1/30 of the conventional theories. The described intrinsic nature of the domains indicates an intrinsic screening in cc domains, which is consistent with the intrinsic surface carrier layer on ferroelectrics.footnotetextWatanabe et al. PRL86332(2001), PRB57,789(1998)

  10. Carbon nanotubes dispersed in liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Ji, Yan

    Liquid crystal elastomers (LCEs), as the name indicates, unite the anisotropic order of liquid crystals and rubber elasticity of elastomers into polymer networks. One of the most notable features of LCEs is that properly aligned LCEs exhibit dramatic and reversible shape deformation (e.g. elongation-contraction) in response to various stimuli. In recent years, carbon nanotubes (CNTs) were introduced into LCEs. Besides enabling remote and spatial control of the actuation via light and electronic field, CNTs are also utilized to align mesogens as well as to improve the mechanical and electronic property of the composites. Some potential applications of CNT-LCE nanocomposites have been demonstrated. This chapter describes the preparation of CNT dispersed LCEs, new physical properties resulted from CNTs, their actuation and their proposed applications.

  11. Improved ferroelectric, piezoelectric and electrostrictive properties of dense BaTiO3 ceramic

    NASA Astrophysics Data System (ADS)

    Baraskar, Bharat G.; Kakade, S. G.; James, A. R.; Kambale, R. C.; Kolekar, Y. D.

    2016-05-01

    The ferroelectric, piezoelectric and electrostrictive properties of BaTiO3 (BT) dense ceramic synthesized by solid-state reaction were investigated. X-ray diffraction study confirmed tetragonal crystal structure having c/a ~1.0144. The dense microstructure was evidenced from morphological studies with an average grain size ~7.8 µm. Temperature dependent dielectric measurement showed the maximum values of dielectric constant, ɛr = 5617 at Curie temperature, Tc = 125 °C. The saturation and remnant polarization, Psat. = 24.13 µC/cm2 and Pr =10.42 µC/cm2 achieved respectively for the first time with lower coercive field of Ec=2.047 kV/cm. The polarization current density-electric field measurement exhibits the peaking characteristics, confirms the saturation state of polarization for BT. The strain-electric field measurements revealed the "sprout" shape nature instead of typical "butterfly loop". This shows the excellent converse piezoelectric response with remnant strain ~ 0.212% and converse piezoelectric constant d*33 ~376.35 pm/V. The intrinsic electrostrictive coefficient was deduced from the variation of strain with polarization with electrostrictive coefficient Q33~ 0.03493m4/C2.

  12. Microstructure and ferroelectricity of BaTiO3 thin films on Si for integrated photonics

    NASA Astrophysics Data System (ADS)

    Kormondy, Kristy J.; Popoff, Youri; Sousa, Marilyne; Eltes, Felix; Caimi, Daniele; Rossell, Marta D.; Fiebig, Manfred; Hoffmann, Patrik; Marchiori, Chiara; Reinke, Michael; Trassin, Morgan; Demkov, Alexander A.; Fompeyrine, Jean; Abe, Stefan

    2017-02-01

    Significant progress has been made in integrating novel materials into silicon photonic structures in order to extend the functionality of photonic circuits. One of these promising optical materials is BaTiO3 or barium titanate (BTO) that exhibits a very large Pockels coefficient as required for high-speed light modulators. However, all previous demonstrations show a noticable reduction of the Pockels effect in BTO thin films deposited on silicon substrates compared to BTO bulk crystals. Here, we report on the strong dependence of the Pockels effect in BTO thin films on their microstructure, and provide guidelines on how to engineer thin films with strong electro-optic response. We employ several deposition methods such as molecular beam epitaxy and chemical vapor deposition to realize BTO thin films with different morphology and crystalline structure. While a linear electro-optic response is present even in porous, polycrystalline BTO thin films with an effective Pockels coefficient r eff = 6 pm V-1, it is maximized for dense, tetragonal, epitaxial BTO films (r eff = 140 pm V-1). By identifying the key structural predictors of electro-optic response in BTO/Si, we provide a roadmap to fully exploit the linear electro-optic effect in novel hybrid oxide/semiconductor nanophotonic devices.

  13. Microstructure and ferroelectricity of BaTiO3 thin films on Si for integrated photonics.

    PubMed

    Kormondy, Kristy J; Popoff, Youri; Sousa, Marilyne; Eltes, Felix; Caimi, Daniele; Rossell, Marta D; Fiebig, Manfred; Hoffmann, Patrik; Marchiori, Chiara; Reinke, Michael; Trassin, Morgan; Demkov, Alexander A; Fompeyrine, Jean; Abel, Stefan

    2017-02-17

    Significant progress has been made in integrating novel materials into silicon photonic structures in order to extend the functionality of photonic circuits. One of these promising optical materials is BaTiO3 or barium titanate (BTO) that exhibits a very large Pockels coefficient as required for high-speed light modulators. However, all previous demonstrations show a noticable reduction of the Pockels effect in BTO thin films deposited on silicon substrates compared to BTO bulk crystals. Here, we report on the strong dependence of the Pockels effect in BTO thin films on their microstructure, and provide guidelines on how to engineer thin films with strong electro-optic response. We employ several deposition methods such as molecular beam epitaxy and chemical vapor deposition to realize BTO thin films with different morphology and crystalline structure. While a linear electro-optic response is present even in porous, polycrystalline BTO thin films with an effective Pockels coefficient r eff = 6 pm V(-1), it is maximized for dense, tetragonal, epitaxial BTO films (r eff = 140 pm V(-1)). By identifying the key structural predictors of electro-optic response in BTO/Si, we provide a roadmap to fully exploit the linear electro-optic effect in novel hybrid oxide/semiconductor nanophotonic devices.

  14. Structural, Magnetic and Dielectric Properties of Fe-DOPED BaTiO3 Solids

    NASA Astrophysics Data System (ADS)

    Guo, Zhengang; Yang, Lihong; Qiu, Hongmei; Zhan, Xuedan; Yin, Jinhua; Cao, Lipeng

    The structural, ferroelectric and magnetic properties of bulk perovskite Fe-doped BaTiO3 (BFTO) prepared by standard solid-state reaction have been investigated. X-ray diffraction (XRD) identifies the tetragonal structure of BFTO samples. Rietveld refinements of XRD data indicates that the doping ions led to ab-plane expansion and out-of-ab-plane shrinkage of the BFTO phases. X-ray photoelectron spectroscopy (XPS) measurements for the prepared samples reveals that Fe3+ and Fe4+ ions replaces Ti4+ ions in the crystal lattice to form single-phase BFTO solids. The results of the temperature-dependent dielectric properties and magnetic hysteresis loops for the BFTO solids show simultaneously the ferroelectric order and ferromagnetic order at room temperature. The doping of magnetic element Fe brings about ferromagnetic order for the samples, and the measured magnetic moment for each Fe atom increases from 0.70 μB to 1.55 μB in BFTO samples. The origin of ferromagnetism of the BFTO samples should be attributed to the double exchange interactions of Fe3+-O2-Fe4+ ions.

  15. Structures and properties of La- and Sm-doped BaTiO3 sputtered films: Post-annealing and dopant effects

    NASA Astrophysics Data System (ADS)

    Wu, C. H.; Chu, J. P.; Chang, W. Z.; John, V. S.; Wang, S. F.; Lin, C. H.

    2008-01-01

    200-nm-thick La- and Sm-doped BaTiO3 thin films with A /B ratio of unity fabricated by magnetron sputtering on the Pt /Ti/SiO2/Si substrate have been characterized. The effects of post-annealing and the amount of dopant on structure and electrical properties were studied. X-ray diffraction studies reveal that the films annealed at 750°C show tetragonal BaTiO3 crystal structure without any detectable second phase formation. X-ray photoelectron spectroscopy results confirm that La substitutes the A site and Sm is in the B site in lightly doped films. La2O3 or Sm2O3 is present in the BaTiO3 structure when the dopant content is more than 1.4at.% La or 1.0% Sm. The permittivity increases with increasing annealing temperature up to 750°C due to the coarse grains and better crystallinity. The leakage current property is found to vary with the type of dopant.

  16. Effects of ultrasonication and conventional mechanical homogenization processes on the structures and dielectric properties of BaTiO3 ceramics.

    PubMed

    Akbas, Hatice Zehra; Aydin, Zeki; Yilmaz, Onur; Turgut, Selvin

    2017-01-01

    The effects of the homogenization process on the structures and dielectric properties of pure and Nb-doped BaTiO3 ceramics have been investigated using an ultrasonic homogenization and conventional mechanical methods. The reagents were homogenized using an ultrasonic processor with high-intensity ultrasonic waves and using a compact mixer-shaker. The components and crystal types of the powders were determined by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The complex permittivity (ε('), ε″) and AC conductivity (σ') of the samples were analyzed in a wide frequency range of 20Hz to 2MHz at room temperature. The structures and dielectric properties of pure and Nb-doped BaTiO3 ceramics strongly depend on the homogenization process in a solid-state reaction method. Using an ultrasonic processor with high-intensity ultrasonic waves based on acoustic cavitation phenomena can make a significant improvement in producing high-purity BaTiO3 ceramics without carbonate impurities with a small dielectric loss.

  17. BaTiO3 and polypropylene nanocomposites for capacitor applications

    NASA Astrophysics Data System (ADS)

    Dong, Daxuan; Tang, Longxiang; Zhu, Lei; Lee, Je; Case Western Reserve University Collaboration; Agiltron, Inc Collaboration

    2013-03-01

    A novel strategy to uniformly disperse 70-nm BaTiO3 ferroelectric nanoparticles in a dielectric polypropylene (PP) matrix is developed in order to achieve high dielectric constant and high energy density for capacitor applications. By modifying BaTiO3 surface with a bis-phosphonic acid-terminated polyhedral oligomeric selsisquioxane (POSS), a nanocomposite with BaTiO3@POSS uniformly dispersed in PP matrix was achieved. The nanocomposite film containing a high nanoparticle content of 30 vol.% exhibited a high dielectric constant of 32 and a breakdown voltage of 220 MV/m, but with a high energy loss. Improvement of this nanocomposite by understanding the interfacial polarization is carried out in this work. The dielectric constant difference between BaTiO3 and PP can generate interfacial polarization and subsequent internal conduction in BaTiO3 particles upon bipolar polarization. Reduction of this internal conduction mechanism will significantly reduce the hysteresis loss in polymer nanodielectrics.

  18. On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Tileli, Vasiliki; Duchamp, Martial; Axelsson, Anna-Karin; Valant, Matjaz; Dunin-Borkowski, Rafal E.; Alford, Neil Mcn.

    2014-11-01

    The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces.The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface

  19. Inorganic nanotubes and nanorods in liquid crystals

    NASA Astrophysics Data System (ADS)

    Drevenšek-Olenik, Irena

    Research efforts that focus on possible improvement of the physical properties of thermotropic liquid crystals by addition of inorganic 1D nanoparticles (inorganic nanotubes, nanorods, etc.) are reviewed. The emphasis is on modification of electro-optic switching characteristics relevant for display-related applications. In most cases the dopants generate a decrease of the threshold voltage for electrooptic switching and also a decrease of the corresponding switching times. We discuss various possible reasons for the observed effects and point out specific characteristics related to 1D nature of the dopants. We also describe investigations of inclusion of 1D nanoparticles into photo-polymerizable nematic liquid crystalline materials. Photo-polymerization in the aligned nematic phase provides a convenient way to fabricate solid polymer films with strongly anisotropic angular distribution of the nanoparticles. Investigations of structural and optical properties of some selected systems are surveyed.

  20. Photovoltaic properties of ferroelectric BaTiO3 thin films RF sputter deposited on silicon

    NASA Technical Reports Server (NTRS)

    Dharmadhikari, V. S.; Grannemann, W. W.

    1982-01-01

    Ferroelectric thin films of BaTiO3 have been successfully deposited on n-type silicon substrates at temperatures above 500 C by RF sputtering in an O2/Ar atmosphere. Analysis by X-ray diffraction patterns show that films deposited at room temperature are amorphous. At temperatures above 500 C, crystalline BaTiO3 films with a tetragonal structure are obtained. The polarization-electric field (P-E) hysteresis loops and a broad peak in the dielectric constant versus temperature curve at Curie point indicate that the RF sputtered BaTiO3 films are ferroelectric. An anomalous photovoltaic effect is observed in these thin films which is related to the remanent polarization of the material. The results on open-circuit and short-circuit measurements provide an important basis for a better understanding of the role of photovoltaic field, photovoltaic current, and the pyroelectric properties in photoferroelectric domain switching.

  1. Interfacial reactions and microstructure of BaTiO 3 films prepared using fluoride precursor method

    NASA Astrophysics Data System (ADS)

    Fujihara, Shinobu; Schneller, Theodor; Waser, Rainer

    2004-01-01

    Interfacial reactions of BaF 2 and TiO 2 were investigated in preparing BaTiO 3 thin films using a fluoride precursor method. Trifluoroacetate solutions were prepared from barium acetate, titanium tetraisopropoxide (TTIP), and trifluoroacetic acid (TFA, CF 3COOH) with additives such as water and acetylacetone. The solutions were deposited on platinized Si wafers by spin-coating, were pyrolysed at 400 °C in air and were finally heated typically at 700 °C in a water vapor atmosphere. The perovskite BaTiO 3 phase was obtained although a small portion of BaF 2 remained unreacted. Thus, the films were characterized as the mixture of BaTiO 3, BaF 2, and amorphous TiO 2. Influence of the solution chemistry on the phase evolution and microstructure was examined in order to discuss the reaction pathway of the perovskite phase.

  2. Second-harmonic generation of single BaTiO3 nanoparticles down to 22 nm diameter.

    PubMed

    Kim, Eugene; Steinbrück, Andrea; Buscaglia, Maria Teresa; Buscaglia, Vincenzo; Pertsch, Thomas; Grange, Rachel

    2013-06-25

    We investigate the second-harmonic generation (SHG) signal from single BaTiO3 nanoparticles of diameters varying from 70 nm down to 22 nm with a far-field optical microscope coupled to an infrared femtosecond laser. An atomic force microscope is first used to localize the individual particles and to accurately determine their sizes. Power and polarization-dependent measurements on the individual nanoparticles reveal a diameter range between 30 and 20 nm, where deviations from bulk nonlinear optical properties occur. For 22 nm diameter particles, the tetragonal crystal structure is not applicable anymore and competing effects due to the surface to volume ratio or crystallographic modifications are taking place. The demonstration of SHG from such small nanoparticles opens up the possibilities of using them as bright coherent biomarkers. Moreover, our work shows that measuring the SHG of individual nanoparticles reveals critical material properties, opening up new possibilities to investigate ferroelectricity at the nanoscale.

  3. Microstructure defects mediated charge transport in Nb-doped epitaxial BaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Zhou, Jian; Jing, Xiaosai; Alexe, Marin; Dai, Jiyan; Qin, Minghui; Wu, Sujuan; Zeng, Min; Gao, Jinwei; Lu, Xubing; Liu, J.-M.

    2016-05-01

    Nb-doped BaTiO3 (BNTO) films were deposited on MgO substrates at different substrate temperatures by pulsed laser deposition. The temperature dependence of their resistivity, carrier mobility and carrier concentration were systematically investigated. It reveals that the BNTO films deposited at lower temperature show higher resistivity and lower carrier mobility, and only show semiconductor characteristics at measurement temperatures ranging from 10 to 400 K. There is a metal-semiconductor transition at about 20 K for the films grown at relatively higher temperature. The intrinsic mechanism responsible for the different charge transport behavior was revealed by microstructure studies. Low crystal quality and high density of microstructure defects, observed for BNTO films grown at low temperatures, are, in particular, massively affecting the charge transport behavior of the BNTO films. The mediated charge transport of the microstructure defects is dominated by the thermal excitation process.

  4. Ferroelectric instabilities and enhanced piezoelectric response in Ce modified BaTiO3 lead-free ceramics

    NASA Astrophysics Data System (ADS)

    Brajesh, Kumar; Kalyani, Ajay Kumar; Ranjan, Rajeev

    2015-01-01

    The crystal structure, ferroelectric, and piezoelectric behaviors of the Ba(Ti1-xCex)O3 solid solution have been investigated at close composition intervals in the dilute concentration regime. Ce concentration as low as 2 mol. % induces tetragonal-orthorhombic instability and coexistence of the phases, leading to enhanced high-field strain and direct piezoelectric response. Detailed structural analysis revealed tetragonal + orthorhombic phase coexistence for x = 0.02, orthorhombic for 0.03 ≤ x ≤ 0.05, and orthorhombic + rhombohedral for 0.06 ≤ x ≤ 0.08. The results suggest that Ce-modified BaTiO3 is a potential lead-free piezoelectric material.

  5. Dielectric Properties of BaTiO3-Based Ceramics under High Electric Field

    NASA Astrophysics Data System (ADS)

    Tsurumi, Takaaki; Adachi, Hiroshige; Kakemoto, Hirofumi; Wada, Satoshi; Mizuno, Youichi; Chazono, Hirokazu; Kishi, Hiroshi

    2002-11-01

    The dielectric properties under a high electric field (ac-field) of BaTiO3-based ceramics with core grains, shell grains and core-shell grains were compared with those of multilayer ceramic capacitors (MLCCs) with these three kinds of grains. The MLCCs with the X7R specification had a core-shell structure, and the relative dielectric permittivity (\\varepsilonr) of the dielectric layers in the MLCCs increased with increasing ac-field. Similar behavior was observed in the MLCCs consisting of only cores, indicating that the core predominantly determined the dielectric properties of MLCCs under high ac-fields. The dielectric properties of MLCCs and ceramic plates consisting of only shell grains showed that the shell was the relaxor ferroelectrics. A slight change in the shell composition yielded a large shift of the peak temperature of \\varepsilonr. The shell improved the temperature stability of \\varepsilonr at low temperatures under low ac-fields. In a ceramic plate with relatively large BaTiO3 grains (approximately 3 μm), the maximum \\varepsilonr was observed at a moderate ac-field, which was explained from the electric displacement vs electric field hysteresis curves of ferroelectric BaTiO3. The MLCCs and ceramics plates with fine BaTiO3 grains (0.4 to 0.5 μm) showed similar dielectric behavior to the MLCC with the core-shell structure. The size effect of BaTiO3 played an important role in determining the temperature stability of \\varepsilonr. For future MLCCs with very thin dielectric layers, a microstructure with fine BaTiO3 grains and grain boundary layers of the shell was proposed.

  6. Effect of surface moisture on dielectric behavior of ultrafine BaTiO3 particulates.

    NASA Technical Reports Server (NTRS)

    Mountvala, A. J.

    1971-01-01

    The effects of adsorbed H2O on the dielectric properties of ultrafine BaTiO3 particulates of varying particle size and environmental history were determined. The dielectric behavior depends strongly on surface hydration. No particle size dependence of dielectric constant was found for dehydroxylated surfaces in ultrafine particulate (unsintered) BaTiO3 materials. For equivalent particle sizes, the ac conductivity is sensitive to surface morphology. Reactions with H2O vapor appear to account for the variations in dielectric properties. Surface dehydration was effectively accomplished by washing as-received powders in isopropanol.

  7. Nanocomposites of carbon nanotube fibers prepared by polymer crystallization.

    PubMed

    Zhang, Shanju; Lin, Wei; Wong, Ching-Ping; Bucknall, David G; Kumar, Satish

    2010-06-01

    Nanocomposites of carbon nanotube fibers have been prepared using controlled polymer crystallization confined in nanotube aerogel fibers. The polyethylene nanocomposites have been investigated by means of polarized optical microscopy (POM), scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD). The individual nanotubes are periodically decorated with polyethylene nanocrystals, forming aligned hybrid shish-kebab nanostructures. After melting and recrystallization, transcrystalline lamellae connecting the adjacent aligned nanotubes develop. Microstructural analysis shows that the nanotubes can nucleate the growth of both orthorhombic and monoclinic crystals of polyethylene in the quiescent state. The tensile strength, modulus, and axial electrical conductivity of these polyethylene/CNT composite fibers are as high as 600 MPa, 60 GPa, and 5000 S/m, respectively.

  8. Carbon nanotubes in thermotropic low molar mass liquid crystals

    NASA Astrophysics Data System (ADS)

    Schymura, Stefan; Park, Ji Hyun; Dierking, Ingo; Scalia, Giusy

    Carbon nanotubes constitute a highly anisotropic form of carbon with outstanding mechanical, thermal and electrical properties. Their dispersion and organization are important but challenging and this chapter describes the advantages of using thermotropic liquid crystals as host for nanotube dispersion and ordering. The self organization of LCs is an attractive way to manipulate nanoparticles such as carbon nanotubes or graphene akes. Compared to standard carbon nanotube composites (e.g. with disordered polymer hosts) the introduction of the nanotubes into an LC allows not only the transfer of the outstanding nanotube properties to the oscopic phase, providing strength and conductivity, but these properties also become anisotropic, following the transfer of the orientational order from the LC to the CNTs...

  9. Photoinduced charge transfer properties and photocatalytic activity in Bi2O3/BaTiO3 composite photocatalyst.

    PubMed

    Fan, Haimei; Li, Haiyan; Liu, Bingkun; Lu, Yongchun; Xie, Tengfeng; Wang, Dejun

    2012-09-26

    A series of Bi(2)O(3)/BaTiO(3) composite photocatalysts with different mass ratios of Bi(2)O(3) vs BaTiO(3) were prepared by an impregnating-annealing method. X-ray diffraction (XRD), high-resolution transmission electron microscopic (HRTEM), and UV-vis diffuse reflection spectroscopy (DRS) confirmed that Bi(2)O(3) and BaTiO(3) coexisted in the composites. The results of surface photovoltage (SPV) experiments showed enhancements of photovoltaic response in composites, which indicated a higher separation efficiency of photoinduced charges due to the establishment of an efficient interfacial electric field between Bi(2)O(3) and BaTiO(3) in the composites. The consistency of phtocatalytic activity and photovoltaic response intensity of photocatalysts showed that the efficiency interfacial electric field between Bi(2)O(3) and BaTiO(3) played an important role in improving the degradation efficiency of Rhodamine B (RhB). The 60%-Bi(2)O(3)/BaTiO(3) sample with the best activity was found by optimizing the mass ratios of Bi(2)O(3) vs. BaTiO(3). On the basis of the work function (WF) measurements, a reasonable energy band diagram was proposed for BaTiO(3)/Bi(2)O(3) composite. It would be helpful in designing and constructing high efficiency heterogeneous semiconductor photocatalyst.

  10. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure

    NASA Astrophysics Data System (ADS)

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Do Kim, Keum; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-01

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization – voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization.

  11. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure.

    PubMed

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Kim, Keum Do; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-08

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization - voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization.

  12. Comparison of rheological, mechanical, electrical properties of HDPE filled with BaTiO3 with different polar surface tension

    NASA Astrophysics Data System (ADS)

    Su, Jun; Zhang, Jun

    2016-12-01

    In this work, three types of coupling agents: isopropyl trioleic titanate (NDZ105), vinyltriethoxysilane (SG-Si151), 3-aminopropyltriethoxysilane (KH550) were applied to modify the surface tension of Barium titanate (BaTiO3) particles. The Fourier transform infrared (FT-IR) spectra confirm the chemical adherence of coupling agents to the particle surface. The long hydrocarbon chains in NDZ105 can cover the particle surface and reduce the polar surface tension of BaTiO3 from 37.53 mJ/m2 to 7.51 mJ/m2, turning it from hydrophilic to oleophilic properties. The short and non-polar vinyl groups in SG-Si151 does not influence the surface tension of BaTiO3, but make BaTiO3 have both hydrophilic and oleophilic properties. The polar amino in KH550 can keep BaTiO3 still with hydrophilic properties. It is found that SG-Si151 modified BaTiO3 has the lowest interaction with HDPE matrix, lowering the storage modulus of HDPE composites to the greatest extent. As for mechanical properties, the polar amino groups in KH550 on BaTiO3 surface can improve the adhesion of BaTiO3 with HDPE matrix, which increases the elongation at break of HDPE composites to the greatest extent. In terms of electrical properties, the polar amino groups on surface of BaTiO3 can boost the dielectric properties of HDPE/BaTiO3 composites and decrease the volume resistivity of HDPE/BaTiO3 composites. The aim of this study is to investigate how functional groups affect the rheological, mechanical and electrical properties of HDPE composites and to select a coupling agent to produce HDPE/BaTiO3 composites with low dielectric loss, high dielectric constant and elongation at break.

  13. Enhancement of nonlinear optical properties of BaTiO3 nanoparticles by the addition of silver seeds.

    PubMed

    Yust, Brian G; Razavi, Neema; Pedraza, Francisco; Elliott, Zakary; Tsin, Andrew T; Sardar, Dhiraj K

    2012-11-19

    Barium titanate (BaTiO3) is a technologically important material because of its nonlinear properties, such as its strong second harmonic generation and high third order susceptibility. While many nonlinear effects have been extensively studied on the bulk scale, there are still questions regarding the strength of nonlinear effects in nanoparticles. The nonlinear properties of BaTiO3 nanoparticles and nanorods have been studied using the closed aperture z-scan technique. Silver was then grown photochemically on the surface of the BaTiO3 nanoparticles, and it was found that the third order susceptibility increases dramatically.

  14. Structure and Catalytic Activity of Cr-Doped BaTiO3 Nanocatalysts Synthesized by Conventional Oxalate and Microwave Assisted Hydrothermal Methods.

    PubMed

    Srilakshmi, Chilukoti; Saraf, Rohit; Prashanth, V; Rao, G Mohan; Shivakumara, C

    2016-05-16

    In the present study synthesis of BaTi1-xCrxO3 nanocatalysts (x = 0.0 ≤ x ≤ 0.05) by conventional oxalate and microwave assisted hydrothermal synthesis methods was carried out to investigate the effect of synthesis methods on the physicochemical and catalytic properties of nanocatalysts. These catalysts were thoroughly characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 physisortion, and total acidity by pyridine adsorption method. Their catalytic performance was evaluated for the reduction of nitrobenzene using hydrazine hydrate as the hydrogen source. Structural parameters refined by Rietveld analysis using XRD powder data indicate that BaTi1-xCrxO3 conventional catalysts were crystallized in the tetragonal BaTiO3 structure with space group P4mm, and microwave catalysts crystallized in pure cubic BaTiO3 structure with space group Pm3̅m. TEM analysis of the catalysts reveal spherical morphology of the particles, and these are uniformly dispersed in microwave catalysts whereas agglomeration of the particles was observed in conventional catalysts. Particle size of the microwave catalysts is found to be 20-35 nm compared to conventional catalysts (30-48 nm). XPS studies reveal that Cr is present in the 3+ and 6+ mixed valence state in all the catalysts. Microwave synthesized catalysts showed a 4-10-fold increase in surface area and pore volume compared to conventional catalysts. Acidity of the BaTiO3 catalysts improved with Cr dopant in the catalysts, and this could be due to an increase in the number of Lewis acid sites with an increase in Cr content of all the catalysts. Catalytic reduction of nitrobenzene to aniline studies reveals that BaTiO3 synthesized by microwave is very active and showed 99.3% nitrobenzene conversion with 98.2% aniline yield. The presence of Cr in the catalysts facilitates a faster reduction reaction in all the

  15. Enhancement of tetragonal anisotropy and stabilisation of the tetragonal phase by Bi/Mn-double-doping in BaTiO3 ferroelectric ceramics

    PubMed Central

    Yabuta, Hisato; Tanaka, Hidenori; Furuta, Tatsuo; Watanabe, Takayuki; Kubota, Makoto; Matsuda, Takanori; Ifuku, Toshihiro; Yoneda, Yasuhiro

    2017-01-01

    To stabilise ferroelectric-tetragonal phase of BaTiO3, the double-doping of Bi and Mn up to 0.5 mol% was studied. Upon increasing the Bi content in BaTiO3:Mn:Bi, the tetragonal crystal-lattice-constants a and c shrank and elongated, respectively, resulting in an enhancement of tetragonal anisotropy, and the temperature-range of the ferroelectric tetragonal phase expanded. X-ray absorption fine structure measurements confirmed that Bi and Mn were located at the A(Ba)-site and B(Ti)-site, respectively, and Bi was markedly displaced from the centrosymmetric position in the BiO12 cluster. This A-site substitution of Bi also caused fluctuations of B-site atoms. Magnetic susceptibility measurements revealed a change in the Mn valence from +4 to +3 upon addition of the same molar amount of Bi as Mn, probably resulting from a compensating behaviour of the Mn at Ti4+ sites for donor doping of Bi3+ into the Ba2+ site. Because addition of La3+ instead of Bi3+ showed neither the enhancement of the tetragonal anisotropy nor the stabilisation of the tetragonal phase, these phenomena in BaTiO3:Mn:Bi were not caused by the Jahn-Teller effect of Mn3+ in the MnO6 octahedron, but caused by the Bi-displacement, probably resulting from the effect of the 6 s lone-pair electrons in Bi3+. PMID:28367973

  16. XMCD studies of thin Co films on BaTiO3

    NASA Astrophysics Data System (ADS)

    Welke, M.; Gräfe, J.; Govind, R. K.; Babu, V. H.; Trautmann, M.; Schindler, K.-M.; Denecke, R.

    2015-08-01

    Different layer thicknesses of cobalt ranging from 2.6 Å (1.5 ML) up to 55 Å (30.5 ML) deposited on ferroelectric BaTiO3 have been studied regarding their magnetic behavior. The layers have been characterized using XMCD spectroscopy at remanent magnetization. After careful data analysis the magnetic moments of the cobalt could be determined using the sum rule formalism. There is a sudden and abrupt onset in magnetism starting at thicknesses of 9 Å (5 ML) of cobalt for measurements at 120 K and of 10 Å (5.5 ML) if measured at room temperature. Initial island growth and subsequent coalescence of Co on BaTiO3 is suggested to explain the sudden onset. In that context, no magnetically dead layers are observed.

  17. Directing peptide crystallization through curvature control of nanotubes.

    PubMed

    Gobeaux, Frédéric; Tarabout, Christophe; Fay, Nicolas; Meriadec, Cristelle; Ligeti, Melinda; Buisson, David-Alexandre; Cintrat, Jean-Christophe; Artzner, Franck; Paternostre, Maïté

    2014-07-01

    In the absence of efficient crystallization methods, the molecular structures of fibrous assemblies have so far remained rather elusive. In this paper, we present a rational method to crystallize the lanreotide octapeptide by modification of a residue involved in a close contact. Indeed, we show that it is possible to modify the curvature of the lanreotide nanotubes and hence their diameter. This fine tuning leads to crystallization because the radius of curvature of the initially bidimensional peptide wall can be increased up to a point where the wall is essentially flat and a crystal is allowed to grow along a third dimension. By comparing X-ray diffraction data and Fourier transform Raman spectra, we show that the nanotubes and the crystals share similar cell parameters and molecular conformations, proving that there is indeed a structural continuum between these two morphologies. These results illustrate a novel approach to crystallization and represent the first step towards the acquisition of an Å-resolution structure of the lanreotide nanotubes β-sheet assembly.

  18. Crystal orbital study on the double walls made of nanotubes encapsulated inside zigzag carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Qiao, Weiye; Li, Yuliang; Huang, Yuanhe

    2015-01-01

    The structure stabilities and electronic properties are investigated by using ab initio self-consistent-field crystal orbital method based on density functional theory for the one-dimensional (1D) double-wall nanotubes made of n-gon SiO2 nanotubes encapsulated inside zigzag carbon nanotubes. It is found that formation of the combined systems is energetically favorable when the distance between the two constituents is around the Van der Waals scope. The obtained band structures show that all the combined systems are semiconductors with nonzero energy gaps. The frontier energy bands (the highest occupied band and the lowest unoccupied band) of double-wall nanotubes are mainly derived from the corresponding carbon nanotubes. The mobilities of charge carriers are calculated to be within the range of 102-104 cm2 V-1 s-1 for the hybrid double-wall nanotubes. Young's moduli are also calculated for the combined systems. For the comparison, geometrical and electronic properties of n-gon SiO2 nanotubes are also calculated and discussed.

  19. Crystal orbital study on the double walls made of nanotubes encapsulated inside zigzag carbon nanotubes

    SciTech Connect

    Zhao, Xin; Qiao, Weiye; Li, Yuliang; Huang, Yuanhe

    2015-01-15

    The structure stabilities and electronic properties are investigated by using ab initio self-consistent-field crystal orbital method based on density functional theory for the one-dimensional (1D) double-wall nanotubes made of n-gon SiO{sub 2} nanotubes encapsulated inside zigzag carbon nanotubes. It is found that formation of the combined systems is energetically favorable when the distance between the two constituents is around the Van der Waals scope. The obtained band structures show that all the combined systems are semiconductors with nonzero energy gaps. The frontier energy bands (the highest occupied band and the lowest unoccupied band) of double-wall nanotubes are mainly derived from the corresponding carbon nanotubes. The mobilities of charge carriers are calculated to be within the range of 10{sup 2}–10{sup 4} cm{sup 2} V{sup −1} s{sup −1} for the hybrid double-wall nanotubes. Young’s moduli are also calculated for the combined systems. For the comparison, geometrical and electronic properties of n-gon SiO{sub 2} nanotubes are also calculated and discussed. - Graphical abstract: Structures and band structures of the optimum 1D Double walls nanotubes. The optimized structures are 3-gon SiO2@(15,0), 5-gon SiO2@(17,0), 6-gon SiO2@(18,0) and 7-gon SiO2@(19,0). - Highlights: • The structure and electronic properties of the 1D n-gon SiO{sub 2}@(m,0)s are studied using SCF-CO method. • The encapsulation of 1D n-gon SiO{sub 2} tubes inside zigzag carbon nanotubes can be energetically favorable. • The 1D n-gon SiO{sub 2}@(m,0)s are all semiconductors. • The mobility of charge carriers and Young’s moduli are calculated.

  20. Novel Piezoelectric Paper‐Based Flexible Nanogenerators Composed of BaTiO3 Nanoparticles and Bacterial Cellulose

    PubMed Central

    Zhang, Guangjie; Liao, Qingliang; Zhang, Zheng; Liang, Qijie; Zhao, Yingli; Zheng, Xin

    2015-01-01

    A piezoelectric paper based on BaTiO3 (BTO) nanoparticles and bacterial cellulose (BC) with excellent output properties for application of nanogenerators (NGs) is reported. A facile and scalable vacuum filtration method is used to fabricate the piezoelectric paper. The BTO/BC piezoelectric paper based NG shows outstanding output performance with open‐circuit voltage of 14 V and short‐circuit current density of 190 nA cm−2. The maximum power density generated by this unique BTO/BC structure is more than ten times higher than BTO/polydimethylsiloxane structure. In bending conditions, the NG device can generate output voltage of 1.5 V, which is capable of driving a liquid crystal display screen. The improved performance can be ascribed to homogeneous distribution of piezoelectric BTO nanoparticles in the BC matrix as well as the enhanced stress on piezoelectric nanoparticles implemented by the unique percolated networks of BC nanofibers. The flexible BTO/BC piezoelectric paper based NG is lightweight, eco‐friendly, and cost‐effective, which holds great promises for achieving wearable or implantable energy harvesters and self‐powered electronics. PMID:27774389

  1. Novel Piezoelectric Paper-Based Flexible Nanogenerators Composed of BaTiO3 Nanoparticles and Bacterial Cellulose.

    PubMed

    Zhang, Guangjie; Liao, Qingliang; Zhang, Zheng; Liang, Qijie; Zhao, Yingli; Zheng, Xin; Zhang, Yue

    2016-02-01

    A piezoelectric paper based on BaTiO3 (BTO) nanoparticles and bacterial cellulose (BC) with excellent output properties for application of nanogenerators (NGs) is reported. A facile and scalable vacuum filtration method is used to fabricate the piezoelectric paper. The BTO/BC piezoelectric paper based NG shows outstanding output performance with open-circuit voltage of 14 V and short-circuit current density of 190 nA cm(-2). The maximum power density generated by this unique BTO/BC structure is more than ten times higher than BTO/polydimethylsiloxane structure. In bending conditions, the NG device can generate output voltage of 1.5 V, which is capable of driving a liquid crystal display screen. The improved performance can be ascribed to homogeneous distribution of piezoelectric BTO nanoparticles in the BC matrix as well as the enhanced stress on piezoelectric nanoparticles implemented by the unique percolated networks of BC nanofibers. The flexible BTO/BC piezoelectric paper based NG is lightweight, eco-friendly, and cost-effective, which holds great promises for achieving wearable or implantable energy harvesters and self-powered electronics.

  2. Crystalline structures, thermal properties and crystallizing mechanism of polyamide 6 nanotubes in confined space

    NASA Astrophysics Data System (ADS)

    Li, Xiaoru; Peng, Zhi; Yang, Chao; Han, Ping; Song, Guojun; Cong, Longliang

    2016-09-01

    The polyamide 6 (PA6) nanotubes were prepared by infiltrating the anodic aluminum oxide templates with polymer solution. Crystalline regions in the nanotube walls were detected by high-resolution transmission electron microscopy (HRTEM). X-ray diffraction (XRD), Fast Fourier Transform (FFT) and differential scanning calorimetry (DSC) techniques were employed to investigate crystallization, crystal faces and thermodynamics. It was found that the crystals were transformed from α-form in bulk to γ-form in nanotubes. It was made a detailed analysis in this article. Moreover, schematic diagram for the crystallizing mechanism of PA6 nanotubes was given to explain PA6 molecules how to crystallize in the nano-pores.

  3. Conformal BaTiO3 Films with High Piezoelectric Coupling through an Optimized Hydrothermal Synthesis.

    PubMed

    Zhou, Zhi; Bowland, Christopher C; Patterson, Brendan A; Malakooti, Mohammad H; Sodano, Henry A

    2016-08-24

    Two-dimensional (2D) ferroelectric films have vast applications due to their dielectric, ferroelectric, and piezoelectric properties that meet the requirements of sensors, nonvolatile ferroelectric random access memory (NVFeRAM) devices, and micro-electromechanical systems (MEMS). However, the small surface area of these 2D ferroelectric films has limited their ability to achieve higher memory storage density in NVFeRAM devices and more sensitive sensors and transducer. Thus, conformally deposited ferroelectric films have been actively studied for these applications in order to create three-dimensional (3D) structures, which lead to a larger surface area. Most of the current methods developed for the conformal deposition of ferroelectric films, such as metal-organic chemical vapor deposition (MOCVD) and plasma-enhanced vapor deposition (PECVD), are limited by high temperatures and unstable and toxic organic precursors. In this paper, an innovative fabrication method for barium titanate (BaTiO3) textured films with 3D architectures is introduced to alleviate these issues. This fabrication method is based on converting conformally grown rutile TiO2 nanowire arrays into BaTiO3 textured films using a simple two-step hydrothermal process which allows for thickness-controlled growth of conformal films on patterned silicon wafers coated with fluorine-doped tin oxide (FTO). Moreover, the processing parameters have been optimized to achieve a high piezoelectric coupling coefficient of 100 pm/V. This high piezoelectric response along with high relative dielectric constant (εr = 1600) of the conformally grown textured BaTiO3 films demonstrates their potential application in sensors, NVFeRAM, and MEMS.

  4. Inverse barocaloric effects in ferroelectric BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Stern-Taulats, E.; Lloveras, P.; Barrio, M.; Defay, E.; Egilmez, M.; Planes, A.; Tamarit, J.-LI.; Mañosa, Ll.; Mathur, N. D.; Moya, X.

    2016-09-01

    We use calorimetry to identify pressure-driven isothermal entropy changes in ceramic samples of the prototypical ferroelectric BaTiO3. Near the structural phase transitions at ˜400 K (cubic-tetragonal) and ˜280 K (tetragonal-orthorhombic), the inverse barocaloric response differs in sign and magnitude from the corresponding conventional electrocaloric response. The differences in sign arise due to the decrease in unit-cell volume on heating through the transitions, whereas the differences in magnitude arise due to the large volumetric thermal expansion on either side of the transitions.

  5. Impact of Fe on structural modification and room temperature magnetic ordering in BaTiO3

    NASA Astrophysics Data System (ADS)

    Rajan, Soumya; Gazzali, P. M. Mohammed; Chandrasekaran, G.

    2017-01-01

    Ba1 - xFexTiO3 (x = 0, 0.005, 0.01) polycrystalline ceramics are prepared using solid state reaction method. Structural studies through XRD, Raman and XPS confirm single tetragonal phase for BaTiO3 whereas a structural disorder tends to intervene with the introduction of smaller Fe ions which reduces the tolerance factor and tetragonality ratio. Grain size of the samples is estimated using SEM micrographs with ImageJ software and chemical composition is confirmed using EDX spectra. Raman spectra measured in the temperature range of 303 K to 573 K showers light on the structural phase transition exploiting a significant disappearance of the 306 cm- 1 mode. Further, structural analyses suggest the entry of Fe into the B-site upon increasing its concentration in BaTiO3. The dopant sensitive modes lying at around 640 cm- 1 and 650 cm- 1 are assigned to lattice strain. A reduction in ferroelectric to paraelectric transition temperature is observed with a transformation from diffused type to normal ferroelectric upon the increased Fe content. The oxidation state of Fe in the BaTiO3 lattice has been decided using EPR Spectra precisely. Room temperature magnetic ordering is observed in Fe substituted BaTiO3 using PPMS. The coexistence of ferroelectric and magnetic ordering is established in the present study for optimized Fe substituted BaTiO3.

  6. Electromagnetic properties and microwave absorption properties of BaTiO 3-carbonyl iron composite in S and C bands

    NASA Astrophysics Data System (ADS)

    Rui-gang, Yang

    2011-07-01

    BaTiO3 powders are prepared by sol-gel method. The carbonyl iron powder is prepared via thermal decomposition of iron pentacarbonyl. Then BaTiO3-carbonyl iron composite with different mixture ratios was prepared using the as-prepared material. The structure, morphology, and properties of the composites are characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron microscopy (SEM), and a network analyzer. The complex permittivity and reflection loss of the composites have been measured at different microwave frequencies in S- and C-bands employing vector network analyzer model PNA 3629D vector. The effect of the mass ratio of BaTiO3/carbonyl iron on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of BaTiO3-carbonyl iron composite has been proposed. The BaTiO3-carbonyl iron composite can find applications in suppression of electromagnetic interference, and reduction of radar signature.

  7. Antibacterial activity of TiO2 nanotubes: Influence of crystal phase, morphology and Ag deposition

    NASA Astrophysics Data System (ADS)

    Li, Huirong; Cui, Qiang; Feng, Bo; Wang, Jianxin; Lu, Xiong; Weng, Jie

    2013-11-01

    TiO2 nanotubes on Ti substrate were fabricated by electrochemical anodization. Ag nanoparticles were deposited on the TiO2 nanotubes by a silver mirror reaction. Antibacterial activity of the nanotubes with different structural features was evaluated by a culture test with Escherichia coli bacteria. The anatase nanotubes showed the highest antibacterial activity among three crystal phases including anatase, rutile and amorphous titania. The diameters of the nanotubes affected the antibacterial activity. The two nanotubes with 200 nm and 50 nm diameters had higher antibacterial rate than those with other diameters. The antibacterial activity of the nanotubes was independent on their lengths. Ag-deposited nanotubes exhibited excellent antibacterial activity and its antibacterial rate was up to approximately 100%. TiO2 nanotubes and Ag-deposited nanotubes on titanium should be potential for antibacterial applications in clinics and industry, especially regarding with their reusability.

  8. Fabrication of BaTiO3 Thin Films Using Modified Chemical Solutions and Sintering Method

    NASA Astrophysics Data System (ADS)

    Tanaka, Kiyotaka; Suzuki, Kazuyuki; Kato, Kazumi

    2008-09-01

    BaTiO3 thin films were fabricated at 650 °C by single sintering using additive-free and diethanolamine (DEA)-modified alkoxide solutions. The BaTiO3 thin films derived from the DEA-modified solution had a flat surface and an rms roughness below 2.5 nm. The grain size on Pt/Ti/SiO2/Si substrates single-sintered at 650 °C for 100 min was estimated to be about 34 to 43 nm. We succeeded in obtaining the electric properties of Pt/BaTiO3/Pt capacitors by single sintering at 650 °C for 1 min. The dielectric constant ɛr and dielectric loss tan δ at 1 MHz were 110 and 0.05, respectively. On the other hand, the grain size on SiO2/Si substrates single-sintered at 650 °C for 100 min reached about 55 to 62 nm. For the thickness and Fourier-transform infrared (FT-IR) spectra of the gel films, it was found that the thickness of the gel films at around 200 °C derived from the DEA-modified solution became abnormally thick and that the intermediate compounds generated during the decomposition of DEA remained in the gel films.

  9. Understanding the peculiarities of the piezoelectric effect in macro-porous BaTiO3.

    PubMed

    Roscow, James I; Topolov, Vitaly Yu; Bowen, Christopher R; Taylor, John; Panich, Anatoly E

    2016-01-01

    This work demonstrates the potential of porous BaTiO3 for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO3 ceramics for piezoelectric applications are manufactured for a range of relative densities, α = 0.30-0.95, using the burned out polymer spheres method. The piezoelectric activity and relevant parameters for specific applications are interpreted by developing two models: a model of a 3-0 composite and a 'composite in composite' model. The appropriate ranges of relative density for the application of these models to accurately predict piezoelectric properties are examined. The two models are extended to take into account the effect of 90° domain-wall mobility within ceramic grains on the piezoelectric coefficients [Formula: see text]. It is shown that porous ferroelectrics provide a novel route to form materials with large piezoelectric anisotropy [Formula: see text] at 0.20 ≤ α ≤ 0.45 and achieve a high squared figure of merit [Formula: see text] [Formula: see text]. The modelling approach allows a detailed analysis of the relationships between the properties of the monolithic and porous materials for the design of porous structures with optimum properties.

  10. Understanding the peculiarities of the piezoelectric effect in macro-porous BaTiO3

    PubMed Central

    Roscow, James I.; Topolov, Vitaly Yu.; Bowen, Christopher R.; Taylor, John; Panich, Anatoly E.

    2016-01-01

    Abstract This work demonstrates the potential of porous BaTiO3 for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO3 ceramics for piezoelectric applications are manufactured for a range of relative densities, α = 0.30–0.95, using the burned out polymer spheres method. The piezoelectric activity and relevant parameters for specific applications are interpreted by developing two models: a model of a 3–0 composite and a ‘composite in composite’ model. The appropriate ranges of relative density for the application of these models to accurately predict piezoelectric properties are examined. The two models are extended to take into account the effect of 90° domain-wall mobility within ceramic grains on the piezoelectric coefficients d3j*. It is shown that porous ferroelectrics provide a novel route to form materials with large piezoelectric anisotropy d33*d31*>>1 at 0.20 ≤ α ≤ 0.45 and achieve a high squared figure of merit d33* g33*. The modelling approach allows a detailed analysis of the relationships between the properties of the monolithic and porous materials for the design of porous structures with optimum properties. PMID:27933117

  11. Microwave dielectric characterisation of 3D-printed BaTiO3/ABS polymer composites

    PubMed Central

    Castles, F.; Isakov, D.; Lui, A.; Lei, Q.; Dancer, C. E. J.; Wang, Y.; Janurudin, J. M.; Speller, S. C.; Grovenor, C. R. M.; Grant, P. S.

    2016-01-01

    3D printing is used extensively in product prototyping and continues to emerge as a viable option for the direct manufacture of final parts. It is known that dielectric materials with relatively high real permittivity—which are required in important technology sectors such as electronics and communications—may be 3D printed using a variety of techniques. Among these, the fused deposition of polymer composites is particularly straightforward but the range of dielectric permittivities available through commercial feedstock materials is limited. Here we report on the fabrication of a series of composites composed of various loadings of BaTiO3 microparticles in the polymer acrylonitrile butadiene styrene (ABS), which may be used with a commercial desktop 3D printer to produce printed parts containing user-defined regions with high permittivity. The microwave dielectric properties of printed parts with BaTiO3 loadings up to 70 wt% were characterised using a 15 GHz split post dielectric resonator and had real relative permittivities in the range 2.6–8.7 and loss tangents in the range 0.005–0.027. Permittivities were reproducible over the entire process, and matched those of bulk unprinted materials, to within ~1%, suggesting that the technique may be employed as a viable manufacturing process for dielectric composites. PMID:26940381

  12. Quantitative study of band structure in BaTiO3 particles with vacant ionic sites

    NASA Astrophysics Data System (ADS)

    Oshime, Norihiro; Kano, Jun; Ikeda, Naoshi; Teranishi, Takashi; Fujii, Tatsuo; Ueda, Takeji; Ohkubo, Tomoko

    2016-10-01

    Levels of the conduction band minimum and the valence band maximum in ion-deficient BaTiO3 particles were investigated with optical band gap and ionization energy measurements. Though it is known that the quantification of the band structure in an insulator is difficult, due to the poor electrical conductivity of BaTiO3, systematic variation in the band energy levels was found that correlated with the introduction of vacancies. Photoelectron yield spectroscopy provided direct observation of the occupancy level of electrons, which is altered by the presence of oxygen and barium vacancies. In addition, the conduction band deviation from the vacuum level was determined by optical reflectance spectroscopy. Our results show that: (1) Introduction of oxygen vacancies forms a donor level below the conduction band. (2) The conduction band is shifted to a lower level by a larger number of oxygen vacancies, while the valence band also shifts to a lower level, due to the reduction in the density of O 2p orbitals. (3) Introduction of barium vacancies widens the band gap. Since barium vacancies can induce a small number of oxygen vacancies with accompanying charge compensation, this behavior suppresses any large formation of donor levels in the gap states, indicating that cation vacancies can control the number of both donor and acceptor levels.

  13. Microwave dielectric characterisation of 3D-printed BaTiO3/ABS polymer composites

    NASA Astrophysics Data System (ADS)

    Castles, F.; Isakov, D.; Lui, A.; Lei, Q.; Dancer, C. E. J.; Wang, Y.; Janurudin, J. M.; Speller, S. C.; Grovenor, C. R. M.; Grant, P. S.

    2016-03-01

    3D printing is used extensively in product prototyping and continues to emerge as a viable option for the direct manufacture of final parts. It is known that dielectric materials with relatively high real permittivity—which are required in important technology sectors such as electronics and communications—may be 3D printed using a variety of techniques. Among these, the fused deposition of polymer composites is particularly straightforward but the range of dielectric permittivities available through commercial feedstock materials is limited. Here we report on the fabrication of a series of composites composed of various loadings of BaTiO3 microparticles in the polymer acrylonitrile butadiene styrene (ABS), which may be used with a commercial desktop 3D printer to produce printed parts containing user-defined regions with high permittivity. The microwave dielectric properties of printed parts with BaTiO3 loadings up to 70 wt% were characterised using a 15 GHz split post dielectric resonator and had real relative permittivities in the range 2.6–8.7 and loss tangents in the range 0.005–0.027. Permittivities were reproducible over the entire process, and matched those of bulk unprinted materials, to within ~1%, suggesting that the technique may be employed as a viable manufacturing process for dielectric composites.

  14. Microwave dielectric characterisation of 3D-printed BaTiO3/ABS polymer composites.

    PubMed

    Castles, F; Isakov, D; Lui, A; Lei, Q; Dancer, C E J; Wang, Y; Janurudin, J M; Speller, S C; Grovenor, C R M; Grant, P S

    2016-03-04

    3D printing is used extensively in product prototyping and continues to emerge as a viable option for the direct manufacture of final parts. It is known that dielectric materials with relatively high real permittivity-which are required in important technology sectors such as electronics and communications-may be 3D printed using a variety of techniques. Among these, the fused deposition of polymer composites is particularly straightforward but the range of dielectric permittivities available through commercial feedstock materials is limited. Here we report on the fabrication of a series of composites composed of various loadings of BaTiO3 microparticles in the polymer acrylonitrile butadiene styrene (ABS), which may be used with a commercial desktop 3D printer to produce printed parts containing user-defined regions with high permittivity. The microwave dielectric properties of printed parts with BaTiO3 loadings up to 70 wt% were characterised using a 15 GHz split post dielectric resonator and had real relative permittivities in the range 2.6-8.7 and loss tangents in the range 0.005-0.027. Permittivities were reproducible over the entire process, and matched those of bulk unprinted materials, to within ~1%, suggesting that the technique may be employed as a viable manufacturing process for dielectric composites.

  15. First-principles study for vacancy-induced magnetism in nonmagnetic ferroelectric BaTiO3.

    PubMed

    Cao, D; Cai, M Q; Zheng, Yue; Hu, W Y

    2009-12-14

    The possibilities of vacancy-induced magnetism in perovskite BaTiO(3) are investigated by first-principles calculations. Calculated results show that both titanium and oxygen vacancies could induce magnetism, but the barium vacancy did not induce magnetism. New and interesting magnetic properties of half-metallic magnetism are found in BaTiO(3) induced by the Ti-vacancy. Based on the density of states and the spin charge density distribution of BaTiO(3), we discuss the different origins of magnetism induced by the partial spin-polarized O 2p states around Ti vacancies and the partially filled d-states Ti around the oxygen vacancies. The discrepancy between the magnetic moments in the cubic phase and the tetragonal phase is due to anisotropic spin polarization induced by structure distortions. Our calculations would enable exploring magneto-electric coupling in nonmagnetic ferroelectric oxides.

  16. Emergence of Long-Range Order in BaTiO3 from Local Symmetry-Breaking Distortions

    NASA Astrophysics Data System (ADS)

    Senn, M. S.; Keen, D. A.; Lucas, T. C. A.; Hriljac, J. A.; Goodwin, A. L.

    2016-05-01

    By using a symmetry motivated basis to evaluate local distortions against pair distribution function data, we show without prior bias, that the off-center Ti displacements in the archetypal ferroelectric BaTiO3 are zone centered and rhombohedral-like across its known ferroelectric and paraelectric phases. We construct a simple Monte Carlo model that captures our main experimental findings and demonstrate how the rich crystallographic phase diagram of BaTiO3 emerges from correlations of local symmetry-breaking distortions alone. Our results strongly support the order-disorder picture for these phase transitions, but can also be reconciled with the soft-mode theory of BaTiO3 that is supported by some spectroscopic techniques.

  17. Formation of secondary phase at grain boundary of flash-sintered BaTiO3.

    PubMed

    Uehashi, Akinori; Sasaki, Katsuhiro; Tokunaga, Tomoharu; Yoshida, Hidehiro; Yamamoto, Takahisa

    2014-11-01

    Recently, Raj et.al. have developed a very unique sintering technique, called flash-sintering [1]. According to their report, fully densified ZrO2-3mol%Y2O3 ceramic bulks were successfully obtained only at 800°C for 5sec. Considering the conventional sintering condition around 1500°C for a few hours necessary to obtain ZrO2-3mol%Y2O3 ceramic bulks, their sintering technique is very attracting from a viewpoint of sintering temperature, soaking time and further the physical phenomena. The flash-sintering is a technique that green compacts were heating under application of high electric field. When furnace temperature reaches at a critical temperature, the electric current abruptly increases and the compact sinters near full density with a very high shrinkage rate. So far, a few studies about flash-sintering were reported for Y2O3 [2], SrTiO3, MgO-Al2O3. To understand the detail mechanism of flash-sintering, more case studies must be necessary. In this study, we focused BaTiO3 widely used for electro-ceramics, which has not been investigated from a viewpoint of flash-sintering.Green compacts were prepared from BaTiO3 raw powders (0.1-m, 99.9%, SAKAI chemical industry Co. Ltd., Lot. No.1308607) after uniaxially pressed at 100MPa into a rectangular shape with 2x10x30mm(3). The green compacts were suspended into a box type furnace by Pt-wires with Pt-based paste. Then, the furnace temperature was raised at 300°C/h under application of electric field ranged from 25V/cm to 350V/cm with monitoring the specimen current. After sintering, the shrinkages, microstructure of the sintered compacts were investigated.Sintering rates at all electric fields were found to be accelerated by applying electric field in BaTiO3. The appearance of abrupt current increment was confirmed over the application of 75V/cm. For example, a density of green compact reached about 90% relative density of BaTiO3 only at 1020°C for 1min at 100V/cm. However, the final shrinkages were revealed to decrease with an increase in electric fields, which is very different from the case of ZrO2-3mol%Y2O3 and Y2O3 ceramics. This fact means that application of high electric fields does not effectively operate for enhancement of shrinkage rates in the case of BaTiO3. In contrast, only gradual current increment was observed at 25V/cm, which is categorized in field-assisted sintering (FAST) process. The density of the green compact at 25V/cm was more than 95%.To investigate the mechanism of the decrease in a total shrinkage with electric fields, the microstructure of flash-sintered compact was observed. As a result, it was found that discharge occurs during flash-sintering process, indicating that the input power due to high electric fields does not work effectively. A typical example of the microstructure near the discharge area is shown in Fig. 1. Fig. 1 is a TEM bright field image taken from BaTiO3 flash-sintered at 100V/cm. As seen in the image, the formation of a secondary phase along the grain boundary can be clearly seen. Diffractometric and EDS analysis have revealed that the secondary phase is BaTi4O9, one of compounds between BaO and TiO2 system. By discharging, grain boundaries partially melt and a part of Ba vaporizes to form BaTi4O9 with cooling. To investigate flash-sintering behaviors, it was concluded that FAST process play an important role to enhance the shrinklage rate in the case of BaTiO3.jmicro;63/suppl_1/i19/DFU048F1F1DFU048F1Fig. 1.TEM bright field image of a secondary phase and the electron diffraction pattern taken from the secondary phase.

  18. Magnetic and nonlinear optical properties of BaTiO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ramakanth, S.; Hamad, Syed; Venugopal Rao, S.; James Raju, K. C.

    2015-05-01

    In our earlier studies the BaTiO3 samples were processed at higher temperatures like 1000oC and explained the observed magnetism in it. It is found that the charge transfer effects are playing crucial role in explaining the observed ferromagnetism in it. In the present work the samples were processed at lower temperatures like 650oC-800oC. The carrier densities in these particles were estimated to be ˜ 1019-1020/cm3 range. The band gap is in the range of 2.53eV to 3.2eV. It is observed that magnetization increased with band gap narrowing. The higher band gap narrowed particles exhibited increased magnetization with a higher carrier density of 1.23×1020/cm3 near to the Mott critical density. This hint the exchange interactions between the carriers play a dominant role in deciding the magnetic properties of these particles. The increase in charge carrier density in this undoped BaTiO3 is because of oxygen defects only. The oxygen vacancy will introduce electrons in the system and hence more charge carriers means more oxygen defects in the system and increases the exchange interactions between Ti3+, Ti4+, hence high magnetic moment. The coercivity is increased from 23 nm to 31 nm and then decreased again for higher particle size of 54 nm. These particles do not show photoluminescence property and hence it hints the absence of uniformly distributed distorted [TiO5]-[TiO6] clusters formation and charge transfer between them. Whereas these charge transfer effects are vital in explaining the observed magnetism in high temperature processed samples. Thus the variation of magnetic properties like magnetization, coercivity with band gap narrowing, particle size and charge carrier density reveals the super paramagnetic nature of BaTiO3 nanoparticles. The nonlinear optical coefficients extracted from Z-scan studies suggest that these are potential candidates for optical imaging and signal processing applications.

  19. Nanostructures of Indium Gallium Nitride Crystals Grown on Carbon Nanotubes

    PubMed Central

    Park, Ji-Yeon; Man Song, Keun; Min, Yo-Sep; Choi, Chel-Jong; Seok Kim, Yoon; Lee, Sung-Nam

    2015-01-01

    Nanostructure (NS) InGaN crystals were grown on carbon nanotubes (CNTs) using metalorganic chemical vapor deposition. The NS-InGaN crystals, grown on a ~5-μm-long CNT/Si template, were estimated to be ~100–270 nm in size. Transmission electron microscope examinations revealed that single-crystalline InGaN NSs were formed with different crystal facets. The observed green (~500 nm) cathodoluminescence (CL) emission was consistent with the surface image of the NS-InGaN crystallites, indicating excellent optical properties of the InGaN NSs on CNTs. Moreover, the CL spectrum of InGaN NSs showed a broad emission band from 490 to 600 nm. Based on these results, we believe that InGaN NSs grown on CNTs could aid in overcoming the green gap in LED technologies. PMID:26568414

  20. Nanostructures of Indium Gallium Nitride Crystals Grown on Carbon Nanotubes.

    PubMed

    Park, Ji-Yeon; Man Song, Keun; Min, Yo-Sep; Choi, Chel-Jong; Seok Kim, Yoon; Lee, Sung-Nam

    2015-11-16

    Nanostructure (NS) InGaN crystals were grown on carbon nanotubes (CNTs) using metalorganic chemical vapor deposition. The NS-InGaN crystals, grown on a ~5-μm-long CNT/Si template, were estimated to be ~100-270 nm in size. Transmission electron microscope examinations revealed that single-crystalline InGaN NSs were formed with different crystal facets. The observed green (~500 nm) cathodoluminescence (CL) emission was consistent with the surface image of the NS-InGaN crystallites, indicating excellent optical properties of the InGaN NSs on CNTs. Moreover, the CL spectrum of InGaN NSs showed a broad emission band from 490 to 600 nm. Based on these results, we believe that InGaN NSs grown on CNTs could aid in overcoming the green gap in LED technologies.

  1. Imprint control of BaTiO3 thin films via chemically induced surface polarization pinning

    DOE PAGES

    Lee, Hyungwoo; Kim, Tae Heon; Patzner, Jacob J.; ...

    2016-02-22

    Surface-adsorbed polar molecules can significantly alter the ferroelectric properties of oxide thin films. Thus, fundamental understanding and controlling the effect of surface adsorbates are crucial for the implementation of ferroelectric thin film devices, such as ferroelectric tunnel junctions. Herein, we report an imprint control of BaTiO3 (BTO) thin films by chemically induced surface polarization pinning in the top few atomic layers of the water-exposed BTO films. Our studies based on synchrotron X-ray scattering and coherent Bragg rod analysis demonstrate that the chemically induced surface polarization is not switchable but reduces the polarization imprint and improves the bistability of ferroelectric phasemore » in BTO tunnel junctions. Here, we conclude that the chemical treatment of ferroelectric thin films with polar molecules may serve as a simple yet powerful strategy to enhance functional properties of ferroelectric tunnel junctions for their practical applications.« less

  2. Contradictory nature of Co doping in ferroelectric BaTiO3

    DOE PAGES

    Ponath, Patrick; O’Hara, Andrew; Cao, Hai-Xia; ...

    2016-11-11

    The growth of Co-substituted BaTiO3 (BTO) films on Ge(001) substrates by molecular beam epitaxy is demonstrated in this paper. Energy-dispersive x-ray spectroscopy and transmission electron microscopy images confirm the uniform Co distribution. However, no evidence of magnetic ordering is observed in samples grown for Co concentrations between 2% and 40%. Piezoresponse force microscopy measurements show that a 5% Co-substituted BTO sample exhibits ferroelectric behavior. First-principles calculations indicate that while Co atoms couple ferromagnetically in the absence of oxygen vacancies, the occurrence of oxygen vacancies leads to locally antiferromagnetically coupled complexes with relatively strong spin coupling. Finally, the presence of amore » significant amount of oxygen vacancies is suggested by x-ray photoelectron spectroscopy measurements.« less

  3. Imprint Control of BaTiO3 Thin Films via Chemically Induced Surface Polarization Pinning.

    PubMed

    Lee, Hyungwoo; Kim, Tae Heon; Patzner, Jacob J; Lu, Haidong; Lee, Jung-Woo; Zhou, Hua; Chang, Wansoo; Mahanthappa, Mahesh K; Tsymbal, Evgeny Y; Gruverman, Alexei; Eom, Chang-Beom

    2016-04-13

    Surface-adsorbed polar molecules can significantly alter the ferroelectric properties of oxide thin films. Thus, fundamental understanding and controlling the effect of surface adsorbates are crucial for the implementation of ferroelectric thin film devices, such as ferroelectric tunnel junctions. Herein, we report an imprint control of BaTiO3 (BTO) thin films by chemically induced surface polarization pinning in the top few atomic layers of the water-exposed BTO films. Our studies based on synchrotron X-ray scattering and coherent Bragg rod analysis demonstrate that the chemically induced surface polarization is not switchable but reduces the polarization imprint and improves the bistability of ferroelectric phase in BTO tunnel junctions. We conclude that the chemical treatment of ferroelectric thin films with polar molecules may serve as a simple yet powerful strategy to enhance functional properties of ferroelectric tunnel junctions for their practical applications.

  4. Influence of defects on ferroelectric and electrocaloric properties of BaTiO3

    NASA Astrophysics Data System (ADS)

    Grünebohm, Anna; Nishimatsu, Takeshi

    2016-04-01

    We report modifications of the ferroelectric and electrocaloric properties of BaTiO3 by defects. For this purpose, we have combined ab initio based molecular dynamics simulations with a simple model for defects. We find that different kinds of defects modify the ferroelectric transition temperatures and polarization, reduce the thermal hysteresis of the transition, and are no obstacle for a large caloric response. For a locally reduced polarization, the ferroelectric transition temperature and the adiabatic response are slightly reduced. For polar defects, an intriguing picture emerges. The transition temperature is increased by polar defects and the temperature range of the large caloric response is broadened. Even more remarkable, we find an inverse caloric effect in a broad temperature range.

  5. Tuning the caloric response of BaTiO3 by tensile epitaxial strain

    NASA Astrophysics Data System (ADS)

    Grünebohm, Anna; Marathe, Madhura; Ederer, Claude

    2016-08-01

    We investigate the effect of epitaxial strain on the electrocaloric effect (ECE) in BaTiO3 by means of ab-initio-based molecular-dynamics simulations. We show that tensile strain can be used to optimize the operation range for ferroic cooling. Strain in the range of ≤ 1% can be used to shift the operation temperature by several hundreds of kelvin both to higher and lower temperatures, depending on the direction of the external field. In addition, the transformation between multi-domain and mono-domain states, induced by an in-plane electric field, results in an additional peak of the adiabatic temperature change at lower temperatures, and a broad temperature interval where the caloric response scales linearly with the applied field strength, even up to very high fields.

  6. Negative Capacitance in BaTiO3/BiFeO3 Bilayer Capacitors.

    PubMed

    Hou, Ya-Fei; Li, Wei-Li; Zhang, Tian-Dong; Yu, Yang; Han, Ren-Lu; Fei, Wei-Dong

    2016-08-31

    Negative capacitances provide an approach to reduce heat generations in field-effect transistors during the switch processes, which contributes to further miniaturization of the conventional integrated circuits. Although there are many studies about negative capacitances using ferroelectric materials, the direct observation of stable ferroelectric negative capacitances has rarely been reported. Here, we put forward a dc bias assistant model in bilayer capacitors, where one ferroelectric layer with large dielectric constant and the other ferroelectric layer with small dielectric constant are needed. Negative capacitances can be obtained when external dc bias electric fields are larger than a critical value. Based on the model, BaTiO3/BiFeO3 bilayer capacitors are chosen as study objects, and negative capacitances are observed directly. Additionally, the upward self-polarization effect in the ferroelectric layer reduces the critical electric field, which may provide a method for realizing zero and/or small dc bias assistant negative capacitances.

  7. Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers.

    PubMed

    Zhang, Dou; Zhou, Xuefan; Roscow, James; Zhou, Kechao; Wang, Lu; Luo, Hang; Bowen, Chris R

    2017-03-23

    There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO3 NFs achieved the maximal energy storage density of 15.48 J/cm(3) due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites.

  8. Enhanced strain effect of aged acceptor-doped BaTiO3 ceramics with clamping domain structures

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Zhou, Zhiyong; Zhao, Xiaobo; Liu, Zhen; Liang, Ruihong; Dong, Xianlin

    2017-03-01

    A clamping domain structure is proposed to improve the amount of non-180° domain switching in BaTiO3 based piezoelectric ceramics. Experimental results show a large unipolar strain of 0.23% at 5 kV/mm in aged 0.5 mol. % Mn doped BaTiO3 ceramics with clamping domain structures, and the normalized strain (d33*= Smax/Emax) reaches 600 pm/V at low electric fields of 2 or 3 kV/mm. In contrast, pure BaTiO3 ceramics with clamping domain structures exhibit no clear polarization constriction or strain enhancement at 3 kV/mm. Electron paramagnetic resonance spectra verify the existence of titanium vacancies, Mn2+ and Mn4+, in 0.5 mol. % Mn doped BaTiO3 ceramics. These results indicate that the enhanced strain effect can be attributed to the combined effect of the clamping domain structure and stabilization of defect dipoles. This method provides a general way to obtain large strain in ferroelectrics.

  9. Strain mediated magnetoelectric coupling in a NiFe2O4-BaTiO3 multiferroic composite

    NASA Astrophysics Data System (ADS)

    Gorige, Venkataiah; Kati, Raju; Yoon, D. H.; Kumar, P. S. Anil

    2016-10-01

    In this paper we demonstrate significant magnetoelectric coupling in ferrimagnetic, NiFe2O4, and ferroelectric, BaTiO3, multiferroic composite bulk materials by measuring temperature dependent magnetization. X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy data show that the two phases coexist with a highly crystalline and sharp interface without any detectable impurities, which enables significant magnetoelectric (ME) coupling. The temperature dependent magnetization data of the composite clearly show the jumps in magnetization curves at the structural phase transitions of BaTiO3, thereby indicating their origin in ME coupling. The change in coercivity of composite sample in different ferroelectric phases of BaTiO3 has been observed compared to the NiFe2O4 sample. The different lattice strains corresponding to different ferroelectric phases of BaTiO3 could be the driving force for modulating the magnetization and coercivity of the composite material. This is clear evidence of strain mediated ME coupling in ferrimagnetic and ferroelectric composite materials.

  10. BaTiO3 integration with nanostructured epitaxial (100), (110), and (111) germanium for multifunctional devices.

    PubMed

    Hudait, Mantu K; Zhu, Yan; Jain, Nikhil; Maurya, Deepam; Zhou, Yuan; Varghese, Ron; Priya, Shashank

    2013-11-13

    Ferroelectric-germanium heterostructures have a strong potential for multifunctional devices. Germanium (Ge) is attractive due to its higher electron and hole mobilities while ferroelectric BaTiO3 is promising due to its high relative permittivity, which can make next-generation low-voltage and low-leakage metal-oxide semiconductor field-effect transistors. Here, we investigate the growth, structural, chemical, and band alignment properties of pulsed laser deposited BaTiO3 on epitaxial (100)Ge, (110)Ge, and (111)Ge layers. Cross-sectional transmission electron microscopy micrographs show the amorphous nature of the BaTiO3 layer and also show a sharp heterointerface between BaTiO3 and Ge. The appearance of strong Pendellösung oscillation fringes from high-resolution X-ray diffraction implies the presence of parallel and sharp heterointerfaces. The valence band offset relation of ΔEV(100) ≥ ΔEV(111) > ΔEV(110) and the conduction band offset relation of ΔE(C)(110) > ΔE(C)(111) ≥ ΔE(C)(100) on crystallographically oriented Ge offer significant advancement for designing new-generation ferroelectric-germanium-based multifunctional devices.

  11. Enhancement of ferroelectric Curie temperature in BaTiO3 films via strain-induced defect dipole alignment.

    PubMed

    Damodaran, Anoop R; Breckenfeld, Eric; Chen, Zuhuang; Lee, Sungki; Martin, Lane W

    2014-09-01

    The combination of epitaxial strain and defect engineering facilitates the tuning of the transition temperature of BaTiO3 to >800 °C. Advances in thin-film deposition enable the utilization of both the electric and elastic dipoles of defects to extend the epitaxial strain to new levels, inducing unprecedented functionality and temperature stability in ferroelectrics.

  12. Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers

    NASA Astrophysics Data System (ADS)

    Zhang, Dou; Zhou, Xuefan; Roscow, James; Zhou, Kechao; Wang, Lu; Luo, Hang; Bowen, Chris R.

    2017-03-01

    There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO3 NFs achieved the maximal energy storage density of 15.48 J/cm3 due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites.

  13. First-Principles Calculation of Solution Energy of Alkaline-Earth Metal Elements to BaTiO3

    NASA Astrophysics Data System (ADS)

    Moriwake, Hiroki; Hirayama, Tsukasa; Ikuhara, Yuichi; Tanaka, Isao

    2007-10-01

    Quantitative analysis of the solution energy of alkaline-earth metal elements to perovskite-type BaTiO3 was carried out by a first-principles calculation combined with thermodynamics theory. The solution energies of neutral solute and a compensated solute with an oxygen vacancy were systematically calculated. They were obtained for two cation sites and four thermodynamical conditions with different chemical potentials of constituent atoms. Both Ca and Sr preferably occupy the Ba site of BaTiO3. On the other hand, Mg occupies the Ti site. This corresponds well to the widely accepted experimental findings regarding site preference. Moreover, under the condition of coexising BaO, CaO and BaTiO3, energy difference between the Ba-site solution and O-vacancy compensated Ti-site solution of Ca ions has been found to be smaller than that of Sr. Under this condition, the O-vacancy compensated Ti-site solution of Ca should be favorable compared with that of Sr. The same number of oxygen vacancies as Ca ions occupying Ti sites can be introduced. This also explains well experimental feature of the Ca-doped BaTiO3-based nonreducible multilayer ceramics capacitor (MLCC) materials regarding solution site of the Ca ion and abundance of O-vacancy.

  14. Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers

    PubMed Central

    Zhang, Dou; Zhou, Xuefan; Roscow, James; Zhou, Kechao; Wang, Lu; Luo, Hang; Bowen, Chris R.

    2017-01-01

    There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO3 NFs achieved the maximal energy storage density of 15.48 J/cm3 due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites. PMID:28332636

  15. Isotactic polypropylene carbon nanotube composites -- crystallization and ordering behavior

    NASA Astrophysics Data System (ADS)

    Georgiev, Georgi; Judith, Robert; Gombos, Erin; McIntyre, Michael; Schoen, Scott; Cebe, Peggy; Mattera, Michael

    2010-03-01

    The field of Polymer Nanocomposites (PNCs) is growing steadily in recent years. We use carbon nanotubes (CNTs) to affect the crystallization behavior of the polymers. Isotactic Polypropylene (iPP) is very widely used and is a good model system to understand the physics of other similar polymers. iPP/CNT PNCs form α, β, and γ crystallographic phases under a variety of crystallization conditions: non-isothermal and isothermal melt crystallization, shear, stress, fiber extrusion, etc. The crystal growth is altered from spherulitic to α-fibrillar upon the nucleation effect of CNTs. We are studying the effect of different temperature treatment schemes and different isothermal crystallization conditions. We found also that the smectic ordering in iPP is improved by the introduction of CNTs. We use Differential Scanning Calorimetry, Wide Angle X-ray scattering, Microscopic Transmission Ellipsometry and Avrami analysis. Research supported by: Assumption College Faculty Development Grant, funding for students' stipends, instrumentation and supplies, the NSF Polymers Program of the DMR, grant (DMR-0602473) and NASA grant (NAG8-1167).

  16. Aligned Carbon Nanotube Thin Films from Liquid Crystal Polyelectrolyte Inks.

    PubMed

    Tune, Daniel D; Blanch, Adam J; Shearer, Cameron J; Moore, Katherine E; Pfohl, Moritz; Shapter, Joseph G; Flavel, Benjamin S

    2015-11-25

    Single walled carbon nanotube thin films are fabricated by solution shearing from high concentration sodium nanotubide polyelectrolyte inks. The solutions are produced by simple stirring of the nanotubes with elemental sodium in dimethylacetamide, and the nanotubes are thus not subject to any sonication-induced damage. At such elevated concentrations (∼4 mg mL(-1)), the solutions exist in the liquid crystal phase and during deposition this order is transferred to the films, which are well aligned in the direction of shear with a 2D nematic order parameter of ∼0.7 determined by polarized absorption measurements. Compared to similarly formed films made from superacids, the polyelectrolyte films contain smaller bundles and a much narrower distribution of bundle diameters. After p-doping with an organic oxidizer, the films exhibit a very high DC electrical to optical conductivity ratio of σ(DC)/σ(OP) ∼ 35, corresponding to a calculated DC conductivity of over 7000 S cm(-1). When very thin (T550 ∼ 96%), smooth (RMS roughness, R(q) ∼ 2.2 nm), and highly aligned films made via this new route are used as the front electrodes of carbon nanotube-silicon solar cells, the power conversion efficiency is almost an order of magnitude greater than that obtained when using the much rougher (R(q) ∼ 20-30 nm) and less conductive (peak σ(DC)/σ(OP) ∼ 2.5) films formed by common vacuum filtration of the same starting material, and having the same transmittance.

  17. [Effect of carbon nanotubes on the crystallization behaviors of MC nylon 6].

    PubMed

    Qiu, Shang-Chang; Zheng, Yu-Ying; Zeng, An-Ran; Guo, Yong

    2011-09-01

    Multi-walled carbon nanotubes bearing hydroxyl group were modified with toluene diisocyanate (TDI) and stabilized with caprolactam. The functionalized carbon nanotubes were used to prepare monomer casting polyamide 6(MC nylon 6)/carbon nanotubes nanocomposites. The results of FTIR proved that isocynate groups have been incorporated into carbon nanotubes successfully. XRD results showed that the addition of the functionalized carbon nanotubes has no significant influence on the crystal structure of MC nylon 6, whereas the untreated carbon nanotubes could hinder the growth of alpha2-crystal of nylon 6; with the loading of 0.3 Wt% of the functionalized carbon nanotubes, the crystallinity degree of the nanocomposites is almost equal to that of pure MC nylon 6, whereas as the loading increased to 0.5 Wt%, the crystallinity degree of MC nylon 6 decreased. DSC revealed that carbon nanotubes in MC nylon 6 acted as effective nucleation agents. The peak temperature of crystallization for MC nylon 6 increased by 10 degrees C from 173.4 to 183.5 degrees C, and the temperature range of crystallization decreased, indicating that the carbon nanotubes act as heterogeneous nucleation agents for MC nylon 6.

  18. DFT study of BaTiO3 (001) surface with O and O2 adsorption

    NASA Astrophysics Data System (ADS)

    Rakotovelo, G.; Moussounda, P. S.; Haroun, M. F.; Légaré, P.; Rakotomahevitra, A.; Parlebas, J. C.

    2007-06-01

    Progress of scanning tunneling microscopy (STM) allowed to handle various molecules adsorbed on a given surface. New concepts emerged with molecules on surfaces considered as nano machines by themselves. In this context, a thorough knowledge of surfaces and adsorbed molecules at an atomic scale is thus particularly invaluable. In this work, within the framework of density functional theory (DFT), we present an electronic and structural ab initio study of a BaTiO3 (001) surface (perovskite structure) in its paraelectric phase. As far as we know the atomic and molecular adsorption of oxygen at surface is then analyzed for the first time in the literature. Relaxation is taken into account for several layers. Its analysis for a depth of at least four layers enables us to conclude that a reasonable approximation for a BaTiO3 (001) surface is provided with a slab made up of nine plans. The relative stability of two possible terminations is considered. By using a kinetic energy cut off of 400 eV, we found that a surface with BaO termination is more stable than with TiO2 termination. Consequently, a surface with BaO termination was chosen to adsorb either O atom or O2 molecule and the corresponding calculations were performed with a coverage 1 on a (1×1) cell. A series of cases with O2 molecule adsorbed in various geometrical configurations are also analyzed. For O2, the most favorable adsorption is obtained when the molecule is placed horizontally, with its axis, directed along the Ba-Ba axis and with its centre of gravity located above a Ba atom. The corresponding value of the adsorption energy is -9.70 eV per molecule (-4.85 eV per O atom). The molecule is then rather extended since the O O distance measures 1.829 Å. By comparison, the adsorption energy of an O atom directly located above a Ba atom is only -3.50 eV. Therefore we are allowed to conclude that the O O interaction stabilizes atomic adsorption. Also the local densities of states (LDOS) corresponding to various situations are discussed in the present paper. Up to now, we are not aware of experimental data to be compared to our calculated results.

  19. Some Aspects of the Failure Mechanisms in BaTiO3-Based Multilayer Ceramic Capacitors

    NASA Technical Reports Server (NTRS)

    Liu, David Donhang; Sampson, Michael J.

    2012-01-01

    The objective of this presentation is to gain insight into possible failure mechanisms in BaTiO3-based ceramic capacitors that may be associated with the reliability degradation that accompanies a reduction in dielectric thickness, as reported by Intel Corporation in 2010. The volumetric efficiency (microF/cm3) of a multilayer ceramic capacitor (MLCC) has been shown to not increase limitlessly due to the grain size effect on the dielectric constant of ferroelectric ceramic BaTiO3 material. The reliability of an MLCC has been discussed with respect to its structure. The MLCCs with higher numbers of dielectric layers will pose more challenges for the reliability of dielectric material, which is the case for most base-metal-electrode (BME) capacitors. A number of MLCCs manufactured using both precious-metal-electrode (PME) and BME technology, with 25 V rating and various chip sizes and capacitances, were tested at accelerated stress levels. Most of these MLCCs had a failure behavior with two mixed failure modes: the well-known rapid dielectric wearout, and so-called 'early failures." The two failure modes can be distinguished when the testing data were presented and normalized at use-level using a 2-parameter Weibull plot. The early failures had a slope parameter of Beta >1, indicating that the early failures are not infant mortalities. Early failures are triggered due to external electrical overstress and become dominant as dielectric layer thickness decreases, accompanied by a dramatic reduction in reliability. This indicates that early failures are the main cause of the reliability degradation in MLCCs as dielectric layer thickness decreases. All of the early failures are characterized by an avalanche-like breakdown leakage current. The failures have been attributed to the extrinsic minor construction defects introduced during fabrication of the capacitors. A reliability model including dielectric thickness and extrinsic defect feature size is proposed in this presentation. The model can be used to explain the Intel-reported reliability degradation in MLCCs with respect to the reduction of dielectric thickness. It can also be used to estimate the reliability of a MLCC based on its construction and microstructure parameters such as dielectric thickness, average grain size, and number of dielectric layers. Measures for preventing early failures are also discussed in this document.

  20. Ultrasensitive quartz crystal microbalance integrated with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Goyal, Abhijat

    In this thesis, an ultrasensitive Quartz Crystal Microbalance (QCM) which can be configured as a versatile (bio)chemical sensor is presented. The high sensitivity of the QCM was achieved via miniaturization using micromachining techniques. The absolute mass sensitivity of sensor was increased by decreasing the thickness and the area of the electrodes of the resonators. Through optimal design, microfabrication, and miniaturization the mass sensitivity of the sensors was increased by more than four orders of magnitude to less than 1 pg/Hz; as compared to 17 ng/Hz for commercially available 5 MHz bulk resonators. Miniaturization of the resonators enables their fabrication in an array format with each pixel of the array being individually addressed. This enables true spatial and temporal mass sensing capabilities. The fabricated resonators were tested for operation in air and water and high quality factors of 7500 and ˜2000 were obtained respectively. A dielectric etch process was developed to achieve the miniaturization of the sensors. The optimization of the dielectric etch process was achieved using statistical techniques such as Design of Experiment (DOE). An etch rate of 0.5 microm/min at rms surface roughness of less than 2 nm was achieved after the optimization process. The process parameters, namely the ICP power, the substrate power, the flow rate of gases, the operating pressure of the etch tool, distance of substrate holder from the source, and the temperature of substrate holder, were quantitatively related to the etch rate and rms surface roughness using least square fit to the etch data. The QCMs were integrated with carbon nanotubes using a simple spray-on technique. It was found that the addition of carbon nanotubes onto the electroded surface of the resonator increased its Q-factor by as much as 100%. It was proposed that the carbon nanotubes due to their high stiffness suppress the out-of-plane flexural vibrations in the QCMs thereby suppressing an

  1. Dielectric Properties of BaTiO3 Codoped with Er2O3 and MgO

    NASA Astrophysics Data System (ADS)

    Hwang, Jin Hyun; Choi, Sang Keun; Han, Young Ho

    2001-08-01

    The effect of Er2O3 and MgO addition on the dielectric properties of BaTiO3 ceramics was studied in a reduced atmosphere. MgO effectively prevented the material from being reduced and suppressed grain growth. An X7R material with moderate temperature dependence was developed by the addition of MgO with higher than 2.0 mol% Er2O3 to BaTiO3, which is ascribed to the decrease in grain size and the grain core-grain shell structure. In the presence of equimolar amount of B-site metal ions, there was no evidence to support the incorporation of Er ions into the octahedral and dodecahedral cation sites.

  2. Single-crystalline BaTiO3 films grown by gas-source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Matsubara, Yuya; Takahashi, Kei S.; Tokura, Yoshinori; Kawasaki, Masashi

    2014-12-01

    Thin BaTiO3 films were grown on GdScO3 (110) substrates by metalorganic gas-source molecular beam epitaxy. Titanium tetra-isopropoxide (TTIP) was used as a volatile precursor that provides a wide growth window of the supplied TTIP/Ba ratio for automatic adjustment of the film composition. Within the growth window, compressively strained films can be grown with excellent crystalline quality, whereas films grown outside of the growth window are relaxed with inferior crystallinity. This growth method will provide a way to study the intrinsic properties of ferroelectric BaTiO3 films and their heterostructures by precise control of the stoichiometry, structure, and purity.

  3. Performance analysis of resistive switching devices based on BaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Samardzic, Natasa; Kojic, Tijana; Vukmirovic, Jelena; Tripkovic, Djordjije; Bajac, Branimir; Srdic, Vladimir; Stojanovic, Goran

    2016-03-01

    Resitive switching devices, memristors, have recenty attracted much attention due to promising performances and potential applications in the field of logic and memory devices. Here, we present thin film BaTiO3 based memristor fabricated using ink-jet printing technique. Active material is a single layer barium titanate film with thickness of ̴100 nm, sandwitched between metal electodes. Printing parameters were optimized aiming to achieve stable drop flow and uniform printed layer. Current-voltage characteristics show typical memristive behavior with pinched hysteresis loop crossed at the origin, with marked differences between High Resistive State (HRS) and Low Resistive State (LRS). Obtained resistive states are stable during numerous switching processes. The device also shows unipolar switching effect for negative voltage impulses. Variable voltage impulse amplitudes leads to the shifting of the energy levels of electode contacts resulting in changing of the overall current through the device. Structural charcterization have been performed using XRD analysis and SEM micrography. High-temperature current-voltage measurements combined with transport parameter analysis using Hall efect measurement system (HMS 3000) and Impedance Analyzer AC measurements allows deeper insigth into conduction mechanism of ferroelectric memristors.

  4. Diamagnetism to ferromagnetism in Sr-substituted epitaxial BaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Singamaneni, Srinivasa Rao; Punugupati, Sandhyarani; Prater, John T.; Narayan, Jagdish

    2016-04-01

    We report on the ferromagnetic-like behavior in otherwise diamagnetic BaTiO3 (BTO) thin films upon doping with non-magnetic element Sr having the composition Ba0.4Sr0.6TiO3 (BST). The epitaxial integration of BST (˜800 nm) thick films on Si (100) substrate was achieved using MgO (40 nm) and TiN (20 nm) as buffer layers to prepare BST/MgO/TiN/Si (100) heterostructure by pulsed laser deposition. The c-axis oriented and cube-on-cube epitaxial BST is formed on Si (100) as evidenced by the in-plane and out-of-plane X-ray diffraction. All the deposited films are relaxed through domain matching epitaxy paradigm as observed from X-ray diffraction pattern and A1TO3 mode (at 521.27 cm-1) of Raman spectra. As-deposited BST thin films reveal ferromagnetic-like properties, which persist up to 400 K. The magnetization decreases two-fold upon oxygen annealing. In contrast, as-deposited un-doped BTO films show diamagnetism. Electron spin resonance measurements reveal no evidence of external magnetic impurities. XRD and X-ray photoelectron spectroscopy spectra show significant changes influenced by Sr doping in BTO. The ferromagnetic-like behavior in BST could be due to the trapped electron donors from oxygen vacancies resulting from Sr-doping.

  5. Atomic and electronic structure of the BaTiO3 -Ge (001) interface

    NASA Astrophysics Data System (ADS)

    Fredrickson, Kurt; Ponath, Patrick; Posadas, Agham; McCartney, Martha; Aoki, Toshihiro; Smith, David; Demkov, Alexander

    2014-03-01

    There is tremendous interest in putting perovskite oxides, such as SrTiO3 (STO) or BaTiO3 (BTO), on semiconductors due to their very high permitivitties. BTO can be grown directly on Ge using an approach similar to the growth of STO in Si. To date, very little is known about the atomic and electronic structure of the BTO-Ge interface. We use molecular beam epitaxy to grow BTO with in-plane polarization directly on Ge(001) using a Sr Zintl buffer layer. This results in an atomically flat, oxygen- and carbon-free Ge surface with very sharp (2x1) reconstruction as observed with reflection high energy electron diffraction. Using scanning transmission electron microscopy, we are able to precisely determine the atomic geometry of the interface, with the exception of the exact positions of the oxygen atoms. In situx-ray photoemission spectroscopy is used to analyze the oxidation state of the interfacial Ge and to determine the valence band offset at the interface. We use density functional theory to determine placement of interfacial O and calculate the valence band offset. The theoretical valence band offset is in good agreement with the photoemission data, strongly suggesting the correctness of the interface geometry. We calculate the effect of O vacancies and ionic substitution at the interfacial layer on the valence band offsets.

  6. Phase transitions in BaTiO3 under uniaxial compressive stress: Experiments and phenomenological analysis

    NASA Astrophysics Data System (ADS)

    Schader, Florian H.; Khakpash, Nasser; Rossetti, George A.; Webber, Kyle G.

    2017-02-01

    The relative permittivity of polycrystalline BaTiO3 was measured from -150 °C to 250 °C at compressive bias stresses up to -500 MPa. Mechanical loading shifted the rhombohedral-orthorhombic, orthorhombic-tetragonal, and tetragonal-cubic phase transition temperatures and produced a pronounced broadening of the dielectric softening in the vicinity of all three transitions. The inter-ferroelectric rhombohedral-orthorhombic and orthorhombic-tetragonal phase transitions were found to be less stress sensitive than the ferroelectric-paraelectric transition occurring between tetragonal and cubic phases at the Curie point. The application of compressive stress resulted in a strong suppression of the relative permittivity, such that at the highest applied stress of -500 MPa, the permittivity in the single phase regions away from the phase transitions was found to display only a weak dependence on temperature between -100 °C and 125 °C. The experimental observations closely followed the predictions of a 2-4-6 Landau polynomial wherein the dielectric stiffness and higher-order dielectric stiffness coefficients are linear functions of uniaxial stress.

  7. Electrical and magnetic properties of hexagonal BaTiO3-δ

    NASA Astrophysics Data System (ADS)

    Kolodiazhnyi, T.; Belik, A. A.; Wimbush, S. C.; Haneda, H.

    2008-02-01

    The electrical resistivity, Hall coefficient, and magnetic susceptibility of n -type hexagonal BaTiO3-δ (hex-BaTiO3-δ) have been measured in the 5-400K temperature range. Above 200K this compound undergoes a transition from an insulating to a semiconducting state. Below 140K Hall effect data indicate the existence of an energy gap of approximately 43meV separating the localized electron ground state from the conduction band. Magnetic measurements reveal a strong magnetic anomaly in hex-BaTiO3-δ with a maximum in the susceptibility at around 160-200K . This anomaly is quite similar to that of the hexagonal BaMg1/3Ru2/3O3 which may indicate that the electron ground state in hex-BaTiO3-δ is comprised of spin singlet Ti3+-Ti3+ dimers. We further propose that the thermal dissociation of these dimers is responsible for the change in the electron transport mechanism in hex-BaTiO3-δ .

  8. Symmetry, strain, defects, and the nonlinear optical response of crystalline BaTiO3/silicon

    NASA Astrophysics Data System (ADS)

    Kormondy, Kristy; Abel, Stefan; Popoff, Youri; Sousa, Marilyne; Caimi, Daniele; Siegwart, Heinz; Marchiori, Chiara; Rossell, Marta; Demkov, Alex; Fompeyrine, Jean

    Recent progress has been made towards exploiting the linear electro-optic or Pockels effect in ferroelectric BaTiO3 (BTO) for novel integrated silicon photonics devices. In such structures, the crystalline symmetry and domain structure of BTO determine which electro-optic tensor elements are accessible under application of an external electric field. For epitaxial thin films of BTO on Si (001), the role of defects in strain relaxation can lead to very different crystalline symmetry even for films of identical thickness. Indeed, through geometric phase analysis of high-resolution scanning transmission electron microscopy images, we map changes of the in-plane and out-of-plane lattice parameters across two 80-nm-thick BTO films. A corresponding 20% difference in the effective electro-optic response was measured by analyzing induced rotation of the polarization of a laser beam (λ = 1550 nm) transmitted through lithographically defined electrodes. Understanding, controlling, and modelling the role of BTO symmetry in nonlinear optics is of fundamental importance for the development of a hybrid BTO/Si photonics platform.. Work supported by the NSF (IRES-1358111), AFOSR (FA9550-12-10494), and European Commission (FP7-ICT-2013-11-619456-SITOGA).

  9. In situ studies on ferroelectric BaTiO3 interface

    NASA Astrophysics Data System (ADS)

    Shin, Junsoo; Braun Nascimento, Von; Plummer, Ward; Zhang, Jiandi; Borisevich, Albina; Meunier, Vincent; Kalinin, Sergei; Baddorf, Arthur

    2012-02-01

    Ferroelectric phase stability in ferroelectric films is critically dependent on the surface and interface phenomena, especially governed by electrostatic depolarization energy. Predictions for the minimum critical film thickness for ferroelectricity have continuously decreased down to few unit cells. We have examined surface/interface atomic structures of ultrathin BaTiO3 (BTO) films grown on conductive SrRuO3 (SRO) and Nb-doped SrTiO3. The surface structure of BTO/SRO was refined using in-situ Low Energy Electron Diffraction (LEED) I-V, resulting to observation of polar distortion in ultrathin (>= 4 ML) BTO films. The in-situ Scanning Tunneling Microscopy (STM) has been performed prior and after BTO deposition on SRO. However, the unusual 2x2 reconstruction is observed for 1-2 ML BTO films and bare SRO by STM. The surface reconstruction of SRO bottom electrode is shown to affect the interface of films deposited subsequently which could be reflected in ultrathin film properties. The in-situ LEED I-V structural studies on 1-2 ML BTO interface have been performed without SRO layer, which kept ultrathin BTO films from the preclusion of reconstructed SRO films.

  10. Interactions between Mn dopant and oxygen vacancy for insulation performance of BaTiO3

    NASA Astrophysics Data System (ADS)

    Chikada, Shunsuke; Kubota, Teppei; Honda, Atsushi; Higai, Shin'ichi; Motoyoshi, Yasuhiro; Wada, Nobuyuki; Shiratsuyu, Kosuke

    2016-10-01

    We performed first-principles calculations and electron spin resonance (ESR) measurements on Mn-doped perovskite BaTiO3 (BT) ceramics in order to investigate the interactions between Mn dopant and O vacancy (VO). We discovered the following two. First, VOs are stabilized at the nearest neighbor O site of Mn at a Ti site and this results in the suppression of VO diffusion. Second, electrons generated by the formation of VOs are trapped in unoccupied Mn-3d orbitals in the BT bandgap. This indicates that the valence state of Mn changes according to the VO density. We synthesized Mn-doped BT by varying the partial pressure of O2 gas and examined the Mn valence states with ESR measurements. We successfully observed that the majority type of Mn ions (2+, 3+, and 4+) depends on O2 gas pressure of the firing atmosphere. According to these theoretical and experimental investigations, we concluded that Mn dopants have two effects, i.e., VO and electron carrier trapping. Moreover, the mechanisms of Mn doping in BT improved the insulation resistance, and the reliability of BT-based ceramic capacitors/condensers were thoroughly examined.

  11. Soft-mode spectroscopy in cubic BaTiO3 by hyper-Raman scattering

    NASA Astrophysics Data System (ADS)

    Vogt, H.; Sanjurjo, J. A.; Rossbroich, G.

    1982-11-01

    Hyper-Raman scattering from cubic BaTiO3 is studied to clarify the controversies about the low-frequency dielectric response in this material. Applying the fluctuation-dissipation theorem, we obtain the imaginary part ɛ''(Ω) of the dielectric function in the wave-number range from 3 to 150 cm-1. ɛ''(Ω) can be adequately described by a classical single-oscillator dispersion formula. In approaching the Curie temperature, we find a continuous decrease of the mode frequency Ω0. The relative damping constant γΩ0 exceeds 2, so that the mode may be referred to as intermediate between oscillator and relaxator. Because of the high damping ɛ''(Ω) can be formally written as the sum of two overdamped oscillator contributions. This would lead to the concept of a soft-mode saturation and an extra dispersion mechanism as has been recently inferred from the far-infrared reflectivity spectrum. However, we do not find any evidence for this mode splitting and, so far, regard it as artificial.

  12. Dielectric relaxation behavior of acceptor (Mg)-doped BaTiO3

    NASA Astrophysics Data System (ADS)

    Yoon, Seok-Hyun; Kwon, Sang-Hoon; Hur, Kang-Heon

    2011-04-01

    Dielectric relaxation behavior of acceptor (Mg)-doped BaTiO3 ceramics was investigated with the increase of Mg concentration up to 0.6 mol. % in the temperature rang of 120 ˜ 540 °C. In the high temperature range above 320 °C, the activation energies of dielectric relaxation (Eτ) showed nearly similar values of ˜ 1.2 eV irrespective of Mg concentration. However, in the low temperature range below 320 °C, they continuously decreased from ˜ 1.2 eV and then saturated to ˜ 0.4 eV with the increase of Mg concentration. The activation energies of electrical conduction (Eσ) of the bulk grain evaluated by impedance analysis also showed almost the same behavior. Such coincidence demonstrates that the observed dielectric behaviors are caused by the space charge polarization at grain boundaries by conducting charge carriers. The disappearance of the dielectric relaxation in submicrometer fine-grain specimen also supports this mechanism. The variation of Eτ and Eσ with the increase of Mg concentration in the low temperature range was supposed to be caused by the dominant hopping conduction between ionized acceptor (MgTi″) and neutral or hole-trapped acceptor (MgTi×).

  13. High ferroelectric polarization in c-oriented BaTiO3 epitaxial thin films on SrTiO3/Si(001)

    DOE PAGES

    Scigaj, M.; Chao, C. H.; Gázquez, J.; ...

    2016-09-21

    The integration of epitaxial BaTiO3 films on silicon, combining c-orientation, surface flatness, and high ferroelectric polarization is of main interest towards its use in memory devices. This combination of properties has been only achieved so far by using yttria-stabilized zirconia buffer layers. Here, the all-perovskite BaTiO3/LaNiO3/SrTiO3 heterostructure is grown monolithically on Si(001). The BaTiO3 films are epitaxial and c-oriented and present low surface roughness and high remnant ferroelectric polarization around 6 μC/cm2. Lastly, this result paves the way towards the fabrication of lead-free BaTiO3 ferroelectric memories on silicon platforms.

  14. High ferroelectric polarization in c-oriented BaTiO3 epitaxial thin films on SrTiO3/Si(001)

    NASA Astrophysics Data System (ADS)

    Scigaj, M.; Chao, C. H.; Gázquez, J.; Fina, I.; Moalla, R.; Saint-Girons, G.; Chisholm, M. F.; Herranz, G.; Fontcuberta, J.; Bachelet, R.; Sánchez, F.

    2016-09-01

    The integration of epitaxial BaTiO3 films on silicon, combining c-orientation, surface flatness, and high ferroelectric polarization is of main interest towards its use in memory devices. This combination of properties has been only achieved so far by using yttria-stabilized zirconia buffer layers. Here, the all-perovskite BaTiO3/LaNiO3/SrTiO3 heterostructure is grown monolithically on Si(001). The BaTiO3 films are epitaxial and c-oriented and present low surface roughness and high remnant ferroelectric polarization around 6 μC/cm2. This result paves the way towards the fabrication of lead-free BaTiO3 ferroelectric memories on silicon platforms.

  15. X-ray absorption fine structure analysis of molybdenum added to BaTiO3-based ceramics used for multilayer ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Ogata, Yoichiro; Shimura, Tetsuo; Ryu, Minoru; Iwazaki, Yoshiki

    2017-04-01

    The effect of slight molybdenum doping of perovskite-type BaTiO3-based ceramics on the reliability of a multilayer ceramic capacitor (MLCC) and on the valence state of molybdenum in the BaTiO3-based ceramics has been investigated by highly accelerated lifetime tests and X-ray absorption fine structure analysis. The molybdenum added to the BaTiO3-based ceramics is located at Ti sites and improves the highly accelerated lifetime and lowers the initial dielectric resistivity in MLCCs. Through sintering in a reducing atmosphere, which is an important process in the fabrication of BaTiO3-based MLCCs, the oxidation state of the molybdenum added could be adjusted from +6 to a value close to +4.

  16. Preparation and characterization of self-assembled percolative BaTiO3-CoFe2O4 nanocomposites via magnetron co-sputtering.

    PubMed

    Yang, Qian; Zhang, Wei; Yuan, Meiling; Kang, Limin; Feng, Junxiao; Pan, Wei; Ouyang, Jun

    2014-04-01

    BaTiO3-CoFe2O4 composite films were prepared on (100) SrTiO3 substrates by using a radio-frequency magnetron co-sputtering method at 750 °C. These films contained highly (001)-oriented crystalline phases of perovskite BaTiO3 and spinel CoFe2O4, which can form a self-assembled nanostructure with BaTiO3 well-dispersed into CoFe2O4 under optimized sputtering conditions. A prominent dielectric percolation behavior was observed in the self-assembled nanocomposite. Compared with pure BaTiO3 films sputtered under similar conditions, the nanocomposite film showed higher dielectric constants and lower dielectric losses together with a dramatically suppressed frequency dispersion. This dielectric percolation phenomenon can be explained by the 'micro-capacitor' model, which was supported by measurement results of the electric polarization and leakage current.

  17. Reduced overpotentials for electrocatalytic water splitting over Fe- and Ni-modified BaTiO3.

    PubMed

    Artrith, Nongnuch; Sailuam, Wutthigrai; Limpijumnong, Sukit; Kolpak, Alexie M

    2016-10-26

    Water electrolysis is a key technology for the replacement of fossil fuels by environmentally friendly alternatives, but state-of-the-art water oxidation catalysts rely on rare elements such as Pt groups and other noble metals. In this article, we employ first-principles calculations to explore the potential of modified barium titanate (BaTiO3), an inexpensive perovskite oxide that can be synthesized from earth-abundant precursors, for the design of efficient water oxidation electrocatalysts. Our calculations identify Fe and Ni doping as a means to improve the electrical conductivity and to reduce the overpotential required for water oxidation over BaTiO3. Based on computed Pourbaix diagrams and pH/potential-dependent surface phase diagrams, we further show that BaTiO3 is stable under reaction conditions and is not sensitive with respect to poisoning by reaction intermediates and hydrogen adsorption. This proof of concept demonstrates that even minor compositional modifications of existing materials may greatly improve their catalytic activity, a fact that is often neglected when larger composition spaces are screened.

  18. Ferroelectric BaTiO3 thin films on Ti substrate fabricated using pulsed-laser deposition.

    PubMed

    He, J; Jiang, J C; Liu, J; Collins, G; Chen, C L; Lin, B; Giurgiutiu, V; Guo, R Y; Bhalla, A; Meletis, E I

    2010-09-01

    We report on the fabrication of ferroelectric BaTiO3 thin films on titanium substrates using pulsed laser deposition and their microstructures and properties. Electron microscopy studies reveal that BaTiO3 films are composed of crystalline assemblage of nanopillars with average cross sections from 100 nm to 200 nm. The BaTiO3 films have good interface structures and strong adhesion with respect to Ti substrates by forming a rutile TiO2 intermediate layer with a gradient microstructure. The room temperature ferroelectric polarization measurements show that the as-deposited BTO films possess nearly the same spontaneous polarization as the bulk BTO ceramics indicating formation of ferroelectric domains in the films. Successful fabrication of such ferroelectric films on Ti has significant importance for the development of new applications such as structural health monitoring spanning from aerospace to civil infrastructure. The work can be extended to integrate other ferroelectric oxide films with various promising properties to monitor the structural health of materials.

  19. Current understanding of structure-processing-property relationships in BaTiO3-Bi(M)O3 dielectrics

    DOE PAGES

    Beuerlein, Michaela A.; Kumar, Nitish; Usher, Tedi -Marie; ...

    2016-09-01

    Here, as part of a continued push for high permittivity dielectrics suitable for use at elevated operating temperatures and/or large electric fields, modifications of BaTiO3 with Bi(M)O3, where M represents a net-trivalent B-site occupied by one or more species, have received a great deal of recent attention. Materials in this composition family exhibit weakly coupled relaxor behavior that is not only remarkably stable at high temperatures and under large electric fields, but is also quite similar across various identities of M. Moderate levels of Bi content (as much as 50 mol%) appear to be crucial to the stability of themore » dielectric response. In addition, the presence of significant Bi reduces the processing temperatures required for densification and increases the required oxygen content in processing atmospheres relative to traditional X7R-type BaTiO3-based dielectrics. Although detailed understanding of the structure–processing–property relationships in this class of materials is still in its infancy, this article reviews the current state of understanding of the mechanisms underlying the high and stable values of both relative permittivity and resistivity that are characteristic of BaTiO3-Bi(M)O3 dielectrics as well as the processing challenges and opportunities associated with these materials.« less

  20. Enhancement of Magnetoelectric Coupling in CoGaxFe2-xO4/BaTiO3 Composite

    NASA Astrophysics Data System (ADS)

    Ni, Yan; Zhang, Zhen; Jiles, David; Nlebedim, Cajetan

    2015-03-01

    Multiferroic materials exhibit magnetoelectric coupling and promise new device applications including magnetic sensors, generators and filters. An effective method for developing magnetoelectric (ME) materials with enhanced ME effect is achieved by the coupling through the interfacial strain between piezoelectric and magnetostrictive materials. In this study, enhancement of magnetoelectric coupling was found by systematically studying the electrical and magnetic properties of CoGaxFe2-xO4/BaTiO3 composite. It is found that Ga doping not only stabilizes the magnetic phase of composites but also increases the sensitivity of magnetoelastic response by 30%. Moreover, Ga doping reduces the electrical conductivity and the dielectric loss of composite. An enhancement of the electrostrain with doping Ga is also observed in CoGaxFe2-xO4/BaTiO3 (x =0.3). As both the sensitivity of magnetostriction and the change in the electric field with strain increase, the ME voltage coefficient also increase. Thus, our work is beneficial for the application of CoFe2O4/BaTiO3-based multiferroic materials. This work was supported by the USDoE, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. The research was performed at Ames Laboratory, operated for the USDoE by Iowa State University (contract # DE-AC02-07CH11358)

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

    NASA Astrophysics Data System (ADS)

    Neeraj; Raina, K. K.

    2014-02-01

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

  2. Spin-Coating and Characterization of Multiferroic MFe2O4 (M=Co, Ni) / BaTiO3 Bilayers

    NASA Astrophysics Data System (ADS)

    Quandt, Norman; Roth, Robert; Syrowatka, Frank; Steimecke, Matthias; Ebbinghaus, Stefan G.

    2016-01-01

    Bilayer films of MFe2O4 (M=Co, Ni) and BaTiO3 were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO3. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm-3 for the CoFe2O4/BaTiO3 and 188 emu cm-3 for the NiFe2O4/BaTiO3 bilayer, respectively were found. For the CoFe2O4/BaTiO3 bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe2O4/BaTiO3 bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems.

  3. Structural, elastic, and electronic properties of new superhard isotropic cubic crystals of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Enyashin, A. N.; Ivanovskii, A. L.

    2008-05-01

    The models of new isotropic cubic crystals of single-layered carbon nanotubes are proposed. The structural, elastic, and electronic properties and the energies of formation of these crystals were calculated using the density functional-based tight binding (DFTB) method. The crystals proposed were found to exhibit extreme compression moduli (550-650 GPa) and a minimum compressibility (0.0018-0.0015 GPa-1); in this case, the type of conduction of the parent nanotubes was retained. For this reason, the above crystals are of interest for the development of new superhard materials with controllable electrophysical properties.

  4. Pseudo Jahn-Teller origin of ferroelectric instability in BaTiO3 type perovskites: The Green's function approach and beyond

    NASA Astrophysics Data System (ADS)

    Polinger, V.; Garcia-Fernandez, P.; Bersuker, I. B.

    2015-01-01

    The local origin of dipolar distortions in ABO3 perovskite crystals is reexamined by means of a novel approach, the Green's function method augmented by DFT computations. The ferroelectric distortions are shown to be induced by the pseudo Jahn-Teller effect (PJTE). The latter involves vibronic hybridization (admixture) of the ground state to same-spin opposite-parity excited electronic bands. Similar to numerous molecular calculations, the PJT approach provides a deeper insight into the nature of chemical bonding in the octahedral cluster [BO6] and, in particular, reveals the local origin of its polar instability. This allows predicting directly which transition ions can create ferroelectricity. In particular, the necessary conditions are established when an ABO3 perovskite crystal with an electronic dn configuration of the complex ion [BO6] can possess both proper ferroelectric and magnetic properties. Distinguished from the variety of cluster approaches to local properties, the Green's function method includes the influence of the local vibronic-coupling perturbation on the whole crystal via the inter-cell interaction responsible for creation of electronic and vibrational bands. Calculated Green's functions combined with the corresponding numeric estimates for the nine electronic bands, their density of states, and the local adiabatic potential energy surface (APES) confirm the eight-minimum form of this surface and feasibility of the PJT origin of the polar instability in BaTiO3. We show also that multicenter long-range dipole-dipole interactions critically depend on the PJTE largely determining the magnitude of the local dipoles. DFT calculations for the bulk crystal and its clusters confirm that the dipolar distortions are of local origin, but become possible only when their influence on (relaxation of) the whole lattice is taken into account. The results are shown to be in full qualitative and semiquantitative agreement with the experimental data for this

  5. Effect of BaTiO3 nano-particles on breakdown performance of propylene carbonate.

    PubMed

    Hou, Yanpan; Zhang, Zicheng; Zhang, Jiande; Liu, Zhuofeng; Song, Zuyin

    2015-05-01

    As an alternative to water, propylene carbonate (PC) has a good application prospect in the compact pulsed power sources for its breakdown strength higher than that of water, resistivity bigger than 10(9) Ω m, and low freezing temperature (-49 °C). In this paper, the investigation into dielectric breakdown of PC and PC-based nano-fluids (NFs) subjected to high amplitude electric field is presented with microsecond pulses applied to a 1 mm gap full of PC or NFs between spherical electrodes. One kind of NF is composed of PC mixed with 0.5-1.4 vol. % BaTiO3 (BT) nano-particles of mean diameter ≈100 nm and another is mixed with 0.3-0.8 vol. % BT nano-particles of mean diameter ≈30 nm. The experimental results demonstrate the rise of permittivity and improvement of the breakdown strength of NFs compared with PC. Moreover, it is found that there exists an optimum fraction for these NFs corresponding to tremendous surface area in nano-composites with finite mesoscopic thickness. In concrete, the dielectric breakdown voltage of NFs is 33% higher than that of PC as the volume concentration of nano-particles with a 100 nm diameter is 0.9% and the breakdown voltage of NFs is 40% higher as the volume concentration of nano-particles with a 30 nm diameter is 0.6%. These phenomena are considered as the dielectric breakdown voltage of PC-based NFs is increased because the interfaces between nano-fillers and PC matrices provide myriad trap sites for charge carriers, which play a dominant role in the breakdown performance of NFs.

  6. Enhancement of the Electrical Properties in BaTiO3/PbZr0.52Ti0.48O3 Ferroelectric Superlattices.

    PubMed

    He, Bin; Wang, Zhanjie

    2016-03-01

    In this study, BaTiO3/Pb(Zr0.52Ti0.48)O3 (BTO/PZT) ferroelectric superlattices have been grown on the Nb-doped SrTiO3 (NSTO) single-crystal substrate by pulsed laser deposition, and their electrical properties were investigated in detail. The leakage current was reduced significantly in the BTO/PZT superlattices, and the conduction mechanism could be interpreted as the bulk-limited mechanism. In addition, a more symmetric hysteresis loop was observed in the BTO/PZT superlattices compared with the pure PZT and BTO films. The BTO/PZT superlattices with the modulation thickness of 9.8 nm showed remarkably improved dielectric properties with dielectric constant and loss of 684 and 0.02, respectively, measured at the frequency of 10 kHz. Based on these experimental results, it can be considered that the BTO/PZT interfaces play a very important role for the enhanced electrical properties of the BTO/PZT superlattices.

  7. Isothermal Crystallization of Poly(ethylene oxide) / Single Walled Carbon Nanotube Nanocomposites

    NASA Astrophysics Data System (ADS)

    Lorenzo, Arnaldo; Chatterjee, Tirtha; Krishnamoorti, Ramanan

    2011-03-01

    The isothermal crystallization behavior of poly(ethylene oxide)/single walled carbon nanotubes (PEO/SWNT) nanocomposites were studied with a focus on the overall crystallization kinetics and the morphological evolution of PEO using differential scanning calorimetry and in-situ small angle x-ray scattering measurements, respectively. The overall crystallization process of the PEO was strongly affected by lithium dodecyl sulfate (LDS) stabilized carbon nanotubes. Further, analysis of the overall crystallization kinetics showed that the PEO chains were topologically constrained by the presence of LDS with an increased energy barrier associated with nucleation and crystal growth, and the nanotubes further act as a barrier to chain transport or enhance the LDS action on the PEO chains. The energy penalty and diffusional barrier to chain transport in the nanocomposites disrupt the PEO crystal helical conformation. This destabilization leads to formation of thinner crystal lamellae and suggests that the crystallization kinetics is primarily controlled by the growth process. This study is particularly interesting considering the suppression of the PEO crystallinity in presence of small amounts of Lithium ion based surfactant and carbon nanotubes.

  8. Correlation of lattice defects and thermal processing in the crystallization of titania nanotube arrays

    NASA Astrophysics Data System (ADS)

    Hosseinpour, Pegah M.; Yung, Daniel; Panaitescu, Eugen; Heiman, Don; Menon, Latika; Budil, David; Lewis, Laura H.

    2014-12-01

    Titania nanotubes have the potential to be employed in a wide range of energy-related applications such as solar energy-harvesting devices and hydrogen production. As the functionality of titania nanostructures is critically affected by their morphology and crystallinity, it is necessary to understand and control these factors in order to engineer useful materials for green applications. In this study, electrochemically-synthesized titania nanotube arrays were thermally processed in inert and reducing environments to isolate the role of post-synthesis processing conditions on the crystallization behavior, electronic structure and morphology development in titania nanotubes, correlated with the nanotube functionality. Structural and calorimetric studies revealed that as-synthesized amorphous nanotubes crystallize to form the anatase structure in a three-stage process that is facilitated by the creation of structural defects. It is concluded that processing in a reducing gas atmosphere versus in an inert environment provides a larger unit cell volume and a higher concentration of Ti3+ associated with oxygen vacancies, thereby reducing the activation energy of crystallization. Further, post-synthesis annealing in either reducing or inert atmospheres produces pronounced morphological changes, confirming that the nanotube arrays thermally transform into a porous morphology consisting of a fragmented tubular architecture surrounded by a network of connected nanoparticles. This study links explicit data concerning morphology, crystallization and defects, and shows that the annealing gas environment determines the details of the crystal structure, the electronic structure and the morphology of titania nanotubes. These factors, in turn, impact the charge transport and consequently the functionality of these nanotubes as photocatalysts.

  9. Hierarchical interfaces induce high dielectric permittivity in nanocomposites containing TiO2@BaTiO3 nanofibers

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Chen, Weiwei; Wang, Jianjun; Shen, Yang; Gu, Lin; Lin, Yuanhua; Nan, Ce-Wen

    2014-05-01

    Interface issues are common and crucial in nanocomposites or nanohybrid systems since the interface area is enormous on the nanoscale. In the 0-3 dimensional polymer nanocomposites, in which nano-inclusions (0-dimension) are embedded in a 3-dimensionally connected polymer matrix, enhanced dielectric permittivity could be induced by the interfacial polarization at the interfaces between the nano-inclusions and the polymer matrix. In this contribution, we propose and demonstrate that the topological structure of the interface plays an equally important role as the area of the interface in determining the dielectric polarization of polymer nanocomposites. TiO2 nanofibers embedded with BaTiO3 nanoparticles are prepared via electrospinning and then fused with polyvinyl difluoride (PVDF) into polymer nanocomposite films. Modulation of hierarchical interfaces is thus achieved for these nanocomposites. The confinement of these additional interfaces inside the TiO2 nanofibers leads to percolated networks formed by the interfacial regions. The dielectric permittivity of the polymer nanocomposites is thus enhanced by ~300% over the PVDF matrix at a low filler loading of 11 vol%. A phase-field simulation study indicates that the enhanced dielectric permittivity could be attributed to the increased polarization in the percolated interfacial regions inside the TiO2 nanofibers. The instantaneous electrical breakdown of the TiO2@BaTiO3 nanofibers studied by the in situ transmission electron microscopy method further reveals the striking feature that the breakdown behavior of the nanofibers changes from semiconductive to metallic with the incorporation of insulating BaTiO3 nanoparticles.Interface issues are common and crucial in nanocomposites or nanohybrid systems since the interface area is enormous on the nanoscale. In the 0-3 dimensional polymer nanocomposites, in which nano-inclusions (0-dimension) are embedded in a 3-dimensionally connected polymer matrix, enhanced dielectric permittivity could be induced by the interfacial polarization at the interfaces between the nano-inclusions and the polymer matrix. In this contribution, we propose and demonstrate that the topological structure of the interface plays an equally important role as the area of the interface in determining the dielectric polarization of polymer nanocomposites. TiO2 nanofibers embedded with BaTiO3 nanoparticles are prepared via electrospinning and then fused with polyvinyl difluoride (PVDF) into polymer nanocomposite films. Modulation of hierarchical interfaces is thus achieved for these nanocomposites. The confinement of these additional interfaces inside the TiO2 nanofibers leads to percolated networks formed by the interfacial regions. The dielectric permittivity of the polymer nanocomposites is thus enhanced by ~300% over the PVDF matrix at a low filler loading of 11 vol%. A phase-field simulation study indicates that the enhanced dielectric permittivity could be attributed to the increased polarization in the percolated interfacial regions inside the TiO2 nanofibers. The instantaneous electrical breakdown of the TiO2@BaTiO3 nanofibers studied by the in situ transmission electron microscopy method further reveals the striking feature that the breakdown behavior of the nanofibers changes from semiconductive to metallic with the incorporation of insulating BaTiO3 nanoparticles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00703d

  10. Hierarchical interfaces induce high dielectric permittivity in nanocomposites containing TiO2@BaTiO3 nanofibers.

    PubMed

    Zhang, Xin; Chen, Weiwei; Wang, Jianjun; Shen, Yang; Gu, Lin; Lin, Yuanhua; Nan, Ce-Wen

    2014-06-21

    Interface issues are common and crucial in nanocomposites or nanohybrid systems since the interface area is enormous on the nanoscale. In the 0-3 dimensional polymer nanocomposites, in which nano-inclusions (0-dimension) are embedded in a 3-dimensionally connected polymer matrix, enhanced dielectric permittivity could be induced by the interfacial polarization at the interfaces between the nano-inclusions and the polymer matrix. In this contribution, we propose and demonstrate that the topological structure of the interface plays an equally important role as the area of the interface in determining the dielectric polarization of polymer nanocomposites. TiO2 nanofibers embedded with BaTiO3 nanoparticles are prepared via electrospinning and then fused with polyvinyl difluoride (PVDF) into polymer nanocomposite films. Modulation of hierarchical interfaces is thus achieved for these nanocomposites. The confinement of these additional interfaces inside the TiO2 nanofibers leads to percolated networks formed by the interfacial regions. The dielectric permittivity of the polymer nanocomposites is thus enhanced by ∼300% over the PVDF matrix at a low filler loading of 11 vol%. A phase-field simulation study indicates that the enhanced dielectric permittivity could be attributed to the increased polarization in the percolated interfacial regions inside the TiO2 nanofibers. The instantaneous electrical breakdown of the TiO2@BaTiO3 nanofibers studied by the in situ transmission electron microscopy method further reveals the striking feature that the breakdown behavior of the nanofibers changes from semiconductive to metallic with the incorporation of insulating BaTiO3 nanoparticles.

  11. Enhancement of output performance through post-poling technique on BaTiO3/PDMS-based triboelectric nanogenerator.

    PubMed

    Ali, Danish; Yu, Bin; Duan, Xiaochao; Yu, Hao; Zhu, Meifang

    2017-02-17

    In the modern era, the invention of new energy sources is important in order to make advances possible in electronic media. A triboelectric nanogenerator (TENG) is considered to be strong design that converts mechanical power into electrical power, using organic (polymer) or inorganic (lead, ceramic etc) materials to initiate the triboelectrification process, followed by charge separation. In this study, a lead-free BaTiO3/PDMS-Al-based TENG was fabricated by mixing tetragonal ferroelectric BaTiO3 nanocrystals in a PDMS matrix to make a composite for a working electrode film. It is worth noting that a new post- poling process has been introduced to align the dipole structures in the BaTiO3 nanocrystals, and to attain a high electron density on the surface of the working electrode film. The output was recorded up to 375 V and 6 μA of close circuit voltage and short circuit current, respectively, at a current density of 0.3 μA cm(-2) and an effective power equal to 2.25 mW at a load resistance of 100 MΩ, and is four times higher than a PDMS-Al-based TENG. This study also reveals the hidden locks that will enable other inorganic materials with a dipole structure to enhance their output using the post-poling technique. The TENG has a vast field of applications due to its stability, the flexibility of its thin films and its biocompatibility. It is also an aid for exploring new TENG devices with enhanced output performance.

  12. Enhancement of output performance through post-poling technique on BaTiO3/PDMS-based triboelectric nanogenerator

    NASA Astrophysics Data System (ADS)

    Ali, Danish; Yu, Bin; Duan, Xiaochao; Yu, Hao; Zhu, Meifang

    2017-02-01

    In the modern era, the invention of new energy sources is important in order to make advances possible in electronic media. A triboelectric nanogenerator (TENG) is considered to be strong design that converts mechanical power into electrical power, using organic (polymer) or inorganic (lead, ceramic etc) materials to initiate the triboelectrification process, followed by charge separation. In this study, a lead-free BaTiO3/PDMS-Al-based TENG was fabricated by mixing tetragonal ferroelectric BaTiO3 nanocrystals in a PDMS matrix to make a composite for a working electrode film. It is worth noting that a new post- poling process has been introduced to align the dipole structures in the BaTiO3 nanocrystals, and to attain a high electron density on the surface of the working electrode film. The output was recorded up to 375 V and 6 μA of close circuit voltage and short circuit current, respectively, at a current density of 0.3 μA cm-2 and an effective power equal to 2.25 mW at a load resistance of 100 MΩ, and is four times higher than a PDMS-Al-based TENG. This study also reveals the hidden locks that will enable other inorganic materials with a dipole structure to enhance their output using the post-poling technique. The TENG has a vast field of applications due to its stability, the flexibility of its thin films and its biocompatibility. It is also an aid for exploring new TENG devices with enhanced output performance.

  13. Electron paramagnetic resonance of Nb-doped BaTiO3 ceramics with positive temperature coefficient of resistivity

    NASA Astrophysics Data System (ADS)

    Jida, Shin'suke; Miki, Toshikatsu

    1996-11-01

    Paramagnetic centers in Nb-doped BaTiO3 ceramics are measured at 77-500 K by electron paramagnetic resonance (EPR) for investigating the role of the centers on the well-known positive temperature coefficient of resistivity (PTCR) effect (PTCR at the Curie temperature). EPR detects four signals; an anisotropically broad singlet signal at g=2.005, a sextet signal due to Mn2+, a Cr3+ signal, and a Ti3+ signal. The former two signals arise in the rhombohedral and cubic phases, but disappear in the tetragonal and orthorhombic phases. The Cr3+ signal appears in all of the phases, while the Ti3+ signal is detected only at low temperatures. The singlet signal also arises in undoped, barium-deficient BaTiO3 ceramics, therefore the signal is attributable to barium-vacancy-associated centers rather than Nb4+ ions or Fe3+ ions proposed by several authors. In this article, we propose that the singlet signal is due to vacancy-pairs of VBa-F+ type, i.e., the vacancy pair of VBa-VO capturing one electron. The electrical resistivity data show a polaronic character of low-temperature conduction and a high resistivity jump around the Curie temperature. The low-temperature polaronic conduction is explained in terms of electron-hopping between Ti4+ and Ti3+ ions. The resistivity jump at the Curie temperature occurs along with the EPR intensity increase of the singlet signal, the Mn2+ signal and the Cr3+ signal. We conclude that the PTCR of Nb-doped BaTiO3 ceramics is strongly associated with the trap activation of the VBa-VO vacancy-pairs and manganese centers at the tetragonal-to-cubic transition.

  14. Band-offsets at BaTiO3/Cu2O heterojunction and enhanced photoelectrochemical response: theory and experiment(Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sharma, Dipika; Satsangi, Vibha R.; Dass Kaura, Sahab; Shrivastav, Rohit; Waghmare, Umesh V.

    2016-10-01

    Band-offsets at BaTiO3/Cu2O heterojunction and enhanced photoelectrochemical response: theory and experiment Dipika Sharmaa, Vibha R. Satsangib, Rohit Shrivastava, Umesh V. Waghmarec, Sahab Dassa aDepartment of Chemistry, Dayalbagh Educational Institute, Agra-282 110 (India) bDepartment of Physics and Computer Sciences, Dayalbagh Educational Institute, Agra-282 110 (India) cTheoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore-560 064 (India) * Phone: +91-9219695960. Fax: +91-562-2801226. E-mail: drsahabdas@gmail.com. Study on photoelectrochemical activity of pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction has been carried out using DFT based band offsets and charge carriers effective mass calculations and their experimental verification. The results of DFT calculations show that BaTiO3 and Cu2O have staggered type band alignment after the heterojunction formation and high mobility of electrons in Cu2O as compared to the electrons in BaTiO3. Staggered type band edges alignment and high mobility of electrons and holes improved the separation of photo-generated charge carriers in BaTiO3/Cu2O heterojunction. To validate the theoretical results experiments were carried out on pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction with varying thickness of Cu2O. All samples were characterized by X- Ray Diffractometer, SEM and UV-Vis spectrometry. Nanostructured thin films of pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction were used as photoelectrode in the photoelectrochemical cell for water splitting reaction. Maximum photocurrent density of 1.44 mA/cm2 at 0.90 V/SCE was exhibited by 442 nm thick BaTiO3/Cu2O heterojunction photoelectrode Increased photocurrent density and enhanced photoconversion efficiency, exhibited by the heterojunction may be attributed to improved conductivity and enhanced separation of the photogenerated carriers at the BaTiO3/Cu2O interface. The experimental results and first-principles calculations compare well, thus suggesting that such calculations have the potential to be used in screening various metal oxide heterojunction before performing the experiments thereby saving precious chemicals, time and energy. Keywords: Photoelectrochemical, Water splitting, heterojunction, Cu2O, BaTiO3 References: [1] Surbhi Choudhary, et al. Nanostructured bilayered thin films in photoelectrochemical water splitting - A review: International Journal of Hydrogen Energy, (2012). [2] Dipika Sharma, Anuradha Verma, V.R. Satsangi, Rohit shrivastav, Sahab Dass Nanostructured SrTiO3 thin films sensitized by Cu2O for Photoelectrochemical Hydrogen Generation. International journal of Hydrogen Energy;42:,4230-4241, 2014.

  15. Confinement effects on the crystallization of poly(ethylene oxide) nanotubes.

    PubMed

    Maiz, Jon; Martin, Jaime; Mijangos, Carmen

    2012-08-21

    In this work, we show the effects of nanoconfinement on the crystallization of poly(ethylene oxide) (PEO) nanotubes embedded in anodized aluminum oxide (AAO) templates. The morphological characteristics of the hollow 1D PEO nanostructures were evaluated by scanning electron microscopy (SEM). The crystallization of the PEO nanostructures and bulk was studied with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The crystallization of PEO nanotubes studied by DSC is strongly influenced by the confinement showing a strong reduction in the crystallization temperature of the polymer. X-ray diffraction (XRD) experiments confirmed the isothermal crystallization results obtained by DSC, and studies carried out at low temperatures showed the absence of crystallites oriented with the extended chains perpendicular to the pore wall within the PEO nanotubes, which has been shown to be the typical crystal orientation for one-dimensional polymer nanostructures. In contrast, only planes oriented 33, 45, and 90° with respect to the plane (120) are arranged parallel to the pore's main axis, indicating preferential crystal growth in the direction of the radial component. Calculations based on classical nucleation theory suggest that heterogeneous nucleation prevails in the bulk PEO whereas for the PEO nanotubes a surface nucleation mechanism is more consistent with the obtained results.

  16. Direct detection of cysteine using functionalized BaTiO3 nanoparticles film based self-powered biosensor.

    PubMed

    Selvarajan, Sophia; Alluri, Nagamalleswara Rao; Chandrasekhar, Arunkumar; Kim, Sang-Jae

    2017-05-15

    Simple, novel, and direct detection of clinically important biomolecules have continuous demand among scientific community as well as in market. Here, we report the first direct detection and facile fabrication of a cysteine-responsive, film-based, self-powered device. NH2 functionalized BaTiO3 nanoparticles (BT-NH2 NPs) suspended in a three-dimensional matrix of an agarose (Ag) film, were used for cysteine detection. BaTiO3 nanoparticles (BT NPs) semiconducting as well as piezoelectric properties were harnessed in this study. The changes in surface charge properties of the film with respect to cysteine concentrations were determined using a current-voltage (I-V) technique. The current response increased with cysteine concentration (linear concentration range=10µM-1mM). Based on the properties of the composite (BT/Ag), we created a self-powered cysteine sensor in which the output voltage from a piezoelectric nanogenerator was used to drive the sensor. The potential drop across the sensor was measured as a function of cysteine concentrations. Real-time analysis of sensor performance was carried out on urine samples by non-invasive method. This novel sensor demonstrated good selectivity, linear concentration range and detection limit of 10µM; acceptable for routine analysis.

  17. Effect of microwave heating on BaTiO3:Nb ceramics with positive temperature coefficient of resistivity

    NASA Astrophysics Data System (ADS)

    Jida, Shin'suke; Suemasu, Takeshi; Miki, Toshikatsu

    1999-08-01

    The microwave heating technique is employed for obtaining high performance positive temperature coefficient of resistivity (PTCR) ceramics of Nb-doped BaTiO3 with a low resistivity at room temperature and a high resistivity jump above the Curie temperature. The grains of the BaTiO3:Nb ceramics prepared by microwave sintering are as large as 20-50 μm even when the Nb content exceeds 0.2 at. %, whereas such large grain size has never been obtained at this high content of Nb by ordinary sintering with an electric furnace. The large grains are also obtained by subjecting the heavily Nb-doped ceramics composed of fine grains to postheating with microwave after ordinary sintering. The room-temperature resistivity decreases down below 10 Ω cm and the PTCR character is obtained by postannealing in air. The mechanism of grain growth by microwave heating is discussed in terms of nonuniform temperature distribution of specimens during heating. The experimental data indicate that the microwave heating technique and the employment of a dopant that forms donor levels even at high doping levels will enable to develop high performance PTCR ceramics.

  18. Strain-induced insulator-metal transition in ferroelectric BaTiO3 (001) surface: First-principles study

    NASA Astrophysics Data System (ADS)

    Lin, Yang; Chang-An, Wang; Cong, Liu; Ming-Hui, Qin; Xu-Bing, Lu; Xing-Sen, Gao; Min, Zeng; Jun-Ming, Liu

    2016-07-01

    The electronic properties of TiO2-terminated BaTiO3 (001) surface subjected to biaxial strain have been studied using first-principles calculations based on density functional theory. The Ti ions are always inward shifted either at compressive or tension strains, while the inward shift of the Ba ions occurs only for high compressive strain, implying an enhanced electric dipole moment in the case of high compressive strain. In particular, an insulator-metal transition is predicted at a compressive biaxial strain of 0.0475. These changes present a very interesting possibility for engineering the electronic properties of ferroelectric BaTiO3 (001) surface. Project supported by the National Natural Science Foundation of China (Grant Nos. 1574091, 51272078, and 51431006), the Natural Science Foundation of Guangdong Province of China (Grant No. 2015A030313375), the Science and Technology Planning Project of Guangdong Province of China (Grant No. 2015B090927006), and the Program for International Innovation Cooperation Platform of Guangzhou City, China (Grant No. 2014J4500016).

  19. Complementary resistive switching in BaTiO3/NiO bilayer with opposite switching polarities

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Wei, Xianhua; Lei, Yao; Yuan, Xincai; Zeng, Huizhong

    2016-12-01

    Resistive switching behaviors have been investigated in the Au/BaTiO3/NiO/Pt structure by stacking the two elements with different switching types. The conducting atomic force microscope measurements on BaTiO3 thin films and NiO thin films suggest that with the same active resistive switching region, the switching polarities in the two semiconductors are opposite to each other. It is in agreement with the bipolar hysteresis I-V curves with opposite switching polarities for single-layer devices. The bilayer devices show complementary resistive switching (CRS) without electroforming and unipolar resistive switching (URS) after electroforming. The coexistence of CRS and URS is mainly ascribed to the co-effect of electric field and Joule heating mechanisms, indicating that changeable of resistance in this device is dominated by the redistribution of oxygen vacancies in BaTiO3 and the formation, disruption, restoration of conducting filaments in NiO. CRS in bilayer with opposite switching polarities is effective to solve the sneak current without the introduction of any selector elements or an additional metal electrode.

  20. Investigation of the structure and thermal behaviour of polymer liquid crystal / single wall carbon nanotubes nanocomposite

    NASA Astrophysics Data System (ADS)

    Exner, G.; Marinov, Y.; Perez, E.

    2017-01-01

    In the present work, nanocomposite of thermotropic polymer liquid crystal poly(heptane-1,7-dyil biphenyl-4,4’-dicarboxilate) and single wall carbon nanotubes was investigated. Nanocomposite films were casted from solution blended polymer liquid crystal and nanotubes. The structure and thermal behaviour of the nanocomposite were investigated by means of X-ray scattering and differential scanning calorimetry. The results show that there are two phase transitions on cooling and a single one on subsequent heating for both the neat polymer liquid crystal and nanocomposite. Hence, the smectic order of the polymer liquid crystal as well as its monotropic behaviour are preserved in the nanocomposite. The isotropic melt - smectic transition temperature in the nanocomposite is several degrees higher and the enthalpy of this process is much lower, suggesting heterogeneous nucleation of this phase on the surface of the nanotubes. The temperature of crystal structure formation during further cooling decreases in the nanocomposite showing a stabilization effect of the nanotubes on the smectic phase. Judging from the smaller enthalpy of the smectic-crystal phase transition and the new crystalline peak in the X-ray scattering patterns of the nanocomposite one could suggest a new crystalline form formation and this crystalline phase coexistence with smectic phases at lower temperatures.

  1. A review of molecular beam epitaxy of ferroelectric BaTiO3 films on Si, Ge and GaAs substrates and their applications.

    PubMed

    Mazet, Lucie; Yang, Sang Mo; Kalinin, Sergei V; Schamm-Chardon, Sylvie; Dubourdieu, Catherine

    2015-06-01

    SrTiO3 epitaxial growth by molecular beam epitaxy (MBE) on silicon has opened up the route to the monolithic integration of various complex oxides on the complementary metal-oxide-semiconductor silicon platform. Among functional oxides, ferroelectric perovskite oxides offer promising perspectives to improve or add functionalities on-chip. We review the growth by MBE of the ferroelectric compound BaTiO3 on silicon (Si), germanium (Ge) and gallium arsenide (GaAs) and we discuss the film properties in terms of crystalline structure, microstructure and ferroelectricity. Finally, we review the last developments in two areas of interest for the applications of BaTiO3 films on silicon, namely integrated photonics, which benefits from the large Pockels effect of BaTiO3, and low power logic devices, which may benefit from the negative capacitance of the ferroelectric.

  2. A review of molecular beam epitaxy of ferroelectric BaTiO3 films on Si, Ge and GaAs substrates and their applications

    PubMed Central

    Mazet, Lucie; Yang, Sang Mo; Kalinin, Sergei V; Schamm-Chardon, Sylvie; Dubourdieu, Catherine

    2015-01-01

    SrTiO3 epitaxial growth by molecular beam epitaxy (MBE) on silicon has opened up the route to the monolithic integration of various complex oxides on the complementary metal-oxide–semiconductor silicon platform. Among functional oxides, ferroelectric perovskite oxides offer promising perspectives to improve or add functionalities on-chip. We review the growth by MBE of the ferroelectric compound BaTiO3 on silicon (Si), germanium (Ge) and gallium arsenide (GaAs) and we discuss the film properties in terms of crystalline structure, microstructure and ferroelectricity. Finally, we review the last developments in two areas of interest for the applications of BaTiO3 films on silicon, namely integrated photonics, which benefits from the large Pockels effect of BaTiO3, and low power logic devices, which may benefit from the negative capacitance of the ferroelectric. PMID:27877816

  3. A review of molecular beam epitaxy of ferroelectric BaTiO3 films on Si, Ge and GaAs substrates and their applications

    DOE PAGES

    Mazet, Lucie; Yang, Sang Mo; Kalinin, Sergei V.; ...

    2015-06-30

    SrTiO3 epitaxial growth by molecular beam epitaxy (MBE) on silicon has opened up the route to the monolithic integration of various complex oxides on the complementary metal-oxide-semiconductor silicon platform. Among functional oxides, ferroelectric perovskite oxides offer promising perspectives to improve or add functionalities on-chip. We review the growth by MBE of the ferroelectric compound BaTiO3 on silicon (Si), germanium (Ge) and gallium arsenide (GaAs) and we discuss the film properties in terms of crystalline structure, microstructure and ferroelectricity. Lastly, we review the last developments in two areas of interest for the applications of BaTiO3 films on silicon, namely integrated photonics,more » which benefits from the large Pockels effect of BaTiO3, and low power logic devices, which may benefit from the negative capacitance of the ferroelectric.« less

  4. Structural evolution across the insulator-metal transition in oxygen-deficient BaTiO3-δ studied using neutron total scattering and Rietveld analysis

    DOE PAGES

    Jeong, I.-K.; Lee, Seunghun; Jeong, Se-Young; ...

    2011-08-29

    Oxygen-deficient BaTiO3-δ exhibits an insulator-metal transition with increasing δ. We performed neutron total scattering measurements to study structural evolution across an insulator-metal transition in BaTiO3-δ. Despite its significant impact on resistivity, slight oxygen reduction (δ=0.09) caused only a small disturbance on the local doublet splitting of Ti-O bond. This finding implies that local polarization is well preserved under marginal electric conduction. In the highly oxygen-deficient metallic state (δ=0.25), however, doublet splitting of the Ti-O bond became smeared. The smearing of the local Ti-O doublet is complemented with long-range structural analysis and demonstrates that the metallic conduction in the highly oxygen-reducedmore » BaTiO3-δ is due to the appearance of nonferroelectric cubic lattice.« less

  5. Electrical and reliability characteristics of Mn-doped nano BaTiO3-based ceramics for ultrathin multilayer ceramic capacitor application

    NASA Astrophysics Data System (ADS)

    Gong, Huiling; Wang, Xiaohui; Zhang, Shaopeng; Tian, Zhibin; Li, Longtu

    2012-12-01

    Nano BaTiO3-based dielectric ceramics were prepared by chemical coating approach, which are promising for ultrathin multilayer ceramic capacitor (MLCC) applications. The doping effects of Mn element on the microstructures and dielectric properties of the ceramics were investigated. The degradation test and impedance spectroscopy were employed to study the resistance degradation and the conduction mechanism of Mn-doped nano-BaTiO3 ceramic samples. It has been found that the reliability characteristics greatly depended on the Mn-doped content. Moreover, the BaTiO3 ceramic with grain size in nanoscale is more sensitive to the Mn-doped content than that in sub-micron scale. The addition of 0.3 mol. % Mn is beneficial for improving the reliability of the nano BaTiO3-based ceramics, which is an important parameter for MLCC applications. However, further increasing the addition amount will deteriorate the performance of the ceramic samples.

  6. Relation between electrical properties of aerosol-deposited BaTiO3 thin films and their mechanical hardness measured by nano-indentation

    PubMed Central

    2012-01-01

    To achieve a high capacitance density for embedded decoupling capacitor applications, the aerosol deposition (AD) process was applied as a thin film deposition process. BaTiO3 films were fabricated on Cu substrates by the AD process at room temperature, and the film thickness was reduced to confirm the limit of the critical minimum thickness for dielectric properties. As a result, the BaTiO3 thin films that were less than 1-μm thick showed unstable electric properties owing to their high leakage currents. Therefore, to overcome this problem, the causes of the high leakage currents were investigated. In this study, it was confirmed that by comparing BaTiO3 thin films on Cu substrates with those on stainless steels (SUS) substrates, macroscopic defects and rough interfaces between films and substrates influence the leakage currents. Moreover, based on the deposition mechanism of the AD process, it was considered that the BaTiO3 thin films on Cu substrates with thicknesses of less than 1 μm are formed with chinks and weak particle-to-particle bonding, giving rise to leakage currents. In order to confirm the relation between the above-mentioned surface morphologies and the dielectric behavior, the hardness of BaTiO3 films on Cu and SUS substrates was investigated by nano-indentation. Consequently, we proposed that the chinks and weak particle-to-particle bonding in the BaTiO3 thin films with thicknesses of less than 0.5 μm on Cu substrates could be the main cause of the high leakage currents. PMID:22616759

  7. Ultrafast Room-Temperature Crystallization of TiO2 Nanotubes Exploiting Water-Vapor Treatment

    NASA Astrophysics Data System (ADS)

    Lamberti, Andrea; Chiodoni, Angelica; Shahzad, Nadia; Bianco, Stefano; Quaglio, Marzia; Pirri, Candido F.

    2015-01-01

    In this manuscript a near-room temperature crystallization process of anodic nanotubes from amorphous TiO2 to anatase phase with a fast 30 minutes treatment is reported for the first time. This method involves the exposure of as-grown TiO2 nanotubes to water vapor flow in ambient atmosphere. The water vapor-crystallized samples are deeply investigated in order to gain a whole understanding of their structural, physical and chemical properties. The photocatalytic activity of the converted material is tested by dye degradation experiment and the obtained performance confirms the highly promising properties of this low-temperature processed material.

  8. Interface induced out-of-plane magnetic anisotropy in magnetoelectric BiFeO3-BaTiO3 superlattices

    NASA Astrophysics Data System (ADS)

    Lazenka, Vera; Jochum, Johanna K.; Lorenz, Michael; Modarresi, Hiwa; Gunnlaugsson, Haraldur P.; Grundmann, Marius; Van Bael, Margriet J.; Temst, Kristiaan; Vantomme, André

    2017-02-01

    Room temperature magnetoelectric BiFeO3-BaTiO3 superlattices with strong out-of-plane magnetic anisotropy have been prepared by pulsed laser deposition. We show that the out-of-plane magnetization component increases with the increasing number of double layers. Moreover, the magnetoelectric voltage coefficient can be tuned by varying the number of interfaces, reaching a maximum value of 29 V/cm Oe for the 20×BiFeO3-BaTiO3 superlattice. This enhancement is accompanied by a high degree of perpendicular magnetic anisotropy, making the latter an ideal candidate for the next generation of data storage devices.

  9. Nanotube liquid crystal elastomers: photomechanical response and flexible energy conversion of layered polymer composites

    NASA Astrophysics Data System (ADS)

    Fan, Xiaoming; King, Benjamin C.; Loomis, James; Campo, Eva M.; Hegseth, John; Cohn, Robert W.; Terentjev, Eugene; Panchapakesan, Balaji

    2014-09-01

    Elastomeric composites based on nanotube liquid crystals (LCs) that preserve the internal orientation of nanotubes could lead to anisotropic physical properties and flexible energy conversion. Using a simple vacuum filtration technique of fabricating nanotube LC films and utilizing a transfer process to poly (dimethyl) siloxane wherein the LC arrangement is preserved, here we demonstrate unique and reversible photomechanical response of this layered composite to excitation by near infra-red (NIR) light at ultra-low nanotube mass fractions. On excitation by NIR photons, with application of small or large pre-strains, significant expansion or contraction of the sample occurs, respectively, that is continuously reversible and three orders of magnitude larger than in pristine polymer. Schlieren textures were noted in these LC composites confirming long range macroscopic nematic order of nanotubes within the composites. Order parameters of LC films ranged from Soptical = 0.51-0.58 from dichroic measurements. Film concentrations, elastic modulus and photomechanical stress were all seen to be related to the nematic order parameter. For the same nanotube concentration, the photomechanical stress was almost three times larger for the self-assembled LC nanotube actuator compared to actuator based on randomly oriented carbon nanotubes. Investigation into the kinetics of photomechanical actuation showed variation in stretching exponent β with pre-strains, concentration and orientation of nanotubes. Maximum photomechanical stress of ˜0.5 MPa W-1 and energy conversion of ˜0.0045% was achieved for these layered composites. The combination of properties, namely, optical anisotropy, reversible mechanical response to NIR excitation and flexible energy conversion all in one system accompanied with low cost makes nanotube LC elastomers important for soft photochromic actuation, energy conversion and photo-origami applications.

  10. Nanotube liquid crystal elastomers: photomechanical response and flexible energy conversion of layered polymer composites.

    PubMed

    Fan, Xiaoming; King, Benjamin C; Loomis, James; Campo, Eva M; Hegseth, John; Cohn, Robert W; Terentjev, Eugene; Panchapakesan, Balaji

    2014-09-05

    Elastomeric composites based on nanotube liquid crystals (LCs) that preserve the internal orientation of nanotubes could lead to anisotropic physical properties and flexible energy conversion. Using a simple vacuum filtration technique of fabricating nanotube LC films and utilizing a transfer process to poly (dimethyl) siloxane wherein the LC arrangement is preserved, here we demonstrate unique and reversible photomechanical response of this layered composite to excitation by near infra-red (NIR) light at ultra-low nanotube mass fractions. On excitation by NIR photons, with application of small or large pre-strains, significant expansion or contraction of the sample occurs, respectively, that is continuously reversible and three orders of magnitude larger than in pristine polymer. Schlieren textures were noted in these LC composites confirming long range macroscopic nematic order of nanotubes within the composites. Order parameters of LC films ranged from S(optical) = 0.51-0.58 from dichroic measurements. Film concentrations, elastic modulus and photomechanical stress were all seen to be related to the nematic order parameter. For the same nanotube concentration, the photomechanical stress was almost three times larger for the self-assembled LC nanotube actuator compared to actuator based on randomly oriented carbon nanotubes. Investigation into the kinetics of photomechanical actuation showed variation in stretching exponent β with pre-strains, concentration and orientation of nanotubes. Maximum photomechanical stress of ∼ 0.5 MPa W(-1) and energy conversion of ∼ 0.0045% was achieved for these layered composites. The combination of properties, namely, optical anisotropy, reversible mechanical response to NIR excitation and flexible energy conversion all in one system accompanied with low cost makes nanotube LC elastomers important for soft photochromic actuation, energy conversion and photo-origami applications.

  11. Growing and characterizing one-dimensional crystals within single-walled carbon nanotubes.

    PubMed

    Hutchison, John L; Sloan, Jeremy; Kirkland, Angus I; Green, Malcolm L H

    2004-01-01

    Single-walled carbon nanotubes (SWNTs) have been used as growth templates for spatially confined crystal growth. The comparative crystallization and high-resolution transmission electron microscopy imaging properties of simple binary halides formed by the alkali iodides MI (M = Li, K, Na, Rb and Cs) within SWNTs are described. The most common structure type observed within SWNTs was the rocksalt archetype, although CsI was observed to form both body-centred cubic (bcc) and rocksalt structure types. ThCl4 was found to form a chain structure of Th[Cl]8 polyhedra. HgI2 crystallized within nanotubes with ultra-narrow (i.e. 0.8 nm) capillaries was observed to form helical 2 x 1 layer crystals.

  12. Mechanism of the emergence of the photo-EMF upon silicon liquid crystal-single crystal contact

    NASA Astrophysics Data System (ADS)

    Budagov, K. M.; Guseinov, A. G.; Pashaev, B. G.

    2017-03-01

    The effect light has on a silicon liquid crystal-single crystal contact at different temperatures of the surface doping of silicon, and when BaTiO3 nanoparticles are added to the composition of a liquid crystal, is studied. The mechanism of the emergence of the photo-EMF in the liquid crystal-silicon structure is explained.

  13. Discotic ionic liquid crystals of triphenylene as dispersants for orienting single-walled carbon nanotubes.

    PubMed

    Lee, Jeongho Jay; Yamaguchi, Akihisa; Alam, Md Akhtarul; Yamamoto, Yohei; Fukushima, Takanori; Kato, Kenichi; Takata, Masaki; Fujita, Norifumi; Aida, Takuzo

    2012-08-20

    Orient and conduct: Triphenylene-based discotic ionic liquid crystals (ILCs) with six imidazolium ion pendants can disperse pristine single-walled carbon nanotubes (SWNTs). When the ILC is columnarly assembled, doping with SWNTs results in macroscopic homeotropic columnar orientation. Combination of shear and annealing treatments gives rise to three different orientation states, which determine the anisotropy of electrical conduction.

  14. Photoluminescent Properties of Composites Based on the Liquid Crystal 5CB with Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Bezrodna, T. V.; Klishevich, G. V.; Nesprava, V. V.; Melnyk, V. I.; Roshchin, A. N.; Skryshevskyi, Yu. A.

    2017-01-01

    We have studied the influence of inorganic particles on the photoluminescent properties of the nematic liquid crystal 5CB in composites based on carbon nanotubes (CNTs) and hybrid nanoparticles consisting of carbon nanotubes and platelets of the organically modified mineral montmorillonite (MMT). We show that the photoluminescence (PL) of 5CB + CNT composites is characterized by excimer emission of the 5CB molecules. Adding carbon nanotubes to the liquid crystal medium leads to a considerable decrease in the photoluminescence intensity, but has practically no effect on the bulk structural alignment in the organic matrix. Hybrid CNT-MMT particles form a uniform coagulation network in the composite with 5CB and significantly disrupt the nematic structure of the liquid crystal. Bent conformations of the 5CB molecules appear which are typical of the liquid crystal monomers. The presence of the indicated 5CB conformers in the system and also the weaker interaction between the liquid crystal and the inorganic filler explain the increase in the photoluminescence intensity for the composite 5CB + CNT-MMT compared with the emission characteristics for the original liquid crystal.

  15. Influence of interfacial coherency on ferroelectric switching of superlattice BaTiO3/SrTiO3

    SciTech Connect

    Wu, Pingping; Ma, Xingqiao; Li, Yulan; Eom, C. B.; Schlom, Darrell G.; Gopalan, Venkatraman; Chen, Long-Qing

    2015-04-11

    Switching behavior of (BaTiO3)8/ (SrTiO3)4 heterostructure superlattice grown on SrTiO3 substrate was studied by employing the phase field method. To investigate the constraint effect of the substrate on switching, three types of superlattice/substrate interface mechanical relaxation conditions were considered, i.e. the fully ommensurate, partially relaxed and fully relaxed. Our simulation results demonstrated that the hysteresis loops under the three types of constraints were very different. The interfacial coherency affects dramatically the coercivity and remanence of the superlattice films. The mechanism of the hysteresis loop varying with interfacial coherency was analyzed by the ferroelectric domain configuration and its evolution during the switching process. The hysteresis loop of fully relaxed superlattice shows application potential on ferroelectric energy storage materials.

  16. Piezoelectric and Triboelectric Dual Effects in Mechanical-Energy Harvesting Using BaTiO3/Polydimethylsiloxane Composite Film.

    PubMed

    Suo, Guoquan; Yu, Yanhao; Zhang, Zhiyi; Wang, Shifa; Zhao, Ping; Li, Jianye; Wang, Xudong

    2016-12-21

    Piezoelectric and triboelectric nanogenerators have been developed as rising energy-harvesting devices in the past few years to effectively convert mechanical energy into electricity. Here, a novel hybrid piezo/triboelectric nanogenerator based on BaTiO3 NP/PDMS composite film was developed in a simple and low-cost way. The effects of the BTO content and polarization degree on the output performance were systematically studied. The device with 20 wt % BTO in PDMS and a 100-μm-thick film showed the highest output power. We also designed three measurement modes to record hybrid, triboelectric, and piezoelectric outputs separately with a simple structure that has only two electrodes. The hybrid output performance is higher than the tribo- and piezoelectric performances. This work will provide not only a new way to enhance the output power of nanogenerators, but also new opportunities for developing built-in power sources in self-powered electronics.

  17. Vacancy-induced magnetism in BaTiO3(001) thin films based on density functional theory.

    PubMed

    Cao, Dan; Cai, Meng-Qiu; Hu, Wang-Yu; Yu, Ping; Huang, Hai-Tao

    2011-03-14

    The origin of magnetism induced by vacancies on BaTiO(3)(001) surfaces is investigated systematically by first-principles calculations within density-functional theory. The calculated results show that O vacancy is responsible for the magnetism of the BaO-terminated surface and the magnetism of the TiO(2)-terminated surface is induced by Ti vacancy. For the BaO-terminated surface, the magnetism mainly arises from the unpaired electrons that are localized in the O vacancy basin. In contrast, for the TiO(2)-terminated surface, the magnetism mainly originates from the partially occupied O-2p states of the first nearest neighbor O atoms surrounding the Ti vacancy. These results suggest the possibility of implementing magneto-electric coupling in conventional ferroelectric materials.

  18. Effects of MgO Doping on DC Bias Aging Behavior of Mn-Doped BaTiO3

    NASA Astrophysics Data System (ADS)

    Hahn, Dong Woo; Hong, Jeong Oh; Han, Young Ho

    2008-07-01

    The capacitance aging of multilayer ceramic capacitors (MLCCs) based on BaTiO3 dielectrics under DC electric fields has been studied. At a DC field of 1 V/µm, the capacitance of MLCC specimens decreased immediately in a very short period (<10 s, the first stage) and then decreased continuously with time (the second stage). Substitution of Mn ions markedly increased the slope of aging curves in the second stage. MgO doping significantly decreased the second stage aging rate of Mn-doped specimens. This aging rate decreased in the second stage with increasing MgO content. This may be due to the existence of a stable defect complex (MgTi''-VO••) inhibiting domain wall motion. MgO-doped specimens showed a small decrease in capacitance in the first stage, which may be due to small grain size and low dielectric permittivity.

  19. Dielectric Properties of Rare-Earth-Oxide-Doped BaTiO3 Ceramics Fired in Reducing Atmosphere

    NASA Astrophysics Data System (ADS)

    Okino, Yoshikazu; Shizuno, Hisamitsu; Kusumi, Shinya; Kishi, Hiroshi

    1994-09-01

    In order to gain an understanding of highly reliable electrical characteristics for the Ho-doped multilayer ceramic capacitors with Ni electrodes, dielectric properties of various rare-earth-oxide-doped BaTiO3 ceramics were studied. The smaller ionic radius rare-earth-oxide (Dy, Ho, Er)-doped samples showed lower resistivity in reducing atmosphere, but higher resistivity in oxidizing atmosphere at the cooling stage, compared with the larger-ion (La, Sm, Gd)-doped samples. Multilayer ceramic capacitors with Ni electrodes using the smaller-ion-doped materials showed smaller aging rate and longer lifetime. We developed Ni-electrode MLCs with X7R specification as 1 µ F in the 2125 type.

  20. The coupled effects of oxygen defect and crystallographic orientation on the electromechanical properties of BaTiO3 nanowires

    NASA Astrophysics Data System (ADS)

    Ghorbanali, Saeed; Shahraki, Mehran Gholipour

    2017-02-01

    Influence of oxygen vacancies on electromechanical properties of individual BaTiO3 (BTO) nanowires (NWs) is investigated, using molecular dynamics simulations. The simulations were performed for defected 0-4% oxygen vacancy defects) tetragonal NWs with axial directions of [001] and [110]. Results show an increase in spontaneous polarization and piezoelectric constant of the individual NWs due to increasing oxygen vacancy concentration, and a decrease in yield stress and Young's modulus. It seems that in individual BTO NWs the softening effect of the oxygen vacancies overcomes the pinning effect and results in enhancement of piezoelectric constant and spontaneous polarization. Results also show that yield stress and Young's modulus of the NWs with axial direction of [001] are higher than those for NWs with axial direction of [110] while it is reverse for spontaneous polarization and piezoelectric constant.

  1. Polar distortion in ultrathin BaTiO3 films studied by in situ LEED I-V

    NASA Astrophysics Data System (ADS)

    Shin, Junsoo; Nascimento, V. B.; Borisevich, A. Y.; Plummer, E. W.; Kalinin, S. V.; Baddorf, A. P.

    2008-06-01

    Phase stability in nanoscale ferroelectrics is governed by the interplay of electrostatic depolarization energy, domain formation, adsorption, and surface band bending. Using in situ low-energy electron-diffraction intensity versus voltage (LEED I-V ), we have characterized 4 and 10 ML BaTiO3 films, grown using pulsed laser deposition with fully compressive strain on a SrRuO3/SrTiO3 substrate. LEED I-V reveals a single surface dead layer and a monodomain vertically polarized state below. The single orientation is attributed to the intrinsic imprint asymmetry and the stability of a polarized phase to compensation of depolarizing charges by dipoles induced by surface stress.

  2. Piezoelectric and Dielectric Properties of Multilayered BaTiO3/(Ba,Ca)TiO3/CaTiO3 Thin Films.

    PubMed

    Zhu, Xiao Na; Gao, Ting Ting; Xu, Xing; Liang, Wei Zheng; Lin, Yuan; Chen, Chonglin; Chen, Xiang Ming

    2016-08-31

    Highly oriented multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films were fabricated on Nb-doped (001) SrTiO3 (Nb:STO) substrates by pulsed laser deposition. The configurations of multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films are designed with the thickness ratio of 1:1:1 and 2:1:1 and total thickness ∼300 nm. Microstructural characterization by X-ray diffraction indicates that the as-deposited thin films are highly c-axis oriented and large in-plane strain is determined in BaTiO3 and CaTiO3 layers. Piezoresponse force microscopy (PFM) studies reveal an intense in-plane polarization component, whereas the out-of-plane shows inferior phase contrast. The optimized combination is found to be the BaTiO3-(Ba0.85Ca0.15)TiO3-CaTiO3 structure with combination ratio 2:1:1, which displays the largest domain switching amplitude under DC electric field, the largest room-temperature dielectric constant ∼646, a small dielectric loss of 0.03, and the largest dielectric tunability of ∼50% at 400 kV/cm. These results suggest that the enhanced dielectric and tunability performance are greatly associated with the large in-plane polarization component and domain switching.

  3. Magnetoelectric effect in laminate composites of Tb1-xDyxFe2-y and Fe-doped BaTiO3

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Fan, Junfeng; Rong, Xiaofang; Cao, Hongxia; Wei, Jianjun

    2007-03-01

    Fe-doped BaTiO3 has been synthesized with sol-gel technique. Its transformation point of ferroelectric to paraelectric and the latent heat of the transformation were observed at 103.27 °C and 169.9 J/mol, respectively. They are a little less than those for pure BaTiO3. Bonded layered composites Tb1-xDyxFe2-y/BaTi0.99Fe0.01O3 have been fabricated. Their magnetoelectric (ME) effect has been investigated. The transverse ME voltage coefficient for the bilayer Tb1-xDyxFe2-y-BaTi0.99Fe0.01O3 and the trilayer Tb1-xDyxFe2-y-BaTi0.99Fe0.01O3-Tb1-xDyxFe2-y can reach 578 (mv Oe-1 cm-1) and 2100 (mv Oe-1 cm-1), respectively, under a bias magnetic field of 350 Oe at room temperature. Those are about 50% larger than those for the bilayer and trilayer composed by pure BaTiO3. It suggests that the doped BaTiO3 can be a new choice of piezoelectrics to compose ME composites.

  4. First principles study of Ca in BaTiO3 and Bi0.5Na0.5TiO3

    NASA Astrophysics Data System (ADS)

    Fongkaew, Ittipon; T-Thienprasert, Jiraroj; Limpijumnong, Sukit

    2015-11-01

    BaTiO3-Bi0.5Na0.5TiO3 is one of the promising candidates as a high-temperature relaxor with a high Curie temperature and several preferred dielectric characteristics. It has been found experimentally for a long time that adding calcium to BaTiO3-Bi0.5Na0.5TiO3 improves its temperature characteristic of the capacitance [J. Electron. Mater. 39, 2471]. In this study, Calcium (Ca) defects in perovskite BaTiO3 and Bi0.5Na0.5TiO3 have been studied based on first-principles calculations. In both BaTiO3 and Bi0.5Na0.5TiO3, our calculations showed that Ca atom energetically prefers to substitute for the cations, that is Ba, Bi, Na and Ti, depending on the growth conditions. In most cases, Ca predominantly substitutes on the A-site without providing additional electrical carriers (serve as either neutral defects or self-compensating defects). The growth conditions where Ca can be forced to substitute for B-site (with limited amount) and the conditions where Ca can be forced to serve as an acceptor are identified. Details of the local structures, formation energies and electronic properties of these Ca defects are reported.

  5. Polarization-Mediated Modulation of Electronic and Transport Properties of Hybrid MoS2-BaTiO3-SrRuO3 Tunnel Junctions.

    PubMed

    Li, Tao; Sharma, Pankaj; Lipatov, Alexey; Lee, Hyungwoo; Lee, Jung-Woo; Zhuravlev, Mikhail Y; Paudel, Tula R; Genenko, Yuri A; Eom, Chang-Beom; Tsymbal, Evgeny Y; Sinitskii, Alexander; Gruverman, Alexei

    2017-02-08

    Hybrid structures composed of ferroelectric thin films and functional two-dimensional (2D) materials may exhibit unique characteristics and reveal new phenomena due to the cross-interface coupling between their intrinsic properties. In this report, we demonstrate a symbiotic interplay between spontaneous polarization of the ultrathin BaTiO3 ferroelectric film and conductivity of the adjacent molybdenum disulfide (MoS2) layer, a 2D narrow-bandgap semiconductor. Polarization-induced modulation of the electronic properties of MoS2 results in a giant tunneling electroresistance effect in the hybrid MoS2-BaTiO3-SrRuO3 ferroelectric tunnel junctions (FTJs) with an OFF-to-ON resistance ratio as high as 10(4), a 50-fold increase in comparison with the same type of FTJs with metal electrodes. The effect stems from the reversible accumulation-depletion of the majority carriers in the MoS2 electrode in response to ferroelectric switching, which alters the barrier at the MoS2-BaTiO3 interface. Continuous tunability of resistive states realized via stable sequential domain structures in BaTiO3 adds memristive functionality to the hybrid FTJs. The use of narrow band 2D semiconductors in conjunction with ferroelectric films provides a novel pathway for development of the electronic devices with enhanced performance.

  6. Mechanism of high dielectric performance of polymer composites induced by BaTiO3-supporting Ag hybrid fillers

    NASA Astrophysics Data System (ADS)

    Fang, Fang; Yang, Wenhu; Yu, Shuhui; Luo, Suibin; Sun, Rong

    2014-03-01

    BaTiO3-supporting Ag hybrid particles (BT-Ag) with varied fraction of Ag were synthesized by reducing silver nitrate in the glycol solution containing BaTiO3 (BT) suspensions. The Ag nano particles with a size of about 20 nm were discretely grown on the surface of the BT. The dielectric performance of the composites containing the BT-Ag as fillers in the matrix of polyvinylidene fluoride (PVDF) was investigated. The relative permittivity (ɛr) of the BT-Ag/PVDF composites increased prominently with the increase of BT-Ag loading amount, and the typical conductive path of the conductor/polymer system was not observed even with a high loading of BT-Ag. The ɛr at 100 Hz for the three BT-(0.31, 0.49, 0.61)Ag/PVDF composites at room temperature were 283, 350, and 783, respectively. The ɛr of the composites was enhanced by more than 3 times compared with that of the composite containing untreated BT nanoparticles at frequencies over 1 kHz and the loss tangent (tan δ) was less than 0.1 which should be attributed to the low conductivity of the composites. Theoretical calculations based on the effective medium percolation theory model and series-parallel model suggested that the enhanced permittivity of BT-Ag/PVDF composites should arise from the ultrahigh permittivity of BT-Ag fillers, which was over 104 and associated with the content of Ag deposited on the surface of BT.

  7. Photoluminescence microscopy on air-suspended carbon nanotubes coupled to photonic crystal nanobeam cavities

    NASA Astrophysics Data System (ADS)

    Miura, R.; Imamura, S.; Shimada, T.; Ohta, R.; Iwamoto, S.; Arakawa, Y.; Kato, Y. K.

    2014-03-01

    Because carbon nanotubes are room-temperature telecom-band emitters and can be grown on silicon substrates, they are ideal for coupling to silicon photonic cavities.[2,3 In particular, as-grown air-suspended carbon nanotubes show excellent optical properties, but cavity modes with large fields in the air are needed in order to achieve efficient coupling. Here we investigate individual air-suspended nanotubes coupled to photonic crystal nanobeam cavities. We utilize cavities that confine air-band modes which have large fields in the air. Dielectric mode cavities are also prepared for comparison. We fabricate the devices from silicon-on-insulator substrates by using electron beam lithography and dry etching to form the nanobeam structure. The buried oxide layer is removed by wet etching, and carbon nanotubes are grown onto the cavities by chemical vapor deposition. We perform photoluminescence imaging and excitation spectroscopy to find the positions of the nanotubes and identify their chiralities. For both types of devices, cavity modes with quality factors of ~3000 are observed within the nanotube emission peak. Work supported by SCOPE, KAKENHI, The Telecommunications Advancement Foundation, The Toyota Physical and Chemical Research Institute, Project for Developing Innovation Systems of MEXT, Japan and the Photon Frontier Network Program of MEXT, Japan.

  8. Two layer 4:4 co-ordinated KI crystals grown within single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Sloan, J.; Novotny, M. C.; Bailey, S. R.; Brown, G.; Xu, C.; Williams, V. C.; Friedrichs, S.; Flahaut, E.; Callender, R. L.; York, A. P. E.; Coleman, K. S.; Green, M. L. H.; Dunin-Borkowski, R. E.; Hutchison, J. L.

    2000-10-01

    The formation of `all surface' 4:4 co-ordinated KI crystals within 1.4 nm diameter single walled carbon nanotubes (SWNT) is reported. KI was inserted into the SWNTs by a capillary method [J. Sloan, D.M. Wright, H.G. Woo, S. Bailey, G. Brown, A.P.E. York, K.S. Coleman, J.L. Hutchison, M.L.H. Green, J. Chem. Soc. Chem. Commun. (1999) 699], whereby the nanotubes were combined intimately with the molten halide. The crystals grew with <0 0 1> (relative to bulk KI) parallel to the tubule axes and were continuous tetragonally distorted bilayer crystals composed of alternating columns of K-I and I-K pairs when viewed along <1 0 0> .

  9. Giant persistent photoconductivity in BaTiO3/TiO2 heterostructures

    NASA Astrophysics Data System (ADS)

    Plodinec, Milivoj; Šantić, Ana; Zavašnik, Janez; Čeh, Miran; Gajović, Andreja

    2014-10-01

    The persistent photoconductivity (PPC) effect in nanotube arrays of barium titanate and TiO2 (BTO/TiO2NT) was studied at room temperature under daylight illumination. The BTO/TiO2NT heterostructures exhibited a giant PPC effect that was six orders of magnitude higher than the dark conductivity, followed by a slow relaxation for 3 h. The PPC in this material was explained by the existence of defects at the surfaces and the interfaces of the investigated heterostructures. The sample was prepared using a two-step synthesis: the anodization of a Ti-foil and a subsequent hydrothermal synthesis. The structural and electrical characteristics were studied by micro-Raman spectroscopy, field-emission-gun scanning electron microscopy, and impedance spectroscopy.

  10. Exploring the alignment of carbon nanotubes dispersed in a liquid crystal matrix using coplanar electrodes

    SciTech Connect

    Volpati, D.; Massey, M. K.; Kotsialos, A.; Qaiser, F.; Pearson, C.; Tiburzi, G.; Zeze, D. A.; Petty, M. C.; Johnson, D. W.; Coleman, K. S.

    2015-03-28

    We report on the use of a liquid crystalline host medium to align single-walled carbon nanotubes in an electric field using an in-plane electrode configuration. Electron microscopy reveals that the nanotubes orient in the field with a resulting increase in the DC conductivity in the field direction. Current versus voltage measurements on the composite show a nonlinear behavior, which was modelled by using single-carrier space-charge injection. The possibility of manipulating the conductivity pathways in the same sample by applying the electrical field in different (in-plane) directions has also been demonstrated. Raman spectroscopy indicates that there is an interaction between the nanotubes and the host liquid crystal molecules that goes beyond that of simple physical mixing.

  11. Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field

    PubMed Central

    García-García, Amanda; Vergaz, Ricardo; Algorri, José F; Zito, Gianluigi; Cacace, Teresa; Marino, Antigone; Otón, José M

    2016-01-01

    Summary Single-wall carbon nanotubes (SWCNT) are anisotropic nanoparticles that can cause modifications in the electrical and electro-optical properties of liquid crystals. The control of the SWCNT concentration, distribution and reorientation in such self-organized fluids allows for the possibility of tuning the liquid crystal properties. The alignment and reorientation of CNTs are studied in a system where the liquid crystal orientation effect has been isolated. Complementary studies including Raman spectroscopy, microscopic inspection and impedance studies were carried out. The results reveal an ordered reorientation of the CNTs induced by an electric field, which does not alter the orientation of the liquid crystal molecules. Moreover, impedance spectroscopy suggests a nonnegligible anchoring force between the CNTs and the liquid crystal molecules. PMID:27547599

  12. Nanotubes.

    PubMed

    Rao, C N; Satishkumar, B C; Govindaraj, A; Nath, M

    2001-02-16

    Carbon nanotubes were discovered soon after the successful laboratory synthesis of fullerenes. Since their discovery in 1991, there has been intensive research activity in the area of carbon nanotubes, not only because of their fascinating structural features and properties, but also because of their potential technological applications. There is increasing experimental evidence to show that carbon nanotubes may find use in nanoelectronic devices, displays, and in hydrogen storage. In this article, we discuss various important aspects related to the synthesis, structure, characterization, and mechanism of formation of multi-walled and single-walled carbon nanotubes, followed by a presentation of the important electronic, mechanical, hydrogen storage, and other properties of the nanotubes. Doping, as well as other chemical manipulations with boron and nitrogen, bring about significant changes in the properties of the nanotubes. Carbon nanotubes also serve as useful templates to make other nanostructures. Layered metal chalcogenides, boron nitride, and other materials form nanotubes and provide considerable scope for study.

  13. Ionic properties of liquid crystals dispersed with carbon nanotubes and montmorillonite nanoplatelets

    NASA Astrophysics Data System (ADS)

    Liu, Hsuan-Hung; Lee, Wei

    2010-10-01

    The ionic properties of liquid crystals doped with one-dimensional carbon nanotubes, two-dimensional montmorillonite, and a mixture of both are investigated. The results indicate that the relaxation times of electrode polarization and ionic conductivity are time-dependent after the cell fabrication regardless of doping. While all of the dopants are effective in capturing impurity ions, the cells containing the hybrid dopant exhibit the feeblest ionic effect at room temperature.

  14. Vacuum filtration based formation of liquid crystal films of semiconducting carbon nanotubes and high performance transistor devices

    NASA Astrophysics Data System (ADS)

    King, Benjamin; Panchapakesan, Balaji

    2014-05-01

    In this paper, we report ultra-thin liquid crystal films of semiconducting carbon nanotubes using a simple vacuum filtration process. Vacuum filtration of nanotubes in aqueous surfactant solution formed nematic domains on the filter membrane surface and exhibited local ordering. A 2D fast Fourier transform was used to calculate the order parameters from scanning electron microscopy images. The order parameter was observed to be sensitive to the filtration time demonstrating different regions of transformation namely nucleation of nematic domains, nanotube accumulation and large domain growth.Transmittance versus sheet resistance measurements of such films resulted in optical to dc conductivity of σ opt/σ dc = 9.01 indicative of purely semiconducting nanotube liquid crystal network.Thin films of nanotube liquid crystals with order parameters ranging from S = 0.1-0.5 were patterned into conducting channels of transistor devices which showed high I on/I off ratios from 10-19 800 and electron mobility values μ e = 0.3-78.8 cm2 (V-s)-1, hole mobility values μ h = 0.4-287 cm2 (V-s)-1. High I on/I off ratios were observed at low order parameters and film mass. A Schottky barrier transistor model is consistent with the observed transistor characteristics. Electron and hole mobilities were seen to increase with order parameters and carbon nanotube mass fractions. A fundamental tradeoff between decreasing on/off ratio and increasing mobility with increasing nanotube film mass and order parameter is therefore concluded. Increase in order parameters of nanotubes liquid crystals improved the electronic transport properties as witnessed by the increase in σ dc/σ opt values on macroscopic films and high mobilities in microscopic transistors. Liquid crystal networks of semiconducting nanotubes as demonstrated here are simple to fabricate, transparent, scalable and could find wide ranging device applications.

  15. Electrical response of liquid crystal cells doped with multi-walled carbon nanotubes

    PubMed Central

    García-García, Amanda; Vergaz, Ricardo; Algorri, José Francisco; Quintana, Xabier

    2015-01-01

    Summary The inclusion of nanoparticles modifies a number of fundamental properties of many materials. Doping of nanoparticles in self-organized materials such as liquid crystals may be of interest for the reciprocal interaction between the matrix and the nanoparticles. Elongated nanoparticles and nanotubes can be aligned and reoriented by the liquid crystal, inducing noticeable changes in their optical and electrical properties. In this work, cells of liquid crystal doped with high aspect ratio multi-walled carbon nanotubes have been prepared, and their characteristic impedance has been studied at different frequencies and excitation voltages. The results demonstrate alterations in the anisotropic conductivity of the samples with the applied electric field, which can be followed by monitoring the impedance evolution with the excitation voltage. Results are consistent with a possible electric contact between the coated substrates of the LC cell caused by the reorientation of the nanotubes. The reversibility of the doped system upon removal of the electric field is quite low. PMID:25821679

  16. Annealing control of magnetic anisotropy and phase separation in CoFe2O4-BaTiO3 nanocomposite films

    NASA Astrophysics Data System (ADS)

    Rafique, Mohsin; Herklotz, A.; Guo, E.-J.; Roth, R.; Schultz, L.; Dörr, K.; Manzoor, Sadia

    2013-12-01

    Multiferroic heteroepitaxial nanocomposite films of BaTiO3 and CoFe2O4 (CFO) have been grown by pulsed laser deposition employing alternating ablation of two ceramic targets. Films grown at temperatures between 650 °C and 710 °C contain columnar CFO grains about 10-20 nm in diameter embedded in a BaTiO3 matrix. The very strong vertical compression of these grains causes large perpendicular magnetic anisotropy. Post-growth annealing treatments above the growth temperature gradually release the compression. This allows one to tune the stress-induced magnetic anisotropy. Additionally, annealing leads to substantial enhancement of the saturation magnetization MS. Since MS of a pure CFO film remains unchanged by a similar annealing procedure, MS is proposed to depend on the volume fraction of the obtained CFO phase. We suggest that MS can be utilized to monitor the degree of phase separation in nanocomposite films.

  17. Oxygen loss, semiconductivity, and positive temperature coefficient of resistance behavior in undoped cation-stoichiometric BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Beltrán, H.; Cordoncillo, E.; Escribano, P.; Sinclair, D. C.; West, A. R.

    2005-11-01

    Stoichiometric BaTiO3 ceramics fabricated from sol-gel-derived powders and sintered at temperatures <=1100 °C are highly insulating and electrically homogeneous. At higher sintering temperatures, samples gradually lose oxygen and the conductivity increases as a consequence. The latter phenomena are very sensitive to the furnace atmosphere and are partially reversible during cooling when partial reoxidation can occur. This results in ceramics that are often electrically heterogeneous with insulating surfaces or grain boundaries but semiconducting grain cores. In samples that were heated at 1450 °C in N2 and quenched, a positive temperature coefficient of resistance (PTCR) effect was observed, associated with an additional impedance arising from space-charge effects. These results demonstrate that, depending on sample processing, insulating cation-stoichiometric BaTiO3 can instead be semiconducting and under certain circumstances, exhibit a PTCR effect, without the need for donor dopant additives.

  18. Dielectric and magnetic characterization of the mixed system (BaTiO3)x(NiFe2O4)1-x

    NASA Astrophysics Data System (ADS)

    Riesco, R.; Peiteado, M.; Bernardo-Maestro, B.; Caballero, A. C.; Cebollada, F.; de Frutos, J.; Gonzalo, J. A.; Aragó, C.

    2015-10-01

    Ceramic composites of the mixed system (BaTiO3)x(NiFe2O4)1-x (x = 1, 0.8, 0.65, 0.6, 0.5, 0.2, 0) have been prepared by hydrothermal synthesis and characterized through dielectric and magnetic measurements. It is shown that, when compared with the first-order phase transition of pure BaTiO3, the ferroelectric response of this mixed system is dramatically smeared by the presence of ferrite and eventually disappears around x ≈ 0.65. The peak of the dielectric constant becomes increasingly smoothed with composition, also diminishing its maximum value as the frequency increases. Moreover, the magnetic behavior is not suppressed by the presence of the ferroelectric perovskite and just qualitative changes occur in the hysteresis parameters on the whole compositional range.

  19. Microstructure and dielectric properties of nano-grained X7R type BaTiO3 ceramic capacitors sintered by 2.45 GHz microwave

    NASA Astrophysics Data System (ADS)

    Chen, Cheng-Sao; Chou, Chen-Chia

    2007-12-01

    Systematic investigation on the effects of microwave sintering on the characteristics of nano-grained BaTiO3 (BT) capacitor materials co-doped with yttrium (Y) and magnesium (Mg) elements was carried out. The granular structure in these materials was observed to be relatively insensitive to the sintering temperature and soaking time. The nano-sized BaTiO3 capacitor materials possessing X7R dielectric constant-temperature (K-T) characteristics have been obtained over a wide range of sintering conditions. Transmission electron microscope (TEM) examinations revealed that the detailed microstructural study of these materials is extremely complicated. The unique K-T properties of the materials are ascribed to the duplex structure in the samples, namely finer grains of paraelectric phase and larger grains of ferroelectric phase.

  20. Fabrication of BaTiO3-Based Dielectrics for Ultrathin-Layer Multilayer Ceramic Capacitor Application by a Modified Coating Approach

    NASA Astrophysics Data System (ADS)

    Tian, Zhibin; Wang, Xiaohui; Zhang, Yichi; Song, Tae-Ho; Hur, Kang Heon; Li, Longtu

    2011-02-01

    The development of multilayer ceramic capacitor (MLCC) with base metal electrode (BME) requires precise controlling of the microstructure in a very thin dielectric layer (<1 µm). In this paper, a modified coating approach for high coverage of BaTiO3 powder for further MLCC application has been developed. The well dispersed and coated BaTiO3 powders are prepared and the relative mechanism has been discussed. Furthermore, the ultrafine grained X7R dielectric ceramics were produced by both conventional mixing and modified coating methods. Compared with the conventional mixing method, the ceramics prepared by the coating approach exhibited better TCC (the temperature coefficient of capacitance) performance, with dielectric constant over 2000 and grain size below 150 nm. In addition, it is found through the coating method the content of additives can be reduced to a relatively smaller amount than that required in conventional mixing method.

  1. Hybridization and electron-phonon coupling in ferroelectric BaTiO3 probed by resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Fatale, S.; Moser, S.; Miyawaki, J.; Harada, Y.; Grioni, M.

    2016-11-01

    We investigated the ferroelectric perovskite material BaTiO3 by resonant inelastic x-ray scattering (RIXS) at the Ti L3 edge. We observe with decreasing temperature a transfer of spectral weight from the elastic to the charge-transfer spectral features, indicative of increasing Ti 3 d -O 2 p hybridization. When the incident photon energy selects transitions to the Ti 3 d eg manifold, the quasielastic RIXS response exhibits a tail indicative of phonon excitations. A fit of the spectral line shape by a theoretical model allows us to estimate the electron-phonon coupling strength M ˜0.25 eV, which places BaTiO3 in the intermediate coupling regime.

  2. Rapid stability of ferroelectric polarization in the Ca, Ce hybrid doped BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Shujuan; Zhang, Lixue; Wang, Jiping; Shi, Xiujing; Zhao, Yingying; Zhang, Dawei

    2016-12-01

    In this work, we report a rapid stability phenomenon of ferroelectric polarization in the Ca, Ce hybrid doped BaTiO3 ceramics (BCaxT+BTCe8) (x = 10, 20, 24, 30 mol%) prepared by separate doping Ca2+ and Ce4+ ions. Double hysteresis loops are identified in the aged BCaxT+BTCe8 samples; meanwhile, the polarization of these loops present a rapid decrease within very short aging time (about 1 h), and then the polarization remains almost unchanged over the followed ~1000 h. This phenomenon is not reported in previous researches. Raman scattering spectrum indicates that oxygen vacancies are generated because of Ca2+ ions entering into Ti sites partly in the BCaxT+BTCe8 samples, and then the oxygen vacancies are quantitatively characterized by half of the Ce3+ content through the XPS test. The emergence of the aging phenomenon is explained through the defect dipole reorientation mechanism. The larger radius of Ca2+ ions is further discussed as a possible reason for the rapid stability phenomenon of ferroelectric polarization. It may provide an effective design method from the viewpoint of the ionic radius to accelerate polarization stability, and thus to facilitate the possible practical applications of the aging effect.

  3. Observation of ferroelectricity at room temperature in ~1 nm thick conducting BaTiO3-δ

    NASA Astrophysics Data System (ADS)

    Lee, Seungran; Baasanforj, L.; Chang, Jungwon; Hwang, Inwoong; Kim, Jungrae; Shim, Seungbo; Song, Jonghyun; Kim, Jinhee

    Efforts to search for new and multi-functionalities in thin-film systems have led important findings of unknown phenomena and functionality which do not appear in bulk systems. As film growth technique is advanced, one can decrease the film thickness even thinner down to ~ nm, its unique physical properties are still appearing. For example, the superconducting metallic state of an LaAlO3/SrTiO3 (LAO/STO) heterostructure was found where LAO is about 3-4 unit cells (uc). An SrRuO3 film exhibited its ferromagnetic metallicity down to 4-6 uc; a few years later, its ferromagnetism was found to be disappeared at 2-3 uc. Meanwhile, theoretical methods have predicted existence of ferroelectrical properties mostly in prototype ferroelectric BaTiO3 (BTO): 3-6 uc. However, experimental verification to find such predicted thickness was hindered by large leakage current. Here we observed that ~1 nm-thick conducting BTO fillms show ferroelectric switching at room temperature (RT), and BTO films are fully-strained on LAO/STO heterostructures thicker than 5 nm thickness. Our experimental results will enlarge applicable functional oxide devices for future applications.

  4. Relating Electronic and Geometric Structure of Atomic Layer Deposited BaTiO3 to its Electrical Properties

    PubMed Central

    2016-01-01

    Atomic layer deposition allows the fabrication of BaTiO3 (BTO) ultrathin films with tunable dielectric properties, which is a promising material for electronic and optical technology. Industrial applicability necessitates a better understanding of their atomic structure and corresponding properties. Through the use of element-specific X-ray absorption near edge structure (XANES) analysis, O K-edge of BTO as a function of cation composition and underlying substrate (RuO2 and SiO2) is revealed. By employing density functional theory and multiple scattering simulations, we analyze the distortions in BTO’s bonding environment captured by the XANES spectra. The spectral weight shifts to lower energy with increasing Ti content and provides an atomic scale (microscopic) explanation for the increase in leakage current density. Differences in film morphologies in the first few layers near substrate–film interfaces reveal BTO’s homogeneous growth on RuO2 and its distorted growth on SiO2. This work links structural changes to BTO thin-film properties and provides insight necessary for optimizing future BTO and other ternary metal oxide-based thin-film devices. PMID:27009677

  5. Rapid stability of ferroelectric polarization in the Ca, Ce hybrid doped BaTiO3 ceramics

    PubMed Central

    Liu, Shujuan; Zhang, Lixue; Wang, Jiping; Shi, Xiujing; Zhao, Yingying; Zhang, Dawei

    2016-01-01

    In this work, we report a rapid stability phenomenon of ferroelectric polarization in the Ca, Ce hybrid doped BaTiO3 ceramics (BCaxT+BTCe8) (x = 10, 20, 24, 30 mol%) prepared by separate doping Ca2+ and Ce4+ ions. Double hysteresis loops are identified in the aged BCaxT+BTCe8 samples; meanwhile, the polarization of these loops present a rapid decrease within very short aging time (about 1 h), and then the polarization remains almost unchanged over the followed ~1000 h. This phenomenon is not reported in previous researches. Raman scattering spectrum indicates that oxygen vacancies are generated because of Ca2+ ions entering into Ti sites partly in the BCaxT+BTCe8 samples, and then the oxygen vacancies are quantitatively characterized by half of the Ce3+ content through the XPS test. The emergence of the aging phenomenon is explained through the defect dipole reorientation mechanism. The larger radius of Ca2+ ions is further discussed as a possible reason for the rapid stability phenomenon of ferroelectric polarization. It may provide an effective design method from the viewpoint of the ionic radius to accelerate polarization stability, and thus to facilitate the possible practical applications of the aging effect. PMID:28004752

  6. BaTiO3 based relaxor ferroelectric epitaxial thin-films for high-temperature operational capacitors

    NASA Astrophysics Data System (ADS)

    Kumaragurubaran, Somu; Nagata, Takahiro; Takahashi, Kenichiro; Ri, Sung-Gi; Tsunekawa, Yoshifumi; Suzuki, Setsu; Chikyow, Toyohiro

    2015-04-01

    The epitaxial growth of 0.6[BaTiO3]-0.4[Bi(Mg2/3Nb1/3)O3] (BT-BMN) relaxor ferroelectric thin-films on (100) Nb doped SrTiO3 substrates has been achieved and the structure is investigated for high-temperature capacitor applications. The post growth annealing decreases the oxygen vacancy and other defects in BT-BMN films, resulting in the enhancement of dielectric constant. An insertion of intermediate SrRuO3 layers as an electrode instead of Pt, sandwiching the film, is found to be more effective in enhancing the dielectric constant. A very high dielectric constant exceeding 400 was achieved from high-temperature annealed film and the film showed an excellent dielectric constant stability of below 11% in the temperature range of 80-400 °C. This will enable smaller, high-temperature tolerant, monolithically integrated thin-film capacitors on power semiconductor devices.

  7. Positive and negative electrocaloric effect in BaTiO3 in the presence of defect dipoles

    NASA Astrophysics Data System (ADS)

    Ma, Yang-Bin; Grünebohm, Anna; Meyer, Kai-Christian; Albe, Karsten; Xu, Bai-Xiang

    2016-09-01

    The influence of defect dipoles on the electrocaloric effect (ECE) in acceptor doped BaTiO3 is studied by means of lattice-based Monte-Carlo simulations using a Ginzburg-Landau type effective Hamiltonian. Oxygen vacancy-acceptor associates are described by fixed local dipoles with orientation parallel or antiparallel to the external field. By a combination of canonical and microcanonical simulations the ECE is directly evaluated. Our results reveal that in the case of antiparallel defect dipoles the ECE can be positive or negative depending on the dipole density. Moreover, a transition from a negative to positive ECE can be observed when the external field increases. These transitions are due to the delicate interplay of internal and external fields and are explained by the domain structure evolution and related field-induced entropy changes. The results are in good qualitative agreement to those obtained by molecular dynamics simulations employing an ab initio based effective Hamiltonian. Finally, a modified electrocaloric cycle, which makes use of the negative ECE in the presence of defect dipoles, is proposed to enhance the cooling effect.

  8. Effect of sintering temperature and oxygen atmosphere on electrocaloric effect of BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Ren, Xue-Chong; Nie, Wei-Li; Bai, Yang; Qiao, Li-Jie

    2015-09-01

    This paper demonstrates the effect of sintering parameters on the electrocaloric effect (ECE) in BaTiO3 ferroelectric ceramics, especially the sintering temperature and atmosphere. The samples were prepared by solid-state reaction method. With the rise of sintering temperature from 1200 °C to 1350 °C, the grain size increases remarkably and the densification is improved. The 1350 °C sintered sample has better ferroelectricity and higher latent heat for ferroelectric-paraelectric phase transition than those of the 1200 °C sintered sample. Correspondingly, it exhibits much better ECE. If the sample is sintered in pure oxygen, instead of in air, all ferroelectricity, dielectric strength and ECE are further enhanced. The sample sintered at 1350 °C in oxygen exhibits an excellent ECE performance with ΔTmax = 1.37 K and ΔSmax = 1.75 J/kg K. Contribution to the Topical Issue "Materials for Dielectric Applications", edited by Maciej Jaroszewski and Sabu Thomas.

  9. Enhanced piezoelectric and mechanical properties of AlN-modified BaTiO3 composite ceramics.

    PubMed

    Xu, Dan; Wang, Lidong; Li, Weili; Wang, Wei; Hou, Yafei; Cao, Wenping; Feng, Yu; Fei, Weidong

    2014-07-14

    BaTiO3-xAlN (BT-xAlN) composite ceramics were prepared by conventional solid state reaction sintering. The effects of the AlN content on the crystalline structures, densities, and electrical and mechanical properties of the BT ceramics were investigated. The BT-1.5%AlN ceramic exhibits a good piezoelectric constant of 305 pC N(-1) and an improved Vickers hardness of 5.9 GPa. The enhanced piezoelectricity originates from interactions between defect dipoles and spontaneous polarization inside the domains due to the occurrence of local symmetry, caused by the preferential distribution of the Al(3+)-N(3-) pairs vertical to the c axis. The hardening of the material is attributed to the improved density, and particle and grain boundary strengthening. Our work indicates that if a suitable doping ion pair is designed, lead-free ceramic systems prepared from ordinary raw materials by a conventional sintering method have a high probability of exhibiting good piezoelectric and mechanical properties simultaneously.

  10. NIR to blue light upconversion in Tm3+/Yb3+ codoped BaTiO3 tellurite glass

    NASA Astrophysics Data System (ADS)

    Kumari, Astha; Rai, Vineet Kumar

    2015-05-01

    Upconversion is an interesting optical property, generally shown by rare-earth doped materials. This unusual optical behavior shown by these rare-earths doped materials are due to their peculiar atomic configuration and electronic transitions. Here, the Tm3+-Yb3+ codoped BaTiO3 glass with TeO2 as former has been prepared by conventional melt and quench technique and the upconversion property has been investigated with the help of near infrared (NIR) to Visible UC study. The generation of the visible UC bands around ˜ 476 nm, ˜ 653 nm, ˜ 702 nm and one NIR UC band at ˜795 nm are assigned due to the 1G4→ 3H6, 1G4→ 3F4, 3F2→ 3H6 and 3H4→ 3H6 transitions respectively. The generations of these upconversion bands have been discussed in detail with the help of energy level diagram. The colour coordinates corresponding to the prepared material have been shown with the help of CIE chromaticity diagram. These glasses can be very appropriately used in the fabrication of solid state laser and as NIR to blue light upconverter.

  11. Time-Dependent Negative Capacitance Effects in Al2O3/BaTiO3 Bilayers.

    PubMed

    Kim, Yu Jin; Yamada, Hiroyuki; Moon, Taehwan; Kwon, Young Jae; An, Cheol Hyun; Kim, Han Joon; Kim, Keum Do; Lee, Young Hwan; Hyun, Seung Dam; Park, Min Hyuk; Hwang, Cheol Seong

    2016-07-13

    The negative capacitance (NC) effects in ferroelectric materials have emerged as the possible solution to low-power transistor devices and high-charge-density capacitors. Although the steep switching characteristic (subthreshold swing < sub-60 mV/dec) has been demonstrated in various devices combining the conventional transistors with ferroelectric gates, the actual applications of the NC effects are still some way off owing to the inherent hysteresis problem. This work reinterpreted the hysteretic properties of the NC effects within the time domain and demonstrated that capacitance (charge) boosting could be achieved without the hysteresis from the Al2O3/BaTiO3 bilayer capacitors through short-pulse charging. This work revealed that the hysteresis phenomenon in NC devices originated from the dielectric leakage of the dielectric layer. The suppression of charge injection via the dielectric leakage, which usually takes time, inhibits complete ferroelectric polarization switching during a short pulse time. It was demonstrated that a nonhysteretic NC effect can be achieved only within certain limited time and voltage ranges, but that these are sufficient for critical device applications.

  12. Relating electronic and geometric structure of atomic layer deposited BaTiO3 to its electrical properties

    DOE PAGES

    Torgersen, Jan; Acharya, Shinjita; Dadlani, Anup Lal; ...

    2016-03-24

    Atomic layer deposition allows the fabrication of BaTiO3 (BTO) ultrathin films with tunable dielectric properties, which is a promising material for electronic and optical technology. Industrial applicability necessitates a better understanding of their atomic structure and corresponding properties. Through the use of element-specific X-ray absorption near edge structure (XANES) analysis, O K-edge of BTO as a function of cation composition and underlying substrate (RuO2 and SiO2) is revealed. By employing density functional theory and multiple scattering simulations, we analyze the distortions in BTO’s bonding environment captured by the XANES spectra. The spectral weight shifts to lower energy with increasing Timore » content and provides an atomic scale (microscopic) explanation for the increase in leakage current density. Differences in film morphologies in the first few layers near substrate–film interfaces reveal BTO’s homogeneous growth on RuO2 and its distorted growth on SiO2. As a result, this work links structural changes to BTO thin-film properties and provides insight necessary for optimizing future BTO and other ternary metal oxide-based thin-film devices.« less

  13. Relating Electronic and Geometric Structure of Atomic Layer Deposited BaTiO3 to its Electrical Properties.

    PubMed

    Torgersen, Jan; Acharya, Shinjita; Dadlani, Anup Lal; Petousis, Ioannis; Kim, Yongmin; Trejo, Orlando; Nordlund, Dennis; Prinz, Fritz B

    2016-04-21

    Atomic layer deposition allows the fabrication of BaTiO3 (BTO) ultrathin films with tunable dielectric properties, which is a promising material for electronic and optical technology. Industrial applicability necessitates a better understanding of their atomic structure and corresponding properties. Through the use of element-specific X-ray absorption near edge structure (XANES) analysis, O K-edge of BTO as a function of cation composition and underlying substrate (RuO2 and SiO2) is revealed. By employing density functional theory and multiple scattering simulations, we analyze the distortions in BTO's bonding environment captured by the XANES spectra. The spectral weight shifts to lower energy with increasing Ti content and provides an atomic scale (microscopic) explanation for the increase in leakage current density. Differences in film morphologies in the first few layers near substrate-film interfaces reveal BTO's homogeneous growth on RuO2 and its distorted growth on SiO2. This work links structural changes to BTO thin-film properties and provides insight necessary for optimizing future BTO and other ternary metal oxide-based thin-film devices.

  14. Integrated silicon nanophotonics: structure and electro-optic properties of BaTiO3 on Si(001)

    NASA Astrophysics Data System (ADS)

    Kormondy, Kristy; Fallegger, Florian; Abel, Stefan; Popoff, Youri; Ponath, Patrick; Posadas, Agham; Sousa, Marilyne; Caimi, Daniele; Siegwart, Heinz; Uccelli, Emanuele; Czornomaz, Lukas; Marchiori, Chiara; Fompeyrine, Jean; Demkov, Alexander

    2015-03-01

    High-quality epitaxial BaTiO3 (BTO) on Si has emerged as a promising material for future electro-optic (EO) devices based on BTO's large effective Pockels coefficient. In order to achieve strong EO coupling, a film must have (1) correct crystallographic orientation with respect to the applied electric field, and (2) low leakage current in the film to sustain a strong electric field. We report on the EO response of BTO films deposited on Si by molecular beam epitaxy. O2 rapid thermal anneal at 600C for 30 min ensures full oxidation of BTO for minimal leakage current with minor change in crystalline structure. EO characterization was performed by analyzing changes of the polarization of a laser beam transmitted through pairs of lithographically defined electrodes. The EO response shows signatures of ferroelectric domains with in-plane polarization. Comparison with normalized responses of c-axis and a-axis films illustrate that a strong EO response is observed even for a mixed film. These results quantify the relationship between BTO structure and EO properties, an important step towards future silicon photonic devices based on ferroelectric oxides.

  15. Hybrid chitosan-Pluronic F-127 films with BaTiO3:Co nanoparticles: Synthesis and properties

    NASA Astrophysics Data System (ADS)

    Fuentes, S.; Dubo, J.; Barraza, N.; González, R.; Veloso, E.

    2015-03-01

    In this study, magnetic BaTiO3:Co (BT:Co) nanoparticles prepared using a combined sol-gel-hydrothermal technique were dispersed in a chitosan/Pluronic F-127 solution (QO/Pl) to obtain a nanocomposite hybrid films. Nanoparticles and hybrid films were characterized by X-ray powder diffraction, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and alternating gradient magnetometry (AGM). Experimental results indicated that the BT:Co nanoparticles were encapsulated in the QO/Pl hybrid films and that the magnetic properties of the QO/Pl/BT:Co nanocomposites are similar to the naked BT:Co nanoparticles. Results indicate that Co doping produces an enhancement in the ferromagnetic behavior of the BT nanoparticle. The coating restricts this enhancement only to low-fields, leaving the diamagnetic behavior of BT at high-fields. Magnetically stable sizes (PSD) were obtained at 3% Co doping for both naked nanoparticles and hybrid films. These show an increased magnetic memory capacity and a softer magnetic hardness with respect to non-doped BT nanoparticles.

  16. Isothermal crystallization kinetics of novel isotactic polypropylene/MoS2 inorganic nanotube nanocomposites.

    PubMed

    Naffakh, Mohammed; Marco, Carlos; Gómez-Fatou, Marián A

    2011-03-17

    Inorganic nanotubes (INT) were used for the first time to prepare advanced polymer nanocomposites by means of the most simple, cost-effective and ecologically friendly way (i.e., melt-processing route). The polymer matrix was isotactic polypropylene (iPP) and the inorganic fillers were molybdenum disulfide nanotubes (MoS(2)). The effect of INT-MoS(2) concentration and the crystallization temperature on the isothermal crystallization behavior of iPP was investigated using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXS). It has been observed that INT-MoS(2) affects the crystallization of nanocomposites remarkably, which can be attributed to the nucleating effect of INT-MoS(2) on the monoclinic α-crystal form of iPP. Other parameters such as the Avrami exponent and the fold surface free energy of crystallization of iPP chains in the nanocomposites were obtained in order to determine the effect of the INT-MoS(2) on them. The addition of INT-MoS(2) remarkably influences the kinetics of nucleation and growth of iPP with a decrease in the fold surface free energy of 11-24%.

  17. Nanoconfinement induced crystal orientation and large piezoelectric coefficient in vertically aligned P(VDF-TrFE) nanotube array

    PubMed Central

    Liew, Weng Heng; Mirshekarloo, Meysam Sharifzadeh; Chen, Shuting; Yao, Kui; Tay, Francis Eng Hock

    2015-01-01

    Vertically aligned piezoelectric P(VDF-TrFE) nanotube array comprising nanotubes embedded in anodized alumina membrane matrix without entanglement has been fabricated. It is found that the crystallographic polar axes of the P(VDF-TrFE) nanotubes are oriented along the nanotubes long axes. Such a desired crystal orientation is due to the kinetic selection mechanism for lamellae growth confined in the nanopores. The preferred crystal orientation in nanotubes leads to huge piezoelectric coefficients of the P(VDF-TrFE). The piezoelectric strain and voltage coefficients of P(VDF-TrFE) nanotube array are observed to be 1.97 and 3.40 times of those for conventional spin coated film. Such a significant performance enhancement is attributed to the well-controlled polarization orientation, the elimination of the substrate constraint, and the low dielectric constant of the nanotube array. The P(VDF-TrFE) nanotube array exhibiting the unique structure and outstanding piezoelectric performance is promising for wide applications, including various electrical devices and electromechanical sensors and transducers. PMID:25966301

  18. Nanoparticle-Based Magnetoelectric BaTiO3-CoFe2O4 Thin Film Heterostructures for Voltage Control of Magnetism.

    PubMed

    Erdem, Derya; Bingham, Nicholas S; Heiligtag, Florian J; Pilet, Nicolas; Warnicke, Peter; Vaz, Carlos A F; Shi, Yanuo; Buzzi, Michele; Rupp, Jennifer L M; Heyderman, Laura J; Niederberger, Markus

    2016-11-22

    Multiferroic composite materials combining ferroelectric and ferromagnetic order at room temperature have great potential for emerging applications such as four-state memories, magnetoelectric sensors, and microwave devices. In this paper, we report an effective and facile liquid phase deposition route to create multiferroic composite thin films involving the spin-coating of nanoparticle dispersions of BaTiO3, a well-known ferroelectric, and CoFe2O4, a highly magnetostrictive material. This approach offers great flexibility in terms of accessible film configurations (co-dispersed as well as layered films), thicknesses (from 100 nm to several μm) and composition (5-50 wt % CoFe2O4 with respect to BaTiO3) to address various potential applications. A detailed structural characterization proves that BaTiO3 and CoFe2O4 remain phase-separated with clear interfaces on the nanoscale after heat treatment, while electrical and magnetic studies indicate the simultaneous presence of both ferroelectric and ferromagnetic order. Furthermore, coupling between these orders within the films is demonstrated with voltage control of the magnetism at ambient temperatures.

  19. Vertical Interface Induced Dielectric Relaxation in Nanocomposite (BaTiO3)1-x:(Sm2O3)x Thin Films

    PubMed Central

    Li, Weiwei; Zhang, Wei; Wang, Le; Gu, Junxing; Chen, Aiping; Zhao, Run; Liang, Yan; Guo, Haizhong; Tang, Rujun; Wang, Chunchang; Jin, Kuijuan; Wang, Haiyan; Yang, Hao

    2015-01-01

    Vertical interfaces in vertically aligned nanocomposite thin films have been approved to be an effective method to manipulate functionalities. However, several challenges with regard to the understanding on the physical process underlying the manipulation still remain. In this work, because of the ordered interfaces and large interfacial area, heteroepitaxial (BaTiO3)1-x:(Sm2O3)x thin films have been fabricated and used as a model system to investigate the relationship between vertical interfaces and dielectric properties. Due to a relatively large strain generated at the interfaces, vertical interfaces between BaTiO3 and Sm2O3 are revealed to become the sinks to attract oxygen vacancies. The movement of oxygen vacancies is confined at the interfaces and hampered by the misfit dislocations, which contributed to a relaxation behavior in (BaTiO3)1-x:(Sm2O3)x thin films. This work represents an approach to further understand that how interfaces influence on dielectric properties in oxide thin films. PMID:26061829

  20. Hydrothermal synthesis and properties of NiFe2O4@BaTiO3 composites with well-matched interface

    PubMed Central

    Zhou, Jian-Ping; Lv, Li; Liu, Qian; Zhang, Yu-Xiang; Liu, Peng

    2012-01-01

    NiFe2O4@BaTiO3 multiferroic composite particles were produced by a simple hydrothermal method in two steps: preparing NiFe2O4 nanoparticles and then synthesizing core-shell nanocomposites. Multiferroic composite ceramics were sintered from these powders. X-ray diffraction, Raman scattering and energy dispersive x-ray analyses indicated that the core-shell composites with a NiFe2O4 core and BaTiO3 shell were formed in the hydrothermal environment. Different types of sharp interfaces were self-assembled owing to the minimization of direct elastic energy. The saturation magnetization of the composites linearly increased with the NiFe2O4 content while the dielectric constant decreased. A dielectric peak appeared at around 460 °C because of the oxygen vacancies in the BaTiO3 ceramics. It resulted in an enhancement of magnetic permeability in the composites, indicating magnetoelectric coupling that was also observed by direct magnetoelectric measurements. PMID:27877501

  1. Excited configurations of hydrogen in the BaTiO3 -xHx perovskite lattice associated with hydrogen exchange and transport

    NASA Astrophysics Data System (ADS)

    Ito, T. U.; Koda, A.; Shimomura, K.; Higemoto, W.; Matsuzaki, T.; Kobayashi, Y.; Kageyama, H.

    2017-01-01

    Excited configurations of hydrogen in the oxyhydride BaTiO3 -xHx (x =0.1 -0.5 ), which are considered to be involved in its hydrogen transport and exchange processes, were investigated by positive muon spin relaxation spectroscopy using muonium (Mu) as a pseudoisotope of hydrogen. Muons implanted into the BaTiO3 -xHx perovskite lattice were mainly found in two qualitatively different metastable states. One was assigned to a highly mobile interstitial protonic state, which is commonly observed in perovskite oxides. The other was found to form an entangled two spin-1/2 system with the nuclear spin of an H- ion at the anion site. The structure of the (H,Mu) complex agrees well with that of a neutralized center containing two H- ions at a doubly charged oxygen vacancy, which was predicted to form in the SrTiO3 -δ perovskite lattice by a computational study [Y. Iwazaki et al., APL Mater. 2, 012103 (2014), 10.1063/1.4854355]. Above 100 K, interstitial Mu+ diffusion and retrapping to a deep defect were observed, which could be a rate-limiting step of macroscopic Mu/H transport in the BaTiO3 -xHx lattice.

  2. A first-principles study on the mechanism of screening depolarizing field in two-dimensional BaTiO3 nanosheets

    NASA Astrophysics Data System (ADS)

    Gao, Haigen; Yue, Zhenxing; Li, Longtu

    2016-03-01

    A first-principles method is employed to study the mechanism of screening depolarizing field in two-dimensional BaTiO3 nanosheets. The geometric structures and ferroelectric properties show that the low-dimensional BaTiO3 with thickness m = 3 is a freestanding ultrathin film. Therefore, the scale of BaTiO3 nanosheets is defined as m = 1 and 2. The stable domain period corresponding to m = 1, 2, and 3 is 2, 2, and 6, respectively. When m = 1 and 2, only the spontaneous polarizations perpendicular to the surfaces are observed, and they are ˜6 and 15 μC/cm2, respectively. This indicates that the depolarizing field still has an effect on spontaneous polarizations. The difference in macroscopic charge density distribution between ferroelectric and paraelectric phases reveals that a dipole is formed at the ferroelectric domain wall, which leads to a decrease in the depolarizing field in the direction [001]. As a consequence, the critical thickness disappears.

  3. Direct observation of oxygen-vacancy-enhanced polarization in a SrTiO3-buffered ferroelectric BaTiO3 film on GaAs

    DOE PAGES

    Qiao, Q.; Zhang, Y.; Contreras-Guerrero, Rocio; ...

    2015-11-16

    The integration of functional oxide thin-films on compound semiconductors can lead to a class of reconfigurable spin-based optoelectronic devices if defect-free, fully reversible active layers are stabilized. However, previous first-principles calculations predicted that SrTiO3 thin filmsgrown on Si exhibit pinned ferroelectric behavior that is not switchable, due to the presence of interfacial vacancies. Meanwhile, piezoresponse force microscopy measurements have demonstrated ferroelectricity in BaTiO3 grown on semiconductor substrates. The presence of interfacial oxygen vacancies in such complex-oxide/semiconductor systems remains unexplored, and their effect on ferroelectricity is controversial. We also use a combination of aberration-corrected scanning transmission electron microscopy and first-principles densitymore » functional theory modeling to examine the role of interfacial oxygen vacancies on the ferroelectricpolarization of a BaTiO3 thin filmgrown on GaAs. Moreover, we demonstrate that interfacial oxygen vacancies enhance the polar discontinuity (and thus the single domain, out-of-plane polarization pinning in BaTiO3), and propose that the presence of surface charge screening allows the formation of switchable domains.« less

  4. Local manifestations of a static magnetoelectric effect in nanostructured BaTiO3-BaFe12O9 composite multiferroics.

    PubMed

    Trivedi, Harsh; Shvartsman, Vladimir V; Lupascu, Doru C; Medeiros, Marco S A; Pullar, Robert C; Kholkin, Andrei L; Zelenovskiy, Pavel; Sosnovskikh, Andrey; Shur, Vladimir Ya

    2015-03-14

    A study on magnetoelectric phenomena in the barium titanate-barium hexaferrite (BaTiO3-BaFe12O19) composite system, using high resolution techniques including switching spectroscopy piezoresponse force microscopy (SSPFM) and spatially resolved confocal Raman microscopy (CRM), is presented. It is found that both the local piezoelectric coefficient and polarization switching parameters change on the application of an external magnetic field. The latter effect is rationalized by the influence of magnetostrictive stress on the domain dynamics. Processing of the Raman spectral data using principal component analysis (PCA) and self-modelling curve resolution (SMCR) allowed us to achieve high resolution phase distribution maps along with separation of average and localized spectral components. A significant effect of the magnetic field on the Raman spectra of the BaTiO3 phase has been revealed. The observed changes are comparable with the classical pressure dependent studies on BaTiO3, confirming the strain mediated character of the magnetoelectric coupling in the studied composites.

  5. Nanocrystalline BaTiO3 powder via ambient conditions sol process (Prop.2001-071)

    SciTech Connect

    Payzant, E Andrew; Wang, X.; Hu, Michael Z.; Blom, Douglas Allen

    2005-01-01

    Nanocrystalline BaTiO{sub 3} particles have been prepared by ambient condition sol (ACS) process starting from soluble precursors of barium and titanium yielding a mixed oxide/hydroxide gel. The gel was peptized and crystallized in water under a refluxing condition. Higher initial pH and Ba/Ti ratio led to smaller crystallite sizes of BaTiO{sub 3} powders. Organic mineralizer, tetramethylammonium hydroxide (TMAH), can adsorb on the BaTiO{sub 3} nuclei and inhibited further growth of the particles. Adding a polymer during BaTiO{sub 3} synthesis led to a smaller particle size and increased redispersibility of the particles in water.

  6. The effects of sintering temperature on dielectric constant of Barium Titanate (BaTiO3)

    NASA Astrophysics Data System (ADS)

    Sandi, DianisaKhoirum; Supriyanto, Agus; Anif; Jamaluddin; Iriani, Yofentina

    2016-02-01

    Barium Titanate (BT) has been synthesized using solid-state reaction method. Raw materials are Barium Carbonate (BaCO3) and Titanium Dioxide (TiO2). These materials are mixed for 6 h and sintered at a temperature of 1000oC, 1100oC, and 1200oC for 2 h. The sintering temperature was varied to investigate its effects on microstructure and dielectric constant of BT. The XRD patterns showed that BT becomes homogenous, with the large lattice parameter as the increase of sintering temperature. The crystal structure of BT is tetragonal. The crystalline size and crystallinity of BT at a sintering temperature of 1000oC are 37 nm and 97%. Those values for BT at a sintering temperature of 1100oC are 38 nm and 96%. At a sintering temperature of 1200oC, the values are 41 nm and 97%. The dielectric constant of BT at a sintering temperature of 1000oC, 1100oC, and 1200oC are 148, 163, and 185, respectively. It can be concluded that sintering temperature affects microstructure and dielectric constant of BT. High sintering temperature produces a high dielectric constant of BT. It indicates that crystalline size increases.

  7. Microscopic distribution of metal dopants and anion vacancies in Fe-doped BaTiO3-δ single crystals

    NASA Astrophysics Data System (ADS)

    Chakraborty, Tanushree; Meneghini, Carlo; Aquilanti, Giuliana; Ray, Sugata

    2013-06-01

    A detailed microscopic structural study on two single crystalline dilute magnetic oxides, BaTi0.95Fe0.05O3-δ with and without perceptible δ, has been carried out. Although it has been reported earlier that varying δ significantly affects high temperature ferromagnetism, the real distribution/redistribution of vacancies and dopant Fe ions inside the 6H hexagonal structure was never probed. This study reveals that oxygen vacancies reduce the dopant Fe3+ ions to Fe2+ and mostly accumulate around these Fe2+ ions. Another distinct trend is the tendency of the dopant Fe ions to get closer instead of being distributed randomly, thereby creating {{Fe}}_{2}^{2+}{{O}}_{9-{\\delta }^{\\prime}} like dimers within the 6H hexagonal unit cell. This experimental observation definitively confirms previous hypotheses based on theoretical models.

  8. Photonic crystal wave guide for non-cryogenic cooled carbon nanotube based middle wave infrared sensors

    NASA Astrophysics Data System (ADS)

    Fung, Carmen Kar Man; Xi, Ning; Lou, Jianyong; Lai, King Wai Chiu; Chen, Hongzhi

    2010-10-01

    We report high sensitivity carbon nanotube (CNT) based middle wave infrared (MWIR) sensors with a two-dimensional photonic crystal waveguide. MWIR sensors are of great importance in a variety of current military applications including ballistic missile defense, surveillance and target detection. Unlike other existing MWIR sensing materials, CNTs exhibit low noise level and can be used as new nano sensing materials for MWIR detection where cryogenic cooling is not required. However, the quantum efficiency of the CNT based infrared sensor is still limited by the small sensing area and low incoming electric field. Here, a photonic nanostructure is used as a resonant cavity for boosting the electric field intensity at the position of the CNT sensing element. A two-dimensional photonic crystal with periodic holes in a polymer thin film is fabricated and a resonant cavity is formed by removing holes from the array of the photonic crystal. Based on the design of the photonic crystal topologies, we theoretically study the electric field distribution to predict the resonant behavior of the structure. Numerical simulations reveal the field is enhanced and almost fully confined to the defect region of the photonic crystal. To verify the electric field enhancement effect, experiments are also performed to measure the photocurrent response of the sensor with and without the photonic crystal resonant cavity. Experimental results show that the photocurrent increases ~3 times after adding the photonic crystal resonant cavity.

  9. Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001)

    NASA Astrophysics Data System (ADS)

    Hsu, Min-Hsiang Mark; Merckling, Clement; El Kazzi, Salim; Pantouvaki, Marianna; Richard, Oliver; Bender, Hugo; Meersschaut, Johan; Van Campenhout, Joris; Absil, Philippe; Van Thourhout, Dries

    2016-12-01

    In this work, we present a systematic study of the effect of the stoichiometry of BaTiO3 (BTO) films grown on the Ge(001) substrate by molecular-beam-epitaxy using different characterization methods relying on beam diffraction, including reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and selected-area electron diffraction in transmission electron microscopy. Surprisingly, over a wide range of [Ba]/[Ti] ratios, as measured by the Rutherford backscattering spectrometry, all the BTO layers exhibit the same epitaxial relationship <100>BTO(001)//<110>Ge(001) with the substrate, describing a 45° lattice rotation of the BTO lattice with respect to the Ge lattice. However, varying the [Ba]/[Ti] ratio does change the diffraction behavior. From RHEED patterns, we can derive that excessive [Ba] and [Ti] generate twinning planes and a rougher surface in the non-stoichiometric BTO layers. XRD allows us to follow the evolution of the lattice constants as a function of the [Ba]/[Ti] ratio, providing an option for tuning the tetragonality of the BTO layer. In addition, we found that the intensity ratio of the 3 lowest-order Bragg peaks I(001)/I(002), I(101)/I(002), and I(111)/I(002) derived from ω - 2θ scans characteristically depend on the BTO stoichiometry. To explain the relation between observed diffraction patterns and the stoichiometry of the BTO films, we propose a model based on diffraction theory explaining how excess [Ba] or [Ti] in the layer influences the diffraction response.

  10. Comprehensive dielectric performance of bismuth acceptor doped BaTiO3 based nanocrystal thin film capacitors

    SciTech Connect

    Liu, SY; Zhang, HN; Sviridov, L; Huang, LM; Liu, XH; Samson, J; Akins, D; Li, J; O'Brien, S

    2012-11-07

    We present a novel approach to preparing bismuth acceptor doped barium titanate nanocrystal formulations that can be deposited in conjunction with polymers in order to prepare a thin film nanocomposite dielectric that exhibits desirable capacitor characteristics. Exploring the limits of dielectric function in nanocomposites is an important avenue of materials research, while paying strict attention to the overall device quality, namely permittivity, loss and equivalent series resistance (ESR). Pushing capacitor function to higher frequencies, a desirable goal from an electrical engineering point of view, presents a new set of challenges in terms of minimizing interfacial, space charge and polarization effects within the dielectric. We show the ability to synthesize BaTi0.96Bi0.04O3 or BaTi0.97Bi0.03O3 depending on nominal molar concentrations of bismuth at the onset. The low temperature solvothermal route allows for substitution at the titanium site (strongly supported by Rietveld and Raman analysis). Characterization is performed by XRD with Rietveld refinement, Raman Spectroscopy, SEM and HRTEM. A mechanism is proposed for bismuth acceptor substitution, based on the chemical reaction of the alkoxy-metal precursors involving nucleophilic addition. Dielectric analysis of the nanocrystal thin films is performed by preparing nanocrystal/PVP 2-2 nanocomposites (no annealing) and comparing BaTi0.96Bi0.04O3 and BaTi0.97Bi0.03O3 with undoped BaTiO3. Improvements of up to 25% in capacitance (permittivity) are observed, with lower loss and dramatically improved ESR, all to very high frequency ranges (>10 MHz).

  11. Preparation and Characterization of BaTiO3-PbZrTiO3 Coating for Pyroelectric Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Raghavendra, R. M.; Praneeth, K. P. S. S.; Dutta, Soma

    2017-01-01

    Harvesting energy from waste heat is a promising field of research as there are significant energy recovery opportunities from various waste thermal energy sources. The present study reports pyroelectric energy harvesting using thick film prepared from a (x)BaTiO3-(1 - x)PbZr0.52Ti0.48O3 (BT-PZT) solid solution. The developed BT-PZT system is engineered to tune the ferro to paraelectric phase transition temperature of it in-between the phase transition temperature of BaTiO3 (393 K) and PbZrTiO3 (573 K) with higher pyroelectric figure-of-merit (FOM). The temperature-dependent dielectric behavior of the material has revealed the ferro- to paraelectric phase transition at 427 K with a maximum dielectric constant of 755. The room-temperature (298 K) pyroelectric coefficient (Pi) of the material was obtained as 738.63 μC/m2K which has yielded a significantly high FOM of 1745.8 J m-3 K-2. The enhancement in pyroelectric property is attributed to the morphotopic phase transition between tetragonal and rhombohedral PZT phases in the BT-PZT system. The developed BT-PZT system is capable of generating a power output of 1.3 mW/m2 near the Curie temperature with a constant rate (0.11 K/s) of heating. A signal conditioning circuit has been developed to rectify the time-varying current and voltage signals obtained from the harvester during heating cycles. The output voltage generated by the pyroelectric harvester has been stored in a capacitor for powering wearable electronics.

  12. Carbon-nanotube electron-beam (C-beam) crystallization technique for silicon TFTs

    NASA Astrophysics Data System (ADS)

    Lee, Su Woong; Kang, Jung Su; Park, Kyu Chang

    2016-02-01

    We introduced a carbon-nanotube (CNT) electron beam (C-beam) for thin film crystallization and thin film transistor (TFT) applications. As a source of electron emission, a CNT emitter which had been grown on a silicon wafer with a resist-assisted patterning (RAP) process was used. By using the C-beam exposure, we successfully crystallized a silicon thin film that had nano-sized crystalline grains. The distribution of crystalline grain size was about 10 ˜ 30 nm. This nanocrystalline silicon thin film definitely had three crystalline directions which are (111), (220) and (311), respectively. The silicon TFTs crystallized by using a C-beam exposure showed a field effect mobility of 20 cm2/Vs and an on/off ratio of more than 107. The C-beam exposure can modify the bonding network of amorphous silicon with its proper energy.

  13. Crystallization of Polymers at liquid/liquid interface templated by single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Li, Christopher

    2012-02-01

    Nanosized single-walled carbon nanotube rings were fabricated by using a Pickering emulsion-based method. By tuning a water/oil/SWNT miniemulsion system, SWNT rings with a diameter of ˜200 nm can be readily achieved. The formation mechanism is attributed to the bending force induced by the curved liquid/liquid interface. Crystallization of polyethylene homo- and copolymers using this unique SWNT rings as the nucleation agent was conducted at the curved liquid/liquid interface. Crystal structure, hybrid morphology and crystallization kinetics were systematically studied. The structure of controlled alternating patterns on SWNT rings has great potential in various applications in large-scale integrated circuits and single-electron devices.

  14. Nanotube

    SciTech Connect

    LEONARD, FRANCOIS; KIENLE, DIEGO; & STEWART, DEREK

    2007-09-13

    This is a source code to calculate the current-voltage characteristics, the charge distribution and the electrostatic potential in carbon nanotube devices. The code utilizes the non-equilibrium Green's function method, implemented in a tight-binding scheme, to calculate the charge distribution and the energy-dependent transmission function, from which the current or the conductance are obtained. The electrostatic potential is obtained by solving Poisson's equation on a grid with boundary conditions on the electrodes, and at other interfaces. Self-consistency between the charge and the electrostatic potential is achieved using a linear mixing method. Different versions of the code allow the modeling of different types of nanotube devices: Version 1.0: Modeling of carbon nanotube electronic devices with cylindrical symmetry Version 1.1: Modeling of planar carbon nanotube electronic devices Version 1.2: Modeling of photocurrent in carbon nanotube devices

  15. X-ray driven channeling acceleration in crystals and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Shin, Young-Min; Still, Dean A.; Shiltsev, Vladimir

    2013-12-01

    Acceleration of particles channeling in a crystal by means of diffracted x-rays via Bormann anomalous transmission was conceived for heavy ions and muons by Tajima and Cavenago [Phys. Rev. Lett. 59, 1440 (1987)], which potentially offers an appreciably high field gradient on the order of GV/cm. The theoretical model of the high gradient acceleration has been studied in two kinds of atomic structure, crystals and carbon nanotubes (CNTs), with analytic calculations and electromagnetic eigenmode simulations. A range of acceleration gradients and cutoffs of the x-ray power (the lowest power limit to overcome the Bremsstrahlung radiation losses) are characterized in terms of the lattice constants, unit cell sizes, and photon energies. The parametric analysis indicates that the required x-ray power can be reduced to an order of megawatt by replacing crystals with CNTs. Eventually, the equivalent dielectric approximation of a multi-wall nanotube shows that 250-810 MeV muons can be synchronously coupled with x-rays of 0.65-1.32 keV in the accelerating structure.

  16. Influence of excess Ba concentration on the dielectric nonlinearity in Mn and V-doped BaTiO3 multi layer ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Yoon, Seok-Hyun; Kim, Sun-Jung; Kim, Sang-Hyuk; Kim, Doo-Young

    2013-12-01

    The effect of excess Ba concentration on the dielectric nonlinearity was investigated in Mn and V-doped BaTiO3 multi layer ceramic capacitors (MLCC) under the same grain size condition, which was described by the Preisach model utilizing the first order reversal curve (FORC) distribution. The high-field dielectric constant and its ac field dependence dramatically changed increasing to a maximum and then decreasing with the increase of Ba concentration. The saturation polarization which scales to the magnitude of spontaneous polarization also showed similar behavior. These results indicate that the dependence of the dielectric constant on the Ba concentration is associated with the variation of both domain wall contribution and the magnitude of the spontaneous polarization, which could be correlated with the same dependence on the Ba concentration of the reversible FORC distribution at zero bias and the irreversible FORC distribution near origin. In the corresponding bulk specimens of the dielectrics of MLCC, almost the same amount of the Ba2TiSi2O8 second phases were detected irrespective of Ba concentration, which shows that the excess Ba incorporate into BaTiO3. Thus, low and high Ba concentration corresponds to Ba-deficient and Ba-rich or Ti-deficient BaTiO3, respectively, which results in a small spontaneous polarization and low domain wall density. The intermediate Ba concentration for the maximum dielectric constant is supposed to be near stoichiometric condition in the ABO3 structure corresponding to large spontaneous polarization and high domain wall density. The excess Ba concentration and its resultant A/B stoichiometry is a crucial factor controlling dielectric properties.

  17. Dielectric properties and microstructure of sintered BaTiO3 fabricated by using mixed 150-nm and 80-nm powders with various additives

    NASA Astrophysics Data System (ADS)

    Oh, Min Wook; Kang, Jae Won; Yeo, Dong Hun; Shin, Hyo Soon; Jeong, Dae Yong

    2015-04-01

    Recently, the use of small-sized BaTiO3 particles for ultra-thin MLCC research has increased as a method for minimizing the dielectric layer's thickness in thick film process. However, when particles smaller than 100 nm are used, the reduced particle size leads to a reduced dielectric constant. The use of nanoparticles, therefore, requires an increase in the amount of additive used due to the increase in the specific surface area, thus increasing the production cost. In this study, a novel method of coating 150-nm and 80-nm BaTiO3 powders with additives and mixing them together was employed, taking advantage of the effect obtained through the use of BaTiO3 particles smaller than 100 nm, to conveniently obtain the desired dielectric constant and thermal characteristics. Also, the microstructure and the dielectric properties were evaluated. The additives Dy, Mn, Mg, Si, and Cr were coated on a 150-nm powder, and the additives Dy, Mn, Mg, and Si were coated on 80-nm powder, followed by mixing at a ratio of 1:1. As a result, the microstructure revealed grain formation according to the liquid-phase additive Si; additionally, densification was well realized. However, non-reducibility was not obtained, and the material became a semiconductor. When the amount of added Mn in the 150-nm powder was increased to 0.2 and 0.3 mol%, insignificant changes in the microstructure were observed, and the bulk density after mixing was found to have increased drastically in comparison to that before mixing. Also, non-reducibility was obtained for certain conditions. The dielectric property was found to be consistent with the densification and the grain size. The mixed composition #1-0.3 had a dielectric constant over 2000, and the result somewhat satisfied the dielectric constant temperature dependency for X6S.

  18. Pressure dependence of the phonon spectrum in BaTiO3 polytypes studied by ab initio calculations

    NASA Astrophysics Data System (ADS)

    Seo, Yu-Seong; Ahn, Jai Seok

    2013-07-01

    We report the first principles investigations on the phonons of three polytypes of BaTiO3 (BTO): paraelectric (PE) cubic Pm3¯m and two ferroelectric (FE) phases, tetragonal P4mm and rhombohedral R3m. The phonon frequencies were calculated using various exchange-correlation functionals, including density functional theory, Hartree-Fock approximation, and their hybrids were reviewed. The pressure-induced interplays between the modes from individual phases were explored by calculating the phonon modes as a function of pressure, P from -15 to 230 GPa. The pressure-sensitive modes of the FE phases showed softening and converged to the modes of the PE phase at pressures below ˜10 GPa. These results on the FE phases can be interpreted as phonon precursors for a change in symmetry from low- to high-symmetry and partly as a theoretical explanation for the pressure-induced mode-coupling behaviors reported by Sood [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.51.8892 51, 8892 (1995)]. As pressure is applied further beyond ˜50 GPa to the cubic PE phase, the lowest F1u mode softens again and diverges into two separate modes of tetragonal FE P4mm at above ˜150 GPa. These phonon-branching behaviors at high pressures provide a clear reconfirmation of the re-entrant ferroelectricity predicted in earlier papers [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.95.196804 95, 196804 (2005); Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.74.180101 74, 180101 (2006); Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.85.054108 85, 054108 (2012)]. The high-pressure-re-entrant FE polarization was not found in the rhombohedral structure. Instead, the centrosymmetric R3¯m phase was favored at above ˜30 GPa. The phonon modes calculated for the phonon-propagation vectors in the high-symmetry directions show that the Pm3¯m phase exhibits polar instability at the Γ point and nonpolar instability at the X, M, and R points under high pressure.

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

    SciTech Connect

    Wu, Pingping; Ma, Xingqiao; Li, Yulan; Gopalan, Venkatraman; Chen , L.Q.

    2012-03-01

    Ferroelectric superlattice heterostructures have recently been explored for potential applications in electronic devices. In this letter we employed the phase-field approach to simulate the domain structure and switching of a (BaTiO3)8/(SrTiO3)3 superlattice film constrained by a GdScO3 substrate. A constricted ferroelectric hysteresis loop was observed with a high saturation polarization but a small coercive field. The shape of the hysteresis loop is understood by analyzing the ferroelectric polarization distributions during switching. It is demonstrated that the constricted loop show a similar mechanism to the exchange coupling effect in magnetic multilayers.

  20. Influences of Orientation on Magnetoelectric Coupling at La1-x Sr x MnO3/BaTiO3 Interface from Ab Initio Calculations

    NASA Astrophysics Data System (ADS)

    Nguyen, Thuy Trang; Yamauchi, Kunihiko; Oguchi, Tamio; Hoang, Nam Nhat

    2017-01-01

    An ab initio study on the magnetoelectric coupling at interfaces of ferromagnetic perovskite Sr-doped LaMnO3 (LSMO) and ferroelectric perovskite BaTiO3 (BTO) with (001) and (111) perovskite orientations is presented. It was found that the interfaces with both orientations exhibit significant magnetoelectric couplings. The effects of the orientation on the magnetoelectric coupling are discussed on the basis of the electronic structure, suggesting that the enhancement of electrostatic-screening-induced magnetoelectric coupling at the (111) interface in comparison with the (001) interface is mainly due to strengthened interfacial coupling.

  1. Monolithic integration of room-temperature multifunctional BaTiO3-CoFe2O4 epitaxial heterostructures on Si(001)

    NASA Astrophysics Data System (ADS)

    Scigaj, Mateusz; Dix, Nico; Gázquez, Jaume; Varela, María; Fina, Ignasi; Domingo, Neus; Herranz, Gervasi; Skumryev, Vassil; Fontcuberta, Josep; Sánchez, Florencio

    2016-08-01

    The multifunctional (ferromagnetic and ferroelectric) response at room temperature that is elusive in single phase multiferroic materials can be achieved in a proper combination of ferroelectric perovskites and ferrimagnetic spinel oxides in horizontal heterostructures. In this work, lead-free CoFe2O4/BaTiO3 bilayers are integrated with Si(001) using LaNiO3/CeO2/YSZ as a tri-layer buffer. They present structural and functional properties close to those achieved on perovskite substrates: the bilayers are fully epitaxial with extremely flat surface, and exhibit robust ferromagnetism and ferroelectricity at room temperature.

  2. Poly(vinylidene fluoride) polymer based nanocomposites with enhanced energy density by filling with polyacrylate elastomers and BaTiO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Yu, Ke; Bai, Yuanyuan; Zhou, Yongcun; Niu, Yujuan; Wang, Hong

    2014-02-01

    Polyacrylate elastomers were introduced into poly(vinylidene fluoride) polymer-based nanocomposites filled with BaTiO3 nanoparticles and the three-phase nanocomposite films were prepared. The energy discharged of the nanocomposite with 3 vol. % polyacrylate elastomers is 8.8 J/cm3, approximately 11% higher compared to that of the nanocomposite without adding polyacrylate elastomers. Large elastic deformation of the polyacrylate elastomers increases Maxwell-Wagner-Sillars interfacial polarization and space charge polarization of the nanocomposites with the electric field increasing, which results in increased maximum polarization and energy discharged of the nanocomposites.

  3. Monolithic integration of room-temperature multifunctional BaTiO3-CoFe2O4 epitaxial heterostructures on Si(001)

    PubMed Central

    Scigaj, Mateusz; Dix, Nico; Gázquez, Jaume; Varela, María; Fina, Ignasi; Domingo, Neus; Herranz, Gervasi; Skumryev, Vassil; Fontcuberta, Josep; Sánchez, Florencio

    2016-01-01

    The multifunctional (ferromagnetic and ferroelectric) response at room temperature that is elusive in single phase multiferroic materials can be achieved in a proper combination of ferroelectric perovskites and ferrimagnetic spinel oxides in horizontal heterostructures. In this work, lead-free CoFe2O4/BaTiO3 bilayers are integrated with Si(001) using LaNiO3/CeO2/YSZ as a tri-layer buffer. They present structural and functional properties close to those achieved on perovskite substrates: the bilayers are fully epitaxial with extremely flat surface, and exhibit robust ferromagnetism and ferroelectricity at room temperature. PMID:27550543

  4. Plasmonic Crystals for Strong Light–Matter Coupling in Carbon Nanotubes

    PubMed Central

    2016-01-01

    Their high oscillator strength and large exciton binding energies make single-walled carbon nanotubes (SWCNTs) highly promising materials for the investigation of strong light–matter interactions in the near infrared and at room temperature. To explore their full potential, high-quality cavities—possibly with nanoscale field localization—are required. Here, we demonstrate the room temperature formation of plasmon–exciton polaritons in monochiral (6,5) SWCNTs coupled to the subdiffraction nanocavities of a plasmonic crystal created by a periodic gold nanodisk array. The interaction strength is easily tuned by the number of SWCNTs that collectively couple to the plasmonic crystal. Angle- and polarization resolved reflectivity and photoluminescence measurements combined with the coupled-oscillator model confirm strong coupling (coupling strength ∼120 meV). The combination of plasmon–exciton polaritons with the exceptional charge transport properties of SWCNTs should enable practical polariton devices at room temperature and at telecommunication wavelengths. PMID:27661764

  5. Mechanochromic photonic-crystal fibers based on continuous sheets of aligned carbon nanotubes.

    PubMed

    Sun, Xuemei; Zhang, Jing; Lu, Xin; Fang, Xin; Peng, Huisheng

    2015-03-16

    A new family of mechanochromic photonic-crystal fibers exhibits tunable structural colors under stretching. This novel mechanochromic fiber is prepared by depositing polymer microspheres onto a continuous aligned-carbon-nanotube sheet that has been wound on an elastic poly(dimethylsiloxane) fiber, followed by further embedding in poly(dimethylsiloxane). The color of the fiber can be tuned by varying the size and the center-to-center distance of the polymer spheres. It further experiences reversible and rapid multicolor changes during the stretch and release processes, for example, between red, green, and blue. Both the high sensitivity and stability were maintained after 1000 deformation cycles. These elastic photonic-crystal fibers were woven into patterns and smart fabrics for various display and sensing applications.

  6. Adsorption of crystal violet onto functionalised multi-walled carbon nanotubes: Equilibrium and kinetic studies.

    PubMed

    Sabna, V; Thampi, Santosh G; Chandrakaran, S

    2016-12-01

    Synthetic dyes present in effluent from textile, paper and paint industries contain crystal violet (CV), a known carcinogenic agent. This study investigates the modification of multiwalled carbon nanotubes by acid reflux method and equilibrium and kinetic behaviour of adsorption of CV onto functionalized multi-walled carbon nanotubes (fMWNTs) in batch system. High stability of the fMWNTs suspension in water indicates the hydrophilicity of fMWNTs induced due to the formation of functional groups that make hydrogen bonds with water molecules. fMWNTs were characterized by Fourier Transform Infra Red (FTIR) spectroscopy and the functional groups present on the fMWNTs were confirmed. Characteristic variation was observed in the FTIR spectra of fMWNTs after adsorption of crystal violet onto it. Adsorption characteristics were evaluated as a function of system variables such as contact time, dosage of fMWNTs and initial concentration and pH of the crystal violet solution. Adsorption capacity of fMWNTs and percentage removal of the dye increased with increase in contact time, adsorbent dosage and pH but declined with increase in initial concentration of the dye. fMWNTs showed higher adsorption capacity compared to that of pristine MWNTs. Data showed good fit with the Langmuir and Freundlich isotherm models and the pseudo-second order kinetic model; the maximum adsorption capacity was 90.52mg/g. Kinetic parameters such as rate constants, equilibrium adsorption capacities and regression coefficients were estimated. Results indicate that fMWNTs are an effective adsorbent for the removal of crystal violet from aqueous solution.

  7. N2 adsorption study on quartz, silver, and carbon nanotube by inductive pulse quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Park, Jang-ik; Yu, Insuk; Seo, Yongho

    2007-03-01

    We utilize an "inductive pulse" quartz crystal microbalance method to study N2 adsorption on quartz, silver, and a single wall carbon nanotube at 77 K. This method is based on radio frequency electric pulse excitation and ring-down signal measurements of quartz crystal resonators located in an induction coil. The surface areas and adsorption strength c are estimated by the Brunauer-Emmett-Teller (BET) model. The estimated c for quartz and silver surface are about 1/5 times smaller than that measured by the conventional method. This is explained as suppression of the self-heating effect, by using our inductive pulse method. We suggest a simple theoretical estimation of self-heating effects on conventional and inductive pulse methods. For the intermediate adsorption range, we analyze our data using the generalized Frenkel-Hasley-Hill (FHH) model with fractal dimension. While the quartz and silver have fractal dimensions of about 2.2±0.1, single wall carbon nanotube has 1.2±0.1, which are explained by its strong adsorptive force.

  8. Lattice screening of the polar catastrophe and hidden in-plane polarization in KNbO3/BaTiO3 interfaces

    NASA Astrophysics Data System (ADS)

    García-Fernández, Pablo; Aguado-Puente, Pablo; Junquera, Javier

    2013-02-01

    We have carried out first-principles simulations, based on density functional theory, to obtain the atomic and electronic structure of (001) BaTiO3/KNbO3 interfaces in an isolated slab geometry. We tried different types of structures including symmetric and asymmetric configurations and variations in the thickness of the constituent materials. The spontaneous polarization of the layer-by-layer non-neutral material (KNbO3) in these interfaces cancels out almost exactly the “built-in” polarization responsible for the electronic reconstruction. As a consequence, the so-called polar catastrophe is quenched and all the simulated interfaces are insulating. A model, based on the modern theory of polarization and basic electrostatics, allows an estimation of the critical thickness for the formation of the two-dimensional electron gas between 33 and 36 KNbO3 unit cells. We also demonstrate the presence of an unexpected in-plane polarization in BaTiO3 localized at the p-type TiO2/KO interface, even under in-plane compressive strains. We expect this in-plane polarization to remain hidden due to angular averaging during quantum fluctuations unless the symmetry is broken with small electric fields.

  9. Magnetic and electrical properties on possible room temperature hybrid multiferroic BaTiO3/La2/3Sr1/3MnO3

    NASA Astrophysics Data System (ADS)

    Ordoñez, John Edward; Gómez, María Elena; Lopera Muñoz, Wilson; Prieto, Pedro Antonio; Thin Film Group Team; Center of Excellence on Novel Materials-CENM, Cali, Colombia Team

    2015-03-01

    We addressed to deposit the ferromagnetic phase of the La1-xSrxMnO3 and the ferroelectric BaTiO3 for possible hybrid multiferroic heterostructure. We have optimized the growth parameters for depositing BaTiO3(BTO) / La2/3Ca1/3MnO3(LCMO) / (001) SrTiO3 by sputtering RF and DC, respectively, in pure oxygen atmosphere and a substrate temperature of 830°C. Keeping fixed the magnetic layer thickness (tLSMO = 40 nm) and varying the thickness of the ferroelectric layer (tBTO = 20, 40, 80, 100 nm). We want to point out the influence of the thicknesses ratio (tBTO/tLSMO) on electrical and magnetic properties. From x-ray diffraction (XRD) analysis, we found the bragg peaks for LSMO maintain its position but BTO peak shift to lower Bragg angle indicating a strained BTO film. Magnetization and polarization measurements indicate a possible multiferroic behavior in the bilayers. Hysteresis loop measurements of bilayers show ferromagnetic behavior. Authors thank Instituto de Nanociencia de Aragón, Zaragoza, Spain. Work partially supported by COLCIENCIAS-UNIVALLE Project 110656933104 Contract No. 2013-0002, CI 7917 and CI 7978.

  10. High-Energy-Density Polymer Nanocomposites Composed of Newly Structured One-Dimensional BaTiO3@Al2O3 Nanofibers.

    PubMed

    Pan, Zhongbin; Yao, Lingmin; Zhai, Jiwei; Fu, Dezhou; Shen, Bo; Wang, Haitao

    2017-02-01

    Flexible electrostatic capacitors are potentially applicable in modern electrical and electric power systems. In this study, flexible nanocomposites containing newly structured one-dimensional (1D) BaTiO3@Al2O3 nanofibers (BT@AO NFs) and the ferroelectric polymer poly(vinylidene fluoride) (PVDF) matrix were prepared and systematically studied. The 1D BT@AO NFs, where BaTiO3 nanoparticles (BT NPs) were embedded and homogeneously dispersed into the AO nanofibers, were successfully synthesized via an improved electrospinning technique. The additional AO layer, which has moderating dielectric constant, was introduced between BT NPs and PVDF matrixes. To improve the compatibility and distributional homogeneity of the nanofiller/matrix, dopamine was coated onto the nanofiller. The results show that the energy density due to high dielectric polarization is about 10.58 J cm(-3) at 420 MV m(-1) and the fast charge-discharge time is 0.126 μs of 3.6 vol % BT@AO-DA NFs/PVDF nanocomposite. A finite element simulation of the electric-field and electric current density distribution revealed that the novel-structured 1D BT@AO-DA NFs significantly improved the dielectric performance of the nanocomposites. The large extractable energy density and high dielectric breakdown strength suggest the potential applications of the BT@AO-DA NFs/PVDF nanocomposite films in electrostatic capacitors and embedded devices.

  11. Dielectric responses of modified BaTiO3 ceramics in multilayer ceramic capacitors to the combined uniaxial stress and dc bias field

    NASA Astrophysics Data System (ADS)

    Yang, Gang; Yue, Zhenxing; Gui, Zhilun; Li, Longtu

    2008-10-01

    Dielectric measurements of modified BaTiO3 in a multilayer ceramic capacitor (MLCC) show that the application of external uniaxial stress perpendicular to electric field in a MLCC can lead to a slight increase in the dielectric permittivity. The additional application of a dc bias results in a significantly suppressed dielectric permittivity in the temperature range from 228 to 453 K. These observations can be explained as a result of domain wall movements in grains with a core-shell structure, due to the combined stress and dc bias field. As the dc bias increased up to 5.6 MV/m, the Curie peak, which has diffuse phase transition characteristics in the absence of dc bias, becomes sharper, and two new peaks are induced at about 250 and 315 K. Furthermore, the first order paraelectric-ferroelectric phase transition of the modified BaTiO3 ceramic becomes stronger with increasing dc bias when a uniaxial stress is also applied.

  12. Enhanced light harvesting in dye-sensitized solar cells coupled with titania nanotube photonic crystals: a theoretical study.

    PubMed

    Guo, Min; Yong, Zehui; Xie, Keyu; Lin, Jia; Wang, Yu; Huang, Haitao

    2013-12-26

    Herein we present a theoretical analysis on the optical properties and the photocurrent enhancement of nanotube-based dye-sensitized solar cells (DSSCs) coupled with a TiO2 nanotube (NT) photonic crystal (PC). It is found that the introduction of a TiO2 nanotube PC produces both Bragg mirror effect and Fabry-Perot cavity behavior, leading to a significant enhancement of light harvesting for photons in the photonic bandgap and at the two band edges. In addition, an increased amount of surface-anchored dye due to the larger surface area in the NT PC layer also causes absorption enhancement in the whole visible spectrum. The effects of structural parameters of the PC, such as the thickness of the PC layer, the axial lattice constant, the diameter of the nanotube, and light incident angle, on the optical properties and photocurrent magnification are thoroughly studied. The optimum structural parameters are proposed, which not only provide guidance but also offer further opportunities in the design and applications of TiO2 nanotube photonic crystals.

  13. Impact of ionic liquid-modified multiwalled carbon nanotubes on the crystallization behavior of poly(vinylidene fluoride).

    PubMed

    Xing, Chenyang; Zhao, Liping; You, Jichun; Dong, Wenyong; Cao, Xiaojun; Li, Yongjin

    2012-07-19

    The impact of pristine multiwalled carbon nanotubes (MWCNTs), an ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], and the ionic liquid-modified MWCNTs (IL-MWCNTs) on the crystallization behavior of melt-crystallized poly(vinylidene fluoride) (PVDF) has been investigated. Pristine MWCNTs accelerate crystallization of PVDF as an efficient nucleation agent, while the formed crystals are mainly nonpolar α crystal form with few polar β crystals. Incorporation of only ionic liquid results in depression of the PVDF melt crystallization rate due to the miscibility of IL with PVDF but leads to a higher content of polar crystals (β and γ forms) than MWCNTs. The ionic liquid and MWCNTs show significant synergetic effects on both the nucleation and the formation of polar crystals for PVDF by melt crystallization. Addition of IL-MWCNTs not only improves the MWCNTs dispersion in PVDF matrix but also increases the overall crystallization rate of PVDF drastically. More important, the melt-crystallized PVDF nanocomposites with IL-MWCNTs show 100% polar polymorphs but no α crystal forms. To the best of our knowledge, this is the first report on the achievements of full polar crystal form in the melt-crystallized PVDF without mechanical deformation or electric field. The IL to MWCNTs ratio and the IL-MWCNTs loading content effects on the crystallization behavior of PVDF in the nanocomposites were also studied. It is considered that the specific interactions between >CF2 with the planar cationic imidazolium ring wrapped on the MWCNTs surface lead to the full zigzag conformations of PVDF; thus, nucleation in polar crystals (β and γ forms) lattice is achieved and full polar crystals are obtained by subsequent crystal growth from the nuclei.

  14. Dielectric and electro-optic measurements of nematic liquid crystals doped with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Peterson, Matthew; Georgiev, Georgi; Atherton, Timothy; Cebe, Peggy

    We studied the effects of carbon nanotubes (CNTs) on the dielectric and electro-optic properties of nematic 5CB liquid crystals (LCs). Samples containing 0.01%, 0.10% and 1.00% CNTs by weight were prepared. Anti- parallel rubbed cells with a nominal thickness of 10 μm were prepared using indium tin oxide coated glass cells and a polyimide alignment layer. The capacitance and dissipation factor were measured using an Agilent 4284A precision LCR meter. From these measurements, the complex dielectric permittivity was determined as a function of frequency. Analysis of the low frequency regime (f <1000 Hz) indicates that 5CB samples containing CNTs have a higher conductance than neat samples. The Fréedericksz transition critical voltage was noted by a sharp increase in capacitance after an initial plateau. Numerical simulations of CNT-facilitated switching show that polarization induced on the nanotubes from capacitive effects can significantly reduce the critical voltage in DC electric fields, in agreement with experimental results. Measurements of the critical voltage over a range of frequencies will also be presented. Research was supported by the National Science Foundation, DMR1206010.

  15. Carbon Nanotube-templated Polymer Single Crystals Serve as Controllable Spacers to Form Novel Battery Architectures

    NASA Astrophysics Data System (ADS)

    Laird, Eric D.; Li, Christopher Y.

    2013-03-01

    One of the many challenges in battery cathode architectures lies in creating a porous structure with tunable features on the 10-100 nm length scale. Stable features of this size are desirable for engineered surface topology as well as charge storage applications. Few materials exist that can satisfy this requirement. Fewer still have high enough electron conductivity to be of use without adding an additional conducting phase. The ``nanohybrid shish kebab'' (NHSK) structure may be a solution to this obstacle. This physical functionalization technique for carbon nanotubes uses polymer single crystals grown from solution to produce a controllable spacer. In our previous work, it was shown that NHSKs can be controllably tuned to have average diameters ranging from 18 to 94 nm for single-walled carbon nanotubes. Films of these materials can easily be made free-standing and are highly flexible. Recent work in extending the functionality of these materials through the formation of ternary composites for battery applications will be presented. Pulsed electrodeposition of MnO2 onto the surfaces of these films forms an electrochemically active layer for lithium cells. High specific cathodic capacity has been observed in a rechargeable battery based on these materials. NSF DMR-0804838, NSF-IGERT DGE-0221664

  16. Observation of self-diffraction by gratings in nematic liquid crystals doped with carbon nanotubes.

    PubMed

    Lee, W; Chiu, C S

    2001-04-15

    Diffraction gratings were studied in cells of the homogeneously aligned liquid-crystal E7 doped with multiwall carbon nanotubes. These phase gratings were induced by interference modulation of two coherent optical beams, in conjunction with an applied dc field that was perpendicular to the unperturbed director axis. Self-diffraction was observed at all angles of incidence of the writing beams, including normal incidence. A superior nonlinear-index coefficient of 5x10(-2)cm(2)/W was obtained after passage of a 44-mW/cm(2) beam through a film with a grating constant of 18 mum under an external voltage of 15 V. The observed phenomenon depends strongly on the applied dc field, and the memory effect in a nematic film depends strongly on the grating constant.

  17. Two-step electrical percolation in nematic liquid crystals filled with multiwalled carbon nanotubes.

    PubMed

    Tomylko, Serhiy; Yaroshchuk, Oleg; Lebovka, Nikolai

    2015-07-01

    Percolation of carbon nanotubes (CNTs) in liquid crystals (LCs) opens the way for a unique class of anisotropic hybrid materials with a complex dielectric constant widely controlled by CNT concentration. Percolation in such systems is commonly described as a one-step process starting at a very low loading of CNTs. In the present study the two-step percolation was observed in the samples of thickness 250 μm obtained by pressing the suspension between two substrates. The first threshold concentration, C(n)(p(1))∼10(-4) wt.%, was sensitive to temperature and phase state of LC, while the second one, C(n)(p(2))∼10(-1) wt.%, remained practically unchanged in the temperature tests. The two-stage nature of percolation was explained on a base of mean-field theory assuming core-shell structure of CNTs.

  18. Two-step electrical percolation in nematic liquid crystals filled with multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tomylko, Serhiy; Yaroshchuk, Oleg; Lebovka, Nikolai

    2015-07-01

    Percolation of carbon nanotubes (CNTs) in liquid crystals (LCs) opens the way for a unique class of anisotropic hybrid materials with a complex dielectric constant widely controlled by CNT concentration. Percolation in such systems is commonly described as a one-step process starting at a very low loading of CNTs. In the present study the two-step percolation was observed in the samples of thickness 250 μ m obtained by pressing the suspension between two substrates. The first threshold concentration, Cnp1˜10-4 wt.%, was sensitive to temperature and phase state of LC, while the second one, Cnp2˜10-1 wt.%, remained practically unchanged in the temperature tests. The two-stage nature of percolation was explained on a base of mean-field theory assuming core-shell structure of CNTs.

  19. Numerical Estimation of the Dependence of Dielectric Constant of BaTiO3 Thick Films on Grain-Size Distribution

    NASA Astrophysics Data System (ADS)

    Yamashita, Kimihiro; Yamazaki, Shozo; Koumoto, Kunihito; Yanagida, Hiroaki

    1981-10-01

    An exponential function of the grain size was assumed in calculating the apparent (total) dielectric constant of BaTiO3 thick films with the average grain diameter known. The function was tested and estimated experimentally, for cases where the grain sizes were calculated using the following methods; the two-dimensional diameter analysis, the Schwartz-Saltykov method and Oel’s method for converting a two-dimensional grain distribution to a spacial grain sizedistribution. Using the present assumed function and the extended logarithmic mixing rule to combine the dielectric constants of individual grains, the grain-size distribution-dependence of the dielectric constant was successfully simulated. From the simulated results it was concluded that the dielectric constants of coarse grains of thick films increase with increase of grain size in the range from room temperature up to 135°C.

  20. Induced Ti magnetization at La0.7Sr0.3MnO3 and BaTiO3 interfaces

    DOE PAGES

    Liu, Yaohua; Tornos, J.; te Velthuis, S. G. E.; ...

    2016-04-01

    In artificial multiferroics hybrids consisting of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and ferroelectric BaTiO3 epitaxial layers, net Ti moments are found from polarized resonant soft x-ray reflectivity and absorption. Moreover, the Ti dichroic reflectivity follows the Mn signal during the magnetization reversal, indicating exchange coupling between the Ti and Mn ions. But, the Ti dichroic reflectivity shows stronger temperature dependence than the Mn dichroic signal. Besides a reduced ferromagnetic exchange coupling in the interfacial LSMO layer, this may also be attributed to a weak Ti-Mn exchange coupling that is insufficient to overcome the thermal energy at elevated temperatures.

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

    SciTech Connect

    Wu, Pingping; Ma, Xingqiao; Li, Yulan; Gopalan, Venkatraman; Chen , L.Q.

    2012-03-01

    Ferroelectric superlattice heterostructures have recently been explored for potential applications in electronic devices. In this letter we employed the phase-field approach to simulate the domain structure and switching of a (BaTiO3)8/(SrTiO3)3 superlattice film constrained by a GdScO3 substrate. A constricted ferroelectric hysteresis loop was observed with a high saturation polarization but a small coercive field. The shape of the hysteresis loop is understood by analyzing the ferroelectric polarization distributions during switching. It is demonstrated that the multilayers stack behave as dipole spring ferroelectric, named in analogy to exchange spring magnets in magnetic multilayers that show similar loops.

  2. Effect of solution combusted TiO2 nanopowder within commercial BaTiO3 dielectric layer on the photoelectric properties for AC powder electroluminescence devices.

    PubMed

    Park, Sung; Choi, Gil Rak; Kim, Youn Cheol; Lee, Jae Chun; Lee, Ju Hyeon

    2013-05-01

    A unique synthesis method was developed, which is called solution combustion method (SCM). TiO2 nanopowder was synthesized by this method. This SCM TiO2 nanopowder (-35 nm) was added to the dielectric layer of AC powder electroluminescence (EL) device. The dielectric layer was made of commercial BaTiO3 powder (-1.2 microm) and binding polymer. 0, 5, 10 and 15 wt% of SCM TiO2 nanopowder was added to the dielectric layer during fabrication of AC powder EL device respectively. Dielectric constant of these four kinds of dielectric layers was measured. The brightness and current density of AC powder EL device were also measured. When 10 wt% of SCM TiO2 nanopowder was added, dielectric constant and brightness were increased by 30% and 101% respectively. Furthermore, the current density was decreased by 71%. This means that the brightness was double and the power consumption was one third.

  3. Structural and Optical properties of poly-crystalline BaTiO3 and SrTiO3 prepared via solid state route

    NASA Astrophysics Data System (ADS)

    Jarabana, Kanaka M.; Mishra, Ashutosh; Bisen, Supriya

    2016-10-01

    Polycrystalline BaTiO3 (BTO) and SrTiO3 (STO) were synthesized by solid state route method and properties of made polycrystalline were characterized by X-Ray diffraction (XRD), Raman Spectroscopy & FTIR Spectroscopy. XRD analysis shows that samples are crystalline in nature. In Raman Spectroscopy measurement, the experiment has been done with the help of JOBIN-YOVN HORIBA LABRAM HR800 single monochromator, which is coupled with a “peltier cooled” charge coupled device (CCD). Raman Spectroscopy at low temperature measurement shows the phase transition above & below the curie temperature in samples. Fourier transform Infrared spectroscopy was used to determine the Ti-O bond length position.

  4. Phase separation enhanced magneto-electric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films.

    PubMed

    Alberca, A; Munuera, C; Azpeitia, J; Kirby, B; Nemes, N M; Perez-Muñoz, A M; Tornos, J; Mompean, F J; Leon, C; Santamaria, J; Garcia-Hernandez, M

    2015-12-09

    We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30-40% upon applying electric fields on the order of 1 kV/cm to the BaTiO3 substrate, corresponding to magnetoelectric coupling constants on the order of α = (2-5) · 10(-7) s/m. Magnetic anisotropy is also affected by the electric field induced strain, resulting in a considerable reduction of coercive fields. We compare the magnetoelectric effect in pre-poled and unpoled BaTiO3 substrates. Polarized neutron reflectometry reveals a two-layer behavior with a depressed magnetic layer of around 30 Å at the interface. Magnetic force microscopy (MFM) shows a granular magnetic structure of the La0.7Ca0.3MnO3. The magnetic granularity of the La0.7Ca0.3MnO3 film and the robust magnetoelastic coupling at the La0.7Ca0.3MnO3/BaTiO3 interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite.

  5. Phase separation enhanced magneto-electric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films

    PubMed Central

    Alberca, A.; Munuera, C.; Azpeitia, J.; Kirby, B.; Nemes, N. M.; Perez-Muñoz, A. M.; Tornos, J.; Mompean, F. J.; Leon, C.; Santamaria, J.; Garcia-Hernandez, M.

    2015-01-01

    We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30–40% upon applying electric fields on the order of 1 kV/cm to the BaTiO3 substrate, corresponding to magnetoelectric coupling constants on the order of α = (2–5)·10−7 s/m. Magnetic anisotropy is also affected by the electric field induced strain, resulting in a considerable reduction of coercive fields. We compare the magnetoelectric effect in pre-poled and unpoled BaTiO3 substrates. Polarized neutron reflectometry reveals a two-layer behavior with a depressed magnetic layer of around 30 Å at the interface. Magnetic force microscopy (MFM) shows a granular magnetic structure of the La0.7Ca0.3MnO3. The magnetic granularity of the La0.7Ca0.3MnO3 film and the robust magnetoelastic coupling at the La0.7Ca0.3MnO3/BaTiO3 interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite. PMID:26648002

  6. Comparative ab initio calculations of SrTiO3/BaTiO3 and SrZrO3/PbZrO3 (0 0 1) heterostructures

    NASA Astrophysics Data System (ADS)

    Piskunov, Sergei; Eglitis, Roberts I.

    2016-05-01

    Using a B3PW hybrid exchange-correlation functional within the density functional theory (DFT) we calculated from the first principles the electronic structure of BaTiO3/SrTiO3 and PbZrO3/SrZrO3 (0 0 1) interfaces. The optical band gap of both BaTiO3/SrTiO3 and PbZrO3/SrZrO3 (0 0 1) interfaces depends mostly from BaO or TiO2 and SrO or ZrO2 termination of the upper layer, respectively. Based on the results of our calculations we predict increase of the Ti-O and Zr-O chemical bond covalency near the SrTiO3/BaTiO3 and SrZrO3/PbZrO3 (0 0 1) interfaces as compared to the BaTiO3 and PbZrO3 bulk.

  7. Orientation of optic axis in wedged photorefractive crystals

    NASA Astrophysics Data System (ADS)

    Kos, Konstantine; Siahmakoun, Azad Z.

    1996-02-01

    A holographic method for finding the orientation of the optic axis of uniaxial photorefractive crystals is proposed. A theoretical procedure for determining the wedge angle of such crystals has also been developed. Two BaTiO 3 crystals grown by the same vender are examined and the resulting measurements lead to the values of wedge angle with an accuracy of about ±0.1°.

  8. Structure-Curie temperature relationships in BaTiO3-based ferroelectric perovskites: Anomalous behavior of (Ba ,Cd )TiO3 from DFT, statistical inference, and experiments

    NASA Astrophysics Data System (ADS)

    Balachandran, Prasanna V.; Xue, Dezhen; Lookman, Turab

    2016-04-01

    One of the key impediments to the development of BaTiO3-based materials as candidates to replace toxic-Pb-based solid solutions is their relatively low ferroelectric Curie temperature (TC). Among many potential routes that are available to modify TC, ionic substitutions at the Ba and Ti sites remain the most common approach. Here, we perform density functional theory (DFT) calculations on a series of A TiO3 and Ba B O3 perovskites, where A =Ba , Ca, Sr, Pb, Cd, Sn, and Mg and B =Ti , Zr, Hf, and Sn. Our objective is to study the relative role of A and B cations in impacting the TC of the tetragonal (P 4 m m ) and rhombohedral (R 3 m ) ferroelectric phases in BaTiO3-based solid solutions, respectively. Using symmetry-mode analysis, we obtain a quantitative description of the relative contributions of various divalent (A ) and tetravalent (B ) cations to the ferroelectric distortions. Our results show that Ca, Pb, Cd, Sn, and Mg have large mode amplitudes for ferroelectric distortion in the tetragonal phase relative to Ba, whereas Sr suppresses the distortions. On the other hand, Zr, Hf, and Sn tetravalent cations severely suppress the ferroelectric distortion in the rhombohedral phase relative to Ti. In addition to symmetry modes, our calculated unit-cell volume also agrees with the experimental trends. We subsequently utilize the symmetry modes and unit-cell volumes as features within a machine learning approach to learn TC via an inference model and uncover trends that provide insights into the design of new high-TCBaTiO3 -based ferroelectrics. The inference model predicts CdTiO3-BaTiO3 solid solutions to have a higher TC and, therefore, we experimentally synthesized these solid solutions and measured their TC. Although the calculated mode strength for CdTiO3 in the tetragonal phase is even larger than that for PbTiO3, the TC of CdTiO3-BaTiO3 solid solutions in the tetragonal phase does not show any appreciable enhancement. Thus, CdTiO3-BaTiO3 does not follow the inference model, which is based on established data and trends for A TiO3 . Rather, our experimental phase diagram for CdTiO3-BaTiO3 suggests that it behaves markedly differently from any other BaTiO3-based systems studied so far.

  9. Crystal orbital studies on the 1D silic-diyne nanoribbons and nanotubes

    NASA Astrophysics Data System (ADS)

    Zhu, Ying; Bai, Hongcun; Huang, Yuanhe

    2016-02-01

    This work presents crystal orbital studies on novel one-dimensional (1D) nanoscale materials derived from a Si-diyne sheet, based on the density functional theory. The two-dimensional (2D) Si-diyne layer is observed to be carbo-merized silicene, with a similar structure to graphdiyne. The 2D Si-diyne and its 1D ribbons and tubes, of different size and chirality, have been addressed systematically. The low dimensional Si-diyne materials studied exhibit relatively high stability, according to phonon-frequency calculations and molecular dynamics simulations. With comparable diameters, the Si-diyne tubes have lower strain energies than silicene and silicon carbide nanotubes. The Si-diyne layer and its 1D derivatives are all semiconductors, regardless of the size and chirality of the strips and tubes. In addition, the band gaps of the 1D Si-diyne nanoribbons and nanotubes with different chirality, always monotonically decrease as their sizes increases. A quantitative relationship between the band gap and the size of the ribbons and tubes was obtained. The mobility of charge carriers for the 1D Si-diyne structures was also investigated. It was found that both hole and electron mobility of the ribbons and tubes exhibit linear increase with increasing size. The electrons have greater mobility than the holes for each strip and tube. In addition, the mechanical properties of the Si-diyne nanostructures were also investigated by calculation of the Young’s modulus and the Poisson’s ratio.

  10. Insulator-to-conductor transition in liquid crystal-carbon nanotube nanocomposites

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan; Garvey, Alfred

    2016-10-01

    A small quantity of carbon nanotubes (CNTs) was dispersed in a liquid crystal (LC) and the LC + CNT hybrid in the isotropic phase was found to exhibit an insulator-to-conductor transition when an external electric field was applied. This effect was probed by measuring the resistance of the system as a function of applied voltage across the LC cell. In an LC + CNT hybrid, the LC molecules self-assemble themselves at the CNT surface due to π-π electron stacking, creating pseudonematic domains (PNDs) surrounding the CNTs. These CNT-embedded PNDs interact with the external electric field even in the isotropic phase of the LC. When the external field is applied, the PND-encapsulated CNTs start to rotate along the field and form wires due to their natural tendency of entanglement. The CNT-wires eventually short the two electrodes of the LC cell, manifesting an insulator-to-conductor transition in the LC + CNT hybrid. Additional studies revealed that the cell spacing and the CNT-concentration had a significant impact on the threshold voltage across the LC cell for the insulator-to-conductor transition process.

  11. Density Functional Theory Study of Bandgap Modulation of Si2N-h2D Crystal Nanoribbons and Nanotubes Under Elastic Strain

    NASA Astrophysics Data System (ADS)

    Ma, ShengQian; Li, Feng; Geng, JiGuo

    2017-04-01

    Since efficient synthesis of C2N holey two-dimensional (h2D) crystal has been possible, bandgap modulation through use of analogous nanoribbon and nanotube structures has attracted strong interest. In this study, bandgap modulation of Si2N-h2D nanoribbons and nanotubes under elastic strain has been deeply researched using density functional theory calculations. The results indicate that the bandgap of Si2N-h2D nanoribbons and nanotubes in zigzag and armchair configurations can be tuned in both directions, namely by stretching or compressing, in the range of ɛ = ( d - d 0)/ d 0 from -10% to 10%. It is also found that the bandgap of Si2N-h2D nanoribbons and nanotubes varies with their width. Therefore, it is predicted that Si2N-h2D nanoribbons and nanotubes have great potential for application in nanoscale strain sensors and optoelectronics.

  12. Ultralow mode-volume photonic crystal nanobeam cavities for high-efficiency coupling to individual carbon nanotube emitters

    PubMed Central

    Miura, R.; Imamura, S.; Ohta, R.; Ishii, A.; Liu, X.; Shimada, T.; Iwamoto, S.; Arakawa, Y.; Kato, Y. K.

    2014-01-01

    The unique emission properties of single-walled carbon nanotubes are attractive for achieving increased functionality in integrated photonics. In addition to being room-temperature telecom-band emitters that can be directly grown on silicon, they are ideal for coupling to nanoscale photonic structures. Here we report on high-efficiency coupling of individual air-suspended carbon nanotubes to silicon photonic crystal nanobeam cavities. Photoluminescence images of dielectric- and air-mode cavities reflect their distinctly different mode profiles and show that fields in the air are important for coupling. We find that the air-mode cavities couple more efficiently, and estimated spontaneous emission coupling factors reach a value as high as 0.85. Our results demonstrate advantages of ultralow mode-volumes in air-mode cavities for coupling to low-dimensional nanoscale emitters. PMID:25420679

  13. Ultralow mode-volume photonic crystal nanobeam cavities for high-efficiency coupling to individual carbon nanotube emitters.

    PubMed

    Miura, R; Imamura, S; Ohta, R; Ishii, A; Liu, X; Shimada, T; Iwamoto, S; Arakawa, Y; Kato, Y K

    2014-11-25

    The unique emission properties of single-walled carbon nanotubes are attractive for achieving increased functionality in integrated photonics. In addition to being room-temperature telecom-band emitters that can be directly grown on silicon, they are ideal for coupling to nanoscale photonic structures. Here we report on high-efficiency coupling of individual air-suspended carbon nanotubes to silicon photonic crystal nanobeam cavities. Photoluminescence images of dielectric- and air-mode cavities reflect their distinctly different mode profiles and show that fields in the air are important for coupling. We find that the air-mode cavities couple more efficiently, and estimated spontaneous emission coupling factors reach a value as high as 0.85. Our results demonstrate advantages of ultralow mode-volumes in air-mode cavities for coupling to low-dimensional nanoscale emitters.

  14. Hydrophilic Modification of Multi-Walled Carbon Nanotube for Building Photonic Crystals with Enhanced Color Visibility and Mechanical Strength.

    PubMed

    Li, Feihu; Tang, Bingtao; Xiu, Jinghai; Zhang, Shufen

    2016-04-28

    Low color visibility and poor mechanical strength of polystyrene (PS) photonic crystal films have been the main shortcomings for the potential applications in paints or displays. This paper presents a simple method to fabricate PS/MWCNTs (multi-walled carbon nanotubes) composite photonic crystal films with enhanced color visibility and mechanical strength. First, MWCNTs was modified through radical addition reaction by aniline 2,5-double sulfonic acid diazonium salt to generate hydrophilic surface and good water dispersity. Then the MWCNTs dispersion was blended with PS emulsion to form homogeneous PS/MWCNTs emulsion mixtures and fabricate composite films through thermal-assisted method. The obtained films exhibit high color visibility under natural light and improved mechanical strength owing to the light-adsorption property and crosslinking effect of MWCNTs. The utilization of MWCNTs in improving the properties of photonic crystals is significant for various applications, such as in paints and displays.

  15. Study on Occupation Behavior of Y2O3 in X8R Nonreducible BaTiO3-Based Dielectric Ceramics

    NASA Astrophysics Data System (ADS)

    Yao, Guofeng; Wang, Xiaohui; Li, Longtu

    2011-12-01

    The effects of Y2O3 on BaTiO3-MgO-MnO2-CaZrO3 nonreducible ceramics were investigated. Specimens with Y2O3 contents ranging from 1.0 to 2.5 mol % were prepared via the solid state method. The Curie temperature (Tc) and the electrical properties were closely related to the occupation behavior of yttrium, which is known as an amphoteric element. Tc increased almost linearly as a function of Y2O3 content when the doping content was low. Transmission electron microscopy (TEM) indicated a typical “core-shell” structure. The lattice parameters corresponding to the grain cores and the shells were determined by X-ray diffractometry (XRD) separately. The relief of the internal stresses arising from the lattice mismatch was responsible for the Tc shift. The specimens doped by a high level of Y2O3 can fulfill the EIA X8R specification with a high dielectric constant (ɛRT > 2400) and a low dielectric loss (tan δ< 1.1%). A high insulation resistivity and a slow degradation rate were obtained when a sufficient amount of Y2O3 was incorporated, which were attributed to the substitution of Ti4+ and the formation of a donor-acceptor complex.

  16. Fabrication and optical properties of InGaN/GaN multiple quantum well light emitting diodes with amorphous BaTiO3 ferroelectric film

    NASA Astrophysics Data System (ADS)

    Peng, Jing; Wu, Chuan-Ju; Sun, Tang-You; Zhao, Wen-Ning; Wu, Xiao-Feng; Liu, Wen; Wang, Shuang-Bao; Jie, Quan-Lin; Xu, Zhi-Mou

    2012-06-01

    BaTiO3 (BTO) ferroelectric thin films are prepared by the sol-gel method. The fabrication and the optical properties of an InGaN/GaN multiple quantum well light emitting diode (LED) with amorphous BTO ferroelectric thin film are studied. The photoluminescence (PL) of the BTO ferroelectric film is attributed to the structure. The ferroelectric film which annealed at 673 K for 8 h has the better PL property. The peak width is about 30 nm from 580 nm to 610 nm, towards the yellow region. The mixed electroluminescence (EL) spectrum of InGaN/GaN multiple quantum well LED with 150-nm thick amorphous BTO ferroelectric thin film displays the blue-white light. The Commission Internationale De L'Eclairage (CIE) coordinate of EL is (0.2139, 0.1627). EL wavelength and intensity depends on the composition, microstructure and thickness of the ferroelectric thin film. The transmittance of amorphous BTO thin film is about 93% at a wavelength of 450 nm-470 nm. This means the amorphous ferroelectric thin films can output more blue-ray and emission lights. In addition, the amorphous ferroelectric thin films can be directly fabricated without a binder and used at higher temperatures (200 °C-400 °C). It is very favourable to simplify the preparation process and reduce the heat dissipation requirements of an LED. This provides a new way to study LEDs.

  17. Magnetic behavior of La2/3Ca1/3MnO3 / BaTiO3 bilayers

    NASA Astrophysics Data System (ADS)

    Ordonez, John E.; Gomez, Maria E.; Lopera, Wilson; Marin, Lorena; Pardo, Jose A.; Morellon, Luis; Algarabel, Pedro; Prieto, Pedro

    2013-03-01

    We have grown ferroelectric BaTiO3(BTO) and ferromagnetic La2/3Ca1/3MnO3 (LCMO) onto (001) SrTiO3 and Nb:SrTiO3 by pulsed laser deposition (PLD) at pure oxygen atmosphere, and a substrate temperature of 820° C, seeking for a multiferroic behavior in this structure. From x-ray diffraction (XRD) we found lattice parameter aBTO=4.068 Å, and aLCMO=3.804 Å, for each individual layer. In the BTO/LCMO bilayer, (002)-Bragg peak for BTO maintain its position whereas (002) LCMO peak shift to lower Bragg angle indicating a strained LCMO film. Magnetization measurements reveal an increase in the Curie temperature from 170 K to 220 K for the bilayer when LCMO (t = 47 nm) is deposited on BTO (t=52 nm) film, while depositing the BTO (50 nm) above LCMO (48 nm) the Curie temperature remains at values close to that obtained for a LCMO single layer (~175 K), deposited under identical growth parameters This work has been supported by Instituto de Nanociencias de Aragón, Zaragoza, Spain, ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' COLCIENCIAS-CENM Contract RC 275-2011 and Research Project COLCIENCIAS-UNIVALLE.

  18. Metastable antiparallel polarization configurations in BaTiO3/PbZr0.2Ti0.8O3 epitaxial bilayer

    NASA Astrophysics Data System (ADS)

    Salev, Pavel; Grigoriev, Alexei

    A combination of LGD and semiconductor theories predicts the electrostatic screening of a large polarization mismatch between BaTiO3 (BTO) and Pb(Zr,Ti)O3 (PZT) ferroelectric layers. The source of this screening is in an increased concentration of interfacial free charge carriers due to the strong bending of electronic bands inside the layers. The enhanced concentration of free charges at the interface can allow for independent polarization reversal in each ferroelectric layer suggesting possible antiparallel polarization configurations in BTO/PZT bilayer. We confirmed these theoretical predictions of layer-by-layer switching by demonstrating double polarization switching in epitaxial BTO/PZT thin films. The layer-by-layer switching leads to formation of head-to-head (H-H) and tail-to-tail (T-T) polarization configurations, which have an enhanced dielectric permittivity when compared to parallel polarization domain configurations. While both H-H and T-T states are unstable at a zero electric field, we found that antiparallel polarization configurations can be stabilized by applying a small bias. Our findings provide a pathway to engineer new multilayer systems with switchable multistate polarizations and dielectric responses.

  19. Multiferroic behavior on nanometric La2/3Ca1/3MnO3 / BaTiO3 bilayers

    NASA Astrophysics Data System (ADS)

    Prieto, Pedro; Ordoñez, John Edward; Gomez, Maria Elena; Lopera, Wilson

    2014-03-01

    We have deposited bilayers of the FM La2/3Ca1/3MnO3 and FE BaTiO3 as a route to design systems with artificial magnetoelectric coupling on LCMO/BTO/Nb:STO system. We maintain a fixed magnetic layer thickness (tLCMO = 48 nm) and varying the thickness of the ferroelectric layer (tBTO = 20, 50, 100 nm). We analyze the influence of the thickness ratio (tBTO/ tLCMO) in electrical and magnetic properties of manganite. From X-ray diffraction analysis we observed that the samples grew textured. Magnetization and transport measurements indicate a possible multiferroic behavior in the bilayer. We found an increase in the Curie and metal-insulator transition temperature in the bilayer in comparison with those for LCMO (48nm)/STO. Hysteresis loops on bilayers show ferromagnetic behavior. This work has been supported by the ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' Colciencias-CENM Research Projects: No. 1106-48-925531 and CI7917-CC 10510 contract 0002-2013 COLCIENCIAS-UNIVALLE.

  20. Improved Dielectric Properties and Energy Storage Density of Poly(vinylidene fluoride-co-hexafluoropropylene) Nanocomposite with Hydantoin Epoxy Resin Coated BaTiO3.

    PubMed

    Luo, Hang; Zhang, Dou; Jiang, Chao; Yuan, Xi; Chen, Chao; Zhou, Kechao

    2015-04-22

    Energy storage materials are urgently demanded in modern electric power supply and renewable energy systems. The introduction of inorganic fillers to polymer matrix represents a promising avenue for the development of high energy density storage materials, which combines the high dielectric constant of inorganic fillers with supernal dielectric strength of polymer matrix. However, agglomeration and phase separation of inorganic fillers in the polymer matrix remain the key barriers to promoting the practical applications of the composites for energy storage. Here, we developed a low-cost and environmentally friendly route to modifying BaTiO3 (BT) nanoparticles by a kind of water-soluble hydantoin epoxy resin. The modified BT nanoparticles exhibited homogeneous dispersion in the ferroelectric polymer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix and strong interfacial adhesion with the polymer matrix. The dielectric constants of the nanocomposites increased significantly with the increase of the coated BT loading, while the dielectric loss of the nanocomposites was still as low as that of the pure P(VDF-HFP). The energy storage density of the nanocomposites was largely enhanced with the coated BT loading at the same electric field. The nanocomposite with 20 vol % BT exhibited an estimated maximum energy density of 8.13 J cm(-3), which was much higher than that of pure P(VDF-HFP) and other dielectric polymers. The findings of this research could provide a feasible approach to produce high energy density materials for practical application in energy storage.

  1. Correlated rattling-ion origins of dielectric properties in reentrant dipole glasses BaTiO3-BiScO3

    NASA Astrophysics Data System (ADS)

    Krayzman, Victor; Levin, Igor; Woicik, Joseph C.; Bridges, Frank

    2015-11-01

    The local structure of the pseudo-cubic solid solution 0.6BaTiO3-0.4BiScO3, which exhibits reentrant dipole-glass behavior, has been determined using the Reverse Monte Carlo method to simultaneously fit (1) neutron and X-ray total scattering data (including the corresponding real-space pair-distribution functions), (2) Bi and Sc extended X-ray absorption fine structure, and (3) patterns of diffuse scattering in electron diffraction. These structural refinements revealed the multi-site probability density distributions for both Bi (14-sites) and Ti (8 sites), whereas Ba and Sc featured normal unimodal distributions. Bi atoms are displaced along both the <111> and <100> directions, while Ti atoms are shifted along <111>. Correlated dynamic hopping of Bi and Ti over their corresponding split sites combined with chemical disorder is proposed as the origin of the strong frequency dispersion observed in dielectric measurements. The existence of split sites also explains the reentrant dipole-glass behavior reported for this system.

  2. First-principles-based calculation of the electrocaloric effect in BaTiO3: A comparison of direct and indirect methods

    NASA Astrophysics Data System (ADS)

    Marathe, Madhura; Grünebohm, Anna; Nishimatsu, Takeshi; Entel, Peter; Ederer, Claude

    2016-02-01

    We use molecular dynamics simulations for a first-principles-based effective Hamiltonian to calculate two important quantities characterizing the electrocaloric effect in BaTiO3, the adiabatic temperature change Δ T and the isothermal entropy change Δ S , for different electric field strengths. We compare direct and indirect methods to obtain Δ T and Δ S , and we confirm that both methods indeed lead to an identical result provided that the system does not actually undergo a first order phase transition. We also show that a large electrocaloric response is obtained for electric fields beyond the critical field strength for the first order phase transition. Furthermore, our work fills several gaps regarding the application of the first-principles-based effective Hamiltonian approach, which represents a very attractive and powerful method for the quantitative prediction of electrocaloric properties. In particular, we consider the full temperature and field dependence of the calculated specific heat for the indirect calculation of Δ T , and we discuss the importance of maintaining thermal equilibrium during the field ramping when calculating Δ T using the direct method within a molecular dynamics approach.

  3. Effect of combined external uniaxial stress and dc bias on the dielectric property of BaTiO3-based dielectrics in multilayer ceramic capacitor: thermodynamics and experiments

    NASA Astrophysics Data System (ADS)

    Yang, Gang; Yue, Zhenxing; Sun, Tieyu; Gou, Huanlin; Li, Longtu

    2008-02-01

    The dielectric properties of (Nb, Y)-doped BaTiO3 in a multilayer ceramic capacitor (MLCC) under combined external uniaxial compressive stress and dc bias field were investigated at room temperature by using a modified Ginsburg-Landau-Devonshire thermodynamic theory and the dielectric measurement. It is found that although dc bias decreases the dielectric properties dominantly, the influence of the external uniaixial compressive stress should not be neglected. When applied along a direction perpendicular to the internal electrode layer in the MLCC, the external uniaixal compressive stress will strengthen the negative effect of dc bias. In contrast, the external uniaxial compressive stress along a direction parallel to the internal electrode layer in the MLCC will increase the dielectric permittivity under dc bias field, i.e. improve the ɛ-V response of the MLCC. Furthermore, although there is a difference between the calculated permittivity and the measured permittivity, the effects of the combined external uniaxial compressive stress and dc bias field on the dielectric permittivity described through two approaches are in good agreement.

  4. Phase Evolution and Nucleus Growth Observation of Solid-State BaTiO3 Powder Prepared by High-Energy Bead Milling for Raw Material Mixing

    NASA Astrophysics Data System (ADS)

    Lee, Ting-Tai; Huang, Chi-Yuen; Chang, Che-Yuan; Lin, Shih-Pin; Su, Che-Yi; Lee, Chun-Te; Fujimoto, Masayuki

    2011-09-01

    The solid-state synthesis, phase evolution, and nucleus growth of the barium titanate (BaTiO3, BT) powder were investigated in this study. Rapid nucleus growth and precursor phase formation of BT were observed at a relatively low temperature of 600 °C by mixing BaCO3 (2 m2/g) and TiO2 (7 m2/g) with a high-energy bead mill. The decomposition of BaCO3 and the formation of the Ba2TiO4 phase were identified by transmission electron microscopy (TEM). On the basis of this observation, the weight loss observed at 600 °C in the derivative thermogravimetry (DTG) curve could also be explained. Furthermore, with increasing calcination temperature, single cubic BT with less than 80 nm fine nuclei/crystallites was observed at 900 °C, and tetragonal BT (c/a > 1.008) with an average particle size of 0.4 µm was obtained at 1000 °C. With regard to the dielectric properties of sintered ceramics, the relative permittivity (ɛr) increased with calcination temperature, and the Curie point also shifted to a progressively higher temperature. However, BT nucleus samples (with low calcination temperatures of 800 and 900 °C) could not satisfy the X7R requirement (Electric Industries Association Standard, the tolerance of capacitance from -55 to +125 °C is ±15%) until calcination temperature increased to 1000 °C.

  5. In situ impedance analysis on BaTiO3-LiCoO2 composite cathodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Teranishi, Takashi; Yoshikawa, Yumi; Sakuma, Ryo; Okamura, Hirokazu; Hayashi, Hidetaka; Kishimoto, Akira; Takeda, Yasuo

    2015-10-01

    In situ electrochemical impedance spectroscopy (EIS) was undertaken to investigate the contribution of a ferroelectric artificial solid electrolyte interface (SEI) to the enhancement of the rate capability of lithium ion batteries. Resistance elements, consisting of the cell reactions, the resistance of the electrolyte, Rsol, that of the Li metal anode reaction, RLi, and the charge transfer resistance, Rct, were measured. A small ferroelectric BaTiO3 (BT) load, ˜1 mol %, notably reduced Rct and Rsol compared with bare LiCoO2 (LC), indicating that loaded ferroelectric BT SEIs effectively promote Li inter/deintercalation into and from the active material, LC, and restrict cobalt ion dissolution into the electrolyte liquid. Lower Rct and Rsol resulted in a significantly higher capacity retention ratio at a 10 C rate compared with the initial cycle for small BT load, ˜1 mol %. The capacity retention dropped rapidly, accompanied by a slight increase in Rct for larger BT loads, 5 and 15 mol %, which may be attributed to the thicker BT layer and the existence of the impurity phase, BaCO3. These results imply that the ferroelectric SEI affected the kinetics of mobile Li ions at the cathode-electrolyte interface, significantly enhancing the rate capability.

  6. Double hysteresis in BaTiO3/PbZr0.2Ti0.8O3 ferroelectric bilayer thin film

    NASA Astrophysics Data System (ADS)

    Salev, Pavel; Grigoriev, Alexei

    2015-03-01

    We observed two hysteresis loops in BaTiO3/PbZr0.2Ti0.8O3 (BTO/PZT) bilayer thin film. The first loop with polarization of 27 μ C/cm2 was measured in the applied voltage of +/- 20 V. The second hysteresis loop with polarization of 76 μ C/cm2 was measured in the applied voltage of +/- 55 V. Both hysteresis loops showed characteristic shape with concave region followed by saturation region in the broad range of applied voltage frequencies providing strong evidence for ferroelectric origin of both loops. We performed computational analysis of BTO/PZT bilayer based on Landau-Ginzburg-Devonshire model including contributions of electronic band structure. We found an increased concentration of free charge carriers at the interface between BTO and PZT which provides compensation for the bound charge due to polarization mismatch of the layers. Moreover, as the free charge effectively screens polarization in one layer from another, polarization switching of individual layers can be possible. This leads to the conclusion that two hysteresis loops can be a result of polarization switching of the individual layers.

  7. Multiferroic Ni0.6Zn0.4Fe2O4-BaTiO3 nanostructures: Magnetoelectric coupling, dielectric, and fluorescence

    NASA Astrophysics Data System (ADS)

    Verma, Kuldeep Chand; Singh, Sukhdeep; Tripathi, S. K.; Kotnala, R. K.

    2014-09-01

    Multiferroic nanostructures of Ni0.6Zn0.4Fe2O4-BaTiO3 (NZF/BT) have been prepared by two synthesis routes, i.e., chemical combustion (CNZF/BT) and hydrothermal (HNZF/BT). The synthesis of CNZF/BT results in nanoparticles of average size 4 nm at 500 °C annealing. However, the synthesis of HNZF/BT with hydrolysis temperature 180 °C/48 h shows nanowires of diameter 3 nm and length >150 nm. A growth mechanism in the fabrication of nanoparticles and wires is given. X-ray diffraction is used to identify the crystalline phase. The transmission electron microscopy shows the dimensions of NZF/BT nanostructures. The ferromagnetism, ferroelectricity, and magnetoelectric coupling show more enhancements in HNZF/BT nanowires than CNZF/BT nanoparticles. The observed polarization depends upon shape of nanostructures, tetragonal phase, and epitaxial strain. The tension induced by the surface curvature of nanowire counteracts the near-surface depolarizing effect and meanwhile leads to unusual enhancement of polarization. The ferromagnetism depends upon superficial spin canting, spin pinning of nanocomposite, and oxygen vacancy clusters. The magnetoelectric coefficient as the function of applied dc magnetizing field under ac magnetic field 5 Oe and frequency 1093 Hz is measured. The nanodimensions of NZF/BT are observed dielectric constant up to 120 MHz. The optical activity of NZF/BT nanostructures is shown by Fluorescence spectra.

  8. High rate capability of a BaTiO3-decorated LiCoO2 cathode prepared via metal organic decomposition

    NASA Astrophysics Data System (ADS)

    Teranishi, Takashi; Katsuji, Naoto; Yoshikawa, Yumi; Yoneda, Mika; Hayashi, Hidetaka; Kishimoto, Akira; Yoda, Koji; Motobayashi, Hidefumi; Tasaki, Yuzo

    2016-10-01

    Metal organic decomposition (MOD) using octylic acid salts was applied to synthesize a BaTiO3-LiCoO2 (BT-LC) composite powder. The Ba and Ti octylates were utilized as metal precursors, in an attempt to synthesize homogeneous BT nanoparticles on the LC matrix. The BT-LC composite, having a phase-separated composite structure without any impurity phase, was successfully obtained by optimizing the MOD procedure. The composite prepared using octylate precursors exhibited a sharper distribution and better dispersibility of decorated BT particles. Additionally, the average particle size of the decorated BTs using metal octylate was reduced to 23.3 nm, compared to 44.4 nm from conventional processes using Ba acetate as well as Ti alkoxide as precursors. The composite cathode displayed better cell performance than its conventional counterpart; the discharge capacity of the metal octylate-derived specimen was 55.6 mAh/g at a 50C rate, corresponding to 173% of the capacity of the conventional specimen (32.2 mAh/g). The notable improvement in high rate capability obtained in this study, compared with the conventional route, was attributed to the higher density of the triple junction formed by the BT-LC-electrolyte interface.

  9. Effects of carbon nanotubes on the physical properties of a nematic liquid crystal N-(4‧-methoxybenzylidene)-4-butylaniline

    NASA Astrophysics Data System (ADS)

    Jber, Nasreen Raheem; Rashad, Alaa Adnan; Shihab, Mehdi Salih

    2013-07-01

    In this work, the nematic liquid crystal (LC) N-(4'-methoxybenzylidene)-4-n-butylaniline (MBBA) was prepared and doped with different concentrations (0.025, 0.05, 0.06, 0.07, 0.08, and 0.1 wt.%) of multi-walled carbon nanotubes (CNTs) at room temperature to study the electric properties of (LC-CNTs) cell. The experimental results showed that capacitance of (LC-CNTs) cell became higher than that of pure LC cell. The dielectric permittivity is determined as a function of applied frequency (100 Hz to 100 kHz) at voltage (5 V); it is found that increasing concentration of CNTs (0.1 wt.%) led to increase in the real part dielectric constant and decrease in imaginary part for (LC-CNTs) cell compared with the pure liquid crystal. Also conductivity of (LC-CNTs) cell was increased with increasing concentration of CNTs more than 0.05 wt.%. Theoretical study was carried out by using PM3 method for stable geometries of a nematic liquid crystal molecule of MBBA assembled parallel on a molecule of single-walled carbon nanotube (CNT). The result showed that the interaction caused by π,π-stacking between MBBA molecule and the wall of CNT and that may lead to formation of the local short range orientation order by LC molecules on the surface of the CNT. The binding energy of the LC molecule on the CNT wall was within the typical van der Waals interaction.

  10. Influence of Ga-concentration on the electrical and magnetic properties of magnetoelectric CoGaxFe2–xO4/BaTiO3 composite

    DOE PAGES

    Ni, Yan; Zhang, Zhen; Nlebedim, Cajetan I.; ...

    2015-03-20

    Multiferroic materials exhibit magnetoelectric (ME) coupling and promise new device applications including magnetic sensors, generators, and filters. An effective method for developing ME materials with enhanced ME effect is achieved by the coupling through the interfacial strain between piezoelectric and magnetostrictive materials. In this study, the electrical and magnetic properties of Ga doped magnetoelectric CoGaxFe2–xO4/BaTiO3 composite are studied systematically. It is found that Ga doping improves the sensitivity of magnetoelastic response and stabilizes the magnetic phase of the composites. More importantly, Ga doping reduces the electrical conductivity of composite, as well as the dielectric loss. An enhancement of the electrostrainmore » with doping Ga is also observed. Quantitative estimation indicates that magnetoelectric coupling is enhanced for Ga-doped CoGaxFe2–xO4/BaTiO3 composites. As a result, the present work is beneficial to the practical application of composite CoFe2O4/BaTiO3-based multiferroic materials.« less

  11. First-principles study of multiferroic properties of Fe3O4/SrTiO3 and Fe3O4/BaTiO3 [001] superlattices

    NASA Astrophysics Data System (ADS)

    Park, Min Sik; Freeman, A. J.

    2007-03-01

    Multiferroic superlattices are good candidates for the study of the interplay between magnetism and ferroelectricity, and important for multifunctional device applications operating at room temperature. Recently, it was found that the magnetoresistance arising at the Fe3O4/BaTiO3 barrier is strongly bias dependent. We calculated the physical properties for multiferroic superlattices of spinel Fe3O4 (as a ferrimagnet) and perovskite SrTiO3, and BaTiO3 (as ferroelectric materials) by using first-principles density functional calculations with the highly precise full-potential linearized augmented plane wave (FLAPW) method. At the interface, the half-metallicity of bulk Fe3O4 is destroyed, and magnetic moments that are different from bulk Fe are obtained. The ferroelectric instability of BaTiO3 near the interface is also discussed. M. Ziese, A. Bollero, I. Panagiotopoulos, and N. Moutis, Appl. Phys. Lett., 88, 212502 (2006). Wimmer, Krakauer, Weinert, Freeman, Phys.Rev.B, 24, 864 (1981).

  12. Ferroelectric substrate effects on the magnetism, magnetotransport, and electroresistance of La0.7Ca0.3MnO3 thin films on BaTiO3

    NASA Astrophysics Data System (ADS)

    Alberca, A.; Munuera, C.; Tornos, J.; Mompean, F. J.; Biskup, N.; Ruiz, A.; Nemes, N. M.; de Andres, A.; León, C.; Santamaría, J.; García-Hernández, M.

    2012-10-01

    La0.7Ca0.3MnO3 optimally doped epitaxial films were grown on ferroelectric BaTiO3 substrates. Electronic transport (magnetoresistance and electroresistance) and magnetic properties showed important anomalies in the temperature interval between 60 and 150 K, below the metal-insulator transition. Scanning probe microscopy revealed changes in BaTiO3 surface morphology at those temperatures. La0.7Ca0.3MnO3 thickness is a critical factor: 120-Å-thick films showed large anomalies sensitive to electric poling of the BaTiO3, whereas the behavior of 150-Å-thick films is closer to that of the reference La0.7Ca0.3MnO3 samples grown on SrTiO3. We propose that, through inhomogenous strain and electric polarization effects, the ferroelectric substrate induces an inhomogenous spin distribution in the magnetic layer. This would imply the coexistence of in-plane and out-of-plane ferromagnetic patches in La0.7Ca0.3MnO3, possibly interspersed with antiferromagnetic regions, as it has recently been theoretically predicted. Substrate poling effects are investigated, and a magnetoelectric coupling is demonstrated.

  13. Isothermal Crystallization of Poly(L-lactide) Induced by Graphene Nanosheets and Carbon Nanotubes: A Comparative Study

    SciTech Connect

    Xu, J.; Chen, T; Yang, C; Li, Z; Mao, Y; Zeng, B; Hsiao, B

    2010-01-01

    Low-dimensional nanoparticles have a strong ability to induce the crystallization of polymer matrices. One-dimensional carbon nanotubes (CNTs) and two-dimensional graphene nanosheets (GNSs), both of which are both carbon-based nanoparticles, provide a good opportunity to investigate the effects of differently dimensional nanoparticles on the crystallization behavior of a polymer. For this purpose, respective nanocomposites of CNTs and GNSs with poly(L-lactide) (PLLA) as matrix were prepared by solution coagulation. Time-resolved Fourier-transform infrared spectroscopy (FTIR) and synchrotron wide-angle X-ray diffraction (WAXD) were performed to probe chain conformational changes and to determine the crystallization kinetics during the isothermal crystallization of the PLLA nanocomposites and neat PLLA, especially in the early stages. Both CNTs and GNSs could serve as nucleating agents in accelerating the crystallization kinetics of PLLA; however, the ability of CNTs to induce crystallization was stronger than that of GNSs. On increasing the content of CNTs from 0.05 to 0.1 wt %, the induction period was shortened and the crystallization rate was enhanced, but the reverse situation was found for GNSs nanocomposites. In the case of neat PLLA, -CH{sub 3} interchain interactions preceded -(COC + CH{sub 3}) interchain interactions during the crystallization. Conversely, in the CNTs and GNSs nanocomposites, the conformational ordering began with -(COC + CH{sub 3}) interchain interactions, which resulted directly in a reduced induction period. Interchain interactions of this type could be explained in terms of surface-induced conformational order (SICO). Finally, the effect of the dimensionality of the nanoparticles on the crystallization behavior of PLLA is discussed.

  14. Effects of conducting polymer poly(3, 4-ethylenedioxythiophene) nanotubes on the electro-optical and dielectric properties of a nematic liquid crystal 4-n-pentyl-4'-cyanobiphenyl host

    NASA Astrophysics Data System (ADS)

    Ghosh, Sharmistha; Nayek, Prasenjit; Roy, Subir Kr.; Gangopadhyay, Rupali; Molla, Mijanur Rahaman; Dabrowski, Roman

    2010-02-01

    We report the results of the optical transmission and the capacitance behavior as a function dc electric field of a pristine liquid crystal and conducting polymer nanotube-liquid crystal composite measured in twisted nematic cells. The threshold and driving voltages have been determined from transmission-voltage curve. There is remarkable reduction in the threshold and driving voltage in the polymer nanotube doped liquid crystal cell which is good from application point of view. The residual dc is also reduced significantly in the doped cell and the reduction is even more than that observed in the carbon nanotube doped same liquid crystal system.

  15. Structure Evolution of BaTiO3 on Co Doping: X-ray diffraction and Raman study

    NASA Astrophysics Data System (ADS)

    Mansuri, Amantulla; Mishra, Ashutosh

    2016-10-01

    In the present study, we have synthesize polycrystalline samples of BaTi1-xCoxO3 (x = 0, 0.05 and 0.1) with standard solid state reaction technique. The obtained samples are characterized by X-ray diffraction (XRD) and Raman spectroscopy. The detail structural analysis has been performed by Rietveld refinement using Fullprof program. The structural analysis reveal the samples are chemical pure and crystallize in tetragonal phase with space group Pm3m. We observe an increase in lattice parameters which results due to substitution of Co2+ with large ionic radii (0.9) for smaller ionic radii (0.6) Ti4+. Moreover peak at 45.5° shift to 45° on Co doping, which is due to structure phase transition from tetragonal to cubic. Raman study infers that the intensity of characteristic peaks decreases and linewidth increases with Co doping. The bands linked with the tetragonal structure (307 cm1) decreased due to the tetragonal-towards-cubic phase transition with Co doping. Our structural study reveals the expansion of BTO unit cell and tetragonal-to-cubic phase transformation takes place, results from different characterization techniques are conclusive and show structural evolution with Co doping.

  16. Phosphorus Cation Doping: A New Strategy for Boosting Photoelectrochemical Performance on TiO2 Nanotube Photonic Crystals.

    PubMed

    Li, Zhenzhen; Xin, Yanmei; Wu, Wenlong; Fu, Baihe; Zhang, Zhonghai

    2016-11-16

    Photoelectrochemical (PEC) water splitting is a promising technique for sustainable hydrogen generation. However, PEC performance on current semiconductors needs further improvement. Herein, a phosphorus cation doping strategy is proposed to fundamentally boost PEC performance on TiO2 nanotube photonic crystal (TiO2 NTPC) photoelectrodes in both the visible-light region and full solar-light illumination. The self-supported P-TiO2 NTPC photoelectrodes are fabricated by a facile two-step electrochemical anodization method and subsequent phosphidation treatment. The Ti(4+) is partially replaced by P cations (P(5+)) from the crystal lattice, which narrows the band gap of TiO2 and induces charge imbalance by the formation of Ti-O-P bonds. We believe the combination of unique photonic nanostructures of TiO2 NTPCs and P cation doping strategy will open up a new opportunity for enhancing PEC performance of TiO2-based photoelectrodes.

  17. Aperiodic TiO2 nanotube photonic crystal: full-visible-spectrum solar light harvesting in photovoltaic devices.

    PubMed

    Guo, Min; Xie, Keyu; Wang, Yu; Zhou, Limin; Huang, Haitao

    2014-09-23

    Bandgap engineering of a photonic crystal is highly desirable for photon management in photonic sensors and devices. Aperiodic photonic crystals (APCs) can provide unprecedented opportunities for much more versatile photon management, due to increased degrees of freedom in the design and the unique properties brought about by the aperiodic structures as compared to their periodic counterparts. However, many efforts still remain on conceptual approaches, practical achievements in APCs are rarely reported due to the difficulties in fabrication. Here, we report a simple but highly controllable current-pulse anodization process to design and fabricate TiO2 nanotube APCs. By coupling an APC into the photoanode of a dye-sensitized solar cell, we demonstrate the concept of using APC to achieve nearly full-visible-spectrum light harvesting, as evidenced by both experimental and simulated results. It is anticipated that this work will lead to more fruitful practical applications of APCs in high-efficiency photovoltaics, sensors and optoelectronic devices.

  18. High dielectric constant and low dielectric loss hybrid nanocomposites fabricated with ferroelectric polymer matrix and BaTiO3 nanofibers modified with perfluoroalkylsilane

    NASA Astrophysics Data System (ADS)

    Zhang, Xianhong; Ma, Yuhong; Zhao, Changwen; Yang, Wantai

    2014-06-01

    Interfacial interaction and compatibility between the ceramic dielectric and polymer matrix have strong impact on the dielectric permittivity and dielectric loss of their composites. In this work, we presented a simple strategy to fabricate flexible dielectric composite of high dielectric constant BaTiO3 (BT) nanofiber and ferroelectric poly(vinylidene fluoride) (PVDF) matrix. The electrospun BT nanofiber was sintered at about 800 °C to form perovskite crystalline. Fluorosilane 1H,1H,2H,2H-perfluorooctyltrimethoxysilane was used to introduce a short perfluoroalkyl chain to the surface of BT nanofiber by silane coupling. The effects of content of modified BT nanofiber on the dielectric performance of the composites were investigated by broadband dielectric spectroscopy. The results in comparison with pure PVDF showed that the dielectric constant increased about 2 times (from 10 to 22) and dielectric loss tan δ reduced about 50% (from 0.12 to 0.06) when the loading of modified BT nanofiber was up to 20 v%. In the same loading fraction of BT nanofibers (10 v%), the dielectric loss of fluorosilane modified sample (tan δ = 0.08) was lower than that of unmodified one (tan δ = 0.1). In the range of 20-100 °C, the k showed almost no dependence on the temperature. However, the dielectric loss revealed a trend of decreasing at first and increased later with the increasing of temperature, and reached the lowest value (tanδ = 0.01) at about 60 °C.

  19. Fabrication of Stretchable Nanocomposites with High Energy Density and Low Loss from Cross-Linked PVDF Filled with Poly(dopamine) Encapsulated BaTiO3.

    PubMed

    Xie, Yunchuan; Yu, Yangyang; Feng, Yefeng; Jiang, Wanrong; Zhang, Zhicheng

    2017-01-25

    In this report, a simple solution-cast method was employed to prepare poly(dopamine) (PDA) encapsulated BaTiO3 (BT) nanoparticle (PDA@BT) filled composites using PVDF matrix cross-linked by the free radical initiator. The effects of both the particle encapsulation and matrix cross-linking on the mechanical and dielectric properties of the composites were carefully investigated. The results suggested that the introduction of BT particles improved permittivity of the composites to ∼30 at 100 Hz when particle contents of only 7 wt % were utilized. This was attributed to the enhanced polarization, which was induced by high permittivity ceramic particles. Compared to bare BT, PDA@BT particles could be dispersed more homogeneously in the matrix, and the catechol groups of PDA layer might form chelation with free ions present in the matrix. The latter might depress the ion conduction loss in the composites. Other results revealed that the formation of hydrogen-bonding between the PDA layer and the polymer, especially the chemical cross-linking across the matrix, resulted in increased Young' modulus by ∼25%, improved breakdown strength by ∼40%, and declined conductivity by nearly 1 order of magnitude when compared to BT filled composites. The composite films filled with PDA@BTs indicated greater energy storage capacities by nearly 190% when compared to the pristine matrix. More importantly, the excellent mechanical performance allowed the composite films to adopt uni- or biaxially stretching, a crucial feature required for the realization of high breakdown strength. This work provided a facile strategy for fabrication of flexible and stretchable dielectric composites with depressed dielectric loss and enhanced energy storage capacity at low filler loadings (<10 wt %).

  20. The influence of Mn on the grain-boundary potential barrier characteristics of donor-doped BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Illingsworth, J.; Al-Allak, H. M.; Brinkman, A. W.; Woods, J.

    1990-02-01

    Two compositions of BaTiO3 positive temperature coefficient of resistance ceramics, prepared identically except for the fact that a small addition of Mn (0.04 at. %) was made to one of them, were studied. The samples were sintered simultaneously in air at 1400 °C for 1 h and then annealed at 1200 ° for 5 h, using a muffle furnace. Room-temperature dielectric measurements in the audio- and radio-frequency ranges confirmed that Mn has a negligible effect on the bulk resistance. Arrhenius plots of resistivity vs 1/[Tɛ'm(T)] were found to give straight lines for Tc

  1. The Effects of Gd/Nd Co-Doping on the Microstructure and Dielectric Properties of BaTiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Tang; Bin; Zhang; ShuRen; Zhou; XiaoHua

    2009-11-01

    In order to obtain X7R (-55 to 125 °C, ΔC/C = ±15% or less) ceramics sintered at a middle temperature, the effects of Gd2O3 and Nd2O3 additives on the microstructure and dielectric properties of BaTiO3 (BT)-Nb2O5-ZnO-borosilicate system were investigated. When the amount of Gd2O3 was stable, the dielectric constant at room temperature (ɛ25 °C) monotonously decreased as the Nd2O3 content increased from 0.1 to 0.7 wt %. Minimal influence was observed on the high temperature coefficient of capacitance (TCC125 °C). In contrast, when the Nd2O3 content remained unchanged and Gd2O3 was increased, the dielectric constant ɛ25 °C at room temperature first declined and then increased and the TCC125 °C value decreased. Additionally, the TCC125 °C value of BT ceramics was positively correlated to the micro-stress. For Gd/Nd co-doped ceramics, TCC125 °C value was determined only by the Gd2O3 content. BT ceramics sintered at 1140 °C in air have the following properties: ɛ25 °C> 3000, tan δ≤1.0%, ρ≥1011 Ω·cm and ΔC/C (-55 to +125 °C) ≤ ±7.5%.

  2. Dielectric Properties and Microstructures of Low-Temperature-Sintered BaTiO3-Based Ceramics with CuBi2O4 Sintering Aid

    NASA Astrophysics Data System (ADS)

    Hasegawa, Tomoyuki; Otagiri, Tadashi

    2006-09-01

    The low-temperature sintering of BaTiO3 (BT) ceramics was investigated by conventional ceramics processing using a CuBi2O4 sintering aid, and the dielectric properties and microstructures of the ceramics were examined. BT powders without CuBi2O4 could not be fully densified at sintering temperatures lower than 1300 °C. However, the addition of CuBi2O4 markedly enhanced the sinterbility of BT powders, and the sintering temperature decreased from 1300 to 920 °C. This may be due to the promotion of liquid-phase sintering. 6.0 wt % CuBi2O4-added BT ceramics sintered at 920 °C exhibited a high density of 5.95 g/cm3. Moreover, to obtain dielectric ceramics with a stable temperature coefficient of capacitance, the effects of ZnO addition on the dielectric properties and microstructures of low-temperature-sintered BT ceramics with a CuBi2O4 sintering aid were also studied. It was found that the addition of ZnO was very effective for improving the temperature coefficient of capacitance and reducing the dielectric loss of the low-temperature-sintered specimens. This is attributable to the microstructural change involving the formation of a core-shell structure, as shown by transmission electron microscopy and X-ray energy-dispersive spectrometry (TEM-EDS). Therefore, a high dielectric constant of 1900, a low dielectric loss of 0.6% and a stable temperature coefficient of capacitance (X7R EIA standard of Δ C/C25 {\\degC}=± 15% in the temperature range from -55 to +125 °C) were obtained for 1.0 wt % ZnO-added BT ceramics with 6.0 wt % CuBi2O4 sintered at 930 °C for 2 h.

  3. Effects of X-Ray Irradiation and Barium Deficiency on Grain Boundary States in BaTiO3:Ta Ceramics

    NASA Astrophysics Data System (ADS)

    Uchida, Yoshiharu; Kai, Ayako; Murata, Takuya; Miki, Toshikatsu

    2004-02-01

    The effects of x-irradiation and Ba deficiency in BaTiO3:Ta ceramics were investigated in conjunction with the mechanism of an abrupt increase in electrical resistivity at the Curie temperature Tc, which was called the mode-I positive temperature coefficient of resistivity (PTCR). X-irradiation decreases the resistivity and the potential barrier height at grain boundaries in the rhombohedral and cubic specimens, but increases the ESR intensity of a singlet signal at g=2.005. On the other hand, introducing Ba deficiency increases the room-temperature resistivity ρRT and the magnitude of resistivity jump ρmode-I at Tc, but both ρRT and ρmode-I become to decrease when Ba deficiency exceeds 0.03 at%. In highly Ba-deficient specimens, the singlet ESR signal also decreases with increasing Ba deficiency. For explaining the irradiation effects, we proposed two models. One is the hole-recombination model, in which trapped-electrons at VBa-associated acceptor levels recombine with the holes created by irradiation. The other is the electron-detrapping model for the electrons trapped by acceptor levels. The explanation of the effects of x-irradiation and Ba deficiency was attempted by assuming VBa-associated centers (VBa, VBa-VO, VBa-F and VBa-F+). We conclude that predominant acceptor states at grain boundaries are VBa-VO-type defects. It is considered that the mode-I PTCR originats from critical changes in the density of states (DOS) of VBa-VO and the Fermi energy at tetragonal-to-cubic transition. This type of trap activation may lead to the formation of VBa-F+ and VBa-F from VBa-VO.

  4. Interactions of carbon nanotubes in a nematic liquid crystal. II. Experiment

    NASA Astrophysics Data System (ADS)

    Agha, Hakam; Galerne, Yves

    2016-04-01

    Multiwall carbon nanotube (CNT) colloids with different anchoring conditions are dispersed in pentyl-cyanobiphenyl (5CB), a thermotropic liquid crystal (LC) that exhibits a room-temperature nematic phase. The experiments make use of CNTs treated for strong planar, homeotropic, or Janus anchorings. Observations with a polarizing microscope show that the CNTs placed in a uniform nematic field stabilize parallel or perpendicular to n depending on their anchoring conditions. In the presence of a splay-bend disclination line, they are first attracted toward it and ultimately, they get trapped on it. Their orientation relative to the line is then found to be parallel or perpendicular to it, again depending on the anchoring conditions. When a sufficient number of particles are deposited on a disclination line, they form a micro- or nanonecklace in the shape of a thin thread or of a bottle brush, with the CNTs being oriented parallel or perpendicular to the disclination line according to the anchoring treatment. The system exhibits a rich versatility, even if until now the weak anchorings appear to be difficult to control. In a next step, the necklaces may be glued by means of pyrrole electropolymerization. In this manner, we realize a true materialization of the disclination lines, and we obtain nanowires capable of conducting the electricity in the place of the initial disclinations that just worked as templates. The advantage of the method is that it finally provides nanowires that are automatically connected to predesignated three-dimensional (3D) electrodes. Such a 3D nanowiring could have important applications, as it could allow one to develop electronic circuits in the third dimension. They could thus help with increasing the transistor density per surface unit, although downsizing of integrated circuits will soon be limited to atomic sizes or so. In other words, the predicted limitation to Moore's law could be avoided. For the moment, the nanowires that we obtain

  5. Polycyclopentene-Crystal-Decorated Carbon Nanotubes by Convenient Large-Scale In Situ Polymerization and their Lotus-Leaf-Like Superhydrophobic Films.

    PubMed

    Xu, Lixin; Huang, Lingqi; Ye, Zhibin; Meng, Nan; Shu, Yang; Gu, Zhiyong

    2017-02-01

    In situ Pd-catalyzed cyclopentene polymerization in the presence of multi-walled carbon nanotubes (MWCNTs) is demonstrated to effectively render, on a large scale, polycyclopentene-crystal-decorated MWCNTs. Controlling the catalyst loading and/or time in the polymerization offers a convenient tuning of the polymer content and the morphology of the decorated MWCNTs. Appealingly, films made of the decorated carbon nanotubes through simple vacuum filtration show the characteristic lotus-leaf-like superhydrophobicity with high water contact angle (>150°), low contact angle hysteresis (<10°), and low water adhesion, while being electrically conductive. This is the first demonstration of the direct fabrication of lotus-leaf-like superhydrophobic films with solution-grown polymer-crystal-decorated carbon nanotubes.

  6. Synthesis and characterization of anatase TiO{sub 2} nanotubes with controllable crystal size by a simple MWCNT template method

    SciTech Connect

    Kim, Ju Hyung; Zhang, Xiao Hui; Kim, Jae Deuk; Park, Hoon Mo; Lee, Sang Bok; Yi, Jin Woo; Jung, Seung Il

    2012-12-15

    Highly crystalline phase-pure anatase TiO{sub 2} nanotubes were produced by performing a simple calcinations process in air of the TiO{sub 2} coated MWCNTs composite material prepared by an in situ sol-gel method. A homogeneous thin coating layer of TiO{sub 2} on the surface of MWCNTs is firstly obtained. Calcination in ambient air at appropriate temperatures is performed to transform phase of TiO{sub 2} into anatase and remove MWCNTs simultaneously, resulting in pure anatase TiO{sub 2} nanotubes. Both end tips of the nanotubes are observed to be closed, probably due to covering up MWCNTs with TiO{sub 2} particles. The crystallization of anatase phase was formed upon 350 Degree-Sign C, and MWCNTs are completely oxidized between 500 and 650 Degree-Sign C, leaving anatase TiO{sub 2} nanotubes with an average crystal size increasing from about 8 to 24 nm as the temperature rises. Moreover, the tubular structure was found to collapse after calcinations at 700 Degree-Sign C. - Graphical abstract: TGA analysis and TEM images of the samples after calcinations in air at different temperatures: (a) before calcinations, (b) 350 Degree-Sign C, (c) 500 Degree-Sign C, and (d) 650 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Highly crystalline and stable phase-pure anatase TiO{sub 2} nanotubes were produced by a simply MWCNT template method. Black-Right-Pointing-Pointer A homogeneous thin coating layer of TiO{sub 2} on the surface of MWCNTs could be obtained. Black-Right-Pointing-Pointer Small crystal size of anatase is formed at lower temperatures and higher temperatures cause significant increase of crystal size from 8 to 24 nm. Black-Right-Pointing-Pointer Convex closed tip structure of TiO{sub 2} nanotubes is formed owing to the good coating of TiO{sub 2}.

  7. Double phase conjugation in tungsten bronze crystals.

    PubMed

    Sharp, E J; Clark Iii, W W; Miller, M J; Wood, G L; Monson, B; Salamo, G J; Neurgaonkar, R R

    1990-02-20

    In this paper we report a new method for double phase conjugation particularly suited to the tungsten bronze crystal strontium barium niobate. It has also been observed to produce conjugate waves in BaTiO(3) and BSKNN. This new arrangement is called the bridge conjugator because the two beams enter opposing [100] crystal faces and fan together to form a bridge without reflection off a crystal face. Our measurements indicate that the bridge conjugator is competitive with previously reported double phase conjugate mirrors in reflectivity, response time, ease of alignment, and fidelity.

  8. Microstructure Analysis of Boron Nanotubes

    DTIC Science & Technology

    2012-05-01

    boron nitride nanotube and nanoparticles in thin film boron nitride prepared by CVD method. Electron micrographs show single...walled nanotubes containing these nonoparticles. The electron diffraction pattern confirms this boron nitride has a hexagonal crystal structure. 15... boron nitride thin film CONCLUSIONS The boron evaporated thin film revealed a large number of nanotubes and nanoparticles. These nanotubes are 25

  9. Inducing injection barrier by covalent functionalization of multiwall carbon nanotubes acting as Moiré crystals

    NASA Astrophysics Data System (ADS)

    Bonnet, Roméo; Barraud, Clément; Martin, Pascal; Della Rocca, Maria Luisa; Lafarge, Philippe

    2016-10-01

    Covalent functionalization of multiwall carbon nanotubes is a direct method to suppress the conduction of the outermost shell, subject to interactions with the environment. The rehybridized sp3 external shell of the functionalized multiwall carbon nanotubes becomes naturally a hybrid injection barrier allowing the control of the contact resistances and the study of quantum transport in the more protected inner shells. Charge transport measurements performed on isolated multiwall carbon nanotubes of large diameter show an increase of the contact resistance and stabilization in the MΩ range. Electronic quantum properties of the inner shells are highlighted by the observation of superlattice structures in the conductance, recently attributed to the formation of a one-dimensional Moiré pattern.

  10. Photorefractive beam-steering system that uses energy transfer in a BaTiO3 crystal for a fiber-array interconnect

    NASA Astrophysics Data System (ADS)

    Mathey, P.; Mercier, R.; Pauliat, G.; Roosen, G.; Gravey, Ph.

    1995-12-01

    A beam-control system to write gratings on a holographic plane is studied. The arrangement is designed to interconnect two 1024 monomode fiber arrays. The beam-control system is composed of one incident beam toward 1024 positions, and a collimating system, which adapts the shape of the deflected beam to the holographic plane. The

  11. An evidence of trap activation for positive temperature coefficient of resistivity in BaTiO3 ceramics with substitutional Nb and Mn as impurities

    NASA Astrophysics Data System (ADS)

    Miki, Toshikatsu; Fujimoto, Akira; Jida, Shin'suke

    1998-02-01

    The mechanism of the electrical resistivity increase above the Curie temperature TC [so-called positive temperature coefficient of resistivity (PTCR) effect] in BaTi1-x-yNbxMnyO3 ceramics is studied with the temperature-dependent resistivity and electron paramagnetic resonance (EPR) data and the calculated energy levels of various Mn-associated centers. The activation energy of trapped electrons at grain boundary interface states is deduced from the resistivity data. The deduced value is found to be nearly equal to the activation energy of Mn2+ and/or singlet EPR signals. This indicates that the EPR signals arising at the cubic phase are due to trapped-electron centers at grain boundaries, and that the centers responsible for the EPR signals contribute to the rise of grain boundary barrier above TC. The PTCR mechanism is separately discussed for mode I of abrupt resistivity jump at TC and mode II of moderate resistivity increase at higher temperatures. From the analyses of resistivity and EPR data, we found that mode II PTCR is well explained by the Heywang model, but mode I PTCR is hardly explained only by the effect of spontaneous polarization proposed by Jonker. Defect models of Mn-VO, Mn-VO-Mn, and Mn-O-Nb-VO type are proposed for Mn associated centers and VBa-VO or VO-VTi-VO type for cation-vacancy-associated centers, taking the local electroneutrality requirement for stable defects and the electronic energy change of substitutional Mn by phase transitions into account. Changes of the electronic energy levels of such defects by phase transitions successfully explain not only the PTCR and EPR data but also the degraded PTCR by incomplete or overabundant oxidation. A part of the Mn-VO centers formed at low Mn contents release electrons at the tetragonal phase forming Mn3+-VO with an effective charge of +1 to act as a charge compensator for negatively charged acceptors at the grain boundary, but the Mn-VO centers hardly act as acceptor-type electron-trapping centers at the cubic phase. At high Mn concentrations, the Mn-VO-Mn type di-Mn center acts as an acceptor-type electron-trapping center at both tetragonal and cubic phases. A trap activation occurs in one type of Mn-O-Mn-VO centers at the tetragonal-to-cubic transition. We conclude that the trap activaiton of the Mn interface states by the tetragonal-to-cubic transition significantly contributes to the PTCR effect of BaTiO3 ceramics with a high content of Mn.

  12. Amorphization and Directional Crystallization of Metals Confined in Carbon Nanotubes Investigated by in Situ Transmission Electron Microscopy.

    PubMed

    Tang, Dai-Ming; Ren, Cui-Lan; Lv, Ruitao; Yu, Wan-Jing; Hou, Peng-Xiang; Wang, Ming-Sheng; Wei, Xianlong; Xu, Zhi; Kawamoto, Naoyuki; Bando, Yoshio; Mitome, Masanori; Liu, Chang; Cheng, Hui-Ming; Golberg, Dmitri

    2015-08-12

    The hollow core of a carbon nanotube (CNT) provides a unique opportunity to explore the physics, chemistry, biology, and metallurgy of different materials confined in such nanospace. Here, we investigate the nonequilibrium metallurgical processes taking place inside CNTs by in situ transmission electron microscopy using CNTs as nanoscale resistively heated crucibles having encapsulated metal nanowires/crystals in their channels. Because of nanometer size of the system and intimate contact between the CNTs and confined metals, an efficient heat transfer and high cooling rates (∼10(13) K/s) were achieved as a result of a flash bias pulse followed by system natural quenching, leading to the formation of disordered amorphous-like structures in iron, cobalt, and gold. An intermediate state between crystalline and amorphous phases was discovered, revealing a memory effect of local short-to-medium range order during these phase transitions. Furthermore, subsequent directional crystallization of an amorphous iron nanowire formed by this method was realized under controlled Joule heating. High-density crystalline defects were generated during crystallization due to a confinement effect from the CNT and severe plastic deformation involved.

  13. Fabrication and characterization of novel composite membranes composed of photonic crystals and TiO2 nanotube array films

    NASA Astrophysics Data System (ADS)

    Tang, Junjie; Zhu, Huili; Wang, Aijun; Chen, Sheng-Li; Yuan, Yao

    2016-05-01

    Novel composite membranes composed of photonic crystals (PCs) and TiO2 nanotube array (TNA) films have been fabricated by combining the room temperature floating self-assembly (RTFSA) method, recently developed by our research group, and the liquid-phase deposition technique. By applying this combined procedure, polystyrene (PS) opal PC/TNA and TiO2 inverse opal PC/TNA composite membranes were prepared. Scanning electron microscopy and ultraviolet/visible spectroscopy analyses showed that the membrane samples possessed very high crystalline quality. Notably, the ordered packing of the PS microspheres from the top to the bottom of the opal PC film was not affected by the surface roughness of the porous TNA substrate. This is attributed to the self-assembly mechanism of the colloidal particles, which produces a three-dimensional ordered structure in the RTFSA method. Herein, the crystallization of the colloidal particles occurred at the surface of the colloidal suspension, and the crystal growth proceeded downward from the surface of the suspension to the substrate.

  14. Effects of carbon nanotubes on electro-optical characteristics of liquid crystal cell driven by in-plane field

    NASA Astrophysics Data System (ADS)

    Jeon, Sang Youn; Shin, Seung Hwan; Jeong, Seok Jin; Lee, Seung Hee; Jeong, Seok Ho; Lee, Young Hee; Choi, Hyun Chul; Kim, Kyeong Jin

    2007-03-01

    Homogeneously aligned nematic liquid crystal (LC) cells doped with carbon nanotubes (CNTs) driven by an in-plane field were fabricated and their electro-optic characteristics were investigated. The effective cell retardation values showed no difference between doped and undoped LC cells in the absence of electric field. However, in the presence of electric field, it was smaller in the CNT-doped cell than in the undoped cell, resulting in the decrease of transmittance. Furthermore, the CNT-doped cell exhibited a slight increase in the driving voltage due to the increase of the twist elastic constant (K22) and the decrease in the decay response time due to the decrease in the rotational viscosity (γ) and γ /K22 compared to the undoped cell.

  15. Cholesteric liquid crystal-carbon nanotube composites with photo-settable reversible and memory electro-optic modes.

    PubMed

    Yaroshchuk, Oleg; Tomylko, Sergiy; Gvozdovskyy, Igor; Yamaguchi, Rumiko

    2013-08-01

    The photoresponsive electro-optical composites based on cholesteric liquid crystal (CLC) with optically controlled chirality and a minute amount of carbon nanotubes (CNTs) are studied. In cells with homeotropic anchoring, these composites exhibit a transition from fingerprint texture to homeotropic nematic texture in the course of photoinduced unwinding of the cholesteric helix. Compared with the CLC counterpart, this transition is much delayed, because of the stabilization of cholesteric filamentary domains by CNTs. The CLC-CNT composites demonstrate dual-mode operation with optical switching between reversible and memory mode. It is found that the memory response is associated with the elastic network of filamentary cholesteric domains that stabilizes the planar CLC texture reached in an electric field. In turn, the reversible mode corresponds to the unwound cholesteric state. Potential applications of this effect are discussed.

  16. Electrohydrodynamic Behaviors in the Multiwalled Carbon Nanotubes Doped Optically Compensated Bend Polymer-Dispersed Nematic Liquid Crystal Cell

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Ning; Wu, Jin-Jei; Ke, Hung-Lin

    2008-11-01

    We fabricated three optically compensated bend (OCB) polymer-dispersed nematic liquid crystal (PDLC) cells doped with a minute amount of multiwalled carbon nanotubes (MWCNTs) and observed the eletrohydrodynamic (EHD) behaviors of LCs in these three MWCNT-doped OCB PDLC cells at 5 or 12 V AC voltage with a frequency of 1 kHz or 60 Hz, respectively. Using the polarizing microscope, we discovered many kinds of domain patterns, including the fingerprint-like domain pattern, the uniform domain pattern, the bean-like domain pattern, the irregular big spot domain pattern, the hexagonal short period lattice domain pattern, and the rectangular period lattice domain pattern. This suggests that some domain patterns differ from the Kapustin-William's domain pattern while others were somewhat similar to the Kapustin-William's domain pattern.

  17. Copper oxide decorated multi-walled carbon nanotubes/ferroelectric liquid crystal composites for faster display devices

    NASA Astrophysics Data System (ADS)

    Malik, Anu; Prakash, Jai; Kumar, Anil; Dhar, Ajay; Biradar, Ashok M.

    2012-09-01

    We present faster display devices based on copper oxide decorated multi-walled carbon nanotubes (MWCNTs) doped ferroelectric liquid crystal (FLC) material. The fastening of the response has been attributed to decrease in rotational viscosity of the FLC material. The ionic impurities were also reduced by doping copper oxide decorated MWCNTs into the FLC material, and the reduction has been attributed to trapping of ions by the guest copper oxide decorated MWCNTs. The observations of fastening the response and reduction of ionic impurities have been verified by experimental data using dielectric and electro-optical studies. The underlying mechanism would certainly help to understand the basic mechanism of interaction of CNTs with FLC molecules and could be applied to fabricate ionic defects free faster display devices.

  18. Mechanism for Solid State Crystal Conversion

    DTIC Science & Technology

    2000-12-30

    about a factor of 10 greater than those observed in Mn-Zn ferrite , YIG and BaTiO 3. It would be very useful to understand the practical and theoretical...Introduction and Background The unique properties of many single crystals provide great benefits in a wide range of magnetic , structural, optical and other...materials. In 1985 Tanji et al.2 reported a solid-solid process for producing Mn-Zn ferrite single crystals. The ferrite method required bringing a polished

  19. Structural and dielectric properties of BaTiO3-Bi(Mg1/2Ti1/2)O3 thin films fabricated by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Moki, Shota; Kimura, Junichi; Kaneko, Noriyuki; Funakubo, Hiroshi; Uchida, Hiroshi

    2014-09-01

    Thin films of the BaTiO3-Bi(Mg1/2Ti1/2)O3 (BT-BMT) solid-solution system were fabricated with the aim of achieving a stable temperature coefficient of capacitance (TCC) favorable for high-temperature electronics. A single perovskite phase with pseudocubic symmetry was obtained for the films fabricated by chemical solution deposition on (111)Pt/TiO2/(100)Si substrates in the composition range of x = 0-0.80 for (1 - x)BT-xBMT. BMT added to the BaTiO3-based films enhanced the crystallinity of the perovskite phase and resulted in saturated P-E hysteresis behavior with remanent polarization of up to 13 µC/cm2. BMT addition led to gradual dielectric relaxation, which also resulted in stable TCC behavior with a relative dielectric constant of approximately 400 in the temperature range of RT - 400 °C, especially for the BT-BMT films with x = 0.20-0.40.

  20. Structural, dielectric and ferroelectric studies of (x) Mg0.25Cu0.25Zn0.5Fe2O4 + (1-x) BaTiO3 magnetoelectric nano-composites

    NASA Astrophysics Data System (ADS)

    Khader, S. Abdul; Muneeswaran, M.; Giridharan, N. V.; Sankarappa, T.

    2016-05-01

    The Particulate nano-composites of ferrite and ferroelectric phases having the general formula (x) Mg0.25Cu0.25Zn0.5Fe2O4 + (1-x) BaTiO3 (x=15%, 30% and 45%) were synthesized by sintering mixtures of highly ferroelectric BaTiO3 (BT) and highly magneto-strictive magnetic component Mg0.25Cu0.25Zn0.5Fe2O4(MCZF). The presence of constituent phases of ferrite, ferroelectric and their composites were probed and confirmed by X-ray diffraction (XRD) studies. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The variation of dielectric constant and dissipation factor as a function of frequency from 100 Hz to 1 MHz at room temperature were carried out using a Hioki LCR Hi-Tester. The dielectric constant and dielectric loss were found to decrease rapidly in the low frequency region and became almost constant in the high frequency region. The electrical conductivity deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in these composites is in conformity with small polaron hopping model. The ferroelectric properties of synthesized magneto-electric nano-composites were measured using P-E loop tracer.

  1. Étude théorique de la photoconductivité et de l'absorption photoinduite de BaTiO{3} et de KNbO{3} dopés au fer

    NASA Astrophysics Data System (ADS)

    Khatib, D.; Radoua, A.; Krätzig, E.

    1998-11-01

    Calculation of conductivity, and study of photoconductivity and light induced absorption in a iron doped BaTiO3 and KNbO3 are performed at many light intensities. The results are interpreted with the help of two impurity levels bands model. This model allows as to calculate a dark conductivity, to explain behaviour of the photoconductivity with a regard to the light intensities, and to study the light induced absorption coefficient by using impurities concentrations. Le calcul de la conductivité et l'étude de la photoconductivité et de l'absorption photoinduite dans BaTiO3 et KNbO3 dopés au fer sont effectués pour différentes intensités d'éclairement. Les résultats sont interprétés à l'aide d'un modèle de bandes à deux niveaux d'impuretés. Il permet de calculer la conductivité, d'expliquer le comportement de la photoconductivité vis a vis de l'intensité de l'éclairement, et d'étudier le coefficient d'absorption photoinduite, en utilisant les concentrations des impuretés.

  2. Octonary resistance states in La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic tunnel junctions

    DOE PAGES

    Yue -Wei Yin; Tao, Jing; Huang, Wei -Chuan; ...

    2015-10-06

    General drawbacks of current electronic/spintronic devices are high power consumption and low density storage. A multiferroic tunnel junction (MFTJ), employing a ferroelectric barrier layer sandwiched between two ferromagnetic layers, presents four resistance states in a single device and therefore provides an alternative way to achieve high density memories. Here, an MFTJ device with eight nonvolatile resistance states by further integrating the design of noncollinear magnetization alignments between the ferromagnetic layers is demonstrated. Through the angle-resolved tunneling magnetoresistance investigations on La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 junctions, it is found that, besides collinear parallel/antiparallel magnetic configurations, the MFTJ shows at least two other stable noncollinear (45°more » and 90°) magnetic configurations. As a result, combining the tunneling electroresistance effect caused by the ferroelectricity reversal of the BaTiO3 barrier, an octonary memory device is obtained, representing potential applications in high density nonvolatile storage in the future.« less

  3. Aperiodic TiO2 Nanotube Photonic Crystal: Full-Visible-Spectrum Solar Light Harvesting in Photovoltaic Devices

    PubMed Central

    Guo, Min; Xie, Keyu; Wang, Yu; Zhou, Limin; Huang, Haitao

    2014-01-01

    Bandgap engineering of a photonic crystal is highly desirable for photon management in photonic sensors and devices. Aperiodic photonic crystals (APCs) can provide unprecedented opportunities for much more versatile photon management, due to increased degrees of freedom in the design and the unique properties brought about by the aperiodic structures as compared to their periodic counterparts. However, many efforts still remain on conceptual approaches, practical achievements in APCs are rarely reported due to the difficulties in fabrication. Here, we report a simple but highly controllable current-pulse anodization process to design and fabricate TiO2 nanotube APCs. By coupling an APC into the photoanode of a dye-sensitized solar cell, we demonstrate the concept of using APC to achieve nearly full-visible-spectrum light harvesting, as evidenced by both experimental and simulated results. It is anticipated that this work will lead to more fruitful practical applications of APCs in high-efficiency photovoltaics, sensors and optoelectronic devices. PMID:25245854

  4. Dynamic crystallization kinetics and nucleation parameters of a new generation of nanocomposites based on isotactic polypropylene and MoS2 inorganic nanotubes.

    PubMed

    Naffakh, Mohammed; Remskar, Maja; Marco, Carlos; Gómez-Fatou, Marián A

    2011-03-31

    Differential scanning calorimetry (DSC) and time-resolved synchrotron X-ray diffraction have been used to investigate the dynamic crystallization behavior and crystalline structure of novel nanocomposites based on isotactic polypropylene (iPP) and molybdenum disulfide inorganic nanotubes (INT-MoS(2)). The influence of the INT-MoS(2) content and different cooling rates on the crystallization behavior has been studied. The crystallization exothermic peak shifted to higher temperature, and the overall crystallization time was reduced by increasing the INT-MoS(2). The dynamic crystallization kinetics was analyzed using the Ozawa-Avrami method, which was successful in describing the dynamic crystallization behavior of these new nanocomposites. On the other hand, study of the nucleation activity using the Dobreva method revealed that the INT-MoS(2) had an efficient nucleation effect on the monoclinic crystal form of iPP. Moreover, this effect was corroborated by the results of the crystallization activation energy, calculated using Kissinger and Takhor methods, which also confirmed the fact that the addition of INT-MoS(2) made the molecular chains easier to crystallize and increased the crystallization rate of iPP.

  5. Applications in crystal engineering: The designed topochemical polymerization of 1,3-butadienes and the construction of organic nanotubes

    NASA Astrophysics Data System (ADS)

    Dinkelmeyer, Brian Douglas

    1999-10-01

    The macroscopic properties of all materials are determined by the molecules from which it is composed and also by the relative orientation of these molecular constituents relative to one another. To rationally design materials with specific properties it is essential that the relative orientation of molecules in the solid be controlled. This is generally not possible at the current state of technology. How a molecule's structure effects and controls its packing in the solid state structure is poorly understood. The crystal structures of even the simplest organic molecules cannot be reliably predicted at the current level of technology. The use of strong directional interactions such as hydrogen bonding interactions however, has been successfully used as a strategy in constructing low dimensional solids. The true test of these designs is in their application in constructing materials with specific properties. Two goals of this group are the design of new topochemical polymerizations and the construction of porous solids. Previous research performed in this group has demonstrated that ureylene and oxalamide functionality predictable and persistently form one-dimensional hydrogen bonded alpha-networks. These functionality have been used previously by this group in constructing layered solids, organizing transition metals and in organizing diacetylenes for topochemical polymerizations. The current work is concerned with using urylene and oxalamide functionality to organize molecules in the solid state for topochemical polymerizations and to construct organic nanotubes. The topochemical reaction of interest is that of 1,3-butadienes. When 1,3-butadienes are irradiated in the solid state they may undergo [2+2] cycloadditions or 1,4-addition polymerization with neighboring molecules. In order to control the reaction it is essential to bring desired reactive centers into close contact while isolating reactive centers that would lead to unwanted products. A general strategy

  6. Crystallization behavior of a barium titanate tellurite glass doped with Eu3+ and Er3+

    NASA Astrophysics Data System (ADS)

    Ferreira, Elivelton Alves; Cassanjes, Fábia Castro; Poirier, Gael

    2013-04-01

    The main objective of this work has been to investigate the crystallization behavior of the glass composition 70TeO2-15BaO-15TiO2 doped with Eu3+ and Er3+ in order to check the possibility of obtaining transparent glass-ceramics containing rare earth-doped BaTiO3 nanocrystals. Glass samples with the ternary composition 70TeO2-15BaO-15TiO2 were synthesized by the melt-quenching method and doped with 0.1% of Eu3+ and Er3+. Thermal properties were investigated by DTA and heat-treatments were applied between Tg and Tx to induce the controlled crystallization of these glasses. One-step and two-step heat treatments were tested and the final glass-ceramics characterized by X-ray diffraction and UV-Vis absorption. It has been shown that transparent glass-ceramics can be obtained after heat-treatment but barium titanate BaTiO3 is hardly precipitated without coprecipitation of another crystalline phase identified as an isostructure of lanthanum tellurate. In addition, the crystalline volume fraction is relatively small in these transparent samples. Finally, Gold doping has been shown to be very effective to promote a volume nucleation and preferential crystallization of BaTiO3 over the other crystalline phases.

  7. Hybrid nanoparticle architecture for cellular uptake and bioimaging: direct crystallization of a polymer immobilized with magnetic nanoparticles on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Depan, D.; Misra, R. D. K.

    2012-09-01

    We describe here the success of an innovative approach of direct immobilization of magnetic nanoparticles (MNPs) onto carbon nanotubes (CNTs). The approach involved functionalization of magnetic nanoparticles and consequent covalent linkage to a copolymer (PE-b-PEG). Next, the immobilized magnetic nanoparticles on the copolymer were directly crystallized on the long axis of CNTs, where the interfacial adhesion comes from electrostatic and van der Waals interaction. The intracellular trafficking of a hybrid nanoparticle system [(PE-b-PEG)-MNP-CNT-FITC] in HeLa cells was monitored using a fluorescent marker, FITC, conjugated to the nanoparticle system. The distribution of the nanoparticle system inside cells was studied by fluorescence microscopy in a time and dose dependent manner, and it was observed that the nanoparticles are located in the cytoplasm and no apparent cell death was observed at the concentration studied. Also, the effect of an externally applied magnetic field on actin cytoskeleton, cell morphology and intracellular uptake of iron was studied. The approach described here is promising for simultaneous imaging and monitoring intracellular uptake.

  8. Ultrasensitive Detection of Cymbidium Mosaic Potexvirus Using a Single-Wall Carbon Nanotube-Functionalized Quartz Crystal Microbalance

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Shiun; Hung, Yao-Ching; Chiou, Jin-Chern; Wang, Hui-Liang; Huang, Hung-Shu; Huang, Li-Chia; Huang, Guewha Steven

    2010-10-01

    We have developed an ultrasensitive, convenient, real-time platform for detecting Cymbidium mosaic potexvirus (CymMV) based on single-wall carbon nanotube (SWNT)-functionalized quartz crystal microbalance (QCM) sensors. Functionalization was achieved by coating the QCM electrode with SWNTs, followed by 1,1'-carbonyldiimidazole-activated Tween 20 (CDI-Tween 20) modification and conjugation of antibodies. Sensitivity was enhanced from 2.18 to 11.5 Hz ng-1 when 0.1 µg mL-1 CymMV was applied. The low limit of detection of SWNT-functionalized QCM sensors was improved from 2.08 to 0.502 ng. The SWNT-functionalized QCM sensor was successfully used to quantify the amount of CymMV contained in infected orchid leaves. Compared to enzyme-linked immunosorbent assay (ELISA), SWNT-functionalized QCM sensors are fast, economical, and ultra-sensitive, with comparable sensitivities. The current study demonstrates the application of QCM sensors as a convenient platform to detect and quantify CymMV.

  9. Broadband and omnidirectional light harvesting enhancement in photovoltaic devices with aperiodic TiO2 nanotube photonic crystal

    NASA Astrophysics Data System (ADS)

    Guo, Min; Su, Haijun; Zhang, Jun; Liu, Lin; Fu, Nianqing; Yong, Zehui; Huang, Haitao; Xie, Keyu

    2017-03-01

    Design of more effective broadband light-trapping elements to improve the light harvesting efficiency under both normal and tilted light for solar cells and other photonic devices is highly desirable. Herein we present a theoretical analysis on the optical properties of a novel TiO2 nanotube aperiodic photonic crystal (NT APC) following an aperiodic sequences and its photocurrent enhancement effect for dye-sensitized solar cells (DSSCs) under various incidence angles. It is found that, compared to regular PC, the designed TiO2 NT APC owns broader reflection region and a desired omnidirectional reflection (ODR) bandgaps, leading to considerable and stable photocurrent enhancement under both normal and oblique light. The effects of the structural parameters of the TiO2 NT APC, including the average lattice constant and the common sequence difference, on the optical properties, ODR bandgaps and absorption magnification of the integrated DSSCs are investigated in detail. Moreover, the angular dependence of photocurrent enhancement and angular compensation effect of such TiO2 NT APCs are also provided to offer a guidance on the optimum structural parameters design under different engineering application conditions.

  10. Hybrid nanoparticle architecture for cellular uptake and bioimaging: direct crystallization of a polymer immobilized with magnetic nanoparticles on carbon nanotubes.

    PubMed

    Depan, D; Misra, R D K

    2012-10-21

    We describe here the success of an innovative approach of direct immobilization of magnetic nanoparticles (MNPs) onto carbon nanotubes (CNTs). The approach involved functionalization of magnetic nanoparticles and consequent covalent linkage to a copolymer (PE-b-PEG). Next, the immobilized magnetic nanoparticles on the copolymer were directly crystallized on the long axis of CNTs, where the interfacial adhesion comes from electrostatic and van der Waals interaction. The intracellular trafficking of a hybrid nanoparticle system [(PE-b-PEG)-MNP-CNT-FITC] in HeLa cells was monitored using a fluorescent marker, FITC, conjugated to the nanoparticle system. The distribution of the nanoparticle system inside cells was studied by fluorescence microscopy in a time and dose dependent manner, and it was observed that the nanoparticles are located in the cytoplasm and no apparent cell death was observed at the concentration studied. Also, the effect of an externally applied magnetic field on actin cytoskeleton, cell morphology and intracellular uptake of iron was studied. The approach described here is promising for simultaneous imaging and monitoring intracellular uptake.

  11. The electrocaloric effect and thermal stability of 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 modified by WO3

    NASA Astrophysics Data System (ADS)

    Wang, Ju; Li, Qiang; Ma, Yuan; Liu, Guocai; Zhao, Yuwei; Fan, Huiqing

    2016-05-01

    The solid-state reaction method is used to prepare the 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 modified by WO3 lead-free ceramic. The unpoled (Bi0.5Na0.5)0.94Ba0.06Ti1-(3/2) x W x O3 with pseudo-cubic structure undergoes transition from ferroelectric to relaxor ferroelectric that happens in the T d. The maximum reversible temperature change |Δ T| = 0.8 K occurs at the room temperature due to the decline of temperature. In addition, |Δ T| = 0.15 K at the (Bi0.5Na0.5)0.94Ba0.06Ti1-(3/2) x W x O3 with x = 0.75 mol% exhibits good thermal stability at the temperature range of 303-413 K.

  12. Giant strain in lead-free piezoceramics Bi0.5Na0.5TiO3-BaTiO3-K0.5Na0.5NbO3 system

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Tao; Kounga, Alain Brice; Aulbach, Emil; Ehrenberg, Helmut; Rödel, Jürgen

    2007-09-01

    Piezoelectric actuators convert electrical into mechanical energy and are implemented for many large-scale applications such as piezoinjectors and ink jet printers. The performance of these devices is governed by the electric-field-induced strain. Here, the authors describe the development of a class of lead-free (0.94-x)Bi0.5Na0.5TiO3-0.06BaTiO3-xK0.5Na0.5NbO3 ceramics. These can deliver a giant strain (0.45%) under both unipolar and bipolar field loadings, which is even higher than the strain obtained with established ferroelectric Pb(Zr ,Ti)O3 ceramics and is comparable to strains obtained in Pb-based antiferroelectrics.

  13. Ceramic synthesis of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 under high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Hui, Jin; Yong, Li; Mou-Sheng, Song; Lin, Chen; Xiao-Peng, Jia; Hong-An, Ma

    2016-07-01

    In this paper, the preparation of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 is investigated at pressure 3.8 GPa and temperature 1100-1200 °C. Experimental results indicate that not only is the sintered rate more effective, but also the sintered temperature is lower under high pressure and high temperature than those of under normal pressure. It is thought that the adscititious pressure plays the key role in this process, which is discussed in detail. The composition and the structure of the as-prepared samples are recorded by XRD patterns. The result shows that the phases of BaTiO3, BaBiO2.77, and Ba2Bi4Ti5O18 with piezoelectric ceramic performance generate in the sintered samples. Furthermore, the surface morphology characteristics of the typical samples are also investigated using a scanning electron microscope. It indicates that the grain size and surface structure of the samples are closely related to the sintering temperature and sintering time. It is hoped that this study can provide a new train of thought for the preparation of lead-free piezoelectric ceramics with excellent performance. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Natural Science Foundation of Education Department of Guizhou Province, China (Grant Nos. KY [2013]183 and LH [2015]7232), and the Research Fund for the Doctoral Program of Tongren University, China (Grant No. DS1302).

  14. In situ and fast detection of single-walled carbon nanotubes by using DNA mediated aggregation method and quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Jang, Kuewhan; Park, Jinsung; Lee, Sangmyung; You, Juneseok; Park, Chanho; Lee, Jaeryung; Park, Woonghwi; Yun, Jinsu; Ahn, Sanghyun; Na, Sungsoo

    2015-07-01

    Carbon nanotubes (CNTs) have attracted great interest from scientific interest to industrial areas. Due to the toxicity effect of CNTs, assessment methods for CNTs are one of the noticeable issues. In this work, we report the in situ and fast detection of single-walled carbon nanotubes (SWCNTs) by using a quartz crystal microbalance. The detection is based on DNA hybridization between the DNA on a quartz electrode and the DNA of aggregated SWCNTs. It is shown that our detection tool is capable of the in situ and fast detection of 5 min with the limit of detection (LOD) of 10 ng ml-1 in distilled water. Furthermore, our detection tool is able to detect SWCNTs in a real practical sample of tap water with the LOD of 100 ng ml-1. Our work sheds light on a direct monitoring tool that could detect and assess the toxicity of SWCNTs in a real environment.

  15. The effect of crystal structure of TiO2 nanotubes on the formation of calcium phosphate coatings during biomimetic deposition

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Kim, Sun; McLeod, John A.; Li, Jun; Guo, Xiaoxuan; Sham, Tsun-Kong; Liu, Lijia

    2017-02-01

    The crystallization process of bioactive calcium phosphate (CaP) species via biomimetic deposition onto anodic TiO2 nanotubes is investigated. The porous surface of nanostructured TiO2 provides an ideal substrate for CaP crystallization. The compositions of CaP coatings are studied using X-ray absorption near-edge structures (XANES) at the Ca K-edge. Using detection modes with different probing depths, both the surface of the CaP coating and the CaP-TiO2 interface are simultaneously analyzed. Calcium phosphate (CaP) species, such as hydroxyapatite (HAp), octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O, OCP), brushite (CaHPO4·2H2O, DCPD), and amorphous calcium phosphate (ACP), are found in the CaP coatings. TiO2 nanotubes of amorphous and anatase phases are comparatively studied to determine their effect on the efficiency of CaP formation and the phase transformation among CaP species in prolonged deposition time. It is found the composition of CaP coating has a strong dependency on the crystal structure of TiO2 substrate and the kinetics (deposition time).

  16. Effect of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes on electro-optical and dielectric properties of a ferroelectric liquid crystal.

    PubMed

    Ghosh, S; Nayek, P; Roy, S K; Gangopadhyay, R; Rahaman Molla, M; Majumder, T P

    2011-04-01

    A detailed comparative study of the dielectric and electro-optical properties of a ferroelectric liquid crystal (FLC) and FLC after having doped with conducting polymer Poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes is done. The electro-optic study reveals a lower electrical response time, rotational viscosity and spontaneous polarization in the FLC/PEDOT nanocomposite system. By fitting the capacitance with voltage in a Preisach model, four dipolar species in both FLC and composites system have been obtained. The orientation of the four dipolar species in the composites system is such that the effective dipole moment in the transverse direction of the FLC molecule is less than that in FLC compound.

  17. Local structural origins of the distinct electronic properties of Nb-substituted SrTiO3 and BaTiO3

    SciTech Connect

    Proffen, Thomas E; Page, Katharine L; Kolodiazhnyi, Taras; Cheetham, Anthony K; Seshadri, R

    2008-01-01

    Relating the minute details of crystal and defect structures to the properties of transition metal oxides is a central preoccupation in condensed matter science. Aiding in these efforts have been the many significant advances in high resolution and high momentum transfer neutron diffraction, which today provide unprecedented precision in describing the location of atoms in functional materials.

  18. Plasmonic gold nanocrystals coupled with photonic crystal seamlessly on TiO2 nanotube photoelectrodes for efficient visible light photoelectrochemical water splitting.

    PubMed

    Zhang, Zhonghai; Zhang, Lianbin; Hedhili, Mohamed Nejib; Zhang, Hongnan; Wang, Peng

    2013-01-09

    A visible light responsive plasmonic photocatalytic composite material is designed by rationally selecting Au nanocrystals and assembling them with the TiO(2)-based photonic crystal substrate. The selection of the Au nanocrystals is so that their surface plasmonic resonance (SPR) wavelength matches the photonic band gap of the photonic crystal and thus that the SPR of the Au receives remarkable assistance from the photonic crystal substrate. The design of the composite material is expected to significantly increase the Au SPR intensity and consequently boost the hot electron injection from the Au nanocrystals into the conduction band of TiO(2), leading to a considerably enhanced water splitting performance of the material under visible light. A proof-of-concept example is provided by assembling 20 nm Au nanocrystals, with a SPR peak at 556 nm, onto the photonic crystal which is seamlessly connected on TiO(2) nanotube array. Under visible light illumination (>420 nm), the designed material produced a photocurrent density of ~150 μA cm(-2), which is the highest value ever reported in any plasmonic Au/TiO(2) system under visible light irradiation due to the photonic crystal-assisted SPR. This work contributes to the rational design of the visible light responsive plasmonic photocatalytic composite material based on wide band gap metal oxides for photoelectrochemical applications.

  19. Self-formation of highly aligned metallic, semiconducting and single chiral single-walled carbon nanotubes assemblies via a crystal template method

    SciTech Connect

    Kawai, Hideki; Hasegawa, Kai; Yanagi, Kazuhiro; Oyane, Ayako; Naitoh, Yasuhisa

    2014-09-01

    The fabrication of an aligned array of single-walled carbon nanotubes (SWCNTs) with a single chiral state has been a significant challenge for SWCNT applications as well as for basic science research. Here, we developed a simple, unique technique to produce assemblies in which metallic, semiconducting, and single chiral state SWCNTs were densely and highly aligned. We utilized a crystal of surfactant as a template on which mono-dispersed SWCNTs in solution self-assembled. Micro-Raman measurements and scanning electron microscopy measurements clearly showed that the SWCNTs were highly and densely aligned parallel to the crystal axis, indicating that approximately 70% of the SWCNTs were within 7° of being parallel. Moreover, the assemblies exhibited good field effect transistor characteristics with an on/off ratio of 1.3 × 10{sup 5}.

  20. Oxygen diffusion in single crystal barium titanate.

    PubMed

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

    2015-05-21

    Oxygen diffusion in cubic, nominally undoped, (100) oriented BaTiO3 single crystals has been studied by means of (18)O2/(16)O2 isotope exchange annealing and subsequent determination of the isotope profiles in the solid by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Experiments were carried out as a function of temperature 973 < T/K < 1173, at an oxygen activity of aO2 = 0.200, and as a function of oxygen activity 0.009 < aO2 < 0.900 at T = 1073 K. The oxygen isotope profiles comprise two parts: slow diffusion through a space-charge zone at the surface depleted of oxygen vacancies followed by faster diffusion in a homogeneous bulk phase. The entire isotope profile can be described by a single solution to the diffusion equation involving only three fitting parameters: the surface exchange coefficient ks*, the space-charge potential Φ0 and the bulk diffusion coefficient D*(∞). Analysis of the temperature and oxygen activity dependencies of D*(∞) and Φ0 yields a consistent picture of both the bulk and the interfacial defect chemistry of BaTiO3. Values of the oxygen vacancy diffusion coefficient DV extracted from measured D*(∞) data are compared with literature data; consequently a global expression for the vacancy diffusivity in BaTiO3 for the temperature range 466 < T/K < 1273 is obtained, with an activation enthalpy of vacancy migration, ΔHmig,V = (0.70 ± 0.04) eV.

  1. Effect of Cooling Rate on the Microstructure and Mechanical Properties of Sn-1.0Ag-0.5Cu-0.2BaTiO3 Composite Solder

    NASA Astrophysics Data System (ADS)

    Yang, Li; Ge, Jinguo; Liu, Haixiang; Xu, Liufeng; Bo, Anbing

    2015-11-01

    The microstructure, interfacial intermetallic compound (IMC) layer, microhardness, tensile properties, and fracture surfaces of Sn-1.0Ag-0.5Cu-0.2BaTiO3 composite solder were explored under three different cooling conditions (water-, air-, and furnace-cooled) during solidification. The average grain size was refined and the volume fraction of primary β-Sn dendrites increased with increasing cooling rate. The thickness of the IMC layer increased as the cooling rate was decreased, and the morphology also transformed from scallop shaped, for a rapid cooling rate, to irregular shaped for slower cooling; a Cu3Sn IMC layer was detected between the Cu6Sn5 IMC and copper substrate under the furnace-cooled condition, but not in water- or air-cooled specimens. The mechanical properties, including the microhardness and tensile properties, improved with rapid solidification due to the combined effects of grain refinement and a secondary strengthening mechanism. Fracture surfaces after tensile tests showed that the amount of dimples decreased and a cleavage-like pattern increased as the cooling rate was decreased from the water-cooled to furnace-cooled condition, so the fracture process transformed from ductile to mixed-mode fracture. A refined microstructure and excellent mechanical properties were obtained for the rapidly cooled sample.

  2. Enhanced electrostricitive properties and thermal endurance of textured (Bi0.5Na0.5)TiO3-BaTiO3-(K0.5Na0.5)NbO3 ceramics

    NASA Astrophysics Data System (ADS)

    Hao, Jigong; Ye, Chenggen; Shen, Bo; Zhai, Jiwei

    2013-08-01

    Textured 0.92(Bi0.5Na0.5)TiO3-0.06BaTiO3-0.02(K0.5Na0.5)NbO3 (BNT-BT-KNN) ceramics have been produced by tape casting with pure-phase (Bi0.5Na0.5)TiO3 templates. Through the approach of texture construction, enhanced electrostrictive response was obtained with an electrostrictive coefficient Q33 (˜0.024 m4/C2 at 60 kV/cm) and good thermostability comparable with that of traditional Pb-based electrostrictors. Even at an electric-field as low as 35 kV/cm or at a temperature as high as 180 °C, samples still possess a large electrostrictive response with Q33 > 0.022 m4/C2, suggesting it is very promising for practical applications as a lead-free electrostrictive material owning to its wide usage range. Moreover, reducing the applied electric-filed or increasing temperature can both induce the predominant to pure electrostriction transition due to the little contributions of electrostriction strain from ferroelectric domain switching. Our work may provide a new recipe for designing high-performance BNT-based lead-free electrostrictive materials by means of texture construction.

  3. Influence of the concentration in Fe-doped BaTiO 3 on magnetoelectric couping of layered composites BaTi 1-xFe xO 3-Tb 1-yDy yFe 2-z

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Wei, Jianjin

    Perovskites BaTi 1-xFe xO 3 has been synthesized with the concentration x ranging from 0.01 to 0.02. Their transformation point of ferroelectric to paraelectric and the corresponding latent heat of the phase transformation were observed to decrease with increasing the doping level of Fe 3+. Bonded layered composites BaTi 1-xFe xO 3-Tb 1-yDy yFe 2-z have been fabricated and their magnetoelectric effect has been investigated. The sample containing a layer of perovskite BaTi 0.985Fe 0.015O 3 was found to show the maximum transverse ME voltage coefficient, which is about 1422 mV Oe -1 cm -1 under a magnetic field of 1580 Oe, in these bilayers. Analysis shows that the Fe-doped BaTiO 3 with doping level at about 1.5% should have largest piezoelectric coefficient in these ceramics BaTi 1-xFe xO 3.

  4. Thermal, dielectric and ferroelectric properties of 0.925BaTiO3-0.075Pb(Zn1/3Nb2/3)O3 ceramic

    NASA Astrophysics Data System (ADS)

    Suchanicz, J.; Nogas-Ćwikiel, E.; Sitko, D.; Handke, B.; Jelen, P.; Klimczyk, P.

    2015-08-01

    New low-lead content 0.925BaTiO3-0.075PbZn1/3Nb2/3O3 (0.925BT-0.075PZN) ceramic was fabricated by the spark-plasma-sintering method. X-ray diffraction measurements showed that the obtained specimen possesses a pure perovskite structure. The microstructure investigation indicated a dense ceramic structure with 95% relative density determined by the Archimedes method. Composition undergoes a sequence of phase transitions as pure barium titanate (BT). Dielectric study revealed that the electric permittivity decreases at its maximum and the phase transition shifts to a higher temperature after lead zinc niobate doping of BT. Besides, the dielectric dispersion and polarization increases and decreases, respectively. Obtained results were discussed in term of the difference between ionic size and its mass and local elastic and electric fields. The results show that investigated ceramic is one of the promising low-lead materials for electronic applications.

  5. Visible Light-Induced Photocatalytic and Antibacterial Activity of Li-Doped Bi0.5Na0.45K0.5TiO3-BaTiO3 Ferroelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Kushwaha, H. S.; Halder, Aditi; Jain, D.; Vaish, Rahul

    2015-11-01

    The visible light-active ferroelectric photocatalyst Bi0.5Na0.45Li0.05K0.5TiO3-BaTiO3 (BNKLBT) was synthesized by a solid-state method and its photocatalytic, photoelectrochemical, and antibacterial properties were investigated. In a chronoamperometric study the current density under visible light was 30 μA/cm2, which is three times more than that observed under dark conditions. The compound's visible light photocatalytic activity was investigated for degradation of an organic dye (methyl orange) and an estrogenic pollutant (estriol).The kinetic rate constants calculated for photocatalytic degradation of methyl orange and estriol were 0.007 and 0.056 min-1, respectively. High photocatalytic and photoelectrochemical activity was a result of effective separation of photo-generated charge carriers, because of the ferroelectric nature of the catalyst. The effect of different charge-trapping agents on photocatalytic degradation was studied to investigate the effect of active species and the degradation pathway. Antimicrobial activity was investigated for Escherichia coli and Aspergillus flavus. The anti-bacterial action of BNKLBT was compared with that of the commercial antibiotic kanamycin (k30).

  6. Enhanced torsional actuation and stress coupling in Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 lead-free piezoceramic system

    PubMed Central

    Berik, Pelin; Maurya, Deepam; Kumar, Prashant; Kang, Min Gyu; Priya, Shashank

    2017-01-01

    Abstract This paper is concerned with the development of a piezoelectric d 15 shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e 15) and piezoelectric transverse shear actuation force comparable to that of lead-based shear-mode piezoceramics. The Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 (NBT-BT-Mn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m–2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d 15 mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m–1 V–1 under quasi-static 150 V drive. The high value of piezoelectric shear d 15 coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. These results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts. PMID:28179958

  7. Study of dielectric behavior of ternary mixtures of epoxy/titanates (MgTiO3, CaTiO3, SrTio3 and BaTiO3) with carbon black

    NASA Astrophysics Data System (ADS)

    Khouni, Habib; Bouzit, Nacerdine; Jiménez, Juan Pablo Martinez; Bouamar, Mohamed

    2016-12-01

    The aim of this paper is to study and to model the dielectric behavior of various ternary composites prepared with epoxy resin (RE), one type of titanates (magnesium titanate MgTiO3, calcium titanate CaTiO3, strontium titanate SrTiO3, and barium titanate BaTiO3) with carbon black (CB). The study has therefore been focused on the effect of adding carbon black to titanate included in an epoxy matrix. The effects have been quantified according to the volume fraction of carbon black. In this work, we present a method based on nonlinear optimization for determining the permittivity of the every constituent, in order to minimize systematic errors and mount the effect of carbon black. The time domain reflectometry (TDR) approach is used to characterize the samples under test in the range from DC to 10 GHz. The conductivity behavior study is performed at a low frequency of 400 MHz, throughout this work. We explain the carbon black effect on the ternary mixtures by using the substitution principle for predicting their dielectric behavior. The experimental results confirm the concordance with the modified Lichtenecker mixture law. To predict the electromagnetic behavior of the ternary composites in quantitative manner, we use a numerical optimization method for identification the parameters of the theoretical model. Finally, these materials find their interest in the miniaturization of electronic components used in microelectronic and telecommunication applications.

  8. Enhanced torsional actuation and stress coupling in Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 lead-free piezoceramic system

    DOE PAGES

    Berik, Pelin; Maurya, Deepam; Kumar, Prashant; ...

    2017-01-09

    This paper is concerned with the development of a piezoelectric d15 shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e15) and piezoelectric transverse shear actuation force comparable to that of leadbased shear-mode piezoceramics. The Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 (NBT-BTMn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m–2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d15 mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m–1 V–1 under quasi-static 150 V drive. The high value of piezoelectric shear d15more » coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. Lastly, these results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts.« less

  9. Thermally stable electrostrains of morphotropic 0.875NaNbO3-0.1BaTiO3-0.025CaZrO3 lead-free piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Qi, He; Zuo, Ruzhong; Fu, Jian; Dou, Mengxian

    2017-03-01

    The 0.875NaNbO3-0.1BaTiO3-0.025CaZrO3 relaxor ferroelectric ceramics were reported to exhibit thermally stable electrostrains (˜0.15% @ 6 kV/mm) from room temperature (RT) to ˜175 °C and comparable strain hysteresis (<13%) to that of typical lead-based piezoelectric ceramics. Dominant strain contribution mechanisms with increasing temperature were analyzed by means of temperature-dependent permittivity, polarization, and strain measurements and synchrotron x-ray diffraction. The rhombohedral (R) and tetragonal (T) morphotropic phase boundary provided a solid structural base for temperature-stable piezoelectric strains from RT to ˜140 °C. The growth of polar nanoregions (pseudocubic) into microdomains (R) and subsequent field-induced R-T phase transition, as well as large electrostrictive effects, sequentially contributed to high electrostrain levels in the proximity of the Curie temperature (from 140 to 175 °C). In addition, the observed low strain hysteresis was attributed to the small strain fraction from domain switching. These experimental results demonstrated that NaNbO3-based relaxor ferroelectrics might be potential lead-free materials for actuator applications.

  10. Broadband Tunable, Polarization-Selective and Directional Emission of (6,5) Carbon Nanotubes Coupled to Plasmonic Crystals.

    PubMed

    Zakharko, Yuriy; Graf, Arko; Schießl, Stefan P; Hähnlein, Bernd; Pezoldt, Jörg; Gather, Malte C; Zaumseil, Jana

    2016-05-11

    We demonstrate broadband tunability of light emission from dense (6,5) single-walled carbon nanotube thin films via efficient coupling to periodic arrays of gold nanodisks that support surface lattice resonances (SLRs). We thus eliminate the need to select single-walled carbon nanotubes (SWNTs) with different chiralities to obtain narrow linewidth emission at specific near-infrared wavelengths. Emission from these hybrid films is spectrally narrow (20-40 meV) yet broadly tunable (∼1000-1500 nm) and highly directional (divergence <1.5°). In addition, SLR scattering renders the emission highly polarized, even though the SWNTs are randomly distributed. Numerical simulations are applied to correlate the increased local electric fields around the nanodisks with the observed enhancement of directional emission. The ability to control the emission properties of a single type of near-infrared emitting SWNTs over a wide range of wavelengths will enable application of carbon nanotubes in multifunctional photonic devices.

  11. Broadband Tunable, Polarization-Selective and Directional Emission of (6,5) Carbon Nanotubes Coupled to Plasmonic Crystals

    PubMed Central

    2016-01-01

    We demonstrate broadband tunability of light emission from dense (6,5) single-walled carbon nanotube thin films via efficient coupling to periodic arrays of gold nanodisks that support surface lattice resonances (SLRs). We thus eliminate the need to select single-walled carbon nanotubes (SWNTs) with different chiralities to obtain narrow linewidth emission at specific near-infrared wavelengths. Emission from these hybrid films is spectrally narrow (20–40 meV) yet broadly tunable (∼1000–1500 nm) and highly directional (divergence <1.5°). In addition, SLR scattering renders the emission highly polarized, even though the SWNTs are randomly distributed. Numerical simulations are applied to correlate the increased local electric fields around the nanodisks with the observed enhancement of directional emission. The ability to control the emission properties of a single type of near-infrared emitting SWNTs over a wide range of wavelengths will enable application of carbon nanotubes in multifunctional photonic devices. PMID:27105249

  12. A strategy to reduce the angular dependence of a dye-sensitized solar cell by coupling to a TiO2 nanotube photonic crystal.

    PubMed

    Guo, Min; Xie, Keyu; Liu, Xiaolin; Wang, Yu; Zhou, Limin; Huang, Haitao

    2014-11-07

    Almost all types of solar cells suffer from a decreased power output when the incident light is tilted away from normal since the incident intensity generally follows a cosine law of the incident angle. Making use of the blue shift nature of the Bragg position of a TiO2 nanotube photonic crystal (NT PC) under oblique incidence, we demonstrate experimentally that the use of the NT PC can partially compensate the cosine power loss of a dye-sensitized solar cell (DSSC). The strategy used here is to purposely choose the Bragg position of the NT PC to be at the longer wavelength side of the dye absorption peak. When the incident light is tilted, the blue shift of the Bragg position results in more overlap with the dye absorption peak, generating a higher efficiency that partially compensates the reduced photon flux due to light inclination. Moreover, the unique structure of the vertically aligned TiO2 nanotubes contributes an additional scattering effect when the incident light is tilted. As a result, the power output of a DSSC coupled with the NT PC layer shows a much flatter angular dependence than a DSSC without the NT PC. At all the incident angles, the DSSC coupled with the NT PC layer also shows a higher power conversion efficiency than the one without. The concept of using NT PC to mitigate the angular dependence of DSSCs can be easily extended to many other optoelectronic devices that are irradiance sensitive.

  13. Research on the effect of crystal structures on W-TiO{sub 2} nanotube array photoelectrodes by theoretical and experimental methods

    SciTech Connect

    Xin, Yanjun; Wang, Yicheng; Ma, Dong; Liu, Huiling; Cheng, Wei

    2013-08-28

    W-doped/undoped TiO{sub 2} nanotube array (TNAs) photoelectrodes with different nanostructures were successfully fabricated using the anodization method. Their morphology and characteristics were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and ultra violet/visible light diffuse reflectance spectra (UV/vis/DRS). Their electronic structure and optical properties were studied by means of first-principle. Photocatalytic (PC) performance of W-TNAs photoelectrodes with different crystal structures was evaluated using the decomposition rates of Rhodamine B (Rh.B) under xenon light illumination. The results demonstrated that W substituting Ti broadened the width of conduction band (CB) and valence band (VB) of anatase and rutile TiO{sub 2}, reduced the band gap of rutile TiO{sub 2} and even caused its red-shift. W incorporated into TNAs photoelectrodes extended light absorption threshold and enhanced its utilization of solar light and PC activity, particularly, the PC performance of W-TNAs photoelectrodes with mixed crystal and rutile crystal structure.

  14. LaI2@(18,3)SWNT: the unprecedented structure of a LaI2 "Crystal," encapsulated within a single-walled carbon nanotube.

    PubMed

    Friedrichs, Steffi; Kirkland, Angus I; Meyer, Rüdiger R; Sloan, Jeremy; Green, Malcolm L H

    2005-10-01

    The novel crystallization properties of nano-materials represent a great challenge to researchers across all disciplines of materials science. Simple binary solids can be found to adopt unprecedented structures, when confined into nanometer-sized cavities, such as the inner cylindrical bore of single-walled carbon nanotubes (SWNT). Lanthanum iodide was encapsulated within SWNTs and the resulting encapsulation composite was analyzed using energy-dispersive X-ray microanalysis (EDX) and high-resolution transmission electron microscopy (HRTEM) imaging techniques, to reveal a one-dimensional crystal fragment, with the stoichiometry of LaI2, crystallizing in the structure of LaI3 with one third of the iodine positions unoccupied. A complete characterization of the encapsulation composite was achieved using an enhanced image restoration technique, which restores the object wave from a focal series of HRTEM images, providing information about the precise structural data of both filling material and host SWNT, and thereby enabling the identification of the SWNT chirality.

  15. Research on the effect of crystal structures on W-TiO2 nanotube array photoelectrodes by theoretical and experimental methods

    NASA Astrophysics Data System (ADS)

    Xin, Yanjun; Wang, Yicheng; Liu, Huiling; Ma, Dong; Cheng, Wei

    2013-08-01

    W-doped/undoped TiO2 nanotube array (TNAs) photoelectrodes with different nanostructures were successfully fabricated using the anodization method. Their morphology and characteristics were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and ultra violet/visible light diffuse reflectance spectra (UV/vis/DRS). Their electronic structure and optical properties were studied by means of first-principle. Photocatalytic (PC) performance of W-TNAs photoelectrodes with different crystal structures was evaluated using the decomposition rates of Rhodamine B (Rh.B) under xenon light illumination. The results demonstrated that W substituting Ti broadened the width of conduction band (CB) and valence band (VB) of anatase and rutile TiO2, reduced the band gap of rutile TiO2 and even caused its red-shift. W incorporated into TNAs photoelectrodes extended light absorption threshold and enhanced its utilization of solar light and PC activity, particularly, the PC performance of W-TNAs photoelectrodes with mixed crystal and rutile crystal structure.

  16. Influence of non-covalent modification of multiwalled carbon nanotubes on the crystallization behaviour of binary blends of polypropylene and polyamide 6.

    PubMed

    Mukhopadhyay, Nabaneeta; Panwar, Ajay S; Kumar, Gulshan; Samajdar, I; Bhattacharyya, Arup R

    2015-02-14

    Blends of polypropylene (PP) and polyamide 6 (PA6) with multiwalled carbon nanotubes (MWNTs) were prepared using different processing strategies in a twin-screw micro-compounder. The effect of MWNTs on the crystallization behaviour of the PP phase and the PA6 phase of the blend has been investigated through non-isothermal crystallization studies by differential scanning calorimetric analysis. Furthermore, the effect of the addition of the compatibilizer (PP-g-MA) and the modification of MWNTs (m-MWNTs) with a non-covalent organic modifier (Li-salt of 6 amino hexanoic acid, Li-AHA) has also been studied in context to the crystallization behaviour of the PP and PA6 phase in the blend. The crystallization studies have indicated a significant increase in bulk crystallization temperature of the PP phase in the blend in the presence of MWNTs. Moreover, the formation of 'trans-lamellar crystalline' structure consisting of PA6 'trans-crystalline lamellae' on MWNTs surface was facilitated in the case of blends prepared via 'protocol 2' as compared to the corresponding blends prepared via 'protocol 1'. Wide angle X-ray diffraction analysis has showed the existence of a β-polymorph of the PP phase due to incorporation of the PA6 phase in the blend. Addition of MWNTs in the blends has facilitated further β-crystalline structure formation of the PP phase. In the presence of m-MWNTs, a higher β-fraction was observed in the PP phase as compared to the blend with pristine MWNTs. Addition of PP-g-MA has suppressed the β-phase formation in the PP phase in the blend. X-ray bulk texture analysis revealed that incorporation of PA6 as well as pristine/modified MWNTs has influenced the extent of orientation of the PP chains towards specific crystalline planes in various blend compositions of PP and PA6.

  17. Strongly enhanced flux pinning in the YBa2Cu3O7 -x films with the co-doping of BaTiO3 nanorod and Y2O3 nanoparticles at 65 K

    NASA Astrophysics Data System (ADS)

    Wang, Hong-Yan; Ding, Fa-Zhu; Gu, Hong-Wei; Zhang, Teng

    2015-09-01

    YBa2Cu3O7 - x (YBCO) films with co-doping BaTiO3 (BTO) and Y2O3 nanostructures were prepared by metal organic deposition using trifluoroacetates (TFA-MOD). The properties of the BTO/Y2O3 co-doped YBCO films with different excess yttrium have been systematically studied by x-ray diffraction (XRD), Raman spectra, and scanning electron microscope (SEM). The optimized content of yttrium excess in the BTO/Y2O3 co-doped YBCO films is 10 mol.%, and the critical current density is as high as ˜17 mA/cm2 (self-field, 65 K) by the magnetic signal. In addition, the Y2Cu2O5 was formed when the content of yttrium excess increases to 24 mol.%, which may result in the deterioration of the superconducting properties and the microstructure. The unique combination of the different types of nanostructures of BTO and Y2O3 in the doped YBCO films, compared with the pure YBCO films and BTO doped YBCO films, enhances the critical current density (JC) not only at the self-magnetic field, but also in the applied magnetic field. Project supported by the National Natural Science Foundation of China (Grant No. 51272250), the National Basic Research Program of China (Grant No. 2011CBA00105), the National High Technology Research and Development Program of China (Grant No. 2014AA032702), and the Natural Science Foundation of Beijing, China (Grant No. 2152035).

  18. Dielectric relaxation and Maxwell-Wagner interface polarization in Nb2O5 doped 0.65BiFeO3-0.35BaTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Wang, Tong; Hu, Jiacong; Yang, Haibo; Jin, Li; Wei, Xiaoyong; Li, Chunchun; Yan, Fei; Lin, Ying

    2017-02-01

    Electrical characterizations of Nb2O5 doped 0.65BiFeO3-0.35BaTiO3 (0.65BF-0.35BT) ceramic were carried out over broad temperature and frequency ranges through dielectric spectroscopy, impedance spectroscopy, and ac conductivity measurements. The dielectric constant and loss tangent are drastically reduced with introducing Nb2O5 into the 0.65BF-0.35BT system. Two dielectric anomalies are detected in the temperature regions of 100 °C ≤ T ≤ 280 °C and 350 °C ≤ T ≤ 480 °C, and the Curie temperature (TC) was confirmed in higher temperature region. A dielectric relaxation with large dielectric constants was detected near the TC. This dielectric relaxation becomes even stronger with the gradual increase in the Nb2O5 content. Impedance spectroscopy results clearly show the contributions of grains and grain boundaries in the frequency range of 100 Hz ≤ f ≤ 1 MHz, and the relaxation processes for grains and grain boundaries are non-Debye-type. The grain boundaries are more resistive than that of the grains, revealing the inhomogeneity in samples. The experimental results are well fitted based on a Maxwell-Wagner (MW) interfacial polarization model below 100 kHz, and the MW interfacial polarization effect becomes more and more obvious with the increase in the Nb2O5 content. The increase in dielectric constant is possibly related to space charge polarization, which is caused by charges accumulated at the interface between the grain and grain boundaries. Frequency dependence of the ac conductivity confirms the MW interfacial polarization effect below 100 kHz.

  19. Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals.

    PubMed

    Scolari, Lara; Gauza, Sebastian; Xianyu, Haiqing; Zhai, Lei; Eskildsen, Lars; Alkeskjold, Thomas T; Wu, Shin-Tson; Bjarklev, Anders

    2009-03-02

    We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant. New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable attenuation on the short wavelength side of the widest bandgap, suggest a potential application of this device as a tunable all-in-fiber gain equalization filter with an adjustable slope. The tunability of the device is achieved by varying the amplitude and the frequency of the applied external electric field. The threshold voltage for doped and undoped liquid crystals in a silica capillary and in a glass cell are also measured as a function of the frequency of the external electric field and the achieved results are compared.

  20. Carbon nanotubes on a substrate

    DOEpatents

    Gao, Yufei [Kennewick, WA; Liu, Jun [West Richland, WA

    2002-03-26

    The present invention includes carbon nanotubes whose hollow cores are 100% filled with conductive filler. The carbon nanotubes are in uniform arrays on a conductive substrate and are well-aligned and can be densely packed. The uniformity of the carbon nanotube arrays is indicated by the uniform length and diameter of the carbon nanotubes, both which vary from nanotube to nanotube on a given array by no more than about 5%. The alignment of the carbon nanotubes is indicated by the perpendicular growth of the nanotubes from the substrates which is achieved in part by the simultaneous growth of the conductive filler within the hollow core of the nanotube and the densely packed growth of the nanotubes. The present invention provides a densely packed carbon nanotube growth where each nanotube is in contact with at least one nearest-neighbor nanotube. The substrate is a conductive substrate coated with a growth catalyst, and the conductive filler can be single crystals of carbide formed by a solid state reaction between the substrate material and the growth catalyst. The present invention further provides a method for making the filled carbon nanotubes on the conductive substrates. The method includes the steps of depositing a growth catalyst onto the conductive substrate as a prepared substrate, creating a vacuum within a vessel which contains the prepared substrate, flowing H2/inert (e.g. Ar) gas within the vessel to increase and maintain the pressure within the vessel, increasing the temperature of the prepared substrate, and changing the H2/Ar gas to ethylene gas such that the ethylene gas flows within the vessel. Additionally, varying the density and separation of the catalyst particles on the conductive substrate can be used to control the diameter of the nanotubes.

  1. Supercritical-assistant liquid crystal template approach to synthesize mesoporous titania/multiwalled carbon nanotube composites with high visible-light driven photocatalytic performance

    SciTech Connect

    Liu, Chen; Li, Youji Xu, Peng; Li, Ming; Huo, Pingxiang

    2014-12-15

    Graphical abstract: We investigate the influence of mesoporous titania content upon the visible-light driven photocatalytic performance of MPT/MWCNTs in phenol degradation. - Highlights: • MPT/MWCNTs were fabricated by liquid-crystal template in supercritical CO{sub 2}. • MPT/MWCNTs show high visible-light driven photoactivity for phenol degradation. • MPT/MWCNTs also show high reusable photoactivity under visible irradiation. • MPT content can control visible-light driven photoactivity of MPT/MWCNTs. • MPT is not easily broken away from from MPT/MWCNT composites. - Abstract: Mesoporous titania (MPT) was deposited onto multiwalled carbon nanotubes (MWCNTs) by deposition of titanium sol containing liquid-crystal template with assistant of supercritical CO{sub 2}. The products were characterized with various analytical techniques to determine their structural, morphological, optical absorption and photocatalytic properties. The results indicate that in photocatalytic degradation of phenol under visible light, the mixtures or composites of MPT and MWCNT show the high efficiency because of synergies between absorbing visible light, releasing electrons and facilitating transfer of charge carriers of MWCNTs and providing activated centers of MPT. Because of the mutual constraint between MPT and MWCNTs on the photocatalytic efficiency, the optimal loading of MPT in MPT/MWCNT-3 for phenol degradation is 48%. Because the intimate contact between MWCNTs and MPT is more beneficial to electron transformation, photoactivity of mixture is lower than that of composites with high reusable performance. The optimum conditions of phenol degradation were obtained.

  2. Magnetic nanotubes

    DOEpatents

    Matsui, Hiroshi; Matsunaga, Tadashi

    2010-11-16

    A magnetic nanotube includes bacterial magnetic nanocrystals contacted onto a nanotube which absorbs the nanocrystals. The nanocrystals are contacted on at least one surface of the nanotube. A method of fabricating a magnetic nanotube includes synthesizing the bacterial magnetic nanocrystals, which have an outer layer of proteins. A nanotube provided is capable of absorbing the nanocrystals and contacting the nanotube with the nanocrystals. The nanotube is preferably a peptide bolaamphiphile. A nanotube solution and a nanocrystal solution including a buffer and a concentration of nanocrystals are mixed. The concentration of nanocrystals is optimized, resulting in a nanocrystal to nanotube ratio for which bacterial magnetic nanocrystals are immobilized on at least one surface of the nanotubes. The ratio controls whether the nanocrystals bind only to the interior or to the exterior surfaces of the nanotubes. Uses include cell manipulation and separation, biological assay, enzyme recovery, and biosensors.

  3. Effects of ferroelectric nanoparticles on ion transport in a liquid crystal

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan; Garvey, Alfred

    2014-10-01

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

  4. Effects of ferroelectric nanoparticles on ion-transport in a liquid crystal

    NASA Astrophysics Data System (ADS)

    Garvey, Alfred; Basu, Rajratan

    2015-03-01

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

  5. Multiwalled nanotube faceting unravelled

    NASA Astrophysics Data System (ADS)

    Leven, Itai; Guerra, Roberto; Vanossi, Andrea; Tosatti, Erio; Hod, Oded

    2016-12-01

    Nanotubes show great promise for miniaturizing advanced technologies. Their exceptional physical properties are intimately related to their morphological and crystal structure. Circumferential faceting of multiwalled nanotubes reinforces their mechanical strength and alters their tribological and electronic properties. Here, the nature of this important phenomenon is fully rationalized in terms of interlayer registry patterns. Regardless of the nanotube identity (that is, diameter, chirality, chemical composition), faceting requires the matching of the chiral angles of adjacent layers. Above a critical diameter that corresponds well with experimental results, achiral multiwalled nanotubes display evenly spaced extended axial facets whose number equals the interlayer difference in circumferential unit cells. Elongated helical facets, commonly observed in experiment, appear in nanotubes that exhibit small interlayer chiral angle mismatch. When the wall chiralities are uncorrelated, faceting is suppressed and outer layer corrugation, which is induced by the Moiré superlattice, is obtained in agreement with experiments. Finally, we offer an explanation for the higher incidence of faceting in multiwalled boron nitride nanotubes with respect to their carbon-based counterparts.

  6. ILQINS hexapeptide, identified in lysozyme left-handed helical ribbons and nanotubes, forms right-handed helical ribbons and crystals.

    PubMed

    Lara, Cecile; Reynolds, Nicholas P; Berryman, Joshua T; Xu, Anqiu; Zhang, Afang; Mezzenga, Raffaele

    2014-03-26

    Amyloid fibrils are implicated in over 20 neurodegenerative diseases. The mechanisms of fibril structuring and formation are not only of medical and biological importance but are also relevant for material science and nanotechnologies due to the unique structural and physical properties of amyloids. We previously found that hen egg white lysozyme, homologous to the disease-related human lysozyme, can form left-handed giant ribbons, closing into nanotubes. By using matrix-assisted laser desorption ionization mass spectrometry analysis, we here identify a key component of such structures: the ILQINS hexapeptide. By combining atomic force microscopy and circular dichorism, we find that this fragment, synthesized by solid-phase peptide synthesis, also forms fibrillar structures in water at pH 2. However, all fibrillar structures formed possess an unexpected right-handed twist, a rare chirality within the corpus of amyloid experimental observations. We confirm by small- and wide-angle X-ray scattering and molecular dynamics simulations that these fibrils are composed of conventional left-handed β-sheets, but that packing stresses between adjacent sheets create this twist of unusual handedness. We also show that the right-handed fibrils represent a metastable state toward β-sheet-based microcrystals formation.

  7. Improved Process for Fabricating Carbon Nanotube Probes

    NASA Technical Reports Server (NTRS)

    Stevens, R.; Nguyen, C.; Cassell, A.; Delzeit, L.; Meyyappan, M.; Han, Jie

    2003-01-01

    An improved process has been developed for the efficient fabrication of carbon nanotube probes for use in atomic-force microscopes (AFMs) and nanomanipulators. Relative to prior nanotube tip production processes, this process offers advantages in alignment of the nanotube on the cantilever and stability of the nanotube's attachment. A procedure has also been developed at Ames that effectively sharpens the multiwalled nanotube, which improves the resolution of the multiwalled nanotube probes and, combined with the greater stability of multiwalled nanotube probes, increases the effective resolution of these probes, making them comparable in resolution to single-walled carbon nanotube probes. The robust attachment derived from this improved fabrication method and the natural strength and resiliency of the nanotube itself produces an AFM probe with an extremely long imaging lifetime. In a longevity test, a nanotube tip imaged a silicon nitride surface for 15 hours without measurable loss of resolution. In contrast, the resolution of conventional silicon probes noticeably begins to degrade within minutes. These carbon nanotube probes have many possible applications in the semiconductor industry, particularly as devices are approaching the nanometer scale and new atomic layer deposition techniques necessitate a higher resolution characterization technique. Previously at Ames, the use of nanotube probes has been demonstrated for imaging photoresist patterns with high aspect ratio. In addition, these tips have been used to analyze Mars simulant dust grains, extremophile protein crystals, and DNA structure.

  8. Epitaxial Approaches to Carbon Nanotube Organization

    NASA Astrophysics Data System (ADS)

    Ismach, Ariel

    Carbon nanotubes have unique electronic, mechanical, optical and thermal properties, which make them ideal candidates as building blocks in nano-electronic and electromechanical systems. However, their organization into well-defined geometries and arrays on surfaces remains a critical challenge for their integration into functional nanosystems. In my PhD, we developed a new approach for the organization of carbon nanotubes directed by crystal surfaces. The principle relies on the guided growth of single-wall carbon nanotubes (SWNTs) by atomic features presented on anisotropic substrates. We identified three different modes of surface-directed growth (or 'nanotube epitaxy'), in which the growth of carbon nanotubes is directed by crystal substrates: We first observed the nanotube unidirectional growth along atomic steps ('ledge-directed epitaxy') and nanofacets ('graphoepitaxy') on the surface of miscut C-plane sapphire and quartz. The orientation along crystallographic directions ('lattice-directed epitaxy') was subsequently observed by other groups on different crystals. We have proposed a "wake growth" mechanism for the nanotube alignment along atomic steps and nanofacets. In this mechanism, the catalyst nanoparticle slides along the step or facet, leaving the nanotube behind as a wake. In addition, we showed that the combination of surface-directed growth with external forces, such as electric-field and gas flow, can lead to the simultaneous formation of complex nanotube structures, such as grids and serpentines. The "wake growth" model, which explained the growth of aligned nanotubes, could not explain the formation of nanotube serpentines. For the latter, we proposed a "falling spaghetti" mechanism, in which the nanotube first grows by a free-standing process, aligned in the direction of the gas flow, then followed by absorption on the stepped surface in an oscillatory manner, due to the competition between the drag force caused by the gas flow on the suspended

  9. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

    2003-01-01

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  10. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon; Zettl, Alexander Karlwalte

    2004-12-28

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  11. Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 piezoelectric materials

    PubMed Central

    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

    2015-01-01

    We synthesized grain-oriented lead-free piezoelectric materials in (K0.5Bi0.5TiO3-BaTiO3-xNa0.5Bi0.5TiO3 (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d33 ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials. PMID:25716551

  12. Silicon/Carbon Nanotube/BaTiO₃ Nanocomposite Anode: Evidence for Enhanced Lithium-Ion Mobility Induced by the Local Piezoelectric Potential.

    PubMed

    Lee, Byoung-Sun; Yoon, Jihyun; Jung, Changhoon; Kim, Dong Young; Jeon, Seung-Yeol; Kim, Ki-Hong; Park, Jun-Ho; Park, Hosang; Lee, Kang Hee; Kang, Yoon-Sok; Park, Jin-Hwan; Jung, Heechul; Yu, Woong-Ryeol; Doo, Seok-Gwang

    2016-02-23

    We report on the synergetic effects of silicon (Si) and BaTiO3 (BTO) for applications as the anode of Li-ion batteries. The large expansion of Si during lithiation was exploited as an energy source via piezoelectric BTO nanoparticles. Si and BTO nanoparticles were dispersed in a matrix consisting of multiwalled carbon nanotubes (CNTs) using a high-energy ball-milling process. The mechanical stress resulting from the expansion of Si was transferred via the CNT matrix to the BTO, which can be poled, so that a piezoelectric potential is generated. We found that this local piezoelectric potential can improve the electrochemical performance of the Si/CNT/BTO nanocomposite anodes. Experimental measurements and simulation results support the increased mobility of Li-ions due to the local piezoelectric potential.

  13. Dielectric behavior of a flexible three-phase polyimide/BaTiO3/multi-walled carbon nanotube composite film

    NASA Astrophysics Data System (ADS)

    Wang, Junli; Qi, Shengli; Sun, Yiyi; Tian, Guofeng; Wu, Dezhen

    2016-11-01

    A three-phase composite film was produced by inserting multi-walled carbon nanotubes (MWCNTs) and BaTiO3 nanoparticles into polyimide (PI). The combination of in-situ polymerization and water-based preparation involved in the experiment ensured fillers’ homogeneous dispersion in the matrix, which led to flexible shape of the composite films. The dielectric properties of composite films as a function of the frequency and the volume fraction of MWCNTs were studied. Such composite film displayed a high dielectric constant (314.07), low dielectric loss and excellent flexibility at 100Hz in the neighborhood of percolation threshold (9.02 vol%) owing to the special microcapacitor structure. The experimental results were highly consistent with the power law of percolation theory.

  14. Soft memory in a ferroelectric nanoparticle-doped liquid crystal

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan

    2014-02-01

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

  15. Hexagonal photonic crystal waveguide based on barium titanate thin films

    NASA Astrophysics Data System (ADS)

    Li, Jianheng; Liu, Zhifu; Wessels, Bruce W.; Tu, Yongming; Ho, Seng-Tiong; Joshi-Imre, Alexandra; Ocola, Leonidas E.

    2011-03-01

    The simulation, fabrication and measurement of nonlinear photonic crystals (PhCs) with hexagonal symmetry in epitaxial BaTiO3 were investigated. The optical transmission properties of a PhC were simulated by a 2-D finite-difference time domain (FDTD) method. A complete bandgap exists for both the TE and TM optical modes. The fabricated PhC has a well-defined stop band over the spectral region of 1525 to 1575 nm. A microcavity structure was also fabricated by incorporation of a line defect in the PhC. Transmission of the microcavity structure over the spectral region from 1456 to 1584nm shows a well-defined 5 nm wide window at 1495nm. Simulations indicate that the phase velocity matched PhC microcavity device of 0.5 mm long can potentially serve as modulator with a 3 dB bandwidth of 4 THz.

  16. 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

  17. Nanotube Sensors

    NASA Technical Reports Server (NTRS)

    McEuen, Paul L.

    2002-01-01

    Under this project, we explored the feasibility of utilizing carbon nanotubes in sensing applications. The grant primarily supported a graduate student, who worked on a number of aspects of the electrical properties of carbon nanotubes in collaboration with other researchers in my group. The two major research accomplishments are described below. The first accomplishment is the demonstration that solution carbon nanotube transistors functioned well in an electrolyte environment. This was important for two reasons. First, it allowed us to explore the ultimate limits of nanotube electronic performance by using the electrolyte as a highly effective gate, with a dielectric constant of approximately 80 and an effective insulator thickness of approximately 1 nm. Second, it showed that nanotubes function well under biologically relevant conditions (salty water) and therefore offer great promise as biological sensors. The second accomplishment was the demonstration that a voltage pulse applied to an AFM tip could be used to electrically cut carbon nanotubes. We also showed that a carefully applied pulse could also 'nick' a nanotube, creating a tunnel barrier without completely breaking the tube. Nicking was employed to make, for example, a quantum dot within a nanotube.

  18. Graphenylene Nanotubes.

    PubMed

    Koch, Andrew T; Khoshaman, Amir H; Fan, Harrison D E; Sawatzky, George A; Nojeh, Alireza

    2015-10-01

    A new type of carbon nanotube, based on the graphenylene motif, is investigated using density functional and tight-binding methods. Analogous to conventional graphene-based nanotubes, a two-dimensional graphenylene sheet can be "rolled" into a seamless cylinder in armchair, zigzag, or chiral orientations. The resulting nanotube can be described using the familiar (n,m) nomenclature and possesses 4-, 6-, and 12-membered rings, with three distinct bond lengths, indicating a nonuniform distribution of the electron density. The dodecagonal rings form pores, 3.3 Å in diameter in graphenylene, which become saddle-shaped paraboloids in smaller-diameter nanotubes. Density functional theory predicts zigzag nanotubes to be small-band gap semiconductors, with a generally decreasing band gap as the diameter increases. Interestingly, the calculations predict metallic characteristics for armchair nanotubes with small diameters (<2 nm), and small-band gap semiconducting characteristics for larger-diameter ones. Graphenylene nanotubes with indices mod(n-m,3) = 0 exhibit a band gap approximately equal to that of armchair graphenylene nanotubes with comparable diameter.

  19. Controlling the quantity of α-Fe inside multiwall carbon nanotubes filled with Fe-based crystals: The key role of vapor flow-rate

    NASA Astrophysics Data System (ADS)

    Boi, Filippo S.; Maugeri, Serena; Guo, Jian; Lan, Mu; Wang, Shanling; Wen, Jiqiu; Mountjoy, Gavin; Baxendale, Mark; Nevill, George; Wilson, Rory M.; He, Yi; Zhang, Sijie; Xiang, Gang

    2014-12-01

    The growth control of α-Fe inside multiwall carbon nanotubes has challenged researchers for more than a decade owing to the coexistence of this phase with Fe3C and γ-Fe. Previously, long heating treatments of 20 h have been used to decompose the encapsulated Fe-phases in C and Fe; however, these methods were limited by an unusual oxidation process leading to nanotube decomposition. In this letter, we report an alternative chemical vapour deposition approach that through an accurate control of the ferrocene-vapour flow-rate allows to achieve the direct encapsulation of 95% of α-Fe without additional heating treatments.

  20. Heteroporphyrin nanotubes and composites

    DOEpatents

    Shelnutt, John A.; Medforth, Craig J.; Wang, Zhongchun

    2007-05-29

    Heteroporphyrin nanotubes, metal nanostructures, and metal/porphyrin-nanotube composite nanostructures formed using the nanotubes as photocatalysts and structural templates, and the methods for forming the nanotubes and composites.

  1. Heteroporphyrin nanotubes and composites

    DOEpatents

    Shelnutt, John A.; Medforth, Craig J.; Wang, Zhongchun

    2006-11-07

    Heteroporphyrin nanotubes, metal nanostructures, and metal/porphyrin-nanotube composite nanostructures formed using the nanotubes as photocatalysts and structural templates, and the methods for forming the nanotubes and composites.

  2. Tailoring crystallinity and configuration of silica nanotubes by electron irradiation

    NASA Astrophysics Data System (ADS)

    Taguchi, Tomitsugu; Yamaguchi, Kenji

    2015-05-01

    SiO2 nanotubes show potential in applications such as nanoscale electronic and optical devices, bioseparation, biocatalysis, and nanomedicine. As-grown SiO2 nanotubes in the previous studies always have an amorphous wall, and here we demonstrate the successful synthesis of single-crystal nanotubes for the first time by the heat treatment of SiC nanotubes at 1300 °C for 10 h under low-vacuum conditions. According to TEM observations, the single-crystal SiO2 was α-cristobalite. We also demonstrate that single-crystal SiO2 nanotubes can be transformed into amorphous SiO2 nanotubes by electron beam irradiation. Moreover, we synthesized a crystalline/amorphous SiO2 composite nanotube, in which crystalline and amorphous SiO2 coexisted in different localized regions. In addition, for biomedical applications such as drug delivery systems, controlling the configuration of the open end, the diameter, and capsulation of SiO2 nanotubes is crucial. We can also obturate, capsulate, and cut a SiO2 nanotube, as well as modify the inner diameter of the nanotube at a specific, nanometer-sized region using the focused electron beam irradiation technique.

  3. Silicon Carbide Nanotube Synthesized

    NASA Technical Reports Server (NTRS)

    Lienhard, Michael A.; Larkin, David J.

    2003-01-01

    Carbon nanotubes (CNTs) have generated a great deal of scientific and commercial interest because of the countless envisioned applications that stem from their extraordinary materials properties. Included among these properties are high mechanical strength (tensile and modulus), high thermal conductivity, and electrical properties that make different forms of single-walled CNTs either conducting or semiconducting, and therefore, suitable for making ultraminiature, high-performance CNT-based electronics, sensors, and actuators. Among the limitations for CNTs is their inability to survive in high-temperature, harsh-environment applications. Silicon carbon nanotubes (SiCNTs) are being developed for their superior material properties under such conditions. For example, SiC is stable in regards to oxidation in air to temperatures exceeding 1000 C, whereas carbon-based materials are limited to 600 C. The high-temperature stability of SiCNTs is envisioned to enable high-temperature, harsh-environment nanofiber- and nanotube-reinforced ceramics. In addition, single-crystal SiC-based semiconductors are being developed for hightemperature, high-power electronics, and by analogy to CNTs with silicon semiconductors, SiCNTs with single-crystal SiC-based semiconductors may allow high-temperature harsh-environment nanoelectronics, nanosensors, and nanoactuators to be realized. Another challenge in CNT development is the difficulty of chemically modifying the tube walls, which are composed of chemically stable graphene sheets. The chemical substitution of the CNTs walls will be necessary for nanotube self-assembly and biological- and chemical-sensing applications. SiCNTs are expected to have a different multiple-bilayer wall structure, allowing the surface Si atoms to be functionalized readily with molecules that will allow SiCNTs to undergo self-assembly and be compatible with a variety of materials (for biotechnology applications and high-performance fiber-reinforced ceramics).

  4. High-Energy Synchrotron X-Ray Diffraction for In Situ Diffuse Scattering Studies of Bulk Single Crystals

    NASA Astrophysics Data System (ADS)

    Daniels, John E.; Jo, Wook; Donner, Wolfgang

    2012-01-01

    High-energy synchrotron x-ray scattering offers a powerful technique for investigation of single-crystal material structures. Large, mm-sized crystals can be used, allowing complex in situ sample environments to be employed. Here, we demonstrate how this technique can be applied for the collection of single-crystal diffuse scattering volumes from the electro-active material 96%Bi0.5Na0.5TiO3-4%BaTiO3 while electric fields are applied in situ. The data obtained allow correlation of the atomic and nanoscale structures with the observed macroscopic electro-active properties of interest. This article presents a recent study relating the nanoscale stacking fault structure in BNT-BT to the relaxor-ferroelectric nature of the material [Daniels et al. in Appl. Phys. Lett. 98, 252904 (2011)], and extends this study with further experimental description and analysis.

  5. Nanotube Radio

    NASA Astrophysics Data System (ADS)

    Jensen, Kenneth; Weldon, Jeff; Garcia, Henry; Zettl, Alex

    2008-03-01

    We have constructed a fully functional, fully integrated radio receiver from a single carbon nanotube. The nanotube serves simultaneously as all essential components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A direct current voltage source, as supplied by a battery, powers the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, we demonstrate successful music and voice reception.

  6. Alkali Halide Nanotubes: Structure and Stability

    PubMed Central

    Fernandez-Lima, Francisco A.; Henkes, Aline Verônica; da Silveira, Enio F.; Nascimento, Marco Antonio Chaer

    2013-01-01

    Accurate density functional theory (DFT) and coupled-cluster (CCSD) calculations on a series of (LiF)n=2,36 neutral clusters suggest that nanotube structures with hexagonal and octagonal transversal cross sections show stability equal to or greater than that of the typical cubic form of large LiF crystals. The nanotube stability was further corroborated by quantum dynamic calculations at room temperature. The fact that stable nanotube structures were also found for other alkali halides (e.g., NaCl and KBr) suggests that this geometry may be widely implemented in material sciences. PMID:24376901

  7. Effect of the Yb3+ Concentration in Up-Conversion and Electrical Properties of Ho3+/Yb3+ Co-doped (0.94Na0.5Bi0.5TiO3-0.06BaTiO3) Ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Qian; Li, Yanxia; Li, Jun; Chai, Xiaona; Zhao, Haifeng; Wang, Xusheng; Yao, Xi

    2016-07-01

    Ho3+/Yb3+ co-doped 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-BT:Ho3+/Yb3+) ceramics were synthesized by solid-state reaction and characterized by x-ray diffraction (XRD), luminescent, dielectric, ferroelectric and piezoelectric measurements. The XRD diffraction data showed that all the ceramics were single phase with a perovskite structure. Bright green up-conversion (UC) emission bands (545 nm) and weak red UC emission bands (660 nm) corresponded to the transitions from (5F4, 5S2) → 5I8 and 4I5 → 5I8, respectively. Furthermore, optimized UC emission intensity was observed in the NBT-BT:0.005Ho3+/0.03Yb3+ samples. The thermal behavior of UC emission in the ceramics was also investigated and the maximum sensitivity based on fluorescence intensity ratio (FIR) technology was approximately 0.0042 K-1 at 100 K. Moreover, relatively good dielectric properties ( ɛ = 4475) and ferroelectric properties ( P r = 32 μ/cm2 and E c = 37 kV) were obtained in NBT-BT:0.005Ho3+/0.005Yb3+. As a multi-functional material, NBT-BT:Ho3+/Yb3+ ceramics may be useful in electro-optical devices.

  8. Dielectric and AC conductivity studies of Nd substituted 0.8BaTiO3-0.2(Bi0.5(1-x)Nd0.5xK0.5)TiO3 lead free ceramics

    NASA Astrophysics Data System (ADS)

    Ramesh, M. N. V.; Ramesh, K. V.

    2016-05-01

    0.8BaTiO3 - 0.2(Bi0.5(1-x)Nd0.5xK0.5)TiO3 (0.01 ≤ x ≤ 0.06) lead free ceramic materials have been prepared by solid state reaction method and followed by high energy ball milling process. X-ray diffraction studies confirm the tetragonal structure of the materials at room temperature. Lattice parameters and density are decreasing with increase of Nd substitution. Microstructure studies were done by using Scanning electron microscope and it found that grain size is decreasing with increase of Nd substitution. Temperature and frequency dependent dielectric studies reveal relaxor behaviour of the materials. Dielectric constant, dielectric loss and Curie temperature are decreasing with Nd substitution. Maximum Curie temperature of 195°C was observed at 1MHz for x=0.01 Nd substituted sample. Degree of diffuseness was calculated from the modified Curie-Weiss law and it is increasing with Nd substitution. AC conductivity is increasing with increase of Nd substitution and observed maximum activation energy of 0.52 eV for x=0.02 Nd substituted sample.

  9. Nanotube cathodes.

    SciTech Connect

    Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

    2006-11-01

    Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop a one-inch-diameter cathode capable of emitting 10 amperes of electron current for one second with an applied potential of 50 kV. This combination of current and pulse duration significantly exceeds previously reported nanotube-cathode performance. This project was planned for two years duration. In the first year, we tested the electron-emission characteristics of nanotube arrays fabricated under a variety of conditions. In the second year, we planned to select the best processing conditions, to fabricate larger cathode samples, and to test them on a high-power relativistic electron beam generator. In the first year, much effort was made to control nanotube arrays in terms of nanotube diameter and average spacing apart. When the project began, we believed that nanotubes approximately 10 nm in diameter would yield sufficient electron emission properties, based on the work of others in the field. Therefore, much of our focus was placed on measured field emission from such nanotubes grown on a variety of metallized surfaces and with varying average spacing between individual nanotubes. We easily reproduced the field emission properties typically measured by others from multi-wall carbon nanotube arrays. Interestingly, we did this without having the helpful vertical alignment to enhance emission; our nanotubes were randomly oriented. The good emission was most likely possible due to the improved crystallinity, and therefore, electrical conductivity, of our nanotubes compared to those in the literature. However, toward the end of the project, we learned that while these 10-nm-diameter CNTs had superior crystalline structure to the work of others studying field emission from multi-wall CNT arrays, these nanotubes still

  10. Sacrificial template method of fabricating a nanotube

    DOEpatents

    Yang, Peidong; He, Rongrui; Goldberger, Joshua; Fan, Rong; Wu, Yi-Ying; Li, Deyu; Majumdar, Arun

    2007-05-01

    Methods of fabricating uniform nanotubes are described in which nanotubes were synthesized as sheaths over nanowire templates, such as using a chemical vapor deposition process. For example, single-crystalline zinc oxide (ZnO) nanowires are utilized as templates over which gallium nitride (GaN) is epitaxially grown. The ZnO templates are then removed, such as by thermal reduction and evaporation. The completed single-crystalline GaN nanotubes preferably have inner diameters ranging from 30 nm to 200 nm, and wall thicknesses between 5 and 50 nm. Transmission electron microscopy studies show that the resultant nanotubes are single-crystalline with a wurtzite structure, and are oriented along the <001> direction. The present invention exemplifies single-crystalline nanotubes of materials with a non-layered crystal structure. Similar "epitaxial-casting" approaches could be used to produce arrays and single-crystalline nanotubes of other solid materials and semiconductors. Furthermore, the fabrication of multi-sheath nanotubes are described as well as nanotubes having multiple longitudinal segments.

  11. Multiwalled Carbon Nanotube Deposition on Model Environmental Surfaces

    EPA Science Inventory

    Deposition of multiwalled carbon nanotubes (MWNTs) on model environmental surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Deposition behaviors of MWNTs on positively and negatively charged surfaces were in good agreement with Der...

  12. Method of making carbon nanotubes on a substrate

    DOEpatents

    Gao, Yufei; Liu, Jun

    2006-03-14

    The present invention includes carbon nanotubes whose hollow cores are 100% filled with conductive filler. The carbon nanotubes are in uniform arrays on a conductive substrate and are well-aligned and can be densely packed. The uniformity of the carbon nanotube arrays is indicated by the uniform length and diameter of the carbon nanotubes, both which vary from nanotube to nanotube on a given array by no more than about 5%. The alignment of the carbon nanotubes is indicated by the perpendicular growth of the nanotubes from the substrates which is achieved in part by the simultaneous growth of the conductive filler within the hollow core of the nanotube and the densely packed growth of the nanotubes. The present invention provides a densely packed carbon nanotube growth where each nanotube is in contact with at least one nearest-neighbor nanotube. The substrate is a conductive substrate coated with a growth catalyst, and the conductive filler can be single crystals of carbide formed by a solid state reaction between the substrate material and the growth catalyst. The present invention further provides a method for making the filled carbon nanotubes on the conductive substrates. The method includes the steps of depositing a growth catalyst onto the conductive substrate as a prepared substrate, creating a vacuum within a vessel which contains the prepared substrate, flowing H2/inert (e.g. Ar) gas within the vessel to increase and maintain the pressure within the vessel, increasing the temperature of the prepared substrate, and changing the H2/Ar gas to ethylene gas such that the ethylene gas flows within the vessel. Additionally, varying the density and separation of the catalyst particles on the conductive substrate can be used to control the diameter of the nanotubes.

  13. Nanotube phonon waveguide

    DOEpatents

    Chang, Chih-Wei; Zettl, Alexander K.

    2013-10-29

    Disclosed are methods and devices in which certain types of nanotubes (e.g., carbon nanotubes and boron nitride nanotubes conduct heat with high efficiency and are therefore useful in electronic-type devices.

  14. Carbon Nanotubes as High-Pressure Cylinders and Nanoextruders

    NASA Astrophysics Data System (ADS)

    Sun, L.; Banhart, F.; Krasheninnikov, A. V.; Rodríguez-Manzo, J. A.; Terrones, M.; Ajayan, P. M.

    2006-05-01

    Closed-shell carbon nanostructures, such as carbon onions, have been shown to act as self-contracting high-pressure cells under electron irradiation. We report that controlled irradiation of multiwalled carbon nanotubes can cause large pressure buildup within the nanotube cores that can plastically deform, extrude, and break solid materials that are encapsulated inside the core. We further showed by atomistic simulations that the internal pressure inside nanotubes can reach values higher than 40 gigapascals. Nanotubes can thus be used as robust nanoscale jigs for extruding and deforming hard nanomaterials and for modifying their properties, as well as templates for the study of individual nanometer-sized crystals under high pressure.

  15. Electromechanical memory effect in a ferroelectric nanoparticle-suspended liquid crystal

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan

    2014-03-01

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

  16. Structure of periodic crystals and quasicrystals in ultrathin films of Ba-Ti-O

    DOE PAGES

    Cockayne, Eric; Mihalkovič, Marek; Henley, Christopher L.

    2016-01-07

    Here, we model the remarkable thin-film Ba-Ti-O structures formed by heat treatment of an initial perovskite BaTiO3 thin film on a Pt(111) surface. All structures contain a rumpled Ti-O network with all Ti threefold coordinated with O, and with Ba occupying the larger. mainly Ti7O7, pores. The quasicrystal structue is a simple decoration of three types of tiles: square, triangle and 30° rhombus, with edge lengths 6.85 Å, joined edge-to-edge in a quasicrystalline pattern; observed periodic crystals in ultrathin film Ba-Ti-O are built from these and other tiles. Simulated STM images reproduce the patterns seen experimentally, and identify the brightmore » protrusions as Ba atoms. The models are consistent with all experimental observations.« less

  17. Nanotube News

    ERIC Educational Resources Information Center

    Journal of College Science Teaching, 2005

    2005-01-01

    Smaller, faster computers, bullet-proof t-shirts, and itty-bitty robots--such are the promises of nanotechnology and the cylinder-shaped collection of carbon molecules known as nanotubes. But for these exciting ideas to become realities, scientists must understand how these miracle molecules perform under all sorts of conditions. This brief…

  18. Versatile Transfer of an Ultralong and Seamless Nanowire Array Crystallized at High Temperature for Use in High-Performance Flexible Devices.

    PubMed

    Seo, Min-Ho; Yoo, Jae-Young; Choi, So-Young; Lee, Jae-Shin; Choi, Kwang-Wook; Jeong, Chang Kyu; Lee, Keon Jae; Yoon, Jun-Bo

    2017-02-28

    Nanowire (NW) transfer technology has provided promising strategies to realize future flexible materials and electronics. Using this technology, geometrically controlled, high-quality NW arrays can now be obtained easily on various flexible substrates with high throughput. However, it is still challenging to extend this technology to a wide range of high-performance device applications because its limited temperature tolerance precludes the use of high-temperature annealing, which is essential for NW crystallization and functionalization. A pulsed laser technique has been developed to anneal NWs in the presence of a flexible substrate; however, the induced temperature is not high enough to improve the properties of materials such as ceramics and semiconductors. Here, we present a versatile nanotransfer method that is applicable to NWs that require high-temperature annealing. To successfully anneal NWs during their transfer, the developed fabrication method involves sequential removal of a nanoscale sacrificial layer. Using this method, we first produce an ultralong, perfectly aligned polycrystalline barium titanate (BaTiO3) NW array that is heat treated at 700 °C on a flexible polyethylene terephthalate (PET) substrate. This high-quality piezoelectric NW array on a flexible substrate is used as a flexible nanogenerator that generates current and voltage 37 and 10 times higher, respectively, than those of a nanogenerator made of noncrystallized BaTiO3 NWs.

  19. Optical properties of titanium dioxide nanotube arrays

    NASA Astrophysics Data System (ADS)

    Abdelmoula, Mohamed; Sokoloff, Jeffrey; Lu, Wen-Tao; Close, Thomas; Menon, Latika; Richter, Christiaan

    2014-01-01

    We present experimental measurements and a theoretical analysis of the near UV to NIR optical properties of free standing titania nanotube arrays. An improved understanding of the optical physics of this type of nanostructure is important to several next generation solar energy conversion technologies. We measured the transmission, reflection, and absorption of the electromagnetic spectrum from 300 nm to 1000 nm (UV to NIR) of titania nanotube arrays. We measured the total, specular, and diffuse reflection and transmission using both single point detection and an integrating sphere spectrometer. We find that the transmission, but not the reflection, of light (UV to NIR) through the nanotube array is well-explained by classic geometric optics using an effective medium model taking into account the conical geometry of the nanotubes. For wavelengths shorter than ˜500 nm, we find the surprising result that the reflection coefficient for light incident on the open side of the nanotube array is greater than the reflection coefficient for light incident on the closed "floor" of the nanotube array. We consider theoretical models based on the eikonal approximation, photonic crystal band theory, and a statistical treatment of scattering to explain the observed data. We attribute the fact that light with wavelengths shorter than 500 nm is more highly reflected from the open than the closed tube side as being due to disorder scattering inside the nanotube array.

  20. Optical properties of titanium dioxide nanotube arrays

    SciTech Connect

    Abdelmoula, Mohamed; Sokoloff, Jeffrey; Lu, Wen-Tao; Menon, Latika; Close, Thomas; Richter, Christiaan

    2014-01-07

    We present experimental measurements and a theoretical analysis of the near UV to NIR optical properties of free standing titania nanotube arrays. An improved understanding of the optical physics of this type of nanostructure is important to several next generation solar energy conversion technologies. We measured the transmission, reflection, and absorption of the electromagnetic spectrum from 300 nm to 1000 nm (UV to NIR) of titania nanotube arrays. We measured the total, specular, and diffuse reflection and transmission using both single point detection and an integrating sphere spectrometer. We find that the transmission, but not the reflection, of light (UV to NIR) through the nanotube array is well-explained by classic geometric optics using an effective medium model taking into account the conical geometry of the nanotubes. For wavelengths shorter than ∼500 nm, we find the surprising result that the reflection coefficient for light incident on the open side of the nanotube array is greater than the reflection coefficient for light incident on the closed “floor” of the nanotube array. We consider theoretical models based on the eikonal approximation, photonic crystal band theory, and a statistical treatment of scattering to explain the observed data. We attribute the fact that light with wavelengths shorter than 500 nm is more highly reflected from the open than the closed tube side as being due to disorder scattering inside the nanotube array.

  1. Recognition unit-free and self-cleaning photoelectrochemical sensing platform on TiO2 nanotube photonic crystals for sensitive and selective detection of dopamine release from mouse brain.

    PubMed

    Xin, Yanmei; Li, Zhenzhen; Wu, Wenlong; Fu, Baihe; Wu, Hongjun; Zhang, Zhonghai

    2017-01-15

    For implementing sensitive and selective detection of biological molecules, the biosensors are been designed more and more complicated. The exploration of detection platform in a simple way without loss their sensitivity and selectivity is always a big challenge. Herein, a prototype of recognition biomolecule unit-free photoelectrochemical (PEC) sensing platform with self-cleaning activity is proposed with TiO2 nanotube photonic crystal (TiO2 NTPCs) materials as photoelectrode, and dopamine (DA) molecule as both sensitizer and target analyte. The unique adsorption between DA and TiO2 NTPCs induces the formation of charge transfer complex, which not only expends the optical absorption of TiO2 into visible light region, thus significantly boosts the PEC performance under illumination of visible light, but also implements the selective detection of DA on TiO2 photoelectrode. This simple but efficient PEC analysis platform presents a low detection limit of 0.15nm for detection of DA, which allows to realize the sensitive and selective determination of DA release from the mouse brain for its practical application after coupled with a microdialysis probe. The DA functionalized TiO2 NTPCs PEC sensing platform opens up a new PEC detection model, without using extra-biomolecule auxiliary, just with target molecule naturally adsorbed on the electrode for sensitive and selective detection, and paves a new avenue for biosensors design with minimalism idea.

  2. Carbon nanotube composite materials

    DOEpatents

    O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

    2015-03-24

    A material consisting essentially of a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes dissolved in a solvent. Un-functionalized carbon nanotube concentrations up to 30 wt % and hydroxylated carbon nanotube concentrations up to 40 wt % can be used with even small concentrations of each (less than 2 wt %) useful in producing enhanced conductivity properties of formed thin films.

  3. EDITORIAL: Focus on Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    2003-09-01

    Filho, R Saito, G Dresselhaus and M S Dresselhaus FTIR-luminescence mapping of dispersed single-walled carbon nanotubes Sergei Lebedkin, Katharina Arnold, Frank Hennrich, Ralph Krupke, Burkhard Renker and Manfred M Kappes Structural properties of Haeckelite nanotubes Ph Lambin and L P Biró Structural changes in single-walled carbon nanotubes under non-hydrostatic pressures: x-ray and Raman studies Sukanta Karmakar, Surinder M Sharma, P V Teredesai, D V S Muthu, A Govindaraj, S K Sikka and A K Sood Novel properties of 0.4 nm single-walled carbon nanotubes templated in the channels of AlPO4-5 single crystals Z K Tang, N Wang, X X Zhang, J N Wang, C T Chan and Ping Sheng Lattice dynamics and symmetry of double wall carbon nanotubes M Damnjanovic, E Dobardzic, I Milosevic, T Vukovic and B Nikolic Optical characterization of single-walled carbon nanotubes synthesized by catalytic decomposition of alcohol Shigeo Maruyama, Yuhei Miyauchi, Yoichi Murakami and Shohei Chiashi Christian Thomsen, Technische Universität Berlin, Germany Hiromichi Kataura, Tokyo Metropolitan University, Japan

  4. EDITORIAL: Focus on Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    2003-09-01

    .4 nm single-walled carbon nanotubes templated in the channels of AlPO4-5 single crystals Z K Tang, N Wang, X X Zhang, J N Wang, C T Chan and Ping Sheng Lattice dynamics and symmetry of double wall carbon nanotubes M Damnjanovic, E Dobardzic, I Milosevic, T Vukovic and B Nikolic Optical characterization of single-walled carbon nanotubes synthesized by catalytic decomposition of alcohol Shigeo Maruyama, Yuhei Miyauchi, Yoichi Murakami and Shohei Chiashi Christian Thomsen, Technische Universität Berlin, Germany Hiromichi Kataura, Tokyo Metropolitan University, Japan

  5. Electric fields can control the transport of water in carbon nanotubes

    PubMed Central

    Ritos, Konstantinos; Borg, Matthew K.; Mottram, Nigel J.

    2016-01-01

    The properties of water confined inside nanotubes are of considerable scientific and technological interest. We use molecular dynamics to investigate the structure and average orientation of water flowing within a carbon nanotube. We find that water exhibits biaxial paranematic liquid crystal ordering both within the nanotube and close to its ends. This preferred molecular ordering is enhanced when an axial electric field is applied, affecting the water flow rate through the nanotube. A spatially patterned electric field can minimize nanotube entrance effects and significantly increase the flow rate. PMID:26712640

  6. Theoretical study of Ge/ BaTiO 3 Interfaces

    NASA Astrophysics Data System (ADS)

    Fredrickson, Kurt; Demkov, Alexander

    2011-03-01

    It has been shown (McKee et al., Phys. Rev. Lett. 81, 3014 (1998), and R. McKee, et al., Science 293 , 468 (2001)) that perovskite oxides SrTi O3 and BaTi O3 (BTO) can be grown epitaxially on Si and Ge, respectively. It would be interesting to achieve the reverse, i.e. to grow for example, Ge on BTO. It is not clear, however, whether one can achieve wetting of BTO by Ge. Theoretically, the energy of the Ge (001) surface is estimated to be anywhere between 591 and 1700 erg/cm2 and the surface energy of BTO is in the range of 1083-1496 erg/cm2 depending on termination and environment. The missing piece of information is the energy of the Ge/BTO interface. We examine five possible Ge/BTO interface structures and calculate their energies using density functional theory to determine which one has the lowest energy, and whether wetting can be achieved.

  7. Peculiarities of electro-optic properties of the ferroelectric particles-liquid crystal colloids

    NASA Astrophysics Data System (ADS)

    Ibragimov, T. D.; Imamaliyev, A. R.; Bayramov, G. M.

    2016-04-01

    Influence of ferroelectric barium titanate particles on electro-optic properties of the liquid crystal (LC) 4-cyano-4'-pentylbiphenyl (5CB) with positive dielectric anisotropy and the LC mixture (H37) consisting of 4-methoxybezylidene-4'-butylaniline and 4-ethoxybezylidene-4'-butylaniline with negative dielectric anisotropy was investigated. It was shown that a presence of particles (1 wt%) in 5CB and H37 decreased the clearing temperature from 35.2 °C to 32.4°C and from 61.2°C to 60.1°C, respectively. The threshold voltage of the Freedericksz effect became 0.3 V for the BaTiO3-5CB colloid while the beginning of this effect for the pure 5CB was observed at 2.1 V. The threshold voltage of the Freedericksz effect increased from 2.8 V to up 3.1 V at additive of particles in H37. A rise time of the BaTiO3-5CB colloid improved while a decay time worsened in comparison with the pure 5CB at all applied voltages. The inverse trends were observed for the H37 matrix, namely, a rise time worsened and a decay time improved. Among other things, the pecularities of Williams' domain formation (WDF) were also investigated in the colloid based on the H37 matrix. It was established that the WDF voltage decreased, a rise time increased and a decay time decreased in comparison with the pure H37. Experimental results are explained by appearance of local electric fields near the polarized ferroelectric particles at application of external electric field and an existence of the additional obstacles (particles) for movement of ions.

  8. Tuning of dielectric, pyroelectric and ferroelectric properties of 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 ceramic by internal clamping

    NASA Astrophysics Data System (ADS)

    Patel, Satyanarayan; Chauhan, Aditya; Kundu, Swarup; Madhar, Niyaz Ahamad; Ilahi, Bouraoui; Vaish, Rahul; Varma, K. B. R.

    2015-08-01

    This study systematically investigates the phenomenon of internal clamping in ferroelectric materials through the formation of glass-ceramic composites. Lead-free 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 (BNT-BT-ST) bulk ferroelectric ceramic was selected for the course of investigation. 3BaO - 3TiO2 - B2O3 (BTBO) glass was then incorporated systematically to create sintered samples containing 0%, 2%, 4% and 6% glass (by weight). Upon glass induction features like remnant polarization, saturation polarization, hysteresis losses and coercive field could be varied as a function of glass content. Such effects were observed to benefit derived applications like enhanced energy storage density ˜174 kJ/m3 to ˜203 kJ/m3 and pyroelectric coefficient 5.7x10-4 Cm-2K-1 to 6.8x10-4 Cm-2K-1 by incorporation of 4% glass. Additionally, BNT-BT-ST depolarization temperature decreased from 457K to 431K by addition of 4% glass content. Glass incorporation could systematically increases diffuse phase transition and relaxor behavior temperature range from 70 K to 81K and 20K to 34 K, respectively when 6% and 4% glass content is added which indicates addition of glass provides better temperature stability. The most promising feature was observed to be that of dielectric response tuning. It can be also used to control (to an extent) the dielectric behavior of the host ceramic. Dielectric permittivity and losses decreased from 1278 to 705 and 0.109 to 0.107 for 6% glass, at room temperature. However this reduction in dielectric constant and loss increases pyroelectric figures of merit (FOMs) for high voltage responsivity (Fv) high detectivity (Fd) and energy harvesting (Fe) from 0.018 to 0.037 m2C-1, 5.89 to 8.85 μPa-1/2 and 28.71 to 61.55 Jm-3K-2, respectively for 4% added ceramic-glass at room temperature. Such findings can have huge implications in the field of tailoring ferroelectric response for application specific requirements.

  9. General solvothermal approach to synthesize telluride nanotubes for thermoelectric applications.

    PubMed

    Liu, Shuai; Peng, Nan; Bai, Yu; Xu, Huiyan; Ma, D Y; Ma, Fei; Xu, Kewei

    2017-03-27

    One-dimensional tellurides are good candidates for thermoelectric applications, but the fabrication of telluride nanotubes is still challenging. To this end, the solvothermal approach is proposed to synthesize Bi2Te3, PbTe, CuxTe and Ag2Te nanotubes. In this scheme, single-crystal Te nanotubes are produced first and then used as the sacrificed template for epitaxial growth of metal telluride. It was demonstrated that polycrystalline telluride nanotubes are produced. Considering Bi2Te3 nanotubes as an example, the pellets are prepared by spark plasma sintering, and the thermoelectric properties are measured. Compared to the nanowire counterpart, the higher-energy barrier to electrons at the grain boundaries (GBs) leads to an optimized power factor of 1.04 mW m(-1) K(-2) at 373 K in the nanotube samples. Furthermore, the thermal conductivity of nanotubes is in the range of 0.503-0.617 W m(-1) K(-1), which is much smaller than that of the nanowires. The ultralow thermal conductivity could be attributed to both the higher potential barrier of GBs and the additional scattering of phonons at the side walls of the nanotubes. In all, a ZT value of 0.74 was obtained at 373 K, which is much higher than that of nanowires. This synthesis route is ready to be extended to other telluride nanotubes.

  10. Gallium-assisted growth of flute-like MgO nanotubes, Ga2O3-filled MgO nanotubes, and MgO/Ga2O3 co-axial nanotubes.

    PubMed

    Jie, Jiansheng; Wu, Chunyan; Yu, Yongqiang; Wang, Li; Hu, Zhizhong

    2009-02-18

    Flute-like MgO nanotubes were successfully synthesized via a simple thermal evaporation method by using Mg(3)N(2) and Ga(2)O(3) as the source materials. The nanotubes are single-crystal cubic MgO, and have [100] orientation. In contrast to conventional nanotubes with intact walls, the flute-like MgO nanotubes possess a unique porous structure. On the nanotubes there are series of holes aligned along the nanotube length with approximate equidistance. Ga(2)O(3)-filled MgO nanotubes and MgO/Ga(2)O(3) co-axial nanotubes were also found in the product. Further investigation confirms that the inner beta-Ga(2)O(3) has an epitaxial growth relation with the outer MgO nanotube due to their perfect lattice matching. A gallium-assisted growth mechanism was proposed to interpret the growth of the flute-like MgO nanotubes. The thermal expansion and evaporation of the filled liquid gallium in MgO nanotubes are likely responsible for the formation of the hole structures on the side walls.

  11. Analog switching in the nanocolloids of ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Kumar, Pradeep; Kishore, Avinash; Sinha, Aloka

    2016-06-01

    Nanoparticle (NP) dispersion in liquid crystals (LCs) results in significant changes in the physical properties of the existing LC mixtures. Two ferroelectric liquid crystals (FLCs), 5 F6T and 6 F6T , have been studied for analog switching. The 5 F6T sample is doped with titanium dioxide (T i O2) NPs of two different concentrations of the same average particle size and another FLC 6 F6T is systematically doped with barium titanate (B a T i O3) NPs of two different average particle sizes at the same concentration. The frequency and temperature dependence of the coercive voltage of FLC nanocolloids has been studied. The V-shaped switching was observed in the case of nano-doped FLCs. The value of inversion frequency for the 5 F6T +1.0 wt.% TiO2 doped sample is 30 Hz while it is 24 Hz for the 6 F6T +0.5 wt.% BaTiO3 (particle size 5-10 nm) doped sample. The conductivity measurements show that the conductivity of doped samples is higher than the conductivity of their parental FLCs and can be considered the main reason for the V-shaped switching in the FLC nanocolloids, which was initially absent in their parental FLCs.

  12. Carbon nanotube nanoelectrode arrays

    DOEpatents

    Ren, Zhifeng; Lin, Yuehe; Yantasee, Wassana; Liu, Guodong; Lu, Fang; Tu, Yi

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  13. Self-organized highly ordered TiO{sub 2} nanotubes in organic aqueous system

    SciTech Connect

    Wan Jun; Yan Xia; Ding Junjie; Wang Meng; Hu Kongcheng

    2009-12-15

    A simple method to achieve self-organized, freestanding TiO{sub 2} nanotube array was constructed, free of corrosive etching process which was traditionally employed to separate TiO{sub 2} nanotubes from the metallic Ti substrate. The TiO{sub 2} nanotube arrays were constructed through potentiostatic anodization of Ti foil in aqueous electrolyte containing NH{sub 4}F and ethylene glycol. The nanotubes in the array were of 45 {mu}m lengths and 100 nm average pore diameters. The effect of NH{sub 4}F concentration on the length of the self-organized nanotube arrays was investigated. Electrochemical and spectroscopic measurements showed that the as-prepared nanotubes possessed large surface areas, good uniformity, and were ready for enzyme immobilization. The as-prepared nanotube arrays were amorphous, but crystallized with annealing at elevated temperatures, as demonstrated by X-ray diffraction (XRD).

  14. Functionalization of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Korneva, Guzeliya

    Carbon nanotubes have unique properties that make them attractive for different engineering applications. However, because of their chemical inertness, carbon nanotubes have to be functionalized in order to acquire additional physico-chemical properties. Large multiwalled carbon nanotubes are different from fullerenes and singlewalled nanotubes because the stresses in their walls are almost relaxed while most chemical methods for fullerene functionalization exploit this effect of stressed bonds. The objective of this work is to develop new methods for functionalization of multiwalled carbon nanotubes. This work is dedicated to study two functionalization methods. The first deals with physico-chemical functionalization by filling the nanotube interior with colloidal suspensions. Irreversible adsorption of functional nanoparticles on the nanotube wall leads to the nanotube functionalization. The second method is purely chemical functionalization, which uses the reaction of cyclopropanation to break pi-bonds in the benzene rings of the nanotubes with formation of new σ-bonds with deprotonated malonate. This so-called Bingel reaction has been used in fullerene chemistry and in this work was applied for the first time to functionalize multiwalled carbon nanotubes. While capillary filling of carbon nanotubes was known long ago, the research community was skeptical about possibility of engulfing nanoparticles into nanotubes by capillary forces. We developed and implemented capillary method to fill nanotubes with different nanoparticles. Using this method, magnetic carbon nanotubes were produced for the first time. Synthesized nanotubes have very high magnetic moment and allow to manipulate them by magnetic field. These magnetic nanotubes have been successfully used in fabrication of carbon nanotube-tipped pipettes for biological probes. The Bingel reaction was studied on three sets of multiwalled carbon nanotubes with diameters: 20nm, 100nm, and 300nm. To estimate the

  15. Structure of boron nitride nanotubes

    SciTech Connect

    Buranova, Yu. S. Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

    2015-01-15

    The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

  16. Structure of boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Buranova, Yu. S.; Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

    2015-01-01

    The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

  17. Nonequilibrium statistical mechanics of nanotube nucleation

    NASA Astrophysics Data System (ADS)

    Artyukhov, Vasilii I.; Yakobson, Boris I.

    A key problem that advanced carbon nanotube applications face is the difficulty of producing pure single-helicity samples. As the elementary processes of nanotube growth are difficult to observe in situ, theoretical understanding of the process is especially important. Direct molecular dynamics simulations offer limited insight due to computational intractability of space- and time-scales involved. We formulated a theory that explains a class of helicity-selective growth experiments, based on classical nucleation theory and crystal growth kinetics.1 However, a general theory of nanotube growth must also include fast irreversible growth beyond the classical near-equilibrium assumption. Here we construct a coarse-grained model allowing us to rigorously investigate the statistical mechanics of nanotube nucleation and trace how helicity emerges from the global nucleation trajectory ensemble. Importantly, our model can handle the whole range of conditions from perfect reversibility driven by energetics to perfect irreversibility driven by configurational entropy of nanotube caps and edges. Our theory generalizes earlier models in a large advance towards ultimate understanding of helicity-selective synthesis. 1 V.I. Artyukhov, E.S. Penev, and B.I. Yakobson, Nat. Commun. 5, 4892 (2014)

  18. High frequency nanotube oscillator

    DOEpatents

    Peng, Haibing [Houston, TX; Zettl, Alexander K [Kensington, TX

    2012-02-21

    A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.

  19. Structure and electronic properties of the double-wall nanotubes constructed from SiO2 nanotubes encapsulated inside zigzag carbon nanotubes.

    PubMed

    Qiao, Weiye; Bai, Hongcun; Zhu, Ying; Huang, Yuanhe

    2012-05-09

    This paper presents ab initio self-consistent field crystal orbital calculations on the structures, stabilities, elastic and electronic properties of the double-wall nanotubes made of SiO(2) nanotubes encapsulated inside zigzag carbon nanotubes based on density functional theory. It is found that formation of the combined systems is energetically favorable when the nearest distance between the two constituents is in the area of the van der Waals effect. The obtained band structures show that all the combined systems are semiconductors with nonzero energy gaps. Based on the deformation potential theory and effective mass approximation, the mobilities of charge carriers are calculated to be in the range of 10(2)-10(4) cm(2) V(-1) s(-1), the same order of magnitude as those of the corresponding zigzag carbon nanotubes. The Young's moduli are also calculated for the combined systems.

  20. Thermal Conductivity of GaN Nanotubes Simulated by Nonequilibrium Molecular Dynamics

    SciTech Connect

    Wang, Zhiguo; Gao, Fei; Crocombette, J.-P.; Zu, Xiaotao; Yang, Li; Weber, William J.

    2007-04-15

    Thermal conductivity of GaN nanotubes along the tube axis is investigated over the temperature range of 600K-2300K using homogeneous nonequilibrium molecular dynamics. In general, the thermal conductivity of nanotubes is smaller than that for the bulk GaN single crystal. The thermal conductivity is also found to decrease with temperature and increase with increasing wall thickness of the nanotubes. The change of phonon spectrum and surface inelastic scattering may account for the reduction of thermal conductivity in the nanotubes, while thermal softening and high frequency phonon interactions at high temperatures may provide an explanation for its decrease with increasing temperature.

  1. One-dimensional carbon nanotube@barium titanate@polyaniline multiheterostructures for microwave absorbing application.

    PubMed

    Ni, Qing-Qing; Zhu, Yao-Feng; Yu, Lu-Jun; Fu, Ya-Qin

    2015-01-01

    Multiple-phase nanocomposites filled with carbon nanotubes (CNTs) have been developed for their significant potential in microwave attenuation. The introduction of other phases onto the CNTs to achieve CNT-based heterostructures has been proposed to obtain absorbing materials with enhanced microwave absorption properties and broadband frequency due to their different loss mechanisms. The existence of polyaniline (PANI) as a coating with controllable electrical conductivity can lead to well-matched impedance. In this work, a one-dimensional CNT@BaTiO3@PANI heterostructure composite was fabricated. The fabrication processes involved coating of an acid-modified CNT with BaTiO3 (CNT@BaTiO3) through a sol-gel technique followed by combustion and the formation of CNT@BaTiO3@PANI nanohybrids by in situ polymerization of an aniline monomer in the presence of CNT@BaTiO3, using ammonium persulfate as an oxidant and HCl as a dopant. The as-synthesized CNT@BaTiO3@PANI composites with heterostructures were confirmed by various morphological and structural characterization techniques, as well as conductivity and microwave absorption properties. The measured electromagnetic parameters showed that the CNT@BaTiO3@PANI composites exhibited excellent microwave absorption properties. The minimum reflection loss of the CNT@BaTiO3@PANI composites with 20 wt % loadings in paraffin wax reached -28.9 dB (approximately 99.87% absorption) at 10.7 GHz with a thickness of 3 mm, and a frequency bandwidth less than -20 dB was achieved from 10 to 15 GHz. This work demonstrated that the CNT@BaTiO3@PANI heterostructure composite can be potentially useful in electromagnetic stealth materials, sensors, and electronic devices.

  2. One-dimensional carbon nanotube@barium titanate@polyaniline multiheterostructures for microwave absorbing application

    NASA Astrophysics Data System (ADS)

    Ni, Qing-Qing; Zhu, Yao-Feng; Yu, Lu-Jun; Fu, Ya-Qin

    2015-04-01

    Multiple-phase nanocomposites filled with carbon nanotubes (CNTs) have been developed for their significant potential in microwave attenuation. The introduction of other phases onto the CNTs to achieve CNT-based heterostructures has been proposed to obtain absorbing materials with enhanced microwave absorption properties and broadband frequency due to their different loss mechanisms. The existence of polyaniline (PANI) as a coating with controllable electrical conductivity can lead to well-matched impedance. In this work, a one-dimensional CNT@BaTiO3@PANI heterostructure composite was fabricated. The fabrication processes involved coating of an acid-modified CNT with BaTiO3 (CNT@BaTiO3) through a sol-gel technique followed by combustion and the formation of CNT@BaTiO3@PANI nanohybrids by in situ polymerization of an aniline monomer in the presence of CNT@BaTiO3, using ammonium persulfate as an oxidant and HCl as a dopant. The as-synthesized CNT@BaTiO3@PANI composites with heterostructures were confirmed by various morphological and structural characterization techniques, as well as conductivity and microwave absorption properties. The measured electromagnetic parameters showed that the CNT@BaTiO3@PANI composites exhibited excellent microwave absorption properties. The minimum reflection loss of the CNT@BaTiO3@PANI composites with 20 wt % loadings in paraffin wax reached -28.9 dB (approximately 99.87% absorption) at 10.7 GHz with a thickness of 3 mm, and a frequency bandwidth less than -20 dB was achieved from 10 to 15 GHz. This work demonstrated that the CNT@BaTiO3@PANI heterostructure composite can be potentially useful in electromagnetic stealth materials, sensors, and electronic devices.

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

    PubMed

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

    2011-01-01

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

  4. Scalability of carbon-nanotube-based thin film transistors for flexible electronic devices manufactured using an all roll-to-roll gravure printing system

    PubMed Central

    Koo, Hyunmo; Lee, Wookyu; Choi, Younchang; Sun, Junfeng; Bak, Jina; Noh, Jinsoo; Subramanian, Vivek; Azuma, Yasuo; Majima, Yutaka; Cho, Gyoujin

    2015-01-01

    To demonstrate that roll-to-roll (R2R) gravure printing is a suitable advanced manufacturing method for flexible thin film transistor (TFT)-based electronic circuits, three different nanomaterial-based inks (silver nanoparticles, BaTiO3 nanoparticles and single-walled carbon nanotubes (SWNTs)) were selected and optimized to enable the realization of fully printed SWNT-based TFTs (SWNT-TFTs) on 150-m-long rolls of 0.25-m-wide poly(ethylene terephthalate) (PET). SWNT-TFTs with 5 different channel lengths, namely, 30, 80, 130, 180, and 230 μm, were fabricated using a printing speed of 8 m/min. These SWNT-TFTs were characterized, and the obtained electrical parameters were related to major mechanical factors such as web tension, registration accuracy, impression roll pressure and printing speed to determine whether these mechanical factors were the sources of the observed device-to-device variations. By utilizing the electrical parameters from the SWNT-TFTs, a Monte Carlo simulation for a 1-bit adder circuit, as a reference, was conducted to demonstrate that functional circuits with reasonable complexity can indeed be manufactured using R2R gravure printing. The simulation results suggest that circuits with complexity, similar to the full adder circuit, can be printed with a 76% circuit yield if threshold voltage (Vth) variations of less than 30% can be maintained. PMID:26411839

  5. Formation of single crystalline ZnO nanotubes without catalysts and templates

    SciTech Connect

    Ivanov, Ilia N; Geohegan, David B

    2007-01-01

    Oxide and nitride nanotubes have gained attention for their large surface areas, wide energy band gaps, and hydrophilic natures for various innovative applications. These nanotubes were either grown by templates or multistep processes with uncontrollable crystallinity. Here the authors show that single crystal ZnO nanotubes can be directly grown on planar substrates without using catalysts and templates. These results are guided by the theory of nucleation and the vapor-solid crystal growth mechanism, which is applicable for transforming other nanowires or nanorods into nanotubular structures.

  6. Deformation behavior of titanate nanotubes subjected to high pressure

    NASA Astrophysics Data System (ADS)

    Ojeda-Galván, H. J.; Rodríguez, A. G.; Santos-López, I. A.; Mendoza-Cruz, R.; Yacamán, M. J.; Handy, B. E.

    2017-01-01

    Nano-sized titania (anatase) and sodium and potassium titanate nanotubes were studied via in situ Raman spectroscopy at hydrostatic pressures up to 6 GPa. Analysis by scanning electron microscopy shows a uniform dispersion of sodium and potassium cations in the nanotubes. The effect of the pressure was observed by significant shifts in the Raman band structure of nano-sized anatase crystals and nanotube titanate. In nano-particulate anatase, the phonon frequencies (143, 395, 517, and 639 cm-1) increase linearly with pressure. In contrast, the upward frequency shifts in the sodium titanate nanotubes (NaTNT) and potassium-modified nanotubes (NaTNT+K) occur in a stepwise fashion. These stepwise changes occur in the nanotube samples between 2 and 4 GPa (ambient pressure phonon bands in NaTNT at 274, 444, 650, and 906 cm-1) and between 4.5 and 5.5 GPa, (phonons 273 cm-1 and 436 cm-1 in NaTNT+K at an ambient pressure). Post-pressure high-resolution transmission electron microscopy analysis shows evidence of nanotube distortions and a 5% contraction in the interlaminar spacing of both NaTNT and NaTNT+K.

  7. Reinforced Carbon Nanotubes.

    DOEpatents

    Ren, Zhifen; Wen, Jian Guo; Lao, Jing Y.; Li, Wenzhi

    2005-06-28

    The present invention relates generally to reinforced carbon nanotubes, and more particularly to reinforced carbon nanotubes having a plurality of microparticulate carbide or oxide materials formed substantially on the surface of such reinforced carbon nanotubes composite materials. In particular, the present invention provides reinforced carbon nanotubes (CNTs) having a plurality of boron carbide nanolumps formed substantially on a surface of the reinforced CNTs that provide a reinforcing effect on CNTs, enabling their use as effective reinforcing fillers for matrix materials to give high-strength composites. The present invention also provides methods for producing such carbide reinforced CNTs.

  8. Gallium nitride nanotube lasers

    DOE PAGES

    Li, Changyi; Liu, Sheng; Hurtado, Antonio; ...

    2015-01-01

    Lasing is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observed characteristics of lasing: a clear threshold, a narrow spectral, and guided emission from the nanotubes. In addition, annular lasing emission from the GaN nanotube is also observed, indicating that cross-sectional shape control can be employed to manipulate the properties of nanolasers. The nanotube lasers could be of interest for optical nanofluidic applications or application benefitting from a hollow beam shape.

  9. Nanomechanics of carbon nanotubes.

    PubMed

    Kis, Andras; Zettl, Alex

    2008-05-13

    Some of the most important potential applications of carbon nanotubes are related to their mechanical properties. Stiff sp2 bonds result in a Young's modulus close to that of diamond, while the relatively weak van der Waals interaction between the graphitic shells acts as a form of lubrication. Previous characterization of the mechanical properties of nanotubes includes a rich variety of experiments involving mechanical deformation of nanotubes using scanning probe microscopes. These results have led to promising prototypes of nanoelectromechanical devices such as high-performance nanomotors, switches and oscillators based on carbon nanotubes.

  10. Growth of horizontally aligned single-walled carbon nanotubes on anisotropically etched silicon substrate

    NASA Astrophysics Data System (ADS)

    Orofeo, Carlo M.; Ago, Hiroki; Ikuta, Tatsuya; Takahasi, Koji; Tsuji, Masaharu

    2010-09-01

    Directional controllability of single-walled carbon nanotubes (SWNTs) is an important issue for future nanoelectronics applications. For direct integration of carbon nanotubes with modern electronics, aligned growth of carbon nanotubes on SiO2/Si is desirable. We developed a new method to horizontally align SWNTs directly on SiO2/Si substrate by creating trenches on Si(100) through anisotropic etching followed by thermal oxidation. The V-shaped trenches highly improved the alignment of SWNTs and the degree of alignment is comparable to the step-templated alignment of carbon nanotubes on crystals. The trenches also improved the density of aligned nanotubes due to the combination of ``trench-guided'' and gas-flow guided alignment. Our new insights on carbon nanotube alignment on SiO2/Si will greatly contribute to future large-scale nanoelectronic applications.Directional controllability of single-walled carbon nanotubes (SWNTs) is an important issue for future nanoelectronics applications. For direct integration of carbon nanotubes with modern electronics, aligned growth of carbon nanotubes on SiO2/Si is desirable. We developed a new method to horizontally align SWNTs directly on SiO2/Si substrate by creating trenches on Si(100) through anisotropic etching followed by thermal oxidation. The V-shaped trenches highly improved the alignment of SWNTs and the degree of alignment is comparable to the step-templated alignment of carbon nanotubes on crystals. The trenches also improved the density of aligned nanotubes due to the combination of ``trench-guided'' and gas-flow guided alignment. Our new insights on carbon nanotube alignment on SiO2/Si will greatly contribute to future large-scale nanoelectronic applications. Electronic supplementary information (ESI) available: SEM images of SWNTs grown under different CVD conditions. See DOI: 10.1039/c0nr00170h

  11. Hemotoxicity of carbon nanotubes.

    PubMed

    Bussy, Cyrill; Methven, Laura; Kostarelos, Kostas

    2013-12-01

    Carbon nanotubes may enter into the bloodstream and interact with blood components indirectly via translocation following unintended exposure or directly after an intended administration for biomedical purposes. Once introduced into systemic circulation, nanotubes will encounter various proteins, biomolecules or cells which have specific roles in the homeostasis of the circulatory system. It is therefore essential to determine whether those interactions will lead to adverse effects or not. Advances in the understanding of how carbon nanotubes interact with blood proteins, the complement system, red blood cells and the hemostatic system are reviewed in this article. While many studies on carbon nanotube health risk assessment and their biomedical applications have appeared in the last few years, reports on the hemocompatibility of these nanomaterials remain surprisingly limited. Yet, defining the hemotoxicological profile is a mandatory step toward the development of clinically-relevant medications or contrast agents based on carbon nanotubes.

  12. Fluidic nanotubes and devices

    DOEpatents

    Yang, Peidong; He, Rongrui; Goldberger, Joshua; Fan, Rong; Wu, Yiying; Li, Deyu; Majumdar, Arun

    2010-01-10

    Fluidic nanotube devices are described in which a hydrophilic, non-carbon nanotube, has its ends fluidly coupled to reservoirs. Source and drain contacts are connected to opposing ends of the nanotube, or within each reservoir near the opening of the nanotube. The passage of molecular species can be sensed by measuring current flow (source-drain, ionic, or combination). The tube interior can be functionalized by joining binding molecules so that different molecular species can be sensed by detecting current changes. The nanotube may be a semiconductor, wherein a tubular transistor is formed. A gate electrode can be attached between source and drain to control current flow and ionic flow. By way of example an electrophoretic array embodiment is described, integrating MEMs switches. A variety of applications are described, such as: nanopores, nanocapillary devices, nanoelectrophoretic, DNA sequence detectors, immunosensors, thermoelectric devices, photonic devices, nanoscale fluidic bioseparators, imaging devices, and so forth.

  13. Fluidic nanotubes and devices

    DOEpatents

    Yang, Peidong; He, Rongrui; Goldberger, Joshua; Fan, Rong; Wu, Yiying; Li, Deyu; Majumdar, Arun

    2008-04-08

    Fluidic nanotube devices are described in which a hydrophilic, non-carbon nanotube, has its ends fluidly coupled to reservoirs. Source and drain contacts are connected to opposing ends of the nanotube, or within each reservoir near the opening of the nanotube. The passage of molecular species can be sensed by measuring current flow (source-drain, ionic, or combination). The tube interior can be functionalized by joining binding molecules so that different molecular species can be sensed by detecting current changes. The nanotube may be a semiconductor, wherein a tubular transistor is formed. A gate electrode can be attached between source and drain to control current flow and ionic flow. By way of example an electrophoretic array embodiment is described, integrating MEMs switches. A variety of applications are described, such as: nanopores, nanocapillary devices, nanoelectrophoretic, DNA sequence detectors, immunosensors, thermoelectric devices, photonic devices, nanoscale fluidic bioseparators, imaging devices, and so forth.

  14. Photonics with multiwall carbon nanotube arrays.

    PubMed

    Lidorikis, Elefterios; Ferrari, Andrea C

    2009-05-26

    We investigate the photonic properties of two-dimensional nanotube arrays for photon energies up to 40 eV and unveil the physics of two distinct applications: deep-UV photonic crystals and total visible absorbers. We find three main regimes: for small intertube spacing of 20-30 nm, we obtain strong Bragg scattering and photonic band gaps in the deep-UV range of 25 approximately 35 eV. For intermediate spacing of 40-100 nm, the photonic bands anticross with the graphite plasmon bands resulting into a complex photonic structure, and a generally reduced Bragg scattering. For large spacing >150 nm, the Bragg gap moves into the visible and decreases due to absorption. This leads to nanotube arrays behaving as total optical absorbers. Our results can guide the design of photonic applications in the visible and deep UV ranges.

  15. Three dimensional carbon-nanotube polymers.

    PubMed

    Zhao, Zhisheng; Xu, Bo; Wang, Li-Min; Zhou, Xiang-Feng; He, Julong; Liu, Zhongyuan; Wang, Hui-Tian; Tian, Yongjun

    2011-09-27

    Eight fascinating sp(2)- and sp(3)-hybridized carbon allotropes have been uncovered using a newly developed ab initio particle-swarm optimization methodology for crystal structure prediction. These crystalline allotropes can be viewed respectively as three-dimensional (3D) polymers of (4,0), (5,0), (7,0), (8,0), (9,0), (3,3), (4,4), and (6,6) carbon nanotubes, termed 3D-(n, 0) or 3D-(n, n) carbons. The ground-state energy calculations show that the carbons all have lower energies than C(60) fullerene, and some are energetically more stable than the van der Waals packing configurations of their nanotube parents. Owing to their unique configurations, they have distinctive electronic properties, high Young's moduli, high tensile strength, ultrahigh hardness, good ductility, and low density, and may be potentially applied to a variety of needs.

  16. Studies on carbon nanotubes and fullerenes under extreme conditions.

    PubMed

    Avasthi, D K; Kumar, Amit; Singhal, Rahul; Tripathi, Ambuj; Misra, D S

    2010-06-01

    Ion beam irradiation of materials can cause defect creation as well as defect annealing depending on the ion beam parameters such as ion fluence and the energy loss of ions in materials. In present review, we report the behaviour of carbon nanotubes under exteme conditions such as laser irradiation and ion irradiation. The reorientation of the crystalline planes in confined single crystal nickel nanorods inside carbon nano tube, induced by heavy ion irradiation, is reported. Axial buckling of nickel nanorods as well as walls of carbon nano tubes in nickel encapsulated carbon nano tubes under swift heavy ion irradiation at high fluence is observed. At high fluence, amorphization of nickel nanorods inside carbon nanotubes is also observed. Axial buckling and amorphization under ion irradiation at high fluence are dependent on the number of walls in carbon nanotubes. High resolution transmission electron microscopy was used to investigate the reorientations, buckling and amorphization of metal filled nanotubes. Synthesis of carbon nanowires by ion irradiation of fullerene and their field emission properties with comparison to that of unirradiated and irradiated carbon nanotubes are reported. An international scenario with future prospects of ion beam studies in carbon nanotube is briefed.

  17. Analytical solutions for elastic binary nanotubes of arbitrary chirality

    NASA Astrophysics Data System (ADS)

    Jiang, Lai; Guo, Wanlin

    2016-12-01

    Analytical solutions for the elastic properties of a variety of binary nanotubes with arbitrary chirality are obtained through the study of systematic molecular mechanics. This molecular mechanics model is first extended to chiral binary nanotubes by introducing an additional out-of-plane inversion term into the so-called stick-spiral model, which results from the polar bonds and the buckling of binary graphitic crystals. The closed-form expressions for the longitudinal and circumferential Young's modulus and Poisson's ratio of chiral binary nanotubes are derived as functions of the tube diameter. The obtained inversion force constants are negative for all types of binary nanotubes, and the predicted tube stiffness is lower than that by the former stick-spiral model without consideration of the inversion term, reflecting the softening effect of the buckling on the elastic properties of binary nanotubes. The obtained properties are shown to be comparable to available density functional theory calculated results and to be chirality and size sensitive. The developed model and explicit solutions provide a systematic understanding of the mechanical performance of binary nanotubes consisting of III-V and II-VI group elements.

  18. Carbon nanotube solar cells.

    PubMed

    Klinger, Colin; Patel, Yogeshwari; Postma, Henk W Ch

    2012-01-01

    We present proof-of-concept all-carbon solar cells. They are made of a photoactive side of predominantly semiconducting nanotubes for photoconversion and a counter electrode made of a natural mixture of carbon nanotubes or graphite, connected by a liquid electrolyte through a redox reaction. The cells do not require rare source materials such as In or Pt, nor high-grade semiconductor processing equipment, do not rely on dye for photoconversion and therefore do not bleach, and are easy to fabricate using a spray-paint technique. We observe that cells with a lower concentration of carbon nanotubes on the active semiconducting electrode perform better than cells with a higher concentration of nanotubes. This effect is contrary to the expectation that a larger number of nanotubes would lead to more photoconversion and therefore more power generation. We attribute this to the presence of metallic nanotubes that provide a short for photo-excited electrons, bypassing the load. We demonstrate optimization strategies that improve cell efficiency by orders of magnitude. Once it is possible to make semiconducting-only carbon nanotube films, that may provide the greatest efficiency improvement.

  19. Tunable multiwalled nanotube resonator

    DOEpatents

    Jensen, Kenneth J; Girit, Caglar O; Mickelson, William E; Zettl, Alexander K; Grossman, Jeffrey C

    2013-11-05

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  20. Tunable multiwalled nanotube resonator

    DOEpatents

    Zettl, Alex K [Kensington, CA; Jensen, Kenneth J [Berkeley, CA; Girit, Caglar [Albany, CA; Mickelson, William E [San Francisco, CA; Grossman, Jeffrey C [Berkeley, CA

    2011-03-29

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  1. Nanotube resonator devices

    DOEpatents

    Jensen, Kenneth J; Zettl, Alexander K; Weldon, Jeffrey A

    2014-05-06

    A fully-functional radio receiver fabricated from a single nanotube is being disclosed. Simultaneously, a single nanotube can perform the functions of all major components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A DC voltage source, as supplied by a battery, can power the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, successful music and voice reception has been demonstrated. Also disclosed are a radio transmitter and a mass sensor using a nanotube resonator device.

  2. Non-equilibrium Dynamics of DNA Nanotubes

    NASA Astrophysics Data System (ADS)

    Hariadi, Rizal Fajar

    Can the fundamental processes that underlie molecular biology be understood and simulated by DNA nanotechnology? The early development of DNA nanotechnology by Ned Seeman was driven by the desire to find a solution to the protein crystallization problem. Much of the later development of the field was also driven by envisioned applications in computing and nanofabrication. While the DNA nanotechnology community has assembled a versatile tool kit with which DNA nanostructures of considerable complexity can be assembled, the application of this tool kit to other areas of science and technology is still in its infancy. This dissertation reports on the construction of non-equilibrium DNA nanotube dynamic to probe molecular processes in the areas of hydrodynamics and cytoskeletal behavior. As the first example, we used DNA nanotubes as a molecular probe for elongational flow measurement in different micro-scale flow settings. The hydrodynamic flow in the vicinity of simple geometrical objects, such as a rigid DNA nanotube, is amenable to rigorous theoretical investigation. We measured the distribution of elongational flows produced in progressively more complex settings, ranging from the vicinity of an orifice in a microfluidic chamber to within a bursting bubble of Pacific ocean water. This information can be used to constrain theories on the origin of life in which replication involves a hydrodynamically driven fission process, such as the coacervate fission proposed by Oparin. A second theme of this dissertation is the bottom-up construction of a de novo artificial cytoskeleton with DNA nanotubes. The work reported here encompasses structural, locomotion, and control aspects of non-equilibrium cytoskeletal behavior. We first measured the kinetic parameters of DNA nanotube assembly and tested the accuracy of the existing polymerization models in the literature. Toward recapitulation of non-equilibrium cytoskeletal dynamics, we coupled the polymerization of DNA

  3. Inkjet Printing of Carbon Nanotubes

    PubMed Central

    Tortorich, Ryan P.; Choi, Jin-Woo

    2013-01-01

    In an attempt to give a brief introduction to carbon nanotube inkjet printing, this review paper discusses the issues that come along with preparing and printing carbon nanotube ink. Carbon nanotube inkjet printing is relatively new, but it has great potential for broad applications in flexible and printable electronics, transparent electrodes, electronic sensors, and so on due to its low cost and the extraordinary properties of carbon nanotubes. In addition to the formulation of carbon nanotube ink and its printing technologies, recent progress and achievements of carbon nanotube inkjet printing are reviewed in detail with brief discussion on the future outlook of the technology.

  4. Effective Growth of Boron Nitride Nanotubes by Thermal-CVD

    NASA Astrophysics Data System (ADS)

    Lee, Chee Huei; Xie, Ming; Meyers, Derek; Wang, Jiesheng; Khin Yap, Yoke

    2009-03-01

    The synthesis of boron nitride nanotubes (BNNTs) are challenging as compared to the growth of carbon nanotubes (CNTs). Most of reported techniques required unique setup and temperatures >1300 ^oC. Here we show that clean and long multiwalled BNNTs can be grown by simple catalytic thermal CVD. This was obtained by a growth vapor trapping approach inspired by the whisker nucleation theory. Based on our new findings, we have achieved patterned growth of BNNTs at desired locations. High resolution TEM shows that these BNNTs are highly crystallized. Besides, the tangential vibrational mode predicted by theory was detected in our BNNTs. This vibration mode could be the fingerprint for BNNTs with high crystallinity.

  5. Observation of the urbach tail in the effective density of States in carbon nanotubes.

    PubMed

    Jones, David A; Lee, Ji Ung

    2011-10-12

    While a number of studies have reported evidence of localized states in carbon nanotube devices, the density distribution of these states has not been reported until now. By measuring trap emission current in carbon nanotube field-effect transistors, we observe a prominent exponential tail in the density of states near the band edge. Since continuous distributions of localized states are typically associated with highly disordered systems, this observation was quite unexpected in carbon nanotubes, which are nearly ideal crystals. This continuum of localized states may explain a variety of phenomena in carbon nanotube systems, including the nearly universal lack of n-type conduction in strongly gated field-effect transistors. While our focus is on carbon nanotubes, this phenomenon may be ubiquitous to low-dimensional semiconductors in nonvacated environments.

  6. Quantum Chemical Study of Water Adsorption on the Surfaces of SrTiO3 Nanotubes.

    PubMed

    Bandura, Andrei V; Kuruch, Dmitry D; Evarestov, Robert A

    2015-07-20

    We have studied the adsorption of water molecules on the inner and outer surfaces of nanotubes generated by rolling (001) layers of SrTiO3 cubic crystals. The stability and the atomic and electronic structures of the adsorbed layers are determined by using hybrid density functional theory. The absorption energy and the preferred adsorbate structure are essentially governed by the nature of the surface of the nanotube. Dissociative adsorption prevails on the outer nanotube surfaces. The stability of the adsorbed layers on the inner surfaces is related to the possibility of the formation of hydrogen bonds between water molecules and surface oxygen atoms, and depends on the surface curvature. The presence of water molecules on the inner surface of the nanotubes leads to an increase of the electronic band gap. Externally TiO2 -terminated nanotubes could be used for the photocatalytic decomposition of water by ultraviolet radiation.

  7. Nanopattern formation using localized plasma for growth of single-standing carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Javadi, Mohammad; Abdi, Yaser

    2017-01-01

    We report a novel method for formation of self-organized single-standing carbon nanotubes by customizing a plasma-based process. The growth of carbon nanotubes by plasma-enhanced chemical vapor deposition provides suitable grounds to utilize plasma-solid interactions for nanopatterning. The bulk plasma is utilized to fabricate carbon nanotubes on the prepatterned Ni catalyst which in turn can confine the plasma to the growth region. The plasma localization leads to a dielectrophoretic force exerted on Ni atoms and can be engineered in order to grow a specific pattern of self-organized single-standing carbon nanotubes. Numerical simulations based on the plasma localization and dielectrophoretic force confirmed the experimental results. This method provides a simple and cost-effective approach to obtain nanopatterned arrays of carbon nanotubes which can be used for fabrication of photonic and phononic crystals, self-gated field emission-based transistors and displays.

  8. Polymer composites containing nanotubes

    NASA Technical Reports Server (NTRS)

    Bley, Richard A. (Inventor)

    2008-01-01

    The present invention relates to polymer composite materials containing carbon nanotubes, particularly to those containing singled-walled nanotubes. The invention provides a polymer composite comprising one or more base polymers, one or more functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers and carbon nanotubes. The invention also relates to functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers, particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having side chain functionalization, and more particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having olefin side chains and alkyl epoxy side chains. The invention further relates to methods of making polymer composites comprising carbon nanotubes.

  9. Transport in Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Datta, S.; Xue, Yong-Qinag; Anantram, M. P.; Saini, Subhash (Technical Monitor)

    1999-01-01

    This presentation discusses coupling between carbon nanotubes (CNT), simple metals (FEG) and a graphene sheet. The graphene sheet did not couple well with FEG, but the combination of a graphene strip and CNT did couple well with most simple metals.

  10. Carbon nanotubes: Fibrillar pharmacology

    NASA Astrophysics Data System (ADS)

    Kostarelos, Kostas

    2010-10-01

    The mechanisms by which chemically functionalized carbon nanotubes flow in blood and are excreted through the kidneys illustrate the unconventional behaviour of these fibrillar nanostructures, and the opportunities they offer as components for the design of advanced delivery vehicles.

  11. Boron Nitride Nanotubes

    NASA Technical Reports Server (NTRS)

    Smith, Michael W. (Inventor); Jordan, Kevin (Inventor); Park, Cheol (Inventor)

    2012-01-01

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  12. Boron nitride nanotubes

    DOEpatents

    Smith, Michael W [Newport News, VA; Jordan, Kevin [Newport News, VA; Park, Cheol [Yorktown, VA

    2012-06-06

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  13. Carbon nanotube filters

    NASA Astrophysics Data System (ADS)

    Srivastava, A.; Srivastava, O. N.; Talapatra, S.; Vajtai, R.; Ajayan, P. M.

    2004-09-01

    Over the past decade of nanotube research, a variety of organized nanotube architectures have been fabricated using chemical vapour deposition. The idea of using nanotube structures in separation technology has been proposed, but building macroscopic structures that have controlled geometric shapes, density and dimensions for specific applications still remains a challenge. Here we report the fabrication of freestanding monolithic uniform macroscopic hollow cylinders having radially aligned carbon nanotube walls, with diameters and lengths up to several centimetres. These cylindrical membranes are used as filters to demonstrate their utility in two important settings: the elimination of multiple components of heavy hydrocarbons from petroleum-a crucial step in post-distillation of crude oil-with a single-step filtering process, and the filtration of bacterial contaminants such as Escherichia coli or the nanometre-sized poliovirus (~25 nm) from water. These macro filters can be cleaned for repeated filtration through ultrasonication and autoclaving. The exceptional thermal and mechanical stability of nanotubes, and the high surface area, ease and cost-effective fabrication of the nanotube membranes may allow them to compete with ceramic- and polymer-based separation membranes used commercially.

  14. Carbon nanotube filters.

    PubMed

    Srivastava, A; Srivastava, O N; Talapatra, S; Vajtai, R; Ajayan, P M

    2004-09-01

    Over the past decade of nanotube research, a variety of organized nanotube architectures have been fabricated using chemical vapour deposition. The idea of using nanotube structures in separation technology has been proposed, but building macroscopic structures that have controlled geometric shapes, density and dimensions for specific applications still remains a challenge. Here we report the fabrication of freestanding monolithic uniform macroscopic hollow cylinders having radially aligned carbon nanotube walls, with diameters and lengths up to several centimetres. These cylindrical membranes are used as filters to demonstrate their utility in two important settings: the elimination of multiple components of heavy hydrocarbons from petroleum-a crucial step in post-distillation of crude oil-with a single-step filtering process, and the filtration of bacterial contaminants such as Escherichia coli or the nanometre-sized poliovirus ( approximately 25 nm) from water. These macro filters can be cleaned for repeated filtration through ultrasonication and autoclaving. The exceptional thermal and mechanical stability of nanotubes, and the high surface area, ease and cost-effective fabrication of the nanotube membranes may allow them to compete with ceramic- and polymer-based separation membranes used commercially.

  15. All-fiber nonlinearity- and dispersion-managed dissipative soliton nanotube mode-locked laser

    SciTech Connect

    Zhang, Z.; Popa, D. Wittwer, V. J.; Milana, S.; Hasan, T.; Jiang, Z.; Ferrari, A. C.; Ilday, F. Ö.

    2015-12-14

    We report dissipative soliton generation from an Yb-doped all-fiber nonlinearity- and dispersion-managed nanotube mode-locked laser. A simple all-fiber ring cavity exploits a photonic crystal fiber for both nonlinearity enhancement and dispersion compensation. The laser generates stable dissipative solitons with large linear chirp in the net normal dispersion regime. Pulses that are 8.7 ps long are externally compressed to 118 fs, outperforming current nanotube-based Yb-doped fiber laser designs.

  16. All-fiber nonlinearity- and dispersion-managed dissipative soliton nanotube mode-locked laser

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Popa, D.; Wittwer, V. J.; Milana, S.; Hasan, T.; Jiang, Z.; Ferrari, A. C.; Ilday, F. Ö.

    2015-12-01

    We report dissipative soliton generation from an Yb-doped all-fiber nonlinearity- and dispersion-managed nanotube mode-locked laser. A simple all-fiber ring cavity exploits a photonic crystal fiber for both nonlinearity enhancement and dispersion compensation. The laser generates stable dissipative solitons with large linear chirp in the net normal dispersion regime. Pulses that are 8.7 ps long are externally compressed to 118 fs, outperforming current nanotube-based Yb-doped fiber laser designs.

  17. TiS2 and ZrS2 single- and double-wall nanotubes: first-principles study.

    PubMed

    Bandura, Andrei V; Evarestov, Robert A

    2014-02-15

    Hybrid density functional theory has been applied for investigations of the electronic and atomic structure of bulk phases, nanolayers, and nanotubes based on titanium and zirconium disulfides. Calculations have been performed on the basis of the localized atomic functions by means of the CRYSTAL-2009 computer code. The full optimization of all atomic positions in the regarded systems has been made to study the atomic relaxation and to determine the most favorable structures. The different layered and isotropic bulk phases have been considered as the possible precursors of the nanotubes. Calculations on single-walled TiS2 and ZrS2 nanotubes confirmed that the nanotubes obtained by rolling up the hexagonal crystalline layers with octahedral 1T morphology are the most stable. The strain energy of TiS2 and ZrS2 nanotubes is small, does not depend on the tube chirality, and approximately obeys to D(-2) law (D is nanotube diameter) of the classical elasticity theory. It is greater than the strain energy of the similar TiO2 and ZrO2 nanotubes; however, the formation energy of the disulfide nanotubes is considerably less than the formation energy of the dioxide nanotubes. The distance and interaction energy between the single-wall components of the double-wall nanotubes is proved to be close to the distance and interaction energy between layers in the layered crystals. Analysis of the relaxed nanotube shape using radial coordinate of the metal atoms demonstrates a small but noticeable deviation from completely cylindrical cross-section of the external walls in the armchair-like double-wall nanotubes.

  18. Templated Growth of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Siochik Emilie J. (Inventor)

    2007-01-01

    A method of growing carbon nanotubes uses a synthesized mesoporous si lica template with approximately cylindrical pores being formed there in. The surfaces of the pores are coated with a carbon nanotube precu rsor, and the template with the surfaces of the pores so-coated is th en heated until the carbon nanotube precursor in each pore is convert ed to a carbon nanotube.

  19. Lipid nanotube or nanowire sensor

    DOEpatents

    Noy, Aleksandr; Bakajin, Olgica; Letant, Sonia; Stadermann, Michael; Artyukhin, Alexander B.

    2009-06-09

    A sensor apparatus comprising a nanotube or nanowire, a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer. Also a biosensor apparatus comprising a gate electrode; a source electrode; a drain electrode; a nanotube or nanowire operatively connected to the gate electrode, the source electrode, and the drain electrode; a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer.

  20. Lipid nanotube or nanowire sensor

    DOEpatents

    Noy, Aleksandr; Bakajin, Olgica; Letant, Sonia; Stadermann, Michael; Artyukhin, Alexander B.

    2010-06-29

    A sensor apparatus comprising a nanotube or nanowire, a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer. Also a biosensor apparatus comprising a gate electrode; a source electrode; a drain electrode; a nanotube or nanowire operatively connected to the gate electrode, the source electrode, and the drain electrode; a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer.

  1. Carbon nanotube array based sensor

    DOEpatents

    Lee, Christopher L.; Noy, Aleksandr; Swierkowski, Stephan P.; Fisher, Karl A.; Woods, Bruce W.

    2005-09-20

    A sensor system comprising a first electrode with an array of carbon nanotubes and a second electrode. The first electrode with an array of carbon nanotubes and the second electrode are positioned to produce an air gap between the first electrode with an array of carbon nanotubes and the second electrode. A measuring device is provided for sensing changes in electrical capacitance between the first electrode with an array of carbon nanotubes and the second electrode.

  2. Terahertz Science and Technology of Macroscopically Aligned Carbon Nanotube Films

    NASA Astrophysics Data System (ADS)

    Kono, Junichiro

    One of the outstanding challenges in nanotechnology is how to assemble individual nano-objects into macroscopic architectures while preserving their extraordinary properties. For example, the one-dimensional character of electrons in individual carbon nanotubes leads to extremely anisotropic transport, optical, and magnetic phenomena, but their macroscopic manifestations have been limited. Here, we describe methods for preparing macroscopic films, sheets, and fibers of highly aligned carbon nanotubes and their applications to basic and applied terahertz studies. Sufficiently thick films act as ideal terahertz polarizers, and appropriately doped films operate as polarization-sensitive, flexible, powerless, and ultra-broadband detectors. Together with recently developed chirality enrichment methods, these developments will ultimately allow us to study dynamic conductivities of interacting one-dimensional electrons in macroscopic single crystals of single-chirality single-wall carbon nanotubes.

  3. Transport Through Carbon Nanotube Wires

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Kwak, Dochan (Technical Monitor)

    2001-01-01

    This viewgraph presentation deals with the use of carbon nanotubes as a transport system. Contact, defects, tubular bend, phonons, and mechanical deformations all contribute to reflection within the nanotube wire. Bragg reflection, however, is native to an ideal energy transport system. Transmission resistance depends primarily on the level of energy present. Finally, the details regarding coupling between carbon nanotubes and simple metals are presented.

  4. Indium telluride nanotubes: Solvothermal synthesis, growth mechanism, and properties

    SciTech Connect

    Zhou, Liyan; Yan, Shancheng; Lu, Tao; Shi, Yi; Wang, Jianyu; Yang, Fan

    2014-03-15

    A convenient solvothermal approach was applied for the first time to synthesize In{sub 2}Te{sub 3} nanotubes. The morphology of the resultant nanotubes was studied by scanning electron microscopy and transmission electron microscopy. Nanotubes with a relatively uniform diameter of around 500 nm, tube wall thickness of 50–100 nm, and average length of tens of microns were obtained. X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to study the crystal structures, composition, and optical properties of the products. To understand the growth mechanism of the In{sub 2}Te{sub 3} nanotubes, we studied the influences of temperature, reaction time, and polyvinylpyrrolidone (PVP) and ethylene diamine (EDA) dosages on the final products. Based on the experimental results, a possible growth mechanism of In{sub 2}Te{sub 3} nanotubes was proposed. In this mechanism, TeO{sub 3}{sup −2} is first reduced to allow nucleation. Circumferential edges of these nucleated molecules attract further deposition, and nanotubes finally grow rapidly along the c-axis and relatively slowly along the circumferential direction. The surface area of the products was determined by BET and found to be 137.85 m{sup 2} g{sup −1}. This large surface area indicates that the nanotubes may be suitable for gas sensing and hydrogen storage applications. The nanotubes also showed broad light detection ranging from 300 nm to 1100 nm, which covers the UV–visible–NIR regions. Such excellent optical properties indicate that In{sub 2}Te{sub 3} nanotubes may enable significant advancements in new photodetection and photosensing applications. -- Graphical abstract: A convenient solvothermal approach was applied to synthesize In{sub 2}Te{sub 3} nanotubes, which has not been reported in the literature for our knowledge. Surface area of this material is 137.85 m{sup 2} g{sup −1} from the BET testing, and such a high value makes it probably suitable for gas sensing and

  5. Structural and crystallization behavior of (Ba,Sr)TiO3 borosilicate glasses

    NASA Astrophysics Data System (ADS)

    Yadav, Avadhesh Kumar; Gautam, C. R.; Gautam, Arvind; Mishra, Vijay Kumar

    2013-10-01

    Various glass samples were prepared by melt quench technique in the glass system [(Ba1- x Sr x ) TiO3]-[2SiO2-B2O3]-[K2O] doped with 1 mole% of La2O3. Infrared spectra show the number of absorption peaks with different spliting in the wave number range from 450 to 4000 cm-1. Absorption peaks occurs due to asymetric vibrational streching of borate by relaxation of the bond B-O of trigonal BO3. Raman spectra show the Raman bands due to ring-type metaborate anions, symmetric breathing vibrations BO3 triangles replaced by BO4 tetrahedra, and symmetric breathing vibrations of six-member rings. The differential thermal analysis of a glass sample corresponding to composition x = 0.0 shows crystallization temperature at 847°C and glass transition temperature at 688°C. X-ray diffraction (XRD) pattern of glass ceramic samples shows the major crystalline phase of BaTiO3 whereas pyrochlore phases of barium titanium silicate. Scanning electron micrographs confirm the results of XRD as barium titanate is major crystalline phase along with pyrochlore phase of barium titanium silicate.

  6. An efficient growth of silver and copper nanoparticles on multiwalled carbon nanotube with enhanced antimicrobial activity.

    PubMed

    Mohan, Raja; Shanmugharaj, A M; Sung Hun, Ryu

    2011-01-01

    Transition metal nanoparticles (NPs) such as silver (Ag) and copper (Cu) have been grafted onto carbon nanotube surface through wet chemical approach leading to the development of densely packed NP decorated carbon nanotubes. Chemically active surface and high-temperature stability are the basic attributes to use carbon nanotubes as the template for the growth of NPs. Ag NP-grafted carbon nanotubes (Ag-MWCNT) are prepared by complexing Ag ion with acid functionalized carbon nanotubes followed by the reduction method. Alternatively, Cu-grafted carbon nanotubes (Cu-MWCNT) are prepared by simple chemical reduction method. X-ray diffraction results reveal that the Ag or Cu NPs formed on the surface of carbon nanotubes are determined to be face centered cubic crystals. The morphology and chemical structure of NP-grafted carbon nanotubes are investigated using transmission electron spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The antimicrobial properties of acid-treated MWCNT (MWCNT-COOH), Ag-MWCNT, and Cu-MWCNT are investigated against gram negative Escherichia coli bacteria. Ag-MWCNT and Cu-MWCNT (97% kill vs. 75% kill), whereas MWCNT-COOH only killed 20% of this bacteria. Possible mechanisms are proposed to explain the higher antimicrobial activity by NP-coated MWCNT. These findings suggest that Ag-MWCNT and Cu-MWCNT may be used as effective antimicrobial materials that find applications in biomedical devices and antibacterial controlling system.

  7. Enhanced electroactive and mechanical properties of poly(vinylidene fluoride) by controlling crystallization and interfacial interactions with low loading polydopamine coated BaTiO₃.

    PubMed

    Jia, Nan; Xing, Qian; Liu, Xu; Sun, Jing; Xia, Guangmei; Huang, Wei; Song, Rui

    2015-09-01

    Poly(vinylidene fluoride) (PVDF) is a semi-crystalline polymer and the polar β-phase of PVDF shows superb electroactive properties. In order to enhance the β-phase of PVDF, extreme low content of BaTiO3 nanoparticles (BT-NPs) coated with polydopamine (Pdop) were incorporated into PVDF matrix by solution casting. The β-phase of the resulting PVDF nanocomposites film was dramatically increased and the d33 value reached 34.3±0.4 pCN(-1). It is found that the Pdop layer could improve the dispersibility and stability of the BT NPs in solution and endow the BT NPs good dispersity in the PVDF matrix. Moreover, the interfacial interaction between PVDF chains and the surface of BT-Pdop nanoparticles (BT-Pdop NPs) were revealed, in which the CF2 groups on PVDF could interact with the electron-rich plane of aromatic ring of Pdop moiety. This interaction, led to the increase of the crystallization activation energy as derived from the DSC nonisothermal crystallization measurement. The α-β crystal transformation, organization of interfacial interactions as well as the prevention of agglomeration of BT-NPs confer the improvement of mechanical and thermal properties of PVDF, such as toughness, tensile strength, elongation at break, and thermal conductivity.

  8. Inorganic nanotube nanofluidics

    NASA Astrophysics Data System (ADS)

    Fan, Rong

    The ability to manipulate charge carriers (electrons and holes) in metal-oxide semiconductor field effect transistors (MOSFETs) has revolutionized how information is processed and stored, and created the modern digital age. Introducing direct field effect modulation in fluidic systems would enable the manipulation of ionic and molecular species at a similar level and even logic operation. Due to strong Debye screening in aqueous solutions, field effect manipulation of ion transport arises only in systems whose dimensions are comparable to the critical Debye Length, i.e. in nanofluidic systems. Nanofluidics has already been explored in various cases, e.g. biological channel proteins and artificial solid-state nanopores. All these two terminal systems usually transport the ions the same way as passive electron conduction in a resistor. My work is aimed at developing nanotube nanofluidic units with a third terminal that can electrically turn on/off and control ion and biomolecule transport. Moreover, the systematic study on "doping" and transient phenomena can provide rich information to assess the electrokinetics theory and fluidic physics in nanoscale. Silica nanotubes were synthesized by oxidation/etching approach using vertical silicon nanowires as templates. A single nanotube was integrated into a metal-oxide-solution field effect transistor (MOSolFET) by interfacing with two microfluidic channels and a metallic gate electrode. Concentration dependence of ionic conductance through single nanotubes revealed the emergence of unipolar environment at low ionic strength regime. In this case, ionic conductance is only associated with majority ions and governed by surface potentials and charge densities. By applying a gate voltage, the ionic conductance can be quickly modulated. The gate voltages alter the surface potential of the silica nanotubes via capacitive coupling through the nanotube wall and the electrical double layer. In a negatively charged silica nanotube

  9. Sorting Carbon Nanotubes.

    PubMed

    Zheng, Ming

    2017-02-01

    Sorting of single-wall carbon nanotubes by their electronic and atomic structures in liquid phases is reviewed in this chapter. We first introduce the sorting problem, and then provide an overview of several sorting methodologies, following roughly the chronological order of their development over the past 15 years or so. Major methods discussed include ion-exchange chromatography, density-gradient ultracentrifugation, selective extraction in organic solvents, gel chromatography, and aqueous two-phase extraction. A main focus of the review is on the common mechanisms underlining all sorting processes. We propose that differences in solvation among different nanotube species are the ultimate driving force of sorting, and we corroborate this proposal by presenting analysis on how the differences are realized in electronic-structure-based sorting and atomic-structure-based sorting. In the end, we offer some suggestions on future directions that may grow out of carbon nanotube sorting. In particular, the prospect of expanding the function of DNA/carbon nanotube hybrid to control inter-particle interactions both inside and outside the nanotube is discussed.

  10. Carbon Nanotubes Based Quantum Devices

    NASA Technical Reports Server (NTRS)

    Lu, Jian-Ping

    1999-01-01

    This document represents the final report for the NASA cooperative agreement which studied the application of carbon nanotubes. The accomplishments are reviewed: (1) Wrote a review article on carbon nanotubes and its potentials for applications in nanoscale quantum devices. (2) Extensive studies on the effects of structure deformation on nanotube electronic structure and energy band gaps. (3) Calculated the vibrational spectrum of nanotube rope and the effect of pressure. and (4) Investigate the properties of Li intercalated nanotube ropes and explore their potential for energy storage materials and battery applications. These studies have lead to four publications and seven abstracts in international conferences.

  11. Thermal rectification in inhomogeneous nanotubes

    NASA Astrophysics Data System (ADS)

    Budaev, Bair V.; Bogy, David B.

    2016-12-01

    Heat transfer in axially inhomogeneous nanotubes is known to be asymmetric with respect to the direction of transfer. This phenomenon is known as the thermal rectification. We demonstrate that thermal rectification in such nanotubes arises due to the interference of phonons excited in the different parts of the nanotube. It is shown that the rectification does not vanish when the thickness of nanotube increases, but it vanishes as the external diameter of nanotubes decreases to a few nanometers. The understanding of the origin of thermal rectification opens a way to the design of devices controlling heat flows that could perform as efficiently as their electronic counterparts controlling electric currents.

  12. Carbon Nanotube Purification and Functionalization

    NASA Technical Reports Server (NTRS)

    Lebron, Marisabel; Mintz, Eric; Smalley, Richard E.; Meador, Michael A.

    2003-01-01

    Carbon nanotubes have the potential to significantly enhance the mechanical, thermal, and electrical properties of polymers. However, dispersion of carbon nanotubes in a polymer matrix is hindered by the electrostatic forces that cause them to agglomerate. Chemical modification of the nanotubes is necessary to minimize these electrostatic forces and promote adhesion between the nanotubes and the polymer matrix. In a collaborative research program between Clark Atlanta University, Rice University, and NASA Glenn Research Center several approaches are being explored to chemically modify carbon nanotubes. The results of this research will be presented.

  13. Friction on a single MoS2 nanotube

    PubMed Central

    2012-01-01

    Friction was measured on a single molybdenum disulfide (MoS2) nanotube and on a single MoS2 nano-onion for the first time. We used atomic force microscopy (AFM) operating in ultra-high vacuum at room temperature. The average coefficient of friction between the AFM tip and MoS2 nanotubes was found considerably below the corresponding values obtained from an air-cleaved MoS2 single crystal or graphite. We revealed a nontrivial dependency of friction on interaction strength between the nanotube and the underlying substrate. Friction on detached or weakly supported nanotubes by the substrate was several times smaller (0.023 ± 0.005) than that on well-supported nanotubes (0.08 ± 0.02). We propose an explanation of a quarter of a century old phenomena of higher friction found for intracrystalline (0.06) than for intercrystalline slip (0.025) in MoS2. Friction test on a single MoS2 nano-onion revealed a combined gliding-rolling process. PACS, 62.20, 61.46.Fg, 68.37 Ps PMID:22490562

  14. Carbon nanotube-based polymer nanocomposites: Fractal network to hierarchical morphology

    NASA Astrophysics Data System (ADS)

    Chatterjee, Tirtha

    scales related to the process are independent of it. For fully grown network in a viscous polymer, cluster dynamics under external shear controls the non-linear behavior of the system. Significant changes in the melting and crystallization behavior of poly(ethylene oxide) along with a decrease in fractional crystallinity has been observed, in these nanocomposites. The observed changes in the SWNT-based nanocomposites far exceed those observed for an equivalent Li+ ion concentration mixture. The identification of the nature of nanotube-polymer interactions and the nanotube's role during polymer crystallization provide the possibility of developing hierarchical materials with controlled multifunctional properties whose directionality can be easily manipulated. For the case where the nanotubes disturb the formation of polymer crystals, the oriented nanotubes, because of the short inter-tube distances even at low nanotube concentrations, cause a templating of the polymer crystals with the lamellar---normals oriented orthogonal to the nanotube axes. On the other hand for the case where nanotubes nucleate the polymer crystals, a "shish---kebab" structure is realized, with the nanotubes and polymer crystals acting as the shish and kebab, respectively.

  15. Growth of GaN nanotubes and nanowires

    NASA Astrophysics Data System (ADS)

    He, Maoqi; Zhou, Piezhen; Mohammad, S. Noor; Halpern, Joshua; Jacobs, Randy; Sarney, Wendy; Salamanca-Riba, Lourdes

    2001-03-01

    We have grown GaN nanowires and nanotubes by direct reaction of Ga metal vapor with NH3 in a simple tube furnace. By varying the ammonia flow rate (20-120 sccm) and temperature (800-1000 ^oC) we have been able to control onset of growth, and the diameters of these cylindrically symmetric nanostructures. The length of the nanowires and nanotubes is determined by the duration of the growth cycle. The nanowires and nanotubes that we have studied are single crystal and have a wurtzite structure. In the first 90 minutes, a 1 or 2 μ thick amorphous GaN matrix is deposited. Soon after pebble like polycrystalline hillocks form. Single crystal nanowires sprout from the sides of the platelets. The diameter of the nanowire is the same as the thickness of the plate, that is the smallest dimension of the face from which it grows. Since the platelet thickness depends on temperature and the ammonia, the thickness of the nanowires is proportional to the temperature and ammonia flow rate. At higher temperatures and flow rates nanotubes and rods start to grow from the flat surface of the plates

  16. Carbon nanotubes: opportunities and challenges

    NASA Astrophysics Data System (ADS)

    Dai, Hongjie

    2002-03-01

    Carbon nanotubes are graphene sheets rolled-up into cylinders with diameters as small as one nanometer. Extensive work carried out worldwide in recent years has revealed the intriguing electrical and mechanical properties of these novel molecular scale wires. It is now well established that carbon nanotubes are ideal model systems for studying the physics in one-dimensional solids and have significant potential as building blocks for various practical nanoscale devices. Nanotubes have been shown to be useful for miniaturized electronic, mechanical, electromechanical, chemical and scanning probe devices and materials for macroscopic composites. Progress in nanotube growth has facilitated the fundamental study and applications of nanotubes. Gaining control over challenging nanotube growth issues is critical to the future advancement of nanotube science and technology, and is being actively pursued by researchers.

  17. Copper-philic carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Belgamwar, Sachin U.; Sharma, Niti Nipun

    2016-04-01

    Carbon nanotube is having poor wet-ability with copper metal. Wet-ability of carbon nanotube was improved by exposing and creating more active sites on the surface of carbon nanotube. Carbon nanotubes were subjected to the prolong ultrasonication treatment of 20×103 Hz and 500W, which helped in disentanglement of carbon nanotube agglomerates and in breaking the weak bonds like pentagonal or heptagonal structure on the surface and on the CNT cap. Disentanglement of the carbon nanotube, resulted in exposing the defective sites on the surface and breaking of weak bonds, which assisted in creating the new defects on the surface. This process results in generates more active sites on the surface and it helps in improving the wet-ability of the carbon nanotube in copper.

  18. Fabrication of titanium dioxide nanotube arrays using organic electrolytes

    NASA Astrophysics Data System (ADS)

    Yoriya, Sorachon

    to ~2 microm. In comparison to DMSO electrolyte, the electrochemical anodization rates are relatively slower in DEG electrolyte; as a result, the nanotube length is typically less than 10 microm. Pore size of nanotubes grown in DEG has been extended from 150 nm up to approximately 400 nm. The approach to pore widening could be achieved by using a specific condition of low HF concentration and prolonged anodization time. The study of evolution of nanotubes grown in DEG electrolytes showed that a fibrous layer was formed in the early growth stages and then was chemically and gradually removed after a long duration, leaving behind the nanotubes with large pore size. In DEG electrolyte, the closer spacing between Ti and Pt electrodes resulted in the larger nanotube morphological parameters due to the enhanced electrode kinetics facilitating the electrode reactions. Furthermore, this dissertation showed possibilities to crystallize the titania nanotube array films at room temperature via anodization in either DMSO or DEG electrolytes. The partially crystallized films could be achieved specifically in the optimum slow growth process conditions. Due to partial crystallization of the as-anodized samples, the high temperature annealing study revealed that the temperatures of phase transformation are 260 ºC and 430°C for respectively amorphous to anatase and anatase to rutile, which are accounted as the lowest phase transformation temperatures reported to date (2010). Finally, the photoelectrochemical properties of the DMSO fabricated nanotubes were investigated. The maximum photocurrent density of ~ 11 mA cm--2 was achieved by using the 46-microm long nanotube array sample with completely open pores, and photoconversion efficiencies of 5.425 % (+/- 0.087) (under UV light) and 0.197 % (+/- 0.001) (under solar spectrum AM 1.5) have been demonstrated. Biomedical applications of the DEG fabricated nanotube arrays films such as blood clotting, hemocompatibility, and drug

  19. Nanotechnology with Carbon Nanotubes: Mechanics, Chemistry, and Electronics

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak

    2003-01-01

    This viewgraph presentation reviews the Nanotechnology of carbon nanotubes. The contents include: 1) Nanomechanics examples; 2) Experimental validation of nanotubes in composites; 3) Anisotropic plastic collapse; 4) Spatio-temporal scales, yielding single-wall nanotubes; 5) Side-wall functionalization of nanotubes; 6) multi-wall Y junction carbon nanotubes; 7) Molecular electronics with Nanotube junctions; 8) Single-wall carbon nanotube junctions; welding; 9) biomimetic dendritic neurons: Carbon nanotube, nanotube electronics (basics), and nanotube junctions for Devices,

  20. Single crystalline magnetite nanotubes.

    PubMed

    Liu, Zuqin; Zhang, Daihua; Han, Song; Li, Chao; Lei, Bo; Lu, Weigang; Fang, Jiye; Zhou, Chongwu

    2005-01-12

    We descried a method to synthesize single crystalline Fe3O4 nanotubes by wet-etching the MgO inner cores of MgO/Fe3O4 core-shell nanowires. Homogeneous Fe3O4 nanotubes with controllable length, diameter, and wall thickness have been obtained. Resistivity of the Fe3O4 nanotubes was estimated to be approximately 4 x 10-2 Omega cm at room temperature. Magnetoresistance of approximately 1% was observed at T = 77 K when a magnetic field of B = 0.7 T was applied. The synthetic strategy presented here may be extended to a variety of materials such as YBCO, PZT, and LCMO which should provide ideal candidates for fundamental studies of superconductivity, piezoelectricity, and ferromagnetism in nanoscale structures.