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Sample records for doped barium titanate

  1. Dielectric function for doped graphene layer with barium titanate

    NASA Astrophysics Data System (ADS)

    Martinez Ramos, Manuel; Garces Garcia, Eric; Magana, Fernado; Vazquez Fonseca, Gerardo Jorge

    2015-03-01

    The aim of our study is to calculate the dielectric function for a system formed with a graphene layer doped with barium titanate. Density functional theory, within the local density approximation, plane-waves and pseudopotentials scheme as implemented in Quantum Espresso suite of programs was used. We considered 128 carbon atoms with a barium titanate cluster of 11 molecules as unit cell with periodic conditions. The geometry optimization is achieved. Optimization of structural configuration is performed by relaxation of all atomic positions to minimize their total energies. Band structure, density of states and linear optical response (the imaginary part of dielectric tensor) were calculated. We thank Dirección General de Asuntos del Personal Académico de la Universidad Nacional Autónoma de México, partial financial support by Grant IN-106514 and we also thank Miztli Super-Computing center the technical assistance.

  2. Review on dielectric properties of rare earth doped barium titanate

    NASA Astrophysics Data System (ADS)

    Ismail, Fatin Adila; Osman, Rozana Aina Maulat; Idris, Mohd Sobri

    2016-07-01

    Rare earth doped Barium Titanate (BaTiO3) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO3 (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO3 downshifted the Curie temperature (TC). Transition temperature also known as Curie temperature, TC where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO3, Er-doped BaTiO3, Sm-doped BaTiO3, Nd-doped BaTiO3 and Ce-doped BaTiO3 had been proved to increase and the transition temperature or also known as TC also lowered down to room temperature as for all the RE doped BaTiO3 except for Er-doped BaTiO3.

  3. Synthesis, microstructure and dielectric properties of zirconium doped barium titanate

    NASA Astrophysics Data System (ADS)

    Kumar, Rohtash; Asokan, K.; Patnaik, S.; Birajdar, Balaji

    2016-05-01

    We report on synthesis, microstructural and relaxor ferroelectric properties of Zirconium(Zr) doped Barium Titanate (BT) samples with general formula Ba(Ti1-xZrx)O3 (x=0.20, 0.35). These lead-free ceramics were prepared by solid state reaction route. The phase transition behavior and temperature dependent dielectric properties and composition dependent ferroelectric properties were investigated. XRD analysis at room temperature confirms phase purity of the samples. SEM observations revealed retarded grain growth with increasing Zr mole fraction. Dielectric properties of BZT ceramics is influenced significantly by small addition of Zr mole fraction. With increasing Zr mole fraction, dielectric constant decreases while FWHM and frequency dispersion increases. Polarization vs electric field hysteresis measurements reveal ferroelectric relaxor phase at room temperature. The advantages of such substitution maneuvering towards optimizing ferroelectric properties of BaTiO3 are discussed.

  4. Electrical properties of lanthanum doped barium titanate ceramics

    SciTech Connect

    Vijatovic Petrovic, M.M.; Bobic, J.D.; Ramoska, T.; Banys, J.; Stojanovic, B.D.

    2011-10-15

    Pure and lanthanum doped barium titanate (BT) ceramics were prepared by sintering pellets at 1300 deg. C for 8 h, obtained from nanopowders synthesized by the polymeric precursor method. XRD results showed formation of a tetragonal structure. The presence of dopants changed the tetragonal structure to pseudo-cubic. The polygonal grain size was reduced up to 300 nm with addition of lanthanum as a donor dopant. Determined dielectric properties revealed that lanthanum modified BT ceramics possessed a diffused ferroelectric character in comparison with pure BT that is a classical ferroelectric material. In doped BT phase transition temperatures were shifted to lower temperatures and dielectric constant values were much higher than in pure BT. A modified Currie Weiss law was used to explore the connection between the doping level and degree of diffuseness of phase transitions. Impedance spectroscopy measurements were carried out at different temperatures in order to investigate electrical resistivity of materials and appearance of a PTCR effect. - Highlights: {yields} Pure and lanthanum doped BaTiO{sub 3} were prepared by polymeric precursors method. {yields} Change of structure from tetragonal to pseudo-cubic. {yields} Lanthanum as a donor dopant influenced on change of ferro-para phase transition. {yields} The diffuseness factor indicated the formation of diffuse ferroelectric material. {yields} Lanthanum affected on PTCR effect appearance in BT ceramics.

  5. Fabrication and characterization of cerium-doped barium titanate inverse opal by sol-gel method

    SciTech Connect

    Jin Yi; Zhu Yihua Yang Xiaoling; Li Chunzhong; Zhou Jinghong

    2007-01-15

    Cerium-doped barium titanate inverted opal was synthesized from barium acetate contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a polystyrene (PS) opal. This procedure involves infiltration of precursors into the interstices of the PS opal template followed by hydrolytic polycondensation of the precursors to amorphous barium titanate and removal of the PS opal by calcination. The morphologies of opal and inverse opal were characterized by scanning electron microscope (SEM). The pores were characterized by mercury intrusion porosimetry (MIP). X-ray photoelectron spectroscopy (XPS) investigation showed the doping structure of cerium, barium and titanium. And powder X-ray diffraction allows one to observe the influence of doping degree on the grain size. The lattice parameters, crystal size and lattice strain were calculated by the Rietveld refinement method. The synthesis of cerium-doped barium titanate inverted opals provides an opportunity to electrically and optically engineer the photonic band structure and the possibility of developing tunable three-dimensional photonic crystal devices. - Graphical abstract: Cerium-doped barium titanate inverted opal was synthesized from barium acetate acid contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a PS opal, which involves infiltration of precursors into the interstices of the PS opal template and removal of the PS opal by calcination.

  6. Electrical properties of niobium doped barium bismuth-titanate ceramics

    SciTech Connect

    Bobić, J.D.; Vijatović Petrović, M.M.; Banys, J.; Stojanović, B.D.

    2012-08-15

    Highlights: ► Pure and doped BaBi{sub 4}Ti{sub 4}O{sub 15} were prepared via the solid-state reaction method. ► The grain size was suppressed in Nb-doped samples. ► The diffuseness of the dielectric peak increased with dopant concentration. ► Niobium affected on relaxor behavior of barium bismuth titanate ceramics. ► The conductivity change was noticed in doped samples. -- Abstract: BaBi{sub 4}Ti{sub 4–5/4x}Nb{sub x}O{sub 15} (BBNTx, x = 0, 0.05, 0.15, 0.30) ceramics have been prepared by solid state method. XRD data indicate the formation of single-phase-layered perovskites for all compositions. SEM micrographs suggest that the grain size decreases with Nb doping. The effect of niobium doping on the dielectric and relaxor behavior of BaBi{sub 4}Ti{sub 4}O{sub 15} ceramics was investigated in a wide range of temperatures (20–777 °C) and frequencies (1.21 kHz to 1 MHz). Nb doping influences T{sub c} decrease as well as the decrease of dielectric permittivity at Curie temperature. At room temperature, undoped BaBi{sub 4}Ti{sub 4}O{sub 15} exhibits dielectric constant of ∼204 at 100 kHz, that slightly increases with Nb doping. The conductivity of BBNT5 ceramics is found to be lower than that of other investigated compositions. The value of activation energy of σ{sub DC} was found to be 0.89 eV, 1.01 eV, 0.93 eV and 0.71 eV for BBT, BBNT5, BBNT15 and BBNT30, respectively.

  7. Characterization of A-site deficient samarium doped barium titanate

    NASA Astrophysics Data System (ADS)

    Ganguly, M.; Rout, S. K.; Woo, W. S.; Ahn, C. W.; Kim, I. W.

    2013-02-01

    Ba1-xSm2x/3TiO3 (0.00≤x≤0.10, in a step of 0.02) ceramics have been prepared through solid state reaction route. Structural studies (XRD, FTIR, Raman) suggested a tetragonal symmetry of all the prepared ceramics and a decrease in tetragonality with increase in Sm content. Rietveld refinement technique has been employed to investigate the details of crystal structure and was found to be tetragonal at room temperature with space group P4mm. Photoluminescence study confirmed formation of shallow defects. The prepared materials are found to show photoemission in the violet, blue and green zone. Optical band gap values calculated from UV-visual diffuse reflectance spectra showed a decreasing trend in band gap values with increase in samarium concentration. Disk shaped pellets were prepared using PVA as binder. Scanning electron microscopy showed a drastic decrease in grain size on doping than undoped barium titanate. A regular increase in the grain size with increase in Sm content in the doped compositions is observed. Dielectric studies were performed over a wide temperature range from 15 K to 600 K at different frequencies. Normal ferroelectric character was obtained for all the compositions. A gradual decrease in the Curie temperature was noticed with increase in samarium content. P∼E hysteresis loops showed a domain pinning effect which increased successively resulting in a decrease in the values of remnant polarization and coercive fields.

  8. Fabrication and characterization of cerium doped barium titanate/PMMA nanocomposites

    NASA Astrophysics Data System (ADS)

    Padalia, Diwakar; Bisht, Garima; Johri, U. C.; Asokan, K.

    2013-05-01

    The cerium doped barium titanate (BaTiO3:Ce)/poly methyl methacrylate(PMMA) polymer nano-composites (PNC) were successfully fabricated via solvent evaporation method with microwaves (2.4 GHz) heating. The X-ray diffraction measurements confirm the formation of barium titanate (BT) with crystallite size ranges from 55 to 62 nm. Differential scanning calorimetry study shows that the glass transition temperature (Tg) directly affected by microwaves heat treatment and particle size of filler. The broadband dielectric spectroscopy was employed to investigate the frequency and temperature dependence of the dielectric properties of the nanocomposites in a frequency range from 75 kHz to 5 MHz and temperature range 80-400 K. The introduction of different BT fillers in PMMA enhance the dielectric constant of PNCs drastically and give a smooth response in frequency range mentioned above. The loss factor of the composite can be suppressed by using cerium doped barium titanate filler rather than pure barium titanate filler.

  9. Structural and electrical characteristics of dysprosium-doped barium stannate titanate ceramics

    SciTech Connect

    Wang, Shijie; Tan, Tai Aik; Lai, Man On; Lu, Li

    2010-03-15

    Effects of dysprosium (Dy) amphoteric doping on the structural, dielectric and electric properties of barium stannate titanate (BTS) ceramics have been studied. X-ray diffraction analyses reveal that all Dy-doped BTS ceramics exhibit cubic perovskite structure until to 1 mol%. Dy doping at the A site shows lower solubility than that at the B site. SEM surface morphologies display that the Dy B site doping is beneficial for the compact and homogeneous grain distribution. The dielectric constant and loss tangent are reduced with increase of the doping levels. Impedance spectroscopy investigation demonstrates that all samples are insulating at room temperature. Doping alters the full resistive regions of pure BTS ceramics to Doped BTS with insulating grain boundaries and semiconducting bulk regions, but the doping contents has little effect on changing the electric structures.

  10. Effect of samarium doping on the dielectric behavior of barium zircomium titanate ceramic

    SciTech Connect

    Badapanda, T.; Sarangi, S.; Behera, B.; Anwar, S.; Sinha, T. P.

    2014-04-24

    Samarium doped Barium Zirconium Titanate ceramic with general formula Ba{sub 1−x}Sm{sub 2x/3}Zr{sub 0.05}Ti{sub 0.95}O{sub 3} [x=0.0,0.01,0.02,0.03,0.04] has been prepared by high energy ball milling. The X-ray diffraction (XRD) patterns confirmed that these ceramics have a single phase with perovskite-type upto x≤0.03 and a small secondary phase exist at x=0.04. The temperature dependent dielectric study shows a ferroelectric phase transition and transition temperature decreases with an increase in the Samarium content.

  11. High temperature dielectric relaxation anomaly of Y3+ and Mn2+ doped barium strontium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Yan, Shiguang; Mao, Chaoliang; Wang, Genshui; Yao, Chunhua; Cao, Fei; Dong, Xianlin

    2014-10-01

    Relaxation like dielectric anomaly is observed in Y3+ and Mn2+ doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysis reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.

  12. Defect properties of cobalt-doped hexagonal barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Langhammer, H. T.; Böttcher, R.; Müller, T.; Walther, T.; Ebbinghaus, S. G.

    2015-07-01

    X-ray diffraction (XRD) patterns, electron paramagnetic resonance (EPR) powder spectra (9 and 34 GHz) and the magnetic susceptibility of BaTiO3 + 0.04 BaO + x/2 Co2O3 (0.001 ⩽ x ⩽ 0.02) ceramics were studied to investigate the incorporation of Co ions in the BaTiO3 lattice and their valence states as well as the development of the hexagonal phase (6H modification) in dependence on doping level x and sintering temperature Ts. At Ts = 1400 °C the 6H modification begins to occur at a nominal Co concentration x of about 0.001 and for x > 0.005 the samples are completely hexagonal at room temperature. Two different EPR spectra were observed in the 6H modification of BaTiO3, which were both assigned to paramagnetic Co2+ ions located at the two crystallographically non-equivalent Ti sites in 6H-BaTiO3. The EPR g tensor values as well as the molar paramagnetic susceptibility, measured in the temperature range 5 K-300 K at a magnetic field of 9 T, were analyzed in the framework of the ligand field theory using the program CONCORD. The combination of EPR and magnetic measurements reveals that in air-sintered 6H BaTiO3, the incorporated Co occurs as a mixture of paramagnetic Co2+ and diamagnetic Co3+ ions, whereas in samples annealed in reducing atmosphere the majority of Co is in the divalent state. The occurrence of Co4+ can be excluded for all investigated samples. The sample color caused by Co2+ and Co3+ ions is beige/light yellow and dark grey/black, respectively. The majority of the Co2+ ions substitutes Ti in the exclusively corner-sharing oxygen octahedra possessing nearly cubic symmetry. The corresponding ligand field parameter B04(3) amounts to about -28 000 cm-1 (Wybourne notation, 10Dq ≈ 20 000 cm-1). In the reduced samples nearly 5% of the detected Co2+ ions occupy the Ti site in the face-sharing oxygen octahedra, which are significantly trigonally distorted. The negative sign of the obtained ligand field parameter B02 ≈ -7300 cm-1

  13. The Effect of Mg Doping on Structural and Luminescent Properties of Barium Strontium Titanate (BST)

    NASA Astrophysics Data System (ADS)

    Khare, A.; Chauhan, N.

    Pure and Mg doped barium strontium titanate (BST) phosphor samples are prepared by solid state reaction (SSR) method at 1300 °c. The prepared samples are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-VIS absorption spectroscopy. The optical properties are studied in terms of mechanoluminescence (ML) and thermoluminescence (TL). The XRD results reveal perovskite structure of samples with XRD peaks corresponding to planes (100), (110), (111), (200) and (211). The SEM micrographs exhibit agglomeration of particles of different shapes. The particle size calculated using SEM and XRD data is found to lie in nano range. The ML intensity is found to depend on applied load while the TL intensity increases with increasing irradiation time.

  14. Blocking effect of crystal–glass interface in lanthanum doped barium strontium titanate glass–ceramics

    SciTech Connect

    Wang, Xiangrong; Zhang, Yong; Baturin, Ivan; Liang, Tongxiang

    2013-10-15

    Graphical abstract: The blocking effect of the crystal–glass interface on the carrier transport behavior in the lanthanum doped barium strontium titanate glass–ceramics: preparation and characterization. - Highlights: • La{sub 2}O{sub 3} addition promotes the crystallization of the major crystalline phase. • The Z″ and M″ peaks exist a significant mismatch for 0.5 mol% La{sub 2}O{sub 3} addition. • The Z″ and M″ peaks separate obviously for 1.0 mol% La{sub 2}O{sub 3} addition. • Crystallite impedance decreases while crystal–glass interface impedance increases. • La{sub 2}O{sub 3} addition increases blocking factor of the crystal–glass interface. - Abstract: The microstructures and dielectric properties in La{sub 2}O{sub 3}-doped barium strontium titanate glass–ceramics have been investigated by scanning electron microscopy (SEM) and impedance spectroscopy. SEM analysis indicated that La{sub 2}O{sub 3} additive decreases the average crystallite size. Impedance spectroscopy revealed that the positions of Z″ and M″ peaks are close for undoped samples. When La{sub 2}O{sub 3} concentration is 0.5 mol%, the Z″ and M″ peaks show a significant mismatch. Furthermore, these peaks separate obviously for 1.0 mol% La{sub 2}O{sub 3} addition. With increasing La{sub 2}O{sub 3} concentration, the contribution of the crystallite impedance becomes smaller, while the contribution of the crystal–glass interface impedance becomes larger. More interestingly, it was found that La{sub 2}O{sub 3} additive increases blocking factor of the crystal–glass interface in the temperature range of 250–450 °C. This may be attributed to a decrease of activation energy of the crystallite and an increase of the crystal–glass interface area.

  15. 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.

  16. Optical behavior of Pr3+-doped barium titanate-calcium titanate material prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyan; Tang, Yanxue; He, Xiyun; Qiu, Pingsun; He, Qizhuang; Peng, Zifei; Sun, Dazhi

    2009-07-01

    Photoluminescence performances of Pr-doped alkaline-earth titanates (Ba,Ca)TiO3 (with rich barium) prepared by a solgel technique are investigated at room temperature. A relatively strong red luminescence is observed in (Ba0.80Ca0.20)TiO3 material when Pr-BaTiO3 material does not exhibit obvious red luminescence. The phenomenon is discussed with respect to the substitute of Ca and the two-photon luminescence effect. The red luminescence is enhanced by a fast thermal treatment. The wavelength range of luminescence near red and infrared light is broadened by the same process as well. These behaviors are ascribed to the randomization of distribution of Ca and Ba at A site in ABO3 perovskite structure. The experimental results provide not only a possible way to develop new materials with pastel visual impression, but also a potential technique to modify photoluminescence properties that can be controlled by external fields because the microscopic structure of BaTiO3, such as electric domains, can be changed by electric field, temperature, and so on.

  17. Dielectric and Ferroelectric Behavior of Bismuth-Doped Barium Titanate Ceramic Prepared by Microwave Sintering

    NASA Astrophysics Data System (ADS)

    Mahapatra, A.; Parida, S.; Sarangi, S.; Badapanda, T.

    2015-08-01

    Bismuth-doped barium titanate ceramics with the general formula Ba1- x Bi2 x/3TiO3 ( x = 0.0, 0.01, 0.025, 0.05) have been prepared by the solid state reaction technique. The phase formation and structural property of all compositions have been studied by x-ray diffraction (XRD) pattern and Rietveld refinement. XRD pattern reports the single phase tetragonal crystal system with space group of P4mm. All compositions have been sintered at 1100°C in a microwave furnace for 30 min. The variation of dielectric constant with respect to temperature and frequency was studied and it was found that the dielectric constant decreases whereas transition temperature increased with the increase in Bi content. The diffusivity parameter was calculated by the modified Curie-Weiss law and the diffusivity increased with the increase in Bi content. The ferroelectric property was studied by the P-E hysteresis loop and it was observed that the saturation polarization decreased, but the coercive field increased with Bi content. The optical band gap was calculated from UV-Visible spectroscopy and found to decrease with Bi content.

  18. Elaboration and characterization of doped barium titanate films for gas sensing

    SciTech Connect

    Romh, M. A. El Fasquelle, D. Mascot, M.; Députier, S.

    2014-11-05

    Barium titanate (BaTiO{sub 3}) thick films were prepared from commercial powder to develop and optimize the film elaboration. Then, BaTiO{sub 3} was doped by strontium and iron to increase the conductivity by a double substitution on site A and B of the perovskite structure in view to develop semiconductor gas sensors. Film inks were prepared by mixing BT and BSTF powder with an organic vehicle, using a ratio of 50:50; 60:40, respectively and deposited on alumina substrates. The BT and BSTF films were sintered at 1100°C for 2h. The structural and physical properties of the films have been studied by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The dielectric measurements showed a huge increase in the a.c. conductivity for the BSTF films, by a factor of 10000 at low frequency, when the temperature ranges from 25°C to 500°C.

  19. Magnetoelectric coupling of multiferroic chromium doped barium titanate thin film probed by magneto-impedance spectroscopy

    SciTech Connect

    Shah, Jyoti Kotnala, Ravinder K. E-mail: rkkotnala@gmail.com

    2014-04-07

    Thin film of BaTiO{sub 3} doped with 0.1 at. % Cr (Cr:BTO) has been prepared by pulsed laser deposition technique. Film was deposited on Pt/SrTiO{sub 3} substrate at 500 °C in 50 mTorr Oxygen gas pressure using KrF (298 nm) laser. Polycrystalline growth of single phase Cr:BTO thin film has been confirmed by grazing angle X-ray diffraction. Cr:BTO film exhibited remnant polarization 6.4 μC/cm{sup 2} and 0.79 MV/cm coercivity. Magnetization measurement of Cr:BTO film showed magnetic moment 12 emu/cc. Formation of weakly magnetic domains has been captured by magnetic force microscopy. Theoretical impedance equation fitted to experimental data in Cole-Cole plot for thin film in presence of transverse magnetic field resolved the increase in grain capacitance from 4.58 × 10{sup −12} to 5.4 × 10{sup −11} F. Film exhibited high value 137 mV/cm-Oe magneto-electric (ME) coupling coefficient at room temperature. The high value of ME coupling obtained can reduce the typical processing steps involved in multilayer deposition to obtain multiferrocity in thin film. Barium titanate being best ferroelectric material has been tailored to be multiferroic by non ferromagnetic element, Cr, doping in thin film form opens an avenue for more stable and reliable spintronic material for low power magnetoelectric random excess memory applications.

  20. Site-selective spectroscopy of the solid-state defect chemistry in erbium-doped barium titanate.

    PubMed

    Bak, John D; Wright, John C

    2005-10-01

    Erbium-doped barium titanate crystals were studied by laser-induced fluorescence spectroscopy. Thirteen spectroscopically distinct erbium ion sites were found. The relative concentrations of the different sites changed as a function of the crystal and its preparation and treatment. One major site was present in all crystals. The site distribution was changed either by growing codoped crystals with donor (La3+) and acceptor (Sc3+) ions or by changing the temperature and partial pressure of the oxygen in the annealing atmosphere. Equilibrium calculations were done to simulate the defect distributions that result from the charge compensation of the erbium ions. Comparison with the observed dependence of the site spectral intensities indicated that the erbium enters the lattice on barium sites. We assigned the dominant site to an erbium ion on a barium site that is locally compensated by a barium vacancy, whereas the other lower-intensity sites corresponded to erbium ions that are locally compensated by an electron and a more complex center of an erbium, a barium vacancy, and a hole. The spectra of one sample showed that its defects were different and were characteristic of a sample that had not equilibrated. The new sites in this sample were assigned to erbium entering the lattice on a titanium site, which was then locally compensated by an oxygen vacancy or a hole. Heating equilibrated the sample and changed the erbium to a barium site. PMID:16853368

  1. Multicomponent doped barium strontium titanate thin films for tunable microwave applications

    NASA Astrophysics Data System (ADS)

    Alema, Fikadu Legesse

    In recent years there has been enormous progress in the development of barium strontium titanate (BST) films for tunable microwave applications. However, the properties of BST films still remain inferior compared to bulk materials, limiting their use for microwave technology. Understanding the film/substrate mismatch, microstructure, and stoichiometry of BST films and finding the necessary remedies are vital. In this work, BST films were deposited via radio frequency magnetron sputtering method and characterized both analytically and electrically with the aim of optimizing their properties. The stoichiometry, crystal structure, and phase purity of the films were studied by varying the oxygen partial pressure (OPP) and total gas pressure (TGP) in the chamber. A better stoichiometric match between film and target was achieved when the TGP is high (> 30 mTorr). However, the O2/Ar ratio should be adjusted as exceeding a threshold of 2 mTorr in OPP facilitates the formation of secondary phases. The growth of crystalline film on platinized substrates was achieved only with a lower temperature grown buffer layer, which acts as a seed layer by crystallizing when the temperature increases. Concurrent Mg/Nb doping has significantly improved the properties of BST thin films. The doped film has shown an average tunability of 53%, which is only ˜8 % lower than the value for the undoped film. This drop is associated with the Mg ions whose detrimental effects are partially compensated by Nb ions. Conversely, the doping has reduced the dielectric loss by ˜40 % leading to a higher figure of merit. Moreover, the two dopants ensure a charge neutrality condition which resulted in significant leakage current reduction. The presence of large amounts of empty shallow traps related to Nb Ti localize the free carriers injected from the contacts; thus increase the device control voltage substantially (>10 V). A combinatorial thin film synthesis method based on co-sputtering of two BST

  2. Influence of lanthanum doping on the dielectric, ferroelectric and relaxor behaviour of barium bismuth titanate ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Varma, K. B. R.

    2009-04-01

    Barium lanthanum bismuth titanate (Ba1-(3/2)xLaxBi4Ti4O15, x = 0-0.4) ceramics were fabricated using the powders synthesized via the solid-state reaction route. X-ray powder diffraction analysis confirmed the above compositions to be monophasic and belonged to the m = 4 member of the Aurivillius family of oxides. The effect of the partial presence of La3+ on Ba2+ sites on the microstructure, dielectric and relaxor behaviour of BaBi4Ti4O15 (BBT) ceramics was investigated. For the compositions pertaining to x <= 0.1, the dielectric constant at both room temperature and in the vicinity of the temperature of the dielectric maximum (Tm) of the parent phase (BBT) increased significantly with an increase in x while Tm remained almost constant. Tm shifted towards lower temperatures accompanied by a decrease in the magnitude of the dielectric maximum (ɛm) with an increase in the lanthanum content (0.1 < x <= 0.4). The dielectric relaxation was modelled using the Vogel-Fulcher relation and a decrease in the activation energy for frequency dispersion with increasing x was observed. The frequency dispersion of Tm was found to decrease with an increase in lanthanum doping, and for compositions corresponding to x >= 0.3, Tm was frequency independent. Well-developed P(polarization)-E(electric field) hysteresis loops were observed at 150 °C for all the samples and the remanent polarization (2Pr) was improved from 6.3 µC cm-2 for pure BBT to 13.4 µC cm-2 for Ba0.7La0.2Bi4Ti4O15 ceramics. Dc conductivities and associated activation energies were evaluated using impedance spectroscopy.

  3. Tuned sensitivity towards H{sub 2}S and NH{sub 3} with Cu doped barium strontium titanate materials

    SciTech Connect

    Simion, C. E. Teodorescu, V. S.; Stănoiu, A.; Sackmann, A.; Ruşti, C. F.; Piticescu, R. M.

    2014-11-05

    The different amount of Cu-doped Barium Strontium Titanate (BST) thick film materials have been tested for their gas-sensing performances towards NH{sub 3} and H{sub 2}S under dry and 50% relative humidity (RH) background conditions. The optimum NH{sub 3} sensitivity was attained with 0.1mol% Cu-doped BST whereas the selective detection of H{sub 2}S was highlighted using 5mol% Cu-doped BST material. No cross-sensitivity effects to CO, NO{sub 2}, CH{sub 4} and SO{sub 2} were observed for all tested materials operated at their optimum temperature (200°C) under humid conditions (50% RH). The presence of humidity clearly enhances the gas sensitivity to NH{sub 3} and H{sub 2}S detection.

  4. Studies of ferroelectric and dielectric properties of pure and doped barium titanate prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    In this work, Barium Titanate (BaTiO3) powders were synthesized via Sol-Gel auto combustion method using citric acid as a chelating agent. We study the behavior of ferroelectric and dielectric properties of pure and doped BaTiO3 on different concentration. To understand the phase and structure of the powder calcined at 900°C were characterized by X-ray Diffraction shows that tetragonal phase is dominant for pure and doped BTO and data fitted by Rietveld Refinement. Electric and Dielectric properties were characterized by P-E Hysteresis and Dielectric measurement. In P-E measurement ferroelectric loop tracer applied for different voltage. The temperature dependant dielectric constant behavior was observed as a function of frequency recorded on hp-Hewlett Packard 4192A, LF impedance, 5Hz-13Hz analyzer.

  5. Selective substitution and tetragonality by Co-doping of dysprosium and thulium on dielectric properties of barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Kim, Jungdae; Kim, Dowan; Kim, Jinseong; Kim, Yong-Nam; Hui, K. N.; Lee, Heesoo

    2011-06-01

    Barium titanate (BaTiO3) ceramics co-doped with rare-earth elements were investigated in terms of selective substitution and tetragonality. The dielectrics were designed by addition of various Dy2O3 and Tm2O3 contents, for a total of 1 mol. % concentration, and analyzed in a temperature range from -55°C to 150°C. The dielectric constant of the 0.7 mol. % Dy2O3 and the 0.3 mol. % Tm2O3 co-doped BaTiO3 was 2250, which was about 27% higher than those of specimens doped with 1 mol. % Tm2O3 and 1 mol. % Dy2O3 at room temperature. The tendency of dielectric properties was verified through the changes of lattice parameters and binding energy. The substitution of Dy3+ led to a decrease of tetragonality and grain growth; however, amphoteric substitution caused by the co-doping of Dy2O3 and Tm2O3 compensated for those adverse effects. It can be concluded that the improvement of dielectric properties originated from the increase of the site substitution rate of Dy3+ and Tm3+ ions according to the ionic size the in rare-earth doped BaTiO3 system.

  6. Effects of Nd-doping on optical and photovoltaic properties of barium titanate thin films prepared by sol–gel method

    SciTech Connect

    Jiang, Weihai; Cai, Wei; Lin, Zebin; Fu, Chunlin

    2013-09-01

    Graphical abstract: - Highlights: • We prepared Nd-doped BTO thin films by sol–gel method. • Addition of Nd to some extent can inhibit the grain growth. • Addition of Nd{sup 3+} ions can decrease band gap. • The remnant polarization of Nd-doped BTO thin films begins to increase and then decreases. • Photovoltaic properties of Nd-doped BTO thin films begin to increase then decrease. - Abstract: Nd-doped barium titanate thin films were prepared via sol–gel spin-coating method and effects of Nd content on microstructure, optical and photovoltaic properties have been investigated. The results show that Nd-doped barium titanate thin films are single tetragonal perovskite phase. Addition of neodymium to some extent can inhibit the grain growth. Substitution of Nd{sup 3+} ions for Ba{sup 2+} on A sites leads to the decrease of band gap. The remnant polarization begins to increase and reach the maximum and then decreases as Nd content increases. The short circuit photocurrent density, open circuit photovoltage and power conversion efficiency of Nd-doped barium titanate thin films begin to increase and reach the maximum and then decrease as Nd content increases.

  7. The generation of optical phase conjugation from cerium doped barium titanate at wavelength of 632.8 nm

    NASA Astrophysics Data System (ADS)

    Sidakum, K.; Buranasiri, P.; Plaipichit, S.; Ruttanapun, C.; Jindajitawat, P.

    2013-06-01

    In this paper, optical phase conjugate beam with the using of different resonator configurations has been investigate. Two types of SPPC resonators were selected to use, the first one is linear resonators formed by crystal surface and the other one is linear resonators formed by single mirror and a photorefractive crystal. In our experiment, cerium doped barium titanate crystal (BaTiO3 : Ce) and He-Ne laser with wavelength of 632.8 nm have been used. From the results of both cases, the angle of the incident beams is optimum at 37.95° respect to the normal line of the surface that parallel to the c-axis of the crystal. The generating time of OPC beam are 150 seconds and 330 seconds for the first and second type resonators, respectively. The reflection ratios are equal to 8.75% and 5% for the first and second type resonators, respectively (the first type resonators could provide better reflection ratio).

  8. Processing science of barium titanate

    NASA Astrophysics Data System (ADS)

    Aygun, Seymen Murat

    Barium titanate and barium strontium titanate thin films were deposited on base metal foils via chemical solution deposition and radio frequency magnetron sputtering. The films were processed at elevated temperatures for densification and crystallization. Two unifying research goals underpin all experiments: (1) To improve our fundamental understanding of complex oxide processing science, and (2) to translate those improvements into materials with superior structural and electrical properties. The relationships linking dielectric response, grain size, and thermal budget for sputtered barium strontium titanate were illustrated. (Ba 0.6Sr0.4)TiO3 films were sputtered on nickel foils at temperatures ranging between 100-400°C. After the top electrode deposition, the films were co-fired at 900°C for densification and crystallization. The dielectric properties were observed to improve with increasing sputter temperature reaching a permittivity of 1800, a tunability of 10:1, and a loss tangent of less than 0.015 for the sample sputtered at 400°C. The data can be understood using a brick wall model incorporating a high permittivity grain interior with low permittivity grain boundary. However, this high permittivity value was achieved at a grain size of 80 nm, which is typically associated with strong suppression of the dielectric response. These results clearly show that conventional models that parameterize permittivity with crystal diameter or film thickness alone are insufficiently sophisticated. Better models are needed that incorporate the influence of microstructure and crystal structure. This thesis next explores the ability to tune microstructure and properties of chemically solution deposited BaTiO3 thin films by modulation of heat treatment thermal profiles and firing atmosphere composition. Barium titanate films were deposited on copper foils using hybrid-chelate chemistries. An in-situ gas analysis process was developed to probe the organic removal and the

  9. Tunable dielectric properties of Barium Magnesium Niobate (BMN) doped Barium Strontium Titanate (BST) thin films by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Alema, Fikadu; Reinholz, Aaron; Pokhodnya, Konstantin

    2013-03-01

    We report on the tunable dielectric properties of Mg and Nb co-doped Ba0.45Sr0.55TiO3 (BST) thin film prepared by the magnetron sputtering using BST target (pure and doped with BaMg0.33Nb0.67O3 (BMN)) on Pt/TiO2/SiO2/Al2O3 4'' wafers at 700 °C under oxygen atmosphere. The electrical measurements are conducted on 2432 metal-ferroelectric-metal capacitors using Pt as the top and bottom electrode. The crystalline structure, microstructure, and surface morphology of the films are analyzed and correlated to the films dielectric properties. The BMN doped and undoped BST films have shown tunabilities of 48% and 52%; and leakage current densities of 2.2x10-6 A/cm2 and 3.7x10-5 A/cm2, respectively at 0.5 MV/cm bias field. The results indicate that the BMN doped film exhibits a lower leakage current with no significant decrease in tunability. Due to similar electronegativity and ionic radii, it was suggested that both Mg2+ (accepter-type) and Nb5+ (donor-type) dopants substitutTi4+ ion in BST. The improvement in the film dielectric losses and leakage current with insignificant loss of tunability is attributed to the adversary effects of Mg2+ and Nb5+ in BST.

  10. Phase stabilisation of hexagonal barium titanate doped with transition metals: A computational study

    SciTech Connect

    Dawson, J.A.; Freeman, C.L.; Harding, J.H.; Sinclair, D.C.

    2013-04-15

    Interatomic potentials recently developed for the modelling of BaTiO{sub 3} have been used to explore the stabilisation of the hexagonal polymorph of BaTiO{sub 3} by doping with transition metals (namely Mn, Co, Fe and Ni) at the Ti-site. Classical simulations have been completed on both the cubic and hexagonal polymorphs to investigate the energetic consequences of transition metal doping on each polymorph. Ti-site charge compensation mechanisms have been used for the multi-valent transition metal ions and cluster binding energies have been considered. Simulations show a significant energetic gain when doping occurs at Ti sites in the face sharing dimers (Ti{sub 2} sites) of the hexagonal polymorph compared with the doping of the cubic polymorph. This energetic difference between the two polymorphs is true for all transition metals tested and all charge states and in the case of tri- and tetra-valent dopants negative solution energies are found for the hexagonal polymorph suggesting actual polymorph stabilisation occurs with the incorporation of these ions as observed experimentally. Oxidation during incorporation of Ni{sup 2+} and Fe{sup 3+} ions has also been considered. - Graphical abstract: The representation of the strongest binding energy clusters for tri-valent dopants—(a) Ti{sub 2}/O{sub 1} cluster and (b) Ti{sub 2}/O{sub 2} cluster. Highlights: ► Classical simulations show a significant energetic gain when doping occurs at Ti sites in the face sharing dimers (Ti2 sites) of the hexagonal polymorph compared with the doping of the cubic polymorph. ► This energetic difference between the two polymorphs is true for all transition metals tested and all charge states. ► In the case of tri- and tetra- valent dopants negative solution energies are found for the hexagonal polymorph suggesting actual polymorph stabilisation occurs with the incorporation of these ions.

  11. Strain-Induced Extrinsic High-Temperature Ferromagnetism in the Fe-Doped Hexagonal Barium Titanate

    PubMed Central

    Zorko, A.; Pregelj, M.; Gomilšek, M.; Jagličić, Z.; Pajić, D.; Telling, M.; Arčon, I.; Mikulska, I.; Valant, M.

    2015-01-01

    Diluted magnetic semiconductors possessing intrinsic static magnetism at high temperatures represent a promising class of multifunctional materials with high application potential in spintronics and magneto-optics. In the hexagonal Fe-doped diluted magnetic oxide, 6H-BaTiO3-δ, room-temperature ferromagnetism has been previously reported. Ferromagnetism is broadly accepted as an intrinsic property of this material, despite its unusual dependence on doping concentration and processing conditions. However, the here reported combination of bulk magnetization and complementary in-depth local-probe electron spin resonance and muon spin relaxation measurements, challenges this conjecture. While a ferromagnetic transition occurs around 700 K, it does so only in additionally annealed samples and is accompanied by an extremely small average value of the ordered magnetic moment. Furthermore, several additional magnetic instabilities are detected at lower temperatures. These coincide with electronic instabilities of the Fe-doped 3C-BaTiO3-δ pseudocubic polymorph. Moreover, the distribution of iron dopants with frozen magnetic moments is found to be non-uniform. Our results demonstrate that the intricate static magnetism of the hexagonal phase is not intrinsic, but rather stems from sparse strain-induced pseudocubic regions. We point out the vital role of internal strain in establishing defect ferromagnetism in systems with competing structural phases. PMID:25572803

  12. Epitaxially-Grown Europium-Doped Barium Titanate Films on Various Substrates for Red Emission.

    PubMed

    Hwang, Kyu-Seog; Jeon, Young-Sun; Lee, Young-Hwan; Hwangbo, Seung; Kim, Jin-Tae

    2015-10-01

    Intense red photoluminescence under ultraviolet excitation was observed in epitaxially-grown europium-doped perovskite BaTiO3 thin films deposited on the SrTiO3 (100), MgO (100) and sapphire (0001) substrates using metal carboxylate complexes. Precursor films prepared by spin coating were pyrolyzed at 250 °C for 120 min in argon, followed by final annealing at 850 °C for 60 min in argon. Crystallinity and epitaxy of the films were analyzed by X-ray diffraction θ-2θ scan and pole-figure analysis. Photoluminescence of the thin films at room temperature under 254 nm was confirmed by a fluorescent spectrophotometer. The obtained epitaxial BaTiO3 thin films on the SrTiO3 (100) and MgO (100) substrates show an intense red-emission lines at 615 nm corresponding to the (5)D0 --> (7)F2 transitions on Eu(3+) with broad bands at 595 and 650 nm. PMID:26726427

  13. Effect of annealing time, weight pressure and cobalt doping on the electrical and magnetic behavior of barium titanate

    NASA Astrophysics Data System (ADS)

    Samuvel, K.; Ramachandran, K.

    2016-05-01

    BaTi0.5CO0.5O3 (BTCO) nanoparticles were prepared by the solid state reaction technique using different starting materials and the microstructure examined by XRD, FESEM, BDS and VSM. X-ray diffraction and electron diffraction patterns showed that the nanoparticles were the tetragonal BTCO phase. The BTCO nanoparticles prepared from the starting materials of as prepared titanium-oxide, Cobalt -oxide and barium carbonate have spherical grain morphology, an average size of 65 nm and a fairly narrow size distribution. The nano-scale presence and the formation of the tetragonal perovskite phase as well as the crystallinity were detected using the mentioned techniques. Dielectric properties of the samples were measured at different frequencies. Broadband dielectric spectroscopy is applied to investigate the electrical properties of disordered perovskite-like ceramics in a wide temperature range. The doped BTCO samples exhibited low loss factor at 1 kHz and 1 MHz frequencies respectively.

  14. High temperature dielectric relaxation anomaly of Y³⁺ and Mn²⁺ doped barium strontium titanate ceramics

    SciTech Connect

    Yan, Shiguang; Mao, Chaoliang E-mail: xldong@mail.sic.ac.cn; Wang, Genshui; Yao, Chunhua; Cao, Fei; Dong, Xianlin E-mail: xldong@mail.sic.ac.cn

    2014-10-14

    Relaxation like dielectric anomaly is observed in Y³⁺ and Mn²⁺ doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysis reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.

  15. Barium Titanate Nanoparticles for Biomarker Applications

    NASA Astrophysics Data System (ADS)

    Matar, O.; Posada, O. M.; Hondow, N. S.; Wälti, C.; Saunders, M.; Murray, C. A.; Brydson, R. M. D.; Milne, S. J.; Brown, A. P.

    2015-10-01

    A tetragonal crystal structure is required for barium titanate nanoparticles to exhibit the nonlinear optical effect of second harmonic light generation (SHG) for use as a biomarker when illuminated by a near-infrared source. Here we use synchrotron XRD to elucidate the tetragonal phase of commercially purchased tetragonal, cubic and hydrothermally prepared barium titanate (BaTiO3) nanoparticles by peak fitting with reference patterns. The local phase of individual nanoparticles is determined by STEM electron energy loss spectroscopy (EELS), measuring the core-loss O K-edge and the Ti L3-edge energy separation of the t2g, eg peaks. The results show a change in energy separation between the t2g and eg peak from the surface and core of the particles, suggesting an intraparticle phase mixture of the barium titanate nanoparticles. HAADF-STEM and bright field TEM-EDX show cellular uptake of the hydrothermally prepared BaTiO3 nanoparticles, highlighting the potential for application as biomarkers.

  16. Magnetoelastic coupling in epitaxial cobalt ferrite/barium titanate heterostructures

    NASA Astrophysics Data System (ADS)

    Gräfe, Joachim; Welke, Martin; Bern, Francis; Ziese, Michael; Denecke, Reinhard

    2013-08-01

    Ultra-thin cobalt ferrite films have been synthesised on ferroelectric barium titanate crystals. The cobalt ferrite films exhibit a magnetic response to strain induced by structural changes in the barium titanate substrate, suggesting a pathway to multiferroic coupling. These structural changes are achieved by heating through the phase transition temperatures of barium titanate. In addition the ferromagnetic signal of the substrate itself is taken into account, addressing the influence of impurities or defects in the substrate. The cobalt ferrite/barium titanate heterostructure is a suitable oxidic platform for future magnetoelectric applications with an established ferroelectric substrate and widely tuneable magnetic properties by changing the transition metal in the ferrite film.

  17. Vacancy ordering in reduced barium titanate

    NASA Astrophysics Data System (ADS)

    Woodward, David I.; Reaney, Ian M.; Yang, Gaiying Y.; Dickey, Elizabeth C.; Randall, Clive A.

    2004-06-01

    A crystal structure is proposed for reduced barium titanate, BaTiO3-δ, δ≈0.33, formed during the degradation of Ni-BaTiO3 X7R multilayer ceramic capacitors. High-resolution transmission electron microscopy and selected-area electron diffraction have been used in combination with computer simulations to show that oxygen vacancies accrete on every third pseudocubic {111} plane, resulting in a cell with space group P3m1. Additionally, from electron energy loss spectroscopy, it is proposed that Ti4+ is reduced to Ti3+ as a mechanism of charge compensation within oxygen-deficient octahedra.

  18. Ferroelastic domains in lead-free barium zirconate titanate - barium calcium titanate piezoceramics

    NASA Astrophysics Data System (ADS)

    Ehmke, Matthias Claudius

    Piezoelectricity was first discovered by Pierre and Jaque Curie in the year 1880. Nowadays, piezoelectric materials are used in many application such as high voltage generation in gas igniters, actuation in micro-positioning devices, generation and detection of acoustic waves, emitters and receivers for sonar technology, ultrasonic cleaning, ultrasound medical therapy, and micropumps for ink-jet printers. The most commonly used piezoelectric material since the 1950's is the solid solution system lead zirconate titanate (PZT) that offers high piezoelectric performance under a large range of operating conditions. However, the toxicity of lead requires the replacement of PZT. The studied lead-free alternatives are commonly based on potassium sodium niobate (KNN) and bismuth sodium titanate (BNT), and more recently zirconium and calcium substituted barium titanate (BZT-BCT). The BZT-BCT system exhibits large piezoelectric coefficients that can exceed even those of most PZT compositions under certain conditions. Piezoelectricity was first discovered by Pierre and Jaque Curie in the year 1880. Nowadays, piezoelectric materials are used in many application such as high voltage generation in gas igniters, actuation in micro-positioning devices, generation and detection of acoustic waves, emitters and receivers for sonar technology, ultrasonic cleaning, ultrasound medical therapy, and micropumps for ink-jet printers. The most commonly used piezoelectric material since the 1950's is the solid solution system lead zirconate titanate (PZT) that offers high piezoelectric performance under a large range of operating conditions. However, the toxicity of lead requires the replacement of PZT. The studied lead-free alternatives are commonly based on potassium sodium niobate (KNN) and bismuth sodium titanate (BNT), and more recently zirconium and calcium substituted barium titanate (BZT-BCT). The BZT-BCT system exhibits large piezoelectric coefficients that can exceed even those of

  19. Study of the photovoltaic effect in thin film barium titanate

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    The feasibility of making non-volatile digital memory devices of barium titanate, BaTiO3, that are integrated onto a silicon substrate with the required ferroelectric film produced by processing, compatible with silicon technology was examined.

  20. Hydrogen diffusion in lead zirconate titanate and barium titanate

    SciTech Connect

    Alvine, K. J.; Vijayakumar, M.; Bowden, M. E.; Schemer-Kohrn, A. L.; Pitman, S. G.

    2012-08-28

    Hydrogen is a potential clean-burning, next-generation fuel for vehicle and stationary power. Unfortunately, hydrogen is also well known to have serious materials compatibility issues in metals, polymers, and ceramics. Piezoelectric actuator materials proposed for low-cost, high efficiency high-pressure hydrogen internal combustion engines (HICE) are known to degrade rapidly in hydrogen. This limits their potential use and poses challenges for HICE. Hydrogen-induced degradation of piezoelectrics is also an issue for low-pressure hydrogen passivation in ferroelectric random access memory. Currently, there is a lack of data in the literature on hydrogen species diffusion in piezoelectrics in the temperature range appropriate for the HICE as charged via a gaseous route. We present 1HNMR quantification of the local hydrogen species diffusion within lead zirconate titanate and barium titanate on samples charged by exposure to high-pressure gaseous hydrogen ~32 MPa. We discuss results in the context of theoretically predicted interstitial hydrogen lattice sites and aqueous charging experiments from existing literature.

  1. Compact pulse forming line using barium titanate ceramic material.

    PubMed

    Kumar Sharma, Surender; Deb, P; Shukla, R; Prabaharan, T; Shyam, A

    2011-11-01

    Ceramic material has very high relative permittivity, so compact pulse forming line can be made using these materials. Barium titanate (BaTiO(3)) has a relative permittivity of 1200 so it is used for making compact pulse forming line (PFL). Barium titanate also has piezoelectric effects so it cracks during high voltages discharges due to stresses developed in it. Barium titanate is mixed with rubber which absorbs the piezoelectric stresses when the PFL is charged and regain its original shape after the discharge. A composite mixture of barium titanate with the neoprene rubber is prepared. The relative permittivity of the composite mixture is measured to be 85. A coaxial pulse forming line of inner diameter 120 mm, outer diameter 240 mm, and length 350 mm is made and the composite mixture of barium titanate and neoprene rubber is filled between the inner and outer cylinders. The PFL is charged up to 120 kV and discharged into 5 Ω load. The voltage pulse of 70 kV, 21 ns is measured across the load. The conventional PFL is made up of oil or plastics dielectrics with the relative permittivity of 2-10 [D. R. Linde, CRC Handbook of Chemistry and Physics, 90th ed. (CRC, 2009); Xia et al., Rev. Sci. Instrum. 79, 086113 (2008); Yang et al., Rev. Sci. Instrum. 81, 43303 (2010)], which increases the length of PFL. We have reported the compactness in length achieved due to increase in relative permittivity of composite mixture by adding barium titanate in neoprene rubber. PMID:22129008

  2. Compact pulse forming line using barium titanate ceramic material

    NASA Astrophysics Data System (ADS)

    Kumar Sharma, Surender; Deb, P.; Shukla, R.; Prabaharan, T.; Shyam, A.

    2011-11-01

    Ceramic material has very high relative permittivity, so compact pulse forming line can be made using these materials. Barium titanate (BaTiO3) has a relative permittivity of 1200 so it is used for making compact pulse forming line (PFL). Barium titanate also has piezoelectric effects so it cracks during high voltages discharges due to stresses developed in it. Barium titanate is mixed with rubber which absorbs the piezoelectric stresses when the PFL is charged and regain its original shape after the discharge. A composite mixture of barium titanate with the neoprene rubber is prepared. The relative permittivity of the composite mixture is measured to be 85. A coaxial pulse forming line of inner diameter 120 mm, outer diameter 240 mm, and length 350 mm is made and the composite mixture of barium titanate and neoprene rubber is filled between the inner and outer cylinders. The PFL is charged up to 120 kV and discharged into 5 Ω load. The voltage pulse of 70 kV, 21 ns is measured across the load. The conventional PFL is made up of oil or plastics dielectrics with the relative permittivity of 2-10 [D. R. Linde, CRC Handbook of Chemistry and Physics, 90th ed. (CRC, 2009); Xia et al., Rev. Sci. Instrum. 79, 086113 (2008); Yang et al., Rev. Sci. Instrum. 81, 43303 (2010)], which increases the length of PFL. We have reported the compactness in length achieved due to increase in relative permittivity of composite mixture by adding barium titanate in neoprene rubber.

  3. Methods for producing monodispersed particles of barium titanate

    DOEpatents

    Hu, Zhong-Cheng

    2001-01-01

    The present invention is a low-temperature controlled method for producing high-quality, ultrafine monodispersed nanocrystalline microsphere powders of barium titanate and other pure or composite oxide materials having particles ranging from nanosized to micronsized particles. The method of the subject invention comprises a two-stage process. The first stage produces high quality monodispersed hydrous titania microsphere particles prepared by homogeneous precipitation via dielectric tuning in alcohol-water mixed solutions of inorganic salts. Titanium tetrachloride is used as an inorganic salt precursor material. The second stage converts the pure hydrous titania microsphere particles into crystalline barium titanate microsphere powders via low-temperature, hydrothermal reactions.

  4. Study of the photovoltaic effect in thin film barium titanate

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    The photoelectric effect in structures consisting of metal deposited barium titanate film silicon is described. A radio frequency sputtering technique is used to deposit ferroelectric barium titantate films on silicon and quartz. Film properties are measured and correlated with the photoelectric effect characteristics of the films. It was found that to obtain good quality pin hole free films, it is necessary to reduce the substrate temperature during the last part of the deposition. The switching ability of the device with internal applied voltage is improved when applied with a ferroelectric memory device.

  5. Agglomeration behavior of solid nickel on polycrystalline barium titanate

    SciTech Connect

    Weil, K Scott; Mast, Eric S; Sprenkle, Vince

    2007-11-01

    This letter describes the phenomenon that takes place between nickel/barium titanate couples when heated under conditions employed in multilayer ceramic capacitor manufacturing practice: a 4hr, 1300°C isothermal anneal in 1% H2 – 99% N2. Dense, sputtered nickel films were observed to dewet the titanate and agglomerate into discrete or interconnected islands via a solid-state process. Up to a critical film thickness value of ~1.4 μm, the degree of agglomeration was found to display an exponential dependence on the thickness of the original nickel film.

  6. Barium titanate nanoparticles: promising multitasking vectors in nanomedicine

    NASA Astrophysics Data System (ADS)

    Graziana Genchi, Giada; Marino, Attilio; Rocca, Antonella; Mattoli, Virgilio; Ciofani, Gianni

    2016-06-01

    Ceramic materials based on perovskite-like oxides have traditionally been the object of intense interest for their applicability in electrical and electronic devices. Due to its high dielectric constant and piezoelectric features, barium titanate (BaTiO3) is probably one of the most studied compounds of this family. Recently, an increasing number of studies have been focused on the exploitation of barium titanate nanoparticles (BTNPs) in the biomedical field, owing to the high biocompatibility of BTNPs and their peculiar non-linear optical properties that have encouraged their use as nanocarriers for drug delivery and as label-free imaging probes. In this review, we summarize all the recent findings about these ‘smart’ nanoparticles, including the latest, most promising potential as nanotransducers for cell stimulation.

  7. Barium titanate nanoparticles: promising multitasking vectors in nanomedicine.

    PubMed

    Genchi, Giada Graziana; Marino, Attilio; Rocca, Antonella; Mattoli, Virgilio; Ciofani, Gianni

    2016-06-10

    Ceramic materials based on perovskite-like oxides have traditionally been the object of intense interest for their applicability in electrical and electronic devices. Due to its high dielectric constant and piezoelectric features, barium titanate (BaTiO3) is probably one of the most studied compounds of this family. Recently, an increasing number of studies have been focused on the exploitation of barium titanate nanoparticles (BTNPs) in the biomedical field, owing to the high biocompatibility of BTNPs and their peculiar non-linear optical properties that have encouraged their use as nanocarriers for drug delivery and as label-free imaging probes. In this review, we summarize all the recent findings about these 'smart' nanoparticles, including the latest, most promising potential as nanotransducers for cell stimulation. PMID:27145888

  8. Study of the photovoltaic effect in thin film barium titanate

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Ferroelectric films of barium titanate were synthesized on silicon and quartz substrates, and the photoelectric effect in the structure consisting of metal deposited ferroelectric barium titanate film silicon was studied. A photovoltage with polarity that depends on the direction of the remanent polarization was observed. The deposition of BaTiO3 on silicon and fused quartz substrates was accomplished by an rf sputtering technique. A series of experiments to study the growth of ferroelectric BaTiO3 films on single crystal silicon and fused quartz substrates were conducted. The ferroelectric character in these films was found on the basis of evidence from the polarization electric field hysteresis loops, capacitance voltage and capacitance temperature techniques and from X-ray diffraction studies.

  9. Nanodielectric system for cryogenic applications: Barium titanate filled polyvinyl alcohol

    SciTech Connect

    Tuncer, Enis; Sauers, Isidor; James, David Randy; Ellis, Alvin R; Duckworth, Robert C

    2008-01-01

    In the current study the focus is on dielectric properties (as a function of frequency and temperature) of a polymeric composite system composed of polyvinyl alcohol and barium titanate nano powder. In the investigations, the temperature range is between 50-295 K, and the frequency range is between $20\\ \\hertz-1\\ \\mega\\hertz$. Polarization and conduction processes are investigated in the linear regime. Dielectric breakdown strengths of samples are also reported. The materials presented have potential to be implemented in cryogenic capacitor or field grading applications.

  10. Enhanced flexoelectricity through residual ferroelectricity in barium strontium titanate

    SciTech Connect

    Garten, Lauren M. Trolier-McKinstry, Susan

    2015-03-07

    Residual ferroelectricity is observed in barium strontium titanate ceramics over 30 °C above the global phase transition temperature, in the same temperature range in which anomalously large flexoelectric coefficients are reported. The application of a strain gradient leads to strain gradient-induced poling or flexoelectric poling. This was observed by the development of a remanent polarization in flexoelectric measurements, an induced d{sub 33} piezoelectric response even after the strain gradient was removed, and the production of an internal bias of 9 kV m{sup −1}. It is concluded that residual ferroelectric response considerably enhances the observed flexoelectric response.

  11. Strain engineered barium strontium titanate for tunable thin film resonators

    SciTech Connect

    Khassaf, H.; Khakpash, N.; Sun, F.; Sbrockey, N. M.; Tompa, G. S.; Kalkur, T. S.; Alpay, S. P.

    2014-05-19

    Piezoelectric properties of epitaxial (001) barium strontium titanate (BST) films are computed as functions of composition, misfit strain, and temperature using a non-linear thermodynamic model. Results show that through adjusting in-plane strains, a highly adaptive rhombohedral ferroelectric phase can be stabilized at room temperature with outstanding piezoelectric response exceeding those of lead based piezoceramics. Furthermore, by adjusting the composition and the in-plane misfit, an electrically tunable piezoelectric response can be obtained in the paraelectric state. These findings indicate that strain engineered BST films can be utilized in the development of electrically tunable and switchable surface and bulk acoustic wave resonators.

  12. Liquid-Phase Processing of Barium Titanate Thin Films

    NASA Astrophysics Data System (ADS)

    Harris, David Thomas

    Processing of thin films introduces strict limits on the thermal budget due to substrate stability and thermal expansion mismatch stresses. Barium titanate serves as a model system for the difficulty in producing high quality thin films because of sensitivity to stress, scale, and crystal quality. Thermal budget restriction leads to reduced crystal quality, density, and grain growth, depressing ferroelectric and nonlinear dielectric properties. Processing of barium titanate is typically performed at temperatures hundreds of degrees above compatibility with metalized substrates. In particular integration with silicon and other low thermal expansion substrates is desirable for reductions in costs and wider availability of technologies. In bulk metal and ceramic systems, sintering behavior has been encouraged by the addition of a liquid forming second phase, improving kinetics and promoting densification and grain growth at lower temperatures. This approach is also widespread in the multilayer ceramic capacitor industry. However only limited exploration of flux processing with refractory thin films has been performed despite offering improved dielectric properties for barium titanate films at lower temperatures. This dissertation explores physical vapor deposition of barium titanate thin films with addition of liquid forming fluxes. Flux systems studied include BaO-B2O3, Bi2O3-BaB2O 4, BaO-V2O5, CuO-BaO-B2O3, and BaO-B2O3 modified by Al, Si, V, and Li. Additions of BaO-B2O3 leads to densification and an increase in average grain size from 50 nm to over 300 nm after annealing at 900 °C. The ability to tune permittivity of the material improved from 20% to 70%. Development of high quality films enables engineering of ferroelectric phase stability using residual thermal expansion mismatch in polycrystalline films. The observed shifts to TC match thermodynamic calculations, expected strain from the thermal expansion coefficients, as well as x-ray diffract measurements

  13. Photoluminescence of barium titanate and barium zirconate in multilayer disordered thin films at room temperature.

    PubMed

    Moreira, M L; Gurgel, M F C; Mambrini, G P; Leite, E R; Pizani, P S; Varela, J A; Longo, E

    2008-09-25

    The emission of wide band photoluminescence showed a synergic effect on barium zirconate and barium titanate thin films in alternate multilayer system at room temperature by 488 nm exiting wavelength. The thin films obtained by spin-coating were annealed at 350, 450, and 550 degrees C for 2 h. The X-ray patterns revealed the complete separation among the BaTiO3 and BaZrO3 phases in the adjacent films. Visible and intense photoluminescence was governed by BaZrO3 thin films in the multilayer system. Quantum mechanics calculations were used in order to simulate ordered and disordered thin films structures. The disordered models, which were built by using the displacement of formers and modifier networks, showed a different symmetry in each system, which is in accordance with experimental photoluminescence emission, thus allowing to establish a correlation among the structural and optical properties of these multilayered systems. PMID:18593105

  14. Structure of thin barium strontium titanate films over strontium titanate

    NASA Astrophysics Data System (ADS)

    Amir, Fatima Zohra

    Ferroelectric thin films have numerous applications: they are being used as sensors and actuators; they feature large electro-optic effects and a high dielectric constant, making them ideal as large integrated capacitors. A crucial aspect of all their applications is the depth dependence of both the strain and the polarization. These two parameters modify their optical and electronic properties. A series of experiments using synchrotron x-ray radiation have been performed to investigate the strain profile of Ba0.5Sr0.5TiO 3 (BST) ferroelectric thin films grown on SrTiO3 (STO) substrates doped with 0.5% Nb by pulsed laser ablation; the samples were grown in Pennsylvania State University. The experiments have been carried out at the beamline X22C of the National Synchrotron Light Source, Brookhaven National Laboratory. Two different techniques were used to study the effects at the interface and the surface: Crystal Truncation Rod Diffraction and Grazing Incidence Diffraction. By a detailed analysis of the strong asymmetry of the finite-thickness oscillations close to the main Bragg peak, together with grazing incidence data, we find evidence for a vertical lattice expansion at the surface together with a distorted region at the interface to the substrate. For two films with different thickness (10 nm and 50 nm) we obtain a similar strain profile. The 10-nm thick film shows a beating in the 001 reflection together with the asymmetry at room temperature. Upon annealing the sample to 725 K over several days, the beating in the Laue oscillations disappears, and the experiment was not reversible. The corresponding model for the strain shows that the enhancement of the lattice parameter at the surface disappeared. The electric field dependence of the surface lattice parameter enhancement was probed by applying a voltage between the surface of the 50nm thick film and the conducting substrate; in addition, switching the voltage from -400 mV to 400 mV reverses 6% of the

  15. Barium titanate nanocomposite capacitor FY09 year end report.

    SciTech Connect

    Stevens, Tyler E.; DiAntonio, Christopher Brian; Yang, Pin; Chavez, Tom P.; Winter, Michael R.; Monson, Todd C.; Roesler, Alexander William; Fellows, Benjamin D.

    2009-11-01

    This late start RTBF project started the development of barium titanate (BTO)/glass nanocomposite capacitors for future and emerging energy storage applications. The long term goal of this work is to decrease the size, weight, and cost of ceramic capacitors while increasing their reliability. Ceramic-based nanocomposites have the potential to yield materials with enhanced permittivity, breakdown strength (BDS), and reduced strain, which can increase the energy density of capacitors and increase their shot life. Composites of BTO in glass will limit grain growth during device fabrication (preserving nanoparticle grain size and enhanced properties), resulting in devices with improved density, permittivity, BDS, and shot life. BTO will eliminate the issues associated with Pb toxicity and volatility as well as the variation in energy storage vs. temperature of PZT based devices. During the last six months of FY09 this work focused on developing syntheses for BTO nanoparticles and firing profiles for sintering BTO/glass composite capacitors.

  16. Study on a flexoelectric microphone using barium strontium titanate

    NASA Astrophysics Data System (ADS)

    Kwon, S. R.; Huang, W. B.; Zhang, S. J.; Yuan, F. G.; Jiang, X. N.

    2016-04-01

    In this study, a flexoelectric microphone was, for the first time, designed and fabricated in a bridge structure using barium strontium titanate (Ba0.65Sr0.35TiO3) ceramic and tested afterwards. The prototyped flexoelectric microphone consists of a 1.5 mm  ×  768 μm  ×  50 μm BST bridge structure and a silicon substrate with a cavity. The sensitivity and resonance frequency were designed to be 0.92 pC/Pa and 98.67 kHz, respectively. The signal to noise ratio was measured to be 74 dB. The results demonstrate that the flexoelectric microphone possesses high sensitivity and a wide working frequency range simultaneously, suggesting that flexoelectricity could be an excellent alternative sensing mechanism for microphone applications.

  17. Ultrasonic de-agglomeration of barium titanate powder.

    PubMed

    Marković, S; Mitrić, M; Starcević, G; Uskoković, D

    2008-01-01

    BaTiO3 (BT) powder, with average particle size of 1.4 microm, was synthesized by solid-state reaction. A high-intensity ultrasound irradiation (ultrasonication) was used to de-agglomerate micro-sized powder to nano-sized one. The crystal structure, crystallite size, morphology, particle size, particle size distribution, and specific surface area of the BT powder de-agglomerated for different ultrasonication times (0, 10, 60, and 180 min) were determined. It was found that the particles size of the BT powder was influenced by ultrasonic treatment, while its tetragonal structure was maintained. Therefore, ultrasonic irradiation can be proposed as an environmental-friendly, economical, and effective tool for the de-agglomeration of barium titanate powders. PMID:17845864

  18. Dielectric behavior of barium modified strontium bismuth titanate ceramic

    SciTech Connect

    Nayak, P.; Badapanda, T.; Anwar, S.; Panigrahi, S.

    2014-04-24

    Barium Modified Strontium Bismuth Titanate(SBT) ceramic with general formula Sr1−xBaxBi4Ti4O15 is prepared by solid state reaction route. The structural analysis of the ceramics was done by X-ray diffraction technique. The X-ray patterns show that all the compositions are of single phase with orthorhombic structure. The temperature dependent dielectric behavior shows that the transition temperature decreases with Ba content but the maximum dielectric constant increases. The decreases of the transition with increase in Ba{sup 2+} ion, may be due to the decrease of orthorhombicity by the incorporation of Ba{sup 2+} ion in SBT lattice.

  19. Lanthanide doped strontium-barium cesium halide scintillators

    SciTech Connect

    Bizarri, Gregory; Bourret-Courchesne, Edith; Derenzo, Stephen E.; Borade, Ramesh B.; Gundiah, Gautam; Yan, Zewu; Hanrahan, Stephen M.; Chaudhry, Anurag; Canning, Andrew

    2015-06-09

    The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped strontium-barium, optionally cesium, halide, useful for detecting nuclear material.

  20. Proton conductivity of potassium doped barium zirconates

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoxiang; Tao, Shanwen; Irvine, John T. S.

    2010-01-01

    Potassium doped barium zirconates have been synthesized by solid state reactions. It was found that the solubility limit of potassium on A-sites is between 5% and 10%. Introducing extra potassium leads to the formation of second phase or YSZ impurities. The water uptake of barium zirconates was increased even with 5% doping of potassium at the A-site. The sintering conditions and conductivity can be improved significantly by adding 1 wt% ZnO during material synthesis. The maximum solubility for yttrium at B-sites is around 15 at% after introducing 1 wt% zinc. The conductivity of Ba 0.95K 0.05Zr 0.85Y 0.11Zn 0.04O 3-δ at 600 °C is 2.2×10 -3 S/cm in wet 5% H 2. The activation energies for bulk and grain boundary are 0.29(2), 0.79(2) eV in wet 5% H 2 and 0.31(1), 0.74(3) eV in dry 5% H 2. A power density of 7.7 mW/cm 2 at 718 °C was observed when a 1 mm thick Ba 0.95K 0.05Zr 0.85Y 0.11Zn 0.04O 3-δ pellet was used as electrolyte and platinum electrodes.

  1. Properties of barium strontium titanate at millimeter wave frequencies

    SciTech Connect

    Osman, Nurul; Free, Charles

    2015-04-24

    The trend towards using higher millimetre-wave frequencies for communication systems has created a need for accurate characterization of materials to be used at these frequencies. Barium Strontium Titanate (BST) is a ferroelectric material whose permittivity is known to change as a function of applied electric field and have found varieties of application in electronic and communication field. In this work, new data on the properties of BST characterize using the free space technique at frequencies between 145 GHz and 155 GHz for both thick film and bulk samples are presented. The measurement data provided useful information on effective permittivity and loss tangent for all the BST samples. Data on the material transmission, reflection properties as well as loss will also be presented. The outcome of the work shows through practical measurement, that BST has a high permittivity with moderate losses and the results also shows that BST has suitable properties to be used as RAM for high frequency application.

  2. Proton conductivity of potassium doped barium zirconates

    SciTech Connect

    Xu Xiaoxiang; Tao Shanwen; Irvine, John T.S.

    2010-01-15

    Potassium doped barium zirconates have been synthesized by solid state reactions. It was found that the solubility limit of potassium on A-sites is between 5% and 10%. Introducing extra potassium leads to the formation of second phase or YSZ impurities. The water uptake of barium zirconates was increased even with 5% doping of potassium at the A-site. The sintering conditions and conductivity can be improved significantly by adding 1 wt% ZnO during material synthesis. The maximum solubility for yttrium at B-sites is around 15 at% after introducing 1 wt% zinc. The conductivity of Ba{sub 0.95}K{sub 0.05}Zr{sub 0.85}Y{sub 0.11}Zn{sub 0.04}O{sub 3-{delta}} at 600 deg. C is 2.2x10{sup -3} S/cm in wet 5% H{sub 2}. The activation energies for bulk and grain boundary are 0.29(2), 0.79(2) eV in wet 5% H{sub 2} and 0.31(1), 0.74(3) eV in dry 5% H{sub 2}. A power density of 7.7 mW/cm{sup 2} at 718 deg. C was observed when a 1 mm thick Ba{sub 0.95}K{sub 0.05}Zr{sub 0.85}Y{sub 0.11}Zn{sub 0.04}O{sub 3-{delta}} pellet was used as electrolyte and platinum electrodes. - Graphical abstract: Potassium doped barium zirconates have been synthesized by solid state reactions. It was found that the solubility limit of potassium on A-sites is between 5% and 10 %. The sintering conditions and conductivity can be improved significantly by adding 1 wt% ZnO during material synthesis. Five percent doping of potassium at A-site can double the total conductivity.

  3. Characterization, sintering and dielectric properties of nanocrystalline barium titanate synthesized through a modified combustion process

    SciTech Connect

    George, C.N.; Thomas, J.K. Kumar, H.P.; Suresh, M.K.; Kumar, V.R.; Wariar, P.R.S.; Jose, R.; Koshy, J.

    2009-04-15

    Nanocrystalline barium titanate has been synthesized through a modified combustion process in a single step for the first time. The as-prepared barium titanate powder is cubic perovskite with lattice constant a = 4.018 A. The phase purity of the nanopowder was examined using thermo gravimetric analysis, differential thermal analysis and Fourier transform infrared spectroscopy. Transmission electron microscopic investigations have shown that the particle size of the as-prepared powder is in the range 20-40 nm. The agglomerate size distribution of the as-prepared powder was studied using atomic force microscopy. The nanoparticles of barium titanate were sintered to 97% of the theoretical density at a temperature of 1350 deg. C for 3 h. The microstructure of the sintered surface was examined using scanning electron microscopy. The dielectric constant and loss factor of the sintered pellets at 1 MHz measured at room temperature were 1223 and 3.5 x 10{sup -3} respectively.

  4. The review of various synthesis methods of barium titanate with the enhanced dielectric properties

    NASA Astrophysics Data System (ADS)

    More, S. P.; Topare, R. J.

    2016-05-01

    The Barium Titanate is a very well known dielectric ceramic belongs to perovskite structure. It has very wide applications in the field of electronic, electro ceramic, electromechanical and electro-optical applications. Barium Titanate has very high dielectric constant as well as low dielectric loss. Substituted dielectrics are one of the most important technological compounds in modern electro ceramics. Its electrical properties can be tuned flexibly by a simple substitution technique. This has encouraged researchers to select a typical cation to be substituted at cationic sites. In the present paper, the review of various synthesis methods of Barium Titanate compound with the effect of different dopants, the grain size on the dielectric properties at various temperatures is discussed.

  5. Phase transition studies in barium and strontium titanates at microwave frequencies

    NASA Technical Reports Server (NTRS)

    Dahiya, Jai N.

    1993-01-01

    The objectives were the following: to understand the phase transformations in barium and strontium titanates as the crystals go from one temperature to the other; and to study the dielectric behavior of barium and strontium titanate crystals at a microwave frequency of 9.12 GHz and as a function of temperature. Phase transition studies in barium and strontium titanate are conducted using a cylindrical microwave resonant cavity as a probe. The cavity technique is quite successful in establishing the phase changes in these crystals. It appears that dipole relaxation plays an important role in the behavior of the dielectric response of the medium loading the cavity as phase change takes place within the sample. The method of a loaded resonant microwave cavity as applied in this work has proven to be sensitive enough to monitor small phase changes of the cavity medium.

  6. Highly aligned arrays of high aspect ratio barium titanate nanowires via hydrothermal synthesis

    SciTech Connect

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

    2015-06-01

    We report on the development of a hydrothermal synthesis procedure that results in the growth of highly aligned arrays of high aspect ratio barium titanate nanowires. Using a multiple step, scalable hydrothermal reaction, a textured titanium dioxide film is deposited on titanium foil upon which highly aligned nanowires are grown via homoepitaxy and converted to barium titanate. Scanning electron microscope images clearly illustrate the effect the textured film has on the degree of orientation of the nanowires. The alignment of nanowires is quantified by calculating the Herman's Orientation Factor, which reveals a 58% improvement in orientation as compared to growth in the absence of the textured film. The ferroelectric properties of barium titanate combined with the development of this scalable growth procedure provide a powerful route towards increasing the efficiency and performance of nanowire-based devices in future real-world applications such as sensing and power harvesting.

  7. Evaluation of antibacterial properties of Barium Zirconate Titanate (BZT) nanoparticle

    PubMed Central

    Mohseni, Simin; Aghayan, Mahdi; Ghorani-Azam, Adel; Behdani, Mohammad; Asoodeh, Ahmad

    2014-01-01

    So far, the antibacterial activity of some organic and inorganic compounds has been studied. Barium zirconate titanate [Ba(ZrxTi1-x)O3] (x = 0.05) nanoparticle is an example of inorganic materials. In vitro studies have provided evidence for the antibacterial activity of this nanoparticle. In the current study, the nano-powder was synthesized by sol-gel method. X-ray diffraction showed that the powder was single-phase and had a perovskite structure at the calcination temperature of 1000 °C. Antibacterial activity of the desired nanoparticle was assessed on two gram-positive (Staphylococcus aureus PTCC1431 and Micrococcus luteus PTCC1625) and two gram-negative (Escherichia coli HP101BA 7601c and clinically isolated Klebsiella pneumoniae) bacteria according to Radial Diffusion Assay (RDA). The results showed that the antibacterial activity of BZT nano-powder on both gram-positive and gram-negative bacteria was acceptable. The minimum inhibitory concentration of this nano-powder was determined. The results showed that MIC values for E. coli, K. pneumoniae, M. luteus and S. aureus were about 2.3 μg/mL, 7.3 μg/mL, 3 μg/mL and 12 μg/mL, respectively. Minimum bactericidal concentration (MBC) was also evaluated and showed that the growth of E. coli, K. pneumoniae, M. luteus and S. aureus could be decreased at 2.3, 14, 3 and 18 μg/mL of BZT. Average log reduction in viable bacteria count in time-kill assay ranged between 6 Log10 cfu/mL to zero after 24 h of incubation with BZT nanoparticle. PMID:25763046

  8. Physical states and properties of barium titanate films in a plane electric field

    NASA Astrophysics Data System (ADS)

    Shirokov, V. B.; Kalinchuk, V. V.; Shakhovoi, R. A.; Yuzyuk, Yu. I.

    2016-07-01

    The influence of a plane electric field on the phase states of barium titanate thin films under the conditions of forced deformation has been studied. The field dependence of a complete set of material constants has been taken in the region of the c-phase, where polarization losses are absent. The material constants are calculated using equations of the piezoelectric effect derived by linearizing the nonlinear equations of state from the phenomenological; theory for barium titanate. It has been shown that there is a critical value of the field at which the electromechanical coupling coefficient reaches a maximum.

  9. Synthesis of 0.1% & 0.2% neodymium doped barium zirconium titanate (BaZr0.2Ti0.8O3) and study of their dielectric behaviour

    NASA Astrophysics Data System (ADS)

    Kumar, Anil; Kumar, Vipin; Gupta, Merry; Ghumman, S. S.

    2015-08-01

    Efforts have been made to ease process of producing widely used multilayered ceramics of Barium Zirconium Titanium Oxides and study their dielectric behaviour and structural properties. For this purpose, adequate proportions of Barium Carbonate, Zirconium Oxide and Titanium Oxide were taken and hand milled for 2 hours. Neodymium composition of the order of 0.1% and 0.2% was used for doping to weight percentage of BaZr0.2Ti0.8O3. The samples were authenticated using raw data obtained from Bruker AXS D8 advance Copper KL alpha source XRD equipment. Further, the samples were studied for their phase transition, composition, single phase perovskite structure using XRD technique. The technique has also been applied to know formation of stable homogeneous solid solution from XRD parameters. The other physical parameters like the morphology, micro structural information, crystal arrangements and topography have also been observed through SEM. The SEM has revealed information related to grain size development and composition of sample with fine agglomerates. For complete study of the compounds the atomic and weight composition has also been examined by Electron Dispersive Spectroscopy patterns. The comparison has been made with other works on ceramics at various frequencies and has yielded very interesting results.

  10. Synthesis of 0.1% & 0.2% neodymium doped barium zirconium titanate (BaZr{sub 0.2}Ti{sub 0.8}O{sub 3}) and study of their dielectric behaviour

    SciTech Connect

    Kumar, Anil Kumar, Vipin; Gupta, Merry; Ghumman, S. S.

    2015-08-28

    Efforts have been made to ease process of producing widely used multilayered ceramics of Barium Zirconium Titanium Oxides and study their dielectric behaviour and structural properties. For this purpose, adequate proportions of Barium Carbonate, Zirconium Oxide and Titanium Oxide were taken and hand milled for 2 hours. Neodymium composition of the order of 0.1% and 0.2% was used for doping to weight percentage of BaZr0.2Ti0.8O3. The samples were authenticated using raw data obtained from Bruker AXS D8 advance Copper KL alpha source XRD equipment. Further, the samples were studied for their phase transition, composition, single phase perovskite structure using XRD technique. The technique has also been applied to know formation of stable homogeneous solid solution from XRD parameters. The other physical parameters like the morphology, micro structural information, crystal arrangements and topography have also been observed through SEM. The SEM has revealed information related to grain size development and composition of sample with fine agglomerates. For complete study of the compounds the atomic and weight composition has also been examined by Electron Dispersive Spectroscopy patterns. The comparison has been made with other works on ceramics at various frequencies and has yielded very interesting results.

  11. Barium titanate nanoparticles and hypergravity stimulation improve differentiation of mesenchymal stem cells into osteoblasts

    PubMed Central

    Rocca, Antonella; Marino, Attilio; Rocca, Veronica; Moscato, Stefania; de Vito, Giuseppe; Piazza, Vincenzo; Mazzolai, Barbara; Mattoli, Virgilio; Ngo-Anh, Thu Jennifer; Ciofani, Gianni

    2015-01-01

    Background Enhancement of the osteogenic potential of mesenchymal stem cells (MSCs) is highly desirable in the field of bone regeneration. This paper proposes a new approach for the improvement of osteogenesis combining hypergravity with osteoinductive nanoparticles (NPs). Materials and methods In this study, we aimed to investigate the combined effects of hypergravity and barium titanate NPs (BTNPs) on the osteogenic differentiation of rat MSCs, and the hypergravity effects on NP internalization. To obtain the hypergravity condition, we used a large-diameter centrifuge in the presence of a BTNP-doped culture medium. We analyzed cell morphology and NP internalization with immunofluorescent staining and coherent anti-Stokes Raman scattering, respectively. Moreover, cell differentiation was evaluated both at the gene level with quantitative real-time reverse-transcription polymerase chain reaction and at the protein level with Western blotting. Results Following a 20 g treatment, we found alterations in cytoskeleton conformation, cellular shape and morphology, as well as a significant increment of expression of osteoblastic markers both at the gene and protein levels, jointly pointing to a substantial increment of NP uptake. Taken together, our findings suggest a synergistic effect of hypergravity and BTNPs in the enhancement of the osteogenic differentiation of MSCs. Conclusion The obtained results could become useful in the design of new approaches in bone-tissue engineering, as well as for in vitro drug-delivery strategies where an increment of nanocarrier internalization could result in a higher drug uptake by cell and/or tissue constructs. PMID:25609955

  12. Modeling of compositionally graded barium strontium titanate from first principles

    NASA Astrophysics Data System (ADS)

    Walizer, Laura Elizabeth

    Barium Strontium Titanate (BaxSr1-xTiO 3 or BST) is a Perovskite alloy of interest for both technological and intellectual reasons. Its ferroelectric and piezoelectric properties make it useful in a variety of electric components such as transducers and actuators, and BST in particular is a material of interest for the development of a ferroelectric RAM for computers.(1) The inclusion of SrTiO3, an incipient ferroelectric, and the fact that the properties of a BST system depend strongly on its relative composition of BaTiO3 (BT) and SrTiO3 (ST), make also this a material of high interest. (2) Compositionally graded systems are of further interest (see e.g., Refs. (3), (4), (5) and references therein), partly because their compositional grading leads to a built-in polarization gradient. Due to this, these systems could act as transcapacitors, devices which act as charge amplifiers in much the same way that transistors act as current amplifiers.(3), (4) Here, compositionally graded BST systems were modeled using a first-principles derived effective Hamiltonian method within Monte-Carlo simulation. (6) The graded systems under consideration had an average Ba composition of 70%. These systems were modeled under stress-free conditions, as well as, under epitaxial strain due to a SrTiO3 substrate. Both the degree of grading and the thickness of the layers were varied. The investigation revealed that graded BST systems behaved differently from bulk BST systems in several ways. First, some graded BST systems possessed both monodomain states qualitatively similar to those found in bulk systems (except that the polarization exhibited a "wave" behavior inside the graded systems), and also states with domain striping. Where this occurred, the monodomain state was lower in energy, and was therefore the ground-state, but the striped domain state was found to be metastable, representing a local energy minimum. Analyzing unstrained compositionally graded systems layer by layer

  13. Screening dynamics in doped titanates

    SciTech Connect

    Rubensson, J.E.; Luening, J.; Eisebitt, S.

    1997-04-01

    The time scale for carrier relaxation in semiconductors is on the same order of magnitude as the life time of shallow core hole states (a few femtoseconds). Resonant Inelastic soft X-ray scattering (RIXS) which involves (virtual) excitations of core levels consequently contains information about the time development of the electronic structure on this time scale. In many cases one can treat the scattering in an absorption (SXA) followed-by-emission (SXE) picture, where simply the rates for various processes can be compared with the intermediate core hole state decay rate as an internal {open_quotes}clock{close_quotes}. By variation of x (0 < x < 1) in La{sub x}Sr{sub 1{minus}x}TiO{sub 3}, the amount of Ti d electrons in the system can be controlled. SrTiO{sub 3} (x=0) is an insulator with an empty Ti d band. With increasing x, electrons are doped into the Ti d-band, and LaTiO{sub 3} (x=1) is a Mott Hubbard insulator with a Ti 3d{sup 1} configuration. In this work the authors demonstrate that the rate for Ti 2p core hole screening in La{sub x}Sr{sub 1{minus}x}TiO{sub 3} is doping dependent. The screening rate increases with the availability of Ti 3d electrons, and they estimate it to be 3.8 x 10{sup 13}/sec in La{sub 0.05}Sr{sub 0.95}TiO{sub 3}.

  14. Electronic structure of barium strontium titanate by soft-x-ray absorption spectroscopy

    SciTech Connect

    Uehara, Y.; Underwood, J.H.; Gullikson, E.M.; Perera, R.C.C.

    1997-04-01

    Perovskite-type titanates, such as Strontium Titanate (STO), Barium Titanate (BTO), and Lead Titanate (PTO) have been widely studied because they show good electric and optical properties. In recent years, thin films of Barium Strontium Titanate (BST) have been paid much attention as dielectrics of dynamic random access memory (DRAM) capacitors. BST is a better insulator with a higher dielectric constant than STO and can be controlled in a paraelectric phase with an appropriate ratio of Ba/Sr composition, however, few studies have been done on the electronic structure of the material. Studies of the electronic structure of such materials can be beneficial, both for fundamental physics research and for improving technological applications. BTO is a famous ferroelectric material with a tetragonal structure, in which Ti and Ba atoms are slightly displaced from the lattice points. On the other hand, BST keeps a paraelectric phase, which means that the atoms are still at the cubic lattice points. It should be of great interest to see how this difference of the local structure around Ti atoms between BTO and BST effects the electronic structure of these two materials. In this report, the authors present the Ti L{sub 2,3} absorption spectra of STO, BTO, and BST measured with very high accuracy in energy of the absorption features.

  15. Microwave assisted synthesis and characterization of barium titanate nanoparticles for multi layered ceramic capacitor applications.

    PubMed

    Thirumalai, Sundararajan; Shanmugavel, Balasivanandha Prabu

    2011-01-01

    Barium titanate is a common ferroelectric electro-ceramic material having high dielectric constant, with photorefractive effect and piezoelectric properties. In this research work, nano-scale barium titanate powders were synthesized by microwave assisted mechano-chemical route. Suitable precursors were ball milled for 20 hours. TGA studies were performed to study the thermal stability of the powders. The powders were characterized by XRD, SEM and EDX Analysis. Microwave and Conventional heating were performed at 1000 degrees C. The overall heating schedule was reduced by 8 hours in microwave heating thereby reducing the energy and time requirement. The nano-scale, impurity-free and defect-free microstructure was clearly evident from the SEM micrograph and EDX patterns. LCR meter was used to measure the dielectric constant and dielectric loss values at various frequencies. Microwave heated powders showed superior dielectric constant value with low dielectric loss which is highly essential for the fabrication of Multi Layered Ceramic Capacitors. PMID:24427875

  16. Preliminary experiments on phase conjugation for flow visualization. [barium titanate single crystals

    NASA Technical Reports Server (NTRS)

    Weimer, D.; Howes, W. L.

    1984-01-01

    Barium titanate single crystals are discussed in the context of: the procedure for polarizing a crystal; a test for phase conjugation; transients in the production of phase conjugation; real time readout by a separate laser of a hologram induced within the crystal, including conjugation response times to on-off switching of each beam; and a demonstration of a Twyman-Green interferometer utilizing phase conjugation.

  17. A study of the microchemistry of nanocrystalline barium titanate with tetragonal and pseudocubic room temperature symmetries

    NASA Astrophysics Data System (ADS)

    Lacey, Robert A.

    The investigation of possible effects of undesired surface species on barium titanate, one of the most utilized ferroelectric ceramics, constitutes the focus of this work. Six commercial barium titanate powders from three manufacturers representing two different synthesis processes, with average particle sizes from 40 nm to 470 nm, were analyzed in this study. Four of the nanopowders exhibited pseudocubic room temperature symmetry. Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopic analysis of the nanopowders was conducted in ambient atmosphere at room temperature. High temperature DRIFT followed incorporating four avenues of analysis: moisture adsorption studies, deuterium oxide exchange studies, carbon dioxide adsorption studies, and high temperature analysis under dry air and UHP nitrogen atmospheres. At the highest temperature used in this study, 1173K, moisture and the accompanying incorporated protonic impurities were still present. The powders readily readsorbed moisture during rapid cooling, 170K/minute, to room temperature. The smallest powder, as received, formed spherical agglomerates up to 10 mum diameter. These sintered as separate units attaining diameters up to 60 mum during intermediate stage sintering. X-ray photoelectron spectroscopy indicated a surface contamination layer of 10 A to 18 A; 50--70% of which was barium carbonate, the balance being atmospheric adsorbed species. Samples cooled at 3K/minute after an 1173K calcine retained cubic symmetry as indicated with high temperature X-ray diffraction. However, spectral evidence was obtained indicating that upon the rapid cooling from the 1173K calcine, a reorientation to the room temperature tetragonal symmetry was observed. Further, SEM and TEM supported this finding with visual evidence of interfacial rearrangement including corroborating electron diffraction analysis. This data, therefore, substantiated the hypothesis that the cause of the room temperature pseudocubic

  18. Comparative analysis of barium titanate thin films dry etching using inductively coupled plasmas by different fluorine-based mixture gas

    PubMed Central

    2014-01-01

    In this work, the inductively coupled plasma etching technique was applied to etch the barium titanate thin film. A comparative study of etch characteristics of the barium titanate thin film has been investigated in fluorine-based (CF4/O2, C4F8/O2 and SF6/O2) plasmas. The etch rates were measured using focused ion beam in order to ensure the accuracy of measurement. The surface morphology of etched barium titanate thin film was characterized by atomic force microscope. The chemical state of the etched surfaces was investigated by X-ray photoelectron spectroscopy. According to the experimental result, we monitored that a higher barium titanate thin film etch rate was achieved with SF6/O2 due to minimum amount of necessary ion energy and its higher volatility of etching byproducts as compared with CF4/O2 and C4F8/O2. Low-volatile C-F compound etching byproducts from C4F8/O2 were observed on the etched surface and resulted in the reduction of etch rate. As a result, the barium titanate films can be effectively etched by the plasma with the composition of SF6/O2, which has an etch rate of over than 46.7 nm/min at RF power/inductively coupled plasma (ICP) power of 150/1,000 W under gas pressure of 7.5 mTorr with a better surface morphology. PMID:25278821

  19. Rapid synthesis of barium titanate microcubes using composite-hydroxides-mediated avenue

    SciTech Connect

    He, Xi; Ouyang, Jing Jin, Jiao; Yang, Huaming

    2014-04-01

    Highlights: • Barium titanate oxides microcubes can be synthesized within 1 min. • Composite-hydroxides-mediated strategy provided a possible large scale production. • BST obtained in the strategy showed fairly good crystallinity and tetragonality. - Abstract: This paper reports the rapid synthesis of barium titanate (BaTiO{sub 3}, BTO) microcubes via composite-hydroxides-mediated reaction within 1 min. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectrum (EDS) results confirmed both cubic and tetragonal lattices in the sample and the uniform microcubes with an average size of 1 μm. Ultraviolet–visible (UV–vis) spectrum indicated that the band gap of the BTO powder was 3.05 eV. Ferroelectric polarization vs. electric field (P–E) tests showed that the ferroelectric domains had formed in the as-synthesized BTO microcubes and sintered ceramics. BTO ceramics sintered at 1100 °C for 3 h showed fairly good tetragonality and possessed a maximum polarization of 0.21 μC/cm{sup 2}, indicating that the sintering temperature for the BTO powders prepared via this method was relatively low. The process and equipment reported herein provided a potential method for the rapid synthesis of titanate based perovskites.

  20. Europium-doped barium bromide iodide

    SciTech Connect

    Gundiah, Gautam; Hanrahan, Stephen M.; Hollander, Fredrick J.; Bourret-Courchesne, Edith D.

    2009-10-21

    Single crystals of Ba0.96Eu0.04BrI (barium europium bromide iodide) were grown by the Bridgman technique. The title compound adopts the ordered PbCl2 structure [Braekken (1932). Z. Kristallogr. 83, 222-282]. All atoms occupy the fourfold special positions (4c, site symmetry m) of the space group Pnma with a statistical distribution of Ba and Eu. They lie on the mirror planes, perpendicular to the b axis at y = +-0.25. Each cation is coordinated by nine anions in a tricapped trigonal prismatic arrangement.

  1. Single-step synthesis of well-crystallized and pure barium titanate nanoparticles in supercritical fluids

    NASA Astrophysics Data System (ADS)

    Reverón, Helen; Aymonier, Cyril; Loppinet-Serani, Anne; Elissalde, Catherine; Maglione, Mario; Cansell, François

    2005-08-01

    Single-step synthesis of ultra-fine barium titanate powder with a crystallinity as high as 90% and without barium carbonate contamination has been successfully performed under supercritical conditions using a continuous-flow reactor in the temperature range 150-380 °C at 16 MPa. To synthesize this bimetallic oxide, alkoxides, ethanol and water were used. The influence of the synthesis parameters on the BaTiO3 powder characteristics was investigated. The results show that the water to alkoxide precursor ratio, the reactor temperature and the Ba:Ti molar ratio of alkoxide precursor play a major role in the crystallization of pure and well-crystallized BaTiO3 nanoparticles. The continuous mode of operation without post-treatments for powder washing, drying or crystallization increase the industrial interest.

  2. Hydrothermal Synthesis and Processing of Barium Titanate Nanoparticles Embedded in Polymer Films.

    PubMed

    Toomey, Michael D; Gao, Kai; Mendis, Gamini P; Slamovich, Elliott B; Howarter, John A

    2015-12-30

    Barium titanate nanoparticles embedded in flexible polymer films were synthesized using hydrothermal processing methods. The resulting films were characterized with respect to material composition, size distribution of nanoparticles, and spatial location of particles within the polymer film. Synthesis conditions were varied based on the mechanical properties of the polymer films, ratio of polymer to barium titanate precursors, and length of aging time between initial formulations of the solution to final processing of nanoparticles. Block copolymers of poly(styrene-co-maleic anhydride) (SMAh) were used to spatially separate titanium precursors based on specific chemical interactions with the maleic anhydride moiety. However, the glassy nature of this copolymer restricted mobility of the titanium precursors during hydrothermal processing. The addition of rubbery butadiene moieties, through mixing of the SMAh with poly(styrene-butadiene-styrene) (SBS) copolymer, increased the nanoparticle dispersion as a result of greater diffusivity of the titanium precursor via higher mobility of the polymer matrix. Additionally, an aminosilane was used as a means to retard cross-linking in polymer-metalorganic solutions, as the titanium precursor molecules were shown to react and form networks prior to hydrothermal processing. By adding small amounts of competing aminosilane, excessive cross-linking was prevented without significantly impacting the quality and composition of the final barium titanate nanoparticles. X-ray diffraction and X-ray photoelectron spectroscopy were used to verify nanoparticle compositions. Particle sizes within the polymer films were measured to be 108 ± 5 nm, 100 ± 6 nm, and 60 ± 5 nm under different synthetic conditions using electron microscopy. Flexibility of the films was assessed through measurement of the glass transition temperature using dynamic mechanical analysis. Dielectric permittivity was measured using an impedance analyzer. PMID

  3. Study of the structure of ferroelectric domain walls in barium titanate ceramics

    SciTech Connect

    Normand, L.; Thorel, A.; Kilaas, R.; Montardi, Y.

    1995-02-01

    Structure of 90{degree} ferroelectric domain boundaries in barium titanate ceramics has been studied by means of Transmission Electron Microscopy and High Resolution TEM. Tilts of specific fringes across domain walls are measured on HREM images and Selected Area Diffraction Patterns. They are in a good agreement with the twin model admitted for these domain boundaries. A computerized method has been developed to give access to quantitative information about atomic displacements across these ferroelectric domain walls. The so calculated displacement field is then compared with Landau-Ginzburg based theoretical predictions.

  4. Strain effect on coercive field of epitaxial barium titanate thin films

    NASA Astrophysics Data System (ADS)

    Choudhury, S.; Li, Y. L.; Chen, L. Q.; Jia, Q. X.

    2008-04-01

    Strain is generally known to increase the coercive field of a ferroelectric thin film as compared to a stress-free single crystal or a strain-relaxed film. We studied the coercive fields and remanent polarizations of (001)-oriented epitaxial barium titanate thin films using the phase-field approach. It is demonstrated, while the remanent polarization decreases as in-plane strain changes from being compressive to tensile, the variation of coercive field with strain is complicated. We noted more than two times drop in coercive field with a reduction of compressive strain of only ˜0.05%, which we attribute to the existence of multiple ferroelectric phases.

  5. Molecular dynamics of poly(ethylene terephthalate)/poly(phenylene sulfide) nanocomposites with barium titanate

    NASA Astrophysics Data System (ADS)

    Konieczna, Monika; Woźniak-Braszak, Aneta; Hołderna-Natkaniec, Krystyna; Jurga, Jan

    2011-04-01

    The relaxation processes and the properties of polymer/ceramic nanocomposites have been studied by the 1H nuclear magnetic resonance methods. Nanocomposites of poly(ethylene terephthalate) PET and poly(phenylene sulfide) PPS with 0.25, 2.5 and 5% wt. barium titanate BT were prepared using a twin screw extruder and injection moulding machine. The spin-lattice relaxation time T1, second moment M2 and the motional parameters as e.g. the activation energies in the nanocomposites were investigated.

  6. Anelastic behavior of barium-titanate-based ceramic materials

    NASA Astrophysics Data System (ADS)

    Duffy, W.; Cheng, B. L.; Gabbay, M.; Fantozzi, G.

    1995-07-01

    The internal friction ( Qsu-1) and Young’s modulus ( E) of BaTiO3-based ceramics were measured vs temperature from -100 °C to 150 °C. Rectangular bars of high-density (96 to 99 pct) ma-terials were driven electrostatically in flexural vibration at a resonance frequency of about 3 kHz, at maximum strain levels of about 10-6. The curves of Q -1( T) and E(T) allow the study of the following three phase transformations: tetragonal to cubic (about 130 °C in pure material), orthorhombic to tetragonal (about 0 °C in pure material), and rhombohedral to orthorhombic (about -80 °C in pure material). Internal friction and modulus data were obtained on pure material and on materials doped with niobium and cobalt to give semiconducting and insulating X7R behavior. Permittivity, dielectric loss, and microstructure data are given and used to aid interpretation of the mechanical measurement data.

  7. A Mechanistic Study of Nanoscale Structure Development, Phase Transition, Morphology Evolution, and Growth of Ultrathin Barium Titanate Nanostructured Films

    NASA Astrophysics Data System (ADS)

    Ashiri, Rouholah

    2014-08-01

    In the present work, an improved method is developed for preparing highly pure ultrathin barium titanate nanostructured films with desired structural and morphological characteristics. In contrast to other approaches, our method can be carried out at a relatively lower temperature to obtain barium titanate ultrathin films free from secondary phases, impurities, and cracks. To reach an in-depth understanding of scientific basis of the proposed process, and in order to disclose the mechanism of formation and growth of barium titanate ultrathin film, in-detail analysis is carried out using XRD, SEM, FE-SEM, and AFM techniques aided by theoretical calculations. The effects of calcining temperature on the nanoscale structure development, phase transition, morphology evolution, and growth mechanism of the ultrathin barium titanate nanostructured films are studied. XRD results indicate that the reaction leading to the formation of the barium titanate initiates at about 873 K (600 °C) and completes at about 1073 K (800 °C). Moreover, secondary phases are not detected in the XRD patterns of the ultrathin films which this observation ensures the phase purity of the ultrathin films. The results show that the ultrathin films are nanothickness and nanostructured leading to the enhancement of rate of diffusion by activating short-circuit diffusion mechanisms. The high rate of the diffusion enhances the rate of the formation of barium titanate and also prevents from the formation of the secondary phases in the final products. SEM and AFM results indicate that the deposited ultrathin films are crack-free exhibiting a dense nanogranular structure. The results indicate that the root-mean square (RMS) roughness of the ultrathin films is in the range of 1.66 to 6.71 nm indicating the surface of the ultrathin films is smooth. RMS roughness also increases with an increase in the calcining temperature which this observation seems to be related to the grain growth process. Finally

  8. Dielectric relaxation of barium strontium titanate and application to thin films for DRAM capacitors

    NASA Astrophysics Data System (ADS)

    Baniecki, John David

    This thesis examines the issues associated with incorporating the high dielectric constant material Barium Strontium Titanate (BSTO) in to the storage capacitor of a dynamic random access memory (DRAM). The research is focused on two areas: characterizing and understanding the factors that control charge retention in BSTO thin films and modifying the electrical properties using ion implantation. The dielectric relaxation of BSTO thin films deposited by metal-organic chemical vapor deposition (MOCVD) is investigated in the time and frequency domains. It is shown that the frequency dispersion of the complex capacitance of BSTO thin films can be understood in terms of a power-law frequency dependence from 1mHz to 20GHz. From the correspondence between the time and frequency domain measurements, it is concluded that the power-law relaxation currents extend back to the nano second regime of DRAM operation. The temperature, field, and annealing dependence of the dielectric relaxation currents are also investigated and mechanisms for the observed power law relaxation are explored. An equivalent circuit model of a high dielectric constant thin film capacitor is developed based on the electrical measurements and implemented in PSPICE. Excellent agreement is found between the experimental and simulated electrical characteristics showing the utility of the equivalent circuit model in simulating the electrical properties of high dielectric constant thin films. Using the equivalent circuit model, it is shown that the greatest charge loss due to dielectric relaxation occurs during the first read after a refresh time following a write to the opposite logic state for a capacitor that has been written to the same logic state for a long time (opposite state write charge loss). A theoretical closed form expression that is a function of three material parameters is developed which estimates the opposite state write charge loss due to dielectric relaxation. Using the closed form

  9. Proton trapping in yttrium-doped barium zirconate

    NASA Astrophysics Data System (ADS)

    Yamazaki, Yoshihiro; Blanc, Frédéric; Okuyama, Yuji; Buannic, Lucienne; Lucio-Vega, Juan C.; Grey, Clare P.; Haile, Sossina M.

    2013-07-01

    The environmental benefits of fuel cells have been increasingly appreciated in recent years. Among candidate electrolytes for solid-oxide fuel cells, yttrium-doped barium zirconate has garnered attention because of its high proton conductivity, particularly in the intermediate-temperature region targeted for cost-effective solid-oxide fuel cell operation, and its excellent chemical stability. However, fundamental questions surrounding the defect chemistry and macroscopic proton transport mechanism of this material remain, especially in regard to the possible role of proton trapping. Here we show, through a combined thermogravimetric and a.c. impedance study, that macroscopic proton transport in yttrium-doped barium zirconate is limited by proton-dopant association (proton trapping). Protons must overcome the association energy, 29 kJ mol-1, as well as the general activation energy, 16 kJ mol-1, to achieve long-range transport. Proton nuclear magnetic resonance studies show the presence of two types of proton environment above room temperature, reflecting differences in proton-dopant configurations. This insight motivates efforts to identify suitable alternative dopants with reduced association energies as a route to higher conductivities.

  10. Microstructural studies of nanocrystalline barium zirconium titanate (BZT) for piezoelectric applications

    NASA Astrophysics Data System (ADS)

    Jamil, Nor Huwaida Janil @; Izzuddin, Izura; Zainuddin, Zalita; Jumali, Mohammad Hafizuddin Haji

    2015-09-01

    Lead-free piezoelectric ceramics based on barium titanate (BaTiO3) with substitution of Zr4+ were prepared using sol-gel method. The Ba(ZrxTi1-x)O3, (BZT) powders with x = 0.0, 0.1, 0.2 and 0.3 were pressed into pellets and sintered at 1250 °C for 2 h. Focusing on the effect of Zr4+ substitutions into BaTiO3 perovskite system, the phase transition and microstructural properties of BZT ceramics were studied using XRD, SEM and EDX spectroscopy. All X-ray diffractograms were fitted using Pawley refinement model. The XRD diffractograms revealed the progressive phase transition from tetragonal to cubic phase as Zr content increased. The crystallite exhibited decreasing trend and was supported by shrinkage in grain size. The EDX analysis confirmed the successful substitution of Ti4+ with Zr4+ in BaTiO3 crystal.

  11. Thermally stimulated currents in amorphous barium titanate thin films deposited by rf magnetron sputtering

    NASA Astrophysics Data System (ADS)

    El Kamel, F.; Gonon, P.; Jomni, F.; Yangui, B.

    2006-09-01

    Thermally stimulated currents (TSCs) are measured in amorphous barium titanate thin films deposited by the rf sputtering technique. The TSC global curve is composed of three overlapping peaks in the 0-200°C temperature range. At 50°C, a first TSC peak is observed that can be related to a shallow-trap level. A second peak due to a dipolar polarization process is observed at 95°C. Finally, a third peak appears at 140°C that is ascribed to the oxygen vacancy motion and their accumulation at electrodes. The different peaks constituting the global TSC spectrum are separately studied by the fractional polarization technique in order to analyze their fine structures and to determine their activation energies.

  12. Barium Titanate Nanoparticles: Highly Cytocompatible Dispersions in Glycol-chitosan and Doxorubicin Complexes for Cancer Therapy

    NASA Astrophysics Data System (ADS)

    Ciofani, Gianni; Danti, Serena; D'Alessandro, Delfo; Moscato, Stefania; Petrini, Mario; Menciassi, Arianna

    2010-07-01

    In the latest years, innovative nanomaterials have attracted a dramatic and exponentially increasing interest, in particular for their potential applications in the biomedical field. In this paper, we reported our findings on the cytocompatibility of barium titanate nanoparticles (BTNPs), an extremely interesting ceramic material. A rational and systematic study of BTNP cytocompatibility was performed, using a dispersion method based on a non-covalent binding to glycol-chitosan, which demonstrated the optimal cytocompatibility of this nanomaterial even at high concentration (100 μg/ml). Moreover, we showed that the efficiency of doxorubicin, a widely used chemotherapy drug, is highly enhanced following the complexation with BTNPs. Our results suggest that innovative ceramic nanomaterials such as BTNPs can be realistically exploited as alternative cellular nanovectors.

  13. Structures of 90{degrees} domain walls in ferroelectric barium titanate ceramics

    SciTech Connect

    Normand, L.; Thorel, A.; Kilaas, R.

    1995-03-01

    Ferroelectric domain walls in tetragonal ferroelectric barium titanate ceramics are studied by means of electron microscopy. SEM and TEM observations are consistent with domain configuration already proposed. Conventional TEM measurements on SADP agree very well with twin-related model currently admitted for ferroelectric domains. In spite of the very small lattice parameter variation during cooling (involving a small spontaneous strain) of BaTiO{sub 3} ceramics, displacements of specific features associated with atomic column positions are measured across domain walls on high resolution images. Using a dedicated image analysis software, these displacements are calculated with a high precision. 2D vector-maps of the atomic displacements show different kinds of atomistic structure for different domain walls.

  14. Microstructural, dielectric and magnetic properties of multiferroic composite system barium strontium titanate – nickel cobalt ferrite

    SciTech Connect

    Pahuja, Poonam Tandon, R. P.

    2015-05-15

    Multiferroic composites (1-x) Ba{sub 0.95}Sr{sub 0.05}TiO{sub 3} + (x) Ni{sub 0.8}Co{sub 0.2}Fe{sub 2}O{sub 4} (where x = 0.1, 0.2, 0.3, 0.4) has been prepared by solid state reaction method. X-ray diffraction analysis of the composite samples confirmed the presence of both barium strontium titanate (BST) and nickel cobalt ferrite (NCF) phases. FESEM images indicated the well dispersion of NCF grains among BST grains. Dielectric constant and loss of the composite samples decreases with increase in frequency following Maxwell-Wagner relaxation mechanism. Composite sample with highest ferrite content possesses highest values of remanent and saturation magnetization.

  15. Nonlinear photonic crystal waveguide structures based on barium titanate thin films and their optical properties

    NASA Astrophysics Data System (ADS)

    Liu, Zhifu; Lin, Pao-Tai; Wessels, Bruce W.; Yi, Fei; Ho, Seng-Tiong

    2007-05-01

    Nonlinear photonic crystal waveguide structures were fabricated from barium titanate thin films using nanolithography. A cascaded Bragg reflector using a strip waveguide was designed and analyzed. Both simulation and experimental results show that there is sufficient refractive index contrast to form a stop band by only etching through the Si3N4 strip layer. The band gap of the Bragg reflector can be engineered through control of the Bragg spacing, thickness, and etching depth of the strip layer. The transmission spectrum of the Bragg reflector waveguide was measured over the spectral range of 1500-1580nm. A 27nm wide stop band was obtained for a millimeter long sample. The nonlinear photonic crystal waveguides are potentially suitable as tunable filters, optical switches, and ultrawide bandwidth modulators.

  16. Structural and Mössbauer investigation on barium titanate-cobalt ferrite composites

    NASA Astrophysics Data System (ADS)

    Leonel, Liliam V.; Silva, Juliana B.; Albuquerque, Adriana S.; Ardisson, José D.; Macedo, Waldemar A. A.; Mohallem, Nelcy D. S.

    2012-11-01

    Perovskite and spinels oxides have received renewed attention due to the possibility of combining both structures in di-phase composites to obtain multifunctional materials. In this work, barium titanate (perovskite)-cobalt ferrite (spinel) composite powders with different microstructures were obtained from thermal treatment of amorphous precursors at 500-1100 °C. The precursors were prepared by combining coprecipitation and sol-gel routes. Lyophilization of ferrite prior to mixing was used as a strategy to control interphase reaction. Mössbauer spectroscopy showed that the dispersion of coprecipitated ferrite in a viscous BaTiO3 precursor gel resulted in superparamagnetic behavior and reduction of the local magnetic field of site [B].

  17. Preparation, characterization, and manipulation of iron platinum, barium titanate, and vanadium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Morris, William Homer, III

    2008-12-01

    New synthesis strategies for preparation of FePt, BaTiO 3, VO2, V2O3, V2O5 , and V6O13 nanoparticles are presented in this thesis. Electron microscopy, diffraction, elemental analysis, and physical property measurement studies confirm the composition and structure of the synthesized material. Also reported is size-selection of ferromagnetic nanoparticles by binding PEG (2000 MW) ligand to particle surfaces and fractionally precipitating more narrowed size cuts. Large (30--100 nm) ferromagnetic nanoparticles are prepared by employing vesicle templates. Barium titanate nanoparticles with an average diameter of 3.8 nm have been synthesized within inverse micelles. A variety of vanadium oxide compositions within the nanometer size regime have been prepared using sol-gel chemistry.

  18. Study of a Flexible Low Profile Tunable Dipole Antenna Using Barium Strontium Titanate Varactors

    NASA Technical Reports Server (NTRS)

    Cure, David; Weller, Thomas; Miranda, Felix A.

    2014-01-01

    In this paper a flexible low profile dipole antenna using a frequency selective surface (FSS) with interdigital barium strontium titanate (BST) varactor-tuned unit cells is presented. The varactor chips were placed only along one dimension of the FSS to avoid the use of vias and simplify the DC bias network. The antenna uses overlapping metallic plates that resemble fish scales as a ground plane to improve the flexibility of the multi-material stack structure. The measured data of the antenna demonstrate tunability from 2.42 GHz to 2.66 GHz and 1.3 dB gain drop when using overlapping metallic plates instead of continuous ground plane. The total antenna thickness is approximately lambda/24.

  19. Nucleation in the presence of long-range interactions. [performed on ferroelectric barium titanate

    NASA Technical Reports Server (NTRS)

    Chandra, P.

    1989-01-01

    Unlike droplet nucleation near a liquid-gas critical point, the decay of metastable phases in crystalline materials is strongly affected by the presence of long-range forces. Field quench experiments performed on the ferroelectric barium titanate indicate that nucleation in this material is markedly different from that observed in liquids. In this paper, a theory for nucleation at a first-order phase transition in which the mediating forces are long range is presented. It is found that the long-range force induces cooperative nucleation and growth processes, and that this feedback mechanism produces a well-defined delay time with a sharp onset in the transformation to the stable phase. Closed-form expressions for the characteristic onset time and width of the transition are developed, in good agreement with numerical and experimental results.

  20. Near-field resonance shifts of ferroelectric barium titanate domains upon low-temperature phase transition

    SciTech Connect

    Döring, Jonathan; Ribbeck, Hans-Georg von; Kehr, Susanne C.; Eng, Lukas M.; Fehrenbacher, Markus

    2014-08-04

    Scattering scanning near-field optical microscopy (s-SNOM) has been established as an excellent tool to probe domains in ferroelectric crystals at room temperature. Here, we apply the s-SNOM possibilities to quantify low-temperature phase transitions in barium titanate single crystals by both temperature-dependent resonance spectroscopy and domain distribution imaging. The orthorhombic-to-tetragonal structural phase transition at 263 K manifests in a change of the spatial arrangement of ferroelectric domains as probed with a tunable free-electron laser. More intriguingly, the domain distribution unravels non-favored domain configurations upon sample recovery to room temperature as explainable by increased sample disorder. Ferroelectric domains and topographic influences are clearly deconvolved even at low temperatures, since complementing our s-SNOM nano-spectroscopy with piezoresponse force microscopy and topographic imaging using one and the same atomic force microscope and tip.

  1. Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

    NASA Astrophysics Data System (ADS)

    Liang, Wei-Zheng; Ji, Yan-Da; Nan, Tian-Xiang; Huang, Jiang; Zeng, Hui-Zhong; Du, Hui; Chen, Chong-Lin; Lin, Yuan

    2012-06-01

    Barium titanate (BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition (PAD) technique. The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion. Crystal structures, surface morphologies, and dielectric performance were examined and compared for BTO thin films annealed under different temperatures. Correlations between the fabrication conditions, microstructures, and dielectric properties were discussed. BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with inr ~ 400 and tan δ < 0.025 at 100 kHz. The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

  2. Ferroelectric domain pattern in barium titanate single crystals studied by means of digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Mokrý, Pavel; Psota, Pavel; Steiger, Kateřina; Václavík, Jan; Doleček, Roman; Vápenka, David; Lédl, Vít

    2016-06-01

    In this article, we report on the observation of a ferroelectric domain pattern in the whole volume of the ferroelectric barium titanate single crystal by means of digital holographic microscopy (DHM). Our particular implementation of DHM is based on the Mach–Zehnder interferometer and the numerical processing of data employs the angular spectrum method. A modification of the DHM technique, which allows a fast and accurate determination of the domain walls, i.e. narrow regions separating the antiparallel domains, is presented. Accuracy and sensitivity of the method are discussed. Using this approach, the determination of important geometric parameters of the ferroelectric domain patterns (such as domain spacing or the volume fraction of the anti-parallel domains) is possible. In addition to the earlier DHM studies of domain patterns in lithium niobate and lithium tantalate, our results indicate that the DHM is a convenient method to study a dynamic evolution of ferroelectric domain patterns in all perovskite single crystals.

  3. Barium iron arsenide, barium cobalt arsenide, barium nickel arsenide single crystals and superconductivity upon cobalt doping

    SciTech Connect

    Ronning, Filip; Sefat, A S; Mcguire, M M; Sales, B; Jin, R; Mandrus, D

    2009-01-01

    The crystal structure and physical properties of BaFe{sub 2}As{sub 2}, BaCo{sub 2}As{sub 2}, and BaNi{sub 2}As{sub 2} single crystals are surveyed. BaFe{sub 2}As{sub 2} gives a magnetic and structural transition at T{sub N} = 132(1) K, BaCo{sub 2}As{sub 2} is a paramagnetic metal, while BaNi{sub 2}As{sub 2} has a structural phase transition at T{sub 0} = 131 K, followed by superconductivity below {Tc} = 0.69 K. The bulk superconductivity in Co-doped BaFe{sub 2}As{sub 2} below {Tc} = 22 K is demonstrated by resistivity, magnetic susceptibility, and specific heat data. In contrast to the cuprates, the Fe-based system appears to tolerate considerable disorder in the transition metal layers. First principles calculations for BaFe{sub 1.84}Co{sub 0.16}As{sub 2} inter-band scattering due to Co is weak.

  4. Preparation and characterization of Grain-Oriented Barium Titanate Ceramics Using Electrophoresis Deposition Method under A High Magnetic Field

    NASA Astrophysics Data System (ADS)

    Kita, T.; Kondo, S.; Takei, T.; Kumada, N.; Nakashima, K.; Fujii, I.; Wada, S.; Suzuki, T. S.; Uchikoshi, T.; Sakka, Y.; Miwa, Y.; Kawada, S.; Kimura, M.

    2011-10-01

    Barium titanate (BaTiO3) grain-oriented ceramics were prepared using electrophoresis deposition (EPD) method under high magnetic field of 12 T. First, BaTiO3 nanoparticles with high c/a ratio of 1.008 and size of 84 nm were prepared by two-step thermal decomposition method with barium titanyl oxalate nanoparticles. Using the BaTiO3 slurry, BaTiO3 nanoparticle accumulations were prepared by EPD method under high magnetic field. After binder burnout, the accumulations were sintered and BaTiO3 grain-oriented ceramics were prepared. Moreover, dielectric properties of their ceramics were investigated

  5. Characterization of hexabarium 17-titanate and its effects on the dielectric properties of barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Xu, Xilin

    The formation of the Ba6Ti17O40 (B6T17) phase is inevitable in BaTiO3 ceramics with excess TiO2. And B6T17 phases in a dendritic morphology were frequently reported. In this study, the formation mechanism for B6T17 having a dendritic morphology, and the effect of this B6T17 phase on the dielectric properties of BaTiO3 ceramics have been investigated. In non-doped BaTiO3, the B6T17 phase exhibited a needle-like morphology when sintered above the eutectic temperature. The needle-like B6T17 phase was more likely to occur on the as-sintered surface of the sample, as the eutectic melt was squeezed out during sintering and densification. The topotactic relationship between the BaTiO3 and B6T17 phases can be used to interpret the formation mechanism for the needle-like B6T17 morphology. When BaTiO3 was doped with Nb5+ or other donor dopants (Ta5+, La3+) and sintered in an oxidizing atmosphere, the B6T17 phase exhibited a dendritic morphology. This dendntic morphology was not observed in Co2+ doped samples. The dendritic morphology may be due to the topotactic relationship between the BaTiO 3 and B6T17 phases and the formation of Ti2O9 groups for hexagonal stacking. Based on experimental results, the B6T17 phase in a dendritic morphology in BaTiO3 ceramics occurs under the following conditions: (1) presence of excess TiO2; (2) sintering above the eutectic temperature to form a eutectic melt; (3) presence of a suitable donor doping level; (4) sintering in an oxidizing atmosphere; and (5) the presence of a fine grain size BaTiO3 matrix. X-ray diffraction analysis was used to characterize the B6T17 phase. The needle-like B6T17 and the dendritic B6T17 have the same preferred (041) reflection showing that they may have the same mechanism for their formation. The content of B6T17 phase in the BaTiO3 ceramics was also estimated by theoretical calculation and by X-ray diffraction phase analysis using the Rietveld method. B6T17 is a linear dielectric material, with a dielectric

  6. Size effects of 109° domain walls in rhombohedral barium titanate single crystals—A molecular statics analysis

    NASA Astrophysics Data System (ADS)

    Endres, Florian; Steinmann, Paul

    2016-01-01

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

  7. Photorefractive properties of cobalt-doped strontium barium niobate crystals

    SciTech Connect

    Bogodaev, N V; Ivleva, Lyudmila I; Lykov, P A; Polozkov, N M; Osiko, Vyacheslav V

    1999-05-31

    The two-wave interaction (at {lambda} = 488 nm) in strontium barium niobate crystals doped with cobalt ions (Co:SBN) was studied. The experimental dependences of the gain coefficient on the grating period and of the grating response time on the writing beam intensity were used to calculate the Debye screening length, the diffusion length, the dark conductivity, and the effective concentration of carrier traps for a series of Co:SBN crystals with different dopant concentrations. The crystals were shown to have high coupling coefficients ({Gamma} = 33 cm{sup -1}) and short optical response times ({tau} = 140 ms for I = 1 W cm{sup -2} ). This, in combination with a high photorefractive sensitivity (S = 39 cm{sup 2} J{sup -1} ), determines the efficiency of their use in the storage of optical information and in laser phase conjugation. (nonlinear optical phenomena)

  8. Laser irradiation in Nd3+ doped strontium barium niobate glass

    NASA Astrophysics Data System (ADS)

    Haro-González, P.; Martín, I. R.; Arbelo-Jorge, E.; González-Pérez, S.; Cáceres, J. M.; Núñez, P.

    2008-07-01

    A local nanocrystalline formation in a neodymium doped strontium barium niobate (SBN) glass has been obtained under argon laser irradiation. The intense emission around 880 nm, originated from the F43/2 (F45/2) thermalized level when the glass structure changes to a glass ceramic structure due to the irradiation of the laser beam, has been studied. The intensities and lifetimes change from this level inside and outside the irradiated area made by the laser excitation. They have been analyzed and demonstrated that the desvitrification process has been successfully achieved. These results confirm that nanocrystals of SBN have been created by the laser action confirming that the transition from glass to glass ceramic has been completed. These results are in agreement with the emission properties of nanocrystals of the bulk glass ceramic sample. The present study also suggests that the SBN nanocrystal has a potential application as temperature detector.

  9. Centrosymmetric tetragonal tellurium doped calcium copper titanate and its dielectric tunability

    NASA Astrophysics Data System (ADS)

    Barman, Nabadyuti; Tripathi, Shalini; Ravishankar, N.; Varma, K. B. R.

    2016-09-01

    Calcium copper titanate on doping Te4+ at Ti4+ sites transformed structurally to centrosymmetric tetragonal double perovskite. Indeed selected area electron diffraction studies carried out on Te doped ceramics corroborate the refined X-ray diffraction data. The dielectric tunability obtained as a function of applied DC field in Te doped calcium copper titanate ceramics was superior to that of undoped samples.

  10. Ion beam synthesis and investigation of nanocomposite multiferroics based on barium titanate with 3 d metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Khalitov, N. I.; Lyadov, N. M.; Valeev, V. F.; Khaibullin, R. I.; Faizrakhmanov, I. A.; Dulov, E. N.; Tagirov, L. R.; Ibragimov, Sh. Z.; Prikhodko, K. E.; Roddatis, V. V.; Maksutoglu, M.; Kazan, S.; Mikailzade, F. A.

    2013-06-01

    Samples of nanocomposite multiferroics have been synthesized by implantation of Co+, Fe+, and Ni+ ions with an energy of 40 keV into ferroelectric barium titanate plates to doses in the range (0.5-1.5) × 1017 ions/cm2. It has been found that nanoparticles of metallic iron, cobalt, or nickel are formed in the barium titanate layer subjected to ion bombardment. With an increase in the implantation dose, the implanted samples sequentially exhibit superparamagnetic, soft magnetic, and, finally, strong ferromagnetic properties at room temperature. The average sizes of ion-synthesized 3 d-metal nanoparticles vary in the range from 5 to 10 nm depending on the implantation dose. Investigation of the orientation dependence of the magnetic hysteresis loops has demonstrated that the samples show a uniaxial ("easy plane") magnetic anisotropy typical of thin granular magnetic films. Ferromagnetic BaTiO3: 3 d metal samples are characterized by a significant shift of the ferromagnetic resonance signal in an external electric field, as well as by a large (in magnitude) magnetodielectric effect at room temperature. These results indicate that there is a strong magnetoelectric coupling between the ferroelectric barium titanate matrix and ion-synthesized nanoparticles of magnetic metals.

  11. Preparation of meta-stable phases of barium titanate by Sol-hydrothermal method

    NASA Astrophysics Data System (ADS)

    Selvaraj, Mahalakshmi; Venkatachalapathy, V.; Mayandi, J.; Karazhanov, S.; Pearce, J. M.

    2015-11-01

    Two low-cost chemical methods of sol-gel and the hydrothermal process have been strategically combined to fabricate barium titanate (BaTiO3) nanopowders. This method was tested for various synthesis temperatures (100 °C to 250 °C) employing barium dichloride (BaCl2) and titanium tetrachloride (TiCl4) as precursors and sodium hydroxide (NaOH) as mineralizer for synthesis of BaTiO3 nanopowders. The as-prepared BaTiO3 powders were investigated for structural characteristics using x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The overall analysis indicates that the hydrothermal conditions create a gentle environment to promote the formation of crystalline phase directly from amorphous phase at the very low processing temperatures investigated. XRD analysis showed phase transitions from cubic - tetragonal - orthorhombic - rhombohedral with increasing synthesis temperature and calculated grain sizes were 34 - 38 nm (using the Scherrer formula). SEM and TEM analysis verified that the BaTiO3 nanopowders synthesized by this method were spherical in shape and about 114 - 170 nm in size. The particle distribution in both SEM and TEM shows that as the reaction temperature increases from 100 °C to 250 °C, the particles agglomerate. Selective area electron diffraction (SAED) shows that the particles are crystalline in nature. The study shows that choosing suitable precursor and optimizing pressure and temperature; different meta-stable (ferroelectric) phases of undoped BaTiO3 nanopowders can be stabilized by the sol-hydrothermal method.

  12. Preparation of meta-stable phases of barium titanate by Sol-hydrothermal method

    SciTech Connect

    Selvaraj, Mahalakshmi; Venkatachalapathy, V.; Karazhanov, S.; Pearce, J. M. E-mail: jeyanthinath@yahoo.co.in

    2015-11-15

    Two low-cost chemical methods of sol–gel and the hydrothermal process have been strategically combined to fabricate barium titanate (BaTiO{sub 3}) nanopowders. This method was tested for various synthesis temperatures (100 °C to 250 °C) employing barium dichloride (BaCl{sub 2}) and titanium tetrachloride (TiCl{sub 4}) as precursors and sodium hydroxide (NaOH) as mineralizer for synthesis of BaTiO{sub 3} nanopowders. The as-prepared BaTiO{sub 3} powders were investigated for structural characteristics using x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The overall analysis indicates that the hydrothermal conditions create a gentle environment to promote the formation of crystalline phase directly from amorphous phase at the very low processing temperatures investigated. XRD analysis showed phase transitions from cubic - tetragonal - orthorhombic - rhombohedral with increasing synthesis temperature and calculated grain sizes were 34 – 38 nm (using the Scherrer formula). SEM and TEM analysis verified that the BaTiO{sub 3} nanopowders synthesized by this method were spherical in shape and about 114 - 170 nm in size. The particle distribution in both SEM and TEM shows that as the reaction temperature increases from 100 °C to 250 °C, the particles agglomerate. Selective area electron diffraction (SAED) shows that the particles are crystalline in nature. The study shows that choosing suitable precursor and optimizing pressure and temperature; different meta-stable (ferroelectric) phases of undoped BaTiO{sub 3} nanopowders can be stabilized by the sol-hydrothermal method.

  13. Study of dielectric properties of Ca doped barium titanate ceramics

    NASA Astrophysics Data System (ADS)

    Pradhan, S. K.; Kumar, Amit; Sinha, A. N.; Kour, P.

    2016-05-01

    Ba1-xCax Zr0.52Ti0.48 O3 ceramics was prepared by sol gel method. The crystallite size was in nano scale range. The dielectric constant was increased with increase in Ca2+ concentration in the sample. The dielectric loss was decreased with increase in ca concentration in the sample. The ac conductivity of the sample was increased with increase in Ca2+ concentration in the sample. The ac conductivity of the sample follows Johnscher power law. AC conductivity analysis shows that the interactions between neighbouring dipoles were decreased with the increase in Ca2+ concentration in the sample.

  14. Synthesis and In vitro Evaluation of Electrodeposited Barium Titanate Coating on Ti6Al4V

    PubMed Central

    Rahmati, Shahram; Basiriani, Mohammad Basir; Rafienia, Mohammad; Yaghini, Jaber; Raeisi, Keyvan

    2016-01-01

    Osseointegration has been the concern of implantology for many years. Researchers have used various ceramic coatings for this purpose; however, piezoelectric ceramics (e.g., barium titanate [BTO]) are a novel field of interest. In this regard, BTO (BaTiO3) coating was fabricated by electrophoretic deposition on Ti6Al4V medical alloy, using sol-gel-synthesized nanometer BTO powder. Structure and morphologies were studied using X-ray diffraction and scanning electron microscopy (SEM), respectively. Bioactivity response of coated samples was evaluated by SEM and inductively coupled plasma (ICP) analysis after immersion in simulated body fluid (SBF). Cell compatibility was also studied via MTT assay and SEM imaging. Results showed homogenous coating with cubic structure and crystallite size of about 41 nm. SEM images indicated apatite formation on the coating after 7 days of SBF immersion, and ICP analysis approved ions concentration decrement in SBF. Cells showed flattened morphology in intimate contact with coating after 7 days of culture. Altogether, coated samples demonstrated appropriate bioactivity and biocompatibility. PMID:27186538

  15. Aligned porous barium titanate/hydroxyapatite composites with high piezoelectric coefficients for bone tissue engineering.

    PubMed

    Zhang, Yan; Chen, Liangjian; Zeng, Jing; Zhou, Kechao; Zhang, Dou

    2014-06-01

    It was proposed that the piezoelectric effect played an important physiological role in bone growth, remodelling and fracture healing. An aligned porous piezoelectric composite scaffold was fabricated by freeze casting hydroxyapatite/barium titanate (HA/BT) suspensions. The highest compressive strength and lowest porosity of 14.5MPa and 57.4% with the best parallelism of the pore channels were achieved in the HA10/BT90 composite. HA30/BT70 and HA10/BT90 composites exhibited piezoelectric coefficient d33 of 1.2 and 2.8pC/N, respectively, both of which were higher than the piezoelectric coefficient of natural bone. Increase of the solid loading of the suspension and solidification velocity led to the improvement of piezoelectric coefficient d33. Meanwhile, double-templates resulted in the coexistence of lamellar pores and aligned macro-pores, exhibiting the ability to produce an oriented long-range ordered architecture. The manipulation flexibility of this method indicated the potential for customized needs in the application of bone substitute. An MTT assay indicated that the obtained scaffolds had no cytotoxic effects on L929 cells. PMID:24863210

  16. Acceleration of osteogenesis by using barium titanate piezoelectric ceramic as an implant material

    NASA Astrophysics Data System (ADS)

    Furuya, K.; Morita, Y.; Tanaka, K.; Katayama, T.; Nakamachi, E.

    2011-04-01

    As bone has piezoelectric properties, it is expected that activity of bone cells and bone formation can be accelerated by applying piezoelectric ceramics to implants. Since lead ions, included in ordinary piezoelectric ceramics, are harmful, a barium titanate (BTO) ceramic, which is a lead-free piezoelectric ceramic, was used in this study. The purpose of this study was to investigate piezoelectric effects of surface charge of BTO on cell differentiation under dynamic loading in vitro. Rat bone marrow cells seeded on surfaces of BTO ceramics were cultured in culture medium supplemented with dexamethasone, β-glycerophosphate and ascorbic acid while a dynamic load was applied to the BTO ceramics. After 10 days of cultivation, the cell layer and synthesized matrix on the BTO surfaces were scraped off, and then DNA content, alkaline phosphtase (ALP) activity and calcium content were measured, to evaluate osteogenic differentiation. ALP activity on the charged BTO surface was slightly higher than that on the non-charged BTO surface. The amount of calcium on the charged BTO surface was also higher than that on the non-charged BTO surface. These results showed that the electric charged BTO surface accelerated osteogenesis.

  17. Studies on electrophoretically deposited nanostructured barium titanate systems and carrier transport phenomena

    NASA Astrophysics Data System (ADS)

    Borah, Manjit; Mohanta, Dambarudhar

    2016-06-01

    We report on the development of nanostructured barium titanate (BaTiO3, BT) films on ~200-μm-thick Ag substrates by employing a cathodic electrophoretic deposition (EPD) technique, where solid-state-derived BT nanoparticles are used as the starting material. Structural, morphological and compositional analyses of the as-synthesized BT nanoparticles and films were performed by X-ray diffraction, electron microscopy and energy-dispersive spectroscopy studies. The synthesized nano-BT system has an average crystallite size of ~8.1 nm and a tetragonality ( c/ a) value ~1.003. To reveal current transport mechanism, the BT films possessing microporous structures and surrounded by homogeneously grown islands were assessed in a metal-insulator-metal (MIM) conformation. The forward current conduction was observed to be purely thermionic up to respective voltages of ~1.4 and 2.2 V as for the fresh and 3-day aged samples. On the other hand, direct tunneling (DT)-mediated Ohmic feature was witnessed at a comparatively higher voltage, beyond which Fowler-Nordheim tunneling (FN) dominates in the respective MIM junctions. The magnitude of current accompanied by FN process was observed to be stronger in reverse biasing than that of forward biasing case. The use of microporous BT films can offer new insights as regards regulated tunneling events meant for miniaturized nanoelectronic elements/components.

  18. Colossal Room-Temperature Electrocaloric Effect in Ferroelectric Polymer Nanocomposites Using Nanostructured Barium Strontium Titanates.

    PubMed

    Zhang, Guangzu; Zhang, Xiaoshan; Yang, Tiannan; Li, Qi; Chen, Long-Qing; Jiang, Shenglin; Wang, Qing

    2015-07-28

    The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium strontium titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morphology of the ferroelectric nanofillers such as increasing the aspect ratio of the nanoinclusions. The effect of the geometry of the nanofillers on the dielectric permittivity, polarization, breakdown strength, ECE and crystallinity of the ferroelectric polymer has been systematically investigated. Simulations based on the phase-field model have been carried out to substantiate the experimental results. With the remarkable cooling energy density and refrigerant capacity, the polymer nanocomposites are promising for solid-state cooling applications. PMID:26132841

  19. Hydrothermal Barium Titanate Thin-Film Characteristics and their Suitability as Decoupling Capacitors

    SciTech Connect

    Raj, P. Markondeya; Lee, Baik-Woo; Kang, Nam-Kee; Tummala, Rao R; Lance, Michael J; Meyer III, Harry M

    2010-01-01

    System integration and miniaturization demands are driving integrated thin film capacitor technologies towards ultrahigh capacitance densities for noise-free power supply, power conversion and efficient power management. Hydrothermal route can deposit crystalline ferroelectric films at low temperatures of less than 150 C. It is hence an attractive route for integrating high permittivity thin film capacitors on organic, silicon or flex substrates. However, hydrothermal films are not commercialized so far because of their inferior insulation characteristics. Embedded hydroxyl groups are attributed to be the cause for high leakage currents, temperature dependent properties and lower Breakdown Voltages (BDVs). This paper discusses the dielectric characteristics such as capacitance density, leakage currents and Temperature Coefficient of Capacitance (TCC) of hydrothermal barium titanate films and correlates them to the embedded water and OH groups, film morphology, stoichiometry and crystallinity. With thermal treatment, majority of the OH groups can be removed leading to improved insulation characteristics. The room temperature I-V characteristics agreed with ionic conduction models for films baked at 160 C while higher baking temperatures of above 300 C resulted in Poole-Frenkel type conduction. A brief perspective is provided on the suitability of hydrothermal thin film capacitors for power supply applications.

  20. Capacitance response and strain sensing properties of barium titanate thin film

    NASA Astrophysics Data System (ADS)

    Hodak, Satreerat; Promsena, Pavarit; Wisittsoraat, Anurat; Hodak, Jose

    2011-03-01

    Strain gauges are devices that convert mechanical stress into an electronic signal. In this research, barium titanate (BaTi O3) films were deposited on flexible borosilicate glasses using a sol-gel method. Interdigitated electrodes were patterned on the films to fabricate a strain gauge. The strain gauge comprised of an array of individual coplanar capacitors on a 1.2x0.4 cm rectangular borosilicate glass of 0.16 mm thickness. A parallelogram clamp and a mechanically amplified piezoelectric actuator were used for supporting the device under test and for the application of the strain, respectively. Measurements of the strain were carried out on a cantilever beam by monitoring the changes in device capacitance and the frequency shift of an oscillator circuit. We obtained the frequency change per unit stress equal to 0.00163 MHz/MPa and the frequency change per unit strain equal to 1.038 x 10-4 MHz/unit strain, respectively. Acknowlegement: Asahi, TRF, CIN, A1B1 and SP2.

  1. Size-dependent ecotoxicity of barium titanate particles: the case of Chlorella vulgaris green algae.

    PubMed

    Polonini, Hudson C; Brandão, Humberto M; Raposo, Nádia R B; Brandão, Marcos Antônio F; Mouton, Ludovic; Couté, Alain; Yéprémian, Claude; Sivry, Yann; Brayner, Roberta

    2015-05-01

    Studies have been demonstrating that smaller particles can lead to unexpected and diverse ecotoxicological effects when compared to those caused by the bulk material. In this study, the chemical composition, size and shape, state of dispersion, and surface's charge, area and physicochemistry of micro (BT MP) and nano barium titanate (BT NP) were determined. Green algae Chlorella vulgaris grown in Bold's Basal (BB) medium or Seine River water (SRW) was used as biological indicator to assess their aquatic toxicology. Responses such as growth inhibition, cell viability, superoxide dismutase (SOD) activity, adenosine-5-triphosphate (ATP) content and photosynthetic activity were evaluated. Tetragonal BT (~170 nm, 3.24 m(2) g(-1) surface area) and cubic BT (~60 nm, 16.60 m(2) g(-1)) particles were negative, poorly dispersed, and readily aggregated. BT has a statistically significant effect on C. vulgaris growth since the lower concentration tested (1 ppm), what seems to be mediated by induced oxidative stress caused by the particles (increased SOD activity and decreased photosynthetic efficiency and intracellular ATP content). The toxic effects were more pronounced when the algae was grown in SRW. Size does not seem to be an issue influencing the toxicity in BT particles toxicity since micro- and nano-particles produced significant effects on algae growth. PMID:25763523

  2. A Search for the Electron EDM using Europium-Barium Titanates

    NASA Astrophysics Data System (ADS)

    Eckel, Stephen P.

    The discovery of a permanent electric dipole moment (EDM) of a fundamental particle would prove a great discovery in modern physics; such an EDM would violate two or three of the core symmetries of the fundamental forces of nature. Many models that go beyond the standard model of particle physics produce EDMs with magnitudes approaching the level detectable by the next generation of experiments. One possibility for such an experiment involves the use of a solid sample at low temperatures. In a paramagnetic material, the unpaired electrons, if they possess an EDM, can interact with the polarization of the sample and produce a magnetization that can be detected. This dissertation discusses an incarnation of such an experiment based on mixed europium-barium titanates. Such an experiment offers several advantages over other solid-state and atomic EDM searches including larger electron EDM induced interactions and the ability to measure without an applied electric field. This experiment has produced the world's best limit on the electron EDM to date from a solid sample, at |de| < 6.05 × 10-25 ecm (90% confidence limit). While this limit represents an improvement in the realm of solid-state experiments, it is not yet competitive with similar molecular and atomic experiments. However, there are many possibilities that could produce a superior solid-state experiment, and these will be discussed.

  3. Microstructural studies of nanocrystalline barium zirconium titanate (BZT) for piezoelectric applications

    SciTech Connect

    Jamil, Nor Huwaida Janil Izzuddin, Izura; Zainuddin, Zalita; Jumali, Mohammad Hafizuddin Haji

    2015-09-25

    Lead-free piezoelectric ceramics based on barium titanate (BaTiO{sub 3}) with substitution of Zr{sup 4+} were prepared using sol-gel method. The Ba(Zr{sub x}Ti{sub 1-x})O{sub 3}, (BZT) powders with x = 0.0, 0.1, 0.2 and 0.3 were pressed into pellets and sintered at 1250 °C for 2 h. Focusing on the effect of Zr{sup 4+} substitutions into BaTiO{sub 3} perovskite system, the phase transition and microstructural properties of BZT ceramics were studied using XRD, SEM and EDX spectroscopy. All X-ray diffractograms were fitted using Pawley refinement model. The XRD diffractograms revealed the progressive phase transition from tetragonal to cubic phase as Zr content increased. The crystallite exhibited decreasing trend and was supported by shrinkage in grain size. The EDX analysis confirmed the successful substitution of Ti{sup 4+} with Zr{sup 4+} in BaTiO3 crystal.

  4. Synthesis and In vitro Evaluation of Electrodeposited Barium Titanate Coating on Ti6Al4V.

    PubMed

    Rahmati, Shahram; Basiriani, Mohammad Basir; Rafienia, Mohammad; Yaghini, Jaber; Raeisi, Keyvan

    2016-01-01

    Osseointegration has been the concern of implantology for many years. Researchers have used various ceramic coatings for this purpose; however, piezoelectric ceramics (e.g., barium titanate [BTO]) are a novel field of interest. In this regard, BTO (BaTiO3) coating was fabricated by electrophoretic deposition on Ti6Al4V medical alloy, using sol-gel-synthesized nanometer BTO powder. Structure and morphologies were studied using X-ray diffraction and scanning electron microscopy (SEM), respectively. Bioactivity response of coated samples was evaluated by SEM and inductively coupled plasma (ICP) analysis after immersion in simulated body fluid (SBF). Cell compatibility was also studied via MTT assay and SEM imaging. Results showed homogenous coating with cubic structure and crystallite size of about 41 nm. SEM images indicated apatite formation on the coating after 7 days of SBF immersion, and ICP analysis approved ions concentration decrement in SBF. Cells showed flattened morphology in intimate contact with coating after 7 days of culture. Altogether, coated samples demonstrated appropriate bioactivity and biocompatibility. PMID:27186538

  5. Improved chemical stability and conductivity of barium cerate nanopowders by Lanthanum doping.

    PubMed

    Lee, Hunhyeong; Park, Inyu; Shin, Dongwook

    2013-09-01

    Despite of the highest proton conductivity, barium cerate electrolytes are well known for the deficiency of chemical stability at elevated temperature under CO2 atmosphere. This work is focused on improving chemical stability of lanthanum doped barium cerate (BCL) powder for electrolyte. Although lanthanum doping causes distortion of perovskite structure lattice, immoderate doping could stabilize structure due to increasing symmetry of structure lattices. The thermogravimetric analysis and AC impedance measurements revealed that the lanthanum doping suppresses the reaction between barium and carbonate and this effect results in sufficient improvement in ionic conductivity in operating temperatures range. It was confirmed that BaCe0.7La0.3O3-delta (BCL30) was the most stable composition and the conductivity of BCL30 is high as 3.8 S x cm(-1) x K at 700 degrees C. PMID:24205607

  6. Structural and optical properties of barium titanate modified bismuth borate glasses

    NASA Astrophysics Data System (ADS)

    Singh, Lakhwant; Thakur, Vanita; Punia, R.; Kundu, R. S.; Singh, Anupinder

    2014-11-01

    Glass samples with composition (70B2O3-29Bi2O3-1Dy2O3) modified with Barium titanate (BT), where BT is added in different successive weight percents, have been synthesized by conventional melt quenching technique. X-ray diffraction studies were performed in order to confirm the amorphous nature of the samples. The density of the samples has been found to decrease with an increase in the BT content, whereas an opposite trend has been observed in the molar volume. The analysis of FTIR and Raman spectra of the samples depicts that the glass network is built up of mainly BiO6, BiO3, BO3 and BO4 units. Its detailed analysis also revealed that the glass structure depends upon the amount of BT in the glass matrix and hence it acts as a modifier in the glass network. Introduction of BT into the glass matrix leads to the conversion of BO3 trigonal units into BO4 tetrahedral units, which results in a decrease in the degree of disorder in the glass network and makes the glass system more stable. The values of Urbach energy obtained for the prepared samples also confirmed the decrease in disorder in the glass network. The optical absorption measurements carried out for well-polished samples show a decrease in optical band gap energy with an increase in BT content whereas the molar refractivity shows the reverse trend. The Hydrogenic excitonic model applied to the studied glasses suggested that the present glass system favors direct transitions. The metallization criterion of the presently studied samples suggests that the prepared glasses may be potential candidates for nonlinear optical applications.

  7. First-Principles Study of Lattice Dynamics, Structural Phase Transition, and Thermodynamic Properties of Barium Titanate

    NASA Astrophysics Data System (ADS)

    Zhang, Huai-Yong; Zeng, Zhao-Yi; Zhao, Ying-Qin; Lu, Qing; Cheng, Yan

    2016-08-01

    Lattice dynamics, structural phase transition, and the thermodynamic properties of barium titanate (BaTiO3) are investigated by using first-principles calculations within the density functional theory (DFT). It is found that the GGA-WC exchange-correlation functional can produce better results. The imaginary frequencies that indicate structural instability are observed for the cubic, tetragonal, and orthorhombic phases of BaTiO3 and no imaginary frequencies emerge in the rhombohedral phase. By examining the partial phonon density of states (PDOSs), we find that the main contribution to the imaginary frequencies is the distortions of the perovskite cage (Ti-O). On the basis of the site-symmetry consideration and group theory, we give the comparative phonon symmetry analysis in four phases, which is useful to analyze the role of different atomic displacements in the vibrational modes of different symmetry. The calculated optical phonon frequencies at Γ point for the four phases are in good agreement with other theoretical and experimental data. The pressure-induced phase transition of BaTiO3 among four phases and the thermodynamic properties of BaTiO3 in rhombohedral phase have been investigated within the quasi-harmonic approximation (QHA). The sequence of the pressure-induced phase transition is rhombohedral→orthorhombic→tetragonal→cubic, and the corresponding transition pressure is 5.17, 5.92, 6.65 GPa, respectively. At zero pressure, the thermal expansion coefficient αV, heat capacity CV, Grüneisen parameter γ, and bulk modulus B of the rhombohedral phase BaTiO3 are estimated from 0 K to 200 K.

  8. Charge Carrier Relaxation Study in Glass-Added Barium Titanate Ceramics Using Thermally Stimulated Depolarization Current

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Zhang, Yong; Liu, Xiaolin; Song, Xiaozhen; Zhu, Jia; Baturin, Ivan

    2016-08-01

    The depolarization process of glass-added barium titanate (BaTiO3) ceramics with two different glass concentrations was investigated using a thermally stimulated depolarization current (TSDC) technique. The TSDC spectra of the glass-added BaTiO3 ceramics show three peaks. The first sharp peak near the Curie temperature is due to pyroelectric current associated with ferroelectric-paraelectric phase transition. The middle temperature peak at about 200°C showed no dependence on the depolarization current peak position in the polarization field, and the activation energies of this peak were between 0.43 eV and 0.55 eV, which are attributed to the behavior of defect dipoles related to oxygen vacancies within the BaTiO3 grains. Moreover, the high temperature peak at around 300°C indicated that the depolarization current peak position depends on the polarization temperature and decreases with increasing polarization field. The activation energy of this high temperature peak was between 0.78 eV and 0.98 eV, which is similar to the activation energy for the motion of oxygen vacancies in perovskite oxides. The high temperature peak could be attributed to the migration of oxygen vacancies across grain boundaries. In this work we developed a model in which oxygen vacancies that originated from the defect within grains migrated from the anode to the cathode and some were trapped at the grain boundaries. It is presented here and successfully interprets the appearance and behavior of these peaks.

  9. Neodymium-doped barium borate glasses as fluorescent concentrators for the infrared spectral range

    NASA Astrophysics Data System (ADS)

    Dyrba, Marcel; Wiegand, Marie-Christin; Ahrens, Bernd; Schweizer, Stefan

    2012-06-01

    Neodymium-doped barium borate glasses are investigated for their potential as fluorescent concentrators for the near infrared spectral range. Additional doping of the glasses with silver oxide and subsequent heat treatment leads to a reduction of the doped silver ions and to the formation of metallic silver nanoparticles. The formation of the silver nanoparticles is indicated by a broad surface plasmon-related extinction band at approximately 410 nm. The influence of the silver nanoparticles on the fluorescence properties is investigated.

  10. Studies on Synthesis, Structural and Electrical Properties of Complex Oxide Thin Films: Barium Strontium Titanate and Lanthanum Strontium Nickelate

    NASA Astrophysics Data System (ADS)

    Podpirka, Adrian A.

    High performance miniaturized passives are of great importance for advanced nanoelectronic packages for several applications including efficient power delivery. Low cost thin film capacitors fabricated directly on package (and/or on-chip) are an attractive approach towards realizing such devices. This thesis aims to explore fundamental frequency dependent dielectric and insulating properties of thin film high-k dielectric constant in the perovskite and perovskite-related complex oxides. Throughout this thesis, we have successfully observed the role of structure, strain and oxygen stoichiometry on the dielectric properties of thin film complex oxides, allowing a greater understanding of processing conditions and polarization mechanisms. In the first section of the thesis, we explore novel processing methods in the conventional ferroelectric, barium strontium titanate, Ba1-xSr xTiO3 (BST), using ultraviolet enhanced oxidation techniques in order to achieve improvements in the dielectric properties. Using this method, we also explore the growth of BST on inexpensive non-noble metals such as Ni which presents technical challenges due to the ability to oxidize at high temperatures. We observe a significant lowering of the dielectric loss while also lowering the process temperature which allows us to maintain an intimate interface between the dielectric layer and the metal electrode. The second section of this thesis explores the novel dielectric material, Lanthanum Strontium Nickelate, La2-xSrxNiO4 (LSNO), which exhibits a colossal dielectric response. For the first time, we report on the colossal dielectric properties of polycrystalline and epitaxial thin film LSNO. We observe a significant polarization dependence on the microstructure due to the grain/grain boundary interaction with charged carriers. We next grew epitaxial films on various insulating oxide substrates in order to decouple the grain boundary interaction. Here we observed substrate dependent dielectric

  11. Magnetic studies of cobalt doped barium hexaferrite nanoparticles prepared by modified sol-gel method

    NASA Astrophysics Data System (ADS)

    Shalini, M. Govindaraj; Sahoo, Subasa C.

    2016-05-01

    M-type barium hexaferrite (BaFe12O19) and cobalt doped barium hexaferrite (BaFe11CoO19) nanopowders were synthesized by modified sol-gel auto-combustion technique and were annealed at 900°C in air for 4 hours. The annealed powders were studied in the present work and X-ray diffraction studies showed pure phase formation after annealing. The average grain size in the nanopowder sample was decreased after doping. Magnetization value of 60 emu/g was observed at 300K for the barium hexaferrite and was reduced to 54 emu/g after doping. The coercivity of 5586 Oe was observed at 300K for the undoped sample and was found to be decreased in the doped sample. As the measurement temperature was decreased from 300K to 60K, magnetization value was increased in both the samples compared to those at 300K. The coercivity of the undoped sample was found to decrease whereas it was increased for the doped sample at 60K. The observed magnetic properties may be understood on the basis of modified exchange interaction and anisotropy in the doped sample compared to that of pure barium hexaferrite.

  12. Impedance spectroscopy and mechanical response of porous nanophase hydroxyapatite-barium titanate composite.

    PubMed

    Dubey, Ashutosh Kumar; Kakimoto, Ken-ichi

    2016-06-01

    The present study aims to develop the porous nanophase hydroxyapatite (HA)-barium titanate (BT) composite with reasonable mechanical and electrical properties as an electrically-active prosthetic orthopedic implant alternate. The porous samples (densification ~40-70%) with varying amounts of BT (0, 25, 35 and 100 vol.%) in HA were synthesized using optimal spark plasma sintering conditions, which revealed the thermochemical stability between both the phases. The reasonably good combination of functional properties such as compressive [(236.00 ± 44.90)MPa] and flexural [(56.18 ± 5.82) MPa] strengths, AC conductivity [7.62 × 10(-9)(ohm-cm)(-1) at 10 kHz] and relative permittivity [15.20 at 10 kHz] have been achieved with nanostructured HA-25 vol.% BT composite as far as significant sample porosity (~30%) is concerned. Detailed impedance spectroscopic analysis was performed to reveal the electrical microstructure of developed porous samples. The resistance and capacitance values (at 500 °C) of grain (RG, CG) and grain boundary (RGB, CGB) for the porous HA-25 vol.% BT composite are (1.3 × 10(7) ohm, 3.1 × 10(-11)F) and (1.6 × 10(7) ohm, 5.9 × 10(-10)F), respectively. Almost similar value of activation energy (~1-1.5 eV) for grain and grain boundary has been observed for all the samples. The mechanism of conduction is found to be same for porous monolithic HA as well as composite samples. Relaxation spectroscopic analyses suggest that both the localized as well as long range charge carrier translocations are responsible for conduction in these samples. The degree of polarization of porous samples has been assessed by measuring thermally stimulated depolarization current of the poled samples. The depolarization current is observed to depend on the heating rate. The maximum current density, measured for HA-25 vol.% BT sample at a heating rate of 1 °C/min is 2.7 nA/cm(2). Formation of oxygen vacancies due to the reduced atmosphere sintering contribute to the space

  13. Ecotoxicological studies of micro- and nanosized barium titanate on aquatic photosynthetic microorganisms.

    PubMed

    Polonini, Hudson C; Brandão, Humberto M; Raposo, Nádia R B; Mouton, Ludovic; Yéprémian, Claude; Couté, Alain; Brayner, Roberta

    2014-09-01

    The interaction between live organisms and micro- or nanosized materials has become a current focus in toxicology. As nanosized barium titanate has gained momentum lately in the medical field, the aims of the present work are: (i) to assess BT toxicity and its mechanisms on the aquatic environment, using two photosynthetic organisms (Anabaena flos-aquae, a colonial cyanobacteria, and Euglena gracilis, a flagellated euglenoid); (ii) to study and correlate the physicochemical properties of BT with its toxic profile; (iii) to compare the BT behavior (and Ba(2+) released ions) and the toxic profile in synthetic (Bold's Basal, BB, or Mineral Medium, MM) and natural culture media (Seine River Water, SRW); and (iv) to address whether size (micro, BT MP, or nano, BT NP) is an issue in BT particles toxicity. Responses such as growth inhibition, cell viability, superoxide dismutase (SOD) activity, adenosine-5-triphosphate (ATP) content and photosynthetic efficiency were evaluated. The main conclusions are: (i) BT have statistically significant toxic effects on E. gracilis growth and viability even in small concentrations (1μgmL(-1)), for both media and since the first 24 h; on the contrary of on A. flos-aquae, to whom the effects were noticeable only for the higher concentrations (after 96 h: ≥75 μg mL(-1) for BT NP and =100 μg mL(-1) for BT MP, in BB; and ≥75 μg mL(-1) for both materials in SRW), in spite of the viability being affected in all concentrations; (ii) the BT behaviors in synthetic and natural culture media were slightly different, being the toxic effects more pronounced when grown in SRW - in this case, a worse physiological state of the organisms in SRW can occur and account for the lower resistance, probably linked to a paucity of nutrients or even a synergistic effect with a contaminant from the river; and (iii) the effects seem to be mediated by induced stress without a direct contact in A. flos-aquae and by direct endocytosis in E. gracilis, but in

  14. Titan

    NASA Technical Reports Server (NTRS)

    Owen, Tobias; Gautier, Daniel; Raulin, Francois; Scattergood, Thomas

    1992-01-01

    The following topics are discussed with respect to Titan: observations of the atmosphere; laboratory simulations and theoretical models of Titan's atmosphere; endpoints of atmospheric chemistry - aerosols and oceans; exobiology; and the next steps in understanding Titan.

  15. Wafer-to-wafer transfer process of barium strontium titanate for frequency tuning applications using laser pre-irradiation

    NASA Astrophysics Data System (ADS)

    Samoto, Tetuo; Hirano, Hideki; Somekawa, Toshihiro; Hikichi, Kousuke; Fujita, Masayuki; Esashi, Masayoshi; Tanaka, Shuji

    2015-03-01

    This paper describes laser-assisted film transfer technology for barium strontium titanate (BST) deposited on a sapphire substrate. BST is a promising ferroelectric material for varactors, which are required for frequency-tunable RF applications. However, the deposition temperature of BST (600 ~ 700 °C) is too high for surface acoustic wave (SAW) substrates. In this study, BST grown on a sapphire substrate at 650 °C was transferred at low temperature (140 °C) to a borosilicate glass substrate as well as a LiTaO3 substrate. The transferred BST films were characterized as tunable capacitors. A key process in the BST film transfer technology is the laser pre-irradiation of a buffer Pt layer beneath BST from the backside of the sapphire substrate to weaken the BST-to-Pt adhesion. The mechanism of delamination at the BST/Pt interface is discussed using a simple 1D heat transfer model.

  16. Brillouin light scattering study of transverse mode coupling in confined yttrium iron garnet/barium strontium titanate multiferroic

    SciTech Connect

    Sadovnikov, A. V. Nikitov, S. A.; Beginin, E. N.; Bublikov, K. V.; Grishin, S. V.; Sheshukova, S. E.; Sharaevskii, Yu. P.

    2015-11-28

    Using the space-resolved Brillouin light scattering spectroscopy we study the transformation of dynamic magnetization patterns in a bilayer multiferroic structure. We show that in the comparison with a single yttrium iron garnet (YIG) film magnetization distribution is transformed in the bilayer structure due to the coupling of waves propagating both in an YIG film (magnetic layer) and in a barium strontium titanate slab (ferroelectric layer). We present a simple electrodynamic model using the numerical finite element method to show the transformation of eigenmode spectrum of confined multiferroic. In particular, we demonstrate that the control over the dynamic magnetization and the transformation of spatial profiles of transverse modes in magnetic film of the bilayer structure can be performed by the tuning of the wavevectors of transverse modes. The studied confined multiferroic stripe can be utilized for fabrication of integrated dual tunable functional devices for magnonic applications.

  17. Structural, optical and magnetic properties of Fe-doped barium stannate thin films grown by PLD

    NASA Astrophysics Data System (ADS)

    James, K. K.; Aravind, Arun; Jayaraj, M. K.

    2013-10-01

    Barium stannate is a wide band gap semiconductor with cubic perovskite structure. Polycrystalline bulk samples of BaSn1-xFexO3d (BFS), with x = 0.00, 0.02, 0.03, 0.05 and 0.10 were prepared by solid-state reaction. In this paper, we report the growth of undoped and Fe doped barium stannate thin films on fused silica substrate using pulsed laser deposition (PLD) technique at a relatively high substrate temperature and low oxygen pressure. The deposited films have wide bandgap and are transparent in the visible region. The X-ray diffraction analysis of the films confirmed the cubic structure. Microstructural studies were carried out using micro-Raman spectroscopy and AFM analysis. Defect induced Raman shifts were observed in the samples. Magnetic studies revealed an increase in magnetic properties for films doped with 10 at% Fe doped samples.

  18. Antibacterial Activity of Silver Doped Titanate Nanowires on Ti Implants.

    PubMed

    Xu, Ziqiang; Li, Man; Li, Xia; Liu, Xiangmei; Ma, Fei; Wu, Shuilin; Yeung, K W K; Han, Yong; Chu, Paul K

    2016-07-01

    A nanostructured film composed of one-dimensional titanate nanowires (TNWs) was employed as a carrier of Ag nanoparticles and chitosan (CS) to improve the surface antibacterial activity and biocompatibility of titanium implants. A TNWs film was produced on a Ti substrate by an alkali hydrothermal reaction and subsequently doped by Ag nanoparticles through an ultraviolet light chemical reduction. The CS nanofilm was deposited on the Ag nanoparticles through a spin-assisted layer by layer assembly method. The results disclosed that Ag nanoparticles were successfully carried by TNWs and homogeneously distributed on the entire surface. Moreover, a CS nanofilm was also successfully deposited on the Ag nanoparticles. Antibacterial tests showed that the samples modified with a higher initial concentration of AgNO3 solution exhibited better antibacterial activity, and that a CS nanofilm could further improve the antibacterial activity of the TNWs. Cell viability and ALP tests revealed that the release of Ag(+) was detrimental for the growth, proliferation, and differentiation of MC3T3, and that CS could lower the negative effects of Ag gradually as the incubation time increased. PMID:27336202

  19. Lead-barium fluoroborate glass ceramics doped with Nd3+ or Er3+

    NASA Astrophysics Data System (ADS)

    Petrova, O. B.; Sevostjanova, T. S.; Anurova, M. O.; Khomyakov, A. V.

    2016-02-01

    Lead-barium fluoroborate glasses in the PbF2-BaF2-B2O3, PbF2-BaO-B2O3, and PbO- BaF2-B2O3 systems doped with rare-earth ions (Nd3+ or Er3+) are synthesized and studied. It is shown that, based on these glasses, it is possible to produce transparent glass ceramics with fluoride crystalline phases, including ceramics with one crystalline phase of the fluorite structure. The spectral and luminescent properties of the doped glasses, glass ceramics, and polycrystalline complex fluorides containing Pb, Ba, and rare ions are studied.

  20. Study of optical properties of cerium ion doped barium aluminate phosphor

    NASA Astrophysics Data System (ADS)

    Lohe, P. P.; Omanwar, S. K.; Bajaj, N. S.; Belsare, P. D.

    2016-05-01

    In the recent years due to their various optical and technological applications aluminate materials have attracted attention of several researchers. When these materials are doped with rare earth ions they show properties favorable for many optical applications such as high quantum efficiencies. These materials are used in various applications such as lamp phosphors, optically and thermoluminescence dosimeter etc Barium aluminate BaAl2O4 doped with Ce is well known long lasting phosphor. This paper reports synthesis of BaAl2O4: Ce phosphor prepared by a simple combustion synthesis. The samples were characterized for the phase purity, chemical bonds and luminescent properties.

  1. Electrically and magnetically tunable phase shifters based on a barium strontium titanate-yttrium iron garnet layered structure

    NASA Astrophysics Data System (ADS)

    Leach, J. H.; Liu, H.; Avrutin, V.; Rowe, E.; Özgür, Ü.; Morkoç, H.; Song, Y.-Y.; Wu, M.

    2010-09-01

    We report on the tuning of permittivity and permeability of a ferroelectric/ferromagnetic bilayer structure which can be used as a microwave phase shifter with two degrees of tuning freedom. The structure was prepared by the growth of a yttrium iron garnet (YIG) layer on a gadolinium gallium garnet substrate by liquid phase epitaxy, the growth of a barium strontium titanate (BST) layer on the YIG layer through pulsed laser deposition, and then the fabrication of a coplanar waveguide on the top of BST through e-beam evaporation and trilayer liftoff techniques. The phase shifters exhibit a differential phase shift of 38°/cm at 6 GHz through permittivity tuning under an applied electric field of ˜75 kV/cm and a static magnetic field of 1700 Oe. By tuning the permeability through the applied magnetic field we increase the differential phase shift to 52°/cm and simultaneously obtain a better match to the zero applied electric field condition, resulting in an improvement in the return loss from 22.4 to 24.9 dB. Additionally, we demonstrate the use of a lead magnesium niobate-lead titanate (PMN-PT) layer to tune the permeability of the YIG layer. This tuning relies on the piezoelectric and magnetostrictive effects of PMN-PT and YIG, respectively. Tuning of the ferromagnetic response through strain and magnetostriction as opposed to applied magnetic field can potentially pave the way for low power consumption, continuously and rapidly tunable, impedance matched phase shifters.

  2. Molecular structures of (3-aminopropyl)trialkoxysilane on hydroxylated barium titanate nanoparticle surfaces induced by different solvents and their effect on electrical properties of barium titanate based polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Fan, Yanyan; Wang, Guanyao; Huang, Xingyi; Bu, Jing; Sun, Xiaojin; Jiang, Pingkai

    2016-02-01

    Surface modification of nanoparticles by grafting silane coupling agents has proven to be a significant approach to improve the interfacial compatibility between inorganic filler and polymer matrix. However, the impact of grafted silane molecular structure after the nanoparticle surface modification, induced by the utilized solvents and the silane alkoxy groups, on the electrical properties of the corresponding nanocomposites, has been seldom investigated. Herein, the silanization on the surface of hydroxylated barium titanate (BT-OH) nanoparticles was introduced by using two kinds of trialkoxysilane, 3-aminopropyltriethoxysilane (AMEO) and 3-aminopropyltrimethoxysilane (AMMO), with different solvents (toluene and ethanol), respectively. Solid-state 13C, 29Si nuclear magnetic resonance (NMR) spectroscopy and high-resolution X-ray photoelectron spectroscopy (XPS) were employed to validate the structure differences of alkoxysilane attachment to the nanoparticles. The effect of alkoxysilane structure attached to the nanoparticle surface on the dielectric properties of the BT based poly(vinylidene fluoride) (PVDF) nanocomposites were investigated. The results reveal that the solvents used for BT nanoparticle surface modification exhibit a significant effect on the breakdown strength of the nanocomposites. Nevertheless, the alkoxy groups of silane show a marginal influence on the dielectric properties of the nanocomposites. These research results provide important insights into the fabrication of advanced polymer nanocomposites for dielectric applications.

  3. Titan

    NASA Astrophysics Data System (ADS)

    Coustenis, Athena

    Titan, Saturn's biggest satellite (second in size among the satellites in our solar system), has attracted the eye of astronomers preferentially ever since its discovery by Dutch astronomer Christiaan Huygens on March 25, 1655. Titan orbits around Saturn at a distance of 1,222,000 km (759,478 mi) in a synchronous rotation, taking 15.9 days to complete. As Titan follows Saturn on its trek around the Sun, one Titanian year equals about 30 Earth years. The sunlight that reaches such distances is only 1/100th of that received by the Earth. Titan is therefore a cold and dark place, but a fascinating one.

  4. The structure and dielectric properties of thin barium zirconate titanate films obtained by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Tumarkin, A. V.; Razumov, S. V.; Gagarin, A. G.; Altynnikov, A. G.; Stozharov, V. M.; Kaptelov, E. Yu.; Senkevich, S. V.; Pronin, I. P.

    2016-02-01

    Submicron thin layers of BaZr x Ti1- x O3 are grown in-situ by RF magnetron sputtering of a ceramic target ( x = 0.50) on a substrate of Pt/ r-cut leucosapphire Al2O3. It is shown that the composition of the ferroelectric layer is not identical to the composition of the sputtered target and is shifted toward barium zirconate. The reasons for such behavior are discussed. The obtained samples are characterized by high breakdown voltages (1 MV/cm and higher). The structural and high-frequency dielectric properties are studied, and high tunability of the capacitance of thin layers is revealed.

  5. Effects of disorder on properties of non-conventionally prepared barium titanate

    SciTech Connect

    Banerjee, A.; Sarkar, S.; Roychowdhury, A.; Das, D.

    2015-06-24

    Barium titanaten (BaTiO{sub 3}) nanoparticles were prepared by non-conventional as well as conventional solid state reaction. A better response about the grain size distribution was obtained in the former. The former was then milled to get grains of successive reduced sizes. The defects induced within the samples were studies by positron annihilation spectroscopy. The effect of defects on dielectric property of sample with finest grains was measured. Dielectric stability with temperature was increased with decreasing grain size and the peak was shifted towards the lower value due to the enhancement of grain boundary defects generated due to milling for long time.

  6. Thermoelectric Properties of Barium Plumbate Doped by Alkaline Earth Oxides

    NASA Astrophysics Data System (ADS)

    Eufrasio, Andreza; Bhatta, Rudra; Pegg, Ian; Dutta, Biprodas

    Ceramic oxides are now being considered as a new class of thermoelectric materials because of their high stability at elevated temperatures. Such materials are especially suitable for use as prospective thermoelectric power generators because high temperatures are encountered in such operations. The present investigation uses barium plumbate (BaPbO3) as the starting material, the thermoelectric properties of which have been altered by judicious cation substitutions. BaPbO3 is known to exhibit metallic properties which may turn semiconducting as a result of compositional changes without precipitating a separate phase and/or altering the basic perovskite crystal structure. Perovskite structures are noted for their large interstitial spaces which can accommodate a large variety of ``impurity'' ions. As BaPbO3 has high electrical conductivity, σ = 2.43x105Ω-1 m-1 at room temperature, its thermopower, S, is relatively low, 23 μV/K, as expected. With a thermal conductivity, k, of 4.83Wm-1K-1, the figure of merit (ZT =S2 σ Tk-1) of BaPbO3 is only 0.01 at T = 300K. The objective of this investigation is to study the variation of thermoelectric properties of BaPbO3 as Ba and Pb ions are systematically substituted by alkaline earth ions.

  7. Titan

    NASA Astrophysics Data System (ADS)

    Müller-Wodarg, Ingo; Griffith, Caitlin A.; Lellouch, Emmanuel; Cravens, Thomas E.

    2014-03-01

    Introduction I. C. F. Müller-Wodarg, C. A. Griffith, E. Lellouch and T. E. Cravens; Prologue 1: the genesis of Cassini-Huygens W.-H. Ip, T. Owen and D. Gautier; Prologue 2: building a space flight instrument: a P.I.'s perspective M. Tomasko; 1. The origin and evolution of Titan G. Tobie, J. I. Lunine, J. Monteux, O. Mousis and F. Nimmo; 2. Titan's surface geology O. Aharonson, A. G. Hayes, P. O. Hayne, R. M. Lopes, A. Lucas and J. T. Perron; 3. Thermal structure of Titan's troposphere and middle atmosphere F. M. Flasar, R. K. Achterberg and P. J. Schinder; 4. The general circulation of Titan's lower and middle atmosphere S. Lebonnois, F. M. Flasar, T. Tokano and C. E. Newman; 5. The composition of Titan's atmosphere B. Bézard, R. V. Yelle and C. A. Nixon; 6. Storms, clouds, and weather C. A. Griffith, S. Rafkin, P. Rannou and C. P. McKay; 7. Chemistry of Titan's atmosphere V. Vuitton, O. Dutuit, M. A. Smith and N. Balucani; 8. Titan's haze R. West, P. Lavvas, C. Anderson and H. Imanaka; 9. Titan's upper atmosphere: thermal structure, dynamics, and energetics R. V. Yelle and I. C. F. Müller-Wodarg; 10. Titan's upper atmosphere/exosphere, escape processes, and rates D. F. Strobel and J. Cui; 11. Titan's ionosphere M. Galand, A. J. Coates, T. E. Cravens and J.-E. Wahlund; 12. Titan's magnetospheric and plasma environment J.-E. Wahlund, R. Modolo, C. Bertucci and A. J. Coates.

  8. Optical planar waveguide in sodium-doped calcium barium niobate crystals by carbon ion implantation

    NASA Astrophysics Data System (ADS)

    Zhao, Jin-Hua; Qin, Xi-Feng; Wang, Feng-Xiang; Fu, Gang; Wang, Hui-Lin; Wang, Xue-Lin

    2013-07-01

    There is great interest in niobate crystals which belong to the tetragonal tungsten bronze (TTB) families owing to their intriguing properties. As one representative of such crystals, CBN (calcium barium niobate) has attracted rapidly growing attention. Because it has a higher Curie temperature than SBN (strontium barium niobate), possesses outstanding ferroelectric and it possesses optical properties. In addition, doped with sodium, CBN will show a higher Curie temperature than pure CBN. We report on the fabrication and characterization of optical planar waveguide in x-cut sodium-doped calcium barium niobate crystal by using C ion implantation. The guided-mode properties at the wavelength of 633 and 1539 nm are investigated through prism-coupling measurements, respectively. By applying direct end-face coupling arrangement, the near-field optical intensity distribution of waveguide modes is measured at 633 nm. For comparison, the modal profile of the same guided mode is also numerically calculated by the finite difference beam-propagation method via computer software BeamPROP. The transmission spectra of the waveguide before and after ion implantation treatments were investigated also. Our experiment results reveal that the waveguide could propagate light with transverse magnetic polarized direction only and it is assumed that the polarization selectivity of CBN crystal may responsible for this phenomenon.

  9. An efficient approach to derive hydroxyl groups on the surface of barium titanate nanoparticles to improve its chemical modification ability.

    PubMed

    Chang, Shinn-Jen; Liao, Wei-Sheng; Ciou, Ci-Jin; Lee, Jyh-Tsung; Li, Chia-Chen

    2009-01-15

    Highly hydroxylated barium titanate (BaTiO(3)) nanoparticles have been prepared via an easy and gentle approach which oxidizes BaTiO(3) nanoparticles using an aqueous solution of hydrogen peroxide (H(2)O(2)). The hydroxylated BaTiO(3) surface reacts with sodium oleate (SOA) to form oleophilic layers that greatly enhance the dispersion of BaTiO(3) nanoparticles in organic solvents such as tetrahydrofuran, toluene, and n-octane. The results of Fourier transform infrared spectroscopy confirmed that the major functional groups on the surface of H(2)O(2)-treated BaTiO(3) nanoparticles are hydroxyl groups which are chemically active, favoring chemical bonding with SOA. The results of transmission electron microscopy of SOA-modified BaTiO(3) nanoparticles suggested that the oleate molecules were bonded to the surfaces of nanoparticles and formed a homogeneous layer having a thickness of about 2 nm. Furthermore, the improved dispersion capability of the modified BaTiO(3) nanoparticles in organic solvents was verified through analytic results of its settling and rheological behaviors. PMID:18977001

  10. Simulations of high permittivity materials for 7 T neuroimaging and evaluation of a new barium titanate-based dielectric.

    PubMed

    Teeuwisse, W M; Brink, W M; Haines, K N; Webb, A G

    2012-04-01

    High permittivity "dielectric pads" have been shown to increase image quality at high magnetic fields in regions of low radiofrequency transmit efficiency. This article presents a series of electromagnetic simulations to determine the effects of pad size and geometry, relative permittivity value, as well as thickness on the transmit radiofrequency fields for neuroimaging at 7 T. For a 5-mm thick pad, there is virtually no effect on the transmit field for relative permittivity values lower than ∼90. Significant improvements are found for values between 90 and ∼180. If the relative permittivity is increased above ∼180 then areas of very low transmit efficiency are produced. For a 1-cm thick pad, the corresponding numbers are ∼60 and ∼120, respectively. Based upon the findings, a new material (barium titanate, relative permittivity ∼150) is used to produce thin (∼5 mm) dielectric pads which can easily be placed within a standard receive head array. Experimental measurements of transmit sensitivities, as well as acquisition of T(2) - and T 2*-weighted images show the promise of this approach. PMID:22287360

  11. Structure and Rheology of Poloxamine T1107 and Its Nanocomposite Hydrogels with Cyclodextrin-Modified Barium Titanate Nanoparticles.

    PubMed

    Serra-Gómez, Rafael; Dreiss, Cécile A; González-Benito, Javier; González-Gaitano, Gustavo

    2016-06-28

    We report the preparation of a nanocomposite hydrogel based on a poloxamine gel matrix (Tetronic T1107) and cyclodextrin (CD)-modified barium titanate (BT) nanoparticles. The micellization and sol-gel behavior of pH-responsive block copolymer T1107 were fully characterized by small-angle neutron scattering (SANS), dynamic light scattering (DLS), and Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy as a function of concentration, pH and temperature. SANS results reveal that spherical micelles in the low concentration regime present a dehydrated core and highly hydrated shell, with a small aggregation number and size, highly dependent on the degree of protonation of the central amine spacer. At high concentration, T1107 undergoes a sol-gel transition, which is inhibited at acidic pH. Nanocomposites were prepared by incorporating CD-modified BT of two different sizes (50 and 200 nm) in concentrated polymer solutions. Rheological measurements show a broadening of the gel region, as well as an improvement of the mechanical properties, as assessed by the shear elastic modulus, G' (up to 200% increase). Initial cytocompatibility studies of the nanocomposites show that the materials are nontoxic with viabilities over 70% for NIH3T3 fibroblast cell lines. Overall, the combination of Tetronics and modified BaTiO3 provides easily customizable systems with promising applications as soft piezoelectric materials. PMID:27245639

  12. Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

    NASA Astrophysics Data System (ADS)

    Cheng, Jihong; Navrotsky, Alexandra

    2004-01-01

    LaGaO 3 perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol-gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa 1- yMg yO 3- δ (LGM), La 1- xSr xGa 1- yMg yO 3- δ (LSGM), and La 1- xBa xGa 1- yMg yO 3- δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of VO·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling.

  13. Effect of B-site europium doping on the hydrogen transport properties of barium cerate

    NASA Astrophysics Data System (ADS)

    Rhodes, James Michael

    Barium cerate doped with europium on the Ce-site (B-site of the ABO3 perovskite structure) has been investigated as a potential material for hydrogen separation. Barium cerate doped with 15 mol% europium (BaCe0.85Eu0.15O3-delta) demonstrated higher electrical conductivity in a hydrogen-containing gas stream than gadolinium-doped barium cerate (BaCe0.85Gd0.15O3-delta), which was known to have one of the highest conductivities (0.027 S/cm 2 compared to 0.021 S/cm2 at 800°C). For europium dopant levels between 5 to 25 mol%, the sample doped with 15 mol% demonstrated higher electrical conductivities in dry forming gas (4% H2/96% N2) dry air, and wet nitrogen. The activation energies in dry air (˜0.60 eV) were indicative of p-type electronic conduction, and the activation energies in hydrogen-containing gases (˜0.35--0.45 eV) were indicative of protonic conduction. With BaCe0.85Eu0.15O3-delta , the onset of n-type electronic conductivity necessary for hydrogen separation was shown to occur at ˜600°C. A gas-tight glass seal was developed to study the hydrogen permeation properties of BaCe0.85Eu0.15O3-delta. The glass seal was a composite of a glass containing strontium oxide, boron oxide, silicon oxide, aluminum oxide, and lanthanum oxide mixed with doped barium cerate powder. The seal would form at temperatures >875°C, allowing for testing down to 650°C. The effect of temperature, feed-side hydrogen partial pressure, and membrane thickness on hydrogen permeation flux of BaCe0.85Eu0.15O 3-delta was investigated. For the range of thicknesses studied (0.75 to 2.00 mm), the performance of BaCe0.85Eu0.15O 3-delta membranes is under mixed control of bulk diffusion and surface kinetics. This mixed control indicates that investigating BaCe 0.85Eu0.15O3-delta membranes thinner than 0.75 mm would result in a limited increase in hydrogen permeation flux unless measures were taken to improve surface kinetics. The need for improved surface kinetics was confirmed when surface

  14. Thermopower studies of rare earth doped lanthanum barium manganites

    NASA Astrophysics Data System (ADS)

    Reddy, G. Lalitha; Lakshmi, Y. Kalyana; kumar, N. Pavan; Rao, S. Manjunath; Reddy, P. Venugopal

    2014-08-01

    Influence of rare earth doping on electrical, magnetic and thermopower studies of La0.34Re0.33Ba0.33MnO3 compound was investigated. Ferro to paramagnetic transition and metal to insulator transition temperatures decrease with decreasing ionic radius of the dopant ion. Electrical resistivity in the entire temperature range is explained by phase separation model. The magnitude of Seebeck coefficient increases with increasing dopant ionic radius. A cross over from negative to positive sign has also been observed in thermopower data with decreasing A site ionic radius (). The low temperature thermopower data has been explained using a qualitative model containing diffusion; magnon drag and phonon drag effects while the paramagnetic insulating part has been analyzed using small polaron hopping mechanism.

  15. Titan!

    NASA Astrophysics Data System (ADS)

    Matson, Dennis L.

    2010-05-01

    Cassini-Huygens achieved Saturnian orbit on July 1, 2004. The first order of business was the safe delivery of the Huygens atmospheric probe to Titan that took place on January 14, 2005. Huygens descended under parachute obtaining observations all the way down to a safe landing. It revealed Titan for the first time. Stunning are the similarities between Titan and the Earth. Viewing the lakes and seas, the fluvial terrain, the sand dunes and other features through the hazy, nitrogen atmosphere, brings to mind the geological processes that created analogous features on the Earth. On Titan frozen water plays the geological role of rock; liquid methane takes the role of terrestrial water. The atmospheres of both Earth and Titan are predominately nitrogen gas. Titan's atmosphere contains 1.5% methane and no oxygen. The surface pressure on Titan is 1.5 times the Earth's. There are aerosol layers and clouds that come and go. Now, as Saturn proceeds along its solar orbit, the seasons are changing. The effects upon the transport of methane are starting to be seen. A large lake in the South Polar Region seems to be filling more as winter onsets. Will the size and number of the lakes in the South grow during winter? Will the northern lakes and seas diminish or dry up as northern summer progresses? How will the atmospheric circulation change? Much work remains not only for Cassini but also for future missions. Titan has many different environments to explore. These require more capable instruments and in situ probes. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

  16. Fluorine contamination in yttrium-doped barium zirconate film deposited by atomic layer deposition

    SciTech Connect

    An Jihwan; Beom Kim, Young; Sun Park, Joong; Hyung Shim, Joon; Guer, Turgut M.; Prinz, Fritz B.

    2012-01-15

    The authors have investigated the change of chemical composition, crystallinity, and ionic conductivity in fluorine contaminated yttrium-doped barium zirconate (BYZ) fabricated by atomic layer deposition (ALD). It has been identified that fluorine contamination can significantly affect the conductivity of the ALD BYZ. The authors have also successfully established the relationship between process temperature and contamination and the source of fluorine contamination, which was the perfluoroelastomer O-ring used for vacuum sealing. The total removal of fluorine contamination was achieved by using all-metal sealed chamber instead of O-ring seals.

  17. Structural, topographical and electrical properties of cerium doped strontium barium niobate (Ce:SBN60) ceramics

    NASA Astrophysics Data System (ADS)

    Raj, S. Gokul; Mathivanan, V.; Kumar, G. Ramesh; Yathavan, S.; Mohan, R.

    2016-05-01

    Tungsten bronze type cerium doped strontium barium niobate (Ce:SBN - Sr0.6B0.4Nb2O6) ceramics were synthesized by solid state process. Cerium was used as dopant to improve its electrical properties. Influence of Ce+ ions on the photoluminescence properties was investigated in detail. The grain size topographical behavior of SBN powders and their associated abnormal grain growth (AGG) were completely analyzed through SEM studies. Finally dielectric, measurement discusses about the broad phase transition observed due to cerium dopant The results were discussed in detail.

  18. Multiferroic properties of nanostructured barium doped bismuth ferrite

    NASA Astrophysics Data System (ADS)

    El-Desoky, M. M.; Ayoua, M. S.; Mostafa, M. M.; Ahmed, M. A.

    2016-04-01

    Multiferroic nanoparticles of Bi1-xBaxFeO3 (x=0.10, 0.15, 0.20, 0.25 mol%) samples were prepared using conventional solid-state method. The nanostructural, multiferroic properties of the prepared samples was investigated. X-ray diffraction (XRD) patterns show the formation of BiBaFeO3 with single-phase rhombohedral-hexagonal structure. Spin canting or impurity phase could be a probable reason for the origin of ferromagnetism. At room temperature, remnant magnetization increased 18 times more than its initial value. A change in the magnetization is observed around 742-833 K. Néel temperature (TN) registers an increase of 30 times of Ba-doped BiFeO3 in comparison with undoped BiFeO3. The dielectric properties were affected by the properties of the substitutional ions as well as the crystalline structure of the present samples. Substitution with Ba2+ ions also improved the ferroelectric polarization with remanent polarization of 89 μC/cm2. The simultaneous occurrence of ferromagnetism and ferroelectric hysteresis loops in BiBaFeO3 multiferroic nanoparticles system at room temperature makes it a potential candidate for information storage and spintronics.

  19. Cobalt ferrite sphere-coated buckhorn-like barium titanate: Fabrication, characterization, its dielectric resonance, and microwave attenuation properties

    NASA Astrophysics Data System (ADS)

    Ji, Renlong; Cao, Chuanbao

    2014-10-01

    Barium titanate (BTO) with different morphology is prepared through hydrothermal method using titania spheres as precursor, then calcined at different temperatures and ultimately coated with cobalt ferrite (BTO/CFO). The dielectric dispersion of the composite containing BTO (75 wt. % ratio in paraffin wax) shows evidence of resonance behaviour in the microwave spectrum, rather than the usually observed relaxation mode. The imaginary part of permittivity (ɛ″) displays a strong peak in the 10-13 GHz frequency region, especially for buckhorn-like BTO (hydrothermally synthesized at 110 °C and calcined at 1100 °C). The dielectric response anomaly of BTO in special morphology is due to the emission of plane acoustic waves caused by electrostrictive and converse piezoelectric effects. An accepted model is adopted to simulate the resonance frequency. The minimum reflection loss of cauliflower-like BTO (hydrothermally synthesized at 110 °C, then calcined at 600 °C for 2 h, 75 wt. % ratio) in paraffin wax reaches -30.831 dB at 10.56 GHz with a matching thickness of 2 mm, lower than all the reported values. When the sintering temperature is changed to 1100 °C (buckhorn-like BTO), the minimum reflection loss value is -24.37 dB at 12.56 GHz under the thickness of 3 mm. After combination with CFO, the value reaches -42.677 dB when the thickness is 5.6 mm. The ginger-like BTO (hydrothermally synthesized at 200 °C and calcined at different temperatures) is inferior in microwave reflection reduction. The electromagnetic interference shielding effectiveness of buckhorn-like BTO composite is calculated to be -12.7 dB (94.6% shielding) at resonance frequency (2 mm, 11.52 GHz). This work clearly shows the potential to tune the dielectric property of ferroelectrics through control of morphology, facilitating new comprehension of the ferroelectrics in microwave regime.

  20. Effect of sulfur hexafluoride gas and post-annealing treatment for inductively coupled plasma etched barium titanate thin films

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Li, Yang; Yao, Zhao; Kim, Hong-Ki; Kim, Hyung-Jun; Kim, Nam-Young

    2014-09-01

    Aerosol deposition- (AD) derived barium titanate (BTO) micropatterns are etched via SF6/O2/Ar plasmas using inductively coupled plasma (ICP) etching technology. The reaction mechanisms of the sulfur hexafluoride on BTO thin films and the effects of annealing treatment are verified through X-ray photoelectron spectroscopy (XPS) analysis, which confirms the accumulation of reaction products on the etched surface due to the low volatility of the reaction products, such as Ba and Ti fluorides, and these residues could be completely removed by the post-annealing treatment. The exact peak positions and chemicals shifts of Ba 3d, Ti 2p, O 1 s, and F 1 s are deduced by fitting the XPS narrow-scan spectra on as-deposited, etched, and post-annealed BTO surfaces. Compared to the as-deposited BTOs, the etched Ba 3d 5/ 2 , Ba 3d 3/ 2 , Ti 2p 3/ 2 , Ti 2p 1/ 2 , and O 1 s peaks shift towards higher binding energy regions by amounts of 0.55, 0.45, 0.4, 0.35, and 0.85 eV, respectively. A comparison of the as-deposited film with the post-annealed film after etching revealed that there are no significant differences in the fitted XPS narrow-scan spectra except for the slight chemical shift in the O 1 s peak due to the oxygen vacancy compensation in O2-excessive atmosphere. It is inferred that the electrical properties of the etched BTO film can be restored by post-annealing treatment after the etching process. Moreover, the relative permittivity and loss tangent of the post-annealed BTO thin films are remarkably improved by 232% and 2,695%, respectively.

  1. Bio-inspired synthesis and laser processing of nanostructured barium titanate thin films: implications for uncooled IR sensor development

    NASA Astrophysics Data System (ADS)

    Livingston, F. E.; Sarney, W. L.; Niesz, K.; Ould-Ely, T.; Tao, A. R.; Morse, D. E.

    2009-05-01

    The Army requires passive uncooled IR sensors for use in numerous vehicle and weapons platforms, including driver vision enhancement (DVE), rifle sights, seeker munitions, and unattended ground sensors (UGSs) and unattended aerial vehicles (UAVs). Recent advances in bio-inspired/biomimetic nanomaterials synthesis, laser material processing, and sensor design and performance testing, offer the opportunity to create uncooled IR detector focal-plane arrays with improved sensitivity, low thermal mass, and fast response times, along with amenability to low-cost, rapid prototype manufacture. We are exploring the use of genotype-inspired, digitally-scripted laser direct-write techniques, in conjunction with the kinetically controlled catalytic process for the growth of nanostructured multimetallic perovskites, to develop a novel approach to the fabrication of precision patterned 2-D focal-plane arrays of pyroelectric perovskite-based materials. The bio-inspired growth of nanostructured, multimetallic perovskite thin-films corresponds to the use of kinetically controlled vapor diffusion for the slow growth of pure, highly crystalline 6-nm barium titanate (BaTiO3) nanoparticles. This unique vapor-diffusion sol-gel route enables the formation of stoichiometric cubic-phase nanoparticles at room temperature and ambient pressure in the absence of a structure-directing template. Novel laser direct-write processing and synchronized electro-optic pulse modulation techniques have been utilized to induce site-selective, patterned phase transformation of microscale aggregates of the BaTiO3 nanoparticles from the non-pyroelectric cubic polymorph to the pyroelectric tetragonal polymorph. This paper reports on our initial collaborative investigations, including comprehensive structural characterization (XRD, TEM, and SEM) of the BaTiO3 nanoparticles and thin-films, along with preliminary laser-induced phase transformation results.

  2. Shallow-trap-induced positive absorptive two-beam coupling 'gain' and light-induced transparency in nominally undoped barium titanate

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    The asymmetry of beam coupling with respect to the orientation of the polar axis in a nominally undoped barium titanate crystal is used to determine the electro-optic and absorptive 'gain' in the usual beam-coupling geometry. For small grating wave vectors, the electrooptic coupling vanishes but the absorptive coupling remains finite and positive. Positive absorptive coupling at small grating wave vectors is correlated with the light-induced transparency of the crystal described herein. The intensity and grating wave vector dependence of the electrooptic and absorptive coupling, and the light-induced transparency are consistent with a model incorporating deep and shallow levels.

  3. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors

    PubMed Central

    2013-01-01

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm2 V–1 s–1. We show that it is possible to solution-process these materials at low process temperature (225–200 °C yielding mobilities up to 4.4 cm2 V–1 s–1) and demonstrate a facile “ink-on-demand” process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

  4. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors.

    PubMed

    Banger, Kulbinder K; Peterson, Rebecca L; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

    2014-01-28

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm(2) V(-1) s(-1). We show that it is possible to solution-process these materials at low process temperature (225-200 °C yielding mobilities up to 4.4 cm(2) V(-1) s(-1)) and demonstrate a facile "ink-on-demand" process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

  5. Barium titanate tape properties for MLCC application using different binder systems

    NASA Astrophysics Data System (ADS)

    Yoon, Dang-Hyok

    Most of multilayer ceramic capacitor (MLCC) industries are currently using solvent-based slip systems, although water-based slips have been receiving increasing attention due to reduced health and environmental hazards. The current work focuses on two main fields to meet the challenges in MLCC processing in aqueous media. One is the comparison between water- and solvent-based slip systems using design of experiments (DOE). The other is the understanding of Ba2+ ion leaching behavior in water and its effect on tape properties. For the first part, twenty four kinds of BaTiO3 slips were investigated using three different binder systems: one solvent-based, and two water-based systems. Tape casting, sintering and characterization were conducted. Slip viscosity and tape strength of the green tape depended significantly on the binder type. It was possible to achieve a higher green density for water-based system than that for a solvent-based one. Most of the green body properties from solvent-based system depended on the ceramic powder. On the other hand, the dispersant was the most significant factor for the green body properties of two water-based systems. Sintered properties such as microstructure and dielectric permittivity for three systems depended significantly on the type of ceramic powder. An optimization was performed for each system by means of a scorecard. By choosing the optimum condition, comparable results were drawn for the water-based system compared to a solvent-based one for MLCC application. For the second part, the amount of Ba2+ ion leaching from BaTiO3 in water was determined by an EDTA titration method. The greater extent and the faster rate of Ba2+ leaching were found at the lower solution pH. The excess free barium ions expressed by means of the Ba/Ti ratio adversely affected most tape properties. To passivate BaTiO 3 surface from Ba2+ ion leaching in water, passivation agent layer (PAL) was formed by drying the slurry after adding a commercial

  6. Structure and phase transition behavior of strontium modified barium zirconium titanate

    SciTech Connect

    Badapanda, T.; Sarangi, S.; Behera, B.; Saha, S.; Sinha, T. P.

    2015-06-24

    Pervoskite ceramics with composition Ba{sub 1-x}Sr{sub x}Zr{sub 0.05}Ti{sub 0.95}O{sub 3} (x= 0.1, 0.2, 0.3, 0.4 and 0.5) have been prepared by high energy ball milling. X-ray diffraction (XRD) patterns confirm that the all the compositions are in single phase. The composition shows tetragonal symmetry upto x=0.3 and with further increase in Sr content the structure changes to cubic. The temperature dependent dielectric behavior shows three phase transition in the parent material which merges with increase in Sr content. The transition temperature and dielectric constant decreases with increase in Sr concentration. The phase transition becomes more diffused with increment in doping concentration. The ferroelectric behavior of the ceramics is studied by the hysteresis loop.

  7. EPDM composite membranes modified with cerium doped lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Zaharescu, T.; Dumitru, A.; Lungulescu, M. E.; Velciu, G.

    2016-01-01

    This study was performed on γ-irradiated ethylene-propylene diene terpolymer (EPDM) loaded with lead zirconate titanate. The inorganic phase has a perovskite structure with general formula Pb(Zr0.65-xCexTi0.35)O3. The three composites with different Ce dopant concentrations revealed the stabilization activity of filler against oxidation proved by chemiluminescence investigation in respect to pristine polymer. The presence of cerium low concentrations in the solid lead zirconate titanate nanoparticles causes significant slowing of oxidation rate during radiation exposure. The improvement in the stabilization feature of filler is correlated with the existence of traps, whose interaction with free radicals assumes medium energy due to their convenient depth.

  8. High permittivity polyaniline-barium titanate nanocomposites with excellent electromagnetic interference shielding response

    NASA Astrophysics Data System (ADS)

    Saini, Parveen; Arora, Manju; Gupta, Govind; Gupta, Bipin Kumar; Singh, Vidya Nand; Choudhary, Veena

    2013-05-01

    Organic conductive polymers are at the forefront of materials science research because of their diverse applications built around their interesting and unique properties. This work reports for the first time a correlation between the structural, electrical, and electromagnetic properties of polyaniline (PANI)-tetragonal BaTiO3 (TBT) nanocomposites prepared by in-situ emulsion polymerization. XRD studies and HRTEM micrographs of these nanocomposites clearly revealed the incorporation of TBT nanoparticles in the conducting PANI matrix. EPR and XPS measurements reveal that increase in loading level of BaTiO3 results in a reduction of the doping level of PANI. The Ku-Band (12.4-18 GHz) network analysis of these composites shows exceptional microwave shielding response with absorption dominated total shielding effectiveness (SET) value of -71.5 dB (blockage of more than 99.99999% of incident radiation) which is the highest value reported in the literature. Such a high attenuation level, which critically depends on the fraction of BaTiO3 is attributed to optimized dielectric and electrical attributes. This demonstrates the possibility of using these materials in stealth technology and for making futuristic radar absorbing materials (RAMs).Organic conductive polymers are at the forefront of materials science research because of their diverse applications built around their interesting and unique properties. This work reports for the first time a correlation between the structural, electrical, and electromagnetic properties of polyaniline (PANI)-tetragonal BaTiO3 (TBT) nanocomposites prepared by in-situ emulsion polymerization. XRD studies and HRTEM micrographs of these nanocomposites clearly revealed the incorporation of TBT nanoparticles in the conducting PANI matrix. EPR and XPS measurements reveal that increase in loading level of BaTiO3 results in a reduction of the doping level of PANI. The Ku-Band (12.4-18 GHz) network analysis of these composites shows exceptional

  9. High permittivity polyaniline-barium titanate nanocomposites with excellent electromagnetic interference shielding response.

    PubMed

    Saini, Parveen; Arora, Manju; Gupta, Govind; Gupta, Bipin Kumar; Singh, Vidya Nand; Choudhary, Veena

    2013-05-21

    Organic conductive polymers are at the forefront of materials science research because of their diverse applications built around their interesting and unique properties. This work reports for the first time a correlation between the structural, electrical, and electromagnetic properties of polyaniline (PANI)-tetragonal BaTiO3 (TBT) nanocomposites prepared by in-situ emulsion polymerization. XRD studies and HRTEM micrographs of these nanocomposites clearly revealed the incorporation of TBT nanoparticles in the conducting PANI matrix. EPR and XPS measurements reveal that increase in loading level of BaTiO3 results in a reduction of the doping level of PANI. The Ku-Band (12.4-18 GHz) network analysis of these composites shows exceptional microwave shielding response with absorption dominated total shielding effectiveness (SET) value of -71.5 dB (blockage of more than 99.99999% of incident radiation) which is the highest value reported in the literature. Such a high attenuation level, which critically depends on the fraction of BaTiO3 is attributed to optimized dielectric and electrical attributes. This demonstrates the possibility of using these materials in stealth technology and for making futuristic radar absorbing materials (RAMs). PMID:23563991

  10. Curie temperature and magnetic properties of aluminum doped barium ferrite particles prepared by ball mill method

    NASA Astrophysics Data System (ADS)

    Chen, Daming; Harward, Ian; Baptist, Joshua; Goldman, Sara; Celinski, Zbigniew

    2015-12-01

    Barium ferrite has attracted considerable interest in the fields of permanent magnets and perpendicular magnetic recording due to its strong uniaxial anisotropy and high Curie temperature (Tc). We prepared aluminum doped barium ferrite ceramics (BaAlxFe12-xO19, 0≤x≤6) by the ball mill method. The powder was milled for 96 h, and after forming pellets, annealed for 48 h in air at 1000 °C. The X-ray diffraction (XRD) data show that there are only single hexagonal phases in the samples without any impurity phase. The crystal lattice constants, a and c, were calculated by Cohen's method. Both a and c decrease with increasing x, ranging from 0.588 nm and 2.318 nm to 0.573 nm and 2.294 nm, respectively. A Vibrating Sample Magnetometer (VSM) and Superconducting Quantum Interference Device (SQUID) were used to investigate Tc and magnetic properties of BaFe12-xAlxO19. It is found that Tc decreases with increasing x, from 425 °C to 298 °C. It is also found that the saturated magnetization (4πMs) decreases with increasing x, while the coercivity (Hc) increases with the increase in x. The anisotropy field was also determined from the SQUID measurement.

  11. Photo-luminescence studies of strontium barium niobate crystals doped with Cr 3+ ions

    NASA Astrophysics Data System (ADS)

    Han, T. P. J.; Jaque, F.; Jaque, D.; Ivleva, L.

    2006-01-01

    This paper reports the photo-luminescence spectroscopic results of Strontium-Barium-Niobate, Sr x,Ba 1- xNb 2O 5 (SBN, x = 0.61 for near congruent composition) crystals doped with Cr 2O, at cryogenic temperature (20 K). The experimental results reveal the need of re-assignment of the Cr 3+ ions defect centres in this material. For first time, a broad emission band in the near infrared region centred at ca. 950 nm is reported. This emission band has micro-seconds decaytime constant and a FWHM band-width > 1700 cm -1 and has been ascribed to the vibronically assisted 4T 2 → 4A 2 transition. A much narrower emission band centred at ca. 764 nm with milli-seconds decaytime constant and a FWHM band-width of ca. 170 cm -1 is correlated to the 2E → 4A 2 radiative transition (R-line).

  12. Formation of Nd 3+ doped Strontium Barium Niobate nanocrystals by two different methods

    NASA Astrophysics Data System (ADS)

    Haro-González, P.; Martín, L. L.; González-Pérez, S.; Martín, I. R.

    2010-08-01

    The study of two different methods to obtain Strontium Barium Niobate nanocrystals has been carried out. Previously, Nd 2O 3 doped SrO-BaO-Nb 2O 5-B 2O 3 glasses were fabricated using the melt quenching process. In the first method, a thermal treatment in an electrical furnace at 620 °C was used to obtain glass ceramic samples. In the second one, the nanocrystals were obtained under continuous Ar laser irradiation in a localized zone in the glass sample. The X-ray diffraction patterns confirmed the formation of SBN nanocrystals in both cases. The optical measurements indicate the incorporation of Nd 3+ ions into the nanocrystals which produces an increment of the luminescence intensity. Moreover, a calibration with the temperature has been carried out for the ratio of the Nd 3+ emissions. This result could let to control the temperature of the laser irradiated zone.

  13. Defective interfaces in yttrium-doped barium zirconate films and consequences on proton conduction.

    PubMed

    Yang, Nan; Cantoni, Claudia; Foglietti, Vittorio; Tebano, Antonello; Belianinov, Alex; Strelcov, Evgheni; Jesse, Stephen; Di Castro, Daniele; Di Bartolomeo, Elisabetta; Licoccia, Silvia; Kalinin, Sergei V; Balestrino, Giuseppe; Aruta, Carmela

    2015-04-01

    Yttrium-doped barium zirconate (BZY) thin films recently showed surprising electric transport properties. Experimental investigations conducted mainly by electrochemical impedance spectroscopy suggested that a consistent part of this BZY conductivity is of protonic nature. These results have stimulated further investigations by local unconventional techniques. Here, we use electrochemical strain microscopy (ESM) to detect electrochemical activity in BZY films with nanoscale resolution. ESM in a novel cross-sectional measuring setup allows the direct visualization of the interfacial activity. The local electrochemical investigation is compared with the structural studies performed by state of art scanning transmission electron microscopy (STEM). The ESM and STEM results show a clear correlation between the conductivity and the interface structural defects. We propose a physical model based on a misfit dislocation network that introduces a novel 2D transport phenomenon, whose fingerprint is the low activation energy measured. PMID:25789878

  14. Static and dynamic photoinduced magnetic effects in yttrium-iron garnet lightly doped with barium ions

    SciTech Connect

    Vorob'eva, N. V. Khalilov, R. Z.

    2012-04-15

    In yttrium-iron garnet lightly doped with barium, direct measurements of the photoinduced changes in magnetostrictive strains disagree with those in magnetostriction constants at 78-100 K. This is attributed to a considerable photoinduced modification of the initial state in this sample due to a redistribution of the charge (during illumination) between cations of the ferromagnetic octahedral sublattice. In the same sample, the temperature dependence of the photoinduced disaccomodation of magnetic permeability characterizing the initial demagnetized state is measured and calculated. A change in the electron mechanism of the phenomenon during the transition to room temperature is shown. The conclusion about the promising prospects for using such samples for remagnetization by light is advanced.

  15. Room temperature optical and dielectric properties of Ca and Ni doped barium ferrite

    NASA Astrophysics Data System (ADS)

    Agrawal, Shraddha; Parveen, Azra; Azam, Ameer

    2016-05-01

    The citrate sol gel combustion method has been used to synthesize (Ba0.9Ca0.1) (Fe0.8 Ni0.2)12O19 hexaferrites. Microstructural analyses were carried out by XRD and FTIR. Optical properties were studied by UV-visible technique in the range of 300-800 nm. The energy band gap was calculated with the help of Tauc relationship shows increases in band gap. Ca and Ni doped barium ferrite annealed at 850°C exhibit significant dispersion in complex permeability. The dispersion in complex dielectric constant can be explained on the basis of Koop's theory based on Maxwell-Wagner two layer models in studied nanoparticles.

  16. Localized desvitrifiation in Er3+-doped strontium barium niobate glass by laser irradiation

    NASA Astrophysics Data System (ADS)

    Haro-González, P.; Martin, I. R.; Lahoz, F.; González-Pérez, S.; Capuj, N. E.; Jaque, D.

    2008-12-01

    Localized desvitrifiation in strontium barium niobate glass doped with Er3+ under laser irradiation has been carried out. The samples of this study have been fabricated by the melt quenching method and doped with 5% mol of Er3+. A 1.5-W cw Ar laser was focused on the sample to obtain desvitrifiation of the glass. Evidence of the changes induced by the Ar laser has been observed through the analysis of the photoluminescence of the Er3+ ions. The transitions corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 have been studied to analyze structure changes. Microluminescence measurements have been carried out to spatially select positions inside and outside the irradiated area. We have observed changes in the emission bands corresponding to these transitions. The emission bands from Er3+ ions in the irradiated zone show a resolved structure while they are broadened outside that area. These changes in the optical properties of the Er3+ ions indicate that the Ar-laser irradiation has produced a change in the local structure of the material. These results show that a localized desvitrifiation has been produced after the laser action and the transition from glass to glass ceramic has been completed.

  17. X-ray Induced Luminescence Spectroscopy of Samarium Doped Barium Sulfate Prepared by Sintering Method

    NASA Astrophysics Data System (ADS)

    Kumeda, T.; Maeda, K.; Shirano, Y.; Fujiwara, K.; Sakai, K.; Ikari, T.

    2015-06-01

    X-ray induced luminescence (XL) properties of phosphor materials made of samarium doped barium sulfate have been investigated. The samples were prepared by sintering method heated at 900-1250 °C for 3 hours in air from the mixture of BaSO4 and Sm2O3. The concentration of Sm were prepared from 0.01-6 at.%. In as-prepared sample, the Sm3+ was detected by photoluminescence (PL). The PL intensity is maximum about 2 at.% with Sm, and then starts decreasing. The PL intensity showed concentration quenching. The XL observed Sm2+ and Sm3+ ions. The XL was shown from the sample sintered up to 1200 °C. The XL intensity increased with Sm concentration up to 1 at.%. The intensity was almost constant larger than 1 at.% Sm. These concentration dependences is different since the X-ray energy absorbed to the host material at once, and the energy transferred to both Sm3+ and Sm2+ ions. Sm doped BaSO4 is found a host for XL phosphor materials.

  18. Short-range order and fractal cluster structure of aggregates of barium titanate microparticles in a composite based on cyano-ethyl ester of polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Krasovskii, A. N.; Novikov, D. V.; Vasina, E. S.; Matveichikova, P. V.; Sychev, M. M.; Rozhkova, N. N.

    2015-12-01

    The distribution of barium titanate (BaTiO3) microparticles in the matrix of cyano-ethyl ester of polyvinyl alcohol and the change in the surface energy upon introduction of shungite carbon nanoclusters into the dielectric composite have been investigated using the methods of scanning electron microscopy and contact angles. The computer processing of the electron microscopy data has demonstrated that the introduction of 0.04% shungite carbon nanoparticles into the composite leads to a decrease in the spatial homogeneity of the quasi-lattice and to an increase in the local density distribution of BaTiO3 microparticles, as well as in the correlation length corresponding to the formation of an infinite cluster of BaTiO3 particles. It has been found that, in this case, the surface energy and dielectric permittivity of the composite extremely increase.

  19. Physical properties and electronic structure of a new barium titanate suboxide Ba1+δTi13-δO₁₂ (δ = 0.11)

    DOE PAGESBeta

    Rotundu, Costel R.; Jiang, Shan; Deng, Xiaoyu; Qian, Yiting; Khan, Saeed; Hawthorn, David G.; Kotliar, Gabriel; Ni, Ni

    2015-04-01

    The structure, transport, thermodynamic properties, x-ray absorption spectra (XAS), and electronic structure of a new barium titanate suboxide, Ba1+δTi13-δO₁₂ (δ = 0.11), are reported. It is a paramagnetic poor metal with hole carriers dominating the transport. Fermi liquid behavior appears at low temperature. The oxidization state of Ti obtained by the XAS is consistent with the metallic Ti²⁺ state. Local density approximation band structure calculations reveal the material is near the Van Hove singularity. The pseudogap behavior in the Ti-d band and the strong hybridization between the Ti-d and O-p orbitals reflect the characteristics of the building blocks of themore » Ti₁₃ semi-cluster and the TiO₄ quasi-squares, respectively.« less

  20. Visible light carrier generation in co-doped epitaxial titanate films

    NASA Astrophysics Data System (ADS)

    Comes, Ryan B.; Smolin, Sergey Y.; Kaspar, Tiffany C.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.; Baxter, Jason B.; Chambers, Scott A.

    2015-03-01

    Perovskite titanates such as SrTiO3 (STO) exhibit a wide range of important functional properties, including ferroelectricity and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications; however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr, we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr3+ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to 2.4-2.7 eV depending on doping levels. Transient reflectance spectroscopy measurements are in agreement with the observations from ellipsometry and confirm that optically generated carriers are present for longer than 2 ns. Finally, through photoelectrochemical methylene blue degradation measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  1. Visible light carrier generation in co-doped epitaxial titanate films

    SciTech Connect

    Comes, Ryan B.; Smolin, Sergey Y.; Kaspar, Tiffany C.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.; Baxter, Jason; Chambers, Scott A.

    2015-03-02

    Perovskite titanates such as SrTiO3 (STO) exhibit a wide range of important functional properties, including high electron mobility, ferroelectricity—which may be valuable in photovoltaic applications—and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications, however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr3+ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to between 2.4 and 2.7 eV depending on doping levels. Transient reflectance measurements confirm that optically generated carriers have a recombination lifetime comparable to that of STO and are in agreement with the observations from ellipsometry. Finally, through photoelectrochemical yield measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  2. Visible light carrier generation in co-doped epitaxial titanate films

    SciTech Connect

    Comes, Ryan B. Kaspar, Tiffany C.; Chambers, Scott A.; Smolin, Sergey Y.; Baxter, Jason B.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.

    2015-03-02

    Perovskite titanates such as SrTiO{sub 3} (STO) exhibit a wide range of important functional properties, including ferroelectricity and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications; however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr, we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr{sup 3+} dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to 2.4–2.7 eV depending on doping levels. Transient reflectance spectroscopy measurements are in agreement with the observations from ellipsometry and confirm that optically generated carriers are present for longer than 2 ns. Finally, through photoelectrochemical methylene blue degradation measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  3. Intrinsic Mobility Limiting Mechanisms in Lanthanum-Doped Strontium Titanate

    NASA Astrophysics Data System (ADS)

    Verma, Amit; Kajdos, Adam P.; Cain, Tyler A.; Stemmer, Susanne; Jena, Debdeep

    2014-05-01

    The temperature dependent Hall mobility data from La-doped SrTiO3 thin films are analyzed and modeled considering various electron scattering mechanisms. We find that a ˜6 meV transverse optical phonon deformation potential scattering mechanism is necessary to explain the dependence of transport on temperature between 10-200 K. Also, we find that the low temperature electron mobility in intrinsic (nominally undoped) SrTiO3 is limited by acoustic phonon scattering. Adding the above two scattering mechanisms to longitudinal optical phonon and ionized impurity scattering mechanisms, excellent quantitative agreement between mobility measurement and model is achieved in the whole temperature range (2-300 K) and carrier concentrations ranging over a few orders of magnitude (8×1017 -2×1020 cm-3).

  4. Barium Doped Li2FeSiO4 Cathode Material for Li-Ion Secondary Batteries.

    PubMed

    Kim, Cheong; Yoo, Gi Won; Son, Jong Tae

    2015-11-01

    Barium-doped Li2Fe(1-x)Ba(x)SiO4 (x = 0, 0.01) cathode materials were synthesized by the sol-gel and electrospinning processes. The structures of the samples were confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. The sizes and the morphologies of the particles and nanofibers were observed by field emission scanning electron microscopy and atomic force microscopy. The initial discharge capacity of Li2FeSiO4 particles was 28 mAh/g, Li2FeSiO4 nanofibers and barium (Ba)-doped Li2FeSiO4 nanofibers showed the discharge capacities of 78 and 85 mAh/g, respectively. The lithium-ion diffusion coefficients of Li2FeSiO4 particles, Li2FeSiO4 nanofibers and Ba-doped Li2FeSiO4 nanofibers were calculated 5.15 x 10-(16), 3.52 x 10(-16), and 2.27 x 10(-15) cm2/s, respectively. The Ba-doped Li2FeSiO4 cathode material showed the highest lithium-ion diffusion coefficient, and its electrochemical properties were better than that of the pristine material. PMID:26726598

  5. Effect of 3d-transition metal doping on the shielding behavior of barium borate glasses: a spectroscopic study.

    PubMed

    ElBatal, H A; Abdelghany, A M; Ghoneim, N A; ElBatal, F H

    2014-12-10

    UV-visible and FT infrared spectra were measured for prepared samples before and after gamma irradiation. Base undoped barium borate glass of the basic composition (BaO 40%-B2O3 60mol.%) reveals strong charge transfer UV absorption bands which are related to unavoidable trace iron impurities (Fe(3+)) within the chemical raw materials. 3d transition metal (TM)-doped glasses exhibit extra characteristic absorption bands due to each TM in its specific valence or coordinate state. The optical spectra show that TM ions favor generally the presence in the high valence or tetrahedral coordination state in barium borate host glass. Infrared absorption bands of all prepared glasses reveal the appearance of both triangular BO3 units and tetrahedral BO4 units within their characteristic vibrational modes and the TM-ions cause minor effects because of the low doping level introduced (0.2%). Gamma irradiation of the undoped barium borate glass increases the intensity of the UV absorption together with the generation of an induced broad visible band at about 580nm. These changes are correlated with suggested photochemical reactions of trace iron impurities together with the generation of positive hole center (BHC or OHC) within the visible region through generated electrons and positive holes during the irradiation process. PMID:24983922

  6. Calcium-doped ceria/titanate tabular functional nanocomposite by layer-by-layer coating method

    SciTech Connect

    Liu, Xiang W.; Devaraju, M.K.; Yin, Shu; Sato, Tsugio

    2010-07-15

    Ca-doped ceria (CDC)/tabular titanate (K{sub 0.8}Li{sub 0.27}Ti{sub 1.73}O{sub 4}, TT) UV-shielding functional nanocomposite with fairly uniform CDC coating layers was prepared through a polyelectrolyte-associated layer-by-layer (LbL) coating method. TT with lepidocrocite-like layered structure was used as the substrate, poly (diallyldimethylammonium chloride) (PDDA) was used as a coupling agent, CDC nanoparticles were used as the main UV-shielding component. CDC/TT nanocomposites with various coating layers of CDC were obtained through a multistep coating process. The phases were studied by X-ray diffraction. The morphology and coating quality were studied by scanning electron microscopy and element mapping of energy dispersive X-ray analysis. The oxidation catalytic activity, UV-shielding ability and using comfort were characterized by Rancimat test, UV-vis spectra and dynamic friction test, respectively. CDC/TT nanocomposites with low oxidation catalytic activity, high UV-shielding ability and good using comfort were finally obtained. - Graphical abstract: Through the control of surface charge of particles calcium-doped ceria/titanate composites with low oxidation catalytic activity, higher UV-shielding ability and excellent comfort was obtained by a facile layer-by-layer coating method.

  7. Synthesis and characterization of rare earth doped barium fluoride nanoparticles and derivatized copper phthalocyanine nanoparticles

    NASA Astrophysics Data System (ADS)

    Bender, Christopher Mark

    1998-12-01

    Nanoparticles of neodymium doped barium fluoride (Nd:BaFsb2) were synthesized for use as the inorganic component of an optical amplifier composite. Microemulsions were used to maintain domain size in the nano-regime (˜100 nm), and decreasing the volume fraction of the aqueous content, while simultaneously increasing the volume fraction of the cosurfactant (methanol), gave a linear relationship between decreasing domain size and increasing volume fraction of alcohol. As Nd was added to the BaFsb2 host, direct incorporation was observed at low dopant levels (0-10 mol-%), a two-phase mixture was observed at intermediate dopant levels (10-50 mol-%), and a nearly amorphous product resulted with very high Nd-dopant levels (>50 mol-%). Fluorescence measurements of the solids showed that concentration quenching was delayed until unusually high levels, probably as a result of the lost crystallinity. Praseodymium and ytterbium codoped barium fluoride (Pr,Yb:BaFsb2) were also synthesized in microemulsions. Though as-prepared powders did not fluoresce, treatment with high temperatures (900sp°C) and dynamic vacuum resulted in products which would fluoresce at 1.3 mum. Lower temperature treatments (500-750sp°C) were used to decrease sintering, however this resulted in Ybsp{3+} products in which Ybsp{3+} fluorescence was quenched by exposure to air. Contamination due to water and hydroxide is believed to be the reason. Ethanolic microemulsions were used to make copper phthalocyanine (CuPc), which was modified with either zinc phthalocyanine (ZnPc) or copper phthalcyaninesulfonic acid by means of a flow system. The sulfonic acid derivative was lost upon aqueous washing. The zinc derivatized product gave a dispersion in n-hexylamine, which was stable for seven days. The mole ratio of Cu:Zn was 1:1 for the solids dispersed in n-hexylamine, and was 6:1 for the solids that were not dispersed. Because underivatized CuPc formed by the same method did not result in a dispersed product

  8. Fe-doped nanostructured titanates synthesized in a single step route

    SciTech Connect

    Costa, A.M.L.M.; Marinkovic, B.A.; Suguihiro, N.M.; Smith, D.J.; Costa, M.E.H.M. da; Paciornik, S.

    2015-01-15

    for the synthesis of nanotitanates. • Fe-doped nanotitanates have been prepared in a single step wet chemistry route. • The morphology of the nanometric titanates is a function of the temperature. • Mössbauer spectroscopy reveals Fe{sup 3} {sup +} in octahedral sites inside nanosheets. • The Fe incorporation in nanosheets improved the visible light absorption.

  9. Structural and luminescence behavior of Er(3+) ions doped Barium tellurofluoroborate glasses.

    PubMed

    Annapoorani, K; Maheshvaran, K; Arunkumar, S; Suriya Murthy, N; Marimuthu, K

    2015-01-25

    Er(3+) doped Barium tellurofluoroborate glasses (BTFBxE) with the chemical composition (30-x)TeO2+30B2O3+20BaO+20BaF+xEr2O3 (where x=0.01, 0.05, 0.1, 0.5, 1.0 and 2.0 in wt%) were prepared following the melt quenching technique. The different vibrational modes of borates and tellurites in the prepared glasses were explored through FTIR and Raman spectra. The optical absorption spectra have been used to determine the ionic/covalent nature of the metal-ligand bond in the prepared glasses with the help of Nephelauxetic ratio (β) and bonding parameter (δ) studies. The optical band gap of direct and indirect allowed transitions were determined from Tauc's plot and the variations of band gap energy with structural arrangements were discussed. The Urbach energy values were determined and the relatively lower values of the Urbach's energy reveal the minimal degree of disorderness in the prepared glasses. The oscillator strengths (fexp and fcal) and Judd-Ofelt (JO) intensity parameters (Ω2, Ω4 and Ω6) were calculated with the application of JO theory and the trends of the JO intensity parameters are found to be Ω2>Ω6>Ω4 for all the prepared glasses with a minimum variation in Ω2 intensity parameter values. A bright green emission was observed from the (2)H11/2+(4)S3/2→ (4)I15/2 transition and the radiative properties such as transition probability (A), stimulated emission cross-section (σP(E)), branching ratio (βr) and radiative lifetime (τ) were calculated using the JO parameters. The suitability of the prepared glasses for the fabrication of photonic devices were also discussed and reported in the present work. PMID:25173526

  10. Investigation of the additive induced doping effects in gelcast soft lead zirconate titanate ceramics

    SciTech Connect

    Guo Dong; Cai Kai; Li Longtu; Gui Zhilun

    2009-09-01

    Due to the high sensitivity of the electrical properties of electronic ceramics to various factors, knowledge about the possible influence of the processing procedure on their electrical performance is critical for applying a new technique to the fabrication of the materials. In this study, various electrical parameters, complex impedance spectra, ferroelectric hysteresis loops, and microstructures of soft lead zirconate titanate (PZT) ceramics formed by the gelcasting technique from suspensions with various dispersants were investigated in comparison with those of the conventional dry pressed ones. We found that the sodium ion, which is the main cation in many commercial surfactants, exhibited obvious hard doping effects; thus causing deteriorated performance of the gelcast PZT ceramics. While a certain impurity ion introduced by a dispersant was also found to induce soft doping characteristics and improve the electrical performance of the materials. The results suggest that the doping effects of the metal ions or impurities introduced by the dispersants, or other additives, should be generally considered for applying a wet processing technique to forming multicomponent electronic ceramics.

  11. Ferroelectric/Dielectric Double Gate Insulator Spin-Coated Using Barium Titanate Nanocrystals for an Indium Oxide Nanocrystal-Based Thin-Film Transistor.

    PubMed

    Pham, Hien Thu; Yang, Jin Ho; Lee, Don-Sung; Lee, Byoung Hun; Jeong, Hyun-Dam

    2016-03-23

    Barium titanate nanocrystals (BT NCs) were prepared under solvothermal conditions at 200 °C for 24 h. The shape of the BT NCs was tuned from nanodot to nanocube upon changing the polarity of the alcohol solvent, varying the nanosize in the range of 14-22 nm. Oleic acid-passivated NCs showed good solubility in a nonpolar solvent. The effect of size and shape of the BT NCs on the ferroelectric properties was also studied. The maximum polarization value of 7.2 μC/cm(2) was obtained for the BT-5 NC thin film. Dielectric measurements of the films showed comparable dielectric constant values of BT NCs over 1-100 kHz without significant loss. Furthermore, the bottom gate In2O3 NC thin film transistors exhibited outstanding device performance with a field-effect mobility of 11.1 cm(2) V(-1) s(-1) at a low applied gate voltage with BT-5 NC/SiO2 as the gate dielectric. The low-density trapped state was observed at the interface between the In2O3 NC semiconductor and the BT-5 NCs/SiO2 dielectric film. Furthermore, compensation of the applied gate field by an electric dipole-induced dipole field within the BT-5 NC film was also observed. PMID:26927618

  12. Trapping of oxygen vacancy at grain boundary and its correlation with local atomic configuration and resultant excess energy in barium titanate: A systematic computational analysis

    NASA Astrophysics Data System (ADS)

    Oyama, Takashi; Wada, Nobuyuki; Takagi, Hiroshi; Yoshiya, Masato

    2010-10-01

    Atomic structures of [001] symmetric tilt grain boundaries (GBs) and their influences on the trapping of oxygen vacancies at GBs in barium titanate (BaTiO3) were analyzed using static atomistic simulation techniques. It is found that the structures are determined to minimize the deficiency in the coordination numbers of Ti4+ ions and to suppress the structural distortion in the vicinity of the GBs. The excess energy of the GB is dependent on the number density of the coordination-deficient Ti4+ ions, indicating that the ionic bonds between Ti4+ and O2- ions are responsible for structural stabilization of GB. It is also found that the GB plays an important role in trapping oxygen vacancies, which acts as a resistance against the oxygen vacancy’s diffusion. The trapping originates from the presence of irregular O2- sites, where oxygen vacancies energetically prefer to reside, influenced by coordination environment. Based on the detailed analyses on origins of GB energy and the trapping in the vicinity of GB, new physical ground that correlates GB energy and capability of oxygen-vacancy trapping are provided, enabling us to predict how much vacancies can be trapped at GBs on the atomic level by micrometer-order measurement of GB energy. Electrical degradation of the BaTiO3 dielectrics used for multilayer ceramic capacitors can be prevented through controlling the characteristics of the GBs to promote oxygen-vacancy trapping at GBs in polycrystalline materials via modifying materials synthesis procedures.

  13. Cobalt phosphate-modified barium-doped tantalum nitride nanorod photoanode with 1.5% solar energy conversion efficiency.

    PubMed

    Li, Yanbo; Zhang, Li; Torres-Pardo, Almudena; González-Calbet, Jose M; Ma, Yanhang; Oleynikov, Peter; Terasaki, Osamu; Asahina, Shunsuke; Shima, Masahide; Cha, Dongkyu; Zhao, Lan; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2013-01-01

    Spurred by the decreased availability of fossil fuels and global warming, the idea of converting solar energy into clean fuels has been widely recognized. Hydrogen produced by photoelectrochemical water splitting using sunlight could provide a carbon dioxide lean fuel as an alternative to fossil fuels. A major challenge in photoelectrochemical water splitting is to develop an efficient photoanode that can stably oxidize water into oxygen. Here we report an efficient and stable photoanode that couples an active barium-doped tantalum nitride nanostructure with a stable cobalt phosphate co-catalyst. The effect of barium doping on the photoelectrochemical activity of the photoanode is investigated. The photoanode yields a maximum solar energy conversion efficiency of 1.5%, which is more than three times higher than that of state-of-the-art single-photon photoanodes. Further, stoichiometric oxygen and hydrogen are stably produced on the photoanode and the counter electrode with Faraday efficiency of almost unity for 100 min. PMID:24089138

  14. Physical Property of Magnesium Doped Barium Hexaferrite Particles By Citrate Precursor Route In Presence Of Surfactants

    SciTech Connect

    Paladiya, Snehal; Chauhan, C. C.; Jotania, R. B.

    2010-12-01

    M-type Barium Magnesium hexaferrite with the composition BaMg{sub 2}Fe{sub 10}O{sub 19} was successfully prepared with and without surfactant by using a citrate precursor route. The obtained precursors were calcined at various temperatures. The crystalline structure, phase analysis and particle size were investigated by using X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) techniques. It is observed that the surfactant addition controls the microstructure of the formed Barium Magnesium hexaferrite particles and the type of surfactant plays a crucial role in deciding the morphology of particles.

  15. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-03-02

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  16. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-11-23

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  17. Participation of MicroRNA-34a and RANKL on bone repair induced by poly(vinylidene-trifluoroethylene)/barium titanate membrane.

    PubMed

    Lopes, Helena B; Ferraz, Emanuela P; Almeida, Adriana L G; Florio, Pedro; Gimenes, Rossano; Rosa, Adalberto L; Beloti, Marcio M

    2016-09-01

    The poly(vinylidene-trifluoroethylene)/barium titanate (PVDF) membrane enhances in vitro osteoblast differentiation and in vivo bone repair. Here, we hypothesized that this higher bone repair could be also due to bone resorption inhibition mediated by a microRNA (miR)/RANKL circuit. To test our hypothesis, the large-scale miR expression of bone tissue grown on PVDF and polytetrafluoroethylene (PTFE) membranes was evaluated to identify potential RANKL-targeted miRs modulated by PVDF. The animal model used was rat calvarial defects implanted with either PVDF or PTFE. At 4 and 8 weeks, the bone tissue grown on membranes was submitted to a large-scale analysis of miRs by microarray. The expression of miR-34a and some of its targets, including RANKL, were evaluated by real-time polimerase chain reaction and osteoclast activity was detected by tartrate-resistant acid phosphatase (TRAP) staining. Among more than 250 miRs, twelve, including miR-34a, were simultaneously higher expressed (≥2 fold) at 4 and 8 weeks on PVDF. The higher expression of miR-34a was concomitant with a reduced expression of all its evaluated targets, including RANKL. Additionally, more TRAP-positive cells were observed in bone tissue grown on PTFE compared with PVDF in both time points. In conclusion, our results suggest that the higher bone formation induced by PVDF could be, at least in part, triggered by a miR-34a increase and RANKL decrease, which may inhibit osteoclast differentiation and activity, and bone resorption. PMID:27312544

  18. Structural and magnetic properties of Vanadium Doped M- Type Barium Hexaferrite (BaFe12-xVxO19)

    NASA Astrophysics Data System (ADS)

    Awadallah, Ahmad; Mahmood, Sami H.; Maswadeh, Yazan; Bsoul, Ibrahim; Aloqaily, Aynour

    2015-10-01

    Precursor powders of barium hexaferrite doped with vanadium, BaFe12-xVxO19 with (x = 0.1, 0.2, 0.3, 0.4, 0.5), were prepared using the ball milling technique and then sintered at different temperatures for 2 h. The structural properties of the prepared samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the magnetic properties were examined by the vibrating sample magnetometry (VSM). XRD and SEM studies of the samples sintered at 1100° C indicated the presence of Ba3V2O8 and α-Fe2O3 non-magnetic oxide phases in addition to BaM hexaferrite phase. The fractions of the nonmagnetic oxide phases were found to increase with increasing x, and sintering the samples at temperatures higher than 1100° C was found to reduce the amounts of these non-magnetic phases only slightly. However, the addition of barium in excess of the stoichiometric ratio was found to remove the α-Fe2O3 oxide, and improve the saturation magnetization of the samples significantly. In addition, washing these samples with HCl was found to improve the saturation magnetization further. The effect of sintering the samples at higher temperatures was also found to reduce the coercivity due to growth of the particle size. However, the coercivity of all samples remained high enough for potential permanent magnet and magnetic recording applications.

  19. Mechanical degradation under hydrogen of yttrium doped barium zirconate electrolyte material prepared with NiO additive

    NASA Astrophysics Data System (ADS)

    Ciria, D.; Ben Hassine, M.; Jiménez-Melendo, M.; Iakovleva, A.; Haghi-Ashtiani, P.; Aubin, V.; Dezanneau, G.

    2016-07-01

    Recently, a novel process was presented to fabricate dense yttrium-doped barium zirconate electrolytes with high proton conductivity. This process was based on the use of a NiO additive during reactive sintering. We show here that materials made from this process present a fast degradation of mechanical properties when put in hydrogen-rich conditions, while material made from conventional sintering without NiO aid remains intact in the same conditions. The fast degradation of samples made from reactive sintering, leading to sample failure under highly compressive conditions, is due to the reduction of NiO nanoparticles at grain boundaries as shown from structural and chemical analyses using Transmission Electron Microscopy. By the present study, we alert about the potential risk of cell failure due to this mechanical degradation.

  20. Thermal and mechanical effects on large field dielectric loss in lanthanum-doped lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.; Jo, Hwan Ryul; Lynch, Christopher S.

    2013-04-01

    Ferroelectric material losses in devices ranging from sonar transducers to energy harvesters result in the conversion of energy to heat. Under small amplitude sinusoidal drive, either electrical or mechanical, the losses are expressed in terms of a loss tangent. This study addressed the effects of temperature and bias stress on large field dielectric loss in the presence of thermal and mechanical loading in lanthanum-doped lead zirconate titanate, Pb0.92La0.08(Zr0.65Ti0.35)0.98O3 (PLZT 8/65/35). This loss is associated with domain wall motion. Large field dielectric loss was experimentally measured using a technique that matches the area within a unipolar electric displacement - electric field hysteresis loop to an equivalent area ellipse-shaped hysteresis loop. The results indicate that the dependence of dielectric loss on bias stress changes with the onset of a thermally induced transition to slim loop behavior. Stress causes the dielectric loss to increase at low temperature and decrease at high temperature. This is consistent with changes in remnant polarization and saturation of the unipolar electric field - electric displacement hysteresis loops.

  1. Effect of composition and temperature on electric fatigue of La-doped lead zirconate titanate ceramics

    NASA Astrophysics Data System (ADS)

    Jiang, Q. Y.; Subbarao, E. C.; Cross, L. E.

    1994-06-01

    Composition and temperature of ferroelectric La-doped lead zirconate titanate ceramics influence its electric fatigue behavior, defined as the degradation of the electrical properties under the action of an ac field applied for a long time. Compositions of rhombohedral symmetry exhibit little or no fatigue compared with those of tetragonal and orthorhombic symmetry. At temperatures higher than the dielectric maximum, no fatigue effect was detected. Compositions close to phase boundaries (FE-AFE, FE-FE, or FE-PE) display significant fatigue behavior. Electric fatigue arises from the pinning of domains by space charges or injected carriers or from microcracking. The former (which are charge related) is accompanied by smaller strains and is recoverable by thermal and electrical treatment, while the latter (arising from microcracking) arises from large incompatible stresses between grains and is a permanent damage. The understanding of the mechanism of electric fatigue gained in the present study provides guidelines for enhancing the long-term reliability of devices based on ferroic materials.

  2. Effect of B-site isovalent doping on electrical and ferroelectric properties of lead free bismuth titanate ceramics

    NASA Astrophysics Data System (ADS)

    Subohi, Oroosa; Kumar, G. S.; Malik, M. M.; Kurchania, Rajnish

    2016-06-01

    In the present work, zirconium modified bismuth titanate ceramics have been studied as potential lead-free ferroelectric materials over a broad temperature range (RT - 800 °C). Polycrystalline samples of Bi4Ti3-xZrxO12 (x=0.2, 0.4, 0.6) (BZrT) with high electrical resistivity were prepared using the solution combustion technique. The effect of Zr doping on the crystalline structure, ferroelectric properties and electrical conduction characteristics of BZrT ceramics were explored. Addition of zirconium to bismuth titanate enhances its dielectric constant and reduces the loss factor as it introduces orthorhombic distortion in bismuth titanate lattice which is exhibited by the growth along (00_10) lattice plane. Activation energy due to relaxation is found to be greater than that due to conduction thus confirming that electrical conduction in these ceramics is not due to relaxation of dipoles. Remanent polarization of the doped samples increases as the Zirconium content increases.

  3. Dielectric properties of doped titanates of transition metals in the millimeter-wavelength range

    NASA Astrophysics Data System (ADS)

    Rinkevich, A. B.; Perov, D. V.; Kuznetsov, E. A.; Pakhomov, Ya. A.; Ryabkov, Yu. I.

    2016-06-01

    Dielectric properties of ceramic titanates of nickel, cobalt, and manganese and their isomorphically substituted solid solutions are studied. Iron and magnesium are used as dopants. Original methods for solid-state synthesis of titanates allow variations in the dispersity of products. The structure and phase composition of products are analyzed. Microwave measurements of permittivity are performed in a frequency interval of 12-38 GHz. Real and imaginary parts of the permittivities of titanates are determined.

  4. Barium enema

    MedlinePlus

    ... series; Colorectal cancer - lower GI series; Colorectal cancer - barium enema; Crohn disease - lower GI series; Crohn disease - barium enema; Intestinal blockage - lower GI series; Intestinal blockage - ...

  5. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

    PubMed Central

    2013-01-01

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail. PMID:24369051

  6. Synthesis and characterization of UV-treated Fe-doped bismuth lanthanum titanate-doped TiO2 layers in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Song, Myoung Geun; Bark, Chung Wung

    2016-06-01

    Dye-sensitized solar cells (DSSCs) based on titanium dioxide (TiO2) have been extensively studied because they constitute promising low-cost alternatives to their conventional semiconductor-based counterparts. However, much of the effort aimed at achieving high conversion efficiencies has focused on dye and liquid electrolytes. In this work, we report the photovoltaic characteristics of DSSCs fabricated by mixing TiO2 with Fe-doped bismuth lanthanum titanate (Fe-BLT). These nanosized Fe-BLT powders were prepared by using a high-energy ball-milling process. In addition, we used a UV radiation-ozone (UV-O3) treatment to change the surface wettability of TiO2 from hydrophobic to hydrophilic and thereby prevented the easy separation of the Fe-BLT-mixed TiO2 from the fluorine-doped tin-oxide (FTO) coating glass.

  7. Magnetic and Microwave Properties of Barium Hexaferrite Ceramics Doped with Gd and Nd

    NASA Astrophysics Data System (ADS)

    Jamalian, Majid; Ghasemi, Ali; Pourhosseini Asl, Mohammad Javad

    2015-08-01

    Substituted barium hexaferrite nanoparticles with the chemical formula BaFe12- x (GdNd) x/2O19 ( x = 0-2, in steps of 0.5) were prepared by a co-precipitation method. Phase identification and crystal structure of the nanoparticles were investigated by x-ray diffraction. The morphology of the nanopowders was investigated by field-emission scanning electron microscopy. Results from Fourier-transform infrared spectroscopy enabled identification of stretching and bending modes. Magnetic properties were measured by use of a vibrating sample magnetometer. The results revealed that saturation magnetization and coercivity decreased as x increased. Investigation of microwave-absorption properties, by use of a vector network analyzer, revealed that the maximum reflection loss of substituted Ba-ferrite of thickness 1.6 mm reached -41.8 dB at a frequency of 4.3 GHz and a bandwidth of 7.5 GHz, with reflection loss being >-20 dB. From these results it was concluded that the composites had good potential as absorbers in the gigahertz frequency range.

  8. Physical properties and electronic structure of a new barium titanate suboxide Ba1+δTi13-δO₁₂ (δ = 0.11)

    SciTech Connect

    Rotundu, Costel R.; Jiang, Shan; Deng, Xiaoyu; Qian, Yiting; Khan, Saeed; Hawthorn, David G.; Kotliar, Gabriel; Ni, Ni

    2015-04-01

    The structure, transport, thermodynamic properties, x-ray absorption spectra (XAS), and electronic structure of a new barium titanate suboxide, Ba1+δTi13-δO₁₂ (δ = 0.11), are reported. It is a paramagnetic poor metal with hole carriers dominating the transport. Fermi liquid behavior appears at low temperature. The oxidization state of Ti obtained by the XAS is consistent with the metallic Ti²⁺ state. Local density approximation band structure calculations reveal the material is near the Van Hove singularity. The pseudogap behavior in the Ti-d band and the strong hybridization between the Ti-d and O-p orbitals reflect the characteristics of the building blocks of the Ti₁₃ semi-cluster and the TiO₄ quasi-squares, respectively.

  9. Physical properties and electronic structure of a new barium titanate suboxide Ba{sub 1+δ}Ti{sub 13−δ}O{sub 12} (δ = 0.11)

    SciTech Connect

    Rotundu, Costel R.; Jiang, Shan; Ni, Ni; Deng, Xiaoyu; Kotliar, Gabriel; Qian, Yiting; Hawthorn, David G.; Khan, Saeed

    2015-04-01

    The structure, transport, thermodynamic properties, x-ray absorption spectra (XAS), and electronic structure of a new barium titanate suboxide, Ba{sub 1+δ}Ti{sub 13−δ}O{sub 12} (δ = 0.11), are reported. It is a paramagnetic poor metal with hole carriers dominating the transport. Fermi liquid behavior appears at low temperature. The oxidization state of Ti obtained by the XAS is consistent with the metallic Ti{sup 2+} state. Local density approximation band structure calculations reveal the material is near the Van Hove singularity. The pseudogap behavior in the Ti-d band and the strong hybridization between the Ti-d and O-p orbitals reflect the characteristics of the building blocks of the Ti{sub 13} semi-cluster and the TiO{sub 4} quasi-squares, respectively.

  10. Hierarchical assembly of Ti(IV)/Sn(II) co-doped SnO₂ nanosheets along sacrificial titanate nanowires: synthesis, characterization and electrochemical properties.

    PubMed

    Wang, Hongkang; Xi, Liujiang; Tucek, Jiri; Zhan, Yawen; Hung, Tak Fu; Kershaw, Stephen V; Zboril, Radek; Chung, C Y; Rogach, Andrey L

    2013-10-01

    Hierarchical assembly of Ti(IV)/Sn(II)-doped SnO₂ nanosheets along titanate nanowires serving as both sacrificial templates and a Ti(IV) source is demonstrated, using SnCl2 as a tin precursor and Sn(II) dopants and NaF as the morphology controlling agent. Excess fluoride inhibits the hydrolysis of SnCl2, promoting heterogeneous nucleation of Sn(II)-doped SnO₂ on the titanate nanowires due to the insufficient oxidization of Sn(II) to Sn(IV). Simultaneously, titanate nanowires are dissolved forming Ti(4+) species under the etching effect of in situ generated HF resulting in spontaneous Ti(4+) ion doping of SnO₂ nanosheets formed under hydrothermal conditions. Compositional analysis indicates that Ti(4+) ions are incorporated by substitution of Sn sites at a high level (16-18 at.%), with uniform distribution and no phase separation. Mössbauer spectroscopy quantified the relative content of Sn(II) and Sn(IV) in both Sn(II)-doped and Ti(IV)/Sn(II) co-doped SnO₂ samples. Electrochemical properties were investigated as an anode material in lithium ion batteries, demonstrating that Ti-doped SnO₂ nanosheets show improved cycle performance, which is attributed to the alleviation of inherent volume expansion of the SnO₂-based anode materials by substituting part of Sn sites with Ti dopants. PMID:23904051

  11. Fabrication of barium- and strontium-doped silica/titania hollow nanoparticles and their synergetic effects on promoting neuronal differentiation by activating ERK and p38 pathways.

    PubMed

    Kim, Sojin; Jang, Yoonsun; Oh, Wan-Kyu; Kim, Chanhoi; Jang, Jyongsik

    2014-07-01

    Pristine, barium-doped, and strontium-doped hollow nanoparticles (p-HNPs, Ba-HNP, and Sr-HNP; HNPs) are prepared by sonication-mediated etching and redeposition (SMER) method and alkali-earth-metal hydroxide solution treatment. The HNPs are investigated to facilitate synergetic neuronal differentiation through alkali-earth-metal doping and in conjunction with nerve growth factor (NGF). PC12 cells are used as model cells for neuronal differentiation. The differentiation efficiency is improved in the presence of the HNPs+NGF, and the neurite length is in the order of Sr-HNP+NGF > Ba-HNP+NGF > p-HNP+NGF > NGF. Silica/titania have increasing effect on both differentiation efficiency and neurite length, and doped barium/strontium influences additional elongation of the average neurite length. Take advantage of hollow structure, NGF is encapsulated into HNPs, and they are further applied for directly inducing differentiation. The maximum differentiation efficiency is 67% in presence of the NGF-encapsulated Sr-HNP, which was 1.3 times higher than previous research. Furthermore, the neurite length is also 2.7 times higher than MnO2 decorated poly(3,4-ethylenedioxythiophene) nanoellipsoids. Ba- and Sr-HNP may offer a possibility for novel application of metal-hybrid nanomaterials for cell differentiation, and can be expanded to other cellular applications. PMID:24574036

  12. Structural and magnetic properties of conventional and microwave treated Ni-Zr doped barium strontium hexaferrite

    SciTech Connect

    Kanagesan, S.; Jesurani, S.; Velmurugan, R.; Prabu, S.; Kalaivani, T.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Saturation magnetization increases whereas the coercivity decreases. Black-Right-Pointing-Pointer The transition from hard phase to soft phase. Black-Right-Pointing-Pointer Therefore, it is used for high-density magnetic recording applications. -- Abstract: M-type hexaferrites of component B{sub 0.5}Sr{sub 0.5}Fe{sub 12-2x}Ni{sub x}Zr{sub x}O{sub 19} were investigated. The XRD patterns show single phase of the magnetoplumbite barium strontium ferrite and no other phases were present. Significant increase in line broadening of the XRD patterns was observed indicating a decrease of grain size. The samples exhibit well defined crystallization; all of them are hexagonal platelet grains. As the substitution level increased x = 0.2-0.8 mol%, the grains are agglomerated and the average diameter increased. The H{sub c} decreases remarkably with increasing Ni and Zr ions content. It was found that the particle size could be effectively decreased and coercivity H{sub c} could easily be controlled by varying the concentration (x) without significantly decreasing saturation magnetization. In particular, Ba{sub 0.5}Sr{sub 0.5}Fe{sub 12-2x}Ni{sub x}Zr{sub x}O{sub 19} with x = 0.2, 0.4, 0.6, 0.8 mol% has suitable magnetic characteristics with particle size small enough for high-density magnetic recording applications.

  13. Magnetic study of M-type doped barium hexaferrite nanocrystalline particles

    SciTech Connect

    Alsmadi, A. M.; Bsoul, I.; Mahmood, S. H.; Alnawashi, G.; Prokeš, K.; Siemensmeyer, K.; Klemke, B.; Nakotte, H.

    2013-12-28

    Co-Ti and Ru-Ti substituted barium ferrite nanocrystalline particles BaFe{sub 12−2x}Co{sub x}Ti{sub x}O{sub 19} with (0≤x≤1) and BaFe{sub 12−2x}Ru{sub x}Ti{sub x}O{sub 19} with (0≤x≤0.6) were prepared by ball milling method, and their magnetic properties and their temperature dependencies were studied. The zero-field-cooled (ZFC) and field-cooled (FC) processes were recorded at low magnetic fields and the ZFC curves displayed a broad peak at a temperature T{sub M}. In all samples under investigation, a clear irreversibility between the ZFC and FC curves was observed below room temperature, and this irreversibility disappeared above room temperature. These results were discussed within the framework of random particle assembly model and associated with the magnetic domain wall motion. The resistivity data showed some kind of a transition from insulator to perfect insulator around T{sub M}. At 2 K, the saturation magnetization slightly decreased and the coercivity dropped dramatically with increasing the Co-Ti concentration x. With Ru-Ti substitution, the saturation magnetization showed small variations, while the coercivity decreased monotonically, recording a reduction of about 73% at x = 0.6. These results were discussed in light of the single ion anisotropy model and the cationic distributions based on previously reported neutron diffraction data for the CoTi substituted system, and the results of our Mössbauer spectroscopy data for the RuTi substituted system.

  14. Structural and optical properties of melt quenched barium doped bismuth vanadate

    NASA Astrophysics Data System (ADS)

    Gupta, Sakshi; Singh, K.

    2013-12-01

    Bi4BaxV2-xO11-δ (0.0 ≤ x ≤ 0.15) is synthesized by melt quench technique followed by sintering. The structural and optical properties of these samples are investigated using X-ray diffraction, Fourier transform infra-red (FTIR) spectroscopy and UV/vis spectroscopy. The γ-phase stabilization occurs at lower dopant concentration than as reported earlier for similar systems. The optical band gap is observed in the range of 1.5-2.0 eV. It shows decreasing trend with increasing dopant amount. FTIR bands become broader with respect to Ba2+ doping concentration.

  15. Luminescence studies of perovskite structured titanates: A review

    NASA Astrophysics Data System (ADS)

    Nag Bhargavi, G.; Khare, Ayush

    2015-06-01

    Apart from widely known dielectric and ferroelectric properties, the perovskite type materials also constitute a class of materials, which are recently investigated for their optical properties. These materials are being used for fabrication of various microelectronics and optoelectronic devices. Photoluminescence (PL), mechanoluminescence (ML) and thermoluminescence (TL) are such phenomena offering numerous applications in different fields like electro-optics, flat panel displays, LED technology, sensors, dynamic visualization etc. This paper briefly reviews the status and new progress in luminescence studies of ferroelectric materials like barium titanate (BT), barium zirconate titanate (BZT), calcium titanate (CT), calcium zirconate titanate (CZT), lead titanate (PT), lead zirconate titanate (PZT), etc., prepared through various methods.

  16. Arsenic-75 and cobalt-59 NMR study of the electron doped barium iron cobalt arsenide

    NASA Astrophysics Data System (ADS)

    Ning, Fanlong

    We report a systematic investigation of the local electronic, magnetic, and superconducting properties of the new iron-based high temperature superconductor Ba(Fe1-xCox) 2As2 (x = 0, 0.02, 0.04, 0.082) through the measurement of 75As and 59Co NMR (Nuclear Magnetic Resonance) lineshapes, Knight shift (K), and spin-lattice relaxation rate (1/T1). The 75As NMR lineshape of the undoped parent compound splits into two sets due to discrete values of hyperfine magnetic field Bchf = +/- 1.32 Tesla below the magnetic ordering temperature to the SDW (Spin Density Wave) state, TSDW. In contrast, for lightly Co doped samples with x = 0.02 and 0.04, the 75As and 59Co lineshapes become broad and featureless below TSDW, indicating that the ground state is no longer the commensurate SDW ordered state. The observed lineshape is consistent with an incommensurate SDW ordered state, or a commensurate state with large distribution of hyperfine field Bhf. In the optimally doped superconductor with x = 0.082 (T c = 22 K), we observe two types of As sites and three types of Co sites, respectively, as expected from a binomial distribution of Co dopants. We found no evidence for induced localized moments in the vicinity of Co dopants. This finding is in remarkable contrast with the case of Zn or Ni doped high Tc cuprates, and suggests that the fundamental physics of iron-based superconductors is different from that of cuprates. The temperature dependences of 75,59K and 75,59(1/ T1T) at both 75As and 59Co sites show that Ba(Fe1-xCo x)2As2 exhibits spin pseudo-gap like behavior down to ˜ 100 K for a broad Co concentration range. Below ˜ 100 K, we observe the enhancement of residual antiferromagnetic spin fluctuations associated with inter-band spin excitations between the hole and electron Fermi surfaces even for x = 0.082. This effect is suppressed in the overdoped sample with x = 0.099, and T c decreases. Therefore, we suggest that antiferromagnetic spin fluctuations play a crucial role

  17. Implications of the band gap problem on oxidation and hydration in acceptor-doped barium zirconate

    NASA Astrophysics Data System (ADS)

    Lindman, Anders; Erhart, Paul; Wahnström, Göran

    2015-06-01

    Charge carrier concentrations in acceptor-doped proton-conducting perovskites are to a large extent determined by the hydration and oxidation of oxygen vacancies, which introduce protons and holes, respectively. First-principles modeling of these reactions involves calculation of formation energies of charged defects, which requires an accurate description of the band gap and the position of the band edges. Since density-functional theory (DFT) with local and semilocal exchange-correlation functionals (LDA and GGA) systematically fails to predict these quantities this can have serious implications on the modeling of defect reactions. In this study we investigate how the description of band gap and band-edge positions affects the hydration and oxidation in acceptor-doped BaZrO3. First-principles calculations are performed in combination with thermodynamic modeling in order to obtain equilibrium charge carrier concentrations at different temperatures and partial pressures. Three different methods have been considered: DFT with both semilocal (PBE) and hybrid (PBE0) exchange-correlation functionals, and many-body perturbation theory within the G0W0 approximation. All three methods yield similar results for the hydration reaction, which are consistent with experimental findings. For the oxidation reaction, on the other hand, there is a qualitative difference. PBE predicts the reaction to be exothermic, while the two others predict an endothermic behavior. Results from thermodynamic modeling are compared with available experimental data, such as enthalpies, concentrations, and conductivities, and only the results obtained with PBE0 and G0W0 , with an endothermic oxidation behavior, give a satisfactory agreement with experiments.

  18. Laser emission in Nd3+ doped barium-titanium-silicate microspheres under continuous and chopped wave pumping in a non-coupled pumping scheme

    NASA Astrophysics Data System (ADS)

    Martín, L. L.; Navarro-Urrios, D.; Ferrarese-Lupi, F.; Pérez-Rodríguez, C.; Martín, I. R.; Montserrat, J.; Dominguez, C.; Garrido, B.; Capuj, N.

    2013-07-01

    Laser action using non-coupled excitation and detection of microspheres made of Nd3+ doped barium-titanium-silicate glass has been demonstrated and measured. The microspheres have also been successfully deposited over Si3N4 strip waveguides with a SiO2 separation layer, thus enabling the laser emission extraction onto a CMOS compatible photonic circuit. The dynamics of the lasing wavelength and intensity has been studied as a function of the pump power and interpreted in terms of thermal effects generated through non-radiative recombination of the excited ions.

  19. Barium Sulfate

    MedlinePlus

    Barium sulfate is used to help doctors examine the esophagus (tube that connects the mouth and stomach), ... dimensional pictures of the inside of the body). Barium sulfate is in a class of medications called ...

  20. Hierarchical assembly of Ti(iv)/Sn(ii) co-doped SnO2 nanosheets along sacrificial titanate nanowires: synthesis, characterization and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Wang, Hongkang; Xi, Liujiang; Tucek, Jiri; Zhan, Yawen; Hung, Tak Fu; Kershaw, Stephen V.; Zboril, Radek; Chung, C. Y.; Rogach, Andrey L.

    2013-09-01

    Hierarchical assembly of Ti(iv)/Sn(ii)-doped SnO2 nanosheets along titanate nanowires serving as both sacrificial templates and a Ti(iv) source is demonstrated, using SnCl2 as a tin precursor and Sn(ii) dopants and NaF as the morphology controlling agent. Excess fluoride inhibits the hydrolysis of SnCl2, promoting heterogeneous nucleation of Sn(ii)-doped SnO2 on the titanate nanowires due to the insufficient oxidization of Sn(ii) to Sn(iv). Simultaneously, titanate nanowires are dissolved forming Ti4+ species under the etching effect of in situ generated HF resulting in spontaneous Ti4+ ion doping of SnO2 nanosheets formed under hydrothermal conditions. Compositional analysis indicates that Ti4+ ions are incorporated by substitution of Sn sites at a high level (16-18 at.%), with uniform distribution and no phase separation. Mössbauer spectroscopy quantified the relative content of Sn(ii) and Sn(iv) in both Sn(ii)-doped and Ti(iv)/Sn(ii) co-doped SnO2 samples. Electrochemical properties were investigated as an anode material in lithium ion batteries, demonstrating that Ti-doped SnO2 nanosheets show improved cycle performance, which is attributed to the alleviation of inherent volume expansion of the SnO2-based anode materials by substituting part of Sn sites with Ti dopants.Hierarchical assembly of Ti(iv)/Sn(ii)-doped SnO2 nanosheets along titanate nanowires serving as both sacrificial templates and a Ti(iv) source is demonstrated, using SnCl2 as a tin precursor and Sn(ii) dopants and NaF as the morphology controlling agent. Excess fluoride inhibits the hydrolysis of SnCl2, promoting heterogeneous nucleation of Sn(ii)-doped SnO2 on the titanate nanowires due to the insufficient oxidization of Sn(ii) to Sn(iv). Simultaneously, titanate nanowires are dissolved forming Ti4+ species under the etching effect of in situ generated HF resulting in spontaneous Ti4+ ion doping of SnO2 nanosheets formed under hydrothermal conditions. Compositional analysis indicates that Ti4

  1. Electron-microscope study of lanthanum-doped lead zirconate-titanate solid solutions

    SciTech Connect

    Ishchuk, V.M.; Presnyakova, O.V.

    1985-12-01

    This paper examines the structure of specimens of lanthanumdoped lead zirconate-titanate solid solutions in the hysteresis region of the phase diagram, using transmission electron microscopy. The electron-microscopic images of PLZT ceramic of composition display an unusual diffraction contrast. An analysis of the images obtained for different orientations of the cleavages of specimens of composition indicate that the second-phase inclusions are cylindrical in the main. The authors hypothesize that the inclusions are a ferroelectric phase in an antiferroelectric matrix.

  2. Sintering and Microwave Properties of Zirconium Tin Titanate Doped with Select Oxides

    NASA Astrophysics Data System (ADS)

    Arantes, Vera Lucia

    2012-08-01

    Zirconium tin titanate (ZST) is often used as a dielectric resonator for the fabrication of microwave devices. Pure compositions do not sinter easily by solid state sintering; therefore, sintering ZST requires sintering aids capable of creating defects that could improve diffusion processes and/or promote liquid phase sintering. The mechanisms by which the additives influence the microstructure and, consequently, the ZSTs dielectric properties are not very clear. The effects of ZnO, Bi2O3, and La2O3, on the stoichiometry and dielectric properties of ZST sintered at different temperatures were investigated in this study.

  3. Correlations between mechanical and photoluminescence properties in Eu doped sodium bismuth titanate

    NASA Astrophysics Data System (ADS)

    Prusty, Rajesh K.; Kuruva, Praveena; Ramamurty, U.; Thomas, Tiju

    2013-11-01

    Nanoindentation technique is utilized to examine mechanical property variation in Eu doped Na0.5Bi0.5TiO3 (NBT). Doping levels of Eu in NBT is systematically varied. Dilute doping results in a linear reduction in both modulus and hardness. At higher concentrations, a recovery of the mechanical properties (to undoped NBT values) is observed. These experimental trends mirror variations in the optical emission intensities with Eu concentration. Observed trends are rationalized on the basis of a model, which hypothesizes phase segregation beyond a critical Eu doping level. Such segregation leads to the formation of pure NBT, nano-Eu saturated NBT, and nano-mixed Eu oxides in the microstructure. Pure NBT is optically inactive, while saturated Eu:NBT is a much better emitter when compared to europium oxide. Hence beyond the critical concentration, luminescence signal comes primarily from the saturated Eu:NBT phase. The model presented is supported by nanoindentation, and spectroscopic results.

  4. Effects of doping of lead titanate with alkaline-earth elements

    NASA Astrophysics Data System (ADS)

    Shilkina, L. A.; Reznichenko, L. A.; Razumovskaya, O. N.; Dudkina, S. I.; Vlasenko, V. G.; Shevtsova, S. I.; Guglev, K. A.; Kozakov, A. T.; Nikol'skii, A. V.

    2016-01-01

    Solid solutions of the (P{b_{1 - {α _1} - {α _2}}}S{r_{{α _1}}}B{a_{{α _2}}}) (0.02 ⩽ α1 ⩽ 0.36, 0.0073 ⩽ α2 ⩽ 0.1339) system with the ratio of Sr and Ba chosen so as to exclude the influence of the size factor on the lead titanate structure have been studied. The studies have been performed using X-ray powder diffraction (XRD), X-ray absorption spectroscopy (EXAFS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). It has been found that the removal of 2.5 at % Pb2+, which presumably occupy oxygen octahedra, from the solid solution leads to a partial relieving of the crystal lattice stress that is observed as the decrease in the parameter c, c/a, and the unit cell volume, with parameter a being unchanged. It has been shown that PbTiO3 contains up to 5 at % of Pb4+ ions at all the preparation conditions. The Sr and Ba atoms replace the Pb atoms in lead titanate in a narrow concentration range 0 < (α1 + α2) ⩽ 0.0273; at higher Sr and Ba concentrations, solid solutions SrPb x Ti1- x O3 → Sr1- y Ba y Pb x Ti1- x O3 are formed.

  5. Towards Mott design by δ-doping of strongly correlated titanates

    NASA Astrophysics Data System (ADS)

    Lechermann, Frank; Obermeyer, Michael

    2015-04-01

    Doping the distorted-perovskite Mott insulators LaTiO3 and GdTiO3 with a single SrO layer along the [001] direction gives rise to a rich correlated electronic structure. A realistic superlattice study by means of the charge self-consistent combination of density functional theory with dynamical mean-field theory reveals layer- and temperature-dependent multi-orbital metal-insulator transitions. An orbital-selective metallic layer at the interface dissolves via an orbital-polarized doped-Mott state into an orbital-ordered insulating regime beyond the two conducting TiO2 layers. We find large differences in the scattering behavior within the latter. Breaking the spin symmetry in δ-doped GdTiO3 results in blocks of ferromagnetic itinerant and ferromagnetic Mott-insulating layers that are coupled antiferromagnetically.

  6. Highly effective dynamic holographic gratings in doped bismuth titanate crystals and applications to metrology

    NASA Astrophysics Data System (ADS)

    Dovgalenko, George E.; Wu, Ying

    2009-05-01

    Highly efficient volume reflective, dynamical holographic gratings in doped Ti12TiO20 crystals have been observed. We demonstrated doped Ti12TiO20 single, electro-optical crystal and experimental set up, which combines high reversibility, small response time, high diffraction efficiency and practically unlimited number of cycles hologram recording, readout and erasing. It allows using doped Ti12TiO20 crystal as an attractive diffractive optical element in Dynamical Holographic Sensor -DHS for metrology applications. The high image contrast of the real time dynamical holographic interferograms without application of external electric field has been obtained for non transparent diffuse reflective objects using commercial available CW He-Ne laser. DHS applications for nondestructive test of the most vital parts engineering constructions to prevent premature failure have has been demonstrated. DHS application for visualization of cryogenic fields in the near zone of cryoultrasonic cancer tissue destructor has been presented.

  7. Tungsten Bronze Barium Neodymium Titanate (Ba(6-3n)Nd(8+2n)Ti(18)O(54)): An Intrinsic Nanostructured Material and Its Defect Distribution.

    PubMed

    Azough, Feridoon; Cernik, Robert Joseph; Schaffer, Bernhard; Kepaptsoglou, Demie; Ramasse, Quentin Mathieu; Bigatti, Marco; Ali, Amir; MacLaren, Ian; Barthel, Juri; Molinari, Marco; Baran, Jakub Dominik; Parker, Stephen Charles; Freer, Robert

    2016-04-01

    We investigated the structure of the tungsten bronze barium neodymium titanates Ba(6-3n)Nd(8+2n)Ti(18)O(54), which are exploited as microwave dielectric ceramics. They form a complex nanostructure, which resembles a nanofilm with stacking layers of ∼12 Å thickness. The synthesized samples of Ba(6-3n)Nd(8+2n)Ti(18)O(54) (n = 0, 0.3, 0.4, 0.5) are characterized by pentagonal and tetragonal columns, where the A cations are distributed in three symmetrically inequivalent sites. Synchrotron X-ray diffraction and electron energy loss spectroscopy allowed for quantitative analysis of the site occupancy, which determines the defect distribution. This is corroborated by density functional theory calculations. Pentagonal columns are dominated by Ba, and tetragonal columns are dominated by Nd, although specific Nd sites exhibit significant concentrations of Ba. The data indicated significant elongation of the Ba columns in the pentagonal positions and of the Nd columns in tetragonal positions involving a zigzag arrangement of atoms along the b lattice direction. We found that the preferred Ba substitution occurs at Nd[3]/[4] followed by Nd[2] and Nd[1]/[5] sites, which is significantly different to that proposed in earlier studies. Our results on the Ba(6-3n)Nd(8+2n)Ti(18)O(54) "perovskite" superstructure and its defect distribution are particularly valuable in those applications where the optimization of material properties of oxides is imperative; these include not only microwave ceramics but also thermoelectric materials, where the nanostructure and the distribution of the dopants will reduce the thermal conductivity. PMID:26998674

  8. Red photoluminescence in praseodymium-doped titanate perovskite films epitaxially grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Takashima, Hiroshi; Ueda, Kazushige; Itoh, Mitsuru

    2006-12-01

    Intense red photoluminescence (PL) under ultraviolet (UV) excitation was observed in epitaxially grown Pr-doped Ca0.6Sr0.4TiO3 perovskite films. The films were grown on SrTiO3 (100) substrates by pulsed laser deposition, and their epitaxial growth was confirmed by x-ray diffraction and reflected high-energy electron diffraction. The observed sharp PL peak centered at 610nm was assigned to the transition of Pr3+ ions from the D21 state to the H43 state. The PL intensity was markedly enhanced by postannealing treatments at 1000°C, above the film-growth temperature of 600 or 800°C. Because the excitation and absorption spectra are similar to each other, it was suggested that the UV energy absorbed by the host lattice was transferred to the Pr ions, resulting in the red luminescence.

  9. Improved performance of cylindrical hybrid supercapacitor using activated carbon/ niobium doped hydrogen titanate

    NASA Astrophysics Data System (ADS)

    Lee, Jeong Hyun; Kim, Hong-Ki; Baek, Esther; Pecht, Michael; Lee, Seung-Hwan; Lee, Young-Hie

    2016-01-01

    A cylindrical hybrid supercapacitor is fabricated using activated carbon positive electrode and H2Ti12-xNbxO25 (0 ≤ x ≤ 0.6) negative electrode materials. The hybrid supercapacitor using H2Ti11.85Nb0.15O25 exhibits the best electrochemical performance. It has a capacitance of 78.4 F g-1, charge transfer resistance (Rct) of 0.03 Ω, capacitance retention of 91.4% after 1000 cycles at 3.0 A g-1 and energy density of 24.3 W h kg-1 at a power density of 1794.6 W kg-1. Therefore, the Nb doped HTO negative electrode material is a promising candidate as an energy storage system for electric vehicles (EVs).

  10. Free energy dependence of pure phase iron doped bismuth titanate from first principles calculations.

    PubMed

    Mayfield, Cedric L; Subramanian, Vaidyanathan Ravi; Huda, Muhammad N

    2015-08-12

    A density functional theory study of Fe substitutions in Bi2Ti2O7 photocatalyst (Fe-BTO) is presented. It models an experiment where H2 production of Fe-BTO peaked for samples loaded with 1% Fe concentration then decreased for samples with heavier loadings. The total energy calculations were used to determine defect formation energies and the chemical potential landscape that suggests the observed formation of Fe2O3 (in samples at 2% Fe concentration) was detrimental to H2 production. Doping configurations as a function of oxygen chemical potential are discussed, and the chemical potential ranges that avoid formation of the Fe2O3 phase in Fe-BTO are predicted. PMID:26199200

  11. Free energy dependence of pure phase iron doped bismuth titanate from first principles calculations

    NASA Astrophysics Data System (ADS)

    Mayfield, Cedric L.; (Ravi Subramanian, Vaidyanathan; Huda, Muhammad N.

    2015-08-01

    A density functional theory study of Fe substitutions in Bi2Ti2O7 photocatalyst (Fe-BTO) is presented. It models an experiment where H2 production of Fe-BTO peaked for samples loaded with 1% Fe concentration then decreased for samples with heavier loadings. The total energy calculations were used to determine defect formation energies and the chemical potential landscape that suggests the observed formation of Fe2O3 (in samples at 2% Fe concentration) was detrimental to H2 production. Doping configurations as a function of oxygen chemical potential are discussed, and the chemical potential ranges that avoid formation of the Fe2O3 phase in Fe-BTO are predicted.

  12. Effect of Sodium-Site Doping on Enhancing the Lithium Storage Performance of Sodium Lithium Titanate.

    PubMed

    Wang, Pengfei; Qian, Shangshu; Yi, Ting-Feng; Yu, Haoxiang; Yan, Lei; Li, Peng; Lin, Xiaoting; Shui, Miao; Shu, Jie

    2016-04-27

    Via Li(+), Cu(2+), Y(3+), Ce(4+), and Nb(5+) dopings, a series of Na-site-substituted Na1.9M0.1Li2Ti6O14 are prepared and evaluated as lithium storage host materials. Structural and electrochemical analyses suggest that Na-site substitution by high-valent metal ions can effectively enhance the ionic and electronic conductivities of Na2Li2Ti6O14. As a result, Cu(2+)-, Y(3+)-, Ce(4+)-, and Nb(5+)-doped samples reveal better electrochemical performance than bare Na2Li2Ti6O14, especially for Na1.9Nb0.1Li2Ti6O14, which can deliver the highest reversible charge capacity of 259.4 mAh g(-1) at 100 mA g(-1) among all samples. Even when cycled at higher rates, Na1.9Nb0.1Li2Ti6O14 still can maintain excellent lithium storage capability with the reversible charge capacities of 242.9 mAh g(-1) at 700 mA g(-1), 216.4 mAh g(-1) at 900 mA g(-1), and 190.5 mAh g(-1) at 1100 mA g(-1). In addition, ex situ and in situ observations demonstrate that the zero-strain characteristic should also be responsible for the outstanding lithium storage capability of Na1.9Nb0.1Li2Ti6O14. All of this evidence indicates that Na1.9Nb0.1Li2Ti6O14 is a high-performance anode material for rechargeable lithium ion batteries. PMID:27052633

  13. Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping.

    PubMed

    Liu, Wen; Sun, Weiling; Borthwick, Alistair G L; Wang, Ting; Li, Fan; Guan, Yidong

    2016-11-01

    Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and titanate as the main adsorption site. Enhanced photocatalytic removal of co-existent Cr(VI) and 4-CP was observed in binary systems, with apparent rate constants (k1) for photocatalytic reactions of Cr(VI) and 4-CP about 3.1 and 2.6 times of that for single systems. In addition, over 99% of Cr(VI) and 4-CP was removed within 120min through photocatalysis by TNS at pH 7 in the binary system. Mechanisms for enhanced photocatalytic efficiency in the binary system are identified as: (1) a synergetic effect on the photo-reduction of Cr(VI) and photo-oxidation of 4-CP due to efficient separation of electron-hole pairs, and (2) autosynchronous doping because of reduced Cr(III) adsorption onto TNS. Furthermore, TNS could be efficiently reused after a simple acid-base treatment. PMID:27318735

  14. Effect of barium titanate (BaTiO{sub 3}) additive on the short-term DC breakdown strength of polyethylene

    SciTech Connect

    Khalil, M.S.; Henk, P.O.

    1996-12-31

    The use of additives to insulating materials is one of the methods to improve certain properties of these materials. Additives can also be used to provide more insight into some processes like conduction, space charge formation and breakdown under certain conditions of field application. In the present paper, the effect of the addition of fine particles 1 wt% BaTiO{sub 3} to plain low density polyethylene (LDPE) on the short-term dc breakdown strength of LDPE at room temperature was investigated. The characteristics of the used polyethylene are as follows: density 0.925 g/cm{sup 3}, melt index 0.25 g/10 min. The BaTiO{sub 3} used was laboratory grade with particle size less than 7 {micro}m. Special cylindrical test samples of both undoped and doped materials were used in this investigation. Stainless steel hemispherically tipped electrodes were embedded in the material by molding. The mean value of the gap length between the electrodes was 0.25 mm. The design of the test sample allows for determining the intrinsic breakdown strength of the material. The Weibull plots were used to analyze the breakdown test results. Analysis of the results indicate that the addition of BaTiO{sub 3} to LDPE has reduced the short term dc breakdown strength of the doped material by about 16% if compared with the corresponding value for the plain LDPE. An attempt is made to correlate between the present results, and earlier published results about the effect of BaTiO{sub 3} on dc conductivity and space charge formation in LDPE.

  15. Microstructure and chemistry of MgO- and CoO-doped nickel-titanate spinels

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Carter, C.B.

    1994-06-01

    Four specimens Me{sub x}Ni{sub 1{minus}x}O - 14.2 mol% TiO{sub 2} (Me=Mg,Co and x=0.1 or 0.2) were prepared by cold pressing and firing. After heating and quenching, slices were examined in a TEM and x-ray spectrometry carried out. Dark-field images were recorded near the [001]-pole of the two cubic phases with spinel (220) reflection. The spinel-structured phase appears bright, the periclase-structured phase dark. In the 20% CoO doped specimen, the spinel and periclase phases form a continuously interpenetrating network (scale 40 nm); examination of the site distributions with ALCHEMI indicates that the Ti cations occupy mostly the octahedral site (tetrahedral site in undoped material). The spinel MgNiTiO{sub 4} is unstable. The arrangements of the some of the faceted particles in groups suggest that a large periclase-structured particle may have subdivided.

  16. Influence of lanthanum doping on the morphotropic phase boundary of lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Hinterstein, Manuel; Schoenau, Kristin A.; Kling, Jens; Fuess, Hartmut; Knapp, Michael; Kungl, Hans; Hoffmann, Michael J.

    2010-07-01

    A phase diagram for morphotropic (Pb0.985La0.01)(Zr1-xTix)O3 is proposed based on a combination of X-ray and neutron powder diffraction experiments and complemented by transmission electron microscopy. Dependent on composition three regions are characterized. The stability range of tetragonal microdomains for high Ti contents, the stability range of rhombohedral microdomains for low Ti contents, and an intermediate stability range of nanodomains. All three regions exhibit a corresponding low temperature configuration. Temperature dependent diffraction revealed that lanthanum doping reduces the sensitivity of the structure to changes in temperature and composition. A continuous transition from pseudorhombohedral to tetragonal symmetry with an intermediate two-phase region at the morphotropic phase boundary is observed. A similar transition of low temperature superstructure phases from pseudorhombohedral to pseudotetragonal with an intermediate monoclinic phase governed by a continuous change in the oxygen octahedral tilt system from a-a-a- over a-a-c- to a0a0c- is identified.

  17. Effect of biphase on dielectric properties of Bi-doped lead strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Li, X. T.; Du, P. Y.; Zhao, Y. L.; Tu, Y.; Dai, J. L.; Weng, W. J.; Han, G. R.; Song, C. L.

    2010-11-01

    Pb 0.4Sr 0.6TiO 3 (PST) thin films doped with various concentration of Bi were prepared by a sol-gel method. The phase status, surface morphology and dielectric properties of these thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer, respectively. Results showed that the thin films with the maximum dielectric constant and minimum dielectric loss were obtained for x=0.15. For x<0.15, only pure PST perovskite phase were in the thin films. For 0.2< x<0.4, the PST/Bi 2Ti 2O 7 biphase were obtained. The thin films with pure Bi 2Ti 2O 7 pyrochlore phase were obtained for x=0.67. The biphase thin films had high tunability and high figure of merit (FOM). The FOM of PST/Bi 2Ti 2O 7 biphase thin film was about 6 times higher than that thin films formed with pure perovskite phase or pure pyrochlore phase.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  19. Significant performance enhancement of yttrium-doped barium cerate proton conductor as electrolyte for solid oxide fuel cells through a Pd ingress-egress approach

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Ran, Ran; Li, Sidian; Jiao, Yong; Tade, Moses O.; Shao, Zongping

    2014-07-01

    Proton-conducting perovskite oxides are excellent electrolyte materials for SOFCs that may improve power density at reduced temperatures and increase fuel efficiency, thus encouraging the widespread implementation of this attractive technology. The main challenges in the application of these oxides in SOFCs are difficult sintering and insufficient conductivity in real cells. In this study, we propose a novel method to significantly enhance the performance of a yttrium-doped barium cerate proton conductor as an electrolyte for SOFCs through a Pd ingress-egress approach to the development of BaCe0.8Y0.1Pd0.1O3-δ (BCYP10). The capability of the Pd egress from the BCYP10 perovskite lattice is demonstrated by H2-TPR, XRD, EDX mapping of STEM and XPS. Significant improvement in the sinterability is observed after the introduction of Pd due to the increased ionic conductivity and the sintering aid effect of egressed Pd. The formation of a B-site cation defect structure after Pd egress and the consequent modification of perovskite grain boundaries with Pd nanoparticles leads to a proton conductivity of BCYP10 that is approximately 3 times higher than that of BCY under a reducing atmosphere. A single cell with a thin film BCYP10 electrolyte reaches a peak power density as high as 645 mA cm-2 at 700 °C.

  20. Electron microscopy of X7R and Y5V type barium titanate multilayer ceramic capacitors with noble and base metal electrodes

    NASA Astrophysics Data System (ADS)

    Feng, Qiquan

    Two types of multilayer ceramic capacitors (MLCCs), Y5V with Ni electrodes and X7R with Ag/Pd electrodes, were characterized by transmission electron microscopy (TEM) and showed quite different microstructures which determined their dielectric behaviors. In X7R-type MLCCs, core-shell structures were observed. The flat dielectric constant-temperature curves obtained from these materials can be interpreted in terms of the internal stress states in individual grains. The stress states were observed using weak beam dark field (WBDF) microscopy. The strain contours observed were formed by distorted crystal planes and were dependent on the stress state of the crystal instead of crystal symmetry. The stress distribution in individual grains was determined by both the thickness ratio of shell and core and the geometrical relationship of the core and the shell. (111) lamella twins and dislocation loops in the paraelectric phases of BaTiO3 doped with Bi2O3 were analyzed by TEM under two-beam conditions. Y5V-type MLCCs based on re-oxidized Ba(Ti 0.88,Zr0.12)O3 (BTZ) materials exhibited frequency relaxation effects. Multi-domain structures coexisting in one grain were observed at dynamical diffraction conditions. Uneven distribution of internal stress and coexistence of multi-phases and multi-domains in individual grains were considered to be responsible for the frequency relaxor behavior observed in these materials. The compatibility of electrodes and dielectrics in cofired MLCCs with both Ni and Ag/Pd electrodes was characterized by TEM using tripod polished samples. NiO lamellae and P-rich intermediate layers were found in highly accelerated life tested (HALT) MLCCs with Ni electrodes. It is believed that Mn ions were reduced by the Ni electrodes, as P-rich and Mn-rich segregated layers were observed in the virginal non-life tested MLCCs. No silver diffusion was found in either the BaTiO3 based perovskite lattices or the flux phases in air-fired X7R type MLCCs.

  1. Barium cyanide

    Integrated Risk Information System (IRIS)

    Barium cyanide ; CASRN 542 - 62 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Ef

  2. Lead zirconate titanate ceramics

    SciTech Connect

    Walker, B.E. Jr.

    1986-12-02

    This patent describes a lead zirconate titanate (PZT) piezoelectric ceramic composition which, based on total composition weight, consists essentially of a solid solution of lead zirconate and lead titanate in a PbZrO/sub 3/:PbTiO/sub 3/ ratio from about 0.505:0.495 to about 0.54:0.46; a halide salt selected from the group consisting of fluorides and chlorides of alkali metal and alkaline earth elements and mixtures thereof except for francium and radium in an amount from about 0.5 to 2 weight percent; and an oxide selected from the group consisting of magnesium, barium, scandium, aluminum, lanthanum, praesodynium, neodymium, samarium, and mixtures thereof in an amount from about 0.5 to about 6 weight percent, the relative amount of oxide being from about 1 to about 4 times that of the halide.

  3. Synthesis of Sm{sup 3+}-doped strontium barium niobate crystals in glass by samarium atom heat processing

    SciTech Connect

    Chayapiwut, Nakorn; Honma, Tsuyoshi; Benino, Yasuhiko; Fujiwara, Takumi; Komatsu, Takayuki . E-mail: komatsu@chem.nagaokaut.ac.jp

    2005-11-15

    New glasses giving the crystallization of Sm{sup 3+}-doped Sr {sub x} Ba{sub 1-} {sub x} Nb{sub 2}O{sub 6} (SBN) ferroelectrics have been developed in the Sm{sub 2}O{sub 3}-SrO-BaO-Nb{sub 2}O{sub 5}-B{sub 2}O{sub 3} system, and the formation of SBN crystal dots and lines by continuous wave Nd:YAG laser (wavelength:1064 nm, power: 1 W) irradiations, i.e., samarium atom heat processing, has been examined. The formation of Sm{sup 3+}-doped SBN non-linear optical crystals is confirmed from X-ray diffraction analyses, micro-Raman scattering spectra, second harmonic generations, and photoluminescence spectra. Sm{sup 3+}-doped SBN crystal dots with the diameters of 20-70 {mu}m and lines with the widths of 20-40 {mu}m are written at the surface of some glasses such as 10Sm{sub 2}O{sub 3}.10SrO.10BaO.20Nb{sub 2}O{sub 5}.50B{sub 2}O{sub 3} (mol%) by Nd:YAG laser irradiations with the irradiation times of 20-70 s for the dots and with the scanning speeds of 1-5 {mu}m/s for the lines. The present study suggests that the samarium atom heat processing has a potential for the patterning of optical waveguides consisting of ferroelectric SBN crystals in glass substrates.

  4. First-principles Studies of the Optical Properties of Eu doped Barium Halides: From Storage Phosphor to Bright Scintillator

    NASA Astrophysics Data System (ADS)

    Canning, Andrew; Medasani, Bharat; Del Ben, Mauro; Bizarri, Gregory

    The Eu doped Ba mixed halide family BaBrX (X=F,Cl,Br,I) changes from being a widely used X-ray Storage Phosphor (BaBrF:Eu) to one of the brightest know new gamma ray detector scintillators (BaBrI:Eu). To help understand these contrasting optical properties and guide in the design of new and improved scintillator detectors, in collaboration with experimental groups, we have performed first principles theoretical studies of these materials. In particular we have studied their electron and hole trapping mechanisms and how that can explain their very different optical properties.

  5. Microstructural and thermal properties of pure BaFe12O19 and Sr doped barium ferrite (Ba0.9Sr0.1Fe12O19) synthesized by auto combustion method

    NASA Astrophysics Data System (ADS)

    Taufeeq, Saba; Parveen, Azra; Agrawal, Shraddha; Azam, Ameer

    2016-05-01

    Nanoparticles (NPs) of Pure BaFe12O19 and Strontium doped Barium Ferrite (Ba0.9Sr0.1Fe12O19) have been successfully synthesized by Auto combustion method using citric acid as a chelating agent and calcined at 450°C for 3 hrs and 850°C for 4 hrs. Microstructural studies were carried by XRD and SEM techniques. Structural studies suggest that the crystal system remains hexagonal even with the doping of Strontium. The XRD analysis confirms the formation of the structures in the nanometer regime and the peaks are the evidence of the crystalline phase. The SEM images shows the morphology of surface of the samples. The thermal property studied by TGA shows the weight loss which is with varying the temperature and weight loss also varies with Sr doping. The TGA analysis exhibits the loss of weight at different temperatures.

  6. Structural Properties of Ferroelectric Lead(Zirconium0.5,Titanium0.5)Oxygen3 Nanotube Array and Electronic Structure of Lao delta-doped strontium titanate

    NASA Astrophysics Data System (ADS)

    Adhikari, Rajendra P.

    In this Dissertation we begin with two introductions on: 1) ferroelectricity and related phenomena, and 2) novel properties of Oxide electronics and the generation of two dimensional electron gas. We then give theoretical background of density functional theory (including LDA+U) and pseudopotentials. The first part of research work is about structural, polarization, and dielectric properties of ferroelectric Lead Zirconate Titanate (PZT) solid solution in the form of a nanotube array, embedded in a matrix medium of different ferroelectric strengths. We use the effective Hamiltonian derived from first-principles and finite-temperature Monte Carlo methods to determine the various properties. We revealed different polarization phases of the system in the absence of an external electric field and explained these properties in microscopic detail. In the second part, we study the effects of compressive biaxial inplane strains on the electronic and structural properties of Lanthanum Oxide delta-doped Strontium Titanate supercell. We use first-principles density functional calculations within the local density approximation including also on-site Coulomb interaction energy. We approached the problem by comparing the band structures, localization of electronic states, and cation-anion displacements of unstrained and strained systems. We found a critical strain above which there are abrupt changes in conduction band dispersions and cation-anion displacements, indicating that inplane biaxial strain can drastically tune the properties of this system, which may have potential technological applications.

  7. Optoenergy storage, stimulated processes in optical amplification with electro-optic ceramic gain media of Nd3+ doped lanthanum lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Wu, Ye; Zhao, Hua; Zou, Yingyin K.; Chen, Xuesheng; Bartolo, Baldassare Di; Zhang, Jingwen W.

    2011-08-01

    Optical amplification was observed in electro-optic (EO) ceramic plates of neodymium doped lanthanum-modified lead zirconate titanate (Nd3+:PLZT), when the pumping and seeding beams are not overlapped temporarily. This striking feature in the gain measurement and the accompanying slowly trailing-off both seen in the optical amplification as well as in the lasing action are satisfactorily explained by electron releasing from the rich vacancy-based carrier traps in the intrinsically disordered ceramics, i.e., the consecutively optical, thermal stimuli are found responsible for the long persistent optoenergy storage, and consequently the slow response of the gain dynamics. These findings in optical amplification, the slowly trailing-off, and the underlying mechanism have opened a new way of developing novel controllable optical devices. The model thus established could serve as a guide in design and refinement of a new generation of products out of this excellent, well commercialized EO PLZT ceramics family and similar others.

  8. Effects of postdeposition annealing on the dielectric properties of antiferroelectric lanthanum-doped lead zirconate stannate titanate thin films derived from pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Yao, Yingbang; Lu, S. G.; Chen, Haydn; Wong, K. H.

    2004-11-01

    Lanthanum-doped lead zirconate stannate titanate antiferroelectric thin films were deposited onto Pt-buffered silicon substrates using the pulsed laser deposition method. The deposition temperature was 570°C. The postdeposition annealing process was carried out in an oxygen-flow tube furnace at temperatures ranging from 650 to 800°C for a duration of 30min; its effects were studied through the variations of the microstructure as well as the electrical and dielectric properties. It was found that an appropriate annealing process at temperatures above 700°Ccould substantially improve the dielectric properties. However, annealing beyond 800°C caused the film properties to deteriorate severely. Explanations were given with regard to the microstructure-property relationship.

  9. Effect of alkaline earth oxides on the formation of surface microphases that protect strontium titanate from reduction

    SciTech Connect

    Aksenova, L.A.; Kostikov, Yu.P.; Leonov, A.I.; Rotenberg, B.A.; Strykanov, V.S.

    1986-08-20

    The authors studied the effect of addition of strontium oxide, barium oxide, and calcium oxide on the formation of surface microphases and the reduction of strontium titanate. The materials were strontium carbonate, barium carbonate, and calcium carbonate (analytical grade) and titanium dioxide (pure grade). X-ray diffraction analysis was carried out on a DRON-2.0 diffractometer (CuK/sub ..cap alpha../, Ni filter). The surface layers were studies in an electron spectrometer by ESCA (exciting irradiation Al/sub K..cap alpha../; bond energy in standard gold sample Au/sub 4/f/sub 1/2/ = 84.1 eV; depth of layer 8 nm). Samplers were prepared according to the usual ceramic technology. It was found that protection from reduction of strontium titanate that is doped with calcium, strontium, or barium oxide is related to the formation of surface microphases that are close to M/sub 2/TiO/sub 4/ in composition and do not undergo reduction when calcined in a medium at low partial pressure of oxygen.

  10. Flexoelectricity in barium strontium titanate thin film

    SciTech Connect

    Kwon, Seol Ryung; Huang, Wenbin; Yuan, Fuh-Gwo; Jiang, Xiaoning; Shu, Longlong; Maria, Jon-Paul

    2014-10-06

    Flexoelectricity, the linear coupling between the strain gradient and the induced electric polarization, has been intensively studied as an alternative to piezoelectricity. Especially, it is of interest to develop flexoelectric devices on micro/nano scales due to the inherent scaling effect of flexoelectric effect. Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} thin film with a thickness of 130 nm was fabricated on a silicon wafer using a RF magnetron sputtering process. The flexoelectric coefficients of the prepared thin films were determined experimentally. It was revealed that the thin films possessed a transverse flexoelectric coefficient of 24.5 μC/m at Curie temperature (∼28 °C) and 17.44 μC/m at 41 °C. The measured flexoelectric coefficients are comparable to that of bulk BST ceramics, which are reported to be 10–100 μC/m. This result suggests that the flexoelectric thin film structures can be effectively used for micro/nano-sensing devices.